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GIFT or
Prof. W.B. Rising
INORGANIC CHEMISTKY.
THE NATIONAL DISPENSATORY: CONTAINING THE NAT-
ural History, Chemifttry, Pbarmacj, Actions and Uses of Medicines, includin^^
those recognized in the Pharmaa)p(Bia8 of the United States, Great Britain,
and Germany, with numerous references to the French Codex. By Alfred
Still6, M.D., LL.D., Professor Emeritus of the Theory and Practice of Medicine
and of Clinical Medicine in the University of Pennsylvania, and John M.
Maisch. Phar. D., Professor of Mat. Med. and Botany in Phila. College of
Pharmacy, Sec'y to the American Pharmaceutical Association. Third edition,
thoroughly revised and greatly enlarged. In one magnificent imperial octavo
volume of 1767 pages, with 311 fine engravings. Cloth, $7.25 ; leather, $8.00 ;
half Bussia, open back, $9.00. With Denison's "Ready Reference Index"
$1.00 in addition to price in any of above styles of binding.
A MANUAL OF CHEMICAL ANALYSIS, AS APPLIED TO THE
Examination of Medicinal Chemicals and their Preparations. Being a Guide
for the Determination of their Identity and Quality, and for the Detection of
Imparities and Adulterations. For the use of Pharmacists, Physicians, Drag-
gists, and Manufacturing Chemists, and Pharmaceutical and Medical Students.
By F. Hoffmann, A.M., Ph.D., Public Analyst to the State of New York, and
F. B. Power, Ph.D., Prof, of Anal. Chem. in the Phil. College of Pharmacy.
Third edition, entirely re-written and much enlarged. In one very handsome
octavo volume of 621 pages, with 179 illustrations. Cloth, $4.25.
MEDICAL PHYSICS. A TEXT-BOOK FOR STUDENTS AND
Practitioners of Medicine. By John C. Draper, M.D., LL.D., Professor of
Chemistry in the University of the City of New York. In one octavo volume
of 734 pages, with 376 woodcuts, mostly original. Cloth, $4.00. Just ready,
CHEMISTRY, GENERAL, MEDICAL AND PHARMACEUTICAL;
Including the Chemistry of the U. S. Pharmacopoeia. A Manual of the General
Principles of the Science, and their Application to Medicine and Pharmacy.
By John Attfield, Ph.D., Professor of Practical Chemistry to the Pharmaceuti-
cal Society of Great Britain, etc. A new American, from the tenth English
edition, specially revised by the Author. In one handsome royal Timo. volume
of 728 pages, with 87 illustrations. Cloth, $2.50; leather, $3.00.
TEXT-BOOK OF PHYSIOLOG Y. B Y MICHAEL FOSTER, M.D.,
F.R.S., Professor of Physiology in Cambridge University, England. Third
American from the fourth English edition, with notes and additions by E. T.
Reichert, M.D. In one handsome royal 12mo. volume of 908 pages, with
271 illustrations. Cloth, $3.25 ; leather, $3.75. Just ready.
Detailed Catalogue sent to any address on application to
LEA BROTHERS & CO., Philadelphia.
INORGANIC CHEMISTRY,
BY
EDAVARD FRANKLAND, Ph.D., D.C.L., LL.D., F.R.S.,
pROirESSOR OF CHEMISTRY IN THE NORMAL SCHOOL OF SCIENCE, LONDON,
AND
FRANCIS R. JAPP, M.A., Ph.D., F.I.C,
ASSISTAKT rBOFESSOR OP CHEMISTRY IN THE NORMAL SCHOOL OP SCIENCE, LONDON.
WITH 51 ILLUSTRATIONS AND A PLATE.
PHILADELPHIA:
LEA BEOTHERS & CO.
1885.
PREFACE.
The Lecture Notes for Chemical Students, already published by
one of us and now in their third edition, were always intended to be
the precursors of text-books on Mineral and Organic Chemistry.
The present volume fulfils this intention so far as Inorganic Chem-
istry is concerned. It is constructed on those principles of Classi-
fication, Nomenclature, and Notation which, after an experience of
nearly twenty years, have been found to lead most readily to the
acquisition of a sound and accurate knowledge of elementary chem-
istry.
In the Introduction we have endeavored to present to the student a
connected account of the chief chemical theories at present prevail-
ing, introducing only so much descriptive matter as is necessary for
the elucidation of the subject. Afterwards, in the descriptive part of
the work, the necessary references to the theoretical portion are given.
In some of the theoretical sections, we have followed modes of treat-
ment adopted by H. Kopp, Lothar Meyer, and Naumann in their
well-known works. We have also to express our obligations to
Pittig's excellent " Grundiss der unorganischen Chemie."
Although it would be out of place, in an elementary work like the
present, to impart detailed instruction in the technical applications
of chemistry, we have not hesitated to give brief outlines of some of
the more important of these applications.
KoRMAL School of Science and
Royal School of Mines,
South Kensington, London.
September, 1884.
237563
TABLE OF CONTENTS.
INTROEUCTION.
CHAPTER I.
MATTER AND FORCE.
PAGB
Mutter and motion. Forces of nature, 33
Distinguishing characteristics of chemical force, 34
CHAPTER II.
ELEMENTS AND COMPOUNDS.
Simple and compound matter, 37
Table of elemeuts, 3d
CHAPTER III.
CHEMICAL NOMENCLATURE.
Nomenclature of elements, 40
Nomenclature of compounds, . i .40
CHAPTER IV.
LAWS OF COMBINATION.
Law of constant proportions, 45
Law of multiple proportions, 46
Law of equivalent proportions, 46
CHAPTER V.
THE ATOMIC THEORY.
Atoms, 43
Molecules, 48
CHAPTER VI.
MOLECULAR WEIGHTS.
Boyle's Law, 52
Law of Charles, 63
Law of Avogadro, 53
Law of Gay-Lussac, 54
Hofmann's volume-symbols, 56
Determination of molecular weights, 59
VUl TABLE OF CX)NTENT8.
CHAPTER VII.
ATOMIC WEIGHTS.
PAGE
Deductions of the atomic weight of an element from the vapor-densitj of its com-
pounds 61
Apparent exception to Avogadro's law, 63
Determination of atomic weights by means of isomorphism, 64
Determination of the atomic weights from the specific heats of the elements in
the solid state, 67
CHAPTER VTII.
CHEMICAL NOTATION. ATOMICITY.
Symbolic notation, 75
Atomicity of elements, 78
Graphic notation, 82
Calculation of formulse, 84
CHAPTER IX.
COMPOUND RADICALS.
List of compound mdicals, 86
Atomic and molecular combination, 87
CHAPTER X.
CLASSIFICATION OF ELEMENTS.
Classification of the elements according to atomicity, '. 88
Classification of the elements according to their atomic weights. The Periodic
Law, 90
Curve of the atomic volumes of the elements, 95
CHAPTER XI.
RELATIONS BETWEEN CHEMICAL COMPOSITION AND SPECIFIC GRAVITY.
ATOMIC VOLUME.
Atomic and molecular volumes, 96
Molecular volume of gases, 96
Molecular volume of solids, 97
Molecular volume of liquids, 98
CHAPTER XII.
CHEMICAL AFFINITY.
Extent and intensity of chemical affinity, 102
Modes of chemical action, 102
Combination. Decomposition, 103
Dissociation, 103
Electrolysis, 104
Electro-chemical equivalents, 107
TABLE OF CONTENTS. IX
CHAPTER XIII.
CHEMICAL HOMOGENEITY.
PAOB
Homngeneitj of gases, 109
Homogeneity of liquids and solids, 109
CHAPTER XIV.
ISOMERISM, METAMERISM, POLYMERISM, ALLOTROPY.
Difierences of chemical character in compounds of the same composition, . . 110
Allotropy, Ill
CHAPTER XV.
HEAT OF CHEMICAL COMBINATION. — THERMOCHEMISTRY.
Laws of thermochemistry • Ill
CHAPTER XVI.
FUSION AND FUSING-POINTS.
Change of volume accompanying fusion, 117
Effect of pressure in altering the fusing-point, 117
Latent beat of fusion, 117
Suspended solidification, 119
CHAPTER XVII.
EBULLITION AND BOILING-POINTS.
Vapor tension, 119
Law regulating boiling-points, 120
Latent heat of vapors, 122
Liquefaction of gases, 123
CHAPTER XVIII.
SOLUTION.
Solubility of gas«s 124
Sohibilitj of liquids, ] 24
Solubility of solids, 126
Saperaaturation or suspended crystallization, 128
CHAPTER XIX.
DIFFUSION.
Phenomena of diffusion 128
Diffusion of liquids. Dialysis, 129
Diffbeion of gases, ; 130
CHAPTER XX.
CRYSTALLOGRAPHY.
Systems of crystals, 132
X TABLE OF CONTENTS.
CHAPTER XXI.
WEIGHTS AND MEASURES.
PAGE
French and English systeniB, 136
Conversion of French into English weights and measures, 136
The crith, 137
NON-METALS.
CHAPTER XXII.
MONAD ELEMENTS.
Section I. Htdrooen, 140
Section II. Chlorin£, 151
Hydrochloric acid, 156
CHAPTER XXIII.
DYAD ELEMENTS.
Seetionl, Oxygen, 160
A llotropic oxygen or ozone, 166
Compounds of oxygen with hydrogen, 169
Compounds of chlorine with oxygen and hydroxyl, 177
CHAPTER XXIV.
TRIAD ELEMENTS.
Seetionl. Boron, * 185
Compound of boron with hydrogen, 187
Compounds of boron with the halogens, 188
Compounds of boron with oxygen and hydroxyl, 190
CHAPTER XXV.
TETRAD ELEMENTS.
Seetionl, Carbon, 193
Compounds of carbon with oxygen, 200
CHAPTER XXVI.
PENTAD ELEMENTS.
Seetionl. Nitrogen, 211
Compounds of nitrogen with oxygen and hydroxyl, 213
Compounds containing nitrogen, chlorine, and oxygen, 228
Compounds of nitrogen with hydrogen and hydroxyl, 230
Compounds of nitrogen with chlorine, bromine, and iodine 236
The atmosphere, 237
TABLE OF CONTENTS. XI
CHAPTER XXVII.
HEXAD ELEMENTS.
PAGE
SeeHonl. SuLPHuii, 243
Compounds of snlphnr with hydrogen, 249
Compounds of sulphur with the halogens, 254
Compound of sulphur with carbon, . . . . ' 256
Compound of sulphur with carbon and oxygen, 258
Compounds of sulphur with oxygen and hydroxyl, 259
Compounds of sulphur with oxygen and chlorine (oxychlorides, acid chlo-
rides), 281
Selenium, 283
Compounds of selenium with hydrogen and chlorine, 285
Compounds of selenium with oxygen and hydroxyl, 286
Tfxi^uRirM, 287
Compounds of tellurium with hydrogen, chlorine, and oxygen, .... 288
CHAPTER XXVIII.
MONAD ELEMENTS.
Seclion IT (oontmtied). Bromine, 290
Hydrobroniic acid, 292
Compoundsof bromine with oxygen and hydroxy 1, 293
Iodine, 295
Hydriodic acid, 298
Compounds of iodine with chlorine, 300
Compounds of iodine witli oxygen and hydroxyl, 301
Fluorine, 306
Hydrofluoric acid, 307
CHAPTER XXIX.
TETRAD ELEMENTS,
Seefibn I (continued). Silicon, 309
Compound of silicon with hydrogen, 311
Compounds of silicon with the halogens, 313
Compounds of silicon with oxygen and hydroxyl, 316
Compoundsof silicon containing sulphur, 320
Tin, . 321
Compounds of tin, 323
Compoundsof tin with the halogens, 324
Compounds of tin with oxygen and hydroxyl, 326
Compounds of tin with sulphur, 328
General character and reactions of the salts of tin, 329
Titanium 330
Compounds of titanium with chlorine 331
Compounds of titanium with oxygen and hydroxyl, 332
Compounds of titanium with nitrogen and with nitrogen and carbon, . . 332
General character and reactions of the titanium compounds, 333
XU TABLE OF CONTENTS.
PAGE
Zirconium, * 333
Compounds of zirooniuni, 334
Thorium, 334
Compounds of thorium, 334
CHAPTER XXX.
PENTAD ELEMENTS.
Section I. {eontinued). Phosphorus, 335
Compounds of phosphorus with hydrogen, 340
Compounds of phosphorus with the halogens, 344
Compounds of phosphorus with oxygen and hydroxy], 348
Compounds of phosphorus with chlorine and oxygen, 359
Compounds of phosphorus with sulphur, 361
Compound of phosphorus with Kulphur and chlorine, 362
Phosphorus compounds containing nitrogen, 363
Vanadium, 364
Compounds of vanadium with chlorine, 365
Compounds of vanadium with oxygen and hydroxyl, 305
Arsenic 366
Compound of arsenic with hydrogen, 367
Compounds of arsenic with the halogens, 369
Compounds of arsenic with oxygen and hydroxyl 370
Compounds of arsenic with sulphur and hydrosulphy], 373
General properties and reactions of the compounds of arsenic, .... 376
NioBUM AND Tantalum, 378
Compounds of niobium and tantalum, 878
Antimony, 378
Compound of antimony with hydrogen, 380
Compounds of antimony with the halogens, 381
Oxides and acids of antimony, 383
Compounds of antimony with sulphur, 387
Sulphantimonites, 389
General properties and reactions of the compounds of antimony, .... 390
Bismuth, 391
Halogen and oxyhalogen compounds of bismuth, 391
Compounds of bismuth with oxygen and hydroxyl, 892
Compoundsof bismuth with sulphur, 395
General properties and reactions of the compounds of bismuth, .... 396
METALS.
CHAPTER XXXI.
DISTINGUISHING CHARACTERISTICS OF THE METALLIC ELEMENTS.
Chief points of difference between metals and non-metals, 397
Relation of the metals to heat, 398
TABLE OF CONTENTS. XUl
PAGE
BelatioDB of the metals to light, . ; . 399
Spectram analysia, 400
BelatioDB of the metals to gravity, 406
Cohesive power, * 407
AUoys, 410
CHAPTER XXXII.
MONAD ELEMENTS.
Sec/ion in. PoTAasujM, 411
Compound of potassium with hydrogen, 413
Compounds of potassium with the halogens, 414
Compounds of potassium with oxygen, 414
Compound of potassium with hydrozyl, 415
Ozy-ealts of potassium, 416
Compounds of potassium with sulphur, 4'JO
Compound of potassium with hydrosulphyl, 421
Sulpho«dt8 of potassium, 423
Compound of potassium with nitrogen and hydrogen, 423
General properties and reactions of the compounds of potassium, .... 424
SoDiOf, 424
Compound of sodium with hydrogen, 426
Compounds of sodium with the halogens, 426
Compounds of sodium with oxygen and hydroxvl 427
Oxy-salts of sodium, 427
Compounds of sodium with sulphur and hydrosulphyl, 435
Sulpho-salts of sodium, 435
Compound of sodium with nitrogen and hydrogen, 435
General properties and reactions of the compounds of sodium, 435
Lithium, 435
Compounds of lithium with the halogens, 436
Compounds of lithium with oxygen and hydroxy!, 436
Oxy-salts of lithium, 437
General properties and reactions of the compounds of lithium, 437
RrBiDiuic, 438
Compounds of rubidium, 438
C«njii, . . .• 439
Compounds of cesium, 440
General properties and reactions of the compounds of rubidium and caesium, 440
l^s AxMoinuM Salts, 440
Compounds of ammonium with the halogens, 441
Compound with hydroxyl, 442
Oxy-salts of ammonium, 442
Compounds of ammonium with sulphur and hydrosulphyl, 446
General properties and reactions of the ammonium salts, 446
SedmlV. Silvee, 447
Compounds of silver with the halogens, 452
Compounds of silver with oxygen, 456
Oxy^altB of silver, i 456
XIV TABLE OF CONTENTS.
PAGE
Compounds of silver with sulphur, 4o9
Sulpho-salts of silver, 459
Compounds of silver with nitrogen and phosphorus, 459
* General properties and reactions of the compounds of silver, 439
CHAPTER XXXIII.
DYAD ELEMENTS.
Section U. Barium, 460
Compounds of barium with the halogcas, 461
Compounds of barium with oxygen, 462
Compound of barium with hydrozyl, 463
Ozj-salts of barium, 4(U
Compounds of barium with sulphur, 467
Compound of barium with hydrosulphyl, 467
General properties and reactions of the compounds of barium, 468
Strontium, 468
Compounds of strontium with the halogens, 4t>8
Compounds of strontium with oxygen and hydroxyl, 469
Ozy-salts of strontium, 469
General properties and reactions of the compounds of strontium, .... 470
Calcium, " 471
Compounds of calcium with the halogens, 472
Compounds of calcium with oxygen, 474
Compound of calcium with hydroxyl, 474
Oxy-salts of calcium, 475
Glass, 480
Compounds of calcium with sulphur, 483
Compound of calcium with phosphorus, 4s3
General properties and reactions of the compounds of calcium, .... 484
On potable water and on the impurities occurring in natural waters, . . 484
Magnesium 507
Compounds of magnesium with the halogens, 508
Compounds of magnesium with oxygen and hydroxyl, 509
Oxy-salts of magnesium, 509
Compounds of magnesium with sulphur and by drosulphyl, 513
Compounds of magnesium with nitrogen and with boron^ 513
Compound of mtignesium with silicon, ' . . . 513
General properties and reactions of the compounds of magnesium, . . . 513
Zinc, 514
Compounds of zinc with the halogens, 516
Compounds of zinc with oxygen and hydroxyl, 517
Oxy-salts of zinc, 518
Compounds of zinc with sulphur, 519
Compound of zinc with the pentad elements, 520
General properties and reactions of the compounds of zinc, 520
Beryllium, 521
Compounds of beryllium with the halogens, 521
Compounds of beryllium with oxygen and hydroxyl, 522
Oxy-salts of beryllium, 523
TABLE OF CX)XTENT8. XV
PAGE
Compound of beryllium with sulphur, 523
General properties and reactions of the compounds of beryllium, .... 623
CHAPTER XXXIV.
DYAD ELEMENTS.
Section Jll. Cadmium, 524
Compounds of cadmium with the halogens, • 525
Compounds of cadmium with oxygen and hydroxyl, 525
Oxy -salts of cadmium, 525
Compound of cadmium with sulphur, 526
General properties and reactions of the compounds of cadmium, .... 526
Mercury, 527
Amalgams, 529
Compounds of mercury with the halogens, 530
Compounds of mercury with oxygen, 532
Oxy-salts of mercury, 533
Compounds of mercury with sulphur, 535
Compound of mercury with nitroq^en, 536
Ammoniacal mercury compounds, 536
Characteristic properties and reactions of the compounds of mercury, . . 537
COPPKR, 538
Compound of copper with hydrogen, .' 542
Compounds of copper with the halogens, 542
Compounds of copper with oxygen and hydroxy), 544
Oxy-salts of copper, 546
Compounds of copper with sulphur, 549
Compounds of copper with nitrogen, phosphorus, and arsenic, 550
General properties and reactions of the compounds of copper, 550
CHAPTER XXXV.
TRIAD ELEMENTS.
Section U, Gold, 651
Compounds of gold with the halogens, 553
Compounds of gold with oxygen and hydroxyl, 554
Oxy-salts of gold, 555
Compound of gold with sulphur, 556
General properties and reactions of the compounds of gold, 556
Thallium, 556
Compounds of thallium with the halogens, 557
Compounds of thallium with oxygen and hydroxyl, 558
Oxy-salts of thallium, 559
Compounds of thallium with sulphur, 560
General properties and reactions of the compounds of thallium, .... 561
Inditm, 561
Compounds of indium with the halogens, 562
Compounds of indium with oxygen and hydroxyl, 562
Oxy-salts of indium, 563
Compounds of indium with sulphur 563
General properties and reactions of the compounds of indium, .... 563
XVI TABLE OP CONTEXTS.
CHAPTER XXXVL
TETRAD ELEMENTS.
PAGE
Section IL Aluminium, 554
Cora pounds of aluminium with the halogens, 566
Compounds of aluminium with oxygen and hydrozyl, 567
Ozj-salts of aluminium, 568
Ultramarine, 573
Porcelain and pottery, 573
Compound of aluminium with sulphur, 576
General properties and reactions of the compounds of aluminium, . . . 576
Gallium, 576
Compounds of gallium, 577
General properties and reactions of the compounds of gallium, 577
CHAPTER XXXVII.
METALS OP THE RARE EARTHS. — ^TETRAD ELEMENTS.
Section III. Cerium, 578
Compounds of cerium, 580
PENTAD JELEMENTS.
Section II. DiDYMiUM, 581
Compounds of didymium, 581
TRL\D ELEMENTS.
Section IV. Lanthanum, 582
Compounds of lanthanum, 582
Yttrium, 582
Compounds of yttrium, 584
Erbium, 584
Compounds of erbium, 584
Terbium, Scandium, Samarium, Dbcipium, 585
General properties and reactions of the rare earth metals, 585
CHAPTER XXXVIII.
TETRAD ELEMENTS.
Seeiuml^. Platinum, 586
Compounds of platinum with the halogens, 588
Compounds of platinum with oxygen and hydroxy!, 589
Oxy-salts of platinum, 590
Compounds of platinum with sulphur, 590
Ammonium compounds of platinum (platinamines), 591
General properties and reactions of the compounds of platinum, .... 591
Palladium, 592
Compound of palladium with hydrogen, 593
Compounds of palladium with the halogens 593
Compounds of palladium with oxygen, 594
TABLE OP CONTENTS. XVU
PAGE
' Falladous 0X7* salts, 594
Compounds of palladium with salphar, 594
General properties and reactions of the compounds of palladium, .... 595
Ibidioc, 695
Compounds of iridium with the halogens, 596
Compounds of iridium with oxygen, 597
Oxy-salts of iridium, 598
Compounds of iridium with sulphur, 598
General properties and reactions of the compounds of iridium, .... 598
Rhodium, 598
Compound of rhodium with chlorine, 599
Compounds of rhodium with oxygen, •. . 599
Oxy-fialtB of rhodium, 599
Compound of rhodium with sulphur, 599
General properties and reactions of the compounds of rhodium, .... 599
OCTAD ELEMENTS.
OsiinjM, 600
Compounds of osmium with chlorine, 601
Compounds of osmium with oxygen, 601
Oxy-salts of oemiimi, 602
Theosmates, 602
Compounds of osmium with sulphur, 602
General properties and reactions of the compounds of osmium, .... 602
RCTHENIUM, 602
Compounds of ruthenium with the halogens, 603
Compounds of ruthenium with oxygen, 603
Oxy-salts of ruthenium, 604
Rathenates and perruthenates, 604
Compound of ruthenium with sulphur, 605
General properties and reactions of the compounds of ruthenium, . . . 605
CHAPTER XXXIX.
TETRAD ELEMENTS.
StetimY. Lead, 605
Compounds of lead with the halogens, 607
Compounds of lead with oxygen, 608
Oxy-salts of lead, 610
Compound of lead with sulphur, 613
General properties and reactions of the compounds of lead, 613
CHAPTER XL.
HEXAD ELEMENTS.
Settim 11. URANnjM, 614
Compounds of uranium with the halogens, 615
Compounds of uranium with oxygen, 615
Oxy-halogen compounds of uranium, 616
Oxy-salts of uranium, 616
Theuranates, 617
XVlll TABLE OF CONTENTS.
PAGK
Compounds of uranium with sulphur, 6l8
General properties and reactions of the compounds of uranium, . . . .618
Molybdenum, 619
Compounds of molybdenum with the halogens 619
Compounds of molybdenum with oxygen, 620
The molybdatee, 621
Phospho-molybdic acid, 622
Compounds of molybdenum with sulphur, 623
General properties and reactions of the compounds of molybdenum, . . . 623
Tungsten, 623
Compounds of tungsten with the halogens, 624
Com[56unds of tungsten with oxygen, 625
The tungstatea, 626
Silico-tungstic acids, 627
The tungsto-tungstates, 628
Compounds of tungsten with sulphur, .* 628
General properties and reactions of the compounds of tungsten, .... 628
CHAPTER XLI.
HEXAD ELEMENTS.
Section III. Chromium, 629
Compounds of chromium with the halogens, • 630
Compounds of chromium with oxygen, 631
Oxy-salts of chromium, 633
The chromites, 634
The chromates, 635
Compounds of chromium with oxygen and chlorine, : 638
Compound of chromium with sulphur, 639
Compound of chromium with nitrogen, 639
General properties and reactions of the compounds of chromium, . . . 639
Manganese, 640
Compounds of manganese with the halogens, 641
Compounds of manganese with oxygen, 642
Oxy-salts of manganese, 646
The manganates, 647
Permanganic acid and permanganates, 648
Compound of manganese with oxygen and chlorine, 649
Compounds of manganese with sulphur, 649
General properties and reactions of the compounds of manganese, . . . 650
Ikon, 660
Compounds of iron with the halogens, 655
Compounds of iron with oxygen, 657
Oxy-salts of iron, 659
The ferrates, 661
Compounds of iron with sulphur, 661
General properties and reactions of the compounds of iron, 662
Cobalt, 663
Compounds of cobalt with the halogens, 664
Compounds of cobalt with oxygen, 665
TABLE OF CONTEJ^TS. XIX
PAGE
Oxy-flalts of cobalt, 666
Compounds of cobalt with snlphur, 667
Ammonium componnds of cobalt (cobaltamines), 668
v^eneral properties and reactions of the compounds of cobalt, 669
^'^CKKL, 670
Compounds of nickel with the halogens, 672
Compounds of nickel with oxygen, 672
Cxy^lts of nickel, . . . '. 673
Compounds of nickel with sulphur, 673
^neral properties and reactions of the compounds of nickel, 674
^'OBWEGIUM, 674
• • • . • '^t • ' "• •
J
INORGANIC CHEMISTRY.
CHAPTER I.
MATTER AND FORCE.
In the most cursory observation of the objects surrounding us, our
attention is arrested by two things — matter and motion. We see
cloads drifting over our heads aud rain falling from these clouds.
The descending water flows in river beds or plunges in cataracts
down precipic^es, making its way in both cases to the sea. The
surface of that sea is in constant motion, whilst ships driven by
wind or steam make their way through its waters. On land,
animal life everywhere exhibits matter in motion. The air is rarely
still, and many of the heavenly bodies are constantly changing their
places in the sky. All this we cannot help observing; a some-
what more minute examination, however, shows us that matter not
only thus suffers a change of place, but that it also frequently
undergoes other changes. Thus water becomes ice or steam, iron
rusts, coal burns, and certain substances such as glass and sealing-
wax acquire, when rubbed, the property of attracting light bodies.
Now this motion of matter and these changes which matter
undergoes are all brought about by what is termed /orce. This
force assumes several different forms, which are sometimes regarded
and generally described as distinct forces : thus the transfor-
mation of water into ice and steam is due to the operation of
two of these forces which act antagonistically to each other, and
are termed cnhesion and heat ; the rusting of iron and the burning
of coal are brought about by chemical force ; the impression pro-
duced upon the eye by the combustion of coal is due to light ; the
attractive power of the glass and sealing-wax is the effect of the
electric force; wHilst the motion of the heavenly bodies and that
of water from the clouds to the sea are the result of the action of
a force called gravity.
The department of knowledge which deals with these phenomena
is termed Natural Science.
Natural science studies and investigates the whole range of
sensible objects. It teaches us the properties of these objects and
tlie various changes which they undergo, either in the ordinary
course of nature or by the application of extraordinary and arti-
84 INORGANIC CHEMISTRY.
ficial means. This vast field of observation and research has been
divided into two great sections^ viz. :
1. Statical sciences.
2. Dynamical sciences.
The statical sciences study objects in a state of rest with
reference to their form, magnitude^ situation, structure, and other
properties; such branches of science are Descriptive Astronomy
and Geology, Mineralogy, Botany, Zoology, Animal and V^etable
Anatomy.
The dynamical sciences take into consideration the changes to
which sensible objects are subject They are subdivided into two
groups. The first group studies these changes without reference to
their causes: such are Physical Astronomy and Geology, and
Animal and Vegetable Physiology. The second group investigates
the changes which bodies undergo with special reference to the
causes of such changes. These are Physics and Chemistir. This
classification of the natural sciences, however, must not be taken
in too strict a sense, especially in the case of the second section,
for the astronomer and geologist are nowadays rarely content to
observe changes without inquiring into their causes: the same is
still more frequently the case with the physiologist, and thus
physics and chemistry are continually appealed to in the development
of astronomy, geology, and physiology.
The force to which the phenomena of chemistry are primarily
ascribed, and which is commonly termed cliemical affinity, is there-
fore closely associated with the other great forces of nature, but it
is sharply distinguished from them, in the first place, by producing
permanent changes in the properties of the bodies subject to its
action. The other forces do not permanently alter the properties
of matter, but when substances are brought under the influence of
chemical force, they are scarcely if at all afterwards recognizable
by the unaided senses. The presence of the bright, hard, colorless
and heavy metal iron, could not even be suspected in the dull, soft,
brown, and comparatively light rust, into which it is converted by
exposure to the air; still less, perhaps, could the rust be credited
with the presence of the colorless and invisible gas, oxygen, which
is held in combination with the iron by chemical energy. The
change is such as is not produced by mixture only. Mechanical
mixture, however intimate, does not conceal the properties of iron
and sulphur, for instance. The magnetic quality of the iron is a.s
marked as ever, and the two constituents may be distinguished
and even separated from each other under the microscope. But
after these substances have been subjected to chemical action, the
most powerful microscope is incompetent to detect either sulphur
or iron, and the magnetic property of the metal almost entirely
disappears. This change of properties is manifested in various
ways: sometimes liquids or gases are converted into solids, or vice
versdy sometimes a change in color, taste, odor, or medicinal pro-
HATTEB AND FORCE. 35
perties is prodaced, and there is always a change of temperature,
sometimes in the direction of heat, and sometimes in that of cold.
With all these changes, however, there is never the slightest altera-
tion in the weight of tiie materials operated upon.
In the second place, chemical affinity cannot act through an
appreciable intervening space. Heat, light, and electricity afPect
bodies at considerable distances, whilst gravity acts through spaces
inconceivably great; but if two substances, between which the
chemical force is energetically exerted when they are in contact,
be placed at the smallest appreciable distance from each other, no
chemical action whatever occurs, even after they have been in close
proximity for years. Of all other forces, cohesion alone requires
this intimate contact If two pieces of plate glass be gently placed
one upon the other, the slightest effort suffices to separate them,
but if they be pressed together, they markedly cohere, and if
strongly pressed for a long time, they can no longer be separated.
The two pieces have become one by cohesion, but the properties of
the glass are unaltered, and cohesive action is thus sharply distin-
guished from chemical action.
The most distinguishing characteristic of the chemical force,
however, is the limitation of its action to fixed and definite quanti-
ties of matter. Each chemical compound not only always contains
the same kinds of matter, but its constituents are always present
in exactly the same proportions, although the specimens of the
compound may have been derived from the most widely different
sources. Thus water obtained from melting snow, from rain, from
steam or from the artificial combination of its constituents, always
consists of oxygen and hydrogen in the proportion of one part by
weight of the latter to eight parts of the former. Again, common
salt, whether obtained naturally from the mines of Cheshire or
Poland, from the brine springs of Germany or America, from the
salt lakes of Russia or Australia, from sea water, or prepared
artificially from its constituents, always consists of chlorine and
sodium in the proportion of 35.5 parts of the former to 23 parts
of the latter. When two bodies combine chemically or become
united together by the chemical Jorce^ they do so in fixed and definite
proportions.
The materials composing our universe are bound together by
a force which, whether regarded as attraction or as pressure, pro-
duces three sets of phenomena differing so much from each other
as to lead to their being commonly referred to three of the distinct
forces already mentioned. One of these is gravitation, which acts
through distances inconceivably great. The second is cohesion,
which acts only through spaces too small to be measured. The
third is chemical attraction or chemical affinity which, like cohe-
sion, also acts through distances too small to be measured, but
which, as already mentioned, is distinguished, both from gravita-
tion and cohesion, by producing a change of properties in the
matter upon which it acts.
Thus a lump of ice presses towards the centre of the earth,
36 INORGANIC CHEMISTRT.
being pulled in that direction by the attraction of gravitation,
which can be overcome by mechanical means.
The lump of ice is made up of smaller pieces, for it can be
broken up into an immense number of particles by mere mechan-
ical effort, and thus cohesive attraction, like gravity, is overcome
by mechanical means; but only partially, for each puticle is made
up of smaller particles still bound together by the same force.
If, however, heat be applied to the ice, another well-marked step
in the conquest of cohesion is gained, and liquidity is induced — a
condition in which the particles of the water move freely about
and amongst each other. But even here cohesion is not completely
vanquished, and the particles still cling to each other with a con-
siderable amount of tenacity. By the application of a gre:\ter
amount of heat, the complete conquest of cohesion is at last
achieved. In the condition of steam, the particles of water no
longer stick together: they are entirely freed from all cohesive
force, and are only restrained from flying asunder to infinite dis-
tances by gravitation and external impediments.
In all these operations, the properties of the water have not
been essentially or permanently altered. Even steam is, like water,
uninflammable and incapable of supporting combustion. More-
over, on cooling, it is reconverted into water with all its properties
unimpaired.
By heat, cohesion has thus been gradually but completely over-
come, and the question now arises, can any further effect be pro-
duced u|K)n water by the same agent? Experiment answers this
question in the affirmitive, for if steam be subjected to the intense
heat of a stream of electric sparks, it is rt-solved into a mixture of
oxygen and hydrogen gases which refuses to condense to water on
cooling, and which explodes by contact with flame. The proper-
ties of the steam have thus been entirely altered, and by this in-
tense heat another remarkable step has been taken in the conquest
of attractive foixje; each particle of steam has been broken up, and
by the change of properties which has followed the rupture, the
attraction overcome is recognized'as that of chemical affinity.
The attractive forces thus operating within a mass of ice are
enormous. They may be expressed in terms either of heat or of
mechanical effort. In terms of heat ice requires as much heat to
melt it, that is to convert it into liquid and ice-cold water, as
would raise the temperature of an equal weight of water from 0° C.
to 79.2° C. Water at 0° requires to convert it into steam as
much heat as would raise its temperature to 637° C. if no steam
were formed. But the separation of the oxygen from the hydrogen
absorbs as much more heat as would raise the temperature of the
steam to 10,315° C. if no separation occurred. In terms of mechan-
ical effort the force required to convert 9 lbs. of ice into water is
equal to that required to raise a weight of one ton to a height
of 433 feet, to overcome the remaining cohesion and convert the
water into steam requires a force sufficient to raise one ton to a
height of 2,900 feet, whilst the power required for the separation
ELEMENTS AND COMPOUNDS. 37
of the two constituents of steam would raise one ton a height of no
less than 22,320 feet.
CHAPTER II.
ELEMENTS AND COMPOUNDS.
All kinds of matter which we meet with on the earth may be
divided into two classes, those which are capable of resolution
into other simpler kinds of matter, and those which defy our
attempts so to resolve them. The former are termed compounds;
the latter, simple bodies or demenis. For example, if red oxide
of mercury be heated, the heat will exert, as in the case of
steam already described, a disintegrating or decomposing action:
the red oxide will break up into two substances — a colorless gas,
oxygen; and a white heavy liquid, mercury. If the mercury and
the oxygen be carefully weighed, it will be found that their weights
are together exactly equal to that of the oxide of mercury employed ;
from which it may be concluded that none of the products of
deoompasition have escaped observation — that the liquid metal
and the colorless gas, and nothing beyond these, went to make
up the red powder. This opinion is confirmed by the fact that it
is possible, under suitable conditions, to reproduce the red powder
from oxygen and mercury. The process of resolving a com-
pound into its constituents is known as analysis; that of building
it up from its constituents is termed synthesis.
Red oxide of mercury is therefore a compound, and its com-
ponents are mercury and oxygen. Can these components be re-
solved into still simpler bodies?
The answer is, the resources of chemical science have not as
yet been able to effect any such resolution. Both mercury and
oxygen may be brought into union with various other bodies, and
may be led by complicated processes from one combination to
another; but at the end of their course they always emerge
unchanged, and, if they do possess constituents, none of these have
been dropped by the way. As no other kinds of matter can be
extracted from them, it is agreed to regard them as elements.
It is quite possible that the elements merely denote the present
limits to our jiowers of effecting chemical decomposition. The
only criterion which we have of the elementary nature of a body
is, as above stated, the purely negative one of our inability to
decompose it; and the history of the science shows us that this
criterion is not necessarily trustworthy.
The following is a list of the seventy elements at present
recognized. The twenty-two most important of these are distin-
guished by the largest type, those next in importance by medium
type, whilst the names of elements which are either of rare occur-
38
INORGANIC CHEMISTRY.
rence, or of which our knowledge is very imperfect, are printed in
small type :
Name.
Symbol.*
Atomic
weight.*
Name.
Symbol.
Atomic
wcijrbL
ALUMINIUM
Al
27
Nickel ....
Ni
58.6
Antimony . . .
Sb
120
Niobium ....
Nb
94
Absenic. . . .
As
75
NITROGEN . .
N
14
Barium ....
Ba
137
Norwegium . . .
Ng
214
Beryllium . . .
Be
9
Osminm ....
Os
198.6
Bismuth . . .
Bi
208.2
OXYGEN . . .
O
16
Boron ....
B
11
Palladium . . .
Pd
105.7
BROMINE. .
Br
80
PHOSPHORUS
P
31
Cadmium . . .
Cd
112
Platinum . . .
Pt
194.4
CaeHium ....
Cs
133
POTASSIUM .
K
39
CALCIUM. .
Ca
40
Rhodium ....
Rh
104
CARBON . .
C
12
Rubidium ....
Rb
85.3
Cerium ....
Ce
140.5
Ruthenium . . .
Ra
104
CHLORINE .
CI
35.5
Samarium ....
Sm
150
Chromium . . .
Cr
52
Scandium ....
Sc
44
Cobalt ....
Co
58.6
Selenium ....
Se
79
COPPER . .
Cu
63.2
SILICON . . .
Si
28.2
Decipium . . .
Dp
159
SILVER . . .
Ag
107.7
Did^mium . . .
Erbium *. . . .
Di
146
SODIUM . . .
Na
23
Er
165.9
Strontium . . .
Sr
87.5
FLUORINE .
F
19
SULPHUR . .
8
32
Gallium ....
Ga
68.8
Tantalum ....
Ta
182
Gold
Au
196
Tellurium ....
Te
125
HYDROGEN
H
1
Terbium ....
Tb
148.8
Indium ....
In
113.4
Thallium ....
Tl
204
IODINE . . .
I
127
Thorium ....
Th
233.4
Iridium. . . .
Ir
192.5
Tin
Sn
118
IRON ....
Fe
56
Titanium ....
Ti
48
Lanthanum . . .
La
188.5
Tungsten. . . .
W
184
LEAD. . . .
Pb
203.5
Uranium ....
U
238.5
Lithium ....
Li
7
Vanadium ....
V
51.3
Magnesium . .
Mg
24.4
Ytterbium ....
Yb
172.8
MANGANESE
Mn
55
Yttrium ....
Y
89.8
MERCURY .
Hg
200
ZINC
Zn
65.3
Molybdenum . .
Mo
95.5
Zirconium ....
Zr
90
It is usual to divide these elements into two great classes —
metals and non-mdak, the latter being sometimes also termed
metalloids. The division is a somewhat arbitrary one, and the
boundary-line between the two classes has been variously drawn
by different chemists. Arsenic, selenium, and tellurium have
been assigned to either catego/y, according as the physical or the
chemical characteristics formed the basis of the classification.
Hydrogen, on the strength of its physical properties, is almost
invariably classed as a non-metal; but its entire chemical beha-
vior would lead to its being placed among the metals. Ad
arrangement of the elements in their electro-chemical order, or a
division into well-marked chemical groups, would perhaps be more
logical.
* For an explanation see Chapter YIIL
CHEMICAL NOMENCLATURE. 39
CHAPTER III.
CHEMICAL NOMENCLATURE.
The study of every science necessitates an acquaintance with the
system of names and peculiar modes of expression which have been
found most convenient to denote the materials and to describe the
phenomena which form its objects. Such names and modes of
expression constitute the groundwork of the language of every
science, and upon the right employment of these depend the precision
and accuracy of scientific definition.
The nomenclature of a science ought to be distinguished by
clearness and simplicity; but it is by no means easy to secure these
conditions in a science like chemistry, where the rapid progress of
discovery necessitates the continual addition of new and the fre-
quent alteration of old names. The chemical name of a substance
snould not only identify and individualize that substance, but it
should also express the composition and constitution of the body,
if a compound, to which it is applied. The first of these conditions
is readily attained; but the second is much more difficult to secure,
inasmuch as our ideas of the constitution of chemical com])ounds —
of the mode in which they are built up as it were — require fre-
quent modification. On this account all attempts to frame a perfectly
consistent system of chemical nomenclature have hitherto been only
partially successful.
The names of the elements can scarcely be said to have been
given according to any rule; many of them are derived from some
prominent property of the bodies themselves, whilst others have a
mythological origin. An attempt has been made to distinguish
the metals by the termination um, as potassium, sodium, etc. ; but
the common metals, such as gold, copper, and iron, still retain their
original names; and one substance, selenium, which at the time of
its discovery was regarded as a metal, has been suffered to retain
its name unchanged, although further research has divested it of
all metallic attributes. An important group of electro- negative*
non-metals — ^fiourine, chlorine, bromine, and iodine — have received
the termination tne; three are distinguished by the terminal
syllable on, viz., carbon, silicon, and boron; and three others have
gen for their final syllable, viz., oxygen, hydrogen, and nitrogen,
these last names being derived from Greek words denoting the
property possessed by these elements of generating respectively acid,
water, and nitre.
When two elementary bodies unite together, they form a
chemical compound of the first order, to which the name binary
compound has been applied. The names of these compounds are
formed from those of tneir constituents, the name of the positive*
* See Electrolysis, Chapter XIL
40 INORGANIC CHEMISTRY.
ooDstituent or some abbreviation thereof, with the termination ie,
preceding that of the negative* constituent, which is made to ter-
minate in ide^ thus :
Potassium and Sulphur form Potassic sulphide.
Sodium " Oxygen " Sodic oxide.
Silver " Chlorine " Argentic chloride.
Zinc '^ Iodine ** Zincic iodide.
Calcium " Chlorine " Calcic chloride.
But the same elements frequently form with each other two
compounds, in which case the one which contains the smaller pro-
portion of the negative element is distinguished by changing the
terminal syllable of the name of its positive constituent into tms,
the terminal to being retained for the compound containing the
larger proportion of the negative element. Thus:
One atom of tin and two atoms of chlorine form stannous chloride.
One atom of tin and four atoms of chlorine form stannic chloride.
Sometimes, however, the same elements form with each other
more than two compounds. In these cases the prefixes hypo and
per are employed as further marks of distinction ; but their use is very
rarely required.
If a binary compound contains oxygen, and forms an acid when
made to unite with water, or a salt when added to a base, it is termed
an anhydride. Thus:
One atom of carbon and two atoms of oxvgen form carbonic anhydride.
Two atoms of nitrogen and five atoms of oxygen form nitric anhydride.
Two atoms of nitrogen and three atonjs of oxygen form nitrous anhydride.
One atom of sulphur and three atoms of oxygen form sulphuric anhydride.
One atom of sulphur and two atoms of oxygen form sulphurous anhydride.
In the following cases, the systematic names have not displaced the
trivial and irregular names used for the same substances:
Systematic name. Trivial or irregular name.
Water.
Sulphuretted hydrogen.
Seleniuretted hydrogen.
Telluretted hydrogen.
Hydrochloric acid.
Hydrobromic acid.
Hydriodic acid.
Hydrofluoric acid.
{Marsh-gas or light carburetted
hydrogen.
Ammonia.
Phosphoretted hydrogen.
Arseniuretted hydrogen.
Antimoniuretted hydrogen.
The term add was originally applied only to su))stances possess-
* See Electrolysis, Chapter XII.
Hydric oxide, .
Hydric sulphide, .
Hydric selenide, .
Hydric telluride, .
Hydric chloride, .
Hydric bromide, .
Hydric iodide,
Hydric fluoride, .
Hydric carbide, .
Hydric nitride, .
Hydric phosphide,
Hydric arsenide, .
Hydric antimonide.
CHEMICAL NOMENCLATURE. 41
ing a sour taste like vinegar; but analogy has necessitated the
application of the same name to a large number of compounds
which have not this property. In the modern acceptation of the
name, an acid may be defined as a compound containing one or
more atoms of hydrogen^ which become displaced by a metal when
the latter is presented to the compound in the form of a hydrate.
The hydrogen capable of being so displaced may be conveniently
termed displaceable hydrogen. An acid containing one such atom of
hydrogen is said to be monobasicy one containing two such atoms
dibasic, etc. Acids of a basicity greater than unity are frequently
termed polybasic acids.
Thus nitric acid gives^ with sodio hydrate, sodic nitrate :
NO3H + ONaH = NOjNa + OH,.*
Nitric acid. Sodic hydrate. Sodic nitrate. Water.
Sulphuric acid gives, with potassic hydrate, potassic sulphate:
SO,H, + 20KH = SO.K, + 20H,.
Sulphuric acid. Potassic hydrate. Potassic sulphate. Water.
And hydrochloric acid gives, with potassic hydrate, potassic chloride :
HCl + OKH = KCl + OH,.
Hydrochloric Potassic Potassic Water,
acid. hydrate. chloride.
When an acid contains oxygen, its name is generally formed
by adding the terminal ic either to the name of the element with
which the oxygen is united, or to an abbreviation of that name;
thus sulphur forms, with oxygen, sulphuric acid; nitrogen, nitric
acid; and phosphorus, phosphoric acid. But it frequently happens
that the same element forms two acids with oxygen; and when
this occure, the acid containing the larger amount of oxygen
receives the terminal syllable ic, whilst that containing less oxygen
is made to end in ous. Thus we have sulphurous acid, nitrous acid,
and phosphorous acid, each containing a smaller proportion of
oxygen than that necessary to form respectively sulphuric, nitric, and
phosphoric acids.
In some instances, however, the same element forms more than
two acids with oxygen, in which case the two Greek words hypo,
under, and hypei; over, are prefixed to the name of the acid. Thus
an acid of sulphur containing less oxygen than sulphurous acid is
termed hyposulphurous acid; and another acid of the same element
containing, in proportion to sulphur, more oxygen than sulphurous
acid and less than sulphuric, might be named either hypersul-
phurous acid, or hyposulphuric acid ; but the latter term has been
adopted. The prefix per is frequently substituted for hyper;
tbita in the case of chlorine, which forms the following four acids
with oxygeo, viz., bypochlorous acid, chlorous acid, chloric acid,
* For an explanation of these formulae see Chapter VIII.
42 INORGANIC CHEHISTRT.
and hyperchloric acid, the latter is generally named perchloric
acid ; but per can only be used as a prefix to the acid containing the
larg^t proportion of oxygen.
Some acids do not contain oxygen amongst their constituents,
but con.«i8t of sulphur or hydrogen united with other elements.
This peculiarity of composition is expressed in their nomenclature
by the prefixes mlpho or svlph (or the equivalent Greek prefixes
(kio or Oil), and hydro or hydr: thus sulpharsenic acid and sulpho-
stannic acid denote acids composed respectively of sulphur, hydro-
gen, and arsenic; and sulphur, hydrogen, and tin; whilst the
names hydrochloric acid and hydriodic acid are given to acids
composed, the first of hydrogen and chlorine, and the second of
hydrogen and iodine. The terminals oua and ic are also applied to
these acids in exactly the same manner as to the oxygen acids;
thus we have sulpharsenious and sulpharsenic acid, the latter con-
taining a larger proportion of sulphur than the former; but the
application of the first of these terminals has not hitherto been
found necessary in the case of hydrogen acids, since no element
has yet been observed to form more than one acid with hydrogen.
The term anhydride (cf. p. 40) is applied to the residue obtained
by the abstraction (in combination with oxygen as water) of all the
displaceable hydrogen from one or two molecules of an oxygen
acid. Thus,
SO,H, — OH, = SO,;
Sulphuric acid. Water. Sulphuric anhydride.
2N0,H — OH, = NA.
Nitric acid. Water. Nitric anhydride.
The term anhydro-acid or pyro-add is applied to such acids as
are formed from two molecules of a poly basic acid (see p. 41) by
elimination of water:
2PO,H, - OH, = PAH,;
Phosphoric acid. Water. Pyrophosphoric acid.
2S0,H, — OH, = SjOjH,.
Sulphuric acid. Water. PyroHulphuric acid.
(Nordhausen sulphuric acid.)
These acids are thus partial anhydrides. The prefix pyro
originally referred to their mode of formation, heat being employed
to drive off the water; but its use has been extended to acids
which have been prepared by other means, and it is to be under-
stood generally as denoting partial anhydricity between two molecules
of the parent acid.*
* This Fense of the prefix pyro must not be confounded with that in which it is
employed in organic chemistry, as in pyrotariaric add, rn/romueic acidj etc. Here
the mode of formation by the action of heat is alone indicated, the compounds
having for the most part nothing further in common, and not being formed from
the parent acid — tartarie aeid, mucie add — according to any fixed rule.
CHEMICAL NOMENCLATURE. 43
The term base is applied to three d&sses of compound8, all of
which are converted into salts by the action of acids. These
are:
1st. Certain compounds of metals with oxygen^ such as sodic oxide
(Na,0), zincic oxide (ZnO), etc.
2d. Certain compounds of metals with the compound radical
hydroxyl (HO), such as sodic hydrate (Na(HO)), zincic hydrate
(Zn(H6y,etc.
3d. Certain compounds of nitrogen, phosphorus, arsenic, and anti-
mony, such as ammonia (NH3).
There are also a few organic compounds to which the name
base is sometimes given, but which are not included in the above
classes; it is, however, unnecessary further to allude to them
here.
The bases of the first class are named in accordance with the
rules already given for compounds of two elements. The following
bases, however, still retain their irr^ular names:
Sjstematic names. Irregular names.
Baric oxide, Baryta.
Strontic oxide, Strontia.
Calcic oxide, Lime.
Magnesic oxide, Magnesia.
Aluminic oxide, Alumina.
Beryllic (Glucinic) oxide, . . . Beryl lia (Glucina).
Zirconic oxide, ...... Zirconia.
The names of the bases belonging to the second class are
formed by changing the terminal syllable of the name of the
metal into ic or ous, and the word hydroxyl into hydrate. Thus
csesinm and hydroxyl from csesic hydrate (Cs(HO)); barium and
hydroxyl, baric hydrate (Ba(HO)2); and iron and hydroxyl, ferric
hydrate (Fe^HO),).
' A few of these bases have trivial or irregular names, which are
almost invariably used instead of the systematic names :
Systematic names. Irregular names.
Potassic hydrate, .... Potash.
Sodic hydrate, Soda.
Lithic hydrate, Lithia.
The bases of the third class are distinguished by the terminal
syllable tne, except nitrine (NH,), which retains its trivial name
ammonia. These bases belong almost exclusively i^ the depart-
ment of organic chemistry, and their nomenclature could not be
advantageously discussed here.
It has been already mentioned that by the mutual action of an
acid and a base upon each other, a mlt is produced. If the salt be
free from oxygen and sulphur, like common salt (NaCl), it is
termed a haioid sail; if it contain oxyg^ it is termed an oxysatt;
44 INORGANIC CHEMISTRY.
and if this oxygen be replaced by sulphur^ it is distinguished as a
€uli)ho8alt.
The haloid salts are named according to the rules of biDary
compounds above given, thus:
Name. Formula.
Sodic chloride, . . . NaCI.
Calcic iodide, . . . • Cal,.
Ferrous bromide, . . FeBr,.
Ferric bromide, . . . Fe^Br^.
Oxy salts are divided into normal^ acid, and basic.
A normal salt is one in which the displaceahle hydrogen of the
acid (see p. 41) is a// exchanged for an equivalent amount of a
metal or of a positive compound radvcoL
The following examples will serve to illustrate this definition
of a normal, or as it is sometimes incorrectly called, a neutral salt,
the displaceahle atoms of hydrogen in the acid, and the metal
by which they have been displaced in the salt, being printed in
italics:
Acid. Normal salt
v:#-:^ «^iA -Krrk rr / Sodic nitrate NO.Mi.
^""<=*««' N^'^'- ■{ Calcic nitmt; . . . m\\W\
s-'ph-o-'i so,fl... .{L-Spff^r: : : ^:^-.
Phosphoriccid.. .... po,fl... .{S:ieT;h''cl;S;r: : ^^.-^
Hypophosphorons acid, . . TO^J^fH^ . Bodic hypophosphite, . POaHgNifi,
Pho«phoro»i8 acid, . " . . . POaFTff,, . Potaraic phosphite, . . POsHiT^
Metaphoephoric acid, . . . POgJ7, . . Lithic metaphosphate, . TO^LL
Pyrophosphoric acid, . . . P^O^Ff^, . Calcic pyrophosphate, . PjO^^V',.
Nordhausen sulphuric acid, . S^Ojlfj, . Sodic pyrosulphate, . « SfiyNa.,
Unknown acid, CrsO^^ . Potassic dichromate, . Cr,Of Jl^
An acid salt is one in which the displaceahle hydrogen of the
axAd is only partially exchanged for a metal or positive compound
radical.
The following examples illustrate the constitution and nomen-
clature of these salts:
Acid. Acid salt
Sulphuric acid, . . SO^.^. Hydric sodic sulphate, . . . SO^HNd.
Carbonic acid, . . COg-Ha? Hydric potassic carbonate, . CO^ITK,
{Hydric disodic phosphate, , "PO^HNa^,
Di hydric sodic phosphate, . l^O^ILNa.
Microcosmic salt VO^B\NB^)Ka.
(Hydric ammonic sodic phosphate.)
Acid salts are produced almost exclusively from polybasic acids.
When the number of bonds'^ of the metal oi* compound positive
radical contained in a salt exceeds the number of atoms of displace-
able hydrogen in the add, the compound is usually termed a baste
salt — as, for instance :
* For an explanation of this term see Chap. VIII.
1
LAWS OF COMBINATION. 45
Acid. Basic salt
C«Wic«id. . . 00^. {S:'e"^!i?^'c carbonate.- ! ! ^5^%.
8a.phanc.cid.. . 80,H.. { Tn^^^ X-;''P'>»|^ ; |g.^«;;V
These and most, if not all, other basic salts do not differ
essentially in their constitution from the normal and acid salts.
This will be seen from the arrangement of their atoms given
under the heading of the different metals entering into their
a>mposit]on.
The molecular compounds (j.t?.) which various substances form
with water of crystallization may be conveniently termed aquafes.
The nomenclature of organic bodies is founded upon the same
principles as that of inorganic compounds; but its discussion
coald not be conveniently introduced here.
CHAPTER IV.
LAWS OF COMBINATION.
As soon as chemists began to realize that the various changes
^V\ch matter undergoes when two or more substances are extracted
from some other substance, or unite to form this substance, are not
changes in the ultimate nature of matter itself, but only in its mode
of combination, it was natural that they should have recourse to the
balance in onler to determine the quantities of the different kinds of
matter entering into each such combination. The results of these
determinations are embodied in the following numerical laws, which
form the groundwork of the science.
Law of (Constant Proportions. — It has already been mentioned
that each chemical substance contains its elements always in the same
fixed proportions. Red oxide of mercury consists of 12.5 parts by
weight of mercury and 1 of oxygen, this projwrtion being absolutely
unvarying. In like manner hydrochloric acid gas always contains
35.5 parts of chlorine to 1 of hydrogen. And in the same propor-
tions in which the elements of a compound may be separated from
each other by analysis, they may by synthesis be made to combine.
An excess of any one of the elements over and above the quantity
required to unite with the rest, will remain unacted upon. If 40
parts of chlorine be brought into contact with 1 part of hydrogen
under the conditions which are necessary for the formation of hydro-
chloric acid, 4.5 parts of chlorine will remain unchanged, and cannot
be made to enter into combination.
The above law is known as the Law of Constant Proportions. It
was in the course of the experimental development of this law that
the great fact first became clear, that matter is indestructible, and, as
far as experience goes, uncreatable. When carbon is burnt in a
vessel containing oxygen it seems to disappear ; but if nothing be
allowed to escape, and if the vessel be accurately weighed both before
46
INORGANIC CHEMISTRY.
and after the oombustioriy the weight will be found not to have
changed. The carbon has merely combined with the oxygen to form
the invisible gas carbonic anhydride. If a burning piece of the
metal sodium be now plunged into the carbonic anhydride thus formed,
the sodium will combine with the oxygen of the carbonic anhydride,
and the carbon will reappear as a fine black dust. In every series of
chemical processes, however complicated, the sum of the weights of
the final products will be neither more nor less than that of the initial
substances.
Law op Multiple Proportions. — In the course of their quan-
titative researches, chemists found that in some cases the same two
elements combined with each other in two or more differerU propor-
tions, to form totally distinct compounds; but as these proportions
were always constant for each such compound, this nf w fact did not
in any way contradict the law just stated. A very simple numerical
relation regulates this variation. Mercury, for example, forms two
compounds with oxygen — the red oxifie, in which the proportion of
mercury to oxygen is as 12.5 : 1; and a black oxide, in which the
proportion is as 25 : 1. The mercury in the first comi)Ound is, there-
fore, to that of the second as 1 : 2. With nitrogen, oxygen forms no
fewer than five different compounds:
Parts by weight
Parts by weight
of nitrogen.
of oxygen.
Nitrous oxide.
0.571
Nitric oxide, .
1.142
Nitrous anhydride.
1.714
Nitric peroxide, •
2.285
Nitric anhydride, .
2.857
The relative proportions of the oxygen uniting with a constant weight
of nitrogen in these five compounds are as 1:2:3:4:5. In all cases
iu which one element unites with another in two or more difiereut pro-
portions these proportions are found to be simple multiples of some
common factor. This law is known as the Law of Multiple Proportions.
Law op Equivalent Proportions. — The foregoing numerical
law was discovered by comparing the different weights of the aame
element which combine with a given weight of some other element.
But when the weights of different elements which combine with a
given weight of various other elements were compared, new and sur-
prising numerical relations became manifest. Thus —
1 part of
chlorine
1 part of
bromine
1 part of
iodine
1 part of
oxygen
1 part of
sulphur
Combines with
Hydrogen, .
Sodium, . .
Potassium, .
Copper, . .
Lead, . .
0.02817
0.0125
0.00787
0.125
0.6479
0.2875
0.1811
2.875
1.099
0.4876
0.3071
4.875
0.891
0.395
0.249
3.95
2.908
1.2906
0.813
12.906
0.0625
1.4375
2.4375
1.975
6.453
LAWS OF COMBINATION,
47
The numbers in each vertical column bear to each other the same
proportion ; thus^ in all the columns —
Hydrogen : Sodiam : Potassium : Copper : Lead,
as . . 1 : 23 : 39 : 31.6 : 103.25
It will be noticed that the numbers for hydrogen^ sodium, and
potassium are the same as those attached to these elements in the
column headed ^'Atomic weight '' in the table of elements, p. 38,
whilst those for copper and lead are less by one-half than the num-
bers in the table. The reason of this will be explained later. (See
Chapter XII., Electro-chemical Equivalents.)
On the other hand —
1 part of
hydrogen
1 part of
sodium
1 part of
potassium
1 part of
copper
1 part of
lead
Combines with |
Chlorine, . . .
Bromine, . . .
Iodine, ....
Oxygen, . - .
Salphiir, . . .
35.5
80
127
8
16
1.544
3.478
5.522
0 348
0.696
0.91
2.05
3.256
0.205
0.41
1.123
2.531
4.019
0.253
0.506
0.343
0.774
1.229
0.0774
0.1548
Here again^ in all the vertical columns —
Chlorine : Bromine : Iodine : Oxygen ; Sulphar.
as.. 36.5 : 80 ; 127 : 8 : 16
The numbers which express the proportions of chlorine, bromine,
and iodine are those given in the table on p. 38 ; whilst those of oxygen
and sulphur are less by one-half.
This law may be expressed thus : The relative proportions by
weight in which the members of any series of elements combine with
the same quantity of another element are the same for their combina-
tions with any other element.
35.6 parts by weight of chlorine, 80 parts by weight of bromine,
127 parts by weight of iodine, 8 parts by weight of oxygen, and 16
parts by weight of sulphur are said to be equivalent, as each of these
weights serves to satisfy the chemical aflRnity of 1 part by weight of
hydrogen. In like manner 1 part by weight of hydrogen, 23 parts
by weight of sodium, 39 parts by weight of potassium, 31.75 parts
by weight of copper, and 103.6 parts by weight of lead are equiva-
lent But the members of the first series are also equivalent to those
of the second : thus 23 parts by weight of sodium combine with 35.5
parts by weight of chlorine, 39 parts by weia;ht of potassium with 80
parts by weight of bromine, etc., as may easily be calculated from the
last table. Thus every element may have an equivalent weight as-
signed to it, according to which it combines with other elements, the
equivalent weight of hydrogen being taken as unity.
48 IKOROAKIC CHEMISTRY.
CHAPTER V.
THE ATOMIC THEORY.
Ix order to account for the remarkable relations just described,
chemists have adopted a theory concerning the ultimate constitution
of matter which is to be found in the systems of some of the ancient
Greek philosophers, but which first received a scientific form at the
bands of Dalton. Dalton supposed matter to consist of exceedingly
minute particles, incapable of further division — atoms (^Tofiot;^ from a
privative, and W/avw, I cut). These atoms possess different weights in
the different kinds of elementary matter, but have always the same
weight for the same kind. The juxtaposition of different elementary
atoms constitutes chemical combination. Thus if the relative weights
of the atoms of potassium and chlorine are as 89 to 35.5, and if the
formation of potassic chloride consists in the juxtaposition of one
atom of the one element to one of the other, then it is evident that
potassic chloride can contain its elements only in the proportion of 39
parts by weight of potassium to 35.5 parts by weight of chlorine. If
the relative weights of the atoms of mercury and oxygen are as 200
to 16, and if red oxide of mercury is a combination of one atom of
each of its elements, it must contain mercury and oxygen in the pro-
portion of 200 to 16. Again, if the black oxide of mercury is a
combination of two atoms of mercury with one of oxygen, the pro-
portion of the former to the latter must be as 400 to 16, or the pro-
portion of mercury in the black oxide is to that in the red as 2 to 1
for equal weights of oxygen.
Thus by the hypothesis of atoms, which possess the same weights
for the same elementary kind, but different weights for the different
elementary kinds of matter, the three great experimental facts of
Constant Proportion, Multiple Proportion, and Equivalent Propor-
tion are referred to one general law.
The atomic theory has, since its adoption by Dalton, undergone
many developments, particularly in the sharp distinction of atoms
from molecules {molecula, diminutive of moles, a mass). The atoms
which enter into chemical combination are supposed to be grouped
into molecules — "little masses." These latter are again grouped
together to form the masses of matter recognizable by the senses.
Thus a solid piece of ice, which contains the atomic weights of hy-
drogen and oxygen in the proportion of 2 to 1, is not to be regarded
as having its atoms thrown together indiscriminately ; it is supposed
to be miide up of a vast number of small independent systems, each
containing two atoms of hydrogen and one of oxygen. The atoms
within the molecule are held together by chemical attraction : the
molecules are kept in their places by cohesion. Neither the atoms
within the molecule nor the molecules within the mass, are supposed
to be in actual contact. When a body expands by heat the distance
THE ATOMIC THEORY. 49
between its molecules is increased, and when it contracts by cooling
this distance is diminished. Neither the atoms nor the molecules in
a solid body are to be conceived as occupying their positions in a state
of rest : various considerations, chiefly of a physical nature, lead to
the conclusion that they execute some sort of vibratory motion about
their positions of equilibrium. The amplitude of vibration increases
with the temperature. If the amplitude of vibration of the molecules
becomes too great for stability, the molecules detach themselves from
their positions of equilibrium, desert the immediate sphere of attrac-
tion of the neighboring molecules, and wander about till they fall
under the dominion of other molecules, to be again released by their
intensity of vibration. This state of things corresponds to liquidity :
coh^ion is alternately overcome and restored, and hence is weakened.
If, however, the energy of the molecules becomes so great as to carry
them beyond the reach of their mutual attraction, they shoot forward
in straight lines until they strike against other molecules or against
the sides of the containing vessel, in which case they rebound and
change their direction, sometimes imparting, sometimes receiving
energy. This represents the gaseous condition of matter. Up to this
Joint the atoms which compose the moIe(*ule have been considered as
eeping together during the wanderings of the molecule itself; but if
the temperature be raised still higher, it may happen that the vibra-
tion of the atoms within the molecule will carry these also beyond
the reach of their mutual attraction, in which case some of them may
separate from the parent molecule, forming among themselves simpler
molecules more capable of existing at a high temperature. This is
the phenomenon of decomposition by heat. It is probable that, at
sufficiently high temperatures, only elementary matter can exist, and
it is possible that even the molecules of the elements (for, as will be
shown later, the atoms of the same element combine with each other
to form molecules) break up into their component atoms. (See
Iodine.)
The motions of the molecules are manifested in the phenomena of
the diffusion of liquids and gases.
In order to give some conception of the aims and scope of the
atomic theory in its most recent developments, it may be mentioned
that modern chemistry seeks to determine not only the nature and
number of the atoms in the molecule, but also their arrangement.
That there must be a special arrangement is shown by the fact that
two or even more totally distinct compounds may exist having the
same number of the same atoms in the molecule. Such compounds
are termed isomeric. The molecule is to be looked upon as a system
composed of various members held together by chemical attraction,
just as the members of one of the cosmical systems are held together by
gravitation. The molecule of acetic acid, for example, contains two
atoms of carbon, four of hydrogen, and two of oxygen. To continue
the astronomical illustration, the two atoms of carbon are supposed to
be united by mutual attraction like the two suns of a double star. One
of these suns possesses three planets in the shape of three atoms of
hydrogen ; the other has two atoms of oxygen as planets ; whilst one
4
50 INORGANIC CHEMiarrBY.
of the oxygen planets has an atom of hydrc^n annexed to it as a
satellite. Of coarse all the members of such a system must attract
each other; but the attraction will be greatest between those which,
cceteris paribus^ are by virtue of their position most subject to each
other's influence. When the molecule is divided at any point, the
two parts, provided the reaction by which the separation has been
effected is not too violent, retain their previous arrangement : thus,
by heating potassic acetate with caustic alkali, it is possible to divide
the molecule of acetic acid at the junction of the two carbon atoms,
in which case the one carbon atom retains its three hydrogen atoms,
and the other its two oxygen atoms — one of these with an atom of
potassium in the place of the hydrogen of acetic acid. In like man-
ner, by the action of phosphorous chloride, the molecule of acetic acid
may be divided so as to split off the atom of oxygen with its hydrogen
atom attached. Both parts again remain unchanged as regards their
internal arrangement*
The facts on which these assertions are based could not with ad-
vantage be introduced into this chapter. They will be fully treated
of in their proper place.
To the unscientific mind there is something peculiarly repellent in
the atomic theory and in the physical conceptions which it involves.
Our notions of a multitude of minute unconnected particles are de-
rived from the sand-heap — ^the symbol of instability — and to realize
that a solid mass, such as an ingot of steel, consists of minute particles
suspended in space without actual contact, is certainly at first sight
difficult. But the student of science must dismiss from his mind all
crude analogies, and learn above all things to distrust his unaided
senses, which in scientific matters are by no means so infallible as
they are considered to be in everyday life. In transmitting to the
mind the phenomena of the external world, the senses first translate
these phenomena into a language of their own, which, however ad-
mirably adapted for its purpose, is only a symbolical representation
of the phenomena themselves. Sound as heard by the ear has no
resemblance to the vibrations of the air; red and violet light as they
affect the eye are in no way like longer and shorter waves of ether :
yet this is what science tells us concerning these phenomena as they
exist outside the sentient subject. And the same holds of the other
forces of nature. But the object of science is to perceive the pheno-
mena as they are in themselves — stripped of the interpretation put
upon them by the senses. Hence it is that many of the greatest
discoveries have apparently contradicted the evidence of the senses.
The magnificent generalization of the conservation of energy, a
pendant to that of the indestructibility of matter, has given to the
dynamical sciences a unity which they formerly lacked, and has laid
down the lines of their future progress. Just as, when we have led
an element through a series of combinations with other elements and
* Lucretius (De Renim Natura) has a remarkable pafvage, which might almost
be regarded as an anticipation of the views of modern chemiBts regarding the con-
stitution of compounds. " It matters much/' he says, " with what t)ther8 and in
what position the same atoms are held together.''
THE ATOMIC THEORY. 61
find that the increase of weight due to the accession of this element
has in all cases been the same, and that we can extract the origi-
nal quantity of the first element, unaltered in all its properties, from
its last combination, we conclude that these various compounds, in
spite of the difierence of their characteristics, all actually contained
this given quantity of the same kind of matter; so, when we trans-
form the motion of a mass of matter into the various other forms of
energy and find that the quantities are in every case equivalent, and
that each of these equivalent quantities can (or could, were it possible
to operate without loss) be transforuied back into the original quan-
tity of motion of matter, we conclude that all these manifestations of
energy actually consisted of the same thing — motion of matter. When
the motion of a mass is suddenly arrested, this motion is converted
into heat — a motion of the molecules. And in all cases of convertible
forms of energy, the amount of this energy, as expressed in terms of
the masses and of the velocities, will be the same, whether the masses
be sensible masses, or whether they be molecules.
A further refinement of speculation as to the nature of atoms has
been introduced by Sir William Thomson in the hypothesis that the
ultimate atoms of the elements consist of various forms of vortex
rings in a perfect fluid, the ether. This would reduce the different
kinds of matter to varieties of motion in one kind of matter, and
wonld account among other things for the indestructibility of matter ;
it being mathematically demonstrable that a vortex ring in a perfect
fluid is indestructible. But it is not necessary in a work like the pres-
ent to do more than refer to this hypothesis.
Fascinating as all these speculations are, they must never be taken
at more than their true value. Even the atomic theory, which ex-
plains perhaps as many heterogeneous facts as any other theory, not
excepting that of gravitation and the undulatory theory of light —
these two theories surpassing it, however, in the important point of
their far higher mathematical development — must not be looked upon
as more than the best existing explanation of the facts as at present
inoum. It may represent the absolute truth; it may be nothing
more than a symbolical expression of certain aspects of the truth.
The real object of a theory is to group the facts round some central
idea from which we may start in our search for fresh facts. The
deductions from the theory are the objects of experiment, and by ex-
periment the theory stands or falls. The greater the number of new
facts a theory predicts, the better is the theory ; but that is all that
can be said of it. No number of verified predictions can establish
the absolute truth of a theory. Of course this does not refer to those
particular cases in which the theory itself may be an ultimately veri-
fiable matter of fact. It can scarcely be so with the atomic theory.
No one has ever seen an atom or a molecule, and from theoretical
considerations derived from the undulatory theory of light, it is
almost certain that no one ever will.
The opposed conception is, that matter fills space continuously and
homogeneously. It is impossible to review here the vast array of
physical evidence which speaks against this conception and in favor
52 INORGANIC CHEMISTBY.
of the atomic theoiy : the chemical evidence forms the subject of this
work. One chemical fact may, however, be specially mentioned at
this point. It has already been stated that the same quantities of the
same kinds of matter frequently combine so as to produce two or
more totally different compounds. With matter homogeneously fill-
ing space this would be inconceivable. Such a difference bespeaks,
as was said before, an arrangement of parts. Furthermore, as in the
state of the finest mechanical subdivision the particles of a chemical
compound all display the same qualities, the parts, by the juxtaposi-
tion and arrangement of which the com|K)und is produced, must be
exceedingly small. We are thus led back to the atomic theory.
How small the ultimate parts of matter are supposed to be may be
judged from Sir William Thomson's calculation that in solids and
iquids the mean distance between the centres of contiguous molecules
is less than ^^^^f^^^^ and greater than 4 6 0TrioiJUTr of a centimetre.
The molecular vibrations, to which reference has already been made,
must of course take place through a correspondingly small range.
{
CHAPTER VI.
MOLECULAR WEIGHTS.
All bodies in the gaseous state are affected equally by pressure.
If a given volume of hydrogen and a given volume of chlorine be
measured at the pre&sure of one atmosphere, and if the pressure in
each case be then doubled, it will be found that the volume of each
has been reduced by one-half. If, on the other hand, the pressure
be reduced to half an atmosphere, the original volume of each will
be doubled. This relation is expressed by saying that the volume of
a gas is, cceteris paribvtSy inversely proportional to the pressure under
which it is measured. This law is named from its discoverer Boyle's
Law, Exceptions to it occur in the case of gases and vapors in the
neighborhood of their point of condensation to liquids, when the
gaseous condition is imperfect. In these the volume decreases more
rapidly than the pressure increases.
In like manner, all bodies in the gaseous state are affected equally
by change of temperature. Every gas, when measured at 0° C,
expands ^^j of its original volume when heated to 1° C, supposing
the pressure to remain constant during the operation. This fraction
is called the co-ejfficient of expansion of gases. The dilatation takes
place in the same ratio for every further increase of temperature:
thus if the volume of a gas at 0° be equal to 1, the volume at t^ will
be 1 H ;- This mightalso be expressed by saying that, the pressure
273.
being constant, the volume of a gas is proportional to its temperature
measured from — 273^. Thus the volume of a gas at 20° is to its
MOLECULAR WEIGHTS. 63
volume at 70° as 273 + 20 : 273 + 70. This law holds for all
gasep, subject to the deviations mentioned in the rase of Boyle's Law.
The relation of the volume of gases to temperature was discovered
by Charles.
The kinetic theory of gases, a theory at present almost universally
accepted by physicists, explains the elasticity and pressure of a gas
as the result of the shock of its molecules against the sides of the
vessel in which it is contained. If the volume of the gas be reduced
by one-half, the number of molecules which strike against the unit of
surface in unit of time will be doubled ; and hence the pressure will be
doubled. If the temperature he raised, the velocity of the molecules,
and hence their energy, will be increased : the shock against the sides
of the vessel is more intense and also more frequent, hence the pres-
sure will be greater. All gases behave in exactly the same manner
in r^ard to temperature and pressure, and the only satisfactory ex-
planation of this uniformity is tlie assumption that equal volumes of
all gases at the same temperature and. pressure contain an equal num-
ber of molecules. In fact this assumption has been deduced as a law
by strict mathematical processes from the kinetic theory of gases.*
This law was first stated as a hypothesis by Avogadro in 1811. It
excited little attention at the time, but is now one of the chief foun-
dations of modern chemical theory.
As equal volumes of all gases contain equal numbers of molecules,
it is evident that the molecular weights of gaseous bodies will be pro-
portional to the weights of equal volumes at the same temperature
and pressure, i.e., to their specific gravities or vapor-densities. If
the molecular weight of hydrogen, as the lightest known gas, were to
be taken as unity, the molecular weights of other gases would be ex-
pressed by the number of times that their specific gravity is greater
than that of hydrogen. As will be shown later, however, the mole-
cule of hydrogen consists of two atoms. Since, therefore, its atomic
weight is taken to be equal to 1, its molecular weight will be 2. I^et
the unknown molecular weight of a gas be M, and let its specific
gravity (referred to that of air as unity), as found by experiment, be
d, then since the specific gravity of hydrogen is 0.0693 :
0.0693: 2 = ei:J!f
and
if = 28.86 d,
or, expressed in words, the molecular weight of a gas may be found
by multiplying its specific gravity (referred to that of air as unity)
by 28.86. From what has been said above, it is evident that the
term gas will here include the vapors of all substances, solid or liquid,
capable of volatilizing without decomposition.
If, on the other hand, the specific gravity of the gaseous body is
referred to that of hydrogen as unity, then, calling this specific gravity
D, we should have
« See Clerk Maxwell, Theory of Heat^ 3d edition, p. 296.
64 INOfiOANIC CHEHI8TRT.
l;2 = D:if
or
M=2D.
That is to saj, the molecular weight of a substance is found hj
doubling its specific gravity in the gaseous state^ the specific gravitj
of hydrogen being taken as unity.
It is evident that the molecular weight will be equal to the sum of
the atomic weights of all the atoms contained in the molecole. (See
Atomic Weights.)
Since in nearly every case of chemical action between two or more
substances, it is the molecules of these substances which act on each
other— either by exchange of atoms or by direct union — ^and since
equal volumes of gas contain, ooderis paribiLS, equal numbers of mole-
cules, it might be expected that in chemical action between gaseous
bodies the volumes entering into reaction would present some simple
relation to each other. Not only is this the case, but' the gaseous
volume of the product of the reaction also follows a very simple law.
Thus:
1 vol. of hydrogen + 1 toI. of chlorine yield 2 vote, of hydrochloric acid.
1 " *' + 1 " bromine vapor *' ** hydrobroniic acid.
2 vote. '* + 1 *' sulphur vapor " ** sulphuretted hydrogen.
2 ** " +1 " oxygen " •* steam.
8 •* " +1 " nitrogen " " ammonia.
The law of combination by volume was discovered by Gay-Lussac.
If the number of molecules in one volume be called n, the first of
the above combinations might be written thus : n molecules of hy-
drogen combine with n molecules of chlorine to form 2n molecules
of hydrochloric acid. As each of the 2n molecules of hydrochloric
acid contains both hydrogen and chlorine, each of the n molecules of
hydrogen and each of the n molecules of chlorine must have been
divided into two parts in order to furnish hydrogen and chlorine for
these 2n molecules. The molecule of hydrc^n therefore consists of
cU least two atoms of hydrogen. The molecule of chlorine is likewise
at least diatomic. Reasons will be given latter for the belief that the
number of atoms in the molecules of these elements is not greater
than two.*
The combination by volume may therefore be written : 2n atoms
of hydrogen combine with 2n atoms of chlorine to form 2n molecules
of hydrochloric acid ; or, dividing by 2n : 1 atom of hydrogen com-
bines with 1 atom of chlorine to form 1 molecule of hydrochloric
* The supposition that the molecules of the great majority of the elements con-
sist of mutually combined elementary atoms, throws light upon a number of other-
wise inexplicable phenomena. Thus elements in the so-called naaceni state — that is,
at the moment at which they are released from their combinations — display much
more powerful affinities, and are much more capable of effecting chemical changes
than when in the free state. The explanation is that in the nascent state, it is the
single atoms which are released from combination, and that being endowed with
free affinities they are especially ready to enter into any fresh combination ; whereas
in the case of the free element, the atoms have combined with each other to form
molecules : not only therefore have the atoms no longer any free affinities, but their
mutual combination has to be broken up before they can enter into union with other
elements.
MOLECULAR WEIGHTS.
55
acid« That is to say, if we represent in this case the atomic propor-
tion of each of the combining elements by one volume, the molecular
proportion of the resulting compound will be represented by two
volumes. The same holds of all the combinations given in the above
list; thus we may write: 2 atomic proportions (or volumes) of hy-
drogen combine with 1 atomic proportion (or volume) of oxygen to
form 1 molecular proportion ( = 2 volumes) of steam.
This is what is meant by the elliptical and somewhat misleading
expression frequently employed, that the molecule of a compound
occupies in the gaseo^us state two volumes. In every case, if we take
such proportions by volume of the gaseous elements as will represent
the atomic proportions* of these elements uniting to form a compound,
the molecular proportion of this compound, if measur^ in the gase-
ous state, will occupy two volumes. Further, as equal volumes of
all gaseous substances contam an equal number of molecules, it is
evident that the molecular proportion of these various combining
elements will also be represented in the gaseous state by two volumes.
But though the molecular proportion may in every case be
represented by two volumes, it by no means follows that the
atomic proportion of the gaseous elements may always be repre-
sented by one volume, though this happens to be the case in the
series of combinations given in the foregoing list In order to
ascertain what volume of a gaseous element corresponds to its atomic
proportion when the molecular proportion is represented by two vol-
umes, it is necessary first to ascertain how many atoms the molecule
of that element contains. This may be found by dividing the mo-
lecular weight, as deduced from th^ vapor-density, by the atomic
weight, as determined by one or more of the methods given in the
next chapter.
Name of element
Molecular
weight
Atomic
weight
Number
of atoms in
molecule.
Mercury,
Cadmium,
Zinc,
Hydrogen,
Oxvgen,
" (asosone), . . .
Chlorine,
Bromine,
Iodine,
Nitrogen,
Sulphur (at 524«), . . .
(at8S0°), . . .
Seleninm,
Tellurium,
Phosphorus,
Arsenic,
200
112
66
2
32
48
71
160
254
28
192
64
158
256
124
800
200
112
65
1
16
16
35.5
80
127
14
32
32
79
128
31
75
1
1
'1
2
2
3
2
2
2
2
6
2
2
2
4
4t
* See following paragraph.
t This list contains all the elements of which the yapor-density has been deter-
mined, and, consequently, all the elements of which the molecular weight is known ;
ibr though other methods of ascertaining the molecular weight will be described,
56 INOBGANIC CHEMISTRY.
The number of atoms contained in the molecules of the various
elements is therefore not always the same.* Thus in the case of
mercury, cadmium, and zinc, the molecular weight is identical with
the atomic weight : the molecules of these elements are monaiomic.
With hydrogen, oxygen, chlorine, nitrogen, and various other ele-
ments, the molecular weight is twice as great as the atomic weight :
the molecules are diaiomic. In oxygen in the form of ozone, on the
other hand, the molecule is Matomic. Phosphorus and arsenic are
examples of ietratomie molecules, while the molecule of sulphur is
hexaiomio at 624**, and diatomic at 860*^, the heavy hexatomic mole-
cule breaking up into three lighter diatomic molecules as the tem-
perature rises.
Kundt and Warburg, by a determination of the velocity of sound
in mercury vapor, have shown that in the case of this vapor there is
no increase of "specific heat at constant volume ** due to motion of
atoms within the molecule, as is the case with gases having molecules
containing more than one atom. The molecule of mercury in the
fiseous state must therefore be assumed to be truly monatomic.
rom this it follows that diatomic molecules really contain only two
atoms, triatomic molecules only three atoms, etc.
It is evident that, whatever volume of a gas is adopted to repre-
sent its molecular proportion, the volume required to represent its
atomic proportion will be inversely as the number of atoms in the
molecule of that gas. If, therefore, the molecular proportion is
represented by two volumes, the volume corresponding to the atomic
proportion will be found by dividing this molecular volume by the
number of atoms in the mole<niIe. Thus we find that for a monat-
omic gas, the volume representing one atomic proportion— K)r, as it
may be termed, the atomic volume — is two volumes; for a diatomic
gas one volume; for a tetratomic gas, half a volume, and so on,
A very convenient expression of these relations is aflTorded by a
notation devised by A. W. Hofmann. In this notation one volume
of an element in the gaseous state is represented by a square I L
within which is written the symbol of the element in question, the
atomic volume of this element bein^ unity ; two volumes by a double
[
square, open in the middle
and half a volume by a tri-
angle r\ . Thus in the case of the elements, these symbols would
be employed as follows :
only that of vapor-densities is applicable in the case of elements. All other elements
are'either non-volatile or volatilise at temperatures and under conditions such as to
render the determination of their density in the gaseous state a problem beyond the
present resources of chemistry. Silver, for example, is volatile only at the temper-
ature of the oxy hydrogen flame. Again, potassium and sodium, though volatile at
relatively low temperatures, yield vapors which attack and combine with the mate-
rial of the vessels employed, and in this way fnrnish discrepant and untrustworthy
results. Hence the molecular weight of all elements other than those contained in
the above table is at the present moment purely a matter of surmise.
* From this it follows that the vapor-density alone of an element furnishes no
clue to its cUcmic weight.
MOLECULAB WEIGHIB.
57
Atomic volnme in the Molecular yohime in
Name of element. gaseoas state. the gaseous state.
Mercury,
Hg
1
1
Hg
Cadmium,
1
Cd
1
Zinc,
■ 1 ■
1
1
Zn,
1
Hydrogen,
H
O
a
Br
I
N
S
Be
Te
Ha
*
Oxygen,
Chlorine,
1 ■
1
Bromine,
1 ■
1
Iodine,
1
1
Nitrogen,
Ne
Sulphur (at 860°), • .
i
1
Selenium,
1
^Se.
1
Tellurium,
Te,
. 1
Phosphorus, ....
^P\
1
1
Arsenic,
Ai\
k
1
Ah
1
In the case of compounds, the symbol of the compound (see
Chemical Notation) is written within the double square representing
the molecular volume in the gaseous state, thus :
Name of compound.
Hydrochloric acid.
Water, ....
Ammonia, etc..
Molecular volume in the
gaseous state.
Ha
I
OHs
I
NH|
I
These volume-symbols may be combined into equations (see
Chemical Notation), which will thus express the relative volumes
* The small Rnbecript Arabic numeral indicates how many atoms of the element
represented bj the atomic symbol are present (see Chemical Notation).
68
IXOBOANIC CHEMISTRY.
of the gaseous elements or compounds taking part in any chemical
action, and the volume of the resulting product or products. Thus :
+
CI
=
HQ
1
or one volume of hydrogen combines with one volume of chlorine
to form two volumes of hydrochloric acid.
+
H =
or two volumes of hydrogen combine with one volume of oxygen to
form two volumes of steam.
H
H
H
+
H =
NH.
or three volumes of hydrogen combine with one volume of nitrogen
to form two volumes of ammonia.
+
a
a
1
=
HgCI,
1
or two volumes of mercury vapor combine with two volumes of
chlorine to form two volumes of the vapor of mercuric chloride.
[>^ + F. =
a
a
a
=
PCI,
1
or half a volume of phosphorus vapor combines with three volumes
of chlorine to form two volumes of the vapor of phosphorus chloride.
Of course in reality these chemical reactions take place not between
atoms, but between molecules, and the reaction of hydrogen with
chlorine, for example, would therefore have to be written :
1
Ha
_j
+
na
I
MOLECULAR WEIGHTS. 69
but the above simplified mode of expression has been adopted in
order that the molecule of the resulting compound may in every
case be represented by two volumes.
To the definitions of the terms molecule and atom already given^
the following may be added :
The molecule of an element or of a compound is the smallest por-
tion c&pable of existing in a free state — ^at all events during any
appreciable interval of time. An atom of an element is the smallest
part of that element capable of entering into or being expelled from
a chemical compound — the smallest part that exists in the molecule
of any of its compounds. The atomic weight of an element expresses
the number of times its atom is heavier than the atom of hydrogen.
The molecular weight of an element or compound is, as already
stated, the sum of the atomic weights of the atoms in its molecule.
The various methods of determining vapor-densities will be fully
described in the part of this work relating to organic chemistry : they
are of great importance in fixing the molecular weights of organic
compounda The principles involved in these methods may be stated
in a few words. The method of Dumas, applicable both to gases
and to vapors, consists in ascertaining the weight of that quantity of
the substance which in the gaseous state occupies a known volume.
In the method of Gray-Lussac, which can be employed only in the
case of vapors, the reverse principle — that of ascertaining the volume
occupied in the gaseous state by a known weight of substance — is
employed. In both cases the temperature of the gas or vapor, and
the pressure at which it is measured, must be carefully noted. The
relation of the weight of a given volume of substance in the gaseous
state to the weight of an equal volume of air or hydrogen at the
same temperature and pressure, constitutes the vapor-density of the
substance. In order that results obtained in the measurement of
gases and vapors may be comparable, it is usual to calculate what the
volumes would have been had the measurement been made under the
pressure of 760 millimetres of mercury (this being the average pres-
sure of the atmosphere), and at the temperature of 0^ C. This pro-
cess is known as ** reduction to standard temperature and pressure.'*
It is employed even in cases where the substance does not exist in
the gaseous state under these conditions of temperature and pressure.
Any other temperature and pressure might have been chosen, and
the relations of the volumes of different gases so reduced would have
remained exactly the same. If v be the volume of a gas or vapor
measured at the temperature of t° C, and under the pressure of p
wilUmetreB of mercury, its volume VaiO^ C and 760 millimetres
will be:
V ^
760(1 + 2^).
This formula may easily be deduced from the laws of Boyle and
Charles.
60 INORGANIC CHEinSTRT.
All other direct methods of determining vapor-densities are modi-
fications of the two just mentioned.
The method of ascertaining the molecular weight from the vapor-
density is unfortunately limited in its application. Allusion has
already been made (p. 56) to the practical impossibility of determin-
ing the vapor-density in the case of the great majority of the elements.
As regards compounds, many of these decompose in assuming the
gaseous state, so that their vapors consist of molecular mixtures more
or less heterogeneous, from the density of which no conclusion can
be drawn as to the molecular weight of the original compound.
In the case of such compounds, an indirect method has to be re-
sorted to. It will be best to illustrate the application of this method
by a case in which the molecular weight has already been deduced
from the vapor-density.
The analysis of a compound gives acertain percentage composition,
from which an empirical formula may be calculated. In this way
the empirical formula CH,0 is obtained for acetic acid. But it is
evident that any multiple of this formula, C,H^O„ CjH.Oa, etc.^
would correspond equally well with the same percentage composition,
and the question therefore arises, which is the true molecular weight ?
Experiment shows that 107.7 parts by weight, or 1 atom of silver,
may be substituted for 1 part of hydrogen in acetic acid ; and further,
that in this manner one-fourth part of the entire hydrogen present in
the acid may be displaced.- As fractions of atoms do not exist, the
only legitimate conclusion is that the number of atoms of hydrogen
in the molecule of acetic acid is four, or some integer multiple of four.
At this point the decision is rendered easy by the knowledge derived
from other sources that acetic acid belongs to the class of the mono-
basic acids in the molecule of which only one atom of hydrogen can
be displaced by silver. Hence the molecular formula of acetic acid
must be C^H^O,. Adding together the atomic weights (see table, p.
38) of all the atoms in the molecule, the molecular weight 60 is ob-
tained.
Now the vapor-density of acetic acid determined at 300° has
been found to l)e 2.08 (air =1). Substituting this value for rf in
the formula l/ = 28.9 X d, we find Jtf = 60.1 as the molecular
weight of acetic acid, a number which agrees very well, within the
limits of experimental error, with that deduced above.
As the operations of weighing, on which the determinations of the
atomic weights depend, can be performed with greater accuracy than
those involved in ascertaining vapor-densities, it is usual to select as
the most trustworthy the molecular weight obtained by adding to-
gether the atomic weights of all the atoms in the molecule, using the
vapor-density only to decide between two or more possible molecular
weights. Thus in the case of acetic acid, the formulae CH,0, C,H^O„
and CsHjO, would represent the molecular weights 30, 60, and
90 respectively. The number 60.1 obtained from the vapor-den-
sity leaves no doubt as to which of these is the true molecular
weight.
Melissic acid is a compound of high molecular weight, not volatile
ATOMIC WEIGHTS. 61
-Without decomposition. Its whole chemical behavior shows that it
belongs to the same class of acids as acetic acid ; this knowledge is
of use in determining the molecular weight. The empirical formula
is Cj^Hj^O, which would correspond to the molecular weight 226.
We have already seen that 107.7 parts of silver can displace I part
of hydrogen in 60 parts of acetic acid. In like manner experiment
shows that 1 part of hydrogen in 452 parts of melissic acid may be
displaced by 107.7 parts of silver. The molecular formula of this
acid is therefore C„H„0, = 452, or twice as great as the empirical
formula^ as was also the case with acetic acid.
When a substance is not volatile without decomposition, and is
moreover incapable of forming compounds from which conclusions
can be drawn as to its molecular weight, the determination of this
latter is beset with still greater difficulties. In this case it is neces-
sary to take the compound, as it were, to pieces, either by breaking it
up into two or more known compounds, or by destroying one part and
leaving the rest intact, the object being in every case to arrive at
compounds of known molecular weight* In this way more or less
trustworthy conclusions as to the molecular weight of the original
compound may sometimes be arrived at ; but this method is far in-
ferior in the certainty of its results to the two already described.
CHAPTER VII.
ATOMIC WEIGHTS.
1. Deduction of the Atomic Weight of an Element from
THE VaPOR-DEKSITY OF ITS COMPOUNDS.
The atomic weight of an element is that weight which is the
greatest common divisor of the various weights of that element oc-
curring in the molecules of its compounds, the atomic weight of hy-
drogen being taken as unity. The atomic weights are thus relative,
not absolute weights.
As the molecular weights of volatile elements and of those com-
pounds which can be vaporized without decomposition have alone
been determined with certainty (all other methods, whatever proba-
bility of accuracy their results may possess, being based more or less
on analogy), it is necessary, in order to determine the atomic weight
of an element according to the alx)ve definition, that it should form
a number of compounds volatile without decomposition. The fol-
lowing tables show the application of this method:
62
INORGANIC CHEMISTRY.
Imol.
Hydrogen, ....
Chlorine,
Oxygen,
Sulphur, ....•<
Nitrogen,
Hydrochloric acid, . .
Hydrocyanic acid, . .
Nitric oxide, ....
Nitroufl oxide, . . .
Water,
Carbonic oxide, . . .
Carbonic anhydride, .
Methylic hydride, . .
Methylic chloride, . .
Methylenic dichloride.
Chloroform, ....
Carbonic tetrachloride,
Dicarbonic hexachloride,
Acetone,
Methylic oxalate, . .
Sulphuretted hydroeen,
Disulphur dichloride, .^
Sulphurous anhydride.
Boric fluoride, . . .
Silicic fluoride, . . .
Mol.
weight
2
71
32
64
192
28
36.5
27
30
44
18
28
44
16
60.5
85
119.5
154
237
58
118
34
135
64
68
104.2
ContalDB parts by weight.
- Mol.
formula.
2 Hydrogen, ...
71 Chlorine, . . .
32 Oxygen,
64 Sulphur,
192 Sulphur
28 Nitrogen,
1 Hydrogen, 35.5 chlorine, . . .
1 Hydrogen, 12 carbon, 14 nitrogen,
14 Nitrogen, 16 oxygen, ....
28 Nitrogen, 16 oxygen, ....
16 Oxygen, 2 hydrogen, ....
12 Carbon, 16 oxygen,
1 2 Carbon, 32 oxygen,
12 Carbon, 4 hydrogen
12 Carbon, 3 hydrogen, 35.5 chlorine,,
12 Carbon, 2 hydrogen, 71 chlorine,
12 Carbon, 1 hydrogen, 106.5 chlorine,'
12 Carbon, 142 chlorine, .... I
24 Carbon, 213 chlorine, . . . .
36 Carbon, 6 hydrogen, 16 oxygen,
48 Carbon, 6 hydrogen, 64 oxygen,
32 Sulphur, 2 hydrogen,
64 Sulphur, 71 chlorine,
32 Sulphur, 32 oxygen,
11 Boron, 67 fluorine, .
28.2 Silicon, 76 fluorine,
!ci,.
O,.
Is:
HCl.
HCN.
NO.
N,0.
OH,.
CO.
CH.Cl.
CH,C1^
CHCl,.
CCI4.
C,CI,.
C,H,0.
C,HA.
SH^
8,CI^
SO,.
BFj.
SiF^.
In the next table the above results are arranged so that the atomic
weights of the various elements under discussion may be deduced.
The first column contains the name of the element; the second, the
relative weights of it occurring in the molecules of its com{K>und8
above enumerated — the smallest of these weights, which generally
coincides with the atomic weight, being placed first; and the third,
the greatest common divisor of these numbers, this last being iden-
tical with the atomic weight :
Element.
Relative weights.
Hydrogen, .
Chlorine, .
Oxygen,
Sulphur, .
Nitrogen, .
Carl)on, . .
Fluorine, .
1,2.3.4,6,
35.5,71,106.5,142,213,
16,32,64.
32,64,192.
14,28,
12,24,36,48
57,76,
G. C. D.
1
35.6
16
32
14
12
19
In this way the atomic weights of these elements have been deter-
mined.
It will l)e noticed that the smallest relative weight of fluorine
occurring in the molecule of either of its compounds above mentioned
is thrice its atomic weight. A compound, hydrofluoric acid, con-
ATOinC WEIOHT3. 63
tainingone atom of fluorine to one of hydrogen, has long been known,
but, though capable of existing as a gas even at ordinary temperatures,
its vapor-density could not be ascertained, owing to its property of
attacking the vessels of glass or porcelain in which it has to be meas-
ured. Latterly, however, the problem has been solved, and hydro-
fluoric acid is found to possess the molecular formula HF = 20,*
and to consist of 19 parts of fluorine to 1 of hydrogen. Organic
compounds of fluorine, containing only one atom of this element in
the molecule, have also been discovered. They are volatile and do
not attack glass, so that their vapor-density may be determined in
the ordinary way. The existence of these compounds places the
number now accepted as the atomic weight of fluorine on a much
surer basis.
It is evident that the above method alone can never afford absolute
certainty as to the atomic weights of the elements, since we can never
be sure that a compound will not be discovered containing in its
molecule either a smaller relative weight of an element than that
which has been deduced from the known compounds of that element,
or some relative weight which is not a rational multiple of the re-
ceived atomic weight. If, for example, a compound containing 8
parts, or 24 (or any odd multiple of 8) parts of oxygen in the mole-
cule were to be discovered, it would be necessary to change the atomic
weight of oxygen from 16 to 8. Fortunately, however, two other
methods of fixing the atomic weight are known (see pp. 65 and 67),
and the agreement prevailing between the numbers determined by
these three totally independent methods, increases enormously the
probability of their correctness.
Apparent Exceptions to Avogadro*8 Law. — There are cases in which
the molecular weights as deduced from the vapor-densities give values
which are less than the sum of the weights of the smallest possible
number of whole atoms which can go to form the compound. The
following three substances, at ordinary temperatures solids, will serve
as illustrations : ,
The vapor- deiisity of ammonic chloride has been found to be 0.89
(air = 1). The molecular weight would therefore be
M = 28.9 X 0.89 = 25.7.
The smallest stoechiometricf molecule is
NH.Cl = 53.5 = 2 X 26.75.
The molecular weight deduced from the vapor-density would
therefore correspond to the formula NjHaClj : in other words, the
accepted atomic weights of nitrogen and chlorine would have to be
halved.
Phosphoric chloride has a vapor-density of 3.65, or only half of
that required by its smallest stoechiometric formula PCI5. The formula
* The above is the molecular weif:ht of hydrofluoric acid at 100^. At 2b^ it has
the molecular weight 40, corresponding to the molecular formula U^Fg. This in no
way invalidates the foregoing conclusions.
t StouJiiomdriCj pertaining to the atomic weights.
64 INOBGA5IC CHEMISTRY.
would therefore havft to be written PjCl j, and the atomic weights of
phosphorus and chlorine would have to be halved.
A still worse complication is introduced by the vapor-density of
ammonic carbamate^ which is 0.89, or only one-third of that which
its smallest possible formula N^HgCOj demands. The molecular
formula would therefore be NiHjCjO^.
In order to introduce whole numbers of atoms into this last formula,
and at the same time into that of ammonic chloride, N^HjClj, it
would be necessary to give to the atomic weight of nitrogen a value
only one-sixth of that now assigned to it, or 2.33 instead of 14. This
would further involve the a^umption that nearly all the other com-
pounds of nitrogen contain at least six atoms of nitrogen.
Fortunately, however, these alterations, which would introduce
indescribable confusion into chemistry, would also be erroneous. It
has been proved that all these compounds decompose in volatilizing.
The molecule of ammonic chloride (NH^Cl) breaks up into one mole-
cule of ammonia (NHj) and one of ' hydrochloric acid (HCl). The
vapor thus contains twice as many molecules as it would have done
had no decomposition taken place; it therefore occupies twice the
volume, and consequently possesses only half the density. The same
holds good concerning phosphoric chloride (PCI5), which breaks up
into equal molecules of phosphorous chloride (PCI3) and free chlorine
(Clj). Ammonic carbamate (NjHgCOj) decomposes into two mole-
cules of ammonia (NH3, NH3) and one of carbonic anhydride (CO^),
so that the volume is three times, and the density only one-third as
great as would be the case if no decomposition had taken place.
Since in all these cases the products of decomposition recombine on
cooling to form the original compound, the difficulty lay in proving
that a decomposition had really taken place. However, this has
been satisfactorily accomplished by various methods, both direct and
indirect ; so that it is not necessary either to doubt the validity of
Avogadro's law, as some chemists were inclined to do, or to intro-
duce intricate and contradictory changes in the accepted atomic
weights.
2. Determination op the Atomic Weights by means of
Isomorphism.*
Many different compounds crystallize in the same or nearly the
same forms. For example, the salts
Plumbic nitrate, PhNgOg.
Baric nitrate, BaNjO^.
Strontic nitrate, SrNjOg.
crystallize in the same forms of the regular system (see Crystallog-
raphy). As any given form of the regular system has invariably the
same angles, the identity of form in the above three cases is absolute.
Again :
* The selection of examples of isomorphism is borrowed from Kopp's TkeoreUtcke
Chemic
ATOMIC WEIGHTS. 65
Nickelous sulphate, NiS04,60Hj,
Nickelous seleniate, NiSeO^jeOHj*
Zincic seleniate, ZnSeO^jBOHa,
crystallize in the same quadratic forms, with angles almost identical in
the three cases, and with the same cleavage.* The following com-
pounds :
Zincic sulphate, ZnSO^JOHj,
Nickelous sulphate, NiSO^jTOHj,
Magnesic sulphate, MgSO^JOHg,
Magnesic seleniate, MgSeO^,70H2,
Magnesic chromate, MgCrO^jTOH,,
crystallize in very similar forms of the rhombic system, with almost
the same angles.
Compounds which, like the above, crystallize in the same or nearly
the same forms, and possess similar constitution, are termed iaomorphous.
In an isomorphous group those elements which occur in all the mem-
bers are called the common elements; those which may be varied with-
OQt producing a change of crystalline form, the corresponding elements.
The corresponding elements are frequently termed the isomorphoiis
elemeniSy although they do not, when isolated, necessarily crystallize in
the same forms. The sense in which the term isomorphous is used when
applied to compounds must not be confounded with that which it bears
in reference to elements. In the former case It means : " possessing the
same form;" in the latter, " producing the same form."
In each of the above groups it will be noticed that all the compounds
contain the same number of atoms. It has further been found by ex-
periment that in an isomorphous group, the corresponding elements
occur in the relative proportions of their atomic weights as determined
hf Avogadro's law. Hence it is only necessary to know the atomic
weight of one of the corresponding elements in a group of isomorphous
compounds in order to determine the atomic weights of all the rest.
But before illustrating this, it will be necessary to describe the various
groups of isomorphous elements. In such a group the analogous com-
pounds which the various members form with the same element or ele-
ments are frequently, but not necessarily, isomorphous.
1. Sulphur^ Selenium, Manganese^ Chromium. — Sulphides and selen-
ides are frequently isomorphous, for instance : PbS and PbSe, AgjS
and Ag,Se. The salts of sulphuric, selenic, manganic, and chromic
acids, with the same base, and containing the same number of molecules
of water of crystallization, are generally isomorphous.
2. Magnesium^ Calcium, Manganese^ Iron, Cobalt, Nickel, Zinc, Cad-
miumj Copper. — The carbonates of these metals crystallize in rhombo-
hedra with rhombohedral cleavage. The cleavage rhombohedra have
almost the same angles. The sulphates are also for the most part iso-
* CUxxDogt 16 the tendency which some crystallized 8ubf<tance8 display when hroken, to
split in directions parallel to the faces of certain crystalline forms of these substances.
The artificial forms thus produced are known as '* cleavage forms."
5
66 INORGANIC CHEMISTRY.
morphous, and the same is the case with the double sulphates of these
metals with potassium and ammonium.
3. Manganese and Iron, both members of the preceding group, also
^" - - - ^1 -
form another group with Chromium and Aluminium. The three
quioxides Fe,0„ Or,0„ and AI,0„ are isomorphous. The sesqui-
oxides of these four metals combine with monoxides of the general
formula R"0 to form the spinelles, which all crystallize in the regular
system and possess the general formula R^'O, R'^^,0,. The sesquioxides
also enter into the composition of the alums, which all crystallize in the
r^ular system.
4. Calcium has also isomorphous relations with Strontiumy Bariumy
and Lead. All four are connected by their carbonates (calcium as
arragonite) ; calcium and lead by their tungstates; strontium, barium,
and lead by their anhydrous sulphates.
A simple enumeration of some of the remaining isomorphous groups
must suffice:
5. Tungsten and Molybdenum,
6. Tin and Titanium.
7. Palladium, Platinum, Iridium^ and Osmium.
8. Potassium and Ammonium.
9. Sodium and Silver.
10. Phosphorus, Arsenic, and Antimony.
11. Chlorine, Bromine, Iodine.
Elements which are isomorphous with the same element are not neces-
sarily isomorphous with each other. It would be incorrect, for exam-
Ele, to say that iron and sulphur must be isomorphous because they are
oth (in different ways) isomorphous with manganese. Only those
elements can be said to be isomorphous which occur in the same true
group of isomorphous compounds ; and in a true group of isomorphous
compounds all the nJembers possess the same crystalline form and an
analogous atomic composition.
It only remains to give an illustration of the method of applying the
law of isomorphism to the determination of the atomic weights. From
the vapor-density of their compounds, chlorine and sulphur have been
found to possess the atomic weights CI = 35.5 and S =: 32. In the
isomorphous sulphates and manganates (isomorphous group 1), the
corresponding elements occur in the proportion of 32 parts by weight
of sulphur to 55 of manganese. In the isomorphous i^erchlorates and
permanganates, the proportion in which the corres|>onding elements
occur is 35.5 parts of chlorine to 55 of manganese. The atomic weight
of manganese is therefore 55. But the metals of the 2d isomorphous
group are contained in their isomorphous carbonates and sulphates in
the following relative proportions: manganese 55, magnesium 24.4,
calcium 40, iron 56, cobalt 58.6, nickel 58.6, zinc 65.3, cadmium 112,
copper 63.2 ; and these are therefore the atomic weights of those ele-
ments. In like manner it is only necessary to refer the proportions in
which the metals of the 4th isomorphous group occur in their isomor-
phous compounds to the atomic weight of calcium just deduced, Ca= 40,
in order to determine the atomic weights of barium, strontium, and lead,
which are thus found to be Ba = 137, Sr = 87.5, Pb = 206.5.
ATOMIC WEIGHTS. 67
The foregoing enumeration of isotnorphous groups includes only
some of the most prominent. There are many others which serve as
connecting links, so that it is possible by means of the law of isomorph-
ism to determine the atomic weights of nearly all the elements.
Isomorphous compounds possess the property of crystallizing together
in various proportions to form homogeneous crystals belonging to the
same system as the compounds themselves. These crystals are generally
distinguished by possessing simpler forms — less variety of faces — than
the crystals of the pure compounds. If the angles of the latter differ
slightly from each other, the angles of the mixed crystals will possess
values which lie between those of the pure compounds. Thus the ter-
minal angle of the cleavage rhombohedron of pure calcium carbonate is
105*^ 6' ; that of pure magnesic carbonate, 107° 25' j whilst in the case
of their isomorphous mixtures, this angle varies between these two
limits, inclining in the direction of the compound which predominates
in the mixture.
A substance which crystallizes in two different forms not reducible
to the same system is termed dimorphous. It sometimes happens that
two dimorphous compounds are isomorphous, in which case the two
distinct forms frequently correspond in the two compounds. This
double isomorphism is known as isodimoi'phism. Antimonious oxide,
Sb,0„ occurs naturally in regular octahedra as senarmontite, and in
rhombic prisms as valentinite. Arsenious anhydride, Aj^O,, is found
in nature in regular octahedra as arsenic bloom and in rhombic prisms
as claudetite, these two forms respectively corresponding with those of
antimonious oxide, with which arsenious anhydride is thus isodi-
morphous.
The law of isomorphism was first enunciated by Mitscherlich, in
1819.
The determinations of atomic weights by means of this law are not
always absolutely certain. This uncertainty has its root in the fact that
various undoubtedly isomorphous compounds are known in which the
number of atoms in the molecule is different. Thus the salts of |)otas-
sium (K) and ammonium (NHJ are isomorphous. Baric permanganate,
BaMujOa, is isomorphous with anhydrous sodic sulphate, Na2SO^.
In none of these compounds can the corresponding elements be said to
be substituted for each other in the proportion of their atomic weights.
3. Determination op the Atomic Weights from the Specific
Heats of the Elements in the Solid State.
If a kilogram of water at 100° be mixed with a kilogram of water
at 0°, the temperature of the mixture will be 50°, the mean of the
other two temperatures. If a kilogram of iron filings at 100° be mixed
with a kilogram of water at 0°, the temperature of the whole will not
be higher than 10°. As, therefore, a given weight of water in cooling
through 50° can raise the temperature of an equal weight of water
through 50°, and as a given weight of iron filings in cooling through
90° can raise an equal weight of water through only 10°, it is evident
that equal weights of iron and water at the same temperature contain
68 INORGANIC CHEMISTRY.
very different amounts of heat Calculated from the above figures, the
quantities of heat contained in equal weights of water and iron at the
50 10 1
same temperature will be as ^^ to w^r, or as 1 to q. And as the heat
which a body gives off in cooling is equal to that which it has taken up
in heating, it will require 9 times as much heat to raise the temperature
of a given weight of water through a given number of degrees, as it
will to raise the same weight of iron through an equal numbetr of de-
grees. The relative capacities of bodies for heat are known as their
specific heats, that of water being taken as unity.
For many reasons it is useful to have a unit of heatf by means of
which the heat evolved or absorbed in chemical or other processes may
be measured. For this purpose that quantity of heat required to irUse
the temperature of 1 gram of water from 0^ to 1° C is employed as the
standard of measurement, and is known as the unit of heaty thermal
unity or calorie. As the specific heat of water is the unit of the specific
heats, it is evident that in order to find how many units of heat are
required to raise the temperature of a body through any number of
degrees of the centigrade scale, it will only be necessary to multiply
together the weight of the body expressed in grams, its specific heat,
and the number of degrees through which its tem|)erature has been
raised.* Thus the quantity of heat required to raise the tempera-
ture of 2 grams of iron through 90°, or of 180 grams through 1°, or of
1 gram of water through 20°, or of 2 grams, through 10°, is in every
case the same, namely 20 thermal units.
Dulong and Petit were the first to determine the specific heats of a
number of the chemical elements, and they arrived at the remarkable
result, that the specific heats of the elements in die solid condition are in-
versely as their atomic weights. If instead of determining the specific
heat of equal weights of the elements, the latter be taken in the propor-
tion of their atomic weights, the specific heats of these atomic weights
will be equal, or as this may be expressed : the capacities for heat of the
atoms of different elements in the solid state are equal: all the elements in
the solid state have the same atomic heat. The atomic heat may be found
by multiplying the 8|>ecific heat of an element by its atomic weight
The average value of the atomic heat for the different elements is 6.4.
The slight variations which the atomic heats of the various elements
display, arise first from the difficulty of determining accurately the
specific heat, and secondly from difference of physical condition in the
elements — the chief disturbing influence depending upon the fact that
the specific heat of an element rises with the temperature, being greatest
near the fusing point, whilst the specific heats are generally determined
between 0° and 100°, and consequently at varying distances from the
fusing points of the different elements.
It is evident that the law of Dulong and Petit must offer a very
valuable means of checking doubtful atomic weights, and of determin-
ing such as are not within the reach of the other two methods. Thus,
* This mode of calculation is based on the assumption that the specific heat of a
body is the same at all temperatures, which is only approximately correct. As will
be shown later, the specific heat increases with the temperature.
ATOMIC WEIGHTS. 69
gold forms no volatile compounds, and its isomorphism with other ele-
ments is not su£Bciently marked to be available as a means of fixing its
atomic weight. But the specific heat of gold has been found to be
0.0324, and this numl)er multiplied by 196, the accepted atomic weight
of gold, gives 6.36, closely approximating to the average atomic heat
of the elements, from which it may be concluded that 196, and no mul-
tiple or sub-multiple of this number, is the true atomic weight of gold.
A glance at the table of specific heats on p. 73, in which the elements
are arranged in the order of their atomic weights, will show that the
deviations from the law of Dulong and Petit follow a certain rule. In
the case of the elements of high atomic weight, the agreement is almost
always good, and with these elements it is to be noted that the varia-
tion of the specific heat with the temperature at which it is determined
is bat small. The notable exceptions to the law are to be found among
the elements which combine the two properties of kno cUomio weight and
low aiomie volume [q. v.). In the following list of these exceptional ele-
ments, the specific heats have been determined at temperatures below
100° C. (212^ F.). The brackets denote indirect determinations (see
Neumann's Law, p. 70) :
Name of element. Atomic heat.
Aluminium, 5.7
Phosphorus, 5.3
Sulphur, 5.1
Nitrogen, (5)
Fluorine, (5)
Oxygen, (4)
Silicon, 3.8
Beryllium (Glucinum), ... 3.7
Boron, 2.7
Hydrogen, (2.3)
Carbon (as diamond and in its compounds), . . 1.8
A reference to Lothar Meyer's curve of the elements (see diagram.
Classification of the Elements according to their Atomic Weights) will
show that the whole of these exceptional elements are to be found in the
lower portions of the first three periods of the curve — a position which,
from the nature of this curve, falls to these elements in virtue of their
low atomic weight and low atomic volume. That low atomic weight
alone is not sufficient to produce deviation from the law of Dulong and
Petit, is very clearly shown by the fact that three elements of low
atomic weight — lithium, sodium, and potassium — which, however,
owing to their relatively high atomic volume, form maxima of the
curve, perfectly conform to the law. A straight dotted line, cutting
the curve, has therefore been drawn to indicate the "limit of validity
of the law of Dulong and Petit" The exceptional elements are all to
be found below this line.
It is probable, however, that even for these exceptional elements
there is a temperature at which they conform to this law. H. F. Weber,
who has carefully determined the specific heats of carbon and silicon
for a great range of temperature, finds that the specific heat rapidly
70
IXOBOANIC CHEMISTRY.
increases with the temperature until a point is reached at which these
elements approximately obey the law; that is to say, the deviations
are not much greater than in the case of aluminium, thus leaving no
reasonable doubt about the atomic weight. Above this point the specific
heat rises only very slowly with the temperature. This lower limit of
conformity to the law lies in the case of silicon at about 200° C, in the
case of carbon aliout 600° C. It is worthy of note that the various
modifications of carbon, which at ordinary temperatures possess widely
different specific heats, have the same specific heat as soon as the above
limit is reached. Boron shows a similar rapid rise of specific heat ; but
the observations have not been carried to temperatures sufficiently high
to determine the lower limit of conformity in the case of this element;
it, however, probably lies between 500° and 600° C.
Dulong and Petit tried without sucoess to extend the law of specific
heat to compounds. This was finally accomplished by Neumann (1 831),
w ho showed that chemically equivalent quantities of similar compounds
have the same capacities for heat. If the product of the molecular
weight into the specific heat be termed the molecular heat of a compound,
this law may be expressed : Similar compounds have the same mdecular
heats For example :
Compound.
Mol.
formula.
Mol.
weight.
Sp. heat
Mol.
heat.
Lithic chloride, . .
Sodic chloride, . .
Potassic chloride, .
Argentic chloride, .
LiCl
NaCl
KCl
AgCl
42.5
68.5
74.5
143.2
0.2821
0.2140
0.1730
0.0911
12
12.5
12.9
13
It is possible in this way to determine the atomic heat of elements
which do not exist at ordinary temperatures in the solid state. Thus,
by subtracting from the molecular heat of potassic chloride, 12.9, the
atomic heat of potassium, 6.6, the atomic heat of chlorine is found to
be 6.3. A study of the above-mentioned chlorides shows that the atomic
heat of chlorine thus deduced varies according to the chloride employed ;
but the method of calculating its value by subtracting the atomic heat
of the other element exaggerates these errors. It is further evident
that the danger of error in this indirect method of determining the
specific heat of an element will be greater the,greater the relative num-
ber of atoms of other elements contained in the molecule of the com-
pound employed. But if the molecular heat of a compound be di-
vided by the number of atoms in the molecule, the variations caused
by difference of physical conditions in different compounds will be dis-
tributed among the atomic heats of the several atoms in the molecule
(which are probably all affected in the same direction by such varia-
tions), and the average atomic heat of the elements contained in that
compound will be obtained. Thus the molecular heats of the above
chlorides divided by 2 give numbers varying from 6 to 6.5, suf-
ficiently approximating to 6.4, the average atomic heat of the elements
in the solid state.
ATOMIC WEIGHTS.
71
In this way Neumann's law has been successfully applied in verifying
the atomic weights of elements, the specific heats of which had not
been directly determined. Thus in the case of barium, strontium, and
calcium, chemists were in doubt whether these elements posseased the
atomic weights Ba = 137, Sr = 87.5, and Ca = 40 ; or, only the half of
these weights, ba = 68.6, sr = 48.8, and ca = 20 — these smaller values
being formerly universally employed. In these two cases the formulae
of the chlorides would be respectively :
Mol. weight
... 208
SrClj, 158.5
Formula.
BaCl«.
CaCl,
111
Formula.
baCl, .
srOl, .
caCl, .
Mol. weight
. 104
. 79.3
. 65.5
The number of atoms in the molecule is in the first case 3, in the
second 2. The specific heats of these compounds were found to be :
Baric chloride, . . 0.0902
Strontic chloride, 0.1199
Calcic chloride, 0.1642
Now the expression
molecular weight X specific heat
number of atoms in molecule
be approximately equal to 6.4, the average atomic heat
ing in this expression the above values, we find for
— ought to
Substitut-
and for
baCl, . .
srCl, . .
caCl, •
BaCl„ .
SrClj} • •
CaCl„ .
104 X 0.0902
2
79.3 X 0.1199
2
55.6 X 0.1642
208
2
X 0.0902
3
168.5 X 0.1199
111
3
X 0.1642
= 4.7,
= 4.75,
= 4.55;
= 6.23,
= 6.33,
= 6.07.
The values 6.23, 6.33, and 6.07 approximate with sufficient close-
ness to 6.4 ; whereas, 4.7, 4.75, and 4.55 differ widely from this num-
ber. The formulffi of the chlorides must, therefore, be written BaClj,
SrCljy aod CaClj, and the three elements must possess the atomic weights
Ba = 137, Sr = 87.5, and Ca = 40. Only a few years ago the specific
heat of metallic calcium was determined for the first time by Bunsen,
and was found to be 0.1704. This number, multiplied by 40, the
72
INORGANIC CHEMISTRY.
atomic weight of calcium, gives 6.82 sb the atomic heat of this element,
thus directly proving the correctness of the above de<luction.
In applying Neumann's law to compounds in which any of the ex-
ceptional elements occur, it is necessary to introduce the special value
for the atomic heat in calculating the molecular heat of the com{K>und.
In the c;ase of the other elements^ the average atomic heat/6.4y may be
employed without sensible error :
Name of
compound.
Molecular
Molecular heat.
formula.
Calculated.
Foand.
Antimonioas salphide,
Pota.sHic pyrophoe-
phate,
Calcic fluoride, . .
Capric oxide, . . .
Silicic anhydride, .
Boric anhydride, . .
Sodic metaborate^ . .
Dicnrbonic hexachlo-
ride,
Succinic acid, . . .
CaF,.
CiiO.
SiO,.
N'a&,.
C,C),.
C,H.O,.
(2 X 6.4) + (3 X 5.1) = 28.1
(4 X 6.4) -f (2 X 5.3) + (7 X 4) = 64.2
6.4 +(2X5) = 16.4
6.4 -h 4 =10.4
3.8 -f(2X4) =11.8
(2X2.7) 4- (3X4) =17.4
6.4 + 2.7 + (2X4) =17.1
(2X1.8) + (6X6.4) =42
(4 X 1.8) + (6 X 2.3) + (4 X 4) = 37
28.6
63.1
16.3
10.2
11.6
16.6
16.9
42.2
36.9
Thus, the molecular heat of a compound is the sum of the atomic heais
of its elemefits.*
This law, like the law of Dulong and Petit, of which it is a corollary,
is only an approximate law. It generally holds in the case of chlorides,
but is an unsafe guide in the case of oxides, especially if the number
of atoms in the molecule be large (see page 70) ; indeed, in some cases,
the attempt to deduce the atomic heat of an element from the molecular
heat of its oxide has led to fallacious results.
The following table contains the specific and atomic heats of all ele-
ments for which the determination has been made. In the case of carbon,
silicon, and boron, the values obtained at higher temperatures are em-
ployed. The elements are arranged in the order of their atomic weights.
The bracketed numbers represent indirect determinations :
* The law of Neumann that the molecular heat of a componnd is the 8nm of the
atomic heats of its elements, taken in connection with the fact that the known elements
possess an atomic heat approximating to 6.4, has a direct bearing npon the view some-
times advanced that many or all of the known elements are in reality compounds. It
is evident either that these supposed compounds do not contain as constituents any of
the known elements, since the^e have already an approximate atomic heat of 6.4, and
the resulting " compound '' element would necessarily possess a higher atomic heat;
or that the mode of combination is totally different from any yel known to chemists.
Further, as all the known elements have approximately the same atomic heat, the con-
clusion appears almost unavoidable, on the "compound " theory, that they are all com-
pounds of exactly the same complexity— containing the same number of constituent
atoms, a degree of uniformity which nature does not usually exhibit.
Kundt and Warburg's proof (p. 56) that the molecule of mercury has no internal
motion of parts, and is, therefore, in all probability truly monatomic, also appears to
militate against the ** compound " theory of the elements.
ATOMIC WEIGHTS. 73
Table of the Specifio Heat of the ElemenJts in the Solid Stale.
Name of element
Hydrogen, ....
Lhhiuniy
Beryllium (Glucinnm),
Boron,
Carbon,
Nitrogen,
Oxygen,
Fluorine,
Sodinm,
Magnesium, ....
Aluminium, ....
Silicon,
Phosphorus, ....
Sulphur,
Chlorine, ...
Potassium, ....
Calcium,
Titanium,
Chromium, ....
Manganese, ....
Iron,
Nickel,
Cobalt
Copper,
Zinc, ......
Gallium,
Arsenic,
Selenium,
Bromine,
Rubidium, . . — '.
Strontium, ....
Zirconium, ....
Molybdenum, . . .
Rhodium,
Ruthenium, ....
Palladium, ....
Silver,
Cadmium, ....
Indium,
Tin,
Antimony, ....
Tellurium, ....
Iodine
Barium,
Lanthanum, ....
Cerium,
Didymium, ....
Tunesten,
Iridium,
Platinum, ....
Gold,
Osmium,
Mercury,
Thallium, ....
Lead,
Bismuth,
Thorium,
Uranium,
Atomic
weight.
1
7
9
II
12
14
16
19
23
24.4
27
28.2
31
32
35.5
39
40
48
52
55
56
58.6
58.6
63.2
65.3
68.8
75
79
80
85.3
87.5
90
95.5
104
104
105.7
107.7
112
113.4
118
120
125
127
137
138.5
140.5
146
184
192.5
194.4
196
198.6
200
204
206.5
208.2
233.4
238.5
Specific
heat.
(2.3)
0.94
0 45
0.5*?
0.46
(0.36)
(0.25)
(0.26)
0.29
0.25
0.21
0.20
0.17
0.16
(0.18)
0.17
0.17
(0.13)
(0.12)
0.12
0.11
0.11
0.11
0.094
0.094
0.079t
0.081
0.075
0.084
(0.077)
(0.074)
0.066
0.072
0.058
0.061
0 0o9
0.056
0.057
0.057
0.066
0.051
0.047
0.054
(0.047)
0.045
0.045
0.046
0.033
0.033
0.033
0 032
0.031
0.032
0.034
0.031
0.031
0.028
0.028
Atomic
heat.
(2.3)
6.6
4.0
5.5
5.5
(5)
(4)
(4.9)
6.7
6.1
5.7
5.6
6.3
5.1
6.4
6,6
6.8
6.2
6.2
6.6
6.2
6.4
6.4
5.9
6.1
5.4
6.1
5.9
6.7
(6.6)
(6.5)
5.9
6.9
6.0
6.4
6.2
6.0
6.4
6.5
6.6
6.1
59
6.9
(6.4)
6.2
6.3
6.7
6.1
6.4
6.4
6.3
6.2
6.4
6.9
6.4
6.4
6.5
6.7
* This is a hy|x>thetical value deduced from the experiments of Weber,
t This 'Value was obtained from a determination performed within a limit of
eleven degrees— ft very narrow range of temperature.
74
INOBOAKIC CHEinSTBY,
Another mode of expressing the above facts consists in stating what
weight of each element has the same capacity for heat as 7 parts by
"Weight of lithium, 7 being the atomic weight of that metal. If the law
of Dulong and Petit were a perfectly strict law, the weights which
satisfy these conditions would be identical with the atomic weights.
In the following table the atomic weights are given side by side with
these "specific heat equivalents" in order to indicate clearly in every
case the extent of the discrepancy between the two values :
Specific Heai Equivalents of Solid Elements.
Name of element.
Lithium,
Beryllium (Glucinum),
Boron,
Carbon,
So<lium
Magnesium, ....
AIiiDiinium, ....
Silicon,
Phofiphorus, ....
Sulphur,
PotaHsium, ....
Calcium,
Manganese, . . » .
Iron,
Nickel,
Cobalt,
Copper,
Zinc, ......
Gallium,
Arsenic,
Selenium,
Bromine,
Zirconium, ....
Molybdenum, . . .
Khoidium,
Ruthenium, ....
Palladium, ....
Silver, '
Cadmium,
Indium,
Tin
Antimony, ....
Tellurium
Iodine,
Lanthanum, ....
Cerium, ......
Didymium, . . » .
Tungsten,
Iridium,
Platinum,
Gold,
Oftmium,
Mercury, . . . . .
Thallium,
Lead,
Bismuth,
Thorium,
Uranium,
Specific heat
0.94
0.45
0.5
0.46
0.29
0.25
0.21
0.20
0.17
0.16
0.17
0.17
0.12
0.11
0.11
0.11
0.094
0.094
0.079
0.081
0.075
0084
0.066
0.072
0.058
0.061
0.059
0.056
0.057
0.057
0.056
0.051
0.047
0.054
0.045
0.045
0.046
0.033
0.033
0.033
0.032
0.031
0.032
0.034
0.031
0.031
0.028
0.028
Welffhts con-
taining equal
quantities
of heat
7
14.6
13.2
14.3
22.7
26.3
31.3
32.9
38.7
41.1
38.7
38.7
54.8
59.7
69.7
59.7
70.0
70.0
83.3
81.2
87.7
78.3
99.7
91.4
113
108
112
118
115
115
118
129
140
122
146
146
143
199
199
199
206
212
206
194
212
212
235
235
Atomic
'weight
7
9
11
12
23
24.4
27
28.2
31
32
39
40
55
56
58.6
58.6
63.2
65.3
68.8
75
79
80
90
95.5
104
104
105,7
107.7
112
113.4
118
120
125
127
138.5
140.5
146
184
192.5
194.4
196
198.6
200
204
206.5
208.2
233.4
238.5
CHEMICAL KOTATION. ATOMICITY. 75
CHAPTER VIII.
CHEMICAL NOTATION. ATOMICITY.
The use of symbols in place of words, for recording the composition
of chemical compounds, and of equations for expressing chemical
changes, has long been necessary to accurate description, and has con-
tributed in an important degree to the development of chemistry into
an exact science. Unfortunately there has been, and still is, much
diversity of opinion amongst chemists as to the best kinds of symbols
to be used, and the extent to which these should be employed for ex-
pressing the constitution, as well as the composition, of chemical com-
pounds. It would serve no useful purpose and would only confuse
the student to review the various systems of notation in actual use
amongst chemists, and the description will therefore be here confined
to two of those systems, which have been extensively used for many
years, and as these systems are based on the doctrine of atomicity, this
subject has been introduced into the present chapter.
oYMBOLic Notation. — Every element is represented by a symbol,
which is frequently the initial letter of the name of the element; but as,
in some cases, the names of two or more elements begin with the same
letter, it is necessary to distinguish them by the use of a second letter
in small type, which is either the second letter of the word, or some
other letter prominently heard in its pronunciation : thus carbon, cad-
mium, cobalt, and cerium all begin with the same letter ; but they are
distinguished by the symbols C, Cd, Co, and Ce. In the use of the
single letters, the non-metallic elements have the preference; thus
oxygen, hydrogen, nitrogen, sulphur, phosphorus, boron, carbon, iodine,
and fluorine are expressed by the single letters O, H, N, S, P, B, C, I,
and F ; whilst the metalsosmium, mercury, nickel, strontium, platinum,
bismuth, cobalt, iridium, and iron are symbolized by two letters each ;
thus Os, Hg (hydrargyrum), Ni, Sr, Pt, Bi, Co, Ir, and Fe (ferrum).
In the selection of the single letters for other cases, preference is given
to the most important element; thus, sulphur, selenium, and silicon
are all non-metallic elements, beginning with the same letter ; but sul-
phur being the most important, the single letter S is assigned to it,
whilst selenium and silicon are denoted respectively by Se and Si.
The symbols of compounds are formed by the juxtaposition of the
symbols of their constituent elements. Such a group of two or more
symbols is termed a chemical formiUa. Thus :
Argentic chloride, AgCl.
Zincic oxide, ZnO.
The symbols not only represent the elements for which they are used,
but they also denote a certain definite proportion by weight of each
element; the formula HCl, for instance, does not merely denote a com-
pound of hydrogen and chlorine, but it signifies a molecule of that
oonpound containing one atom (1 part by weight) of hydrogen, and
76 IXOBOANIC CHEMIBTBY.
one atom (35.5 parts bv weight) of chlorine. When, therefore, the
molecule of a compound contains more than one atom or combiniDg
proportion of any element, it is necessary to express the fact in its
formula : this is done by the use of a small subscript coefficient placed
after the symbol of the element :
Zincic chloride, ZnCI,.
Ferric chloride, FcjCI^.
Stannous chloride, SnCI,.
Stannic chloride, SnCl^.
When it is necessary to denote two or more molecules of any com-
pound, a large figure is placed before the formula of the compound ;
such a figure then affects every symbol in that formula : thus SSOiH,
means three molecules of the compound S04H2,
The changes which occur during chemical action are expressed by
equations, in which the symbols of the elements or compounds, as they
exist before the change, are placed on the left, and those which result
from the reaction on the right. Thus, taking an example from each of
the five kinds of chemical action (see Chemical Affinity) we have
(1) Zn + CI, = ZnCl,.
Zinc Chlorine. Zincic chloride.
(2) 2HC1 + Zn = ZnCl, + K..
Hydrochloric Zinc. Zincic Hydrogen,
acid. chloride.
(3) SO.Cu + (XO,),Ba = SO.Ba + (N03),Cu.
Cupric Baric nitrate. Baric Ciipric
sulphate. sulphate. nitrate.
(4) (CN)0(NH,) = N,H,(CO).
Amnionic cyanate. Urea.
(5) 20H, = O, 4- 2H,.
Water. Oxygen. Hydrogen.
' The Sign +, as seen from the foregoing examples, is placed between
the formulae of the molecules of the different substances which are
brought into contact before the reaction, and of those which result from
the change. This sign must never be used to connect together the con-
stituents of one and the same chemical compound.
The sign — is only very rarely used in chemical notation, but when
employed it has the ordinary signification of abstraction ; thus,
SO,H, — OH, = SO..
Sulphuric Water. Sulphuric
acid. anhydride.
Use of the Braeket. — The bracket has been employed in various senses
in chemical formulae ; but in the present work it is used in notation
for one purpose only, viz., for expressing chemical combination between
CHEMICAL NOTATION. ATOMICITY. 77
two or more elements which are placed perpendicularly with rep^ard to
each other, and next to the bracket in a formula. Thus in the follow-
ing cases,
I. n. m.
I CH3 ^ O Ba y
iCH. NOpj
the formula No. I. signifies that two atoms of carbon are directly united
with each other, No. II. that two atoms of carbon are linked together,
as it were, by an atom of oxygen, the latter being united to both carbon
atoms; whilst in like manner, No. III. indicates that one atom of
oxygen in the formula of the upper line is linked to another atom of
oxy^n in the formula of the lower line, by an atom of barium.
Use of Thick Letters. — As a rule, the formulsd in this book are so
written as to denote that the element represented by the first symbol of
a formula is directly united with all the active bonds (see p. 81) of the
other elements or compound radicals following upon the same line:
thus the formula S02(OH)2 (sulphuric acid) signifies that the hexad
atom of sulphur is combined with the four bonds of the two atoms of
oxygen, and also with the two bonds of the two semimolecules of
hydroxyl. Such a formula is termed a constitutional fotimda.*
Occasionally, however, owing to the atomic arrangement of a com-
pound not being known, its formula cannot be written according to
this rule ; and in order to prevent such formulas, whether molecular or
em.piricalj'f from being mistaken for constitutional formulre, the first
symbol of a constitutional formula will always be printed in thick type.
As a rule, the element having the greatest number of bonds will occupy
this prominent position. Thus :
Sulphuric acid, .... S02(OH)2.
Water, OH^.
Nitric acid, TifOJiOU).
Microcosmic salt, . . . . PO(OH)(ONHJ(ONa).
* For farther information on this snbject see Atomicitt of Elkscents and Com-
pound Radicals.
t A moUeuhr formulaf sometimes called ro/io/Mi/, is one in which the atomic compo-
sition of a molecule is expressed, but without reference to the manner in which the
elements are combined amongst themselves. An empirical formula merely expresses,
{>J the smallest integers, the proportional number of atoms of each element entering
into the composition of a compound. Thus the three formule of ferric hydrate are
written;
Empirical formnla^ FeHsOj.
Molecular form nla^ Fe^HgO^
Constitutional formula, Fe,(OH)«.
Constitutional or rational formula are therefore essentially molecular formulae, whilst
empirical formul» afford no indication of the number of atoms contained in a molecule ;
they are, in fact, only used to express the composition of substances, the molecular
weights of which are either unknown or cannot be inferred from analogy.
78 inorganic chemistbt.
Atomicity of Elements.
It has been already stated that the atomic weight of an element is
the smallest proportion by weight in which that element enters into oris
expelled from a chemical compound. The atoms of the various elements,
the relative weights of which are thus expressed, possess very different
values in chemical reactions. Thus, an atom of zinc is equivalent to
two atoms of hydrogen, for when zinc is brought into contact with steam
at a hi^h temperature, one atom of zinc ex)>els from the steam two
atoms of hydrogen, and occupies their place, thus :
OHj + Zn = OZn + H,.
Water. Zincic oxide.
Again, when zincic oxide is brought into contact with hydrochloric
acid, the place of the zinc becomes once more occupied by hydrogen,
but two atoms of hydrogen are found to be necessary to take the place
of one atom of zinc :
OZn + 2Ha = ZnCl, + OH,.
Zincic Hydrochloric Zincic Water,
oxide. acid. * chloride.
In like manner, one atom of boron can be substituted for three atoms
of hydrogen, one of carbon for four, one of nitrogen for five, and one
atom of sulphur for no fewer than six atoms of hydrogen.
This combining value of the elementary atoms, which was first dis-
covered in the compounds of certain metals with organic radicals, is
termed their atomicity ^ equivalence^ valency , or aiomrfixing power ; and
an element, with an atom-fixing power equal to that of one atom
of hydrogen is termed a monad, one with twice that power a dyad,
with thrice a triad, with quadruple a tetrad, with quintuple a pentad,
and with an atom-fixing power equal to six times that of hydrogen, a
hexad.
To avoid any speculation as to the nature of the tie which enables an
element thus to attach to itself one or more atoms of other elements, each
unit of atom-fixing power will be named a bond, — ^a term which in-
volves no hypothesis as to the nature of the connection. A monad
element has, obviously, only one such bond ; a dyad, like zinc, two ; a
triad, like boron, three, and so on. The number of bonds possessed
by an elementary atom may be usefully symbolized by lines in the fol-
lowing manner:
Hydrogen, H —
Zinc, — Zn —
Boron, B
I
Carbon, — C —
I
H',
Carbon, . .
• c%
Zn",
Nitrogen, .
. N%
B'",
Sulphur,
. S^'.
CHEMJCAL NOTATION. ATOMICITY. 79
Nitrogen, N
Sulphur. — fe —
/\
In symbolic notation, the same idea is conveyed by the.use of dashes
and Roman numerals placed above and to the right of the symbol of
the element, thus :
Hydrogen, . .
Zinc, ; . • .
Boron, . .
Elements with an odd number of bonds are termed perisaads, whilst
those with an even number are named arfiads.
With very few exceptions, elements, either alone or in combination,
are never found to exist with any of their bonds free or disconnected ;
hence, the molecules of all elements with an odd numher of bonds are
generally diatomic, and always polyatomic ; that is, they contain two or
more atoms of the element united together. Thus :
Symbolic. Graphic.
Hydrogen, Hj H— H
Chlorine, CI, CI— CI
Nitrogen, N% N=N
P=P
Phosphorus, . . . . P\ ||| |||
P=P
An element, with an even number of bonds, however, can exist as a
roonatomic molecule, its own bonds apparently satisfying each other.
Thus:
Symbolic. Graphic.
V /
Mercury, . . . .
. . Hg"
Cadmium, . .
. . CM"
Zinc, . . . .
. . Zn"
-Zn-
It is, nevertheless, obvious that such an element may also exist as a
polyatomic molecule. Oxygen furnishes us with an example of this ;
for, in its ordinary condition, it is a diatomic molecule, and, in the al-
lotropic form of ozone, a triatomic molecule :
Symbolic. Graphic.
Oxygen, . . . ; . O'^^ 0=0
O— O
Ozone, 0''3 \/
O
80 INOBGANIC CHEMIBTBT.
In order to avoid the anneoeasary aae of atomicitj-marks in sym-
bolic notation, they will never be attached to a monad, or to oxygen,
which, it must be remembered, is always a djad. Neither will the
atomicity coefficient be attached to the tetrad element carbon, in the
forraulse of organic bodies, unless this element plays the part of a dyad,
an occurrence of extreme rarity. When not otherwise marked, there-
fore, carbon must always be understood to be a tetrad.
It will also, as a rule, be unnecessary to mark the atomicity of the
elements which are expressed by symbols in thick type, because their
atomicity is clearly indicated by the sum of the atomicities of the ele-
ments or compound radicals plac*ed to their right, or connected with
them perpendicularly by a bracket. Thus^ in the formula
/oci„
each atom of carbon is united with three atoms of the monad chlorine,
whilst the bracket indicates that the two atoms of carbon are also united
by one bond of each, thus denoting 0 to be a tetrad element
From what has just been said with regard to carbon, it is evident that
the atomicity of an element is, apparently at least, not a fixed and in-
variable quantity ; thus, nitrogen is sometimes eouivalent to five atoms
of hydrogen, as in ammonic chloride (N^'H^Cl), sometimes to three
atoms, as in ammonia (N'"Hs), and sometimes to only one atom, as in
nitrous oxide (ON,). But it is found that this variation in atomicity
takes place, with very few exceptions, by the disappearance or develop-
ment of an even number of bonds; thus, nitrogen, except in nitric
oxide (NO), and dissociated nitric peroxide (NO,), is either a pentad, a
triad, or a monad ; phosphorus and arsenic, either pentads or triads;
carbon and tin, either tetrads or dyads ; and sulphur, selenium, and
tellurium, either hexads, tetrads, or dyads.
These remarkable facts can be explained by a very simple and ob-
vious assumption, viz. : That one or more pairs of bonds belonging to
the atom of an element can unite, and^ having saJbaraied each oUieVy be"
come, as it were, latent Thus, the pentad element, nitrogen, becomes a
triad when one pair of its bonds becomes latent, and a monad, when
two pairs, by combination with each other, are, in like manner, rendered
latent, — conditions which may be graphically represented thus:
Pentad. Triad. Monad.
\l/ I o
N —X— N—
/\ o o
And in the case of sulphur :
Dyad.
O
CHEMICAL NOTATION. ATOMICITY. 81
Adopting this hypothesis, it will be convenient to distinguish the
maximum namber of bonds of an element as its absolute atomicity, the
number of bonds united together as its latent atomicity, and the number
of bonds actually engaged in linking it with the other elements of a
compound as its active atomicity. The sum of the active and latent
atomicities of any element must evidently always be equal to the
absolute atomicity. Thus in sulphuric acid (S^02Ho2) the absolute and
active atomicities are both = vi, therefore the latent atomicity = 0. In
sulphurous acid ("S^^'OHog) the active atomicity = iv, and consequently
the latent = vi — iv = ii ; whilst in sulphuretted hydrogen (^'^S^Hg)
the active and latent atomicities are respectively ii and iv.
The apparent exceptions to this hypothesis nearly all disappear on
investigation. Thus iron, which is a dyad in ferrous compounds (as
FeClj), a tetrad in iron pyrites fPeS'^g)? and a hexad in ferric acid
(FeO,(OH)2), is apparently a triaa in ferric chloride (FeClg) ; but the
vapor-density of ferric chloride shows that its formula must be doubled
— ^that, in fact, the two atoms of the hypothetical molecule of iron (Fcj)
have not been completely separated. The formulse of the ferrous and
ferric chlorides and of ferric acid then become
Symbolic. Graphic
Ferrous chloride, . . ^Te'^Cl^ CI— Fe— CI
o
„f'TeCl,
CI— Fe— CI
2 ci— Fe— CI
o
CI CI
Ferric chloride, . . . ''Te'^'^Cle CI— Fe=Fe-Cl
a ci
/"Feci, I I
o
II
Ferric acid, . . Fe^O,(OH),. H— O— Fe-O— H
II
O
It will be remarked that the number of bonds supposed to be com-
bined with each other in the atom of iron in ferrous chloride is expressed
82 INORGANIC GHEMI8TBY.
in one of the above fornialsB by the atomicity numeral iv placed to the
left of the symbol y whilst the analogous union of three bonds of eai^h
atom of iron in ferric chloride is expressed by the three dashes '" to
the left of the symbol Fe,. These coefficients of latent atomicity will
noty however, be used in the case of the single atom of an element, the
student beini^ supposed to have made himself acquainted with the
absolute atomicity of every element, as expressed in the Table given in
Chap. X. For a similar reason it will also rarely be necessary to express
the same idea in graphic notation. Thus, for instance, ammonia will
be drawn
H H
I and not I
H— N— H H— N— H
o
It will be necessary, however, to employ these coefficients in sym-
bolic formulae where two or more atoms of the same element are joined
together under such circumstances that the number of bonds uniting
them cannot be found by subtracting the coefficient of active atomicity
from the alisolute atomicity of the element, as in hydric persulphide
('S',H,), for instance, which might otherwise be viewed as '"S'jHj,
or^S',H,.
In rare cases, in which oxygen links together two elements or radicals
in the same line of a formula, a hyphen is placed before and after the
symbol O, thus;
/ OHj-O-OMeO
\ 0H,.O-0MeO-
Diacetic glycol.
Graphic Notation. — ^This mode of notation, although far too
cumbrous for general use, is invaluable for clearly showing the arrange-
ment of the individual atoms of a chemical compound. It is true that
it expresses nothing more than the symbolic notation of the same com-
pound, if the latter be written and understood as above described;
nevertheless the graphic form affi>rds most important assistance, both
in fixing upon the mind the true meaning of symbolic formulae, and
also in making comparatively easy of comprehension the probable
internal arrangement of the very complex molecules frequently met
with both in mineral and organic compounds. It is also of especial
value in rendering strikingly evident the causes of isomerism in organic
bodies; and it is now almost universally employed by chemists in de-
scribing the result*! of their new discoveries.
Graphic notation, like the above method of symbolic notation, is
founded essentially upon the doctrine of atomicity, and consists in
representing graphically the mode in which every bond in a chemical
compound is disposed of. Inasmuch, however, as the principles in-
volved are precisely the same as those already described under the heads
of SYMBOLIC NOTATION and ATOMICITY OF ELEMENTS, it is Unneces-
sary here to do more than give the following comparative examples of
symbolic and graphic formulse :
CHEMICAL NOTATION. ATOMICITY.
83
Water, .
Nitric acid,
Symbolic.
OH,.
NO,(OH).
Ammonic chloride, NH^Cl.
Sulphuric anhydride, SO^
Sulphuric acid, . • S02(OH)2.
Carbonic anhydride, CO,.
Potassic carbonate, . 0O(OK)2.
Marsb-gas, . . • OH4.
Graphic.
H— O— H
O
II
N— O— H
II
O
H
H— N— CI
/\
H U
O
II
8=0
II
O
o
II
H— O— S— O— H
II
o
o=c=o
K— O— C— O— K
II
o
H
H— C— H
i
Ammonic carbonate, 00(ONH,)y H— if— O— C— O— >C-H
i h i
Zincic nitrate, .
NO,0 )
Za" V
N0,0 j
O O
II II
N— O— Zn— O— N
II II
o o
It must be carefully borne in mind that these graphic formulte are
intended to represent neither the shape of the molecules, nor the bup-
84 INOBOANIG CHEMISTRY.
posed relative position of the coDstituent hypothetical atoms. The lines
coDDecting the different atoms of a compound, and which might with
equal propriety be drawn in any other direction, provided
they connected together the same elements, serve only to O
show the definite disposal of the bonds, the latter again ||
being only a concrete symbolic expression of an abstract N — 0 — H
train of reasoning; thus the formula for nitric acid indi- ||
Gates that two of the three constituent atoms of oxygen are O
combined with nitrogen alone, and are consequently united
to that element by both their bonds, whilst the third oxygen atom is
combined both with nitrogen and hydrogen.
The lines connecting the different atoms of a compound are but crude
symbols of the bond of union between them ; and it is scarcely neces-
sary to remark that no such material connections exist, the bonds which
actually hold together the constituents of a compound being, as regards
their nature, entirely unknown.
It deserves also to be here mentioned that graphic, like symbolic
formulce, are purely statical representations of chemical compounds:
they take no cognizance of the amount of potential energy associated
with the different elements. Thus in the formulae for marsh-gas and
carbonic anhydride,
H
H— C— H 0=C=0
Marsh -gas. Carbon ic anhydride.
there is no indication that the molecule of the first compound contains a
vast store of force, whilst the last is, comparatively, a powerless mole-
cule.
Calculation of Formula. — By quantitative analysis the rela-
tive weights of the various constituents of a compound body are dis-
covered, and these relative weights are usually expressed in parts per 100.
From these numbers the formula of the compound has to be calculated.
The percentage composition expresses the relative proportions of the
component elements in terms of a common unit; in the formula, the
froportion of each element is expressed in terms of its atomic weight,
n order, therefore, to ascertain in what proportion of their atomic
weights the elements occur in the compound, it is only necessary to
divide the proportion of each element in 100 parts of the compound
by the atomic weight of that element. Thus the analysis of acetic acid
yields the following percentage composition :
In 100 parte.
Carbon, 40.00
Hydrogen, 6.66
Oxygen, 53.33
99.99
COMPOUND RADICAU3, 85
Dividing each of these numbers by the atomic weight of the element
. , 40.00 ^ ^o 6.66 ^ ^^ , 63.33 ^ ^^
m question, we find: -r-^- =3.33; — -— = 6.66; and -y^r- = 3.33.
Therefore the atomic proportion of carbon : hydrogen : oxygen in
acetic acid is as 3.33 : 6.66 : 3.33, or as 1 : 2 Tl. The formula of
acetic acid would thus be CH,0.
This is, however, only the empirical formula, or smallest possible
proportion of the atomic weights. We have already seen (p. 60)
that the molecular formula of acetic acid is C2H4O2, or twice as great
as the above.
CHAPTER IX.
COMPOUND RADICAUS.
The term compound radical may be applied to any group of two or
more atoms, which takes the place and performs the functions of an
element in a chemical compound. In practice, however, it is only
applied to any such group when met with in numerous chemical com-
pounds.
An element is a simple radical^ and enters into combination in the
following manner, a, 6, c, and d being monad elements, a'' a dyad, a"'
a triad, and a'^ a tetrad element :
a' + 6 = ai,
a" + 26 = a'%
a''' + 36 = a''%
etc. etc.
A group of elements replacing a, a", or a"' in the above equations
is a compound radical^ as in the following examples :
(a''6) + 6 = (a"6)6,
[a'^by + 26 = (a'''6)"6»
(a'"6c) + 6 = (■a"'6c)6,
i^aHY" + 36 = (a*^6)'"63,
(a»-6o)" + 26 = (a*^6c)"6„
[a'^bcd) + 6 = (a»^6cd)6.
The group of elements (a"6) constitutes a compound monad radical
equivalent to one atom of hydrogen or chlorine. The group (a'"6)" is
a compound dyad radical, etc It is therefore evident that a polyad
element is essential to every compound radical ; in fact a compound
radical consists of one or nurre atoms of a polyad element in which one or
more bonds are unsatisfied; and it is either a monody dyad, triads etc.,
radical, a4ieoTding to the number of monad aioms required to satisfy its
active atomicity. Such a radical, when a monad, triad, or pentad, can-
not exist as a separate group : like hydrogen or nitrogen, when isolated,
it combines with itself, forming a duplex molecule. It is only by the
86 INORGANIC CHEMISTRT.
anion of two atoms or groups of atoms that the vacated bonds can in
these cases be satisfied.
From the above definition of a compound radical, it is evident that
an almost infinite number of such bodies must exist; for in the com-
pounds of every polyad element it is only necessary to vacate successive
lx)nds to create each time a new compound radical. Thus marsh-gas
CHf minus one atom of hydrogen gives the compound radical methyl
CHjj minus two atoms of hydrogen, it forms methylene (CH,)" ; and
by the abstraction of three hydrogen atoms it is transformed into the
triad radical formyl (CH)'"; but, except in a "few cases, it is not ad-
vantageous thus to incorporate, as it were, compound radicals, which,
instead of simplifying notation and nomenclature, would, if thus multi-
plied, only embarrass them. No compound radical, therefore, ought to
receive recognition as such, unless it can be shown to enter into the
composition of a lai^e number of compounds.
The following are the names, symbols, and formulae of the inorganic
compound radicals recognized in the notation of this volume :
Hydroxyl, . .
Hydrosulphyl, ,
Ammonium,
Ammonoxyl, .
Amidogen, • .
Molecular Sexnimolecular Semlmoleoular
formulee. formulffi. symbols.
(OH), OH Ho.
(SH)j SH Hs.
(NH,), NH, Am.
(ONH\ OXH, Amo.
(NH,), NH, Ad.
In addition to these, certain compounds which metals form with
oxygen are also regarded as compound radicals — for instance,
Molecular Semimolecular Semimolecular
formulae. formulae. eymbols.
Potassoxyl, . . (OK), OK Ko.
Zincoxyl, . . . (O^Zn) ^ Zn" Zno".
The essential character of these last compound radicals is that the
whole of the oxygen they contain is united with the metal by one bond
only of each oxygen atom, as seen in the following graphic formulse :
Hydroxyl,. — O— H
Potassoxyl, — ^O — K
Zincoxyl, _0— Zn— O—
The metal thus becomes linked to other elements by these dyad atoms
of oxygen. The functions of such compound radicals will be sufficiently
evident from the following examples of compounds into which they
enter, and in which their position is marked by dotted lines.
O -: :
Mi
Nitric acid,. . . . N-!-0 — H !
II I I
O ■'■ .i
COMPOUND RADICALS.
87
Potassic salphate, .
K-
• = O : ;
1 II ! I
_o-i-s-i-o-K i
MM i
:■ O [ ^
Baric nitrate, . .
o
II
N-i
II i
O i
-- i O
1 11
_0— Ba— O-i-N
i 11
' O
Zincic salphate, . .
O
K
ir
o
^V 1
\o/
It is not necessary to dignify all these metallic compound radicals
with names ; the chief point of importance about them is their abbrevi-
ated notation, in which the §mall letter o is attached to the symbol of
the metal, the atomicity of the radical being marked in the usual
manner. Although the small letter o in these symbols of combining
quantities has no more reference to the composition of the radical than
the d in the corresponding symbol of amidogen, yet it may usefully
remind the reader that oxygen is always a constituent of the compound
radicals so symbolized. It must be borne in mind that the number of
atomsof oxygen in any radical of this class depends upon its atomicity:
thus a monad contains only one atom of oxygen, a dyad two, and a
triad always three atoms of oxygen. The use of any but monad and
dyad metallic compound radicals is very rare.
It is also in some cases convenient to recognize as a radical the atomic
group which remains when all the hydroxyl is abstracted from an
oxyacidy as for instance :
Acid.
Xitrous acid, .
Xitric acid,
Sulphuric acid,
Phosphoric acid,
It is evident that the atomicity of these elements must be the same
as the basicity of the acids from which they are derived.
Atomic and Molecular Combination.
In all the cases of chemical combination already considered, a union
of atoms has been invariably contemplated. This atomic union is gen-
erally attended by the breaking up of previously existing molecules —
two such molecules, by the mutual exchange of their atomic constitu-
ents, producing two new and perfectly distinct molecules. Thus, when
chlorine unites with hydrogen to form hydrochloric acid, a molecule of
Acid radical.
. . NOHo
. . NO^Ho
. . SOjHo^
. . POH03
Nitrosyl, ....
Nitroxyl, ....
Sulphuryl, . . .
Phosphoryl, . . .
(NO)
(NO,)
(SO,)"
(PO)'"
88 INORGANIC CHEMISTRY.
chlorine and one of hydrogen yield up their oonBtituent atoms, forming
two molecules of hydrochloric acid,
CI, + H, = 2HC1.
In comparatively rare cases, two molecules combine to form only one
new molecule ; thus a molecule of carbonic oxide and one of chlorine
combine to form one melecule of carbonic oxydichloride or phosgene gas :
but the union is even here essentially atomic ; for after combination both
the oxygen and chlorine are directly united with the atom of carbon:
0"0 + CI, = 0»^OC1,.
CarboDic oxide. Chlorine. Phosgene gas.
Chemists are, however, compelled to admit an entirely different kind of
union, which not unfrequently occurs, and which in conformity with the
atomic hypothesis, may be appropriately termed molecular union or moU-
eular combination. In the formation of such compounds, no change takes
])lace in the active atomicity of any of the molecules. It is this kind of
combination which holds together salts and their water of crystalliza-
tion, as, for instance,
Sodic chloride crystallized at — 10° C, . . NaCl,20H,.
Sodic bromide crystallized below + 30° C, . . NaBr,20H,.
Sodic iodide crystallized below + 50° C, . . NaI,20H,.
Alum, . . ". S,03('AP"ArKo„240H,.
Numerous other instances of molecular combination might be adduced ;
but it is only necessary here to point out that such molecular unions
will be distinguished from atomic combinations by the use of the comma,
as in the above and following examples :
Tetramethylammonic tri-iodide, . . . NMeJ,!,.
Tetramethylammonic pentiodide, . . . NMe4l,2r,.
Tetramethylammonic lodo-dichloride, . . NMe4l,Clj.
In all cases molecular combination seems to beof a much more feeble
character than atomic union ; for, in the first place, such bodies are
generally decomposed with facility; and secondly, the properties of
their constituent molecules are markedly perceptible in the compounds.
Thus the above periodides of the organic bases greatly resemble iodine
in appearance.
CHAPTER X.
CLASSIFICATION OP ELEMENTS.
It has been already mentioned that the elements may be divided into
two great classes, the metals and the non-metals or metalloids. A
second division into positive and negative elements has also been ex-
plained. A third and still more important classification is founded
upon the atomicity of the elements. In the following cla&<^ified table,
all three methods are embodied, the names of the metalloids being
printed in heavy type, and those of the metals in common type, whilst
the names of the positive elements are printed in Roman characters,
CLASSIFICATION OP ELEMENTS.
89
and those of the negative in italics. In addition, the different classes
are also divided into sections, consisting of elements closely related in
their chemical characters.
a
o
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90 INORGANIC CHEMISTRY.
Oamficaiion of the Elements according to their Atomic Weights. — The
Periodic Law. — The idea of a possible connection between the atomic
weights of the elements and their properties was first sngrgested by the
observation that in many cases similar elements could be arranged in
groups of three, in which the atomic weight of the intermediate element
was approximately the arithmetical mean of the atomic weights of the
highcHt and lowest Examples of such groups, which were termed
" triads," are
P = 31, As = 75, Sb = 120 —
^l^i^ = 75.5.
CI = 35.5, Br = 80, I = 127 —
^'■' + ^^^ = 81.25.
Ca = 40, Sr = 87.6, Ba = 137 —
^n^ = 88.5.
been pro-
The most complete expression of these relations that has yet
posed is to be found in the ** periodic law of the elements/'
The fact that the properties of the elements vary |>eriodically with their
atomic weights was first shown by Newlands in 1864.* More complete
and systematic expressions of the same law were published a few years later
by Mendeleef and by Lothar Meyer. The most precise of these systems is
thatofMendeleef, which has lately attracted much attention on account
of the number of new facts which it has enabled its author to predict.
The following is a brief outline of the method followed by Mendeleef.
If all the elements whose atomic weights lie between 7 and 35.5 be
arranged in the arithmetical order of their atomic weights, thus :
Li = 7; Be =9.4;B= 11; C= 12; N = 14; 0 = 16; F= 19;
.Na=23;Mg=24;Al = 27.3;Si=28;P = 31;S=32;Cl = 35.5,
certain definite relations may be perceived. The character of the ele-
ments is here seen" to be subject to regular modification, so that, step by
* Newlands was the first to point ont that the elements, when arranged in the
arithmetical order of their atomic weights, exhibit a periodic recurrence of similar
properties*. He stated that each such period consists of neven elements, and that, with
the eighth element, properties resembling those of the first recur. To this relation he
gave the name of the Law of Octnres^ comparing the periods of recurrence with the oc-
taves of the musical scale, and the elements within the period with the notes included
in the octave. Newlands's system is therefore in all essential points identical with that
of Mendeleef, which was published in 1869; except that Newlands failed to recognize
the existence of the *' transitional elements" — Mendeleef 's eighth group (see table, p.
92) — which divide the other elements into groups of two octaves each.
The fact that Mendeleef 's table, published five years later than the first table given
by Newlands, is undoubtedly more perfect in its details, has led some chemists to as-
cribe the discovery of the periodic law to the former invest igator. This is manifestly
unjust. The credit of originating an idea is due solely to him who first formulates it,
and this is irrespective of any subsequent development which the idea may undergo at
the hands of others, provided that the central idea itself remains unaltered. No one,
for example, has ever suggested that the authorship of the modern atomic theory is to
be ascribed to Cannizzaro instead of to Dalton, because the rectification of the atomic
weights was the work of the former chemist.
_J
CLAJ58IFICATION OP ELEMENTS. 91
step, as the atomic weights vary, the characters of the elements also
vary, and by comparing the series of elements from Li to F with the
series from Na to CI, it is manifest that this variation is a periodic one,
the same changes of character which are met with in traversing the
first series, being again found in the second series: thus Li corresponds
to Na, Be to Mg, B to Al,* etc. The regularity of the change in trav-
ersing a period may be seen by comparing with each other the oxides
of one such series of elements, writing these so as to show the relative
quantities of oxygen with which the same number of atoms of the va-
rious elements combine, instead of employing the molecular formulse of
the oxides :
Na,0; MgrA; MO,; Si A; P20«; sA; ciAt
(MgO) (SiO,) (SO3)
Here the proportion of oxygen in the various oxides throughout the
period is as 1 : 2 : 8 : 4 : 5 : 6 : 7. At the same time there is a regu-
lar gradation from left to right from the most electropositive element,
through the various intermediate stages, to the most electronegative
element. This periodic recurrence of the same properties with the
gradual increase of the atomic weight has been formulated by Mende-
leef thus : The properties of the jelements are a periodic Junction of their
atomic weights.
Following out this principle, Mendeleef has tabulated the whole of
the elements on the same plan (see table, page 92).
The Roman numerals indicate the groups or families of similar ele-
ments, which are thus arranged in vertical columns ; the Arabic nu-
merals refer to the series or periods, which are arranged horizontally.
As regards the latter, it is to be noted that there are two kinds of pe-
riods— the one following the even Arabic numerals, the other the odd.
If we confine our attention to a single group, we find that the elements
of the even periods correspond with each other in their properties, and
that the element^ of the odd peri<x]s likewise correspond with each
other, but that there is less correspondence of the members of one of
these classes with those of the other. Thus, in Group II., the corre-
8|)onding elements of the even series are Be, Ca, Sr, and Ba ; of the odd
series, Mg, Zn, Cd, and Hg.
The series 2 and 3 are termed by Mendeleef " short periods "; the
remaining series are grouped together in pairs — thus, 4 and 5, 6 and 7,
8 and 9, etc. — the two series of such a pair together constituting a
"long period." That is to say, if we traverse the series 3 we find a
periodic repetition of the chemical characteristics already met with in
series 2; but in order to meet with a similar periodic change of char-
acteristics— €.^., in order to pass from a highly electropositive to a highly
electronegative element — it is necessary to traverse the entire double-
series 4 and 5, and again the double-series 6 and 7, and so on. The
full significance of this arrangement — at first sight, perhaps a somewhat
arbitrary one — will be shown further on.
* On this snpposition Al would have to be regarded as triadic. This would be in
hannony with the observed vapor-density of aluminic methide, A^CH,),, at 240^.
t Perchloric anh/dride is not known ; but the corresponding acid has been pre-
pared. •
92
INORGANIC CHEMI8TBY.
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CLASSIFICATION OF ELEMENTS. 93
In passing from the left to the right there is in every series, taking
each group in thai series in succession, a gradual increase in the quan-
tity of oxygen with which the elements can unite. The members of
the different groups taken in order exhibit a regular change (generally
an increase) of atomicity, odd and even atomicities alternating. Gronp
VIII. is anomalous. In this group there are always three elements
in each series, instead of, as in the other groups, only one element.
These elements of Group VIII. do not, when taken in any series in
the order of their atomic weights, exhibit the above alternation of odd
and even atomicity : they are all even ; but their atomicity decreases
with a rise of atomic weight. They are termed by Mendefeef " trans-
itional elements," and their place is between the even and the odd se-
ries of a long period. This transitional group will be referred to again
later on.
The grouping together of sodium, silver, and copper as similar ele-
ments is justified by the isomorphism of some of the cuprous and ar-
gentic compounds, and of someof the latter again with the corresponding
sodium compounds.
Mendeleef has employed this periodic law in the correction of doubt-
ful atomic weights, and in the prediction of undiscovered elements.
Thus, indium was formerly believed to be a dyad with the atomic
weight 76, and its oxide was therefore supposed to possess the formula
InO. With this atomic weight, it would take its place between arsenic
and selenium. But there is no vacant space for it in this part of the
table, and it would, moreover, have no analogy with the elements with
which it would have to be grouped. Mendeleef pointed out that by
assuming indie oxide to possess the formula In^O,, with an atomic
weight for the metal of 114, indium would take its place in series 7
between cadmium and tin, and as an analogue of aluminium. The cor-
rectness of this view has been demonstrated by the determination of
the specific heat of indium by Bunsen.
Again, chemists were uncertain whether uranium had the atomic
weight 60 or 120. Mendeleef showed that no element of either of
these atomic weights and of the properties of uranium would find a
fitting place in the table, but that by assigning to it the atomic weight
240 (238.5), it would take its place as an analogue of chromium, mo-
lybdenum, and tungsten. This change has been justified by the results
of the determination of the specific heat of uranium and by the vapor-
deosity of various uranium compounds.
Again, the determinations of the atomic weight of molydenum left
it uncertain whether this element possessed the atomic weight 92 or 96.
The former of these weights would place it before niobium, and in a
group of elements with which it presents no analogy. In order that it
might take its place in Group VI. as an analogue of chromium, its
atomic weight must be higher than 94, the atomic weight of niobium.
A careful determination basin fact shown that the atomic weight of
molybdenum is 95.5.
Again, tellurium was supposed to have the atomic weight 128. In
order that it might take its place in the same group as its chemical
analogues sulphur and -selenium, it was necessary that its atomic weight
94 INORGANIC CHEMISTRY.
should be lower than 127, the atomic weight of iodine. A recent de-
termination by improved methods has shown that the atomic weight of
tellurium is 125.
It will be noticed that in the foregoing table one element, osmiam,
has been placed in a position different fmm that indicated by its atomic
weight as at present determined. Osmium from its properties ought to
have an atomic weight lower than that of iridium, instead of higher
than that of gold. It remains to be seen whether experiment will, as
in the preceding cases, verify this prediction.
Mendeleef has shown that the properties, both chemical and physical,
of an element may be to a certain extent predicted from the properties
of what he terms its " atomic analogues." By this term he understands
not its chemical analogues, but the two elements which stand on either
side of it in the same series, together with the two elements which stand
above and below it in the same group. Thus As, Br, S, and Te are the
atomic analogues of Se.
It will be observed that there are in the table a number of gaps.
These correspond, according to Mendeleef, with elements which have
not yet been discovered. If such a gap is surrounded by the requisite
atomic analogues, it is possible to predict the properties of the unknown
element. Thus in the positions III. 4, III. 5, and IV. 6, Mendeleef
placed three unknown elements to which he gave the names ekaboroUj
ekaluminium, and ekasilicon — following a system of nomenclature which
he has devised for the designation of such unknown elements and which,
while referring these to known elements of the same group, distinguishes
them by prefixing the Sanscrit numerals eka, dvi, tri, etc., according to
their position in the group. Concerning ekaluminium, he states that
it has an atomic weight of about 68, and a specific gravity of about 6.0,
and that it forms a sesquioxide. These predictions were verified by
the discovery of gallium, which has an atomic weight of 68.8, a specific
gravity of 5.9, and forms an oxide of the formula Qa^O,. The new
metal scandium is possibly Mendeleefs ekaboron.
The above prediction of the specific gravity of ekaluminium (gallium)
is rendered possible by the fact that the physical as well as the chemical
properties of the elements are periodic functions of the atomic weight.
This may be illustrated by reference to the magnetic properties of
the elements. Faraday divided all substances into two classes : those
which are attracted by a magnet, or paramagnetic bodies, aud those
which are repelled by a magnet or diama^netie bodies. In the case of
the elements, the magnetism of the following has been determined :
Paramagnetic Elements,
K, C, Ti, Ce, N, O, Cr, iT, Mn, Fe, Co, Ni, Rh, Pd, Os, Ir, Pt.
Diam^gnetic Elements.
H, Na, Cu, Ag, Au, Zn, Cd, Hg, Tl, Si, Sn, Pb, P, As, Sb, Bi, S, Se,
CI, Br, I.
An inspection of these two classes does not reveal any apparent con-
nection between the chemical and the magnetic properties of the ele-
CLASSIFICATION OP ELEMENTS. 95
ments. Thus we find that elements, chemically so closely related as
potassium and sodium, oxygen and sulphur, nitrogen and phosphorus,
titanium and silicon, are separated in the two classes. Camelley has,
however, pointed out that the paramagnetic elements are, without ex-
ception, to be found in the even series of Mendeleef's table and the dia-
magnetic elements without exception in the odd series. Further, the
paramagnetic power of the members of a paramagnetic group of elements
(thus Fe, Co, Ni) diminishes, and the diamagnetic power of the mem-
bers of a diamagnetic group of elements (thus P, Sb, Bi, or H, Cu, Ag,
Au) increases, with increasing atomic weight.
The fact that the physical properties of the element* are a periodic
function of their atomic weights is, however, most strikingly shown by
the curve given in the annexed diagram. This curve, which is in
reality a graphic expression of the periodic law, was first constructed by
Lothar Meyer. It is given here as supplementing in a remarkable
manner Mendeleef s table.
In this curve the abscissse represent the atomic weights, and the
ordinates the atomic volumes of the various elements in the solid state.'*'
The curve is therefore primarily a graphic representation of the varia-
tion of the atomic volume with the atomic weight. But a brief inspec-
tion shows that it is much more than this.
In the first place then, as regards the atomic volume, the curve shows
in the plainest manner that this varies periodically with the atomic
weight: at one point it reaches a maximum, then gradually decreases
with increasing atomic weight till it falls to a minimum, again rising to
a maximum, and so on. Each of these compound periods of decrease
and increase corresponds with one hollow of the wave of the curve ex-
tending from crest to crest. A comparison of this curve with Mende-
leefs table is highly instructive, especially when we consider that the
two were constructed quite independently of each other. In the curve
the periods of change of atomic volume — the hollows — are distinguished
by Roman numerals. Periods II. and III. of the curve correspond with
MendeleePs two " short periods," series 2 and 3 of the table. The large
hollows of the curve, IV., V., etc., correspond with Mendeleef's " long
periods:" thus Perio<l IV. of the curve is the " long period " made up
of series 4 and 6 of the table ; Period V. is the " long period " made up
of series 6 and 7 of the table, and so on. (The latter part of the curve
has not been finished for want of data.) The alkali metals with which
Mendeleers periods commence are always found at the maxima of the
curve. Mendeleef's " transitional elements " of Group VIII., the metals
which lie between the even and odd series of a ** long period," are always
found at the minima of the large hollows. Osmium cannot, Avith its
* TJie atomic volumes of the elements are the relative volumes occupied by atomic
qaantities, i.e., quantities taken in the proportion of the atomic weights. These atomic
vohimee may be found by dividing the atomic weights of the elements by their specific
xnvities (see following chapter). In the diagram, wherever the elements are not
Known in the solid state, the hypothetical course of the curve is represented by a dotted
line. As regards the rather irregular course of the curve in some parts, it is to be noted
that the specific gravities of the elements have not always been determined under
strictly comparable conditions. Thus the specific gravitv of potassium is determined
a few d^rees below its fusing-point ; that of platinum al>out 2000° below the fusing-
point
96 IKOBGAKIC CHEMISTRY.
present atomic weight, be made to fit into this curve, any more til
into MendeleePs table.
Various other periodic relations between the atomic weights and j
physical properties of the elements have been indicated on the diagij
by appending to each part of the curve a list of the physical properl
of the elements to which that part refers. Thus, elements possesaj
the same physical properties are to be found in corresponding pai
the curve. It is to be noted, however, that the alternation of " el
positive— electronegative," which occurs only once in Period II.
only once in Period III. of the curve, occurs twice in Period IV.
twice in Period V. This is in harmony with the fact already refei
to that Periods II. and III. correspond each with one series of Mei
leefs table ; Periods IV. and V. each with two series.
It is quite inconceivable that the remarkable relationships expreJ
by the periodic law should be a work of chance.
No explanation of the periodic law has yet been offered. At pre
it is an empirical law, established by careful ex[Kjriment,and comp
son. It stands in the same relation to chemistry as did the law
Kepler to astronomy before the time of Newton. Its explanation
in all probability constitute the chemical theory of the future.
CHAPTER XI.
RELATIONS BETWEEN CHEMICAL COMPOSITION AND SPECIF
GRAVITY. ATOMIC VOLUME.
The relative volumes which atomic or molecular quantities (qui
ties taken in the proportion of the atomic or molecular weights) of
stances occupy, may be found by dividing the atomic or mole(
weights of these substances by their specific gravities. The quot
thus obtained are termed atomic volumes and molecular volumes res
ively.
It must not be supposed that these quotients express the reli
volumes occupied by the atoms or molecules. In the gaseous state
molecules are separated from each other by distances which are i
mously great compared with the diameters of the molecules themse
In the solid and liquid states, the atomic volumes could only repn
the relative volumes of the atoms, provided that the spaces betweei
atoms were in every case proportional to the size of the atoms-
assumption for which there is not the slightest ground. The aU
volumes, therefore, represent the relative volumes of the atoms, plu^
relative volumes of their interstitial spaces.
The molecular volumes of gases have already been treatec
(p. 54), and may be dismissed in a few words. As the spe
gravities or vapor-densities of gaseous bodies are proportiona
their molecular weights, the quotient j — ^^— will in
® ' ^ vapor-density
RELATIONS BETWEEN CHEMICAL COMPOSITION, ETC.
97
cases possess the same value. The value of this quotient is either
28.9 or 2, according as the vapor-density is referred to air or to
hydrogen (see p. 63).
The laws which govern the relations between composition and specific
gravity are less simple in the case of solids and liquids; but here also
very striking regularities are manifested.
As the specific gravity of a solid or liquid denotes the weight jn
grams of one cubic centimetre of the substance, so the atomic or mole-
cular volume, if the atomic or molecular weight be expressed in grams,
will represent cubic centimetres. The atomic weight of sulphur is 32,
its specific gravity 2. The atomic weight of lead is 206.5, its specific
gravity 11.37. The atomic volume of sulphur is therefore 16, that
of lead 18.2. In grams and cubic centimetres this may be expressed
as follows : If 2 grams of sulphur occupy the volume of I c.c, 32.grams
will occupy 16 c.c. If 11.37 grams of lead occupy the volume of 1
c.c, 206.5 grams will occupy 18.2 c.c.
Among the elements, the various members of an isomorphous group
frequently exhibit approximate equality of atomic volume.
Iron, . . .
Cobalt, . .
Copper, . .
Manganese,
Nickel, . .
Atomic
weight.
56
58.6
63.2
55
58.6
Specific
gravity.
7.79
8.60
8.95
8.00
8.90
Atomic
volume.
7.2
6.8
7.1
6.9
6.6
Again:
Tridiitro,
Palladium,
Platinum,
Rhodium,
192.5
105.7
194.4
104
22.38
11.40
21.53
12.10
8.6
9.2
9.0
8.6
The members of an isomorphous group of compounds generally have
approximately the same equivalent volume. In the group of the spi-
nelles, which crystallize iu forms of the regular system, these relations
are as follows :
Molecular
weight.
Specific
gravity.
Molecular
volume.
MpO,AIA
Zn(),AI,0,
MnUAA
ZuO,Cr,()„ * .
ZnO,Fe,Oj, .
FeO,Fe,0,
142.4
183.3
224
233.3
241.3
232
3.45
4.58
4.87
5.31
5.13
5.09
41.3
40.0
46.0
43.9
47.0
45.6
98 INORGANIC CHEMISTBT.
The subject of atomic and equivalent volumes of solids has been in-
vestigated by H. Kopp, SchroJer, and others.
The molecular volumes of liquids, when compared at the same tem-
perature, display no regularities. If, however, these volumes be deter-
mined at temperatures at which the tensions of the vapors of the liquids
are equal, that is to say, at temperatures at which the energy of the
molecules which fly off from the surface of each liquid is equal, and at
which temperatures consequently the liquids are in the same condition
as regards the weakening of the force of cohesion, important laws be-
come manifest. Under such conditions, it seems that each element has
one or more fixed atomic volumes, and that the molecular volume of a
compound in the liquid state is the sum of the atomic volumes of its
elements. As the vapor-tensions of most liquids have not been deter-
mined for a variety of temperatures, it is usual to compare the mole-
cular volumes at the boiling-points of the liquids, at which tempera-
tures the tensions of their vapors are equal to the normal atmo^rpheric
pressure (see p. 120).
These laws may be deduced and expressed as follows:
1. A diflerence of n.CH, in the formula of liquid compounds corre-
sponds to a difference of n.22 in the molecular volume. Thus, methylic
formate (C^H^O,), methylic acetate (C^H^O,), ethylic acetate (CJIgO,),
and methylic bntyrate (CjHjoO,), whose formulae differ by OH,, differ
in molecular volume by nearly 22, (For a comparison of the experi-
mental with the calculated results, see table, p. 101.)
2. Isomeric liquids, belonging to the same chemical ty\ye, such as
acids and ethereal salts, alcohols and ethers, ketones and aldehydes,
have the same molecular volume. Thus, the molecular volumes of
propionic acid, ethylic formate and methylic acetate, all of which have
the formula CgH,0„ closely approximate to 86.
3. The substitution of one atom of oxygen for two of hydrogen causes
a slight increase of molecular volume. The molecular volume of alco-
hol (C.UJO) is between 61.8 and 62.5, that of acetic acid (CjH.O,) lies
between 63.5 and 63.8. Cy mene (CioH,^) and cuminaldehyde (t\<,H„0)
differ similarly in their molecular volumes.
4. In two liquids belonging to the same chemical type, the substitu-
tion of one atom of carbon for two atoms of hydrogen produces no
change of molecular volume. This may be seen in the case of ethylic
benzoate (C^Hj^Oj) and ethylic valerate (Cyllj^Oj); benzaldchyde
(C,HgO) and valeraldehyde (CjHioO); cymene (CiqHiJ and butvl
(c.ii.,).
As the addition of CH, to the formula of a compound produces an
increase of 22 in the equivalent volume (Law 1), this number may be
supposed to represent the equivalent volume of CH,. And since (Law
4) the exchange of C for Hj causes no change of molecular volume, the
atomic volume of C may be taken to be equal to that of H,. Hence,
22
the atomic volume of C is equal to ^- = 11, and that of H, is also equal
to 11, or that of H = 5.5. From the increase in molecular volume
which the substitution of O for H, causes, the atomic volume of O may
be calculated to be equal to 12.2. In this case when O is substituted
BELATIONS BETWEEN CHEMICAL COMPOSITION, ETC. 99
for H„ both its bonds are attached to the same atom of carbon, as for
example when alcohol is converted into acetic acid.
H H HO
H— C— C— O— H H— C— C— O— H
Alcohol. Acetic acid.
It will be convenient, in discussing the subject of atomic volumes, to
represent oxygen thus attached by the ordinary symbol O, whereas
oxygen which serves to unite two elements or groups of elements, as in
the case of hydroxylic oxygen, or of oxygen in ethylic oxide, will be
distinguished by the symbol (J^. It is found that the atomic volume of
© is different from that of O. The value of the former may be de-
duced froDQ the molecular volume of water.
Molecular volume of ©H2 = 18.8
11
7.8
Atomic
a
H,
= 1:
u
u
©
From these four atomic volumes,
Atomic volume of C
=r
11
t(
«
H
=
5.5
((
C(
0
=
12.2
li
a
©
=
7.8
the molecular volumes of compounds containing only these* four ele-
ments may be calculated. The numbers so deduced approximate very
closely to those obtained by experiment. It is evident that the value
to be assigned to the atomic volume of oxygen will depend upon the
constitution of the compound, and that, conversely, the molecular vol-
ume of a compound containing oxygen will afford a means of ascer-
taining the part which this element plays in its constitution. A few
examples will suffice.
The graphic formula of acetone is
H H
H— C— C— C— H.
1 II 1
H 0 H
From this formula follows :
Atomic volume of C, =
H, =
" " 0 =
33
33
12.2
Molecular volume of acetone = 78.2
100 INORGANIC CHEMISTRY.
The molecular volume of acetone as determined by experiment is
between 77.3 and 77.6.
The graphic formula of alcohol has been given on p. 99. The
molecular volume would be calculated thus :
Atomic volume of C, = 22
H, = 33
© = 7.8
Molecular volume of alcohol = 62.8
The observed volume is between 61.8 and 62.5.
The graphic formula of acetic acid has been given on p. 99. Its
molecular volume would be as follows:
Atomic volume of C,
= 22
H«
= 22
« " o
= 12.2
©
= 7.8
Molecular volume of acetic acid = 64.0
The experimental value is between 63.5 and 63.8.
The subject of the molecular volumes of liquids has been investigated
chiefly by H. Kopp, to whom the enunciation of the above laws is due.*
The following table contains a list of his determinations of molecular
volumes at the boiling-point for a number of liquids into the composi-
tion of which only carbon, hydrogen, and oxygen enter. The third
column contains the temperatures at which the determinations were
made.
* Recently the subject has been studied bj Thorpe, Ramsay, and others.
RELATIONS BETWEEN CHEMICAL COMt'OSmOS, ETC. IDl
Molecular Volumes of Liquids containing Carbon, Hydrogen, and
Oxygen.
Molecular volume.
Substance.
Formula.
Temperaiure.
Observed.
Calculated.
Benzene, ....
QH,
80° C.
176° F.
96 0— 99.7
99.0
Cymene, ....
Cj.Il,,
175
347
183.5—185.2
187.0
Naphthalene, . .
Aldehyde, . . .
C,J!.
218
424
149.2
154.0
C.,H,n
21
70
56.0— 56.9
56.2
Valeraldehyde, . .
c;i",.*>
101
114
117.3—120.3
122 2
Benzaldehyde, . .
CJ].<>
179
354
118.4
122.2
Ciiminaldehyde, .
Ci.M]'>
236
457
189.2
188.2
Butyl,
C,!!,/
108
226
184.5—186.6
1870
Acetone, ....
CM^y
.56
133
77.3— 77.6
78.2
Water
©ii.
100
212
18.8
18.8
Methylic alcohol, .
CH,®
59
138
41.9- 42.2
40.8
Eihylic
C,He®
78
172
61.8— 62.5
62.8
Amvlic "
CeHe©
13.5
275
123.6—124.4
128.8
Phenol
104
381
103.6-104.0
106.8
Benzylic alcohol, .
c\\w
213
415
123.7
128.8
Formic acid, . .
CJI,u©
99
210
40.9- 41.8
42.0
Acetic " . .
G,n^<»©
118
244
63.5— 63.8
64.0
Propionic " . .
c,n,()©
137
279
85.4
86.0
Bntvric *' . .
C,[I,C)©
156
313
106.4-107.8
108.0
Valeric " . .
C, II 1,1 J©
175
347
130.2—131.2
130.0
Benzoic " . .
CJr,n(r>
253
487
126.9
130.0
Ethylic oxide, . .
C,11,„0
34
93
105.6—106.4
106.8
Acetic anhydride, .
C.HeOj®
138
280
109.9—110.1
109.2
Methylic formate, .
C,H,0®
36
97
63.4
64.0
Methylic acetate, .
CsH.O®
55
131
83.7— 85.8
86 0
Ethyiic formate, .
CsHgO©
65
131
84.9— 85.7
86.0
Ethylic acetate,
C.HgO®
74
165
107.4—107.8
108 0
Methylic butyrate, .
C5H10O©
93
199
125.7—127.3
130.0
Ethyiic propionate,
CsH^oO®
93
199
1258
130.0
Methylic valerate, .
C«Hi,0®
112
234
148.7—149 6
152.0
Ethylic butyrate, .
CeFi„0®
112
234
149.1—149.4
152.0
Bntylic acetate, . .
CeH,,0®
112
234
149.3
152.0
A my lie formate, .
C.H,,0©
112
234
149.4—150 2
1520
Ethylic valerate, .
C,H,,0®
131
268
173.5-173.6
174.0
Amylic acetate, . .
CHj.O©
131
268
173.3—175.5
174.0
Amvlic valerate, .
C^nHj,/*©
188
370
244.1
240.0
Meihvlic benzoate.
C,tl/i<»>
190
374
148.5—150.3
1520
Ethvfic
209
408
172.4—174.8
174 0
AmVlic "
266
511
247.7
240.0
Ethylic cinnamate,
c,;nj,(^©
260
500
211.3
207.0
Methylic salicylate,
L\H^im,
223
433
156.2-157.0
159.8
Ethylic carbonate.
CtiK^m,
126
259
138.8-139.4
137.8
Methvlic oxalate, .
CJl^OM,
162
324
116.3
117.0
Ethyiic
c^nj\i?^.
186
367
166.8-167.1
161.0
Ethylic succinate, .
c,H,,ixe:
217
423
209.0
205.0
In like manner, from the molecular volumes of the liquid chlorides,
bromides, and iodides, the atomic volume of CI has been determined to
be equal to 22.8, that of Br = 27.8, and that of I = 37.5.
Elements of varying atomicity like nitrogen and sulphur seem to
follow some less simple law. It is possible that the atomic volumes of
these elements may vary in some way with their atomicity; but the pre-
cise nature of this variation has not been a.scertained. The subject requires
thorough investigation by the light of modern constitutional formula.
lOa-. : I' : /i ••• • • ••• INORGANIC CHEMISTRY.
CHAPTER XII.
CHEMICAL AFFINITY.
Chemical affinity has been referred to at some length in the opening
pages of this introduction. It may be measured as regards its extent
and as regards its intensify, A measure of the relative extent of the
chemical affinity of two or more elements for some other element is af-
forded by the number of atoms of this element with which each can
combine. Extent of affinity is thus directly connected with atomicity.
Relative intensity of affinity of two or more elements for any given ele-
ment refers to the resistance which their compounds with this element
oflPer to decomposition. The measure of this intensity is the quantity
of heat evolved in combination or required for decomposition.
Extent and intensity of affinity are quite independent of each other.
Thus copper and mercury in the compounds CuO and HgO have the
same extent of affinity for oxygen ; but since mercuric oxide breaks up
at a relatively low temperature into its constituents, whereas cupric
oxide does not undergo decomposition until a temperature above 1000° C.
has been reached, and then yields up only a portion of its oxygen, the
intensity of affinity for oxygen is much greater in the case of copper.
Again, the extent of affinity of carbon towards hydrogen is four times
as great as that of chlorine. This may be seen in raethylic hydride
(OH^land hydrochloric acid (HCl). But whereas carbon and hydrogen
cannot be made to combine directly at all, chlorine and hydrogen unite
with evolution of great heat. Here the element of greatest extent of
affinity has least intensity of affinity. One atom of phcw^phorus can
unite with three atoms of chlorine, giving off much heat, and forming a
compound which may be distilled without decomposition ; one atom of
silver can unite with only one atom of chlorine, and the resulting com-
pound is decomposed by the action of daylight. Here extent and
intensity of affinity go together.*
Modes op Chemical Action. — Matter undergoes chemical change
in five different ways, viz. :
1st. By the direct combination of elements or compounds with each
other.
2d. By the displacement of one element or group of elements in a
body by another element or group of elements.
* The above can be regarded only as an approximately correct statement. In nearly
every so-called direct combination of elements there is a preliminary decomposition of
elementary molecules :
H, + Cl2=2HCl.
Here the affinity of hydrogen for chlorine is the force which strives to bring about the
reaction, and in this it is opposed by the two affinities of hydrogen for hydrogen, and
of chlorine for chlorine, which have to be overcome before the reaction can occur.
Thus, the apparently lower affinity of carbon for hydrogen may in reality consist in a
higher affinity of carbon for carbon — the affinity of hydrogen for hydrogen remaining,
of course, the same in both reactions.
For the same reason the heat of combination is a complex quantity, and cannot be
regarded a^ an infaUibU measure of the intensity of affinity (see Thermochemistry).
CHEMICAL AFFIXn'Y. 103
3d. By a mntual exchange of elements or groups of elements in two
or more bodies.
4th. By the rearrangement of the elements or groups of elements
already contained in a body.
5th. By the resolution of a compound into its elements, or into two
or more less complex compounds.
Illustrations of these five modes of chemical action have already been
given (p. 76).
Combination. — The part of this subject which refers to the fixed
proportions in which the elements combine, has been fully treated of
under Lains of Combination (Chap. IV.). But not only are the pro-
portions by weight in which every combination takes place perfectly
definite, but the amount of heat liberated or absorbed in each combi-
nation is also a fixed quantity (see-Hea^ of Chemical Combination, Chfip.
XV.).
Decomposition. — The forces which accomplish the resolution of a
compound, either into simpler compounds, or into its elements, have
been referred to on pp. 36 and 49. The chief of these forces are heat and
electricity. The action of heat has frequently been described in the
course of this introduction.
In the decomposition of compounds by heat two cases may be distin-
guished, according as the products of decomposition have, or have not,
a tendency to re-combine and form the original compound. Decompo-
sition in which this regenerative tendency exists is known as dissocia-'
tion. The phenomena of dissociation have been very carefully studied, and,
in regard to these, definite laws have been deduced ; whereas in the case
of the more complex phenomena of ordinary decomposition by heat
general principles have yet to be discovered.
Decomposition by means of the electric current is termed dectrolysisy
and the compound which is thus decomposed is termed an dectrolyt^.
The electrolyte must be in the liquid condition^-either in solution or in
a state of fusion. The current from a voltaic battery, when passed
through the electrolyte, decomposes it into two constituents known as
ions. The terminals of the battery, which are immersed in the elec-
trolyte and on the surfaces of which the separation of the ions occurs,
are termed electrodes. The material of the electrodes may vary accord-
ing to circumstances, but plates of platinum are generally employed in
the case of solutions.
Dissociation, — Examples of dissociation have already been given (see
Apparent Exceptions to Avogadro's Law, p. 63). Further examples of
dissociable compounds are — ^the aquates of some salts, which by heating
give off their water of crystallization ; and the carbonates, most of which
at a suflSciently elevated temperature evolve carbonic anhydride. A
very important law of dissociation is, that the volatile products given
off by a substance undergoing dissociation have a constant tension for
each temperature. This tension corresponds exactly in character to the
tension of the vapor of a liquid, and its amount may be measure<l in the
same way (see Chap. XVII.). The tension of dissociation depends en-
tirely on the temperature, being higher for higher temperatures; and
is quite independent both of the space filled by the volatile products
104 INOUGANIC CHEMISTRY.
and of the quantity of substance which has already undergone decom-
position. Thus Debray {Compt. Rend., 64, 603) has shown that the
tension of dissociation of calcic cartxmate is not altered by the addition
of an excess of quicklime — the solid product of decomposition.
Decx)m position may also be effected by means of the electric spark,
which may be applied either in the form of the voltaic arc or as the
induction spark. In both cases the electric discharge acts solely by Us
heating effect, and its action must therefore not be confounded with
electroly^i8. It differs from other sources of heat in being at the same
time local and more intense. If a series of induction sparks be passed
through carbonic anhydride, those molecules which lie in the path of
the s[>ark are broken up by the heat into carbonic oxide and oxygen.
The moment the molecules of the two latter gases pass beyond the
immediate sphere of the spark, they reach a relatively cold region,
the temperature of which lies far below their temperature of combina-
tion, so that they can continue to exist in the free state.
If, in the above experiment, the proportion of decomposed car-
bonic anhydride be allowed to pass beyond a certain limit, re-combina-
tion of the oxygen and carbonic oxide will take place with explosion.
This occurs as soon as a sufficient number of molecules of the two latter
gases are present to propagate the heat of combination through the
body of the gas. This propagation is impossible as long as their
molecules are separated by a large number of indifferent molecules of
carbonic anhydride.
Elecirolysis, — The following are the laws of electrolysis :
1. The liquid condition is necessary to electrolysis.
2. Electrolytes must be compounds and conductors of the electric
current. These compounds generally consist of a conductor and a
non-conductor of electricity.
3. Compounds which suffer electrolysis when dissolved in water do
60 also when fused.
4. The electrolyte is resolved into two constituents, which, impelled
in op|K)site directions, are eliminated at the opposing surfaces of the
two electrodes, and never in the intervening liquid.
6. Oxygen, chlorine, bromine, iodine, and acids appear at the positive
electrode, and are, therefore, electro-negative; whilst hydrogen, metals,
and alkalies are evolved at the negative electrode, and are, therefore,
electro- positive.
6. The quantity of electricity which passes through the electrolyte
is always directly proportional to the quantity of the electrolyte which
is decomposed.
7. All compound molecules possessing the same active atomicity to
be overcome, require, if decomposable, the same quantity of electricity
to decompose them. Therefore, if the same electric current be passed
through a number of metallic solutions in succeasion, the metails will
be reiUiced in the ratio of their atomic weights divided by their active
atomicities.
8. The quantity of electricity which a compound molecule requires
to decom{X)se it, is equal to the quantity which that molecule evolves
when it is formed in the generating cell of the battery.
CHEMICAL AFFINITY.
105
9. The quantity of electricity evolved by the union of two or more
bonds, is capable of effecting the disruption of the same number of
bonds in any compound susceptible of electrolysis.
The following is a list of weights of various chemical compounds
requiring for their decomposition equal quantities of electricity:
Water,
iiO^'H,)
9.0 grams.
Hydrochloric acid, .
HCl
36.5 **
Argentic chloride, .
AkCI
143.2 "
Cupric chloride, . . .
}(0/^Cl,)
i(^Cu%CJ,)
67.1 "
Cuprous chloride. .
98.7 "
Plumbic chloride, .
KPb^^ci,)
138.7 "
Antimonions chloride,
j(Sb''^Cl,)
76.5 "
Plumbic iodide, . .
i(pb^a,)
230.2 "
Plumbic acetate, . .
i(Pb^'Aoj)
162.2 "
Ciipric sulphate, . .
79 6 "
Zincic sulphate, . .
}(SO,Zn^0
80.6 "
Stannous chloride, .
i(Sn^'Cl,)
94 5 "
Ferrous chloride,
i(Fe^^Cl,)
i(^Fe^^%a,)
63.5 "
Ferric chloride, ....
54.2 "
Thus if the electric current were passed through argentic chloride,
cupric chloride, and cuprous chloride, included in the same circuit; by
the time 148.2 grams of argentic chloride had been decomposed, the
quantities of cupric and cuprous chlorides which had undergone decom-
position would be 67.1 grams and 98.7 grams respectively. The weight
of silver deposited from the first salt would be 107.7 grams; that of
copper from the other two 31.6 grams and 63.2 grams, the quantity
being in every case in the proportion of the atomic weight of the metal,
divided by its active atomicity.
What is termed Beamidary action in electrolysis takes place when the
primary products of decomposition exert a chemical action, either on
the solvent, or on other substances which are present, or on the elec-
trolyte itself. Thus when a solution of sodic chloride is electrolyzed,
the salt is broken up into sodium and chlorine. The sodium, however,
does not make its appearance as such, but decomposes the water with
evolution of hydrogen and formation of sodic hydrate :
Na^ + 2OH2
Water.
= H,
+ 20NaH.
Sodic hydrate.
Hydrogen and chlorine are thus obtained in the electrolysis of a solu-
tion of sodic chloride, but the hydrogen is a secondary product. Aj^ain,
if a mixed solution of hydrochloric and hydriodic acids is electrolyzed,
no chlorine is evolved, since chlorine instantaneously liberatas iodine
from the hydriodic acid, regenerating? hydrochloric acid. Again, if the
positive electrode consists of an oxidizable metal, the electronegative
element or gn>up will combine with it. Thus, if acidulated water be
electrolyzed with copper as the positive electrode the copper will go into
solution, and form a copper salt with the acid.
The electrolysis of sulphuric acid and plumbic sulphate has of late
106 INORGANIC CHEMISTRY.
acquired great importance in connection with secondary batteries or
accumulators as an economic means of storing: energy. Various forms
of storage battery have been suggested, but all are modifications of the
original invention of Plants. They consist essentially of plates com-
posed of or coated with plumbic sulphate, these plates being arranged
as in primary batteries and immersed in dilute sulphuric acid.
When an electric current, either from a primary battery or a dynamo-
electric machine, is passed through the cells of a secondary battery, em-
ploying the plates of plumbic sulphate as electrodes, the intervening
hexa basic sulphuric acid is electrolyzed according to the following
equation :
BHo, = SO3 + 30 + SU^
On + plate. On — plate.
The sulphuric anhydride thus liberated is immediately reconverted
into hexabasic sulphuric acid :
SO3 + 30Hj = SHo,.
The nascent oxygen in contact with the plumbic sulphate on the
positive plate converts the lead salt into plumbic peroxide (PbO,),
liberating sulphuric anhydride, which in contact with water regenerates
hexabasic sulphuric acid as just described.
The nascent hydrogen on the negative plate converts the plumbic
sulphate into lead and hexabasic sulphuric acid :
. SO^Pbo'' + H, + 20H, = Pb + BHo,.
Plumbic Hexabasic
sulphate. sulphuric acid.
Under the influence of an electric current, therefore, the opposing
plates of the secondary battery become coated, the one with plumbic
peroxide, and the other with metallic lead, the latter being in a spongy
state; and they are in a highly electro-polar condition. On joining
them by a conductor, a powerful electric current, with an electromotive
force of about 2.4 volts for each cell, flows through the conductor from
the plate coated with })eroxide of lead to that coated with spongy lead,
whilst within the cell the current passes through the dilute sulphuric
acid in the opposite direction, viz., from lead to peroxide of lead, de-
composing the acid as in charging. As, however, the current now
flows in a direction opposite to that during charging, the ions are
liberated on the opposite plates. On the positive plate, which was
formerly the negative electrode, the chemical change is as follows :
PbO^ + H, = PbO + OHy
Plumbic Plumbic
peroxide. oxide.
The plumbic oxide, which is thus formed in contact with sulphuric
acid, is converted into plumbic sulphate.
On the negative plate, which was the positive electrode, the follow-
ing action takes place :
CHEMICAL AFFINiry. 107
Pb + O + BHo, = SOjPbo" + 30H^
Hezabasic Plumbic
sulphuric acid. sulphate.
During the discharge, therefore, both plates return to their original
condition.
Instead of discharging the plates imraediatelv, however, the energy
invested in them may, with but inconsiderable loss, be allowed to re-
main stored for weeks, or even months, ready at any moment to yield
a powerful electric current available for the production of light, heat,
or mechanical power.
Electrochemical Eguivalents. — For some time after the revival of the
atomic theory in its chemical form by Dalton, chemists were at a loss
which of several possible atomic weights of an element to accept as the
true one. The laws of vapor-density, of specific heat, of isomorphism,
were enunciated not very long after ; but as their significance was not
generally perceived, their application as a means of checking the atomic
weights was out of the question. In the midst of the uncertainty which
prevailed, the law of electrolysis as stated by Faraday was eagerly wel-
comed. According to this law the quantities of various electrolytes
decomposable by the same current are chemically equivalent, and the
quantities of the several elements eliminated in such decompositions are
also chemically equivalent. On this principle chemists constructed
tables of equivalents of the elements, representing the relative weights
which are eliminated in electrolysis, that of hydrogen being taken as
unity. Such equivalents would be, for example:
H
— —
1
0
—
8
CI
=
35.5
8
=
16
Pb
etc.
103.25
This mode of procedure was thus far strictly legitimate, inasmuch as
the above weights can replace each other in chemical combination, and
are therefore equivalent. But most chemists went further than this,
and assumed that these equivalents were identical with the atomic
weights of the elements. By this means the significance of the above-
mentioned three important laws was effectually obscured, and a true
chemical classification was for many years rendered impossible.
Furthermore, the system of equivalents was not logically carried out.
The electrolytic equivalent of antimony is 40 ; but instead of this the
number 120, its present atomic weight, was adopted. The same hap-
pened with several other elements.
Another objection to this system is that the equivalent of an element
does not, like its atomic weight, represent a constant quantity, but
varies with the active atomicity. This may be seen in the case of cop-
per in its cuprous and cupric salts.
A knowledge of the so-called equivalent notation is necessary for the
study of many important works on chemistry in which it is employed.
108 INORGANIC CHEMISTRY.
The old equivalent formuire may be converted into modern atoofiic
formula), either by doubling the number of the perissad, or by halving
that of the artiad atoms (see p. 79). Thus :
Old so-called equiya- Atomic
lent formula. formula.
Water, HO Mfi
Sulphuric acid, HSO^ H^SO,
Nitric acid, HNO^ HNO,
Ferric chloride, Fefil^ FegCI^
In modern works equivalent formulae, when quoted^ are generally
written as above, in italics.
The fact that a single atom of one element may be equivalent to two
or more atoms of another, sufficiently explains the discrepancies between
atomic and equivalent proportions noticed in treating of the law of
equivalent proportions (see p. 47).
CHAPTER XIII.
CHEMICAL HOMOGENEITY.
A CHEMICALLY homogencous substance is one in which all the mole-
cules are exactly alike. It is evident from this definition that such a
substance will exhibit constant composition : if it is a simple body, it
will yield on analysis no other body; if it is a compound, it will con-
tain the same ingredients in unvarying proportion. But in the case of
compounds, analysis alone cannot furnish complete evidence of the
homogeneous nature of a substance : for example, it is plain that a mix-
ture of molecular proportions of manganous oxide (MnO) and manganic
peroxide (MnOj), would yield analytical results corresponding to man-*
ganic oxide (MlljOj). Hence, other means of identification are necessary,
and these are frequently to be found in the physical properties of the
substance.
Thus, all substances, in whatever physical state they exist — gaseous,
liquid, or solid — possess a definite specific gravity at a given temper-
ature. The specific gravities of the more important chemically homo-
geneous substances have been determined, and it is thus frequently
possible to identify a substance, as it is not probable that a mixture
accidentally possessing a percentage composition the same as that of a
true chemical compound, would also have the same specific gravity.
This characteristic is least certain in the case of solids, where a slight
alteration in physical condition, such as that produced in metals by
hammering, is suflScient to cause a change in the specific gravity. Such
variations, however, occur within narrow limits.
The number of the characteristics available for establishing the chem-
ical homogeneity of substances varies with the complexity of the phys-
CHEMICAL HOMOGENEITY. 109
ical state, being greatest in the case of solids, and smallest in the case
of liquids.
Gases. — A mixture of equal volumes of raethylic hydride (CH^) and
propylic hydride (CjHg) would yield not only the same analytical re-
sults asethylic hydride (CjHe), but would also possess the same specific
gravity. In this case the best method of determining whether the gas
is single or a mixture, is to submit it to diffusion. For this purpose,
it is transferred to a tube over mercury, closed at the upper extremity
by a porous diaphragm (graphite or gypsum). By the law of diffusion
iq.v.) the lighter molecules will pass through the diaphragm more rap-
idly than the heavier molecules. If, therefore, in the above case, on
examining the residual gas, the proportions of carbon and hydrogen be
found to have changed, it may be concluded that the original gas was a
mixture ; if these proportions remain the same, then either the gas is
single or it is a mixture in which each gas is present in the ratio of its
coefficient of diffusion, a case which must necessarily be of very rare
occurrence. Sometimes the gas is submitted to the action of various
absorbents — caustic potash, potassic pyrogallate, fuming sulphuric
acid. If part be absorbed by any of these reagents, whilst part remains
unacted upon, it is at once proved that the gas is a mixture.
Liquids, — When a liquid can be distilled without decomposition, its
boiling-point affords one of the best tests of its homogeneity. Every
chemical compound which is capable of volatilizing without decompo-
sition, has, at a giveft barometric pressure, a fixed boiling-point, at
which it must distil from the first to the last drop. As a rule, a mix-
ture of two liquids of different boiling-points will begin to boil alx)ut
the boiling-point of the lowest, and a thermometer placed in the vapor
will in turn indicate all tem|>erature8 up to the boiling-point of the
highest. Mixed liquids may be separated by fractiorml distiUaiicm ;
the fractions of the distillate passing over at different temperatures are
collected separately, and these fractions are redistilled until liquids of
constant boiling-point are obtained. Some liquids cause the plane of a
ray of polarized light which passes through them to rotate to the right
or to the left, and, as this rotation is constant for a given stratum of a
given liquid, the action on polarized light may be frequently employed
in the case of such liquids as a test of their purity.
Solids. — When a solid possesses the property of crystallizing, its crys-
talline form offers the surest means of identifying it. If the crystals
are so well developed that their angles may be measured, the values of
these angles, coupled with the analytical results, suffice to pJace the
identity of any substance for which such determinations have previously
been made, beyond all possibility of doubt. Even when the crystals
are too small to admit of measurement, a microscopic examination will
generally be sufficient to decide whether they are homogeneous or mixed.
Heterogeneity of crystalline form does not necessarily involve chemical
difference; a substance may be dimorphous. Thus the sublimate of
arsenious anhydride frequently contains, side by side, rhombic prisms
and regular octahedra. When solids are fusible, they possess a con-
stant fiising-point This property is of great value in identifying
organic substances, of which the greater number fuse within the limits
no INORGANIC CHEMISTRY.
of the mercurial thermometer. As mixtares fuse at a lower tempera-
ture than the mean fusing-point of their constituents, impurities gener-
ally tend to lower the fusing-point. Every soluble solid, when pure,
has a fixed solubility for each of its solvents at a given temperature.
This solubility generally increases with the temperature (see Solubility).
If the various ingredients of a mixture possess very different solubilities,
this property may be taken advantage of in order to effect their separa-
tion, as the least soluble will crystallize out first, and, by repeated
recrystallization, may generally be obtained pure. What is known as
fractional crystallization consists in evaporating the solution of a sub-
stance until sufficiently concentrated to crystallize. The liquid is then
separated from the crystals and evaporated until a fresh crop of crystals
is obtained. This process is repeated until the solution is exhausted.
If the last crop of crystals is exactly like the first, as regards composi-
tion, form, fusing-point, etc., it may be concluded that the substance
was homogeneous. The reverse of fractional crystallization is fractional
solution. The solid substance is successively extracted with small por-
tions of the solvent. In this way the more soluble ingredients, if such
are present, will be removed. Sometimes various solvents are employed
in succession, according to the nature of the substances suspected to be
present in a mixture; and in this way a separation may frequently be
effected. Fractional precipitation consists in adding to a solution a
precipitant in quantity insufiicient to precipitate the whole of the sub-
stance present. In a mixture, the various ingredients will probably be
affected in varying degrees by the precipitant — that, for example, which
has the greatest affinity for the precipitant will be found chiefly in the
first fraction. By redissolving this fraction and partially precipitating
it, and repeating this operation each time with the partial precipitates,
one of the ingredients of the mixture may usually be obtained pure.
This process is seldom necessary in the case of inorganic compounds, as
with these a sharp separation by means of precipitants is generally at once
possible. Fractional saturation is analogous to fractional precipitation,
and depends on the varying degrees of affinity which the ingredients of
a mixture exhibit towards the saturant A mixture of bases, for example,
is imperfectly saturated with an acid ; a mixture of acids, with a base.
These fractional methods are chiefly of use in the case of organic
compounds, which very seldom possess properties such as to render
them separable from each other by a single operation. In the case
of single substances such methods afford a guarantee of purity by the
correspondence of the different fractions ; and, in the case of mixtures,
they yield, by systematic repetition, a means of separating the various
ingredients.
CHAPTER XIV.
ISOMERISM, METAMERISM, POLYMERISM, ALLOTROPY.
Compounds which, while possessing the same percentage composi-
tion, exhibit differences of chemical and physical character, are termed
isomeric. Metamerism and polymerism are special cases of isomerism ;
HEAT OF CHEMICAL COMBINATION. THERMOCHEMISTRY. Ill
metameric compouDds have the same molecular weight, the difierencc
in properties depending on difierenoe of arrangement of the atoms
within the molecule ; in polymeric compounds the molecular weights
are different, one being a multiple of the other. Examples of meta-
merism and polymerism are most common among the compounds of
carbon, where the frequency of high molecular weights and the prop-
erty which carbon possesses of repeatedly combining with itself, favor
variety of atomic arrangement. The compounds propionaldehyde,
acetone, allylic alcohol, propylenic oxide, and trimethylenic oxide, all
possess the molecular formula CjU^O, and are, therefore, metameric.
The hydrocarbons of the ethy lenic or CnHjn series, ethylene (CjH^), propy-
lene (CgHj), butylene (C^Hg), etc., are polymeric. The single members
of this group may possess metamers ; thus, there are three butylenes
of the formula 04113 — butylene, isobutylene, and pseudobutylene.
Allotropy stands in the same relation to elements that isomerism does
to compounds. Many of the elements exist in several different modi-
fications, possessing entirely distinct properties. Carbon is known in
three forms: as charcoal, as graphite, and as diamond. Sulphur and
phosphorus also possess allotropic modifications. One of the most
striking and instructive instances of this phenomenon is found in the
case of oxygen in its two modifications of common oxygen and ozone.
It is probible that allotropy is to be explained by reference rather
to polymerism than to metamerism. It is certainly conceivable that
molecules containing equal numbers of only one kind of atom should
differ through the arrangement of these atoms within the molecule; but
a difference of properties can more easily be accounted for by supposing
that the molecules of the allotropic modification contain different
numbers of atoms, and in the only case of true allotropy in which the
molecular weights of the allotropic modifications are known, this is
found to be the case. Common oxygen contains two atoms in the
molecule, whereas ozone contains three.
It is to be noted that allotropy has been observed only in the case of
polyad elements. The atoms of a monad element can only combine with
eacli other in pairs, thus H — H, and in this way all variety, either in the
number of atoms in the molecule, or in their arrangement, is excluded.
CHAPTER XV.
HEAT OP CHEMICAL COMBINATION. THERMOCHEMISTRY.
Thermochemistry, that branch of the science which deals with the
heat liberated orabsorl>ed in chemical action, has been studied in great
detail by Berthelot, Thomsen, and others. The first-named chemist
has published {Ann. Chim. Phys. [4], VI., and [5], IV.) a summary of
the results obtained in this field, and from this source the annexed
account is extracted. He enunciates as the three fundamental laws of
therm<x;hemi8try the following:
1. Law of Molecular Work. — The quantity of heat liberated in any
reaction is a measure of the sum of the chemical and physical work
performed in that reaction.
112 INORGANIC CHEMISTRY.
2. Law of the Ejuivalence of Heat aixd Chemical Change, — When a
system of bodies, simple or compound, taken in definite conditions,
undergoes physical or chemical changes which are capable of bringing
the system into a new state without producing any mechanical effect
external to the sjrstera, the quantity of heat liberated or al)sorbed during
these changes depends solely on the initial and final states of the
system, and remains the same, whatever be the nature and order of the
intermediate states.
3. Law of Maximum Work. — Every chemical change, accomplished
without tJie intervention of foreign energy, tends to the production of
that body, or system of bodies, in the formation of which most heat is
liberated.*
The first two laws are corollaries of the law of the conservation of
energy; the third must be developed more in detail. It is possible
to conceive the necessity of this law by considering that the system
which has given off most heat no longer possesses the energy necessary
to accomplish a fresh transformation. Every fresh change involves the
performance of work, and this work cannot be i)erformed without the
intervention of foreign energy. On the other hand, a system capable
of liberating heat by a fresh change, still possesses the energy requisite
to produce this change without foreign aid. It is in the same way that
a system of heavy bodies tends to that arrangement of its parts in which
the centre of gravity is as low as possible; but the system will only
attain to this arrangement should no foreign obstacle intervene. This
is, however, rather an illustration than a demonstration.
In the equations which will now be employed in proof of this law,
the atomic and molecular weights are to be understocxl in grams. The
units of heat will then be calories (see p. 68). The latter are written
to the right of the equation, and denote the heat liberated by the com-
bination represented in the equation, supposing the combining quantities
to be taken, as stated above, in the proportion of grams*
Combinaiion. — According to the law of maximum work, oxygen, in
combining with other bodies, will form a higher oxide or a lower oxide,
according as the one or the other stage corresponds to the greater lib-
eration of heat.
In the formation of nitrous anhydride from two molecules of nitric
oxide and one atom of oxygen, the thermal effect is as follows :
2'N"0 + O = NA, .... 20,000 cal.
Nitric Nitrous
oxide. anhydride.
But when two molecules of nitric oxide combine with two atoms
of oxygen to form nitric peroxide, the calorimetric equation is :
2'N''0 + O, = 'NA, . . . . 34,000 cal.;
Nitric Nitric
oxide. peroxide.,
* Jt ought to be mentioned that the nniversal validity of the law of maximam work
has l)een called in question. Some of the objections urged against the law have been
successfully met by its author; but there are anomalies connected with the phenomena
of heat of neutralization which do not appear capable of explanation on Berthelot's
theory. (See more fully p. 116.)
HEAT OF CHEMICAL COMBINATION. THERMOCHEMISTRY. 113
or, the qoantity of heat liberated is greater by 14,000 calories. There-
fore, whenever an excess of oxygen is present, nitric peroxide ought to
be formed. Not only is this the case, but nitrous anhydride combines
directly with oxygen to form nitric peroxide :
. . . 14,000 oal,
NA + o
= 'NA,
Nitrous
Nitric
anhydride.
peroxide.
On the other hand, hydrogen in combining with oxygen to form
water yields :
H, + O = OHj 69,000 cal.,
Water.
whereas, when these two elements unite to form hydroxyl, the effect
is:
H, + Oj = 'O'jH,, 47,000 cal.,
Hydrozjl.
<^
ving a difference of 22,000 calories in favor of the lower oxide,
'hen oxygen and hydrogen combine, water ought, therefore, to be
formed, whilst hydroxyl ought to have a tendency to decompose into
water and oxygen.
Furthermore, the formation of hydroxyl, starting from water and
oxygen, ought to be accompanied by an al^rption of heat. This com-
pound cannot, therefore, be formed without the intervention of some
foreign energy — for instance, that of a simultaneous chemical action.
There are several compounds, in the formation of which, starting
from their elements, heat is absorbed. Such, for example, are the ox-
idea of nitrogen, the oxides of chlorine, chloride of nitrogen,' acetylene,
cyanogen, etc. ; and none of these can be produced by the mere inter-
action of their elements, acting by their intrinsic energy.
Acetylene, for example, is formed by the direct union of carbon and
hydrogen ; but this combination does not take place under the influence
of chemical affinity alone : it requires the aid of the electric arc. The
oxides of nitrogen are all derived from nitric peroxide, which can be
formed from its elements only under the influence of intense heat (elec-
tric discharge, simultaneous combustion of hydrogen). The oxides of
chlorine are produced by the action of chlorine on the alkaline oxides;
but this is because their formation is accompanied by that of an alkaline
chloride, the production of which is attended with liberation of much
heat.
Decompimtum. — A body that has been formed directly from its ele-
ments with liberation of heat will not spontaneously decompose ; the
intervention of external enei^ is necessary to separate its elements.
Such forms of external energy are heat, light, electricity, a simultane-
ous chemical action and the energy of disaggregation developed by so-
lution. The action of this last agent is displayed in the case of salts of
weak acids, and those of certain feebly basic metallic oxides.
114 IMOBOANIO CHEMISTRY.
If, however, a com pound be formed with absorption of heat, it will
be capable of effecting its own decomposition. This is the case with
the oxides of ohlorine, which explode under the slightest disturbing in-
fluence; to this class belong chloride of nitr(^n, ammonic nitrite, etc.,
bodies which decompose spontaneously at ordinary temperatures. When
bodies formed with absorption of heat do not readily undergo sponta-
neous decomposition, they show a marked tendency to enter into direct
combination or to undergo fresh chemical changes — such as polymeric
condensation, breaking up into groups, complex decomposition — all of
which changes are accompanied by liberation of heat. Bodies formed
with absorption of heat are, moreover, particularly sensitive to the ac-
tion of so-called caialytic or contact agents. Such agents do not in
these cases usually introduce any special energy into a reaction ; they
merely serve to liberate a store of pre-existent potential energy.
Subditution, — Substitutions also take place according to the law of
maximum work. Chlorine, in combining with hydrogen or the metals,
liberates more heat than bromine, and bromine liberates more than
iodine. Therefore bromine decomposes the iodides, expelling iodine,
and forming bromides ; chlorine decomposes both bromides and iodides,
expelling bromine and iodine, and forming chlorides. In the same
manner, whenever one metal displaces another from its salts, the forma-
tion of the new salt is attended with a greater liberation of heat. From
this follows the well-known direct relation between the electromotive
force of the metals and their heat of oxidation.
Double Decomposition, — In general one hyd rated base displaces
another from its salts, when it liberates more heat in combining with
the same acids.* This is the case when the hydrates of the metals are
precipitated by alkaline solutions. Thus :
fNO,
^Pbo" + 2KHo = 2NO,Ko + PbHo,
(NO,
Plumbic Potaasic Potaasic nitrate. Plumbic hydrate.
Ditrate. hydrate.
This reaction liberates 12,200 cat. if all the compounds are in solu-
tion, and 45,600 cal. if they are in the solid state. In the same way,
one acid expels another from its salts, when it liberates more heat in
combining with the same base ; at least, this is so in all cases whereeach
of the acids forms only one salt with the base. But all these relations
are only then strictly true, when the heat liberated by the acids, bases,
and salts is calculated for these bodies in the same physical condition,
namely, the solid state. The following example will show how a change
of physical condition and the special combinations formed with the
solvent may affect the result. Gaseous hydrochloric acid acts upon dry
mercuric cyanide, forming mercuric chloride and hydrocyanic acid :
2HC1 + HgCy, = 2HCy + HgCl, . . + 10,600 cal,
Hydrochloric Mercuric Hydrocyanic Mercuric
acid. cyanide. acid. chloride.
* See, however, p. 115.
HEAT OP CHEMICAL COMBINATION. THESMOCHEMISTRy. 116
But hydrocyanic acid in solution acts u)>on mercuric chloride in solu-
tion, forming mercuric cyanide and hydrochloric acid. This reversal
of the reaction is explained by the fact that two molecules of hydro-
cyanic acid in solution liberate in acting upon mercuric oxide 31,000
cal., whilst a solution of hydrochloric acid liberates only 19,000 cal.
There are therefore +12,000 cal. liberated in the reaction in the wet
way, a result which experiment completely confirms. Theory, there-
fore, predicts this reversal of the reaction (corresponding to the change
in the thermal sign. This change is due to the intervention of a new
chemical reaction attended by liberation of heat, the combination of
gaseous hydrochloric acid with water, by which the hydrochloric acid
has yielded up a portion of its energy.
The same principle of maximum work enables us to produce a num-
ber of compounds which could not be obtained directly, because their
formation is attended with absorption, and their decomposition with
liberation of heat. This end is attained by the device of a double de-
composition bringing about the simultaneous formation of some other
compound, the production of wliich is attended with a liberation of heat
greater than the absorption first mentioned. For example^ in the for-
mation of bydroxyl from oxygen and water,
OH, + O = '0'^, —21,800 cal.
there is absorption of heat, and the reaction cannot therefore take place
directly. In order to accomplish it, baric oxide is made to combine
with oxygen, thereby liberating 11,800 cal. ; and the baric dioxide thus
obtained is acted on with dilute hydrochloric acid, forming baric chlo-
ride and hydroxyl, with liberation of 22,000 cal. more. The formation
of baric chloride furnishes the supplementary energy which is employed
in producing hydroxyl.
The rules given by Berthclot for the relation between the heat of
neutralization of acids and bases, on the one hand, and their mutual
affinity on the other, do not hold good in the case of solutions. In fact,
the very reverse is frequently the case. Thomsen has made a series of
careful determinations of the heat of neutralization of various acids and
bases, and he shows that in mixed solutions of equal equivalents of two
acids with a quantity of a base only sufficient for the neutralization of
one, the larger portion of the base is frequently appropriated by that
acid with which it evolves least heat in neutralization. This is in
direct opposition to Berthelot's law of maximum work. Ostwald,
by measuring the contraction or expansion which occurs on mixing
solutions of acids and bases, has arrived at the same conclusion. It
appears, therefore, that the heat of netUralization cannot be regarded o«
a measure of affinity. Thomsen shows that every base and every acid
has a fixed heatrequivalenty which is liberated in its neutralization, and
that the heat of neutralization in any given case is the sum of the heat-
equivalents of acid and base. This follows from the fact that, if any
two acids be neutralized with a given base, the difference between their
heats of neutralization will be the same for their neutralization with
116 INOBGANIO OHEMISTBY.
any other base, provided always that acids, bases, and salts id every
case remain in solution. The same holds for the neutralization of
bases with various acids : the difference between the heats of neutral-
ization of auy two bases with a given acid is the same for their
neutralization with any other acid. It follows from this that ihe heat
of neuiralixation is independent of the degree of affinity between add
and base. Odtwald has shown that a precisely similar law regulates
the contraction or expansion which occurs when solutions containing
equivalent quantities of acid and base are mixed : the difference in the
d^ree of chancre of volume for any two acids with any given base is
the same with any other base ; each acid and each base produces its own
definite and invariable change of volume, and the change of volume in
any given case of neutralization is the sum of the changes for acid and
base. The heat of neutralization appears to be greater the greater the
contraction, or the smaller the expansion. Taking these facts together,
the conclusion seems unavoidable that the heat of neutralization is
directly connected, n4)t with chemical affinity , bvA with the changes which
occur in the aggregation of the solution — expansion and contraction.
The great obstacle to the interpretation of thermochemical data lies in
the fact that, under the conditions of temperature at which calorimetric
determinations are possible, there is no such thing as mere direct com-
bination of elements. The thermal equation,
H -h CI = HCl 22,000 cal.
is a fiction. This equation ought to be written
H, + CI, = 2HCI 44,000 cal.
and the thermal effect 44,000 cal. is in reality the algebraic sum of
three distinct thermal effects — the heat absorbed by the separation of
hydrogen from hydrogen, the heat absorbed by the separation of chlo-
rine from chlorine, and the heat liberated by' the union of hydrogen with
chlorine. If the first of these be denoted by x, the second by y, and the
third by «, we should have —
2z — {x f- y) = 44,000 cal.
Every thermal equation (except such as contain elements with mona-
tomic molecules) is therefore a single equation with three unknown
quantities, which are consequently undeterminable.
If hydrochloric acid could exist at a temperature at which the mole-
cules of hydrogen and chlorine dissociate into single atoms, then the
conditions of the first of the above thermal equations would be realized
and X and y would be eliminated. But if there are such conditions,
they lie far above the range of temperature at which such determina-
tions are at present possible.
lUSION AND FU8ING-POINTB. 117
CHAPTER XVI.
FUSION AND FU8ING-POINTS.
Th£ molecular changes which correspoDd to the passage of a body
from the solid to the liquid state have already been discussed. As these
changea depend on the energy of the molecules, and as this energy will
be constant for any given body at a given temperature, it is evident that
every substance which is fusible at all ought to have a fixed fusing-
point, and such is, with few exceptions, the case. The use of the
fusing-poiut as a means of identifying substances and testing their pu-
rity has also been described.
Change of Volume Accompanying Fimon, — Most substances in
passing from the solid to the liquid state expand : the melted substance
is the specifically lighter. With water and bismuth the reverse is the
case; these bodies expand in solidifying. Thus^ ice floats on the sur-
face of water ; and closed vessels, in which water is frozen, burst with
the internal pressure.
J^ed of Pressure in Altering the Fusing-point, — If a body expands
in fusing, increase of pressure will tend to raise the fusing-point. In
this case, the pressure acts counter to the energy of the molecules. The
eflect is very slight: according to Bunsen, a pressure of 156 atmos-
plieres is necessary to raise the fusing-point of spermaceti from 47.7° C.
to 50.9° C. If, on the contrary, fusion is accompanied by contraction,
an increase of pressure will lower the fusing-point, the pressure in this
case aiding the energy of the molecules. The effect in the case of
water is a lowering of the fusing-point by .0075° C. for each atmos-
phere. Mousson succeeded, by means of very great pressure, in melt-
ing ice at —18° C.
Latent Heat of Fusion, — If a given weight of water at 100° C. be
mixed with an equal weight of water at 0° C, the temperature of the
mixture will be 50° C. If a given weight of water at 100° C. be
mixed with an equal weight of powdered ice at 0° C, the temperature
of the mixture will be only 10.4° C. If we suppose that, in this last
case, a gram of each was taken (though in practice the experiment could
not be accurately performed with such small quantities), the gram of
water at 100° C. in cooling to 10.4° C. will have given off 100 —
10.4 = 89.6 calories. But in giving off this quantity of heat, it has
melted one gram of ice and raised the temperature of the resulting gram
of water 10.4° C. This last rise of temperature will represent 10.4 ca-
lories. Therefore, as the heat given off is equal to the heat taken up:
Melting of 1 gram of ice + 10.4 cal. = 89.6 cal. ; or
Melting of 1 gram of ice = 79.2 cal.
In other words, when one gram of ice at 0° C. is converted into one
gram of water of the same temperature, 79.2 calories — a quantity of
heat sufficient to raise the temperature of an equal weight of water
1 1 8 INOBaAHIO CHEMISTBY.
79.2° C. — disapi^ears. This quantity of heat is known as the latent
heaJt of fusion of ice, or, as it is sometimes termed, the hitent heat of water.
The energy of motion represented by this latent heat is taken up by the
molecules in some form which does not affect the thermometer: it occa-
sions no rise of temperature, but only brings about a difference in the
condition of the molecules in regard to each other, each molecule being
enabled to overcome the attraction of its immediate neigh bon^, and to
wander through the liquid.
All substances capable of assuming the liquid state posse&s latent heat
of fusion. Water has the highest latent heat of all known liquids.
The disap|)earance of heat in the liquefaction of ice may l)e roughly
shown by heating over a flame a vessel containing pieces of ice. As
long as any ice remains unmelted, the temperature will* rise very little
above 0° C., all the heat which is taken up by the water being instantly
employed in melting the ice. By first pounding the ice so as to increase
the surface, and stirring continually so as thon)ughly to mix the ice and
water, the temperature of the whole may be kept at 0° C. As soon as
the ice is melted, the temperature of the water will begin to rise as usual
until the boiling-point is reached, when the temperature will again re-
main constant.
The heat which disappears when a body passes from the solid into
the liquid state, is again evolved in the passage from the liquid to the
solid state. (See suspended solidification.)
The cold which is produced by the solution of solids is attributable
to the same muse. (See solubility,) In the process of solution, a solid
in contact with its solvent may l>ecome liquid without the application
of heat. Hence, when the latent heat of liquefaction of the solid dis-
appears, the temperature of the whole is lowered, the heat of liquefac-
tion being taken from the mass itself. This is the principle involved
in freezing-mixtures. In such mixtures, the more rapid the process of
solution or liquefaction without application of external heat, the greater
is, cceleris paribus, the degree of cold attainable, there being less time
for heat to be taken up from without. A mixture of 5 parts of amnionic
chloride, 6 of potassic nitrate, and 19 of water, produces a reduction of
temperature from + 10° to — 12° C. A solution of common salt in
water freezes at a much lower temperature than pure water; if, there-
fore, salt be added to snow, the latter will melt. In this case there is
simultaneous liquefaction of the snow and solution of the salt; but
owing to the great latent heat of water, the cold is derived chiefly from
the former source. A mixture of three parts of snow with one of com-
mon salt produces a cold of — 22° C. If equal weights of snow and dilute
sulphuric acid, previously cooled to — 7° C, be mixed, the tempera-
ture will sink as low as — 51° C.
The researches of Guthrie into the nature of the solid compounds
which various salts form with water, have thrown great light upon the
mode of action of freezing- mixtures and upon the degree of cold attain-
able by their means. Guthrie shows that all salts which are capable of
dissolving in water form definite solid compounds with this solvent,
and that every such compound has a fixed fusing-poiut. To the com-
pounds of this class which are solid only at temperatures below 0° C,
EBULUTION AND BOILINGKPOINTS. 119
he has given the name cryohydratea. The same salt frequently forms
more than one cryohydrate. Thus sodic chloride, which at — 10° C.
crystallizes with 2OH2, combines at a still lower temperature with 10.5
OHj, yielding a compound fusing at — 22° C. The important law
holds good that the fusing^point of that cryohydrate which is formed
at the lowest temperature is the limit to the degree of cold attainable
with a given freezing mixture, since any further abstraction of heat from
the mixture occasions, not depression of temperature, but separation of
the cryohydrate. Thus the greatest degree of cold which can be pro-
duced with a mixture of ice and sodic chloride is — 22° C. Further,
the maximum effect from a freezing mixture is obtained when the in-
gredients are employed in the proportions requisite for the formation of
the cryohydrate.
Suspended Solidificaiion. — Although it is not possible (at least at
ordinary pressures) to heat a substance a single degree above its fusing-
point without producing liquefaction, yet many substances, when fusfd,
DQay be cooled many degrees below their fusing- point without solidify-
ing. This state, which is known as suspended solidification^ is moAt
readily produced in bodies from which air is excluded. Water inclosed
in a small glass vessel from which the air has been removed may be
cooled as low as — 8° or — 10° C. without solidifying. The fusing-
point of phosphorus is 54° C. ; but if melted under water, it may be
cooled to 32° C. without becoming solid.
If a liquid body, thus cooled below its fusing-point, be touched with
a portion of the same body in the solid state, solidification instantly
ensues, and the temperature of the mass rises to the fusing-point. The
cause of this rise in temperature is the latent heat of fusion, which is
again evolved when the body passes back into the solid state. Solidi-
fication may also frequently be induced in such cases by agitation.
CHAPTER XVII.
EBULLITION AND BOILINGKPOINT8.
When the molecules of a liquid, in the course of their wanderings,
reach the free surface of the liquid, they are carried by the force of their
motion, should this happen to be in an upward direction, into the air.
Here they behave like the molecules of a gas, striking against other
molecules — either of the air or of their own kind — sometimes proceed-
ing further upwards, sometimes being thrown back into the liquid. If
the space above the liquid is unlimited, the molecules above the liquid
will gradually wander away from it and no longer be exposetl to the
risk of tailing into it again, whilst their place will be constantly taken
by fresh molecules from the surface. This is the phenomenon of spon-
taneous evaporation at ordinary temperatures. If the space al>ove the
liquid is limited, the diffusion of molecules into it from the liquid will
goon as before; but a point will be reached at which the number of
120 INOBOAKIO 0HEMI8TKT.
molecules which fall hack into the liquid is as great as that of the
molecules which leave its surface^ upon which the evaporation will
appear to cease, though in reality it is going on as before. The space
is then said to be saturated with vapor. The quantity of vapor which
will thus diffuse into a given space is constant for a given temperature
and independent of the pressure. Thus at a given temperature the
same quantity of tapor will diffuse into a vacuum and into an equal
space containing air, the only difference being that the vacuum will
fill more rapidly with vapor, as there are no molecules of air to oppose
the passage of the molecules of vapor. This vapor exerts a pressure,
and as this pressure must be proportional to the quantity of vapor
present in the unit of spaoe^ it will also be constant for any given tem-
perature. This pressure is known as the ienmon of the vapor of the
liquid. Its action may be illustrated, and its amount measured, as fol-
lows: Two barometer-tubes are filled with mercury and inverted over
a mercury trough. The mercury will stand equally high in both, and
the height of the column will represent the pressure of the atmosphere.
A few drops of water are now introduced into one of the tubes by al-
lowing the water to rise through the mercury in the tube. In a very
short time this column of mercury will show a marked depression,
corresponding to the tension of the vapor of water for that temperature.
If this barometer-tube be surrounded with a second wider tube, which
can be filled with water of various temperatures, it will be noticed that
as the temperature rises, the mercury in the barometer-tube sinks, cor-
responding to' the increased vapor tension. The difference in height
between the columns of mercury in the two barometer-tubes at any
given temperature^ will give the vapor tension of water for that tem-
perature. When the temperature reaches 100° C, the boiling-point of
water, the mercury inside and outside the tube with the water will stand
at the same level — in othei* words, the tension of the vapor inside the
tube exactly balances the pressure of the atmosphere. Hence the im-
portant law : The temperature at which a liquid boils is that at which
the tension of its vapor is equal to the atmospheric pressure. The mo-
ment this point of equality is passed, the molecules from the surface of
the liquid stream forth freely into space, carrying before them the layer
of air which presses upon them. Bubbles of vapor are formed in the
interior of the liquid, rise through it, and are discharged at its sur-
face.
From the above law it follows, that by lowering the pressure, the
boiling-point of a liquid may also be lowered. Water will boil in a
vacuum at ordinary temperatures, if means be taken to absorb the
aqueous vapor as quickly as it is formed. In like manner, by raising
the pressure, the boiling-point may be raised. By heating water in a
strong closed vessel, by which means the liquid is subjected to the pres-
sure of its own vapor, the temperature may be raised far above 100° C.
without causing ebullition. There is, however, for every liquid a fixed
temperature beyond which no degree of pressure will suffice to restrain
the liquid from passing into the gaseous state. This temperature is
known as the critical point. If the liquid be heated in a very strong
glass tube, the surface of the liquid, when the critical point is reached,
EBtrLLinoir Ain> boilikq-points. 121
will be seen to disappear, and the whole tube will be filled with traoF-
parent vapor, almost of the Fame density as the liquid itself.*
The law that the tension of a vapor is constant for a given tempera-
tare and independent of the pressure, holds only for what are known as
saiurcUed vapors — vapors in contact with an excess of their liquids.
When the space is not saturated with the vapor, and there is none of
the liquid present from which a greater supply may be derived, the
vapor behaves, in regard to temperature and pressure, like a true gas:
for example, a forcible diminution of the volume would cause a corre-
sponding increase in the pressure. In the case of a saturated vapor such
a diminution of volume would only occasion a partial condensation of
the vapor, the pressure remaining as before. Non-saturated vapors are
also termed superheated.
When a liquid assumes the gaseous form, its molecules have to over-
come, besides the pressure resting on the liquid, the force of cohesion,
that is, of their mutual attraction. Hence anything which tends to in-
crease the force of cohesion will raise the boiling-point of the liquid.
As the attraction between the molecules of a substance and those of the
liquid in which it is dissolved is greater than that of the molecules
of the liquid for each other, it is clear that the presence of any solid
substance in solution will increase the force of cohesion, and conse-
quently raise the boiling-point of the liquid. Hence it is that aqueous
solutions of salts boil above 100^ C. The boiling-point of such solu-
tions rises with the concentration.
The boiling-point of a liquid is best ascertained by means of a ther-
mometer immersed in the vapor of the liquid. The temperature at
which the liquid enters into ebullition varies with the nature of the
vessel in which it is contained ; but the temperature of its vapor or
steam is constant. Water boils in a glass vessel at a higher temperature
than in a vessel of iron, owing to the greater adhesion between water
and glass, which hinders the formation of bubbles of steam at the points
of contact of the liquid and the vessel. By heating in a glass vessel water
from which the air had been previously expellei by boiling, the tem-
perature may be raised several degrees above 100° C. without ebulli-
tion supervening. When this slate of molecular inertia is from any
cause disturbed, ebullition suddenly commences with explosive violence,
and the temperature sinks to 100° 0. Liquids thus heated above their
boiling-points are said to be superheated, and the phenomenon of sudden
percussive ebullition is commonly known as bumping.
Various attempts have been made to discover some law connect-
ing the boiling-point of a liquid with its constitution or molecular
weight. Such laws as have been deduced hold only for compounds
belonging to the same group, and generally only for a few members of
* AccordiDg to Ramsay, however, the critical point is merely the temperature at
which the liqaid in the tube has the same specific gravity as its vapor, and a gas may
be liquefied at any temperature, provided sufficient pressure be applied.
122
IMOBOANIC CHEMI8TBY.
such a group. Moreover, the correspondence between experiment anci
theory is seldom more than approximate. A very few examples will suf-
fice. The normal alcohols of the general formula OnH2ii4-i Ho dis-
play among their lower members a difference of boiling-point amount-
ing to about 19.5° C. for every difference of CH, in the molecular
formula. For a similar difference of CH, in the normal fatty acids of
the general formula OnH2ii+i (OOHo), the difference of boiling-point
is about 22° C. The difference l)ecomes, in the case of the acids, rap-
idly less for the higher members.
Normal alcohols.
Ethyl ic alcohol,
Propylic "
Butyl ic "
A ray lie "
Hexylic "
Heptylic "
0,H,Ho
CjHyHo
0,H,Ho
0,H„Ho
O.H13H0
0,H,,Ho
Normal fatty acids.
Acetic acid
Propionic acid
Butyric acid
Valeric acid
Caproic acid
OH,
OOHo
0,H.
OOHo
OOHo
0«H.
OOHo
O.H„
OOHo
0 H
CEnanthylic acid -l qq^
0,H„
Caprylic acid ^ q^^jj^
Pelargonic acid ■< /j?-\|j
BoiliDg-point.
78°
97.4
116.9
137
167.5
176
Boiling-point-
118°
140.7
163
184.5
205
223.5
236.5
253.5
Difference.
19.4
19.5
20.1
20.5
19.5
Difference.
22.7
22.3
21.6
20.5
18.5
13
17
LcUent Heat of Vapors. — It has already been mentioned that bodies,
in passing from the solid to the liquid state, take up heat without ex-
hibiting any rise of temperature, the heat which thus disappears being
employed in producing a change in the molecular condition. The same
phenomenon is observed in a still more marked degree during the pas-
sage from the liquid to the gaseous state. If two thermometers be
introduced into a flask of water boiling over a flame, one being plunged
in the liquid, the other suspended in the steam, both will register the
same temperature, 100° C. (The theraometer in the liquid may happen
to be a fraction of a degree higher; see Boiling-points.) This temper-
ature will be preserved by both thermometers, as long as there is any
liquid left, though all the time heat is being communicated to the
water. The heat which thus disap|>ears in causing a change of mole-
cular condition, is known as the latent heat of steam, and is evolved
EBULUTION AND BOILING-POINTS. 123
again in exactly the same quantity when the steam is eondeosed. This
last fact is turned to account in the determination of the latent heat of
steam. If steam be passed into a kilogram of water at 0^ C. till the
temperature of the latter reaches 100° C, it will be found tliat the
weijjjht of the water has increased to 1.186 kilograms ; in other words,
0.186 kilogram of steam at 100° C, in being converted into water at
100° C, gives offbeat sufficient to raise the temperature of 1 kilogram
of water through 100° C. ; therefore, 1 kilogram of steam will raise
6.37 kilograms of water through 100° C. or 537 kilograms through 1°
C. ; or 1 gram of steam will raise 537 grams of water through 1° 0.
The latent heai of steam is therefore 637 calories.
Steam has the highest latent heat of all known vapors. It is this
which renders it such a valuable heating agent when the heat has to be
carried to a distance from its source.
The phenomena of latent heat, both of liquids and vapors, were first
observed and studied by Black.*
Liquefaction of Oases. — The fact that the non-saturated or super-
heated vapors of liquids behave like true gases leads naturally to the
converse idea that the gases may be nothing more that the superheated
vapors of liquids unknown under ordinary conditions of temperature
and pressure. There are two methods of condensing a vapor to a
liquid, one being refrigeration, and the other pressure; pressure hav-
ing, as we have already seen, the effect of raising the boiling-point of
the liquid. This last method was that chiefly employed by the earlier
experimenters in this field, of whom Faraday may be mentioned as the
chief. Faraday's earlier method consisted in generating the gas to be
liquefied from some suitable substance contained in one of the limbs of
a bent sealed glass tube. The other limb was immersed in cold water,
and in this extremity of the tube the gas, liquified by its own pressure,
condensed. In this way Faraday succeeded in liquifying chlorine,
cyanogen, ammonia, and some other gases. In his later experiments,
however, he combined cold with pressure, and thus liquefied carbonic
anhydride, nitrous oxide, and other gases. There were, however, a
Dumber of gases — oxygen, hydrogen, nitrogen, carbonic oxide, nitric
oxide, and marsh-gas — which till quite lately defied all efforts to re-
duce them to the liquid state. The reason of this was, that the earlier
experimenters relied chiefly on pressure to produce liquefaction, and it
was not till the discovery of the phenomenon of the critical point by
Andrews, that it became evident that at ordinary temperatures no
amount of pressure could liquefy these gases.f Now, however, by the
united agency of intense cold and enormous pressure, the problem has
* The expression " latent heat," though atill in very general urc, must be regarded
as a survival, as it no longer expresses the views of physicists regarding this phenome-
non. The heat which has disappeared as such in the above process is no longer heat,
and onght not, properly speaking, to be called by this name. It has performed the
work of overcoming cohesion ; it is no longer present in that form of molecular vibra-
tion recognizable as heat, and possibly exists only as the potential energy of position of
the molecules. It would be just as admissible to apply the epithet 'Matent" to the
heat which disappears when a steam-engine is employed to raise a weight, because the
potential energy of the raised weight can be reconverted into heat.
t See, liowever, p. 121, footnote.
124 INOBGAKIC CHEMISTBY.
been solved simultaneously by two workers in this field, MM. Pietet
and Cailletet (See Hydrogen,) To give an idea of the difficulties to
be surmounted in these experiments, it will suffice to mention that
oxygen required a pressure of 300 atmospheres and a temperature of
—110° C. (—166° R), for its liquefaction,* and that hydrogen did not
succumb till a pressure of 650 atmospheres, coupled with a temperature
of —140° C. (—220° F.), had been reached..
In the descriptions of the various gases the temperatures and pressures
of liquefaction will be given.
CHAPTER XVIII.
eoLurioN.
Solubility is the property which many substances — gaseous, liquid,
and solid^ possess of mixing homogeneously with some liquid employed
as a solvent. Gaseous and solid bodies, when in solution, assume for
the time being the liquid state.
Solubility cf Gases, — The solubility of gases is known as absorption.
Some gases, such as hydrogen and nitrogen, are soluble in water to a
very slight degree only ; others, like carlx)nic anhydride, chlorine, and
sulphuretted hydrogen, are dissolved in moderate quantity; whilst
others again, like hydrochloric acid and ammonia, are extremely soluble,
the volume absorbed being in the case of the last-mentioned gas at 0°
more than a thousand times that of the water employed. In the case
of gases slightly or only moderately soluble, the quantity absorbed is
approximately proportional to the pressure. This fact may be accounted
for by the assumption that the gas occupies the spaces between the
molecules of the liquid as it would auy other empty space: the quan-
tity which can be pressed into this space will then be proportional to
the pressure. The solubility generally decreases as the temperature rises.
Hence this law may be expressed by saying that the volume of these
gases absorbed is constant for a given temperature, being less for higher
temperatures, and independent of the pressure. For those gases which
are very soluble, this law does not hold. In these cases, the solubility
is the result of a powerful affinity between the molecules of the gas
and those of the solvent. Such absorptions are accompanied by great
evolution of heat — partly the latent heat of the gas, partly the heat of
chemical combination.
Solubility of Liquids- -Miscibility. — ^The following views on solubility
have been enunciated by Dossios : Let there be two liquids A and J?,
and let the single molecules of each be represented by a and 6 respect-
ively, and let the attraction of similar molecules be expressed by a^y bb^
* According to the still more recent results of Wroblewski and OUewski, oxygen
liquefies at the somewhat lower temperature of — 136^ under a pressure of only 22.5 at-
mospheres.
80LT7TIOK. 126
and that of dissimilar molecules by ab. Then if ofr be greater than
aa + bby the liquids will obviously be miscible in all proportions.
But if a6 be less than aa + bb^ the attraction ab can effect the mixture
of the two liquids only with the aid of the energy of their molecules.
At the surface of separation of the two liquids, dingle molecules of A
will sometimes be carried, by the force of their own motion, among the
molecules of B, where they will wander about until they happen again
to reach the surface of separation, when they will for the most part be
retained by the other molecules of A, At length a condition will be
reached in which as many molecules a return to ^ as leave it, and as
this is the case, B is saturated with A. The same holds' in regard to
the saturation of A with B. Two such liquids will dissolve in each
other only up to a certain point. An example of this is afforded by
the behaviour of ether and water towards each other. If equal volumes
of these liquids be agitated together, the ether dissolves about ^'j of its
bulk of water, whilst the water takes up J of its bulk of ether.
When two liquids are miscible in all proportions, the force which
comes into play is the preponderating attraction of dissimilar molecules.
The heat which is liberated by the approximation of these dissimilar
molecules will therefore be greater than that absorbed in the separation
of similar molecules. Hence, in most cases where two liquids are
miscible in all proportions, heat is evolved by their mixture. A
remarkable exception to this rule is presented by a mixture of equiv-
alent proportions of ethylic oxalate and amylic iodide, a depression of
temperature amounting to 9.3^ occurring when the liquids are suddenly
blended.
Solubility of Solids. — Let ^ be a solid body, and B a liquid, and let
the single molecules and their attractions be designated as above.
Then the forces which strive to prevent solution will be aa and 66,
those which tend to induce it, a6, and the energy of the molecules.
The attraction ab must be less than cuiy otherwise the liquid and the
solid would form a solid compound. The molecules a are carried
away from A by their energy, plus the attraction a6, wander through
the liquid and sometimes return to A. When as many molecules
return to A in unit of time as leave it, the solution is saturated. As
the projection of the molecules of ^ among those of B is dependent in
part on the molecular energy, it is evident that the solubility will in-
crease with the temperature. This is generally found to be the case;
the cause of some apparent exceptions to this rule will be mentioned
later.
The diagram (p. 126) is a graphic representation of the relations
between temperature and solubility in the case of various salts, the sol-
vent being water. The abscissas express the temperatures ; the ordi-
nates, the number of parts of anhydrous salt soluble in 100 ])arts of
water.
The method of using this diagram will be evident on inspection.
Thus at 0° C, 100 parts of water dissolve 26 parts of magnesic sul-
phate; at 40** C, 45 parts; at 100°, 74 parts. As the increase of solu-
bility of magnesic sulphate is proportional to the increase of tempera-
ture, the line representing its solubility will l>e straight. The more
126
INOBGANIC 0HBMI8TBY.
rapid the increase of solubility in a salt, the more its curve will ap-
proach the vertical; the slower this increase, the more nearly horizontal
the curve will be. In the ca.se of sotlic chloride, which is almost
equally soluble at all temperatures, the curve is nearly horizontal. If
the solubility increases more rapidly than the temperature, the curve
will show this by bending upwards. In the case of potassic nitrate
Fio. 1 .—Solubility op Salts in 100 Parts op Water.
1
1
<2
Temperature.
and plumbic nitrate the solubility at 0^ of these two salts in 100 parts
of water is 13 and 40 parts respectively ; at 46® C, both salts are
equally soluble, 100 parts of water dissolving 85 parts of each ; whilst
at 73° C, the solubility of potassic nitrate is 150 parts aeainst 108
parts of plumbic nitrate. Tlius, by rise of temperature, the relative
SOLUTION. 127
solobilities of these two salts have been reversed, the more soluble be-
coming the less soluble. This is shown in the diagram by the inter-
section of the curves. The point of intersection indicates the tempera-
ture of equal solubility.
The solubility of sodic sulphate presents a singular anomaly. At
0® C, the solubility in 100 parts of water is 5 parts; it increases more
rapidly than the temperature, till at 33° C, it is 61 parts; then it sud-
denly decreases, and goes on decreasing the higher the temperature rises.
This anomaly would be quite inexplicable, if we were forced to assume
that it is the same body which is contained in the solution above and
below 33° C; but closer examination shows this assumption to be un-
necessary. Below 33° C, the solution deposits crystals of the formula
SOsNaOjylOOH,; above this temperature the salt which separates out
possesses the formula 80,Nao2,OH,.* The latter salt is less soluble
than the former, hence the change in the solubility. The higher the
temperature, the greater the quantity of 8O2Nao2,10OH2 which dissoci-
ates into SO^Nao^jOHj and water. There is no diflSculty in conceiving
that a Fait may exist in different states in its solutions, at one time with
more, at another time with less water of crystallization. Anhydrous
oobaltous chloride is blue, as is also the aqnate 0oCl2,2OH2; whilst the
aqnate OoCl^GOH, is pink, and dissolves in water with this color. . If
to a concentrated aqueous solution of the pink salt a dehydrating agent —
strong hydrochloric acid, or absolute alcohol — be added, the solution
becomes blue. If less alcohol be added, the solution remains pink in
the cold ; but on heating, the color changes to blue, and on cooling
returns to pink again. Here we have a dissociation perfectly analo-
gous to that of the higher aqnate of sodic sulphate, the presence of the
anhydrous cobaltous chloride (or of the lower aquate) being denoted by
the change of color in the solution.
Solution is almost invariably attended with contraction, the volume
of the substance dissolved, together with that of the solvent, being
greater than that of the resulting solution. The only known exception
among anhydrous salts occurs in the case of ammonic chloride, the so-
lution of which is accompanied by expansion. The most marked con-
traction is displayed by dehydrated salts which form definite compounds
with water. Contraction also takes place when asolution of asubstance
is further diluted with the solvent.
Solution is attended with absorption of heat. In those rases in which
heat appears to be liberated, the substance enters into definite chemical
combination with the solvent, in which process heat is evolved. The
compound thus formed dissolves with absorption of heat. The excess
of thermal effect due to chemical combination produces the rise of tem-
perature. Caustic potash (KHo) dissolves in water with liberation of
great heat. But the crystalline aquate KHo,20H„ which is obtained
by cooling a ooncentrateil solution of caustic potash, dissolves in water
with absorption of heat.
The absorption of heat which attends solution is for the most part
attributable to the latent heat of liquefaction of the substance (see Latent
* Genenllr itated to be anhydroos. See, however, Thomsen, DetU. chem, Oet. Ber ,
11,2042.
128 INOBGANIC 0HEMI8TBT.
Heat of Faaion). It is difficult to give an exact account of the various
thermal items which go to make up the total thermal effect of solution,
as the process is of a complex nature. The explanation formerly in
vogue, according to which the fall of temperature during solution is
entirely due to the latent heat of liquefaction of the substance^ solution
itself being caused by the excess of affinity of solvent for substance over
that of substance for substance plus that of solvent for solvent, is mani-
festly untenable. According to this explanation, solution itself would
always be accompanied with liberation of heat, the absorption of heat
which is observed being attributable to the excess of heat which becomes
latent in the liquefaction of the substance. The absorption of heat
during solution would therefore be less than the latent heat of fusion.
But very often the reverse is the case. The latent heat of fusion of 1
gram of potassic nitrale is 49 calories ; but by dissolving the same weight
of this salt in 20 grams of water at 20° C, 81 calories are absorbed.
SuperacUuration or Suspended OrysiaUization, — When a solution con-
tains at a given temperature more salt than the coefficient of solubility
of that salt indicates, the solution is said to be supersaturcUed, or the
crystallization is said to be suspended. The phenomenon is analogous
to that of suspended solidification, observed in the case of fused solids.
It occurs most readily with salts which form more than one aqnate, and
is unknown in the case of anhydrous salts. It may be induced by dis-
solving, with the aid of heat, a salt which has a tendency to form a
supersaturated solution, and allowing the clear liquid, which must be
free from undiasolved substance, to cool, excluding dust. On dropping
into such a solution a crystal of the aquate which would be formed at
that temperature, crystallization immediately ensues with elevation of
temperature, the latent heat of liquefaction being evolved. A salt well
suited for this experiment is sodic sulphate. No other aquate or modi-
fication of a salt than the one which is formed at the given tempera-
ture will induce crystallization ; thus sodic sulphate of the formula
8O2Nao2,0H„ crystallized above 33° C, may be added to a supersatu-
rated solution of sodic sulphate at ordinary temperatures without effect ;
whilst the addition of the smallest fragmen t of the aquate SOjNaOjylOOH,
causes instantaneous crystallization.
CHAPTER XIX.
DIFFUSION.
If water be carefully poured on a concentrated solution of a salt con-
tained in a tall glass vessel, the liquids will be seen to form two distinct
layers, the specifically heavier solution of the salt remaining at the bottom.
After standing for some time, however, the salt will be found to be
equally distributed throughout the liquid. If a solution of a colored
salt, such as cupric sulphate or potassic dichromate, be employed, the
progress of this distribution or diffusion^ as it is termed, will be rendered
pirrusioN. 129
visible to the eye by a gradation of shades, extendin:^ from the bottom
to the surface of the liquid, and ranging throujj^h every intermediate tint
from the color of the concentrated solution to absolute colorlessness. At
last, when the process of diffusion is complete, the liquid will exhibit a
uniform tint throughout.
In like manner, if two tall glass vessels be placed mouth to montli,
one over the other, and separated by a glass plate, the upper l)eing filled
with air and the lower with chlorine, then, if the glass plate be carefully
withdrawn, the lower vessel will be seen to be filled with the yellowish-
green chlorine, whilst the gas in the upper vessel is colorless. But afler
a short time, the yellowish-green color will begin to extend into the
upper vessel, and this will continue until the entire gas presents one
uniform tint The upward progress of the chlorine may further be
made visible by the gradual bleaching of a strip of moist carmine-paper
attached to the inside of the upper vessel and extending from top to
bottom.
In both these cases, the force of diffusion is sufficient to overcome the
counteracting force of gravity. The heavier molecules of the salt find
their way upwards through the lighter molecules of the water ; the lat-
ter penetrates downwards, diluting the concentrated solution. Chlorine
is nearly two and a half times heavier than air ; yet its molecules grad-
ually rise through those of the oxygen and nitrogen of the air, whilst
the latter find their way into the lowest parts of the vessel. In both
experiments the ultimate result is uniform mixture.
This diffusion has its source in the independent motions of the mole-
cules. These motions have already been referred to on various occa-
sions in this introduction^ while discussing the gaseous and liquid states
of matter.
The phenomena of diffusion were first thoroughly investigated by
Graham, to whom is due the deduction of various important laws in
regard to this subject.
IHffudon of Lupiida. — The quantities of a salt which pass in equal
times from a solution into the adjacent water are proportional to the
weight of salt originally in solution. (This law does not hold for very
concentrated solutions.)
Rise of temperature increases the velocity of diffusion. This must
evidently be the case, as the velocity with which the molecules move
increases with the temperature.
Different substances have different velocities of diffusion. Isomor-
phous salts frequently possess equal velocities of diffusion.
Mixed solutions of salts, which do not act chemically on each other,
do not diffuse at the same rates as when separate, the difference in their
rates of diffusion, being increased by mixture. Double salts may fre-
quently be decomposed by means of the unequal velocity of diffusion of
their component single salts.
Dialysis. — In the course of his investigations on the diffusion of
liquids, Graham made the remarkable discovery that certain substances
when in solution diffuse through porous membranes, such as bladder of
parchment, whereas others do not possess this property. He found
further, that the substances which thus diffuse are al ways crystallizable,
9
130 INOBOANIC CHKMI8TBY.
whereas thoee which are unable to pass throagh the membrane are
amorphous. He thus divided all substances into cryHUilloids and colloids
(from x6XXa^ glue), and founded upon the above observations a method
of separating these two classes of substances. This method, to which
he gave the name of dialysiSf is carried out as follows : A piece of blad-
der or parchment paper is tied tightly over the bottom of a glass cylin-
der open at both ends. The liquid to be dialyzed is poured into the
cylinder, so as to rest on the membrane, the lower surface of which is
kept in contact with water. The crystallizable substance diffuses freely
through the membrane and mixes with the water, whilst the colloid
remains in the cylinder. By constantly changing the external water, a
pure solution of the colloid may be ultimately obtained.
The explanation of the phenomenon is as follows: The porous mem-
brane, although itself insoluble, takes up water. This may be shown
by the great increase in bulk which a piece of bladder undergoes when
placed in water. Through the medium of this absorbed water the mole-
cules of the crystalloid are enabled to diffuse. It is possible that the
molecules of colloids, on the other hand, are much larger, or are aggre-
gated into small masses, so that they are unable to pass through the
pores of the membrane.
The membrane must itself be a colloid. Dialysis has been performed
with an artificial membrane of amorphous silicic acid.
Diffusion of Oases. — Gkises may diffuse either freely into each other,
as in the experiment already mentioned, or through very fine openings.
A porous diaphragm of gypsum or compressed graphite constitutes a
system of such fine openings. Owing to the exceedingly small dimen-
sions of the molecules of a gas, they pass through the pores of such a
diaphragm almost unimi^eded. The law of free diffusion, and of dif-
fusion through diaphragms, is the same, and may be stated to be as
follows: The velocities of diffusion of any two gases are inversely as the
square roots of their densities. Thus the densities of hydrogen and
oxygen are as 1:16, and their velocities of diffusion are as 4 : 1. The
kinetic theory of gases informs us that the mean velocities of the mole-
cules of any two gases are inversely profK)rtional to the square roots of
their densities. The above law may therefore also be expressed :
The velocities of diffusion of any two gases are directly as the mean velo-
cities of their molecules. The extreme velocity with which hydrogen
diffuses may be well shown by the following experiment: A tube,
closed at the upper end with a thin plate of gypsum, is filled with hy-
drogen, and the lower end is plunged into water. Since the hydrogen
passes out through the pores of the gypsum much more rapidly than
the air can enter, the water rises in the tube.
The degree of agreement between theory and experiment for the
above law will be seen from the following table, which contains deter-
minations of the velocities of diffusion of some of the commoner gases.
In these experiments the gas to be examined was contained in a tube,
closed at one end with a porous plug of gypsum, and at the other with
mercury or water, according to the nature of the gas. The quantity of
the gas which escaped through the porous diaphragm, and the quantity
of air which entered, were carefully determined. In this way it was
CRY8TALL0GBA?HY.
131
fonnd that if the density of a given gas, referred to air as unity, be rf,
then the volume of this gas which diffuses in the same time as one
volume of air, is equal to s/l, as expressed in the foregoing law.
This calculated value is given in the third column, and the observed
volume in the fourth column of the table :
Name of gas.
Density of
^'-
Volume of gas
which dlffViaed In
the same time as
one volume of air.
Hvdrogen,
Methylic hvdride
Ethylene,
Carbonic oxide,
Nitrc^en
OzTffen,
Sulphuretted hydrogen, . .
Nitrons oxide,
CSarbonic anhydride, . . .
Balphurous anhydride, . .
0.0694
0.555
0972
0.972
0.972
1.111
1.1805
1.527
1.527
2.222
8.7947
1.3414
1.0140
1.0140
1.0140
0.9487
0.92<»4
0.8091
0.8091
0.6708
3.83
1.344
1.0191
1.0149
1.0143
0.9487
0.95
0.82
0.812
0.68
CHAPTER XX.
CRYSTALLOGRAPHY.
When a solid separates from its solution, or when a fused or vapor-
ous substance solidifies, the molecules frequently arrange themselves in
definite geometrical forms, known as crystals. A crystal is a poly-
hedron, more or less symmetrical, bounded by plane surfaces which
intersect at definite angles. Crystals possess not only external, but
also internal structure, their internal structure frequently causing them
to exhibit a definite cleavage parallel to certain faces of the crystal.
Mica, calcite, and fluor spar are instances of very perfect cleavage.
As some of the faces of a crystal are generally impeded in their growth,
crystals seldom attain to their ideal, or Bymmetrical development ; but
as the faces always grow in planes parallel to themselves, the value of
the angles remains constant. In measurements of crystals, it is conse-
quently only the value of the angles which is r^uxled, and from
these the ideal form of the crystal may be constructed by geometrical
methods.
Substances which thus spontaneously assume definite external form,
are said to be cryetaUized. Those solids which are devoid of all crystal-
line structure are termed amorphyas. Glass and resin are instances of
amorphous bodies.
The crystalline form assumed by a substance may be either simple
or compound, according as the faces are of one or of more than one
kind. Every compound form may be resolved into the two or more
simple forms of which it is compounded.
In a compound crystal, the form which possesses the largest faces,
132 INOBGANIO CHElilSTBY.
and which consequently determines the character of the crystal, is
termed the dominant fornix the others are the subordinaie forms.
The various simple forms which occur in any compound crystal ber
long to one and the same system. Six systems of crystals are recognized,
and to one or other of these all crystals may be referred. These sys-
tems are distinuruished according to the mode of arrangement of cer-
tain imaginary line's or axes, which intersect and bisect each other in
one point, and are supfxised to be drawn between two opposite solid
angles, or i>etween the central points of two opposite surfaces or of two
opposite edges of the crystal.
The following is a list of the various systems, with the arrangement
of the axes peculiar to each :
1. The regular system. Three equal axes, intersecting at right angles.
2. The quadratic system. Three axes intersecting at right angles.
Two of the axes are equal ; the third is longer or shorter than the other
two, and is termed the principal cuds.
3. The rhombic system. Three unequal axes intersecting at right
angles.
4. The monoclinio system. Three unequal axes. Two intersect ob-
liquely, and the third is perpendicular to their plane.
5. The triclinic system. Three unequal axes which intersect obliquely.
6. The hexagonal system. This system has four axes. Three equal
axes lie in one plane, and intersect at angles of 60^ ; the fourth, or prtn-
cipal axis, is longer or shorter, and is perpendicular to this plane.
In each system that form of crystal, in which the faces intersect all
three axes at their normal length, is known as the fundamental form.
In the first five systems, the fundamental form is an octahedron, differ-
ing for each system ; in the sixth, or hexagonal system, it is a dihexa-
hedron, or double six-sided pyramid. All other forms which occur in
a system are derived from the fundamental form by variation of the
relative length of the axes. A very simple law governs this variation.
If the half-lengths of the three axes be represented by a, 6, and c, re-
spectively, then these three values will express the distances from the
point of intersection of the axes at which the axes are cut by any
plane which can constitute one of the faces of the fundamental form.
The fundamental form is therefore designated by the ratio, a: b:c. In
the derived forms, either one or two of these values may 1^ varied by
some rational multiple, which may be either an integer or a fraction,
but will seldom be complex : thus derived forms may occur in which
the ratio of the semi-axes is a : 26 : 2o, or a : 6 : 3c, or a : ^6 : ^c, or any
other ratio derived by some such simple process from the ratio of the
fundamental form.
1. Regular System, — The fundamental form is the regular octahedron
(Fie. 2). This form is inclosed by eight equilateral triangles ; it has
twelve equal edges, with an angle of 109° 28' 16", and six equal four-
plane solid angles. The three equal and right-angled axes terminate
in the solid angles. The ratio for this form is a : a : a. (Examples :
alum, magnetic iron ore.)
A second form of the regular system is the cube (Fig. 3). It has
six equal square faces, twelve equal right-angled edges, and eight equal
CRYSTALXOGRAPHY.
133
tbree-plnne solid angles. The three equal and right-angled axes ter-
minate in the centres of the faces. Ektch face consequently intersects
one axis at its normal half-length a, and lies parallel to the other two
axes, or, as this is expressed in crystal lographical terminology, inter-
sects them at an infinite distance. The ratio of this form is, therefore,
Fio. 2.
a : 00 : 30 • In combination the octahedron cut) oft the nolid angles of
the dominant cube, and the cube cuts off the solid angles of the domi-
nant octahedron. (Examples of cube: rock salt^ fluorspar.)
A third form is the rhombic dodecahedron (Fig. 4). It has twelve
equal rhombic faces, twenty-four equal edges with angle^of 120^, eight
equal three-plane solid angles (corresponding in position to the solid
angles of the cube), and six equal four-planesolid angles (corresponding
to those of the octahedron). The three .equal' and right-angled axes
Fio. 4.
Fig. 5.
terminate in the four-plane solid angles. Each face intersects two of
the semi-axes at the normal distance a; the third at an infinite distance.
The ratio of this form is therefore a : a : oo. (Example: garnet.)
In combination, the dodecahedron cuts off the edges of the o(*tahedron
and of the cube ; whilst the cube cuts off the four-plane solid angles,
and the octahednm the three-plane solid angles of the dodeftthedrou.
Hemihedral Forms of the Regular System. — Hemihedral forms are such
as would be generated by supposing the alternate faces of a crystal to
extend till the other alternate faces disappear. In this way the regular
tetrahedron (Fig. 6) miy be developed from the octahedron. (In the
134
INOBGANIO OHEMISTBT.
figure the octahedron is drawn inside the tetrahedron.) In combina-
tion with a dominant cul)e, the tetrahedron cuts off alternate soh'd angles
of the cube, as in the case of the mineral boracite,
2. Quadratic System. — The fundamental form of this system is the
quadratic octahedron or double four-sided pyramid with square base
(Fig. 6). It is inclosed by eight isosceles triangles, through the vertices
Fio. 7.
of which the principal axis passes. The edges are of two kinds, ver-
tical and lateral ; the vertical and lateral solid angles are also distinct.
(Example: copper pyrites.)
Another form is tiie prism of ihefirti order, the four faces of which
intersect the two seconaary axes at the normal distance and lie parallel
to the princi))al axis. This prism is inclosed at both ends, either by a
terminal plane which intersects the principal axis at right angles, or by
the quadratic octahedron, as in Fig. 7.
3. Rhombic Sy^em. — The fundamental form is the rhombic octahe-
dron, or double four-sided pyramid with rhombic base (Fig. 8). It is
inclosed by eight scalene triangles. The edges are of three kinds, and
Fio. 8.
Fio. 9.
there are also three kinds of solid angles. In this system there are
three prisms which run parallel to the three axes. That which is par-
allel to the longest or principal axis, is termed the prism, and is placed
vertically; the other two, which are parallel to the two secondary axes,
are termed domes, and cross each other at right angles in the horizontal
plane. There are also three different terminal planes, which are re-
CBY8TALI/)GBAPHY.
136
spectively perpendicular to the three axes. Sulphur, either native or
crystallized from solutions, belongs to the rhombic system.
4. Monoolinio System. — The fundamental form would l>e a double
pyramid with rhombic base (Fig. 9), in which the axis of the pryamid
is inclined obliquely to the Iwise. This is, however, a compound form,
as it is composed of two distinct sets of four faces each, one of which
sets frequently occurs in combination without the other. There is,
in fact, in this system, no single form which can inclose space. (Ex-
amples : gypsum, hornblende!)
5. THdinie System. — In this system, parallel and opposite pairs of
faces only are equal. The octahedron (Fig. 10) is therefore a combi-
Fio. 10.
Fio. 11.
nation of four jwiirs of faces, any of which pairs may occur in com-
pound forms without the others. This is the least symmetrical of all
the systems. Cuprie stdphate is triclinic.
6. Hexagonal System. — The fundamental form is the double six-sided
pyramid (Fig. 11). It is inclosed by twelve isosceles triangles, of
which the vertices terminate in two groups of six each in the ends of
the principal axis. The lateral edges form a regular hexagon. Fig.
12 shows this form in combination with the hexagonal prism of the
first order as it occurs in quartz.
Fio. 13.
The most important of the hemihedral forms of the hexagonal sys-
tem is the rhxmbohedron, which is derived from the double six-sided
pyramid by the development of alternate faces. Fig. 13 shows the
136
INORGANIC CHEMKTRT.
principal rhombohedron of calcite. The rhombohedroD is incloeed by
six rhombic faces. It has six vertical edses, which unite in two groups
of three each in the ends of the principal axis ; and six lateral edges,
which form a zig-sag line nnind the crystal, and in the middle points
of which the secondary axe^i terminate. The sum of the angles of a
lateral and a vertical edge is always equal to two right angles.
CHAPTER XXI.
WEIGHTS AND MEASURES.
The weights and meiuiures employed in this book are chiefly those
of the French decimal system, founded upon the metre, which is iq^ouoth
part of a quadrant of a great terrestrial circle. The following tables,
published by Messrs. De La Rue and Co., will enable the stutlent to
convert these into their English equivalents whenever it may be neces-
sary.
French Measure* of Length.
Millimetre. .
Centimetre, .
Decimetre, .
Metre. . . .
Decametre, .
Hectometre, .
Kilometre, .
Myriometre, .
In EnKlkfh
inches.
0.nBl«7
0.»»371
3.93708
3».37a79
898.707U0
3937.07900
In EngllAh
feet — 12
inches.
0.003281
0.032809
0.328090
3.280899
32.808992
828.089920
39370.79000 32H0.899200
393707.90000 32808.992000
In En^lflh
yards — 8
In English 'in English
fiithoms — 6 I miles —
feet. 1760 yds.
O.OOIffiKlK
0.0109303
0.1O9Sfi33
1.09S(»31
10.9:i63310
109.3H.S3100
10g3.fi331()00
1093B. 331 0000
0.00054<W
o.<io:>4r»K2
0.a'>46Hl6
0..54«8irt.%
5.4fiKirWi5
M.lWKvxiO
54fi.8lfi.ViOn
MfiK.ieriSooo
0.0000006
. 0.0000062
I 0.0000621
0.0006214
0.0062188
0.0621382
0.6218824
. 6.2138244
1 inch ^ 2.539954 centimetres.
1 foot — 3.0179449 decimetres.
I yard — 0.9143ft» metre.
I mile — 1.6093149 kilometre.
French Measures of Sttrface.
In English In English I In English
In English square yards poleit — i roods —
square feet. — 9 square 272.25 square ; 10890 square
feet. feet. feet.
In English
acres —
4&'ifi0 8q.
feet.
Centiare or sq. metre,
Are or 100 sq. metres.
10.764299
1076.429934
.lP603:i
119.608326
0.03953«
3.9538290
0.0009K85
0.0988457
"metf«i,**! ^?'T .**]}• '®'®*2-^***^* 11960.832602 [ r96.882K«9 j 9.8845T:4
0.0002471
0.0247114
2.4711481
1 square inch — 6.4M:i6fi9 square centimetres.
1 square foot — 9.28996»<3 square decimetres.
1 square yard — 0.83609715 Miuare metre, or centiare.
1 acre - 0.40467102 hecure.
WfilOHTB AND HEA8UBEB.
137
French Measures of Capadiy.
1 In cubic
In cubic 1 feet —
inches. 1 1?28 ruble
. inches.
In pints » In gallons In bushels
84.65923 -8pints- l-Ssals.-
cublc 277.27884 | 22lS. 19075
inches. | cubic inches, cubic ins.
1
MUlilltre or cubic 1 n iwsinft
centimetre. . . .|| ^'^^^
Centilitre or 10 cubic \ a aim?
centimetres . . . f, ®*^^
DeciUtre or 100 cubic \ t - ,^071
centimetre*. . . .f! *-^"^^
litre or cub. decimetre.; 61 .02705
Decalitre or centiBtere. I 610.27ii52
""SSRSfre"^."*'."'}' ««^-<^l^
Myriolitreordecastere. 610270.51519
0.000085
0.000358
0.008532
0.03.5817
0.»»n6A
8.581658
35.816581
858.165807
0.00176 0.0002201
0.01761 0.0022010
0.17606 0.0220097
1 .76077 0.2200987
17.60773 2.2009668
176.07784 22.0096677
1760.77841 ; 220.0966767
17607.78414 2200.9667675
1
0.0000275
0.0002751
0.0027612
0.0275121
0.2751208
2.7512085
27.5120846
275.1208459
1 cubic inch « 16.386176 cubic centimetres.
1 cubic foot — 28.31.'S312 cubic decimetres, or litres*.
1 gallon — 4.54S858Utras. .
French Measures of Weight.
In Enffllah
grains.
In troy
ounces —
480 grains.
In
avoirdupois
lbs.-
7000 grains.
In cwts. Tons —
— 112 lbs.- 20 cwts.—
784000 LVtSOOOO
grains. grains
MilliKTam, .... 0.01.548
Centurram, .... 0.15482
Decigram 1.54323
Gram, 15.43235
Deca^nun 154.32849
Hectogram 1548.28488
Kilogram 1 154S2.S4880
Myriogram 154828.48800
0.000082
0.000822
0.003215
0.082151
0.821507
8.215073
82.1.W27
821.507267
0.0000022
0.0000220
0.0002205
0.0220462
0.2204621
2.2046218
22.0462126
0.0000000
0.0000002
0.0000020
0.0000197
0.0001968
0.0019684
0.0196841
0.1968412
0.0000000
0.0000000
0.0000001
0.0000010
0.0000098
0.0000984
0.0009842
0.0098421
1 grain -
1 troy OS. -
• 0.064709 gram.
81.108496 grams.
lib. avoir.— 0.453593 kilogr.
1 cwt. — 60.802877 kllogrB.
Temperatures are expressed upon the Centigrade scale, where the
equivalent in d^rees Fahrenheit is not also given, and barometric mea-
surements are given in millimetres.
For the ready conversion of gaseous volumes into weights, the c/'flA,
or standard multiple proposed by A. W. Hofmann, has been adopted
in the present work. The crith is the weight of one litre or cubic deci-
metre of hydrogen at O*' C. and at a pressure of 760 millimetres of
mercury. The following is Hofmann's description of the value and
applications of this unit.
" The actual weight of this cul)e of hydrogen, at the standard tem-
perature and pressure mentioned, is 0.0896 gram ; a figure which I
earnestly beg you to inscribe, as with a sharp graving tool, upon your
memory. There is probably no figure in chemical science more impor-
tant than this one to be borne in mind, and to be kept ever in readiness
for use in calculation at a moment's notice. For this litre-weight of
hydrogen = 0.0896 gram (I purposely repeat it) is the standard mul-
tiple, or coefficient, by means of which the weight of one litre of any
other gas, simple or compound, is computed. Again, therefore, I say,
do not slip this figure— -0.0896 gram. So important, indeed^ is this
138 INOBOASnO CHEMIErTBT.
standard weight unit, that some name — the simpler and briefer the
better — is needed to denote it For this purpose I venture to sugeest
the term criih, derived from the Greek word xpt^, signifying a bwey-
Gorn, and iigurativelj employed to imply a small weight. The weight
of 1 litre of hydrogen being called 1 crith, the volume-weight of other
gases, referred to hydrogen as a standard, may be expressed in terms of
this unit.
'^ For example, the relative volume-weight of chlorine being 35.5,
that of oxygen 16, that of nitrogen 14, the actual weight of 1 litre of
each of these elementary gases, at 0° C. and 0".76 pressure, may be
called respectively 35.6 criSis^ 16 criths, and 14 criths.
^' So, aeain, with reference to the compound gases, the relative volume-
weight of each is equal to half the weight of its product-volume. Hy-
drochloric acid (HCl), for example, consists of 1 vol. of hydrogen + 1
vol. of chlorine z=^ 2 volumes ; or, by weight, 1 + 35.5 = 36.5 units ;
whence it follows that the relative volume- weight of hydrochloric acid
gas is ^ = 18.25 units ; which last figure therefore expresses the num-
ber of eritha which one litre of hydrochloric acid gas weighs at 0° C.
temperature and 0*.76 pressure ; and the crith being (as I trust you
already bear in mind) 0.081>6 gram, we have
18.25 X 0.0896 = 1.6352
as the actual weight in grams of hydrochloric acid gas.
^^So, once more, as the product-volume of water-gas (H^O) (taken at
the above temperature and pressure) contains 2 vols, of hydrc^n -f 1
vol. of oxygen, and therefore weighs 2 + 16 = 18 units, the single vol-
ume of water-gas weighs -| = 9 units; or, substituting as before the
concrete for the abstract value, 1 litre of water-gas weighs 9 criths;
that is to say, 9 X 0.0896 gram, = 0.8064 gram.
^'In like manner the product-volume of sulphuretted hydrogen (H^S)
= 2 litres of hydrogen, weighing two criths, + 1 litre of sulphur gas,
weighing 32 criths, together 2 + 32 = 34 criths, which, divided by 2,
gives 1 = 17 criths == 17 X 0.0896 gram = 1.5232 gram = the weight
of 1 litre of sulphuretted hydrogen at standard temperature and pres-
sure.
'' And so, lastly, of ammonia (NH,), it contains in 2 litres 3 litres of
hydrogen, weighing 3 criths, and 1 litre of nitrogen, weighing 14 criths ;
its total product volume-weight is therefore 3 + 14 = n criths, and
its single volume or litre-weight is consequently
^2" = 8.5 criths = 8.5 X 0.0896 gram = 0.7616 gram.
**Thus, by the aid of the hydrogen-litre- weight or crith ^= 0.0896
gram, employed as a common multiple, the actual or concrete weight
of 1 litre of any gas, simple or compound, at standard temperature and
pressure, may be deducea from the mere abstract figure expressing its
volume-weight relatively to hydrogen."
The number expressing in criths the weight of 1 litre of any gas or
vapor being identical with its s|>ecific gravity compared with hydrogen
WEIGHTS AND MEASURES. 139
taken as anity^ it is easj, when this number is known, to calculate the
specific gravity of the gas compared with air taken as unity. For this
purpose it is only necessary to multiply by .0693, which is the specific
gravity of hydrogen compared with air s= 1.
Thus the specific gravity of oxygen compared with air is
16 X .0693 = 1.1088;
of chlorine,
35.5 X .0693 = 2.46015;
of hydrochloric acid,
18.25 X .0693 = 1 264726.
NON-METALS.
CHAPTER XXII,
MONAD ELEMENTS.
Section I.
HTDBOOEN, H^
Atomic wdghi = 1. Molecular weight = 2. Molecular volume l \ L
1 Utre weighs 1 criih. Atomicity \ being the standard of comparison.
Liquefies at —140° C. (—220° F.) under a pressure of 650 atmo-
spheres.
History. — Paracelaus^ in the sixteenth century, first noticed that when
iron is dissolved in sulphuric acid a gas is evolved, which he, however,
assumed to be air. Hydrogen was first thoroughly investigated by
Cavendish in 1766, who gave to it the name o( inflammable air.
Occurrence. — In the free state, hydrogen occurs in the gases of vol-
canoes (Bunsen). It is also evolved in small quantities during the fer-
mentation and spontaneous decomposition of animal and vegetable
matters, and is therefore present in the intestinal gases of some animals,
and in the gases which issue from petroleum springs. It occurs in-
closed in the carnallite of the Stassfurt potash mines, where it appears
to have been formed by the action of ferrous chloride upon water in
absence of air :
6reCI, + 60H, = 2Pe,Cle + FeJB[o, + SH^
Ferrous Water. Ferric Ferric
chloride. chloride. hydrate.
It has been found occluded in meteoric iron (Graham). Spectroscopic
observation shows that free hydrogen exists in the sun, in certain stars,
and in nebnl8B,the temperature of these bodies being too high to permit
of the union of the hydrogen with other elements.
In combination, hydrogen occurs in enormous quantities in nature.
Water contains hydrogen (one-ninth of its weight), and from this fact
the name hydrogen (from &^/e>, water ; and r^wdm^ I bring forth) is de-
rived. , In small quantities it occurs combined with nitrogen as ammo-
nia in the air; whilst with sulphur, as sulphuretted hydrogen, and
with chlorine, as hydrochloric acid, it is found in mineral and volcanic
HTDBOOEN.
141
springs. It is an important constituent of nearly all animal and v^e-
table substances, and occurs in many minerals.
I^rmaratian. — 1. Hydrogen is obtained in a state of purity by the
electrolysis of acidulated water (see Electrolysis). The most convenient
apparatus for this purpose is that devised by Bunsen (Fig. 14). The
internal vessel a6, is filled up to the bend of the tube d with dilute sul-
phuric acid (1 volume of chemically pure sulphuric acid to 10 volumes
of water). The positive electrode b consists of an amalgam of mercury
and zinc, which is not attacked by the acid except when the current is
passing. A platinum plate, o, forms the n^:ative electrode. The con-
necting wires are fused through the glass. The whole is inclosed in an
outer vessel, ee, filled with alcohol to prevent the wires from being
Fig. 14.
heated by the passage of the current, which is generated by two or
three Bunsen's or Grove's cells. The oxygen which would otherwise
be given off at 6, combines with the zinc to form zincic oxide, which
dissolves in the sulphuric acid. A stream of pure hydrogen is evolved
at 0, and is dried by passing through concentrated sulphuric acid con-
tained in the bulbs/. A concentrated solution of zincic sulphate collects
over the positive electrode, but this may be removed by pouring in
fresh liquid at a, which will cause the saturated solution to flow off at d,
2. Potassium and sodium decompose water at ordinary temperatures
with evolution of hydrogen —
20H, + Na, = 20NaH + H,.
Water. Sodic
hydrate.
142
INORGANIC CHEMISTRY.
In the case of potassium, the action takes place with such violence
and evolution of heat as to ignite the hydrogen. The safest mode of
performing the experiment with sodium is to inclose the metal in a
short piece of lead tubing, a (Fig. 16), y^ inch in diameter, hammered
together at one end. The sodium is tightly rammed into the tube,
which is then thrown into water. The weight of the lead causes the
sodium, which is specifically lighter than water, to sink. The gas is
steadily evolved from the open end of the tube, and may be collected
in an inverted glass cylinder 6, previously filled with water. The
usual method of performing the experiment, by throwing the sodium
Fig. If.
on water and pressing it under the mouth of the inverted cylinder by
means of a small net of wire gauze, is not unattended with danger,
owing to the escape of globules of sodium through the meshes of the
gauze; for when sodium decomposes water in a confined space, it some-
times occasions a violent explosion.
3. Very pure hydrogen may be obtained by dissolving magnesium
in dilute sulphuric acid. The method of applying this reaction is the
same as that described in the following paragraph.
4. Hydrogen is most conveniently prepared for laboratory purposes
by acting on zinc with sulphuric acid —
SO,Ho, +
Zn
= SOgZno"
+
H,.
Sulphuric
Zincic
acid.
sulphate.
The zinc is previously granulated by melting it and pouring it into
water. The sulphuric acid, diluted with six or seven times its weight
HYDBOGEN.
143
of water, is poured through the funnel tube a (Fig. 16) upon the zinc
contained in the flask. The gas is washed by allowing it to bubble
through the water in the Woulff 's bottle by and may be collected in
cylinders or bell-jars over the pneumatic trough. In this and in all
other methods of preparing hydrogen, it is necessary, if the gas is to be
inflamed, to be perfectly certain that all air has first been expelled from
the apparatus by the evolved gas. This is best ascertained by collect-
ing a small quantity in a test-tube over water and igniting it, the tul)e
being held mouth downwards. If the gas burns quietly, the air has
been sufficiently expelled ; if it takes fire with a slight explosion, the
evolation of gas must be continued. Neglect of these precautions may
lead to very dangerous explosions. Hydrogen prepared by this method
Fig. 16.
is apt to be contaminated with the following impurities : arseniuretted
hydrogen, if the zinc or sulphuric acid contains arsenic; nitrous and
nitric oxides, if nitric acid is present in the sulphuric acid ; phospho-
retted hydrogen, if the zinc contains phosphorus; sulphuretted hydro-
gen or sulphuric anhydride, if hot acid be added to the zinc. These
impurities impart an unpleasant odor to the gas. In order to remove
them, Dumas passes the gas through two U-tubes, filled with broken
glass, which is moistened in the first tube with plumbic nitrate, to ab-
sorb sulphuretted hydrogen, and in the second with argentic sulphate,
to absorb arseniuretted and phosphoretted hydrogen. The gas then
passes through a third IT-tube filled with pumice moistened with strong
caustic potash ; and then, in order to dry it thoroughly, first through a
tube containing calcic chloride, and afterwards through one filled with
phosphoric anhydride.* Hydrogen, no matter how prepared, is apt to
* The use of concentrated sulphuric acid as a desiccating agent ought to be avoided,
if a very pure gas is required, as hydrogen slowly reduces this acid in the cold with
formation of sulphurous anhydride.
144
INOBOANIC CHSMI8TBY.
contain traoes of nitrogen, derived in part from nitrogen dissolved in
the liquids employed, but chiefly introduced by diffusion through the
joints of the apparatus. There is no method known of removing this
nitrogen. Oxygen, when present in traces, may be got rid of by leav-
ing the gas in contact with spongy platinum, which causes the hydro-
gen and oxygen to combine to form water. If the oxygen were present
in large quantities, the introduction of sp<mgy platinum would occasion
an explosion.
Hydrochloric acid diluted with twice its weight of water may be sub-
stituted for dilute sulphuric acid in the above mode of preparation —
2HC1 + Zn = ZnCl, + Hr
Hydrochloric Zincic
acid. chloride.
Iron may also be substituted for zinc —
8O,H0i + Fe = SO,Feo'' + H,;
Sulphuric acid.
Ferrous sulphate.
but in this case the gas has an unpleasant odor, occasioned by the pres-
ence of volatile hydrocarbons which are formed from the carbon con-
tained in the iron. These may be absorbed by charcoal.
Fig. 17.
5. When hydrogen is required in very large quantities for manufac-
turing or other purposes, it is best prepared by passing steam over iron
turnings or wire contained in an iron tube, and heat^ to redness in a
furnace (Fig. 17). The iron combines with the oxygen of the water
HYDROGEN. 145
to form triferric tetrozide (magnetio oxide of iron), whilst hydrogen is
liberated.
3Fe + 40H, = ""(JTe.Y'K)^ + 4H^
Water. Tiiferrio tetroxide.
The tube b ed eisof iron, and the wider portion, which contains
the tomings, is dosed at c and d by iron screws. The steam is gene-
rated in the flask a, and the hydrogen is collected in the cylinder/ at
the pneumatic trough.
Charcoal may be substituted for iron turnings in the forgoing ex-
periment ; but in this case it is necessary to pass the gas through slaked
lime to absorb the carbonic anhydride which is formed at the same
time:
C + 20H, = OO, + 2H^
Water. Carbonic
anhydride.
If, however, the temperature be raised too high, carbonic oxide will
be formed ; and this gas cannot be removed from the hydrogen by any
process practicable on a large scale. It is very diflScult, if not impos-
sible, to obtain hydrogen free from carbonic oxide by this process.
Further Modes of FormaUon. — 1. When sodium is heat^ in gaseous
hydrochloric acid, it combines with the chlorine, liberating hydrogen :
2HC1 + Na, = 2NaCl + H^
Hydrochloric Sodic
acid. chloride.
2. When zinc is heated with a solution of potassic hydrate, preferably
in contact with iron, hydrogen is evolved. The zinc displaces the hy-
drogen of the potassio hydrate :
20KH + Zn = ZnKo, + H^j.
Potaseic Potaflsic
hydrate. zinc oxide.
3. The aqueous solutions of the salts of ammonia, with the exception
of the nitrate, when acted upon with zinc, evolve hydrogen. The gas
is given off even at ordinary temperatures, but the evolution is more
rapid at 40° C. (104° F.). With a mixture of zinc and iron, and a
solution of an ammonium salt containing free ammonia, hydrogen is
evolved as rapidly as from zinc and dilute sulphuric acid (Lorin).
4. On heating formates or oxalates with an excess of a caustic alkali,
hydrogen is given off:
OHOKo + HKo = OOKoa + H^
PotaaBic Potamic Potaasic
formate. hydrate. carbonate.
{oOKo + 2HKo = 20OKO, + H^
Potaasic Potaaaic Potaaaic
oxalate. hydrate. carbonate.
10
146
INORGANIC CHEMISTRY.
Salts of several other organic acids also evolve hydrogen under the
same conditions.
5. By the action of intense heat, such as that of the electric spark,
upon steam, the latter is decomposed into its elements, oxygen and hy-
drogen.
6. In the destructive distillation of many organic substances con-
taining hydrogen, this gas is evolved, partly in the free state and partly
in the form of hydrocarbons and other organic compounds. It is there-
fore found in large quantities in illuminating gas, which is obtained
by the destructive distillation of coal, oil, or resin.
Properties, — Hydrogen is a colorless gas, devoid of taste and smell,
about fourteen and a half times lighter than air. Its specific gravity
is 0.0693 (air =1). Owing to its lightness, it may be collected in
Fio. 18.
aiiiiiimifc^iBiis
;'WPllIiliP
inverted vessels by upward displacement, and may be retained in such
vessels, even when these are open, for some time; but if the vessels be
turned mouth upwards the gas will escape in a few seconds. The ex-
periment of pouring hydrogen upwards from one vessel into another
may be shown by the following arrangement. An inverted beaker
(Fig. 18) is suspended from one of the arms of a moderately delicate
balance, and is accurately counterpoised. On pouring hydrogen upwards
JBYDROGEN.
147
iDto the beaker, as seen in the figure, the arm of thelmlanee irom which
the beaker is suspended will rise.
The lightness of hydrogen may also be demonstrated by the following
experiment A delivery-jet, a (Fig. 19), bent downwards, is placed in
the path of the rays of an electric lamp, so as to cast a clear image on
the screen. As soon as hydrogen is allowe<] to pass through the jet,
the upward movement of the gas will be visible on the screen in the-
shape of a succession of streaks and shadows rushing upwards from the
jet, denoting the passage of a medium possessing a refractive power
different from that of the surrounding air.
Owine to its lightness, hydrogen may be used for filling balloons.
Soap-bubbles filled with the gas rise rapidly through the air.
Hydrogen cannot support animal life. Small animals placed in a
vessel of the gas die speedily. This effect is not due to any specifically
poisonous action of the gas, but simply to the exclusion of oxygen,
which is essential to life. If mixed with air, it may be breathed for
some time, and, as long as it is contained in the lungs, imparts to the
voice a peculiar squeaking tone.
Hydrogen is very inflammable. It burns in air with a pale blue
flame, which is intensely hot, but emits scarcely any light. Mixed
with suitable proportions of air or oxygen it explodes violently in con-
tact with flame.
Hydrogen is only slightly soluble in water. Its solubility is the
same for all temperatures between 0*" and 20*" C. (32^-68*' F.), at which
temperatures water dissolves about one-fiftieth of its volume of the gas.
Platinum and iron at a red heat are permeable to hydrogen gas.
148 INORGANIC CHEMISTRY.
But the metal which poenesses this property id the highest degree, and
permits the passage of hydrogen at temperatures far Mow redness, is,
as has been shown by Graham, palladium. This action is connected
with the property which these metals possess of absorbing hydrogen
when heated and retaining it when cold, a property which was termed
by Graham occlusion. The absorptive power of a metal for hydrogen
may be determined by the following method : The weighed metal, for
example palladium, is introduced into a glazed porcelain tube, to which
a Sprengel pump is attached. In this pump, by the fall of mercury
down along tube, a more perfect vacuum is produced than can be ob-
tained by other means. The porcelain tube is exhausted, and heated
to redness. Hydi^gen is then admitted and passed over the metal for
a considerable time, after which the metal is allowed to cool in the gas.
The tube is then exhausted a second time and heat again applied, when
the hydrogen which has been occluded will be Evolved at the reduced
pressure, and may be pumped off and collected in a measuring-tube at
the bottom of the fall-tube of the pump. In this way Graham found
that palladium at a red heat occludes more than 900 times its volume
of hydrogen. Even at ordinary temperatures this metal can occlude
no less than 376 times its volume of the gas. The hydrogen thus ab-
sorbed assumes the solid state, and forms a true alloy with palladium.
To hydr(^n in this condition Graham applied the name hydrogemum^
in order to denote its metallic character. The density, teujacity, and
electric conductivity of the alloy are less than those of pure {telladium.
In examining, by means of the Sprengel vacuum, the meteoric iron
of Lenarto (containing 90.88 p. c. iron, 8.46 nickel, and 0.66 cobalt^,
Graham found that this metallic substance yielded, when heated to red-
ness, 2.85 times its volume of a gas containing 85.68 per cent, of hydro-
gen. As red-hot iron at ordinary atmospheric pressure does not absorb
more than half its own volume of hydrogen, the above observation
would seem to suggest that this meteorite had, during some period of its
existence, been exposed to hydrogen of greater pressure than the atmos-
phere of our earth. Spectroscopic observation points to the presence of
atmospheres of hydrogen in the sun and fixed stars.
Hydrogen was liquefied for the first time in 1877 by Pictet and
Cailletet, who achieved this triumph of experimental skill indepen-
dently and almost simultaneously. The difference between the two
methods consisted chiefly in the means of refrigeration employed.
Pictet employed only external, Cailletet chiefly internal, refrigeration.
In the first case, the cooling is produced by means of ordinary refriger-
ants; in the second, it depends on the fact that a gas, if permitted to
expand suddenly, undergoes a great depression of temperature. The
latter phenomenon may be shown first by saturating the air under the
receiver of an air-pump with moisture and then exhausting. At each
stroke of the pump the receiver will fill with fog, owing to the conden-
sation pf the aqueous vapor by the cold produced.
Cailletet's apparatus Is represented in Fig. 20. The tube a6, shown
separately in Fig. 21, is filled with perfectly dry hydrogen, and its
lower extremity is then plunged under the mercury contained in the
strong wrought-iron reservoir o, represented in section in the figure.
HYDROGEN.
149
After the tube has been firmly screwed into its place, a freezing mixture
is introduced into the cylinder e and the hydraulic pump represented to
the right of the figure is put in action. The water which is thus
forced into the reservoir o, presses on the surface of the mercury, caus-
ing it to rise within the tube a^ and thus to compress the gas power-
fully. In this way a pressure of 200 atmospheres is obtained, which
Fio. 20.
is roistered by the manometer d. In order to compress the gas still
further, a steel plunger, worked by the wheel /, is employed, and by
this means the pressure may be increased to 300 atmospheres. As soon
as this pressure is reached the gas is allowed to expand suddenly. This is
accomplished by means of a screw worked by the wheel /^, the unscrew-
Fro. 21.
ing of which permits the water to flow out of the reservoir at g. At the
moment of expansion the tube containing the hydrogen becomes filled
with fog, showing that the gas has condensed to minute particles of
liquid. Most gases can be obtained in a coherent liquid state by means
of this apparatus, but in the case of hydrogen and some of the other
150
INOBGANIC CHEMISTBY.
less coercible gases the phenomenon can be shown only by the produc-
tion of a fog. This, however, is sufficient to prove the fact of lique-
faction ; for the moment a colorless gas loses its transparency it ceases
to be a gas.
Pictet's apparatus is much more complicated. The outer casing of
the condenser C(Fig. 22) is filled with liquid sulphurous anhydride.
By means of the double pump ABy which possesses cylinders of the
capacity of 3 litres each, and is worked by a steam-engine at the rate
of 100 strokes per minute, the gaseous sulphurous anhydride is pumped
Fig
off from the condenser as quickly as it is vaporized. By this rapid
evaporation the temperature of the condenser is kept as low as — 66° C.
( — 86*^ F.). The gaseous sulphurous anhydride drawn off by the pump
passes into a second condenser D, cooled by a current of water. Here
it again liquefies under pressure, and is returned by the tube d to the
first condenser, so that a constant circulation of sulphurous anhydride
is kept up in the direction of the arrows. The outer case of a thin! con-
denser, jUf is filled with liquid carbonic anhydride, which boils off
under the action of the pumps EF, producing a refrigeration of — 140°.
The gaseous carbonic anhydride passes from the pumps into the inner
tube JBTof the condenser C, where it is liquefied under a pressure of 6
atmospheres by the cold produced by the evaporation of the sulphurous
anhydride. It is then returned in the liquid state by the tube k to Hy
GHIiOBINIL 161
SO that a circulation of carbonic anhydride is kept up. The hydrogen
to be liquefied is generated by the action of heat on a mixture of per-
fectly dry potassic hydrate and potassic formate contained in a strone
wrought-iron retort L, . It passes into the very strong glass tube My
where it is liquefied at a pressure of 660 atmospheres by the cold pro-
duced by the evaporation of the liquid carbonic anhydride. On sud-
denly opening the stopcock Ny the hydrogen escapes with enormous
violence in the form of a liquid jet, and, if present in any considerable
quantity, solidifies by the rapidity of its own evaporation, the solid
particles striking against the ground with a sound as of small shot. It
has been found quite impossible to collect the solid or liquid hydrogen
when it has once escaped from the tube.
Since the above results were obtained, Wroblewski and Olzewski
have successfully employed in the liquefaction of gases the intense cold
produced by the evaporation of liquid ethylene in vcuyiio.
Section II.
CHLORINE, CI2.
Atomic weight ^ 36.5. Molecular weight = 71. Molecular volume \ I I-
1 litre weighs 36.6 eriik8. Has not been solidified. Liquefies ai 1 6.6**
C. (69.9° F.) under a pressure 0/ 4 atmospheres. Atomicity '. Etyi-
dence 0/ atomicity, HCt.
History, — Chlorine was discovered by Scheele in 1774. Berthollet
(1786) supposed it to be a compound of hydrochloric acid with oxygen,
a view held till 1809^ when Gay-Lussac and Thenard suggested that it
might be regarded as an element. Davy in 1810 declar^ in favor of
the latter view, and contributed greatly to its general acceptance by
chemists.
Preparation, — 1. Chlorine is most conveniently prepared by gently,
heating a mixture of manganic peroxide and hydrochloric acid. The
reaction takes place in two stages :
a. MnOj + 4HC1 = MnCl^ + 20fl,.
Manganic Hydrochloric Manganic Water,
peroxide. acid. perchloride.
6. MnCl^ = MnCla + CI,
Manganic Manganous Chlorine,
perchloride. chloride.
The chlorine should be generated in a large flask (Fig. 23) heated
over a sand>bath S, and may be washed by passing it through water, in
order to absorb hydrochloric acid. If required dry, it should pass
through a second wash-bottle containing concentrated sulphuric acid.
Owing to its great specific gravity, it may be collected by downward
displacement. If it is desired to collect it at the pneumatic trough, the
water must be warmed, as cold water absorbs the gas rapidly. Mercury
162
INOBOAKIO OHEMIBTBY.
Aannot be employed in collecting the gas, as it is instantly attacked by
chlorine.
When a larger quantity of chlorine is required for laboratory pur-
poeesy the generating flask may be replaced by a large leaden WoulflP's
bottle heated in a steam jacket. Into this bottle a charge of a quarter
of a hundred-weight of manganic peroxide may be introduced at once.
Fio. 23.
2. The hydrochloric acid required for the preparation of chlorine
may be formed in the course of the reaction. Thus, by heating a mix-
ture of sulphuric acid, sodic chloride, and manganic peroxide, chlorine
is liberated :
MnO, + 2SO,Ho, + 2NaCl =
= SO;!faoi
■f
Manganic Sulphuric Sodic
Sodic
peroxide. acid. chloride.
sulphate.
SO,Mno" + 20H, + 01^
Manganous Water,
sulphate.
The sulphuric acid acts on the sodic chloride, producing hydrochloric
acid, which in its turn acts on the manganic peroxide as in 1. In this
reaction all the chlorine present is evolved.
If in process 1 a mixture of manganic peroxide, hydrochloric acid,
and sulphuric acid be employed, the whole of the chlorine will also be
liberated:
MnO, + SOjHo,
Manganic Sulphuric
peroxide. acid.
+ 2HC1 = SOjMno" + 20H, +
Hydrochloric Manganous Water,
acid. sulphate.
ci.
i
CHIX>RIȣ. 163
Other perozideB and oxidizing agents may be substituted for the
manganic peroxide in process 1. In this way plumbic peroxide, baric
peroxide, or potassic dichromate, may be employed. Any oxide will
yield chlorine with hydrochloric acid, provided that the corresponding
chloride eith^ does not exist, or is unstable at the temperature employed.
With potassic dichromate the reaction is as follows :
fOrOJKo
O + 14HC1 = 2KC1 + 'Or'",Cl, + 70H, + 3C1^
OrOJKo
Potamic Hydrochloric PoUmic Chromic Water,
dichromate. acid. chloride. chloride.
When required on a very large scale for manufacturing purposes, as
for example in the production of bleaching powder, chlorine is fre-
quently prepared by reaction (1) from hydrochloric acid and manganic
peroxide. The mixture is contained in large tanks made of Yorkshire
flagstones fastened together with iron clamps, and made tight by means
of vulcanized caoutchouc. The tanks are inclosed in an outer casing
through which steam passes.
3. When gaseous hydrochloric acid mixed with air is passed through
a red-hot tube charged with fragments of brick to increase the heating
surface, the hydrogen of a portion of the hydrochloric acid combines
with the oxygen of the air to form water, and chlorine is liberated. By
passing the gaseous products through water^ the undecomposed hydro-
chloric acid is absorbed, and a mixture of chlorine with nitrogen and
oxygen is obtained. If the fragments of brick are impregnated with
cupric sulphate, the reaction takes place much more thoroughly, and
the greater part of the hydrochloric acid yields its chlorine in the free
state. This latter process is now employed in the manufacture of bleach-
ing powder. The cupric sulphate remains apparently unaltered during
the reaction, and requires but seldom to be renewed. Cuprous chloride
may be substituted for cupric sulphate. Actions of this class^ in which
the mere presence of a substance appears to determine chemical change
in other bodies, the substance itself remaining apparently unchang^,
are termed eaJUilyHc. The final reaction in the above cases is expr^sed
by the following equation :
4HC1 + O, = 20H, + 2CV
Hydrochloric add. Water.
But it is more probable that, in the case of the cuprous chloride, the
reaction takes place in two stages, cupric chloride being continually
formed and immediately aflerwards decomposed :
(a,) 'Ou',Cl, + 2HC1 + O = 20nCl, + OH,.
Cnprons Hydrochloric Cupric Water,
chloride. acid. chloride.
(h.) 20uCl, = 'Oii',Cl, + CI,
Cupric Cuprous
chloride. chloride.
164 INOBOANIO CHEMIBTBT.
In fact, when cuprous chloride, moistened with hydrochloric acid, is
heated in air, cupric chloride is formed according to equation (a). On
raising the temperature, chlorine is evolved and cuprous chloride asain
produced according to (6). In the process just described these reactions
follow each other so closely as to present the appearance of a single
continuous action.
It is probable that all so-called catalytic actions depend in like man-
ner upon the formation of some unstable intermediate compound, which,
being decomposed as fast as it is formed, escapes observation.
Platinum black, and finely divided chromic oxide, exhibit when
heated a similar catalytic action on a mixture of hydrochloric acid and
air.
4. Certain metallic chlorides, as auric and platinic chlorides, evolve
the whole of their chlorine when heated :
PtCl^ = Pt + 2Cly
Platinic chloride.
5. When strong aqueous hydrochloric acid is submitted to electroly-
sis with carbon electrodes, it is decomposed into its elemeants, hydro-
gen being evolved at the negative and chlorine at the positive electrode.
Properties. — Chlorine is a greenish-yellow gas. Its name, from
X^topd^^ greenish-yellow, is derived from this property. It is uninflam-
mable in air, and possesses a powerfully irritating odor, even when greatly
diluted with air. It is one of the heaviest among substances that are
gaseous at ordinary temperatures, being 2.44 times heavier than air.
The vapor-density of pure chlorine determined under ordinary pressures
is constant up to 1600^, and corresponds with the molecular formula
CI,. If, however, the chlorine be mixed with air in order to diminish
the pressure of the chlorine, the vapor-density will show a gradual
diminution as the temperature rises — a diminution amounting at 1600^
to about 16 per cent This diminution is due to a partial dissociation
of the molecules of the gas into single atoms. This dissociation, which
in the case of chlorine is incomplete at the highest temperatures which
can be commanded in such determinations, extends further in the case
of bromine and, in the case of iodine vapor diluted with air^ is complete
at 1400° (see Bromine and Iodine).
Water at 20° C. (68° F.) dissolves about twice its volume of chlo-
rine, the solution possessing the color and odor of the gas. The solu-
bility decreases rapidly as the temperature rises. If the water be cooled
with ice while chlorine is passed into it, a crystalline compound of chlo-
rine and water of the formula CljlOOH, is formed.
When exposed to the air, even at low temperatures, these crystals
rapidly give off chlorine and melt; but if pressed auickly between cold
filtering-paper and sealed up in a glass tub^, they do not decompose till
the temperature rises to 38° C. (IW)° F.), when the chlorine which they
evolve is liquefied by its own pressure, and forms a layer of liquid
chlorine under the layer of saturated chlorine water in the tube. If
the tube be bent at an obtuse angle as in Fig. 24, and the empty limb
a be plunged into a freezing mixture, the liquid chlorine will distil
GHIiOBINE. 166
over and oondense in a. This was the method originallj employed by
Faraday in the liquefaction of chlorine.
Fig. 24.
.r\
Chlorine water is a powerful oxidizing agent : thus it instantaneously
converts sulphurous acid into sulphuric acid. In this reaction thechlo-
rine combines with the hydrogen of the water, and the oxygen which is
thus set at liberty acts in the nascent state on the sulphurous acid :
BOH02 + CI, + OH, = BO,Ho, + 2HCI.
SalphuroQS acid. Water. Sulphuric acid.
Chlorine water may be preserved for a considerable time, if kept in
a well-stoppered botue and in a dark place. Under the influence of
light the chlorine combines with the hydrogen of the water, as above,
am] oxygen is evolved.
Chlorine has very powerful affinities. It combines directly with
hydrogen to form hydrochloric acid. When mixed in equal volumes
and exposed to direct sunlight, hydrogen and chlorine combine with
explosion.
Chlorine removes hydrogen from its compounds with carbon. When
a rag moistened with turpentine is plunged into a jar of chlorine, the
chlorine and hydrogen unite, with evolution of heat and light, whilst
carbon is liberated.
CioH,e + 8CI2 = 16HC1 + IOC.
Tuipentine. Hydrochloric acid.
The same phenomenon is exhibited when a burning taper is intro-
duced into a jar of chlorine ; the hydrogen of the taper continues to
bum, but the carbon separates out, forming dense clouds of soot.
By a more moderate action, chlorine may be made to displace hydro-
gen in compounds of carbon with hydrogen, a proceas known as ^ubsti-
tukon. Thus when equal volumes of marsh-gas and chlorine are ex-
posed to diffused daylight, mcthylic chloride and hydrochloric acid are
formed :
OH, + CI, = OH3CI + HCl.
Marsh-gaa. Meth^lic Hydrochloric
* chlonde. acid.
Moist chlorine combines directly at ordinary temperatures with all
the metals, except iridium, and with most of the metalloids. It has
not been made to combine directly with carbon. Many of the elements.
166 INORGANIC CHEMIfirrBY.
such as phosphoms and finely divided arsenic, antimony, and copper,
inflame when introduced into the gas, owing to the heat evolved in
combination.
Chlorine is employed to bleach linen and cotton fibre, and to destroy
vegetable coloring matters. (On the mode of its employment for this
and similar purposes see Bleaching Powder) The action takes place
in presence of water, and is an oxidizing action as already described.
Dry chlorine does not bleach. When chlorine water is added to a
solution of indigo, the blue color disappears. Chlorine has no action
on most mineral colors, or on printing and China inks, in which the
black substance is finely divided carl)on. Black writing ink, however,
which is the iron salt of an organic acid, is at once bleached by it.
This diflerence may be shown by obliterating a printed page with
writing ink and then dipping it into chlorine water, when the printed
characters will reappear.
Chlorine is also employed as a disinfectant, as it possesses the
property of destroying putrefactive organisms, miasmata, and noxious
vapors — ^the products of decomposition of organic matter.
Chlorine is a powerful poison. Inhaled in a diluted condition it
provokes coughing ; in larger quantities it produces spitting of blood,
and, when concentrated, immediate death.
H7DB00HL0BI0 AOID, Odorhydrio Add, Muriatio Add.
HCL.
Molecular wdghi r= 36.6. Moleetdar volume I I I- 1 lUre weighs 18.26
criths. Has not been solidified. Condenses at 10° C. (50° F.) under
a pressure of 40 aimospheres.
History.^^The aqueous solution of hydrochloric acid has been known
from very early times. The gas itself was discovered by Priestley in
1772, who was enabled to collect it by means of his mercurial pneu-
matic trough.
Occurrence. — Hydrochloric acid is given ofl'in large quantities from
active volcanoes. Some rivers which take their rise in the Andes
contain from 0.1 to 0.2 per cent, of hydrochloric acid.
Preparation. — 1. Hydrochloric acid gas is formed by the direct
union of its elements, as described under chlorine. This experi-
ment may be shown by means of the following arrangement;. Two
stoppered glass vessels of exactly equal capacity (Fig. 25) are united
by a tube which may be closed by a stopcock. After closing the
stopcock, one of these is filled with chlorine and the other with
hydrogen, and the stoppers are replaced. On opening the stopcock
in the dark, diffusion will cause the gases to mix, an action which
will be more rapid if the part of the apparatus containing the chlo-
rine be placed uppermost. If the apparatus be now exposed to the
diffused light of a well-lighted room (but not to direct sunlight,
otherwise an explosion will occur) the color of the diluted chlorine.
HTDBOCHLOBIC ACID. 167
at first visible^ will rapidly disappear. The reaction may be com-
pleted by exposure to sunlight forva few minutes^ there being no
longer any danger of explosion. If one of the stoppers
be now removed under mercury, there will be no rise of ^^®« 25.
the mercury in the vessel, showing that no contraction
has occurred during combination and also that no free
chlorine remains. If water colored blue with litmus
be poured on the surface of the mercury, and the appa-
ratus be raised until its orifice is alK>ve the mercury,
but under the water, the latter will rush in, completely
filling the double vessel (a proof that no free hydrogen
remains), whilst the blue tint turns to red owing to the
action of the acid. Equal volumes of hydrogen and
chlorine therefore combine without change of volume to
form hydrochloric acid gas.
2. For laboratory purposes hydrochloric acid is best
prepared by the action of sulphuric acid on common
salt. The salt (1 part) is contained in a large flask, and
the sulphuric acid (2 parts) previously diluted with a
very small quantity of water, is poured in gradually
through a funnel tube reaching to the bottom of the
flask, as in the apparatus for the preparation of hydro-
gen (Fig. 16, page 143). A rapid disengagement of gas
takes place. Towards the end of the process the reac-
tion may be aided by the application of a gentle heat.
BOjHoi + Naa = BOjHoNao + HCl.
Salphuric acid. Sodic Hydric sodic Hydrochloric
chloride. sulphate. acid.
If only half of the above quantity of sulphuric acid be
employed without adding water, the decomposition occurs according to
the equation :
BO,Ho, + 2NaCl = BO^Nao, + 2HC1.
Sulphuric acid. Sodic Sodic sulphate. Hydrochloric
chloride. acid.
and the normal sulphate is formed ; but, in this case, a much higher
temperature is required to expel the whole of the hydrochloric acid.
The gas must be collected by downward displacement, or over mer-
cury, as it is instantaneously absorbed by water. If, however, the
aqueous solution is required, the gas may be passed at once into water.
(For the preparation of hydrochloric acid on the manufacturing scale,
see Sodic Sulphate.)
Properties, — Pure hydrochloric acid is a colorless gas, of a sharp
and snfibcating odor. It does not support combustion. Its specific
gravity is 1.247 (air = 1). On escaping into the air it fumes strongly,
owing to its forming with the aqueous vapor of the air a compound
which is less volatile than water, and which consequently separates as
168 INOBOANIC OHBMierrBY.
fog. Water at 0^ C. absorbs 603 times its volame of hydrochloric acid
gas, forming a fuming, powerfully acid solution which parte with a
portion of ite gas when the temperature is raised. Water absorbs hy-
drochloric acid gas with such rapidity that it rushes into a space con-
taining this gas as into a vacuum. This may be shown by the follow-
ing experiment: A wide tube of thin glass, closed at the top, is filled
over mercury with pure hydrochloric acid gas, and, a small porcelain
crucible being inserted under the tube, the tube with the crucible is
lifted out of the mercury and lowered into a vessel of water. In this
position it remains unaltered, as the tube is closed by the mercury in
the crucible; but if the tube be raised out of the mercury so that ite
orifice is under water (as in Preparation 1) the water will rush in with
such violence as to shatter the top of the tube. The success of this
experiment depends upon the perfect purity of the hydrochloric acid
gas ; the least trace of air mixed with the gas forms an unabsorbed
layer of indifferent gas above the rising column of liquid, thus not only
checking the rapidity of absorption, but acting as a cushion to break
the shock against the top of the tube.
Hydrochloric acid is employed in the laboratory chiefly in the form
of ite aqueous solution. The strong fuming acid possesses at 16^ C
(69^ F.) a specific gravity of 1.21, and contains about 43 per cent, of
HCl. The commercial acid is frequently contaminated with sulphurous
and sulphuric acids, free chlorine, arsenic, and iron.
If the saturated solution of hydrochloric acid be heated, it gives off
w and becomes weaker as the temperature rises, till at 1 10^ 0. (230^
F.) under the normal pressure a solution containing 20.24 per cent, of
HCl, and corresponding very closely with the formula HClySOH,,
distils over unchanged. If this acid, which distils at 110^ C, be diluted
with water and subjected to distillation, a weak acid comes over at first,
and the acid in the retort becomes gradually stronger till it contains
20.24 per cent, of HCl, when it again distils unchanged at 110^ C. It
was long supposed that this solution with constant boiling-point repre-
sented a definite aquate or hydrate, but Roecoe and Ditraar have shown
that this correspondence with the formula HC1,80H2 is a result of
chance, and that, by varying the pressure, solutions of varying strength,
but constent for each pressure, may be obtained. The lower the pressure
the higher is the percentage of HCl contoineil in the residual acid.
The specific gravity of an aqueous solution of hydrochloric acid
increases with the percentage of acid. In the following teble the column
headed d contains the specific gravities at 15^ C. (59^ F.), that headed
p the corresponding percentages of hydrochloric acid. It is thus only
necessary to determine the specific gravity of a sample of aqueous acid
in order, by reference to the table, to ascertain ite approximate strength :
HTDBOCHLORIC ACID. 169
Bpeeific Oraviiy Table of Aqueous Hydrochloric Acid ai 15^ (Kolb).
rf.
p.
d.
p.
1.212
42.9
1.125
24.8
1.210
42.4
1.116
23.1
1.205
41.2
1.108
21.5
1.199
39.8
1.100
19.9
1.195
39.0
1.091
18.1
1.190
37.9
1.083
16.5
1.185
36.8
1.075
15.0
1.180
35.7
1.067
13.4
1.175
34.7
1.060
12.0
1.171
33.9
1.052
10.4
1.166
33.0
1.044
8.9
1.161
32.0
1.036
7.3
1.157
31.2
1.029
5.8
1.152
30.2
1.022
4.5
1.143
28.8
1.014
2.9
1.134
26.6
1.007
1.5
Hydrochloric acid gas is only partially decompoHed by the passage of
a series of electric sparks.
The composition of hydrochloric acid gas has been demonstrated
by means of synthesis (1). It remains to show how it may be proved
by analysis.
For this purpose, a measured volume of gaseous hydrochloric acid is
introduced into a bent tube over mercury (Fig. 26). A piece of sodium
is then pushed up through the mercury by means of a thin iron wire
Fio. 26.
till it lodges in the curved end of the tube. On heating that part of
the tube by means of a flame, the sodium decomposes the gas, com-
bining with the chlorine to form sodic chloride and liberating hydrogen.
As soon as the reaction is complete, the tube is allowed to cool and the
residual gas is measured, when it will be found that the original volume
has been reduced by one-half. The residual gas may be inflamed or
otherwise shown to possess the properties of hydrcigen.
Suppose, therefore, in order to simplify the calculation, that the
original volume of the gas, at standard temperature and pressure, was
2 litres:
2 litres of hydrochloric acid gas weigh . . . 36.5 criths.
Subtract the weight of 1 litre of residual hydrogen, 1 .0 "
. And there remain, 35.5 ''
160 INORGANfO CHBICISTBT.
which 18 the weight of 1 litre of chlorine. One volume of chlorine
therefore combines with one volume of hydrogen to forfn two volumes
of hydrochloric acid gas.
Hydrochloric acid may be converted into salts termed chlorides by
the action of certain metals as already described^ and also by the action
of the metallic hydrates or oxides:
OKH + HCl = KCl + OH,.
PotaMic Hydrochloric Potaasic Water,
hydrate. acid. chloride.
ZnO + 2HC1 = ZnCI, + OH^
Zincic Hydrochloric Zincic Water,
oxide. acid. chloride.
Hydrochloric acid produces in the solutions of the salts of lead a
white precipitate of plumbic chloride (PbCI,), soluble in excess of water.
With mercurous salts it give^ a white precipitate of mercumus chloride
C'Hg'jCI,), insoluble in excess of water, but readily soluble if chlorine
be passed into the solution. Ammonia causes this precipitate to blacken.
With the soluble salts of silver, hydrochloric acid yields a white pre-
cipitate of argentic chloride (AgCl), insoluble in water, in chlorine
water, and in nitric acid, but soluble in ammonia. This precipitate
blackens when exposed to light.
CHAPTER XXIII.
DYAD ELEMENTS.
SBCnON I.
ozraEN, o^
Atomic weight = 16. Molecular weight = 32. Molecular volume I i L
1 litre weighs 16 criihs. Liquefies at —136° C. (—212.8° F.) under
a pressure of 22.5 atmospheres. Atomicity ''. Evidence of aJtomir
city —
Water, OH,.
Potassic hydrate. OHK.
Argentic oxide, OAg,-
Hypochlorous' anhydride, OCI,
History. — Oxygen was discovered by Priestley in 1774, and a year
later independently by Scheele. The name oxygen^ ''the acid-pro-
ducer'^ (from dfwc, sour, and ^ewaw, I bring forth) was given to it by
Lavoisier, who regarded it as an essential constituent of all acids, a rule
which subsequent discovery has shown to be subject to exception.
OXYGEN. 161
Occurrence. — Oxygen is the most plentiful and widely distributed of
the elements. It is found in the free state, mechanically mixed with
nitrogen, in the atmosphere, of which it constitutes slightly over a 6fth
part by volume. It occurs in combination in water, in most minerals,
(forming nearly one-half by weight of the earth's crust), and in almost
all animal and v^etable compounds.
Preparation. — 1 . When mercuric oxide (HgO) is heated to redness, it
is decomposed into mercury and oxygen —
2HgO = 2Hg + O,.
Mercuric oxide.
The operation may be performed in a retort of hard glass, and the
oxygen collected over water at the pneumatic troueh. This method,
which was that firstemployed by Priestley, is too costly for ordinary use.
2. Many peroxides, when heated, lose a part of their oxygen, and
are reduced to a lower stage of oxidation. This is the case with man-
ganic peroxide (MnOj), plumbic peroxide (PbO,), and baric peroxide
(BaO,). The first of these peroxides is found in large quantities in
nature, and may be advantageously employed as a source of oxygen.
The decomposition cannot be effected in glass vessels, owing to the
high tem|)erature required. In order to obtain the oxygen, the man-
ganic peroxide is placed in an iron bottle fitted with a delivery tube,
and the bottle is heated to bright redness in a furnace. The manganic
peroxide parts with one-third of its oxygen, undergoing reduction to
tri manganic tetroxide —
SNtaO, = »^(Bfn3)^"0, + O,.
* Manganic Trimanganic
peroxide. tetroxide.
3. For laboratory purposes, oxygen is most conveniently prepared
by heating potassic chlorate in a Florence flask or hard glass retort.
The salt parts with the whole of its oxygen (39.18 per cent of its
weight), forming potassic chloride —
fOCl
2<0 = 2KC1 + 30,.
(OK
Potassic Potassic
chlorate. chloride.
The gas may be collected as in Preparation 1. The salt fuses before
giving off its oxygen. The heat required for the decomposition is
somewhat high, particularly towards the close of the operation, and is
apt to soften the glass retort. By mixing the chlorate, however, with
about one-eighth of its weight of manganic peroxide, the oxygen is
given off at a much lower temperature. In this case the chlorate does
not fuse. The manganic peroxide is found unchanged at the end of
the proces.s, and its action probably consists in taking up oxygen to
form a higher oxide, which immediately decomposes into manganic
11
162 INORGANIC CHEMISTRY.
peroxide and free oxygen. Other sabstaoces, such as ferric oxide and
spongy platinum, also aid in liberating oxygen from potassic chlorate.
Commercial manganic peroxide is occasionally adulterated with coal-
dust. When this adulterated peroxide is heated with potassic chlorate,
sudden explosive combustion of the coal at the exi>ense of the oxygen
of the chlorate takes place, and from this cause fatal accidents have
occurred. It is therefore advisable to test the manganic peroxide first
by heating a small quantity with potassic chlorate in a test-tube.
4. When a non-salifiable peroxide of an electropositive element is
heated with sulphuric acid, a sulphate of the lower and salifiable oxide
is formed, and the excess of oxygen, above what is required for the
salifiable oxide, is evolved. In this way manganic peroxide when
heated with sulphuric acid parts with half its oxygen —
+ o,.
2MnO, + 2BOjHo, =
= 2B02Mno"
+ 20H,
Manganic Bulpharic
ManganoiiB
Water.
peroxide. acid.
sulphate.
An analogous reaction occurs when potassic dichromate is heated
with sulphuric acid —
(OrO^o
2^ 0 + 8BO,Ho, = 2BO,Koj +
(OrO^o
Potassic Salpbaric Potassic
dichromate. acid. sulphate.
2B,0,('Cr'"A)'' + 30, + 80Hr
Chromic sulphate. Water. «
It will assist the student to understand the mechanism of complicated reactions like
the above, if he fixes his attention upon that portion of the equation which refers to
the actual process under consideration — in this case the preparation of oxygen. Thus
he would write the first of the above equations —
MnO, = MnO + 0.
and the second —
Manganic Manganoua Oxygen,
peroxide. oxide.
2CrOj = CrA + 30.
Chromic Chromic
anhydride. oxide.
The formation of manganous, potassic, and chromic sulphates, and of water, is neces-
sary to the occurrence of the actual reactions ; but the use of the above abbreviated forms
of the equations will help the student to realize what is the essence of these processes
— the r^uction of a higher oxide to a lower and basic oxide with liberation of
oxygen.
All the equations given in this chapter — with the exception of the above abbreviated
forms — are what are known as molecular equations ; that is to say, none but molecular
quantities of the substances taking part in the reactions are therein represented, at
least in the case of substances of known molecular weight. It is obvious tnat the pro-
portions by weight would remain unaltered if the quantities employed in these equa-
tions were all halves. Thus in 1 we should have —
HgO = Hg + O,
OXYGEN. 163
the only objection being that O represents a semi-molecule of oxygen — a quantity
which does not exist in the free state. Such equations are termed atomic. The use of
atomic equations is often convenient and is ouite unobjectionable if it be borne in mind
that such eq'iations are employed only as abbreviations.
6. When concentrated sulphuric acid is allowed to trickle slowly
over fragments of brick contained in an earthenware retort heated to
bright redness, the acid is decomposed into oxygen, sulphurous anhy-
dride, and water (Deville and Debray) —
BO^Ho, = BO2 + OH, + O.
Sulphuric Sulphnrous Water,
acid. anhydride.
On passing the mixed gases through water, the sulphurous anhydride
is absorbed, whilst the oxygen passes on and may be collected as usual.
When this method is employed on the large scale, the concentrated so-
lution of sulphurous anhydride thus obtained may be afterwards trans-
ferred to the leaden chambers and employed in the manufacture of
sulphuric acid. (See Sulphuric acid.)
6. If a concentrated aqueous solution of bleaching powder be gently
heated with a small quantity of cobaltic oxide (OOjOj), the whole of the
oxygen contained in the bleaching powder will be given off —
Oa(OCl)Cl — OaCl, + O.
Bleaching powder. Calcic chloride.
The cobaltic oxide appears to undergo no change in the reaction, and the
same quantity may be used repeatedly. The gas is evolved with great
regularity. It is best, in order to avoid frothing, to employ a clear
solution of bleaching powder. Cupric oxide may be substituted for
cobaltic oxide.
7. It has been mentioned (2) that baric peroxide (BaOj), when
heated, parts with a portion of its oxygen —
BaOj = BaO + O.
Baric peroxide. Baryta.
By passing a current of air over the baryta thus obtained, whilst the
temperature is allowed to fall below that required for the decomposition
of baric peroxide, the baryta takes up oxygen and is reconverted into
peroxide. Theoretically an unlimited quantity of oxygen may be ob-
tained from the same quantity of baric peroxide by the alternate repe-
tition of these processes (Boussingault). In practice, however, the
baryta is found to combine with the silica of the porcelain tubes to form
a silicate which is incapable of taking up oxygen.
8. A similar alternate method is that prop<^ed by Tessie du Motay.
When potassic manganate (BfnOsKos) is heated in a current of steam,
oxygen is evolved, whilst caustic potash and lower oxides of manganese
remain. On heating the mixture of caustic potash and oxides of man-
ganese with free access of air, oxygen is absorbed and the manganate
is regenerated.
164 INORGANIC CHEMISTRY.
9. Oxygen roay be obtaiued by the electrolysis of water acidulated
with aulphuric acid (see Introduction, p. 106).
10. When a mixture of steam and chlorine is passed through a red-
hot porcelain tube, the chlorine combines with the hydrogen of the
water, liberating oxygen :
20H, + 2C1, = 4HC1 + O^
The porcelain tube ought to be filled with fragments of porcelain in
order to increase the heating surface. The gases issuing from the tube
are washed by passing through a solution of caustic potash, by which
the hydrochloric acid and the excess of chlorine are absorbed.
11. Oxygen is evolved in nature, in a remarkable manner, by the
decomposition of atmospheric carbonic anhydride by the green leaves
of plants under the influence of sunlight. The plant assimilates the
carbon of the carbonic anhydride, whilst the oxygon escapes into the
atmosphere. This decomposition may be shown experimentally by
placing fresh mint or parsley under a glass cylinder inverted over a
pneumatic trough, and filled with water saturated with carbonic anhy-
dride. On exposing the whole to sunlight oxygen is liberated in mi-
nute bubbles from the leaves of the plant, and collects in the upper part
of the cylinder.
Properties. — Oxygen is a colorless, tasteless, inodorous gas, slightly
heavier than atmospheric air, its specific gravity being 1.10563 (air =
1). It is but slightly soluble in water; 1 volume of water at 0° C.
dissolves about 0.04 volume of oxygen.
Oxygen possesses powerful chemical aflSnities, and has l^een made to
combine with every known element except fluorine. Some few metals,
like pot&ssium and sodium, are attacked by dry oxygen at ordinary
temperatures, and become covered with a coating of oxide; the ma-
jority remain bright under these circumstances. Many others become
oxidized only when moisture is present to aid the oxygen. Others, like
copper and mercury, combine with oxygen only at higher tem|>eratures;
whilst platinum, gold, and silver are not acted upon directly by oxygen
at any temperature.
The chemical actions of atmospheric air are all dependent on the
presence of oxygen, air being practically nothing more than oxygen
diluted with about four times its bulk of nitrogen. These chemical
actions are displayed in much greater intensity by undiluted oxygen.
Combustion, for example, is chemical combination, sufficiently violent
to be attended with evolution of heat and light. In the case of the
combustion of a body in air, the presence of an indifferent diluent —
nitrogen — greatly moderates the violence of the action ; in the first
place, by causing combination to take place more slowly, owing to the
interposition of a number of molecules which do not )>articipate in the
reaction, and secondly, by lowering the temperature of the whole, the
indifferent gas appropriating to itself part of the heat derived from
chemical combination. In pure oxygen, all the phenomena of combus-
tion are exhibited in their utmost intensity. Sulphur burns in air with
a pale blue flame, emitting a feeble light ; but in oxygen its flame be-
• OXYGEN. 165
comes strongly luminous. The light emitted by phosphorus burning
in oxygen is of such dazzling brilliancy that it can scarcely be supported
by the eye. A match, extinguished but still glowing, bursts into fiame
when plunged into oxygen. Many substances incapable of undergoing
combustion in air, burn readily in oxygen. If a bundle of thin iron
wires, tipped with burning sulphur to start the combustion, be plunged
into ajar of oxygen the iron will begin to burn, throwing off dazzling
scintillations. The temperature developed in the combustion of iron
is 80 high that if the jar of oxygen be closed below by a porcelain dish
containing water, the globules of molten oxide will fall through the
water and imbed themselves in the glaze of the porcelain.
Hydrogen burns in oxygen ; and hence it is customary to term hy-
drogen a combustible gas and oxygen a supporter of combustion. But
it may easily be shown that these terms are relative and interchange-
able. If an inverted jar of hydrogen be lighted at the mouth and a jet
of oxygen from a gas-holder be passed up through the burning hydrogen
into the jar, the oxygen will ignite in the flame and will continue to
bum inside the jar in the atmosphere of hydrogen. Flame is merely
the visible manifestation of the chemical union of gases ; this union
can take place only at the surface of contact of the two gases, and its
nature and manner will be the same, whether the hydrogen is streaming
into the oxygen or the oxygen into the hydrogen.
The very high temperature produced in the chemical union of oxy-
jren and hydrogen is turned to account in the oxy-hydrogen blowpipe.
The hydrogen is burnt from a nozzle, through the centre of which a
blast of oxygen passes. The flame thus produced possesses such a low
illuminating power as to be scarcely visible in bright daylight ; but its
temperature is enormously high. Platinum readily fuses in the flame,
and silver may be distilled by means of it — a method of purifying sil-
ver which was adopted by Stas in his classical researches on the atomic
weights.
In all cases of combustion in oxygen, compounds known as oxides
are formed. In the case of the combustion of hydrogen, the oxide is
water, which is deposited as dew on the sides of the vessel in which the
experiment is performed. If the gases are mixed before a light is ap-
plied, the combination takes plac*e with explosion. This explosion is
most violent when the two gases are employed in the proportions in
which they combine to form water — two volumes of hydrogen to one
of oxygen.
Oxygen is the only gas which can support respiration. An animal
placed in air previously deprived of oxygen speedily dies. Pure oxygen
at ordinary pressures may be inhaled with impunity, but compressed
oxygen is a powerful poison.
Oxygen is rapidly absorbed by a solution of sodic dithionite (hydro-
sulphite) or by one of potassic pyrogallate, the liquid assuming in the
latter case a deep brown color. By this means oxygen may be removed
from mixtures of gases in which it is present. A solution of cuprous
chloride in ammonia also absorbs oxygen, but more slowly, becoming
of an intense blue color. If the colorless gas, nitric oxide, be added to
free oxygen or to a mixture containing free oxygen, reildish fumes are
166
INORGANIC CHEMISTRY.
produced owing to the formation of higher oxides of nitrogen,
fumes are readily soluble in water.
These
ALLOTBOPIO OZTQEN, or OZONE, O.
Molecular weight = 48.
criths. Liquefied at —
atmoBpheres.
Mokcular volume DZJ. 1 litre weighs 24
■105° C. (—157° F.) under a presmre of 125
Histoiy. — In 1785 Van Marum first notioed that oxygen through
which electric sparks had been passed acquired a peculiar odor. Sch5n-
bein in 1840 investigated the subject, and gaAre to the substance which
is the cause of this odor the name ozone ('iUt», to smell). He showed
that ozone is also contained in the oxygen evolved in the electrolysis of
acidulated water, and that it is produced when phosphorus is allowed
to oxidize slowly in moist air.
0Grurrenee.—O2X)ue is found in minute quantities in country air and
in sea air. It is rarely present in the air of towns, as it is destroyed by
the organic impurities which occur in such air.
Preparation, — 1. Ozone is best obtained by the action of the silent
electric discharge upon oxygen. A glass tube, A (Fig. 27), coated inside
with tinfoil, or silvered internally, is surrounded by a second tube, B,
Fi(k. 27.
coated on the inside with tinfoil. This arrangement constitutes a spe-
cies of Leyden jar, with double glass walls and a vacant space between
them. The apparatus, which is known as a " Siemens induction tube,''
is so constructed that a gas, passed in at E^ flows between the tubes and
emerges at F. If, at the same time, the inner and outer coatings are
connected, by means of the binding-screws Cand -D, with the terminals
of an induction coil in action, the gas is subjected to a series of silent
electrical discharges. When oxygen is thus treated, it is partially con-
verted into ozone, which may be recognized by its peculiar odor and
powerful oxidizing properties. If the ozonized oxygen be passed into
a solution of potassic iodide, iodine is liberated with formation of po-
tassic hydrate :
OZONE. 167
2KI + OH, + O = 20KH + I^
Potassic Water. Potaasic
iodide. liydrate.
If a little starch has been added to the potassic iodide beforehand, the
presence of the slightest trace of free iodine is instantly manifested hy
a deep blue coloration. This reaction is, however, common to most
oi^idizing agents.
It has hitherto proved impossible to convert the whole of the oxygen
into ozone. Under the most favorable circumstances not more than
one-fourth is thus converted.
The electric spark is not nearly so powerful an agent for the conver-
sion of oxygen into ozone as the silent discharge. Indeed if the spark
be allowed to pass through oxygen which has already been ozonized by
the silent discharge, a considerable proportion of the ozone is recon-
verted into oxygen.
2. If one or two sticks of clean moist phosphorus be placed in a
bottle of air or oxygen, a portion of the.oxygen will, after the lapse of
an hour or two, be converted into ozone. The phosphorus must then
be removed and the gas washed with water to remove the phosphorous
acid, otherwise the ozone will gradually disappear.
3. If water acidulated with sulphuric or chromic acid be electrolyzed,
the oxygen evolved at the positive electrode is found to contain ozone.
The quantity is, however, very small, not exceeding ^J^ part of the
weight of the oxygen.
4. Ozone is formed in very minute quantity during the evaporation
of water (Gorup-Besanez), particularly when the water is dissipated in
the form of spray. This probably accounts for the presence of ozone
in sea-air, in which it may even bedetected by its odor.
The nature of the substance formed in these reactions remained for a
long time unexplained. The first experiments which threw any real
light on the subject were those of Andrews and Tait. The method
employed by these investigators was as follows: The oxygen to be
ozonized was inclosed in a tube terminating in a capillary siphon con-
taining sulphuric acid. By means of the rise and fall of this liquid in
the limbs of the siphon, the changes of volume of the gas inclosed in
the tube could be measured. Two platinum wires were fused into the
oxygen tube, and by means of these a silent electric discharge was passed
through the oxygen. It was observed that, when the oxygen was
ozonized, contraction occurred, never, however, exceeding ^\ of the
entire volume. On heating the ozonized oxygen to 300° C. (572° F.\
it r^ained its original volume, and no longer contained ozone. A thin
seal^ glass tube containing a solution of potassic iodide was then in-
troduced into the oxygen tube, and after the maximum ozonization had
been attained, the sealed tube was broken. The ozone liberated iodine
from the solution, but no change of volume was observed in the gas,
and on heating to 300° C. (572° F.) no expansion took place. The
amount of iodine liberated was exactly equivalent to the oxygen which
had apparently disappeared in the contraction which took place when
ozone was formed. It was thus evident that ozone in acting on potassic
168 INOROANIC CHEMISTRY.
iodide yielded its own volame of ordinary free oxygen plus a certain
volume of oxygen employed in the oxidation, this last volume being
equal to the original contraction. In order to determine the molecular
weight of ozone, it was therefore only necessary to know the relation of
these two volumes to each other, but for this purpose the volume of
ozone present in the gas had to be ascertained. This was first accom-
plished by Soret, who found that oil of turpentine has the property of
absorbing the entire molecule of ozone, whilst it has no action on the
unchang^ oxygen present in the mixture. A sample of ozonized
oxygen was divided into two parts: one of these was subjected to the
action of heat, and the other to the absorbent eflGect of oil of turpentine.
It was found that the contraction which took place with the oil of tur-
pentine was exactly twice as great as the expansion caused by heat.
From this it follows that three volumes of oxygen condense to form two
of ozone, or, the molecule of ozone contains three atoms (O5). The
oxidizing effect of ozone on potassic iodide is therefore to be expressed
as follows:
O3 + 2KI + OH2 = O, + I2 + 20KH.
Ozone. Potaasic Water. Oxygen. Potassic
iodide. hydrate.
Properties. — Ozone is a colorless gas possessing an odor somewhat
resembling that of chlorine. It has never been obtained in the
pure state (unless the liquid ozone described further on represents the
pure substance), but is always diluted with a large excess of oxygen.
When dry it may be preserved for a long time. At a temperature of
about 250° C. (482° F.) it is at once reconverted into ordinary oxygen.
It is also decomposed by contact with the peroxides of manganese and
lead at ordinary temperatures, these peroxides apparently undergoing
no change in the process. Hydroxyl and ozone mutually decompose
each other with evolution of oxygen :
O, + {gg = OH, + 20,.
Ozone. Hydroxyl. Water. Oxygen.
Ozone is a powerful oxidizing agent. Organic matters are rapidly
corroded by it. Most metals are oxidized by its action. Silver be-
comes covered with a film of argentic peroxide, which in its turn has
the property of decomposing ozone like the peroxides above mentioned.
Mercury is also acted upon by ozone, the smallest trace of which causes
the mercury to lose its brilliant surface and to adhere to glass. The
oxidizing action of ozone depends on the readiness with which it is de-
composed into oxygen :
03 = 0, + O.
The molecule of oxygen thus formed is stable and inert ; whilst the
atom, being in the nascent state, with its bonds at liberty, is ready to
combine with any suitable atoms that may be present, No contraction
WATER. 169
takes place in these oxidations, O3 and O2 alike representing two
voluines.
Paper moistened with manganoussulphate turns brown when exposed
to the action of ozone, owing to the formation of hydrated manganic
peroxide. Paper stained black with plumbic sulphide becomes white
when acted upon with ozone, the plumbic sulphide (PbS) being oxidized
to the sulphate (SO^Pbo^')-
When subjected to a temperature of — 105°, produced by the evapo-
ration of liquid ethylene, and a pressure of 125 atmospheres, ozone
condenses to an indigo-blue liquid, which only slowly evaporates at
ordinary pressure (Hautefeuille and (/happuis).
Some chemists have described a third variety of oxygen, to which
they gave the name anlozone ; but antozone has been conclusively
shown to be nothing more than hydroxyl.
COMPOUNDS OF OXYGEN WITH HYDROGEN.
WATER, Hydrio Oxide.
H— O— H OHy
Molecular weight =18. Molecular volume QII. 1 lUre of waJUr-vapor
weighs 9 eriths. Fuses at 0° C. Boils at 100° C.
History. — Water was one of the four elements of the ancients.
Priestley first observed that when hydrogen is burned in a vessel con-
taining air or oxygen, drops of water are deposited on the sides of the
vessel. The compound nature of water was first conclusively demon-
strated by Cavendish, Watt, and Lavoisier.
Occurrence, — Water in all its forms is widely diffused in nature. In
the solid form it exists as snow or ice; in the liquid state it constitutes
seas, lakes and rivers; whilst as a colorless gas it is contained in all
naturally occurring air, however dry. In a state of minute subdivision
it exists as clouds and mist. In combination it is found in various
minerals, particularly in those of the class known as zeolites^ as water of
crystallization.*
Formation. — 1. Water is formed by the direct union of hydrogen
and oxygen (see Oxygen, p. 165). This union takes place in the pro-
portion of 2 volumes of hydrogen to 1 of oxygen. Before, however,
proving this fact directly by synthesis, it will be convenient to prove it
indirectly by analysis, employing the method of electrolysis. For this
purpose the apparatus represented in Fig. 28, which consists of a U-
tube ho containing electrodes of platinum and connected with a reser-
voir globe 6, may be employed. Water acidulated with sulphuric acid
is poured into the globe and allowed to fill the two limbs of the U-tube,
* It i'b eanallj possible, however, that these minerals merely contain the dements of
water, whicti are eTolved as water when the mineral is heated ; in other words, the
water, as such, is not pre-existent in the mineral.
170
INORQANIC CHEMISTRY.
FiQ. 28.
after which the glass stopcocks are closed. On passing the electric
current, the gases will be evolved from the electrodes and will collect
in the limbs of the U-tube, the displaced water rising into the globe.
The hydrogen, which is evolved at the nega-
tive electrode, will be found to occupy a
volume twice as great as that of the oxygen,
which is evolved at the positive electrode.
The quantity of oxygen is, however, slightly
Mil below the theoretical amount, owing to the
iM greater solubility of oxygen in water, and
9 also owing to the fact that a small portion
of this gas is liberated as ozone, which oc-
cupies only two-thirds of the volume of
ordinary oxygen. On opening the stop-
cocks the pressure of the water forces out
the gases, which may be identified by the
usual tests.
After arriving at these results, the fact
that 2 volumes of hydrogen combine with
1 volume of oxygen to form 2 volumes of
steam, may be shown by means of the
apparatus represented in Fig. 29. A tube
abj closed at one end and known as a eudi-
ometer, is filled with mercury and inverted
over a tall vessel of mercury. At the upper
t*- — " end of the eudiometer, platinum wires
are fused through the glass for the purpose
of passing an electric spark. A portion of the tul>e, ac, having a length
of about 45 centimetres measured from the top, is divided by marks on
the glass into three parts of equal capacity. The whole of this portion
of the eudiometer is surrounded by a wider glass tube d, through which
steam from the flask /can be passed. The eudiometer with the steam-
jacket is supported by the lower clamp, so that, by shifting this clamp,
the whole can be raised or lowered in the ve^^sel of mercury. The
upper clamp is not shifted during the experiment ; it fits loosely round
the tube, and serves only to mark a fixed height above the surface of
the mercury in the vessel. When the experiment is to be performed,
the apparatus is adjusted so that the position of this clamp coincides
with the lowest of the three divisions on the eudiometer, and steam is
passed into the steam-jacket. The mixture of gases obtained by the
electrolysis of water is now introduced so as to fill the three divi-
sions of the eudiometer. The gases are thus measured at 100° C, and
the height of the column of mercury cb in the eudiometer tube is marked
by the upper clamp. The eudiometer is now lowered until the open
end presses against a pad of india rubber at the bottom of the mercury
vessel, the object of this being to prevent the expulsion of the mercury
from the tube during the explosion. On passing the spark, the gases
combine and a flash of light is seen to fill the tube, but no sound is
heard. The tube is now raised till the top of the column of mercury
again coincides with the upper clamp, when it will be found that the
WATER.
171
aqueouB vapor fills two divisions of the tube. This measurement is
in every respect comparable with the first, since the mixed gases on the
one hand and the aqueous vapor formed by their union on the other,
are both measured at the same temperature, 100^ C, and under the
same pressure — that of the atmosphere less that of the column of
mercury cb. The aqueous vapor has no tendency to condense to water,
since it is measured under reduced pressure.
It is thus found that 3 volumes of the electrolytic mixture of oxygen
and hydrogen, consisting of 1 volume of the former to 2 of the latter,
combine to yield 2 volumes of vapor of water.
On cutting off the supply of heating steam, the aqueous vapor will
condense and the mercury will rise and fill the eudiometer,* the volume
occupied by the condensed water being inappreciable.
* Always Buppoeing, of course, that the height of the eudiometer above the surface
of the mercury is not greater than that of the barometer less the tension of aqueous
vapor for the prevailing temperature.
172
INORGANIC CHEMISTRY.
2. Water is not only formed during the combustion of hydrogen in
oxygen or air, but also when any compound containing hydrogen is
burned in oxygen or air. If the elements combined with the hydrogen
are readily oxidizable, they will also unite with the oxygen. The fol-
lowing reactions illustrate this :
OH, +
Ma rah -gas.
20, = 00, + 20H,
Carbonic
anhydride.
Water.
SiH, + 20, = SiO, + 20H,.
Silic'inretted Silicic Water,
hydrogen. anhydride.
2SH, 4- 30, = 2SO, + 20H,.
Sulphuretted Sulphurous Water,
hydrogen. anhydride.
3. Water is formed as a secondary product in numberless other
chemical reactions, as for instance in the action of acids on the hydrates
of the metals :
OKH + HCl = OH, + KCl.
Pota.«8ic Hydrochloric Water. Potassic
hydrate. acid. chloride.
In like manner it is produced when the elements of water are elimi-
nated from some compounds under the influence of heat or dehydrat-
ing agents :
CaHo, = CaO +
Calcic hydrate. Calcic oxide.
OH,.
Water.
4. Water is formed when certain oxides are heated in a current of
hydrogen. The oxygen combines with the hydrogen to form water,
and the metal is reduced to the metallic state. Thus :
CuO + H,
Cupric oxide.
Cu + OH,
Water.
This reaction has been employed to determine the proportions by weight
in which oxygen and hydrogen combine to form water. For this pur-
pose a weighed quantity of cupric oxide is heated to redness in a current
of perfectly dry hydrogen. The water which is formed in the reaction
is absorbed in a weighed tube filled with some substance which has a
powerful aflBnity for water, such as phosphoric anhyilride or pumice
moistened with sulphuric acid. The increase in weight of this tube
gives the weight of water formed. The loss of weight of the tube
with the cupric oxide determines the weight of oxygen consumed.
The difference of these two values is the weight of hydrogen. In this
way it has been found that 1 part by weight of hydrogen combines
with 8 parts by weight of oxygen to form water.
FropertieB, — Pure water is a tasteless, inodorous liquid. In layers
WATER. 173
of only moderate thickness it appears colorless ; but when viewed in a
layer several yards thick, it is seen to possess a peculiar bluish-green
tint, somewhat resembling that of the edge of a sheet of window-glass.
Water solidifies at 0° C. to ice, and boils at 100° C. under a pressure
of 760 millimetres. The melting of ice and the boiling of water are
employed to fix the points of 0° and 100° on the centigrade ther-
mometer. Water is a bad conductor of heat and electricity. The
rapid equalization of temperature which takes place in a mass of water,
particularly when heat is applied to it from beneath, is due to convec-
tion currents.
Between the temperatures of 0° and 4° C. (32°-39° F.) water forms a
remarkable exception to the law of expansion of bodies under the influ-
ence of heat, inasmuch as between these tem-
peratures it contracts when heated, and ex- Fio. 30.
pands in cooling. Above the temperature of
4° C. (39°F.) it expands in the usual manner
when heated. This point of 4° C. (39° F.) is
therefore known as the point of maximum
density of water, and it is to this density
(= 1) that the densities of solids and liquids
are referred. The fact that the density of
water is greatest at 4° C. (:^9° F.) may be
fihown by the following experiment. A tall
glass cylinder (Fig. 30) filled with water of
ordinary temperature, is furnished with two
thermometers, one at the surface, the other ^ .■
at the bottom, of the liquid. Round the
middle of the vessel on the outside is a second vessel fills with a freez-
ing mixture. When the cold is applied, it will be seen that the lower
thermometer begins to sink, whilst the upper one remains almost
stationary, and this continues till the lower thermometer registers 4° C,
when the temperature at the bottom of the vessel remains constant.
After a short time, the upper thermometer begins to fall and does not
stop till the freezing point is reached and ice is formed.
In solidifying, water undergoes sudden expansion. The specific gAv-
ity of water at 0° C. is 0.99987 ; that of ice at the same temperature
is 0.91662. Most other sutetances contract in passing from the liquid
to the solid state. Ice floats readily on the surface of water. The force
which can be exerted by the expansion of water in freezing is enormous.
A cast-iron shell filled with water and closed by means of a screw may
be burst by exposing it to a freezing temperature. The splitting and
crumbling of rocks in winter is, in like manner, produced by the
freezing and expansion of the water which has penetrated into their
crevices.
The solidification of water is, in reality, a crystallization, though it
is difficult to obtain ice in distinct crystalline forms. These may be
seen, however, in the case of snow, the flakes of which when magnified
exhibit the form of six-pointed stars. The crystal I ographieal system
is hexagonal.
Water is an excellent solvent for a great number of substances, and
174
INORGANIC CHEMISTRY,
in this character plajrs a most important part both in nature and in the
laboratory. The water which filters through rocks and soils extracts
from these a portion of their soluble constituents. The dissolved sub-
stances are carried by rivers into the sea or into inland lakes without
outlet. In every case evaporation goes on, producing concentration,
and the water is returned in a distill^ form as rain or dew to the land
to repeat this process of extraction. In this way the sea and the salt
lakes have received the solid substances held in solution, the quantity
of which is constantly, though very slowly increasing. (For a de-
scription of the variou8 sul^stances contained in natural waters, see OcU-
eium.)
The subject of solubility of salts in water has been treated of at some
length in the Introduction (p. 126).
Beadions. — 1. By the action of water many metallic oxides are con-
verted into hydrate^:
OK, + OH, =
= 20KH,
Potaasic Water.
Potassic
oxide.
hydrate.
BaO + OH, = BaHo,.
Baric oxide. Water. Baric hydrate.
2. It transforms many anhydrides into acids :
HA + OH, = 2HO,Ho.
Nitric anhvdride. Water. Nitric acid.
BO, +
Sulphuric
anhydride.
PA +
Phosphoric
anhydride.
OH, = SO,Ho,.
Water.
Sulphuric
acid.
30H, = 2POHog.
Water.
PhoA^horic
acid.
3. It also unites molecularly, as water of crystallization, with many
compounds to form aquates (see p. 45), as in the following instances :
BaCl,20H„ Baric chloride.
SO,Nao„100H„ Sodic sulphate.
S,O3Ko,('Ar'',O,r,240H,
Alum.
For a description of some other subjects connected with water —
latiCnt heat of water, and of steam, tension of aqueous vapor, absorp-
tion of gases by water, etc., see Introduction.
HTDROXYL* 175
HTDBOXTL, Hydrie Peroxide,
H— oJ-O— H Ho, or | J^
Probable molecular weight = 34.
History. — Hydroxyl was discovered by Thenard in 1818.
Occurrence. — It occurs in very small quantities in the atmosphere,
and in dew^ rain, and snow.
Preparation. — 1. A dilute solution of hydroxyl may be obtained by
passing a current of carbonic anhydride through water in which baric
peroxide is suspended :
jgBa" + OO, + OH, = OOBao" + {gg
Baric Carbonic Water. Baric Hydroxyl.
peroxide. anhydride. carbonate.
2, The most convenient method of preparing hydroxyl consists in
dissolving moid hydrated baric peroxide in dilute sulphuric acid (Thom-
sen, Ber. d. deutsch. chem. Oes.y 7, 73). The pure moist hydrated baric
peroxide, which should be preserved moist from the time of its prepa-
ration, is gradually added to the dilute sulphuric acid (1 part of con-
centrated acid to 5 of water), care being taken to leave the acid slightly
in excess. The liquid is filtered from the baric sulphate, and the excess
of sulphuric acid is removed from the filtrate by precipitating exactly
with baryta-water. The liquid, again filtered from the baric sulphate,
now contains nothing but hydroxyl and water. The water must be
removed by evaporation at ordinary temperatures in vacuo over sul-
phuric acid, as hydroxyl is rapidly decomposed by boiling. In this
way the solution may be concentrated till a specific gravity of 1.452 is
attained, when the liquid evaporates without change in the composition
of the residue.
Properties. — Hydroxyl is a colorless, slightly syrupy liquid, devoid
of odor, and possessing a strong metallic taste. It bleaches and blisters
the skin. It does not solidify at —30'' C. (—22° F.). At ordinary tem-
peratures it is gradually and s[K)ntaneou6ly decomposed into oxygen
and water; when heated to 100° C. this decomposition takes place with
explosive violence. When diluted with water, or in presence of a small
quantity of sulphuric acid, it is much more stable.
Like ozone, and all other bodies which are formed with absorption
of heat, hydroxyl is particularly sensitive to catalytic action. Plati-
num, or carbon, in a finely divided state, effects its instantaneous decom-
position into oxygen and water, these substances apparently undergoing
no change in the process. Platinum does not possess any marked affinity
for the elements of hydroxyl, nor does carbon at ordinary temperatures.
On the other hand, iron, tin, and antimony are M-ithout action on hy-
droxyl, though their affinity for oxygen is very great
The general characteristics of hydroxyl are those of a powerful oxi-
176 INORGANIC CHEMISTRY.
dizing agent. Finely divided metallic arsenic is converted by it into
arsenic acid, with evolution of heat and light. Black plumbic sulphide
(PbS) is converted into the white sulphate (SOjPbo"). For this reason
hydroxy] is employed in restoring old paintings in which the white lead
has, in course of time, been blackened by sulphurous exhalations. It
also bleaches organic coloring matters, changing the color of dark hair
to pale gold, a property which has led to its use as a hair dye.
But it also acts as a deoxidizing agent. Argentic oxide and hydroxyl
mutually decompose each other, yielding metallic silver, water, and free
oxygen.
OAg, + jgg = 2Ag + OH, + O,.
Argentic oxide. Hydroxyl. Water.
Silver has a very slight affinity for oxygen, and its oxide is easily de-
composed. The atom of oxygen given off by the hydroxyl combines
with that of the oxide of silver to form a molecule of free oxygen,
liberating metallic silver. By this reaction Brodie first demonstrated
the diatomic character of the oxygen molecule ; for if an excess of either
reagent be employed, this excess remains unaltered. The oxides of gold
and platinum behave similarly with hydroxyl. These reactions take
place with almost explosive violence.
An analogous mutual decomposition occurs when hydroxyl is brought
in contact with various peroxides, such as those of manganese and lead.
The hydric peroxide is reduced to water, and the metallic peroxide to
the salifiable oxide, whilst the two oxygen atoms thus liberated unite
to form a molecule of oxygen as in the cases already described :
|2g + MnO, = OH, + BInO + O,.
Hydroxyl. Manganic Water. Manganous
peroxide. oxide.
A similar case is the mutual decomposition of ozone and hydroxyl
with formation of water and liberation of oxygen (see p. 168).
Hydroxyl precipitates the hydrates of calcium, barium, and stron-
tium from their solutions in the form of peroxides :
BaHo, + {oh = {o"^*" + 20H,.
Baric hydrate. Hydroxyl. Baric peroxide. Water.
If to a solution of hydroxyl acidulated with sulphuric acid a few drops
of pota.ssic dichromate be added, the unstable compound, perchromic
acid, is formed. On agitating the mixture with ether, the perchromic acid
will be extracted from the aqueous solution, imparting to the superna-
tant ether a magnificent but fugitive blue color. This reaction is char-
acteristic of hydroxyl, as no other known substance effects the oxidation
of chromic to perchromic acid.
Hydroxyl, like other oxidizing agents, liberates iodine from potassic
iodide, as may be shown by the blue color which is produced when
C0MPOUKD8 OP CHLOBINE — HYPOCHLOBOtJS ANHYDRIDE. 177
starch-paste has been added to the solution of the iodide. Hydroxy!
is, however, the only oxidizing agent which can liberate iodine in
presence of ferrous sulphate.
Hydroxyl is soluble in ether, and may be extracted from an aqueous
solution by shaking with this solvent. The ethereal solution is more
stable than the aqueous solution, and may be distilled without decom-
position.
COMPOUNDS OF CHLOBINE WITH OXYGEN AND
HYDROXYL.
Chlorine forms several compounds both with oxygen alone and with
oxygen and hydroxyl ; but none of these can be produced by direct
combination. The following list contains all that ai% known :
Hypochlorous anhydride, ; . OCIj.
Chloric peroxide, '0'(OCI)
Hypochlorous acid.
Chlorous acid,t .
Chloric acid, . .
Perchloric acid, . .
or'"0r^O,
OCIH, or OlHo.
/OCl
\0H.
OCl
OClHoor
fOCl
\0Ho
fOCl
(OHo
or
(OH
CI— O— CI.
d— O— 0--
CClf *
H— O— CI
H— 0—0— CI
H— O— O— O— CI
roci
or J § . H— O— O— O— O— CI.
[oH
HTPOOHLOROnS AHHTDBIDE.
ocv
Mokeular vmght = 87. Molecular volume I I L 1 lUre of hypochlorous
anhydride vapor weighs 43.6 criths. Boils about 20° C. (68° F.).
Preparation. — Hypochlorous anhydride is obtained by passing chlo-
rine over mercuric oxide at a low temperature :
* See PeriodfUes. AUmieity of Iodine.
t Chlorom anhydride, €1,0], has not been prepared. What was formerly believed
to be this compound has been conclugively shown to be nothing more than a mixture
of chloric peroxide with free chlorine (Garzarolli-Thumlackh, Liebig'ii AnnaUn, 209,
184).
12
178 INORGANIC CHEliXSTRY.
2HgO +
2C1, =
(HgCl
(HgCI
Mercuric oxide.
Mercuric Hypochlorous
ozjchloride. anhydride.
The mercuric oxide, which must be prepared by precipitation and dried
at a temperature not exceeding 300° C. (572® F.), is conveniently
contained in a horizontal tulje through which a current of chlorine
thoroughly dried by sulphuric acid slowly passes. The apparatus ter-
minates in a U-tube surrounded by a freezing mixture, and in this
tube the hypochlorous anhydride, liquefied by cold, collects.
Properties. — Hypochlorous anhydride is, at ordinary temp)eratures, a
yellowish gas, possessing an odor somewhat resembling that of chlorine.
By means of a freezing mixture it may be condensed to an orange-red
liquid boiling about 20° C. (68° F.). It is a very unstable compound^
and decomposes readily into its elements with explosion and evolution
of heat. A slight shock, even the scratch of a file on the vessel in
which it is contained, is often sufficient to determine its violent explo-
sion. Exposure to direct sunlight has the same effect The application
of a flame also produces explosion, but with less violence. Arsenic,
phosphorus, and the alkali metals ignite in contact with it, at the same
time causing its explosion.
Water dissolves 200 times its volume of the gas, forming a yellow
solution of hypochlorous acid, which possesses powerful bleaching and
oxidizing properties.
CHLORIC PEROXIDE.
'O'(OCl) or '''Cr^O^-
Molecular weight = 67.5. Molecular volume i i L 1 litre of chloric
peroxide vapor weighs 33.75 crUhs. BoUs at 20° C. (68° F.).
History. — This compound was discovered by Davy in 1815.
Preparation. — Chloric peroxide is obtained by the action of concen-
trated sulphuric acid on potassic chlorate:
fOCl i^^
3 ■( Q^'^j + 2SO^o, = ^ O + 2SO,HoKo + OH, + 2'0'(OC1).
Potassic Sulphuric Potassic Hydric potassic Water. Chloric
chlorate. acid. perchlorate. sulphate. peroxide.
The finely powdered potassic chlorate (1 part) is added in small por-
tions to the concentrated sulphuric acid (5 parts), avoiding any rise of
temperature. On very gently warming the retort containing the mix-
ture, by surrounding it with warm water, the gas is evolved. Care
must be taken that the level of the liquid inside the retort is higher
than that of the water outside, otherwise an explosion may occur owing
to the heating of the gas.
HYPOCHLOROUS ACID. 179
Properties. — Chloric peroxide is a greenish-yellow gas, possessing an
irritating odor. It must be collected by displacement, as it attacks
mercury and is soluble in water, which takes up twenty times its vol-
ume of the gas. Exposed to the cold of a mixture of snow and salt, it
condenses to a dark-red liquid which solidifies in a bath of liquid car-
bonic anhydride and ether.
It is a very unstable and dangerous compound, frequently exploding
from the slightest cause. It is a powerful oxidizing agent. Phospho-
rus, organic and other combustible substances, ignite when brought in
contact with it. If a drop of concentrated sulphuric acid be allowed .
to fall on a mixture of equal parts of potassic chlorate and sugar (sepa-
rately powdered and cautiously mixed on a card with a feather), the
chloric peroxide thus liberated ignites the sugar, and the whole mass
deflagrates brilliantly.
If the aqueous solution of chloric peroxide be saturated with a base,
a mixture of chlorate and chlorite is formed :
20KH + 2'0'(OC1) = jgg^ + OClKo + OH,.
PoUflsic Chloric peroxide. Potassic Potassic Water,
hydrate. chlorate. chlorite.
As the molecular formula of chloric peroxide, deduced from its vapor-
density, is ClOj, this compound can be formulated only on the suppo-
sition that its gaseous molecule contains either one or three unsatisfied
bonds.*
HYFOOHLOBOnS ACID.
OCIH or ClHo.
Moleeular weight = 52.6.
Preparation. — 1. Hypochlorous acid is formed by the action of
water on hypochlorous anhydride :
OCl, + OH, = 2ClHo.
Hypochlorous Water. Hypochlorous
anhydride. acid.
* Several similar cases are known, thus :
Nitric oxide, ^^'O or ''^'^O.
Nitric peroxide (at 140^) ^*'0, or ''^Nq |
Hypovanadic chloride, ^V'^Cl^.
Molybdic pentachloride, ^Mo'Clft.
Tungstic pentachloride, 'W^Cl,.
The above are the molecular formulae of these compounds as deduced from their
vapor-densities, and in every case the presence of an odd number of unsatisfied bonds
must be assumedi It is perfectly conceivable, however, that in the liquid or solid
state, two such molecules mutually satisfy each other's affinity, so as to produce a sat-
urated molecule of twice the molecular weight. In fact, in the case of nitric peroxide,
the vapor-density just above the boiling point of this compound corresponds rather
with the formula < 2q' than with the formula ''N**Oj. Nitric oxide, and chloric
peroxide, in some of their reactions, behave as if they possessed molecular formnlie
twice as great as those deduced from their vapor-densities.
180 INORGANIC CHEMISTRY.
2. If chlorine water be shaken with an excess of precipitated mer-
curic oxide^ the yellow color of the solution rapidly disappears, and
hypochlorous acid along with mercuric oxychloride is formed :
(HgCl
2HgO + OHj + 201, = <0 + 2ClHo,
(HgCl
Mercnric Water. Mercuric Hypochloroas
oxide. oxychloride. acid.
The solution of hypochlorous acid may be decanted from the insoluble
oxychloride. If only 1 molecule of mercuric oxide is employed for
every 2 molecules of chlorine, hypochlorous acid is formed as before ;
but a chloride instead of an oxychloride of mercury is formed, and re-
mains in solution along with the hypochlorous acid. Thus :
HgO + OH, + 2C1, = HgCl, + 2ClHo.
Mercuric Water. Mercuric Hypochlorous
oxide. chloride. acid.
3. Another method consists in adding to a solution of bleaching-
powder (Ca(OCl)Cl) dilute nitric acid in quantity sufficient to saturate
half the calcium:
fNO,
20a(OCl)a + 2NO,Ho = OaQ, + <^ Cao" + 2aHo.
(NO,
Bleaching- Nitric acid. Calcic Calcic Hypochlorous
powder. chloride. nitrate. acid.
On subjecting the mixture to distillation, an aqueous solution of hypo-
chlorous acid passes over.
Properties. — Hypochlorous acid has not been prepared in a state of
purity. The aqueous solution produced by the absorption of hypo-
chlorous anhydride in water is a yellow liquid of a penetrating odor,
possessing powerful oxidizing properties. Black plumbic sulphide is
changed by it into white plumbic sulphate. Only the dilute aqueous
solution can be distilled without decomposition.
Hypochlorous and hydrochloric acids mutually decompose each other,
yielding chlorine and water :
ClHo + HCl = CI, + OHj.
Hypochlorous Hydrochloric Water,
acid. acid.
The chlorine is thus evolved from both compounds.
In like manner a mutual decomposition takes place between hypo-
chlorous acid and argentic oxide, both compounds giving off oxygen :
OAg, + 2ClHo = 2AgCl + OH, + O,.
Argentic Hypochlorous Argentic Water,
oxide. acid. chloride.
CHLORIC ACID. 181
SypochlorUes, — Hypochlorous acid converts raetallic oxides and
hydrates into hypochlorites :
OKH + ClHo = ClKo + OH^
Potassic Hypochlorous Potassic Water,
hydrate. acid. hypochlorite.
Hypochlorous is a very weak acid. The carbonic anhydride of the
air is able to expel the acid from the moist salts. The hypochlorites
are almost unknown in a state of purity.
When chlorine is passed into a cold dilute solution of an alkaline
hydrate, a mixture of chloride and hypochlorite is formed : - ~
20KH + CIj = KCl + CIKo + OH^.
Potassic hydrate. Potassic Potassic Water.
chloride. hypochlorite.
But when the hydrate of an alkaline earth is employed, the dyad
character of the metal determines the formation of a compound which
is simultaneously a chloride and a hypochlorite, one of the bonds being
united with chlorine and the other with chloroxyl. Thus the calcium
compound (bleach ing-powder) has the graphic formula CI — Ca — O —
CaHo, + CI, = Oa(OCl)Cl + OH,.
Calcic hydrate. Bleaching-powder. Water.
Many chemists have considered that bleaching-powder is a mixture
of calcic chloride with calcic hypochlorite in molecular proportions ;
but the properties of the compound do not support this view. Calcic
chloride is deliquescent and soluble in alcohol : whereas bleaching-
powder, if properly prepared, does not deliquesce, and no calcic chlo-
ride can be extracted from it with alcohol.
By the action of the stronger acids bleaching-powder yields free
chlorine :
Ca(OCl)CI + SO,Ho, = SO,Cao'' + OH, + CI,.
Bleachiog-powder. Sulphuric acid. Calcic sulphate. Water.
OHLORIO ACID.
OCl
O
OH
Molecular weight = 84.5.
tOHo <»'
loi
Higtorjf. — ^This compound was discovered by Berthollet in 1786.
Preparation. — Chloric acid is prepared by the action of dilute sul-
phuric acid upon baric chlorate :
182
INOBOANIC CHEUI8TBT.
''oa
Bao'^ + 80^0, = 2|§^'^ + SO,Bao'^
OCl
B&ric chlorate. Sulphuric acid. Chloric acid. Baric sulphate.
The point of complete precipitation must be exactly attained, so that
no excess of either reagent is present. This may be ascertained by
testing a couple of samples of the supernatant liquid— -one with sul-
phuric acid and the other with baric chlorate. No precipitate ought to
be produced in either case. The clear liquid must be decanted from
the precipitate of baric sulphate, and evaporated in vctcuo over sul-
phuric acid. In this way it may be concentrated till it contains 40 per
cent, of chloric acid, beyond which point it decomposes.
Properties, — Thus prepared, chloric acid is a syrupy liquid of a yel-
lowish color, possessing powerful oxidizing properties. A few drops
of the acid falling upon paper produce instantaneous ignition. Sulphur
and phosphorus are also inflamed by it. The dilute solution bleaches
vegetable colors. It is a monobasic acid.
By boiling, it is decomposed into perchloric acid, water, chlorine,
and oxygen :
foa
= ^O + OH,
(OHo
Chloric acid. Perchloric acid. Water.
OCl
OHo
+ CI, + 20,
Chlorates. — Potassic chlorate may be prepared by passing an excess
of chlorine into a hot concentrated solution of potassic hydrate :
60KH + 3C1, =
Potassic
hydrate.
6KC1 + {^o + 2®^*-
Potaasic Potassic
chloride.
chlorate.
Water.
The chlorate is less soluble than the chloride, and separates out in tabu-
lar crystals. It may be purified by recrystallization.
Cafcic chlorate is formed when chlorine is passed through boiling
milk of lime :
OCl
O
6CaHo, + 6CI2 = \ Cao" + 50aCl, + SOH^j.
OCl
Calcic hydrate.
Calcic
chlorate.
Calcic
chloride.
Water.
By the addition of potassic chloride to the calcic chlorate, potassic
chlorate is formed ; the latter is then separated from the very soluble
calcic chloride by crystallization :
PERCHLORIC ACID. 183
roci
O
Cao" + 2KC1 = ^{^0 + OaCI^
^OCl
Calcic chlorate. Potaasic Potassic Calcic
chloride. chlorate. chloride.
This is the method by which potassic chlorate ie prepared on a large
scale.
All the chlorates are soluble in water and many are deliquescent.
The chlorates yield no precipitate with argentic nitrate; but, on
ignition, they paft with their oxygten, and the resulting chloride, when
dissolved in water, gives with argentic nitrate a white precipitate of
argentic chloride. Treated with concentrated sulphuric acid, the dry
chlorates evolve a yellow gas (ClOj).
PEBCHLOBIO ACID.
fOCl
^O or^
(OHo
OCl
o
o •
OH
Molecular weight = 100.5.
History. — Perchloric acid was discovered by Count Stadion in 1815.
Preparation. — It has already been mentioned (p. 182) that perchloric
acid is formed when chloric acid is heated. The best method, however,
of obtaining it consists in decomposing a perchlorate with sulphuric
acid:
roci roci
2{0 + SO^Ho, = 2^0 + SO^Ko^
(OKo (OHo
Potaasic Sulphuric acid. Perchloric Potaasic
perchlorate. acid. sulphate.
Pure dry potassic perchlorate is distilled from a small retort with four
times its weight of concentrated (previously boiled) sulphuric acid.
At a temperature of 110° C. (230° F.), dense fumes are evolved and
a colorless or slightly yellow liquid, consisting of pure perchloric acid,
distils over. If the distillation be continued, the liquid distillate
solidifies to a crystalline mass, consisting of an aquate of the formula
OCl
O , OHj. If this crystalline aquate be re-distilled, it breaks up
OHo
into the pure acid, which passes over first, and an aqueous acid boiling
at 203^ C. (397° F.) (Roscoe).
Properties, — Pure perchloric acid is a colorless volatile liquid with a
specific gravity of 1.782 at 16.5° C. (59.9° F.). It fumes strongly in
SO]
I
184 INOBQAKIG CHEMISTRY.
contact with moist air. It is one of the most powerful oxidizing a^nts
known : brought in contact with oi^nic substances, it causes them to
inflame with explosive violence. A few drops, falling upon charcoal,
produce ignition and explosion. In contact with the skin, it causes
dangerous wounds which do not heal for months. The pure acid can-
not be re-distilled without decomposition : the liquid in the retort be-
comes gradually darker in color, and ultimately explodes. Perchloric
acid decomposes spontaneously at ordinary temperatures, and sealed
glass tubes containing this substance burst from the internal pressure
even when kept in the dark.
Aqueous perchloric acid reddens litmus, but does not bleach. Unlike
the other oxygen acids of chlorine, it is not reduced, in a diluted state,
by sulphurous anhydride or sulphuretted hydrogen.
Preparation of Potaasic Peixhlorate, — 1 . When potassic chlorate is
heated, it fuses and gives oflF oxygen, but after a short time the fused
mass becomes pasty and the evolution of gas ceases. In order to expel
the remainder of the oxygen, a much higher temperature is necessary.
If the operation be interrupted at the end of this first stage, it will be
found that only one-third of the total oxygen from the chlorate has
been expelled, and that the fused mass in the retort contains, along
with potassic chloride, a new salt, potassic perchlorate :
OKo = ^^ + <^ + ^=
roci
OCl
= A.Vyl -I-
(OKo
PotasRic Potassic Potassic
chlorate. chloride. perchloride.
The fused mass is powdered and treated with water to remove the
potassic chloride. The undissolved residue is digested with warm
hydrochloric acid so long as chlorine or its oxides are evolved, and in
this way any unaltered chlorate is converted into chloride. A final
washing with water removes the chloride, leaving the perchlorate in a
state of purity.
2. When potassic chlorate is gradually added to boiling nitric acid,
chlorine and oxygen are evolved, whilst potassic nitrate and perchlorate
are formed :
20^
fori f°^'
^{ OKo + 2NO,Ho = 2NO,Ko + OH, + ^ O + CI, +
Potassic Nitric Potassic Water. Potassic
chlorate. acid. nitrate. perchlorate.
These salts are then separated by crystallization.
Potassic perchlorate is soluble in 65 parts of water at 15° C.
(59° F.).
The perchlorates are all soluble in water, and some of them are deli-
quescent. They require a higher temperature for their decomposition
than the chlorates; they are not attacked by hydrochloric acid, and do
not yield chloric peroxide when heated with concentrated sulphuric acid.
BORON. 185
CHAPTER XXIV.
TRIAD ELEMENTS.
Section I.
BORON, B,.
Atomic weight =11. Probable molecnUar weight = 22. Sp, gr., ada-
marUhie variety^ 2.68. Atomicity '". Evidence of atomicUy :
Boric chloride, B'^'Clj.
Boric fluoride, B^'F,.
Boric ethide, B'^'Etj.
history. — Boron was first prepared from boric anhydride by Gay-
Lussacand Thenard in 1808, and immediately afterwards independently
by Davy.
Occurrence. — Boron is found only in combination with oxygen, either
as free boric acid, or united with various bases to form borates. Of
these last, the commonest is borax or tincal, a sodic borate.
Preparation :
CL. Amorphoxis Boron, — 1. This variety may be obtained by heating
boric anhydride with sodium :
BA + 3Na, = 30Na3 + B^.
Boric anhydride. Sodic oxide.
After the reaction, which is somewhat violent, has ceased, the fused
mass is allowed to cool, and is then dissolved in dilute hydrochloric
acid. The boron remains behind as a fine brown powder.
2. Another method consists in passing the vapor of boric chloride
over heated potassium :
2BC1, + 3K, = 6KC1 + B^.
Boric chloride. Potaasic chloride.
/9. Adamantine B,oron, — On fusing boric anhydride with aluminium,
the boric anhydride is reduced :
A], + BA = 'A1'"A + B,.
Boric anhydride. Aluminic oxide.
The boron thus formed dissolves in the molten aluminium, and on cool-
ing is deposited in crystals in the interior of the mass. The aluminium
is dissolved in caustic soda, leaving the crystals of diamond boron
(Wohler and Deville).
The so-called graphOoid boron, which is formed in laminsB during
the preparation of adamantine boron, is a definite compound of boron
and aluminium, of the formula Al^B^.
186 INORGANIC CHEMISTRY.
Properties. — Amorphous boron is a brown powder, infusible at a
white neat in an atmosphere of a gas which is without chemical action
upon it, but fusible in the electric arc.
Adamantine or diamond boron forms transparent octahedral crystals
which vary in color from an almost imperceptible honey-yellow to a
deep garnet-red, and possess a lustre and refractive power almost equal
to those of the diamond. In hardness it lies between corundum and
diamond. Its specific gravity is 2.68.
Adamantine boron is, strictly speaking, not a pure variety of boron.
The crystals always contain a small quantity of aluminium and, in
cases where the crucible has been lined with charcoal in their prepara-
tion, also carbon (Hampe, Liebig'a AnnaJen^ 183, 75).
A pure adamantine boron is stated to have been obtained by fusing
amorphous boron with silver.
Reactions. — 1. When amorphous boron is heated in air, it burns,
forming boric anhydride, which fuses, coating the boron and preserving
it from further oxidation.
2. Amorphous boron decomposes hot sulphuric acid :
B, + 3SO2H02 = BA + 30H, + 38O2.
Sulphuric acid. Boric Water. Sulphurous
anhydride. anhydride.
3. Nitric acid, even when only slightly concentrated, attacks it in
the cold :
B2 + 6NO2H0 = 2BH03 + 3WA.
Nitric acid. Boric acid. Nitric peroxide.
4. At a red heat it decomposes alkaline carbonatps, sulphates, and
nitrates, forming borates :
B, + 30ONao3 = 2BNao3 + 30''O.
Sodic carbonate. Trisodic Carbonic
borate. oxide.
B2 + 38O2KO2 = 2BK08 + 3SO2.
PotasBic Tripotassic Sulphurous
sulphate. borate. anhydride.
B, + 6NO2K0 = 2BK03 + 3'N*%0,.
Potassic Tripotassic Nitric
nitrate. borate. peroxide.
5. Fused with potassic hydrate it forms a borate, with evolution of
hydrogen:
B, + 60KH = 2BK03 + 3H2.
Potassic hydrate. Potassic borate.
6. It is one of the very few elements which unite directly with
BORON. 187
nitrogen. When strongly heated in a current .of this gas, it is con-
verted into white boric nitride :
Boric nitride.
This compound is, however, best prepared by heating to bright redness
a mixture of 1 part of anhydrous borax with 2 parts of amnionic chlo-
ride. The boric nitride is thus obtained as a white amorphous powder.
It is a very stable substance, and is only slowly acted upon by boiling
solutions of alkalies or acids. Fused with caustic potash, it forms po-
tassic borate with evolution of ammonia :
BN''' + 30KH = BK05 + NH3.
Boric nitride. Potassic Potassic Ammonia,
hydrate. borate.
When heated in a current of steam, the nitride is decomposed in a sim-
ilar manner, yielding boric acid and ammonia.
Adamantine boron is much less easily attacked by heat and by rea-
gents than the amorphous variety. It does not fuse in the flame of the
oxy-hydrogen blowpipe. Heated in oxygen to the temperature of
combustion of the diamond, it undergoes only superficial oxidation ;
but it enflames at a red heat in chlorine, and is converted into boric
chloride. Acids do not attack it at any temperature; but when fused
with hydric potassic sulphate, boric anhydride is formed :
6SO,HoKo + B, = B2O3 + 3SOjjKo2 + SOH^ + SSO^.
Hydric potassic Boric Potassic Water. Sulphurous
sulphate. anhydride. sulphate. anhydride.
COMPOUND OF BORON WIIH HYDROGEN.
BOBIO HTDRmE.
BH,?
Preparation, — This compound is obtained, mixed with a very large
excess of hydrogen, by the action of hydrochloric acid upon magnesic
boride (F. Jones):
B^Mfe + 6HC1 = 2BH5 + SMgClj.
Magnesic Hydrochloric Boric Magnesic
boride. acid. hydride* chloride.
The magnesic boride is prepared by heating boric anhydride with mag-
nesium filings.
Properties, — ^Boric hydride is a colorless gas with a characteristic
odor. It produces nausea and headache when inhaled, even in moder-
ate quantity. It is sparingly soluble in water, to which it imparts its
odor.
188 INORGANIC CHEMISTRY.
Reddions, — 1. Boric hydride burns with a green flame, producing
boric anhydride and water:
2BII3 + 3O2 = BA + 30H,.
Boric hydride. Boric anhydride. Water.
2. Burnt with an insufficient supply of air, it yields water and free
boron:
2BH3 + 30 = B, + 30Hj.
Boric hydride. Water.
This may l)e shown by holding a cold surface of white porcelain in the
flame, when a brown film of boron is deposited.
3. When passed through a red-hot tube it is deoomjX)sed into its ele-
ments, and the boron is deposited as a brown film beyond the heated
portion of the tube.
4. It combines with ammonia to form a compound of unknown
composition.
5. From a solution of argentic nitrate it throws down a black pre-
cipitate containing both silver and boron.
COMPOUNDS OF BORON WITH THE HALOGENS.*
BOBIO CHLOEIDK
BCI3.
Molecular weight = 117.5. Mokcular volume [HEl 1 litre of boric
chlo7ide vapor weighs 68.75 criths. Sp. gr. 1.36 at 17° C. (52.6° F.).
BoUb at 18-23° C. (64.81° F.).
Preparation. — I. Amorphous boron spontaneously inflames in chlo-
rine forming boric chloride. In the case of the crystalline modifica-
tion, it is necessary to heat the boron in order to induce combination.
2. Boric chloride is best prepared by the action of chlorine on a mix-
ture of boric anhydride and charcoal heated to redness:
BA + 3C1, + 3C = 2BCI3 + 300.
Boric anhydride. Boric chloride. Carbonic oxide.
The mixture of boric anhydride and charcoal is contained in a porcelain
tube heated in a furnace. The gaseous boric chloride passes through a
Y-shaped tube immersed in a freezing-mixture, where it condenses, and
drops through the lower limb of the tube into a flask beneath, which
is also surrounded by a freezing-mixture. The boric chloride may be
freed from excess of chlorine by digestion with mercury.
* Halogensy "salt producers" (from SXj, sah; and yeyK^w, I bring forth), 19 a collective
name ioT the Sour elements chlorine, bjomine, iodine, and fluorine.
COMPOUNDS OF BOBON WITH THE HALOGENS. 189
The above process is one frequently employed for obtaining chlorides
of elements from their oxides. The chlorine alone cannot separate the
boron from the oxygen, nor can the carbon alone detach the oxygen
from the boron ; but by the united action of the chlorine and the car-
bon this decomposition is effected.
Properties. — Boric chloride is a colorless, very mobile, strongly refract-
ing- liquid, boiling at 18.23'' C. (64.81° F.). Its specific gravity at
17° C. is 1.35. When heated it expands very rapidly. It fumes in
the air, and is decomposed by water with formation of hydrochloric and
boric acids :
BCI3 + 30H, = 3HC1 + BH03.
Boric Water. Hydrochloric Boric
chloride. acid. acid.
With gaseous ammonia it yields a molecular compound 3NH3,2BCl8,
which forms a white crystalline powder.
BORIC BROMIDE.
BBr,.
MoUeuIar toeight = 251. Molecuiar volume \ | 1. 1 litre 0/ boric bromide vapor weigh*
125.5 criM«. Sp.gr. of liquid =2.69, BoUsat^°C.
This compound is prepared by passing bromine vapor over a red-hot mixture of
boric anhydride and charooal in a manner similar to tnat described under the prepa-
ration of boric chloride. It is purified by rectification from mercury, and forms a
colorless mobile liquid.
Its reactions and decompositions resemble those of boric chloride.
BOBIO FLUORmE.
BF,.
Molecular weight = 68. Molecular volume I i I. 1 litre weighs 34 criths.
History. — Boric fluoride was discovered by Gay-Lussac and Thenard
in 1808.
Preparation. — 1. If a mixture of 2 parts of fluorspar and 1 part of
boric anhydride, both thoroughly dried, be heated to redness in an iron
retort, boric fluoride is evolveid as a colorless gas, and may be collected
over mercury :
2BA + 30aF, = BjCao'', + 2BF3.
Boric anhydride. Calcic fluoride. Calcic borate. Boric fluoride.
2. A better method consists in heating together in a flask 2 parts of
fluorspar, 1 part of boric anhydride, and 12 parts of sulphuric acid :
BA + 30aF, + 3SO,Ho3 = 3SOHo,Cao" + SBFj.
Boric Calcic Sulphuric acid. Dihydric calcic Boric
anhydride. fluoride. sulphate. fluoride.
Properties. — Boric fluoride is a colorless gas, possessing a very pun-
gent odor. Its vapor density (air = 1) is 2.312. Water absorbs 700
190 INOBOAKIC GHEMISTBT.
times its volume of the gas. Its great affinity for water causes it to
fume strongly in the air. A pieoe of dry paper introduced into the gas
is charred by the abstraction of the elements of water from the cellu-
lose.
It combines with gaseous ammonia to form three distinct compounds,
BFj^Hj,— BF3,2NH3,— and BF^SNH,. The first is a white solid ;
the others are colorless liquids. The two last evolve ammonia on heat-
ing, and are converted into the solid compound.
Hydrofiuoboric Add. — By the action of water on boric fluoride, hy-
drofluoboric acid (BF3,HF) is formed :
4BF3 + 30H, = 3(BF3,HF) + BHo,.
Boric fluoride. Water. Hydrofiuoboric acid. Boric acid.
The solution obtained by saturating water with boric fluoride is an oily
fuming liquid with a specific gravity of 1.77. It chars organic bodies.
Hydrofiuoboric acid acts upon metallic hydrates, forming salts known
as borofluoyides :
BF3,HF + OKH = BF3,KF ^ OH^
Hydrofiuoboric Potassic Potassic Water,
acid. hydrate. borofluoride.
Possibly the boron in these compounds is pentadic ; thus B^F^H and
B^F.K.
COMPOUNDS OF BORON WITH OXYGEN AND
HYDROXVL.
Boric anhydride, ^203.
Monobasic boric acid, 1 BOH
Metaboric acid, . . J
Tribasic boric acid, 1 BHo^
Boric acid, ... J ^'
BOBIO ANHYDRIDE, Borado anhydride.
BA.
Molecular weight = 70. Sp. gr. 1.83.
Preparaiion, — Boric anhydride is obtained by heating boric acid to
redness:
2BH03 = B,Os + 30H,.
Boric acid. Boric anhydride. Water.
Properties. — Freshly prepared boric anhydride is a colorless trans-
parent vitreous solid, which, however, when exposed to the air gradu-
ally absorbs moisture and becomes opaque. When fused at a red heat,
it forms a viscous liquid like melted glass. At a white heat it volatile
BOMO ACID. 191
izes. Although boric acid is one of the weakest acids, the non-volatility
of its anhydride at any but the highest temperatures enables it to expel
stronger volatile acids from their salts when heated with them. The
sulphates are converted into borates with evolution of sulphuric anhy-
dride:
SSOjNaOa + B2O3 = 2BNao3 + 3SO3.
Sodic sulphate. Boric Sodic Sulphuric
anhydride. borate. anhydride.
Boric anhydride dissolves most metallic oxides when fused with them,
yielding in many cases characteristically colored glasses — a property
which has led to its employment as a blowpipe reagent. By gradually
volatilizing at a white heat the boric anhydride in which a metallic
oxide is dissolved, the latter may frequently be obtained in a crystallized
form, and in this way many minerals have been artificially produced.
Alumina crystallizes from this solvent in the hexagonal forms of corun-
dum, and a mixture of alumina and magnesia yields octahedral crystals
of spinelle. These artificial products are identical in all their physical
and chemical properties with the natural minerals.
BORIO AOID, Boradc aoidj Orihoboric acid.
BH03.
Molecular weight = 62. Sp. gr. 1.479.
Occurrence. — In some parts of the volcanic districts of Tuscany, jets
of gas or steam, known as aoffioni or fumaroUs, escape through fissures
in the ground. This steam contains traces of boric acid. Bround the
soffioni pools of water, called lagoons, have collected, into which the
steam passes, and in these the boric acid accumulates.
The method of extracting the acid is as follows : — Above the sojloni,
cisterns of glazed masonry are constructed, so that the vapors from two
or more somoni pass into each cistern. The highest cistern is filled by
temporarily directing the waters of a stream into it. At the end of
twenty-four hours the water from this first cistern, having taken up a
certain quantity of boric acid, is run off into a lower cistern, and
its place is supplied by fresh water. The water remains in the sec-
ond cistern for twenty-four hours, and is then run into a third cistern.
This treatment is continued till the water has passed through six or
seven cisterns, when it contains about 2 per cent of boric acid. It is
then transferred to tanks, where it remains for twenty-four hours in
order to allow the suspended earthy impurities to settle. The clear
liquid is then allowed to run in a thin stream over a long roof of cor-
rugated sheet lead, heated from beneath by the steam of a sojlone.
In this way a considerable concentration is effected. The liquid is
finally evaporated in pans to the crystallizing point. The crude sub-
stance thus obtained is recrystallized from boiling water. The crystals
are placed in wicker baskets to drain, and afterwards dried in a kiln
which is heated by the steam of a soffione. The lagoons of Tuscany
192 INORGANIC CHEMISTRY.
yield about 750,000 kilograms of boric acid yearly. Artificial sojffumi
are now produced by boring.
Salts of boric acid also occur in nature. The mineral tinoaly or nat-
ural borax^ an abnormal sodic borate of the formula
B,O,Nao„10OHj,
is found in Thibet.
Preparation. — Boric acid may be obtained by the action of hydro-
chloric acid on borax :
BANao, + 2HC1 + 5OH2 = 4BHo, + 2NaCL
Borax. Hydrochloric acid. Water. Boric acid. Sodic chloride.
One part of borax is dissolved in 2J parts of boiling water and an
excess of concentrated hydrochloric acid is added. On cooling, the boric
acid crystallizes out in thin plates.
For laboratory purposes boric acid is best prepared by recrystallization
of the commercial acid.
Properties. — Boric acid, as crystallized from water, forms lustrous
laminae, unctuous to the touch. One hundred parts of water at 10° C.
dissolve 2 parts, at 100° C, 8 parts, of boric acid. The solution turns
blue litmus wine-red, and turmeric paper, even in presence of hydro-
chloric acid, brown. When the aqueous solution is boiled, the boric
acid volatilizes with the steam, as in the soffioni. Boric acid is also
slightly soluble in alcohol, and communicates to the flame of the alcohol
a characteristic green coloration.
At a temperature of 100° C, boric acid parts with the elements of
water, and is converted into metaboric acid, BOHo:
BHoi = BOHo + OH^
Boric acid. Metaboric acid. Water.
Metaboric acid forms stable salts, such as sodic metaborate (BONao)
and magnesic metaborate
({&')
When boric acid is heated for a long time to 140° C. (284° F.)
tetraboric acid is formed as a brittle vitreous mass :
4BH03 = B^Hoa + 5OH2.
Boric acid. Tetraboric acid. Water.
The tetraborates are also stable compounds. Anhydrous borax
(B^OjNaOg) is sodic tetraborate.
The normal borates or orthoborates, derived from the tribasic acid
(BH03), are the least stable of the compounds of boric acid. ^
CARBON. 193
BORIC SULPHIDB.
MoUeular weight » 118.
Prmaratian. — Boric sulphide is formed when the vapor of snlphur is passed over
beatea boron ; but it is best prepared hy heating to brignt redness a mixture of lamp-
black and boric anhydride in a current of carbonic disulphide vapor:
2BjO, + 3CS'', + 3C = 2B,8''a + 6C^'().
Boric Carbonic Boric Carbonic
anhydride, disulphide. sulphide. oxide.
Properties. — Boric sulphide is thus obtained as a solid, yellowish- white, fusible, vit-
reons mass, which mav be volatilized in a current of sulphuretted hydrogen, and then
forms silky needles. It has a pungent odor, and its vapor irritates the eyes. Water
at once decomposes it into sulpnuretted hydrogen and boric acid :
B,S'', + 60H, = 3SH, + 2BHo,.
Boric Water. Sulphuretted Boric
sulphide. hydrogen. acid.
CHAPTER XXV.
TETRAD ELEMENTS.
Section L
OABBON, C.
Atomic weight = 12. Atomicity " and *\ Evidenoe of atomicity:
Carbonic oxide, 0"0.
Carbonic tetrachloride, O^^Cl^.
Marsh-gas, O^^H^.
Chloroform, O^^HClj
Occurrence. — Carbon exists in the free state in three distinct allo-
tropic modifications, as amorphous carbon, as graphite, and as diamond,
all of which are found in nature. In combination with oxygen as car-
bonic anhydride, it occurs in the air. It is a constituent of all organic
substances, and upon its varied combining powers the infinite mani-
foldness of the animal and vegetable kingdoms ultimately depends.
General Properties, — The following properties are common to carbon
in all its modifications : It is solid, infusible, probably non-volatile at
the highest temperatures that can be artificially produced, and insoluble
in all known solvents at ordinary temperatures.
a. Amorphoxis Carbon. — The chief varieties of amorphous carbon
are : Charcoal, lamp-black, gas-carbon, and coke.
Occurrence.— Amorphous carbon is found in nature as mineral char-
coal.
13
194
INORGANIC CHEMISTRY.
Charcoal,
Preparation. — When wood is heated to redness in closed vessels, the
cellulose (CgHKjOg);^ gives off its oxygen and hydrogen, partly as water,
partly along with a portion of the carbon in the form of oxides of car-
bon and of more or less complex organic compounds. When these
various gaseous and liquid products of destructive distillation have
ceased to be evolved, the charcoal remains behind in the retort as a
black, non-lustrous substance, preserving the form of the wood from
which it was prepared. The liquid products of distillation constitute
wood-tar, and their nature will be described under Organic Chemistiy.
In order to obtain the greatest possible yield of charcoal, care must
be taken to expel all moisture from the wood before raising the tem-
perature to redness, otherwise the charcoal at a red heat will decompose
the water, forming carbonic anhydride or carbonic oxide and liberating
hydrogen.
The distillation is performed in cast- iron retorts. The wood to be
carbonized is placed in a perforated iron case F (Fig, 31), known as a
sUpy which is then introduced into the retort A. The volatile products
Fig. 31.
of decomposition are led by the pipe L into the furnace B, where they
are burned, a saving of fuel thus being effected. In well-arranged
works at the present day, these products are condensed, acetic acid and
wood-naphtha being obtained from them. One hundred parts of wood
yield on an average 27 parts of charcoal.
In countries where wood is plentiful, a method of carbonizing in
heaps is employed, the heat being produced by the combustion of a part
of the wood. This is the oldest process of charcoal-burning. The
logs are piled on end in a heap (Fig. 32), and a space is left in the
middle to serve as a flue. The wnole is covered with turf and earth,
small apertures being made at the base of the heap to admit air. Fire
is applied from below, and the action of the heat is carefully regulated
by opening or closing the air-holes in different parts of the heap. The
charcoal obtained by this method is inferior in quality to that produced
by carbonizing in retorts.
A very pure charcoal for special laboratory purposes is obtained by
carbonizing sugar in a closed platinum vessel. If it is necessary to get
CARBON.
196
rid of the last traces of hydrogen, the product must be strongly ignited in
a current of chlorine. This charcoal possesses the advantage of contain-
ing no silica, and may therefore he employed in the preparation of
volatile chlorides (see bojio chUyiide, p. 188), which would otherwise
be contaminated with silicic chloride (SiClJ.
Another variety of charcoal is animal charcoal or bon&ilack, pro-
duced by the carbonization of bones in closed vessels, A fetid oil of
very complex character distils over during the process. The charred
mass which remains in the retort is afterwards coarsely granulated, in
Fig. 32.
which form it is employed to decolorize liquids. Animal charcoal
which has lost its decolorizing properties by repeated use may have
these restored by again heating it in closed vessels, A very pure ani-
mal charcoal is obtained by carbonizing dried blood which has been
mixed with potassic carbonate, in order to render the product more
porous. The potash is afterwards extracted with hydrochloric acid.
Properties, — The qualities of the product vary with the temperature
employed. The best wood-charcoal for laboratory and metallurgical
purposes is prepared at a high temperature, and is a hard brittle sub-
stance with a lustrous fracture. When struck, it emits a metallic
sound. Common charcoal is a bad conductor of heat and electricity;
but by exposing it for a long time in closed vessels to a very high
temperature, it becomes an excellent conductor.
The elimination of the oxygen and hydrogen from the wood in the
formation of charcoal leaves the mass in an extremely porous condition.
196 INOBOANIO CHEMISTRY.
and the infusibility of the charcoal causes it to retain this porosity. A
very small piece of charcoal may thus expose an enormous surface, and
hence all phenomena dependent upon surface action are displayed in a
high degree by this substance. To this class belong the condensation
of gases and decolorizing of liquids.
The absorbent }>ower of wo<^d-charcoal for gases may be shown by
cooling a fragment of freshly ignited charcoal under mercury, and
then passing it into a tube filled with gaseous ammonia over the mer-
curial trough (Fig. 33). The mercury will rapidly rise in the tube as
the ammonia is absorbed. The following list gives the volumes of
some of the principal gases absorbed by one volume of boxwood -char-
coal at 0° C., and under a pressure of 760 mm., as determined by
Hunter :
Absorption of gases by charcoal —
Hydrogen, 4.4
Nftrogen, 15.2
Oxygen, 17.9
Carbonic oxide, 21.2
Carbonic anhydride, 67.7
Nitric oxide, 70.5
Nitrous oxide, 86.3
Ammonia, 171.7
As a rule the most easily liquefiable gases are absorbed in greatest
quantity by charcoal.
Noxious effluvia are in like manner absorbed by charcoal, and at the
same time undergo oxidation at the expense of the oxygen condensed
in its pores, a property which has led to the use of charcoal for disin-
fecting purposes.
The property of decolorizing liquids depends upon the absorption of
the coloring matter in the pores of the charcoal. Animal charcoal is
best suited for this purpose, inasmuch as the inorganic matter contained
in the bones increases the porosity of the product. If a red wine be
warmed with freshly ignited animal charcoal and then filtered, the
filtrate will be colorless. In the process of sugar refining the raw
syrup is decolorized by filtration through animal charcoal. Charcoal
filters are also employed for the purification of water for drinking
purposes, but they are not to be recommended, owing to the stimulus
which animal charcoal gives to the development of animalcular life.
Lamp-black — When certain organic substances rich in carbon, such
as resins, essential oils, and heavy hydrocarbons, are burned in air, the
supply of oxygen is insufficient for complete combustion, and the flame
smokes. A porcelain dish or any cold object held in the flame is quickly
covered with a finely divided black deposit. This is the substance
known as lamp-black.
On a large scale, the tar, resin, or other highly carbonaceous substance
is burnt with a limited supply of air, and the heavy smoke is made to
pass through chambers, where the lamp-black settles.
Lamp-black, after strong ignition in a stream of chlorine in order to
CARBON. 197
free it from the hydrogen which the ordinary product always contains,
is one of the purest forms of amorphous carbon.
Lamp-black is employed in the manufacture of printing ink and
China ink, and also as a common black paint.
Coke. — ^When coal is subjected to destructive distillation in the
manufacture of coal-gas, a number of volatile products are expelled,
and an impure amorphous carbon, known as coke, remains in the retort.
Coke is also prepared by burning coal in heaps, as in the conversion of
wood into charcoal ; but in the coking-heap the central flue is built of
fire-bricks. The coking is tlius eflected by the combustion of a portion of
the coal. As soon as smoke ceases to be given off, the air-holes at the
bottom of the heap are closed with wet sand, or, more frequently, the
fire is quenched with water. At the present day most of the coke is
obtained by partially burning the coal in specially constructed coking
ovens. The coke prepared in ovens is denser and of better quality
than that obtained by other means. Coke does not ignite readily, nor
is its combustion well maintained, except in large masses and with the
aid of a rapid current of air ; but its combustion produces a very high
teraj^erature, and is unattended with the production of smoke. It is
largely used in iron smelting and other metallurgical operations.
Gas Carbon. — This substance is also product in the manufacture
of coal-gas. When the heavier hydrocarbons formed from the coal
pass over the red-hot walls of the retort, they deposit a portion of their
carbon in an exceedingly dense and coherent form. The gas carbon so
obtained forms a gray, very hard mass, possessing a metallic lustre.
It is an excellent conductor of heat and electricity. The carbon-plates
of the Bunsen battery, and sometimes the carbon-rods for the electric
arc-light, are made from this material.
A very pure form of amorphous carbon is obtained by the action of
potassium at a high temperature on carbonic anhydride or a carbonate:
SCOj + 2K, = C + 200Koj.
Carbonic anhydride. Potassic carbonate.
The carbon must be carefully washed with hydrochloric acid to free it
from the last traces of alkali.
Rea^ction. — By treatment with a mixture of potassic chlorate and
fuming nitric acid, amorphous carbon is converted into brown com-
pounds soluble in water. Potassic permanganate, in alkaline solution, or
nascent electrolytic oxygen, converts it into mellitic acid, '^'0'g(COHo)g,
and other products.
Coal. — This substance consists of the remains of a former flora. It
is the result of a decomposition which woody fibre has undergone
during long geological periods under varying conditions of temperature
and moisture, and with exclusion of air. Under these circumstances the
hydrogen and oxygen of the wood have been gradually reduced in
quantity by elimination, partly as water and partly in combination with
a portion of the carbon as methylic hydride {the fire-damp of the miner)
and carbonic anhydride. The process is thus very similar to that
which occurs when wood is converted into charcoal by heating in closed
198
INOBOANIO GHEMISTRT.
vesseli«. The degree of change which the woody fibre has undergODe
varies with the age of the coal : thus lignite, a more recent forma-
tion, preserves its fibrous structure and contains a large percentage of
oxygen and hydrogen ; whereas anthracite, which is found in the oldest
carboniferous deposits, is dense and amorphous, and contains a very
high percentage of carbon.
The following is a list of some of the chief varieties of coal :
Lignite or Brown Coal is generally of more recent date than the
chalk formation ; whilst true coal is older than the chalk. Its specific
gravity is also lower than that of true coal. It yields a powdery coke
and bums with a comparatively smokeless flame.
Bituminous or Caking Coal. — The greater number of English coals
belong to this class. Bituminous coal fuses and eakes together on heat-
ing, giving off much smoke and gas, and yielding a lustrous coke.
Oannel cool is a variety of bituminous coal. It contains a large per-
centage of hydrogen, and is much in request for purposes of gas manu-
facture.
AnUiracite. — This is a very hard coal with a conchoidal fracture. It
is of an iron-black color, with a semi-metallic lustre, and its smooth
surface frequently displays iridescence. It splinters when heated, and
ignites with difficulty, burning with very little flame and no smoke,
and giving out an intense heat. It is much used as a steam coal and
also for smelting purposes.
The following table shows the average composition of coals from
different localities in Great Britain. The last column contains the
thermal effect as measured by the number of pounds of water at 100^
0. which were found to be converted into steam in a Cornish boiler by
1 pound of the coal :
Tahle showing the Average Composition of Coals from different Localities.
LocaUty.
Sp.gr.
Carbon.
Hydro-
gen.
Nitro-
gen.
Sal-
phur.
Oxygen.
Ash.
Percentage
of coke
left by each
coal.
Evap-
orating
power
Wales, . .
Durham. .
Lancashire,
Scotland, .
Derbyshire,
1.815
1.256
1.273
1.259
1.292
83.78
82.12
77.90
78.53
79.68
4.79
5.31
6.32
5.61
4.94
0.98
1.35
1.80
1.00
1.43
1.24
1.44
1.11
1.01
4.16
5.69
9.53
9.69
10.28
4.91
8.77
4.88
4.08
2.65
72.60
60.67
60.22
54.22
69.32
9.06
8.37
7.94
7.70
7.58\
fi. Graphite.
Occurrence. — This variety of carbon constitutes the mineral plumbago
or black-lead. It is found in various crystalline rocks, such as granite,
gneiss, and piorite. It is possibly of vegetable origin, and in this case
corresponds to the most complete transformation of vegetable substance,
inasmuch as it never contains more than traces of hydrogen. The
geological formations in which it (xxiurs are likewise much older than
the carboniferous strata.
Preparation. — 1. When the diamond is exposed to the heat of the
electric arc in an atmosphere devoid of oxygen, it swells up and is
GABBON. 199
converted into a black mass of graphite. The various forms of amor-
phous carbon are also converted into graphite under these conditions.
2. Cast iron is a compound of carbon and iron. In the molten
state the iron dissolves more carbon than is required for combination,
and, on cooling, this excess separates out as crystalline scales of graphite.
When gray pig-iron is dissolved in an acid, the graphite remains
behind.
Properties. — Graphite crystallizes in six-sided plates, in which form
it sometimes occurs in nature; but it is more frequently found in
granular, foliated, or fibrous masses. The natural variety is grayish-
black, with a metallic lustre (hence the name blaek'lead\ and is unctu-
ous to the touch. Its specific gravity varies from 1.8 to 2.4. It is
soft enough to leave a mark on paper, a property which is turned to
account in the manufacture of black-lead pencils. It conducts heat
and electricity well.
Reaction, — If 1 part of pure ffraphite be heated for some days on a
water-bath to 60^ with 3 parts oi potassic chlorate and sufficient con-
centrated nitric acid to render the whole fluid, a portion of the graphite
is converted into graphitic acid (CnH^Og), and by the repetition of this
treatment pure graphitic acid may be obtained in thin yellowish trans-
parent crystals (Brodie). When heated, graphitic acid decomposes with
violence, evolving gas, and yielding a very bulky finely-divided black
powder of pyrographiiic oxide (CaHjOJ which is dissolved by a mix-
ture of potassic chlorate and nitric acid. Baric graphitate detonates
violently when heated.
Applications. — Graphite is chiefly employed in the manufacture of
blacK-lead pencils. Other uses are : the coating of iron-work as a pre-
servative against rust, the polishing of gunpowder, the lubrication of
machinery, and the preparation of plumbago crucibles.
y. Diamond.
Occurrence. — ^This gem is found in alluvial deposits produced by the
disintegration of a particular micaceous rock known as Uacolumite.
It has also been found in matrix in the rock itself. The principal
diamond fields are those of Brazil and the Cape of Good Hope.
Among all the known allotropic modifications of the elements, the
diamond is remarkable as the only one which has not been produced
artificially.
Properties. — ^The diamond crystallizes in forms derived from the
regular octahedron. The faces of the crystals are very frequently con-
vex. The finer specimens are transparent and colorless. Colored
varieties are not uncommon. It possesses a characteristic and brilliant
lustre, known as the adamardine lustre, which is due to its very high
refractive and dispersive power. This lustre is artificially intensified
by cutting. The diamond is the hardest of known substances, and can
be cut only by means of its own dust, the gem being pressed against a
revolving steel plate covered with diamond-dust and oil. Its specific
gravity is 3.55. It is a non-conductor of electricity.
In closed vessels, it may be heated to very high temperatures with-
out undergoing change, but when subjected to the heat of the electric
arc it is converted into graphite. When intensely heated in air or
200 INORGANIC CHEMISTRY.
oxygen it burns, forming carbonic anhydride, and leaving a small
quantity of ash. The diamond contains neither hydrc^n nor oxygen.
The diamond is not attacked by a mixture of potassic chlorate and
nitric acid.
Unlike boron and silicon, the diamond does not dissolve in molten
aluminium.
Applications. — Besides its well-known use as an ornament, the dia-
mond is employed in the arts. Diamonds are used for cutting glass,
for which purpose only the natural curved edge of the crystal is suit-
able, as the cut or broken diamond merely scratches the glass super-
ficially. The rock-boring apparatus employed in tunnelling and well-
sinking is frequently fitted with diamonds set in the edge of a steel
ring. Diamond-dust is the best grinding and polishing material for
hard substances. For these purposes, inferior varieties of diamond
may be employed. The optical properties of the diamond have caused
it to be used for microscopic objectives; but the great difficulty of
grinding lenses of so refractory a material has limited this application.
COMPOUNDS OF CARBON WITH OXYGEN.
OARBONIO ANHYDRIDE.
OO,.
Molecular weight = 44. Molecular volume \ 1 \ 1 litre weighs 22
criths. Fme8at—5T'C.{—70.6°F.) Boils behw Us fusing point.
History. — ^This gas was discovered by Van Helmont in the seven-
teenth century. It was further studied by Black, but its tnie chemical
nature was first demonstrated by Lavoisier.
Occurrence. — Carbonic anhydride occurs in small quantity in the
atmosphere, to the extent of about 3 volumes in 10,000 volumes of air.
All spring-water contains it in solution, and in the case of some springs
arising in volcanic districts, the quantity of carbonic anhydride dis-
solved is so great as to cause the water to effervesce strongly. In such
volcanic districts, the gas is often given off from fissures in the earth,
and this continues for thousands of years after the cessation of active
volcanic phenomena.
Preparalitm. — 1. When carbon is burned in an excess of oxygen or
air carbonic anhydride is formed :
C + O, = OO^.
Carbonic
anhydride.
Unless an excess of oxygen or air is employed, carbonic oxide is also
formed.
This method is sometimes employed when carbonic anhydride is
required in very large quantities for manufacturing purposes, as in the
preparation of white lead. Coke is burnt in atmospheric air for such
applications.
CARBONIC ANHYDRIDE. 201
2. The method usually employed in the laboratory, for the prepara-
tion of this gas in a state approximating to purity, depends on the fact
that carbonates are easily decomposed by stronger acids, and that the
carbonic acid thus produced instantly breaks up into carbonic anhy-
dride and water. Calcic carbonate in its naturally occurring varieties,
as chalk or marble, is the salt usually employed for this purpose. The
marble, broken into coarse fragments, is introduced into a flask fitted
with a funnel and delivery tube as in the apparatus for the preparation
of hydrogen (Fig. 16, p. 143), and the flask is half-filled with water.
Hydrochloric acid is then poured through the funnel until the gas is
evolved in a sufficiently rapid stream :
OOCao" + 2HC1 = OO^ + OH^ + OaCI,.
Calcic Hydrochloric Carbonic Water. Calcic
carbonate. acid. anhydride. chloride.
Other carbonates may be substituted for calcic carbonate and other
acids for hydrochloric acid in the above reaction :
OOKo, + SOjHojj = OOj + OH2 + SOjKo,.
Potassic Sulphuric Carbonic Water. Potassic
carbonate. acid. anhydride. sulphate.
OOHoKo + NOjHo = OO, + OH, + NO,Ko.
Hydric potassic Nitric acid. Carbonic Water. Potassic
carbonate. anhydride. nitrate.
3. Sulphuric acid cannot be employed, in the foregoing way, with
marble in the preparation of carbonic anhydride, as the insoluble calcic
sulphate coats the marble and prevents further action. But if concen-
trated sulphuric acid be poured upon chalk and then a little water be
added, the gas is evolved in a steady current, as the acid under these
conditions produces a disintegration of the chalk.
4. Most carbonates, when strongly heated, evolve carbonic anhy-
dride, as for example when chalk or marble is calcined to form quick-
lime:
OOCao" = OaO + OO^.
Calcic Calcic Carbonic
carbonate. oxide. anhydride.
The carbonates of the alkali 'metals are the only exceptions to this
rale.
Formation. — When any substance containing carbon is burned in air,
the carbon is converted into carbonic anhydride, the hydrogen with
which the carbon is generally associated forming water. In this way
immense quantities of carbonic anhydride are continually discharged
into the atmosphere in the combustion of coal and wood.
Active combustion is a rapid oxidation. But combined carbon may also
undergo slow oxidation with production of carbonic anhydride. Thus
the slow oxidation of the animal tissues of the living body produces the
carbonic anhydride which is given off from the lungs during respira-
202 INORGANIC CHEMI8TBT.
tion. This may be showD by breathing through lime-water, which is
thus rendered turbid.
In fermentation, decay, and putrefaction, processes in which complex
chemical changes take place in organic matter under the influence of
minute living organisms, part of the carbon of the substance is often
evolved along with a portion of its oxygen as carbonic anhydride.
Thus in the fermentation of grape-sugar with yeast at a temperature of
about 22° :
CeH,A = 20,H,Ho + 200^
Grape-sugar. Ethylic alcohol. Carbonic
anhydride.
A similar evolution of carbonic anhydride occurs during the forma-
tion of coal.
OirculcUion of Carbon in Nature, — All the carbon present, in every
form of combination, in the bodies of plants and animals is derived
ultimately from the carbonic anhydride of the air. Plants, by means
of the chlorophyll, or green coloring matter of their leaves, and with
the aid of sunlight, decompose this carbonic anhydride, evolving the
oxygen, and retaining the carbon for the purpose of building up their
tissues. Animals — the herbivora directly, the carnivora indirectly —
derive their entire nourishment from plants. The carbon is thus trans-
ferred to the bodies of animals, where it serves, by its oxidation, as a
source of vital heat and of energy of motion. The oxygen necessary
for this oxidation is absorbed during respiration by the haemoglobin or
red coloring matter of the blood, which thus serves as a carrier of oxygen
to the tissues; and the carbonic anhydride formed in the oxidation is,
as already stated, expelled with the breath and thus finds its way back
into the atmosphere.
A similar cycle of operations occurs with hydrogen. The plant de-
composes, under the same conditions, either the aqueous vapor of the
atmosphere or the water contained in its own juices, evolving the oxygen
and assimilating the hydrogen. A portion of the oxygen, either from
the carbonic anhydride or from the water, or from both, is at the same
time retained by the plant. During the oxidation of the animal tissues
the hydrogen is for the most part re-oxidized to water, and in this form
is exhaled or otherwise expelled from the body.
The plant thus inhales carbonic anhydride and aqueous vapor, and
exhales oxygen. Animals inhale oxygen and exhale carbonic anhydride
and aqueous vapor. In this way the action of the one tends to balance
that of the other.
Broadly speaking, the functions of the plant may be said to be «yn-
thettoalj those of the animal analyticaL
Propertiea. — Carbonic anhydride is a colorless gas, with a slightly
pungent odor and an acidulous taste. It does not support either com-
bustion or respiration : the flame of a taper, plunged into the gas, is
extinguished, and animals are rapidly asphyxiated by it. Its physio-
logical action is that of a narcotic poison. In small quantities it may
be breathed with impunity ; but air containing 0.6 per cent, produces
headache and oppression, and the presence of even 0.2 per cent, is suf-
ficient to render air unwholesome.
CARBONIC ANHYDRIDE.
203
The specific gravity of carbonic anhydride is, according to Regnaalt,
1.5241 (air = 1). It is thus rather more than one and a half times
heavier than air. Owing to its great density it may be collected by
displacement, and may be poured from one vessel into another like a
liquid. On lowering a taper into the vessel into which the gas has been
poured, the flame will be extinguished as soon as it is immersed in the
carbonic anhydride. In like manner, if a counterpoised beaker be sus-
pended from one arm of a balance (as in the experiment for demon-
strating the lightness of hydrogen, with the exception that in the case
of carbonic anhydride the beaker is suspended mouth upwards), then,
on pouring the heavy gas from another vessel into the beaker, the arm
of the balance supporting the beaker will be depressed by the weight of
the gas. This property, which causes carbonic anhydride to collect at
the lowest level, is sometimes the source of fatal accidents, as in cases
where wells or beer-vats containing this gas have been incautiously
entered. The phenomena of the Grotto del Cane and of the Poison
Valley in Java are due to the same cause. Carbonic anhydride is
formed in coal-mine explosions by the combustion of the fire-damp
Fig. 34.
(methylic hydride, OH^), and it frequently happens that miners who
escape the violence of the explosion are asphyxiated by the after-damp.
It has been shown, however, that the after-damp generally also contains
the much more deadly carbonic oxide.
When carbonic anhydride is subjected to a pressure of 36 atmo-
spheres at a temperature of 0° C, it condenses to a colorless liquid.
The liquefaction of the gas may be conveniently effected by means
of the apparatus shown in Fig. 34, devised by Thilorier. Into the
strong wrought-iron generator gr, hydric sodic carbonate, stirred up with
a little over twice its weight of water, is introduced. Sulphuric acid is
poured into the inner tube (represented by dotted lines in the figure)
204 INORGANIC CHEMISTRY.
and the head of the generator is screwed on. The generator, which
swings upon trunnions on the stand «, is then turned over so as to allow
the sulphuric acid to flow out of the tube and mix with the hydric
sodic carbonate. Carbonic anhydride is liberated according to the
equation —
20OHoNao + SO3H02 = 200, + SO^Nao, + 20H,,
Hydric sodic Sulphuric Carbonic Sodic Water,
carbonate. acid. anhydride. sulphate.
On bringing the apparatus back into its former position, the carbonic
anhydride, liquefied by pressure, rises to the surface and floats as a layer
on the solution of sodic sulphate. The generator is then connected by
the copper tube t with the wrought-iron receiver r. On opening the
screw-taps w and t, applying a gentle warmth to the generator, and cool-
ing the receiver, the liquefied anhydride distils over into the latter vessel.
The screw-tap v is then closed ; the generator is disconnected, emptied,
recharged, and the above operations repeateci. Six or seven charges
suffice to fill the receiver. The nozzle n is then attached to the receiver
in place of the tube L An improved form of Thilorier's apparatus has
been constructed, in which the liquefied anhydride, instead of being
distilled, is forced over in the liquid state into the receiver by means of
water pumped in at the base of the generator.
Liquid carbonic anhydride is colorless and very mobile. Under the
influence of heat it expands more rapidly than any known substance,
surpassing even the gases in this respect. The following table shows
this rapid alteration of density :
Temperature.
Sp.gr.
—10° C. (14° F.)
.9951
+ 0° C. (32° F.)
.9470
+20° C. (68° F.)
.8266
Carbonic anhydride at — 78° exerts a pressure of 760 mm. When
the liquid is exposed to the air the heat rendered latent by its evapora-
tion causes it to solidify. The following apparatus
^^' ^^' (Fig. 35) is well adapted for procuring solid carbonic
^H anhydride. It consists of a circular brass box in two
HI halves, one of which fits over the other as a lid, each
^jIH half being furnished with a hollow handle covered with
^^^B^ wood or some other bad conductor of heat. Through
^^^^^^^ a small tubular opening in the circumference the nozzle
of the screw-tap of the wrought-iron cylinder con-
taining the liquefied carbonic anhydride is inserted.
On opening the screw-tap a jet of liquid carbonic
anhydride is projected with great violence into the
brass box, and striking at a tangent to its internal
circumference, flows round it, solidifying in the
process, and filling the interior with a snow-like
mass. On opening the box, the snowball of solid carbonic anhydride
may be removed.
Solid carbonic anhydride thus prepared is a coherent white powder,
CARBONIC ANHYDRIDE. 205
resembling snow in appearance. It may be exposed for a short time
to the air ; but eventually disappears as gas^ without previously melting.
Though its temperature is so low, it may be touched without incon-
venience, as the gas which it evolves forms a non-conducting layer
around it; but if it be pressed upon the skin, it produces a blister like
that caused by a burn. It is soluble in ether, and in this condition its
evaporation can be conveniently employed as a source of cold. When
the solution of carbonic anhydride in ether is evaporated in vacuo, the
temperature sinks so low as — 110° C. ( — 166° R). By means of the
depression of temperature thus produced, liquid carbonic anhydride
contained in a tube may be frozen into a transparent ice-like solid.
Water at 15° C. (59° F.) dissolves its own volume of carbonic
anhydride under a pressure of 760 mm. The quantity of gas absorbed
is approximately proportional to the pressure. (See Introduction, p.
124.) If water be saturated with the gas at a higher pressure, and the
pressure be suddenly removed, evolution of gas ensues. The solubility
of carbonic anhydride decreases rapidly at higher temperatures, and the
whole of the dissolved gas may be expelled by boiling.
Composition. — 1. When carbon is burned in oxygen, it is found that
the volume of the carbonic anhydride formed is exactly equal to that
of the oxygen employed. It is thus evident that carbonic anhydride
contains its own volume of oxygen. In this way the composition by
weight of carbonic anhydride may be deduced. Suppose the volume
of oxygen employed to have been 1 litre —
1 litre of (X>2 formed weighs 22 criths.
Deduct the weight of 1 litre of O . . . . 16 '*
There remain : carbon, 6 "
Therefore 6 parts by weight of carbon combine with 16 of oxygen to
form 22 parts of carbonic anhydride. Expressed in atomic weights^
this gives —
Proportion of carbon is to oxygen as 12 : 32,
corresponding to the formula OOj.
2. The composition by weight of carbonic anhydride can be directly
determined by ascertaining the weight of this gas which is formed
when a known weight of pure carbon (diamond or purified graphite) is
burnt in a current of oxygen. This was the method employed by
Dumas and Stas. The oxygen is contained in the Woulff's bottle a
(Fig. 36), from which it is expelled during the operation by dilute
caustic potash, this liquid being employed in order to prevent the gas
from being contaminated by the carbonic anhydride contained in ordi-
nary water. It then passes through three U-tubes 6, o,and d, the first
containing pumice moistened with strong potash, the second fragments of
solid potash, and the third pumice moistened with concentrated sulphuric
acid. The oxygen, thus thoroughly freed from carbonic anhydride and
moisture, passes on through the glazed porcelain tube ef, which contains
the weighed portion of carbon placed in a platinum boat This tube is
206
INORGANIC CHEMISTRY.
heated to redne&s in the furnace F, and the carbon in the boat thus
burns in the current of purified oxgen. As carbonic oxide may be
formed in this combustion, the gases
are passed through a second tube gh
of refractory glass, containing granu-
lated cupric oxide, and heated to
redness by means of charcoal placed
in the iron trough q. In this way
any carbonic oxide is converted into
carbonic anhydride at the expense of
the oxygen of the cupric oxide. The
mixture of carbonic anhydride and
oxygen passes on through the U-tube
ky containing pumice and sulphuric
acid ; then through the Liebig's bulbs
m, containing a strong solution of
potash, by which the greater part of
the carbonic anhydride is absorbed ;
then through the tube n filled with
pumice moistened with strong potash,
in order to absorb the last traces of
carbonic anhydride. The tube o,
containing fragments of solid potash,
serves to arrest any moisture which
may be given off from the tube n.
The last tube, p, also containing
fragments of solid patash, is intro-
du^ in order to prevent access of
carbonic anhydride and moisture from
the air to the tube o. The tubes fc,
m, n, and o are accurately weighed
both before and after the combustion
of the carb(m. If the experiment
has been properly conducted so as to
exclude every trace of moisture, and
if the carbon employed has been per-
fectly free from hydrogen, the tube
Ic ought to show no increase in weight.
The increase in weight of the tubes
m, n, and o gives the weight of car-
bonic anhydride formed. The weight
of carbonic anhydride, minus the
weight of carbon employed, gives the weight of oxygen consumed. In
this way it has been found that 1 gram of carbon yields 3.666 grams
of carbonic anhydride. The weight of oxygen consumed is therefore
2.666 grams, from which it follows that 32 parts by weight of oxygen
combine with 12 of carbon to form 44 of carbonic anhydride, a result
which exactly coincides with that obtained by the foregoing method.
The platinum boat ought to be weighed both before and after the ex-
periment in order to determine the weight of ash, which is present in
CARBONIC ANHYDRIDE. 207
even the purest forms of carbon. This weight is then deducted from
the weiirht of carbon originally taken.
Heactions. — 1. Carbonic anhydride is decomposed by the action of
intense heat, sach as that of the electric spark, into carbonic oxide and
oxygen :
OO, = 00 + 0.
Carbonic Carbonic
anhydride. oxide.
Only a small portion of the carbonic anhydride is thus decomposed,
inasmuch as,, when the proportion of the products of decomposition
passes a certain limit, they again combine with formation of carbonic
anhydride (see Introduction, p. 104).
2. When potassium is heated in an atmosphere of carbonic anhydride,
the gas is decomposed with liberation of carbon :
300, + 2Kj = 200Koa + C.
Carbonic Potaaeic
anhydride. carbonate.
3. Carbonic anhydride acts upon metallic hydrates, forming carbo-
nates *
00a + 2KHo = OOKoj + OH^
Carbonic Potaaeic Potassic Water.
anhydride. hydrate. carbonate.
OO, + KHo = OOKoHo.
Carbonic Potassic Hf dric potassic
anhydride. hydrate. carbonate.
OOa + OaHo, = OOCao" + OH^.
Carbonic Calcic Calcic Water,
anhydride. hydrate. carbonate.
The carbonates are very stable compounds. The alkaline carbonates
may be exposed to a white heat without undergoing decomposition ; all
other carbonates are decomposed at higher temperatures into metallic
oxide and carbonic anhydride :
OOCao" = OaO + OO3.
Calcic Calcic Carbonic
carbonate. oxide. anhydride.
The alkaline carbonates are soluble in water ; all other carbonates
are insoluble.
Free carbonic acid, OOHo,, is not known in a state of purity, but
the solution of carbonic anhydride in water contains this acid. This is
shown by the fact that the solution reddens litmus, a property not
possessed by carbonic anhydride. Moreover, a solution of carbonic
anhydride saturated under pressure loses its gas much more rapidly when
freshly prepared than when the saturated solution has been preserved
under pressure for some time, as in the case of artificial aerated waters.
208 INORGANIC CHEBflSTRT.
This seems to denote that at first mere solution takes place, bat that in
course of time the carbonic anhydride combines chemically with the
^Bvater *
CO, + OH, = OOHo,.
Carbonic Water. Carbonic
anhydride. acid.
With inorganic bases carbonic acid almost always acts as a dibasic
acid, forming acid and normal salts. The acid carbonates of the alka-
lies are the only acid carbonates known in the solid state. Ethereal salts
of the tetrabasic acid, OH04, have, been prepared (see Organic " Chem-
istry). Dicuprie carbonatey OCuo",, which occurs as the mineral
mysorine, may be regarded as a salt of the tetrabasic acid.
Owing to the insolubility of the carbonates of the alkaline earths,
lime water or baryta water is rendered turbid by carbonic anhydride,
or by a solution of a carbonate. An excess of carbonic anhydride dis-
solves the precipitate, owing to the formation of an acid carbonate,
which, however, can exist only in solution.
OABBONIO OXIDE.
00.
Molecular weight == 28. Molecular volume 1 1 I- 1 lUre weighs 14
critha. IMpiejiable by great pressure and cold.
History. — Carbonic oxide was discovered by Lasonne in 1776.
Preparation. — 1. When carbonic anhydride is passed over red-hot
charcoal, it gives up half of its oxygen to the charcoal, and carbonic
oxide is formed :
00, + c = 200.
Carbonic Carbonic
anhydride. oxide.
2. In like manner red-hot iron reduces carbonic anhydride to the
lower stage of oxidation :
40O, + 3Fe = *^(Pe3r«H3, + 40O.
Carbonic Tri ferric Carbonic
anhydride. tetroxide. oxide.
The reaction may be carried out by passing carbonic anhydride over
iron turnings contained in a tube of porcelain or iron heated to redness
in a furnace.
3. Instead of acting on free carbonic anhydride, this gas may be em-
ployed in the nascent state. Thus, if any of the carbonates which evolve
carbonic anhydride at higher temperatures be heated to redness with
charcoal or iron filings, carbonic oxide will be produced:
OOCao" + C = OaO + 20O.
Calcic Lime. Carbonic
curbonate. oxide.
CARBONIC OXIDE. 209
4. Carbonic oxide is also formed when ferric or zincic oxide is heated
to redness with charcoal :
ZnO + C =
= Zn
+ CO.
Zincic
Carbonic
oxide.
oxide.
5. Concentrated sulphuric acid, from its strong affinity for water, has
the power of abstracting the elements of water from a number of organic
substances. Thus, when oxalic acid is heated with concentrated sul-
phuric acid, water is removed, and a mixture of equal volumes of car-
bonic anhydride and carbonic oxide is evolved :
{o8h: = OH. + CO, + CO.
Oxalic acid. Water. Carbonic Carbonic
anhydride. oxide.
The carbonic anhydride may be absorbed by passing the mixed gases
through a strong solution of sodic hydrate. The carbonic oxide is thus
obtained in a state of purity.
6. In like manner, when formic acid or a formate is heated with con-
centrated sulphuric acid, pure carbonic oxide is evolved :
tCOHo -
= OH^ + OO.
Formic acid.
Water. Carbonic
oxide.
7. The most convenient method of obtaining carbonic oxide for lab-
oratory purposes consists in heating potassic ferrocyanide with from
eight to ten times its weight of concentrated sulphuric acid (Fownes).
The flask containing the mixture must be gently heated in order to
start the reaction, which afterwards continues of itself. The evolution
of gas is apt to be somewhat violent. The reaction takes place accord-
ing to the following equation :
re"C.NeK, + 6OH2 + 6SO2H0, = 600
Potassic Water. Sulphuric Carbonic
ferrocyanide. acid. oxide.
+ 2SO,Ko, + SO^eo" + 3S0j(NH,0)j.
Potassic Ferrous Amnionic
sulphate. sulphate. sulphate.
The water necessary for the reaction is derived partly from the water of
crystallization of the potassic ferrocyanide, which is an aquate of the
formula Fe"CgN5K4,30H2, and partly from the commercial sulphuric
acid, which never possesses the concentration corresponding to the pure
dibasic acid SOjHoj.
FormcUion. — When air enters a coal fire at the lower part of a grate
or stove, the carbon combines with the oxygen of the air, forming car-
14
210 INORGANIC CHEMISTRY.
bonic anhydride. The carbonic anhydride passes upwards through the
glowing carbon, and is in this way (see Reaction 1, p. 208) reduced to
carbonic oxide, which may frequently be seen burning with a peculiar
bluish flame where it escapes into the air at the upper part of the fire.
Sometimes this carbonic oxide passes off unburnt, involving great waste
of fuel. The same formation of carbonic oxide occurs on a large scale
in blast furnaces.
Carbonic oxide is also formed in the destructive distillation of many
organic substances containing oxygen. For this reason, it is a never-
failing constituent of coal-gas.
Properties, — Carbonic oxide is a colorless gas, devoid of taste, but
possessing a faint odor. It is only very slightly soluble in water.
Neither the gas nor its aqueous solution has any action on litmus. It
is readily inflammable, and bums in air or oxygen with a pale blue
flame, forming carbonic anhydride :
00 + 0 = OO^
Carbonic Carbonic
oxide. anhydride.
Mixed with half its volume of oxygen, as expressed in the above equa-
tion, it explodes on the approach of a burning body.
It is perfectly stable at all known temperatures.
In its physiological action it displays the characteristics of a violent
narcotic poison. Traces of it, if present in air, are sufficient to cause
giddiness and headache when inhaled ; in larger doses it produces in-
sensibility, and even death. Small animals die quickly in an atmos-
phere containing 1 per cent, of this gas. Its action seems to depend on
the formation of a compound of carbonic oxide with the haemoglobin
of the blood, by which the latter is prevented from exercising its
function as an absorbent of oxygen. Carbonic-oxide-hsemoglobin pos-
sesses a characteristic absorption s|)ectrum, by means of which the
presence of carbonic oxide in the blood, in cases of poisoning by this
gas, may be recognized. Owing to the readiness with which carbonic
oxide is formed, such cases of [>oisoning, both accidental and inten-
tional, occur not infrequently when the products of combustion from
stoves or braziers are allowed to escape into dwelling-rooms.
Readiona, — The following reactions of carbonic oxide all depend
upon its peculiar character as a compound containing dyad carbon.
The carbon p&sses readily into its normal tetradic condition, and in
this way carbonic oxide is enabled to form additive compounds.
1. At high temperatures carbonic oxide acts as a reducing agent,
taking up oxygen and forming carbonic anhydride. Many of the
oxides of the metals are reduced to the metallic state when heated in
the gas, which in this way plays an important part in many metallur-
gical operations.
2. At a temperature of 80° C. (176° F.) carbonic oxide is readily ab-
sorbed by potassium, forming a compound of the formulae /^qt^*
3. Carbonic oxide and chlorine in equal volumes unite under the in-
fluence of sunlight to form carbonic oxydkhloride or phosgene gas:
NITBOGEIf. 211
OO + CI, = OOCljf
Carbonic Carbonic
oxide. oxydichloride.
Carbonic oxydichloride has a suffocating odor. At lower temperatares
it condenses to a colorless liquid, boiling at 8.2° C.
4. Carbonic oxide is readily absorbed by a solution of cuprous
chloride in hydrochloric acid, or by solutions of cuprous salts in ammo-
nia. The compound with cuprous chloride crystallizes in fatty scales
possessing the formula CO(CuCl)2,20Hjj.
Composition. — The composition of carbonic oxide is most readily as-
certained by exploding the gas with oxygen in a eudiometer. 100 c.c.
of carbonic oxide and 100 c.c. of oxygen are introduced into the eudio-
meter, making a total of 200 c.c.
Afler the passage of the electric sjmrk, it is found that the volume
has been reduced to 150 c.c. Of these, ICK) c.c. are absorbed by caustic
potash, proving them to be carbonic anhydride. The remaining 60 c.c.
are found to consist of pure oxygen. Therefore the carbonic oxide has
yielded its own volume of carbonic anhydride, taking up half its vol-
ume of oxygen in the process. But it has already been proved (p. 206)
that carbonic anhydride contains its own volume of oxygen ; carbonic
oxide therefore contains half its volume of oxygen. Expressing the
volumes in litres :
1 litre of carbonic oxide weighs 14 criths.
J litre of oxygen weighs 8 "
u
Difference, 6 "
The difference is the weight of carbon. In carbonic oxide the pro-
portion of carbon to oxygen is, therefore, as 6 : 8, or, in atomic weights,
as 12 : 16, and the formula of this compound is therefore GO.
The compounds of carbon with chlorine, nitrogen, and hydrogen, will
be described under Organic Chemistry.
CHAPTER XXVI.
PENTAD ELEMENTS.
Section I.
NITBOOEN, Azote, N,.
Atomic weight = 14. Molecular weight = 28. Molecular volume i I I-
1 litre weighs 14 criths. Liqaefiable by great pressure and cold.
Atomicity ^, which, by the mutual saturation of pairs of bonds, becomes
reduced to '" or to ' (see p. 80). Evidence of aiomiciiy :
Nitrous oxide, ONj
Ammonia, N'^'Hs.
Ammonic chloride, N^H4C1.
Phosphoric fluoride (analogy), . . P^F^.
History. — Nitrogen was discovered by Rutherford in 1772. He
found that when an animal was allowed to breathe the air confined
212 INORGANIC CHEMISTRY,
under a bell-jar, and the impure air thus obtained was treated with a
caustic alkali, a gas remained behind, incapable of supporting combus-
tion or i*espiration. The name nitrogen signifies " the nitre-producer "
(from nitrum, nitre, and r^dio^ I bring forth), and refers to the fact
that this element is a constituent of nitre.
Occurrence, — Nitrogen occurs in the free state in the atmosphere, of
which it forms about four-fifths by volume. Recently its presence in
the sun and in some nebulae has been rendered probable by spectrum
analysis. In combination it is found in minute quantity as ammonia
in the atmosphere, and it is also a constituent of numerous animal and
vegetable substances.
Preparation. — 1. Nitrogen is most readily obtained from atmospheric
air by the removal of the oxygen. For this purpose the combustion of
phosphorus is usually employed. The phosphorus is placed in a small
porcelain crucible, supported by a cork floating on water, and, after
setting fire to the phosphorus, a bell-jar is placed over it. The phos-
phorus burns, combining with the oxygen, and forming dense white
clouds of phosphoric anhydride, which are speedily absorbed by the
water. The nitrogen thus obtained is never quite pure, inasmuch as
the phosphorus ceases to burn before the last traces of oxygen have been
removed. It may be purified by leaving it in contact with moist phos-
phorus, which by its slow oxidation completely removes the remaining
oxygen. Moist alkaline sulphides, moist ferrous sulphide, and a number
of other easily oxidizable substances, act in a similar manner in remov-
ing oxygen from gaseous mixtures.
2. Very pure nitrogen may be obtained by passing a current of air,
freed from carbonic anhydride and moisture, over metallic copper con-
tained in a tul)e of hard glass, and heated to redness in a furnace. The
oxygen of the air combines with the copper, forming cupric oxide, whilst
the nitrogen passes on unchanged and may be collected.
3. On heating a concentrated solution of ammonic nitrite or a mixture
of ammonic chloride and potassic or sodic nitrite, nitrogen is evolved :
N'''0(N-H,0) = N, + 2OH2.
Ammonic nitrite. Water.
NH«CI + NONao = NaCl + N, + 20Hy
Ammonic Sodic Sodic Water,
chloride. nitrite. chloride.
4. Nitrogen is given off when ammonic dichromate, or a mixture of
potassic dichromate with amnionic dichloride, is heated :
r0rO,(N^H,O)
^O = N, + OrA + 40H,.
(0rO,(N-H,O)
Ammonic chromate. Chromic oxide. Water.
5. When chlorine is passed through an excess of an aqueous solution
of ammonia, the chlorine combines with the hydrogen of the ammonia,
forming hydrochloric acid, which unites with the excess of ammonia,
and nitrogen is liberated :
(X>MPOUin>S OF NTTBOGEN. 213
8NH, + 8C1, = 6NH,a + N^.
Ammonia Ammonic chloride.
The entraDce of each bubble of chlorine into the solution is attended
with a flash of light. Great care must be taken that the ammonia is
always in excess^ otherwise the very dangerously explosive compound,
nitrous chloride, will be formed.
Properties. — Nitrogen is a colorless, tasteless, and inodorous gas,
slightly lighter than air. It is not capable of supporting either com-
bustion or respiration. A lighted taper is extinguished, and small ani-
mals die when plunged into this gas. It is not, however, poisonous,
as is evident from the fact that it is contained in such large quantities
in atmospheric air. Water dissolves only 0.026 of its bulk of the gas.
Nitrogen is neither acid nor alkaline. It is one of the most indifferent
bodies known, combining directly with only very few of the elements.
COMPOUNDS OF NITROGEN WITH OXYGEN AND
HYDROXYL.
Nitrous oxide {hyponitroua anhydride), ONg N — O — ^N
^\
or, "N',0 II >0
W
Nitrio oxide, 'N"0 — N=0
rHO O O
Nitrons anhydride, .......< O || ||
(NO N— O— N
fNO 0=N=O •
Nitric peroxide, |^q» 0=l!r=0
and, HO, 0=N=0
O O
(NO, II II
Nitrio anhydride, < O N— O— N
(NO, II II
O O
" f NHo N-O— H
Hyponitronsacid, | jj^^ N-0_H
Nitrons acid, NOHo 0=N— O— H
O
II
Nitrio acid, NOjHo N— O— H
O
214 INORGANIC CHEMISTRY.
The most important member of the above group, and the starting-
point for the preparation of all the others, is nitric acid. This com-
pound will be described first.
NITBIO AOn), Aquafortis.
NO,Ho.
Molecular weight = 63. Fuses at —50° C. (—58'^ F.). Boils at
86° C. (186.8° F.).
Htdory. — Nitric acid was known to the alchemists. Lavoisier
showed that it contained oxygen, but its exact composition was first
ascertained by Cavendish.
Production, — 1. When a series of electric sparks is passed between
platinum points in a glass globe containing air, red fumes of nitric per-
oxide {q,v,) are formed. On shaking the contents of the gjobe with water,
the red fumes disappear, and the water acquires an acid reaction, arising
from the presence of nitric acid in solution. It was in this way that
the formation of nitric acid was studied by Cavendish. The production
of red fumes is enormously increased by passing the sparks through
compressed air.
In like manner, nitric acid is formed when hydrogen is burned in
oxygen containing a small proportion of nitrogen, or when an excess of
the gases obtained by the electrolytic decomposition of water is mixed
with air and exploded in a eudiometer. Nitric acid is also produced in
the combustion of ammonia in oxygen.
2. When nitrogenous animal matter is slowly oxidized by the action
of tli^ air, at a temperature between 20° and 30° C. (68°-86° F.), in
presence of water and powerful bases, nitric acid is formed, and com-
bines with the bases to form nitrates. In this way the nitrites and
nitrates which are found in the shallow well waters of towns have been
formed from the nitrogenous matter contained in ^the soil. In hot
climates, particularly in districts where there is little rain, the nitrates
make their appearance as an efflorescence on the- surface of the soil, as
in India and in Chili.
This natural formation of potassic nitrate is imitated artificially in
the so-called nitre plantations. In these, animal matters mixed with
lime and ashes, are placed in loose heaps, exposed to the air but shel-
tered from rain. From time to time the heaps are watered with urine
and stable runnings. The nitre bed is usually lixiviated every three
years, and the product, consisting chiefly of calcic nitrate, is converted
by treatment with potassic carbonate into potassic nitrate, which is
purified by crystallization. In this way a cubic metre of earth may,
under favorable conditions, be made to yield as much as 20 kilps. of
nitre.
Nitrification appears to depend upon the presence of an organized
ferment.
Manufaxsture, — Nitric acid is prepared by distilling potassic nitrate
NITRIC ACID. 215
(nitre) or sodic nitrate (cubic nitre or Chili saltpetre) with concentrated
sulphuric acid :
NO^Ko + SO2H02 = SO2H0K0 + NO2H0
Potassic Sulphuric Hydric potassic Nitric acid,
nitrate. acid. sulphate.
By employing two molecules of potassic nitrate to one of sulphuric
acid, a saving of sulphuric acid is effected, but a higher temperature is
required, which destroys some of the nitric acid. In this case the reac-
tion takes place in two stages, of which the first is expressed in the above
equation, whilst in the second, the hydric potassic sulphate acts upon
another molecule of potassic nitrate :
SOjHoKo + NOgKo =
= SO2K02 + NOjHo
Hjdric potassic Potassic
Potassic Nitric acid,
sulphate. nitrate.
sulphate.
A further disadvantage of the second method lies in the fact that the
normal potassic sulphate can be removed from the retort only in the
solid state, whereas the hydric potassic sulphate, from its greater fusi-
bility, can be poured out.
On a commercial scale the distillation is performed in cast-iron cylin-
ders A (Fig. 37) lined with fire-clay and heated over a furnace. The
distillate is condensed in large stoneware Woulff's bottles, B, each con-
FiG. 37.
nected with the one following. The last of these leads into a coke
tower, down which a stream of water trickles. Any fumes of nitric
peroxide which have escaped condensation in the Woulff's. bottles are
absorbed by the water in the coke tower.
Chili saltpetre is generally employed in the manufacture of nitric acid.
It is cheaper than nitre, and, owing to the lower atomic weight of
sodium, yields a larger proportion of nitric acid.
The acid thus obtained may be purified by distillation with its own
volume of concentrated sulphuric acid. The distillate contains from
99.5 to 99.8 per cent, of NOgHo.
216 INORGANIC CHEMISTRY,
Properties. — Pure nitric acid is a colorless fuming liquid of sp. gr,
1.63. It has an irritating odor, and is powerfully corrosive, cauterizing
the skin and staining it yellow. It begins to boil at 86° C. (187° F.),
but is partially decomposed into nitric peroxide, oxygen, and water, so
that gradually the distillate becomes weaker, and the boiling point rises,
till at last an acid containing 68 per cent, of NOjHo, and boiling at
120.5° C. (248.9° F.), distils over under ordinary pressure without
further change. This acid has a sp. gr. of 1.414 at 16° C. (59° F.),
artd is the ordinary concentrated nitric acid of commerce. If a weaker
acid be distilled, the liquid in the retort becomes gradually more con-
centrated, till the acid containing 68 per cent, is obtained, which then
distils unchanged. Notwithstanding the constancy of its boiling point,
this acid is not a definite compound. By varying the pressure under
which the distillation is performed, acids of varying strength may be
obtained, but for each of these pressures, there is a fixed strength of
acid with a constant boiling point. Under a pressure of 70 mm. an
acid containing only 66.7 per cent, of NOjHo distils over between 65°
and 70° C. (149°-158° F.). The higher pressure thus corresponds to
the grater strength of acid, the reverse being the case with hydrochloric
acid (see p. 158).
When concentrated nitric acid is mixed with water, diminution of
volume and elevation of temperature ensue. The following table con-
tains the specific gravities of various strengths of aqueous acid at 0° and
16° C. (32°-59° F.), as determined by J. Kolb:
Per cent. NOjHo. Sp. gr. at 0° C. (82^ P.). Sp. gr. at 15° C. (59^ F.).
100.00 1.659 1.530
90.0 1.622 1.495
80.0 1.484 1.460
70.0 1.444 1.423
60.0 1.393 1.374
50.0 1.334 1.317
40.0 1.267 1.251
30.0 1.200 1.185
20.0 1.132 1.120
15.0 1.099 1.089
10.0 1.070 1.060
5.0 1.031 1.029
The decomposition which concentrated nitric acid undergoes under
the influence of heat is expressed by the following equation :
^ 4NO,Ho == 20H, + 2'N^O, + O,.
Nitric acid. Water. Nitric peroxide.
This decomposition is very rapid at 100° C, and on this property the
powerful oxidizing action of hot nitric acid depends.
Concentrated nitric acid, when exposed to the action of light, turns
yellow, owing to a decomposition similar to the above.
ReaotUms, — 1. With metallic oxides or hydrates nitric acid yields
nitrates :
NITRIC
ACID.
OEH
+ NOjHo =
= NOjKo
+
OH,.
Potassic
hydrate.
Nitric acid.
Potassic
nitrate.
Water.
FbO +
2NO,Ho =
n8?^"
+
OH,
Plumbic
oxide.
Nitric acid.
Plumbic
nitrate.
Water.
2J7
2. The action of nitric acid upon metals is of a somewhat complicated
character, varying not only with different metals, but also, for the same
metal, with the strength of the acid employed and the temperature at
which the reaction takes place. Nitrates of the metals are formed, but
at the same time another portion of the nitric acid is reduced to some
lower oxide of nitrogen. Thus, silver, copper, and mercury, are attacked
by nitric acid acid with formation of nitrates and evolution of nitric
oxide :
fNO,
3Ca + 8NO,Ho = 3^ Cuo" + 2'H"0 + 40H,
(NO,
Nitric acid. Cupric nitrate. Nitric oxide. Water.
With very concentrated acid, nitric peroxide (W^O^) is generally
evolved, and when the reaction takes place at a high temperature, a
portion of the nitric acid is completely reduced to nitrogen. When
silver is slowly dissolved by weak nitric acid in the cold, nitrous acid
is formed.
When nitric acid acts upon copper in presence of much cupric nitrate,
the ji^as evolved consists chiefly of nitrous oxide.
When nitric acid acts upon a more electro-positive metal, such as
zinc, nitrous oxide is evolved, and when a very concentrated acid is
employed, ammonia is formed and combines with the excess of nitric
acid:
4Zn + 10NO,Ho = ON, +
Nitric acid. Nitrous oxide.
(NO,
4-( Zno"
Ino,
Zincic nitrate.
+ 50H,.
Water.
(NO,
4Zn + 9NO^o = 4^ Zno" + 30H, + NH3.
Nitric acid. Zincic nitrate. Water. Ammonia.
By the action of zinc in an alkaline solution, the whole of the nitric
acid present is reduced to ammonia by the nascent hydrogen. The
ammonia may be distilled off and absorbed in a solution of hydrochloric
acid. This method is employed in the quantitative estimation of nitric
acid.
3. The general action of nitric acid is that of a powerful oxidizing
agent Sulphur, phosphorus, carbon, amorphous boron and silicon.
218 INORGANIC CHEMISTRY,
arsenic, and iodine, are converted by treatment with nitric acid into
sulphuric, phosphoric, carbonic, boric, silicic, arsenic, and iodic acids.
In the case of phosphorus the oxidation takes place with explosive vio-
lence, and if the concentrated acid be dropped upon hot sawdust or
finely powdered charcoal, the latter inflames.
It has been mentioned under the heading of hydrochloric acid that
oxidizing agents liberate chlorine from this acid. In this way chlorine
is evolved from a mixture of nitric and hydrochloric acids:
NOjHo + 3HCa = NOCl + 20H, + Cl^
Nitric acid. Hydrochloric Nitrons Water,
acid. oxychloride.
(Nitrosylic chloride.)
This mixture was known to the alchemists, who gave to it the name
aqtui-regia, from its power of dissolving gold, the kir^ of metals. It is
employed in the laboratory as a solvent for gold, platinum, and various
ores. The solvent action depends on the presence of the chlorine
evolved in the above reaction.
The action of nitric acid on organic compounds will be studied in
connection with these (Organic Chemistry).
Nitrates, — Nitric acid is generally monobasic. The numerous so-
called basic nitrates may, however, be r^^rded as salts of trilmsic and
pentabasic nitric acid (tlOHo, and NHo^). Graham first pointed out
that in basic salts the base frequently replaces the water of crystalliza-
tion of the normal salt. This supposed water of crystallization must,
therefore, in as far as it may be replaced by a base, be regarded as
water of constitution. Thus cupric nitrate
( Jq^Cuo'^SOH^) and basic cupric nitrate (2o*^"^"»20uO,OH2)
might be formulated jtqtt ^ Cuo'^jOH, and wqA //Cuo",0H2.
The monoba-sic nitrates are all soluble in water.
At a high temperature the nitrates are all decomposed. They gen-
erally evolve, first, pure oxygen, then nitric peroxide, or a mixture of
nitrogen and oxygen, whilst an oxide of the metal is left.
The presence of nitrates in solution may be recognized by the follow-
ing characteristic reaction : The solution supposed to contain a nitrate
is mixed in a test-tube with a solution of ferrous sulphate. Concen*
trated sulphuric acid is then poured down the side of the sloping tube,
so as to sink to the bottom of the liquid without mixing with it. If a
nitrate is present, a chai-acteristic brown coloration will be visible at the
surface of contact of the two layers. The explanation of this is that
the nitric acid, liberated by the sulphuric acid, is reduced by the fer-
rous sulphate to nitric oxide, the latter dissolving in the excess of fer-
rous sulphate with a brown color.
KITRIC ANHYDRIDE. 219
NITRIC ANHTDBIDE.
NA.
Probable molecular weight = 108. Fuses at 29.5° C. Boils at 45° C.
History. — Nitric anhydride was discovered by Deville in 1849.
Preparation, — 1 . This compound is formed when dry chlorine is passed
over dry argentic nitrate contained in a U-tube and heated in a water-
bath. The reaction takes place in two stages. In the first of these
nitric dioxychloride, a volatile liquid, is formed :
NOjAgo + CI2 = NO2CI + AgCl + O.
Argentic Nitric Argentic
nitrate. dioxychloride. chloride.
In the second the nitric dioxychloride acts on the unattacked argentic
nitrate :
NO,Ago + NO.Cl = NA + AgCl.
Argentic Nitric Nitric Argentic
nitrate. dioxychloride. anhydride. chloride.
The reaction begins at 95° C. (203° F.), and, when once started, con-
tinues, even when the temperature is allowed to fall as low as 60° C.
(140° F.). All unnecessary heating must be avoided, as the anhydride
is totally decomposed at a temperature very slightly above that required
for its formation. The anhydride distils over, and is condensed in a
tube surrounded by a freezing mixture.
2. Nitric anhydride may also be obtained by abstracting the elements
of water from nitric acid by means of phosphoric anhydride :
2NO2H0 = NA + OH,.
Nitric acid. Nitric Water,
anhydride.
The phosphoric anhydride is added very gradually to the concentrated
nitric acid, cooled by ice, and the pasty mass is afterwards distilled at a
low temperature. The anhydride collects as a crystalline mass in the
receiver.
Properties, — Nitric anhydride forms large colorless prisms, which fuse
at 29.5° C. (85.1° F.) It boils with decomposition and evolution of
brown fumes about 45° C. (113° F.). When sealed in a glass tube, it
may be preserved unaltered, if kept in a cool place; but, in a warm
room, gradually undergoes decomposition into oxygen and nitric perox-
ide, ultimately fracturing the tube with the internal pressure.
When thrown into water the anhydride hisses violently, evolving
great heat, and combining with the water to form nitric acid :
NA + OH2 = 2NOjHo.
Nitric Water. Nitric acid,
anhydride.
220 INORGANIC CHEMISTRY.
NFFROUS OXIDE^ Hyponttroua Anhydride, Laughing Gas.
Molec\dar weight = 44. Molecular volume I I L 1 litre weighs 22
criths. Fuses at —101° C. (—149.8° F.)- Boils at —88° C.
(—126.4° F.).
History. — This compound was discovered by Priestley in 1772.
Preparation. — 1. Nitrous oxide is formed by the action of dilute
nitric acid upon zinc :
(NO,
lONO^Ho + 4Zn = ON, + 4^ Zno" + 60H,.
(NO,
Nitric acid. Nitrous oxide. Zincic nitrate. Water.
This method does not, however, yield the compound in a state of purity,
and is never employed in its preparation.
2. Nitrous oxide may readily be obtained in large quantity by heat-
ing ammonic nitrate. Under the influence of heat, the elements of
water are removed from this salt and nitrous oxide is formed :
NO,(N-H,0) = 2OH2 + ON,
Ammonic nitrate. Water. Nitrous oxide.
The ammonio nitrate, previously dried, is heated in a flask to which a
delivery tube is attached. The heat must not be applied too suddenly,
otherwise the decomposition takes place with explosive violence, and
nitric oxide is formed. The gas is purified by passing it first through
a solution of ferrous sulphate, in order to absorb nitric oxide, and then
through caustic potash, to free it from chlorine derived from ammonic
chloride contained in the commercial nitrate. It may be collected over
mercury, or over warm water, in which it is less soluble than in cold
water.
Properties. — Nitrous oxide is a colorless pjas with a faint pleasant
odor, and a sweetish taste. Its density is 1.627 (air = 1). Water dis-
solves about four-fifths of its volume of the gas, and alcohol takes up a
still larger quantity.
Nitrous oxide supports the combustion of bodies which burn in oxy-
gen. A glowing match is rekindled when plunged into the gas, and
burns almost as brightly as in oxygen. Phosphorus burns with a flame
of dazzling brightness. Feebly burning sulphur is extinguished by the
gas, but, if burning strongly, the combustion continues with great
vigor.
All combustions in nitrous oxide are effected solely at the expense of
the oxygen contained in the gas, the nitrogen taking no part in the re-
action. In order that combustion may continue, it is necessary that the
temperature of the burning body should be sufficiently high to decora-
pose the nitrous oxide into nitrogen and oxygen. If this condition is
HYPONITROU8 ACID. 221
not fulfilled^ combustion ia impoesible, as may be seen in the case of
feebly burning sulphur. Strictly speaking, therefore, nitrous oxide, as
such, does not support combustion. It does so only by the agency of
one of its products of decomposition— oxygen.
Nitrous oxide was first liquefied by Faraday, by heating ammonic
nitrate in a bent tube (see p, 165). It may be most conveniently lique-
fied with the aid of a force-pump, cooling the wrought-iron receiver
with ice. Liquid nitrous oxide is colorless, and very mobile. It boils
at — 88° C. (—126,4° F.) under atmospheric pressure, whilst at 0° C.
the tension of its vapor is 30 atmospheres. By means of the cold pro-
duced by its own evaporation, or by plunging a tube containing it into
a bath of solid carbonic anhydride in ether, and allowing this freezing
mixture to evaporate m vacuo, liquid nitrous oxide may oe frozen into
colorless crystals resembling in appearance ammonic nitrate. By the
evaporation in vacuo of a mixture of liquid nitrous oxide and carbonic
disulphide, a degree of cold equal to —140° C. (—220° F.) may be
obtained. Liquid nitrous oxide, in spite of its low boiling point, may
be preserved in open glass tubes for over half an hour. If mercury be
poured into this liquid, the metal is instantly frozen.
Nitrous oxide, when inhaled, acts as a narcotic poison. In smaller
doses it pnxhices temporary nervous exhilaration or intoxication ; hence
the name laughing gai. It is employed in minor surgical operations
as an anaesthetic.
Composition, — The composition of nitrous oxide may be ascertained
by heating sodium in a bent glass tube containing a measured volume
of the gas over mercury (see p. 159). The sodium combines with the
oxygen of the gas, forming solid sodic oxide, and liberating the nitrogen.
After the action is finished, the gas remaining in the tube is found to
possess exactly the same volume as the gas employed, and may be shown
to consist of pure nitrogen. Hence nitrous oxide contains its own vol-
ume of nitrogen. Expressing the volumes in litres —
1 litre of nitrous oxide weighs 22 criths.
Deduct weight of litre of nitrogen, ... 14 "
There remain 8 "
which is the weight of J litre of oxygen. One litre of nitrous oxide
therefore contains 1 litre of nitrogen and J litre of oxygen ; or, 2
volumes of nitrogen combine with 1 volume of oxygen to form 2 vol-
umes of nitrous oxide. Expressed in atomic weights, 28 parts by
weight of nitrogen combine with 16 of oxygen to form 44 of nitrous
oxide.
HTFONITROUS ACID.
///NHo
\NHo-
Kwjwn only in iU aoto, or in aqueous solution.
lYeparation of Argentic HyponitrUe (''''N^aAgo,). — When an aqueous solution of po-
tassic nitrate is treated with sodium amalgam in the proportion of four atoms of sodium
to one molecule of nitrate, a reduction of the nitrate takes place according to the fol-
lowing equation :
222 INORGANIC CHEMISTRY.
2HO,Ko + 4H, = ^'N'jKo, + 40H;.
PoUaslc Potaasic Water,
nitrate. hyponitrite.
Potassic nitrite is formed as ao intermediate product in this reaction, and a saving
of sodium amalgam may be efiected by starting from the nitrite :
2HOKo + 2H, = ^^N^jKo, + 20H,.
Potassic Potassic Water,
nitrite. hTponitrito.
The alkaline liquid obtained by either of these processes is then accnrately neutral-
ized with acetic acid, and argentic nitrate is addea. Aitcentic hyponitrite is thus ob-
tained as a greenish-yellow precipitate, which, by solution in dilute nitric acid and
precipitation with ammonia, acquires a pure yellow color.
iVa/MT^.— Argentic hyponitrite may be dissolved in weak acids without suffering
immediate decomposition, but the solution is very unstable.
A solution of potaraic hyponitrite acidulated with acetic acid undergoes decomposi-
tion on heating, the liberated hyponitrous acid breaking up into nitrous oxide and
water :
'^^Ho, = ^'N',0 + OUr
Hence nitrous oxide may be considered as the anhydride of hyponitrous acid.
The acid salts of hyponitrous acid are known only in solution. Thus baric hypo-
nitrite, ^^ < n-Bao^^, which is insoluble in water, dissolves in aqueous hyponitrous acid
with formation of an acid salt The existence of this salt proves that hyponitrous
acid must be at least dibasic.
NITROUS AlTHTDBmS.
Probable molecular weight = 76.
Preparation. — 1. When nitric acid is heated along with bodies ca-
pable of taking up oxygen, such as arsenioua acid or starchy nitrous
anhydride is formed :
AsA + 2NO2H0
= A8,0. + NA + OHr
Arsenious Nitric acid.
Arsenic Nitrous Water.
anhydride.
anhydride. anhydride.
The nitrous anhydride thus obtained is mixed with nitric peroxide.
2 Nitrous anhydride may also be prepared by mixing 4 volumes of
nitric oxide with 1 volume of oxygen. Direct combination takes place
according to the equation :
2'N"0 +
0
= N,0,
Nitric oxide.
Nitrous
anhydride.
Properties. — Nitrous anhydride prepared by either of the above reac-
tions is a reddish gas, which by passing through a U-tube immersed in
a freezing mixture, may be condensed to a blue liquid. It is a very
unstable compound,' and undergoes gradual decomposition, even below
0° C, into nitric oxide and nitric peroxide :
NITROUS ACID. 223
NA = '^"O + w^o,
Nitrous Nitric Nitric
anhydride. oxide. peroxide.
On warming, this deoompoeition is very rapid.
The addition of a small quantity of water to nitrous anhydride con-
verts it into nitrous acid :
NA + OH, = 2NOHo.'
Nitrous Water. Nitrous
anhydride. acid.
A larger quantity of water decompose the compound with efferves-
cence : nitric oxide is evolved, and nitric acid remains in solution :
3NA + OH, = 2NO,Ho + 4'N"0.
Nitrous Water. Nitric acid. Nitric oxide,
anhydride.
The two foregoing reactions illustrate strikingly the inadequacy of
chemical equations as expressions of chemical change. In the first
equation, the proportion of water to nitrous anhydride is three times as
great as in the second; yet the first stands for a reaction in which only
a small quantity of water is required, and the second for a reaction
which occurs only in presence of an excess of water. The reason of
this discrepancy is that ordinary equations take no account of the rela-
tive masses of the reacting substances, and the mass of a substance is
frequently an important factor, determining in some cases the direction
of the chemical change.
NITROUS AGID.
NOHo.
Molecular weight = 47.
Preparation. — Nitrous acid may be obtained by mixing liquefied
nitrous anhydride with water as above described. It cannot he pre-
pared in a state of purity, and is an exceedingly unstable compound.
Deconipoeiiions, — 1. In the presence of much water nitric acid and
nitric oxide are formed :
3NOHo = NO,Ho + 2'H"0 + OH^.
Nitrons acid. Nitric acid. Nitric oxide. Water.
2. Under some circumstances nitrous acid acts as a reducing agent :
2NOHo + O, = 2NO2H0.
Nitrous acid. Nitric acid.
In this way acidulated solutions of the nitrites decolorize potassic per-
manganate, reduce soluble chromates to green chromic salts, and precipi-
224 INORGANIC CHEMISTRY.
tate gold and mercuiy in the metallic state from solutions of their
salts.
3. In many other oases nitrous acid displays oxidizing properties :
4NOHo = 4'N"0 + 20H, -f O^
Nitrous add. Nitric oxide. Water.
Thus acid solutions of the nitrites liberate iodine from potassic iodide
and bleach a solution of indigo.
Nitrites. — With metallic oxides or hydrates^ nitrous acid forms ni-
trites *
OKH + NOHo = NOKo + OH^
Potassic Nitrous Potassic Water,
hydrate. acid. nitrite.
The alkaline nitrites may be most readily obtained by cautiously
heating the nitrates. An addition of copper or lead facilitates the re-
action by aiding in the removal of the oxygen :
2NO2K0 = 2NOK0 + O,.
Potassic Potassic
nitrate. nitrite.
The temperature must not be raised too high, otherwise the nitrite will
be decomposed. The alkaline nitrites are soluble in alcohol, and may
thus be separated from unaltered nitrate, which is insoluble.
The nitrites evolve reddish vapors when treated with dilute acids,
and may thus be distinguished from the nitrates, which do not possess
this property.
NITRIC OXIDE.
Molecular weight = 30. MolemUir volume I I L 1 litre weighs 15
eriths. Liquejvable by great pressure and cold.
History. — Nitric oxide was discovered by Van Helmont, who, how-
ever, failed to recognize its true character. It was first investigated by
Priestley.
Preparation, — 1. Nitric oxide is formed when nitric acid acts upon
mercury or copper :
(NO,
3Ca + 8NO,Ho = 3^ Cuo" + 2'H"0 + 40Hr
(HO,
Nitric acid. Gupric nitrate. Nitric oxide. Water.
The gas is purified by passing it through a solution of caustic soda.
Nitric oxide thus prepared is apt to contain nitrous oxide and free
nitrogen, particularly towards the end of the reaction. In order to
purify the product, advantage is taken of the property which nitric
NITRIC OXIDE. 225
oxide possesses of dLssoIving in a conoentrated solution of ferrous sul-
phate. The solution of this salt absorbs the gas in large quantity,
forming a compound of the formula 2S02Feo'VN"0, which remains
dissolved in the liquid, imparting to it a deep brown color. On heating
this brown liquid, pure nitric oxide is evolved,
2. Nitric oxide may be readily obtained in a state of purity by acting
upon nitric acid with ferrous sulphate. A convenient mode of apply-
ing this reaction consists in introducing into a retort 30 grams of nitre
with 240 grams of ferrous sulphate, and pouring in through a funnel
260 cubic centimetres of a mixture of sulphuric acid with three times
its bulk of water :
eSO^Feo'' + 2NOaKo + SSO^Ho, = 2'N"0 + 3^ SO,— ('Fe^'A)"*
(SO,--
Ferrous Potassic Sulphuric Nitric Ferric sulphate,
sulphate. nitrate. acid. oxide.
+ 2SO2H0K0 + 4OH2.
Hydric potassic Water,
sulphate.
Properties, — Nitric oxide is a colorless gas of density 1.039 (air = 1).
Water dissolves one-twentieth of its volume of the gas. Neither the
gas nor its aqueous solution exerts any action upon litmus.
The molecular formula NO, deduced from the vapor-density of this
compound, is anomalous. This formula involves the assumption that
the molecule contains an odd number of unsatisfied bonds (see Note,
p. 179).
Although nitric oxide contains, for the same volume of nitrogen,
twice as much oxygen as nitrous oxide, it does not support combustion
BO readily, owing to its greater stability. Feebly ignited charcoal is
extinguished when plunged into the gas, whereas strongly glowing
charcoal bums in it with great brilliancy. Phosphorus may be melted
in the gas without igniting, and the flame of feebly burning phosphorus
is extinguished by it; but phosphorus already well ignited continues to
bum in it, emitting an intense light. Sulphur, even when burning
strongly, is extinguished by nitric oxide. A mixture of nitric oxide
and the vapor of carbonic disulphide burns with a vivid blue flame,
very rich in chemically active rays.
Reactions. — 1. When nitric oxide and oxygen are mixed, a reddish
gas is formed, consisting of nitrous anhydride and nitric peroxide, both
of which compounds are produced by the direct union of the nitric oxide
with the oxygen :
4'N"0 + O, = 2N'"A-
Nitric oxide. Nitrous anhydride.
2'N"0 + O, = ^-,0,.
Nitric oxide. Nitric peroxide.
These gases are absorbed by water, to which they impart an acid
reaction.
15
226 INOBOANIC CHEMISTRY.
2. Nitric oxide also combines directly with chlorine to. form nitrous
oxychloride (j.t?.) :
2'N"0 + CI, = 2NOCL
Nitric oxide. Nitroas oxychloride.
(Nitroeylic chloride.)
The direct union which occurs in the above cases is probably de-
pendent on the presence of a free bond in the nitrogen atom of nitric
oxide, and the reactions consist in the saturation of this free bond by
some suitable element.
Composition. — ^The composition of nitric oxide may be determined in
the same manner as that of nitrous oxide (see p. 221), but potassium
must be employed, as sodium merely melts in the gas without decom-
posing it. After the reaction is finished, it is found that the original
volume has decreased by one-half, and that the residual gas is pure
nitrogen.
1 litre of nitric oxide weighs 15 criths.
Deduct weight of J litre of nitrogen, ... 7 "
There remain 8 "
which is the weight of J litre of oxygen. One litre of nitric oxide con-
tains therefore J litre of nitrogen and J litre of oxygen ; or 1 volume
of nitrogen combines with 1 vol. of oxygen to form 2 vols, of nitric
oxide. Expressed in atomic weights, 14 parts by weight of nitrogen
combine with 16 of oxygen to form 30 of nitric oxide.
NITRIC PEROXIDE.
'N^^O- at higher temperaturea,
{NO
jjq', or H^^O^, at lower temperalurea.
Molecular weight = 46 and 92. Molectdar volume CD. 1 litre weighs
23 to 46 criths. Fuses erf — 9° C. (15.8° F.). BoUs at 22° C.
(71.6° F.).
Preparation. — 1. Nitric peroxide may be obtained by the union of
2 volumes of nitric oxide with 1 of oxygen (see preceding page). The
red gas thus formed may be condensed in a U-tube immersed in a
freezing mixture.
2. ifitric peroxide is most conveniently prepared by the action of
nitric acid on arsenious anhydride :
AsA + 4NO2H0 = ASaO^ + 2^*%0, + 20H,.
Areenious Nitric acid. Arsenic Nitric Water.
anhydride. anhydride. peroxide.
NITRIC PEROXIDE. 227
Small fragments of arsenioas anhydride are introduoed into a retort
with sufficient nitric acid of sp. gr. 1.393 to cover them. The reaction
takes place on gently heatings and a mixture of nitric peroxide and
nitrous anhydride condenses in the receiver, which is cooled by a freezing
mixture; By passing a slow current of oxygen through this mixed pro-
duct, the whole of the nitrous anhydride is converted into peroxide.
3. Certain nitrates, when subjected to destructive distillation, are
decomposed into nitric peroxide, oxygen, and an oxide of the metal.
Plumbic nitrate is well suited for this purpose :
{i
NO,
Pbo" = + PbO + IT^O, + O.
NO.
Plumbic nitrate. Plumbic oxide. Nitric peroxide.
The thoroughly dried plumbic nitrate is heated in a retort connected
with a U-tube which is drawn out at its further extremity to a fine
opening and surrounded by a freezing mixture. The liquefied nitric
peroxide collects in the tube, whilst the oxygen escapes through the
fine opening.
4. It is also formed by the action of nitric acid on tin :
Sn, + 20NO,Ho = Sn^O^Hoio + 6OH3 + lO'N^O,.
Nitric acid- Metastannic acid. Water. Nitric
peroxide.
5. Nitric peroxide is also formed by the action of nitric dioxychloride
on argentic nitrite :
NO Ago + NOjCl = {5oJ + ^^^'
Argentic Nitric dioxychloride. Nitric Argentic
nitrite. (Nitroxjlic chloride.) peroxide. chloride.
Properties. — Nitric peroxide is a volatile liquid which solidifies
at — 9° C. (15.8° F.), forming a white fibrous crystalline mass. Nitric
peroxide displays remarkable changes of color, dependent upon the
temperature. Just above its fusing point it is a colorless liquid. At
0° C. it assumes a yellow tint, which deepens through orange to brown
as the temperature rises to 22° C. (71.6° F.), when the nitric peroxide
enters into ebullition, yielding a reddish-brown vapor. This vapor also
assumes a darker color as its temperature is raised, becoming at last
almost black.
The vapor of nitric peroxide possesses a characteristic absorption
spectrum.
These changes of color correspond to definite changes of molecular
condition, as may be seen from a study of the vapor-density of nitric
peroxide at difierent temperatures. At a temperature very little above
its boilingpoint it possesses a vapor-density below that required for the
formula IX^^JO^, but nearer to this value than to that required for
'N*^©,. As the temperature rises the vapor-density diminishes, till at
140° C. it corresponds exactly with the latter formula. There is, there-
228 INOBGANIC CHEMISTRY.
fore, even at the boiling point of nitric peroxide, a partial dissociation
of the larger molecules, 'N*%04, into the smaller, W^Oj ; but the greater
number of the former still remain intact The decrease in vapor-
density corresponds with an increase in the relative number of disso-
ciated molecules. It is probable that this dissociation b^ins even in
the liquid state, as denoted by the change of color (see Note, p. 179).
Liquid nitric peroxide is a powerfully corrosive substance, and its
vapor is very irritating when inhaled even in small quantity.
Reactions, — 1. With metallic hydrates and oxides it yields a mix-
ture of nitrite and nitrate in equivalent proportions :
'N^O, + 20KH = NO,Ko + NOKo + OH,.
Nitric Potaraic Potassic Potassic Water,
peroxide. hydrate. nitrate. nitrite.
It thus behaves like a compound anhydride — a view of its chemical
character which is supported by its formation from nitric dioxychloride
and argentic nitrite (see above).
2. A small quantity of water acts like a metallic hydrate, producing
a mixture of nitrous and nitric acids:
'N^O, + OH3 = NO,Ho + NOHo.
Nitric peroxide. Water. Nitric acid. Nitrons add.
But an excess of water decomposes it into nitric oxide and nitric acid :
SlI^O, + 20Hj = 4NO,Ho + 2'N"0.
Nitric peroxide. Water. Nitric acid. Nitric oxide.
CkymposUion. — The composition of nitric peroxide may be ascertained
by passing the vapor of a known weight of the gas over red-hot me-
tallic copper. The oxygen of the peroxide combines with the copper,
and may be determined by ascertaining the increase in weight of the
latter. The nitn^n is liberated, always mixed however with a small
quantity of nitric oxide, and may be collected and measured. The
proportion of nitric oxide must also be determined. From these data
the composition of the peroxide may be calculated.
COMPOUNDS CONTAINING NITROGEN, CHLORINE, AND OXYGEN.
NITROnS OZTCHIaORIDB, NUrogylic Chloride, Chloronitrous Gas.
Noa.
Molecular weight = 65.5. Mdeeuiar volume I I I. 1 litre veighs 32.75 criths. Boils
at 0° C.
Preparatian, — 1. By the direct union of chlorine and nitric oxide:
2'N'^O + CI, = 2WOC1.
Nitric Chlorine. Nitrous
oxide. oxychloride.
(Nitroeyllc chloride.)
iflTRIC DIOXYCHLORIDE. 229
2. It is also evolved along with chlorine from a mixtnre of nitric and hydrochloric
acids (see Aquorreffia, p. 218) :
NO,Ho + 3Ha = NOCl + 20H, , + CI,.
Nitric Hydrochloric Nitrous Water,
acid. acid. oxychloride.
ProperHa, — Nitrons Oiychloride is an orange-colored gas, which, in a freezing-
mixtare, condenses to a red Aiming liauid possessing an odor of aqua-regia.
ReaelUmf. — 1. Nitrous oxychloride is decomposed by water into nitrous and hydro-
chloric acids :
NOa + OH, = NOHo 4- HCl.
Nitrous Water. Nitrous Hydrochloric
oxychloride. acid. acid.
In like manner it yields, with metallic oxides and hydrates, a mixture of nitrite and
chloride :
NOa + 20KH == NOKo -|- KCl + OH,.
Nitrous Fotassic Potasslc Potaaslc Water,
oxychloride. hydrate. nitrite. chloride.
Nitrons oxychloride belongs to the class of chlorides of the acid radicals, a view
regarding its constitution which is expressed by the name nitrosylie ehhride. These
chlorides are derived from the corresponding acids by the substitution of chlorine for
hydroxy!. Water decomposes them into the corresponding acid and hydrochloric
acid, as in the foregoing reaction.
2. Nitrous oxychloride attacks mercury. The chlorine combines with the metal to
form mercurous chloride, whilst nitric oxide is liberated :
2N0C1 + Hg, = ^g',Cl, -h 2'JSf''0.
Nitrous Mercurous Nitric
oxychloride. chloride. oxide.
It is without action on gold or platinum.
The corresponding bromine compound, NOBr, has also been prepared.
NITRZC DIOXYCHLORIDE NUroxylic Chloride^ ChloropemUric Cha,
NO,a.
Mclecidar weight = 81.6. Mdeeular volume I I I 1 litre weighs 40.75 eriths. BmU
at 5*» C. (41« F.).
Prepcwation, — 1. By passing nitric peroxide and chlorine together through a heated
glass tobe:
^''A -I- CI, = 2N0,C1.
Nitric peroxide. Nitric dloxychloride.
(Nltroxyllc chloride.)
2. By the action of chlorine on argentic nitrate as already described (see Nitric
Anhydride, p. 219).
3. By the action of sulphuric dioxychlorhydrate (sulphurylic chlorhydrate) on
nitric acid :
BOjClHo -f NO,Ho = SOjHo, -h N0,C1.
Sulphuric Nitric Sulphuric Nitric
dioxychlorhydrate. acid. acid. dloxychloride.
4. It is most readily obtained by heating plumbic nitrate with phosphoric oxy tri-
chloride:
(NO,
INO,
Plumbic Phosphoric Triplumbio Nitric
nitrate. oxytrichloride. diphosphate. dloxychloride.
The action of the chlorine compounds of phosphorus on acids and their salts is a
general method for the preparation of the chlorides of the acid radicals.
230 INORGANIC CH£HISTRT.
Properties. — Nitric oxydhloride is a heav^ yellow oil boiling at 5® C. (41® F.).
Reaction. — Water decompoeee it into nitric and hydrochloric acids :
HO,a + OH, = HOjHo + Ha.
Nitric Water. Nitric Hydrochloric
diozychloride. acid. acid.
Bases effect a similar decomposition, yielding a mixture of nitrate and chloride.
COMPOUNDS OF NITROGEN WITH HYDROGEN AND
HYDROXY!.
AMMONIA.
NH,.
Molecular weight = 17. Molecular volume UJEl 1 lUre ioelghs 8.5
criths. i^Wescrf— 75°C.(— 103°F.). .Boifeoi— 38.6° C.(— 37.3^ F.).
History, — The aqueous solution of arainonia was known to the alche-
mists. The gas was first obtained by Priestley, who also observed its
decomposition by the electric spark. Berthollet first ascertained its com-
position.
Occurrence. — Ammonia occurs in small quantity in the air as carbo-
nate, and in rain-water, especially in that which falls during thunder-
storms, as nitrite and nitrate. Most fertile soils contain ammonia. As
chloride and sulphate it is found in the neighborhood of active volca-
noes. AFong with boric acid, it occurs, as salts of ammonia, in the
lagoons of Tuscany (p. 191), having probably been formed by the ac-
tion of subterranean steam upon boric nitride :
BN'" -h 30H, = BH03 + NH,.
Boric nitride. Water. Boric acid. Ammonia.
It also occurs, in the form of its salts, in animal fluids, particularly in
putrid urine, and in the juices of plants.
Formation. — Ammonia is formed : 1. By the decay of animal and
vegetable matters containing nitrogen. It is from this source that the
atmospheric ammonia is derived.
2. By the destructive distillation of these nitrogenous matters. The
ammonia of commerce is thus obtained. Formerly, horn, hoofs, and
bones were distilled for this purpose, and hence the name spirits of
hartshorn was given to ammonia ; but its chief source at the present
day is the ammoniacal liquor of gas works, in which it occurs as a by-
product from the distillation of coal. Volcanic ammonia is also a
product of the destructive distillation of nitrogenous vegetable matter,
being formed only where the lava has flowed over fertile soil.
3. By the action of nascent hydrogen (from zinc and caustic alkali)
on nitric and nitrous acids.
4. Ammonia is also formed synthetically from its elements when the
silent electric discharge is passed through a mixture of nitrogen and hy-
drogen (Donkin).
Preparation. — Ammonia may be prepared from any of its salts by
AMMONIA.
231
heating these with slaked lime. The chloride is usually employed for
this purpose :
2NH,C1 + OaHoj = OaO, + 2NH3 + 20H,.
Ammonic Calcic Calcic AmmoDia. Water,
chloride. hydrate. chloride.
One part of ammonic chloride is mixed with 2 parts of slaked lime in
powder, and the whole is heated in a flask. If gaseous ammonia is re-
quiredy the gas evolved may be dried by passing over quicklime (calcic
chloride absorbs gaseous ammonia), and may be collected either over
mercury or by upward displacement. When an aqueous solution is re-
quired the gas is passed direct into water, which is contained in a series
of Woulff's bottles fitted with safety-tubes. The delivery tubes must
pass to the bottom of the liquid, otherwise only the upper layer would
be saturated, as the aqueous solution of ammonia is lighter than water.
Properties. — Ammonia is a colorless gas, with a very pungent odor.
Its density is 0.589 (air = 1). It turns red litmus blue, and yellow
turmeric paper brown. It neutralizes acids, uniting directly with them
to form salts (see Reactions).
Ammonia may be liquefied by cold or pressure. Faraday first ob-
tained it in the liquid state by heating argentic ammonio-chloride in
one limb of a bent sealed tube, whilst the other was immersed in a
freezing mixture. The argentic ammonio-chloride is prepared by pass-
ing ammonia over dry argentic chloride, which in this way absorbs 320
Fio. 38.
times its volume of the gas. The double compound parts with all its
ammonia when heated to 112° C. (233.6'* F.). By conducting the
heating in a bent sealed tube as above described, the ammonia is lique-
fied by the joint action of its own pressure, and of the cold of the freez-
ing mixture. Calcic ammonio-chloride may be substituted for the
argentic compound in the above experiment. Ammonia may also be
liquefied by the action of cold alone at a temperature of — 40° to — 60°
C. ( — 40° to — 57° F.), by passing the gas through a tube immersed in
a mixture of ice and crystallized calcic chloride.
Liquid ammonia is a mobile, colorless, highly refracting liquid, boil-
ing at —38.6° C. (—37.3° F). At —10° C. (14° F.) it has a sp. gr. of
0.65. When subjected to a temperature below —75° C. (—103° F.)
it solidifies to a white crystalline translucent mass.
232
INORGANIC CHEMI8TBV.
The oold produced by the rapid evaporation of liquid ammonia has
been utilized in Carry's apparatus for the artificial production of ice.
Two strong wrought-iron vessels, A and B (Fig. 38), are connected by a
tube of the same material. A contains an aoueous solution of ammonia
saturated at 0^ C. When ice is to prepared by means of this apparatus,
heat is applied to Aj whilst B is immersed in cold water. Gaseous
ammonia is evolved from Ay and condenses under its own pressure be-
tween the double walls of the receiver B, When a sufficient quantity
of the gas has been driven off, A is cooled by means of water, whilst
the water to be frozen is introduced into a metal cylinder, C, into the
cavity of the receiver B, the space between receiver and cylinder being
filled with alcohol, which does not freeze, and serves as a conducting
medium. Ab the liquid in A cools, it rapidly reabsorbs ammonia,
which boils off from B as fast as the pressure is removed, producing a
great depression of temperature by means of the heat which becomes
latent, and freezing the water contained in the metal cylinder.
Ammonia is exceedingly soluble in water. Water at 0° C. absorbs
more than 1100 times its volume of the gas, evolving great heat in the
process. When the ammonia is pure, the absorption is instantaneous, the
water rushing into the space occupied by the gas as into a vacuum.
The affinity of the two substances for each other is nevertheleas slight,
as the solubility of ammonia in water decreases rapidily at higher tem-
peratures, and the gas is completely expelled from the liquid by boiling.
When exposed to the air, the aqueous solution also parts with nearly
all its gas by diffusion. When ammonia is removed in the gaseous
state from its solution, the heat which was liberated during the process
of solution is again absorbed : thus by sending a rapid current of air
from a foot blower through concentrated aqueous ammonia, the gas is
expelled, and the temperature sinks below — 40° C. ( — 40° F.).
Speeifio Oraviiy Table of Aqueous Ammonia at 14° C.
d.
P-
d.
P-
0.8844
36
0.9347
17
0^864
35
0.9380
16
0.8885
34
0.9414
15
0.8907
33
0.9449
14
0.8929
32
0.9484
13
0.8953
31
0.9520
12
0.8976
30
0.9555
]1
0.9001
29
0.9593
10
0.9026
28
0.9631
9
0.9052
27
0.9670
8
0.9078
26
0.9709
7
0.9106
25
0.9749
6
0.9133
24
0.9790
5
0.9162
23
0.9831
4
0.9191
22
0.9873
3
0.9221
21
0.9915
2
0.9251
20
0.9959
1
0.9283
19
0.9975
0.6
0.9314
18
0.9991
0.2
AMMONIA. 233
The foreeoing table (Carias) gives the specific gravity of the aqueous
solntions of ammonia of various strengths at 14^ C. (57.2^ F.). The
oolumn d contains the specific gravities, the column p the corresponding
percentages of ammonia.
Ammonia does not support combustion and does not burn in air
unless the latter be heated. When mixed with oxygen, however, it is
readily inflammable, burning with a pale yellow flame.
At a bright red heat ammonia is decomposed into its elements. This
decomposition, which is best effected by electric sparks, afibrds a means
of ascertaining the composition of the gas.
Seactions. — 1. Ammonia is decomposed by chlorine (see p. 212).
Bromine and iodine have a similar action. Under certain conditions,
when chlorine and iodine are employed in excess, the explosive com-
pounds, nitrous chloride and nitrous iodide (q-v.) are formed.
2. When ammonia is passed over charcoal heated to redness in a tube,
ammonic cyanide is formed and hydrogen is evolved :
2NH3 + C = N-H,(CN) + H^
Ammonia. Ammonic cyanide.
3. The metals of the alkalies, when heated in gaseous ammonia,
replaoe the hydrogen atom for atom :
NH, + Na = NNaH, + H.
Ammonia. Sodic amide.
4. Ammonia unites directly with acids, forming the ammonium
in which the atomicity of nitrogen is ^ :
N'^'H, + HCl = N-H.Cl.
Hydrochloric Ammonic
acid. chloride.*
N"'H, + N»0,Ho = N'0,(N»H,0).
Nitric acid. Ammonic nitrate.!
2N'"H,. + SO,Ho, = BO,(N'H,0),.
Sulphuric acid. Ammonic sulphate.^
When a glass rod moistened with hydrochloric acid is brought close
to a liquid evolving ammonia, white fumes of ammonic chloride are
H HO
* H-N— H. t H— N— 0-N.
A. /\ h
H O H
J H— N-0-&-0— N— H.
234 INORGANIC CHEMISTRY.
formed. If the ammonia is in oombinatioDi the substance most be
warmed with a solution of caustic alkali before applying this test
Ammonic chloride forms with platinic chloride a yellow crystalline
double salt of the formula PtCl4,2NH4Cl^ almost insoluble in water,
and insoluble in alcohol or ether. This salt is employed in the quanti-
tative determination of ammonia.
ComposUiGn. — ^The composition of ammonia may be ascertained in the
following manner. A measured volume of gaseous ammonia is intro-
duced into an eudiometer tube over mercury. The tube is furnished
with platinum wires fused into the glass for the purpose of passing the
electric spark, which is furnished by an induction coil. The spark is
allowed to pdss through the gas as long as any increase of volume is
observed. The resulting mixture of gases is then measured ; an excess
of oxygen is added, and the whole is exploded by means of the spark.
Two-thirds of the contraction which follows the explosion represents
the volume of hydrogen contained in the mixture. The following
example will illustrate the use of this method :
The mixture of gases resulting from the decom-
position of 100 cubic centimetres of am-
monia is found to measure 200 cc.
Add 100 cc. of oxygen, 100 cc.
Total, 300 cc
After explosion there remain 75 cc.
Contraction, .... 225 cc
The hydrogen contained in the 200 cc. is therefore f X 225 =160 cc,
and the nitrogen is 200 — 150 = 50 cc; the two gases are therefore
present in the proportion of 3 volumes of hydrogen to 1 volume of
nitrogen. Further, as the mixed gases occupied twice the volume of
the ammonia, it is evident that these 4 volumes in combining have
undergone the normal condensation to 2 volumes. Expressing £e vol-
umes in litres :
1 litre of nitrogen weighs 14 criths.
3 litres of hydrogen weigh 3 "
The proportion by weight in which these elements are combined is
therefore, 14 parts by weight of nitrogen to 3 of hydrogen. Dividing
each of these numbers by the atomic weight of the corresponding ele-
ment^ the atomic proportion 1 : 3, represented by the formula NH^, is
arrived at.
AMHODiUM — htbboxyi^minb;. 235
AMMONIUM.
fNH,
\NH,-
This monad radical has never been obtained in the free state, but its
compounds are perfectly analogous, in crystalline form and other prop-
erties, to those of potassium. These facts have led some chemists to
consider the group NH^ as a metal, to which they have given the name
ammonium, a hypothesis which is considered to receive support from
the production of an unstable amalgam of this radical. All the com-
pounds of mercury with metals are found to possess metallic lustre ;
and this is the case with the amalgam of ammonium. It may be pre-
pared by two different processes.
1. If a solution of ammonio chloride be electrolyzed, the n^ative
electrotrode being mercury and the positive a platinum plate, the mer-
cury is observed to swell up owing to the formation of a spongy metal-
lic mass. The solution ought to contain an excess of ammonia, other-
wise the explosive compound, nitrous chloride, may be formed at the
positive electrode.
2. On pouring into a slightly warmed solution of ammonic chloride
an amalgam of potassium or sodium, the amalgam is found to swell
enormously, owing to its conversion into ammonium amalgam, whilst
potaasic or sodio chloride is simultaneously formed :
Hg,Na„ + mNH.Cl = Hg„(N^H,U + mNaCl.
Sodic amalgam, Ammonic chloride. Ammonium amalgam. Sodic chloride.
Ammonium amalgam rapidly decomposes into mercury, ammonia,
and hydrogen, the ammonia and hydrogen being liberated in the pro-
portion of 2NH3 to H, :
2Hg»(N^H,L = 2nHg + 2mNH3 + mH^^
Ammoniam amalgam. Mercury. Ammonia.
Ammonium plays the part of a compound monad radical, and its salts
are isomorphous with those of potassium ; they are all volatile, unless
the acid from which they are derived is fixed. They will be more fully
described along with the metals of the alkalies.
HTDBOXTLAMDn;.
NH,Ho.
This remarkable compound, which was discovered by Lessen, may
be regarded as ammonia in which one atom of hydrogen has been dis-
placed by hydroxyl.
Preparation. — 1. Hydroxylamine is formed by the direct union of
nitric oxide with nascent hydrogen :
236 INORGANIC CHEMISTRY.
2'N"0 + 3H, = 2NH,Ho.
Nitric oxide. HydroxjlamiDe.
Nitric oxide is passed into a miztare in which hydrogen is being gen-
erated — thus into a flask containing tin and dilute hydrochloric acid.
2. Nitric and nitrous acids also yield hydroxylamine when added to
the above reducing mixture :
NO,Ho + 3H, = NH^o + 20H^
Nitric acid. Hydroxylamine. Water.
In these reactions the hydroxylamine remains in solution combined
with the hydrochloric acid.
Properties. — Free hydroxylamine is known only in its aqueous solu-
tion, which is colorless, devoid of odor, and powerfully alkaline. On
distilling the solution, part of the base passes over with the steam, but
the greater part is decomposed with formation of ammonia. The solu-
tion possesses reducing properties and precipitates silver and mercury
in the metallic state from the solutions of their salts.
Hydroxylamine is a mon-acid base. Its salts, which crystallize well,
are formed, like those of all amine bases, by the direct union of base
and acid without elimination of water.
COMPOUNDS OF NITROGEN WITH CHLORINE,
BROMINE, AND IODINE.
NXTBOUB OHLOBIDE.
NCI,?
Preparation. — Nitrous chloride is formed when chlorine is passed
into a solution of ammonic chloride warmed to about 30^ C. :
N^H.Cl + 3C1, = N'^Cl, + 4HC1.
The same reaction takes places when a solution of ammonic chloride
is electrolyzed, the chlorine which is evolved at the positive electrode
acting on the ammonium salt.
Properties. — Nitrous chloride is a yellow oil, of specific gravity 1.6,
possessing a disagreeable, pungent odor. Its vapor irritates the eyes.
Nitrous chloride is the most dangerously explosive substance known.
A slight rise of temperature, or the mere contact with certain bodies —
such as fats, phosphorus, or arsenic — is suflScient to cause it to decom-
pose instantaneously with explosive violence into its elements. Very
frequently explosion occurs without apparent cause.
Ammonia decomposes it with formation of ammonic chloride and lib-
eration of nitrogen. Its formation is therefore prevented by the pres-
ence of an excess of ammonia (see Nitrogen, p. 213).
THE ATM08PHEKE. 237
The formula of this compound has not been ascertained with cer-
tainty : it may contain hydrogen, and it is possible that the compounds
intermediate between ammonia and nitrous chloride may exist :
NH3, NH,C1, NHCl,, NClj.
NITROUS BROMIDE.
NBr,?
This compound is obtained as a dark-red, very explosive oil by
adding an aqueous solution of sodic or potassic bromide to nitrous chlo-
ride:
NCI3 + 3KBr = NBr, + 3KC1.
Nitrous Potassic Nitrous Potassic
chloride. bromide. bromide. chloride.
miBons lODms.
NI,.
When aqueous or alcoholic ammonia is poured on finely powdered
iodine^a black substance is formed which is highly explosive, and, when
dry, detonates on the slightest touch. The product varies in composi-
tion, according as aqueous or alcoholic ammonia is employed. A nitrous
hydrodiniodide is formed at tlie same time:
4NH3 + 31, = NI3 + 3NH,L
Ammonia. Nitrous iodide. Ammonic
iodide.
3NH, + 21, = NHI, + 2NH,I.
Ammonia. Nitrous Ammonic
hydrodiniodide. iodide.
THE ATMOSPHERE.
The atmosphere of the earth consists of a mixture of gaseous, h'quid,
and solid matters. The chief gaseous constituents are nitrogen, oxygen,
a small quantity of carbonic anhydride, and a varying proportion of
aqueoas vapor. Water also occurs in the liquid state in minute parti-
cles in the form of mist. The solid matters consist of ice particles,
volcanic and other dust, sporules and metaUic salts — notably sodic
chloride — in a finely divided state.
The atmosphere is generally considered to extend to a height of about
46 miles above the earth's surface, this estimate being based upon ob-
servations of the length of time during which the twilight is visible in
the zenith. Meteorites^ however, ignite at an elevation of about 200
238 INORGANIC CHEMI8TBT.
miles, proving the presenoe of a medium which, though of too great
tenuity to reflect light, still possesses density, and offers resistance to
the passage of bodies through it. It is probable that even this height
does not denote the upper limit of the atmosphere.
Owing to the effect of gravitation and the elasticity of the atmos-
phere, the lower strata have a much greater density than the higher
strata. If the density, instead of thus gradually decreasing with the
elevation, were uniform throughout, and identical with that which pre-
vails at the earth's surface, the entire height of the atmosphere would
be only about 5 miles. This diminution of density is such that at a
height of about 3 miles the barometric pressure is only half as great as
at the earth's surface, and consequently one-half of the atmosphere lies
below this height.
According to the very accurate determinations of Renault the weight
of 1 litre of pure dry air at 0° C, and under a pressure of 760 milli-
metres of mercury (the average barometric pressure at the level of the
sea — a pressure commonly referred to as that of 1 atmosphere) in the
latitude of Paris, is 1.2932 grams. Air is thus 773 times lighter than
water, 10,500 times lighter than mercury, and 14.45 times heavier than
hydrogen. A column of the height of the atmosphere and of 1 inch
square weighs 15 lbs. Thus 27,000,000 tons rest upon every square
mile of the earth's surface.
The luminous rays of the sun pass through the atmosphere without
appreciably heating it, except in so far as they are intercepted and ab-
sorbed by suspended solid or liquid matter ; but the rise of temperature
from the latter cause is not great. The dark heat-rays, however, are
partly absorbed, and this absorption is due to aqueous vapor. These
dark rays represent, however, but a fraction of the total radiant en-
ergy of the sun, of which the greater part therefore reaches the earth
unimpaired. Here both the visible and the invisible rays are converted
by al^rption into heat ; and radiation from the earth's surface in the
form of dark heat is for the most part intercepted by aqueous vapor.
In this way, the earth which has been heated by the sun imparts its
heat to the air immediately resting upon it, and the aqueous vapor acts
as a trap for the solar rays, allowing them to enter freely in the form
of luminous heat, but preventing their escape when they are once con-
verted into dark heat. Thus a too rapid cooling of the earth's surface
during the absence of the sun, and the consequent great inequalities of
temperature, are prevented. The air, thus heated by contact with the
earth, expands, and, becoming lighter, rises, and shares its heat with
the strata above, whilst air from some colder quarter flows in to supply
its place. The air is thus in constant motion, and differences in com-
position of the atmosphere in various places, which might arise from
local causes, are prevented. To this heating and cooling, and to the
varying quantities of aqueous vapor present in hot and in cold air, the
variations of the barometric pressure are due. Equalization of tempe-
rature is also effected by the condensation of aqueous vapor during a fall
of temperature, the latent heat of vaporization being recovered in this
process.
The highest atmospheric temperature (temperature in shade) that has
THE ATMOBPHEBE. 239
been obferved is about 49*^ C. (120.2° F.); the lowest —49° C.
(_66.2° F.).
The expansion of air by heat is 0.003665 of its volume measured at
0° C. for every 1° above 0° C.
As r^ards the chemical composition of the atmosphere, the propor-
tion of oxygen to nitrogen is nearly constant ; the proportions of the
.other constituents are subject to considerable variation. The following
table contains determinations of the relative quantities of oxygen and
nitrogen present in dry air freed from carbonic anhydride. As is usual
in the analysis of gaseous mixtures, the results are expressed in parts by
volume.
Composition of Atmospherio Air from various LoccUities. In 100
parts by volume.
Oxygen. Nitrogen.
Parts by volame. Parts by volnme.
a* T> *k 1 ^ IT •* 1 / 20.885 79.115
St. Bartholomew's Hospital, . * \ OQ 999 79 001
p .^ J 20!913 79.087
^*™' \ 20.999 79.001
T ^^^a J 20.918 79.082
^^^^' 120.966 79.034
T^„i^« J 20.912 79.088
-^^^'^°^ 1 20.982 79.018
Berlin I ^0.908 79.092
^^""' \ 20.998 79.002
T^ , . , / 20.916 79.084
^^^*^' i 20.982 79.018
p J 20.909 79:091
^^°^^** \ 20.993 79.007
Montanvert, 20.963 79.037
Summit of Pichincha, 16,000 ft. . | g^'^g^ ^9 012
North American Prairie, . . . 20.910 79.090
South America, 20.960 79.040
T . 1^ ^T n / 20.918 79.082
Liverpool to Vera Cruz, . . . 1 20.965 79.035
18,000 ft above London, . . . 20.885 79.115
Mn«.i.^*., / 20.876 79.124
Manchester, \ 20.888 79.112
41 • /T K iQKi\ j 20.420 79.580
Algiers (June 5, 1851), . . . . j 20.396 79.605
Bay of Bengal (Feb. 1, 1849), . | 20.460 79.540
Ganges (March 8, 1849), . . . { ^J^SJ 79.613
These analytical results, except in the case of the three localities last
mentioned, display a remarkable uniformity. The cause of the varia-
tion in the case of the sample from Algiers is unexplained ; but as re-
240 INOBOANXC CHEMISTRY.
gards the sample from the Bay of Bengal and the Granges, it is to be
noted that these were collected during an outbreak of cholera when the
water contained large quantities of putrefying organic matter.*
The presence of a very small quantity of the oxygen as ozone has al-
ready been referred to (p. 166).
The average proportion of carbonic anhydride present in air is about
0.03 per cent.; but the amount may vary considerably owing to local
causes. Thus the effect of animal life is to increase the proportion of car-
bonic anhydride ; that of vegetable life to diminish it (see p. 202). In
putrefaction and in combustion, large quantities of this gas are given off.
In Ijondon, combustion and respiration daily send into the air at least
200,000,000 cubic feet of carbonic anhydride. Each ton of coal consumed
furnishes about 3 tons of carbonic anhydride, and abstracts 2.75 tons of
oxygen from the air. The variations due to the above causes are very
noticeable : thus in crowded and ill-ventilated rooms, the air may contain
as much as 0.3 per cent of carbonic anhydride ; air from the centre of
London contains 0.11 per cent. Near the surface of the ocean, both oxy-
gen and carbonic anhydride are slightly in excess during the day, and
slightly deficient during the night. This is due to the fact that these
gases are more soluble in water than nitrogen : in the night time the
cold water dissolves them in larger quantity, and this dissolved excess
is again expelled when the water is heated by the sun's rays during the
day. At great altitudes the proportion of carbonic anhydride appears
to increase: thus the air at the Grands Mulets was found to contain 0.1
per cent
The proportion of aqueous vapor present in the air varies greatly.
The maximum quantity of aqueous vapor which a given volume of air
can take up is constant for a given temperature, and independent of the
pressure. When air has taken up this maximum quantity it is said to
be saturated with moisture. The amount necessary for saturation at a
given temperature can be calculated from the tension of the vapor of
water for that temperature. In this way it is found that 1 cubic metre
of air can take up the following weights of aqueous vapor:
At 0° C. ( 32° R), 4.871 grams.
At 10° C. ( 50° F.), 9.362 grams.
At 20° C. ( 68° F.), 17.157 grams.
At 30° C. ( 86° F.), 30.096 grams.
At 40° C. (104° F.), 60.700 grams.
The air is very seldom saturated with moisture. When the tempera-
ture of air containing aqueous vapor falls, as soon as the point is passed
at which the quantity of aqueous vapor present corresponds to satura-
tion, a separation of the excess of this vapor in the form of mist, rain,
snow, or hail b^ins. This point is known as the dew-point, and by
* The oxygen in the foregoing samples was determined by exploding the air with
hydrogen and noting the contraction. If, as is quite conceivable, the air in the above
abnormal cases contained traces of marsh-gas derived from the decomposition of organic
mntter, a smaller contraction would be observed, and the percentage of oxygen would
be found too low.
THE ATMOSPHERE. 211
deteriniDing it aocaratelj, the quantity of aqueoas vapor present in in-
completely saturated air may be ascertained. The usual proportion by
volume of aqueous vapor in air, varies from 0 to 5 per cent.
The question of the proportion of aqueous vapor present in air is of
great importance in meteorology; but in the chemical examination of
air the aqueous vapor is taken into acoount only in so far as by its vol-
ume it diminishes the absolute quantity of the other constituents present
in a given bulk. It is usual, in the analyses of gases, to eliminate the
aqueous vapor from the result by calculation.
Other constituents of the air, which are, however, present only in
minute quantity, are salts of ammonia, namely, the carbonate, nitrate^
and nitrite. Ammonia is given off in the putrefaction of animal and
v^etable matter. Oxides of nitrogen are formed whenever a flash of
lightning passes through air : rain-water, especially if collected after a
thunderstorm, contains nitrates and nitrites. The presence of these
nitrogenous compounds in the air is of great importance to plant life,
as it IS from this source alone that plants which have not been supplied
with a nitrogenous manure obtain the nitrogen necessary for their
growth. Plants cannot assimilate free nitrogen.
Another product of putrefaction which is constantly being given off
into the air is marsh-gas. It is doubtful, however, whether the pres-
ence of this compound in air has been proved, except in the neighbor-
hood of putrefying matter.
Although the various guises which together make up the atmosphere
possess very different specific gravities, they display no tendency to sepa-
rate from each other. On the contrary, by the laws of diffusion, any
number of gases which are brought into contact have a tendency to be-
come thoroughly mixed, even although there are no actual currents in
the gases, and even although the lighter gases may be uppermost at the
commencement of the process. The influence of currents of air in pre-
serving uniformity of composition has already been referred to.
As regards the suspended matter in the atmosphere, this may, as
already stated, be both solid and liquid. These particles, even when
present in small quantity, are rendered visible to the eye by their
property of reflecting light: thus when a ray of light passes through a
dark room, the path of the ray appears luminous. By filtration
through cotton wool, or by subsidence, the particles are removed, and
the path of a ray of light through air thus purified ceases to be visible.
These particles are never absent from air under ordinary conditions.
When solid particles are present in quantity snfiicient to obstruct visibly
the passage of light, they constitute a dust-haze. Piazzi Smyth ol>-
served a strong dust-haze on the summit of the Peak of Teneriffe at an
altitude of 12,000 feet. Minute liquid particles constitute ordinary
mist or fog. V\^l\en the surface of the sea is violently agitated by the
wind, palrticles of sea-water are thrown into the air in the form of
spray : these are carried far inland by the wind, yielding by evajwra-
tion solid particles of sea salt, a substance which is scarcely ever absent
from air. The yellow flashes which a Bunsen flame emits from time
to time, while burning in air^ are due to sodium compounds, as may be
proved by spectroscopic examination. In the neighborhood of the sea
16
242 INOBOANXC CHEMISTRY.
the quantity of sodic chloride present in air is of course greater than
further inland. At Laud's End for example, the rain water contains
as much as 0.033 per cent, of this salt. At great altitudes in Switzer-
land the air almost always containfi minute particles of snow, which
may be seen by putting the eye in shadow and looking into sunshine.
Among the organic solid particles present in air, are to be reckoned the
fferms of putrefactive and other fermentations. This is shown by the
fact that air which has been effectually freed from all suspended matter
by filtration does not induce putrefaction in milk, flesh, urine, and other
readily alterable animal substances, however long these may be leflt in
contact with it.
If a Bunsen flame be placed under the path of a ray of light in a dark
room, the heated air rising from the flame appears like a black smoke,
owing to the absence of suspended matter in the products of combus-
tion. The same phenomenon may be shown, though in a less striking
manner, by substituting for the flame a flask filled either with oil
heated to 120°-130° C. (248°-266° F.), or with ice-cold water, and
concentrating the ascending or descending current of air upon the path
of the ray by means of a conical paper funnel. This phenomenon has
not yet received any satisfactory explanation.
It has been shown by Lodge that the electrification of air also rapidly
removes the suspended particles contained in it.
That the oxygen and nitrogen, which form the chief constituents of
the atmosphere, are present in a state of mere mechanical mixture and
not, as was formerly supposed, in chemical combination, is proved by a
variety of considerations. Thus the proportion by volume of the two
gases to each other is highly complex, 21 volumes of oxygen to 79 vol-
umes of nitrogen being the simplest proportion that can be assumed ;
whereas in compounds of only two elements much simpler relations
prevail. No contraction occurs when oxygen and nitrogen form air,
and there is no case known in which two gases unite chemically in un-
equal proportions by volume without contraction. When oxygen and
nitrogen are mixed in the above proportions, no heat is evolved, nor is
there any other sign of chemical combination ; nevertheless, the mix-
ture displays all the properties of air. When air is dissolved in water,
the proportion of its constituents is totally altered, owing to the greater
solubility of oxygen ; thus, dissolved air contains, in 100 volumes, 32.6
volumes of oxygen and 67.5 volumes of nitrogen. Again, air which
has been forced through a thin caoutchouc membrane contains 41.6
volumes of oxygen to 68.4 volumes of nitrogen, owing to the property
which oxygen possesses of passing more r^ily through caoutchouc.
If air were a chemical compound, the proportion of its constituents
could not be thus altered by solution or by osmosis.
SULPHUR. 243
CHAPTER XXVII.
HEXAD ELEMENTS.
Section I.
SULPHUR, S^
Atomic weight = 32. Molecular weight = 64. Molecular volume I l I
at 1000*^ C, biU only one-third of this at its boiling-point. 1 litre of
sulphur vapor weighs 32 oriths. Rhombic variety fuses ai 114.5^ C.
(238.1° F.). BMa ai 445° C. (833° F.). AtomicUy ^ *% and ^.
Evidence of atomicity:
Salpharetted hydrogen, 8"Hjp
Triethylsulphiuic iodide, S^'EtjI.
Sulphuric oxydichloride {Sulphurylio
Monde), B^Ofi]^
Sulphuric iodide, S^Is*
Sodic dinitroeulphate, S'*0(NO),Nao,.
History. — This element has been known from the earliest historical
times.
Occurrence. — Sulphur occurs both native and in combination. Na-
tive sulphur is found chiefly in the neighborhood of volcanoes : thus
in Sicily, whence the greater part of the native sulphur of commerce is
obtained. In combination it occurs either with metals alone as sul-
phides, or with metals and oxygen as sulphates. Of the former the
most important as sources of sulphur are ferric disulphide or iron py-
rites (FeS'^s) and copper pyrites (Fe^Cu^S^). The sulphides of zinc,
lead, mercury, and antimony are important ores of these metals. The
most commonly occurring sulphates are calcic sulphate — which is found
in two forms, as gypsum (SHo^Cao"), and as anhydrite (BO,Cao") —
baric sulphate, or heavy spar (SO^Bao'^), and magnesic sulphate, which
also occurs in two forms, as kie8erite(SOHo2Mgo'')^and as Epsom salts
SBOHo2Mgo'',60H2). The sulphates of calcium, magnesium, and so-
lium occur in natural waters. Of gaseous compounds, both sulphurous
anhydride (80,) and sulphuretted hydrogen (SH,) are of frequent oc-
currence in volcanic exhalation, the latter being also found in many
mineral waters. Sulphur is a constituent of many complex organic
compounds in the animal and vegetable kingdoms.
Formation of Volcanic Sulphur. — ^This is probably due to the mutual
decomposition of the two volcanic gases, Rulphurous anhydride and
sulphuretted hydrogen, in presence of water. In this reaction penta-
thionie acid and water are formed, whilst sulphur is liberated :
fSOjHo
(SOjHo
80,Ho
580, + 6BH, = U^W + 40H, +• 6S.
lo
Bulpharoos Bulphareltod Pentathionic Water,
anhydride. hydrogeD. add.
244 INORGANIC CHEMISTRY.
Manufacitwre. — !• Native Bulphur is usually mixed with large quan-
tities of earthy matters, from which it is separated by fusion. In Sicily,
the heat for this purpose is obtained by the combustion of a portion of
the sulphur itself. The sulphur ore is built up into a large heap over
a pit sunk into the ground. The heap is ignited from beneath, and as
the heat slowly penetrates through the mass, the sulphur melts and
flows into the pit, which is so arranged that the liquid product can be
drawn off during the process. By this method more than half the sul*
phur burns away as sulphurous anhydride.
2. Sulphur is also obtained by distilling iron pyrites:
3FeS, = 'XJfesrS, + S^
Ferric Triferric
disulphide. tetrasulphide.
The reaction is analogous to that which takes place in the preparation
of oxygen from manganic peroxide (p. 161). The distillation is per-
formed in fire-clay cylinders. It is, however, in every way more eco-
nomical to bum the pyrites in kilns, a method which has been generally
adopted. The kiln is lighted from below ; part of the sulphur which,
in the process of distillation in cylinders, remains in combination with
the iron, burns, forming sulphurous anhydride; the remainder distils
off and is condensed. The exhausted pyrites is from time to time with-
drawn from the lower part of the kiln, and a fresh charge is introduced
at the top, thus rendering the process more continuous. By this method
one-half of the total sulphur is obtained from the pyrites :
+ 380, + 3S.
Sulphurous
anhydride.
Bv passing the products through heated charcoal a larger yield can
be obtained.
Sulphur is obtained in a similar manner from copper pyrites in the
process of roasting the ore in the first stage of copper-smelting.
8. The cdkati-ioaste obtained in the manufacture of sodic carbonate
{q.v.) may be made to yield considerable quantities of sulphur. This
waste, which remains after the extraction of the sodic caroonate from
the blach-ash by lixiviation, consists essentially of insoluble calcic oxy-
sulpbide, a combination of calcic sulphide with calcic oxide in varying
proportions. Without removing the waste from the lixiviating vats, a
current of air is blown through it, by which means the calcic sulphide
contained in the oxysulphide is oxidized with considerable rise of tem-
perature, yielding a mixture of soluble polysulphides of calcium and
calcic thiosulphate :
(a.) 20aS + O + OH, = Oa(S",)" + OaHo,,
Calcic stilphide. Water. Calcic disulphide. Calcic hydrate.
(6.) Ca(S",)'' + 30 = SoJ^CaV'.
Calcic disulphide. Calcic thiosulphate.
3PeS, + 60, =
= '-(Jfe,)^.
Ferric
Triferric
disulphide.
tetroxide.
HULPHUB. 245
Calcic sulphide is also liberated from its combination with the lime and
becomes soluble. The oxidation is allowed to proceed till one-half of
the sulphur has been converted into thiosulphate, and the remainder
into calcic sulphide or polysulphide^ after which the whole is lixiviated,
and the solution treated with hydrochloric acid. The sulphur is lib-
erated, as represented by the following equation :
20aS + BoJ^CaW + 6HC1 = 4S + SOaCl, + 30H,.
Calcic Calcic Hydrochloric Calcic Water,
sulphide. thiosulphate. acid. chloride.
Calcic polysulphides undergo an analogous decomposition with calcic
thiosulphate when treated with hydrochloric acid, but the quantity of
sulphur liberated is proportionately larger.
The sulphur thus obtained is melted under superheated water.
4. Sulphur is obtained in the purification of coal-gas. The crude
gas contains sulphuretted hydrogen. In order to remove this impurity^
the gas is pafisea through ferric hydrate, which absorbs the sulphuretted
hydrogen with formation of ferrous sulphide and separation of sulphur :
Pe,Hoe + 38H, = 2FeS + S + 60H^
Ferric Sulpharetted Ferrous Water.
hydrate. hydrogen. sulphide.
When the mixture has lost its absorptive power, it is exposed to the air
in a moist state, ferric hydrate being thus regenerated and sulphur set
frifc:
2FeS + 30H, + SO = Pe,Ho, + Sj^.
Ferrous sulphide. Water. Ferric hydrate.
In this condition the mixture is again employed in the removal of sul-
phuretted hydrogen. These alternate processes of absorption and oxi-
dation are repeated till the mixture contains half its weight of sulphur,
when the latter is separated by distillation.
Refining. — Crude sulphur is generally contaminated with earthy im-
purities, from which it is separated by distillation. The operation is
conducted as shown in Fig. 39. The crude sulphur is first introduced
into the iron jwt A, where it is melted. The greater part of the im-
purities sink to the bottom, and the melted sulphur is run off into the
retort £, whence it is distilled into the large brick- work chamber C
When the distillation is conducted rapidly, so as to keep the tempera-
ture of the chamber above the melting-point of sulphur, the letter con-
denses in the liquid state and collects on the floor of the chamber,
whence it may be drawn off by the tap 2), to be run into slightly conical
box-wood moulds. The sulphur thus obtained is known as roll sulphur.
When the distillation proceeds slowly, and the tempemture of the
chamber is consequently lower, the sulphur is deposited as a fine crystal-
246
INORGANIC CHEMISTRY.
line dust on the walls and floor of the chamber. This form is termed
flowers ofsulphw\
Fig. 39.
Properties. — Sulphur is capable ot existing in several allotropic modi-
fications, of which the following are the most important :
Specific
gravity,
. 2.06
i5. Monoclinic (prismatic), . . 1.98
r. Plastic, 1.95
d. Powder, 1.96
Oandition.
a. Rhombic (octahedral),
Behamor with earbonie
disulphide.
Soluble.
Transformed into «.
Insoluble.
Insoluble.
The rhombic form is that in which sulphur occurs in nature. This
form displays great yariety of crystalline combinations: the most fre-
quently occurring combination, in which the rhombic octahedron is
dominant, is shown in Fig. 40. Rhombic sulphur is insoluble in
water, somewhat soluble in alcohol, ether, and hydrocarbons, readily
soluble in carbonic disulphide and disulphur dichloride. From these
solvents it is again deposited in the rhombic form. Rhombic sulphur
fuses at 114.6° C. (238.r F.).
The behavior of melted sulphur is anomalous. Just above its fusing-
point it forms a clear, yellow, mobile liquid ; but on raising the tem-
perature the color deepens, changing to a reddish -brown, whilst the
liquid becomes viscid. At about 230° C. (446° F.) it is almost black,
SULPHUR.
247
and is so thick that the vessel in which it is contained may be inverted
without spilling the contents. Heated above this temperature it again
becomes liquid, still however preserving its dark color, till at 447° C.
(836° F.) it boils, giving off a reddish-brown vapor. One litre of this
vapor at 524° C. (975° F.) weighs 96 criths, whereas above 860° C.
(1680° F.) the weight of 1 litre of sulphur vapor is 32 criths, or only
Fro. 40.
one-third of the first-mentioned value. From this it follows that above
860° C. the molecule of sulphur contains two atoms, but that just
above its boiling-point, the molecule is hexatomic.
If sulphur, heated to its boiling-point, be allowed to cool gradually,
the above changes are observed in the reverse order.
The rhombic variety of sulphur may also be obtained by melting sul-
phur in large masses, and, by slow cooling with exclusion of air, allow-
ing it to remain in a state of superfusion, or suspended solidification.
Fig. 41.
At a temperature of about 90° C. (194° F.), the superfused sulphur
deposits rhombic crystals. If the melted sulphur be allowed to cool
more rapidly, the second or monoclinic variety is obtained. This last
experiment is best performed by fusing about a kilogram of sulphur in
a Hessian crucible, and allowing it to cool till a crust has been formed
over the surface. Two holes are then broken in this crust, and the
crucible is inclined so as to allow the sulphur which still remains
liquid to run out. The interior of the crucible (Fig. 41) is found to be
lined with long thin transparent prisms, belonging to the monoclinic
system. These fuse at 120° C. (248° F).
The system in which sulphur crystallizes is determined by the con-
248 INORGANIC CH£MI8TBY.
ditions of temperature ander which the crystallization occurs, and the
crystals of each system are unstable at the temperature of formation of
those of the other system. Thus, when a transparent crystal of rhom-
bic sul}»hur, which has been deposited at ordinary temperatures, is ex-
posed for some time to a temperature just below its fusins-point, it loses
its transparency and, on examination, is found to have been converted
into an aggr^ation of minute monoclinic crystals. On the other hand,
the transparent crystals of monoclinic sulphur, which are formed at a
higher temperature, become opaque after remaining for some time at the
ordinary temperature, having changed iuto aggr^ations of small rhom-
bic crystals. This latter change may also be effected by scratching the
monoclinic crystals : in this case the transformation takes place rapidly,
and is found to be accompanied by a liberation of heat. The rhombic
modification is that into which all other forms of sulphur.(exoept the ^
variety) spontaneously change at ordinary temperatures.
If melted sulphur at a temperature just above its fusing-point be
poured into cold water, it solidifies to a yellow, brittle mass. But if
the temperature of the melted sulphur be raised above the point of
maximum viscosity, and the dark-colored mobile liquid thus obtained
be poured in a thin stream into water so as to effect its cooling as rap-
idly as possible, a totally different phenomenon is observed. Under
these conditions, the sulphur forms plastic, amber-colored, transparent
threads, whirh may be drawn out or kneaded between the fingers. This
is the variety known as pUutio sulphur. After standing for some time
at ordinary temperatures it becomes brittle and opaque. At a temper-
ature of 100° it is suddenly converted into rhombic sulphur, the change
being accompanied by evolution of heat.
If the brittle sulphur resulting from the spontaneous change of the
plastic variety be treated with carbonic disulphide, part of it is dissolved,
whilst part remains behind as a brown amorphous powder. A light
yellow amorphous powder, insoluble in carbonic disulphide, is also ob-
tained by treating nowers of sulphur with this solvent as long as any-
thing is dissolved. The same insoluble variety separates out when a
solution of sulphur in carbon disulphide is exposed to sunlight concen-
trated by means of a lens. At a temperature of 100° C, these amor-
phous varieties pass into the ordinary rhombic modification.
All the varieties of sulphur are insoluble in water.
The so-called milk of sulphur is nothing more than sulphur in a
finely divided state, obtained by decomposing calcic pentasulphide, or
any other polysulphide, with hydrochloric acid :
48.
^\s,yvfi
+ 2HC1 =
OaCl,
+ SH, +
Calcic
Hydrochloric
Calcic
Sulphuretted
pentagulphide.
acid.
chloride.
hjdrogen.
It is soluble in carbonic disulphide, and is probably the rhombic
variety.
Reactions — 1 . When heated in air or oxygen to its temperature of
ignition, sulphur burns with a blue flame, forming sulphurous anhy-
dride:
8ULPHUBETTED HYDR9GEN. 249
S + O, = SO,.
Snlphnroiw
anhydride.
A slow, phosphorescent combustion occurs when sulphur is heated to
about 180^ C. (356° F.) in air. No flame is visible in daylight; but
in the dark a grayish-white flame, quite distinct from the ordinary blue
flame of burning sulphur, appears to hover over the heated surface.
The product of combustion is in this case also sulphurous anhydride.
In presence of air and moisture, finely divided sulphur is spontane-
ously oxidized at ordinary temperatures^ to sulphurous and sulphuric
acidb.
2. Sulphur also unites directly with chlorine, bromine, iodine, phos-
phorus, hydrogen, and various other non-metal«.
3. It combines directly with many metals when heated with them,
forming sulphides:
K, + S = 8K,.
Potaasic sulphide.
Fe + 8 = FeS.
Ferrons sulphide.
When united exclusively with positive elements or radicals, sulphur
is almost invariably a dyad ; it is then analogous to oxygen, as will be
seen from the following formulse:
Oxygen compounds, . . OK,, OKH, 00„ OOKo,.
Sulphur " . . SKj, SKH, OS",, OSKs,.
Uses. — Sulphur is employed in the arts in the manufacture of gun-
powder and for tipping common lucifer matches. . In the form of sul-
phurous anhydride it is a useful bleaching agent. Its most important
application, however, is in the manufacture of sulphuric acid.
COMPOUNDS OF SULPHUR WITH HYDROGEN,
Sulphuretted hydrogen, SHj.
Hydrosulphyl, 'S',Hj or Hs^
Hyposulphurous hydrosulphate, . . . SHs,.
SULPHURETTED HTDBOOEN, Hydrosulphuric Acid, Sulphy-
drio Acid.
SH,. H— S— H.
Motectdar weight = 34. . Molecular volume I I I- 1 litre weighs 17 crOhs,
Solid ai —85.6° C. (—121.9° F.). lAqueJied under a presmre of 17
atmospheres at 10° C. (50° F.).
History. — This compound was first investigated by Scheele.
Occtirrenee. — Sulphuretted hydrogen is evolved along with other
gases from volcanoes and fumaroles. It occurs also in hepatic mineral
260 INORGANIC CHEMISTRY.
waters, sach as those of Harrogate, and in waters which contain sul-
phates along with organic matters.
FortMxi&on and Preparation. — 1. Sulphuretted hydrogen is formed
in small quantity by the direct union of its elements when hydrogen,
together with the vapor of sulphur, is passed through a red-hot tube, or
even when hydrogen is p&ssed into boiling sulphur :
H, + S = SH^
. Salpharetted hydrogen.
2. The most convenient method of preparing the gas for laboratory
purposes consists in acting on ferrous sulphide with dilute sulphuric
acid:
PeS" + BO.Ho, = SH, + SO,Feo".
Ferrous Sulphuric Sulphuretted Ferrous
sulphide. acid. hjdrq^en. sulphate.
The ferrous sulphide, broken into coarse fragments, is introduced into
a flask similar to that used in the preparation of hydrogen, and the acid,
diluted with about 6 times its bulk of water, is poured in through a
funnel. The gas is washed by passing it through water.
Hydrochloric acid may be substituted for sulphuric acid in the above
reaction :
PeS" + 2HC1 = SH, + PeCl,.
Ferrous Hydrochloric Sulphuretted Ferrous
sulphide. acid. hydrogen. chloride.
The use of sulphuric acid is, however, much more convenient in practice.
3. Sulphuretted hydrogen prepared from ferrous sulphide generally
contains free hydrogen, generated by the action of the acid upon metallic
iron, which is often present in the sulphide as an impurity. Pure sul-
phuretted hydrogen may be obtained by decomposing precipitated anti-
monious sulphide, or native antimonious sulphide {gray antimony ore),
with hydrochloric acid aided by a gentle heat :
Sb,S'', + 6HC1 = 38Hj + 2SbCl,.
Antimonious Hydrochloric Sulphuretted Antimonious
sulphide. acid. hydrogen. chloride.
If the native compound he employed, it ought to be first treated with
dilute hydrochloric acid, in order to remove any carbonates that may
be present
4. Sulphuretted hydrogen is formed in small quantity along with
sulphurous anhydride when steam is passed over boiling sulphur, or
even when sulphur is boiled with water :
3S + 2OH2 = 2SH, + SO,.
Water. Sulphuretted Sulphurous
hydrogen. anhydride.
The sulphuretted hydrogen and sulphurous anhydride mutually decom-
pose each other in the distillate with separation of sulphur, only a por-
tion of the former gas remaining (see p. 243).
SUIiPHURETTED HYDROGEN. 251
6. Sulphuretted hydrogen is formed when sulphur is heated along
with paraffin, aniline, and various other organic bodies. The reac-
tions which take place in these cases are very complicated and cannot be
followed by means of equations.
6. It is evolved during the putrefaction of organic bodies containing
sulphur, and also when these bodies are subjected to destructive distil-
lation. It thus finds its way into illuminating gas, from which it has
to be removed in the process of purification.
Properties. — Sulphuretted hydrogen is a colorless gas possessing the
disgusting odor of putrid eggs. The very offensive odor of the gas pre-
pared from ferrous sulphide is, however, in. part due to the presence of
volatile sulpho-carbon compounds derived from the iron. It is sliehtly
heavier than air. It is combustible, burning in air or oxygen with a
bluish flame, and forming sulphurous anhydride and water:
SH, + 30 = SO, + OH^
Sulphuretted Sulphurous Water,
hydrogen. anhydride.
When the supply of oxygen is insufficient for complete combustion,
water only is formed, and sulphur is deposited.
Water absorbs about three times its volume of sulphuretted hydrogen,
yielding a colorless solution possessing the taste and odor of the gas.
The aqueous solution is a useful laboratory reagent. It parts with the
whole of its gas on boiling. Exposed to the air, the gas in solution is
quickly oxidized with separation of sulphur, water being formed at the
same time.
Sulphuretted hydrogen has a powerfully poisonous action when in-
haled, especially in the case of small animals. The intensity of the
action in various animals appears to be connected with the rapidity of
circulation of the blood. An atmosphere containing j-^ of the gas
suffices to kill a bird, whilst j^jf is necessary to kill a dog, and t;^ to
kill a horse. Cold-blooded animals are totally unaffected by this pro-
portion of sulphuretted hydrogen.
Meadions. — 1. 8ulphurett«l hydrogen is immediately decomposed
by chlorine with separation of sulphur:
SH, + CI, = 2HC1 + S.
Sulphuretted Hydrochloric
hydrogen. acid.
A similar reaction takes place with bromine. In the case of iodine,
the formation of hydriodic acid and the liberation of sulphur take place
only in the presence of water. The reason of this is that the reaction
SH, + I, = 2HI + S,
Sulphuretted Hydriodic
hydrogen. acid.
is attended with an absorption of heat, and consequently, according to
the laws of thermochemistry (p. 115), cannot take place without the
252 INORGANIC CHEMIBTBT.
aid of some extraneous energy. When water is present, the heat evolved
by the absorption of the hydriodic acid by water, furnishes this energy ;
the thermal sign of the equation becomes positive and the reaction
possible.
2. Sulphuretted hydrogen is decomposed by many compounds rich
in oxygen, such as ferric hydrate :
Te'",Hoe + 3SH, =
Ferric Sulphuretted
hydrate. hydrogen.
This reaction is employed on a large scale in the purification of coal-
gas (see p. 245).
In like manner it reduces concentrated sulphuric acid, which cannot
therefore be employed in drying the gas:
2reS"
+
s
+
60Hr
Ferroin
Water.
sulphide.
SH, +
SO^Oj
= 80, + S + 20H^
Sulphuretted
Sulphuric
Sulphurous Water.
add.
anhydride.
Fuming nitric acid, when dropped into a jigr of sulphuretted hydrogen,
oxidizes it with explosive violence.
3. The sulphydrates aud sulphides of the metals are produced by the
action of sulphuretted hydrogen on the hydrates and oxides; thus:
OKH + SH, = BKH + OH^
Potaasic Sulphuretted Potassic Water,
hydrate. hydrogen. sulphydrate.
BaHo, + 28H, = BaHs, + 20H^
Baric Sulphuretted Baric Water,
hydrate. hydrogen. sulphydrate.
OAg. + SH, = SAg, + OH^
Argentic Sulphuretted Argentic Water,
oxide. hydrogen. sulphide.
OuO + SHj = OuS + OHj^
Cupric Sulphuretted Cupric Water,
oxide. hydrogen. sulphide.
Upon this property, and upon the varying behavior of the different
metallic sulphides towards weak acids, is based the use of sulphuretted
hydrogen as a reagent in analysis. Some of these sulphides are insol-
uble in weak acids : sulphuretted hydrogen, therefore, precipitates them
from an acid solution of the salts of their metals :
SOaCuo'' + SH, = OnS + BOfiy
Gupric Sulphuretted Cupric Sulphuric
sulphate. hydrogen. sulphide. acid.
Others are soluble in weak acids, but insoluble in alkaline solutions.
The precipitation of these sulphides is most conveniently effected by the
SULPHURETTED HYDROGEN. 253
addition of an alkaline sulphide (ammonic sulphide is most comuionly
employed for this purpose) to the neutral or alkaline solution of the
salty vhen double decomposition takes place, thus :
ZnCl, + S(NH,), = ZnS + 2NH,C1.
Zincic Ammonic ZiDcic Ammonic
chloride. sulphide. sulphide. chloride.
A third class of metals yields sulphides which are soluble in water,
and are therefore not precipitated either in acid or in alkaline solutions.
It is thus possible to divide the metals into three groups, according to
the behavior of their sulphides, and this division forms one of the
foundations of inorganic qualitative analysis.
4. Most metals when heated in sulphuretted hydrogen combine with
the sulphur to form sulphides, whilst hydrogen is liberated :
Sn + SHj = Sn"S + H^
Sulphuretted Stannous
hydrogen. sulphide.
Silver becomes tarnished when exposed at ordinary temperatures to
the action of sulphuretted hydrogen in presence of air, owing to the
formation of a superficial coating of argentic sulphide {q. t?.), but the ac-
tion is very slow unless moisture be present.
Composition. — The composition of sulphuretted hydrogen is best
ascertained by heating in it some metal which combines with the sul-
[>hur liberating the hydrogen. Tin is usually employed for this purpose
see above). (Potassium or sodium cannot be used, as in these cases
the metal displaces only one-half of the hydrogen, combining with a
semi-molecule of hydrosulphyl to form a sulphydrate.) The operation
is performed in a bent tube over mercury as described in the analysis of
hydrochloric acid (p. 159). After the action is complete and the tube
has been allowed to cool, it will be found that the hydrogen occupies
exactly the same volume as the sulphuretted hydrogen employed. Sul-
phuretted hydrogen thus contains its own volume of hydrogen. There-
fore:
Weight of 1 litre of sulphuretted hydrogen, 17 criths.
Deduct weight of 1 litre of hydrogen, . . 1 crith.
There remain 16 criths.
which is the weight of half a litre of normal sulphur vapor. Calcu-
lating to whole volumes, 2 volumes of hydrogen combine >vith 1 volume
of sulphur vapor to form 2 volumes of sulphuretted hydrogen. By
weight, the proportion of hydrogen to sulphur is as 1 : 16 or as 2 : 32,
and the formula of the compound is therefore SH^.
254 INOBOANIC OHEMISTBr.
HTDBOSULPHTL, Hydrie Penulphide.
'8'^, or Hs^
H— S— S-H.
Probable molecular weight = 66. Sp, gr. 1.769.
Prepctration, — When a solution of calcic disulphide is poored into an
excess of cold concentrated hydrochloric acid, hydrosulphjl separates
out as a heavy yellowish oil :
'S'A" + 2HC1 = 'S'JH, + OaCI^
Calcic Hydrochloric HydroetUphjl. Calcic
disolphide. acid. chloride.
The calcic disulphide is prepared by boiling milk of lime with an
excess of sulphur and filtering. The solution must be poured into the
acid, and not the reverse, as hydrosulphyl is much more stable in con-
tact with acids than in contact with alkalies. The calcic disulphide
prepared as above, is always mixed with higher polysulphides, but
these also yield hydrosulphyl, mixed however with sulphur.
Properties. — Hydrosulphyl is a heavy yellowish liquid possessine a
fetid odor. It closely resembles hydroxy! in its properties, bleachmg
organic coloring matters and reducing argentic oxide. It is very un-
stable, and is gradually decomposed into sulphuretted hydrogen and
free 8uli>hur. Owing to this fact and to the property which hydro-
sulphyl possesses of dissolving sulphur, it has been found almost im-
possible tO' obtain it in a state of purity, and its composition is more a
matter of conjecture, based upon its analogy with hydroxyl, than a
strict analytical result.
HTPOBUZaPHUROVa HYDROSTTIiPHATB.
(He
SHfi^ or ^8'^
Probable moleeuiar weight ^ 98.
Pirparaiion. — When a cold satnrated solution of strychnine in alcohol is mixed with
an alcoholic solution of jellow amnionic sulphide, a compound is formed crvstallixing
in orange needles of the formula B„H^N,0,tH^. Bjr the action of concentrated su£
phuric acid upon this compound, and subsequent dilution with water, hyposulphnrous
hydrosulphate is- liberated as a yellow oily oody. It closely resembles m its proper-
ties hydroeolphyl, and, like that substance, undergoes spontaneous deooroposition into
sulphuretted hydrogen and sulphur.
COMPOUNDS OF SULPHUR WITH THE HALOGENS.
Disulphur dichloride, ^ '8^jC\^.
Hyposulphurous chloride, SCI,.
Sulphurous chloride, SCI4.
Disulphur dibromide, ^B'^Br^
Disulphur diniodide, '^'t^f
Sulphucic iodide, SI^.
DI8ULPHUR DICHLOBIDE — SULPHUROTTB CHLORIDE. 255
DIBULPHDB DIGHLOKIDE.
'S',C1,.
Molecular weight =135. Molecular volume CD. 1 litre of dmUphur
dichloride vapor toughs 67.5 critha. Spedfio gravity of liquid 168.
£ai& erf 139° C. (282.2^ F.).
Preparation. — A current of thoroughly dried chlorine is passed over
the surface of heated sulphur contained in a retort The disulphur
dichloride distils over as fast as it is formed and collects in the cooled
receiver. The process must be interrupted before all the sulphur is
converted into the chloride, and the product must be purified by rectifi-
cation.
S, + CI, = 'S'jCl,.
DiBulphar dichloride.
Properties. — Disulphur dichloride is an amber-colored, fuming
liquid, possessing a disftgreeable pungent odor. Its vapor irritates the
eyes. It dissolves sulphur freely, a property which is utilized in the
manufacture of vulcanized india-rubber.
Reaction, — In contact with water it is gradually decomposed with
fonuatiou of hydrocliloric acid and sulphurous anhydride, whilst sul-
phur is deposited :
2'S',C1, + 20H, = 4HC1 + SO, + 38.
I>i8a]phur Water. Hydrochloric Sulphurous
dichloride. acid. anhydride.
HTP06VLPHUR0V8 CHIaORIDE.
SCl^
This compound is prepared bj saturating disulphur dichloride with chlorine at 0°. On
removing the excess of chlorine by a stream of dry carbonic anhydride, the hyposul-
phurous chloride remains behind as a dark-red liouid. It is very unstable, sponta-
neoasly decomposing at ordinary temt>erature8 into ai^ulphur dichloride and chlorine.
On attempting to distil it, this decomposition takes place rapidly. With water it is
decomposed bke disulphur dichloride.
STTLPHUROVS CHLORIDB.
SCI4.
Solphorous chloride is obtained as a yellowish-brown, very mobile liquid by satu-
rating disulphur dichloride with chlorine at a temperature of from — 2Cr to — 22^ C.
(--4^ to — 8^ F.). It is even less stable than the foregoing compound, and can exist
only at temperatures below — 20® C. ( — 4° F.). When removed from the freeiing
mixture it rapidly evolves chlorine, and is converted into hypoeulphurous chloride.
Water decomposes it with violence, forming sulphurous anhyaride and hydrochloric
acid :
SCI4 -h 20ri, = SO, -h 4HC1.
Sulphurous Water. Sulphurous Hydrochloric
chloride. anhydride. acid.
256 INOBOANIG CHEMI8TBT.
DISULPHUR DIBROMIDB.
This compound is formed bj the direct anion of its elements. It forms a hea?T
red liquid wnich distils with partial decomposition between 210° and 220° C.
DI8T7LPHX7R DINXODIDB.
fW T
Disulphur diniodide is obtained as a dark-graj crystalline man bj heating sulphur
and iodine together under water.
SULPHXTRIC lODIDB.
This substance is obtained in crystals when a solution of iodine and sulphar in
carbonic disulphide is allowed to evaporate. It is interesting as a compound of
hexadic sulphur in which all the six bonds are satisfied bj monads.
COMPOUND OF SULPHUR WITH CARBON.
OABBONIO DISULPHIDE, Bisulphide of Carbon.
Molecular weight = 76. Molecular volume I I I. 1 litre of carbonic
disulphide vapor weighs 38 criths. 8p.gr. of liquid 1.293. Fuses at
—100° C. (—130° F.). Boils at 46.6° C. (115.9° F.).
History, — Carbonic disulphide was disoovered by Lampadius in 1796.
Preparation. — 1. This compound is formed by the direct combina-
tiou of its elements at a high temperature. A tubulated earthenware
retort, filled with pieces of charcoal and furnished with a vertical porce-
lain tube luted to the tubulure and passing to the bottom of the retort,
is heated to redness. Fragments of sulphur are introduced one at a
time through the porcelain tube, the latter being closed at the top after
each addition. The sulphur volatilizes and its vapor combines with
the carbon forming carbonic disulphide, which distils over and is con-
densed as a liquid and collected under water:
c + s, = os^
Carbonic disulphide.
Sulphuretted hydrogen is formed at the same time owing to the combi-
nation of the sulphur with the hydrogen which is invariably present in
charcoal. The crude product is redistilled in order to free it from dis-
solved sulphur. Thus prepared it possesses a peculiar, fetid odor, due
to the presence of other volatile sulphur compounds. These may be
CARBONIC DISULPHIDE. 257
removed by shaking the liquid with mercury or corrosive sublimate,
subjecting it afterwards to a further distillation.
2. It is also formed when charcoal is heated with iron- or copper-
pyrites. This was the method employed by Lampadius. The reaction
IS due to the sulphur which is given off by the pyrites on heating, and
is essentially the same as the foregoing :
C + 2FeSj = OS", + 2FeS".
Iron-pyrites Carbonic Ferrous
(Ferric disulphide). disulphide. sulphide.
It is to the occurrence of iron-pyrites in coal that the presence of car-
bonic disulphide vapor in coal-gas is due. This impurity, on account
of the difficulties attending its removal, has long been the source of
annoyance both to the gas manufacturer and the consumer.
Properties, — Carbonic disulphide is a colorless, powerfully refracting,
mobile liquid. When pure, it possesses a sweetish, ethereal odor. It
solidifies at — 116° C. ( — 177° F.) and fuses at — 110° C. { — 166°
F.). It dissolves sulphur, phosphorus, iodine, caoutchouc, oils, and fats.
Sulphur and phosphorus may be obtained in crystals by the spontaneous
evaporation of their solutions in carbonic disulphide. It is extensively
employed in manufacturing processes as a solvent.
Carbonic disulphide is exceedingly inflammable. Its vapor inflames
in the air at 149° C. (300° F.), and may be ignited by bringing a test
tube of paraffin heated to this temperature in contact with it. It burns
with a blue flame, yielding carbonic anhydride and sulphurous anhy-
dride :
OS", + 30a = OOj + 2SO3.
Carbonic Carbonic Sulphurous
disulphide. anhydride. anhydride.
A mixture of the vapor with air or oxygen explodes with great violence
on the approach of a flame. Mixed with nitric oxide and inflamed, the
vapor burns, emitting a brilliant blue light, very rich in rays of high
refrangibility.
Carbonic disulphide is highly poisonous. Its vapor, inhaled in large
3uantities, proves sjieedily fatal, and even in minute quantity is very
angerous when habitually inhaled (as, for instance, in factories in
which it is employed), owing to a specific action on the nervous system.
BeaxstUyns. — 1. Heated potassium burns in the vapor of carbonic
disulphide with formation of potassic sulphide and liberation of carbon :
OS", + 2K, = 2SK, + C.
Carbonic Potassic
disulphide. sulphide.
2. When brought into contact with a solution of an alkaline hydrate,
carbonic disulphide is decomposed, a carbonate and a sulphocarbonate
being formed :
60KH + 30S", = 20S"Ksj + OOKo, + SOH,.
Potassic Carbonic Potassic Potassic Water,
hydrate. disulphide. sulphocarbonate. carbonate.
17
258 INOBGANIG CHEMIBTBY.
3. In contact with solutions of alkaline sulphides, carbonic disul-
phide also forms alkaline sulphocarbonates :
8K3 + CS'', = OS'^Ks^
Potamic Carbonic Potaasic
sulphide. disalphide. sulphocarbooate.
4. When the vapor of carbonic disulphide is passed over heated
calcic hydrate it is decomposed, carbonic anhydride and sulphuretted
hydrogen being evolved :
CS, + 2CaHo, = 20aO + CO, + 2SH^
This reaction has been successfully employed in removing carbonic
disulphide from illuminating gas.
Carbonic disulphide is, as has already been pointed out, the sulphur
compound corresponding to carbonic anhydride. A carbonic mono-
sulphide, corresponding to carbonic oxide, has not been prepared.
SULPHOCARBONIC ACID.
Preparation, — ^This compound is obtained as a reddish-brown oily liquid by the
action of hydrochloric acia on amnionic sulphocarbonate :
CS^^NH^S), + 2HC1 = CS^'Hs, + 2NH4a.
Ammonic Hydrochloric Sulpho- Ammonic
salpboc&rbonate. acid. carbonic acid. chloride.
COMPOUND OF SULPHUR WITH CARBON AND
OXYGEN.
CARBONIC OXTSULPHIDE.
COS''.
Mdeeular weight = 60. Molecular volume I I I- 1 UJkre of carbonic
oxysulphide weighs 30 criths. Gaseous.
History. — This gas, which in composition lies intermediate between
carbonic anhydride and carbonic disulphide, was discovered by C. von
Than.
Occurrence. — It appears to exist in solution in the waters of certain
mineral springs.
Preparation. — 1. Carbonic oxysulphide is formed when a mixture
of carbonic oxide and sulphur vapor is passed through a heated tube :
CO + S — COS".
Carbonic Carbonic
oxide. oxysulphide.
CX)MPOUND8 OP SULPHUB WITH OXYGEN AND HYDROXYL, 259
2. It is moet readily obtained bj the action of moderately strong sul-
phuric acid upon potassic sulphocjanide :
CNKs + 2SO^o, + OH, = COS''
Potassic Solphuric Water. Carbonic
ffalpbocyanide. acid. oxysalphide.
+ SOjHoKo + SO,Ho(N^H40).
Hydric potassic Hydric ammonic
sulphate. sulphate.
By regulating the temperature a steady evolution of the gas is obtained.
Properties, — Carbonic oxysulphide is a colorless gas with a peculiar
odor. It is readily inflammable, and forms with oxygen a mixture
which explodes on the approach of a flame. It is soluble in its own
volume of water, to which it imparts its characteristic odor.
Reactions, — 1. A platinum wire heated to whiteness by means of
the voltaic current decomposes the gas into sulphur and carbonic oxide,
the latter occupying the same volume as the carbonic oxysulphide
employed.
2. With caustic alkalies it yields a mixture of carbonate and sulphide:
COS" + 4KHo = OOKoj + SK, + 20H,.
Carbonic Potassic Potassic Potassic Water,
oxysulphide. hydrate. carbonate. sulphide.
COMPOUNDS OF SULPHUR WITH OXYGEN AND
HYDROXYL.
In these compoands the sulphur is either a dyad, a tetrad, or a
hexad.
Sulphurous anhydride, SO,. 0=S=0.
O
II
Sulphurous acid, . . SOH04. H— O-rS— O— H.
O
II
Sulphuric anhydride, . SO,. 0=S=0.
O
o
o o
Pyrosnlphurio acid fSO^o || ||
{Dihydric disul- < O . H— O— S— O— 8— O— H.
phate), (.SjOHo
O O
260
INOBGANIC CHEUISTBT.
fSO,— O)
Uo,-oj
Persulphuric anhydride^
Thi«ulphuric acid \sO,HoH8.
Dithionous acid {Hydro- ( SOHo
stUphurous aeid), . . \ SOHo'
Dithionic acid,
fSOjHo
•\SO,Ho-
Trithionic acid {Svipho-f^'^'*
dithionic actd), . . . j oq Wq
rso,Ho
Tetrathionic acid {Din \ S"
gidpho-dithUmie octef), ) S"
[SO^Ho
^4_o-_^=o.
o=
o o
o
Pentathionic acid (Trt-
sulpho-ditkionie acid),
rso^o
S"
S"
S"
H— O— S— S— H.
11
o
H— O— S-S— O— H.
II II
o o
o o
II II
H— O— S— S— O— H.
II II
o o
o o
II II
H— O— S-^S— S— O— H.
II II
o o
o o
II II
H— G-S-S-S— S— O— H.
II II
o o
o o
II II
H— O— S-S-S— S— S— O— H.
II II
o o
SULPHUROUS AlfHTDBIDE.
SO,
Molecular weight = 64. Molecular volume I I I- 1 litre toeighs 32
eritha. SoUd at — 76° C. (—104.8° F.). Liquid under a pretgure
of two atmospheres at 7° C. (44.6° F.).
Occurrence. — This compound, which is gaseous at ordinary tempera-
tures, occurs in nature as a volcanic product, either in the gases issu-
SrLPHUROUS ANHYDRIDE.
261
ing from volcanoes^ or dissolved in volcanic springs. If is also found
in small qaantities in the air of towns^ being derived in this case from
the combustion of the pyrites contained in coal. It is evolved in the
operation of roasting sulphureous ores.
Preparation. — 1. When sulphur is burnt in air or oxyf^en, direct
combination takes place according to the following equation :
8 + O, = SO,.
Solphnrous anhydride.
This is the process employed when sulphurous anhydride is required
on a lai^ scale^ as in the manufacture of sulphuric acid. In this case
the combustion of pyrites is frequently substituted for that of sulphur.
2. It may also be prepared by heating a mixture of about three parts
by weight of sulphur with four of manganic peroxide :
S, + MnOj = SO, + MnS".
Mangranic Snlphnroas Manganous
, peroxide. anhydride. sulphide.
3. The foregoing processes consist in oxidizing sulphur. But it is
also possible to start from a higher oxide of sulphur and^ by depriving
it of a portion of its oxygen, to descend to sulphurous anhydride.
Thus, if concentrated sulphuric acid be heated with copper or mercury,
an oxide of the metal is formed, which combines with the excess of acid
to form a sulphate, and the sulphuric acid is reduced to sulphurous
acid. This latter, being a very unstable compound, is decomposed into
sulphurous anhydride and water. Thus :
2SO2H02 + Cu
Salphuric acid.
2SO2H0, + Hg
Sulphuric acid.
= SO, + SO,Cuo" + 20H,,
Sulphurous Cupric Water,
anhydride. sulphate.
= so, + SOjHgo" + 20H,.
Sulphurous Mercuric Water,
anhydride. sulphate.
It is necessary for the purpose to employ metals which do not evolve
hydrogen with sulphuric acid, otherwise the sulphurous anhydride
would be conti^ninated with this gas. The method with copper is that
generally resorted to for laboratory purposes. The copper in the form
of turnings or clippings is introduced into a capacious flask fitted with
safety and delivery tubes. The acid is poured on the copper, and heat
is applied to start the reaction. The heat must then be moderated,
otherwise the mixture is apt to froth over.
4. Charcoal may be substituted for copper in the foregoing reaction,
but in this case the sulphurous anhydride will he mixed with half its
volume of carbonic anhydride.
2SO,Ho, + C = 2S0, + 00, + 20H,.
Sulphuric add. Sulphurous Carbonic Water,
anhydride. anhydride.
262 INOROAKIC CHEMI8TBY.
For the purposes for which salphurous anhydride is usaally required
in the laboratory — e.g,y in the preparation of the alkaline sulphites or
of an aqueous solution of the gas — ^the presence of carbonic anhydride
is not objectionable. Sulphurous anhydride in excess expels carbonic
anhydride from the alkaline carbonates^ and the latter gas is nearly in-
soluble in water saturated with sulphurous anhydride.
6. If sulphur be heated with concentrated sulphuric acid, the two
processes of oxidation of the sulphur and reduction of the sulphuric
acid occur simultaneously^ and sulphurous anhydride is obtained from
both sources :
280aHo, + S = 3SO, + 20H,.
Sulphuric acid. Sulphurous Water,
anhydride.
Properties. — Sulphurous anhydride is a colorless gas possessing the
suffocating odor of burning sulphur. Its specific gravity is 2.211
(air = 1). It reddens a solution of litmus and afterwards bleaches it.
Sulphurous anhydride may be liquefied at ordinary pressures by the
aid of cold. The apparatus employed for this purpose consists or a
glass worm surrounded by a mixture of ice and salt. The lower open-
ing of the worm passes through the neck of a small strong flask^ which
is also surrounded by a freezing-mixture. The neck of the flask, which
has been previously contracted at one point, must be sealed with the
blowpipe when a sufficient quantity of the liquid has been collected.
Another method of obtaining liquid sulphurous anhydride consists
in sealing into a thick glass tube a mixture of one part of sulphur with
five parts of sulphuric anhydride. The following reaction occurs :
s + 2SO3 = 3SO2.
Sulphuric Sulphurous
anhydride. anhydride.
The change takes place spontaneously. The contents of the tube as-
sume a blue color which in the course of a few days disappears, the
two solid substances having been transformed into a colorless liquid.
Liquid sulphurous anhydride may be employed to produce intense
cold by its evaporation. When evaporated rapidly in vacuo, the tem-
perature of the sulphurous anhydride sinks to — 76° C. ( — 104.8°
F.), at which point the liquid solidifies to a white mass.
Reactions, — 1. Water readily absorbs sulphurous anhydride, forming
a solution of sulphurous acid. On cooling to 0° C. cubical crystals of
the formula SOHo^yHOHj are deposited :
SO2 + OH2 = SOHo,.
Sulphurous Water. Sulphurous
anhydride. acid.
Water at 0° C. dissolves 80 times its volume of sulphurous anhydride,
and 39 times its volume at 20° C. (68° F.). The solubility decreases
rapidly as the temperature rises, and by boiling the liquid, the whole
of the gas is expelled.
SUI^HUBOUS ANHYDRIDE. 263
2. Sulpharous anhydride when passed into solutions of the metallic
hydrates produces sulphites. If the sulphurous anhydride be in excess,
an acid sulphite is obtained :
OKH + SO, = SOHoKo.
Potassic Sulphurous Hydric potassic
hydrate. anhydride. sulphite.
If the metallic hydrate be in excess the normal sulphite is formed^
thus:
20KH + SO, = SOKo, + OH,.
Potassic Sulphurous Normal potassic Water,
hydrate. anhydride. sulphite.
Sulphurous acid^ when acted upon by metallic hydrates, produces
the same salts :
OKH + SOHo, = SOHoKo + OH,;
20KH + SOHo, = SOKo, + 20H,.
The sulphites, with the exception of those of the alkalies, are difficult
of solution in water.
3. Sulphurous anhydride, when passed over metallic peroxides,
unites directly with them to form sulphates.
PbO, + SO, = SO,Pbo".
Plumbic Sulphurous Plumbic
peroxide. anhydride. sulphate.
The plumbic peroxide glows spontaneously when introduced into the
gas.
4. In presence of substances which readily unite with hydrogen, sul-
phurous anhydride decomposes water, forming sulphuric acid and liber-
ating hydrogen. It thus acts as a powerful reducing agent :
SO, + 20H, = SO,Ho, + H,.
Sulphurous Water. Sulphuric acid,
anhydride.
It IS upon this property that its bleaching powers depend. Vegetable
colors exposed to the action of a solution of sulphurous acid are trans-
formed into colorless compounds. The coloring matters are not de-
stroyed, as is the case in bleaching with chlorine, and may be restored
to their original condition by exposure to the air. It is therefore neces?
sary to wash the bleached fabric thoroughly with pure water in order
to prevent the color from returning. It is probable that in many cases
the sulphurous acid enters directly into combination with the coloring
matter to form a colorless compound, as the color may frequently be
restored by treatment with weak alkaline or acid solutions. Sul-
phurous acid is employed in bleaching wool and silk, on which chlo-
rine would act injuriously. The yellow color which new flannel
assumes when first washed with soap is an instance of the action of
264 INORGANIC CHEMI8TBT.
alkalies in restoring a color which has been discharged by solpharous
acid.
5. Sulphurous anhydride^ in presence of water^ converts iodine into
hydriodic acid :
I, + SOj + 20H, = 2HI + SOjHoj.
Sulpharous Water. Hvdriodlc Sulphuric
anhydride. acid. acid.
On the other hand, sulphuric acid and hydriodic acid mutually decom-
pose each other according to the equation :
2HI + SOjHo, = I, + SO, + 20H,.
Hydriodic Sulphuric Sulphurous Water,
add. acid. anhydride.
This reaction is the reverse of that first mentioned. The relative affin-
ities of the substances here entering into chemical action vary with the
concentration, and the predominance of the one or the other of these two
reactions depends upon the proportion of sulphurous anhydride present
in solution. Bunsen has shown that when the solution does not contain
more than 0.05 per cent, of sulphurous anhydride, the influence of the
second of the above reactions disappears, and the reduction of iodine to
hydriodic acid is complete. Beyond this degree of concentration the
second reaction comes into play, and the reduction is only partial.
Bunsen has founded upon these observations a method for the quanti-
tative determination of iodine, and indirectly of a vast number of oxi-
dizable or reducible substances (Bunsen, Ann. Chem, Pharm., 86, 265,
or Watts, DidUmary of Chem., First Ed., 1, 266).
6. At a temperature of 1200° C. (2192° F.) sulphurous anhydride
18 decomposed into sulphur and oxygen, part of the oxygen combining
with the undecomposed sulphurous anhydride to form sulphuric anhy-
dride. Tyndall has shown that sulphurous anhydride undergoes a
similar decomposition when a l)eam of sunlight is passed through a long
tube filled with this gas. A white mist, consisting of finely divided
sulphur and sulphuric anhydride, appears in the tul^ :
380^ = 2SO3 + S.
Salphurous Sulphnric
anhydride. anhydride.
Detection. — Sulphites are recognized by the suffocating odor of sul-
phurous anhydride which they evolve on the addition of a strong acid,
such as sulphuric acid :
SOKoj + SO2H02 = SOjKoj + SO2 + OH,.
Potassic Sulphuric Potassic Sulphurous Water,
sulphite. acid. sulphate. anhydride.
When solutions of sulphites are mixed with a solution of argentic
nitrate, a white precipitate of argentic sulphide is formed :
SULPHURIC ANHYDRIDE. 265
SOKo,
+
2NO,Ago =
= SOAgo, +
2NOjKo.
Potaasic
Argentic
Argentic
Potassic
Bulphite.
nitrate. '
Bulphite.
nitrate.
When this argentic sulphite is boiled with water^ it beoomes black,
owing to the separation of metallic silver :
SOAgo, + OH, = SO,Ho, + Ag,.
Argentic Water. Sulphuric
sulpiiite. acid.
When a strip of paper moistened with potassic iodate and starch is
exposed to the action of sulphurous anhydride, it assumes a magnificent
blue color, owing to the reduction of the iodic acid to iodine, and the
formation of iodide of starch. This is a very delicate test for traces of
sulphurous anhydride.
Oompomtion, — The composition of sulphurous anhydride may be
readily determined by synthesis. A piece of sulphur is introduced into
a flask of oxygen inverted over mercury, and the height of the mercury
in the neck of the flask is carefully noted. The sulphur is then inflamed
by means of a platinum wire rendered incandescent by the electric
current. The sulphur burns in the oxygen, forming sulphurous anhy-
dride. When the combustion is complete, the apparatus is allowed to
cool, and the height of the mercury is again noted. It will be found
that the volume of gas is the same as before. Sulphurous anhydride
therefore contains its own volume of oxygen. Supposing 2 litres of
oxygen to have been taken, and 2 litres of sulphurous anhydride to
have been formed :
Weight of 2 litres of sulphurous anhydride, 64 criths.
Deduct weight of 2 litres of oxygen, ... 32 criths.
There remain 32 criths.
which is the weight of 1 litre of normal sulphur vapor. Therefore 1
volume of sulphur vapor has combined with 2 volumes of oxygen to
form 2 volumes of sulphurous anhydride. By weight : sulphurous
anhydride contains 32 parts of sulphur combined with 32 (or 2 X 16)
parts of oxygen, and its formula is therefore SO,.
SULPHTTRIC ANHTDBIDE.
SO,.
Jfoleeular weight = 80. Molecular volume i I I. 1 litre of sulphurio
anhydride vapor weighs 40 criths. Fuses aU 6° C. (60.8° F.). Boils
erf 46° C. (114.8° F.).
Preparation. — 1. When a mixture of two volumes of sulphurous an-
hydride with one of oxygen is passed over heated spongy platinum,
sulphuric anhydride is formed :
266 INOBOANIC CHEMI6TRT.
SO, + O = SO,.
Sulpharoiu Sulphuric
anhydride. * anhydride.
The sulphuric anhydride condenseB in a cooled receiver in the form of
fine white needles. The platinum appears to undergo no change in the
process, and may be used for any length of time.
The above reaction has been elaborated into an ingenious manufac-
turing proce&s. The mixture of gases is obtained from concentrated
sulphuric acid, which is allowed to fall drop by drop on to fragments
of red-hot brick, when the following decomposition takes place :
SO,Ho, = SO, + O + OH^
Sulphuric Sulphurous Water,
acid. anhydride.
The mixed gases are freed from water by passing through concentrated
sulphuric acid, and are then led over heated spongy platinum as already
described.
2. When Nordhausen sulphuric acid (q.v.) is gently heated in a re-
tort, sulphuric anhydride distils over, whilst ordinary sulphuric acid is
left:
rsOjHo
^o =
(SOjHo
SO^Ho,
+ 80,.
Nordhausen
sulphuric acid.
Sulphuric
acid.
Sulphuric
anhydride.
3. A similar reaction takes place when the so-called anhydrous sodic
bisulphate (disodic disulphate, sodic pyrosulphate), a salt of Nordhausen
sulphuric acid, is heated. This sodic pyrosulphate is prepared by heat-
ing hydric sodic sulphate to low redness, two molecules of the latter salt
parting with one of water :
SO,Nao
2SO,HoNao = ^O + OH,
fS(
= is;
SOjNao
Hydric sodic Sodic Water.
sulphate. pyrosulphate.
When the pyrosulphate is heated to bright redness it is decomposed as
follows :
SOjNao
O = SOjNao, + SO..
^SOjNao
Sodic Sodic Sulphuric
pyrosulphate. sulphate. anhydride.
{i
4. Sulphuric anhydride may also be prepared by directly abstracting
the elements of water from sulphuric acid by heating it with phosphoric
anhydride :
SULPHURIC ACID. 267
SOjHoj + PjO^ = SOs + 2PO2H0.
Sulphuric Phosphoric Sulphuric Metaphosphoric
acid. anhydride, anhydride. acid.
Properties, — Sulphuric anhydride is capable of existing in two dis-
tinct modifications. When the melted anhydride is rapidly cooled, it
b^ina to solidify at 16° C, forming long transparent colorless prisms,
which fuse again at the same temperature. This modification is some-
times distinguished as the a anhydride. If, however, the liquefied
substance be kept for some time at a temperature of 25° C. (77° F.),
the whole gradually solidifies to a tangled mass of fine white needles.
These needles liquefy gradually at a temperature above 50° C. (122° F.),
without possessing a constant fusin^-point, and when once liquefied may
be converted into the a andydride by cooling to 16° C. (60 8° F.).
This second variety is distinguished as the fi anhydride.
Liquid sulphuric anhydride possesses between the temperatures of
25° and 45° C. (77-1 13°F.) a mean coefficient of expansion of 0.0027,
almost three-fourths of the co-efficient of expansion of eases. At
46° C. (114.8° F.), it boils, and is converted into a colorless vapor.
Sulphuric anhydride possesses a considerable vapor-tension at ordinary
temperatures and gives off dense white fumes in contact with air, owing
to the combination of its vapor with the moisture of the air to form
sulphuric acid, a liquid of lower vapor-tension than water.
The same combination takes place when the solid anhydride is thrown
into water, the reaction being accompanied with a hissing as of a red-
hot iron.
8ULFHUBI0 ACID.
SO,Ho,.
Molecular weight = 98. 8p. gr. 1.85. JBoib at 330° C. (626° F.),
undergoing dissoddtion into sulphuric anhydride and water.
History. — Sulphuric acid was known to the alchemists, who prepared
it by distilling ferrous sulphate.
Occurrence. — In. combination with bases sulphuric acid is found in
numerous minerals (p. 243 ; see also Sulphates). In the free state it
occurs in volcanic waters, being formed by the oxidation of sulphurous
acid.
Preparation. — 1. Sulphuric acid is formed by the direct union of
sulphurous anhydride with hydroxyl, the sulphur passing from the
tetradic into the hexadic condition :
SO, + Ho,- = SOjHo,.
Sulphurous Hydroxyl. Sulphuric
anhydride. acid.
2. Dry sulphurous anhydride cannot take up oxygen without the
aid of heated spongy platinum or some other substance which can act
268 INORGANIC CHEMISTRY.
as a carrier of oxygen, but in its aqueous solution as sulphurous acid
it readily absorbs oxygen from the air, and is converted into sulphuric
acid:
SOHo, + O = SOjHo,.
SulphurooB acid. Sulphuric acid.
3. It is formed by the addition of water to sulphuric anhydride:
SO, + OHj = SOjHo,.
Sulphuric Water. Sulphuric
aniiydride. acid.
4. By the action of nitric peroxide and oxygen on sulphurous anhy-
dride a peculiar white crystalline compound, known as crystals of the
leaden chamber, is formed, which, accoitling to Briining and De la Prov-
ostaye, possesses the empirical formula SjNjO^ :
2SO, + IX^O, + -^
Sulphurous Nitric White crystalline
anhydride. peroxide. compound.*
fSC
o = ^o
(sc
If a small quantity of water is present the compound has the follow-
ing composition (Weltzien) :
2S0, +
Sulphurous
annydride.
It will be perceived that the first of these substances is an anhydride
of the second. Both are compound anhydrides of sulphuric and nitrous
acids, and are decomposed by a small quantity of water into sulphuric
acid and nitrous anhydride :'
'N'%0, +
0
+ OH, =
= 2SO^N"'0,)Ho.
Nitric
Water.
Weltzien's crystalline
peroxide.
compound.
{
SO,(N"'0,)
O + 20H, = 2SO,Ho, + NA-
SO,(N"'0,)
White crystalline Water. Sulphuric Nitrous
compound. acid. anhydride.
In the manufacture of sulphuric acid on the large scale, the reaction
takes place in presence of an excess of water, by which the nitrous
anhydride is transformed into nitric acid and nitric oxide.
O O
* 0=N--0— i- O-S— 0— N=0.
SULPHURIC ACID. 269
SNA + on, = 2NO,Ho + 4'N''0.
Nitrous Water. Nitric acid. Nitric oxide,
anhydride.
The nitric oxide combines with oxygen, reproducing nitric peroxide,
which is then ready to take part in the same procew^es a second time.
The nitric acid is reduced to nitric peroxide by the action of sulphurous
anhydride :
BO, +
2NO,Ho =
= sOjHoj + rs'\o,.
Sulpharoas
Nitric acid.
Sulphuric Nitric
anhydride.
acid. peroxide.
The whole of the nitric peroxide has thus, after taking part in this
series of reactions, returned to its original condition. Theoretically,
therefore, a small quantity of this substance ought to be able to convert
an indefinitely great quantity of sulphurous anhydride, oxygen, and
water into sulphuric acid. In practice, however, there is considerable
loss of nitric peroxide which must be constantly replaced.
On the above reactions the commercial process for the manufacture
of sulphuric acid is founded. The following is a brief outline of the
operations : ,
The sulphurous anhydride is procured by the combustion either of
sulphur or of iron pyrites in a furnace A (Fig. 42), constructed for
this purpose. The gas passes on, mixed with nitrogen and oxygen,
into a large leaden chamber, of which there are two or more connected
consecutively by means of wide passages. The sheet-lead, of which
the walls of these chambers are constructed, is soldered by melting its
edges together with the hydrogen blow-pipe. A junction in which any
other metal had been employed would not resist corrosion by the sul-
phuric acid, as a voltaic action would be thus set up with the lead.
The gases from the pyrites burners, before entering the chambers,
traverse an arrangement, E, known as a "Glover's tower." This
consists of a tall leaden tower lined with fire-brick and filled with
broken flints, or, less frequently, furnished with shelves. At the top
of this tower are two reservoirs; one filled with dilute acid from the
chambers, the other containing a strong acid saturated with nitric per-
oxide and derived from the " Gray-Lussac tower " (see p. 270) in a later
stage of the process. As the two acids from the reservoirs mix in trick-
ling down over the flints, the nitric peroxide, which is insoluble in
dilute acid, is liberated, and is carried by the gases from the pyrites
burners into the leaden chamber. At the same time this dilute acid,
meeting the hot gases, is deprived of a considerable portion of its water^
which is carried into the leaden chamber in the form of steam to fur-
nish the water necessary to the formation of sulphuric acid ; and a con-
centration is thus economically effected.
The oxides of nitrogen required to supply the place of those unavoid-
ably lost during the process, are prepared from a mixture of sodic
nitrate and sulphuric acid contained in nitre-pots which are placed at
the entrance to the chambers and heated by the pyrites burners. As
the mixture of sulphurous anhydride, oxides of nitrogen, and oxygen
270
INORGANIC CHEMISTRY.
passes through the first chamber, the reactions already described (see
Preparation 4) take place. Jets of steam from the boiler B are con-
stantly blown into the chamber, thus furnishing the water necessary for
the formation of the acid. In order to save the fuel required for the
Fio. 42.
jft. ^ ^^ i. A Jt I O
jiil-i^«f. r-'tilfri-^i *,*-J*-.
production of steam, Sprengel recommends that, instead of steam, water,
in the form of fine spray, should be blown in. The sulphuric acid
collects on the bottom of the chamber, and the liberated oxides of nitro-
gen pass on into the second chamber. Here the gases meet with a
fresh supply of steam, and the sulphurous anhydride which has escaped
the reaction in the first chamber is converted into sulphuric acid.
Nothing ought to escape from the last chamber but nitric peroxide, an
excess of oxygen, and the nitrogen of the air. The nitric peroxide is
recovered by passing the spent gases through the (Jay-Lussac tower C,
which is similar in construction to the Glover tower, except that it is
filled with fragments of coke. Concentrated sulphuric acid is intro-
duced at the top of this tower and, meeting the nitric peroxide, which is
passing in the contrary direction, absorbs it. This acid, saturated with
nitric peroxide, is drawn off at the bottom of the tower, and utilized in
SULPHURIC ACID. 271
the Glover's tower as already described. The circulation of the gases
throagh the chambers is kept up by means of the draught of a tall chim-
ney connected with the Gay-Lussac tower.
The acid is not allowed to attain a specific gravity greater than 1.55
or 1.6 in the chambers, as beyond this point it absorbs oxides of nitrogen.
The further concentration is effected partly in the Glover's tower and
partly by evaporation in large retorts of glass or platinum.
In practice about 95. per cent, of sulphur is converted into sulphuric
acid, and about 2 parts of sodic nitrate are required for every 100 parts
of sulphur.
The acid thus prepared contains lead derived from the chambers
and arsenic from the pyrites. Nitrous anhydride is also present. This
last impurity may be removed by the addition of some ammonic sul-
phate :
+ 2N,.
SO^NH^O), + NA =
SO2H0, + 30H,
Ammonic Nitrous
Sulphuric Water.
sulphate. anhydride.
acid.
The arsenic may be got rid of by adding hydrochloric acid and boiling,
when it passes off as arsenious chloride, along with the excess of hydro-
chloric acid. The sulphuric acid must finally be purified by re-dis-
tillatioD.
Properties. — Sulphuric acid, concentrated as far as possible by boiling,
still retains 1.5 per cent, of water. When this acid is cooled to 0° C,
the pure acid of the formula SOjHoj, crystallizes out in colorless prisms
fusing at 10.5° C. (50.9° F.). When the pure acid is heated it first
gives off sulphuric anhydride, until it contains 1.05 per cent, of water,
when it distils unchanged. Ordinary commercial sulphuric acid does
not contain more than 94 per cent, of SOjHoj.
Sulphuric acid boils at 330° C. (626° F.), undergoing dissociation
into sulphuric anhydride and water, which, however, immediately re-
unite when the vapor is condensed. Owing to this dissociation, the
vapor-density is only half as great as it would be if no decomposition
had taken place :
SOjHoj == SO, + OHy
2 vols. 2 vols.
(Cf. also p. 64.)
When diluted with water and cooled to 0° it deposits lai^e prismatic
crystals of the formula SO^HogjOHj, fusing at 7.5° C. This may be
r^:arded as a tetrabasic acid of the formula SOH04. This is substan-
tially the acid which runs from the Glover's tower, and is known in
commerce under the name of " brown acid," having a specific gravity
of 1.720. Salts of this tetrabasic acid are known.
A third hydrate, S02Ho2,20H2, corresponding to a hexabasic acid,
SHO0, was obtained by Graham by evaporating dilute sulphuric acid at
100° C. in vacuo till it ceased to lose weight. Salts of this hexabasic
acid are also known. The formation of this hydrate also corresponds
to the maximum contraction which takes place when sulphuric acid
and water are mixed (see below).
272
INORGANIC CHEMISTBY.
Pure dibasic sulphuric acid is a heavy oily colorless liquid. It has
a very strong aiBnity for water. When the two liquids are mixed
great heat is evolved, the temperature frequently rising above 100^ C.
The mixing must be performed gradually, care being taken to pour the
acid into the water; if this order be reversed, the hot acid will be
thrown about by the explosive ebullition of the water. The mixture
is accoi^panied by diminution of volume : the maximum contraction,
amounting to 8 per cent., occurs when 1 molecule of acid is mixed with
2 of water.
The following table contains the specific gravities of aqueous sul-
phuric acid of various strengths at a temperature of 16° C. :
Specific OravUy Table of Sulphuric Acid <rf 15° C. (J. Kolb).
Degrees
(Bailing).
Specific
gravity at
Percentage
of
SOjHo,.
Degrees
(Baum6).
Specific
gravity at
IS*':
Percentage
of
SO,Hob.
0
1.000
0.9
34
1.308
40.2
1
1.007
1.9
35
1.320
41.6
2
1.014
2.8
36
1.332
43.0
3
1.022
3.8
37
1.345
44.4
4
1.029
4.8
38
1.357
45.5
6
1.037
6.8
39
1.370
46.9
6
1.045
6.8
40
1.383
48.3
7
1.052
7.8
41
1.397
49.8
8
1.060
8.8
42
1.410
51.2
9
1.067
9.8
43
1.424
52.8
10
1.075
108
44
1.438
64.0
11
1.083
11.9
45
1.453
65.4
12
1.091
13.0
46
1.468
66.9
13
l.IOO
14.1
47
1.483
68.3
14
1.108
15.2
48
1.494
59.6
15
1.116
16.2
49
1.614
61.0
16
1.125
17.3
50
1.530
62.5
17
1.134
18.5
51
1.540
64.0
18
1.142
19.6
52
1.563
65.5
19
1.152
20.8
53
1.680
67 0
20
1.162
22 2
54
1.697
68.6
21
1.171
23.3
55
1.615
70.0
22
1.180
24.5
66
1.634
71.6
23
1.190
25.8
57
1.652
73.2
24
1.200
27.1
68
1.671
74.7
25
1.210
28.4
59
1.691
76.4
26
1.220
29.6
60
1.711
78.1
27
1.231
31.0
61
1.732
79.9
28
1.241
32.2
62
1.753
81.7
29
1.252
33.4
63
1.774
84.1
30
1.263
34.7
64
1.796
86 5
81
1.274
36.0
65
1.819
89.7
32
1.285
37.4
66
1.842
100.0
33
1.297
38.8
Owing to the affinity of sulphuric acid for water, it frequently re-
moves the elements of water from organic compounds. In this way
oxalic acid ( < noji ) '^ decomposed into carbonic anhydride, car-
bonic oxide, and water (p. 209. Sugar, wood, and other substances
SUIiPHUfilO AOID.
273
belonging to the class of the earhohydrates, so called because the oxygen
and hydrogen which they contain in combination with carbon are
present in the proportions necessary to form water, are charred by the
action of strong sulphuric acid. Its powerfully corrosive action on the
animal tissues is due to the same cause.
Sulphates. — Sulphuric acid forms several classes of salts, of which
the following compounds may be taken as typical examples :
Hydricpotaasic sulphate, . SO,HoKo.
O
II
H— O— S— O— K
II
O
Potaasic sulphate,
. SOjKo,.
Zindc sulphate, .... SO^no".
K— O— S— O— K
II
O
o
/O. II
ZnC >8
\)/
O
Tetrabasic zinoic sulphate. \ OQ/no"
.a II XX
Hexahasic zincic sulphate. \ ay„.„
(TVmnotc mlphate.) . . / ^^^ »'
Zn
V
i/V^i.
*tS^ffi°A^}«».«^'-
18
H
A^H
H
274 IKOBOANIC CHEHISTBT.
H
i
O
k .
o
Gypsum dried at 200° C. \ ^^ ^ ,, r\./^ i
iOcMc^phate.). . ,}^Ofiao . ^q/^
O
The sulphates of barium and lead are insoluble in water ; those of
calcium^ strontium, and silver sparingly soluble ; all other normal sul-
phates are readily soluble.
FTBOSULPHUBIO AGID. Dihydrio DiMphaJte. Nordhausen
Sulphuric Add.
{
BO^o
O
SO,Ho
JfVepanrfton. — 1. This compound is formed hj the action of sul-
phuric ozychlorhjdrate on sulphuric acid :
SO,Ho
SO,aHo + BOjHo, = -(o + Ha.
uHo
Solpharic Sulphuric Pyroeulphuric Hjrdro-
ozychlorhydrate. acid. acid. chloric acid.
2. Sulphuric anhydride is dissolved bj concentrated sulphuric acid,
with formation of pjrosnlphuric acid :
BO^o, + BO,
= ^O .
Sulphuric acid. Sulphuric Pjroeulphuric
anhydride. acid.
The result of the reaction is a strongly fuming liquid, which, when
cooled to 0° C, deposits the pyrosulphuric acid in the form of large
colorless crystals, fusing at 36° C. (96° F.). On heating, pyrosul-
phuric acid is decomposed into sulphuric acid and sulphuric anhydride,
3L It is prepared on a large scale by distilling dried ferrous sulphate
PYROSTTLPHURIO ACID. 275
in earthenware retorts. The ferrous sulphate is decomposed into ferric
oxide^ sulphurous and sulphuric anhydrides :
2SO,Feo'' =
= 'eA
+ so, + so..
Ferrous
Ferric
Sulphurous Sulphuric
sulphate.
oxide.
anhydride, anhydride.
Crystallized ferrous sulphate has the formula SOHo3Feo",60H2.
It parts with its water of crystallization at 100° C. ; but in order to
convert the resulting compound SOHojFeo" into SOjFeo" and water,
a much higher temperature is necessary, and in practice it is found im-
possible completely to dehydrate large quantities of the salt. Water is
therefore given off in the distillation of the ferrous sulphate, and com-
bines with the sulphuric anhydride to form the fuming acid. The
presence of sulphurous anhydride is objectionable, as this gas, in esca))-
ing, carries away with it considerable quantities of the volatile sulphuric
anhydride. The water and the sulphurous anhydride are, however,
chiefly given off in the earlier part of the process. This process takes
place in two stages. In the first of these the dihydric ferrous sulphate
is converted, with evolution of sulphurous anhydride and water, into
diferric sulphate — a compound derived from the hexabasic acid :
2SOHo,Feo'' = S('Fe'"Ar + SO, + 20H,.
Dihjdric ferrous Diferric sulphate. Sulphurous Water,
sulphate. anhydride.
In the second stage the diferric sulphate breaks up into sulphuric anhy-
dride, which distils over, and ferric oxide, which remains in the retort :
B('re'",0,r = SO, + Te'^'A-
Diferric sulphate. Sulphuric Ferric oxide,
anhydride.
The first portion of the distillate, consisting of a weak acid, is therefore
rejected, and the product is only collected when the white fumes of the
anhydride begin to make their appearance. The resulting brownish
liquid is the NordhaiLsen sulphuric acid of commerce. The production
of sulphurous anhydride may be greatly reduced, and the yield of sul-
phuric anhydride correspondingly increased, by a preliminary oxidation
of the ferrous sulphate to ferric sulphate. This is accomplished by
drying the ferrous salt at a relatively high temperature with free access
of air.
Character. — Pyrosulphuric acid may be regarded as derived from
two molecules of sulphuric acid by the abstraction of one molecule of
water :
fSO^Ho
2SO,Ho, — OH, = ^O
UO2H0
Sulphuric Water. Pyrosulphuric
acid. acid.
It is thus a semi-anhydride, possessing the properties both of an
anhydride and of an acid. If it were possible for the molecule of
276 INOBGANIO CHEMISTRY.
pjroeulphuric acid to part with a seoond molecule of water^ we
should obtain an anhydride, ^SC >S/ , the true anhydride of
pyrosulphuric acid, polymeric with ordinary sulphuric anhydride, SO,.
It is possible that the modification of sulphuric anhydride melting
above 60° corresponds with this anhydride of higher molecular weight.
The formation of sodic pyrosulphate has already been described
(p. 266).
FBRSULPHURIC ANHTDRIDB.
Preparation, — This componnd, disoovered by Berthelot, was prepared bv subjecting
a mixture of eaual volumes of sulphurous anhydride and ozvgen to the action of the
silent electric discharge of a Siemens tube (p. iG6). At the end of ten honrs the sub-
stance was thus obtained in the form of drops of a sjmpj liquid, which at 0° solidified
to needles resembling those of sulphuric anhydride.
Properties, — Penulphuric anhydride dissolves in water, but the solution is almost
instantly decomposed into sulphuric acid and free oxygen.
SA + 20H, = 2SO,Ho, + O.
The solution in concentrated sulphuric acid is more stable, but slowly evolves oxygen.
The addition of spongy platinum to the solution causes the oxygen to be given off at
once.
Persulphuric anhydride is an oxidizing agent It converts ferrous into ferric salts^
and oxidizes sulphurous to sulphuric anhydride.
With baryta water it vields oaric persulphate, which is soluble in water, bat the so-
lution speedily deposits insoluble baric sulphate with evolution of oxygen.
THIOSULPHURIO AOID (formerly termed Hyp<mJ.phurous Add).
SOjHoHs (hypothetical).
This acid is not known in the free state, as, when liberated from its
BsAt^, it almost instantly undergoes decomposition (see below).
PreparaJHon of ThumdphcUes {formerly HyposulphUea). — 1. Sodic
thiosulphate is formed when a solution of sulphite is boiled with flowers
of sulpnur :
BONao, + S = SOjNaoNas.
Sodic sulphite. Sodic thiosulphate.
This formula for sodic thiosulphate is true of the salt only afler ex-
posure to a temperature of 215° C. (419° F.). The composition of the
salt when dried at a lower temperature is SOHojNaoNas. This peculi-
arity of containing a molecule of water of constitution which can be
expelled only at a high temperature, and, in many cases, not without
decomposition of the salt, is shared by most of the other thiosulphates ;
but plumbic thiosulphate contains no hydrogen, and, after drying at
100° C, has the formula S0,( gPb)"
2. Sodic thiosulphate may also be obtained by passing sulphurous
THIOSULPHURIC ACID. 277
anhydride into a solution of sodic sulphide. The reaction in this case
is of a complex character. First^ the sulphurous acid decomposes the
alkaline sulphide, yielding sodic sulphite and liberating sulphur, which
acts upon the sodic sulphite according to (1), forming sodic trisulphate.
The equations are :
3SOHoij + 2SNa3 = 2BONaOi + 3S + SOH^
Sulphurous Sodic Sodic Water,
acid. sulphide. sulphite.
SONao, + S = SOjNaoNas.
Sodic sulphite. Sodic thiosulphate.
3. When sulphur is warmed with a solution of caustic soda^ a mix-
ture of sulphide and thiosulphate is formed : ^
6NaHo + 48 = SO,NaoNas + 2SNa3 + 30Hj^
Sodic hydrate. Sodic thiosulphate. Sodic sulphide. Water.
The sodic sulphide generated in this reaction may be converted into
thiosulphate by passing sulphurous anhydride into the solution {Prepor
ration 2.).
4. When a persulphide of an alkali or of an alkaline earth is ex-
posed to the air in a moist state, oxygen is absorbed and a thiosulphate
is produced :
'S'A + 30, = So/^CaV'.
Calcic persulphide. Calcic thiosulphate.
The calcic sulphide from the soda waste (see soda manufacture) is fre-
quently employed for this purpose. • Sometimes instead of oxidizing the
soda waste by the action of the air, it is treated with sulphurous anhy-
dride. In either case the calcic thiosulphate is extracted with water,
converted into the sodium salt by means of sodic carbonate or sulphate,
and purified by crystallization.
5. Sodic thiosulphate is formed by the action of iodine on a solution
of sodic sulphide and sodic sulphite :
SNa, + SONao, + I, = SOjNaoNas + 2NaI.
Sodic Sodic ' Sodic Sodic
sulphide. sulphite. thiosulphate. iodide.
ReaetUms. — 1. The thiosulphates, when acted upon by acids, evolve
sulphurous anhydride, whilst sulphur is precipitated :
SOjNaoNas + 2HC1 = 2NaQl + OH, + 8 + 80^
^ Sodic Hydrochloric Sodic Water. Sulphurous
thiosulphate. acid. chloride. anhydride.
2. Sodic thiosulphate dissolves argentic chloride, forming a double
salt of the formula SOHojNaoAgs :
278 INORGANIC CHEMieTBY.
SOjNaoNaa + A^l + OH,
= Naa + BOHo^XaoAgs.
Sodic * Argentic Water.
Sodic Sodic aii^ntic
thiosulphate. chloride.
chloride. thioenlphate.
It 18 this property which has led to the employment of sodic thiosal-
phate in photography as a means of fixing photographs. The photo-
graphic paper, sensitized by impregnation with argentic chloride, is
blackened in those parts which are exposed to the action of light. In
order to render permanent the picture thus produced, it is necessary
to remove the unaltered argentic chloride, and this is acoomplisbed by
steeping the picture in a bath of sodic thiosulphate.
DITHIONOUB ACID, Hydro8ulphur<nu Add.
p J SOHo,
ISOHo •
Preparation, — When zinc is introduced into an aqueous solution of sulphurous
anhyaride in a vessel from which air is excluded, the metal unites directlj with the
anhydride to form zincic dithionite:
280, + Zn = {eo^no. .
SnlphUTOUs Zincic
anhydride. dithionite.
or if we assume the presence of sulphurous add in the liquid :
2S0H0, + Zn = {IqZuo'' + OH,.
Sulphurous Zincio Water,
acid. dithionite.
Reaction, — The yellow liquid obtained by the above process possesses powerful
reducing properties. When exposed to the air, it absorbs oxygen rapidly with great
evolution of heat, the dithionous acid being converted into sulphurous acid :
{loHo + O + OH, = 280Hor
DithionouB acid. Water. SulphurouB acid.
It also precipitates silver and mercury in the metallic state from the solutions of
their salts.
Schiitzenberger has proposed to use it for the estimation of dissolved oxygen in
water.
DITHXONIC ACID, Hypowlphwrie Add,
fSOjHo
ISOjHo*
Preparation. — 1. Powdered manganic oxide is suspended in water and a current of
sulphurous anhydride is passed through the liquid, when the manganic oxide grad-
ually dissolves. The solution contains manganous dithionate :
MnO, + 2S0, = |®^»Mno''.
Manffanlo Sulphurous Manganous
oxide. anhydride. dithionate.
This solution is next treated with baric sulphide, which precipitates manganous sul-
phide, whilst baric dithionate is formed and remains in solution :
* The formula SOHHo was formerly erroneously assigned to this acid.
TBITHIONIO ACID. 279
Manganous Baric Manganona Barlo
dithionate. sulphide. sulphide. dithiooate.
By adding snlphiiric acid to a solution of the baric dithionate> baric sulphate is pre-
cipitated, and dithionic acid remains in solution :
Bario Sulphuric Barlo Dithionic
dithionate. acid. sulphate. acid.
The solation of dithionic acid may be evaporated tn vacuo over snlphnric acid till it
attains a specific gravity of 1.347, but beyond this point it decomposes into sulphuric
acid and sulphurous anhydride. The dilute acid undergoes the same change on lx>iling.
2. Dithionic acid is also formed when a dilute solution of iodine in potassic iodide
is added to a dilute solution of hjdric sodic sulphite :
SSOHoNao + It
Hydrlc sodic
sulphite.
About 20 per cent, of the sulphite is thus transformed. The remainder is converted
into sulphate. .
IHihUnuUeB, — The dithionates moetlv crystallize well. Thej may be obtained either
by neutralizing a solution of the acid with a base, or by exactly precipitating a solu-
tion of baric dithionate with a soluble sulphate.
TRITHIOmC ACID, SulphodUhionic Add, SuiphureUed Hypasulphurie Acid,
fSOjHo
[ 80,Ho
iVflpctratum. — 1. By digesting flowers of sulj^hur at a temperature of between 60®
and 60° Ci with a concentrated solution of hydric potassic sulphite, potassic trithionate
and potassic thiosulphate are formed :
rsOjHo
— \80,Ho
+
2NaI.
Dithionic
Sodic
acid.
iodide.
r80,Ko
= 2U'
6SOK0H0 + 28 = 2^8'^ + SOjKoKs + 30H,.
[ SO,Ko
Hydrlc potaaaic Potassic Potassic Water,
sulphite. trithionate. thioaulphate.
2. Potassic trithionate may also be obtained by saturating a very concentrated solu-
tion of potassic thioeulphate with sulphurous anhydride:
rso^ifo
280,KoK8 + 880, « 2 -^ 8^' + S.
i80,Eo
Potaaric Sulphurous Potaaslc
thioaulphate. anhydride. trithionate.
3. The same salt is formed when a solution of potassic ai^entic thiosulphate is
boiled:
rso,Ko
280,KoAg8 = ^8^' + SAgj,.
(80,Eo
Potaaslc aiventlc Potassic Argentic
thioaulphate. trithionate. aulphide.
4. By adding iodine to a solution of sodic sulphite and thioaulphate, sodic trithionate
and sodic iodide are formed :
280 INOBGANIC CHEMISTRT.
rSOsNao
SONao, + SOjNaoNas + I, == 4 8'^ -f 2NaI.
(sO^ao
Sodie Sodic Sodic Sodlc
lulphite. thlosulphate. tiithionate. iodide.
aqueous 8olatioii of trithionic acid may be obtained bj deoompoaing the pota»-
salt with hjdrofluosilicic acid :
r80,Eo fSO.Ho
JS'^ + S1F4,2HF = i&'' + SIF4,2KF.
(80,Eo (80,Ho
Potassic Hydrofluo- Trithionic Potaaaic
trithionate. silicic acid. add. stlicofluorlde.
An
nnm
The liquid is filtered from the insoluble potaasic silicofluoride. The free acid is
very unstable, and spontaneously decomposes into sulphuric acid, sulphurous anhydride,
and free sulphur :
f 80,Ho
J 8'^ = SO-Ho, + SO, + 8.
l80,Ho
Trithionic Solphnilo Sulphnroos
acid. acid. anhydride.
8odium amalfi^am converts a trithionate into a mixture of sulphite apd thiosulphate,
thus reversing the process of its formation from these salts:
f
80,Nao
S'^ 4- Na, = SONao, -f SO.NaoNas.
(80,Nao
Sodic • Sodic Sodic
trithionate. sulphite. thiosulphate.
TBTRATSIOmC ACID, Dimdphodithianic Aeid, BiaulphureUed HyponUphuric Acid,
SO,Ho
80,Ho
PreparaUon, — When iodine is added to a solution of a thiosulphate, an iodide and
a tetrathionate of the base are formed :
80,Nao
f/, 4- 2NaL
^ SO,Nao
Sodic Sodic Sodic
thiosulphate. tetrathionate. iodide.
280,NaoNas + I, ==r
This action of iodine, in coupling together two atoms of sulphur in two molecules
of substances containing the group Hs (or its equivalent, Es, Nas, etc.) is character-
istic of this element, and meets with many applications in organic chemistry.
If baric thiosulphate be employed, baric tetrathionate will be formed, and by de-
composing this salt with dilute sulphuric -acid an aqueous solution of tetrathionic acid
may be obtained. The dilute solution may be boiled without decomposition; but,
when concentrated, the acid breaks up into sulphurous acid, sulphuric acid, and free
sulphur.
Sodium amalgam reconverts the tetrathionates into thiosulphate :
rSOjNao
I 8''
1 8'' + Na, = 2SO,NaoNas.
[ SO,Nao
Sodic tetrathionate. Sodlc thiosulphate.
SULPHUROUS OXTDICHLOBIDE.
281
PENTATHIONIC ACID, Tristdphodithionie Acid, TritulphureUed
Hypotulphuric Acid,
r SOjHo
8''
. SO,Ho
PreparaHon,-—!. This acid may be obtained by passing sulpharetted hydrogen into
a solution of sulphurous anhydride:
f SOjHo
8^'
8'^ -h 40H, + 68.
8'^
, SO,Ho
Water.
6SH, + 5S0, =
Sulphuretted
hydrogen.
Sulphurous
anhydride.
Pentatfalonlc
acid.
2. It 18 also formed by the action of disulphur dichloride on baric thioeulphate :
.0
2S0^Ba + ^S^gCl, =
Baric Disulphur
thiosnlphate. dichloride.
SO,-,
8^' I
&'' Bao^' + BaCl,
8'^ I
80,-'
Baric Baric
pentathionate. chloride.
+ a
The aqueous solution of the acid may be concentrated till it attains a specific gravity
of 1.6, but beyond this point it decomposes, evoWing sulphurous anhydride. The
pentathlonates are unstable, and have been but imperfectly examined.
COMPOUNDS OF SULPHUR WITH OXYGEN AND CHLORINE
{OXYCHLORIDES, ACID CHLORIDES).
These compounds may be regarded as derived from the corresponding oxy-acids of
sulphur by the substitution of chlorine for hydroxyl (see acid chlorides of the nitro-
gen acids, p. 229).
Acid chloride. Corresponding acid.
Sulphurous oxychloride {Thionylic
lipnurous
chloride), ......... SOCl,
Sulphuric ozydichloride {Sulphun^ic
ckiorids) so,a.
Sulphuric oxychlorhydrate {Sulphur-
yUc ehlarhydraU), 8O.GIH0
r80,Gl
Pyroaolphurylic chloride^ . . . AO
(so,a
Sulphurous acid, .
' Sulphuric acid, . .
Pyrosulphuric acid,
. SOHo,
. SOjHo,
f80,Ho
.^O
SULPHUROUS OZYDICHIiORIDE, ThUmylic Chloride
*S0C1,.
MoUeutar wdghi = 119. MoUeular tdume fTT. 1 litre of ndphurous oxydiddoride
vapor weight 69.5 erOkt, Specific gravity (
[.675. BoiU at 78<» C. ( 172.4** F.).
Prqxiration, — 1. When dry sulphurous anhydride is passed over phosphoric chlo-
" " ide
ride, sulphurous ozydichloride and phosphoric oxytrichloride are formed
SO, + PCI5 == SOOl, -h POCl,.
Sulphurous Phosphoric Sulphurous Phosphoric
anhydride. chloride, oxydlchloride. oxytrichloride.
282 INORGANIC CHEMISTRY.
2. It maj also be obtained by heating togeth^
trichloride in sealed tubes to 150^ C. (302^ F.)
2. It maj also be obtained by heating Jo^ther calcic sulphite and phosphoric ozj-
3S0Cao'^ + 2P0C1, = 38001^ + {^Cao'V
Calcic Phosphoric Buljphuroiu Calcic
sulphite. oxytrichloride. oxydichloride. phosphate.
I\vpertie$, — Sulphurous oxydichloride is a ooloriess liquid, possessing a pungent
odor.
JZeoe^um. — Water gradually decomposes sulphoroos oxydichloride into sulphurous
and hydrochloric acids :
SOa, + 20H,
« SOHo,
+ 2Ha.
SulphurouB Water.
Sulphurooa
Hydrochlorio
oxychlorlde.
add.
add.
8tn«PHl7RIC OZYDICHXiORIDB, Sulphurylie Chloride.
80,01,.
Molecular weight = 135. Mbleeular volume | j |. 1 litre of sulphuric ozydiehloride vapor
weighs 67.6 criihe, Speeifie gravity of ^t^i7l766. Boils at TO"" C. (Ids'" F.).
Preparation, — 1. Sulphuric oxydichloride is formed by the direct union of sulphur-
ous anhydride and chlorine, either in sunlight or when the two gases are passed into
glacial acetic acid or through camphor which immediately liquefies, and the saturated
solution, after standing for some time, subjected to distillation:
80, + CI, = 80,a,.
Sulphuric
oxydichloride.
Sulphurous Sulphuric
anhydride. oxydlcl '
2. It may also be prepared by heating sulphuric oxychlorhydrate (see below) in
sealed tubes for 12 hours to a temperature of from 170° to 180° G. (338°-356° F.).
280,ClHo
= 80,C1, 4-
80,Ho,.
Sulphuric
Sulphuric
oxydichloride.
Sulphuric
oxychlorhydrate.
Mdd.
Properties. — Sulphuric oxydichloride is a ooloriess fuming liquid with a sufibcating
odor.
Reactions, — 1. A small quantity of water decomposes it into sulphuric oxychlorhy-
drate and hydrochloric acid :
80,C1, + OH. = 80,ClHo + HCl.
Sulphuric Water. Sulphuric Hydrochloric
oxydichloride. oxychlorhydrate. acid.
2. An excess of water converts it into sulphuric and hydrochloric acids:
80,01, + 20Hi = 80,Ho, -f 2HCL
Sulphuric Water. Sulphuric Hydrochlorio
oxydichloride. acid. acid.
8nLPUUKIC OXY CULORU Y URATE, Sulphurylie ChlorhydraU,
80tClHo.
Molecular weight = 116.6. Molecular volume j I |. 1 litre of suljphuric oxychlorhydraie
vapor weighs 58.25 criihs. Specific gravity ofUquid 1.776 at 18° (J. (64.4° F.). Bods at
158° C. (316.4° F.).
Preparation, — 1. Sulphuric anhydride and hydrochloric acid unite directly to form
sulphuric oxychlorhydrate :
SELENIUM. 283
80, 4- Ha = so,aHo.
Sulpharic Hydrochloric Sulphuric
anhydride. acid. oxychlorhydrate.
2. It may be obtained by distilling a mixture of solpharic acid and phosphoric
chloride .
SSOiHot + PCI5 « 8SO,CiHo -f KHHo -f 2HC1.
Sulphuric Phosphoric Sulphuric Metaphosphoilo Hydrochloric
acid. chloride. oxychlorhydrate. add. acid.
^ ProperHa. — Salphuric oxychlorhydrate is a colorless, stronely fuming liquid. When
distilled it nndergoes partial dissociation into sulpharic anhydride and hydrochloric
add.
ReaetUm, — Water decomposes it with violence, forming sulphuric and hydrochloric
acids :
SOiClHo + OH, = SCHo, + HCl.
Sulphuric Water. Sulphuric Hydrochloric
oxychlorhydrate. acid. . acid.
PTROSXTLPUUKYliIC CHIiOR3a>B.
r 80,01
l80,a
MoUeular weight = 216. Molecular volume FTl- 1 litre of pyrosulphurylie chloride vapor
veighe 107.5 eriths. SpeeUic gravity 0/ Koutd 1.819 ai 1S° C. (64.4'' F.). BoiU at
146° C. (294.8<> F.). ^^ ^
Preparation, — 1. This oompoond is formed when salphuric anhydride is heated with
phosphoric chloride:
280, + PCI5 = Jo + poa,.
( 80,01
Sulphuric Phoephorio Pyrosulphurylie Phosphoric
anhydride. chloride. chloride. oxytrichloride.
2. It is also produced by the action of disulphor dichloride on solphoric anhydride :
r80,a
^8^01, + 680, = iO -f 680r '
f80,a
i80,a
Dlsulphur Sulphuric Pyrosulphurylie Sulphurous
dichloride. anhydride. chloride. anhydride.
JVopertteg.— Pyrosulphurylie chloride is a heavy, colorless, fuming liquid.
arvli
Redetion, — In contact with water it is slowly decomposed into sulphuric and hydro-
chloric acids :
■^O + 30H, = 280,Ho, + 2HC1.
Pyrosulphurylie Water. Sulphuric Hodrochloric
chloride. acid. acid.
SELENIUM, Se^
Atomic weight == 79. Molecular weight = 158. Molecular volume
I I L 1 litre of selenium vapor weighs 79 oriths. 8p, gr., aTnorphouSj
4.28 ; crystaUized, 4.8. Fuses at 217° C. (422.6° F.). BoiU about
700° C. (1292° F.). AtomicUy ", ^ and ^. Evidence of atomicity :
Seleniuretted hydrogen, .... Be'^Hj.
Selenious chloride, Se^^CI^.
Selenicacid, Se^OjHoj.
History. — Selenium (from trtXijvTi, the moon) was discovered in 1817
by Berzelius in a deposit from a sulphuric acid chamber. The name
284 INORGANIC CHEMISTRY.
was given on account of the analogy of this element with tellurium
{tellufty the earth).
Occurrence, — Selenium is generally found in very small quantities
along with sulphur, both native and combined. Less frequently it
occurs alone in comt)ination with metals in a few rare minerals, as the
selenides of lead, copper, silver, and mercury.
When iron- or copper-pyrites containing selenium is employed in the
manufacture of sulphuric acid, the selenium forms a red deposit in the
chambers.
Preparation. — ^The red deposit from the sulphuric acid chambers is
digested with a warm solution of potassic cyanide until the red color
disappears. Soluble potassic selenocyanide is formed :
KCy -f Se = BeKCy.
Potassic Potafisic
cyanide. aelenocyanide.
On adding an excess of hydrochloric acid to the filtered solution, sele-
nium is precipitated as a red amorphous powder, the liberated seleno-
cyanic acid being instantly decomposed in presence of strong acids into
hydrocyanic acid, which remains in solution, and selenium.
Properties. — Selenium, like sulphur, exists in various modifications.
When precipitated from solutions by means of acids, it forms an amor-
phous brick-red powder, which, when heated along with the liquid,
turns black and cakes together below 100° C. When melted and rapidly
cooled, selenium solidifies to a black, shining, amorphous mass, with a
conchoidal fracture. This variety is soluble in carbonic disulphide,
and possesses a specific gravity of 4.28. The solution deposits mono-
clinic crystals, isomorphous with tliose of monoclinic sulphur. The
fusing point of soluble selenium cannot be determined, as this substance
softens gradually on heating.
When amorphous selenium is heated for some time to a temperature
of 97'' C. (206.6° F.), it is converted into the crystalline modification.
This change is attended with evolution of great heat, the temperature
of the mass rising above 200° C. Crystalline selenium is of a dark
gray color, with a metallic lustre and granular fracture. Its specific
gravity is 4.5. The same variety is obtained when melted selenium is
allowed to cool very slowly. It is insoluble in carbonic disulphide.
This modification conducts the electric current. Its electrical resistance
is greatly diminished by exposing the substance to light, but is again
restored on shading it from the light — a property which is turned to
account in the construction of the photophone.
When a solution of an alkaline selenide is exposed to the air, minute
black crystals of selenium separate out, possessing a specific gravity of
4.8. They are insoluble in carbonic disulphide.
The vapor-density of selenium, like that of sulphur, decreases as the
temperature rises. Above 1400° C. (2552° F.) it possesses the normal
vapor-density corresponding with the molecular weight Se^ = 158.
The following determinations of the vapor-density (air = 1) illustrate
this decrease :
SELENIUBETTED HYDROGEN. 285
Temperatare. Vapor-denaity.
860° C. (1580° F.) 7.67
1040°" (1804° ") 6.37
1420°" (2588° ") 5.68
Selenium dissolves in faming sulphuric acid, with a green color.
Reaction. — When heated in the air selenium burns, forming selenious
anhydride, SeO,, at the same time giving off an odor of decayed horse-
radish.
Nitric acid oxidizes selenium to selenious acid, SeOHoj, whereas sul-
phur under the same conditions yields sulphuric acid.
COMPOUNDS OF SELENIUM WITH HYDROGEN AND
CHLORINE.
SELENIUBETTED H7DB0OEN, Hydroselenie Add.
SeH^
MdecuUvr weight = 81. Molecular volume QH. 1 litre weighs 40.5
crUJiB.
Preparation. — This compound is formed by the action of dilute hy-
drochloric acid upon ferrous selenide :
PeSe" + 2HC1 = SeH, + PeCl,.
FerroQs Hydrochloric Seleniaretted Ferrous
selenide. acid. hydrogen. chloride.
Properties. — Seleniuretted hydrogen is a colorless gas, possessing an
odor resembling that of sulphuretted hydrogen, but much more power-
ful. Inhalation of a single bubble of seleniuretted hydrogen through
the nose destroys for some time the sense of smell. Like sulphuretted
hydrogen it produces precipitates in solutions of most of the heavy
metals. It is decomposed by heat into its elements. The degree of
this dissociation varies in a remarkable manner, being less at a higher
than at a lower temperature. Thus the dissociation begins at 150° C.
(302° F.), iacreases gradually up to 270° C. (518° F.), then decreases
gradually as the temperature rises, till at 520° C. (968° F.) it almost
entirely ceases. At still higher temperatures it again increases.
When ignited, seleniuretted hydrogen burns in air with a blue flame,
yielding selenious anhydride and water :
SeHj + 30 = BeO, + OH,.
Seleniuretted . Selenious Water,
hydrogen. anhydride.
There are two chlorides of selenium, 'Se'^Cl, and SeCl^.
286 IKOBGANIC CHEMI8TRT.
COMPOUNDS OF SELENIUM WITH OXYGEN AND
HYDROXY!.
Selenious anhydride, SeO,.
Selenioiis acid, SeOHo,.
Selenic acid, SeO^Ho,.
SELENIOUS ANHYDRIDE.
BeOy
Preparation. — Selenious anhydride is formed by the direct com-
bination of its elements, when selenium is burned in a stream of
oxygen.
It may also be obtained by heating selenious acid :
SeOHo, = SeO, + OH^
Selenious Selenious Water,
acid. anhydride.
Properties. — Selenious anhydride crystallizes in prisms, and when
heated sublimes without fusing.
Reaction. — Dissolved in water it forms selenious acid by a reaction
the reverse of the foregoing.
SELENIOUS ACID.
SeOHo,.
Preparation. — 1. As above, by dissolving selenious anhydride in
water.
2. It is formed when selenium is oxidized with nitric acid :
Se + O, + OH, = SeOHo^.
Water. Selenious acid.
Properties. — Selenious acid is a white, very soluble substance,
crystallizing in prisms. It forms normal, acid, and superacid salts :
Normal potassic selenite, • . . . SeOKo,.
Hydric potassic selenite, .... SeOHoKo.
Superacid potassic selenite, . . . SeOHoKo,SeOHo2.
Reaction. — Reducing agents, such as sulphurous acid, stannous chlo-
ride, etc., precipitate red amorphous selenium from its solutions :
SeOHoj, + 2SOHoj = Se + 2SO2H02 + OH,.
Selenious acid. Sulphurous acid. Sulphuric acid. Water.
BELENIO ACID — TELLURIUM. 287
SELENIO AOm.
SeOjHoa.
PreparaHon, — 1. The most conveoient method of obtaining thi8 acid
consists in suspending argentic selenite in water^ and adding bromine
until a perceptible reddish coloration is visible :
SeOAgOa + Brj + OH, = BeOaHoa + 2AgBr.
Argentic selenite. Water. Selenic acid. Argentic bromide.
On evaporating the filtered liquid a concentrated solution of selenic
acid remains.
2. Potassic seleniate is prepared by fusing selenium or metallic selen-
ides with nitre. The potassic salt thus formed is then converted into a
plumbic salt, and, by decomposing the latter with sulphuretted hydro-
gen, selenic acid is obtained.
Properties. — Selenic acid is not known in a state of purity. The
roost concentrated aqueous solution contains 97.4 per cent, of the acid.
Further evaporation causes it to decompose into selenious anhydride,
oxygen, and water. The solution has a specific gravity of 2.627, and
closely resembles in its properties concentrated sulphuric acid.
It is remarkable as being the only single acid which dissolves gold.
In this process it undergoes reduction to selenious acid.
Readion, — When heated with hydrochloric acid, selenic acid is re-
duced to selenious acid, chlorine being liberated :
BeOjHo, + 2HC1 = SeOHo, + OH, + CX^
Selenic Hydrochloric Selenious Water,
acid. acid. add.
Selenic anhydride has not been prepared.
TELLURIUM, Te,.
Atomic weight = 1 25. Molecular weight = 250. Molecular volume I I L
1 litre of tellurium vapor weighs 125 criths. 8p. gr. 6.2. Fuses at
490^-600° C. (914°-932° F.). AtomicUy ", ^ and ^ Evidence of
aiomieity:
Tellnretted hydrogen, Te"H^
Tellurous chloride, Te^^Cl^.
Telluric acid, Te^K^jHoj.
History, — ^Tellurium (from teJluSj the earth) was first recognized as a
distinct substance by Mulier von Ileichenstein, in 1782.
Occurrence. — It is found in very small quantities both in the native
state and as the tellurides of metals.
Preparation. — Bismuthic telluride, Bi^Te^'g, a substance occurring in
288 INORGANIC CHEMISTRY.
nature sa the mineral tetradymiiey is fus^ with a mixture of eodic car-
bonate and finely-powdered charcoal. The fused mass yields on lixivi-
ation with water, a solution of sodic telluride, which on exposure to the
air, deposits tellurium as a gnj powder. The pulverulent tellurium
may be fused into a coherent mass under sodic chloride.
Properties. — Tellurium is a silver-white crystalline substance with a
metallic lustre. At a high temperature it may be distilled. It dis-
solves in fuming sulphuric acid with a deep red color.
Reaction, — When heated in air it bums with a blue flame^ forming
tellurous anhydride, TeO,.
COMPOUNDS OF TELLURIUM WITH HYDROGEN,
CHLORINE, AND OXYGEN
TELLURXTTED HTDBOOKN.
TeH^
Molecular weight = 127. Molecular volume GD. 1 litre weighs 63.5
crUks.
Preparcrfion. — Telluretted hydrogen is obtained by the action of
dilute hydrochloric acid on ferrous or zincic telluride :
ZnTe'' -I- 2HC1 = TeH, + ZnCl^
Zincic Hydrochloric Tellaretted Zincic
tellaride. acid. hjdrogen. chloride.
Properties. — ^Telluretted hydrogen is a colorless gas of a fetid odor,
resembling that of sulphuretted hydrogen. It exhibits the same anom-
alies of dissociation as seleniuretted hydrogen. It may be ignited in
air, and bums with a blue flame, forming tellurous anhydride and
water :
TeH, -h 30 = TeO, + OH^
Telluretted Tellnrous Water,
hydrogen. anhydride.
There are two chlorides of tellurium, Te'^Cl^and TeCl^.
Tellurous Anhydride^ TeO,. — ^This compound is prepared like seleni-
ous anhydride (p 286), which it closely resembles in properties.
l^eUurous Acid. — TeOHoj. — This acid is obtained as a white floccu-
lent precipitate, when a solution of tellurium in dilute nitric acid is
poured into water. It is decomposed at a temperature of 40^ C. (104^ F.)
into anhydride and water. It dissolves more readilv in hydrochloric
acid than in water. Sulphurous acid precipitates tellurium from the
solution (see Selenious Acid, p. 286).
Tellurous acid is a dibasic acid, forming acid and normal salts.
Thus:
Hydric potassic tellurite, TeOHoKo.
Normal potassic tellurite, TeOEo|.
TELLURIC ACID. 289
Tetratellurites, produced by the combination of the normal tellurites
with tellurous anhydride, are also known :
o o o o
Dipotassic tetratel- || || || ||
lurite, K— O— Te— O— Te— 0— Te— O— Te— O— K.
Telluric Anhydride, TeOj. — Telluric anhydride is prepared by care-
fully heating telluric acid. It forms an orange-yellow mass. When
strongly heated it is decomposed into tellurous anhydride and oxygen.
It is insoluble in water, boiling concentrated hydrochloric acid dis-
solves it slowly, converting it, with evolution of chlorine, into tellurous
anhydride :
TeO, + 2HC1 = TeO, + OH, + CI,.
Telluric Hydrochloric Tellurous Water,
anhydride. acid. anhydride.
Telluric Acid, Te02Ho2. — In order to prepare this compound tellu-
rium is fused with a mixture of caustic potash and potassic chlorate.
The tellurium is oxidized at the expense of the oxygen of the potassic
chlorate to telluric anhydride, which combines with the alkaline base
to form potassic tellurate :
Te + jgg^ = TeO, + KCl.
Potamic Telluric Potassic
chlorate. anhydride. chloride.
TeO, + 2KHo = TeO,Ko, + OH,.
Telluric Potassic Potassic Water,
anhydride. hydrate. tellurate.
The fused mass is dissolved in water, and a solution of baric chloride
is added, when insoluble baric tellurate m precipitated:
TeOjKo, + BaCl, = TeO,Bao'' + 2KC1.
Potassic Baric Baric Potassic
tellurate. chloride. tellurate. chloride.
The baric tellurate is suspended in water, and decomposed with the
exact quantity of sulphuric acid. In this way insoluble baric sulphate
and free telluric acid are formed. On evaporating the filtered solution,
large colorless monoclinic crystals of hexabasic telluric acid, TeHo^, are
deposited. On heating to 160^ these crystals part with two molecules
of water, yielding dibasic telluric acid, TeO,Ho„ as a white amor-
phous mass.
Telluric acid forms a series of somewhat complex salts. Among the
potassium salts, for example, tellurates, ditellurates, and tetratellurates
are known.
19
290 IKOBGAJflO CHEMISTRY.
Tetrahydric dipotassic tellurate, . . . TeHo^KosjSOH,.
r TeHo^Ko
Octohjdric dipotassic ditellarate, . . < O
t TeHo^Ko
f TeHo,Ko
O
TeO,
O
TeO,
O
TeHo,Ko
Octohydric dipotassic tetrateHarate, .
CHAPTER XXVIII.
MONAD ELEMENTS.
Section II. {Continued from Chapter XXII.)
BROMINS, Br,
2*
Atomic weight = 80. MoUeular weight = 160. Molectdar volume
i I I- 1 lUre of bromine vapor wdghs 80 criths. 8p. gr. 3.187.
Fuses at— 24,5° C. (—12.1^ F.). Boils at 63^ C. (146.4° F.).
Atomicity ', Evidence of atomicity :
Hydrobrornic acid, HBr.
Potassic bromide, KBr.
Argentic bromide, AgBr.
History. — ^Bromine (from PpH^fio^, a stench) was discovered in 1826,
by Balard, in the mother-liquors obtained in the crystallization of
common salt from sea-water.
Occurrence. — Bromine does not occur in the free state in nature. It
is found in combination with metals as bromides, sodic bromide being
the most common. This salt occurs in small quantity in sea-water,
particularly in the water of the Dead Sea, and in greater abundance in
many salt springs and deposits of rock salt. The salt mines of Stass-
furt furnish 20,000 kilos, of bromine yearly.
. Preparation. — 1. The mother-liquors of saline wataps containing
bromides are treated with chlorine as long as the color of the liquid
continues to become darker. In this way bromine is liberated, and
may be distilled off and collected in a cooled receiver :
2NaBr + CI, = 2NaCl + Br,.
Sodic bromide. Sodic chloride.
An excess of chlorine must be avoided, as this would occasion the for-
mation of a chloride of bromine.
BBOMINE. 2^1
On a large scale the mother liquors are mixed with an excess of sal- •
phuric or hydrochloric acid, and a quantity of manganic peroxide
exactly sufficient to liberate the bromine present (see Equation, Prepay
ration 2) is added. As long as an excess of the peroxide is avoided,
there is no danger of obtaining a product contaminated with chlorine,
since any chlorine which might be liberated would at once set free its
equivalent of bromine.
2. Bromine may also be obtained from pure bromides, in a reaction
similar to that employed in the preparation of chlorine, by heating
them with sulphuric acid and manganic peroxide :
2NaBr + MnOj +' 2SO2H0, = Br, •+
Sodic Manganic Sulphuric
bromide. peroxide. acid.
SO^Nao, + SOjMno'' + 20H,
Sodic sulphate. Man^iranous Water,
sulphate.
Properties. — ^Bromine is a heavy reddish-brown liquid, transparent
only in thin layers. Its vapor possesses a cousiderable tension at ordi-
narv temperatures. If a few drops be poured into a flask, the latter
will be speedily filled with the reddish-brown vapor. At a tempera-
ture of —24.6° C. (—12.1*^ F.) bromine solidifies to a crystalline
mass with a slight metallic lustre. Bromine has a powerful and un-
pleasant odor, resembling that of chlorine. Its vapor attacks the eyes
and the organs of respiration. It is an irritant poison. When brought
in contact with the skin, it produces dangerous wounds.
Throughout a considerable range of temperature above its boiling
point, bromine has a vapor-density corresponding with the molecular
formula Br,. At higher temperatures the vapor-density diminishes,
owing to a partial dissociation of the molecules of the vapor into single
atoms. This dissociation, which occurs more readily than in the case
of chlorine, but less readily than in the case of iodine, is not complete
at 1600'' C. (2912'' F.), the highest temperature that has been em-
ployed in such determinations.
bromine is soluble in about thirty times its weight of water at ordi-
nary temperatures, the solubility decreasing as the temperature rises.
The solution is of a reddish color, and, when exposed to a temperature
of 0° C. deposits crystals of a hydrate, Br2,100H2, melting at 15° C.
(59° F.). Bromine is more soluble in ether and carbonic disulphide
than in water, and when an aqueous solution is agitated with either of
these solvents, the bromine is extracted from the water and passes into
the new solvent, which separate from the water as a dark-colored layer,
on allowing the liquid to stand.
Moist bromine oleaches vegetable colors, but less powerfully than
chlorine.
Bromine combines directly with many of the metals to form bro-
mides. Antimony and tin inflame spontaneously in the vapor, and
burn with great brilliancy. Potassium and bromine, when brought
together at ordinary temperatures, unite, frequently with explosion ;
292 INORQANIC CHEMISTRY.
but sodium must be heated to 200^ C. in contact with bromine vapor,
before any action occurs.
HTDBOBROHIO AOID.
HBr.
Molecidar weight = 81. Molecular volume I I I 1 litre of hydrobromic
acid weighs 40.5 criths. Fuses at —73° C. (—99.4° F.). BoUs
at _69° C. (—92.2° F.).
»
Preparation. — 1. When a mixture of hydrogen and bromine vapor
is passed through a red-hot tube, or when a mixture of hydrogen and
bromine vapor is burned in air, hydrobromic acid is formed by the
direct combination of its elements :
H, + Br, = 2HBr.
Hydrobromic acid.
2. It may be obtained by heating potassic bromide with phosphoric
acid:
3KBr + POHo^ = POKo, + 3HBr.
Potassic PhoBphoric Potaraic Hydrobromic
bromide. acid. phosphate. acid.
Sulphuric acid cannot be substituted for phosphoric acid in this re-
action, as a portion of the hydrobromic acid is then decomposed, with
liberation of bromine :
SOjHo,
+ 2HBr =
Br,
+ 20H,
+ SO,.
Salpharic
Hydrobromic
Water.
Sulphurous
acid.
acid.
anhydride.
3. It is formed by the action of water upon phosphorous tribromide
or phosphoric pentabromide :
P"'Br, + 3OH2 = P0H3 + 3HBr.
Phosphorous Water. Phosphorous Hydrobromic
tribromide. acid. acid.
PBr^ + 40H, = POH03 + 5HBr.
Phosphoric Water. Phosphoric Hydrobromic
pentabromide. acid. acid.
These reactions may be most conveniently applied by gradually
dropping the requisite quantity of bromine into water containing amor-
phous phosphorus. The bromides of phosphorus are decomposed at the
moment of their formation :
P + Br, + 40H, = POH05 + 5HBr.
Water. Phosphoric Hydrobromic
acid. add.
COMPOUNDS OP BROMINE WITU OXYGEN AND HYDROXYL. 293
This is the method most usually employed in the laboratory for the
preparation of hydrobromic acid.
4. It may also be obtained in aqueous solution by passing sulphur-
etted hydrogen through water containing bromine :
SH, + Br, = 2HBr + 8.
Sulphuretted Hjdrobromic
hydrogen. acid.
Prop^ic«.^Hydrobromic acid is a colorless gas, with a pungent
odor. It fumes strongly in contact with moist air. By means of
pressure and cold it may be liquefied, and when cooled to — 73° C.
( — 99.4° F.) solidifies to a colorless crystalline mass. Water absorbs
more than its own weight of the gas, yielding a powerfully acid liquid.
When a solution, saturated at a low temperature, is subjected to distil-
lation, the liquid in the retort gradually becomes weaker, until it con-
tains 48 per cent, of hydrobromic acid, when it distils unchanged
between 125° and 126° C. (257°-259° F.), and possesses a specific
gravity of 1.49 at 14° C. (57° F.). When an acid containing leas than
48 per cent, is distilled, the liquid in the retort gradually l)ecomes more
concentrated till the above percentage is attained. This aqueous solu-
tion does not correspond with any definite hydrate, and its composition
may be altered by altering the pressure under which the distillation
takes place.
Reactions. — 1. Chlorine decomposes the acid with liberation of
bromine :
2HBr + Cla = 2HC1 + Br,.
Hydrobromic acid. Hydrochloric acid.
2. By the action of atmospheric oxygen a small quantity of bromine
is liberated from hydrobromic acid in aqueous solution, but the decom-
position is soon arrested :
4HBr + O, = 20H, + 2Br^
Hydrobromic acid. Water.
3. In contact with metallic oxides and hydrates bromides are formed.
Argentic bromide, AgBr, and mercurous bromide, ^B^^Bv^, are insol-
uble in water; plumbic bromide, PbBrj, is sparingly soluble; all the
other bromides dissolve readily.
COMPOUNDS OF BROMINE WITH OXYGEN AND
HYDROXYL.
Hypobromous acid, OBrH.
{OBr
O .
OH
The graphic formulae of these compounds are analogous to those of
the corresponding chlorine compounds, given on page 177.
294 INORGANIC CHEMISTRT.
HTPOBBOMOnS AOID.
OBrH.
Preparation. — An aqueous solution of this very unstable compound
maj be obtained by agitating mercuric oxide with bromine- water :
2HgO + OH, +
2Br,
= 20BrH
Mercaric Water.
oxide.
Hypobromoua
acid.
+
(HgBr
(HgBr
Mercuric
oz7broioid&
The corresponding anhydride, OBr^ has not been prepared.
BROHIO AOm.
fOBr
\0Ho- ■
Preparation. — Bromic acid is best prepared by decomposing a solu-
tion of baric bromate with the requisite quantity of sulphuric acid :
rOBr
Bao" 4- SO,Ho, = ii^^ + SO,Bao".
OBr
Baric Sulphuric Bromic Baric
bromate. acid. acid. sulphate.
The aqueous solution may be concentrated in ixiouo till it contains 1
molecule of acid to 7 of water. Beyond this point it is decomposed
into water, bromine, and oxygen. The same decomposition takes place
when the dilute solution is boiled :
^{oHo = 2Br, + 20H, + 50^
Bromic acid. Water.
Bromic acid closely resembles chloric acid in its properties.
Preparation of Bromates. — 1. When bromine is added to a solution
of a metallic hydrate, a mixture of bromate and bromide is formed :
6KH0 + 3Br2 = 6KBr + i^^^ + SOH,.
Pota*«ic Potaasic Potassic Water,
hydrate. bromide. bromate.
The potassic bromate is much less soluble than the bromide, and may
be separated from it by crystallization.
lODINB. 295
2. Potassic bromate is also formed when bromine is added to a solu-
tion of potassic hydrate or carbonate, and chlorine is passed into the
liquid :
6KH0 + Br + 5C1 = 5KC1 + i^^^ + 30H^
Potassic Potassic Potassic Water,
hjdrate. chloride. bromate.
In this way the whole of the bromine is converted into bromate.
Character of the BromaJtea. — Some of the bromates, when heated, lose
oxygen, and are transformed into bromides :
2{oKo = 2KBr + 30,
Potassic Potassic
bromate. bromide.
Others evolve bromine and a portion of their oxygen, leaving metallic
oxides :
^OBr
O
Mgo'' = 2MgO + 2Br2 + 60,.
O
OBr
Magnesic Ma^esic
bromate. oxide.
IODINE, I,
2-
Atomic weight = 1 27. Molecular weight = 254. Molecular volume I I L
1 litre of iodine vapor weighs 1 27 criths, 8p, gr, 4.95. Ftises ai
114° C. (237° F.). 5ot& a6otJ6 200° C. (392° F.). AUmicUy'*
Evidence of atomicity :
Hydriodic acid, HI.
Potassic iodide, KI.
Argentic iodide, Agl.
History > — Iodine was discovered in 1812 by Courtois in the mother-
liquors of soda prepared from the ashes of sea-weed. The first thorough
investigation of its properties is due to Gray-Lussac.
Occurrence. — Iodine is always found in combination with metals,
generally associated with chlorine. In this form it occurs in small
quantities in some mineral springs and in sea- water, from which last it
is absorbed in larger quantity by various kinds of sea-weed. From
these the iodine of commerce is obtained. It has also been detected in
6ome marine animals, such as sponges and oysters. The iodides of silver
and lead occur as rare minerals.
* See, however, Periodates.
296
IXORQANIC CHEMISTRY,
Manufacture. — Sea-weed is burned in pite, the temperature being
kept as low as possible in order to prevent loss from volatilization of
the salts of iodine. The ash thus obtained is known as kdp. The
soluble salts, consisting of alkaline carbonates, sulphates, chlorides,
bromides, and iodides, are extracted from the ash with water. The so-
lution is evaporated, and the carbonates, sulphates, and chlorides are
removed by crystallization. To the mother-liquor, containing the
Fio. 43.
bromides and iodides, sulphuric acid is added, which causes a separa-
tion of sulphur, owing to the presence of sulphides and sulphites. The
sulphur and crystals of sulphate are removed, and the liquid is trans-
ferred to a large iron retort A (Fig. 43), lined with lead. Heat is ap-
plied and manganic peroxide is added in small portions at a time. Iodine
is thus liberate according to the equation :
2NaI
+ MnOj + 2SO,Ho, =
= SO.Nao,
Sodic
Manganic Sulphuric
Sodic
iodide.
oxide. acid.
sulphate.
+ SOjMno" + I, + 20H,.
Manganous sulphate. Water.
and, distilling over, is condensed in a series of stoneware receivers, 6 66,
fitting one into the other as in the figure.
When the iodine ceases to distil over, the receiver is changed, and more
manganic peroxide is added. This liberates the bromine, which, on
account of its superior affinity for hydrog^en and bases, is given off later
than the iodine (see equation, p. 297). The bromine is distilled off and
collected.
Sometimes the dried sea-weed is carbonized in retorts and the result-
ing charcoal lixiviated with water. In this way the loss of iodine by
volatilization is avoided ; but, on the other hand, it is found impossi-
ble to extract the whole of the iodine salts from the charcoal.
Properties. — Iodine forms bluish-black tabular rhombic crystals,
with a metallic lustre. It possesses a peculiar and irritating odor, dis-
tantly resembling that of chlorine. Wheu heated, it gives off a vapor
IODINE. 297
of a magnificent violet color (hence the name of this element, from
io€tdjj<:^ violet-colored). At higher temperatures and when free from
admixture of air, this vapor assumes a deep blue tint. The vapor pos-
sesses a characteristic absorption-spectrum.
The vapor-density of iodine at temperatures up to 700*^ C. (1292°
F.) corresponds with the molecular formula Ij. Above this tempera-
ture the vaj)or-density diminishes as the temperature rises, till at 1400°
C. (25.52° F.) it is somewhat less than two-thirds of the vapor-density
below 700° C. This diminution is due to a partial dissociation of the
molecules of iodine into free atoms. If the iodine vapor be mixed with
four-fifths of its volume of air, in order to reduce the pressure of the
iodine vapor and thus increase the dissociation, the vapor-density of
the iodine at 1400° C. is only half as great as at 700° C. ; that is to say,
the vapor-density corresponds with the molecular formula I, and the
iodine vapor at that temperature is mon-atomic. At temperatures above
1400° C. no further diminution occurs under these circumstances.
Iodine is very slightly soluble in water, but dissolves readily in pres-
ence of hydriodic acid or of soluble iodides. Alcohol dissolves it more
freely, w^hilst in ether, chloroform, and carbonic disulphide, it is very
readily soluble. The aqueous, ethereal, and alcoholic solutions are
brown ; those in chloroform and carbonic disulphide are violet.
The smallest trace of free iodine imparts to starch paste a splendid
blue color, which disappears on heating, but returns, although with
diminished intensity, on subsequent cooling. ^
Reactions. — 1. Iodine is expelled by chlorine and bromine from all
its compounds with electro-positive elements :
2KI + CI2 = 2KC1 + I2.
Potassic iodide. Potafisic chloride.
2KI + Br, = 2KBr + I,.
Potaseic iodide. Potassic bromide.
2. With a solution of calcic hydrate, iodine yields a liquid which
bleaches in alkaline solution, and therefore probably contains ccUoio
iodohypiodite :
OaHoj + I2 = Oa(OI)I + OH,.
Calcic hvdrate. Calcic Water,
iodohypiodite.
The bleaching power diminishes gradually on standing, and more rap-
idly on boiling or by exposure to light. When the bleaching property
has disappeared, the solution contains only a mixture of calcic iodate
and calcic iodide.
3. Iodine unites directly with metals and non-metals, the process
of combination being frequently accompanied with evolution of heat
and light. Phosphorus ignites when brought into contact with solid
iodine, and powdereil antimony, when thrown into iodine vapor, bursts
into flame.
298 INORGAKIC CHEMISTRT.
HTDSIODIO AOID.
HI.
Molecular weight = 128. Molecular volume EH 1 lUre ofhydriodic
add weighs 64 cr^A*. Fums at —55° C. (—67° F.).
Preparation, — 1. Hydriodic acid is formed by the direct union of its
elements when a mixture of iodine vapor and hydrogen is passed through
a red-hot tube or over spongy platinum gently heated :
H, + I2 = 2HT.
2. It is formed when an iodide is heated with phosphoric acid :
SKI + POHo, = 3HI + POK03.
Potassic Phosphoric Hjdriodic PotAssic
iodide. acid. acid. phosphate.
Sulphuric acid cannot be substituted for phosphoric acid in this reac-
tion^ as it liberates iodine from hydriodic acid :
2HI + SO,Ho, = I, + SO, + 20H,.
Hydriodic Sulphuric Sulphurous Water,
acid. acid. anhydride.
An aqueous solution of hyriodic acid may however be prepared by de-
composing a solution of baric iodide with the exact quantity of dilute
sulphuric acid, the sulphuric acid being in this case immediately with-
drawn from the reaction in the form of insoluble baric sulphate.
3. It is also formed by decomposing phosphorous triiodide by water :
PI3 + 3OH2 = PHo, + 3HI.
Phosphorous Water. Phosphorous Hydriodic
triiodide. acid. acid.
4. It may be prepared by heating together water^ potassic iodide,
iodine, and amorphous phosphorus :
4KI + P, + 51, + SOHj = 14HI + 2POHoKo^
Potassic Water. Hydriodic Hydric dipotassic
iodide. acid. phosphate.
An aqueous solution of hydriodic acid prepared by Method 5 (see
l)eIow) may be advantageously substituted for the solution of potassic
iodide in the above reaction. Tlie amorphous phosphorus is placed in
a retort with the neck sloped slightly upwards, and a solution of 2 parts
of iodine in 1 part of aqueous hydriodic acid (b. p. 127°) is allowed to
drop gradually through the tubulure from a stoppered funnel. Graseous
hydriodic acid is evolved in a steady stream. When the action begins
to slacken^ a gentle heat may be applied.
HYDRIODIC ACID. 299
5. A solution of hydriodic acid may be readily obtained by passing
sulphuretted hydrogen through water in which iodine is suspended :
2SH, + 21, = 4HI + S^
Sulphuretted Hydriodic
hydrogen. acid.
As the reaction proceeds the unattacked iodine dissolves in the aqueous
hydriodic acid and facilitates the decomposition.
Properties. — Hydriodic acid is a colorless gas, fuming in contact with
moist air, and possessing a pungent odor. At a temperature of 0*^ C.
and under a pressure of 4 atmospheres, it condenses to a colorless liquid
which solidifies at —55° C. (—67° F.).
It is readily decomposed by heat A hot glass rod plunged into a
vessel filled with the gas, causes the immediate separation of violet
vapors of iodine.
It is readily absorbed by water, forming a strongly acid liquid. A
solution saturated at 0° C. has a sp. gr. of 2. Aqueous hydriodic acid
behaves on distillation like hydrochloric and hydrobromic acids (^.t^.).
The strongest acid obtainable by distillation has a sp. gr. of 1.67, con-
tains 57.7 per cent, of hydriodic acid, and boils at 127° C. {260.6° F.).
When a weaker or a stronger acid is distilled, the composition of the
distillate gradually becomes stronger or weaker until an aoid of the
above strength and boiling-point distils over unchanged. This acid
does not correspond with any definite hydrate and, as in the case of
hydrochloric and hydrobromic acids, the composition of the distillate
may be made to vary by varying the pressure under which distillation
takes place.
The aqueous solution when pure is colorless, but in contact with the
oxygen of the air, it rapidly becomes brown from separation of iodine,
which dissolves in the aqueous acid :
4HI + O2 = 20H, + 21^.
Hydriodic acid. Water.
Oxidizing agents have a similar action. Owing to this property of
readily parting with its hydrogen, hydriodic acid is frequently em-
ployed as a reducing agent, particularly at higher temperatures and in
the case of organic substances.
Reactions. — 1. Chlorine and bromine decompose hydriodic acid,
liberating iodine :
2HI + CI, = 2HC1 + I,.
Hydriodic acid. Hydrochloric acid.
2. Mercury rapidly decomposes it, with liberation of hydrogen:
2HI + 2Hg = 'Hg'J, + H,.
Hydriodic acid. Mercaroas iodide.
3. With metallic oxides, hydrates, and some salts, it forms iodides.
300 INOROAKIC CHEMISTBY.
Even argentic chloride is transformed by hydriodic acid into argentic
iodide:
AgCl + HI = Agl + HCl.
Argentic Hydriodic Argentic Hydrochloric
chloriile. acid. iodide. acid.
Iodides, — ^The iodides closely resemble the chlorides and bromides.
Argentic iodide, Agl, mercurous iodide, 'Hg'^I,, mercuric iodide, Hgl,,
and cuprous iodide, 'QvJ^^y are insoluble in water; plumbic ioilide,
Pbr,, dissolves very slightly ; the other iodides are r^ily soluble.
COMPOUNDS OF IODINE WITH CHLORINE.
Hypiodous chloride, ICl.
lodous chloride, ICI3.
These compounds are formed by the direct union of their elements.
HTPIODOnS CHLORIDE.
ICl.
Molecular weight = 162.5. Fuses at 24.7° C. (76.5° F.). Boils at
101° C. (213.8° F.).
Preparation. — ^This compound is obtained by passing dry chlorine
over iodine, interrupting the operation as soon as the whole of the iodine
has liquefied. The reddish^brown liquid thus obtained solidifies on
standing.
Properties, — Hypiodous chloride forms large prismatic crystals of a
hyacinth-red color.
Reaction. — Water decomposes it with formation of iodic acid, hydro-
chloric acid, and free iodine :
5IC1 + 30H, = /5L + 5HC1 + 2k
+ 30H, = |5Jj^ + 5HC1 + 21^
lypiodous Water. Iodic acid. Hydrochloric
chloride. acid.
lODOnS OHLORIDE.
ICl,.
Molecular weight = 233.5.
Preparation, — lodous chloride is formed by the action of an excess
of chlorine upon iodine or upon the foregoing compound.
Properties. — It forms long yellow crystals which sublime at ordinary
temperatures. It fuses at 20°-25° C. (68°-77° F.), with dissociation
into hypiodous chloride and free chlorine.
IODIC ANHYDRIDE. 301
ReoAstion, — ^With water it is decomposed, yielding the same products
as hypiodous chloride (see preceding compound) :
5ia
+ 90H, = 3{g^^ + 15HC1 + I,.
lodous Water. Iodic acid. Hydrochloric
chloride. acid.
COMPOUNDS OF IODINE WITH OXYGEN AND
HYDROXYL.
roi
o
o.
o
OHo*
01
o .
OHo
Iodic anhydride,
Iodic acid, .
Periodic acid.
The graphic formulae of these compounds are analogous to those of
the corresponding chlorine compounds given on p. 177.
IODIC ANHTDBIDE.
«•
Prqxtration. — This compound is formed when iodic acid is heated
to 170° C. :
rgi
loi
Iodic acid. Iodic Water,
anhydride.
Properties. — Iodic anhydride is a white crystalline powder possessing
a sp. gr. of 4.48.
Reactions.— 1. When heated to 300° C. (672° F.) it is decomposed
into iodine and oxygen.
2. Gaseous hydrochloric acid decomposes it with elevation of tem-
perature, iodous trichloride and water l>eing formed, and chlorine libe-
rated:
302 IKOBOANIC CHEMI8TBY.
I,0, + lOHCl = 2ia, + 50H, + 2CI^
Iodic Hydrochloric lodow Water,
anhydride. acid. trichloride.
3. It dissolves in water, forming iodic acid.
IODIC Aom.
roi
t OHo-
Preparation. — 1. Iodic acid may be obtained by decomposing a solu-
tion of baric iodate with the equivalent quantity of sulphuric acid :
roi
^ fOI
Bao" + SO,Ho, = 2 1 5^^ + SO,Bao".
.01
Baric iodate. Sulphoric acid. Iodic acid. Baric salphate.
The aqueous solution of iodic acid may be evaporated at 100° C. without
decomposition.
2. It is best prepared by oxidizing iodine with strong boiling nitric
acid :
6NO^o + I2 = 2{gjj^ + 20H, + 2NA + ^\0,.
Nitric acid. Iodic acid. Water. Nitrous Nitric
anhydride. peroxide.
3. It is also formed when chlorine is passed into water in which
finely powdered iodine is suspended :
I, + 6OH2 + 5C1, = 2 1 2^^ + lOHCl.
Water, Iodic acid. Hydrochloric
acid.
Properties. — Iodic acid forms colorless rhombic crystals of sp. gr,
4.629. It is very soluble in water. At a temperature of 170° C.
(338° F.) it gives off water, and is converted into anhydride.
• Reactions. — 1. In contact with hydriodic acid it forms water and
iodine :
{oHo + ^H^ = 2°^» + 3^»-
Iodic acid. Hydriodic Water,
acid.
2. It is reduced by many other deoxidizing agents :
IODIC ACID. 303
r
^{oHo + 6SH, = I, + 6S + <
Iodic acid. Sulphuretted Water,
hydrogen.
^{oHo + *^» + ^°H» = I« + 6SO,Ho^
Iodic acid. Sulphurous Water. Sulphuric acid,
anhydride.
Preparation of lodates, — lodates may be obtained by the following
methods :
1. By treating solutions of metallic hydrates with iodine^ and sep-
arating the iodate by crystallization :
6KH0 + 31, = 5KI + {oKo + ^°^«-
PotaFsic Potassic Potassic Water,
hydrate. iodide. iodate.
2. By dissolving iodine in potassic hydrate and treating the mixture
with chlorine :
12KH0 + I, + 5C1, = lOKCl + SJJ]^^ + 60H,.
Potaasic Potaasic Potassic Water,
hydrate. * chloride. iodate.
In this way the whole of the iodine is converted into iodate.
3. By heating together potassic chlorate and iodine :
I , roci _ j^, foi
Potassic Hypiodous Potassic
chlorate. chloride. iodate.
Chara^der 0/ lodates, — ^The iodates are nearly all insoluble in water;
those of the alkalies are the most soluble.
Iodic acid, though a monobasic acid, forms hyper-acid salts. Thus
in the case of potassium, the following salts are known :
Normal potassic iodate, < q^ .
. ., . . , (01 roi
Acid potassic iodate, < qxt- , < qtt •
Di-acid potassic iodate, < q^ , 2 < qu .
All the iodates are decomposed by heat. Some break up into iodides
and oxygen, others into metallic oxides, iodine, and oxygen :
304
INORGANIC CHEIflBTRT.
{oL = KI + 30.
Potamic Potaasic
iodate. iodide.
roi
o
Mgo" = MgO + I, + 50.
o
Magneslc iodate. Magnesic oxide.
PERIODIC ACID.
{
01
o .
OHo
Preparation. — I. Periodic acid is obtained by decomposing plumbic
periodate with sulphuric acid :
roi
o
o
roi
Pbo"
O
o
.01
+ 80.H0, =
= 2^0 +
(OHo
BO,Pbo"
Plambic
Sulphuric
Periodic
Plumbic
pe
riodate.
acid.
acid.
sulphate.
2. Argentic periodatile is deoompoeed on boiling with water into an
insoluble basic salt of the formula lO^HAgsyOHj and free periodic
acid:
fOI
2^0 + 20H, = lO.HAfoOH, +
(OAgo
Argentic Water. Basic argentic Periodic
periodate. periodate.
roi
(OHo
acid.
The periodic acid remains in solution and may be obtained on evap-
roi
oration in crystals of the formula \ O ,20H2.
roi
(OHo
3. It is also formed when iodine is added to an aqueous solution of
perchloric acid : '
roi
roci
2<^0 +
I,
= 2-10
(OHo
(OHo
Petchloric acid.
' Periodic acid.
+ CI,
PERIODIC ACID.
305
Properties, — Normal periodic acid, < O , has not been obtained.
(OHo
The crystals which are formed when an aqueous solution of the acid is
evaporated, contain two molecules of water of crystallization, which
they retain at 100° C. They fuse between 130° and 136° C. (266°-
277° F.), and are slowly converted into iodic anhydride, oxygen, and
water. At 200° C. (392° F.) this change takes place rapidly.
Preparation of Period ates. — 1. Sodic periodate may be prepared by
passing chlorine through mixed solutions of sodic hydrate and sodic
iodate :
fOI
tONao
Sodic
iodate.
+ 2NaHo + CIj =
Sodic
hydrate.
= i
01
o
ONao
Sodic
periodate.
+ OH, + 2NaCl.
Water.
Sodic
chloride-
2. A basic baric periodate may be obtained by heating baric iodate :
roi
o
Bao"
O
01
Baric iodate.
01
o
o
= ^ Bao",4BaO
O
O
^01
Basic baric periodate.
+ 41, + 90,
This basic baric periodate is not decomposed at a red heat, whereas the
other periodates part with their oxygen at this temperature.
Charaeter of the Periodaies, Aiomieit'ii of Iodine. — Periodic acid forms a series of
remarkably complex salts, the classification of which is attended with some difficulty.
Their constitution may, however, be readily explained on the supposition that, in this
acid, iodine possesses the character of a heptad. Of course this would involve the
assumption tnat iodine is ])entadic in iodic acid, and triadic in iodous trichloride, whilst
an extension of these atomicities to chlorine and bromine would be unavoidable. As,
however, in these elements the monadic character is by far the most prominent, it has
been thought advisable to adhere for the present to this classification. Future investi-
gation may establish their polyadic character. In this connection it is worthy of note
that electronegative elements exhibit as a rule a more polyadic character in their com-
binations with oxyeen than in their combinations with hydrogen and metals.
The following table contains a list of the periodic acids and their salts, formulated
both with heptadic and with monadic iodine, showing the greater simplicity resulting
from the former method. The names of periodic acids which are known only in the
ibrm of their salts, are inclosed within brackets:
306
INOBOANIC CHEHI8TRT.
Name of oompoiind.
With IirU.
With I'.
(Monobasic penodic acid) ^
(Tribasic periodic acid)
Pentabanic periodic add
(Tetrabaaic anhydroperiodic acid)...
(Octobasic anhjdroperiodic acid).....
Potaasic periodate
Triargentic periodate..
Triplumbic periodate
Pentargentic periodate
Trihjdric diargentic periodate
Pentabaric periodate -
Tetrmrgentic anhjdroperiodate
Tetrazincic anbydroperiodate
10,Ho
fIO,Ho,
0
( IO,Ho,
riOHo^
0
ilOHo,
IO,Ko
IO,Ago,
5g;pbo-.
lOAgOfc
lOHojAgo,
r 10. Ago,
0
I.IOZiio'%
••O^VHo
••0'VHo,OH,
»»0^',IHo,20H,
2»^0'',IHo,OH,
.2*»0'^IHo,30H,
»'0'^.IKo
••0'VAgo,OAg.
;:g;>{pbo-2Fi>o
•'0'',"rAgo,20Ag,
2»»0^yAgo,OAg„80H,
;:g:>fBao-4Bao
2«'0'yAgo,OAg,
l:g;>[Zno^3ZnO
The periodatea are, as a rule, only aparingly soluble in water.
FLUORINE, Fg?
Atomic weight =19. Molecular weight = 38 (?).
dence of atomicity :
Atomicity '. Evi-
Hydrofluoric acid, HF.
Occurrence, — Fluorine occurs in nature in combination with metals
as fluorides. The most common of these is calcic fluoride or fluorspar,
OaF,, known also as the Derbyshire spar. Cryolite, a mineral occurring
in Greenland, is a double fluoride of sodium and aluminium, possessing
the formula ^Al'^^^F^GNaF. Fluorine also occurs in small quantity
in various other minerals, such as apatite, topaz, etc. In the animal
kingdom it has been found in minute traces in the enamel of the teeth
and in the bones.
Attempts to isolate FliuyiHne, — Little is known of fluorine in the free
state. So great is the affinity of this element that as soon as it is ex-
pelled from one combination it enters into another. Its isolation has
from time to time been announced, but a repetition of the experiments
by other investigators has, till lately, failed to confirm the supposed
results. Ai^ntic fluoride is decomposed at a red heat by chlorine,
bromine, or iodine, with formation of a chloride, bromide, or iodide of
silver; but the liberated fluorine instantly combines with the material
of which the vessels elhployed in the experiment are composed. Ves-
sels of glass, silver, gold, platinum, and graphite have been tried^ but
HYDROFLUORIC ACID, 807
withoat success. In like manner in the electrolysis of fused fluorides,
the fluorine combines with the material of the positive electrode.
The attempt to employ vessels of fluorspar in the' above decomposi-
tions has proved unsuccessful.
Latterly, however, Brauner, in heating eerie tetrafluoride, has found
that it is converted into diceric hexafluoride, whilst a gas is evolved
which smells like chlorine, and liberates iodine from potassic iodide.
The reaction probably occurs according to the equation :
20eF, = 'Oe'",F, + F,.
Ceric Diceric
tetrafluoride. hezaflaoride.
COMPOUND OF FLUORINE WITH HYDROGEN.
HTDBOFLUOBIC ACID.
HF.
O
Molecular weight = 20.* Molecular volume DD. 1 litre vreighs 10
eriths. Bails at 19.4° C. (66.9° F.). Sp.gr. of liquid 0.9875 at 13^
C. (65° F.).
Preparation, — 1. Hydrofluoric acid may be obtained by heating
calcic fluoride or cryolite with concentrated sulphuric acid in a Teaden
or platinum retort (Fig. 44), which is connected with a U-tube of the
same metal :
OaF, + BOjHo, = 2HF + BO,Cao".
Calcic Sulphuric Hydrofluoric Calcic
fluoride. acid. acid. sulphate.
A very concentrated acid distils over and condenses in the U-tube, which
is cooled by a freezing mixture. If an aqueous solution is required, the
acid may be passed at once into water.
2. In order to obtain a perfectly anhydrous acid, the double fluoride
of hydrogen and potassium (HF,KF), which must be previously fused
in order to free it from the last traces of moisture, is heated in a plati-
num retort. The condenser and receiver must also be of platinum.
The anhydrous hydrofluoric acid distils over, whilst potassic fluoride
remains behind in the retort. The condensation is effected by means of
* Kletzinskj has found that hydrofluoric acid at a temperature jupi ahove its boiling-
point poseessea a yapor-density corresponding with the molecular weight 40, and there-
fore with the molecular formula H,F,. Mallet, experimenting at a temperature of 25^
C. (77'' F.), arrived at the same result The vapor-density at these temperatures is
twice as great as at 100^ C, at which temperature it corresponds as above with the
formula HF. The existence of such a molecule as H,F, could best be accounted for on
the supposition that fluorine is a triad in this compound, thus: H — F^F — H. This
Tiew flinds further support in the existence of a hydrie potassic fluoride, which would
thus be formulated : H — F^F — K, The greater molecular weight of hydrofluoric
acid at lower temperatures accounts also for the relatively high lx)iling-point of this
acid as compared with the other bydracids.
308 INOBGANIC CHEMISTRY.
a freezing miztare^ and great care is required in performing the opera-
tion, owing to the dangerous properties of the anhydrous acid.
Fio.44.
Properties, — Anhydrous hydrofluoric acid is a colorless, mobile liquid
which fumes strongly in contact with the air. It may be cooled to
—84° C. (—29.2° F.) without solidifying. Water absorbs the gaseous
acid readily, forming a solution which, when saturated, possesses a sp.
gr. of 1.25. This solution gives off a portion of its acid on distillation
until the sp. gr. has decreased to 1.15, when it distils unchanged at
120° C. (248° F.), and contains from 36 to 38 per cent, of anhydrous
acid. This acid of constant boiling-point does not correspond with any
definite hydrate.
The concentrated acid when brought in contact with the skin produces
dangerous wounds which are very difficult to heal. The vapor of the
anhydrous acid when inhaled has been known to prove fatal.
Reactions, — 1. Aqueous hydrofluoric acid dissolves many of the
metals with evolution of hydrogen and formation of fluorides :
Fe + 2HF = FeF, + H,.
Hydrofluoric Ferrous
acid. fluoride.
2. It acts upon silicic anhydride and silicates, forming silicic fluoride
and water :
BiOj + 4HF = BiF, + 20H,.
Silicic Hydrofluoric Silicic Water,
anhydride. acid. fluoride.
Thus hydrofluoric acid dissolves glass. This characteristic projjerty is
employed as a test for hydrofluoric acid and fluorides. All metallic
fluorides, when treated with sulphuric acid, evolve hydrofluoric acid.
The substance to be tested is placed in a small platinum or leaden dish
with concentrated sulphuric acid, and the dish is covered with a piece
of glass coated with wax, on which characters have been traced, so as
to remove the wax from the parts written upon. The vessel is very
gently warmed, and the glass is allowed to remain over it for about a
Quarter of an hour. On removing the wax, the presence of hydro-
fluoric acid will be indicated by the etching of the exposed parts of
the glass. This method is frequently employed in etching scales on
glass, the fumes from a mixture of powdered fluorspar and sulphuric
SILIOON. 309
acid being employed for this purpose. Etchings produced by means
of the aqueous solution of the acid are transparent and cannot be seen
at a distance ; when the gaseous acid is employed^ the etched surface is
dull, for which reason the use of the gaseous acid is preferred.
It is evident from the above that neither glass nor porcelain vessels
can be employed in the preparation or storing of hydrofluoric acid.
The aqueous solution is generally kept in vessels of caoutchouc or
guttapercha.
Pure and perfectly dry hydrofluoric acid is without action upon
glass (Gore) ; but the slightest trace of moisture induces the action just
described.
Fluorides. — The fluorides are formed by dissolving metals in hydro-
fluoric acid or by acting with this acid on oxides, hydrates, or carbon-
ates. The fluorides of the alkalies and of silver are soluble; those of
the alkaline earths are insoluble. Nearly all the fluorides form molecu-
lar compounds with hydrofluoric acid, such as the double fluoride of
hydrogen and potassium already mentioned.
CHAPTER XXIX.
TETRAD ELEMENTS.
Section I. {Continued from Chapter XXV.).
SILICON, SUidurriy Si.
Atomie weight = 28.2. Sp. gr, (crysUdlized) = 2.49. Atomicity *^,
al8o a pseudo^riad. Evidence of atomicity :
Silicic chloride, Bi^^Cl^.
Silicic fluoride, • Bi*%.
Disilicic hexachloride, . . . < gjni^
History. — Silicon was first isolated by Berzelius in 1810.
Occurrence. — Silicon is, with the exception of oxygen, the most abun-
dant and widely distributed of the elements. It does not occur in the .
free state. In combination with oxygen it forms the mineral quartz or
silica, which is the anhydride of silicic acid : whilst the compounds of
silica with bases constitute the chief constituents of the rocks which
compose the earth's crust, and consequently of the soils, which have
all been produced by the disintegration of the rocks. From the soils
the silicon is absorbed by plants, in the ashes of which it may
always be detected.
Preparation, — 1. Silicon is liberated when silicic anhydride is re-
duced oy heating it with sodium :
310 INOBGANIO CHEIOBTBT.
8iO, + 2Na, = Si + 20Na^
Silicic Sodic
anhydride. oxide.
This method is not, however, adapted for the preparation of pure silioon.
The reaction may be shown by heating sodium in a test-tube of Bohe-
mian glass, when the glass speedily blackens owing to the reduction of
the silica.
2. Pure silioon may be readily obtained by heating potassic silico-
fluoride with potassium :
SiKjF, + 2K, = Si + 6KF.
PotasBic Potaflsic
silicofluoride. flaoride.
Sodium may be substituted for potassium in this reaction. The fused
mass is allowed to cool, and the potassic fluoride is then dissolved in
water, when the silicon remains l)ehind as a brown amorphous powder.
3. Silioon is deposited in the same amorphous condition when sodium
is heated in a current of the vapor of silicic chloride : —
BiCI, + 2Na, = Si + 4NaCl.
Silicic Sodic
chloride. chloride.
4. In order to obtain silicon in the crystallized condition, advantage
is taken of the property which this element possesses of dissolving at a
high temperature in certain metals, such as zinc or aluminium, and
crystallizing from these metallic solutions on cooling. A mixture of 15
parts of dry potassic silicofluoride, with 4 parts of sodium in thin slices,
is thrown into a red-hot Hessian crucible; 36 parts of granulated zinc
are quickly added, and the mass is covered with a layer of fused sodic
chloride. The lid is then replaced and the whole is heated for some
time to a temperature below the boiling point of zinc. On dissolving
the cooled regulus of zinc in acids, the crystallized silicon remains be-
hind.
5. Crystallized silicon may also be obtained by heating together in a
crucible 1 part of aluminium with 5 parts of glass free from lead, and
10 parts of powdered cryolite ('AI'",Fe,6NaF). The silica of the glass
is reduced at the expense of the aluminium.
Propertiea. — Amorphous silicon is a brown powder, devoid of lustre.
It inflames when heated in the air, but cannot be entirely burnt, even
in oxygen, as the silica which is formed coats the particles and prevents
further oxidation. It is insoluble in water, and is not attacked by acids,
except hydrofluoric acid, which dissolves it readily. When heated with
exclusion of air it becomes denser, and is no longer combustible.
Crystallized silicon forms dark lustrous octahedra, which possess a
sp. gr. of 2.49 and are hard enough to scratch glass. It may be heated
to whiteness in oxygen without burning. At a very high temperature
it fuses. It conducts electricity imperfectly. Acids are without action
upon it, with the exception of a mixture of nitric and hydrofluoric acids,
which dissolves it slowly.
finJCIC HTDBIBE. 311
Recustions. — 1. When amorphoas mlicon is heated in oxygen, silicic
anhydride is formed.
2. Both varieties of silicon may be burned in a stream of chlorine,
silicic chloride being produced. Owing to the volatile nature of the
silicic chloride, the whole of the silicon may be thus converted.
3. When amorphous silicon is treated with hydrofluoric acid, or the
crystallized variety with a mixture of nitric and hydrofluoric acids, hy-
drofiuosilicic acid is formed : —
Si + 6HF = SiHJF. + 2H,.
Hjdroflaoric Hydrofluo-
acid. silicic acid.
4. Amorphous silicon when boiled with caustic alkalies, yields an
alkaline silicate, with evolution of hydrogen : —
Si + 4KHo = SiKo, + 2H,.
Potassic Potaflsic
hydrate. silicate.
CrystalliEed silicon must be fused with the alkali in order that this re-
action may take place.
COMPOUND OF SILICON WITH HYDROGEN.
SnJOIC HYDRIDE, SUieiuretted Hydrogen.
SiH,.
Molecular weight = 32.2. Molecular volume I I L
Prejparatum. — 1. When dilute sulphuric acid is decomposed by a
feeble electric current passing from electrodes of aluminium containing
silicon, silicic anhydride is evolved at the negative electrode.
2. It may also be obtained by decomposing magnesic silicide with
hydrochloric acid :
SiMg'', -f 4HC1 = 2MfirCl, + BiH,.
Maffnesic Hydrochloric Magnesic Silicic
silicide. acid. chloride. hydride.
The magnesic silicide is prepared by heating together in a closed cruci-
ble 40 parts of anhydrous magnesic chloride, 36 parts of dried sodic
eilicofluoride, 10 parts of fused sodic chloride, and 20 parts of sodium
in thin slices. The fused mass is broken into fragments and intro-
duced into a flask fitted with safety and delivery tubes. The flask and
the delivery tube are filled with water from which the air has been ex-
pelled by boiling, and hydrochloric acid is then poured through the
funnel of the safety tube into the flask. Silicic hydride is evolved and
18 collected over previously boiled water in the pneumatic trough.
312 IKOBGANIC CHEMIBTBT.
3. Silicic hydride prepared by either of the foregoing processes is
always coataruinated with hydrogen ; but if ethylic silico-orthoformate,
a substance obtained by the action of silicon-chloroform (q.v,) on abso-
lute alcohol, be placed in contact with sodium, it breaks up into ethylic
orthoeilicate ana pure silicic hydride, the sodium remaining unaffected:
4ffiH(C,H,0), = SiH, + 3Bi(C,H,0),.
Ethylic silico- Silicic Ethylic
orthoformate. hydride. orthosilicate.
Properties, — Silicic hydride is a colorless gas. When prepared from
magnesic silicide it inflames spontaneously in contact with air, and
burns with a brilliant white flame evolving dense clouds of silicic an-
hydride. The pure gas is not spontaneously inflammable, but it
acquires this property when it is gently warmed, or when the pressure
18 reduced, or when it is diluted with hydrogen.
Reactions. — 1. Burned in the air or oxygen, silicic hydride yields
silicic anhydride and water :
BiH, + 20, = ffiO, + 20Hr
Silicic Silicic Water,
hydride. anhydride.
2. With chlorine it explodes spontaneously, forming silicic chloride
and hydrochloric acid :
BiH, + 4C1, = BiCl, + 4HC1.
Silicic Silicic Hydrochloric
hydride. chloride. acid.
3. When heated, it is decomposed into amorphous silicon and free
hydrogen, the latter occupying twice the volume of the original gas,
4. It IS decomposed at ordinary temperatures by a solution of potas-
sic hydrate, yielding four times its volume of hydrogen :
SiH, + 2KHo + OH, = BiOKo, + 4H^
Silicic Potassic Water Potassic
hydride. hydrate. silicate.
5. It precipitates some of the heavy metals in the form of silicides
from the solutions of their salts :
2SO,Cuo"
+ SiH, =
= SiCu", +
2BO,Ho,
Capric
SiUcic
Cupric
Sulphuric
sulphate.
hydride.
silicide.
acid.
SILICIC CHLOBIDB — DI8ILICIC HEXACHLORIDE. 313
COMPOUNDS OF SILICON WITH THE HALOGENS.
SILICIC CHLORIDE.
BiCl,.
MoUeular vmght = 1 70.2. Molecular volume I I I- 1 lUre of the vapor
weighs 85.1 criOia. Sp. gr. of liquid 1.52. BoiU at 59° C. (138.2° F.).
PreparaMon, — 1. Silicic chloride is formed by the direct combination
of its elements when silicon is burnt in chlorine.
2. It is most conveniently prepared by heating a mixture of finely
divided carbon and silicic anhydride in a stream of dry chlorine :
810, + 20 + 2C1, = BiCl, + 2C0.
Silicic Silicic Carbonic
anhydride. chloride. oxide.
Properties. — Silicon tetrachloride is a colorless mobile liquid^ fuming
strongly in contact with air.
Reaction. — Water decomposes it instantaneously with formation of
silicic and hydrochloric acids:
BiCl, + 40H, = BiHo, + 4HC1.
Silicic Water. Silicic Hydrochloric
chloride. acid. acid.
DI8ILICIC HEZACHZiORIDB.
rsici,
isici,-
MoUeuUur weight = 269.4. Molecular volume I 1 I 1 litre of the vapor weighs 134.7
crilhs, Sp,gr.o/liguidl^, i^'oaes a* — 1° C. (30.2° F.). -BaiZ* a/ 147° C. (296.6° F.}.
Preparation, — 1. This componnd is formed in small quantity when the yapor of
silicic chloride is passed over silicon heated above 1000° C. :
asia*
+
Si
- o/SlCl,
= Msici,-
SUlclo
chloride.
DlaUleic
hexachloride.
2. It is more easily prepared by gently heating disilicic hexiodide {q.v,) with mer
curie chloride :
{«|j + SHgCl. =» {««. + SHglr
Dlalllcic Mercuric Disilicic Mercuric
hexiodide. chloride. hexachloride iodide.
IVoperties* — Disilicic hexachloride is a mobile, colorless liquid, which at a tempera-
ture of — 1° C. solidifies to a crystalline mass. It possesses the peculiarity of beinj^
stable only below 350° C. and above 1000° C, whilst at intermediate temperatures it
dissociates into silicic chloride and silicon. A similar abnormal behavior has already
been noted in the case of seleniuretted and telluretted hydrogen.
IUa€ti4m. — With water it is decomposed into silicon-oxalic acid and hydrochloric
add:
314 INOBOANIC CHElflBTBT.
Dislllcic Water. SiliooD-oxallo Hydrocblorio
hexachloride. acid. acid.
8IIJCOR CHIaOROFORlC SUieic Hydrctrieklonde.
SlHCl,.
MoUctUar weight = 135.7. Moleadar volume m. 1 litre of (Ke vapor weighM 67.85
crit/a. Sp. gr, of liquid 1.6. BoiU at SG"" C. (^.S"" F.)
Freparation, — Silicon chloroform ia formed when silicon ib heated to dull rednen in
a current of hydrochloric acid gas :
8i + 3Ha = ana, + h^
Hydrochloric Silicon
add. chloroform.
Propeiiiu, — Silicon chloroform is a colorless liquid. It is yery inflammable, and
burns with a green-edged flame. A mixture of its vapor with air explodes in contact
with a heated body.
BeadianM, — 1. It is decomposed by chlorine at ordinary temperatures :
siHa, -f- CI, =: sicu + Ha.
silicon Silicic Hydrochloric
chloroform. chloride. acid.
2. By contact with water it is transformed into tiUtoformic ankydride, or ditUieie
hydrotrioxide:
rsiHO
2aiHa, + 30H, = -^O -f 6HC1.
isiHO
Silicon Water. Sllicoformlc Hydrochloric
chloroform. anhydride. acid.
Silicon bromoform, SIHBr,, and $ilieon iodoform, BiRl^ haye also been prepared.
SILICIC BROBODB.
81Br«.
MoUadar weight = 348.2. Molecuiar volvme m. Fuses at —IZ"* C. (6.6** F.). Boih
at 153^ C. (307.4° F.). Sp, gr. of liquid 2.813 at 0° C.
Preparation. — This substance is obtained by a method analogous to that employed
in the preparation of the chloride, bromine-vapor being substituted for chlorine.
Properties. — It is a fuming, colorless liquid.
Beaction. — Water decomposes it with formation of silicic and hydrobromic acids :
SlBr^ + 40H, =: SIH04 + 4HBr.
Silicic Water. Silicic Hydrobromic
bromide. acid. acid.
IXailieie hexabromide, < SiBr'' ^ '^^ known.
SILICIC lODIDB.
Molecular weight = 536.2. Afoleeular volume JTl. Fuses at 120,5° C. (248.9'* F.).
Boils in carbonic anhydride at 290® C. (554° FT^
JVgiara<um.---Thi8 compound is formed by the direct union of its elements when a
mixture of iodine vapor and carbonic anhydride is passed over red-hot silioon. The
SILICIC FLUORIDE. 315
carbonic anhydride Berres to carry off the vapor of the silicic iodide as feet as it ia
formed, and thus to prevent its deoompoflition.
Propertiea,— Silicic iodide crystallizes in colorless octahedra. It may be distilled in
a corrent of carbonic anhydride. It is soluble in carbonic disulphide.
BeactioM. — 1. Water decomposes it into silicic and hydriodic acids.
2. Absolute alcohol decomposes it, with production of silicic anhydride, ethylic
iodide, and hydriodic acid :
SlI^ + 2EtHo
= 810, -f 2EtI 4- 2HI.
SUicio AlcohoL
iodide.
SUicic EthvUo Hydriodic
anhydride. iodide. acid.
^j', has been obtained by heating silicic iodide with finely
divided silver :
2811, + Ag, = {g}{| + 2AgI.
eiUcic DiBllicic AxvenUc
iodide. hexlodlde. iodide.
It forms hexagonal crystals, fusing with decomposition at 250° C.
SILICIC FLUORIDE.
BiF,.
Molecular weight = 104.2. Molecular volume I I 1. 1 litre weighs
62.1 Griihs. Fuses at —140° C. (—220° F.). BoUs at —107° C.
(—160.6° F.).
Preparation. — Silicic fluoride is prepared by heating together, in a
flask furnished with a delivery tube, quartz sand^ fluorspar, and an
excess of concentrated sulphuric aoid :
+ 2BOHo,Cao''.
Dihydric calcic
sulphate.
The gas may be collected in perfectly dry glass vessels over mercury.
Properties. — Silicic fluoride is a colorless gas with a very pungent
odor. It fumes strongly in contact with air. Under a pressure of 30
atmospheres, or at a temperature of — 107° C. ( — 160.6° F.)^ it con-
denses to a colorless liquid, which at a still lower temperature solidifies.
It is not altered by exposure to the heat of powerful electric sparks.
Reaction. — Water decomposes it with formation of silicic and hydro-
fluosilicic acids :
BiO, + 2CaF,
+ 2SO,Ho.
= BiF,
Silicic Calcic
Sulphurio
Silicic
anhydride. fluoride.
acid.
flnoride.
3BiF, + 40H, =
= BiHo,
+ 2SiH,F,.
Silicic Water.
Silicic
Hydrofluosilicic
fluoride.
acid.
acid.
When the gas is passed into water, the silicic acid separates out as a
gelatinous mass, whilst the hydrofluosilicic acid remains in solution.
To prevent the delivery tube from being stopped up, it must dip under
mercury at the bottom of the vessel in which the water is contained.
The liquid is afterwards filtered from the silicic acid and evaporated at
316 INOBGAiaC CHEMI8TBT.
a low temperature. The aqueoas solution t>f hydrofluosilicic acid thas
obtained forms a fuming acid liquid, which on further evaporation de-
composes into silicic fluoride and hydrofluoric acid.
With metallic oxides, hydrates, and some salts, hydrofluosilicic acid
produces silioofluorides :
SiH,F, + 2KHo = SiK,F, + 20Hy
Hydrofluo- Potaasic ^ Pota»ic Water,
silicic acid. hydrate. silicofluoride.
In contact with an excess of base the silioofluorides are decomposed,
yielding silicates and fluorides :
SiKjFe + 8KH0 = BiKo, + 6KF + 40H,.
Potaaeic Potassic Potassic Potassic Water,
silicoflaoride. hydrate. silicate. fluoride.
The silioofluorides of barium and potassium are insoluble in water.
ZXfUidc hexofiuoride has been prepared by passing silicic fluoride over melted silicon ;
3SIF4 + Si — 2{^^».
Silicic Dislliclc
fluoride. hexafluoride.
It forms a fine white powder.
COMPOUNDS OF SILICON WITH OXYGEN AND
HYDRXPXYL,
Silicic anhydride, SiO,.
Silicic acid, SiHo^ and BiOHo,.
Other Modifications of Silicic Acid,
Bi,03Ho, Bi^pjoHo,
Bi^O.Ho, Bi.03Ho3
BiAHo, BigOiflHo,
BiAHo,.
BILIOIC ANHYDRIDE, Silica.
BiOy
Molecular weight =: 60.2. Sp, gr, {amorphous) 2.2, {tridymite)^ 2.3,
(quartz) 2.69.
Occurrence. — Some of the forms in which silicic anhydride is found
in nature have already been alluded to (p. 309). It occurs in the crys-
tallized condition as quartz and tridymite, and in an amorphous form
as opal.
SILICIC ANHYDRIDE. 317
Preparation. — It may be obtained by heating silicic acid to 100° C.
Water is given off and amorphous silicic anhydride remains.
Properties. — As quartz or rock crystal, silicic anhydride occurs in the
form of hexagonal prisms terminated by a hexagonal pyramid (Fig. 45).
The crystals are sometimes colorless, sometimes colored by the presence
of various oxides. Amethyst quartz, rose quartz, smoky quartz, are
Fig. 45.
varieties of this description named according to their color. Occa-
sionally quartz occurs in large crystalline masses as quartzose rock. It
ha<^ a sp. gr. of 2.69, and is bard enough to scratch glass.
Tridymite is a second crystallized variety of silicic anhydride found
in various trachytic rocks. Like rock crystal, it crystallizes in forms
belonging to the hexagonal system ; but the relations of the axes vary
in the two minerals, so that the forms of the one cannot be referred to
those of the other. The sp. gr. of tridymite is 2.3.
Amorphous silicic anhydride, when artificially prepared, forms a white,
very fine powder. As opal, amorphous silica occurs in transparent or
translucent masses with a conchoidal fracture. The sp.gr. of the arti-
ficial variety is 2.2 ; that of the natural 2.3.
Silicic anhydride in all its forms is insoluble in water at ordinary
temperatures. It dissolves slightly, however, if heated with water un-
der pressure to low redness, and, on cooling, crystallizes from the solu-
tion in the form of quartz. In like manner, when a solution of an al-
kaline silicate is heated in a sealed glass tube, a portion of the silica
from the glass is dissolved, forming an acid silicate. On cooling, the
excess of silica separates out. If the separation takes place above 180°
C. (366® F.) the silica is obtained as quartz; below this temperature
tridymite is formed ; at ordinary temperatures it is deposited in the hy-
drated condition as amorphous silicic acid.
Acids, with the exception of hydrofluoric, are without action upon
silicic anhydride. With aqueous hydrofluoric acid hydrofluo-silicic acid
is formed :
BiO, + 6HF = SiHjF, + 20H,.
8ilicic Hydrofluoric Hydrofluosilicic Water,
anhydride. acid. acid. i
All the modifications of silicic anhydride, when fused with an excess
of a caustic alkali or an alkaline carbonate, combine with the base to
form a soluble silicate :
diO, + 2CK)Nao, = SiNao^ + 20O,.
Silicic Sodic Sodic Carbonic
anhydride. carbonate. silicate. anhydride.
318 INOBOANIG CHEMierrBT.
The amorphous variety^ if it has not been ignited too strongly^ dissolves
in boiling solutions of caustic alkalies.
snjoio Aom.
Tetrabasicy . . SiHo^ Dibasic^ . . . SiOHo,.
Preparaiion. — 1. Silicic acid may be obtained by decomposing a
solution of sodic or potassic silicate with hydrochloric acid :
BiNao, + 4HC1 = SiHo, + 4Naa.
Sodic Hydrochloric Silicic Sodic
silicate. acid. acid. chloride.
If the solution of the alkaline silicate is concentrated, the silicic acid
separates out as a white gelatinous precipitate; but if a dilute solution
of the silicate be poured into an excess of hydrochloric acid, the silicic
acid remains dissolved. The clear solution obtained by the latter
method maybe freed from the sodic chloride and excess of hydrochloric
acid by dialysis (see Introductions p. 130). The silicic acid, being a
colloid, is unable to pass through the membrane of the dialyzer, whilst
the other substances in solution diffuse freely through into the surround-
ing liquid. The solution of silicic acid may be concentrated by boiling in
a flask until it contains 22 per cent, of the tetrabasic acid, but beyond
this point it solidifies to a jelly. • When evaporated in a dish the solu-
tion is ai)t to gelatinize round the edges, and then the whole mass solid-
ifies. The concentrated solution also gelatinizes spontaneously when
allowed to stand for a few days, and the same effect is produced instan-
taneously by passing carbonic anhydride into the solution, or by the
addition of a trace of an alkaline carbonate.
2. Gelatinous silicic acid may be obtained by passing a stream of car-
bonic anhydride through a solution of an alkaline silicate:
SiNao, + 40H, -[- 40O, = SiHo, + 40OHoNao.
Sodic Water. Carbonic Silicic Hydric sodic
silicate. anhydride. acid. carbonate.
A reaction similar to this is the cause of the disint^ration of granitic
rocks. The carbonic anhydride which is held in solution in all natural
waters acts upon the alkaline silicates contained in the rocks.
3. Gelatinous silicic acid is also formed when silicic fluoride is passed
into water (p. 315).
Prop^r^.— ^Silicic acid, like most other weak polybasic acids of even
basicity, has a great tendency to give off water and form an anhydride.
It is therefore exceedingly doubtful whether any of the silicic acids
have been prepared in a state of purity. By allowing gelatinous silicic
acid to dry in the air, a compound having approximately the composi-
tion represented by the formula Si^OgHog is obtained, and this, when
dried at 100° C, parts with more water, yielding a hydrate of the formula
8i5H^oHo4. These substances are, however, very diflScult to obtain of
" SiHcic anhydride, • . . • SiO,.
BlUdC ACID. 319
fixed compoeitioD, and they possess none of the other characteristics of
definite chemical compounds.
SiKccUes. — ^The preparation of alkaline silicates has already been de-
scribed (p. 317).
Silica and the silicates form a very important class of minerals. The
following list contains a few examples :
Sand
Flint
Rock crystal
Quartz
Opal
Chalcedony
Peridote {Dimagne&ic silicate), BiMgo''^.
Pbenacite {Diberyllic silicate)^ BiBeo",.
Willemite {Dizinoic sUicate), SiZno",.
Zircon {Zrconic sUieate), SiZro*^.
Enstatite {Monomaffneaic sUicaie), .... SiOM go''.
rSiNaOj
Yorke's Sodic silicate, .< O
(SiNao,
{Si
oiCao"Mgo".
Talc ( Tetramagneaie penUmHoate), . . . SifOfMgo"^.
Ophite (Noble Serpentine), -( O Mgo'V
Okenite {Teirahydrie oaleio dinlicaU),
(SiHo,—,
J O Cao".
I SiHo,— '
rSiHoMgo''
Serpentine {IHhydrie] trimagneaie dialieaie), < Mgo"
( SiHoMgo"
Steatite {HHmagnesie tetramlieate), . . . Si«0,Mgo'V
r SiHoMgo"
Meerschaam {Tetrahydrio dimagnemo triali-] wtt
<wfe), ]o *
tsiHoMgo"
rSiOHo-,
Pyrophyllite {Dihydrio aluminie tefo-owK- J SiO~2 1 ti *
cate) 1SiO_?^'? •
[SiOHdJ
ADOTth\te{AhmmuiccUmo'di»iUoaU),. . . Zij^kyfi^'^Oaa".
Labradorite (A!uminio calcic trisUicate), . . < SiCao" — Alo^.
iSiO -^
320 INOBOAKIC GHElflSTRT.
fSiCao'' ,
Grossularia (Aluminio tricalcic trmlicate), . < SiOfto"-:-Alo^.
(BiCao'' '
Emerald {TriberyUic aluminio hescaaHicaie), . Si^jO^Alo^^Beo'V
f8iO__,
Chloropal {Fen^ trisUieatel < SiO— Feo^»,30Hy*
(BiO •
Felspar. Orthoee (Dipotassie aluminic hexor ( ai r\Tr a i^ti
sUicaie), . . . ^^ |SiAKo,Alo.
COMPOUNDS OF SILICON CONTAINING SULPHUR.
SILICIC SniiPHIDB.
PreparcUion.-—!. Silicic Rulphide i« formed by the direct union of its elements when
amorphous silicon is heated in sulphur vapor.
2. It is more conveniently obtained by passiuff the vapor of carbonic disulphide
over a mixture of silicic anhydride and charcoal heated to redness :
810, + CS, 4-
C
= SIS'^
+
2C0.
Silidc Carbonic
Silicic
Carbonic
anil ydride. disulphide.
sulphide.
oxide.
Properties. — Silicic sulphide forms white silky needles resembling asbestos in ap-
pearance. It may be sublimed without decomposition. In contact with water it forms
silicic acid and sulphuretted hydrogen :
SIS'', + 40H, = 8IH04 + 28H,.
Silicic Water. Silicic Sulphuretted
sulphide. acid. hydrogen.
8ILICIC TRICHLORSTTIiPHHYDRATR
8iClsHs.
MoUctdar weight = 167.7. Molecular volume m BoiU at 96° C (204.8® F.).
Preparation. — This compound is obtained bv passing a mixture of silicic chloride
vapor and sulphuretted hydrogen through a recl-hot porcelain tube :
SiCl^ 4- 8H, = SlClgHs + Ha.
silicic Sulphuretted Silicic frichloi^ Hydrochloric
chloride. hydrogen. sulphhydrate. acid.
Properties. — Silicic trichlorsulphhydrate is a colorless fuming liquid, boiling at
96® C. (204.8° F.). Water decomposes it, forming silicic acid, hydrochloric acid, and
sulphuretted hydrogen :
Silicic trichlor- Water. Silicic Hydrochloric Sulphuretted
foilphhydrate. acid. acid. hydrogen.
SlCljHs 4- 40H, = SIH04 + 3HC51 + 8H1.
Silicic E
acid.
Fee'* = (^Fe'^',0,)''
TIN. 321
TIN, Sn.*
Atomic weight = 118. 8p, gr. 7.28. Fuses at 228*^ C. (442.4^ F.).
Aicmidty " and ^'^ atyi also a pseudo-triad. Evidence of aiomidty:
Stannous chloride (at 900^ C), Sn"Cl,.
Stannic chloride, Bn»^Cl^.
History. — Tin has been known from the eariiest historical times.
The tin-mines of Cornwall were celebrated before the Roman invasion,
and from these the Phoenician merchants supplied the metal to the
ancient world.
Occurrence. — Tin is never found in the free or native state. In
combination with oxygen as tin-stone or stannic anhydride, it occurs
in veins in the primitive rocks, and sometimes in alluvial deposits
(stream tin). Tin-stone is the only ore from which the metal is ex-
tracted. The mines of Cornwall, above referred to, and those of
Devonshire, furnish the chief supply ; those of Malacca and Banca
come next in importance.
Extraction. — ^The tin-stone is first crushed and washed in order to
free it from earthy impurities. It is then roasted in a reverberatory
furnace, by which means the iron- and copper-pyrites with which it is
contaminated are oxidized. The iron is thus converted into ferric
oxide, with evolution of sulphurous anhydride, whilst the copper forms
cupric sulphate. The roasted mass is again washed, the cupric sul-
phate being thus dissolved and the ferric oxide mechanically removed.
The finely divided tin-stone thus purified is mixed with charcoal and
reduced in a furnace :
SnO, H- C, = Sn + 200.
Stannic anhydride. Carbonic oxide.
The tin obtained by the above process is generally contaminated with
various foreign metals (iron, copper, lead, arsenic, antimony), from
which it may be separated by liquation. This process consists in
melting the crude tin at the lowest possible temperature on the bed of
a reverberatory furnace. The tin, by virtue of its lower fusing-point,
melts first, and flows off, leaving a less fusible alloy of tin with the
other metals.
Properties. — Tin is a white metal with a high metallic lustre. When
warm it emits a peculiar odor. In hardness it is intermediate between
lead and zinc. It is malleable and may be beaten into thin leaves
(tin-foil). At a temperature of 200° C. it becomes brittle. It fuses at
228° C. (442.4° F.),and when exposed to the air in a molten condition
* This element, whilst exhibiting all the phynical properties of a metal, behaves in
most of its chemical relations like a non-metal. Its compoands resemble those of car-
bon, silicon, and titanium, and it can be most conveniently studied in connection with
these elements. For similar reasons antimony, bismuth, and a few other metallic ele-
ments have, in the present work, been dashed with the non-metals.
21
322 INOBOANIC OHEMIBTRY.
undergoes superficial oxidation. At a white heat it enters into ebul-
lition and burns with a brilliant white light, forming stannic anhy-
dride. It is also oxidized when heated to redness in a current of steam.
At ordinary temperature it resists the action of air and moisture.
If a bar of tin be bent backwards and forwards a faint crackling
sound is heard, and the point of flexure becomes hot. These effects
depend upon the breaking and friction of the crystals within the mass.
The crystalline structure of tin may be readily shown by brushing the
surface of a piece of the metal (which has been cast but not hammered)
with warm dilute aquarregia, when it becomes covered with fine crystal-
line markings, resembling in appearance, watered silk. Tin thus pre-
pared was formerly much used for ornamental purposes under the name
of moir^e mStallique. Crystals of tin may be readily obtained by fusing
a large quantity of the metal, allowing it partially to solidify in the
crucible, then breaking a hole in the crust which forms on the surface,
and pouring out the molten metal. The interior of the crucible will
be found to be lined with crystals of tin.
Becustiona. — 1. Hot concentrated hydrochloric acid dissolves tin with
evolution of hydrogen and formation of stannous chloride :
Sn + 2HC1 = BeCI, + H,.
Hydrochloric Stannous
acid. chloride.
2. Heated with concentrated sulphuric acid it forms stannous sul-
phate, sulphurous anhydride being evolved :
Sn + 2BO2H0, = BOjSno" + SO, + 20H,.
Sulphuric Stannous Sulphurous Water,
acid. sulphate. anhydride.
3. Nitric acid of sp. gr. 1.3 acts upon it violently, oxidizing it to
metastannic acid (BngO^HOjo). Nitric acid of sp. gr. 1.5 does not attack
tin.
4. Cold dilute nitric acid dissolves it slowly without evolution of gas,
stannous nitrate being formed. At the same time a portion of the
nitric acid undergoes reduction to ammonia, which combines with the
excess 'of nitric acid :
4Sn + 9NO,Ho = 4jQ«no" + NH3 + 30H,
Nitric acid. Stannous nitrate. Ammonia. Water.
6. Caustic alkalies dissolve tin when fused with it, a soluble stannate
being formed, whilst hydrogen is evolved :
Sn + 20KH + OH2 = BnOKo, + 2Hy
Potassic Water. Potassic
hydrate. stannate.
6. It combines directly with sulphur, phosphorus, chlorine, bromine,
and iodine.
00HP0UND8 OF TEN. 323
UsfiS. — Tinning. — Tin is frequently employed in coating other metals
to preserve them from rust, a process known as tinning. Ordinary
tin-plate is iron which has been thus treated. The surface of the metal to
be tinned is thoroughly freed from every trace of oxide, which would
otherwise prevent the adhesion of the tin, and the metal is then plunged
into a bath of melted tin, covered with a layer of grease to exclude the
air. The film of tin which adheres to the surface forms an alloy with
the metal, and ouinot be separated from it mechanically. The tinning
of copper is efiected in a similar manner.
Alloys, — Numerous alloys of tin are employed in the arts. Plumber^s
solder is an alloy of tin and lead, the proportion of tin increasing with
the degree of fusibility required."*" Mne solder consists of 2 parts of tin
and 1 of lead ; oommon solder of equal parts of tin and lead ; and
coarse solder of 1 of tin and 2 of lead. Britannia metal consists of
eqaal parts of brass, tin, and antimony, and is employed as a cheap
substitute for silver in the manufacture of teapots, etc. Pewter is a
similar alloy, in which, however, the lead and tin greatly predominate.
The alloys of tin with copper will be treated of under the heading of
the latter metal.
COMPOUNDS OF TIN.
The following are the names and probable constitutional formulae of
the principal compounds of this metal :
Stannous chloride (at 900°), BnCl,.
Stannic, chloride, • . . SnCl^.
Stannous oxide, .... SnO.
Stannic oxide or anhydride, SnOj.
Stonnous oxydichloride'', . | gj^j . 0=Sn=Sn<^| •
Stannous hydrate, . . . SnHo,. « O — H
O
Stannic acid, •SnOHo,. H— O— Sn— O— H.
Potassic stannite, . . . SnEo,.
Dipotassic stannate, . . . 8nOEo2,40H2.
O
Distannic trioxide, . • {^q^, 0=&i— Sn=0;
or
Stannous stannate, . . . BnOSno". 0=Sn<Q>8n.
* With regard to the ftuioe points of alloys, or of any mixtures of fusible sabetanoes
which do not chemically combine, the law holds that the fusing point of the mixture
is lower than the main fusing point of the constituents in the proportion in which they
are present.
324
INOBOANIC CHElflSTBY.
Metastannio acid (dried at
lOO^C), ...."'
Dipotassio metastanoate.
Stannous salphide, . .
Stannio salphide, . .
SnHo^
SnHo^
O
8nO .
O
SoHo,
O
SnHo^
rSiiHo,Ko
O
SnHo^
O
SnO
O
SnHo,
O
SnHo^o
8nS".
Distannic trisulphide, . . < OnG//S"y
or
•\BiiS"
Stannous Bolphoetannate, . 8DS^'Sns'^
Stannous sulphate, . . • SO^no'^.
8
S=^— Sn=S
S=Sn<|>Sn.
O
" o
S<5<Sn.
COMPOUNDS OF TIN WITH THE HALOGENS.
a. Stannotia Compounds.
Stannous chloride.— ?7f> to 700° C. "Bn"2Cl^; mol wt. = 378.
Between 880° and 970° C. SnCl,* ; md. wt. = 189. Fuses at 250° 0.
(482° F.). BoiU ahovi 618° C. (1144.4° F.).
Preparatum, — 1. By heating a mixture of 1 part of tin-filings with
2 parts of mercuric chloride :
Sn + HgCla = SnCljj + Hg.
Mercuric Stannous
chloride. chloride.
* For the sake of greater simplicity in the formuls, the smaller molecular formulc
have been employed for the stannous compounds.
2SnCl, + OH, =
= "Sn",OCl2
Stannoos Water.
Stannous
chloride.
oxydichloride.
OOMPOUKDB OF Tm. 325
The mercury distils off, and the stannous chloride remains as a' vitreous
mass, which may also be distilled at a higher temperature.
2. By dissolving tin in hydrochloric acid : •
8n + 2HC1 = SnCI, + H,.
Hydrochloric Stannous
acid. chloride.
On evaporation of the aqueous solution, prismatic crystals of the for-
mula SnCI^/iOH,, are obtained. The crystals dissolve in a small
quantity of water, but a larger quantity decomposes them with forma-
tion of stannous oxydichloride and free hydrochloric acid :
+ 2HC1.
Hydrochloric
acid.
Stannous chloride readily unites with oxygen or chlorine, and hence
acts as a powerful reducing agent Mercury and gold are precipitated
by it in the metallic state from solutions of their salts. The presence
of an excess of hydrochloric acid prevents the separation of insoluble
stannous oxydichloride during the reducing process :
HgO + BnCl, + 2HC1 = Hg + SnCl, + OH,.
Mercaric Stannous Hydrochloric Stannic Water,
oxide. chloride. acid. chloride.
In like manner ferric, manganic, and cupric salts are reduced to ferrous,
manganous, and cuprous salts. Chromic acid is converted into chromic
oxide.
Stannous chloride is employed as a mordant in dyeing and calico-
printing.
iSCannous bromide^ SnBr,, is obtained by dissolving tin in hydrobromic acid. It
forms a grayish- white crystalline mass, readily soluble in water.
Stannous iodide, fibilg, may be prepared by acting upon finely divided tin with hy-
driodic acid, or by precipitating a concentrated solution of stannous chloride with po-
tassic iodide. It crystallizes in sparingly soluble red needles, which are decomposed
by an excess of water. It is volatile at a red heat.
StannouB fiuoridef 8nF„ is obtained in white lustrous monoclinic crystals by dissolv-
ing tin or stannous hydrate in hydrofluoric acid and evaporating the solution in vacuo,
6. Stannic Compounds.
Stannic chloride, SnCl4. — Molecular weight = 260. Molecular
vohme UH 8p. gr. of liquid 2.267 at 0° C. Boils aH 15° C. (239° F.).
— ^This compound may be prepared either by the combustion of tin in
a current of chlorine, or by heating a mixture of 1 part of tin-filings
with 4 parts of mercuric chloride :
Sn + 2HgCl, = SnCl, + 2Hg.
Mercuric Stannic
chloride. chloride.
The stannic chloride distils over^ and is collected in the receiver.
INOBGANIO CHEMIBrTBT.
Stannic chloride is a colorless mobile liquidy which fumes powerfully
in contact with moist air. It unites with water, evolving great heat,
and forming a crystalline aquate, 8aCl4,30H2. It dissolves in a small
quantity of water, but an excess of water decomposes it, with formation
of stannic and hydrochloric acids.
It unites with the soluble metallic chlorides to form cUorodannaies,
Ammonic chlorostannate (NH4)2SnCle is the pink soli of the dyer.
Stannic chloride is also used in dyeing.
SUinnic bromide, 8oBr| {molecular volume FTl )» iB obtained as a white, fusible cry^-
illine mass by the direct union of tin and bromi
boils at 201*» C. (393.8*» F.).
talline mass by the direct union of tin and bromine. It fuses at 30° C. (86° F.), and
Stannic iodide^ 8nl|, is prepared hj heatinj; together tin and iodine. It cryatallizeB
in orange-colored octahedra, which fuse at 146^ C. (294.8° F.). It boils at 295° C.
(563° F.).
Stannic fiuoride, SnFf. The free oomponnd has not been prepared. Nameroos
doable fluorides of tetraaic tin with other metals are, however, known : thus, potaeeie
etannicofiuoride, SnKJF^OHt \ *^^ ttawnicoftuoride, SnNa,Fe. and others. These stan-
nicoflnorides correspond with the silioofluorides (p. 316), with which thejr are, as a
role, isomorphous.
COMPOUNDS OF TIN WITH OXYGEN AND HYDROXYL.
a. Slannous Compounds.
Stannous oxide, SnO. Molecular weight = 134. — 1. When stan-
nous oxalate is heated to decomposition in a closed vessel, stannous
oxide remains :
IJgSno" '= BnO + 00, + CO.
Stannous Stannous Carbonic Carbonic
oxalate. oxide. anhydride. oxide.
2. Stannous hydrate, SnHo^, is obtained as a white precipitate hj
adding sodic carbonate to a solution of stannous chloride. It is con-
verted into black stannous oxide by heating to 80° C. in an atmos-
phere of carbonic anhydride. If the stannous hydrate be boiled with
a quantity of caustic alkali insufficient to dissolve it, the remaining
hydrate is converted into small black shining crystals of the oxide
(f'remy).
Stannous oxide is a black powder of sp. gr. 6.666. When heated in
the air it becomes incandescent, and is converted into stannic oxide.
With acids it yields the stannous salts.
6. Stannic Compounds.
Stannic oxide or Stannic anhydride, SnO,. Molecular toeighi
= 150. — Stannic anhydride occurs in nature as tin-stone, crystallizing
in forms belonging to the quadratic system. The crystals are generally
dark-colored, owing to the presence of ferric and manganic oxides.
Stannic anhydride may be obtained artificially as a white, insoluble,
amorphous powder by igniting stannic or metastannio acid. Amor-
00MP0UKD6 OF TIN. 327
phoas stannic oxide assomes, on heating, a yellowish-brown color,
which disappears on cooling. It may be obtained in quadratic crystals
like those of native tin-stone, by heating it strongly in a current of
gaseoas hydrochloric acid.
Stannic anhydride is insoluble both in acids and in alkalies. It may
even be fosed with alkaline carbonates without undergoing change.
By fusion with a caustic alkali it is rendered soluble, a stannate of the
base being formed.
Stannic acid, SnOHoj. — ^This acid is obtained as a colorless, gela-
tinous precipitate by decomposing a solution of stannic chloride with
calcic carbonate, care being taken to avoid an excess of the precipitant :
SnCl, + 20OCao" + OH3 = SnOHo, + 20aCl, + 20O,.
Stannic Calcic Water. Stannic Calcic Carbonic
chloride. carbonate. acid. chloride. anhydride.
When dried in vaevLo it has the composition expressed by the above
formula.
It is soluble both in acids and in alkalies. With hydrochloric acid
it yields a solution of stannic chloride. The stannic salts of the oxy-
acids are very unstable. With bases it forms the stannatea. The alka-
line stannates crystallize well. Sodic stannate (SnONaOj^SOH,) is em-
ployed in dyeing as a mordant, under the name of ^' preparing salt."
Metastannic acid, SngO^HoiQ. — This compound, which is poly-
meric with stannic acid, is prepared by oxidizing tin with nitric acid,
and drying, at 100° C, the white powder {SnfiJlo^^,&OH^) thus ob-
tained. By ignition it is converted into ordinary stannic anhydride.
Metastannic acid is insoluble in water. Hydrochloric acid combines
with it without dissolving it, but the double compound thus formed is
soluble in pure water, from which solution it is precipitated by boiling,
or by the addition of concentrated hydrochloric acid. By prolonged
digestion with concentrated hydrochloric acid, metastannic acid is con-
verted into stannic chloride.
MetoBtanndtea. — Only two of the hydrogen atoms of metastannic
add are .replaceable by bases. Fotassic meiastannate, SngO^HogKo,, is
soluble in water, but insoluble in concentrated caustic potash.
It may be prepared by dissolving metastannic acid in cold caustic
pota.sh, and then adding solid caustic potash to the solution. It is gummy
and uncrystallizable. The sodium salt, which may be obtained in a
similar manner, forms crystalline granules.
D18TANNIG TRioxiDE or Stannous stannate. ^8n'^^,0, or SnOSno'^— The
hydrate corresponding with this oxide is prepared by boiling a solution of stannoUB
chloride with freshly precipitated ferric hydrate :
2SnCl, + ^e^'^.Ho* = ^Sn'^^Ho, (?) + 2FeCl,. '
StannouB Ferric Distannlc Ferrous
chloride. hydrate. hexahydrate. chloride.
The hydrate forms a gray slimy precipitate, which, by heating in a current of carbonic
anhydride, is converted into black distannic trioziae.
All the oxygen compounds of tin are reduced to the metallic state
by ignition in a current of hydrogen or carbonic oxide, or by heat-
ing with charcoal.
328 INOBOAKIC GHElfSSTTBY.
COMPOUNDS OF TIN WITH SULPHUR.
Stannous sulphide, SnS", may be prepared by heating together
metallic tin and sulphur, when the two snbstanoes unite with incan-
desoeuoe. It forms a laminar crystalline mass of a bluish-gray color.
It may also be obtained as a dark brown precipitate by passing sul-
phuretted hydrogen into a solution of a stannous salt.
SnCI, + BH, = SnS" + 2HC1.
Stannous Sulphuretted Stannous Hydrochloric
chloride. hydrogen. sulphide. acid.
Stannous sulphide dissolves in hot concentrated hydrochloric acid,
yielding stannous chloride and sulphuretted hydrogen, by a reaction the
reverse of the above.
It is soluble in a solution of an alkaline disulphide, forming a sul-
phostannate of the alkali :
Stannous IMpotaaBic Potaasic
sulphide- disulphide. sulphoetannate.
From this solution it is precipitated by acids as stannic, not as stan-
nous, sulphide:
BnS"K8, + 2HC1 = SnS'', -|- 2KC1 + SH,.
Potassic Hydrochloric Stannic Potassic Sulphuretted
sulphoetannate. acid. sulphide. chloride. hydrogen.
Stannic sulphide, BnS'V — This compound cannot be prepared
by merely heating tin and sulphur together. The addition of some
volatile substance is necessary in order to lower the temperature during
the reaction. An amalgam of 12 parts of tin and 6 parts of mercury
is powdered, and heated with 7 parts of sulphur and 6 parts of am-
monic chloride in a glass retort. Ammonic chloride, mercury, and
siilf^hur, along with mercuric sulphide and mercurous chloride, vola-
tilize, and the stannic sulphide remains in the flask as a mass of golden-
yellow flakes with a metallic lustre. It is not certain whether the
ammonic chloride takes part in the reaction or whether it acts merely
by its volatilization.
Amorphous stannic sulphide is obtained as a brown precipitate by
passing sulphuretted hydrogen into an acid solution of a stannic salt.
After drying at ordinary temperatures, it still contains water of hydra-
tion, with which it parts on heating.
Amorphous stannic sulphide dissolves in hot concentrated hydro-
chloric acid, and the solution contains stannic chloride. Hot concen-
trated nitric acid also decomposes it. It is soluble in alkaline sulphides
with formation of sulphostannates :
Stannic Potassic Potassic
sulphide. sulphide. snlphostannate.
COMPOUNDS OP TIK. 329
and in caustic alkalies with formation of a mixture of stannate and
sulphostannate :
SSnS", + 60KH = SnOKo, + 2BnS"Ks2 + 30H,.
Stannic Potassic Potassic Potassic Water,
sulphide. hydrate. stannate. sulphostannate.
Crystalline stannic sulphide is insoluble in all single acids, but solu-
ble in aqna-regia. Alkalies and alkaline sulphides also dissolve it
Both the varieties of stannic sulphide are decomposed at a bright red
heat into free sulphur and stannous sulphide.
Crystalline stannic sulphide is employed in the arts under the name
of mosaic gold in the production of imitation bronze surfaces. It was
known to the alchemists.
Sulphosiannatea. — Only the alkaline sulphostannates are soluble in
water. Putassic sulphostannate is uncrystallizable. The sodium salt^
SnS"Naa2,70H2, crystallizes in yellow regular octahedra.
DlSTANNOrS TRI8ULPHIDE, Or STANNOUS SULPHOSTANNATE,
'Sn"'jS''3 or Sn8''Sns." — This compound is prepared by heating to
low redness a mixture of 3 parts of stannous sulphide and 1 part of
sulphur. It forms a grayish-yellow mass with a metallic lustre. When
treated with hot concentrated hydrochloric acid, one half of the tin
goes into solution as a stannous salt, the other half remaining behind
as stannic sulphide. This reaction would seem to denote that the sub-
stance is not, as is frequently assumed^ a distinct sulphide of tin, but a
stannous sulphostannate.
All the sulphides of tin are reduced to the metallic state when heated
to redness in a current of hydrogen.
Genekal character and reactions of the salts of tin. —
The dannoua salts, when in solution, absorb oxygen from the air, and
are converted into stannic salts. CavMic alkalies precipitate from
the solutions white stannous hydrate, which is soluble in an excess
of alkali. When an alkaline solution of stannous oxide is boiled,
metallic tin separates out and an alkaline stannate remains in solution.
Ammonia and the alkaline carbonates produce a precipitate of stannous
hydrate, which is, however, not dissolved by an excess of the precipitant.
With sulphuretted hydrogen in acid or neutral solutions, the whole of
the tin is precipitated as brown stannous sulphide, almost insoluble in
colorless ammonic sulphhydrate, readily soluble in yellow ammonic
sulphide. In alkaline solutions of stannous salts the precipitate is
either not formed at all or else the precipitation is incomplete. With a
solution of auric chloride the stannous salts yield, if added in small
quantity, a purple precipitate of aurostannous stannate (Sn^OgAuOj-
8no",40H2), known as purple of Cassius ; an excess of the stannous
salt produces a brown precipitate of metallic gold.
The stannic sails yield with caustic alkalies a white precipitate of
stannic acid soluble in excess of alkali ; and the solution gives no pre-
cipitate on boiling. With sulphuretted hydrogen a yellow precipitate of
stannic sulphide is formed, soluble in alkalies and alkaline sulphides.
330 INORGANIC CHEMI8TRT.
TITAHIUM, Ti.
Atomic weight = 48. Sp. gr. 5.3. Atomicity " and *^, also a pBeudo4Tiad.
Evidence of atomicity i
Titanoas oxide, Ti"0.
Titanic tetrachloride, Ti'^Cl*.
iTiCI
Tin''
History. — ^Titanium was discovered by Gregor id 1789.
Occurrence. — ^Titanium is one of the rarer elements. It is never
found in the free state. As titanic anhydride (TiO,) it occurs in three
rare minerals — rutile, anatase, and brookite — and as ferrous titanate
(TiOFeo'') in titaniferous iron ore.
Preparation. — 1. Metallic titanium is most readily obtained by heat-
ing potassic titanofluoride with potassium in a covered crucible :
TiK,F. + 2K, = Ti H- 6KF.
Potaseic Potassic
titanofluoride. flaoride.
On dissolving the product of the reaction in water the titanium remains
as a gray amorphous powder.
2. It may also be obtained in the form of prismatic crystals by heat-
ing sodium in the vapor of titanic chloride :
TiCl, + 2Na, = Ti + 4NaCl.
Titanic chloride. Sodic chloride.
Properties. — Amorphous titanium forms a gray powder which, when
heated in the air, or when thrown into a flame, burns with brilliant
scintillations, forming titanic anhydride. At ordinary temperatures it
does not decompose water, but at 100® C. hydrogen is evolved and
titanic acid is formed :
Ti + 30H, = TiOHo, + 2H^
Water. Titanic acid.
It dissolves in hydrochloric and dilute sulphuric acids with evolution
of hydrogen and formation of titanous salts.
The following are the names and probable formulse of the chief com-
pounds of titanium :
CI
Titanic tetrachloride, TiCl^. CI— Ti— CI.
CI
OOMPOT7KDS OF TITANIUM. 331
a CI
Dititanic hezachloride, < TiCi'' ^^ — "^^ — ^' — ^^"
CI CI
Titanous oxide, ....... TiO. Ti=0.
Titanic oxide or anhydride (Rotile, 1 m-Q
Anatase, Brookite), / '*
O
II
Titanic acid, TiOHo^ H— O— Ti— O— H.
Titanic sulphide, TiS'V
Ti
Titanic dinitride, lX'\Tu N N.
N
Trititanic tetranitride, Ti^N'",. N=Ti Ti Ti=N.
Ill
N
COMPOUNDS OF TITANIUM WTTH CHLORINE.
Titanic Chloride, TiCl^.
Moleoular weight = 190. Molecular volume I \ \- 8p. gr. of liquid 1.76.
Boik at 136° C. (276.8° F.).
This substance is prepared by heating a mixture of titanic anhydride
and finely divided carbon in a current of chlorine :
TiO, H- 2C H- 2C1, = TiCl^ + 200.
Titanic Titanic Carbonic
anhydride. chloride. oxide.
It is a colorless strongly fuming liquid, which combines with a small
quantity of water to form a crystalline compound, but is decomposed
by an excess of water with separation of titanic acid.
{TlCl
MQi't is formed when a mixture of the yapor of the tetra-
chloride with dry hydrogen is passed through a red-hot tube:
2TiCl4 + H, = {^cl; + 2Ha.
Titanic Dititanic
chloride. hezachloride.
It forms dark violet scales, which cannot be re-sublimed without decomposition. It is
deliquescent, and dissolves in water to form a violet solution, which absords oxygen
from the air, and becomes colorless.
332 IKOBGANIG CHEHISTBT.
COMPOUNDS OF TITANIUM WITH OXYGEN AND HTDROXTL.
TUanouB oxides TIO, has not been prepared in a state of parity. A hydrate, which
has also not been isolated, is formed as a black precipitate when ammonia is added to
the solution of a titanoas salt prepared by dissolving titaninm in a dilate acid. On
boiling the liquid with the precipitate, the color of the latter chan^ to blue and ulti-
mately to white, the oxide having been converted into titanic acid at the expense of
the oxygen of the water, whilst hydrogen is evolved.
Titanic oxide or anhydride, TiO,. — ^The hydrate of this oxide,
ietrabasic titanic (midy TiHo^, is obtained as a white precipitate when
ammooia is added to a solution of titanic chloride. This hydrate pos-
sesses both basic and acid properties, combining both with acids and
with alkalies. When dried in vacuo, it parts with the elements of one
molecule of water, and is converted into the acid TiOHo,. At a higher
temperature the rest of the water is eliminated, and titanic anhydride is
left as a white amorphous powder, which on ignition becomes denser,
and of a dark reddish-brown color. Titanic anhydride occurs in nature
as rti^ife, crystallizing in reddish-brown quadratic prisms of sp. gr. 4.3;
as analase in quadratic pyramids, irreducible to the forms of rutile,
and having a sp. gr. of 3.9 ; and as brookite in rhombic crystals of 4.1
sp. gr. Titanic anhydride is thus trimorphous. It may be obtained
artificially in the same forms by passing a mixture of hydrochloric acid
and steam over heated titanofluoride. At very high temperatures rutile
is formed ; at temperatures between the boiling-points of zinc and cad-
mium, crystals of brookite are deposited; whilst below the boiling-
point of cadmium anatase is obtained. Titanic anhydride is insoluble
in alkalies, and in all acids except hydrofluoric and hot concentrateil
sulphuric. The tUanatea have not been thoroughly investigated. All
the normal titanates are insoluble in water.
DUitanie trioxidt^ ^2^8» ^ obtained as a black powder by igniting titanic anhydride
in a current of hydrogen. When heated strongly in air it is oxidiwd to titanic anhy-
dride. Hydrochloric and nitric acids are without action upon it. Sulphuric acid dis-
solves ity yielding a violet solution.
COMPOUND OF TITANIUM WITH SULPHUR.
ZYtonie sulphide^ T1S^^,« is formed when a mixture of the vapor of titanic chloride
with dry sulphuretted hydrogen is passed through a red-hot tube :
TICU + 2SH, = TIS'% + 4Ha.
Titanic Sulphuretted Titanic Hydrochloric
chloride. hydrogen. sulphide. acid.
It forms brass-yellow scales resembling mosaic gold. It burns when heated in the air,
yielding titanic and sulphurous anhydrides. By exposure to moist air it is slowly de-
composed, with evolution of sulphuretted hydrogen.
COMPOUNDS OF TITANIUM WITH NITROGEN AND WITH NITROGEN
AND CARBON,
Titanic dinitridet ^N^^,Ti, is obtained by heating titanic anhydride in a current of
nitrogen :
mo, -f- 2NH, = Off'^Ti + 20H, + H,.
It is a dark violet-colored powder with a coppery tinge.
ZIBOONIUM. 333
A second nitride, TIJN4, iriiitanie teiranitnde, is obtained in the form of a copi)er-
colnred metallic mass when the doable compound of titanic chloride with ammonia
(TlCl4,4NH,) is heated in a current of gaseous ammonia :
8T1CU 4- 4irH, = TlaN^ + 12Ha.
Titanic Ammonia. Trititanic Hydrochloric
chloride. tetranitride. acid.
This compound was formerly mistaken for metallic titanium.
When trititanic tetranitride is strongly heated in a current of hydrogen, a third nitride,
TigNc, peiUoUitanic hexanUridet is proouced in the form of golden-yellow scales, with a
Btrone metallic lustre.
Alithe nitrides of titanium, when heated with easily reducible oxides, such as those
of copper, lead, and mercury, deflagrate brilliantly, the oxides undergoing reduction
to the metallic state.
Titanic ctanonitride. — TijNjCCN). — This remarkable compound, which was also
formerly mistaken for metallic titanium, is frequently found in blast-furnaces which
have been used for smelting titaniferous iron. It forms copper-colored metallic cubes,
which are hard enough to scratch glass, and possess a sp. gr. of 5.3. The prooess by
which this substance m formed may be imitated on a small scale by heating titanic an-
hydride, mixed with charcoal, in a current of nitrogen :
5010, 4- lie + 2N. = TiftNgfCN) -f lOCO.
Titanic Titanic Carbonic
anhydride. cyanonitride. oxide.
It is insoluble in acids. Heated in a current of steam it yields titanic anhydride,
ammonia, and hydrocyanic acid. Heated in chlorine, titanic and cyanic chlorides are
formed, whilst nitrogen is liberated.
General character ani> reactions op the tptanium oom-
POUNDB. — The titanous salta are unknown except in solution. With
alkaline carbonates they yield a black precipitate^ which becomes blue,
and ultimately white.
The alkaline titanatea are of a yellowish color. They are insoluble
in water, but soluble in hydrochloric acid. On boiling the hydroc*hlorio
acid solution, white titanic acid is precipitated ; ammonia produces the
same efTect. With microcosmic salt the titanates yield in the reducing
flame of the blowpipe a violet glass which becomes colorless in the
oxidizing flame.
ZntCONIUM, Zr.
Atomie weight = 90. Sp. gr. 4.15. Atomicity *\ Evidence of atom-
icUy:
Zirconic chloride, ZrCl^.
Zirconio fluoride, ZrF^.
Occurrence. — In combination with silicon and oxygen as zirconic
silicate, it forms the rare mineral, zircon^ SiZro*\
Preparation. — Zirconium is obtained by heating potassic zircono-
fluoride with potassium :
ZrK,F« + 2K, = Zr + 6KF.
Potassic Potassic
zirconofluorlde. fluoride.
On treating the mass with dilute hydrochloric acid the zirconium
remains behind as a black amorphous powder. By employing alumin-
334 INORGANIC CHEMI8TRT.
ium to reduce the potassic ziroonoflaoride the zirooniam may be obtained
in crystalline plates.
Reaction. — -When heated in air, amorphous zirconium readily bums,
forming zirconic oxide. The crystallized variety is oxidized only
superficially, even at a white heat, but may be burnt with the aid of
the oxyhydrc^en blowpipe.
Zirconic chloridt^ 2rCl4 (moUeidar volume FTD* is prepared like titanic chloride (p.
831). It 18 a white crystalline mass, which, when treated with water, yields an ozy-
chloride of the formula ZrOCls^SOH,. Zircorue bromidcj ZrBr^, is also known, and
reeemblee the chloride in its properties and reactions.
2^ircome fiuoiHde, ZrF^, is obtained by heating a mixture of zirconic oxide and fluor-
apar to whiteness in a current of gaseous hydrochloric acid :
aO, + 2CaF« -f 4Ha = ZrF^ + 2CaCl, + 20Hj.
Zirconic Calcic Hydrochloric Zirconic Calcic Water,
oxide. fluoride. acid. fluoride. chloride.
It is a colorless crystalline transparent subetanoe, volatile at a white heat, and solnble
in a solution of hydrofluoric acid. With the fluorides of the metal it forms ziroono-
fluorides, of which the most important is notaasic tirconojluoride, ZrK,F«.
Zirconic oxidt^ zireoniay ZrO,, is formea by burning zirconium in air, or by heating
the hydrate. It is a white infiisible powder. When heated in the oxyhydrogen blow-
pine It emits a yery intense light. Concentrated sulphuric acid dissolyes it with diffi-
culty. When fused with alkaline carbonates, it expels carbonic anhydride, and com-
bines with the base to form a zirconate. On treating the fused mass with water, the
urconate is decomposed, and tirconic hydrtUef ZrHOf, separates out as a yoluminous pre-
cipitate. The same precipitate is obtained by adding ammonia to the cold solution of
a salt of zirconium. It dissolyes readily in dilute acids. When ammonia is added to
a hot solution of a zirconium salt a hydrate of the formula ZrOHO| is precipitated.
This second hydrate dissolyes with diflSculty in acids.
The method of fusing with an alkaline carbonate is employed in obtaining ziroonia
from its minerals.
THORIUM, Th.
Atomic weight = 233.4. 8p.gr. 11 .23. AtomieUy l^
Occurrence. — This substance is of even rarer occurrence than zirconium. It is a con-
stituent of the yery rare minerals thorite, monamte, and euxenite.
Preparation, — It may be obtained as a dark graj powder by heating thoric chloride
with potassium or sodium.
The following are some of its principal compounds :
Thoric chloride, ThQ^.
Thoric fluoride, ThF4,40H,.
Potassic thorofluoride, ThK,Fc20H,.
Thoric oxide, thoria ThO^
Thoric silicate (iAorite), BlTho*%20H,.
PHOSPHORUS. 335
CHAPTER XXX.
PENTAD ELEMENTS.
Section I. {Continued, from Chapter XXVI.).
PHOSPHORUS, P,.
Atomic weight = 31. Molecular weight = 124. Molecular volume CD.
1 litre of phosphorus vapor weighs 62 criths. 8p. gr. 1.83. Fuses at
44-46° C. (111-118° F.). Boils at 290"" 0. (554° F.). Atom^vniy '",
and ^. Evidence of atomicity :
Phosphorous hydride, P'^Hj.
Phosphorous chloride, P^'Clj^
Phosphoric chloride, P^Clg.
Phosphonic iodide, P^H^I.
Phosphoric fluoride, P^Fj.
History. — ^Phosphorus was discovered in 1669 by Brand, an alche-
mist of Hamburg, who obtained it by evaporating urine to dryness,
and distilling the residue with sand. The process was kept secret; but
in 1680 Boyle succeeded in preparing phosphorus, employing the same
method. In 1769 Gahn showed that calcic phosphate is a constituent
of bones, and in 1771 Scheele published a method of obtaining phos-
phorus from this source.
Occurrence, — Phosphorus is never found in the free state in na-
ture. It generally occurs combined with oxygen and a metal to form
a phosphate. The principal naturally occurring phosphates are 08-
• PO
ieolile {esiramadurite, sombrerite) or caicic phosphaie, pQCao",, and
apatite or calcic chhrophosphatey (POy^CeLO^'J^OCaGl). Calcic phos-
phate is widely distributed in small quantities as a constituent of the
primitive rocks, by the disintegration of which it passes into the
soil. From the soil the phosphorus is absorbed by plants, where it
accumulates chiefly in the seed. From plants it passes into the bodies
of animals, in which it is found in still greater quantity. Calcic phos-
phate forms the chief inorganic constituent of the bones, whilst phos-
phorus in complex organic combinations is always present in the 'sub-
stance of the nerves and brain, and in smaller quantity in the other
tissues. In the slow oxidation of the living animal substance which is
constantly going on, the phosphorus is eliminated in the urine as phos-
phates of sodium, potassium, and magnesium.
Preparation. — 1. Calcined bones, which consist of calcic phosphate
with a slight admixture of calcic carbonate, are digested with sufficient
sulphuric acid to decompose the whole of the carbonate and two-thirds
of the phosphate. In this way the tricalcic diphosphate is converted
into tetrahydric calcic diphosphate :
PACao'', + 2SO,Ho, = PAHo.Cao'' + 2SO,Cao''.
Tricaldc diphos- Bulphurio Tetrahydric calcic Calcic sulphate,
phaie (Bone-aah). acid. diphosphate.
336
INORGANIC CHEMISTRY.
The tetrahydric calcic diphoephate is extracted with water from the
calcic sulphate, evaporated to a syrup, mixed with charcoal, and heated
to dull redness in an iron pot, stirring all the time. Under the influ-
ence of heat the tetrahydric calcic diphosphate parts with water, and is
converted into calcic metaphosphate, which is thus obtained intimately
mixed with charcoal :
PAHo.Cao'' = PACao'' + 20H^
Tetrahydric calcic Calcic Water.
diphoBphate. metaphosphate.
The mixture is then transferred to earthenware retorts and heated to
bright redness, when the following reaction takes place :
SPACao'' + IOC = PACao'', + lOOO + P,.
Calcic Tricalcic Carbonic
meiaphoBphate. diphosphate. oxide.
The phosphorus distils over, and is collected under water, whilst the
carbonic oxide escapes carrying with it a small quantity of phosphorus
Fio. 46.
vapor, which causes it to inflame on coming in contact with the air.
The apparatus employed in this distillation varies in different factories;
one form is shown in Fig. 46.
PHOSPHORUS. 337
The explanation of the process is as follows : Normal salts of tribasic
phosphoric acid are not acted upon when heated with charcoal^ but
phosphoric anhydride, under these circumstances, is readily reduced.
If we r^ard a salt as a compound of anhydride and base, it will be
seen that the salts of monobasic phosphoric acid contain more anhydride
in proportion than the tribasic acid. Thus :
3PACao" = PaOjCao'', + 2PA.
The reduction takes place to the extent of the excess of anhydride above
what is necessary for the formation of tricalcic diphosphate. Accord-
ingly, ia the above process two-thirds of the phosphorus present are
reduced.
Sombrerite, an impure calcic phosphate found in the West Indies, is
frequently substituted for bone-ash.
2. If sand be added to the mixture in the above distillation, calcic
silicate is formed, and the whole of the phosphorus is expelled (Woh-
ler):
2PACao'' + IOC + 2810^ = 2SiOCao'' + lOOO + P,.
Calcic Silicic Calcic Carbonic
metaphoephate. anhydride. silicate. oxide.
3. If a mixture of bone-ash and charcoal be heated to redness in a
current of gaseous hydrochloric acid, the whole of the phosphorus is
liberated, and calcic chloride remains (Cary-Montrand) :
PACao'', H- Cs + 6HC1 = 30aCl, + 80O + 3H, + P,.
Tricalcic Hydrochloric Calcic Carbonic
diphosphate. acid. chloride. oxide.
This process has not, however, proved successful on a manufacturing
scale.
The crude phosphorus is always contaminated by particles of charcoal
and other impurities carried over during the distillation. From these
it is freed, either by fusing it under water and pressing it through
wash-leather bags, or by partially oxidizing it with a mixture of po-
tassic dichromate and sulphuric acid. The oxidation is attended with
efiervescence, which causes the impurities to rise to the surface, leaving
the phosphorus pure. The purified phosphorus is cast into sticks.
Properties. — Phosphorus exists in several allotropic modifications.
Common or octahedral phosphoruSy the modification obtained in the
processes above described, is, when freshly prepared, a colorless trans-
parent solid. Very frequently, however, it displays a faint yellowish
tinge due to the presence of some impurity. It has a sp. gr. of 1.83.
It is a non-conductor of electricity. At ordinary temperatures it may
be cut with a knife like wax, but about 0^ C. it becomes brittle. At
a temperature of 44-45° C. (111-113° F.) it fuses to a coloriess oily
liquid, which readily retains its fluidity several degrees below its so-
lidifying point. It boils at 290° C. (564° F.). The molecular weight
of phosphorus, deduced from the vapor-density, is 124, showing that
338 INORGANIC CHEMISTRY.
the molecule of phosphorus consists of four atoms, aud this tetratomic
molecule does not break up even at a temperature of 1040° C. (1840°
F.) (Deville and Troost) ; but at a higher temperature, the vapor-
density has a value lying between the values required for Pj and P| re-
spectively, showing that a partial dissociation has taken place (Victor
Meyer).
Phosphorus is a very inflammable substance, igniting in the air a few
d^rees above its fusing-point For this reason it must always be pre-
served and cut under water. Under the influence of air and light it
becomes covered, when kept under water, with a white opaque crust,
due to a partial oxidation. It ought therefore to be kept in the dark.
When exposed to the air at ordinary temperatures phosphorus under-
goes slow oxidation, and gives off a white vapor, which has a powerful
odor of garlic. In a dark room both the phosphorus and the vapor are
luminous with a greenish-white light. At a few d^rees below 0° C.
the oxidation and the luminosity cease. In pure oxygen under ordi-
nary pressures phosphorus is not luminous at temperatures below 15°
C. ; but by rarefying the oxygen, or adding some inactive diluent, such
as nitrogen, hydrc^en, or carbonic anhydride, the phosphorus again
becomes luminous. The luminosity of phosphorus in air is also pre-
vented by the presence of minute traces of certain gases or vapors, such
as defiant gas, sulphuretted hydrogen, and turpentine.* When phos-
phorus is exposed to the air in large quantities, the heat of oxidation is
frequently sufficient to melt, and finally to ignite, the mass. The same
effect is produced by exposing phosphorus to the air in a finely divided
condition, so as to increase the oxidizable surface. This may be shown
by pouring a solution of phosphorus in carbonic disulphide ui)on filter-
ing paper, and allowing the liquid to evaporate. In the dark the
paper becomes brightly luminous, and at last bursts into flame.
Phosphorus is insoluble in water, slightly soluble in ether, turpen-
tine, and benzine, readily soluble in disulphur dichloride, phosphorous
chloride, and carbonic disulphide. One part by weight of the latter
solvent dissolves from seventeen to eighteen parts of phasphorus. By
the spontaneous evaporation of this solution it may be obtained in trans-
parent crystals belonging to the regular system, generally octahedra or
rhombic dodecahedra. When phosphorus is kept in the dark in sealed
vacuous tubes, it spontaneously sublimes, and is deposited on the sides
of the tubes in very lustrous and perfect crystals.
Phosphorus may be finely granulated by melting it under water, and
agitating until it solidifies again. The addition of a small quantity of
urea to the water prevents the adhesion of the granules, and by this
means a higher degree of subdivision is attained.
Phosphorus is an exceedingly poisonous substance. Even the fumes
have a very deleterious action when inhaled, producing caries of the
bones of the jaw.
Red or Amorphous Phosphorus, — This variety was discovered by
Schrotter in 1845. It is formed when ordinary phosphorus is exposed
* According to Chappuis, the luminosity of phosphorus depends upon the presence
of ozone. Sul^tances which destroy ozone prevent the luminosity.
PH06PHORT7S. 339
to the action of the heat or light in an atmosphere devoid of oxygen.
It is beet prepared by heating phosphorus for some time in a closed
vessel to 230-250'' C. (446-482° F-). On a manufacturing scale,
iron vessels are employed for this purpose^ and it is not necessary to
fill the apparatus with any artificial atmosphere, as the oxygen is
speedily removed from the air by the combustion of a small portion of
the phosphorus. Any rise of temperature above 250° C. must be care-
fully avoided, since at 260° C. (500° F.) amorphous phosphorus is re-
converted into the ordinary modification, the change being accompanied
with evolution of heat and taking place, in the case of large quantities,
with explosive violence. Amorphous phosphorus is, however, formed
when ordinary phosphorus is heated under pressure in closed iron
vessels to 300° C. (572° F.), the change taking place in a few minutes.
When ordinary phosphorus is heated with a small quantity of iodine
or selenium, an iodide or selenide is formed, and the excess of phos-
phorus ia instantaneously converted into the red variety.
Amorphous phosphorus, prepared by any of the above methods, in-
variably contains a small quantity of white phosphorus, the presence of
which renders the product dangerously inflammable. From this it may
be freed by grinding the crude amorphous phosphorus under water, and
subsequently treating it with carbonic disulphide, which dissolves the
unaltered phosphorus, or still more advantageously by boiling with
caustic soda (see Phosphoretted Hydrogen). Thus purified, amorphous
phosphorus forms a reddish-brown powder of sp. gr. 2.15. It is de-
void of taste and smell, is not poisonous, may be exposed to the air for
any length of time without undergoing change, and is not luminous in
the dark. When heated it does not fuse, and inflames in the air only
at a temperature of 260° C. (500° F.), being converted at the same
time into ordinary phosphorus. It is insoluble in the solvents which
dissolve ordinary phosphorus, such as carbonic disulphide and sulphur
chloride. It conducts electricity feebly.
RhombohedraJ Phosphorus, — This variety is obtained when phos-
phorus is heated with metallic lead in sealed tubes for eight or nine
hours to a temperature below redness. On dissolving the cooled lead
in dilute nitric acid, small, well-defined, violet-black rhombohcdra,
having a sp. gr. of 2.34, remain. This modification may also be ob-
tained by heating amorphous phosphorus under pressure to 580° C.
(1076° F.).
According to some chemists red phosphorus and rhombohedral phos-
phorus are identical.
A fourth modification, obtained as a black mass by quickly cooling
melted phosphorus, has been described ; but it has been shown that
this substance is produced only when metals are present, the color being
due to the formation of metallic phosphides.
Eeadions. — Owing to its affinity for oxygen, phosphorus acts as a
powerful reducing agent. Platinum, gold, silver, and copper are de-
posited in the metallic state, when white phosphorus is left in contact
with the solutions of their salts. When sodic carbonate is heated to
redness with phosphorus, the carbonic anhydride is reduced and car-
bon is set free. When dry finely divided phosphorus is mixed with
340 IKOBGAKIC GHEMIBTBT.
substanoee which readily part with oxygen, each as potaasic chlorate or
metallic peroxides, very slight friction is sufficient to cause the explo-
sive oxidation of the phospTiorus.
The other reactions of phosphorus will be described in connection
with its compounds.
Uses, — Phosphorus is employed chiefly in the manufacture of ladfer
matches. In the commoner sorts, the matches are tipped first with
sulphur, and then with a mixture of phosphorus and potassic chlorate
made into a paste with glue. They ignite by friction on any rough
surface. The sulphur serves to transmit the combustion from the phos-
phorus to the wood. Nitre is frequently substituted for potassic chlo-
rate, as the matches thus prepared ignite more quietly ; whilst, in order
to get rid of the disagreeable smell of burning sulphur, this substance
is replaced by paraffin. In the safety matehes the phosphorus is sepa-
rated from the other inflammable materials. The matches are tipped
with a mixture of potassic chlorate, potassic dichromate, red lead, and
antimonious sulphide, and are ignited by friction on a prepared surface
coated with amorphous phosphorus and antimonious sulphide. These
matches do not readily ignite on an unprepared surface, but by rubbing
them rapidly over a smooth slate, or a sheet of ground glass, they may
be inflamed.
COMPOUNDS OF PHOSPHORUS WITH HYDROGEN.
Phosphorus forms with hydrogen three compounds. These cannot
be obtained by the direct combination of their elements.
p/p/i
Liquid " « . . . . 'f '',H,.
Gaseous *' " .... PH3.
OASEOUS PHOSHPOBETTED HTDBOOEN.
Pkoaphine.
H
PH,. I
H— P— H
Molecular weight = 34. Molecular volume CD. 1 litre weighs 17 criihs.
Preparation, — 1. Phosphoretted hydrogen may be obtained by
heating hypophosphorous acid:
2PHH0, = PH3 + POH03.
HypophoBDhorons Phosphoretted Phoephoric
acia. hydrogen. acid.
2. A similar decomposition occurs when phosphorous acid is heated :
GASEOUS PH06PH0BETTED HYDBOGEN. 341
4PHo, = PHs + SPOHos.
Phosphorous Phosphoretted Fhosphoric
acid. hydrogen. acid.
3. When phosphorus is heated with a solution of sodic or potassio
hydrate, phosphoretted hydrogen is evolved, whilst an alkaline hypo-
phosphite remains in the retort:
30NaH + P, + 30H, = SPHHoNao + PH,.
Sodic hydrate. Water. Sodic Phosphoretted
hypophosphite. hydrogen.
The gas prepared by this process contains free hydrogen and liquid
phosphoretted hydrogen, the presence of this latter substance render-
ing the gas spontaneously inflammable in contact with air. By employ-
ing an alcoholic solution of caustic alkali, a gas is obtained which does
not inflame spontaneously, the liquid phosphoretted hydrogen remain-
ing in this ca^ dissolved in the alcohol.
4. Phosphoretted hydrogen is evolved when calcic phosphide is
treated with water:
PjCa, + 60H, = 2PHs + 30aHoj.
Tricalcic Water. Phosphoretted Calcic
diphosphide. hydrogen. hydrate.
The gas is also in this case contaminated with the vapor of liquid
phosphoretted hydrogen.
5. Pure phosphoretted hydrogen is most readily obtained by allow-
ing concentrated caustic potash to drop very gradually upon phosphonio
iodide (q^v.) contained in a flask :
PHJ + OKH = PH3 + KI + OH,.
hoephonic Potassic Phosohoretted Potassic Water,
iooide. hydrate. hyarogen. iodide.
Fropertiea — ^Phosphoretted hydrogen is a colorless gas possessing an
odor resembling that of garlic. It is combustible in air or oxygen,
burning with a very brilliant white light, and evolving a cloud of phos-
phoric acid. When pure it is not spontaneously inflammable ; but the
presence of a small quantity of the vapor of liquid phosphoretted
hydrogen (T^jH^) in the gas suffices to impart to it. this property, of
which it may again be deprived by leaving it in contact with finely di-
vided charcoal, which absorbs the liquid compound, or by exposing it
to the action of sunlieht, by which the liquid compound is decomposed.
On the other hand, the pure gas may be rendered spontaneously inflam-
mable by the addition of a trace of nitrous anhydride.
If the pure gas be mixed with oxygen no action is observed ; but, on
suddenly rarefying the mixture, combination takes place with explosion.
This phenomenon is possibly allied to that of the luminosity of phos-
phorus in rarefied oxygen.
If the spontaneously inflammable gas be allowed to bubble through
342 INOBOANIC CHEMI8TRT.
water^ each bubble, on escaping into the air and inflaming, forms a
smoke-ring of phosphoric ^cid.
Phosphoretted hydrogen is a highly poisonous gas. When inhaled,
even in a very diluted condition, it produces difficulty in breathing, and
ultimately death.
Reactions. — 1. By combustion in oxygen it yields metaphosphoric
acid and water :
PH, + 20, = POjHo + OH,.
Phosphoretted Metaphosphoric Water,
hydrogen. acid.
2. In contact with chlorine it forms phosphoric chloride and hydro-
chloric acid :
PH3 + 4C1, = PCla + 3HC1.
Phosphoretted Phosphoric Hydrochloric
hydrogen. chloride. acid.
3. When passed through a solution of cupric sulphate, it produces a
black precipitate of cupric phosphide :
2PHs + SSOjCuo'' = PjCu", + 380,Ho^
Pho8phoretted Capric Cupric Siripharic
hydrogen. sulphate. phosphide. acid.
4. When passed through a solution of argentic nitrate, metallic
silver is deposited, whilst nitric and phosphoric acids are formed :
PH, + 8N0,Ago + 40H, = POH03
Phosohoretted Argentic Water. Phosphoric
hyarogen. nitrate. aad.
+ 4Ag, + 8NO,Ho.
Nitric acid.
5. It unites directly with hydrochloric, hydrobroraic, and hydriodic
acids, when the dry gases are brought together, forming compounds
analogous to the haloid salts of ammonium :
PH3 + HBr = PH,Br.
Phosohoretted Hydrobromic Phosphonic
hyarogen. acid. bromide.
Phosphoretted hydrogen and hydrochloric acid unite only under the
influence of pressure and cold (Ogier).
Phosphonic iodide is also formed by the action of iodine on phos-
phoretted hydrogen. The reaction takes place in two stages:
PH, + 31, = PI, + SHI;
phoruB Hydriod
aide. acid.
and
Phosphoretted .Phosphonu Hydriodic
hydrogen. iodi<f
PH3 + HI = PHJ.
Phosphoretted Hydriodic Phosphonic
hyarogen. acid. ioaide.
Phosphonic iodide is, however, most conveniently prepared by the
following method (A. W. Hofmann) : 10 parts of phosphorus are dis-
LIQUID PH06PHOR£TT£D HYDROGEN. 343
solved in carbonic disulphide in a retort, and 17 parts of iodine are
gradually added, cooling during the operation. The carbonic disul-
phide is then distilled off, a stream of dry carbonic anhydride being
finally passed through the apparatus to remove the last traces of the
carbonic disulphide, and 6 parts of water are very slowly added by
means of a dropping-funnel. A violent reaction takes place, the heat
of which volatilizes the phosphonic iodide as it is formed. Towards
the close heat is applied to the retort. A slow stream of carbonic
anhydride must be passed through the apparatus during the whole
operation, in order to prevent the entrance of air, which might other-
wise occasion an explosion. The phosphonic iodide condenses in large
lustrous quadratic crystals in a wide tube attached to the neck of the
retort.
The following equation expresses the reaction :
13P + 91 + 21OH2 = 7PHJ + 2HI + 3PAH()4.
Water. Phoephonic Hydriodic Pyrophosphoric
iodide. acid. acid.
Phosphonic iodide is employed in the laboratory as a powerful re-
ducing agent, available particularly at high temperatures.
ChmposUion. — When a series of electric sparks is passed through
phosphoretted hydrogen, it is gradually decomposed into its elements.
The spark should pass between carbon {)oints, since, when platinum is
employed, a fusible phosphide of platinum is formed, which melts,
putting an end to the experiment. It is found that two volumes of
phosphoretted hydrogen yield three volumes of hydrogen when thus
treated. Expressed in litres :
2 litres of phosphoretted hydrogen weigh ... 34 criths.
Deduct weight of 3 litres of hydrogen, ... 3 "
There remain, 31 "
which is the weight of i litre of phosphorus vapor. Therefore J vol-
ume of phosphorus vapor in combination with 3 volumes of hydrogen
yields 2 volumes of phosphoretted hydrogen, or 31 parts by weight of
phosphorus combine with 3 parts by weight of hydrogen to form this
compound, and its formula is, therefore, PH3.
LIQUID PHOSPHORETTED HTDROOEN.
H H
T^H,or{|^;. L|
H H
Molecular weight = 66. Molecular volume CD. 1 litre of (he vapor
toeighs 33 criths.
Preparation. — This compound is formed along with gaseous phos-
phoretted hydrogen by the action of water at a temperature of 60-70^
344 IKOROAKIC CHEHISTBY.
C. (140-158° F.) on calcic phosphide obtained by passing the vapor of
phosphorus over lime heatei to redness (see Caleie Ph^hide). This
latter substance probably contains, in addition to calcic pyrophosphate,
a mixture of dicalcic (T",Ca",) and tricalcic diphosphide (PjCa"^, and
from these two phosphides the liquid and gaseous phosphoretted hydro-
gens are respectively formed :
T'',Ca", + 40H, = T'',H, + 20aHo,.
Dicalcic Water. Liquid phoB- Calcic
diphoBphide. phoretted hydrogen. hydrate.
(For the formation of gaseous phosphoretted hydrogen from tricalcic
diphosphide, see p. 341.) The gas evolved is passed through a U-tube
immersed in a freezing mixture, and in this the liquid compound con-
denses.
Properties, — It is a colorless, powerfully refracting liquid which
inflames instantly in contact with air.
Beaotion. — By exposure to sunlight, or by contact with hydrochloric
acid, it is decomposed into solid and gaseous phosphoretted hydrogens :
5'P",H, = 6PH, -}- {pjpi^gp?
Liquid phospho- Gaseous phoepho- Solid phospho-
retted hydrogen, retted hydrogen. retted hydrogen.
The hydrochloric acid suffers no change. A very small quantity of
the acid therefore suffices to decompose a practically unlimited quantity
of the phosphorus compound.
SOLID PHOBPHORBTTBD HYDROaBN.
rp(p///H)//
Moleeular weight = 126 ?
PrejMraiion. — Solid phosphoretted hydrogen is obtained by dissolving calcic phos-
phide in concentrated hydrochloric add, or By the action of light upon the liquid phos-
phoretted hydrogen.
Properties.— It forms a yellow powder which turns darker on exposure to lieht
When strongly heated in an atmosphere of carbonic ayhydride, it is aecomposed into
its elements. It is doubtful whether this substance has ever been prepared in a state
of purity, and its exact composition is uncertain.
COMPO UNDS OF PHOSPHOR US WITH THE HALOGENS.
Phosphorous chloride, PClj.
Phosphoric chloride, PCI5.
Phosphorous bromide, PBr,.
Phosphoric bromide, PBr^.
(PI
Diphosphorous tetriodide, < pj' .
Phosphorous iodide, PI,.
Phosphoric fluoride, PF^,
PHOBPHOROnS OHLOBIBE — ^PHOSPHORIC CHLORIDE. 345
PHOSPHOROUS CHLOBIDE.
CI
CI— P— CI
PCI,. I
-P-
MoUcfular weight = 137.5. Molecular volume I I I. 1 litre of phos-
phorous trvMoride vapor weighs 68.75 crUhs. Sp.gr. 1.613. Boils at
76° C. (168.8° F.).
Preparation. — This compound is obtained by heating amorphous
phosphorus in a retort while a current of dry chlorine is passed over it
through the tubulure. The phosphorous chloride distill^ off as fast as
it is formed^ and collects in a cooled receiver. In order to free it from
pentachloride, it is redistilled over ordinary phosphorus.
Properties. — Phosphorous chloride is a colorless fuming liquid with
a very pungent odor. It does not solidify at — 115° C. ( — 175° F.).
Reactions. — 1. With water it yields hydrochloric and phosphorous
acids :
PCI, + 30H, = 3HC1 + PHo,.
PhoBphorouB Water. Hydrochloric Phoephoroos
chloride. acid. acid.
2. With sulphuretted hydrogen it forms hydrochloric acid and
phosphorous sulphide :
2PC1. + 3SH, = 6HC1 + PjS'V
Phosphorous Sulphuretted Hydrochloric Phosphorous
chloride. hydrogen. acid. sulphide.
PHOSPHO&IO CHLOBIDE.
CI
I
PCi^. CI— P— CI
♦ di ci
Molecular weight = 208.5. Molecular volume 1 I L 1 litre of undis-
sodated phosphoric chloride vapor weighs 104.25 oriihs. Volatilizes
below 100° C.
Pr^araiion. — Phosphoric chloride is formed by the direct union of
the trichloride with chlorine. A stream of dry chlorine is passed on to
the surface of the trichloride contained in a flask cooled by water.
Great heat is evolved in the reaction. The liquid ultimately solidifies
to a crystalline mass.
Properties. — Phosphoric chloride is a crystalline powder with a faint
yellowish tinge. It fumes in contact with moist air^ and possesses a
846
IKOBOANIC CHEMISTRY.
very irritating odor. It sublimes readily, but cannot be fused under
ordinary pressure. In a sealed tube, under the pressure of its own
vapor, it fuses at 148° C. (298.4° F.), and on cooling, solidifies in pris-
matic crystals. At higher temperatures it possesses a vapor-density
only half as great as is required for the molecular weight corresponding
to the formula PClj, the reason of this being that the compound under-
goes dissociation into PClj and CI, (Introduction, p. 64). This disso-
ciation is only partial at lower temperatures, and its progress may be
traced by means of the change of color which the vapor undergoes as
the temperature rises, phosphoric chloride yielding a colorless vapor
which becomes yellowish-green as the proportion of free chlorine
increases. This dissociation is to a great extent checked by allowing
the phosphoric chloride to volatilize in an atmosphere of phosphorous
chloride vapor, and in this way Wurtz determined the vapor-density
of phosphoric chloride with a result closely agreeing with the normal
density required for the formula PClj.
Reactions. — 1. A small quantity of water converts it into phosphoric
oxytrichloride with formation of hydrochloric acid :
PCI5 + OH2 = POCI3 + 2HC1.
Phosphoric Water. Phosphoric Hydrochloric
chloride.
oxytrichloride.
acid.
2. With an excess of water, it yields phosphoric and hydrochloric
acids:
PCI5 + 40H, = POHo, + 5HCI
Phosphoric Water. Phosphoric Hydrochloric
chloride. acid. acid.
3. By its action on alcohols and acids, the chlorides of the radicals
of the alcohols and acids are obtained, thus :
/OH,
\ CHjHo
Etbylic
alcohol.
/OH,
tOOHo
Acetic
acid.
+
PCI, =
Phosphoric
chloride.
+ PCI.
Phosphoric
chloride.
/OH,
1 0H,C1
Ethylic
chloride.
= {??»
OOCl
Acetylic
chloride.
+ HCl + POCl,.
Hydrochloric
acid.
Phosphoric
oxytrichloride.
+ HCI + POCly
Hydrochloric Phosphoric
acid. oxytrichloride.
4. When phosphoric chloride acts on organic compounds containing
oxygen attached with both its bonds to the same atom of carbon, a
direct exchange of one atom of oxygen for two atoms of chlorine is
effected:
/0.H,
tCOH
Benzaldehyde.
+ PCI.
= {?•-?•-
Phosphoric
chloride.
CCljH
Benzalchloride.
+ POCl,.
Phosphoric
oxytrichloride.
PH06PH0BIC FLUORIDE. 347
These properties render phosphoric chloride an invaluable agent in
the investigation of organic compounds.
Phosphorowbromde.'PBTf {moleeviar volume FJ^), is prepared bv the action of bro-
mine on amorphous phosphorus. It forms a faming colorless liquid of sp. gr. 2.925 at
0** C, boiling at 175*^ C. (347° F.). Its chemical behavior is analogous to that of the
chloride.
Phosphoric bromid€, PBr^, is obtained by the direct union of the tribroroide with
bromine. It is a yellow crystalline solid which melts to a red liquid, and is decom-
posed at 100° C. into the triWomide and free bromine. Its reactions resemble those of
the corresponding chloride. ^^
Diphosphorous tetriodidey 'V^^ (mol^etdar volume I I |), is prepared by dissolying
5 parts of phosphorus in carbonic disulphide, and gradually adaing 41 parts of iodine,
cooling well with water during the operation. On concentrating the solution by distill*
ing on the carbonic disulphine, diphospliorous tetriodide crystallizes out in orange-
colored prisms fusing at 110° C. (230° F.). Water decomposes it with formation of
h^driodic and phosphorous acids and liberation of phosphorus in the amorphous con-
dition :
B'T'\J^ H- 120H, = 12HI + 4PHo, + P,.
Diphoephorous Water. Hydrlodic Phosphorous
tetriodide. acid. acid.
Phosphorous iodide^ Pis, is obtained in the same manner as the foregoing compound,
but employing 12 parts of iodine to 1 of phosphorus. It forms dark-red, deliquescent
crystals, fusing at 55° G. (131° F.). It cannot be distilled without decomposition. By
the action of water it yields hydriodic and phosphorous acids :
PI, -f 30H, = SHI -h PHo,.
Phosphorous Water. Hydriodic Phosphoroos
iodide. acid. acid.
PHOSPHOBIC FLUORmS.
F
PF«. F— P— F
/\
Molecular weight = 126. Molecular volume CD. 1 litre ofphoaphorio
fluoride weighs 63 crUhs.
Preparation, — ^This compound is formed when arsenious fluoride is
added to phosphoric chloride :
SAsFj + 3PC1, =
5A8C1, + 3PF,.
Arsenious Phosphoric
Arsenious Phosphoric
fluoride. chloride.
chloride. fluoride.
Properties. — Phosphoric fluoride is a colorless gas which fumes in
contact with moist air, and possesses a very irritating odor. It is not
inflammable. It is not decomposed by a series of electric sparks, either
when the pure gas is employed, or when it is mixed with oxygen or
hydrogen.
Recustions. — 1. Water decomposes it, forming phosphoric and hydro-
fluoric acids :
348
INORGANIC CHEBOSTBT.
PF, + 40H, = POHoj + 5HF.
Water. Phoephoric Hydrofluoric
Phoephoric
flaoride.
Phoephoric
acid.
acid.
2. It unites with dry atnmoniay forming a white solid compoand of
the formula p^PF^fiVHy
Phosphoric fluoride is particularly interesting as an example of the
union of pentadic phosphorus with five monad atoms to form a com-
pound capable of existing in the gaseous state, and even of sustaining
very high temperatures without dissociation.
COMPOUNDS OF PHOSPHORUS WITH OXYGEN AND
HYDBOXYL.
Hypophosphorous acid,
Phosphorous anhydride, . . ^2^3?
H
I
PHHo^ H— O— P— O— H
O O
II II
P— O— P?
Phosphorous acid, .... PHo,.
Phosphoric anhydride, • , "^fii*
Phosphoric acid (tribasic), . POH03.
Metaphosphoric acid (°io°0"\poH
basic), j ^ ^'
H
A
H— O— P— 0— H
O 0
II I
P— O— P
II I
o o
0
H— O— P— O— H
i
o
II
o
ooMPOCiire of PHoePHOBira with qztoen aitd hydboxtl. 349
O O
Pyrophoephoric acid (tetra- 1 p q go,. H-O-P-O-P-O-H
basic), J2S4
i A
Hexabasic phoBphoric acid^ . P^OyHo^.
Sodiam salt (Fleitmann and^j
Henneberg) {Hexasodio te- VP^OyNaOj.
irapho9phate)y j
o o o
Na-<)— P— O— P— O— P— O— P— O— Na
i i i i
Na Na Na Na
Dodecabasic phosphoric acid, PioOj^Hoia.
Sodium salt (Fleitmann ^
and Henneberg) (Dade- VPioOigNaOu.
casodic decaphosphaJte) . )
O
Na— O— P-
A
O
-O^P-
o
-O— P— O— Na
i
Phog)horo8opho8phoric acid Ip p,Ho,.
{HypopnogphoTw acta), • )
H
-P— O— P— O— P— O— H
350 INORGANIC CHEMIBTBY.
HYTOPHOSPHOROUS AOID.
PHHo^
Mbleeidar tDeighi = 66. Fuses at 17.4° C. (63.3° F.).
Preparation. — When phosphorus is heated with a solution of baric
hydrate, phosphoretted hydrogen is evolved and baric bypophosphite
is formed :
3BaHo, + 2P, + 60H, = ^J^JJ^o" + 2PH,.
Baric Water. Baric Phosphoretted
hydrate. hvpophosphite. hydrogen.
Any phosphoric acid which is formed at the same time combines with
the barium to form insoluble baric phosphate, which may be removed
by filtration. To the solution of baric bypophosphite a quantity of
dilute sulphuric acid exactly sufficient to precipitate the barium is
added, and in this way a solution of hypophosphorous acid is obtained.
The clear solution is evaporated over a flame, without, however, allow-
ing it to boil, until the temperature rises to 130° C. (266° F.). On
cooling to 0° C. the liquid thus obtained, hypophosphorous acid is de-
posited in crystals.
Properties, — Hypophosphorous acid forms white laminae fusing at
17.4° C. (63.3° F.).
Reactions. — 1. When strongly heated, hypophosphorous acid is de-
composed into phosphoric acid and phosphoretted hydrogen :
2PHH0, = POH03 + PHj.
Hypophosphorous Phosphoric Phosphoretted
acid. acid. liydrogen.
2. It readily absorbs oxygen from the air, and is ultimately con-
verted into phosphoric acid :
PHHoj + Oj = POH03.
Lospho
acid.
Hypophosphorous Phosphoric
acid.
Its affinity for oxygen causes it to act as a powerful reducing agent.
It precipitates many of the metals in the metallic state from the solu-
tions of their salts and, when heated with sulphuric acid, reduces it to
sulphurous acid, and even to sulphur.
Hypophosphites. — Hy|>ophosphorous acid is a very weak acid, and
although it contains two semi-molecules of hydroxyl, its acid power is
exhausted as noon as the hydrogen of one of these is replaced by a
metal. It therefore acts as a monobasic acid (cf. OrthophosphaJtes).
The. hypophosphites are all soluble in water, and some are crystallizable.
They exhibit the same reducing properties as the free acid, and undergo
a similar decomposition on heating.
PHOSPHOROUS ANHYDRIDE — ^PHOSPHOROUS ACID. 361
PHOSPHOROUS ANHTDRIDE.
PA(?).
Molecular weight =110 (?).
Preparation, — When phosphorus is gently heated in a slow current
of dry air, it burns with a greenish flame, forming a compound having
the composition of an anhydride of phosphorous acid.
Properties. — ^This compound is a white amorphous fusible powder
which may be sublimed. It has an odor of garlic.
Reactions. — By allowing the above compound to deliquesce, with
exclusion of oxygen, carefully avoiding any rise of temperature, a
yellow solution is obtained which has a neutral reaction, and may, by
dialysis, be proved to contain a colloid. If the solution be now heated,
a reddish substance of unknown composition separates, and the solution
contains phosphorous acid, PH03. When the so-called anhydride is
dissolved in water in the ordinary way, the temperature rises so high
as to bring about the above decomposition at once, and a solution of
phosphorous acid is obtained with separation of the reddish substance.
From the above, it is probable that the compound obtained when
phosphorus is burnt in a limited supply of air is not the true anhydride
of phosphorous acid, but a compound of the same composition with a
higher molecular weight (compare the molecular weights of arsenious
anhydride and antimonious anhydride). The hydrate which this com-
pound forms is neutral, and is therefore not phosphorous acid. The
colloidal condition of this hydrate also points to a higher molecular
weight. Phosphorous acid is formed only when this hydrate is decom-
posed by heating (Reinitzer).
PHOSPHOROUS ACID.
PH03.
Molecular weight = 82. Fuses at 70° C. (158° F.).
Preparation. — 1. Phosphorous acid is formed by the action of
water upon the so-called phosphorous anhydride as above described,
2. It may also be obtained by the spontaneous oxidation of phos-
phorus in moist air. In this process, however, a portion of the phos-
phorous acid always undergoes further oxidation to phosphoric acid.
Phoephorosophosphoric acid (q.v.) is also formed.
3. It is b^t obtained in a state of purity by the action of water on
phosphorous chloride (see p. 345). It is not necessary to prepare the
phosphorous chloride separately. Phosphonis is melted under water, and
a stream of chlorine is passed through the phosphorus, the phosphorous
chloride being thus decomposed by the water as fast as it is formed.
The reaction must be interrupted before all the phosphorus has disap-
4PHo, =
3PpHo,
Phosphorous
Phoephoric
acid.
acid.
362 INOBGAinC CHEHISTBT.
pearedy otherwise the excess of the chlorine in presence of water will
oxidize the phosphorous acid to phosphoric acid. The solution of Hydro-
chloric and phosphorous acids is evaporated, gradually raising the
temperature to 180^, by which means tne last traces of water are ex-
pelled.
Properties. — Phosphorous acid is a white, crystalline, very soluble
mass, fusing at 70° 0. (158° F.).
BeadUms,—!. Whefn heated above 180° C. (356° F.), it yields phos-
phoric acid and phosphoretted hydrogen :
+ PH,.
Phosphoretted
hjdiogen.
2. When treated with oxidizing agents, or when exposed to the air,
it yields phosphoric acid :
2PH03 + Oj = 2POH03.
PhoephorooB Phosphoric
acid. acid.
Owing to its affinity for oxygen it acts as a powerful reducing agent.
Solutions of silver salts, when warmed with it, deposit metallic silver;
mercuric chloride is reduced to mercurous chloride ; and cupric sulphate
yields a precipitate of cuprous hydride.
PhoaphUea, — Phosphorous acid is a tribasic acid ; but only the mono-
basic and dibasic salts are stable. The normal sodium salt, PNao^, is
obtained by dissolving phosphorous acid in an excess of sodic hydrate
and adding absolute alcohol to the solution, when the salt is precipi-
tated as an uncrystallizable syrup. It is decomposed by water (Zim-
mermann).
The phosphites are decomposed on heating, with evolution of phos-
phoretted hydrogen and formation of metaphosphates and pyrophos-
phates. The soluble salts have a reducing action.
PH08PH0BI0 ANHYDRIDE.
PA-
Molecular weight = 142.
PreparcUion. — Phosphoric anhydride is obtained by burning phos-
phorus in an excess of dry air or oxygen. A stream of air, dried by
passing through a U-tube containing pumice moistened with sulphuric
acid, is drawn by means of an aspirator, attached to the tube C, through
the three-necked globe (Fig. 47). Thoroughly dried phosphorus is in-
troduced through the tube B into the capsule A, and is then lighted by
touching it with a hot wire, the tube being then closed with a cork.
As soon as one piece of phosphorus is consumed, a fresh piece is intro-
duced in the same way, and is now at once ignited by the hot capsule.
HETAPHOePHORIO ACID.
353
The phosphoric anhydride collects in the globe, whilst any particles
which are carried off by the current of air are retained in the bottle.
Fig. 47.»
Properties, — Phosphoric anhydride is a white, voluminous, amor-
phous powder, which may be sublimed at a high temperature.
Sedction, — When brought in contact with water it hisses violently,
evolving great heat and dissolving with formation of metaphosphoric
acid :
PA + OH2 = 2P0aHa
Phoephoric Water. Metaphosphoric
anhydride. acid.
When exposed to the air it rapidly absorbs moisture and deliquesces.
It is the most powerful desiccating agent known, and is employed in
the laboratory for removing moisture from gases and liquids. Many
substances containing oxygen and hydrogen are decomposed by it, as it
abstracts these elements in the proportions necessary to form water.
METAPHOSPHOBIO AOID.
POjHo.
Molecular weight = 80.
Preparation. — 1. Metaphosphoric acid is formed by dissolving phos-
phoric anhydride in cold water (see above).
2. It noay be obtained by heating tribasic phosphoric acid to redness :
POHoj = PO2H0
Orthophoephoric Metaphosphoric
acid. acid.
23
+
OH2.
Water.
354 INOBOANIC CHEMIBTBT.
Properties. — Metaphosphorio acid forms a transparent vitreous quubb
which 18 readily soluble in water. It is fasible, and at a high tempera-
ture may be volatilized. Its solutions coagulate albumen.
Reaction, — In aqueous solul^oUy metaphosphorio acid is gradually
converted into tribasic phosphoric add :
PO,Ho + OH, = POHo^.
taphoBphoric Water. Orthophoflpho
acid. acid.
This change takes place rapidly on boiling.
MetaplZsphaies. — These salts may be ootained :
1. By igniting the dihydric phosphate of a fixed base:
POHogNao = POjNao + OHj,
Dihydric aodic Sodic Water,
phosphate. metaphosphate.
2. By igniting a monohydric phosphate which contains one atom of
a volatile base:
POHoNao(N^H,0) = PO,Nao + HH, + OH,.
Hydric sodic amnionic Sodic Ammonia. Water,
phosphate. metaphosphate.
3. By igniting a dihydric pyrophospliate :
PjOjHo^Nao, = 2POjNao + OH,.
Dihydric disodic Sodic Water,
pyrophosphate. metaphosphate.
Properties of the Metapho^haJtes. — The metaphosphates are remark-
able as existing in several distinct modifications, referable to different
polymeric varieties of metaphosphorio acid. Most of these acids form
double salts, and from the relative number of atoms of the two bases
contained in such a salt, the minimum molecular weight of the acid
may be determined. Thus, hexametaphosphoric aoict, P^OigHo^, forms
a double salt of the formula
RO^aoCao",^. ,
PeO^NaoCao",^*^
The soluble metaphosphates are converted into dihydric tribasic phos-
phates by continued boiling with water ; the insoluble metaphosphates
are oonverted in a similar manner by boiling with dilute nitric acid.
The soluble metaphosphates yield with argentic nitrate a gelatinous
white precipitate of argentic metaphosphate.
PYROPHOBPHORIO ACID. 356
PTR0FH08FH0BI0 AOID.
Molecular weight = 178.
PreparcUion. — 1. Pyropho8phoric acid is prepared by heating tribasic
phoephoric acid for some time to 213^ C. :
2POHoi = PAHo^ + OH,.
Phosphoric Pjrophosphoric Water,
acid. acid.
2. An aqueous solution of this acid is obtained by suspending plumbic
pyrophosphate (prepared by precipitating sodic pyrophosphate with a
soluble lead salt) iu water, and decomposing it with sulphuretted hy-
drogen:
PAPbo", + 2SH, = 2PbS" + PAHo,.
Plnmbic Sulphuretted Plumbic Pyrophoephoric
pyrophosphate. hydrogen. sulphide. acid.
Properfic8.— -Pyrophosphoric acid forms a colorless opaque crystal-
line mass. It is readily soluble in water. The solution does not coagu-
late albumen.
Reactions, — 1. In solution, pyrophosphoric acid is converted slowly
at ordinary temperatures, rapidly on boiling, into tribasic phosphoric
acid :
PAHo^ + OH, = 2POHos.
Pyrophoephoric Water. Orthophoephoric
acid. acid.
2. On heating to redness it yields metaphosphoric acid :
P,0,Ho.
= 2PO,Ho
+
OH^
Pyrophosphoric
Metaphosphoric
i
Water,
acid.
acid.
Pyrophosphates. — ^These salts are prepared by heating tribasic phos-
phates in which two atoms of the hydrogen of the acid are replaced by
a fixed base :
2POHoNao, = PjOjNao^ + OH,.
Hydric disodic Sodic Water,
phosphate. pyrophosphate.
2POMgo"(NH,0) = PAMgo", + 2NH, + OH^
Magnesic ammonic Magnesic Ammonia. Water,
phosphate. pyrophosphate.
Pyrophosphoric acid is a tetrabasic acid and forms four classes of
salts. Only the alkaline pyrophosphates are soluble in water ; but
the other pyrophosphates are soluble in acids, and generally also
356 INOBOANIC CHEiaSTRY.
in an excess of an alkaline pyrophosphate, forming, in the latter case, solu-
ble double salts. With argentic nitrate the alkaline pyrophosphates
yield a white granular precipitate of argentic pyrophosphate ; with solu-
ble salts of copper, a double salt, of the formula p'oVaoCuo"^*^^''*
is obtained. The solutions of the pyrophosphates are perfectly stable,
even when boiled. By boiling with dilute acids, however, the pyro-
phosphates are converted into tribasic phosphates.
FH08FH0BI0 AOID, Tribasic Phosphoric Acid, Orthophosphorie
Acid.
, POH05.
Molecular weight = 98- Fuses at 38.6° C. (101.5° F.).
Preparation. — 1. This acid is formed when phosphoric anhydride,
metaphosphoric acid, or pyrophosphoric acid is boiled with water for
some time:
PA + 30H, = 2POH03.
Phosphoric Water. Orthophosphoric
anhydride. acid.
2. It is best prepared in a state of purity by heating amorphous
phosphorus with concentrated nitric acid. The oxidation is complete
when red fumes cease to be evolved on the addition of fresh nitric acid.
The excess of nitric acid is then driven off by evaporation.
3. It is formed by the action of water upon phosphoric chloride
(p. 346) and phosphoric oxytrichloride {q.v.).
4. It is prepared on a large scale by treating 3 parts of bone-ash or
phosphorite with 2 parts of sulphuric acid and 10 parts of water, heat-
ing the mixture for some days :
PACao", + 3SOjHo, + 60Hj
= 2POH03 + 38Ho,Cao".
Tricalcic Sulphuric Water,
phosphate. acid.
Phosphoric Gypsam
acid. (Tetrahydric
calcic sulphate).
The solution ia filtered from the insoluble calcic sulphate.
The phosphoric acid prepared by any of the above methods, must be
heated to 150° C. (302° F.) to expel the last traces of water.
Properties. — Phosphoric acid forms transparent prisms, fusing at
38.6° C. (101.5° F.). When exposed to the air, it deliquesces to a
syrupy liquid. Its solution does not coagulate albumen.
Phosphates. — Phosphoric acid is a tribasic acid, forming three classes
of salts, of which the following are examples :
Trisodic phosphate, PONaa„20H,.
Hydric d isodic phosphate, ... . POHoNao,, 1 2OH2.
Dihydric sodic phosphate, . . . POHosNao^OH,.
PHOBPUORIC ACID.
367
The normal acUts, with the exception of those of the alkalies, are in-
soluble in water. Trilithic phosphate (POLio,) is only sparingly sol-
uble. The solutions of the normal alkaline phosphates have an alkaline
reaction. In solution they are decomposed by carbonic anhydride with
formation of monohydric phosphates :
PONao,- + CO, + OH, = POHoNao, + OOHoNao.
Trisodic Carbonic Water. Hydric disodic Hjdric sodic
phosphate. anhydride. phosphate. carbonate.
Dilute acids produce this change in the insoluble normal phosphates,
dissolving them with formation of monohydric phosphates.
The monohydric phosphaies of the alkalies are soluble in water, and
have a feebly alkaline reaction.
The dihydrio phosphates have an acid reaction. These compounds
are sometimes referred to as superphosphates.
The heavy metals form, as a rule, only normal phosphates, the other
phosphates existing only in solution in presence of an excess of acid.
If argentic nitrate be added to a solution of any of the alkaline phos-
phates, a yellow precipitate of triargentic phosphate is formed :
PONaos + SNOaAgo = POAgo, + SNO^Nao.
Trisodic Argentic Triargentic Sodic
phosphate. nitrate. phosphate. nitrate.
POHoNaOj + 3NO,Ago = POAgo, + 2NO,Nao + NOjHo.
Hydric disodic Argentic Triargentic Sodic Nitric acid,
phosphate. nitrate. phosphate. nitrate.
POHojNao + 3NOjAgo == POAgo, + NO^Nao + 2VOJE[o.
Dihydric sodic Argentic Triargentic Sodic Nitric add.
phosphate. nitrate. phosphate. nitrate.
It is worthy of note that, in the second of these reactions, by the mix-
ture of two solutions, one of which is neutral and the other slightly
alkaline, an acid liquid is produced.
The soluble phosphates also yield a white crystalline precipitate of
ammonic magnesic phosphate, tO(N''H^O)Mgo",60H2, when a clear
solution of magnesic sulphate and ammonic chloride containing an excess
of ammonia is added to their solutions ; this precipitate is insoluble in
water containingfree ammonia, and on ignition is converted into magnesic
pyropho8phate,T?203Mgo",. With a solution of ammonic molybdate in
nitric acid, they yield, especially on warming, a yellow precipitate of
ammonic phosphomolybdate (q.v,).
The following are some of the more important naturally occurring
phosphates :
Apatite (i?>anco/ite) .... PjOjCao^/I^Ca" j.*
Vivianite, . P2O2Feo"j,80H2.
Wavellite, P,O('Al'''A)^,120H,.
Pyromorphite, P303Pbo''Y^jPb'' V
* In this mineral, chlorine and flaorine displace each other isomorphously.
368 XKOBOANIO 0HEM18TBT.
Some of the acids of phosphorus have a tendenoy to exhibit a basicity
lower than their hydricity. Thus, though phosphoric acid forms tri-
basic salts, the last equivalent of base is so loosely attached, that in the
case of the soluble tribasic phosphates, it is removed by carbonic anhy-
dride. In the case of phosphorous acid, a weaker acid, the tribasic salts
are decomposed even by water, whilst hypophosphorous acid, a still
weaker acid, forms, only salts with one equivalent of base, though its
formula would show it to be dibasic
PHOSPHOROaOPHOSPHORIC ACID {Hypaphtmphorie AM).
MoUeuiar weight =a 324.
Preparation, — When phoephonis is allowed to oxidize spontaneoosly by exposure to air
and in contact with water, an acid liquid is obtained, which contains phoepnorous add,
phoephoric acid, and phosphoroeopnosphoric acid. As the latter acid, when in aola-
tion, gradually undergoes decomposition, the liquid is to be removed at the end of about
three days. On adding sodic acetate a crystalline precipitate of tetrahydrie tetrasodicphot-
pharoBophogphatej P404EIo^Nao4,120Hy is formed, which bj recrystallization may be
obtained in tabular crystals. The free acid is prepared by precipitating the barium
salt with sulphuric acid or the lead salt with sulphuretted hyarojB^en.
BeaetUma, — Phosphorosophosphoric acid can be obtained only in solution. On eyap-
oration oyer sulphuric acid, or eyen on standing at ordinary temperatures, it under-
goes decomposition into phosphorous and pyrophosphoric acids :
Tfi^Uo^ -f OH, = PAH04 -h 2PHo,.
Phoepboroflo* Water. Fyrophoflphorlo Phosphoro
phospnoric acid. acid. acid.
PhouphorowphogphateB. — These salts crystallize well. Owing to the high basicity of
the acid, they are generally complex. The phoephorophoephates of potassium will
serye as examples :
Potassic phosphorosophosphatlB, P404Ko|»160H,
Dihydric hexapotassic phosphoroeophosphate, p404EIo,Koe,60ir,.
Tetrahydrie tetrapotassic phosphorosophosphate, p404Ho4Ko4,40EL, also 60H,.
Pentahydric tripotassic phosphorosophosphate, p404Ho5Ko9,20Ut.
Hexahydric dipotassic phosphorosophosphate, P404HoeEo,.
That phosphorosophosphoric acid has at least the molecular weight here ascribed to it
is rendered probable by the existence of such a salt as pentahydric tripotassic phosphor-
osophosphate, and by the aboye decomposition of the free acid into a mixture of phos-
phorous and pyrophosphoric acids.
PHOSPHORIC OXYTBICHLORIDE. 859
COMPOUNDS OF PHOSPHORUS WITH CHLORINE
AND OXYGEN.
PHOSFHOBIO 0X7TBI0HL0BIDE, Phaspharylic Odoride.
CI
POCls. CI— P— CI
II
o
Molecular weight = 163.6. Molecular volume i l L 1 lUre bf phos-
phoric oxytrichloride vapor weighs 76.75 criths. 9p. gr. 1.7. Fuses
at —1.6° C. (29.3° ¥.). Bails at 110° C. (230° F.).
Prgxtrcrfion. — 1. Phosphoric oxytrichloride may be prepared by de-
composing phosphoric chloride with a limited quantity of water :
PCI5 + OH, = POCI3 + 2HC1.
Phosphoric Water. Phosphoric Hydrochloi
chloride. oxytrichloride. acid.
2. It is formed when oxygen is passed through boiling phosphorous
chloride :
PCI, + O = POCls.
PhoephorooB Phosphoric
chloride. oxytrichloride.
3. It may be readily obtained by heating together in a sealed tube a
mixture of phosphoric chloride and phosphoric auhydride :
P,0, + 3PC1, = 6P0C1,.
Phosphoric Phosphoric Phosphoric
anhydride. chloride. oxychloride.
4. It 18 formed by the action of phosphoric chloride on various or-
ganic and inorganic compounds containing oxygen (p. 346), and is best
prepared by heating dried oxalic acid or boric acid with phosphoric
chloride :
{oOHo + ^. = J'OC's + 00« + 00 + 2Ha.
Oxalic Phosphoric Phosphoric Carbonic Garbonio Hydrochloric
acid. chloride, oxytrichloride. anhydride. oxide. acid.
2BHoj + 3PC1, = 3P0C1, + B,0, + 6BC1.
Boric Phosphoric Phosphoric Boric HydrochU
acid. chloride. oxytrichloride. anhydride. acid.
Properties. — Phosphoric oxytrichloride is a colorle^ powerfully re-
fracting liquid which fumes in contact with moist air. In a freezing
360
INOBOANIC CHEMISTRY.
mixture it solidifies at — 10° C. (14° F.) to a laminar crystalline i
fusing at —1.5° C. (29.3° F.).
Readions. — 1. By contact with water it is slowly transformed into
hydrochloric and phosphoric acids :
POCI3 + 30H, = POHo^ + 3Ha.
Phoephoric Water. Phosphoric Hydrochloric
ozytrichloride. acid. acid.
2. By distillation with the salts of acids, it yields the corresponding
acid chlorides :
3SO,Pbo" +
Plambie
salphate.
J OH,
*tOONao
Sodic
acetate.
2POC1, =
PhoBphoric
PO
Pbo", + 380,C1,.
OBDh
-icnl<
+ POCl, =. 3
Phosphoric
ozjtrichloride.
PO
Plumbic
phosphate.
OH,
COCl
Acetylic
chloride.
, hunc
ozydichloride.
+ PONaOj.
Sodic
phosphate.
Phosphoric oxytrichloride is itself the acid chloride of phosphoric
acid. This relation, which is better expressed by the name Fhoaphorylie
chloride, is displayed in the above decomposition of this substance with
water«
The corresponding bromine compound POBr, {moUeular volume rTl ) is obtained in
a similar manner by the action of a limited qiiantitj of water on phosphoric bromide.
It forms a crystalline mass fusing at 45-46*' C. (113-115° P.), and boiling at 195"* C.
(o83° F%),
P7ROPHOSPHORTLIC CHLORIDB.
PACI4.
o o
a— p— o— p— CI
I
ci
I
Cl
BoUi with partiod deoompontion at 210-
Molecular weight = 252. Sp, gr, 1.58 at 7** C.
215° C.
Prejoaration. — This compound is prepared by passing gaseoas nitric peroxide into
phospnorous chloride, and distilling the liquid thus obtained. The portion which
passes over between 200° and 230° 0. is pyrophosphorylic chloride. This product
must be purified by rectification. The reaction is a very complicated one, and cannot
be expressed by a single equation. The by-products are phosphoric oxytrichloride,
phosphoric anhydride, nitrous oxychloride, and nitrogen.
iVopertieg.— Pyrophosphorylic chloride is a colorless fuming liquid.
Reactions, — 1. Water decomposes it instantaneously with formation of orthophos-
phoric (not pyrophosphoric) and hydrochloric acids:
PACI4 + 60H,
Pyrophosphorylic Water,
chloride.
= 2P0H0, + 4HC1.
Orthophosphorlc
acid.
Hydrochloric
acid.
2. When treated with phosphoric chloride, phosphoric oxjrtrichloride is formed :
PACI4 + PC1« = 3P0aa.
Phosphoric
oxytrlciLlorlde.
Fyrophosphorylic
chloride.
Phosphoric
ohloride.
TETKAPH08PHOBUS TBISULPHIBXi — ^PHOePHOROUS SULPHIDE. 361
COMPOUNDS OF PHOSPHORUS WITH SULPHUR.
Tetraphospbonis trisulphide,
S 8 S
II / \ II
»'(P,)^S",. P— P — P— P.
S 8
Phosphorous salpbide,
P^'
P— 8— P.
S 8
Phosphoric snlphide,
P^".-
Diphosphoric tetrasulphide, . 'P^S"^.
P— S— P.
II II
s s
s s
I II
p— p.
I II
s s
These compounds are all formed by the direct union of their elements.
Amorphous phosphorus and sulphur are heated together in the propor-
tions required by the formulse. With ordinary phosphorus^ the combi-
nation is apt to take place with explosive violence.
TBTRAPH08PH0RUS TRISUIJ'HIDB.
MoUeular weight = 220. Molecular voluTne \ \ I 1 litre cf the vapor weighs 110 criUiS.
Fu»e% ai U^" C. (SSO-S^* F.j. BoUe between, ^Wf" and 400° C.
Preparation, — A mixture of amorphous phosphorus and snlphor in the proportions
expressed bj the formula P^Sj is heated for eight hours to a temperature of 260® C.
(500^ F.)- The substance is thus obtained as a yellow translucent mass, which is puri-
fied by crystallization from carbonic disulphide.
Propertiee. — It forms yellowish prisms with a pyramidal termination.
BeoBtiotu — Boiling with water slowly decomposes it, with formation of phosphorous
acid, phosphoretted hydrogen, and sulphuretted hydrogen : '
^*(F,)^*8'', -h 90H,
TetraphoBphoma Water.
Biilpbiae.
3PHo, + PH, -f 3SHr
Phosphorous Phosphoretted Sulphuretted
acid. hydrogen. hydrogen.
PHOSPHOROUS SXTLPHIDB.
Moieadasr weight » 158.
Preiparaiion. — As above.
Properties, — Phosphorous sulphide forms a gr^sh -yellow crystalline mass melting
at about 290° C. (554° F.). It has not been obtained in definite crystals, and has not
been distilled.
Reaction, — Water decomposes it, forming phosphorous acid and sulphuretted
hydrogen :
P«8'^ + 60H, = 2PHo, +. 3SH,.
Phosphorous Water. Phosphoroas Sulphuretted
sulphide. acid. hydrogen.
362 INOBOANIO CHEMISTfiY.
FH08FH0BI0 SULPHIDE.
Molecular weight == 222, Molecular volume I I L 1 lUre of the tfopor
weighs 111 criths. Fuses at 274-276° C. (525-529^ F.). BoUs
at 530° C. (986° F.).
Preparation. — As above. The process may also be modified by dm-
solving ordinary phosphorus and sulphur in the molecular proportioDS,
P^S'^s, in carbonic disulphide, and heating the solution in sealed tubes
for 8-10 hours to 210° C. (410° F.). On cooling, the phosphoric
sulphide is deposited on the walls of the tube in well-formed crystals.
Properties.— It forms pale-yellow crystals generally grouped in tufts.
Reactions, — 1. By direct combination with alkaline sulphides it
forms the sulphophosphates :
P,S'', + 3SK, = 2PS"K83.
Phosphoric Potassic PotsMic
sulpnide. sulphide. sulphophoBphate.
2. With water phosphoric sulphide yields phosphoric acid and sul-
phuretted hydrogen :
P,S", + 80H, = 2POHoi + 6SH,.
Phosphoric Water. Phosphoric Solphuretted
sulpliide. acid. hydrogen.
Phosphoric sulphide is employed in the laboratory for the purpose of
replacing oxygen by sulphur in organic compounds.
DIPHOSPHORIC TBTRAStTLPHIDB.
MoUeular weight =:^\W* l?V«e« erf 296-298** C.
PrcDaratitm. — Phosphorus and salphar in the proportions corresponding with the
formula P^S^ are dissolved in carbonic disulphide and heated in sealed tubes.
Properties, — It is thus obtained in the form of yellow transparent acicnlar ctystals.
It boih without decomposition.
COMPOUND OF PHOSPHORUS WITH SULPHUR AND CHLORINE.
PHOSPHORIC SUIaPHOTRICHLORIDIL
CI
ps^'cis. d— p— CI.
I
Molecular foeighi =s 169.5. Moleeular volume I I I. 1 litre of the vapor w»gh» 84.75
eritha, Sp. gr, of liquid 1.636 a* 20*» C. 5oaran26° C. (269** F.).
Preparatum, — 1. Phosphoric sulphotrichloride is best prepared by heating together
phospnoric sulphide and phosphoric chloride for a few minutes to 150° C. (302? F.) :
* The vapor-density of this compound has been determined with a result which
would point to the formula P,S^. This anomalous result is possiby due to the employ-
ment of too low a temperature in the determination.
PHOSPHORUS COMPOUNDS OONTAINIK0 KITBOOEN. 363
Phosphoric Phosphoric Phosphoric
sulphide. chloride. sulphotnchloride.
2. It 18 also formed by the action of sulphuretted hydrogen upon phoephoric
chloride :
PClft -f SH, = PS^'a, + 2Ha.
Phosphoric Sulphuretted Phosphoric Hydrochloric
chloride. hydrogen, sulphotnchloride. acid.
ProperHei. — It is a colorless fuming liquid.
JUacHon8.—l. Water slowly deoompoees it, yielding hydrochloric acid, phosphoric
•cid, and sulphuretted hydrogen :
PS'^a, -f 40H, = POHo, + 8HC1 + SH^
Phosphoric Water. Phosphoric Hydrochloric Sulphuretted
sulphotnchloride. acid. acid. hydrogen.
2. With alkalies it yields the salts of sulphophosphoric acid (PS^^Ho,) :
PS^^Cl, + 60KH = PS'^Ko, + 3KCI + 30H^
Phosphoric Potassic Potasslc Potassio Water,
sulphotrichloride. hydrate. sulphophosphate. chloride.
The corresponding bromine compound PS^^Br, is also known.
PHOSPHORUS COMPOUNDS CONTAINING NITROGEN.
These substances possess considerable theoretical interest as examples of a class
of compounds largely represented in organic, but of rarer occurrence in ihorganic,
chemistry.
Phospkam, PN(NH)^^, is prepared by psssing gaseous ammonia over phosphoric
chloride as long as the gas is absorbed, and then igniting the product in a current
of carbonic anhydride or some other indifferent gas :
PClg + 7NHa = PN(NH)^' + SNH^Cl.
Phosphoric Ammonia. Phospham. Ammonio
chloride. chloride.
Phospham is a white powder, insoluble in water.
Pkosphamimide^ PO(NH)^^(NH,), remains behind as a white powder when the
product of the action of gaseous ammonia on phosphoric pentachloride is extracted
with water :
pas + 7NH, + OH, = PO(NH)^'(NH,) -f SNH^CL
Phosphoric Ammonia. Water. Phosphamlmide. Ammonio
chloride. chloride.
Photphoric oxytriamide, PO(NH,),, is obtained as a white amorphous powder by
the action of gaseous ammonia on phosphoric oxytrichloride :
POa, + 6NH, = PO(NH,)a + SNH^Cl.
Phosphoric Ammonia. Phosphoric Ammonio
ozytricnloride. oxytriamide. chloride.
The product is well washed with water to remove the ammonic chloride. When
this, or the foregoing compound, is ignited in an atmosphere free from oxygen, am-
monia is given off, and phisphoric ozunitridey PON, remains as a white powder.
PyropfMsphotriamic addf P,Os(NH,)sHo, is prepared by saturating pnosphoric oxy-
trichloride with gaseous ammonia without cooling, heating the product to 220° C, and
finally boiling it for a short time with water :
2P0CU + 9NH, + 20Ha = PA(NH,),Ho + GNH^Q.
Phosphoric Ammonia. Water. Pjrrophosphotriamic Ammonic
oxytrichloride. add. chloride.
364 INORGANIC CHEMISTRY.
It forms aD amorphous insoluble powder, which is suocessivelr converted bj continuons
boiling with water into soluble ^ophosphodiamie aeidj Pfi^{NKf\Hnt, and pyrophca-
pkamie acidf p20,(N[I,)Ho,, this last compound being finally transformed into a mix-
ture of ammonic phosphate and phosphoric acid.
VANADIUM, V,?
Atomic weight = 51.3. Probable mdeeular toeighi = 205.2. Sp. gr. 5.5.
AtomieUy ''' and ^. Evidence of atomicity:
Vanadous chloride, V'Cl,.
Vanadic oxytrichloride, V'OCI,.
History. — This rare element was discovered in 1801, by Del Rio,
who obtained it from a Mexican lead-ore. He failed, however, to rec-
ognize its true nature, and ultimately regarded it as impure chromium.
In 1830 it was rediscovered independently by Sefstrdm. Metallic
vanadium was first isolated by Roscoe.
Ocewrrence. — Vanadium occurs sparingly in various lead and iron
ores. The cupric and bismuthous vanadates constitute the rare minerals
volbortliite aod pucherite. A relatively rich source of vanadium has
lately been found in the Bessemer slag of the Creusot iron works, which
contains as much as 1.5 per cent, of this element
Preparation, — Metallic vanadium is obtained by heating vanadous
chloride to bright redness in a current of dry hydrogen :
2VCls + 3H, = V, + 6HC1.
VanadouB Hydrochloric
chloride. acid.
Properties. — As above prepared it forms a silvery, crystalline mass,
of sp. gr. 5.5. It does not oxidize, either in dry or in moist air, even
at 100° C. When strongly heated in air or oxygen it burns, forming
vanadic anhydride, VjO^. It does not fuse at a red heat. Hydrochloric
acid is without action upon it; concentrated sulphuric acid dissolves it
on heating ; and nitric acid, even when dilute, attacks it energetically,
dissolving it to form a blue solution. Fused with caustic alkalies it
yields a vanadate of the base with evolution of hydrogen.
COMPOUNDS OF VANADIUM WITH CHLORINE.
Hjpovanadous chloride, . . . i . < rrni'
Vanadous chloride, .... . . s VClj.
Hypovanadic chloride, ^*'Cl4 or | ^^<'
HypowmadmLB cMoride.'VS^X^y is obtained in apple-green micaceoaa plates by paw-
ing the vapor of the trichloride mixed with hydrogen through a red-hot tube:
2Va, + H, = ^'^Cl* + 2HC1.
VanadouB Hypovanadoua Hydrochlorio
chloride. chloride. acid.
VANADIUM. 366
It is hygroeoopic, and dissolves in water, yielding a violet solution.
Vanadou9 chloride, VCla, is prepared from hjpovanadic chloride, which is decom-
posed slowly at ordinary temperatures, rapidly at its boiling-point, into vanadous chlo-
ride and free chlorine. It forms peach-blossom-colored tabular crystals, is non-volatile,
and deliqaesoes when exposed to the air. ^^
Hypovanadie chloride^ ^V*''Gl4 (mcleeular vdume I I I ). is formed by the action of an
excess of chlorine on metallic vanadium. It may also be obtained by repeatedly pass-
ing the vapor of the oxy trichloride, mixed with chlorine, over charcoal :
2V0Cla + C, + CI, = 2^»^Cl4 -f 2C0.
Vanadic Hypovunadic Carbonic
oxytrichloride. chloride. oxide.
It is a dark-brown liquid, boiling at 164° C, and having a sp. gr. of 1.8584 at 0° C.
Water decomposes and dissolves it, yielding a bine liquid. The molecular formula,
VCI4, as deduced from the vapor-density of this compound, is anomalous. In such a
compound, vanadium would be tetradic, in violation of the law regulating the variation
of atomicity ; otherwise, the presence of a single free bond must be assumed (see note,
p. 179).
COMPOUNDS OF VANADIUM WITH OXYGEN AND HYDROXYL.
Hypovanadous oxide, ^^^Oj.
Vanadous oxide, ^sOg.
Hypovanadic oxide, ^V'^O^.
Vanadic anh)tdride, V2O..
Metavanadic add, .......... VO3H0.
Tribasic vanadic acid, VOH03.
Pyrovanadic acid, V.JO8H04.
Hypotfanadoua oxide, ^^\0^y is formed when the vapor of the oxytrichloride, mixed
with hydrogen, is passed through a red-hot tube :
2V0C1, + 3H, = '^r'\0^ + 6HC1.
Vanadic Hypovanadous Hydrochloric
oxytrichloride. oxide. acid.
It is a gray powder, with a metallic lustre. Acids dissolve it, yielding a lavender-
colored solution, which instantly becomes brown on exposure to the air.
Hvpovanadous oxide was mistaken by Berzelius for metallic vanadium.
Vanadous oxide, VgO^, remains behind as a black lustrous powder when vanadic an-
hydride is heated to redness in a current of hydrogen. Even at ordinary temperatures
it slowly absorbs oxygen, forming hypovanadic oxide, ^V'^O^, and, when gently warmed
in air, glows and is converted into vanadic anhydride. It is insoluble in acids.
Hypovanadic oxide, '^V*%04, is formed as above by the spontaneous oxidation of vana-
dous oxide. It may also be obtained by fusing together equal molecular proportions
of vanadous oxide and vanadic anhydride :
VA + VA = 2'v"A.
Vanadous Vanadic Hypovanadic
oxide. anhydride. oxide.
It is a blue powder, consisting of minute shining crystals. When exposed to moist
air it is slowly converted into an olive-green hydrate. Acids dissolve it with diflSculty,
yielding a blue solution.
Venwdic anhydride^ VgOs- — Minerals containing vanadium are fused with nitre, and
the mass is extracted with water. The solution, which contains an alkaline vanadate
alone with various impurities, is then almost neutralized with nitric acid and precipi-
tated with baric chloride. The precipitate, consisting of baric vanadate and other
barium salts, is decomposed by boiling with dilute sulphuric acid, and the solution,
filtered from the baric sulphate, is neutralized with ammonia and evaporated to a small
bulk, after which pieces of ammonic chloride are placed in the solution. This causes
the ammonic metavanadate, which is very insoluble in a concentrated solution of am-
monic chloride, to be deposited in small crystals. These are washed with a solution
366 IKOBGA17IC GHE1CI8THT.
of ammonic chloride, and decomposed bj igDition in an open cnicible, when pare vir
nadic anhydride remains behind.
Vanadic anhydride is a reddish-brown man which melts at a red heat^ and solidifies
in a crystalline form on cooling. It is very slightly soluble in water, to which it im-
parts a yellowish tinge. Both acids and alkalies dissolve it readily. The acid solu-
tions yield with reducing agents firet a blue, and afterwards a green coloration.
Vanadaies. — The various forms of vanadic acid are known only in their salts. The
ordunfanadates (or tri basic vanadates), the mOaffanadaie^ and the pyrovanadaUsB are
isomorphons with the corresponding compounds of phosphorus. In addition to
these, a fourth series is known, the tetravanadatfO, of which diamn^onic tetravanadaUf
Yfi^(l^ Hfi)^,40H^, is an example:
Ammonic metavanadate, V0,(KH40).
Argentic ortho vanadate, VOAgo,.
Argentic pyrovanadate, V,0BAgO4.
Vanadinite, ▼,0,PlW4(aPb'') •
ARSENIC, As,.
AtomiG weight = 75. Molecular weight = 300. Molecular volume 1 1 L
1 Utre of arsenic vyoor weighs 160 criiha. 8p. gr. 6.6 to 6.9. Volatile
at 180° C. (366° F.). Atomicity "' and \ Evidence of atomicity:
Arseniuretted hydrdgen, As'^'Ug.
Arsenious chloride, A8'"Cl3.
Tetrethylarsenic chloride, Ag^Et^Cl.
History. — Arsenic was known to the alchemists, but Brand, and
later Scheele, first investigated its chemical nature.
Occurrence, — Arsenic is widely distributed in nature. It occurs both
in the free state and in combination with various other metals in the
form of ores. Of the latter the principal are : realgar, 'As^jS", ; orpi-
meni, Ab^^\ ; arsenical pyrites^ 'A8",(FejS"2)"2 ; and arsenical iron,
'As^^Fe^^. It is found in small quantities in other minerals, such as
iron pyrites, for which reason sulphuric acid which has been manufac-
tured from pyrites is generally contaminated with arsenic. In minute
traces it occurs in some mineral waters, and in the water and mud of
many rivers. It is also contained in coal-smoke (derived in this case
from the pyrites of the coal), and consequently in the air of towns.
Preparation. — 1. Arsenic is obtained by heating arsenical pyrites.
The arsenic volatilizes and may be condensed, whilst ferrous sulphide
remains behind :
'AB'VFe^"^)", = As, + 4FeS".
Ferroarsenioos Ferrous
sulphide. sulphide.
2. It may also be prepared from arsenious anhydride, a substance
produced in the roasting of many ores. The arsenious anhydride is
reduced by heating with charcoal :
AB3O5 + 30 = 2As + 30O.
Arsenious Carbonic
anhydride. oxide.
ABSENIURETTED HYDBOGEN. 367
Properties. — Arsenic, like phosphorus, is known in more than one
form. When arsenic is sublimed in a current of hydrogen, it is de-
posited close to the heated portion of the tube in crystals, but further
on, where the tube is colder, amorphous arsenic collects. The crystal-
line variety forms acute rbombohedra, with a steel-gray color and a
metallic lustre, possessing a sp. gr. of 5.727. In dry air it may be pre-
served without change, but in presence of moisture it becomes coated
with a blackish-gray crust due to oxidation. When heated under or-
dinary pressure, it volatilizes without fusing ; but by inclosing it in a
sealed tube, so as to subject it to the pressure of its own vapor, it may
be fused. The vapor is lemon-color^, and possesses an odor of garlic
The molecular weight of arsenic, as deduced from the vapor-density,
is 300, showing that the molecule of this element is, like that of phos-
phorus, tetratomic. At the highest temperature at which the vapor-
densily of arsenic has been determined (yellow heat), a partial disso-
ciation is, however, found to have occurred, and the value for the vapor-
density lies between those required for Asj and A84 (Victor Meyer).
The amorphous variety forms a black mass with a vitreous lustre.
Its sp. gr. is 4.71. When heated to 360° C. (680° F.) it is converted
into the crystalline or metallic variety^ great heat being liberated in the
transformation. It is much more permanent in air than crystalline
arsenic. Amorphous arsenic may also be obtained as a gray powder.
This variety is deposited in the coldest parts of the tube during the sub-
limation in hydrogen.
Becustiona. — 1. When heated in air or oxygen arsenic burns, forming
arsenious anhydride. In like manner, when arsenic is treated with
oxidizing agents, arsenious anhydride and arsenic acid are produced.
2. When finely-divided arsenic is introduced into chlorine, it inflames
spontaneously, yielding arsenious chloride.
It also combines directly with most of the other elements.
Use. — A small quantity of arsenic is added to the lead which is used
in the maniifacture of shot, as it is found that this addition enables the
metal more readily to assume the spherical form, and at the same time
renders it harder.
COMPOUND OF ARSENIC WITH HYDROGEN.
ABSENIUBETTED HTDROGEN, Arsenious Hydride.
A8H3.
Molecular weight = 78. Molecular volume 1 1 1^ 1 litre weighs 39
crUhs. Boils at —40° C. (—40° F.).
Preparation. — 1. This gas is obtained in the pure state by the action
of dilute sulphuric or hydrochloric acid on an alloy of arsenic and zinc :
AHjZn", + 3SO,Ho, =
= SSO^no"
+ 2A8H5.
Anenious Salphuric
Zincic
Arseniuretted
zincide. Mid.
sulphate.
hydrogen.
368 INOBOANIC CHEMXffTBY.
2. It is formed bv the action of nascent hydrogen upon soluble
arseiiic compounds : thus by the introduction of arsenious acid into an
apparatus evolving hydrogen from zinc and sulphuric acid :
AbHo, + 3Hj = AbHj + 80H,;
Areenioos Aneniaretted Water,
acid. hydrogen.
In this case the gas is mixed with an excess of hydrogen.
Prapertiea. — Arseniuretted hydrogen is a colorless gas of a very dis-
agreeable odor. At — 40^ C. it condenses to a colorless and trans-
parent liquid which does not solidify at —100° C. (—148° F.). Water
dissolves it but slightly. It is devoid of basic properties.
It is one of the most poisonous substances known. Gehlen, of Got-
tingen, lost his life by incautiously smelling a leaky joint of an appa*
ratus in which he was preparing the gas, in order to de'tect the escape.
Reactions. — 1. When burnt with free access of air it forms water
and arsenious anhydride :
2A8H5 + 30j = A82O3 + 30Hj.
ArFeninretted * AreenioiiB Water,
hydrogen. anhydride.
2 When burnt with a limited supply of air, it yields water and
free arsenic:
4ABH3 + 30j == As, + 6OH2.
Arseniuretted Water,
hydrogen.
Thus if a piece of white porcelain be held in the flame of arseniuretted
hydrogen burning in air, a black shining spot of metallic arsenic is
deposited on the porcelain.
3. When exposed to a low red heat, it is decomposed into arsenic
and hydrogen. This reaction, coupled with the formation of arseniu-
retted hydrogen by the action of nascent hydrogen on soluble com-
pounds of arsenic, is employed as a means of detecting minute traces of
this element.. (See Marsh! 8 Ted^ Redctions of Arsenic.)
4. When passed through a solution of argentic nitrate, it yields a
precipitate of metallic silver, whilst arsenious and nitric acids remain
in solution :
eNOjgAgo + 30Hj + A8H3 = 6NO,Ho + AbHo, + 3Ag,.
Aigentic Water. Arseniuretted Nitric Arsenious
nitrate. hydrogen. acid. acid.
ABSENIOTJB CHLORIDE. 369
COMPOUNDS OF ARSENIC WITH THE HALOGENS.
ABSENIOUS OHLORIDE.
A8CI3.
Atomic weight = 181.5. Molecular volume 1 I 1. 1 litre of araeniotis
chloride vapor weighs 90.75 criths. 8p. gr. 2.205. Boils at 134° C.
Preparation. — 1. Arsenious chloride is obtained by the action of dry
chlorine on arsenic. The product must be left in contact Vith arsenic^
in order to free it from excess of chlorine, and then rectified.
2. It may also be prepared by distilling arsenic with corrosive sub-
limate :
Aflj + eHgClj ±= STHg'/)!, + 2ASCI3.
Mercuric Mercuroos Arsenious
chloride* chloride. chloride.
3. It. is most readily obtained by distilling a mixture of arsenious
anhydride, sodic chloride, and concentrated sulphuric acid :
Asp, + 6NaCl +
6SO,Ho, =
= 2A8CI3
Arsenious Sodic
Sulphuric
Arsenious
anhydride. chioridd.
acid.
chloride.
+ eSOjHoNao + 30H,.
Hydric sodic Water,
sulphate.
In this way hydrochloric acid, in the preparation of which arsenical
sulphuric acid has been employed, always contains arsenic.
4. When a solution of arsenious anhydride in aqueous hydrochloric
acid is boiled, arsenious chloride volatilizes along with the steam :
AS2O3 + 6HC1 = 2A8CI3 + 3OH2.
Arsenious Hydrochloric Arsenious Water,
anhydride. acid. * chloride.
PraperHes.-^Areenious chloride is an oily liquid which does not
solidify at — 29° C. It fumes strongly in contact with moist air. It
is extremely poisonous.
Peactions. — 1. A small quantity of water dissolves it, forming a clear
solution, from which needle-shaped crystals of arsenious chlordi hydrate
are deposited on standing :
A8CI3 + 2OH2 = AsClHoj + 2HC1.
Arsenious Water. Arsenious Hydrochloric
chloride. chlordihydrate. acid.
2. An excess of water decomposes it into arsenious anhydride and
hydrochloric acid :
24
370 INOBGAKIC CHEHIBTBY.
2A8CI3 + 30H, = 6HC1 + A82O3.
Araenious Water. Hydrochloric AreeniooB
chloride. acid. anhydride.
3. It absorbs gaseoas ammonia, forming a crystalline compouDd of
the formula A8Cl3,2HHs.
ABaENious BROMIDE, AsBr, (molecular volume I ^ I ), is prepared by adding finely
powdered arsenic to a solation of bromine in carbonic disulphide. It crystallizes in
colorless deliouescent prisms, fusing between 20® and 25° C. (68-77° F.). It boils at
220° C. (428° F.). Water decomposes it like the chloride.
Arsenioub iodide. As I, (moleaUar volume I I I ), is prepared in a similar manner,
and forms lustious brick-red lamins.
Absenious fluobidb, AbF, (molecular volume FTl ), is obtained by distilling a
mixture of 1 part of powdered fluorspar and 1 part or arsenioos anhydride with 5 parts
of concentrated sulphuric acid :
As,0, + 6HF «= 2A«F, + 30H^
It is a colorless fuming liquid of sp. gr. 2.7, boiling at 63° C. (146° F.). Brought in
contact with the skin it produces very dangerous wounds. Water decomposes it like
arsenious chloride.
Arsenic pentafluobide, AsFa, is known only in the form of the double com-
pound, AbF«,EF, obtained by dissolving potassic arsenate in hydrofluoric acid.
COMPOUNDS OF ARSENIC WITH OXYGEN AND
HYDROXYL.
Arsenious anhydride, (ABjOj),.
Arsenic anhydride, ......... ASjO,.
Arsenious acid, AsHo^
Arsenic acid, • AsOHo^
ABSENIOUS ANHTDBIDE, Arsenic^ White Arsenic, IVhite Oxide
of Arsenic.
(A8,0,V
Molecular weight = 396. MoUetJar volume I i I- 1 lUre of arsenious
anhydride vapor weighs 198 eriths. Sp, gr. {octahedral) 3.69, {amar--
phous) 3.74.
Occurrence. — Arsenious anhydride is found in nature in two rare
minerals : in the octahedral form as arsenic bloom and in rhombic crys-
tals as claudetite.
Preparation. — It is formed when arsenic is burnt in air or oxygen.
In this way, it is obtained as a by-product in the roasting of arsenical
ores in various metallurgical operations. The arsenious anhydride sub-
limes and is condensed in large flues.
Properties. — Commercial amorphous arsenious anhydride forms, when
first prepared, a colorless vitreous mass, which after a time becomes
ABSENIOra ACID. 371
white and opaque, owing to its gradual transformation into the crystal-
line variety. This change is accompanied by a decrease in the sp. gr.
from 3.74 to 3.69. Crystalline arsenious anhydride is soluble in 80
parts of cold water; the amorphous modification in 25 (larts; hydro-
chloric acid increases the solubility. The hot saturated solution in
hydrochloric acid deposits octahedral crystals; if a solution of the
amorphous variety be employed, the formation of each crystal is attended
with a flash of light visible in the dark. When the octahedral anhy-
dride is heated, it sublimes without fusing, and is again condensed in
€)ctahedral crystals; under pressure, however, it may be fused, and* is
thus converted into the amorphous modification.
A second crystalline modification of arsenious anhydride, belonging
to the rhombic system, is sometimes found in the arsenic flues. It is
also deposited from a solution of an excess of the anhydride in boiling
caustic potash, or from a solution of argentic arsenite in nitric acid.
Arsenious anhydride has a faint, sweetish metallic taste, and, when
taken internally, acts as an irritant poison. A dose of 0.06 gram has
been known to prove fatal. The best antidote is freshly prepared
ferric hydrate (Te'^'^Hog), which must be administered in a large dose
as soon as possible after the poison has been swallowed. The arsenious
acid is oxidized by the ferric hydrate to arsenic acid, which combines
with the excess of ferric hydrate to form a basic ferric arsenate, insol-
uble in water and in the liquids of the stomach. By keeping, the fer-
ric hydrate becomes crystalline and inactive: it is therefore prepared,
when wanted, by adding calcined magnesia to a solution of ferric chlo-
ride or sulphate:
Te'",Cl,
+ 3MgO + 30H, =
= Te'",Ho,
+
3MgCl^
Ferric
Magnesia. Water.
Ferric
Magnesic
chloride.
hjdrate.
chloride.
The magnesic chloride, which is simultaneously formed in this reaction,
serves by its aperient action to remove the various matters as speedily
ajB possible from the stomach.
In spite of the poisonous properties of arsenious anhydride, it is pos-
sible by long use to train the system to support relatively large doses
of this substance. In Styria, the practice of arsenic eating is stated to
be not uncommon. An arsenic eater has been known to consume 0.3
gram of arsenious anhydride at once without perceptible ill-effect. The
practice is asserted by the arsenic eaters to improve the complexion and
to prevent shortness of breath.
Uses. — Arsenious anhydride is employed in the preparation of arsen-
ical pigments and in the manufacture of glass.
ARSENIOUS AOID.
ASH03.
Molecular weight = 126.
When arsenious anhydride is dissolved in water the solution reddens
litmus feebly, and contains arsenious acid. This acid cannot however
372 IKOROANIC CHEMISTRY.
be isolatedy since on concentration the solution deposits crystals of the
anhydride.
Arsenitea. — ^There are two classes of arsenites : the ortharsenites, de-
rived from the acidAsHo,; and the metarsenites, derived from the
acid AaOHo. Only the arsenites of the alkali-metals are soluble in
water. They yield with argentic nitrate a yellow precipitate of triar-
gentic arsenite, AsAgOg. Among the arsenites important by their uaes,
may be mentioned dUiydrio potassie araenitey AsHojKo, employed in
medicine under the name of Fawler^s solution; and hydriccupric arBen-
it€, AsHoCuo'^y which forms the pigment Sched^s green. &)hwein/urt
green, a double metarsenite and acetate of copper of the formula
3Aa,OjCuo",0u(C,HA)»
is prepared by boiling arsenious acid with cupric acetate.
ARSENIC ANHTDRIDE.
AbA.
Molecular weight = 230.
Preparation. — This compound is obtained by heating arsenic acid
nearly to redness :
2ABOH05 = 30Hj + ASjOj.
Arsenic Water. Arsenic
acid. anhydride.
Properties. — It forms a white porous mass.
Reactions. — 1. It dissolves in water with formation of arsenic acid.
2. When heated to bright redness it fuses and is decomposed into
arsenious anhydride and oxygen.
3. With gaseous hydrochloric acid it yields, even at ordinary tem-
peratures, arsenious trichloride, chlorine, and water :
Asfi, + lOHCl = 2A8CI3 + 2C1, + 50H,.
Arsenic Hydrochloric Arsenious Water,
anhydride. acid. trichloride.
AESENIO ACID.
AsOHo,.
Molecular weight = 142.
Preparation. — Arsenic acid is prepared by treating arsenious anhy-
dride with nitric acid :
ASjO, + 2NO,Ho + 20H, = 2A80Ho, + Np,.
ABSENIG ACID. 373
Properties. — When a eolatien of arsenic acid is evaporated to a syrup,
and then cooled below 15*^ C. (59° F.), crystals of the formula
2A8OHos,0H2 are deposited. These crystals part with their water of
crystallization at 100° C, and are converted into ortharsenic acid,
AsOHoy When this acid is heated to 180° C. (356° F.) it fuses and
gives off water, and on cooling, hard shining prismatic crystals of
pyrarsenic acid, ASjOsHo^, separate out. If the heating be carried to
206° C. (403° F.), the whole is converted into a white nacreous mass
of metarsenic acid, AsOjHo. These three acids correspond to the three
varieties of phosphoric acid ; but the pyro- and metarsenic acids differ
from the pyro- and meta-phosphoric acids in being capable of existing
only in the solid state. In solution they are at once converted into
ortharsenic acid, and the same is the case with their salts, which may be
prepared in the same way as the corresponding salts of meta- and pyro-
phosphoric acid (pp. 854 and 355).
Reactiona, — 1. When arsenic acid is distilled with fuming hydro-
chloric acid, arseniou» trichloride, chlorine, and water distil over :
AsOHo, + 5HC1 = AbCI, + Cl^ + 40H,.
ArRenic Arsenious Water,
acid. trichloride.
In the receiver the reverse reaction takes place, arsenic acid and hydro-
chloric acid being regenerated.
2. Sulphurous acid reduces it to arsenious acid :
AbOHo^ + SOH02 = ABH03 + SOjHo,.
Arsenic Sulphurous Arsenious Sulphuric
acid. acid. acid. acid.
Other reducing agents act in a similar manner.
Arsenates. — The arsenates are isomorphous with the corresponding
phosphates. Arsenic acid is a tribasic acid, and forms three series of
salts; normal, monohydric, and dihydric. The alkaline arsenates are
soluble in water; of the others only the dihydric salts are soluble, but
all dissolve readily in acids.
The following arsenates occur in nature :
Haidingerite, 2AsOHoCao",0H2.
Pharmacolite, 2A8OHoCao",50H2.
Cobalt bloom, A82O2Coo"3,80H3.
Mimetesite (isomorphous with py- 1 /q .
romorphite,vanadinite,and ap- >AB303Pbo'"ip,Pb").
atite, pp. 357 and 366), . . j \^i /
For the reactions of the arsenates, see General Reactions of Arsenic.
374 TKOPOAKIO CHEKISTBY.
COMPOUNDS OF ARSENIC WITH SULPHUR AND
HYDROSULPHYL.
Realgar, {^;; = 'As",S'V
Sulpharsenious anhydride (-4r- AajS"
aenums 8iUphide\ *^ **
Sulpharseoio anhydride {Arsenic Agg//
mlphide)y . , * *'
Sulpharsenious acid^ .... AsHs,.
Sulpharsenic acid, AsS^'Hs,.
DIASSENIOUS DISULPHIDE, Realgar.
'^">8''„or{^«|; .
Molecular weight = 214. 8p. gr. 3.5.
Occurrence. — This substance occurs in nature as the mineral realgar.
Preparation, — 1. It may be obtained artificially by heating together
sulphur and arsenic in the proportions expressed by the formula.
2. A second method consists in heating in an iron retort a mixture of
arsenical pyrites and iron pyrites:
Arsenical Ferric Diarsenious Ferrous
pyrites. disulphide. disiilphide. sulphide.
The diarsenious disulphide distils over, whilst ferrous sulphide remains
in the retort. Most of the realgar of commerce is prepared by this
method.
Properties. — Native realgar occurs in ruby-colored monoclinic prisms
and also massive. The artificial product forms a dark-red crystalline
mass. It fuses readily and may be distilled without decomposition.
Reaction. — 1. When heated in contact with air it burns with forma-
tion of arsenious and sulphurous anhydrides :
'AB"aS'', + 70 = AsA + 2SOj.
Diarsenious Arsenious Sulphurous
disulphide. anhydride. anjdride.
SULPHABSENIOTTS ANHYDRIDE, Arsenious
Sulphide, Orpiment.
As^'V
Molecular weight = 246. 8p. gr. 3.5.
Occurrence, — Sulpharsenious anhydride occurs native as the mineral
orpiment.
8ITLPHABSENIOUS ANHYDRIDE. 375
Prqparation. — It may be obtained by precipitating a solution of ar-
senious anhydride in hydrochloric acid with sulphuretted hydrogen :
2A8CI3 + 3SH, = 6HC1 + Ab^'V
Arsenioos Sulphuretted Hydrochloric Arsenioos
chloride. hydrogen. acid. sulphide*
Properties. — Native orpiment forms lemon-colored rhombic prisms.
The substance obtained by precipitation is a yellow powder, which fuses
to a reddish liquid, and may be distilled without decomposition.
JReadiona, — 1. Arsenious sulphide dissolves in caustic alkalies, pro-
ducing an arsenite and a sulpharsenite:
AfljS", + 40KH = AbHoKoj + AbHsKs, + OH^.
Arsenious Potassic Hjdric dipotassic Salphjdric Water,
sulphide. hydrate. arsenite. disulphopotassic
sulpharsenite.
By the addition of an acid the arsenious sulphide is reprecipitated :
AsHoKo, + AsHsKsa + 4HC1 = 4KC1
Hydric dipotassic Sulphydric Hydrochloric Potassic
anenite. disulphopotassic acid. chloride,
sulpharsenite.
+ As^", + 30H,.
Arsenious Water,
sulphide.
2. It dissolves in alkaline sulphides, forming sulpharsenites :
AI2S", + 3SK2 = 2A8K83.
Arsenious Potassic Potassic
sulphide. sulphide. sulpharsenite.
Sulpharsenites. — These salts correspond to the arsenites. Only the
alkaline salts are soluble. On the addition of an acid to their solutions
arsenious sulphide is precipitated, and sulphuretted hydrogen is evolved :
2AsKs, + 6HC1 = 6KC1 + As^", + 3SH,.
Potassic Hydrochloric Potassic Arsenious Sulphuretted
Bulphanenite. acid. chloride. sulphide. hydrogen.
CbQmdal Anenious Sulphide. — On saturating a pure aqueous solution of arsenious
anhydride with sulphuretted hydrogen, the liquor assumes a yellow color with a reddish
fluorescence ; but no precipitate is formed, in this condition the solution contains a
colloidal modification of arsenious sulphide, which may be separated from unaltered
anenioiis anhydride by dialysis. By spontaneous evaporation this soluble sulphide is
obtained in transparent amorphous masses of a yellow or reddish-yellow color with a
conchoidal fracture. Acids and various metallic salts precipitate ordinary insoluble
arsenioos sulphide from the solution.
376 INOBGANIC OHEUIBTBY.
SULPHABSENIO ANH7DBIDE, Arsmia Sulphide.
Molecular weight = 310.
Preparation. — 1. Sulpharsenic anhydride may be prepared by fusing
together arsenious sulphide and sulphur in the required atomic propor-
tions.
2. It is obtained as a yellow precipitate by adding hydrochloric acid
to a solution of a sulpharsenate:
2AsS"Ks3 + 6Ha = 6KC1 + Ab^S''^ + 3SH^
Potaasic Hydrochloric Potassic Arsenic Sulphuretted
sulpharsenate. acid. chloride. sulphide. hydrogen.
It cannot, as was formerly supposed, be prepared by passing sulphuret-
ted hydrogen through a solution of arsenic acid. The yellow precipi-
tate formed under these circumstances is a mixture of arsenious sulphide
and sulphur in the proportion ASjS", -|- S^.
Sulpharaenaies. — These salts may be prepared by passing sulphuretted
hydrogen through solutions of arsenates:
AsOHoNao, + 4SHj = AsS"HsNas, + 40H^
Hydric disodic Sulphuretted Sulphydric Water,
arsenate. hydrogen. disulphosodic
sulpharsenate.
General Properties and Reactions of the Compounds op
Arsenic. — Owing to the frequency of cases of poisoning, both accidental
and intentional, with arsenic, the detection of this silbstance, even when
present in the minutest traces, becomes a matter of great importance.
For a detailed account of the methods to be employed and of -the pre-
cautions to be taken, in a toxicological investigation of this kind, special
works on analytical chemistry must be consulted.
a. Arsenites. — From the hydrochloric acid solution of an arsenite or
of arsenious anhydride, sulphuretted hydroyen precipitates yellow ar-
senious sulphide. The precipitate is form^ slowly in the cold, more
rapidly on warming; it is soluble in ammonic sulphide, caustic alkalies,
ammonic carbonate, and hydric potassic sulphite ; almost insoluble in
hydrochloric acid. Soluble arsenites yield in neutral solution with ar-
genUo nitrate a yellow precipitate of argentic arsenite, soluble both in
nitric acid and in ammonia. With a solution of arsenious anhydride
the yellow precipitate only makes its appearance on the careful addition
of ammonia, so as to neutralize the free nitric acid.
b. Arsenates. — Only the alkaline arsenates are soluble in water.
From neutral solutions argentic nitrate precipitates reddish-brown triar-
gentic arsenate, soluble in ammonia. A mixture of magnesic sulphate,
ammonic chloride, and ammonia gives a white crystalline precipitate of
ammonic magnesic arsenate (AsOMgo"Amo,60H,), isomorphous with
the corresponding phosphorous compound (p. 357). Sulphuretted hydra^
NIOBIUM AND TANTALUM. 377
gen in acid solutions first reduces the arsenic acid to arsenious acid with
separation of sulphur ; after which the arsenious acid is precipitated as
arsenious sulphide. In the cold, the reduction of arsenic acid by sul-
phuretted hydrogen takes place with extreme slowness; the action is
greatly aided by keeping the liquid at a temperature of from 60° to 70®
C. (122-158° R) while passing in the sulphuretted hydrogen.
Marsh's Test. — If any of the oxygen or halogen compounds of ar-
senic be introduced into an apparatus in which hydrogen is being gen-
erated from zinc and dilute sulphuric acid, the arsenic is evolved as
arseniuretted hydrogen together with an excess of hydrc^n. If the
escaping gas be ignited and a cold surface of white porcelain be held in
the flame, a black lustrous film of metallic arsenic is deposited upon
the porcelain. In like manner, if the gas be passed through a strongly
heated glass tube, metallic arsenic condenses as a lustrous mirror just be-
yond the heated portion. These thin films of arsenic are at once dissolved
by a solution of sodic hypochlorite. (Distinction from antimony.) The
sulphur compounds of arsenic, and metallic arsenic itself, do not yield
arseniuretted hydrogen under the above conditions. The presence of
nitric acid and other oxidizing agents prevents the formation of arseni-
uretted hydrogen. In applying Marsh's test, and all similar tests, it is
necessary to ascertain by a blank experiment that the reagents employed
are free from arsenic.
Reinsch^s Test. — If a solution of an arsenic compound in hydrochloric
acid be boiled with a piece of pure bright copper, the surface of the
metal becomes covered with a dark-gray coating of arsenide of copper.
If this coating be separated, dried, and then heated in a small glass
tube, a portion of the arsenic is oxidized to arsenious anhydride, which
forms a sublimate of minute transparent octahedra in the tube. To this
sublimate the above confirmatory tests may be applied. This test ought
never to be trusted when the mixture contains a chlorate or a nitrate, as
a portion of the copper will then be dissolved, and the traces of arsenic
which are generally present in the purest copper will be precipitated on
the remaining copper.
All compounds of arsenic, when heated in a narrow bulb-tube with a
mixture of sodic carbonate and potassic cyanide, are reduced to me-
tallic arsenic, which sublimes and collects as a mirror in the colder part
of the tube. When heated with sodic carbonate on charcoal in the
reducing flame of the bloi^pipe, the arsenic compounds evolve a char-
acteristic odor of garlic.
inOBIUM, Nb, and TANTALUM, Ta.
Atomic weighU: Nb=^ 94, Ta== 182. AUmunty '" and \
Oceurrenee. — ^These two very rare elements generally occur together as tantalates and
niobates.
Preparation, — Very liftle is known of them in the free state. They may be obtained
as black powders by heating potassic nioboflaoride and potassic tantalofluoride with
potasHinm or sodium.
The following are some of the principal compounds of these elements:
S78 INORGANIC CHEMISTRY.
COMPOUNDS OF NIOBIUM.
Nfobic chloride NbCL.
Niobic oxjtrichJoride, NbOGU.
Niobic fluoride, NbFs.
Potassic niobofluoride, NbK.Ff.
Hyponiobous oxide, ^b^'iOi.
Hjponiobic oxide, ^Nb**a04.
Niobic anhydride, NbiO^.
COMPOUNDS OF TANTALUM,
These correspond with the above compounds of niobium, with the single exception
that hypotantalous oxide has not been prepared.
ANTIMONY, Sb,?
Atomic weight = 120. Probable molecular weight = 480. 8p. gr. [crys^
taUine) 6.7, (amorphous) 6.78. Fuses at 430° C. (806° F.). Alo-
wieity '" and \ Evidence of aiomioUy :
Antimonious chloride, Bb'^'Clj.
Antimonio tetretho-chloride (tetrethyl \ a^TiTi. r^i
stiboni^ chloride), ^^1^ M,U.
Antimonic chloride, SVCl^.
History. — Many of the compoands of antimony have been known
from very early times. In the fifteenth century Basil Valentine de-
scribed the preparation of metallic antimony.
Occurrence. — Antimony is rarely found native. Sometimes it occurs
alloyed with other metals in various minerals. Combined with oxygen,
it occurs as valentinite or antimonious oxide, and as antimony ochre or
diantimonious tetroxide. The chief source of antimony is gray anti-
mony ore or stibnite, which consists of antimonious sulphide. Sulpb-
antimonites also occur, such as miargyriie, an argentic raeta-sulphanti-
monite.
a. Crystalline Antim,ony,
Preparation. — 1. Antimony may be obtained by fusing the powdered
native sulphide with iron filings: *
8b^", + 3Fe = 3FeS" + 2Sb.
Antimonious Ferrous
sulphide. sulphide.
2. In preparing antimony on a lai^e scale, the sulphide is first
roasted in contact with air, when it is partially converted into antimo-
nious oxide:
2Sb2S", + 90, = 2SbA + 680,.
Antimonious Antimonious Sulphurous
solphide. oxide. Anhydride.
ANTIMONY. 879
The roasted mineral is then fused with charcoal and sodic carbonate.
The reaction takes place in two stages: first, the remaining sulphide is
converted into oxide by the sodic carbonate, and subsequently the oxide
is reduced by the carbon :
1. 8b^"3 + SOONaOj = 300, + 3SNa, + SbA-
AntimoDioiis Sodic Carbonic Sodic Antimonious
sulphide. carbonate. anhydride. sulphide. * oxide.
2. BbA + 30 = 30O + Sb,.
Antimonious Carbonic
oxide. oxide.
3. Pure antimony may be obtained by redbcing with charcoal the
oxide formed by the action of nitric acid upon crude antimony.
Properties, — Antimony is a bluish-white lustrous metal^ with a crys-
talline fracture. By slow cooling it may be obtained in rhombohedra,
closely approximating to the cube. It fuses at 480^ C, and may be dis-
tilled at a white heat.
fi. Amorphous Antimony.
Preparation. — ^This variety, discovered by Gore {Phil. Trans. ^ 1858,
p. 185), is obtained by the electrolysis of a solution of tartar emetic in
antimonious chloride.
Properties. — Amorphous antimony has the appearance and lustre of
polished steel, with a peculiar mammillated surface, and an amorphous
fracture. It contains 5 or 6 per cent, of antimonious chloride derived
from the electrolyte. When heated or struck it undergoes a molecular
change, which spreads rapidly through the entire mass and is attended
with a rise of temperature from 15° to 250° C. At the same time
fumes of antimonious chloride are evolved. After this change the metal
is- found to possess an increased density and to have acquired a granular
fracture.
Reactions. — 1. When antimony is heated to redness in air it burns,
forming antimonious oxide. If a small quantity of antimony be heated
on charcoal to its point of ignition, and then thrown on to a large sheet
of paper folded into the form of a tray, the metal breaks up into a
number of globules, which dance about on the surface of the paper,
burning brilliantly, and leaving black intermittent streaks behind them.
2. With hot concentrated sulphuric acid it yields antimonious sul-
phate with evolution of sulphurous anhydride :
2Sb +
6SO,Ho, =
= s30,(8bAr
+ 3BO, +
60H,.
Snlphoric
Antimonious
Sulphurous
Water.
add.
sulphate.
anhydride.
Uses. — Metallic antimony is employed only in the form of its alloys,
to which it imparts the valuable property of expanding on solidification.
This renders them especially suitable for taking sharp casts. The most
important alloys containing antimony are type metal and Britannia
380 INOBGANIO CHEHISTBY.
COMPOUND OF ANTIMONY WITH HYDROGEN.
ANTmONIUBETTED HTDEOOEN, Aniimonuma Hydride.
Molecular toeigJd = 123.
SbH,.
This compound is unknown in the pure condition.
Preparation, — 1. It is prepared by the action of hydrochloric acid
upon an alloy of zinc and antimony:
8b,Zn''3 + 6HC1 = 2SbH3 + 3ZnCl^
Anlimonious Hydrochloric Antimonious Zincic
ziQcide. acid. hydride. chloride.
2. It is formed by the action of nascent hydrogen, evolved from zinc
and sulphuric acid, upon soluble antimony compounds:
SbClj + 3H, = SbH, + 3HC1.
AntimoniouB AntimoniouB
chloride. hydride.
In both these reactions the antimonious hydride is always mixed with
much hydrogen.
Properties. — It is a colorless gas, possessing a most offensive odor. It
burns with a bluish flame.
Reactions, — 1. When burnt in air or oxygen it yields water and an-
timonious oxide:
2SbH, +
30,
= BbA + 30H,,
Antimonious
Antimonious Water.
hydride.
oxide.
2. When burnt with a limited supply of air, the hydrogen alone is
oxidized, the antimony being deposited :
4SbH3 + 30, = Sb, + 60H,.
Thus, if a cold surface of porcelain be held in the flame of antimo-
nious hydride, a dull black spot of metallic antimony is formed.
3. When passed through a red-hot tube, it is decomposed, like ar-
senious hydride, into its elements.
4. When transmitted through a solution of argentic nitrate, it pro-
duces a black precipitate of antimonious argentide, thus differing from
arsenious hydride (p. 368):
3NO,Ago
+ BbH. =
3NO,Ho + BbAg,.
Argentic
Antimonious
Nitric Antimonious
nitrate.
hydride.
acid. argentide.
ANTIMONIOUS CHLORIDE. 381
From the composition of this compound, and from that of some of its
analogues, the composition of antimonious hydride is inferred.
Antimonious hydride, SbHs.
Antimonious bromide, SbBrj.
Antimonious argentide, SbAgj.
Antimonious zincide, SbaZn^'j.
Antimonious ethide (7We^Ayb^i&m«), . . . SbEtj.
Antimonious amylide ( Triamylstibine)^ . . SbAy^.
COMPOUNDS OF ANTIMONY WITH THE HALOGENS.
Antimonious chloride, SbCIj.
Antimonic chloride, SbCI^.
Antimonious bromide, SbBr,.
Antimonious iodide, Sblg.
Antimonious fluoride, SbF^.
Antimonic fluoride, SbF^.
ANTIMONIOnS CHLORIDE.
SbCla.
Molecular weight = 226.6. Molecular volume i I I. 1 litre of ardhno^
nioua chloride vapor weighs 113.25 criths. Fuses at 72"^ C. (161.6®
F.). £oife o^ 223° C. (433.4° F.).
Preparation. — 1. This compound is formed when chlorine is passed
over excess of metallic antimony or antimonious sulphide :
2Sb + 3C1, = 2SbCl3.
Antimonious
chloride.
28bjS''8 + 9Cla = 4SbCl3 + S'S'^Cl^.
Antimonious Antimonious Disnlphur
sulphide. chloride. dichloride.
The product must be purified by distillation.
2. It may also be prepared by dissolving antimonious sulphide in
hydrochloric acid, or antimony in aqua-regia, evaporating, and distill-
ing the product :
BbjS", + 6HC1 = 38H, + 2SbCls.
Antimonious Hydrochloric Sulphuretted Antimonious
sulphide. acid. hydrogen. chloride.
2Sb +
- 6HCa +
6HO,Ho
= 2SbCls + 60H, + 3'H^O,,
Hydrochloric
add.
Nitric
acid.
Antimonious Water. Nitric
chloride. peroxide.
382 IKOROANIC CHEHI8TBY.
The receiver must be changed as soon as the distillate b^ins to
solidify, and the product which is collected above this point must be
purified by repeated rectification.
8. It may be conveniently obtained by the distillation of a miztare
of 1 part of powdered antimony with 3 parts of mercuric chloride, or
of 3 parts of antimonious sulphide with 7 parts of mercuric chloride :
Sb, + 4Hga3 = ' 28bCl3 + '8b",Hg", + 'Hg'^Cl^
Mercuric Antimonious Dimercuric Mercurous
chloride. chloride. diantimonide. chloride.
Sb^S", + 3HgCl, = 2SbCl, + 3HgS.
Antimonious Mercuric Antimonious Mercuric
sulphide. chloride. chloride. sulphide.
4. Another method consists in distilling together antimonious sul-
phate and sodic chloride :
S,0,Sbo'",
+ 6NaCl
= 2SbCI, +
380,Nao,.
Antimonious
Sodic
Antimonious
Sodic
sulphate.
chloride.
chloride.
sulphate.
JPropertiea. — Antimonious chloride is a soft, colorless, laminated crys-
talline mass. From its consistency and fusibility, it was formerly
known as butter of arUimony. It is deliquescent and powerfully cor-
rosive.
Beadion. — With water it produces antimonious oxyMoride, which is
thus obtained as a white powder :
BbCl, + OH, = 2HC1 + BbOCl.
^ Antimonious Water. Hydrochloric Antimonious
chloride. acid. ozychloride.
Long-continued action of water transforms this compound into anti-
monious oxide :
2SbOCl + OH3 = 2HC1 + BbA.
Antimonious Water. Hydrochloric Antimonious
ozy chloride. acid. oxide.
ANTIMONIC CHLORIDE.
SbCl,.
Moleeular weight = 297.5. Fuses at 0° C.
Preparation. — ^It is obtained by acting upon antimony with excess of
chlorine, or by passing this gas over antimonious chloride, when the
latter liquefies, producing antimonic chloride :
OZIDEB AND AdSS OF XSTJilOSY. 383
2Sb + 501, = 2SbCl,.
AntixDonic
chloride.
SbCl, + CI, = SbCl,.
Antimonious Antimonic
chloride. chloride.
Properties, — Antimonic chloride is a colorless, fuming liquid. It is
readily decomposed on heating into antimonious chloride and free
chlorine, and thus behaves towards many substances as a chlorinating
agent.
Ileadions, — 1. With a small quantity of water, it forms antimonic
ozytrichloride, analogous to phosphoric ox}rtrichloride :
BbCl, + OH, = BbOClj + 2HC1.
Antimonic Water. Antimonic Hydrochloric
chloride. oxjtrichloride. acid.
2. An excess of water transforms antimonic chloride into orthanti-
monic acid, or pyrantimonic acid corresponding to pyrophosphoric acid :
SbCl^ + 40H, = SbOHoa + 5HC1,
Antimonic Water. Orthantimonic Hydrochloric f
chloride. acid. acid.
+ lOHCl.
Hydrochloric
acid.
3. By the action of sulphuretted hydrogen, antimonic sulphotri-
chloride is formed :
BbCl, + SH, = BbS'^Cls + 2HCI.
Antimonic Sulphuretted Antimonic Hydrochloric
chloride. hydrogen, sulphotrichloride. acid.
Antimimioua hromidey 8bBr,, resembles antimonious chloride. It crystallizes from
carbonic disulphide in colorless octahedra. It fuses at 90° C. (194° F.), boils at 275''
C. (527° F.), and by the action of water is converted into the oxyftrtwiide, SbOBr.
AnHmonious iodide, Bbl,, crystallizes in red hexagonal plates, and, when acted upon
by water, forms the oxyiodvdej 8bOI.
Antimonious fluoride, SbFs, is obtained by evaporating a solution of antimonious
oxide in excess of hydrofluoric acid. It crystallizes in colorless prisms or scales, and
deliquesces with formation of the oxyfiuoride, 8bOF.
Antinumie fluoride, BbFj, is left behind as a gummy mass when a solution of anti-
monic acid in hydrofluoric acid is evaporated in vacuo,
OXIDES AND ACIDS OF ANTIMONY.
Antimonious oxide or anhydride, .... (Sb203)2.
Diantimonic tetroxide, '8b*%0^.
Antimonic anhydride, SbjO^.
Metantimonious acid, SbOHo.
Orthantimonic acid, SbOHoj?
Metantimonic acid, SbOgHo.
Pyrantimonic acid, SbgOaHo^.
or 2SbCl5 +
70H, =
= Sb^Ho^
Antimonic
Water.
Pyrantimonic
chloride.
acid.
384 IKOBOAKIC CHEMISTRY.
ANTIMONIOUS OXmE, or ANHYDRIDE.
(SbAV
Molecular w^gH = 576. Molecular volume EQ 1 lUre of aniimo-
niou8 oxide vapor weighs 288 criihs. Sp. gr. (octahedral) 6,25,
{rhombic) 5.55.
Occurrence. — Antimonious oxide is found in natare in two rare
minerals : in the rhombic form as valentinite^ and in the octahedral
form BS aenarmorUUe.
Preparation, — 1. It is formed when antimony is barnt in air or
oxygen.
2. It is most readily obtained by pouring a solution of antimonious
chloride in dilute hydrochloric acid into a boiling solution of sodio
carbonate :
28bCl3 + SOONaoj = BbA + 30O, + 6NaCl.
Antimonious Sodic Antimonioos Carbonic Sodic
chloride. carbonate. oxide. anhydride. chloride,
3. When metantimonions acid is heated to 100° C, it is converted
into antimonious anhydride, with eh'mination of the elements of water:
28bOHo =
OH, + SbA-
Metantimonioiu
Water. Antimonioos
acid.
oxide.
Properties. — Antimonious anhydride may be obtained in two dis-
tinct crystalline forms — in rhombic prisms and in regular octahedra —
corresponding with the two forms of arsenious anhydride, with which
substance it is therefore isodimorphoiLa. When antimony is heated in
a slow current of air, rhombic prisms of the oxide are formed in the
immediate neighborhood of the metal ; further on a mixture of prisms
and octahedra is deposited ; whilst in the colder parts of the tube the
crystals consist of octahedra alone. Antimonious oxide in both its
forms is colorless, but when heated, assumes a yellow tint, which disap-
pears again on cooling. When air is excluded, it may be fused and
sublimed. Water does not dissolve it.
Reactions. — 1. When heated to redness in air, it burns like tinder,
forming diantimonic tetroxide:
SbA + o = 'Sb«%o«.
Antimonious Diantimonic
oxide. tetroxide.
2. It is really reduced to the metallic state by ignition ^ith charcoal
or hydrogen :
MKTANTmOMIOUS ACID — DIANTIICONIC TETBOZIDE. 385
BbA + 3C = 2Sb + 300.
Antimonious CSarboDic
oxide. oxide.
BbA + 3H2 = 2Sb + 30H,.
Antimonious Water,
oxide.
3. It is readily dissolved by a hot solution of hydric potassio tartrate
(cream of tartar), forming potassic antimonylic tartrate (tartar emetic) :
rooHo roo(Sb'"02)
[COKo tCOKo
Hjdric potassic Antimonious Potassic antimonylic Water.
tartrate (cream oxide. tartrate (tartar
of tartar), emetic).
4. Hydrochloric acid dissolves it with formation of antimonious
chloride :
SbA + 6HC1 = 2SbCl3 + 30H^
Antimonious Hydrochloric Antimonious Water,
oxide. acid. chloride.
ICBTANTIMONIOnS ACID.
BbOHo.
Molecular weight = 153.
I^eparaHon. — Metantimoniousacid is obtained by pouring a solution of antimonious
chloride into a cold solution of sodic carbonate :
2SbCl8 + SCONaoj + OH, = 2SbOHo + SCO, + GNaCl.
Antimonious Sodic Water. MetantlmoniouB Carbonic Sodic
chloride. carbonate. acid. anhydride. chloride.
JProperties, — It forma a white amorphous powder, which is insoluble in water.
ReaHumz. — 1. It is decomposed by heat (p. 384).
2. It is dissolved by an excess of alkaline hydrates, producing ill-defined anti-
monites. .
It also possesses weak basic properties and forms salts in which the monad group
(8bO) replaoes the hydrogen of the acid. Potassic antimonylic tartrate is an ex-
ample.
DIANTIMONIC TETROXIDE, Antimonylic Antimonate,
fSbO,
\SbO,
= 'Sb%0„ or Sb-02(Sb'"02).
Molecular weight = 304.
Occurrence. — Diantimonic tetroxide is found native as oervantite.
Preparation. — 1. It is obtained by igniting antimonic anhydride, or
the white solid produced by the action of nitric acid upon metallic
antimony :
25
386
INOBOANIC CHKUIBTBT.
2SbA =
Antimonic
anhydride.
2'Sb''A +
Diantimonic
tetrozide.
2. When antimonious oxide is heated in contact with air, it is con-
verted into diantimonic tetroxide (p. 384).
Properties. — Diantimonic tetroxide is a white, infusible and non-
volatile powder. When heated, it turns yellow, but becomes white
again on cooling.
Reaction. — When boiled with a solution of hydric potassic tartrate, it
is decomposed, potassic antimonylic tartrate and metantimonic acid
being formed :
fOOHo
J OHHo
1 OHHo
tcOKo
Hydric potassic
tartrate.
+ 8b^O,(Sb'''0,) =
^ 0O(Sb''
OHHo
OHHo
OOKo
'O,)
+ SbOjjHo.
Antimonylic
antimonate.
Potassic antimonylic
tartrate.
Metantimonic
acid.
This reaction seems to indicate that this oxide is in reality an anti-
monylic antimonate as formulated in the above equation.
ANTIMONIO ANHTDBIDE.
BbA.
MokcuJar weight = 320. Sp. gr. 6.6.
Preparation. — It is obtained by heating the corresponding acids to
280°C. (536°F.):
2SbOHo3
Orthantimonic
acid.
+
30Hr
Water.
2Bb0^o
Metantimonic
acid.
+
+
Water.
20H,.
Water.
= SbA
Antimonic
anhydride.
= BbA
Antimonic
anhydride.
Sb,0^o« = BbA
Pyrantimonic Antimonic
acid. anhydride.
Properties. — Antimonic anhydride is a pale yellow amorphous sub-
stance, insoluble in water.
Reactions. — 1. When heated it is decomposed into antimonylic anti-
monate and oxygen (supra). This decomposition begins at 300° C.
2. Fused with potassic carbonate, it produces potassic metanti-
monate :
SbjO^ + OOKoj = 28b02Ko + 00^
Antimonic Potassic Potassic Carbonic
anhydride. carbonate. metantimonate. anhydride.
COMPOUNDS OP ANTIMONT WITH SULPHUR. 387
ORTHAHTIMONIC ACID.
SbOHog?
Prmaraiion. — This acid is said to be formed by the action of water upon antimonic
chloride (p. 383).
MSTANTIMONIC ACID.
SbOjHo.
Preparation, — 1. It is obtained by the action of nitric acid containing a little hydro-
chloric acid on metallic antimony :
Sb, -h 4NO,Ho = 2SbO,Ho + NA + 'N^^,0, + OH,.
Nitric Metantimonic Nitrous Nitric Water,
acid. acid. anhydride. oxide.
2. It is also formed by the spontaneous dehydration of orthantimonic acid, or of
pyrantimonic acid :
SbOHo, = OH, + SbOjHo.
OrthantimoDic Water. Metantimonic
acid. acid.
Sb,0,IIo, =
= OH,
+ 2SbO,Ho.
Pyrantimonie
Water.
Metantimonic
acid.
acid.
Properties.'^Jt is a soft white powder, sparingly soluble in water. The solution
reddens litmus.
Reaction, — By the action of alkaline hydrates, it produces either metantimonates or
orthantimonates :
SbO,Ho 4- OKH = SbO,Ko -f OH,.
Metantimonic Potanic Potasslc Water,
acid. hydrate. metantlmonate.
SbO,Ho + OKH = SbOHo,Ko.
Metantimonic Potaasic Dihydrlc potassic
acid. hydrate. orthantimonate.
PTRAM TIMONIC ACID, Parantimiimic Add (MetarUimame Add of Fremy).
8b,0,Ho4.
Preparation, — 1. It is formed by the action of water upon antimonic chloride (p.
}3).
2. It is also obtained by acidifying solutions of pyrantimonates :
Sb,0,Ho,Ko4 -f 2HC1 = SbjOaHo^ + 2Ka.
Dihydrlc dipotaselc Hydrochloric Pyrantimonic Potassic
pyrantimonate. acid. acid. chloride.
Dihydric dipotassic pyrantimonate is prepared by fusing antimonic anhydride with
an excess of potassic hydrate, and extracting the mass with water, when an alkaline
solution containing dihydric dipotassic pyrantimonate, BbjOsHojKo,, is obtained.
This solution produces precipitates in solutions of sodium salts, the sodic pyranti-
monate thus formed having the formula 8b,0,Ho,Nao„60H,.
COMPOUNDS OF ANTIMONY WITH SULPHUR,
Antimonious sulphide, .... Sb^'',.
Antimonic sulphide, SbjS^'^.
388 INORGANIC CHEMISTRY.
ANTIMONIOnS SULPHIDE, 8uiphanUm<mi(m8 Anhydride.
Molecular weight = 336.
Occurrence, — ^Antimonious salphide is found in nature as stUmite or
gray antimony ore.
Preparation. — 1. It may be obtained by heating together antimony
and sulphur, or antimonious oxide and sulphur, in the proper molec-
ular proportions :
8b, + 38, = 28b,S"3.
Antimonious
sulphide.
28bA + 9S = 2Sb^", + 380,.
Antimonious Antimonious Sulphurous
oxide. sulphide. anhydride.
2. It is precipitated when sulphuretted hydrogen is passed through
a solution of antimonious chloride :
2SbCl, + 38H2 = 8b^"3 + 6HC1.
Antimonious Sulphuretted Antimonious Hydrochloric
chloride. hydrogen. sulphide. acid.
Properties, — The native sulphide occurs in dark-gray radiating crys-
talline masses, with a metallic lustre — less frequently in rhombic prisms.
The precipitated substance is an orange-red amorphous powder, con-
taining water of hydration which may be expelled by heating. Anti-
monious sulphide is readily fusible, and may be sublimed.
Reajdions. — 1 . Hot hydrochloric acid decomposes it, forming anti-
monious chloride and sulphuretted hydrogen (see p. 381).
2. It dissolves with decomposition in solutions of alkaline hydrates,
yielding a mixture of antiraonite and sulphantimonite :
8b^"3 + 6KHo = SbKs3 + SbKo, + 30H^
Antimonious Potassic Trisulphopotassic Tripotasslc Water,
sulphide. hydrate. sulphantimonite. antimonite.
The addition of an acid reproduces and precipitates the antimonious
sulphide :
SbKsj + 8bKo3 + 6HC1 = Sb,S''3
Trisulphopotassic Tripotassic Hydrochloric Antimonious
sulphantimonite. antimonite. acid. sulphide.
+ 6KC1 + 30H,.
Potassic chloride. Water.
3. It dissolves in a solution of an alkaline sulphbydrate, forming a
sulphantimonite:
Sb^S", + 6KH8 = 2SbKs3 + 3SH2.
Antimonious Potassic Trisulphopotassic Sulphuretted
sulphide. sulphhydrate. sulphantimonite. hydrogen.
SULPHAin?IMONITE8 — ANTIMONIC SULPHIDE. 389
8X7LPHA1VTIMONITES.
Many solphantimonites occur in nature :
Orthosulphaniirnonites.
Oeneralformulai : BbMsg and BbsMs^^,.
Dark-red silver. TMeulphargeniic gulphantimonite, . BbAgs,.
Boulangerite. TrinUphopluinbic mdphantimonitef . . BbiPbs^^s.
Boumonite. DigvlphopturnbU sulphoeuprom stdphcmti'
fMmite, •Sb.Pbs^^/Cu.S'^,)^'-
MetasidphaniimonUes,
Qeneralformui^: BbS^^Ms and Bb^^^Ms^^
Miargyrite. SuhhargerUic metasulphanHmoniUf . . BbS^'Ags.
Zinkenite. SulpM^umhk metaaulpharUimonitej . . Bbj&^^Pbs^^,
Antimony copper glance. Sulphocuprous metamtph-
antinumUe, Sbfi'\(Cu^S'\y',
Berthierite. Sulphoferrous tnetamUphantimoniie, . . Bb^^\Fei'^,
• PyromdpharUimonites,
Qeneralfwmvlx: BbaS^^Ms^ and Sbj^S^^Ms^',.
Feather ore. Sulphaplumbie pyrosulphaniimonite, . . BbjS^^Pbs^^^
Fahl ore. Sulphocuprosoferrom pyrodulphantimonUe, . Bb^S^'^CCuaFeS^',)'^.
A soluble eoUoidal ?nodt/Eea^ion of antimonious sulphide corresponding with colloidal
arsenious sulphide (p. 375) is also known.
ANTIMONIO SULPHIDE, Sulpfuintimanio Anhydride.
Molecular weight = 400.
Preparation, — 1. It is precipitated as a yellowish-red powder when
sulphuretted hydrogen is passed through a solution of antimonic
chloride :
2fSbC\ + 5SH2 = Sb^S^', + lOHCl.
Antimonic Sulphuretted Antimonic Hydrochloric
chloride. hydrogen. sulphide. acid.
2. The same precipitate is formed by the addition of an acid to a
solution of a sulphantimonate:
2BbS''Na% + 6HC1 = Sb^S''^ + 6NaCl + 3SH,.
Trisulphosodic Hydrochloric Antimonic Sodic Sulphuretted
sulphantimonate. acid. sulphide. chloride. hydrogen.
BeadionB. — 1. When heated it is decomposed into antimonious sul-
phide and free sulphur.
2. Boiling hydrochloric acid decomposes it into antimonious chloride,
sulphuretted hydrogen, and sulphur :
390 INOBGANIC CHEUI8TBY.
8b^", + 6HC1 = 2SbCl, + 38H, + 8^
Antimonic Hydrochloric Antimonioos Sulphuretted
sulphide. acid. chloride. hydrogen.
3. It dissolves in a solution of an alkaline sulphide, forming a sulph-
antimonate :
Bb,S'', + 3SK, = 28bS"K8y
Antimonic Potassic TrisulphopotasBic
sulphide. sulphide. sulphantiuionate.
4. It is soluble in a solution of an alkaline hydrate, a mixture of
antimonate and sulphantimonate being formed :
48b^", + 240KH = 38bOKo, + SSbS^Ks, + 120H^
Antimonic Potassic Tripotassic Trisulphopotassic Water.
sulphide. hydrate. antimonate. sulphantimonate^
General Properties and REAcrriONS of the Compounds of
Antimony :
Antimonious Compounds. — Solutions of antimonious oxide in acids
became milky on dilution with water. The milkiness disappears on
addition of tartaric acid. (Distinction from bismuth compounds.) Std-
phuretted hydrogen precipitates from acid solutions orange-colored anti-
monious sulphide, soluble in concentrated hydrochloric acid, in caustic
alkalies, and in ammonic sulphide, almost insoluble in ammonic car-
bonate, insoluble in hydric potassic sulphite. If a hydrochloric acid
solution of the sulphide or of any other compound of antimony be
brought into a platinum dish along with a piece of zinc, the antimony
is deposited by voltaic action as a black coating adhering to the plati-
num, whilst any tin which may be present is precipitated as a gray
powder on the zinc. The hydrochloric acid solution of an antimonious
compound precipitates toM in the metallic form from its solutions.
Antimonic Compounas, — These yield in acid solution with sulphuretted
hydrogen a yellowish-red precipitate of antimonic sulphide which is
soluble in the same reagents as the antimonious compound.
The compounds of antimony when introdueed into Marsh's apparatus
(p. 377) evolve antimoniuretted hydrogen. The flame of this gas de-
posits, upon a cold surface of porcelain, a stain of metallic antimony,
which is blacker and less lustrous than that of arsenic. A mirror of
metallic antimony is also formed when the gas is passed through a
heated tube. These coatings may be distinguished from those of arsenic
by their almost total insolubility in sodic hypochlorite. When heated
with potassic cyanide upon charcoal in the reducing flame of the blow-
pipe, compounds of antimony yield a brittle metallic regulus, and the
charcoal becomes covered with a white incrustation; but no odor of
garlic is perceptible as in the case of arsenic.
BISMUTH — BISMUTHOUB CHLORIDE, 391
BISMUTH, B14?
Atomic weight = 208.2. S-p. gr. 9.83. Fuses at 265° C. Atomicity "'
and ^. Emdenoe of atomicity :
V
Bismuthoufl chloride, Bi'^Cla-
Bismuthous oxide, Bi^'jO,.
Bismuthous ethide, Bi'"Et5.
Bismuthous dichlorethide, Bi'^'EtClj-
Bismathic anhydride, Bi^O^.
Metabismuthic acid, Bi^OjHo.
Occurrence. — ^Bismnth is found principally in the metallic state, but
it also occurs in combination with oxygen, sulphur, and tellurium.
Preparation. — 1. The method of extraction from the ores formerly
consisted in heating the crude native bismuth in sloping iron tubes
placed in a furnace. The metal fused and ran off, whilst the impuri-
ties were left in the tubes. The bismuth thus obtained was contami-
nated with sulphur, arsenic, iron, and other metals.
2. At the present day large quantities of bismuth are obtained as a
by-product in the manufacture of smalt (g.t?.). The crude bismuth is
purified by fusing at the lowest possible temperature, when the more
fusible bismuth runs off, leaving the iron, nickel, and other impurities
behind.
3. It may be obtained in the pure state by dissolving commercial bis-
muth in nitric acid, precipitating the basic nitrate by the addition of
water, and reducing the precipitate by ignition with charcoal.
Properties. — Bismuth is a grayish- white metal with a slight reddish
tinge. It crystallizes in rhombohedra which approximate closely to
the cube. At a very high temperature it volatilizes. It is not oxid-
ized by exposure to the air at ordinary temperatures, but, when strongly
heated, burns, forming bismuthous oxide.
' Uses. — Metallic bismuth is employed in the preparation of fusible
alloys, such as Ros^s metal and Wood's metal {q.v.).
No compound of bismuth with hydrogen is known.
HALOGEN AND OXYHALOOEN COMPOUNDS OF
BISMUTH.
BISMUTHOUS OHLOBIDE.
BiCls.
M6Uctdar weight = 314.7. Molecular volume i i i- 1 litre of bis-
muthous Moride vapor weighs 157.35 criths.
Preparation. — 1. It is formed when dry chlorine is passed over
metallic bismuth :
392 INORGANIC CHEMISTBY.
Bi, + 3C1, = 2BiCl,.
Bismuthoos
chloride.
2. It may be obtained by evaporating a solution of bismuth in hydro-
chloric acid containing a little nitric acid, and distilling the residue.
3. Another method consists in distilling bismuth with mercuric
Chloride :
Bi, + 6HgCl, = 2BiCl, + 3'Hg',Cl^
Mercaric BUmuthoos Mercurous
chloride. chloride. chloride.
Properties. — It forms a white fusible deliquescent mass which may
be distilled.
JReaetion. — Water decomposes it, precipitating 6i8mti^u9 oxyohloride
as a white powder :
BiCl, + OH, = BiOCl + 2HC1.
Bismuthous Water. Bismuthoiis Hydrochloric
chloride. ozjchloride. acid.
QIQ,', IB obtained as a black amorphous mass
by heating bismuthous chloride with bismuth.
BiSMUTHOus BROMIDE. BIBrj,, furms yellow prisms fusing at 200^ C. Water converts
it into bismuthous oxybromidey BIO Br.
Bismuthous iodide, BlI,, is obtained by heating a mixture of bismuth and iodine.
It sublimes in lustrous, dark-gray hexagonal plates. By boiling with water it is de-
composed into hydriodic acid and copper-colored hianutkoua oxywdide, BiOr.
Bismuthous fluoride, BIP,. is obtained as a white powder by evaporating a solu-
tion of bismuthous oxide with an excess of hydrofluoric acid :
Bl,0, + 6HF = 2BIF, + 30H,.
Bismuthous Hydrofluoric Bismuthous Water,
oxide. acid. fluoride.
COMPOUNDS OF BISMUTH WITH OXYGEN AND
HYDROXYL.
Dibismuthous dioxide,
/BiO
\BiO'
Bismuthous oxide, BijO^.
Dibismuthic tetroxide, 'Bi*%04,
Bismuthic anhydride, Bi^Oj.
Bismuthous oxyhydrate, or metabismuthous acid, BiO Ho.
Metabismuthic acid, BiOjHo.
DIBIBBiUTHOUS DIOXIDE.
/BIO
IBIO-
Molecular weight = 448.4.
PmpcaraJtion, — When a mixture of stannous and bismuthous chlorides is poured into
an excess of dilute caustic potash, a black precipitate of dibismuthous dioxide is formed.
The reaction takes place in two stages. In the first, dipotassic stannite and tripotassic
bismutliite are formed ; these salts then react upon each other :
BI8MUTHOU8 OXIDE. 393
2BIK0, -h SnKo, + 30H, = ^l'',0, + SnOKo, + 60KH.
Tripotassic Dipotassic Water. Dibismutboua Dlpotossic Potasslc
bisznuthite. stannite, dioxide. stannate. hydrate.
The precipitate of dibismuthons dioxide ifust be filtered and washed out of contact with
air and then dried by heating in a current of carbonic anhydride. It is thus obtained
as a gray crystaUine powder.
RtactwM, — 1. The moist substance when exposed to the air oxidizes spontaneously to
bisDiuthous oxide :
^^',0, 4- O = BljO^.
Dibismuthous Blsmuthous
dioxide. oxide.
Id the same way when the dried compound is heated in the air, it glows like tinder
and is converted into bismuthous oxide.
2. Hydrochloric acid decomposes it into bismuthous chloride and bismuth :
S^Bl'^O, + 12HC1 =
4B1C1, -h
Bl,
+
eoHr
DiblnnuthouB Hydrochloric
Bismuthous
W&ter.
dioxide. acid.
chloride.
BISMUTHOUS OZmS.
Bi,0,.
Molecular weight = 464.4. 8p. gr. 8.2.
Occurrence. — This substance is found in nature as the rare mineral
bismuth ochre.
Preparation, — 1. It is formed when bismuth is burnt in air or
oxygen.
2. It is left behind when the nitrate, carbonate, or hydrate is heated :
2N,0,Bio''' ^ Bi,0, + 3NA + 30,.
Bismuthous Bismuthous Nitrous
nitrate. oxide. anhydride.
2NO^Bi"'Ho,0) = BijOs + 20H, + N,0, + O^
Bismuthous nitrate Bismuthous Water. Nitrous
dihydrate. oxide. anhydride.
OO(BiOj), = Bi,0, + 00,.
Bismuthylic Bismuthous Carbonic
carbonate. oxide. anhydride.
2BiOHo = BijOs + OH,.
Bismuthous Bismuthous Water,
oxy hydrate. oxide.
3.. When bismuthous hydrate is dissolved in a solution of potassic
hydrate and boiled, it parts with the elements of water, and is precipi-
tated as bismuthous oxide.
Properties. — Bismuthous oxide is a yellow insoluble powder, which
becomes darker on heating, and then fuses. The oxide obtained by
boiling the solution of the hydrate in caustic alkali is crystalline.
394 INORGANIC CHEMISTRY.
Reaction. — It is difisolved by hydrochloric, nitric, and sulphuric
acidsy forming the bismuthous chloride, nitrate, and sulphate:
BiCl,.
NjO.Bio'^.
S3OeBl0"V
Bismuthous
Bismuthous
BbmiithouB
chloride.
nitrate.
sulphate.
Salt8 of Bismuthous Oxide. — ^These salts are soluble only in water
containing an excess of acid. Pure water decomposes them into basic
salts and free acid :
NjO^Bio''' + 20H, = NOj(Bi'"HoP) + 2NO,Ho.
Bismuthous Water. Bismuthous nitrate Nitric
nitrate. dihydrate. acid.
BISMUTHOUS OZTHTDRATE, Metalnsrnutfuma Acid.
BiOHo.
Preparation. — By pouring a solution of bismuthous nitrate in dilute
nitric acid into dilute ammonia or potassic hydrate, a precipitate is
formed, which probably contains orthobismuthous acid. On drying
this precipitate at 100^ C, metabismuthous acid is obtained as a white
amorphous mass:
NjO^Bio''' + SOKH = BiHoj + 3NO,Ko.
Bismuthous Potassic Orthobismuthous Potassic
nitrate. hydrate. acid. nitrate.
BiHoa = BiOHo + -OH^.
Orthobismuthous Metabismuthous Water,
acid. acid.
Reaction, — By heat or by boiling with caustic alkali, water is expelled
and bismuthous oxide is formed (see p. 393).
An unstable metabismuthite is produced by fusing. bismuthous oxide
with sodic carbonate :
BijO, + OONao, = 2BiONao + OO^
Bismuthous Sodic Sodic Carbonic
oxide. carbonate. metabismuthite. anhydride.
BI8MUTHIC ANH7DBIDB.
BIA.
Preparaiion, — This compound is obtained as a brown powder by heating bismnthic
acid to 130° C.
MeacUom. — 1. When heated to the boiling point of mercury it loses oxygen, being
converted either into bismuthous oxide or into dibismuthic tetroxide :
METABI8MUTHIC ACID— DIBISMUTHOUS BISULPHIDE. 395
Bl^Oj - B1,0, + O,;
Bismuthlo BlKmuthouB
anhydride. oxide.
2BI,05 >- 2^Bl"A -f O,.
Blsmuthic Dibismuthic
andydride. teiroxide.
2. When heated in a current of hydrogen, it is readily reduced to bismuthous
oxide.
3. Heated with hydrochloric acid it evolves chlorine, producing bismuthous
chloride and water:
BlaOj -h lOHCl == 2Bias + 50H, + 2a,.
Blsmuthic Hydrochloric Bismuthous Water,
anhydride. add. chloride.
4. Sulphurous acid converts it into bismuthous sulphate:
3Bi.0j -h 6SOH0, = 2S,0,Bio^'^, -f B1,0, -f 60H,.
Blsmuthic Sulphurous Bismuthous Bismuthous Water,
anhydride. acid. sulphate. oxide.
6. When heated with sulphuric or nitric acid it evolves oxygen, producing bis-
muthous sulphate or nitrate :
BIjOj -h 3SO,Ho, = S,0,Bio''^ + 30Hg + O,;
Bismuthlo Sulphuric Bismuthous Water,
anhydride. acid. sulphate.
BljOs + 6NO,Ho = 2N80eBio^'^ -|- 30H, -|- O^
Blsmuthic Nitric Bismuthous Water,
anhydride. acid. nitrate.
BflETABISMUTHIC ACID.
B10,Ho.
Reparation, — Metabismuthic acid is obtained as a red deposit by passing chlorine
through a solution of potassic hydrate containing bismuthous oxide in suspension :
40KH + 2C1, + B1,0, = 2B10,Ho -f 4KC1 + OH,.
Potassic Bismuthous Metabismuthic Potassic Water,
hydrate. oxide. acid. chloride.
Reaction. — It dissolves in a hot solution of potassic hydrate. By the addition of an
acid to the liquid a salt, said to have the composition
BftO^HoEo,
IB precipitated.
COMPOUNDS OF BISMUTH WITH SULPHUR.
Dibismuthoufl disulphide, 'Bi^'jS'V
Bismuthous sulphide^ Bi^S'',.
DIBISMTJTHOUS DI8X7LPHIDB.
{^// or ^r/,8'V
^p, gr. 7.3.
PreparaJtiim. — Dibismnthoos disulphide is obtained as a mass of gray, metallic
ftcicular crystals by fusing together bismuth and sulphur in the proper molecular
proportions.
396 INOBGANIG CHEMI8TBY.
BISMUTHOUS SULPHIDE.
Sp. gr. 6.4.
Occurrence, — ^Bismuthous Bulphide is found native as the rare mineral
bismuth glance. It forms rhombic crystals and foliated or fibrous
masses with a metallic lustre.
Preparation, — 1. It maybe obtained by fusing tc^ther bismuth and
sulphur in the proper molecular proportions.
2. It is also obtained as a blackish-brown powder by precipitating
bismuth solutions by sulphuretted hydrogen :
2BiCl3 + 3SH, = BijS''3 + 6HC1.
BismuthouB Sulphuretted Bismuthous Hydrochloric
chloride. * hydrogen. sulphide. acid.
Reaction, — This compound is not dissolved by alkaline hydrates or
sulphydrates.
A few sulphobismuthites are found in nature:
Kobellite. Trisviphoplurnbic 1 g; pug//
sulphobism/athite j ^ *'
Needle ore. IMmlplwplumbic- j Bi,Pba",('Ca'A)".
dicuprous sulpnootsmtUhtte J ^ '
Bismuthoxia ielluride, BigTe^'j, occurs native as telluric bismuth or tei-
radymite. It forms gray, metallic, rhombohedral crystals or foliated
masses. A portion of the tellurium in this mineral is generally replaced
by sulphur.
Genebal Pbopebties and Reactions of the Compounds of
Bismuth. — The salts of bismuth with colorless acids are colorless.
Their solutions have an acid reaction. Dilution with water causes the
solutions to become milky, owing to the separation of a basic salt.
Mineral acids redissolve this basic salt ; but the presence of tartaric
acid does not prevent or remove the milkiness as in the case of anti-
mony. Caustic alkalies and ammonia precipitate white bismuthons
hydrate, insoluble in excess. Sulphuretted hydrogen gives a brown
precipitate of bismuthous sulphide, insoluble in aramonic sulphide and
in caustic alkalies, soluble in hot nitric acid. Potassic chromaie pre-
cipitates yellow bismuthous chromate, soluble in nitric acid, insoluble
in caustic alkalies. (Distinction from plumbic chromate.) Heated on
charcoal in the reducing flame the bismuth compounds yield a brittle
metallic bead, whilst the charcoal becomes covered with a yellow incrus-
tation.
THE METALS.
CHAPTER XXXI.
DISTINOUTSHINO CHARAOTERISTICS OF THE METALLIC ELEMENTS.
t'
There are certain broad differences which prevail between metallic
and non-metallic elements, so that as a rule members of the one class
may be readily distinguished from those of the other. The most ob-
vious of these differences are physical.
Thus tlje power of reflecting light is much more marked in the
metals than in the non-metals. This power, when intensified by the
perfect or almost perfect opacity of the reflecting substance — a property
possessed in the highest degree by the metals — constitutes the phe-
nomenon of metallic lustre. The non-metals are generally either trans-
parent or translucent: they admit light into their interior, where it is
either transmitted further, or absorbed and dispersed, and they cannot
therefore possess the high reflecting power — the power of giving back
the whole or nearly the whole of the light which falls upon them —
necessary to the production of the metallic lustre. Smoothness of sur-
face is, however, a necessary condition of metallic lustre, and for this
reason finely-divided metals do not possess this property. Gold, silver,
platinum, and other metals may be obtained in this condition by pre-
cipitation from their solutions; but these non-lustrous powders assume
a lustre under the burnisher.
Again, the metals are much better conductors of heat and of elec-
tricity than the non-metals.
The above broad physical differences have their counterparts in the
chemical characters of the elements ; thus a metal uniting with oxygen
generally yields a base or alkali, whilst the compounds of the non-
metals with oxygen generally passess acid properties.
But nature abhors classification, and renders futile all our attempts
to form exclusive families of her productions. The animal and vege-
table kingdoms merge into each other, so that it is impossible to
predicate definitely of the intermediate members to which class they
belong — whether they are to be regarded as plants or as animals. In like
manner the metals and the non-metals gradually approach and overlap
each other in respect of nearly all the so-called distinctive properties
just enumerated.
Thus, as regards lustre, we find that various non-metals possess a
lustre which is distinctly metallic in character — for example, graphite,
the popular name for which, black-Zead, is derived from this property.
Iodine is another instance : the crystals of this substance have a lustre
398 INORGANIC CHEMISTRY.
resembling that of graphite, and not much inferior to that of metallic
arsenic when sublimed in a glass tul)e.
Again, as r^ards opacity, which was stated to be a general property
of the metals, we find that this rule is not absolute. Gold in very thin
leaves transmits a green light, silver a blue light, whilst, on the other
hand, graphite is opaque, and iodine nearly so.
Again, as regards the power of conducting heat and electricity, carbon
in the form of graphite shares this power with the metals.
As to chemical character also, the classification above given does
not always hold. Thus some metals yield acids with oxygen — chromic
acid, manganic acid, molybdic acid, and others. But no non-metal
C* ' Is a decided base with oxygen. Tellurium and arsenic yield no
, and the basic properties of antimony and bismuth are very weak.
Although, therefore, the division of the elements into metals and
non-metals cannot lay claim to rigid accuracy, it may, in the present
state of the science, be r^arded as a good practical classification. With
the few exceptions just enumerated, it is no more difficult to distinguish
a metal from a non-metal than to distinguish an animal from a plant.
RelcUiona of the Metals to Heal.
Expaimon by Heat. — Metals as a rule expand more on heating than
non-metals. The following table gives the length to which the unit
length of a number of substances, measured at 0^ C, expands when the
substance is heated to 100° C. (212° F.). This value, diminished by
unity, is therefore the coefficient of linear expansion for a rise of 100° C. :
Expansion of Solids by Heat.
One part by length measured at 0° C. measures at 100° C. :
English flint glass, 1.000811
French glass tube, 1.000861
Platinum, . 1.000844
Palladium, 1.001000
Untempered steel, 1.001079
Antimony, 1.001083
Iron, 1.001182
Bismuth, 1.001392
Gold, 1.001466
Copper, 1.001718
Brass, 1.001866
Silver, 1.001909
Tin (East India), 1.001937
Lead, 1.002848
Zinc, 1.002942
Fusibility. — Another important property of metals is their degree of
fusibility. This is almost as varied in the different metals as the range
of temperature at our command. On the one hand mercury fuses at
—39.5° C. (—39.1° F.), and gallium with the heat of the hand, whilst
RELATIONS OF METALS TO LIGHT. 399
iridium scarcely melts in the oxyhydrogen flame, requiring the voltaic
arc for its complete liquefaction. Kuthenium is still more infusible,
and osmium has never been melted. The following table contains the
f using-points of some of the metals :
Name of metal. Fusing-point.
Mercury, —39.6'' C
Gallium, +30.1 "
Potassium, 62.5 "
Sodium, 95.6 "
Lithium, 180 ^'
Tin, 228 ''
Bismuth, 268 ''
Thallium, 294 "
Cadmium, 820 ''
Lead, 326 "
Zinc, 420 ''
Antimony, 430 ^*
Silver, \ . 1040 "
The fusing-point of alloys is always lower than the mean fusing-point
of their constituents — taking the relative proportion of the constituents
into account in calculating this mean; and sometimes lower than the
lowest fusing-point of any of the constituents. Thus Wood's fusible
metal, which is an alloy of 4 parts of bismuth, 2 of lead, 1 of tin, and 1
of cadmium, fuses at 60.5° C. (140.9° F.). The alloy of potassium
and sodium is liquid at ordinary temperatures.
Volatility. — All metals are volatile, but usually only at very high
temperatures. Mercury boils at 360° C. (680° F.), but is volatile at
ordinary temperatures, as may be shown by suspending a piece' of gold-
leaf from the stopper of a bottle containing mercury : in course of time,
-the gold-leaf becomes white, owing to the absorption of the vapor of
mercury. Arsenic volatilizes below redness without first assuming the
liquid form. Cadmium boils at 860° C. (1580° F.) ; zinc at 1040° C.
(1904° F.). Potassium and sodium are aistilled in their manufacture.
Lead is volatilized in the process of lead smelting, and means are em-
ployed to condense the lead which would thus otherwise escape. Even
copper is perceptibly volatile at the temperature of the smelting furnace.
Relations of Metals to Light.
Colors of Solid Metals. — Most metals appear nearly colorless when
polished. Some, however, exhibit, even when viewed in the ordinary
way, specific colors : thus copper is red ; and gold, calcium, and barium
display shades of yellow. By causing the light to be reflected several
times from thefr surfaces, some metals, which under ordinary conditions
appear colorless, may be made to exhibit color, whilst in the case of the
colored metals the particular shade is intensified or altered. Thus by
multiple reflection the following metals display the annexed colors:
400 INORGANIC CHEMISTRY.
Copper, scarlet
Gold, red
Silver, pure yellow
ZIdc, indigo blue
Iron, violet.
At large angles of incidence — that is, when the light falls very ob-
liquely upon the surface — all metals reflect white light. But their
specific reflective power for the different rays varies more as the inci-
dent light becomes more perpendicular.
Colors of Ignited Liquid Metals. — At high temperatures, metals in
the liquid state generally emit white light ; but molten copper gives
out a ruddy glow, and molten gold emits a beautiful green light.
Colars of Ignited Vaporous Metals. — All metallic vapors exhibit at
very high temperatures characteristic phenomena of color, and some
possess, even at relatively low temperatures, colors more or less marked.
Thus tin gives a blue vajwr ; copper a green ; silver a green of a different
shade; gold a blue; and sodium a yellow. The nature of the colors
which metallic and other vapors display at high temperatures forms
the subject matter of Spectrum Analysis.
Spectrum Analysis.
The study of the colors of the vaporous elements at high tempera-
tures has developed, in the hands of chemists, into an invaluable
method of analysis, surpassing in scope and delicacy all other known
methods. This method is known as spectrum analysis^ and the instru-
ment by means of which the discrimination of the colors of the vapors
is effected is the spectroscope. Although this method has been em-
ployed by chemists only since 1860, it has already been the means of
enriching chemistry with several new metals. It has further demon-
strated that some elements which were formerly believed to have been
obtained in a state of purity have in reality been contaminated with
foreign matter : a state of things which has rendered necessary a revi-
sion of some of the atomic weights. But the achievement of spectrum
analysis which appeals most powerfully to the imagination is the crea-
tion of an entirely new branch of chemical science, that of celestial
chemistry f in which, by the application of the spectroscope to the exami-
nation of the light emitted by solar and stellar matter, chemists have
been enabled to prove the presence of many of our terrestrial elements
in the sun and stars. In addition to this, the spectroscope has fur-
nished us with information concerning the physical constitution of
these luminaries, and even concerning their rate of motion, which
would formerly have been deemed unattainable.
The form of spectroscope most generally employed for chemical pur-
poses is represented in Fig. 48. The rays of light to be examined
pass through a vertical slit situated at the end of the tube A, and
turned from the spectator in the diagram. After being rendered
parallel by means of a lens, they fall upon the prism P. The spec-
trum is viewed directly by means of the telescope B. In this way it is
SPECTRUM ANALYSIS.
401
not only magnified^ but is made to exhibit a greater degree of sharpness
of detail than it would possess if thrown upon a screen. The tube C
carries a transparent horizontal graduated scale, which is illuminated
bj a small luminous gas-flame placed at the end of the tube and not
Fig. 48.
represented in the diagram. In looking through the telesco|)e this
scale is seen reflected in the face P of the prism. In this way it is
viewed simultaneously with the spectrum, the various parts of which
may thus be referred to the divisions of the graduated scale. In order
to compare light from two different sources, one half of the slit, which
is represented on a larger scale in Fig. 49, is covered by a small prism
oA. The light from one source, F, Fig. 48, situated iu front of the
Fio. 49.
slit passes directly through the uncovered half of the slit; the light
from the second source,/, which must be placed to the side of the slit,
passes through the covered portion of the slit by total reflection in the
small prism. Various arrangements of the small prism are employed
for this purpose; one of the simplest is that represented in Fig. 60.
The light from /, Fig. 50, enters the equilateral prism cde perpen-
dicularly to the face de, is totally reflected at r from erf, and emerging
from the prism perpendicularly to ce, enters the slit s. As the direction
of the rays of light on entering and on quitting the prism is perpen-
26
402 INORGANIC CHEMISTRY.
dicular to the faces of the prism, no refraction occurs with this prism.
At the same time the light from F cannot enter the slit through the
frisra, and can pass only through the uncovered portion of the slit,
n this way the two spectra from the two sources of light may be viewed
simultaneously^ one above the other, and as in both spectra the light
passes through the same slit and is refracted by the same prism P,
there will be perfect correspondence of the similar parts of each : rays
of the same wave-length will be found in the same vertical line in the
two spectra, and thus coincidences may be observed and studied.
In order to understand the principles upon which spectrum analysis
is based, it will be necessary to consider what is the precise nature of
the phenomena observed when bodies are heated to the temperature
at which they become self-luminous. If a liquid or a solid be thus
gradually heated, and at the same time examined with the spectroscope,
the red end of the spectrum will be observed first. The body is then
at a low red heat. As the temperature rises, the orange rays will be
added ; then the yellow, and so on from the less refrangible to the
more refrangible rays, until the entire visible spectrum from red to
violet can be seen. The body is then white-hot, and the white light
which it emits is thus seen to be compounded of every wave-length in the
visible spectrum.* The spectra of glowing solids and liquids are there-
fore continuous. The molecules of solids and liquids are hampered by
cohesion, and are not free to take up those vibrations which are peculiar
to them. We may conceive that in diflFerent parts of the mass cohesion
is overcome to a varying extent at the same time, and that molecular
groupings of every possible degree of variety and complexity are vi-
brating, each with its specific rate of vibration. We should thus have
the simultaneous emission of light of every wave-length— of every
degree of refrangibility.
Grases or vapors behave otherwise. Their molecules are free to os-
cillate unimpeded by each other ; and the molecules of any one element,
being all of the same kind, execute at a given temperature vibrations
* In addition to the visible spectrum, there is an invisble region of ravs of lower
refrangibility than the red — the infra-red rays — and a second invisible region of rays
of higher refrangibility than tlie violet — the ultra-violet rays. These two invisible por-
tions, which lie on either side of the visible spectrum, have by the aid of photography
been rendered accessible to spectroscopic study.
SPEOTRUM ANALYSIS. 403
identical in nature and in velocity, and consequently, if heated to the
temperature at which they become self-luminous, emit light of definite
wave-lengths and therefore of definite color, not a mixture of light of
all wave-lengths, or white light. Every element, therefore, in the state
of self-luminous vapor, and at a temperature sufficiently high, displays
a spectrum peculiar to itself, and consisting of definite lines or bands.
The dark spaces between these lines or bands correspond to those wave-
lengths of light which the atoms or molecules of the element do not
excite.
In this way the spectroscopic examination of the elements in the con-
dition of self-luminous vapor affords a means of distinguishing between
them — a means more expeditious, less liable to misinterpretation, and,
as we shall see presently, more delicate than the ordinary chemical tests.
The identification of the elements by means of the spectroscope is
greatly facilitated by the arrangement for comparing spectra already
described (p. 401). For example, if the spectrum of a sutetance under
examination appears to be that of barium, it is only necessary to ex-
amine, simultaneously with this spectrum, the spet^trum of an actual
specimen of barium by means of the comparing prisDi : the coincidence
or non-coincidence of the lines in the two spectra will at once inform
us whether our surmise is correct, or the reverse.
The metallic vapors for examination may in many cases be obtained
by heating the metal or its compounds in the Bunsen flame. Some-
times, however, a higher temperature is necessary, in which case the
electric arc or the induction spark may be employed as the source of
heat. In the case of metals, it is sufficient to pass the spark between
poles of the metal, when a sufficient quantity is volatilized to give a
spectrum. It is to be borne in mind, however, that in this method the
spectra of the gases through which the spark passes (oxygen, nitrogen,
etc.) will also be visible.
As regards the certainty of identification of the elements by spectro-
scopic means, a noteworthy point is the ease with which metallic vapors,
the colors of which appear to the eye almost or entirely identical, may
be discriminated with theaid of the spectroscope. The red colors which
lithium and strontium compounds respectively impart to the Bunsen
flame, though distinguishable by a trained eye, are yet extremely sim-
ilar; but the flame spectrum of lithium consists of a bright red line
and a very weak line in the yellow, whilst that of strontium contains
several lines in the red, one in the orange, and one in the blue. The
flame colors of the compounds of potassium, csesium, and rubidium are
to the eye absolutely identical, and there are, moreover, no character-
istic qualitative tests by which the compounds of these elements may
be distinguished, but their spectra present the mast marked differences.
So similar are these elements, that it is probable that by chemical means
alone caesium and rubidium could never have been discovered. Indeed
csesiuiti had, previous to its spectrascopic recognition as a distinct ele-''
ment, l)een confounded with potassium (see Csesium).
The delicacy of the spectroscopic tests for the elements is due to the
minuteness of the quantity of self-Iumiuous vapor necessary to impart
to the luminiferous ether a perceptible impulse. The highest degree
404 INORGANIC GHEMISTBT.
of delicacy is manifested in the case of sodium^ a quantity of which
less than the yoooo'tfTTCop ^^ ^ gram may be detected. This almost
inconceivable delicacy is due to two causes : in the first place the spec-
trum of sodium consists of one double line in the yellow, henoe the
entire effort of the atoms is concentrated upon one part, and that the
most luminous of the spectrum ; and, secondly, the atomic weight of
sodium is low, so that a smaller quantity is required to produce an
effect. Thallium also gives only one line, but it is in the green
— ^a portion of the spectrum which affects the eye less powerfully;
and the atomic weight of thallium is high; hence the reaction is
in this case less delicate. In the case of lithium j^p^Jyg^^ of a gram
may be detected. With the induction spark 7^00^000^ ^^ ^ gram of
copper gives a brilliant spectrum, and 0.2 of a milligram of copper
keeps up this spectrum for six hours.
In identifying an element by means of its spectrum, it is not neces-
sary that every line in the spectrum should be perceived. In almost
all spectra there are certain lines brighter than the rest, and these are
frequently visible when the quantity of substance vaporized is insuffi-
cient for the perceptible production of the fainter lines. The presence
of one of these prominent or characteristic lines is sufficient for the
identification of an element.
Nearly all metallic compounds are decomposed into their elements at
a temperature below that at which their vapors become luminous. On
this account the spectra of the compounds of the metals with the non-
metals are frequently the same as those of the metals themselves.*
But this is not always the case, especially at comparatively low tempera-
tures. Thus copper and cuprous chloride give the same spectrum in
the electric arc, but not in the Bunsen fiame. In many such cases there
is a temperature at which a compound gives its own peculiar spectrum
plus that of each of its elements.
When no chemical combination occurs, spectra of any number of
elements can co-exist side by side without confusion. In this way the
qualitative analysis of mixed materials may be safely made. It is only
necessary to identify in the mixed spectrum the more characteristic
lines of the various elements.
Gases which under ordinary pressures give a line spectrum behave
otherwise under high pressures. As the pressure increases, the
lines gradually broaden, until ultimately the spectrum becomes con-
tinuous. This is again a case in which the freedom of atomic vibration
is interfered with by the too great proximity of the atoms to each
other.
All bodies capable of vibration possess the power of taking up or
absorbing those waves which they would cause by their own vibration.
Thus a finger-glass may be made to sound by singing its own note
close to it. The same law holds with regard to the vibrating atoms
* The non-metals require a higher temperature than many of the metals in order
that they may exhibit their characteristic spectra. Thus in tiie case of the decomposed
compound of a metal with a non-metal, it frequently happens, as above stated, that the
spectrum of the metal alone is visible.
BPECTRUM ANALYSIS. 405
and molecules of a gas. If we examine with a spectroscope a source of
white light yielding a continuous spectrum — a white-hot solid or liquid
— and then introduce between the slit of the spectroscope and the source
of white light, a layer of sodium vapor, then according to the relative
temperatures of the source of white light and the sodium vapor, one of
three things will happen : either the Rodium vapor is hotter — i,e,, pos^
©eases greater energy of atomic vibration — than the white-hot solid or
liquid, in which case it will emit more yellow light than it receives
from the latter, and a bright yellow sodium line will be visible in the
otherwise continuous spectrum ; or it is of the same temperature, when
it will emit just as much as it receives, and only the continuous spec-
trum will be seen ; or, finally, it is colder, in which case it will absorb
more than it emits, and &dark sodium line will be visible on the back-
ground of the continuous spectrum. This is in accordance with the
law of exchanges. Its chief importance in connection with the present
subject lies in the explanation which it affords of the phenomena ob-
served in the spectroscopic study of the heavenly bodies.
Solar and Cellar Spedra, — If the light from the sun be examined
spectroscopically, the phenomena observed do not correspond either
with those of an incandescent gas, or with those of an incandescent
solid or liquid. The visible solar spectrum consists of a band of
colored light stretching from the red to the violet ; but this colored
spectrum is crossed by a vast number of fine dark lines. These lines
were first observed by Wollaston. They were afterwards mapped by
Praunhofer, a German optician, for which reason they are known as
the Fraunhofer lines.
If we examine simultaneously by means of the comparing prism the
solar spectrum and the spectrum of a metallic element, we find that in the
case of many metallic elements, such, for example, as iron or calcium,
every bright line in the spectrum of the metallic element corresponds in
position, breadth, and intensity with a dark line in the solar spectrum.
We have already seen that the bright line of sodium may be reversed
and converted into a dark line. The dark lines in the solar spectrum
have a similar origin. In the sun, we have in the first place an incan-
descent nucleus, solid or liquid, the source of light, and capable of yield-
ing a continuous spectrum. Owing to the high temperature of the sun,
the elements, of which the mass of this luminary is composed, are in
part volatilized, and we have thus an atmosphere of incandescent vapor
surrounding the incandescent nucleus. Through this atmosphere all
light from the nucleus must pass. The temperature of the solar atmos-
phere is necessarily lower than that of the nucleus; hence metallic
vapors contained in this atmosphere absorb more light than they emit,
and the lines of their spectra consequently appear dark on the continu-
ous spectrum of the nucleus. The nucleus of the sun is distinguished
as the photosphere; its atmosphere, in which this selective absorption
occurs, as the chromosphere. Under certain conditions it is possible to
submit the light from the chromosphere alone to spectroscopic exami-
nation, and in this case a spectrum of bright lines on a dark ground,
corresponding with that of a glowing gas, is obtained.
The origin of the dark lines in the solar spectrum was first satisfao-
406 INORGANIC CHEMISTRY.
torily explained by Kirchhoff, who verified hie theory by an elaborate
series of observations. The same explanation had, however, been pre-
viously suggested by Stokes.
The alternative hypothesis, that the coincidence of the bright lines of
the spectra of the metallic elements with the dark lines of the solar
spectrum is due to chance, and not to the presence of these elements in
the solar atmosphere, is untenable. In the case of the spark spectrum
of iron. Angstrom has counted no fewer than 460 lines, each of which
coincides with a dark line in the solar spectrum. The probability of
460 chance coincidences in the spectrum of one metal is inconceiv-
ably small; and, when we take into account the fact already men-
tioned, that the coincidence of the lines is one not merely of position,
but in every case one also of breadth and intensity, this small proba-
bility becomes still further diminished. We must therefore conclude
that the various elements which yield these lines are really present in
the solar atmosphere.
The following is a list of the metallic elements which have thus
been detected in the atmosphere of the sun :
H, Na, K, Rb, Cs, Li, Ba, Sr, Ca, Mg, Al, Cr, Be, Ce, La, Yt, Zn,
Mn, Ni, Co, Fe, U, V, Pb, Bi, Ou, Cd, Pd, Ir, Sn, Mo, Ti.
The spectroscopic study of the stars has afforded much information
concerning the constitution of these bodies. The moon and planets
exhibit the same spectrum as the sun, which is in accordance with the
fact that they shine by the reflected light of that luminary. The fixed
stars are found to be bodies constituted like our sun, although differing
greatly both from the latter and from each other. The 8|)ectra of the
greater number display dark lines. Many terrestrial elements have
already been detected in the stars. Thus Aldebaran contains hydrogen,
sodium, magnesium, calcium, iron, tellurium, antimony, bismuth, and
mercury; whilst in Sirius sodium, magnesium, and hydrogen have
been detected.
The spectra of the irresolvable nebulie, on the other hand, display
bright lines. This shows that these nebulae consist of masses of incan-
descent gas, without a solid or liquid nucleus — ^a discovery which affords
powerful support to the Kant-lAplaoe hypothesis of the origin of the
solar system.
Rdations of (he Metals to Oramty.
Spedfio Gravity of Metals. — A table of specific gravities of substances
consists of a series of numbers indicating the relative quantities of
matter contained in equal volumes of these substances. The measure
of the quantity of matter is, oceteris paribus, the weight Since in the
case of solids and liquids the specific gravity of water at 4° C. is taken
as unity, we may put it that the number expressing the specific gravity
of a solid or liquid substance indicates the number of times that a giv^i
volume of this substance is heavier (or lighter) than an equal volume
of water at 4° C. For an account of the methods by which the specific
gravity is determined a work on physics must be consulted; but the
following relation, which is useful to remember, may be mentioned
COBEBIVE POWER. 407
here: The number expressing the specific gravity of asolid or liquid also
expresses the weight in grams of one cubic centimetre of the substance
measured at the temperature at which the specific gravity was deter-
mined. This is due, in the first place, to the fact that, in the metric
system, the unit of weight is the weight of the unit of volume of water
at 4° C. (1 cubic centimetre of water at 4° C. weighs 1 gram); and,
secondly, to the fact above mentioned, that the specific gravities of solids
and liquids are referred to that of water at 4° C. as unity.
The metals exhibit a very wide range in their specific gravities, vary-
ing from 0.594 in the case of lithium, the lightest of known solids, to
22.477 in the case of osmium, the heaviest.
The following table contains the specific gravities of some of the more
important metals:
Name of Metal. Sp. gr.
Osmium, 22.477
Iridium, 22.40
Platinum, 21.50
Gold, 19.26
Mercury, 13.596
Lead, 11.37
Silver, 10.47
Copper, 8.95
Cadmium, 8.66
Iron, 7.79
Tin, 7.29
Zinc, . ' 6.92
Aluminium, ....... 2.67
Magnesium, 1.74
Sodium, ^ 0.974
Potassium, 0.865
Lithium, 0.594
Cohesive Power.
The properties of matter which are dependent upon cohesion, that is
to say, upon the mutual attraction of the molecules of a substance, are
tenacity f fuirdness, brittlenese, rnxiUeabUity, and ductility. These very
important properties are passessed by the various metals in very differ-
ent degrees. Upon them depends the value or otherwise of the metals
for the purposes of art and manufacture.
The ienaoity of a substance is the resistance which that substance
opposes to the separation of its parts. This separation may be sought
to be eflPected either by strain or by crushing weight. The tenacity of
a metal towards strain may be determined by suspending weights by a
wire of the ' metal, and noting the weight sufficient to cause rupture.
By repeating this operation with wires of different metals, care being
taken that the wires are, in every case, of equal cross-section, a table of
relative tenacities may constructed. In the following table the tenacity
of lead is taken as unity : »
408 INORGANIC CHEMISTRY.
Rdative Tenacity of ifetals.
Lead, 1
Tin, 1.3
Zinc, 2
Palladium 11.5
Gold, 12
Silver, 12.5
Platinum, 15
Copper, 18
Iron, 27.5
Nickel, 41.2
Steel, 42
This means that if a lead wire of given thickness willl support, as
maximum load, say 1 kilogram, a steel wire of the same thickness will
8up|X)rt 42 kilograms. The tenacity of cobalt is greater than that of
iron. The tenacity of most metals is diminished by annealing; that
is, by heating the metal and allowing it to oool slowly.
Resistance to strain and to crushing weight are distinct properties.
Thus the three kinds of iron range as follows in regard to their order
of tenacity:
strain. Crushing weight.
Wrought iron. White cast iron.
Gray cast iron. Gray cast iron.
White cast iron. Wrought iron.
Hardness is the resistance which a substance opposes to penetration,
or to change of form generally. It is not easy to determine hardness
with quantitative accuracy; but we may readily ascertain which of two
substances is the harder by endeavoring to scratch the one with the
other. In this way a scale of standard substances has been prepared,
each of which is harder than its predecessor :
Scale of Hardness, (Mohs.)
1. Talc. 6. Felspar.
2. Gypsum or rock salt. 7. Quartz.
3. Calcite. 8. Topaz.
4. Fluorspar. 9. Corundum.
6. Apatite. 10. Diamond.
Thus, a substance which scratches fluorspar but is scratched by apatite,
has a hardness lying between 4 and 5. The numerals denote simply
order, not degree of hardness. This scale is much employed by min-
eralogists.
Among the metals, titanium, manganese, chromium, and ruthenium
are so hard as to scratch glass, whilst sodium may be moulded with the
fingers. The native alloy of osmium and iridium is exceedingly hard,
and is employed on this account in the manufacture of the nil^ of gold
pens.
BriUleness is the incapacity of a substance to undergo change of form
— by bending, hammering, or otherwise — without rupture. Among the
MALLEABILITY AND DUCTTILITY. 409
metals, brittleneps is generally associated with a crystalline structure ; the
crystalline metals, antimony, arsenic, and bismuth, fly into fragments
under the hammer. Tenacious metals frequently possess a fibrous struc-
ture. Thus, the highly tenacious metals, wrought iron and wrought
copper, are fibrous, as may be seen by fracturing a bar of the metal by
repeated bending and ol^rving the surface of fracture ; whereas, cast
iron and dowly deposited electrolytic copper are crystalline and brittl<^.
Fibrous wrought iron, when kept in a state of vibration for a great
length of time, undergoes a slow molecular rearrangement whereby the
fibrous structure becomes crystalline. To this cause is sometimes due the
snapping of the axles of railway carriages and of the shafts of screw
steamers.
Malleability and DudiUty. — Malleability is the property of being
reducible to thin leaves, either by hammering or by passing between
rollers. The most malleable of the metals is gold ; it has been beaten
into leaves jgiio^Tfth of an inch in thickness. 1 square decimetre of
this leaf weiehs less than 20 milligrams. Silver and copper may also
be hammered into thin leaf. The remaining metals in the accompany-
ing table may be reduced to thin foil by rolling, but not by hammering:
Order of Malleability.
1. Gold.
2. Silver.
3. Copper.
4. Tin.
5. Platinum.
6. Lead.
7. Zinc.
8. Iron,
Ductility is the capability of being drawn into wire. The metal is
first formed into rods; these are then drawn through holes in a steel
draw-plate. The holes, through which the wire passes, diminish in
size by regular gradation. The process of drawing is continued until
the requisite degree of tenuity is attained. Sometimes it is necessary
toanneal the wire from time to time during the process of drawing.
Very fine gold and silver wire is drawn through an aperture in a ruby.
Most malleable metals are ductile, but in an order somewhat different
from that of their malleability :
Order of DuctilUy,
1. Gold.
2. Silver.
3. Platinum.
4. Iron.
5. Copper.
6. Palladium.
7. Aluminium.
8. Zinc.
9. Tin.
10. Lead.
410 INORGANIC CHEMISTRY.
Thus iron, by virtue of its superior tenacity, is more ductile than some
of the more malleable metals. A non-malleable metal cannot be duc-
tile. Gold wire has been drawn buVo*^ of an inch in diameter. Wires
of gold and platinum have been obtained by Wollaston r^jo^nr^^ ^^ ^°
inch in diameter. This extraordinary degree of tenuity was attained
by placing a wire of gold or platinum in the axis of a cylinder of silver,
then drawing the compound wire in the ordinary way and dissolving
off the silver with nitric acid. Soft metals, such as sodium and potas-
sium, may be obtained in the form of wire by forcing them through an
aperture in a steel die. This has of course nothing to do with the
true ductility of these metals: the wires are pressed, not drawn. True
ductility, as above stated, is dependent to a great extent upon te-
nacity.
The properties of malleability and ductility vary in each metal with
the temperature. Copper is tough and malleable at ordinary tempera-
tures; but at a temperature approaching its fusing-point it becomes so
brittle that it may be reduced to jwwder. In reference to this property
copper is said to be " hot short." The behavior of zinc in this respect
is peculiar: at ordinary temperatures it is moderately brittle: between
100° and 160° C. (2r2°-262° F.) it is so malleable and ductile that
it may be wrought with facility: whilst at 205° C. (401° F.) it is
more brittle than at ordinary temperatures, and may be pulverized in a
mortar.
Alloys.
Many metals, when fused along with others, unite with these to form
a homogeneous metallic mass known as an all()3'. In some such cases
chemical combination appears to take place: thus the union of sodium
with mercury is accompanied with evolution of heat and light; in
others the combination is merely one of mutual solution. The chem-
ical compounds which are formed are difficult to isolate, as they are
generally soluble in all proportions in an excess of any of the constit-
uents. The best characterized chemical compounds are always those
which result from the union of elements differing most widely in their
properties — thus of the most positive with the most negative elements;
and in such compounds the properties of the constituent elements are
obliterated. The metals, on the other hand, standing, as they do, near
to each other in the electrochemical scale, form compounds which are
devoid of sharply-defined characteristics, and in which the properties of
the constituent metals are preserved. Thus all alloys possess metallic
lustre, and are good conductors of heat and electricity.
Very few pure metals possess properties which fit them, as such, for
use in the arts. Thus pure copper is soft, and cannot be worked on the
lathe. By alloying it with zinc it is converted into the hard and work-
able brass. In like manner before gold and silver can be coined, these
metals must be alloyed with a certain percentage of copper in order to
impart to them the necessary hardness and durability. Thus the prop-
erties— sometimes even the defects — of one metal are employed to cor-
rect or modify those of another in the preparation of alloys.
Alloys of metals with mercury are known as amalgams (g.t?.).
POTASSIUM. 411
The properties of the various alloys will be treated of later on in
connection with one or other of their constituent metals.
The law regulating the fusing-point of alloys has already been
referred to (p. 399).
CHAPTER XXXII.
MONAD ELEMENTS.
Section III.
POTASSIUM, K,?
Atomic weight = 39. Probable molecular weight = 78. 8p, gr. 0.865.
FvMS at 62.5° C. (144.5° F.). Boils at a low red heat. AUmicity '.
Evidence of atomicity :
Potassic chloride, . . . : KCl.
Potassic iodide, KI.
Potassic hydrate, KHo.
Potassic sulphide, SK^.
Sidory. — Potassium was first isolated in 1807 by Davy, who obtained
it by tlie electrolysis of potassic hydrate.
Occurrence, — The salts of potassium are widely distributed in na-
ture. Double silicates of potassium with aluminium and other metals
fbrm a variety of important minerals, which are among the proximate
constituents of the igneous rocks. By the disintegration of these rocks
soik are produced. From the soils the potassium is absorbed by plants,
in the juices of which it occurs as the potassium salts of organic acids.
From plants it passes into the bodies of animals.
Further, in the inorganic world, the chloride, bromide, and iodide of
potassium are found in sea-water, in mineral springs, and in solid saline
deposits, whilst the nitrate occurs in tropical climates as an efflorescence
on the soil.
Preparation. — 1. When a piece of solid potassic hydrate, slighly
moistened in order to increase its conducting power, is placed between
the poles of a powerful voltaic battery, decomposition takes place ac-
cording to the following equation :
20KH = Kj + H3 + O,.
Potassic
hydrate.
Potassium and hydrogen are liberated at the negative pole. The po-
tassium forms metallic globules which inflame in contact with air, and
must be removed and preserved under petroleum.
This was the method of preparation originally employed by Davy.
412
INORGANIC CHEMISTRY.
2. Potasslnm may also be obtained by the action of metallic iron on
potassic hydrate at a strong white heat :
40KH + 3Fe = ''{Te^y'''0, + 2K, + 2H^
Magnetic iron
Potassic
hydrate.
oxide.
3. The most convenient method of preparing potassium consists in
heating potas^^ic carbonate to a white heat with charcoal. Hydric po-
tassic tartrate (cream of tartar) is first ignited in a closed crucible, when
the following decomposition takes place :
2 ^
OOKo
OHHo
OHHo
^ OOHo
Hydric potassic
tartrate.
= OOKoj + 50H, + 400 + 3C.
Potassic
carbonate.
Water.
Carbonic
oxide.
The residue, consisting of potassic carbonate and finely divided carbon,
is mixed with charcoal and distilled at a white heat from an iron retort
R (Fig. 51) :
OOKoj +20 = 300 + Kj.
Potassic
carbonate.
Carbonic
oxide.
The vapor of potassium condenses in a copper receiver r, from which air
is excluded. If the neck of the retort b^mes choked during the pro-
FiG. 61.
cess, it may generally be cleared by means of an iron rod A, introduced
through the lateral tube of the receiver. Should this fail, the fire-bars
COMPOUND OF POTASSIUM WITH HYDROGEN. 413
B, which are movable, must be withdrawn, so as to allow the fire to
fall on to the hearth.
The potassium obtained by the above process is contaminated with
carbonic oxide, from which it must be freed by redistillation. A
n^lect of this precaution may lead to dangerous accidents, as when
the crude potassium is preserved, even under petroleum, a black pow-
der is formed which explodes violently on the slightest friction.
Properties. — Potassium is a silvery-white metal, brittle and crystal-
line at 0° C, but at ordinary temperatures soft like wax. The freshly
cut surface of the metal has a brilliant lustre, which it almost instantly
loses when exposed to air, owing to the formation of oxide. For this
reason it is necessary to keep the metal immersed in some liquid devoid
of oxygen, such as petroleum. When heated in air it infiames and
burns with a violet light, forming a mixture of peroxides of potassium.
By melting potassium in a sealed tube filled with coal-gas, allowing
the metal partially to solidify, and then pouring off the liquid portion,
well formal crystals of potassium may be obtained.
Reactions. — 1. Potassium decomposes water, even at its freezing
point, with great energy, the heat evolved being sufficient to cause the
ignition of the liberated hydrogen :
Kj + 2OH2 = 2KHo + H,.
Water. Potassic
hydrate.
2. It inflames spontaneously in an atmosphere of chlorine. It also
inflames when brought in contact with bromine, the reaction taking
place with explosive violence. In these cases potassic chloride (KCl)
and bromide (KBr) are formed.
3. When potassium is ignited in a stream of carbonic anhydride, a
portion of the latter is reduced, with liberation of carbon :
2K, + 300, = 200x02 + a
Carbonic Potassic
aDhydride. carbonate.
Uses. — Owing to its powerful' affinity for electro-negative elements,
potassium is employed in the laboratory to expel elements, less strongly
electro-positive than itself, from their combinations with electro-negative
elements. Thus, by its means, boron and silicon may be prepared from
their oxides, and aluminium, magnesium, and other metals from their
chlorides. The more readily obtainable sodium has, however, almost
totally superseded it for these purposes.
COMPOUND OF POTASSIUM WITH HYDROGEN.
PoioMic hydride, K4H2. — When potassium is heated ip a current of pure hydrogen,
the gas is absorbed by the metal, and potassic hydride is formed. The absorption
begins at 200** C. (392° F.), and is most rapid about 300° C. (572° F.). The hydride is
a brittle crystalline mass, with a silvery metallic lustre. It may be fused in an atmos-
phere of hydrogen. Under ordinary pressures it may be heated to 410° C. (770° F.)
without change, but in a vacuum it b^ins to dissociate at 200° C. (392° F.). It in-
flames spontaneously in conact with air.
414
INORGANIC CHEMISTBY^
COMPOUNDS OF POTASSIUM WITH THE HALOGENS.
PoTASSic CHLORIDE^ KCI, oocurs native in saline deposits as the
mineral sylvine. In smaller quantities it is found in sea- water and in
brine-springs. It crystallizes in colorless cubes, and possesses a saline
taste. It dissolves in 3 parts of water at ordinary temperatures, and is
more soluble at higher temperatures. Alcohol does not dissolve it.
It forms molecular compounds— double salts — with various other me-
tallic chlorides. Potassic plcUinio chloride {poiassic chloroplatinate\
PtCl4,2KCl, is obtained as a granular precipitate, consisting of minute
octahedra, when solutions of the two chlorides are mixed. This salt is
almost insoluble in cold water^ and is used in the quantitative determi-
nation of potassium.
PoTASSic BROMIDE, KBr, forms colorless cubes of sp, gr. 2.69,
readily soluble in water, slightly soluble in alcohol.
PoTASSic IODIDE, KI, is prepared by digesting iron filings, water,
and iodine together, filtering the colorless solution, and precipitating
the iron by potassic carbonate :
Fe + I, =
Fel,;
Ferrous
iodide.
Fel, + OOKo, = 2KI + OOFeo".
Ferroos Potaasic Potassic Ferrous
iodide. carbonate. iodide. carbonate.
It crystallizes in cubes of sp. gr. 2.9.
peratures in 0.7 part of water and in 40 parts of alcohol.
It dissolves at ordinary tern-
The aqueous
solution dissolves large quantities of iodine. Potassic iodide forms
molecular compounds with many other metallic iodides.
Potassic fluoride, KF, is obtained by neutralizing hydrofluoric
acid with potassic carbonate. At ordinary temperatures it is deposited
from its solutions in crystals of the formula KF,20H2, but above 35°
C. (95° F.) it crystallizes in anhydrous cubes. It is deliquescent.
The solution attacks glass. It forms numerous double fluorides: the
so-called acid fluoride has the formula KF,HF. Potassic silicofluoride,
SiFgKa ( = SiF4,2KF), which is formed as a gelatinous precipitate
when hydrofluosilicic acid is added to the solution of a potash salt^ may
also be regarded as belonging to this class.
COMPOUNDS OF POTASSIUM WITH OXYGEN.
Potassic oxide, OKj. K— O— K
Pota«ic dioxide^
Potassic tetroxidc; .
OK-
roK
O
O '
OK
K— O— O-K.
K— 0~0— O— O— K.
COMPOUND OP POTASSIUM WITH HYDROXYL. 415
PoTASSic OXIDE, OK2, 18 formed by the spontaneous oxidation of po-
tassium at ordinary temperatures in dry air. It may also be obtained
by heating potassic hydrate with potassium :
2KHo + Kj = 20Ka + H,;
Potassic Potiusic
hydrate. oxide.
or by fusing together, in a current of nitrogen, potassic peroxide and
potassium.
Potassic oxide is white, fusible, and, at high temperatures, volatile.
It is very deliquescent, and combines violently with water to form
potassic hydrate. When moistened with water it becomes incandescent.
Potassic dioxide, K^Oj, is formed with evolution of oxygen when
the tetroxide is dissolved in water.
Potassic tetroxide, Potaasio peroxide^ KjO^, is prepared by fusing
potassium in a current of oxygen. It is a chrome-yellow powder.
Water decomposes it as above (see Potassic dioxide).
COMPOUND OF POTASSIUM WITH HYDROXYL.
Potassic hydrate, Caustic potash^ Potash, KHo or OKH, is i>re-
pared by boiling in an iron vessel a solution of potassic carbonate with
calcic hydrate:
COK03 + OaHo, = 2KHo + COCao".
Potassic Calcic Potassic Calcic
carbonate. hydrate. hydrate. carbonate.
1 part of potaf«ic carbonate is dissolved in 12 parts of water, and
milk of lime is added till a sample of the filtered liquid no longer effer-
vesces when treated with an acid. (With a concentrated solution of the
carbonate, the reaction does not take place; in fact a concentrated solu-
tion of potassic hydrate decomposes calcic carbonate with formation of
potassic carbonate and calcic hydrate.)
The clear solution of potassic hydrate is decanted from the precipitate
of calcic carbonate, and is concentrated, first in a covered iron pot, and
afterwards in a silver basin, until all the water has been driven off
and the fused oily hydrate remains. This solidifies on cooling to a
crystalline mass.
It is also formed by the action of potassium upon water (see p. 413)
and by dissolving potassic oxide in water:
OK, + OH2 = 20KH.
Propaiies. — Potassic hydrate is a hard white brittle substance, with
a slightly fibrous fracture. It fuses below a red heat, and at higher
temperatures volatilizes without decomposition. It is very deliquescent.
It dissolves in about half its weight of water, yielding a highly caustic
solution, which, when exposed to the air, rapidly absorbs carbonic anhy-
416 INORGANIC CHEMISTRY.
dride. Hot conoentrated solations deposit on oooling quadratic plates,
or octahedra, of the formula KHo,20H2, readily soluble in alcohol.
ReacHom. — By contact with acids, potassic hydrate produces potas-
sium salts :
KHo 4 HCl = KCl + OH^.
Potassic Hydrochloric PotasAic Water,
hydrate. acid. chloride.
KHo + 80,Ho, = SO,HoKo + OH,.
Potaaeic Sulphuric Hydric potassic Water,
hydrate. acid. sulphate.
2KHo + SO,Ho, =
= SO,Ko,
+ OH^
Potassic Sulphuric
Potassic
Water.
hydrate. acid.
sulphate.
OXY'SALTS OF POTASSIUM.
Potassic nitrate, Nitres Saltpetre, NOjKo. {Occurrenceyfomiation,
nitre plantationSy see p. 214.) Nitre is manufactured in large quantities
from Chili saltpetre (sodic nitrate) by the double decomposition of the
latter salt with potassic chloride. Equal molecular proportions of the
two salts are dissolved in hot water until the specific gravity of the
solution attains to 1.5. Sodic chloride, which is almostequally soluble
in hot and in cold water, separates out, whilst the solution deposits
potassic nitrate on cooling. The product is technically known as " eon-
verted nitre." Potassic nitrate is dimorphous. It crystallizes most
frequently in longitudinally striated six-sided prisms belonging to the
rhombic system, but may also be obtained in minute rhombohedra,
isomorphous with those of sodic nitrate. It has a cooling saline taste.
It dissolves in four times its weight of cold water, and in a third of its
weight of boiling water, but is insoluble in alcohol. It fuses at 339^^ C,
and at a red heat is decomposed with evolution of oxygen and forma-
tion of potassic nitrite. At a very high temperature it is converted into
potassic oxide. Owing to its property of thus parting with oxygen, it
oxidizes most of the elements when heated with them, frequently with
explosive violence.
Gunpowder, — Gunpowder is a mixture of 75 parts of nitre, 10 parts of sulphur, and
15 parts of charcoal. The composition varies, however, in different countries, and
also according to the purpose for which the i^owder is intended. The separate ingre-
dients are finely powaered, then intimately mixed, adding a small quantity of water;
the mixture is pressed by hydraulic power into a hard cake, which is then granulated.
The grains are sorted according to size, polished, and finally dried. The principal pro-
ducts of the combustion of gunpowder are nitrogen, carbonic anhydride (with traces of
carbonic oxide), potassic sulphate, and potassic carbonate. The explosive force of gun-
powder is due to the sudden evolution of gases occupying a volume several hundred
times greater than that of the original substance.
Potassic nitriUj NOKo, is prepared by fusing th^ nitrate, either alone or with lead,
the oxidizable metal serving to remove the oxygen from the nitrate. The mass is ex-
.tracted with water, and the solution evaporated and allowed to crystallize. The un-
. changed nitrate separates out first, whilst the nitrite remains in the 'mother liquor,
from which it may be obtained by further evaporation in small prismatic deliquescent
^crystals. It is insoluble in absolute alcohol.
OOUPOUNDS OF POTASSIUM. 417
{OCl
OKo- (P^pa^*io^> P' 182.) This salt
forms lustrous tabular crystals belonging to the monoclinic system,
soluble in 16 parts of oold, and in 2 parts of boiling water. It fuses
at 334^ C. (633^ F.), and is decomposed at 352° C. (666° F.) into
oxygen, potas^io chloride, and potassic perchlorate. At a still higher
temperature it parts with the whole of its oxygen, and is converted
into potassic chloride (pp. 184 and 161).
It is a powerful oxiaizing agent, and, alon^ with sulphur or anti-
monious sulphide, forms detonating mixtures which explode by percus-
sion or friction, owing to the sudden combustion of the oxidizable
ingredient at the expense of the oxygen of the potassic chlorate.
fOCl
Potassic perchlorate, < O (Preparation, p. 184), crystal-
(OKo
lizes in rhombic prisms, soluble in 70 parts of cold, in 6 parts of boiling
water, insoluble in alcohol. When heated to about 400° C. (752° fT)
it is decomposed into oxygen and potassic chloride.
PotoBiie bromaU^ < OEo' ^ ^^ prepared by paasing chlorine into an Aqueous
solution of Lmol. of bromine with 6 molecules of potassic carbonate:
eOOKoj + 601, + Br, *= 2|g|'^ + lOKCl -f SCO,.
Potassic Potassic Potawic Carbonic
carbonate. bromate. chloride. anhydride.
(See also p. 319.) It crjstallizefi in rhombohedra, sparingly soluble in water. It
resembles in its properties the chlorate.
Potastie iodaUj \ oKo' — ^^<'"'^® ^ passed into water, in which iodine is sus-
pendedy until all the iodine dissolves, t'otassic chlorate is then added, when potassic
lodate is formed with eyolution of chlorine:
i« + {§^0 = {§L + ^-
Hvpiodous Potassic Potassic
chloride. chlorate. iodate.
(See also p. 803.) It forms small, lustrous, regular crystals, soluble in 13 parts of%
cold water. It decomposes on heating into oxygen and potassic iodide. {Hyperacid
iodaUB, p. 303.)
fOI
Pbtaaue pertodate, <0 , is prepared like the sodium salt {q.v,). It forms small
(OKo
rhombic crystals which require 300 times their weight of cold water for solution.
Between 250'' and 300^ C. (482-572° F.) it undergoes decomposition into oxygen and
potassic iodate; at a hiffher temperature it parts with all its oxygen, and is converted
into potassic iodide. (For the formulae of the more complex periodates, see p. 306.)
Potassic carbonate, OOKoa, is obtained from the ashes of land
plants. Wood ashes, when lixiviated, yield a solution of potassic car-
bonate, contaminated with small quantities of sodic carbonate, potassic
and sodic chlorides, and potassic sulphate. When the solution is evap-
orated, the impurities crystallize out first, leaving the more soluble
potassic carbonate in the mother liquor, from which it may be obtained
in the crystallized form by further evaporation. On a large scale it is
27
418 INOBGANIG GHElflBTRY.
prepared from native potassic chloride by a process similar to that by
which sodic carbonate is obtained from sodic chloride (see Leblanc's
process). Verj pare potassic carbonate may be obtained by igniting
hydric potassic tartrate (cream of tartar) and extracting with water the
mixture of potassic carbonate and carbon (see p. 412). It crystallizes
from its aqueoos solution in colorless, lone, pointed monoclinio prisms
of the formula 20OEo,,30H2. This salt, when dried at 100^ C, has the
formula COEO|,0H ; at a higher temperature it becomes anhydroas.
The anhydrous salt is fusible, and, at a bright red heat, volatile. It is
deliquescent and very soluble in water, but insoluble in alcohol. The
solution has a strong alkaline reaction. — Hydric potctsrio carbonate^
OOHoKo, is formed when carbonic anhydride is passed into a ooacen-
trated solution of the normal carbonate :
OOKo, + CO, + OH, = 2OOH0K0.
Potassic Carbonic Water. Hydric potassic
carbonate. anhydride. carbonate.
It crystallizes in anhydroas monoclinic prisms, which are soluble in
3-4 parts of cold water. When the dry salt is heated, or when its
aqueous solution is warmed to 80^ C. (176^ F.), it is decomposed into
normal carbonate, carbonic anhydride, and water.
Potassic sulphate, SOjKoi, is obtained in large quantities as a by-
f)roduct in many manufacturing processes. It forms anhydrous, oolor-
ess, rhombic crystals, with a bitter, saline taste, which are soluble in
10 parts of cold, in 4 parts of boiling water. It decrepitates on heating,
and fuses at a bright red heat. — Hydric potassic sulphate^ SOjHoKo, is
obtained as a by-product in the preparation of nitric acid (p. 215), and
may be prepared by heating 1 molecule of the normal salt with 1 mole-
cule of sulphuric acid. From solutions containing an excess of acid, it
crystallizes in tabular rhombic crystals. It fuses about 200® C. (|392*^ F.),
and may be obtained in monoclinic crystals by the slow solidifacation of
the fused salt. It is readily soluble in water, but an excess of this sol-
vent decomposes it into the normal salt and free sulphuric acid. For
this reason^ only the normal salt is deposited from dilute solutions.
•Heated above its fusing-point, ft parts with the elements of water and
^ fSO,Ko.
is converted into potassic pyrosulphate, < O , which, at a temperature
(SOjKo
of 600® C. (1112® F.), breaks up into normal sulphate and sulphuric
anhydride (cf. p. 266).
Potassic sulphite, SOKo2,20H[2, is prepared bypassing sulphurous
anhydride into a solution of potassic carbonate until the carbonic anhy-
dride is expelled. It forms monoclinic octahedra, which are very soluble
in water and somewhat deliquescent. The solution possesses an alkaline
reaction and a bitter taste. When heated, the salt is decomposed,
yielding potassic sulphate, potassic sulphide, and potassic hydrate. —
Hydric potassic sulphite, SOHoKo, is obtained by saturating a concen-
trated solution of potassic carbonate with sulphurous anhydride. It
forms very soluble monoclinic prisms.. The addition of alcohol to the
COMPOUNDS OP POTASSIUM. • 419
aqueous solution causes the salt to be deposited as a mass of acicular
crystals. It has an alkaline reaction and remits an odor of sulphurous
anhydride. Exposed to the air in solution^ it is gradually oxidized to
sulphate.
rsOKo
I^)iamcpyroaulpkUe, ^ O , is formed when sulphuroos anhydride is passed into
isOKo
a warm concentrated solution of potassic carbonate until effervescence ceases and the
liquid assumes a greenish tinge. On cooling, it is deposited in granular crystals.
Potauic dithumatef < a(jKo* ^ Prepared bj exactly precipitating the barium salt
(9.0.) with potassic sulphate. It forms hexagonal crystals, soluble in 16 parts of cold,
in 1^ parts of boiling water. On heating, it is decomposed into potassic sulphate and
sulphurous anhydride.
Potassic tkicitdphaU, 280,KoK8,30H,. — ^This is prepared like the sodium salt
(q-v.). The salt of the above formula is deposited from its aqueous solution at ordi-
nary temperatures, and crystallizes in rhombic octahedra. At temneratures above 30^
C. (86^ F.), the solution deposits thin four-sided prisms of the formula 3SO,KoE8,OH,.
At 200** C. (892° F.) the water of crystallization is expelled, and at a still higher
temperature the salt is decomposed into a mixture of potassic sulphate and penta-
sulphide:
4SO^oK8 = SSOjKo, + K,S5.
Potassic Potassic Potassic
tbiofiulphate. sulphate. pentosulphide.
Pbtassie sdenaJU, SeOiEo,, is prepared by fusing selenious anhydride with nitre, ex-
tracting with water, and evaporating. It crystallizes in forms exactly resembling those
of potassic sulphate. It may be distinguished from this salt by evolving chlorine when
heated with hydrochloric acid, at the same time undergoing reduction to potassic sele-
nite. The se^tte, SeOKo,, forms granular, very soluble deliquescent crystals.
Potax8ictdluraU,TeO^Yio^, Hydrie poiame teUurcOe, 2TeO^UoKo,SOH2. These salts
are obtained by adding the rei^uisite quantities of telluric acid to solutions of potassic
carbonate. The neutral salt is very soluble, the acid salt sparingly soluble, in cold
water. Other more complex tellurates of potassium are known (see pp. 289, 290).
Potassic Phosphates, — a. Potaasio orthophosphatef* POKo^, is
prepared by igniting 2 molecules of phosphoric anhydride with 3 mole-
cules of potassic carbonate, dissolving in water and evaporating. It
forms colorless, very soluble needles. — Hydric dipotassic orthophoa-
phaUy POH0K02, may be obtained in solution by adding potassic car-
bonate to a solution of phosphoric acid till a slight alkaline reaction is
produced. It is uncrystallizable. — Dikydric potassic orthophosphate,
POHo^Koy is prepared by adding phosphoric acid to a solution of
potassic carbonate till the liquid has a strongly acid reaction. On
evaporating, large colorless quadratic crystals, very soluble in water,
are obtain^.
fPOKo,
b. Potassie pyrophosphate, < O ,30Hj, is prepared by igniting
(POK02
hydric dipotassic phosphate (cf. p. 355). It may also be obtained
by almost neutralizing a solution of phosphoric acid with alcoholic
potash, then adding alcohol as long as milkiness is produced, and sepa-
rating, drying and igniting the syrupy precipitate. The mass is
extracted with water and evaporated to the point of crystallization.
It forms a radio-crystalline mass, very soluble in water. One molecule
of water of crystallization is driven off at 100° C, but a temperature of
300® C- (672° F.) is required to render the salt anhydrous. In the
420 IKOBOAKIC GHEMI8TBY.
anhydrous state it is deliquesoent. — Dihydric dipotasaic pyrophagphaU,
PjO^HosKoj^ is obtained by precipitating with alcohol the solution of
the neutral salt in acetic acid. The syrupy mass is washed with alco-
. hoi to remove the potassic acetate and dried over sulphuric acid. It
forms a white deliquescent mass.
c. Potassic metaphospkate, POjKo, is prepared by igniting dihydric
potassic phosphate (cf. p. 354). It is thus obtained as a translucent
mass, almost insoluble in water, readily soluble in dilute acids. Meta-
phosphates of complex oGfnstitution are also known (p. 354).
Potassic fhosphite^ PHoKo,. — ^This salt is obtained bj neutralizing the aqueous acid
with potassic hydrate or carbonate and evaporating in vacuo. It is deliquescent and
very soluble, and can only with difficulty be obtained in a crystalline form.
Potassia arsenates. — These are prepared like the corree()ondin^ phosphates, with which
they are isomorphous, and which tney closely resemble in their other properties. Po-
tassic arsenate, AaOKo| , forms deliq uesoent need les ; hydric dipotassic arsenate, AsOHoKO|b
is uncrystallizable and deliquescent ; dihydric potassic arsenaief AaOHo^Eo, which is
most readily obtained by fusing arsenious acid with nitre, extracting with water and
evaporating, forms large soluble quadratic crystals.
Very little is known concerning the €WMnites of potassium.
Potassic antimonates. — When a mixture of 1 part of powdered antimony with 4 parts
of nitre is deflagrated, and the mass extracted with tepid water, potassic mekaUimonate,
8bO,Ro, remains as a white powder, almost insoluble in cold water. When this sub-
stance is boiled with water it gradually dissolves, taking up the elements of water and
forming dihydric potassic antimonatCf which, on evaporating the solution to a syrup, sepa-
rates out in granular crystals of the formula 28bOHo,Ko,30H2. By fusing antimonic
acid or either of the above antimonates with a large excess of potash, dissolving the
mass in water and evaporating, warty crystals of tetrapotassic pyrantimonale, SbiOjEo^,
are obtained. This salt is stable in solution only in presence of an excess of caustic
potash ; pure water decomposes it into free potash and dihydric dipotassic pyrantimonate
[metantimonate of Fremy), 8byQ,Ho,Ko,.60H|^ a granular, almost insoluble powder,
which is converted by long boiling with water into soluble dihydric potassic antimo-
Date (see above.)
Potassic berate. — The metahoratef BOKo, is prepared by fusing together equal mole-
cules of boric 'anhydride and potassic carbonate. It is very soluble, and cry tall izce
with difficulty. Exposed to the air in solution, it absorbs carbonic anhydride and is
converted into hydric potassic diborate, B,0,HoKo,20H.. A dipotassic tetraborate,
B^OjKo^OOHi, is obtained by mixing hot concentrated solutions of 1 molecule of po-
tassic carbonate and 2 molecules of boric anhydride, and cooling to 6^ C. (42.8^F.). The
salt crystallizes in hard, transparent, prismatic crystals, with a vitreous lustre. When
a boiling solution of potassic carbonate is acidified with boric acid, it deposits on cooling
pripmatic crystals of A^rie potassic hexaborate, B(OsHoKo,40Hs.
Potassic silieale is formed when silicic acid or amorphous silicic anhydride is dissolved
in potassic hydrate. It is generally prepared by fusing together potassic carbonate
and white quartz sand. No compound of definite composition is known. Potassic
silicate, under the name of soluble glass, is employed as a cement.
COMPOUNDS OF POTASSIUM WITH SULPHUR.
The following have been obtained:
Dipotassic sulphide, . . . SK^ K — S — K
Dipotassic disulphide, . . KgS,. K — S-— S — K
Dipotassic trisulphide, . . K^S,. K— S— S— S— K
Dipotassic tetrasulphide, . KjS^. K— S — S— S— S— K
Dipotassic pentasulphide, . K^- K— S— S— 8— S— S— K
Dipotassic heptasulphide, . Kj^? K-^S— S— S— S-^5— S— S— K
COMPOUNDS OF POTASSIUM. 421
DiPOTASSio SULPHIDE, SE„ is formed when potassic salphate is
reduced by igDition with carbon or in a current of hydrogen :
SO,Ko2 +
4H,
= SK, +
40H^
Potassic
Dipotassic
sulphide.
Water.
sulphate.
It is a reddish crystalline mass, which deliquesces when exposed to the
air.
A solution of dipotassic sulphide may be obtained by dividing a con-
centrated aqueous solution of potassic hydrate into two equal parts, sat-
nrating one part with sulphuretted hydrogen so as to form potassic
sulphhydrate (g.t?.), and then adding the other part:
KHo + KHs = SK, + OH,.
Potassic Potassic Dipotassic Water,
hydrate. sulphhydrate. sulphide.
The concentrated solution deposits deliquescent prismatic or tabular
crystals of the formula SEj^SOH,.
Dipotasaie diavlphide, Kfi^ is formed when the sulphhydrate is oxidized by exposure
to air :
2KHs + O = K,S, + OH,.
Pota»lc Dipotassic Water,
sulphhydrate. dlsulphide.
By evaporation in vacuo the disulphide id obtained as an orange-colored mass.
The other polysulphides of potassium are prepared by fusing dipotassic sulphide
with sulphur. Below 600*» C. (1112** F.) the pentodvlphide is formed ; between 600**
and 800^ C. (1112-1472*' F.) the Utragulphide; and at 900** C. (1652*» F.) the trUtd-
pMde, They are brownish-yellow solids with an alkalide reaction. Exposed to moist
air they emit an odor of sulphuretted hydrogen.
Solutions of these polysulphides are formed when solutions of dipotassic sulphide are
boiled with the requisite quantities of flowers of sulphur. In tnis way crystallized
aquates of some of these sulphides may be obtained, for example KsS4,20Hs, which
forms orange-colored laminse.
COMPOUND OF POTASSIUM WITH HYDBOSULPHYL.
Potassic sttlphhtdrate, KHs, is obtained by heating potassium
in a current of sulphuretted hjdrc^n :
2SH, + K, = 28KH + H„
Sulphuretted Potassic «
hydrogen. sulphhydrate.
or by passing sulphuretted hydrogen over potassic carbonate heated to
low redness:
OOKo^ + 2SH, = 2SKH + CO, + OH,.
Potassic Sulphure'tted Potassic Carbonic Water,
carbonate. hydrogen. sulphhydrate. anhydride.
422
INOBOANIC CHEMISTBY.
It forms a flesb-oolored crystalliDe mass^ which melts at low redDeas
to a yellow liquid.
A solution of potassic sulphhjdrate may be obtained by saturating
an aqueous solution of potassic hydrate with sulphuretted hydrogen :
KHo + SH, = KHs + OH,.
Potassic Salphuretted Potassic Water,
hydrate. hydrogen, solphhydrate.
The solution, when concentrated in vacuo, deposits colorless rhom-
bohedra of the formula 2EHs,OH2.
Reactions of potassic solphhydrate^ dipota^ssic sulphide and the higher
potassic sulphides, — 1. Potassic sulphhydrate and dipotassic sulphide,
when acted upon by acids, yield sulphuretted hydrogen :
Kfls + HCl = KCl + 8H,.
Potassic Hydrochloric Potassic Sulpharetted
sulphhydrate. * acid. chloride. hydrogen.
SK, + 2HCI = 2KCI + 8H^
Potassic Sulphuretted
chloride. hydrogen.
Di potassic Hydrochloric
sulphide. acid.
2. The higher sulphides, when similarly treated, yield sulphuretted
hydrogen with precipitation of sulphur :
KA + 2HC1 = 2Ka + SH, + 8,.
Dipotassic Hydrochloric Potassic , Sulphuretted
trisulphide. acid. chloride. hydrogen.
3. When dipotassic sulphide is exposed in aqueous solution to the
action of the air, it absorbs oxygen and is converted into a mixture of
potassic thiosulphate and potassic hydrate :
2SK, + OH, + 20,
= SOjKoKs + 2KHo.
Dipotassic Water,
sulphide.
Potassic Potassic
thiosulphate. hydrate.
4. A mixture of the higher potassic sulphides with potassic thio-
sulphate, known under the name of hepar sulphuris or liver of sulphur,
may be obtained as a brown mass by heating potassic carbonate with
sulphur :
30OKo, + 4S,
Potassic •
carbonate.
SCOKo^ + 6Sj
Potassic
carbonate.
= 2KjjSs + SOjjKoKs + 30Or
Dipotassic Potassic Carbonic
trisulphide. thiosulphate. anhydride.
= 2KA + SOjKoKs + 30O,.
Dipotassic Potassic Carbonic
pentasulphide. thiosulphate. anhydride.
6. The last mixture, when acted upon by acids, undergoes suc-
cessively the following decomposition :
COMPOUNDS OF P0TA8BIUM, 423
2KA + SO^KoKs + 6HC1 = 6KC1
Dipotassic Potassic Hydrochloric Potassic
pentasalphide. thioeulphate. acid. chloride.
+ SOjjHoHs + 2SH, + 48,;
Thioeulphuric Salphuretted
acid. hydn^en.
then —
SO3P0H8 = SO, + 8 + OH,;
Thiosulphnric Sulphnroas Water,
add. anhydride.
and finally —
rso^o
5SH, + 680, = ^S''3 + 40H, + 58.
ISO^Ho
Soipharetted Salphurous Pentathionic Water,
hydrogen. anhydride. acid.
SULPHO'SALTS OF POTASSIUM.
Potasnc sulpharaenaie, AaS'^'^Ess, is prepared b^ dissolving arsenic sulphide, or
anenious snlpnide together with solphnr, in a solution of potassic sulphide or potassic
Bulphhydrate:
AMfi^\ + 3SK, = 2AikS''^KB8.
Anenio Potassio Triix>tfljBsic
sulphide. Bulphide. sulpharsenate.
A«,S^^ + SSKj + S, = AaS^^Ks,.
Arsenioufl Potassic Tripotaasic
sulphide. nilplilde. sulpharsenate.
It is also formed when a solution of tripotassic arsenate is saturated with sul-
phuretted hydrogen :
AaOKo, + 3SH, = AaS^^Ks, + 30H,.
Tripotaabic Sulphuretted Tripotasslo Water,
arsenate. hydrogen. Balpharsenate.
It is obtained as a deliquescent crystalline mass of the formula AflS^^EssyOH, (per-
haps AbHoHsKss).
Potaasic sulphafUimonatef SbS^^Ess, may be obtained in the same manner as the
sulpharsenate, employing the corresponding sulphides of antimony. In practice, it is
prepared by heating together finely powdered antimonious sulphide, sulphur, potassic
carbonate, slaked lime and water, nltering and evaporating. It forms yellow deli-
quescent crystals of the formula 28bS^^K8s,90Hi.
Treated with dilute acids in the cold, the alkaline sulpharsenates and sulphantimo-
nates yield the corresponding acids ▲sS'^'^Hss and SbS^'^Hss. On boiling the solutions
these acids are decomposed into arsenic and antimonic sulphides respectively, and sul-
phuretted hydrogen :
2AiiS'^H8, = AbS'\ + 3SH,.
Sulph arsenic Arsenic Sulphuretted
acid. sulphide. hydrogen.
COMPOUND OF POTASSIUM WITH NITBOOEN AND HTDROQEN
' PoUune amide, NKHt, is obtained by heating potassium ^entlv in a current of dry
gaseous ammonia. The potassium fuses in the gas to a blue liquid, which solidifies on
cooling to a flesh-colored mass. Water decomposes it with violence into ammonia and
potassic hydrate :
424 INORGANIC CHBMI8THT«
HKHt + OH, = NH, 4- OKH.
Potamio Water. Ammonia. Potassic
amide. hydrate.
When stronglj heated in an atmosphere free from oxjgen, it is decomposed into
ammonia and potassic nitride:
3NKH, « 2NHi + HKs.
Potanic Ammonia. Potassic
amide. nitride.
Potassic nitride is a greenish-black substance which, in contact with air, sponta-
neoasly inflames.
General. Properties and Reactions of the Compounds of
Potassium. — ^The salts of potassium with colorless acids are colorless.
Platinic chloride precipitates from hydrochloric acid solutions of potash
salts a yellow crjstalliDe powder of potassic platinic chloride (PtCl^,-
2KC1), very sparingly soluble in water, insoluble in alcohol and ether;
this salt, when heated to redness, is decomposed with evolution of chlo-
rine, leaving potassic chloride and metallic platinum/ HydrofluosUicic
aeid gives a gelatinous precipitate of potassic slicofluoride, SiK^F«.
Tartaric acid in excess precipitates from moderately concentrated solu-
tions hydric potassic tartrate, < (juHo^COH^i ^ * white crystalline
powder. The compounds of potassium impart to a non-luminous flame
a violet coloration which, when viewed through blue cobalt glass or a
solution of indigo, appears red. The spectrum of potassium contains
two characteristic lines — Ka in the red and K/5 in the violet — both coin-
cident with lines of the solar spectrum.
SODIUM, Na,?
Atomic weight = 23. Probable molecular weight = 46. Sp. gr, 0.97.
Fuie» at 96.6^ C. (172° F.). 5o£& aiared heat. AtomieUtf '. Em-
dence of atomicity :
Sodic chloride, NaCl.
Sodic hydrate, ONaH.
Sodic oxide^ ONa^.
History. — Metallic sodium was first obtained by Davy, in 1807, by
the electrolysis of sodic hydrate.
Occurrence. — Sodium is an abundant and widely distributed element.
It does not occur in the free state. In combination with silicic acid it
is found in many minerals and rocks, and in soils. As nitrate, or Chili
saltpetre, it forms large beds on the surface of the ground in dry districts
in Chili and Peru. As carbonate and as iodide it occurs in the ashes
of sea plants. The chloride is, however, the form in which it is found in
the greatest abundance — thus, as rock salt, in sea water, and in the water
of salt springs. The borate and sulphate also occur in nature.
Preparation. — 1. Davy obtained sodium by electrolyang, betweai
SODIUM. 425
the poles of a powerfal battery, solid sodic hydrate moistened with water
(see PotasBium, p. 411):
20NaH = Na, + H, + O,.
2. Sodium is also liberated from the hydrate by acting upon it with
metallic iron at a strong white heat. The reaction is the same as in the
case of potassium (p. 412).
3. On a manufacturing scale, sodium is prepared by distilling from a
cylindrical iron retort a mixture of dry sodic carbonate and cnarooal,
to which a small quantity of chalk is added to prevent the fusion of
the mass and the consequent separation of the charcoal :
OONao, + 20 = Na, + 300.
Sodic Carbonic
carbonate. oxide.
Pr(yperHe8. — Sodium resembles potassium in its properties. It is a
lustrous, silver-white metal, which almost instantaneously tarnishes from
oxidation when exposed to the air. At a temperature of — 20° C.
( — 4^ F.) it is hard, but at ordinary temperatures it is of the consistence
of wax. When heated in air it bums with a yellow flame, forming
oxides of sodium. By fusing it in a tube filled with coal-gas, allowing
it partially to solidify, and pouring off the still liquid portion, it may
be obtained in crystals.
Reactions. — The reactions of sodium are similar to those of potassium,
but less energetic. Thus, sodium decomposes water with evolution of
hydrogen, the metal moving rapidly on the surface with a hissing noise,
but the heat developed is not sui&cieut to inflame the hydrogen. If,
however, the water be previously heated above 60° C. fl40° F.), or if,
by rendering the water viscid with glue, or by placing tne metal on wet
blotting paper, the sodium be prevented from moving, and therefore
from too rapidly cooling, the hydrogen will inflame. Under these cir-
cumstances, the reaction is, however, sometimes attended with a violent
explosion. Sodium is not acted upon by dry chlorine or bromine, even
when gently heated with these reagents; in presence of moisture, how-
ever, chloride and bromide of sodium are formed.
Uses. — Sodium, like potassium, is employed in the preparation of
various metals and metalloids from their oxides or chlorides. It acts
by combining with the oxygen or chlorine, and liberating the element
which it is desired to isolate. On account of its greater cheapness and
lower atomic weight, it is generally preferred for this purpose to potas-
sium (see p. 413). It is thus used in the arts, in the preparation of
aluminium and magnesium from their chlorides. In the laboratory
it is also employed as a source of nascent hydrogen. The substance to
be submitted to the hydrogenating action is brought, along with water
or alcohol, in contact with the solium (preferably in the form of an
amalgam, or alloy of the metal with mercury — the mercury being added
in order to moderate the violence of the reaction), and in this way the
hydrogen from the water or alcohol^ instead of being liberated, combines
with the substance.
426 INOBGAIillG CHEMIBTBY.
COMPOUND OF SODIUM WITH HYDROGEN.'
Sodk hydride^ Na|Hs. Sodiam when heated to a tempentare between 900° and
420° C. (572°w88° F.) in a current of dry hydrogen, absorbs the gas with formatioo
of sodic hydride, a silvery metallic mass of sp. gr. 0.959, which is toft at ordinary tem-
peratures,'but at lower temperatures brittle. It ftises at a somewhat lower temperature
than sodium. It b more permanent in air than the corresponding potassium com-
pound. It begins to dissociate under ordinary pressures at 420" C. (788" F.) ; w toeito,
at 300" C. (672° F.).
COMPOUNDS OF SODIUM WITH THE HALOGENS.
SoDiG CHLORIDE {ptmifnon saltjj NaCI. — ^This important compound
occurs in sea-water (2.5 to 3 per cent), in salt springs, and as rock salt.
The most celebrated salt mines are those of Wiehczka, in Galicia, in
which the salt deposit is 600 miles long, 20 miles broad, and 1200 feet
thick. When the salt is pure, as is sometimes the case with rock salt,
it is obtained direct by ordinary mining operations. Generally, how-
ever, it is contaminated with earthy matters, from which it must be
freed by dissolving in water and recrystallizing. Salt is also obtained
from sea-water : in warm climates, by allowing the water to evaporate
in shallow basins; in cold climates, by letting it freeze and removing;
the ice, the salt remaining in the liquid. Chloride of sodium is formed
when sodium is burnt in chlorine. It crystallizes in large colorless
anhydrous cubes belonging to the regular system ; from solutions con-
taining urea it is deposited in octahedra. Below — 10^ C it crystallizes
from water in monoclinic plates of the formula NaCI,20H2, which at
ordinary temperatures part with their water of crystallization and fall
to pieces, being converted into a number of minute cubes. It is almost
equally soluble in hot and cold water : at 0° C. water takes up 36 parts,
at 100^ C. 89 parts. Alcohol does not dissolve it. At a red heat it is
fusible and volatile.
Sodic bromidey NaBr, is prepared by neutralizing hydrobromic acid
with sodic carbonate, or by decomposing ferrous bromide (FeBr,) with
a solution of sodic carbonate (see Potassic iodide, p. 414). It crys-
tallizes from its aqueous solution above 30^ C. in anhydrous cubes;
below this temperature in monoclinic prisms of the formula NaBr,20H2.
It is readily soluble both in water and in alcohol.
Sodic iodidcy Nal, is prepared like the bromide, which it also resem-
bles in its crystallographical characteristics. Above 20° C. it crystal-
lizes from water in anhydrous cubes ; at lower temperatures in mono-
clinic forms with 2 molecules of water of crystallization. Both water
and alcohol dissolve it freely. Like pota<«ic iodide it forms double
compounds with the iodides of the heavy metals.
Sodic Jluoridey NaF, is obtained by neutralizing hydrofluoric acid
with sodic carbonate. It crystallizes in anhydrous cubes, which are
soluble in 26 parts of cold, very slightly noore soluble in boiling water.
It forms numerous double compounds with other fluorides and with
hydrofluoric acid. The mineral cryolite is an aluminio-sodic fluoride of
the formula Al,F„6NaF. Sodic dlioofluoride, SiF^Na, (=SiF^,2NaF),
forms small lustrous hexagonal crystals, sparingly soluble in water.
COHPOUHDB OF SODIUM. 427
COMPOUNDS OF SODIUM WITH OXYGEN AND
HYDROXYL.
SoDic oxiD£, ONa,. — When sodium burns in air a mixture of sodic
oxide with disodic dioxide (Na^O,) is formed. By heating this mixture
to a very high temperature, the dioxide parts with half its oxygen, and
is converted into sodic oxide, which is thus obtained as a gray mass
with a conchoidal fracture. Water converts it, with evolution of great
heat, into the hydrate.
f ONa
Disodio dioxidey < q^ , is obtained by heating sodium in oxygen
gas till the weight becomes constant It is a white substance, which
becomes yellow on heating, but turns white again on cooling. In con-
tact with water, it evolves great heat, and parts with some of its oxygen.
Sodic hydrate {Caustie soda), NaHo. — This compound is formed
by the action of water upon sodium or upon sodic oxide. It is prepared
by acting upon a boiling solution of sodic carbonate with milk of lime :
OONao, + OaHo, = 2NaHo + OOCao".
Sodic Calcic 8odic Calcic
carbonate. hydrate. hydrate. carbonate.
The solution of sodic hydrate is decanted from the insoluble calcic car-
bonate and concentrated, first in an iron and lastly in a silver basin.
Most of the sodic hydrate of commerce is obtained in the manufacture
of sodic carbonate (see Leblanc's process), the calcic oxide, which is
formed in roasting the black ash, acting upon a portion of the sodic
carbonate when the mass is treated with water. The caustic soda
remains in the mother liquors after the separation of the other salts —
carbonate and sulphate. A small quantity of sodic nitrate is added
in order to oxidize the sodic sulphide to sulphate. — Sodic hydrate is
an opaque white fibrous substance of sp. gr. 2.00, resembling potassic
hydrate in nearly all its properties. It fuses below redness, and at a
higher temperature volatilizes. When exposed to the air in large masses,
it does not deliquesce, but merely becomes moist on the surface, after
which a coating of the non-deliquescent carbonate is formed, which pro-
tects it from further action. It is very soluble, both in water and in
alcohol, yielding powerfully caustic solutions. The concentrated aqueous
solution, when exposed to a low temperature, deposits crystals of the
formula 2NaHo,70H„ which fuse at 6° C. (43° F.) to a liquid of sp.
gr. 1 .405. Its solutions absorb carbonic anhydride from the air. With
acids it yields the corresponding sodium salts :
NaHo + NOjHo = NO,Nao + OH^
Sodic Nitric acid. Sodic nitrate. Water,
hydrate.
OXY-SALTS OF SODIUM.
Sodic nitrate {Chili saltpetre), N02Nao, occurs, more or lees con-
taminated with other salts, in enormous deposits in Chili and Peru.
It can be readily purified by crystallization, and forms rhombohedral
428 INORGANIC GHEMI8TRT.
crystals fusing at SIS'" C. (SSS"" F.). It is soluble in about its own
weight of water. Owing to its slightly deliquescent character, it cannot
be used in the manufacture of ordinary gunpowder, but it has been em-
ployed in the case of powders in wliich extreme rapidity of combustion
IS not essential. In other respects it resembles potassic nitrate. It is
used in the preparation of " converted nitre " (p. 416), and nitric acid,
and also as a manure.
Sodie nitriU, NONao, is prepared like the potaMiom salt (p. 416). It forms colorlesa
rhombohedra, and is lesR deliquescent than the potassium salt. It is soluble in alcohoL
SodieehhraUj < q^^^^i ^ formed in the same manner as the potassium salt (p. 182),
but, owing to its solubility and the impossibility of separating it from the chloride
which is formed simultaneously, cannot be so prepared. It is most readily obtained
by neutralizing a solution of chloric acid with sodic carbonate and evaporatine. It
forms large transparent crystals belonging to the regular system, and exhibiting hemi-
hedral faces, which in some crystals are positive, in others negative. These crystals
possera a corresponding action on the ray of polarized light, the positive crystals being
dextrorotatory, the negative Isevorotatory. It is soluble in its own weight of water at
ordinary temperatures, and in half its weight at 100° C. In other respects it resembles
the potassium salt.
(OCl
Sodie perchloratej k O , is prepared by neutralizing perchloric acid with sodic hy-
(ONao
drate or carbonate. It is a deliquescent salt, readily soluble in water, soluble also in
alcohol.
Sodic bromate^ i ONao * ^" P>^P<li^ ^^^e the potassium salt (p. 417). It forms small
lustrous crystals, soluble in about 3 parts of water at ordinary temperatures. Below
—4° G. (25° F.) it crystallizes in four-sided prisms containing water of crystalliaation.
Sodic iodaie, < oNao * ^ obtained in the same manner as the potassium salt (p. 417).
It crystallizes at ordinary temperatures with one molecule of water of crystallization
in silky needles. It is soluble in 11-12 parts of water. Below 6° C. (41° F.) it is
deposited in transparent rhombic prisms with 5 molecules of water of crystallization.
It forms well -crystallized double salts with the chloride, bromide, and iodide of sodium.
The compound with sodic chloride has the formula
2{gJj^^.3NaCl,90H,.
fOl
Sodie periodaiet < O ,30Ht. When chlorine is passed into a solution of sodic
I ONao
iodate in caustic soda, a sparingly soluble basic salt of the formula I0rHNai,OFTi is
deposited, which, when dissolved in dilute nitric acid and evaporated, is converted
into the normal salt lOgNao.SOHs. (On the formulation of the periodates, see p.
305.) The normal salt forms colorless hexagonal crystals, soluble in 12 parts of water
at ordinary temperatures. The crystals part with their water of crystallization at
100° C. Heated to 276° C. (527° F.) the anhydrous salt gives off oxygen, and is con-
verted into iodate.
Sopio CARBONATE, OONao,, occuFs in the soda lakes of Egypt and
Hungary, and in the volcanic springs of Iceland. It constitutes the
greater part of the ash of sea plants, from which source it was formerly
obtained. The two methods at present employed in its preparation are:
the process of Leblane and the ammoniar-soda procesSj both of which
start from sodic chloride.
1. Lehlano^s Process, — ^This process consists of two parts : the con-
version of the sodic chloride into sodic sulphate or salt cake, known as
the sdU'Cake process ; and the manufacture of sodic carbonate or soda
OOMFOX7ND6 OF SODIUM. 429
af^h from the salphate, known as the soda-ash process. In the first of
these processes the sodic chloride is treated, in a large hemispherical
cast-iron pan heated over a furnace, with the requisite quantity of sul-
phuric acid. The hydrochloric acid which is evolved passes through
towers filled with coke, over which a stream of water trickles, and is
thus absorbed. After heating for some time, the mixture of acid and
salt solidifies, upon which it is transferred from the iron pan to the bed
of a reverberatory furnace, where the decomposition is completed.
In the soda-ash processs, the sodic sulphate or salt cake, as it is tech-
nically termed, is mixed with crushed chalk or limestone and small
coal, and gradually heated in a reverberatory furnace. The action
takes place in the two following stages :
and
SOjNao, + 40 = SNa, + 40O,
Sodic Sodic Carbonic
sulphate. sulphide. oxide,
SNa, + OOCao" = OONao, + OaS",
Sodic Calcic Sodic Calcic
sulphide. carbonate. carbonate. sulphide.
the calcic sulphide combining with the excess of calcic oxide (formed
from the chalk), and yielding insoluble calcic oxysulphide.
These reactions take place simultaneously in the above operation.
When the change is complete, the mass, which is known SA'blaxik ash,
is allowed to cool, and is then extracted with water, which dissolves
the sodic carbonate, leaving behind the insoluble oxysulphide. On
evaporating, the sodic carbonate crystallizes out, and may be purified
by recrystallization.
A portion of the chalk is converted by the heat into quicklime, and
this gives rise to the formation of sodic hydrate when the mass is treated
with water. This sodic hydrate may be recovered from the mother
liquors of the carbonate (p. 427).
2. Ammonia'Soda Process, — By the action of hydric ammonic car-
bonate on a concentrated solution of sodic chloride, hydric sodic car-
bonate and ammonic chloride are produced :
COHcKN^H.O)
+ NaCl =
OOHoNao + NH,CI.
Hydric ammonic
Sodic
Hydric sodic Ammonic
carbonate.
chloride.
carbonate. chloride.
The sparingly soluble hydric sodic carbonate separates out, whilst the
ammonic chloride remains in solution. By heating the hydric sodic
carbonate, it is converted, with evolution of carbonic anhydride, into
the normal salt :
200HoNao =
= OONao,
+ 00, + OH,.
Hydric sodic
Sodic
Carbonic Water.
carbonate.
carbonate.
anhydride.
The carbonic anhydride is employed in reconverting into hydric am-
monic carbonate^ the ammonia recovered from the ammonic chloride.
430 INOBOANIO CHEMI8TBT.
Sodic carbonate ciystallizes at ordinary temperatores in efflorescent
monoclinic crystals of the formula OOXaOjjlOOHj, fusing at 60° C.
(122° F.) to a clear liquid, which gives off water, and deposits a
pulverulent salt, with one molecule of water of crystallization. At
temperatures between 30° and 50° C. (86-122° F.) it is deposited in
rhombic crystals with TOH,. It is readily soluble in water, with a
maximum solubility at 38° C. (100° F.).
100 parts of water dissolve:
At 0° C. (32° F.), . . 7 parts of anhydrous salt
At 15° C. (59° F.), . . 16 parts of anhydrous salt.
At 38° C. (100° F,), . . 51 parts of anhydrous salt
At 104° C. (219° F.), . . 45 parts of anhydrous salt.
Anhydrous sodic carbonate fuses at a bright red heat, and may be
volatilized at a white heat The chief consumption of sodic carbonate
is in the manufacture of glass, in soap-making, and in bleaching
calico.
Hydric sodic oarbonaUy OOHoNao, occurs naturally in many mineral
waters. It is formed when a concentrated solution of the normal car-
bonate is saturated with carbonic anhydride. The crystallized normal
carbonate also absorbs carbonic anhydride with evolution of heat, a
property which is taken advantage of in the preparation of the salt on
a large scale. The acid carbonate can be readily separated from the
normal carbonate by its more sparing solubility. Hydric sodic carbon-
ate is also obtained in the preparation of sodic carbonate by the ammo-
nia-soda process (p. 429). It forms monoclinic prisms, soluble in
10-1 1 parts of water at ordinary temperatures. When its solution is
heated^ the salt parts with a portion of its carbonic acid^ yielding the
so-called sesquicarbonate,0ONao2,20OHoNao,20H„ which may ^ ob-
tained in crystals by cooling the solution. The sesquicarbonate also
occurs in large deposits in Africa and South America, the natural pro-
duct being known as trona or twao. If the solution of hydric sodic
carbonate be boiled for a sufficient length of time^ it is entirely decom-
posed into normal carbonate, carbonic anhydride, and water. The same
decomposition takes place when the dry salt is heated.
Potassic sodic earbonatej C?OKoNao,60H».— This salt crystallizes from the solution of
a mixture of potassic and sodic carbonates. It forms eMorescent monoclinic crystals.
It cannot be recrjrstallized from water without decomposition. The anhydrous salt
fuses at a red heat more readily than either potassic or sodic carbonate. On account
of this property it is employed in mineral analysia for the decomposition of silicates bj
fusion.
Sodic sulphate {Qlavher^s «aft), SOgNaOg, occurs in nature in the
anhydrous form as the mineral thenardite, and with ten molecules of
water of crystallization as OlavAer^» salt Olauberiie is a native sodic
calcic sulphate of the formula oqjsj Cao''. Sodic sulphate often oc-
curs in sea- water and in the water of brine springs. It is prepared in
enormous quantities under the name of aaU cake as a preliminary step
in the manufacture of sodic carbonate by Leblanc's process (p. 429).
OOMPOTTKDS OP SODIUM. 431
It crystallizes at ordinary temperatures in large colorless efflorescent
monoclinic prisms of the formula SOjNaOjylOOHj, which fuse at 33° C.
in their water of crystallization. It is very soluble in water, with a
maximum solubility at 33° C.
100 parts of water dissolve:
At 0° C, ... . 6 parts of anhydrous salt.
At 20° C, .... 20 parte of anhydrous salt
At 33° C, . . . . 50.6 parte of anhydrous salt.
At 103° C, . . . . 42.65 parte of anhydrous salt.
(See also p. 127). A solution saturated at 33° C. deposite, when heated
above this temperature, small rhombic octahedra of the formula
SOjNaOa,©!!, (formerly supposed to be anhydrous; see, however,
Thompson, Ber. d, deidaeh. chem. Oea., 11, 2042), This monaquate is
always deposited from solutions at temperatures above 40° C. (101° F.).
When a solution, saturated at 33° C. (91° F.) is cooled, it does not, if
protected from the air, deposit crystals, and in hermetically sealed ves-
sels, may be preserved for an indefinite period in this supersaturated
condition ; but the introduction of a fragment of the solid salt, or even
contact with dust from the air, which probably always contains the
solid salt, id sufficient to determine the solidification of the liquid to a
magma of crystals, this process being accompanied by a rise of temper-
ature. When the supersaturated solution i6 evaporated in vacuo over
sulphuric acid, 'it deposite crystals of a salt having the formula
SOjNaOjjTOHj, this probably being the form in which the substance
is present in the supersaturated solution. Crystallized sodic sulphate
dissolves in concentrated hydrochloric acid with great absorption of heat.
A useful freezing mixture is obtained by pouring 5 parte of the acid
upon 8 of the sulphate. — Hydrie 8odio8ulphate,BOJloJ^ei0^is prepared
like the potash salt (p. 418). It crystallizes at ordinary temperatures
in monoclinic prisms with 1 aq.;* above 60° C, in anhydrous triclinic
forms. It is readily fusible^ Heated above ite fusing point it parte
with the elements of water, yielding sodic pyrosulphate, S^05.Nao2 ; at
a still higher temperature sulphuric anhydride is expelled and the nor-
mal sulphate remains.
Tripofassie sodic disulphaie, BOsKos.SOsKoNao, is obtained in hexagonal plates when
mixed solutions of sodic and potassic sulphate are allowed to crystallize. At the mo-
ment of crystallising, the salt emits flashes of light, visible in the <&irk, th» phenomenon
being most striking when the temperature of the solution is about 40^ C.
SoDic SULPHITE, SONaOjjTOHj, forms monoclinic crystals^ readily
soluble in water and possessing an alkaline reaction, w hea the solu-
tion is heated, it deposite an anhydrous salt, which dissolves again on
cooling. Hydric sodio sulphite^ SOHoNao, crystallizes in smaJl lus-
trous prisms, readily soluble in water, and possessing an acid reaction*
The salt evolves sulphi>rous anhydride when exposed to the air, and
is spontaneously oxidized to sulphate. Sodic pyroaiUphite, S205^ao2, is
* In the aquates the symbol "-aq,." is frequently employed to denote a molecule of
water of crystallization.
20aS"
432 INOBQANIG CHEMI8TBT.
also knowD. The sulphites of sodium are prepared like the correspond-
ing potassium salts (p. 418).
Sodie dithwnaU, { go^Nao'^^^** " prepared like the potaasiam salt (p. 419).
It forniB transparent rhombic priBms, readilj lolable in water.
SoDio THI06ULPHATE (Sodic hyposulphite), SO^NaoNaSySOHj.
(Preparation, see p. 277.) This salt is obtained on a large scale from
aoda waste^ the insoluble matter which remains after the extraction of the
sodic carbonate from the black ash in Leblanc's process. By exposing
this residue in a moist condition to the air, the calcic sulphide (or 0x7-
sulphide) which it contains is oxidized to calcic thiosulphate, calcic
hydrate being formed at the same time :
+ 20, + OH, = SoigCa) + OaHoy
Calcic ' Water. Calcic Calcic
sulphide. thioeulphate. hydrate.
The calcic thiosulphate is extracted with water and decomposed witli
sodic sulphate, thus yielding sodic thiosulphate and insoluble calcic
sulphate. Sodic thiosulphate forms large, well defined monoclinic crys*
tals, readily soluble in water and somewhat deliouescent. It fuses at
56° C. (133° F.) in its water of crystallization. When the dry salt is
heated it is decomposed like the potassium salt (p. 419) into a mixture
of sulphate and sulphide. The aqueous solution dissolves the chloride,
bromide, and iodide of silver, a property which has caused the salt to
be employed in fixing photographic prints. Sodic thiosulphate is also
used as an antichlore^ to destroy the excess of the chlorine employed in
bleaching vegetable fibre.
Sodic tdenaU, 8eOsNaos,10OHs) is prepared like the potassiiim salt (p. 419). It
closely resembles sodic sulphate in its properties.
&odic tellvrcUef TeOsNaoi, resembles the potassiam salt.
Sopic Phosphates :
a. Sodic phosphcUey PONao3,120H2, is prepared by fusing 2 mole-
cules of hyaric disodic phosphate with 1 molecule of sodic carbonate,
dissolving in water and crystallizing; or by evaporating a solution of
bydric disodic phosphate in caustic soda. The salt crystallizes in thin
six-sided prisms, readily soluble in water, efflorescent in dry air. The
solution, which has a strong alkaline reaction, absorbs carbonic anhy-
dride from the air, the third atom of sodium being thus abstracted to
form carbonate, whilst hydric disodic phosphate remains. — Hydric
disodic phosphate i^^ phosphate of soda") POHoNao2,120H2, is obtained
by adding sodic carbonate or sodic hydrate to orthophosphoric acid until
the liquid has a slight alkaline reaction, and then evaporating to the
crystallizing point. On a large scale the orthophosphoric acid for this
purpose is obtained by decomposing bone-ash with the reouisite quan-
tity of dilute sulphuric acid and filtering from the insoluble calcic sul-
phate. The salt forms efflorescent monoclinic prisms, soluble in 4.5-5
G0MP0UND6 OF SODIUM. 433
parts of water at ordinary temperatures. The solution has a weak
alkaline reaction. At 37® C. (99° F.) the crystals fuse in their water
of crystallization. At temperatures above 30° C. (86° F.) the solution
deposits non-efflorescent crystals of a salt with 7 aq. When heated to
redness hydric disodic phosphate parts with the elements of water^
forming tetraaodic pyrophosphate, PjOjNao^. Hydric sodic phosphate
was formerly much used in calico-printing under the name of "dung
substitute," but is now superseded by the cheaper sodic arsenate. —
IHhydric sodic phosphate, POHo^NaOjOH,, is obtained by adding
phosphoric acid to the disodic salt until the solution no longer yields
a precipitate with baric chloride, and then evaporating. ^ It crys-
tallizes in rhombic prisms, readily soluble in water, yielding an acid
solution.
Hydric potcuiic wdic phosphate^ POHoKoNao,70H,, is prepared by adding potassic
carbonate to a solution ot dihydric sodic phosphate until the liquid has a slight alkaline
reaction. It forms soluble monoclinic crystals.
6. Sadie pyrophosphaie, P2O3Nao4,10OIT2, is prepared by heating
hydric disodic phosphate to redness, dissolving the mass in water and
allowing to crystallize (p. 355). It is thus obtained in large monoclinic
crystals, soluble in 10-12 parts of water at ordinary temperatures, and
in their own weight of water at 100° C. The aqueous solution may
be boiled without alteration, but when boiled with hydrochloric, nitric,
or even acetic acid, the salt takes up the elements of water, at the same
time parting with a portion of its base to the acid, and is converted
into dihydric sodic phosphate. — Dihydric disodic pyrophosphate,
PjOjHosNaOs, separates as a crystalline powder when alcohol is added
to a solution of the normal pyrophosphate in acetic acid. It may be
boiled with water without decomposition.
Dipatassie disodic pyrophosphcUCj PsOjKojNao,, is obtained by neutralizing a solution
of the acid sodium salt with potassic carbonate. It forms soluble acicular crystals.
c. Sodic metaphosphaie, POjNao, is prepared by igniting either dihy-
dric sodic phosphate, or hydric ammonic sodic phosphate, or dihydric
disodic pyrophosphate (see Metaphosphaies, p. 354). According to the
temperature to which the substance has been heated and the rate of
cooling, products differing widely in their properties, but all possessing
the same percentage composition, are obtained. When the substance is
heated to redness and rapidly cooled, the product is a vitreous deliques-
cent mass, which dissolves readily in water and remains behind on
evaporation in the form of an uncrystallizable gum. If the cooling
has been effected more slowly, there is formed, in addition to the
uncrystallizable salt, a compound which is deposited from the solution
in monoclinic prisms of the formula PO2Nao,20H2. A third modifi-
cation is obtained by limiting the temperature to 315° C. (599° F.).
On extracting with water, an almost insoluble metaphosphate remains
as a white powder. These differences are supposed to depend upon
polymeric modification (see p. 354.)
28
434 INOBOAKIO CHEMIBTRT.
SodU anenaies. — The sodic anenates are prepared like the phosphates, which thej
also resemble in properties. Sodie anenaUf AflONaos,120Hi, is very soluble in water,
and is converted hy the carbonic anhydride of the air into the monohydric salt. HydrU
diBodie ar$enaU, AB0IIoNaos,l2OH3, closely resembles the corresponding phosphate,
crvRtallizing in large efflorescent monoclinic prisms. Like the phosphate, it may be
obtained from hot solutions in non-efflorescent crystals with 7 aq. At a red heat it
parts with the elements of water, yielding sodUpyranenaU, A8iOBNao4, which, however,
cannot exist in solution, but, in contact with water, at once r^enerates hydric disodic
arsenate. Dihydrie iodic artenate, ABOHotNao,OHi. obtained by adding arsenic acid
to sodic carbonate till the solution no longer precipitates baric chloride, forms large
soluble rhombic prisms.
Sodic anltmofidte.— When a solution of dihydrie dipotassic pyrantimonate is added to
the solution of a sodium salt, a granular crystalline precipitate of dihydrie dimxiic pyran-
timonate, SbfOsHosNaot 60Hs, is prodncfKi. This salt is insoluble in water.
Sodic antimonite, — A solution of antimonioun anhydride in caustic soda deposits lus-
trous rhombic oclUihednL of aodiemetantimonitefBloO'SBuOySOfl ft ^^^^^ insoluble in cold,
sparingly soluble in boiling water. Very concentrated solutions sometimes deposit
rhombic prisms of dihydrie Mdic trimetarUimoniie, SbsOsHosNao.
Sodic borate. — The metnborate, BONao,40H„ is prepared by fusiDg
together equal molecules of boric anhydride and sodic carbonate, or by
boiling a solution of borax with the necessary quantity of sodic hydrate,
evaporating to a syrup and allowing to crystallize over sulphuric acid.
It forms lai^e triclinic crystals, readily soluble in water. The solution
has an alkaline reaction, and absorbs carbonic anhydride from the air.
A metaborate with 2 aq. is obtained in long acicular crystals by fusing
the above »alt in its water of crystallization and then allowing it to crystal-
lize, or by crystallizing in presence of a large excess of sodic hydrate. —
Sodic tetraborcUe (borax), B^O^Nao^lOOH,. This salt occurs in the water
of some lakes in Thibet, from which it is obtained by evaporation and
crystallization. The natural product, known as tinoal, formed at one
time the chief supply of this salt; but at present most of the borax of
commerce is prepared from the boric acid obtained from the lagoons of
Tuscany (p. 191.) The boric acid is either added to a boiling solution
of sodic carbonate, or boric acid is heated with half its weight of anhy-
drous sodic carbonate, in a reverberatory furnace, and the mass, after
cooling, extracted with water. The salt crystallizes in monoclinic prisms,
soluble in 14 parts of water at ordinary temperatures and in half their
weight of water at 100° C. The solution has an alkaline reaction.
At temperatures above 60° C. (140° F.) borax crystallizes from concen-
trated solutions in regular octahedra, with 5 aq. (octahedral borax).
When heated borax parts with its water of crystallization, iutumescing
and forming a porous white mass, which, at a higher temperature, fuses
to a clear glass. In a state of fusion, it dissolves metallic oxides, with
many of which it yields characteristically colored flaxes. This prop-
erty, which depends upon the presence of an excess of boric anhydride
in the salt, is utilized in the employment of borax as a blowpipe reagent.
It is also used in soldering oxidizable metals, to dissolve the oxide in
order to expose clean metallic surfaces. Further applications are : in
various metallurgical operations as a flux, in the preparation of enamels,
and in fixing colors on porcelain.
Sodic silicate, 810Xao<,80H3, is prepared bj diRsolving 1 molecule of amorphous
silicic anhydride in a solution of 2 molecules of sodic hydrate, eTaporatine to a synip,
and cooling by means of a freezing mixture, stirring at the same time. The salt, siter
LITHIUM. 436
being purified by recrystallization, forms lai^ moDOclinic crystalB, very soluble in
water. Both in solution and in the dry state it absorbs carbonic anhydride from the
air, undergoing decomposition » with separation of amorphous silicic acid. Soluble 9oda
gUiu may oe obtained m the same manner as the (lotassium compound. On a large
scale it is prepared by heating together 100 parts of quartz sand, 60 parts of anhydrous
sodic sulphate, and 15 to 20 parts of charcoal dust. The charcoal, by taking up part
of the oxygen of the sulphate, facilitates the decomposition of this salt by the silicic
anhydride. Soluble soda glass is employed as a cement, in coating buildmg stone in
order to preserve it from decay, and in fixing colors in fresco paintings. The alkaline
silicates are important constituents of glass {q.v),
COMPOUNDS OF SODIUM WITH SULPHUR AND HYDROSULPHTL.
Sodic sulphide, Sodie potysulpkideSf and Sodic tndphkydratc. — These compounds are pre-
pared like the eorresponding potassium compounds, which they closely resemble.
SULPHO-SALTS OF SODIUM.
Sodie afidpharsenaUy 2ABS^^NaPs,150H^ is prepared like the potassium compound.
It forms large, colorless monoclinic prisms, readily soluble iu water. •
Sod%enUphafUmonaU{Seklipp^8mlt), SbS^^Nas.,90H„ is obtained like the potash
salt. It crystallizes in large pale yellow tetrahedra, readily soluble in boiling water.
When exposerl to the air, the crystals undergo superficial decomposition, burning
coated witii a reddish-brown layer of antimonic sulphide.
COMPOUNDS OF SODIUM WITH NITROGEN AND HYDROGEN.
Sodie amidey NNaH^ is formed when so<Hum is gently warmed in a current of dry
gaseous ammonia. The sodium fuses, yielding a greenish-blue liquid, which, on cool-
ing, solidifies to a crystalline mass, whilst the color at the same time changes, through
brown and olive-green, to a fiesh tint In presence of moisture and under the influence
of heat, it behaves like potassic amide (pp. 423, 424).
General. Properties and Reactions of the Compounds op
Sodium. — The salts of sodium are as a rale more soluble than those of
potassium. The only insoluble sodium ealt is the dihydric disodic pyr-
antimonate (SbjOjHojNao^GOH^) (p. 434). Sodium compounds color
tlie non-luminous flame an intense yellow. The color is invisible when a
piece of cobalt glass or a solution of indigo is interposed between the
flame and the eye. The flame spectrum of sodium consists of a double
line in the yellow^ coincident with D in the solar spectrum.
UTHITJM, Lis?
Atomic weight = 7. Probable molecular weight = 14. Sp, gr = 0.59.
Fuses at 180° C. (356° F.). Atomicity '. Evidenoe ofatomicUy:
Lithic chloride, LiCl.
Lithic hydrate (lithia), OLiH.
History. — Lithic hydrate was discovered by Arfvedson in 1817.
The metal was first isolated by Bunsen,
Occurrence. — Lithium is a constituent of several rare minerals, such
as fepicfo/t^ (lithia m\ceL)y petalUe^spodumene, eiud triphyline. By the
aid of spectrum analysis, lithium has been shown to be very widely dis-
436 INOBGANIC CHEMIBTBT.
tributed : thus it occurs in minute quantities in the ashes of plants and
in many mineral waters.
Preparation. — Metallic lithium cannot, like potassium or sodium, be
reduced from its oxygen compounds by heating with charcoal. It is
obtained by the electrolysis of the fused chloride. For this purpose
a battery power of five or six Grove's cells is required. The positive
pole is of hard gas coke, the evolved chlorine having no action upon
this substance; for the negative pole, an iron wire is employed. A
globule of molten metallic lithium soon forms on the iron wire under
the surface of the fused chloride. As soon as this globule has attained
the size of a pea, it is lifted out of the chloride along with the iron wire
by means of a small iron spoon, a coating of litbic chloride protecting
it from instantaneous oxidation, and is allowed to cool under petroleum.
The globule is then detached from the wire and these operations are
repeated until a sufficient quantity of the metal has bf«n obtained.
The globule must not be permitted to attain too great a size, otherwise
it will detach itself from the iron wire and rise to the surface of the
fused chloride, where it generally inflames.
Properties, — Lithium is a silver-white metal, harder than potassium
or sodium, but softer than lead. It has a sp. gr. of 0.59, and is thus
the lightest solid known. It floats on petroleum. It is less oxidizable
than potassium or sodium, but speedily tarnishes when exposed to the
air. Heated in air to a temperature considerably above its fusing-point,
it inflames, burning with an intense white light. It decomposes water,
without however inflaming, even when the water is hot. The solution
contains lithic hydrate, LiHo.
COMPOUNDS OF LITHIUM WITH THE HALOGENS.
These compounds are prepared by dissolving the hydrate or carbonate
in the corresponding hydracid.
Lithic chloride, LiCl, crystallizes in anhydrous octahedra, having
the taste of common salt. At temperatures below 10® C. (50*^ F.) it
crystallizes with 2 aq. It is deliquescent and readily soluble in alcohol
or in a mixture of alcohol and ether, by which means it may be sepa-
rated from the other chlorides of this group. It volatilizes below a
red heat.
LWiic iodide, Lit^SOH,, forms very deliquescent needles.
Lithic fluoride, LiFjCrjst&Wizes in small opaque white granular crystals^ sparingly
Bolable in water.
COMPOUNDS OF LITHIUM WITH OXYGEN AND
HYDROXYL.
Lithic oxidCj OLi^ is obtained as a white spongj mass, containing a certain quantitj
of a higher oxide, by burning lithium in dry oxygen.
Lithic hydrate {Lithia), LiHo, is prepared like the hydrate of potas-
sium, which it also resembles in most of its properties. It is, however,
COMPOUNDS OF LITHIUM, 437
less solable in water than potassic hydrate, and does not deliqaesoe when
exposed to the air. Fused lithic hydrate corrodes platinum power-
fully^ and should therefore always be prepared in a silver capsule.
0XY-SALT8 OF LITHIUM.
These are for the most part obtained by neutralizing the acid with
lithic hydrate or carbonate.
Liihui nitrate, NO,Lio, crystallizes at 16® C. (59® F.) in anhydrous rhombohedra,
below 10® C. (50® F.) in thin prisms of the formula 2N02Lio,50H,. It is deliques-
cent and very soluble in water.
roci
Lithic perehhrate^ •{ O , is a deliquescent salt, readily soluble in alcohol.
(OLio
Lithio earbonaJtey OOLio,, occurs in small quantities in various
mineral waters. It is prepared by precipitating a solution of lithic
chloride or nitrate with potassic, sodic, or ammonic carbonate. It is
thus obtained as a white crystalline powder, sparingly soluble in cold
water. The solution is alkaline and deposits the salt by slow evapora-
tion in small prisms. At a bright red heat lithic carbonate undergoes
partial decomposition, evolving carbonic anhydride. Owing to its in-
solubility, this salt is frequently employed in separating lithium from
potassium and sodium.
LiJtkic ndphaie, BOAao^jOH^, forms flat, monoclinic prisms or tables, readily
soluble in water, soluble also in alcohol.
FoicLuie litkic mdphate, SsOcKo^Lio,. — Hexagonal crystals.
IMie dUhiofuUey i sO*Lio*^^^»' ^® P'^P^'ed by exactly precipitating a solution of
baric dithionate with lithic sulphate and evaporating the resulting solution of lithic
dithionate to crystallization. It forms large rhombic crystals, readily soluble in water
and somewhat deliquescent. It is insoluble in alcohol.
Lithic phosphaiey 2POLio3,OH2, is precipitated, slowly in the cold,
instantaneously on heating, when hydric disodic phosphate is added to
a solution of a lithium salt. If the solution is rendered alkaline by the
addition of sodic hydrate or carbonate, the precipitation of the lithium
is complete. Lithic phosphate forms a white crystalline powder, very
sparingly soluble in water (1 part of the salt requires 2500 parts of water
at ordinary temperatures for solution), still less soluble in water contain-
ing ammonia. When heated, it parts with its water of crystallization,
but does not fuse, even at a red heat. This salt is employed in the esti-
mation of lithium. — Dihydrie lithic phoaphatCy POHOaLio, is formed
when either the preceding saU, or lithic carbonate, is dissolved in an
excess of phosphoric acid and the solution evaporated. It is thus ob-
tained in large, very soluble, deliquescent crystals, with an acid reaction.
Genebax. Properties and Reactions op the Compounds op
Lithium. — Lithium is distinguished from the other metals of the alkali
group by the sparing solubility of its normal carbonate and phosphate
438 IMOBOANIC CHEIflSTRY.
and by the solubility of lithio chloride in a mixture of alcohol and
ether. Lithium com|K>unds color the non-luminous flame carmine-red.
The spectrum of lithium dfsplajs a bright line Lia in the red, and a
faint line Li/9 in the yellow. At the temperature of the ozyhydrogen
flame a brilliant blue line makes its appearance.
RUBIDIUM, Rb,?
Atomio weight = 85.3. Probable molecular weight = 1 70.6. Sp. gr. 1 .62.
Fuses at 38,5° C. (101.3° F.). AtomioUy \ Evidence of aJUmuMy :
Rubidic chloride, RbCI.
Ruhidic iodide, Rbl.
Rubidic hydrate, RbHo.
History. — Rubidium was discovered in 1860 by Bunsen and Kirch-
hoff with the aid of spectrum analysis.
Occurrence, — This rare metal is widely distributed in nature, but
always in very minute quantity. It occurs along with potassium in
many minerals (frequently in lepidolite), in the ashes of plants, and in
some mineral springs. It was first obtained from the water of a
spring at Diirkheim in Baden.
Preparation. — 1. Metallic rubidium may be obtained by the elec-
trolysis of the fused chloride as in the preparation of lithium (p. 436).
2. A more advantageous process consists in distilling a mixture of
rubidic carbonate and carbon obtained by charring rubidic tartrate, as in
the corresponding method for the preparation of potassium (p. 412).
Properties, — Rubidium is a lustrous white metal, with a yellowish
tinge. It is soft like wax, even at —10° C. (14° F.). It fuses at 38.5°
C. (101.3° F.), and boils below a red heat, yielding a greenish-blue
vapor. Exposed to the air, it instantly becomes covered with a bluish-
gray film* of oxide and speedily inflames spontaneously. It burns, with
vivid incandescence, in chlorine and in the vapors of bromine, iodine,
sulphur, and arsenic. In contact with water it behaves like potassium.
COMPO UND8 OF R UBIDIVM.
Rubidic chloride, RbCl, crystallizes in transparent colorless cubes,
possessing a vitreous lustre. It is more soluble than potassic chloride
(100 parts of water at 7° C. dissolve 83 parts), and is easily fusible
and volatile. It forms double salts with other metallic chlorides. The
most important of these double chlorides is rubidic pkUinic chloride
(PtCl^,2RbCl), which is even less soluble than the corresponding po-
tassium compound, and is employed in the separation of rubidium.
BuMdic bromide, RbBr, crystallizes in lustrous cubes with sabordinate octahedral
facets and is soluble in its own weight of water at ordinary temperatures.
Rubidic iodide, Rbl, resembles the bromide. It dissolves in 0.7 part of water at
ordinary temperatures.
CJESIUM. 439
Rubidic hydrate, RbHo, resembleB the potaasiam compound, bat is a more powerful
base.
Rvhidie niiraie, NO.Bbo, forms hexagonal crystals, soluble in 2.3 parts of water at
10« C. {50<> F.).
BMdic ehhraUf | ORbo'""'''^^ '*^' forms small prismatic crystals, soluble in 20-
25 parts of water at ordinary temperatures.
fOCl
Bvbidic perehloraUf < O , forms small hard lustrous rhombic crystals. It is less
( ORbo
soluble than the corresponding potassium salt, 1 part of the salt requiring 92 parts of
water at 21® C. (70° F.) for its solution.
RvMdijG carb(ynate. — The normal salt, OORboj,©!!^, forms indistinct
crystals with a strong alkaline reaction. The water of crystallization
is expelled by heating. It is readily soluble in water. Exposed to the
air it deliquesces and absorbs carbonic anhydride, forming the a/sidsaU
OOHoRbo, which crystallizes in non-deliquescent prisms with a vitreous
lustre.
Rubidic «M/pAate.— The norriMl talU SOjRbo,. crystallizes in large, hard, rhombic
crystals with a vitreous lustre, more soluble in water than the potassium salt. The
akd aaJif 80,HoRbo, forms short rhombic prisms.
Ruhidic dithionaU, i qq Rk^» forms hard, hexagonal crystals, with a vitreous
lustre.
Rubidic boratc^A tetraborcUe of the formula B405Rbo^60H, is known. It forms
small lustrous crystab belonging to the rhombic system.
OJESIUM^Cs,?
Atomic weight = 133. Probable m^olecidar weight = 266. Sp. gr, 1.88,
Fuses at 26.5° C. (79.7° F.). Atomicity '. Emdenoe of aJLomicity :
Csesic chloride, CsCl.
Csesic hydrate, CsHo.
History, — This metal, which is even rarer than rubidium, was dis-
covered simultaneously with the latter in the water of the Diirkheim
spring by Bunsen and Kirchhoff, in 1860.
Occun*ence. — The rare mineral poUux, which occurs in the granite of
Elba, is a silicate of aluminium, sodium, and caesium, and contains 32
per cent, of the latter metal. In minute traces ctesium is found in a
variety of minerals, and in many mineral springs.
Preparation.-^MetsMic caesium cannot be obtained by the methods
usually employed in the isolation of the alkali metals. Heating the
oxide or carbonate with charcoal yields no result ; whilst, in the elec-
trolysis of the fused chloride, .the reduced metal immediately acts upon
the undecomposed chloride, yielding a blue compound of unknown com-
position— possibly a subchloride. If, however, fused ccesic cyanide,
Cs(CN), mixed with a quarter of its weight of baric cyanide, Ba(CN)j,
in order to increase the fusibility, be subjected to electrolysis, pure me-
tallic caesium is obtained in coherent masses.
Properties. — ^Caesium is a lustrous white metal. At ordinary tern-
440 INOROANIC CHEMISTRY.
peratures it is soft It fuses at 26.5° C. (79.7° F.). When exposed
to the air it oxidizes rapidly, and finally inflames spontaneously. Thrown
on to water it behaves like potassium. Csesium is the most electro-
positive of the elements.
COMPOUNDS OF CJSSIUM.
Cjesic chloride, CsCl, crystallizes in indistinct cubes, which are
very soluble and deliquescent. It fuses below redness, and is more
easily* volatilized than potassic chloride. When heated in moist air it
is partially converted into hydrate. It forms double salts with other
metallic chlorides. Oobsic aniimoniouB chloride (SbCl^fCsCl) is obtained
as a white crystalline precipitate by the addition of antimonious chloride
dissolved in hydrochloric acid to a solution of cffisic chloride. Casio
'plaiinio chloride (PtCl4,2CsCl) forms a yellow crystalline precipitate,
even less soluble than the corresponding rubidium salt.
Oassic hydrate, CsHo, is a caustic, crystalline substance resembling potassic hydrate.
Oacsic nitrate^ NOjCso, crystallizes in hexagonal prisms, and is less soluble In water
than the potassium salt.
Oaeaie carboiuiU.^Boih the normal and the acid carbonate resemble in almost every
respect the rubidium salts. The normal carbonate is soluble in alcohol.
Ccesic sulphate. — The nmrmal 9aU. SO,Cso^ forms prismatic crystals very soluble in
water. Hydric ocesieaulphatej SOgHoCso, crystallizes in small rhombic prisms.
General Properties and Reactions of the Compounds op
Rubidium and CiESiUM. — The salts of rubidium and ceesium cannot
be distinguished from those of potassium by the ordinary chemical
testa. Like these they yield precipitates with platinic chloride and tar-
taric add Csesic platinic chloride (PtCl4,2CsCI) is more difficultly
soluble in boiling water than rubidic platinic chloride (PtCl42RbCl),
and this again is more difficultly soluble than the potassium compound.
In this way a separation of the three metals may be effected. Csesium
may also be separated from rubidium by the solubility of its normal
carbonate in alcohol. The flame colorations of the caesium and rubidium
compounds resemble closely that of potassium. . By means of the char-
acteristic spectra, however, the compounds of the three metals may be
readily distinguished. The spectrum of rubidium consists of two lines,
Rba and Rb/9, in the violet, and two lines, Rb<J and Rb;*, in the red,
together with other fainter lines. The most characteristic lines in the
spectrum of caesium are Csa and Cs/9 in the blue.
THE AMMONIUM SALTS.
{JTTT
j»rT* has already been referred
to (p. 235) in connection with the compounds of nitrogen. Its salts
closely resemble those of the alkalies^ and may therefore be appropri-
ately treated of at this point.
THE AMMONIUM SALTS. 441
COMPOUNDS OF AMMONIUM WITH THE HALOGENS.
Ammonic chloride, NH^Cl. — This compound occurs in small
quantities in the neighborhood of volcanoes, being generally formed
when lava flows over fertile land. The nitrogenous v^etable mater,
thus subjected to a destructive distillation, furnishes ammonia, the lat-
ter combining with the hydrochloric acid which is almost always pres-
ent in volcanic gases. Ammonic chloride is prepared by neutralizing
the ammoniacal liquor from the gas-works — the ammonia being in this
case a product of the destructive distillation of fossil vegetable matter —
with hydrochloric acid, and purifying the crude ammonic chloride by
crystallization and sublimation. The aqueous portion of the distillate
obtained in the preparation of animal charcoal from bones is also very
rich in ammonia, and serves as a source of the chloride. Ammonic
chloride crystallizes from water in small indistinct octahedra or cubes,
which are generally grouped in fern-shaped a^regations. When
heated, it does not fuse, but sublimes, undergoing dissociation into
ammonia and hydrochloric acid, which again unite as the temperature
falls. When sublimed in large quantities, it forms semi-transparent,
tough, fibrous masses. Dissociation also takes place when a neutral solu-
tion of the salt is boiled: a small quantity of ammonia passes off with
the steam, and free hydrochloric acid is found in the solution. In pres-
ence of an excess of hydrochloric acid this dissociation does not occur,
and solutions of ammonic chloride may be evaporated at 100° C. with-
out loss. Ammonic chloride is soluble in 2\ parts of water at ordinary
temperatures and in its own weight of water at 100° C. Absolute
alcohol does not dissolve it. Ammonic chloride forms double salts with
various metallic chlorides: ammonic plaiinio chloridey PtCl4,2NH4Cl,
crystallizes in minute octahedra, almost insoluble in water, and insol-
uble in a mixture of alcohol and ether. This double salt, which closely
resembles the corresponding potassium compound, is employed in the
quantitative determination of ammonia. When heated, the double salt
is decomposed, platinum being left behind in the finely divided con-
dition in which it is known as spongy platinum. Ammonic chloride
has numerous uses. It is employed in medicine, in dyeing, in solder-
ing, and tinning — in which last process it serves to produce A clean
metallic surface, either by reducing the oxides at a high temperature,
or by converting them into fusible chlorides — in the preparation of
ammonia and ammonic carbonate, as a laboratory reagent, and as a
manure.
Ammonic bromide^ NH^Br. — This compound is prepared by the
direct union of hydrobromio acid with ammonia, or by the addition
of bromine to aqueous ammonia, nitrogen being evolv^ in the latter
reaction :
4HH3 + 3Br = 3NH,Br + N.
Ammonia. Ammonic bromide.
It crystallizes in colorless cubes, readily soluble in water, less soluble
in alcohol. The crystals become moist in contact with the air, and
442 IMOBOAKIO CHEMISTRY.
assume a yellow color^ owing to the separation of bromine. It sub-
limes without fusing.
Ammonic iodidcy NH^I. — This salt is prepared by the direct union of
ammonia and hydriodic acid, or more conveniently by adding to a hot
saturated solution of potassic iodide the equivalent quantity of ammonic
sulphate, precipitating the potassic sulphate with alcohol, and evapo-
rating the solution. It crystallizes in colorless cubes, readily soluble in
water and in alcohol. It may be sublimed in an atmosphere free from
oxygen. Exposed to the air, it assumes a yellow color, due to the
liberation of iodine. Ammonic iodide is employed in photography.
Ammonic fluoride, NH^F, is obtained by evaporating a solution of
hydrofluoric acid supersaturated with ammonia and kept alkaline with
ammonia during the evaporation, or by heating in a platinum vessel a
mixture of 1 part of ammonic chloride with 2| parts of sodic fluoride,
when the ammonic fluoride sublimes and condenses in crystals on the
cooled lid of the vessel. It crystallizes in colorless hexagonal prisms
or laminae, deliquescent in moist air, readily soluble in water, sparingly
soluble in alcohol. On evaporation, the neutral aqueous solution gives
off ammonia and yields rhombic prisms of hydrie ammonie fluciide,
NH^FjHF. Dry ammonic fluoride absorbs gaseous ammonia, which
it again |)arts with on heating. The dry salt decomposes silicates when
heated with them. * Ammonic fluoride is employed in etching glass.
Ammonic ailicofluoride, SiF^(NHJ^ is readily soluble in water.
COMPOUND WITH HYDROXYL.
Ammonic hydrate, NH^Ho. — This compound has not been iso-
lated, but may be considered to exist in the aqueous solution of am-
monia, which is |>owerfully alkaline, slightly caustic, and possesses the
other properties of the solutions of the alkaline hydrates.'*' On evapo-
ration the ammonic hydrate undergoes dissociation into ammonia and
water : NH^Ho = HHj + OH3. (For the other properties of aqueous
ammonia, see p. 232.)
Ammonic oxide, 0(N'H4)2, is unknown.
0XY-8ALTS OF AMMONIUM.
These are, as a rule, prepared by neutralizing aqueous ammonia or am-
monic carbonate with the oxy-acid. Special methods will be described
under the corresponding salts.
Ammonic nitrate, NOjlJ^^Hfi), or NOjAmo, forms six-sided
prisms belonging to the rhombic system. It dissolves in about half its
weight of water at 18° C. (64° F.), with great absorption of heat
* Kohlrausch, however, finds that, whereas the amnionic sal to, when in Bolotion,
possess the same electrolytic conductivity as the corresponding potassium salts, aqueous
ammonia is a bad conductor of the current, whilst a solution of potassic hydrate con-
ducts the current well. From this he concludes that an aqueous solution of ammonia
contains little or no ammonic hydrate.
THE AMMONIUM SALTS. 443
In moist air it deliquesces^ at the same time losing ammonia and be-
coming acid. When heated, it is decomposed into nitrous oxide and
iitrater (p. 220). At low temperatures it absorbs gaseous ammonia with
great avidity, taking up at — 10° C. (14° F.) two molecules of am-
monia, and yielding a compound of the formula N(NH2)2Ho2Amo.
This substance is a colorless liquid of sp. gr. 1.05, which does not
solidify at — 18° C. (0° F.). As the temperature rises this compound
dissociates, till at 28.5° C. (83.3° F.) it parts with one molecule of am-
monia, and is converted into a white crystalline mass, of the formula
NO(NH2)HoAmo. This substance also suffers dissociation as the
temperature rises, giving off ammonia and yielding at 80° C. (176° F.)
pure ammonic nitrate.
Ammonic NiTRrTE, NOAmo, is formed in small quantity when
phosphorus undergoes slow oxidation in contact with moist air; also
during the combustion of hydrogen or hydrc^enous substances in air,
and by the action of ozone on dilute ammonia. It may be obtained in
crystals by passing simultaneously ammonia, nitric oxide, and oxygen
into a dry flask. It is most easily prepared by the double decomposi-
tion of ai^ntic nitrite with ammonic chloride, or of baric nitrite with
ammonic sulphate, the solution obtained by either of these methods
being filtered from the insoluble precipitate and evaporated in a desic-
cator over quickline. Thus obtained it forms a crystal line, very soluble
mass. It decomposes slowly at ordinary temperatures into nitrogen
and water (p. 212). When heated to 60-70° C. (140-168° F.), or
when struck, it detonates. In concentrated aqueous solution it under-
goes mpid decomposition, the process being accelerated by heat and
retarded by dilution.
Ammonic ddorate, < q a qio? ^ prepared bj nefitraiizing chloric acid with ammonia
or ammonic carbonate, or by the double decomposition of ammonic silicofluoride with
potassic chlorate, filtering from the innohible potassic silicofluoride and evaporating
over sulphuric acid. It crystallizes in colorless prisms or slender needles, readily
soluble in water or alcohol. When dry the crystals turn yellow and frequently
explode spontaneously with great violence. This explosive decomposition takes
place at once on heating to somewhat above 100° G. The aqueous solution on boiling
evolves nitrogen and chlorine.
fOCl
Ammonie perchloraUf < O . — ^Large rhombic crystals, soluble in 5 parts of
(OAmo
water.
Amm/onie bram/au^ \ OAmo* ^^"°^ white needles or crystalline grannies. The dry
salt explodes spontaneously like the chlorate.
Ammonie iodaJte^ < OAmo* — L"®*"^*^ quadratic crystals, soluble in 38 parts of water
at ordinary temperatures and in 6.9 parts of boiling water. At 150"^ G. (302^ F.) it
decomposes with a hissing noise, yielding equal volumes of oxygen and nitrogen,
together with iodine and water.
Ammonic capbonate :
Normal ammonic carbonate^ 0OAmo2. — ^This salt is deposited as a
crystalline powder when a concentrated solution of the sesquicarbonate
{vide infra) is saturated with gaseous ammonia^ and in large tabular
crystals when a hot solution of the sesquicarbonate in dilute aqueous
444 IKOBGiLNIC GHEMiarrRT.
ammonia 18 allowed to cool. It is a very unstable salt When exposed
to the air it rapidly parts with ammonia and is converted into hydric
ammanic carborUUe, OOHoAmo. It dissociates completely at 58^ C.
(136^ F.) into carbonic anhydride, ammonia, and water. It is soluble
at ordinary temperatures in its own weight of water, but only spar-
ingly soluble in concentrated ammonia. — Hydric ammonio carbonate,
COHoAmo, occurs in a crystallized form in guano beds. It may be
obtained from the commercial sesquicarbonate either by exposing the
latter salt to the air, when it parts with ammonia, yielding the acid
carbonate ; or by treating the sesquicarbonate with a small quantity of
water, which dissolves the normal carbonate, leaving the acid carbonate.
It is also deposited when a concentrated solution of the sesquicarbonate
is exposed to a low temperature, or is mixed with alcohol, or is satu-
rated with carbonic anhydride. It crystallizes in hard lustrous rhombic
prisms. It sublimes at 60-65° C. (140-149° F.). It dissolves in
about 8 parts of water at ordinary temperatures. The solution slowly
evolves carbonic anhydride and becomes ammoniacal. This decompo-
sition is very rapid above 36° C. (97° F.), the liquid effervescing when
warmed. It is insoluble in alcohol, but on long standing under alcohol
dissolves as normal carbonate, with evolution of carbonic anhydride.
Ammonio seBquicarbonaie, 0OAmo2,20OHoAmo. — This salt is pre-
pared on a large scale by heating ammonic chloride or sulphate with
calcic carbonate, when the sesquicarbonate sublimes. It forms a trans-
lucent, crystalline mass, which is usually coated with an opaque layer
of the acid carbonate. Its c*om position varies, generally approximating
however to the above formula. It has an ammoniacal odor, and is
gradually converted by exposure to air into the acid salt. *
Ammonic sulphate:
Ammonic svlphaie, SOjAmo,, is found native as maacagnine. It is
prepared on a large scale by passing the ammonia from the ammoniacal
liquors of the gasworks into sulphuric acid. It forms colorless rhom-
bic crystals, isomorphous with the potassium salt. .It is soluble in
twice its weight of cold, in its own weight of boiling, water ; insoluble
in alcohol. It fuses at 140° C. (284° F.), and above 280° C. (536° F.)
is decomposed into ammonia, nitrogen, water, and ammonic sulphite, the
latter subliming. — Hydric ammonio svlphaJte^ SOjHoAmo, crystallizes
from a solution of the normal salt in concentrated sulphuric acid in
deliquescent thin rhombic crystals. It is soluble in its own weight of
cold water, also in alcohol.
Ammonic sulphate is employed in the manufacture of ammonia-
alum ; also as a manure.
Ammonic poUutie sulphai^y SOsAmoKo, is obtained by evaporating a solution of mo-
lecular quantities of amnionic potassic sulphates. It crystallizes in lustrous scales.
Ammonic §odic iulpkaUy 80sAmoNao,20Hi, is prepared like the foregoing. It is
also deposited in crystals when mixed solutions of sodic sulphate and ammonic chloride,
or of sodic chloride and ammonic sulphate, are evaporatea. The salt is permanent in
air.
Ammonic aulphiUj 80Amo„OH„ is obtained by neutralizing an aqueous solution of
sulphurous anhydride with ammonia, and then adding alcohol. The salt separates in
monoclinic crystals, readily soluble in water. By exposure to the air it is oxidized to
THE AMMOKITTM SALTS. 445
ammonic sulphate. When a solation of this salt is saturated with snlphurons anhy-
dride and evaporated over sulphuric acid, it deposits crystals, not of the acid salt, but
r SOAmo
of ammoTiic pyrotulphUef i O . This salt evolves sulphnrons anhydride when
( SOAmo
exposed to the air, at the same time undergoing oxidation to ammonic sulphate.
* Ammonic dithionaie, < flo*Amo'^^*' ^® obtained by the double decomposition of
baric dithionate with ammonic sulphate. It forms colorless capillary crystals, very
soluble in water, insoluble in alcohol.
Ammonic thitmdphaU (Ammonie hyposulphite), SBOsAmoAmSjOHs, is prepared by
decomposing calcic thiosulphate with ammonic carbonate. It forms deliquescent, very
soluble acicolar crystals or rhombic plates.
Ammonic phosphate :
a. Ammonic phosphate, POAmOjjSOHj, occurs sometimes in guano.
It is formed when a concentrated solution of hydric diammonie phos-
phate is mixed with ammonia^ and is deposited in small prismatic or
aeicular crystals, which when exposed to the air*part with ammonia,
yielding hydric diammonie phosphate. When boiled for some time in
aqueous solution, it is converted into dihydric ammonic phosphate.
When strongly heated, it yields, like all the other ammonic phosphates,
metaphosphoric acid. — Hydric diamm^onio phosphate, POHoAmo,, is
prepared by evaporating an ammoniacal solution of phosphoric acid,
care being taken to keep the ammonia slightly in excess during the
process. It forms large colorless monoclinic crystals, soluble in 4 parts
of cold, more readily in boiling, water; insoluble in alcohol. Exposed
to the air it gradually parts with ammonia. — Dihydric ammonic phos^
phaie, POHojAmo, is prepared by adding phosphoric acid to ammonia
till the solution is strongly acid and no longer precipitates baric chloride,
and evaporating to the crystallizing point; or by boiling a solution of
the monohydric salt It crystallizes in quadratic octahedra, which are
permanent in air. It in somewhat less soluble than the foregoing salt.
Hydric ammonic sodic phosphaie {Microcosmic salt),
POHoAmoNao,40H2.—
This salt occurs in guano and in putrid urine. It is prepared by dis-
solving 6 parts of hydric disodic phosphate and 1 part of ammonic
chloride in 2 parts of boiling water, and allowing the liquid to cool.
It forms large colorless monoclinic prisms, very soluble in water, yield-
ing a solution which gives off a portion of its ammonia on evaporation.
It fuses easily, water and ammonia being expelled, and sodic meta-
phosphate left. Microcosmic salt is employed in the laboratory as a
blowpipe reagent, the sodic metaphosphate, which remains on heating
it, possessing the property of dissolving various metallic oxides at a
high temperature to yield characteristically colored fluxes or glasses.
Diammonie sodic phosphaUf POAmosNao,40H3, separates in lustrous white pearly
laminfe when strong ammonia is addeti to a cold saturated solution of the fore^oine.
It evolves ammonia when exposed to the air, and is converted into hydric ammonic
sodic phosphate.
b. Ammonic pyj'ophosphaie, Tfi^Amo^, separates in small aeicular
laminffi when alcohol is added to a solution of pyrophosphoric acid
446 INORGAKIC GHEMI8TBT.
supersaturated with ammonia. Its solution gives off ammonia when
boiled^ yielding dihydric diammonic pyrophaaphate, PjOjHojAmoj,
which may be precipitated from its solution by tne addition of alcohol
as a syrupy mass, becoming crystalline on standing,
c. Amvumio mdaphosphales are also known.
Ammanie horaU, — The normal ealt has not been prepared. Diammotue Utraborale,
B4()5Amo,,40Hi, crystallizes from a volution of boric acid in warm concentrated am-
monia in quadratic crystals, which give off ammonia when exposed to the air. When
this salt is dissolved in water and the solution evaporated by heat, colorless trans-
parent rhombic crystals of hydric ammanie tetrabonUe^ BfO^HoAmOySOHs, are deposited
on cooling.
COMPOUNDS OF AMMONIUM WITH SULPHUR AND HYDRO-
SULPHYL.
Ammonie «uipAu2e, 8 A mi, is obtained in lustrous crystals by the union of 2 volumes
of ammonia with 1 volume of sulphuretted hydrogen at a temperature of — 18^ C.
(0° F.). Above this temperature it dissociates, evolving amnonia, and yielding oai-
monic mdphhydraU^ AmHs.
AiftMoyiG SULPHHYDRATE, AmHs, 18 formed by the direct union of
equal volumes of ammonia and sulphuretted hydrogen at ordinary tem-
peratures. It is best prepared by passing sulphuretted hydrc^n into
alcoholic ammonia, when the sulph hydrate separates out in a crystalline
form. The aqueous solution employed as a laboratory reagent is ob-
tained by saturating aqueous ammonia with sulphuretted hydrogen.
Ammonic sulphhydrate forms large colorless laminse. It volatilizes
readily, with dissociation into ammonia and sulphuretted hydrogen,
which reunite on cooling. It becomes yellow, both in the solid state
and in solution, when exposed to the air, owing to the formation of
polysulphides of ammonium. The solution precipitates many metals
in the form of sulphides from the solution of their salts, and dissolves
sulphur to form ammonic polysulphides.
Ammonic peniandphide^ AmiS}, is prepared b^ alternately passing ammonia and sul-
phuretted hydrogen into a mixture of ammonic sulphhydrate and flowers of sulphur
until the liouid solidifies on cooling. The mixture is then heated to 50° G. (122° F.)
and allowed to cool with exclusion of air, when the pentasulphide is deposited in
orange-yellow rhombic prisms. Water decomposes them with precipitation of plastic
sulphur.
Amm<mic hepttisulphide, Am^S^, is formed by the spontaneous decomposition of the
foregoing compound in presence of air :
3(NH4),S5 = 2(NH,)A + Wn, + NH^Hs.
Ammonic Ammonic Ammonia. Ammouic
pentasulphide. heptasulphide. sulphhydrate.
It forms niby-red crystaln, which are not decomposed by heat below 300° C. (572° F.),
but are slowly decomposed by water.
General Properties and Reactions of the Ammoniuic
Salts. — The ammonium salts are all volatile — some with decom*
position^ others with dissociation, in which last case the dissociated
BILVEB. 447
constituents reeombine on cooling to form the original salt, as in the
case of ammonic chloride (p. 64). Ammonium salts yield with plcUinic
chloride and with tartaric acid precipitates closely resembling those ob-
tained with potassium salts ; ammonic platinic chloride (PtCl4,2NH^CI),
however, leaves only a residue of spongy platinum on ignition. All
ammonium salts, when warmed with ccUcio hydrate, or with concen-
trated cavstic potash or caustic soda, evolve gaseous ammonia, which
may generally be recognized by its characteristic smell, or in case the
quantity is very minute, by the white fumes of ammonic chloride
which are formed when a glass rod moistened with hydrochloric acid
is held over the mixture. The smallest trace of ammonia in aqueous
solution may be detected by means of a solution of mercuric iodide in a
mixture of potassic iodide and caustic potash (Nessler's reagent), with
which it yields a brown coloration', or, if present in larger quantity, a
brown precipitate, of NHg"(Hg"Ho)HI. This reaction does not occur
in presence of alkaline sulphides or cyanides.
MONAD METAUB.
Section IV.
SILVER, Ag,?
Atomic weight = 107.7. Probable molecular weight = 215.4. 8p. gr.
10.57. FMAejs at 1040° C. (1904° F.). AtomurUy '. Evidence of
atomicity:
Argentic chloride, AgCl.
Argentic iodide, Agl.
Argentic oxide, OAg,.
History. — This metal has been known from the earliest times.
Occurrence. — Silver occurs native, occasionally in large masses. Native
silver is rarely pure: it contains gold, copper, and other metals. In
combination, silver occurs as argentic sulphide in silver glance (SAg,) ;
as sulphantimonite in pyrargariie or dark-red silver ore (SbAgPj) ; as
chloride in kerargyrite or horn-silver (AgCl). The bromide, iodid*^,
telluride, antimonide, and arsenide are rare minerals. Galena, or plumbic
sulphide, the commonest form of lead ore, generally contains small quan-
tities of silver. Silver also occurs in minute traces in sea- water.
Extr(ustian. — Although silver is very readily reducible from its com-
pounds (the mere application of heat being generally suiBcient for this
purpose), yet the extraction of silver from its ores is a matter of con-
siderable practical difficulty. The ores of silver are frequently mixed
with earthy impurities, from which they cannot be mechanically sepa-
rated, or they occur along with the ores of other metals, which are apt
to undergo reduction at the same time, and thus contaminate the pro-
duct. The process of extraction varies with the nature of the ore ;
but the methods employed may be divided into three cla!!$ses according
448 INORGANIC CHEMI8TRT.
as they depend upon cupeUation, upon amalgamation, or upon reactions
in the tod way.
a. CiipeUatUm Process. — ^This process is employed in separating
silver from lead. The alloy of silver and lead, obtained from argen-
tiferous lead ores, is fused in a reverberatory furnace, the hearth of
which is composed of burnt clay. Over the molten metal, which rests
upon the concave surface of this hearth or cupel, a rapid current of air
is blown. The lead is thus oxidized, and the fused oxide escapes by
flowing off through lateral openings in the hearth, whilst the silver
remains in the cupel. At first the fused oxide flows off in large quan-
tity, hut towards the end of the operation it forms thin films upon the
surface of the silver, exhibiting the colors of Newton's rings. At last,
as the film of oxide finally disappears, the bright surface of the silver
is perceived. This phenomenon is 'known as the "fulguration" of
the metal. The removal of the oxide is aided by skimming.
When the lead is sufficiently rich in silver, it is cupelled at once;
but if the silver is present in a proportion less than one-tenth of a per
cent., the lead is subjected to a preliminary process, which has for its
object the concentration of the silver in a relatively small portion of the
lead. In this process, invented by Pattinson, the metal is fused in
iron pots and allowed to cool slowly. As soon as the temperature has
sufficiently fallen, crystals of pure lead are formed ; these are constantly
removed by means of perforated ladles, and this is continued until the
lead in the pot has been reduced in quantity by about two-thirds. In
this way the greater part of the silver is left behind in the pot, and by
systematic recrystallization, pureand nearly desilverized lead on the one
hand, and a lead very rich in silver on the other, may be obtained.
The rich lead is cupelled as above described.
Instead of treating the lead by Pattinson's process, it may be fused,
and zinc, in the proportion of 11.2 lbs. for every 7 ozs. of silver present
per ton of lead, added. The whole is thoroughly stirred and then
allowed to settle* The zinc extracts the greater part of the silver from
the lead and rises to the surface, where it solidifies first, and may be
removed as a solid cake. This cake is then heated to redness in a cur-
rent of air, by which means the zinc is converted into zincic oxide, and
may be separated from the unaltered silver by washing.
Sometimes poor silver ores are roasted along with galena. The
lead thus obtained contains the whole of the silver, which may then be
separated by cupellation.
6. ATnalgamaUon Process. — The amalgamation process formerly em-
ployed in Europe was conducted as follows: The finely-ground ore was
mixed with common salt and roasted in a reverberatory furnace. By
this means the silver, which was mostly present in the form of sulphide,
was converted into chloride. The roasted ore was again ground very
fine and then introduced, along with scrap iron and water, into casbt
which were made to revolve by machinery. The chloride was thus
reduced to metallic silver :
2AgCl + Fe = PeCl, + Ag,.
Argentic Ferrous
chloride. chloride.
SILVER. 449
Mercarj was then introduced into the revolving casks. The mercury
combined with the silver to form a liquid amalgam^ which was sepa-
rated and subjected to distillation, when the mercury passed over and
the silver remained in the retort. A modification of this proces is
employed in Nevada. Some trouble is occasioned in this process by the
tendency of the mercury to form minute globules, which, along with
the silver contained in them, are lost in washing. This " flouring," or
''sickening," as it is termed, which is due to the formation of a film of
mercuric sulphide, may be prevented by the addition of about 2 per
cent, of sodium to the mercury, the mercuric sulphide being thus re-
duced to metallic mercury, with formation of sodic sulphide.
The method of amalgamation employed in Mexico differs from the
above, the scarcity of fuel in the silver-producing districts precluding
the application of the roasting process. The ore is first ground very
fine with water in a mill. The paste thus obtained is spread on a
paved floor, and mixed with a small quantity of common salt, after
which it is allowed to stand for a day. About 1 per cent, of a substance
known to the miners as magistral — ^a mixture of crude ferric and cupric
sulphates obtained by roasting copper pyrites — is added, and the whole
is again thoroughly mixed. Mercury is now poured in, and the mixing
is renewed. All these processes of incorporation are efiected by the
treading of blindfolded mules. The mercury is added in successive
portions, at intervals of some days, during the working of the heap, the
entire quantity of mercury employed being about six times the weight
of the silver contained in the ore. The time required for working a
heap varies from a fortnight to two months. At the end of the time
the liquid amalgam, which contains all the silver, is separated from the
earthy and other impurities by washing, and, after pressing in sacks to
free it from the excess of mercury, is subjected to distillation.
The nature of the chemical changes which occur in the Mexican pro-
cess is not thoroughly understood, but the action is supposed to take
place as follows : The cupric sulphate undergoes double decomposition
with the sodic chloride, yielding sodic sulphate and cupric chloride.
The latter salt reacts with the argentic sulphide, converting it into
argentic chloride :
20uCla + SAg, = 'Ou'aCl, + 2AgCl + S.
Cupric Argentic Cuprous Argentic
chloride. sulphide. chloride. chloride.
The cuprous chloride thus formed dissolves in the sodic chloride pres-
ent, and is thus enabled to act upon a fresh quantity of argentic sul-
phide :
'Ou',Cl, + SAgj = 'Ou'aS'' + 2AgCl.
Cuprous Argentic Cuprous Argentic
chloride. sulphide. sulphide. chloride.
The silver chloride held in solution by the sodic chloride is reduced by
the metallic mercury, with formation of marcurous chloride :
2AgCl + 2Hg = 'Hg',Cl, + Ag,.
Argentic Mercurous
chloride. chloride.
29
460 INORGANIC CHEMISTRY.
The whole of this mercurous chloride is lost in washings representing
a loss of mercury equal to nearly twice the weight of the silver ob-
tained.
c. Extraction in the Wet Way, — When argentiferous copper pyrites
is roasted, the sulphides of iron, copper, and silver take up oxygen, and
are converted into sulphates. By carefully regulating the temperature,
a point may be reached at which the sulphates of iron and copper are
decomposed, yielding insoluble oxides, whilst the more stable argentic
sulphate remains unaltered, and may be obtained in solution afterwards
by lixiyiating the roasted mass with hot water. A small quantity of
undecomposed copper salt goes into solution at the same time. The
silver is precipitated from the solution by metallic copper. (Ziervogel.)
Another method consists in roasting the ore with common salt, so as
to convert the silver into chloride, which is then extracted with a cold
dilute solution of sodic thiosulphate. From this solution the silver is
precipitated as sulphide by sodic sulphide. The argentic sulphide is
reduced to metal by heating to a high temperature in a curi^nt of air.
(Percy-Patera.)
The burnt pyrites obtained in the manufacture of sulphuric acid
contains, in addition to copper, a small quantity of silver, amounting to
about half an ounce to the ton. This small quantity may be profitably
separated by adding to the tank-liquor obtained in the extraction of the
copper (see Copper) a solution of kelp. In this way the silver, which
is present in the tank-liquor in the form of chloride, and is kept in
solution by the sodic chloride with which the burnt pyrites has been
roasted, is precipitated as argentic iodide. A trace of gold, which is
precipitated at the same time, is afterwards separated.
Preparation of Pure SUver, — In order to obtain pure silver advan-
tage is taken of the insolubility of the chloride. Ordinary silver is
dissolved in dilute nitric acid, when gold, if present, remains undis-
solved. The silver is precipitated from the filtered solution as chloride
by hydrochloric acid. The washed and dried chloride is fused in a
crucible with an excess of sodic carbonate. The silver collects as a
regulus at the bottom of the crucible. Another method is to reduce
the argentic chloride by laying it on a plate of zinc under dilute hydro-
chloric acid. The reduced silver is carefully washed with hydrochloric
acid to free it from adhering traces of zinc, and is then dried. By this
means it is obtained as a fine gray powder, devoid of metallic lustre.
In this last form it is known as " molecular" silver (a misnomer, as it
is very far from heipg in a state of molecular subdivision) and is used
in organic research for acting upon organic compounds of the halogens.
Propciiies. — Silver has a white color, with a tinge of yellow, and pos-
sesses great lustre when polished. In the form in which it is obtained by
the ignition of some organic silver salts, it is white like porcelain, owing
to the roughness of its surface, and the consequent absence of metallic
lustre. Of all the metals it is the best conductor of heat and electricity.
It is a soft metal, standing between copper and gold in hardness. In
malleability and ductility it is inferior only to gold ; it can be beaten
into leaf 0.00025 mm. in thickness, and can be drawn into wire of which
180 metres weigh 0.1 gram. In very thin films, as in the case when it
SILVER.
451
is deposited apon glass from ammoniaeal solutions by means of reducing
agents, it transmits blue light. It possesses great tenacity ; the break-
ing weight for a wire 2 millimetres in diameter being 85 kilograms.
Its specific gravity is 10.57. It crystallizes in regular octahedra. Na-
tive silver also occurs in dendritic forms. It fuses at 1040° C. (1904°
F.), and may be distilled at a white heat by means of the oxyhydrogen
blowpipe, a process which was employed by Stas in purifying silver for
the purpose of determining its atomic weight. When melted in contact
with air, pure silver absorbs about 22 times its volume of oxygen, which
it again gives up at the moment of solidification. As the metal cools,
the outer crust solidifies first, and the gas evolved from the interior
then escapes through this crust in sudden bursts, carrying with it small
particles of molten silver. This phenomenon is known as the '' spit-
ting " of silver. The presence of a small quantity of copper prevents
the absorption of oxygen. Pure air, oxygen, and water are without
action upon silver at all temperatures, but ozone oxidizes it superficially
to peroxide.
BecLctiona. — 1. Silver is blackened by sulphuretted hydrogen in pres-
ence of oxygen, argentic sulphide being formed. For this reason silver
articles exposed to the atmosphere become discolored. Pure sulphuret-
ted hydrogen, however, is without action upon silver at ordinary tem-
peratures, and the metal may even be heated with an aqueous solution
of sulphuretted hydrogen to 200° C. (392° F.) without blackening.
2. Silver is acted upon by hot concentrated sulphuric acid :
Ag, + 2SO2H02 = SOjAgOa + 2OH3 + BO^
Argentic Water. Sulphurous
sulphate. anhydride.
Sulphuric
acid.
3. Dilute nitric acid readily dissolves silver :
3Ag, + SNOjHo = eNOjAgo +
8NO,Ho =
Nitric
acid.
eNOjAgo
Argentic
nitrate.
40H,
Water.
+ 2'N"0.
Nitric
oxide.
4. At a red heat silver decomposes hydrochloric acid :
Ag, + 2HC1 = H, + 2AgCl.
Hydrochloric Argentic
acid. chloride.
Strong aqueous hydriodic acid dissolves silver, even at ordinary tem-
peratures, with evolution of hydrogen and formation of argentic iodide.
Ueea. — Pure silver is very little employed in the arts, as it is too soft
to resist wear. In order to increase its hardness and tenacity, it is
alloyed with a small proportion of copper, an addition which does not
affect its color, and in this form it is employed for plate, ornaments,
coinage, etc. Standard silver is an alloy of silver and copper of a given
composition fixed by law, and this standard varies in different countries.
In England the standard contains 92.5 per cent, of silver. In France,
Germany, and Austria, the standard for coinage contains 90 per cent.
452 INOBOANIC CHEMISTRY.
of sil ver, whilst there are other standards for plate and jeweller's work.
What is termed the fineness of silver is the number of parts of silver
per mille which the alloy contains ; thus the English standard silver
has a fineness of 925.
Pure silver is employed in the manufacture of various laboratory
vessels; this metal, unlike glass and platinum, being capable of resist-
ing the action of fused caustic alkalies.
Silver is also employed in electroplating. For this purpose the ob-
ject to be silvered, which must possess a conducting surface, is made the
negative electrode; the positive electrode consists of a plate of silver.
The electrodes are immersed in a solution of argentic cyanide in an ex-
cess of potassic cyanide. The electrolytic silver is deposited as a coherent
coating on the object to be silvered, and the cyanogen, liberated at the
negative electrode, combines with the silver of the electrode to form
argentic cyanide, which dissolves in the excess of potassic cyanide, so
that the strength of the electrolytic solution remains constant From
silver solutions other than the above, the electrolytic silver is generally
deposited in the form of a non-coherent powder.
The silvering of glass is effected by means of a mixture of an am-
moniacal solution of silver with milk-sugar, or some other suitable
organic reducing agent. The solution is contained in a flat shallow
vessel, and the glass is suspended so that the surface to be silvered,
which must previously have been thoroughly cleaned, may be in contact
with the surface of the liquid. A bright coherent mirror of silver is
thus deposited on the glass. Reflectors for astronomical telescopes are
now extensively prepared by this method.
COMPOUNDS OF SILVER WITH THE HALOGENS.
Argentic chi^ride, AgCl, occurs native, as herargyrUey or horn-
silvery in Mexico, Peru, and Chili, also in the Harz. Horn-silver crys-
tallizes in forms belonging to the regular system, but more frequently
occurs in wax-like, translucent masses. Its specific gravity varies from
5.3 to 5.4. Argentic chloride is obtained as a curdy precipitate by the
addition of hydrochloric acid, or a soluble chloride, to the solution of
a silver salt. When pure it is white; but under the influence of light
it speedily assumes a violet tint, passing into black. The reason of this
phenomenon, which is turned to account in photography, is not thor-
oughly understood, but the change is supposed to be due to the forma-
tion of a lower chloride, or to the liberation of metallic silver. The
action is only superficial, and the quantity of chlorine evolved extremely
small. Argentic chloride fuses at about 260° C. (500° F.) to a clear,
yellow liquid, which solidifies to a translucent, horny, sectile mass. It
IS insoluble in water and dilute acids ; slightly soluble in concentrated
hydrochloric acid, and in concentrated solutions of the alkaline chlorides;
readily soluble in ammonia, potassic cyanide, sodic thiosulphate, and in
a concentrated solution of mercuric nitrate. On evaporation, the solu-
tions in hydrochloric acid and in ammonia deposit the agentic chloride
in octahedra. In contact with oxidizable metals, such as iron or zinc,
00MP0UXD8 OF SILVER. 453
it is reduced^ in presence of water, to metallic silver, the addition of a
little acid favoring the reaction. The dry chloride absorbs gaseous
ammonia to form the compound 2AgCl,3NHs, which parts with its
ammonia at 37.7° C. ^100° F.), and was employed by Faraday in the
liquefaction of ammonia (p. 231). This compound is also obtained in
large transparent rhombohedra, when a solution of argentic chloride in
concentrated ammonia is allowed to stand in an imperfectly closed
bottle.
Ar^aUouB chloride, AgiCl,, is obtained by treating argentous oxide (q.v.) with hydro-
chloric acid. It forms a black powder, which is decomposed by ammonia into metallic
silver and argentic chloride, the latter dissolving in the ammonia. Nitric acid decom-
poses it in a similar maimer, the silver in this case dissolving, whilst the chloride is left.
Argentic bromide, AgBr, occurs native as bromargyrite in Mexico
and Chili, also at Huelgoet in Britanny. It generally forms concretions,
but is also found crystallized. It may be prepared by precipitating
solutions of silver salts with hydrobromic acid. At ordinary tempera-
tures, hydrobromic acid converts argentic chloride into argentic bromide;
at 700° C. (1292° F.), on the other hand, this reaction is reversed, and
the bromide is converted by hydrochloric acid into chloride. Precipi-
tated argentic bromide is a faint yellow substance, soluble with difficulty
in dilute ammonia, readily soluble in concentrated ammonia. The dry
bromide does not absorb ammonia; but a double compound with am-
monia, corresponding to that of the chloride, is deposited from the am-
moniacal solution. Argentic bromide fuses below a red heat. It is
employed in photography in the preparation of " dry plates."
Argentic iodide, Agl, is of very rare occurrence. It is found as
iodargyirite, in Chili, Mexico, and Spain, in the form of thin hexagonal
plates which are slightly elastic. It is obtained as an amorphous yellow
precipitate when potassic iodide is added to the solution of a silver salt.
Concentrated hydriodic acid dissolves metallic silver with evolution of
hydrogen ; from this solution lustrous laminae of the formula AgI,HI
are deposited on cooling; and these, on exposure to the air, are speedily
decomposed, yielding argentic iodide. When the mother liquor from
these crystals is exposed to the air, or when it is left in contact with
excess of metallic silver, it deposits argentic iodide in hexagonal prisms.
Argentic chloride and bromide are converted by hydriodic acid with
violent reaction into the iodide ; but above 700° C. (1292° F.) gaseous
hydrochloric acide converts the iodide into chloride. Argentic iodide
closely resembles the chloride and bromide, but differs from these in its
almost perfect insolubility in concentrated ammonia, whicli, however,
has the effect of turning it white. It is soluble in sodic thiosulphate,
though not so readily as the chloride. It also dissolves in a concen-
trated solution of potassic icxlide, the hot solution depositing on cooling
acicular crystals of the formula AgI,HI ; from this solution the iodide
IS precipitated by dilution with water. It fuses at a dull red heat,
yielding a yellow liquid which becomes darker colored at a higher tem-
perature, and on cooling solidifies to a yellow mass with a sp. gr. of
6.687. The sp. gr. of the precipitated iodide is 5.807, that of the crys-
tallized variety 5.47-5.64. Fizeau has made the remarkable observa*
454 INOBGANIC CHEMISTRY.
tion that between the temperatures of —10'' and +70° C. (14° and
158° F.) argentic iodide contracts on heating and expands on cooling.
Pure argentic iodide is not acted upon by light, but in presence of sub-
stances which are capable of combining with the liberated iodine it is
slowly blackened. A slight admixture of argentic nitrate produces
this effect By exposure to light, however, even for a very short time,
argentic iodide paases into a peculiar active condition, in which it pos-
sesses the property of immediately precipitating upon its surface black,
finely-divided metallic silver from solutions of silver salts in presence
of some reducing agent, such as pyrogallic acid. Upon this property
the application of argentic iodide in photography depends, and the
process of thus blackening the iodide is that of " developing" the pho-
tographic image. Dry argentic iodide absorbs gaseous ammonia, form-
ing a white compound, 2AgI,NH3, which, when exposed to the air,
parts with ammonia, and is reconverted into yellow argentic iodide.
Argentic fluoride, AgF, is prepared by dissolving argentic oxide
or argentic carbonate in hydrofluoric acid, and evaporating the solution.
Argentic fluoride crystallizes either in colorless quadratic pyramids
with 1 aq., or in prisms with 2 aq. It is deliquescent, and soluble in
half its weight of water. It is not readily obtained in an anhydrous
state When the compound AgF,OH, is dried in tfacuo, it undergoes
partial decomposition, and a brownish-yellow earthy mass is formed,
which, when heated with exclusion of air, may be fused, and on cooling
solidifies to a black horny sectile mass. Unlike the chlorides of many
of the metals, which in the fused state may be subjected to electrolysis,
fused argentic fluoride conducts the electric current without undergoing
decomposition. When heated in moist air it is reduced to the metallic
state. The dry fluoride absorbs 844 times its volume of gaseous am-
monia; at higher temperatures ammonia reduces it to metallic silver.
COMPOUNDS OF SILVER WITH OXYGEN.
The following three oxides of silver are known :
Argentous oxide (argentous quad ran toxide), . OAg^.
Argentic oxide, OAg^.
Argentic peroxide, | q^|.
Argentous oxide, OAfc^, is obtained by heating argentic citrate in a current of hjdro-
een to 100° C. ; on adding potassic hydrate to the solution of the bronze-colored mass
tnus obtained, argentous oxide is precipitated. It forms a black powder. Hydrochloric
and hydrobromic acid conyert it into argentous chloride and bromide. Oxy-acids de-
compoAC it, yielding an argentic salt and metallic silyer. On heating, it breaks up into
metallic silver and oxygen.
Argentic oxide, OAgj, is prepared by precipitating nitrate of silver
with potassic hydrate or baryta- water, taking care to avoid the forma-
tion of carbonate; or by boiling freshly precipitated argentic chloride
with a concentrated solution of potassic hydrate. When precipitated
in the cold, it forms a dark-brown powder, which becomes black and
G0MP0UKD6 OF SILVER. 466
anhydrous on drying at 60° or 70° C. (140-158° F.). The recently
precipitated and still moist broim oxide is in some respects more active
m its combining properties than the dried black oxide; thus it absorbs
carbonic anhydride from the air and substitutes hydroxyl for chlorine
in the chlorides of organic ammonium bases; it therefore probably con-
sists of the hydrate AgHo^ which has not, however, been prepared in a
state of purity. One part of argentic oxide dissolves in about 3000
'parts of water, the solution possessing a marked alkaline reaction. The
sp. gr. of the dry oxide is 7.25. In the dry state it acts as a powerful
oxidizing agent, inflamiug various oxidizable substances, such as sulphur,
amorphous phosphorus, and the sulphides of arsenic and antimony,
when triturated along with them. At a temperature of 250° C. (482°
F.) it is decomposed into silver and oxygen, whilst in a current of
hydrogen it undergoes reduction to metallic silver at 100° C. Argentic
oxide is the salifiable oxide of silver :
OAg, + SO,Ho, =
= SO,Ago, + OH,.
Argentic Sulpharic
Argentic Water.
oxide. acid.
snlphate.
Strong ammonia converts argentic oxide into fulminating silver (j.w.).
Argerdio /peroxide, < qa^' — ^^^'® compound is formed by the action
of ozone on finely divided silver. When a concentrated solution of
argentic nitrate is submitted to electrolysis, argentic peroxide ia deposited
on the positive electrode. In like manner, in the electrolysis of acidu-
lated water, if a silver plate be employed as positive electrode, the
nascent oxygen combines with the silver, and the plate becomes coated
with argentic peroxide. It forms minute black lustrous octahedra,
which are frequently attached to each other. It is decomposed a little
above 100° C. into oxygen and argentic oxide. Chlorine rapidly con-
verts it at ordinary temperatures into argentic chloride and oxygen.
Hydroxyl and argentic peroxide mutually reduce each other, oxygen
being evolved from both substances :
2{oAg + 2{gg = 2Aa + 20H, + 30^
Argentic Hydroxyl. Water,
peroxide.
Argentic peroxide possesses more powerful oxidizing properties than
argentic oxide : when triturated with antimonious sulphide, the mixture
deflagrates; sulphuretted hydrogen inflames in contact with the peroxide,
the latter being converted into argentic sulphide; in aqueous ammonia
the peroxide dissolves with evolution of nitrogen ; when warmed in
hydrogen it is reduced to metallic silver with a slight explosion. It
seems to possess the properties of a weak base, forming salts which are
stable only in solution with an excess of acid. Thus concentrated sul-
phuric acid dissolves it, forming a green liquid ; but, on diluting with
water, oxygen is evolved, and the solution contains argentic sulphate.
With strong nitric acid it yields a brownLsh-red solution, which on dilu-
456 INOBOANIC GUEMISTBT.
tion with water deposits the unchanged peroxide, the latter then redis-
Bolving in the dilate acid with evolution of oxygen and formation of
argentic nitrate.
0XY-8ALT8 OF SILVER.
Argentic nitrate, NO,Ago. — ^This salt is prepared by dissolving
silver in dilute nitric acid, evaporating the solution, and allowing it to
crystallize. It is thus obtained in colorless rhombic tabular crystals of
sp. gr. 4.3, which fuse at 198° C. (388° F.), and solidify on cooling to
a fibrous crystalline mass. Argentic nitrate is soluble in half its weight
of water at ordinary temperatures, less soluble in nitric acid ; soluble in
four parts of boiling alcohol. The aqueous solution has a neutral reac-
tion. Argentic nitrate has a disagreeable metallic taste, and is very
poisonous. Applied to the flesh of animals, it acts as a powerful caustic,
destroying the vitality of the part ; the fused salt, cast into sticks, in
which form it is known as lunar caustic, is employed in surgery for this
purpose. The pure salt is not altered by exposure to light ; but in con-
tact with organic substances, light S])eedily blackens it. The hot con-
centrated solution dissolves argentic chloride slightly, argentic bromide
more readily, and still more readily argentic iodide and cyandide. From
these solutions the following compounds are deposited in needles on
cooling :
N02Ago,AgCl; NOjAgo, AgBr ; 2NOjAgo,AgI;
NO,Ago,2Ag(CN).
These compounds are all deoom})06ed by water with precipitation of the
chloride, bromide, etc. Solid argentic nitrate absorbs gaseous ammonia,
yielding a compound NO^AgOjSNHs.* A concentrated solution of
argentic nitrate, when saturated with ammonia, deposits rhombic crystals
of the formula N02Ago,2NH3.t Argentic nitrate is extensively em-
ployed in photography. It also forms the basis of most of the indelible
inks used for marking linen.
Argentic nitrite, NO Ago, is precipitated when concentrated solutions of potaHsic nitrite
and argentic nitrate are mixed. It crjrstallizes in colorless or yellow prisms, which are
sparingly soluble in cold, more readily soluble in warm water. At a temperature be-
tween 90° and 140^ C. (162-284° F.) it is decomposed into metallic silver, nitric oxide,
and argentic nitrate :
4NOAgo = 2NO,Ago + 2'VO + Ag,.
Apffentlc Argentic Nitric
nitrite. nitrate. oxide.
Argentic tidoraie, I qV , is obtained by dissolving argentic oxide in chloric acid.
It is more readily prepared by passing chlorine into water in which argentic oxide is
suspended; a mixture of chloride and hypochlorite (cf. p. 181) is thus formed, the
latter decomposing in the dark at 60° C. (140° F.) into chloride and chlorate :
saAgo = 2Aga + {%^l^.
Argentic Argentic Aigentlc
hypochlorite. chloride. chlorate.
* N(NH,),Ho,fN»AgH80).
t N.NFj, ),Ho, Ago or NO(NH,)Ho(N^AgH,0).
OOMPOUNDB OF SILVER. 467
The liquid is filtered from the chloride and evaporated. Argentic chlorate crystallizes
in white opaque quadratic prisms, soluble in 10 parts of cold water. It fuses at 230^
C. (446® F.), and decomposes at 270° C. (618° F.) into oxygen and argentic chloride,
a trace of chlorine being evolved at the same time. When rapidly heated it defla-
grates. A mixture of ai^gentic chlorate with sulphur detonates with great violence on
friction.
Argentic bromaie, < q aLv» *nd argentic iodate, < S a -o» *re obtained as sparingly
soluble precipitates by the addition of solations of the corresponding potash salts to a
solution of argentic nitrate.
ArpaUie pervodtUe. — When argentic nitrate is added to a neutral or slightlv acid
solution of an alkaline periodate, a dark-brown pr^ipitate of the formula OsiAgo,-
20Ag3 is obtained, which when heated to 200° C. (392° F.) is decomposed into argentic
iodide, metallic silver, and oxygen. This salt dissolves in nitric acid, and deposits on
evaporation orange-colored octahedra of argentic metaperiocUUe, OglAgo, which is de-
composed by water into free periodic acid and an insoluble yellow salt of the formula
20,IAgo.OAg„30H,.*
Argentic carbonaiCj COAgo,, is precipitated when potassic or sodic carbonate is added
to a solution of argentic nitrate. It forms a pale-yellow amorphous powder, insoluble
in water. When exposed to light, or when warmed, it blackens. At a temperature
of 100° C. it evolves carbonic anhydride, and is converted into argentic oxid^.
Argentic sulphate, SO^AgOj, is prepared by dissolving silver in
hot concentrated sulphuric acid, or by precipitating a concentrated solu-
tion of argentic nitrate with sulphuric acid. It forms small lustrous
crystals belonging to the rhombic system, of sp. gr. 5.4. It is soluble
in about 200 parts of cold and in 68.35 parts of boiling water; more
readily soluble in dilute sulphuric or nitric acid. At a dark red heat
it fuses without decomposition ; at a higher temperature it breaks up
into metallic silver, oxygen, and sulphurous and sulphuric anhydrides.
The solid salt absorbs two molecules of gaseous ammonia, forming the
compound 80,Ag02,2NH3 = S02(N^AgH30)2. A solution of the salt
in warm aqueous ammonia deposits on cooling quadratic crystals of
the compound S03Ago,.4NH3 = S{'NH^\UoJi^''Af:UjO;)—Hydrio
argentic sulphate, SOjHoAgo, crystallizes in pale yellow prisms from
a solution of the normal salt in less than three parts of sulphuric acid.
If more sulphuric acid be employed, double compounds of th^ acid salt
with sulphuric acid are obtained.
Argentic sulphite^ 80 Ago,, is prepared by dissolving; argentic oxide in sulphurous
acid, or by precipitating argentic nitrate with an alkaline sulphite or with sulphurous
acid, avoiding an excess of the precipitant. It crystallizes in white shining needles, or
forms a cnrdy precipitate, only slightly soluble in water. When exposed to light, it
blackens. At a temperature of 100° C. it is decomposed into sulphurous anhydride,
aigentic sulphide, and metallic silver :
2SOAgo, = SOjAgo, + 80, + Ag,.
Argentic Aigentic ' Sulphurous
sulphite. sulphate. anhydride.
Argentic dithionaie^ < BO^Afo' ^^^ ^^ prepared by dissolving aigentic carbonate in
the aqueous acid. It crystallizes in rhombic prisms.
Argentic ihionUphate {Argentic hyposulphite), 80,AgoAg8. — When a dilute solution
* On the formulation of these compoands on the basis of heptaie iodine, e.g., lOAgo^,
lOfAgo, and IOHo|Ago„ see p. 305.
458 INOBGANIO CHEMISTRY.
of argentic nitrate is added to an excees of a solation of sodic tbioBolphate, a graj'
precipitate is formed, coneisting of a mixture of argentic sulphide with argentic Uiio-
sulphate. The thoroughly washed precipitate is treated with ammonia which extracts
the thiofiulphate. On carefully neutralizing the ammoniacal solution with nitric acid
the argentic thiosulphate is reprecipitated as a white powder, sparingly soluble in
water. It must be quick W dried by pressure, as in the moist state it readily decom-
poses into argentic sulphide and sulphuric acid :
SOjAgoAgs + OH, = 8Ag, + SO,Ho,.
Argentic Water. Argentic Sulphario
thiosulphate. sulphide. acid.
Sodic argeiUic thiosulphate, 80,NaoA|^20H„ is obtained by gradually adding, with
constant stirring, a solution of sodic thiosulphate to a solution of argentic nitrate till
the precipitate no longer redissoWes. On adding alcohol to the filtrate, the doable
salt separates in lustrous laminae.
Argentic Phosphate :
a. Arffentie orthophosphate, POAgo,, is precipitated when argentic
nitrate is added to a solution of any normal or monofajdric alkaline
phosphate, nitric acid being liberated in the latter case. It forms a
yellow amorphous precipitate, insoluble in water, readily soluble in
nitric acid and in ammonia. It becomes dark-colored when exposed to
light. When heated it assumes a deep orange-red color, and fuses at a
strong red heat without decomposition. — Hydric diargentic (nihophos-
phaky POHoAgo,, is deposited as a white crystalline powder when
ether is added to a solution of the normal salt in excess of phosphoric
acid.
6. Argentic pi/rophoy>hate, PgOjAgo^, is obtained as a white precipi-
tate when argentic nitrate is added to solutions of either normal or
acid pyrophosphates of the alkali metals. It is insoluble in water,
readily soluble in nitric acid or ammonia. It fuses without decompo-
sition below redness, yielding a dark brown liquid which solidifies on
cooling to a radio-crystalline mass. Under the influence of light it
turns red.
c. Argentic metaphosphate, POjAgo. — The various modifications of
metaphosphoric acid yield corresponding silver salts. Thus, if argentie
nitrate be added to a solution of the vitreous sodic metaphosphate, an
amorphous white precipitate of the silver salt is obtained; whereas
crystallizable sodic trimetaphosphate yields, when so treated, well-
formed crystals of argentic trimetaphosphate, P3O^AgO3,0H2.
Argentic arseruUe, AsOAffOg, is obtained as a reddish-brown amorphoos precipitate
when an alkaline arsenate is added to the solution of a silver salt The same salt may
be obtained as a dark-red crystalline powder by precipitating a boiling solution of
argentic nitrate with a concentrated solution of arsenic acid. It is insoluble in water,
r^ily soluble in nitric acid and in ammonia. When heated it fuses, yielding a
reddish-brown glass on cooling.
Argentic arsenite, AsAgOa, is prepared by cautiously adding ammonia to a mixed
solution of argentic nitrate and arsenious acid as long as a precipitate is produced, it
forms a yellow precipitate, readily soluble in nitric acid and in ammonia. On heating^
it decomposes into arsenious anhydride, argentic arsenate, and metallic silver:
5ABAgo, = SAflOAgo, + Ab^Os + SAg,.
Argentic Argentic Arsenious
arsenlte. arsenate. anhydride.
OOMPOUKD6 OF 8ILVEB. 459
By boiling with sodic hydrate it is decomposed into arsenic anhydride, which disRolves
with formation of sodic arsenate, and metallic silyer, the latter being mixed with ar-
gentous oxide (OAg^).
COMPOUNDS OF SILVER WITH SULPHUR.
Aro£NTIC sulphide, 8Ag2« — This compouDd occurs native as silver
glance or argentUe in blackish-gray regular crystals' with a metallic
lustre. It has a sp. gr. of from 7.196 to 7.356. Artificial crystals of
argentite are obtained when silver is heated in a current of sulphuretted
hydrogen, and the same substance may be prepared as a crystalline
mass by fusing together silver and sulphur. A black amorphous pre-
cipitate of argentic sulphide is formed when sulphuretted hydrogen is
passed into solutions of silver salts. Argentic sulphide is insoluble in
water, soluble with decomposition in strong nitric acid, insoluble in am-
monia. When heated in air, avoiding too high a temperature, it is oxi-
dized to argentic sulphate. Cupric chloride in presence of sodic chloride
converts it into argentic chloride (see Mexican Amalgamation Process).
8ULPH0-8ALTS OF SILVER.
Argentic sulpharteniUy AsAgs,, occurs native as pi^ouatite or light red silver ore, in red
translucent rhombohedral crystals. It generally contains more or less antimony, which
is present in isomorphoiis replacement of a portion of the arsenic.
Araentie sulpharUimoniiej Sb Ags,. occurs as pyrargyrile or dark red eilver ore, in rhom-
bohedral crystals, isomorphous with the preceding. It varies in color from dark red
to grayish-black, is opaque, and poesesses metallic lustre.
COMPOUNDS OF SILVER WITH NITROGEN AND PHOSPHORUS.
Fulminating silver. — ^This compound is formed when freshly precipitated argentfo
oxide is dissolved in strong ammonia, and the solution is evaporated with the aid of a
gentle warmth. It forms black crystals, which when drv explode violently on the
slightest touch, and even when moist may be made to explode by shaking the liouid
in which they are immersed. Owing to the dangerous character of this compound ita
composition has not been ascertained with certainty. It is possibly argentic amide,
HAgH,.
Argentic phoephide is formed when phosphorus is added to molten silver, or when
argentic phosphate is fused with charcoal. It is thus obtained as a dark gray mass,
which, when strongly heated, parts with a portion of its phosphorus. This compouna
haa not been obtained of constant composition.
General Properties and Reactions op the Compounds op
Silver. — The salts of silver with colorless acids are colorless. The
soluble salts are neutml to test-paper, have an acrid metallic taste^ and
act as violent irritant poisons. From solutions of silver salts cavMio
alkalies precipitate brown argentic oxide. Ammonia also precipitates
the oxide, which is soluble however in an excess of the precipitant.
Sulphuretted hydrogen gives a black precipitate of argentic sulphide, in-
soluble in ammonic sulphide, soluble in hot nitric acid. The hvdraeids
precipitate the corresponding haloid compounds of silver (p. 452).
Hydrocyanic add and potassio cyanide give a curdy precipitate of ar-
gentic cyanide (AgCy) soluble in excess of potassic cyanide. Argentic
evanide is decomposed on ignition, leaving a residue of metallic silver.
Copper, zinCy iron, and other oxidizable metals, further, sulphurous acid
460 INOBOAKIO CHEMI8TBT.
and/«rraiw aviipluUe, precipitate metallic silver from the solutions of its
salts. Insoluble compounds of silver, when heated with sodic carbonate
on charcoal before the blowpipe, are reduced to metallic silver. The
silver compounds give no flame spectrum ; but the spark spectrum ex-
hibits two characteristic bright lines in the green.
CHAPTER XXXIII.
DYAD ELEMENTS.
Section II.
BARIUM, Ba.
Atomic weight = 137. Probable molecular weight = 137. Sp. gr. be-
tween 4.0 and 5.0. Atomicity ". Evidence of atomicity :
Baric chloride, Ba'^Clj.
Baric hydrate, Ba^'Ho,.
Baric oxide, Ba"0.
History. — Metallic barium was first prepared by Davy in 1808.
Occurrence. — Barium is never found native. It occurs abundantly
as sulphate in the mineral heavy-spar and as carbonate in wiiherite. In
many calcium minerals it sometimes replaces a portion of the calcium,
with which it is isoraorphous. Traces of it are found in various mineral
waters and in sea-water.
Preparation. — Barium is not reduced from its oxide, hydrate, or
carbonate, by heating with charcoal. It may be obtained by the fol-
lowing methods :
1. By the electrolysis of the fused chloride (see Preparation of Lith-
ium, p. 436). The barium is thus obtained in the form of a metallic
powder.
2. By electrolyzing moistened baric hydrate, carbonate, nitrate, or
chloride, the n^ative electrode being formed of mercury. A liquid
amalgam of barium is thus obtiiined, which may be freed from the ex-
cess of mercury by pressing through a cloth. The solid amalgam
which remains is only slowly oxidized by exposure to the air. On
subjecting it to distillation mercury passes over and metallic barium
remains in the retort as a porous mass.
3. By acting with sodium amalgam upon a hot concentrated solu-
tion of baric chloride, barium amalgam is obtained, which is further
treated as above.
4. Barium amalgam is also obtained by passing the vapor of potas-
sium or sodium over baric oxide or chloride strongly heated in an iron
tube, and extracting the mass with mercury.
Properties. — Barium is a pale yellow metal. Its fusing-point appears
to be higher than that of cast-iron. It is rapidly oxidized by expo-
COMPOUNDS OF BARIUM. 461
sore to the air, and decomposes water at ordiDary temperatures like
sodium :
Ba + 20H, = H, + BaH(v
Water. Baric hydrate.
COMPOUNDS OF BARIUM WITH THE HALOi^ENS.
Baric chloride, BaCIs^OHj, may be prepared either from the native
carbonate or from the native sulphate. The carbonate is dissolved in
hydrochloric acid, and the liquid is digested with an excess of the car-
bonate in order to precipitate iron and other foreign metals that are
present. The addition of a small quantity of baric hydrate facilitates
this precipitation. The filtered liquid is acidified with hydrochloric
acid and evaporated. In order to prepare baric chloride from the
native sulphate, this mineral is ground to a fine powder and then
strongly heated with calcic chloride, limestone, and coal. The follow-
ing reactions occur :
SO^Bao" + 4C = BaS'' + 400.
Baric Baric Carbonic
sulphate. sulphide. oxide.
BaS'' + OaCl, = BaCl, + OaS".
Baric Calcic Baric Calcic
sulphide. chloride. chloride. sulphide.
The calcic sulphide unites with the calcic oxide present to form an
insoluble calcic oxysulphide, which remains behind when the baric
chloride is extracted with water. — Baric chloride crystallizes in colorless
lustrous rhombic tables, with 2 aq., permanent in air. The sp. gr. of
the crystallized salt is 3.05. It has an unpleasant bitter taste, and,
like all the soluble salts of barium, is very poisonous. The anhydrous
salt is soluble in 3 times its weight of water at 10° C. (50° F.), and in
about 1§ times its weight of water at 100° C. It is almost insoluble
in concentrated hydrochloric and nitric acids ; in the dilute acids it is
soluble, but less freely than in water. Absolute alcohol does not dis-
solve it. When heated above 100° C, the crystallized salt parts with
its water of crystallization, and is converted into a white powder fusible
at a red heat. When fused in air a small quantity of the salt is con-
verted into baric oxide with evolution of chlorine ; when heated in a
current of steam hydrochloric acid is given off below the fusing-point
of the salt, and baric hydrate is formed. — Baric chloride is chiefly used
in the preparation of the pigment permanent white, which consists of
artificial baric sulphate.
Barie bromide, BaBr^20Hi, is prepared by dissolviug baric carbonate in hydro-
bromic acid. The following method is the most convenient : 12.5 parts of bromine
and 1 part of amorphous phosphorus are brought together under water. As soon as
the color of the bromine has disappeared the liquid, which now contains hydrobromic
and phosphoric acid, is neutral izea with baric carbonate, rendered alkaline with baryta
water, filtered from the insoluble baric phosphate, and evaporated to the point of orys-
462 INOBOAJ7IC CHEMISTBV.
tallization. Baric bromide closelj reeembles the chloride, bat is soluble in absolute
alcohol.
Baric iodide^ BaIt,20Ht, is prepared like he bromidei substituting iodine for bro-
mine. It forms large, colorless, rhombic crystals, which are very deliquescent, and
are soluble in alcohol. When exposed to tlie air it assumes a reddish tint, owing to
the liberation of iodine. It may be heated in a closed vessel without decomposition,
but when heated in air the whole of the iodine is expelled, and baric oxide is formed.
Baric fiuoruU, BaFt, is obtained by neutralizing nydro6uoric acid with baric car-
bonate or hydrate, or by precipitating a concentrated solution of baric nitrate with
potassic or sodic fluoride. It forms a white granular crystalline powder, sparingly
sohible in water, readily soluble in nitric, hydrochloric, and hydrofluoric acids.
Baric nlteofluoridef SiBaFg, is precipitated as a white crystalline powder, when hy-
drofluosilicic acid is added to the solution of a barium salt. It is almost Insoluble in
water, requiring 3600 parts of cold, and 1200 parts of boiling water for its aolution ;
totally insoluble in alcohol.
COMPOUNDS OF BARIUM WITH OXYGEN.
Baric oxide [baryta), BaO. Ba==0.
fiaric peroxide, BaQ > Ba^ | .
Bario oande, BaO. — This is the oxide which is formed by the com-
bustion of the metal in air. It may be prepared by heating the nitrate,
gently at first, in order to avoid frothing, and afterwards to bright
redness. The frothing may also be prevented by mixing the nitrate
with its own weight of baric sulphate, the presence of the insoluble
sulphate in the product not being objectionable for many purposes to
which the baric oxide may be put, for instance in the preparation of
baric hydrate. The carbonate may also be converted into baric oxide
by heating to a very high temperature, but the whole of the carbonic
anhydride can be expelled only with difficulty ; however, by mixing
the carbonate with carbon, or with some substance which yields carboo
when heated, such as tar or resin, the conversion into baric oxide is
greatly facilitated, carbonic oxide being evolved, thus :
OOBao" + C = BaO + 20O.
Baric Baric Carbonic
carbonate. oxide. oxide.
Much of the baryta employed in sugar refining (p. 464) was prepared
by this method. Baric oxide is a grayish- white, porous, friable mass,
of sp. gr. 4.73. It is fusible in the flame of the oxyhydrogen blowpipe.
It slakes with water, forming baric hydrate, the combination taking
place with such energy that, if an excess of water is avoided, the mass
becomes incandescent.
Baric peroxide^ Ba>^ > , is formed when baric oxide is heated to low
redness in oxygen or air. Baric hydrate is also converted into the per-
oxide under these circumstances, but less readily, inasmuch as it fuses
below the temperature at which the al)sorption of oxygen occurs. The
product obtained by these means is not pure, a portion of the baric
OOMPOITNBS OF BARIUM. 463
oxide or hydrate escaping conversion. It is also contaminated with
iron, silica, and other matters derived from the vessels in which it has
been prepared. In order to obtain the substance in a state of purity,
the finely-powdered crude product is added in small portions at a time
to an excess of dilute hydrochloric acid, any considerable rise of temper-
ature being avoided. The crude peroxide dissolves, with formation of
baric chloride and hydroxy 1 (cf, p. 176). To the solution, after filter-
ing from insoluble matters, baryta water is carefully added until the
silica and ferric oxide, along with a small quantity of hydrated baric
peroxide regenerated by the action of the hydroxyl upon the baric
hydrate, are precipitated :
{gg + BaHo, = Bag| + 20H^
Hjdroxjl. Baric hydrate. Baric peroxide. Water.
This liquid is again filtered, and then supersaturated with baryta. In
this way the whole of the remaining hydroxyl regenerates baric perox-
ide, which is precipitated in minute prisms or laminae of the formula
BSq > jSOHj. In the moist Condition this aquate may be preserved
for any length of time in closed vessels, and forms a convenient source '
of hydroxyl. By drying at 130° C, or at ordinary temperatures in
vacuoy it is converted into anhydrous baric peroxide. — Baric peroxide
forms a white impalpable powder, insoluble in water, but forming with
it the aquate BaQ > ,80H3. It fuses at a bright red heat, and is de-
composed into oxygen and baric oxide. Heated with steam it evolves
oxygen at the same temperature at which the peroxide is formed, and
is converted into baric hydrate. Dilute acids dissolve it with formation
of a barium salt and hydroxyl; with concentrated sulphuric acid it
forms baric sulphate, whilst oxygen mixed with traces of ozone and
hydroxyl is evolved. When heated in a current of sulphurous anhy-
dride it becomes incandescent, and is converted into baric sulphate :
80, + {gBa = SO^^Baj".
SulphurooB Baric Baric
anhydride. peroxide. sulphate.
COMPOUND OF BARIUM WITH HYDROXYL.
Baric hydrate, BaHo,. — This compound is formed, with great
evolution of heat, by the direct union of baric oxide with water. A
hot concentrated solution of equivalent quantities of baric nitrate and
sodic hydrate deposits, on cooling, crystals of baric hydrate. Potassic
hydrate may be substituted for sodic hydrate in this reaction; but
ammonia does not precipitate baric hydrate from solutions of barium
salts. On a large scale, baric hydrate is prepared as follows : By heating
464 tSfOBOANIC CHEHI8TBT.
powdered heavy-epar with carbon a crude baric sulphide is obtained.
Moist carbonic anhydride is passed over the heated sulphide^ convert-
ing it into carbonate :
BaS" + 00, + OH, = OOBao" + SH,.
Baric Carbonic Water. Baric Sulphuretted
sulphide. anhydride. carbonate. hydrogen.
Superheated steam is then passed over the heated carbonate^ which
parts with carbonic anhydride and forms baric hydrate :
OOBao'' + OH, = BaHoi + CO,-
Baric Water. Baric Carbonic
carbonate. hydrate. anhydride.
— Baric hydrate crystallizes from water in large four-sided prisms or
plates, of the formula BaHoj^SOH,, which are soluble in 20 parts of
water at ordinary temperatures, and in 3 parts at 100® C. The solution
of the hydrate, generally known as baryta water, is much used in
chemical analysis, particularly in the determination of carbonic anhy-
dride, which it rapidly absorbs, with formation of insoluble baric cai^
bonate. The crystals of the hydrate are efflorescent, and when exposed
in vaciio over sulphuric acid, give off the greater part of their water of
crystallization, leaving a white powder of the formula BaHojyOH,.
When heated, the whole of the water of crystallization is expelled, and
the hydrate fuses at a red heat, solidifying on cooling to a crystalline
mass. It cannot be converted into baric oxide by the action of beat
alone. Heated in a current of air, it is converted into baric peroxide
with elimination of water :
BaHo, + O = Ba^l + OH,.
Baric hydrate. Baric peroxide. Water.
Baric hydrate was extensively employed in sugar-refining for sepa-
rating crystal I izable sugar from molasses. It forms with cane sugar
an insoluble compound of the formula QjHjsOnBaO, which when sus-
pended in water and treated with carbonic anhydride is decomposed,
yielding insoluble baric carbonate and sugar, the latter dissolving.
Strontic hydrate^ which, unlike the barium compound, is not poisonous,
has of late been substituted for baric hydrate in the sugar industry.
OXY^SALTS OF BARIUM.
NO
Baric nitrate, jjQ^Bao". — ^This salt is prepared by dissolving
the carbonate or the crude sulphide (p. 461) in dilute nitric acid. It
crystallizes in colorless, lustrous, regular octahedra, of sp. gr. 3.2. It is
soluble in 12 parts of cold, in 3 parts of boiling water ; almost insoluble
in concentrated nitric acid ; insoluble in absolute alcohol. It fuses at
OOMPOUND6 OF BASIlTlf. 465
597° C. (1 107° F.). Heated to redness it decomposes, giving off oxygen,
nitrogen, and nitric peroxide, whilst a residue of pure baric oxide remains.
It is lai^ly employed inpyrotechny for ttie preparation of green fire.
IffO
Baric nitriUf j|QBao^^,OH,. — Baric nitrate is moderately heated so as to convert it
into nitrite ; carbonic anhydride is then passed into the solution of the fused salt to
precipitate any baryta that may have been formed ; an excess of alcohol is added to
precipitate unaltered nitrate, and the filtered solution is evaporated to the crystallizing
poinL It is most readilv prepared pure by adding baric chloride to a boiling solution
of argentic nitrite, and filtering from the argentic chloride. It forms colorless prisms,
very soluble in water.
f oa
Barie ehloratef > q Bao^^,OH^ is formed when chlorine is passed into a hot solu-
l OCl
tion of baric hydrate, but its separation from the chloride which is formed at the
same time is a matter of difficulty. It is best prepared by neutralizing a solution of
chloric acid with baric carbonate and evaporating to the crystallizing point. It crys-
tallizes in colorless monoclinic prisms, with 1 aq., soluble in 4 parts of cold, in less
tha^ 1 part of boiling water,
f OCl
I ^
Baric pereMoraief \ QBao^^,40H„ is prepared by neutralizing perchloric acid with
loa
baric hydrate or carbonate. It crystallizes in long deliquescent prisms, readily solu-
ble in water and in alcohol.
Baric carbonate, OOBao". — This salt occurs abundantly in nature
as vntherite. It may be prepared by pouring a solution of baric chlo-
ride or nitrate into an excess of a solution of ammonic carbonate, and
washing the precipitate with hot water. The native carbonate forms lus-
trous crystals belonging to the rhombic system, of sp. gr. 4.29-4.35 ; that
prepared by precipitation is a dense white powder. It is insoluble in
pure water; slightly soluble in water containing carbonic anhydride,
probably with formation of an unstable acid carbonate. It fuses at a
white heat, giving off carbonic anhydride very slowly ; but it is more
readily decomposed by heat in presence of carbon, or when steam is
passed over it (pp. 462 and 463). The artificial carbonate is employed
in chemical analysis. Witherite is used in the preparation of the other
salts of barium and as a rat poison.
Baric sulphate, SO^Bao'', occurs in large quantities as heavy-spar,
sometimes forming distinct veins. It is frequently found in large
rhombic crystals. The sp. gr. of the mineral varies between 4.3 and
4.72. By precipitating solutions of barium salts with dilute sulphuric
acid, baric sulphate is obtained as a white impalpable powder of sp. gr.
4.53. It is insoluble in water, slightly soluble in dilute acids. When
freshly precipitated it is readily soluble in concentrated sulphuric acid
at 100^ C, the solution depositing, on cooling, lustrous prisms of diliy"
rso^Ho
drie baric svlphaie, < Bao^^ • If the acid solution is exposed to the
iSO.Ho
air it absorbs moisture, and deposits silky needles of a salt having the
30
466 INOBOANIC CHEMI8TKY.
rso,Ho
formula < Bao'^ ,20H2. Both these salts are deoomposed by water,
tSO,Ho
yielding sulphuric; acid and the neutral salt. Artificial baric sulphate
is used as a pigment, under the name of permanent white or blancfixe.
The finely ground mineral b also employed for this purpose, but is too
crystalline and transparent, and hence lacks " body."
{lolB-" =
= SOiBao''
Baric
Bario
dithionate.
sulphate.
(80,1
Barit pyrotvlphalt, \ O fiao'^'^. — Precipitated baric sulphate diaiolves in fuming
(so, J
sulphuric acid, and the solution, on heating to 150° C. (302® F.), deposits lustrous gran-
ular crystals of this salt. It decomposes at a dull read heat, without previously fusing.
Baric ndj^hitej BOBa.(/^t is obtained as a white crystalline precipitate by the addition
of an alkaline sulphite to the solution of a barium salt. It crystallizes from its solu-
tion in warm aqueous sulphurous acid in six-sided prisms. When heated in air it is
converted into sulphate ; in closed vessels it yields, when heated, a mixture of sulphate
and sulphide.
4SOBao^' = SSOaBao'' + BaS.
Baric sulphite. Baric sulphate. Baric sulphide.
Baric dxthwnaUj | ^*Bao^^,20Hs.'— Preparation, see p. 278. This salt crystalliKs
in large, lustrous, monoclinic crystals, soluble in 4 parts of water at 18° C. (64° F.), in
1.1 part at 100° C. The solution may be boiled without undery^ing decomposition;
but when boiled with hydrochloric acid, it evolves sulphurous anhydride, and baric
sulphate is precipitated. In like manner, when the dry salt is ignited it breaks up into
sulphurous anhydride and baric sulphate:
-4- SO,.
Sulphurous
anhydride.
Baric dithionate is employed in the preparation of the other dithionates.
Baric tAiosu/pAote, fiK)>( az/BaV^yOHs, is obtained as a sparingly soluble crystal-
line precipitate when sodic thiosulphate is added to a solution of baric chloride.
Baric orthopho6phate, poBao''^^'*®^*' ^ prepared by add-
ing hydric disodic orthophosphate to a solution of baric chloride rendered
strongly alkaline with ammonia. It forms a white precipitate^ insolu-
ble in water, soluble in dilute nitric and hydrochloric acids. — Hydric
baric orthophosphate, POHoBao", is precipitated when hydric disodic
orthophosphate is added to neutral solutions of barium salts. It is a
white crystalline powder, slightly soluble in water, readily soluble in
dilute acids. — Tetrahydric baric orthophosphate, poHo ^^"' ^ ^"^
tained by evaporating a solution of the monacid salt in phosphoric
acid. It forms colorless crystals, apparently triclinic, with an acid
reaction. It is soluble without decomposition in a small quantity of
water ; excess of water precipitates jthe monacid salt, whilst free phos-
phoric acid remains in solution.
CX>MP0nKD6 OF BARIUM. 467
COMPOUNDS OF BARIUM WITH SULPHUR.
Baric sulphide^ BaS^^, is obtained by passing sulphuretted hy-
drogen over the heated oxide. It is prepared on a large scale by heat-
ing heavy-spar \7ith carbon. The materials must be thoroughly in-
corporated ; otherwise, owing to their infusibility, the action will be
only partial. The finely ground heavy-spar is mixed with powdered
bituminous coal ; the latter fuses, yielding by its decomposition a carbon
which permeates the entire mass of the sulphate, and insures its com-
plete reduction. The sulphide obtained by this method is always con-
taminated with the excess of carbon, and is only used for the prepara-
tion of the various salts of barium (see p. 464). Baric sulphide forms
a white mass which, when exposed to the air, absorbs water, oxygen,
and carbonic anhydride, and is gradually converted into a mixture of
sulphate and carbonate. Water dissolves it, but the solution contains
a mixture of hydrate and sulphhydrate :
2BaS'' + 20H, = BaHoj + BaHsj.
Baric Water. Baric Baric
sulphide. hydrate. salphhjdrate.
The so-called Bolognian phosphorus is a sulphide of barium prepared
by heating 5 parts of precipitated baric sulphate with 1 part of carbon.
It must be sealed up while still hot in glass tubes. After exposure to
sunlight, or to any other light rich in chemically active rays, it displays
in the dark a brilliant orange-colored light, and retains this phospho-
rescent property, though with gradually diminishing intensity, for some
time. The luminosity may be renewed indefinitely often by fresh ex-
posure to light. The sulphides of calcium and strontium are also phos-
phorescent, and emit a green, blue, violet, or red light, according to the
mode of preparation. These various sulphides are at present manufac-
tured under the name of luminous paintSy and are employed for coating
clock-faces, match-boxes, and other objects which it is desired to render
luminous in the dark. It is necessary, in order that these paints may
preserve their efficiency unimpaired, that they should be protected from
the moisture of the air. This is effected by a transparent coating of
glass or varnish.
Baric tetrasulphidef BaSf.OHt) is obtained in pale-red rhombic prisms by boiling a
solution of banc sulphhydrate with sulphur and allowing the solution to cool. It is
readily soluble in water.
Various other polysulphides of barium have been prepared. They are unstable
compounds, which in contact with water are decomposed with formation of the tetra-
sulphide.
COMPOUND OF BARIUM WITH HYDROSULPHYL.
Baric mdjohhydraUj BaHss, is formed along with baric hydrate by the action of water
on baric sulphide {supra). It may be prepared pure by saturating a solution of baric
hydrate with sulphuretted hydrogen. It forms colorless very soluble crystals, contain-
ing water of crystallization. When heated with exclusion of air, It parts with the
water of crystallization, and at a higher temperature evolves sulphuretted hydrogen,
whilst baric sulphide remains.
468 inoboakic chemistbt.
General Properties akd Reacttons op the Compounds of
Barium. — ^Tbe salts of barium with colorless acids are colorless. The
soluble salts have a bitter taste and are poisonous. Baric chloride and
baric nitrate are both insoluble in absolute alcohol. Suiphurio ooid and
soluble sulphates produce in solutions of barium salts a white precipi-
tate of baric sulphate insoluble in dilute acids. Alkaline oarbonaies
precipitate baric carbonate. Hydroftuosilioio add gives a colorless crys-
talline precipitate of baric silicofluoride. Patassie chromate tiud potassie
dichromate precipitate yellow baric chromate, insoluble in acetic acid.
Barium salts color the non-luminous flame yellowish-green. Of the
numerous lines in the complex spectrum^ the two green lines, Baa and
Bsifi, are the brighest.
BTBONTnm, Sr.
Atomic weight = 87.5. Probable molecular wdghi = 87.5. Sp.gr. 2.5.
Fuses at a red heat. Atomicity ". Evidence of atomicity :
Strontic chloride, Br'^Cl,.
Strontic hydrate, Br"Hoy
Strontic oxide, Sr''0.
History. — ^Hope showed in 1792 that the mineral strontianite con-
tained a new earth. The metal was first isolated by Davy in 1808.
Occurrence. — Strontium occurs as carbonate in strontianiiey and as
sulphate in celestine. Traces of it are present as carbonate in many
kinds of limestone, marble, and chalk. It also occurs in minute quan-
tities as chloride and sulphate in brine-springs, mineral waters, and
sea-water.
Preparation. — Strontium is most readily prepared by the electrolysis
of the fused chloride. By this means it is obtained in coherent pieces
sometimes weighing half a gram. — By heating a saturated solution of
strontic chloride with sodium-amalgam, an amalgam of strontium is
formed, from which the mercury may be expelled by heating.
Properties. — Strontium is a yellow malleable metal. It undei^oes
rapid oxidation on exposure to the air, burns with a brilliant light when
heated, and decomposes water at ordinary temperatures.
COMPOUNDS OF STRONTIUM WITH THE HALOGENS.
Strontic chloride, SrCls,60H„ is prepared like the barium salt
(p. 461). It crystallizes in deliquescent hexagonal needles or prisms of
sp. gr. 1.603, r^ily soluble in water, soluble also in alcohol. When
heated, it parts with its water of crystallization, leaving the anhydrous
salt in the form of a white powder, which fuses at a higher tempera-
ture. The anhydrous chloride absorbs dry ammonia, forming the com-
pound BrCl2,8NH,.
Strontic bromide, SrBn,60Hs, is prepared like the barium salt (p. 461). It resem-
bles strontic chloride in its properties.
OQMPOnNDS OF STRONTIUM. 469
Strontie lodidAf SrT},70H» is prepared like the barium salt (p. 462). It crystallizes
in six-sided plates, and is verir soluole. When heated in air it parts with iodine, and
is converted into strontie oxide.
Stnyntic fluoride^ SrF}, is prepared like the barium salt (p. 462), which it also resem-
bles in its properties.
Strontie iUicojiuoride, 8iSrFc,20Ht, is obtained by neutralizing hydrofluosilicic acid
with strontie carbonate, and evaporating to the crystallizing point. It forms monoclinic
crystals, readily soluble in water.
COMPOUNDS OF STRONTIUM WITH OXYGEN AND
HYDBOXYL.
Strontie ozide^ Strontia, . . BrO. Sr=0.
Strontie peroxide, .... BFq V . Sr^ | .
Strontie hydrate, .... BrHo,. H— O— Sr— O— H.
Strontic oxide, BrO. — ^This eompound is prepared like baric oxide
(p. 462). It forms a grayish- white, infusible, porous mass resembling
baric oxide in its properties and reactions. It combines with water to
form strontie hydrate, BrHoj.
Strontie peroxide,BTQ >, separates in crystalline laminse with 8 aq.
when a solution of hydroxyl is added to an excess of a solution of strontic
hydrate. In dry air or when heated to 130° C. it parts with its water
of crystallization, leaving the pure peroxide as a white powder. This,
when heated to redness, evolves oxygen, and is converted into strontic
oxide, without however first fusing, as in the case of baric peroxide.
Strontic hydrate, BrHo2,80H2, is formed as above by the action of
water upon strontic oxide. It resembles baric hydrate, but is somewhat
less soluble in water, and, when strongly heated, parts with water and
is reconverted' into the oxide.
OXY-SALTS OF STRONTIUM.
Strontic nitrate, vq^^^o'^ — This salt is prepared by dissolving
the native carbonate in nitric acid. It crystallizes from hot concen-
trated solutions on cooling in anhydrous octahedra of sp. gr. 2.96, and
from cold dilute solutions in large monoclinic prisms with 4 aq., which
effloresce when exposed to the air. It is soluble in twice its weight of
water at 16° C. (59° F.), and in its own weight of water at 100° C,
but is insoluble in alcohol. — Strontic nitrate is employed in pyrotechny
in the manufacture of red fire.
r OCl
Strontic ehhraief ; ^Sro^^^SOH,, is prepared by dissolving the carbonate in chloric
i OCl
Hcid. It forms deliquescent crystals, very soluble in water.
470 INOBOANIC CHEMIBTBY.
Strontic carbonate, OOSro", occurs native as sirontianite in
rhombic crystals, isomorplious with those of arragoniie^ one of the
forms of native calcic carbonate. It is obtained as a white insoluble
precipitate when an alkaline carbonate is added to the solution of a
strontium salt.
Strontic sulphate, BO^ro", occurs native as cdestine in rhombic
crystals, or in fibrous masses, generally of a light blue color, from which
property the name of the mineral is derived. Sulphuric acid precipi-
tates strontic sulphate as a white powder from solutions of strontium
salts. The precipitate is generally crystalline, and has a specific gravity
of 3.07. It is slightly soluble in cold, less soluble in hot water ; the
presence of acids increases the solubility. The aqueous solution pro-
duces in solutions of barium salts a strong turbidity. It fuses at a
bright red heat, yielding a vitreous mass on cooling. When digested
with solutions of alkaline carbonates in the cold, or with hot mixed
solutions of 2 parts of potassic carbonate with 1 part of potassic sul-
phate, it is completely converted into strontic carbonate, a property
sharply distinguishing it from baric sulphate, which under these cir-
cumstances undergoes no change. With concentrated sulphuric acid,
strontic sulphate behaves like baric sulphate (p. 465), yielding an acid
salt which is decomposed by excess of water into the normal salt and
free sulphuric acid.
Strimiic sulphiU, SOSro^^— PrefMired like the barium salt (p. 466)
resembles.
f SO
Strordie dithionaUj < 2o'^™^''»^^*' — Prepared like the bariam salt {\
soluble hexaffonal crystals.
/O \''
StrontU thumdphaUy SO^f g/^Sr j ,50H,, is prepared by dissoWing i
solution of strontic hydrate, and then saturating with snlphnrous anhy
277). It forms lustrous monoclinic crystals, readily soluble in water.
The orUutphoaphcUes of strontium correi«pond closely, both in properties
preparation, witn those of barium.
General Properties and Reactions of the Compc
Strontium. — The salts of strontium closely resemble those oi
Those formed with colorless acids are colorless. The soluble
a bitter taste, but are not poisonous. Strontic chloride is i
absolute alcohol ; strontic nitrate is insoluble in this solveo'
solutions of strontium salts alkaline carbonaJtes precipitate stn
bonate. Strontic sulphate is slightly soluble: a solution of
produces in solutions of barium salts a precipitate of baric «
HydrofluosUwic aeld and soluble ohromates give no precipil •
strontium salts. Strontium compounds color the non-luminou
brilliant red. The flame-spectrum is complex : the lines Sr
orange, Sr/5 and Srr in the red, and Sr^ in the blue are the bri^
CALCIUM. 471
CALCIUM, Ca.
Atomio weight = 40* Probahk molecular tteiglU == 40. Sp.gr. 1.578.
AtomieUy ". Evidence of atomicity :
Calcic chloride, Ca"Cl,.
Calcic hydrate, Ca^Ho,.
Calcic oxide, Ca''0.
History. — Lime, and its use in the preparation of mortar, have been
known from the earliest times. The metal was first isolated by Davy
in 1808.
Occurrence. — The compounds of calcium occur in nature in enor-
mous quantities and widely diffused. As carbonate it occurs under a
great variety of forms, as calc-^pary marblcy limestonCy etc. Calcic sul-
phate also occurs in large quantities : either as the anhydrous sulphate
(SOjCao") in anhydrite^ or as tetrahydric calcic sulphate (BHo4Cao") in
gypsum. The compound silicates of calcium with other metals form a
series of minerals which are among the proximate constituents of the
various rocks. From the rocks and soils it is extracted by the water
which percolates through them, so that spring and river water are rarely
free from salts of calcium, chi^y the carbonate and sulphate. Calcium
is necessary to the existence of most forms of organized matter : in
combination with various organic acids it occurs in plants, whilst the
bones of animals contain calcic phosphate and carbonate. Spectrum
analysis has demonstrated the presence of calcium in the sun and in
some of the fixed stars.
Preparation. — ^Davy prepared impure calcium in the form of a
metallic powder by electrolyzing calcic chloride with mercury as a neg-
ative electrode, and heating the calcium amalgam so as to expel the
mercury. It is most readily prepared by the electrolysis of the fused
chloride. Pieces of pure calcium weighing as much as four grams may
be thus obtained. Another method consists in heating calcic iodide with
sodium. Calcium is also very readily obtained by heating to redness a
mixture of 3 parts of fused calcic chloride, 4 parts of zinc, and 1 part
of sodium, when an alloy of zinc and calcium, containing from 10 to 16
per cent, of the latter metal, collects at the bottom of the crucible. This
alloy is transferred to a crucible made of gas coke, which is packed
inside a larger Hessian crucible, and the whole is heated to a tempera-
ture sufficiently high to volatilize the zinc. The fused calcium, which
remains as a button at the bottom of the coke crucible, is not so pure as
that obtained by electrolysis.
Prop«rfo*e8.— -Calcium is a yellow metal, lustrous when freshly cut.
It is about as hard as gold, and is very malleable. It does not oxidize
readily in dry air, but in moist air it speedily becomes coated with hy-
drate, the action gradually extending throughout the whole mass. It
decomposes water at ordinary temperatures with violent evolution of
hydrogen. Dilute nitric acid dissolves it, the reaction taking place
with such violence that the metal sometimes inflames. Concentrated
472 INORGANIC CHEMISTRT.
nitric acid, on the other hand, is without action upon calcium at ordi-
nary temperatures, a freshly-cut surface of the metal remaining bright
in contact with the acid ; and it is not until the temperature has been
raised to near the boiling-point of the acid that oxidation takes place.
This phenomenon is analogous to that of the so-called ** passive state"
of iron (q.v.). When heated in air calcium burns, emitting a brilliant
yellow light.
COMPOUNDS OF CALCIUM WITH THE HALOGENS.
CAiiCic CHLORIDE, CaCl,,60H2, occurs in sea-water, river-water,
and spring-water. It is obtained as a by-product in several manufac-
turing operations, as for example in the preparation of ammonia (p.
231), of potassic chlorate (p. 182), etc. In order to prepare pure calcic
chloride from a crude manufacturing product, or from the product
obtained by dissolving marble in hydrochloric acid, chlorine-water is
added to the solution until the smell of the chlorine can be distinctly
perceived. By this means any manganous or ferrous compounds which
may be present are oxidized. Milk of lime is added until the solution
is alkaline, the liquid is heated, and the precipitate, consisting of ferric,
manganic, and aluminic hydrates, together with the excess of lime, is
filtered off. The solution is acidified with pure hydrochloric acid and
evaporated either to the crystallizing point or to dryness, according to
the purpose for which the salt is required. — Calcic chloride crystallizes
in large transparent hexagonal prisms of the formula
0aCl2,60H2,
isomorphous with those of strontic chloride, soluble in half their weight
of water at 0'' C. (32° F.) and in one^uarter of their weight at 16° C.
(60.8° F.). The crystals fuse at 29° C. (84.2° F.) in their water of
crystallization, and are therefore soluble in hot water in all proportions.
They deliquesce when exposed to air, yielding an oily liquid. Concen-
trated solutions of calcic chloride boil at a much higher temperature
than pure water, and are employed in the laboratory as baths, when
constant temperatures above 100° C. (212° F.) are required. In vcumo
over sulphuric acid the crystallized salt parts with 4 aq. ; the remain-
ing 2 aq. can be expelled only. above 200° C.(392° F.). The anhy-
drous salt thus obtained is a white porous mass which, when heated to
redness, fuses and, if the fusion be performed with free access of air,
acquires an alkaline reaction, owing to the conversion of a small
Quantity of the chloride into oxide. On cooling, the fused salt solidi->
es to a colorless, translucent, crystalline mass, of sp. gr. 2.205^ The
anhydrous salt, both in the porous and in the fused form, absorbs water
with great avidity, and is therefore used for drying gases and liquids.
The porous form is best suited for drying gases, on account of the
greater surface which it exposes; whilst, in the case of liquids, fused
calcic chloride is preferred, as the porous variety would absorb too
much of the liquid to be dried. The anhydrous salt dissolves in water
00MPOUKD8 OP CALCIUM. 473
With evolution of heat. It is also soluble in absolute alcohol, forming
with it a crystallized compound^ which is decomposed hj water. The
aquate,
OaCl»60Hj^
dissolves in water with great absorption of heat, and when mixed with
snow in the proportion of 1.44 parts of the former to 1 of the latter,
produces a depression of temperature equal to — 54.9® 0. ( — 66.8 F.)
(Hammerl). — When a solution of calcic chloride is boiled with calcic
hydrate and filtered hot, it deposits on cooling white acicular crystals
of diocUeie oxychlorhydrate, < O ,70H2. — ^Anhydrous calcic chloride
(OaHo
absorbs gaseous ammonia with great avidity, forming the compound
OaClsjSMHj as a white powder, which, by the action of water or of
heat, or by exposure to the air, is resolveid into its constituents. Owing
to this property of absorbing ammonia, calcic chloride cannot be
employed in drying that gas.
Oalcie bromide, CaBr^ — Prepared like baric bromide (p. 461). Resembles calcic
chloride in its properties.
Calcic iodidCf Cal,. — Prepared like baric iodide (p. 462). Besemblef* calcic chloride
in most of its properties. When heated in contact with air it parts with the whole of
its iodine, yielding ^calcic oxide.
Calcic fluoride, CaF,, occurs abundantly in nature 9& fluor-spar^
sometimes massive, sometimes crystallized in octahedra, cub«s, and other
forms belongine to the regular system. When pure it is colorless,
but the mineral generally exhibits a variety of tints — blue, violet,
green, red, etc.— due to the presence of impurities. It also occurs
in the ashes of plants, in bones, and in the enamel of the teeth. It is
formed as a granular powder when calcic hydrate or carbonate is di-
gested with aqueous hydrofluoric acid, and as a gelatinous precipitate
when a soluble fluoride is added to the .solution of a calcium salt. It
can be artificially obtained in microscopic octahedra by heating the pre-
cipitated salt with very dilute hydrochloric acid for several hours in
sealed tubes to 240° C. (464° F.), or by heatingcalcic silicofluoride
with a solution of calcic chloride to 250° C. (482° F.). It dissolves in
2000 parts of water at 16° C. (59° F.), and is somewhat more soluble
in dilute acids. Fluor-spar phosphoresces in the dark when heated.
At a red heat it fuses without decomposition. Fluor-spar is employed
as a flux in various metallurgical operations. The brilliantly colored
varieties are manufactured into ornamental vases, dishes, and other
articles.
Oaleic silieofiuoridey SiCaFe,20H,.— Prepared by dissolving calcic carbonate in hy-
drofluosilicio acid and evaporating to the crystallizing point. Soluble, monoclinio
crystals.
474 INORGANIC GHEBOBTRY.
COMPOUNDS OF CALCIUM WITH OXYGEN.
Calcic oxide^ . . OaO. Ca=0.
OV /^
Oalcic peroxide, . OaQ > . Cacf | .
Calcic oxibe {QuioJdime)^ CaO. — ^Thia sabstance is prepared on a
large scale by burning limestone or chalk (impure calcic <airbonate) in
kilns. In the continuous process of lime-burning, now frequently em-
ployed, the limestone mixed with coal is introduced at the top of the
furnace, and the quicklime withdrawn at the lower part. Calcic oxide
may be obtained on a small scale by strongly heating pure marble or
calc-spar in a crucible with a perforated bottom, this arrangement being
adopted to allow the furnace gases to pass over the heated carbonate,
and thus assist the decomposition by carrying off the carbonic anhydride
as fast as it is evolved. In an atmosphere of carbonic anhydride calcic
carbonate may be heated to whiteness without change. Calcic oxide
forms a white amorphous mass, of sp. gr. 3.08. It is infusible at the
highest temperatures which can be artificially produced. When heated
in the oxyhydrogen flame, it emits an intense light, this arrangement
constituting the so-called lime-light. When exposed to the air, it
absorbs water and carbonic anhydride, and is converted into carbonate.
It combines with water to form calcic hydrate : when large pieces of
lime are moistened with water, they speedily become very not, give off
steam, and crumble to a white powder — a process which is known as
the slaking of the lime. Quicklime is employed in the laboratory for
drying gases and liquids.
OiZctc peroxide^ C$Lq | . — Prepared like stronlic peroxide (p. 469), which it closelj
resembles.
COMPOUND OF CALCIUM WITH HYDROXYL.
Calcic hydrate {slaked lime), OaHoj, is obtained as above by
slaking lime with water. It forms a white amorphous powder, of sp.
gr. 2.078. It is sparingly soluble in water, and less soluble in hot than
in cold water, one part of the hydrate dissolving in 600 to 700 parts of
water, at ordinary temperatures, and requiring twice that quantity at
100° C. (212° P.). The solution, which is known as lime-water, has an
alkaline reaction, and absorbs carbonic anhydride from the air, forming
a precipitate of insoluble calcic carbonate; when evaporated in vacuo,
it deposits small tabular or prismatic crystals of calcic hydrate. When
lime-water is prepared from ordinary lime, it is best to treat the slaked
lime several times with water in order to remove traces of baric and
strontic hydrates and soluble salts of the alkalies, with which it is
usually contaminated, before using it to make the solution. Milk of
Ume is cakic hydrate mixed with a quantity of water insufficient for its
OOMPOT7NDB OF CALCIUM. 476
solutiouy and thus formiDg a thick milky liquid. At a red heat calcic
hydrate is decomposed into calcic oxide and water. When made into
a paste with water and exposed to the air^ it gradually solidifies to a
hard mass, and the action is more rapid when sand is mixed with the
lime. Such a mixture of one part of freshly slaked lime, made into a
paste with water, and three or four parts of sharp sand, constitutes or-
dinary building mortar. The hardening or setting of mortar is due to
the formation of calcic carbonate and not, as was formerly supposed, to
a gradual combination of the sand with the lime to form calcic silicate.
The sand merely acts by its mass in preventing a too great contraction
of the calcic hydrate whilst setting. Hydraulic moiiar or Roman
cement, which has the property of setting under water, is prepared from
a limestone containing silica or clay (aluminic silicate). This limestone
requires care in burning: if the temperature be permitted to rise too
high the lime is vitrified and will not slake. The lime thus prepared
consists of a mixture of calcic and aluminic silicates, and combines with
water, without sensible elevation of temperature, to form a hard m^ss
upon which water has no further action. Portland cement is a hy-
draulic mortar prepared from chalk and clay found in the valley of the
Medway. Lime is also used in tanning for removing hair and wool
from skins ; in the preparation of the caustic alkalies (p. 415) j in sugar
refining, for precipitating acids and nitrogeneous substances from the
juice ; and as a manure, in order to render clay soils lighter.
OXY-SALTS OF CALCIUM.
NO
Calcic kitrate, ^qK^slo^'jAOH^, occurs as an efflorescence on
moist walls, particularly in stables and other places where there is much
organic refuse. It is contained in fertile soil, and in great quantity in
the soil of nitre plantations (p. 214). It may be prepared by dis-
solving the carbonate in nitric acid. Calcic nitrate is deposited, by
slow evaporation from concentrated aoueous solutions, in monoclinic
crystals with 4 aq. The anhydrous salt is a white deliquescent mass.
It is soluble also in alcohol.
Oalcie nitrite, JjQCao''',OH,.— Prepared like the barium salt (p. 464). Colorless,
yery soluble prisms.
r OCl
Ckdcic chhraUf | ^ Cao'',20H,.— Prepared like the barium salt (p. 465. See also
I OCl
preparation of potassic chlorate, p. 182). Very soluble, deliquescent crystals.
OCl
Calcic hypochlorite, oni^*' ^ diflScult to prepare in a state of
purity. It is formed, along with calcic chloride, when chlorine is
passed into cold milk of lime :
20aHo, + 2C1, = Jgjca + OaCl, + 20H,.
Galcic hydrate. Calcic Calcic Water.
hypochlorite. chloride.
476 INOBOAKIG CHEMISTRY.
Bleaching powder or chloride of lime, the substanoe obtained by the
action of chlorine upon dry slaked lime^ was formerly considered to be
a mixture of calcic hypochlorite with calcic chloride ; but most chem-
ists at present r^ard it as calcic chloro-hypochlorite, Ca(OCl)Cl :
OaHo, + CI, = Oa(OCl)Cl + OH,,
Caldo Calcic chloro- Water,
hjdrate. hypochlorite.
The dry slaked lime is spread in a layer on the floor of a long, low-
roofed chamber, of lead or flagstones, into which the chlorine is pafted.
In practice it is not found possible to efiect the absorption of the entire
quantity of chlorine corresponding to the above equation : the commer-
cial product contains from 20 to 35 per cent, of available chlorine — ^that
is, chlorine which is liberated as such when the bleaching powder is
treated with sulphuric or hydrochloric acid :
+ ci^
Oa(OCl)Cl
+ 80,Ho, =
= BO,Cao''
+ OH,
Calcic chloro-
Sulphuric
Calcic
Water.
hypochlorite.
acid.
sulphate.
Water converts calcic chloro-hypochlorite into a mixture of calcic
chloride and calcic hypochlorite :
20a(OCl)a = OaCl, + Oa(OCl),.
. Calcic chloro- Calcic Calcic
hypochlorite. chloride. hypochlorite.
A solution of bleaching powder, filtered from the unattacked calcic
hydrate which the commercial product always contains, and evapo-
rated in t'flcwo, deposits crystals of calcic hypochlorite of the formula
Ca(OCl)2,40H,. Owing to its instability, this salt is difficult to obtain
pure. Bleaching powder is a white powder with a faint odor of hypo-
chlorous acid. When heated to redness, it evolves oxygen with forma-
tion of calcic chloride. Concentrated solutions also give ofl^ oxygen on
boiling, and even dilute solutions may be made to part with the whole
of their oxygen by boiling them with a small quantity of the hydrates
of cobalt, nickel, manganese, iron, etc. (p. 161). Inr closed vessels it
undergoes decomposition from causes not understood, this decomposition
occasionally taking place with such violence as to give rise to explosions.
Its chief employment is in bleaching. In this operation the cloth is
first dipped in a dilute solution of bleaching powder and afterwards
passed through very dilute sulphuric or hydrochloric acid. The hypo-
chlorous acid is thus liberated in presence of hydrochloric acid — the
latter being either added as such or set free from the calcic chloride by
the sulphuric acid — and these two acids mutually decompose each other
with liberation of chlorine (p. 180), which in the moist state destroys
the organic coloring matter, and thus bleaches the cloth. Chloride of
lime is also used as a disinfectant.
Similar bleaching compounds are formed by the action of chlorine
upon baric and strontic hydrates.
CSOMPOUNDB OF CALdUK. 477
Calcic carbonate, OOCao". — ^This compound occurs abundantly
and widely distributed in nature, in the crystallized form as oaldte or
calc-sparsLndarragonitef in crystalline masses as niarble, and in an amor-
phous or crypto-crystalline condition as liTnestone and chalk ; also in
coral, shells of molluscs, egg-shells and bone-^h. It is an important
constituent of soils and is contained in nearly all spring and river water.
It is precipitated from solutions of calcium salts by the addition of an
alkaline carbonate. Calcic carbonate is dimorphous, occurring in
rhombohedral crystals of sp. gr. 2.70 to 2.75 as calcite, and in rhombic
prisms of sp. gr. 2.92 to 3.28 as arragonite. It is precipitated from hot
solutions as a fine crystalline powder displaying the forms of arragonite ;
from cold solutions it is deposited as an amorphous powder which
gradually becomes crystalline, assuming the forms of calcite. It is in-
soluble in pure water, somewhat soluble in water containing carbonic
anhydride, giving rise to what is known as the temporary hardne88 of
vmter. The solubility is due to the formation of dihydrie calcic carbonate,
jjQTT Cao", which, however, can exist only in solution. On boiling
the solution this salt decomposes into carbonic anhydride, which is
expelled, water, and insoluble calcic carbonate; and the temporary
hardness is thus removed. The removal of the temporary hardness
may also be effected by adding lime-water as long as a precipitate of
calcic carbonate is formed. The solution of dihydrie calcic dicarbonate
also parts with its carbonic anhydride on exposure to the air, depositing
calcic carbonate. In this way the various calcareous deposits, such as
calcareous tufa, stalactites, etc., from natural waters are formed. Some-
times the solution yields six-sided prisms of the formula 0OCao",60H2,
which part with their water of crystallization at 19° C. Calcic carbon-
ate is more readily decomposed at a red heat into oxide and carbonic
anhydride than baric and strontic carbonates (see preparation of calcic
oxide, p. 474).
Calcic sulphate, BOgCao". — The anhydrous salt occurs as the
mineral anAydn<6, either in rhombic crystals, or in crystallo-granular
masses. More commonly, however, calcic sulphate is found in the hy-
drated condition as tetrahydt-ic calcic sulphate (BHo^Cao" = BOjCao",-
2OH2) in the mineral gypsum, either in monoclinic prisms as selenite,
or in fibrous satiny masses as satin-spar, or in the crystallo-granular
form as crystalline gypsum or alabaster. It occurs in the soil and in
most natural waters. The tetrahvdric sulphate is precipitated as a
crystalline powder from solutions of calcium salts, if not too dilute, by
the addition of sulphuric acid. Gypsum is sparingly soluble in water,
requiring 487 parts of water at 0° C. (32° F.) and 433 parts of water
at 35° C. (95'' F.) for solution. Above 35° C. its solubility again
decreases, one part of the salt requiring more than 500 parts of water at
100° C. (212° F.) to dissolve it. It is much more soluble in dilute
acids and in solutions of ammoniacal salts and of sodic chloride than
in pure water. Solutions of sodic thiosulphate dissolve it very readily.
It parts with most of its water of hydration between 100° C. (212° F.)
and 120° C. (248° F.), forming burnt gypsum or plaster of Paris. If
the salt which has been dehydrated at this temperature is mixed with
N
478 I.VOBGANIG GHEinKTBY.
water, it combines rapidly with the water to form the tetrahydric sul-
phate, and if the water has been added only in quantity sufficient to
form a thin paste, the whole speedily solidifies to a white mass, at the
same time underj^^ing slight expansion. Upon these properties the
use of plaster of Paris in taking casts is based, the property of expand-
ing during solidification causing it to fill the crevices of the mould and
thus reproduce all the details of a design. Ordinary plaster of Paris
is much more soluble in water than gypsum, requiring for solution only
82 parts of water at 22"^ C. (71.6° F.). A solution prepared by shaking
the salt with water at the ordinary temperature and quickly filtering,
soon deposits crystals of gypsum. If gypsum is heated to above
200° C. (392° F.) it parts with the whole of its water of hydration,
yielding the anhydrous sulphate; but in this condition it combines only
very slowly with water, and does not solidify. Gypsum which has
been thus overheated is said to be dead burnt. If it is dehydrated at a
temperature of 600° C. (932° F.), it also takes up water very slowly,
the process requiring several weeks for completion, but the product of
re-hydration is a hard mass, denser than ordinary gypsum, and trans-
lucent like alabaster ; and this mass may be converted into ordinary
plaster of Paris by dehydrating at a low temperature. At a red heat
anhydrous calcic sulphate fuses, solidifying to a crystalline mass. A
solution of an alkaline carbonate converts gypsum at ordinary tempera-
tures into calcic carbonate. When heated with concentrated sulphuric
acid to 100° C. (212° F.), it is converted into a porous crystalline mass
of dihydric calcic mdphate, SO^H ^*^"> whilst part goes into solution,
and, on cooling, separates in flat prisms with a silky lustre, having
the formula qq^lj Cao",2BOjHo,. Both these salts are decomposed
by water into gypsum and sulphuric acid.
OaUk dipotamc tulphaU, oo'Ko^^^'*^^*' — '^^^ double salt occurs native in mono-
clinic crystals as wngenite. If equal parts of plaster of Paris and anhydrous potassic
sulphate be mixed with less than their weight of water, the whole suddenly solidifies.
By employing a larger proportion of water a mixture may be obtained which yields
casts exhibiting a polished surface.
Oodeic disodic atdphaUj ao'v!!^^^^ occurs native as glauberiU. An aquate of the
formula gQ*j^^Cao''',20H, is obtained in acicular ciystals by heating a mixture of
plaster of Paris and sodic sulphate with water.
Oaleic sulphite, S0Cao''',2OH^— Prepared like the barium salt (p. 466), which it
also resembles.
Calcic dilhionate, | g^'Cao''',40H^— Prepared like the barium salt (p. 278). Very
soluble, hexagonal crystals.
OoUeic thisouLphaJte, SO/ g,/Ca^ ,60H,.— P^par«d like the strontium salt (p. 470).
Triclinic prisms, readily soluble in water.
POCao"
Calcic orthophosphate, pqq r^Cao", occurs as osteolUe and
aombrerite. When crystallized with 2 aq. it forms the mineral omUhite.
COMPOUNDS OP CALdUM. 479
As a double phosphate and fluoride of the formula PsOsCao"^( j,Ca" ) ,
in which a portion of the fluorine is sometimes isomorphously replaced
by chlorine, it occurs in hexagonal crystals as the mineral apatite. Phos-
phoriie is an impure and massive apatite. Calcic orthophosphate is con-
tained in the soil, from which it is taken up by plants, and thus finds
its way into the bodies of animals. It forms the chief constituents of
the bones and teeth of animals, of the scales of fishes, etc. Coprolites,
supposed to be the fossilized excrement of extinct animals, consist for
the most part of calcic orthophosphate. Calcic orthophosphate is ob-
tained as a white gelatinous precipitate by adding ordinary (monohydric)
sodic phosphate in excess to a solution of calcic chloride, previously
rendered alkaline with ammonia. It is almost insoluble in water, but
is decomposed by continued boiling into an insoluble basic salt and an
acid salt which dissolves. It is moderately soluble in solutions of various
salts and in water containing carbonic anhydride. By means of this
last property, the calcic phosphate contained in the soil is rendered sol-
uble, so as to be assimilable by plants. It is readily soluble in hydro-
chloric, nitric, and acetic acids, and is reprecipitated by ammonia from
the acid solutions. — Hydrio caldo orthophosphate^
POHoCao'',20H2,
occurs native as brvshite. It is obtained as a crystalline precipitate on
adding calcic chloride to an acetic acid solution of ordinary sodic phos-
phate.— Tetrahydrio oaldo orthophosphate,
POHOjp „ QTT
is prepared by evaporating a solution of either of the preceding salts
in aqueous phosphoric acid. It forms rhombic tables or lamince. A
small quantity of water converts it into insoluble monohydric phosphate
and free phosphoric acid, but the precipitate disappears if left in contact
with the liquid and stirred with it from time to time. If shaken up
with a hundred times its weight of water, tetrahydric calcic phosphate
speedily dissolves, but on boiling the solution, the monohydric phos-
pnate separates as an anhydrous precipitate, and the liquid contains
phosphoric acid. Sodic acetate also precipitates the monohydric phos-
phate from the solution. The tetrahydric phosphate gives off its water of
crystallization at 100° C. (212° F.) ; when heated to 200° C. (392° R)
it parts with the elements of water, and is converted into a mixture of
calcic pyrophosphate and metaphosphoric acid :
2PAHo,Cao" = PACao'', + 2PO,Ho + 30H„
Tetrahydric calcic Calcic Metaphosphoric Water,
orthophosphate. pyrophosphate. acid.
but when the mixture is heated to a higher temperature, pure calcic
metaphosphate remains :
480 INOBOANIO CHEldSTBT.
PACao", + 2POjHo = 2PACao" + OH^
Calcic Metaphoephoric Calcic Water,
pyrophosphate. acid. metaphosphate.
The so-called superphosphate qf lime is a mixture of the preceding salt
with calcic sulphate, and is obtained by actin? upon bone-ash or a native
calcic phosphate with two-thirds of its weight of sulphuric acid. It is
employed as a manure, and also in the manufacture of phosphorus.
Ocdeic hypophosphUe, pHHo^^^^' ^ prepared by boiling phoephorus with milk of
lime:
SCaHo, + 2P4 + 60H, = sJ^j^^Cao'^ -f 2PH,.
Calcic Water. Calcic Phosphoretted
*hydrate. hypophosphlte. hyarogen.
On evaporating the solution the salt is obtained in monoclinic prisms. When heated
it evolves phosphoretted hydrogen and water, leaving calcic pyrophosphate :
^HHo^^"' == 2PH, + PACao^'t + OHi.
Calcic Phoephoretted Calcic Water,
hypophosphlte. hydroden. pyrophosphate.
Calcic hypophosphlte is used in medicine.
Silicates of Calcium, — The following silicates of calcium occur in
nature :
Wollastonite. Calcic silicate, BiOCao".
Okenite. Tetrahydric calcic disUicaie, . . . SijOHo^Cao".
Gurolite. Tetrahydric dicalcic trisilicate, . . BijOjHo^Cao",.
Xonaltite. Dihydric tetraccUcic tetrasilicatey . . Bi^O^HogCao"^.
Most of the natural silicates are compound silicates of calcium with
other metals.
Glass.
The several varieties of glass consist of amorphous mixtures of po-
tassic. or sodic silicate with calcic or plumbic silicate. Bohemian or
potash-glass is a potassic and calcic silicate. It is less fusible and resists
the action of acids and alkalies better than the other varieties, for which
reasons it is largely used for laboratory vessels and for combustion tub-
ing. Crown-glass {soda-glass, window-glass, plate-glass) is a sodic and
calcic silicate. It has a bluish-green tinge, which may be seen on the
edge of a sheet of window-glass. Bottle-glass is merely a crown-glass
manufactured from commoner materials. Its dark-green color is due
to the presence of iron, and its brown or black appearance to finely
divided carbon. It also contains alumina. Flint-glass is a potassic
and plumbic silicate. It is remarkable for its density, lustre, and re-
fracting power. It is the most fusible variety of glass, and is most
readily attacked by chemical reagents.
The silica employed in glass-making is introduced as quartz, white
sand, pulverized flints, or ordinary sand, according to the quality of the
COMPOUNDS OF CALCIUM. 481
glass required. The alkalies are added as pearl-ash (potassic carbonate)
and as purified soda-ash (sodic carbonate). For luferior varieties of
soda-glass^ salt cake (sodic sulphate) is substituted for sodic carbonate ;
in this case carbon is added, which reduces the sulphate to sulphite,
the sulphurous anhydride being then expelled by the silicic anhydride
at the high temperature at which the glass is prepared. The calcium
is added in the form of marble^ limestone, or chalk. In Bohemia, wol-
lastonite, a native calcic silicate, is employed. In the case of flint-glass^
the lead is added as red-lead, white-lead, or litharge, the first of these
being employed for the finer sorts.
The iron which is invariably present, even in the purest materials,
would, if uncorrected, impart to the glass a green tinge, due to the
formation of ferrous silicate. In order to obtain a colorless glass, an
oxidizing agent is added to the mixture to convert the ferrous into a
ferric salt, the latter having only a faint yellow tinge, which, when the
iron is present in small quantity, is not perceptible. The oxidizing
agents most frequently employed in the case of the various sorts of
calcium-glass, are manganic peroxide, arsenious anhydride, and potassic
or sodic nitrate; whilst, in the case of flint-glass, red-lead is used. The
manganic dioxide decolorizes not only by its oxidizing action, but also
by its proj^erty of producing a violet tint, complementary to the green
of the ferrous silicate, the two colors thus neutralizing each other.
The materials are mixed with a certain quantity of broken glass or
"cullet," and are then frittedy or heated to a temperature at which they
begin to agglomerate. In this process of fritting, moisture and gases,
such as carbonic anhydride, are expelled, and the frothing in the subse-
quent fusion is thus greatly diminished. The mass is then fused in pots
made of a very refractory fire-clay, the fusion being continued until all
the bubbles of gas have escaped, and the contents of tlie pot form a
homogeneous liquid. The temperature is then allowed to fall until the
glass becomes sufficiently viscid to permit of its being worked — either
by the glass-blower, or by rolling it into plates, as in the case of plate-
glass, or by pressing into moulds.
Glass which has been suddenly cooled after fusion possesses the
singular combination of properties of resistance to fracture on the one
hand, and on the other, extraordinary brittleness as soon as incipient
fracture has, by scratching or otherwise, been induced. These proper-
ties are exhibited in a high degree by the so-called RuperVs drops,
which are prepared by allowing melted glass to fall in drops into cold
water. The glass solidifies in the form of elongated, pear-shaped drops,
rounded at one end and produced to a thin tail at the other. The thick
portion of these drops may be subjected to considerable violence — by
pressure or by hammering — without breaking ; but if the end of the
thin tail be nipped off, the whole drop disintegrates with a slight ex-
plosion, and is converted into a fine powder.
The tenacity of glass thus treated is probably due to the wholly amor-
phous condition of the mass — the glass being cooled before the mole-
cules have time to arrange themselves in the manner necessary to the
production of a crystalline structure. Ordinary annealed glass (see
below) is for the most part amorphous, but that it is also to some ex-
31
482 IKOBGAKIC CHEMISTRY.
tent cryBtalline may be shown by etching the surface with hjdroflaoric
acid, when the crystalline structure becomes visible under the microscope.
It will also be shown further on that glass may be made to acquire a
highly crystalline structure by protracted heating to its softening point,
a process the reverse of the above. The effect of a crystalline structure
in diminishing tenacity depends upon the disturbance of the homo-
geneity of the mass which the growth of crystals within it necessitates,
and, further, upon the unequal tenacity of most crystals in various
crystallographical directions, a property which is manifested in the pro-
duction of cleavage surfaces (see Crystallography, p. 131).
On the other hand, the parts of a mass of glass thus suddenly cooled,
are in the state of tension or strain. Owing to the low conducting
power of glass, the outer portions cool and solidify first, and in this
way the inner portions, which cool later, are prevented from contract-
ing to the extent which they otherwise would. The moment this
state of unstable equilibrium is disturbed — as in the above experiment,
by nipping off the tail of the drop — the whole system breaks down,
and the potential energy of this tension expends itself in the disintegra-
tion of the mass.
The same phenomenon is exhibited, although in a lesser degree, in
the case of articles of glass which have been cooled by exposure to air.
Such articles are apt to crack when scratched or when exposed to sud-
den change of temperature. A bottle of thick unannealed glass may
be broken to fragments by dropping into it a small sharp fragment of
flint.
In order to prevent fracture from this cause, all articles of glass are
subjected to a process of very slow cooling, termed annealing^ in a
suitable furnace. In this way the cooling and solidification occur
homogeneously throughout the mass, the molecules can arrange them-
selves in the positions which they would naturally assume, and the
state of strain cannot arise.
A peculiar process, intended to replace that of annealing, and at the
same time to impart to the glass new and valuable properties of dura-
bility, has been introduced within the last few years by De la Bastie.
The glass, heated almost to redness, is dipped into oil or paraffin,
previously heated to 300° C. (672° F.), and is then allowed to cool
slowly. Glass which has been subjected to this treatment, and which
is known 9A toughened glass, is much less fragile than ordinary annealed
glass : it resists sudden changes of temperature better, and is not so
readily broken by rough usage. When broken, however, by a hard
blow, it splits up into innumerable fragments. In like manner, a sheet of
toughen^ glass cannot be cut with a diamond, as the whole instantane-
ously disintegrates. The glass is, therefore, to some extent at all events,
in a state of internal strain similar to that of the Rupert's drops.
Indeed, cases have occurred in which articles of toughened glass have,
suddenly and without apparent cause, exploded with some violence.
The following table contains the results of the analysis of various
kinds of glass:
COMPOTJND6 OF CALCIUM.
Composition of various kinds of Olass.
483
~
Bohemian glass.
Crown glass.
Bottle-glass.
Flint-glass.
a.
6.
e.
d.
e.
/
9-
h.
8lO„ . . .
OK^ . . .
ONa^ . . .
CaO, . . .
A1,0„. . .
Mg(^ . . .
• Pe,0,.. . .
MnO, . . .
PbO, . . .
12.7
2.5
10.3
0.4
as"
a2
69.2
16.8
3.0
7.6
1.2
2.0
a5
62.8
22.1
69.2
8.0
3.0
13.0
f3.6
\ 0.6
ll.6
60.0
69.0
1.7
lao
19.9
1.2
a5
7.0
51.9
13.8
42.5
11.7
3.1
22.3
8.0
12.6
• 2.6
0.6
1.8
4.0
1.2
83.3
43.5
98.1
99.3
100.0
99.0
98.6
99.3
99.0
100.0
o. Hard Bohemian glass. 6, Softer Bohemian glass, c, Bohemian crown-glass.
dy Qerraan crown-glass, e, French bottle-glass. / English bottle-glass, g^ English
flint-glass, h^ Guinaud's glass for optical purposes.
Certain kinds of glass, when exposed for some time to a temperature
at which they soften, acquire a crystalline structure, and become opaque.
This process of change, known as devUrifiealion, occurs most readily in
lime-glass which contains an excess of silica. Flint-glass does not
devitrify! When glass is imbedded in sand or gypsum to prevent
chjinge of form, and heated strongly for several hours, it is converted
into a white opaque mass, known as R^aumur^s porcelain. Glass which
readily devitrifies cannot be worked before the blowpipe.
Colored glasses are obtained by the addition of various oxides to the
lass. The coloring oxides mostly employed are the following :
Red, cuprousoxide, alsopurple of Cassius. Violet, manganic dioxide.
Blue, cobaltous oxide. Green, cupric oxide, chromic oxide, ferrous
oxide, the latter producing a dull bottle-green. Yellow, antimonic
oxide. Yellow, with a greenish fluorescence : uranic oxide.
COMPOUNDS OF CALCIUM WITH SVLPHUR.
Caleie nUpkide, CaS^^.— Prepared like the barium compound (p. 467). White i
which in moist air gradually evolves sulphuretted hydrogen. Luminous in the dark
after exposure to light (see p. 467).
Calcic diavlphidc, ^^^'^ \ i^^st '^ deposited in jellow crystals from the solution
obtained by boiling milk of lime with sulphur and filtering hot
COMPOUND OF CALCIUM WITH PHOSPHORUS.
Calcic phosphide, ^^^,Ca,(?). — This compound has not been prepared pure. It is
formed by the direct combination of metallic calcium and phosphorus, when the two
sabstances are heated together under petroleum. It may be obtained mixed with calcic
pyrophosphate by passing the vapor of phosphorus over lime heated to redness :
14CaO + 14P
calcic
oxide.
S^P^^Ca, + 2PACW,.
Calcic Calcic
phosphide. pyrophosphate.
484 IKORGAKIO CHEMISTRT.
The mixtare thus obtained* which forms a reddish-brown mass, is employed in the
preparation of liquid phoephoretted hydrogen (p. 343). It also contains trtetdcic dt"
pkoiphidef PjCai.
Gbkeual Pfoperties and Reactioks of the Compounds of
Calcium. — The calcium salts, as a rule, closely resemble in their
properties those of barium and strontium. Those formed with color-
less acids are colorless. Calcic nitrate and calcic chloride are both
soluble in absolute alcohol. From solutions of calcium salts alkaline
carbonates precipitate calcic carbonate. The sulphate of calcium is
more soluble than that of strontium ; in dilute solutions of calcium
salts sulphuric acid and soluble sulphaies produce a precipitate only on
addition of alcohol. Amnionic oxalate pre<'ipitates white calcic oxalate,
soluble in hydrochloric and in nitric acid, insoluble in acetic acid.
Calcium compounds color the non-luminous flame yellowish-red. The
flame spectrum is complex ; the two most characteristic lines are Caa in
the orange, and Ca/5 in the green.
On Potable Water and on the Impurities occurring in
Natural Waters.
In describing the properties of water (p. 173), it was mentioned that
natural waters always contain impurities; and as some of the most
important of these are compounds of two of the metals belonging to
the section under consideration, it will be convenient to return here to
the subject in order to complete the chemical history of water.
Pure water never occurs in nature ; as soon as it quits the vaporous
condition, and assumes the form of clouds and rain, it becomes more or
less contaminated by atmospheric impurities. When it reaches the
earth, it flows over surfaces, or percolates through strata, more or less
soluble, and tlius acquires further impurities in addition to, or some-
times in the place of, those which it had previously contracted from the
atmosphere. It thus becomes, in some cases more, in others less, suit-
able for domestic use. The nature of the changes which water suflTers
from such influences must obviously depend, to a great extent, upon
the character of the geological formations over or through which it
passes. If the formation be hard and insoluble, then little saline or
other matter is taken up. Thus the River Loka, in Sweden, contains
only 0.07 part of solid matter in 100,000 parts of water. Loch Kat-
rine contains 3.2 parts per 100,000, Ullswater Lake 3.9 parts, and the
Dee at Aberdeen 5.7 parts per 100,000 parts of water. As a rule,
however, water meets with more soluble matter than this, and the pro-
portion generally varies from 7 to 50 parts in 100,000 parts of water.
Thus the Thames and Lea contain about 30 parts, and the water of
deep wells sunk into the chalk about 40 parts, per 100,000.
An excessive amount of these foreign matters renders the water
unpalatable, and constitutes it a mineral or abnormal water. Such ac-
cumulations of soluble saline matter take place in the ocean, which
contains from 3140 to 4000 parts per 100,000, and in lakes without
outlet. Thus the Dead Sea, which is 1312 feet below the level of the
Mediterranean, and is fed by the Jordan and six other streams (con-
taining on the average 104 parts of soluble solid matter per 100,000)
POTABLE WATERS. 485
contains 22,857 parts of solid matter per 100,000. And the Elton
lake in Russia contains 27,143 parts per 100,000, although upwards of
200,000 tons of salt are annually extracted from it. '
We propose here, however, to confine attention chiefly to drinking
or ]>otable water — a subject which is, year by year, acquiring an in-
creased sanitary importance.
Numerous researches, made by both' physiologists and chemists, have
led investigators to the conclusion that several, at least, of those dis-
eases, which are propagated in the manner of epidemics, diffuse them-
selves by living germs or spores, which, finding a suitable nidtia in the
bodies of animals, there multiply and produce that specific disturbance
of the normal vital functions which characterizes a disease of the
zymotic class. It is indeed in consequence of the extensive prevalence
of this view respecting the mode of propagation of such diseases that
the term zymotic (from (^ufx6af, I ferment) has come to be almost uni-
versally employed to designate them.
Tjong continued observations and carefully compiled statistical records
have conclusively demonstrated that drinking-water is the chief medium
through which zymotic diseases, especially cholera and typhoid fever,
are propagated. In these latter diseases the infectious or zymotic
matter is contained in the discharges from the intestinal canal of the
patient. Many of our arrangements for disposing of these secretions
have the effect of diffusing them through water, and the drinking of
such polluted water not unfrequently conveys the infection to whole
communities. Shortly stated, it is absolutely necessary for the propa-
gation of cholera and typhoid fever, that the excrements of persons
suffering from these diseases should be swallowed by other persons.
That such an unspeakably disgusting mode of infection is not only
possible, but imminent over a very large proportion of the inhabitants
of Great Britain, is conclusively prov^ by the numerous analyses of
the water used by them for drinking. So far from the horrible prac-
tice just indicated being exceptional, it is the rule. It is a widely
spread custom, both in towns and villages, to drink either the water of
rivers into which the excrements of man are discharged, or the water
from shallow wells which are largely fed by soakage from middens,
sewers, or cesspools. Thus many millions of the population are daily
exposed to the risk of infection from typhoidal discharges, and periodi-
cally to that from cholera dejections.
It would obviously be of the very highest importance to mankind,
if the presence of cholera or typhoid poison in water could be demon-
strated by chemical or microscopical analysis. This is, however, at
present impossible. It is only by their action on human beings that
their presence can be proved. But, chemical analysis can show us the
presence, in water, of excremental matter, or of the characteristic
products of its decomposition, although it cannot distinguish between
normal and infected excrement.
From this point of view, therefore, the analyical examination of
water assumes an importance second to no other application of chem-
istry. It would be out of place, however, in this work to describe the
mode of performing these analyical operations, and we shall therefore
486
INORGANIC CHEMISTRY.
confine ourselves to an enumeration of the data obtained in watev
analysis and to the interpretation of these data.
Water Analysis, — ^The exhaustive chemical examination of a sample
of water is one of the most tedious and troublesome operations known
to chemists. It requires weeks, sometimes even months, for its oomT
pletion. This arises partly from the great multiplicity of separate sub-
stances which may be present in the water, both in solution and in
suspension, partly from the very minute proportion in which these
substances sometimes exist, and partly on account of the difficulties
attending their exact determination, when they are difiused through
vast volumes of water. Such an exhaustive examination includes:
1. The extraction and separate volumetric measurement of the dis-
solved gases.
2. The separate determination of the weight of each constituent of
the saline matters in solution.
3. The determination of the two chief elements of the organic matters
in solution.
4. The separation of the suspended matters, if any, and the determi-
nation of their total weight when dry.
6. The separation and determination of each mineral constituent of
the suspended matters.
6. The separation and determination, as far as possible, of each or-
ganic constituent of the suspended matters.
Fortunately, many of the more tedious and laborious of these opera-
tions may be omitted, if the object of the analysis be only to ascertain
the suitability or otherwise of the water for domestic or manufacturing
purposes. Thus, the extraction and volumetric measurement of the
gases may be safely dispensed with ; since, in the present state of our
knowledge, the gaseous constituents of water throw but little light upon
its character. The existence of dissolved atmospheric gases in water
doubtless adds to its platability ; recently boiled water, for instance, has
a notoriously flat and vapid taste, but the solution of these gases by
water is so rapid as almost to preclude the possibility of lack of aeration
in natural waters. This is seen from the following comparison of the
proportional volumes of atmospheric gases expelled on boiling 100 cubic
centimetres of rain-water, Welsh and Cumberland upland surface water.
Loch Katrine water as delivered in Glasgow, Thames water as de-
livered in London, and water drawn from deep wells in the chalk, re-
spectively :
Volume and Composition of the Gases dissolved in 100 Oubic Cenii-
metres of Various Waters,
Rain
water.
Cumljer-
land
mountain
water.
Loch
Katrine
water.
Thames
water.
Deep
chalk well
water.
Nitrogen,
Oxygen,
Carlx)nic anhydride, .
1.308 C.C.
0.637 "
0.128 "
1.424 C.C.
0.726 "
0.281 "
1.731 C.C.
0.704 "
0.118 "
1.325 cc.
0.588 "
4.021 "
1.944 cc
0.028 "
5.520 «
2.073 "
2.431 "
2.548 "
5.934 "
7.492 **
POTABLE WATEBS. 487
A comparison of the numbers in the foregoing table shows that the
total volume of dissolved atmospheric gases differs but little, even in
waters from the most widely different sources. It was at one time sup-
posed that the proportion of oxygen in these gases was an important
item in the history of the water, and a deficiency of this gas was be-
lieved to indicate the presence of putrescent organic matters ; but the
subsequent discovery that deep well waters (in which putrescent or-
ganic matter is certainly not present) contained little or no dissolved
oxygen, deprived this analytical fact of much of its importance.
The large proportion of carbonic anhydride which is present in
Thames water and in deep chalk well water scarcely adds to the
effective aeration of these waters, because nearly the whole of this car-
bonic anhydride is in chemical combination with lime, and not in the
condition of dissolved gas.
The separate determination of the weight of each constituent of the
saline matters in solution is also rarely required. These constituents
have, with very few exceptions, no appreciable influence upon the whole-
someness of the water ; hence, in the great majority of cases, it is not
necessary to determine the weight of each. Certain of them, however —
ammonia, nitrates, nitrites, and chlorides — are very useful in tracing
the previous history of the water, and the separate determination of
these must, therefore, on no account be omitted. Moreover, if the
presence of lead, arsenic, or barium be suspected, these poisonous metals
must be carefully sought for, and, if found, their respective quantities
determined. The degree of hardness ought also to be ascertained in
all cases.
The separation and determination of each mineral constituent of the
suspendea matters may be dispensed with, unless poisonous substances
occur amongst them.
The sepamte determination of each organic constituent of the sus-
pended matter is of comparatively little use in the present state of our
knowledge, because it is impossible to distinguish, amongst the sus-
pended matters in water, those which are injurious from thosk which
are harmless. The really injurious organic suspended matters are
probably not merely organic but organized matters, entozoic ova, or
zymotic germs, capable of reproduction in the human body with the
simultaneous development of disease. Investigations of this class
belong rather to microscopical than to chemical analysis, but even mi-
croscopic research is not yet competent to reveal any facts of direct im-
portance in connection with such oi^nized suspended matters.
The microscope has rarely if ever discovered, even in the most pol-
luted drinking water, any germ or organism which is known to be
deleterious to human health ; but by showing the presence of living
oi^nisms in water, it proves, either that the water has not been so effi-
ciently filtered as to remove these organisms, or that it has subsequently
become polluted by them; and thus it is indirectly demonstrated that
the water has not been treated, preserved, or stored under such condi-
tions as would preclude the access of deleterious germs or organisms.
A microscopic examination of the suspended matters in potable waters
thus becomes indirectly of considerable importance.
488 INORGANIC CHEMISTBY.
The analytical determinatioDS, deemed sufficiently important to
warrant the expenditure upon them of the necessary time and labor,
are the following; those which are of primary importance being printed
in bold type:
In Solution.
1. Total solid matters.
2. Organic carbon, or carbon contained in the organic matter
actually present.
3. Organic nitrogen, or nitrogen contained in the organic mat-
ter actually present.
4. Ammonia.
6. Nitrogen as nitrates and nitrites.
6. Total combined nitrogen.
7. Estimation of the previous sewage or animal contamination.
8. Chlorine.
9. Temporary, permanent, and total hardness.
Jti Suspension.
10. Mineral matters in suspension.
11. Organic matters in suspension.
We have now to explain the object and significance of each of these
determinations.
1. Total Solid Matters in Solution, or Total Solid Impurities. — When
water is evaporated to dryness, there is left behind a solid residue con-
taining the mineral and organic matters with which the water had be-
come contaminated since its condensation from the atmosphere. Leav-
ing out of consideration the quality of the ingredients contained in
potable waters, the proportion of solia residue left on evaporation affords
an approximate, though rough, indication of the comparative purity of
such waters. On the one hand it may be safely concluded, that waters
leaving' very large residues on evaporation are unfit for domestic use,
whilst on the other, those containing very small residues are, on this
account alone, well adapted for such purposes, and but very rarely con-
tain amongst their constituents any which are seriously objectionable.
Not only do waters leaving small residues on evaporation generally
possess a superiority for domestic purposes, but they are also much more
valuable than less pure waters for a large number of manufacturing
purposes. Thus, for the feeding of steam boilers, their use precludes
the formation of incrustations, which not only seriously interfere with
the transmission of heat from the fuel to the water, but are probably a
frequent cause of disastrous explosions.
2. Organic Carbon. — From a sanitary point of view, the most im-
portant constituent of the total solids is organic matter, and various
processes have from time to time been devised for the quantitative de-
termination of this matter or of some of its constituents. The problem
is surrounded with unusual difficulties, and hitherto no method, worthy
of any d^ree of confidence, has been discovered by which the weight
of organic matter dissolved in water can be even approximately deter.
POTABLE WATEBS. 489
mined. Even of several analytical processes which do not pretend to
the estimation of the total weight, and aim at the quantitative deter-
mination of only some of the elemeitts of the organic matter, there is
only one which yields trustworthy results. This process is both trouble-
some and tedious, and requires considerable manipulative skill ; but it
is the only method which throws any light whatever upon the actual
pollution of water by organic matter. It consists in transforming by
combustion in close vessels the carbon and nitrogen of the organic mat-
ter into carbonic anhydride and free nitrogen, and then measuring the
respective volumes of these gases. By a simple calculation, the weights
of carbon and nitrogen contained in the original organic matter present
in the water can be arrived at, from these volumetric determinations,
with great precision. The weight of organic carbon, or carbon contained
in the organic matter found in different samples of water, indicates the
amount of organic matter with which the water is contaminated, but it
does not indicate the source, animal or vegetable, whence that organic
matter was derivrf. Cadeina paribtis, the smaller the proportion of
organic carbon, the better the quality of the water. Even if the source
of the organic matter be altogether vegetal, experience has shown that
a proportion of organic carbon larger than 0.2 part in 100,000 parts of
water is undesirable, because it renders the water slightly bitter and
unpalatable. A larger proportion of organic carbon, if it be contained
in animal matter, does not interfere with the palatability of the water,
but it exposes the consumer to the risk of infection, and potable water
which contains organic matter, even only partially derived from animal
sources, should not yield much more than 0.1 part of organic carbon
from 100,000 parts of water.
8. Organic Nitrogen. — The character of the organic matter con-
tained in potable water, that is to say, its animal or vegetable origin,
may in most cases be judged of by the relative proportions in which the
two elements, carbon and nitrogen, occur hi the organic matters. Hence
the necessity for determining the amount of organic nitrogen in waters
used for domestic purposes. This determination, taken in connection
with that of organic carbon, frequently affords information of great
value as to whether the organic matter is of animal or vegetable origin ;
and this information acquires additional importance and trustworthi-
ness when it is subsequently tested by a chemical investigation of the
previous history of the water as revealed by the proportions of the
chief products derived from sewage and animal matters, viz., ammonia,
nitrates, nitrites, and chlorine. The smaller the absolute quantity of
organic nitrogen, and the less the proportionate amount as compared
with organic carbon, the better is the quality of the water as regards
present or actual pollution, and the less likely is the water to contain
any organic matters of animal origin. In connection with this part of
the analytical investigation, however, it must l)e borne in mind that
vegetable organic matter is far from being destitute of nitrogen. Peat,
for instance, which is a form of v^etable matter least likely to contain
nitrogen, yields to water organic su&stances in solution containing much
nitrogen. Doubtless, different samples of peat vary in the nitrogenous
character of the soluble vegetable matter which they contain ; but, on
490 INOBOANIC CHEMISTRY.
the average, the proportion of nitrogen to carbon may be taken to be
N : C = 1 : 12, and it is found that such peaty matters dissolved in
water may, after prolonged exposure to oxidizing influences, lose carbon
so much more rapidly than nitrogen, as materially to increase the pro-
portion of the latter element to the former.
XLe following table shows the proportion of nitrogen to carbon in
waters containing organic matter of peaty origin :
Proportion of
carbon to 1 part
of nitrogen.
Unoxidized peaty matter contained in upland surface
water, 11.92
Peaty matter contained in upland surface water after
exposure to atmospheric oxidation in natural lakes
or artificial reservoirs, 5.92
Peaty matter contained in spring water, .... 3.21
Thus the proportion of carbon to nitrogen in the peaty organio mat-
ter of water decreases rapidly as oxidation progresses. After storage
for weeks or months in lakes it is reduced to one-half its original
amount; but after the water containing the peaty matter has been sub-
jected to the powerful oxidizing influences which accompany filtration
through porous strata, it reappears as spring water with a greatly aug-
ment^ proportion of ominic nitrogen, although the absolute quantity
has greatly diminished. In other words, large quantities of both carbon
and nitrogen have been oxidized and converted into mineral matter, but
the carbon has undergone this transformation more rapidly than the
nitrogen.
This concentration of nitrogen during oxidation assimilates oxidized
vegetable to unoxidized animal organic matter in chemical composition,
so far, at least, as the proportion between the chief elements, nitrogen
and carbon, is concerned. There is still, however, a considerable di&r-
ence in this respect between these two kinds of organic matter; but even
this disappears when the water containing animal organic matter is sub-
jected to oxidizing influences; for whilst vegetable organic matter suffers
a concentration of nitrogen during oxidation, animal organic matter
exhibits, as a rule, a concentration of carbon, and a diminution in the
proportion of nitrogen under the same influence.
Thus the proportions of nitrogen to carbon in soluble vegetable and
animal organic matters vary in opposite directions during oxidation ; a
fact which renders more difficult the decision as to whether the organic
matter present in any given sample of water is of animal or vegetable
origin. This difficulty can, however, be greatly diminished or entirely
overcome by an appeal to the previous history of the water as revealed
partly by a knowledge of its source, and of the kind of contamination
to which it has been exposed, and partly through the information af-
forded by chemical analysis. .In the first place, if the water is known
by an inspection of its source to have been polluted by animal matters,
and to have been subjected, after such pollution, only to the slight oxida-
tion effix^ted in rivers or streams, a portion at least of the organic matter
which it contains must have been derived from animal matter. For
POTABLE WATERS. 491
there is no river in Great Britain long enough to completely oxidize or
destroy the soluble animal organic matter present in polluted water. In
the second place, if the water is found, on analysis, to contain consid-
erable quantities of one or more of the mineral compounds — ammonia,
nitrates, and nitrites — into which animal organic matter is resolved
during its decomposition or oxidation, the inference may be drawn that
the soluble organic matter of such water is derived from animal souroes.
But this inference must only be provisional ; it must stand or fall by an
investigation into the source of the water ; for although the presence of
the products of the decomposition of animal matter indubitably con-
victs the water of previous pollution, yet it is obviously possible, from
the facts and considerations which have just been adduced, that the
whole of the original organic matter may have been oxidized and con-
verted into innocuous mineral compounds during the prolonged filtra-
tion of the water through a great thickness of porous strata, and that
the water so purified may afterwards have become contaminated with
vegetable matter only. In other words, water polluted by animal mat-
ters may become pure spring water, retaining only the innocuous evi-
dence of its former pollution, and may then become polluted by the
soluble matter of peat. Such water would be suspicious owing to the
evidence of its previous pollution, which it still bears about with it,
and it could only be cleared from this suspicion on proof of efficient
purification after its pollution by animal matter. To render the water
safe for domestic use the animal pollution must have occurred before it
became spring water.
It is upon this part of the investigation of potable water that the
next four determinations have a very important bearing.
4. Ammonia. — This mineral nitrogenous compound is rarely absent
from potable waters, which derive it, sometimes from the atmosphere,
but more usually from decomposing animal matters. Rain water fall-
ing in LfOndon sometimes contains as much as 0.21 part of ammonia in
100,000 parts of water, but this is exceptional, and the proportion rarely
exceeds one-third of that amount. The average quantity present in 71
samples of rain water collected at Rothamsted, near St. Albans, was
0.049 part in 100,000 parts of water. In river water the proportion
rarely exceeds 0.01 part, in unpolluted well water it is usually less,
whilst in spring water it is either absent altogether or present in only
very minute proportion. On the other hand, it often abounds in the
water of much polluted shallow wells. The proportion of ammonia in
the London shallow well waters sometimes rises as high as 2.75 parts
in 100,000 parts of water. In contact with animal matter and under
the operation of oxidizing influences, ammonia is very rapidly converted
into nitrites and nitrates, and its presence therefore in considerable pro-
portion in shallow well waters indicates their very recent contamination
with animal matters. Its occurrence in water from deep wells, however,
does not permit of the same inference being drawn, because we find that
in such water the decomposition of nitrates not unfrequently gives rise
to ammonia. This is particularly the case in very deep wells, and in
those which are sunk into the Chalk beneath the London Clay. The
ammonia which occurs under such circumstances is obviously still more
492 INORGANIC CHEMISTRY.
remote from the animal matter whence it originated, than the nitrates
from which it was immediately derived, and which were themselves
generated by the oxidation of animal matter.
The chief significance attaching to the determination of ammonia in
potable water lies in the circumstance that this compound is derived
almost exclusively from the decomposition of animal matter. It is
obvious, however, from the consideration just mentioned, that all infer-
ences to be drawn from its presence must be controlled by a study of
the physical and chemical history of the water.
5. Nitrogen as NitraJtes and Nitrites. — In the presence of oxygen, the
nitrogen of animal matters is transformed, in great part, into nitric acid
and nitrous acid ; and these, by combining with the basic substances
always present in polluted water, are in their turn transformed into
nitrates and nitrites. This transformation takes place most rapidly and
completely when the polluted water soaks through aerated soil. Thus
97 per cent, of the combined nitrogen of London sewage is converted
into nitrates during its slow percolation through a stratum of gravelly
soil only 5 feet thick.
Whilst the oxidation of animal matters in solution in water yields
abundance of nitrates and nitrites, vegetable matters furnish under like
circumstances none, or mere traces, of these compounds. Upland waters,
which have been in contact only with mineral matters or with the vege-
table matter of uncultivated soil, contain, if any, mere traces of nitrogen
in the form of nitrates and nitrites ; but as soon as the water comes into
contact with cultivated land, or is polluted by the drainage from farm-
yards or human habitations, nitrates in abundance make their appear-
ance. The presence of these salts in sufficient quantity is, therefore,
trustworthy evidence of the previous pollution of the water with animal
matters. It must be borne in mind, however, that nitric and nitrous
acids are present, though in but minute quantity, in the atmosphere,
and that rain washes them out of the air through which it falls. In
71 samples of rain water collected at Rothamsted the proportion of
nitrogen as nitrates and nitrites varied from 0 to 0.044 part in 100,000
parts of water. Even the highest proportion, which occurred only once,
is a very small one, and one that is never met with in unpolluted upland
waters.
6. Total combined Nitrogen. — The element nitrogen may exist in
water in four forms; viz.: firstly as a constituent of organic matter,
secondly as a constituent of ammonia, thirdly as a compound of nitrates
and nitrites, and fourthly as a constituent of dissolved atmospheric air.
In the last case, the nitrogen is in the free or elementary condition ; and
as it neither pollutes the water nor throws any light upon its previous
pollution, it may be left out of consideration. In all the other three
forms, the nitrogen is combined with other elements, constituting either
polluting matter or the resultant of previously existing polluting mat-
ter. With a slight deduction for the minute amount of this element
which is met with in combination in rain water, the determination of
total combined nitrogen sums up, as it were, the evidence of the pad
and present pollution of each water by nitrogeneous organic matter of
either animal or vegetable origin. The evidence is unfortunately de-
POTABLE WATEBS. 493
fective, especially in spring and summer, because some of the compounds
containing nitrogen constitute an important part of the food of both
animal and vegetable organisms. Combined nitrogen also suffers dimi-
nution whenever the organic matter in the water enters into putrefac-
tion or undergoes oxidation in the absence of atmospheric oxygen and
in the presence of nitrates and nitrites. The latter salts supply, under
these circumstances, the oxygen required to transform the carbon and
hydrogen of the organic matter into carbonic anhydride and water,
whilst their nitrogen is converted only to a slight extent into ammonia,
the rest being set free and consequently ceasing to exist as combined
nitrogen. It is thus that the water of very deep wells frequently retains
few or no traces of the nitrates and nitrites which it previously held in
solution, whilst a comparatively small proportion of ammonia is found
in their place. The artesian wells of London afford striking instances
of this destruction of nitrates and consequently of combined nitrogen.
7. Previoiu Sewage or Animal Contamination. — It has been
-established by very numerous chemical analyses, that animal matters
dissolved in water, such as those contained in sewage, the contents of
privies and cesspools, or farmyard manure, undergo oxidation in lakes,
rivers, and streams very slowly, but in the pores of an open soil very
rapidly. When this oxidation is complete, they are resolved into min-
eral compounds; — their carbon is converted into carbonic anhydride,
and their hydrogen into water, products which can no longer be iden-
tified in the aerated waters of a river or spring ; but their nitrogen is
transformed partly into ammonia, chiefly however into nitrous and
nitric acids, which, combining with the bases present in nearly all water
that has been in contact with the earth, form nitrates and nitrites, and
frequently remain dissolved in the water for a long time; — there con-
stituting a record of the sewage or other analogous contamination, to
which it has been subjected since its last descent to the earth as rain.
It is convenient to have a concrete expression for the amount of pre-
vious animal contamination revealed by this record of the past history
of water. Such an expression is obtained by taking as a standard of
comparison the amount of total combined nitrogen contained in solution
in 100,000 parts of average London sewage. Although a considerable
proportion of this nitrogen is found at the sewer outfall in the condition
of ammonia, it is well known that in the perfectly fresh sewage the
nitrogen of this ammonia was present as a constituent of animal organic
matter. The earlier analyses of London sewage made by Hofraann and
Witt, give the number 8.363 as the amount of total combined nitrogen
contained in 100,000 parts of average London sewage. More recent
analyses show that 100,000 parts of average London sewage now con-
tain only 7.06 parts of total combined nitrogen. This difference is
doubtless owing to the more abundant supply of water to the metropolis
at the later period. For simplicity, however, a round number (10) is
assumed as the amount of total combined nitrogen in solution in 100,000
parts of average London sewage.
In estimating, in terms of this standard, the previous animal contam-
ination of water, from the proportion of nitrogen, in the form of
ammonia and of nitrates and nitrites, which it holds in solution, it is
494 IKOBOAKIO CHEMI8TBT.
necessary to bear in mind that rain water itaelf contains these sub-
stances, although in minute quantities. The average composition of
samples of rain water collected at Rothamsted gives the amount of
nitrogen in these forms as 0.032 in 100,000 parts of water.
After this number (0.082) has been substracted from the amount of
nitrogen, in the forms of nitrates, nitrites, and ammonia, found in
100,000 parts of a potable water, the remainder, if any, represents the
nitrogen derived from oxidized animal matters with which the water
has been in contact. Thus a sample of water which contains, in the
forms of nitrates, nitrites, and ammonia, 0.326 part of nitrogen in
100,000 parts, has obtained 0.326 — 0.032 = 0.294 part of that
nitrogen from animal matters. Now this last amount of combined
nitrogen is assumed to be contained in 2940 parts of average London
sewage, and hence such a sample is said to exhibit 2940 parts of pre-
vious sewage or animal contamination in 100,000 parts ; or in other
words, 100,000 lbs. of the water contain the mineral residue of an
amount of animal organic matter equal to that found in 2940 lbs. of
average London sewage.
It must not be forgotten, however, that the absence of nitrogen in
these forms is not absolutely conclusive evidence of immunity from this
pollution. There are several agencies at work by which this testimony,
as to the amount of animal matter previously in the water, may be
weakened or altogether destroyed. Thus we look in vain for the full
evidence of previous animal pollution in the effluent water from fields
irrigated with sewage; because the growing plants have removed a
considerable proportion of ammonia, nitrates, and nitrites, from the
liquid as it flows amongst their rootlets. In like manner the aquatic
vegetation of rivers, lakes, and reservoirs, slowly removes these com-
pounds from the water, and to that extent destroys the evidence of
anterior animal contamination. Nitrates and nitrites are also rapidly
destroyed when the organic matter in the water containing them enters
into putrefaction, a condition which often occurs in streams or reser-
voirs containing much polluting organic matter. The same not unfre-
quently takes place in water-bearing strata far removed from the surface,
although the water in this case may contain but a comparatively small
amount of organic matter ; the latter, however, cut off from a supply
of atmospheric oxygen — as in the Chalk beneath the London Clay for
instance — accomplishes its oxidation at the expense of the nitrates or
nitrites, and thus destroys them. Owing to this cause, the evidence of
previous animal contamination is not met with in the water of some
deep wells in which it might otherwise be expected to occur.
The previous animal contamination of turater, as deduced from chem-
ical analysis, must therefore always be regarded as a minimum quantity;
it does not denote the comparative freedom of different samples of
water from anterior pollution ; but whenever analysis shows this ex-
cess of nitrogen in the shape of nitrates, nitrites, and ammonia, the
water stands convicted of previous contamination at least to the extent
so indicated.
The importance of the history of water as regards its anterior pollu-
tion with organic matters of animal origin, does not arise from the
POTABUB WATERS. 495
presence of the inorganic residues (nitrates, nitrites, and ammonia) of
the original polluting matters, for these are in themselves innocuous,
but from the risk lest some portion (not detectable by chemical or
microscopical analysis) of the noxious constituents of the original animal
matters should have escaped that decomposition, which has resolved
the remainder into innocuous mineral compounds. This evidence of
previous contamination implies, however, much more risk when it occurs
in water from rivers and shallow wells, than when it is met with in the
waters of deep wells or of deep-seated springs. In the case of river
water, there is great probability that the morbific matter, sometimes
present in animal excreta, will be carried rapidly down the stream,
escape decomposition, and produce disease in those persons who drink
the water; for the organic matter of sewage undergoes decomposition
very slowly when it is present in running water. In the case of shal-
low well water, the decomposition and oxidation of the organic matter
are also very liable to be incomplete during the rapid passage of pol-
luted surface water into shallow wells. lu the case of deep well and
spring water, however, if the proportion of previous contamination do
not exceed 10,000 parts in 100,000 parts of water, this risk is very
inconsiderable, and may be regarded as nil if the direct access of water
from the upper strata be rigidly excluded ; because the prolonged filtra-
tion to which such water has been subjected in passing downward
through so great a thickness of soil or rock, and the rapid oxidation of
the organic matters contained in water, when the latter percolates
through a porous and aerated soil, afford a considerable guarantee that
all noxious constituents have been removed.
It has been already stated that chemical analysis cannot discover the
noxious ingredient or ingredients in water polluted by infected sewage
or animal excreta; and as it cannot thus distinguish between infected
and non-infected sewage, the only perfectly safe course is to avoid
altogether the use, for domestic purposes, of water which has been pol-
lute with excrementitious matters.
Nevertheless, as it is very difficult in some localities to obtain water
which has not been more or less polluted by excrementitious matters,
it is desirable to classify such previously contaminated drinking waters
into
Reasonably safe water.
Suspicious or doubtful water.
Dangerous water.
BeasoTiably Safe Water, — Water, although it exhibits previous sew-
age or animal contamination, may be regarded as reasonably safe whei|
it is derived either from deep wells (say 100 feet deep), or from deep-
seated springs; provided that all contaminated surface water has been
rigidly excluded from the well or spring, and that the proportion of
previous contamination does not exceed 10,000 parts in 100,000 parts of
water.
Suspicuma or doubtful waJler is, first, river or flowing water which
exhibits any proportion, however small, of previous sewage or animal
contamination ; and, secondly; well or spring water containing from
496 INOBGANIC CHEMISTAT.
10,000 to 20,000 parts of previoas coDtaminatlon in 100,000 parts of
water.
Dangermis tocUer is, first, river or flowing water which exhibits more
than 20,000 parts of previous animal contamination in 100,000;
secondly, river or flowing water containing less than 20,000 parts of
previous contamination in 100,000 parts, but which is known, from an
actual inspection of the river or stream, to receive sewage, either dis-
charged into it directly or mingling with it as surface drainage;
thirdly, as the risk attending the use of all previously contaminated
water increases in direct proportion to the amount of such contamina-
tion, well or deep-seated spring water exhibiting more than 20,000
parts of previous contamination in 100,000 must be regarded as dan-
gerous.
Eiveror running water, containing less than 10,000 parts of previous
animal contamination, should only be provisionally placed in the claijs
of suspicious waters, pending an inspection of the banks of the river
and tributaries ; which inspection will obviously transfer it either to
the dass of reasonably safe waters, if the previous contamination be
derived exclusively from spring water, or to the class of dangerous
waters, if any part of the previous contamination be traced to the di-
rect admission of sewaee or excrementitious matters.
8. Chlorine. — The chlorine found in potable waters is always com-
bined with other elements, and chiefly with sodium in the form of sodic
chloride or common salt. A knowledge of the proportion of chlorine
in water often throws important light upon the history of the water as
regards its previous contamination with the liquid, as distinguished
from the solid excrements of animals. Human urine contains about
500 parts of chlorine or 824 parts of common salt in 100,000 parts,
whilst upland surface water free from previous or present pollution
rarely contains more than 1 part of chlorine or 1.648 parts of common
salt in the same weight ; and it is pre^nt in but comparatively minute
proportion in the solid excrements of animals. It is scarcely necessary
to state that the determination becomes valueless, for the purpose of
indicating previous sewage contamination, in the neighborhood of the
sea and of natural deposits of salt The normal proportion of chlorine,
as common salt, existing in British waters which have never been pol-
luted by excrementitious matters is, as just stated, about 1 part in
100,000 parts of water ; but it varies considerably in different parts of
the country. Thus at the Land's End with a strong wind from the
S.W. even rain water contains as much as 21.8 parts of chlorine in
100,000 parts, while the Grelder Burn at Balmoral contained on March
9th, 1872, only 0.35 part in 100,000 parts. Unpolluted rivers and
lakes in inland countries contain still less. Thus the Ehine at Schafl^-
hausen contains only 0.2 part, and the lakes of Zug and Zurich 0.27
and 0.17 part respectively in 100,000 parts of water. The proportion
of chlorine in rain water varies in like manner, and the variation is also
here doubtless due to the varying distance from the sea at which the rain
falls. Thus whilst rain water at the Land's End was found to contain
21.8 parts, the average proportion of rain falling in the centre of India
was only 0.03 part.
POTABLE WATERS. 497
9. Hardness. — Some of the mineral sabstances which occur in solu-
tion in potable waters communicate to the latter the quality of hardness.
Hard water decomposes soap, and cannot be efficiently used for washing.
The chief hardening ingredients met with in potable waters are the
salts of lime and magnesia. In the decomposition of soap, these salts
form curdy and insoluble compounds containing the fatty acids of the
soap, and the lime and magnesia of the salts. So long as this decompo-
sition goes on, the soap is useless as a detergent, and it is only after all
the lime and magnesia salts have been decomposed at the expense of
the soap, that the latter begins to exert a useful effect ; as soon as this
is the case, however, the slightest further addition of soap produces a
lather when the water is agitated, but this lather is again destroyed by
the addition of a further quantity of the hard water. Thus the addi-
tion of hard water to a solution of soap, or the converse of this opera-
tion, causes the production of the insoluble curdy matter above men-
tioned. These facts render intelligible the process of washing the skin
with soap and hard water: The ekin is first wetted with the water and
then soap is applied; the latter soon decomposes all the hardening salts
contained in the small quantity of water with which the skin is covered,
and there is then formed a strong solution of soap which penetrates into
the pores. This is the process which goes on whilst a lather is being
produced in personal ablution ; and now the lather, and the impurities
which it has imbibed, require to be removed from the skin, — an opera-
tion which can be performed in one of two ways, viz., either by wiping
the lather off with a towel, or by rinsing it away with water. In the
former case, the pores of the skin are left filled with soap solution ; in
the latter they become clogged with the greasy, curdy matter which re-
sults from the action of the hard water upon the solution which had
previously gained possession of the pores of the cuticle. As the latter
process of removing the lather is the one universally adopted, the ope-
ration of washing with soap and hard water is analc^iis to that used
by the dyer and calico printer when he fixes his pigments in calico,
woollen, or silk tissues. The pores of the skin are filled with insoluble,
grea«ty, and curdy salts of the fatty acids contained in the soap, and it
IS only because the insoluble pigment produced is white, or nearly so,
that such a repulsive operation is tolerated. To those, however, who
have been accustomed to wash in soft water, the abnormal condition of
the skin thus induced is for a long time extremely unpleasant.
Of the hardening salts present in potable water, carbonate of lime is
the one most universally met with ; and to obtain a numerical expres-
sion for this quality of hardness, a sample containing 1 lb. of carbonate
of lime or its equivalent of other hardening salts in 100,000 lbs. is said
to have one d^ree of hardness, fkch degree of hardness indicates the
destruction and waste of 12 lbs. of the best hani soap by 100,000 lbs.
or 10,000 gallons of the water, when used for washing.
Hard water frequently becomes softer after it has been boiled for
some time. When this is the case, a portion at least of the original
hardening effect is due to the acid carbonates of lime and magnesia.
These salts are decomj)Osed in boiling water into free carbonic anhy-
dride, which escapes, and the carbonates of lime and magnesia. The
S2
498 INOROAKIO CHEMISTRY.
latter, being nearly insoluble in water, cease to exert more than a very
slight hardening effect. As the hardness resulting from the carbonates
of lime and magnesia is thus removable by boiling the water, it is
designated temporary hardnesSy whilst the hardening effect which is due
chiefly to the sulphates of lime and magnesia, and cannot be got rid of
by boiling, is termed permanent hardness. The total hardness of a
water is therefore commonly made up partly of temporary and partly
of permanent hardness.
Hard water not only acts injuriously when it is used for washing;
but, when it is employed for the generation of steam, it forms trouble-
some and dangerous incrustations in the boiler. A constant supply
of hot water has become almost a necessity in every household, but
great difficulties are thrown in the way of its attainment by the supply
of hard water to towns, owing to the formation of thick calcareous crusts
in the heating apparatus. Waters which have much temporary hard-
ness are most objectionable in this respect, and the evil is so great
where the heating is effected in a coil of pipe, as practically to prevent
the use of this most convenient mode of heating water.
The hardne&s of rain water varies from 0° to 10°. The latter d^ree
of hardness is, however, only attained near the seashore and in rough
weather. At Rotharosted, in seventy-one samples, it never exceeded
L7° and averaged only 0.49°. The hardness of water which has once
touched the earth depends obviously upon the character of the gather-
ing ground or water-bearing stratum over or through which it passes,
and also upon the length of time during which it luis been in contact
with the earth. Calcareous and magnesian soils or strata cause the
water passing over or through them to be hard. If the calcareous or
magnesian matter contain carbonate of lime or carbonate of magnesia,
a portion at least of the hardness will be temporary. If, on the other
hand, gypsum (sulphate of lime) be the calcareous material, the hard-
ness will be permanent. Unpolluted water collected from Igneous
rocks, either as surface drainage or springs, is the softest. Its hardness
varies from 0.4° to 5.9°, and averages 2.4°. Next to this in softness,
must be ranged the unpolluted waters from Metamorphic, Cambrian,
Silurian, and Devonian rocks, the Millstone Grit, London Clay, and
Bagshot Beds, which range from 0.4° to 32.5°, and average 5.6°.
The Lower Greeusand also yields very soft water (about 4° of hard-
ness) when the water does not previously percolate through calcareous
strata, but this is so rarely the case as to prevent any reliance from
being placed upon the softness of Greensand water. The hardness of
unpolluted Greensand water sometimes ranges as high as 44°.
Amongst the slightly calcareous strata, the New Bed Sandstone
generally yields water of medium hardness; a large proportion of the
hardness is, however, frequently permanent. In fifty-one samples of
unpolluted New Bed Sandstone water, the temporary hardness ranged
from 0° to 19.8°, and averaged 7.7° ; whilst the total hardness varied
from 5.7° to 35.7°, and averaged 17.9°.
Of true calcareous strata, the Mountain Limestone yields water of
least total hardness, whilst the permanent hardness is in general only a
small proportion of the total. The analysis of nineteen samples of un-
POTABLE WATERS, 4t9
polluted limestone water showed a total hardness varying from 9.8^ to
27.9°, and averaging 15.7°. The permanent hardness ranged from
3.3° to 12.9°, and averaged 7.1°.
The Dolomite or Magnesian Limestone generally imparts to water
great hardness, of which a large proportion, and sometimes nearly the
whole, is permanent. This stratum occupies, however, a comparatively
small area in this country, and the water is consequently but little used
for domestic purposes. In five samples the total hardness varied from
14.7° to 67.3°, and averaged 41.2°; whilst the permanent hardness
varied from 8,3° to 40.8°, averaging 24.8° ; and the temporary hanl-
ness from 0.8° to 26.5°, averaging 16.4°.
The Lias yields water of variable, but nearly always great, hardness.
The permanent hardness of water from this geological formation is also
almost invariably high. In ten samples, the total hardness ranged
from 10.3° to 50°, and averaged 29° ; the permanent hardness varied
from 1.7° to 17.4°, averaging 8.2° ; and the temporary hardness from
8.6° to 36.3°, averaging 20.9°.
The Oolite and Chalk strata yield water of great, but chiefly tempo-
rary, hardness. In forty-two samples of unpolluted Oolitic water, the
total hardness ranged from 4.2° to 35.2°, and averaged 22.4° ; the
permanent hardness varied from 3.5° to 13.5°, averaging 6.1° ; whilst
the temporary hardness was from 0° to 25.7°, and on uie average 16.3°.
In ninety-five samples of unpolluted water from the Chalk, the total
hardness ranged from 12.4° to 50°, and averaged 26.1°; the perma-
nent hardness ranged from 2.7° to 13.8°, averaging 6.1° ; whilst the
temporary hardness varied from 6.8° to 38.6°, and averaged 20.2°.
The Chalk beneath the Londpn Clay yields water which is usually
much softer than that obtained from Chalk which is not covered by an
impervious stratum. In fourteen samples of water from this source,
the total hardness ranged from 0.9° to 48.6°, the average being 18.9°;
the permanent hardness varied from 0.9° to 25.4°, but this extreme
number and the extreme of total hardness occurred only in the water
from a deep well at Harrow- on-the-Hill. Omitting this well, the ex-
treme total hardness was 28.2° and the extreme permanent hardness
9.7° ; whilst, omitting the Harrow sample, the temporary hardness
varied from 0° to 21.2, and averaged 7.1°.
The Coal Measures yield water of very variable hardness, owing to
the variety in chemical composition presented by these rocks. The
surface waters are generally very soft, but those derived from springs
and deep wells are not unfrequently very hard. In sixty samples, the
total hardness varied from 2.3° to 75°, and averaged 14.7° ; the per-
manent hardness ranged from 1.2° to 48.5°, and averaged 9.6° ; whilst
the temporary hardness varied from 0° to 28.2°.
Water obtained from any stratum permeable to the foul liquids of
sewers, middens, and cess-pits is always hard, and generally exhibits a
large proportion of permanent hardness. The food of man and beast
contains considerable quantities of lime, nearly the whole of which, in
the adult, is discharged in the liquid and solid excrements. In 258
samples of shallow well water polluted by excrementitious matters to
such an extent as to exhibit evidence of 10,000 parts and upwards of
500 IKOBGANIC CHEMISTRY,
previous sewage or animal ooDtaniination, the total hardness ranged
from 9.8° to 191°, and averaged 50.7° ; the permanent hardness varied
from 3.8° to 164.3°, and averaged 31.7°; whilst the temporary hard-
ness ranged from 0° to 49.2°, and averaged 19°.
10. Mineral Matters in Suspension. — ^The mineral matters in suspen-
sion in potable water are almost invariably of an innocuous character,
but they diminish or altogether destroy the transparency and brilliancy
of the water, and impart a repulsive appearance, which often leads to
the rejection of a wholesome water for a bright and sparkling though
dangerous one. Slow filtration through sand is almost invariably effec-
tive for the removal of visible suspended matters, but the washings of
clay soils are very difficult to render bright by sand filtration ; and in
all cases filtered water, if turbid previous to filtration, may always he
shown, by suitable optical means, to be full of minute suspended parti-
cles, although to unassisted vision it is perfectly clear and transparent
11. Organic Matters in Suspension. — The oi^nic matters in sus-
pension in potable water possess not only all the objectionable qualities
of similar matters of mineral origin, but in addition they are sometimes
actively injurious, and they always promote the development of crowds
of animalcules. Their presence in drinking water is therefore much
more objectionable than is the occurrence of mineral matters in suspen-
sion. Like the suspended mineral matters, the finely divided organic
matters in suspension cannot be entirely removed by sand filtration.
The Sixth Report of the Rivers Pollution Commission gives the
result of the chemical examination of 1272 samples of potable water
collected under the most widely different conditions, and comprehend-
ing 81 samples of rain water, 372 samples of surface water, 419 sam-
ples of shallow well water, 180 samples of deep well water, and 220
samples of spring water. This extended investigation of watera which
have drained from the surface of, or percolated tlirough the most im-
portant geological formations of. Great Britain affonds, the Commis-
sioners say, a broad basis hitherto unattainable upon which to found
conclusions as to the relative merits of potable waters from these various
sources. The results of this research are quite conclusive as to the
sources from which the best water for domestic purposes is to be ob-
tained. They show that rain water contains the smallest proportion of
total solid impurity, but by no means the smallest proportion of that
most objectionable of impurities, organic matter. The rain drops con-
centrate within themselves the organic dust and dirt diffused through
vast volumes of atmospheric air, and everywhere visible when a ray
of sunlight illuminates them. Rain water, collected from the roofs of
houses at a distance from towns, carefully stored and filtered, may be
made into a fairly good and wholesome potable water ; but when it is col-
lected from the surface of uncultivated land, allowed to subside in lakes
or reservoirs, or filtered through sand, it becomes of good quality for
domestic, and still more so for manufacturing purposes. Numerous
large towns, both in England and Scotland, are supplied with water
of this description. Non-calcareous strata are generally selected as
gathering ground, and then the water is soft and well adapted both
for washing and for almost all manufacturing operations. It is nearly
POTABLE WATEHS. 501
always wholesome, but sometimes suffers in palatability by contaiDing
an excessive quantity of peaty matter in solution. This evil may be
materially abated by the use of sand filters.
Seeing that rapid filtration through a few feet of sand can materially
improve the quality of surface water, by removing some of the organic
impurity which it contains in solution, we are prepared to find a much
greater improvement when the water is drawn from deep wells or
springs, to which it could only gain access by slow natural percolation
through a great thickness of porous rock or earth'. Under such cir-
cumstances, the powerful oxidizing influences of a porous and aerated
soil are brought to bear upon the organic matter dissolved in the water.
It is not, therefore, surprising to find that surface water should be
almost, or even quite, exhaustively purified from such matter, by the
natural intermittent filtration which transforms it into spring or deep
well water. Mere exposure to the air, however, even if accompanied by
vident agitation, is comparatively powerless for the removal of pollut-
ing organic matter from water.
Surface water, draining from cultivated land, is always more or less
polluted with the organic matter of manure. Such water, of course,
contributes very largely to rivers and streams which have already de-
scended from their mountain or upland sources. Even when not con-
taminated by the actual admission into it of the sewage of towns and
villages, it is not of suitable quality for domestic purposes, but when it
is further polluted by excremental drainage, its use for drinking and
cooking becomes fraught with great risk to health. Still more dan-
gerous to health is the water drawn from shallow wells, no matter upon
what geological formation they may be sunk, when they are situated,
as is usually the case, near privies, drains, or cesspools. Many severe
outbreaks of epidemic disease have been traced to the use of such water
in villages and towns, and there is strong reason to believe that sporadic
attacks of typhoid fever often occur in isolated country houses from the
same cause.
In respect of wholesomeness, palatability, and general fitness for
drinking and cooking, waters may be classified in the following order
of excellence :
Wholesome. / l'. lE^p welf^ter. } ^^ palatable.
( 3. Upland surface water. 1 Moderately pala-
{4. Stored rain water. j table.
6. Surface water from cultivated
land.
{6. River water to which sewage Y Palatable,
gains access.
7. Shallow well water.
Preference should always be given to spring and deep well water for
purely domestic purposes, over even upland surface water — not only on
account of the much greater intrinsic chemical purity and palatability
of these waters, but also because their physical qualities render them
peculiarly valuable for domestic supply. They are almost invariably
602 INORGANIC CHEMISTRY.
clear, colorless, transparcDt, and brilliantr— qualities which add greatly to
their acceptability as beverages — whilst their uniformity of temperature
throughout the year renders them cool and refreshing in summer and
prevents them from freezing readily in winter. Such waters are of in-
estimable value to communities, and their conservation and utilization
are worthy of the greatest efforts of those who have the public health
under their charge.
The foregoing remarks have reference exclusively to the use of water
for drinking and cooking — applications of paramount importance from
a sanitary ]K)int of view ; but a large proportion of the water supplied
for domestic purposes is used for washing, whilst in many towns con-
siderable volumes are used in manufactories. For all these latter pur-
poses it is of the utmost importance that the water should be soft — ^a
quality that is not always associated with wholesomeness and palata-
bility. Classified according to softness, the waters from the various
sources fall into the following order:
1. Rain water.
2. Upland surface water.
3. Surface water from cultivated land.
4. Polluted river water.
6. Spring water.
6. Deep well water.
7. Shallow well water.
The interests of the laundress and of the manufacturer are thus evi-
dently opposed to those of the householder, inasmuch as they lead to a
preference for moderately palatable or even unwholesome water over
that which is very palatable and wholesome. Most of the hard waters
from springs and deep wells can, however, be easily and cheaply ren-
dered soft, and the interests of the householder and manufacturer thus
made identical. In Clark's process of softening water with lime, the
sanitary authorities of towns have at their disposal a method of render-
ing hard water from springs or deep wells available for washing and
manufacturing purposes, without diminishing either its palatability or
its wholesomeness.
The influence of geological formation upon the palatability and
wholesomeness of water is very considerable. In the case of surface
water this influence is to a great extent masked, or indeed often alto-
gether annulled, by superficial de]K)8it8of vegetable matters, such as peat,
upon the rocks; and thus, except in respect of hardness and saline
constituents, unpolluted surface waters from the most widely different
geological formations differ but little in the proportions of organic mat-
ter which they contain, and consequently in their palatability and whole-
someness. But when the water percolates or soaks through great thick-
nesses of rock, its quality, when it subsequently appears as spring or
deep well water, depends greatly upon the nature of the material through
which it has passed. Wlien the formation contains much soluble saline
matter, the water becomes loaded with mineral impurities, a8 is fre-
quently the case when it percolates through certain of the Carboniferous
POTABLE WATERS. 503
rocks, the Lias, and the Saliferous Marls. When the rock is much
fissured, or permeated by caverns or passages, like the Mountain Lime-
stone, for instance, the effluent water differs but little from surface drain-
age, and retains most of the organic impurities with which it was origi-
nally charged. But when the rock is uniformly porous, like the Chalk,
Oolite, Greensand, or New Red Sandstone, the organic matter, at first
present in the water, is gradually oxidized and transformed into innocu-
ous mineral compounds. In effecting this most desirable transforma-
tion, and thus rendering the water sparkling, colorless, palatable, and
wholesome, the following water-bearing strata are the most efficient :
1. Chalk.
2. Oolite.
3. Greensand.
4. Hastings Sand.
5. New Red and Conglomerate Sandstone.
This is seen from the following table, in which the average composi-
tion of unpolluted water from various sources is contrasted :
504
INORGANIC CHEMISTRY.
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INORGANIC CHEMISTRY.
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MAGNESIUM. 507
HAONESIUM, Mg.
Atomic weight = 24.4. Probable moleoular weight = 24.4. Sp. gr.
1.743. Fuses at a red heat. Volatilizes at a red heat. Atomicity ''.
JSvidence of atomicity :
Magnesic chloride^ Mg^Clj.
Magnesic oxide, Vlg^'O.
Magnesic hydrate, Hg^'Hoj.
History, — Magnesic sulphate was described and its medicinal prop-
erties pointed out by Grew at the close of the seventeenth century.
The metal was first isolated by Davy.
Occurrence. — ^The compounds of magnesium are widely distributed
in nature. It occurs as carbonate in mxignesite, COMgo" ; as dihydric
magnesic sulphate in kieseritCy SOHosMgo^^, and Epsom salts,
8OHo,Mgo",60H,j as silicate in enstatitey SiOMgo", in ophite or
noble serpentine, BijOMgo^^, in talCy Si5O0lVf go'^^, and other minerals.
In combination with other bases, as double salts, it occurs in enormous
quantities as dolomite^ a carbonate of isomorphous calcium and mag-
nesium, mCOCao'>COMgo" ;* as jfcainife, SOaKo(^jMg),30Hj; as
camallUey MgClstKClyGOH,; and in a great number of silicates. The
sulphate and chloride are also found in saline springs and in sea-water.
It occurs in small Quantities in the animal and vegetable kingdoms :
thus, in the bones oi animals and in the seeds of plants.'
Preparation. — Magnesium may be obtained by the electrolysis of the
fused chloride, but is more conveniently prepared by the action of
sodium on the chloride. A mixture of 6 parts of fused magnesic
chloride, 1 part of powdered fluorspar, 1 part of a mixture of sodic and
potassic chloride in equal molecular proportions, and 1 part of sodium
in small pieces, is thrown into a red-hot crucible, which is quickly
closed. As soon as the reaction is over the crucible is removed from
the fire and allowed to cool to below redness, after which the contents
are stirred with a pipe-stem, in order to cause the globules of magnesium
to unite. When quite cold, the solidified slag is broken up, and the
magnesium removed. Magnesium is now manufactured on a large
scale.
Properties. — ^Magnesium is a silver-white lustrous metal, of sp. gr.
1.743. The pure metal preserves its lustre in dry air, but becomes
covered with a film of oxide when exposed to the action'of moisture.
At a higher temperature it may be pressed into the form of wire or
ribbon, an operation which must be performed with exclusion of air.
It fuses at a red heat, and may be distilled in a current of hydrogen.
Magnesium wire or ribbon may be ignited at the flame of a candle, and
burns with an intensely brilliant white light very rich in chemically
active rays, a property which has led to its use in photography. Pure
* See p. 65.
508 INOBOANIC CHEMISTRY.'
magnesium does not decompose water even at 100° C. (212® F.). Dilate
acids dissolve it with violent evolution of hydrogen. Unh'ke zinc it
does not evolve hydrogen when heated with solutions of caustic alkalies.
This is due to the fact that the magnesic hydrate, which would be
formed, is not soluble in the alkali. Magnesium gives off hydn^n
when heated with solutions of ammonia salts, the magnesium dissolving
in the form of a double salt of magnesium and ammonium.
Uses. — Except for laboratory purposes, magnesium is employed ex-
clusively in the production of the magnesium light. Besides its appli-
cation in photography already referred to, the magnesium light has been
used in signalling. The light has been seen at sea at a distance of
28 miles.
COMPOUNDS OF MAGNESIUM WITH THE HALOGENS.
Magnesic chloride, MgCl^ — This compound occurs in sea-water
and in salt deposits. It is formed when the metal, the oxide, or the
carbonate, is dissolved in hydrochloric acid. On concentrating the solu-
tion, the chloride is deposited in monoclinic crystals of the formula
MgOljiSOHj, which when heated give off their water of crystallization,
but at the same time are partially resolved into magnesic oxide and
hydrochloric acid. In order to obtain the anhydrous salt in a state of
purity, 12 parts of the commercial oxide are dissolved in hydrochloric
acid ; the solution is shaken with an excess of oxide, in order to pre-
cipitate alumina and iron, and, after filtering, evaporated to dryness with
27 parts of ammonic chloride. The resulting magnesic amnionic chloride
is carefully heated to expel the water of crystallization, and is afterwards
ignited in a platinum crucible, until fumes of ammonic chloride cease
to be given off, and the whole has fused to a clear liquid. The
anhydrous chloride solidifies on cooling to a colorless laminated crystal-
line mass with a lustrous fracture. It deliquesces when exposed to moist
air, dissolves in water with evolution of heat, and is also readily soluble
in alcohol. It volatilizes at a bright red heat. Magnesic chloride is
employed in dressing cotton goods. — Magnesic chloride combines with
magnesic oxide to form oxychlorides of varying composition. If strongly
ignited magnesia be made into a paste with a concentrated solution of
magnesic chloride, the mixture solidifies in the course of a few hours to
a solid mass, sufficiently hard to be polished.
Magihesie potaasic chloride, MgCl2,KCly60H^ occurs native as cantaUUe in large de*
posits at Stas8furt, and is frequently deposited from the last mother-liquors of sea-water
and brine-springs. It forms colorless rhombic prisms, which deliquesce on exposure
to the air. On heating, the water of crystallization is expelled without decomposition
of the salt, and the anhydrous salt fuses at a red heat. Anhydrous caroallite may be
employed in the preparation of magnesium by means of sodium.
Magnesic ammoni/: chloride, MgCl^NFI^CUGOH,* is deposited in small rhombic
crystals from mixed solutions of magnesic and ammonic chlorides. It is soluble in 6
parts of water.
Magnetic oaleie chloride, 2MgC]^CaCl2,120H^ occurs native in deliquescent masses
as (at^ydrite, at Stassfnrt.
Magiuaic bromide, MgBr,, occurs in sea-water and in saline springs. A solution
of magnesia in hydrobromic acid deposits needle-shaped crystals of the formula
COMPOUKD8 OP MAGNESIUM. 509
MgBr^60H,, which when heated behave ]ike the aquate of niagnesic chloride. Mag-
nesic bromide forms double salts with the alkaline bromides.
Magnesic iodide, Mgl,, occurs in dea-water and in saline springs, and may be pre-
pared by dissolving magnesia in hydriodic acid. It forms deliquescent crystals which
readily decompose when heated.
Magnetie fluoride^ MgF,, occurs native as seilatU in colorless qnad ratio crystals. It
18 obtained as a white insoluble powder by digesting magnesia with hydrofluoric acid.
By fusion with common salt this powder is converted into crystals having the same
form as sellaite.
Magnedc 9odie fluoride, MgF^NaF. — This salt is obtained in insoluble, cubical crys-
tals by fusing magnesic chloride with a large exce&s of sodic fluoride and cooling slowly.
It is also formed by digesting magnesia with a solution of sodic fluoride.
COMPOUNDS OF MAGNESIUM WITH OXYGEN AND
HYDROXY!.
Magnesic oxide. Magnemby . MgO. Mg=0.
Magnesic hydrate, . • . . MgHo,. H — O — Mg — O — H.
Magnesic oxide (Magnesia), MgO, occurs native as peridase, a
rare mineral found at Monte Somma, near Naples. The natural com-
pound forms regular octahedra, generally of a greenish color, due to the
presence of ferrous oxide. It is formed when magnesium burns in the
air. It is usually prepared by prolonged ignition of the carbonate, and
18 thus obtained as a bulky white powder known as magnesia usta, or
calcined magnesia. It is insoluble in water. It possesses a sp. gr. of
3.07, but when very strongly ignited, its sp. gr, is increased to 3.61, the
substance becoming at the same time crystalline. By heating magnesia
in a current of gaseous hydrochloric acid, it is obtained in cr>'stals
identical with those of periclase. It fuses in the oxyhydrogeu flame.
Magnesia is employed in medicine.
Magnesic hydrciej MgHo,, occurs native as bi'ueite in colorless laminated masses. By
the addition of sodic or potassic hydrate to solutions of magnesia salts, a gelatinous
precipitate is obtained, which, afterdrying at 100® C. (212° F.), consists of pure magnesic
•hydrate. It forms a white powder, almost inHoluble in water, in solutions of sodic and
potaRsic hydrate, and in aaueous ammonia ; readily soluble in solutions of ammonia salts.
It absorbs carbonic anhydride from the air. At a low red heat it is decomposed into
fnagnesia and water. The magnesia formed at this low temperature has the property
of again itaking up water, with evolution of heat, to form the hydrate.
OXY-8ALT8 OF MAGNESIUM.
MoffneaUi niCrafe, w(v^^^^^ GOH,^ forms deliquescent monoolinic prisms, soluble in
half their weight of cold water, soluble also in alcohol. The vater of crystallization
cannot be completely expelled without partial decomposition of the salt.
Maqnesic carbonate, OOMgo", occurs native as m/ognesite, some-
times in rhombohedral crystals isomorphous with those of calcite,
more frequently massive. The native carbonate generally contains
iron and manganese. By precipitating a hot solution of a magnesia
salt with potassic or sodic carbonate, and boiling the precipitate with
610 INORGANIC CHEMISTBY.
water as long as any acid carbonate is dissolved, a basic magnesio
{CHo,(OMgHo)
Mgo
CH03
Mgo
CHo,(OMgHo)
is obtained. This compound also occurs native as hydromagnessile ia
acicular monoclinic crystals or amorphous masses. Ry precipitating
a magnesia i=alt with a large excess of sodic carbonate, and boiling
with the solution until the precipitate becomes crystalline, a carl>onate ia
fCHoj(OMgHo)
ft
obtained having the formula O.Ho4Mgo"(OMgHo)2= < Mgo'
(CHo^OMgHo)
The pharmaceutical preparation known as magnesia alba is a mixture
of various complex carbonates of magnesia, obtained by precipitating
soluble magnesia salts with sodic carbonate, and varies in composition
according to 'the mode of preparation. It forms a very light, bulky
white powder. When vuignma alba is suspended in water and the
liquid saturated with carbonic anhydride, the powder dissolves with
formation of an acid carbonate. On allowing the solution to stand,
carbonic anhydride gradually escapes, and a salt of the formula
COMgo'^jSOHj separates in fine needles, which when exposed to the
air part with their water of crystallization and become opaque. At a very
low temperature crystals of a salt having the formula C0Mgo",50Hj
are deposited. When the solution of the acid carbonate is evaporated
to dryness, anhydrous magnesic carbonate remains as a fine powder,
which under the microscope exhibits rhombic forms corresponding to
those of arragonite. But if the solution be heated under pressure to
300^ C. (572® F.), at the same time allowing the carbonic anhydride to
escape gradually, the anhydrous carbonate is obtained in minute rhom-
l)ohedra, identical with those of native magnesite. Magnesic carbonate
is, therefore, isodimorphous with calcic carbonate. When the salt
COMgo'',30H2 is boiled with water it gives off carl)onic anhydride, and
is converted into a basic salt, whilst when heated in the dry state to
300° C. (572° F.), it is entirely decojuposed into carbonic anhydride and
magnesia. Native magnesite is not altered by boiling with water, and
does not evolve carbonic anhydride at 300° C. It is also only slowly
attacked by acids in the cold.
Magnesic dipoiassie earbonaUf -jQg^Mgo^^,40H^ is formed when magnesia alba ia
digested with a solution of hydric potassic carbonate for some time at a temperature
of 00-70° C. It forms small rhombic prisms, which are decomposed by water.
Magnesic diammonic earbonate, Qfyj^Q^S^'^^^^i^ separates in colorless rhombic
crystal;*,, when a solution of magnesia salt is added to a lar^e excess of a mixed solu-
tion of ammonic carbonate and free ammonia. It is almost insoluble in water.
Magnesic calcic carbonate. — This compound, which, as the mineral dolomite^ forms
entire mountain ranges, is not a true double salt, but an isomorphous mixture of mag-
nesic and calcic carbonates in varying proportions. As biUer'Spar it occurs cryBtallised
in rhombohednk It is employed, in the preparation of magnetia alba.
Magnesic sulphate, S02.Mgo".j — A dihydric magnesie sulphate^
SOHo^Mgo'^, occurs in layers in the salt-beds at Stassfurt as the
COMPOUNDS OF MAGNESIUM. 511
mineral kieseriie. It generally forms granular masses, and is almost
insoluble in water, but when allowed to remain lon^ in contact with
water gradually dissolves with formation of the salt SOHo2Mgo'',60Ha.
The latter compound occurs native as epsomite or Epsom salt, both solid
as an efflorescence of fibrous crystals, and in solution in many mineral
waters. Magnesic sulphate is deposited from hot concentrated solu-
tions in large transparent rhombic prisms of the above formula
SOHo2Mgo-",60Ha, isomorphous with the corresponding aquates of
zincic and nickelous sulphates; but a salt having the same composition
is sometimes deposited from cold supersaturated solutions in monoclinic
forms isomorphous with those of ferrous sulphate, SOHo2Feo",60H2,
with which magnesic- sulphate also crystallizes in varying proportions.
Above 70° C. (158° F.) it separates from its solutions in monoclinic
crystals of the formula SOHo2Mgo'',50H2; at 0° C. (32° F.) a salt
having the composition SOHogMgo'^llOHj is deposited. Epsom salt
is soluble in four-fifths of its weight of water, still more soluble in
water at 100° C. (212° F.), insoluble in alct^hol. It has an unpleasant
bitter taste. When heated, it fuses in its water of crystallization, which
is given off below 150° C. (302° F.), leaving the salt SOHoaMgo'';
this in turn, when heated above 200° C. (392° F.), parts with the ele-
ments of water, and is converted into the anhydrous sulphate SOaMgo",
which fuses at a red heat without decomposition. The acid salt, ^dihy-
drie magnesic disuIphatCy oq^tj Mgo", crystallizes in six-sided tables
from a solution of the anhydrous normal salt in concentrated sulphuric
acid. It is instantly decomposed by water. Large quantities of Epsom
salt were formerly prepared from dolomite by treating the mineral with
sulphuric acid and then separating the soluble Epsom salt from the in-
soluble calcic sulphate ; but at the present day nearly all the Epsom salt
is obtained from the kieserite of Stassfurt. The crude kieserite from
the upper salt layer, or AbraumsaJzy is placed in sieves suspended in
water. Sodic and magnesic chloride dissolve, the kieserite disintegrates
and falls through the meshes of the sieve in a fine powder, whilst earthy
impurities are retained by the sieve. The powdered kieserite is then
pressed, while wet, into wooden moulds, where it speedily solidifies to
a hard mass, owing to the combination of the water with a portion of
the kieserite to form Epsom salt, which binds the powder together.
The mass is then powdered, and is either brought into the market as
kieserite, or is converted firet into Epsom salt. Kieserite is employed
as a manure, and in the preparation of potassic and sodic sulphate.
Epsom salt is used as a purgative. It is also employed in dressing
cotton goods and in aniline dyeing. — Magnesic sulphate forms double
salts with the alkaline sulphates. Magnesic dipotassio disvlphaie^
«Q*fr^ Mgo",60H2, and magnesic diammonic disulphate,
are deposited, from mixed solutions of magnesic sulphate with potassie
or witn ammonic sulphate, in monoclinic crystals. The potassium saltt
occurs native at Stassfurt as the mineral sch&aite.
612 INORGANIC CHEMI8TRT.
Magnesie orihophotphaUy poMeo'^^^^^^' occurs in bones and the seeds of pIuiCi.
It is obtained as a white puWenilent precipitate when a solution of trisodic ortboph<»-
phate is added to a solution of a magnesia salt It is almost insolnble in water, bat
dissolves readily in dilute acids. A double phosphate and fluoride of magoesiam
having the formula POMgo^^( F^^ / ^^^^^^^ ><^ rooDoclinic crystals as the mincfal
WLffnerite. — Hydrie maanesic orthojf^iowphaiej POHoMgo^^TOH,, is deposited in hex-
agonal needles when ailute solutions of ma^esic sulphate and hjdric disodic phos-
phate are mixed. When concentrated solutions are employed, the salt is obtaioed as
an amorphous precipitate which becomes crystalline on standing. It is sparingly
soluble in water, and is decomposed by boiling into the normal salt which is deposited
and free phosphoric acid which remains in solution. — Tetrahydric magnaie diortko-
pkosphaU nas not been prepared.
Magnesie potagmc arihophosphaie, POKoMg</',60H^ and magnetic wdie orikaphtm-
phaU, PONaoMgo^^,90nt, are obtained in minute crystals by adding to solutions of
potassic or sodic dihydric orthophosphate the requisite quantity of magnesia. Both
saltA are decomposed by washing with water.
Magnetic ammonic orihophotphaie^ POAmoMgo'^^ieOH^ separates from putrid urine*
and is frequently a constituent of urinary calculi ; it occurs also in guano in rhombic
crystals as mtanite or titnmie. It separates as a crystalline powder when hydrie disodic
phosphate is added to a mixed solution of a magnesia salt with an ammonia salt and
free ammonia. In dilute solutions the precipitate is not formed till after some time;
it then attaches itself in small crystals to the sides of the vessel, particularly to parts
which have been rubbed with a glass rod in stirring the liquid. It is almost totally
insoluble in water, especially in water containing ammonia. When ignited, it is oon-
▼erted into magnesie pyrophosphate ;
2POAmoMgo'' = P/),Mgo'', -f- 2HH, + OH^
Magnesie ammonic Magnesie Ammonia. Water,
orthophosphate. pyropooapbate.
Magnesie ammonic phosphate is employed in the estimation both of magnesia and of
phosphoric acid.
Magnetic artenaU^ AaOMffo^'^^^^' *°*^ hydrie magnetic araenate^
A»OHoMgo'^70H»
are prepared like the corresponding phosphates, and form white precipitates, almost
insoluble in water, readily soluble in acids. Tetrahydrie magnesie dianenaie is soluble
in water, but uncrystallizable.
Magnetic ammonic arsenate, AaOAmoMgo^^jCOH,, is prepared like the correspond-
ing phosphate, which it resembles in almost every particular. When dried at 100** C.
(212® F.), it parts with |i of its water of crystallization, yielding the salt —
(ABOAmoMgo^02.OH^ or ABjOHo.Amo.Mgo'^,.
The rest of the water cannot be expelled without partial decomposition of the salt, a
portion of the ammonia being driven off and a portion of the arsenic acid undergoing
reduction to arsenious acid. This water is therefore probably to be regpuded as water
of constitution, as represented in the second of the above formulae. Magnesie ammonic
arsenate is employea in the estimation of arsenic acid.
Magnetic borates. — When magnesia and boric anhydride are fused together at a very
high temperature, and the fused mass is allowed to cool slowly, nacreous crvstals of
trimagnesic diortkoborate, bmIo-'^^^^''' ^^ formed. The same salt with 9 aq. is
obtained by precipitating a solution of a magnesia salt with borax. No precipitate i»
formed in the cold, but on boiling the solution the salt,
jlM|o''Mgo",90H,.
separates as an amorphous white powder, which dissolves again on cooling. A doable
dioctoborate and chloride of the formula BijOigMgo'^/ ^,»Mg jj, occurs native, in laige
crystals belonging to the regular system, as hoa^aciU and massive as siattfurtUt, The
COMPOUNDS OF MAGNESIUM. 513
name compound may be obtained artificially in the crvRtallized form by fusing mag-
netic ortlioborate with boric anhydride, raagnesic chloride, and sodic chloride, allow-
ing the mass to cool slowly, anc) treating with dilute hydrochloric acid, when the
crystals of boracite remain undissolved.
Magnesio silicates. — A number of maf^nesic silicates occur in nature
as minerals. Peridote is a dimagnesic silicate {prthosUicate) of the for-
mula SiMgo^'y It occurs in rhombic crystals, generally green-colored,
owing to the presence of iron, or in granular m&^^ses. Enstatite is mono-
magnesic siUaUe (metcmlioate) SiOMffo". It forms monoclinic crystals,
which generally contain iron. The following natural magnesic silicates
are also known :
Ophite or noble serpentine. Trimagnesic disiliccUe, Si20Mgo''3.
Meerschaum. Tetrahydric dimagnesie irisilicate, . SijOjHo^Mgo",.
Steatite. Trimagnesic tetrasilicatfy Si^OgMgo'^g.
Talc. Tetramagnesic peniasilicatey SigQgMgo''^.
Numerous natural compound silicates of magnesium with other
metals are also known.
COMPOUNDS OF MAGNESIUM WITH SULPHUR AND WITH
HYDROSULPHYL,
3fagn€sie sulphide, MgS^^. — Magnesium is not acted upon by sVilphur at the boiling-
point of the latter; but when the metal is heated to redness in the vajjor of sulphur,
magnesic sulphide is formed. It may also be prepared by passing the vapor of car-
bonic disulphide over red-hot magnesia. It forms a gray or brown, hard, brittle slag.
Water decomposes it, yielding a mixture of magnesic hydrate and sulphhydrate.
When an excess of sodic sulphide is added to the solution of a magnesium salt, the
precipitate which is formed consists not of magnesic sulphide, but of magnesic hydrate.
Magnesic sulphhydrate, MgHs,, has not been prepared pure. It may be obtained in
solution by passing sulphuretted hydrogen into water in which matrnesia is suspended.
On evaporating the solution, sulphuretted hydrogen is given off and magnesia re-
COMPOUNDS OF MAGNESIUM WITH NITROGEN AND WITH BORON.
Magnetic nitride, N2Mg„ is prepared by heating magnesium in nitrogen or gaseous
ammonia. The product is an amorphous greenish-yellow mass, which in contact with
water, or even in moist air, is decomposed with formation of ammonia and magnesia :
N,Mg8 -f 30H, = 2NH8 + 3MgO.
Magnesic nitride. Water. Ammonia. Magnesic oxide.
Magnesie boride, B^Mgg, is formed when magnesium is heated with amorphous boron
in a closed crucible. It can be obtained, mixed with magnesia, by heating boric an-
hydride with magnesium. In contact with hydrochloric acid, it evolves boric hydride,
BHf, mixed, however, with a large excess of hydrogen.
COMPOUND OF MAGNESIUM WITH SILICON.
Maanei
dride, i
hydride, p. 311.
General Properties and Reactions of the Compounds of
Magnesium. — The salts of magnesium with colorless acids are colorless.
33
614 INORGANIC CHEMISTRY.
The soluble salts have a bitter taste. The hydrates of the alkalies and
of baryta precipitate from solutions of magnesium salts gelatinous mag-
nesic hydrate, insoluble in an excess of the precipitant. When salts of
ammonia are present in sufficient quantity, no precipitation occurs with
the above reagents in the coldy owing to the formation of double salts of
ammonium and magnesium, which are not decomposed at ordinary
temperatures. For the same reasons the salts of magnesium are only
imperfectly precipitated by ammonia. Sodic carbonate precipitates a
basic carbonate ; ammonium salts prevent the precipitation. Ammo-
nio phosphate gives a white crystalline precipitate of magnesic am-
monic phosphate, POAmoMgo'',60Hj, very sparingly soluble in
water, insoluble in aqueous ammonia. Magnesium compounds im-
part no coloration to the non-luminous flame. The spark spectrum
of magnesium displays characteristic lines in the green, coincident
with lines of the solar spectrum.
ZmO, Zn.
Atomic weight = 66.3. Molecular weight = 65.3. Molecular and
atomic volum^e I I )- 1 lUre of zinc vapor weighs 32.65 enths. Sp.
^.6.8 to 7.2. i?u8^^a<420°C.(788°F.), £ot&aa040°C.(1904°F.).
Atomicity ''. Evidence of aiomiciiy :
Zincic chloride, Zn"CI,.
Zincic oxide, Zn"0.
Zincic hydrate, Zn"Hoj.
History, — The ores of zinc were employed by the ancients in the
preparation of brass, which they obtained by melting copper with these
ores; but zinc was not recognized as a distinct metal till the sixteenth
century.
Occurrence. — Zinc is asserted to have been found native near Mel-
bourne, in Australia. It occurs as oxide (ZnO) in red zinc ; as sul-
phide (ZnS'') in the mineral zinc^lende; as carbonate (OOZno") in
calamine, or zinc-spar ; as silicate (SiZno"„OH,) in siliceous calamine,
or zinc-glass; and as double oxides of the general formula 'R"202Ro"
in franiclinite (Te^gO^Zno'') and gahnite or zinc-spinette TAl^'jO^Zno'').
Extraction. — Zinc is obtained from the carbonate, less frequently
from the sulphide. Siliceous calamine, red zinc and franklinite are also
worked. The first operation in the process of extracting the zinc con-
sists in roasting the ore in order to convert it into oxide. In the case
of the carbonate this is efFe<*ted simply by expulsion of carbonic anhy-
dride ; the sulphide is oxidized by the oxygen of the air with evolution
of sulphurous anhydride. In roasting the sulphide it is necessary to
avoid the formation of zincic sulphate, as this salt would, in the subse-
quent reducing process, be reconverted into sulphide and thus lost
The roasted ore is then mixed with half its weight of powdered coal,
and distilled from fire-clay tubes or from muffles placed in a furnace.
At first a finely divided powder known as zinc^ustj and consisting of
ZINC. 515
a mixture of zinc with zincic oxide, frequently also aocompanied by
cadmium^ passes over. Afterwards the liquid metal distils over and is
collected in iron receivers, from which it is removed from time to time
during the distillation and cast into plates.
Commercial zinc is seldom pure. It generally contains lead, iron,
carbon, and sometimes arsenic and cadmium. It may be obtained
almost pure by redistillation from clay retorts, the first portions of the
distillate, which contain arsenic and cadmium, being rejected, and the
operation being interrupted before all the zinc has passed over. The
iron, lead, and other less volatile impurities remain in the retort. In
order to prepare perfectly pure zinc, the crude metal is dissolved in
sulphuric acid, and sulphuretted hydrogen is passed through the acid
solution of zincic sulphate. In this way lead, cadmium, and arsenic
are precipitated as sulphides. The filtered solution is boiled to expel
sulphuretted hydrogen, and the zinc is precipitated as carbonate by the
addition of sodic carbonate. The zincic carbonate is converted into
oxide by ignition, and the oxide is reduced by distillation from a porce-
lain retort with pure charcoal prepared from sugar. Any iron which
may have been contained in the purified carbonate remains in the
retort.
Properties. — Zinc is a white lustrous metal, with a slightly bluish
tinge. It has a crystalline, somewhat laminar fracture, and may be
obtained in crystals by fusing the metal, allowing it to partially solidify,
and then pouring off the still liquid portion. It generally crystallizes
in flat hexagonal pyramids, but occasionally exhibits forms belonging
to the regular system, especially when it contains traces of copper. At
ordinary temperatures it is brittle; between 100° C. (212° F.), and
150° C. (302^ F.), it is so malleable and ductile that it may be rolled
into plates and drawn into wire; at 205° C. (401° F.) it again becomes
so brittle that it may be powdered in a mortar. It may be distilled at
a bright red heat. In dry air it preserves its lustre at ordinary tem-
peratures ; in moist air it becomes covered with a thin coating of basic
carbonate, which preserves it from further action.
Readiona, — 1. When heated in air, zinc inflames, emitting a brilliant
bluish light, and giving off clouds of zincic oxide. The combustion of
zinc is best shown by pre&sing thin zinc turnings into the form of a cyl-
inder ; this, when ignited at a flame, readily burns.
2. Pure zinc is very slowly attacked by dilute sulphuric and hydro-
chloric acids, but the addition of a few drops of platinic chloride to the
liquid causes the zinc to dissolve rapidly, with evolution of hydrogen,
the finely divided platinum, which is deposited on the zinc, forming
with the latter a voltaic couple. For the same reason commercial zinc,
which always contains traces of electronegative metals, is rapidly dis-
solved by dilute acids. In cold nitric acid the metal dissolves without
evolution of gas, the nascent hydrogen being employed in reducinganother
portion of the acid to ammonia ; in hot nitric acid it dissolves with evo-
lution of nitric oxide, nitrous oxide, and free nitrogen, whilst ammonia is
also formed. When zinc is acted upon by hot dilute sulphuric acid, or
by concentrated sulphuric acid even in the cold, sulphuretted hydro-
516 INORGANIC CHEMISTRY.
gen, formed by the reduction of a portion of the acid, is mixed with the
hydrogen which is given off:
5SO,Ho, + 4Zn = 4SO^no" + SH^ + 40H^
Sniphnric Zincic Snlphuretted Water,
acid. sulphate. hydrogen.
3. Zinc also dissolves in warm solutions of potassic, sodic, and
aramonic hydrate, with evolution of hydrogen and formation of a
double oxide :
20KH + Zn = ZnKo, + H,.
PotasBic Dipotassic
hydrate. zincic oxide.
4. It slowly decomposes aqueous vapor at 100° C. (212° F.) :
20H, + Zn = ZnHoj + H^.
Water. Zincic hydrate.
Uses. — Zinc, in the form of sheets, is employed for roofing and other
purposes in which lightness and the power of resisting the action of
the weather are required. In order to preserve iron from rust, the
metal is sometimes coated with zinc, in which condition it is known as
galvanized iron. Zinc is used in the preparation of plates for voltaic
batteries. The finely divided powder obtained in the distillation of
zinc, and known as zinc-dust, is frequently employed as a reducing
agent in organic chemistry, many oxygenated organic substances, which
are unacted upon by all other reducing agents, parting with their oxy-
gen when distilled with zinc-dust. The use of zinc in the desilveriza-
tion of lead has already been described (p. 448).
COMPOUNDS OF ZINC WITH THE HALOGENS.
Zincic chloride, ZnClj.
Moleeviar weight = 136.8. Molecular volume 1 1 L
Zinc foil inflames spontaneously at ordinary temperatures in chlorine
gas and burns, forming zincic chloride. The chloride may also be ob-
tained by dissolving zinc in hydrochloric acid, evaporating the solu-
tion, and distilling the residue; or by distilling anhydrous zincic sul-
phate with sodic or calcic chloride. Zincic chloride is a white very
deliquescent mass. At ordinary temperatures it is soft like wax; it
fuses somewhat above lOO*' C. (212° F.) ; at a higher temperature it
sublimes in white needles, and may be distilled without decomposition.
It is very soluble both in water and in alcohol. The concentrated so-
lution is powerfully caustic: it destroys vegetable fibre, and therefore
cannot be filtered through paper. When a little hydrochloric acid is
COMPOUNDS OP ZINC. 517
added to a syrupy eolntioD of zincic chloride, the liquid deposits deli-
quescent octahedra of the mouaquate, ZnCljjOH,. The solution of
zincic chloride canuot be evaporated without decomposition : hydro-
chloric acid is given off, and an oxychloride of zinc remains. Oxychlo-
rides of varying composition, consisting of mixtures of ZnHoCl and
ZnHoj, are also obtained by heating the concentrated solution of zincic
chloride with zincic oxide, and then adding water, when the oxychlo-
rides are precipitated. In the same way, by boiling the solution of the
chloride with the requisite quantity of oxide, a plastic mass is obtained
which, like the mixture of magnesic chloride and magnesia (p. 508)
speedily becomes quite hard. — Owing to its great affinity for water,
zincic chloride frequently abstracts the elements of water from organic
substances, thus producing new compounds, a property of which appli-
cation is made in organic research. It is also used as a caustic in med-
icine, for which purpose it is cast into sticks. — Zincic chloride forms
crystalline, deliquescent double salts with the chlorides of the alkalies:
for example, dipoiasmo zineio chloride, ZnCl2,2KCl ; disodio zindo cfdo^
ride, ZnCl„2NaCl.
Zijieie bromidSy ZnBrt, is prepared like the cliloride. It crystallizes in very deli-
qnescent prisms, is readily fusible, and may be sublimed in white needles.
Zincic iodide, ZnU. — Zinc filings and iodine, when heated together, unite to form the
iodide. Zincic iodide is readily fusible, and sublimes in colorless needles. From a
concentrated aqueous solution it crystallizes in deliquescent regular octahedra. The
concentrated solution takes up oxygen from the air, with liberation of iodine. In like
manner, when zincic iodide is heated in air, iodine is giren off, and zincic oxide is
produced. Zincic iodide combines with the alkaline iodides to form double salts.
Zincic fluoride, ZnFj, is obtained by dissolving zincic oxide in aqueous hydrofluoric
acid. On evaporation, the solution deposits small, shining, rhombic octahedra of the
formula ZiiFs,40Hs, sparingly soluble in water. Zincic fluoride forms crystalline
doable salts with potassic and other fluorides. The potassium salt has the formula
ZnF,,2KF.
Zincic silicofluoride, SiZnFe,60Hs, forms very soluble hexagonal crystals.
COMPOUNDS OF ZINC WITH OXYGEN AND
HYDROXYL.
Zincic oxide, .... ZnO. Zn=0.
Zincic hydrate, . . . ZnHoj. H— O— Zn— O— H.
Zincic oxide, ZnO, occurs native, sometimes in hexagonal crystals,
more frequently in granular masses, as red zinc ore, the color being due
to an admixture of manganese. It is formed when zinc is burnt in air
(p. 616). On a large scale it is prepared by distilling zinc from earth-
enware retorts, allowing the zinc vapor to burn as it issues from the
retort, and passing the products of combustion through chambers in
which the oxide collects. It may also be prepared by igniting the basic
carbonate obtained by precipitating the solution of a zinc salt with an al-
kaline carbonate. The zincic oxide prepared by combustion is a white floc-
culent substance, and was known to the alchemists as lana philoaophica ;
that obtained by the ignition of the carbonate is an amorphous powder.
The artificial oxide may be obtained in the hexagtmal forms of the
518 INORGAKIC CHCMISTRY.
natural variety by ignitiDg it strongly in a current of oxygen. Crystals
of zincic oxide are also sometimes found in the cooler parts of the muffles
of the zinc furnaces. Zincic oxide has a sp. gr. of 5.6. It is insoluble
in water, readily soluble in acids. When heated it assumes a yellow
color, changing to white again on cooling. When heated in the oxy-
hydn^en name it does not fuse, but emits a brilliant light, and on
cooling continues to phosphoresce for some time in the dark. Zincic
oxide is employed as a very permanent white pigment under the name
of zinc white. As the sulphide of zinc is also white, zinc white does
not change color when exposed to sulphurous exhalations, possessing in
this respect a marked superiority over white lead.
Zincic hydrtUCy ZnHoj, is precipitated as a white amorphous powder
by the addition of sodic or potassic hydrate, or ammonia, to the solution
of a zinc salt. The precipitate is insoluble in water, but soluble in an
excess of the precipitant. It may be obtained in a crystalline form by
immersing a sheet of zinc, round which a copper wire has been wound,
in a solution of the hydrate in ammonia ; rhombic prisms of the hy-
drate are formed upon the surface of the zinc. A saturated solution
of the hydrate in caustic potash deposits on standing r^ular octahedra
of the formula ZnHo2,0H2. When heated, zincic hydwte is readily
decomposed into zincic oxide and water.
OXY'SALTS OF ZINC.
Zincic nitratCf ^r^Zno^^fiOHi, separates from a conceDtrated solution of the oxide
in nitric acid in deliquescent, colorless, fonr-sided prisms. It is readily soluble in
water and in alcohol. At 36^ C. (96.8^ F.) it fuses in its water of ciystallization, and,
when heated to 100^ C. (212^ F.), parts with water and nitric acid, yielding a basic
salt.
Zincic carboTicUe, OOZno", occurs native in translucent rhombohedra
as calamine. The native carbonate is rarely pure, a portion of the zinc
being generally replaced by calcium, iron, and other metals isomorphous
with zinc. Zincic carbonate is precipitated when hydric potassic car-
bonate is added to the solution of a zinc salt. Normal potassic and
sodic carl)onates precipitate basic zincic carl)onates of variable compo-
sition. The basic precipitate is insoluble in water and in solutions of
potassic and sodic carbonate, but soluble in ammonic carbonate.
Zincic sulphate ( White vitriol), SOjZno'', is prepared on a large
scale by roasting the native sulphide and extracting the mass with
water, but is most readily obtained pure by dissolving zinc in sulphuric
acid. At ordinary temperatures it crystallizes in large transparent
rhombic prisms of the formula SOHo^no",60H^ isomorphous with
Epsom salt (p. 511), soluble in two-thirds of their weight of water at
ordinary temperatures, in one-sixth of their weight of boiling water ;
insoluble in alcohol. The crystals eiBSoresce slowly in air, and, when
heated to 100° C. (212° F.), or exjwsed in vacuo oversulphuricacid, part
with 6 aq., leaving the salt SOHojZno", which is converted at a temper-
ature of 240° C. (464° F.) into anhydrous zincic sulphate (SOjZno")
and water. At temperatures above 40° C. (104° F.) solutions of zincic
COMPOUNDS OF ZINC. 519
sulphate deposit monoclinic crystals having the formula SOHo^Zno'V
50H,, also isomorphous with the corresponding mc^nesium salt. When
the anhydroas salt is heated to a high temperature it gives off sulphur-
ous anhydride and oxygen, yielding a basic salt, a hot saturated solu-
tion of which deposits on cooling lustrous laminsB of the formula
80(OZnHo)4. The same compound may be obtained by boiling a
solution of zincic sulphate with zincic oxide. At a white heat the
anhydrous sulphate is converted into zincic oxide. Zincic sulphate
forms double sulphates with the sulphates of the alkalies, zmoic dipo-
taasie dmJphcUe, gQ*|^^Zno^^,60H2, and ziuGic diammonio disulphate,
or\\ Zno",60H„ which are isomorphous with and closely resemble
the corresponding magnesium compounds. Mixed solutions of zincic
and magnesic sulphates deposit crystals containing the two salts in
variable proportions. — Zincic sulphate is employed in medicine and in
calico printing.
Zineie orthaphosphale. — The normal or trizincie salt, pQ«"^/,Zno^',40Hi, is formed
when hydric disodic phosphate is added to a solution of a zinc salt. It is a white
precipitate, which, when deposited from cold solutions, is ffelatinons, bnt becomes
crystalline on standing or on heating. — The acid phosphates have not been prepared.
Zincic ailiccUc — A dtzincic silieatCy SiZni/^2, occurs native in hexagonal prisms as
fpiUemite. It may be obtained artificially in the crystallized form by passing silicic
fluoride over zincic oxide heated almost to whiteness, or by the action of zincic fluoride
on silicic anhydride. — The same compound with 1 aq., SiZno^^'s OHi — perhaps to be
regarded as 8iO(OZnHo)3 — occurs in rhombic crystals as the mineral zinc glass or
siliceous eaiamine.
COMPOUNDS OF ZINC WITH SULPHUR.
Zincic sulphide, ZnS", occurs native as zinc blende, either crystal-
lized in forms belonging to the regular system, or mnssive. The color
of the mineral varies from a [wtle yellow, in the purer specimens, to a
brown or black in the massive variety, due to the presence of iron and
other impurities. Zincic sulphide is occasionally found in hexagonal
prisms as the mineral wurtzUe. It is obtained as a white amorphous
precipitate when sulphuretted hydrogen is passed through a solution of
zincic acetate. From neutral solutions of zinc salts with mineral acids
the zinc is only partially precipitated by sulphuretted hydrogen, and in
acid solutions no precipitate is pr«»duced. All zinc salts, however, are
completely precipitated by the addition of alkaline sulphides or sulph-
hydrates to their solutions. The precipitated zincic sulphide is insolu-
ble in water and in acetic acid, but readily soluble in mineral acids with
evolution of sulphuretted hydrogen. Zincic sulphide is difficultly fusi-
ble. When the amorphous sulphide is heated to a very high tempera-
ture in a current of sulphuretted hydrogen, or sulphurous anhydride, it
sublimes in colorless hexagonal crystals identical with those of wurtzite.
Drizineie dipotasaie ietramdphidc, S4Zn3Kt.
K— S— Zn— S— Zn— S— Zn— S— K.
This compound is obtained by fusing together 1 part of zincic sulphide, 24 parts of
potaasic carDonate, and 24 parts of sulphur, at a rea heat for ten minutes. On extract-
620 INORGANFC CHEMISTRY.
ing the cooled mam with water, the double sulphide remains in the form of colorless
transparent laminm, which may be boiled with water without decomposition. — The cor-
responding sodium com{)ound BfZnjNa,, may be obtained in a similar manner, and
forms a pale flesh-c<3lored crystalline powder.
Zincxc pentasulphidef SsZn, is obtained as a white precipitate by the addition of po-
ta&sic pentasiilphide to the neutral solution of a zinc salt It asanraes a pale yellow
color on drving, and, when heated with exclusion of air, gives off sulphur, and is ooo-
Terted into the monosulphide.
COMPOUNDS OF ZINC WITH THE PENTAD ELEMENTS,
Zindc nitride, NsZn,. — When zinc ethyl (see Organic Chemistry) b acted upon bj
gaseous ammonia, ethylic hydride is evolved, and zinc diamii*e is formed :
Zn(C,H5), + 2NH, = ZnfNH,), + 2{^'^».
Zinc ethyl. Ammonia. Zinc Ethylio
diamine. hydride.
The zinc diamine thus obtained is a white amorphous powder, which is decomposed
by water with formation of ammonia and zincic hydrate:
ZnNH,), 4- 20 FT, = ZnHo, + 2NH,.
Zinc Water. Ziucic Ammonia,
diamine. hydrate.
When zinc diamine \» heated to low redness in absence of air, ammonia is evolved,
and zincic nitride remains as a green powder:
3Zn(NH,), = NiZn, + 4NH3.
Zinc Zincic Ammonia,
diamine. nitride.
In contact with water zincic nitride b decomposed with great evolution of heat, yield-
incf ammonia and zincic oxide.
Zincic phosphide, P^Zn,, is prepared by heating finely divided zinc in the vapor of
phosphorus. An impure compound b obtained by heating a mixture of phosphoric
anhydride, zincic oxide, and charcoal. Zincic pho-ipliide forms a steel-gray metallic
ma8s, which dissolves in hydrochloric acid with evolution of phosphoretted hydrogen.
Zincic (jurunide^ As^Zn,, is formed with incandescence when zinc and arsenic are
heated together in the proportions required by the formula. It b a gray, brittle me-
tallic mass, which, when acted upon by dilute hydrochloric acid, evolves pure arseni-
uretted hydrogen (p. 367).
Zincic antimonide, Bb^Zog, b obtained as a white crystalline metallic mass by fusing
together 57 parts of antimony and 43 parts of zinc By allowing the fused com()Ouna
partially to solidify, and pouring off the still liquid portion, it may be obtained in well-
formed hexagonal prisms. When treats with hydrochloric acid, it evolves a mixture
of hydrogen and antimoniuretted hydrogen (p. 380). — A dizineic diantimonide of the
formula ''Sb'^aZn,. crystallizing in rhombic octahedra, is prepared by fusing ($8.5 parts
of antimony with 31.6 parts of zinc.
General Properties and Reactions of the Compounds op
Zinc. — The salts of zinc are colorless when the constituent acid is so.
They have an astrin^nt metallic taste, and are poisonous. From their
solutions caustic alkalies and ammonia precipitate white zincic hydrate,
soluble in excess of the precipitant. Alkaline carbonates precipitate a
basic carbonate, soluble in ammonic carbonate, but not in excess of po-
tassic or sodic carbonate. Baric carbonate does not precipitate solutions
of zinc salts. SuJphuretted hydrogen gives no precipitate in acid solu-
tions, except in the case of salts of organic acids iu solutions acidulated
COMPOUNDS OF BERYLLIUM. 621
with these acids; ammonio sulphide precipitates white hydrated zincic
sulphide. Potassicferrocyanide gives a white precipitate of zincic fer-
rocyanide. Heated on charcoal in the reducing flame of the blowpipe,
zinc compounds yield a characteristic incrustation of zincic oxide, yel-
low while hot, white when cold. If this incrustation be moistened with
cobaltous nitrate and again heated, it assumes a fine green color (Rin-
mannas green). The salts of zinc do not color the non-luminous flame.
The spark spectrum of zinc shows characteristic lines in the red and in
the blue.
BEBTLLIUM, Be.
(Sometimes termed Glucinum, symbol G.)
Atomic weight = 9. Probable molecular weight = 9. Sp. gr. 2,1 . Fuses
ai a red heat. Atomieity ". Evidence of atomicity :
Beryllic chloride, Be'^CI^.
Beryl! ic oxide, Be"0.
Beryllic hydrate, Be^Hoj.
History. — Beryllic oxide was prepared by Vauquelin in 1798. Wohler
first isolated the metal in 1828.
Occurrence, — Beryllium occurs in combination in a few rare minerals.
Beryl, a native double silicate of beryllium and aluminium of the for-
mula SijOg('Al'"20g)^*Beo"3, is the most abundant source of the beryl-
lium compounds. This mineral crystallizes in hexagonal prisms, gen-
erally opaque, and of a greenish tint. The precious stone emerald is a
transparent beryl of a brilliant green color; bluish-green specimens,
when transparent, are known as aquamariney and are also employed as
gems. The mineral phenacite is a silicate of beryllium having the for-
mula SiBeo'V
Preparation. — Metallic beryllium is prepared by passing the vapor
of beryllic chloride along with a current of hydrogen over heated so-
dium, and afterwards fusing the metal thus obtained in a crucible under
sodic chloride.
Properties. — Beryllium is a lustrous silver-white malleable metal of
sp. gr. 2.1. It fuses below the melting point of silver. When fused
in air it becomes covered with a thin coating of oxide, which checks
further oxidation ; but when heated in a finely divided state it inflames,
burning with a very brilliant light. It does not decompose water, even
at 100° C. (212° F.). Dilute hydrochloric acid dissolves it readily in
the cold, with evolution of hydrogen, but dilute sulphuric acid does not
attack it till heated, whilst nitric acid, even when hot and concentrated,
acts upon it only very slowly. It is not attacked by ammonia, but
dissolves readily in caustic potash with evolution of hydrogen.
COMPOUNDS OF BERYLLIUM WITH THE HALOGENS.
Beryllic chloride^ BeCl2. — Molecular weight = 80. Molecular vol-
ume QD. — The anhydrous chloride is obtained in lustrous, colorless,
needle-shaped crystals by passing chlorine over a heated mixture of
522 INOBOAKIC CHEIflSTRY.
berjilic oxide and charcoal. It is readily fusible and volatile. The
crystals deliquesce rapidly when exposed to air, and, when thrown into
water, dissolve with a hissing sound, evolving heat The aqueous
solution, which may also be obtained by dissolving the oxide in hydro-
chloric acid, deposits, by spontaneous evaporation over sulphuric acid,
colorless crystals of the formula B6Cl2,40H2, from which the water of
crystallization cannot be expelled without decomposition of the salt.
Beryllie bromide, BeBrt, and Beryllic iodide, BeTt, are both obtained in the form of
colorless needles by the direct union of their element*.
Beryllic fivaride, BaFs. — The anhydrous salt is not known. The solution of beryllic
hydrate in hydrofluoric acid deposits on evaporation an amorphous mass, which when
further heated gives off water and hydrofluoric acid* beinf? partially converted into
oxide. It forms double fluorides with the fluorides of the alkali metals.
COMPOUNDS OF BERYLLIUM WITH OXYGEN AND
HYDROXYL.
Beryllic oxide, Beryllia^ . BeO. Be:=0.
Beryllic hydrate, .... BeHo^ H— O— Be— O— H.
Beryttie oxUle or BeryUiay BeO. — This oxide is prepared from the
mineral beryl, a beryllic aluminic silicate (p. 521). The finely
powdered mineral is fused with three parts of anhydrous potassic
carbonate, and the cooled mass is treated with concentrated sul-
phuric acid, the excess of acid being expelled by heating. On
extracting with water, the sulphates of beryllium, aluminium, and
potassium dissolve, whilst the silica remains and may be filtered
ofi; The solution is evaporated until a crust begins to form on the
surface. On standing, the greater portion of the alumina crystal-
SO.KO-,
lizes out as potash alum, S^* ('Al'",Oj)^240H2, the beryllia
SO,Ko— I
remaining in solution. A fresh crop of alum crystals may be obtained
by the further exaporation of the mother liquor from the first crop.
The filtered liquid from the second crop of crystals is then poured into
an excess of a warm solution of ammonic carbonate, and the whole is
allowed to remain for some days in a stoppered bottle, agitating from
time to time. The precipitate, consisting of alumina and ferric oxide,
is filtered off, and the beryllia is precipitated from the solution, either
as basic carbonate by protracted boiling, or as hydrate by acidulating
with hydrochloric acid and afterwards rendering alkaline with am-
monia. By ignition the carbonate or hydrate is converted into oxide.
Thus prepared beryllia forms a white bulky amorphous powder of sp.
gr. 3.08, resembling magnesia in appearance. It is insoluble in water,
and, after being strongly ignited, does not dissolve in dilute acids. Like
magnesia, it becomes crystalline by exposure to a very intense heat.
Beryllic hydrate, B^Kch, is obtained as a gelatinous precipitate when ammonia is
added to a solution of a beryllium salt. After drying at 100^ C. it forms a bulky white
COMPOUNDS OF BERYLLIUM. 523
powder, which at a hi|<her temperature is ood verted into the oxide. It ia insoluble in
water, soluble in solutions of caustic potash, caustic soda, and ammonic carbonate, but
insoluble in ammonia. If the solution in caustic potash be diluted and boiled, the
bervUic hydrate is reprecipitated. From the solution in ammonic carbonate a precipi-
tate of a basic beryllic carbonate separates on boiling. Beryllic hydrate dissolves in a
boiling solution of ammonic chloride with formation of beryllic chloride and with lib-
eration of ammonia.
OXY'SALTS OF BERYLLIUM.
NO. ^
BeryUie nitrate, ../^Beo^^ydOHs, forms deliquescent crystals, readily soluble in
alcohol. At a temperature of 2oO^ C. it is completely converted into oxide.
JBeryilie earbonaU. — The precipitate produced in solutions of beryllium salts by alka-
line carbonates is a basic beryllic carbonate of the formula CHo(OBeHo)8,30Hs. This
salt dissolves in water containing carbonic anhydride, and the solution, when evapo-
rated over sulphuric acid in an atmosphere of carbonic anhydride, deposits crystals of
the normal carbonate. COBeo^^,40H9. These, on exposure to the air, spontaneously
part with carbonic anhydride and are re-converted into the basic salt.
Beryllio sulphate, SOHo2Beo",30H2, crystallizes from aqueous solu-
tions in quadratic octahedra, which are soluble in their own weight of
water at ordinary temperatures, and eflBoresce on exposure to the air.
The water of crystallization is expelled at 110° C, leaving the salt
SOHojBeo". This salt is stable at 1 60° C, but at a higher temperature
the water of constitution is expelled and the anhydrous salt SOjBeo" re-
mains. At a red heat the anhydrous salt is converted into beryllia. From
solutions containing free sulphuric acid, beryllic sulphate crystallizes in
large efiSorescent monoclinic prisms of the formula SOHosBeo^'^BOEJ^,
isomorphous with those of Epsom salt.* Mixed solutions of beryllic
and magnesic sulphates deposit crystals containing the two metals in
variable proportions.
Beryllic orih(mhwphate.—K hydrio beryllic 'phmphaie, POHoBeo''',30Ht, is obtained as
a white amorphous precipitate when hydric disodic phosphate is added to the solution
of a beryllium salt. When the sodic phosphate is added to a solution containing
beryllic nitrat« and ammonic chloride, the triple salt, disodic diammonic heryUicfhM-
phcUe, P30sNaO}(NH/))sBeo^'',70H9, is precipitated as a white crystalline powder.
BeryUie silicate, Slbeo^^t, occurs native in hexagonal crystals as phmaeUe,
COMPOUND OF BERYLLIUM WITH SULPHUR.
BeryUie tndphide, BeS^^, is formed as a gray infusible mass when beryllium is heated
in Kulphur vapor. Alkaline sulphides precipitate only beryllic hydrat;e from solutions
of beryllium salts.
GENfSRAL Properties and Reactions of the Compounds of
Beryllium. — The salts of beryllium with colorless acids are colorless ;
they have a sweety slightly astringent taste and an acid reaction. Ocnistio
alkalies, ammonia, and ammonio suljyhide precipitate white ilocculent
beryllic hydrate, in the ca.se of the last precipitant with evolution of
sulphuretted hydrc^en. The precipitate is soluble in excess of caustic
alkali, but not in excess of ammonia. Beryllic hydrate is soluble in
ammonio oarbonaie, and may thus be separated from alumina, along
* Marignaoi however, doubts whether these salts are really isomorphous.
E24 INORGANIC CHEMISTRY.
with which it is usually precipitated in analysis. Beryllium salts do
not color the non-luminous flame. The spurk spectrum contains two
characteristic lines in the blue.
CHAPTER XXXIV.
DYAD ELEMENTS.
Section III.
OADMnm, cd.
Atomic weight =112. Molecular weight =112. Molecular and atomic
volume II i- 1 litre of cadmium vapor weighs 56 critha. Sp. gr. 8.6.
Fuses at 320° C. (608° F.). Boils at 860° C. (1680° F.). Atomi-
city ". Evidence of atomicity :
Cadmic chloride, 0d"Cl2.
Cadmic oxide, Cd"0.
History. — Cadmium was discovered independently and almost simul-
taneously by Stromeyer and by Hermann in 1817.
Occurrence. — Cadmium occurs in small quantities in many zinc ores.
A fibrous zinc blende found at Przibram in Bohemia contains as much
as from 2 to 3 per cent, of cadmium. The rare mineral greenockite is a
sulphide of cadmium (OdS'^).
Preparation. — In the process of extracting zinc from ores containing
cadmium, the latter metal distils over first, and is for the most part
oxidized by the air in the receivers. By distilling these first portions
with powdered coal at as low a temperature as possible, cadmium is
obtained almost pure. In order to purify it thoroughly, it is dissolved
in dilute sulphuric or hydrochloric acid and precipitated from the acid
solution by sulphuretted hydrogen, the zinc remaining in solution. The
cadmic sulphide is redissolved in concentrated hydrochloric acid, and
the cadmium is precipitated from the solution by an excess of amnionic
carbonate, which dissolves any arsenic and copper that may be present.
The cadmic carbonate is converted by ignition into oxide, which by dis-
tillation with a tenth of its weight of powdered coal yields the pure
metal.
Properties. — Cadmium is a white lustrous metal, with a fibrous frac-
ture. When pure it is very malleable and ductile. It loses its lustre
by exposure to the air, and when heated in air burns, giving off a brown
smoke of cadmic oxide. Dilute sulphuric and hydrochloric acids dis-
solve it slowly with evolution of hydrogen. Nitric acid rapidly dis-
solves it. Zinc precipitates it in the metallic form from the solution
of its salts.
COMPOUNDS OF CADMIUM. 525
COMPOUNDS OF CADMIUM WITH THE HALOGENS.
Cadmic chloride, OdClj. — A solution of the metal or of the oxide
in hydrochloric acid deposits on evaporation colorless prisms of the
composition OdCl2,20H2, which efflorestje when exposed to the air.
The water of crystallization may be expelled by heat without decompo-
sition of the salt. The anhydrous chloride fuses below a red heat, and
at a higher temperature may be sublimed in colorless laminse. One
hundred parts of water at 20° C. dissolve 141 parts of the anhydrous
salt, and the solubility scarcely varies with the temperature. It forms
a number of crystalline double chlorides with the alkaline and many
other chlorides.
Cddmic bromide^ Cd6r3. is prepared by digesting cadmium with bromine and water.
On evaporation the solution yields efflorescent acicular crvstals of the formula CdBrs-
4OH3, which on heating become anhydrous. At a higher temperature the salt fuses
and sublimes in colorless laminse. It forms double bromides willi the bromides of the
alkalies and alkaline earths.
Otdmic iodide, Cdit, is pi*epared like the bromide. It crystallizes from water in
fnsible hexagonal plates. When heated it is decomposed with evolution of iodine.
One hundred parts of water at 20** C. (68° F.) dissolve 93 parts of the salt ; at 100° C.
(212° F.), 133 parts. It is also soluble in alcohol. If forms numerous double iodides
with the iodides of other metals. Cadmic iodide is employed in photography.
COMPOUNDS OF CADMIUM WITH OXYGEN AND
HYDROXYL.
Cadmic oxide, . . . CdO. Cd=0.
Cadmic hydrate, . . OdHo^. H— O— Cd— O— H.
Cadmic oxide, CdO, may be prepared like the oxide of zinc by the
combustion of the metal. It is thus obtained as a brown amorphous
powder. When cadmic nitrate is ignited the oxide remains in the form
of microHcopic octahedra, which by reflected light appear blue-black, by
transmitted light brown. It is insoluble in water, readily soluble in
acids. It is infusible even at a white heat. When heated on charcoal
before the blowpipe, it is reduced, the metal at the same time volatilizing
and burning with formation of a brown incrustation of cadmic oxide
on the charcoal.
Cadmic hydraie, CdHos. is obtained by precipitating the solution of a cadmium salt
with potassic or sodic hydrate, and drying the precipitate at 100° C. (212° F.). It
forms a white powder, insoluble in water and in solutions of potassic and sodic hydrate ;
readily soluble in ammonia and in acids. It absorbs carbonic anhydride from the air.
At 300° C. (572° F.) it is converted into oxide.
OXY'SALTS OF CADMIUM.
Cadmic nitrate, IlX|Cdo^^,40Hs, crystallizes in deliquescent prisms, soluble in
alcohol.
Oadmie earbonctte. — A precipitate approximating in composition to that of the normal .
626 INORGANIC CHEinSTRY.
salt, COCclo^^ is obtained by adding in the cold a solution of a cadmium salt to an
excess of an alkaline carbonate. The precipitate formed at a higher temperature, or
vith a smaller quantity of alkaline carbonate, is a basic salt of varying composition.
Cadmic sulphate, SO,Cdo", is deposited from its solutions by sponta-
neous evaporation at ordinary temperatures in large colorless mono-
clinic crystals of the formula SSO^Cdo^jSOHj. A boiling solution
containing an excess of sulphuric acid deposits warty crystals of a salt
SOjCdo^'yOHj. The anhydrous salt is soluble in less than twice its
weight of water at ordinary temperatures; somewhat more soluble at
100° C. (212° F.). The normal salt is converted by heating into a basic
compound of the formula S02(OCdHo)j|, sparingly soluble in water and
crystallizing in pearly scales. Cadmic sulphate is employed in med-
icine.
COMPOUND OF CADMIUM WITH SULPHUR.
Cadmic sulphide, OdS", occurs native in yellow hexagonal prisms
as the rare mmersl greenockite. It is obtained as an amorphous powder
of a pure yellow color when a solution of a cadmium salt is precipitated
with sulphuretted hydrogen or with an alkaline sulphide. It is soluble
in concentrated nitric and hydrochloric acids, and in hot dilute
sulphuric acid. It fuses at a white heat, and solidifies on cooling in
micaceous scales. By fusing the precipitated sulphide with potassic
carbonate and sulphur, extracting the cooled mass with water, or by
passing the vapor of sulphur over cadmic oxide heated to the highest
possible temperature, cadmic sulphide may be obtained in hexagonal
crystals.
General Properties axd Reactions of the Compounds
OP Cadmium. — The salts of cadmium with colorless acids are color-
less. Caustic alkalies precipitate from solutions of the salts white cadmic
hydrate, insoluble in excess of the precipitant. Ammonia gives the
same precipitate, readily soluble however in excess. Ammonio car-
bonate precipitates cadmic carbonate, insoluble in excess. Sulphuretted
hydrogen precipitates from a hydrochloric acid solution yellow cadmic
sulphide, insoluble in ammonic sulphide and in potassic cyanide, but
soluble in hot dilute sulphuric acid. Heated on charcoal before the
blowpipe, cadmium compounds give a brown incrustation of cadmic
oxide. Cadmium compounds do not color the non-luminous flame.
The spark spectrum displays characteristic lines in the red, green, and
blue.
MERCURY. 527
MEROURT, Hg.
Atomic weight = 200. Molecular weight = 200. Molecular and atomic
volume i I I. 1 litre of mercury vapor weighs 100 criths. Sp. gr, 1 3.69.
Fuses at —39.5° C. (—39.1° F.). Boils at 367.25'' C. (675.05° F.)
(Regnault). Atomicity ", also a pseudo-monad, Evidence of ato^
miciiy:
Mercuric chloride, Hg^Clj.
Mercuric oxide, Hg"0.
Mercurous chloride, 'Hg'jClg.
Mercurous oxide, 'Hg'gO.
History, — Mercury has been known from almost the earliest historic
times.
Occurrence. — Mercury is found native in minute globules dis.semi-
nated through its ores. It occurs in combination as chloride and iodide,
and also with gold and silver in the form of amalgams. Its most
abundant ore is mercuric sulphide or cinnabar. The most important
mines are those of Idria in Carniola, Almaden in Spain, Napa Valley
in California, and at Wolfsstein and Landsberg in the Bavarian Palati-
nate.
ExtroAstion. — At Idria the ore — a mixture of cinnabar with earthy
matters — is placed on the top of a perforated arch, under which the
furnace is situated. After clasing the aperture through which the ore
has been introduced the furnace is lighted. -The flame, along with an
excess of air which is allowed to enter by openings constructed for that
purpose, plays through the perforations of the arch upon the ore,
oxidizing the sulphur to sulphurous anhydried, and volatilizing the
mercury. The products of combustion pass through stone chambers,
in which the mei-cury condenses, and thence into a tower, through
which a stream of water trickles, removing the last traces of mercury
from the escaping gases. At Almaden, the mercury vapor, instead of
passing into stone chambers, is condensed in a series of stoneware bottles
termed aludels, open both at top and bottom, and so arranged that the
neck of each tits into the bottom of the next.
A furnace, in which from 50 to 60 tons of ore can be distilled in
one operation, can be filled and the charge worked off in a day ; but
four or five days must be allowed to elapse before the furnace is suffi-
ciently cool to be recharged. In order to obviate this loss of time, a
continuous process has been devised in which the ore, along with char-
coal, is introduced from time to time at the top of the furnace whilst
the ashes are withdrawn at the bottom.
In the Bavarian Palatinate the ore is mixed with lime and distilled
from iron retorts. Mercury passes over, and a mixture of calcic sul-
phide and sulphate remains. In Bohemia the ore is distilled with
smithy-scales.
Mercury obtained by any of the above processes is freed from me-
chanical impurities by filtering through linen. It is generally sent into
the market in iron bottles.
528 INORGANIC CHEMISTRY.
Preparation of Pure Mercury, — Commercial mercury is generally
contaminated with small Quantities of fomgn metals which it holds in
solution. The presence of these impurities is manifested by a diminu-
tion of the fluidity of the mercury, accompanied by a tendency to ad-
here to glass or porcelain ; a globule of pure mercury runs rapidly and
coherently over a clean inclined surface of porcelain ; but when the
mercury Is impure the globule becomes considerably elongated in its
course, and generally leaves l)ehind it on the porcelain a dark-colored
track of oxide in which traces of the metal are retained. Mercury
may be freed from these impurities by distillation, the surface of the
metal being covered during the operation with a thick layer of iron-
filings to diminish spirting. A very pure product may be obtained by
conducting the distillation in a Sprengel vacuum. Mercury may also
be purified by agitating it with dilute nitric acid, or by leaving it in
shallow vessels in contact with the acid, when the impurities are dis-
solved first. Mercury is also very effectively purified by leaving it for
several days under a layer of concentrated sulphuric acid. Pure mer-
cury ought to leave no residue when dissolved in nitric acid, evaporated,
and ignited.
Properties. — Mercury is a silver-white, very lustrous metal. It is
liquid at ordinary temperatures, but solidifies at — 39.5° C. to a tin-
white, malleable, and sectile mass, crystallizing in r^ular octahedra.
It contracts during solidification. Mercury volatilizes sensibly at ordi-
nary temperatures: a piece of gold leaf suspended in a closed vessel
over mercury becomes in course of time white and silvery, owing to
the absorption of the mercurial vapor by the gold. Mercury boils at
357.26° C. (675.05° F.), yielding a colorless vapor. Pure mercury un-
dergoes scarcely any altemtion in air at ordinary temperatures, though
a very thin film of mercurous oxide is formed on the surface; but at
a temperature near to its boiling point it gradually absorbs oxygen with
formation of red mercuric oxide. Hydrochloric acid, even when hot
and concentrated, is without action upon mercury. Sulphuric acid
does not attack it in the cold ; but the hot concentrated acid dissolves
it with evolution of sulphurous anhydride. When the metal is present
in excess, and the temperature is not allowed to rise to the boiling
point of the mixture, a mercurous salt is formed ; an excess of acid leads
to the formation of a mercuric salt. Cold dilute nitric acid dissolves
it, yielding mercurous nitrate; when an excess of the metal is boiled
with the dilute acid a basic mercurous nitrate is obtained. Hot concen-
trated nitric acid in excess dissolves it with evolution of nitric oxide
and formation of mercuric nitrate. When a rapid stream of water
from a tap is directed from a height of three or four inches upon the
surface of a large mass of mercury, bubbles of mercury are formed and
float on the sur^« of the water. These transmit blue light through
the thin metallic film, and deposit on bursting a minute globule of
mercury. When mercury is triturated with sugar, grease, and various
other substances, it is obtained in a very finely divided state, the union
of the particles of the metal being prevented by the interposition of the
foreign substance. This process is known as the " deadening " of the
mercury. In the case of gray mercurial ointment, which is prepared
MERCURY. 629
by this method, the mercury forms Dearly uniform globules having a
diameter of 0.001 to 0.004 mm. The vapor of mercury when inhaled
acts as a poison, producing salivation. The finely divided mercury
when taken internally has a similar action ; but liquid mercury has
been swallowed without noticeable ill effects.
Z7«««. — Mercury is invaluable to the physicist and the chemist. Many
important physical observations could not have been made without the
aid of apparatus of which mercury forms an essential part. The chemist
employs mercury in collecting and measuring gases which are soluble
in water, and also for the preparation of the mercurial compounds. It
is further used in silvering mirrors, in extracting gold and silver from
their ores by the amalgamation process, and in medicine.
Amalgams.
The alloys of the various metals with mercury are known as amal-
gams. Some amalgams are formed by the direct union of their con-
stituents, the combination either taking place spontaneously at ordinary
temperatures, or requiring the aid of heat. Gold, silver, tin, sodium,
and many other metals may be thus directly amalgamated. In other
cases an indirect process must be resorted to. If the metal is more
electro-positive than mercury, it may frequently be amalgamated by
immersing it in the solution of a salt of mercur}* ; in this way an amal-
gam of copper may be prepared. Other indirect methods of amalga-
mation arei the electrolysis of a solution of the metal, employing
mercury as the negative electrode, and the action of an amalgam of so-
dium upon the solution.
Potaasivm arfialgam. — Potassium and mercury combine with con-
siderable rise of temperature, but without incandescence. The amalgam
is solid when it contains 1 part of potassium to 96 parts of mercury,
but liquid when the proportion of mercury rises to 140 parts. The
solid amalgam crystallizes in cubes.
Sodium amalgam. — Sodium and mercury combine violently at ordi-
nary temperatures, the process being attended with a hissing noise and
vivid incandescence. An amalgam containing 100 parts of mercury to
1 of sodium is viscid ; with 80 parts of mercury, pasty ; with 40 parts,
solid ; and with 30 parts, hard.
The amalgams of potassium and sodium when brought in contact
with water evolve hydrogen. Sodium amalgam is employed as a re-
ducing agent in organic cnemistry (p. 426). It is also used in the ex-
traction of gold and silver (p. 449).
Iron amalgam. — Iron may be amalgamated by rubbing its clean
surface with sodium amalgam.
Ammonium amalgam, — See p. 236.
Copper aTTUiigam, — When copper is immersed in a solution of nitrate
of mercury, the mercury is deposited on the surface of the copper. By
treating finely divided or precipitated copper in this way, and then
triturating it under warm water with the requisite quantity of mercury,
an amalgam of copper may be obtained. Copper amalgam containing
30 per cent of copper is hard enough to scratch tin, but has the re-
34
530 INORGANIC CHEMISTRY.
markable property of beooming soft and plastic bj heatiDg to 100^ C.
(212° F.) and kneading in a mortar, recovering its hardness in the
course of a few hoars. As it has the same density in the soft as in the
hard state, it may be employed to stop cavities, which it exactly fills on
solidifying. In this way it has been used for stopping teeth.
Cadmium amalgam possesses the same plastic properties as the above,
and is also employed in dentistry.
Tin amalgam. — Tin dissolves in mercury with absorption of heat.
According to the relative proportions the amalgam is eitlier liquid, or
solid and crystalline. Tin amalgam is employed in silvering mirrors.
COMPOUNDS OF MERCURY WITH THE HALOGENS.
a. Mereuroua Compounds.
Mercurous chloride, Calomdy ISLg'ju^. — Molecular weight =
471. — This compound occurs in lustrous quadratic crystals or crystal-
line crusts as the rare mineral hom-quickiilver. It is precipitated by
the addition of hydrochloric acid or a soluble chloride to a solution of
mercurous nitrate. It is also precipitated when a solution of mercuric
chloride is saturated with sulphurous anhydride and the liquid is warmed
to 70° C. (158° F.) or 80° C. (176° F.). Calomel is generally pre-
pared, however, in the dry way by subliming together 4 parts of mer-
curic chloride with 3 parts of metallic mercury. The sublimation is
performed in a cast-iron cylinder, and the calomel vapor is passed into
the upper part of a large brick chamber, where it condenses in a fine
powder, as in the process of preparing flowers of sulphur. The pro-
duct must be thoroughly washed with large quantities of warm water
in order to remove any unaltered mercuric chloride. When the vapor
is allowed to condense on a cold surface, the mercurous chloride is ob-
tained as a fibrous crystalline mass of sp. gr. 7.1. Mercurous chloride
assumes a gray tint under the action of light, owing to the separation
of metallic mercury. When heated it sublimes without fusing. It
possesses a vapor density only half of that required by the formula
'YLg'JC^'y but investigation has shown that the supposed vapor of
calomel consists of a mixture of the vapors of mercuric chloride and
mercury, which reoombine on 'cooling :
'Hg'^Cl, = HgCl, + Hg.
Mercurous Mercuric 2 yols.
chloride. chloride, 2 vols.
It is insoluble in water, in alcohol, and in dilute acids in the cold. By
boiling with hydrochloric acid it is converted into mercuric chloride,
which dissolves, and metallic mercury. In contact with caustic potash
it blackens, owing to the forntiation of mercurous oxide. — Calomel is
much used in m^icine.
Mer<MT<nu
nitrate with
hromidef 'Hg.'iBr2, is prepared by precipitating a solution of mercurous
bydrobromic acid or with a soluble bromidei and also by subliming a mix-
OOMPOUNDS OF MERCURY. 631
ture of mercuric bromide and metallic mercorj. It doeelj resembles the chloride in
its properties, and, like that compound, possesses a vapor density only half of that re-
quired by its formula.
Mercurous iodide, ^Hg''2ls, may be obtained by triturating 10 parts of mercury with
6.7 parts of iodine, adding sufficient alcohol to moisten the mass. The product must
be washed with alcohol in order to remove anv mercuric iodide. It forms a yellowish-
green powder, which fuses at 290^ C. (554° F.), yielding a black liquid. It sublimes
below this temperature, and by careful sublimation may be obtained in yellow rhombic
ccystals. These, when heated to 70° C. (158° F.), assume a red color,' which deepens
as' the temperature rises, till at 220° C. (428° F.) it attains to a deep garnet-red. This
change of color is not accompanied by any change in composition, and the crystals
recover their original color on cooling. When quickly heated, raercurous iodide is
decomposed into mercuric iodide and metallic mercury, and the same change takes
place gradually at ordinary temperatures. It is only sparingly soluble in water. In
contact with a solution of potassic iodide it is decomposed into mercuric iodide, which
dissolves with formation of potassic mercuric iodide, and metallic mercury.
Mercurous fluoride, ^g'jFa, is prepared by dissolving freshly precipitated mercurous
carbonate in hydrofluoric acid and evanoratlng the solution.' It forms small yellow
crystals, which are partially deoomposea by pure water with separation of mer'curous
oxide. When the ary fluoride is heated in a glass vessel, mercury sublimes and the
glass is corroded.
6. Mercuric Compounds.
Mercuric chloride, Con^osive sublimcUe, HgClj. — Mokcular
weight =211, Molecular volume DD.— This compound is formed
when mercury is heated in an excess of chlorine; also when mercuric
oxide is dissolved in hydrochloric acid, or mercury in aqua-regia. It
is generally prepared by heating a mixture of mercuric sulphate and
common salt ; the mercuric chloride sublimes and condenses as a color-
less, transparent, crystalline mass in the upper part of the vessel. A
small quantity of manganic dioxide is added to the mercuric sulphate
in order to oxidize any mercurous salt which may be present. Mercuric
chloride crystallizes from its aqueous solution in long colorless rhombic
prisms, having a sp. gr, of 5.4. It fuses at 265° C. (509° F.) and boils
at 295° C. (563° F.). It is soluble in from 14 to 15 parts of water at
ordinary temperatures, in 2 parts of water at 100° C. (212° F.). It
also dissolves in 3 parts of alcohol and in 4 parts of ether. Mercuric
chloride is exceedingly stable, dissolving in concentrated nitric acid and
sulphuric acid without decomposition. On heating the sulphuric acid
solution the mercuric chloride sublimes out of the concentrated acid
unchanged. Mercuric chloride is a violent poison. It is employed in
medicine and as an antiseptic for anatomical preparations. — Mercuric
chloride forms the following crystal! izable double salts with the alka-
line chlorides :
HgCl^Cl,OH,; HgCl„2KCl,OH2; 2H8rCl2,KCl,20H, ;
HgCl2,2NaCl; 2HgCl„2NaCl,30H2; HgCl^NH.Cl;
HgCl„2NH,Cl,0H,
{sal alembroih). It also combines with hydrochloric acid to form the
crystallized compounds HgCl„HCl and 2HgCl„HCl, both of which, on
exposure to air, effloresce and part with the whole of their hydrochloric
acid. — By boiling a solution of mercuric chloride with mercuric oxide,
or by adding to the solution a quantity of caustic alkali insufficient for
532 INOROANIC CHEMI8TRT.
complete precipitation, various oxychlorides of mercury, many of which
are crystallizable, may be obtained. The compound
HgACl,^ CI— Hg— O— Hg— O— Hg— O— Hg— CT
forms lustrous golden-yellow scales.
Mercuric hromidef HgBn, is obtained hj the direct nnion of mercary with an ezcen
of bromine. It is less soluble than the chloride, and c^stallizes from water in lostious
lamintt, from alcohol in rhombic needles or prisms, it sublimes readily.
Mercuric iodide, Hgl,, is prepared by triturating 10 parts of
mercury with 13 parts of iodine, adding sufficient alcohol to moisten
the mass; or by mixing solutions of 10 parts of mercuric chloride and
12J parts of potaseic iodide. The product obtained by the direct com-
bination of iodine with mercury is a brilliant red crystalline powder ;
that prepared by precipitation is at first of a pure yellow, but speedily
becomes red on standing. It is insoluble in water, readily soluble in
alcohol or in solutions of {lolassic iodide and of mercuric chloride, yield-
ing colorless solutions. From the alcoholic solution it is deposited in
red quadratic octahedra. When mercuric iodide is heated to 160® C.
(302° F.) it suddenly changes its color to yellow ; at 238° C. (460.4° F.)
it fuses to a yellow liquid and volatilizes in yellow lustrous rhombic
crystals, which on standing or sometimes even during the process of
cooling, are converted into aggr^ates of the red crystals. This change
into the red modification, which is accompanied by evolution of heat,
takes place instantaneously on scratching the yellow crystals. Mercuric
iodide yields with potassic and aramonic iodides double salts of the
formul» 2(Hgl2,Kl),30H, and 2(HgI„NH,I),30H2, which crystal-
lize in yellow prisms.
Mercuric fiuoride^ HgFs. — Mercuric oxide added to hrdroflnoric acid is converted
into a yellow crystaUine powder consisting of mercuric ozifftuoride^ HgFHo, and the
solution yields on evaporation orange-colored crystals of the same compound. An
excess of water decomposes the oxy fluoride, even in the cold, into hydrofluoric acid and
mercuric oxide. By repeatedly treating the oxyfluoride with concentrated hydrofluoric
acid, mercuric fluoride is obtained as a white crystalline mass of the formula EigFs,20H«.
The same compound is formed when mercuric oxide is added to a large excess of hydro-
fluoric acid containing 50 per cent. HF. When heated to 50° C. (122® F.) it is con-
verted into the oxyfluoride. In contact with water it is decomposed into hydrofluoric
acid and mercuric oxide.
COMPOUNDS OF MERCURY WITH OXYGEN.
Hg
Mercurous oxide, 'VLgfjd. J ^>0.
Mercuric oxide, HgO. Hg=0.
Mercurous oxide, 'Hg'gO. — ^This compound is obtained as a black
S)wder by precipitating a mercurous salt with potassic or sodic hydrate.
y the action of light it is decomposed into mercuric oxide and metallic
mercury;; for this reason it must be washed and dried in the dark. It
COMPOUNDS OP MERCURY. 633
18 decomposed in the same manner when heated to 100^ C. (212^ F.).
Acids dissolve it, yielding the mercurous salts.
Mercuric oxide, HgO, is formed as a red crystalline powder when
mercury is heated in air to a temperature near its boiling-point. It is
most conveniently prepared by thoroughly triturating mercuric nitrate
with an equal weight of mercury and cautiously heating the mixture
until acid fumes cease to be evolved. When prepared on a large scale
by this method, it is sometimes obtained in small brick-red rhombic
crystals, having a sp. gr. of 11.136. It is precipitated as a yellow
amorphous powder when potassic or sodic hydrate is added to the solu-
tion of a mercuric salt. Mercuric oxide is not quite insoluble in water,
to which it imparts an alkaline reaction and a metallic taste. When
carefully heated it assumes a deeper color, gradually passing into black,
but recovers its original tint on cooling. At a red heat it is totally de-
composed into mercury and oxygen. When heated with bodies which
take up oxygen it oxidizes them : a mixture of mercuric oxido and sul-
phur explodes with great violence on heating. ^ Mercuric oxide is grad-
ually blackened by exposure to light, owing to a partial decomposition.
OXY'SALTS OF MERCURY.
a. Mercurous Salts.
Mercurous nitrate. — When mercury is dissolved in cold dilute
nitric acid the solution deposits colorless monoclinic tables or prisms of
the normal salt tdrahydrie mercurous dinitrate, jiqtt ^('Hg'jOg)''. It
dissolves without decomposition in water containing nitric acid, but in
contact with an excess of pure cold water it is decomposed, yielding the
basic salt hydric mercurous nitrate^ NOHoCHg'^Oa)", as a yellow crys-
talline powder which is converted on boiling with water into mercuric
nitrate and metallic mercury. Other basic mercurous nitrates are
known, some of which crystallize well. Thus when the crystals of the
normal salt are heated with their mother liquor in contact with an
excess of mercury, the solution deposits on cooling colorless, lustrous,
non -efflorescent, rhombic prisms of hydric dimercurous trinitratey
NjOgHoCHg'jOg)'^ If, on the other hand, the crystals of the normal
salt are left for some time in the cold in contact with the mother liquor
along with an excess of mercury, lustrous triclinic prisms of tetrahydric
pentamercurous hexanitrate, afiJIoJJHg'2^2y\^ ^^^ formed. — ^The
normal mercurous nitrate forms numerous crystal lizable double salts
with the nitrates of other metals.
I OCl
Mercurous ehbraU, \ ^('^%\0%Y\ is obtained in colorless rhombic prisms by dis-
{ oa
solving freshly precipitated mercurous oxide in chloric acid. When heated to 250*^ C.
it decomposes into mercuric chloride, mercuric oxide, and oxygen.
634 INORGANIC CHEMISTRY,
f OCl
jo
Mereur<m$ f>erehloraUt \ Q(^Hg^0t)^^,6OHti is obtained in oolorleas deliquescent
is
needles by dissolving mercurous oxide in an aqueous solution of perchloric acid,
f OBr
Merewvuf bromatef ^ Q(^Hg'^sOs)'^^ is deposited in colorless laminae when solutions
i OBr
of mercurous nitrate and potassic bromate are mixed. An excess of water decom-
poses it with formation of a baitic salt.
Mercurou9 carbonate^ CO(''Hg^tOs)^^, is precipitated ss a jellow powder when a m>1u-
tion of mercurous nitrate is poured into an excess of hydric potassic carbonate or hvdric
sodic carbonate. Mercurous carbonate decomposes at 130® C. (266° F.) into carbonic
anhydride, mercury, and mercuric oxide.
Mercurous sulphate, BOjCHg'jO,)", is obtained as a white crystalline
mass by gently heating sulphuric acid with an excess of mercury. If
the temperature be raised too high, a mercuric salt is formed at the
same time. Mercurous sulphate is also deposited in minute colorless
prisms when dilute sulphuric acid is added to a solution of mercurous
nitrate. It is only slightly soluble in water. When heated it fuses to a
reddish-brown liquid which solidifies on coqling to a crystalline mass.
With careful heating it may be sublimed.
6. Mercuric Salts.
NO
Mercuric nitrate, vQ^^go". — This salt is prepared by boiling
mercury with an excess of nitric acid until a portion of the liquid, when
removed and tested with a solution of common salt, yields no precipi-
tate. The normal salt is, on account of its deliquescent nature, very
difficult to obtain in a crystallized state. When the solution is evap-
orated over sulphuric acid, large deliquescent crystals of dihydric dimer-
curie tetraniiraiCy N^OyHogHgo'^j) are obtained. A hydrated normal
salt is deposited in tabular crystals of the formula N^O^Hgo'^SOHj,
when a solution of the nitrate in nitric acid is cooled to — 15° C; the
crystals fuse at ordinary temperatures. Mercuric nitrate has a great
tendency to form basic salts: a solution of an excess of mercuric oxide
in hot, moderately strong nitric acid, deposits on cooling colorless
rhombic crystals of tetrahydric dimercurio dinitrate, NjOHo^Hgo",.
When this salt, or any of the normal salts, is treated with cold water, a
still more basic salt, dihydric trimercuric diniti-ate, N20Ho2Hgo"5, is
formed as a white powder, and this, when boiled with an excess of
water, gradually parts with all its acid and is converted into mercuric
oxide.
Merfturic carbonate. — The mercuric carbonates are basic compounds of ill-defined
character and uncertain composition. They form brown amorphous powders.
Mercuric sulphaiCf SOgHgo". — This salt is prepared by heating mer-
cury with one and a half times its weight of sulphuric acid until the
excess of acid is expelled. It is thus obtained as a white crystalline
COMPOUNDS OF MERCURY. 535
mass, which when heated turns first yellow and afterwards brown, but
becomes white again on cooling. At a red heat it decomposes into
mercury, oxygen, and sulphurous anhydride. When treated with a
email quantity of water it forms white crystals of dihydrie mercuric
mUphatey BOHogHgo'^, but an excess of water decomposes it, especially
on boiling, into free sulphuric acid and a yellow insoluble basic salt,
irimercuric sulphate^ SHgo"^, formerly known as turpeth mineral {turpe-
tum mineraU).
JWereurie orthophotphaUy ponfo^^^^®'^' — '^^^^ ^^^ ^ precipitated as a heavy white
insoluble powder when ordinarj sodic phosphate is added to a solution of mercuric
nitrate. Mercuric chloride cannot be substituted for the nitrate.
JBonUes and silicates of mercurj have not been prepared.
COMPOUNDS OF MERCURY WITH SULPHUR.
Merewrie aulpkide, ^Hg^^S^^, is precipitated as a black powder by pouring a dilute
solution of mercurous nitrate into a dilute solution of amnionic sulph hydrate. It may
also be prepared by treating freshly precipitated calomel with ammonic sulphhydrate.
It is a very unstable compound, and is decomposed even by a gentle heat into mercury
and mercuric sulphide.*
Mercuric sulphide. Cinnabar , FermiKon, HgS". — This compound
occurs native in red hexagonal crystals, and also in granular masses, as
the mineral dnnabavy constituting the most abundant ore of mercury.
By triturating mercury with sulphur, the sulphide is obtained as a black
amorphous powder; the product thus formed is known in pharmacy as
Aethiops mineralia. The same black modification is obtained by pre-
cipitating a mercuric salt with an excess of sulphuretted hydrogen.
When the black amorphous sulphide is sublimed with exclusion of air,
it is converted into the crystalline variety, which condenses on a cold
surface, generally as a red fibrous mass, but sometimes in distinct crystals
having the form of a native compound. By digesting with warm solu-
tions of alkaline persulphides, the black sulphide is also converted into
the red sulphide. The finely ground red sulphide is employed as a
pigment under the name of vermilion^ and is prepared on a large scale
in the wet way by the following method : 100 parts of mercury are
thoroughly triturated with 38 parts of flowers of sulphur, and the mass
is then digested for several hours at a temperature of 45-50° C. (1 13-
122° F.) with a solution of 25 parts of caustic potash in 150 parts of
water, renewing the water as fast as it evaporates. As soon as the ver-
milion has attained the proper shade the operation is interrupted and
the product is quickly washed with water, as by the further action of
the potash the color changes to brown. Vermilion prepared in the
wet way has a finer shade than that obtained by sublimation. Mer-
curic sulphide is insoluble in hydrochloric, nitric, and sulphurid acids,
but soluble in aqua-regia and in hydriodic acid. Ammonic sulphide
does not dissolve it, but it is soluble in potassic and sodic sulphides in
* According to some chemists the so-called mercurous sulphide is merely a mixture
of mercuric sulphide and mercury.
636 INORGANIC CHEMISTRY.
presence of free alkali. The solution in potassic sulphide deposits
colorless needles of mercuric dipotassie mlphide, HffKsj^SOH, The
sodium compound has the formula HgNao^^SOH^ Both compounds
are decomposed by an excess of water with separation of black sulphide.
By digesting the black sulphide with a solution of mercuric chloride,
or by fusing the dry sulphide with an excess of mercuric chloride
and extracting the mass with water, trimercuric distdphodiehloridey
5|g]Hg8" = CI— Hg-^— Hg— S— Hg— CI, is obtained as a white
powder which is amorphous when prepared in the wet way, and crys-
talline when prepared in the dry way. The same substance is formed
as a white precipitate when sulphuretted hydrogen is passed into a solu-
tion of mercuric chloride, but is converted by an excess of sulphuretted
hydrogen into black sulphide. Mercuric sulphide forms numerous
other double compounds with* mercuric salts.
COMPOUND OF MERCURY WITH NITROGEN.
Mercuric nitride^ NjHg^^,, is formed when mercuric oxide, prepared bj precipitatioD
and dried at a low temperature, is heated to 100° C. in a current of ammonia :
3HgO + 2NHj = H,Hg^', -|- 30H,.
Mercuric Ammonia. Mercuric Water,
oxide. nitride.
The product is treated with dilute nitric acid to free it from any unaltered mercuric
oxide. It forms a dark*brown powder, which explodes with great violence bj heat,
friction, or contact with concentrated sulphuric acid. By cautjously heating with
caustic alkalies it is decomposed without aetonation, yielding ammonia and sublimed
meroury.
AMMONIACAL MERCURY COMPOUNDS.
These compounds iire derived from the ordinarv ammonium salts by the replace-
ment of one or more atoms of hydrogen in the latter by mercury. The mercury
may be present either as Hg^^ or as ^Hg^*, and each of these dyad radicals may
either replace two atoms of hydrogen in a single ammonium molecule, or may replace
two atoms of hydrogen in two different ammonium molecules ; in the latter case uniting
the two ammonium groups to a single molecule. The free mercury-ammoniums have
not been prepared.
a. MercuroMmtMrniuvi Cowvponndi,
Mercurommmonic chloride, NHi^Hg^aCl, is obtained as a black insoluble powder by
the aeiion of aqueous ammonia on mercurous chloride :
'Hg'.CI,
-f 2NH,
= HH,'Hg',a -f
NH4CI.
Mercurous
Ammonia.
MercuToe-
Ammonic
chloride.
ammonlc chloride.
chloride.
Gaseous hydrochloric acid decomposes it, yielding mercurous chloride and ammonic
chloride:
. NH/Hg^Cl + 2HC1 = 'Hg'.Cl, + NH,a.
Mercuros- Hydrochloric Mercurous Ammonic
ammonic chloride. acid. chloride. chloride.
When heated, it first gives off ammonia and nitrogen, and afterwards mercurous chlo-
ride and metallic mercury.
Mercurnsammonic nitrcUCf HOj(N»H»'Hg^jO). — This compound, known as McrcuriuM
iolubilia Hahnemannif is precipitated in the form of a black powder when aqueous am-
COMPOUNDS OP MERCURY. 537
Ibonia is added to a solation of mercnrotis nitrate. It is with difficulty obtained in a
state of purity, and is generally mixed with metallic mercury.
Mereurosodiammonic diehUnid^ wu'oiH i ' ^ foi^m^ as ^ black powder by the
action of gaseous ammonia upon mercurous chloride. When heated, or when exposed
to the air, it evolires ammonia, leaving mercurous chloride.
b, Mercuramnumiiim CompouTuk.
IXnurcurammonic oxide^ W^*^*^' — ^^^'^ mercuric oxide is treated with concen-
trated ammonia, dimercurammonic hydrate is obtained as a pale yellow powder having
the formula NHg^''2Hoy20H3. By sudden heating of by friction it deflagrates without
explosion. When heated to 80° C. (176° F.) in a current of ammonia it gives off water,
leaving the pure hydrate NHg^^sHo, which at 100° G. (212° F.) parts with the elements
of water, and is converted into the oxide. Dimercurammonic oxide is a brown powder,
which on heating or by friction explodes violently.
Ma-euranmionic chloride, NHaHg^^Cl. — This compound, known as infwible white pre-
dpitatej is prepared by precipitating a solution of mercuric chloride with an excess of
ammonia:
HSCI,
Mercurous
+
2NH5
==
HHaEIg^'Cl
Mercurammonlc
+
NH.Cl.
Amnionic
chloride.
chloride.
chloride.
At a temperature below a red heat it is decomposed without fusion, yielding ammonia,
nitrogen, and mercurous chloride. Water decomposes it, slowly in the cold and quickly
on heating, with formation of ammonic chloride and an aqoate of dimercurammonie
chloride, NHg'^a,OH,.
Dimerewammonie chloride, NHg^^sCl, is obtained as a yellow powder by the action
of alcoholic hydrochloric acid on dimercurammonic oxide (see above), or by treating
mercurammonic chloride with water (see preceding compound). When heated to 300°
C. (572° F.) it decomposes into metallic mercury, mercurous chloride, and nitrogen.
Mereuridiammoniediehloride, Jjh'cI^^^^' — '^^^ compound, known as fusible tohite
predpUatey is obtained by adding a solution ef mercuric chloride to a boiling solution
of ammonic chloride and ammonia as long as the precipitate which is at first formed
continues to dissolve. The liauid on cooling deposits colorless regular dodecahedra,
which fuse when heated, and then decompose, yielding nitrogen, ammonia, mercurous
and mercuric chlorides, and ammonic chloride.
Hydroocydimereurammonic iodide, NHHg^^(Hg''Ho)I, is formed by the action of an
excess of aqueous ammonia upon mercuric iodide :
4NHj + 2HgT, -f OH2 = NHHg'^(Hg'^Ho)I + 3NHJ.
Ammonia. MercuTlc Water. Hydroxydimercur- Ammonic
iodide. ammonic iodide. iodide.
It is most readily obtained by adding ammonia to a solution of mercuric potassic
iodide containing an excess of potassic hydrate. This liquid, which is known as
N€S8l€r*8 8oltUio7i, is employed in testing for minute traces of ammonia. When the
Quantity of animonia is too small to yield with this reagent a precipitate of hydroxy-
dimercurammonic iodide, it manifests its presence by a yellow coloration. Hydroxy-
dimerctirammonic iodide is a reddish-brown powder, which fuses when heated, and at
a higher temperature decomposes with a violent explosion.
Characteristic Properties and Reactions of thk Com-
pounds OF Mercury. — The normal salts of mercury with colorless
acids are colorless ; some of the basic salts are yellow. The sofuble
Baits have an acid metallic taste^ and act as irritant poisons. If a
strip of copper be introduced into a solution of any mercury compound,
metallic mercury is deposited on the copper. All compounds of mer-
cury, when heated in a test-tube with dry sodic carbonate, yield a gray
sublimate consisting of minute globules of mercury. .
538 INORGANIC CHEMISTRY.
a. Mereurous saltSy when in solution, yield with caustic alkalies black
mercurous oxide. Ammonia precipitates black mercurosammonium
compounds (p. 536). Sulphurdted hydrogen and ammonic stUphide pre-
cipitate black mercurous sulphide, insoluble in nitric acid, soluble in
aqua regia. Hydrochloric add precipitates while mereurous chloride,
and potamc iodide green mercurous iodide. Stannous chloride precipi-
tates mercurous chloride, which is converted by an excess of the stan-
nous chloride into gray metallic mercury.
b. Mercuric ealts give, with solutions of caustic alkalies, a yellow
precipitate of mercuric oxide. Ammonia precipitates a white mercur-
ammonium compound (p. 637). Sulphuretted hydrogen gives a ^white
precipitate, which passes through r^ to black, and then consists of
mercuric sulphide ; this precipitate is insoluble in nitric and in hydro-
chloric acid, soluble in aqua-r^ia. Potassic iodide precipitates salmon-
red mercuric iodide, soluble both in mercuric chloride and in potassic
iodide. Stannous chloride precipitates mercurous chloride, which is then
converted into metallic mercury.
The mercury compounds give no flame-coloration. The spark spec-
trum displays bright lines in the green and blue.
COPPER, Cu.
Atomic weight = 63.2. Probable molecular weight = 63.2. 8p. gr. 8.9.
Fuses at 1330° C. (2426° F.). Atomicity ", oho a pseudo-monad.
Evidence of atomicity:
Cupric chloride, Cn"Cl,.
Cupric oxide, 0ti"O.
Cuprous chloride, 'Ou'aClj.
Cuprous oxide, 'Ou'^O.
History, — Copper has been known from prehistoric times. Owing to
its occurring in the native state, it formed the material for tools and
weapons in early ages when the metallurgical processes necessary for
the extraction of iron from its ores were unknown.
Occurrence. — Native copper occurs in various localities, particularly
in the neighborhood of Lake Superior, where it is sometimes found in
enormous masses. In the Minnesota Mine, in 1857, a mass of copper
weighing 420 tons was found. In combination it occurs as cuprous
oxide, 'Ou'jO, in red copper ore or ruby-ore; much more rarely as cu-
pric oxide, OnO, in tenorUe. It also occurs as cuprous sulphide, 'Ou'jS",
in copper glance ; as cupric sulphide, OnS", in indigo copper; as a
double sulphide of copper and iron, diferric cuprous tetrasulphide,
I FeS''^'^"'*®'*)''* ^^ copper pyrites ; as basic carbonates in malachiiey
rOHoCuo"
0O(OCu"Ho)-, and a2unte,< Cuo" . It also occurs in minute
(OHoCuo''
quantity in sea-weed, and as a necessary constituent of the blue blood
of various marine animals, such as the cuttle-fish. In this blue blood
COPPER. 639
the copper is present in the form of hcemocyanin, a complex organic
compound, which acts as a carrier of oxygen and thus exercises the same
functions which hsemoglobin, an organic substance containing iron, ex-
ercises in the red blood of the higher animals. In the arterial blood
the bsemocyanin is blue, in the venous blood it becomes colorless, a
change identical with that which occurs when a cop{)er salt passes from
the higher or cupric to the lower or cuprous state of oxidation.
detraction. — ^The process of copper'STneltinff, by which copper is ob-
tained from Its ores, varies with the nature of these ores ; thus, the
oxides or carbonates may be reduced directly by heating with charcoal,
but in the case of the sulphides the ore must be first roasted in order to
convert the sulphur into sulphurous anhydride. The process employed
in England is as follows: The mixed ore, which consists of copper
pyrites and cupric carbonates, tt^ther with iron pyrites and siliceous
impurities, and which ought to contain about 13 per cent, of copper, is
first calcined on the bed of a reverberatory furnace. Air is admitted
through aii^holes, and plays along with the flame of the furnace upon
the surface of the ore, which is turned over from time to time by means
of long rakes introduced through doors opening on the bed. In this
way the sulphides of iron and copper are partially converted into oxides.
The next process consists in the fusion of the calcined ore with metcU
dag, a siliceous slag obtained in a subsequent operation, to which fluor-
spar is also frequently added in order to increase its fusibility. The fu-
sion is performed on the bed of a reverberatory furnace, the so-called
ore-furnace, the temperature of which is much higher than that of the
calcining furnace. The oxides of copper which are present react with
the unaltered sulphide of iron, yielding oxide of iron, which is taken
up by the slag, and cuprous sulphide, which combines with the excess
of ferrous sulphide to form the so-called coarse metal, the latter collect-
ing under the slag in a depressed basin on the hearth of the furnace,
whence it can be drawn ofl^ through a tap-hole. The coarse metal has
very much the composition of ordinary copper pyrites. The slag, which
contains all the siliceous matters from the ores, together with a great
portion of the iron, and is almost free from copper, is known as ore-fur^
nace dag. The coarse metal is next powdered and calcined, by which
means a partial oxidation is again effected, and the mass is then fused
along with the refinery slag from the final process. The decomposition
which takes place is the same as that which occurs in the fusion of the
calcined ore, except that in the present case practically the whole of the
iron is oxidized and passes into the slag, whilst the copper collects at
^the bottom of the furnace in the form of cuprous sulphide, 'Ou'jS",
known ^Bfine metal (also white metal). The slag, which is termed m^etal
dag, contains about 3 per cent, of copper, and is employed as above
described in the fusion of the calcined ore. The fine metal is then
roasted in a reverberatory furnace. A portion of the cuprous sulphide
is thus oxidized to cuprous oxide, which then reacts with another por-
tion of cuprous sulphide yielding metallic copper:
2'0ii',O + 'Ou'^" = 6Cu + BOj.
Cuprous Cuprous Sulphurous
oxide. sulphide. anhydride.
540 INOROAKIG CHEMISTRY.
The copper thus obtained is covered with black blisters, and is therefore
known as blister copper. It contains small quantities of iron, arsenic,
lead, and other metals. It is refined by fusion on the bed of a furnace
in a current of air. In this way the foreign metals are oxidized and
combine with the siliceous materials of which the bed of the furnace
is composed to form a slag, which is skimmed off. This slag, which is
very rich in copper, is known as refinery slag, and is employed as above
described. The refined copper is known as dry copper. It contains a
certain quantity of cuprous oxide, which would render it brittle when
cold. It is therefore subjected to a process of toughening . For this
purpose the surface of the fused metal, after the removal of the slag, is
covered with a layer of powdered anthracite (charcoal was formerly
used) and a pole of green birch or oak is thrust into it. The reducing
gases, evolved by the destructive distillation of the wood in contact with
the hot metal, effect the conversion of the cuprous oxide into copper,
and this reduction is further facilitated by the violent agitation of the
entire mass caused by the escaping gases, the particles of carbon being
thus carried down under the surface and brought in contact with every
part of the metal. This process is known as poling. After continuing
this treatment for twenty minutes the pole is withdrawn, and a sample
of the metal is removed and cast in an ingot mould ; the bar of copper
is cut half through and then broken by bending in a vise ; an examina-
tion of the fracture enables the refiner to say whether the required de-
gree of toughness has been attained. If this point has been passed,
the metal is over-poled and less tenacious; it may be toughened again
by fusion for a short time in contact with air. The nature of the
change which occurs in over-poling is not perfectly understood; by some
chemists the loss of tenacity is attributed to a too complete reduction
of the cuprous oxide, others believe that foreign oxides are reduced at
the close of the operation, and that the metals from^hese become al-
loyed with the copper.
Large quantities of copper are now obtained by extraction in the wet
way. The quantity of iron pyrites burnt in the sulphuric acid works
of this country amounts to 500,000 tons per annum, and this substance
contains on an average 3 per cent, of cop})er, the whole of which re-
mains in the burnt pyrites. It would be impossible, by the ordinary
processes of copper-smelting, to extract this small quantity, but it has
been found that by roasting the burnt pyrites with from 12 to 15 per
cent, of common salt, and lixiviating the mass with water, the whole
of the copper is obtained in solution in the form of cupric chloride, and
may be precipitated as metallic copper by scrap iron. ,
Commercial copper generally contains traces of various other metals,
especially silver, arsenic, and iron. Pure copper is best obtained by
heating the pure oxide in a current of hydrogen, or by electrolyzing a
solution of pure cupric sulphate.
Properties. — Copper is a lustrous metal with a peculiar red color.
This color can be seen in its full intensity only when the light, before
reaching the eye, has been reflected several times from the surface of
the metal (p. 399). Copper crystallizes in cubes or octahedra. It is
ojie of the most tenacious of metals^ and is very malleable and ductile;
COPPER. 541
it may be beaten into thin leaf, or drawn into fine wire. Very thin
copper leaf transmits a greenish-blue light. In dry air, copper tarnishes
only very slightly at ordinary temperatures, but in contact with water
or in moist air it becomes coated with basic carbonate. When heated
in air or in oxygen it is converted superficially into black oxide, which
may be readily detached in scales. Clopper is quite insoluble in dilute
hydrochloric or sulphuric acid as long as air is excluded ; but with ad-
mission of air, or in contact with some more electro-negative metal, such
as platinum, it gradually dissolves. Finely divided copper slowly dis-
solves in boiling hydrochloric acid with evolution of hydrogen. Con- ^
centrated sulphuric acid is without action upon it at ordinary tempera-
tures; but with the hot concentrated acid cupric sulphate is formed and
sulphurous anhydride evolved (p. 261). Dilute nitric acid attacks it
violently, even in the cold, with formation of cupric nitrate and evolu-
tion of nitric oxide (p. 224). Ammonia dissolves the metal slowly in
presence of air. Iron, zinc, phosphonis, and many other readily oxi-
dizing substances, precipitate copper in the metallic state from the solu-
tions of its salts.
Uses. — Copper is employed for a great variety of purposes in the arts,
and is especially valuable where great flexibility combined with tenacity
is required. It is used for bell-wire and for thafire boxes of locomo-
tive boilers, its high conductivity for heat peculiarly fittin^it for the latter
purpose. The electric conductivity of copper is higher than that of any
other known metal, with the exception of silver; hence copper wire is
extensively employed for electrical purposes, as in the construction of
induction coils, dynamo-electric machines, electric-light leads, and sub-
marine tel^raphs. Owing to its property of being readily deposited in
a coherent metallic form from the solutions of its salts by electrolysis,
copper is much used in the process of electrotyping, by means of which
statues, bas-reliefs, and other works of art are reproduced. Copper,
is, however, chiefly employed along with other metals in the form of
alloys.
Alloys of copper. — The most important alloys of copper are those
which it forms with zinc and with tin. The following is the composi-
tion of the principal zinc alloys of copper :
Parts of copper. Parts of zinc.
Brass (English), 2 1
Tombac,. ..••..•• 5 1
Muntz metal, 3 2
These alloys are all harder than copper. Brass is readily worked and
does not clog the file like copper. Tombac is very ductile and malle-
able. Duich metal is tombac beaten out into leaves mii^js ^^ &" ^"^h in
thickness. Muntz metal is employed in the sheathing of ships, for
which purpose it is rolled while hot into sheets. The color of these
alloys is lighter the greater the proportion of zinc.
The following list contains the names and composition of the prin-
cipal alloys of copper with tin :
542 INOBGANIC CHEMISTRY.
Parts of copper. Puts of tin.
Speculum metal, 2 1
Bell metal, 4 to 6 1
Gun metal, 9 1
Speculum metal has a steel-gray color and takes a high polish. The
quality of this alloy is said to be improved by the addition of a small
quantity of arsenic, but this was denied by the late Lord Rosse. Bell
metal has a yellowish-gray color and is very hard and sonorous. Gun
metal is yellow and slightly malleable. All these alloys are brittle
when cooled slowly, but acquire a certain d^ree of malleability when
heated and then suddenly cooled by plunging into water.
Bronze is a copper-tin alloy of approximately the composition of gan
metal, but with the addition of 2 or 8 per cent of zinc. PhoajJiar^
bronze is a valuable alloy obtained by fusing copper with phosphide
of tin. It is exceedingly hard, tenacious, and elastic.
COMPOUND OF COPPER WITH HYDBOQEK
Cuprous hydride^ 'Cu'jHa, is formed by the reducing action of a solution of hypo-
phosphorous acid u(X)n cupric sulphate. When the mixed solutions are heated to a
temperature not higher than 70° C. (158° F.), the liquid assumes a green color and
the nydride sepamtes in the form of a yellow precipitate which becomes brown oa
standing. The liquid must be quickly cooled and the precipitate filtered off. Cu-
prous hydride is a very unstable compound, and is decomposed at 60° C. (140** F.)
into hydrofi^en and metallic copper. It inBames spontaneously in chlorine. Hydro-
chloric acid dissolves it with evolution of hydrogen and formation of^cuprous chloride.
COMPOUNDS OF COPPER WITH THE HALOGENS.
a. Cuprous Ccmpounda.
Cuprous chloride^ 'Ou'jClj. — Molecular weight = 197.4. Molecular
volume 1 I i — When finely divided copper or thin copper leaf is intro-
duced into chlorine the metal ignites spontaneously, burning with a red
light and yielding a mixture of cuprous and cupric chlorides. When
copper is heated in a current of gaseous hydrocloric acid, cuprous chlo-
ride is formed and condenses in the colder parts of the tube. Cuprous
chloride is further obtained by dissolving cuprous oxide in hydrochloric
acid, or by reducing a solution of cupric chloride with stannous chloride.
It may be readily prepared by boiling a solution of cupric chloride in
hydrchloric acid with copper filings, with the addition of a few drops
of a solution of platinic chloride, the precipitated platinum serving to
establish a voltaic action with the copper. On pouring the filtered
solution into water from which the air has been expelled by boiling,
the cuprous chloride separates as a white crystalline powder consisting
of microscopic tetrahedra. Cuprous chloride may also be obtained by
slowly adding an intimate mixture of 2 parts of cupric oxide with I
part of zinc dust to concentrated hydrochloric acid, until the liquid is
saturated, and pouring the solution into water as above. Cuprous chlo-
ride may be obtained in distinct r^ular tetrahedra by crystallization
wn
COMPOUNDS OP COPPER. 543
from a solution in hot concentrated hydrochloric acid. On exposure
to air it absorbs oxygen and water, forming a cupric oxychloride. Ex-
posure to sunlight with exclusion of air turns it violet if moist^ but if
dry it only acquires a faint yellow tinge. When heated it fuses, and
on cooling solidifies to a crystalline mass ; at a higher temperature it
may be volatilized without decomposition. It is insoluble in water, but
soluble in concentrated hydrochloric acid^ in aqueous ammonia, and in
sodic thiosulphate, yielding colorlorless solutions which possess the
property of absorbing various gaseous hydrocarbons of the acetylene
series (see Oi^nic Chemistry), and also carbonic oxide, to form com-
pounds. Thus with acetylene, '"O'fi^y it forms a dark-red powder
which explodes on heating, and is believed to possess the composition
'^'O'VCu'jH
O . When a solution of cuprous chloride in hydrochloric
/'O'VCu'^H
acid is saturated with carbonic oxide, it deposits nacreous scales of a
compound probably of the formula 0O(CuCl)2,20H2. This compound
is very unstable, readily evolving carbonic oxide, so that its composition
has not been determined with certainty. The solution of cuprous chlor
ride in ammonia deposits colorless rhombic dodecahedra of cupro^amTnonio
(NH,C1
chloride -l 'C\x\ . The same compound is obtained by heating copper
(NH3CI
turnings with a concentrated solution of ammonic chloride. The crystals
undergo partial decomposition on exposure to the air. On heating they
evolve ammonia. Cuprous chloride isalso solubleinconcentrated solutions
of the alkaline chlorides, forming double compounds. The potassium
compound crystallizes in octahedra of the formula '0u'2^l2,4KCl.
Cfuprom bromidej ^Cu'iBn, 18 prepared like the chloride, which it closely resembles.
Cuprous iodide^ ^Cu^alt, is precipitated when potassic iodide is added to a solution of
cupric sulphate, half the iodine being liberated :
2SO,Cuo^^ + 4KI = 'CvL\li + 2SO,Koa + I2.
Cupric Potassic Cuprous Potasaic
sulphate. iodide. iooide. sulphate.
The whole of the iodine is precipitated as cnproas iodide if a reducing agent, such as
sulphurous acid or ferrous sulphate, is present : *
2SO,Cuo^^ + 2SOaFeo^^ + 2KI = ^CuMj
Cuprio Ferrous Potassic Cuprous
sulphate. sulphate. iodide. iodide.
SO, .
H- SO,— (^Fe^^^Oe)'' + SO,Ko,.
SO, •
Ferric sulphate. Potassic
sulphate.
Cuproos iodide is a grayish-white crystalline powder, insoluble in water and in dilute
acids. It fuses at a red heat. It is the only known iodide of copper.
Cuprous flttoridet ^Cu^sFi, is prepared by treating cuprous hydrate with hydrofluoric
acid. It forms a red fusible powder, insoluble in water, soluble in hydrochloric acid.
611
INORGANIC CHEMIBTBY.
6. Capric Compounds.
Ouprie cfUoridey OuCl^, is prepared by dissolving copper in aqaa-
regia^ or cupric oxide or carbonate in hydrochloric acid, and evapo-
rating the solution. It crystallizes from water in green rhombic prisms
with 2 aq« ; these, when heated, part with their water of crystallization
without losing hydrochloric acid, and yield the anhydrous compound.
The concentrated aqueous solution is green, the dilute solution is blue.
Cupric chloride is also soluble in alcohol. At a red heat it evolves
chlorine and is converted into cuprous chloride. — Anhydrous cupric
chloride absorbs gaseous ammonia, and is converted into a blue powder
having the composition OuCl^yGNHs. An aqueous solution of the chlo-
ride, when saturated with ammonia, deposits dark-blue octahedra of a
compound, OuCla,4NH8,OH,. Both these compounds when heated to
fNH^Cl
150° C.areoonverted into cMprammoniccAforidc, < C^'' 9 which forms
iNH,Cl
a green powder. — Double compounds with the chlorides of potassium
and ammonium, OuCl2,2KCl,20H2, and OuCl2,2NH,Cl,20H„ are ob-
tained by allowing mixed solutions of the chlorides to crystallize. —
When a solution of cupric chloride is digested with cupric hydrate,
cupric oxychlorides of varying composition are obtained. A compound
rouci
of this class having the formulae O lOH, occurs native in Chili as
(OuHo
the mineral aJtacamite^ a green sand consisting of minute rhombic
prisms. The pigment, Brunswick ffreen, is a cupric oxychloride pre-
pared by exposing to the air copper foil moistened with hydrochloric
acid or ammonic chloride.
Cupric bromidey CuBn, is prepared like the chloride. It forms dark-colored crystals.
Cupric iodide is unknown.
Cupric fluoride, CuFa, is prepared by treating the oxide with aqaeous hydrofluoric
acid. It crystallizeB from water in small blue crystals with 2 aq.
COMPOUNDS OF COPPER WITH OXYGEN AND
HYDROXYL.
Cuprous quadrantoxide,
Cuprous oxide,
rou-i
Cu'
CuV
On J
Cn— Cu.
I >
Cu— Cu/
{So A>
Cu''
Cupric oxide, OuO Ou=0
COMPOUNDS OF COPPER. 645
CuHo
fCuHc
Cuprous hydrate, . . 4'0u',O,0H„ or \ ^^O
OuHo
O— Cu— Cu— O— Cu— Cu— O— Cu— Cu— O— Cu— Cu— O
ir A
Q TT
Cupric hydrate, .... OuHo, C!u<q rr
CViprotM quadrantoonde, CiiX), is obtained in a hrd rated condition as a very unstable
green powder by adding a solution of cupric sulphate to a dilute solution of stannous
chloride in caustic potash.
Cuprous oxide, '0u',O, occurs native as red copper-ore, forming
red octahedra belonging to the regular system, but is more frequently
found massive. When copper is su|)erficially oxidized by heating in
air, the outer portions of oxide consist of cupric oxide, but the inner
portions, which are adjacent to tlie unaltered metal, have a composition
approximating more closely to that of cuprous oxide. When a mix-
ture of cuprous chloride with anhydrous sodic carbonate is heated in a
closed crucible and the mass is lixiviated with water, cuprous oxide
remains as a red powder. The precipitate of cupric hydrate produced
by caustic alkalies in a solution of cupric sulphate redissolves on the
addition of grape sugar, yielding a blue solution, which when gentlj
heated deposits cuprous oxide as a red crystalline precipitate consisting
of minute octahedra. The reduction is effected at the expense of the
grape sugar, which undergoes oxidation. Thus prepared, cuprous oxide
undergoes no change when exposed to the air at ordinary teraperatur&s,
but when heated in air is converted into cupric oxide. With exclusion
of air it may be fused at a red heat. It is insoluble in water, but
soluble in aqueous ammonia, yielding a colorless liquid, which rapidly
absorbs oxygen from the air and becomes blue. Hydrochloric acid
converts it into colorless cuprous chloride, soluble in an excess of the
acid. With most of the oxy-acids it does not yield cuprous salts: in
some cases one-half of the copper present in the oxide dissolves to form
a cupric salt, the other half remaining behind as metallic copper ; in
other cases the whole of the oxide dissolves, yielding a cupric salt, the
cuprous oxide undergoing oxidation at the expense of a portion of the
acid. Thus with dilute sulphuric acid the reaction takes place accord-
ing to the first of these modes :
'Ou'P + SO,Ho, =
= BOfiuo''
+ Cii + OHj^
Cuprous Sulphuric
Cupric
Water,
oxide. acid
sulphate.
With hot concentrated sulphuric acid, on the other hand^ the seeeod
reaction occurs:
35
546 INORGANIC CHEHI8TBT.
'0u',O + 380,Ho, =
= 2SO2CUO"
+ so, +
30H,.
Cuprous Sulphuric
Cupric
Sulphnroas
Water.
oxide. acid.
sulphate.
anhydride.
Nitric acid dissolves the whole as cupric nitrate with evolution of nitric
oxide.
Cupric oxide, CuO. — This oxide occurs sparingly in nature as the
mineral tenorite. It is obtained by igniting metallic copper in air, or
by igniting cupric nitrate. It forms black scales or powder, according
to the mode of preparation. When strongly ignited it cakes together,
and at a white heat fuses, parting with a portion of its oxygen and being
converted into an oxide of the formula CugO,. When heated to red-
ness with carbon, or in a current of carbonic oxide or hydrogen, it is
reduced to the metallic state. In a similar manner, when organic sab-
stances containing carbon and hydrogen are heated with it, these two
constitqents are oxidized to carbonic anhydride and water, for which
reason it is employed in the ultimate analysis of organic compooods.
It is also used to impart a green color to glass. It dissolves in acids,
yielding the cupric salts.
Cuprous hydrate^ 4^Cii^iO,OHi, is obt&ined as a bright yellow precipitate when a
solution of cuprous chloride in hydrochloric acid is poured into an excess of cold caostic
alkali. It retain? its water of hydration at 100° C. (212'' F.), but parts with it com-
pletely at 360° 0. (680° F.). It is soluble in ammonia and hydrochloric acid, yielding
the same compounds as cuprous oxide. When exposed to the air it undergoes oxida-
tion and becomes blue.
Cupric hydrate, OuHoj, is obtained as a pale blue bulky precipi-
tate when an excess of caustic potash or soda is added to the solution
of a cupric salt in the cold. It is insoluble in excess of the precipitant
except in presence of certain organic substances, such as sugar and tar-
taric acid. When the precipitate is heated with the alkaline liquid it
blackens, and is partially converted into cupric oxide; but after wash-
ing and drying at onlinary temperatures it may be heated to 100° C.
(212° F.) without giving off water. Cuprous hydrate is soluble in
aqueous ammonia, yielding a blue solution, which possesses the remark-
able property of dissolving cellulose in its various forms— cotton, linen,
paper, etc. The cellulose is precipitated in the amorphous state by
acids, salt, sugar, and various other substances.
OXY'SALTS OF COPPER.
NO
Cupric kitrate, jtq^Cuo",30H2. — ^The solution of copper or
cupric oxide in nitric acid yields on evaporation blue prismatic crystals
of the above composition. These are deliquescent and soluble in
alcohol. The anhydrous salt has not been prepared, as the aquate,
when heated to about 65° C. (149° F.), parts with nitric acid and
water, yielding a green basic salt of the formula NOHo(OCuHo)^
Owing to the readiness with which cnpric nitrate is decomposed with
liberation of nitric acid, this salt possesses oxidizing properties. Moist
COMPOUNDS OF COPPER. 547
crystals of the nitrate^ wrapped up in tinfoil, act violently upon it,
oxidizing it to stannio oxide, frequently with emission of sparks. On
evaporating mixed solutions of cupric nitrate and ammonic nitrate over
a flame, when a certain concentration is attained the whole liquid sud-
denly deflagrates like loose gunpowder, evolving a dense brown cloud
of finely divided cupric oxide. Cupric nitrate is employed in dyeing
and calico-printing in some cases in which an oxidizing agent is re-
quired to produce the color on the fibre. — A concentrated solution of
cupric nitrate in ammonia deposits dark blue rhombic crystals of a
compound —
''^uo'MNH - NOHo(NH,)fNH30c „y'
Cupric carbonates. — The normal carbonate is unknown. Various
basic carbonates occur in nature. Mysorin is dicupric carbonate,
OCuo'V Malachite is dicupric carbonate dihydrate, 0O(OCu"Ho)2.
It forms monoclinic crystals of a brilliant green color, more frequently
botryoidal masses, with a structure which is generally fibrous. The
massive variety takes a high polish, and is employed for ornamental
purposes. The same compound is formed as a green rust by the joint
action of water and air upon copper, and is then known as vo'digris.
rOHoCuo''
Bltce malachite or azurite is a dihydric tricupric dicarbonate, < Cuo"
(OHoCuo''
It occurs in dark-blue monoclinic crystals.
Cupric sulphate {Dihydric aipric sulphate), 8OHo2Cuo",40H2.
— This salt, also known as blue vitriol, is obtained on a large scale by
roasting copper pyrites and lixiviating the mass with water. The iron
chiefly remains behind as oxide, whilst the cupric sulphate dissolves,
and on evaporation is deposited in crystals of the above formula. The
first crystallization is relatively pure; the crystals from the mother
liquor contain iron (as ferrous sulphate), from which they can best be
freed by recrystallization with the addition of nitric acid. Ferrous sul-
phate is capable of crystallizing with cupric sulphate in varying pro-
portions (see below), and the two substances cannot be completely
separated by crystallization. The addition of nitric acid converts the
ferrous sulphate into a ferric salt, which does not possess this property. —
Cupric sulphate is thus obtained in large blue triclinic crystals, soluble in
2J partsof water at ordinary temperatures, in ^part atl60°C. (212° F.).
The crystals effloresce in dry air, and part with the four molecules of
water of crystallization at 100° C. (212° F.), leaving the salt SOHojCuo",
which at a temperature above 200° C. (392° F.) is converted into anhy-
drous cupric sulphate, SO^Cuo", a colorless salt which rapidly attracts
moisture and becomes of a blue color. — Various basic sulphates of cop-
per are known. By heating the normal sulphate to redness for several
hours, dicupric sulphate, SOCuo",, is obtained as an orange-yellow
powder. Cold water converts this salt into ordinary cupric sulphate,
which dissolves, and an insoluble green basic sulphate of the formula
8Ho2(OCu''Ho)4, dihydric tetraciipric sulphate dihydrate, a substance
which occurs native as the mineral brochantite. With boiling water the
548 INOBOANIC CHEMISTRY.
oraiifre-jellow powder yields another basic sulphate — hydrie trieupne
tulphaU trihydrate, SOHo(OCu"Ho),. — A concentrated solution of
cupric sulphate in ammonia deposits, especially on the aildition of alco-
hol, dark-blue rhombic crystals of the compound SO,Cuo",4NHj,OH,
/NH,Ov"
=SHo,(NH,), I Cu" 1 ,0H. which on heating to 1 50° C. (S02° F.) is
/NH,Ov"
f.), Cu" ,(
\nh,o/
nt
NHjOi"
Cu" 1.
NH,0/
converted into a green powder, consisting of cmprammonic mdphaU^
/NHjOv
SOJ Cu^' I . Anhydrous capric sulphate absorbs gaseous ammonia
with great avidity, yielding the compound 80,Cuo",5NH3. — Cupric
sulphate forms with the alkaline sulphates double salts crystallizing in
monoclinic forms, and.isomorphous with the corresponding double salts
of the alkalies with zinc and magnesium. Thus with potassic sulphate
rso^Ko
it forms dipotassic cupric disulphaiey < Cuo" ,60H^ — From mixed so-
(80,Ko
liitions of cupric sulphate with one of the sulphates of the dyad metals,
magnesium, zinc, nickel, and iron (ferrous), crystals are deposited, con-
sisting of isomorphous mixtures of the two sulphates present If cupric
sulphate predominates in the solution, the mixed crystals are triclinic
like those of cupric sulphate, and like the latter salt contain 5 aq.
(including the molecule of water of constitution) ; if the other sulphate
predominates, the mixed crystals ansume the form of this sulphate,
rhombic or monoclinic, and, like the rhombic and monoclinic sulphates
of this isomorphous group, contain 7 aq. (including the molecule of
water of constitution). — Cupric sulphate is employed in the preparation
of pigments containing copper, in calico-printing, and in electrotyping.
Capric phonphaUs, — The normal phosphate, 'I Cuo^^ >30H^ is meet readily pre-
l POCu</^
?ared pure by digesting cnpric carbonate with dilute phosphoric acid and heating to
0° C. (158° F.) the blue solution thus obtained. The salt separates as a bluish-green
powder, insoluble in water, soluble in acids and in ammonia. It is also formed when
tijdric disodic phosphate is added to an excess of a solution of a normal cupric salt.
If, on the other hand, the solution of the cupric salt be added to an excess of the alka-
line phosphate, a precipitate is obtained similar in appearance^ but consisting of hydrie
cupric phosphtUey POHoCuo'^. When the normal phosphate is heated with water In
sealed tub^, it is decomposed into free phosphoric acid and a basic salt — dieupncpho$'
phaU hydrate^ POCuo'^(OCu VHo) — which also occurs in nature as the mineral libethemU,
and crystallizes in dark olive-green rhombic prisms. Another native basic cupric
phosphate is the mineral phosphochaldU, PO{OCuHo)j, tricupric photpKate trthy<haUf
which forms green monoclinic crystals or botrvoidal masses.
riUOCuo'^
Oupric arsenates. — The normal arsenate, i Cno^^ t^OHi, is obtained by heating
tAsOCuo^'
together cupric nitrate and calcic arsenate. It forms a bine amorphous powder. Baste
arsenates also occur as minerals, and correspond closely to the basic phosphates, with
' wli ich they are isomorphous. Olivenite is a dicuprie arsoiote hydratCy AaOCuo''(OCu''Ho).
Cupric arseniie. — Hydrie cupric arsenate, A«HoCuo'^, a compound employed as a pig-
ment under the name of ScheeU^s ffreeUy is prepared by adding to the solution of a
cupric salt a solution of arsenions anhydride^ and then carefully neutralizing with am-
monia or caustic soda. It is of a light green color. It is insoluole in water, but readily
soluble in caustic potash, yielding a blue liquid. The solution gradually deposits cu-
prous oxide.
COMPOCTNDB OP CX>PPER. 549
Ouprie filicates. — Two of. these oocnr in nature. DtoptasCf a hydrie cuprie 8m4i(Ue
irihydric cuprie
hydraU, 8IOUo(OCn'^Ho), fomiR emerald-green hexagonal crystals. Ckry&ocoUa is a
w/icote Aydrate, Si Ho,(OCu^'Ho). It forms green botryoidal i
COMPOUNDS OF COPPER WITH SULPHUR.
Cuprous sulphide, ...."< /j«S". | y>S
Cuprie sulphide, ..... OuS''. Cu=S
Cuprous sulphide, 'Ou',S. — This compound occurs native as cop-
per glance, and forms lead-gray rhombic tables or prisms with a me-
tallic lustre, and having a sp. gr. of 6.5 to 5.8. The same compound
is obtained as a black, brittle mass by heating together 4 parts of cop-
per filings and 1 part of sulphur, or by burning copper in sulphur
vapor.
CuPRiC sulphide, OuS, also occurs native as the mineral indigo-
coppery but much less abundantly than the cuprous compound. It
sometimes forms dark-blue hexagonal crystals with a semi-metallic
lustre, but more frequently occurs massive. Its sp. gr. is 4.6. It may
be obtained as a blue powder by heating finely divided copper with
flowers of sulphur, avoiding a temperature higher than the boiling
point of sulphur. It is obtained as a black amorphous precipitate when
sulphuretted hydrogen is passed into solutions of cuprie salts, and in
this condition is readily oxidized if exposed to the air while still moist.
The precipitated sulphide is insoluble in potassie and sodic sulphides,
somewhat soluble in yellow ammonic sulphide, readily soluble in po-
tassie cyanide and in hot nitric acid. When cuprie sulphide is heated
with exclusion of air, or in a current of hydrogen, it parte with half
its sulphur and is converted into cuprous feulphide. — When an ammoni-
acal solution of a copper salt is precipitated with sulphuretted hydro-
gen a black precipitate of cuprie sulphide is obtained. If this precipi-
tate be washed for a very long time with sulphuretted hydrogen water,
until the last traces of ammonia compounds are removed, the black sul-
phide at last goes into solution, yielding a dark-brown liquid which is
believed by some chemists to contain a colloidal modification of the
sulphide. Solutions of salts precipitate from the liquid insoluble cuprie
snlphide. On evaporation the black liquid dries up to a black lustrous
' film. Similar colloidal modifications of sulphides have been obtained
in the case of various other heavy metals.*
* It is, however, probable that these so-called colloidal salpliides are nothins^ more
than ordinary sulphides in a state of very fine subdivision. Ebell, who has advanced
this view, has shown that the finest ultramarine, obtained by grinding and levigation,
can be removed by filtration from liquids containing; a salt in solution; but if the ultra-
marine upon the filter be washed with pure water, it passes through the filter as soon as
the salt solution has been sufficiently removed, and yields a blue liquid which to the eye
is perfectly transparent, but which under the microscope is seen to contain minute sus-
pended particles of ultramarine. In pure water these minute particles show no ten-
dency to subside; but the addition of a small quantitv of the solution of a salt pre-
<^pitates the ultramarine. If the salt solution be added to a drop of the blue liquid
550 WORGANIC CHEMISTBY.
COMPOUNDS OF COPPER WITH NITROGEN, PHOSPHORUS, AND
ARSENIC
Ouprtms wUride, N)(^Cu^s)^^s, is obtained as a dark green powder when gaseous am-
monia is passed over finely-divided cupric oxide heated to 250® C. :
eCnO + 4NH, = N,('Cu^)'^« + Nj + 6OH1.
ipric Ammonia. Cnprous
Lide. nitride.
Cupric Ammonia. Cnprous ^Water.
oxide " *'
At 300° O.y it is decomposed, with a slight explosion, into its elements.
Cuprotu phosphide, P2(''Cu^,)^^,, is formed when cuprous chloride is heated in a car-
rent of phosphoretted hydroeen, or when the vapor of phosphorus is passed over copper
foil heated to low redness. By fusing the compound under a layer of borax it may be
obtained in the form of a silver-white regulus of sp. gr. 6.59, very brittle, and ca^Able
of taking a polish. Hydrochloric add is almost without action upon it, but nitric acid
dissolves it readily.
Cupric phosphide, FsCu^^s, is prepared in a similar manner by passing phosphoretted
hydrogen over heated cupric chloride. It forms a black lustrous powder, which when
heated in a current of hydrogen is converted into cuprous phosphide. It is also formed
as a black precipitate when phosphoretted hydrogen is passed into. the solution of a
cupric salt (p. 342).
Cuprous arsenide, AM^i^Cu^^Y^ occurs in Chili as the mineral domeykite, forming
tin-white or silver-white masses. Other arsenides of copper also occur as minerals.
General Properties and Reactions of the Compounds of
Copper. — The soluble compounds of copper >bave a disagreeable me-
tallic taste, and are poisonous, causing vomiting and death.
a. Cuprous Compounds. — The cuprous salts are colorless. They are
generally insoluble in water, but soluble in hydrochloric acid and am-
monia. In solution they rapidly al^sorb oxygen from the air, and are
converted into cupric salts. Caustic alkalies precipitate yellow cuprous
hydrate, which is converted on boiling into red cuprous oxide.
b. Ouprio Compounds. — ^The cupric salts are white in the anhydrous
state, blue or green when hydrated. They are nearly all soluble. The
solutions redden blue litmus. Caustic alkalies precipitate blue cupric
hydrate, which on boiling is partially converted into cupric oxide and
becomes black. The presence of sugar, tartaric acid, and various other
organic substances, renders the cupric hydrate soluble in an excess of
alkali. Ammonia gives a similar precipitate^ which is, however, soluble
in excess, yielding a deep-blue liquid. Sulphuretted hydrogen precipi-
tates from acid solutions brownish-black cupricsulphide, slightly soluble
in yellow ammonic sulphide, readily soluble in potassic cyanide, and in
hot nitric acid. Potassic ferroeyanide gives a brown precipitate, in-
soluble in hydrochloric acid.
From solutions of copper com()Ounds sdnc and iron precipitate me-
tallic copper. All compounds of copper, when heated with sodic car-
bonate on charcoal in the reducing flame of the blowpipe, yield a bead
of metallic copper. A borax bead containing a copper salt, and heated
under the microscope, the separate particles of ultramarine are seen to unite into aggre-
gations, each consistini? of a number of particles. On evaporation, the blue liquid
yields a lustrous blue film adhering to the sides of the vessel.
The behavior of this finely-divided ultramarine — a substance which cannot in any
sense be regarded as eottoidrd — corresponds therefore, in all the above particulars, with
that of the metallic sulphides referred to.
GOLD. 551
in the oxidizing flame, is green while hot and blue when cold ; in the
reducing flame the bead is colorless if the proportion of copper be small,
but, if the proportion of copper be lai^e, the bead is red from the
presence of reduced copper. The compounds of copper color the non-
luminous flame green or blue. Cupric chloride gives a handed flame-
spectrum', this being the spectrum of the compound. The spark-spec-
trum of copper contains a number of lines, among which some of those
in the green are especially prominent.
CHAPTER XXXV.
TRIAD £LEK£NTS.
Section II.
GOLD, Au2?
Atomie weight = 196. Probable molecular weight = 392. 8p, gr. 19.3
to 19.5. Fu9es at 1240^ C. (2264^ F.). AtomicUi/ ' and '''. Evi-
dence of atomicity :
Aureus chloride, AuCl.
Aureus iodide, An I.
Auric chloride, Au^'Clj
Auric hydrate, Au^'Hoj.
Hifftory. — Gold has been known and prized from the earliest his-
torical times.
Occurrence. — Gold occurs widely distributed, but mostly only in
small quantity. It is almost always found in the native state, some-
times in crystals, sometimes in dendritic forms produced by the regular
aggregation of crystals, but most frequently in irregular masses termed
nuggets. In matrix it is found disseminated throughout quartz veins
or reefs. The alluvial deposits produced by the disintegration of the
auriferous rocks form the chief sources of the metal. The principal
gold-fields are those of California and Australia. Grold is still extract^ J
from the sand of rivers in Hungary and Transylvania, but the idi-
portance of these sources has diminished since the discovery of the
Australian and Californian fields. Native gold generally contains more
or less silver; if the percentage of silver exceeds 36 percent, this
native alloy is termed elednim. Gold is found in combination with
bismuth and tellurium in a few rare minerals, and alloyed with mer-
cury as an amalgam. Traces of the metal occur in many ores of silver,
copper, and lead, and in iron pyrites. In spite of the smallness of the
quantity present, it is possible in some of these cases to extract the gold*
with profit (see p. 450).
552 INORGANIC CHEMLSTRY.
Ejdraction, — Native gold is mechanically separated from the alluvial
deposits with which it is mixed by washing away the lighter earthy
particles — either by the simple manual processes of pan-washing or
cradle-washingy or, on a large scale, by hydraulic gold-mining. In the
latter process enormous jets of water are employed to remove the whole
of the alluvial deposit down to the bed-rock. The stream *of water,
carrying with it the disintegrated deposit, flows throu(2:h a long sloping
tunnel bored in the rock. Along the bottom of the tunnel are placed
" sluice-boxes " containing a small quantity of mercury. The particles
of gold fall into the sluice-boxes and are arrested by the mercury with
which they form an amalgam. The tunnel is cleared at intervals of
from ten to twenty days : the amalgam of gold is removed, and the
mercury expelled by distillation. In qaaiiz-mining the auriferous
quartz is stamped to a fine powder by special machinery^ and the gold
extracted by amalgamation.
Refining, — One of the simplest and most efficient refining processes
is that devised by F. B. Miller. The gold, which must not contain
more than 10 |>er cent of silver, is melt^ in a clay crucible glazed in-
side with l)orax, and a current of chlorine is passecl through the molten
metal. The silver is thus converted into argentic chloride, which rises
to the surface and is prevented from volatilizing by a layer of fused
borax ; other foreign metals, such as zinc, antimony, bismuth, and tin,
are volatilized as chlorides. The metal thus purified contains from 99.1
to 99.7 per cent, of gold.
Pure gold may be prepared by di&solving the metal in aqua-regia,
and, after expelling the excess of nitric acid, precipitating the gold by
some reducing agent, such as ferrous sulphate. The finely divided gold
is obtained in a coherent form by fusion with a mixture of borax and
nitre.
Properties, — ^Grold is a lustrous metal, of a yellow color when the
light is only once reflected, but red when the light is several times re-
flected from the surface of the metal before reaching the eye (p. 400).
It is the most malleable aqd ductile of the metals (pp. 409 and 410).
Very thin gold leaf transmits green light. When pure it is nearly as
soft as lead. It fuses at 1240'' C. (2264° F.), the molten metal emit-
ting a bluish-green light. At very high temperatures it is volatile. It
is quite unalterable in air, oxygen, and steam, at all temperatures. No
single acid, with the exception of selenic, has any action upon it ; but
aqua-regia, and all other liquids containing or evolving chlorine, dis-
solve it with formation of auric chloride (AuClj). It combines with
chlorine and bromine at ordinary temperatures, and with phosphorus
when heated in its vapor. It is precipitated from its solutions by most
other metals, and by most reducing agents. Ferrous sulphate precipi-
tates it as ^ brown powder without metallic lustre; oxalic acid, in
glistening yellow scales.
Uses, — Gold is employed for coinage, for ornaments, and in gilding.
Non-metallic surfaces are gilt with gold-leaf. Metals are gilt by electro-
deposition, employing a solution of auric chloride in potassic cyanide
• (the solution contains auric potassic cyanide, AuCy3,KCy) and using a
gold plate as positive electrode.
COMPOUNDS OP GOLD. 653
Alloys. — Pure gold is employed in the preparation of gold-leaf
and of the solutions for electro-gildings but owing to its softness is not
suited for the manufacture of objects which have to resist the wear of
ordinary use. For jewellery or coinage gold is therefore alloyed with
copper, or with silver, or with both, these admixtures imparting to the
gold the requisite hardness. The copper alloy has a reddish tinge, that
with silver is whiter than pure gold.
The proportion of gold in an alloy is frequently expressed in corotg, or parts per 24 :
thus 24-carat gold is pure gold, 22-carat gold contains 22 parts of gold in 24 parts of
the alloy, and so on. In most countries the composition of various standard alloys for
jewellery and coinage is fixed by law. In England there are five legal standards : 22-
carat — the standard gold employed for coinage, the two remaining parts in this case
consisting of copper — 18, 15, 12 and 9-carat gold. In the case of coinage standards,
however, it is more usnal to express the proportion of gold in parts per mille of. the
alloy, this expression being known as the fineness of the alloy. Thto English 22-carat
standard gold has thus a fineness of 916.66. Most other European countries employ a
coinage standard having a fineness of 900.
Gold forms two classes of compounds, aurous and auria. In the first
of these it is a monad, in the second a triad.
COMPOUNDS OF GOLD WITH THE HALOGENS.
a. Aurou8 Compounds,
Aureus chloride^ And, is obtained by heating auric chloride, AuGs, to 185° G.
(365^ F.). It is a yellowish -white powaer, which is decomposed at a higher tempera-
ture into gold and 'chlorine. Water decomposes it into metallic gold and the trichloride.
Aurous iodide^ Aul, is formed by the action of hydriodic acid upon auric oxide :
Au,0» + SHI = 2AuI -f 30Hj + 21,,
Aurto Hydriodlo Aurous Water,
oxide. acid. iodide.
and in all similar cases when the formation of an auric iodide might be expected, the
latter compound undergoing decomposition into Aul + Ij — thus by the action of po-
tassic iodide upon auric chloride :
AqCU
+
SKI
=
Aul
+
L
+
3KC1.
Auric
Potassic
Aureus
Potassic
chloride.
iodide.
iodide.
chloride.
— Aurous iodide forms a lemon-yellow powder, which is decomposed, slowly at ordi-
nary temperatures, rapidly on heating, into its elements.
6. Aurio Compounds.
AXTRIC CHLORIDE, AuCI,. — ^This compound is obtained by the action
of chlorine upon gold, or by dissolving gold in aqua-regia, eva[K>rating
to dryness, taking up with water, evaporating again to dryness, and
heating carefully to 160° C. (302° F.). The anhydrous chloride forms
a brown crystalline deliquescent mass. Though aecomposed at 185° C.
(365° F.), as already mentioned, into aurous chloride and chlorine, it
may be sublimed in a current of chlorine at 300° C. (572° F.), and is
thus obtained in long red needles. When a hot concentrated aqueous
554 INORGANIC CHEMISTRY.
solution of auric chloride is allowed to cool, an aquaie of the formula
AuC]s,20H2, is deposited in large orange-colored crystals.
Auric chloride forms namerons compoands with other metallic chlorides and with
hydrochloric acid. The hydrochloric acid compound, sometimes called hydratLric aeid,
has the formula AaCls,HCl,30Hi, and crystallizes from the concentrated solution of
cold in aqua-regia in long yellow needles. Auric potassie chloride forms two aqnates —
(AaC]»,ECl)i,OHi, crystallizing in needles, and AuCls,HCI,20Hs. crystallizing in large
rhombic tables. Auric sodic chloride, AuCU.NaCl,20Hi, crystallizes in yellowish-red
prisms. ^urieommtrntceA/oriVie forms light yellow rhombic tables, (AuCl„NH4Cl)«oOHt,
or monoclinic plates (AuCI„NH4Cl)504Hs. These double chlorides are sometimes
referred to as JdorauraUSf thus potaasic chlorauraU.
Auric bromide, AuBr^, forms a black crystalline mass.
Auric iodide. Aula, is not known as such, but several double compoands of this
iodide with iodides of other metals have been prepared.
COMPOUNDS OF GOLD WITH OXYGEN AND
HYDROXYL.
Aureus oxide^ OAuj. Au — O — ^Au.
rAuo
Auric oxide {Auric anhydride) < O . 0= Au — O — Au=0.
(AuO
/O— H
Auric hydrate, . • . . . AuHo,. Au(^0 — H.
Auroua oxide, OAu,, is obtained as a violet-black powder by the
action of dilute caustic potash upon aureus chloride. At 150° C.
(302° F.) it is decomposed into its elements. With hydrochloric acid it
yields auric chloride and metallic gold :
30Au, + 6HC1 = 2AuCls + 2Au, + 30Hj.
Aureus Hydrochloric Auric Wat«r.
oxide. acid. chloride.
Sulphuric and nitric acids are without action upon it, but aqua-r^a
dissolves it readily.
Auric oxide {Auric anhydride), AUjO,. — This compound is pre-
pared by heating a solution of auric chloride with magnesia and treat-
ing the precipitate, which consists of rnagneaic aurate,
AuO'^S^ >
with concentrated nitric acid, in which the whole dissolves. Water
precipitates auric hydrate, A11H03, as a reddish-yellow powder, which
by gentle heating is converted into the oxide. It forms a brown
powder which is partially decomposed at 100° C. (212° F.), wholly at
245° C. (473° F.), into its elements. It Ls the anhydride or auric arid,
AuOHo, and dissolves in dilute caustic potash to form pota^io auraJte,
which crystallizes in light yellow needles of the formula AuOKOySOH,.
COMPOUNDS OF GOLD. 555
— A derivative of auric anhydride is fulminating goldy a compound
which is formed by the union of four molecules of ammonia with
one of auric anhydride, and which may be regarded as possessing
rAu(NH2)(NH,0)
the constitution < O . It is best prepared by treating
Uii(NH2)(NH,0)
^uric hydrate with aqueous ammonia. It forms a yellowish-brown
or greenish-yellow powder, which when dry explodes with great vio-
lence by heat or percussion. A similar compound, which however
appears to contain chlorine, separates when ammonia is added to a solu-
tion of auric chloride.
Auric hydrate^ A11H03, may be obtained either as above described, or
by electrolyzing dilute sulphuric acid, employing a gold plate as posi-
tive electrode, when the hydrate is formed as a yellow crust on the
electrode.
OYY-SALTS OF GOLD.
Simple oxy-salts of gold are not known. Double salts have however
been prepared, 8uch as the double thiosulphate of gold and sodium^
S02AuoAus,3802NaoNas,40H2, which might also be formulated —
SHo^NaoAus-i
SHoNaoNas
Q * A odohydric diaurous hexaaodio
8Ho,NaoNasl' tetrathiosuiphate.
SHojNaoAusJ
It is formed when a dilute neutral solution of auric chloride is added
to an excess of a solution of sodic thiosulphate. A reduction of the
gold from the auric to the aurous condition occurs, the red liquid which
is at first formed becoming colorless. The salt is then precipitated by
the addition of strong alcohol. It crystallizes in colorless needles
which have a sweet taste. Neither the gold nor the thiosulphuric acid
can be detected by the usual tests: the gold is not precipitated by re-
ducing agents, and no separation of sulphur occurs on the addition of
dilute acids.
Double sulphites of gold with the alkali metals are also known.
Aurous amnionic sulphite has the formula
8OAmo2,38OAuoAm6,30H2.
Purple of Caasivs. — This remarkable compound is obtained as a
flocculent purple precipitate when a very dilute mixed solution of
stannous and stannic chloride is gradually added to a dilute neutral
solution of auric chloride. It contains one or both of the oxides
of tin. Its nature is not known with certainty, but it is supposed
to be a hydrated stannous diaurous distannaie,
Sn2O2Sno''Auo2,40H,.
656 INORGANIC CHEMISTRY.
Its oompoeitioD, however, is apt to vary with the mode of preparation.
The compound is decomposed by acids with separation of metallic gold.
It is insoluble in solutions of caustic potash and caustic soda, but
soluble in ammonia, yielding a deep purple liquid which is bleached
by exposure to light with deposition of metallic gold and formation
of ammonic stannate. Purple of Cassius is employed to impart a
magnificent red color to glass. The color depends upon the presence
in the glass of metallic gold in a state of minute subdivision.
COMPOUND OF GOLD WITH SULPHUR.
Diauraus dumfphidey 'B'jAu,, is precipitated by sulphuretted hydro-
gen from cold solutions of auric chloride :
2AuCl, + 38H, = 'S',Au, + 6HC1 + S.
Auric Sulphuretted Diaurous Hydrochloric
chloride. hydrogen. disulphide. acid.
It forms a black precipitate, insoluble in water, soluble in solutions
of the alkaline sulphides, with formation of double sulphides such as
SXaAu:
'S',Au, + 2SNa,
= 28NaAu +
'8',Na^
Diaurons Disodic
Sodic aurous
Disodic
disulphide. sulphide.
sulphide.
disulphide
From hot solutions of gold salts sulphuretted hydrogen precipitates
metallic gold.
General Properties and Reactions of the Compounds of
Gold. — Gold is precipitated from its solutions by most reducing agents
— ^'9'f ferrous sulphate^ mercurous nitratef oxalio cudd, formic acidy «u/-
phurous acid — as finely divided metallic gold. A mixture of stannous
and stannic chlorides produces a characteristic precipitate of purple of
Cassius (p. 655). All gold, compounds are converted into metallic
gold when ignited with exposure to air. The compounds of gold do
not color the non-luminous flame.
Section III.
THALLIUM, Tl,?
«^.
Atomic weight = 204. Probable molecular weight = 408. 8p. gr l\A
to 11.9. Fuses at 294° C. (561.2° F.). AtomicUy ' and "'. Evi-
dence of atomicity :
Thallous chloride, TICK
Thai lous oxide, OTljj.
Thallic chloride, Tl'"Cls.
History, — Thallium was discovered by Crookes in 1861, while exam-
ining spectroscopically a seleniferous deposit from a sulphuric acid
COMPOUNDS OF THALLIUM. 657
manufactory in the Harz. It was at first supposed to be a non-
metaly allied to sulphur. In 1862 it was discovered independently by
Lamy, who first recognized its metallic character and succeeded in iso-
lating it.
The name thallium, derived from 0(MS^, a green twig, was given to
this element in allusion to the bright green line which constitutes its
visible spectrum and by means of which it was discovered.
Ooourrence. — Thallium occurs widely distributed in nature, but only
in small quantities. Certain varieties ef pyrites — notably Belgian,
Westpbalian, and Spanish pyrites-— contain traces of thallium, and
when such pyrites is burnt in the manufacture of sulphuric acid, the
thallium condenses and collects in the form of thallous oxide, along
with arsenious anhydride and other substances, as a fine dust in the
flues of the pyrites bnrners. Salts of thallium occur in minute
quantity in some mineral springs. As an essential constituent^ it is
found only in the rare mineral crookesitey a selenite of copper^ silver,
and thallium, containing from 16 to 18 per cent, of the latter metal.
Pi^eparation. — When the flue dust containing thallium is treated with
dilute sulphuric acid, the thallium goes into solution as thallous sulphate,
SO2TI02, and may be precipitated as sparingly soluble thallous chloride
by the addition of hydnwhloric acid to the filtered solution. The
washed chloride is separated and reconverted into sulphate by treat-
ment with sulphuric acid, heating to expel the hydrochloric acid. The
sulphate is purified by crystallization, and from the solution of the pure
sulphate metallic thallium is obtained by elecjtroljrsis or by precipitation
with zinc. The metal, which is thus deposited in soft laminar crystals
or as a spongy mass, may be obtained in a coherent form by fusion in a
covered crucible under potassic cyanide.
Properties. — ^Thallium is a heavy metal, white like tin, and sofl
enough to be scratched with the finger-nail. It may be distilled at a
white heat in a current of hydrogen. When exposed to the air it
tarnishes superficially, and is converted into thallous oxide. It does
not decompose water below a red heat, and is best preserved in closed
vessels under water. With access of air it slowly dissolves in water,
with formation of thallous hydrate, which in solution absorbs carbonic
anhydride, and is ultimately converted into carlx)nate. Dilute acids
readily dissolve it. It is precipitated in the metallic state from its solu-
tions by zinc, but it precipitates lead, copper, mercury, and silver from
the solutions of their salts.
Thallium forms two classes of compounds — ^thallous compounds, in
which the metal is monadic, and thallic compounds, in which it is^tri-
adic. The members of the first class are the most numerous and best
characterized.
COMPOUNDS OF THALLIUM WITH THE HALOGENS.
a. ThaJlous Compounds.
Thallous chloride, TlCl, Molecular volume, i i i- — This compound
is obtained as a curdy precipitate when hydrochloric acid is added to a
568 INORGANIC CHEMISTRY.
not too dilate solution of thallous hydrate or a thalloos salt. It is
colored violet by exposure to light. It is soluble in 360 parts of water
at ordinary temperature, in from 60 to 60 parts at lOO'^ C. (212^ R).
From the hot saturated aqueous solution it crystallizes in cubes. It is
less soluble in water containing hydrochloric acid than in pure water.
It is readily fusible, yielding a yellow liquid, which solidifies to a white
crystalline mass. At higher temperatures it volatilizes.
Thallous bromide, TIBr, forms a Tellow precipitate. It is leas soluble in water than
the chloride, which it closely reseml^les.
ThaUouM iodide. Til, is precipitated as a yellow cryBtalliDe powder when potawic
iodide is added to the solution of a thallous salt. It is almost insoluble in water. Ex-
posure to sunlieht colors it green. It is readily fusible, and solidifies to a red crystal-
line mass, which becomes yellow on standing. At a higher temperature it may be snb-
limed with partial decomposition.
Thallous JluorUUt TIF, is prepared by dissolving thallous carbonate in hyiirofluoric
acid and evaporating. It crystallizes in colorless, verv lustrous anhydrous octahedra,
or, with water of crystallization, in hexagonal plates. It dissolves readily in water, and
is fusible and volatile. When exposed to sunlight it becomes dark-colored. 8olniion8
containing an excess of hydrofluoric acid deposit on evaporation over sulphuric acid
in vacuo regular crystals of an acid fluoride, T1F,HF.
h, ThaUic Compounds.
ThaMic chloride, TICI3, is formed when thallous chloride is suspended
in water and chlorine passed into the liquid. On evaporation in f)acuo
colorless deliquescent prisms of the formula TlCls^OHj are deposited.
Chlorides of thallium intermediate between thallous and thallic chloride are known.
In these the thallium is in the triadic condition :
Tetraihailie haxLchlortde, i •|n(TK^''CnCl ' *^ f«r™ed when metallic thallium is
strongly heated in a current of chlorine. A yellowish-brown mass is thus obtained,
sparingly soluble in cold, but readily soluble in boiling water, and crystallizing from
the solution in yellow laminae.
DithaUic tetrachloride, < nnni'" — When metallic thallium or thallous chloride is
cautiously heated in chlorine, a comi)ound of the above composition is obtained, which,
on heating more strongly, parts with chlorine, and is converted into tetrathallic
hexacliloride.
ThaUic bromide, TlBr,, and thalUc iodide, Tils, are also known. They resemble the
chloride, but are less stable.
COMPOUNDS OF THALLIUM WITH OXYGEN AND
HYDROXYL.
Thallous oxide, . . . OTl,. Tl— O— Tl.
T1=0
(TIO I
ThalHc oxide, . . . Ao . O
(TIO I
Tl=0
Thallous hydrate, . . TlHo. Tl— O— H.
Thallic oxyhydrate, . . TlOHo. 0=T1— O— H.
Thallous oxide, OTl,. — Metallic thallium when exposed to the
air taruishes, owing to the formation of a coating of tliallous oxide.
C0MP0UND8 OF THALLIUM. 559
The oxide may be obtained pure by heating the hydrate to 100° C.
(212° F.) with exclusion of air. It forms a black powder which fuses
at 300° C. (572° F.) to a dark-yellow liquid. It attracts moisture from
the air, and dissolves in water with formation of thallous hydrate.
Thallic oxide, TI3O3. — This oxide is formed when thallium burns
in oxygen, and may also be obtained by heating thailic oxyhydrate to
100° C. (212° F.). It is a dark-red powder, insoluble in water. At a
red heat it evolves oxygen, and is converted into thallous oxide. Hot
concentrated sulphuric acid dissolves it with evolution of oxygen and
formation of thallous sulphate. When acidulated water is electrolyzed,
employing a positive electrode of thallium, the metal becomes covered
with a black deposit of thallic oxide.
Thallous hydrate, TlHo, is formed when thallium is simulta-
neously acted upon by water and air or oxygen. It is most readily
obtained pure by precipitating thallous sulphate with baric hydrate
and evaporating the filtrate. It crystallizes in colorless or faint-yellow
rhombic prisms, having the com[K)sition TIHo,OH2. It is readily
soluble in water and in alcohol, yielding powerfully alkaline solutions.
The brown stain which it produces upon turmeric paper disappears,
however, after a time, owing to a peculiar destructive action which the
hydrate exercises upon the coloring matter. Thallous hydrate is con-
verted at 100° C., or in vacuo at ordinary temperatures, into thallous
oxide.
Thallic oxyhydrate, TlOHo. — This compound is produced as a brown
precipitate when freshly precipitated thallous chloride is warmed with
a solution of sodic hypochlorite. It is also formed by the action of a
caustic alkali upon thallic chloride. It is a brown powder, which at
100° C. (212° F.) is converted into thallic oxide.
OXY-SALTS OF THALLIUM,
a. ThaUouB Salts,
Thallcms nitraie, NOgTlo. — This salt is obtained by dissolving the
metal in nitric acid. The solution deposits opaque white rhombic
prisms, soluble in about 10 parts of water at the ordinary temperature,
very readily soluble in boiling water. It fuses without decomposition
about 205° C ; but is decomposed at a higher temperature.
Thallous carbonate, COTI02, is formed when a solution of thallous
hydrate, or metallic thallium moistened with water, is exposed to the
air. It is best prepared by saturating a solution of the hydrate with
carbonic anhydride and evaporating to the crystallizing point. It is
deposited from the aqueous solution in long, lustrous monoclinic prisms.
It dissolves in 20 parts of cold water, yielding a solution with an alka-
line reaction. It is fusible without decomposition, but at higher tem-
peratures evolves carbonic anhydride.
Thallous svlphatey SOjTloj, crystallizes in rhombic prisms, and is
isomorphous with potassic sulphate. It is soluble in 20 parts of
water at ordinary temperatures and in 5 parts at 100° C. (212° F.).
560 INORGANIC CHEMISTRY.
When air is excladed, it fuses at a red heat without deoomposition ;
but when heated in air, it is decomposed with evolution of sul-
phurous anhydride. — Hydrio thallous tnUphate is deposited from so-
lutions oontaining a large excess of sulphuric acid. It crystallizes
in short thick prisms, having the formula SO^HoTlo^SOH. — With
the sulphates of the dyad metals thallous sulphate forms double salts,
fSO,Tlo
such as the double sulphate of zinc and thallium, < Zno^' fiOJl^f
(SOjTlo
corresponding with the double sulphates of ammonium and potassium
with the dyad metals, and like these, oontaining 6 molecules of water
of crystallization.
ThdUow phosphate, POTlo,, is obtained as a white crystalline precipitate when a
thallous salt is added to a solution of ordinary sodic phosphate oontaining ammonia.
It dissolves in 200 parts of cold and in 150 parts of boiling water. It is soluble in no-
Intions of ammonia salts. — Hydrie dithaUous phosphate, P0HoTloi,OHs, is prepared bj
neutralizing a Kolution of phosphoric acid witn thallous carbonate. The solution
deposits on evaporation rhombic crystals, which part with their water of crystallization
at 200^ C, and at a red heat are converted into a vitreous mass of thalions pyrophosphate,
PsOgTlo4.— DiAyrfric ihaUous phoshate, POHo»Tlo, is prepared by adding to a solution
of thallous carbonate sufficient phosphoric acid to produce a distinctly acid reaction,
and then evaporating. It forms nacreous monodinic prisms or lamina?, readily soluble
in water. At a red heat it is converted into metaphosphate.
5. ThaUkacdU,
(NO,—,
ThaUie nitraU, < NO,— Tlo^'^^'iSOHa, is deposited in colorless crystals from the sola-
tion of the thallic oxide in concentrated nitric acid. Excess of water decomposes the
salt with separation of thallic oxyhydrate.
Thallic sulphate, Bfi^W^^riOlit, crystallizes in thin colorless laminae from a solu-
tion of thallic oxide or hydrate in warm dilute sulphuric acid. Water decomposes it
in the cold. When heated it gives off sulphuric acid, sulphuric anhydride^ and ozy-
gei^, and is converted into thallous sulphate.
COMPOUNDS OF THALLIUM WITH SULPHUR.
«
Thallous sulphide^ STl,. — This compound is obtained as a brownish-
black amorphous precipitate when sulphuretted hydrogen is passed into
an alkaline or acetic acid solution of a thallium salt. From a solution
of thallous sulphate containing a trace of free sulphuric acid, it is
deposited in minute^ lustrous, dark-blue tetrahedra. It may be ob-
tained as a black, lustrous, crystalline mass by fusing tliallium with
sulphur in absence of air. — Thallous sulphide is insoluble in water, in
alkalies, or alkaline sulphides, and in potassic cyanide^ soluble with
diflSculty in acetic acid, readily soluble in sulphuric and in nitric acid.
The precipitated snlphide, when exposed to the air in a moist state, un-
dergoes oxidation to sulphate. By heating in a current of hydrogen,
thallous sulphide is reduced to metallic thallium.
ThaUic sulphide, 'SlS'^ is prepared by fusing thallium with an excess of sulphur,
expelling this excess at a low temperature with exclusion of air. It is a black amor-
phous readily fusible substance, in warm weatlMr it is soft like pitchy but below 12° C.
INDIUM. 661
it is brittle. Hot dilate salpharic acid dissolves it withoat separation of sulphur
Thallic sulphide is the anhyride of a sulpho-acid, TlS^^Hs. The potassium salt of this
acid, patasne tulphoihaUcUef TlS^^Ks, is obtained by fusing together 1 part of thallous
sulphate with 6 parts of potassic carbonate and 6 parts of sulphur, extracting the cooled
maaa with water. The sulphothallate remains behind as a dark oochineal-red powder,
consisting of microscopic quadratic plates.
General Properties aKd Reactions op the Compounds op
Thallium. — The salts of thallium are geoerally colorless. They have
a disagreeable metallic taste and are poisonous. Zinc precipitates
metallic thallium from solutions of the salts. Sulphuretted hydrogen
precipitates neutral or slightly acid solutions of thallium salts only par-
tially, and solutions containing an excess of a mineral acid not at all.
Ammonie sulphide precipitates the whole of the thallium as brownish-
black thallous sulphide^ insoluble in alkaline sulphides. Thallous
salts yield precipitates with the hydradda and soluble haloid salts (see
p. 558). Thallium compounds impart to the non-luminous flame a
magnificent emerald-green coloration. The spectrum of the thallium
flame consists of one bright green line.
INDIUM^ In,?
Atomic weight = 113.4. Probable molecular weight = 226.8. 8p, gr,
7.3 to 7.4. Fuses ai 176° C. (348.8° F.). AtomicUy '". Evidence
of aiomiciiy :
Indie chloride, In^'Clj.
Indie hydrate, In'^Ho,.
History. — Indium was discovered in the year 1863 by Reich and
Richter in the zinc blende of Freiberg by means of the spectroscope.
It received its name from the characteristic indigo-blue line which its
spectrum exhibits.
Occurrence, — Indium occurs in minute traces in various zinc blendes,
particularly in that of Freiberg. The best source of the metal is the
zinc from Freiberg, which contains on an average 0.05 per cent of in-
dium.
PrqparaMon. — Freiberg zinc is treated with a quantity of dilute hy-
drochloric acid or sulphuric acid not quite sufficient to dissolve it, and
is boiled with the liquid until gas ceases to be evolved. In this way
any indinm which may have gone into solution is precipitated upon the
undissolved zinc. The spongy metallic mass which remains, and which,
in addition to indium and zinc, usually contains lead, arsenic, cadmium,
copper, tin, and iron, is dissolved in nitric acid and the solution boiled
down with sulphuric acid until all the nitric acid is expelled, after which
it is diluted with water, filtered from plumbic sulphate, and precipitated
with a large excess of ammonia. The precipitate, which contains all
the indium and iron, along with traces of the other metals present, is
washed, dissolved in a small quantity of hydrochloric acid, and, after
adding hydric sodic sulphite, boiled until the smell of sulphurous anhy-
662 INOBOANIC CHEMI8TRV.
dride has disappeared. In this way the whole of the indiam is precip-
itated as basic iudic sulphite hydrate (see Indie Sulphite). It is, how-
ever, still contaminated with lead, and, in order to free it from this
impurity, it is dissolved in aqueous sulphurous acid, separated by
filtration from undissolved plumbic sulphite and reprecipitated by
boiling, when the pure basic sulphite is obtained. In order to prepare
metallic indium, the sulphite is dissolved in hot hydrochloric acid, the
solution precipitated with ammonia, and the precipitate of indie hydrate
ignited and afterwards reduced in a current of hydrogen. |
Properties. — Indium is a non-crystalline, silver-white, lustrous metal.
It is softer than lead and very malleable. It undergoes no change in
air at ordinary temperatures, but when strongly heated in air, bums
with a blue flame, giving off a brown smoke of indie oxide which con-
dehses on a cold surface as a yellow incrustation. Water, even at its
boiline-point, is without action upon the metal. Dilute hydrochloric
and sulphuric acids dissolve it slowly with evolution of hydrogen ; nitric
acid dissolves it readily.
COMPOUNDS OF INDIUM WITH THE HALOGENS.
Indie chloride, JnCl^. — Moleetdar volume I I I. — This compound
is prepared by heating the metal, or a mixture of the oxide with
carbon, in a current of chlorine. It sublimes, without previous fusion,
in soft, colorless laminae. It is deliquescent, and hisses when thrown
into water, evolving great heat The solution may be evaporated on
the water-bath without decomposition, but on heating to a higher tem-
perature to expel the last traces of water, hydrochloric acid is evolved
and oxychlorides are formed.
The bromide and iodide, which resemble the chloride in their properties, maj be
obtained bj the direct union of their dements.
COMPOUNDS OF INDIUM WITH OXYGEN AND
HYDBOXYL.
Iudic oxide,
ln=0
flnO I
. . . .<0 . O .
(InO I
ln=0
/O— H
Indie hydrate, . . . InHoy In^^ — H.
N)— H
Indio oxide, hlfit, is formed as a pale yellow powder when the metal
is burned in air or oxygen. It may be prepared by heating the hydrate
or the nitrate. When heated it becomes reddish-brown, but recovers
its original color on cooling. — By heating the oxide to 300° C. (672° F.)
in a current of hydrogen a black powder is obtained which, unless
IMPOUNDS OF INDIUM. 563
allowed to cool thoroughly before bringing it in contact with air, is
pyrophorio. It appears to contain the lower oxide 'Ill"20j.
Iridic hydrate, rnHoj, is obtained as a white gelatinous precipitate
when ammonia is added to the solution of an indium salt After dry-
ing at 1D0° C. it forms a white horny mass, which at a higher temperature
is converted into the oxide. The freshly precipitated hydrate is soluble
in excess of potash and soda, but not in ammonia. It separates from
the alkaline solution, slowly on standing, rapidly on boiling, or on the
addition of ammonic chloride.
OXY-SALTS OF INDIUM.
Indie nUrcUef N80«Tno''^,4OHs, crystallizes from ite nentral nqneous Bolution with
difficulty. From solutions containing an excess of nitric, acid it is deposited in tufts of
deliqnescent needles.
Indie sulvfuUe^ SsOelno^^'i, does not crystallize. By evaporation of its solution to
dryness ana heating to 100^ C. (212^ F.) it is obtained as a gummy mass having the
composition S30«lno^'^,90H2 ; this when heated to 300° C. (672** F.) is converted into
the anhydrous salt. When a solution of indie sulphate containing an excess of sul-
phuric acid is evaporated in vacuOj deliquescent crystals of dthydric di- indie tetraaulphate,
S408Ho,In^^^j,8OH2, are deposited.
IHammonie di-indie tetrasuJpkaie (Indium canmonia alum), &fis(^li40)2lT^o^^^2 240Hj,
crystallizes from mixed solutions of indie and ammonic sulphates in well-defined,
colorless, regular octahedra. These dissolve in half their weight of water at 16° C, and
in a quarter of their weight at 30° C. (86° F.). At 36° C, (96.8° F.) the crystals fuse
in their water of crystallization, and from the solution an octo-aquate is deposited in
monoclinic crystals. Similar octo-aquates of the double sulphates of indium with
sodium and potassium have also been prepared, but the aquates with 24 aq., or alums,
are not known.
Indie nUphiie. — A basic indie sulphite of the formnla Eh08(0,TnHo)^''j(OInHo,)„60Hj,
teirindie trisukphite hexahydraUy is deposited as a white crystalline powder when the
solution of an indium salt is boiled with hydric sodic 8ul])hite. It is insoluble in water,
but readily 'soluble in acids. It dissolves in aqueous sulphurous acid, but is reprecip-
itated from this solution by boiling. This property is turned to account in the separa-
tion of indium from other metals (p. 562).
COMPOUNDS OF INDIUM WITH SULPHUR
Indie sulphide, InS^^ is obtained as a brown infusible mass by the direct union of
its elements at a red heat. It is precipitated as an amorphous yellow powder when
sulphuretted hydrogen is passed into the solution of an indium salt, but the precipita-
tion is complete only when the liquid is kept neutral during the whole operation, or
when sodic acetate has been added. — Ammonic sulphide produces in solutions of indium
salts a white precipitate of a sulphhydrate which dissolves in an excess of the precip-
itant on heating and separates out again on cooling. — Indie sulphide is the anhydride
of a sulpho-acid, mdphindie add, InS^'^Hs. Potassi/i mUpkindate, InS^^Ks, is prepared
by heating together I part of indie oxide, 6 parts of potassic carbonate, and 6 parts of
sulphur, at first at a gentle heat, afterwards more strongly. On extracting the cooled
mass with water the sulphindate remains behind in the form of bright hyacinth-red,
quadratic plates. Acids readily decompose it.
General Properties and Reactions op the Compounds op
Indium. — The salts of indium with colorless acids are colorless. Zinc
precipitates the metal from the solutions of its salts. Cavstic alkcUiea
precipitate white gelatinous indie hydrate, slightly soluble in excess, but
reprecipitated on boiling. Sulphuretted hydrogen gives no precipitate in
solutions containing an excess of mineral acid ] from acetic acid solu-
tion indie sulphide is precipitated. The same precipitate is produced
664 INOBGANIC CHEMISTRY.
by ammonie sulphide. The compoanda of iDdium color the non-la minous
flame dark-blue. The spectrum exhibits an intense line in the indigo
and a less marked line in the violet
CHAPTER XXXVL
TETRAD ELEMENTS.
Section II.
ALTJMuiiOM, Al.
Atomic weight = 27, Molecular weight unknmxm. 8p. gr, 2.67. Fmmm
about 700° C. (1292° F.). AUmicUy *^, but is always a pseudMriad.
Evidence of atomicity : analogy of iron and chromium.
History. — Alumiuium was first isolated by Wohler in the year 1827,
but it was first obtained in the massive form by Deville in 1854.
Occurrence. — Aluminium is, with the exception of oxygen and sili-
con, the most abundant and widely distributed of the elements. It is
always found in combination with oxygen. The oxide AljO, ooenrs as
corundum, ruby, or sapphire ; the hydrate as hydrargiUite, diaspore, and
bauxite; whilst the compound silicates of aluminium with other metals
form a vast number of important minerals which are among the proxi-
mate constituents of the various rocks (see Silicates, p. 319).
Preparation. — Aluminium cannot be reduced directly from its oxide.
It may be obtained by passsing the vapor of the chloride over heated
potassium or sodium, and by the electrolysis of fused sodic aluminic
chloride, Al2Clg,2NaCl. On a large scale aluminium is prepared from
bauxite, a native aluminic oxyhydrate of the formula Al^OHo^, in
which a portion of the aluminium is isomorphously replaced by iron.
This mineral contains about 50 per cent, of alumina. When heated
with caustic soda in a reverberatory furnace the alumina forms sodic
aluminate, AljOjNaOj, which can be extracted with water, whilst the
iron remains behind as insoluble ferric oxide. By passing carbonic an-
hydride through the solution of the aluminate, aluminic hydrate is pre-
cipitated, which by drying and heating is converted into alumina.
This is mixed with powdered coal and common salt, and the mixture
is made into balls, which are introduced into a fire-clay retort and
heated to whiteness, while a current of dry chlorine is passed over them.
The following reaction occurs :
AlA + 3C + SClj = A1,C1, + SCO.
Alumina. AlumiDic Carbonic
chloride. oxide.
The aluminic chloride volatilizes along with the sodic chloride as sodic
aluminic chloride, which is condensed. It is now only neceasary to
ALUMINIUM. 665
reduce this double chloride with sodium. For this purpose the double
chlorides is heated with sodium and cryolite (a native sodic aluminic
fluoride of the formula Al,Fj,6NaF), this last acting as a flux. In prac-
tice 100 kilos, of the double chloride, 35 kilos, of sodium, and 40 kilos.
of cryolite are employed in one operation. This mixture is heated, with
gradual rise of temperature, on the hearth of a reverberatory furnace.
The reduced aluminium fuses and collects on the hearth, whence it is
drawn off and cast into ingots. The metal thus obtained contains iron
and silicon.
Alomininm may also be prepared from cryolite by mizihg the finely powdered
mineral with sodic and potassic chloride and heating the mixture in a crucible with
sodium. The yield by this method is small and the metal impure.
Properties. — Aluminium is a white metal, closely resembling zinc in
color and hardness. It may be rolled into very thin foil or drawn into
fine wire, and possesses at the same time great tenacity. It is most
readily worked at a temperature between 100° C. (212° F.) and 160°
C. (302° F.). It is not volatile at the highest temperatures that can
be artificially produced. It is not oxidized by exposure to the air at
ordinary temperatures, and is only superficially oxidized when fused in
oxygen ; but in the form of foil or wire it may be burnt in oxygen,
and emits a dazzling white light. Aluminium, when pure, does not
decompose water, even at a red heat, but does so at 100° C. (212° F.)
if the aluminium contains traces of sodium. It is soluble in caustic
alkaline solutions and in hydrochloric and sulphuric acids. Nitric
acid in all d^rees of concentration is without action upon it. Organic
acids alone scarcely attack it, but dissolve it rapidly in presence of
chlorides, such as common salt ; a fact which precludes its employment
in the manufacture of utensils which have to come in contact with food.
Uses, — Its lightness, tenacity, unalterability in air, and other valu-
able properties, together with the abundance of its occurrence in nature,
would probably render aluminium one of the most useful of metals,
were it not for the. difficulties attending its production in large quantity.
For many purposes it might, for example, replace zinc and iron. At
present, however, it is chiefly used in the manufacture of various physi-
cal instruments, especially beams of delicate balances, in which a com-
bination of lightness and inflexibility is essential.
Aluminium bronze. — Aluminium forms alloys with most of the other
metals ; those with copper are the most important. Aluminium bronze
is an alloy containing 90 parts of copper to 10 parts of aluminium, and
is prepared by fusing the two metals together. Electrolytic copper is
generally employed for this purpose, the quality of the alloy being de-
pendent on the purity of the copper. The presence of iron is especially
prejudicial. The alloy is brittle at first, but by repeated fusion becomes
malleable. It has the color of gold, and resists the action of the air. It
yields sharp castings, and is more easily worked than steel. Its tenacity is
equal to that of cast steel, and more than twice that of gun-metal, whilst
its resistance to flexure is thrice that of gun-metal. It is employed in
the manufacture of imitation gold ornaments and of physical instrument?.
Alloys of aluminium with silver and with tin have also found appli-
cation in the arts. '
566 INORGANIC CHEMISTRY.
COMPOUNDS OF ALUMINIUM WITH THE HALOGENS.
Aluminic chloride, Al^Cl^. — Molecular volume i i i- — This com-
pound is formed when alarninium is heated in chlorine. (Preparation,
see p. 664.) — If contaminated with ferric chloride, which imparts to it
a yellow color, it may be purified by mixing it with iron filings, or better
with aluminium filings, and re-subliming. In either case the ferric
chloride is converted into the much less volatile ferrous chloride.
Aluminic chloride when perfectly pure is a white crystalline subetanoe.
It sublimes readily at ordinary pressures without fusing, but aiay be
f^ised under the pressure of its own vapor, or when rapidly heated in
large quantity. By sublimation it is sometimes obtained in hexagonal
tabular crystals. It attracts moisture from the air, and evolves hydro-
chloric acid. The solution of the metal or the oxide in hydrochloric
acid deposits on concentration colorless needle-shaped crystals of the
aquate Al,Clo,120H2, which on heating are decomposed into water,
hydrochloric acid, and alumina. Aluminic chloride forms a large num-
ber of compounds with the chlorides of other elements. Polas»ic alur
minic chloride, AljCle,2KCl, and sodic aluminic chloride, Al,Clg,2NaCl,
are formed when aluminic chloride is heated with potassic and sodic
chlorides. The sodium compound fuses without decomposition at 185® C.
(365° F.), and is volatile at a red heat. It is employed in the prepa-
ration of aluminium.
Aluminic bromide, Al^Br^. — Molecular volume | | | —Aluminium and bromine unite
with incandescence to form this compound. It may be most readily obtained by pass-
ing bromine vapor over a red-hot mixture of alumina and carbon. It may be purified
by repeated eut>Iimation with aluminium in a sealed tube. It forms deliquescent,
colorless, lustrous lamins, fusing at 90'' C. (194° F.), and boiling between 265° C.
(509° F.) and 270° C. (518° F.). Concentrated aqueous solutions denonit colorless
needles of the aquate Ai,Br« 120Hs, which on healing are deeomposea like the cor-
responding chlorine cc»mpound. Aluminic bromide K)rms fusible double bromides
with the bromides of the alkali melaLs: thus, potassic aluminic bromide, Al,Br^2KBr.
Aluminic iodide, ALilf. — Molecular volume I I |. — This compound is formed with in-
candescence when aluminium and iodine are cautiously heated together in a sealed
tube. It is also formed when argentic iodide is heated with aluminium filings. —
Aluminic iodide is a white crystalline mass, fusing at 185° C. (865° F.), and boiling at
360° C. (680° F.). Its vapor is combustible, and forms an explosive mixture with air.
The products of combustion are alumina and iodine. It is decomposed in the same
way when heated in contact with air. When exposed to the air it fumes and deli-
quesces. It is readily soluble in water, alcohol, and bisulphide of carl)on. It forms
an aouate, AI2T0.I2OH3, and unites with the alkaline bromides to form double iodides,
all of which compounds closely resemble the corresponding chlorides and bromides.
Aluminic fluoride, AljFe, is formed by the action of gaseous or aqueous hydrofluoric
acid upon alumina or aluminic hydrate. At a bright red heat it sublimes in colorless
rhombohedra, closely approximating to cubes. It is insoluble in water, and is not de-
composed by acids. — Aluminic fluoride forms insoluble double fluorides with the fluo-
rides of the alkali metals. The most im|)ortaDt is aluminic sodic fluoride, Al3F€,6NaF,
which occurs as the mineral cryolite in enormous deposits on the coast of Greenland.
It may be artificially obtained by fusing together its component fluorides. It forms a
white, translucent mass. It is decomposed by sulphuric acid with evolution of hydro-
fluoric acid. Boiling with caustic alkalies, or with calcic hydrate and water, also
decomposes it. In the decomposition with calcic hydrate insoluble calcic fluoride is
formed, whilst sodic aluminate goes into solution :
= 6CaFa + AljNao. + 60FT,.
Calcic Sodic Water,
fluoride. aluminate.
Al2Fe.6NaF
+ 6CaHo2
Sodic aluminic
Calcic
fluoride.
hydrate.
COMPOUNDS OF ALUMINIUM. 567
On this reaction is based an industrial prooess for the preparation of soda and aluminium
salts from cryolite.
COMPOUNDS OF ALUMINIUM WITH OXYGEN AND
HYDROXYL.
O
Aluminic oxide {AJumina), <. aiqO. 0=A1 — A1==0.
H— O O— H
Aluminic hydrate {HydrargUlMe), | ^^. H— O— AI— AI— O— H.
H— O a— H
Aluminicoxydibjdrate (i)ta«pore)< aioHo* 0=A1 — A1=0
H
k
Aluminic oxide {Alumina)^ Al^Oj. — This oxide occurs native in
hexagonal crystals, sometimes colorless, sometimes variously colored
owing to the presence of other oxides. Crystallized alumina is harder
than any known substance with the exception of the diamond and crys-
tallized boron. The colorless or gray crystals are known as corundum;
the red crystals, the color of which is due to chromium, constitute the
gem ruby; whilst sapphires are crystals of alumina colored blue,
probably by cobalt. In an impure state, contaminated with iron and
silica, alumina occurs in large masses as emery. The latter mineral,
when powdered and levigated, is employed for grinding and polishing
surfaces of glass and metal, purposes for which from its hardness it is
admirably suited. Alumina is obtained as a white amorphous powder
by heating the hydrate or ammonia alum ; in the latter case it is diffi-
cult to expel the last traces of sulphuric acid. It may be obtained in
the crystallized condition by the action of aluminic fluoride upon boric
anhydride at a high temperature. -Fremy and Feil have prepared
crystallized alumina on a large scale by heating together equal weights
of alumina and red-lead in a clay crucible to bright redness for a con-
siderable time, sometimes as much as twenty days. The cooled mass
consisted of two layers : one a vitreous mass of plumbic silicate, the
silica of which had been derived from the material of the crucible ;
the other crystalline, and containing cavities which were filled with
well-formed crystals of corundum. By the addition of from 2 to 3
per cent, of potassic dichromate to the above mixture crystals of ruby
were obtained ; the color of sapphires was produced by adding a small
quantity of cobaltous oxide, together with a trace of potassic dichromate.
By heating a mixture of equal weights of alumina and baric fluoride,
with a small quantity of potassic dichromate for a length of time to a
very high tem{>erature in a glass furnace, magnificent crystals of ruby
668 INORGANIC CHEMISTRY.
were obtained. The reaction in this case depends upon the formation
of aluminic fluoride which is then decomposed by the furnace gases.
The crystals of ruby are deposited in the upper part of the crucible. —
Crystallized or strongly ignited alumina is insoluble in acids at ordi-
nary pressures, but dissolves in concentrated sulphuric acid when heated
with it in sealed tubes. It is also attacked by fusion with hydrie po-
tassic sulphate or potassic hydrate, after which treatment it dissolves in
water. Alumina is fusible in the oxyhydrogen flame.
Aluminie hydrate^ Al^Ho^, occurs as hydrarffiUiie in small hezi^nal
crystals. When ammonia is added to the solution of an aluminium
salt a white gelatinous precipitate is formed, which afcer drying at
ordinary temperatures has the composition AI2HO02OH2. This when
heated slightly above 300° C, is converted into cUiiminie oxydxkydrcde^
AI2O2H02, a compound which occurs in nature as the mineral diaspore
in rhombic crystals. An aluminic oxyhydrate, corresponding with the
formula AljOHo^, aluminic oxytdrahydratej occurs as the mineral
batunie, but a portion of the aluminium in this compound is isomor-
phously replaced by iron. All the aluminic hydrates are converted
into the oxide by heating. — Aluminic hydrate is insoluble in ammonia,
but when freshly precipitated dissolves readily in acids and in solutions
of potassic and soaic hydrate. When dried oy a moderate warmth, or
when allowed to stand under water, it becomes difficultly soluble in
acids and alkalies. — Freshly precipitated aluminic hydrate dissolves in
a solution of aluminic chloride, and if the liquid thus obtained be sub-
jected to dialysis, hydrochloric acid passes through the dialyser, till at
last only a neutral tasteless solution of colloidal aluminic hydrate
remains. This soluble modification of aluminic hydrate is very un-
stable : the solution coagulates after standing for some days, and the
same change takes place immediately on the addition of traces of acids,
alkalies, or salts. Aluminic hydrate possesses the property of pre-
cipitating organic coloring matters from their solutions. Upon this
property the application of the salts of alumina as mordants in dyeing
and in the preparation of the so-called lakes depends.
Aluminalea, — Aluminic oxydihydrate behaves towards stronj^r bases like a weak
acid. Its salts, in which both the hydrogen-atoms of the ox^dihjdrate are replaced
by metal, are known as cduminates. The alnminates of potassium and sodium are pre-
pared by dissolving aluminic hydrate ip caustic potash or soda ; by evaporation in
tacuo, the pot^issic aluminate may be obtained in hard lustrous crystals of the fonnnla
Al^OjKOj.dOHi. Sadie aluminate^ AliOsNaos, has not been obtained in the crystal-
lized state. It is used as a mordant. Beryilie alttminate^ ALOsBeo^"^, occurs in nature
as the mineral chryaoberyl in green rhombic crystals. The aluminates of the metals of
the magnesium group occur in nature as the spinelles, crystallised in forms belong-
ing to the regular system. Examples of these are : magnesic akanincUe or spinettey
AlaO.Mgo^^, and stnete alwninate or zine spin^le^ AljOtZno^^ The two latter com-
)X)unas may be prepared artificially by passing the vapor of aluminic chloride over
strongly heated magnesia or zincic oxide, or by heating alumina and boric anhydride
with these oxides to a white heat for several days.
0XY-8ALTS OF ALUMINIUM.
Aluminie nitrate, Nj0„('Al''''206)'*,18OH„ crystallizes from a concentrated solntibn
of the hydrate in nitric acid in deliquescent monoclinic prisms. On heating to 150^
C. (302° F.) the salt is decomposed, leaving a residue of alumina. It is employed in
calico-printing as a mordant.
COMPOUNDS OP ALUMINIUM. 569
Altjminio sulphate, S3Oj('AF"jOe)^,180H2, occurs as the mineral
heramohalUe, It is prepared on a large scale by dissolving aluminic
hydrate, obtained from cryolite or bauxite and as free from iron as
possible, in sulphuric acid ; or by decomposing china clay, a hydrated
aluminic silicate, with sulphuric acid. The solution is evaporated till
it solidifies on cooling. A soft mass is thus obtained which is cut into
blocks. It is difficultly crystallizable, and forms thin, flexible, na-
creous laminae. It dissolves in twice its weight of cold water. When
heated, it first fuses in its water of crystallization, then swells up, and is
converted into a white porous mass of the anhydrous salt. Aluminic
sulphate is employed as a mordant and in weighting paper. — Basic sul-
phates are formed when a solution of the normal sulphate is precipitated
with an insufficiency of ammonia, or by boiling its solution with the
freshly precipitated hydrate. A compound of this felass, aluminic svl-
phate tetrahydrate, ^^j^Ay^^fi^o^^'ylOR^y occurs in nature as the
mineral aluminite.
The Alums.
Among the most important salts of alumina are the double sul-
phates which it forms with the alkalies, known as the alums. Of
these the principal are potash alum or common alum, dipotamc
SOsKot
gQ I
cUuminic tdra-sulphcUey g^^ ('Al'"20fl)^,240H2, and ammonia alum,
so^kJ
in which the potassium of the preceding compound is replaced by
ammonium. The object of preparing these salts, which are exten-
sively used by the dyer and calico-printer, is to obtain compounds of
alumina in a very pure form, and especially as free from iron as possi-
ble. The alumina is alone valuable.
The Dame alum is not restricted to compounds of alumina: it is employed to desig-
nate a class of tetrasulphates which, like potash alum, contain in their molecule two
atoms of a monad metal (or the equivalent of a monad metal, such as NH4) together
with one hexadic metallic group — of which ^AK-^'t mav be taken as a type — and
which crystallizes with 24 aq. in regular octahedra. Almost any monad metal may
enter into the composition of an alum : thus, besides the alums above mentioned,
alums have been prepared containing sodium, csesium, rubidium, silver, and thallium.
The hexadic group 'AK'-'t may be replaced by the isomorphous groups ^Ct^^\ 'Fe^^\
and 'Mn'^-'j. It even appears that this group of two pseudo-triiSs may be replaced by
two true triads: thus an ammonia indium alum has been prepared containing the
hexadic group Ins (p- 563).
The following system of nomenclature is as a rule applied to thes^i compounds. It
the monad metal be potassium, the name of this metal is not introduced into the name
of the compound : thus chrome alum means potassium chromium alum. If the hexadic
group be ^AV^\ aluminium is not named : thus by ammonia alum is understood ammo-
nia aluminium alum. If the alum contain neither potash nor aluminium, both metals
present must be named : thus, ammonia chrome alum.
Selenic acid forms a similar series of alums. These may be regarded as sul-
phuric alums in which sulphur has been replaced by the isomorphous selenium.
SeO,Ko-|
The potash alum of this series has the formula ||q"Z VAl^^\0^y\2iOTLi,
SeO^KoJ
A class of pteudo aluma also exists in which the two monad atoms are replaced by
one dyad atom. These pseudo alums also contain 24 aq. in the molecule, but do not
crystallise in the regular system (see PBeudo Alums).
570 INORGANIC CHEMISTRY.
A flolation containing two or more octahedral alams deposits octahedral crxstals, in
which the various alums present may be contained in any proportion.
Potash cdum crystallizes from mixed solutions of aluminic and
potassic sulphates. It is formed in nature, especially in volcanic
districts, by the action of sulphurous acid and oxygen upon rocks
containing potassic and aluminic silicates. In the neighborhood
of Naples and at Solfatara it occurs in quantity sufficient to render
its extraction profitable. Large quantities of very pure alum, the
so-called Roman alum, are obtained from the mineral alum d(me or
aluniie, a basic double silicate of potash and alumina of the formula
tiraxJ ('Al'"jHo40,)" , which occurs at Tolfa and in Hungary.
The mineral is mixed with fuel and roasted, either in heaps or in
kilns, after which it is moistened and exposed to the air for several
weeks. The mass gradually disintegrates, and is then extracted with
water, when alum goes into solution and alumina remains behind.
The liquid is concentrated and allowed to crystallize. — Alum is,
however, inore frequently prepared from alum ahak, a* bituminous
shale containing iron pyrites disseminated through its maas. The
shale is exposed in heaps to the air, by which means the iron py-
rites (PeS",) is gradually oxidized to ferrous sulphate and sulphuric
acid, the latter of which then decomposes the aluminic silicate present
in the shale. The process is generally shortened by first roasting the
shale, in order to effect a partial oxidation, after which the roasted
shale is moistened and exposed to the air as above descrit)ed. The
oxidized shale is lixiviated with water and the solution evaporated.
A considerable quantity of the ferrous sulphate present crystallizes
out and is removed. If, however, the shale has been exposed to
the air for a sufficient length of time, the ferrous sulphate is oxi-
dized to ferric sulphate, the presence of which is less objectionable.
The concentrated mother liquor containing aluminic sulphate is now
heated to boiling, and solid potassic sulphate is dissolved in it.
The potassic sulphate combines with the alumriic sulphate to form
alum. If any considerable quantity of ferric sulphate is present it
is advantageous to add, along with the potassic sulphate, a quan-
tity of potassic chloride equivalent to the ferric sulphate, the two
latter salts yielding by double decomposition potassic sulphate and
the very soluble ferric chloride. The presence of ferrous sulphate
is objectionable, as a loss of potassium salt is occasioned by the
rsOaKo
e,^ Feo"
formation of ferrous dipotassic disulphate,< Feo" . The hot solution,
Uo,Ko
which now contains the alum, is well stirred till cold. In this way
the alum is deposited in small crystals, which are less apt to retain
impurities from the mother liquor than the large crystals which
would be formed were the liquid permitted to cool undisturbed. The
small crystals, known as alum mealy are washed with cold water, dis-
solved in boiling water, and the solution allowed to crystallize in large
COMPOUNDS OP ALUMINIUM. 571
barrels with movable staves, which are afterwards taken to pieces in
order to remove the large crystals of alam which line their sides. — Aium
crystallizes in large colorless transparent r^ular octahedra, which as a
rule also exhibit subordinate cubical faces. From solutions containing
free caustic alkali, or basic alum, the alum crystallizes by spontaneous
evaporation in cubical crystals, which have exactly the same composi-
tion as octahedral alum. The crystallized alum is soluble in 7 parts of
water at 20^ C. (68° F.), and in less than J part at 100° C. (212° F.).
The solution has a faint acid reaction and a sweet astringent taste. The
crystals are insoluble in alcohol. When heated they fuse in their water
of crystallization, which is expelled by continued heating, leaving a
white porous mass known as burnt alum. This dissolves slowly in
.water. Anhydrous alum may be obtained in six-sided crystals by fusing
alumina with hydric potassic sulphate, and removinj^ the excess of this
salt from the fused mass with hot water.
Ammonia ai.um {diammonio aluminio tetrasulphcUe),
S03(NHP).
S0iNH,0)J
This com)K)und was formerly prepared from alum shale by methods
similar to those employed in the manufacture of potash alum. The
roasted shale was treated with sulphuric acid, and into the acid solution
of aluminic sulphate, ammonia, obtained from the ammoniacal liquors
of the gas-works, was passed. The alum was purified by crystalliza-
tion. Since the introduction of cheap potash salts from the Stassfurt
beds, the manufacture of ammonia alum in England has practically
ceased. — Ammonia alum crystallizes in large colorless octahedral
crystals, in appearance indistinguishable from the potash salt. Its
solubility is also almost the same as that of potash alum.
Sodaalum, &flfi'SaOi{^AV^^20^y\2jOH2, is difficult to purify on account of its great
soIubiHtj. It dissolves in its own weight of water at ordinary temperatures. It is not
manufactured.
Aluminic phosphates. — ^The normal orthophosphate, aluminio
PO
diphoaphatef -pfJ^f^^^^O^y^ is obtained as a hydrated gelatinous pre-
cipitate when hydric disodic phosphate is added to the neutral solution
of an aluminium salt. It is soluble in alkalies, but not in ammonia;
and in mineral acids, but not in acetic acid. — Various basic phos-
phates of alumina occur in nature. The mineral wavellite, which forms
rhombic crystals or radiating masses, is a basic phosphate of the formula
P,O('Al'"jOfl)^3,120Ha. Calaite, which when colored greenish- blue
by oop|>er constitutes the gem orienial turquoise, has the formula
PO('Ar'',Ho30,)''^0H,.
Aluminic silicates. — ^The silicates of alumina, both simple and
compound, form a large class of important minerals. A detailed de-
scription of these belongs rather to mineralogy than to chemistry ; but
the names and formulae of some of the more important may be here
given.
Kaolin {porcdain day, duna day), < O {'A.V"fioJO^Y''.
672 INOBOANIC CHEHI8TBT.
Aada]as\le{d>iatlolUeeyaniUjibro- \ atrw a 1"/ n vr
lUe, simmanUe, j-wv^Al ,UJ .
Bocholzite IxenoUme), .... Si), . \K*r\\H'
Miloschine, SiHo,('Al'^',H.),0,)".
Alophane, SiHo^'AI"',HoA)",(2 or 4)0H^
C!ollyrite, . SiHo,('Al'",Ho,0).40Hr
Poroelain clay of Paasau, . . . gjg^'Al'",Ho,OJ'\
rSiHo^
O ('
SiHoJ
SiHo„
Razoamoffikin, SiHo,('Al"'0,)^
"WRpthitP aU)('-A-l"'jHoOj)\
"'°"'''*®' g^('Al"'^oO,r
Cimolite {kaoUn of Ellenbogm), . §qI ('Al'",©,)"-
SiHoJ
BiOHo,
Agalmatolite, ffi^^ ('AI"',0,)^
SiOHoJ
Malthacite, SigO„Ho,('Al'",0,)
rSiHojNao
Analcime, J |j('Al'" A)''.
,Tl
-fSi'
SiHojNao
SiONao— ,
fSiO— , I
Albite, >ffioII('^^"'Ar-
UiO— ' I
SiONa — -I
LepidoHte, Si,08Ko,Lio4('Al"',0,)^('Al"',FA)"-
Petalite, Si„0«Nao,Lio«('Al'",0,r,.
PORCELAIN AND POTTERY. 673
Spodoraene, * . . . 6iifi^!,Uo^{'AV''fi;)\
Wernerite, aijCao''('AV\0,)^.
Prehnite, Si3HoAo"2('Al'"A)^-
Zoisite,
'ai'"a/
Saponite, Si,(Mgo",Ho,oCAl'''Ar.
Topaz, Si3('AP''AF)X'Al'"AF2yX'Al'''204F)'".
(See also Silicates, p. 319.)
Ultramarine.
Various native double silicates of aluminium with other metals con-
tain sulphur as an essential constituent. One of these, a double silicate
and sulphide of aluminium' and sodium, forms the mineral lapis lazuli,
prized for its splendid blue color, and employed as a material for vases
and inlaid or mosaic work. It is sometimes found crystallized in dode-
cahedra, but generally occurs massive. It has not as yet been found
possible to express the composition of this mineral by means of a
formula. The powdered mineral was formerly employed as a valuable
blue pigment under the name of vMramarine, a substance which is now
prepared artificially. For this purpose china clay (infra) is heated in
crucibles along with sodic sulphate and charcoal. The sodic sulphate
is reduced to sodic sulphide, which then combines with the aluminic
silicate. The product is a white mass, which, however, speedily be-
comes green. This substance, known as green vMramarine, is also
employed as a pigment. When green ultramarine is heated with sul-
phur, allowing the sulphur to burn off' in air, it assumes a blue color,
and is thus converted into the ordinary blue ultramarine of commerce.
The same change is effected when green ultramarine is heated with am-
monic chloride, or when ctflorine is passed over it, but the sulphur
method is employed in practice. No difference in chemical composition
can be detected between the green and the blue modification. When
ultramarine is treated with hydrochloric acid, it is decolorized with evo-
lution of sulphuretted hydrogen and separation of amorphous silicic acid.
It is used in paper-staining, in calico-printing, and as an oil paint.
Porcelain ani> Pottery.
Porcelain and pottery in all their forms are manufactured
primarily from clay, an aluminic silicate. This material possesses
§l|ii&cient plasticity to allow of its being moulded into any desired
form, whilst by the action of heat it is rendered sufficiently
hard and tenacious to resist the wear of every-day use. The
fSiHoT
purest clay is kaolin or china day, < O ('Al^'gHojOJ^^ which is
(SiHoJ
formed from felspar, aijOf;Ko^'AV''f>^Y\ by weathering, the grad-
574 INORGANIC CHEMIBTBY.
I
ual action of water removing the potash together with a portion of the
Bilicic acid, and leaving an alurainic silicate. Kaolin sometimes oocnrs
in six-sided tablets, hut generally forms a white or yellowish- white
mass. The commoner clays consist of kaolin with various impurities
— calcic and magnesic carbonates, ferric oxide, sand, and organic mat-
ter. Kaolin does not fuse when heated, but bakes together into a hard
porous mass; in order, therefore, to increase the durability of utensils
manufactured from it, the kaolin is mixed with some fusible material,
technically known as a frit^ which by its fusion binds the whole
together. The materials added are ground feldspar, quartz-sand,
chalk, gypsum, bone-ash, and sodic or potassic carbonate — the nature
of the frit varying with the quality of the ware required. The mate-
rials are carefully ground under water and mixed. The mixing is an
operation of great nicety, inasmuch as it is necessary to preserve the
same composition of the mixture for a given kind of ware; and as the
composition of the clay is apt to vary, this constancy of composition
can only be attained by suitably varying the proportions of the other
ingredients : thus, if the clay should happen to contain a larger quan-
tity of silicia, less quartz-sand will have to be added, and so on. The
presence of organic matter is objectionable, as organic substances disen-
gage gas during the firing, and are thus liable to spoil the work. By
allowing the mixture to stand in a moist state for a considerable length
of time, the organic matter undergoes putrefaction, and is thus got rid
of. The plastic mass is then moulded into the required form, either on
the potter's wheel, or by means of moulds. The articles are then
allowed to dry at ordinary temperatures, and are then in some cases
subjected to a preliminary process of firing at a relatively low tempera-
ture, known as baking, after which they are glazed. The glaze is of
various kinds, according to the nature and quality of the ware ; but in
every case it consists of some material which in the subsequent firing
fuses, and imparts to the porous ware a smooth vitreous surface, impei^
meable to liquids. The glaze is generally employed in the form of a
fine powder, which is either suspended in water, into which the baked
articles are dipped, or is dusted upon their surface. Another mode of
glazing consists in volatilizing in the porcelain kiln some material which
is thus deposited on the surface of the articles, and forms with the
silica which they contain a fusible glaze (salt-glazing). The finer sorts
of porcelain and earthenware are not exposed to the direct action of the
flame in firing, but are inclosed in fire-clay crucibles, known as saggers^
by which means they are protected from the action of the smoke and
ash. The porcelain kiln consists of a tall reverberatory furnace, divided
usually into three stories or floors, through which the flame passes. The
upper story is employed for baking, the two lower for firing. The firing
is continued during eighteen hours, after which the kiln is allowed to
cool slowly for three or four days in order -to anneal the ware.
Porcelain or China, — This is the finest description of ware. It was
manufactured in China before the Christian era ; but the art of making
true porcelain was not discovered in Europe till the commencement of
the 18th century. There are two chief classes of porcelain : hard par-
e^lain, to which class the Chinese, German and Sdvres porcelain belong;
PORCELAIN AND POTTERY. 575
and tender porcelain, produced especially in England. Great care has
to be exercised in the selection of the materials in order that the result-
ing: porcelain may be c(9orless. The presence of ftrric oxide and
organic matter is to be avoided. The purest kaoh'n forms the basis of
all porcelain ; and upon the nature of the frit the difference in proper-
ties of the various kinds of porcelain depends. In the case of hard
porcelain, the frit consists of calcic and potassic silicates : thus the paste
employed at Sevres for ornamental porcelain has the composition :
Washed kaolin, 62 parts ; chalk, 4 ; quartz-sand, 17 ; felspar, J 7. The
glaze for this porcelain consists of a mixture of felspar and quartz. In
the case of English porcelain, a frit consisting of bone-ash or a mineral
phosphate, together with borax, is employed. This frit is much more
fusible than the preceding, and the porcelain thus obtained is softer.
This porcelain is glazed with an easily fusible mixture of bone-ash,
Elumbic oxide, potashes, sand, and borax. Tender porcelain must be
aked before applying the glaze, and then fired; hard porcelain is
sometimes glazed after drying at ordinary temperatures. The reason
for this difference in treatment is to be found in the fact that in the case
of tender porcelain the glaze is very much more fusible than the mass,
whilst with hard porcelain this is not the case.
Porcelain forms a white, translucent, homogeneous mass. Hard
porcelain resists sudden changes of temperature and the action of acids
and alkalies much better than gla&s, and is for this reason employed in
the manufacture of laboratory vessels.
Stoneware differs from porcelain in being always opaque and generally
more or less colored. The materials employed are not so pure, and
generally contain ferric oxide. It is more fusible than porcelain. In
order to glaze this ware, the process known as salt-glazing is employed.
The articles to be glazed are dipped in sand and water, and then grad-
ually heated to a very high temperature in the kiln. A quantity of
common salt is then thrown into the kiln. The salt volatilizes, forming
with the sand a fusible sodic silicate, which combines with the other
silicates present to yield a glass or glaze, and coats the ware, rendering
it impervious to water. The explanation of the process is as follows :
Silicic anhydride alone is not capable of decomposing sodic chloride at
any temperature; but when the two substances are strongly heated
together in presence of the vapor of water, hydrochloric acid is ex-
pelled and sodic silicate formed :
SiO, + 2NaCl + OH^ = SiONao^ + 2HC1.
Silicic Sodic Water. Sodic Hydrochloric
anhydride. chloride. silicate. acid.
The water is furnished by the combustion of the fuel. At the same
time another portion of sodic chloride acts upon the ferric silicate con-
tained in the clay, yielding sodic silicate and volatile ferric chloride:
SiaOjCFe'^Pe)'' + 6NaCl = SSiONao, + Te,C],.
Ferric silicate. Sodic chloride. Sodic silicate. Ferric chloride.
The iron present oo the outer surface of the ware is thus removed.
576 XNORGANIG CHElflBTBY.
Earthenware.— Th\a ware differs from the two preceding varieties,
inasmuch as no fusion or vitrification occurs during firing, and the
body of the ware remains porous. A piece of ungli^ed earthenware
adheres to the tongue. In the manufacture of fine earthenware a paste
is employed consisting of a mixture of fine plastic clay and ground
flints. This mass burns white on firing, and is afterwards glaz^ with
an opaque lead glaze. Common earthenware is prepared from inferior
day.
In the manufacture of (xmimonpottery tvare — ^bricks, flower-pots, etc.
— impure clays are employed. The color, red or yellow, is due to the
presence of ferric and other oxides in the clay.
Fire-bricks, melting crucibles, and other articles which are required
to resist a high temperature, are prepared from a pure clay rich in
silica. In order to lessen the shrinkage which this clay suffers in firing,
a quantity of finely powdered burnt clay (broken pots of the same ma-
terial) is added.
COMPOUND OF ALUMINIUM WITH SULPHUR.
Aluminie tulphide, AlsS^^,, is formed as a black mass, which acquires metallic lustre
under the burnisher, by the union of aluminium with sulphur at a red heat, and may
also be obtained as a white vitreous substance by passing the vapor of carbonic disul-
phide over alumina heated to whiteness :
2A1,0, -f 3CS'', = ZA]S'\ H- SCO,.
Aluminie Carbonic Aluminie Carbonio
oxide. disulphide. sulphide. anhydride.
Water decomposes it, yielding aluminie hydrate and sulphuretted hydrogen. — Alka-
line sulphides and sulphhydrates precipitate aluminie hydrate from solutions of alumi-
nium salts.
General Properties and Reactions of the Compounds of
Aluminium. — The salts of aluminium with colorless acids are colorless.
They have a sweet but very astringent taste. Their solutions redden
blue litmus. Caustic alkalies, ammonia, ammonic carbonate^ baric ear-
bonaief and ammonic sulphide, all precipitate aluminie hydrate — in the
case of the carbonates with evolution of carbonic anhydride, and in the
case of ammonic sulphide with evolution of sulphuretted hydrogen.
The precipitate is r^ily soluble in caustic alkalies, only very spar-
ingly soluble in ammonia. If aluminium compounds be ignited before
the blowpipe, then moistened with cobaltous nitrate and again ignited, a
Sale blue mass (Thenard's blue) is obtained. Aluminium compounds
o not color the non-luminous flame. The spark-spectrum of alumi-
nium is very complex.
OALLTOM, Ga.
Atomic weight = 68.8. Molecular weight unknovm. 8p. gr. 5.9. Fu9^
erf 30.1° C. (86.2° F.). Atamiciiy ^\ but is always a pseudo4riajd.
EfMence of atomicity : analogy wUh aluminium.
History, — GralHum was discovered in 1875 by Lecoq de Boisbaudran
with the aid of the spectroscope.
GALLIUM. 577
Occurrence, — GaUinm is one of the rarest elements. It occurs in
minute traces in the zinc blende from Pierrefitte in the Pyrenees, from
Austria and from Bensberg. The blende from the latter source, which
is the richest in gallium, contains only 0.0016 per cent, of this metal.
Extraction, — The zinc ores containing gallium are dissolved in acid
— hydrochloric acid, sulphuric acid, or aqua-regia, according to the
nature of the ore — and the solution is partially precipitated with metallic
zinc. The gallium, along with the other foreign metals originally con-
tained in the zinc ore, is precipitated upon the zinc. The precipitate is
redissolved in hydrochloric acid and the solution again treated with
metallic zinc. This precipitate is again dissolved in hydrochloric acid,
and sulphuretted hydrogen is passed into the solution. The liquid is
filtered from sulphides, and, after expelling the sulphuretted hydrogen
by boiling, fractionally precipitated with sodic carbonate as long as
spectroscopic examination shows the presence of gallium in the fractions.
The various fractions are dissolved in sulphuric acid, the solution
evaporated to dryness, and the residue heated so as to expel the excess
of acid. On treating with hot water, basic gallic sulphate separates, and
must be filtered off hot. The basic sulphate is dissolved in the smallest
possible quantity of sulphuric acid, and, after adding ammonic acetate, the
gallium is precipitated from the solution as sulphide by means of sul-
phuretted hydrogen. In order to obtain metallic gallium the sulphide is
again dissolved in sulphuric acid and, after adding an excess of caustic
potash, in which the gallic hydrate is soluble, the liquid is subjected to
electrolysis, employing electrodes of platinum. The' electrolytically
deposited gallium is washed with dilute nitric acid, and is then pure.
Properties. — Gallium is a bluish-white metal of sp. gr. 5.9. It fuses
at the low temperature of 30.1° C. (86.2° F.), and remains for a long
time in a state of su perfusion, even at 0° C, but when touched with a
piece of the solid metal instantly solidifies in pyramidal crystals. The
metal when fused is silver-white and more lustrous than in the solid
state. It dissolves with evolution of hydrogen in hydrochloric acid
and in caustic potash. Nitric acid is almost without action upon it in
the cold, but dissolves it on heating. When a solution of gallic chloride
is warmed with metallic zinc, gallic oxide or a basic salt is precipitated.
COMPOUNDS OF GALLIUM,
Oallie ehhridej 'Ga'^^'aClg, forms soluble, deliqnepcent, colorless needles. Excess of
water decomposes it with separation of an oxy-chloride.
Gallic ozidcy ^Oa'^'^aO,, is a white precipitate insoluble in water, but soluble in caus-
tic alkalies and in ammonia.
SO,-'
Gallie tvlphaUf S02-(''Ga'^''»0«)'*, is very soluble. From mixed solutions of
SO,-J
thb salt with ammonic sulphate, regular crj'stals of ammonium gallium alum^
80j.\moT
on I
gJJ«~('G*''^«0,)'*,24OHt, are deposited.
SolAmoJ
General Properties and Reacftons of the Compounds op
Gallium. — Gallium is most readily recognized by means of its spark
37
578 INORGANIC CHEMISTRY.
epeetrura, which consists of two lines in the violet. The flame ppeo-
trani shows only one of these lines, and that but faintly. The oUier
characteristic properties of the gallium compounds are given above.
CHAPTER XXXVII.
METALS OF THE RARE EARTHS.
ThB metals of this group occur, generally together, in a few rare
minerals. Their separation is a matter of extreme diflSculty owing to
the similarity of their compounds. Indeed it is doubtful in the case of
most of them whether pure compounds have ever been obtained — a fact
pointed to by the discrepant results arrived at by careful exi)€rimenters
in the determination of the atomic weights of these elements. The
most important metals of this group are cerium, lanthanum, didymium,
yttrium, and erbium.
TETRAD ELEMENTS.
Section III.
CEBIUM, Ce.
Atomic weight ^ 140.5. Molecular weight unknown. Sp, gr, 6.728.
Atomicity *', also a p8eudo4iiad: Evidence of atomicity :
{Oe'"Cl
Ceric oxide, 0e*^O,.
History, — Ceria was discovered by Klaproth in 1803, but was first
recognized as the oxide of a new metal by Berzelius and Hisinger.
Occujrence. — Cerium always occurs together with lanthanum and
didymium. The most abundant source of these three metals is the
mineral cerite., in which they occur as silica te«. They also occur in
monazite as phosphates, and in fluocerite as fluorides.
Preparation. — Separation of Cerium^ Lanthanumy and Didymium.
— Finely powdered cerite is mixed with concentrated stilphuric acid so
as to form a thick cream, and the mixture is heated in a Hessian cruci-
ble— first gently in order to expel the acid, finally to low redness. The
cooled contents of the crucible are powdered and added in small por-
tions at a time to water at 0° C, great care being taken to avoid any rise
of temperature. The solution, after filtering from sand and other in-
soluble matters, is treated with sulphuretted hydrogen in order to pre-
cipitate copper, bismuth, molybdenum, and lead. After removing these,
chlorine is passed in to reoxidize the iron and, after acidifying with
CERIUM. 579
hydrochloric acid, oxalic acid is added in excess. In this way the
cerium, lanthanum, and didymium — together with any yttrium and
erbium, if present — are precipitated as oxalates. The precipitate is
strongly ignited, by which means the oxalates are converted into oxides.
These are dissolved in nitric acid and the solution evaporated to a syrup.
The synipy solution is then diluted with water and poured into a large
excess of boiling water containing 2 c.c. of sulphuric acid to the litre.
The cerium is thus precipitated as a basic eerie sulphate. This precipi-
tate is dissolved in sulphuric acid and re-precipitated as basic sulphate
by again pouring into boiling water, repeating these operations until
the solution of the cerium salt in sulphuric acid no longer shows the
absorption spectrum of didymium. The cerium compound may then
be regarded as pure.
In order to obtain the lanthanum and didymium from the filtrate
from the first precipitation of basic eerie sulphate, this liquid is first
boiled with pulverized magnesite, which precipitates the rest of the
cerium as oxide, whilst the lanthanum and didymium remain in solu-
tion. The lanthanum and didymium are then precipitated by the ad-
dition of oxalic acid to the solution acidified with hydrochloric acid, the
oxalates are converted as above into oxides, these are dissolved in sul-
phuric acid, the solution is evaporated to dryness, and the salt heated to
low redness. The anhydrous sulphates thus obtained are dissolved in
five times their weight of ice-cold water, adding the salt to the water in
small quantities at a time, and never allowing the tem{)erature to rise
above 6® C. (41° F.). On warming the solution, the greafer part of the
lanthanum separates ont as a sulphate of the formula SgOgLao'^'g^QOFIj,
carrying down with it, however, a small quantity of didymium. This
precipitate is filtered off hot, employing a hot-water funnel ; the solu-
tion is reserved for the preparation of a pure didymium compound. In
order to free the precipitate of lanthanous sulphate from didymium, it
is necessary to repeat the operations of dehydrating at low redness, dis-
solving in ice-cold water and precipitating by warming the solution,
until the solution no longer shows the spectrum of didymium. For
this purpose from six to eight repetitions of this series of operations are
generally necessary.
In order to obtain a pure didymium salt the mother liquor from the
first precipitation of the lanthanous sulphate is fractionally precipitated
with oxalic acid. When the oxalic acid is very gradually added, the
precipitate which is at first formed redissolves ; but at length a point is
reached when a permanent precipitate of crystalline, pink-colored didy-
mous oxalate separates out. This oxalate is converted into oxide, then
into sulphate, which is fractionally precipitate<l in the same way. After
several repetitions of this treatment a pnxluct is obtained, from the
spark-spectrum of which the lanthanum lines are absent.
The metals were originally prepared by heating the chloride with
sodium. They may, however, he obtained more readily and in a state
of greater purity by the electrolysis of the fused chlorides.
Properties. — Metallic cerium passesses the color and lustre of iron.
It is malleable and ductile. It tarnishes in moist air. Its fusing-point
lies between those of antimonv and silver. When heated in air it burn*
580 INORGANIC CHEMISTRY.
even more brilliantly than magnesium. It slowly decomposes cold
water. Dilute sulphuric and hydrochloric acids rapidly dissolve it
with evolution of hydrogen ; but cold concentrated sulphuric acid and
concentrated nitric acid are without action upon it
COMPOUNDS OF CERIUM.
Cercms chloride, 'Oe'^jCl^. — Finely-divided metallic cerium inflames
when thrown into chlorine, yielding a yellowish- white deliquescent mass
of cerous chloride. This compound is also formed when chlorine is
p&«!sed over a strongly heated mixture of cerous oxide and carbon.
When a solution of the oxide in hydrochloric acid is evaporated over
sulphuric acid, an aquate of the formula 'Oe'"2d5,50H2 is obtained in
crystals. On heating, this salt is decomposed with formation of an oxy-
chloride, but by the addition of ammonic chloride this decomposition
may be prevented and the anhydrous chloride obtained.
The bromide and todw/c have also been prepared.
CermiA fluoride^ ^Ce'^'tF,, is a white precipitate. — Ceric fluoride^ CeF^jOHs, is a
brownish powder obtained by the action of hydrofluoric acid upon ceric hydrate.
When cautiously heated it first loses water and a part of its flnorine as hydrofluoric
acid ; on heating more strongly, a gas is given off which smells like chlorine and lib-
erates iodine from a solution of potasslc iodide — probably free fluorine (Brauner).
CerotLS oxide, 'Oe'^'^Oj, is formed when the oxalate, or the carlx)nate,
or ceric oxide, is heated in a current of hydrogei). It is a bluish-green
powder, which absorbs oxygen from the air, and is converted into ceric
oxide. — Ceroits hydrate is thrown down as a bulky white precipitate
when a caustic alkali is added to the solution of a cerous salt Expo-
sure to the air colors it yellow, owing to oxidation.
Ceric oxide, CeOg, is obtained by heating the oxalate or the nitrate
in air or oxygen. Thus prepared it forms a colorless or faint-yellow
powder, but by heating cerous chloride with borax in a wind furnace for
forty-eight hours, it may be obtained in crystals belonging to the regu-
lar system. On heating, it becomes darker in color, but resumes its
original tint on cooling. Hydrochloric act dissolves it, yielding a yel-
low solution, which when warmed evolves chlorine, and then contains
cerous chloride. With concentrated sulphuric acid it also yields a yellow
solution, which possesses oxidizing properties and evolves oz<3nized
oxygen. — The hydrate has the formula OejOHo^.
Cerom nitrate, Ng0,3(''Ce^''^a0,)''*,12OHa, is best prepared by dissolving ceric oxide
in nitric acid with the addition of alcohol, the latter substance acting as a reducing
agent. It forms a crystalline mass.
Ceric nitratCf N^OgCeo**, is formed when ceric oxide is dissolved in concentrated
nitric acid. It is soluble in strongly acid solutions, but excess of water decomposes it
with separation of a basic salt. It forms double salts with other nitrates.
Cerous mlphaie, SgOgCCe'^gOeyS^OHg, is deposited in large ootahedra
or prisms when a solution of ceric oxide in sulphuric acid is mixed with
alcohol or sulphurous acid and allowed to evaporate spontaneously.
Hot solutions deposit the anhydrous salt in minute crystals, which are
COMPOUNDS OF DIDYMIUM. 581
floliible in six parts of cold and sixty parts of boiling water. — Cerous
potcumc mlphate, SjOi^KogCCe'^jOj)'*, separates as a white crystalline
powder when an excess of potassic sulphate is added to a solution of the
preceding salt. It is sparingly soluble in water, and almost insoluble
in a concentrated solution of potassic sulphate. Cerous sulphate forma
similar double salts with the sulphates of sodium and ammonium.
Ceric sulpliate, S2O4Ceo*%70H2, is a yellow crystalline mass.
Cerotts phosphate^ PjOa(''Ce^''''20e)^*, occurs a« monaxUe, A portion of the cerium in
this mineral is isomorphouslj replaced by lanthanum and didjmium.
PENTAD ELEMENTS.
Section II.
DIDTMIUM, Di.
Atomic iceight =: 14Q. iloleeidar weight unknown, a8^. ^r. = 6.544.
Atomicity '" and ^.
Histoi-y, — Didymium was discovered by Mosander in 1841.
Occurrence and Preparation. — See Cerium, p. 578.
Properties. — In its properties didymium resembles the two foregoing
metalsy except that it has a slightly yellow tint.
COMPOUNDS OF DIDYMIUM.
Didymoua chloride^ DiClj, is a rose-colored crystalline mass. Its
solutions deposit rose-red crystals with 6 aq.
Didym'ms oxide, Di20s, is prepared by igniting the oxalate or the
hydrate. It forms a white or bluish powder, neither fusible nor vola-
tile, which when strongly ignited gives a continuous spectrum inter-
sected by bright bands, corresponding in position with the dark bands
of the absorption spectrum of the didymium salts (cf. Erbia, p. 584). —
Didymous hydrate, DiHog, is obtained as a pale pink-colored precipitate
by adding a caustic alkali or ammotiia to the solution of a didymous
salt.
Didymic oxide, Di205, is obtained as a chocolate-colored mass by heat-
ing the basic nitrate of didymium to dull redness in a current of
oxygen.
Didymous nitraiej N80er)io^''^,60H2, forms large roee-red deliques»cent crystals.
Didymous sulphate, S806Dio^^''t,8Oll2, crystallizes in soluble, rose-red monoclinic
prisms.
582 INORGANIC CHEMISTRY.
TRIAD ELEMENTS.*
Section IV.
LANTHANUM, La.
Atomic weight = 138.5. Molecidar weight unknoion. Sp. gr. 6.163.
Atomicity '" f
History. — Lanthanum was discovered by Mosander in 1839.
Occurrence and Preparation, — See Cerium, p. 578.
Propeiiies. — Lanthanum is a malleable metal of an iron-gray color.
The freshly cut surface is very lustrous, but speedily tarnishes on ex-
posure to air. In its behavior towards water and acids it resembles
cerium, except that it is attacked in the cold both by concentrated and
by dilute nitric acid.
COMPOUNDS OF LANTHANUM.
Lanthanous chloride^ I^ftClj, is prepared like cerous chloride, which it
resembles in its properties.
Lanthanous oxide, T^^v '^ obtained as a white powder by heatins:
the oxalate or the nitrate. It combines with water with evolution of
heat, and is converted into the hydrate LaHo,.
Lanthanous nitrate ^ NsOjLao^'^jCOHa, forms colorless, deliquescent, tabular crystals.
Lnthanovs sulphate, S30gLao"'2,90H2, crystallizes in six-sided prisms.
The anhydrous salt is readily soluble in ice-cold water, but on gently
warming the solution the above aquate separates in microscopic star-
shaped crystals, which at 13° O. dissolve in less than 6 parts of water,
but at 100° C. require 115 parts for their solution. (See Separation of
Lanthanum, p. 579.)
YTTRIUM, Y.
Atomic weight = 89.8. Molecular weight unknown. Atomicity "' f
History, — The earth yttria was discovered by Gadolin in 1794.
Occurrence, — This element occurs, always accompanied by erbium,
in a few very rare minerals: thus as silicate in gadolinite and orthiie
(along with cerium, lanthanum, didymium, beryllium, iron, and other
metals) ; also as tantalate, niobate, and phosphate. Recently, however,
the spectroscope has shown yttrium to be a very widely diffused
element (Crookes).
* The remaining elements of this group have been classed as triadic; but it is quite
possible that they may be only.pseudo-triadic.
YTTRIUM. 683
Preparation. Separation of Yttrium and Erbium, — Gradolinite is
decofn posed with hydrochloric acid and evaporated to expel the excess
of acid. The residue is extracted with dilute hydrochloric acid, and
the solution is heated to boiling and precipitated with oxalic acid.
The precipitate, which contains, in the form of oxalates, all the yttrium
and erbium, along with calcium, cerium, lanthanum, didymium, and
traces of manganese and silica, is washed by decantation and heated in
an open platinum dish, until the oxalic acid is totally destroyed. The
mixed oxides thus obtained are dissolved in nitric acid, and a concen-
trated solution of potassic sulphate is added, which precipitates the
cerium, lanthanum, and didymium as double sulphatas of these metals
with potassium. From the filtrate the yttrium and erbium are again
precipitated as oxalates, the oxalates converted by heating into oxides,
the lattfer redigsolved in nitric acid, and the solution examined with the
spectroscope for didymium, the presence of which metal can be readily
detected by its characteristic absorption spectrum. If didymium is
present, the precipitation with potassic sulphate and the other operations
must l)e repeated until a solution is obtained which does not give the
didymium spectrum. A trace of calcium is got rid of by precipitating
the yttrium and erbium as hydrates by ammonia. In order to separate
the yttrium and erbium, the pure hydrates are dissolved in nitric acid,
and the mixed nitrates are carefully heated in a platinum dish over a
small flame until the first bubbles of nitrous anhydride begin to make
their appearance. The moment this point is reached, the dish is rapidly
cooled in order to prevent further decomposition, and the residue is
dissolved in a quantity of warm water just sufficient to prevent the
solution from becoming turbid on boiling. This solution deposits on
cooling needles of a basic nitrate of erbium, which is, however, still
contaminated with yttrium. Further crops of this salt, but still
less pure, are obtained from the mother liquors. The purer crops are
mixed, dissolved in nitric acid, again heated to incipient decomposition,
and treated as above, repeating this operation until a pure erbium salt
is obtained. In order to separate the yttrium in a state of purity from
the erbium, with which it remains mixed in the mother liquors in the
form of nitrate, the solution is evaporated to dryness, the residue
heated to redness, and, after cooling, extracted with water; the solu-
tion thus obtained is again evajwrated to dryness, heated, and the
residue extracted with water, repeating these operations until a solution
is obtained which no longer gives an absorption spectrum of erbium.
From this solution, which contains a basic yttric nitrate, the yttrium is
Crecipitated by oxalic acid. The pure oxalate of yttrium is converted
y ignition into the oxide.
Properties. — Pure metallic yttrium and erbium have not been pre-
pared. By heating the mixed chlorides of the two metals with sodium, a
black powder has been obtained, which assumes a metallic lustre under
the burnisher. This metallic substance burns brilliantly when heated
in air. Water decomposes it slowly at ordinary temperatures, more
rapidly on boiling. Acids dissolve it readily, with evolution of hydrogen.
The attempt to prepare yttrium and erbium by the electrolytic de-
composition of the chlorides has not proved successful.
684 INORGANIC OHEMISTUY.
COMPOUNDS OF YTTRIUM.
Ytirous chloride, YCl,. — Wheo the above described impure yttrium
is heated in chlorine, it is converted into a non-volatile chloride. By
dissolving the oxide in hydrochloric acid and evaporating, an aquate of
the formula YCl3,60H, is obtained^ which when heated evolves, hydro-
chloric acid. By heating the aquate with ammonic chloride anhydrous
yttrous chloride may be obtained.
The bromide and iodide closely fesemble the chloride.
YUrous Jluoride occurs in combinatioD with the fluorides of oerium and calcium in
the mindral yUrocerite,
Ytirous oxide {Yttria), YjOj, is obtained as a yellowish-white powder
by igniting the oxalate (see p. 683). It is neither fusible nor volatile.
When strongly heated it emits a pure white light, which when exam-
ined by means of the spectroscope, gives a perfectly continuous spectrum,
without any trace of lines or bands, a behavior which affords a means
of distinguishing this oxide from that of erbium. Water neither dis-
solves it nor converts it into hydrate. Mineral acids slowly dissolve it,
yielding salts. — Yttrous hydrate, YH05, is obtained as a gelatinous pre-
cipitate when alkalies are added to solutions of yttrium salts.
Yttrous nitrate, NjO«Yo''^,60Ha, is readily Rolublp, and forms long needles permanent
in air. A basic nitrate of the formula N308Yo'''',YH0j,3OH», is obtained by healing
the normal nitrate to incipient decomposition and crystallizing from a small quantity
of water.
Yttrous sidphate, S308Yo''''i,8OH2, is deposited from its solutions in well-formed
crystals, which become anhydrous only at a high temperature. The anhydrous salt is
much more soluble than the crystallized aquate. A saturated solution of the anhy-
drous salt prepared at 15^ C. (59° F.) deposits a portion of the salt in the hydrated
state on warming.
EEBIUM, Er.
Atomic weight = 165.9. Molecular weight unknown. Atomicity ^".
Histoiy, — Erbium was discovered in 1843 by Mosander.
Occurrence^ Preparation, and Propetiies, — See Yttrium, p. 5S3.
COMPOUNDS OF ERBIUM.
These resemble the compounds of yttrium.
Erbous oxide {Erbia), Er^Oj, is obtained by igniting the oxalate or
nitrate. It forms an amorphous mass of a yellowish color. It does
not fuse at the highest temperatures, but, when strongly heated, emits
a greenish light, which, when examined spectroscopically, gives a con-
tinuous spectrum, intersected however by bright bands, the position of
which agrees with that of the dark bands in the absorption spectrum
of the solutions of erbium salts. Towards acids erbia behaves like
TERBIUM. 585
yttria. — Erboua hydrate^ ErHoj, is precipitated by alkalies from the
solutions of the salts of erbium.
Erbous nitraie. — A basic nitrate of the formula NjOjEro'^^.ErHoj.SOFIj, obtained
like the ourresponding yttrium salt, is employed in the separation of erbium from
yttriiim.
Erbous sulphaUf Ss08Ero''''2,8OH2, is deposited from its solutions at 100° C in well-
formed crystals. It closely resembles in its properties yttrous sulphate.
All the salts of erbium when in solution display a spectrum with
characteristic absorption bands.
TBRBITTM, Tr.
Atomic weight = 148.8 (?).
Very little is known concerning this element, which occurs along with yttrium and
erbium in samarskite. The metal has not been isolated, and even its compounds have
not been obtained free from erbium. The above atomic weight is therefore to be re-
garded only as an approximation.
Another metal, ytterbium (atomic weight ^ 172.8) has lately been added by Marignac
to the list of the metals of the rare earths. It occurs in crude erbia. Its oxide is
white and gives no absorption spectrum.
Scandium, Sc {oUomin weight = 44). — Very little is yet known concerning this rare
element, which was discovered by Nilson in 1879. The metal has not yet been iso-
lated. It occurs along with the other rare earths in gadolinite and euxenite. It is
separated by means of the property which its nitrate possesses of undergoing decompo-
sition at a relatively low temperature.
Scandous oxide, Sc20s, is a white infusible powder. Its salts closely resemble those
of the other metals of this group.
Samarium. Sm [atomic weight = 150), was discovered by Lecoq de Boisbaudran in
samarskite. It is easily recognizable by means of its characteristic spectrum. The com-
pounds of this element resemble those of didymium. Samarotis chloride^ 8inCls,60Ff 2,
forms laiige tabular deliquescent crystals. Samarova oxide, BmaOs, is a white or faint-
yellow powder. The solutions of its salts have a deep yellow color.
Decipium, Dp (atomic weight = 159?) was discovered' bv Delafontaine in the samars-
kite of North Carolina. It has not yet been found possible coippietely to separate its
compounds from those of didymium. The solutions exhibit a characteristic absorption
spectrum.
General Properties and Reactions of the Compounds op
THE Rare Earth Metals. — The corresponding compounds of these
various metals are characterized by their great similarity, so that their
separation is generally a matter of difficulty. The methods for the
separation of the principal members of the group — yttrium, erbium,
cerium, lanthanum, and didymium — have already been given (pp. 578
and 583).
686 INORGANIC CHEMISTRY.
CHAPTER XXXVIII.
• TETRAD ELEMENTS.
Section IV.
PLATIHTJM, Pt.
Atomic weight = 194.4. Molecular weight unknown, 8p, gr. 21.5.
Fuses aboiU 2000° C. (3632° F.). AtomieUy " and *\ Evidence of
atomicity :
Platinous chloride, Pt"Clj.
Platinous oxide, Pt"0.
Platinic chloride, W^C\.
Platinic oxide, Pt^^Oj.
History. — Platinum was first recojrnized as a distinct metal in the
eighteenth century, though it was known as a refractory metallic sub-
stance a couple of centuries earlier.
Occui-rence. — Platinum occurs only in the native state. Native plat-
inum is never pure: it contains from 50 to 80 per cent, of platinum,
the remainder consisting of iridium, palladium, rhodium, osmium, and
ruthenium — which, together with platinum, constitute the so-called
platinum metals — also gold, iron, and copper. This impure metal, or
platinum ''ore," usually forms minute grains, although larger masses
or nuggets are also found. It occurs most frequently in the sand of
rivers and in alluvial deposits. The chief localities from which platinum
is obtained are the Urals, Borneo, California, Brazil, and Peru. Traces
have been found in the auriferous sands of the Rhine. The supply
from Russia is ten times as great as that from all the other parts of the
world taken together, and amounts to about 800 cwt. yearly.
Extraction. — The following is the method employed at St. Peters-
burg in treating the platinum ore: The ore is first digested with dilute
aqua-regia, which extracts the gold ; then with concentrated aqua-regia,
as long as anything dissolves. The insoluble portion consists of grains
of a native alloy of osmium and iridium. The solution contains the
platinum as platinic chloride, along with small quantities of other metals.
Ammonic chloride is now added to the solution, and in this way the
platinum is precipitated as ammonic platinic chloride (PtCl4,2NH4Cl)
along with the small quantity of iridium which is present. The pre-
cipitate of ammonic platinic chloride is decomposed by heat, employing
as low a temperature as possible, in order that the platinum may be ob-
tained in a finely divided state. The metallic powder is formed into a
cake by pressing it into a conical mould of brass, aft€r which the cake
is heated to whiteness, and welded into an ingot by hammering. In
this form the platinum may be drawn into wire or rolled into plate,
and otherwise worked like the most ductile metals. Instead of weld-
ing the platinum, Deville and Debray fuse the metal in a lime crucible
by means of the oxy-coal-gas blowpipe.
Deville and Debray have also attempted to obtain platinum from its
PLATIXUM. 587
ores in the dry way. For this purpose the ores are fused with galena,
glass, and borax. The iron present in the ore is thus converted into
sulphide. Litharge is then gradually added. The litharge and galena
react to yield metallic lead, the sulphur burning off as sulphurous anhy-
dride (see Lead^ Extraction of). The platinum and the other metals
contained in the ore, with the exception of osmiridium, dissolve in the
lead. The liquid portion is ladled off from the osmiridium, cu [Milled,
and the resulting platinum fused in a lime crucible as above described.
This process has been abandoned; as the platinum obtained by it is not
sufficiently pure.
Preparation of pure Platinum. — In ortler to obtain pure platinum,
commercial platinum is dissolved in aqna-regia, and from the solution,
after expelling the excess of acid, the platinum and iridium are precipi-
tated by caustic soda ss platinic hydrate (PtHo^) and iridic hydrate
(IrHoJ. A little alcohol is now added, and the liquid with the pre-
cipitate is boiled. Platinic hydrate is not altered by this treatment,
but iridic hydrate is converted into a lower hydrate of the formula
iFjHog, and on reacidifying with hydrochloric acid, these hydrates go
into solution, yielding the corresponding chlorides. Di-iridic hexa-
chloride is not precipitated by ammonic chloride, so that on adding to
the liquid an excess of this reagent the whole of the platinum is thrown
down in the form of pure ammonic platinic chloride, which, after wash-
ing, IS converted by ignition into pure metallic platinum.
Propertiea, — Platinum is a white metal with a tinge of gray, capable
of taking a high polish. When obtained by heating to redness com-
pounds of platinum — for example, ammonic platinic chloride — it forms
a loosely coherent gray mass, known as spongy platinum. In the very
finely divided condition in which it is depasiteti from the solutions of
its chloride by the action of reducing agents, it forms plaiinum blaxiky a
black powder, quite devoid of metallic lustre. Platinum is very malle-
able and ductile. Perfectly pure platinum has about the same hardness
as copper, but the presence of a small quantity of iridium increases its
hardness considerably. In the form of very thin wire it can be fused
in the flame of a candle; * in larger masses it requires the heat of the
oxyhydrogen flame for its fusion. The fusing-point has been estimated
by Deville at 2000° C. (3632° F.). It does not combine directly with
oxygen at any temperature, but possesses in the molten state the
property of absorbing oxygen. The absorbed oxygen is expelled dur-
ing the solidification of the metal, which thus exhibits the phenomenon
of "spitting'' (see Silver, p. 451). In like manner hydrogen passes
through a diaphragm of red-hot platinum, owing to the property which
the metal possesses of dissolving the gas. The red-hot metal is, how-
ever, impermeable to oxygen, nitrogen, carbonic anhydride, and other
gases. Cold platinum has the power of condensing various gases, espe-
cially oxygen, upon its surface. This action is exhibited in a very high
degree by platinum black, which, owing to it«» state of extremely fine
subdivision and consequently increased surface, is capable of thus con-
* It is pomible that the fusion in this case is due to the formation of a fusible car-
bide of platinum.
588 INORGANIC CHEMISTRY.
densing eight hundred times its volume of oxygen. To this property
IS due the so-called catalytic action of platinum in bringing sbont the
combination of various gases. Thus platinum black, when introduced
into a mixture of oxygen and hydrogen, determines the explosion of the
mixture. Sulphurous anhydride and oxygen, when ]>assed over plati-
num black, form sulphuric anhydride; hydrogen and iodine unite to
yield hydriodic acid — the action in this and in the former case being
aided by gently heating the finely divided metal. A heated spiral of
platinum wire, when plunged into a mixture of ether vapor and air, or
of alcohol vai>or and air, continues to glow, and eifects the oxidation of
the organic sul)stance. Indeed, the wire need only be warmed to 50^ C
in order to glow when introduced into the vapor. — Platinum is not
attacked by any single acid ; but aqua-regia, or any other liquid in
which chlorine is contained or is being evolved, dissolves it. It is oxi-
dized by fusion with caustic alkalies or with nitre. Fused alkaline
cyanides also attack it. It unites directly with silicon when heated
with it, to form a brittle silicide; and with phosphorus and arsenic it
yields fusible compounds. With many of the metals it forms fusible
alloys. A knowledge of these facts is of importance in working with
vessels of platinum : thus phosphates ought never to be heated with
carbon or with filter-pa])er in a platinum crucible, and the heating of*
compounds of easily reducible metals in such vessels is to be avoided
altogether. Platinum vessels ought never to be heated over a smoky
flame, as, owing to the alternate formation and oxidation of a carbide
of platinum, the metal becomes blistered and porous. Contact with
burning charcoal is also to-be avoided, as the platinum combines with
the silicon reduced from the ash. — Platinum may be sublimed at a red
heat in a current of chlorine, and may thus be obtained in crystals.
The sublimation of the platinum is only apparent and depends in
reality upon the formation and decomposition, in rapid succession^ of a
chloride of platinum.
Uses. — The high fusing-point of platinum, and its power of resisting
chemical action, h^ve caused it to be extensively employed in the man-
ufacture of vessels for laboratory purposes. Thus platinum crucibles
and evaporating basins, platinum toil and wire, are in constant requi-
sition in the proc*esses of chemical analysis. Large platinum stills are
used for the concentration of sulphuric acid. The marked electro-
negative character of platinum renders it capable of forming, with
elet^tropositive metals, such as zinc, voltaic combinations of high electro-
motive force. Grove's battery is a combination of this description.
Platinum forms two series of compounds: plaiinous compounds, ia
which the metal is dyadic; and platinie compounds, in which it is
tetrad ic.
COMPOUNDS OF PLATINUM WITH THE HALOGENS.
a. Platinous Compounds.
Platinous chloride, PtClj, is obtained by heating platinie chloride to
225-230^ C. (437-446° F.). It forms a grayish-green powder, insolu-
COMPOUNDS OF PLATINUM. 589
ble in water, soluble in hot hydrochloric acid, yielding a reddish -brown
solution. It unites with other metallic chh^rides to form double salts:
thus the compounds PtCl2,2KCl and PtCl2,i'NH4Cl are obtained in large
red prisms by adding potassic and ammonic chloride to the solution of
platinous chloride in hydrochloric acid, and evaporating the liquid. —
When platinous chloride is heated in a current of oar&)nic oxide, the
gas is al>sorbed with formation of the compounds PtCIgiOO, PtCl2,2CO,
and PtClajSCO. It also unites directly with ethylene (''CjH^) and other
unsaturated hydrocarbons.
PkUiwms hrcmidty PtBn, is prepared by heating hydric platinic bromide to 200° C.
It forms a bn)wn mass.
Plniirums iodide, Ptij. is obtained as a black powder by warming platinous chloride
with a concentrated solution of potassic iodide.
6. Platinic Compounds.
Platinic chloride, PtCl4, is prepared by dissolving platinum in
aqua-regta, destroying the nitric acid by repeated evaporation with
hydrochloric acid, and heating to expel the excess of hydrochloric acid.
It crystallizes from water in large red non-deliquescent crystals of the
formula PtCl4,50H2. — Platinic chloride forms numerous double salts
with other chlorides: thus with hydrochloric acid it forms the com-
pound PtCl4,2HCl, which is deposited in brownish-red deliquescent
prisms with 6 aq. from the solution of platinic chloride in hydrochloric
acid. Potassic platinic chloride, PtCl4,2KCl, and ammonic platinic
chloride, PtCl4,2«H4Cl, are obtains! as yellow crystalline precipitates,
consisting of microscopic octahedra, when platinic chloride is added
to solutions of potassic and amnionic chloride. These precipitates
are almost insoluble in water and quite insoluble in alcohol. Sodic
platinic ddoride crystallizes in reddish-yellow prisms of the formula
PtCl4,2NaCl,60H2, readily soluble in water and in alcohol. The dif-
ference in the solubility of these compounds is turned to account in the
separation of the alkali metals.
Platinic bromide, PtBr4, has not been prepared, but hydrie platinic bromide j
PtBr4.2IiBr,90fI«, is known.
Platinic iodide, PtF^, Beparatefl as a black powder when potassic iodide is added to a
solution of platinic chloride and the liquid warmed.
COMPOUNDS OF PLATINUM WITH OXYGEN AND
HYDROXYL.
Platinous oxide, .
Platinous hydrate,
Platinic oxide,
. PtO.
. RHo,.
. PtOj.
Pt— O.
H— 0— Pt— 0— H.
O-Pt-O.
H O O H
H-O 0— II
Platinic hydrate, .
. PtHo,.
590 INORGANIC CHEMISTRY.
Plaiinous oxide, PtO. — This compound is obtained as a grayish-
black powder by gentiv heating the corresponding hydrate.
Plaiinous hydrate, PtHoj, is a bulky black powder, obtained by
digesting platinous chloride with warm caustic pota.'^h. Boiling caustic
potash decomposes it with separation of metallic platinum and forma-
tion of platinic oxide. It acts as a weak base and yields with the
hydracids the corresponding haloid salts ; but the oxy-acids, with the
exception of sulphurous acid, decompose it.
Platinic oxide, PtO,, is a black powder obtained by gently heating
platinic hydrate.
Platinic hydraie, PtHo4. — A solution of platinic chloride is precipi-
tated by boiling with caustic potash, and the precipitate is treated with
acetic acid to remove the (K)tash, when a white compound of the formula
PtHo4,20H2 remains. This, on drying at 100° C, parts with 2 aq. and
assumes an amber-brown color. Platinous hydrate acts both as a weak
l>ase and as a weak acid. The salts which it forms with bases are
known as platinafes. Baric platinate is a yellow powder of the formula
PtHo,Bao",30H2.
OXY'SALTS OF PLATINUM.
Very few of the simple oxy-salts of platinum have been prejared,
but various double salts are known.
Platinous tulpkiie is obtaine<] v» a guramy mfiss of unknown composition by evapo-
rating the solution of platinous hydntte in sulphurous acid. — Potasnc platinous ful-
phitey 8()Pto^^380Ko,,20H2 crystallizes in readily soluble needles. Sodi^ plalimmt
sulphite, S0Pto'''',3SONa<>,7OH2, is a sparingly soluble crystalline precipitate.
Platinonitrites. — Platinnni forms a series of remarkable compounds with the nitrites
of other metals. These compounds do not behave like ordinary double salts: the
platinum cannot be detected in their solutions by the ordinary reagents. They may be
regarded as salts of platinonitrous acid, H^Pti ^02^4.— Potasiic platin<mUriie, KiPt(N(''2l4,
is deposited in small lustrous prismatic crystals when solutions of potassic nitrite and po-
tafisic platinous chloride are warmed together. Its solutions are not precipitated either by
alkalies or by sulphuretted hydrogen. — Amnionic plat inonitrite, {'SlI^'2Ft{'SCh]^,20lh,
crystallizes in prisms. It decomposes with sudden incandescence when heated.
COMPOUNDS OF PLATINUM WITH SULPHUR
PkUtJious sulphide, PtS''''. — This compound may be obtainefl as a black amorphons
powder by passing sulphuretted hydrogen over moistened platinous chloride, or in a
crystalline form by fusing platinous chloride with sodic carbonate and sulphur, and
lixiviating the ma«s with water.
Platinic sulphide, PtS^''i. — Sulphuretted hydrogen precipitates, from solutions of
platinic salts, black platinic sulphide, and this compound then unites with a further
quantity of the gas to form light-brown hydric platinic sulphide, an unstable com-
pound which parts with sulphuretted hydrogen when exposed to the air. — By fusini?
a mixture of spongy platinum, potassic carbonate, and sulphur, and extracting the
mass with water, an insoluble dipotassic diplatinaus siUphodiplati*kite, < p*pfa//Ks' ^
obtained in thin lead -gray ^x-sided tablets. When heate*! in a current of gaseous
hydrochloric acid, this compound evolves sulphurretted hydrogen, and is converted
into pfitiissic chloride and a platinic sulphide of the formula Pt2S^^9 (possibly, how-
f PtPts^'' \
ever, Pt^S'^^j = •< p*.p» //S'''' ), which remains as a steel-gray powder on extracimg
the mass with water.
COMPOUNDS OF PLATINUM. 591
AMMONIUM COMPOUNDS OF PLATINUM
[PL ATIN AMINES).
Platinum forms a remarkable class of ammonium bases, the salts of
which may be empirically formulated as double compounds of platinum
salts with two or more molecules of ammonia. In this respect these
compounds resemble the cobaltamines {q.v.). They have been divided
into no fewer than twelve distinct classes. The members of one class
are sometimes isomeric with those of another class. A complete account
of these compounds would go beyond the scope of the present work.
The following will serve as examples :
Pl<jloaoteiTammonic chloride (chlorideof*" Reisers first base") is obtained in colorless
prisms of the formula-! Pt'''' )OH„ when platinons cliloride is dissolved in an
i NHj(N'HJCl
excess of boiling aqueous ammonia and the solution evaporated. It forms with plati-
nous chloride an insoluble double salt, crystallizing in dark green needles of the
(NHslN'HjCl
formula -< Vt^^ .PtCL, also known as the green 8aU of Magnus, This compound,
iNH,(N;HJCl
which is interesting as* the first discovered of the platinum ammonium compounds,
mav be obtained direct bv supersaturating with ammonia a hot solution of platinous
rNH,(N'H,)Ho
chloride in hydrochloric acid. — PUUo90tetrammonic hydrate, < Pt^^ , is pre-
InH,(N'HJHo
pared by precipitating a solution of the sulphate with baric hydrate and evaporating
the filtrate, it crystallizes in deliquescent needles. It acts as a caustic, absorbs
carbonic anhydride from the air, and precipitates the metals as hydrates from tlie
solutions of their salts.
f NH3CI
Platosodiammonie chloride (chloride of "Beiae^s second base") A Pf'' . — This com-
pound, which is isomeric with the green salt of Magnui>, is formed when platosote-
trammonic chloride is heated to between 220° and 270° C. (430-618° F.). It forms
microscopic, yellow rhombohedra. It is sparingly soluble in water, and is formed as
a precipitate when hydrochloric acid is added to the solutions of other salts of this
base. Both the hydrate and the oxide are known. The latter compound, which has
the formula •{ Pt'^ O, is obtained by heating platosotetrammonic hydrate to 110° C.
iNH,-
PlaUnodiammonic ddoride (chloride of **0erhard^8 base"),i Ft 01, , is formed by the
iNHaCl
direct union of platosodiammonie chloride with chlorine, when the gfis is passed
through water in which this salt is suspended. It crystaUizes in minute yellow
octahedra.
fNHJN'HJCI
Plaiinotetrammonie chloride ("Oroi^ chloride") \ PtCL . — This compound is
|nH,{N'H,)C1
formed in a similar manner by the union of platosotetrammonic chloride with chlo-
rine, or, by treating platinodiammonic chloride with ammonia. It crystallizes in
yellow octahedra of the regular system.
Gexeral Properties and Reactions of the Compounds op
Platinum. — a. Platirwua Compounds. — These are of subordinate inte-
rest. The platinous salts are of a red, brown, or green color.
b. Platinio Compounds. — The platinic salts have a yellow color. With
cavMio soda they give a yellow precipitate of platinic hydrate, soluble
592 INORGANIC CHEMISTRY.
in an excess of the alkali. Sulphuretted hydrogen precipitates, slowly in
the cold, more rapidly on heating, platinic sulphide, wUeh is soluble in
a large exc^s of ammonic sulphide. Potassic chloride and ammonic
chloride produce yellow crystalline precipitates of potassic platinic
chloride and amnionic platinic chloride. Stannous chloride in acid solu-
tions produces a dark coloration, owing to the reduction- of the platinic
salt to the platinous stage, but no separation of metallic platinum occurs.
Ferrous sulphate precipitates metallic platinum, but only after protracted
boiling. Oxalic acid does not reduce the salts of platinum (separation
from gold); but by lx)iling with soluble formates in alkaline solution,
metallic platinum is precipitated. All platinum compounds, when
ignited with access of air, are converted into metallic platinum.
PALLADIUM, Pd.
Atomic weight = 105.7. Molecular weight unknown, Sp. gr. 11.4.
Atomicity " aixd^^. Evidence of atomicity :
Palladous chloride, Pd"Cl,.
Palladous oxide, Pd"0.
Palladic chloride, Pd^^CI^.
Palladic oxide, Pd^^O,.
History. — Palladium was discovered by Wollaston in 1803.
Occurrence. — Granules of this metal, sometimes in the form of octa-
hKlra, occur in the platinum ore of Brazil. Alloyed with platinum and
other metals, it occurs in all ores of platinum.
Preparation. — One method of separation of palladium from the
other metals of the platinum-group with which it occurs, depends upon
the fact that palladium is precipitated as insoluble palladous iodide by
the careful addition of potassic iodide to the solution of palladous chlo-
ride. The other metals remain in solution. An excess of the precipitant
is to be avoided, as it dissolves the palladous iodide. The iodide loses
its iodine when strongly heated, and is converted into spongy palladium.
— In order to extract the palladium from platinum ore, the solution
which is obtained after dissolving the ore in aqua-regia and removing
the platinum by precipitation with ammonic chloride, is treated with
mercuric cyanide. In this way a precipitate of palladous cyanide is
produced, which by ignition may be converted into the metal.
Properties. — Palladium is a silver-white lustrous metal. It sometimes
occurs crystallized, either in octahedra or in small hexagonal plates.
Palladium is the most fusible of the platinum metals and can be welded
at a red heat more readily than platinum. When heated to low redness
it undergoes superficial oxidation, and assumes a blue color, but at a
higher temperature regains its lustre. It is soluble in hot nitric acid
and in hot concentrated sulphuric acid. Hydrochloric acid dissolves
spongy palladium in presence of air. It is not altered by exposure to
air or to sulphuretted hydrogen. — Spongy palladium, like spongy plat-
inum, is capable of effecting the combination of oxygen and hydrogen
when introduced into a mixture of these gases. If the two gases are
present in the proportions necessary to form water, the palladium
CX)MPOUKDS OF PALLADIUM. 593
becomes red-hot, causing explosion ; but if a considerable excess of
oxygen is present or if air be substituted for oxygen, the combination
takes place slowly at ordinary temperatures without explosion. In the
case of a mixture of hydrogen, marsh-eas and air, it is possible to effec^t
the slow combustion of the hydrogen, leaving the marsh-gas untouched,
and in this way the hydrogen present in a mixture of combustible gases
may be determined. — If a piece of palladium foil be heat^ in the flame
of a spirit lamp, or in a coal-gas flame, the foil becomes covered with
cauliflower-like excrescences of soot, and when these are burnt they
leave a skeleton of filaments of metallic palladium, whilst the foil is
found to have become porous. In like manner, when spongy palladium
is heated in a current of ethylene, the gas is decomposed with separa-
tion of carbon at a temperature at which ethylene alone is perfectly
stable. These phenomena probably depend upon the affinity of palla-
dium for hydrogen, palladium hyJride (q-v.) being successively formed
and decomposed. In the formation of this compound carbon is liberated
from the gases present in the flame; in its decomposition the palladium
disintegrates.
Uses, — Palladium is used for the graduated scales of physical instru-
ments and also for coating silver goods.
COMPOUND OF PALLADIUM WITH HYDROGEN.
Palladium hydride, Pd^Hg. — This compound is formed by the direct
union of its elements when palladium is heated in a current of hydrogen,
or when this metal is employed as negative electrode in the electrolysis
of dilute sulphuric acid. — Palladium hydride is a lustrous metallic mass
with a specific gravity of 11.06. It conducts electricity. It parts with
its hydrogen only very gradually at ordinary temperatures, but rapidly
on heating. On exposure to the air in a finely divided state it becomes
red hot, owing to the absorption of oxygen and oxidation of the hydrogen
to water. It acts as a reducing agent; thus it precipitates metallic
mercury from solutions of the salts of that metal.
COMPOUNDS OF PALLADIUM WITH THE HALOGENS,
a. Palladous Comp(mnd».
Palladous chlo^nde, PdCIj.— When a solution of palladium in aqua-
r^ia is evaporated to dryness, the palladic chloride which is at first
formed is decomposed and converted into palladous chloride, which
remains as a brown deliquescent mass. This compound may also be
obtained as a red crystalline sublimate by heating palladous sulphide
(PdS'') in a current of dry chlorine. In this form it dissolves only
slowly in water. — Like the corresponding platinum compound it forms
nu merous double chlorides. Potasaic palladous oMoride has the formula
PdCl2,2KCl.
PaUmloui bromide is not known in the pure state.
Palladous iodide^ Pdlj. — This compound is precipitated as a black
|)owder when potassic iodide is added to solutions of palladous chloride
38
694 INORGANIC CHEMISTRY.
or nitrate. It is soluble in an excess of potassic iodide. Iodine may
be estimated as palladous iodide in presence of chlorine and bromine.
6. PaUadic Gompowids.
Of these only the chloride is known, and this has been obtained only
in solution. It forms, however, well-characterized double salts, corre-
sponding to those of platinum : thus potassic palladic chloride,, PdCI^,-
2KC1, which crystaUizes in brownish-red octahedra; and ammanic pal-
ladic chloride, PdCI^,2NH^Cl, which forms a sparingly soluble red
crystalline powder.
COMPOUNDS OF PALLADIUM WITH OXYGEN.
fPd ^\
Hypopalladous oxide, . < p^O. | yO.
Palladous oxide, . . . PdO. Pd=0.
Palladic oxide, . . . PdO,. 0=Pd=0.
Hypopalladous oxide, 'Pd'jO, is obtained as a black powder by heating
palladous hydrate to low redness as long as oxygeu is evolved. Acids
decompose it with separation of metallic palladium and formation of
palladous salts. When heated in a current of hydrogen it is reduced
with sudden incandescence.
Palladous oxide, PdO, is prepared by careful ignition of the nitrate.
It forms a black powder which dissolves with difficulty in acids. When
brought into hydrogen at ordinary temperatures it is instantaneously
reduced with incandescence. — Alkaline carbonates precipitate from
solutions of palladous salts a dark-brown hydrate, which dissolves
readily in acids.
Palladic oxide, PdOj, is a black powder obtained by boiling potassir^
palladic chloride with caustic potash and washing the precipitate with
hot water.
PALLADOUS OXY-SALTS.
Palladous nitrate, N204Pdo", is prepared by dissolving the metal or
the oxide in nitric acid. On evaporation the solution deposits long
brown deliquescent prisms.
Palladous mdphate, SO^Pdo''^,20H2, ib obtained by dissolving the metal in gulphnric
acid, with the addition of nitric acid, and evaporating. It forms brown soluble cryslaJs,
which are decomposed by excess of water with separation of a basic salt.
A series of ammonium compounds of palladium, corresponding with those of plati-
num, is known.
COMPOUNDS OF PALLADIUM WITH SULPHUR
These correspond with the oxides.
HypopaJlacious sulphuUy ^'PSl^^^\ is formed when either palladous sulphide or pal-
ladic sulphide is heated in a current of carl>onic anhydride. It is most readily ob-
tained by fusing together at a red heat a mixture of palladous sulphide, potassic car-
bonate, sulphur, and ammonic chloride. On dissolving the mass in water, hypopallad-
ous sulphide remains as a brittle, green, metallic regulus. It ii only slowly attacked
by nitric acid. /
IRIDIUM. 595
Palladous sulphide, PdS'^ is obtained as a grayish-white metallic mass by heating
the metal in the vapor of sulphur, when combination occurs with incandescence. Tlie
same compound is precipitated as a black amorphous powder when sulphuretted hy-
drogen is passed int^) solutions of palladous salts.
JPaUadic 8ulphidej Pd8^%. — When palladous sulphide is fused with sulphur and sodic
carbonate, aodie stUpho^aUadaie^TdS^^ ^as^, is formed. On decomposing this com-
pound with hydrochloric acid, palladic sulphide is obtained as a dark-brown powder.
It dissolves readily in aqua-regia.
General Properties and Reactions op the Compounds of
Palladium. — The palladous salts are for the most part soluble, yield-
ing solutions which, when concentrated, are brown or reddish-brown,
when dilute, yellow. Both sulphuretted hydrogen in acid solution and
ammonic sulphide precipitate black palladous sulphide, insoluble in
excess of ammonic sulphide, but soluble in boilincr hydrochloric acid.
Caustic alkalies precipitate brown basic salts of palladium, soluble in an
excess of the alkali on heating, ^mmoma gives a flesh-colored precipi-
tate of a palladammonium compound, soluble in excess of ammonia.
Poiassic iodide precipitates black palladous iodide. Ferrous sulphate
precipitates metallic palladium, the action being facilitated by heat.
All palladium compounds yield on ignition in air metallic palladium.
XRIDIUM, Ir.
Atmaic weight = 192.5. Mokcular weight unhiovm. 8p, gr, 22.38.
Atomicity " and *"", also a pseudo-triad. Evidence of atomicity :
Iridous sulphide, Ir"S".
Di-iridic hexachloride, ^lr"\i\,
Di-iridic trioxide, 'Ir'^gOg.
Iridic chloride, Ir^'Ci^.
Iridic oxide, Ir^'Oa.
History. — Iridium was discovered in 1804 by Smithson Tennant.
Occurrence, — Iridium occurs in most ores of platinum in the form
of granules of the alloys platiniridium and osmiridium.
Extraction, — For the preparation of iridium the residue which re-
mains when the platinum ore is treated with aqtia-regia is employed.
This residue, which consists chiefly of iridium and osmium, but con-
tains small quantities of all the other platinum metals, is fused with
from 20 to 30 times its weight of zinc. On dissolving the zinc in hy-
drochloric acid, the platinum metals remain as a fine powder. This
powder is mixed with from 3 to 4 parts of anhydrous baric chloride,
and the mixture is heated to low redness in a current of dry chlorine.
On dissolving in water, ruthenium remains behind, whilst the other
platinum metals dissolve as double chlorides of barium with the plati-
num metal. Sulphuric acid is then added so as exactly to precipitate
the barium. The liquid, which now contains the platinum metals as
chlorides, is heated in an atmosphere of hydrogen in a flask on a water-
bath. In this way the metals are reduced from their aqueous solution.
During the whole of this operation air must be carefully excluded, as
the finely divided metals would bring about the explosive combination
of the hydrogen with the oxygen of the air. Platinum and palladium
596 INORGANIC CHEMISTRY.
are first reduced, then rhodium. Before the iridium is precipitated if
undergoes reduction to di-iridic hexachloride, 'Ir'",Clj, the presence to
whicli is manifested by an olive-green coloration of the liquid. At this
point the operation is interrupt^, and after filtering off the reduced
metals, the iridium is precipitated from the filtrate by first oxidizing it
with nitric acid to iridic chloride, IrCl^, and then adding a solution of
potassic chloride, with which it forms a black, almost insoluble crystal-
line precipitate of potassic iridic chloride, IrCl^j'iKCl. This on igni-
tion yields spongy iridium. A trace of ruthenium may be removed
by fusing the spontjy metal with nitre. On lixiviating the fused mass
with water the ruthenium dissolves as potassic ruthenate^ leaving the
iridium.
Properties, — Iridium is a white metal, which when polished has a
lustre resembling that of steel. It is harder than platinum, and much
more brittle. It is also more refractory than platinum, but may be
fused in the oxyhydrogen flame. Very finely divided iridium (iridium
black) dissolves iu aqua-regia and oxidizes when heated in air. Corn-
pact iridium is not attacked under any of these conditions, but may be
oxidized by fusion with potassic hydrate to which nitre or potassic chlo-
rate has been added. Iridium black is obtained as an impal|>ab1e pow-
der by ex|)osing an alcoholic solution of di-iridic sulphate to sunlight.
It is more energetic in its catalytic action than platinum black. A small
quantity brought upon paper moistened with alcohol causes ignition.
Uses, — An alloy of 1 part of iridium with 9 parts of platinum is ex-
tremely hard and elastic, capable of taking a high polish, and unal-
terable in air. It has been employed in the preparation of standard
measures of length. Gold pens are sometimes tipped with an alloy of
iridium and osmium.
COMPOUNDS OF IRIDIUM WITH THE HALOGENS.
a, Di-iridic Compounds,
Di- iridic hexachloride/b^'^fi]^. — This compound is formed when the
metal is heated in chlorine. It is most readily obtained by heating one
of its alkaline double chlorides, such as potassic di-iridic chloride,
'rr^'jClg^eKCl, with concentrated sulphuric acid and pouring the cooled
liquid into water, when the chloride separates as a pale olive-green pre-
cipitate, insoluble in water and in acids. It may be obtained in a solu-
ble form by treating a solution of iridic chloride with sulphurous anhy-
dride until the solution has become green. — ^The alkaline double chlo-
rides are formed when the corresponding iridic double chlorides are
reduced in aqueous solution with sulphurous anhydride or sulphuretted
hydrogen. Potassic di-iridic chloride^ 'Ir"'2Cl<„6KCl,60H2, sodic di-
iridic chloridey 'Ir'"2d6,6NaCl,240H2, and ammonic di-iridio chloride,
'Ir'"/Jlg,6NH,CI, 30H„ all form olive-green crystals, soluble in water,
insoluble in alcohol.
Di-iridic hexabromidey ''Ir''''',Brj,80Ii„ is deposited in light olive-green six-sided
crystals when a solution of iridic hydrate, IrHo^, in hydrobromic acid is evaporateti.
The iridic bromide does not appetir to be capable of existing : the solution evolves
bromine and contains the lower bromide. Di iridic hexabromide forms double bro-
mides corresponding with the double clijorides.
COMPOUNDS OF IRIDIUM. 597
6. Iridic Compounds,
Iridic cfUoridey IrCI^, is obtained as a black mass by dissolving irid-
ium blacky di-iridous trioxide, or di-iridic hexachloride in aqua-regia,
and eva}>orating the solution at a temperature below 40° C. (104°F.). On
heating to a higher temperature chlorine is evolved, and the solution
contains the lower chloride. — It forms with the chlorides of the alkalies
double chlorides, isoraorphous with those of platinum. Poiasaic iridic
chloride^ IrCl4,2KCl, and ammonic iridic chloride, IrCl4,2NH4Cl, crys-
tallize in minute dark-red octahedra, sparingly soluble in cold water.
Sodic iridic chloride, IrUl4,2NaCl, is readily soluble in water, and forms
black tabular crystals or prisms.
Iridie bromide, IrBr^, is not known ; but numerous double bromides corresponding
i^iih the double chlorides have been prepared.
Iridic iodide^ Jrl^, is obtained as a black powder bj the action of potassic iodide upon
the solution of the chloride in hydrochloric acid.
COMPOUNDS OF IRIDIUM WITH OXYGEN.
O
Di-iridic trioxide, 'lr'"j,0,-
i^
o o
Iridic oxide, . . IrOj. 0=lr=0.
Di-iridic trioxide^ 'Ir^'gOs- — ^This compound is formed when finely
divided iridium is heated in air. At a higher temperature it is again
decomposed into oxygen and metal. It is most readily prepared by
heating a mixture of potassic iridic chloride and sodic carbonate to low
redness :
2IrCI,.(KCl),
+
4COXao2 =
= 'Ir'^A
+ 8NaCl
+
Potasuic iridic
Sodic
Di-indic
Sodic
chloride.
carbonate.
trioxide.
chloride.
4KCI + 4COj + O.
P(>ta*ssic Carbonic
chloride. anhydride.
On extracting the mass with water the oxide remains behind as a black
powder. Hydrogen, even at ordinary. temperatures, reduces it to the
metallic state. — When a solution of potassic di-iridic chloride is pre-
cipitated by a small quantity of caustic potash with exclusion of air,
yellowish-green di-iridic hexahydrate, 'Ir^'aHog, is obtained. It is solu-
ble in excess of alkali, and oxidizes on exposure to air.
Iridic oxide, IrO,. — When moist di-iridic hexahydrate undergoes
spontaneous oxidation by exposure to air, it is converted into iridic hy-
drate, IrHo^. The same compound is obtained by precipitating iridic
chloride with caustic alkali. It forms an indigo-blue powder, which is
not atacked by dilute acids with the exception of hydrochloric. When
carefully heated in a current of carbonic anhydride it is converted into
iridic oxide, which is thus obtained as a black powder insoluble in acids.
598 INOBQANIC CHEMISTRY.
OXY'SALTS OF IRIDIUM,
Theoe are comparatively unimportant. Salts of the unknown iridoiut oxide, ZrO,
have been prepared ; thus a todie iridoua sulphiU of the formula S404Na<i,Iro'",K50n.
is known. An oxy-8aIt corresponding to di-iridic trioxide is di-iridie irisulphUf,
S/>8(''Ir'^%Oj)",f)OH^ which is obtained aa a crystalline powder by dissolving the
hexy hydrate in sulphurous acid and evaporating. No iridic ozy -salts are known.
Ammonium compounds of iridium corresponding with those of platinum have been
prepared.
COMPOUNDS OF IRIDIUM WITH SULPHUR.
Iridmi^ sulphide, XxS^^y lm obtained as a lustrous metallic mass when the metal is
heated in the vapor of sulphur.
IH' iridic trisulphidty ^Ir'^'^'^s, is obtained as a brown precipitate when sulphuretted
hydrogen is passed into the solution of a di-iridic salt.
Iridic mlphide, IrS''''^ — This compound is prepared by beating the finely divided
metal with sodic carbonate and sulphur, extracting the mass with water. The iridic
sulphide remains as a black powder.
General Properties and Reactions of the Compounds of
Iridium. — A not too dilute solution of an iridic salt yields with am-
vwnic chloride a dark-red crystalline precipitate of amnionic iridic
chloride. From the solution of an iridic salt svlphureti^d hydrogen
precipitates brown di-iridic trisulphide ('Ir'^jS^^) with separation of
sulphur. Ferrous ^^/ia/6 decolorizes the solution of an iridic salt;
zinc precipitates black spongy iridium.
BHODIUM, Eh.
Atomic weiglii = 104. Molecular weight unknown, 8p.gr, 12.1. Atom-
icity " and *^, also a pseudo-triad. Evidence of atomicity :
Rhodous oxide, Rh"0.
Dirhodous hexachloride, • . 'Bh^'^Cl^.
Dirhodous trioxide, Ttth'^'jOj,
Rhodic hydrate, Rh^'Ho^.
Rhodic oxide, Rh^'O^
History. — Rhodium was discovered by Wollaston in 1804, aud
afterwards investip^ated more thoroughly by Berzelius and Claus.
Occurrence, — The metal occurs in small quantity in platinum ore.
Extradition, — The only source of rhodium is the platinum residue
already referred to. The mixture of platinum, palladium, and rhodium
precipitated by hydrogen in the process of separating the platinum
metals isredissolved in aqua-regia, and the platinum is precipitated by
potassic chloride. After expelling the excess of acid, the rhodium may
be precipitated as sodic dirhodous sulphite^ SgOgNao^CRh'^'aO^)^, by boil-
ing the dilute solution with hydric sodic sulphite. The metal may be
precipitated by reducing ageutis from the solutions of its salts and fused
into a coherent mass in the oxyhydrogen furnace.
Properties. — Rhodium is a malleable metal, resembling aluminium
in color and lustre. Its fusing- point lies between that of platinum
and that of iridium. When heated in air it undergoes superficial oxida-
tion. Pure rhodium is insoluble in all acids and in aqua-regia. If,
however, it is alloyed with an excess of platinum, or with zinc, lead, and
other oxidizable metals, aqua-r^ia dissolves it.
CJOMPOUNDS OF RHODIUM. 599
COMPOUND OF RHODIUM WITH CHLORINE.
Dirhodic hexachloride, 'Rh'^jClg. — This is the only halogen compound
of rhodium which is known with certainty. The anhydrous chloride
is formed when the finely divided metal is heated in chlorine. It is
an insoluble rose-red powder. By dissolving dirhodic hexahydrate in
hydrochloric acid and evaporating the solution, a dark-red hydrated
chloride is obtained, which on heating is converted into the anhydrous
chloride. Dirhodic hexachloride forms double salts with the alkaline
chlorides.
COMPOUNDS OF RHODIUM WITH OXYGEN.
Ehodous oxide, . BhO. Rh=0.
O
Dirhodic trioxide, 'Rh'^'^Oj. Rh— Rh.
II II
O O
Rhodic oxide, . RhOj. 0=Rh=0.
Rhodous oxuhy BhO. — This compound is formed with incandascence
when the hexahydrate is heated. It is a dark-gray powder, insoluble
in acids.
Dirhodic trioxide, 'Rh'^'j^sj ^s obtained as a gray spongy lustrous mass
by heating the nitrate. It does not dissolve in acids. — Dirhodic hexa-
hydrate is prepared by the action of hot caustic potash upon sodic di-
rhodic chloride, 'Rh'''2Cle,6NaCl,30H2. It is a brownish-black gela-
tinous precipitate, difficultly soluble in acids. By the action of caustic
soda upon the double chloride in the cold, yellow crystals of the hy-
drate 'Rh'"jHog,20H2 are obtained. These dissolve readily in acids.
Rhodic oxide, BhOj, is obtained by repeatedly fusing finely divided
rhodium with caustic potash and nitre. It is a brown powder, insoluble
in acids.
OXY'SALTS OF RHODIUM,
Thes€ are derived from dirhodic trioxide.
Dirhodic niiratey NgOi2(''Rli'''^a^6^**' is nncrystallizable.
Dirhodic sulphate^ SjOj('Rh'''V^«)'Sl-OHa, is obtained as a yellow soluble crystal-
line mass by evaporating the solution of the yellow hydrate in sulphuric acid.
Dirhodic stdphite, S,03(''Rh^''',<)6)'',60Ha, remains as a yellow, difficultly crystalliza-
able mass when the solution of the yellow hydrate in sulphurous acid is evaporated.
Ammonium compounds of rhodium have been prepared.
COMPOUND OF RHODIUM WITH SULPHUR.
Rhodous sulphide, RhS^^. — This compound is formed as a fused metallic mass when
rhodium is heated in the vapor of sulphur.
General Properties and Reactions of the Compounds of
Rhodium. — The solutions of the dirhodic salts are sometimes rose-
colored, sometimes yellow. Cavstio alkalies give a yellow precipitate,
^hich, on heating the liquid with the precipitate^ becomes brownish-
600 INORGANIC CHEMISTRY.
black, and then consists of dirhodic hexahydrate. Sulphuretted hydro-
gen trnd amnionic sulphide give, after protracted action aided by heat, a
brown precipitate, probably a dirhodic trisulphide ('Rh'"2S"3). Potable
iodide precipitates sparingly soluble yellow dirhodic hexioJide. Zinc
precipitates black metallic rhodium.
/
OCTAD ELEMENTS.
OSMIUM, Os.
Atomic weight =198.6? Molecular weight unknown, Sp. gr. 22.477.
Atomicity ^^, *',/*, and ^*", also a pseudoAriad. Evidence of aiami-
city:
Osmous oxide, 0s"O.
Diosmic trioxide, 'Oa^'jOj.
Osmic chloride, Os«^Cl^.
Potasaic osmate, Os^*02Ko2.
Osraic peroxide, Os^""©^.
Hidory, — Osmium was discovered, in 1804, by Smithson Tennant.
OccufTence. — It occurs alloyed with iridium, in the ores of platinum.
This alloy, known as o^wi/ridiuTn, remains behind when theoreistreatal
with aqua-regia.
Extraction, — If in the preparation of iridium (p. 695) the mixture
of the finely divided platinum metals with baric chloride be heated in
a current of moist chlorine, the greater part of the osmium is volatilized
a«5 osniic peroxide, and may be condensed in a cooled receiver. The rest
of the osmium may be recovered if the solution containing the chlorides
of the platinum metals, which remains after the precipitation of the
barium in the above operation (p. 595), be mixed with excess of nitric
acid and distilled. The aqueous distillate contains the asmium as per-
oxide. On adding to the solution of the peroxide ammonia and am-
rnonic sulphide, the osmium is precipitated as osmic persulphide, OsS'V
This is mixed with sodic chloride and heated in a slow current of
chlorine. On extracting with water, a solution of sodic osmic chloride,
OsCl4,2NaCl, is obtainecl, from which on the addition of amnionic
chloride the osmium is precipitated as ammonic osmic chloride,
OsCl^,2NH^Cl. When this is ignited in a covered crucible, metallic
osmium is obtained as a spongy mass.
By fusing spongy osmium with tin, and dissolving the tin with
hydrochloric acid, osmium is obtained in crystals.
Properties. — Osmium is not fusible at the highest temperatures,
though it is volatile when heated to the fusing-point of iridium. Heated
in air it burns, forming: osmic peroxide, and if a quantity of finely
divided osmium be ignited at one point, the ignition is propagated
throughout the mass. Aqua-regia also oxidizes the finely divided
metal to peroxide. Crystallized osmium forms cubes. In this con-
dition it feas asp. gr. of 22.477, and is therefore the heaviest substance •
known.
COMPOUNDS OF OSMIUM. 601
COMPOUNDS OF OSMIUM WITH CHLORINE.
Diosmic hexachloride, 'Os^'aClg, is known only in the form of its
double chloride. Potassio diosinic chloride, 'Os"'2d5,6KCl,60H2,
forms dark-red crystals.
Osmtc chloride^ OsCl^, is obtained as a red sublimate when the metal
is heated in dry chlorine. It dissolves in water yielding a yellow so-
lution, which gradually deposits lower oxides of osmium, and becomes
colorless. The solution then contains osmic peroxide and hydrochloric
acid. Osmic chloride forms double salts.
COMPOUNDS OF OSMIUM WITH OXYGEN.
Osmous oxide, . OsO. Os=0.
O
Diosmic trioxide, 'Os'^'aO,. Os— Os.
II II
O O
Osmic oxide, . OsOg. 0=0s=0.
O
II
Osmic peroxide, . OsO^. 0=0s=0.
II
O
Osmousy)xidey OsO, is obtained as a grayish-black powder, insoluble
in acids, by heating a mixture of osmous sulphite, SOOso", with sodic
carbonate, in a current of carbonic anhydride.
Diosmic trioxide, 'Oa'^jOg, is prepared by heating potassic diosmic
chloride with sodic carbonate. It is a black powder, insoluble in acids.
Osmic oxide, OsOj, is obtained in a similar way from potassic osmic
chloride, ObC14,2KC1. Thus prepared it forms a grayish-black pow-
der; but by heating osmic hydrate in a current of carbonic anhydride,
it is obtained in copper-colored masses, possessing a metallic lustre. —
Osmic hydrate, OSH04, is formed as a black precipitate when reducing
agents, such as alcohol, are added to the aqueous solution of osmic per-
oxide.
Osmic peroxide {Osmic anhydridey Osmic acid), OsO^. Molecular
volume i I L — This remarkal)le compound is formed when the finely
divided metal, or any of the lower oxides of osmium, is heated iu air
or oxygen, or dissolved either in nitric acid or in aqua-regia. If the
finely divided metal has l)een previously ignited with exclusion of air,
these solvents are without action upon it. Osmic peroxide forms long
colorless prisms or needles, with a powerful and irritating odor. Thiy
sublime even at ordinary temperatures, and when gently heated fuse to
a colorless liquid, which boils without decomposition at 100° C. Osmic
peroxide dissolves in water, yielding a neutral solution with a powerful
odor and a burning taste. Alcohol and ether precipitate from the solu-
tion osmic hydrate. Sulphurous anhydride colors the solution in turn
602 INORGANIC CHEMISTBY.
yellow, brown, green, and finally blue, at which point the liquid con-
tains osnioas sulphite. The vapor of osmic peroxide, even when lai^ly
diluted with air, attacks the lun^, producing dangerous inflammation
of the mucous membrane. It also acts violently upon the eyes, and
may even cause blindness, owing to the deposition of a film of metallic
osmium upon the eye. Brought in contact with the skin, onmic perox-
ide produces a painful eruption, which is very difficult to heal.
OXYSALTS OF OSMIUM.
These are few in number, and unimportant
Osmous sulphitfy Bi^Osu^^, is obtained by passing snlphnrous anhydride into a solu-
tion of osmic peroxide until the solution assumes a blue color, and then addin^^ s^xlic
sulphate. The osmium salt, which is sparingly soluble in a solution of sodium sul-
phate, is deposited as a dark-blue precipitate. — Hydric potassie otmous gulphite^
Bs(\HojKo^{h{o^\AOlitf is obtained as a rose-red precipitate oy heating a solution of
pota«sic diosmic chloride (p. 601) with potassic sulphite.
The Osmates.
Neither osmic acid, OaOjHo,, nor its anhydride, OsOj, is known;
but some of the salts of cxsmic acid have been prepared.
Potassic osmaie, 0802Ko2,20H, is obtained by adding alcohol or po-
tassic nitrite to a sufficiently concentrated solution of the peroxide in
potassic hydrate. The peroxide is reduced and unites with the alkali
to form ]>otassic osmate, which gradually separates as a dark-red cr}'s-
talline powder.
Baric osnude, OaOgBao", forms black lustrous prismatic crystals.
COMPOUNDS OF OSMIUM WITH SULPHUR.
The sulphides of osmium have been but little studied. Osmium combines with sul-
phur when heated in its vapor, and sulphuretted hydrogen precipitates osniinm as
sulphide from its solutions. From solutions containing osmium in its lower stages of
oxidation a yellow sulphide is precipitated ; whilst solutions of the peroxide give a
brown precipitate of osmic permlphitJef Os8^^4.
General Propertfes and Reactions op the Compounds op
Osmium. — Osmium and its compounds are best characterized by the
readiness with which they yield the volatile peroxide, recognizable by
its powerful odor, AH osmium compounds when boiled with nitric
acid give oflf* vapors of the peroxide.
BUTHENIUM, Bu.
Atomic weight = 104, Molecular weight ^lnkno^on. 8p, gr, 12.26.
Atomicity ", *', ^*, and ^"*, also a pseudo-triad and a pseudo-heptad.
Evidence of atomicity :
Ruthenous oxide, Ru"0.
Diruthenic hexachloride, Tttu^'jCle.
Ruthenic chloride, . * Etf^Cl^,
Potassic ruthenate, Ru'^^jKo,.
Potassic perruthenate, 'Ru^",08Ko,.
Ruthenic peroxide, Eu^*^^.
COMPOUNDS OF RUTHENIUM. 603
HiMory. — Ruthenium was first directly recognized as a new metal
by Glaus, in 1846.
Occurrence, — Ruthenium is found alloyed with the other platinum
metals in platinum ore. Combined with sulphur it occurs as the min-
eral faurite, 'Ru'",S"3.
Extraction. — The insoluble residue of ruthenium obtained in the
preparation of iridium (p. 596) may be purified by fusion with a mix-
ture of potassic hydrate and nitre. On treating the fused mass with
water the ruthenium goes into solution as potassic ruthenate. The
orange- red solution is boiled with an excess of nitric acid until the color
has disappeared; in this way the ruthenium is precipitated as diru-
thenic trioxide, which by ignition in a graphite crucible is converted
into the metal. It may be fused into a coherent mass in a lime cruci-
ble by means of the oxyhydrogen flame.
Properties. — Ruthenium is a white metal, hard and brittle V\ke irid-
ium, and still more difficultly fusible than this metal. The finely
divided metal is oxidized when heated in air. Aqua-regia attacks it
only very slowly.
COMPOUNDS OF RUTHENIUM WITH THE HALOGENS.
Ruthenous chloride, BuCl,, is prepared by gently heating the finely
divided metal in a current of chlorine. It is a black crystalline pow-
der, insoluble in acids.
DinUhenic hexachloride, Bu^'^Clg, is obtained as a yellow crystalline
deliquescent mass by dissolving diruthenic hexahydrate in hydrochloric
acid and evaporating to drynea<». It forms double chlorides with the
chlorides of the alkalies: 'Eu'"2Cl5,4KCl, and 'Ru'",Cle,4NH,Cl.
Diruthenic heziodidey ^"Rn^^^l^, ifl obtained as a black powder when potaesic iodide
is added to a solution of the chloride.
Ruthenic chloride, RuCl^, is obtained as a reddish-brown mass by
dissolving ruthenic hydrate in hydrochloric acid and evaporating. It
forms with the chlorides of the alkalies double chlorides, corresponding
with thase of platinic chloride. The potassium compound has the form-
ula EuCl4,2KCl, and crystallizes in red regular octahedra.
COMPOUNDS OF RUTHENIUM WITH OXYGEN.
Ruthenous oxide, . BuO. Ru=0.
O
Diruthenic trioxide, 'Ru'^jOj. Ru
n — Ru
Eutbenic oxide, • EuOj.
Buthenio peroxide, RuO^.
O O
0=Ru=0.
0
II
O— Ru— O.
1
O
604 INORGANIC CHEMISTRY.
Rvjthenous oxide, BuO, is obtained by calcining ruthenous chloride
with sodic carlK)nate and extracting the cooled mass with water, when
the oxide remains as a dark-gray powder insoluble in acids.
Dindhenic irioxidey 'Ru'^'jOj, is formed when finely divided ruthe-
nium is heated for a considerable time in contact with air. It is a
bluish-black powder, whicli does not part with ite oxygen even at a white
lieat. Acids are without action upon it. — JXruthenie hexahydraie,
'Eu'"jHo^. is obtained asadark-browd precipitate when a caustic alkali '
is added to a solution of diruthenic hexachloride. It dissolves in acids,
yielding a yellow solution.
RiUhenic oxidcy BuOj, is prepared by heating ruthenic sulphide in
air or by heating finely divided ruthenium very strongly in a current
of air. In the latter ca«e the oxide sublimes in green quadratic pyra-
mids, isomorphous with those of tin-stone and rutile. — Ruthenic hydrate,
EuHo^jSOHj, is a dark-red powder obtained l)y precipitating solutions
of ruthenic salts with caustic alkali. It deflagrates on heating.
Ruthenic peroxidey BuO^. — In order to prepare this compound a so-
lution of )>otassic ruthenate {infra) is introduced into a retort and a
rapid current of chlorine is passed through the liquid. In the oxida-
tion which oc<*urs considerable heat is evolved, and the ruthenic perox-
ide which is formed volatilizes in the current of chlorine, and condenses
in the neck of the retort and in the well-cooled receiver as a yellow
crystalline mass consisting of rhombic prisms. It is purified by fusion
under a small quantity of water. The crystals fuse at 40° C. (104° F.)
to a liquid which boils a little above 100° C yielding a golden-yellow
vapor with an extremely irritating odor. Tlie experiment of distilling
the i)eroxide alone ought never to be performed, as the heated substance
is apt to decompose with violent explasion. The com{K)und ought to
be volatilized as above at a lower temperature in a current of some gas.
Moiht ruthenic peroxide is rapidly decomposed with evolution of oxy-
gen and formation of diruthenic hexahydrate ; the dry substance is
more stable. It is sparingly soluble in water.
OXY-SALTS OF RUTHENIUM, -
These are unimportant and have been little studied.
Hvtheni/i sulpkaiej 81O4RU0'', is obtained by oxidizing ruthenic sulphide with nitric
acid and evaporating the solution. It is a deliquescent powder resembling in ap|)ear-
ance mosaic gold,
RUTHENATES AND PERRUTHENATES.
Two oxides of ruthenium — ruthenic anhydride, BuOj, and perni-
thenic anhydride, Bu^O^ — intermediate between ruthenic oxide and
ruthenic peroxide, are known only in the form of the salts of their
acids.
Polassic ndhenate, BuOsKo^, is formed when finely divided ruthe-
nium is fused with a mixture of caustic potash and nitre or potassic
chlorate. It di&solves in water, yielding a reddish-yellow solution with
an astringent taste. The solution colors organic substances black.
Potassic jyerruthenate, 'Bu'",06Ko2, is formed when chlorine acts upon
the pre<:ediiig salt in aqueous solution :
LEAD 605
2Ru02Koa
+
Cl,
= 'Ru"'AKo,
+ 2KC1.
Potassic
Potassic
Potassic
ruthenate.
perruthenate.
chloride.
The dark-green solution deposits small black crystals isomorphous with
potassic permanganate.
AmmoDium compounds of ruthenium have been prepared.
COMPOUND OF RUTHENIUM WITH SULPHUR.
IHruthenie trimlphide^ ^Ru^^^S^^y — This compound occurs as the mineral laurite in
some platinum ores. It crystalizes in octahedra. A part of the ruthenium is generally
replaced by osmium. The same compound is obtained as a dark metallic powder by
precipitating solutions of ruthenium salts with sulphuretted hydrogen and drying the
precipitate in a current of carbonic anhydride.
Genekal Properties and Reactions of the Compounds op
Ruthenium. — Solutions of ruthenic salts yield with potassic chloride
and amnionic chloride dark-red crystalline precipitates of the corre-
sponding double chlorides. Sulphuretted hydrogtn fjr&t changes the
color of the liquid to blue, and afterwards precipitates brown diruthenic
trisulphide. Zinc also changes the color of the solution to blue, and
afterwards decolorizes it with precipitation of black metallic ruthenium.
The formation of a volatile peroxide (p. 604) is common to this metal
and osmium.
CHAPTER XXXIX.
TETRAD ELEMENTS.
Section V.
LEAD, Pb.
Atomic weight = 206.5. Molecular weight unhnown, Sp. gr. 11.37.
Fiises at 326° C. (619° F.). Boils at a white heat. Atomicity " and'\
Sometime also a pseudo-triad. Evidence of atomicity :
Plumbic chloride, Pb^CIj.
Plumbic oxide, Pb"0.
Plumbic tetrethide, Ph'^Et^.
Plumbic peroxide, Pb*'Oj.
Diplumbic hexethide, ........ Pb^'jEtg.
History. — Lead has been known from the earliest historical times.
The alchemists, who believed that a connection existed between the
metals and the planets, designated lead Satwm, a name which is still
preserved in the expression " saturnine poisoning,'' sometimes applied
to poisoning by lead.
Occurrence. — Lead occurs widely distributed in nature. Native lead
has been found in small quantities in volcanic tufa. The chief ore of
606 INORGANIC CHEMISTRY.
lead IS the sulphide, or galena^ PbS". Other lead minerals are the
carbonate or cenuifnte, OOPbo", and the sulphate or anglefdte, SO^Pbo''.
It also occurs as phosphate, arsenate, chromate, and molybdate. Eng-
land and Spain furnish the chief supply of lead. In England the
most important mines are those of Cornwall and Cumberland.
Extraction. — Lead is chiefly obtained from galena. This ore is first
roasted in a reverberatory furnace, by which treatment a portion of the
sulphide is converted into oxide or sulphate. The temperature of the
furnace is then raised, when the oxide and sulphate react with the unal-
tered sulphide, and a mutual reduction to metallic lead occurs, with
evolution of sulphurous anhydride.
PbS" + 2PbO = 3Pb + 80,.
Plumbic Plumbic Sulphurous
sulphide. oxide. anhydride.
PbS" + SOjPbo" = 2Pb + 2SO,.
Plumbic sulphate.
The above process can be employed only with ores of lead which are
free from other metallic sulphides. In the case of ores containing py-
rites, zinc-blende and other impurities, the jyrecipitation process is em-
ployed. In this process the ore is reduced l>y fusion with cast iron,
less of this metal being employed than is required to reduce the whole
of the galena present. The iron combines with the sulphur to form
ferrous sulphide, which rises to the surface with the other sulphides,
w^nlst the molten lead sinks to the bottom of the furnace, and can be
drawn ofl;
The lead obtained by either of the alwve processes always contains
silver. This is profitably extracted by Pattinson's process of des?ilveri-
zation (p. 448). The oxide obtained in cupelling the portions of lead
rich in silver is reduced by heating with carbon in a low blast-furnace.
Lead generally contains antimony, tin, and other impurities, the
presence of which renders the metal hard. The process of removing
these impurities, known as softening or improving the lead, consists in
partially oxidizing it in a shallow cast-iron pan on the bed of a rever-
beratory furnace. The impurities are oxidized more readily than the
lead, and pass into the layer of oxide which forms on the surface of the
metal.
Properties. — licad is a bluish- white metal, lustrous on the freshly cut
surface. It is very soft and may be cut with a knife or scratched with
the nail. It may be rolled into sheets of foil, but, owing to its want of
tenacity, cannot be drawn into thin wire, though it may be formed into
wire by pressing through a narrow opening. I^ead contracts in solidi-
fying, and objects cast in this metal frequently contain cavities. It may
be obtained in regular octahedra by fusing a quantity of the metal,
allowing it partially to solidify and then pouring off the liquid portion.
It may also l>e obtained in the form of an aggregation of lustrous
laminae (lead-tree) by the electrolysis of solutions of its salts, or by
suspending a piece of zinc or iron in such a solution. A clean and
bright surface of lead speedily tarnishes on exposure to air, owing to
oxidation. The fused metal becomes covered with a black film of sub-
COMPOUNDS OP LEAD. 607
oxide, which at a higher temperature is converted into yellow oxide.
Pure water is without action upon lead as long as air is excluded, but
in presence of air plumbic hydrate is formed, which is somewhat solu-
ble in water. The presence of minute quantities of carbonates and
phosphates in water greatly diminishes this solubility and prevents the
corrosion of the lead. These facts are of great importance from a sani-
tary point of view, owing to the universal employment of lead pipes
for conveying a supply of water, and the poisonous character of the
compounds of lead. Fortunately almost all natural waters contain
carbonates or phosphates, and the lead is thus protected from corrosion.
Dihydrlc calcic dicarlwnate — the solution of calcic carbonate in carbonic
acid — ^an impurity present in most natural waters, is especially eflfica-
cious in this respect, causing a film of insoluble basic plumbic carbo-
nate to be formed upon the isurface of the lead. Basic plumbic carbonate,
00(OPb"Ho)3 dissolves in pure water only to the extent of a sixtieth
of a grain to the gallon : when a solution of plumbic hydrate in dis-
tilled water is exposed to the air carbonic anhydride is absorbetl and
the basic carbonate is deposited in silky crystals. Lead resists to a great
extent the action of sulphuric and hydrochloric acids, but dissolves
readily in nitric acid.
Uses, — The ease with which lead may be worked and its power
of resisting the action of air, moisture, and acids, have led to its
employment for various purposes: thus it is used for wat*^r-pipes, for
roofing houses, and in the construction of sulphuric acid chambers.
Rifle bullets and small shot are also made of this material, about 0.5
per cent, of arsenic being added in the latter ca«e in order to aid the
metal in assuming ih^ spheri(«il form. Various alloys of lead are also
used in the arts. Type metal is an alloy of 2 parts of lead, 1 of anti-
monv and 1 of tin. Plumbei'^s solder is an alloy of lead and tin
(p. 323).
COMPOUNDS OF LEAD WITH THE HALOGENS.
Plumbic chloride, PbCIa. Molecular volume I 1 L — This com-
pound has been found in the crater of Vesuvius as the mineral cotun-
nite. Hydrochloric acid attacks lead only very slowly, but hot aqua-
regia dissolves it readily, depositing crystals of the chloride on cool-
ing. It is best prepared by dissolving the oxide or the carl)onate in
hydrochloric acid. It is also preci|>itated as a crystalline powder when
hydrochloric acid or a soluble chloride is added to a not too dilute
solution of a lead salt. — Plumbic chloride crystallizes from water in
long, colorless, lustrous prisms. It is soluble at ordinary temperatures
in 130 parts, at 100^ C. in less than 30 parts of water. When fused
with exclusion of air, it solidifies on cooling to a white horn-like mass,
but if air be admitted, it is converted into oxychloride. Oxychlorides
of varying composition are obtaintnl by fusing; together plumbic oxide
and plumbic chloride, or by precipitating a solution of plumbic chloride
with an insufficiency of lime-water or ammonia. Those which are rich
in chlorine are white; those which are rich in oxygen are yellow.
Some of these compounds are employed as pigments. Cosset yellow is
608 INORGANIC CHEMISTRY.
an oxy chloride obtained by beating plumbic oxide with amnionic chlo-
ride. A white oxychloride, prepared by precipitating plumbic chloride
with lime-water, is employed as a substitute for white lead.
Plumbic perchloridef PbCl4, exiKtfl only in solution. When plumbic peroxide is
dissolved in well-cooled concentrated hyorochloric acid, a stronglj ozydizing liquid,
which evolves chlorine on heating, is obtained.
Ptumbie bromidefThBTf, rei<en)bles the chloride.
Plumbic iodide, Pblj. — This compound is precipitated as a crystal-
line yellow i>owder when a soluble iodide is added to a solution of a
lead salt. It is almost insoluble in cold, but dissolves slightly in hot
water, yielding a colorless solution, which on cooling deposits the iodide
in yellow laminse. Plumbic iodide, when heated, becomes first red,
then black, and finally fuses to a dark-colored liquid, which on cooling
solidifies to a yellow crystalline mass. It dissolves in solutions of the
alkaline iodides to form double salts.
Plumbic jluorifh, PbF,. is precipitated as a white almost insoluble powder, when
hydrofluoric acid is added to the solution of a lead salt.
COMPOUNDS OF LEAD WITH OXYGEN.
( Pb ^\
Plumbous oxide, . . . ^ Pb^' I /^*
Plumbic oxide, . . . PbO. Pb=0.
Diplumbic trioxide, . . PbOPbo". 0=Pb
8>
r-s>pb
Triplumbic tetroxide, . PbPbo'V p'b<f
Plumbic peroxide, . . Pb02. 0=Pb=0.
Plumbous oxide y 'Pb'gO, is best prepared by heating plumbic oxa-
late to 300° C. with exclusion of air:
{^^' -
= {IJO + 300, + OO.
Plumbic
Phimbous Carbonic Carbonic
oxalate.
oxide. anhydride. oxide.
It is a black powder. When lead is fused in air, avoiding tcx) high a
temperature, the same compound is formed as a gray film on the sur-
face of the metal. When heated to redness with exclusion of air,
plumbous oxide is decomposed into plumbic oxide and metallic lead ;
if air is admitted, it burns like tinder and is totally converted into
plumbic oxide. It slowly undergoes the same conversion when exposed
to the air in a moist state. With acids it yields plumbic salts with
separation of metallic lead.
CX)MPOUNDS OF LEAD. 609
Plumbic oxide (Litharge), PbO. — This compound 13 prepared by
heating lead in air or by igniting plumbic carbonate or nitrate. It is
obtained as a by-product in various metallurgical operations — notably
in Pattinson's process for the dasilverization of lead (p. 448) — Plumbic
oxide is a yellow powder, which when strongly heated fuses, and on
cooling solidifies to a yellow micaceous mass, sometimes with a shade
of red. It is slightly soluble in water, to which it imparts an alkaline
reaction. Acids dissolve it, forming the various salts of lead. Car-
bonic oxide at 100° C, and hydrogen at 310° C, reduce it to metallic
lead. Plumbic oxide absorlis carbonic anhydride from the air. — Litharge
is employed in the preparation of various salts and pigments of lead, in
the manufacture of flint-glass, and in glazing earthenware.
Diplumbic oxydihydraie, PbjOHog, is precipitated when ammonia is
added in excess to a solution of plumbic nitrate. Caustic alkalies may
be substituted for ammouia, but in this case an excess of the precipitant
must be avoided, as this would dissolve the plumbic hydrate. It is a
white bulky precipitate, difficult to obtain free from basic salts. It is
slightly soluble in water. — The hydrate PbHo^ has not been pre-
pared.
DipluwhiG trioodde, PbOPbo", is precipitated as a reddish -yellow
powder, when sodic hypochlorite is carefully added to a solution of
plumbic hydrate in caustic soda. It is decomposed at a red heat into
plumbic oxide and oxygen. Hydrochloric acid dissolves it completely
in the cold, yielding a yellow liquid, which speedily evolves chlorine
and then contains plumbic chloride. Oxy-acids take up half the lead
of this oxide to form plumbic salts, whilst the other half remains
undissolved as plumbic peroxide.
Triplumbic tetroxide, PbPbo"2. — This compound appears to be
contained in red-lead or mmiwm, which is, however, a substance of
varying composition, interme<liate between plumbic oxide and diplum-
bic trioxide. When finely divided litharge or plumbic carbonate is
heated in air for twenty-four hours to dull redness, it is converted into
a heavy scarlet crystalline powder. It becomes dark when heated, but
recovers its original color on cooling. At a red-heat it is decomposed
like the trioxide into plumbic oxide and oxygen. Li its behavior
towards acids it also resembles that compound. — Red-lead is employed
as a pigment, also for electrical storage batteries, and in the manufac-
ture of the finer sorts of flint-glass. For the latter purpose the excess
of oxygen which it contains serves to eflFect the combustion of organic
matters, and thus to prevent tlie reduction of the lead which would
cause the glass to blacken.
Plumbic peroxide {Puce-colored oxide of lead), PbOj, is most
readily obtained by treating diplumbic trioxide or red-lead with nitric
acid, when the peroxide remains as a dark-brown amorphous powder.
The same compound is formed when chlorine is passed into an alkaline-
solution in which plumbic hydrate is suspended. It is also deposited
on the positive electrode when the solution of a lead salt is electrolyzed.
It occurs native in black six-sided prisms as plaUnerite. At a red heat
it is decomposed like the other higher oxides of lead into plumbic
oxide and oxygen. When introduced into an atmosphere of sulphur-
610 INORGANIC CHEMISTRY.
OU8 anhydride, it is converted with incandescence into plumbic sul-
phate :
PbO, + 8O2 = SO,Pbo".
Plumbic Sulpharous Plumbic
peroxide. anhydride. sulphate.
Sulphuric acid dissolves it with evolution of oxygen and formation of
plumbic sulphate; hydrochloric acid dissolves it with evolution of
chlorine and formation of plumbic chloride; nitric acid is without ac-
tion upon it. — A porous mass of plumbic peroxide, generated by elec-
trolysis, forms the negative plate in the Plante secondary battery and
other electrical storage batteries constructed on the same principle
(see p. 106).
0XY-8ALTS OF LEAD,
Plumbic nitrate, < Pbo", is best prepared by dissolving litharge
in an excess of nitric acid and evaporating to the crystallizing point.
The salt forms colorless octahedral crystals, soluble in twice their weight
of cold water, much less soluble in water containing nitric acid. It i^
almost insoluble in alcohol. At a red heat it fuses and is decomposed
into plumbic oxide, nitric peroxide, and oxygen. When thrown upon
red-hot charcoal, it deflagrates. It is employed as a mordant in dyeing
and calico-printing. — A boiling aqueous solution of plumbic nitrate
di&solves plumbic oxide, and on cooling deposits acicular crystals of
plumbic nitrate hydrate^ N03(OPb"Ho). Other basic nitrates, of the
forrauJjB N303Pbo"(OPb"Ho)3 and NPbo''3(OPb"Ho), are obtained by
precipitating solutions of the normal nitrate with ammonia.
(NO
Plumbic nilriU, i }^Ik)^',OHj. — This compound is most readily obtained by accurately
I NO
precipitating argentic nitrite with plumbic chloride and evaporating the solution
in vacuo over sulphuric acid. It forms soluble yellow prisms or laminae. If the
solution be boiled, nitrogen is evolved and a basic nitrite is formed. If a solution
of plumbic nitrate in fifty times its weight of water be boiled with one and a half parts
of lead for twelve hours, the liquid deposits on cooling flesh-colored needles of
dipluvibic nitHte hydraUj NPbo'^^lOPb'^Ho). If carbonic anhydride be passed
into the solution of this salt, three-fourths of the lead is precipitated as carbonate,
and the liquid contains the normal nitrite. If a solution of plumbic nitrite
be digested with metallic lead for a few hours at a temperature of 75^ C. (167® F.), a
yellow liquid is obtained, which on coolinj? deposits lustrous yellow tabular crystal**
(NHojPbo'^
of dihydric diplumbic nitrate nitHte^ i Pbo^^ , — a salt formerly termed " basic hypo-
(no
nitrate of lead." Various other basic nitrites of lead have been prepared.
Plumbic carbonate, OOPbo", occurs native as the mineral ceruB-
site in lustrous transparent rhombic crystals, isomorphous with those
of arragonite. The same salt is obtained as a white crystalline pre-
cipitate by pouring a solution of plumbic nitrate into a solution of
sesquicarbonate of ammonia. The carbonates of sodium and jiotassium
cannot be employed for this purpose, as these precipitate mixtures
COMPOUNDS OP LEAD.
611
of basic plumbic carbonates, the corapa<iition of which varies with the
coDceDtration and the temperature. White lead is a basic carbonate of
lead — triplumbio dicarbovale dihydraiCy nr)/oPh"TT^r ^"* ^^ '^
manufactured on a large scale as a pigment by one or other of the
following processes :
(1) Dutch Process. — This is the oldest process and yields the finest
product, but the operations are somewhat tedious. Glazed earthen-
ware pots are filled to a quarter of their depth with weak malt vinegar.
In each pot, above the surface of the liquid and resting on a wooden
support, a thin sheet of lead coiled into a spiral is placed vertically, or
a series of cast gratings is put into the pot, and the pot is covered with
a plate of lead. The pots are then embedded in spent tan-bark or
horse-dung on the floor of a shed. The first layer of pots is then cov-
ered with boards, and a second layer, arranged like the first and also
embedded in tan-bark or horse-dung, is built up over these, and so on
till the shed is full. The pile generally reaches a height of from 18 to
20 feet, and contains about 12,000 pots with from 60 to 60 tons of
lead. The action which takes place is as follows : The heat evolved
by the fermentation of the bark or dung volatilizes the acetic acid in
the vin^ar, which gradually in presence of the oxygen of air, which
for this purpose must have free access to the heap, converts the lead
superficially into basic plumbic acetate :
/OH,
\COHO
Acetic
acid.
+ 2Pb + Oj
= 2{??»
CO(OPb"Ho)-
Plumbic acetate
hjdrate.
The carbonic anhydride which is given off during the fermentation
then acts upon the basic acetate, converting it into basic carbonate
(white lead) and normal acetate:
6
/OH3
\\
0O(OPb''Ho)
Plumbic acetate
hydrate.
+ 2CO, =
+ 3
Carbonic
anhydride.
CH,
CH,
Plumbic
acetate.
CO(OPb"Ho)p. „
CO(OPb"Ho)^'^
Tri plumbic dicarbonate
dihydrate.
+ 20H,.
Water.
The normal acetate then reacts with a fresh portion of lead in presence
of oxygen and water, and regenerates the basic acetate :
/CH,
\CH,
Plumbic
acetate.
-f- Pb + O H- OH3
= 2{CH3
CO(OPb"Ho)-
Water.
Plumbic acetate
hydrate.
*612 INORGANIC CHEMISTBT.
The basic acetate is again acted upon by the carbonic anhydride as
above. In this way the process is theoretically continuous, and a small
(|uantity of acetic acid ought to suffice for the conversion of an un-
limited quantity of lead. In practice 100 lbs. of acetic acid are
required to convert 50 tons of lead into white lead. At the end
of from four to five weeks the conversion is nearly complete ; the pile
is taken to pieces and, on uncoiling the spirals, the white lead peels off
in flakes from the unaltered lead if any of the latter is left. The
crude product is ground while moist, and well washed to free it from
acetate.
(2) Thenard^s Process, — A solution of basic plumbic acetate of lead
is first prepared by boiling sugar of lead with litharge. The basic car-
bonate is then precipitated from this solution by passing in carbonic
anhydride. As a pigment, the product lacks opacity^ and is conse-
quently deficient in " Ixxly " or " covering power.
(3) Milner^s Process, — In this process, which yields good results,
an oxychloride of lead is converted into white lead by the action of
gaseous carbonic anhydride. A mixture of litharge, common salt, ami
water is ground for some hours. Into the mixture of caustic soda and
plumbic oxychloride thus obtained, carbonic anhydride is passed until
the liquid is neutral. At this point the operation must be interrupted,
otherwise the product will be spoiled.
White lead is a white amorphous powder. Its chief drawbacks are
its poisonous character, and the fact that it is blackened by sulphuretted
hycirc^en.
Plumbic sulphate, SOjPbo", occurs native as anglesite in trans-
parent rhombic crystals. It is obtained as a heavy white crystalline
precipitate when sulphuric acid or a soluble sulphate is added to the
solution of a lead salt. The precipitate is almost insoluble in water,
and still less soluble in dilute sulphuric acid ; but concentrated
sulphtiric acid dissolves about 6 per cent, of its weight of the sulphate.
It is also slightly soluble in dilute hydrochloric and in dilute nitric
acid, whilst sodic thiosulphate and many ammonia salts, particularly
the acetate and the tartrate, dissolve it readily. When plumbic
sulphate is boiled with a solution of amnionic sulphate, the liquid
deposits on cooling minute lustrous crystals of plumbic diammonic disul-
( SOjAmo
phateJ Pbo" . Pure water decomposes this salt with separation of
(SOjAmo
insoluble plumbic sulphate. By treating the normal salt with ammonia,
diplumbic sulphate^ SOPbo^jj is obtained.
Plumbic dithxonaU, | |^»Pbo'',40H^ or 1 3Ho*Pbo'^ is best prepared by Deutral-
izing a solution of dithionic acid with plumbic carbonate. It forms large colorless
hexagonal crystals, readily soluble in water.
Plumbic chromates. — See Chromates.
Pliimbk phosphates, — The nomud orlhophovphaU, P,0,Pbo^^s, is obtained as a white
amorphous precipitate when hydric diaodic phosphate is added to a solotion
of an excess of plumbic acetate. It is Insoluble in water and acetic acid, readily
COMPOUNDS OP LEAD. 613
soluble in nitric acid and canstic potash. — Hydrie plumbic phosphaie, POHoPbo''^,
is precipitiited by free phosphoric acid from a solution of plumbic nitrate as a
white crysialline powder. — A double phosphate and chloride of lead of the formula
PjOsPbo-'^^fQPb^^j occurs in nature in hexagonal crystals as the mineral pyromor-
phii^ It is isomorphous with apatite (p. 357).
Plumbic caraenateit. — These resemble the phosphates. A native double arsenate and
chloride corresponding to pyromorphite is the mineral, mimeUsUe,
AiHO,Plx)".(gjPb"),
which forms hexagonal crystals. Intermediate gradations between pyromorphite and
mimetesite occur, in which the phosphorus and arsenic replace each other isomor-
phonsly.
Plumbic borates. — When the solution of a lead salt is precipitated with borax, octo-
hydrie diplumbic hexabonUe, Bg08Ho8Pbo'''j, is formed. When this is warmed with
ammonia it is converted into a white powder of dihydric plumbic diborate^ BaOHoaPbo'''.
— By fusing together plumbic oxide and boric anhydride, a transparent vitreous mass
(Faraday's heavy glass) is obtained, which possesses a much higher refractive power
than flint-glass.
Plumbic silicate — No definite silicate of lead has been prepared. When silica is
fuped with plumbic oxide a vitreous mass is obtained. Plumbic silicate is one of the
constituents of flint-glass.
COMPOUND OF LEAD WITE SULPHUR.
Plumbic sulphide, PbS". — As the mineral galena this compound
forms the principal ore of lead. It occurs in regular cubes with a
blnish-gray color and a brilliant metallic lustre ; also in crystalline
masses. It possesses a very perfect cubical cleavage. The same com-
pound is formed as a leaden-gray crystalline mass when lead is fused
with sulphur, and as an amorphous black powder by precipitating a
solution of lead salt with sulphuretted hydrogen. It fuses without
decomposition at a bright red heat when air is excluded, and may even
be sublimed in a current of hydrogen or carbonic anhydride. In this
way it is obtained in small cubical crystals. When fused with access
of air it is converted into plumbic sulphate. It dissolves in hot con-
centrated hydrochloric acid with evolution of sulphuretted hydrogen.
Dilute nitric acid converts it into nitrate with separation of sulphur;
the concentrated acid oxidizes it to sulphate. — When sulphuretted
hydrogen, in quantity insufficient for complete precipitation, is passed
into a solution of plumbic chloride, red and yellow sulpho-chlorides of
varying composition separate out :
Cl—Pb— S— Pb—Cl,
and CI— Pb— S— Pb— Pb— S— Pb— CI.
General Properties and Reactions of the Compounds of
Lead. — The salb? of lead are mostly colorless. They have a sweet,
astringent, metallic taste, and are poisonous. When continually intro-
duced in minute quantities into the system, the salts of lead act as a
cumulative poison. The soluble normal salts with strong acid redden
litmus ; the basic salts, on the other hand, have an alkaline reaction.
Caudic alkalies and ammonia precipitate white basic salts of lead, solu-
ble in excess of caustic alkali, insoluble in ammonia. Sulphuretted
hydrogen and ammonic mlphide produce a black precipitate of plumbic
614 INORGANIC CHEMISTRY.
sulphide, which is converted by fuming nitric acid into white insoluble
plumbic sulphate, whilst dilute nitric acid converts it into soluble plum-
bic nitrate with separation of sulphur. SiUphurio acid and soluble sul-
phates precipitate plumbic sulphate, very sparingly soluble in water,
still less soluble in dilute sulphuric acid, insoluble in alcohol, but solu-
ble in solutions of various ammonium salts, such as the acetate and the
tartrate. Hydrochlwnc a/^id and soluble chlorides yield with not too
dilute solutions a white precipitate of plumbic chloride, soluble in hot
water. Potassic ohromate precipitates yellow plumbic chroraate ; po-
tassic iodide yellow plumbic iodide. All compounds of lead, when
heated with sodic carbonate or potassic cyanide uj3on charcoal in the
reducing flame, yield a malleable bead of metallic lead. The lead
compounds give a faint flame spectrum, containing lines in the green
and a characteristic spark spectrum.
CHAPTER XL.
HEXAD ELEMENTS.
Section II.
URANIUM, U.
U'
Atomic weight = 238.5. Molecular weight unknovm, Sp, gr. 18.7. At-
omicity ^"y ^', and ^"* ?* ; aUo a p8eudo4riad and a pseudo-pentad,
Etyidence of atomicity :
Uranous chloride, ......... U^'Cl^.
' "T'^CI,
Uranic oxide, U^^O,.
Diuranic decachloride, \ U'^n^'
History. — Klaproth first pointed out in 1789 the existence of anew
metal in the mineral pitchblende, and to this metal he gave the name
uranium. The metal was isolatetl by Peligot in 1842.
Occurrence. — Uranium is of rare occurrence, and is never found
native. Its chief ore is pitohblendey an impure uranous diuranate,
•jQ^ Uo*^. It also occurs as phosphate in uranium mica, and as carbon-
ate in liebigite.
Preparation. — Metallic uranium is obtained by the action of sodiara
upon uranous chloride, UCl^. The two substances are heated together in
* Uranium and molybdenum, which have been included in the hexadic group, ap-
pear to be capable of exercising octadic functions: thus in peroranic anhydride (UOi)
and molybdic persulphide (MoS^).
COMPOUNDS OP URANIUM. 615
a porcelain crucible with the addition of potassic chloride as a flux. The
|X)rcelain crucible is packed in powdered charcoal within a larger cru-
cible. The whole is heated, at first to redness, afterwards to a higher
temperature so as to fuse the uranium, which is thus obtained as a black
regulus.
Properties. — Metallic uranium has a silvery lustre, but tarnishes by
exposure to the air, becomingin course of time steel-blue, and ultimately
black. It is hard and somewhat malleable. When heated in air it
burns with scintillations, forming uranous diuranate. It does not de-
compose water even at its boiling-point. Acids readily dissolve it.
COMPOUNDS OF URANIUM WITH THE HALOGENS.
Diuranoxis hexachloride, 'U'^jCI^, is obtained in dark-brown needles
by heating uranous chloride to redness in a current of hydrogen. It
dissolves in water, yielding a purple solution, which rapidly absorbs
oxy^n from the air.
Uranous chloride^ UCI4, is prepared by heating a mixture of charcoal
and any of the oxides of uranium in a current of dry chlorine. It is
volatile at a red heat, and may be obtained by sublimation in dark-
green octahedra, possessing a metallic lustre. It is very deliquescent,
and hisses when thrown into water. Its solutions absorb oxygen from
the air, and turn yellow.
Uranotuhromidef UBr^, and urcoious jtmridt, UF4, have also been prepared.
Diuranic decachloride {Uranic peivtdchloride)^ 'U^jCIiq. — This com-
pound is formed along with uranous chloride in the preparation of
the latter compound, especially when the temperature is not permitted
to rise too high. As it is more volatile than uranous chloride, it collects
in a part of the tube further removed from the source of heat If the
current of chlorine be sufficiently slow, the decachloride forms black,
needle-shaped crystals. The compound rapidly deliquesces on exposure
to air. It begins to decompose at 120° C. into uranous chloride and free
chlorine.
COMPOUNDS OF URANIUM WITH OXYGEN.
Uranous oxide, ....
Uranic oxide {uranic an- 1
hydride), . . . . /
Peruranic anhydride, . .
•The remaining oxides of uranium — UjO^ = UOUo*', uranous ura-
note, and Vfi^ = tjq^Uo'^, urancms diuranate — are regarded as com-
binations of the two first oxides with each other.
TJO,.
o=u=o.
0
uo,.
II
o=u=o.
0
TJO,.
II
o=u=o.
II
0
616 INORGANIC CHEMISTRY.
Vranoua oxide, UO,. — ^This oxide remains when any of the higher
oxides of uranium, or uranic oxalate, is heated in a current of hydrogen.
It forms a brown |)owder, which when heated in air burns with form-
ation of uranous diuranate. Strong acids dissolve it, yielding green
solutions of uranouH salts, from which alkalies precipitate dark-brown
ill Kwu lent uranous hydrate, UHo^.
Uranio oxide ( Uranic anhydride), UO3, is obtained as abrownish-
yellow powder when uranic nitrate is heated in an oil bath to 250° C.
until nitrous fumes cease to be evolved. At higher temperature it
parts with oxygen, and is converted into uranous diuranate. Uranic
oxide acts both as a basic oxide and as the anhydride of an acid : thus,
on the one hand, it combines with acids to form salts in which the dyad
radical uranyt (U^'Oj)" plays the part of a dyad metal, and, on the
other, it unites with alkalies to form the uranates {q.v.y — A uranic
hydrate is also known, but is very difficult to obtain of constant compo-
sition.
Uranous diuranate (Green oxide of uranitim), ttq^C^o^^ occurs
native in an impure state ss pitchblende. It is obtained as a green pow-
der when uranous or uranic oxide, or ammonic uranate is gently heated
in air. It is difficultly soluble in hydrochloric and sulphuric acids,
readily soluble in niJric acid.
Uranous uranate {Black oxide of uranium), UOUo*^, or < tjq^Oj
is obtained as a black powder when any of the other oxides of uranium,
or ammonic uranate, is strongly ignited in air. It is used in painting
on porcelain.
OXY-HALOGEN COMPOUNDS OF URANIUM.
Uranylic chloride, UOjClg, is formed when uranous oxide is heated in
a current of chlorine. It is a yellow, deliquescent, and very soluble
mass, which is readily fusible, but volatilizes with some difficulty. It
unites with the alkaline chlorides to form well-crystallized doublesalts:
thus U02C1,2KC1„20H2, and UO2Cl2,2NH,Cl,20H,.
Uranylic bromide, UOjBrj, and uranyUcfiuorid^ UOaFj, have also been prepared.
OXY'SALTS OF URANIUM.
a. Uranous Salts.
SO
Uranous sulphate, oq^Uo*^, occurs native, but partially oxidized
to uranic sulphate as uranium vitriol or johannite. It is formed when
uranous oxide is dissolved in sulphuric acid. The most convenient
mode of preparing the salt consists in dissolving the green oxide in
sulphuric acid, adding alcohol, and exposing the whole to sunlight.
The liquid at first contains a mixture of a uranous and a uranic salt,
but under the above conditions the uranic salt is reduced to the uranous
stage, and the uranous sulphate, which is insoluble in dilute alcohol,
COMPOUNDS OF URANIUM. 617
separates in crystals containing 4 aq. From aqueous solutions it crys-
tallizes in green prismatic crystals with 8 aq. Excess of water decom-
poses it with separation of a green basic salt.
Uranous pho9phaie, — A hydric uranous phosphate^ p202Ho2Uo*',20H8, is formed as a
green gelntinons precipitate when hydric disodic phosphate is added to a solution of
uranous chloride.
b. Uranic ( Uranylic) SaUa.
In the salts the dyad radical uranyl (U^^Oj)" plays the part of a
dyad metal. They are characterized by possessing a yellow color with
a magnificent green fluorescence.
Uranylio nitrcvte^ ^^C) r\> U^^OjjGOHj, is obtained by dissolving
any of the oxides in nitric acid and evaporating the solution. It crys-
tallizes in large greenish-yellow rhombic prisms.
Uranylic sulphates, — The normal salt, 8O2<q>U'^2>30H2, is de-
posited in small lemon-yellow crystals when a solution of the nitrate
is mixed with sulphuric acid and evaporated. A hot solution of this
salt in moderately concentrated sulphuric acid deposits on cooling
deliquescent, yellowish-green, fluorescent crystals o£ hydric uranylio sul-
' SOgHo
phate, < UOj. If, on the other hand, the normal salt be dissolved in
lU
SO^Ho
fuming sulphuric acid, small yellow crystals of uranylic pyrosvlphatsy
SOj— O.
O J>U^2» *re obtained. These attract moisture with great
SO2— O^
avidity, and dissolve with a hissing noise when thrown into water.
Uranylic sulphate forms double salts with the sulphates of the
alkali metals; thus poiassic uranylic sulphate^
j-SO^Ko
-| UO2 ,20H2, forms yellow monocHnic crystals.
O
8O2K0
Phosphates and arsenates of uranyl occur native as rare minerals.
THE URANATES.
Besides behaving as a bane towards acids, uranic oxide behaves
towards strong bases as the anhydride of an acid, forming salts
called uranates, in which the group uranyl (UOg)" plays the part
of an acid radical. These salts are, however, not derived from a
normal uranic acid of the formula UOjHog, corresponding to
sulphuric acid, but from an anhydro-acid or diuranic acid of the
1
fUO,Ho
formula < O , correspondinc: to disulphuric or dichromic acid. Free
iuO^Ho ^ '
diuranic acid has not been obtained.
618 INOKGANIC CHEMISTRY.
ruo,Ko
Poidsaic^ uranaley < O , is formed when uranic oxide is fused
iUOjKo
with an excess of potassic carbonate, and remains behind as a yellow
powder when the mass is extracted with water.
fUOjNao
Sodio uranate, < O , is obtained in a similar manner by fusing
(UOjNao
uranic oxide with sodic carbonata If is pre|>ared on a large scale
from pitch blende, and is employed under the name of uranium ydlow
in painting on porcelain and in the preparation of a beautiful greenish-
yellow fluorescent glass.
fUO,(N . ,
Ammonie uranaUy -j () , is formed as a yellow precipitate wheo ammooia
rUOjCN'PI^O)
-^ <) ,1
irau>l sa
fUO,(OBi
( UO,(OBi
is added to the solution of a urau>l salt. On heating, it is conTerted into pure uranous
diuranate.
(UO,(OBi'''Ho,)
Bianuihoug uranate hydraU^ i O tOH„ or 1JO,Ho(OBi^'^Ho,), ocdire
( UO,(OBi'^'Ho,)
native as uranoapherUe in brick -red hemispherical aggregations.
A series of peruranates has recently been obtained by the action of
hydroxyl upon uranylic salts in alkaline solution. Sodio peruranaUj
UOjNao^jSOHj, forms golden-yellow needles. The peruranates are
very unstable, and have not yet been thoroughly examined.
COMPOUNDS OF URANIUM WITH SULPHUR.
Uranous sulphide, US'V — ^This compound is obtained as a grayish-
black amorphous powder by passing sulphuretted hydrogen over
uranous chloride heated to redness. At a white heat a crystalline
product is obtained. It is slowly decomposed in moist air with evo-
lution of sulphuretted hydrogen. It is insoluble in dilute hydrochloric
acid, but concentrated acids dissolve it readily.
Uranylic svJphide, UOjS", is a dark-brown precipitate obtained by
adding ammonie sulphide to a solution of uranylic nitrate.
General Properties and Reactions of the Compounds of
Uranium:
a. Uranous Salts, — The uranous salts are green. In solution they
absorb oxygen from the air and are converted into uranic salts, whilst
their color changes from green to yellow. Caustic alkalies and ammonia
produce in their solutions a dark-brown flocculent precipitate of uranous
hydrate. This absorbs oxygen and is converted into uranic hydrate,
which at the same time combines with the base to form an insoluble
uranate. Sulphuretted hydrogen gives no precipitate in acid solutions;
ammonie sulphide precipitates a black sulphide.
b. Uranic ( Uranylic) Salts.-^-The uranic salts are yellow. From tlieir
solutions caustic alkalies or ammonia precipitate a yellow insoluble ura-
nate of the base. The hydric carbonates of the alkalies and ammonie
carbonate precipitate yellow double carbonates of uranium with alkali
or ammonium, which are readily soluble in an excess of the precipitant.
COMPOUNDS OP MOLYBDENUM. 619
Sulphuretted hydrogen gives no precipitate in acid solution ; ammonic
sulphide precipitates dark-brown uranylic sulphide, readily soluble in
dilute acids, even in acetic acid. Potassic ferrocyanide gives a reddish-
brown precipitate.
The uranium compounds yield with borax and microcosmic salt beads
which in the reducing flame are green, in the oxidizing flame yellow.
The uranium compounds do not color the non-luminous flame.
MOLTBDENUM, Mo.
Atomio weight = 95.5. Molectdar weight unknovm. Sp. gr, 8.6.
Atomicity ^\ *^, ^\ and ^"*?* Evidence of atomicity:
Hypomolybdous chloride, Mo^Clg.
Molybdous chloride, Mo'^Cl^.
Molybdic anhydride, Mo^KDj.
History. — Metallic molybdenum was first obtained by Hjehn in
1782.
Ocmirrence. — Molybdenum is of rare occurrence. It is found in
combination with sulphur as molybdenite^ MoS",; with oxygen in
molybdenum ochre or native molybdic anhydride, MoO^^; and as plum-
bic molybdate, MoOjPbo" in vmlfenite. Many iron ores contain traces
of molybdenum, which thus finds its way into the pig-iron.
Preparation, — Metallic molybdenum is obtained by heating molybdic
anhydride or one of the chlorides to redness in a current of hydrogen.
In the case of the oxide the reduction is .always incomplete, and it is
necessary to purify the product by heating in a current of dry gaseous
hydrochloric acid, when the unattacked oxide volatilizes as molybdic
hydroxy-chloride, MoOHoj^Cla.
Properties. — Pure molybdenum is a silver-white metal. It appears
to be infusible at the highest temperature that can be artificially pro-
duced, but if it contains carbcm it may be fused by the oxy-hydrogen
flame. It is permanent in air at ordinary temperature, but, when
heated in air, undergoes oxidation and is ultimately converted into
molybdic anhydride. It is not attacked by dilute hydrochloric or sul-
phuric acid, but hot ocmcentrated sulphuric acid dissolves it with a
brown color. It is readily soluble in nitric acid and aqua-regia.
COMPOUNDS OF MOLYBDENUM WITH THE
HALOGENS.
Hypomolybdaiis chloridcj MoClj, is formed when dimolybdoushexa-
chloride is heated in a current of dry carbonic anhydride:
'Mo'",Cl« = MoCl, + MoCl,.
Diinolybdous Hypomolybdous Molybdous
hezachloride. chloride. chloride.
The tetrachloride volatilizes, whilst hypomolybdous chloride remains
as a yellow amorphous powder. Hypomolybdous chloride is stable
* See note, p. 614.
620 INORGANIC CHEMISTRY.
when exposed to air at ordinary temperatures, but is decomposed when
heated in air. It is insoluble in water, but soluble in hydrochloric
acid. .
A hypomolybdovM bromide^ MoBri, has rIro been prepared.
Dimolybdoua hexachloride, 'Mo'^jde? is obtained as a reddish-brown
powder, resembling in appearance amorphous phasphorus, when mo-
ly bdic pentachloride is heated to 250^ C. in a current of hydrogen. It is
insoluble in water and in hydrochloric* acid. When strongly heated,
it yields a mixture of hypomolybdous chloride and molybdous chlo-
ride.
Dimdybdous hexabromidef 'Mo'^^jBr^, is also known.
Molybdotis Moridej M0CI4, is formed as above by heating the di mo-
lybdous hexachloride. It is a brown crystalline powder, which when
exposed to air deliquesces to a brown liquid. It may be volatilized
with pailial decomposition in a current of carbonic anhydride.
Molybdous iodide, M0I4, is obtained by dissolving molybdous hydrate, M0H04, in
hydriodic acid and evaporating the solution.
Molybdic penta<Jiloride, M0CI5. Molecular volume i 1 L — ^This com-
pound is ol)tained by heating molybdenum or molybdous sulphide in
a current of chlorine. It forms a lustrous, radio-crystalline ma^ss, which
fuses at 194° C. (481° F.) and boils at 26rf° C. (614° F.). It fumes
on exposure to air, and gradually deliquesces. The molecular formula,
MoCl^, as deduced from the vapor density of this compound, is abnor-
mal, as this formula would necessitate the assumption either of pentadic
molyl)denum or of the presence of an odd number of free affinities in
the molecule (see p. 179, footnote).
COMPOUNDS OF MOLYBDENUM WITH OXYGEN.
Hypomolybdous oxide, . . . MoO.
O
{MoO ^''^
«» qO. 0=Mo — Mo=0.
Molybdous oxide, MoOj. 0^»Mo=0.
O
II
Molybdic anhydride, . . M0O3. 0=Mo=0.
Hypomolybdous oxide, MoO, a])pears to be formed as a black powder
by the action of hot caustic potash upon hypomolybdous chloride.
Dimo/ybdous bnoxide, ^VLo^^'jOy — When di molybdous hexachloride is
decomposed with a caustic alkali, dimolybdous hexahydrate, 'Mo'^jHoj,
is obtained as a dark-brown powder, and this, when heated with exclu-
sion of air, parts with water and is converted into dimolybdous triox-
ide. It forms a gray metallic powder, insoluble in acids.
Molybdous oxide, MoOj. — This oxide is obtained, like the preceding,
by heating the corresponding hydrate in absence of air. Thus pre-
pared it forms a brown powder. When Bodic trimolybdatey MOjOgNaOj,
is fused with a third of its weight of zinc, and the mass extracted with
THE M0LYBDATE8. 621
water, molybdous oxide remains in the form of dark-blue prisms which
appear violet-red by transmitted light It is insoluble in water, hydro-
chloric acid, and caustic potash. Hot nitric acid oxidizes it to molyb-
dic acid. — Molybdous hydrate, MoHo^, is obtained as a reddish-brown
precipitate by treating molybdous chloride with ammonia.
MoLYBDic ANHYDRIDE, M0O3. — This compound is most readily
prepared by roasting the native sulphide, MoSg, in air. After the sul-
phur has burnt off, the impure molybdic anhydride is extracted with
ammonia, and the ammonium salt thus obtained is purified by crystal-
lization. The ammonium salt may be converted into the anhydride
either by heating it in small portions with free access of air, or by de-
composing it with nitric acid, evaporating to dryness, and washing the
residue thoroughly with water, when the anhydride remains undis-
solved. It forms a while powder which turns yellow on heating, but
becomes white again on cooling. It fuses at a red heat, and may be
sublimed in lustrous laminsB. It is insoluble in water and acids, but
dissolves readily in caustic alkalies and ammonia.
Molybdic acid, MoOjHoj, separates as a white crystalline f owder
from the solution of a'molybdate to which hydrochloric or nitric acid
has beeu added. The compound is insoluble in water, but dissolves in
an excess of acid. From hot solutions a molybdic acid of the formula
MOgOi^Hogis deposited. A soluble colloidal modification of molybdic
acid is obtained by dissolving sodic molybdate in hydrochloric acid and
subjecting the solution to dialysis ; a yellow acid liquid remains, which
yields on evaporation a gummy deliquescent mass. When a solution of
molybdic acid in hydrochloric acid is treated with zinc the liquid be-
comes first blue, then green, and finally brown, owing to the formation
of various molybdous and hypomolybdous molybdates.
Numerous oxy-halogen compounds of molybdenum have been pre-
pared. They are generally volatile, and are mostly decomposed by
water. The following list contains some of the compounds of this class :
Molybdic oxytetrachloride, MoOCl^.
Molybdic dioxydichloride, MoOjClg.
Molybdic dioxydibromide, MoOjBrg.
fMoOClj
Dimolybdic trioxy-hexachloride, • . •< O
(M0OCI3
THE MOLYBDATES.
The salts of molybdic acid may be divided into the following classes :
Normal molybdates, M0O2R02.
Di molybdates, VLo^O^B^o^,
Trimolybdates, MOjOgRoj.
Tetramolybdates, Mo^OnRoj.
Heptamolybdates, MO7O12R05.
Octomolybdates, MOgOjjRoj.
Decamolybdates, MOj^Oj^Ko^.
in which R stands for a monad metal.
622 INORGANIC CHEMISTRY.
All these salts, with the exception of the heptamolybdates, are de-
rived from dibasic acids.
Poiassic molybdafes. — The normal salt, MoOsKo,, is obtained by
fusing together equal molecular proportions of potassic carbonate and
molylxiic anhydride, dissolving the mass m water, and evaporating the
filtered solution over sulphuric acid. It forms small soluble deliques-
cent crystals. — The dimolybdate has not been obtained. — ^The irimolyb-
datey MOjOgKos^SOIIj, is prepared like the normal salt, employing the
requisite proportions of anhydride and carbonate. It crystallizes in
flexible silky needles. — Other potassic molybdates have been obtained.
Sodic molybdates, — ^These are prepared like the potassium salts.
Normal sodia molybdatey Mo02Nao2,20H2, forms nacreous laminse or
acute rhombohedra; sodic rfimo/y6rfa/6, MOjO^Nao^, small silky needles;
sodic trimofybdatey MOjOgNao^TOHj, very fine, sparingly soluble
needles. Sodic molybdates corresponding to all the various classes in
the alx>ve list have been prepared.
Of the other molybdates, those of barium, strontium, and calcium are
either only sparingly soluble or insoluble in water, the magnesium and
zinc salts are soluble and crystallize well. Normal plumbic molybdate,
MoOjPbo", occurs native in yellow quadratic crystals as umlfenite.
Phosphomolybdic Acid.
Molybdic acid forms with phosphoric acid a remarkable compound
hexabasic acid, which may be regarded as a combination of 2 molecules
of phosphoric acid with 22 molecules of molybdic anhydride. Both
this acid and its salts contain large and varying proportions of so-called
water of crystallization, which is very possibly present as water of con-
stitution. Owing to the complexity of these salts and the absence of
all certain knowledge with regard to their constitution, it will be sim-
plest to formulate then\as molecular combinations.
Phosphomolybdic acid, 2POHo3,22Mo03. — This compound is ob-
tained by boiling ammonic phosphomolybdate with aqua-regia, and
allowing the solution to evaporate spontaneously. From this solution
it crystallizes in yellow triclinic prisms with 20 aq., from pure water in
cub«i» with 50 aq., and from concentrated nitric acid in rhombic crys-
tals with 40 aq.
Ammonic phospliomolybdatey 2POAmo3,22Mo03,120H2, is precipi-
tated as a yellow crystalline |X)wder when orthophosphoric acid or a
soluble orthophosphate is added to an excess of a solution of ammonic
molybdate in nitric acnd. It is insoluble in water and in dilute acids.
In solutions containing an excess of phosphoric acid no precipitate is
formed.
Potassic phosphomolybdate^ 2POKo3,22Mo03,120H,, is obtained in
minute four-sided prisms by boiling the ammonium salt with caustic
potash, or by precipitating a potash salt with a solution of phosphomo-
lybdic acid.
A second series of phosphomolybdates derived from an acid of the formula
2P()Ho,,oMoO„ is obtained by spontaneous evaporation of a solution of the above
salts in excess of alkali or ammonia. Thus from an ammoniacal solution of the yel-
low precipitate of ammonic phosphomolybdate in ammonia, lustrous prisms of a salt,
2POAmos,5Mo03,70II» are deposited.
COMPOUNDS OF MOLYBDENUM. 623
COMPOUNDS OF MOLYBDENUM WITH SULPHUR.
MoLYBDOUS SULPHIDE, MoS^'g; occurs native OS mo/y6den//€ in lead-
gray hexagonal crystals, or in masses closely resembling graphite in
appearance, with which it was formerly confounded. It is obtained as
a lustrous powder when molybdic anhydride is heated in a current of
sulphuretted hydrogen :
MoOs + 3SH2 = MoS"^ + S + 30H,.
Molybdic Sulphuretted Molybdous Water,
anhydride. hydrogen. sulphide.
The trisulphide, when heated with exclusion of air, is also converted
with evolution of sulphur into the disulphide. When heated in air,
molybdous sulphide is oxidized to molybdic anhydride and sulphurous
anhydride.
Molybdic sulphide [Molybdic svljphanhydride), MoS"2, is precipitated
when hydrochloric acid is added to the solution of a molybdate pre-
viously saturated with sulphuretted hydrogen. It is a dark-brown
powder which dissolves in solutions of alkaline sulphides, forming
sulphomolybdates. Poiamc aulphomolybdate, MoS'^aKsj, forms pris-
matic crystals, which by reflected light appear green with a metallic
lustre, and by transmitted light ruby-red.
Molybdic persulphide^ MoS"^. — When a solution of potassic molyb-
date is saturated with sulphuretted hydrogen and then boiled, a mixture
of molybdous sulphide with molybdic sulphide is precipitated, and the
solution contains potossic pei-sulphomolybdate, MoS'^jKsj, which crys-
tallizes in small, transparent, red scales. On adding hydrochloric acid
to the solution of this salt molybilic persulphide, MoS"^, is precipitated
as a reddish-brown powder.
General Properties and Reactions op the Compounds of
Molybdenum. — The hypomolybdouseindmolybdousfi&h&Hre of relatively
slight importance. The molybdcdes and mo/y6rf/c acid give characteristic
reactions with reducing agents. Thus, if metallic zinc l>e added to a
dilute hydrochloric acid solution of a molybdate, the liquid becomes
blue, then green, and finally dark-brown. Sulphuretted hydrogen first
colors the acid solution blue, and then precipitates molybdic sulphide;
but the whole of the molybdenum can be precipitated only by repeated
treatment with sulphuretted hydrogen, allowing the solution to stand
in a warm place. Potasmc ferrocyanide gives a reddish-brown precipi-
tate. The compounds of molybdenum yield, with borax and with
microcosmic salt, beads which in the oxidizing flame are colorless or
pale yellow; in the reducing flame the borax bead is brown, and the
bead of microcosmic salt green.
TUNGSTEN, W.
Atomic weight z= IS 4. Molecular weight unknown, 8p. gr, 19.129.
Atomicity ", *'', and ^. Evidence of atomicity :
Hypotungstous chloride, W'Clj.
Tungstous chloride, W^^Cl*.
Tungstic hexachloride, W^Cl^.
624 INORGANIC CHEMISTRY.
History. — Tungstic acid was first obtained by Scheele from the
minenil scheelite in 1781.
Occurrenoe. — Tungsten occurs only in oombination, and almost
invariably in the form of tungstates. Wolfram is a tungstate of iron
and manganese ; scheelUe is a calcic tungstate, WO,Cao" ; and adieelitine
is a plumbic tungstate, WO,Pbo". Tungstic anhydride, WO3, occurs
as the rare mineral wolfram ochre.
Preparation. — Metallic tungsten is prepared by the reduction of the
oxides or chlorides in a current of hydrogen. The reduction of the
chlorides may also be effected by means of sodium, and that of the
oxides by carbon. The metal has not been obtained in the coherent
state.
Properties. — Tungsten forms a lustrous metallic powder, which,
when the reduction has been effected at a white heat, consists of minute
quadratic plates. It is unalterable in air at ordinary temperatures, but
when heated to redness in air is converted into tungstic anhydride.
Nitric acid oxidizes it slowly, aqua-r^ia rapidly, to tungstic acid.
The quality of steel is stated to be improved by the addition of
tungsten.
COMPOUNDS OF TUNGSTEN WITH THE HALOGENS.
Hypotwngstoua chloride, WC1„ is most readily obtained by heating
the tetrachloride in a current of carbonic anhydride (see Tungstous
chloride). It forms a gray non-volatile powder, which is decomposed
by exposure to the air. In contact with water it slowly evolves hydro-
gen, and is converted into brown hydrated dioxide, whilst the liquid
contains hydrochloric acid.
Hypotungatous hromid^y ^^^Br,, and hypoturigsious iodidey WI„ have also been prepared.
Tungstous chloridey WCIg, is formed during the preparation of the
pentaehloride from the hexachloride. As it is non-volatile, it remains
l)ehind in the process of sublimation. It forms a yellowish-brown
infusible crystalline mass. When strongly heated with exclusion of pir
it splits up into tungstic pentaehloride, which volatilizes, and hypo-
tungstous chloride, which remains :
3WC1, = 2WCI5 + WClj.
Tungstous Tungstic Hypotiingstous
chloride. pentaehloride. chloride.
It is hygroscopic, and is decomposed by water into hydrochloric acid
and brown hydrated tungstous oxide.
Tungstic pentachloride, WCl^. Molecular volume 1 i i- — This
compound may be obtained by careful distillation of the hexachloride in
a current of hydrogen. It is best, however, to carry the reduction as far
as the formation of the tetrachloride, which may be done by employing
a higher temperature, and then to decompose the tetrachloride l)y
heating still more strongly in a current of carbonic anhydride, when it
breaks up into pentachloride and dichloride (see Tungstous chloride).
It forms black lustrous needles, fusing at 248^ C. (478° F.) and boiling
COMPOUNDS OP TUNGSTEN. 625
at 275.6° C. (528° F.). The vapor is yellowish-green. (As regards the
anomalous molecular weight of this compound, as deduced from the
vapor density, see p. 179, footnote.) It is very hygroscopic, and is
decomposed by water with separation of a blue compound supposed to
be a tungstous tungstate.
TuNGSTic HEXACHLORIDE, WCl^. Molecular volume QU. — When
tungsten is heated in a current of chlorine, combination occurs with
incandescence, and the hexachloride is formed. The metal employed
must be perfectly free from oxide, and the chlorine must contain neither
air nor moisture, otherwise the product will be contaminated with
oxytetrachloride, WOCl^. It forms a violet-black crystalline mass,
f^m^^ at 275° C. (527° F.) and boiling at 346,7° C. (654° F.). In the
neighborhood of its boiling-point the vapor possesses a density corre-
sponding with the formula WCl,; at higher temperatures the density
is less, owing to dissociation. Puretungstic hexachloride is not altered
by exposure to air, but when it contains oxychloride it undergoes
decom|K)8itionj evolving fumes of hydrochloric acid. In like manner
the pure hexachloride is not decomposed by water until heated with it,
but that which contains oxychloride is at once decomposed in the cold
with formation of a greenish oxide. It is soluble in carbonic disulphide,
yielding a reddish-brown solution, from which it is deposited in brown
six-sided plates.
COMPOUNDS OF TUNGSTEN WITH OXYGEN.
Tungstous oxide, WOj, is obtained when tungstic anhydride is heated
to low redness in a current of hydrogen. Too high a temperature must
be avoided, as otherwise metallic tungsten will be formed. On the
other hand, if too low a temperaturp be employed, tungstous tungstate,
W03(02W*''0)", is obtained as a blue powder. Tungstous oxide is a
brown powder, which is scarcely attacked by acids. When freshly
prepared it is pyrophoric, and must be allowed to remain for some time
in an atmosphere of hydrogen before exposing it to the air.
Tungstic anhydride, WO3, occurs native as the rare mineral
wolfram ochre. It is best obtained from wolfram, a tungstate of
manganese and iron. The finely powdered mineral is digested for
several days on the water-bath with hydrochloric acid, and finally with
aqua-regia. The insoluble portion, which consists of tungstic acid
along with unattacked wolfram and gangue, is washed with water and
extracted with ammonia, which dissolves the tungstic acid. The ara-
Qionic tungstate is converted into the anhydride by ignition. — Tungstic
anhydride is a yellow powder, which is fusible at a very high tempera-
ture, and may be volatilized at a white heat. Exposure to light colors
it green. It may be obtained in greenish crystals by fusion with borax,
or by igniting a mixture of sodic carbonate and sodic tungstate in a
current of gaseous hydrochloric acid. It dissolves in caustic soda and
caustic potash, but is insoluble in ammonia and in acids.
Tungstic acid. — This acid exists in several modifications. When
an acid is added to a cold solution of a tungstate, a white precipitate is
obtained, which when dried by exposure to air possesses the composition
40
626 INORGANIC CHEMISTRY.
WOH04. When this compound is dried over sulphuric acid it parts
with water, and is converted without change of color into the dibaidc
acid, WOjHoj. The latter compound may also be obtained asa jellow
precipitate by pouring the hot solution of a tungstate into hot nitric
acid, or by boiling an insoluble tungstate with nitric acid. Theseacids
are insoluble in water. In contact with zinc and hydrochloric acid,
tungstic acid is colored first blue and afterwards brown, owing to the
formation of tungstous tungstate and of a lower oxide — probably the
hydrated dioxide. — A soluble melatungstic acid, W^OiiHoj,70H^ is
obtained by decomposing baric metatungstate (see Tungstates^ with
sulphuric acid, or plumbic metatungstate with sulphuretted hydrogen,
and evaporating at ordinary temperature. It forms soluble y^low
octahedra. The solution has an acid rea<*tion, and may be concentrated
to a syrup, but on boiling the concentrated solution a separation of
ordinary insoluble tungstic acid occurs. — A second soluble modification,
colloidal tungstic acid, is obtained like the corresponding modification
of molybdic acid (p. 621) by adding to a 5 per cent, solution of sodic
tungstate a quantity of hydrochloric acid sufficient to combine with the
sodium, and subjecting the liquid to dialysis. The solution may be
boiled either alone or with acids without depositing ordinary tung>:tic
acid. The colloidal acid may be obtained by evaporation as a vitreous
mass, which may be heated to 20 J^ C. (392° F.) without being converted
into the insoluble modification. The vitreous acid dissolves slowly but
completely in one-fourth of its weight of water. When strongly heated,
all the modifications of tungstic acid are converted into the anhydride.
As in the case of molybdenum, oxy-halogen compounds of tungsten
have been prepared :
■ Tungstic oxytetrachloride, WOCI4.
Tungstic dioxydichloride, WOgCl,.
Tungstic dioxydibromide, WO^Brg.
THE TVNQ8TATES.
Tungstic acid forms a series of very complex salts. These resemble
in many respects the salts of molybdic acid, especially in the case of the
polytunr/states, which correspond with the polymolybdates, and are
formed by the combination of the normal salt with the anhydride in
varying proportions. The complexity is further increased by the exist-
ence of a separate class of salts, the mdaiungdaieSj which are distin-
guished by not yielding a precipitate on the addition of an acid, except
after prolonged boiling.
Potassic tungstaies. — The normal salt is obtained by adding tungstic
anhydride in small quantities at a time to fused potassic carbonate, dis-
solving the cooled mass in hot water. The solution deposits on cooling
prismatic crystals of the formula WO3Ko22,0H2. When a solution of
the normal salt is boiled with tungstic anhydride as long: as the latter
dissolves, a duodecatungstate of the formula W^OjiKoi^,! lOH, sej^arates
in lustrous scales as the liquid cools.
Sodic tungstates. — ^The normal salt, WO2Na02,20H2, is obtained like
THE TUNG8TATE8, 627
the potassium salt, and crystallizes in thin rhombic prisms. The following
is a list of the sodic tungstates which have been prepared :
Disodic ditiingstate, . . . WO2Nao220H2.
Disodic ditungstate, . . . W2O5Nao2,20H2.
Tetrasodic tritungstate, . . WjO^Nao^JOHj.
Tetrasodic pentatungstate, . W5O,3N'ao4,ll0H2.
Hexasodic heptatungstate, . WyOigNaOglBOHj, or 210H,.
Decasodic dodecatungstate, . Wi2O3iNaoi,„2l0H:2, or 250H2,or 28OII2.
The dodecatungstate, also known as sodie paratungstatCy is manufac-
tared by roasting the mineral wolfram with soda ash and extracting the
fused mass with water. The solution is almost neutralized with hydro-
chloric acid and tiien left to crystallize. At ordinary temperatures the
aquate with 28 aq. is deposited in large triclinic crystals ; at higher
ternperatures^ the other aquates given in the above list are obtained. This
salt is sometimes employed as a mordant, and also in rendering cotton
and linen fabrics uninflammable. — Sodic metcUungstatey W40,iNao2,-
lOOH,, is obtained by boiling normal sodic tungstate with tungstic anhy-
dride. It crystallizes in efflorescent octahedra, which are soluble in less
than one-tenth of their weight of cold water,
Ammoni4i tungsUUes, — The normal salt has not been prepared, but various polytung-
states and a nietatungstate are known.
The following tungstates occur as minerals.:
Calcic tungstate (scheelite^i , . . . 1 . . WOaCao'^.
Plumbic tungstate (atofzUe), "WOiPbo^^
Ferrous tungstate (farberite), WOjFeo'^
Manganous tungstate (hilbneriU) "WOsMno^^.
An isomorphous mixture of the last two compounds constitutes the mineral wolfram,
A classotphospho-tungstcUes is known, corresponding with the phospho-
molybdates.
SUieo lunatic Acids,— Some of the polytungstic acids combine with silicic acid to
form peculiar compound acids. When sodic or potassic heptatungstate is boiled with
gelatinous silicic acid, salts of silico-Hodeeatungstic aeidy SIWisOg^FlOg, are formed. In
order to obtain the free acid, mercurous nitrate is added to the solution of the salts, and
the precipitate of mercurous silicotungstate, after washing, is decomposed with hydro-
chloric acid. The filtrate from the mercurous chloride deposits on spontaneous evapo-
ration large, colorless, lustrous, quadratic octahedra of the above acid with 29 aq.
When heated it fuses in its water of crystallization and deposits at a temperature of 5Z° C.
rhombohedra containing 22 aq. It forms both normal and acid salts : thus the three
potilSBic silicotungstates have had the following formuhe assigned to them :
SiW„O^Ko8,140H2,
8iWi,0ajHo4K04,16OH„
2SiWi,034Ho^>Ko»,250Ha.
If gelatinous silicic acid be boiled with an ammonic polytungstate, the ammonium
salts of two other siliootungstic acids are formed : of a silicodecatungatic aeidf Si WioOxeHog,
30rTs, and of a silico-dodecatungstic acid isomeric with that above described. This
second dodeca-acid is known as tungsto-silieic acid. It crystallizes in triclinic prisms
with 20 aq., and its salts are distinguished from those of ordinary bilico-tun^stic acid
by greater solubility, bv crystallizing in different forms, and by- containing a different
number of molecules oi water of crystallization.
The Tungsto-tunostates.
These compounds, which may be regarded as combinations of the tungstates with
628 INOROANIO CHEMISTRY.
Potnnic tungsto-tungtiale^
tnnirstous oxide, are obtained bv the redaction of the polytungstates. They are chanc-
terized by metallic lustre, and nave been employed as bronse powders.
' "WOjEo
O
WO . — ^Tungstic anhydride is added to fused potasnc
O
, WOjKo
tungstate as long as it dissolves. The mass thus obtained is then red need by gently
heating in a current of hydrogen, and is then extracted successively with water, hydnv
chloric acid, caustic potash, and again with water. It is thus obtained in dark-blue
needles, with a coppery lustre.
Sodic tungfto-tungstalR^ WsO^Naot, may be obtained either by a method similar to the
above, or by fusing a polytimgstate of sodium with tin, and extracting the mass with
caustic soda and hydrochloric acid. It crystallizes in golden cubes, with a fine metallic
lustre.
COMPOUNDS OF TUNGSTEN WITH SULPHUR.
Tungdous sulphide^ ^S,", is formed when the trisnlphide is heated
with excluRion of air, or when tungstic anhydride is heated in a current
of sulphuretted hydrogen :
wo, + 3SH, =
WS", + s +
30H,.
TuncHtic Sulphuretted
anhydride. hydrogen.
TungHtous
sulphide.
Water.
It forms a blue-black crystalline powder.
Tungstic sulphide {Tangstio sulphanhydride), W8"j, is obtained like
the corresponding molybdenum compound by saturating the solution of
a tungstate with sulphuretted hydrogen and then adding an acid. It is
a dark-brown powder, which dissolves in alkaline sulphides with form-
ation of sulpho-tungstates. Potassic sidphobrngdcUe^ WS^'s^^t forms
yellow prismatic crystals.
General Properties and Reactions of the Compounds of
Tungsten. — The insoluble compounds of tungsten can be obtained in
a soluble form as alkaline tungstates by fusion with an alkali, prefer-
ably with the addition of nitre. When metallic zinc or tin is introduced
into the hydrochloric acid solution of a tungstate, the liquid assumes a
deep-blue color. Ammonic sulphide produces in the solution of a tung-
state no precipitate, but if hydrochloric acid be added to the liquid thus
obtained, tungstic sulphide is precipitated as a dark-brown powder.
The tungsten compounds yield with microcosmic salt a bead which, in
the oxidizing flame, is colorless or pale yellow, in the reducing flame
blue. On the addition of ferrous sulphate, the bead assumes a blood-
red color in the reducing flame.
CHROMIUM. 629
CHAPTER XLI.
HEXAD ELEMENTS.
Section III.
OHBOBUnM, Cr.
Atomic weight =62. Molecular weight unknown, i^. gr. 7.3 (Bunsen).
Atomicity ", % ^, and possibly- "^ ; also a pseudo-triad. Evidence
of aiomicUy:
•
Chromous chloride^ Or^Clj.
Cr'^'Cl,
Or'^'Cl,-
Chromic chloride, <
Chromic perfluoride, Or^Fj.
Chromic anhydride, Or^O,.
Perchromic acid, \ Or^^OsHo
History, — Chromium was discovered by Vanquelin in 1797, and in-
dependently by Klaproth about the same time.
Occurrence, — Chromium does not occur abundantly, and is never
found in the free state. Its chief natural compounds are those which
it forms with other metals, together with oxygen. Of these the most
abundant is chrome iron ore, 'CFjOjFeo''. It also occurs as plumbic
chromate, OrOjPbo", crocoisite. The color of various minerals and
gems, such as serpentine, chromic mica, and the emerald, is due to the
presence of small quantities of chromium.
Preparation. — Chromium may be reduced from its chloride by means
of zinc. For this purpose the chloride is heated with zinc in a Hessian
crucible, employing a mixture of potassic chloride and sodic chloride as
a flux. The zinc regulus is treated first with cold and afterwards with
warm dilute nitric acid, as long as anything dissolves. The metallic
chromium remains as a gray powder. For the above reaction, it is not
necessary to prepare anhydrous chromic chloride : the mixture of chro-
mic chloride and potassic chloride obtained by the reduction of potassic
dichromate with hydrochloric acid and alcohol is evaporated with the
addition of sodic chloride, and the mass thus obtained is carefully dried
and employed as above. — Chromium may also be obtained by heating
chromic oxide to a very high temperature with sugar in a lime crucible.
— Bunsen has prepared the metal by the electrolysis of a solution of
chromous chloride containing chromic chloride.
Properties. — Metallic chromium, reduced from the chloride by zinc,
is a light-gray crystalline powder, in which, by the aid of the micro-
scope, tin-white lustrous octahedra may be perceived. Prepared by elec-
trolysis, it is deposited on a platinum electrode as a coherent plate. It
is more difficultly fusible than platinum, and as hard as corundum. It
is only slowly oxidized when heated in air with a Bunsen or hydrogen
flame, but burns with brilliant scintillations in the oxy-hydrogen flame.
630 INORGANIC CHEMISTRY.
When thrown on potafisic chlorate which has been heated to incipient
fusion, it is oxidized with dazzling incandescence^ yielding potaseic ehro-
mate. Hydnwhloric acid dissolves it readily with evolution of hydro-
gen ; dilute sulphuric acid scarcely attacks it in the cold, but when hot
dissolves it, also evolving hydrogen ; nitric acid, even when hot and
concentrated, does not act upon it. The hardness of steel is greatly
increased by the addition of 0.6 to 0.75 per cent, of chromium.
COMPOUNDS OF CHROMIUM WITH THE HALOGENS.
a, Chromous Compounds.
Chromous chlorides, OrClj. — A solution of this compound is obtained
when the metal is dissolved in hydrochloric acid. The anhydrous chlo-
ride is best prepared by gently heating chromic chloride in a current of
dry hydrogen. It forms a white crystalline mass, and dissolves in
water, yielding a blue solution, which rapidly absorbs oxygen from the
air and possesses powerful reducing pn)perties.
Chrcmmu bromide, CrBr,, is prepared in a similar manner from chromic bromide.
It resembles the chloride in its properties.
6. Chromie Compounds.
Chromic chloride, 'OFjCI,, is prepared by heating a mixture ^f
chromic oxide and carbon in a current of dry chlorine. It forms lus-
trous scales, of the color of peach-blossom, which may be sublimed in
a current of chlorine. When heated in air, it evolves chlorine and is
converted into chromic oxide. Pure chromic chloride is almost insolu-
ble in water at ordinary temperatures, and dissolves only slowly when
boiled with water for a considerable time, but in presence of a very
minute quantity of chromous chloride, it dissolves readily in cold ^vater,
yielding a green liquid. Stannous chloride and other reducing agents
produce the same effect. The green solution, which may also be obtained
by dissolving chromic hydrate in hydrochloric acid, yields, by evapora-
tion over sulphuric acid, green, very soluble needles of the compound
'Or2Cl5,120Hj,. These, when heated,>part with water and hydrochloric
acid, and are converted into an oxychloride. By heating in a current
of gaseous hydrochloric acid, they may, however, be converted into the
anhydrous violet chloride.
Chromic bromidet ^Cr^Br., is prepared like the chloride. It forms black hexagonal
scales, with a siibmetallic lustre. The crystals exhibit, by transmitted light, olive-green
and red dichroism.
Chromic ftttoride, ^Cr^Fe, is obtained by dissolving chromic hydrate in hydrofluoric
acid. On evaporating the solution a green crystalline mass is obtained, which fiises at
a red heat, and at a very high temperature sublimes in lustrous regular octahedra.
c. Perchromic Compounds.
Only one of these is known — the perfiuoride. In all circumstances
where the formation of a perchloride or perbromide might be expected,
chlorine or bromine is evolved, and the corresponding chromic com-
pound is formed.
COMPOUNDS OF CHROMIUM. 631
Chromic perfiuoride, OrF^, is prepared by beating a mixture of calcic
fluoride and ignited plumbic chromate with concentrated sulphuric acid
in a retort of lead or platinum :
CrOjPbo" H- 30aFj + 4SO,Ho, = OrF, +
Plambic Calcic Sulphuric Chromic
chromate. fluoride. acid. fluoride.
SOjPbo'' + SSOjCao'' + 40H,.
Plambic Calcic Water,
sulphate. sulphate.
A red gas passes over, which condenses to a red fuming liquid. In con-
tact with water it is decomposed, yielding chromic and hydrofluoric
acids.
COMPOUNDS OF CHROMIUM WITH OXYGEN.
O
Chromic oxide, • . . joS^- C)=Cr— Cr=0.
Chromic anhydride, . . OrOj. 0=Cr=0.
Chromous oxide^ CrO, is not known, but its hydrate and several of
its salts have been prepared. — Chrovwus hydrate, CrHoj, is obtained as
a brownish-yellow precipitate by the addition of caustic potash to a so-
lution of chromous chloride. It readily absorbs oxygen, and must be
dried with exclusion of air. When heated in absence of air, it parts
with water and hydrogen, being converted into chromic oxide :
2CrHo3 = OrA + OHj + H^.-
Chromous Chromic Water,
hydrate. oxide.
Chromic oxide, 'CrOgj. — This oxide occurs native as the mineral
chrome-ochre, contaminated with earthy impurities. It is formed when
chromic hydrate, chromic anhydride, or diammonic dichromate, is heated :
^ = loJo^ + N, + 40H,.
CrO,(Nn,0) ^ ^"^
Diammonic Chromic Water,
dichromate. oxide.
i
It IS most readily obtained by heating a mixture of equal parts of dipo-
tassic dichromate and sulphur, or of dipotassic dichromate and ammonic
chloride. On extracting the residue with water, the chromic oxide re-
mains undissolved. It is a dark-green amorphous powder, which fuses
in the oxy-hydrogen flame, and solidifies to an almost black, crystalline
mass. It may be obtained in lustrous, dark-green, hexagonal crystals
by passing the vapor of chromic oxydichloride, GrOfil^, through a red-
hot tube. The strongly ignited oxide is almost insoluble in acids.
632 INORGANIC CHEMLSTRT.
Chromic oxide is used as a pigment under the name of chrome ffreeriy
and in the preparation of ^reen glass and enamel.
Chromic hydrate, 'Cr^Hog. — Ammonia produces in solutions of
chromic salts free from alkali a pale-blue precipitate of a hydrate which,
after drying over sulphuric acid, has the formula '0x^110^,4011^ In
a vacuum it slowly parts with 3 aq., and when heated to 220** C. in a
current of hydrogen is converted- into the hydrate 'CTjO^Hop Another
hydrate of the formula 'CTjOHo^, employed as a pigment under the
name of Guignet^^ green, in pre|>ared by fusing dipotassic dichromate
with boric acid, and extracting the mass with water. These hydrates
are difficultly soluble in acids. Freshly precipitated chromic hydrate
dissolves slightly in aqueous ammonia,yielding a peach-blossom-colored
solution. This solubility de|)ends upon the formation of a chromamine
corresponding with the cobaltamines (q.v.). The freshly precipitated
hydrate also dissolves in a solution of chromic chloride, and fn>m the
solution thus obtained the greater part of the hydrochloric acid may be
removed by dialysis, leaving a soluble colloidal modification of chromic
hydrate. (Graham found in the liquid remaining in thedialyser 1 rool.
of hydrochloric acid to 33 mols. of chromic hydrate). The dark-green
solution is not precipitated by dilution or by boiling, but the addition
of the slightest trace of a salt causes it to coagulate. — The prec^ipitate
produced in solutions of chromic salts by caustic alkalies, which dis-
solves in an excess of the precipitant, and is reprecipitated by boiling,
always contains alkali ; and this cannot be removed by washing.
Chromic anhydride, OrO^ — In order to pr*^pare this compound,
1^ volumes of concentrated sulphuric acid are added to one volume of
a cold saturated solution of dipotassic dichromate. On cooling, the
chromic anhydride crystallizes out in long red needles. It may be freed
from the excess of acid by allowing it to drain upon a porous tile, in
which condition it is sufficiently pure for most purposes. In order to
obtain it quite pure, the crystals must be filtered off, employing a filter
of asbestos or spun glass, as organic substances instantly reduce the
anhydride, and the substance must be washed upon the filter with pure
nitric acid free from nitrous anhydride, and finally freed from the nitric
acid by warming in a current of dry air. — Chromic anhydride forms
either a woolly mass of fine re<l needles, or red prisms. It is very soluble
in water, yielding a reddish-brown solution, which becomes yellow on
dilution. It is also soluble both in concentrated and in dilute sulphuric
acid, but it is almost insoluble in a sulphuric acid containing from 16
to 17 per cent, of water — a property which is utilized in its preparation.
It fuses without decomposition when heated, but at 250° C. {482° F.)
is resolved into chromic oxide and oxygen. It is very readily re-
duced to chromic oxide, and therefore acts as a powerful oxidizing
agent. Sulphurous anhydride, sulphuretted hydrogen, nitrous anhy-
dride, and most organic substances effect its reduction. Alcohol poured
upon the dry anhydride inflames. Glacial acetic acid, however, dissolves
it without decomposition. Both the aqueous and the acetic acid
solutions of chromic anhydride are employed in organic chemistry
as oxidizing agents, the latter solution being particularly efficacious,
owing to the fact that the acetic acid generally also acts as a solvent for
the organic substance which is to be oxidized. Sometime, instead of
OXYH3ALT8 OP CHROMIUM. 633
aqueous cliromic anhydride, a solution of dipotassic dichromate in dilute
sulphuric acid is employed as an oxidizing agent. When heated with
hydrochloric acid, chromic anhydride evolves chlorine, and is converted
into chromic chloride; heated with concentrated sulphuric acid it gives
off oxygen, yielding chromic sulphate.
Chromic acid, CrOjHoj. See Chromates.
Perchromic add, < nrO^H (^)' — When hydroxyl is added to a
solution of chromic anhydride or of a chromate acidified with sulphuric
acid, a deep-blue coloration is produced. The compound thus formed,
which is possibly a perchromic acid of the above composition, speedily
decomposes with evolution of oxygen, and the solution contains only
chromic acid. On agitating the blue solution with ether, this solvent
extracts the blue compound from the water, and rises to the surface as a
dark-blue layer. The ethereal solution, though somewhat more stable
than the aqueous solution, leaves only chromic anhydride on evapora-
tion. The formation of this blue compound is a very delicate and char-
acteristic test, both for chromic anhydride and for hydroxyl — indeed,
for the latter substance it is the only thoroughly characteristic test.
The other oxides of chromium generally enumerated are difficult to obtain of con-
stant composition. A chromaus dichromic tetroxide^ ^Ctfi^Cro^^j is probably formed in
the process of preparing the metal by electrolysis, l3ut appears (o be mixed with metallio
chromium. The substance known as chromic dioxide, CrO^ is probably a compound of
chromic anhydride with chromic oxide ; by washing with water it is decomposed into
these two substances.
OXY'SALTS OF CHROMltlM.
a, Chromous Salts.
The chromous salts are of slight importance. They are readily
oxidizable, and absorb oxygen from the air.
Chromous sulphate, BOfiro^^, is known only in solution. It is formed when
metallic chn>mium is dissolved in dilute sulphuric acid. IHpotasstc chromous sul-
rSOjKo
phaiCf -I Cro^^ , 60H,* is prepared by dissolving potassic sulphate in a solution of
I SO.Ko
chromous chloride, adding alcohol, and then allowing the mixture to stand for some
time with exclusion ot air. It crystallizes in blue monoclinic prisms, which on expo-
sure to air quickly become green from oxidation.
Chromous phosphate, PjOjCro^'si and chromous carboTiate, COCro''^. have also been
prepared.
b. Chromous Salts.
Chromic oxide forms with acids the chromic salts, in which the
hexadic group ('Cr''',)^ displaces six atoms of hydrogen in the acid.
The aqueous solutions, prepared by dissolving the salts in cold water,
are violet colored ; on heating, the color changes to green, and on cool-
ing, the violet color returns only after a considerable time. Crystal-
lis^ salts can be obtained only from the violet solutions : the green
solutions yield, by evaporation or on the addition of alcohol, green
amorphous masses. The violet solutions alone contain a pure chromic
salt ; this, on warming, is decomposed into basic salt and free acid, the
chemical change being accompanied by the above change of color.
634 INORGANIC CHEMISTRY.
Otromie nitraU, N«0,,(''Cr^^'j06)'"',18OHi, is prepared by dissoWing chromic hydrate
in nitric acid. It furnis red, soluble, monoclinic crystals.
Chromic Sulphate, SjOjCCr'^'jO^)'*,! 60 H„ is prepared by dissolv-
ing chromic hydrate in ito own weight of concentrated sulphuric acid.
The solution, which is green at first, becomes blue on standing, and
deposits a vioIet-blue crystalline mass of the above salt This may be
purified by dissolving in cold water and precipitating with alcohoL
From its solution in cold dilute alcohol it is deposited in blue r^ular
octahedra. The aqueous solution prepared in the cold has a violet
color, which changes to green on boiling.
DiPOTASsic Chromic Sulphate (Chrome alum),
SOjKo.
^o I
So _ ('C''''"A)^240H,.— This compound is best prepared by dis-
SO,KoJ
solving equal molecular proportions of dipotassic dichromate and sul-
phuric acid in water and passing sulphurous anhydride into the solu-
ti«»n :
fOrO^o • ^^
{O + SO,Ho, + 3SO, = ^' ('Cr"'Ar + OH^
Dipotassic Sulphuric Sulphurous Chrome 'Water*
dichromate. acid. anh^-drtde. alum.
Other reducing agents, such as alcohol, 'may be employed instead of
sulphurous anhydride, but in this case it is necessary to add a larger
quantity of sulphuric acid. Chrome alum crystallizes in deep ruby-red
octahedra, which by reflected light appear almost black. It dissolves
in cold water with a reddish-violet color, which becomes green on boil-
ing. After standing for a long time it recovers its original color.
Chrome alum is employed in dyeing and calico-printing, and in tanning.
— Ammonia chrome alum is prepared like the potassium compound,
which it closely resembles in its properties.
THE CHROMITES.
Chromic oxide possesses the property of combining with other
oxides — especially with the oxides of the dyad metals — to form com-
pounds which may be regarded as salts of the acid 'OrjOjHo,. To this
particular hydrate of chromium the name cAromot<« ad<i may therefore
be applied, and these compounds would then be termed chromites. It has
already been mentioned that when chromic hydrate is precipitated by
caustic alkalies, the precipitate contains alkali which cannot be removed
by washing. This is due to the formation of a chromite of the alkali.
Only the chromites of the dyad metals, however, have been obtained as
well characterized compounds. These crystallize in regular octahedra,
and belong to the same class as the aluminates of the dyad metals
(p. 568), or as magnetic oxide of iron (q.v.), all of which also crystallize
in regular octahedra, and may be regarded as formed by the combina-
tion of a monoxide with a sesquioxide.
THE CHROMATE8. 635
Ztneie diromite/ Crfi^Zno^^f in obtained in lustrous blackish-green octahedra bj fusing
a mixture of zincic oxide and chromic oxide with boric anhydride.
3fanyanousfekromUey ^Cr^O^Mno^^, is obtained in a similar manner, substituting man-
ganous oxide for zincic oxide. It forms very hard iron-gray octahedra.
Ferrous chromite, 'OTjOjFeo", occurs in nature as the mineral
chrome iron oi*e. It generally occurs in crystalline masses ; but distinct
octaliedral crystals are also found.
THE CHR0MATE8.
These are the salts of the unknown chromic acid, CrOjHog. This
acid possibly exists in the aqueous solution of chromic anhydride, but
on evaporating this solution only chromic anhydride is obtained.
Hydroxy! does not appear to be capable of entering into stable combi-
nation with the radical chrorayl (CrOj)". Not only does chromic acid
part spontaneously with the elements of water to yield an anhydride ;
but not even the acid chromates arecapable of existmg. Thus in all cases
in which the formation of hydrio potassio chromate might be expected, two
molecules of this salt combine, with elimination of one molecule of water,
rCrOaKo
anhydro-salt dipotassic dichromaiey \ O
(CrO^o
When chromic oxide, a chromic salt, or any substance containing
chromium is fused with nitre, the chromium is oxidized by the oxygen
of the nitre, and a yellow mass is obtained which contains potassic
cfaromate, OrOjKo,. Formerly this compound was prepared by heat-
ing chrome iron ore with nitre, bat at the present day potashes are sub-
stituted for the more costly nitre, and the oxidation is effected by means
of the oxygen of the air. Chrome iron ore is first roasted and then
finely ground. A mixture of roasted and powdered ore, crude pot-
ashes, and lime is first dried at 1 50° C. (302° F.) and then heated to bright
redness in the oxidizing flame of a reverberatory furnace. The addition
of the lime prevents the fusion of the mass, which is thus kept in a
pasty condition. During the operation the heated mass is constantly
stirred, so as to expose fresh surfaces to the oxidizing action of the flame.
As soon as the oxidation is complete the charge is withdrawn, and, after
a)oling, is lixiviated with the smallest possible quantity of boil idg water.
If the solution should contain calcic chromate, potassic sulphate is added
in quantity sufficient to convert it into the potassium salt, the calcium
being at the same time precipitated as sulphate. The solution now
contains potassic chromate, but it would be impossible to separate this
salt by crystallization from the other salts present, owing to its ready
solubility. It is therefore necessary to convert it into the less soluble
dichromate. For this purpose a quantity of sulphuric acid sufficient
to saturate half the potassium present as chromate is diluted with twice
its volume of water and added to the solution :
rOrO^Ko
20rOaKo2 + SOjHo, = ^ O + SO2K02 + OH,.
( CrOjKo
Potamic Sulphuric Dipotassic Potassic Water.
chromate. acid. dichromate. sulphate.
636 I140BGANIC CHEMISTRY.
The normal chromate is soluble in twice its weight of cold water, whilst
the dichromate requires ten times its weight of water for solution; the
f;reater part of tne dichromate therefore crystallizes from the above
iquid on cooling. The mother liquor, which contains potassic sul-
phate, is employed in the extraction of another roasted charge. The
potassio dichromate is purified by crystallization. (For the properties
of this salt see below.)
P0TA68IC CHROMATE, OrO,Ko,. — (For the mode of formation, see
preceding paragraph.) In order to obtain this salt in a state of purity
an excess of caustic potash is added to a solution of the dichromate.
The color of the solution changes from orange-red to yellow, and
on evaporation yellow rhombic crystals of the normal chromate are
deposited. The crystals are isomorphous with those of potassic
sulphate, with which salt it is capable of crystallizing in all propor-
tions. It is soluble in twice its weight of cold water, yielding a yellow
solution. It has an alkaline reaction. The pure salt undergo^
decomposition when its solutions are evaporated : crystals of the di-
chromate are first deposited ; afterwards when the solution begins to
contain more free alkali, the normal salt crystallizes out. Acids, even
carbonic, decompose it with formation of dichromate. On heating, it
turns red and fuses at a high temperature without decomposition,
recovering its original color on cooling.
fCrOjKo
Dipotaasio diehromale, < O . — (For the mode of preparation,
(OrOjKo
see p. 635.) This salt crystallizes in large garnet-red triclinic prisms
or tabular crystals. It is soluble in 10 parts of water at ordinary
temperatures, more readily soluble in boiling water. The solution
has an acid reaction. The salt fuses below a red heat without decom-
position, but at a white heat is decomposed into normal chromate,
chromic oxide and oxygen. When heated with concentrated sulphuric
acid it evolves oxygen and yields a green solution which, after dilution
with water, deposits on standing crystals of chrome alum. It is a vio-
lent poison.' — Dipotassic dichromate is the starting point in the prepa-
ration of the other chromium compounds, ft is employed as a
lalx)ratory reagent, as an oxidizing agent, in dyeing and calico-printing,
and in the process of producing [)ermanent carbon photographs.
{CrO.Ko
O
OrO, , and Dipotassic tetrachromnJtey
O
OrOjKo
Cr^OiiKo^, are deposited from solutions of the foregoing salt in nitric
acid. They form deep-red crystals, which are decomposed by water
into dichromate and chromic anhydride.
Sodif. chromatef CrOsNao,, is obtained when a solution of potaneic chromate with an
excess of caustic soda is evaporated at 0°, It crystallizes at a low temperature in iaiige
yellow transparent deliquescent prisms of the formula C?rO»Noaj,10OH», isomorphoiis
with crystallized sodic sulphate, from warm solutions in anhydrous crystals. — DUodU
dichrojnate, Cr80&Naos,20H3, forms deliquescent red prisma.
TH£ CHR0MATE8. 637
Amnionic ehromatey 0rO2(N^H4O)2, and diammonic dichromatey
0r2O5(N'H3O)2, are obtained by adding the requisite quantity of am-
monia to an aqueous eolation of chromic anhydride. They resemble
in almost every respect the corresponding potash salts. When heated
they are decomposed into nitrogen, water, and chromic oxide — th^
normal salt also evolving ammonia. In the case of the dichromate,
this decomposition is attended with incandescence, and the chromic
oxide swells up to a bulky mass resembling green tea in appearance.
Baric chromatb, OrO^Bao", is obtained as a yellow crystalline
precipitate when the solution of a chromate or dichromate is added to
the solution of a barium salt. It is insoluble in water arid in acetic acid,
soluble in hydrochloric and in nitric acid. It also dissolves in a hot
aqueous solution of chromic anhydride, and the liquid deposits on
cooling red crystals of baric dichromatey 0r2O5Bao'',20H2. These are
decomposed by water into chromic anhydride and normal chromate. —
Baric chromate constitutes the pigment yellow ultramarine.
Stronlie ehromate, CrO^Sro^'', doeely resembles the bariam salt, but is much more
readily soluble in water and in acetic acid.
Oaleic chromate, CrO,Cao^'',20H,, is obtained in large yellow prismatic crystals by
digesting marble with a solution of chromic anhydride and evaporating the liquid
over sulphuric acid.
Mw/nesie chromate, ChrOjMgo'^JOH,, forms soluble lemon-yellow rhombic crystals,
and is isomorphous with magnesic Riilphate.
rCrOjKo
Dvpoioisk magnesui chromate, \ Mgo^^ ,2011,, is deposited in yellow tabular crystals
(CrO.Ko
when a solution of dipotassic dichromate in neutralized with magnesia and then evapo-
r CtO.lN'H^O)
rated. Diammonic magnene chromate, < Mgo ,^OlI^ is isomorphous with diam-
(CrO,(N'H40)
monic magnesic sulphate (p. 511).
Zincic chromates. — The normal salt is not known, but various basic chromates of zinc
have been prepared. Dizincie chromate dihydrate, CrO,(OZn^''H())^OH,, is obtained
as a yellow precipitate when normal potassic chromate is added to a solution of an
excess of zincic sulphate.
Plumbic chromate, OrOjPbo", occurs native as crocoisUe in red
monoclinic crystals. The same substance is obtained as a bright yellow
precipitate when potassic chromate or dichromate is added to the s<»lu-
tion of a lead salt. This precipitate is employed as a pigment under
the ndLvae of chrome yeJlow, It is insoluble in water and acetic acid,
but soluble in nitric acid and in caustic potash. When heate<i it fuses
without decora po**it ion, and solidifies to a crystalline mass. Organic
compounds, when lieated with it, undergo complete oxidation: it is
therefore employe*! in the ultimate analysis of such compounds, particu-
larly of those which contain sulphur and chlorine or the metals of the
alkalies and alkaline earths. — Chrome yellow is employed in calico-
printing. The cloth is first mordanted with the solution of a lead salt.
On afterward immersing it in a solution of potassic chromate, the
chrome yellow is developed on the fibre of the monlanted parts. —
Diplumbic chronuUSy OrOPbo",, a basic salt, constitutes the chrome red
of commerce. It is formed as a red powder by boiling chrome yellow
with normal potassic chromate, or by digesting it with cold caustic
soda. It is also obtained as a vermilion-colored crystalline powder by
638 INORGANIC CHEMISTRY.
fusing chrome yellow with nitre. Chrome orange is a mixture of
chrome red and chrome yellow. It is prepared by precipitating the
solution of a lead salt with a weak alkaline solution of potaasic chro-
mate.
Argentic chromate, OrOjAgo^, is formed as a red aystalline pre-
cipitate when a dilute solution of normal potassic cbromate is added to
a concentrated solution of argentic nitrate. It may be obtained in
dark-green crystals by boiling diargentic dichromate with water, or by
allowing a solution of the dichromate in ammonia to evaporate. The
green crystals yield a red powder. It is insoluble in water, but
dissolves in nitric acid, in ammonia, and in solutions of the alkaline
chromates. — Diargentic dichromate^ OTjO^Agti,, is obtained as a scarlet
precipitate when a solution of pota.«sic dichromate is gradually added
to a solution of argentic nitrate. When hot dilute solutions arc
employed the salt gradually separates in red triclinic crystals.
Mercuric rJtromate, CrOiELgo^^. — The normal salt is obtained in garnet-red rhombic
prisms by boiling mercuric oxide with a solution of chromic anhydride. Excess of
water decomposes it with separation of the red amorphous basic salt, trimercwie
ehratTiaU, Ctllgo^'s, — a decompoRition which exactly corresponds with that which
occurs when normal mercuric sulphate is treated with water (p. f535). Potansic chro-
mate produces in solutions of mercuric and mercurous salts precipitates of basic chro-
mates of mercury.
COMPOUNDS OF CHROMIUM WITH OXYGEN AND
CHLORINE.
Chromic oxydichloride (Chromylic chloride^ OrOjClj), Molecular
volume \ \ 1. — This comjwund may be theoretically derived from
chromic acid by the substitution of chlorine for hydroxyl. It may
therefore be regarded as the chloride of the acid radical chromyl
(CrOj)", and b«irs the same relation to chromic acid that sulphurylic
chloride, SOjClj, does to sulphuric acid. In order to prepare this
compound, a fused mixture of 10 parts of common salt and 12 parts of
dipotassic dichromate is broken into small pieces and introduced into a
retort, after which 30 parts of faintly fuming sulphuric acid are intro-
duced. The reaction begins of its own accord. The dark reddish-
brown vapors are condensed in a cooled receiver. In order to free the
product from dissolved chlorine, it must be repeatedly rectified in a
current of dry carbonic anhydride. The same compound is formed
when a dry mixture of chromic anhydride and ferric chloride is dis-
tilled.— Chromic oxydichloride is a mobile liquid, which appears almost
black by reflected light, but exhibits a blood-red color by transmitted
light. It boils at 128° C. (244° F.). It possesses a specific gravity of
1.92 at 25° C. (77° F.). In contact with moist air it fumes strongly,
and when dropped into water is decom|)08ed with violent ebullition,
yielding chromic and hydrochloric acids. It has a most energetic
action upon ox idizable substances: thus it acts upon phosphorus with
explosive violence, whilst sulphur, sulphuretted hydrogen, ammonia,
and many organic bodies^ such as alcohol, inflame when brought in
contact with it.
CJiromic oxycfUorhydrate ( Chromylic chlorhydraie, Chlorochromic a/sid)^
OrOjCIHo^ a compound corresponding with sulphuric oxychlorfaydrate
COMPOUNDS OF CHROMIUM. 639
(SOjClHo), has, like chromic acid itself, not been isolated. The non-
existence of this compound is a further instance of the inability of the
seraimolecule of hydroxyl to attach itself to the radical chromyl (see
p. 638). Salts of chromic oxychlorhydrate, known as chlorochromateSy
have, however, been prepared. Poiassic chlorochronuUe is obtained by
gently warming 3 parts of dipotassic dichromate with 4 parts of con-
centrated hydrochloric acid and a little water :
fOrOjKo
^O + 2HC1 = 20rO,ClKo + OH^.
(OrOjKo
Dipotaflsic Hydrochloric Potassic Water,
dichromate. acid. chlorochromate.
It crystallizes in large red prisms or tables having a specific gravity of
2.497. An excess of pure water decomposes it into pot&ssic chloride
and chromic anhydride; but it may be recrystailiased from dilute
hydrochloric acid. When heated at 100° C. it evolves chlorine.
COMPOUND OF CHROMIUM WITH SULPHUR.
nrQ//^^^ ^ ohtained by the direct union of i(8 elements under the
influence of heat. It is also formed when chromic oxide is heated to whiteness
in the vapor of carbonic disulphide, or when chromic chloride is heated in a cur-
rent of sulphuretted hydrogen. — Chromic sulphide is a gray-black powder with a
metallic lustre. It possesses a specific gravity of 3.77. Concentrated nitric acid is
without action upon it. When heated in air it is converted into chromic oxide. — Sul-
phuretted hydrogen produces no precipitate in solutions of chromic salts, and alkaline
sulphides precipitate chromic hydrate with liberation of sulphuretted hydrogen.
COMPOUND OF CHROMIUM WITH NITROGEN
Chromic nitridej \ Ct\^^^' ^ formed by the direct union of its elements when nitro-
gen is passed over metallic chromium at a red heat; also by the action of gase-
ous iimmonia upon heated chromide chloride. — It forms a heavy black powder which
inflames when heated to 200° C. (392** F.) in contact with air. Heated with exclusion
of air to a temperature higher than that at which it is formed, ii is decomposed into
its elements. Chlorine is without action upon it at ordinary temperatures, hut when
the snbfltance is heated in a current of chlorine it is converted with a series of slight
explosions into chromic chloride and free nitrogen. The explosions are due to the
formation and immediate decomposition of nitrous chloride. It roav be ignited without
change in hydrogen and in steam. It is not att.icked by hydrochloric or nitric acid,
or by aqueous caustic potash. Concentrated sulphuric acid dissolves it, yielding a
green liquid which, when diluted with water and allowed to stand, deposits crystals of
ammonia chrome alum :
S0l(N'H,0)J
General Properties and Reactions of the Compounds of
Chromium. — a. Chromous compounds, — These are of subordinate im-
portance. They are distinguished by their powerful reducing proper-
ties. They rapidly absorb oxygen from the air, and are thus converted
into chromic compounds.
b. Chromic salts. — These are derived from chromic , oxide. Their
solutions are violet-colored or green ; they have A sweetish astringent
640 INORGANIC CHEMISTRY.
taste, an acid reaction towards litmus, and are poisonous. Ammonia
Eroduces a bulky precipitate of chromic hydrate, which is slightly solu-
te in a lai^e excess of ammonia, yielding a peach-colored solution.
Catistie alkalies precipitate ^reen chromic hydrate, soluble in an
excess of an alkali in the cold, but precipitated on boiling. Stdphu-
retted hydrogen gives no precipitate; ammonic sulphide precipitates
chromic hydrate with evolution of sulphuretted hydrogen. When a
chromium com[K)und is fused with a mixture of sodic carbonate and
nitre, an alkaline chromate is formed which dissolves in water, yielding
a yellow solution.
c. Chromates. — The soluble chromates yield with lead salts a yellow
precipitate of plumbic chromate; with argentic nitrate^ red argentic
chromate. When heated with concentrated hydrochloric acid they
evolve chlorine, and the color of the liquid changes to green. Sulphur
retted hydrogen reduces the chromates in acid solution to chromic salts
with separation of sulphur; alcohol and sulphtiroits acid effect the
same reduction.
Chromium compounds yield, with borax and with microcosmic salt,
beads which are emerald-green, both in the oxidizing and in the reduc-
ing flame. Chromium compounds do not color flame, but yield a
characteristic spark-spectrum containing bright lines in the green and
in the blue.
MANGiiNESE, Mn.
Atomic weight = 55. Molecuiar treight unknovm. 8p. gr. 7.99. Atom-
icity ", *^, ""*, and possibly """ ; also a pseudo-triad and a pseudo-
heptad. Evidence of atomicity :
Manganous chloride, Mn^Clj.
Manganic peroxide, Mn^^O,.
Potassic manganate, Mn^^OjKoj.
Potassic permanganate, \ Mn^*0 Ko'
History. — The black oxide of manganese was known to the ancients,
who were acquainted with its use in removing impurities from glass.
They confounded it, however, with magnetic oxide of iron.
Occurrence. — Manganese is widely distributed in nature. It is never
found native. The chief ores of manganese are the oxides, and of
these the most important is manganic peroxide or pyrohisite,
MnOj. Others are dimanganic trioxide or braunite, Mn^O,; man-
ganous dimanganic tetroxide or Aatt«9mannii^, < MnO^°^"' ^^ ^''^
occurs as manganous sulphide in manganese blende, KnS^^, and as
manganous carbonate, COM no'', in manganese spar. It is present in
small quantity in a number of other minerals, particularly silicates, so
that in almost all rocks and soils traces of manganese are to be found.
It o<'Curs in minute quantities in the bodies of plants and animals.
Preparation. — Manganese cannot be reduced from its oxides by
means of hydrogen ; but the reduction may be effected by heating the
oxide with carbon to intense whiteness. A mixture of 10 parts of
OOMPOU13D6 OF MANGANESE. 641
manganous diraanganic tetroxide, MnjOjMno" (obtained by the igni-
tion of the native peroxide), with 1 part of charcoal and 1 part of an-
hydrous borax, is heated to whiteness in a carbon crucible. The regu-
lufi of manganese thus obtaine<1 contains carbon, together with silicon
derived from the ash of the charcoal. Pure manganese may be obtained
by heating manganous manganic oxide (prepared from the artificial
dioxide) in a lime crucible with a quantity of carbonized sugar insuffi-
cient for its total reduction. The lime crucible is placed inside a Hes-
sian crucible, the intervening space is filled with charcoal, and the
whole is heated in a wind-furnace.
Properties. — Manganese is a grayish-white metal with a reddish
tinge. It LS very hard and brittle. It fuses at a white heat. It
oxidizes rapidly in moist air, and must therefore be preserved under
rock-oil. Slanganese is rapidly dissolved by dilute acids, and the finely
divided metal decomposes water with evolution of hydrogen when
gently warmed with it.
COMPOUNDS OF MANGANESE WITH THE HALOGENS.
Manganous chloride, MnCla- — The anhydrous chloride is formed
when the metal is burnt in chlorine, or when any of the oxides or the
carbonate is heated in a current of dry hydrochloric acid. The residues
from the preparation of chlorine by the action of hydrochloric acid
upon manganic peroxide may be employed as a source of manganous
chloride. This solution contains manganous chloride contaminated
with ferric chloride, and sometimes with the chlorides of copper,
barium, and calcium, together with an excess of hydrochloric acid.
The solution is evaporated to ex[>el the acid, diluted, and about an
eighth of the solution precipitated with sodic carbonate. The precipi-
tate, consisting of manganous carl)onate and ferric hydrate, is well
washed, added to the rest of the solution, and boiled with it. In this
way the iron is precipitated by the manganous carbonate, whilst an
equivalent quantity of manganese goes into solution as chloride:
'Pe^Cl, + 30OMno'' + SOH^ = Te^IIo, +
Ferric Miinganous Water. Ferric
chloride. carbonate. hvdrate.
SMnCl, + 3CO2.
Manganous Carbonic
chloride. anhydride.
The complete precipitation of the iron is ascertained by filtering a
sample of the liquid and testing with potassic ferrooyanide. Should
copper be present it is best removed with sulphuretted hydrogen. Cal-
cium and barium are got rid of by precipitating the manganese with
ammonic sulphide, washing the precipitate, and redissolving in hydro-
chloric acid. The concentrated solution depasits pink-colored mono-
clinic tabular crystals of the aquate, MnCl2,40H2, which on heating are
decomposed with evolution of hydrochloric acid. If, however, a solu-
tion of this compound be mixed with ammonic chloride, pink regular
crystals of the double chloride, MiiCl2,2NH^CI,OH2, are deposited, from
41
642 INOBQANIC CHKMKTRY.
which, by careful heating, the water of crystallization may be expelled
withoat further deoompoeition of the salt ; and the anhydrous double
chloride, when heated to a higher temperature, parts with ammonic
chloride, leaving anhydrous manganous chloride. The anhydrous chlo-
ride forms a pink, micaceous, easily fusible mass, which is gradually
decomposed by exposure to moist air.
The other chlorides of manganese — manaanie perehloridej MnCIf, and dimanganie
hecaehloridef ^Mn^Cls — are known only in solution. When the correspond inj? oxides
— manganic peroxide, MnO,, and dimanganic trioxide, ""Mn^O, — are dissolved in cold
hydrochloric acid, these chlorides are formed ; but on heating they are decomposed
with evolution of chlorine, and the solutions contain manganous chloride.
ManganouB bromidtf MnBr,, is obtained like the chloride, which it closely resembles
in properties. It also forms an aquate, MnRr^40H,.
Manganous iodide, Mnl|, is a white deliquescent mass.
ManganouB jtuoride^ MnFx, is obtained by dissolving manganous carbonate in hydro-
fluoric acid. It forms pale-red crystals, insoluble in pure water, soluble in aqueous
hydrofluoric acid.
Manganic verptoride^ BfnF4, is known only in solution. It is formed when manganic
peroxide is aissolved in concentrated hydrofluoric acid. Water precipitates from the
solution manganic peroxide, but on the addition of potassic fluoriae a rose-red precipi-
tate of the double fluoride, MnF4.2KF, is formed.
COMPOUNDS OF MANGANESE WITH OXYGEN.
Manganese forms a large number of oxides, some of which are of
great complexity. The following are the most important and best
characterized :
Manganous oxide, . . . KhO.
O-Mn-O
^'Sx"; /:""^^"'!{J£8Mno". 0=l_]vln=0.
or BShMno'V Mn/ NMh/ ^Mn.
Dimanganic trioxide, . . BfilOMno". 0=Mn<' yMn.
i«-oO- o=M„Oi„=0.
Manganic peroxide, . . KxiOj. 0=Mn=0.
O O
{MnO " ''
*- qK), 0=Mn — Mn=0.
O O O
Manganous oxide, MnO, is formed when the carbonate or any of
the higher oxides is heated in a current of hydrogen. It may be pre-
pared by fusing anhydrous manganous chloride with sodic carbonate
to which a little ammonic chloride has been added. It is a grayish-
green powder, which, if it has been prepared at a low temperature, ab-
COMPOUNDS OF MANGANESE, 643
sorbs oxygen from the air and turns brown, but if it has been more
strongly heated is permanent in air at ordinary temperatures. When
heated to whiteness with exclusion of air, it fuses without loss of oxy-
gen ; if air be admitted, it is converted on heating into manganous
dimanganic tetroxide. It cannot be reduced to metal by heating in a
current of hydrogen. By heating in a current of hydrogen containing
a trace of hydrochloric acid, it is obtained in the form of small green
transparent octahedra with an adamantine lustre. Manganous oxide is
the chief salifiable oxide of manganese.
Manganese hydrate, BlnHoj, is obtained as a white precipitate
when a caustic alkali is added to the solution of a manganous salt from
which the air has been previously expelled by boiling. When exposed
to the air it speedily turns brown from oxidation. It dissolves in
solutions of ammonia salts.
Manganous dimanganic tetroxide (DimangarKms manganite)
'BIlljOjMno", or B[nMno'^2> o<«urs as hauamannite in brownish- black
acute quadratic pyramids. This compound represents the most stable
stage of oxidation of manganese : thus when the higher oxides are
intensely heated, they evolve oxygen and are reduced to this stage,
whilst, on the other hand, when manganous oxide or manganous car-
bonate is heated in air, oxygen is absorbed and the same compound is
produced. The artificial oxide is a reddish-brown powder which, by
gentle heating in a slow current of hydrochloric acid, is converted into
crystals identical with those of the natural compound. Warm aqueous
hydrochloric acid dissolves it with evolution of chlorine and forma-
tion of manganous chloride :
MnMno", + 8HC1 = SBInCl^ + CI, + 4OH2.
Dimanganous Hydrochloric Manganous Water.
maugHDite. acid. chloride.
Dilute oxy-acids — sulphuric or nitric — dissolve two-thirds of the man-
ganese to form a manganous salt, whilst one-third remains as manganic
peroxide :
MnMno", + 4NO,no =
= 2N,0,Mno''
+ MnO, + 2OH2.
Dimanganous Nitric acid,
manganite.
Manganous
nitrate.
Manganic Water,
peroxide.
There are no salts corresponding to this oxide. Its reactions are
most readily accounted for on the assumption that it is a dimanganous
manganite, as formulated in the two foregoing equations.
Dimanganic tbioxide, MnOMno" (or ^mnjO^). — This compound
occurs as the mineral brauniie in brownish-black lustrous quadratic
pyramids. It may be obtained as a black powder by heating any of
the other oxides of manganese in oxygen. — A dimavganic dioxydihy"
dratej BInHojMno" (or 'Mn^OjHoj), occurs as manganite in dark-gray
rhombic crystals. The same compound is formed by the spontaneous
oxidation of moist manganous hydrate in air.
The constitution of the above oxide and hydrate cannot be fixed with
certainty. On the one hand, they both yield, with hot nitric acid,
manganous nitrate with separation of manganic peroxide :
2N02H0 =
= NAMno"
+ MnO, + OH,.
Niiric
Manganous
Manganic Water.
acid.
nitrate.
peroxide.
644 INOBOANIC CHEMISTRY.
Mn,0, +
Di manganic
trioxide.
This reaction would be best accounted for by the first of the alternative
formulae above given, in which one atom of manganese is in the dyadic,
the other in the tetradic condition. On the other hand, dimanganic
trioxide occasionally acts as a basic oxide — in the formation of diman-
ganic hexachloride, for example — ^yielding salts in which the manganese
is apparently a pseudo-triad. This behavior would be better expmined
by the formula 'MlljOj.
Manganic peroxide {Manganic dioxide, black oxide of manganene),
IllnOj. — This is, as regards its usefulness, by far the most important of
the ores of manganese. It occurs in large quantities as pyrolusite —
sometimes in black or dark-gray rhombic prisms, more generally in
fibrous or amorphous masses. It may be obtained artificially by care-
fully igniting manganous nitrate :
H^O.Mno"
= BInO, + TffA-
Manganous
nitrate.
Manganic Nitric
peroxide. peroxide.
The ignited mass is extracted with boiling nitric acid, and the undis-
solved residue of manganic peroxide well washed and then moderately
heated. It is also formed by the action of nitric acid upon manganous
dimanganic tetroxide or dimanganic trioxide (p. 643). The same oxide
is obtained in a hydrated state when a manganous salt is precipitated
with an alkaline solution of a hypochlorite. When heated to low
redness, manganic peroxide parts with one quarter of its oxygen, yield-
ing dimanganic trioxide ; at bright redness it parts with one-third of its
oxygen, and is converted into manganous dimanganic tetroxide. It
dissolves in cold hydrochloric acid with formation of manganic per-
chloride; on heating, chlorine is evolved and manganous chloride
remains in solution. Nitric acid and dilute sulphuric acid are without
action upon it; concentrated sulphuric acid dissolves it on heating with
evolution of oxygen and formation of manganous sulphate. In pres-
ence of oxalic acid and other oxidizable substances it dissolves in dilute
acids in the cold. — Manganic peroxide forms, with basic oxides, com-
pounds which may be regarded as salts of a manganous acid of the
formula Mn^O^Ho,. Dipotasaic pentamanganiie, Mn^O^Kos, is a yellow
powder which separates out when carbonic anhydride is passed into a
solution of potassic manganate :
+
SMnOjKoa + I8OO2 + 90112
= MnPj^Koj
Potassic Carbonic Water.
Di potassic
manganate. anhydride.
pentamanganite
5'Mn,0,Ko, + I8COH0K0.
Pdtassic Hydric {jotassic
permanganate. carbonate.
Manganic peroxide is used in the production of colorless glass (p. 481).
It also serves as a cheap source of oxygen, when this gas is required in
COMPOUNDB OF MANQANEBfi. 645
large quantities; but its chief employment is in the preparation of
chlorine for the manufacture of bleach ing-powder.
JRegenercUion of Manganic Pei^oxide. Weldon^s Process, — Formerly
the residues of manganous chloride obtained in the manufacture of
chlorine were allowed to run to waste. At the present day, by means
of a process devised by Weldon, the greater part of the manganese is
reconverted into manganic peroxide and recovered in this form. For
this purpose the chlorine residues (see Preparation of Chlorine, p. 161),
which contain, along with manganous chloride, ferric chloride and
other impurities, are first treated with calcic carbonate in order to neu-
tralize the excess of acid and to precipitate the iron. To the clear solu-
tion of manganous chloride and calcic chloride thus obtained milk of
lime is added in the proportion of 1 J molecules of calcic hydrate to
each molecule of manganous chloride. The mixture of manganous hy-
drate, calcic hydrate and calcic chloride is then heated by means of a
current of steam to a temperature of from 55° to 75° C. (131°-167°
, F.), after which air is blown through the liquid. Manganous hydrate
alone is oxidized only to hydrated dimanganic trioxide, but in presence
of excess of lime a rapid oxidation of the manganous hydrate to man-
ganic peroxide occurs. The manganic peroxide is obtained in combi-
nation with calcic oxide, as calcic manganite, MnOCao^', and it is upon
the formation of this compound that the greater readiness of oxidation
depends. The oxidation is continued until about three-fourths of the
manganese has been converted into peroxide. About 2 cubic metres
of air are blown in for every pound of manganic peroxide regenerated,
and the time required for the regeneration of a ton of the peroxide is
five hours. The " manganese-mud " is allowed t4) settle and, after run-
ning off the liquid, is pressed into a solid cake. In this form it is em-
ployed in the prepanition of chlorine. It usually contains about 33
per cent, of manganic peroxide in combination with lime.
Permanganic anhydride, < iur«r)^« — This compound is obtained by
the action of sulphuric acid upon pota<«ic permanganate. The finely
powdered pure salt (the absence of chlorine is es|)ecially essential,
as, otherwise, dangerous explosions may occur, owing to the forma-
tion of oxides of chlorine) is gradually added to well-cooled concen-
trated sulphuric acid. From the olive-green solution thus obtained
reddish-brown oily drops of the anhydride gradually separate — the more
readily if the solution be allowed to absorb moisture from the air — and
sink to the bottom. Permanganic anhydride is a very unstable com-
pound : when rapidly heated it decomposes with a violent explosion.
it undergoes slow decomposition at ordinary temperatures, evolving
bubbles of oxygen which carry with them violet fumes of the anhy-
dride. It is a powerful oxidizing agent: when brought in contact
with paper^ alcohol, or other organic substances, it causes their ignition.
It rapidly absorbs moisture from the air, and dissolves in water with
great rise of temperature, yielding a violet- colored solution of perman-
ganic acid, a portion of the substance being at the same time decom-
posed by the heat evolved. The acid cannot be isolated.
646 INORGANIC CHEMISTRY.
OXY'SALTS OF MANGANESE.
a. Manganous Salts.
Manganoii^ nitrate^ NjOfMno^^jGOH^ i» prepared by disAolving the carbonate in ni-
tric acid. It is difficultly crystallizable and very deliquescent. When heated it fuse*,
and is converted into manganic peroxide.
Manganous oarbonate, OOMno", occurs native as manganese spar in
pink hexagonal crystals. The native compound generally contains
iron, calcium, and magnesium. It is precipitated as a white powder
when an alkaline carbonate is added to the solution of a manganous
salt. When exposed to the air in a moist state it speedily becomes
brown from oxidation.
Manganous 8ULPH4.TE, SOaMno". — Commercial black oxide of
manganese is made into a paste with concentrated sulphuric acid, and
the mixture is heated in a crucible, first gently, and afterwards to ■
redness, in order to convert the ferric sulphate into insoluble ferric
oxide. The mass is lixiviated, and the solution is digested with a
small quantity of manganous carbonate, in order to precipitate the last
traces of iron. At a temperature below 6° C. pink rhombic crystals of
the formula SOHoaMno^jeOH^, isomorphous with ferrous sulphate,
are deposited. From 7° to 20° C. triclinic crystals of the formula
SOHo2Mno",40H2, isomorphous with cupric sulphate, are obtained.
Several other equates are known. All these salta become anhydrous
at 200° C. (392° F.).— With the sulphates of the alkalies manganous
sulphate forms double salts, isomorphous with the corresponding double
sulphates of the other metals of the dyadic group with the alkalies. Di-
rso^Ko
potassio manganous sidphaleA Mno",60H„ forms monoclinic crystals.
(SO^o
SO,— 1
fSO,-|
Aluminio manganous tdrasiilphate, < Mno"('Al"',O4)^,240Hj. —
(SO3-I
This double sulphate occurs as the mineral apjohnite. It has the
composition of an alum, and is frequently termed i»a?i^an€8eaftimtniuw»
aluihy but inasmuch as it possesses, in common with the other salts in
which two atoms of a monad metal in alum are displaced by one atom
of a dyad metal, a crystalline form differing from that of the ordinary
alums, mnny chemists refer it to a separate class — that of the jweurfo-
alums. Other pseudo-alums are known containing iron, zinc, and mag-
nesium, as dyad metals.
f SO
Manganous dUhionate, < oq^ Mno"30H2. — Finely powdered man-
ganic peroxide is suspended in water, and sulphurous anhydride is
passed into the liquid, avoiding any rise of temperature. The salt crys-
tallizes in pale-red soluble rhoml)ohedra. It forms the starting-point
for the preparation of the other dithionates.
THE MANGANATES. 647
Manganou8 silicate, BiOMno^^, occurs native as rhodonite in brownish-red crystals. —
Dimanganous nticaU, SiMno'^'^a, forms the mineral tephroiUf which crystallizes in quad-
ratic forms.
6. Manganic Salts.
so,-
Manganic sulphate (Dimanganio trisulphale) SO, — ('Mn"',0,)^, is
SO,-,
obtained by the action of sulphuric acid upon hydrated manganic per-
oxide. It is a green powder which deliquesces on exposure to air^ and
is decomposed at 160° C. (320° F. ) with evolution of oxygen.
Dipotassic dimanganio tetrasulphate {Manganese alum)y
SO^oH
SoJko_|
is formed when potassio sulphate is added to a solution of manganic
sulphate in dihite sulphuric acid. It crystallizes from very concentrated
solutions in violet-colored regular octahedra. Excess of water decom-
poses it; manganic hydrate being deposited. With ammonic sulphate
a corresponding ammonia manganese alum is obtained.
THE MANOANATES.
Neither manganic anhydride, BI21O3, nor manganic acid^ MnOjHo,^
have been prepared ; but salts of this acid^ called manganaies, are known.
These are isomorphous with the corresponding sulphates.
Potassic manganate, MnO^Ko,. — When manganic peroxide is fused
with caustic potash a deep-green mass is obtained, which contains potas-
sio manganate. When the fusion is performed out of contact with air^
the reaction takes place according to the equation —
3MO3 + 2KHo = MnO^o, + 'Mn^Og + OH^;
Manganic Potassic Potassic Dimanganio Water,
peroxide. hydrate. manganate. trioxide.
but if air be admitted, or if nitre or potassic chlorate be added to the
mixture, the whole of the manganic peroxide is a>nverted into manga-
nate. The mass dissolves without decomposition in a small quantity of
water, and the dark-green solution deposits, on evaporation in imcuo,
rhombic crystals of potassic manganate, which, when first prepared, are
almost black, and display metallic lustre, but become dull and green-
colored by exposure to the aif. Potassic manganate is stable only in
solutions which contain an excess of free caustic alkali ; when these
solutions are diluted with a large quantity of water, the manganate is
decomposed with separation of manganic peroxide and formation of
potassic permanganate :
3MnO,Ko, + 20H, = {J^qKo + "^^» + ^^^^"^^
Potaasic Water. Potassic Manganic Potassic
manganate. permanganate. peroxide. hydrate.
648 INOBOANIC CHEMISTRY.
The oolor of the solution changes at the same time from green to violet
The same decomposition occurs when carbonic anhydride is passed into
the alkaline solution of a manganate.
Sodie mangannie, MnO^Nao,, is prepflred in a similar manner bj fusing manganic
peroxide with sodic nitrate. It is deponited from its alkaline solutioos in crystals of
the formula MnO,Nan,,10OH2. isomnrphous with Glauber's salt
Baric manganate, MhOsBao^'^, is obtained by fusing manganic peroxide with baric
nitrate and extracting the mass with water. It is a green powder, insoluble in water.
Acids decompose it.
PERMANGANIC ACID AND THE PERMANGANATES.
Permanganic acid, < MnO^H ' ^ J^^ow only in solution. The solu-
tion is obtained, as already described (p. 645), by dissolving per-
manganic anhydride in water, or, more readily, by decomposing a
solution of baric permanganate with the equivalent quantity of sul-
phuric acid. The solution is deep-red by transmitted and blue by
reflected light. When heated, or even when exposed to light^ it evolves
oxygen with separation of hydrated man^nic peroxide.
PoTASSic PERMANGANATE, < MnO^K^* — "^^^ green mass obtained
in the preparation of potassic manganate (p. 647) is extracte<l with
boiling water. In this way the manganate is decomposed with for-
mation of permanganate (p. 647). If an excess of alkali is present
carbonic anhydride ought to be passed into the liquid. The precipitate
of hydrated manganic peroxide is removed by filtration through asbestos
or glass-wool (filters of pa|^)er, calico, or other organic substance would
be attacked). The clear liquid, when allowed to evaporate, deposits
crystals of potassic permanganate. These are isomorphous with potassic
perch lorate. For this reason, if potassic chlorate has T)een employed in
the preparation of the permanganate, the latter salt is apt to be con-
taminated with perchlorate, from which it cannot be freed by crystalli-
zation, as the two salts crystallize together in all proportions. Potassic
permanganate forms large rhombic prisms, which are deep-red by trans-
mitted and almost black by reflected light, with a metallic lustre. The
salt is soluble in 16 parts of water at ordinary temperatures, mpre readily
soluble in boiling water, yielding a solution of a deep purple color. The
solution is a powerful oxidizing agent and destroys most organic sub-
stanoes. A solution of crude potassic permanganate, or more commonly
of the sodium salt, is employed as a disinfectant under the name of
"Condy's Disinfecting Fluid." By exposure to the air the solution of
permanganate is gradually reduced by organic matter from the atmo-
sphere, changing its color from purple to blue, and at last to green.
Owing to these changes this substance was formerly known as mineral
chameleon. Boiling with concentrated caustic alkali converts potassic
permanganate into manganate with evolution of oxygen :
t MnOgKo
+ 2KHo =
= 2Mn02Ko,
+ o
+0H..
Potassic
permanganate.
Potassic
hydrate.
Potassic
manganate.
Water.
COMPOUNDS OF MANGANESE. 649
the chemical change being accompanied by a change in the color of the
liquid from purple to green. When the dry salt is heated to 240° C.
(4)4° F.) it evolves oxygen and is converted into a mixture of manga-
nate and manganic peroxide : •
PotasBic Pot&ssic Manganic
periuanganate. manganate. peroxide.
Sodie permanganate^ < MnO^Nao' ^* Prepared Jike the potassium salt. It is mann-
factiired on a large Poile as a disinfectant bj fusing black oxide of manganese with
crude caustic soda in shallow iron vessels.
Ammonic permanganaie, < MnO^Amo' ^® obtained by decomposing the barium salt
with ammonic sulphate. It is isomorphons with the potassium salt, which it closely
resembles, but is more soluble. It is readily decomposed on heating.
JBaric permanganate, < uff^o'^*^^^* — ^^''^onic anhydride is passed through water in
which baric manganate is sunpended, and, after filtering from the baric carbonate, the
red solution thus obtained is rapidly evaporated. It forms large deep-red rhombic
crystals, readily soluble in water.
Argentic permanganate, \ 'Mn.O J>^6* separates in large red crystals, when warm solu-
tions of argentic nitrate and potassic permanganate are mixed and allowed to stand.
It is sparingly soluble in cold water.
COMPOUND OF MANGANESE WITH OXYGEN AND
CHLORINE.
Pennanganic hexoxy-dichhridey < MnoVl — ^^ order to obtain this
compound sodic chloride is added to a solution of potassic permangan-
ate in concentrated sulphuric acid. A yellow gas is evolved, which
condenses in a freezing mixture, yielding a greenish -brown liquid. In
contact with moist air it emits red fumes. Water decomposes it with
formation of permanganic and hydrochloric acids ; but these substances
at once react upon each other, yielding chlorine and manganic peroxide.
It explodes violently on heating.
COMPOUND OF MANGANESE WITH SULPHUR.
Manoanous sulphide, BlnS", occurs native as manganese blende
in steel-gray granular masHen, and occasionally in black cubical crys-
tals. The same compound is obtained as a greenivsh-gray powder liy
heating any of the oxides of manganese in a current of sulphuretted
hydrogen. Alkaline sulphides produce in solutions of raanganous
salts a flesh-colored amorphous precipitate of hydrated manganous
sulphide, which is readily soluble in dilute acids^ even in acetic, with
evolution of sulphuretted hydrogen, and when exposed to the air be-
comes brown from oxidation. By prolonged contact, or by heating,
with an excess of the alkaline sulphide, the precipitate is transformed
into a green crystalline powder of the formula SMnSyOHj. — Manganous
sulphide unites with the sulphides of the alkali metals to form double
650 INORGANIC CHEMISTRY.
oomponnds. A double sulphide of this description is disulphopotasgic
trimanganous dimlphide, tut^it' Mns".
%
Manganic disulphide, MnS^^,, occurs in nature as the mineral koMerUe in dark red-
dish-brown regular crystals.
Characteristic Properties and Reactions of the Com-
pounds OF Manganese. — The rnanganous salts are of a pale ro^e
color. Caustic alkalies precipitate white mangaiious hydrate, which
speedily oxidizes and becomes brown. Ammonia only partially precip-
itates the manganese as hydrate ; in presence of an excess of ammonic
chloride ammonia does not produce any precipitate, but the solution on
standing absorbs oxygen from the air, and deposits hydrated trimanganic
tetroxide. Alkaline carbonaies precipitate basic manganous carbonate;
baric carbonate does not precipitate manganous salts in the cold. Am-
monic sulphide precipitates flesh-colored hydrated manganous sulphide,
soluble in dilute acids, even in acetic acid.
All manganous oompounds, when fused with sodic carbonate and
nitre, yield a green mass containing an alkaline manganate. With
borax or microcosm ic salt, they give a bead which is amethyst-colored
in the oxidizing flame, and colorless in the reducing flame. Manganous
chloride colors the non-luminous flame green : the spectrum of the flame
exhibits lines in the green and yellow. The spark-spectrum of manga-
nese contains a large number of lines.
IRON, Fe.
Atomic weight = 56. Molecular weight unknotcn. Sp, gr, 7.8. Atom-
icity'', *^, and ^. Evidence of atomicity :
Ferrous chloride, Fe"Clj,
Ferric disulphide, Pe^'S'V
Ferric chloride Te'"j,Clc.
Potassic ferrate, Fe^^OjKoj.
History. — The process of obtaining iron from its ores has been known
from very early times. Owing to its abundance, to the ease with which
it can be reduced to the metallic state, and to its valuable properties^ it
is by far the most important of the metals.
Occutrence, — Iron is the most abundant and widely diffused of the
metals, with the exGeptir>n of aluminium. Native iron, which is of
rare occurrence, may be divided into two kinds — meteoric iron, of extra-
terrestrial origin, and telluric iron. Meteoric iron sometimes occurs in
considerable masses : the largest have been found on the island of Disko,
off* the coast of Greenland, where there are fifteen of these blocks, the
two largest weighing 21,000 and 8,000 kilos. Weapons and imple-
ments of meteoric iron have been found among the Eskimos, and also
among tribes in Central Africa. Meteoric iron is never pure : it con-
tains varying quantities of other metals, notably nickel and cobalt, the
proportion of the first of these sometimes ranging &s high as 30 per
cent. On the snow-fields of Northern Europe and Asia the snow is
IRON. 651
found to inclose minute magnetic particles possessing the composition of
meteoric iron. It is probable that this meteoric dust is continually fall-
ing upon the earth ; but its presence can be detected with certain ty^only
in hxjalities which, like the above, are sufficiently remote from all
sources of terrestrial dust. Telluric iron occurs in small spiculsa dissem-
inated througti various basalts and lavas. Masses of terrestrial iron
have also been observed in cases in which the fire of burning coal-mines
has acted upon ores of iron. This variety is known as natural ated.
Iron most frequently occurs in combination with oxygen or sulphur.
In combination with oxygen it is found as ferric oxide, 'FejOj,
in red hcemaiUe, or specular iron ore ; as ferroas diferrie tetroxidey
\ FeO^^^''^ ^^ ma^me^io iron ore; as tetraferrlc trioxyhexahydrate,
Fe^OjHoj, in brown hasmcUite ; and as ferrous carbonate, OOFeo'' in
spcUhose iron ore. The disulphide, FeS^gj is of very common occur-
rence as iron pyj'iies. Iron is also found in the form of a sulphide in
copper pyiites, < ^ rA'Cu^^^'^^', Silicates of iron are contained in
nearly all rocks, and by the disintegration and decomposition of these
rocks the oxide of iron is produced which imparts to the soil its red
color. From the soil plants extract the iron which is a necessary con-
stituent of the chlorophyll, or green coloring matter of their leaves.
Iron is also a necessary constituent of the haemoglobin, or red coloring
matter of the blood. The chlorophyll of plants enables them, with
the aid of sunlight, to decompose the carbonic anhydride and aqueous
vapor of the atmosphere : a portion of the oxygen resulting from this
decomposition is evolved, whilst the other products of decomposition
are used in building up the tissues and principles of the plant. The
hsemoglobin of the blood acts as a carrier of the oxygen which is ab-
sorbed during respiration, and which serves for the oxidation of the
animal tissues. In this way the respiratory functions both of plants
and of animals are dependent upon the presence of iron.
The presence of iron in extra-terrestrial space is proved by its occur-
rence in meteorites, and, further, by the results of spectrum analysis,
which show that this metal is present in the sun and in many of the
fixed stars.
Extraction. — The important and complex subject of the metallui^y
of iron can only be briefly sketched here.
The compounds of iron from which the metal is extracted are the
oxides, the hydrates, and the carbonate. The chief ores are: magndie
iron orey red hoemaiUe, brown hcemaiitey spaHiose iron ore, and clay iron-
stone or argillaceous iron ore, which is a spathose iron mixed with clay
or sand. Black band is a variety of clay iron-stone containing from
20 to 25 per cent, of coal. The ores are first calcined or roasted. In
this process water and carbonic anhydride are expelled, whilst most of
the sulphur, which may be present, is oxidized and burnt oflF as sul-
phurous anhydride. At the same time the ore is rendered more friable
and porous. The ore is then reduced by heating with coal, limestone,
and occasionally silicates, in a hot-blast furnace. This furnace consists
of a lofty shaft of strong masonry lined with fire-brick. The internal
652 INORGANIC CHEMISTRY.
space is narrower towards the bottom, where the molten metal collects.
The furnace is 6r8t lighted or bloum in, after which alternate layers of
a mixture of calcined ore and limestone on the one hand, and of ooal
on the other, are thrown in at the top until the furnace is full. A
powerful blast of air, previously heated to from 350° to 700^ C.
(662-1292® F.), is forced in through pipes or tuyires placed at the
bottom of the furnace. The chemical changes which occur in tlie
furnace are as follows: The oxygen of the air on entering the furnace
unites with the carbon to form carbonic anhydride, which in turn is
converted into carbonic oxide by contact with the heated carbon. The
carbonic oxide in passing upwards over the heated ferric oxide reduces
it to finely-divided iron. The part of the furnace in which this change
occurs is termed the *' zone of reduction." At the same time the fusible
flux of silicate of lime coats the particles of metal and protects them
from oxidation. As the reduced iron sinks into the hotter parts of the
furnace it begins to combine with carbon ; this part of the furnace is
therefore known as the " zone of carburation." At this point the iron
also takes up phosphorus derived by reduction from phosphates con-
tained in the ore. The metal gradually sinks till it reaches the hottest
part of the furnace — the " zone of fusion " — wh^n it melts and runs
down to the hearth or lowest part of the furnace. Here it would be
exposed to the danger of oxidation from the blast; but the fusible slag
floats on the surface of the molten metal and protects it. The excess
of slag runs ofi* regularly through an oj>ening. From time to time
the molten iron is tap))ed and cast into bars known as pigs. As fast as
the charge in the furnace sinks, fresh ^hai^es of ore, limestone, and
coal are introduced. In this way a blast-furnace may be kept con-
tinuously at work for many years.
The crude iron thuH obtained, known as pig iron or cetd iron, contains
from 3 to 6 per (»ent. of carbon, together with varying quantities of
manganese, silicon, sulphur, phosphorus, arsenic, and antimony. The
carbon is present in two forms : partly in chemical combination, and
partly as particles of graphite mechanically disseminated throughout the
mass of the metal. When cast iron is dissolved in acids, the carbon
displays a different behavior according to the form in which it is present:
the mechanically disseminated carbon is left behind unchanged, whilst
the chemically combined carbon enters into combination with hydrogen
to form complex hydrocarbons, gaseous and liquid. According to color
and other properties, the following varieties of cast iron are distin-
guished : White cast iron, which contains the whole of its carlH)n in
the combined condition ; and gray oast iron, which, in addition to the
combined carbon, contains graphite disseminated throughout its mass.
Various intermediate stages are classed as mottled cast irons, Spiegeleisen,
Spiegel, or specular pig iron is a white iron containing the highest per-
centage (3.5 to 6 per cent.) of combined carbon. White iron is formed
when the temperature of the blast furnace is low. It contracts on
solidification, and therefore cannot be used for castings. Gray iron is
formed when the tem|)erature is high. It expands on solidifying, and
is suitable for foundry work.
Cast iron is brittle and cannot, as a rule, be forged. In order to
IRON. 653
impart to it the property of malleability, the greater portion of the
carbon and the other foreign substances must be removed by a process
of oxidation. In this way the cast iron is converted into wrought iron.
The process most commonly employed in the production of wrought
iron hsi\i2i,tof pvddliag : the wrought iron is fused along with powdered
haematite on the hearth of a reverberatory furnace, employing a flux of
blast-furnace slag. During the process, the metal is stirred to promote
oxidation. The silicon is first converted into silicic anhydride, which
is taken up by the bases of the slag ; afterwanls, the carbon is burnt oif
as carbonic anhydride. A comparatively low temperature is essential
to the effectual removal of the phosphorus, since at a high temperature
the iron reduces the phosphates contained in the slag and takes up
phosphorus.
Wrought iron contains from 0.15 to 0.5 per cent, of carbon. The
lower the proportion of carbon the more malleable and the less readily
fusible is the iron. Rolled and hammered wrought iron, containing 0.3
per cent, of carbon, has a fibrous structure; if the percentage rises to
0.5, the structure becomes granular and crystalline. The hardness of
the metal also increases with the percentage of carbon. Wrought iron
is of a clear gray color, and capable of taking a high polish. At a red
beat it softens and may be welded. The physical properties of iron are
powerfully modified by the presence of minute quantities of various
impurities : thus sulphur renders the metal " red-short " — ^that is, brittle
at high temperatures; phosphorus renders it "cold-short," or brittle
at ordinary temperatures.
If the proportion of chemically combined carbon in iron lies between
0.6 and 2 per cent., the product is known as ateeh In chemical compo-
sition, steel therefore stands midway between wrought iron and cast
iron, and it may in fact be produced from the former of these by in-
creasing, and from the latter by diminishing, the proportion of carbon
present. Steel was formerly exclusively prepared from wrought iron
by the cementation process. In this process bars of wrought iron are
packed in powdered charcoal or soot, and heated to bright redness for
from seven to ten days, according to the nature of the product required.
In this way the iron takes up the carbon necessary for its conversion
into steel. The exact mode in which this is accomplished is not perfectly
understood, though various hypotheses have been made with regard to
this process. The bars of steel, after their conversion, exhibit a peculiar
blistered appearance due to the producti(m of gas within the mass of
the metal. This imperfection is removed by hammering and rolling,
or by melting the steel. Puddled steel is an inferior quality of steel pre-
pared from cast iron by arresting the proceas of puddling at a point short
of the production of wrought iron. In the Bessemer* process of steel
making, cast iron is melted, and then transferred to a ve:«el known as
a Cfmverter^ through the bottom of which a powerful bla»<t /)f air is
blown. The silicon, manganese, and carbon are thus oxidized, and so
great is the heat evolved that the temperature of the molten metal rises
considerably. Formerly the process was interrupted at the jwint of
formation of steel, but at the present day the oxidation is carried on
until the whole of the carbon is removed — a point much more readily
651 INORGANIC CHEMISTRY.
ascertained — after which the molten spiegel is added in quantity exactly
sufiicient to convert the whole into steel.
Steel is of a clear gray color, and possesses a granular structure. It
may be forged and welded like wrought iron, and fuses at a lower
temperature than the latter. It possesses the property of becoming
intensely hard and brittle when heated to redness and then suddenly
cooled — for example, by plunging into water. This hardness and
brittleness can be removed in any required degree by heating the hard-
ened steel to temperatures between 200° and 300° C. (392-572° F.)
and then allowing it to cool. This process is known as tempering. The
lower the temperature employed, the harder will be the resulting steel.
If the surface of the object to be tempered be first polished, it will ex-
hibit shades of color on heating, due to the formation of films of oxide
of varying thickness. By observing these colors the workman is enabled
to judge with sufficient accuracy of the temperature which he is em-
ploying. The specific gravity of hardened steel is somewhat lower
than that of wrought steel. In hardened steel the whole of the carbon
is present in the combined state^ whereas wrought steel also contains
graphitic carbon.
Preparation of Pure Iron. — ^The purest iron of commerce is piano-
forte wire, which contains only about 0.3 per cent, of impurities — for
the most part carbon. Chemically pure iron is prepared by heating
the pure oxalate or oxide in a current of hydrogen. It is thus obtained
in the form of a black powder, which, when the reduction has been
effected at a sufficiently low temperature, is pyrophoric, spontaneously
oxidizing with incandescence when exposed to the air. If heated to a
higher temperature during reduction, the product is denser and no
longer spontaneously oxidizable. It qiay be fused into a regulus in a
lime crucible by means of the oxyhydrogen flame. Very pure iron
may also be obtained by fusing wrought iron with ferric oxide under a
layer of melted glass free from lead.
Properties, — Pure iron is almost silver-white, and is capable of tak-
ing a high polish. It has a specific gravity of 7.84. It is softer, more
malleable, and less tenacious than wrought iron. It is fusible only at
the very highest temperatures. It does not undergo any change in dry
air at ordinary temperatures ; but In moist air containing carbonic an-
hydride it becomes coated with ferric hydrate or iron rust. The pro-
cess of rusting takes place very slowly at first, but goes on rapidly as
soon as a thin coating of rust has been formed upon the surface of the
metal. When heated in air, iron becomes coated with ferrous diferric
tetroxide, < PeO^^^"' which, on hammering, flies off in scales {smithy
scales). It burns brilliantly when heated in oxygen, emitting showers
of dazzling sparks, and yielding the foregoing oxide. It burns also in
sulphur yapor. It combines directly with the halogens, and at a high
temperature with carbon. At a red heat it decomposes water, with evo-
lution of hydrogen^ and formation of ferrous diferric tetroxide. Dilute
hydrochloric or sulphuric acid dissolves it with evolution of hydrogen,
and when the metal contains chemically combined carbon, hydrocai^
bons are mixed with the hydrogen, imparting to it a peculiar and disa-
COMPOUNDS OF IRON. 656
greeable odor. Nitric acid of sp. gr. 1.35, or lower, dissolves iron
with violent evolution of nitrous fumes and formation of ferric nitrate;
but under certain circumstances iron may be kept immersed for any
length of time in nitric acid without the slightest action, or diminution
of its brightness of surface. This condition, which is known as the
passive state of iron, is produced when the metal is immersed in nitric
acid of sp. gr. 1.45 or higher. The iron which has been thus rendered
passive is not acted upon by dilute nitric acid. The same condition is
induced when iron is made the positive plate of a voltaic couple in
nitric acid : for example, when it is introduced into nitric acid of sp.
gr. 1.35 in contact with a piece of platinum. The platinum may then
be removed, and the iron remains passive. Passive iron does not pre-
cipitate copper from its solutions, but if a piece of passive iron which
has been dipped into the solution of a copper salt be scratched, the cop-
per is instantly deposited on the whole surface of the iron. Passive
iron is powerfully electronegative towards ordinary iron, and a voltaic
couple may be constructed consisting of passive iron in concentrated
nitric acid and ordinary iron in a solution of sodic sulphate, the two
liquids being separated by a porous diaphragm. The phenomenon of
passivity in iron depends upon the formation of a thin film of ferrous
diferric tetroxide upon the surface of the metal. Thus iron may be
rendered ])assive by moderately heating it. The deposition of copper
in the case above described depends upon the fact that by scratching
the passive metal the film of oxide is removed at that part and a sur-
face of iron exposed ; a voltaic action then sets up between the electro-
positive iron and the electro-negative oxide, and the hydrogen which is
liberated on the surface of the latter reduces it, converting it into iron,
which in its turn reduces the copper. The voltaic action between iron
and ferrous diferric tetroxide nuiy be employed in rendering the metal
pa^ssive : thus if one end of a bright iron wire be heated so as to oxidize
it, and then the wire be dipped, with the oxidized end first, into nitric
acid of sp. gr. 1.35, the whole wire is rendered passive. — Iron is at-
tracted by the magnet, and may also be magnetized, but parts with its
magnetism almost instantaneously, whilst steel is capable of permanently
assuming the polar state.
COMPOUNDS OF IRON WITH THE HALOGENS.
a. Ferrous Compounds.
Ferrous chloride, PeCl,, is prepared by heating iron in gaseous
hydrochloric acid. A solution of this compound is obtained by dis-
solving iron in aqueous hydrochloric acid. The anhydrous diloride
sublimes in colorless fusible six-sided scales. When volatilized in an
atmosphere of gaseous hydrochloric acid, it possesses a vapor density
lying between the densities required for the molecular formulse FeCla
and "Fe2Cl4 respectively. It is therefore probable that the iron in this
compound is at lower temperatures tetradic and at higher temperatures
dyadic. When heated in air ferrous chloride is converted into ferric
chloride, which volatilizes, and ferrk; oxide:
656 INORGANIC CBEMISTRV.
6PeCl,
+
30
= ^6,01,
+
TeA.
Ferrous
Ferric
Ferric
chloride.
chloride.
oxide.
It is deliquescent, and soluble both in water and in alcohol. The aque-
ous solution, when concentrated out of contact with air, deposits pale-
green deliquescent crystals of the formula FeCI„40H,. The crystals
absorb oxygen from the air and undergo decomposition. Ferrous chlo-
ride forms double compounds with the chlorides of the alkalies. Potas-
8ic ferrous chloride^ FeCl2,2KCl,20Fl2, is deposited from mixed solu-
tions of its component chlorides in bluish-green monoclinic crystals.
Ferrous bromide, FeBr,, is obtained as a yellowish crystalline mass when bromine
vapor is passed over iron filings heated to low redness. The aqneons solution, pre-
pared by dissolving iron in hydrobromic acid, deposits on concentration the aquate,
FeBvifiOHt, in p^reen tabular crystals.
Ferrous iodide^ Felj. is obtained as a grav laminated mass by heating iron filings in a
closed crucible and adding small quantities of iodine. An excess of iodine is then
added, and the heating is continued until vapors of iodine cease to escape. The aque-
ous solution, which is readily obtained by digesting iron filinirs with iodine and water,
deposits on evaporation green crystals of the formula Fer2,40lls.
Ferrous fluoride, FeFj. — When iron is disnoived in hydrofluoric acid, sparingly solu-
ble green crystals of tlie compound FeFs,80Hs are deposited, which, when heated with
exclusion of air, bedbme anhydrous.
6. Ferric Compounds,
Ferric CHiiORiDE/Pe,Clg. Molecular volume UU. — This compound
18 obtained in the anhydrous state by gently heating iron wire in a cur-
rent of chlorine, and in solution by dissolving ferric oxide in hydro-
chloric acid or iron in aqua-regia. The anhydrous compound forms
dark-brown hexagonal plates, which possess a green metallic lustre, and
appear red by transmitted light. It is fusible, and volatilizes more'
readily than the ferrous com[K)und. It deliquesces in moist air, and is
readily soluble in water ; the dilute solution is yellow, the concentrated
solution is dark-brown, and of an oily consistency. It is also soluble
in alcohol and in ether: the latter solvent extracts the compound from
the aqueous solution when agitated with it. The aqueous solution when
concentrated over sulphuric acid deposits yellow prismatic crystals of
the compound TeaClgjl'iOHj, and at a still higher degree of concen-
tration brownish-red crystals having the formula 'FejClgjGOHj. When
the hydrated chloride is heated, it parts with water and hydrochloric
acid, yielding an oxychloride, which at a higher temperature decomposes
into volatile anhydrous ferric chloride and ferric oxide. A dilute aque-
ous solution, containing less than 4 per cent, of ferric chloride, is <le-
composed on heating into soluble colloidal ferric hydrate (p. 668) and
free hydrochloric acid, this chemical change being accompanied by a
change in the color of the liquid froji yellow to red. When a concen-
trated aqueous solution is evaporated by heat it parts with hydrochloric
acid and an insoluble oxychloride of vary ing composition separates out.
— Ferric chloride forms numerous double compounds. Potassic fanrie
chloride^ Fe2Cl6,4KC],20H2, is deposited in garnet-red crystals from
mixed solutions of ferric and potassic chlorides. Anhydrous ferric
chloride absorbs gaseous ammonia, yielding thecompound 'i'ejCJ5,2NH3,
which in appearance is indistinguishable from ferric chloride.
COMPOUNDS OF IRON. 657
Ferric bromicUy -TeaBr,, is prepared by heating iron in an excess of bromine vapor.
In its properties it closely resembles the chloride.
FerHe iodide has not been obtained. It appears, however, to be capable of existing at
higher temperatures. When the heated mass which is obtained in the preparation of
ferroas iodide (p. 656), and which remains after all the vapors of iodine have been ex-
pelled, is allowed to cool, it suddenly evolves, at a temperature somewhat below redness,
lai^e quantities of iodine vapor, a phenomenon which is probably due to the decompo-
sition of ferric iodide contained in the mass.
Ferric fluoride, ^Te^F^, is formed when ferric oxide is dissolved in hvdrofluoric acid.
It forms colorless sparingly soluble crystals of the formula 'TejFj.OOh^. By heating
these in a platinum crucible over the blowpipe, the water of crystallization is expelled,
and the anhydrous fluoride is obtained as a fused mass. It sublimes in small trans-
parent almost colorless cubes, isomorphous with aluminic fluoride.
COMPOUNDS OF IRON WITH OXYGEN.
Ferrous oxide, .... FeO.
O— Fe— O
Ferrous diferric tetroxide f TeOj^s „ rv x^ t/ r\
{Magnetic oxide), . .jPeO^^- 0=Fe-Fe=0.
O
Ferric oxide, . . . . | j.^qO. 0=Fe— Fe=0.
Ferrovs oxide, "FeO, is difficult to prepare in a state of purity. It is
obtained as a black powder by heating ferric oxide to redness in a
mixture of equal volumes of carbonic anhydride and carbonic oxide, or
by heating ferric oxide to 300° C. (572° F.) in a current of hydrogen.
The product obtained by the latter method undergoes oxidation with
incandescence if exposed to air when freshly prepared, but loses this
pyrophoric property after remaining for twelve hours at ordinary tem-
peratures in an atmosphere of hydrogen.
Ferrous hydrate, FeHo^, is formed when caustic alkali is added to
the solution of a ferrous salt. The precipitation, washing and drying
must be performed in an atmosphere free from oxygen. When pure it
forms a white powder, but generally has a greenish tint, owing to the
difficulty of entirely excluding oxygen. When exposed to the air it
rapidly absorbs oxygen, and is converted into ferric oxide, sometimes
with incandescence.
Ferrous diferric tetroxide {Magnetic oxide\ TeaOjFeo". —
This compound occurs native in black lustrous octahedra and other
forms belonging to the regular system, more fi:equently, however, in
granular masses, constituting the mineral magnetic iron ore. It is
formed when iron is heated in steam or carbonic anhydride, with libera-
tion of hydrogen and formation of carbonic oxide respectively. On the
other hand, by precisely the reverse reactions, hydrogen and carbonic
oxide reduce heated oxides of iron to the metallic state. When iron is
heated in air it becomes coated with magnetic oxide in the form of so-
railed iron Bcale or smithy scales. This is not, however, a pure com-
pound : the outer portions approximate more in composition to ferric
oxide, 'FCjO,, the inner portions, which are next the metal, to that of
ferrous oxide. Ferrous diferric tetroxide is attracted by the magnet,
42
658 INORGANIC CHEMISTRY.
and the native variety frequently possesses the property of attracting
iron. This naturally magnetic variety of the mineral is known as
loadstoney and itA magnetism is derived from that of the earth.
Ferric oxide, Te^O,, occurs as specular iron ore in lustrous steel-
gray hexagonal crystals, also massive, as the important iron ore red
haematite. It may be obtained artificially in reddish-brown lustrous
scales by carefully heating a mixture of ferrous sulphate and common
salt, extracting the mass with water :
2SO,Feo'' = TeA + SO, + SO3.
FerrouB Ferric oxide. Sulphuroas Sulphuric
Bulphate. anhydride, anhydride.
The same compound is obtained in the amorphous condition as a reddish
powder by heating ferric hydrate or ferrous sulphate alone. The native
oxide and the strongly ignited amorphous oxide dissolve with great diffi-
culty in acids. Amorphous ferric oxide, obtained as a by-product in the
manufacture of fuming sulphuric acid (p. 274), is employed as a red
pigment under the name of rouge. It is also used in polishing jewellers'
goods and metallic surfaces generally.
Ferric HYDRifTE, Te,Hog, is obtained as a bulky reddish-brown
precipitate by adding ammonia to a solution of ferric chloride.
When dried at ordinary temperatures it has the composition
represented by the above formula, but when heated to 100°
C, or when boiled with water, or even when left for a long
time in contact with water, it undergoes partial dehydration,
and is converted into the compounds of the formulse \ V^HaP ^^^
I FeOHo* ^[7^*^*^ ^f *^'s composition occur in nature as needle iron
ore or broum iron ore. Ordinary iron rust has the composition
(PeOHo
PeHo,
O , and this compound also occurs in nature as brown hoemaHU.
PeHo^
PeOHo
Various other complex hydrates occur as well-characterized minerals.
A soluble ferric hydrate is also known. Thus a solution of ferric chlo-
ride dissolves large quantities of freshly precipitated ferric hydrate,
yielding a dark-red liquid. The same solution may be obtained by
adding ammonic carbonate to a solution of ferric chloride until a point
is reached at which the precipitate of ferric hydrate no longer redis-
solves. If either of these solutions be subjected to dialysis, ferric chlo-
ride passes through the dialyser and a dark-red liquid remains, con-
taining only 1.6 per cent, of hydrochloric acid to 98.5 of ferric oxide.
Traces of alkalies and salts cause the solution to coagulate. Ail the
ferric hydrates are converted on heating into ferric oxide.
COMPOUNDS OP IRON. 659
OXY-SALTS OF IRON.
a. Ferrous Salts,
Ferrous nitrate, NjO^Feo'^jCOHj, is best prepared by decompoeing ferrous sulphate
with baric nitrate. Crystals can be obtained only from well-cooled solutions. The
crystals are very unstablei and by exposure to air are speedily converted into a red-
dislnbrown powder.
Ferrous carbonate, OOFeo", occurs native as spaihose iron ore
in rhombohedral crystals, which, however, generally contain varying
quantities of the isoraorphous carbonates of calcium, magnesium, and
manganese. This compound may be obtained artificially in microscopic
rhombohedra by heating a solution of ferrous sulphate with an excess
of hydric sodic carbonate in sealed tul)es to 150'' C. (302'' F.). Alka-
line carbonates produce in solutions of ferrous salts a white precipitate
of ferrous carbonate, which speedily becomes dark-colored from oxida-
tion, and when exposed to air is eventually transformed into ferric
hydrate with evolution of carbonic anhydride. Ferrous carbonate is
soluble in water containing carbonic anhydride. It is in this form that
iron usually occurs in chalybeate springs. ,
Ferrous sulphate [Oreen viiriot), SOHo2Feo'',60H2. — This salt
is prepared on a large scale by exposing moistened iron pyrites, FeS"2»
to the air. The soluble ferrous sulphate, together with the excess of
sulphuric acid, thus formed, runs off into tanks, where the excess of
acid is also converted into ferrous sulphate by the addition of scrap iron.
It is best prepared in a state of purity by dissolving pure iron wire in
sulphuric acid, employing an excess of the metal. It forms large pale-
green monoclinic crystals, which effloresce in dry air. These are solu-
ble in 1| times their weight of water at ordinary temperatures, and in
J of their weight of boiling water. The salt loses its 6 molecules of
water of crystallization at 100° C; at 300° C. (572° F.) it parts with
its water of constitution, leaving white anhydrous SOjFeo'-. The
anhydrous salt is decomposed when heated to redness, yielding ferric
oxide, together with sulphurous and sulphuric anhydrides (p. 658).
The moist salt absorbs oxygen from the air and turns brown. Ferrous
sulphate also crystallizes in the rhombic forms of zincic sulphate.
Crystals of this form may be obtained by introducing a small crystal
of zincic sulphate into a supersaturated solution of ferrous sulphate.
If, on the other hand, a crystal of cupric sulphate be employed to
st^rt the crystallization, trinclinic crystals of the formula SOHogFeo",
40H„ isomorphous with those of cupric sulphate, are obtained. Fer-
rous sulphate crystallizes in all proportions with sulphates of copper,
zinc, manganese, and the other metals of the isomorphous dyadic group,
and cannot be purified by crystallization if any of these are present.
Ferrous sulphate is employed in the preparation of inks, iron mor-
dants, etc. — Ferrous sulphate forms, with the sulphates of the alkalies,
double sulphates isomorphous with the double sulphates of the metals
of the magnesium group with the alkalies. Ammonic ferrous sulphate,
( SO2 Amo
< Feo'' ' ,60H2, is obtained by dissolving equivalent quantities of fer-
t SO, Amo
660 INORGANIC CHEMISTRY.
rous sulphate and ammonic sulphate in a small quantity of hot water
and allowing the solution to crystallize. It forms transparent bluish -
green monoclinic crystals. It is much more permanent in air than fer-
rous sulphate, and for this reason is largely used instead of this salt in
volumetric analysis.
Ferrous phoaphalef FsOsFeo^'^s,80EI,. — This compound occurs as the miueral vivianiie
in thin monoclinic prisms, generally of bluish-green tint. It is precipitated on the
addition of hydric disodic phosphate to a solution of ferrous sulphate as a white
amorphous powder which rapidly becomes blue from oxidation.
Ferrous aUicaUj EUFeo^^^ occurs native as the mineral /ayalUe. It also forms the
chief constituent of refinery-alagy obtained in the process of refining iron previous to
puddling. It also occurs in combination with other silicates in a great variety of min-
erals.
6. Ferric SaUs.
Ferric nitrate^ NeOij {'Fe^^^OeY^ *8 obtained by dissolving iron in
an excess of nitric acid, and carefully evaporating the solution. On
adding nitric acid, crystals of the nitrate are deposited, sometimes with
12, sometimes with 18 aq., according to the concentration of the solu-
tion and the quantity of nitric acid employed. The crystals are deli-
quescent and readily soluble in water, but only sparingly soluble in
nitric acid. The brown aqueous solution is decomposed on boiling,
with separation of brown insoluble basic nitrates. Ferric nitrate is
employed as a mordant.
so,-
Ferric mtphaie^ B02-{'Ft'" f)^^fiOK^ occurs native in hexagonal
crystals as the mineral coquimbiie. It is best prepared by dissolving
10 parts of ferrous sulphate in water, together with 4 parts of concen-
trated sulphuric acid, and adding to the hot solution small quantities of
nitric acid until a portion on testing with potassic ferri-cyanide no
longer gives a blue precipitate. The reaction is as follows :
6S02Feo" + SSO^Ho, + 2NO,Ho = SSjO^CFe'^'A)^
Ferrous Sulphuric Nitric Ferric sulphate,
sulphate. acid.- acid.
+ 2'N''0 + 40Hr
Nitric Water,
oxide.
By evaporation the anhydrous salt is obtained as a white mass. It is
soluble in water, yielding a brown solution, but insoluble in concen-
trated sulphuric acid. Basic ferric sulphates of varying compositTou
are obtained by boiling the dilute solution of ferric sulphate or by
adding to its solution a quantity of alkali insufficient for complete pre-
cipitation.
Dipoiamc diferric tetrasulpJiate {Iron alum),
s8^^
SOJ- ('Fe'",O.r,240H,.-
soJkJ
This compound is obtained when the calculated quantity of potassic
sulphate is dissolved in a solution of ferric sulphate, and the conoen-
COMPOUNDS OP IRON. 661
trated solution is kept at a temperature of 0° C. The alum is depos-
ited in violet octahedra, soluble in 5 parts of water at ordinary tem-
peratures.
Ferric phosphate^ P20j(^Fe^^^j08)'*,4OH2, is obtained as a white precipitate when
hydric disodic phosphate is added to a solution of ferric chloride. It is insoluble in
water and in acetic acid, but soluble in mineral acids.
Ferric 8iIicateB.—A dihydrie diferric d{sUi4xUej ^S^('Fe''''j08)'' occurs native as the
mineral anihroaiderite. Ferric silicates also occur in combination with other silicates
in a large number of minerals.
THE FERRATES.
Neither ferric acid, FeO,Ho„ nor its anhydride, PeO,, is known.
When ferric acid is liberated from its salts, it is instantaneously decom-
posed into ferric hydrate and free oxygen.
Potasaie ferrate, PeO^Ko,. — This compound is prepared by suspend-
ing freshly precipitated ferric hydrate in caustic potash and passing a
rapid current of chlorine through the liquid, care being taken, however,
that the temperature does not rise above 40° C. (104° F.). It is also
formed when a positive electrode of cast iron is employed in the elec-
trolysis of caustic potash, and when finely divided iron is fused with
nitre. It forms small dark-red crystals, which appear almost black
by reflected light. It dissolves in water, yielding a red solution which
on standing deposits ferric hydrate and becomes colorless, oxygen being
evolved. The same change takes place instantaneously on heating.
Sodie ferrate, PeOaNaoi, is prepared like the potash salt, which it clo^ly resembles.
Baric ferratej PeOjBao^^, is obtained as a red insoluble precipitate when baric
chloride is added to the solution of the potash salt. It is moderately stable and may
be heated to 100° C. without decomposition.
COMPOUNDS OF IRON WITH SULPHUR.
Ferrous sulphide, PeS", is formed- by the direct union of its
elements. Red-hot wrought iron or steel, but not cast iron, undergoes
apparent fusion when brought in contact with a roll of sulphur, owing
to the formation of the more fusible monosnlphide. The same com-
pound is formed with evolution of heat when a mixture of iron filings
and sulphur is moistened with water and allowed to stand at ordinary
tem|>eratures. It is best prepared by throwing a mixture of 3 parts of
iron filings and 2 parts of sulphur in small portions at a time into a
red .hot Hessian crucible. It is thus obtained as a black porous mass,
which at a higher temperature fuses, solidifying^ to a grayish-yellow,
crystalline, metallic mass, of sp. gr. 4.79. The alkaline sulphides
precipitate from solutions of ferrous or ferric salts black amorphous
ferrous sulphide. In this form it is readily oxidized if exposed to the
air in a moist state. Dilute hydrochloric or sulphuric acid dissolves
ferrous sulphide with evolution of sulphuretted hydrogen.
Diferric irimlpMdej < PeS"^"' — '^^'® compound cannot be pre-
pared by precipitating a ferric salt with ammonic sulphide^ as under
662 INORGANIC CHEMISTRY.
these circumstances a mixture of ferrous sulphide with sulphur is
obtained. It is formed when iron is heated with its own weight of
sulphur, avoiding too high a temperature. It is thus obtained as a
yellowish metallic mass of sp. gr. 4.41. This com}K>und may be
regarded as the sulphanhydride of the sulpho-acid, < « S'^R * "^^^^
acid is not known, but its salts have been prepared. Thus potassic
{FeS"Ks
FfiS"K ' ^ obtained in the form of red^ lustrous, flexi-
ble needles when a mixture of 1 part of finely-divided iron, 6 parts
of dry potassic carbonate, and 6 parts of sulphur is fused and the cooled
mass extracted with water. Copper pyrites A jigQ//('Cu'^"j)", is the
cuprous salt of this sulpho-acid Heptaferric octogidphide {Magndie
pyi'Ues), Fe^Sg, occurs native in brownish-yellow metallic, hexagonal
crystals, more frequently, however, massive. This substance is attracted
by the magnet, and is sometimes itself magnetic.
Ferric Disulphide, FeS"^- — This compound occurs native in two
distinct forms. As iron pyrites it is found in lai^ quantities, either
massive or in brass yellow crystals belonging to the regular system. It
has a specific gravity of 5.185. The same compound is obtained artifi-
cially by heating finely-divided iron with excess of sulphur to a tem-
perature below redness. The native compound ap()ears to have been
formed by the reducing action of organic matter upon ferrous sulphate
dissolved in water, and hence it is chiefly found along with the remains
of organic matter such as coal, peat, etc. Sometimes it assumes the form
of the piece of organic matter by which the reduction has been efiected :
thus wood, roots, ammonites, and other organized forms are found
accurately repnxluced in this material. Maroastte^ or radiated pyrites,
the second form of ferric disulphide, occurs in pale brass-yellow rhombic
crystals with a sp. gr. of 4.68 to 4.86. Neither of the forms of iron
pyrites is magnetic. It is not attacked' by dilute acids or by cold
concentrated sulphuric acid ; but hot concentrated sulphuric acid slowly
dissolves it with evolution of sulphurous anhydride. Hot nitric acid
also oxidizes and dissolves it. When heated in a current of hydrogen
.it is reduced to the monosulphide. It burns with a flame when heated
in air, yielding sulphurous anhydride and ferric oxide. In this way it
is employed in enormous quantities in the manufacture of sulphuric
acid.
General Properties and Reactions op the Compounds op
Iron:
a. Ferrous salts. — ^The aquates of these salts are green, the anhydrous
salts are white. Caustic alkalies precipitate white ferrous hydrate,
which speedily oxidizes by exposure to the air and becomes green.
Ammonia only partially precipitates solutions of ferrous salts as hydrate ;
in presence of an excess of amnionic chloride no precipitate is produced
by ammonia, but the amraoniacal solution absorbs oxygen from the air,
and a film of ferric hydrate forms upon the surface. Stifphuretted hydro-
ffcii does not precipitate ferrous salts in acid solution ; ammonie sulphide
precipitates black hydrated ferrous sulphide, which is readily oxidized
COBALT. 663
by exposure to air. Potassie ferrocyanide gjives a white precipitate of
dipotassic ferroiw ferrocyanide (Fe^'Cy^Fe'^Kj), which rapidly oxidizes
and becomes blue. Pota89io ferricyanide occasions a deep-blue precipi-
tate of ferrous ferricyanide (Turnbull's blue) (Fe'VFe'^',Cyi,). Oxidiz-
ing agents convert the ferrous into ferric salts.
b. Ferric aalta. — ^These have a yellow or reddish-brown color.
Caustic alkaiiea and ammonia give a reddish-brown bulky precipitate of
ferric hydrate, insoluble in excess. Sulphuretted hydrogen does not
precipitate the iron but reduces it to the ferrous state, whilst finely
divided white sulphur is deiKwited. AmTnonie SftUphtde precipitates
black ferrous sulphide with se{)aration of sulphur. Potassicferrocyanide
gives a deep-blue precipitate of ferric ferrocyanide (Prussian blue)
(3Fe^'Cy2,2'Fe"'2Cy6)' Potassie ferricyanide gives no precipitate with
solutions of ferric salts ; but the color of the liquid changes from yellow
to reddish-brown. Soluble thiocyanates give a blood-red coloration
which is not destroyed by hydrochloric acid. Baric carbonate precipi-
tates the whole of the iron in the cold as ferric hydrate with evolution
of carbonic anhydride. /8bc{ic oc^a^ colors neutral solutions dark-red,
and, on boiling, the whole of the iron is precipated as basic ferric acetate.
The beiizoaies and succinates of the alkali-metals produce in neutral
solutions bulky insoluble brown precipitates.
All compounds of iron when heated with sodic carbonate on charcoal
in the reducing flame yield a black magnetic powder. Borax and
microcosmic salt give with iron compounds beads which in the reducing
flame are bottle-green and in the oxidizing flame yellow, or, if the
quantity of iron is very small, colorless. The compounds of iron do
not color flame. The spark-spectrum of the metal contains many
hundreds of bright lines coincident with lines of the solar spectrum.
COBALT, Co.
Atomic weight = 58.6. Molecular weight unknown. Sp. gr. 8.5 to 8.7.
Atomicity' ^f *', and ""* ? ' Also a pseudo-triad. Evidence of atomicity :
Cobaltous chloride, Oo^'Cla.
Cobaltic disulphide, Oo^^S'V
f Oo'^'O
Cobaltic oxide, < (Jq/z/q^*
History. — Cobalt was discovered by Brandt in 1735.
Occurrence. — Metallic cobalt occurs in small quantity in meteoric
iron. Its chief ores, which are not very widely distributed, are the
" ( Ab
arsenides and arsenical sulphides, such as speiss-cobalt, < Ab^^^^' ^^^
{As
. (Co''S'')"2. In almost all the cobalt minerals a por-
tion of cobalt is replaced by nickel, iron, and other isomorphous metals.
Cobalt is present in the solar atmosphere.
Extraction. — The ores of cobalt, which consist, as above stated, of
mixed arsenides and sulphides of cobalt, nickel, and iron, and generally
contain, in addition, copper, bismutli, and other metals, are first roasted
664 INOROANIC CHEMISTRY.
in a current of air. In this way an impure cofaaltous arsenate, known
ad zoffre, is obtained, whilst large quantities of arsenious anhydride are
volatilized, this product being carefully condensed. The roasted mass is
extracted with hydrochloric acid until the residue is free from cobalt.
On evaporating the solution chlorine is evolved, the arsenic acid l>eing
reduced by the hydrochloric acid to arsenious acid, which crystallizes
out. The remainder of the arsenic is got rid of bj oxidizing the arseni-
ous acid back to arsenic acid by the addition of bleaching |x>wder, care-
fully avoiding an excess, and then exactly neutralizing with milk of
lime. In this way ferric hydrate is precipitated, carrying with it all the
arsenic acid. The solution is then again acidified with hydrochloric acid
and treated with sulphuretted hydrogen in order to precipitate copper,
bismuth, etc The cobalt is then precipitated from the weak acid solution
as cobaltic oxide, by the careful addition of bleaching powder. An excess
of the precipitant is to be avoided, as this would bringdown the nickel.
Thecrude oxide, whicth still contains nickel and iron, is washed and ignited.
It is thus converted into cobaltous dicobaltic tetroxide, < n^nf^^'^
in which form it is used in imparting a blue color to glass and porcelain.
In order to obtain pure metallic cobalt, the commercial oxide is dis-
solved in hydrochloric acid, and the solution evaporated to a small
bulk. Ammonic chloride and an excess of ammonia are then added.
Any ferric hydrate which is precipitated is filtered off, and the solution
is exposed to the air for some days until a portion of the liquid, when
treated with excess of concentrated hydrochloric acid, does not become
blue. Excess of concentrated hydrochloric acid is then added to the
entire liquid, which is now heated to boiling and evaporated. Almost
the whole of the cobalt separates as purpureo-cobali chloride, OOjCI^,-
(NHj)!^, in the form of a red crystalline powder. This, when heated in
a current of hydrogen, is reduced to spone^y metallic cobalt, which may
be obtained in the form of a regulus by fusion in a crucible of lime or
graphite. The oxides of cobalt are also reduced to the metallic state
when heated in a current of hydrogen.
Properties. — Metallic cobalt is almost white, with a faint reddish
tinge, and is capable of taking a high polish. It is malleable and very
tenacious. It is magnetic, and, unlike iron and nickel, is attracted by
the magnet also when red hot. Its fusing-point lies somewhat lower
than that of iron. The compact metal is oxidized neither in air nor in
water at ordinary temperatures ; but when heated in air it undergoes
slow oxidation. It dissolves slowly in dilute sulphuric and hydrochlo-
ric acids with evolution of hydrogen, and is readily soluble in dilute
nitric acid.
COMPOUNDS OF COBALT WITH THE HALOGEN.
Cobaltous chloride, OoCIj, is obtained by dissolving any of the
oxides of cobalt in hydrochloric acid and evaporating. In the case of
the oxides higher than cobaltous oxide the solution evolves chlorine.
The concentrated liquid deposits dark-red monoclinic crystals of the
formula OoCl3,60H2. These, when heated to 120° C. (248° F.), are
COMPOUNDS OP COBALT. 665
converted into a dark-blue crystalline powder possessing the formula
CoCl„20Ha, and at a temperature above 140° C. (284° F.), this salt be-
comes anhydrous. The anhydrous salt sublimes in a current of chlorine,
yielding dark-blue scales, which, when exposed to air, absorb moisture
and bea)rae pink-colored. The anhydrous chloride dissolves slowly in
water, yielding a pink-colored solution, and in absolute alcohol with a
blue color, which becomes pink on the addition of water. Most cobal«
tons salts exhibit this property of possessing a pink or rose-color in the
highly hydrated condition, and a blue or violet color in the slightly
hydrated or anhydrous condition. Owing to this property a solution
of a cobaltous salt may be employed as a so-called sympathetic ink.
Characters inscribed upon paper with a dilute solution of cobaltous
chloride are invisible under ordinary conditions, but appear blue when
the paper is warmed to expel the moisture, gradually disappearing
again on cooling, owing to the absorption of moisture from the air. In
like manner a not too dilute pink-colored solution of cobaltous chloride
becomes blue on the addition of an excess of strong hydrochloric acid,
owing to the abstraction of water from the salt in solution.
Oobaitie eUoride^ '^COsClf, is probably formed when cobaltic oxide is dissolved in cold
}iydr(x:hloric acid, but the solution speedily evolves chlorine, and contains cobaltous
chl pride.
Cobcdious bromide^ CoBri, resembles the chloride in properties and mode of prepara-
tion. The aqiiate. CoBra.^OH,, is dark-red, the anhydrous salt green.
Ck)baUou9 iodide. Cols. — This compound is obtained by dif^esting finely divided cobalt
with iodine and water. It forms either brownish-red prisms of the formula Cora,601Is,
or small preen very deliquescent crystals of the formula C0I2.2OH2. When heated to
130^ C. (266° F.), the salt is converted into a black graphite-like mass of the anhydrous
iodide.
ChbaUous fluoride, CoF„20H2, is obtained in rose-red crystals by dissolving the car-
bonate in hydrofluoric acid and evaporating the solution.
COMPOUNDS OF COBALT WITH OXYGEN.
Cobaltous oxide, . . OoO. q p ^
Cobaltous dicobaltic te- f OoO^ /r r\ r^ ni r\
troxlde ioooC°«- 0=Co-Co=0.
Cobaltic oxide, . . A n^rfl. /^
(UOU o=Co— Co=0.
Cobaltous oxide, OoO, is formed when cobaltous hydrate or
cobaltous carbonate is heated with careful exclusion of air. It is best
prepared by strongly heating either of the higher oxides in a current of
carbonic anhydride. It forms a greenish-brown powder, readily soluble
in acids. When heated in hydrogen or carbonic oxide it is reduced to
metal.
CobaltouB hydrate, OoHoj. — On the addition of a caustic alkali to
the solution of a cobaltous salt a blue basic salt is precipitated, which
on boiling is converted into the rose-red hydrate. This, on exposure to
air, speedily turns brown from oxidation. It is insoluble in caustic
alkalies^ but dissolves in ammonia with a reddish color.
666 INORGANIC CHEMISTRV.
Cobnltous dieobaltie tdroxidey 'Oo,OjCoo''. — This compound is formed
M^hen either of the other oxides, or cobaltoas nitrate, is strongly ignited
in air. It forms a black non-magnetic powder.
CobaUte oxide^ 'OOjOj, is prepared by gently igniting^ cobaltous nitrate.
It is a dark-brown powder which dissolves in cold acids, yielding brown
solutions of unstable cobaltic salts. On warming or evaporating the
solutions decomposition ensues — in the case of the hydracids with
evolution of halogen, in the case of the oxy-acids with evolution of
oxygen — ^and a cobaltous salt remains in solution.
Cobaliie hydrate, 'OOjHo,, is obtained as a black amorphous precipi-
tate by adding an alkaline hypochlorite to the solution of a cobaltous
salt. It behaves towards acids like cobaltic oxide.
0XY-8ALTS OF COBALT.
Cobaltous niiraJte^ ISfiJCoo^fiOYl^y forms red, very soluble deliques-
cent monoclinic prisms.
CohaUovLi earhcnaUy COCoo''. — The anhydrous salt is obtained in bright-red micro-
scopic oclahedra by heatin|; cobaltous chloride to 140° C (284° F.) with a sohition of
hydric sodic carbonate which has been previously saturated with carbonic anhydride.
An aqnateof the formula COCoo''''2,60H2 is prepared by mixing asolntion ofcoballous
nitrate with the above sohition of hydric sodic carbonate saturated with carbonic anhy-
dride, and exposing the mixture for some time to a low temperature. — Normal alkaline
carbonates precipitate from solutions of cobaltous salts blue or violet basic carbonates.
Cobaltous sulphate, SOjCoo". — This salt is prepared by dis-
solving the oxide, hydrate, or carbonate in sulphuric acid. Its solutions
de(>osit at ordinary temperatures dark-red monoclinic crystals of diky-
dric eobaltous sulphate, SOHo2Coo",60H2, isomorphous with ferrous
sulphate. The same salt occurs native as cobalt vUrioL Various other
aquates are known. — Cobaltous sulphate forms with the sulphates of
the alkalies double salts, which correspond exactly with the double
sulphates of zinc, magnesia, etc., with the alkalies. Thus, dipotamc
cobaltous sulphate^ gQ*jr^Coo",60H„ forms monoclinic crystals.
CobalUms phogphate. — The normal salt, PtOsCoo^^, is obtained as a rose-red hydrated
precipitate when hydric disodic phosphate is added to the solution of a cobalton? salt.
— Hydric cobaltous phosphate^ ^IPOHoCoo'^fiOHi, is prepared by dividing a qiiantitvof
the foregoing salt into two equal portions, dissolving the one portion in the smallest
possible quantity of hydrochloric acid and then adding the other. It forms thin violet
lam i me.
CohaUous arsenaie. — The normal salt, ASjOjCoo^^g.SOH,, occurs native as cobaU-Uotm
or erythrine in peach -blossom -colored needles, or in earthy incrustations. This mineral
has been formed by the spontaneous oxidation of speiss-oobalt and other native arRenites
of cobalt. Zaffire is an impure basic arsenate of cobalt, prepared by roasting 6peis.<-
cobalt. It is employed in painting on glass and porcelain, for which purpose it must
be free from iron.
SUicaies of Cobalt. — These have not been prepared in a state of purity.
When an alkaline silicate is added to the solution of a cobaltous salt a
blue hydrated silicate of cobalt is precipitated. Smalt is a cobalt-potash
glass — a mixed silicate of cobalt and potassium. In a finely groand
condition it is employed as a blue pigment. It is prepared on a large
COMPOUNDS OF COBALT. 667
scale from 8pei6S-coI)aIt or cobalt-glance. The ore is roasted at a low
temperatare, so as to oxidize the cobalt, leaviug the nickel, iron, and
other impurities, the presenoe of which would be detrimental to the
purity of color of the smalt, as far as possible unaltered. The roasted
ore is then fused with quartz-sand and potashes. The oxidized cobalt
is taken up by the silica and unites with the potassic silicate to form
smalt, whilst the nickel, iron, copper, bismuth, arsenic, etc., collect as
a regulus at the lx)ttom of the melting-pot. The glass is then finely
ground under water. It contains from 6 to 7 per cent, of cobalt and
from 60 to 70 per cent, of silica. Smalt is less frequently emf)loyed
as a pigment than formerly, owing to the introduction of artificial
ultramarine; but it possesses the advantage over the latter pigment of
not being altered by acids.
Two other cobalt pigments are also manufactured : Thenard^8 blue
or cobcUt tUtramarinCy which is obtained by precipitating mixed solu-
tions of alum and oobaltous sulphate with sodic carbonate and igniting
the precipitate; and RinmanWs green, which is prepared in a similar
manner by igniting the precipitate produced by sodic carbonate in
mixed solutions of cobaltous sulphate and zincic sulphate. Nothing is
known concerning the constitution of these pigments.
It has already been mentioned (p. 666) that the simple cobaltic salts
are capable of existing only in solution. Double cobaltic salts are,
however, known which possess a considerable degree of stability.
Potam<i cobaUio niirUe, N^O^('Co'^'20,)^,6NOKo.— This salt is formed
as a yellow crystalline precipitate when potassic nitrite is added to the
solution of a cobaltous salt acidified with acetic acid. Nitric oxide is
evolved in the reaction :
200C12 +
lONOKo
+
4NOHo =
= N,0,('Co'"A)^6NOKo
Cobaltous
Potassic
Nitrous
Potassic cobaltic nitrite.
chloride.
nitrite.
acid.
+ 4K01 + 2'N"0 + 20Hj.
Potassic Nitric Water,
chloride. oxide.
COMPOUNDS OF COBALT WITH SULPHUR.
Cobaltous stTLPHiDE, OoS", is formed as a gray, metallic, crystal-
line mass when cobalt is fused with sulphur. It may be obtained in
long, thin, very lustrous needles of a yellowish-gray color by fusing a
mixture of anhydrous cobaltous sulphate and baric sulphide with an
excess of sodic chloride. Ammonic sulphide precipitates from solutions
of cobaltous salts black amorphous hydrated cobaltous sulphide, scarcely
soluble in cold dilute hydrochloric acid. Concentrated hydrochloric acid
dissolves it with evolution of sulphuretted hydrogen.
Other sulphides, 'OOgS^a and CoS"2, are obtained by heating oobalt-
ous sulphide with sulphur in a current of hydrogen.
CobaUoua dioobattio tetrasulphidey OOaS^aCos", occurs native in steel-
gray or copper-red regular octahedra as the mineral cobalt pyrites.
and is converted into the compound CoCl2,6NH, = -
668 INORGANIC CHEMISTRY.
AMi/ONlUM COMPOUNDS OF COBALT {COBALTA-
MINES).
The cobaltamines are of two classes— cobaltous and cobaltic. Their
salts possess the empirical composition of additive compounds of one
molecule of a cobaltous or a cobaltic salt with a certain number of
molecules of ammonia. The salts of the first class are formed by the
direct union of gaseous ammonia with anhydrous cobaltous salts. In
the formation of the cobaltamines of the second class the oxygen of the
air also plays a part. Thus the solution of a (K)baltous salt in aqueous
ammonia rapidly absorbs oxygen and is converted into a cobaltic ammo-
nium base. Various bases belonging to this class are known. They
all possess characteristic colors^ and from these their names are derived.
a. Cobalioiuji Ammonium Compounds,
CobaUosammonie chlorides, — Anhydrous cobaltoas chloride absorbs dry ammonia gas,
r NH,a
NH,
NH,
Co'' , which is thus ob-
Nff,
NH,
I NH.Cl
tained as a pale pink powder. The same compound is de(>osited In red octahedral
crystals when the chloride is dissolved in concentrated aqueous ammonia and the
solution allowed to stand in a well-stoppered bottle. When heated to 120® C. (248°
F.) it parts with four molecules of ammonia and is convert^ into cobaUoso-diammonie
fNHjCl
dichhride, \ Co'' .
lNH,a
A nitrate of the empirical fornrula N202Coo'^6NH3,20H|, and a sulphate,
80,Coo",6NH3, have also been prepared.
h, CohaUic Ammonium Compounds.
These may be divided into four principal series, of which the chlorides may serve
as examples :
Empirical
formula.
Dlcobaltic-hezammonic {diehro-eobcdiie) chloride, . 'Co,C1^6NH,.
Dicobaltic-octammonic (praseo- and fuseo-^nbcdtic) ) /q^ qi 8NH
chloride, > * ^' '*
Dicobaltic-decammonic (raseo- and purpureo^obaUic \ /^ qi iawtt
chloride, / * * •"
Dicobaltic-dodecammonic {luteo-cobalti4i) chloride, 'Co2Cle.l2NH,.
The «o^-names (see above) are giv^n in brackets. It will be observed that some of
these bases exist in isomeric modifications.
The above compounds behave like chlorides of complex ammonium bases. Thus
the chlorine may oe replaced by hydroxyl, and the resulting compounds are hydrates
possessing an alkaline reaction and a purely alkaline, as opposed to a metallic, taste.
Again, the chlorides form double compounds with platinic and auric chlorides.
r-NH,Cl
r Co-NH,Cl
IHchro-cob<dtic chloride [DicobcLUic hexammonic chloride) - r-wH'ci i^^^t- — ^^^
(Vnh'ci
^NHjCl
compound is formed when a solution of cobaltous chloride in aqueous ammonia
is exposed to the air until tlie separation of black cobaltic hydrate commences. On
Pras€fhcobalUe ekhridef
CJOMPOUNDS OF COBALT. 669
adding an ezoesB of concentrated hydrochloric acid and allowing the liquid to stand
for some time, the cobaltamine chloride is deposited in dark-colorecl laminae or
feather-shaped crystals. The dichroism of this compound is best exhibited by break-
ing a large crystal ; the splinters display different colors.
. r^!NH2(N'H4)Ci
' Co-WH,Cl
, jqu PI
r— Nh'cI i20H,. — This compound is generally
Co-NH^Cl
' ^NH,(N^H0C1
formed along with the preceding and other cobaltamines, remaining in the filtrate
after these have been precipitated with concentrated hydrochloric acid. On saturat-
ing the liquid with ammonic chloride the praseo-compound separates in bright-green
glistening needles.
^NH^fN^HJCl
r Co-NH,(N^HJCl
I ■ TTH CI
jRoaeo-eobcdtio chloride, j r— Nh'cI |20H^ — If a solution of cobaltous chlo-
[ Co^Nh'(N'H4)C1
^NH,(N'Hja
ride in aqueous ammonia be oxidized by exposure to the air until a sample on
testing with excess of strong hydrochloric acid no longer assumes a blue color, the
liquid contains the roseo-componnd. This may be separated by supersaturating the
solution with strong hydrochloric acid, carefully avoiding any rise of temperature
when the roseo-salt is deposited as a brick-red powder. The two molecules of water,
which in the above formula) are represented as water of crystallization, are in reality
water of constitution, inasmuch as they cannot be expelled without converting the
compound into purpureo-eobaltie chloride^ a salt which, though differing totally in its
properties from the roseo-salt, possesses the same chemical composition, excepting that
It is anhvdrous. The purpureo-salt cannot be converted into the roseo-salt merely by
recrystallizing from water. The dry roseo-salt slowly changes at ordinary tempera-
tures into the purpureo-salt. This change takes place more rapidly in solutions, and
on boiling is practically instantaneous.
A numoer of other roseo-salts have been prepared.
Purpur€<h€obaUie chloride. — This compound possesses, as above stated, the same com-
position as the foregoing, less two molecules of water. It is obtained by the same pro-
cess as the roseo-salt, except that after supersaturating with strong hydrochloric acid
the liquid is heated to boiling. The red powder which separates is purified by re-
crystallization from hot dilute hydrochloric acid. The compound is thus obtained in
small purple crystals. It may be converted into the roseo-com pound by dissolving in
dilute aqueous ammonia and adding the solution drop by drop to carefully-cooled
strong hydrochloric acid.
The salts of the purpureo-base with the various other acids have also been pre-
pared.
f Co-NHJN'HJCI
Luteo-eobaUie chloridey i r-NH*(N^H*ici '~~^^ nielhod of preparing the luteo- or
[ C^Nh|(N'HJC1
^NH,(N'H,)C1
dodecamine-compounds yielding perfectly certain results has vet been discovered.
They are formed along with the other cobaltamines in the oxiaation of ammoniacal
solutions of cobaltous salts, especially in presence of ammonic chloride, and must be
separated from these by systematic crystallization. Luteo-cobaltic chloride crystallizes
in reddish-yellow monoclinic prisms.
The above list includes only the principal cobaltamines. Various
other complex bases of this class have been prepared.
General Properties and Reactions op the Compounds of
Cobalt. — The aquates of the cobaltous salts are usually red ; the an-
hydrous salts are blue. With cauntic alkalies their solutions yield in
the cold a blue precipitate of a basic salt, which on boiling is converted
into pink cobaltous hydrate. Ammonia produces a similar precipitate
670 INORGANIC CHEMISTRY.
soluble in excess, yielding a reddish solution which absorbs oxygen
from the air and becomes reddish-brown. In presence of salts of am-
monia no precipitate is produced on addition of ammonia. Svlpht^
reded hydrogen gives no precipitate in presence of strong acids; ammcnie
aiUphide precipitates black hydrated cobaltous sulphide, insoluble in
alkalies and alkaline sulphides, scarcely soluble in dilute hydrochloric
acid, readily soluble in aqua-regia. Potasidc ferrocyanide gives a green
precipitate of cobaltous ferrocyanide (Co'^jFe^'Cyj), and potassic ferric
cyanide a reddish-brown precipitate of cobaltous ferricyanide (Co'V
'Fe'"jCyi,). Potassic cyanide precipitates pale-brown cobaltous cyanide,
which dissolves in an excess of the alkaline cyanide, yielding a double
cyanide of potassium and cobalt. From this solution acids precipitate
cobaltous cyanide. If, however, to the solution containing the double
cyanide, together with an excess of potassic cyanide, a small quantity
of hydrochloric acid insufficient to cause a precipitate be added, and the
liquid be boiled, potassic colmlticyanide (K^'Co^'jCy^) is formed, and
in the solution of this salt neither acids nor ammonic sulphide occasion
. a precipitate. (Distinction between the compounds of cobalt and nickel.)
All the compounds of cobalt when heated with sod ic carbonate on char-
coal in the reducing flame yield shining white metallic particles which
are attracted by a magnet. Cobalt compounds color the borax and
micr(xx)8mic salt beads deep-blue, both in the oxidizing and in the re-
ducing flame. They do not yield a flame-spectrum.
NICKEL, m.
Atomic weight = 58.6. Molecular weight unknown. 8p. gr, 8.9. Atom-
icity ", *', and '* ? Also a pseudo-triad. Evidence of atomicity :
Nickelous chloride, Ni'^Clj.
Nickelic disulphide, Ni^^S'V
f Ni'"0
Nickelic oxide, < jjfifffQ^'
History, — Metallic nickel was first obtained by Cronstedt in 1751.
Occurrence, — Nickel occurs in the native state in meteoric iron, of
which it is an invariable constituent. Its chief ores are its compounds
with arsenic, antimony, and sulphur; and in these it is generally asso-
ciated with cobalt. Kupjer nickel, so called from its oopper-red color,
f AsNi
is a dinickelous diarsenide, < AgM' 5 *^^'^ ^^ *^® raosi important ore of
f As
the metal. A nickelous diarsenide," < *^Ni, also occurs as ar«entca/
nickel. Other minerals are millerite or nickel blende, a nickelous sul-
{As
. (Ni"S")"2; and
breithauptUe, a dinickelous diantimonide, < ouir-' In New Caledonia
a source of nickel has lately been discovered in the mineral gamierik^
a nickelous silicate of the formula 2Si4O3Nio"5,30H2, which occurs
NICKEL. 671
there in large quantities. This ore is remarkable as being free from
cobalt. Nickel has been detected in the solar atmosphere.
Eodradion, — The process of extracting nickel from its ores is iden-
tical with that employed in the extraction of cobalt (p. 663) up to the
point at which the cobalt is precipited as cobaltic oxide by bleaching-
powder. From the solution thus freed from cobalt the nickel is pre-
cipitated as hydrate by the addition of milk of lime. The precipitate
is ignited and afterwards, in order to remove the excess of lime, treated
with dilute hydrochloric acid, in which the ignited oxide of nickel is in-
soluble. The purified oxide is reduced by heating with carbon.
Pure nickel may be prepared by heating pure nickelous oxalate with
exclusion of air. The metallic powder thus obtained may be fused
into a regulus in a lime crucible.
jJgNio" = Ni + 200^.
Nickeloas oxalate. Carbonic anhydride.
Properties, — Nickel is almost silver-white, with a faint yellowish
tinge. It is capable of taking a high polish. It is very hard, but at
the same time malleable and ductile. Nickel fuses at a somewhat
lower temperature than cobalt. It is attracted by the magnet, but loses
this property at a high temperature. It is not oxidized either in air or
water at ordinary temperatures, and is oxidized only with difficulty
when heated in air. It decomposes steam slowly at a red-heat and is
converted into nickelous oxide. It dissolves slowly in dilute hydro-
chloric and sulphuric acids, but is readily soluble in dilute nitric acid.
Concentrated nitric acid renders it " passive " like iron.
The commercial metal contains carbon along with traces of cobalt,
iron, copper, and other metals. The presence of carbon has the same
effect upon nickel as upon iron : it diminishes the malleability and low-
ers the fusing-point of the metal.
Nickel plating. — Nickel may be electrolytically deposited in a coher-
ent coating from a solution of pure diammonie nickelous svJphate^
OQ* A qjqNio''. a plate of pure nickel serves as the positive elec-
trode. Iron and steel are frequently coated with nickel, both on ac-
count of the beauty and permaneiKje of the metallic surface thus
obtained, and also as a protection against rust.
Alloys of nickel. — Nickel yields with copper valuable alloys of a
silver-white color. The material of the small coinage in the United
States, in Germany, in Belgium, in Switzerland, and in Brazil, is an
alloy of 1 part of nickel with 3 of copper. As tins alloy is more val-
uable than copper, the coins are smaller and consequently more port-
able than copper coins possessing an equal value, whilst, owing to the
hardness of the alloy, this coinage is also very durable Chinese pack-
ff/ng is an alloy of copper, nickel, and zinc. German silver or nickel
silver is a similar alloy, consisting, as a rule, of 5 parts of copper, 2 parts
of nickel, and 2 parts of zinc. When first prepared it is crystalline
and brittle; but by rolling and hammering, heating and allowing to
cool, it is rendered tenacious and malleable.
672 INORGANIC CHEMISTRY.
COMPOUNDS OF NICKEL WITH THE HALOGENS.
NiCKEiX)U8 CHLORIDE, NiCl,, 18 obtained as a yellow earthy mass
by dissolving the oxide or the carl)onate in hydrochloric acid and evap-
orating the solution to dryness. It may be sublimed in a current of
chlorine, and is thus obtained in lustrous golden-yellow laminsB. It
dissolves in water, yielding a green solution which deposits on evapo-
ration green monoclinic prisms of the formula NiCljyOOHj.
Niekehtu bromide^ NlBr,, is prepared by heating finely divided nickel in bromine
vapor. Combination occurs with incandescence, and the nickelous bromide Bublimes
in golden-vellow scalf^. The compound deliquenoes in moist air. The gre^n aqueous
solution deposits on evaporation deliqnei«cent needles of the aquate NIBrj.30Hx.
Nickelous iodide^ m^st is obtained in a similar manner by heating spongy nickel in
iodine vapor. It forms black lustrous laminae which dissolve in water, yielding a
green solution. The aquate NiBr^.HOH, forms bluish-green deliqnescent prisms.
Niekdom ftuoridty Nir,, is prepared by evaporating the solution of the carbonate iu
hydrofluoric acid. Bluish-green crystals of the formula NiP„30H, are deposited,
which on boiling with pure water are decomposed with separation of an insoluble oxt-
fluoride.
COMPOUNDS OF NICKEL WITH OXYGEN.
Nickelous oxide, . . . NiO
Nickelic oxide, . . . j w jqO 0=Ni — ^Ni=0.
NiCKEiiOUH OXIDE, NiO, occurs native as the rare mineral bungeniU
in green, translucent, regular octahedra. It may be obtained artificially
in crystals by heating a mixture of nickelous sulphate and potassic sul-
phate to a high tem|)erature. In the crystallized condition it is with
difficulty attacked by acids. By igniting the hydrate or carbonate it is
obtained as a gray amorphous powder, readily soluble in acids.
Nickelous hi/drate, NiHo^, is an apple-green precipitate, obtained by
adding caustic alkalies to the boiling solution of a nickelous salt. The
precipitate is washed with hot water and dried. Acids dissolve it
readily. It is insoluble in potassic hydrate and sodic hydrate, but
ammonia dissolves it, yielding a blue solution, from which it is repre-
cipitated as a green crystalline powder on expelling the ammonia by
boiling.
NicKELic OXIDE, 'Ni^O,, is prepared by careful ignition of the
nitrate. It is a black powder which dissolves in hydrochloric acid
with evolution of chlorine, and in sulphuric acid with evolution of oxy-
gen. Ammonia dissolves it with evolution of nitrogen.
S'Ni^Oj + 2NH3 = 6NiHo, + N,' + 30H,.
Nickelic oxide. Ammonia. Nickelous hydrate. Water.
Niokelio hydrate, 'Ni^Ho^. — This compound is obtained as an amor-
phous black powder when chlorine is passed through water (or prefer-
ably through a solution of an alkaline hydrate or carbonate) in which
nickelous hydrate is suspended ; or by warming a solution of a nickelous
salt with an alkaline hypochlorite. Towards acids and ammonia it
behaves like nickelic oxide.
CX>MP0UND8 OP NICKEL. 673
OXY'SALTS OF NICKEL.
Nickelous nitratey NgO^Xio^'jGOHg, is obtained by dissolving the
metal, the oxide, or the carbonate in nitric acid. It crystallizes in
deliquescent green raonoclinic prisms.
Nickelous nitrite^ NjOjNio", is prepared by decomposing nickelous sulphate with
baric nitrite and evaporiiting the filtrate over sulphuric «cid. It forms reddish-yellow
crystals, which, when dry, may be heated to 100^ C. without decomposition, but in
solution are decomposed at 80° C. (176° F.) with separation of a basic salt. — It forms
with the nitrites of other metals double salts : tUw** DOtassicnickehus nitrite^ N^O^Nio'^,-
4N0Ko, and baric nickeJbm nitrite^ NjOiNio'-'/iNjOsBao'''. On adding pota^sic nitrite
to the mixed solution of a nickel salt with a salt of barium, stirontium, or calcium, the
triple salts,
NANio^^N,0,Bao'',2NOKo ; NA^^Jo''.N202Sro'^2NOKo; and
NjO,Nio'^N,0,Cao'^2NOKo,
are precipitated as sparingly soluble yellow crystalline powders, consisting of minute
octabedra. The^^e salts closely resemble in appearance potassic cobaltic nitrite.
Owing to the formation of these salts it is not possible, in presence of the metals of the
alkaline earths, to separate cobalt from nickel by means of potasnic nitrite.
Nickelous carbonate. — The anhydrous salt, CONio'^, forms pale-green microscopic
octaliedra; the aquate, CONio''^,60Hj, cryst«llizes in minute rhombohedra or prisms
Both are obtained like the corresponding cobalt compounds (p.
Nickelous sulphate. — This salt is obtained by dissolving metallic
nickel, or its oxide, hydrate, or carbonate, in dilute sulphuric acid. At
ordinary temperatures it crystallizes from neutral solutions in green
rhombic prisms of the formula SOHo2Nio",60H2, isomorphous with
magnesic sulphate. At temperatures between 30^ and 40° C. (86-104°
F.), or from solutions containing an excess of acid, bluish-green
quadratic pyramids of the formula SOHo2Nio",50H2, are obtained.
This aquate is also deposited at temperatures above 50° C. (122° F.),
but in monoclinic forms. 100 parts of water at 16° C (60° F.) dis-
solve 37.4 parts of anhydrous salt. — Anhydrous nickelous sulphate
absorbs dry ammonia and is converted into a violet-white powder of
the composition SOjNio'^jGNIIj. — Nickelous sulphate forms double
salts with the sulphates of the alkali metals and ammonia. Dvamnionio
nickelous sulphate, ar^A Nio",60H2, a salt employed in nickel
electro-plating (p. 671), is prepared by adding ammonic sulphate to a
concentrated solution of pure nickelous sulphate. Tlie double salt
separates as a crystalline powder and is purified by recrystallizatiou.
Nickelous phosphaU, PjOjNio^^^, is formed as a pale-green hvdrated precipitate
when hydric dismlic phosphate is added to the solutiou of a nickel s;ilt. On heating,
it becomes anhydrous and turns yellow.
Nickelous arsenate, As20iNio^''8,80na, occurs native as the mineral nickel bloomy in
green capillary crystals or as an efflorescence.
COMPOUNDS OF NICKEL WITH SULPHUR.
Nickelous sulphide, NiS", occurs native as millet'Ue or capillary
pyrites in brass-yellow hexagonal and generally capillary crystals. It
is formed when nickel and sulphur are heated together. Ammonic
sulphide precipitates frqm solutions of nickel salts black hydrated
43
674 INORGANIC CHEMISTRY.
amorphous nickelous sulphide, and if yellow aramonic sulphide h^
been employed, an excess of this precipitant dissolves a portion of the
precipitate, yielding a brown solution. The precipitate is slowly oxi-
dized by exposure to the air when moist. The precipitated compound
dissolves with difficulty in hydrochloric acid ; and this acid is totally
without action upon the native sulphide or upon that prepared in the
dry way.
Nickdic difulphide, N1S''''>, is obtained by fusing a mixture of nickelous carbonate and
Bodic carbonate with an exceu of sniphnr. On extracting the mass with water the
disulphide remains as a dark inm-gray impalpable powder.
General Properties and Reactions op the Compounds of
Nickel. — The aquates of the salts of nickel are of an apple-green color ;
the anhydrous salts are yellow. Caustic alkalies precipitate pale-green
nickelous hydrate, which is not altered either by boiling or by exposure
to air. Ammonia gives a similar precipitate, soluble in excess, yield-
ing a greenish-blue liquid ; in presence of salts of ammonia no precipi-
tate is formed. SulphureUed hydrogen produces no precipitate in solu-
tions with strong acids ; ammonic sulphide precipitates, black hydrated
nickelous sulphide, slightly soluble in excess, yielding a brown solution.
The sulphide is scarcely soluble in dilute iiydrochloric acid, readily
soluble in aqua-regia. Poiassio ferrocyanlde precipitates greenish-whire
nickelous ferrocyanide(Ni "2 Fe"Cvg); potassic ferriet/anide precipitates
yellowish-brown nickelous ferricyanide (Ni"Y^^'"2Cyi2)- Potasfi'tc
cyanide produces a yellowish -green precipitate of nickelous cyanide,
soluble in excess of the precipitant with formation of a double salt
From this solution acids reprecipitate nickelous cyanide, and if the
solution be warmed with sodic hypochlorite the nickel is precipitatai
as black hydrated nickelic oxide. (Cobalt is not precipitated under
these circumstances by sodic hypochlorite). The compounds of nickel,
when heated with sodic carbonate on charcoal in the reducing flame,
yield white shining magnetic particles of metallic nickel. With b«»rax
and microoosmic salt the compounds of nickel yield characteristically
colored fluxes. In the oxidizing flame the borax bead is violet while
hot, reddish-brown when cold ; the microcosmic salt bead is red or re<l-
dish-brown while hot, yellow, or reddish-yellow when cold. In the
reducing flame the microcosmic salt bead undergoes no change, whiij^t
the borax bead turns gray and clouded, owing to the separation of
metallic nickel. The nickel compounds do not color flame.
NORWEGIUM, Ng.
Atomic weight = 214 ? Sp. gr. 9.441. Fuses at 254° C. (489° F ).
This rare metal has been recently discovered by Dahll in a specimen of Norwegian
nickel glance. Very little is yet known concerning it. In most of its properties it
closely resembles bismuth, bat differs from this element in the solubility of its oxide in
an excess of potassic hydrate, or of alkaline carbonates, on boiling. Assuminj; the
correctness of the above atomic weight, the oxide possesses the formula Xg^Os- Excess
of water decomposes its salts with precipitation of basic compounds.
INDEX.
\* In order that names of compounds may as far as possible appear under the headings
of their respective elements^ the numerical prefixes di^ tri, eiCy have been omitted in the Jndex,
except in cases where they serve to distinguish compounds that might otherwise be confounded.
Abraumsalz, 511
Absorption of gases by charcoal, 196
Accumulators, electrical, 106
Acid, arsenic, 372
arsenions, 371
auric, 554
bisulphu retted hyposulphuric, 280
boracic, 191
boric, 191
bromic, 294
carbonic, 208
chlorhydric, 156
chloric, 181
chlorochromic, 638
chromic, 634
chromous, 634
disulphodithionic, 280
dithionic, 278
dithionous, 278
ferric, 660
graphitic, 199
hydriodic, 298
hydrobromic, 292
hydrochloric, 156
hydrofluoboric, 190
hydrofluoric, 307
hydrofluosilicic, 315
hydrofielenic, 285
hydrosulphuric, 249
hydrosulphnrous, 278
hypobromous, 294
hypochlorous, 179
hyponitrous, 221
hypophosphoric, 358
hypophoephoroiis, 350
hyposuiphuric, 278
hvposulphurous, 276
iodic, 302
manganic, 647
roetabismuthic, 395
metabismuthous, 394
metaboric, 192
roetantimonic, 387
metantimonic, of Freray, 387
metantimonious, 385
metaphosphoric, 353
Acid, metarsenic, 373
metastannic, 327
metatungstic, 626
molybdic, 621
muriatic, 156
nitric, 214
nitrous, 223
Nnrdhaiisen sulphuric, 274
orthantimonic, 387
ortharsenic, 373
orthoboric, 191
orthophosphoric, 356
osmic, 601
parantimonic, 387
pentathionic, 281
perchloric, 183
perchroraic, 633
periodic, 304
permanganic, 648
phosphomolybdic, 622
phosphoric, 356
phoephorosophosphoric, 358
phosphorous, 351
platinonitrous, 590
pyrantimonic, 387
pyrarsenic, 373
pyrophospliamic, 364
pyrophosphodiamic, 364
pyrophosphoric, 355
pyrophosphotriamic, 363
pyrosulphiiric, 274
selenic, 287
selenious, 286
silicic, 318
silicon-oxalic, 313
silico-tungstic, 627
stannic, 327
Bulphhydric, 249
sulphindic, 563
sulphocarbonic, 258
sulphodithionic, 279
sulphuretted hyposulphuric, 279
sulphuric, 267
sulphurous, 262
telluric, 289
tellurous, 288
676
INDEX.
Acid, tetrathiotiicy 280
thioRiiIphnric, 276
titanic, 332
trisulphodithionic, 281
trisulphuretted hydrosulphuric, 281
trithionic, 279
tungstic, 625
tungstic, coUoidal, 626
tungsto-silicic, 627
vanadic, 366
Acids, definition of, 40
^thiops mineralis^ 535
Affinity, chemical, 34, 102
After-danip, 203
Agalmatolite, 572
Air, 237
analyses of, 239
not a compound, 242
Alabaster, 477
Albite,572
Aldebaran, elements detected in, 406
Alkali waste, 244
Allophane, 572
Allotropv, 110
Alloys, 410
Alum, 569
shale, 570
stone, 570
Alumina, 567
Alnminates, 568
Aluminic bromide, 566
chloride, 566
Unoride, 566
hydrate, 568
hvdrate, collodial, 668
iodide, 566
manganons sulphate, 647
nitraie, 568
oxide, 567
oxydi hydrate, 568
oxytetrahydrate, 568
phosphate, 571
silicate, 571
sodic fluoride, 566
sulphate, 569
sulphide, 576
Alnminio-sodic fluoride, 426
Aluminite, 569
Aluminium, 564
bronze, 565
general properties and reactions of
the compounds of, 576
Alums, 569
Alunite, 570
Amalgamation process for ezti'action of
silver, 448
Amalgams, 529
Amidogen, 86
Ammonia, 230
alum, 571
chrome alum, 634
gallium alum, 577
Ammonia-soda process, 429
Ammoniacal cobalt compounds, 668
mercury compounds, -536
Ammoniacal platinum coropoands, 591
Ammonic borate, 446
bromate, 443
bromide, 441
carbonate, 443
chlorate, 443
chloride, 441
chlorostannate, 326
chromate, 637
dichromate, 637
di-iridic chloride, 596
dithionate, 445
ferrous sulphate, 659
fluoride, 442
heptasulphide, 446
hydrate, 442
hyposulphite, 445
indie sulphate, 563
iodate, 443
iodide, 442
iridic chloride, 597
magnesic chromate, 637
nickelous sulphate, 673
nitrate, 442
nitrite, 443
palladic chloride, 594
pentasulphide, 446
perchlorate, 443
permanganate, 649
pliosphate, 445
phosphomolybdate, 622
platinic chloride, 441
platinonitrite, 590
potassic sulphate, 444
pyrophosphate. 445
pyrosulphite, 445
silicofluoride, 442
sodic phosphate, 445
sodic sulphate, 444
sulphate, 444
8ulf>h hydrate, 446
sulphide, 446
sulphite, 444
thiosulphate, 445
tungstate, 627
uranate, 618
Ammonium, 86, 235
amalgam, 235
general properties and reactions of
the salts of, 446
salts of, 440
Ammonoxyl, 86
Analcime, 572
Anatfl.se, 332
Andalusite, 572
Anglesite, 612
Anhydride, antimonic, 386
antimonious, 384
arsenic, 372
arsenious, 370
auric, 554
bismnthic, 394
boracic, 190
boric, 190
carbonic, 200
INDEX.
677
Anhydride, carbonic, decomposition of by
plants, 164
chloroas, non-existence of, 177
chromic, 632
hypochlorous, 177
hyponitrous, 220
iodic. 301
molybdic, 621
nitric, 219
nitrous. 222
osmic, 601
permanganic, 645
persulphiiric, 276
phosphoric, 266
pho«tphoroufl, 351
selenious, 286
silicic, 316
silicoformic, 314
stannic, 326
sulphantimonic, 389
sulphantinionious, 388
sulpharsenic, 376
sulpharseniouH, 374
sulphuric, 265
sulphurous, 260
telluric, 289
tellurous, 288
titanic. 382
tungstic, 625
nranic, 616
Tanadic, 365
Anhydrides, definition of, 40, 42
Anorthite, 319
Anthracite, 198
Anthrosiderile, 661
Antimonic chloride, 382
fluoride, 383
oxy trichloride, 383
sulphide, 389
sulphotrichloride, 383
tetrethochloride, 378
Antimonious amylide, 381
argentide, 381
bromide, 383
chloride. 381
ethide, 381
fluoride, 383
hydride, 381
iodide, 383
oxide, 3S4
oxy bromide, 383
oxychloride, 382
oxy fluoride, 383
oxyiodide, 383
sulphide, 388
zincide, 381
Antimoniuretted hydrogen, 380
Antimony, 378
amorphous, 379
copper glance, 389
crystalline, 378
general properties and reactions of,
390
ochre, 378
Antimonylic antimonate, 385
Apatite, 357, 479
Apjohnite, 646
" Aq," use of symbol, 431
Aquafortis, 214
Aquamarine, 521
Aqua-regia, 218
Aquates, 45
Aqueous vapor, 240
Argentic amide, 459
arsenate, 458
arsenite, 458
bromate, 457
bromide, 453
carbonate, 457
chlorate, 456
chloride, 452
chromate, 638
dichroraate, 638
dithionate, 457
fluoride, 454
hyposulphite, 457
iodate, 457
iodide, 453
metaphosphate, 458
nitrate, 456
nitrite, 456
orthophoephate, 458
oxide, 454
periodate, 457
permanganate, 649
peroxide, 455
phosphate, 458
phosphide, 459
pyrophosphate, 458
sulphantimonite, 459
sulpharsenite, 459
sulphate, 457
sulphide, 459
sulphite, 457
thiosulphate, 457
Argentite, 459
Argentous oxide, 454
chloride, 453
Argillaceous iron ore, 651
Arragonite, 477
Arsenates, 373-376
Arsenic, 366
fluoride, 370
general properties and reactions of the
compounds of, 376
poisoning, antidote for, 371
sulphide, 376
Arsenical iron, 366
nickel, 670
pyrites, 366
Arsenious bromide, 370
chlorhvdrate, 369
chloride, 369
fluoride, 370
hydride, 367
iodide, 370
sulphide, 375
sulphide, colloidal, 375
Arsenites, 372, 376
Arseniuretted hydrogen, 367
678
INDEX.
ArtiadH, 79
Atacamite, 544
Atmosphere, 237
com position of, 239
weight of, 238
Atom, definition of, 59
*' Atomic analogues," 94
Atomic heat, 68
theory, 48
weight definition of, 61
weight, determination of by Aroga-
dro's law, 61
weight, determination of by means of
iHomorphism, 64
weight, determination by Neumann's
Jaw, 71
weight, determination of by means of
specific heat, 67
weights, list of, 38
volume, 96
volumes, curve of, 95
Atomicity, 78
active, 81
absolute, 81
latent, 81
law of variation of, 80
of elements, 88
Atoms, 48
nature of, 51
Auric ammonic chloride, 554
chloride, 553
hydrate, 555
oxide, 554
potassic chloride, 554
sodic chloride, 554
Aurous ammonic sulphite, 555
chloride, 553
iodide, 553
oxide, 554
sodic thiosulphate, 555
sulphide, 556
Avogadro's law, 53 '^
apparent exceptions to, 63
Azote, 211
Azurite, 547
Baking porcelain, 574
Baric bromide, 461
carbonate, 465
chlorate, 465
chloride, 461
chromate, 637
dichroniate, 637
dithionate, 466
ferrate, 661
fluoride, 462
hvdrate, 463
iodide, 462
manganate, 648
nickelous nitrate, 673
nitrate, 464
nitrite, 465
orthophoHphate, 466
osmate, 602
Baric oxide, 462
perchlorate, 465
permanganate, 649
peroxide, 463
platinate, 590
pyrosulphate, 466
silicofluoride, 462
sulphhydrate, 467
sulphate, 465
sulphide, 467
sulphite, 466
tetrasulphide, 467
thiosulphate, 466
Barium, 460
amalgam, 460
general properties and reactions of
the compounds of, 468
Baryta, 462
water, 464
Bases, definition of, 43
Batteries, secondary, 106
storage, 106
Bauxite, 568
Bell metal, 542
Berth elot, laws of thermochemistry. 111
Berthierite, 389
Beryl, 521
Beryllia, 522
Beryllic aluminate, 568
bromide, 522
carbonate, 523
chloride, 521
fluoride, 522
hvdrate, 522
iodide. 522
nitrate, 523
oxide, 522
phosphate, 523
silicate, 523
sulphate, 523
sulphide 523
Beryllium, 521
general properties and reactions of the
compounds of, 523
Bessemer process of steel making, 653
Bismuth, 391
general properties and reactions of
the compounds of, 396
glance, 396
ochre, 393
telluric, 396
Bismutbous bromide, 392
chloride, 391
dichlorethide, 391
ethide, 391
fluoride, 392
iodide, 392
nitrate, 394
nitrate dihydrate, 393, 394
oxide, 393'
oxide, salts of, 394
oxvbroniide, 392
oxvchloride, 392
oxvhvdrate, 394
oxviodide, 392
INDEX.
679
BlsiDiithons sulphide, 396
telluride. 396
iiranate, 618
Bitter-spar, 510
Black ash, 429
Black band, 651
Black-lead, 199
BUmcjhe, 466
Bleaching, 476
Bleaching powder, 181, 476
Blister copper, 540
Blue malachite, 547
Blue vitriol, 547
Boiling points, 119
influence of pressure upon, 120 •
method of determining, 121
relation of to molecular weight,
121
Bolognian phosphorus, 467
Bonds, 78
Boracite, 512
Borates, 192
Borax, 434
Boric-bromide, 189
chloride, 188
ethide, 185
fluoride, 189
hydride, 187
nitride, 187
sulphide, 193
Borofluorides, 190
Boron, 185
adamantine, 185
amorphous, 186
graph itoid, 185
Boulangerite, 389
Boyle, law of, 52
Bonmonite, 389
Bracket, use of, 76
Brass, 541
Braunite, 643
Breithauptite, 670
Britannia metal, 323
Brittleness, 408
Brochantite, 547
Bromargyrite, 453
Bromates, 295
Bromides, 293
Bromine, 290
hydrate, 291
Bronze, 542
Bnxjkite, 332
Brown haematite, 658
Brown iron ore, 658
Brucite, 509
Brunswick ^reen, 644
Brushite, 479
Bucholzite, 572
Bunsenite, 672
Butter of antimony, 382
Cadmic bromide, 525
carbonate, 525
chloride, 525
Cadmic hydrate, 525
iodide, 525
nitrate, 525
oxide, 525
sulphate, 526
sulphide, 526
Cadmium, 524
amalgam, 530
general properties and reactions of
the compounds of, 526
Csesic antimonious chloride, 440
carbonate, 440
chloride, 440
hvdrate, 440
nitrate, 440
platinic chloride, 440
sulphate, 440
Ciesium, 439
general properties and reactions of the
compounds of, 440
Calaite, 571
Calamine, 518
siliceous, 519
Calcic bromide, 473
carbonate, 477
chlorate, 475
chloride, 472
chlorohypochlorite, 181, 476
chlorophosphate, 335
chromate, 637
dithionate, 478
fluoride, 473
hydrate, 474
hypochlorite, 475
hypophosphite, 480
iodide, 473
iodohypiodite, 297
nitrate, 476
nitrite, 476
orthophosphate, 478
oxide, 474
oxychlorhydrate, 473
peroxide, 474
phosphate, 479
phosphide, 344, 483
potassic sulphate, 478
silicates, 480
silicofliioride, 473
sodic sulphate, 478
sulphate, 477
sulphide, 483
sulphite, 478
thiosulphate, 478
tnngstate, 627
Calcined magnesia, 509
Calcite, 477
Calcium, 471
general properties and reactions of the
componnds of, 484
Calc-spar, 477
Calomel, 530
Calorie, 68
Capillary pyrites, 673
Carat, definition ofj 553
Carbon, 193
680
INDEX.
Carbon, bisulphide of, 256
circulation of in OAture, 202
Carbonates, 207
Carbonic disiilphide, 256
oxide, 208
oxide, compound of with (wtasfiinm,
210
oxydichloride, 211
oxysiilphlde, 258
Carbon V 1 ic chloride, 211
Carnallite, 508
Caifsel yellow, 607
Cast iron, 652
Caustic potash, 415
soda, 427
Celestine, 470
Cementation pn)ce89 of steel making, 653
Ceric fluoride, 580
hvdrate, 580
nitrate, 580
oxide, 580
sulphate, 581
Cerite, 578
Cerium, 578
Cerous chloride, 580
fluoride, 580
hydrate, 580
nitrate, 580
oxide, 580
phosphate, 581
potassic sulphate, 581
Cervantite, 385
Chrilcedony,319
Chalk, 477
Charcoal, IM
absorption of gases by, 196
animal, 195
Charles, law of, 53
Chemical action, modes ot^ 102
affinity, 102
combination, heat of, 111
equations, 76
formula. 75
homogeneity, 108
nomenclature, 39
notation, 75
Chiastblite, 572
Cliili saltpetre, 427
China, 574
China clay, 572, 573
Chlorates, 182
Chloraurates, 554
Chloride of lime, 476
Chlorine, 151
hydrate, 154
oxygen compounds of, 177
Chloric peroxide, 178
Chlorochromates, 639
Ciiloronitrous gas, 228
Cliloropal, 320
Chloroi>ernitric gas, 229
Chlorophyll, iron in, 651
Chromates, 635
Chrome alum, 634
iron ore, 635
Chrome ochre, 631
orange, 637
red, 637
yellow, 637
Chromic bn>mide. 630
chloride, 630
dioxide, 634
fluoride, 630
hvdrate, 632
hvdrate. colloidal, 632
nitrate, 634
nitride, 639
oxide, 031
oxychlorliydrate, 638
oxydichloride, 638
perfluoride, 631
sulphate, 634
sulphide, 639
Chromites, 634
Chromium, 629
general properties and reactions of
the compounds of, 639
Chromosphere, 405
Chromous bromide, 630
chloride, 630
chromic oxide, 633
hvdrate, 631
oxide, 631
phosphate, 633
sulphate, 633
Chromvlic chlorhydrate, 638
chloride, 638
Chrvsobervl, 568
Chrysocolla, 549
Cimolite, 572
Cinnabar, 535
Clay, 573
Clav iron-stone, 651
Coal, 197
Coal-gas, purification of, 245
Coarse metal, copper, 539
Cobalt, 663
ammonium Compounds of, 668
bloom, 666
general properties and reactions of
the compounds of, 669
pyrites, 667
ultramarine, 667
vitriol, 666
Cobaltamines, 668
Cobaltic chloride, 665
hydrate, 665
oxide, 666
Cobaltosammonic chloride, 668
Cobaltoso-diammonic dichloride, 668
Cobaltons arsenate, 666
bromide, 665
carbonate, 666
chloride, 664
dicobaltic tetrasulphide, 667
dicobaltic tetroxide, 665
fluoride, 665
hydrate. 666
iodide, 665
nitrate, 666
INDEX.
C81
Cobal 10118 oxide, 665
phosphate, 666
Bilicate, 666
sulphate, 666
sulphide, 667
Coheiiive power, 407
Coke, 197
Colloidal sulphides, 549
Colloids, 130
Collyrite, 572
Combination, 112
atomic, 87
by volume, 54
laws of, 45
molecular, 87
Combustibles, 165
Combustion, 164
supporters of, 165
Compound radicals, 85
Compounds, binary, 39
Common salt, 426
Condy's disinfectinf^^ fluid, 648
Constant proportions, law of, 45
Conversion of volumes into weights, 137
" Converted nitre," 416
Copper, 038
alloys of, 541
amalgam, 529
compounds of with oxygen and hy-
droxyl, 544
general properties and reactions of
the compotmds of, 550
glauce, 549
pyrites, 538, 662
smelting, 539
Coprolites, 479
Coquimbite, 660
Corrosive sublimate, 531
Corundum, 567
Cotnnnite, 607
Cream of tartar, 385
Crith. definition of, 137
Critical point, 121
Crookesite, 557
Crvohydrates, 118
Cryolite, 426, 566
Crystallization, suspended, 128
fractional, 110
water of, 88
Crystallography, 131
Crvstalloids, 130
** Crystals of the leaden chamber," 268
Crystals, systems of, 132
Cupellation process for extraction of sil-
ver, 448
Cnprammonic chloride, 544
sulphate, 548
Cupric arsenate, 548
arsenite, 548
bromide, 544
carbonate, 547
chloride, 544
fluoride, 544
hydrate, 544
nitrate, 544
Cupric oxide, 546
oxychloride, 544
phosphate, 648
phosphide, 342, 550
silicate, 549
silicide, 312
sulphate, 547
sulphide, 549
Cuprosammonic chloride, 543
Cuprous acetylide, 543
arsenide, 550
bromide, 543
chloride, 542
fluoride, 544
hvdrate, 546
hydride, 542
iodide, 543
nitride, 550
oxide, 544
phosphide, 550 •
quad ran toxide, 544
sulphide, 549
Cuttle-fish, copper in blood of, 53S
Cyanite, 672
Dal ton, atomic theory, 48
Dark red silver ore, 459
Decipium, 585
Decomposition, 103, 113
Dialvsis, 129
Diamond, 199
Diantimonic tetroxide, 386
Diarsenious disulphide, 374
Diaspore, 568
Dibismuthous dioxide, 392
disulphide, 395
tetrachloride, 392
Dichro-cobaltic chloride, 668
Didymic oxide, 581
Didyraium, 581
Didvmous chloride, 581
"hjrdrate, 581
nitrate, 581
oxide, 581
sulphate, 581
Di ferric trisulphide, 661
DiflTusion, 128
ofgases, 109, 130
of liquids, 129
Di-iridic hexabromide, 596
hexachloride, 596
hexahvdrate, 597
trioxide, 597
trisulphide, 598
trisulphite, 598
Dimanganic diox yd i hydrate, 643
hexachloride, 642
trioxide, 643 .
Dimanganous manganite, 643
Dimercurammonic chloride, 537
oxide, 537
Dimolyl)dic trioxy-hexachloride, 621
Dimolyl)dous hexabromide, 620
hexachloride, 620
682
INDEX.
Diinolybdous hexahydrate, 620
trioxide, 620
Dimorphisin, 67
Diosmic hexachloride, 601
trioxide, 601
Diopside, 319
DiopUi8e, 649
Di phosphoric telrasulphide, 362
Di phosphorous tetrioaide, 347
Di plumbic trioxide, 609
Di(X)taRsic disulphide, 421
Dirhodic hexahydrat«, 599
trioxide, 599
Diruthenic hexachloride, 603
hexahydrate, 604
hexiodide, 603
trioxide, 604
Dii^easeH, zjmotic, propacfation of, 485
Dlsilicic hexabromide, 314
hexachl5ride, 313
hexafluoride, 316
hexiodide, 315
hvdrotrioxide, 314
Diosdic dioxide, 427
Dissociation, 103
Distannic trioxide, 327
Distillation, fractional, 109
DLsulphur dibromide, 256
dichloride, 255
diniodide, 256
Di thai lie tetrachloride, 558
*Dithionate«, 279
Dititanic hexachloride, 330 .
trioxide, 332
DIuranic decachloride, 615
Diuranous hexachloride, 615
Dolomite, 510
Double decomposition, 114
Dry copper, 540
Ductility, 409
Dulong and Petit, law of, 68
Dulong and Petit's law, exceptions to, 69
limit of validity of, 69
Dutch metal, 541
Dyad elements, 160, 460, 524
Earthenware, 576
Ebullition, 119
percussive, 121
Electrolysis, 103
laws of, 104
Electro-silvering, 452
Electrum, 551
Elements and compounds, 37
classification of, 88
list of, 38
molecular weights of, 56
Emerald, 320, 521
Emery, 567
Enstatite, 513
Epsomite, 511
E(>som salt, 511
Equations, chemical, 76
Equivalence, 78
Eauivalence of heat and chemical change,
law of, 112
Equivalent proportions, law of, 46
Equivalents, electrochemical, 107
Erbia, 584
Erbium, 584
Erbous hydrate, 585
nitrate, 585
oxide, 584
sulphate, 585
Erythrine, 666
Estramadurite, 335
Ethylic orthosilicate, 312
silico-orthoformate, 312
Euxenite, 334
Expansion by heat, 398
Fahl ore, 389
Fayalite, 660
Farberite, 627
Feather ore, 389
Felspar, 320
Ferrates, 661
Ferric bromide, 657
clilorlde, 656
disulphide, 662
fluoride, 657
hydrate, 658
hydrate, colloidal, 658
iodide, 657
nitrate, 660
oxide, 658
phosphate, 661
silicate, 661
sulphate, 660
Ferrous bromide, 656
carbonate, 659
chloride, 655
chromite, 635
diferric tetroxide, 657
fluoride, 656
hvdrate, 657
iodide, 656
nitrate, 659
oxide, 657
phosphate, 660
silicate, 660
sulphate, 659
sulphide, 661
tungstate, 627
Fibrolite, 572
Fine metal, copper, 539
Firedamp, 203
Flint, 319
Fluocerite, 578
Fluorides, 308
Fluorine, 306
Fluor-spar, 473
Force, 33
Forces, attractive, 36
Formulae, calculation of, 84
chemical, 75
constitutional, 77
empirical, 77
INDEX.
683
Formn]», graphic, 82
molecular, 77
rational, 77
so-called equivalent, 108
Fowler's solution, 372
Francolite, 357
Franklinite, 514
Fraunhofer lines, 405
Freezing-mixtures, 118
Frit (porcelain), 674
Fulminating gold, 555
silver, 459
Fiisco-cobaltic chloride, 668
Fusible metal, Wood's, 399
Fusing-point, influence of pressure upon,
117
Fusion, 117
change of volume accompanying, 117
latent heat of, 117
Gadolinite, 583
Gahnite, 514
Galena, 613
Gallic choride, 577
oxide, 577
sulphate, 577
Gallium, 576
general properties and reactions of
the compounds of, 577
Gamierite, 670
Gas carbon, 197
Gases, diffusion of, 130
expansion by heat, 52
linuefaction'of, 1J3
relation of, to pressure, 52
solubility of, 124
Gav-Lussac, law of, 54
" Gerhardt's base,*' chloride of, 591
German silver, 671
Gilding, 552
Glance-cobalt, 663
Glass, 480
annealing, 482
Bohemian, 480
bottle, 480
colored, 483
composition of, 483
crown, 480
devitrification of, 483
flint, 480
making, 480
plate, 480
potash, 480
soda, 480
toughened, 482
unannealed, 481
window, 480
Glauberite, 478
Glauber's salt, 430
Glucinum, 521
Gold, 551
fineness of. 558
fulminating, 555
Gold, general properties and reactions of
the compounds of, 550
mining, hydraulic, 552
standard, 553
Graphite, 198
Gray antimony ore, 388
Greenock ite, 526
•' Green salt of Magnus," 591
Green vitriol, 659
" Gros' chloride," 591
Grossularia, 320
Guanite, 512
Guignet's green, 632
Gun metal, 542
Gunpowder, 416
Gurolite, 580
Gypsum, 477
burnt, 477
Heematite, brown, 658
red, 658
Hfpmocyanin, 539
Haemoglobin, iron in, 651
riaidingerite, 373
Haloid salts, definition of, 43
Hardness, 408
Hausmannite, 643
Heat, atomic, 68
molecular, 70
specific, 67
specific, table of, 73
unit of, 68
Heavy glass, Faraday's, 613
Heavy-spar, 465
Hemihedral forms, 133
Hepar sulphuriSy 422
Heptaferric octosulphide, 662
Hexad elemenU, 243. 614, 629
Hexagonal system, 135
Homogeneity, chemical, 108
Horn-quicksilver, 530
Horn -silver, 452
Hiibnerite, 627
Hydracids, definition of, 42
Hydrargillite, 568
Hydrate, definition of, 43
Hydric ammonic sodic phosphate, 445
oxide, 169
peroxide, 175
persulphide, 254
potassic sodic phosphate, 433
potassic tartrate, 385
Hydrogen, 140
displaceable, 41
liquefnction of, 148
occlusion of, by metals, 148
Hydrogeniura, 148
Hvdroniagnesite, 510
Hydrosulphyl, 86, 254
Hydroxvdimercurammonic iodide, 537
HVdroxyl, 86, 175
Hydroxylamine, 235
Hypiodous chloride, 300
684
INDEX.
Hypochloritefl, 181
Hvpomolvl)donH bromide, 620
chloride, 619
oxide, 620
HypopalladoiiR oxide, 594
sulphide, 594
Hypophofiphites, 350
HypoBiilphiirous chloride, 255
bydroBulphate, 254
Hypotungfltous bromide, 624
chloride, 624
iodide, 624
Hypovanadic chloride, 365
oxide, 365
Hypovanadous chloride, 364
oxide, 365
Ice, 173
artificial production of, 232
Indie chloride, 562
hydrate, 563
nitrate, 563
oxide, 562
sulphate, 563
sulphide, 563
sulphite, 563
Indigo copper, 549
Indium, 561
ammonia alum, 563
general properties and reactions of the
compounds of, 563
Introduction, 33
Induction tube. 166
lodargyrite, 453
lodates, 303
Iodides, 300
Iodine, 295
as a heptad, 305
lodous chloride, 300
Ions, 103
Iridic bromide, 597
chloride, 597
hydrate, 597
iodide, 597
oxide, 597
sulphide, 598
Iridium, 595
black, 596
general properties and reactions of
the compounds of, 598
IridouR sulphide, 598
Iron, 650
alum, 660
amalgam, 529
general properties and reactions of
the compounds of, 662
meteoric, 650
passive state of, 655
pyrites, 662
telluric, 650
Irresolvable nebulae, spectra of, 406
Isomerinm, 110
Ismorphism, 64
Johannite, 616
Kaolin, 572, 573
of EUenbogen, 572
Kelp, 296
Keramohalite, 569
Kerargyrite, 452
Kiefferite, 511
Kobellite. 396
Kupfer nickel, 670
Labradorite, 319
Lamp-black, 196
Lana phihmphica^ 517
Lanthanous chloride, 582
hydrate, 582
oxide, 582
sulphate, 582
Lanthanum, 582
Lapis lazuli, 573
Latent heat of fusion, 117
vapors, 122
Laughing gas, 220
Laurite, 605
Lead, 605
basic "hyponitrate" of, 610
compounds of, with oxygen, 608
desilverization of, 448
general properties and reactions of
the compounds of, 613
Leblanc's process for the manufacture of
sodic carbonate, 428
Lepidolite, 435, 572
Lii)ethenite, 548
Liebigite, 614
Light red silver ore, 459
Lignite, 198
Lime, chloride of, 476
kilns, 474
milk of, 474
superphosphate of, 480
Limestone, 477
Liquids, diffusion of, 129
solubility of, 124
Litharge, 609
Lithia, 436
Lithic carbonate, 437
chloride, 436
dithionate, 437
fluoride, 436
hvdrate, 436
iodide, 436
nitrate, 437
oxide, 436
perchlorate, 437
phosphate, 437
sulphate, 437
Lithium, 435
general properties and reactions of
the compounds of, 437
Liver of sulphur, 422
INDEX.
685
Loadstone, 658
Lucifer matches, 340
Luminous paints, 467
I^nteo-cobaltic chloride, 669
Magnesia, 509
Magnesia alba, 510
Magnesia iLSta, 509
Magnesic aluminate, 568
ammonic arsenate, 512
ammonic carbonate, 510
ammonic chloride, 508
ammonic orthophosphate, 51 2
ammonic sulphate, 511
arsenate, 512
borate, 512
boride, 513
bromide, 503
calcic carbonate, 510
calcic chloride, 508
carbonate, 51 0
chloride, 508
chromate, 637
fluoride, 609
hydrate, 509
io'dide, 509
nitrate, 510
nitride. 513
orthophoB[)hate, 512
oxide, 508
phosphate, 512
potassic carbonate, 510
potassic chloride, 508
potasj^ic orthophosphate, 512
potassic sulphate, 511
silicate, 513
silicide, 311, 513
sodic fluoride, 509
sodic orthophosphate, 512
sulphate, 510
sulphydrate. 513
sulphide, 513
Magnesite, 509
Magnesium, 507
general properties and reactions of
the compounds of, 513
light, 508
Magnetic iron ore, 657
oxide, 657
properties of elements, 94
• pyrites, 662
Malachite, 547
Malleability, 409
Malthacite, 572
Manganates, 647
Manganese, 640
ahim, 647
black oxide of, 644
blende, 649
characteristic properties and reactions
of tlie compounds of, 650
Manganic dioxide, 644
disiilphide, 650
perch loride, 642
Manganic perfluoride, 642
peroxide, 644
peroxide, regeneration of, 645
sulphate, 647
Manganite, 643
ManganouB bromide, 642
carbonate, 646
chloride, 641
chromite, 635
di manganic textroxide, 643
dithionate, 646
fluoride, 642
hydrate, 643
iodide, 642
nitrate, 646
oxide, 642
silicate, 647
sulphate, 646
sulphide, 649
timgstate, 627
Marble, 477
Marcjisite, 662
Marsh's test, 377
Match©*, safety, 340
Matter, 33
Mnximuro work, law of, 112
Measures of capacity, 137
length, 136 "
surface, 136
weight, 137
Meerschaum, 319, 513
Mendeleef, arrangement of elements, 91,
92
Mercurammonic chloride, 537
Mercuridiammonic dichloride, 537
Mercuric bromide, 532
carbonate, 534
chloride, 531
chromate, 638
fluoride, 532
iodide, 5o2
nitrate, 534
nitride, 536
oxide, 533
oxy chloride, 532
phosphate, »535
potassic sulphide, 636
sulphate, 534
sulphide, 535
sulphochloride, 536
Mercurius solubilis Hahnemann^ 536
Mercurosammonic chloride, 536
nitrate. 536
Mercurosodiammonic dichloride, 537
Mercurous brotnate, 534
bromide, 530
carbonate, 534
chlorate, 533
chloride, 530
fluoride, 531
iodide, 531
oxide, 533
nitrate, 533
perch lorate. 534
sulphate, 534
686
INDEX.
MercuroiiB nnlphide, 535
Mercury, 527
general propertiefl and reactions of
the compounds of, 537
Metallic elements. diHtinf^uishing charac-
terJHticfl of the, 397
Metal slag, cop|)er, 53^
Metals, 397
colors of ignite<l liquid, 400
expansion of by heat, 898
fusibility of, 398
of the rare earths, 578
order of ductility of, 409
order of malleability of, 409
relations of, to gravity, 406
relations of, to heat, 398
' relatione of, to light, 399
relative tenacity of, 408
specific gravity of, 406
volatility of 399
Metamerism, 110
Metaphosphates, 354
Metastannates, 327
Metatnngstates, 626
Meteoric iron, 650
of Lenarto, 148
Meyer, Lothar, curve of atomic volumes, 95
Miargyrite, 389
Microcosm ic salt, 445
Milk of lime, 474
Millerite, 673
Miloschine, t')72
Mimetesite, 613
Mineral chameleon, 643
Minium, 609
Moirie miUdlique, 322
Molecular heat, law of, 70
volume, 96
volume of ga^es, 96
volume of liquids, 98
volume of solids. 97
volumes, calculation of, 99
volumes of liquids, table of, 101
weight, calculation of, 53
weight, determination of, 60
weights, 52
weights of elements, 55
work, law of. 111
Molecule, definition of, 59
Molecules, 48
size of, 52
Molvbdates, 621
Molybdenite, 623
Molybdenum, 619
general pro}ierties and reactions of the
comix>unds of, 623
Molybdic dioxydibromide, 621
dioxydichloride, 621
oxytetrachloride, 621
pentaohloride, 020
persulphide, 623
sulphide, 623
Molvbdous chloride, 620
'hydrate, 621
iodide, 620
I Molvbdous oxide. 620
I 'sulphide, 623
' Monad elements, 140, 290, 411-447
Monazite, 334
Monoclinic system, 134
Mortar, 475
hvdraulic, 475
Mosaic gold, 329
> Muntz metal, 541
; Multiple profMrtions, law of, 46
I Mysorin, 547
Nascent state, 55
Needle iron ore, 658
Needle ore, 396
Nessler's solution, 537
Neutralization, change of volume in, 116
heat of, 116
Neumann, law of molecular heat, 70
Nickel, 670
allovs of, 671
bloom, 673
general properties and reactions of the
compounds of, 674
glance, 670
plating,^671
silver, 671
Nickelic disulphide, 674
hydrate, 672
oxide, 672
Nickelous arsenate, 673
bromide, 672
carbonate, 673
chloride, 672
fluoride, 672
hvdrate, 672
iodide, 672
nitrate, 673
nitrite, 673
oxide, 672
phosphate, 673
silicate, 670
sulphate, 673
sulphide, 673
Niobium, 378
compounds of, 378
Nitrates, 218
Nitre, 416
plantations, 214
Nitnc dioxvchloride, 229
oxide, *224
peroxide, 226
Nitrification, 214
Nitrogen, 211
oxygen compounds of, 213
Nitrosylic chloride, 228
Nitrous bromide, 237
chloride, 236
hyd rod in iodide, 237
iodide, 237
oxide, 220
oxychloride, 228
Nitroxylic chloride, 229
Nomenclature, chemical, 39
INDEX.
687
Non-metals, 140
Notation, chemical, 75
graphic, 82
symbolic. 76
Norwegium, 674
Octad elements, 600
Okenite, 319, 480
Olivenite, 549
Opal, 317
Ophite, 319, 513
Ore-furnace, copper, 539
slag, copper, 539
Ornithite. 478
Orpiment, 374
Orthite, 582
Osmates, 602
Osminm, 600
general properties and reactions of
the compounds of, 602
Osmic chloride, 601
hydrate, 601
oxide, 601
peroxide, 601
sulphide, 602
Osmirinium, 600
Osmous oxide, 601
sulphite, 602
Osteolite, 335, 478
Over- poling copper, 540
Oxygen, 160
allofcropic, 166
diatomic molecule of, 176
Oxy- hydrogen flame, 165
Ozone, 166
Ozonizer, 166
Packfong, 671
Pall ad ic chloride, 594
oxide, 594
sulphide, 595
Palladium, 592
spongy, 592
general properties and reactions of the
compounds of, 595
hvdride, 593
Palladous bromide, 593
chloride, 593
hydride, 593
iodide, 593
nitrate, 594
oxide, 594
sulphate, 504
Rulphide, '^95
Passive iron, 655
Pentad elements, 211, 335, 581
Pentatitanic hexanitride, 333
Perchlorates. 184
Peridote, 319, 513
Periodates, 305
F^eriodic law, 90
Perissadfl, 79
Permanent white, 466
Permanganates, 648
Permanganic hexoxy-dichloride, 649
Perruthenates, 604
Peruranates, 618
Petalite, 435, 572
Pewter, 323
Pharmacol ite, 373
Phenacite; 319, 523
Phosgene gas, 210
Phospham, 363
Phosphamimide, 363
Phosphates, 356
Phosphine, 340
Phosphites, 3'o2
Phosphochalcite, 548
Phanphonic bromide, 342
chloride, 342
iodide, 342
Phosphor-bronze, 542
Phosphoretted hvdrogen, gaseous, 340
liquid, 343
solid, 344
Phosphoric bromide, 347
chloride, 345
chloride, action of, upon organic com-
pounds, 346
fluoride, .S47
oxynitride, 363
oxytriamide, 363
oxy tri bromide, 360
oxytrichloride, 359
oxy trichloride, action upon organic
compounds, 360
sulphide, 361
sulphotrichloride, 362
Phosphorite, 479
Phosphorosphosphates, 358
Phasphorous bromide, 347
chloride, 345
iodide, 347
sulphide, 3^2
Phosphorus, 335
amorphous, 338
compounds of with sulphur, 361
octahedral, 337
oxygen compounds of, 348
red, 338
rhombohedral, 339
Phosphorylic chloride, 359
Phosphotungstates, 627
Photosphere, 405
"Pink-salt," 326
Pitchblende, 616
Plaster of Paris, 477
Platinamines, 591
Plati nates, 590
Platinic bromide, 689
chloride, 589
hvdrate, 590
iodide, 589
oxide, 590
sulphide, 500
Plati n iridium, 595
Platinodiammonic chloride, 591
Platinonitrites, 690
688
IND£X.
Plntinotetraminonic rhioride, 591
Platinous bromide, 589
chloride, 587
Jivdrate, 590
iodide, 589
oxide, 590
sulphide, 590
salphite, 590
Platinum, 586
black, 587
general properties and react ione
the con)()ound8 of, 591
Bpongy, 587
PlatoHodiammonic chloride, 591
PJatoAotetrammonic chloride, 591
hydrate, 591
Plattnerite, 609
Plumbic ammonic sulphate, 612
arsenate. 013
borate, 613
bromide, 608
carb<»nate, 610
chloride, 007
chromate 637
dithionate, 612
fluoride, 608
iodide, 608
molybdate, 622
nitrate, 610
nitrate nitrite, 610
nitrite, 610
oxide, 609
oxychloride, 608
oxy hydrate, 609
perchloride, 608
plioHphate, 612
silicate, 613
sulphate, 612
sulphide. 613
sulphochloride 613
tungstate, 627
PlumbouB oxide, 608
Polins: copper, 540
Polymerism, 110
Polytungstates, 626
Porcelain, 573
clay, 572
clay of Passau, 572
glazing. 574
hard, 574
tender, 575
Portland cement, 475
Potafih, 415
alum, 570
Potnssic aluminic bromide, 566
aluminic chloride, 566
amide, 423
antimonate, 420
antimony lie tartrate, 385
arsenate, 420
aurate, 554
borate, 420
bromate, 417
bromide, 414
carbonate, 417
of
' Potassic chlorate, 417
chloride, 414
chlorochromate, 639
cbloroplatioate, 414
chromate, 636
chromic sulphate. 634
chromous sulphate, 633
cnbal tic nitrite, 667
cobaltous sulphate, 666
cupric sulphate, 548
dichromate, 636
di-iridic chloride, 596
diosmic chloride, 601
dioxide, 414
dithionate, 419
ferrate, 661
ferric chloride, 656
ferric sulphate. 6()0
fernms chloride, 656
fluoride, 414
hydrate, 415
hydride, 413
iodate, 417
iodide, 414
iridic chlt>ride, 597
lithic sulphate, 437
magnesic cliromate, 637
manganate, 647
manganic sulphate, 647
manganite, 644
manganous sulphate, 646
manganous sulphide, 649
metantimonate (of Fremy), 420
metaphosphate, 420
metaxtannate, 32/
molyl)date, 622
nickelous nitrate, 673
nitrate, 416
nitride, 424
nitrite, 416
oxide, 415
orthophosphate, 419
osmate, 602
osmous sulphite, 602
palladic chloride, 594
palladous chloride, 593
perchlorate, 417
periodate, 417
permanganate, 648
perruthenale, 604
persulphomolybdate, 623
phosphate, 419
phosphite, 420
phosphomolybdate, 622
platinic chloride, 414, 589
platinonitrite, 590
platinons sulphite. 590
plalinous sulphodiplatinate,.o90
polysulphides, 421
pyrantimonate, 420
pyrophosphate, 419
pyrosulphate, 418
pyrosulphite, 419
ruthenate, 604
seienate, 4] 9
INDEX.
689
Potafisic selenite, 419
silicate, 420
silicofluoride, 414
silico-tuDgstate, 627
sodic carbonate, 430
Bodic pyrophosphate, 433
Btannicofluoride. 326
sodic sulphate, 431
sulphantirnonate, 423
8ulpliart>enate, 423
sulphate. 418
sulphhydrate, 421
sulphide, 42U
sulphindate. 563
sulphite, 418
sulphocarbonate, 257
Bulphoferrite, 662
sulphomolybdate, 623
sulphoetannate, 328
sulphothallate, 561
sulpho-tungstate, 628
teliurate, 419
tetrachromate, 636
letroxide, 415
thiosulphate, 419
titanofluoride, 330
trichromate. 636
tungstate, 626
tnngsto-tuDgstate, 628
uranate, 618
uranylic sulphate, 617
zincic chloride, 617
zirconoflnoride, 333
Potassium, 411
amalgam, 529
general properties and reactions of the
compounds of, 424
Potassoxyl, 86
Pottery, 573
ware, 576
Praseo-cobaltic chloride, 669
Precipitation, fractional, 110
Prehnite, 573
'* Preparing salt," 327
Proustite, 459
Pseudo-alums, 646
Pucherite, 364
Puddling, 653
Purple of Cassins, 555
Purpureo-cobaltic chloride, 669
Pyranlimonates, 387
Pyrargyrite, 459
Pyrographitic oxide, 199
Pyrolusite, 644
Pyromorphite, 613
Pyrophosphates, 355
Pvrophosphorvlic chloride, 360
Pyrophyllite, 319
PyroBulphurylic chloride, 283
Quadratic system, 134
Quartz, 316
Quicklime, 474
I Radiated pyrites, 662
Radicals, acid, chlorides of, 229
compound, 85
Rare earth metals, general properties and
reactions of the compounds of, 585
Rare earths, metals of the, 578
Razoumotlskin, 572
Realgar, 373
Reaumur's porcelain, 483
Red copj)er ore, 545
hasmatite, 658
lead, 609
phosphorus, 338
zinc ore, 517
Refinery slag, copper, 540
Regular system, 132
Reinsch's test, 377
'• Reiset's first base," chloride of, 591
*• Reiset's second base," chloride of, 591
Rfaodic chloride, 599
nitrate, 599
oxide, 599
sulphate, 599
sulphiTe, 599
Rhodium, 598
general properties and reactions of
the compounds of, 599
Rhodonite, 647
Rhodous oxide, 599
sulphite, 599
Rhombic system, 134
Rinmann's green, 667
Rock crystal, 319
Roman alum, 570
Cfment, 475
Roseo-cobaltic chloride, 669
Rouge, 658
Rubidic borate, 439
bromide, 438
carbonate, 439
chlorate, 439
chloride, 438
dithionate, 439
hvdrate, 439
i<>dide, 438
nitrate, 439
perch lorate, 439
platinic chloride, 43S
sulphate, 439
Rubidium, 438
general properties and reactions of the
compounds of, 440
Ruby, 567
artificial, 567
Rupert's drops, 481
Ruthenates. 604
Ruthenic cliloride, 603
hydrate, 604
oxide, 604
peroxide, 604
sulphate, 604
sulphide, 605
Ruthenium, 602
general properties and reaction?? of the
compounds of, 605
44
C90
INDEX.
Ruthenous chloride, 603
oxide, 604
Rutile, 332
Sal alembroth, 531
Salt-cske procees, 428
Saltpetre, 416
Salts, acid, de6nition of, 44
baAic, definition of, 44
definition of, 43
haloid, definition of, 43
normal, definition of, 44
oxy-, definition of, 43
sulpbo-, definition of, 44
Samarium, 585
SamarouB chloride, 585
oxide, 585
Sand, 319
Saponite, 573
Sapphire, 567
artificial, 567
Satin-spar, 477
Saturated rapors. 121
Saturation, fractional, 1 ID
Scandium, 585
Scandous oxide, 585
Scheele's green, 548
Scheelite, 6*^7
Sohlippe's salt, 435
Schonite, 511
Schweinfurt green, 872
Sciences, clasftification of, 34
Secondary action in electrolysis^ 105
Selenite, 477
Selenium, 283
Seleniuretted hydrogen, 285
Sellai'te, 509
Senarniontite, 384
Serpentine, 319
noble, 319, 513
Silica, 316
Silicates, 319
Siliceous calamine. 519
Silicic bromide, 314
chloride, 313
fluoride, 315
hydride, 311
hyd rot rich loride, 314
iodide, 315
sulphide, 320
trichlorsulphhydrate, 320
Silicium, 309
Siliciuretted hydrogen, 311
Silicofluorides, 316
Silicon, 309
bromoform, 314
chloroform, 314*
iodoform, 314
Sillimanite, 572
Silver, 447
general properties and reactions of the
compounds of> 459
glance, 459
standard, 451
Silvering, 452
Sirius, elements detected in, 406
Slaked lime, 474
Smalt, 666
Soda alum, 571
Soda-aah process, 429
Sodic aluminate, 568
aluminic chloride, 566
amide, 435
antimonate, 434
antimonite, 434
ai^entic thiosulphate, 458
arsenate, 434
borate, 434
bromate, 428
bromide, 426
carbonate, 428
chlorate, 428
chloride, 426
chromate, 636
dichromate, 636
di-iridic chloride, 596
dithionate, 432
ferrate, 661
fluoride, 426
hydrate, 427
hydride, 426,
hyposulphite, 432
iodate, 428
iodide, 426
iridic chloride, 597
iridous sulphite, 598
manganate, 648
metaphosphate, 433
molybdate, 622
nitrate, 427
nitrite, 428
oxide, 427
perchlorate, 428
periodate, 428
permanganate, 649
peruranate, 618
phosphate, 432
polysulphides, 435
platlnic chloride, 590
platinous sulphite, 590
pyrantimonate, 434
pyrarsenate, 434
pyrophoRphate, 433
pyro6ulphite,431
selenate, 432
isilicate, 434
silicate ( Yorke's), 319
silicofluoride, 426
stannicofluoride, 326
sulphantimonate, 435
Bulpharsenate, 435
sulphate, 430
sulph hydrate, 435
sulphid:e, 435
sulphite, 431
sulphostannate, 329
tellnrate, 432
thiosulphate, 432
tungstate, 626
INDEX.
691
fiodic tungBto-tnngstate, 628
iiranate, 618
zincic chloride, 517
Sodium, 424
amalgam, 529
general properties and reactions of
the compounds of, 435
Solder, 323
Solidification, suspended, 119
Solids, solubility of, 125
Solubilities, diagram of, 126
Solubility of gases, 124
liquids, 124
solids, 125
Soluble soda glass, 435
Solution, 124
fractional, 110
Sombrerite, 478
Spathoee iron ore, 659
Specific gravity, relation of to chemical
composition, 96
heat, 68
heat equivalents, 74
heats, table of, 73
Spectra of gases,- 402
of solids and liquids, 402
solar and stellar, 405
Spectroscope, 400
Spectrum analysis, 400
delicacy of, 403
Specular iron ore, 658
pig iron, 652
Speculum metal, 542
Speiss cobalt, 663
Spiegeleisen, 652
Spinelle, 568
Spodumene, 573
Stannates, 327
Stannic bromide, 326
chloride, 325
fluoride, 326
iodide, 326
oxide. 326
sulphide, 328
fluorides, 326
Stannous aurous stannate, 555
bromide, 325
chloride, 325
fluoride, 325
hvdrate,326
icKlide, 325
oxide, 326
stannate. 327
sulphide, 328
Stassfurtite, 512
Steatite, 319, 513
Steel, 653
natural, 651
tempering, 654
Stibnite, 388
Stolzite, 627
Stoneware, 575
Strontianite, 470
Strontic bmmide, 468
carbonate, 470
Strontic chlorate, 469
chloride, 468
chromate, 637
dithionate, 470
fluoride, 469
hydrate, 469
iodide, 469
nitrate, 469
orthophoHphate, 470
oxide, 469
peroxide, 469
silicofluoride, 469
sulphate, 470
sulphite, 470
thiosulphate, 470
Strontium, 468
general properties and reactions of
the compounds of, 470
Strnvite, 512
Substitution, 114
Sulphanhydride, molybdic, 623
tungstic, 628
Sulphantimonates, 389
Sulphantimonites, 389
Sulpharsenates, 376
Sulpharsenites, 375
Sulphates, 273
Sulphhvdrates, 252
Sulphides, 252
Sulphites, 263
Sulpho-acids, definition of, 42
Sulphobismuthites, 396
Sulphocarbonates, 258
Sulphophosphates, 362
Sulphostannates, 329
Sulphur, 243
allotropic modifications of, 246
halogen compounds of, 254
liver of, 422
oxygen compounds of, 259
plastic, 248
rhombic, 247
Sulphuretted hydrogen, 249
Sulphuric iodide. 256
oxychlorliydrate, 282
oxydichloride, 282
Sulphurous chloride, 255
oxydichloride, 282
Sulphury lie chlorhvdrate, 282
Sulphurylic chloride, 282
Sun, elements detected in, 406
Superheated vapors, 121
Supersaturation, 128
Sylvine, 414
Syngenite, 478
Tachydrite, 508
Talc,' 31 9, 513
Tantalum, 378
compounds of, 378
Tarter emetic, 385
Tellurates, 289
Telluretted hydrogen, 288
Telluric bismuth, 396
692
INDEX.
Tellurites, 289 I
Tellurium, 287
Tenacity, 415 I
Tenorit'e, o46
Tephroite, 647
Terbium,' 585
Tetrad elementit, 193, 309, 564, 578, 5b5,
605
Tetradymite, 228, 396
TetraphoRphoroiis trisulphide, 361 1
Tetrathallic hexachloride, 558
Thallic bromide, 558 |
chloride, 558
nitrate, 560
oxide, 558
Bulphate, 559
sulphide, 560
Thallium. 556
general properties and reactions of,
the compounds of, 561
Thalloiis bromide, 558
carbonate, 559
chloride, 557
fluoride, 558
hydrate, 559
iodide, 558
nitrate, 559
oxide, 558
oxy hydrate, 559
phosphate, 560
pyrophosphate, 560
sulphate, 560
sulphide, 560
zincic sulphate, 560
Thenard's blue, 667
Thermochemistry, 111
Thick letters, use of, 77
Thio-acids, definition of, 42
Thionvlic chloride, 281
Thorite, 330
Thorium, 330
compounds of, 330
Tin, 321 .
amalgam, 530
character and reactions of salts of,
329
compoun<ls of, 323
Tincal, 192. 434
Tinning, 323
Titanates, 332
Titanic chloride, 331
cyanonitride, 333
nitride, 333
oxide, 332
sulphide, 332
Titanium, 330
compounds of, 331
general character and reactions of,
383
Titanous oxide, 332
Tombac, 541
Topaz, 573
Toughening copper, 540
Triad elements, 185, 551> 582
Triads, 90
Triamylstibine, 381
Triclinic svstem, 135
Tridymite,'317
Triethylstibine, 381
Triethylsulphinic iodide. 243
Triphyline, 435
Tri plumbic tetroxide, 609
Trititanic tetranitride, 333
Tungstates, 626
Tungsten, 623
general properties and reactions of
the compounds of, 628
Tungstic dioxydibromide, 626
dioxydichloride, 626
hexachloride, 625
oxytetrachloride, 626
pentachloride, 624
sulphide, 628
Tungsto-tunffstates, 628
Tungstous chloride, 624
oxide, 625
sulphide, 628
Turpeth mineral, 535
Turquoise, 571
Type metal, 607
Ultramarine, 573
Ultramarine, green, 573
Unit of heat, 68
thermal. 68
Uranates, 617
Uranic hvdrate, 616
oxide, 616
pentachloride, 615
Uranium, 614
general properties and reactions of
the compounds of, 618
mica, 614
vitriol, 616
yellow, 618
Uranous bromide, 615
chloride, 615
diuranate, 616
fluoride, 615
hydrate, 616 .
oxide, 616
phosphate, 617
sulphate, 616
sulphide, 618
uranate, 616
Uranospherite, 618
Uranyl, radical, 616
Uranvlic bromide, 616
chloride, 616
nitrate, 617
pyrosulphate, 617
sulphate, 617
sulphide, 618
Valency, 78
Valentinite, 384
Vanadates, 366
Vanadinite, 366
INDEX.
693
Vanadium, 364
VaDadous chloride, 365
oxide, 365
Vapor density, determination of, 59
tension, 120
Vapors, latent heat of, 122
Verdi j^ris, 547
Vermilion, 535
Vivianite, 660
Volborthite, 364
Volume-symbols, 56
Wagnerite, 512
Water, 169
analysis, 486
maximum density of, 173
mineral, 484
of crvstallization, 88
potable, 484
temporary hardness of, 477
Waters, ammonia present in, 491
average composition of, unpolluted
potable, 504
chlorine in, 496
eases dissolved in, 486
hardness of, 497
mineral matters in suspension in, 500
natural, impurities occurring in, 484
nitrogen as nitrates and nitrites in,
492
organic carbon in, 488
organic matter in suspension in, 500
organic nitrogen, 489
potable, classification of, 501
potable, dangerous, 496
potable, safe, 495
potable, suspicious, 495
previous sewRge or animal contami-
nation in, 593
total combined nitrogen in, 492
total solid matters dissolved in, 488
Wavellite, 571
Weights and measures, 136
Weldon's process for the regeneration of
manganic peroxide, 645
Wemerite, 573
White arsenic, 870
lead, 611
lead, Dutch process of manufacturing,
611
lead. Miller's process of manufactur-
ing. 612
lead, Thenard's process of manufac-
turing. 612
metal, copper, 539
precipitate, fusible, 537
vitriol, 518
Willemite, 519
Witherite, 464
Wolfram, 627
ochre, 625
Wollastonite, 480
Wood's fusible metal, 399
Worthite, 672
Wrought iron, 653
Wulfenite, 622
Xenotime, 572
Xonaltite, 480
Yellow ultramarine, 637
Ytterbium, 585
Yttria, 584
Yttrium, 582
Yttroc^rite, 584
Yttrous chloride, 584
fluoride, 584
hydrate, 584
nitrate, 584
oxide, 584
sulphate, 584
Zaffre, 666
Zinc, 514
diamine, 520
general properties and reactions of the
compounds of, 520
glass, 519
spinelle, 514, 568
Zincic aluminate, 568
aromonic sulphate, 519
antimonide, 520
arsenide, 520
blende, 519
bromide, 517
carbonate, 518
chloride, 516
chromate, 637
chromite, 635
fluoride, 517
hydrate, 517
iodide, 517
nitrate, 518
nitride, 520
oxide, 517
oxychloride, 517
pentasulphide, 520
potassic sulphate, 519
potassic sulphide, 519
phosphate, 519
phosphide, 520
silicate, 519
silicofluoride, 517
sulphate, 518
sulphide, 519
Zincoxvl, 86
Zinkenite, 389
Zircon, 319. 333
Zirconia, 334
Zircon ic bromide, 334
chloride, 333
fluoride, 333
hydrate, 334
oxide, 334
Zirconium, 333
Zoisite, 573
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A Conspectus of the Medical Sciences ; Containing Handbooks on Anatomy,
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ITEILL, JOHN, M. 2>., cmd SMITH, F. G., M. JO.,
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An Analytical Compendium of the Various Branches of Medical
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LUDLOW, J.L.,M.I>.,
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4 LiA Bbothibs t Go.'s Publications — ^Dictionaries.
nUNGLISON, BOBLjEY, M.D.,
Late Profeuor of InatUuUt of Medicine in the Jefenon Medical OoUege of PhiladetpMa.
MEDIOAL LEXICON; A Diotionarvof Medical Science: Oontainiiig
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handsome royal octavo volume of 1139 pa^es. Cloth, $6.50; leather, raised bands, $7.50;
yeiy handsome half Russia, raised bands, |8.
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medical science. Starting with this view, the inmiense demand which has existed for the
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the language is s^ken. Special pains have been taken in the preparation of the present
edition to maintain this enviable reputation. The additions to the vocabulary are more
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taken with the mechanical execution. The volume now contains the matter of at least
four ordinaiy octavos.
A book of which every American ought to be I work has been well known for aboat forty years,
prond. When the learned author of the work | auid needs no words of praise on our part to reoom-
passed away, probably all of us feared lest the book i mend It to the members of the medical, and like-
shonld not maintain Its place In the advamdng ; wise of the pharmaceutical, profession. The latter
science whose terms It defines. Fortunately, Dr. { especial Iv are in need of a work which gives ready
Richard J. Dunglison, haring assisted his father in , and reliable information on thousands of subjects
the revision of scTeral editions of the work, amd | and terms which they are liable to encounter In
having been, therefore, trained In the methods | pursnins their dailyvocations, but with which they
and imbued with the spirit of the book, has been cannot oe expected to be familiar. The wotk
able to edit it as a work of the kind should be , before us fkilly supplies this want— ilm«ru»nJb«r^
edited— to carry it on steadily, without Jar or inter- I nal of Pharmacy^ Feb. 1S74.
ruption, alony the grooves of thought it has trar- ; Particular care has been devoted to derivaUon
elled dunng its lifetime. To show the magnitude | and accentuation of terms. With regard to the
of Uitf task which Dr. Dunglison has assumed and utter, indeed, the present edition may be consld-
carried through. It is only necessary to state that ered a complete "Pronouncing Dictionary of
more than six thousand new subjecte have been ; Medical Science.** It is perhaps the moet reliable
added In the present edition.— PAOoWpAia Medical \ work published for the busy practitioner, as itcon-
T^mec, Jan. 3, 1874. ' tains information upon every medical subject, in
About the first book purchased by the medical I ^^SZl^'l^l^^^^^M^S^J!^
student is the Medical Dictionary. The lexicon S?i{^V<»r V^/i^^e^Southem Meduxd Record,
explanatory of technical terms is simply a «>i«^«a I . ,*'^, ^, ,. ^ .^ . ...
noA. In a science so extensive and with such col- ' A valuable dictionary of the terms employed in
Uterals as medicine, it is as much a necessity also , medicine and the allied sciences, and of the relsr
to the practising physician. To meet the wants of i tions of the subjects treated under each head.^ It
students and most physicians the dictionary must ' well deserves the authority and popularity it has
be condensed while comprehensive, and practical obtained.— ^rtfwA Med, Jour., Oct 31, 1874.
while perspicacious. It was because Dunglison*s i Few works of this class exhibit a grander menu-
met these indications that it became at once the ment of patient research and of scientific lore.—
dictionary of general use wherever medicine was ; London Lancet, May 13, 1875.
studied in the English language. In no former I Dunglison*s Dictionary is incalculably valuable,
revision have the alterations and additions been i and indispensable to every practitioner of medi-
so great The chief terras have been set in black cine, pharmacist amd dentist— H'es<«m LcmeeL
letter, while the derivatives follow in small caps; March, 1874.
»n WTMgement which greatly fwilitatesw | i^ ^^ t^e rare merit thatit certainly has no rival
—Ctnannati Lancet tmd CTmtc, Jan. 10, 1874. j^ ^^ie English language for accuracy and extent of
As a standard work of reference Dunglison*B , references. — London Medioal QaxeUe.
HOBLYN, BICHABD 2>., M. D.
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Landmarks, Medical arid Surgical, by the distinguished Anatomist, Mr. Luther Holden,
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type and illustration in anatomical study.
This well-known work oomes to us as the latest \ There Is probably no work used so universally
American from the tenth English edition. As its i bv physicians and medical students as this one.
title indicates^ It has passed through many hands ' It is oeserving of the confidence that they repose
and has received manv additions and revisions, j in it. If the present edition is compared with that
The work i.*) not susceptible of more improvement issued two years ago, one will readily see how
Taking it all in all. its size, manner of make-up,
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tne wants of the student and practitioner. — MedieeU
much it has been improved in that time. Many
pages have been added to the text, especially in
those parts that treat of histology, and many new
.. J — ... „^ .V. cuts have been introduced and old ones moaified.
practitioner. — MedieeU ' — Journal of the Aineriean Medical Aeeodation, Sept.
Record, SepL 16, 1883. 1 1,1883.
Amo for sale SEPASATB—
HOLiyEN, ZUTSJEB, F. B. C. 8.,
Surgeon to St. Barthol-omexo'a and the Foundling Hospitals, London,
Landmarks^ Medical and Surgical. Second American from the latest revised
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This little book is all that can be desired within
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valuable to the young surgeon or physician, »ince
every examination of a patient. It is written in , „ .
language so clear and concise that one ought ; sician and Surgeon^ Nov. 1881.
almost to learn it by heart. It teaches diagnosis by
external examination, ocular and palpable, of the
bodv, with such anatomical and physiological facts
aa airectly bear on the subject It is eminently
the student's and young practitioner's book. — Phy^
WILSON, BBASMVS, F. B. 8.
A System of Htunan Anatomy, General and Special. Edited by W. H.
GoBREGHT, M. D., Professor of General and Surgical Anatomy in the Medical CoUejfe of
Ohio. In one large and handsome octavo volume of 616 pages, with 397 illustrations.
Cloth, $4.00; leather, $5.00.
8MITH, H. H., M. !>., and SOBNFB, WM. F.,M.I).,
Enieritus Prof, of Surgery in the Univ. of Penna., etc. Late Prof. ofAnat in the Univ. of Penna.
An Anatomical Atlas, Illustrative of the Structure of the Human Body. In one
large imperial octavo volume of 200 pages, with 634 beautiful figures. Cloth, $4.50.
CLJELAND, JOHN,'m1d., F. It. S.,
Professor of Anatomy and Physiology in Queen*s College, Oalufay.
A Directory for the Dissection of the Human Body. In one 12mo.
volume of 178 pages. Cloth, $1.25.
6
LsA Brothers & Co.'s Publications — ^Anatomy.
AZLEN, HABBISOIf, M. 2>.,
ProfMtor oj Phsftiology in the UnivertUif of Penmytoama,
A Syvtem of Haman Anatomy, Including Its Medical and Snmcal
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Extract from Introduction.
It is the design of this book to present the facts of human anatomy in the manner best
suited to the requirements of the student and the practitioner of medicine. The i^ithor
believes that such a book is needed, inasmuch as no treatise, as fieur as he knows, contains, in
addition to the text descriptive of the subject, a systematic presentation of such anatomical
facts as can be applied to practice.
A book which will be at once accurate in statement and concise in terms ; which will be
an acceptable expression of the present state of the science of anatomy ; which will exclude
nothing that can be made applicable to the medical art, and which will thus embrace all *
of surgical importance, while omitting nothing of value to clinical medicine, — ^would appear
to have an excuse for existence in a country where most surgeons are general practitioners,
and where there are few general pra(;^itioners who have no interest in surgery.
It Ifl to be oonsidered a study of applied Rnatomy I care, and are simply superb. There is as much
in its widest sense— a systematic presentation of ' of practical application of anatomical points to
" ' ' i the j the every ' . - ..
Our I to those c
such anatomical facts as can be applied to the j the every-day 'wants of the medical cliiiiefan as
"• - " ■ " . '" I to those of the
Reneral practitio
feeling of surprised gratification thAt so many
practice of medicine as well as of suigeiy. Our ' to those of the operating
author is concise, accurate and practical in his > Reneral practitioners willread
>n. In fact, few
le work withonta
statements, and succeeds admirably in infusing reeling of surprised gratification thAt so many
■ ' • - - , . . .. concerning which they may never hate
' ' '1 presented for their con-
which is destined to be
h great | Record, Not. 25,1882.
statements, and succeeds admirably in infusing feeling of surprised grati
an interest into the study of what is generally con- points, concerning which
sidered a dry subject The department of Histoid ihought before are so well ]
ogy is treated in a masterly manner, and the sideration. It is a work n
ground is travelled over by one thoroughly funil- the best of its kind in any language.-
farwith it The Illustrations are made witn - • "
CLAJRKB, W, B., JF.B. C.8. Jb LOCKWOOI),C, B., JF.R. C.8.
DemoMtratort of Anatomy at St. Bartholomew** HotpUal Medical Schoolf London.
The Dissector's Manual. In one
49 illustrations. Limp cloth, red edges, i
MawudSf page 3.
This is a very excellent mamual for the use of the
student who desires to learn anatomy. The meth-
ods of demonstration seem to us very satisfactory.
There are many woodcuts which, for the most
pocket-size 12mo. volume of 396 pages, with
51.50. Just ready. See StudenU^ Series of
part, are good and instructive. The book is neat
and convenient. We are glad to recommend it~
Boston Medical, and Surgical Journal, Jan. 17, 1884.
TBMVES, JFBJEDESICK, F. B. C. S.,
Senior Demonstrator of Anatomy and Aseistant Surgeon at the London HoapitaL
Surgical Applied Anatomy. In one pocket-size 12mo. volume of 540 pages,
with 61 illustrations. Limp cloth, red edges, $2.00. Just ready. See Student^ S^ies qf
Manuals, page 3.
He has produced a work which will command a I
larger circle of readers thim the class for which it
was written. This union of a thorough, practical
acquaintance with these fimdamental branches, I
aaickened by daily use as a teacher and practi-
oner, has enabled our author to prej
which it would be a moat difficult I
The American Practitioner Feb. 1884.
a work
to excel.—
CVBNOW, JOBJff, M. n., F. B. C. P.,
Professor of Anatomy at King's College, Physician at King's OoUege SoepitaL
Medical Applied Anatomy. In one pocket-size 12mo. volume. Preparing.
See StudetUt^ Series of ManuaUf page 3.
BBLLAMTf JSDWAJRD, F. JB. C. S.,
Senior Assistant-Surgeon to the Charing^Oross Hospital, London,
The Student's Guide to Surgical Anatomy : Being a Description of the
most I«iportant Surgical Regions of the Human Body, and intendea as an Introduction to
operative Surgery. In one 12mo. volume of 300 pages, with 50 illustrations. Cloth, $2.25.
HARTSHORNETS HANDBOOK OF ANATOMY
AND PH7SIOLOOY. Second edition, revised.
In one royal 12mo. volume of 310 pages, with 220
woodcuts. Cloth, $1.76.
HORNER'S SPECIAL ANATOMY AND HISTOlr
OGY. Eighth edition, extensively revised and
modified. In two octavo volumes of lOOT pages,
with S20 woodcQts. Cloth, 96.00.
Lea Bbothkrs & Co.'s Publioations — Physics, Phjrsiol., Anat. 7
DBAPEB, JOHN C, M. J>., LZ. !>.,
Profesaor of ChwnUtry in the UniverHiy of the OUy of New York.
Medical Physics. A Text-book for Students and Practitioners of Medicine. In
one octavo volume of 734 pages, with 376 woodcuts, mostly original. Cloth, $4. Jusi ready .
Prom the Preface.
The fact that a knowledge of Physics is indispensable to a thorough understanding of
Medicine has not been as fully realized in this country as in Europe, where the admirable
works of Desplats and Gariel, of Bobertson and of numerous German writers constitute a
branch of educational literature to which we can show no parallel. A full appreciation
of this the author trusts will be sufficient justification for placing in book form the sub-
stance of his lectures on this department of sdenoe, delivered during many years at the
University of the City of New York.
Broadly speaking, this work aims to impart a knowledge of the relations existing
between Physics and Medicine in their latest state of development, and to embody in the
pursuit of this object whatever experience the author has gained during a long period of
teaching this special branch of applied science.
Certainly we have no text-book as foil as the ex-
cellent one he has prepared. It begins with a
statement of the properties of matter and energy.
Aftor these the special departments of physics are
explained, acoustics, optics, heat, electricity and
magnetism, closing with a section on electro-
biology. The applications of all these to physiology
and medicine are kept constantly in view. The
text Is amply Illustrated and the many difficult
points of the subject are brought forward with re-
markable clearness and ability.— Ifedteot cmd Surg-
ical Reporter^ July 18, 1885. q.
The volume from beginning to end teems with
useful information. Take the book as a whole
amd it is one of the most valuable scientific
treatises given to the medical profession for a
number of years. It is profVisely and handsomely
illustrated. The work should nave a place upon
and Medical
, July 18,1885. q'.
This is the only work with which we are ao-
every physician^s library shelf. — Maryland MedictU
I, July"
JaumflU, July 18, 1885. q.
quainted in which physics is treated with reference
to medicine. Preceptors who are axious that their
pupils should have a scientific knowledge of med-
icine, should make this work a text-book, and re-
quire a thorough study of it— Oineinnati Medical
^«w«, July 18, 1886. q.
BOBBBTSON, J. McOBEOOB, M. A., M. B.,
Muirhead Demoneirator of Phyeiologyt University of Olasgow.
Physiological Physics. In one I2mo. volume of 537 uages, with 219 illustra-
tions. Limp cloth, $2.00. Jitst ready. See Students^ Series of Manuals, page 3.
The title of this work sufficiently explains the ! ments. It will be found of great value to the
nature of its contents. It is designed as a man- 1 practitioner. It is a csreftilly prepared book of
ual for the student of medicine, an auxiliary to ! reference, concise and accurate, and as such we
his text-book In physiology, and it would be particn- heartily recommend it—Journal of the Amertean
larly uselhl as a guide to his laboratory experi- 1 Medtcait Aasociationf Deo. 6, 1884.
J> ALTON, JOHW C, M. J).,
Profeeeor Emeritut q^ Phytiology in the OoUege of Physidane and Surgeone^ New York,
Doctrines of the Circulation of the Blood. A History of Physiological
Opinion and Discovery in regard to the Circulation of the Blood. In one handsome
12mo. volume of 293 pages. Cloth, $2. Just ready.
Dr. DaIton*swork Is the fruit of the deep research
of a cultured mind, and to the busy practitioner it
cannot fail to be a source of instruction. It will
inspire him with a feeling of gratituto and admir-
ation for those plodding workers of olden times,
who laid the foundation of the magnificent temple
revolutionised the theories of teachers, than the
discovery of the circulation of the blood. This
explains the extraordinary interest it has to all
medical historians. The volume before us is one
of three or four which have been written within a
few years by American physicians. It is in several
of medical science a.<« it now stands.— iVett? Orleans ' respects the most complete. The volume, though
Medical and Surgical Journal^ Aug. 1885. ' small in size, is one of the most creditable con-
In the progress of physiological study no fact tributions from an Americanjpen to medical history
was of greater moment, none more completely that has appeared.— Afed. A Surg. Rep.^ Dec. e, 1884.
BY THE SAME AUTHOR.
The Topographical Anatomy of the Brain. In three very handsome quarto
volumes comprising 178 pa^ee of descrij^tive text. Illustrated with 48 full page photo-
graphic plates of Brain Sections, with a like number of explanatory plates, as well as many
woodcuts through the text.
BBLL. F. JBFFBBY, M. A.j
Profeteor of Comparative Anatomy at King's VoUsge^ London.
Comparative Physiology and Anatomy. In one 12mo. volume of 661 pages,
with 229 illustrations. Limp cloth, $2.00. Just ready. See StndeTUe^ Series of Maniuds^^AgeS,
ELLI8, QBOBGjE fWjEtt,
Emeritus Professor of Anatomy in University College, London.
DemonstratLons of Anatomy. Beins a Guide to the Knowledge of the
Human Body by Dissection. From the eighth ana revised London edition. In one very
handsome octavo volume of 716 pages, with 249 illustrations. Cloth, $4.25 ; leather, $5.25.
BOBBJRTS, JOHN~B^rM., M. I).7~
Prof, of Applied Anat. and Oper. Surg, in PhUa. Polyclinic and OoU. for Oraduates in Medicine.
The Compend of Anatomy. For use in the dissecting-room and in preparing
for examinations. In one 16mo. volume of 196 pages. Limp cloth, 75 cents.
8 LxA. Bbothxbs & Co.'b Pubuoationb — Physiologry* Chemistry.
J>ALTON, JOHN C, M. !>.,
ProfMwr of Physiology in th€ OblUge of Phytieiam tmd Surffeona, New Tcrk, etc
A Treatise on Human Physiology. Designed for the use of Students and
Practitioners of Medicine. Seventh edition, thoroughly revised and rewritten. In one
venr handsome octavo vohime of 722 pages, with 252 beautiful ensravingB on wood. Cloth,
f5.00 ; leather, $6.00 ; very handsome half Russia, raised bands, $6.50,
The merits of Profe«Bor DaJton's text-book, bis
smooth and pleasing style, the remarkable clear-
ness of his descriptions, which leave not a chapter
obscure, his cautious Judgment and the general
correctness of his facts, are perfectly known. They
hare made his text-book the one mont familiar
to American students.— Af«d. Record^ March 4, 1882.
Certainly no physiological work has ever issued
from the press that presented its subject-matter in
a clearer and more attractive light. Almost every
page bears evidence of the exhaustive revision
that has taken place. The material] is placed in a
more compact form, yet its delightftil charm is re>
tained, and no subject is thrown into obm^urity.
Altogether this edition is &r in advance of any
previous one, and will tend to keep the prvfeaaion
posted as to the moet recent additions to our
physiological knowledge.— 3fteAtj7an Medical Naa^
April, 18&.
One can scarcely open a college catalosiie that
does not have mention of Dalton's Phynologyju
the recommended text or consultation-book. For
American students we would unreservedly recom-
mend Dr. Dalton's work.- Va. Med. Monthly, inljy^i^
FOSTER, MICHAEL, M. J>., F. B. 8.,
Preleetor in Physiology and Felloto of Trinity College, Cambridge, England,
Text-Book of Physiology. Third American from the fourth English edition,
with notes and additions by £. T. Keichebt, M. D. In one handsome royal 12mo. volume
of 908 pages, with 271 illustrations. Cloth, $3.25; leather, $3.75. Juat reedy.
to know.and what may be pasced over by them as
not important. From the beginning to the end,
Dr. Foster's work upon physiology is so well-
known as a text-book in this country, that it needs
but little to be said in regard to it. There is
scarcely a medical college in the United States
where it is not in the hands of the students. The
author, more than any other writer with whom
we are acquainted, seems to understand what
portions of the science are essential for students
physiology is taught in a systematic manner. To
this third American edition numerous additions,
corrections and alterations have been made, so
that in its present fotro the u.«>efulness of the boc.k
will be found to be much increased. — Cincinnati
Medical K'tvs, July 1886.
FOWJEB, HENBY, M. B., F. B. C. 8.,
&eaminer in Physiology, Royal College of Surgeons of England.
Human Physiology. In one handsome pocket-size 12mo. volume of 396 pages,
with 47 illustrations. Cloth, $1.50. See Student^ Series of ManuaJs, page 3.
The prominent character of this work is that of
Judicious condensation, in which an able and suc-
cessful effort appears to have been made by its
accomplished author to teach the greatest number
of facts in the fewest possible words. The result
Is a specimen of concentrated intellectual pabu-
lum seldom surpassed, which ought to be care-
ftiUy ingested and digested by every practitioner
who desires to keep himself well informed upon
this most progressiTe of the medical sciences.
The volume is one which we cordially recommend
to every ono of our readers. — The American Jom>
nal of the Medical Sciences, October, 1884.
This little work is deserving of the highest
praise, and we can hardly conceive how the main
facts of this science could have been more clearlv
or conci.«!ely stated. The price of the work ia snch
as to place it within the reach of all, while the ex-
cellence of its text will certainly secure for It most
favorable commendation ^Cincinnati Lancet aitd
CVmif.Feb. 16,1884.
CABPBNTBB, WM. B., M. B., F. B. 8., F. G. 8., F. Ij. 8.,
Eegistrar to the University of London, etc
Principles of Human Physiology. Edited by Henry Power, M. B., Lond.,
F. R. C. 8., Examiner in Natural Sciences, University of Oxford. A new American from the
eighth revised and enlarged edition, with notes and additions hy Francis G. Smith, M. D.,
late Professor of the Institutes of Medicine in the University of Pennsylvania. In one
very large and handsome octavo volume of 1083 pages, with two plates and 373 illus-
trations. Cloth, $5.50; leather, $6.50; half Russia, $7.
FOWNE8, GBOBGB, Ph. B.
A Manual of Elementary Chemistry; Theoretical and Practical. Em-
bodying Watts' Inorganic Chemistry. New American edition. In one large royal 12mo.
vohime of over 1000 pages, with 200 illustrations on wood and a colored plate. Cloth,
$2.75 ; leather, $3.25. In a few days.
A notice of the previous edition is appended.
The book opens with a treatise on Chemical
opei
Physics, including Heat, Light, Mi^netism and
Electricity. These subjects are treated dearly
Mid briefly, bat enough is given to enable the stu-
dent to comprehend the facts and laws of Ghemis-
It is the fashion of late years to omit
istry but their
try proper.
these topics from works on chemist .
omission is not to be commended. As was required
by the great advance in the science of Chemistry
of late years, the chapter on the General Principles
of Chemical Philosophy has been entirely rewrite
ten. The latest views on Equivalents, (Juanti va-
lence, etc., are clearly and ftiUy set forth. This
last edition is a great improvement upon its nrede-
oessora, which is saying not a little or a book that
has reached its twelfth edition.— OAto Medical Re-
corder, Oct., 1878.
Wohler's Outlines of Organic Chemistry. Edited by Frmo. Translated
by Ira Bemsen, M. D., Ph. I). In one 12mo. volume of 550 pages. Cloth, $3.
GALLOWATS QUALITATIVE ANALYSIS. New
edition.
LEHMANN'S MANUAL OP CHEMICAL PHTB-
lOLOGY. In one octavo volume of 327 pages,
with 41 illustrations. Cloth, f2.25.
CARPENTER'S PRIZE ESSAY ON THE USE AND
Abuse or Alcohouc Liquoks nr Health axd £>is-
BASX. With ezplanationsof scientific words. Small
12mo. 178 pages. Cloth, 60 cents.
Lea Bbothkbs & Co.'s Publications — Ghemlstary.
9
FB,ANKLANI),B.,J>. C.L.,F.R.8.,&JAPP,F,It.,F.I. C,
fUxtKe Normal
Profestor of Ckemistry in the Normal School
of Science, London.
Assist, Prof, of Chemistri
School of Science^ j
Inorganic Chemistry. In one handsome octavo volume of 600 pages, with 61
woodcuts and 2 lithographic plates. Cloth, $3.75; leather, $4.75. In a few days.
This work on elementary chemistry is based upon principles of classification, nomen-
clature and notation which have been proved by nearly twenty years experience in teaching
to impart most readily a sound and accurate knowledge of the science.
ATTFIELD, JOSIfi^Ph. D.,
Professor of Practical Chemistry to the Pharmaceutical Society of Oreat Britain, tie.
Chemistry, General, Medical and Fharmaoeutioal; Including the Chem-
istry of the U. S. Pharmacopoeia. A Manual of the General Principles of the Sdence,
and their Application to Medicine and Pharmacy. A new American, from the tenth
English edition, specially revised by the Author. In one handsome royal 12mo. volume
of 728 pages, with 87 illustrations. Cloth, $2.50; leather, $3.00.
A text-book which passes through ten editions
in sixteen years must hare good qualities. This
iatry. a book which is so well known that it is
hardly necessary to do more than note the appear-
ance of this new and improved edition. It seems,
howeyer, desirable to point out that feature of the
book which, in all probability, has made it so
popular. There can be little doubt that it is its
thoroughly practical character, the expression
beins used in its best sense. The author under-
stands what the student ought to learn, and is able
to put himself in the student's place and to appre-
ciate his state of mind.— ^InMrtean Chemical Jour^
nal, April, 1884.
It is a book on which too much praise cannot be
bestowed. As a text-book for medical schools it
is unsurpassable in the present state of chemioal
science, and having been prepared with a special
view towards medicine and pharmacy, it is alike
indispensable to all persons engaged in those de-
partments of science. It includes the whole
chemistry of the lastPharmacopceia.— Pioc(/lc Medi-
cal and Sugrical Journal, Jan. ISSi.
BLOXAM, CHARLES L.,
Professor of Chemistry in King's College, London.
Chemistry, Inorganic and Organio. New American from the fifth Lon-
don edition, thoroughly revised and much improved. In one very handsome octavo
volume of 727 pages, with 292 illustrations. Cloth, $3.75 ; leather, $4.75.
the best manuals of general chemistry in the Eng-
lish language.— Detroit Lancet, Feb. 1884.
The general plan of this work remains the
same as in previous editions, the evident objeoi
being to five clear and concise descriptions of all
known elements and of their most important
compounds, with explamations of the chemical
laws and principles involved. We gladly repeat
now the opinion we expressed about a former
edition, that we regard Bloxam's Chemistry as
Comment fh>m us on this standard work is al-
most superfluous. It differs widely in scope and
aim flrom that of Attfield, and in its wi^ is equally
beyond criticism. It adopts the most direct meth-
ods in stating the principles, hypotheses and facts
of the science. Its language is so terse and lucid,
and its arrangement ox matter so logical in se-
quence that the student never has occasion to
complain that chemistry is a hard study. Much
attention is paid to experimental illustrations of
ehemical principles and phenomena, and the
mode of conducting these experiments. The book
maintains the position it has always held as one of
one ol the best treatises on general and applied
chemistry.— ilmmean Jour, ofPharmacy, Dec 1888.
SIMON, W., Ph. D., M. J).,
Professor of Chemistry and Toxicology m the College of Physieians and Surgeons, Baltimore, and
Professor of Chemistry in the Maryland College of Pharmacy.
Manual of Chemistry. A Guide to Lectures and Labbratory work for Beginners
in Chemistry. A Text-book, specially adapted for Students of Pharmacy and M^icine.
In one 8vo. vol. of 410 pp., with 16 woodcuts and 7 plates, mostly of actual deposits,
with colors illustrating 56 of the most important chemical reactions. Cloth, $3.00; also
without plates, cloth, $2.50. Just ready.
This book supplies a want lonjg felt by students
of medicine and pharmacy, and is a concise but
thorough treatise on the subfect. The long expe-
rience of the author as a teacher in schools of
medicine and pharmacy is conspicuous in the
perfect adaptation of the work to the special needs
of the student of these branches. The colored
plates, beautifully executed, illustrating precipi-
tates of various reactions, form a novel and valu-
able feature of the book, and cannot fail to be ap-
preciated by both student and teacher as a help
over the hard places of the BOlence.— Maryland
Medical Journal, Nov. 22, 1884.
BEMSEN, LRA, M. !>., Fh. !>.,
Professor of Chemistry in the Johns Hopkins University, Baltimore,
Frincii)le8 of Theoretical Chemistry, with special reference to the Constitu-
tion of Chemical Compounds. Second and revised edition. In one handsome royal 12mo.
Yolume of 240 pages. Cloth, $1.75. Just ready.
The book is a valuable contribution to the chemi-
cal literature of instruction. That in so few years
a second edition has been called for indicates that
many chemical teachers have been found ready
to endorse its plan and to adopt its methods. In
^is edition a considerable proportion of the book
has been rewritten, much new matter has been
added and the whole has been brought up to date.
We earnestly commend this book to every student
of chemistry. The high reputation of the author
assures its aoouracv in all matters of fact, and its
Indicious conservatism in matters of theory, com-
Dined with the fulness with which, in a small
compass, the present attitude of chemical science
towards the ooustltution of compounds is con-
sidered, gives ita value much be vond that accorded
to the average text-books of the day. —American
Journal of Science, March, 1884.
10 Lea Brothers & Co.'s Publications — Chemistry.
CHARLES, T. CBANSTOVN, M. !>., F. C. 8., M. 8.,
Formerly A»»t. Prof, and Demontt. of Chemistry and Chemical Phygia, Queen^i OMege, BelfaeL
The Elements of Fhysioloffical and Pathological Chemistry. A
Handbook for Medical Students and Practitioners. Containing a general accoont of
Nutrition, Foods and Digestion, and the Chemistry of the Tissues, Organs, Secretions aiMi
Excretions of the Body in Health and in Disease. Together with the methods for pre-
paring or separating their chief constituents, as also for their examination in detail, and
an outline syllabus of a practical course of instruction for students. In one handsome octayo
volume of 463 pages, with 38 woodcuts and 1 colored plate. Cloth, $3.50.
Dr. Charies' manaAl admirably fUlflls its inten-
tion of giving his readers on the one hand a sum-
mary, comprehensive but remarkably compact, of
the mass of facts in the sciences which hare be-
The work is thoroughly trustworthy, and in-
.brmed throughout by a genuine scientific spirit
The author deals witn the chemistry of the diges-
tiT6 secretions in a systematic mauiner, which
leaves nothing to be desired, and in reality sup-
plies a want in Engiish literature. The book ap-
pears to us to be at once full and systematic, and
to show a Just appreciation of the relative import-
ance of the various subjects dealt with. — British
Medical Joumai^ November 29, 1884.
come indispensable to the physiclaui : and, on the
other hand, of a system of practical directions so
minute that analyses often considered formidable
may be pursued by any intelligent person.—
Archives of Medicine^ Dqc 1884.
HOFFMANN, F., A.M., Fh.D., & FOWEB F.B., Fh.D.,
Public Analyst to the StaU of Ifac York. Prof, of Anal^ Chem. in the PhiL OoU. of Pharmacy.
A Manual of Chemical Analysis, as applied to the Examination of Medicinal
Chemicals and their Preparations. Being a Guide for the Determination of their Identity
and Quality, and for the Detection of Impurities and Adulterations. For the use of
Pharmacists, Physicians, Dniegists and Manufacturing Chemists and Pharmaceutical and
Medical Students. Third edition, entirely rewritten and much enlarged. In one very
handsome octavo volume of 621 pages, with 179 illustrations. Cloth, $4.25.
We congratulate the author on the appearance
of the third edition of this work, published for the
the Information it undertakes to supply is both
extensive and trustworthy. The selection of pro-
cesses for determining the purity of the substan-
ces of which it treats is excellent and the descrip-
tion of them singularly explicit. Moreover, It is
exceptionally free from typographical errors. We
have no hesitation in reeommending it to those
who are engaged either in the man u facta re or the
testing of medicinal chemicals. — London Phctrma-
eeutical Journal and TVansaetionSt 1883.
CLOWF8, FRANK, I). Sc, London,
Senior Seience-Master at the High School^ NewcasUe-under-Lymey etc
An Elementary Treatise on Practical Chemistry and Qualitative
Inorganic Analysis. Specially adapted for use in the Laboratories of Schools and
Colleges and by Beginners. Third American from the fourth and revised English edition.
In one very handsome royal 12mo. volume of about 400 pages, with about 50 illustrations.
Cloth, $2.50. In a few days.
The style is clear, the language terse and vigor- I and text book. — Medical Record^ July 18. 1885.
ous. Beginning with a list of apparatus necessary We may simply repeat the favorable opinion
* mlcal work, he gradually unfolds the sub- ' which we expressed after t*
for chemical work, he (gradually unfolds the sub- ' which we expressed after the examination of the
feet from its simpler to its more complex divisions. ; previous edition of this work. It is practical in its
It is the most readable book of the kind we have ! aims, and accurate and concise in its statements,
yet seen, and is without doubt a systematic, |
Intelligible and fully equipped laboratory guide |
yet seen, and is without doubt a systematic, | —i4m«rtcrtn Jbumoio/ PAarmaw, August, 1SS5.
Inl ...
BALFB, CHABLF8 H., M. D., F. JR. C. P.,
Assistant Physician at the London Hospital.
Clinical Chemistry. In one pocket-size 12mo. volume of 314 pages, with Id
illustrations. Limp cloth, red edges, $1.50. See Shidents* Series of Manuals, page 3.
This is one of the most instructive little works
that we have met with in a long time. The author
is a physician and physiologist, as well as a chem-
ist, consequently the book is unqualifiedly prac-
tical, telling the physician Just wnat he ougnt to
know, of the applications of chemistry in medi-
cine. Dr. Ralfe is thoroughly acquainted with the
latent contributions to his science, and it is quite
refreshing to find the subject dealt with so clearly
and simply, yet in such evident harmony with the
modern scientific methods and spirit. — Medical
Record^ February 2, 1884.
CLASSEN, ALEXANDER,
Profess&r in the Royal Polytechnic School^ Aix4a^Chapelle.
Elementary Quantitative Analysis. Translated, with notes and additions, by
Edoab F. Smith. Ph. D., Assistant Professor of Chemistry in the Towne Scientific School,
University of Penna. In one 12mo. volume of 324 pages, with 36 illust. Cloth, $2.00.
It is probably the best manual of an elementary i and then advancing to the analysiB of minerals and
nature extant insomuch as its methods are the such products as are met with in applied chemis-
best.f It teaches by examples, commencing with try. It is an indispensable book for students in
single determinations, followed by separations, | chemistry.— Boston Jottmal of Chemistry, Oct 1878.
GREENE, WILLIAM M., M. D.,
Demonstrator of Chemistry in the Medical Department of the University of Pennsylvania.
A Manual of Medical Chemistry. For the use of Students. Based upon Bow-
man's Medical Chemistry. In one 12mo. volume of 310 pages, with 74 illus. Cloth, $1.75.
It is a concise manual of three hundred pages,
giving an excellent summary of the best methods
of aniuysing the liquids and solids of the body, both
for the estimation of their normal constituents auid
the recognition of compounds due to pathologieal
conditions. The detection of poisons is treited
with sufficient ftilnees for the purpose of the stu-
dent or practitioner.— £o«fon Jl. of Cft^m., June, *80.
Lea Bkothers & Go.'s PtmucATioNS — ^Pharm., Mat. Med., Therap. 11
BHUNTON, T. LATTDMItf M.D.,l}.8c., F.JR.8., F.M.C.P.,
Lecturer on Materia Medica and Therapeutics at 8t. BartholomeM^t Hoipitai^ Londony etc
A Text-book of Pharmaoology, Therapeutics and Materia Medica;
Including the Pharmacy, the Physiological Action and the Therapeutical Uses of Drugs.
In one handsome octavo volume of about 1000 pages, with 188 illustrations. Cloth, $5.50 ;
leather, $6.50. In press.
It is with peculiar pleasure that the early appearance of this long expected work is
announced by the publishers. Written by the foremost authority on its subject in Eng-
land, it forms a compendious treatise on materia medica, pharmacology, pharmacy, and
the practical use of medicines in the treatment of disease. Space has been devoted to the
fundamental sciences of chemistry, physiology and pathology, wherever it seemed necessary
to elucidate the proper subject-matter of the book. A genend index, an index of diseases
and remedies, and an index of bibliography close a volume which will undoubtedly be of
the highest value to the student, practitioner and pharmacist.
oompUed that a reference to any special point is
at once obtainable. Dr. Bronton is neyer satisfied
with vague generalities, but giyes clear and pre-
cise directions for prescribing the yarious drugs
and preparations. We congratulate students on
being at last placed in possession of a scientifio
It is a scientific treatise worthy to be ranked with
the highest productions in physiology, either in
our own or any other language. Eyerything is
practical, the dry, bard facts of physiology being
pressed into seryice and applied to the treatment
of the commonest oomplamts. The information
Is so systematically arramged that it is ayailable
for immediate use. The index is so carefully
K 1 .
treatise of enormous practical importance.— 2!^
Laneety June 27, 1885.
PABBISH, EDWAMD,
Late Professor of the Theory and Practice of Phannaey in the Philadelphia College of Pharmacy.
A Treatise on Fharmaoy : designed as a Text-book for the Student, and as a
Guide for the Physician and Pharmaceutist. With many Formulae and Prescriptions.
Fifth edition, thoroughly revised, by Thomab S. Wiegakd, Ph. G. In one handsome
octavo volume of 1093 pages, with 256 illustrations. Cloth, (5 ; leather, $6.
No thoroughgoing pharmacist will fail to possess | Each page bears eyidence of the care bestowed
himself of so useful a guide to practice, amd no
physician who properly estimates the yalue of an
accurate knowledge of the remedial agents em-
ployed by him in daily practice, so fur as their
mlscibillty, compatibility and mosteffectiye meth-
ods of combinaUon are concerned, can afford to
leaye this work out of the list of their works of
reference. The country practitioner, who must
always be in a measure his own pharmacist will
find it indispensable.— Zouimtts Medical News,
March 29, 1884.
This well-known work presents itself now based
upon the recently reyised new Pharmacopcsia.
page 1 ._ _
upon It^ and conyeys yaluable information ttotn
the rich store of the editor's experience. In taot,
all that relates to practical pharmacy— apparatus,
S recesses and dispensing— has been arranged and
escribed with clearness in its various aspects, so
as to afford aid and adyice alike to the stuaentamd
to the practical pharmacist The work is Judi«
ciously illustrated with good woodcuts— ilmerican
Joitmal of Pharmacy^ January, 1884.
There is nothing to equal Parrish's Phamuiey
in this or any other language.— Jkmdon Pharma-
ceutical JoumaL
HJEBMAJnf, J>r. L.,
Professor of Physiology in the University of Zurich,
Experimental Pharmacology. A Handbook of Methods for Determining the
Physiological Actions of Drugs. Translated, with the Author's permission, and with
extensive additions, by Bobebt Meade Smith, M. D., Demonstrator of Physiology in the
University of Pennsylvania. In one handsome 12mo. volume of 199 pages, with 32
illustrations. Cloth, $1.50.
MAISCS, JOHNM., Fhar. D.,
Professor of Materia Medica and Botany in the Philadelphia College of Pharmacy,
A Manual of Organic Materia Medica; Being a Guide to Materia Medica of
the Vegetable and Animal Kingdoms. For the use of Students, Druggists, Pharmacists
and Physidans. New (second) edition. In one handsome royal 12mo. volume of 550
pages, with 242 illustrations. Cloth, $3.00. Just ready.
This work contains the substance, — ihepractical
** kernel of the nut" picked out so that the stu-
dent has no superfluous labor. He can confidently
aecept what this work places before him, without
any fear that the gist of the matter is not in it.
Another merit is that the drugs are placed before
him in such a manner as to simplify yery much
the study of them, enabling the mind to grasp
them more readily. The illustrations are most
BBUCE, J. JUITCHBLLTm.'B., F. B. C. P.,
Physician and Lecturer on Materia Medica and Therapeutics at Charing Cross HosptUU, London,
Materia Medica and Therapeutics. An Introduction to Bational Treat-
ment. In one pocket-size 12mo. volume of 555 pages. Limp doth, $1.50. Just ready.
See StudenUf Series of Manuals, page 3.
QBIFFITH, BOBJEJRT JEGLESFIJELD, M. D.
A Universal Formulary, containing the Methods of Preparing and Adminis-
tering Officinal and other Medicines. The whole adapted to Physicians and Pharmaceut-
ists. Third edition, thoroughlv revised, with numerous additions, hj Joss M. MAmcH,
Phar.D., Professor or Materia Medica and Botany in the Philadelphia (JoUege of Pharnuu^.
In one octavo volume of 775 pages, with 38 illustrations. Cloth, $4.50 ; leather, $5.50.
excellent, being very true to nature, and are alone
worth the price of the book to the student To the
practical ptiysician and pharmacist it is a valuable
work for handy reference and for keeping firesh
in the memory the knowledge of materia medica
and botany already acquired. We can and do
heartily recommend iU—Medical and Surgical B^
porter, Feb. U, 1886.
12 Lba Bbothebs t Co.'s Pubucations — ^Mat. Med.» Therap.
STILLB, A., M. JD., LL. JD., & MAI8CH, J. M., Phar. JD.,
Profeator Bmeritut of th* Thwry and Prae- Prof, of Mat Med. and Botany in Phila.
Hee of Medicine and of Clinical Medicine CoUeae of Pharmaeu, Sec^jfto tke Ameri-
in th4 Univereity of Pennaylvania. can Pharmaceutical Aesociaiion.
The National Dispensatory: Containing the Natural Histoiy^Chemistry, Phar-
macy, Actions and Uses of Medicines, including those recognized in the Pharmacopoeias of
the United States, Great Britain and Germany, with numerous references to the French
Codex. Third edition, thoroughly revised and greatly enlarged. In one magnificent
imperial octavo volume of 1767 pages, with 311 nne engravinga Cloth, $7.25;
leather, $8.00-j half Russia^ open back, $9.00. With Denison's "Ready Eeference Index"
$1.00 in addition to price in any of above styles of binding. Just ready.
In the present revision the authors have labored incessantly with the view of mi^lring
the third edition of The National BiBPENaAxoRY an even more complete represen-
tative of the pharmaceutical and therapeutic science of 1884 than its first edition was of
that of 1879. For this, ample material has been afforded not only by the new United
States Pharmacopceia, but by those of Germany and France, which have recently appeared
and have been incorporated in the Dispensatory, together with a large number of new non-
officinal remedies. It is thus rendered the representative of the most advanced state of
American, English, French and German pharmacology and therapeutics. The vast amount
of new and important material thus introduced may be gathered from the fact that the
additions to this edition amount in themselves to the matter of an ordinary full-sized octavo
volume, rendering the work larger by twenty-five per cent, than the last edition. The
Therai)eutic Index (a feature peculiar to this work), so suggestive and convenient to the
practitioner, contains 1600 more references than the last edition — ^the General Index
3700 more, makine the total number of references 22,390, while the list of illustrations
has been increased by 80. Every effort has been made to prevent undue enlargement of
the volume by having in it nothing that could be regardea as superfluous, yet care has
been taken that nothing should be omitted which a pharmacist or physician could expect
to find in it.
The appearance of the work has been delayed by nearly a year in consequence of the
determination of the authors that it should attain as near an approach to absolute ac-
curacy as is humanly possible. With this view an elaborate and laborious series of
examinations and tests have been made to verify or correct the statements of the Pharma-
copoeia, and very numerous corrections have been found necessary. It has thus been ren-
dered indispensable to all who consult the Pharmacopceia.
The work is therefore presented in the full expectation that it will maintain the
position universally accorded to it as the standard authority in all matters pertaining to
its subject, as registering the furthest advance of the science of the day, and bs embody-
ing in a shape for convenient reference the recorded results of human experience in the
laboratory, in the dispensing room, and at the bed-side.
Comprehensive in scope ^^ vast in design and ■ up to date. The work has been very well dooe, a
did '
•i 1^^' ] Its completeness as to subjects, the com prehen-
We have much pleasure in recording the appear* I sivenessof it« descriptive language, the thoroagh-
ance of a third edition of this excellent work of ' ness of the treatment of the topics, its brevity not
reference. It is an admirable abstract of all that sacrificing the desirable features of information
relates to chemistry, pharmacy, materia medica, , for which such a work is needed, make this vol-
pharmacology and therapeutics. It may be re- j ume a marvel of excellence.— PAamMc<»tfiea< £•-
garded as embodying the Pharmacopceias of the , cord, Aug. 15, 1884.
civilised nations of the world, all being brought i
FABQVHARSON, ROBERT, M. D.,
Lecturer on Materia Medira at St. Mary's Hospital Medical SehooL
A Guide to Therapeutics and Materia Medica. Third American edition,
specially revised by the Author. Enlarged and adapted to the U. S. Pharmacopoeia by
Fbank Woodbury, M. D. In one handsome 12mo. volume of 524 pages. Cloth, 12^25.
Dr. Farquhar9on*8 Therapeutics Is constructed nmned pages— one side containing the recognlfed
upon a plan which brings before the reader all the physiological action of the medicine, and the other
essential points with reference to the properties of the disease in which observers fwho are nearly al-
drugs. It impresses these upon him in such a way ways mentioned) have obtainea from It Rood re-
as to enable him to take a clear view of the actions suits — make a very good arrangement. The early
of medicines and tlie disordered conditions in ' chapter containing rules for prescribing Is excel-
which they must prove usefUl. The double-col- lent— Canarfa Med. and Surg. Journal^ Dea 1882.
STILLi, ALFRED, M. 2>., LL. !>.,
Professor of Theory and Practice of Med. and of Clinical Med, in the Univ. of Pemna.
Therapeutics and Materia Medica. A Systematic Treatise on the Action and
Uses of Medicinal Agents, including their Description and History. Fourth edition,
revised and enlarged. In two large and handsome octavo volumes, containing 1936 pagesi
Cloth, $10.00; leather, $12.00; very handsome halt Russia, raised bands, $13.00.
We can hardly admit that it has a rival in the ! in pharmacodynamics, but as by far the most ootn-
multitnde of its citations and the fulness of its I plete treatise upon the clinical and practical dd*
research into clinical histories, and we must assign . of the question.— £o<^on Medical and Surgical Jouf
'\ a place in the physician's library; not, indeed, nal^ Nov. 6^1874.
ftilly representing the present state of knowledge •
LiA BaoTHEBS & Co.'s Publications — ^PatboL, Hlstol. 13
COATS, JOSBPM, M. D., F. F. JP. S.,
Pathologut to the OUugow Wettem Inftrman/.
A Treatise on Pathology. In one very handsome octavo volume of 829 pages,
with 389 beautiful illuBtrations. Cloth, $5.50 ; leather, $6.50.
The work before as treats the subject of Path* | condition efTected in structaree by disease, and
ology more exteneirely than It is usually treated
In similar works. Medical students as well as
physicians, who desire a work for study or refer-
ence, that treats the subjects in the various de-
partments in a very thorough manner, but without
prolixity, will certainly give this one the prefer-
ence to any with which we are acquainted. It sets
forth the most recent discoveries, exhibits, in an
interesting manner, the changes from a normal
points out the characteristics of various morbid
agencies, so that they can be easily recognised. Bat|
not limited to morbid anatomy.it explains ftilly how
the functions of organs are disturbed by abnormal
conditions. There is nothing belonging to its de-
partment of medicine that is not as fully elucidated
as our present knowledge will admit— OlfMinnati
MediealNews, Oct. 1883.
GBEEN, T. HBITRY, M. J>.,
Lecturer on Pathology and Morbid Anatomy at Charing'Orou Hotpital Medical School^ London.
Pathology and Morbid Anatomy. Fifth American from the sixth revised
and enlarged Engliah edition. In one very handsome octavo volume of 482 pages, with
150 fine engravings. Cloth, $2.50.
The fact that this well-known treatise ha» so : No work in the English language Is sp admirably
rapidly reached its sixth edition is a strong evi- j adapted to the wants of the student and practi-
dence of its popularity. Tho author is to be con- ; tioner as this, and we would recommend it most
gratulated upon the thoroughness with which he earnestly to every one.— Nashville Journal of Mtd^
Has prepared this work. It is thoroughly abreast ; eine ar.d Surgery ^ Nov. 1884.
with all the most recent advances in pathology, i
WOODMBAI), G. 8iM87MrbTi~-E\k. C. P. E.,
Demomtrator of Pathology in the University of Edinburgh.
Practical Pathology. A Manual for Students and Practitioners. In one beau-
tiful octavo volume of 497 pages, with 136 exquisitely colored illustrations. Cloth, $6.00.
It forms a real guide for the student and practi- j The author merits all praise for having produced
tioner who is thoroughly in earnest in his en- a valuable work. — Medical Record^ Mity 31, 1884.
deavor to see for himself and do for himself. To I It is manifestly the product of one who has him-
the laboratory student it will be a helpful com- ! selftravelled over the whole field and who is skilled
panion, and all those who may wish to familiarize
themselves with modem methods of examining
morbid tissues are strongly urged to provide
themselves with this manual. The numerous
drawings are not fancied pictures, or merely
schematic diagrams, but they represent faithfully
the actual images seen under the microscope.
not merely in the art of histology, but in the obser-
vation and interpretation of morbid changes. The
work is sure to command a wide circulation. It
should do much to encourage the pursuit of path-
ology, since such advantages in histoloaioal study
have never before been offered. — The Lancet, Jan.
6, 1884.
8CHAFJER, JSnWABJD A., F. H. S.,
Aaaistant Profeuor of Physiology in University College, London,
The Essentials of Histology. In one octavo volume of 246 pages, with
281 illustrations. Cloth, $2.25. Shortly,
COBNIL, v., and BAJfTFIBB, L.,
Prof, in the Faculty of Med. of Paris. Prof, in the College of France,
A Manual of Pathological Histology. Translated, with notes and additions,
by E. O. Shakespeare, M. C, Pathologist and Ophthalmic Surgeon to Philadelphia
Hospital, and by J. Henry C. Simes, M. D., Demonstrator of Pathological Histology in
the University of Pennsylvania. In one very handsome octavo volume of 800 pages, with
860 illustrations. Cloth, $5.50 ; leather, $6.50 ; half Russia, raised bands, $7.
KLEIN, E., M. JD., F. JR. 8.,
Joint Lecturer on General Anat. and Phys. in the Med. School of SL Bartholomew's Hosp., London.
Elements of Histology. In one pocket-size 12mo. volume of 360 pages, with 181
illus. Limp cloth, red edges, $1.50. See Student^ Series of Manuals^ page 3.
Although an elementary work, it is by no means
superficial or incomplete, for the author presents
in concise language nearly all the fundamental facte
regarding the microscopic structure of tissues.
The illustrations are numerous and excellent We
commend Dr. Klein's Elements most heartily to
the Bindent.— Medical Record, Dec. 1, 1883.
IPEPPEB, A. J., M. B., M. S., E. B. C. 8.,
Surgeon and Lecturer at SL Mary's Hospital, London.
Surgical Pathology. In one pocket-size 12mo. volume of 511 pages, with 81
illustrations. Limp cloth, rea edges, $2.00. See Students' Series of MantuiU, page 3.
illustrated. The student will find in it nothing
It is not pretentious, but it will serve exceed-
ingly well as a book of reference. It embodies a
great deal of matter, extending over the whole
field of ^
that is unnecessary. The list of subjects covers
the whole range of surgerj'. The book supplies a
very manifest want and should meet with sue-
»«>.«« v/ surgical pathology. Its form is practical, t«.j ...n.iii^oi. ■*€.». »u^ ^^..^^.v. ...^».
its language is clear, and the information set ' cess.— Atfto York Medical Journal, May 31, 1884.
forth is well-arranged, well-indexed and well- i
■CHAFER'S PRACTICAL HISTOLOOY. In one 1 OGY. Translated by JoaspH Lsiot, M.D. In one
handsome royal 12mo. volume of 308 pages, with I volume, very large imperial quarto, with KM
40 illustrations. I copper-plate figures, plain and colored and dee-
GLUGF8 ATLAS OF PATHOLOGIOAL HI8T0L- 1 criptive letter-press. Cloth, 14.00
14
Lea BB0THEB8 t Co/8 Publications— Practloe of Med.
FLINT, AUSTIN, M. !>.,
Prof, of th€ PrindpUt and PraclicM of Mod. and of Clin, Med, in BelUvue ffo$piua MoiAcal OoUog^, N. T.
A Treatise on the Principles and Practice of Medicine. Designed for
the use of Students and Pnictitionen of Medicine. With an Appendix on the Reeeardies
of Koch, and their bearing on the Etiology, Patholo^, Diaffnoeis and Treatment of
Phthisis. Fifth edition, revised and largely rewritten In one laige and closely-printed
octovo volume of lldO pages. Qoth, $5.50 ; leather, |6.60 ; half Bussia, $7.
Koch's disooveiT of the bacillus of tubercle ^ves promise of being the greatest
boon ever conferred by science on humanity, surpassi^ even vaccination in its benefits to
mankind. In the appendix to his work^ Professor Flint deals with the subject from a
practical standpoint, discussing its bearings on the etiology, pathology, diagnosiB, prog-
nosis and treatment of pulmonary phthisis. Thus enlarged ana completed, this standard
work will be more than ever a necessity to the physician who duly appreciates the re-
spoDsibility of his calling.
This work is so widely known and aeeepted mm
the best American texi-book of the pimctiee of
A well-known writer and lecturer on medicine
recently expressed an opinion, in the highest de-
gree oompUmentarv of the admirable treatise of
jjr. Flint, and in eulogizing it, he described it ac-
curately as *' readable and reliable/* No text-book
is more calculated to enchain the interest of the
stadent and none better classifies the multitadi-
BUDJects included in it It has already
won its way in England, that no inconsiderable
number of men use it alone in the study of pure
medicine; and we can say of it that it is in every
way adapted to serre, not onlv as a complete guide,
but also as an ample instructor in the science ana
practice of medicine. The style of Dr. Flint is
always polished and engaging. The work abounds
In perspicuous explanation, and is a most valuable
text-book of medicine.— London Medital Newt.
medicine that it would seem hardly worth whUeto
give this, the fifth edition, anything more than a
passing notice. But even the meet cursoiy exami-
nation shows that it is, practically, much more
tlian a revised edition: it is, in &cl rather a new
work throughout. This treatise will undoubtedly
continue to nold the first place in the estimation
of American physicians and students. No
our medical writers approaches Professor Flint in
clearness of diction, breadth of view, and, what we
regard of transcendent importance, rational esti-
mate of the value of remedial agents. It is thoi^
on, . . _
regard of transcendent importance, rational esti-
mate of the value of remedial agents. It is thoi^
oughly praetieal, therefore pre-eminently the hook
for American readers.— iSt. Louia Clin, Ree^ ICar. *8L
HAJtTSHOBNB, HMNMT, M. D., ii. !>.,
Laldy Profeuor of Hygiene in the Umeeni^ qf Penntyhnnia.
Essentials of the Principles and Fraotioe of Medioine. A Handbook
for Students and Practitioners. Firth edition, thoroughly reyised and rewritten. In one
royal 12mo. volume of 669 pages, with 144 illustrations. Cloth, $2.75 ; half bound, $3.00.
Within the compass of 600 pages it treats of the
reneral
Huding
npass
cine,
„ ... >pe, etc.), general thei^
apeuucs, nosology, and special patholosy and prac-
tice. There is a wondenUl amount oflnformation
contained in this work, and it is one of the best
of its kind that we have aeen.—OUugow Medical
Journal, Nov. 1882.
An indispensable book. No work ever exhibited
a better average of actual practical treatment than
had a better opportunity than Dr. Hartshome for
condensing all the views of eminent praotitionen
into a 12mo. The numerous illustrations will be
very useftil to students especially. These
tials, as the name saggesis, are 'not intended U>
supersede the text-books of Flint and Barthdow,
but they are the most valuable in alibrding the
means to see at a glance the whole literature <» any
' '" ..... . . ^Chieago
»rsede the text-boo)
they are the most
ns to see ata glance
disease, and the most valuable treatment-
Medical Journal tmd Jfiramtfisr, April, 1882.
BBI8TOWJS, JOHN SYJEJt, M. !>., F. M. C. P.,
Phytieian and Joint Lecturer on Medicine at SL Thomas'' HotpitaL
A Treatise on the Practice of Medicine. Second American edition, revised
by the Author. Edited, with additions, by Jameb H. Hutchinson, M.D., physician to the
Pennsylvania Hospital. In one handsome octavo volume of 1085 pag^ with iUustratious.
Cloth, $5.00 ; leather, $6.00; very handsome half Bussia, raised buids, $6.50.
are appropriate and practical, and greatly
its userolness to Amerioan readers.— A«/^
ieal and Surgical JoumcU, March, 1880.
concise. The additions made by Dr. Hutchinson '
The reader will find every conceivable subject
connected with the practice of medioine ably pre-
sented, in a style at once clear, interesting and
The additions made by Dr. HutcnmBO]
, add to
faloMed-
WATSON, SIB TBOMAS, M. D.9
Late Phytieian in Ordinary to the Queen,
Lectures on the Principles and Practice of Physic. A new American
from the fifth English edition, fkiited, with additions, and 190 illustrationiB^ by Henbt
Habtbhobke, a. M., M. B., late Professor of Hygiene in the University of Pennsylvania.
In two large octavo volumes of 1840 pages. Cloth, $9.00 ; leather, $11.00.
LECTURES ON THE STUDY OP FEVER. By
A. HuMox. M. D., M. R. I. A. In one octavo
volume or 806 pages. Cloth, $2.60.
STOKES* LECTURES ON FEVER. Edited by
John William Moore, M. D., F. K. Q. C. P. In
one octavo volume of 280 pages. Clotn, $2.00.
A TREATISE ON FEVER. By Robut D. Lyoio,
K. C. G. In one 8vo. voL of 3fi4 pp. Cloth, f2J6w
LA ROCHE ON YELLOW FEVER, considered in
its Historical, Pathological, Etiological and
Therapeutical Relations. In two large and hand-
some octavo volumes of li68 pp. Cloth, 17.00.
A GKNTUBT OF AMSBIOAN BCEDICIMB, 1776-1876. By Drs. £. H. Olaxu, H. J.
BioKLOW, S. D. Gaoss, T. G. Thokas, and J. S. Bxllihqb. In one 12mo. volume of S70 pages. Cloth, tLS6.
Lea Brothers & Co/s Publications — Systems of Med. 15
For Sale by Subscription Only.
A System of Practical Medicine.
BY AMERICAN AUTHORS.
Edited by WILLIAM PEPPER, M. D., LL. D.,
FBOYOBT Ain> PSOFEBBOB OF THE THSOBT AND PRACTICE OF MEDIdNB AND OF
dJNICAL MEDICINE IN THE UNIYEBSITY OF FENNSYLYANIA,
Assisted bj LouiB Starr, M. D., Clinical PiofeBsor of the Difleases of Children in the
Hoepital of the Univeisity of Pennsylvania.
In five imperial octavo volumes. eojUainvngahotU 1100 pages each^ with iUustroHons, Price per
volume, doth, $5 : leather, f 6 ; half Russia, raised bands and open back, $7. Volume L
(General Patnology, Sanitary ticience and General Diseafles) contains 1094 pages,
wiih 24 iUustra/tums and is just ready. Volume 11. (General Diseases [con-
tinued] and Diseases of the Digestive System) contains 1312 pages,
vnih 27 illustrations, and is just ready. Volume III (Diseases of
the Bespiratory, Circulatory and Haematopoietic Systems)
c(mtaining about 1050 pages, wiU be ready October Isi,
and the subsequent volumes at intervals of four
months thereafter.
The publishers feel pardonable pride in announcing this magnificent work. For
three years it has been in active preparation, and it is now in a sufficient state of forward-
ness to justify them in calling the attention of the profession to it as the work in which
for the first time American medicine is thoroughly represented by its worthiest
teachers, and presented in the full development of the practical utility which is its
preeminent characteristic. The most able men — ^from the East and the West, from the
T^orth and the South, from all the prominent centres of education, and from all the
hospitals which afibrd special opportunities of study and practice^have united in
generous rivalry to bring together this vast ag^egate of specialized experience.
The distinguished editor has so apportioned the work that each author has had
assigned to him the subject which he is peculiarl^r fitted to discuss, and in which his views
will be accepted as the latest expression of scientific and practical knowledge. The
practitioner will therefore find these volumes a complete, authoritative and unfailing work
of reference, to which he may at all times turn with full certainty of finding what he needs
in its most recent aspect, whether he seeks information on the general principles of medi-
cine, or minute guioance in the treatment of special disease. So wide is the scope of the
work that, wiUi the exception of midwifery and matters strictly surgical^ it embraces the
whole domain of medicine, including the departments for which the physician is accustomed
to rely on special treatises, such as diseases of women and children, of the genito-urinary
organs, of the skin, of the nerves, hygiene and sanitary science, and medical ophthalmology
and otol(^. Moreover, authors have inserted the formulas which they have found most
efficient m the treatment of the various afiections. It may thus be truly r^^arded as a
Complete Llbbary of PRAcricAi< Medicine, and the general practitioner possessing it
may feel secure that he will require little else in the daily round of professional duties.
In spite of every efibrt to condense the vast amount of practical information fiir-
nished, it has been impossible to present it in less than 5 large octavo volumes, containing
about 5500 beautifully printed pages, and embodying the matter of about 15 ordinary
octavos. Illustrations are introduced wherever they serve to elucidate the text.
As material for the work is substantially complete in the hands of the editor, the pro-
fession may confidently await the appearance of the remaining volumes upon the dates
above specified. A detailed prospectus of the work will be sent to any adoress on appli-
cation to the publishers.
It Is A large undertaking, but qalte Justiflable in ; this country as authorities on the particular topics
the case of a progressive nation like the United on which they deal, whilst the others show by the
States. At any rate, if we may judge of future
TOlnmes fh>m the nrst it will be Justified by the
result. We have nothing but praise to bestow
upon the work. The articles are the work of
writers, many of whom are already recognized in
way they have handled their subjects that they
are fully equal to the task they had undertaken.
* * * A work which we cannot doubt will make
a lasting reputation for itself.~Xoru2on Medical
nmei and Qautte, May 9, 1885.
REYNOLDS, J. MUSSJSZZ, M. J).,
^ofemrr of the Prineiplet and Practice of Medicine in University College^ London.
A System of Medioine. With notes and additions by Henby Habtshorne,
A. M., M. D., late Ftofessor of Hygiene in the University of Pennsylvania. In three large
and handsome octavo volumes, containing 3056 double-columned pages, with 317 illustra-
tions. Prioe per volume, cloth, 15.00 ; sheep. |6.00 ; very handsome ha£f Bussia, raised bands,
$6.50. Per set, doth, (15; leather, (18; half Bussia, |19.50. Sold tmly by stt6soriptum.
16
Lka Brothebs & Co.'b Pdbucations — Clinical Med., etc
8TILLE, ALFRED, M. !>., LL, D.,
ProfeMor Emeritus of the Theory €Md Practice of Med, and of Clinical Med. in the Univ. of j
Cholera: Its Origin, History, Causation, Symptoms, Lesions, Prevention and Treat-
ment. In one handsome 12mo. volume of 1C3 pages, with a chaK. Cloth, $1.25. Jyui. readf.
The threatened importation of cholera into the country renders peculiarly timely
this work of an authority upon the subject so eminent as Professor Still^. The histoiy
of previous epidemics^ their modes of propagation, the vast recent additions to our
knowledffe of the causation, prevention and treatment of the disease, all have been handled
80 skilfully as to present with brevity the information which every practitioner should
possess in advance of a visitation.
for A rational system. Altogether, the monograph
is ODe (hat will have an excellent influence on the
Srofessional mind. — Medical and Surgical Reporter ,
agust 1, 1885. q.
This timelv little work is full of the learning
and good Judgment which marks all that comes
fh>m the pen of its distinguished author. What
he has to say on treatment is characterised by
hia.usual caution and his well-known preference
FLINT, AUSTIN, M. D.
Clinical Medicine. A Systematic Treatise on the Diagnosis and Treatment of
Diseases. Designed for Students and Practitioners of Medicine. In one large and huid-
8ome octavo volume of 799 pages. Cloth, $4.50 ; leather, $5.50 ; half Russia, $6.00.
li is here that the skill and learning of the great ! sistently with brevity and clearness, the difftnrent
clinician are displayed. He has giren us a store* subjects and their several parts reoeiTing the
houseof medical knowledge, excellent for the stu- ' attention which, relatirely to their importeace,
dent, convenient for the practitioner, the result of: medical opinion claims for them, is still more difB-
a Ions life of the most faithful clinical work, col- cult. Thfs task, we feel bound to say, has been
leotea by an energy as vigilant and systematic as i executed with more than partial succeaa by Dr.
untiring, and weighed by a Judgment no less clear , Flint, whose name is already familiar to students
than his observation is close.— iircAivM of Jfedictne, : of advanced medicine in this country as that of
To give an adequate and usefUl conspectus of the ' subJectSL and of numerous papers exhibiting much
extensive fleldofmodem clinical medicine is a task i orlglnslitv and extensive research.-- 7 As IhMin
ofno ordinary difficulty; buttoacmmplishthiscon- I Jow^mI, Dec. 1879.
By the Sraie Author.
Essays on Conservatiy e Medicine and Kindred Topics. In one very hand-
flome royal 12mo. volume of 210 pages. Goth, $1.38.
BJROADBJENT, W. S., M. !>., F. JB. C. P.,
Phytieian to and Lecturer on Medicine at SL Mary's HotpitaL
The Pulse. In one 12mo. volume. See Serin of Clinical ManuaU, page 3.
SCJETBJSIBJEB, BB. JOSEPH.
A Manual of Treatment by Massage and Methodical Muscle Sz-
eroise. Tmnslated by WAiiTSK Menbeubon, M. B., of New York. In one handsome
octavo volume of about 300 pages, with about 125 fine engravings. Preparing.
IINLAYSON, JAMES, M. B., Bdiior,
Physician and Leduror on CXmieal Medicine in the Glasgow Western If^krwuKry^ etc
Clinical Diaarnosis. A Handbook for Students and Practitioners of Medicine.
With Chapters bv Prof. Gairdner on the Physiognomy of Disease ; Prof. Stephens on
Diseases of the Female Organs; Dr. Bobertson on Insanity; Dr. Gemmell on Physical
Diagnosis : Dr. Coats on Laryngoscopy and Poet-Mortem Ezaminatione^ and by the £ditar
on OEUBe-taKing, Family History and Symptoms of Disorder in the Vanoua Systems. In
one handsome 12mo. volume of 546 pages, with SB illustrations. Goth, $2.63.
FBNWICK, SAMUBL, M. B.,
Assistant Physician to the London EonpUaL
The Student's Guide to Medical Diagnosis. From the third revised and
enlarged English edition. In oae very handsome royal 12mo. volume of 328 pages^ with
87 illustrations on wood. Cloth, $2.25.
TANNBB, TBOMASHAWKES, M. B.
A Manual of Clinical Medicine and Physical Diagnosis. Third American
from the second London edition. Revised and enlarged by TxIiBUBY Fox, M. D.
In one small 12mo. volume of 362 pages, with illustrations. Cloth, $1.50.
FOTHFBGILL, J. M., M. B., Edin., M. B. C. B., Land.,
Physician to the Oity of London Hospital for Diseases of the Chest
The Practitioner's Handbook of Treatment ; Or, The Prindples of Thera-
peutics. New edition. In one octavo volume. Preparing.
STURGES' INTRODUCTION TO THE STUDY
OF CLINICAL MEDICINE. Being a Guide to
the InvefltigatioD of Diseaae. In one handsome
l2mo. volume of 127 pages. Cloth, 11.26.
DAVIS' CLINICAL LECTURES ON VARIOUS
IMPORTANT DISEASES. By N. 8. Data
M. D. Edited by FaAn H. Davis, M. D. Saeond
edition. 12mo. 287 pages. Cloth, I1.7A.
Lea. Bhothkbs & Co.'s Publioatioms — Hygrlene, Blectr., Pract. 17
BICMABDSON, B. W., ^.A., M.J>., ZL. D., F.B.8,, F.8.A.
Fellow of the Boyal College of Pkysiciane, London.
Preventive Medicine. In one octavo volume of 729 pages. Cloth, $4; leather,
$5 ; veiy handsome half Bussia, raised bands, $5.50.
Dr. Richardson haa succeeded in producing a
work which is elevated in conception, comprehen-
sive in scope, scientific in character^ systematic in
arrangement^ and which is written m a clear, con-
cise and pleasant manner. He evinces the happy
foculty of extracting the pith of what is Icnown on
the subject, and of presenting it in a most simple,
intelligent and practical form. There is perhaps
no similar work written for the eeneral public
thatoontains such acomplete, reliable and instruc-
tive collection of data upon the diseases common
to the race, their origins, causes, and the measures
for their prevention. Tne descriptions of diseases
are clear, chaste and scholarly ; the discussion of
the question of disease Is comprehensive, masterly
and fViIly abreast with the latest and best knowl-
edge on the subject, and the preventive measures
advised are accurate, explicit and reliable.— -TA«
American Journal of the Medical Sciences, April, 1894.
This is a book that will surely find a place on the
table of every progressive physician. To the
medical profession, whose duty is auite as much to
prevent as to cure disease, the book will be a boon.
—-Boston Medical and Surgteal Journal, Mar. 6, 1884.
The treatise contains a vast amount of solid, valu-
able hygienic information.— ifedieo^ and Surgical
Reporter, Feb. 23, 1884.
BAMTBOLOW, BOBBBTS, A. M., M. JD., LL. JD.,
Prof, of Materia Medica and General Therapeutics in the J^erson Med, Coll. ofPhila., etc
Medical Electricity. A Practical Treatise on the Applications of Electricity
to Medicine and Surgery. Second edition. ^ "^ ^ ' ' * o^^r*
pageS) with 109 illustrations. Cloth, $2.50.
The second edition of this work following so
goon upon the first would in itself appear to be a
saffldent announcement; nevertheless, the text
has been so considerably revised and condensed,
and so much enlarged by the addition of new mat-
ter, that we cannot foil to recognise a vast improve-
ment upon the former work. The author has pre-
pared his work for students and practitioners— for
those who have never acouaintea themselves with
the subject, or, having aone so, find that after a
time their knowledge needs refreshing. We think
he has accomplishedthis object The book is not
too voluminous, but is thoroughly practical, sim-
ple, complete and comprehensible. It is, more-
over, replete with numerous illustrations of instru-
ments, appliances, eUu^Medical Reeordf November
In one very handsome octavo volume of 292
A most excellent work, addressed by a practi-
tioner to his fellow-practitioners, and therefore
thoroughly practical. The work now before as
has the exceptional merit of clearly pointing out
where the benefits to be derived from electricity
must come. It contains all and everything that
the practitioner needs in order to understand in-
telligently the nature and laws of the axent he is
making use of; and for its proper application in
practice. In a condensed, practical form, it pre-
sents to the physician all that he would wish .to
remember after perusing a whole Iibrai7 on medical
electricity, including the results of tne latest in-
vestigations. It is the book for the practitioner,
and the necessity for a second edition proves that
it has been appreciated by the profession.— PA^si-
cian cmd Surgeon, Dec 1882.
tb:e tbaB'Book of tbeatment.
A Comprehensive and Critical Beview for Practitioners of Medi-
cine. In one 12mo. volume of 320 pages, bound in limp cloth, with red edges, |1.25.
This work presents to the practitioner not only a complete classified account of all
the more important advances made in the treatment of Disease during the year endine
Sept. 30, ISSIL but also a critical estimate of the same bj a competent authority. Each
department or practice has been fully and concisely treated, and into the consideration of
each subject enter such allusions to recent pathological ana clinical work as bear directly
upon treatment. As the medical literature of all countries has been placed under contri-
bution, the references given throughout the work, together with the separate indexes of
subjects and authors, will serve as a guide for those who desire to investigate any thera-
peutical topic at greater length.
can Journal of the Medical ScienceStkpx\\,\%^.
It is a complete account of the more important
advances made in the treatment of disease. Ex-
treme pains have been taken to explain clearly in
the fewest possible words the views of each
writer, and the details of each subject. One of
the principle points about the book is its practical,
yet concise language. Each editor has well per-
formed his duty, and we can si^ with truth that
it is a volume well worth buying for frequent use.
— Virginia Medical Monthly, March, 1885.
In a few moments the busy practitioner can re-
fresh his mind as to the principal advances in
treatment for a year past. This kind of work is
peculiarly useftil at the present time, when current
literature is teeming with innumerable so-called
advances, of which the practitioner has not time
to determine the value. Here he has, collected
from many sources, a rUunU of the theories and
£acts which are new, either entirely or in part, the
decision as to their novelty being made by those
who by wide reading and long experience are
ftilly competent to render such a verdict.— iimeri-
HABEB8HON, 8. O., M. !>.,
SenUyr Physician to and late LecL on Principles and Praetiee of Med. at Ouf^s Hospital, London.
On the Diseases of the Abdomen; Comprising those of the Stomach, and
other parts of the Alimentary Canal, OBsophaffus, Csecum, Intestines and Peritoneum. Second
American fi*om third enlarged and revisea English edition. In one handsome octavo
volume of 554 pages, with illustrations. Cloth, |3.50.
•FAVrS TREATISE ON THE FUNCTION OP DI-
GESTION; its Disorders and their Treatment
From the second London edition. In one octavo
Toltune of 238 pages. Cloth, 12.00.
•CHAMBERS* MANUAL OF DIET AND REGIMEN
IN HEALTH AND SICKNESS. In one hand-
some octavo volume of 302 pp. Cloth, |2.76.
BARLOW'S MANUAL OF THE PRACTICE OF
MEDICINE. With additions by D. P. Cokdm,
M.D. 1 vol. 8vo., pp. 608. Cloth, $2.B0.
TODD'S CLINICAL LECTURES ON CERTAIN
ACUTE DISEASES. In one octavo volume oif
820 pages. Cloth, 12.60.
HOLLAND'S MEDICAL NOTES AND REFLEO-
TIONS. 1 vol. 8vo., pp. 493. aoth, $3.60.
18 LiA Bbothxrs & Co.'s Pubuoations — ^Throat, Ijimgs, Heart.
COHEN, J. 80LI8, M. !>.,
Lecturer on Loryngoteopy and DisMMa of the Throat and Chest tn the Jelfereon Medical ObUege,
Diseases of the Throat and Nasal Passages. A Guide to the Diagnosis and
Treatment of Affections of the Phazynx, (Esophagos, Trachea, Lanrnx and Nares. Third
edition, thoroughly revised and rewritten, with a large number of new illustrations. In
one ve^ handsome octavo volume. Preparing.
8BILBB, CARL, M. JD.,
Lecturer on Laryngoeeopy in the Univerttty of Penmylivaniia,
A Handbook of Diagnosis and Treatment of Diseases of the Throat,
Nose and Naso-Fharynx. Second edition. In one handsome royal 12mo. volome
of 294 pages, with 77 illustrations. Cloth, $1.75.
the essentUIs of diagnosis and treatment In difl>
eases of the throat and nose. The art of laryngos-
copy, the anatomy of the throat and noae and the
patnology of the macons membrane are discussed
It is one of the best of the practical text^books
on this subject with which we are acquainted. The
present edition has been increased in size, but its
eminently practical character has been main- «-
tained. Many new illustrations have also been I with conciseness and ability. The work is pro-
introduced, a case-record sheet has beeu added. ! fosely illustrated, excels in many essential feat-
and there are a valuable bibliography and a good ' ureji, and deserves a place in the oflBoe of the
index of the whole. For any one who wishes to
make himself fiunillar with the practical manage-
ment of cases of throat and nose disease, the book
will be found of great value.— i^sw York Medteal
Journal^ June 9. 1883.
The work before us is a concise handbook upon
practitioner who would inform himself as to the
nature, diagnosis and treatment of a class of dis-
eases almost inseparable from general medical
practice. With advanced students the book must
be very popular on aooount of its oondenaed style.
—LouisvilU Medical Nmce, June 26, 1883.
BBOWmS, liBNirOX, F. B. C. a., BdifU,
Senior Surgeon to the Centra London T%roat and Ear Hoepital, etc
The Throat and its Diseases. Second American from the second igngiii^h edi-
tion, thoroughly revised. With 100 typical illustrations in colors and 50 wood engrayings,
designed and executed by the Author. In one very handsome imperial octavo volnme of
about 350 pages. Preparing.
FLINT, AUSTIN, mTK,
Profeuor of the Prindplet and Practice of Medidne in BetUmte Hoipital Medical OoUcge, if. F.
A Manual of Auscultation and Percussion ; Of the Physical Diagnosis of
Diseases of the Lungs and Heart, and of Thoracic Aneurism. Third edition. In one hand-
some royal 12mo. volume of 240 pages. Cloth, $1.63.
It is safe to say that there is not in the English • the results of his oareftil stady and ample ex-
language, or any other, the equal amount of clear, * * .-—*-- ^.-- AX,. ... -
exact ana comprehensible information touching
the physical exploration of the chest, in an equal
number of words. Professor Flint's language is
the physical exploration of the chest, in an equi
number of words. Professor Flint's language 1
precise and simple, conteying without dubiety
Krience in such wise that the young will find ft the
st source of instruction, and the old the most
pleasant means of roTiving and complementing
their knowledge.— ilm«7-t«an PrtutUiOHer, Jane,
1888.
BY THE SAME AUTHOR.
Physical Exploration of the Iiungs by Means of Auscultation and
Percussion. Three lectures delivered before the Philadelphia County Medical Society,
1882-83. In one handsome small 12mo. volume of 83 pages. Cloth, $1.00.
A Practical Treatise on the Physical Exi)loration of the Chest and
the Diagnosis of Diseases Affecting the !Etespiratory Organs. Second and
revised edition. In one handsome octavo volume of 591 pages. Cloth, $4.50.
Phthisis : Its Morbid Anatomy, Etiology, Symptomatic Events and
Complications, Fatality and Prognosis, Treatment and Physical Diag-
nosis; In a series of Clinical Studies. In one handsome octavo volume of 442 pages.
Cloth, $3.50.
A Practical Treatise on the Diagnosis. Pathology and Treatment of
Diseases of the Heart. Second revised and enlarged edition. In one octavo volume
of 550 pages, with a plate. Cloth, $4.
OBOS8, S. JD., M.JD., ZL.I>., D.C.Z. Oxon., LL.JD. Cantab.
A Practical Treatise on Foreign Bodies in the Air-passages. In one
octavo volume of 452 pages, with 59 illustrations. Cloth, $2.75.
FULLER ON DISEASES OF THE LUNGS AND
AIR-PASSAGES. Their Pathology, Physical DI-
aipiosis. Symptoms and Treatment. From the
second and revised English edition. In one
octavo volume of 475 pages. Cloth, $3.50.
8LADE ON DIPHTHERIA; its Nature and Treat-
ment, with an account of the History of its Pre-
valence in various Countries. Second and revised
edition. In one 12mo. voL, pp. 158. Cloth, $1.25.
WAL8HE ON THE DISEASES OF THE HEART
AND GREAT VESSELS. Third American edi-
tion. In 1 vol. 8vo., 416 pp. Cloth, $3.00.
SMITH ON CONSUMPTION; Its Early and Reme-
diable Stages. 1 vol. Svo., pp. 253. 01oth»$2.S5.
LA ROCHE ON PNEUMONIA. 1 vol. 8vo. of 490
pages. Cloth, $3.0a
WILLIAMS ON PULMONARY CONSUMPTION;
Its Nature. Varieties and Treatment. With an
analysis of one thousand cases to exempli^ its
duration. In one Svo. voL of 903 pp. C^oth, ^..50.
JONES' CLINICAL OBSERVATIONS ON FUNC-
TIONAL NERVOUS DISORDERS. Second Am-
erican edition. In one handsome ootavo volume
of 340 pages. Cloth, $9.26.
Lka Brothebs & Go.'s Pobuoations — ^Nerr. and Ment. Dls., etc. 19
MITCXLELL, 8. WBIB, M. D,,
Phytidan to OriftopoBdie Hospital and the If^iirmary for Diaeases of the Ifervout 8ytUm^ PhUa^ etc,
Iieotures on Diseases of the Nervous Svstem; Especially in Women.
Second edition. In one 12mo. volume of 288 pages. Cloth, $1.75. Just ready.
We feel sure that the new edition of Dr. Mitch-
eirs admirable lectures will bereceiyed on this
side of the Atlantic with more than ordinary at-
tention. His subject, the nervous disorders of
women, is one that interests erery practitioner,
and his views on treatment are mduafly receiving
general acceptanoe.— Zondon Meiical limes om,
Gazette, July 4, 1886.
M088^ JAMES, M.D., F.B. C.P., LL. J>.,
Smior AssistaM Physician to the Manchester Boyal Infirmary,
A. Text-Book on Diseases of the Nervous System. In one handsome
octavo volume of 600 pages, fully illustrated. Shortly.
WA MTTsTON, ALLJJT McZAIfE, M. J).,
Attending Physician at the Hospital for Epilepties and ParalyticSf BVackwetPe Island^ N. 7,
Nervous Diseases ; Their Description and Treatment. Second edition, thoroughly
revised and rewritten. In one octavo volume of 698 pages, with 72 illustrations. Cloth, $L
When the firstedition of this good bookappeared
we gave it our emphatic endorsement and the
present edition enhances our appreciation of the
' ' " '" 9 a safe guide to students of
One of uie best and most
Book and its author as a safe
clinical neurology.
characterized this book as the best of its kind In
any language, which is a handsome endorsement
ft-om an exalted source. The improvements in the
new edition, and the additions to it, will Justify Its
purchase even by those who possess the old.—
critical of English neurological journals, Brain, has Alienist and Neurotogist, April, 1&2.
TVKH, DAJnJEL HACK, M. D.,
Joint AiUhor of The Manual of Psychological Medicine^ etc.
niustrations of the Influence of the Mind upon the Body in Health
and Disease. Designed to elucidate the Action of the Imagination. New edition.
Thoroughly revised and rewritten. In one handsome octavo volume of 467 pages, with
two colored plates. Cloth, (3.00.
method of interpretation. Guided by an enlight-
ened deduction, the author has reclaimed for
It is impossible to peruse these Interesting chap-
ters without being convinced of the author's per-
fect sincerity, impartiality, and thorough mental
grasp. Dr. Tuke has exhibited the requisite
amount of scientific address on all occasions, and
the more intricate the phenomena the more firmly
has he adhered to a physiological and rational
science a most interesting domain in psychology,
previously abandoned to charlatans and empirics.
This book, well conceived and well written, must
commend itself to every thoughtlUl understand-
ing.—A'eto York Medical /oumoZ, September 6, 1884.
CLOU8TON, THOMAS 8., M. D., F. M. C. P., L. B. C. 8.,
Lecturer on Mental Diseases in the Unwersity of Edinburgh,
Clinical Lectures on Mental Diseases. With an Appendix, containing an
Abstract of the Statutes of the United States and of the Several States and Territories re-
lating to the Custody of the Insane. By Chables F. FoifiOM, M. D., Assistant Professor
of Mental Diseases, Medical Department of Harvard University. In one . handsome
octavo volume of 541 pa^es. illustrated ¥dth eight lithographic plates, four of which
are beautifully colored. Clotn, |4.
The practitioner as well as the student will ac-
cept the plain, practical teaching of the author as a
forward step m the literature of insanity. It is
refreshing to find a physician of Dr. Clouston's
experience and high reputation giving tlie bed-
side notes upon which his experience has been
founded and his mature Judgment established.
Such clinical observations cannot but be useful to
tioner in guiding him to a diag-
Ing the treatment, especially m
doubtful cases of mental dis-
the general practitioner in guiding him to a dh
nosis and indicating the tr ' ' ••
many obscure and ak>ubtful
ease. To the American reader Dr. Folsom's Ap-
pendix adds greatly to the value of the work, and
will make it a desirable addition to every library.
—American Psychological Journal, July, 1884.
k viiui«j»i uudt;i YBViuus UMiiuuv ULUi w useful to
i^^Dr. Folsom's Abstract may also be obtained separately in one octavo volume of
108 pages. Cloth, $1.50.
8AVAGB, GBOBGE B., M. D.,
Lecturer on Mental Diseases at Guy^s Hospital, London.
Insanity and Allied Neuroses. Practical and Clinical. In one 12mo. vol
ume of 551 pages, with 18 typical illustrations.
Clinical Manucis, page 3.
Cloth, $2.00. Just ready. See Series o;
As a handbook, a guide to practitioners and stu*
dents, the book fulnls an admirable purpose. The
many forms of insanity are described with char-
acteristic clearness, the illustrative cases are care-
ftilly selected, and as regards treatment, sound
common sense is everywhere apparent.
> nas written an excellent
We re-
peat that Dr. Savage
manual for the practitioner and student*— Am-
erican Journal of Jmanity, April, 1885.
PZATFAIB, W. 8., M. I)., F. M. C. P.,
The Systematic Treatment of Nerve Prostration and Hysteria,
one handsome small 12mo. volume of 97 pages. Cloth, |1.00.
In
Blandford on Insanity and its Treatment: Lectures on the Treatment,
Medical and Legal, of Insane Patients. In one very handsome octavo volume.
2© Lba Bbothkrs & CJo.'b Publications — Surgery.
GB088, 8. JD., jr. JD., ii. JD., JD. C i. Oxon., LL. D.
leriMritac Profettor of Surgery in the J^^m%on Medical CblUge of PhUadelphiiL
A System of Sorgerjr : Pathologicfd, Diagnostic, Therapeatic and OperatiTe.
Sixth edition, thoroughlj revised and ^[reatly improved. In two laige and beMitifullj-
Srinted imperial octavo volumes containing 2382 pages, illustrated by 1623 engravings,
trongly bound in leather, raised bands, (15 ; half Russia, raised bands, (16.
Dr. Grose' SytUm of Suraery has long been the < mmterUl has been Introduced, and altogether the
standard work on that suoject for students and , distinguished author has reason to be satisfied
practitioners.— Zofidon Lancet^ May 10, 1884. that he has placed the work Ailly abreast of the
The work as a whole needs no commendation. I «tate of our knowledge.— Afed. iZeeoni, Nov. 18, 1882.
Kany years ago it earned for itself the enviable rep- His System of Surgery^ which, since its first edi-
Htatfon of the leading American work on surgery, tion in 1869, has been a standard work fh this
and it is still capable of maintaining that standard. I country as well as in America, in "the whole
The reason for this need only be mentioned to be i domain of surgery," tells how eaniest and labori-
appreciated. The author has always been calm ous and wise a surgeon he was, how thoroughly
*^ abased his con- be appreciated the work done by men in other
countries, and how much he contributed to pro-
and iudicious in his statements, has ^
elusions on rquch study and personal experience,
has been able to grasp his subject in its entirety,
mote the science and practice of surgery in his
and, above all, has conscientiously adhered to • own. There has been no man to whom America
truth and fact, weighing the evidence, pro and is so much Indebted In this respect as the Nestor
eon, accordingly. A considerable amount of new i of surgery.— 5r»<ttA Medical Journal, May 10, 18St
ASHHUBST, JOHN, Jr., M. D.,
Profeseor of Clinical Surgery, Untv. of Penna., Surgeon to the Episcopal SotpUal, PhUadaphia.
The Principles and Practice of Surgery. Fourth edition, enlarged and
revised, in one large and handsome octavo volume of about 1100 pages, with about 575
illustrations. Shortly,
GOULD, A. PEABCE, M. 8., M. B,, F. B. C. S„
AsaUtant Surgeon to Middlesex Hospital.
Elements of Surgical Diagnosis. In one pocket^ize 12mo. volume of 5S9
pages. Cloth, (2.00. Just ready. See Studentt^ Series of ManuaU, page 3.
The student and practitioner will find the | and if practitioners would devote a portion of their
principles of surgical diagnosis very satisfoctorlly ' leisure to the study of it, they would receive
set forth with all unnecessary verbiage eliml- immense benefit in the way of refreshing their
nated. Every medical student attending lectures I knowledge and bringing it up to the present state
should have a copy to study during thelntervals, | of progress.— Oncinna/i Medual News, Jan.^ 18S5.
OIBNMT, V.B., m7d7,
Surgeon to the Orthopcedic Hospital, New York, etc.
Orthopsadic Surgery. For the use of Practitionen and Students. In one hand-
some octavo volume, promsely illustrated. Preparing.
BOBEItT8, JOHN B., A. M., M. B.,
Lecturer on Anatomy and on Operative Surgery at the Philadelphia School of Anatomy.
The • Principles and Practice of Surgery. For the use of Students and
Practitioners of Mwiicine and Surgery. In one very nandsome octavo volume of about 500
pages, with many illustrations. Preparing.
BELLAMY, EDWABD, ^7b7c. 8.,
Surgeon and Lecturer on Surgery at Coring Oross Hospital, London.
Operative Surgery. Shortly. See Studmi^ Series of Manuals, page 3.
8TIMSON, LBWIS A., B. A., M. B.,
Prof of Pathol. Anal, at iM Univ. of the City of New York, Surgeon and Curator to Bellevue Hasp.
A Manual of Operative Surgery. New (second) edition. In one very hand-
some royal 12mo. volume of about 500 pages, with about 850 illustrations. Cloth, $2.50.
Shordy.
A notice of the previous edition is appended.
This volume is devoted entirely to operative sur- 1 every student should possess one. This work
gery, and is intended to familiarize the student does away with the necessity of pondering over
with the details of operations and the different I larger works on surgery for descriptions of opera-
modes of performing them. The work is hand- I tiona^as It presents In a nutshell what is wanted
somely illustrated, and the descriptions are clear by the surgeon without an elaborate search to
and well-drawn. It is a clever and useful volume ; | find it— Afan/tond Medical Journal, August, 1878.
PIRRIE'S PRINCIPLES AND PRACTICE OP
SURGERY. Edited by John Nkill, M. D. In
one 8vo. vol. of 784 pp. with 316 illus. Cloth, $8.75.
COOPER'S LECTURES ON THE PRINCIPLES
AND PRACTICE OF SURGERY. In one SvavoL
of 767 pages. Cloth, 92.00.
8KEY*8 OPERATIVE SURGERY. In one vol 8vo.
SARGENT ON BANDAGING and OTHER OPERA-
TIONS OF MINOR SURGERY. New edition,
with a Chapter on military surgery. One 12mo.
volume of .383 pagen, with 187 cuts. Cloth, $1.75.
MILLER'S PRINCIPLES OF SURGERY. Fourth
American fVom the third Edinburgh edition. In
one 8vo. vol. of 638 pages, with 340 illustrations.
MILLER'S PRACTICE OF SURGERY. Fourth ' "^'^^^^^P*^^ '^^'^^^ ^°*^**"**- Cloth. 13.0.
and revised American from the last Edinburgh i GIBSON'S INSTITUTES AND PRACTICE OF
edition. In one large 8to. vol. of 682 pages, with I SURGERY. Eighth edition. In two octavo vols.
864 illustrationa. Cloth, $8.76. I of 066 pages, with 34 plates. Leather 96.50.
Lea Brothers & Co.'s Publications — Surgery.
21
EBICSSBN, JOHN E., F. M. 8., F. M. C. 8.,
Professor of Surgery in University College^ London^ etc
The Science and Art of Surgery ; Being a Treatise on Surgical Injuries, Dis-
eases and Operations. From the eighth and enlarged English edition. In two large and
beautiful octavo volumes of 2316 pa^es, illustrated with 984 engravings on wood.
Cloth, $9; leather, raised bands, $11 ; naif Russia, raised bands, |12. Just ready.
After the profession has placed its approval upon
a work to the extent of purchasing seven editions,
it does not need to be introduced. Simultaneous
with the appearance of this edition a translation
is being made into Italian and Spanish. Thus
this favorite teztrbook on surgery holds its own in
pite of numerous rivals at the end of thirtv years.
It is a grand book, worthy of the art in the interest
of which itiswrltten.— /)««rortXance<,Jan.lO, 1885.
After being before the profession for thirty
years and maintaining dunng that period a re-
putation as a leading work on surgery, there is not
mufh to be said in the way of comment or criti-
cism. That it still holds its own goes without say-
ing. The author inftises into it his large experi-
ence and ripe Judgment. Wedded to no school,
committed to no theory, biassed bv no hobby, he
imparts an honest personality in his observations,
ana his teachings are the rulings of an impartial
Judge. Such men are always safe guides, ana their
works stand the tests of time and experience.
"Such an author is Erlchsen, and such a work is his
Surgery.'-Mediecd Record^ Feb. 21, 1886.
BRYANT, THOMAS, F. R. C. S.,
Surgeon and Lecturer on Surgery at Guy's Hospital, London,
The Practice of Surgery. Fourth American from the fourth and revised Eng-
lish edition. In one large and very handsome imperial octavo volume of 1040 pages, with
727 illustrations. Cloth, |6.60; leather, $7.50; half Russia, $8.00. Just ready.
The treatise takes in the whole field of surgery,
that of the eye, the ear, the female organs, ortho-
piodies, venereal diseases, and military surgery,
as well as more common and general topics. All
of these are treated with clearness and with
sufficient fVilness to suit all practical purposes.
The illustrations are numerous and well printed.
We do not doubt that this new edition will con-
tinue to maintain the popularity of this standard
work.— Jfedica^ aind Surgical Reporter^ Feb. 14, *86.
This most magnificent work upon surgery has
reached a fourth edition in this country, showing
the high appreciation in which it is held by the
American profession. It comes f^esh ftom the
pen of the author. That it is the very best work
on surgery for medical students we think
there can be no doubt The author seems to have
understood Just what a student needs, and has
Srepared the work accordingly. — Oincinnati Medic<U
7ewSt January, 1885.
By the same Author.
Diseases of the Breast. In one I2mo. volume. Preparing, See Series of Clinical
Manuals, page 3.
BUTLIN, HBNBY T., F. JB. C. 8.,
Assistant Surgeon to St. Bartholomeui's Hospital, London.
Diseases of the Tonsue. In one 12mo. volume of 466 pages, with 8 colored
plates and 3 woodcuts. Cloth, $3.50. Just ready. See Series of Clinical ManuaU, page 3.
F8MABCS, Br. FBIEBBICH,
Professor of Surgery at the University of Kielt etc.
Early Aid in Injuries and Accidents. Five Ambulance Lectures. Trans-
lated hy H. K. H. Princess Christian. In one handsome small 12mo. volume of 109
pages, with 24 illustrations. Cloth, 75 cents.
the methods of affording flrst treatment in casea
of frost-bite, of drowning, of suffocation, of loss of
conpciousness and of poisoning are described;
and the fifth lecture teaches how injured persons
may be most safely and easily transported to their
homes, to a medical man, or to a hospital. The
illustrationa in the book are clear and good.— Ifedi-
eal Times and Qazette, Nov. 4, 1882.
The course of instruction is divided into five
sections or lectures. The flrst, or introductory
lecture, gives a brief account of the structure and
organization of the human body, illustrated by
clear, suitable diagrams. The second teaches how
to give Judicious help in ordinary injuries— contu-
sions, wounds, heemorrhage and poisoned wounds.
The third treats of first aid in cases of fracture
and of dislocations, in sprains and in burns. Next,
TREVES, FREDERICK,' eTr. C. S.,
Assistant Surgeon to and Lecturer on Surgery at the London Hospital.
Intestinal Obstruction. In one pocket-size 12mo. volume of 522 pages, with 61
illustrations. Limp cloth, blue edges, $2.00. Just ready. See Series of Clinical* Manuals,
page 3.
A standard work on a subiect that has not been
eo comprehensively treated oy any contemporary
English writer, its completeneRS renders a full
review difficult, since every chapter deserves mi-
nute attention, and it is impossible to do thorough
BALL, CHARLES B., M. Cli., Dub., F. R. C. S. E.,
Surgeon and Teacher at Sir P. Dun^s Hospital, Dublin.
Diseases of the Rectum and Anus. In one 12mo. volume of 550 pages.
PrejHvring. See /Series of Clinical Manuals, page 3.
BBUITT, BOBJEBT, M. M. C. 8., etc.
The Principles and Practice of Modem
London edition. In one 8vo. volume of 687 pages, with 432 illus.
justice to the author in a few paragraphs. Intes-
tinal Obfitrvction is a work that will prove of
equal value to the practitioner, the student, the
pAthologi.st, the physician and the operating bvlt-
geoxk.—British Medical Journal^ Jan. 31, 1886.
From the eighth
[oth, $4 ; leather, $6.
22 Lea Brothkrs & Co.'s Publications — Surgery.
holmjES, timothy, m. a.,
Surgeon and Lecturer on Surgery at St. Oeorg^s So^pUal, London,
A SvBtem of Surgery ; Theoretical and Practical. IN TREATISES BY
VARIOUS AUTHORS. American edition, thorouqhly revised and re-edited
hv John H. Packard, M. D., Surgeon to the Episcopal and St Joseph's Hospitals,
rhlladelphia, assisted by a corps of thirty-three of tne most eminent American surgeons.
In three laige and very handsome imperial octavo volumes containing 3137 double-
columned pages, with 979 illustrations on wood and 13 lithographic plates, beautifully
colored. Price per volume, cloth, $6.00 ; leather, $7.00 ; half Russia, $7.50. Per set, doth,
$18.00 ; leather, $21.00 ; half Russia, $22.50. Sold only by wJbBertptum.
VoLXTVE I. contains General Pathology, Morbid Processes, Injttrebs in Gen-
eral, Complications of Injuries and Injuries of Regions.
Volume 1 1, contains Diseases of Organs of Special Sense, Circulato&t Sys-
tem, Digestive Tract and Genito-Urinary Organs.
Volume III. contains Diseases of the Respiratory Organs, Bones, Joints and
Muscles, Diseases of the Nervous System, Gunshot Wounds, Oferattvx and
MmoR Surgery, and Miscellaneous Sl^bjects (including an essay on Hospitals).
This great work, issued some years since in England, has won such universal confi-
dence wherever the language is spoken that its republication here, in a form more
thoroughly adapted to the wants of the American practitioner, has seemed to be a duty
owing to the profession. To accomplish this, each article has been placed in the hands of
a gentleman specially competent to treat its subject, and no labor has been spared to bring
each one up to the foremost level of the times, and to adapt it thoroujB^hljr to the practice
of the country. In certain cases this has rendered necessary the substitution of an entirely
new cisay for the original, as in the case of the articles on Skin Diseases, on Diseases <u
the Absorbent System, and on Antesthetic& in the use of which American practice differs
from that of England. The same careful and conscientious revision has been pursued
throughout, leading to an increase of nearly one-fourth in matter, while the series of
illustrations has been nearly trebled, and the whole is presented as a complete exponent
of British and American Surgery, adapted to the daily needs of the working practilioner.
In order to brinff it within the reach of every member of the profession, the five vol-
umes of the origfinal have been compressed into three by employing a double-oolumned
royal octavo p^^ fti^<l i^ ^^^ improved form it is offered at less than one-half the price of the
original. It is printed and bound to match in every detail with Reynolds' System of Medi-
cine. The work will be sold by subscription only, and in due time evezy member of the
profession will be called upon and offeretd an opportunity to subscribe.
The authors of the original English edition are | the library of any medical nian. It is more wieldly
men of the front rank in England, and Dr. Packard and more uaeftil than the English edition, and with
has been fortunate in secaring as his American I its companion work— "Reynolds* System of Medi-
coa4Jutors such men as Bartholow, Hyde, Hunt I cine*'— will well represent the present state of oar
Conner, Stimson, Morton, Hodeen, Jewell ana science. One who is ikmiliar with thoee two works
their colleagues. As a whole, tne work will be i will be (Urly well Aimished head-wlee and hand-
solid and substantial, and a valuable addition to | wise.— 7%« Medical New, Jan. 7, 11182.
8TIM80N, LEWIS A., B. A., M.D.,
Profeaeor of Pathologieal Anatonw at the Univertiljj of tKe City of New York, Surgeon and Curator
to Bellevue Sospital^ Surgeon to the Preebyterian MoepUal, New York, etc
A Practical Treatise on Fractures. In one very handsome octavo volume of
S98 pages, with 360 beautiful illustrations. Cloth, $4.75 ; leather, $5.75.
the surgeon in AilI praotiee.— JV. O. Medkal and
Surgical Journal, March, 188S.
The author gives in clear language all that the
practical surgeon need know of the science of
fractures, their etiology, symptoms, processes oi
The author has given to the medical profession
in this treatise on fractures what is likely to be-
come a standard work on the sublect It is certainly
not surpassed by any work written in the English,
or, for that matter, any other language. The au-
thor tells us in a short, concise and comprehensive
manner, all that is known about his subject There
is nothing scanty or superficial about ft, as in most
other treettises ; on the contrary, everything is thor-
ough. The chapters on repair of fractures and their
treatment show him not only to be a profound stu-
dent, but likewise a practical surgeon and patholo-
gist His mode of treatment of the different fract-
union, and treatment according to the latest de-
velopments. On the basis of mechanical analysis
the author accurately and clearly explains the
clinical features of fractures, and by the same
method arrives at the proper diagnosis and rational
treatment A thorough explanation of the patho-
logical anatomy and a carefhl description of the
various methods of procedure make the book ftiU
uresiseminentlvsoundandpractical. Weconsider of value for every practitioner.-0«i«nii6tatt /*
thiswprkoneof the best on fractures: and it will CAirur^it, May 19, 1883.
be welcomed not only as a text-book, but also by | '^
MABSH, HOWABD, F. B. C. S.,
Senior Aeeietant Surgeon to aand Lecturer on Anatomy at SL BarthaUimmo^e HotpUat, Lomdon.
Diseases of the Joints. In one 12mo. volume. Preparing, See Serin of dmteoi
ManvaUy page 3.
BICK, T. BICKEBING, F, B. C. S.,
Surgeon to and Lecturer on Surgery at SL George' e Hospital, London.
Fractures and Dislocations. In one 12mo. volume. Preparing. See Saria
-of Clinical ManualSf page 3.
LxA BaoTHBBS & Co.'s Pdblioations — Frac., Dlsloc., Opbthal. 23
HAMILTON, FBAIfKH., M, !>., LL. !>.,
Surgeon to BeUmme ffotpital^ Nmo York,
A Practical Treatise on Fractures and Dislocations. Seventh edition,
thoroughly reyised and much improved. In one very handsome octavo volume of 998
pages, with 379 illustrations. Cloth, |5.50
open back, $7.00. Jusi ready.
Hamllton*s great experience and wide acquaint-
ance with the literature of the subject have enabled
him to complete the labors of Malgaigne and to
place the reader in poBseesion of the advances
made during thirty years. The editions hare fol-
lowed each other rapidly, and they introduce us
to the methods of practice, often so wise, of his
American colleagues. More practical than Mal-
gaigne's work, it will serve as a valuable guide to
the practitioner in the numerous and emoarrass-
ing cases which come under his observation.—
Archives OintralM de MMecine^ Paris, Nov. 1884.
This work, which, since its first appearance
twenty-five years ago, has gone through many
editionji, ana been much enlarged, may now be
ikirly regarded as the authoritative book of refer-
ence on the subjects of fractures and dislocations.
Each successive edition has been rendered of
leather, $6.50 ; very handsome half Bussia,
cent work, and especially of the recorded re-
searches and improvements made by the author
himself and his countrymen.— £n<tsA Medical
Journal, May 9, 1886.
With its first appearance in 1859, this work took
ranlL among the classics in medical literature,
and has ever since been quoted by surgeons the
world over as an authority upon the topics of
which it treats. The surgeon, if one can be found
who does not already Icnow the work, will find it
scientific, forcible and scholarly in text, exhaustive
in detail, and ever marked by a spirit of wise con-
servatism.—Xout«vi/<6 Medical New$, Jan. 10, 1886.
For a quarter of a century the author has been
elaborating and perfecting his work, so that it
now stands as the best of its kind in any lan-
guage. As a text>book and as a book of reference
and guidance for practitioners it is simply in valu-
greater value through the addition of more re- | able. — New Orleant Med. and Surg. JourTClfCfor.lWL.
jULBn, hejsj&y je., f. n. c. s..
Senior Au*t Surgeon, Royal Westminater Opkthalmic Hoap. ; late CUnieal A9$% Moorfield»f London,
A Handbook of Ophthalmic Science and Practice. In one handsome
octavo volume of 460 pages, with 125 woodcuts, 27 colored plates, and selections from the
Test-types of Jaeger and Snellen. Cloth, $4.50 ; leather, $5.50. Just ready.
This work is distinguished by the great num- I and typical illustrations of all important eye
ber of colored plates which appear in it for illus- 1 affections, placed in Juxtaposition, so as to be
tratlng various pathological conditions. They are i grasped at a glance. Beyond a doubt it is the
very oeautifUl in appearance, and have been | best illustrated nandbook of ophthalmic science
executed with great care as to accuracy. An ex- [ which has ever appeared. Then, what is still
amination of the work shows it to be one of high better, these illustrations are nearly all original,
standing, one that will be reinrded as an authority '" " .......
among ophthalmologists. The treatment recom-
mended is such as me author has learned from
actual experience to be the best. — CHncinnati Medi-
cal Neae, L>ec. 1884.
It presents to the student concise descriptions
We have examined this entire work with great
care, and it represents the commonly accepted
views of advanced ophthalmologists. We can most
heartily commend this book to all medical stu-
dents, practitioners and specialists. — Detroit
Lancet, Jan. 1885.
WJELLS, J. SOELBBBG, JF. Jt. C. 8.,
Professor of Ophthalmology in King's College Hospital, London, etc,
A Treatise on Diseases of the Eye. Fourth American from the third London
edition. Thoroughly revised, with copious additions, by Chableb S. Bull, M. D., Surgeon
and Pathologist to the New York Eye and Ear Infirmary. In one large octavo volume of
822 pages, with 2o7 illustrations on wood, six colored plates, and selections from the Test-
types of Jaeger and Snellen. Cloth, $5.00; leather, $6.00; half Bussia, $6.50.
The present edition appears in less than three : shows the fidelity and thoroughness with which
years since the nnblication of the last American the editor has accomplished his part of the work,
edition, and yet, itop the numerous recent inves- | The illustrations throughout are good. This edi*
tigations that have been made In this branch of tion can be recommended to all as a complete
medicine, many changes and additions have been | treatise on diseases of the eye. than which proba-
required to meet the present scope of knowledge ' bly none better exists.— 3fedi«u J36eortl,Aug.l8,*83.
upon this subject. A critical examination at once ;
NXSTTLE8HIP, EI)WABI>, F. B. C. 8.,
Ophthalmic Surg, and Leet. on Ophth. Surg, at St. Thomas' Hospital, London.
The Student's Guide to Diseases of the Bye. Second edition. With a chap-
ter on the Detection of Color-Blindness, by Whxiam Thomsok, M. D., Ophthakuologist
to the Jefferson Medical Ck)llege. In one royal 12mo. volume of 416 pages, with 138
illustrations. Cloth, $2.00.
This admirable guide bids fair to become the
favorite text-book on ophthalmic surgery with stu-
dents and general practitioners. It bears through-
out the imprint of sound Judgment combined with
vast experience. The illustrations are numerous
and well chosen. This book, within the short com-
pass of about 400 pages, contains a lucid exposition
of the modem aspect of ophthalmic science. —
Medical Beeord, June 23, 1888.
BBOWNB, EDGAR A.,
Surgeon to the Liverpool Eye and Ear Infirmary and to the Dispensary for Skin Diseases.
How to Use the Ophthalmoscope. Being Elementarv Instructions in Oph-
thalmoscopy, arranged for tne use of Students. In one small royal 12mo. volume of 116
pages, witn 35 illustrations. Cloth, $1.00.
LAWSON ON INJURIES TO THE EYE. ORBIT
AND ETELID6 : Their Immediate and Remote
Effects. 8 TO., 404 pp., 02 illus. Cloth, $3.50.
LAURENCE AND MOON'S HANDY BOOK OF
OPHTHALMIC SURGERY, for the use of Prac-
titioners. Second edition. In one octavo vol-
nme of 227 pages, with 66 lUust Goth, $2.76.
CARTER'S PRACTICAL TREATISE ON DISEAS-
ES OF THE EYE. Edited by Johx Gasnr, M. D.
In one handsome ootaTO Tolume.
24 Lba Bbothibs & Go.'s PtrsLiCATiONs — OtoL, Urin. DIs., Dent.
BUBJTETT, CHAMLES H., A. M., M. J),,
Profeisor of Otology in tke Philadelphia Polffclinit ; Pretidmt of the AnurieoH Otologieal SocUty.
The Ear. Its Anatomy, Physiology and Diseases. A Practical Treatiae
for the use of MetUcal Students and Practitioners. New (second) edition. In one handsome
octavo volume of 580 pages, with 107 illustrations. Cloth, $4.00 ; leather, $5.00. Justrtad^.
We note with pleasure the appearance of a second I carried out, and much new matter added. Dr.
edition of this valuable work. When it first came , Burnett's work must be regarded as a very ralna-
out it was accept^'d by the profe«««ion as ono of ble contribution to aural surgery, not only on
the standard works on modern aural surgery in account of its comprehensiveness, but because it
the English language; and in his second edition contains the results of the careful personal obeerva-
Dr. Burnett has fully maintained his reputation, tion and experience of this eminent aural surgeon,
for the book is replete with valuable information ^London Lancet^ Feb. 21, 1885.
and suggestions. The revision has been carefully
rOLITZEB, ADAM,
Imperial- Roj/tU Prof, of Aural Therap. in the Univ, of Vienna.
A Text-Book of the Ear and its Diseases. Translated, at the Author's re-
quest, hj Jambs Patteb-sox CAasELL8, M. D., M. R. C. S. In one handsome octaro vol-
ume of SOO pages, with 257 original illustrations. Cloth, $5.50.
The work itself we do not hesitate to pronounce section, and this again by the patholoffical physl-
the best upon the subject of aural diseases which ology, an arrangement which serves to aeep up the
has ever appeared, systematic without being tofi int«rest of the student by showing the direct ap-
difflise on oosolete subiecto, and eminently prac- , plication of what has preceded to the study of dis-
tical in every sense. The anatomical deHcriplions ease. The whole work can be recommended as a
of each separate division of the ear are admirable, reliable guide to the student, and an efficient aid
and pro^sely illustrated by woodcuts. Thev are , to the practitioner in his treatment— Boston JCcd-
followed immediately by the physiology of the ical ami Surgical Journal, June 7, 1883.
ROBERTS, WILLIAM, Mn.,
Lecturer on Medicine in the Manche&ier School of Medicine, etc
A Practical Treatise on Urinary and Benal Diseases^ including Uri-
nary Deposits. Fourth American from the fourth London edition. In one hand-
some octavo volume of 609 pages, with 81 illustrations. Cloth, $3.50. JuH ready.
The peculiar value and finish of the book are ' directly or indirectly to the diagnosis, prognosis
derived fk'om its resolute maintenance of a clinical , and treatment of urinary diseases, and possesses
and practical character. This volume is an.un- . a completeness not found elsewhere in our laa*
rivalled exposition of everything which relates I guage.— TAs Medical Chronicle, July, 1886u q.
GROSS, S. D., M. JD., ZL. JO., D. C. i., etc.
A Practical Treatise on the Diseases. Izgnries and Malformations
of the Urinarjr Bladder, the Prostate Gland and the Urethra. Third
edition, thoroughly revised by Samuel W. Gross, M. D., Professor of the Principles of
Surgery and of Clinical Surgery in the Jefferson Medical College, Philadelphia. In one
octavo volume of 574 pages, with 170 illustrations. Cloth, |4.50.
MOBBIS, HBNBT, M. B., F. B. C. S.,
Surgeon to and Lecturer on J^irgery at Middleeex Hotpital, London,
Surgical Diseases of the Kidney. In one 12mo. volume. Preparing, See
Series of Clinical Manuah, page 3.
LUCAS, CLEMEUTT, M. B., B, S., F. B. C, S.,
Senior Aetietant Surgeon to Ouy'e Hoepital^ London,
Diseases of the Urethra. In one 12mo. volume. Preparing, See Serm
of Clinical ManualSy page 3.
TBOMBSON, SIB BlENBY,
Surgeon and Profeeeor of CUnical Surgery to. UnivertUy OoUege Hotpital, London,
Lectures on Diseases of the Urinary Organs. Second American from the
third English edition. In one 8vo. volume of 203 pp., with 25 illustrations. Cloth, $2.25.
By the Same Author.
On the Pathology and Treatment of Stricture of the Urethra and
Urinarr Fistulea. rrom the third English edition. In one octavo volume of 359
pages, with 47 cuts and 3 plates. Cloth, $3.50.
COLBMAN, A., L. B. C. JP., F. B. C. S., JEocam. L. JD. 8.,
Senior Dent. Surg, and LecL on Dent. Surg, at SL Bartholomew** Rosp. and the Dent Hoep., London.
A Manual of Dental Surgery and Pathology. Thoroughly revised and
adapted to the use of American Students, bjr Thomas C. Stellwagen, M. A., M. D,
B. D. S., Prof, of Physiology at the Philadelphia Dental College. In one handsome octavo
volume of 412 psges, with 331 illustrations. Cloth, $3.25.
BASHAM ON RENAL DISEASES: A ainlcal I one 12mo. vol of SOi pages, with 21 tUnslntloBa
Ouide to their Diagnosis and Treatment In | Cloth, •2.00.
Lea Brothers & Co.'s Publications — Venereal, Impotence.
25
BUMSTJEAJD, F. J.,
M. JD., LL. JO.,
LaU Professor of Venereal Diseases
cU the VoUege of Physictam and
Surgeons^ New York, etc
and TAYLOR, JB. IF.,
A. M., M. JD.,
Surgeon to Charity Hospital^ New Yorkj Prof, of
Venereat and Skin Diseases in the University of
Vermont^ Pres. of the Am. Dermatologieal Ass^n.
The Pathology and Treatment of Venereal Diseases. IncludiDs the
results of recent inyestigations upon the subject. Fifth edition, revised and largely re-
written, by Dr. Taylor. In one large and handsome octavo volume of 898 pages with
139 illustrations, and thirteen chromo-lithographic figures. Cloth, $4.75 ; leather, $5.75 ;
very handsome half Russia, $6.25.
It is a splendid record of honest labor, wide
research, Just comparison, careful scmtiny and
original experience, which will always be held as
a high credit to American medical literature. This
is not only the best work in the English language
upon the subjects of which it treats, but also one
which has no equa. in other tongues for its clear,
comprehensive and practical handling of its
themes.— Amenean Journal of the Medical SdeneeSt
Jan, 1884.
Itis certainly the best single treatise on vene-
real in our own, and probably the best in any lan-
gu^e. — Boston Medical and Surgical Journal^ April
The character of this standard work is so well
known that it would be superfluous here to pass in
review its general or special points of excellence.
The verdict of the profession has been passed; it
has been accepted as the most thorough and com-
plete exposition of the pathology and treatment of
venereal diseases in the language. Admirable as a
model of clear description, an exponent of sound
pathological doctrine, and a guide for rational and
successful treatment, it is an ornament to the medi-
cal literature of this country. The additions made
to the present edition are eminently judicious*
from the standpoint of practical utility.— JoumeU oj
Ctttaneous and Venereal Diseases^ Jan. 1884.
COBNIL, v.,
Professor to the Faadtf^ of Medicine of Paris, and Physician to the Lourdne HospitaL
Syphilis, its Morbid Anatomy, Diagnosis and Treatment. Specially
revisea oy the Author, and translated with notes and additions by J. Henry C. Simes.
M. D., Demonstrator of Pathological Histology in the University of Pennsylvania, ana
J. William White, M. D., Lecturer on Venereal Diseases and I)emonstrator of Surgerv
in the University of Pennsylvania. In one handsome octavo volume of 461 pages, with
84 very beautiful illustrations. Cloth, $3.75.
the whole volume is the clinical experience of the
author or the wide acquaintance of the translators
The anatomical and histological characters of the
hard and soft sore are admirably described. The
multiform cutaneous manifestation? of the disea^^e
are dealt with histologically in a masterly way, a.<i
we should indeed exj^t them to be. ana the
accompanying illustrations are executed carefully
and well. The various nervous lesions which are
the recognized outcome of the syphilitic dyscrasia
are treated with care and consideration. Syphilitic
epilepsy, paralysis, cerebral syphilis and locomotor
ataxia are subjects full of interest; and nowhere in
with medical literature more evident. The anat-
omy, the histology, the pathology and the clinical
features of syphilis are represented in this work In
their best, most practical and most instructive
form, and no one will rise from its perusal without
the feeling that his grasp of the wide and impor*
tant subject on which it treats is a stronger and
surer one.— TA« London Practitioner, Jan. 1882.
HUTCHINSON, JONATHAN, F. JR. 8., F. M. C. 8.,
Consulting Surgeon to the London Hospital.
Syphilis. In one 12mo. volume. Preparing. See Series of Clinical ManualSf page 8.
GM088, 8AMUFL W., A. M., M. J>.,
Professor of the Principles of Surgery and of dinieal Surgery in the J^erson Medical College.
A Practical Treatise on Impotence, Sterility, and Allied Disorders
of the Male Sexual Organs. Second edition, thoroughly revised. In one very hand-
some octavo volume of 168 pages, with 16 illustrations. Cloth, $1.50.
The author of this monograph is a man of posi-
tive convictions and vigorous style. This is iusti-
fied by his experience and by his study, whicn has
cone hand in hand with his experience. In regard
to the various organic and Amctlonal disorders of
the male generative apparatus, he has had ex-
ceptional opportunities for observation, and his
book shows that he has not neglected to compare
his own views with those of other authors. The
result is a work which can be safely recommended
to both physicians and surgeons as a guide in the
treatment of the disturbances it refers to. It is
the best treatise on the subject with which we are | 1883.
acquainted.— 7*^0 ir^dt^a^ News, Sept. 1, 1883. |
This work will derive value from the high stand-
ing of its author, aside from the fact of its passing
so rapidly into its second edition. This is, indeed,
a book that every physician will be glad to place
in his library, to he read with profit to himself,
and with incalculable benefit to his patient. Be-
sides the subjects embraced in the title, which are
treated of in their various forms and degrees,
spermatorrhoea and prostatorrhoea are also fully
considered. The work is thoroughly practical in
character, and will be especially useful to the
general practitioner.— 3feaica{ Record, Aug. 18,
CVLLERIEB, A., & BVM8TEAJ), F. J., M.D., LL.D.,
Surgeon to the H6p\tal du Midu Late Professor of Venereal Diseases in the College of Physicians
and Surgeons, New York,
An Atlas of Venereal Diseases. Translated and edited hy Frkeman J. Bum-
stead, M. D. In one imperial 4to. volume of 328 pages, double-columns, with 26 plates,
oontaining about 150 figures, beautifuUv colored, many of them the size of life. Strongly
bound in doth, $17.00. A specimen of the plates and text sent by mail, on receipt of 25 cts.
HILL ON SYPHILIS AND LOCAL CONTAGIOUS I FORMS OF LOCAL DISEASE AFFECTING
DISORDERS. In one 8vo vol. of 470 p. Cloth. $3.26. PRINCIPALLY THE ORGANS OF GENERA-
LEE'S LECTURES ON SYPHILIS AND SOME | TION. In one 8vo. toI. of 246 pages. Cloth, $2.26.
26 Lea Brothers k Co/s Publioations — Diseases of Skin.
JTTDJB, J. NEVINa, A. M.9 M. D.,
Proft»9or of Dermatology and Venereal DUeoMM in Bueh Medical CbUsge, Ckicagc
A Practical Treatise on Diseases of the Skin. For the lue of Students and
Practitioners. In one handsome octavo volume of 570 pages, with 66 beautiful and elab-
orate illustrations. Cloth, $4.25 ; leather, $5.25.
The author has given the student and practl- I clan In active practice. In dealing with these
tioner a work adnnrably adapted to the wants of j questions the author leaves nothing to the pre-
each. We can heartily commend the book as a sumed knowledge of the reader, but enters tbor-
valuable addition to our literature and a reliable I oughly into the most minute description, so that
guide to students and practitioners in their studies I one is not only told what should be done nnder
and practice.— .4m. Joum. of Med. Set., Julv,l883. I given conditions but how to do it as well. It is
Especially to be praised are the practical sug- i therefore in the best sense ** a practical treatise."
gestions as to what iflay be called the common- , That it is comprehensive, a glance at the index
sense treatment of eczema. It is quite impossible , will show.— Marvtand Medical JoumaL, July 7, 1883.
to exaggerate the Judiciousness with which the j Professor Hvae has long been known as one of
formulsB for the external treatment of ecxema are I the most intelligent and enthusiastic represent*-
selected, and what is of eaoal importance, the fUll i tives of dermatology in the west. His nomerons
and clear instructions for their use. — Lonaon Medi- . contributions to the literature of tbis specialty
eal Times and Oaiette. July S8. 1883. | have gained for him a favorable recognition as a
The work of Dr. Hyde will be awarded a high i careful, oonscientioas and original observer. The
position. The student of medicine will find it remarkable advances made in our knowledge of
peculiarly adapted to his wants. Notwithstanding 1 diseases of the skin, especially from the stand-
the extent of the subject to which It is devoted, 1 point of pathological histology and improved
yet it is limited to a single and not very large vol- 1 methods of treatment, necessitete a revision of
ame. without omitting a proper discussion of the > the older text-books at short intervals in order to
topics. The conciseness of the volume, and the ' bring them up to the standard demanded bv the
setting forth of only what can be held as facts will march of science. This last contribution of Dr.
also make it acceptable to general practitioners. Hyde Is an efTort in this direction. He has at-
— Cincinnati Medical NeiM, Feb. 1883. I tempted, as he Informs as, the task of presenting
The aim of the author has been to present to his in a condensed form the results of the latest ob-
readers a work not only expounding the most servation and experience. A careftil examinatiod
modem conceptions of his sublect, but presenting of the work convinces us that he hasaoeomplishen
what is of standard value. He nas more especially | his task with painstakins fidelity and with a cred-
devoted its psges to the treatment of disease, and itable result.---J(n(rttaZ o/ Cutaneotu and Venereal
by his detailed descriptions of therapeutic meas- Diseatee, June, 1883.
ures has adapted them to the needs of the physi- |
FOX, T., M.D., F.B. C. IP., and FOX, T. C, B.A., M.M. C.8.,
Physician to the Department for Skin Dieeaeee, Phyeieian for Dieeaeet of the Skin to the
Univertity Oouege Hospital^ London. Westm/inater HoepUail^ London.
An Epitome of Skin Diseases. With Formulse. For Students and Prac-
titioners. Third edition, revised and enlarged. In one very handsome 12mo. volume
of 238 pages. Cloth, $1 .25.
The third edition of this convenient handbook | manual to lie upon the table for instant reference,
calls for notice owing to the revision and expansion . Its alphabetical arrangement is suited to this use,
which It has undergone. The arrangement of skin , for all one has to know is the name of the disease,
diseasesinalphabeticalorder. which is the method and here are its description and the appropriate
of classification adopted in this work, becomes a i treatment at hand and ready for instant applieih
positive advantage to the student. The book is ' tion. The present edition has been very <»u'efbUy
one which we can strongly recommend, not only revised and a number of new diseases are de-
to students but also to practitioners who require a ! scribed, while most of the recent additions to
compendious summary of the present state of i dermal therapeutics find mention, and the formn-
derTCi&UAof^.— British Medical Journal^ July 2, 1883. ' lary at the end of the book has been considerably
We cordially recommend Fox's Epitome to those I augmented.— 77^ Medical News, December, 1883.
whose time Is limited and who wish a handy I
MOMBI8, MALCOLM, M. !>.,
Joint Lecturer on Dermatology at S^. Mary's Hospital Medical School^ London.
Skin Diseases ; Including their Definitions, Symptoms, Diagnosis, Prognosis, Mor-
bid Anatomy and Treatment. A Manual for Students and Practitioners. In one 12mo.
volume of 316 pages, with illustrations. Cloth, $1.75.
To physicians who would like to know something j for clearness of expression and methodical ai^
about skin diseases, so that when a patient pre- rangement is better adapted to promote a rationsl
sents himself for relief they can make a correct
diagnosis and prescribe a rational treatment, we
unhesitatingly recommend this little book of Dr.
Morris. The affections of the skin are described
conception of dermatology— a branch confessedly
difficult and perplexing to the beginner.—^ Lotas
Courier of Medietne^ April, 188a
, ... J i. i 11- I The writer has certalnlv given in a small compass
in a terse, lucid manner, aiid their several charao- | » i^rge amount of well-compiled information, and
ukinafi^a an rklalnlv <aAt. fnrt.n fhar. Hiacriinala will rw» u:- i!Ai.i^ v.^i. ^ >> #._» wi~ iA.t. >.*u..
teristics SO plainly set forth that diajguosls will be , his little book compares favorably with any other
easy. The treatment in each case is such as the which has emanated fh)m England, while in many
experience of the most eminent dermatologists ad- points he has emancipated himself fhjm the stnb-
vises.— arkJinnati Medical News, April, 1880. bomly adhered to errors of others of his country-
This is emphatically a learner's book ; for we ' men. There is certainly excellent material in the
can safely say, that in the whole range of medical ! book which will well repay perusal. — Boston Msd.
literature there is no book of a like scope which I and Surg. Journ.^ March, 1880.
WILSON, FBASMUS, F.B.S.
The Student's Book of Cutaneous Medicine and Diseases of the Skin.
In one handsome small octavo volume of 535 pages. Cloth, $3.50.
HILLIER, THOMAS, M. D.,
Physician to the Skin Department of University OoUege^ London.
Handbook of Skin Diseases; for Students and Practitioners. Second Ameri-
can edition. In one 12mo. volume of 353 pages, with pktee. Cloth, $2.25.
Lka Brothers & Co.'s Publications — ^Dis. of Women.
27
Air AMJEBICAJff SYSTEM OF GYNMCOLOGT.
A System of Gynseoolon-, in Treatises by Various Authors. Edited
by Matthew D. Mann, M. D., Profesaor of Obstetrics and Gynocology in the Uni-
versity of Buffalo, N. Y. In two handsome octavo volumes, richly illustrated. In active
vreparaiion,
LIST OP CONTRIBUTORS.
WILLIAM H. BAKER, M. D.,
FORDYCB BARKER, M. D.,
ROBERT BATTEY, M. D.,
SAMUEL C. BUSEY, M. D.,
HENRY P. CAMPBELL, M. D.,
HENRY C. COE, M. D.,
E. C. DUDLEY, M. D.,
GEORGE J. ENGELMANN, M. D.,
HENRY F. GARRIGUES, M. D.,
WILLIAM GOODELL, M. D.,
EGBERT H. GRANDIN, M. D..
SAMUEL W. GROSS, M. D.,
JAMES B. HUNTER, M. D.,
A. REEVES JACKSON, M. D.,
EDWARD W. JBNKS, M. D.,
WILLIAM T. LU8K, M. D.,
MATTHEW D. MANN, M. D.,
ROBERT B. MAURY, M. D.,
PAUL P. MUND6, M. D.,
C. D. PALMER, M. D.,
WILLIAM M. POLK, M. D.,
THADDEU8 A. REAMY, M. D.,
A. D. ROCKWELL, M. D..
ALEX. J. C. SKENE, M. D.,
R. 8TANSBURY SUTTON, A. M.. M. D..
T. GAILLARD THOMAS, M. D.,
ELI VAN DE WALKER, M. D.,
W. GILL WYLIE, M. D.
TMOMAS, T. GAILLARD, M. !>.,
Profesaor of Diseoues of Women in the OoUege of Phyeiciant and Surgeons, N. 7.
A Practical Treatise on the Diseases of Women. Fifth edition, thoroughly
revised and rewritten. In one large and handsome octavo volume of 810 pages, with 266
illustrations. Cloth, f 5.00 ; leather, $6.00 ; very handsome half Russia, raised bands, $6.50.
The words which follow " fifth edition" are in i rioas one. As a book of reference for the bnsy
this case no mere formal announcement. The
alterations and additions which hare been made are
both numeroas and important The attraction
and the permanent character of this book lie in
the clearness and trath of the clinical descriptions
of diseases; the fertility of the author in thera-
Seutio resources and the fulness with which the
etails of treatment are described; the definite
character of the teaching; and last, but not least,
the evident candor which pervades it We would
alao particularize the ftilness with which the his-
tory of the subject is gone into, which makes the
book additionally interesting and gives it value as
a work of reference. — London Meaical Times and
Gaxetie, July 30, 1881.
practitioner it is unequalled.— ^<wton Medical any
ISurgieal Journal. April 7, 1880.
It has been enlarged and carefully revised. It Is
a condensed encycTopsedia of gyusecological medi-
cine. The style of arrangement, the masterly
manner in which each subject Is treated, and the
honest convictions derived fVom probably the
largest clinical experience in that special^ of any
in this country, all serve to commend it in the
highest terms to the pract|;jkloner. — NaehvUU Jour,
of Med. and Surg., Jan. 1881.
That the previous editions of the treatise of Dr.
Thomas were thought worthy of translation into
German, French, Italian and Spanish, is enough
I to give it the stamp of genuine merit At home it
The determination of the author to keep his has made its way mto the library of every obstet-
book foremost in the rank of works on gynsecology i rician and gyntBCologist as a safe guide to practice,
is most gratifying. Recognising the fact that this ' No small number of additions have been made to
can only be accomplished by frequent and thop- the present edition to make it correspond to re-
ough revision, he has spared no pains to make the cent improvements in treatment— Pa<»/lc Medical
present edition more desirable even than the pre- i and Surgical Journal, Jan. 1881.
EDIS, AMTMUn W^M. D^Lcm^^F.M. C.P., M.R. C.S.,
A89itt. Obstetric Physician to Middlesex Hospital, late Physician to BHtish Lying-in Hospital.
The Diseases of Women. Including their Pathology, Causation, Symptoms,
Diagnosis and Treatment. A Manual for Students and Practitioners. In one handsome
octavo volume of 576 pages, with 148 illustrations. Cloth, $3.00 ; leather, $4.00.
It is a pleasure to read a book so thoroughly i The greatest pains have been taken with the
good as this one. The special qualities which are
conspicuous are thoroughness In covering the
whole ground, clearness of description ana con-
ciseness of statement Another marked feature of
the book is the attention paid to the details of
many minor surgical operations and procedures,
as, for instance, the use of tents, application of
leeches, and use of hot water injections. These
are among the more common methods of treat-
ment, and yet very little is said about them In
many of the text-books. The book is one to be
warmly recommended especially to students and
general practitioners, who need a concise but com-
plete riwmi of the whole subject Specialists, too,
will find many useful hints in its pages.— Lofton
Med. and Surg. Joum., March 2, 1882.
sections relating' to treatment A liberal selection
of remedies Is given for each morbid condition,
the strength, mode of application and other details
being fully explained. The descriptions of gynee-
cological manipulations and operations are flill,
clear and practical. Much care has also been be-
stowed on the parts of the book which deal with
diagnosis— we note especially the pages dealing
with the differentiation, one from another, of the
difTerent kinds of abdominal tumors. The prac-
titioner will therefore find in this book the kind
of knowledge he most needs in his daily work, and
he will be pleased with the clearness and ftilness
of the information there given.— T/^ Practitioner,
Feb. 1882.
BAMNES, BOBEBT, M. D., F. B. C. F.,
Obstetric Physician to St. Thomas' Hospital, London, etc
A Clinical Exposition of the Medical and Surgical Diseases of Women.
In one handsome octavo volume, with numerous illustrations. New edition. Preparing.
WEST, CBjLMLESTmTb.
Lectures on the Diseases of Women. Third American from the third Lon-
don edition. In one octavo volume of 543 pages. Cloth, $3.75 ; leather, $4.75.
28 Lka Bbothebs & Co.'b Pdblioations— Dis. of Women, Mldwty.
EMMET, THOMAS ADDIS, M. JO., LL. D.,
Surgeon to th4 Woman* t Hospital^ New York, eU,
The Frinoiples and Practice of Gynscoloffy; For the use of SttidenU and
Practitioners of Medicine. New (third) edition, thoroughly revised. In one large and veir
handsome octavo volume of 880 pages, with 150 illustrations. Cloth, $5 ; leather, H.
{Just ready.)
We are in doabt whether to congratulate the The time has parsed when Emroet*s Gynmeologp
author more than the profession upon the appear- was to be regaroed as a boolc for a single couatff
ance of the third edition of this weil-lcnown work, or for a single generation. It has always been hu
Embodying, as it does, the life-long experience of aim to popularize gynsscology, to bring it within
one who has conspicuously distinguished himself easy reach of the general practitioner. The orig-
as a bold and successful operator, and who has inalitv of the ideas, aside from the perfect con-
devoted so much attention to the specialty, we fidence which we feel In the author's statements,
feel sure the profession will not fail to appreciate compels our admiration and respect. We roar
the privilege thus offered them of perusing the well take an honest pride in Dr. Kmmet's worK
▼lews and practice of the author. His earnestness and feel that hie book can hold its own against the
of purpose and conscientiousness are manifest, criticism of two continents. It represtents all that
He gives not only his individual experience but , is most earnest and most thoughtful in American
endeavors to represent the actual state of gyn»- , gynsscology. Emmet's work will continue ts
oological science and ^ri.^Britiih Medical Jour- i reflect the individuality, the sterling integritvand
naf. May 16, 1886. the kindly heart of its honored author iong'afler
No jot or tittle of the high praise bestowed upon ' smaller books have been forgotten.—Amerteoit
the first edition is abated. It is still a book of Journal o/ Obstetrics, May, 1886.
marked personality, one based upon large clinical ' Any work on gynsscology by Emmet mast
experience, containing large and valuable ad- | always have especial Interest and value. He has
ditions to our knowledge, evidently written not for many years been an exceedingly busy pras-
only with honesty of purpose, but with aconscien- titionerln this department Few men have had
tious sense of responsibility, and a book that is at , his experience and opportunities. As a guids
once a credit to its author and to American med- \ either for the general practitioner or specialist^
leal literature. We repeat that it is a book to be it Is second to none other. No one can read
studied, and one that is indispensable to every Emmet without pleasure, instruction and profit,
practitioner giving any attention to gyuBscology.— | —Cineinnati Lancet and Ctuite, Jan 31, 1885.
American JourncU of the Medical Selencea^ April, 1886.
nvircAjr, j. matthbws, m.i>., ll. d., f. jj. s. je., etc.
Clinical Leotures on the Diseases of Women ; Delivered in Saint Bar-
tholomew's Hospital. In one handsome octavo volume of 175 pages. Cloth, |1.50.
They are In every way worthy of their author ;
indeed, we look upon them as among the most
auu^TVVt, WW iWtk. upuu VltVIM ma MlUVUg blJO IllUSli
valuable of his contributions. They are all upon
matters of great interest to the general practitioner.
8ome of them deal with subjects that are not. as a
rule, adequately handled In the text-books ; others
of them, while Maring upon topics that are usually
treated of at length in such works, yet bear such a
stamp of individuality that, If widely read, as they
certainly deserve to be, they cannot tail to exert a
wholesome restraint upon the undue eagerness
with which many young physicians seem bent
upon following the wild teMhings which so infest
the gynsBcology of the present daj.r^N. Y. Medical
Journal, Marcn, 1880.
MAY, CHARLES H., M. D.
Late House Surgeon to Mount Sinai Hospital^ New Yerk.
A Manual or the Diseases of women. Containing a concise and systematic
exposition of theory and practice. In one 12mo. volume of about 350 pages. In press.
HODGE, HUOHL., M. D.,
Emeritue Profeuor of Obeteirice^ etc, in the University of Penntylvania.
On Diseases Peculiar to Women; Including Displacements of the Uterus.
Second edition, revised and enlarged. In one beautifully printed octavo volume of 519
pages, with original illustrations. Cloth, $4.50.
By the Same Author.
The Principles and Practice of Obstetrics. Illustrated with large litho-
graphic plates containing 159 figures from original photographs, and with numerous wood-
cuts. In one large quarto volume of 542 double-columned pages. Stronglj bound in
cloth, $14.00.
. * « * Specimens of the plates and letter-press will be forwarded to any address, free by
mail, on receipt of six cents in postage stamps.
BAM8BOTHAM, FRANCIS H., M. D.
The Principles and Practice of Obstetric Medicine and Surgery :
In reference to the rrocessof Parturition. A new and enlarged edition, thoroughly revised
by the Author. With additions by W. V. Keating, M. I)., Professor of Obstetrics, etc,
in the Jefferson Medical College of Philadelphia. In one large and handsome imperial
octavo volume of 640 pages, with 64 full-page plates and 43 woodcuts in the text, contain-
ing in all nearly 200 beautiful figures. Strongly bound in leather, with raised bands, $7.
ASHWELL'S PRACTICAL TREATISE ON THE I AND OTHER DISEASES PECULIAR TO WO-
DISEA8ES PECULIAR TO WOMEN. Third MEN. In oneSvo. vol. of 464 paRes. CJoth.fiSO.
American from the third and revised London MEIGS ON THE NATURE, SIGNS AND TBBAT-
editfon. In one 8vo. vol., pp. 620. Cloth. I3..V). ' MENT OF CHILDBED FEVER. In one Sto.
CHURCHILL ON THE PUERPERAL FEVER | volume of 846 pages. Cloth, J2.00.
Lea Bbotheks & Co.'s Publications — Midwifery. 29
PZATFA TH, W. S., M. I>., F. B, C. P.,
Profutor of Gbttetrie Medicine in King's College, London, etc,
A Treatise on the Science and Practice of Midwifery. New (fourth)
American, from the fifth English edition. Edited, with additions, by Bobebt F. Hab-
Ris, M. D. In one handsome octavo volume of 654 pages, with 3 plates and 201 engrav-
ings Cloth, $4 ; leather, f 5 ; half Russia, $5.50. Just ready.
This excellent work needs no commendation.
For many years it has maintained a deseryedly
high reputation among teachers as a text book,
ana in the profession as a guide to the practical
experiences which attend the obstetrician. The
present edition, under the supervision of Dr. Har-
ri8» has been carefully reyised, and many portions
rewritten, and the whole work has been adapted to
the wants and circumstances of this continent. —
Buffalo Medical and Surgical Journal, Aug. 1886. q.
In the short time that this excellent and highly
esteemed work has been before the profession It
has reached a fourth edition In this country and a
fifth one in England. This fact alone speaks in
high praise of It and it seems to us that scarcely
more need be said of it in the way of endorsement
of its yalue. As a text book for students and for
the uses of the aeneral practitioner there is no
work on obstetrics superior to the work of Dr.
Playfalr. Its teachings are practical, written in
plain language, and afford a correct understanding
of the art or midwifery. No one can be disap-
pointed in it. — Cincinnati Medical News, June, 188ft.
BABinES, BOBEBT, M. D., tmd FAIfCOXTBT, M. !>.,
Pkyt. to thB Oeneral Lying-in Hosp,, Land. Obttetrie Phys. to SL Thomat' ffoep., Lond,
A System of Obstetric Medicine and Surgery, Theoretical and Clin-
ical. For the Student and the Practitioner. The Section on Embryology contributed by
Prof. Milnes Marshall. In one handsome octavo volume of about 1000 pages, profusely
illustrated. Cloth, $5 ; leather, $6. In a few dayt.
BARKBB, JFOBDYCJE, A7M.,~M~n., LL. I>. JEdin.,
Clinical Profetsor of Midwifery and the Diieaset of Women in the Bellevue Hospital Medical College,
New York, Honorary Fellow of the Obstetrical Societies of London and Edinburgh, etc., etc.
Obstetrical and Clinical Essays. In one handsome 12mo. volume of abowt
300 pages. Preparing.
KING,. A. F. A., M. D.,
Professor of Obstetrics and Diseases of Women tn the Medical D^ixsrtmmt of the ColumMan Univer'
sity, Washington, D. C, and in the University of Vermont, etc.
A Manual of Obstetrics. Second edition. In one very handsome 12mo. volume
of 331 pages, with 59 illustrations. Cloth, $2.00.
It must be acknowledged that this is just what { densed style of composition, the writer has pre-
it pretends to be— a sound guide, a portable eplt- , sented a great deal of what it is well that eyery
ome. awork in which only indi^peuMable matter obstetrician should know and be ready to practice
has been presented, leaving out all padding and or prescribe. The fact that the demand for the
chaff, and one in which the student will find pure volume has been such as to exhaust the first
wheat or condensed nutriment— iVewOr/eontfifed- edition in a little over a year and a half speaks
ieal and Surgical Journal , May, 1884. well for its popularity. — American Journal of the
In a series of short paragraphs and by a con- , Medical Sciences, April, 1884.
LANDIS, HENBY G., A. M., M. D.,
Professor of Obstetrics and the Diseases of Women in Starling Medical College, Columbus, 0.
The Management of Labor. In one handsome 12mo. volume of about 300
pages, with 30 illuHtrations. Shortly.
BABNES, FANCOilBT, M. J>.,
Obstetric Physician to St. Thomas' Hospital, London,
A Manual of Midwifery for Midwives and Medical Students. In one
royal 12mo. volume of 197 pages, with 50 illustrations. Cloth, $1.25.
JPABVIN, TJBCHOPHILUS, M. !>., LL. I).,
Professor of Obstetrics and the Diseases of Women and Children in the Jeferson Medical College.
A Treatise on Midwifery. In one very handsome octavo volume of about 556
pages, with numerous illustrations. In press.
FABBT, JOBEPf S^mTik,
Obstetrician to the Philadelphia Hospital, Vice-President oj the Obstet. Society of Philadelphia.
Sxtra - Uterine Pregnancy: Its Clinical History, Diagnosis, Prognosis and
Treatment. In one handsome octavo volume of 272 pages. Cloth, $2.50.
TANNBB, THOMAS JELAWKES, M. D.
On the Signs and Diseases of Pregnancy. First American from the second
English edition. Octavo, 490 pages, with 4 colored plates and 16 woodcuts. Cloth, $4.25.
WINCKEL, F.
A Complete Treatise on the Pathology and Treatment of Childbed,
For Students and Practitioners. Translated, with the consent of the Author, from the
second German edition, by J. R. Chadwick, M. D. Octavo 484 pages. Cloth, $4.00.
30 Lea Bbothebs & Co.'s Publications — ^SUdwfy., 1Mb. Childn.
LEISMMAIf, WILLIAM, M. D.,
Btgku Prcfettor of Midwiftry in tht UmvergUy of OUugow^ Oc
A System of Midwifery, Including the Diseases of Pregnancy and the
Puerperal State. Third American editian, revised bythe Author, with additions by
John S. Pabbt, M. D., Obstetrician to the Philadelphia Hospital, eta In one large and
very handsome octavo volume of 740 paffes, with 20d illustrations. Cloth, $4.50 ; leather,
$5.50; very handsome half Bussia, rajsed bands, $6.00.
The aathor is broad in his teachings, and dis-
onsses briefly the comparatiye anatomy of the pel-
vis and the mobility of the pelTlc articulations.
The second chapter is doTOted especially to
the stad> of the pelris, while in the third the
ik for students during their attendance upon
lectures, and have great pleasure in recommend-
female organs of generation are introduced.
The structure and derelopment of the ornm are
admirably described. Then follow chapters upon
the yarious subjects embraced in the study of mid- ; present day it has no supei
wifery. The descriptions throughout the work are guage.— Oonoda Laneet, Jai
plain and pleasing. It is sufficient to state that in I To the American stude
proMration of the present edition the author has
maoe such alterations as the progress of obstetri-
cal science seems to require, and we cannot but
admire the ability with which the task has been
performed. We consider it an admirable text-
book ' -
ing it As an exponent of the midwifery of the
.... - ^(^^ .
^ _^ ^ ^ ^(
Ihis, the Inst edition of this well-known work,eTery j must prove admirably^adaptodT'Complete in'aU Its
recent adranoement in this field has been brought parts, essentially modem m its teachinss, and w
present day it has no superior in the English lan-
^^ , . *an. 1880.
student the work before us
lilts
recenc aaTanoemeni in uiis neia naa De«n orougnt ; parts, essentially modem In its teachings, and with
forward.— i%y»tctan and Burgeon, Jan. 1880. demonstrations noted for clearness and precision.
We gladly welcome the new edition of this ex- it will nin in favor and be recognised as a work
oellenftext-book of midwifeiy. The former edi- ■ of stanaard merit. The work cannot tedl to be
tlons have been most &Torably received by the I popular and is cordially recommended.— J7. O.
profession on both sides of the Atlantic In the Med. and Stsrg. Joum., Maroh, 1880l
smith:, j. LEWI87M^n7, ~
aUueal Profeseor of Dueaset of OiUdrm m the BeUmnie Hospital Medical OolUge, N. F.
A Complete Practical Treatise on the Diseases of Children. Fiith
edition, thoroughly revised and rewritten. In one handsome octavo volume of 836 pages,
with illustrations, doth, $4.50 ; leather, $5.50 ; veiy handsome half Russia, raised bands, $6.
This is one of the best books on the Bubject with which we venture to say will be a favorable one.—
which we have met and one that has given us i Dublin Journal of Medical Science, March, 1883.
satisfaction on every occasion on which we have ' There is no book published on the subjects of
consulted It, either as to diagnosis or treatment which this one treats that is Its equal in value to
It is now in its fifth edition and in Its present form i the physician. While he has said Just enough to
is a very adequate representation of tne subject it > impart the information desired by general practl-
treats of as at present understood. The important i tioners on such questions as etiology, pathology,
subject of in&nt hygiene is fully dealt with in the I prognosis, etc, he has devoted mora attention to
eariv portion of the hook. The great bulk of the ' the diagnosis and treatment of the ailments which,
work is appropriately devoted to the diseases of he so accurately describes ; and such information
infancy and childhood. We would recommend ! is exactly what is wanted by the vast m^ority of
any one in need of information on the subject to "fiunily physicians.'*— Fa. Ifod. ifon^A/y, Feb. 1882.
procure the work and form his own opinion on it, |
KEATnfG, JOHirM,,^Mrb.,
Leeturer on the Diseasee vf Children at the Unhcrsity of Pennayl^jaina, etc
The Mother's Guide in the Management and Feeding of Infants. In
one handBome 12mo. volume of 118 pages. Cloth, $1.00.
Works like this one will aid the physician im- ' the employment of a wet-nurse, about the proper
mensely, for it saves the time he is constantly giv- . food for a nursing mother, about the tonic effects
ing his patients in instructing them on the sub- 1 of a bath, about the perambulator versus the nurses,
jecls here dwelt upon so thoroughly and prac- arms, and on many other subjects concerning
tically. Dr. Keating has written a practical book, i which the critic might say, " surely this is obvi-
has carefiilly avoided unnecessary repetition, and ' ous," but which experience teaches us are exactly
successfully instructed the mother in such details i the things needed to be insisted upon, with the rich
of the treatment of her child as devolve upon her. I as well as the poor.— Iiondon Lancet, January, 28 1882.
He has studiously omitted giving prescriptions, , a book small in sise, written in pleasant stvle, in
and instructs the mother when to call upon the language which can be readily understood 6y any
4pctor,as his duties ave totally distinct from hers. ' mother, and eminently practical and safe: in (act
—Amm-ican Journal of Obstetrics, October, 1881. j a book for which we have been waiting a long
Dr. Keating has kept clear of the common fault ' time, and which we can most heartily re<K>mmena
of works of this sort, viz., mixing the duties of i to mothers as the book on this subject. — Hew York
the mother with those proper to the doctor. There , Medical Journal and CH>steirictU JSerieio, Feb. 1882.
is the ring of common sense in the remarks about I
OWEN, EDMUNJ), M.ls^F. B. cTs.,
Surgeon to the Children's Hospital, Oreat Ormond St., London.
Surgical Diseases of Children. In one 12mo. volume. Preparing. See Series
of Clinical Manuals^ page 3.
WEST, CHAMLES, M. D.,
Physician to the Hospital for Sick Children, London, etc
Lectures on the Diseases of Infancy and Childhood. Fifth American
from 6th English edition. In one octavo volume of 686 pages, doth, 14.60 ; leather, f5.50.
By the Same Author.
On Some Disorders of the Kervous System in Childhood. In one small
12mo. volume of 127 pages. Cloth, $1.00.
CONDIE^S PRACTICAL TREATISE ON THE I Tised and augmented. In one octavo volame of
DISEASES OF CHILDREN. Sixth edition, re- | 779 pages. Cloth, $S.25 ; leather, |6.».
Lea Brothsrs & Co.'s Publications — ^Med. Juris. 9 MisceL
31
TIDT, CHABLB8 MJEYMOTT, M. B., JF. C. S.,
Profttsor of Chtmittry and of ForenHc Medicine and Public ffeaUh at the London Hoepiial^ etc.
Ijegal Medicine. Volume II. L^itimacy and Paternity, TreffMncy, Abor-
tion, Bape, Indecent Exposure, Sodomy, B^iality^ Live Birth, Infanticide^ AspLjxia,
Drowning, Hanging, Strangulation, Sunocation. Making a very handsome imperiaJ oc-
tavo volume of 529 pages. Cloth, $6.00 ; leather, f 7.00.
Volume I. Containing 664 imperial octavo pages, with two beautiful colored
plates, aoth, $6.00; leather, $7.00.
The satiBfaction expressed with the first portion
of this work is in no wise lessened by a perusal of
the second volume. We find it characterised by
the same fttlness of detail and clearness of ex-
pression which we had occasion so highly to com-
mend in our former notice, and which render it so
valuable to the medical Jurist The copious
tables of cases appended to each division of the
subject, must have cost the author a prodigious
amount of labor and research, but they constitute
one of the most valuable features or the book,
especially for reference In medico-legal trials.—
American Journal of the Medical SeieneeSf April, 1884.
TATZOB, AJjFBED S., Jf. I>.,
Lecturer on Medical Jurisprudence and Ckemittrf/ in Ouy^s HoepUal, London.
A Manual of Medical Juxispnidenoe. Eighth American from the tenth Lon-
don edition, thoroughly revised and rewritten. Edited by John J. Bebbb, M. D., Professor
of Medical Jurisprudence and Toxicology in the University of Pennsylvania. In one
large octavo volume of 937 pages, with 70 illustrations. Cloth, $5.00 ; leather, $6.00; half
Bussia, raised hands, $6.60.
^The American editions of this standard manual
have for a long time laid claim to the attention of
the profession in this country: and the eighth
oomes before us as embodyins the latest thoughts
and emendations of Dr. Taylor upon the subject
to which he devoted his life with an assiduity and
success which made him facile princepe among
English writers on medical Jurisprudence. Both
the author and the book have made a mark too
deep to be affected by criticism, whether it be
censure or praise. In this case, however, we should
only have to seek for laudatory terms.— ^msrieon
Journal of the Medical Seienees, Jan. 1881.
This celebrated work has been the standard au-
thority in its department for thirty-seven years,
both in England and America. In both the profes-
sions which it concerns, and it is improbable that
it will be superseded In many years. The work is
simply indispensable to every pnysioian, and nearly
so to every liberally-educatiBd lawyer, and we
heartily commend the present edition to both pro-
fe8slons.~il{&or^ Law Journal^ March 26, 1881.
By the Same Author.
The Principles and Fraotioe of Medioal Jurisprudenoe. Third edition.
In two handsome octavo volumes, containing 1416 pages, with 188 illustrations. Cloth, $10 ;
leather, $12. Just ready.
For years Dr. Taylor was the highest authority
in England upon th^ subject to which he gave
especial attentlo
Judgment excel U
is therefore well that the work of one who, as Dr.
ipecial atteniion. His experience was vast, his
lagment excellent, and his skill beyond cavil. It
Stevenson says, had an "enormous grasp of all
matters connected with the subject," should be
brought up to the present day and continued in
its authoritative position. Tc accomplish this re-
sult Dr. Stevenson has subjected it to most carefkil
editing, bringing it well up to the time8.~^m«v
ngj
Of
can Journal of the Medical Scieneee, Jan. 1884.
By the Same Author.
Poisons in Belation to Medical Jurisprudence and Medicine. Third
American, from the third and revised English edition. In one large octa;^ volume of 788
pages, aoth, $5.50 ; leather, $6.50.
BEPPBB, AUGUSTUS J., M. 8., M. B., F. B. C. S.,
Examiner in Forentic Medicine at the University of London.
Forensic Medicine. In one pocket-size 12mo. volume. Preparing. See StudenUf
Series of MamudSy page 3.
LJEA,JB[BNBTC.
Superstition and Force : Essays on The Wager of Law. The Wager of
Battle, The Ordeal and Torture. Third revised and enlarged edition, in one
handsome royal 12mo. volume of 552 pages. Cloth, $2.50.
This valuable work is in reality a history of civ-
ilisation as interpreted by the progress of Jurispru-
dence. . . In ** Superstition and Force '* we have a
philosophic survey of the long period intervening
Detween primitive beu*barity and civilized enlight-
enment There is not a chapter in the work that
should not be meet careftilly studied : and however
well verged the reader may be in tne science of
Jurisprudenoe, he will find much in Mr. Lea's vol-
ume of which he was previously Ignorant The
book is a valuable addition to the literature of so-
cial science.— Westminster SevieWf Jan. 1880.
By the Same Author.
Studies in Church History. The Rise of the Temporal Power— Ben
eflt of Clergy— Excommunication,
octavo volume of 605 pages. Cloth, $2.50.
The author is pre-eminently a scholar. He takes
up every topic allied with the leading theme, and
traces it out to the minutest detail with a wealth
of knowledge and impartiality of treatment that
compel admiration. The amount of information
compressed into the book is Extraordinary. In no
other single volume Is the development of the
New edition. In one very handsome royal
Jugt ready.
primitive church traced with so much clearness,
and with so definite a perception of complex or
conflicting sources. The fifty pages on the arowth
of the papaov, for Instance, are admirable for con-
ciseness and freedom from prejudice. — Boston
Traveller, May 8, 1883.
Alien's Aitatomy , , , .
Americmn JqutimI of Lb* M«dl^L £^letic0i
Amciirlcaii Syslem ot ijy euei^ a t{wy .
Amcrtiaa Bjritem ttf Pr&ctlc^iluiMlklae
*AiilttiUTiBl'it t^rgfiy ....
Afthwf'll on T>1$Hii»« of WoDaea
AttfloldflCl^pinlfllry ... *
Eftll on ihP Hertiinii and Anos
Barkers Ubi(tvlrt(%l upti VJUnlc&l ^aajti^
Bftmair MMwUbry
*fiiim«i OQ Pl>tfw»iw or Woraen
B*rDc?i^ ByaTem of ObntHiii; M^ldiie
Burlholoiv' on Eleirtrlrlly
Hftahani uti Eietml L>bi;fiu<iVfi .
Bell'!^ CotnpikrAUTC Phj^bology «fid AOfttomy
BcJiAiuy'tBuTS'lcaJ Artitomy
Bluiclfbrd on Tniqiiih^r
Bio sum '!^ f 'lTpm!iHry
Bci w n J. : L 1 1 s F ■ r Li« ' I iciil OiemlitrT
• BnHtu\4H' s I'ri.^ iK^t.r Medlciiift .
BrofrUlK'tu iHi \he Piilsi*
Browuc on ibe D[iljihiilii3oecop<
Brnwniion ihf Tnrnul
Brucif's Muter) a ^iii<4|1fiih audi TlietHiieiUii'TS
Bruniun'i Mat^rto, Medicu and Theniixfuikt^
Eryjimon the Ureajit ....
•Dry ant"! Pnctlce off^rwry
*Btiiust«w!l on V'pnerml DUw*
*Burij?u on lti«» Kftr * * * .
ButllR on tli«s Tumrue . » * ^
CSiTppatjpr oil ilie Tfi* and Abuiit of AJ^liol
•CwpieniiT'H Human PhyalnJo^ ,
QiTi^r im (he Kya . . , ,
Cpu t iiry i if A Q 1 V rirmi M L^lrln*^
cliiiiiiibe^ra un Dlel- ahtl hrgluivn
CliariRa' Phynluluiiical and ItaUiolOfl'lcal tlietii.
ChurciiLll on Puf^rperul Fever
ClAfkennd LockWDiid> DlaA«crrdr«' Mannal
'M Quibtitlliittve AoaiyKia
i'a DlBcc-Eor
Qloi»nt4)n on Inwinliy
(JowflB* Practlca] C'ucniLatry
oati" FaLholfwy . , » .
otiftn Oil tbg Til mat , . . ,
nlpiuan'» ]>eiitai HurBfiJT
Oudle uii I>lNeanefl uri'-hudr^n
. Oper't* LeclurOa qq Sufgery
Cori^U ciu i^yiihlLke ....
*CQmlJ mod lUinvleKi PHthoJo|]c!a] Hlittolo^-
Curoow's ML^lk-nl AniiloRiy
lAJton on the i^rcul&tiuu
*DfttlOD^i HuDumPliyiilioloiry
Uttlton'H TopcvraphlcfiJ AHatomy of tbe Br&Ui
HwkVW CUnicalLifeiutie*
Draper's MwHpuI Phy»toi
X> r I ] ] 1 1 ' R ;M f jtl cm Wu rgcTy-
I>unc4iniiij l>i^*-ii,'j-i-?n>f Wompn
'*I>Linti:U.Miuit'R MetlUiil Li^cilonaiy ,
Eidii on DiM'aHHH of Women ^.
£U Ifl' Demo hNi JUi lotisofAnatOiiiy
Knuuet'ft ttynn^coloj^'
•EilctiPitJi'b 1^2 »t4;n] of Siimery
^Ekmarcb'B Early Aid In I e>J[1] riband Aoctd'ta
Farqiihartion'a TheraneuUe^ an it Mat. Me^i.
Fenwlck'^ MMlcal l>ia^nuii]»
FlT)Uyn(>ii'fi I'Mhkcal DiAgnodlA
Flint on Aum.'ttUiitlioii and Percunaioc
Flint on PUthislA . . , .
KUnL oil Phyfllcal I^TploratJoo of Uie Lnnga
Flint on Iti'siiirnioryOT^na
Flint OH the* IH fan
•FISiiL ?i ninlciil MiHllclne
FMiu'r Ertmiyfl . . . *
• Pllnls PriM.M Ire of Medicine
Folwoin'ti Ijftwa of V. y. on Dualody of Inwne
FuMltT'hi l'TiV^3ulL>iP* . , . .
•FothtrKin H ICaiidhookof TrPttttoenl .
Fown<?H' FJenu'iita-ry i."hen^Utn'
Fox on DIfij'ilHt'fl f^^tnc^ hkhl +
FninkUijjd anni Jupjk's Itmrgfinlc (.lipmlairy
Fuller on ihp Lunitrfianfl Air I^a»inJ?es .
(jflllrpwiiyHi Al]a5y?vLM , . + ^
(J ! h n i^ }■ ' !^ f >r t 111 I puMl t c Hn rgery
GlTwion's f^iirgfty ....
CilngeV PallJoloETcuI Hiatolog^', by Lfldy
dould'^^Ltr^kcul IHagnofih .
HirayV Anutumy . . ,
G r**i J t'H M Hi [4 -al Ch eu i ist ry .
Qrpen'fi I'lithi^li'Ky ftTitl M-^iHrt Aoatomy
G Hill Ill's Uhi\i*i-H4il I-'nriijnInry
Or^^i^uo Foi'f*iun Bndii^i In Afr-PvjiHagea
Grow oit Imp* j[{-nc.'p nnd MtiTlUty .
Gri>sHnn Vrtnuiy Lkrffiinis
•tirofti" S^'itvtiii urSurkTery
}Iaii(^r^hiVn fill thi' Abilntiien
• JIuniNLoEi i-ii h'rncHfre^ ini4l Htylocallon!!
lliLTlliltfiU M|6 >tTVI.i.U", hi*^pJVif«5
Hnri^Jinrcht*'-^ Aiiatotny imd Pliy'^lmlj.'vfy .
JtnrTHiiurcn s rmiHi^tHtim of tht'^fM. iScltnce*
IlHr".'4(,,.rno> I-JK!4tiJil«J:^of MLtlJeloe
H 1 ' r n 11 1 r I r 1 > K v t jt^l m v u lul Fh ft rw lat^oloe^'
Hill (Ji- sv [.hills .....
IIIIJ], r s Ihiiidhijok nf.Skin Diseases
If.ii.lyri'< ^hNliral Dkntorjary
Ifiiilirr^ iin 'L^rinLi'M . ^ * ,
Hodijp'ri U^teleiiicit
6
8
27
15
20
28
0
21
29
17
2»
27
29
17
24
3 7
8,20
6
19
9
9
14
3,10
23
18
11
11
8,21
21
25
24
8.21
8
8
23
14
17
10
28
6
10
5
19
10
13
18
24
30
20
25
13
26
8,6
7
8
7
16
7
21
28
4
27
7
28
21
21
12
16
16
18
18
18
18
18
16
16
14
19
8
16
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26
9
18
20
13
8,20
5
10
13
11
18
25
U
20
17
23
19
6
3
14
11
Ho^mann and Pow«-*i Cliemlcftl Aoalj^U
Hotrlni'if Lajidmarku . + . .
H'^ilaiKl <i MrtlU^L Notes and R^necUonB
•] ! ■ i iii-s' SyMi'm of nSurffpn'
Hi 'ii^r'si AjiA[oniy and lil^olog!)'
i-i»r>on Fever
< iilnaoii Do^yphlJUi
!i on the D1«»i34««of IheSklti .
' ^ < L\ Hand d eh! j on Nervous Dlsordfirn
I ■^ Oplithaliiiit! l*t!Jeii(?e and Pjactlc*
.liiiffon Tfifant!^
L. - MjiiiUfrl oroi^teiiics .
:;is HbHtnlofry
> nil LtitHiT ♦ ■ . .
u... 'lie on PiiPLinjk'tnia, MtU.u1a, etc .
't. ""^lip on Yellow Frvpr ,
■■ I ri<.'e and Mot>n'» ftptkthalmlcBnrifii^rv
. '"I on the Eye, Orbit ami Ky^Ud
STUfllpw In rhurrh HlfiUiry
r^Mtlon and Forre
.inn .
h<^ra1eal FLiy^olOKy .
^Midwlftrv
<<n I'Ueaseaof ineUretliim .
i,v'ii Mfinual ori^xiunlaiitlonB
- r rr Fi^i'rr * + , , .
< -'.inh. ^THttfrla McdicA .
I' Jotnm
■i^-s of Wonieii *
B
R
B
B
Si
Be
S( •
Sc:.:
Sf ■.
S«- -,
8iii..
8Kl■^
81... 1.
Sim-
Sim:;
•g-IM
St. ,
*^: \
81.
St
8t
ililbed Fever
' tireofftufgi^ry .
. iji!t'H..fSnrifefy
.i,:4^of Writijf't] .
V Kidney fl
^..•, -.,i,,.,, .- ,^ •^ndViimof UpcI. Sti.
..'%tik|i I? II I N.^riiM^i ttf the £#yo »
M fFi] liL^oa'w^4jf 4*lLlldren
I' J i^h'B I*r»cttral Ph(imiaf!y
r\ MTi I-A I ra- Uterine Prfifrnaoey
M - Miihv[f,'ry ....
ri [ ii^^i»^tLon Hnif \\M Dlfiordeni
■ ' I 'M-ii^r Medldne .
.r^loil Pathology
i. niriifi toiti DUidcalloaa
-: L*sn or*^urgery
i.iH^ i>n Xf-rvp Fro^tmtlon and nysteria
L -^ 1 ji i r' A M kl w L fpry .
: ff-r mi itii" Karand \xr _
■ ■!')* Human Physiology
' '"i fllnlfiil (.'heiulfttry
('■: .jtliaiii on Partnrltlon
. -1 o'm Thi?.rjretical (.'liemiHtTy ,
■ riHiida' f?ji'!+ti*ln of Medicine
.Lidsoii^H Preventive Medicine
1: ' Mil Urlnikry' Disease*
nfiples anil PnwMlce ofdurgi^ry
rhysloloitltml Pbyalca
■slmmry of Bcleiice
■■"- 1 M^roM'il
:Mi MlUlAiy Bnrgerr
' . hicUtdlnff Hyiltfla .
. I'.* of Hiiitolocy,
•. i'- l[|.:..l,..i;y
I'lli^i-r ill] Ma»i>ia|tc ,
r MH ilir Throat, ^one and NajKhPhao'nx
''-^4ift']|nlirjil ManonLq
.riH MftiniHl of ChenilHtry
■■.i OpiTulivf ^^Ujljery
' Kiu Dipbthc'rla . . , .
ii 'Edward I OTi Con OTDipllon .
1 1 < H, H.)aml Hornpr'n Anatojnical Atlas
Mj i,J. Ivewls] onChtldreji
I Ml i^laolrrii ....
.' i^ Mulsrh'fl Nailonal t.iiHt)eii%alory
.i^''a Thera^kcutlcs and Materia MedlCMi
■ nil ,m l-'riii'tiErefll . . i .
■■.' tjiirg'erj' ♦
KM I ,
students' Series of Maouals .
Sturgea' Clinical Medicine .
Tanner on Signs and Diaeases of Pre^ancy
Tanner's Manual of Clinical Medicine .
Taylor on Poisons ....
•Taylor's Medical Jurisprudence .
Taylor's Prln. and Prac of Med. Jorisprudence
•Thomas on Diseases of Women .
Thompson on Stricture
Thompson on Urinary Organs
TIdv's Lcgsil Medicine ....
Todd on Acute Diseases
Treves' Applied Anatomy
Treves on Intestinal Obstruction .
Tuke on the Influence of Mind on the Body
Wabhe on the Heart ....
Waiaon's Practice of Physic .
•WelLs on the Eye ....
West on Diseases of Childhood
West on Diseases of Women
West on Nervous Disorders In Childhood
Williams on Consumption .
Wilson's Handbook of Cutaneous Medicine
Wilson's Human Anatomy ...
Winckel on Pathol, and Treatment of Childbed
Wdhler's Organic Chemistry
Woodhead'sPractical Pathology .
Year-Book of Treatment
Bookfl marked * are also bound in half Russia.
LEA BROTHERS & CO., Philadelphia.
THIS BOOK 18 lyUE OK THE LAST DATE
STAMPED BELOW
AN INITIAL FINE OF 25 CENTS
WILL BK A88ES8KD FOR FAILURE TO RETURN
THIS BOOK ON THE DATE DUE. THE PENALTY
WILL INCREASE TO SO CENTS ON THE FOURTH
DAY AND TO SI. OO ON THE SEVENTH DAY
OVERDUE.
NOV 11 193k
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OCT 101935
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AN 5 1963
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