THE LIBRARY
OF
THE UNIVERSITY
OF CALIFORNIA
DAVIS
GIFT OF
JIM HUNT
A PRACTICAL TREATISE
MANUFACTURE OF COLORS
PAINTING.
COMPRISING
THE ORIGIN, DEFINITION, AND CLASSIFICATION OF COLORS; THE
TREATMENT OF THE RAW MATERIALS; THE BEST FORMULA
AND THE NEWEST PROCESSES FOR THE PREPARATION
OF EVERY DESCRIPTION OF PIGMENT, AND THE
NECESSARY APPARATUS AND DIRECTIONS
FOR ITS USE; DRYERS; THE TESTING,
APPLICATION, AND QUALITIES
OF PAINTS, ETC. ETC.
JU.'JWS BY
MM.)RIFFAULT, VERGNAUD, AND TOUSSAINT.
REVISED AND EDITED BY M. F. MALEPEYRE.
TRANSLATED FROM THE FRENCH
BY
A. A. FESQUET,
CHEMIST AND ENGINEER.
ILLUSTRATED BY EIGHTY ENGRAVINGS.
PHILADELPHIA:
HENRY CAREY BAIRD,
INDUSTRIAL PUBLISHER,
406 WALNUT STREET.
LONDON:
SAMPSON LOW, MARSTON, LOW & SEARLE,
CROWN BUILDING, 188 FLEET STREET.
1874.
LIBRARY
UNIVERSITY OF CALIFORNIA
1. J. ABUNDBL1'
Entered according to Act of Congress, in the year 1874, by
HENRY CAREY BAIRD,
in the Office of the Librarian of Congress, at Washington. All rights reserved.
PHILADELPHIA t
COLLINS PRINTER,
705 Jayne Street.
. J. ARUNDELL
PREFACE.
THE volume here presented to the American pub-
lic, derived as it is from the last and greatly im-
proved Paris edition of the well-known work of MM.
Riffault, Vergnaud, and Toussaint, edited by M. F.
Malepeyre, is believed to be by far the most tho-
rough and complete treatise upon the important sub-
ject which it considers, ever published in the English
language.
It comprises some account of those pigments now
known to have been used by the ancients ; the prin-
ciples of color as developed by Chevreul ; thorough
descriptions of the nature and properties of the raw
materials used, and the processes and machinery for
the manufacture of an immense variety of pigments;
the combinations necessary in the compounding of
those colors, hues, and tones which are the results
of the mixture of colors ; practical information as to
dryers ; and a variety of analyses and tests of pig-
ments, and much other useful information.
The translator has devoted great care and attention
to the faithful rendering of the production of the
French authors, while the publisher has at the same
IV PREFACE.
time endeavored to present the book in a neat and
creditable form, and both trust that their efforts will
be appreciated, and that the book will meet with a
rapid and extended sale as well in Great Britain as
in the United States.
PHILADELPHIA, June 25, 1874.
CONTENTS.
INTRODUCTION ON THE COLORS EMPLOYED BY THE ANCIENTS.
PAGE
White used by the Egyptians and Eomans . . . . -17
Blacks and Browns . . . . . .19
Yellows 20
Red used by the Egyptians .....
Red employed by the Greeks and Romans . . . .21
Grecian Purple, also called Tyrian Purple . . . .25
Blues 26
Greens . . . . . . • .30
CHAPTER I.
ORIGIN, DEFINITION, AND CLASSIFICATION OF COLORS.
SECTION I.
ORIGIN OF COLORS.
SECTION II.
DETERMINATION AND DEFINITION OF COLORS.
SECTION III.
PHYSICAL EFFECTS OF COLORS. .
Colors of the Rays of the Solar Spectrum
Primary Colors ......
Complementary Colors .....
Contrast of Tone ......
Contrast of Colors .....
SECTION IV.
CLASSIFICATION OF COLORS.
Mmary Colors
3inary Colors
Binary Mixed Colors
Tertiary Colors (pure)
Tertiary Colors (mixed)
46
46
46
46
47
48
48
48
49
49
VI CONTENTS.
SECTION V.
GENERAL METHOD OF PREPARING COLORS.
CHAPTER II.
MANUFACTURE OP COLORS.
SECTION I.
WHITE COLORS.
PAGE
'§ 1. Whites with Lime Basis . . . . . .53
1st. Carbonate of Lime . . . . . .53
3d. White of Sulphate of Lime . . . . .55
§ 2. Whites with Lead Basis . . . . . .55
1st. Kremnitz Process . . . . . .59
3d. Holland or Dutch Process . . . .63
Analyses — Krems' White . . . .76
Precipitated White Lead of Magdeburg . . 76
White Lead of Unknown Manufacture . . 76
Krems' White . . . . . .77
White Lead prepared by the Author in Imitation of
the Holland Process . . . . .77
3d. The French or Clichy Process of Thenard . . 78
Preparation of the Oxide of Lead . . .80
Manufacture of the White Lead . . . .80
4th. Pattinson Process . . . . . .85
5th, Woolrich Process . . . . . .93
6th. Versepuy Process . . . . . .93
7th. Wood, Benson, and H. Grimeberg Processes . . 97
8th. Mullin's Process . . . . . .105
9th. Schuzenbach Process . . . . . 110
10th. Sewell Process ..... . Ill
Explanation of the Apparatus .... 113
llth. Crompton Process ...... 115
Mode of working the Apparatus . . .119
13th. Gannal Process . . . . . .135
13th. Rostaing Process . . . . . .126
14th. Mulhouse White Lead . . . . .126
15th. Silver White or Light White . . . .137
16th. Testing the Purity of White Leads . . .137
17th. Composition of White Leads . . . .134
18th. Processes for Rendering the Manufacture of White Lead
less Unhealthy . . . . . .137
A. Ward Machine for the Manufacture of White Lead . 138
B. Apparatus of Mr. Th. Lefevre for pulverizing White
Lead 140
CONTENTS. Vll
PAGE
Casting of the Lead . . . . .146
Building the Beds . . . . .147
Taking the Beds apart . . . . .148
Picking up .... 149
Dry Grinding of Scales of White Lead . . . 149
Grinding White Lead in Water . . .150
Drying Rooms ...... 150
Powdering Lump White Lead . . . 151
Packing White Lead . . . . .153
C. Safe Apparatus of Mr. Ozouf . . . .154
D. J. Poelmann's Machine for Separating the White Lead
from the Metal . . . . . .154
E. Precautions taken to render the Manufacture of White
Lead less Unhealthy . . . . 155
§ 3. White of Basic Chloride of Lead . . . . .158
§ 4. White of Sulphite of Lead . . . . .159
§ 5. White of Tungstate of Lead . . . . .159
§ 6. Antimonite of Lead ...... 160
§ 7. Antimoniate of Lead . . . . . .161
§ 8. Antimony Whites . . . . . .' . .161
1st. Antimony White of MM. Bobierre, Ruolz, and Rousseau 161
3d. Antimony White of MM. Valle and Barreswfll . . 162
3d. Antimony White of MM. Hallett and Steuhouse . . 164
§ 9. Zinc White . . . . . . .164
1st. Manufacture of Zinc White of Mr. Leclaire . . 166
Manufacture . .. . . . .167
Description of the Apparatus .... 169
Mode of Operation.— 1. With the Retorts . . 177
2. Air Furnace . . . . .178
3. Reverberatory Furnace or Coke Oven . .178
4. Horizontal Tubular Furnace . . .178
2d. Mode of Fabrication by Murdoch . . . .180
3d. Manufacture of Zinc White at Portillon, near Tours . 182
4th. Snow White, Zinc White, Hopper White . . 183
5th. Saint-Cyr White . . . . . .184
6th. Vitry White . . . . . . .184
7th. Various Pigments obtained with Zinc White . . 184
Azure-White, Pearl-Gray, Slate-Gray, Straw-Yellow,
Stone Color, Chamois, Dark Chamois, Lemon, Gold-
Yellow, Tint of Azure-Blue, Water-Green, Grass-
Green, Olive-Green, Bronze-Green . . . 185
8th. Various Processes for the Manufacture of Zinc White . 185
9th. Uses of Zinc White, and Dryers . . . .186
10th. Adulteration of Zinc White . . . .189
llth. Danger and Salubrity of Zinc White . . .190
12th. Use of Blende as a Substitute for White Lead and Zinc
White 191
Vlll CONTENTS.
PAGE
§ 10, Baryta Whites ....... 192
1st. Natural Sulphate of Baryta . . . .192
3d. Artificial Sulphate of Baryta, Blanc Fixe . . .193
SECTION II.
BLUE COLORS.
§ 1. Prussian Blue ....... 199
1st. Manufacture ef Ordinary Prussian Blue . . . 200
First Process ...... 200
Second Process ...... 203
2d. Brunnquell Process ...... 205
3d. Karmrodt Process ...... 219
Karmrodt's Experiments with Furnace . . . 223
I. By using 1.5 kilogrammes of Carbonate of Am-
monia . . . . . . 223
II. With Animal Substances . . . 223
III. With Animal Substances and the Alkalized
Charcoal af 30 kilogrammes of Wood Char-
coal, 20 of Russian Potash and the Precipitate
of 4 kilogrammes of Sulphate of Iron, and 3
of Potash . . . .224
4th. Schinz Process ...... 226
5th. Determination ®f the Value of the Fused Materials . 230
Preparation of the Titrated Liquor . . . 234
Analytical Operation ..... 234
6th. Preparation of Prussian Blue by the Stephens Process . 235
First Improvement ..... 235
Second Improvement ..... 237
7th. English Process for the Manufacture of Prussian Blue . 239
§ 2. Paris Blue ........ 244
First Process ....... 247
Second Process . . . . . . .250
Third Process . . . . . . .251
Fourth Process . . . . . . .252
§ 3. Monthiers' Blue . . . . . . .253
§ 4. Testing the Value of Prussian Blue and its Adulterations . 254
§ 5. Mineral Blue, Antwerp Blue . . . . .256
§ 6. Thenard Blue, or Cobalt Blue (Subphosphate of Cobalt) . 257
§ 7. Blue Hydrated Oxide of Copper. Peligot Blue . . .261
§ 8. Blue of Mangauate of Lime. . . . . .262
§9. Indigo ........ 264
§ 10. Blue Carmine, Indigo Carmine, Blue of England or Holland . 268
§11. Ultramarine Blues . . . . . . .269
1st. Real or Native Ultramarine Blue .... 270
Ultramarine-lazulite ..... 270
Analyses . . . . . . .272
CONTENTS. IX
PAGE
2d. Artificial Ultramarine ..... 274
Analyses ....... 275
A. Guimet Process ...... 277
B. Gmelin Process . . . . . .278
C. Tiremon Process . . . . . .280
D. Weger Process . . , . . .281
Ultramarine for Printing . . . . .282
E. Pruckner Process . . . . . .283
F. Winterfield Process . . , . . .288
G. Brunner Process ...... 289
Choice of the Raw Materials .... 290
Analysis of Ultramarine . 296
H. Dippel Process . . . . . .300
I. Habich Process . . . . . . 301
K. Gentele Processes . . . . . .304
1. Manufacture of Ultramarine Green . . . 305
2. Manufacture of Ultramarine Blue . . . 318
L. Fiirstenau Process . . . . . .323
M. White Ultramarine . . . . . .327
N. Trial and Analysis of Ultramarines . . .329
1st. Artificial Ultramarine of the First Quality . . 332
2d. Inferior Qualities . . . . .332
Biichner's Tests . . . . . .333
(a. ) Resistance to the Action of Alum . . 333
(b.) Trial of the Coloring Power . . .334
(c.) Trial of the Printing Power . . .336
(d.) Trial of the Glazing Power . . - .337
(e.) Trial for the Proportion of Gelatine (size) . 337
0. Composition of Ultramarines .... 339
3d. Cobalt Ultramarine ..... 340
§ 12. Blue Ashes. Lime Blue. Copper Blue. Mountain Blue . 341
1. Manufacture of Ashes in England .... 342
II. Gentele' s Researches . . . . .345
III. Distinguishing Blue Ashes of England and of France . 350
IV. Natural Color, called Mountain Blue, Azurite, and Arme-
, nian Stone ....... 350
§ 13. Smalt ........ 351
§ 14. Creruleum ........ 354
§ 15. Litmus ........ 356
§ 16. English Sky Blue . . . . . . .356
SECTION III.
YELLOW COLORS.
Yellows in General ....... 358
§ 1. Ochres ........ 308
§ 2. Rut (Rivulet) Ochre .... .361
X CONTENTS.
PAGE
§ 3. Italian and Sienna Earths . . . . . .361
§ 4. Vienna Red. Antwerp Red. Terra Rosa . . .362
§ 5. Mars Yellows 362
§6. Curcuma or- Terra Merita . . . . . .364
§ 7.,Stil-de-grain ...... . 366
§8. Weld Lake 368
§ 9. Lakes of Quercitron and Yellow Wood . . . .371
§ 10. Chrome Yellows . . . . . . .372
1. Neutral Chromate of Lead . . . . .373
2. Basic Chromate of Lead . . . . .375
3. Jonquil Chrome Yellow of Winterfeld . . .376
4. Cologne Yellow . . . . . .377
5. Chromate of Lime ...... 378
6. Chromate of Baryta . . . . . .378
A. Chrome Yellow 379
B. Chrome Red or Basic Chromate . . . .385
C. Greens by Mixtures (Cinnabar Green, Chrome Green) . 386
§ 11. Various Chromates . . . . . . .387
1. Chromate of Zinc . . . . . .388
Wagner's Analysis ..... 391
2. Chromate of Baryta . . . . . .391
3. Orange-red Sulphide of Antimony .... 392
4. Mixed or Compound Colors ..... 393
5. Lemon Yellow . . . . . .395
6. Pale Yellow . . . . . . .395
§ 12. Basic Chromate of Tin, Mineral Lake .... 395
§ 13. Naples Yellow . . . . . . .397
§ 14. Cadmium Yellow 400
§ 15. Yellow of Antimony and Zinc ..... 401
§ 16. Turner Yellow. Kassler Yellow. Cassel Yellow. Montpellier
Yellow. Verona Yellow. Mineral Yellow . . .403
§ 17. Mineral Straw -yellow . . . . . .406
§ 18. Mineral Turbith .... .406
§ 19. Orpin or Orpiment. Yellow Sulphide of Arsenic. Yellow Re-
algar. . . . . . . .407
§20. Arsenite of Lead ..... .409
§ 21. Massicot. Litharge . . . . . .409
§22. Iodide of Lead .... .410
§ 23. Uranium Yellow . . . . . . .411
§24. Gamboge .... .417
§25. Jaune Indien (Indian Yellow). Purree .... 417
§ 26. Aurum Mussivum. Mock Gold. Mosaic Gold. Cat's Gold.
Painter's Bronze, etc. .... . 420
§ 27. Nankin Yellow ' . 421
§28. Chlorophyl ........ 421
CONTENTS. XI
SECTION IV.
RED COLORS.
PAGE
§ 1. Red Ochre 423
§ 2. Colcothar. English Red or Rouge .... 424
§ 3. Armenian Bole. Ochreous Clay. Lemnos Earth. Oriental
Bole. Red Bole .425
§ 4. Iron Minium ....... 425
§ 5. Red-Brown ........ 426
§ 6. Red Lead or Minium ...... 426
§ 7. Orange Mineral . . . . . . .428
§ 8. Realgar, or Ruby of Arsenic . . . , .429
§ 9. Cinnabar and Vermilion . . . . . .430
1. Manufacture by the Dry Way . . . 430
2. Manufacture by the Wet Way . . . .431
A. Kirchoff Process . . . . . .432
B. Brunner Process ...... 432
C. Jacquelin Process ...... 433
D. Firmenich Process ...... 434
§ 10. Iodide of Mercury . . . . . . .439
§11. Chromates of Mercury . . . . . .439
§ 12. Chromate of Copper. Maroon-red .... 440
§ 13. Chromate of Silver. Purple-red . . . . .440
14. Sulphide of Antimony. Vermilion of Antimony . . 441
1. Preparation of the Chloride of Antimony . . . 446
2. Preparation of the Hyposulphite of Lime . . . 447
3. Preparation of Vermilion of Antimony . . . 448
4. Properties of the Vermilion of Antimony . . . 452
§ 15. Sulpho-antimonite of Barium ..... 453
§ 16. Cobalt Pink .454
§ 17. Arseniate of Cobalt, Metallic Lime .... 455
§ 18. Purple of Cassius ....... 455
119. Madder Lake . . . . . . .458
1. Robiquet and Colin Process . . . . .460
2. Persoz Process . . . . . .461
3. Lefort Process . . . . . .462
4. Khittel Process . . . . . .463
5. Lake of Garanceux ...... 567
6. Sacc Process ....... 469
7. Kopp Process . . . . . . .469
8. Adulteration of Lakes . . . . .471
A. Red and Pink Lakes . . '. . .471
Santaline . . . . . .472
Lakes of Brazil Wood.— First Process . . 472
Venice Lake, ball shape. — Second Process . . 472
Brazil Lake.— Third Process . . . .472
Carmine Lake . 473
,
Xll CONTENTS.
PAGE
B. Voilet Lakes 473
Campeachy Lakes . 473
Alkanet . . . . . .474
Orchil . . . . . . .474
Prussian Blue . . . . . .474
C. Black Lakes . . . . . .474
Charcoal and Lampblack .... 474
Black Campeachy Lakes .... 475
Lake with Cochineal Basis . . . .475
Black Sumach Lake, etc. . . . .475
§ 20. Violet, Chocolate, Brown, and Red Lakes of Rhamnoxanthin
and Elder Berries . . . . . .475
§ 21. Madder Carmine . . . . . . .477
§ 22. Lake of Red Woods . . . . . .477
§ 23. Vegetable Violet . . . . . . .484
§ 24. Carthamus Red. Carthamin. Garthamic Acid. Vegetable Red.
Spanish Red. Red in Plates. Portuguese Red. Leaf Red.
Chinese Rouge for the Face ..... 484
§ 25. Indian Red ...... .486
§ 26. Cochineal Carmine . . . . . . .487
1. Process of the Old French Encyclopedia . . 489
2. Ordinary Process ...... 490
3. Chinese Process . . . . . .490
4. German Process ...... 491
5. Process by Cream Tartar ..... 491
6. Process with Wool and Formation of a Lake . . 491
7. Wood Process . . . . . .492
. 8. Greltey Process . . . . . .492
§ 27. Carmine Lake. Paris Lake. Vienna Lake . . 493
§ 28. Amrnoniacal Cochineal ...... 494
§ 29. Red and Violet from Archil . . . . .495
§ 30. Perchloride of Chromium .... .499
§31. Chrome Red . . . . . . .500
SECTION V.
BROWN AND BLACK COLORS.
I. BROWNS.
§ 1. Mars Browns ..... .500
§2. Iron Minimum ....... 501
Analyses ........ 502
Employment of Iron Minimum ..... 503
§ 3. Vandyke Brown ....... 504
§ 4. Manganese Brown ....... 505
§5. Brown of Manganate of Lead . . . . . 506
§ 6. Prussian Brown . . . . . . .506
CONTENTS. Xlll
PAGE
§ 7. Red-Brown ........ 507
§ 8. Gilt-Brown .... .507
§ 9. Chicory-Brown ..... .507
§ 10. Ulmin-Brown ..... .507
§ 11. Bistre ........ 508
§ 12. Bitumens or Asphaltum . . 509
Bitumen Naphtha .... .509
Bitumen of Judea or Asphaltum .... 509
Bitumen or Retin Asphaltum ..... 509
§ 13. Sepia 510
§14. Umber . . . . . . . .511
§ 15. Sienna Earth . . .511
§ 16. Cologne and Cassel Earths . . . ... 512
§ 17. Puce with Chromate of Manganese .... 512
II. BLACKS.
A. Mineral Blacks.
§ 1. Schist or Shale Black . . . . . .512
§ 2. Bituminous Coal Black . . . . . .513
£ 3. Black of Chromate of Copper ... .514
§ 4. Ebony Black . . . . . . .515
B. Vegetable Blacks.
§ 5. Peach-stone Black . . . . . . .515
§ 6. Fusain (Spindle Tree, Prickle Wood) Black . . 515
§ 7. Grape-vine Black . . . . . . .515
§ 8. Cork Black ........ 516
§ 9. German Black . . . . . . .516
§ 10. Frankfort Black 516
Rl. Lampblack .517
First Process.— Resin Black . . . . .518
Second Process.— Tar Black . . . . .519
Third Process.— Oil or Lampblack . . 521
2. Chrome or Aniline Black . . . . . .524
3. Various Blacks . . . . . . .225
§ 14. Inks .528
C. Animal Blacks.
15. Bone Blacks . . . . . . .529
§ 16. Ivory Black . . . . . . .530
| 17. Candle Black . . . . . . .530
§ 18. Prussian Black 531
§ 19. China or India Ink . ..... 531
XIV
CONTENTS.
SECTION VI.
GREEN COLORS.
PAGE
§ 1. Green Verona Earth . . . . . .532
§2. Malachite ........ 534
§ 3. Iris-Green ........ 534
§4. Sap-Green ........ 534
§ 5. Picric Acid Green ..... . 537
§ 6. Bremen Green. Bremen Blue. Verditer Blue and Green . 538
§ 7. Brunswick Green ....... 543
§ 8. Scheele's Green . . . . . . .543
§ 9. Schweinfurt Green . . . . . . .545
First Process . . . . . . .545
Second Process ....... 545
Third Process . . . . . . .546
Fourth Process ....... 543
§ 10. Mittis Green. Vienna Green. Kirchberger Green . . 547
§ 11. Green Ashes ....... 548
§ 12. German Green without Arsenic ..... 548
§ 13. Erlaa Green . . . . . . .549
§ 14. Mineral Green . . . . . . .549
§ 15. Paul Veronese Green . . . . . .550
§ 16. English Green . . . . . . .550
§ 17. Neuwied Green . . . . . . .550
§18. Milory Green. Silk Green. Green Cinnabar. Leaf Green . 551
§ 19. Green of Stannate of Copper . . . . .552
§ 20. Eisner Green . . . . . . .553
§ 21. Green Cinnabar . . . . . . .553
§ 22. Green Lakes. Vegetable Green. Grass-green. China Green . 554
§ 23. Mineral Green Lake . . . . . .556
§ 24. Rinmann Green. Cobalt Green. Zinc Green . . . 556
§ 25. Chrome Green ....... 561
§ 26. Emerald Green . . . . / . .563
§ 27. Titanium Green . . . . . . .568
§ 28. Green Ochre . . . . . .571
§29. Green Ultramarine . . . . . . .571
§ 30. Verdigris ........ 572
§ 31. Crystallized Verdet. Distilled Green. Crystals of Venus . 573
SECTION VII.
COLORS FROM SULPHATE OF ZINC.
Delicate Light Yellows, called Roman Yellows . . . 574
Chamois Yellows ........ 574
Yellow Chamois ........ 574
Dark Chamois ........ 575
Gold Yellows 575
CONTENTS. XV
PAGE
Dark Gold- Yellows . . . , . . .575
Greens resembling Scheele's Greens ..... 575
Dark Greens ........ 575
Yellowish-Greens . . . . . . ... 575
Grays . . . . . . . .575
Bronzes ......... 575
Dark Bronzes ........ 575
Pinks 575
Dark Pinks . . . . . . .575
Whites 576
CHAPTER III.
DRYING AND ADHERENCE OF COLORS.
SECTION I.
DRYER FOR ZINC WHITE.
SECTION II.
DRYING OILS.
SECTION III.
POWDERED DRYER OP GUYNEMER.
SECTION IV.
VARIOUS DRYERS. ZUMATIC DRYER.
1. Benzoate of Cobalt, and Benzoate of Manganese . . . 583
2. Borate of Cobalt . . . . . . .584
I Employment of Resins .... . 584
Borate of Manganese ....... 585
ZumaticLake . . . . . . .587
SECTION V.
SPREADING, DRYING, AND ADHERING PROPERTIES OP OIL PAINTS.
Chevreul's Memoir on Oil Painting ..... 588
CHAPTER IV.
BRONZING.
SECTION I.
REAL BRONZE, COLOR WHICH IT ACQUIRES IN THE AIR.
SECTION II.
VARIOUS BRONZE COMPOSITIONS FOR METALS.
XVI CONTEXTS.
SECTION III.
RECIPE FOR THE ORDINARY BRONZE OF THE FOUNDERS.
SECTION IV.
MODE OF APPLYING THE BRONZING MIXTURES.
SECTION V.
MODE OF GIVING THE PROPER BRONZE COLORATION, WITHOUT
LAMPBLACK.
SECTION VI.
BRONZING OF GUN BARRELS.
SECTION VII.
BRONZING PLASTER OF PARIS.
SECTION VIII.
GREEN BRONZE.
APPENDIX.
PAGE
Mill for Grinding Colors . . . . . . .604
Mill for Dry Indigo . . . . . . .607
Improvements in the Manufacture of Oils, Varnishes, and Colors, by
MM. H. Bessemer and J. S. C. Hey wood .... 608
Description of an English Mill for Grinding Colors . . . 626
Hermann's Mill ........ 629
The Metric System of Weights and Measures .... 631
Tables showing the Relative Values of French and English Weights
and Measures, etc. . . . . . . 633
INDEX . 641
MANUFACTURE
OF
COLORS FOR PAINTING.
uc
j
INTRODUCTION ON THE COLORS EMPLOYED BY
THE ANCIENTS.
SEVERAL ancient writers, and especially Theo-
phrastes, Pliny, and Vitruvius, have transmitted to us
interesting data regarding the colors known in their
times, and which were so skilfully employed for
adorning their public and private buildings. In our
time, the chemists, Sir Humphry Davy, Chaptal, and
Vauquelin, and the painter, Merimee, have analyzed
these materials, and have also examined the modes of
preparing and applying them. We think that it will
be found useful to reproduce here a few extracts from
ese important researches, in order better to appre-
iate the progress of this branch of chemistry since
e days of old.
White used l>y the Egyptians and Romans. — The
white employed by the Egyptians is remarkably fast
and well preserved. Merimee thinks that it is sim-
ply plaster of Paris (sulphate of lime) mixed with
a certain glue or mucilage, the nature of which he
could not ascertain.
In certain vessels discovered in the excavations of
the baths of Titus, at Rome, various pigments were
found, which were analyzed by Davy, and which cor-
2
18 MANUFACTURE OF COLORS.
responded with those of the fresco paintings of that
palace, or those of fragments of stucco work discov-
ered in the ruins.
The same chemist ascertained that, in general, the
ancient whites were soluble with effervescence in
the acids, and presented the characteristics of car-
bonate of lime.
The whites contained in the vases of the baths of
Titus, where many mixed colors were found, appeared
to Davy as being of different kinds, that is, very
finely pulverized chalk, another white slightly yel-
lowish, like cream, and perfectly comminuted clay.
Moreover, none of the whites examined by this
chemist, whether in these baths or in any monument
of Roman antiquity, contained a trace of white lead,
although Pliny and Vitruvius, especially the latter,
claim that white lead was a commonly used paint,
produced by the action of vinegar upon lead.
In all Egyptian pictures, whether made upon wood
or canvas, the priming coat is always some kind of
a white, and the colors applied afterwards, although
opaque, are somewhat wanting in depth and bright-
ness, on account of a certain transparency in the
groundwork. What was the nature of the size
employed, is an important question, because these
pictures were not cracked, as are so many of our own
old ones. Egypt possesses mimosa trees, which pro-
duce a gum, and as gelatin glue was known, the colors
may have been sized with these two substances ; but
Merimee supposes that a more supple material, like
gum tragacanth, or any similar mucilage, was pre-
ferred.
"Wi th what tools were these pigments applied ? The
answer to this question seems obvious, since the
INTRODUCTION. 19
invention of the brush or pencil is so natural, that it
cannot have escaped the attention of the Egyptians.
Blacks and Browns. — Davy found in several places
fragments of stucco painted black. By several tests,
he ascertained that acids and alkalies were without
action upon the colors, but that they burned with
nitre, and had all the properties of a pure carbona-
ceous substance.
In the vessels filled with mixed paints, which we
have already mentioned, Davy found no black, but
various kinds of browns — one had the color of to-
bacco ; another was a dark red-brown ; and a third
was a dark olive-brown. The former two were ochres
which, very likely, had been calcined at various
degrees ; the third yielded oxides of manganese and
of iron, and produced vapors of chlorine when treated
by hydrochloric acid.
" All the ancient authors," says Davy, "describe
the artificial blacks of Greece, or Rome, as carbona-
ceous substances, manufactured from burned resins,
giving a kind of lampblack, or from the calcination
of ordinary soot, or of wine lees. Pliny asserts that
a natural fossil black is found, and also another pre-
pared from an earth having the color of sulphur." It-
is probable, according to Davy, that these substances
are manganese and iron ores.
" It is evident that the ancients were cognizant of
manganese ores, from their paintings on glass."
>avy examined two samples of purple glass of Ro-
man manufacture ; and both were colored with man-
ganese oxide. Pliny speaks of various brown ochres,
one especially, which he calls cicerculum, coming
from Africa, and which probably contains manga-
lese. Theophrastes mentions a mineral substance
20 MANUFACTURE OF COLORS.
which takes fire when oil is poured upon it, a pro-
perty which, according to Davy, belongs to no other
actually known mineral substance, except a manga-
nese ore found in Derbyshire.
The browns, in the pictures of the baths of Livia,
and of the Aldobrandini Wedding, are considered by
Davy as mixtures of ochres with blacks. Those of
the Aldobrandini Wedding yield iron when treated by
hydrochloric acid, but the dark shades are unacted
upon by the acid or alkaline solutions.
Yellows. — Davy discovered, in a room of the baths
of Titus, a large earthenware pot, holding a large
quantity of yellow paint, which, after analysis, was
found to be a mixture of yellow ochre and chalk
(carbonate of lime). There were in the same vessel
three different kinds of yellow, two of which were
yellow ochre mixed with variable proportions of
chalk, and the third one yellow ochre mixed with red
lead.
The yellow most esteemed by the ancients was the
ochre of Athens. Vitruvius asserts that at his
epoch the mine was abandoned.
According to Davy, the ancients possessed two
other paints which were yellow or orange — the auri
pigmentum, the color of which resembles gold, and
which appears to be orpiment (sulphide of arse-
nic) ; and a pale sandaraca, which Pliny asserts to
be found in gold and arsenic veins, and which was
imitated at Rome by a partial calcination of white
lead. From what Pliny says, Davy infers that the
lightest kind of orpiment resembles sandaraca, and
that another paint, called sandaraca by the Romans,
was of a bright yellow, like that of the beak of the
blackbird.
INTRODUCTION. 21
Davy saw no example of the use of orpiment in
old fresco paintings. A deep yellow, somewhat
orange, and which covered a piece of stucco work,
was a mixture of litharge and red lead. This chemist
considers that it is very probable that the ancients
employed several lead colors, such as massicot (lith-
arge), white and red leads.
The yellows of the Aldobrandini "Wedding are en-
irely ochres. Davy also examined the colors of a
pretty painting upon the walls of a house of Pompeii,
and ascertained that they were made of yellow and
red ochres.
An examination of the Egyptian collection of
Pas sal aqua, made by a commission of celebrated
French chemists, under the direction of Merimee,
demonstrated the fact that among the colors em-
ployed by the Egyptians there are two kinds of yel-
low ; one, and the most usual, is nothing else than a
light yellow ochre abundantly found in the vicinity
of beds of iron ore. The other, lighter and brighter,
was a sulphide of arsenic (orpiment). This latter
substance may be produced artificially, but, as it is
also found as a mineral, it is probable that it has
been employed in this state.
Red used by the Egyptians. — The red employed in
the fine collection of Passalaqua is, the greater part
of it, a red ochre obtained by the calcination of yel-
low ochre. "Vitruvius asserts that a fine red ochre
was obtained from Egypt.
It is not improbable that vermilion may have been
employed in some places. Cinnabar was known
in India from the earliest ages, and the Egyptians
may have obtained it by trade.
Red employed ~by the Greeks and Roman*. — Among
22 MANUFACTURE OP COLORS.
the substances contained in a large earthenware vase
filled with colors mixed with clay and lime, and
found in an open room of the baths of Titus, Davy
found different kinds of reds. One was bright,
and with an orange tinge ; another was a pale red ;
and the third was purplish. The first one, on ex-
posure to the heat of an alcohol lamp, became darker
and even fused when the blowpipe blast was applied.
Further tests demonstrated that it was red lead.
The second became black by heating, but reacquired
its former color on cooling. Calcination in a glass
tube proved that the only volatile substance was
water. Chemical tests demonstrated that it was an
iron oxide.
The third sample, of a purplish-red color, was
treated in the same manner, and was found to be an
ochre of a different color.
After examining the fresco paintings of the baths
of Titus, Davy ascertained that all of these colors
had been used ; the ochres especially for shadowing
the pictures, and the red lead for ornamenting the
borders.
The same chemist found upon the walls another
red of a tone different from those found in the vase ;
it was brighter, and had been employed in several
rooms. A small quantity of this color, scraped from
the walls, and submitted to chemical tests, proved to
be vermilion or cinnabar, since metallic mercury was
obtained by calcination with iron filings.
The same color was also found upon several frag-
ments of stucco work.
In the Aldobrandini Wedding all the reds are
ochres. These reds, tested with acids, alkalies, and
chlorine, showed neither red lead nor vermilion.
INTRODUCTION. 23
Red lead, says Davy, was known by the Greeks
and Romans. According to Pliny this paint was
accidentally discovered in a fire which took place at
the Piraeus, near Athens. White lead exposed to that
fire was transformed into red lead, and the process
was imitated in manufactures.
Theophrastes, Vitruvius, and Pliny describe several
red earths used for painting. The earth from Sinope,
that of Armenia, and African ochre produced a red
paint by calcination.
Cinnabar or vermilion was called minium by the
Romans. " Theophrastes," says Davy, " asserts that
it was discovered by the Athenian Callias, in the
349th year of Rome. It was prepared by lixiviating
silver ores."
Yermilion, according to Pliny, was always highly
esteemed by the Romans, and its value rose so high
at one time that, to prevent a further increase, the
government fixed its price.
Davy found in the baths of Titus another broken
vessel, filled with a light pink color, which faded by
exposure to the air down to a cream color ; but the
unexposed parts had a lustre like carmine.
After several experiments this learned chemist as-
certained that it was composed of silica, alumina,
and lime, with no other mineral substance but a
slight proportion of oxide of iron. Heated with
oxygen in a glass tube, this color did not burn and
became somewhat red. The gas escaping from the
tube, being passed through lime-water, gave a pre-
cipitate of carbonate of lime. Another portion of
color was also mixed with chlorate of potassa and
heated in a small glass retort; when fusion took
24 MANUFACTURE OF COLORS.
place there was a slight combustion, and the escaping
gas precipitated lime-water.
It appears from these experiments that this color-
ing substance was a compound with some material
of animal or vegetable origin. Davy put some of it
upon a heated iron, and there was scarcely any smoke,
but a slight smell resembling that of hydrocyanic
(prussic) acid.
"When caustic potassa was melted with this color,
the vapors had no ammoniacal smell, although there
was a light cloud in the presence of hydrochloric
acid ; " but," Davy says, " this is far from being an
evident proof of the presence of animal matter."
This chemist made a comparison of this color with
the vegetable lake made from madder, and an animal
lake made from cochineal at the same degree of dilu-
tion and fixed upon alumina. The madder lake,
dissolved in concentrated hydrochloric acid, recovered
its color by the addition of alkalies, whereas the same
results did not take place with the old color. The
solution of madder lake in diluted hydrochloric acid
became of a fallow brown after the addition of per-
chloride of iron, whereas there was no change of
color with the old lake. The latter and that from
cochineal became darker in weak alkalies, and
brighter in weak acids. There was, however, this
difference ; the old lake was more easily destroyed
by concentrated acids. Like animal and vegetable
lakes, it was immediately destroyed by a solution of
chlorine.
The smoke produced by the cochineal lake, melted
with caustic potassa, was greater, and there was a
strong ammoniacal smell. The combustion of the
madder and cochineal lakes, in oxygen, was not more
INTRODUCTION. 25
vivid in appearance than that of the old lake. Davy
ascertained that the loss in weight of the latter by
combustion, was about one-thirtieth, made up for the
greater part of the water combined with the clay of
that pigment. This fact prevented Davy from deter-
mining its composition by the process of ultimate de-
composition, since the results could not be certain.
From all these experiments, Davy thinks that it is
impossible to determine whether this lake is of vege-
table or animal origin, and he adds : u If it is of ani-
mal origin, it may be Tyrian or marine purple, and
this question may possibly be solved by making com-
parative experiments with the purple shell."
Davy could find no instance where this lake had
been employed in the old fresco paintings. The pur-
ple-reds of the baths of Titus were mixtures of red
ochres and copper blues.
Grecian Purple, also called Tyrian Purple. — The
Ostrum of the Romans, and the purple of the Greeks,
was considered by these nations the finest color, and
it was extracted from a shell. Vitruvius asserts that
this color varied with the countries from which the
shell was exported. That from the northern coun-
tries was deeper and more violet ; whereas that from
the southern regions was more red. This author
adds that the color was obtained by beating the shell
with iron tools, and that the purple liquor separated
from the debris of the animal was mixed with a cer-
tain proportion of honey.
Dr. Edward Bancroft, in his experimental researches
on the physical properties of fast colors, remarks:
'The purple so celebrated among the ancients ap-
pears to have been discovered at Tyr, about twelve
centuries before the Christian era. This dye was
26 MANUFACTURE OF COLORS.
extracted from a univalve shell (murex), of which
there were two species, and which were found on the
shores of the Mediterranean. The throat of the ani-
mal was incised, or it was ground whole, and the
mixture was allowed to digest for several days with
salt and water in leaden vessels. During the last
period of the Roman Empire, the use of this precious
dye was restricted to a few dignitaries, under the
heaviest penalties.
" In 1683, a man, who was making a living in Ire-
land by marking linen with a fine crimson color, ex-
tracted from a sea-shell, found out after some
researches on the coasts of Sommersetshire and
"Wales, quantities of buccina, which gave forth a
viscous and whitish liquor when bled near the head.
Marks made with this liquor would, by contact with
the air, become of a soft green color which, by expo-
sure to the sun, turned by degrees to a fast and fine
purple. In 1769, De Jussieu found on the western
coast of France, a species of buccinum similar to the
garden snail ; and the following year, de Reaumur
observed that on the coasts of Poitou this same shell-
fish was very abundant. The same naturalist had
already found, in 1736, on the shores of the Mediter-
ranean, thepurpura, the only species of murex which
was then known. All these shell-fish furnish a
liquor, which, to a greater or less extent, possesses
the above-mentioned properties."
According to Pliny, the finest purple was of a dark
pink, and he asserts that it was employed for impart-
ing a finishing lustre to the sandyx, which was a
compound of ochre and sandaraca calcined together,
and resembling our crimson.
Blues. — This color, as bright as ultramarine, was
INTRODUCTION. 27
found in the collection of Passalaqua, and is a sort
of blue ash, vastly superior to that manufactured at
the present .time. The latter, indeed, is rapidly acted
upon by heat, acids, and alkalies, and even becomes
green by age ; on the other hand, the Egyptian blue
resists the action of all these agents, and retains its
brightness after thirty centuries.
A blue color, taken from an Egyptian grave at
Thebes, was analyzed by Yanquelin. This blue was
quite fusible. Heated with the blowpipe upon char-
coal, and with the addition of cream tartar, it gave
metallic copper. The approximative result obtained
by this chemist was : —
Silica 70
Lime ......... 9
Oxide of copper 15
Oxide of iron ....... 1
Soda and potassa ...... 4
" I do not know," says he, " whether this color was
prepared by the wet or the dry way ; but it is certain
that the constituent parts are thoroughly combined,
since concentrated acids remove but traces of copper
and lime, and nothing at all at a second treatment."
Yauquelin saw a similar color produced in the bed
of a copper melting furnace, at the manufactory of
Eomilly ; the chemical composition and the tone of
the blue were the same. This Egyptian blue is more
than thirty centuries old, and if certain parts have
been slightly altered, it is only at the surface. Theo-
phrastes speaks of this blue color, as being manufac-
tured at Alexandria, and having been discovered by
a king. "We read in Yitruvius that Yestorius, on his
return to Italy, gave its composition. It was prepared
at Pozzuoli, by triturating together copper filings,
28 MANUFACTURE OF COLORS.
sand, and natron, and forming balls which were after-
wards heated in a potter's oven.
Davy succeeded in making a blue color similar to
that of Egypt, by strongly heating for two hours a
mixture of —
Pulverized silicious stone . . . . .20
Carbonate of soda . . . . . .15
Copper filings 3
"The blue prepared by this chemist," says Julia
de Fontenelle, "differs from that analyzed by
"Vauquelin, by melting at a lower temperature than
the Egyptian blue ; this result appears to be due to
the greater proportion of carbonate of soda."
" The blues employed by the ancients," says Davy,
"are pale or dark, according as the proportion of
carbonate of lime is greater or less ; but when the
carbonate of lime is removed by acids, they have the
same body and appearance, that is to say, a highly
comminuted blue powder, similar to the finest smalt
and ultramarine blues. This powder is hard, retains
its color at a red heat, and fuses at a higher temper-
ature." Davy ascertained that this blue color was
not altered by the acids ; aqua regia, however, after
a protracted boiling with it, becomes yellow, and
shows the presence of copper. A certain quantity
of this color was kept fused for half an hour with
double its weight of hydrated potassa ; the mass was
of a greenish-blue, and after treatment with hydro-
chloric acid, gave a proportion of silica greater than
three-fifths of the primitive weight. The coloring
matter was easily dissolved in ammonia, impart-
ing to the latter an intense blue color, from which
Davy concludes that it was oxide of copper. The
residue was a notable quantity of alumina with a
small proportion of lime.
INTRODUCTION. 29
The small amount of lime found in that color did
not appear to Davy sufficient to explain its fusibility ;
the presence of an alkali was therefore suspected, and
after the proper treatment, a residue of .sulphate of
soda was obtained. This was a proof that the color
was a frit, colored by oxide of copper. According to
Davy, there appears to be little doubt about this blue
being that described by Theophrastes.
Pliny mentions other kinds of blues, which he calls
sands (arence^ and which were mined in Egypt,
Scythia, and Cyprus. Davy believes that they were
various preparations of lapislazuli, and the blue
carbonates or arseniates of copper.
Pliny and Yitruvius speak of the Indian blue, the
former stating that it was combustible. Evidently
it was a kind of indigo.
Davy examined several blues from fresco paintings
in the ruins of the monument of Caius Cestius ; one
was of a dark indigo color, and yielded a small pro-
portion of carbonate of copper; but the basis of the
color was the above described frit. The blues of the
Aldobrandini Wedding, from their resistance to the
heat and acids, are believed by Davy to be com-
pounds of Alexandria blue.
In diggings made in 1814, at Pompeii, anti in the
presence of Davy, a small pot was found, holding a
pale blue color. It was nothing else than a mixture
of lime and Alexandria frit.
M. Grirardin, Professor of Chemistry at Lille, has
analyzed a substance of a light blue color, found in
a Gallo-Roman city of the department of Seine-Infe-
rieure. After treatment with weak hydrochloric
acid, which removed a certain proportion of carbonate
of lime, the residue was of a very fine azure-blue color.
The composition of the substance was as follows: —
30 MANUFACTURE OF COLORS.
Silica 49.4
Alumina . . . . . . .6.4
Lime, with traces of magnesia and iron . . 19.5
Soda . . . 15.5
Oxide of copper 9.3
100.1
After having mentioned the analyses made by
Chaptal and Davy, Mr. Girardin passes to the fol-
lowing extract from the Histoire de la Chimie^ hy
Hoefer : " The manufacture of blue was invented at
Alexandria, and Nestorins for a long time prepared
it at Pozzuoli. Sand and natron (carbonate of soda)
are ground together as fine as flour, and then mixed
with copper filings and a little water, in order to
make a paste. Balls are. made with this paste, and
are allowed to dry; lastly, they are put into pots, and
heated in a furnace in order that they may fuse and
produce a blue color." Mr. Girardin then adds : —
" This color, which is remarkable for its beauty
and durability, could actually be prepared by calcin-
ing for two hours in a furnace a mixture of —
Silicious sand ....... 60 parts
Soda ash 45 "
Copper filings . ... . . . 10 **
Greens. — Merimee says that he saw no bright
greens in the above-mentioned Egyptian collection.
All of them being olive-green, he believed at first
that they were made of a kind of chlorite, inferior in
brightness to Verona earth, still in use by our paint-
ers. But he soon found out by analysis that copper
was the coloring element.
A fragment, detached from the ceil ing of the baths
of Livia, was of a dark sea-green, like the ground-
work. Davy ascertained that the coloring substance
INTRODUCTION. 31
was soluble with effervescence in acids, and when
precipitated and redissolved in ammonia, it imparted
the blue color due to the oxide of copper. " There
are," says Davy, " different tones of green employed
in the baths of Titus, and also upon the fragments
found in the monument of Caius Cestius." In the
vases holding mixed colors, already mentioned, Davy
found three different varieties of green ; one, with an
olive shade, was Verona earth ; the other was a pale
grass-green, and had the appearance of being carbon-
ate of copper mixed with chalk ; the third was sea-
green, and was a combination of copper mixed with
a blue copper frit.
All of the greens examined by Davy, in the baths
of Titus, were copper compounds. The green of a
grapevine was so bright that it was suspected to
contain arsenic, like Scheele's green, but analysis
demonstrated that it was pure carbonate of copper.
Vitruvius speaks of chrysocolla as a substance
found naturally in copper mines, and Pliny mentions
artificial chrysocolla, made with a clay found in
proximity to metallic veins. This clay was probably
impregnated with copper, and Davy believes that the
natural chrysocolla was a carbonate of copper,
whereas the artificial chrysocolla was clay impreg-
nated with sulphate of copper, and rendered green
by some yellow substance.
Davy thinks that the name of chrysocolla is de-
rived frcfm the green powder employed by gold-
smiths, having carbonate of copper as a component
part.
Among the substances found in the baths of Titus,
some were of a grass-green color. Davy at first
thought that they were specimens of natural chryso-
32 MANUFACTURE OF COLORS.
colla, but he afterwards ascertained that they were
carbonate of copper. There were also round nodules
of the red sub-oxide of copper, which, it is surmised,
were due to nails or small plates of copper converted
into oxide and carbonate, by the action of the air
during several centuries.
According to Theophrastes, the ancients were well
acquainted with verdigris. Vitruvius speaks of it
as a color, and it is likely that many ancient greens
which are now carbonates, were primitively employed
in the form of acetates.
The ancients had glass of a very handsome dark
green color. Davy ascertained that they were col-
ored by the oxide of copper ; but it does not appear
that such glasses were powdered and then used as
paints.
All the greens of the Aldobrandini Wedding were
shown by Davy to be derived from copper.
In March, 1809, Chaptal reported to the Academy
of Science the results of his examination of seven
samples of paints found at Pompeii, in a color store.
The first of these colors was a natural product, a
greenish and soapy clay, such as is found in several
countries. This color appeared to Chaptal as being
analogous to Verona earth.
Number two was a fine yellow ochre, freed by
washing from all the foreign substances impairing
either its purity or its fineness. Since this substance
becomes red by calcination at a moderate heat, its
yellow color, which was fully preserved, seems to
Chaptal an additional proof that the ashes which
buried Pompeii were but moderately hot.
Number three was a brown-red, similar to that
employed at the present time for coarse paintings
INTRODUCTION. 33
upon barrels and doors, windows, etc. This color is
produced by the calcination of yellow ochre.
Number four was a very light, white, and close-
grained pumice-stone.
The three other samples were compound colors,
which Chaptal was obliged to analyze, in order to
arrive at their constituent parts.
Number five was an intense blue, in small frag-
ments of equal size and shape. The exterior was
lighter than the inside, the color of which was deeper
and brighter than the finest blue ashes.
This color produces but a slight effervescence with
hydrochloric, nitric, and sulphuric acids ; it even
becomes brighter, and chlorine has no effect upon it.
There is, therefore, no similarity, according to Chap-
tal, to ultramarine blue, since the latter is destroyed
by the four above-named reagents, as has been ob-
served by Clement and Desormes.
Ammonia has no action upon it. Heated with a
blowpipe, it darkens and forms a reddish-brown frit.
It colors borax a greenish-blue. Treated with po-
tassa upon a platinum support, it produces a greenish
frit, which becomes brown and then copper-colored.
This frit is partly soluble in water; hydrochloric
acid, poured into the solution, produces a gelatinous
precipitate. Oxalate of ammonia gives another pre-
cipitate with the separated liquor.
Nitric acid dissolves with effervescence the residue
unacted upon by the alkali. The solution is green, and
gives with ammonia a precipitate which is redissolved
by an excess of the reagent; the liquor is then blue.
"This color," says Chaptal, "appears, therefore, as
a compound of oxide of copper, lime, and alumina; it
contains the elements of blue ashes, but its chemical
3
34 MANUFACTURE OF COLORS.
properties are different. It appears to be not a pre-
cipitate but a frit, that is to say, the beginning of a
vitrification."
It appears that the process by which the ancients
obtained that color, is lost to us. All that we know
is that such a blue was employed centuries before
Pompeii was buried in ashes. " Descotil," adds
Chaptal, " has observed a bright blue with a vitreous
lustre upon the hieroglyphic paintings on an Egyp-
tian monument, and he ascertained that the color was
due to copper.
" From its component parts, that color may be com-
pared with our modern blue ashes ; but in regard to
usefulness, we may substitute for it the ultramarine
and azure blues."
Number six is a light blue sand, mixed with a few
whitish granules. Chemical tests demonstrated the
presence of the same substances found in the preced-
ing number. "We may," says Chaptal, "consider it
as a similar compound with greater proportions of
silica and alumina."
The color of number seven is a handsome pink.
The material is smooth and is reduced to an impalpa-
ble powder between the fingers, coloring the skin a
pretty carnation pink. By heat this color blackens,
and lastly turns white, without any sensible smell of
ammonia. This color is soluble in hydrochloric acid
with a slight effervescence, and ammonia produces in
the solution a flocculent precipitate entirely soluble
in potassa. An infusion of gall-nuts, and the hydro-
sulphate of ammonia fail to show the presence of
any metal.
We may, according to Chaptal, consider this pink
color as a true lake, the coloring principle of which
INTRODUCTION. 35
is absorbed by alumina. Its properties, shade, and
the nature of its coloring principle render it almost
entirely analogous with madder lake. The preserva-
tion of this lake for nineteen centuries, without
being scarcely at all altered, is a wonderful phenome-
non for chemists.
Such, says Chaptal, is the nature of the seven colors
which were submitted to him, and they seem to have
been especially intended for painting. Nevertheless,
he observes that if we examine the varnish or glaze
of Roman potteries, the debris of which are so plen-
tiful wherever the armies of Rome established them-
selves, we can easily believe that most of these color-
ing earths could also have been employed for glazing
those potteries.
The azure blue, the red and yellow ochres, and the
blacks, are colors which, according to Davy, do not
seem to have been altered. at all in the fresco paint-
ings. The vermilion is darker than the cinnabar of
Holland, and the lustre of the red lead is inferior to
that sold at the present time. The greens are gene-
rally dull.
"The principle of the composition of the Alexan-
dria frit," adds Davy, "is perfect, i. e., to incorporate
the color in a composition resembling stone, in order
to prevent the disengagement of any elastic fluid, or
the decomposing action of the atmosphere. It is a
kind of artificial lapis-lazuli, the coloring substance
of which is thoroughly combined with a very hard
silicious stone.
" It is likely that other colored frits could be made,
and it would be worth while to try whether a fine
purple, from gold oxide, could not be rendered use-
ful for painting, by incorporating it with a glass.
36 MANUFACTURE OF COLORS.
" "When frits cannot be employed, the experience of
seventeen centuries demonstrates that the best colors
are metallic combinations, insoluble in water, and
saturated with oxygen or some acid substance. In
red ochres, the oxide of iron is saturated with oxy-
gen ; in the yellow ochres, the metal is combined with
oxygen, and sometimes with carbonic acid. These
colors have remained unchanged. The carbonates of
copper, which contain an oxide and an acid, have been
but slightly altered."
Several parts of the figures and ornaments on the
outside of the baths of Titus, present only traces of
ochreous colors, and Davy thought it likely that
vegetable, such as indigo, or animal colors, or differ-
ent colored clays, had been employed.
To sum up, the most minute investigations, and the
most thorough examinations of ancient monuments,
have revealed to chemists none others than white,
black, yellow, brown, red, blue, and green colors.
ORIGIN, ETC., OF COLORS. 37
CHAPTEE I.
ORIGIN, DEFINITION, AND CLASSIFICATION OF
COLORS.
SECTION I.
ORIGIN OF COLORS.
THE decomposition of a ray of light furnishes seven
distinct colors — violet, indigo, blue, green, yellow,
oran/e, and red, which are generally called the normal
colors. We may, however, say that blue, yellow, and
red are really the only primary colors, since they are
sufficient to reproduce all the others. White is the
reunion of the seven colors, or the light of a solar
ray ; and Hack is the entire absence of this light.
The whites employed in painting are not a mix-
ture of all the colors ; they are natural or chemical
compounds, which reflect light without decomposing
it as other pigments do. The blacks absorb and pre-
vent the luminous intensity of the other colors.
In general, the pure color of a substance is that
of the color of the prismatic spectrum which it
reflects to our eyes. A blue substance reflects blue
rays only, and absorbs all others. A yellow body
reflects but yellow rays ; a red body reflects but red
rays, etc. A white substance reflects all the rays of
the spectrum, and it is their confused reunion with the
same degree of intensity that appears white to our
eyes. A black substance absorbs all the colors of
the spectrum and reflects none.
38 MANUFACTURE OF COLORS.
The combination of the seven colors of the prisma-
tic spectrum produces hues which can be varied ad
infinitum, by the proper mixture of pigments. These
hues are often called secondary colors in contradis-
tinction with the normal colors of the spectrum.
The coloring substances employed for painting are
either natural or artificial ; but, as they are generally
too light, they are mixed with white lead, which im-
parts to them body and durability.
The admixture of white with these colors renders
them more luminous by diminishing the intensity of
their pure color. On the other hand, black renders
the other colors less luminous by a kind of absorp-
tion, without sensibly altering their specific character.
The effects resulting from the mixture of colors
with blacks or whites, are totally different from those
due to the mixture of colors together. This should
be remembered by the painter, for it is almost im-
possible to obtain bright hues with an admixture of
black. It has even been observed that the grays ob-
tained by the combination of black and white, are
not so fine and advantageous as the gray shades
resulting from the combination of the primary colors.
We shall not, in this place, tarry any longer on the
innumerable phenomena of the art of coloring, since
we shall return to them when speaking of the manu-
facture of colors, which requires a thorough knowledge
of the coloring substances, whether natural or artifi-
cial, and of the manner of using them. Without
insisting more than is necessary upon the systematic
division of normal or secondary colors, whether nat-
ural or artificial, we shall proceed to fully examine
the various processes for extracting and purifying,
or manufacturing, all the colors or pigments for
ORIGIN, ETC., OF COLORS. 39
painting. These colors are : the whites, blues, y el-
low s. Hacks, reds, and greens ; and in order to facili-
tate our researches, we shall follow the above order,
and put the oranges and violets after the reds, and the
browns with the blacks. As for the combinations
necessary to arrive at a given hue or tone, we shall
state the general principles, necessary in the majority
of cases, and sufficient to obtain an infinite variety of
hues and tones.
SECTION II.
DETERMINATION AND DEFINITION OF COLORS.
The study of colors, in regard to their nature and
their reactions upon each other, is highly interesting.
"We are indebted to M. Chevreul for a new method
and nomenclature, which, sooner or later, will prevail
in the arts, and which is based upon the chromatic
circles invented by this learned chemist.
In this method, all the colors are derived from in-
variable types or standards, disposed in a certain
order comprising the hemispherical chromatic con-
struction.
We know that every color, whatever be its nature,
is either simple or compound, luminous or sombre,
that is, pure or 'broken. Here is the mode, by means
of the hemispherical chromatic construction, of arri-
ving at the comparison and determination of colors
or of their modifications : —
Let us suppose a circle, divided into three equal
parts, by three radii ; at the end of any one of these
radii we write the word red ; at the extremity of the
other radius on the right, we write yellow ; and at the
end of the other radius blue. "We then divide each
40 MANUFACTURE OF COLORS.
of these intervals by other radii, termed orange,
between the red and the yellow ; green between the
yellow and the blue, and violet between the red and
the blue. Still subdividing each of these ten divi-
sions, we have the orange-red, the orange-yellow, the
green-yellow, the green-blue, the violet-blue, and the
violet-red. We then divide each interval into six
equal parts, and fill the first one, from the radius
" red," for instance, with red, and the other five with
proper mixtures of red and yellow, in such a manner
that the change in hue is gradual. These five spaces
are called : first red, second red, third red, fourth-red,
and fifth red. "We operate in the same manner with
all the other colors.
The primitive circle is, therefore, subdivided into
seventy-two equal angular parts, each of them hav-
ing a name which does not change. We understand
that any simple or compound color, but pure, i. e.,
without admixture of gray, must correspond with one
of the seventy -two primitive types or standards, or
be found between two consecutive types. But the
latter case seldom happens, and it is always possible
to interpolate by one-half, one-third, one-quarter, etc.
The broken colors are determined in the same
manner, by means of types or standards. Indeed, let
us suppose that a quadrant is placed perpendicular to
the plan of each color of the first circle, and that the
quadrant is divided into ten equal parts. Each sec-
tion will receive the color modified in tone, the first
by -j*o of black, the second by T\ of black, and so on,
until the tenth contains }$, that is to say, pure black.
In practice, the hemispherical chromatic construc-
tion is reduced to ten chromatic circles. The first
contains the pure colors ; the second the chromatic
ORIGIN, ETC., OF COLORS. 41
gamuts, or scales, broken withTV of black; the third
the colors broken with T\ of black, and so on.
All the pure colors are not equally intense, and their
coloring power is modified by white. Mr. Chevreul
indicates the depth of the color by the distance from
that color to the centre of the circle, in the following
manner : Any one of the radii which separate the
seventy-two hues, is divided into twenty-two equal
parts by twenty-one equidistant points, through
which the same number of circumferences are made
to pass. Therefore, every angular section of the
seventy-two hues is divided into twenty-two spaces.
In order to fill each of these divisions, we suppose
that all the hues are gradually tinted or toned in
such a manner that, the centre being white, the first
space is slightly tinted, the second a little more, the
third still more, and so on until the twentieth, which
is near the black. The first division, or white, is
marked 0 ; the last is black, and is marked 21. The
whole graduation is a gamut, or scale, of which there
are seventy-two in the whole circle. The parts of
this gamut are called tones. The first tone is that com-
prised between the first and second circumferences ;
the second tone is that between the second and third
circumferences, and so on.
The color of many chemical products and coloring
substances is often an indication of their purity, and
it is therefore necessary to define well their colora-
tion, and to fix it between stated limits so that but
slight variations should be allowed.
We shall add that a manufacturer of Paris, Mr.
Digeon, has undertaken to provide the public by
chromo-engravings, with the chromatic circles of Mr.
Chevreul, and that he has succeeded perfectly well in
42 MANUFACTURE OF COLORS.
this work, which requires both skill and patience.
The series of these circles is cheap enough, and should
be found in the shop of every painter or manufacturer
of colors.
Since Mr. Chevreul has published his fundamental
ideas upon the definition and the manner of naming
colors, he has communicated to the Academy of
Sciences several new details, which better express
their nature and applications.
"The arrangement,'' says he, "described in my
work on the Laws of the Simultaneous Contrast of
Colors, under the name of the hemispherical chromatic
construction, comprises upon a circular plane 72 dis-
tinct colors, which I call a pure gamut. Each gamut
comprises 20 tones of the same color, the intensity of
which increases from the centre, which is white, to
the circumference, outside of which the normal black
is supposed to be. The first 10 tones, at least, of
each of the 72 gamuts of the circle, contain but pri-
mary colors, such as red, blue, and yellow, or binary
colors, so called because they are compounds of two
primaries. These first 10 tones, at least, being with-
out black, are called pure tones, and are characteristic
of the chromatic circle of 72 gamuts, just mentioned,
and which I call ISTo. 1, as will be explained further
on. 12 gamuts have the following names : red,
orange-red, orange, orange-yellow, yellow, yellow-green,
green, green-blue, blue, blue-violet, violet, violet-red / and
60 gamuts are by series of five, between two of the
above-mentioned gamuts. The series or interpolated
gamuts are numbered 1, 2, 3, 4, 5, to which is added
the name of the preceding gamut, in the order men-
tioned. For instance, the gamuts comprised between
ORIGIN, ETC., OP COLORS. 43
the red and orange-red are, 1st red$ 2d red, 3d red,
4th red, and 5th red, and so on.
" But are these 1440 hues and tones, belonging to
72 gamuts, sufficient to denominate all colors? Evi-
dently not. We now have to demonstrate how the
quadrant of the hemispherical chromatic construction
completes the modification of all the tones of the
chromatic circle by the addition of black. The colors
are rendered gray, or broken, not only for the first 10
tones, at least, without black, belonging to the 72
gamuts, or scales, of the circular plan, but also for
the other tones already broken.
"The quadrant being supposed mobile upon its
axis, and perpendicular to the centre of the circular
plan, describes during its rotation, a hemisphere,
which comprises all the modifications possible by the
mixture with black of the 20 tones of each of the 72
gamuts. In order to understand, let us make the
quadrant coincident with one of the gamuts of the
circular plan, the red for instance. The quadrant is
divided by ten equidistant radii, including the axis,
and the latter is also divided into 20 equal parts for
the 20 tones of graduated mixtures of white and
black corresponding to the 20 tones of the red gamut
of the circular plan. Each of the spaces formed by
the 9 other radii of the quadrant, comprises 1 gamut
of 20 tones of red shaded with black, the latter being
increased uniformly from the red gamut shaded with
black of the circular plan to the axial gamut of nor-
mal gray. We shall then have 9 gamuts of broken
red thus made : 1st red, T\ + TO black ; 2d red, -fs -f
T\ black ; 3d red, TV + fV black ; 4th red, T% + T4<>
black; 5th red, T5o+T5o black; 6th red, TV + T6o
black ; 7th red, -^ + ^ black ; 8th red, T2¥ + T^ black ;
44 MANUFACTURE OF COLORS.
9th red, TV + T9o black. "What is said about the red
can be applied to the 71 other gamuts of the circular
plan.
" Thus, for each gamut of the circular plan, there
are 9 gamuts of the color, broken in all its tones by
quantities of black, increasing regularly (to the eye)
from the circular plan to the axis of the quadrant.
The hemispherical chromatic construction therefore
comprises —
"I. 72 gamuts, said to loe pure, because the first 10
tones, at least, of each of them contain no black.
"II. 72 gamuts, said to be broken, because their
first 10 tones, at least, contain black.
" These 72 broken gamuts comprise 12,960 tones.
" III. Lastly, by adding the 20 tones of the gradu-
ated norjnal black, we have —
72 gamuts, each with 20 tones = 1,440 tones
648 gamuts broken in the 20 tones = 12,960 "
1 gamut of normal grays = 20 "
14,420 "
\ "Let us suppose that the color of any substance
corresponds to 11 tones of the gamut 3 red broken by
f\, we shall write : 3d red, 11 tones, T\.
" ^ow, we will understand that if the 72 gamuts
broken by T^ of black are put in a circle, and the 72
gamuts broken by T2^ of black are put in another
circle, and so on, we shall have 9 circles of broken
colors. By adding to them the first circle contain-
ing the first 10 pure tones, at least, we shall have 10
chromatic circles, and the broken circles will be num-
bered Mos. 2, 3, 4, 5, 6, 7, 8, 9, and 10.
" Up to the present time, the manufacture of the
Gobelins has produced but 1440 tones of the first
ORIGIN", ETC., OF COLORS. 45
chromatic circle, and 72 tenth tones of the 648 broken
gamuts.
" On the other hand, a skilful artist, Mr. Digeon,
has produced, cheap enough for the trade, colored
plates comprising the 10 tones of the 10 chromatic
circles. He has also, by means of a prism of bisul-
phide of carbon, and conformably to the rays of
Fraunhofer, reproduced the position of 15 standard
colors corresponding to 15 standard colors of the first
chromatic circle. In this manner it will always be
possible to find these types again, and to interpolate
afterwards the other colors of that first circle.
" Lastly, Mr. Digeon has made three plates which
show to the eyes —
" I. How a color, blue for instance, which between
the limits of white, 0 color, up to black, representing
21 tones, may give 20 distinct tones by one of my
established rules.
" II. How a color and its hues, by going from red
to yellow, from yellow to blue, and from blue to red,
may, according to the same rule, give 72 gamuts of
distinct colors.
" I set great stress on what I have just said (i. e.,
the artifice by which I succeed in reducing an inde-
finite property, such as a given color, to well-defined
types or standards constituting the 20 tones of that
color, and the color in general considered as having
its hues in definite types of 72 gamuts), because this
method may be applied to the study of properties or
relative properties which belong to various sciences,
the object of which is the study and classification of
bodies."
46 MANUFACTURE OF COLORS.
SECTION III.
PHYSICAL EFFECTS OF COLORS.
Colors of the rays of the solar spectrum.
1. RED. 5. BLUE.
2. Orange. 6. Indigo.
3. YELLOW. 7. Violet.
4. Green.
The reunion of the rays RED, YELLOW, and BLUE = White.
u " YELLOW and RED = Orange.
" " YELLOW and BLUE = Green.
" " RED and BLUE = Violet.
Since YELLOW, RED, and BLUE are sufficient to
produce all the other colors, they have been called
the primary colors.
The reflected colors which, being added to those
absorbed, reproduce the white, are called complement-
ary colors.
Absorbed Colors. Corresponding Complementary
Colors.
Green (Blue and Yellow) Red
Violet (Red and Blue) Yellow
Orange {Red and Yellow) Blue
Red Green (Blue and Yelloiv)
Yellow Violet (Eed and Blue)
Blue Orange ( Yellow and Bed)
Mr. Chevreul calls contrast of tone, the modification
experienced by two colors of the same nature, but of
different tones, when they are contiguous one to the
other.
Example. — "When two bands of the same color, but
of different intensity, are placed parallel and conti-
guous to each other, they are modified in their tones,
which are no longer the same as when they were
viewed separately, or at a certain distance from each
ORIGIN, ETC., OF COLORS.
other. The general observed phenomenon is this :
the color of the two bands is entirely changed at the
line of contact, and that band with the less depth of
tone appears still lighter, but not uniformly so. The
portions nearest the line of contact are the lightest,
and the tone goes on increasing in depth up to a cer-
tain place, where the band retains its natural color.
On the other hand, the darker band is modified in
another manner : the portions nearest the line of con-
tact are darkest, and the tone goes on decreasing in
depth up to a certain place, where the band reac-
quires its natural color.
When two stripes of different colors, but sensibly
equal in tone, are parallel, and in contiguity, their
colors produce upon the eye an effect different from
that felt if they are seen separately, or at a certain
distance from each other. Each one absorbs a cer-
tain number of rays, and reflects the complementary
ones, which, reacting one upon the other, modify the
examined color. This optical phenomenon is called
by Mr. Chevreul contrast of colors.
Examples : —
Modification by Contrast.
Juxtaposited
Colors.
Orange.
Green.
Orange.
Indigo.
Green.
Indigo.
Green.
Yiolet.
Red.
Blue.
Corresponding Com-
plementary Colors.
Blue
Red
Blue
Orange-Yellow
Red
Orange-Yellow
Red
Yellow changing
to Green
Green
Orange
= Reddish-Orange.
= Bluish-Green.
= Orange changing to Yellow.
= Indigo changing to Blue.
= Green changing to Orange- Yellow.
= Indigo changing to Red.
= Green changing to Yellow.
= Yiolet changing to Red.
= Red changing to Orange.
= Blue changing to Green.
MANUFACTURE OF COLORS.
Mr. Chevreul, in his celebrated work on the con-
trast of colors, has fully explained the meaning of
simultaneous contrast, successive contrast, and mixed
contrast. We advise persons desirous of gaining
further information on this subject, to consult that
work.
Primary Colors.
Red
Yellow
Blue
Binary Colors (pure)
Orange (yellow
and red)
Lilac (red and
blue)
SECTION IY.
CLASSIFICATION OF COLORS.
Subdivisions.
( Deep red (crimson, gros rouge, fine red).
•s Cherry-red.
( Rose-pink.
f Bouton d'or.
•< Immortelle.
( Straw.
( Bleu de France (gros bleu).
•< Ultramarine (medium blue).
( Celestial blue.
Subdivisions.
C Deep orange.
•< Medium orange.
v Light orange (Nankeen).
t Yiolet eveque (deep lilac).
•3 Medium lilac.
(Light lilac (Hortensia).
j f Deep green (qrass-qreen).
Green (yellow and \ **
< Medium green (Scheele's green).
( Light green (water-green).
BINARY MIXED COLORS.
Orange-red, in which red predominates.
Orange-yellow,
Lilac-red,
Lilac-blue,
Greenish-yellow,
Greenish-blue,
yellow
red
blue
yellow
blue
ORIGIN, ETC., OF COLORS. 49
Tertiary Colors (pure). Subdivisions.
j Black (black-black, blue-black, dead
Black (red, yellow, and I Uack^ bright Uack).
blue) • | Iron-gray.
[ Pearl-gray.
Tertiary Colors (mixed.) Subdivisions.
Garnet (light green and ( Puce (flea color) or (deeP 9arnet)-
f ,. -c Medium garnet.
(.Light garnet or (tobacco).
j ( Bronze.
Bronze (lilac, blue, and \
77 \ i 01lve-
yellow) . . . ; _ , , ,
C Reseda.
, t Maroon (brown-solitaire, bistre).
Brown (orange, red. and \
} ) °°d-
CHazelnut (stone-drab).
SECTION Y.
GENERAL METHOD OF PREPARING COLORS.
We cannot do better than to present to manufac-
turers of colors, the observations of a skilful chem-
ist, Mr. Kletzinsky, as embodied in a memoir, the
general principles of which are here reproduced.
A fact which appears to be beyond doubt, says Mr.
Kletzinsky, is that, in the chemical manufacture of
colors, the wet way presents many advantages over
the dry way. This was long since demonstrated in
the manufacture of vermilion by the wet way, that is,
by precipitating a salt of oxide of mercury with a sul-
phur solution. The vermilion produced is much
superior to all the other kinds of cinnabar obtained
by sublimation or the dry way. It is physically im-
possible by the dry method, and by the mechanical
operations of pulverizing, sifting, grinding, and even
levigating (floating), to arrive at a molecular com-
minution equal to that obtained by the wet way, that
50 MANUFACTURE OF COLORS.
is, by the precipitation of a coloring substance by the
mixture of two limpid and pure solutions. It is also
a well acknowledged fact that to the molecular grain
of a pigment, that is, its degree of comminution, are
due its freshness, intensity, tone, body, and facility
of entering into mixtures.
Therefore, if a high degree of comminution is one
of the most important conditions for artistic and house
painting, it becomes still more so when we have to
produce given hues by the intimate and thorough
mixture of two or more colors. For instance, we
desire to make a leaf-green by mixing together
chrome yellow and Berlin blue ; it is evident that we
will obtain a^good and constant green color, with the
proper freshness and brightness, only by a previous
thorough comminution of each separate color, and
afterwards by their intimate admixture, so that the
blue and yellow rays will be reflected from the same
point, and will become blended and produce the green
optical effect on the eyes of the observer. As such
a result will evidently be reached more easily and
cheaply by the wet way than by the long and tedious
method of grinding, the principle of " mixeolytical"
colors is entitled to our serious attention for a great
many chromatic productions, and in the chemical
manufacture of colors. This principle is :—
"Choose two couples of solutions in such a man-
ner that each couple is capable by itself, when mixed,
of producing a precipitate possessing all the necessary
qualities of a chemical color."
Let a, b and c, d be these two couples of solutions ;
a and Z>, by their admixture, produce the blue ; and
c and cZ, under the same circumstances, result in yel-
low. If now, with the proper chemical knowledge,
ORIGIN, ETC., OF COLORS. 51
we choose such solutions that a and c, 5 and d, be
mixed without decomposition, or production of in-
desirable precipitates, we have realized the mixeo-
lytical principle, since the mixture of the double
solution a c with the double solution b d, will imme-
diately give the precipitate of the new mixeolytical
green color. Since a thorough solution is perfectly
homogeneous, and all its parts have the same density
and give the same yield, we immediately see that
the precipitated pigment will have a fineness and a
uniformity of hue and tone which cannot be attained
by colors prepared by mixing and grinding.
The following mixtures are examples of the above
mentioned method : —
1.
Mixed double solution (a, c). Mixed double solution (b, d).
Neutral chromate of potassa, Yellow . Acetate of lead.
Yellow prussiate of potassa, Blue . . Acetate of iron. ^
Resulting in a DEEP GREEN color, which maybe brightened with
nitric acid.
2.
Sulphuretted hydrogen solu-
tion ..... Yellow . Nitrate of cadmium.
Yellow prussiate of potassa, Blue . . Nitrate of iron.
Together, a SCHEELE'S GREEN, which is not poisonous.
3.
Phosphate of soda (in excess) Blue . . Nitrate of copper (in
excess).
Neutral chromate of potassa, Yellow . Nitrate of lead.
Together, a LIGHT LEAF-GREEN.
4.
Yellow prussiate of potassa, Blue. . Perchloride of iron.
Chloride of barium . . White . Sulphate of ammonia.
Together, a CELESTIAL or MARIE-LOUISE BLUE.
52 MANUFACTURE OF COLORS.
5.
Sulphuretted hydrogen (solu-
tion). .... Brown . Chloride of tin.
Yellow prussiate of potassa, Blue . . Percbloride of iron.
Together, an OLIVE GREEN, which may be brightened with very
diluted nitric acid.
6.
Sulphuretted hydrogen (solu-
tion) Brown . Chloride of tin.
Yellow prussiate of potassa, C asset's red. Sulphate of copper.
Together, a DEEP BISTRE color, having a good bod}'.
These few examples are sufficient to give an idea
of the almost boundless series of permutations with
mixeolytical combinations. It is not only possible
to multiply the mixtures, but the relative proportions
of the solutions may also be varied to produce as
many tones and hues of the same color as may be
desired, and that much more easily than in the usual
method of grinding a mixture of two colors.
It is well understood that experiments should be
made with titrated solutions, i. e., those the composi-
tion and yield of which are well known, and also with
graduated vessels of a known volume. It is the only
way of reproducing in the course of manufacture a
color or shade which is satisfactory, and which may
previously have been obtained by a chance hit, or
otherwise.
WHITE COLORS. 53
CHAPTER II.
MANUFACTURE OF COLORS.
SECTION I.
WHITE COLORS.
WE have previously explained what is the origin
of colors, how they are determined and classified,
and what is their general mode of preparation. We
have now to examine the processes employed in the
preparation of every one of them, and we shall begin
with the white colors which are employed not only
directly as pigments, but also for lightening a great
many other colors.
For a long time, chalk white and white lead were
almost the only whites in use; but, of late, the pain-
ter's palette has become furnished with several new
white pigments, such as zinc-white, baryta-white, or
blanc-fixe, which, from their peculiar properties, have
been found very advantageous for house painting.
We shall describe their manufacture very carefully,
without, however, neglecting the description of the
more recent processes for the preparation of white
lead, processes which are very varied, and many of
which are now in use.
§ 1. Whites with lime basis.
1st. Carbonate of lime.
The clialk whites, or carbonates of lime, are quite
abundant ; they form large deposits in England, and
54 MANUFACTURE OF COLORS.
in France, especially near Rouen, and at Meudon, and
Bougival, near Paris. This white is sometimes yel-
lowish, but oftener grayish or entirely white. Its
fracture is earthy, fine, and without any polish. It
is soft, without greasy feeling, leaves its marks, and
adheres to the tongue. Chalk contains a small pro-
portion of silica, sometimes magnesia, and about 2
per cent, of clay. There is iron in some samples.
Prepared chalk is called Spanish white, or white of
Bougival, Champagne, or Troyes, according to the
place of its manufacture. It is prepared as follows : —
After picking out the coarser impurities, it is
ground in a mill and formed into rolls, in which shape
it is found in the trade. For painting purposes it is
further purified by stirring in clear water, allowing it
to settle, and decanting the first water, which is gen-
erally yellow and dirty. The washing is repeated,
and the chalk is floated out into another vessel, after
passing through a silk sieve. After settling, the
water is decanted, and the pasty white residue is
formed into cylindrical rolls 10 to 12 centimetres in
height, and 5 to 6 in diameter. These are allowed to
harden and dry in the air, and are then ready for
painting, whitewashing ceilings, and for distemper
painting with size.
Mr. Laze thinks that if chalk whites are not sub-
stituted for white lead, it is due to the presence in the
former of a certain proportion of sand, which it is
difficult to remove. Better results are obtained by
sifting than by simple washing. A well -prepared
chalk-white, mixed with a little blue, and a dryer,
may be employed for oil painting.
WHITE COLORS. 55
2d. White of sulphate of lime.
The natural sulphate of lime, also called gypsum,
or crude plaster of Paris, is chosen as pure and white
as possible, and then finely powdered and sifted.
This white is employed for the grounds of paper-
hangings, and also with size for house painting.
Some manufacturers adulterate zinc- white with it.
§ 2. Whites with lead basis.
The finest ceruse whites, or white leads, are those
manufactured at Krems, or Kremnitz (Hungary).
But, as their preparation requires numerous opera-
tions, involving great labor, and much time, chemists
have endeavored, by new and more rapid, simple,
and cheap processes, to diminish the time and cost of
manufacture, without sensibly altering the quality of
the products.
In the order of their qualities, the white leads by the
Holland process come after those of Krems, and next
those of Clichy, which will be mentioned further on.
Before describing various processes of this manu-
facture, the products of which are the basis of nearly
all pigments for house and artistic paintings, we shall
present a few general observations on the preparation
of white lead which are due to Mr. Benson, a skilful
chemist and manufacturer, and which may be applied
to any kind of white lead, and are therefore useful to
manufacturers.
The white lead manufactured by the Clichy process,
that is, by the precipitation of a basic acetate of lead
with carbonic acid, is different from that of Kremnitz.
And, although the manufacture has been largely
extended, we believe that the processes could be
improved and rendered cheaper.
56 MANUFACTURE OF COLORS.
At the same time, we agree with practical painters,
that the Clichy or chemical white lead is less dense
and possesses less body than the Kremnitz white.
This fact, demonstrated by experience, notwith-
standing a few contradictions, has caused several
chemists and manufacturers to go back to the Krem-
nitz process, and to try at the same time to diminish
the length of the operation. Many have been the at-
tempts to employ the oxides of lead abundantly found
in the trade, and to do away with the employment of
boxes which requires so much time for the simulta-
neous oxidization and carbonatation of the lead.
Of litharge, Mr. Benson remarks that it is seldom
specially manufactured except for certain .wants in
the arts, and that it is a secondary and abundant pro-
duct obtained in all the lead works which extract
silver from lead.
The quantity of litharge produced in England, where
a great many lead mines are in active operation, is
much in excess of the consumption in the arts. It
is therefore necessary to reduce to the metallic state
that excess of litharge, notwithstanding a loss of 7
per cent, of its metal, either by sublimation or by
combination with the earthy substances of the fuel
with which it is in contact during the operation.
Litharge being a protoxide of lead, it was believed
that in order to transform it into white lead, it was
sufficient to combine it with carbonic acid. It is a
mistake which has given birth to many erroneous
processes.
In all of these processes the litharge is transformed
into a basic salt, which is precipitated in the form of
a carbonate by a stream of carbonic acid. The pre-
WHITE COLORS. 57
cipitate thus obtained is white, but the painters who
first used it said that it was not white lead. On the
other hand, several chemists having found in it, by
analysis, a correct relation between the oxide of lead
and the carbonic acid, thought that the painters were
prejudiced.
Dr. Ure appears to have been among the first to
ascertain the difference between white lead and the
precipitated carbonates. White lead is anhydrous,
amorphous, and opaque in oil; whereas Dr. Ure
found out by microscopic observations that the pre-
cipitated carbonate was partly crystalline and trans-
lucent.
There is a remedy for this inconvenience which
appears to have been already in use for some time.
The mode of operation either for the crystalline car-
bonate or the amorphous one is after all the same.
In both cases the lead is converted into a basic
acetate, decomposed afterwards by carbonic acid ;
but for the crystalline carbonate the operation is
modified by the pressure of the liquid in which it
takes place.
In one process the carbonate is deposited in a solu-
tion, in the other the molecules remain all the time in
the solid state and have no opportunity of being
symmetrically grouped.
Therefore, in order to produce an amorphous car-
bonate or white lead from litharge, the oxide of lead
should be combined with such a small proportion of
acetic acid that the resulting basic acetate is insolu-
ble, and there should be just enough dampness to
allow of the action of the carbonic acid.
The process becomes then a counterpart of that in
general use, with the exception that in this case the
58 MANUFACTURE OF COLORS.
lead is in the oxide state, whereas in the ordinary
method the oxidization and carbonatation proceed
simultaneously.
This process is actually practised on a very large
scale in a manufactory near Birmingham. The pro-
portion of acetic acid employed is less than ^-Q of
the weight of the litharge, which should feel simply
moist to the hand.
The combustion of coke gives a cheap supply of
carbonic acid, and a powerful stirring machinery is
employed to hasten the operation by constantly pre-
senting fresh surfaces to the action of the gas.
The result is that the operation is finished in as
many days as months were required by the old meth-
ods ; that the product is of a purer white, more opaque
and with more body, and that in every respect it is at
least equal to the white lead of the trade.
Before describing this process more completely, it
is important to state certain facts which are not suffi-
ciently known.
It is quite remarkable that the protoxide of lead
known under the name of massicot, and that called
litharge, behave differently when they are brought up
nearly to a red heat. The massicot absorbs oxygen
rapidly and becomes the ordinary red lead of the trade ;
on the contrary, this absorption is very slow, and some-
times fails entirely, with litharge. On the other hand,
should litharge and massicot be wet with diluted
acetic acid and exposed to a stream of carbonic acid,
the litharge will be converted into carbonate even
before the massicot is acted upon.
Another fact is, that white lead and oil combine
with such energy, that if linseed oil is poured upon
a large quantity of white lead, and the mass allowed
WHITE COLORS. 59
to stand for a few hours, the temperature becomes so
high that the oil is carbonized and colors the whole
a dark black.
It is also not generally known that white lead
destroys the coloring principle of linseed oil. If
sulphate of baryta be mixed with linseed oil, and
white lead with a similar proportion of the same oil,
the latter will appear whiter. After allowing these
two mixtures to rest for a few days, a certain propor-
tion of oil will rise to their surface. In the first case
the oil has not been modified, in the second it has
become almost entirely white, and has acquired a cer-
tain degree of rancidity.
The coloring principle of the oil, as some persons
might believe, is not combined with the white lead but
is destroyed. Indeed, should we dissolve the lead by
means of some acid, the oil is separated, and as white
as that which was on the top of the mixture.
Such a transformation requires a great excess of
white lead, and the precipitated carbonates are not so
advantageous for painting.
Basing their operations upon the above considera-
tions, Mr. Benson, and Mr.~W. Gossage, another distin-
guished chemist, have established a manufacture of
white lead by an improved Kremnitz process, which
we shall now examine.
1st. Kremnitz process.
The manufacture of white lead by this improved
process requires oxides of lead and acetic acid, or
acetates of lead and carbonic acid.
The oxides of lead are well known and abundant
in the trade. Any oxide of lead, whatever is its pre-
60 MANUFACTURE OF COLORS.
paration, which may be cheaply combined with car-
bonic acid, is satisfactory for this process.
Among the various oxides of lead found in the
trade, litharge and massicot are the best for this
operation. Red lead or minium does not suit at all.
The acetic acid employed should be free from
coloring substances, which would discolor the white
lead and impair its value. Acetic acid, free or already
combined with oxide of lead, is used. The acid, as
every chemist knows, may be obtained nearly colorless
by the distillation of vinegar, or by the decomposition
of the acetate of lime, or of any other combination of
acetic acid with earthy, alkaline, or metallic bases.
It is not necessary to reproduce in this place the
manner of effecting these decompositions, which is
known to every manufacturer. Moreover, such an
acetic acid is at the present day a product of the
chemical trade.
"When acetate of lead is used, the neutral acetate
or sugar of lead, and the basic solutions called
Extract of Saturn and Goulard9 s water, are employed.
Carbonic acid may be obtained by several methods
actually in use ; but that which is preferred on account
of its cheapness consists in collecting the gas result-
ing from the combustion of charcoal, coke, or anthra-
cite.
In order to obtain a carbonic acid entirely satisfac-
tory for the manufacture of good white lead, it is
absolutely necessary that the fuels used should be
entirely deprived of bituminous or volatile substances,
that is to say, be nearly pure carbon with fixed sub-
stances (earths).
These materials are burned in a stove or oven, and
the gases produced, which are a mixture of carbonic
WHITE COLORS. 61
acid, nitrogen, and undecomposed air, are passed
through a series of metallic pipes, so disposed in the
air or in water, that the gases are cooled off to a
moderate temperature.
In order to arrest any particles of unburt carbon,
or any other substance which may injure the color of
the white lead, the gases are passed through filters
filled with irregular fragments of lead, such, for
instance, as may be obtained by pouring the molten
metal into cold water.
A small stream of water is allowed to percolate
through the lead filters, which, therefore, are kept
constantly wet during the passage of the gas, and aid
considerably in its purification. When the presence
of sulphur is suspected in the fuel employed, a small
proportion of alkali is added to the water of the filters. •
Notwithstanding this precaution, it is better to be
very particular in the choice of the fuel intended for
the production of carbonic acid.
The carbonic acid already in the atmosphere could
be employed for carbonating the oxide of lead, if its
proportion were not so small. The operation would
be so slow, that, in every respect, it is preferable to
prepare carbonic acid by artificial means.
The following is the manner of manufacturing
white lead with the above indicated materials: —
If the oxide of lead is in big lumps, it is necessary
to grind it down to a powder, which needs not to be
so very fine. Litharge seldom requires this operation,
and may be employed in the state in which it is
bought.
The oxide of lead is mixed with the necessary pro-
portion of acetic acid, or acetate of lead, and sufficient
water is added to make a consistent paste. This
62 MANUFACTURE OF COLORS.
paste is spread in thin layers over trays covered with
sheet lead, and these trays are disposed one on top
of the other in a room for the purpose, into which
enters the carbonic acid, either pure, or mixed with
other gases which cannot have any bad effects upon
the beauty of the product. The carbonic acid is
absorbed, and combines with the oxide of lead to
make ceruse or white lead.
During the operation, the absorption is aided and
rendered more rapid, by stirring with rakes the layers
of lead, and thus presenting fresh surfaces to the
action of the carbonic acid.
If the gas is dry, or does not carry with it sufficient
dampness, a certain quantity of water is added to the
mixture so as to render it more ready to absorb the
carbonic acid. The proper degree is easily arrived
at after several trials during the operation.
As the operation progresses, the oxide of lead, which
was colored, becomes white; and when all of the
mixture is free from colored parts, the treatment is
finished, since all of the oxide has been transformed
into carbonate.
The length of the operation varies with the propor-
tion of acetic acid or of acetate employed, the rapidity
of production of carbonic acid, and the attention
given in stirring and in maintaining the proper degree
of dampness. With the proportions of oxide of lead,
acetic acid, or acetate, given further on, and a pro-
duction of carbonic acid sufficiently rapid, and the
proper care, the carbonatation requires from three to
six days.
It has been found economical to mix at once part
of the oxide of lead with the whole of the proportion
of acetic acid or of acetate, and when this oxide is
WHITE COLORS. 63
very nearly transformed into carbonate, to add a new
proportion of oxide without any more acetic acid or
acetate of lead. This new mixture, being exposed to
the action of the carbonic acid, the free oxide is very
rapidly converted into carbonate. A new proportion
of oxide is again added, and the operation is continued
as before, and always with a proper amount of mois-
ture.
These successive additions of oxide are repeated
(without more acetic acid or acetate) until the pro-
portion of acetic acid or of acetate is reduced to one-
fourth, or even less, of that which was in the primi-
tive mixture.
"When the carbonatation is finished, the mixture is
spread in a stove-room, and allowed to dry. Then it
is ground in a mill with water in the ordinary man-
ner. The ground and floated product is dried again,
and is white lead for painting and all other purposes.
The carbonated mixture may be ground immediately
after its removal from the trays, without drying it
first; but the latter operation improves the quality of
the white.
For 100 kilogrammes of oxide of lead, we employ
the same weight of a solution of acetic acid which
contains 23 litres of No. 24 or proof vinegar. When
we use acetate of lead, either solid or in solution, we
take of either a quantity yielding the proportion of
acetic acid just mentioned.
2d. Holland or Dutch process.
We now pass to the details of the operations by
the Holland process, with various observations and
comparisons made in several large French works, by
64 MANUFACTURE OP COLORS.
Mr. R. Combes, and reported by him to the Academy
of Sciences.
The Holland or Dutch process comprises the fol-
lowing operations: —
1st. Fusion and casting of the lead in sheets of
variable thicknesses, or into rectangular or round
grates (buckles).
2d. Alternate layers made of lead and stable ma-
nure, or spent tan. The lead is put into pots holding
weak acetic acid, and remains in the beds from thirty-
five to forty days when stable manure is employed,
and from seventy to ninety days when spent tan is
used.
3d. Successive uncovering of the layers of lead, the
greater part of which has become carbonate. Sepa-
ration of the white lead from the non-corroded metal.
First grinding and separation of the blue lead.
4th. Grinding the white lead with water under
stones.
5th. Moulding and drying the floated white lead.
6th. Grinding and sifting the dry white lead, and
packing in barrels that which is to be sold powdered.
7th. The white lead which is to be made into paste
with oil is not sifted, but mixed with from 7 to 10
per cent, of its weight of oil. The mixture is effected
in a closed stirrer, and then passed between a series
of horizontal cast-iron rollers. "When the paste has
become fine and homogeneous, it is received in a tank
filled with water, from which it is taken and packed
for sale.
I. The fusion of the lead is effected in cast-iron
kettles, and no dangerous fumes are emitted unless
old lead or the residues of previous operations, still
covered with carbonate, are melted. In well-disposed
WHITE COLORS. 65
works, the kettle is placed under a hood receiving its
draft either from the chimney flue of the furnace itself,
or from another stack with a good draft. The top
edge of the furnace is connected with the hood by
means of a metallic prism or cylinder, having doors
which are open for charging the lead, or for casting
into moulds the fused metal. These precautions seem
to us sufficient for protecting the men from the
noxious fumes. Moreover, the fusion of the lead is
intermittent.
II. The forming of the layers of lead and stable
manure or spent tan, presents no danger. The buckles
or the thin sheets of lead rolled into spirals, are put
into earthenware pots, and there supported upon two
or three projections. The vinegar is at the bottom
of the pot.
In one of the lead works of the department of
the Seine, the lead is cast into rectangular grates, or
buckles, which form layers upon pots more shallow
than usual, and holding the vinegar only.
III. The separation of the white lead from the non-
corroded metal, and the first dry pounding and sift-
ing, are the most unwholesome parts of the manufac-
ture. In nearly all of the works of Paris, the work-
man picks up by hand the large and slightly adher-
ing scales of white lead, and separates the remainder
by twisting and bending in every direction the non-
corroded lead. This hand picking is generally done
in the bed itself, and sometimes in a special room
where the whole of the corroded metal is carried, in
the shape it comes from the pots.
This picking, however, where the hands are con-
stantly covered with carbonate of lead, is not the most
dangerous part of the operation, because the thick
6
66 MANUFACTURE OF COLORS.
scales are separated without much dust. But as the
metallic lead still retains a certain quantity of white
lead strongly adhering, it was formerly beaten with
a wooden rammer, thus producing a fine dust, which
was inhaled by the workman. This operation is there-
fore the most dangerous, and is now substituted in
several works by mechanical means, which imperil
the health of the men much less. The buckles or
sheets with their still adherent white lead are put, one
by one, upon an endless cloth, which carries them to
an inclined hopper, from which they pass between two
pairs of grooved rollers, and thence through an in-
clined cylindrical sieve. What passes through the
holes of the sieve is received into a hopper, which de-
livers it into a trough on wheels. The metallic lead
falls from the lower opening of the sieve into another
trough. The whole of the machinery is inclosed in
tight wooden partitions, the only free opening o1
which is that for the passage of the endless cloth.
The trough filled with white lead is removed when
the dust has subsided, and its contents are mixed
with the scales picked up by hand.
The next dry grinding is, in the majority of cases,
still effected under vertical stones, rolling upon a
horizontal bed. The ground lead is then shovelled
into a cylindrical metallic sieve with fine holes, and
inclosed in a wooden box. The powdered white lead
is collected at the bottom of the box, and the small
flattened particles of metallic lead, fall from the lower
end of the sieve into a special receiver. The sifted
white lead is mixed with water, and thoroughly
ground under mill-stones.
In several manufactories in the neighborhood of
Lille, the scales of white lead are powdered between
WHITE COLORS. 67
several pairs of horizontal grooved rollers. The
divided substances fall upon one or several metallic
sieves, and from them into hoppers which conduct
them to a receiving trough, where they are moistened
with a spray of water. The metallic lead falls into a
separate room. The whole of the grinding rollers
and sieves occupy the height of a story, and are
inclosed in wooden partitions. The upper hopper is
kept filled with the scales of white lead, so as to pre-
vent the escape of dust. Moreover it may be entirely
losed with a trap door. These dispositions are a
t hygienic improvement on the old process of
anufacture.
In those works of the department of the Seine,
where the lead is cast into grates or buckles, and not
into sheets, the separation of the white lead and its
dry pulverization and sifting are effected by mechani-
cal apparatus following one another, and placed in
closed rooms.
The first room contains a series of three pairs of
grooved rollers which separate the white lead from
the non-corroded metal, and another series of three
pairs of smooth rollers which grind the scales of white
lead. There is an opening at each opposite extremity
of the room : one for the passage of the endless cloth
carrying the corroded buckles ; and the other for the
escape of the cleaned lead which slides upon a sheet-
iron apron, perforated with holes and made to shake
by machinery. These grates or buckles of metallic
lead are received by one or two workmen, who put
apart the thin ones for remelting, and separate and
straighten those which are thick enough to go into
the beds again.
The scales of white lead, separated by the grooved
68 MANUFACTURE OF COLORS.
rollers, fall upon an endless cloth placed under the
shaking apron of perforated sheet iron, and are brought
upon the three pairs of smooth rollers, between which
they are powdered. The powder falls upon an inclined
plane, which conducts it to a pit, from which it is
taken up by an endless bucket strap (inclosed in
tight wooden troughs), and carried to the top of an
upper room, where the metallic sieve for the separa-
tion of the blue from the white lead is. The metallic
portions are received in a distinct place, and the white
lead falls on to the floor of the room, from which it
is removed when the dust has settled. In this
operation, the men who receive the buckles of lead
from the rollers, are still exposed to the dust of the
white lead, and remain but a few days at that work.
To sum up : the separation of the scales of white
lead, and their dry grinding and sifting, cannot be
considered a wholesome manufacture anywhere, al-
though there have been many improvements made
and hygienic precautions taken in most of the works
we have visited. Certain manufacturers have tried to
obviate the not very great danger of picking white
lead with the hand, by furnishing the men with
gloves. This precaution seems to us insufficient,
because gloves are often an impediment to the work,
and the men will be tempted to leave them off.
In the works where the separation of the white
lead from the non-corroded metal is not done by
hand, there is still danger of inhaling fine white lead
dust, when the thick buckles are straightened and
struck with the mallet. Lastly, a very fine lead dust
escapes from the rooms containing the grinding
apparatus, either from the apertures for the inlet or
:
WHITE COLORS. 69
outlet of the substances, or from the openings cut in
the wooden partitions for the passage of the shafting.
The causes of danger would quite cease to exist,
if the separation of the scales of white lead, their
grinding and sifting, were effected underwater; or,
at least, if the white lead and the metallic residues
were subjected to sprays of water immediately after
they leave the grinding apparatus. Such is the mode
f operation, as we learn from data of Mr. Le Play,
the English white lead works. There, all the
etallic residues are cast anew, before returning to
e beds. We call the attention of manufacturers and
f the public administration to this method, which
resents no serious difficulties, since it is generally
practised in England. The white lead is also de-
prived, by washing, of certain soluble salts which
may injure its purity; moreover the subsequent ope-
ration is always effected with the aid of water. '
IV. The white lead is mixed with water in troughs,
as to form a soft paste which passes successively
through several horizontal mill-stones before it is
thoroughly comminuted. This wet grinding is abso-
lutely without danger, since the men do not touch
the white lead with their hands, but carry it in scoops
or ladles.
V. In all the works which we have visited, the
soft paste of white lead is poured into conical earthen-
ware pots, which are dried in a stove room. The
greater part of the water is expelled, and the blocks
becoming contracted, are easily removed from the
pots. Their thorough drying is finished in another,
or the same, stove room.
The sides of the pots are coated with white lead,
which is generally scraped off with an iron tool. This
70 MANUFACTURE OF COLORS.
operation is performed by women or children, and is
not without inconvenience. It is remedied in certain
works, by washing the pots in water; but this
involves more labor and expense. Part of the white
lead is sold, after drying, in the shape of conical
blocks, which are wrapped in paper and put into
barrels, care being taken not to break them. This
handling of white lead is not entirely wholesome,
although, with the proper precautions, it is not dan-
gerous.
In an establishment of the department of the Seine,
the white lead is not put into pots ; but the soft paste
is poured upon a cloth which is then folded so as to
form a square flat bag. Several such bags, separated
by square wooden trays, are afterwards squeezed in a
hydraulic press, which expels the greater part of the
water. After unfolding the cloth, the block of white
lead is cut into prisms or bricks having sufficient
consistency to be carried immediately into the drying
room. A small proportion of the product of these
works is sold in the shape of dry prisms; but their
packing in barrels is not done with the same care as
with the conical blocks, because the products go to
consumers sufficiently learned to know that the ex-
ternal shape of white lead is no proof of its good or
bad quality. The bricks or prisms of white lead are
compressed in the barrel by the cylinder of a hydraulic
press,
VI. The greater part of the white lead in lumps
requires to be ground and sifted again before it is
ready for sale. This second grinding, in the majority
of works, is still done with vertical stones rolling
upon a stone bed. The ground stuff is shovelled into
the hopper of a cylindrical silk sieve, inclosed in a
WHITE COLORS. 71
wooden box, where the fine white lead falls. That
which has not passed through the meshes of the sieve
is collected in another box, and ground anew. The
sifted white lead is removed from its box, after the
dust has subsided, and packed in barrels either by
shaking, or by a slight ramming.
The grinding, sifting, and packing of the dry white
lead by the foregoing method, are evidently danger-
ous on account of the dust floating in the workshop.
The inconveniences can be considerably diminished,
by inclosing within wooden partitions the mill-stones
and the sieve, as is practised in lead works at Lille,
where the vertical stones have been replaced by hori-
zontal ones of white marble. Each pair of stones is
within a drum, on top of which is a hopper filled with
the lumps of white lead, coarsely broken by means of a
*otary grooved cone placed within it. The powdered
taterial is, by centrifugal force, projected against the
[rum, and falls by two diametral openings into the
;ieve below, which is also well inclosed. In order to
prevent the dust from flying during the packing, the
white lead is compressed by means of a wooden disk,
of nearly the same diameter as that of the barrel, and
pressed downwards by a screw.
VII. The works in the neighborhood of Lille
sell the greater part of their products in the shape
of powder or lumps : that is, about one-third in lumps
and two-thirds in powder. A manufacturer of the de-
partment of the Seine has all the apparatus necessary
for grinding the white lead in oil, and seven-eighths of
his production is sold as a paste holding from 7 to 9
per cent, of oil. The prisms of white lead are ground
in a kind of coffee mill, which delivers a not very fine
powder. The powder is then put into a horizontal
72
MANUFACTURE OF COLORS.
cylinder, with a certain proportion of oil, and mixed
by means of iron paddles fixed to the shaft running the
length of the cylinder. From thence the paste passes
between a series of cast-iron rollers, and becomes fine
and homogeneous. More oil is added if necessary.
The finished paste is kept under water in large tubs,
from whence it is taken for packing.
Thus, when white lead is ground in oil in good
apparatus, like those we have seen in operation, it is
not necessary to grind it into a fine powder, and we
avoid one of the most unwholesome operations. It is
therefore highly advantageous that all the white lead
(and we believe that by far the greater part of the
white lead is always ground in oil) should be mixed
with oil in the works themselves, instead of in many
separate shops, where the men are subject to lead
colics, from want of proper precautions and apparatus.
It appears certain, from what we have seen in a lead
works at Birmingham, and from the data of Mr. Le
Play, that the English manufactories deliver the
greater part of their products in the shape of a paste
holding from 8 to 9 per cent of oil.* It is highly
desirable that the same thing should be done in
France.
In the majority of white lead works, certain
hygienic precautions are required of the workmen.
Thus, when they leave work, they wash their hands,
arms, and faces. Soap, fuller's earth, and sometimes
tubs filled with a solution of sulphide of potassium,
are put at their disposal. In one of the Paris works,
* In England, at least in several works, there are three brands
of white lead paste; the first is pure white lead with from 8 to 9
per cent, of oil; the other two qualities contain sulphate of baryta
in the proportions of about 15 and 25 per cent.
WHITE COLORS. 73
tubs for sulphuretted baths are placed in a room near
the boilers which furnish the necessary steam.
The men are alternately put to the unwholesome
parts of the work, and do not remain long there. A
cloak-room where the men leave their working clothes
after work, exists in several factories. Nearly every-
where they receive gratuitously the first cares of a
physician who is paid by the manufacturer.
The work-rooms are generally large and well ven-
tilated, especially where the dry white lead is ground
and sifted. However, the walls and the shafting are
covered with white lead dust, even when the grinding
apparatus is inclosed; and this demonstrates that the
grinding operation is not entirely innocuous.
Our own observations and the data we have col-
lected, allow us to state that the general manufacture
of white lead is not so dangerous as some persons may
believe, and this is proved by statistics collected in
the hospitals of Paris for several years past. There
are, however, great differences in regard to salubrity,
between the different works we have visited. No-
where have the old processes failed to receive some
improvement; but, even the most perfect works are
open to some objections in regard to the separation
of the white lead from the non-corroded metal, and
the dry grinding and sifting, which precedes the wet
grinding between the horizontal stones.
Before proceeding further, we believe that it is now
desirable to add a few theoretical considerations on
the manufacture of white lead, which are due to Mr.
Pelouze, who has paid great attention to that sub-
ject.
4 The Holland process," says Mr. Pelouze, "which
has been carried on at Lille, where it has become a
74 MANUFACTURE OF COLORS.
prominent manufacture, consists in exposing sheet
lead to the vapors of vinegar and to the gases of stable
manure. The vinegar used is that made from inferior
beer, and contains but a small proportion of acetic
acid. From the examination I have made of that
vinegar, and with the numbers furnished to me by
MM. Lefebre and D6coster, manufacturers of white
lead at Lille, the weight of real acetic acid is less than
1£ per cent, of the weight of lead employed, and in
good corroding operations nearly the whole of the
metal is transformed into white lead. Mr. Graham,
in England, has arrived at similar results, and with
even a less percentage of acetic acid. It is therefore
impossible that the carbonic acid of the white lead
should be derived from the decomposition of the
vinegar.
" Moreover, manufacturers are well acquainted with
the fact, that no white lead is obtained when drafts
are not established between the different parts of the
beds.
"The theory of this process is therefore very simple.
The air produces the oxidization, and the vinegar,
volatilized by the heat of the fermenting manure,
unites with the oxide of lead, being then displaced
by the carbonic acid disengaged by the manure. A
considerable portion of the acetic acid is found in the
unwashed white lead made by the Holland process.
" I believe that such is the reaction, and since I
have left Lille where I was able to study that manu-
facture, I have held this theory as being the most
rational.
" I have made an experiment which well demon-
strates the mode of action of the vinegar in the forma-
tion of white lead. I have compounded an artificial
WHITE COLORS. 75
atmosphere of oxygen and carbonic acid, and in it I
have placed a piece of sheet lead exposed to the vapors
of vinegar in a cup underneath. After three months
the lead was covered with a crust of white lead, the
proportion of which was in the ratio of the oxygen
and carbonic acid absorbed, whereas most of the
vinegar was found in its previous state. The pro-
portion of acetic acid causing the transformation into
white lead was so small that it could not be ascer-
tained.
" Another very curious experiment, in my own opin-
iori, fully demonstrates the true action of acetic acid
in the formation of white lead, and the necessity of
employing in that manufacture an acid which may
produce with oxide of lead a basic or subsalt which
may be decomposed by carbonic acid.
"If in the preceding experiment we substitute for
the vinegar formic acid which does not produce basic
salts with oxide of lead, there is no white lead formed
even after a contact of several years of the vapors of
formic acid, the lead and the gases, oxygen and car-
bonic acid. Formic acid, however, is very near to
acetic acid in its affinities and its volatility ; but as
it does not make basic salts with oxide of lead, and
as the neutral formiate of lead is not decomposed by
carbonic acid, it is therefore unsuitable for the manu-
facture of white lead."
Mr. Hochstetter thought, notwithstanding the pre-
ceding observations, that it was still necessary to
directly ascertain whether air was the only oxidizing
agent in the manufacture of white lead, especially in
the Holland process.
Adding to his own experience the explanations of
the above-mentioned chemists, he attributes the form-
76 MANUFACTURE OF COLORS.
ation of white lead to two distinct causes in the
Holland process : —
First, to the subacetate of lead which results from
the contact of the air, lead, and acetic acid. This
salt is decomposed into carbonate of lead and neutral
acetate in an atmosphere saturated with carbonic acid
and dampness.
Second, to the decomposition of the neutral acetate
by wet carbonic acid. Carbonate of lead is produced
and acetic acid is displaced.
For a long time it has been stated that white lead
is not a neutral carbonate of lead, but a subcarbonate
or a combination of neutral carbonate with a six
basic acetate. The examination of this question was
of practical interest, since the lesser consistency of
the Holland white lead was due in the opinion of Mr.
Mulder to the presence of an hydrated oxide of lead.
The author has therefore repeated the analyses of
the latter chemist nearly in the same manner, and the
results have been as follows : —
Krems' White.
Washed. Atoms.
Calculated
Oxide of lead .
. 83.77
83.97
8
84.06
Water .
. 1.01
0.84
1
0.85
Carbonic acid
. 15.06
15.03
7
14.05
99.84 99.84
Precipitated White Lead of Magdeburg.
Oxide of lead .... 85.93 ... 3 86.3
Water 2.01 ... 1 2.3
Carbonic acid . . . 11.89 ... 2 11.3
White Lead of Unknown Manufacture.
Oxide of lead .... 86.40 ... 3 86.3
Water 2.13 ... 1 2.3
Carbonic acid 11.52 2 11.3
WHITE COLORS. 77
Krems1 White.
Washed. Atoms. Calculated.
Oxide of lead .... 86.25 ... 3 86.3
Water 2.21 ... 1 2.3
Carbonic acid . . . 11.37 ... 2 11.3
White Lead Prepared by the Author in Imitation of the
Holland Process.
Oxide of lead 84.42 8 84.6
Water 1.36 1 0.8
Carbonic acid . . .... 14.45 Y 14.5
These experiments prove, indeed, that none of the
samples examined are a pure neutral carbonate, and
that the missing carbonic acid is replaced by water.
It seems, therefore, that white leads may often be
variable combinations of carbonate and of hydrate of
lead. We shall again examine this point further on.
The author has prepared a white lead by pre-
cipitating the subacetate of lead with carbonic acid
until the liquor began to be acid. The precipitate
perfectly washed with boiling water, gave : —
Washed. Atoms. Calculated.
Oxide of lead 86.02 3 86.4
Water 2.44 1 2.3
Carbonic acid . . . . . 11.45 2 11.3
Corresponding to the formula 2(PbO.C02) -f PbO.HO.
This white lead suspended in water and submitted
for a long time to a stream of carbonic acid does not
change. But if a few drops of acetic acid are added
before the treatment with carbonic acid, it becomes
neutral carbonate. -
The author has prepared, by precipitation, nume-
rous samples of white lead, and all had the composi-
tion of the French white lead. However, he does
not decide on the question of the body or covering
property, between the white lead prepared by the Hoi-
78 MANUFACTURE OF COLORS.
land and French processes. By microscopic exami-
nation no sensible difference of texture was detected,
nor was any sample with a crystalline texture. If
the good quality of white lead be due to the absence
or to the presence of but a slight proportion of
hydrate, it is now possible to obtain, by precipitation,
a white lead answering to this condition.
3d. The French or Clichy Process, by Thenard.
Thenard was the first to point out a process for the
manufacture of white lead, which was applied later
by Mr. Hoard in a large establishment near Paris, the
products of which are known under the name of
Clicliy white lead. The chemical reactions on which
this process is based are as follows : —
If a solution of basic acetate of lead, sometimes
called Extract of Saturn, be treated with carbonic
acid, part of the oxide of the salt is converted into
carbonate of lead, and the remainder becomes neutral
acetate. By adding a new proportion of litharge or
oxide of lead to the solution of neutral acetate, this
becomes basic again by the solution of the oxide.
"We see, therefore, that these reactions permit of the
manufacture of white lead by a continuous and
economical production of basic acetate.
"Without thoroughly considering all the manipula-
tions of this process we shall indicate the mode of
operation.
A solution of basic acetate of lead, marking from
16° to 18° Be., is made by boiling a solution of neu-
tral acetate (sugar of lead) with very finely powdered
oxide of lead (litharge). There is no difficulty in
this operation.
When the litharge has become dissolved, and the
WHITE COLOTtS. 79
basic solution is well saturated, the liquor is decanted
from the impurities in the litharge or the acetate,
into a closed vessel. Then the carbonic acid is
introduced, which gas may be produced by several
methods, such as the calcination of chalk or the com-
bustion of carbon. At all events the gas should be
previously well washed, so as not to add impurities
to the white lead.
As soon as it is ascertained that all the basic
excess of oxide of lead is transformed into carbonate,
the liquors are allowed to settle. The carbonate
falls to the bottom, and the supernatent solution of
neutral acetate is decanted to be boiled again with
oxide of lead, and become, as we have said, basic
acetate.
There is, however, at each operation a certain loss
of neutral acetate, which must be replaced and ren-
dered as small as possible by careful manipulation.
The settled carbonate of lead is first washed with
a small proportion of water, which is added to the
decanted solution of acetate. The washing is then
continued with larger quantities of water, which are
thrown away, since they are too poor in acetate.
.The paste of white lead is put into pots, and dried in
the stove room.
This Clichy white lead is in impalpable powder and
as white as snow ; but, compared with those of Krems
and Holland, it has less density 'and body, that is,
covers less.
The manufacture of white lead, by the The*nard
process, has been established at Portillon, near Tours,
by MM. Pallu and Delaunay, with a perfect under-
standing of its theory. Thanks to a report made in
1856 to the "Societe d'Encouragement" by MM. A.
80 MANUFACTURE OF COLORS.
Chevalier, F. Barral, and Gaultier de Claubry, we are
enabled to explain this manufacture.
Preparation of the oxide of lead. — The works of
Portillon, as stated by the above delegates, contain
five furnaces with double fire-places, four of which
are in constant operation, and use bituminous coal as
fuel. The furnaces are built directly in the rock, and
calcine 1800 kilogrammes of lead at each operation.
The leads employed bear the best brands of Andalusia
and of England, and are analyzed at the works so that
the best only may be received. The bed of each furnace
is built with fire-brick holding as little silica as possi-
ble. The shape is nearly circular, about 3.40 metres
in diameter, and with two lateral fire-places. It is
hollow, so as to retain the molten metal. The vault
is surbased, and 60 centimetres (0.60 metre) is the
greatest distance between the bed and the ceiling of
the vault.
During the heating, the gases of the combustion
escape through an opening or hood, placed in front of
the aperture used for charging the metal or extracting
the oxide. This hood connects with an upper fur-
nace where the transformation of the oxide of lead
into red lead takes place.
Twelve hours are required for oxidizing 1500 kilo-
grammes of lead ; but the oxide still contains a large
proportion of metal or blue lead, which is separated
and returns to the calcining furnaces. Half of the
oxide produced is for the manufacture of white lead,
and the other half for that of red lead.
Manufacture of the white lead. — The oxide of lead
intended for the preparation of white lead is moistened
with water, and spread over a wooden floor above two
saturating pans lined with copper. These pans are
WHITE COLORS. 81
supplied with stirrers composed of a wooden frame
with bronze projections, which reach to about 1 or 2
centimetres from the bottom. One of the pans is
raised above the other, so that the excess of liquid in
the upper one may run by a spout into the lower one.
The latter pan, at the middle of its height, is connected
with a duplex bronze pump.
The two pans are filled with water rendered acid
by about one-fortieth of pure pyrol igneous acid
marking 30 acetimetric degrees. While the stirrers
are in motion, a certain proportion of damp oxide of
lead is poured in, and becomes dissolved in part. The
pump is then set to work, and forces the solution into
three large tanks, lined with copper, placed in an upper
story, and which connect with each other. These tanks
have stirrers like those of the saturating pans, and
which are kept in motion during the whole operation.
Besides the pipes for conducting the liquors, these
three apparatus are provided with pipes and inverted
gutters, perforated with numerous small holes, through
which a continuous stream of carbonic acid escapes.
The average specific gravity of the solution is 5° Be.
During this operation the pump takes from the
saturating pans the solution of basic acetate, and
carries it into the precipitating tanks where it is
brought into contact with the carbonic acid. The
white lead is immediately formed, and the liquid,
which must still retain a certain proportion of basic
acetate, passes into the settling tanks where the white
lead becomes deposited. The liquor then goes back
to the saturating tanks, and the operation begins
anew. It is, as we see, a system of circulation in
which machinery performs most of the work, and
hand labor is reduced to a minimum.
6
82 MANUFACTURE OF COLORS.
After a certain length of time, the settling tank is
sufficiently filled with white lead, that is, when this
material reaches the level of the overflow. The solu-
tion is then made to pass into other vessels and the
white lead is washed in washing tanks, which are pro-
vided with wooden horizontal stirrers having a rotary
motion.
The settled white lead is covered with twice its
volume of pure water and stirred. Three washings
take place, and at each, the material is allowed to
deposit, and the water ahove is decanted.
The white lead is then conducted into large basins
built of porous stones, which absorb part of its damp-
ness. After a few days, the material is divided into
blocks which are still quite wet, and which are
pounded by wooden vertical stamps falling into a
wooden trough inclined from the front backwards.
This stamping renders fluid the white lead which
appeared half dry before. The stuff is then put into
small movable boxes, holding about 400 kilogrammes,
and which are carried to the drying-room. It is
sufficient, for filling the pots, to open and close the
trap-doors at the bottom of these boxes.
When the white lead is to be sold in powder, the
stamped paste is run into wooden frames, which are
set upon a brick platform heated underneath. "When
dry, it is put upon a distributor similar to that used
for red lead, but larger, and which projects it upon a
sheet-iron ventilator having four wings. The venti-
lator is inclosed within cast-iron plates, and is followed
by a rectangular trough of the same metal, about 1
metre long. At the top end of the trough there is a
sheet-iron pipe 35 centimetres in diameter, 8 metres
long, and nearly vertical, which communicates at its
WHITE COLORS. 83
upper end with a large sheet-iron chamber, to the bot-
tom of which are fixed two funnels or hoppers closed
by lateral sliding plates. Below the opening of the
vertical pipe, and in the cast-iron trough, there is a
cast-iron hexagonal prism which rotates and pulver-
izes the coarse portions of white lead which have not
reached the upper chamber, and delivers them back to
the ventilator. The white lead deposited in the iron
chamber above is in impalpable powder.
The distributor, like that for red lead, has an aspi-
rator, so that there is no danger of dust being inhaled
by the men.
The above operations apply to the preparation of
white lead in lumps and in powder, as is generally
required by the trade. However, for several years
past, part of the white lead has been ground in oil,
which is a hygienic progress, since numerous cases of
lead colic have been observed among those who
grind white lead in the shops of color dealers.
The grinding of white lead in oil is done at the
works of Portillon as follows : the stamped and still
damp material is introduced into a kneading machine
with the given proportion of oil, and soon transformed
into dough, which is removed through a side opening.
The paste is then ground between metallic rollers
heated by steam, and the water expelled. After
another passage through an ordinary grinding appa-
ratus, the paste is put into zinc cans soldered or closed
tight.
The carbonic acid used for the manufacture of
white lead, and which passes through the solution of
subacetate, is produced by the combustion of cheap
charcoal dust, cemented into bricks by means of a
small quantity of clay. The gas is aspirated from the
84 MANUFACTURE OF COLORS.
combustion furnace by means of a series of inverted
drums plunging into water, and which act as pumps.
Here are also a few data on a modification of this
process, practised in England, and the description of
which is due to Mr. Preisser.
The lead is smelted in a cast-iron kettle with a
spout, which delivers it upon the bed of a large
reverberatory furnace, in which air is constantly in-
jected by a ventilator. The lead becomes divided,
offers A large surface to the air, and runs into a
channel the lateral sides of which are perforated with
small holes. The lead is oxidized, and the litharge
escapes through small apertures which may be opened
at the same time. The silver, if any, remains at the
bottom of the channel. This mode of preparing
litharge is very easy and rapid.
The litharge is then finely divided, and, after being
moistened with 1 per cent, of acetate of lead dissolved
in water, is put into horizontal troughs, closed on top
and communicating one with the other. A stream
of impure carbonic acid, produced by the combustion
of coke in a reverberatory furnace, with air projected
by two powerful centrifugal ventilators, passes all
the while through the layers of oxide. The pressure
exerted by the ventilators is sufficient to overcome
the resistance of the layers of litharge. The gases
are cooled in pipes immersed in water.
In order to bring all the particles of oxide into
contact with the carbonic acid, and aid the combina-
tion, a system of rakes, moved by machinery, keeps
the mass constantly stirred.
The white lead obtained by this process is good for
painting, and is perfectly white. It covers well, and is
WHITE COLORS. 85
preferred in England to that prepared in the wet
way, which contains crystalline particles.
4th. Pattinson Process.
By means of a chemical reaction, by double ex-
change of bases and acids, Mr. Pattinson obtains
carbonate of lead on the one hand, and on the other a
solution of lime salt, the nature of which depends on
that of the lead salt employed. The salts which he
perfers are the chloride and the nitrate.
Here are the chemical phenomena observed when
carbonate of lime and chloride of lead react on each
other. Equivalent proportions of these substances
are triturated together, that is, 140 parts of chloride
of lead, and 50 of carbonate of lime, and sufficient
water is added to make a thin paste. After a certain
length of time, indications of chemical reaction ap-
pear, the paste becoming thicker, drier, and nearly
hard. Afterwards the solid mass begins to deli-
quesce, and soon resolves itself into a concentrated
solution of chloride of calcium, and a white precipi-
tate of carbonate of lead mixed with undecomposed
carbonate of lime and chloride of lead.
After decanting the solution of chloride of calcium,
and replacing it by pure water, the former decompo-
sition continues ; and if this operation be repeated
several times, accompanied by trituration of the sub-
stances, the carbonate of lime and the chloride of
lead are quite entirely decomposed, and the residue
is nearly pure carbonate of lead. This complete de-
composition requires from seven to fifteen days, and
still there remain traces of chloride of lead and car-
bonate of lime, which may be detected by chemical
analysis.
86 MANUFACTURE OF COLORS.
The reaction is quite similar, either in its nature
or in the length of time required, when we triturate
together equivalent proportions of nitrate of lead
(166 parts) and of carbonate of lime (50 parts).
Moreover, it has been ascertained that the decomposi-
tion of the nitrate or chloride of lead is more rapid
when, instead of pure water, a solution of carbonic
acid gas is employed. Indeed, carbonate of lime is
soluble in water impregnated with carbonic acid, and
is in a form which renders the reaction more rapid
and complete. As soon as the soluble carbonate oJ
lime has \been decomposed the free carbonic aci<
causes the solution of another proportion, which ii
decomposed in its turn, and so on, the operatioi
being continued with the same proportion of carboni<
acid until the decomposition is complete, if the mix-
ture has. been made in accurate chemical proportions.
But as the water impregnated with the carbonic aci<
becomes by degrees a more and more concent rate<
solution of lime salt, it is. preferable, towards the en<
of the operation, to replace it by fresh water holding
carbonic acid. It is even better to change the watei
several times, so as to insure the decomposition ol
the entire carbonate of lime employed. It is als<
necessary to stir the contents frequently.
After these observation we now pass to the prac-
tical process of the white lead manufacture.
The mill in use is similar to that employed in
pottery and earthenware factories for grinding flint
stones in water. A strong wooden tank, bound with
iron, has its bottom filled with blocks of quartz or of
French burr, cemented together, and with a level sur-
face. Other large stone blocks are made to revolve
over the lower surface, and grind to a fine powder
WHITE COLORS. 87
the hard and brittle substances which have been
put into the mill with the addition of water. For our
purpose the running stones need not be so heavy as in
pottery works, because the materials do not require
the same degree of comminution. We should avoid
employing iron whenever this metal may be in con-
tact with the ground substances, and use copper for
the metallic parts of the inside of the tank.
In a mill of that kind, 4 metres in diameter and 1
metre high, the charge is 1066 kilogrammes of chlo-
ride of lead and 380 kilogrammes of carbonate of
lime, the best of which is washed chalk. As much
water is added as will just not run over by the motion
of the stones, and the grinding operation lasts six
hours. After that the tank is almost entirely filled
with water, and allowed to stand till the next day,
when the deposit is found to be carbonate of lead
mixed with the undecomposed carbonate of lime and
chloride of lead. The supernatant liquor is a clear
and concentrated solution of chloride of calcium,
nearly free from lead, and which is decanted by means
of a siphon or a stopcock. A new quantity of water
is put into the mill, and the grinding is repeated for
a few hours, followed by a settling and a decanting
on the next day, and so on, until from the seventh
to the fifteenth day, when the solution has no taste, and
the decomposition is complete.
The white substance at the bottom of the mill
is nearly pure carbonate of lead, with but traces of
chloride of lead and carbonate of lime, and is removed,
dried, and prepared in the ordinary manner for the
trade.
A modification of this process consists in adding,
at first, an excess of chloride of lead, that is, 1264
88 MANUFACTURE OF COLORS.
kilogrammes for 380 kilogrammes of carbonate of
lime, and grinding, settling, and decanting the liquors
until all the carbonate of lime is decomposed, which
is ascertained by the absence of a bitter taste in the
solution. Then the excess of chloride of lead is
transformed into carbonate by the addition of about
200 kilogrammes of soda crystals, or an equivalent
proportion of carbonate of potassa. The liquor
should remain slightly alkaline. The grinding is
continued until all the chloride of lead has become
carbonate; and, afterwards, the chloride of sodium
or potassium is removed by washing. In this manner
the length of the operation is shortened and the car-
bonate of lead is purer.
The inconvenience of this method is that, beside
the greater expense due to the alkaline carbonate, a
small proportion of chloride of lead is dissolved in
the washing liquors before the carbonate of lime is
throughly decomposed. It is true that the lead may
be recovered from the last washings by a precipitation
with a sulphide of potassium or sodium.
If, instead of grinding in pure water, we use a
solution of carbonic acid, the operation is performed
as follows : A vessel, barrel-shape, which may be
of wood, copper, or lead, and about 0.75 metre in
diameter and 1.20 in height, is tightly bound with iron,
and has its heads sufficiently stout to resist the neces-
sary pressure. It revolves upon two trunnions, one of
which carries a fast and a loose pulley, so that motion
may be given or arrested at will. The other trunnion
is hollow, and has a stopcock communicating by a
universal joint with the pump, which forces the car-
bonic acid into the vessel.
Through a side opening, 50 to 75 millimetres in
WHITE COLORS. 89
diameter, 70 kilogrammes of chloride of lead and 25
kilogrammes of carbonate of lead are introduced.
The vessel is then nearly filled with pure water, the
opening is closed with a screwed plate, and carbonic
acid is forced through the hollow trunnion under a
pressure of from four to five atmospheres. After
closing the stopcock, the barrel is set in motion, and
revolves about twenty times per minute. . The sub-
stances begin to react one upon the other: the car-
bonic acid with which the water is saturated dissolves
he carbonate of lime and presents it to the chloride
f lead in such a state that the decomposition is im-
ediate. The reaction is continued for two or three
ays, and is then so near the end that but little
carbonate of lime and chloride of lead remain unde-
composed ; and, in their stead, there is carbonate of
lead and a concentrated solution of chloride of cal-
cium. The motion of the barrel is then discontinued,
and, when the contents have had time to settle, the
clear liquid is siphoned off through the lateral open-
ing and replaced by fresh liquor, which is saturated
with carbonic acid as previously. The barrel is made
to revolve for two or three days more, when the decom-
position is completed, and the carbonate of lead ob-
tained requires but a thorough washing and drying.
In this second mode of operation an excess of
chloride of lead may be employed to promote a more
rapid decomposition of the carbonate of lime. The
remaining chloride of lead is decomposed in the barrel
with a slight excess of an alkaline carbonate, as we
have already explained.
When nitrate of lead is employed the operation is
the same as with the chloride, whether we use pure
water or that saturated with carbonic acid. The
90 MANUFACTURE OF COLORS.
equivalent proportions are for the stone mill — 1264
kilogrammes of nitrate of lead and 380 kilogrammes
of carbonate of lime, and, for the revolving vessel, 83
kilogrammes of nitrate of lead and 25 kilogrammes of
carbonate of lime.
In either case the substances are allowed to react
upon each other until the decomposition is complete.
The resulting white lead is then washed, dried, and
packed in the usual manner.
Sometimes, also, a solution of carbonate of lime in
water saturated with carbonic acid is effected in the
revolving apparatus, and is poured into tanks holding
the solution of either chloride or nitrate of lead. A
pure carbonate of lead is immediately precipitated.
We shall now quote from Mr. F. Heeren, a manu-
facturing chemist, who has carefully studied a pecu-
liar white lead, prepared by another Pattinson process.
"The white lead of Mr. Pattinson is distinguished
from the ordinary kind by its composition, which is
a basic chloride and an oxychloride of lead, instead
of a combination of oxide of lead with carbonic acid.
"Mr. Pattinson prepares his white lead from crude
galena (sulphide of lead) abundant in England, and
which often contains silver. This latter metal is
entirely collected, and the sulphur is also employed.
" The finely powdered galena is heated in closed
lead vessels with concentrated hydrochloric acid,
which is produced in large quantities in soda works,
and which is very cheap. By this treatment the
sulphur is transformed into hydrosulphuric acid
(sulphuretted hydrogen) which is burned in the
furnace of sulphuric acid chambers, and thus assists in
the production of sulphuric acid. The lead is trans-
formed into chloride, and as this salt is but slightly
WHITE COLORS. 91
soluble, large volumes of boiling water are employed
in order to separate the sulphide of silver contained
in the gelena. The boiling solution of chloride of
lead, in order to pass to the basic state, needs to be
mixed with lime-water. It is absolutely necessary
that the mixing should be effected very rapidly in
order to obtain the basic chloride of lead in the shape
of an exceedingly fine powder which covers well. A
slow and gradual mixing results in a crystalline pre-
cipitate which does not cover well.
" Another condition is that the proportion of lime
should be exactly calculated for neutralizing half of
the chlorine of the chloride of lead, and that the pre-
cipitated basic salt should contain equal atoms of
chloride and of oxide of lead. The clear solution of
lime is in one tank, the hot one of chloride of lead is
in another tank, and they are mixed together by
regulating their running into a third tank by means
of stopcocks.
" One inconvenience of this manufacture is, that,
the chloride of lead being but slightly soluble even in
boiling water, very large vessels are needed, and the
consumption of fuel to heat the water is considerable.
A neutral chloride of lead requires about twenty-two
times its own weight of boiling water to be dissolved,
and theoretically for fifty kilogrammes of Pattinson's
white lead 1219 litres of boiling water are required
for the chloride of lead, plus 4420 litres for the lime,
altogether 5639 litres, occupying a cube having 1.80
metres in every direction.
6 When experimenting with this process on a small
scale, I have found out another difficulty, i. e., when
powdered galena is treated with hydrochloric acid,
the surface of the grains is soon coated with chloride
92 MANUFACTURE OF COLORS.
of lead which arrests the action of the acid. The
entire galena is dissolved only when a large excess of
hydrochloric acid is employed sufficient to dissolve
the whole of the chloride of lead formed. However,
the expense of such an excess of acid may be avoided
by decanting the hot solution into another vessel as
soon as the action ceases, and allowing it to become
cold and to deposit the chloride of lead. The cold
acid is decanted and used again upon the galena, and
when saturated with chloride let to cool off.
" The chloride of lead thus obtained and drained,
is washed with small proportions of cold water in
order to remove the free acid and any iron salt which
otherwise would discolor the white lead. It is then
dissolved in boiling water.
" Several samples of Pattinson's white lead which
I have examined, are not pure white, but with a
slight brownish shade which is scarcely sensible when
a small proportion of black or blue is added to them.
On the other hand, it covers particularly well. I have
ground equal parts of Pattinson's and Krems white
lead with equal proportions of oil, and I painted with
them surfaces of equal area; the Pattinson white
lead had evidently the best covering power. It is
very bulky, possesses great body, and absorbs a large
proportion of oil."
5th. Woolrich Process.
Commercial lead is granulated by means similar
to those used for making lead shot, and the granules
are put into a cylindrical or hexagonal stoneware
vessel, which may be made to revolve upon a central
shaft passing through two holes at the opposite ends
of the vessel. During the motion the lead is kept
WHITE COLORS. 93
constantly wet with a neutral solution of acetate of
lead of specific gravity 1.6. By the mutual attrition
of the granules of lead, aided by the above solution,
particles become separated which are washed out
every twelve hours. Fresh proportions of granulated
lead moistened as we have said, are then added to
make up the loss by attrition and decomposition. The
separate particles with the washings are collected in
a closed vat, through which is injected carbonic acid
produced by the combustion of charcoal or coke. The
substances are kept stirred by proper machinery, and
there is produced a carbonate of lead which settles in
a few hours, and is removed after the washing liquors
have been decanted.
A hexagonal vessel 55 centimetres in diameter,
and 1.60 metre high, will hold from 400 to 500
kilogrammes of lead.
6th. Versepuy Process.
An Italian once made the observation that when
granulated lead is comminuted by friction, it becomes
transformed into white lead by absorbing carbonic
acid. Mr. Versepuy thus states the improvements
he has brought to that system : —
:< Fragments of lead are put into a stone cylinder
(made of Volvic lava if possible) and covered with
water. After twelve hours of rotary motion, the
metallic mud is poured into a wooden tub having a
wooden stirrer in the middle and two ventilators on
the upper surface with the proper capping to prevent
the liquor from running over.
"The inside surfaces of the stone cylinder become
coated with a layer of white lead which prevents
further waste of stone, and is believed to act as a
94 MANUFACTURE OF COLORS.
leaven for the oxidization of the molecules of lead
during the further operations.
" It is not necessary in a regular operation to
employ lead in a thorough state of division.
"Water is necessary for separating the particles of
lead produced by mutual attrition.
" The metallic mud should be removed from the
stone cylinder and from the undivided lead, in order
to aid its oxidization by an energetic stirring.
" The carbonic acid of the air is sufficient to pro-
duce the carbonate, and no advantage has been found
in the use of artificial carbonic acid or of an atmos-
phere of this gas in the tub. The same may be said
of an addition of acetic or nitric acid or of one of
their salts.
" This process, as we see, is very easy and economi-
cal. The operation is not complicated by the addi-
tion of any chemical agent, and mechanical manipu-
lation alone is sufficient to bring about the transfor-
mation of the metal into white lead.
"In this process everything favors the manufac-
turers of lead who own the raw material and may
utilize the water-power generally abundant in the
neighborhood of mines."
Since giving this description, Mr. "Versepuy has
improved his processes, which are thus described in
his patent of July 15th, 1846 : —
" I propose to oxidize lead at the ordinary tempera-
ture, under the influence of an energetic stirring, and
of the intimate and simultaneous contact of the metal
with air and water. The oxide thus obtained is car-
bonated by a liquid constantly saturated with car-
bonic acid.
"The process maybe divided into three distinct
operations : —
WHITE COLORS. 95
"First, the division of the lead to as great an ex-
tent as practicable, in order to obtain large surfaces
of corrosion.
" Second, the oxidization of the lead by the oxygen
of the air, and the immediate removal of the pellicle
of oxide by washing and stirring. The oxidization
may be aided by an energetic oxidizing agent, an
acid for instance.
" Third, the carbonatation of the oxide by its con-
tact with carbonic acid gas obtained by any desired
method.
" I know that similar processes have already been
tried, but the experimenters have never succeeded,
because they were not sufficiently aware of the im-
portance of each operation and of its results. They
have never employed a current of air sufficiently
energetic to furnish enough oxygen to the metal — or
an auxiliary oxidizing agent — or a subsequent, dis-
tinct, and well-conducted carbonatation.
" Here is the mode of operation which I found to
succeed best : —
" I. The lead is melted in a closed furnace, which
is a protection against the fumes being inhaled by
the men, and poured into cold water through a fine
metallic sieve. Small and light granules are thus
obtained which present a great surface to corrosion.
"II. The granulated lead is placed in the cylinder
P (Fig. 1), with one-fifth of its weight of water, and
a small proportion of some oxidizing agent. A pipe
K brings into the cylinder a brisk current of air,
forced in by means of a fan or of a screw-blowing
machine like Fig. 2. The pipe K passes through the
stuffing-box i, and the air is divided by a rose at J,
before it escapes from the cylinder at j'. A rapid
96
MANUFACTURE OF COLORS.
rotary motion is imparted to the cylinder, the inside
metal parts of which are of lead, in order not to injure
the oxide. The friction of the granules together and
Fig. 2.
against the sides of the cylinder, at the same time
with the chemical reaction which takes place, gives an
increase of temperature of from 55° to 60° C., and it
is important to keep it up
by making the operation
continuous. The rotary
motion of the cylinder
should not be too rapid,
so as not to keep together
by centrifugal force the
mass of granules, which,
on the contrary, should
fall and describe a curve.
This operation lasts about twenty-four hours, and
then the thick and yellowish liquid is removed from
the cylinder.
" III. The above mixture is diluted with twice its
weight of water, and poured into the cylinder M,
WHITE COLORS. 97
which may be of wood lined with lead. An inner
stirrer presents fresh surfaces to the action of carbonic
acid, and makes at least one hundred and fifty evolu-
tions per minute. A pipe D brings in the carbonic
acid gas produced by any desired method, and forced
in by mechanical action.
"It is possible to use the small proportion of car-
bonic acid held in atmospheric air, in which case the
carbonatation is slow, or the carbonic acid gas em-
anating from mineral springs, or from the reaction of
an acid upon a carbonate, or that produced in a lime-
kiln or from a fireplace. In the latter cases, a
screw-blowing machine, Fig. 2, is very suitable, since
the gases are cooled and separated from the ashes in
the water of the apparatus.
"In from fifteen to thirty minutes, according to
the quantity of material in operation, the action
is complete, the mass of oxide becomes white, and
there is an elevation of temperature of from 60 to
65° C. The white lead and water may then be re-
moved.
" It is well understood that the stream of carbonic
acid escaping from this cylinder passes into other
similar apparatus to complete its condensation.
' The white lead thus produced is by the usual
processes brought into the commercial shape."
In an addition to his patent (July 15th, 1847), Mr.
Versepuy expresses his disbelief in the usefulness of
an auxiliary oxidizing agent.
7th. Wood, Benson, and H. Gruneberg Processes.
We owe to Mr. Wood a process for manufacturing
white lead, which consists in introducing granulated
lead and water into a revolving; and horizontal hex-
98 MANUFACTURE OF COLORS.
agonal box, the two ends of which have openings for
the circulation of the air. A hydrated protoxide of
lead is formed, which is removed through a side open-
ing provided with a sieve, and which is saturated
separately with carbonic acid.
Mr. Griineberg, after a careful study of this method,
found out that a cause of failure was the formation,
in the revolving apparatus, of a peroxide of lead con-
jointly with the desired protoxide. By the treatment
with carbonic acid, the peroxide remains as such, and
colors the white lead a pink or reddish hue. As proof
that this coloration is due to the peroxide, the white
lead is dissolved in diluted nitric acid, and if the
washed residue be treated with hydrochloric acid and
a gold leaf, the latter becomes dissolved, thus show-
ing the presence of a peroxide.
Nevertheless. Mr. Griineberg uses for his process
the Wood apparatus, that is to say, a hexagonal re-
volving prism made of stoneware unacted upon by
acids. During the operation, the lead is submitted
to the simultaneous action of atmospheric air, acetic
acid, and carbonic acid gas. The atmospheric air
enters through openings on the heads of the prism,
and the acetic and carbonic acids through the hollow
axis.
In order to aid oxidation, the inside of the appara-
tus is provided with projecting ribs, which cause the
lead to fall down and to present fresh surfaces to the
action of the air. By means of the simultaneous re-
action of the air, of the solution of acetate of lead, and
of carbonic acid, the process resembles the Holland
method, except that it takes place in a revolving
apparatus. The conditions are excellent, since the
film of white lead on the surface of the metal is cou-
rt
g
:
WHITE COLORS. 99
stantly removed and fresh metallic surfaces are pre-
sented to the chemical agents. Eight days are suffi-
cient by this method for completely transforming
into white lead a given weight of lead which would
require two months by the Holland process.
The mutual friction of the lead, and the chemical
reactions which take place, cause an elevation of
temperature which is very advantageous and prevent
any crystallization of the white lead. This pigment,
washed out now and then from the apparatus, is so
fine that the ordinary operations of grinding and
floating are entirely unnecessary.
The mechanical motion added to the chemical
reactions, gives in one operation a product which
simply needs washing and drying to be ready for
sale. The formation of a peroxide is also avoided,
since, as soon as the protoxide is formed it changes
to a basic acetate, and has no time to absorb a larger
proportion of oxygen.
However simple this process may appear, it never-
theless presents many practical difficulties, and the
oxidation requires a great deal of care.
The introduction of air and carbonic acid should
be effected in certain fixed proportions. An excess of
carbonic acid does not produce the neutral carbonate
of lead (PbO.CO2) and the liquid in the apparatus is
all in a foam which envelops the lead and prevents
the access of the air. Thus, no oxidation takes place,
and the yield of white lead becomes low.
We should endeavor to produce the compound
2(PbO.CO9) + PbO.HO, and, on that account, the
substances inside of the revolving apparatus should
be kept in the basic state. This condition is ascer-
tained by trying the liquors with yellow turmeric
100 MANUFACTURE OF COLORS.
paper, which should turn brown. A basic milk of
white lead does not foam, but runs smooth and leaves
the granules of lead perfectly clean and ready to be
oxidized.
There should never be so much carbonic acid as
completely to decompose the basic acetate of lead, but
merely the proportion necessary to saturate a quantity
corresponding to the oxide formed. But as it is not
easy to remain always within the proper limits, it
will be well frequently to test the liquors with the
turmeric paper.
The basic excess of hydrated oxide of lead should
not, however, remain with the white lead, because it
renders the oil paints made with this pigment yellow.
Indeed, this oxide PbO.HO forms with the fatty
acids of the oil, a colored soap which requires a long
time to become decomposed by the action of light and
the carbonic acid of the air. By its transformation
into carbonate of lead, the desired whiteness re-
appears.
Moreover, a white lead with an excess of PbO.HO
has a great specific gravity, and as demonstrated
by analysis, has a composition near to the formula
3(PbO.CO') + 2(PbO.HO). This excess of oxide is
removed by adding to the thin paste of white lead,
enough acetic acid to prevent the turmeric paper
from becoming brown. The white lead has then the
composition 2(PbO.CO2) + PbO.HO which is a
durable combination without basic properties.
As this operation cannot be well done in the re-
volving apparatus itself, the white lead is washed off
with a very weak solution of subacetate of lead, into a
special tub where it is treated with acetic or carbonic
acid. The neutralized white lead is then allowed to
WHITE COLORS. 101
settle at the bottom of other tubs, and the solution of
subacetate is employed again for the oxidizing opera-
tion. The deposit is finally washed with pure water
and drained in a centrifugal apparatus.
The ordinary centrifugal apparatus with perforated
sides cannot be used for this purpose, because the
paste of the white lead soon clogs up the cloth spread
inside of the drum, and the water cannot be forced
out. It has therefore been thought more advan-
tageous to separate the water from the white lead by
means of the difference in their specific gravities,
according to the law that the centrifugal power of a
body is proportional to its increase of specific gravity.
After having tried a revolving drum without holes on
its sides, it was found that the thin paste of the white
lead was not following the same rapid motion of the
drum, and that by bringing the apparatus to a rest, the
water was diluting the white lead again. In order to
obviate this inconvenience, radial partitions were put
inside of the drum, and these carrying the liquid with
them, a complete separation took place in ten minutes.
The white lead, as a thick paste, lies against the sides
of the drum, and the clear water is on the top of it
and may easily be decanted. The white lead is then
put into pots, and dried first at the ordinary tempera-
ture, and afterwards in a stove.
The white lead prepared by this process remains
wet until it is packed, and there is no danger of its
dust being inhaled by the workmen. Nearly all the
work is done by machinery.
Observed under the microscope, this white lead
shows no angular or translucent parts; it is formed
of exceedingly small spheres, scarcely as large as
those obtained by the Holland process. These spheres
102
MANUFACTURE OF COLORS.
are entirely opaque, and this quality, with their fine-
ness, explains their great body or covering power.
The composition of this white lead, in the various
stages of its manufacture, is determined by decom-
posing a sample of it, dried at 120° C. with nitric acid
in the Geisler apparatus for determining by loss the
carbonic acid. Another portion of the dried substance
is melted in a covered porcelain crucible, so as to
ascertain by loss the carbonic acid and water. After
deducting the carbonic acid of the first test, the
difference or water allows of the calculation of the
hydrated protoxide of lead. On the other hand, the
proportion of carbonate of lead is calculated from that
of carbonic acid.
An analysis of the white lead manufactured by this
process gave : —
PbO
CO'
HO
86.34
11.34
2.32
100.00
And, as the calculated composition of the formula
2(PbO.CO2) + PbO.HO, is
PbO 86.37
CO3 11.32
HO 2.31
we see that the manufactured product contains a
slight excess (0.12 per cent.) of neutral carbonate of
lead.
In the Benson process, modified by Mr. "Wollner,
finely pulverized litharge is introduced into a long
horizontal wooden cylinder, with about 1 per cent, of
neutral acetate of lead, and sufficient water to make
a thin paste. The apparatus revolves slowly, and a
WHITE COLOKS. 103
continuous stream of carbonic acid gas, obtained by
the combustion of coke, is introduced through the
hollow axis. In order to absorb this gas as thoroughly
as possible, it is made to pass through several similar
cylinders connected together. The evaporated water
is replaced and the paste kept in a semi-fluid state.
After a few days all the litharge is transformed into
white lead, which is ground in two consecutive mills,
and compressed and dried.
Mr. Griineberg has still modified this process by
adding to the litharge about 50 per cent, in weight of
granulated lead. The latter not only reduces to a
great degree of comminution the white lead formed,
but also causes by its oxidation an elevation of
temperature which aids the operation considerably,
since the litharge is transformed into white lead in
half the time previously necessary. This white lead
does not require any further grinding, being already
finer than the ordinary ground white lead, and having
great body.
It has often been observed that in this process or
that of Mr. Benson, the ordinary commercial litharge
is not sufficiently pure, being often contaminated
with the oxides of copper and iron. The oxide of
copper imparts to the white lead mixed with oil, the
property of soon becoming yellow in contact with the
air; and this is explained from the reduction of the
copper oxide by the essence of turpentine mixed with
the paint. For instance, a sample of white lead,
strongly impregnated with oxide of copper, was
ground with linseed oil and turpentine, and spread
upon a pane of glass which was then exposed to the
air and the light. After a few days the coat had
become yellow, and, being scraped, was treated with
104 MANUFACTURE OF COLORS.
ether in order to dissolve the oil. The residue was
then dissolved in hydrochloric acid, filtered rapidly,
and the filtrate treated with ammonia. The liquor
was colorless at the beginning, but became blue by
degrees from the top. This proves the presence of
the oxide of copper. Another sample of the same
white lead was also ground with pure linseed oil,
without turpentine, and spread upon a pane of glass.
After exposure to the light and the air the coat re-
mained white, which proves that the yellow discolora-
tion was due to the essence of turpentine.
A fine commercial white lead requires, therefore,
that the litharge be free from copper. The finely
powdered oxide of lead may be treated with a solution
of carbonate of ammonia until the liquors are no
longer colored blue. But, as this operation is slow
and somewhat costly, it is preferable to transform
into litharge a pure metallic lead, and the white lead
will not then become yellow.
We may add a few observations on the chemical
states in which oxide of copper impairs the colors of
white lead paints, or, on the other hand, does not
injure them sensibly. It has been observed that,
when the liquors holding copper were precipitated by
carbonate of soda, the paint remained perfectly white.
This fact is easily explained theoretically, since the
carbonate of copper is not, like the oxide, reduced by
the essence of turpentine. As a proof, the following
experiments were made : —
I. 500 grammes of Goslaer litharge were trans-
formed into white lead by the Benson process, with
a solution of neutral acetate of lead and a stream of
carbonic acid. The product was well washed and
dried.
WHITE COLOKS. 105
II. An equal quantity of the same litharge was
very finely powdered, and treated with a solution of
carbonate of ammonia until fresh liquors were no
longer colored blue. This litharge was then trans-
formed into white lead, like the former sample.
III. 500 grammes of the same litharge were dis-
solved, without previous purification, in the shape of
a solution of subacetate of lead, which, after fitration,
was completely precipitated by carbonate of soda.
The product was well washed and dried.
The white leads obtained by these three methods
were ground in linseed oil and essence of turpentine,
and coats laid over equal surfaces.
No. I. began to turn yellow after twenty-four
hours. No. II. remained perfectly white. No. III.,
which had as much copper as No. I., but in the car-
bonate state, was not discolored.
It results from these experiments that, in general,
copper in white lead may be the cause of its turning
yellow, when the metal exists in the form of oxide
(CuO), but not in that of carbonate.
8th. Mullin's Process.
The improvements claimed in the patent of Mr.
Mullin are: First, A process for the separation of
metallic oxides from the fused metals, by forcing
gases or atmospheric air through the metallic mass
by means of a compressing apparatus. There are
also the means of removing the alloys, or the oxides
from the surface of the bath. Second, A process for
the manufacture of white lead by submitting the
oxides to the fumes of vinegar and to carbonic acid.
Third, The employment of magnets for separating
the iron from the metals with which it is mixed.
10G
MANUFACTURE OF COLORS.
I. The apparatus for melting the metals and sepa-
rating the oxides (Fig. 3) is composed of a furnace
A A, supporting a kettle or boiler B c, which is heated
by the fireplace D. A tube a terminated by a ball &,
Fig. 3.
hollow and with longitudinal slits, is immersed in B,
and communicates in an upper story with a holder c
(Fig. 4), in which a pump d compresses the gas or
air, or their mixture, which passes through the fused
metal and oxidizes it. The flow of gas or air is regu-
lated by the valve e.
The oxide is removed by the revolving rake F, the
endless chain of which is carried by two pulleys HH.
The tension is regulated by the screws^/, and the
oxide passes upon the inclined spout j, which is
made of iron rods sufficiently close to retain the oxide,
and hot enough to melt the non-oxidized metal, and
return it to the bath. The oxide falls into the box K.
The tube a may raised or lowered by means of the
counterweight li and the flexible tube g. Two safety
WHITE COLORS. 107
valves ij are placed, the one upon the pipe />•, and the
other upon the holder c. To the latter is also added
a gauge I to indicate the pressure, which should be
sufficiently energetic to overcome the column of
Fig. 4.
molten metal, and to maintain a constant flow of gas.
Another pipe m connects, the pump d with a gas
holder, when gas, instead of atmospheric air, is
employed. In the case of air, the pipe m is dis-
connected at n. The piston of the pump d is set in
motion by the side rod o, attached to the crank p
which is fixed on the same axis as the pulley q.
Fig. 5 shows the disposition which prevents the
admixture of the metal with the oxide. The inclined
metallic plate A, of iron or other metal, is attached to
the pipe B, a little above the perforated ball c. The
current of air is conducted by A up to the edge r of
the kettle, and there is no agitation on the surface of
the bath, where the oxidation takes place.
108
MANUFACTURE OF COLORS.
Fig. 6 explains another mode of oxidizing metals.
Black oxide of manganese is put into the iron pot A,
Fig. 5.
Fig. 6.
having holes at B and D, and a handle s. When this
pot is immersed in the bath, the metal penetrates
through B, and heats the manganese, which disen-
gages oxygen and rapidly oxidizes the metal.
If the metal employed he lead holding silver, the
latter, not being oxidized, goes down to the bottom oi
the kettle, from which it is removed through the plug
N (Fig. 7), of the pipe MO, which is kept hot by a
fire at R.
Fig. 7.
II. The oxide of lead obtained by any one of these
processes is ground, sifted, and washed, and then put
WHITE COLORS.
109
into the trays t t (Fig. 8), which are lined with lead
and hermetically closed
with covers. These trays Fig- 8-
are placed in a lead box,
and the room is kept at a
temperature of from 38° to
48° C. The 1 ay ers of oxide
of lead are about 3 centi-
metres thick, and are kept
wet with water. When
the apparatus is filled with the litharge, then begins
the introduction of the fumes of vinegar distilled in
an ordinary still, and of carbonic acid kept in a gas
holder in an adjoining room. Before removing the
covers of the trays, the stopcocks in the pipes through
which the vinegar vapors and the carbonic acid pass
are turned off. By these means, when the proper
temperature has been maintained, the oxide of lead is
transformed into carbonate.
Another method of manufacturing white lead,
proposed by the same inventor, consists of a series of
large stoneware jars a (Fig. 9), in which are suspended,
by woollen or cotton cords, several sponges v, which
do not touch the sides of the jars.
By capillary attraction, a solution
of neutral acetate of lead held in
x keeps the sponges wet. The
salts of lead are transformed into
carbonates by a current of carbonic
acid which passes through the jars.
The sponges are then removed,
and washed in pure water. After
settling, the clear liquors are de-
canted for a future operation.
Fig. 9.
110 MANUFACTURE OF COLORS.
III. Should the metallic oxides contain iron, this
is removed in the following manner : A wooden table
or trough y (Figs. 10 and 11) is furnished with a
certain number of magnets £, the poles of which pass
Fig. 10. Fig. 11.
through the bottom of the table. The latter is inclined
30° and has a slow oscillating motion. The oxide
delivered by the hopper a, and the iron is arrested 1
the magnets.
9th. Schuzenbach Process.
Carbonate of lead may be produced by a great many
chemical decompositions, but the product is not white
lead. Nevertheless the inventors are not to be dis-
couraged, and have tried many ways of arriving at
results more or less satisfactory. There are a great
many processes described, some of which show great
ingenuity. On that account, and in order to give
some idea of what has been done in that direction,
we shall examine several of these methods.
The principal inconvenience of the ordinary pro-
cesses for the manufacture of white lead, is that they
are unhealthy. The method proposed by Mr. S.
WHITE COLORS. Ill
Schuzenbach, of Friburg, seems to be entirely whole-
some. It is also said to require less capital, and less
room, and to give a larger product.
In a room so arranged as to be heated from 40° to
60° C., several wooden tubs are placed close to each
other. These tubs are filled with alternate layers of
shavings impregnated with vinegar, and lead plates
or buckles, each layer being separated by perforated
wooden partitions which can be easily removed, and
allow of the free circulation of gases and vapors. The
tubs are then closed with wooden covers, and kept at
the proper temperature until the shavings have become
dry. The lead buckles, which are almost entirely
corroded, are then removed and deprived of the
adhering white lead by being placed in water. The
shavings being moistened with vinegar, the operation
may be begun anew.
The white lead thus produced should always be
washed with pure water in order that the various
acetates of lead, copper, or iron, be dissolved and
separated from the insoluble carbonate. After several
washings, the product is dried.
The first waters employed for washing, may be
decanted for saving the acetates of lead or copper still
held in them.
10th. Sewell Process.
This process comprises four distinct operations:
First, an improved method of making oxide of lead;
Second, the production of a white lead of superior
quality, which contains less carbonic acid than the
average commercial white lead ; Third, the employ-
ment of carbonic acid produced by other means than
by combustion in the air ; Fourth, a mode of washing
112 MANUFACTURE OP COLORS.
the white lead, by which the foreign substances are
removed.
I. The incompletely oxidized lead, that is, that
mixed with a certain proportion of metallic lead and
red lead, is kept at a red heat in a reverberatory fur-
nace for three or four hours, and stirred all the time.
When the whole has become transformed into pro-
toxide of lead, it is immediately thrown into a closed
vessel to prevent further oxidization by contact with
the air.
II. During the second operation, the solution ol
oxide of lead is precipitated either by an alkali com-
bined with a certain proportion of carbonic acid, or
by carbonic acid alone. In the first case, the oxide
of lead is dissolved in weak nitric or acetic acid, and
to the solution is added potassa, soda, or ammonia,
in quantity sufficient to neutralize the acid. When
carbonic acid is used, the solution of acetate of lead
is stirred all the time that the gas is passing through
it. As soon as the solution acquires an acid reaction
the flow of carbonic acid is stopped.
III. The carbonic acid may be obtained by mixing
one part of coke dust with seven parts of finely pul-
verized sulphate of lime, or ten of sulphate of baryta,
or eight parts of sulphate of strontia. These various
mixtures are kept at a cherry-red heat in an ordinary
gas retort as long as carbonic acid is produced,
which, after cooling over the water of the main pipe,
goes to a gas holder before being used in the manu-
facture of white lead.
Another method of generating carbonic acid gas
consists in passing steam through a clay retort filled
with finely broken coke and kept at a cherry-red heat.
The steam is decomposed, and carbonic acid and other
are uroduced and collected in a ^as holder.
WHITE COLORS. 113
IV. The white lead is washed tinder pneumatic
and hydrostatic pressure, in order to remove the acid
and other substances before it is dried.
Explanation of the Apparatus. — Fig. 12 is a trans-
verse section of a cast-iron receiver a a lined with
copper, in order to prevent the contact of the white
lead with the iron. &, cover held by screws, c, space
occupied by the white lead which is to be washed.
Fig. 13 is a section of the inverted receiver with
its cover on.
Fig. 13. Fig. 14.
Fig. 12.
Fig. 14 is a longitudinal section of the same
receiver, held in a wooden frame.
Fig. 15 is another longitudinal section, but in an
inverted position, which is that of the apparatus
during the operation. The groove at d d is packed
tight with tow when the cover is on. A thick brass
plate e e (Figs. 16 and 17), perforated with holes, is
attached to the cover. The holes are slanting near
the cover, and this disposition allows of a communi-
cation between themselves, and a narrow passage
between the plate and the cover. The copper tubes
ff, fast in the cover, communicate with the narrow
114
MANUFACTURE OF COLORS.
passage back of the plate e e, and carry the water
which passes through the holes of the plate during
the washing of the white lead.
Fig. 15.
Fig. 17.
Fig. 10.
The receiver a is supported on the frame by two
hollow trunnions g, 7i, lined with copper, g is closed
with a plug during the operation, and h carries the
tube fc, which delivers the water brought by the tube
I. m is the connecting stuffing-box. After the re-
ceiver is filled with white lead the cover is put on,
and the apparatus is turned upside down by means of
pinion and wheel gear.
A pump injects the water through I and fc upon the
surface of the white lead, and forces it through that
substance and a filtering cloth o, spread upon the
plate e. The water escapes from the holes of the
plate into the narrow passage behind, and finally
through the tubes jf/. The washing should be con-
tinued until the water remains perfectly clear.
During this operation the white lead has been
strongly compressed against the cover of the appa-
ratus, and the water remaining above is run out
through the plug hole g. The apparatus is then
WHITE COLOKS. 115
brought to its former position, the cover raised by
means of the screw jp, and the white lead removed.
llth. Crompton Process.
This process consists —
First In purifying the gases obtained from bitu-
minous coal burned by atmospheric air introduced in
a peculiar manner ;
Second. In washing the white lead in a solution of
carbonate of soda, or any analogous chemical prepa-
ration, the proportions of which are indicated fur-
ther on ;
Third. In employing a basic nitrate of lead for the
production of carbonate of lead;
Fourth. In using litharge, massicot, or any protoxide
of lead, boiled with nitric acid or nitrate of lead, and
exposing the hot solution to the action of carbonic
acid ;
Fifth. In condensing and purifying the carbonate
>f lead thus obtained by a simple, new, and economi-
cal method.
For these various operations we need: 1. A special
apparatus for the production of white lead by means
of litharge, massicot, or protoxide of lead, and this
apparatus is provided with a pair of forge bellows, a
safety valve, and other accessories ; 2. A cylindrical
cast-iron furnace with a cover of the same material,
which is held by a screw and luted with clay,in order
to prevent the access of the air; 3. A large cylindri-
cal wrought-iron vessel which can be hermetically
closed, and which contains a diaphragm of metallic
gauze and a stirrer. The air or gases circulate
through a conduit of a spiral form, and escape above
by a central opening ; 4. A copper pump for removing
MANUFACTURE OF COLORS.
Fig. 18.
WHITE COLORS. 117
the liquors from the various receivers, and forcing them
upon cloth sieves disposed on top of other tanks ; 5.
Lastly, the other vessels, pipes, stopcocks, and acces-
sories necessary for obtaining the gases, washing, and
separating the carbonate of lead.
The following figures will explain the apparatus:
In Fig. 18 A represents the bellows; B, the rod for
operating it; c, a weight necessary to overcome the
resistance of the air introduced into the furnace; D,
safety valve, and E the tuyere.
F is the furnace composed of a cast-iron cylinder,
stout enough for the purpose ; a', cast-iron cover which
may be removed at will ; &', clamp fastened to the
edge of the furnace, and through which passes the
screw c' which compresses the cover against the clay
luting put between it and the cylinder.
The flame passes through the cast-iron pipe G into
the cast-iron cylinder H i, called the flame receiver.
K is a double-elbow pipe starting from the top of
H i, which can be cleaned of ashes and dust through
movable covers fixed on the top and bottom.
M is a branch pipe fixed at o on the tuyere E, and
which, without passing through the furnace, carries
the blast to the lower part of the flame receiver H i.
Fig. 19 shows the shape and direction of the pipe
M, and the same letters answer for the corresponding
parts of the previous figure. At N and o are stop-
cocks, the former on the tuyere and the latter on the
pipe M, which has an area of one-fifth of that of the
tuyere.
p is a large w rough t-iron cylinder called the washer,
which is tightly closed, and through which pass the
gases of combustion. Q K is a disk carrying under-
neath it a spiral T T made of thin sheet iron, and com-
118
MANUFACTURE OF COLORS.
mimicating at it with the pipe K which delivers the
hot gases. After circulating through the spiral, the
Fig. 19.
gases escape through an opening in the centre of the
plate Q R, and thence rise to the upper part of p.
Fig; 20 is a horizontal section of the spiral T T.
Fijr. 20.
The central opening through which the cooled and
washed gases escape is shown at s.
u is a diaphragm of close metallic gauze, which is
spread upon a perforated copper plate, and forms a
complete separation between the upper and the lower
part of P. v, w, stopcocks, and x funnel with a stop-
cock. Y vertical shaft of the stirrer passing through
the stuffing-boxes z.
The hot gases, after circulating through the spiral
WHITE COLORS. 110
T T, escape at s, and traversing the diaphragm u, pass
out at a.
&, c are copper receivers fitted with copper jackets
d d, which leave between them the spaces e e for the
circulation of the steam. /, pipe conducting the steam
into those spaces, g, pipe for the escape of the
condensed steam, li li, stopcocks for removing air.
The receiver c contains white lead, and 6 holds
litharge.
i (Fig. 21) is a copper pipe forming a spiral at the
bottom of the receiver c. One end of the coil is
i. 21.
closed and the other is connected with the pipe a. It
is perforated with a quantity of small holes which
allow of the escape of the hot gases.
Jc is the horizontal arm of a stirrer placed in the
vessel b holding litharge.
'Z, ra, are copper pumps extracting the liquors from
&, c, through the pipes o, n dipping into the apparatus.
The liquors are then discharged through the pipes p,
g, into the receivers r, s, after having traversed the
cloth sieves placed on top, and spread upon the
wooden frames t t.
Mode of working the Apparatus. — The cover of the
furnace r is removed, and some burning charcoal is
thrown in. The stopcock x of the tuyere is then
opened, that at o remaining closed, and the blast is
120 MANUFACTURE OF COLORS.
applied. After a while the furnace is charged witl
bituminous coal of the best quality.
When the fire is well lighted, the cover is luted
down and fastened with the screw c', and the stopcock
at o is opened in order to complete the combustion
of the fuel near the tuyere, before the gases are
allowed to escape. In this manner the volatile por-
tions from the fuel above the tuyere are forced to
pass through the flame, where they are burned and
decomposed before reaching the receiver H I.
The gases on arriving in this receiver are at a very
high temperature, and find themselves brought in
contact with another volume of air forced through
the pipe M. This quantity of air is in such a ratio
to that passing through the furnace, that the whole
of the sulphuretted hydrogen is transformed into
sulphurous acid and aqueous vapors. On the other
hand, the carbonic oxide is converted into carbonic
acid, and any combination of carbon and hydrogen
becomes carbonic acid and water.
We should avoid passing through M more air than
is needed, otherwise the temperature in H i will be-
come lowered so much, that the decoinpositon of the
sulphuretted hydrogen and of the hydrocarbons will
no longer take place.
The blast being well regulated, we throw into the
washer p five kilogrammes of carbonate of soda and
the same weight of carbonate of lead, and through
the funnel x we pour enough water to cover the plate
Q R to the level of the stopcock v.
The receivers &, c, are then almost entirely filled
with distilled water. In 5 we put twenty -five kilo-
grammes of litharge and ten of nitrate of lead, or any
othei; quantity, provided, however, that this quantity
WHITE COLORS. 121
of nitrate be ^ of the weight of water held in the
receiver.
Steam is admitted into the spaces e e of the jackets,
until the contents of the vessel are boiling, and the
stirrer Jc is made to revolve.
The rods of the plungers of the pumps Z, m, are
fixed upon a common axis which makes thirteen
revolutions per minute. The pump m extracts the
liquors from Z>, and delivers them to the filtering
apparatus s, from which they flow into c/ the other
pump Z takes the liquors from c with more or less
suspended white lead, and after filtration at r, lets
them fall into b.
Thus the air forced by the bellows passes through
the furnace, and the hot gases of combustion pass into
H i, thence by the pipe K through the washer p, thence
again by a through the coil i, from which they escape
in a multitude of bubbles into the receiver c.
By the succession of these various operations the
white lead mixed with the liquors of c, is carried to
the filter r upon which it is collected. The liquors b
pass through the filter s, upon which they leave a
certain proportion of uudissolved litharge.
When the filters r, s, are entirely filled with white
lead and litharge, they are removed and replaced by
new ones.
With a furnace in constant operation, the charges
are renewed every eight hours.
The stirrer in the washer p has a very slow motion,
and the litharge in b should not be in such quantity
as to prevent the free running of the stirrer Jc.
The water in p is always maintained at the level of
v, and the dirty liquors from time to time removed
at w, are replaced by fresh ones.
122
MANUFACTURE OF COLORS.
The liquors of l> and c should occasionally be tried,
in order to see whether any leakage takes place, or if
they remain of a proper strength. If a sample of
boiling liquor from & does not give on cooling, a pre-
cipitate of nitrate of lead, this substance is in insuffi-
cient proportion and more should be added.
After having described the apparatus and the
various operations by which carbonate of lead is pro-
duced, it is now desirable to explain the processes
of Mr. Crompton by which this substance is put into
commercial shape, and the nitrate of lead mixed with
the carbonate on the filter, recovered.
To the former apparatus already described, we
add : 1. A square box B (Fig. 22), the bottom of
which is formed of a close canvas filter x; 2. A large
tub; 3. Another tub holding a vertical bronze shaft,
provided with a series of blades
slightly inclined, so as to divide the
mass of carbonate of lead and com-
press it at the same time towards
the bottom.
The substance on the filter 7* is
placed in the box up to the level c,
and fresh water is poured upon it to
dissolve the nitrate of lead. The
washing is continued until a sample
of the filtered liquor ceases to be-
come white by the addition of a solution of carbonate
of soda.
All the washings are collected underneath in the
tub D, and are afterwards used in the litharge receiver
b. In this manner all the nitrate of lead is saved.
The washed white lead from the box B is thrown
into the tub E (Figs. 23 and 24) holding the bronze
Fig. 22.
WHITE COLORS. 123
shaft F with its inclined blades G G. By the motion
of the stirrer the mass of carbonate of lead is made
thoroughly homogeneous, and the separated water
passes into the false bottom H through a cloth spread
upon the perforated partition.
Fig. 23. Fig. 24.
The water is removed by the stopcock L, and the
carbonate of lead is conducted by the inclined gutter
K into the hopper L', from which it is ground between
the stones z z, to fall into the tub M. Lastly, it is
formed into lumps and dried.
To sum up, Mr. Crompton claims the following
points as new : —
I. The employment of carbonic acid and gases
produced by bituminous coal, which is burned in such
a manner, by a peculiar introduction of air, that the
vapors which otherwise might injure the quality of
the product are destroyed.
II. The manufacture of white lead by a mixture of
nitric acid and oxide of lead, in such proportions that
124
MANUFACTURE OF COLORS.
there be an excess of oxide ; or by keeping at the
point of ebullition a mixture of litharge, massicot, or
any oxide of lead, with a solution of commercial nitrate
of lead. A pure carbonate of lead is obtained by
passing a stream of carbonic acid through these hot
solutions.
III. The constant recovery of the nitric acid or
nitrate of lead employed, serving for fresh additions
of litharge.
IV. The purification of the carbonate of lead by
successive washings, which were not practised before
the above process was invented.
Mr. Crompton, since his patent of September 7th,
1838, has obtained other certificates of improvements
of the dates of February 6th and July 18th, 1839.
The improvements of the patent of February 6th,
1839, are :—
1. The employment of anthracite, coke, and any
other carboniferous substances, instead of charcoal
generally used for the pn duction of carbonic acid.
Also, the purification of the gases of the combustion,
and the destruction of the vapors which may injure
the purity of the carbonate of lead. This purification
is done as follows : —
By a second combustion effected, as we have already
seen, in a flame receiver by means of a new addition
of atmospheric air. The combinations of sulphur,
carbon, and hydrogen, are thus transformed into
water and carbonic and sulphurous acids.
By condensing the sulphurous acid and the still
remaining sulphuretted hydrogen, in solutions hold-
ing neutralizing substances.
2. The use of the nitrate of lead, instead of the
acetate, hitherto employed.
WHITE COLORS. 125
3. The proper degree of temperature necessary to
keep in solution the basic nitrate of lead, which is
very slightly soluble in the cold.
This improvement is not limited to the foregoing
combinations: the mode of preparing carbonic acid
is equally good whether we employ the acetate or
the nitrate of lead. We may also use the nitrate of
lead in connection with carbonic acid made from
charcoal, and produce the carbonate of lead in hot
solutions, whatever be the acid employed.
Lastly, the precipitation of the carbonate of lead in
hot liquors, has a great effect on its mode of aggre-
gation.
The first patent indicates hot solutions of nitric acid
or of nitrate of lead as solvents, and the purification
of the carbonic acid whatever be the solvent employed.
The last patent of July 18th, 1839, comprises the
heating of the lead solutions during their preparation,
as well as during their precipitation by carbonic acid.
The solvent is acetic acid or the acetate of lead.
The temperature should be about 60° C., or a little
above. The solution is composed as follows: —
Pure acetate of lead or its equivalents in oxide
of lead and acetic acid .... 10 parts.
Litharge (oxide of lead) . . . . 25 "
Water 200 "
These proportions may vary somewhat, however.
12th. Gannal Process.
This process consists: —
1. In granulating the lead;
2.. In reducing the granules to a finer degree of
comminution by mutual attrition in a leaden cylinder;
126 MANUFACTURE OF COLORS.
3. In oxidizing the metal by the introduction of air
into the apparatus ;
4. In carbonating the oxide with a mixture of air
and carbonic acid ;
5. In aiding the oxidation by an addition in the
apparatus of nitric acid or nitrate of lead ;
6. In washing the product thus obtained ;
7. In hastening its desiccation by a previous pres-
sure which expels most of the water;
8. In dividing the pressed paste into square blocks ;
9. In drying these blocks in a stove-room.
This process has been improved by Mr. Versepuy,
as we have already seen.
13th. Rostaing Process.
Mr. de Ttostaing, in 1858, proposed for the manu-
facture of white lead and massicot a process based
upon the pulverization of metals submitted, when
melted, to centrifugal action. A continuous stream
of molten lead falls upon a metallic disk, 0.25 metre
in diameter, making* a maximum of 2000 revolutions
o
per minute, and is projected with great force tangen-
tially to its circumference. Four or five minutes are
sufficient to thus pulverize about 100 kilogrammes
of lead. The fine metallic powder, being still hot, is
rapidly oxidized in its passage through the air, and
may be converted into massicot or red lead, or may be
combined with carbonic acid. This process has not
been put into practice.
14th. Mulhouse White Lead.
This is a combination of sulphuric acid and oxide of
lead, being the residue of the manufacture of acetate
of alumina. It is thoroughly washed with water,
WHITE COLORS. 127
through a silk sieve, and drained upon cloth
filters. It is afterwards moulded in the shape of a
truncated cone, and dried. This product, misnamed
white lead, cannot be used for oil painting, since it
has no body — does not cover. We mention it because
it is frequently emplo}Ted for adulterating real white
lead.
,This sulphate of lead may by transformed into car-
bonate by boiling it with a solution of carbonate of
soda or of potassa. But this operation renders it
more expensive than real white lead, and the product
is still contaminated with a certain proportion of
sulphate of lead.
15th. Silver White or Light White.
This white, often employed for decorating and for
artistic painting, is a white lead of the first quality
which has been peculiarly well washed.
A superior quality of silver white for delicate oil
painting may be obtained by dissolving 500 grammes
of acetate of lead in 2 litres of boiling water and
diluting with 4 litres more of water. Then a solution
of 370 grammes of soda crystals in 2 litres of boil-
ing water, is slowly poured into the former liquors,
stirring all the while. The two mixed solutions are
allowed to settle for two hours, when the supernatant
liquid is decanted. The precipitate is washed five
or six times by decantation, then drained upon a
cloth, and dried in the dark at a gentle heat.
16th. Testing the Purity of White Leads.
We should carefully avoid mixing with white lead
substances which may impair its brightness, since a
128
MANUFACTURE OF COLORS.
pure white is its main quality. We shall see further
on what its composition is.
White lead should be kept in closed vessels, other-
wise it will acquire a brown shade. It forms the
basis of a great many pigments. It should, for good
paintings, be pure and without admixtures ; however,
house painters add to it variable proportions of chalk
or Meudon white, but the painting is without con-
sistency or durability. Here is the process indicated
by Watin for distinguishing white lead from chalk.
A hole is made in a piece of charcoal, which is then
ignited and a pinch of white lead thrown in. Air is
blown upon the charcoal in order to keep up the com-
bustion, and the white lead first turns yellow, and
after a few minutes becomes reduced to bright glob-
ules of metallic lead. Chalk (carbonate of lime), on the
other hand, may lose its carbonic acid by the opera-
tion, but the lime will remain as a white powder upon
the charcoal.
If we desire to ascertain the proportion of car-
bonate of lime mixed with the carbonate of lead, we
weigh 100 grammes of the sample, and mix them
with 50 grammes of charcoal powder. The whole
being smelted in a crucible, a button of metallic lead
is produced, which is weighed. We then add 24
per cent, to the number obtained, and subtracting this
sum from the previous 100 grammes, the difference
is the weight of the carbonate of lime. The 24 per
cent, repvesent about the weight of the carbonic acid,
water, and oxygen separated from the carbonate of lead.
These two tests would be sufficient if carbonate of
lime were the only foreign substance of the mixture.
But as sulphate of lead may also be present, we are
obliged to employ tests by the wet way. For in-
WHITE COLORS. 129
stance we put 25 grammes of the sample into a glass
flask, and pour gradually upon it nitric acid diluted
with six times its weight of water. The acid is added
as long as an effervescence takes place, and we heat
the vessel gently. • If all the substance be dissolved,
we conclude that there is no sulphate of lead. Should
there be an insoluble deposit, we throw the whole
upon a filter and wash it thoroughly. The sulphate
of lead collected is then dried and weighed. Let us
suppose that its weight is 7 grammes. The filtered
liquor contains chalk and the dissolved white lead ;
their separation is effected by adding ammonia until
the liquor smells of it slightly. The precipitate
of oxide of lead is collected upon a filter, washed,
dried and weighed. Let the supposed weight be 10
grammes ; we know that 100 parts of oxide of lead
are equal to 1 19.78 parts of white lead ; therefore 10
grammes of oxide represent 11.978 grammes of white
lead, that is, 12 grammes without fractions. De-
ducting from the 25 grammes of sample the sum of
the weights of sulphate and carbonate of lead, there
remain 6 grammes of carbonate of lime. Lime may
be ascertained and determined by pouring into the
liquor, filtered from the oxide of lead, a solution of
oxalate of ammonia which will produce a white pre-
cipitate of oxalate of lime. The results are only
approximate, as we do not wish to complicate the
operations which require a certain amount of chemical
knowledge in order to operate with certainty. We
have also found samples of white lead which were
mixed with sulphate of baryta or clay; these sub-
stances remain in the insoluble residuum.
Here are the processes employed by Mr. Louyet
for ascertaining the impurities of white lead : —
9
130
MANUFACTURE OF COLORS.
"I was intrusted, some time since, with three
different samples of white lead, intended for exporta-
tion. It is probable that the destination of these pro-
ducts induced the manufacturer to think that it was
useless to remain within bounds, and that the ignorance
of the consumers would prevent them from ascertain-
ing that what was sold as white lead could be as pro-
perly called sulphate of baryta as white lead.
"One gramme of sample No. 1, heated to redness
in a platinum crucible until complete trans-
formation into oxide of lead, gave a loss of . 0.100 gramme.
"A second calculation gave the same weight.
" For one gramme of sample No. 2, calcined in
the same manner, the loss was
" Sample No. 3, 1 gramme, loss . . .
0.049 gramme.
0.037 "
" The calcined product No. 1 was boiled with pure
nitric acid, then water was added and the boiling con-
tinued. The insoluble residuum was yellowish, al-
though the liquor was strongly acid. After filtration
the residue was well washed with boiling water and
calcined. Its weight was 0.305 gramme after de-
ducting the ashes of the filter.
"I will observe that the residuum of No. 1 was
darker than that of No. 2, and this latter darker than
No. 3, which was quite white. The residuum of No.
1, after being heated with the blowpipe upon charcoal
and with soda, stained a permanent black the piece of
silver upon which it had been put wet.
"This is a characteristic of sulphates. It was
proved that the sulphate mixed with the carbonate
of lead was sulphate of baryta, by boiling it with a
solution of carbonate of soda, filtering, and dissolving
the washed residue upon the filter with hydrochloric
WHITE COLORS. 131
acid. The liquor obtained gave a heavy white pre-
cipitate with sulphuric acid.
"The solution resulting from the treatment of
white lead 2sTo. 1 with nitric acid was precipitated
with sulphuric acid, and the calcined sulphate of
lead weighed 0.765 gramme, corresponding to 0.563
gramme of oxide of lead, or 0.674 gramme of neutral
carbonate. Calculated from the proportion of oxide
of lead, that of carbonic acid is 0.111 gramme, whereas
the loss by calcination of the white lead is only 0.100
gramme. I admit that this difference is due to the
fact that all of the oxide of lead is not carbonated,
but that a certain proportion remains in the hydrated
state. But, as the equivalent of water is smaller
than that of carbonic acid, it follows that the number
is too high if we suppose that all of the oxide is com-
bined with carbonic acid, and we must subtract 0.011
from 0.674 ; there remains 0.663 gramme. White
lead ~No. 2 was treated in the same manner, and
the residue insoluble in nitric acid weighed 0.660
gramme after being washed and calcined. The pro-
portion of sulphate of lead from the nitric solution
was 0.360 gramme, corresponding to 0.264 gramme
of protoxide of lead. But here the number calcu-
lated for carbonic acid differs but little from that
found by direct experiment. In this case, as in the
former, the number obtained for carbonate of lead is
a little low, and the loss may be added to it. Indeed,
the sulphate of lead is slightly soluble in acid liquors,
and the precipitation by the oxalate of ammonia
would have given more accurate results. It follows
that the calculated number for carbonic acid would
have been a little higher, and above that found by
direct experiment.
132 MANUFACTURE OF COLORS.
" But I repeat the observation already made, that a
portion of the oxide of lead in white lead is in the
hydrated state. One gramme of the sample No. 3
gave an insoluble residuum equal to 0.718 gramme,
and a precipitate of sulphate of lead weighing 0.277
gramme, which corresponds to 0.203 of oxide of lead
or 0.243 of carbonate of lead.
" The composition of the samples was, therefore, as
follows: —
White lead. Sulphate of baryta.
1 gramme sample No. 1 . . . 0.695 0.305
1 " . " No. 2 ... . 0.340 0.660
1 " " No. 3 . . . 0.282 0.118
" These analyses, the last one especially, show that
I was right in saying that these products may in-
differently be called white lead or sulphate of baryta."
"White lead is often mixed with that sulphate of
baryta which is called blancfixe or baryta white, and-*
which is prepared from the carbonate of baryta. It
is an adulteration which ceases to be objectionable
when the manufacturer makes the composition known.
Belgian and German manufacturers sell various
qualities of white lead, the compositions of which are
known by the names they bear; thus : —
1. Krems white is a pure white lead ;
2. Venice white is a mixture of equal parts of si
phate of baryta and white lead ;
3. Hamburg white is a mixture of —
Sulphate of baryta . . . . .2 parts.
White lead 1 part.
4. Holland white is composed of —
Sulphate of baryta 3 parts.
White lead ...... 1 part.
WHITE COLORS. 133
A bluish tinge is often imparted to white lead
with a small proportion of indigo.
It is said that the following mixtures are generally
found in the French color trade : —
White lead. Sulphate of baryta.
White lead (superfine) ... 85 15
No. 1 . . . TO 30
No. 2 . . . 60 40
No. 3 . . .40 to 50 60 to 50
In order to ascertain whether a sample of white
lead is mixed with sulphate of baryta or sulphate of
lead, it is treated with nitric acid diluted with two or
three parts of distilled water. Pure white lead is
entirely dissolved, whereas the above sulphates remain
unacted upon by the reagent.
Mr. A. Bacco has indicated a simple process by
which white leads may be tested by the wet way.
"The quality of white leads," says he, "as every
chemist knows, depends on their extreme opacity,
which is the greater as their molecules are amorphous
and their composition more basic. In experimenting
upon a crystalline white lead, with little body, I have
ascertained that it may be improved by digesting it
in a carbonated alkaline solution, rendered slightly
caustic by an addition of a small quantity of quick-
lime. The entire operation is performed in the cold.
"But as a white lead should be basic, in order to
have body, I have tried a process for ascertaining
whether a white lead is more or less basic, and I
have succeeded with a solution of neutral chromate of
potassa poured upon wet white lead. This latter
substance is converted into a chromate of lead, which
is neutral, basic, or six basic, according as the white
134
MANUFACTURE OF COLORS.
lead itself is more or less basic, and the degree is
shown by a change of coloration.
"If the chromate be lemon-yellow, the white lead
is neutral and of inferior quality; an orange color
indicates a white lead slightly basic, but if the color
be a scarlet-red we may be sure that the white lead
is highly basic. Indeed, every chemist knows that
the neutral chromate of lead is lemon-yellow, the tri-
basic orange-yellow, and the six-basic fire-red.
"We may then conclude that the degree of colora-
tion thus obtained gives a sure indication of the
quality of white leads."
All these methods of ascertaining the purity of
white leads appear to us far from entirely satisfactory ;
and, by reading the following paragraph, it will be
seen that the composition of this product is not so
simple as is supposed, and that a thorough chemical
analysis will alone give correct indications of the
quality of white lead.
17th. Composition of White Leads.
Mr. Mulder, of Utrecht, has published the results
of experiments made by Mr. Ylaandern upon the
composition of twenty-seven samples of white lead of
Holland manufacture. The results are sufficiently
interesting to be reproduced here. In the analyses
the hygroscopic water has not been determined sepa-
rately.
CO3 .
HO .
PbO .
I. II. Calculated. Equivalents.
11.4 11.4 11.4 = 2
2.3 2.4 2.3 = 1
86.4 86.5 86.3 = 3
or
PbO,HO + 2C03,PbO.
WHITE COLORS.
135
in.
IV.
v.
VI.
VII.
VIII.
IX.
X.
XI.
Calcu-
XII. lated.
Equiva*
leuts.
co-
12.4
12.2
12.0
12.4
12.0
12.3
12.3
12.0
12.3
12.2 12.2
= 5
HO
2.0
2.1
2.0
2.1
2.0
2.1
2.3
1.8
2.1
2.0 2.0
= 2
PbO
85.0
85.6
85.9
85.7
86.1
85.4
85.5
85.6
85.5
85.6 85.8
= 7
or
2PbO,HO-}-5C03,PbO.
XIII.
XIV.
XV.
XVI.
XVII.
XVIII.
XIX.
Calcu-
lated.
Equiva-
lents.
CO2
12.7
12.7
12.5
12.7
12.5
12.9
12.9
12.7
= 3
HO
2.3
1.7
2.1
1.9
1.9
1.2
2.1
1.7
= 1
PbO
85.2
85.5
85.8
85.4
85.7
85.3
85.1
85.6
= 4
or
PbO,HO-f 3C09,PbO.
XX.
XXI.
XXII.
XXIII.
XXIV.
XXV.
XXVI.
XXVII.
Calcn- Equiva-
lated. leuts.
co-
13.1
13.5
13.5
13.2
13.0
13 3
13.2
13.1
13.4
=
4
HO
2.0
1.5
1.6
1.7
1.8
1.8
1.9
2.0
1.4
=
1
PbO
83.4
84.7
849
85.2
85.2
85.1
85.0
85.1
85.2
=
5
or
PbO,HO + 4C02,PbO.
Thus, the samples of white lead which were ex-
amined had the following compositions : —
Two, PbO,HO + 2C02,PbO.
Ten, 2PbO,HO + 5COa,PbO.
Seven, PbO,HO -f 3C02,PbO.
Eight, PbO,HO + 4C09,PbO.
Therefore, Holland white lead is a hydrated oxide
of lead with 2, 2|, 3, or 4 equivalents of neutral
carbonate of lead. 2 and 3 are met with in the trade
not so frequently as 2| and 4.
Mr. Mulder regrets that he does not know the
manufacturers by whom these products were made,
because he would then have been able to ascertain
whether the white lead of a given manufacture pre-
served the same composition.
On the other hand, Mr. W. Baker has demonstrated
that white lead made by the Holland process has no
fixed composition, but that it is a carbonate of lead
holding a variable proportion of hydrated oxide,
136 MANUFACTURE OF COLORS.
which depends on the conditions attending the cor-
roding process. Thus, from the same bed, using the
same tan and acetic acid, samples may be taken pre-
senting variable proportions of carbonate and hydrate
of lead. Near the walls, where the aqueous and car-
bonic vapors escape freely, there are sometimes found,
under certain circumstances, small translucent crys-
tals of neutral carbonate with a sweet taste. On the
corroding surface there is often seen a thin crust, the
composition of which is nearly that of the neutral
carbonate. The quantity and the quality of the
water employed in grinding and washing white lead
have also an effect on the composition of the product.
Here are a few analyses of dry white lead from various
manufacturers, which quite agree with those of Mr.
Mulder.
No. I.
Calculated.
Equivalents.
CO3 .
.
. 11.03
11.4
= 2
HO .
.
. 2.23
2.3
i
PbO.
.
. 86.11
86.3
— ,>
No. II.
CO2 .
...
. 12.17
12.7
= 3
HO .
.
' . 1.66
1.7
= 1
PbO .
.
. 85.37
85.6
= 4
No. III.
No. IV.
CO3
. 13.37
13.48
13.4
== 4
HO
. 1.11
1.46
1.4
j^
PbO
84.71
84.88
85.2
== 5
The hygroscopic water does not generally amount
to more than 0.05 per cent.
The white lead No. I. was from London, No. II.
from Newcastle, and Nos. III. and IV. from Sheffield.
Moreover, what still demonstrate the variety in the
composition of white leads are the following analyses
of crusts separated from the leads : —
WHITE COLORS. 137
CO*. HO. PbO.
No. 1. Solid crust of good quality . . 12.49 1.60 85.24
No. 2. " " " " . 12.31 1.73 85.77
No. 3. Crust with scaly surface . . . 15.14 0.53 83.86
No. 4. Hard crust, not very deeply corroded 15.14 0.60 84.10
No. 5. Colorless, crystalline, and tranlucent
crusts ....... 15.71 0.75 83.53
No. 6. Colorless and crystalline crusts taken
from a mass sweet to the taste . . . 16.11 0.49 83.39
No. 7. Neutral carbonate, calculated . . 16.50 83.50
It is evident that Nos. 5 and 6 are neutral car-
bonate with a trace of hydrate, and that Nos. 3 and 4
show the passage from the neutral carbonate to the
normal corroded product, the composition of which
may be represented by the formula —
PbO,HO-f-3COa,PbO.
18th. Processes for Rendering the Manufacture of White Lead
less Unhealthy.
The manufacture of white lead presents various
manipulations which are quite unhealthy, because of
the continual handling of a poisoning substance, and
especially of the white lead dust flying about the
work-rooms and being inhaled by the men.
The cause of humanity before all, and possibly an
economy in the manufacture, demand of us to search
for the means of diminishing the danger. It is only
of late that this question in public hygiene has been
brought into serious consideration, and has been suc-
cessfully resolved. We owe much in this respect to
the exertions of the " Societe d'Encouragement," and
we shall borrow from its bulletin a few interesting
documents which relate to successful improvements
carried into this manufacture.
138
MANUFACTURE OF COLORS.
A. The Ward Machine for the Manufacture of White Lead.
In order to appreciate, at its real value, the inven-
tion of this machine, we should remember that white
lead is a powerful poison, which, by the ordinary pro-
cesses, is reduced into a very fine dust, penetrating
the pores of the skin, the respiratory organs, and the
lungs. Thus, the clothes of the men working in
such a manufacture are constantly impregnated with
this impalpable powder, in the same manner as those
of millers are with flour.
The health of these poor men is soon seriously im-
paired, their complexions become livid, and they soon
fall into a state of languor and consumption, pro-
duced by inflammation of the viscera.* In a few
years they decay and die before the time nature had
allotted to them.
It is, therefore, a great humanitarian service to
endeavor to preserve from death so many men working
in this dangerous manufacture, and Mr. Ward thinks
that he has attained this great result, which, however,
has also attracted the attention of Messrs. Schuzen-
bach and Gannel.
His apparatus comprises: —
I. A trough, 4 metres long, 2 metres wide, and
1.30 metres deep.
II. Two brass rollers, superposed, for grinding the
substances. The lower one is entirely immersed in
water, and the upper one partly so, their line of con-
tact being 30 centimetres below the level of the
water. Motion is imparted to them by means of a
* In the autopsy of men from white lead works, lead was always
found attached to the viscera. There was, therefore, no doubt of
their premature death and of the cause of it.
WHITE COLORS. 139
crank or pulley, fixed to the axis of the upper cylin-
der, which is connected with the lower one by
pinions.
Counterweights are also fixed to the extremities of
the upper axis, giving a sufficient pressure, and, at
the same time, allowing an upward motion of the
cylinder, should too great a mass of metal become
engaged between the rolls.
III. An oaken platform, perforated with a quantity
of holes, 15 or 16 millimetres in diameter, and serving
as a sieve for the material which leaves the rolls.
This platform is maintained at about 8 centimetres
below the rollers by means of wooden blocks (hold-
fasts) above and below it.
IV. A wooden inclined plane for feeding the
rollers.
An outlet is left on one side of the trough for the
water. The white lead, which is quite finely pul-
verized, falls easily through the holes of the platform,
whereas the laminated metal remains on top and is
raked out.
As the non-corroded metal is separated from the
white lead entirely under water, no dangerous dust can
be raised.
Lastly, the metallic plates are allowed to drain
upon an inclined trough, and to become dry before
they are used or melted anew.
" It may be inquired," says the inventor, " why
the substances are not wetted before passing through
the rolls. The answer is this : —
"1. They would become pasty, and their passage
through the rolls be difficult.
"2. This paste would not be well sifted.
"3. A certain proportion of metallic lead is neces-
140 MANUFACTURE OF COLORS.
sary to the operation, and should not be removed
before the substances are passed through the cylin-
ders."
Fig. 25 shows the apparatus, which has been
already explained.
Fig. 25.
A, inclined plane for feeding the rollers.
B, the superposed brass rollers for grinding the
substances.
C, wooden trough.
D, oaken partition perforated with holes.
E, crank, here indicated as a means of imparting
motion. It can be substituted by pulleys, for in-
stance, driven by water or steam power.
F, pinion fixed to the axis of the upper cylinder,
and driving the lower one.
G G, two counterweights bearing upon the axis of
the upper roller.
H, water outlet.
B. Apparatus of Mr. Th. Lefevre for Pulverizing White Lead.
Mr. Th. Lefevre, manufacturer of white lead at
Lille, patented, in 1849, an apparatus for grinding
white lead, the description of which is as follows : —
WHITE COLORS. 141
" The ordinary process for pulverizing "white lead
blocks consists in grinding them between two hori-
zontal stones, the upper one of which is revolving.
The powder is then sifted in order to separate the
coarse portions. This mode of operation, whatever
be the precautions taken, is open to the objection of
producing in the works a very light dust of white
lead, which is inhaled by the men and produces that
dangerous sickness called lead colic.
" We have tried to replace this dangerous method
by one presenting no cause of insecurity to the men,
and we have succeeded by the use of an apparatus
actually in operation in our own works.
" Instead of working two horizontal stones in the
open air, we keep them in a tight inclosure. The
lower stone is steady, whereas the upper one re-
volves and receives its motion from a vertical shaft
passing through the middle of the lower stone, and
fixed to a three-branched rynd in the upper one. A
copper cover screwed upon the casing of the stones,
supports the distributor of white lead. This distri-
butor is made of two truncated cones, one of which,
the exterior, is bolted upon the copper cover. The
interior one is fixed to a vertical revolving shaft.
Both cones are cast with grooves in opposite direc-
tions.
' The lumps of white lead are first reduced in size
in the distributor, then finely powdered between the
stones, and lastly, sifted in sieves kept in hermetically
closed boxes.
"Fig. 26 is a vertical section of the apparatus
passing through the line A B c D (Fig. 27).
" Fig. 27 is a horizontal section passing through
the line E r G H (Fig. 2(5).
142
MANUFACTURE OP COLORS.
Fte. 26.
Fisr. 27.
" Figs. 28 and 29 represent another transverse and
vertical section of the apparatus.
WHITE COLORS.
143
Fig. 28.
" Fig. 30 is the distributor on a larger scale.
" This distributor is made of cast-iron and is lined
inside with a bronze casting filled with grooves.
Another grooved cone A revolves inside, and
breaks the lumps or blocks of white lead
into small fragments, which fall between
the stones G K.
" B, vertical iron shaft, fixed to the small
distributing cone, and rising up to the
capital c, on top of which there is a screw
144 MANUFACTURE OF COLORS.
which allows of the raising or lowering of the shaft,
in order to regulate the delivery of the white lead to
the stones G K.
"c, cast-iron capital supported by four columns,
and which maintains the vertical shaft in its bearings.
" D, F conical gearing driving the shaft B by means
of the pulley E, fixed upon the horizontal shaft F'.
k< G, upper stone of white marble, which could be
substituted by a burr-stone. A three-branched rynd is
fixed in the central opening, and receives the shaft i.
The under surface of the stone (Figs. 31 and 32) has
Fig. 31. Fig. 32.
throe grooves or ways J J J for delivering the pulver-
ized white lead.
" K, lower steady stone of the same material as the
upper one and grooved. It is perforated in the centre
with a square hole which is filled with a box L of
iron on the sides, and copper on the top.
" This box is divided into six compartments, three
for the grease and three for the brasses. The latter
are regulated by the screws N N N. Three or four
screws P P maintain the level of the stone.
"The stones are supported by a framework upon
which is screwed a hermetical copper cover, bearing
the distributor of the white lead.
" Between the stones and their casing there is an
empty space P', which receives the projected white
lead. Two opposite openings deliver it into the
WHITE COLORS. 145
rectangular zinc spouts o o, which, in their turn, con-
duct the pulverized material into the revolving sieves
o' o', held in hermetically closed boxes. These sieves
are a check on the neglect of the men, because the
stones, when properly set, grind well enough without
the necessity of sifting.
" Q R, conical gearing driven by the fixed pulley
T. T' is a loose pulley.
" u u, brackets supporting the shaft s.
" v w, conical gear driving a pulley Y fixed upon
the shaft x, and transmitting its motion to the pulley
E of the distributor.
" z, pulley on the shaft s driving* the two sieves
o' o' by means of the pulley and pinions B' D' E'.
" The shaft of the revolving stone stands upon a
cast-iron or steel step a' fixed upon cross-bars H' bolted
to the four columns i'.
"j', screw under G' for raising or lowering the
upper stone G.
" K', main driving shaft upon which are fixed the
pulleys L'."
Mr. Th. Lefevre has not only invented the above
described apparatus, but he has since organized his
works on an entirely salubrious system of manu-
facture. We cannot describe it better than by present-
ing the report made by MM. Barreswill, Salvetat, and
Chevalier to the " Societe d'Encouragement."
The works of Mr. Th. Lefevre, founded in 1825, have
since then received many improvements. A steam-
engine of thirty horse-power gives motion to all the
machinery of the works. Several small railroads
carry the crude or prepared materials in every direc-
tion, and are a great saving of arduous labor.
Gas is manufactured in the place, and is used from
10
146 MANUFACTURE OF COLORS.
120 burners. The stack of the gas furnace is 33
metres high. The retorts are made of clay, and the
cracks are closed with a mixture of powdered glass,
borax, and pipe clay.
There are from eighty to one hundred and twenty
men employed in the works, the smaller number
in dull times. Mr. Lefevre produces yearly from
1,600,000 to 1,800,000 kilogrammes of white lead
thus subdivided : —
White lead in scales from . . 45 to 50,000 kilogrammes
" " lumps " . . 300 " 350,000 "
" powdered " . 1100 " 1,200,000 "
" ground in oil " . . 150 " 200,000 "
The consumption of the latter article increases
daily and its manufacture follows the progression.
The good quality of the products of these works
has been acknowledged in the national exhibitions,
and at the World's Fair, London.
The mode of manufacture is the Holland process,
and we shall successively describe the operations
which we have seen practised.
Casting of the lead. — This operation is effected in a
special room called the foundry, and the lead employed
is either new metal or that which has not been entirely
corroded. In the latter case certain precautions are
taken to protect the men from the vapors produced
during the fusion. Thus the metal is put through
front sliding-doors, into a cast-iron kettle entirely
covered with a hood, the top of which communicates
by means of a pipe, with the stack of the furnace, 12
metres high, and having a strong draft.
Before being put into the kettle, the lead is for
some time kept in a hot place, where all dampness is
removed. Thus is avoided the danger of the molten
WHITE COLORS. 147
metal being thrown out, as when wet lead is introduced
into a fused bath.
When the lead is melted, it is cast into sheets
about 60 centimetres long, 1.0 wide, and a few milli-
metres thick, and weighing 1 kilogramme on an
average. These sheets are then carried into another
and adjoining room, where they are cut in two and
rolled into the shape of a spiral which fills the pots of
the beds.
These operations present none or very little danger.
In nineteen years, a single melter only has suffered
from lead disease.
Building the beds. — There are forty-eight beds at
the works of Mr. T. Lefevre at Moulins-Lille. They
are stone built, and begin .at 1 metre below the level
of the ground. Their dimensions are 5 metres long,
4 wide, and 6 high.
Stable manure is employed, but other works use
spent tan. In the latter case the operation is slower,
and requires from sixty to ninety days, instead of
forty, as with stable manure.
A banquette, 30 centimetres wide and 40 high, is
built around the bed with the manure from a preceding
operation, while the middle is filled with a layer of
fresh manure 40 centimetres high. This first layer
receives about 1200 pots, into each of which there is
poured about a fourth of a litre of vinegar. A spiral
of lead is then put into each pot, and rests upon two
inside knobs which prevent it from touching the
vinegar.
The whole is then covered with flat leaden sheets,
then with pieces of scantling from 10 to 12 centime-
tres square, in order to leave room for a draft, and
lastly with boards. Another banquette of old manure
148 MANUFACTURE OF COLORS.
is formed upon the first layer, and the middle space is
filled with fresh manure. Pots, vinegar, and lead are
arranged as previously explained, and the building up
of the bed goes on until there are seven or eight
layers.
In about six weeks the conversion of the lead into
carbonate is complete, or nearly so.
On an average, each bed requires —
1. 8 two-horse loads of stable manure ;
2. 300 litres of vinegar per layer, or 2400 per bed;
3. 1200 to 1500 kilogrammes of lead per layer, or
from 10,000 to 12,000 kilogrammes per bed.
Four men build two layers per day, or a bed in
four days : that is, sixteen days work per bed.
There is no insalubrity in the building of the beds.
Gas-burners may be used when desired.
Talcing the beds apart. — When the time necessary
for the corrosion of the lead has expired, the beds are
taken apart in the following manner: The manure,
boards, and pieces of scantling of the top layer are
removed. The corroded lead is then emptied into a
small wooden box, and the largest portions of uncor-
roded metal are picked apart. There must be a little
dust produced, but the testimony of many workmen
is that this operation is attended with very littli
danger to health. In another establishment at Lille,
the men are allowed to smoke when taking the bed*
apart, and the manager certifies that many cases ol
sickness are thus prevented.
In Mr. Woelmann's works the lead from the beds is
never melted anew ; the uncorroded portions are used
for covering the pots.
12.000 kilogrammes of lead give on an average:
First, carbonated lead 10,000 kilogrammes; second,
WHITE COLORS. 149
non-corroded lead 4000 kilogrammes. Therefore, the
increase of weight of the 8000 kilogrammes of lead
which are corroded is 25 per cent.
The taking apart of the beds is done with naked
hands. Gloves are not very handy to work with
unless they are very supple, in which case they be-
come expensive.
Picking up. — Before 1842 the white lead from the
beds was carried to the picking room, where the car-
bonate was separated from the metal. As this opera-
tion requires the beating and unrolling of the sheets,
it is very unhealthy on account of the great quantity
of flying dust. Strong drafts kept in the room were
insufficient as a preventive of danger, and were
attended with loss of material. Moreover the opera-
tion was slow.
The separation of the white lead from the uncor-
roded metal is now effected in Mr. Lefevre's works by
a special machine, kept separate in a tight enclosure.
This machine is on an upper floor, 3 metres above the
ground. The metal, with the adhering white lead, is
carried by an endless leather apron to a series of two
pairs of grooved rollers, which separate the greater
part of the white lead. The remainder is removed
by the friction of the metal in a revolving drum,
covered by metallic gauze. The white lead is received
into a large closed box. The portions of blue lead
which are sufficiently large are rolled up into spirals
for the pots, whereas the small fragments are melted
anew.
As soon as the dust has subsided, the white lead is
removed from the receiving box.
Dry grinding of scales of white lead. — Formerly the
scales separated from the metal were ground under
150 MANUFACTURE OF COLOKS.
vertical running stones, and the product was sifted,
what passed through the sieve being mixed with
water and then ground under horizontal stones.
At the present time the scales are carried by me-
chanical means to the first story, and fall into large
troughs, from which they are taken to a hopper
provided with a distributor. The scales pass first
between two grooved rollers, which break them and
separate the blue lead still remaining. Three other
pairs of rollers bring the white lead to the proper
degree of comminution for the wet grinding. All
this work, which formerly was so dangerous, is now
done by machinery, and every precaution is taken to
prevent the escape of the white lead dust. All of
the rollers are kept in perfectly tight casings, and the
whole apparatus is also enclosed by light partition
walls. All the doors are double. We see, therefore,
that in these fine works all precautions that hygiene
may suggest have been taken.
Grinding white lead in water. — The white lead
which has been dry powdered between the rollers, is
sifted, and the fine portions fall into a closed cistern
under ground, where they are wet with water.
The wret white lead is then ground under horizontal
stones, twenty of which are in use. A soft paste is
thus obtained, which is received in tubs, and these
are carried by mechanical arrangements to the drying
room. There the paste is put into porous conical
pots, which are ranged upon shelves.
Drying rooms. — These rooms are heated during
the winter by means of large cast iron stoves, burning
bituminous coal. In summer a proper ventilation is
sufficient to dry the white lead.
Mr. Lefevre tried to light the drying rooms with
WHITE COLORS. 151
the gas manufactured in the works, but he has been
obliged to abandon the idea, since the sulphuretted
hydrogen of the gas blackened the surface of the
lumps of white lead, transforming it into lead sul-
phide. This inconvenience we think may be avoided
by carrying off the gases of the combustion through
a hood and pipe placed above the burners ; or by using
a gas containing but a very slight proportion of sul-
phuretted hydrogen.
The white lead in pots remains for ten to twelve
days in ordinary drying rooms, and loses the greater
part of its water. The lumps become consistent, and
contract enough to be easily removed from their pots.
Their desiccation is then completed upon the shelves
of other drying rooms, heated at from 40° to 50° C.,
with hot air. The lumps which have preserved their
shape are wrapped in blue paper ; those which have
been broken are powdered. The pots are cleaned
with iron knives, and as the adhering white lead is
still moist, this operation is considered to be quite
devoid of danger.
Powdering lump white lead. — For several years
the demand for lump white lead has been decreasing,
and the greatest consumption is that of the powdered
product.
By the old process, the lumps of white lead were
pulverized under vertical stones running upon hori-
zontal stone platforms, and the powder was then
sifted. Notwithstanding the care and attention
which were taken, there was always a very fine dust
of white lead flying about the rooms, and the men
were subject to lead colic.
Instead of vertical stones working in the open air,
Mr. Lefevre employs horizontal stones enclosed with-
152 MANUFACTURE OF COLORS.
in a perfectly tight metallic drum. The lower stone
does not move, but the upper one makes two hundred
and seventy-six revolutions per minute.
On the top of the metallic drum there is a kind of
coffee mill, which breaks the lumps of white lead be-
fore they pass between the stones. With four pairs
of such stones (white marble), it is possible to powder
every day, 31,000 kilogrammes of white lead.
The pulverized product is thrown off against the
drum by centrifugal force, and falls into closed
troughs by two diametrically opposite openings. The
troughs deliver it into metallic revolving sieves,
enclosed within a box with double doors. The sifted
powder is received in a wagon holding about 1200
kilogrammes of substance, which is removed only
when the dust has entirely subsided.
Since Mr. Besancon, in his works at Ivry near the
gate of Fontainebleau (Paris), has established appara-
tus for grinding white lead in oil ; the employment of
this product has increased so rapidly, that this manu-
facturer sells seven-eighths of his white lead ground
in oil.
Mr. Lefevre has also established this preparation in
his works. The powdered white lead is put with oil
into an apparatus similar to a kneading machine, the
blades of which thoroughly mix the substances. The
paste obtained is then passed through three pairs of
rollers, which laminate and finish it for the packing
barrels.
Mr. Lefevre also uses horizontal stones for grinding
white lead in oil ; five pairs of such stones are em-
ployed, besides the twenty other pairs for the grind-
ing in water.
WHITE COLORS. 153
The men employed at grinding always wear gloves
of lamb skin.
Packing white lead. — This operation is often a
cause of lead colic. To prevent the production of
dust", Mr. Lefevre lets the white lead into the barrel
slowly and carefully, and then compresses it by means
of a screw, which pushes down a wooden block of a
diameter slightly less than that of the barrel. A new
addition of white lead is compressed in the same
manner, and the operation is continued until the
barrel is thoroughly filled.
The packing of the lump white lead is effected as
follows : Rows of lumps, already wrapped in paper,
are formed as close as possible ; and when the barrel
is half filled, it is shaken after it has been covered
with several thicknesses of cloth. These are removed
when the dust has subsided ; but there is very little
dust when the lumps are wrapped in paper. The
packer has always two barrels on hand, so as not to
lose time, and when one is filled, the cover is imme-
diately put on.
All the rooms in Mr. Lefevre's works are kept per-
fectly clean, and the clothing of the men is of such a
nature as to prevent the contact of the white lead
with the skin.
From what precedes, we see that MM. Lefevre &
Co. have taken all possible precautions for protect-
ing their men from lead diseases, which are always
dangerous and sometimes mortal. They have im-
proved the operations of casting the lead, taking
the beds apart, separating the white lead from the
spirals, grinding the white lead in water or oil, filling
and emptying the drying pots, dry grinding, and sift-
ing and packing.
154: MANUFACTURE OF COLORS.
C. Safe Apparatus of Mr. Ozouf.
Mr. G. H. Ozouf, to whom we owe several ingeni-
ous apparatuses for the manufacture of gaseous
waters, has invented, for the preparation of \\hite
lead by the Thenard process, an apparatus which
rapidly combines the carbonic acid with the acetate
of lead in a closed vessel, into which both are pumped
by steam-power. Under pressure, the combination is
said to be instantaneous, and there is produced a
white lead of excellent qualtity, which needs but to
be separated and dried. The description of this in-
teresting apparatus is found in the Technologiste, vol.
xxii. p. 519, year 1861.
D. J. Poelmann's Machine for Separating the White
Lead from the Metal.
Mr. J. Poelmann, manufacturer of white lead, has
also endeavored to render the operations less unhealthy
by inventing a machine for separating the white lead
from the non-corroded parts of the coils or buckles.
Figs. 33 and 34 represent two vertical sections of
the apparatus. A is the ground-floor of the works, B
that of the second story, and c that of the third. D,
under the roof. E, box to hold the corroded lead before
the white lead is separated. F, crank driving the
gearing p p, which carries the box. G, wooden ladder
with iron rails fixed upon, H H, pulleys, carrying the
cord attached to the box E. K, trough delivering the
material to the metallic sieve L. M, reservoir for the
sifted white lead. Q, small car upon which the box
E is fixed. R, latticed loft on the roof for ventilation.
8, draw beam for opening the trap-door i of the
trough K, when the box empties itself of its contents.
WHITE COLORS.
Fig. 33.
155
The metallic lead, separated from the white scales,
is received into a separate box, tightly closed.
E. Precautions taken to render the Manufacture of White Lead
less unhealthy.
Ill the examination made by the delegates of the
Societe d'Encouragement, of the manufacture of white
lead at Portillon, near Tours, and which we have
already described, the salubrity of the processes was
156
MANUFACTURE OF COLORS.
Fig 34.
especially considered. The conclusions of their report
may be found interesting.
1. The works are well adapted for this manufacture,
and the calcining furnaces, being built in the rock,
preserve their heat.
2. All possible precautions have been taken for
saving the men from the toxical action of the lead
preparations.
WHITE COLORS. 157
3. The workshops are well ventilated, and supplied
with railroads, hoists, and other labor-saving appli-
ances.
4. The men are obliged to dress in a complete set
of working clothes, which are furnished, washed, and
kept in order at the expense of the administration.
There are hot baths in the works.
5. A doctor, paid by the direction, gives the neces-
sary medical care to the sick, and every week makes
a general inspection at the works. Thus, a beginning
of lead disease is prevented from becoming dangerous
by suitable regimen.
6. Lastly, we consider that the manufacture of
white lead at the works of MM. Lallu & Delaunay is
as harmless as practicable, and that every precaution
has been taken to prevent the contact of poisonous
substances. Mechanical has been substituted for
hand work wherever it has been possible ; and where
manual labor cannot be replaced there is no danger.
We have had the pleasure of seeing that a complete
suit of working clothes was furnished by the direction
to the men, and that they could not enter the work-
rooms without them. At the end of the day, and
before getting their own clothes, the men have a
thorough washing with soap and water. Besides all
these precautions, all the men are examined every
week by a doctor, who frequently orders medicated
baths prepared in the works.
We have also seen with great satisfaction that the
manufacture of white lead ground in oil is daily in-
creasing at Portillon. When its employment shall
become general, and no lump white lead is sold, we
may rely on a termination being put to the diseases
due to white lead.
158 MANUFACTURE OF COLORS.
§ ^3. White of "basic chloride of lead.
For some time past the effort has been made to
replace white lead or carbonate of lead by a basic
chloride of lead, which is much less soluble in water
than the neutral chloride. Being uncrystalline, it
possesses great body or covering power.
According to Mr. L. Brumlen, of New York, the
lead is finely granulated by passing it through metallic
sieves, and then put into three wooden tubs 1.50
metre in diameter and 0.60 deep, which are disposed
so as to empty their contents one into the other by
opening spigots placed near their bottoms. The
top vessel is filled with vinegar (one litre of which
saturates 350 grammes of carbonate of soda) or with
a solution of neutral acetate of lead holding a little
over 5 per cent, of it.
The lead which has been thus moistened becomes
rapidly oxidized, and there is formed a neutral acetate
of lead. By repeating the operation the basic acetate
is obtained, and this will be the more readily pro-
duced if the solution already contains the neutral
acetate. Up to this point the process does not present
anything very new, since it is generally employed
for preparing neutral acetates. The same person
also states that litharge may just as well be dissolved
in acetic acid.
The solution of acetate of lead is precipitated in
the state of neutral chloride by hydrochloric acid —
the clear liquid and the washings are used again as
acetic acid. The neutral chloride of lead is then
digested with basic acetate of lead until it has ex-
tracted sufficient lead from the latter to become basic.
The clear liquor is decanted, and contains a neutral
WHITE COLORS. 159
acetate of lead. The precipitate of basic chloride of
lead is washed and dried.
The solution of neutral acetate of lead of the second
operation is employed for the preparation of the basic
acetate. Therefore, there is very little waste of acetic
acid, which is the costly material.
§ 4. White of sulphite of lead.
Carbonate of lead is not the only salt o.f this metal
which will furnish a white pigment, and several
attempts have been made to substitute other salts for
the carbonate.
Sulphite of lead is a white and insoluble powder,
which possesses body and does not blacken by the
contact of sulphuretted hydrogen. Mr. Scoffern, who
has proposed its employment, says that it is obtained
in the following manner: Sulphurous acid is prepared
by heating sawdust with concentrated sulphuric acid,
and the gas is passed through a solution of basic
acetate of lead. There is formed a precipitate of sul-
phite of lead, and the liquor is a solution of neutral
acetate which may be rendered basic by boiling it
with litharge, as in the Th6nard process
§ 5. White of tungstatv of lead.
Large quantities of tungstate of soda are employed
in English dye works as a mordant substitute for tin
salts. 50 kilogrammes of tunstate of soda are dis-
solved in the smallest possible quantity of boiling
water, and another hot and concentrated solution of
acetate of lead is poured into the former as long as a
precipitation takes place. After settling, the liquor
is decanted, and the tungstate of lead is drained and
washed. The liquors contain the soluble acetate of
160 MANUFACTURE OF COLORS.
soda, but the basic salt of lead is transformed into the
acid tungstate by a treatment with nitric acid (sp. gr.
1.3) or acetic acid (sp. gr. 1.05), diluted with their
volume of water. The mixture is stirred now and
then, and when the precipitate has acquired a certain
consistency, the liquor is decanted, and the tungstate
is washed with cold water. After draining upon
cloth filters it is dried upon porous stones, which are
heated at a moderate temperature in stove rooms.
The decanted liquors or washings are saved on
account of the oxide of lead they hold.
This process, as well as the two following, has been
indicated by Mr. Spilsburg. The pigments obtained
are costly, do not cover better than white lead, and
are open to the same inconveniences.
§ 6. Antimonite of lead.
If we boil fifty parts of metallic antimony with
twenty parts of concentrated sulphuric acid, sulphu-
rous acid is disengaged, and there remains a white
saline mass, which is a sulphate of antimony. This
salt is heated until it no longer produces acid fumes,
and is then transformed into antimonious acid by a
calcination in a crucible with twenty-one parts of dry
carbonate of soda. The fused substance is boiled in
water, and the solution is decomposed by neutral
acetate of lead. The precipitate is a heavy antimo-
nite of lead, which is separated from the liquor hold-
ing acetate of soda. The pigment is collected upon
filtering cloths, and when it has become pasty, it is
formed into lumps which are dried upon bricks in a
stove room, at the temperature of 60° C.
WHITE COLORS. 161
§ 7. Antimoniate of lead.
A mixture of one part of sulphide of antimony and
five parts of nitrate of potassa, is deflagrated in a red-
hot crucible, or upon the bed of a reverberatory fur-
nace. The calcined product is almost entirely soluble
in boiling water, and the solution is decomposed by
another of neutral acetate of lead. The precipitate is
separated, washed, and dried in a stove-room. This
antimoniate, when pure, is white, heavy, and possesses
a certain body.
§ 8. Antimony whites.
Many attempts have been made for employing the
oxide of antimony in painting, but they seem to have
met with but little success, although the antimony
white possesses many good qualities. It stands water,
is as opaque as white lead, is scarcely acted upon by
sulphurous fumes or sulphuretted hydrogen, and it
produces durable painting especially suitable for out-
side work.
1st. Antimony White of MM. Bobierre, Ruolz, and Rousseau.
It is intended by this process to substitute for
white lead a substance which contains no lead, is not
so dangerous to the health of workmen, and which
may be obtained at a price equal or less than that of
white lead.
After many experiments, these manufacturers gave
the preference to the oxide of antimony, which may
be prepared by known processes ; nevertheless, they
consider that the following method is more econom-
ical : —
"In an apparatus, which may be modified in many
ways, a brick oven or a cast-iron furnace for instance,
11
162 MANUFACTURE OF COLORS.
there are made to play on the heated surface of sul-
phide of antimony, a draft of air and a jet of steam
which may be regulated for each kind of sulphide
employed. All the sulphur escapes in the state of
sulphurous acid, which may be saved, and the anti-
mony is converted into the white oxide, which is
collected in receivers placed at the end of the heating
apparatus.
u This product may also be prepared in an ordinary
roasting furnace, but it is not so comminuted as that
obtained with the aid of steam. Oxide of zinc, other
white oxides, and certain compounds prepared in a
similar manner, acquire peculiar properties which
were, until now, unknown.
" The product thus prepared may be ground im-
mediately in oil, without passing through the opera-
tions of drying, pulverizing, sifting, etc.
" Considering the abundance and the cheapness of
the natural sulphide of antimony, the white oxide
may be obtained at a cheaper rate than white lead.
Moreover, its covering power is at least twice that of
the best white lead."
2d. Antimony White of MM. Voile and Barreswill.
Here is the process of MM. Yalle and Barreswill,
as explained by themselves : —
" "We wish to record the results which we have
obtained in our study of various chemical compounds,
intended as substitutes for white lead in oil painting.
" Many experiments have already been made on
this subject, and are found in the treatise on painting
by Mr. de Montabert. It results from our own re-
searches : 1st, that several lead compounds, other
than the carbonate, may be used the same as white
WHITE COLORS. 163
lead. 2d, that antimony, after lead and bismuth, is
the metal which furnishes white pigments with the
best covering power. This observation, mentioned
by Mr. de Montabert, has since been pointed out
anew by Mr de Euolz (Technologists, 5th year, page
155).
" The same as with white leads, the body or cover-
ing power of antimony whites varies with their mode
of preparation.
" Mr. de Montabert states his preference for the
oxide of antimony ; ours is for Algaroth powder,
which appears to us to possess properties similar to
those of white lead. However, we reserve for our-
selves the right of employing the oxide (prepared
from the oxichloride and carbonate of soda) sublimed
or not. Here is the mode of preparation of this new
white : —
" The Algaroth powder is obtained by the treat-
ment of the sulphide of antimony by hydrochloric
acid. The sulphuretted hydrogen is made to burn,
and the sulphurous acid produced is employed in lead
chambers for the manufacture of sulphuric acid.
"The clear and settled chloride of antimony is
decomposed by water.
" The hydrochloric acid resulting from this decom-
position, and which still retains small proportions of
antimony, is used for condensing hydrochloric acid
gas, or for separating the gelatin from bones.
''We also manufacture the new antimony white by
treating with hydrochloric acid, either the residue of
antimony ore calcined at a low temperature, or the
product of the action of sulphuric acid upon the
sulphide of antimony.
"The sulphurous acid resulting from the treatment
164 MANUFACTURE OF COLORS. ,
of the antimony ore is employed, either for the manu-
facture of sulphuric acid, or for that of sulphurous
acid and sulphites ; in fact for all the uses of sulphu-
rous acid.
" For the manufacture of antimony whites, Alga-
roth powder, and oxide by the dry or by the wet way,
we make no difference whether the sulphide of anti-
mony contains iron or not."
3d. Antimony White of MM. Hallett and Stenhouse.
MM. G. Hallett and J. Stenhouse employ a natural
oxide of antimony, or an ore where the sulphide and
the oxide are associated together. The mineral is
finely pulverized, and separated from its gangue by
washing and mechanical processes. The heavy me-
tallic portions are calcined in a reverberatory furnace,
and the sulphur is driven off as sulphurous acid.
The residue is mostly antimonious acid, which, after
being further powdered, is mixed with oil or varnish.
The product is often contaminated with small pro-
portions of lead, copper, or iron, which diminish its
whiteness. In such a case it is reserved for inferior
painting.
The pure antimony white is less affected by sul-
phuretted hydrogen than white lead. It possesses
more body than zinc white, but less than white lead.
§ 9. Zinc white.
For a century the unalterability of zinc white was
known by chemists, and Courtois, of the Laboratory
of Dijon, mentioned it in 1770 to the academy of that
city. Three years later Guyton de Morveau pub-
lished a memoir on the same subject, which was
reprinted in the Encyclopedic Methodique des Arts et
WHITE COLORS. 165
Metiers, then published. After several experiments,
this learned chemist proved, in the presence of the
Prince de Conde, that painting done with tartrate
of lime, tin white, and zinc white, and exposed to the
contact of sulphuretted hydrogen, was not changed
in color.
In 1796, Mr. Atkinson, of Harrington, took out a
patent for the application of zinc white, and Guy ton
de Morveau, in the Annales des Arts et Manufactures,
claimed for France the priority of invention, since, in
1781, Courtois had begun the manufacture of zinc
white on a large scale, and that stores existed at
Paris and at Dijon for the sale of that material.
Moreover, zinc white was already employed in France
for artistic paintings, for mixing with other colors, etc.
The inside paintings of the man-of-war le Lanyuedoc
having been done with zinc white, in 1786, a commis-
sion for its examination made the following report : —
I. The painting with zinc white is handsome, but
not so bright as that with white lead ;
II. The smell of the fresh zinc paint is not so
strong or disagreeable as that of white lead ;
III. The zinc paint took six days to dry, whereas
four days were sufficient for white lead ;
IY. 250 grammes of zinc white and the same quan-
tity of nut oil were sufficient to cover a surface of a
little above 3.80 square metres, etc.
A copy of this report being transmitted to the
Marshal de Castrie, then Secretary of the Navy, he
recommended zinc paint for the insides of ships.
In a report made at the Institut, in 1808, by Four-
croy, Bertholet, and "Vauquelin, we remark the follow-
ing passage: "Among the products manufactured by
Mr. Mollerat there is a zinc white, the use of which
1G6 MANUFACTURE OF COLORS.
should be strongly recommended. Its defects are so
slight in comparison with those of white lead, that it
should be adopted, at least in house painting. Be-
sides its salubrity, it gives purer colors ; and, if its
brightness is less at the beginning, it does not darken, j
"With equal weights it covers a larger surface than !
carbonate of lead, and, although it is more dry under
the brush, this is easily remedied by charging the
brushes oftener, or giving another coat."
Lastly, in September, 1844, Mr. Mathieu sent to
the Academy of Sciences a memoir on the oxide of
zinc, in which he says that he obtains that product in
a state of great purity, and by a much cheaper pro-
cess than those then followed. Mr. Mathieu does not
indicate the process, but he insists on the economy
of the new method, and on the future of the oxide of
zinc, which ought to take the place of white lead in
the majority of cases. Moreover, it does not compro-
mise the health of the men employed in its manu-
facture.
How is it then that, notwithstanding all these re-
searches, successful trials, and honorable testimonials,
the zinc white has not reached the place it ought to
occupy in the arts ?
A contractor in painting work at Paris, Mr. Le-
claire, after acquiring a full knowledge of what had ,
been done before him, has established at Courcelles,
near the Seine, large wrorks for the manufacture of
zinc white, and has added several important improve-
ments.
_
1st. Manufacture of Zinc White, by Mr. Leclaire,
Mr. Leclaire has established in his works a Silesian
furnace with ten retorts. An arrangement of scrapers
WHITE COLORS. 167
keeps the mouths of the retorts constantly open, and
in front of them is a very small chamber, the floor of
which is movable, and with a door which opens in the
room where the furnace is. The top of this small
chamber is connected with the tipper part of the con-
densing rooms, which stand on the right and left of
the furnace, and are deeper than the level of the fur-
lace floor.
A powerful draft exists at the end of a series of
;loth drums which receive the last particles of oxide
>f zinc. The floors of the condensing rooms are pro-
rided with hoppers, through which the oxide falls
ito the barrels.
Manufacture. — When the furnace is at the proper
jmperature, the door of the small chamber is opened,
the zinc is introduced into the retort. The door
is then closed and luted, and the movable floor lifted,
combustion of the zinc begins immediately, and
»es only when all the metal is burned out, that is,
>xidized by the oxygen of the air which comes through
;he lower part of the chamber. The oxide of zinc,
^cording to its degree of lightness, is carried to a
greater or less distance, and is collected in the hop-
pers placed at the bases of the different condensing
apparatuses.
With two furnaces it is possible to produce every
day 6000 kilogrammes of oxide of zinc, which is sold
at from 70 to 75 francs per 100 kilogrammes.
There is no more difficulty in painting with zinc
white than with white lead. Zinc white may be per-
fectly well mixed with oil, without grinding, by ope-
rating as follows : The zinc white, oil, and essence of
turpentine are mixed together, and allowed to stand
168 MANUFACTURE OF COLORS.
for about six minutes ; the whole is then stirred with
a brush and passed through a sieve.
Zinc white, whether alone or mixed with other pig-
ments, is used for oil and water colors, for varnish,
and for distemper painting, etc. Zinc white may
also be used : I. In the manufacture of smooth papers
and of visiting cards as a substitute for white lead ;
II. As a component part of mastics for keeping tight
the joints of steam engines ; III. For a face powder,
colored with a small proportion of carmine; IV. And
in the manufacture of Brussels laces.
Zinc white may be mixed with various pigments
possessing durability, such as the oxides of iron,
charcoal, oxide of manganese, ultramarine, etc. etc.,
and will then furnish colors, the tones of which will
remain permanent, and this is a great advantage in
painting.
The white or gray pigments prepared with the
zinc oxide are not, like those with a basis of white
lead, altered by hydrosulphuretted fumes. Repeated
trials have been made which prove that painting with
zinc oxide stands well in privies, and in those places
where Bareges (sulphur) baths are administered.
An experiment has also demonstrated that zinc
paints may be employed, like red lead and orange
mineral, for preserving iron from oxidation.
Mr. Leclaire has indicated a method of preparing
drying oil without lead, but with the peroxide of
manganese. 200 parts of boiled linseed oil and 10
parts of peroxide of manganese are boiled together
for six and eight hours, and the mixture is frequently
stirred. After cooling and filtration, the oil has
become a good dryer.
Lastly, Mr. Leclaire has also prepared variously
WHITE COLORS.
109
colored pigments, with zinc as a basis, for artists and
house painters. These pigments are : —
1. Gold button (bouton d'or) yellow ; 2. Lemon yel-
low ; 3. Pale yellow; 4. Baryta yellow; 5. Dark
English green; 6. Light English green; 7. Milori
green ; 8. Green earth.
We find in the Technologiste the following descrip-
tion of a process for the manufacture of the oxide of
zinc : —
Zinc white may be prepared by the distillation of
zinc ore or of the metal in special furnaces.
Fig. 35.
Fig. 36.
Description of the apparatus. — Fig. 35 is a hori-
>ntal section of a glass furnace, with certain modifi-
itions which will be explained
irther on, and with the additional
fixtures necessary for the manu-
facture and the condensation of
zinc white.
Fig. 36 is a transverse section of
the furnace.
Fig. 37 is a longitudinal section.
A, door of the furnace. B, fire-
place, c c, retorts made of clay or
of any other substance able to stand a high tempera-
ture. There are five retorts on each side, but the
170 MANUFACTURE OF COLORS.
number may vary. D D, openings of the retorts,
through which the products of the distillation escape.
F F, iron rods or scrapers for keeping the mouths of
the retorts open. E E, horizontal bar to which the
scrapers are attached. By pushing it backwards and
forwards, the scrapers do their work. Motion is im-
parted by hand or by power. G G, hoppers which
receive the heavy portions of the calcined zinc. They
are placed below the mouths of the retorts, and their
lower parts are connected by short pipes with a
general trough G1, which delivers the products into
the receiver G2.
It is well understood that these hoppers receive
only the heavy portions of the distilled products, or
the scrapings from the mouths of the retorts, the
weight of which is too considerable to be carried by
the draft into the oxidizing chamber.
Fig. 37.
H is a small iron cage which isolates each retort
from the others, and which stands upon a low wall.
It may be moved or shifted by means of a crane or of
rollers. The open part of these cages is in front of
the mouths of the retorts, so that the distilled products
may pass from the cage into the oxidizing chambers
WHITE COLORS. 171
and condensers. In Fig. 35 some of these cages
are represented, the others are not. Their back
part may be opened or closed, as desired, j is an
opening on the floor K, which is closed with a hinged
trap door, raised or lowered by means of a chain i,
one end of which passes through the partition, so as
to operate without opening the cage. Other ways of
moving this trap door may be devised.
The arrangements H, i, j could be adapted to the
furnaces where zinc is smelted. There is always a
certain proportion of zinc oxide formed which is lost,
and which could be saved in the above-described
manner, or by closing with a cloth the space where
the zinc is collected. If the iron cage or chamber be
used, a small opening is made on the partition i,
which is closed with a glass, so as to allow of the
watching of the distillation. The same result will be
obtained by fixing iron plates on each side of the
opening of the retorts. Another movable plate will
be used as a cover.
K, floor carrying the cages H, and separating this
part of the apparatus from the oxidizing chamber.
The air drafts may be introduced into the chamber
having K for the floor, or through the floor itself,
which, then, should be hollow. Fresh air is neces-
sary, in order to lower the temperature of the cham-
ber above the floor.
L, hot air pipe communicating with the hoppers
G G, and carrying away the white oxide into the
oxidizing chamber. Instead of hot air, cold air may
be passed through the cages H, or, if it be thought
desirable, a mixture of cold and hot air may be intro-
duced.
M, oxidizing room, where the metallic vapors are
172 MANUFACTURE OF COLORS.
oxidized by atmospheric air, as soon as they escape
from the retorts. N, portion of the oxidizing chamber,
where there are cloths for sifting the products. The
lower part is hopper shaped, and conducts the oxide
of zinc into receivers below. There are valves, regis-
ters, etc., for letting the product in or out.
The whole of the product may be collected with-
out loss, by means of properly arranged vessels or
receivers filled with water, and provided with two
tubes. One of the latter communicates with the
oxidizing room, and dips, at the other end, into the
water of the receiver. It conducts the zinc white
from the oxidizing room into the receiver. The end
of the other tube does not dip into water, but takes in
the air of the receiver and produces a vacuum in the
other tube, thus forcing the descent of the products,
o, o are the receivers for the oxide, p, P, partitions
of metallic wire, or cloth, for allowing the air to pass
through, and for sifting and retaining the products.
Q, exhaust tube for moving the air through the sifting
surfaces, and attracting the products towards the
receivers.
R is another tube or hood placed on top of the
opening of each retort, and intended for the escape of
the volatilized products, when the charge is put in,
and when the communication with the oxidizing room
is closed by the trap-door J. The hood R carries the
volatilized products, by suitable conducts not seen in
the figure, into the oxidizing room, or into a special
condensing apparatus. A draft may be produced,
either by heating the hood, or by an exhauster. This
hood is closed during the distillation, as long as the
metallic vapors pass directly into the oxidizing cham-
WHITE COLORS.
173
ber. In this case, the vacuum or exhaust is produced
by the lost heat of the furnace.
In the preceding arrangement, the retorts are sep-
arated each from the other, and we readily understand
that this result may be arrived at by other analogous
methods. For instance, the floor K may be disposed
so as to be raised or lowered at will, in order to sep-
arate the retorts one from another. It may be divided
into as many sections as there are retorts, so that, by
raising or lowering one of them, the communication
with the oxidizing room may be established or closed.
Fig. 38.
The retorts may also be separated by partitions and
rendered independent of each other. The hood R
Fig. 39.
may have such dimensions and exhausting power as
to carry all of the products into the condensing rooms.
Fig. 38 represents a horizontal section of another
furnace for the manufacture of zinc white. *
174 MANUFACTURE OF COLORS.
Fig. 39 is a longitudinal section.
Fig. 40 is a transverse section.
This furnace is closed on top, either by a cover
which may be moved for charging the retorts, or by
a hopper filled with the sub-
stances for the operation. It
could be hermetically closed on
top, and opened on the sides for
charging. Lastly, the materials
, may be introduced through the
opening B, and in this case, an ,
inclined plane is so disposed as
to receive the materials.
All these dispositions, and
others, are well known, and we shall only examine
the principal details.
A, air furnace of proper size. B, opening through
which the products pass into the oxidizing room c,
which is arranged as in the preceding figures. Be-
tween the various hoppers of the oxidizing room, there
are metallic or cloth sieves, to arrest the heavier pro-
ducts or the impurities carried away through B. The
oxide of zinc, being very light and comminuted, passes
through these screens. The opening B may be pro-
vided with a register or damper, for closing the com-
munication between the furnace and the oxidizing
rooms, whenever the circumstances require it.
The charging hole may be provided with a hopper,
or any other apparatus for delivering the materials as
the distillation progresses. Besides the current of air
caused by the draft or blast, and necessary for the
combustion, another injection of air could be made to
furnish the necessary oxygen to the vapors of zinc,
either in the furnace or in the flue B.
WHITE COLORS.
175
The furnace may be circular in shape, or horizontal,
or more or less inclined. Instead of one opening B,
several may be made at different heights, even near
the fireplace ; in which case the products, as soon as
formed, are carried directly into the oxidization room,
without being obliged to pass through the materials
piled above. A reverberatory furnace may be em-
ployed, and also a coke-oven ; but in the latter case,
there should be a fireplace heating the furnace by
means of flues circulating under the hearth or sole,
and in the side walls. A top opening will be used
for charging, and a side one for the passage of the
products into the oxidizing and condensing rooms.
Fig. 41.
Fig. 42.
Fig. 41 is a horizontal view of another kind of
furnace for the manufacture of oxide of zinc.
Fig. 42 is a transverse section.
Fig. 43 is a longitudinal section.
We see that this furnace consists of two horizontal
and parallel flues or retorts, with fireplaces receiv-
ing a blast of air. A A, flues built of fire bricks.
B B, tuyeres for hot or cold air blast, c, lower part
of the fireplace, where the cinders and ashes are
collected. These are removed now and then through
a lower opening. But if large ash pits J j are left
176 MANUFACTURE OF COLORS.
in the brickwork, the part c is closed with a grate or
damper. With grate bars sufficiently close to retain
the ore, and large enough to let the cinders fall through,
a natural draft of air may be substituted for the arti-
Fig. 43.
ficial blast. In this case, the proper fluxes should be
added to the ore, for transforming the earthy parts
into fluid cinders.
D D are fireplaces opening into the same arched
flue F. The charge of ore and coke is piled up to the
level a. E E, brickwork separating the fireplaces.
The air may be admitted into the flue F, either by
compression or exhaustion, for oxidizing the metallic
vapors and carrying them into the condensing rooms.
At each end of the flue F, there are dampers G G,
establishing the communication with the condensing
or collecting rooms. H H are these rooms, which are
arranged in the manner previously described. In-
stead of two rooms only one may be used, if desired,
ill are the openings for charging, which stand im-
mediately above the fireplaces. They are closed by
a tight cover, or by a metallic hopper filled with the
ore mixture, which is thus dried.
We readily see that this apparatus may be modified
in several ways. For instance, instead of two series
WHITE COLORS. 177
of tuyeres, only one, or a greater number, may be
employed. The number and the sizes of the fireplaces
may vary. The brickwork may be raised still higher,
and less space left for the passage of the air and
the metallic vapors. The two collecting chambers
may be replaced by one. These modifications do
not change the principle of the invention, which
consists in a horizontal tubular flue, connected with
one or several fireplaces using a natural or forced
draft of air, and which communicates with rooms into
which the products of the combustion are driven by
exhaustion or by compressed air.
Mode of operation. — 1. With the retorts. — Ingots
zinc are charged into the retorts, which have
n previously brought to a white heat. As soon as
e whole charge is in, the iron cage H is closed,
d the trap-door on the floor is lifted, so as to
t the retort into direct communication with the
idizing room. The vapors of the distilled zinc
come oxidized by the air, and the white oxide is
nstantly drawn into the receiving or condensing
om by the vacuum maintained in the pipe R. The
xide is arrested by metallic screens which allow
of the passage of the air, and falls into hoppers,
which deliver it into the receivers. "When the retort
is empty, the trap-door is closed, the damper over
the hood is lifted, and a new charge is put in, and
the operation continues as before.
If we operate with a zinc ore, or an oxide of this
metal, it is mixed with half its weight of charcoal,
coke, or bituminous coal, as is done in the ordinary
treatment of zinc ores.
If the ore is a blende, that is, a sulphuret, it is
12
178 MANUFACTURE OF COLORS.
necessary to add a certain proportion of peroxide of
manganese, carbonate of lime, or oxide of iron, in the
ratio of the sulphur contained in the ore.
2. Air furnace. — When we employ the air furnace,
the charge of ore is mixed with the above-mentioned
substances, and with a certain proportion of a proper
flux. As soon as the zinc becomes separated from
the foreign substances with which it was combined,
its vapors are rapidly oxidized, and the zinc white is
collected in the rooms already mentioned.
3. Reverberatory furnace or coke oven. — The working
of the reverberatory furnace is so well known, that it
is useless to describe it here. The mode of charging
and cleaning it is the same as with other ores. This
method, however, does not appear so advantageous as
the others. When furnaces, similar to coke ovens,
are employed, they are charged while very hot with
metallic zinc or its oxides, alone or mixed with coal.
A current of air passes, either through the furnace,
or only at the opening through which the metallic
vapors escape to go into the collecting room. If the
metal be employed with this apparatus, or any similar
one, it may be made to fall by drops by passing it in
the molten state through a metallic sieve.
4. Horizontal tubular furnace. — After the furnace
has been brought up to the proper temperature with
bituminous coal or coke, the mixture of ore and fuel
is thrown in through the openings 1 1 1, with a certain
proportion of aluminous or calcareous flux to suit the
nature of the gangue. The space F is left open.
When blende is used without previous calcination,
the ore is mixed with peroxide of manganese, car-
bonate of lime, or oxide of iron, in proportion to the
sulphur held by the blende. The ore is decomposed,
WHITE COLORS.
170
and the metallic vapors are oxidized and collected in
the manner previously explained.
Immediately after charging, and until the mass is
in an incandescent state, gases and solid but light
substances are disengaged, which, if received in the
collecting rooms, would impair the whiteness of the
products. This is the reason why two condensing
rooms are employed, one on each side. One of these
rooms receives the products distilled before the whole
mass is in the incandescent state, and the other, by a
change of dampers, is employed for the pure products.
The disposition of the collecting or condensing rooms
is common to all the various processes.
Fig. 44.
Fig. 46.
Figs. 44, 45, and 46 represent a furnace built in
the manner of those employed in the manufacture of
gas, but possessing the fixtures necessary to the dis-
i
180 MANUFACTURE OF COLORS.
tillation of zinc, the oxidization of its vapors, and the
collection of the oxide.
Any number of such furnaces could be disposed one
near the other, each having several retorts. The same
letters in these figures correspond with similar parts
in the preceding cuts ; therefore, it is useless to ex-
plain them anew. The only difference is, that the
retorts may be charged from the same room in which
the fireplace is. The retort is open at both ends D, D',
the latter being that used for charging. During the
distillation, this opening is kept hermetically closed.
"With this disposition it is possible to dispense with
the chamber or cage H, and with the floor K. Never-
theless, this apparatus is not so advantageous as
others, and should be employed only in case of neces-
sity.
2d. Mode of Fabrication by Murdoch.
A method of manufacturing the oxide of zinc,
several years older than that previously described,
has been indicated by Mr. Murdoch. Although there
is a great analogy in the chemical processes, we shall
mention it here, in order t6 complete the data relating
to the oxidization of zinc.
By the ordinary methods of preparing the oxide of
zinc, air is allowed to enter the retorts or vases hold-
ing the metal, and oxidizes the metallic vapors. Part
of the oxide is collected in pipes adapted to the retort,
but the greater portion remains in the retort mixed
with impurities.
The improvement consists : 1st, In preventing the
access of the air to the molten zinc or to the
zinc furnishing materials held in the retort, and in
burning the metallic vapors on the outside of that
I
WHITE COLORS. 181
vessel in which they have been generated; 2d, In
passing the mixture of air and oxide through sieves
or screens, which retain the oxide ; 3d, In producing
a strong air blast or draft (by a blowing machine or.
otherwise) which is passed through the rooms where
the oxide is produced and collected. The operation
is thus assisted considerably.
For the manufacture of zinc oxide by this process,
five rooms are employed : the retort room, the air
room, the oxidizing room, that for the collection, and
lastly, the inspection room.
The first of these rooms contains the furnace of the
itort or generating vessel; and it is there that the
Derations of charging and cleaning take place. The
>tort which receives the zinc or its ore is of clay,
id will stand a white heat. It has two openings,
of which is for charging and cleaning, and is kept
jrmetically closed during the distillation ; the other
the outlet through which the metallic vapors
scape into the oxidizing room.
The air room communicates with the outside
:mosphere, and is provided with metallic or cloth
;reens which allow of the passage of the air, but
'event that of the floating dust. The air is therefore
a measure purified.
One of the extremities of the retort penetrates on
to one side of the oxidizing room, and, as soon as the
metallic vapors appear, they burn in contact with the
air which comes from the air room. The white fumes
or flakes resulting from this combustion and which
are oxide of zinc, or flowers of zinc, are carried by the
draft into the collecting room. A flue or trough
connects the latter room with the stack of the furnace
and thus creates the draft. Several screens of cloth
182 MANUFACTURE OF COLORS.
or metallic gauze are placed before the opening of the
air trough, so as to retain the oxide of zinc. These
screens are now and then, or constantly, shaken, in
order to separate the adhering oxide which, other-
wise, would obstruct the passage of the air.
The inspection room is on the opposite side of the
entrance of the retort in the oxidizing room. The
partition wall has two openings : one with a colored
glass to diminish the glare of the burning metal, and
to allow of the watching of the operation; the other
with a small door for passing and using a scraper,
should the opening of the retort become obstructed.
3d. Manufacture of Zinc White at Portillon, near Tour*.
The owners of the white lead works at Portillon
have also established, at the same place, the manu-
facture of zinc white with a furnace holding seven
retorts. The oxide of zinc, of which about 2000 kilo-
grammes are produced every day, goes upwards after
its formation, and is collected in a series of cloth
cylinders, delivering it into barrels through their
lower extremities, which are easily closed and opened.
There cannot be a loss of oxide, since the air draft
has to pass through 600 metres of collecting space
before it escapes into the atmosphere. The zinc white
is ground in oil by processes similar to those em-
ployed, and already described, for the grinding of
white lead at the same works. The oxide of zinc is
put wet into the kneading machine, but the oil sepa-
rates the water when the paste is passed through the
grinding cylinders.
WHITE COLORS. 183
4th. Snovj White i Zinc White, Hopper White.
The oxide of zinc, obtained by the combustion of
the metallic vapors in atmospheric air, is not homo-
geneous. About one-half of the product is exceed-
ingly light, and is called snow white; the remainder
is more dense, and goes under the name of zinc white.
Painters affirm that the latter possesses greater body
or covering power than the former. Therefore, seve-
ral manufacturers have tried whether it would not be
possible to produce the dense quality without admix-
ture of snow white. The thorough separation of the
;wo oxides is not considered practicable. Mr. Bou-
[uette's process consists in arranging and regulating,
drafts of air in such a manner, near the outlets of
the retorts, that the light snow white is carried
ipwards into a room above the furnace, whereas the
leavy white falls into a hopper underneath the dis-
:illing vessels. The operation is not very regular.
We should remark that the zinc white collected at
:he beginning of the condensing apparatus, near the
furnace, is a mixture. of oxide of zinc with metallic
sine, and a greater or less proportion of cadmium,
iron, and copper. The oxide from the tail end of the
uidensing rooms is always lighter, and the two
:inds are generally mixed together.
Mr. Sorel thus describes a process for separating
:hem : " A certain quantity of zinc, put into large
iufl9.es, is heated only to the point of fusion, and is
ten inflamed. The burning will soon cease if care be
lot taken to constantly rake off the oxide formed on
the molten surface. The zinc, which is all the time
in contact with the oxygen of the air, produces a very
light oxide, which is carried away by the draft into
184: MANUFACTURE OF COLORS.
the collecting rooms above the furnace. The oxide
remaining on the surface of the bath is generally
contaminated with other metallic oxides, and is
made to fall into a receiver or hopper near the fur-
nace. It bears the name of liopper white, and is not
so white as that which has been volatilized. The
advantage of this process is simply the separation of
the two oxides.
"Hopper white covers more than snow white,
but it is not so bright. In order to impart greater
density to snow white it has been suggested to cal-
cine it in clay crucibles, or, better still, to make it
into a paste with water, and to form lumps which are
dried in a stove room. The white, after these opera-
tions, is more difficult to grind, but it covers more
and has a better appearance."
5th. Saint-Cyr White.
Another product, manufactured at the works of
Portillon, and called Saint-Cyr white, is a mixture of
white lead and zinc white.
6th. Vitry White.
This is a mixture in variable proportions of zinc
white with sulphate of baryta. It is now seldom
met with in the trade under that name, and, if sold
as zinc white, constitutes a fraud which should be
punished.
tth. Various Pigments obtained with Zinc White.
Zinc white is also employed as a basis of various
. pigments employed in painting. 100 parts in weight
of zinc white and —
WHITE COLOHS.
185
1
pai
1
u
100
U
2.5
u
6
»
3
it
3
u
10
u
2.5
u
2.5
u
10
ii
0.9
u
0.2
u
8
u
100
u
8
a
50
ii
12
u
400
"
6
u
6
u
part of indigo
charcoal
gray zinc oxide
chromate of zinc or lead
yellow ochre
yellow ochre ^
vermilion i
sienna earth
chrome yellow)
Prussian blue I
chrome j^ellow
Prussian blue )
madder lake )
Prussian blue
chrome yellow^
Prussian blue J
yellow ochre
black
chrome 3rellow \
Prussian blue >
black )
= azure- white.
= pearl-gray.
= slate-gray.
= straw-yellow.
= stone color.
= chamois.
= dark chamois.
= lemon.
= gold-yellow.
= tint of azure-blue.
= water-green.
= grass-green.
= olive-green.
= bronze-green.
For obtaining pure or mixed hues, the following
substances are also employed: Ultramarine, cobalt
blue, Prussian red, ivory, bone and lamp blacks,
oxide of manganese, etc.
8th. Various Processes for the Manufacture of Zinc White.
Many processes and apparatuses have been de-
scribed and proposed for the manufacture of zinc
white. They are generally based upon the oxidation
of zinc vapors by the oxygen of the air. Some
replace the retorts by muffles, or heat the zinc
directly upon the hearth of the furnace , others em-
ploy a pot of fire clay. Certain manufacturers
use a draft of pure air ; others claim that the gases
of the combustion of coke or charcoal, which have
been passed and purified through lime, give a better
186 MANUFACTURE OF COLORS.
oxidized zinc white. In countries where rich zinc
ores are found, zinc white is advantageously prepared
by the reduction of the ore with charcoal.
The great quantities of .sulphate of zinc produced
in galvanic batteries, are now without use. All its
component parts may be utilized in the following
manner. By a calcination in a clay vessel, the
sulphate of zinc, when pure, is transformed into a
white and light oxide for painting, and into sulphu-
rous acid which may be dissolved in water, or used for
the manufacture of sulphites, which are now employed
in large quantities. Pure oxygen is also formed.
All these processes, conducted with the proper care,
may furnish a zinc white of good quality. But we
do not feel that we should fill up this manual with
more extended explanations of methods, which, after
all, do not appear superior to those which are well
known and tried.
We should add that metallic zinc necessarily in-
creases in weight, by combining with the oxygen of
the air, and that one hundred parts of metal should
give about one hundred and twenty-four of oxide.
But in practice, the result is only from one hundred
and ten to one hundred and twelve parts of white, on
account of the loss occasioned by the impurities of
the metal, and the waste of oxide carried away in the
air, and escaping through cracks in the apparatus.
9th. Uses of Zinc White, and Dryers.
Zinc white mixes readily with all the liquids
employed for white lead, such as oil and essence of
turpentine; and as it is always in an impalpable
powder, it does not need a protracted grinding to
acquire the proper consistency. Glue size may also
l>e employed.
WHITE COLORS. 187
The advantages of zinc white are, that it is scarcely
poisonous; that it does not change the colors with
which it is mixed, and that it does not darken by the
fumes emitted by sulphuretted hydrogen or animal
substances. On the other hand, it is slow drying,
and dryers are necessary.
We have already seen, that in 1845, Mr. Leclaire
had employed the peroxide of manganese for the
quick drying of the zinc white. Here is the instruc-
tion published by the Society of the Yieille-Mon-
tagne, in a manual for the painters with zinc white : —
" The peroxide of manganese is broken into pieces
of the size of peas, and after sifting the smaller par-
ticles, the remainder is thoroughly dried upon a piece
of sheet-iron, but without being calcined. It is then
wrapped in a piece of strong cloth, which is after-
wards placed in a small basket of wire gauze with
very narrow meshes.
" "Well clarified linseed oil is poured into a kettle,
which is held upon an iron plate above the fireplace,
and the basket of peroxide of manganese is suspended
in it from an iron rod crossing the kettle.
" The oil is brought to a temperature a little below
the point of ebullition, and maintained there. Too
much heat will cause the oil to boil over, and there is
then great danger of fire. The heating should last
twenty-four hours for large quantities of oil.
" The operation is completed and successful, when
the oil has acquired a reddish tinge. It is then left to
cool, is filtered, and packed in glass or stoneware
bottles, which are carefully closed.
" The same manganese may be used any number of
times ; indeed it is better when it has already been
employed. Before using it again, it is coarsely broken
188 MANUFACTURE OF COLORS.
in a mortar and new manganese added ; the whole is
then sifted, and the proportion is fifteen parts of the
mixture to one hundred parts (in weight) of oil.
"The first time manganese is used, it is put into
the oil only on the second day of the heating, because
fresh oils hold a little water, and the new manganese
might act too powerfully and cause the inflammation
of the liquid.
"If the manganese has already been used, it is put
into the oil on the first day, before lighting the fire.
Less heating is needed with fresh than with old man-
ganese. In either case, the fire is urged but mode-
rately, and the basket of manganese must be entirely
covered with oil, without touching the sides of the
kettle.
" If the dryer be too thick from a strong heating,
essence of turpentine may be added to it when it is
nearly cold, otherwise there is danger of inflammation.
The proportion of the essence should be sufficient
to reduce the dryer to the proper consistency for
using and keeping it."
In his Cliimie des Couleurs, Mr. J. Lefort makes the
following observations on dryers: —
" In order to render dryers suitable for every kind
of painting, and to facilitate their transportation, it
has been proposed to mix them with slaked caustic
lime. But as the latter contains an excess of water,
it is heated at a moderate temperature in a draft of
hot air, until the powder feels dry. The combination
is a real drying calcareous soap, which being ground
with colors and ordinary linseed oil, is a good sub-
stitute for drying oil. From four to six parts of dry-
ing soap in powder, are sufficient for one hundred
parts of oil.
WHITE COLORS. 189
" Peroxide of manganese, especially when powdered,
communicates to the oil a reddish tinge which is dis-
agreeable for fine white painting. Of late years,
this inconvenience has been remedied by the use of
white salts of manganese ; and experience proves that
the majority of soluble salts of protoxide of mangan-
ese and zinc (sulphates, chlorides, acetates), when
ground with ordinary linseed oil and zinc white, im-
part to the latter the drying property it was deficient
in.
" It is absolutely necessary that these various salts
should be entirely deprived of their combined water.
Therefore, they are thoroughly dried upon plates
heated at from 80° to 100° C., until they are perfectly
white and opaque. They are then mixed in equal
proportions, and finely powdered.
"These dryers which have been patented, and which
are constantly employed in painting with zinc, are
composed of sulphate of zinc and acetate of mangan-
ese, or of sulphate of manganese and acetate of zinc.
Three or four parts are sufficient with the proper
quantity of ordinary linseed oil, for one hundred parts
of zinc white."
Moreover, we shall examine anew, in a subsequent
chapter, the various dryers and compositions which
have been proposed.
10th. Adulteration of Zinc White.
Zinc white is adulterated with sulphate of baryta
and sulphate of lime.
The first adulteration is recognized by dissolving
the oxide of zinc in diluted nitric acid, when the sul-
phate of baryta remains as an insoluble residuum.
The separation of the sulphate of lime is more
190 MANUFACTURE OF COLORS.
difficult. The adulteration is generally made with a
perfectly white sulphate of lime, in impalpable powder,
which is sometimes called atomic sulphate. The sus-
pected sample of zinc white is dissolved, with the aid
of heat, in a small quantity of concentrated nitric
acid. The solution is diluted with five or six times
its weight of distilled water, then saturated with
ammonia, and a few drops of oxalate of ammonia
poured in. The precipitate of oxalate of lime is col-
lected upon a filter, calcined, and transformed into
carbonate which is weighed. A solution of chloride
of barium, poured into the filtered liquor, produces a
sulphate of baryta which is insoluble in water and in
concentrated acids.
If the sample be already ground in oil, 10 grammes
of it are calcined in a porcelain crucible, and when all
the oil is decomposed, the cold residuum is treated
by distilled water. A few drops of nitric or sulphuric
acid poured into the liquor, will disengage sulphu-
retted hydrogen in greater proportion as the sample
is more adulterated.
If the oil has been rendered drying by compositions
of lime and sulphate of zinc, these substances should
be determined by analysis, and taken into account in
the search for the adulteration of the sample.
llth. Danger and Salubrity of Zinc White.
When this pigment began to be largely used in
painting, its salubrity was considerably discussed.
Some persons pretended that it was as dangerous as
white lead; others, on the contrary, that it was
entirely innocuous. Facts were brought forward by
each party; but, without burdening this volume with
all the documents on the question, it is certain that
WHITE COLORS. 191
zinc white is not so dangerous as white lead to the
health of either the workmen or that of the consumers.
Nevertheless, it is not entirely innocuous, and, in
certain cases, it has produced slight sickness, which
may be avoided by care in its manipulation.
12th. Use of Blende as a Substitute for White Lead o.nd Zinc White.
Blende, or sulphide of zinc, in the opinion of Mr.
de Certeau, may be advantageously and cheaply sub-
stituted for white lead or zinc white in all the colors
for painting. Its impalpable powder ground in dry-
ing oils, with or without essence of turpentine, will
cover at least as well as white lead and zinc white,
and the coats flow more easily under the brush. This
color is very fast and durable, and does not change
the other pigments with which it is mixed.
The only disadvantage of blende is that it is always
more or less colored. The inconvenience is slight
with those blendes which are colored a honey-yellow,
and which are rightly considered the purest. That
variety, when finely comminuted, gives a grayish-
white powder with a yellow tinge, which may be
employed for light colors in house painting. Mixed
with 1 per cent, of artificial ultramarine, it produces
a gray coat, slightly greenish. If, instead of blue, a
small proportion of vermilion or ochre be added, the
color is pinkish. With chrome yellow and a little
red, we obtain a chamois. A pearl -gray is obtained
by increasing .the whiteness of the blende with ten or
twenty per cent, of zinc white, and adding 1 per cent,
of black.
Brown or reddish blendes cannot be employed in
the preparation of light colors, such as those we have
just mentioned; but they may be successfully used
192 MANUFACTURE OF COLORS.
for dark colors, such as brown, black, maroon, olive-
green, mahogany, etc.
There is no advantage in using roasted blendes,
instead of the natural ones ; because, by roasting,
blende loses about one-sixth of its weight, generally
becomes darker, and covers less. However, as roast-
ing changes the color of the substance sensibly, it is
an easy process of obtaining certain tones and hues,
which could not be produced so cheaply in another
way. Therefore, roasted blende may, by its mixture
with the natural one, add new tones and hues to the
colors resulting from this material.
Powdered blende is far from being as dangerous as
white lead. Therefore, in the opinion of Mr. de
Certeau, that substance possesses the advantage of
popularizing the use of oil paints as well by a great
reduction in prices, as by diminishing the use of a
dangerous substance (white lead).
§ 10. Baryta whites.
1st. Natural Sulphate of Baryta.
The sulphate of Baryta, or Barytes, heavy spar,
Barytine, Baroselenite, hepatite, stinking stone, Bo-
logna stone, etc., is a white or reddish substance, very
dense, which is found in the natural state forming
veins with the ores of lead, silver, mercury, etc., and
in many other rocks. It contains 34.37 parts of
sulphuric acid and 65.63 parts of baryta.
Heavy spar is employed in the manufacture of a
handsome white color, entirely innocuous, fast and
resisting most reagents, but with little body or cover-
ing power. This white, fixed with glue size, is
largely employed in the manufacture of paper hang-
ings. It is also used for adulterating white lead and
WHITE COLORS. 193
zinc white. We have previously said, that, in Ger-
many, it was customary to add to it white lead for the
preparation of Venice and Hamburg whites. In
Austria, the pure sulphate of baryta is still sold under
the incorrect name of Tyrolese white lead.
In preparing the sulphate of baryta for the arts,
the whitest lumps of native ore are picked out, and
coarsely broken, and charged into reverberatory fur-
naces. The heat applied is solely intended for dis-
integrating the substance, and arriving at a finer
degree of pulverization. The grinding is done
dry, and the fine resulting powder is thrown into
large tanks filled with water. By stirring, and then
letting it stand a little while, the heavier and coarser
particles fall to the bottom. The water above,
which has the appearance of milk, is decanted into
settling basins, where the lighter suspended material
has time to deposit. After another decantation of the
clear liquor, the pasty white is collected, and dried in
the air or in a stove room. It is then a very bright
and dense white.
2d. Artificial Sulphate of Baryta, Blanc Fixe.
For several years we have found in the market,
under the name of Wane fixe (fast white), an arti-
ficial sulphate of baryta, which is much better than
the native sulphate. We owe it principally to Mr. F.
Kuhlmann, of Lille, one of the greatest manufacturing
chemists of France. Mr. Kuhlmann, in a memoir,
read before the Academy of Sciences, has described
the mode of preparation and the properties of this
product, and we cannot do better than to present an
extract from that memoir, which we do as follows: —
" In order to produce the artificial sulphate of
13
194 MANUFACTURE OF COLORS.
baryta at a moderate price, I have endeavored first to
reduce the cost of the acids which constitute the
main expense of its manufacture. I have, therefore,
tried more completely to condense the acid vapors,
part of which are lost in our soda works to the preju-
dice of the manufacturers, of the public health, and
of vegetation.
"By putting the natural carbonate of baryta (withe-
rite), large deposits of which are to be found in the
north of England, in contact with the vapors escaping
from the salt decomposing furnaces or from the lead
chambers, I have succeeded in saving a large propor-
tion of the uncondensed vapors which no longer in-
commode the neighborhood or injure vegetation.
" In my works the baryta, dissolved by the con-
densed acids, is converted into the artificial sulphate
by an addition of sulphuric acid. The recovered
nitric and hydrochloric acids return to take part in a
new operation, and increase the yield. I thus realize
the double advantage to which my experiments have
tended.
"But there is a loss of hydrochloric acid much
greater than that resulting from imperfect condensing
apparatus, i. e., that resulting from the manufacture
of chlorine or bleaching powder, which consumes the
greater proportion of the acid.
" There is no chemist who has not deplored the
fact, that more than one-half of the hydrochloric acid
used, is lost in the state of chloride of manganese.
This loss, in practice, amounts to two-thirds, on
account of the impurities in the oxide of manganese.
Its magnitude may be made apparent in considering
that the manufacture of artificial soda, in France,
consumes per year orer sixty millions of kilogrammes
WHITE COLORS. 195
of common salt. I think that I am below the reality
in saying that the indicated loss amounts to two
millions of francs per year, in France alone.
" That great loss has caused many to make search
as to whether the residue of the manufacture of chlo-
rine could not be made available and valuable. Not-
withstanding many trials, the new uses have been
few, and absorbing but a small proportion of the
waste materials. This chloride of manganese has
been applied to the purification of gas light, to the
production of ammoniacal salts, and to disinfecting
cesspools. In the large works of Mr. Tennant, near
Glasgow, experiments have been made to regenerate
the oxide of manganese, so as to use it again in the
manufacture of chlorine. All their uses amount to
little as regards the enormous quantity of residue.
In the majority of cases, the price at which the chlo-
ride of manganese is sold is scarcely sufficient to
cover the expense of concentration or calcination.
" Therefore, the liquid residue of the manufacture
of chlorine has generally remained a cause of embar-
rassment to chemical works, and even of danger to
general salubrity, whether it was let into running
waters or lost in the ground through absorbing wells.
"After having condensed the acids lost in the air,
all my efforts have tended to the saving of those
held in the liquid residue.
"I have had the satisfaction of succeeding com-
pletely by using a reaction analogous to that by
which Leblanc gave to France the manufacture of
artificial soda.
"In the Leblanc process, a mixture in proper
proportions of sulphate of soda, chalk, and coal, is
196 MANUFACTURE OF COLORS.
transformed, at a high temperature, into insoluble
oxy sulphide of calcium and soluble carbonate of soda.
"In my process, a mixture in proper proportions
of natural sulphate of baryta, chloride of manganese,
and coal, is transformed under the influence of a high
temperature, into insoluble sulphide of manganese,
and chloride of barium, which is easily separated by
washing. The reaction may be represented by the
formula —
BaO,S03 -f MnCl + 4C = BaCl + MnS + 4CO.
"A similar reaction applies equally well to the
chloride of iron, which constantly accompanies the
chloride of manganese.
" The coal intervenes always as a deoxidizing
agent, and is converted into carbonic oxide.
"After several preliminary trials, rendered neces-
sary by the impurities of the materials employed, the
correct proportions were determined upon. The re-
sults are beyond my expectations, inasmuch as I am
now able to transform native sulphate of baryta into
chloride of barium without a loss of more than 3 to 4
per cent, of sulphate of baryta lost or undecomposed.
" Here is the practical mode of working : The
transformation is effected in large reverberatory fur-
naces, similar to those employed for decomposing
common salt in soda works, with a hearth divided
into two compartments by a low wall. When these
furnaces have been heated for a certain length of time,
the portion most remote from the fireplace is charged
with a finely-pulverized mixture of native sulphate of
baryta and bituminous coal ; and above it there is
poured the liquid residue from the manufacture of
chloride, the free acid of which has been previously
WHITE COLORS. 197
saturated with chalk or, better still, with native car-
bonate of baryta. The mixture is well stirred, and is
thickened by the heat. When it has become a thick
paste it is passed over the partition wall, with proper
iron tools, into the compartment near the fire. There
the mass becomes swollen and soon disengages small
gas jets of carbonic oxide, similar to those produced
at a certain period of the soda manufacture, but, in
this case, having a green tinge due to the baryta.
After an hour of calcination at a red heat, the semi-
fluid paste, which has a little more consistency than
that of crude soda, is removed from the furnace, and,
when cold, forms a black mass of chloride of barium,
with the sulphides of manganese and iron, and a
small proportion of hyposulphite of baryta. After
several days of exposure to the air, the mass becomes
disintegrated, and the hyposulphite passes to the
state of sulphate of baryta. The substances are then
lixiviated with hot water in an apparatus disposed
like that for crude soda.
" The liquors are a clear solution of nearly pure
chloride of barium. Should there be a slight excess
of sulphide of barium, causing a yellow coloration,
there is poured in, until complete decoloration, a
solution of chloride of manganese (residue of the
manufacture of chlorine) which has been deprived of
iron by digestion with powdered carbonate of baryta.
Conversely, any excess of chloride of manganese is
separated with sulphide of barium. Thus, we see
that there is no practical difficulty in obtaining a very
pure chloride of barium.
"Such is the method followed in my works for
utilizing the residue of the manufacture of chlorine.
198 MANUFACTURE OF COLORS.
As it is of great importance, I shall give a few more
details.
" The solution of chloride of barium, obtained from
the raw product, marks 24 or 25° Be. When it has
been purified in the manner indicated above, chamber
acid (sulphuric), diluted with water to mark 30° Be.,
is poured into it as long as a precipitate is formed.
The whole is then well stirred and let to stand. The
sulphate of baryta is rapidly deposited, and the
syphoned, liquors constitute a hydrochloric acid
marking 6° Be.
" The artificial sulphate thus obtained is washed
in a methodical way, in order to remove the last trace
of free acid. It is then drained to the consistency of
a firm paste in cloth filters, and the operation will be
more rapid if the filters are pressed, or subjected to
centrifugal action. When the paste has become thick
enough, it is packed in barrels, and contains from 30
to 32 per cent, of water.
"It may be dried and moulded into lumps, like
white lead. However, in the majority of cases, it is
more advantageous to use it in the pasty state,
because, once dried, it does not reacquire the same
degree of comminution it possessed at the time of its
precipitation.
" If I insist upon this method of utilizing the waste
of the manufacture of chlorine, it is because it appears
to me as presenting many economical results. Thus,
in the preparation of satin paper hangings and of
glazed pasteboard, the artificial sulphate of baryta,
under the name of blancfixe, has found its place. Its
consumption extends considerably for distemper and
silicious painting, and for calsomining ceilings. The
BLUE COLORS. 199
actual production of my works amounts to 2000
kilogrammes per day.
" This substance possesses an unexpected property,
upon which I shall insist : it seems to form a slow,
but intimate, combination with the soluble alkaline
silicates, and with these salts forms pigments of
unmatched whiteness, possessing a certain lustre, and
entirely unacted upon by sulphuretted hydrogen. It
may also be employed for fixing other colors. A
paint made of a mixture of zinc white and blanc fixe,
acquires such an adherence and durability, that it may
be safely applied upon old oil painting. Such a
result is of the greatest importance for Paris, London,
Brussels, and other large cities, where carefully built
dwellings are covered with expensive oil paintings,
which require to be often renovated."
SECTION II.
BLUE COLORS.
The same substances which furnish blue present a
very great many tones of that color. It will also be
remarked that the purest and brightest blues are, at
the same time, the most durable.
The Hues most frequently used in painting are:
Ultramarine, Cobalt blue, Prussian blue, mineral blue,
Indigo, various kinds of azure, etc.
§ 1. Prussian blue.
This color was discovered in 1720 by Diesbach, of
Berlin, and then studied out, theoretically and prac-
tically, by many chemists and manufacturers.
Prussian blue is now considered by all chemists to
200 MANUFACTURE OF COLORS.
be a combination of cyanogen with iron in two states
of oxidation; that is to say, a combination in vari-
able proportions of protocyanide and sesquicyanide
of iron with a little water.
As the composition of Prussian blue is not con-
stant, and may vary with the proportions of the
two cyanides of iron, this pigment is found in the
trade, possessing a variable intensity of coloration.
This diversity is due not only to the variable propor-
tions of the cyanides, but also to the mode of prepa-
ration, the quality of the raw materials, and to the
care in the manufacture. The average composition
of Prussian blue is : three equivalents of protocyanide
of iron, two of sesquicyanide, and nine equivalents of
water.
When pure, and recently precipitated, it is in the
shape of blue flakes, which are so deeply colored that
they appear black. After drying, the lumps are blue-
black, with a reddish reflex.
The pure article of the laboratories is made by
pouring a solution of yellow prussiate of potash
(ferrocyanide of potassium), into a salt of sesquioxide
of iron. This process is too long and expensive to be
used in the arts, and other methods are employed, one
of which begins with the preparation of the cyanide
of potassium, by the calcination of carbonate of potassa
with animal substances.
1st. Manufacture of Ordinary Prussian Blue.
A. First process. — The animal substances ordinarily
employed in the manufacture are: dried blood, hair,
wool, waste from skins and leather, flesh, animal oils,
soot, and bone black, etc.
Dried blood is preferred for the preparation of the
BLUE COLORS. 201
cyanide. The fresh blood is rapidly evaporated in
cast or sheet-iron pans, and the mass is constantly
stirred with an iron tool, until it is entirely clotted.
The drying is then finished in the sun, and the
powdered material is kept for use in open vessels.
10 parts of the powdered blood are moistened with
1 part of pure carbonate of potassa dissolved in water,
and 1 per cent, of iron filings are added to the mix-
ture, which is heated in a cast-iron pan for seven or
eight hours, and at a red heat. During the first hours
of the calcination, abundant fumes are disengaged,
which possess a very disagreeable smell, and are
afterwards replaced by bright and reddish-white jets
of flame. The mixture is stirred, and, when it is in
the state of quiet fusion and does not emit jets of
burning gases, the cover is put upon the kettle, and
the heat continued for two hours more. The cakes of
the cooled product are lixiviated with hot water until
all the soluble matters are removed.
The resulting blood lye, as it is sometimes called,
is a light yellow, and smells of prussic acid strongly.
It is not a solution of pure cyanide of potassium, but
contains, besides, a certain amount of carbonate of
potassa, of sulphates and phosphates of potassa and
lime, of sulphide of potassium, etc.
This concentrated and filtered lye is poured by
degrees into a hot solution of one-half part of pure
sulphate of iron, and a variable proportion of alum,
depending on the quality of the blue desired. The
quality more generally called Prussian blue is ob-
tained with one part of alum to seven or eight parts
of sulphate of iron. The ordinary blue employs one
part of alum to two or three parts of sulphate of iron;
202 MANUFACTURE OF COLORS.
and the inferior qualities are made with equal parts
of sulphate of iron and alum.
At each addition of the cyanide lye to the iron
solution, there is an abundant production of hydro-
sulphuric and carbonic acids, and the escape of these
gases is aided by stirring the liquor with a wooden
rod. The precipitate is brownish-green, and is
washed with pure water, until it turns entirely blue.
After settling, and decanting the liquors, the blue
precipitate is placed upon a cloth filter, where it is
washed with water holding a small proportion of
sulphuric acid. The drained blue is then pressed in
boxes, in order to remove the greater part of its water,
and the thick resulting paste is divided into rectan-
gular blocks, which are dried in the dark, or in a
stove-room, the temperature of which should not be
above 25° to 30° C.
Prussian blue, in the opinion of Mr. Bourgeois, is
the next in purity of tones after ultramarine and co-
balt blues ; and, although it is inferior to these in
durability, it contains much more coloring power —
from ten to eleven times, with equal volumes. It is
to be regretted that all the alkalies alter Prussian
blue, so that, if it be combined with other alkaline
pigments, it may rapidly change or disappear. Mr.
Bourgeois indicates a process for ascertaining the
presence of Prussian blue in suspected samples of
lazulite and cobalt blues, which is based upon the
discoloration of Prussian blue by alkalies. A pinch
of ultramarine or cobalt blue, is digested for about
one hour in a small quantity of lime-water. The
presence of Prussian blue will be detected by the lime-
water turning lemon yellow, and by an ochreons pre-
cipitate.
BLUE COLORS. 203
Large quantites of Prussian blue are used by house
painters and decorators, and by manufacturers of
paper hangings.
Of all blues, Prussian blue is the most intense.
Mixed with white lead, the hue is slightly greenish.
A mixture of one gramme of Prussian blue and ninety
grammes of white, produces a sky blue ; two hundred
grammes of white, and one of blue, give an azure white.
In order to judge well of the beauty of a Prussian
blue, it should be incorporated with from fifty to one
hundred times its weight of fine white lead. Mixed
with from fifteen to twenty times its weight of chrome
yellow, it produces handsome greens, not very lasting
however. Prussian blue is employed either with glue
size or oil ; but, in the latter case, it should not be
kept too long without being applied, because it be-
comes thick and does not flow well under the brush.
The pure blue ground in oil produces velvety blacks
which could not be arrived at by the employment of
black pigments. We should remark that old damp
walls destroy the color of Prussian blue, by the nitrate
of lime they contain. There is produced by double
decomposition, a ferrocyanide of calcium, and a nitrate
of iron.
B. Second process. — We have seen that in the first
process, a lye of impure cyanide of potassium was
prepared. As this operation is unwholesome, on
account of the deleterious gases produced, other
modes of manufacture have been adopted, which
allow of the manufacture of Prussian blue in in-
habited places. The ferrocyanide of potassium (yel-
low prussiate of potash) is employed, and may be
prepared in a special locality, in the following man-
ner : —
204 MANUFACTURE OF COLORS.
This second process has nearly everywhere taken
the place of the first. The mixture consists of seventy-
five parts (kilogrammes for instance) of good car-
bonate of potassa, fifty parts of horn or leather waste,
and three of iron filings. The potash is introduced
first into a furnace which we shall describe further on.
"When it has arrived at the point of igneous fusion,
the iron filings are introduced and mixed in the mass
with an iron tool, which has been heated red before-
hand, otherwise the stuff attaches to it and renders the
operation difficult.
When the mass is thoroughly in fusion, a shovelful
of horn waste or animal charcoal is thrown into it
every ten minutes. At the last addition of animal
matter, a strong heat is maintained for about one and
a half hours, and the operation is completed when jets
of carbonic oxide burn on the surface of the bath.
The substances are then removed with red-hot iron
ladles, and deposited in iron kettles, where they are
afterwards boiled with water. After two boilings,
settlings, and decantations, the residue is removed
and again thoroughly washed in cloth sacks. All
the liquors are evaporated to the proper degree, and,
by cooling, give crystals of ferrocyanide of potassium,
which are rendered purer by another solution and
crystallization.
With the proportions indicated above, the product
is from seventeen to twenty parts of ferrocyanide.
The mother liquors are evaporated to dryness, and
their potassa is used for another operation. The
charred residue is of no value.
The calcination of the substances is effected in a
reverberatory furnace having the following dimen-
sions: height of arch 0.50 metre, over the horizontal
BLUE COLORS. 205
bed or hearth, which is 1 square metre. The fireplace
is sideways, Om.21 X Om.48, and bridge wall is Ora.27
or 0.5 metre wide. On top of the arch, there is an
opening covered with a sheet-iron hood and chimney.
The wide working front of the furnace is closed by
two cast-iron doors, having on their line of junction
a hole large enough to introduce and operate the
stirring hooks.
The animal charcoal is prepared either in cylinders
or in cast-iron pots, or in muffles of the same metal.
"We shall also indicate a few of the more recent pro-
cesses which have been proposed for the manufacture
of ferrocyanide of potassium or of Prussian blue.
2d. Brunnquell Process.
Mr. ~R. Brunnquell, who has managed for a long
time a manufactory of ferrocyanide of potassium,
near Bremen, has published in Berlin a long memoir
on this subject. We cannot reproduce it entirely, but
we shall give some extracts taken from the Technolo-
gists, vol. 18, pages 243 and 291.
Let us state first that the author has examined
several processes for the manufacture of ferrocyanide
of potassium, and particularly, the one in which the
ammonia produced during the carbonization is
brought in contact with potassa and charcoal, at a
high temperature. He observes that, however advan-
tageous these processes may appear, they are not well
adapted for manufacturing operations.
Considering the defects of the actual process, there
remains for the manufacturer to dimmish the loss by
a careful attention to certain details of the operation.
There are two ways of arriving at this result: First,
to aid, as far as practicable, the secondary formation
206
MANUFACTURE OF COLORS.
of cyanogen (by ammonia and incandescent charcoal):
second, to avoid the loss of potassa by using pure
animal substances, and by preventing the contact of
the ashes of the fireplace. The author, from his owi
experience, indicates the following mode of operation,
A horizontal reverberatory furnace* is generally
adopted at the present time, the hearth of which it
made of a cast-iron dish, 10 to 12 centimetres deep,
1.5 metres in length, and 1.2 metres wide, and several
centimetres thick. The furnace is so constructed thai
the working space is no greater than is necessary, and
the arch is as flat as it is possible to build it. The
flue from the fireplace has a damper, by which th«
flame may be made to pass into an opening connected
with a metallic hood and chimney. This arrangement
saves the men from being annoyed by the gases and
by too much heat. The author enlarges on the advan-
tage of heating by gases, by which oxidization and
ashes are prevented. The flame may even be. made
deoxidizing. There is certainly no manufacture]
who has not observed the great quantity of ashes
deposited after twenty-four hours in the cast-iron
dish of a newly heated furnace, especially, when the
draft is good. We know also, how deleterious is the
* These furnaces, notwithstanding many defects, present three
important advantages: I. There is a considerable economy of fuel;
II. The work is easy and rapid. Where, in other furnaces, 4
charges were a day's work, in these, from 7 to 8 charges, each
double the former in weight, were effected; III. The furnaces cost
less and last longer. — In England, where fuel and iron are cheap,
and labor high, the metallic egg-shaped furnaces are used, and the
stirring is done by power. No other but carbonized animal sul
stances can be charged there, and they must be mixed with th<
potassa in the furnace, whereas their mixture is more thorough in
revolving cylinders.
BLUE COLORS. 207
action of these ashes upon the contents of the bath,
especially when peat or bituminous coal is burned.
With a furnace of the above construction, the
author proposes a mode of operation, which has already
been employed in several works, and which may be
described as follows: The charge is composed of 100
kilogrammes of potash, two-thirds of which is from
the evaporated mother liquors, and one-third of fresh
potash; 20 kilogrammes of animal charcoal obtained
by the carbonization of substances poor in nitrogen,
and the nature of which is not well adapted for a direct
treatment; from 65 to 70 kilogrammes of pure animal
matters, as dry as practicable ; and 8 kilogrammes of
iron. The fire is urged until all the potash is
thoroughly fused, which state is more rapidly reached
with the aid of two or three stirrings. Then the ash
pit is closed* and the damper turned on for charging
one-half of the animal charcoal. The fire is urged
again, and the stirring is continued vigorously, until
the mass has acquired the proper consistency and
potassium is produced, which is ascertained by the
formation of blue flames of oxide of carbon, and by a
peculiar white cloud of burning vapor of potassium.
In this state, the fused mass is in the proper state for
transforming into cyanogen the ammonia disengaged
from the animal substances. The latter are then put
in, those richer in nitrogen first, but not in large
pieces or in considerable quantities, which would
prevent their rapid sinking and their equal distribu-
tion in the bath, and would produce gas too rapidly
c When the furnace is heated by means of a gas generator, a
reducing flame will be obtained by diminishing, or stopping
entirely, the entrance of the air necessary to complete combustion.
208 MANUFACTURE OF COLORS.
at one spot. The ammonia will not have time to be
transformed. When the 65 to 70 kilogrammes of
dried animal substances have been charged in, the
mass begins to be hard and dry, and difficult to fuse.
No time should then be lost in adding the remaindei
of the animal charcoal, which, being in a fine powder,
is more readily incorporated, and reduces the cyanide
of potassium (cyanate of potassa?) already formed.
Lastly, after another thorough stirring, the working
door is closed for a little while, and the contents oi
the furnace are rapidly removed into an iron vessel,
which is immediately covered.
It does not seem advantageous to work at any on<
time with charges much greater or less than the indi-
cated proportions ; but the author does not say that
these numbers are the only correct ones, and the
manufacturer, in certain cases, will do well to modify
them. Mr. Brunnquell has made many experiments
for the purpose of establishing to a certainty, the
composition of the charges in the ratio of the nitrogen
held by the animal substances ; but he soon found out
that the result depended upon so many other circum-
stances, which often could not be explained, that it
impossible to establish rules adapted to all modifier
tions. The manufacturer who has a careful foreman,
who can be trusted, should give him a certain liberty
of action in this respect. Practice will point out the
time when the charge is completed, and does not
require any new additions ; or how different animal
matters should be treated. Thus, hair and leather
waste render the mass hard and dry ; whereas with
sinews, rags, etc., the charge remains fluid and easily
worked.
Mr. Brunnquell remarks, and rightly so, that the
BLUE COLORS. 209
value of the raw materials is not in a direct ratio with
their per cent, of nitrogen. A substance with twice
as much nitrogen as another, may have a value more
than double, because with the same loss of potassa, the
same labor, and the same consumption of fuel, the
production of ferrocyanide is much greater. Old shoe
leather should be employed with moderation, since
the author, after careful washings, ascertained that it
contained a large proportion of sand and other impu-
rities.
In regard to the addition of iron filings or turnings,
Mr. Brunnquell states that it does not increase the
yield, but saves the cast-iron vessels in which the
operation takes place. It results from experiments
made by Mr. Fleck, that a cast-iron crucible will
stand 100 operations without the addition of iron. If
the latter be introduced into the charges, the vessel
will last through from 350 to 400 operations. The
iron tools which are constantly exposed to the action
of the fused mass, are always covered with a coat of
sulphide of iron. On the contrary, the iron scraps in-
troduced during the operation, have scarcely the time
to be transformed into sulphide before they are re-
moved from the furnace.
At all events, the whole indicated proportion of
iron scraps should be added at the beginning of the
operation, with the animal charcoal. Certain manu-
facturers put in the iron scraps during the last period
of the heat, and cannot expect to save their crucibles
and cast-iron hearths. The author learned that, in a
German establishment, it was considered as very
important to let the iron scraps become oxidized
beforehand ; but he made no direct experiment, and,
should there be any advantage in the precaution,, it
14
210 MANUFACTURE OF COLORS.
would be more simple to use pure spathic iron or iroi
scales.
Here is a little more advice on the manner ol
treating the calcined charges. When cold, they ar
coarsely broken, then digested for twenty-four hoir
in water at the temperature of from 50° to 60° C. wit!
frequent stirrings, and lastly, boiled. After settling
the liquor is decanted, and the residue is washed wit!
water. The other manipulations present no difficult;
The main point is the manner of working the char^
and a peculiarity of this manufacture is, that it is
more easy to obtain a good product, than a great deal
of it. The only difficulty in the way of the quality,
is the separation of the sulphate of potassa from the
crude ferrocyanide, and the best method consists in a
complete reduction during the calcination of the
charge.
The process which we are going to describe, and
which was experimented upon by the author conjointly
with Mr. "Weber, consists in transforming ammonii
into cyanide of ammonium, by heating the forim
substance with charcoal or other carbon materials
A distinguishing feature is the transformation of tl
cyanide of ammonium thus obtained, into cyanide
potassium, and that of the latter into ferrocyanide
the wet way. The operation consists in passing th<
gases and ammonia, produced by the carbonization
of the animal substances, through tubes holding in-
candescent charcoal. The ammonia becomes cyanide
of ammonium, which is put in contact with an aqueous
solution of potassa and with an iron compound. The
result is ferrocyanide of potassium. Here are the
principal advantages of this process : —
I. There is no great loss of potassa, and th
BLUE COLORS. 211
expense of revivifying this alkali is entirely done
away with;
II. It is possible to replace potassa by soda, which
is much cheaper ; .
III. It is possible to employ bones, the residuary
black of which is generally sufficient to cover the
cost of the bones and of the calcination. Therefore,
the ammoniacal gases cost nothing;
IV. It is possible to save for a further operation
the ammonia which has escaped transformation into
cyanide during the calcination. The secondary am-
moniacal salts may also be utilized, by adding them,
with a certain proportion of lime, to the raw materials.
Several questions relating to the process of manu-
facture have been resolved by the author, as follows : —
1. The transformation takes place without difficulty,
and on a scale sufficiently large to base upon it a
system of preparation of cyanogen compounds. As a
proof of the possibility of the reaction, we may cite the
production of the cyanide of ammonium from ammonia
and carbonic oxide, or from the gaseous nitrogen
oxide and alcoholic vapor under the influence of
spongy platinum.
2. The gases, other than ammonia, which are pro-
duced at the same time during the carbonization, are
not an obstacle to this process of manufacture.
3. The transformation of the cyanide of ammonium
into ferrocyanide of potassium, is effected without
loss.
The easiest method of operating this transformation
would be that proposed by Mi*. Binks, that is, with
an aqueous solution of potassa. But we cannot do
so, because the carbonate of potassa is not decom-
posed, either by hydrocyanic acid or by cyanide of
212 MANUFACTURE OF COLOKS.
ammonium.* Caustic potassa, on account of the
excess of carbonic acid in the gases, cannot be used.
We must, therefore, have recourse for this decompo-
sition to intermediary substances, and the author
chooses the sulphate of protoxide of iron. If cyanide
of ammonium, or hydrocyanic acid and carbonate of
ammonia, be passed through a solution holding an
excess of sulphate of iron, sulphate of ammonia and
cyanide of iron are produced. We thus obtain a
double result: first, all the ammonia is collected in
the state of sulphate, which pays largely for the
expense of the iron salt ; second, the cyanide of
ammonium is instantaneously transformed into an
insoluble and fixed compound, which, after a treat-
ment with the carbonates of potassa or soda, may
furnish a ferrocyanide of either of these bases.
During the process of manufacture, the carboniza-
tion is effected so as to expel all the nitrogen in the
gaseous form, instead of preserving it in the carbona-
ceous residuum, as in former methods. If bones be
employed, the quality of the resulting bone black
should be considered, and it matters little whether or
not a small percentage of nitrogen remains in it. We
* More recently the author has made several direct experiments
which clearly prove that carbonate of potassa, either in solution in
water, or at a high temperature, decomposes cyanide of ammonium
completely. But, as he has never been able to realize this transfor-
mation in his experiments on a large scale, and has always remarked
that hydrocyanic acid was disengaged, especially when the alkaline
liquors were boiled, Mr. Brunnquell considers this fact as a positive
proof that carbonic acid has intervened, and that, instead of cyanide
of ammonium, hydrocyanic acid (with a little undecomposed car-
bonate of ammonia) was obtained. Therefore, theoretically speak-
ing, there must be a way of transforming at once all the nitrogen
into cyanogen.
BLUE COLOKS. 213
*•
know that the good quality of bone black depends on
the following conditions : the bones employed should
not be deprived of their fat ; the carbonization must
be complete, and effected without gaseous pressure.
When other raw materials are used, it is important
to obtain all the nitrogen ; therefore, a first carboni-
zation transforms them into a charcoal easily pul-
verized, which is then thoroughly mixed with slaked
lime, and calcined again. The residue is a very good
manure or compost.
The carbonizing furnaces are disposed like those of
gas works, and the number and the sizes of the retorts
are made to suit the importance of the manufacture.
The outlet pipes all dip into a common horizontal main,
where the distilled animal oil is condensed, and there
is formed a hydraulic joint, which produces a certain
pressure. All the products thus become mixed before
they reach the calcining tubes made of fire clay. There
is also the advantage that the flow of gases is quite
regular, because the small volume of gases produced
by a retort at the end of the distillation, is counter-
balanced by the large volume of gases issuing from
another retort which has been recently charged. If
we suppose that three retorts are employed, and that
the carbonization of a charge lasts six hours, one retort
will be filled every two hours. The pipes connecting
with the hydraulic main should be provided with
stopcocks in case an accident should happen. They
should also be at least six centimetres in diameter,
short, and easy of access in every direction.
The transformation of the ammonia into cyanide of
ammonium takes place when the gases pass through
the fire-clay pipes, which are heated to an intense
red heat, and filled with wood charcoal, broken into
214 MANUFACTURE OF COLORS.
pieces of the size of walnuts. Numerous trials have
proven that iron pipes cannot be used for this purpose,
because, when cyanide of ammonium, or hydrocyanic
acid, or cyanogen are brought into contact with iron
at a red heat, they split into their elements, and form
a carbide of iron. In three experiments made with
gunbarrels, not a trace of cyanide of ammonium was
found. The author tried to employ in this manu-
facturing process, an iron cylinder, by protecting its
inside with a carbonaceous surface obtained by the
calcination of several coats of tar. But the results
of the working operation were far from satisfactory,
since the yield was but 4 per cent. This was possibly
due to the fact that he had not, at that time, ascer-
tained the great proportion of carbonic acid contained
in the gases; and that the caustic potassa, intended for
the absorption of the cyanide of ammonium, had been
transformed into carbonate, and even bicarbonate.
The best process for protecting the iron tubes was
found to be several coats of a mixture of clay and ox
blood, gently heated after each successive coat.
During the first experiments with sulphate of iron,
instead of a solution of potassa, too much heat was
applied, and the iron pipes were burned. Although it
does not appear entirely impossible to use metallic
pipes, those made of fire clay seem to be preferable in
every respect. These pipes have a smaller diameter
than the retorts, and their extremities are so disposed
as to receive cast-iron joints. The smaller their diame-
ter and the greater their length, the better it is for the
operation. Those used by the author were 10 centi-
metres in diameter and 2 metres long. The internal
disposition of the furnace is also that of furnaces for
gas retorts, where the greatest possible number of
BLUE COLORS. 215
retorts are to be heated throughout their whole length,
with the smallest consumption of fuel. A very good
furnace is that of Croll for gas, with the combined
employment of clay and cast-iron retorts.
With this disposition it has been possible to heat
seven retorts and seven pipes with one fireplace.
The filling of the pipes with charcoal is not absolutely
necessary, because the other gases accompanying the
ammonia may furnish the carbon for the cyanogen ;
but charcoal, on account of its porousness, aids in the
transformation. The extremities of the pipes are
closed with perforated disks of fire clay, which pre-
vent the joints from becoming obstructed. Before
the gases are allowed to pass through, the pipes
should be of an intense red heat. In addition to the
ordinary losses of manufacture, there are undecom-
posed tarry vapors, which dirty the liquors. A very
intense red heat is the temperature necessary for the
formation of cyanogen. As in previously described
processes, the yield depends on regularly conducted
operations.
We have seen that the transformation of the cya-
nide of ammonium into cyanide of potassium, and
then into ferrocyanide of potassium, is effected by the
intermediation of the sulphate of iron. The only diffi-
culty in the practical operation is to arrive at a com-
plete absorption of the cyanide of ammonium in the
solution of sulphate of iron, and that without a strong
pressure of gases, which not only impairs the quality
of the bone black, but causes losses of a portion of the
gases through leaks in the apparatus. The author
uses, for this purpose, apparatus which is very simple
and permits of regulating at will the rapidity of the
operation. Let us suppose a box, aboint 2 metres long,
216
MANUFACTURE OF COLORS.
60 centimetres wide, and 20 centimetres deep, in which
are placed four flat, shallow pans, 5 centimetres high,
and put one on top of the other in an inverted posi-
tion (Fig. 47). On the bottom of each pan, towards
one of the ends, there is a narrow opening. The box is
Fig. 47.
filled with the liquor, and the mixture of gases, which is
introduced below the first pan, expands until it gains
the opening. It then passes into the second pan, and,
in the same manner, into the third and fourth. Theo-
retically speaking, there is constantly a layer of gases,
of 4 x 1.20 metres = 4.80 square metres in area, in
contact with the liquid, and the distance followed by
the gases is 4x2 metres = 8 metres, under a pressure
of only 0.20 metre of water. The box is also provided
with a stopcock for removing the liquors, a funnel
which dips a little below the level of the liquid, and
an outlet pipe for the washed gases, which are after-
wards burned under the fireplace. In order to pre-
vent explosions the gases to be burned are made to
pass through a small box filled with fine metallic gauze.
Should a precipitate take place in the liquors, it is
recommended to employ a stirring apparatus with
blades in each compartment of the box, and the ver-
tical shaft of which passes through a stuffing-box.
In the figurfe, a a is the pipe which conducts the
BLUE COLORS. 217
gases into the box ; A, sheet-iron box ; & & & 5, sheet-
iron inverted pans ; c c, handles for moving the pans ;
d, funnel;/1, outlet pipe for the gases; x x, level of
the liquor.
Instead of a large absorbing apparatus, it will be
more advantageous to employ two smaller ones, so
disposed as to pour the liquors from one into the
other. In this manner the sulphate of iron will be
entirely precipitated without loss of cyanide of ammo-
nium. The liquor running from the first box will,
therefore, hold only sulphate of ammonia in solution,
cyanide of iron in suspension, and a small proportion
of hydrated oxide and sulphide of iron.* The sul-
phate of ammonia is separated from the filtered
liquors by evaporation, and is sold to the alum
makers, or is mixed with lime and animal substances
for the production of cyanogen. The precipitate of
cyanide of iron is boiled with potassa and transformed
into ferrocyanide. Lastly, the residues of iron are
either thrown away, or dissolved in hydrochloric acid,
to be used instead of sulphate of iron.
There is no difficulty in the preparation and crys-
tallization of the ferrocyanide of potassium, because
the materials employed are quite pure. If the iron
precipitate has been sufficiently washed, and then
boiled with a solution of purified potassa, the liquors
con tain but a small proportion of carbonate of potassa,
besides the ferrocyanide. The author believes that
soda may be employed, and experiments on a large
scale have furnished a pure yellow ferrocyanide of
K For the preparation of 300 parts of ferrocyanide of potas-
sium, we need 187.3 parts of cyanide of ammonium. The latter
requires for its formation 600 parts of sulphate of iron, and pro-
duces 243 parts of sulphate of ammonia.
218 MANUFACTURE OF COLORS.
sodium, but in small crystals. The iron deposit lei
after the treatment with the alkalies, should be wash<
and drained. The washings are kept for making
fresh solutions of potassa. The mother liquors
also put to the same use.
If we compare the old and the new processes, w<
find:—
First, that in the latter there is a saving of labor.
The fusion of the potassa and animal matters, whicl
requires two workmen, is entirely avoided, and OIK
workman is sufficient for two carbonizing furnaces
and a great many clay pipes, since these require to
opened but once every two or three days for the pur
pose of adding a little charcoal. The labor require
for the treatment by the sulphate of iron is mucl
less than that required for lixiviating the carbonize(
cakes of raw materials. Moreover, the labor entailed
by the revivification of the salts of the mother liquors
is entirely obviated.
Second, the consumption of fuel in the new process
is somewhat greater, because the formation of the
cyanogen is slower. But, supposing that the con-
sumption be double, this inconvenience is more than
counterbalanced by the advantages of the method.
It is acknowledged that the process presents cer-
tain difficulties, which may, however, be overcome; but
the great saving in potassa, and the possibility of sub-
stituting soda for it, are very important economical
results.
In concluding, the author remarks that the method
he proposes, that is, the production of the cyanogen
before its combination with the fixed alkalies, may
possibly lead to the employment of atmospheric air.
During the experiments made on the production of
cyanogen from the nitrogen of the air, MM. "Woehler,
BLUE COLORS. 219
Erdmann, and Marchand have remarked that this
preparation succeeds only in the presence of steam or
of hydrate of potassa. This observation, and other
analogous ones, have caused many chemists to sup-
pose that there was always a formation of ammonia.
Direct experiments have also proven the production
of ammonia from nitrogen and steam in contact with
red-hot charcoal, Mr. Fleck has communicated to
the author the results of such experiments, by which
he obtained quite a large proportion of ammonia; but
in several cases, and without ascertained causes, no
ammonia was formed. It seems that this mode of
formation should be studied more thoroughly, and
directly, that is, for instance, by mixing with nitro-
gen, variable measured proportions of steam, and
then transforming the ammonia thus produced into
cyanide of ammonium by the process indicated. We
shall thus avoid most of the practical difficulties up to
the present time encountered, in the preparation of
the cyanide of potassium from the nitrogen of the
air, for instance, among others, that of the rapid de-
struction of the clay pipes by the fused potassa.
3d. Karmrodt Process.
In the Bulletin of the Society for the Advancement
of Arts, Berlin, 1857, there is a memoir of Mr. C.
Karmrodt upon the ferrocyanide of potassium and its
manufacture by a new process, which we shall repro-
duce in part.
The author points out the destructive action of the
vapors, disengaged from wood and animal substances,
upon the cyanide of potassium in the nascent state,
and states that experiments made with charges of
250 kilogrammes of potassa and 250 kilogrammes of
220
MANUFACTURE OF COLORS.
the substances mentioned below, gave the following
yields in ferrocyanide of potassium : —
10 charges with woollen rags, 15.22 per cent, of ferrocyanide.
10 " " horn waste, 16.26 " u
10 " " cow's hair, 11.94 " "
10 " " leather waste, 13.52 " "
10 " " good charred horn, 16.23 " "
10 " " woollen rags, 11.57 " "
Shoeing that only from one-seventh to one-third of
the nitrogen present in the raw materials was utilized.
Mr. Karmrodt demonstrates the advantages resulting
from the previous carbonization of the raw substance
and then passes on to the description of his new pr<
cess for the manufacture of ferrocyanide of potassiui
as follows : —
In order to combine in the most advantageoti
manner the production of the cyanide cf potassiui
Fig. 48.
with ammoniacal gases, and the working of the charge
with the nitrogenized charcoal, I have invented the
BLUE COLORS. 221
furnace which is represented in the vertical section
in Fig. 48.
The cast-iron cylinder A, for calcining, is 1.20 me-
tres long and 0.15 metre in diameter on top, the lower
portion being a little larger. Its thickness is 25
millimetres, and it carries four tubes, a, ft, c, d, cast
with it, 5 centimetres in diameter and from 36 to 40
in length. The tube or pipe & is connected by flange
joints and another small pipe, with the carbonizing
vessel B, which is pear-shaped, and about 30 centi-
metres in diameter. The pipe d penetrates the brick
flue e, which continues around the vessel B, and ends
at/. The other pipes a, c, are employed for cleaning
those which are opposite, and are generally closed
with a plug of clay. The carbonizing vessel B, and
the calcining cylinder A, are both closed with a cover
which may be made gas tight. Under the cylinder,
there is a square iron frame in which the register g
slides horizontally. At about 30 centimetres above,
there is also an annular grate h h.
When the calcining cylinder is charged with alka-
lized charcoal, it is heated with a charcoal fire. Some
time afterwards, the space i i is closed with an iron
cover, and the draft takes place through a flue placed
under the pipe Z>, which thus establishes a heating
system common to A and B. When the calcining
cylinder A has been brought to a red heat, the animal
substance is quickly introduced into the carbonizing
vessel B, which is immediately closed with its cover
luted on. The gases produced by the carbonization
escape through the pipe 5, pass through the whole
length of the cylinder A, and coming out at d, are
burned under the vessel B, and increase its tempera-
ture considerably. By this disposition, all the pro-
222 MANUFACTURE OF COLORS.
ducts of the combustion of the fuel and of the carbon-
ization of the animal matters, are expelled through
the flue f^ and go to the chimney, or are utilized for
evaporating the liquors. ~No disagreeable smell
disengaged and the carbonizing operation lasts froi
three-quarters of an hour to one hour and a quarts
When the carbonization is completed, and win
the gases passing through the cylinder have form<
a certain portion of cyanide of potassium, the regisl
g is removed, and the contents of A fall into a sheet
iron box placed below, and which is closed tight
After cooling, the materials are thrown into water
small portions at a time, because, should all the chai
coal saturated with cyanide of potassium be thro1
at once into the water, the elevation of temperatui
would be such as to decompose a large portion of tl
cyanide.
The water is then slowly heated up to from 75(
80° C., and the charcoal is separated from the soluti<
by means of a metallic sieve. A well-washed chai
coal may be used for another operation, or it is us<
as fuel, and its ashes are carefully lixiviated, becam
they are rich in potassa.
The alkalized charcoal is prepared as follows:
an iron kettle, 20 parts of good Russian potash ai
dissolved in 10 parts of water, and there is mixed ii
it the wet, but washed, precipitate resulting from tl
mixture of 8 parts of sulphate of iron and 6 parts
potash. 30 parts of charcoal, broken to the size of
filbert, lare then stirred with the mixture, and the
whole is dried at a moderate temperature. Coke
may be cheaper than charcoal, but the lixiviation re-
quires more water, and its ashes have scarcely any
value. The sulphate of potassa resulting from the
BLUE COLORS. 223
precipitation of the sulphate of iron, is used in the
manufacture of alum.
Mr. Karmrodt has made experiments with the fur-
nace above described, and the results are: —
I. By using each time 1.5 kilogrammes of Carbonate of Am-
monia (crude and yielding 21 per cent of Nitrogen).
Ferrocyanide of potassium obtained
with the carbonate of ammonia. "Utilized nitrogen.
Per 1.5 kilog. Per cent. Per cent. Approximately.
1. 0.500 kilog. 33.3 per cent. 31.74 per cent. £
2. 0.625 " 41.5 " 39.68 " f
3. 0.562 " 37.5 " 35.71 " J
The greater proportion of assimilated (utilized)
nitrogen in these experiments, in comparison with
the results obtained with gunbarrels, is possibly due
to the greater surface of reacting substances, and to
the pressure of the gases during their passage.
II. With Animal Substances.
The alkalized charcoal of these experiments was
prepared with 15 kilogrammes of horn charcoal
(yielding 7 per cent, of nitrogen), and 10 kilogrammes
of potash. After the addition of the washed precipi-
tate resulting from 4 kilogrammes of sulphate of iron
with 3 kilogrammes of potassa, the dried mixture
weighed 22 kilogrammes.
In each operation there were 5 kilogrammes of this
alkalized charcoal, corresponding to 3 A kilogrammes
of horn charcoal, placed in the calcining cylinder;
and it received the gases produced in the carbonizing
vessel from 1.5 kilogrammes of horn (yielding 16 per
cent, of nitrogen).
224 MANUFACTURE OF COLORS.
The nitrogen employed was therefore : —
a. In the alkalized charcoal . . . 238 grammes.
b. In the >raw horn to be carbonized . 240
478
which should have produced altogether 2.39 kilo-
grammes of ferrocyanide of potassium.
Ferrocyanide of potassium Utilized -nitrogen.
obtained with
1.5 kilog. of horn,
1. 770.31 grammes.
2. 664.06 "
3. 712.50
In these experiments, there remained in the car-
bonizing vessel 1.203 kilogrammes of horn charcoal,
which, after fusion with potassa, gave 109.37 grammes
of ferrocyanide of potassium. To sum up, the results
were : —
1. 770.31 grammes of ferrocyanide = 154.06 grammes of nitrogen.
2. 664.06 " =122.81 "
3. 712.50 " —142.50
4. 109.37 " = 20.31
2256.24 " =439.68 "
whereas the whole of the nitrogen employed was 3
X 478 = 1434 grammes.
III. With Animal Substances, and the Alkalized Charcoal of 30
kilogrammes of Wood Charcoal, 20 of Russian Potash, and
the Precipitate of 4 kilogrammes of Sulphate of Iron by 3 of
Potash.
In each operation, there were used 5 kilogrammes
of alkalized charcoal, upon which were passed the
gases of 1.5 kilogrammes of raw horn. The results
were : —
BLUE COLORS. 225
1. 574.22 grammes of ferrocyanide =114.84 grammes of nitrogen.
2. 461.00 " = 92.19 "
3. 457.03 " = 91.41 "
4. 156.25* " = 31.25 " %
1648.50 " =329.69 "
The whole quantity of horn employed was 4.5 kilo-
grammes = 620 grammes of nitrogen. We see there-
fore, that in this series of experiments, the proportion
of nitrogen utilized is about one-half of the whole.
Now, if we suppose that in the second series of
experiments with animal alkalized charcoal and the
same quantity of horn as in the third series, there
were produced as much ferrocyanide of potassium as
in the latter case, it would result that the overplus of
38.4 parts of ferrocyanide is due to the alkalized
animal charcoal.
If we compare together the yields which should be
obtained, we find that, with the alkalized animal
charcoal, about £ of the nitrogen is utilized. Indeed,
10.2 kilogrammes of horn charcoal (at 7 per cent, of
nitrogen) contain 710 grammes of nitrogen, which
should have produced 3580 grammes of ferrocyanide
of potassium, while the result was only 600 grammes. f
* This ferrocyanide comes from the treatment of the charcoal
left by the carbonization of 4.5 kilogrammes of raw horn, in three
operations.
f Although, from the numbers admitted by Mr. Karmrodt, it
would seem that the yields have been really those obtained at the
end of the operation, we should remark that in the most careful
mode of working, there are always losses which cannot I5e avoided,
and which are sometimes due to unknown causes. The proportions
of nitrogen indicated for various animal substances are average
numbers. In order to facilitate the calculation, it has been as-
sumed that ferrocyanide of potassium contains 20 per cent, of
nitrogen, whereas the real proportion is 19.87 per cent.
15
226 MANUFACTURE OF COLORS.
Although this method for the manufacture of fer-
rocyanide of potassium is far from the desired per-
fect^on, we must admit, from the experiments, that
it presents several advantages over the usual pr
cesses : —
1. A greater proportion of nitrogen is utilized.
2. The liquors, and the resulting commercial sail
are less impure than when the ordinary process o]
fusion is followed.
3. The loss of alkaline salts is small, while it
considerable in the method by fusion.
4. The residues are small.
A manufacturing establishment, working by thii
method, should have several furnaces of the patten
indicated, since the daily production of one furna<
is only twelve kilogrammes of ferrocyanide of p<
tassium.
It is possible to increase the dimensions of tin
apparatus, and to put four cylinders in one furnace,
so as to produce fifty kilogrammes. A cheaper fuel
than charcoal may be employed, and burned in a fin
place common to the four cylinders.
4th. Schinz Process.
In the apparatus of Mr. C. Schinz, cyanide of po-
tassium is formed by the contact of potassa with
nitrogen, or with the products of the distillation of
nitrogenized substances in closed vessels.
Figs. 49, 50, and 51 represent the apparatus, a,
feeding cast-iron cylinder placed on top of the appa-
ratus, and closed tight with the cover &. c c, cast-iron
plate supporting a, and perforated with a hole corre-
sponding to the diameter, in the clear, of the cylin-
der. Underneath is an iron frame in which slides
BLUE COLORS.
227
a register or damper e, having a hole e', which may
be made coincident or not with the opening of the
lower plate. This damper is moved by an arrange-
ment ^ of rack and pinion.
Fig. 49.
Fig. 50.
Fig. 51.
The lower part of this iron frame covers a flue #,
which communicates through a circular grate with a
vertical retort li, placed immediately below the open-
ing already mentioned. The circular grate is mova-
ble, in order to be cleaned when necessary.
The furnace is placed under the flue g g, and from
this flue and through the sides i i, of the furnace,
there are two gas pipes i' i', one on each side.
The vertical retort Ji is made of sheet iron, and is
enclosed in sand kept in a special space, so that the
retort may expand and contract when heated or cooled.
The fireplace, which is lined with fire-bricks, is placed
around the lower part of the retort, and is separated
228 MANUFACTURE OF COLORS.
from the sand by a cylinder Tc It, of refractory cla
The retort li is supported by another flue I Z, simila
to g g, and is connected by means of a grate wit
another cylinder m, which is immediately below th
retort h, but has a diameter a little larger. Th
cylinder m receives the substances delivered into it
and, being hermetically closed, protects them fro
contact with the air while they are cooling off. It i
supported by a rectangular box n n, in which moves
by rack and pinion, a piston which closes or ope
the aperture o, placed sideways of the axis of the
apparatus. The receiver q rolls on small wheels, and
its top fits close to the piston-box nn. A cylindrical
metallic sieve r may be put in, or removed from the
receiver g, by means of handles. A system of levers
raises the rails r' r', and causes the receiver to be
firmly pressed against the box n n.
The mode of operation is as follows : the feeding
cylinder a is filled with pieces of wood charcoal or
coke, of the size of a walnut, which are mixed with
certain proportion of dried potassa and filings or oxi
of iron. The cover & is put on, and the damper e
made to slide by means of the rack and pinion,
that the charge put in a falls into the retort Ji. The
diameters of the cylinders a, h, and m increase succes-
sively in size, and the substances acquire a conica
shape, which is advantageous to the regular flow
gases and prevents the obstruction of the grates.
The nitrogenized gases come into the retort by t
gas pipes. The formation of the potassium take
place only in that portion of the retort which is sur-
rounded by fire ; but, as by its volatility this metal
rises upwards, it meets its nitrogen gas and is trans-
formed into cyanide of potassium. These dispositions
BLUE COLORS. 229
aid the chemical action, and there is no loss of po-
tassium by volatilization. The remainder of the gases
escape through the lower grate and flue, but not be-
fore they have passed through a mass of materials
sufficient to transform the whole of the nitrogen into
cyanogen. If the materials contained in the retort
are in a pulverulent state, the flow of the gases may be
aided by an exhauster, similar to those used in gas
works.
When the operation has been continued long enough
for the production of a certain quantity of cyanide of
potassium, the sliding damper o is opened, and a
portion of the product is made to fall into the receiver
q. A fresh charge is then put into a, and the opera-
tion continues in the manner already explained.
The apparatus may be modified for distilling nitro-
genized substances, by removing the lower grate and
flue.
The advantages of this apparatus are : —
1. An economy of fuel, because a portion of the
heat generally lost is here used.
2. A saving of potassa or its combinations, because
the special disposition of the apparatus prevents its
volatilization.
3. A saving of nitrogenized substances, on account
of the large surfaces presented by the reacting sub-
stances, and because the reaction takes place in closed
vessels.
4. An increased yield, resulting from the above
causes, and because the products are protected from
the contact of the air, until they are sufficiently cold,
and until there is no longer any danger of the cya-
nogen being transformed into cyanic acid. Moreover,
230 MANUFACTURE OF COLORS.
the cyanogen gas is free from all compounds of sul-
phur and phosphorus.
5. A saving of labor, since the operation is con-
tinuous, and is effected with mechanical appliances.
5th. Determination of the Value of the Fused Materials.
It is an old complaint, says Mr. Brunnquell,
that the manufacture of ferrocyanide of potassium
is so backward, notwithstanding the progress oi
chemistry applied to the arts. Indeed, in the best
managed works, the yield is only one-third of what it
should be, and the remainder of the materials are en-
tirely destroyed or valueless. Moreover, few of the
recent processes have been adopted ; and the manu-
facture by the -nitrogen of the air, experimented upon
in France and in England, has been abandoned. It
appears, therefore, that the old process is still gener-
ally practised, and manufacturers should endeavor
to work it to the best advantage. It is highly im-
portant to determine the truth relative to certain
questions, which have often been put forward, but
never settled in a satisfactory way; for instance,
whether it is preferable to employ carbonized, 01
simply dried animal substances ; whether the po-
tassa should be previously mixed with the animal
matters, or the latter added only when the potassa
is melted ; whether the fusion should be rapid and
effected under a high temperature, or slow and at a
low temperature, etc. There remain also to be decided
whether purified potassa is preferable ; whether the
greater yield obtained in closed vessels is not more
than counterbalanced by the greater cheapness of the
open apparatus, and the greater facility of working,
etc. Lastly, we should determine the best propor-
BLUE COLORS. 231
tions between the potassa and the other materials.
As an example of the doubt still left on these points,
we shall give a few receipts.
1. MM. Hcefflmayer and Priickner, in 1837, gave
the following proportions : —
100 kilogrammes of blood for 28 to 30 kilogrammes of potassa.
100 " horn " 33 to 35 " "
100 " leather " 45 to 48 " "
That is to say, the less potassa, as the substances are
richer in nitrogen, while it should be the opposite.
2. Mr. Gentele, in 1837, also gave certain propor-
tions (Technologiste, vol. xii. p. 240) : —
For 65 kilogs. of bone black . . . 100 kilogs. of potassa at 50°.
" 100 " raw animal matters 100 " " "
We see, therefore, how variable are the "hard
facts" presented by practical men.
3. An English periodical, the London Journal of
Arts, of July, 1852, recommends from 15 to 20 kilo-
grammes of potassa for 100 kilogrammes of animal
substances. With such a proportion of animal sub-
stances, it will be impossible to produce a fusion, and
the experiments of Mr. Schinz prove that 100 kilo-
grammes of potassa will fuse at most from 130 to
140 kilogrammes of animal matters.
If, in a general way, and as Mr. Fleck advises,
an average proportion of equal parts of potassa and
animal substances be adopted, we should nevertheless
modify the ratio with the nature of the substances
employed, as their yield in nitrogen is quite variable.
Satisfactory answers to the important questions
here mentioned cannot be made except after a great
many experiments. The analytical chemist has not
232 MANUFACTURE OF COLORS.
generally occasion to handle the fused materials, and
the manufacturer possesses no rapid process for deter-
mining the composition of each fused batch, in order
to be enabled to undertake a series of experiments
without stopping the manufacturing operations, and
without being obliged to arrive at the yield of each
batch by a separate crystallization.
The following process gives results which are more
than sufficiently accurate for practical use. It does
not require much time, or a great chemical knowl-
edge. Moreover, as manufacturing chemists possess
no accurate way of testing the ferrocyanides, this
method will be of some interest to them.
This method is based upon the precipitation of the
ferrocyanide of potassium held in an acid solution of
a sample from the fused mass, by a titrated solution
of iron. There were two difficulties to overcome.
The first was the determination of the exact point of
saturation, which is not readily ascertained on account
of the property possessed by Prussian blue of remain-
ing suspended for a long time in the liquor. The secon<
was the known property of Prussian blue, of carryiiij
down with it a certain proportion of ferrocyanide oi
potassium. The first difficulty was overcome by a pe-
culiar mode of operation, which is of general interest,
inasmuch as it seems to open a new field in volumetric
analysis, especially when there are intensely colored
precipitates. A drop of the liquor, colored by a pre-
cipitate, is deposited upon a piece of unsized paper.
The precipitate remains where it has touched the
paper, but the liquor spreads itself around, and forms
a colorless ring, which, by means of a proper reagent,
may be made to assume a characteristic coloration.
In our special case, a blue color is obtained with
BLUE COLORS. 233
an iron solution before the saturation, and with a so-
lution of ferrocyanide after saturation.
The point where the first reaction ceases, and
where the second begins, is within the limits of two
to four drops, and the accuracy of the test is within
J to J of 1 per cent., which is quite sufficient in
practice.
The second difficulty is overcome by direct experi-
ment, and two or three tests agreeing together will
show that the proportion of precipitated ferrocyanide
of potassium is one-twentieth of the quantity present.
The sulphocyanide of potassium present in the fused
substances is no impediment to the analysis, because
no sulphocyanide of iron is formed until all the ferro-
cyanide of potassium is precipitated. We have said
enough for experienced chemists; however, we advise
the employment of a moderately concentrated solu-
tion of a salt of peroxide of iron. The iron, held in
the solution occupying 100 divisions of a graduated
burette, is carefully determined after its precipitation
with ammonia. The weight found will be used for
determining that of the sample to be taken, in order
that each division of the burette be equal to 1 per
cent, of ferrocyanide of potassium.
The formula is —
2.257
1 : 2.257 + -go" :: n : xi
in which n is the quantity of oxide of iron found in
100 volumes of the titrated liquor, and x the weight
of the raw fused mass to be employed for the test.
As the fused mass is very hygroscopic and difficult
to grind, it is advisable to take a certain weight of it,
and reduce by calculus the number of divisions of the
titrated liquor or percentage to the weight x. For
234 MANUFACTURE OF COLORS.
instance, if 8.98 grammes of sample show 12.5 divi-
sions, or 12.5 per cent., x grammes will give y per
cent.
Preparation of the titrated liquor. — A pure sul-
phate of iron, without copper or excess of base, is
prepared as follows: Dissolve in boiling water 250
grammes of sulphate of iron, and add a small quantity
of sulphuric acid and a few clean scraps of iron. Let it
stand until the liquor is clear and of a pure green color,
then filter it rapidly, and allow it to cool in a covered
vessel. After the crystals have been dried in several
successive sheets of unsized paper, 83.28 grammes of
them are weighed and dissolved in about 750 grammes
of water. The solution is heated in a porcelain dish,
and nitric acid is added several times, until red vapors
cease to be disengaged. The liquor is then, together
with the washings of the dish, poured into a vessel
holding 1 litre, and when it is cold, sufficient pure
water is added to make up the capacity of a litre. 100
cubic centimetres of this titrated liquor will precipitate
10 grammes of pure ferrocyanide of potassium. There-
fore, every cubic centimetre poured out will corre-
spond to 1 per cent.
Analytical operation. — Different portions of the
fused substances are ground together, and 10 grammes
weighed. This is dissolved in warm water, the solu-
tion is filtered, and the residue is washed several times
Avith warm water. A few drops of the titrated liquor
are then added, which produce a brown and blue pre-
cipitate. To neutralize the free alkali of the solution,
hydrochloric acid is then poured in, the more slowly
as the brown precipitate gradually disappears, and the
blue one becomes more apparent. No account is
BLUE COLORS. 235
taken of the gelatinous silica which is separated.
Then four or five drops of the titrated liquor are
poured in, and a drop of the blue liquor is deposited
by means of a glass rod upon a piece of unsized
paper. The colorless ring formed around the blue
precipitate is touched with another rod wet with a
solution of a salt of peroxide of iron, and if a blue
color appears, the operation is continued as before.
"When the ring becomes brown-red, from the presence
of sulphocyanide, the test is made with a solution of
ferrocyanide, until a blue again appears. We should
remark: First, that the coloration takes place only
after a certain length of time ; second, that it appears,
in the majority of cases, in the middle of the border,
and not at the extreme edge. In order to see how
accurate this test is, the liquor is filtered at the end
of the operation, and an addition of ferrocyanide will
give a very pale blue coloration, if any.
The manufacturer should also note, before the test
is made, the total weight of the fused mass, which
weight may often vary from unknown causes.
6th. Preparation of Prussian Blue by the Stephens Process.
The invention comprises : —
1. Several improvements in the manufacture of the
ferrocyanides of potassium and sodium.
2. A process for rendering Prussian blue soluble,
and therefore better adapted for dyeing, printing, and
writing.
We shall describe these two improvements succes-
sively, in the order presented by the inventor.
First improvement. — This consists in collecting the
gaseous products, which, in the ordinary preparation
of ferrocyanides with animal substances, are lost in
23(5 MANUFACTURE OF COLORS.
the air, and in converting them into the ferrocyanide
of sodium or of potassium. There is, therefore, a
greater yield of the ferrocyanides.
The apparatuses necessary for these operations are
simple enough to be explained in writing, without
having recourse to drawings. These apparatuses
are : —
1. An iron retort filled with alkali and animal
matters, or any other substance holding nitrogen and
producing ammonia. This retort should be brought
to a dark read heat. It is provided with a cover,
which is carefully luted on during the operation.
2. Another retort similar to the preceding one.
3. An hermetically closed vessel, of a cylindrical, or
any other convenient, shape. It is charged with an
alkali, and should be maintained at a red heat during
the whole operation.
4. A closed vessel, holding an alkaline lye, and
provided, for the escape of gases, with a pipe similar
to a lamp burner.
5. A pipe connecting the retort with the cylinder,
and delivering into the latter vessel the gases result-
ing from the carbonization of the animal substances
in the retort.
6. A tube delivering the gases from the retort into
the vessel holding the caustic lye. It is already
understood that the retort and the cylinder are
placed in furnaces, the fire of which is regulated by
appropriate dampers.
Everything being arranged in the aforesaid manner,
the gases produced in the carbonizing retort pass
into the cylinder holding fused potassa (or soda), and
form there a certain quantity of ferrocyanide of potas-
sium (or of sodium). The portion of the gases which
BLUE COLORS. 237
has not combined with the alkali, escapes through the
tube into the closed vessel, and there forms another
combination with the alkaline lye. Lastly, the un-
combined gas escapes through the burner. The state
of the operation is watched by burning the gas, and
when the flame becomes small and weak, the commu-
nication between the retort and the cylinder is inter-
rupted. The second retort, which has been charged
with fresh substances, is then connected with the
cylinder, and the operation proceeds as before.
When the gaseous products of a certain number of
charges have traversed the cylinder charged with
alkali, it is opened, and its contents, consisting of
more or less ferrocyanide of potassium or of sodium,
are poured into a closed iron vessel where they cool
off. They are then lixiviated with pure water, in the
ordinary way.
The decomposition of the carbonized animal sub-
stances may be completed in the same retort, by
increasing the fire, and stirring the contents. During
that time, the carbonization goes on in the other
retort, at a lower temperature.
A similar effect, that is, the absorption of the
gaseous products, may be obtained by placing in a
conical iron chimney, with a grate at the bottom, dry
potassa or soda, and passing the gases through it.
This chimney, with its contents, may be removed
when the flame becomes weak. The alkali is used
for several operations, and is then treated in the ordi-
nary manner for the extraction of the ferrocyanide of
potassium or sodium.
Second improvement. — This consists in submitting
the Prussian blue to a treatment, by which it becomes
more easily soluble. The Prussian blue resulting
233 MANUFACTURE OF COLORS.
from the combination of ferrocyanide of potassium,
and of an iron salt, or the ordinary commercial article,
is put into an earthenware pot, and just covered with
some concentrated acid.
We may employ hydrochloric, or sulphuric, or any
other acid, having sufficient action upon the iron;
nevertheless, hydrochloric acid is to be preferred. If,
however, sulphuric acid be used, it should be diluted
with an equal volume of water, when the paste of blue
and acid begins to turn white.
The Prussian blue should remain in the acid from
24 to 48 hours, or even longer. The mixture is then
well stirred in a large quantity of water, in order to
remove the iron salts. After settling, the liquid is
siphoned off. A new quantity of water is then added,
and the operation is continued until all of the acid and
soluble iron salts are removed. When the washing is
complete, a few drops of a solution of ferrocyanide of
potassium produce no precipitate in the liquors. The
blue is then drained upon a filter.
The Prussian blue, thus prepared, contains less
iron than the ordinary commercial article. It is this
modification which renders it more easily soluble.
The drained product may be slowly dried in a stove
room.
After this preparation, the blue is thoroughly mixed
with oxalic acid, and pure water is added by small
portions at a time, in quantity variable with the
greater or less degree of concentration desired. The
proportion of oxalic acid varies also writh that of the
water added.
It will be ascertained by trial that Prussian blue,
which has been macerated in the aforesaid manner,
will require for its solution a much smaller propor-
tion of oxalic acid.
BLUE COLORS. 239
One part of oxalic acid will dissolve six parts of
Prussian blue, weighed before maceration in hydro-
chloric or sulphuric acid. These proportions are
sufficient for a concentrated solution ; but more oxalic
acid will be needed for a more dilute solution.
A Prussian blue, which has not been macerated in
the strong acids, will require from two to three times
its weight of oxalic acid, and yet, there will be a ten-
dency to precipitation in the solution.
The principal obstacle to the employment of this
fine color for dyeing, printing, and writing resulted
from its supposed insolubility; but the process which
we have just indicated, and which produces an en-
tirely soluble Prussian blue, renders it applicable
to the dyeing and printing of every cloth and sub-
stance which may be dyed and printed.
The process indicated above is not the only one
known for rendering Prussian blue soluble. An
aqueous solution of this color may also be obtained
by precipitating the nitrate or sulphate of sesqui-
oxide of iron, and possibly the perchloride, with a
great excess of ferrocyanide of potassium. The pre-
cipitate is very soluble in pure water, but insoluble
in water holding chloride of sodium or various other
salts. This property allows of the separation of the
precipitate.
7th. English Process for the Manufacture of Prussian Blue.
The following process, usually employed in Eng-
land, gives a Prussian blue quite as fine as that of
Berlin, and has a great analogy with the method
actually practised in France.
Ox blood, mixed with oxide of iron, is dried in a
reverberatory furnace, the bed and sides of which, to
240 MANUFACTURE OF COLORS.
a height of about twenty to twenty-five centimetres,
are formed of cast-iron plates bolted together, and
with the joints made tight by a clayish cement.
During the operation, the mass is continually stirred
with an iron bar. This furnace should have a high
stack with a good draft, so as to carry away the
vapors, which are singularly fetid. When the blood
is perfectly dried, which is a tedious process, it is
removed from the furnace and broken into fragments
while it is still hot. The division will be more diffi-
cult if the blood be cold. In fine weather, its drying
may be completed in the sun. When it is not imme-
diately mixed with the alkali, the powdered blood
should be kept in open vessels and in a cool and
aerated place, otherwise it will ferment and produce
a disagreeable smell, and becoming viscous, it will
be difficult to mix with the alkali.
The "blood lye" or solution of crude ferrocyanide is
advantageously prepared with soda, which is cheaper
than potassa. The proportions are one part of dry
soda to six parts of perfectly dried blood. The soda
ash should be free from sulphides, and on that ac-
count it is preferable to use the crystals, which are
completely dried.
The mixture of oxide of iron, blood, and alkali
calcined in a large cast-iron crucible or kettle, which
is covered, without, however, entirely excluding th
contact of the air. This imperfect closing of th
vessel is for the purpose of diminishing the rapidit
of the combustion.
The two operations of calcination, and desiccatio
of the blood, are conducted simultaneously, and wit
economy of fuel. The calcining vessel is placed o
the forepart of the reverberatory furnace, near th
BLUE COLOftS. 241
fire-bridge, where the intensity of the fire is greatest.
The drying of the blood takes place near the chimney.
The mixture to be calcined soon softens, takes fire,
and sinks considerably. The cover of the vessel is
then raised with a hook, and a new portion of materials
is introduced, and so on, until the vessel is filled.
After ten hours of calcination, the vapors cease to
catch fire, and the animal substances are entirely
charred. The temperature is then raised, so as to
redden the metallic vessel. The alkaline charcoal
enters into a sort of fusion, and sticks to the spatula
with which k is stirred. After one hour more of red
heat, the contents are removed with an iron ladle, and
thrown into an iron vessel, which holds a volume of
cold water about double that of the blood used.
After boiling, the liquor is filtered through several
thicknesses of cloth, and the residue is again boiled
and filtered.
All of the liquors and washings are collected in
large but shallow cisterns, and exposed to the air.
The}7 are stirred now and then, in order to decompose
the sulphides. "When the lye no longer gives a black
precipitate with the acetate of lead, it is treated with
two parts of alum, and one-half part of sulphate of
iron, for each part of dry carbonate of soda employed.
The sulphate of iron has been previously oxidized by
its ebullition with a very small proportion of nitric
acid, or by passing some chlorine through it. The
same result may be obtained by calcining it in the
air, at a very low temperature. The alum and
sulphate of iron are dissolved only when they are
going to be used. The mixture of the liquors is
effected by pouring the solution of the sulphates into
that of ferrocyanide, and stirring continually. The
16
242 MANUFACTURE OF COLORS.
precipitate of Prussian blue is washed several times
by decantation with pure water. The washing should
be continued as long as the liquor precipitates by the
addition of ammonia. The blue is collected upon
cloths, which are folded and pressed when it has
acquired a certain consistency. The drying is effected
in the shade and in stove-rooms, the temperature of
which latter should not be over 25° C.
When the blue is sold in paste for distemper paint-
ing, and the printing of paper hangings, it is evidenl
that it ought not to be pressed.
As long as Prussian blue is pasty and wet, it pre-
serves its pure color. But it seldom happens even
after the best conducted drying in a well ventilated
room, that the blue fails to acquire a slightly green
tinge, which defect is not seen in the fine Berlin
blues. This defect is attributed to the production of
a small quantity of ammonia, resulting from the
decomposition of prussic acid.
The addition of a certain proportion of acid sulphate
of potassa preserves the fine color of the Prussian
blue, and admits of its employment with vegetable
and essential oils. This salt results from the decom-
position of nitrate of potassa by sulphuric acid, and
is cheap, and easily found in the trade. It is probable
that the acid sulphate of soda would have the same
effect.
The expense of manufacture may be diminished
by substituting for the alum a sulphate of alumina,
which may be prepared on the spot, and does not
require to be free from iron. This sulphate of alumina
is prepared by making a stiff paste of clay and sul-
phuric acid, and moulding it into bricks, which are
heated in a little space left at the end of the blood
BLUE COLORS.
243
drying furnace. The liquor resulting from the lixi-
viation of these bricks is employed, directly and with-
out evaporation, with the sulphate of iron and the
solution of crude ferrocyanide.
An important condition, in the manufacture of
Prussian blue, is to effect the calcination at the proper
temperature. An excess of heat is injurious to the
yield. In general, it is better to calcine longer and
at a lower temperature.
A few manufacturers employ the crystallized ferro-
cyanide of potassium, with which they obtain the
Prussian blue directly, and without the addition of
acid. But it is easy to see that this process is not
economical. The crystallized prussiate is obtained
after saturation of the excess of alkali in the crude
"blood lye." Subsequently, when mixing alumina
with the Prussian blue, which contributes to its beauty
and its velvety appearance, another alkali is employed
for precipitating the alumina from the alum. There
results therefore a double employment of chemicals,
whereas, in the ordinary process, the excess of alkali
in the raw solution of ferrocyanide decomposes the
alum.
A manufacturer of Glasgow proposed to use the
bone black which had been used for clarifying the
sugar of refineries. This black, which was used only
as manure, is again calcined with one-thirtieth part
of alkali. The result is an abundant production of
alkaline prussiate, without those disagreeable smells
produced by blood and other uncalcined animal sub-
stances. The most interesting part of the process is,
that the residue left after the lixiviation of the
cyanides is a very energetic discolorizing substance,
which is sold again to the sugar refiner. It appears
244 MANUFACTURE OF COLORS.
that the same material may be used several times
successively for clarifying sugars and producing
cyanides.
§ 2. Paris Hue.
Paris blue, also called TurribulVs ~blue^ is a very
handsome dark violet-blue pigment, in which the
proportions of protocyanide and sesquicyanide do not
appear to be in the same ratio as in the ordinary
Prussian blue. It is said that its chemical formula
is represented by 3 equivalents of protocyanide and
1 of sesquicyanide of iron.
Paris blue is prepared by different processes, the
products of which are not always uniform in tone and
in intensity of coloration. Generally, a green and
pure protosulphate of iron is precipitated by the red
prussiate of potash (ferri cyanide of potassium), and
the mode of operation is the same as with the ordi-
nary Prussian blue.
The sulphate of iron may also be precipitated by a
solution of raw ferrocyanide, and the excess of alkali
removed by washings with pure water. The precipi-
tate is then treated by hypochlorite of lime (bleach-
ing powder) dissolved in cold water, and lastly,
washed with dilute hydrochloric acid, and rinsed in
pure water.
Paris blue is also produced by dissolving separately
in 15 parts of water, 6 parts of sulphate of protoxide
or of peroxide of iron, and six parts of yellow prussiate
of potassa. The two liquors are mixed, and there are
added to them one part of sulphuric acid, and twenty-
four parts of concentrated hydrochloric acid. The
whole is stirred, and, after standing a few hours, is
treated by a filtered solution of hypochlorite of lime
BLUE COLORS. 245
(bleaching powder) dissolved in eighty parts of water.
This latter solution is poured by small quantities at
a time, and stopped when there is an effervescence due
to the disengagement of chlorine. The precipitate is
then allowed to settle, and it is afterwards washed
several times with pure water by decantation. After
draining, it is moderately heated with dilute nitric
acid, until it has acquired a fine dark blue color.
According to Mr. Raymond, a handsome quality of
Paris blue is obtained by precipitating a nitrate of
sesquioxide of iron with the yellow prussiate (ferro-
cyanide of potassium) or with "blood lye."
Mr. R,. Warington, who has carefully studied the
Turnbull blue, states that several efficient reagents
may be employed in its preparation, that is, 1, the
bichromate of potassa ; 2, the chlorate of potassa ; 3,
a soluble persalt of iron ; 4, a solution of hypochlorite
of lime.
" When bichromate of potassa is used, only one-
third of one equivalent should be taken, because this
salt gives three equivalents of available oxygen. One
equivalent of chlorate of potassa is sufficient for the
oxidization, and sufficient hydrochloric acid should
be added for decomposing the salt and setting its
acid at liberty. Hypochlorite of lime (bleaching
powder) is open to the objection of producing a quan-
tity of sulphate of lime, when sulphate of iron or
sulphuric acid is used. In the third case, when a
persalt of iron is the oxidizing agent, the sulphate of
peroxide is to be preferred. One equivalent of it is
necessary for one equivalent of oxygen, and there is
produced enough sulphuric acid to combine with the
oxidized potassium after the iron has been reduced to
the protoxide state.
246 MANUFACTURE OF COLORS.
" In the preparation of the sulphate of peroxide of
iron, bichromate of potassa or chlorate of potassa is
more advantageous than nitric acid, and there should
be a sufficient proportion of sulphuric acid to dissolve
the oxide of chromium produced. The decomposition
of the chlorate of potassa should always be effected
with hydrochloric acid. Since the protosulphate of
iron absorbs one-half of one equivalent of oxygen to
become sesquisulphate, it is evident that one-sixth
of one equivalent of bichromate of potassa, or one-
tenth of one equivalent of chlorate of potassa with
the required proportion of acid, is sufficient for the
transformation. When the oxidizing solution is pre-
pared with the chlorate of potassa, this solution, after
the oxidization of the white Prussian blue, may be
precipitated by ferrocyanide of potassium for a new
operation. If the bichromate of potassa be used, the
protoxide of chromium will be precipitated to a cer-
tain extent by the ferrocyanide of potassium, and will
contribute to the brightness of the color."
Mr. G. C. Habich, a chemist who has paid great
attention to the manufacture of Paris blue, has pro-
posed several valuable improvements, which render
its preparation more certain and more economical.
" Among those coloring materials," says he, " which,
from their numerous uses, require to be manufactured
on a large scale, Prussian blue is certainly foremost.
" Its great qualities of body, and intensity of colora-
tion, will always insure it a large sale ; moreover, its
mixture with chrome yellow produces a fine green
cinnabar or leaf green (JLaubgrun).
" The methods followed in certain works for the
manufacture of this product, appear to me too ex-
pensive. Thus many persons still prefer the process
BLUE COLORS. 247
by which the white precipitate, resulting from the
decomposition of ferrocyanide of potassium by sul-
phate of iron, is rendered blue by means of sulphuric
and nitric acids, although it is impossible to obtain
with this product a good commercial green.
" I shall explain several processes by which the
preparation of this product will be certain and
economical.
"First Process. — This process is based upon the
treatment of the white precipitate by the chlorine
held in aqua regia.
"The precipitate of ferrocyanide of potassium
(yellow prussiate) by the sulphate of protoxide of
iron, is prepared in the ordinary manner; but the
sulphate employed should be, as far as possible, free
from oxide (basic sulphate). This result is arrived
at by keeping in the acid solution of sulphate of iron,
a small quantity of metallic iron, which, at the same
time, precipitates the copper which may be present.
Besides, it is desirable to operate the precipitation
in the hot blood lye (crude prussiate of potassa), in
order to avoid an absorption of oxygen, and a prema-
ture change of the precipitate to a blue color. Only
the blue produced by the action of chlorine, nitric
acid, etc., upon the white precipitate, possesses the
intensity required in this pigment. That resulting
from the oxidization by the air, even after all the
hydrate of oxide of iron has been removed by hydro-
chloric acid, never produces a fine color, especially
for the preparation of greens.
" In regard to the proportion of sulphate of iron,
the general mistake is in employing too little of it.
When ninety kilogrammes of sulphate of iron have
been added to one hundred kilogrammes of ferro-
248 MANUFACTURE OF COLORS.
cyanide of potassium, a drop of iron solution in the
filtered liquor produces no precipitate. However, the
white precipitate has carried with it a certain propor-
tion of ferrocyanide, which maybe removed by wash-
ing. This proportion of a costly chemical is there-
fore lost, and in order to avoid its waste, we propose
the following mode of operation. The iron solution
is poured into that of ferrocyanide, which is stirred
all the time, until precipitation no longer takes place,
then one volume of the same iron solution, equal to
one-ninth of that already poured in, is added. If we
continue the stirring for about fifteen minutes, we
maybe sure that the whole of the ferrocyanide carried
down by the precipitate is decomposed. We have,
therefore, reached the degree of economy which may
be expected at this period of the manufacture.
" The precipitate which has been left to drain until it
has become a thick magma, is then peroxidized (blued)
with a mixture of nitric and hydrochloric acids,
prepared several days beforehand. The proportions
naturally depend upon the degree of concentration of
these acids, which is ascertained by means of a good
hydrometer, and of corresponding tables found in
treatises on chemistry. The mixture is so made that
there are in weight 54 parts of anhydrous nitric acid
and 36.5 parts of anhydrous hydrochloric acid. The
proportion of aqua regia necessary for turning to blue
the white precipitate, is 10.7 parts of anhydrous nitric
acid (in the mixture) for 100 parts of ferrocyanide of
potassium employed for the precipitation. Let us
suppose that the nitric acid marks 30° Be. (sp.
gr. = 1.256 according to Graham), and the hydro-
chloric acid 23° Be. (sp. gr. = 1.185) ; the first of
these acids, according to the tables of Dr. Ure, con-
BLUE COLORS. 249
tains 35.4 per cent, of anhydrous nitric acid, and the
second 37.25 per cent, of anhydrous hydrochloric acid.
From the preceding data, the aqua regia mixture will
be 100 kilogrammes' of the commercial nitric acid
(holding 35.4 kilogrammes of anhydrous acid), and
62.2 kilogrammes of the commercial hydrochloric
acid (holding 23.9 kilogrammes of anhydrous acid).
Lastly, 40 kilogrammes of this mixture will be suffi-
cient for bluing the precipitate resulting from 100
kilogrammes of ferrocyanide of potassium.
" The aqua regia is added by small portions at a
time to the white precipitate, which is placed in a
wooden tub, and is stirred all the while. It now
remains to ascertain whether too much acid has been
added, or if the intensity of the color may still be
raised by a fresh addition of acid. Such defects may
result from an improper preparation of the aqua regia.
" A small quantity of the blue color is put into a
glass, and a drop of aqua regia is mixed with it. Then
a blue mark is made with that sample of color upon
a piece of paper, and is compared with a similar mark
made with the stuff in the tub. If this addition of
acid has increased the intensity of the blue, too little
aqua regia has been employed, and more should be
poured in. On the other hand, if the test sample has
become slightly greenish, the proportion of the acids
has been sufficient or too considerable. In order to
decide this point, a new sample from the tub is put
into a test glass, and a very small quantity of white
precipitate is added to it. Should the color become
more intense, we have the proof that too much acid
has been added. This defect is remedied by adding
by degrees a certain proportion of the white pre-
cipitate, of which there should always be a certain
250 MANUFACTURE OF COLORS.
stock on hand, which is preserved in well-closed glass
or stoneware jars.
" The washings and the other operations are then
effected in the ordinary manner.
"Second Process. — The white precipitate of ferro-
cyanide of potassium by sulphate of iron, is rendered
blue by a solution of perchloride of iron, which is
reduced to the state of protochloride and may be used
for another precipitation, instead of sulphate of iron.
" This perchloride of iron is made with iron ore,
free from clay and carbonate of lime, and which may
be brown or red hematite. If such an ore cannot be
had, then the residue of the manufacture of sulphate
of iron, known under the names of caput mortuum,
colcotar and English rouge, may be employed. Th<
oxide of iron, whatever its origin, is finely groum
and then treated in a lead tank with the crude hydn
chloric acid of the soda works, which generally con-
tains a certain proportion of iron. The mixture
frequently stirred for several days, and when th<
liquor is saturated with iron, it is decanted int<
another vessel, where it becomes entirely clear. It ii
this solution of perchloride of iron, which is used foi
bluing.
" The white precipitate is prepared in the mannei
already described, and drained. The magma it
rapidly heated to the boiling point in a copper vessel,
and then poured into a tub and stirred with the solu-
tion of perchloride of iron, which is admitted until
the color has acquired its greatest intensity. In thi*
operation, it is not necessary to watch the bluing
with the same attention as when the aqua regia ii
used, because an excess of perchloride does not altei
the purity of the color. This perchloride of iron is
BLUE COLORS. 251
therefore added to a slight excess, that is, until a
filtered sample of the liquor is turned decidedly blue
by a few drops of a solution of ferrocyanide of potas-
sium. When this point is reached, the liquor is filtered
out (if it be desired to save nearly all of it), or the
precipitate is left to settle, and the clear portion is
decanted.
" This liquor, as we have said, is a solution mostly
of protochloride of iron. It is poured upon old scrap
iron, and may be used instead of sulphate of iron for
a precipitation with ferrocyanide of potassium. This
saving is one advantage of this method.
" The color is washed, etc., in the ordinary manner.
"Third Process. — In this method, the white precip-
itate is rendered blue by a solution of perchloride of
manganese. The economy of the process depends on
local circumstances, and on this account, it is neces-
sary to state that the price of manganese ore is based
upon its yield in binoxide, and that the less oxidized
ores generally mixed with it may be dissolved in
cold hydrochloric acid. Therefore, by treating an
ordinary ore by hydrochloric acid, the value of the
ore becomes enhanced, and there is obtained at the
same time a very good reagent for bluing the white
precipitate.
" The mode of operation is exactly the same as
with the perchloride of iron. As the solution of pro-
tochloride of manganese, resulting from the bluing
treatment, is without particular value to the manu-
facturer, we should avoid adding an excess of per-
chloride. Therefore, samples of blue are frequently
taken, and their intensity compared. This is the only
test practicable, by reason of the easy decomposi-
252 MANUFACTURE OF COLORS.
tion of the perchloride of manganese. The remaining
manipulations are as usual.
" The residues of the manganese ores, after their
treatment by hydrochloric acid, are carefully washed
and dried before being sold as peroxide or purified
manganese.
"Fourth Process. — A solution of chromic acid is
also, an excellent reagent for bluing the white pre-
cipitate of ferrocyanide of potassium by sulphate of
iron. The only disadvantage of the method is, that
the resulting salt of oxide of chromium is difficult
to place on the market.
" The following is the mode of operation : 10 parts
of bichromate of potassa are dissolved in 100 parts oJ
hot water, and when the solution is cold, 13.5 parl
of concentrated sulphuric acid are added to it. Th<
mixture is kept in closed glass vessels.
" The white precipitate, prepared as usual, and i:
the form of a magma, is heated to the boiling poinl
The chromic liquor is then added, until the maximui
of intensity in the liquor is reached.
" Before closing these remarks on Prussian blue,
shall again point out the mistake made by certaii
manufacturers who prepare the blue with the inten-
tion of producing greens by an admixture of chrome
yellow, and who believe that their mode of operatioi
is perfect, whereas it is wrong. I am acquainte<
with manufacturers who neglect all the precaution*
we have mentioned, and who allow the white precipi-
tate of ferrocyanide of potassium by sulphate of iroi
to become blue by the contact of atmospheric ail
They certainly ignore the fact, that by their process
they lose a notable proportion of the ferrocyanide
which is the most expensive material of the manu-
BLUE COLORS. 253
facture. It has been established by accurate chemical
experiments, that 50 per cent.* of the ferrocyanide
employed in the precipitation of a salt of protoxide
of iron, is carried down with the white precipitate,
and that during the bluing, the greater part of this
ferrocyanide is dissolved and washed away. This
loss is prevented or greatly diminished when one of
the above processes is followed in bluing. When it
is desired to avoid ony waste, the liquor decanted or
filtered from the white precipitate should be collected
in a special tank, and precipitated by a solution of
sulphate of iron."
§ 3. Monthiers' Hue.
Mr. Monthiers has discovered that Prussian blue
will combine with ammonia, and that the resulting
color is finer and more durable than the ordinary
article. The mode of operation is as follows : —
Pure hydrochloric acid is saturated with iron, and
the resulting solution of protochloride of iron is mixed
with an excess of aqua ammonia. The liquor is fil-
tered, and the filtrate is received in a solution of
ferrocyanide of potassium. The resulting white pre-
cipitate is collected upon a filter, and left exposed to
the contact of the air, when it soon becomes blue.
It is then washed with a solution of tartrate of
ammonia, in which it is not soluble like the ordinary
blue, in order to dissolve any excess of oxide of iron
held in it. The washing is continued until nothing
more is dissolved, when the article is dried at a low
temperature.
* More likely 5 per cent. See p. 233. — TRANS.
254 MANUFACTURE OF COLORS.
§ 4. Testing the value of Prussian blue, and its
adulterations.
There are in the market, under different names,
many coloring substances having Prussian blue for
a basis, and which often contain quite a large pro-
portion of some white substance. The common sorts
of greens for house painting are mixtures of Prussian
blue, chrome yellow, or some other organic yellow,
with a greater or less proportion of white material.
As Prussian blue may easily be transformed into
ferrocyanide of potassium, Mr. Brunnquell thinks
that the method which has already been explained
for testing the crude ferrocyanide, may be applied to
the analysis of Prussian blue and its mixtures.
The operation is as follows : Boil 6.79 grammes of
the color to be tested with a solution of caustic
potassa until all the blue or green coloration has dis-
appeared ; then filter, and wash the residue several
times with hot water. The liquors are tested as has
already been explained. In this case, as there is no
sulphocyanide of potassium, the test is continued
until there is no longer a blue coloration with the
ferric solution. At this period of the operation the
volume of this solution, which has been poured out,
is noted, and a few more drops added, until the blue
coloration reappears with a solution of ferrocyanide.
One-half of the number of these drops is added to the
volume previously noted, and the percentage of Prus-
sian blue is obtained as accurately as may be done by
a volumetric test. If the blue precipitate does not
deposit well upon the paper, but runs towards the
edges, some common salt, or other indifferent salt, is
added to the tested solution. There is a Prussian
BLUE COLORS. 255
blue which is soluble in pure water, but not in a
solution of common salt.
There are several ways of testing the commercial
white cyanide of potassium. Baron Liebig has given
a process which seems as accurate as possible.
Messrs. Fordos and Gelis have also published a
method which does not appear so accurate, and which
requires the employment of iodine, an expensive sub-
stance. As practical manufacturers are generally
opposed to the preparation of test liquors, which re-
quire a certain degree of skill in manipulation, Mr.
Brunnquell refers again to his method in case it be
desired to avoid the expense necessitated by the Lie-
big process. The mode of operation is as follows : —
Dissolve 9.246 grammes of cyanide of potassium in
a small quantity of water, and add about the same
quantity of the solution of pure sulphate of iron.
The whole is boiled for some time with a solution of
potassa, and then filtered, and the residue washed.
The liquors are treated in the manner explained in
§ 1 and § 2. Each degree (volume) of the titrated
liquor corresponds to 1 per cent, of pure cyanide of
potassium.
The substances generally employed for adulterating
Prussian blue are : Alum, an excess of oxide of iron,
starch, the carbonate and the sulphate of lime,
alumina, and sulphate of baryta.
The alum, oxide of iron, and alumina are dissolved
by digesting the blue in sulphuric acid, diluted with
eight to ten times its weight of water. After filtering,
an excess of ammonia is added to the liquor, and
there is produced an abundant reddish precipitate of
alumina and oxide of iron. Caustic potassa will dis-
256 MANUFACTURE OF COLORS.
solve the alumina ; the blue remains undissolved in
the acid.
Starch is recognized by the eye, with or without
the aid of a microscope. But the best test consists in
boiling the Prussian blue in water, and filtering it. A
drop of iodine solution in the cold filtrate produces
with starch an intense blue coloration.
Each time that a Prussian blue, stirred in pure
water, effervesces by the addition of an acid, it is a
proof that it is mixed with a carbonate, and if the
filtered liquor, rendered neutral, gives a white pre-
cipitate with oxalate of ammonia, carbonate of lime
is the adulterant.
Plaster of Paris (sulphate of lime) is detected by
boiling the sample of Prussian blue in water slightly
acidulated with nitric acid. The liquor is filtered,
and the blue remains upon the filter. A few drops of
a solution of chloride of barium, added to the filtrate,
will produce a white precipitate of sulphate of baryta.
We have already seen that Prussian blue is ren-
dered soluble after a treatment with hydrochloric
and oxalic acids; therefore, if, after a sample has
been rendered soluble, there remains upon the filter
a white substance, insoluble in water and acids, we
conclude that this blue has been adulterated with
sulphate of baryta.
§ 5. Mineral blue, Antwerp blue.
Mineral or Antwerp blue is a mixture, in variable
proportions, of Prussian blue, alumina., magnesia, and
oxide of zinc. Its color varies from a light to a dark
blue, and it is employed for oil and distemper paint-
ing, and especially for paper hangings.
It is prepared like Prussian blue, with this differ-
BLUE COLORS. 257
ence, that the sulphates of magnesia and zinc, and the
alum, are added to the lye of crude ferrocyanide of
potassium. The remainder of the operation is as
usual.
The name of "mineral blue" is sometimes given to
white earths (kaolins, etc.), colored with indigo and
hydrated oxide of copper. A small quantity of Ndrd-
hausen sulphuric acid decomposes Prussian blue, and
dissolves indigo without changing its color. A few
drops of ammonia, poured into the liquor, will pro-
duce an intense blue coloration if copper be present.
§ 6. Thenard Hue, or cobalt blue (subphospliate of
cobalt).
The discovery of this fine color is due to the chem-
ist Thenard. This blue is a basic phosphate of
cobalt, which, being calcined with alumina, gives a
pigment sufficiently handsome to replace ultramarine
blue, which is more expensive. Cobalt blue could be
advantageously substituted for ultramarine, even for
delicate paintings, except for one single defect,
. pointed out by Mr. Bourgeois, it has a violet hue
under artificial light, and this naturally defeats the
colored combinations of the artist.
Cobalt blue acquires all its intensity of coloration
only after exposure to the air. Messrs. Bourgeois and
Colomb have succeeded in giving it sufficient body ;
and, although not so pure in color as ultramarine, it
produces, with silver white, different tones. It should
always be remembered that the tones produced with
cobalt blue will become more intense after a long
exposure to the air, and that they acquire a slightly
greenish tinge, which is not the case with ultra-
marine.
17
258 MANUFACTURE OF COLORS.
The preparation of cobalt blue, according to The-
nard, is as follows : The roasted cobalt ore from
Tunaberg, Sweden, is heated with an excess of dilute
nitric acid, and the solution is evaporated nearly to
dryness in a porcelain or platinum dish. The residue
is boiled with water, and filtered, in order to separate
a deposit of arseniate of iron. A solution of basic
phosphate of soda is then poured into the filtrate, and
there is produced a precipitate of basic phosphate of
cobalt, which is violet, but may become of a pink
color by remaining under water.
This precipitate is washed and collected upon a
filter. While it is still gelatinous, one part of it is
thoroughly mixed with eight parts of hydrated alu-
mina, recently precipitated from a solution of potassa
alum by ammonia. The mixture is first dried in a
stove-room, or upon a furnace, until it is dry enough
to be brittle. It is then calcined at a cherry-red
heat for half an hour, in a covered clay crucible. The
resulting blue color is kept in glass jars.
The operation will always be successful, if the
alumina has been prepared with a sufficient excess of
ammonia, and if it has been washed several times
with very clear water.
In this preparation of cobalt blue, the phosphate of
cobalt may be replaced by the arseniate of cobalt.
But, instead of one part of the violet precipitate of
phosphate of cobalt, one-half part of the arseniate
will be sufficient for eight parts of gelatinous alu
mina. The arseniate of cobalt can be obtained
precipitating the solution of cobalt with one of arse
ate of potassa.
As the gelatinous alumina, necessary for the manu-
facture of cobalt blue, enters into the preparation of
ate
by
:i
BLUE COLORS. 259
several other colors, we shall here explain its prepara-
tion. The alum is dissolved in a quantity of water,
at least three times that strictly necessary for the
solution, and is then precipitated by an excess of
ammonia. After stirring, the precipitate is left to
settle, and the liquor is decanted with a siphon.
Several washings are made with pure water, and the
liquors are decanted or siphoned off. Lastly, the
residue of gelatinous alumina is collected upon a
filter.
Cobalt blue, mixed with whites, gives light blue
tones, with a slightly violet tinge. It is very durable,
becomes more intensely colored in the air, and resists
the action of fire, acids, and alkalies.
The beauty, or rather the intensity, of Thenard
blue, depends on the proportions of alumina added.
"With equal parts of phosphate of cobalt and of
hydrated alumina, the blue is greenish; with four to
five parts of alumina to one of phosphate, the blue is
pure. Intermediate tones and hues will be obtained
by varying the proportions.
Several modifications have been introduced in the
manufacture of cobalt blue, the most important of
which is that of Mr. Binder, described in the Tech-
nologiste, v. 5, page 55.
" I dissolve 6 kilogrammes of alum, free from iron,
in a vessel of lead or earthenware, and filter the boil-
ing solution into a wooden tub, 1.7 metre high and 1
metre in diameter, one-third filled with pure water.
I then precipitate the alumina with a solution of
potassa ; the tub is filled with water, and, after set-
tling and decantation of the clear liquor, I add a new
quantity of water, and so on, until the washings no
longer precipitate by the chloride of barium.
260 MANUFACTURE OF COLORS.
"I dissolve 500 grammes of sesqui oxide of cobalt
in 1500 grammes of hydrochloric acid at 22° Be., and
evaporate the solution to dryness. The residue is
again* dissolved in 3 kilogrammes of hydrochloric
acid, and a stream of sulphuretted hydrogen is passed
through it, in order to separate the foreign metals
which may be present. I filter, evaporate again to
dryness, and dissolve the residue in enough water to
obtain from 4.5 to 5 kilogrammes of solution.
"When these two preliminary operations are com-
pleted, I precipitate 3, 4, 5, or 6 kilogrammes of the
cobalt solution (according to the intensity of colora-
tion desired) with ammonia. A too great excess of
this reagent is to be avoided, because it may redis-
solve the cobalt. After the precipitate has been
thoroughly washed, I pour it into the water which
holds the divided alumina in suspension. The mix-
ture should be constantly stirred for at least half an
hour, in order to have a perfect mixture of the two
precipitates.
"If the supernatant liquid be of a reddish hue, it
is a proof that a small proportion of cobalt has been
dissolved. A little ammonia is then added, and the
precipitate is allowed to settle. After decantation,
a new quantity of water is added, and so on, several
times. The precipitate is collected in a fine cloth
bag, drained, pressed, and dried in a stove-room.
Lastly, it is calcined at a red heat for two or two and
one-half hours, in clay crucibles.
"After cooling, the color is finely ground in a mill,
dried, ground again upon a slab, and sifted. 6 kilo-
grammes of the cobalt solution give the finest color,
and 3 kilogrammes the clearest."
It has also been proposed to replace alumina by
BLUE COLOKS. 261
lime, in the manufacture of cobalt blue. Mr. Boullai-
Marillac, the inventor of the process by which the
color obtained is a phosphate of lime and of oxide of
cobalt, claims that the product is richer and more
velvety in appearance than the Thenard blue.
§ 7. Blue Jiydrated oxide of copper. Peligot Hue.
The hydrated oxide of copper, precipitated from
the solution of a copper salt, by an excess of potassa
or soda, becomes black rapidly, even if the washing
be effected with cold water. Mr. Peligot, in 1858,
succeeded in obtaining a blue hydrated oxide of
copper, which resists boiling water, and may be
heated at 100° C., without being altered. It is true
that it retains traces of ammonia, but the proportion
is no greater than that of the foreign matters always
found in precipitated oxides.
Mr. P61igot prepares his blue with all the soluble
salts of copper, the sulphate being preferred. A very
dilute solution of the copper salt is treated with an
excess of ammonia, and then precipitated by potassa
or soda. Instead of aqua ammonia, an ammoniacal
salt may be employed. The same color is also pro-
duced by adding a large quantity of water to a
slightly ammoniacal solution of nitrate of copper.
The color is not so deep as that of English blue
ashes, but it is purer.
Concentrated aqua ammonia dissolves from seven
to eight per cent, of this hydrate, and this liquor is
the best dissolvent for cellulose and other substances
more or less soluble in the reagent of Mr. Schweitzer,
that is, an ammoniacal solution of oxide of copper.
262 MANUFACTURE OF COLORS.
§ 8. Blue of manganate of lime.
Mr. Kuhlmann made, in 1841, a series of experi-
ments for extracting potassa from feldspar in an
economical way. The best results were obtained by
melting powdered feldspar with chloride of calcium.
It was possible to extract, by this method, twenty
parts of chloride of potassium from certain kinds of
feldspar.
While trying economical processes for the prepara-
tion of the chloride of calcium, Mr. Kuhlmann calcined
in large furnaces a mixture of chalk and of the resi-
dues of the manufacture of chlorine, which are com-
posed of chloride of manganese and of a certain pro-
portion of chloride of iron. The result of this calci-
nation is a mass of chloride of calcium, colored green
by a protoxide of manganese.
During the repairs made on a furnace, employed
for six months in effecting these calcinations, Mr.
Kuhlmann remarked that in the mass of chloride of
calcium nearest the fireplace, and where the heat was
the greatest and oxidizing, there were cavities filled
with magnificent black crystals, whereas the super-
ficial portions of the mass were of the brightest blue.
The black crystals are formed of a certain oxide of
manganese, with 3.5 per cent, of oxide of iron, and
their composition corresponds to the natural ore,
called pseudo-morphic Hausmannite or acerdese.
Mr. Kuhlmann ascertained that the blue substance
was a manganate of lime, which, on account of its
magnificent coloration, should attract the attention
of chemists. All the attempts made up to the present
, by Messrs. Chevillot, Edwards, Forchhammer,
BLUE COLORS. 263
and Fromherz, in order to prepare it, have been
unsuccessful.
In the opinion of Mr. Kuhlmann, the formation of
this manganate is probably due to the decomposition
of the chloride of calcium by steam, and to a certain
solution of the lime in the undecomposed chloride of
calcium. Baron Liebig attributes the alkalinity of a
solution of chloride of calcium, to the partial decom-
position of the chloride in water. Mr. E. Krauss has
stated that the decomposition is the greater, as the
chloride has been oftener moistened with water and
then calcined. Lastly, Mr. Pelouze has recently
pointed out the rapid decomposition of chloride of
calcium, under the influence of steam at a high tem-
perature.
If the attempts for obtaining the manganate of lime
have been unsuccessful, it is due, according to Mr.
Kuhlmann, to the lime not being under so favorable
conditions for acting upon the manganese oxide, as
when it is in solution in the chloride of calcium.
A great solubility is not necessary to explain the
reaction, because we may admit that once a portion
of lime becomes transformed into manganate, another
equal portion will dissolve in the chloride.
Such as it is accidentally produced in reverberatory
furnaces, the manganate of lime is of an ultramarine
blue and appears crystalline. It is insoluble in water,
although not durable when in contact with it. Like
all manganates, it is easily transformed into a per-
manganate under the influence of weak acids, and
even of carbonic acid.
When the arts, Mr. Kuhlmann concludes, by ap-
propriate proportions and apparatus, shall have suc-
ceeded in manufacturing a cheap manganate of lime,
264 MANUFACTURE OF COLORS.
they will have become enriched with a most precious
agent for discoloration and disinfection.
§ 9. Indigo.
It was only about the middle of the sixteenth cen-
tury, that indigo was brought from India to Europe.
This coloring substance is furnished by the leaves of
several plants, called Indigotifera, on account of this
property. The plants most generally employed for
its preparation are —
1. Indigotifera argentea, or wild indigo. Its yield
in indigo is less than that of the other plants, but in
quality it is the best.
2. Indigotifera tinctoria, or French indigo. It pro-
duces the greatest proportion of color, but in regard
to quality it comes the last.
3. Indigotifera disperma or guatemala. This plant
grows higher and is more ligneous. The quality of
its indigo is better than that of the preceding.
4. Indigotifera anil or anil. Its indigo is the least
oxidized.
5. Lastly, the polygonum tinctorium, the cultivation
of which is recommended in France, the nerium tine-
torium, and many other plants.
The greater part of these plants are indigenous to
India and Mexico, and have been introduced into the
two continents of America, into China, Japan, Mada-
gascar, Egypt, etc. They belong to the Diadelphia
decandria of Linnaeus, of the family of Leguminous
plants. The indigo is extracted from these plants in
the following manner : when the leaves have attained
their maturity, they are collected, washed, cut, and
placed in tanks with a certain proportion of water.
They are kept down by means of boards loaded with
BLUE COLORS. 265
stones. The fermentation soon begins, the liquor be-
comes green and acid, and a great number of bubbles
and rainbow colored particles rise to the surface.
The liquor is then run into a lower tank, where it is
stirred, and the indigo is separated by the addition of
a sufficient quantity of lime-water. The deposit is
washed several times with water, and dried in the
shade.
Pure indigo is firm, odorless, and tasteless, of a
violet-blue color, unaltered in the air, insoluble in
water and ether, and but slightly soluble in boiling
alcohol, from which it separates by cooling. It is
easily decolorized by chlorine, and according to cer-
tain experiments, by essence of turpentine. If it be
heated in a retort, a portion is volatilized and con-
denses in the shape of copper-colored needles, while
the remainder is decomposed. Weak acids do not
dissolve it, but nitric acid transforms it into a yellow
and bitter principle. It is easily dissolved by con-
centrated sulphuric acid. Cold hydrochloric acid
does not react upon indigo, but, with the aid of heat,
it acquires a yellow color, due to the decomposition
of a small quantity of indigo.
Indigo loses its blue color by a protracted contact
with deoxidizing substances. Deoxidized indigo is
soluble in water, especially with the aid of alkalies.
When kept in suspension in water, it is deoxidized
by sulphuretted hydrogen, hydrosulphate of ammonia
(sulphide of ammonium), protosulphate of iron (green
copperas), potassa, and the protoxide of tin. In
dyeing operations it is generally deoxidized with the
following substances : —
266 MANUFACTURE OF COLORS.
Protosulphate of iron ... 2 parts.
Slaked lime 3 "
Finely powdered indigo . . . 1 "
Water 150 "
All of these substances are put into a glass matrass,
and are kept there for several hours at a temperature
of 40° to 50° C. The lime forms with the sulphuric
acid an insoluble sulphate of lime, and the protoxide
of iron is precipitated as peroxide after having taken
the oxygen from the indigo. The blue color is
restored by an oxidation resulting from exposure to
the air. The solution of indigo in sulphuric acid is
deoxidized by iron filings or zinc.
Commercial indigo is never pure, and the pure
article is obtained by sublimation in closed vessels,
the sublimate being in needle-like crystals. The
fracture of good indigo is smooth, and the portion
rubbed with a finger-nail acquires a coppery lustre.
The qualities generally preferred are light, and with
a deep and bright- violet blue color.
There are in the trade at least sixty varieties of
indigo, the better known of which are denominated
by the names of the countries they come from,
thus : —
1. Indian indigo is called Bengal, Madras, Con
mandel, etc.
2. Guatemala indigo, indigo jlore ; this is the moj
esteemed of all.
According to Mr. Chevreul, commercial indigo i*
composed of — an immediate principle (indigotin
a red resin soluble in water, a greenish-red substam
soluble in water, carbonate of lime, alumina, silicj
and oxide of iron.
BLUE COLORS. 267
Berzelius has found in it — gluten, brown, red, and
blue coloring principles, fecula, silica, alumina, oxide
of iron, and lime.
According to Messrs. Dumas and le Royer, pure
indigo is composed of —
Carbon 73.26
Nitrogen 13.75
Hydrogen .... 2.83
Oxygen . . . . 10.16
100.00
Indigo is generally applied with size, because oil
renders it black or green. It possesses less bright-
ness than Prussian blue. Mixed with a white, the
resulting blue is grayish, and the exterior becomes
decolorized.
Indigo is sometimes adulterated with various sub-
stances. Prussian blue is detected with a caustic
lye of potassa, the color of the sample losing part of
its intensity. Pure indigo is not acted upon by this
solution. Fuming sulphuric acid decolorizes Prus-
sian blue, and dissolves the indigo without changing
its color. Chlorine decolorizes indigo, and has no
immediate action upon Prussian blue. Lastly, if the
suspected sample be burned, and the ashes be treated
with hydrochloric acid, the solution will give with
ammonia and the ferrocyanide of potassium, charac-
teristic tests of the presence of iron, should Prussian
blue be present. The proportion and the appearance
of the ashes give also good indications ae to the
quality of the indigo.
Indigo, on account of its high price, and of the
indefinite color of its mixtures, is not employed by
painters. It is used by manufacturers of paper
hangings.
268 MANUFACTURE OF COLORS.
§ 10. Blue carmine, indigo carmine, Hue of England
or Holland.
Nordhausen sulphuric acid dissolves indigo almost
entirely. In accordance with the proportions of acid
held in it, this solution bears different names. Thus,
indigo purple is formed of equal equivalents of acid
and indigo ; eight to ten parts of indigo, and sixteen
to twenty of sulphuric acid, constitute indigo carmine
or sulplioindigotic acid. Generally, painters mingle
these two solutions under the names of Saxony blue,
Hue in liquor, and composition blue.
A blue carmine is sometimes employed in painting,
which is obtained by precipitating Saxony blue or
the blue in liquor by potassa. The operation is as
follows : —
A frigorific mixture is made with common salt and
broken ice, in which there is placed a vessel holding 4
kilogrammes of fuming sulphuric acid. 1 kilogramme
of finely powdered indigo is then added to the acid,
by small portions at a time, and stirred all the while.
"When the solution is complete, the clear liquor is
decanted, and a solution of tartrate of potassa is
added to it until precipitation no longer takes place.
After settling and decanting, the precipitate is col-
lected and washed with cold water until the wash-
ings cease to be acid. The color is then drained
upon a filter, and dried in the dark. Blue carmine
has a very bright bluish hue, which does not stand
the action of light. It is employed, with size, in the
manufacture of artificial flowers.
There is also a color, called blue of JUngland, blue
of Holland, and plait of indigo, which is fine enough,
but wanting in durability. It is a mixture, in unde-
BLUE COLORS. 269
termined proportions, of Prussian blue, indigo, smalt,
chalk, and starch, which is thickened and rendered
homogeneous with a mucilage of rice flour, and dried
in the shape of lumps or troches.
One of the reasons why indigo carmine is often sold
in the pasty shape, is that it becomes covered with a
white efflorescence, when it has been dried and kept
for some time. This efflorescence is due to salts in
the waters employed for washing, which salts are left
purposely, in order to prevent a loss of carmine, which
is soluble in pure water. However, the pasty state
is objectionable on account of the greater difficulty
and cost in transportation, and of the opportunity
of adding an excess of water. By the experiments of
Mr. J. J. Pohl, it is demonstrated that a small quan-
tity of glycerin will prevent the efflorescence of
indigo carmine, and will permit it to be kept for
years without any deleterious effect upon the beauty
of the product, or upon the colors it produces on
tissues. An addition of 3 to 4 per cent of glycerin,
calculated from the weight of dry carmine, is sufficient
to arrive at that result, and the present low price of
glycerin cannot be a bar to this mode of preservation.
§ 11. Ultramarine Hues.
The coloring substance known under the name of
ultramarine blue, has been the subject of a great num-
ber of chemical researches. The operations of the
chemists have been of two kinds : first, analysis has
been resorted to, in order to arrive at the composition
of the native ultramarine ; second, from the synthesis
of the results obtained, there has resulted an artificial
preparation of a similar compound.
270 MANUFACTURE OF COLORS.
1st. Real or Native Ultramarine Blue.
Ultramarine is extracted from lazulite, lapis lazuli,
or azure Hue lazulite, a mineral which belongs to the
granitic rocks. This substance, which is remarkable
for its fine azure-blue color, is not altered even by a
violent fire.
Ultramarine-lazulite is generally found in rolled
and scattered lumps ; the finest comes from Prussia,
China, and the Great Bucharia. It is a dense and
opaque stone, of a pure or dirty blue color, and gold
spangles are scattered in the gangue. The ultrama-
rine blue is separated from this stone by the follow-
ing process, indicated by Thenard : The stone is
disintegrated by being brought to a red heat, and
then thrown into cold water ; it is afterwards pow-
dered and intimately mixed with twice its weight of
a mastic, composed of resin, wax, and boiled linseed
oil. The resulting paste is wrapped in a cloth,
and kneaded in hot water several times, in order to
express the color. The first water is generally dirty
and thrown away ; the second gives a blue of the first
quality; the third a blue inferior to the former; the
fourth water a still inferior product, and so on, until
the product is so pale, that it is called ultramarine
ash. These liquors are allowed to settle, and the
different blues require but another finer grinding,
effected with the greatest cleanliness, before they are
dried. This operation is based upon the property of
ultramarine blue, of being less adhering to the mastic
than the foreign matters with which it is associated.
Thenard observes, that if, as is customary with
certain color manufacturers, the hot red stone be
thrown into vinegar, instead of water, the yield will be
BLUE COLORS. 271
diminished, because the acid, although weak, attacks
the color at a high temperature.
As ultramarine blue, on account of its variety,
beauty, and durability, is exceedingly costly, and,
according to Thenard, is sold at prices ranging from
80 to 200 francs per 30 grammes, it is not employed
for ordinary painting.
It will be easy to ascertain whether ultramarine is
mixed with cobalt blue, by digesting a pinch of the
sample in nitric acid. After a little while, the ultra-
marine is entirely decolorized, while the cobalt retains
its blue color.
It may also happen that ultramarine is adulterated
by Prussian blue and indigo. The latter substance
will be detected by placing a small quantity of the
sample upon incandescent charcoal, and there is
produced a bluish vapor, accompanied by the cha-
racteristic smell of burning indigo. If the sample be
treated at a moderate temperature with ammonia, the
Prussian blue is decomposed, but its color will reap-
pear by pouring into the liquor a few drops of acid
nitrate, persulphate, or perchloride of iron.
" The preparation of native ultramarine," says Mr.
Brunner, " is effected mostly by mechanical processes,
tending to separate it from the foreign matters.
Although the methods may differ in certain particu-
lars, they are all based upon a levigation (floating) of
the powdered substance.
" When lazulite, after several calcinations, followed
by immersions in cold water, has become sufficiently
brittle, it is finely ground. This powder is combined
with a fused mixture of wax, resin, pitch, and oil,
and then worked with hot water in a stone mortar.
The mineral gangue settles, while the ultramarine
272 MANUFACTURE OF COLORS.
remains suspended in the liquid. By repeating this
operation several times with the proper care, the blue
colored substance is separated as completely as prac-
ticable, and it is sorted into different qualities, which
are sold at different prices. The inferior quality, con-
taining a certain proportion of gangue, is called ultra-
marine ash. The high price of the first quality, be-
sides the cost of a long and tedious labor, is due
especially to the small amount collected, that is,
according to Clement and Desormes, from two to
three per cent, of the best lazulite.
" We owe the first analysis of this substance to the
two afore-named chemists, who have found in it —
Silica 35.8
Alumina 34.8
Soda ... . 23.2
Sulphur 3.1
Carbonate of lime 3.1
100.0
"Many years after, C. Gr. Gmelin made a new
analysis of a sample of average quality, obtained
from Paris. The composition was —
Silica 47.306
Alumina . 22.000
Soda (with potassa) 12.063
Lime ........ 1.546
Sulphuric acid .... . 4.679
Sulphur . . . 0.188
Water, resinous matter, and loss . . . . 12.218
100.000
" I am not acquainted with other analyses of ultra-
marine, except those just indicated. On the other
hand, several analytical researches have been made
upon the lazulite itself, the mineral which furnishes
BLUE COLORS.
273
this expensive color. Although it is impossible to
draw rational conclusions from analyses made with
different samples of such a complicated mineral,
nevertheless the effort has been made to arrive by
this process at some indications upon the nature of
the coloring substance. Here are the results of these
analyses : —
Klaproth. L. Gmelin. Varrentrapp.
Silica
Alumina .
Soda
Liine
Sulphur .
Sulphuric acid .
Oxide of iron .
Chlorine .
Water
Carbonic acid .
Magnesia .
46.0
49
45.50
14.5
11
31.76
8
9.09
H.5
16
3.52
0.95
4.0
2
5.89
3.0
4
0.86 (metal)
0.42
2.0
0.12
10.0
"The most important technical question was, to
ascertain which were the elements composing the blue
color. On this subject opinions differed.
"Margraff, who, as early as 1758, had published a
few researches upon lazulite, combated the opinion,
then general, that this mineral contained copper; but
at the same time he thought that the color was due
to iron.
" Guyton-Morveau believed that the coloring prin-
ciple was a sulphide of iron, and many chemists were
of the same opinion. Even more recently, Mr. Var-
rentrapp was of the same belief, although Clement &
Desormes certified that not a trace of iron was found
in a fine sample of ultramarine. But the latter
chemists say nothing about the nature of the color-
ing material."
18
274 MANUFACTURE OF COLORS.
2d. Artificial Ultramarine.
A few accidental observations gave the idea of
undertaking researches upon the artificial preparation
of a substance similar to the coloring material of
lazulite.
Thus Goethe, in his travels in Italy (Palermo,
April 13th, 1787), mentions that in Sicily they use a
certain vitreous substance formed in lime-kilns. It
is sawed into slabs, which are used, instead of lapis
lazuli, for the decoration of altars, mausolea, and
other ornaments of religious temples.
Another observation, made by Tessart, in a French
soda-works, gave more precise data upon the possi-
bility of forming a blue combination, similar to ultra-
marine. This manufacturer had noticed that a sub-
stance of a fine blue color was formed in the soda
furnace, when a certain kind of sandstone had been
employed for its construction ; but that the color dis-
appeared when bricks were the building material.
Vauquelin found in this blue compound, separated
from about 44 per cent, of sand mechanically mixed,
sulphate of lime, sulphate of soda, chloride of sodium,
silica, alumina, and a small proportion of sulphur and
iron; and, from this analysis, he demonstrated the
analogy existing between this compound and the
native ultramarine.
Therefore, there remained but to discover, by syn-
thetical researches, a method by which such a com-
pound could be reproduced, and the problem was
resolved in France. Mr. Guimet was the first to put
into the market a product nearly as fine as real ultra-
marine, and, at the present time, he still manufactures
one of the finest known.
BLUE COLORS. 275
Savans and manufacturers worked the subject with
great energy, and the latter, possibly in an empirical
manner, but certainly after analytical researches,
discovered several processes for preparing products
which are now abundant in the trade. It is but
natural that few precise data have been made known,
because it is not customary for manufacturers to
publish their processes. But it is certain that these
processes are sure, and improved, if we judge from
the fine qualities of ultramarine which are now in the
market, and at very moderate prices.
Without any doubt, this manufacture has been
greatly aided by the publication, in 1828, of a memoir
of C. Gr. Gmelin, in which this chemist gives a precise
formula for the preparation of artificial ultramarine.
But, although it may be true that this formula is not
to be trusted in every particular, or that it does not
always furnish an identical product, or that it does
not admit of its manufacture at the present low prices,
it is but justice to assert that this memoir must have
been the point of departure for all the researches
made up to the present time.
More recently, Messrs. Eisner and Yarrentrapp
have published the analysis of two kinds of artificial
ultramarine. Here are the results of their re-
searches : —
Varrentrapp. Eisner.
Soda .... 21.416 33.00
Potassa . . . . 1.752
Lime .... 0.021
Alumina .... 23.304 20.50
Silica . . . . 45.604 40.00
Sulphuric acid . . . 3.830 3.40
Sulphur .... 1.6.85 4.00
Iron 1.063 1.00 oxide.
Chlorine Traces. —
276 MANUFACTURE OF COLORS.
The formula given by Gmelin for the chemical
preparation of ultramarine, may be condensed as
follows : —
Gelatinous silica (prepared in the ordinary manner
from a natural silicate) is dissolved in a solution of
caustic soda, and pure hydrated alumina is added,
until the proportions amount to thirty -five parts of
anhydrous silica, and thirty of anhydrous alumina.
The mixture is evaporated and brought, by stirring
carefully, to the state of a dry powder, which is ground
and thoroughly mixed with an equal weight of
sublimed sulphur. There is added to this mixture
another compound of equal parts of carbonate of soda
and sublimed sulphur, equal in weight to that of the
dry silico-aluminous powder. The whole is then in-
troduced into a closed crucible, and kept for two
hours at a strong red heat. The greenish mass thus
obtained is again heated either in crucibles or in clay
tubes, but without the access of the air, until it has
acquired the desired blue color. Gmelin thinks that
this last operation is the most difficult, and he
describes several modes of operation for arriving at a
satisfactory result.
Lastly, Gmelin suggests, that in manufacturing
operations, it may be possible to replace the hydrate
of alumina by clay, deprived of its iron by a treal
ment with hydrochloric acid, and afterwards washed.
Independently of this formula, two more have bee]
made known : —
According to Robiquet, a mixture of 2 parts
kaolin, 3 of sulphur, and 3 of dry carbonate of sod.
are heated in a clay retort until vapors cease to
disengaged. After cooling, the retort is broken, th<
powdered mass is washed with water, and the remain-
BLUE COLORS. 277
ing powder is heated again until the sulphur is
expelled.
Tiremon melted 1075 parts of crystallized carbonate
of soda in its water of crystallization, and added 5
parts of red sulphide of arsenic, a quantity of gelati-
nous alumina equal to 7 parts of calcined alumina,
100 parts of sifted clay, and 221 parts of sublimed
sulphur. The mass was carefully evaporated to dry-
ness in a crucible, and then calcined at a red heat.
Lastly, the product was kept again at a dull red heat
in a covered dish, and stirred constantly for two
hours.
We shall now add further particulars on each of
the modes of preparation, with the exception of the
Guimet process, which is still kept secret.
A. Guimet Process.
The Societe d? Encouragement proposed, in 1824, a
premium for the manufacture of an ultramarine pos-
sessing all the qualities of that extracted from lapis
lazuli. This premium was awarded to Mr. Guimet,
on December 3d, 1828.
We here reproduce an extract from the report made
by Mr. Merimee, in the name of the committee on
chemical arts.
"In 1824, you proposed a premium of 6000 francs
for the manufacture of an ultramarine blue possessing
all the qualities of that extracted from lapis lazuli ;
this problem, to which you attached great importance,
is completely resolved.
" Mr. Guimet, a graduate of the polytechnic school,
obtained, one year ago, results which you would
have applauded, but he thought that his work was
278
MANUFACTURE OF COLORS.
not complete as long as he could see new improve-
ments.
"At that time several artists made the trial of his
ultramarine, and certified that they found it equal to
that imported from Italy. The experiment may be
seen in the Apotheosis of Homer, painted by Mr.
Ingres on the ceiling of the gallery of the museum.
The drapery of one of the principal figures is painted
with Mr. Guimet's ultramarine, and no other painting
presents such a bright blue.
"Neither has your committee on chemical arts
neglected the experiments by which the indentity of
quality of the new color with that extracted from
lazulite, may be ascertained. It has verified in it all
the characteristics of a pure ultramarine.
" This discovery will mark an epoch in the history
of painting ; it is one of which the chemical arts may
be proud, etc."
Chaptal, the President of the Society, while pre-
senting the premium to Mr. Guimet, remarked that
Mr. Horace Yernet, in a very large picture, the Battle
of Fontenoy, had employed Guimet' s ultramarine ex-
clusively, which he considers as superior to that pre-
pared from lazulite.
So much for the Guimet process.
B. Gmelin Process*
The process of Mr. Guimet being still kept a secret,
Gmelin, professor of chemistry at Tubingen, has pub-
lished the following process for the manufacture of
ultramarine. Although it may be advantageously
modified in several ways, we present it as given by
the inventor.
" Silica and alumina, in the hydrate state, are pre-
BLUE COLOKS. . 279
pared — the first, by smelting finely powdered quartz
with four times its weight of carbonate of potassa,
dissolving the fluid mass in water, and precipitating
by hydrochloric acid ; the second, by precipitating a
solution of alum with ammonia. These two precipi-
tates should be carefully washed with boiling water.
Then the proportion of the dry substance is deter-
mined by calcining a small quantity of the wet article.
A certain quantity of hydrated silica, the weight of
which is noted down, is dissolved in a solution of caus-
tic soda, which should be as saturated as practicable.
For every twenty-two parts of silica (calculated as
anhydrous), there are added seventy parts of alumina
(also calculated as anhydrous), and the whole is evapo-
rated down to the state of a wet powder, taking care
to stir the mixture during the whole operation.
" Two parts of sulphur and one of dry carbonate of
soda are gradually brought to a middling red heat in
a Hessian crucible, with a well fitting cover. When
the mass is fused, the above mixture is projected into
it by very small quantities at a time, and before new
additions are made, the effervescence due to the
escape of steam must have ceased. The crucible is
left one hour longer at a moderate red heat, and then
allowed to cool off. It contains ultramarine, mixed
with an excess of sulphide of sodium, which is
separated by washings. If the color contains an
excess of sulphur, the latter is expelled by a calcina-
tion at a moderate heat. If all the portions of the
ultramarine are not thoroughly calcined, the finest
parts are separated by levigating the finely powdered
substance in water.
" Ultramarine resists fire and alkalies, but not the
action of certain acids."
280
MANUFACTURE OP COLORS.
C. Tiremon Process.
Take-
Sifted powder of the crude clay of Dreux . . 100 parts.
Gelatinous alumina, corresponding to an anhydrous
proportion of . . . . . . . . 7 "
Dry carbonate of soda (400 parts), or crystallized . 1075 "
Sublimed sulphur 221 "
Sulphide of arsenic ....... 5 "
Mix with the carbonate of soda, melted in its water
of crystallization, the powdered sulphide of arsenic,
and when the latter has become partly decomposed,
add the washed gelatinous alumina, which is obtained
by the precipitation of alum with carbonate of soda.
Lastly, add the clay and the sublimed sulphur, which
have been mixed beforehand. When the mass has
become compact by evaporation, it is introduced into
a covered crucible, which is heated slowly at the
beginning in order to expel all remaining dampness,
and then brought to a red heat. The fire should be
conducted in such a manner that the product is agglu-
tinated (sintered), but not fused.
After cooling, the product is heated again to expel
the excess of sulphur, and then ground and washed in
pure water. The powder which remains in suspen-
sion in the liquid, is collected upon a filter. When
the mixture has been well made the whole may be
employed, otherwise many portions remain colorless.
There are brown fragments, resulting from the corro-
sion of the crucible, when the mixture has been com-
pletely fused. These defects do not appear if the
operation has been conducted with the proper care.
The blue is drained upon the filter without further
washings, and dried. The product is of a fine bluish-
green; and, if it be heated for some time, with occa-
BLUE COLORS. 281
sional stirrings, it acquires a very handsome blue
color.
D. Weger Process.
Preparation. — Grind together 8 parts of pure fer-
ruginous clay (bole), J part of hydrated alumina, 9
parts sublimed sulphuiy and 8 parts of fused caustic
soda, dissolved in 20 parts of water. When a homo-
geneous paste has been obtained, it is heated for one
or two hours in a glass or porcelain retort, until there
are no longer steam or sulphur fumes distilled over.
The porous and greenish residue is then calcined in
a Hessian crucible, in order to remove the excess of
sulphur, and then (when cold) washed with pure
water. The bluish-green powder is again calcined in
a flat dish, which is covered and brought to an
incipient red heat. During this operation, which
lasts about one and a half hours, the powder is con-
stantly stirred. Lastly, the color is washed and levi-
gated (floated).
When the porous green mass, called ultramarine
green, and obtained from 'the first calcination, is
broken into pieces of the size of a pea, and exposed
to the air for some time, it becomes transformed into
a magnificent ultramarine lazulite blue, under the
influence of the dampness in the air.
When dry caustic soda is thoroughly mixed with
the indicated proportions of clay, alumina, and sul-
phur, and the mixture packed tightly in a Hessian
crucible, there is obtained, after one to two hours of
calcination at a clear red heat, a product which, when
cold, possesses a pink-red hue, very handsome and
uniform.
Green ultramarine, in the opinion of Mr. Weger, is
282 MANUFACTURE OF COLORS.
a combination of blue ultramarine with a double
proportion of sulphur. Therefore, by expelling the
excess of sulphur by calcination, the second color is
obtained from the first.
Ultramarine for printing. — The preparation of a
printing color with ultramarine is very simple. A
good quality of ultramarine is very finely ground, and
mixed with linseed, or nut, or purified poppy oil. If
the latter cannot be had, some old and perfectly clear
oil may be used. One-twentieth of hydrated alumina,
like that employed in the preparation of the ultrama-
rine, is also added. Then a small quantity of good
white Venice soap is finely ground upon the slab.
In order to ascertain whether a sufficiency of soap
has been added, a brush charged with the color is
dipped into pure water, and we observe whether the
color and the water mix well together or not. If the
mixing be satisfactory, the proportion of soap is suffi-
cient, because an excess wrill change the hue of the
color. However, in case the printing mixture should
be too compact, a little soap water, of which a supply
should be kept at hand, may be added.
It is possible to print with this mixture upon tissues
of cotton and wool, and even upon silk and paper.
The color does not become hard, as is the case when
the thickening is gum.
Miniature painting itself will find in this color
vigorous and pure tones, and every intelligent artist
sees the advantages it presents.
For theatrical decorations and paper hangings,
where glue size is employed, the above mixture can
be applied with the greatest success. It will impart
an unequalled brightness and purity of color to
flowers, fruits, shadows, etc., without any danger of
the paint scaling off.
BLUE COLORS. 283
E. Pruckner Process.
Mr. C. P. Pruckner, manufacturer at Hof, in
Bavaria, has published a memoir on the manufacture
of ultramarine blue, which has been translated and
printed in the Technologiste, v. 6, pages 299-345. We
borrow from it the following description, and we note
that the raw materials are clay, sulphate of soda, char-
coal, and an iron salt, which is generally green vitriol.
" The clay employed in the manufacture of artificial
ultramarine has the greatest influence upon the color
produced; and it is likely that the failure of many
experiments is due to the use of a clay holding too
much iron. I use a white clay, remaining white after
calcination, and which, therefore, contains very little
iron. It is a kind of kaolin, of a dull color, which
sticks to the tongue, forms with water a paste pos-
sessing little plasticity, and which is found in the
principality of Eeuss, near Roschitz. It is employed
in the manufacture of porcelain, and contains from
forty-two to forty-three per cent, of alumina. It is
evident that, the other conditions being the same, the
more aluminous clay is to be preferred.
" In the manufactory of Nuremberg, the clay most
generally employed is a white sigillaria earth (bolus
alba), which comes from Teschenrenth, in the High
Palatinate.
"At Nuremberg, the sulphate of soda resulting
from the preparation of hydrochloric acid is bought,
either already refined, or in the crude state. In the
latter case, it is refined in the color works, and this
operation, which we shall examine further on, is in-
tended to remove the free hydrochloric acid and the
iron salts, which impair, and even destroy, the blue
color of the ultramarine.
284 MANUFACTURE OF COLORS.
" Roll sulphur is too well known to need explana-
tion.
" The charcoal from dry wood answers all that is
required of it. Mineral coal is sometimes employed,
and it should give the least amount of ferruginous
ashes.
"The calcination of the mixtures is effected in
muffles, heated in a reverberatory furnace, since it is
much more easy to regulate the temperature and to
watch the operation, than when crucibles are em-
ployed. These muffle furnaces, in the clear, are from
0.9 to 1 metre in width and length. The muffles
themselves are from 0.55 to 0.60 metre wide, and from
0.30 to 0.37 metre high. In order to save fuel, 2 or
3 may be placed in the same furnace. The muffles
are constructed of fire clay, in the same manner as the
pots of glass works. Their front openings may be
closed by cast-iron doors sliding upon rollers. These
doors and the back parts of the muffles have each
a narrow slit, for watching the operation and giving
passage to the air. It is well understood that the
furnaces are provided with dampers for regulating
the draft and the temperature. The durability of the
muffles is increased by supporting them upon three
arches or brick walls resting upon the bed of the
furnace. The spaces between these walls form flues
from 0.20 to 0.23 metre square. When the fuel is
charcoal, it may be introduced by an opening on top,
as in assay furnaces.
" The conversion of the sulphate of soda into sul-
phide of sodium is effected in a furnace analogous to
those employed in the manufacture of soda. In our
works I have replaced the single lateral fireplace by
two smaller ones, opposite to each other, and I have
BLUE COLORS. 235
found by experience that this disposition gives a
saving of time and labor, especially when the bed of
the furnace is more than 2 metres in length.
"Let us now pass to the preparation of the raw
materials, and to the manufacture of ultramarine
blue.
" The dry clay, coarsely broken with wooden stamp-
ers, is placed in rectangular wooden vats, 2 metres
long and 1 metre wide, where it is covered with water,
and left to rest for several days. The resulting paste
is then floated, as in porcelain works, for separating
the sand and the coarse portions. The purified clay,
in the state of soft paste, is kept under a shed, and
its yield in dry clay is accurately determined each
time that it is used for the preparation of ultramarine.
"The purification of the crude sulphate of soda is
done by calcination in a reverberatory furnace, by
which the free hydrochloric acid is expelled. The
crude salt is broken into pieces of about 1 cubic
decimetre, and plunged into water for a very short
time, because experience has proven that the free acid
is much more easily removed from the wet than from
the dry salt. The furnace is filled with these lumps,
with sufficient spaces left for the free access of the
flame. The temperature is gradually raised to an
incipient red heat, and is maintained until there is no
free acid left. The calcined salt is immediately bro-
ken, under stamps or between stones, into grains of
the size of blasting powder, which are mixed with
the charcoal and slaked lime, in revolving tuns.
The proportions are : —
Sulphate of soda ...... 100 parts.
Powdered charcoal . . . . 33 "
Lime slaked in the air . . 10 u
286 MANUFACTURE OF COLORS. *
" The ground mixture is spread upon the bed of
the reverberatory furnace, and covered 3 to 4 centi-
metres deep with slaked lime, which is compressed
with a flat iron shovel. All the doors of the furnace
are then closed, and when the mass is thoroughly in
fusion, it is rapidly stirred, and a few shovelfuls of
charcoal dust are thrown in. The bath is left un-
disturbed for some time, until gas jets no longer burn
at the surface. The sulphide of sodium is then re-
moved with iron ladles, and poured into shallow cast-
iron moulds, in which it solidifies.
" The sulphide of sodium and the carbonate of soda
thus obtained are dissolved in boiling water, and the
liquor is left to settle, out of contact of the air, in
tubs, in which it deposits carbonate of soda, sulphate
of soda, and charcoal in very minute particles. The
sulphate of soda is treated in the aforesaid manner
for another operation, and it is very important that
all of the charcoal should be deposited, because a
trace of it is sufficient to impair the brightness of
the ultramarine. The clear and decanted solution is
then heated, saturated with powdered sulphur, and
concentrated by ebullition until it contains 25 per
cent, of dry bisulphide of sodium, and marks about
25° Be. From 40 to 50 parts of sulphur are em-
ployed for each 100 parts of fused sulphide of
sodium.
" After the solution of sulphide of sodium has
deposited the slight excess of sulphur contained in
it, it is decanted into glass carboys, which are care-
fully closed, in order to prevent the contact of the
air.
" The raw materials being prepared, the prepara-
tion of ultramarine is as follows : 50 kilogrammes of
BLUE COLORS. 287
the above solution of sulphide of sodium are evapo-
rated in a shallow cast-iron pan to a syrupy consist-
ency; then a quantity of washed and wet clay, cor-
responding to 12.5 kilogrammes of dry clay, are
added to it, and the whole is thoroughly mixed with
an iron spatula. While the mass is still pasty enough
to be stirred, there is added to it a solution of 150
grammes of sulphate of iron, free from copper, which
is also carefully mixed. The stirring is continued
until the mixture is entirely dry, when the substances
are finely powdered.
" This powder is charged into the muffles, and spread
in layers 6 to 8 centimetres deep, which correspond
to a weight of 15 to 20 kilogrammes. The fire is
continued for about one hour after the material has be-
come red, and frequent stirrings are given, at the
same time that the air is allowed free access. The
mass becomes successively colored a liver color, then
red, green, and blue. This operation requires a great
deal of attention and practice, because too little heat
produces no ultramarine, and an excess of tempera-
ture impairs the beauty of the color.
" The substance is then removed from the muffle,
and purified by washings with water. The liquors,
which contain sulphate of soda and sulphide of so-
dium, are generally thrown away, but they might be
used for the preparation of the sulphide of sodium.
The precipitated ultramarine is collected and drained
in cloth bags, and then dried in a stove-room. Its
color is generally a dark green or a blackish-blue.
" The dry mass is finely ground, passed through a
silk sieve, and calcined again by portions of 5 to 7
kilogrammes, in muffles kept specially for this opera-
tion, and which are 45 to 50 centimetres wide, and 80
288 MANUFACTURE OF COLORS.
to 90 centimetres long. A dark red heat is sufficient
for this calcination. As soon as the blue color begins
to appear, the powder is constantly stirred with an iron
tool, until the whole is of a pure blue. The operation
lasts from one-half to three-quarters of an hour, and
there is no advantage in continuing it longer, or in
having a more intense fire. The powder is removed,
and left to cool in the air upon granite slabs. It
often happens, but not always, that the color acquires,
while cooling, greater brightness and beauty.
" The ultramarine blue is afterwards ground under
granite stones, 1.5 metres in diameter, then washed
and floated and sorted, according to its degree of
fineness, into the numbers $, 1, 2, 3, 4, etc.
" An excellent method for ascertaining the quality
of ultramarine blue consists in heating it in a glass
tube, placed upon a lighted alcohol lamp, and through
which is passed a stream of hydrogen. The pigment
will be the better and the more durable, as its blue
color is longer in disappearing. Native ultramarine
loses its color only after one or two hours, or even
longer; the best artificial ultramarine of Nuremberg
(mark 0) ceases to be blue after half an hour, and the
inferior quality (mark 5) after a few minutes only."
F. Winterfield Process.
Mr. "Winterfield has proposed a process for the
manufacture of ultramarine blue, which he claims to
give a produce as fine as Guimet's ultramarine, and
at a very low price.
"200 parts of soda ash (from the evaporation of
the mother-liquors of the crystallized carbonate of
soda) are dissolved in boiling water, and there are
added 100 parts of powdered sulphur, 4 of sulphate of
BLUE COLORS. 289
iron dissolved in water, and 100 parts of powdered
clay. The whole is thoroughly mixed and evaporated
to dryness. The dry and finely powdered mixture
is introduced into vessels of fire-clay, holding about
4 to 5 kilogrammes, and which may be closed with
a clay cover. These vessels are heated in a furnace,
and their contents are stirred now and then with an
iron rod. When the mass begins to sink down, and
acquires a blue-black coloration, passing to a green
when cold, this operation is finished. For quantities
of 5 kilogrammes, about four hours of continuous
calcination are necessary. The cooling of the mass
should take place out of contact with the air, the
cover is therefore carefully luted upon the vessel.
The cold substance is then coarsely broken, dirty-
looking fragments are removed, and the remainder is
washed with hot water. The still wet powder is
finely ground. By this treatment, and under the
action of the air, the green color passes to a fine blue.
The clay employed is not very plastic, and is quite
free from iron. Its color, before calcination, is a
grayish-white. It is strongly calcined, in order to
destroy the organic substances which may have been
present, and then finely ground before use. The soda
ash requires also to be calcined, in order to destroy
the organic substances. The best vessels for this
operation are a kind of fire-clay retorts, placed ob-
liquely in the furnace, so that their opening is not
exposed to the fire. The aperture is .closed with a
perforated cover, through which the stirring rod
passes."
G. Brunner Process.
Mr. C. Brunner has published in the Technologists,
vol. 8, pp. 110-162, a very interesting memoir on the
19
290 MANUFACTURE OP COLORS.
manufacture of artificial ultramarine, from which we
take the following extracts : —
Before explaining the process itself, says he, which
I have verified by a great many experiments, I shall
make some remarks on the choice of the raw mate-
rials, and he continues : —
1. Silica. — I have used a gravel, or coarse silicious
sand, found near Lengnau, Canton of Berne. It is
known in the country under the name of Hupererde,
and is employed as a cement in the manufacture of
fire-bricks, crucibles, and other articles, which must
stand a very high temperature.* I have always used
it perfectly ground and floated.
2. Alumina. — Instead of this substance, I have
employed the potassa alum ; and, although a small
proportion of iron does not appear disadvantageous,
I advise purifying the alum by a second crystalliza-
tion. I have heated it until it acquires the properties
and the appearance of the alumen ustum of the phar-
macopoeia. On a small scale, this operation may be
performed in a silver dish; but in manufacturing
works a special furnace will be needed. At all events,
it is tedious work. The burnt alum is then pulver-
ized, and a sample of it is calcined at a moderate red
heat in a platinum dish, in order to determine the
proportion of water it still contains. This determi-
* The analysis of this sand is as follows: —
Silica 94.25
Alumina 3.03
Lime 1.61
Oxide of iron .... 0.94
Loss O.IT
100.00
BLUE COLORS. 291
nation is not very accurate, because, according to the
degree of red heat used, there are variable proportions
of sulphuric acid disengaged with the steam, but it is
sufficiently accurate for practice.* The burnt alum
is kept in well-closed vessels.
3. Sulphur. — For the calcination of the mixtures,
ordinary sublimed sulphur may be used ; but in the
last combination with sulphur it is better to purify it
by distillation.
4. Charcoal. — The ordinary wood charcoal is finely
powdered.
5. Carbonate of soda. — The crystallized carbonate
of soda is made to effloresce in the air of a hot room,
and the resulting powder is heated in a dish until all
the water disappears.
The preparation of the ultramarine is made in the
following manner: A mixture is made of —
Silica (huper) . . . . . . 70 parts.
Burnt alum (calculated anhydrous) . . 240 "
Powdered charcoal 48 "
Sublimed sulphur . . . . . . 144 "
Anhydrous carbonate of soda . . . 240 "
In order to obtain a thorough mixture, the mate-
rials are first incorporated together in the ordinary
manner, in a mortar or dish, and then in a powdering
apparatus, made of a thick copper flask, tinned inside,
and holding about 2 litres. I put in from 15 to 30
grammes of the mixture, and from 600 to 700 grammes
of coarse granules of cast-iron. The flask is closed,
and shaken vigorously for eight or ten minutes, and
* Further experiments have demonstrated that powdered alum,
dried in the air, may be successfully employed ; the tedious opera-
tion of burning it may therefore be dispensed with.
292 MANUFACTURE OF COLORS.
the contents are sifted upon a metallic sieve, which
retains the iron granules.
The success of the operation depends especially on
a careful and thorough mixture. The powder must
be really impalpable, and an ordinary magnifying
glass should show no difference of coloration in the
particles.
A Hessian crucible is then entirely filled with this
mixture, and closed with a luted cover. The crucible
is rapidly raised to a moderate red heat, which is main-
tained for one hour and a half. The degree of tem-
perature is important, but, after a little practice, it is
easily learned; at all events, an excess of heat is to be
avoided. "When the operation is successful the cold
contents of the crucible appear as a sunken and porous
mass, partly greenish-yellow and partly reddish-yel-
low, resembling liver of sulphur, and occupying
about two-fifths of its former volume. If it be hard
and fused, brown, and of a still more reduced volume,
the heat has been too great.
The porous pieces are easily detached from the
crucible, and are thrown into water. The mass
softens, and there results a solution of sulphide of
sodium, and a greenish-blue powder which precipi-
tates. The powder is washed several times with
water, which may be hot, and until the liquor becomes
tasteless. The residue is then dried.
The washed product is in the state of a light pow-
der, of a clear ash-gray color. A small sample is
heated in a porcelain dish with a small quantity of
sulphur, in order to see whether the combustion of
the latter substance causes it to assume a bluish tinge.
This coloration will always be feeble, about like that
of blued linens.
BLUE COLORS. 293
This product is then intimately mixed with an
equal weight of sulphur, and one-and-a-half times its
weight of anhydrous carbonate of soda, in the manner
already explained. Another calcination is made at
the same temperature, and the volume of the mass
diminishes again, but less than formerly. After cool-
ing, the contents of the crucible are washed in water,
and the residue is dried.
This new product, calcined with sulphur in a por-
celain dish, should, this time, acquire a more intense
bluish hue.
The amount of washed substance is about the same
as after the first calcination. A third calcination
with sulphur and carbonate of soda, in the proportions
previously stated, is followed by a more thorough
washing. It is even useful to boil the product in
water, and to finish the washing upon a filter, until
the liquors are no longer colored black by the acetate
of lead. The future color of the product depends
partly upon the fulfilment of these precautions.
Another test with burning sulphur is made to see
whether a fine blue color will appear. If it be satis-
factory, the product passes to the finishing operation ;
in the contrary case, it is again calcined with sulphur
and carbonate of soda. Ordinarily, three calcinations
are sufficient ; but, if they have been effected at too
low a temperature, a fourth calcination is necessary.
The dry and bluish-green powder is passed through
a gauze sieve, in order to separate a few hard brown
granules, which come from the crucible or from the
compound itself fused at certain points.
The last operation, that is, a combustion with sul-
phur, is made upon a plate of cast-iron, on the surface
of which there is spread a layer, two to three milli-
294 MANUFACTURE OF COLORS.
metres thick, of pure powdered sulphur. An equal
quantity, or a little more, of the dry powdered pro-
duct is dusted over the sulphur by means of a sieve.
The cast-iron plate is heated upon a charcoal fire
until the sulphur becomes inflamed, and the tempera-
ture should be such that all the sulphur will burn
out without the product being too much calcined.
It is sometimes necessary to remove the charcoal fire.
On a large scale, this combustion should be effected
in furnaces provided with doors for regulating the
access of the air, and, therefore, the intensity of the
combustion. This operation is repeated three and
even four times with the same powder, which, after
each combustion, is removed from the plate and
ground. "When the product has attained its greatest
intensity of coloration, the whole operation is finished.
In the manufacture of large quantities, it will be well
to base the mode of working upon experiments made
on small samples, which are mixed with half of their
weight of sulphur, and spread upon a cast-iron plate.
This last operation somewhat diminishes the volume
of the product, and imparts to it a porous and flaky
appearance. I have been unable, with a magnifier,
to discover any sign of crystallization. For its em-
ployment, the product requires to be ground again
finely. The yield in finished product is about one
hundred and sixty parts of the materials previously
indicated.
Before finishing, I shall point out several experi-
ments, which, in my opinion, throw some light upon
the origin, the formation, and the chemical composi-
tion of artificial ultramarine.
During the first calcination of the mixture, there if
already formed a chemical compound of sulphur,
BLUE COLORS. 295
sodium, silica, and alumina. This compound is now
but slightly colored, and sometimes not at all. That
there is a combination is proven by the fact that the
well-washed powder is decomposed by acids ; sulphu-
retted hydrogen is disengaged, and gelatinous silica
is precipitated. The addition of powdered charcoal
to the mass, during this first calcination, is not abso-
lutely necessary, but it prevents the fusion of the
mass. Such addition is useless for the other calcina-
tions.
During the second calcination with sulphur and
carbonate of soda, the proportion of sulphur, and
possibly of sodium, increases, although the weight of
the product is not much greater. The increase in the
proportion is certainly not considerable, and is coun-
terbalanced in part by the losses of manipulation.
In this state, the washed and dried product, although
but slightly colored, possesses a real bluish-green hue,
which, after combustion with sulphur in the open air,
passes to a pure but pale blue.
In the next operation, that is, a third calcination
with sulphur and carbonate of soda, the proportion of
sulphur still increases. The washed and dried pro-
duct is of an intense blue color with a green reflex,
and is finished, although it is yet wanting in the
remarkable brilliancy possessed by ultramarine.
Some persons may think* that these three operations
may be united in one, whether by calcining longer, or
by increasing the proportion of the materials ; but
direct experiments made in that direction have not
furnished satisfactory results.
The subsequent combustion with sulphur is, theo-
retically speaking, the most remarkable part of the
whole operation. The product acquires by this treat-
296 MANUFACTURE OF COLORS.
ment its real coloration, and it increases in weight from
10 to 20 per cent. This increase is variable, and
depends partly on the quality of the product before
the combustion, and partly on the manner in which
this combustion is conducted.
It may seem difficult to arrive constantly, by three
calcinations, at precisely the same degree of color and
quality ; but in practice, when large amounts of mate-
rials are worked at a time, a greater regularity is ob-
tained. I insist upon the point, that a great degree
of cqmminution and a perfect mixture of the mate-
rials, produce a great yield. Indeed, if we neglect
these precautions, the product will be filled with a
quantity of whitish specks, and will never acquire a
fine color; it may even acquire a brownish hue.
During the combustion with sulphur, the powder in-
creases in weight. This increase is not always con-
stant, and may, by combustions repeated ten and even
fifteen times, amount to 20 per cent. After three or
four successive combustions, the color has acquired
its greatest intensity, and the increase of weight may
be 5 to 10 per cent.*
In order to compare the increase of weight with
the proportion of sulphur, I have determined this in
samples of the mixture before the calcination, and
after each heat.
The following analysis gives the centesimal com-
position of the ultramarine which has not been
burned with sulphur : —
* Clement and Desormes had already published the fact, that
real ultramarine increases in weight about 1 per cent., when it is
heated in oxygen.
BLUE COLORS. 297
Silica 35.841
Alumina 27.821
Lime 2.619
Oxide of iron . . . . . 2.475
Sodium 18.629
Sulphur .5.193
Oxygen (calculated from loss) . . . 7.422
And as 100 parts, after the combustion with sul-
phur, become 110.16, holding 12.811 of sulphur, while
the other substances are not changed, it results that
ultramarine burned with sulphur should be composed
of—
Silica . . . . . . . 32.544
Alumina 25.225
Lime 2.377
Oxide of iron 2.246
Sodium 16.910
Sulphur 11.639
Oxygen (calculated from loss) . . . 9.039
If now we distribute the oxygen between the sul-
phur and the sodium, on the supposition that they
form sulphate of soda, we have, instead of the last
three elements : —
Sulphate of soda . 20.157 )
Sodium . . 10.337 C = 17.421 sulphide of sodium.
Sulphur . . 8.084 )
We see, therefore, that the sulphide of sodium is
in the monosulphide state, since theory requires
10.337 of sodium and 7.149 of sulphur.
It is evident that this mode of representation, like
those used for complicated compounds, cannot be ab-
solute, and presents only a theoretical interest. Sul-
phur may be combined with the sodium, calcium, and
iron; in which case a part of the sodium should be
298 MANUFACTURE OF COLORS.
calculated as soda. But these speculations cannot
be verified by analysis.
If, after ultramarine has reached the greatest color-
ing intensity by its combustion with sulphur, this
treatment be continued, there comes a time when the
product no longer increases in weight. If it be heated
without sulphur, its weight diminishes, and its blue
color becomes lighter, resembling that of certain kinds
of native ultramarine, and it often acquires a slightly
lilac hue. Besides these chemical changes, there is
also another mechanical transformation ; the powder
ceases to be light and flaky, and becomes dense and
granular. Mr. Brunner, however, has not always
succeeded in producing this change. In many sam-
ples found in the market this phenomenon is easily
produced ; in others, it is less apparent, even after
heating for hours together. An ultramarine modified
in this manner and treated by hydrochloric acid, does
not disengage hydrosulphuric acid, and contains,
therefore, no unoxidized metallic sulphide. It may
be thought that there should be an increase of weight
resulting from oxidization ; but the diminution in
weight may possibly be explained by supposing that,
while part of the sulphur of the sulphide of sodium
burns, the resulting soda combines with the silica or
other elements of the compound. Since the volatil-
ized sulphur possesses a greater weight than the
oxygen which takes its place, there must result a
lesser yield.
These pale ultramarines, at all events, may be use-
fully applied in the arts, and it is likely that some
may be found among the manufactured products.
There are still three points to be decided : —
BLUE COLORS. 299
"1. How far necessary is the proportion of lime
found in nearly all commercial ultramarine blues ?
"2. Is the presence of iron useful, or unfavorable,
to the production of the color ?
U3. Is soda absolutely necessary, or is it not pos-
sible to replace it by potassa?
" The presence of lime is not absolutely necessary,
and this is proven by the small proportion of it in the
indicated mixtures. Moreover, I have checked the
exactness of this conclusion by direct experiments,
in which I have added as much as 8 per cent, of lime
in certain mixtures. There was no difference what-
ever between the products obtained and those made
without lime.
" Iron is neither important nor absolutely neces-
sary. Indeed, a mixture made according to the pre-
ceding formula, but with materials free from iron,*
and without using iron granules during the pulveri-
zation, has given a product entirely similar to that
prepared in the ordinary manner. However, the fine
artificial ultramarine of Guimet, and the native one
imported from Rome, show the presence of iron by
delicate analytical tests.
" It does not seem important to me to investigate
whether a large proportion of iron is to be avoided in
the color; but, a priori, it seems that it should be so.
"Lastly, a question which appears to me very in-
teresting is, whether the blue coloration is principally
due to a sodium compound, or if it cannot be pro-
duced with potassa.
* The silica was prepared by calcining the huper with the car-
bonates of soda and potassa, filtering, and precipitating the silica
with hydrochloric acid. The iron in the charcoal has not been
considered.
300 MANUFACTURE OF COLORS.
" I have, therefore, conducted an operation accord-
ing to the preceding formula, with the exception that
the carbonate of soda was replaced by carbonate of
potassa, prepared from the combustion of cream of
tartar. After three calcinations of the mixture there
was obtained a white mass, which, being burned with
sulphur, did not acquire any blue coloration, although
it disengaged an abundance of sulphuretted hydrogen
by a treatment with hydrochloric acid.
" It is then demonstrated, in conformity with the
assertion of Grmelin, that potassa (without soda) does
not produce a blue ultramarine, but that a similar
colorless compound is obtained. This experiment
seems to be a further proof that the blue color is not
due to the presence of iron."*
H. Dippel Process.
In a pamphlet published by Mr. J. P. Dippel, of
Cassel, on the preparation of artificial ultramarine,
this chemist recommends the following process as
having been for a long time advantageously practised
in manufactories.
The materials are clay, Glauber salt (sulphate of
soda) with an excess of sulphuric acid, bituminous
coal, and sulphur ; each of which should possess cer-
tain qualities. The first three are mixed in certain
* I had already written the above memoir when one of Mr. C.
P. Pruckner, upon the manufacture of ultramarine, fell into my
hands. Time and circumstances prevented me from experiment-
ing with his mode of preparation, which resembles that of Gmelin,
and to compare it with mine. It seems, however, possible to
arrive at the same results in different ways, although I differ from
the opinion of Mr. Pruckner, who believes that the presence of
iron is absolutely necessary.
BLUE COLORS. 301
proportions, and then brought to a red heat in a cru-
cible. After cooling, the mass is removed from the
crucible and then calcined again in a tube, with the
access of the air. The product is afterwards steeped
in water, ground wet, and lastly heated to produce
the blue color in the following manner : the powder
is mixed with sulphur, and heated in the presence of
just enough air to cause an incomplete oxidization of
the sulphur. When the fine blue color has been de-
veloped the pigment is ground again, then floated and
dried.
J. Habich Process.
Mr. Gr. C. Habich has published in the Technologists,
vol. xvii. p. 411, the following remarks on ultramarine
and its manufacture: —
"Two kinds of ultramarine blue may be distin-
guished from their behavior in presence of concen-
trated acids. When cold hydrochloric acid is poured
upon ultramarine, the color disappears, part of the
sulphur is disengaged as hydrosulphuric acid, and the
other part settles with the remainder of the powder.
It is then that there appears a characteristic difference
due to the modes of preparation. When ultramarine
has been manufactured from artificial aluminous sili-
cates, gelatinous silica is precipitated. On the con-
trary, when white clay has been used, there is no pro-
duction of gelatinous silica.
u When the manufacture of ultramarine took a
foothold in Germany, the first named process was em-
ployed ; and although it is too expensive, it never-
theless presents a real scientific interest.
" Soda, white sand, sulphur, and powdered bitu-
minous coal were melted together, and the resulting
302 MANUFACTURE OF COLORS.
mass being dissolved in water, gave a solution of
polysulphide of sodium and of silicate of soda, with
which another hot solution of alum was precipitated.
The result of the decomposition was an abundant
production of sulphuretted hydrogen, and a precipi-
tate of silicate of alumina and of sulphur. This pre-
cipitate was washed, dried, and introduced into a
boiling bath of soda and sulphur. The molten mass,
when the operation was successful, crumbled in hot
water, and deposited a very finely comminuted pow-
der of a bluish-green color, called green ultramarine,
which, being entirely deprived of soluble salts by a
careful washing, was dried. This green ultramarine
was then rendered blue by a calcination with sub-
limed sulphur, as we shall see further on.
" We see that this process, on account of the mate-
rials employed, was very expensive. On the other
hand, we must acknowledge that the purity of color
of the product was far superior to that of the ultra-
marines prepared with clay by the present process.
" This last process is more economical, and its mode
of operation varies with different manufactures. I
shall explain that which I found to succeed the best.
" Preference is given to that kind of white clay
which is found in various localities, near Worms for
instance, and which is called lenzine (lenzinite). It
is thoroughly deprived, by floating, of all the sandy
parts which may be mixed with it, then dried and
finely powdered. 10 parts (in weight) of this powder
are mixed with 22 parts of Glauber salt (anhydrous
and free from iron), 3 of sublimed sulphur, and 3.5
parts of colophony.
" This mixture is charged into pots, made of a scarcely
plastic clay, to which a certain proportion of sand is
BLUE COLORS. 303
sometimes added. These vessels are made upon a
potter's wheel, and, after a protracted desiccation, they
are burned. Their shape is conical, thirty centime-
tres in diameter at the bottom, and of an equal height.
The aperture of each, after the charge is put in, is
closed with a cover, which is luted on with clay. The
mixture should be strongly compressed.
"The pots are then placed in the same oven in
which are burned the empty ones; but as the latter
do not require as uniform a temperature as the former,
they are put near the fireplace and near the chimney
flue, while the central part of the oven is reserved for
the filled pots.
"A heat in these furnaces lasts three days, and
the fire should be maintained until the mass "in the
pots has sunk and has become agglutinated. After
cooling in the furnace, the pots are broken, and the
surface of the calcined mass is cleaned of any extra-
neous matter, which generally comes from the pots
themselves. It is then coarsely ground, and calcined
in a reverberatory furnace or in a cast-iron dish, as
long as sulphur vapors are disengaged.
" This calcined mass is lixiviated with water, until
most of the soluble salts are removed. The liquors
are evaporated to dry ness, and give Glauber salt.
" The washed bluish-green powder is ground again
to a fine magma, under hard quartz stones, because
soft stones become impregnated with the material,
and crumble easily.
" The schlamm or colored magma is floated (levi-
gated) in a special apparatus, which gives on one
side a highly comminuted powder, and on the other
a coarse article which is ground again.
" This levigated powder is thoroughly washed with
304 MANUFACTURE OF COLORS.
water, until a sample ceases to be improved by the
operation, or until two samples from two consecutive
washings have exactly the same coloration. The
pigment is then collected upon a filter, drained and
dried. It has a pure, but pale bluish-green hue.
" The operation by which the blue color is made to
appear is conducted in a horizontal cast-iron cylinder,
placed above a fireplace and covered with brickwork.
On the top of the cylinder there are several openings
for charging the sulphur and allowing the access of
the air. These apertures may be closed when desired.
This cylinder also contains a stirring apparatus, the
blades of which come very near to the bottom.
"This apparatus is about one-half filled with the
powder, which has been passed through a fine hair
sieve. The fire is then urged until all the material
becomes red hot. For every 100 parts of sifted pow-
der introduced into the cylinder, 6 parts of sublimed
sulphur are thrown in through the apertures. As
soon as the sulphur has caught fire the fire is removed,
and the stirring apparatus is set in motion. A little
while after, fresh fire is put upon the grate bars, and
3 per cent, more of sulphur is added. A moderate
heat is continued, the mass is constantly stirred, and
.air is largely admitted, until the color has acquired
its greatest intensity.
" When this color is left exposed for a long time to
moist air, it may happen that it will agglomerate and
form hard lumps. It is a proof that it still retains
soluble salts, and that it has not been sufficiently
washed."
K. Gentele Processes.
Mr. J. G. Gentele, a learned manufacturer, has
published a very interesting memoir on the prepara-
BLUE COLORS. 305
tion of artificial ultramarine. We borrow from the
Technologiste, vol. xviii. pp. 389-411, several extracts
from this memoir.
"The preparation of artificial ultramarine blue is
described in all the works on chemistry, but in a
summary way, and without sufficient details for
manufacturers. This manufacture, which was al-
already important in respect to painting, has still
gained in interest, since ultramarine has been suc-
cessfully used for calico printing. This has deter-
mined us to lay before the public all the practical
data which we have been enabled to collect in our
own practice, or from the French and German works
which we have visited.
" The manufacture of artificial ultramarine is di-
vided into two distinct operations — first, the prepara-
tion of the green ultramarine ; second, the transforma-
tion of the latter into ultramarine blue. The beauty
of the final product depends on the quality of the
former, and, therefore, the first operation requires all
the attention of the manufacturer. I shall describe
separately the preparation of each of these products.
1. Manufacture of Ultramarine Green.
"-Raw materials. — The following substances are
used, at the present time, for the preparation of ultra-
marine green: —
1. Aluminous silicate, kaolin for instance.
. Anhydrous sulphate of soda, ) sometimes in solutioa
6. Anhydrous carbonate of soda,J
4. Sulphide of sodium, as a secondary product of the manu-
facture.
5. Sulphur.
6. Wood charcoal, or bituminous coal.
20
306 MANUFACTURE OF COLORS.
"All of these materials require to be carefully
chosen, and to be submitted to certain preparatory
operations. These operations generally require me-
chanical appliances, which form the heaviest outlay
in the building of the works.
"The most advantageous aluminous silicate is por-
celain clay, or kaolin, or a white clay, the composition
of which should not be very different from that of
kaolin. A small proportion of magnesia and lime is
not objectionable; but a clay, holding more than 1
per cent, of oxide of iron, should be admitted only
after previous experiments. Kaolins present all the
desired qualities, and are not scarce, and French and
German manufacturers have no difficulty in getting
what they need. Formerly, ordinary clays were
worked with an addition of alumina, artificially pre-
pared; silica was also added to clays. At the present
time all these costly additions are dispensed with by
a judicious choice of clays, which, after calcination,
should have a composition corresponding approxi-
mately to the formula APO3,2SiO3. No account is
taken of small proportions of lime, magnesia, and
oxide of iron, and it matters not whether the silica is
or is not entirely in chemical combination. It often
occurs that clays in their natural state do not pre-
sent the desired composition, from being mixed with
sand and other mineral substances. But, as the me-
chanical operations to which the clays are submitted
retain most of these foreign materials, it results that
clays so treated are very near the indicated compo-
sition.
" The preparatory working of the clay, in order to
remove its mechanical impurities, is effected in ex-
actly the same manner as in porcelain works, that is,
BLUE COLORS. 307
by levigation or floating. The washed clay is dried,
slightly calcined, and then immediately ground to a
fine powder. There are, however, manufacturers who
do not calcine or grind it.
" The floating of the clay is done either by hand or
by power. When the clay is slow to soften in water
it is coarsely ground between two stones, and then
made into a thin paste, which is allowed to deposit
its coarsest impurities. The pure clay is stirred again
in water, and the light particles settle in other tanks.
After decanting the water, the pasty mass is collected
and pressed in sacks, and dried by heat, or in the air
upon porous slabs of plaster of Paris. When pure
and washed kaolin is bought, it is evident that these
manipulations are dispensed with.
" The slight calcination given to clay is effected in
an ordinary reverberatory furnace, at a temperature
not above the beginning of a cherry-red heat. By
this operation the earth loses all its combined water,
becomes friable, and ceases to be plastic ; in fact, it
can easily be powdered, which is the intent of this
calcination.
" The clay is pulverized under stamps, or under a
vertical stone revolving upon a horizontal one, and is
then passed through a series of fine metallic sieves.
The coarse portions are ground again.
" If the sulphate of soda be employed in the anhy-
drous state its quality should be considered. It should
not contain free acid, and if it be sold by the soda
manufacturers, free from iron and lead, so much the
better. When such a salt cannot be had, a Glauber
salt is bought which contains no free hydrochloric
acid. It is dissolved in water, and the excess of sul-
phuric acid is saturated with a small quantity of milk
308 MANUFACTURE OF COLORS.
of lime, which at the same time precipitates the oxide
of iron. The clear liquor is decanted and made to
crystallize. The sulphate of lime and the excess of
lime remain in the deposit. The crystallized sulphate
of soda is slowly dried in a cast-iron kettle, or, what
is better, upon slabs of fire-clay on the bed of a
reverberatory furnace. In either case the product is
an anhydrous Glauber salt (sulphate of soda). The
clear liquors may also be directly evaporated, without
being made to crystallize, in a pan which is always
kept full of fresh liquor. At a certain degree of con-
centration an anhydrous sulphate is precipitated,
which is fished (removed) with perforated ladles.
This salt is deprived of all adhering water by a
slight calcination in the reverberatory furnace.
"The Glauber salt, either bought anhydrous or
rendered so by the above process, is ground and passed
through sieves, which should not be too fine. The
ground salt should be kept in closed vessels, because
it may become compact by attracting atmospheric
moisture. This salt may be bought of manufacturers
who evaporate pure liquors and calcine the residue
afterwards ; but it is difficult in ultramarine works to
dispense with the necessary apparatus for this treat-
ment, because, during the course of the operations,
there are produced washing liquors containing sul-
phate of soda, which ought to be evaporated. The
salt, thus prepared, always contains small proportions
of chloride of sodium and of sulphate of lime, whi
form no impediment to the manufacture.
" The carbonate of soda is also used in the anh
drous state, and it can be bought as pure and as d
as desired. The dry carbonate of soda (soda ash) of
the manufacturers is the salt precipitated during the
>ns
;
BLUE COLORS. 309
evaporation of the liquors of crude soda, and calcined
afterwards. A small quantity of sulphate of soda in
it presents no inconvenience. This carbonate of soda
is powdered like the sulphate, and is kept in the
same manner.
" The ultramarine works which do not use directly
the sulphide of sodium in solution, should be provided
with a certain number of evaporating kettles, made
of wrought or cast iron, and heated by the waste heat
of the calcining and evaporating furnaces. The
liquors are evaporated to dryness, and are constantly
stirred towards the end of the operation. The sul-
phide of sodium is powdered, and kept, in the same
manner as the sulphate and carbonate of soda. In
making the mixtures this sulphide of sodium is
reckoned as a simple sulphide.
" The sulphur employed is in refined rolls. It is
also ground and passed through a fine sieve.
" The carbon necessary in the manufacture of ultra-
marine may be derived from bituminous coal, or
from the charcoal of any kind of wood. The impuri-
ties of the large pieces of charcoal are removed by
sifting, and those of the small fragments by a leviga-
tion. The impurities, which are heavier, fall to the
bottom of the tank, and the floating charcoal is re-
moved and dried. The more caking kinds of bitu-
minous coal are preferred, provided their percentage
of ashes is small.
"The two kinds of coal are always reduced to a
very fine powder either by trituration with common
balls in a revolving cylinder, as is done for cannon
powder; or by grinding with water in sand-stone
or granite mills, until the coal or charcoal forms
an impalpable powder, easily separated from the
310 MANUFACTURE OP COLORS.
water. The settled powder is collected, drained, and
dried upon shelves. It is again ground and sifted
before use. This last method is very convenient for
either charcoal or bituminous coal.
" While compounding the mixture, it is necessary
that the component parts should be in the correct
proportions, and, also, that the mixture should be
thoroughly homogeneous. The more this condition is
fulfilled the better the results. "When dry materials
are used it is advantageous to weigh small quantities
of them, and to mix them in a trough with a spatula.
The mixture is then passed through sieves of medium
fineness, stirred again, sifted anew, and so on, until
the proper result is arrived at. The sifting of the
mixture of materials should be done by small quanti-
ties at a time, and no new material put upon the
sieve until it is entirely empty.
"Another method has been adopted in several
factories. Thus, instead of using the sulphate and the
carbonate of soda, or the sulphide of sodium, in the
dry state, they measure solutions of these salts, mark-
ing a certain hydrometric degree, which corresponds
to a given proportion of dry salt. The powdered
kaolin is put into these solutions, and the whole is
evaporated to dryness. The powdered charcoal is
sometimes added to them. The dried mixture is then
slightly calcined in a reverberatory furnace, pow-
dered, and rendered homogeneous by consecutive stir-
rings and siftings. Lastly, the powdered sulphur is
added and mixed in the same manner.
" The respective proportions of the raw materials
vary considerably with different manufacturers, never-
theless care should be had —
" 1. That the soda, either as sulphate or carbonate,
BLUE COLORS.
311
be in sufficient quantity to saturate half of the silica
in the kaolin ;
" 2. That the proportions of sulphur and soda be
such as to produce a bisulphide or a polysulphide of
sodium ;
"3. Lastly, that in the mixture there remain enough
sulphur and sodium to form a mono-sulphide of so-
dium, when all of the green ultramarine, resulting
from the silica and alumina, is extracted from the
mixture.
" The German manufacturers compose their mix-
tures in a manner different from that of the French.
The latter employ only the carbonate of soda, while
the former use only the sulphate of soda, or a mixture
of sulphate and of carbonate. In either case, the
results appear identical. In the case of sulphate of
soda, more carbon and sulphur are employed. With
the carbonate of soda, no carbon is required, and a
great deal of sulphur is needed. It appears that the
German mode of manufacture is more economical.
" I now give the formulae employed in factories, and
which may be used for such mixtures : —
y
II.
III.
Kaolin, calculated dry ....
Anhydrous sulphate of soda
Anhydrous carbonate of soda .
Coal
100
83 to 100
It
100
100
12
100
41
41
17
Sulphur
60
13
"During the course of manufacture, there is ob-
tained a lye of sulphide of sodium, and a portion
of this salt may be usefully substituted for part of
the sulphate or carbonate of soda. This sulphide is
introduced, either evaporated and dry, or in solu-
312 MANUFACTURE OF COLORS.
tion, according as the various substances are mixed
dry or wet. In these solutions of sulphide of sodium,
the proportion of sodium alone, and not that of sul-
phur, is to be considered. It has been ascertained
that 100 parts of anhydrous carbonate of soda may
be replaced by about 80 parts of dry sulphide of
sodium; and 100 parts of dry sulphate of soda, by
about 60 parts of dry sulphide.
" The principal operation now to be done with the
mixture is its calcination. It is necessary that the
mixture should be brought to the proper degree of
high temperature, without the contact of the air, and
that the heat should be maintained long enough to
penetrate the whole mass as uniformly as practicable.
" An irregular and defective calcination never gives
advantageous results even with the best mixtures.
In order to operate under the best conditions this
process employs vessels resembling crucibles or the
seggars of porcelain works, which are heated in
ovens built of fire-clays, and in the shape of small
porcelain ovens. There is a great waste of heat in
these kinds of furnaces, and in a majority of ultrama-
rine works it is partly utilized in evaporating the
mother-liquors or the wet mixtures.
"The crucibles or calcining vessels are made of
good fire-clay, which should not become soft or
break at the temperature required for the operation.
They may be formed upon a potter's wheel, like
flower pots; and if their shape is that of seggars, the
diameter is 15 or 16 centimetres, and the height from
8 to 10. The top edge should be level. Only a small
number of flat covers are needed, because with the
seggar-like vessels the bottom of one becomes the
cover of that upon which it rests.
BLUE COLORS. 313
"When crucibles are employed, their shape is
represented by Fig. 52 ; and the cover is de-
pressed so as to receive the bottom of the next
crucible.
" This last shape appears to be the most
convenient, because, although the crucibles
may be placed close to each other, there is enough free
space between them to permit the heat to circulate.
With seggar-shaped vessels it is necessary to isolate
each column, and then there is danger that it will
topple over.
" The calcining furnaces are generally built one
against the other, with a single partition wall. The
following cuts give an idea of the shape which has
been found to be the best : —
Fig. 53. Fig. 54.
"Fig. 53 is a transverse section of the calcining
furnace.
" Fig. 54 is a longitudinal section.
" Fig. 55 is a horizontal section near the bed of the
furnace.
" A, fireplace ; &, grate ; c, ash pit with door ; cZ,
door of the fireplace ; e e 6, flues going from the fire-
place into the calcining space or room.
314 MANUFACTURE OF COLORS.
" B, calcining room ; ff, floor or bed of this room,
perforated with the flues e e e, which may be rendered
smaller by wedge bricks put into them ; g g, brick
walls. In front of this furnace there is a large
charging door c, which is closed with fire-bricks
during the calcination. The floor or bed of the fur-
nace is made level wTith fire-bricks, placed on top of
the arch which covers the fireplace. D is the arch
closing the calcining room, and provided with four
flues Ti h, for the escape of the heated gases, which are
collected in the general flue E, and go, either under
the evaporating kettles, or directly to the chimney.
"In other factories they use the round porcelain
ovens with three fireplaces ; but these furnaces take
more room, and the fire is not so easily regulated as
in the preceding one, with a single fireplace.
" In all ultramarine works there is a small experi-
mental furnace, which contains from six to eight
crucibles or seggar vessels. It is in it that the mix-
tures are tried before they are prepared on a large
scale. This small furnace is especially useful for
testing new qualities of clays, since the experiment
is much more rapid than a chemical analysis. At the
same time there 'is more certainty that the results
obtained on a small scale will be reproduced on a large
one.
"The composition or mixture to be calcined is put
into the crucibles or seggars with a small shovel, and
then strongly stamped in with a wooden tool, with-
out, however, breaking the vessels. The calcining
room is then filled nearly to the top with piles of
these crucibles, and care is taken that the apertures of
the flues are left free. The changing door is closed
with firebricks without cement in the joints ; but the
BLUE COLOTCS. 315
outside interstices are filled with a plastering of sand
and clay. The firing is then begun.
" We understand that it is indifferent whether the
furnace be heated with bituminous coal, wood, or
peat, provided the fireplace suits these different fuels.
" The temperature is slowly raised to a light red, or
an incipient white heat. "When beginning the manu-
facture, it is necessary to make a few trials of heat
in the experimental furnace. The degree of heat is
seen through an opening, 5 centimetres in diameter,
left in the charging door, and which is closed with a
movable clay plug.
" The time required for a heat, in the above fur-
naces, varies from seven to ten hours, with the indi-
cated compositions. The less the excess of sulphide
of sodium in the mixture, after calcination, the longer
this composition requires to be heated, to arrive at a
given result.
"When the calcination is complete, the furnace is
left to cool, with all the apertures closed ; and, as
soon as the temperature has become low enough, the
crucibles are removed and a new charge is put in.
In this manner, three charges per furnace may be
made in a week. The calcined mass in the crucibles
has sunk and is grayish, and often yellowish-green.
The crucibles are immersed into fresh water, or into
the washing liquors of green ultramarine, and the
contents are dissolved. The separated mass is then
washed in appropriate tanks, with several waters, and
the last liquors, which are weak, are reserved for
solutions or washings, instead of pure water. The
ultramarine thus obtained is composed of porous
fragments, large and small, which are ground wet in
mills similar to those employed for porcelain compo-
316 MANUFACTURE OF COLORS.
sitions. The operation is continued until a very great
degree of comminution is obtained. The ground
powder is then washed several times by decantation
(that is, by stirring in water, settling, and removing
the liquor), and then collected upon filters and dried.
"When the substance is dry, it is again stamped, and
passed through fine hair sieves. In this state, it may
be sold as green ultramarine, or transformed into blue
ultramarine.
" Only a good quality of green ultramarine will
permit of the preparation of a fine ultramarine blue.
When, after the proper care in the operations, an
inferior product is obtained, the cause of such a result
must be found in the wrong preparation of the mixture,
and, especially, in too small an excess of sulphide of
sodium. The unequal coloring of a product should
be attributed to a mixture which has not been made
sufficiently homogeneous. When the crucibles break,
the portions of material adjoining the cracks are
colored blue by the action of the air ; but this is no
great inconvenience. Brown specks show that the
heat has not been sufficient, and that all the carbon
has not been burned. These defective portions should
be washed and treated anew like clay.
" If, in the above indicated mixtures, we calculate
the results of the reactions of their elements, without
taking into account the accidental proportions of
lime and iron, we find for the formula I. —
I in 100 parts of anhydrous kaolin.
55.55 silica
42.00 alumina
Lime, oxide of iron.
43.72 soda }
22.51 sulphur }> in 100 parts of andydrous sulphate of soda.
33.77 oxygen j
17.00 carbon.
BLUE COLORS. 317
The result is composed as follows : —
(42.00 alumina,
(a) 67.83 silicate of alumina
(25.83 silica,
(6) 59.63 silicate of soda { 29*^ sil|°a'
(29.72 soda,
since half of the silica has been taken from the alu-
mina in the kaolin, and there remain —
(c) 19.00 sodium,
22.55 sulphur,
that is to say, there remains a mixture of a bisulphide,
and of a monosulphide of sodium, in which the bisul-
phide contains 13.70 of sodium and 18.90 of sulphur,
and the monosulphide, 5.85 of sodium and 3.65 of
sulphur.
" If, from these elements A, we deduct those B of
green ultramarine, as they result from my analyses*
upon 143 parts of this substance, we shall easily
understand how the blue color results. In the fol-
lowing subtractions, no account is taken of the small
proportion of lime and oxide of iron held in kaolin,
because these substances produce no reaction.
APO',SiO*. NaO,SiO*. NaS9. NaS.
A 67.83 59.63 32.60 9.00
B 67.65 57.09 15.07
0.18 2.54 17.53 9.00
" There remains therefore a notable excess of mono-
and of bisulphide of sodium, which is afterwards
washed out.
* In a previous memoir, the author gives analyses of 10 commer-
cial ultramarines, blue and green, and he infers from them that both
green and blue ultramarines have an analogous composition, that
is, an atom (old style) of silicate of alumina united with an atom
of silicate of soda ; without deciding, however, whether the green
or blue color invariably belongs to these double silicates.
318 MANUFACTURE OF COLORS.
" In the mixture of formula II. the proportion of
kaolin is the same as in formula L, and therefore its
component parts are the same. The anhydrous soda
gives —
58.64 soda, and there is, besides,
60.00 sulphur,
12.00 carbon.
" After the reaction, we have the same quantity of
silicate of soda and of silicate of alumina as in the pre-
ceding case. The charcoal is sufficient for reducing
all the soda; and there is also enough sulphur for
reducing all the sulphuric acid, and forming with
sodium 59.66 parts of bisulphide of sodium. If we
operate the subtractions as above, we have —
A
B
0.18 2.54 44.59
" There remains, in this case, a much greater ex-
cess of sulphide of sodium than in the preceding ope-
ration, and it is evident that the composition of the
mixture may oscillate between more extended limits,
since, besides the reactions in different proportions,
there is formed only a certain excess of sulphide of
sodium. However, it is also necessary that the car-
bon added should be burned.
" The calculation of the mixture of the formula III.
furnishes analogous results.
2. Manufacture of Ultramarine Blue.
" Blue ultramarine is always prepared from green
ultramarine, and this operation presents no difficulty.
The transformation of the green product may be
effected in different ways ; but up to the present time,
*03,Si03.
NaO,SiO".
NaS3.
67.83
59.63
59.66
67.65
57.09
15.07
BLUE COLORS. 319
manufacturers use one method only, that is, a cal-
cination with sulphur at a low temperature. The
sulphur is transformed into sulphurous acid, and a
portion of the sodium is oxidized, and is separated
from the green ultramarine in the state of sulphate
of soda. The sulphur held by this green ultramarine
remains whole, but combined with only a small quan-
tity of sodium.
" This calcination is done by two different methods,
which may be called respectively the French and
German methods, from the countries in which they
are employed, although there are several German
factories which use the French method.
" In the German mode of calcination, there are used
small cast-iron cylinders, imbedded in brickwork,
above a fireplace. The back part of each of these
cylinders is not movable, and is provided with a hole
for resting in it one extremity of the shaft of a revolv-
ing stirrer. The front part, made of wrought iron, is
movable, and has several holes; one for the other end
of the stirring shaft, a small one below, and a larger
one above, for the introduction of the sulphur. All
these openings may be closed at will. There is another
hole on top of the cylinder for the escape of the vapors
of burning sulphur, and an iron pipe is fitted to it,
in order to prevent the escape of material during the
rotation of the stirrer.
" This cylinder is charged, either by means of a
small shovel passing through the upper opening, or
by removing the front part, and immediately replacing
it when the sulphur is in. At the same time, the
shaft of the stirring apparatus is fixed in the two
central holes, and a crank handle is attached to the
projecting part in front. Each factory possesses
320 MANUFACTURE OF COLORS.
several such cylinders, and their number depends upon
the size of the works. Up to the present time, these
cylinders have been made of cast-iron, although clay
seems to be just as good, and even more durable.
" The fire being lighted, the cylinder is charged
with 12 to 15 kilogrammes of green ultramarine and
closed. The stirrer is moved now and then, in order
to heat the ultramarine uniformly. When the tem-
perature has been raised to the point at which a small
quantity of sulphur, projected through the upper
opening, will become inflamed, the fire is moderated,
so as not to increase the heat. Half a kilogramme of
sulphur is then charged in, the stirrer is revolved,
and the upper opening is left open to admit the air
necessary for the combustion of the sulphur. After-
wards, the stirrer is revolved more slowly, until it is
seen that all the sulphur is burned out. A sample
of the powder, being taken out with a small iron
spoon, appears of a bluish-green color. More sulphur
is added, stirred, and burned as long as the intensity
of color increases. "When the maximum of intensity
is reached, the pigment will lose its qualities if this
treatment be longer continued. The powder is then
scraped out into a sheet-iron box, which also receives
the small quantities of material which fall during the
operation. A new charge of green ultramarine is
immediately put into the cylinder.
"In many localities, the last calcination is done
according to the method we have just described,
except that there is an immediate washing, grinding,
drying, and sifting, before the ultramarine has become
entirely blue. In this manner, the coloring is more
uniform, because there are no more green specks in-
side or out.
BLUE COLORS. 321
"The blue calcined colors are ready for the
market, when they have been washed, dried, and
sifted.
" The intensity of the blue color depends on that of
the green, but grinding generally diminishes the
depth of the color. Light blues are sometimes pro-
duced in the course of manufacture, and these mixed
with dark ones form the medium quality. But, most
generally, the light-colored qualities are produced by
the addition of white pigments.
" In the French method of calcination, muffles are'
used, that is, a furnace into which the flame of the
fireplace does not penetrate. Fig. 56 is a longitudinal
section of a furnace of that kind, Fig. 57 a transverse
Fig. 56. Fig. 57. Fig. 58.
section, and Fig. 58 a horizontal section at the level
of the bed of the muffle.
" The fireplace A is placed under the bed B, which
rests upon a low arch. Several flues, q q q, conduct
the flame into the space left between the dome d d of
the muffle, and the concentric arch e e of the furnace.
c is the chimney. The fireplace A is composed of
grate bars a a, an ash-pit 5, and doors c c. In front
of the muffle there is an opening f, closed by a slid-
ing-door D, which may be raised or lowered by means
of a counter-weight and pulley. This opening is
21
322 MANUFACTURE OF COLORS.
covered by an arched mantle g </, which conducts the
sulphur fumes to the chimney, and prevents them
from passing into the work-room. All the parts in
direct contact with the fire are built of good fire-
brick, cut and polished by friction upon each other.
The number of muffle furnaces depends on the size of
the works.
" The green ultramarine is evenly spread upon the
bed, in layers 4 to 5 centimetres thick. The door is
then closed, and the fire urged until the sulphur pro-
jected into the muffle becomes inflamed. A shovel-
full of sulphur is charged in, and stirred with an iron
hook, the door being raised just enough to allow of
the motion of the hook. After the combustion of
this sulphur, and an examination of a sample, a new
quantity of sulphur is charged in, stirred, and so on,
until the consecutive samples show no improvement
in the purity and intensity of the color. No greater
heat is required than that necessary for the sulphur
to catch fire as soon as it is put in.
" The transformation of green ultramarine into blue
is more rapid with this mode of operation, than with
the cylinders, because there is greater access of the
air, and therefore more sulphurous acid produced,
and less volatilization of sulphur. As soon as the
ultramarine has acquired the desired color, it is raked
out into a sheet-iron box placed under the door. The
furnace is charged again, and the operation progresses
as before. We have already indicated the further
treatment of the color.
" When ultramarine blue is washed by the process
of displacement, there are obtained quite concentrated
solutions of sulphate of soda, which may be utilized
after precipitating by lime the iron contained therein.
BLUE COLORS. 323
" Ultramarine increases in weight by its combina-
tion with sulphur, and the increase, after washing
the product, may amount to several hundredths. If
the washings have not been thorough, the ultra-
marine will form compact masses in the packing
barrels."
In further researches upon ultramarine, Mr. J. G.
Gentele has ascertained that ultramarine green, boiled
for a long time with a solution of sal ammoniac, and
then transformed into blue ultramarine, possesses a
purer color and a lesser greenish tinge than any of
the ultramarines which have not been treated in this
manner.
He concludes from these experiments, that sal am-
moniac (and probably gaseous and dry hydrochloric
acid) is the most remarkable bluing agent of ultra-
marine green, because^ even employed in great excess,
it does not act upon the ultramarine blue already
formed.
L. Furstenau Process.
The old methods of manufacturing ultramarine,
such as have been introduced into the majority of the
South German works, and are still retained in certain
localities, are so inconvenient, especially when great
quantities of a given product are to be prepared, that
many attempts have been made to modify them.
Several Eheinish manufacturers have devised the
preparation of ultramarine in a large reverberatory
furnace, the bed of which is first heated below, and
then above, by the returning flame. These furnaces
contain enough material to produce about 600 kilo-
grammes of ultramarine, but their construction is
such that the calcination is not regular and uniform,
324 MANUFACTURE OF COLORS.
and that the substances are not protected against
impurities.
This consideration has determined Mr. C. Fiir-
stenau to propose another method, which seems to
obviate all the inconveniences named, and which
allows of the treatment of large quantities of material
without the introduction of dust and impurities. At
the same time the success of the operation does not
depend on the men so much as before.
The ultramarine is calcined in fire-clay boxes, which
may hold from 300 to 350 kilogrammes of material,
and which are located on each side of a double rever-
beratory furnace, resembling a smalt furnace, but
with a lower fireplace.
This furnace is composed of two stories A and B,
the lower one being heated by the direct heat of the
fireplace, and the upper one by the hot gases of the
combustion. The internal chimney, the arch, and the
bed of the first story are built of fire-bricks ; ordinary
bricks are employed for the second story; the pillars
and outside work are of stone. The bed of the upper
story A is covered with cast-iron plates, in order to
avoid the wear and tear resulting from the introduc-
tion and removal of the calcining boxes. The boxes
themselves are made of fire-clay slabs, 25 millimetres
thick, with joints rabbeted and luted with clay. All
of these joints are strengthened externally, in order
to possess the required firmness.
The composition for dark alum ultramarine is as
follows : —
Kaolin, slightly calcined . .100 parts in weight.
Calcined soda ash (95°) . . 90 " "
Refined roll sulphur . . .100 " "
Colophony 6 " "
Dry pine charcoal 4 " "
BLUE COLORS. 325
Each of these substances, with the exception of
the colophony, is reduced to a fine powder in revolv-
ing barrels by means of cannon balls. These barrels
or tuns are of beech wood, a little over 1 metre in
length, 0.65 metre at the largest diameter, and 0.55
in diameter at the ends. The staves are from 20 to
30 millimetres thick. These tuns are closed like
those used for amalgamating, and the aperture is 13
to 14 centimetres in diameter, with a felt packing for
preventing the escape of the powder.
The cannon balls employed are from 7 to 8 centi-
metres in diameter, and about 18 kilogrammes of
them are introduced into each tun. The velocity is
equal to 36 revolutions per minute.
As soon as the materials have become sufficiently
comminuted they are mixed with colophony, broken
into pieces of the size of walnuts, and the mixture is
made to rotate for four hours more. The resulting
grayish powder is placed, without packing it tight,
in the fire-clay boxes. These are closed, and then
introduced into the furnace. When all the apertures
of the furnace have been luted, the fire is urged to
bring the temperature as rapidly as possible to the
melting point of an alloy composed of equal parts of
gold and silver. This temperature is kept up for
five to six hours, and the fire is watched by an opening
left in the cleaning flue. In order to ascertain the
state of the composition, there is a small clay pipe, 25
millimetres in diameter in the clear, one end of which
penetrates the calcining box, while the other end pro-
jects about 5 centimetres from the furnace wall. Sam-
ples are taken now and then with a small iron spoon
passed through this pipe, and resembling, on a smaller
scale, the tools used for removing the powder from
326 MANUFACTURE OF COLORS.
blast holes. If, after cooling, these samples become
green, the fire is allowed gradually to die out, the
chimney-damper is closed, and the furnace is per-
mitted to cool off for twenty-eight hours.
After two days the bluish-green mass is extracted
from the boxes, ground under vertical stones, and
still more finely comminuted in revolving tuns.
The powder is then charged in cast-iron boxes, 45
centimetres high, having a length of 65 centimetres
on top and 55 on the bottom, and a width of 55 centi-
metres on top and 50 on the bottom. The thickness
of the metal is 5 millimetres. These boxes are well
closed with iron covers, and then introduced before
the fire is begun, into the upper part of the furnace,
which may contain nine of them ; they remain there
until twelve hours after the fire is run down. This
mode of oxidation and of desulphurization is imitated
from the mode of oxidizing red lead, and may be
repeated without impairing the color.
The blue thus obtained is carefully washed and
finely ground in water under horizontal quartz or
granite stones. The revolving stone is in perfect
equilibrium, and the surfaces of the two stones should
be polished by grinding a mixture of sand and clay
in water. The lower stone is tightly inclosed within
a kind of ring, which rises 10 centimetres above the
top of the upper stone, and which is closed with a
cover. The circumference of the upper stone is pro-
vided with two inclined bands of sheet iron, which
scoop the pigment and bring it on top, in order to pass
again between the two grinding surfaces. With a
revolving stone 1 metre in diameter, the velocity is
fifteen revolutions per minute. A charge is com-
posed of 25 kilogrammes of powder plus the quantity
BLUE COLORS. 327
of water necessary. As soon as the color has acquired
the desired brightness and firmness, which point is
ascertained by examining a dried sample, the paste is
received and drained in cloth bags, and then dried in
cast-iron pots, placed in the upper portion of the
furnace after the calcining boxes have been removed.
The dry color is sifted and packed for the market.
M. White Utramarine.
Notwithstanding the researches of Gmelin, Tire-
mon, Weger, Pruckner, "Winterfeld, Brunner, Dippel,
Buchner, Habich, and Grentele, we see that there still
exists a great deal of incertitude relative to the com-
position and mode of formation of artificial ultrama-
rine. More recently, Mr. H. Hitter, of Liinebourg,
has tried to throw some light on this subject, and he
has made known the results of his experiments in a
work published at Gcettingen, in 1860, under the
title of Uber das Ultramarin, which should be con-
sulted by all persons interested in this manufacture.
The most interesting part of the work of Mr.
Eitter is the discovery of a white ultramarine pro-
duced at a temperature of 900 to 950° C., which de-
monstrates that the sulphide of iron is not the coloring
principle of ultramarine, either green or blue.
This white ultramarine, which is easily transformed
into green and blue ultramarine, is composed of —
Silica 39.66
Alumina 31.1*7
Soda 14.75
Potassa 1.60
Sulphide of sodium .... 8.09
Bisulphide of sodium .... 4.88
Sulphide of iron . . . . .0.11
100.26
328 MANUFACTURE OF COLORS.
The experiments of Mr. Ritter have been published
through extracts in the Technologists, vol. xxii., !N~o. for
March, 1861. They are too extensive to reproduce
here, and we shall, therefore, give only the conclusions
of the work.
1. The combination, which takes place during the
calcination of the sulphide of sodium and the silicate
of alumina, is colorless; it is formed of silicate of
soda, silicate of alumina, and a monosulphide, with a
small proportion of polysulphide of sodium ; but it
contains no oxidized combinations of sulphur.
2. If a portion of the sodium be removed (by chlo-
rine or sulphurous acid, for instance) from the sul-
phide of sodium of white ultramarine, the proportion
of sulphur corresponding to this eliminated sodium
combines with the remaining sulphide of sodium and
forms a polysulphide.
3. The white ultramarine thus transformed becomes
ultramarine blue by the absorption of oxygen, that
is, by an oxidized combination of sulphur with a
portion of the sulphide of sodium. This blue ultra-
marine is a combination of silicate of soda, silicate of
alumina, a polysulphide of sodium, and a soda salt
with an acid from the sulphur.
4. The sulphide of potassium, calcined with silicate
of alumina, does not form a combination similar to
that of ultramarine, but there results only a silicate
of alumina and potassa without sulphur.
5. Moreover, it is very probable that the oxidized
combination of sulphur, held in blue ultramarine, is
a hyposulphite or a sulphite of soda, and the former
hypothesis seems the more likely.
BLUE COLORS. 329
N. Trial and Analysis of Ultramarines.
I. Mr. Guimet has proposed the following manner
of comparing ultramarines : —
" I weigh," says he, " a decigramme of each sample
of ultramarine to be tried, and as many times 6 deci-
grammes of white as there are samples of ultramarine.
The white I use is the best quality of Meudon white
(chalk), which I keep in a bottle large enough to
hold material for 1000 trials.
" I then mix upon a white marble slab, or, more
simply, upon a piece of smooth and well-sized paper,
1 decigramme of blue and 6 decigrammes of white.
This operation is effected rapidly by using a flexible
painter's knife, with which the blue and white are
crushed and mixed, until the whole presents to the
eye no difference of coloration.
uLet us now suppose that we have made four
mixtures, having each a different degree of colora-
tion; it is evident that the ultramarine which has
produced the greatest intensity of coloration is the
richest and the most valuable.
u Taking now the darkest and the lightest samples,
I try, by successive additions of white, to render the
tone of the dark one equal to that of the light one ;
and if I have had to use 6 decigrammes more of white,
I conclude that the blue, which bears twice as much
white to produce the same azure tone, is twice as rich
in coloring power, and twice as valuable in money
value.
" I have chosen a simple ratio to render my reason-
ing more clear; but we understand that this trial will
give us very approximately the relative values of blues.
" Sensible scales are necessary for weighing 1 deci-
330 MANUFACTURE OF COLORS.
gramme; but with ordinary scales, the weight of the
samples may be increased. For instance, we may
take 1 gramme of blue and 6 grammes of white ; the
only inconvenience is that the mixing is a little longer.
"It results from the above stated facts, that ultra-
marine blues have a value in a direct ratio to their
coloring power. This property is generally due to
the fineness of the pigment. A great degree of com-
minution is always advantageous, but it is absolutelv
necessary for artistic painting and calico printing.
On that account, I prepare special qualities for these
uses, although I pay a great deal of attention to the
grinding of all my blues.
" The results agree with what I have said, since the
paper manufacturers prefer my blue to all others,
even at a higher price. Most of my production is
thus sold, especially in foreign countries.
" Calico printers want bright and very finely ground
blues ; my dark quality is generally preferred, since
it is better fixed upon the cloth, and does not scratch
the printing rollers."
II. Ultramarine, says Mr. J. P. Dippel, is distin-
guished from all the other blue pigments by its ex-
ternal appearance, especially by its soft qualities, and
the intensity and purity of its color.
A simple process for distinguishing ultramarine
from other pigments which resemble it, Thenard or
cobalt blue for instance, consists in moistening the
sample with hydrochloric acid. Ultramarine is en-
tirely decolorized, and there is produced sulphuretted
hydrogen, which is easily recognized by its smell.
An addition of indigo is detected by heating, and
this substance emits purple vapors. Mountain blue
becomes greenish, and lastly black, by heat. Prussian
BLUE COLORS. 331
blue becomes brown when heated, or boiled with a
solution of caustic potassa. Smalt and cobalt blue
preserve their color in acids.
A good ultramarine should be of a dark-blue color,
without grit and foreign admixtures. Ground with
oil, it should not be decolorized by being heated in a
crucible, or upon a red-hot piece of iron. It should
also dissolve in concentrated acids without efferves-
cence.
In order to determine the value of ultramarines,
pieces of paper are colored with the different samples,
and the tones of color are compared. While the ultra-
marine is mixed with a solution of glue or gum, if we
observe a red or brown substance of a dirty color on
the surface of the liquor, this ultramarine contains an
excess of sulphide of sodium, which will change its
color when used.
As it is possible that pipe-clay has been added to
the ultramarine during the bluing calcination, in order
to obtain light tones of color, the darkest kinds should
generally be preferred. However, we should remark
that there are ultramarines which, by an energetic
calcination, have acquired more durability, but which
are lighter colored. These are in no way inferior to
the dark kinds.
III. Mr. C. P. Priickner, chemist and manufacturer
at Hof. has found a process for determining the quality
and durability of ultramarines, by a treatment with
hydrogen. This gas, at a certain temperature, re-
moves the sulphur from the ultramarine, and renders
it reddish. Therefore, by heating the ultramarine in
a glass tube, connected with a hydrogen generator,
and passing the gas through, this chemist has obtained
332 MANUFACTURE OF COLORS.
the following results with several samples of ultra-
marine at his disposal: —
1. Artificial ultramarine of the first quality (No.
0). — This ultramarine began to turn reddish, and
after half an hour the blue color had entirely disap-
peared and passed to a greenish-gray.
2. Inferior qualities. — The inferior qualities of arti-
ficial ultramarine lose their color more rapidly. The
No. 5 of Nuremberg manufacture was decolorized
after a few minutes, and became a grayish- white.
3. A sample bought at Venice by Mr. Priickner,
and certified to have been prepared from broken pieces
of lapis lazuli, was submitted to the same treatment.
After one hour, its color was still sensibly blue.
4. A sample of a remarkably fine native ultrama-
rine, left in 1805 (at wrhich time no artificial ultrama-
rine was manufactured) in the corner of a pharmacy
as a useless substance, was treated in the same man-
ner. After two hours of contact with hydrogen gas
in a hot tube, all the color was not destroyed.
" It results from these observations," Mr. Priickner
adds, " that artificial ultramarine treated by hydrogen
behaves differently from real native ultramarine pre-
pared from lazulite, and it is probable that a similar
result will be observed in painting. A similar exam-
ple is found in cinnabar ; the product prepared by the
wet way presenting properties entirely different from
the cinnabar produced by the dry way, or sublimed,
when it is employed in the manufacture of wafers
and sealing wax. The former especially, when colored
by cinnabar (vermilion) prepared by the wet process,
are more blackish-red than intensely red. The same
effect is seen with sealing wax, although the vermilion
BLUE COLORS. 333
(wet way) is brighter than that which has been
sublimed.
"Generally speaking, the durability of color of ul-
tramarine is influenced by the fixity of the substances
entering into its composition, and by the intensity of
the calcination. Repeated heatings in closed vessels
increase the durability of ultramarine, but they are
always accompanied by a diminution in the intensity
of the color, which may become a pale blue. By this
process, the ultramarine acquires such a durability
that acids do not destroy this pale blue color."
IV. Mr. "W. Biichner has made a special study of
the practical testing of artificial ultramarines. The
following is his mode of operation: —
(a.) Resistance to the action of alum. — As there is
no ultramarine which will completely resist for a long
time a hot and saturated solution of alum, we must,
for those kinds of tests, remain within the limits of
technical operations, and draw conclusions only after
check-tests have been made with different ultrama-
rines. The length of time required for the action of
an alum solution upon ultramarine is an important
consideration, and requires comparative trials. We
should here remark, that a coarse-grained ultrama-
rine resists the action of alum better than an ordinary
ultramarine ; it is not, however, suitable for paper
manufacturers and calico printers, on account of its
feeble coloring power, and the coarseness of its grain.
Such experiments require, 1st, a saturated and cold
solution of alum; 2d, a few test glasses; 3d, a deli-
cate scale ; 4th, a graduated burette.
Five centigrammes of the ultramarine to be tested
are weighed carefully, and placed in a glass, which is
marked with a suitable sign or number, when com-
334 MANUFACTURE OF COLORS.
parative experiments are going on at the same time.
Then an accurately measured volume of the cold and
saturated alum solution is poured upon the color, and
the whole is stirred with a glass rod. After a few
minutes, several hours, or several days, we may see
how the destruction of the ultramarine color pro-
gresses, and its degree of resistance. An ultramarine
which with an equal coloring power resists the longer,
is evidently the better. The reaction may be rendered
more rapid by immersing all the test glasses in the
same vessel holding hot water. If we consider that
in the manufacture of paper, the pulp becomes sen-
sibly heated during the work, this last experiment
shows why we should prefer an ultramarine which
resists the action of alum. But in order to arrive at
a still more technical conclusion, we may, instead of
a pure alum solution, employ a solution of glue in
which alum is added. By cooling, the ultramarine
remains suspended in the jelley, and the action is
more energetic.
(Z>.) Trial of the coloring power. — The aspect of a
color, whether dark or clear, is the result of the refrac-
tion of light, and it is well known that colors appear-
ing alike may possess a coloring power widely differ-
ent. In order easily to ascertain the difference, it is
necessary to dilute the color with a powdered white
body. The apparatus, etc., consist of a delicate pair
of scales, a mixing dish, and a certain quantity of
lenzinite,* sulphate of baryta, or white lead. One
gramme of lenzinite and five centigrammes of ultra-
marine are carefully mixed in the dish, but without
* Lenzinite is a kind of white cla}', found in scattered lumps
near Kail, in the Eifeld.
BLUE COLORS. 335
grinding'. The other samples are worked in the same
manner, and when the comparison is made, it is often
a subject of astonishment to see the difference in
coloring power of certain kinds of ultramarine. It
is, of course, necessary that these experiments should
be made with scrupulous exactness, and an un-
practised eye may cause great mistakes. The mix-
tures are placed one near the other, or one upon the
other, and they are slightly compressed with the
spatula. Or they may be put into glasses with equal
volumes of water. The distinction should be made
only when the difference in tint or hue is perfectly
apparent. The hue may sometimes be a pale blue, or
a greenish-blue, or a reddish-blue, or a pink blue.
But the most intense color will always be recognized.
It now remains to be seen which of these kinds
are the best. It seems proven that the pure blue red
qualities are the best for paper manufacturers, calico
printers, and paint grinders, and that the greenish-
blue ones are more advantageous for fancy papers.
For a long time, I had the idea to express the
coloring power as is done in estimating the power of
alcohol, bleaching powder, etc., by a scale, but we
have no unit upon which to base ourselves, and, if for
ultramarine a scale were to be constructed from the
best sample, this same sample should be in the hands
of all those who make similar tests. In order to ren-
der the operation possible, I have under the name of
ultramarinometer (ultramarinomesser\ adopted a nor-
mal or standard color, the mixture of which with any
kind of wrhite substances, gives the degree of the scale.
Any person having a few grammes of this color, or
an ultramarine of the same coloring power, may
336
MANUFACTURE OF COLORS.
determine the coloring power of any sample, with the
following table : —
Scale of the Ultramar inometer.
2 grammes of lenzinite with 0.5 gramme of ultramarine g ve 10° of coloring power.
0.3 9
0.2 8
0.1 7
0.05
0.03
0.02
001
0.005 2
0.003 1
"When the above scale has been prepared, 2 grammes
of lenzinite are mixed with 0.5 gramme of ultramarine,
and the mixture is compared with those of the scale.
That with which the tested mixture agrees the best
gives the degree of the coloring power of the sample
of ultramarine.
(c.) Trial of the printing power. — A substance
suitable for printing should be finely comminuted
and require little thickening. The degree of fineness
may be ascertained with a magnifying glass, or by
rubbing the powder with the finger upon a piece of
writing paper. If the substance contains coarse por-
tions, and is not fine and homogeneous, it will be
perceived by the sense of feeling. If no coarse grains
are felt, and if, after striking the paper from under-
neath, a notable portion of the ultramarine remains
adhering to the paper, this ultramarine appears to
answer the purpose. A pinch of this powder is also
rubbed against a polished piece of brass, which should
not be scratched by it. But the best proof is that of
the coloring power, because when it is high the de-
gree of comminution must, of course, be satisfactory,
BLUE COLORS. 337
taking however into consideration the accidental im-
purities which are often to be found.
(d.) Trial of the glazing power. — The property in
ultramarine of acquiring a glaze is an advantage
sought for in many of its applications. This property
supposes a great fineness of body, a high coloring
power, and the necessity of but a small amount of
size. A single coat of glue size upon paper will en-
able us to ascertain this property. If, after this size
has become dry, a glaze be obtained by a few strokes
of a soft brush, then the ultramarine is satisfactory,
because, in the manufacture of glazed papers, there
is always added a small quantity of wax soap in
order to aid the fixing of the printing colors. Such
a result will be more readily obtained by using a wax
soap, or brushes charged with powdered talc; but
even with these means no ultramarine will glaze well
if it does not do so without them.
(e.) Trial for the proportion of gelatine (size). — How-
ever simple such a problem appears, it cannot be
solved except by a practical trial. A lean and com-
mon ultramarine will always require a great deal of
glue, and, even with a good glue, its adherence will
soon be defective. A small quantitative test may be
made as follows : A certain quantity of ultramarine
and glue is weighed, and the latter, after solution in
water, is put into a graduated vessel. Then by adding
this solution to the blue by small quantities at a time,
and reading the number of divisions left after the
proper result is obtained, we know the proportion em-
ployed. The sizing should be such that no ultrama-
rine will be removed when the paper thus colored is
dry and is rubbed with another piece of white paper.
It is well known that moderate prices increase the
22
338 MANUFACTURE OF COLORS.
consumption of a product considerably, and the em-
ployment of ultramarine will attain enormous pro-
portions when it shall be possible to obtain it at a
low price. On the other hand, when the selling price
is scarcely above the cost, the manufacturer is weighed
down and cannot undertake improvements. The ap-
plications are therefore limited on account of the im-
perfection or of the inferior quality of the product.
In regard to ultramarine, the comparison of the prices
of different manufacturers will never be satisfactory
if the color of the product be alone considered ; be-
cause it is a well-known fact that two kinds of ultra-
marine, similar in appearance, may be different in
their coloring power, and vary in price as 100 does to
200, independently of the other properties. Therefore,
if we desire to establish comparisons of prices, it is
absolutely necessary that we should take into ac-
count the intimate properties of ultramarine in order
to arrive at its real value.
V. Mr. Barreswill has indicated the following pro-
cess for ascertaining, very approximately, the value
of ultramarine : —
An artificial sulphate of baryta is prepared by de-
composing a solution of nitrate of baryta, or of
chloride of barium, with sulphuric acid. The pre-
cipitate is well washed and dried. Two small
mortars receive each 20 grammes of sulphate of
baryta ; on the other hand from 0.5 to 1 gramme of
ultramarine is weighed in two porcelain dishes of a
known weight. One of these dishes contains the
standard ultramarine, and the other the sample to be
compared. A certain proportion of the standard blue
is then mixed with the sulphate of baryta, and small
portions of the tested sample are added to the baryta
BLUE COLORS. 339
of the other mortar, until the two tints have the same
intensity. Weighing now the ultramarines left in
both dishes, the differences of weight give the com-
parative value desired.
Ultramarine is sometimes adulterated with starch,
which is easily detected by a tincture of iodine. The
blue ashes are recognized by throwing a pinch of
the suspected sample into aqua ammonia ; pure ultra-
marine produces no change, whereas the blue ashes
are dissolved and color the liquor an intense blue.
0. Composition of ultramarines.
The blue and green ultramarines have been analyzed
by several chemists, who, from all the results of
their analyses, have put forth theoretical views
which have not yet resolved the problem of their
composition.
Those persons who may be interested in these
questions will find in the Repertoire de Chimie pure et
appliquee, November, 1861, p. 420, an excellent re-
sume, made by Mr. A. Scheurer-Kestner, of the
opinions of Messrs. Eisner, Brunner, Stceltzel, Breun-
lin, Gentele, Wilkens, Bitter, Boeckmann, etc. These
opinions often disagree, and appear to have been re-
cently overthrown by an experiment of Mr. E. Guignet,
who has extracted, by means of bisulphide of carbon,
notable proportions of sulphur from various samples
of ultramarine, without decomposing the blue or
changing its intensity. Artificial ultramarines, there-
fore, contain free sulphur, and the differences in
coloration, durability, etc., of these blues may pos-
sibly be explained by the greater or less proportion
of that sulphur. The greenish tinge of certain blues,
printed with albumen, and then submitted to the
340 MANUFACTURE OF COLORS.
action of steam, may possibly be caused by the pre-
sence of more or less free sulphur.
At all events the observation of Mr. Guignet is of
great practical importance, and will possibly permit
of the manufacturers changing their formula, or their
mode of operation, in order to prepare durable pro-
ducts of a fixed composition.
3d. Cobalt ultramarine.
Cobalt ultramarine, or Gahn's ultramarine, from
the name of the inventor, is a combination of alumina
with the oxide of cobalt. This combination does not
appear to be in definite proportions, since it varies
with the different works in which this pigment is
made.
Its preparation consists in making a solution of
alum, that is, a double sulphate of alumina and potassa
(or ammonia), and dissolving in it a certain propor-
tion of nitrate, sulphate, or chloride of cobalt. The
whole is then precipitated by another solution of car-
bonate of soda or potassa. The resulting abundant
and pink- white precipitate is a mixture of carbonate
of cobalt and of hydrated alumina, which is carefully
washed with hot water, dried, and calcined in a cru-
cible at a high temperature. After cooling, the pro-
duct is ground into a fine powder which resembles
the blue ultramarine of the first quality, but appears
violet under artificial light. By varying the propor-
tions of cobalt more or less intense tones of blue will
be obtained. If a great purity of color be desired
the materials employed should not contain iron.
Cobalt ultramarine unites quite well with other
pigments used in oil painting, and is scarcely poison-
ous.
BLUE COLORS. 341
§ 12. Blue ashes. Lime Hue. Copper Hue.
Mountain Hue.
The composition of this color, which is of a sky
blue, has been a secret for a long time. It was im-
ported from London, and was prepared with the
copper resulting from the treatment of silver bullion.
Pelletier was the first chemist who, after having
analyzed a sample of fine English blue ashes, suc-
ceeded in preparing them in France. In order to
obtain blue ashes of a constantly fine quality, it is
necessary, according to this chemist : 1. To mix
powdered lime with a weak solution of nitrate of
copper (CuO.NO5), and to employ these substances
in such proportions that all of the lime is saturated
by the nitric acid, that is, by keeping always a certain
excess of undecomposed nitrate of copper ; 2. To
wash the precipitate several times; 3. To drain it
upon a cloth ; 4. To grind it with 7 to 10 per cent of
its weight of lime ; 5. To dry it.
This process, described by Pelletier, is not that
followed by manufacturers. It appears that the
latter obtain the blue ashes by pouring a solution of
commercial potash into one of sulphate of copper,
washing the precipitated carbonate of copper, and
grinding it with lime, to which a small proportion
of sal ammoniac has been added. This salt, being
decomposed by the lime, increases the brightness of
the color, with which it forms a kind of ammonium
compound of a deep blue.
Another blue ash, called arseniate of copper, is
obtained by dissolving 5 kilogrammes of arseniate of
potassa in 32 litres of hot water, and pouring into it
another solution of 3.5 kilogrammes of sulphate of
342 MANUFACTURE OF COLORS.
copper. The precipitate is washed with water, then
drained upon a cloth, and dried in the shade.
Blue ashes with size are often employed for the-
atrical decorations and painted papers. They present
the inconvenience of turning green after a few days,
especially when they are exposed to the action of
solar light. Ground in oil, they become dark, and
lose part of their beauty. Those made in England,
of which we shall explain the preparation, are more
durable. "When blue ashes are ground upon a slab
with a muller, they feel very greasy, but afterwards
they become much more fluid.
I. Manufacture of the ashes in England. — We have
already seen that the nitrate of copper, resulting from
the parting of silver, is generally used ; but it appears
that any soluble copper salt, the acid of which will
make a soluble salt with lime, is just as convenient.
Therefore, the cheap sulphate of copper may be first
decomposed by the acetate of lead or the acetate of
lime, and, in some localities, by the chloride of calcium.
We should observe that, if we cannot, by this double
decomposition, accomplish the combining of exactly
the whole of the sulphuric acid with the lime (which,
however, is not difficult after a few trials), it is pre-
ferable to have a small excess of sulphate of copper
in the liquor rather than one of lime salt.
The solution of copper resulting from this double
decomposition should contain but a very small pro-
portion of sulphate of lime. It is filtered, after
having settled in a cool place for at least 24 hours.
The filtered solution is diluted with pure water
until its specific gravity becomes about 18° Be.
On one hand, a milk of lime is prepared with very
white and well-burned lime, which is slaked and
mixed with a large quantity of pure water. The
BLUE COLORS. 343
milk is kept stirred for a long time in a lead-lined
tun, having a stopcock at a few centimetres above
the bottom. After one minute given for the settling
of the sand and other impurities, the milk of lime is
drawn out through the stopcock, and is then allowed
to settle entirely in other vessels lined with lead, or
in copper pans. When the deposit has acquired a
certain consistency, it is ground in a mill similar to
those employed for indigo, mustard, enamels, etc.,
and which should contain no iron. The axis is of
hard bronze or brass. The lime should be ground
long enough to destroy any hard and coarse portions,
and, as a further security, it is passed through a very
fine copper sieve.
As the mixture of lime and copper solution must
be made in certain proportions, the quantity of dry
material in the copper liquor and in the milk of lime
is determined by drying samples of them. This test
is made, for instance, upon 1 litre of the solution of
copper, and the same volume of milk of lime; but
the latter should be well stirred before taking the
sample. The proportions for mixing are 1 part of
well-dried lime, and 1.75 parts of dry copper salt. We
should observe that the quantity of lime may be con-
siderably increased above this proportion at the ex-
pense, however, of a lesser intensity in the coloration
of the product. The proportions which we have just
indicated generally furnish the finest color. In
order to ascertain whether the correct amount of lime
has been added, a sample of the clear liquor above the
colored precipitate is tried with ammonia, which should
produce but a faint blue. If the coloration be deep,
more milk of lime is added, and the whole is thoroughly
mixed.
344 MANUFACTURE OF COLORS.
When the precipitate has become well settled, the
clear liquor is decanted, and the color is carefully
washed with pure and limpid water. It is then
drained upon cloth filters until it has acquired a cer-
tain consistency, and forms a green paste.
For the subsequent operations, it is necessary to
determine the proportion of water held in this green
paste, in order to compound the ingredients. A few
grammes are slowly and cautiously dried, and the
loss in weight indicates the proportion of water.
This paste generally loses three-fourths of its weight
in drying. On this hypothesis 25 kilogrammes of
paste are stirred, in a leaden tub, with 50 litres of pure
water, to which are added 2.5 kilogrammes of the wet
lime, which are immediately stirred without loss of
time, this rapidity being an essential condition. After-
wards, 1.5 litres of a solution of the best kind of
pearlash potash, marking 15° Be., and filtered clear,
are added, and immediately and vigorously stirred in.
The mixture is then carried, without loss of time, to
the mill already mentioned, in which it is ground for
a long time, because the beauty of the pigment de-
pends greatly upon a homogeneous mixture.
On the other hand, for the 50 litres of green paste
there has been prepared a clear solution of 0.5 kilo-
gramme of pure sal ammoniac in 10 litres of water,
and another solution of 1 kilogramme of sulphate of
copper in 10 litres of water.
The liquid paste of the mill is then drawn into a
stoneware jar, and, immediately after, the two solu-
tions of sal ammoniac and sulphate of copper are
poured in at the same time. The jar is closed with a
good cork, which is held tight by a string, and luted
over with a mastic of tallow and rosin, soft enough to
BLUE COLORS. 345
yield to the fingers. The jar is moved in every
direction and shaken as much as possible.
After standing for four or five days, the contents
of the jar are poured into a lead-lined tub of a capa-
city of about 250 litres. Water is added up to a few
centimetres from the top, the whole is stirred, then
left to settle, and the clear liquid decanted, and so
on, at least eight times. The clear water of the last
washing is tried with a piece of turmeric paper, and,
if the yellow color becomes brown-red, the washing
should be continued.
The deposit thus obtained is called, in England,
verditer in paste. The greater portion of that manu-
factured is used in that state by manufacturers of
paper hangings. For other arts, and for exportation,
the paste is slowly dried, and becomes solid and
brittle.
This manufacture requires great cleanliness, well-
ventilated rooms, no sulphuretted gases, etc. Pure
waters have a great influence on the beauty of the
product.
II. A skilful manfacturing chemist, Mr. L. G.
Gentele, has published, in the Technologiste, vol. xvii.
page 341, the results of researches made by himself
upon the preparation of several copper colors, and
especially of blue ashes.
"The blue colors," says he, "found in the trade,
and prepared especially with oxide of copper, are :
The mountain blue, the green-blue of Bremen, and
the calcareous blue, or blue ashes in paste. As far
as I know, no accurate researches on the latter pro-
duct have been published ; and the circumstances
under which it is formed are so peculiar, that I suspect
that colors made in a similar manner may be com-
pounds in chemical proportions.
346 MANUFACTURE OF COLORS.
" One kind of blue ashes in paste is obtained by
the precipitation of sulphate of copper with a very
thin milk of lime added in excess, and cold, and by
thoroughly washing the precipitate, which may then
be dried without turning black. The preparation of
another kind of blue ashes in paste, resembling moun-
tain blue, is made by precipitating, in the cold, a
solution of 100 parts of sulphate of copper and 12.5
parts of sal ammoniac with a milk of lime prepared
from 30 parts of quicklime. The liquor remains blue
for a few days, and when this coloration has disap-
peared the pigment is made. In order to obtain very
pure colors the lime is ground after having been
slaked, and the milk of lime formed is left to stand
for several weeks before it is employed.
"As the latter color is not obtained without sal
ammoniac, I have concluded that this substance is
of absolute necessity in its preparation. I have,
therefore, prepared a solution of ammoniacal sulphate
of copper with excess of ammonia, that is, I have
added ammonia in sufficient quantity to dissolve the
first precipitate, and to impart a strong ammoniacal
odor to the solution, which was filtered afterwards in
order to separate a small quantity of oxide of iron.
"By pouring, drop by drop, this solution into
lime-water, I have immediately obtained a blue pre-
cipitate, and the liquor took a bluish coloration only
when all of the lime was combined. The precipitate
formed before the coloration of the liquor was sepa-
rated and washed ; then a portion A was dried and
kept to be analyzed.
" If, on the other hand, the milk of lime be poured,
drop by drop, into the ammoniacal copper solution,
there is also produced a precipitate, which by stirring is
BLUE COLORS. 347
completely redissolved, and remains so for a long time,
when the liquor is tepid. Lastly, when a permanent
precipitate has been formed, and has been separated
by filtration, the liquor, after standing for several
days, deposits crystals of a magnificent blue, several
centimetres in length, but no thicker than a hair,
which break into small pieces when the liquid is
stirred. These crystals B were separated in order
to be analyzed.
" The compound A was not entirely pure, on ac-
count of the presence of a small proportion of carbon-
ate of lime, formed during the washings and drying.
This product greatly resembles Bremen blue, except
that it is slightly greenish, flaky, and amorphous.
Under the action of heat, it behaves like the hydrated
oxide of copper of the Bremen blue, but it bears a
greater elevation of temperature before it becomes
brown.
"The analysis made of it gave as result —
Water 18.76
Sulphuric acid 11.20
Oxide of copper .... . 46.85
Lime . . . . . . . 16.19
Loss . 7.00
100.00
" The loss consists of carbonic acid. The propor-
tion of lime, not combined with sulphuric acid, re-
quires 6.5 of carbonic acid. Therefore the analysis
becomes —
("11.20 sulphuric acid,
(. 7.84 lime,
C 8.35 lime,
( 6.50 carbonic acid,
46.85 oxide of copper,
18.76 water.
348 MANUFACTURE OF COLORS.
" This precipitate, thoroughly washed in pure water,
became very soluble in ammonia, whereas, previous
to the washings, it was insoluble. We should there-
fore suppose that this precipitate, before being dried
and washed, holds a combination of lime, which,
during the drying operation, combines with carbonic
acid, and sets at liberty the hydrated oxide of copper.
As the washings carry away the sulphate of lime, it
is difficult to decide upon the composition of the
precipitate.
" The compound B may be obtained pure in the
shape of crystals, or rather of a crystalline precipi-
tate. It is generally impure in commercial blue
ashes in paste. This blue is very bright, and resists
the action of the air well. The thicker crystals possess
the blue color of mountain blue, although slightly
lighter in tone. Heated, these crystals acquire a
brown color, of a glassy -brightness. They are in-
soluble in water, but very soluble in the sulphate of
ammonia.
" Their analysis gives the following composition :—
Lime 16.19
Oxide of copper 33.56 33.44
Sulphuric acid ...... 23.83
Water 26.01 27.00
99.59
" This compound is not obtained by digesting sul-
phate of lime with ammoniacal sulphate of copper
containing an excess of ammonia.
"From the behavior of caustic lime with ammo-
niacal sulphate of copper, and also from the differences
presented by the two precipitates, we may establish
rules for the method of preparing this color, and
foresee the circumstances which will influence its
BLUE COLORS. 349
good or bad quality. For instance, the compound B
is not formed, when the proportion of lime is such as
to precipitate entirely the sulphuric acid of the sul-
phate of copper. Out of 7 atoms of sulphate of
copper in the liquor, 5 are precipitated by hydrated
lime, and the last two are decomposed by ammonia.
A greater proportion of lime will produce a precipi-
tate holding a certain quantity of the compound A,
which is less valuable, and impairs the quality of the
color. A smaller proportion of lime renders the
color finer and more crystalline, because it crystal-
lizes partly in the excess of solution. It is therefore
possible, by an incomplete decomposition and a smaller
yield, to obtain a finer and more crystalline color.
" If we calculate the proportions necessary for the
formation of the color, we have —
7 equivalents of sulphate of copper ;
2 " " ammonia;
5 " " lime.
And if, instead of 2 equivalents of ammonia, we
take 2 equivalents of sal ammoniac and 2 of lime, the
weights become —
100 parts of sulphate of copper;
24 " " lime;
22.5 " " sal ammoniac,
which proportions will furnish the purest color.
:< Examination has also been made as to how a solu-
i tion of ammoniacal sulphate of copper, with excess of
ammonia, behaves with caustic potassa or soda. Either
of these alkalies produces in this solution a fine blue
precipitate, but the liquor does not become decolor-
ized, except by evaporating the ammonia. By wash-
; ing this precipitate, its color becomes lighter and
lighter, and finally resembles that of Bremen blue.
350 MANUFACTURE OF COLORS.
It is composed of hydrated oxide of copper, but it
contains also a small proportion of carbonic acid.
" It is a remarkable fact that this precipitate, even
when heated in the presence of a great excess of
potassa or soda, does not become brown, as is the case
when a solution of sulphate of copper is precipitated
by a slight excess of these bases.
" The presence of ammonia renders the hydrated
oxide of copper much more durable. This circum-
stance explains a useful manipulation in the prepara-
tion of Bremen blue. Indeed, if, for changing to a
blue the precipitate obtained from a copper salt by an
alkali which is not entirely caustic, we employ a
caustic lye of potassa with an addition of ammonia or
of sal ammoniac, we are much more certain of success,
because a passage to a black color, which is to be
feared, does not then occur even with a great excess
of caustic potassa lye."
III. Since blue ashes are manufactured in England
better than in France, it is necessary to be able to
distinguish one from the other. The following pro-
cess has been proposed : —
When the blue ashes are in paste, a sample is
thoroughly dried at a low temperature, and then
heated in a glass tube with a small quantity of fused
caustic potassa or soda. The French blue ashes
disengage ammonia, easily recognized by its smell,
while the English product does not present the same
phenomenon.
The English blue ashes, the manufacture of which
is still kept a secret, are a carbonate of copper of a
rather dark blue, but less pure in color than the
hydrated oxide of copper of Mr. Peligot.
IV. The natural color, called mountain blue, azurite,
BLUE COLORS. 351
and Armenian stone, is a basic carbonate of copper,
found in quartz rocks in Siberia, the Tyrol, Bohemia,
Saxony, Hesse, England, and France. This substance
is rare and expensive, and possesses a very rich sky-
blue color, of which blue ashes are an imitation.
The native product is always more durable than the
artificial one.
§13. Smalt.
Smalt, which is also known under the names of
azure blue, smalt blue, zaffer Hue, Saxony blue, enamel
blue, starch blue, cobalt glass, etc., appears to be,
according to Mr. Ludwig, a double silicate of potassa
and cobalt, mixed with variable quantities of lime,
alumina, magnesia, oxide of iron, oxide of nickel, and
sometimes of arsenic and carbonic acid, and water.
The intensity of the color, in the opinion of the same
chemist, depends on the greater or less proportion of
the double silicate.
The crude materials employed in the manufacture
of smalt are, cobalt ore, sand, and potassa. The min-
eral generally used in Saxony, where this color is
prepared the best, is a speiss or arsenide of cobalt and
iron.
The broken ore is roasted at a red heat in a rever-
beratory furnace, which has a very high stack for car-
rying far up into the air the arsenical and sulphurous
fumes. When vapors cease to be disengaged, and
when the material begins to be pasty, the roasted
product is removed from the fire, cooled, pulverized,
and passed through a silk sieve. This powder is
called zaffer.
A pure sand free from iron, mica, talc, or lime, is
also calcined and thrown into cold water, while still
352 MANUFACTURE OF COLORS.
red-hot. It is then powdered, washed with hydro-
chloric acid, and dried.
The potassa should be pure, and contain no lime,
sand, or chloride of sodium.
It is difficult to indicate beforehand the propor-
tions for the mixture, because we must be guided by
the nature of the cobalt ore, or by the quality, or by
the tone of color which is to be produced. The cobalt
and sand are first added, and then the potassa ; the
whole is introduced into clay pots having each a hole
in the bottom, which may be closed. The pots are
then placed in a glass furnace heated by a wood fire.
After four, five, or six hours of calcination, the mate-
rial is melted, and forms three layers ; the upper one,
or dross, is composed of sulphate and arseniate of
potassa, and chloride of potassium ; the lowest one is
composed of ore and of unmelted substances, and the
intermediary one is the blue glass.
The greater part of the dross is taken off with
hot iron ladles, and the lowest layer of unmelted
materials is removed through the bottom hole. After
this hole has been closed again, the melted blue
glass is ladled out into basins filled with cold water.
The pots are charged again, and a new operation
begins.
The glass is removed from the water, dried, and
pulverized under horizontal stones. The powder is
then levigated (floated), in order to obtain various
degrees of fineness, which are designated by the
names of smalt of the first, second, third, and fourth
fire, or by other marks distinctive of their color or
degree of comminution.
Independently of the ordinary smalt, there is another
darker blue, with a very fine grain, and which is gen-
BLUE COLORS. 353
erally called Eschel blue or Laundry Hue. It is ob-
tained by mixing finely powdered zaffer with a smalt
of good quality. It is distinguished from the real
smalt by stirring it in water ; after a few seconds, the
zaffer is precipitated, whilst the smalt remains in sus-
pension in the liquid.
In order to obtain a smalt of a magnificent blue, it
should be prepared with a pure oxide of cobalt. The
ore is finely ground, and treated by boiling nitric acid,
which makes nitrates of cobalt and of iron, and arsenic
acid. The liquor is decanted, diluted with water, and
decomposed by a solution of carbonate of soda. There
is produced a soluble arseniate of soda, and a precipi-
tate of the carbonates of cobalt and iron, which is
collected, carefully washed, dried, and then calcined.
The resulting oxide of cobalt, holding a small propor-
tion of oxide of iron, is mixed with sand and potassa.
The smalts of Saxony, most generally found in the
market, are marked with the following letters, of
which F, M, and O indicate the proportion of cobalt,
and C, CB the degree of fineness of the grain : —
H, Common smalt.
E, Eschel variety.
B, Bohemian smalt.
CF, Fundamental color.
FC, Fine color.
FCB, Fine color from Bohemia.
FE, Fine Eschel.
MC, Medium color.
MCB, Medium color from Bohemia.
ME, Medium Eschel.
OC, Ordinary color.
OCB, Ordinary color from Bohemia.
OE, Ordinary Eschel.
In order to indicate a smalt which contains more
cobalt than F, several F's are added ; thus FFFC is
23
354 MANUFACTURE OP COLORS.
of a higher price than FFC, and this is more valu-
able than FC. On the other hand, if the blue con-
tains less cobalt than OC, ordinary color, a number
is employed ; thus OC2, OC3, indicate that the smalt
contains one-half or one-third of the cobalt of the
ordinary quality.
If azure blue be employed for inside painting, it
has the inconvenience of turning green and black ;
moreover, the difficulty of grinding it fine enough
prevents its employment for artistic painting. Its
principal use is for giving an azure color to signs, for
instance, which are painted with ordinary blue oil
paint, and then dusted over with the smalt. It
changes less in size than in oil, and on that account
is much used in fresco painting. It dries rapidly.
§ 14. Coeruleum.
Coeruleum is a new blue color for oil and water
painting, which is due to the English house of G.
Rowney & Co. It is a light blue, slightly greenish,
and does not appear violet under artificial light. It
covers very well, it is not granular, and is especially
well suited for painting a transparent sky blue.
Cceruleum is not altered by solar light or an im-
pure atmosphere, and caustic alkalies and strong acids
are without action upon it at the ordinary tempera-
ture. According to Mr. S. Bleekrode, it belongs to
the colors with a basis of cobalt oxide, although it is
distinct from the silicate of cobalt and potassa or
soda, as Mr. Ludwig calls smalt blue, or from the
aluminate of cobalt of Gahn, the cobalt ultramarine
of Binder, and the phosphate of alumina and cobalt
of Th&iard.
Coeruleum is entirely soluble in hot hydrochloric
BLUE COLORS. 355
acid, and the light-blue coloration of the solution be-
comes a violet red when it is diluted with water.
The primitive color reappears by concentration, and
the pigment is restored if the solution be evaporated
to dryness. Nitric acid dissolves the cobalt and
leaves a white residue, which is mostly composed of
stannic acid. The green coloration of this solution
shows the presence of a small proportion of iron and
nickel. Concentrated sulphuric acid does not dis-
solve coeruleum ; but the same acid, diluted with 4
volumes of water, produces a partial decomposition.
Acetic acid and caustic potassa do not act upon it at
the temperature of ebullition.
Coeruleum is principally a combination of an oxide
of tin with the oxide of cobalt. The greenish-blue
reaction by which oxide of tin is recognized with the
blowpipe is generally known. Berzelius mentions a
stannate of cobalt, which he prepares by adding a
solution of stannate of potassa to one of cobalt.
The bluish precipitate thus formed becomes of a light-
red color after washing, and then brown. If it be
calcined at a white heat, its color is changed into a
light blue.
The composition of coeruleum is —
Oxide of tin (stannic acid) .... 49.66
Oxide of cobalt 18.66
Sulphate of lime and silica .... 31.68
100.00
The stannate of cobalt of formula SnO2.CoO re-
quires 75 parts of stannic acid, and 37.5 parts of ox-
ide of cobalt ; the ratio is therefore as 2:1. The
formula of coeruleum is, therefore, 3(SnO2.CoO) +
356 MANUFACTURE OF COLORS.
SnO2, that is, a stannate of cobalt mixed with stannic
acid and sulphate of lime.
It is said that there is in the market an imitation
of coaruleum, prepared by mixing French ultramarine
with a small proportion of Naples yellow and white
lead.
§ 15. Litmus.
This coloring1 substance is manufactured in Au-
vergne, Dauphine, Holland, etc., from several lichens,
especially the Variolaria orcina of Achard. The pro-
cess consists in grinding them, and making a paste
with urine and half of their weight of crude potash.
Care is taken to replace the evaporated urine. After
40 days of putrefaction the mixture acquires a purple
color. It is then put into another trough, with urine,
and the blue color is developed. The paste is after-
wards mixed with lime and urine. The last prepara-
tion consists in giving a certain consistency to the
paste, by the addition of carbonate of lime, and
moulding the mixture into small cubes, which are
dried.
Litmus is used only in distemper painting, or for
giving an azure color to ceilings. It is often pre-
ferred for violet and lilac body grounds, on account
of its hue. This color is not durable, and becomes
red by the action of acids. It becomes violet with
glue size, and black with oil.
§ 16. English sky Hue.
Although this blue has little to do with painting,
we think that the two following processes may be
profitably given, since the products are largely used
in the household, and manufacturers of colors should
BLUE COLORS. 357
know how to prepare them. The following formula
has been given by "W. Story: Take a large glass
vessel, or an iron kettle (but in the latter case it is
not necessary to use iron filings), and put into it 1
kilogramme of fine indigo in powder, and 3 kilo-
grammes of sulphuric acid at 66° Be. ; stir, and let
stand for 24 hours, at most.
On the other hand, dissolve 10 kilogrammes of
potash in 20 litres of water, and pour 2 litres of this
solution into the indigo mixture, and stir well. After-
wards add 1 kilogramme of finely-cut blue (Castile)
soap, stir continually, and add the solution of potassa
until the whole appears as a dry powder(?). Pour on
then 1 litre of pure water and the remainder of the
potash solution. Lastly, mix 0.5 kilogramme of finely
powdered alum. After standing for three days, the
mixture is made into balls, which are dried in the air,
and employed for bluing linens.
Balls of Wuy.
Indigo 1 kilogramme.
Sulphuric acid at 67° Be. . . . 6 kilogrammes.
White potash ..... 15 "
White soap ...... 1 kilogramme.
Quicklime ...... 100 grammes.
Common salt 100 "
The powdered indigo is purified in 10 litres of al-
cohol, then in dilute hydrochloric acid, and after
drying in the shade or in a moderately hot stove-room,
is ground again very fine. It is then dissolved in
sulphuric acid, and the solution is poured into a lead-
lined vessel, in which the other ingredients are
added. When the paste is thick enough it is moulded
into balls.
358 MANUFACTURE OF COLORS.
SECTION III.
YELLOW COLORS.
Yellows in general. — Yellow pigments are derived
from many substances, some of them being natural,
and the others artificial products. It is to be re-
gretted that the light and bright tones of yellow are
often wanting in fastness and durability. Iron, anti-
mony, lead, chromium, arsenic, cadmium, and several
vegetable substances, such as weld, quercitron bark,
Persian and Avignon berries, yellow wood, curcuma,
saffron, and ahoua, are the raw materials used at the
present time for the manufacture of yellows. Yellow
ochre, Rut ochre, raw Italian earth, raw Sienna earth,
and Mars yellow are iron compounds. Naples yellow,
mineral yellow, chrome yellow, Cologne yellow, Turner
yellow, mineral gamboge, antimony yellow, orpin,
massicot, etc., are artificial colors manufactured from
antimony, lead, chromium, and arsenic. Lastly,
Avignon berries, terra-merita, saffron yellow, stil de
grain, and weld yellows, those from quercitron bark,
and yellow wood, are extracted from various vegetable
substances.
§ 1. Ochres.
This is the name given to various clays, the paste
of which is more or less fine, smooth, opaque, dull,
easily broken, adhering to the tongue, and, when wet,
emitting a peculiar clayish smell. Those of good
quality are greasy to the touch and are easily ground.
On the other hand, those which are dry and sandy
are more difficult to grind, and are, therefore, less
esteemed.
Ochres are colored brown, yellow, red, and reddish-
YELLOW COLORS. 359
yellow; nevertheless we put them together under
the same head, because, by calcination, they all be-
come red or brown. The good qualities of ochres
are in direct ratio with the number of washings or
float ings they have been submitted to. Their color
is due to the oxides of iron they contain. In fact,
ochres are compounds of clay and oxide of iron.
Yellow ochre, more or less pure, is a true yellow,
but earthy looking. There are many varieties of it,
and it will be sufficient to give as examples the two
following, which are well fitted for painting.
I. Ochre from Saint- Georges-sur-la- Free (Cher).
It is composed of —
Clay 69.5
Peroxide of iron 23.5
Water 7.0
100.0
It is of a handsome yellow, of very fine grain.
II. Ochre from la Berjaterie (Nievre). Its compo-
sition is —
Clay 64.4
Peroxide of iron 26.6
Water 9.0
100.0
Its color is as deep as the preceding one, but not
so finely granulated. Very good ochres are also
extracted from Pourrain, Diges, and Toucy (Yonne).
When yellow ochre is calcined, water escapes, and
the substance becomes red. It is then red ochre.
For removing the water from the hydrated Qxide
of iron, and, at the same time, causing the red colora-
tion to appear, the yellow ochre is broken into small
pieces which are calcined upon a plate of cast-iron,
heated from below. When the substance has ac-
360 MANUFACTURE OF COLORS.
quired the desired tone of color, it is quickly coolecj
by being thrown into water. After several washings
the deposit is dried in the open air. The greater the
proportion of iron, the brighter the ochre; but we
must suppose that the clay contains no organic sub-
stances capable of reducing the metal.
Ochres are not generally sold as they are extracted
from their beds, but are dried in the sun, pulverized,
and sifted to a greater or less degree of fineness as
desired by the trade. For still finer ochres, they are
ground in a mill, and floated in large cisterns. The
longer the time required for the ochre to subside, the
finer its quality. The deposits are collected, dried
in the sun, and sold powdered or in lumps.
It has been attempted to manufacture ochres of
various degrees of fineness, by submitting the powder
to a powerful blast of air in rooms or troughs of great
size. The greater the comminution, the greater the
distance the powder is carried away. By collecting
the products in the order in which they have settled,
we obtain ochres of every degree of fineness.
The yellow ochres are generally sold in powder or
in lumps; but the red ochres, called Prussian red,
brown-red, red earth, and Nuremberg red, are sold
in the powdered state, whereas the retailers deliver
them in the form of paste. It is sufficient to grind
the red ochres with a small proportion of water and
of chloride of calcium. This salt, on account of its
hygrometric properties, maintains a certain dampness
in the paste.
Mr. Cochois calcines his ochres in perfectly tight
ovens, or in closed iron vessels. The product is then
washed for the purpose of removing the foreign sub-
stances. The tones and hues may be varied at will
by calcination.
YELLOW COLORS. 361
Mr. de Rostaing, as we have already seen in the
articles on white lead, has invented a process for
pulverizing fused metals by centrifugal force. With
cast-iron, it seems possible to produce very cheaply
oxides and iron colors for painting. But this process
has not been applied on a large scale.
Pure yellow ochre with glue size, or oil, acquires
the color of gingerbread, and is used for painting
stone floors. Mixed with red ochre and a white pig-
ment, it produces the various tones of wood and stone.
The mixture with black is olive-green.
§ 2. Rut (rivulet) ochre.
This ochre is a hydrate of sesquioxide of iron,
mixed with clay and silica. It is generally found in
the rivulets in the vicinity of iron mines. Its color
is brownish-yellow, and it forms earthy and pulveru-
lent masses. Its tone becomes darker with glue size,
and with oil it resembles chocolate. Mixed with
from 10 to 12 times its own weight of white lead, it
has the color of oak wood.
This ochre is composed of —
Sesquioxide of iron 83
Silica ........ 5
Water 12
100
§ 3. Italian and Sienna earths.
Italian earth resembles in tone of color Rut ochre,
but is brighter. On the other hand, Sienna earth is
neither so bright nor so fast ; indeed it is more easily
changed by many foreign substances. In their raw
state, these earths are brown-yellow with an orange
tinge ; calcined, they are of a fine brown-red. All
362 MANUFACTURE OF COLORS.
these natural raw ochres, used for ordinary and dis-
temper painting, necessitate no other preparation but
their thorough washing and floating in water in order
to allow the foreign substances to settle down and
be separated. The washed pigment is collected upon
paper filters held upon stretched cloths, and when it
has become sufficiently dry, it is formed into troches
which are completely dried upon other gray blotting
papers.
§ 4. Venice red. Antwerp red. Terra rosa.
There are to be found in the trade, under the names
of Venice red, Antwerp red, and terra rosa, other
ochres which have very likely been prepared in the
same manner as ordinary red and yellow ochres.
Venice red is a splendid red ochre which comes
from Italy ; but its preparation and the exact place
from which it is extracted, are not well known.
Antwerp red is a fine ochre which is exported from
Flanders.
Lastly, terra rosa is an Italian ochre, which is lilac-
red when in powder, and deep red when ground in
oil. It would be extensively used in the arts were
it better known, and to be had in larger quantities.
§ 5. Mars yellows.
Whatever be the care taken in the preparation of
ochres, they always have an earthy look, which pre-
vents them from being used in fine painting. The
effort has been made in the arts to manufacture a
product having the same durability as ochres, but
purer, and of a brighter color. The best known pro-
cess for this purpose is that of Mr. Bourgeois, and
is as follows : —
YELLOW COLORS. 363
Sulphate of iron is prepared by dissolving an ex-
cess of clean wrought iron in sulphuric acid diluted
with 4 or 5 parts of water. The crystallized sulphate
is dissolved in pure water, and an equal quantity of a
solution of alum is mixed with it, and poured into a
pine tub to about 1 centimetre above the bottom. The
tub is then filled with pure water which has not been
filtered upon charcoal, because it may contain car-
bonic acid, which will alter the oxide of iron. The
mixture is precipitated by a solution of American
potash. After a thorough stirring and settling for
24 hours, the water is decanted, and the precipitate
collected with a wooden spatula. After draining
upon paper, the deposit is formed into troches, which
are allowed to dry upon blotting paper.
This preparation, which is supposed to be a mix-
ture of hydrated oxide of iron, carbonate of iron, and
alumina in variable proportions, is of a fine gold-
brown yellow. If it be calcined at different tempera-
tures, and under particular conditions which are held
secret, the product is an iron or Mars violet, red,
brown, and orange. It is probable that during these
operations the oxide of iron, mixed with alumina,
becomes more or less peroxidized and dehydrated.
As the Mars yellow is quite expensive, and requires
a great deal of practice for its successful manufac-
ture, the effort has been made to substitute other
preparations for it, such as a mixture of sulphate of
lime and oxide of iron made as follows : —
One kilogramme of protosulphate of iron (green
copperas) is dissolved in 20 litres of water, and into
this solution is poured a sifted milk of lime, prepared
by diluting in 40 litres of cold water one kilogramme
of very white quicklime. A green precipitate is
364 MANUFACTURE OF COLORS.
thus formed, which is washed several times with cold
water, and then exposed to the air. It soon becomes
peroxidized, and acquires a yellow tinge.
A reddish-yellow is also prepared by precipitating
a solution of sulphate of sesquioxide of iron with
carbonate of soda. The deposit of hydrated sesqui-
oxide is washed, but its color is never pure. Part of
the reddish tinge may be removed by adding a small
proportion of alum.
The artificial ochre (oxide of iron and alumina) is
a good substitute for the natural ochres ; it is of a
gold brown-yellow, and, when mixed with white lead,
many tones and hues may be obtained, which are very
fine and durable.
The various tones and hues of natural ochres are
due to foreign matters, which it is very difficult and
expensive to separate. On the contrary, the combina-
tions of Mars yellow with other fast colors allow of
the production of all the desired colors and hues,
which possess great durability.
$ 6. Curcuma or terra merita.
This root is also known under the names of Souchet,
Indian saffron, Curcuma rotunda, and C. long a (Lin.)?
according as it is round or elongated. These two kinds
come from the East Indies, and differ but slightly.
The elongated one is more commonly found in the
trade, and is cylindrical, twisted, nearly as thick as
the little finger, and orange-yellow inside. Its frac-
ture resembles wax, the thin envelope is like shagreen,
its taste is hot and bitter, and the smell is analogous
to that of ginger.
The round curcuma forms ovoid tubercles, nearly
as big as English walnuts, and, when newly gathered,
YELLOW COLORS.
365
united with filaments. The envelope is gray, and
presents many circular rings. The properties of this
curcuma are the same as those of the preceding one.
Berthollet once examined a sample of curcuma from
Tabago, and found it superior to that generally met
in the trade, not only as to the size of its roots, but
also in the greater proportion of its coloring principle.
This substance is of a deep color, and no other
yellow is brighter, but it is not lasting (fast). Com-
mon salt and sal ammoniac are the best mordants to
fix this color, although they darken it towards a
brown. A small proportion of hydrochloric acid is
also recommended. The best roots are very fragrant,
heavy, compact, and saffron-yellow. Their quality is
best judged when fresh and whole, although they are
employed dry and powdered. Painters use curcuma
for painting floors.
From an analysis by Yogel and Pelletier, the com-
position of curcuma is —
Yellow coloring matter, or curcumin,
Brown " "
Substance analogous to extracts,
Lignin,
Amylaceous fecula,
Gum in small proportions,
Bitter and fragrant volatile oil,
Chloride of sodium.
It is with ether that is extracted the neutral sub-
stance of a splendid yellow color, although not very
fast, which is called curcumin.
In order to give more durability and greater depth
to the orange-yellow color of curcuma, it is often
mixed with Avignon berries and carthamus.
366 MANUFACTURE OF COLORS.
§ 7. Stil-de-grain.
Stil-de-grain is a lake prepared with the buckthorn
of the dyers (JRJiamnus infectorius, Lin.), the berries
of which contain a yellow coloring substance, called
rhamnin, which turns deep yellow with alum, and
yellowish-brown with alkaline carbonates.
The berries of the buckthorn which grows at
Avignon, in France, are called Avignon berries even
in Spain and Italy. They are generally preferred on
account of their cheapness, although the proportion
of coloring principle is greater in those grown in the
East, and which are known by the names of Persian
berries, Andrinople berries, Turkey and Morea berries.
These fruits or berries are small, of a yellowish-green,
with two or three united shells or envelopes. Their
smell is strong and nauseous, and their taste bitter
and disagreeable. They blacken by age, and their
quality deteriorates. They are gathered before com-
plete ripeness, and give a fine yellow without fastness.
Stil-de-grain is prepared by boiling for one hour, 1
kilogramme of berries in 8 litres of water, and pass-
ing the decoction through a sieve. The berries re-
maining upon the sieve are again boiled in 4 litres of
water. This second decoction is also passed through
the sieve and mixed with the first. The liquors are
then filtered, and 1 kilogramme of powdered alum
dissolved in them. When cold, the alumina is pre-
cipitated with carbonate of soda, and carries with it
the coloring matter, which will be the darker as less
alum is employed.
Another process. — The berries are gathered before
maturity, then bruised and put into a kettle with 4
to 5 parts of water and \ of alum. The yellow
YELLOW COLORS. 367
liquor obtained after half an hour of ebullition is
filtered and mixed with J to f of a part of very white
and fine chalk, which has been stirred in a small quan-
tity of water and passed through a fine sieve. After
stirring and settling, the liquor is decanted, and the
precipitate is washed and drained upon a frame.
When it has acquired the proper consistency it is
divided into troches which are dried at a low tempera-
ture.
The color which is sold as stil-de-grain is not al-
ways prepared exclusively with Avignon berries ; it
is quite customary to boil the berries with variable
quantities of weld (woad), quercitron bark, curcuma,
yellow wood, etc., and to add to the solution holding
alum, potash, or chalk, until all the coloring principle
is precipitated. In such case proceed as follows : —
Boil 250 grammes of Avignon berries, 250
grammes of curcuma, and 180 grammes of cartha-
mus, in 8 litres of water, and reduce to 6 litres ; re-
move the kettle from the fire, and add 125 grammes
of powdered sulphate of ammonia. The liquor being
filtered through a cloth, and cooled off enough to
allow of the fingers being held in, pour it slowly
upon 1.5 kilogrammes of powdered Paris white,
which is continuously stirred with a spatula.
Then throw the mixture upon a cloth fixed to a
wooden frame, and pour back on top the filtering
liquors until they pass clear and colorless.
The Paris white, which has become yellow upon
the filter, is left there until it has acquired sufficient
consistency to be divided into small lumps, which are
allowed to dry thoroughly.
Stil-de-grain is a fine yellow color, without fast-
ness. It is employed for painting scenery in theatres,
floors, etc.
368 MANUFACTURE OF COLORS.
The coloring matter of Persian berries has been
examined by Mr. Kane, who has extracted by means
of ether a yellow substance called chrysorhamnin.
This by boiling in water becomes oxidized and trans-
formed into xanthorhamnin. Since then Mr. J. Ortlieb,
chemist at Lille, has ascertained that the coloring
principle of Persian berries is held in the state of
glucosides, soluble in water. These glucosides may
be split, either spontaneously or under the influence
of acids, into sugar and coloring substances, which
are — 1. Gold-yellow granules of crystalline appear-
ance, produced in a fermenting decoction, and called
rhamnin; 2. Another coloring matter afterwards
spontaneously deposited, and named hydrate of rham-
nin ; 3. Lastly, a product of transformation by the
aid of sulphuric acid, the hydrate of oxyrhamnin.
There is the same analogy between rhamnin and the
hydrate of oxyrhamnin as between the chrysorhamnin
and the xanthorhamnin of Mr. Kane. Oxyrhamnin
is isomeric with euxantic acid, the coloring principle
of Indian yellow.
§ 8. Weld lake.
Weld or "Woad (reseda luteola) is a plant which
contains several coloring principles in its leaves,
stem, and seeds. Mr. Chevreul gives the name of
luteolin to one of these principles, which is yellow,
bright, and not easily altered by the air or dampness.
It is soluble in water, and becomes under the action
of potassa, soda, ammonia, lime, and baryta, of a
deep-yellow color. Weld is used in the preparation
of a lake, which is a compound of luteolin with
alumina, or of luteolin with lime and alumina.
The weld is cut into small pieces, which are put
YELLOW COLORS. 369
into an enamelled or varnished pot with sufficient
water to cover them. When the water is near the
boiling point, a weight of alum equal to that of the
weld is added and dissolved. After boiling for some
time the liquor is filtered and precipitated with a
solution of potash until the latter begins to dissolve
part of the alumina, which is ascertained when the
effervescence ceases. The whole is then thrown upon
a filter and washed several times with hot water. The
color is put into the shape of troches.
"We find in an English paper the following process
for extracting from weld a pure yellow in impalpable
powder : —
Put about 2 kilogrammes of fine levigated chalk
into a copper kettle with 2 kilogrammes of pure
water. Boil, and stir with a spatula of white wood,
until the chalk is thoroughly tempered. Add then
for each kilogramme of chalk from 180 to 200 grammes
of powdered alum. There is an effervescence pro-
duced, due to the disengagement of carbonic acid,
and the contents of the kettle may run over if the
addition of the alum is not gradual. When no more
carbonic acid escapes, the kettle is removed from the
fire.
Another kettle receives the weld, roots upwards,
and enough water is poured in to cover all the parts
of the plant which hold seeds. A quarter of an
hour's boil is given, and the plants are removed, roots
upwards, to a perforated tub, where they are allowed
to drain. These drainings, mixed with the liquor of
the kettle, are filtered through a funnel, and contain
the coloring material.
There is no practical way of ascertaining exactly the
proportion of weld corresponding to a given weight
24
370 MANUFACTURE OF COLORS.
of chalk, since the quantity of seeds in a package of
weld is variable. But should there be too much
coloring matter prepared, it may be kept without
decomposition, in stoneware or wooden vessels, for
several weeks.
Heat again the kettle holding the aluminous pre-
cipitate, and pour into it the decoction of weld until
the desired tone of color is reached. Then boil for a
few minutes, when the operation is finished. In order
to ascertain that the maximum of color is obtained,
take now and then a small sample of the mixture,
and put it upon a piece of chalk, where it will dry
immediately. If then the pigment be spread with a
brush upon a piece of white paper, it will be easy to
judge of the depth of the color.
The contents of the kettle are poured into a stone-
ware or wooden vessel, where they are allowed to
settle for twenty- four hours. The liquors being de-
canted, the deposit is spread over pieces of chalk, and
dries rapidly.
The decanted liquors may be employed for a second
boiling, adding the water necessary to make up the
bulk. The plant itself may be boiled twice, and there
is a certain saving of coloring matter by so doing.
"We should avoid exposing this coloring substance
to the contact of iron, which acts upon it.
Manufacturers of paper hangings consume the
greater proportion of weld lake, two kinds of which
are to be found in the trade : I. Superfine lake; II.
Lake No. 1. It is to be regretted that this color
is not fast, and on this account it is rarely employed
for oil or water colors.
MM. P. Schutzenberger and A. Paraf have recently
YELLOW COLORS. 371
made the analysis of luteolin, the coloring principle
of weld, and have found its composition to be —
Carbon 62.068
Hydrogen .... 3.448
Oxygen 34.484
100.000
The chemical formula of luteolin, dried at 150° C.,
is, therefore, C24H8O10 ; that of crystallized luteolin
is C24H10O12.HO.
By treating, at 200° C., luteolin with anhydrous
phosphoric acid, we obtain a red substance which
with ammonia makes a violet solution.
When luteolin is heated in sealed tubes with
caustic ammonia, for three or four days, and at the
temperature of 100° C., it becomes entirely dissolved,
and the solution is of a deep-yellow. This liquor,
being evaporated to dryness, leaves a dark residue
called fateofamide, which does not disengage am-
monia by a treatment with caustic lime. On the other
hand, it produces ammonia with caustic potassa.
§ 9. Lakes of quercitron and yellow wood.
Quercitron, such as is found in the trade, is a fawn-
colored powder mixed with fibrous portions, ground
from the bark of an American oak (quercus nigrd).
This bark contains a yellow principle called querci-
trin, which, viewed with a magnifying glass, appears
of a light and slightly grayish-yellow. Alum- water
changes it to a fine yellow. By processes similar to
those employed with weld, it is possible to obtain
from quercitron a lake, which is not, however, so
handsome as that made from weld.
Yellow wood (Morus tinctorid) contains a coloring
372 MANUFACTURE OF COLORS.
principle called, by Mr. Chevreul, morin. Alum,
with a decoction of yellow wood, furnishes a canary-
yellow precipitate. This wood may, therefore, be
employed for the preparation of a yellow lake, which,
however, in beauty and durability, is inferior to that
of weld.
We shall examine, further on, new processes for the
manufacture of vegetable lakes of a red color, and
which may be applied to the preparation of yellow
ones.
§ 10. Chrome yellows.
Chemistry and the arts are indebted to Vauqueliii
for the discovery of chromium, a peculiar metal which
he found, in 1797, in a sample of Siberian red lead
(chromate of lead). Vauquelin distinguished in the
new metal the remarkable coloring power of its com-
binations ; indeed, the name which he chose means
color. Among the combinations of chromium those
most employed in the arts are the chromates of lead,
lime, and baryta. The neutral chromate of lead is of
a very fine and bright yellow, which is used for
printing on cloths and on porcelain, for paper hangings,
and for house and carriage painting. All the other
chromates have different colors, and Thenard believes
that several of them will be employed for various
colors and hues which cannot be obtained from other
substances.
Since all the other chromates are prepared with
chromate of potassa, we think it desirable that we
should endeavor to cause its preparation to become
well known.
One of the processes for the manufacture of this
salt consists in calcining at a high temperature a
mixture of nitrate of potassa and chrome ore, the
YELLOW COLORS. 373
latter being a compound of the oxides of chromium
and iron, with some silica, alumina, and magnesia.
The proportion of nitre is one-half, or, at most, two-
thirds of the weight of the chrome ore when it is very
hard. Should too great an excess of nitre be present,
the earthy substances would be corroded by the alkali
of the nitrate, and the chromate be rendered impure.
The oxygen, disengaged from the nitre by heat,
oxidizes the iron and acidifies the chromium. The
chromate of potassa is freely soluble in water, and is
separated by washing the calcined residuum. The
insoluble portions still contain a certain proportion
of undecomposed chrome ore.
Chromate of potassa is of a fine lemon-yellow color,
crystallizes in prisms, and is composed of —
Chromic acid . . . . .100
Potassa 92.307
It is also known under the names of neutral chro-
mate and yellow chromate of potash. There is another
well-known salt, the bichromate of potassa, or acid
chromate, which is of a handsome red color, and
crystallizes in quadrangular prisms. It is less soluble
in water than the neutral chromate, and contains
twice as much coloring substance (chromic acid).
Its composition is —
Chromic acid ..... 100
Potassa 46.153
1 . Neutral Chromate of Lead.
A neutral chromate of lead, of a very rich tone,
will be obtained by dissolving, for instance, 10 kilo-
grammes of neutral chromate of potassa in 100 litres
of hot water. "We also dissolve in another vessel, 20
kilogrammes of neutral acetate of lead (sugar of lead)
in 50 litres of water. When the solution of chromate
374 MANUFACTURE OF COLORS.
of potassa is boiling, we carefully pour into it that of
acetate of lead, and allow the precipitate to settle.
This latter is washed several times by decantation,
drained upon cloth filters, and dried in a stove-room.
There should remain a small excess of chromate of
potassa in the liquor, in order to prevent the forma-
tion of a basic chromate of lead, which will impair the
light yellow of the neutral chromate.
If we substitute nitrate of lead for the acetate, the
product will be still brighter. The proportions will
then be, forty-two parts of nitrate of lead, and nine-
teen parts of bichromate of potassa. The composition
of the neutral yellow chromate of lead is —
Chromic acid ....... 31. Yl
Oxide of lead 68.29
100.00
Baron Liebig has indicated another process for the
manufacture of a very dense neutral chromate of
lead : —
The sulphate of lead, left as a cheap secondary pro-
duct in dye works, is digested and stirred in a warm
solution of neutral chromate of potassa. A double
decomposition takes place, by which a soluble sulphate
of potassa and an insoluble chromate of lead are
formed. The liquors are decanted, and the precipi-
tate is washed, drained, divided into square prisms,
and dried in a stove-room at the temperature of 50° C.
This chromate is cheaper, and quite as fine as the
preceding one, although it is more dense and does
not cover so well. It generally contains a certain
proportion of undecomposed sulphate of lead.
Neutral chromate of lead possesses great body,
and a fine yellow color, the tones of which vary con-
YELLOW COLORS. 375
siderably with different manufacturers. It can be
had from a light yellow to an orange-red, and these
differences are due to the mode of preparation.
2. Basic Chromate of Lead.
This yellow, known in the trade under the names
of gold yellow or orange paste, possesses a reddish-
yellow hue, which is quite pleasing. It is a combina-
tion of chromic acid with more oxide of lead than
is contained in the neutral chromate.
The most economical process for preparing this
basic chromate or chrome yellow consists in boiling,
for one hour at most, fifteen parts of chromate of lead
with two parts of caustic lime fused in a small pro-
portion of water. By the reaction which takes place,
a soluble chromate of lime is formed, and the remain-
ing basic chromate of lead is washed, drained, dried,
and heated in a crucible until the desired hue is
obtained.
We may also treat three parts of neutral chromate
of lead by two parts of oxide of lead. Or, a solution
of acetate of lead may be poured into another boiling
solution of chromate of potassa, holding an excess of
caustic potassa or soda. The precipitate resembles
vermilion.
A basic chromate of lead is prepared by boiling,
for several hours, equal weights of white lead and
chromate of potassa. There is formed a soluble
carbonate of potassa, and a basic chromate of lead,
which is heated in a crucible until it acquires a scarlet
color.
Lastly, if we melt in a crucible nitrate of potassa,
and add dry and powdered chromate of lead by small
quantities at a time, there is a production of red
376 MANUFACTURE OF COLORS.
nitrous fumes, of chromate of potassa, and of basic
chromate of lead, which latter sinks to the bottom.
The chromate of potassa is poured out while it is still
hot, and the crucible is left to cool off. The chromate
of lead is removed, washed several times, drained,
and dried in a stove-room. Its color is cinnabar red.
The trade furnishes a quantity of basic chromates
of lead, with hues varying from a reddish-yellow to a
vermilion-red.
Mr. Merimee asserts that alumina, added to inferior
qualities of chromates, preserves their brightness.
It is probable that the variations in hue and tone
are often due to small proportions of sulphate of lead,
and of chromates of lime, baryta, and alumina, almost
always found in chromates of lead.
3. Jonquil Chrome Yellow of Winter/eld.
The jonquil chrome yellow of Mr. Winterfeld is a
basic chromate of lead which is not calcined. There-
fore, the oxide of lead is hydrated. It is prepared as
follows : —
Dissolve 33 parts of acetate of lead in 100 parts of
pure water, and filter. The clear liquor is kept in a
vessel of sufficient capacity to hold about twice that
volume of liquid.
In another vessel dissolve 22 parts of crystallized
carbonate of soda in 60 parts of pure water, and filter.
The soda solution is then slowly poured, stirring
all the while, into that of acetate of lead, and there
results a white precipitate which is allowed to settle.
The supernatant liquor is a solution of acetate of
soda.
During these operations, another solution has been
prepared with 17.15 parts of neutral chromate of
YELLOW COLORS. 377
potassa in 50 parts of water. It is poured upon the
precipitate of carbonate of lead, and the stirring is
continued until all of the chromate of potassa is
decomposed, that is,- until the clear liquor is no longer
colored yellow.
The chrome yellow thus obtained is washed with
pure water, drained upon a filter, pressed, and then
cut into blocks and dried. The product is 27 parts
of chrome yellow, from the proportions indicated
above.
The jonquil chrome yellow of Winterfeld is the
lighter in color, as the proportion of acetate of lead
is greater.
4. Cologne Yellow.
This yellow is obtained by decomposing sulphate
of lime and chromate of lead with a solution of soda.
Another way is to have very finely powdered
•sulphate of lime kept floating in a solution of chro-
mate of potassa, and to precipitate with neutral ace-
tate of lead.
This color is very bright and fast, and is used for
distemper painting. It is a compound of chrome
yellow with the sulphates of lime and lead.
Troches of this yellow, analyzed by Mr. Boutron-
Chartard, had the following composition : —
Sulphate of lime 60
Sulphate of lead ....... 15
Chromate of lead . . . . . . .25
100
Chrome yellows are in great demand for oil paint-
ing, on account of their brightness and durability.
Moreover, mixed with vermilion, they give chamois
hues ; with white lead, straw yellow and jonquil ;
378 MANUFACTURE OF COLORS.
with Prussian blue, magnificent greens, which are
not, however, lasting.
Since these pigments possess great intensity or
coloring power, they are often adulterated with sul-
phate of lime, chalk, white lead, sulphate of lead,
starch, etc. Several of these substances, however,
cannot be considered as fraudulent mixtures because
they result from the mode of preparation itself, or
have been added to arrive at a desired tone of color.
Nevertheless, as the manipulations necessary for
ascertaining the foreign substances are quite com-
plicated, we advise the consumer not to make the
analysis himself, but to entrust it to the hands of an
experienced chemist.
5. Chromate of Lime.
If we pour chromate of potassa into a solution oi
chloride of calcium, nitrate of lime, or other solubli
lime salt, we obtain a precipitate of chromate of lim<
which is of a fine straw-yellow color, and is used i]
distemper painting. Its covering power is small, bul
it does not blacken like the chromates of lead.
In the manufacture of chromate of lime the solu-
tions employed are — one of bichromate of potass
saturated with carbonate of soda, and one of chloride
of calcium obtained by dissolving chalk in hydr
chloric acid. The latter solution is slowly poured
into the former, and the precipitate of chromate of
lime is allowed to settle and is then drained, washed,
and dried.
6. Chromate of Baryta.
A solution of bichromate of potassa is saturated
with carbonate of soda, and, after evaporation and
cooling, a double chromate of potassa and soda is
YELLOW COLORS. 379
obtained. On the other hand, carbonate of baryta is
dissolved in hydrochloric acid, and the chloride of
barium is made to crystallize. Two separate solu-
tions are effected, one with 25 parts of the double
chroraate, and the other with 20 parts of chloride of
barium ; these are mixed cold, or better still, hot, and
are kept well stirred. The precipitate is a fine lemon-
yellow chromate of baryta.
This pigment is employed in the manufacture of
paper hangings, and for adulterating chrome-yellows.
It is open to the objection of darkening in the air,
and is sometimes improperly called ultramarine yellow.
We shall again examine the chromate of baryta fur-
ther on.
We now introduce an extract from a memoir pub-
lished by Mr. Habich in the Technologiste, vol. xviii.
page 171, upon the manufacture of the neutral chrome
yellow, the red or basic chromate, and the chrome
green.
A. Chrome Yellow.
The manufacturers of chrome yellow, who distin-
guish themselves by the beauty of their products and
by their skill in obtaining a given hue, says Mr.
Habich, employ soluble lead salts. It is true that
the sulphate of lead, obtained in large quantities in
dye works, gives a cheaper chrome yellow ; but its
hue is not constantly the same, and it is far inferior
in depth and brightness of color to other chrome
yellows prepared by other processes. On the other
hand, it t appears to suit very well for certain green
colors obtained by mixture, such as the green cinna-
bar, the chrome green, etc.
We have first to explain how to prepare a solution
of lead.
380 MANUFACTURE OF COLORS.
Small wooden tubs, 45 to 50 centimetres high and
1 metre in diameter, are disposed one on top of the
other, so that their contents may pass through a
spigot at the bottom into the lower ones. Four such
tubs are sufficient for the apparatus.
These tubs are filled with thin ribbons of lead
prepared as follows: The molten lead is slowly
poured, by means of an iron ladle, into water which is
kept stirred with a broom. Practice will soon teach
how to arrive at the greatest thinness of metal, the
main points being to ascertain the proper height of
the ladle above the surface of the water and the
thickness of the stream of molten lead.
When all the tubs are charged with lead the spig-
ots are closed, and the upper tub is filled with strong
alcohol vinegar, which should be, as far as practicable,
free from the coloring and extractive matters, gum,
sugar, etc. After a few minutes the spigot ii
opened in order to allow the liquor to run into th<
second tub, and afterwards into the third and th<
fourth. This first passage of the vinegar througl
these tubs dissolves but a slight proportion of lea<
Indeed, this first operation simply consists ii
thoroughly wetting the metal, and aiding its furthei
oxidation, which is seen to progress favorably whei
the lead becomes covered with a bluish-white pellicle.
For dissolving the oxide of lead formed the first tul
is again filled with vinegar. After half an hour thi
liquor of the first tub is emptied into the second, an<
so on until the solution is saturated with lead. It if
then collected in a larger tub below. When th<
oxidation of the lead goes on rapidly, the saturate
liquor contains a basic acetate of lead, which,
exposure to the carbonic acid of the air, is soon
YELLOW COLORS. 381
covered with a white film of carbonate of lead. For
the manufacture of chrome yellow enough acetic acid
is added to this solution for slightly reddening blue
litmus paper. The liquor is then put into large
settling tanks for the deposition of the impurities,
and there should always be a good supply of it at hand.
Another tank also contains a stock of a solution of
bichromate of potassa prepared as follows : 25 kilo-
grammes of this salt are dissolved in ten times their
weight of hot water, in a copper kettle, and then
poured into the tank with enough water to make
about 5 hectolitres. Altogether 20 parts of water to
1 of bichromate of potassa.
In order to operate rapidly and with certainty, the
following articles are needed : 1, a tub of white
pine, 1.25 metres high, and of equal diameter, with
several holes at different heights, and closed with
plugs ; 2, a small wooden tub, holding about 2 hecto-
litres, and provided with a spigot near the bottom ;
3, two pails, holding each from 10 to 12 litres ; 4, a
graduated tube ; 5, a barrel covered with a filter ; 6,
a wooden platform or tray edged all round.
Before beginning the operation it is necessary to
ascertain the degree of concentration of the lead
liquor, which depends on the very variable strength
of the vinegar employed. Experimental tests . are
therefore applied, in order to ascertain how many
volumes of the solution of lead are necessary to
saturate ten volumes of the chromic solution, that is,
to obtain after precipitation a liquor holding neither
oxide of lead nor chromic acid.
Ten volumes of the solution of bichromate of
potassa are measured in the graduated tube, and then
poured into a tumbler, which also receives the water
382 MANUFACTURE OF COLORS.
with which the tube is rinsed. The same tube is now
filled with the lead solution, and the volume noted.
It remains now to let the lead liquor fall into that of
bichromate, drop by drop, as long as a precipitate
takes place. The volume of lead solution poured out
is marked down, and indicates the number of volumes
of the stock of lead solution necessary to precipitate
ten volumes of the liquor of bichromate.
For obtaining the various hues of chrome yellow
there are several methods, which are based upon the
chemical composition of the different yellows obtained
from chromium. These compositions should there-
fore be carefully studied if we desire to operate witl
certainty.
When we precipitate a solution of lead by one
red bichromate (acid) or of yellow chromate (neutral
of potassa, the dark lemon-yellow precipitate is, ii
either case, a neutral chromate of lead, which has the
same composition, that is, 112 parts of oxide of
to 52 parts of chromic acid.
There is another combination called chrome red,
and we shall see its preparation further on. It con-
tains but one-half of the chromic acid of the neuti
chromate, that is, 26 parts of acid to 112 parts of oxide
of lead. If the chromic solution holds a certain quan-
tity of free alkali, the latter separates from the
solution a proportional amount of oxide of lead,
which, mixing with chromate of lead, colors it red.
If, therefore, we are enabled to prepare the mixtures
with accuracy, it will be possible to produce all the
desired tones and hues ranging from dark lemon-
yellow to chrome-red. The process consists in adding
a caustic lye of known strength to the washed pre-
cipitate of neutral chromate.
YELLOW COLORS. 383
There are two double combinations of neutral chro-
mate with sulphate of lead (Cologne-yellow) corres-
ponding with the formulae PbO.CrO3 + PbO.SO3 and
PbO.OO3+2PbO.SO3. The first takes place when a
corresponding proportion ©f sulphuric acid is added to
the chromic solution employed for precipitating the
lead liquor. A solution, prepared as we have previously
said, holds 2.6 kilogrammes of chromic acid per hecto-
litre, and requires 1.82 kilogramme of concentrated
sulphuric acid. The precipitate, formed and collected
upon a filter, increases in volume considerably. After
drying, it is a very light pigment of a light lemon-
yellow color, which is remarkably fine.
The second combination takes place when the pro-
portion of sulphuric acid is 3.65 kilogrammes per
hectolitre of chromic solution. It does not increase
in volume as does the former article, but, after drying,
the pigment is of a sulphur color, with a smooth
fracture.
The first combination is employed especially for
preparing ordinary chrome yellows, mixed with the
sulphates of baryta, lime, etc., and is remarkable for
its covering power. The second combination is par-
ticularly suitable for the bright greens resulting from
the mixture of Prussian blue with chrome yellow.
Since the tones of color of these two combinations
are so different, it is evident that by varying the pro-
portion of sulphuric acid, it will be possible to obtain
all the intermediate tones between light lemon yellow
and sulphur yellow.
The success in the preparation of certain chrome
yellows often depends upon the mode of working,
which I shall now indicate.
For preparing the combination PbO.CrO3 + PbO.
384 MANUFACTURE OF COLORS.
SO3, a tub is filled to two-thirds of its capacity with
water, and then with the quantity of lead liquor neces-
sary for decomposing 125 litres of chromic solution
holding 6.25 kilogrammes of bichromate of potassa.
This quantity of chromic solution is held in the small
tub, and is mixed with 3.25 kilogrammes of sulphuric
acid. This mixture is then allowed to run slowly into
the lead solution, which is kept constantly stirred.
After settling, the supernatant liquor, rich in acetic
acid, is decanted, and the deposit is twice washed with
water in the tub, before it is collected and drained upon
a cloth. As soon as drained, the pulp is spread upon a
wooden tray. These operations of washing and drain-
ing should be effected as rapidly as possible, in order
that the pulp shall not swell on the cloth, but on the
tray. Indeed, should the swelling take place upon
the cloth, the pulp would become denser when spread
upon the tray, and would thus lose a portion of that
lightness which is so much sought for in it. When
everything goes on without loss of time, the pulp is
spread upon the trays, which are deposited in a cool
place as long as the swelling continues, and until th<
paste has acquired consistency. The mass is then
cut into large cubes, which are dried in the sun.
Their crust is generally disfigured by the crystalliza-
tion of a certain proportion of undecomposed chromate
of potassa, which cannot be removed by the most
thorough washing. This is made to disappear by
means of a brush, taking care not to inhale the flying
dust. The sweepings are kept for an inferior quality
of yellow, or for the preparation of green cinnabai
(chrome green).
The second sulphur yellow combination is obtain*
in the same manner, only that the proportion of sul-
YELLOW COLORS. 385
phuric acid is double, that is, 6.5 kilogrammes per
125 litres of chromic liquor. The precipitate is rap-
idly washed, filtered, drained, and pressed. The cut
blocks are dried in the shade in a well-ventilated
room. If all these operations are not effected rapidly,
it may happen that a slight admixture of the first com-
bination will cause the pigment to swell up, and thus
destroy the smooth and even fracture required by the
trade.
B. Chrome Red or Basic Chromate.
Chrome red is another color, the preparation of
which is nearly related to that of chrome yellow.
All the chrome reds, from the darkest cinnabar red
to a minium red without lustre, are simply distin-
guished by the size of the crystals of their powder,
and the observation may easily be made with a micro-
scope. If various chrome reds of the same hue, but
with different intensities of color, are reduced by
grinding to the same degree of comminution, their
powder will then possess the same intensity of color-
ation, but the brightness disappears.
Therefore, if chrome reds are desired very bright
and intense in color, we should search for the condi-
tions which aid in the formation of the crystals. One
of the best processes consists in avoiding all agita-
tion, which may prevent the formation of crystals or
destroy them.
I recommend in that respect, the following method:
Chrome yellow is precipitated in the usual manner,
without sulphuric acid, and is washed carefully.
After draining, the mass is well stirred, and six or
eight equal samples are taken from it and put into
glass vessels of the same size and thickness of
25
386 MANUFACTURE OF COLORS.
material. Each sample receives a different volume of
a caustic lye of potassa or soda, marking about 20°
Be. For instance, to 5 volumes of paste we add 2,
2|, 3, 3|, 4, 5, etc. volumes of lye. The different mix-
tures are thoroughly and rapidly stirred, but the
chemical reaction is allowed to take place without
any disturbance. After examination of the quality
of the products, the relative proportions of pulp and
lye* are noted down for the best hues of color. If
there be a stock of lye of known strength, this experi-
ment is sufficient to reproduce on a large scale the
desired color.
The operation is then performed in a large tub,
which receives the mixture of pulp and caustic lye in
the proportions previously found. The changes in
the color are soon perceived, and the reaction requires
about twelve hours. After that length of time, the
lye which has appropriated a great deal of chromic
acid is decanted. The pigment is carefully washe<
with pure water once in the tub, and the mass ii
gently stirred. The washing is continued upon th<
filters, by throwing water upon the pulp, and in thii
mariner there is less friction between the crystal)
which retain their deep color.
It is well understood that a very dark chrome red,
which is highly crystalline, is not expected to possess
great covering power.
C. Greens by Mixtures (Cinnabar Green, Chrome Green).
This branch of the manufacture of colors presents
but few interesting facts.
* Too considerable a proportion of caustic lye will fail to deepen
the red color. Indeed, chrome red is entirely soluble in an excess
of lye, and forms needle-like crystals, holding potassa, when the
caustic solution has absorbed carbonic acid from the air.
YELLOW COLORS. 387
Many manufacturers have tried, without success,
to prepare a fine chrome green having a smooth
fracture, by mixing Paris blue with pure chrome
yellow. A good product will be obtained if a light
chrome yellow with smooth fracture be employed, and
if the mixture be compressed immediately after the
addition of the blue.
A chrome green, with smooth fracture, may be
prepared by an admixture of recently precipitated
hydrate of alumina. A solution of 12 kilogrammes
of alum (free from iron) in hot water, is decomposed
by a clear lye of soda. The precipitate is washed and
mixed with about 5 kilogrammes of finely ground
sulphate of lime, 7 hectolitres of the above indicated
chrome solution, and the required proportion of Prus-
sian blue. The lead solution is then added.
For the manufacture of green cinnabar it is important
to add a small proportion of indigo carmine, which
gives great brightness and a bluish tinge. This is the
best method for preparing that bright pigment called
silky green or seiden grim ; and in the manufacture
of fancy papers, it has been customary fora long time,
to increase the brightness of the coats of green cin-
nabar with a final coat of a solution of indigo carmine.
§ 11. Various chromates.
Chromate of zinc was first proposed as a yellow
pigment by MM. Leclaire and Barruel. They gave
it the name of butter cup (bouton d'or) yelloiv, and
thus describe its preparation in the patent they have
conjointly taken out : —
388 MANUFACTURE OF COLORS.
1. Ghr ornate of Zinc.
" The chromate of zinc is a salt of which little is
known. Yery few authors mention it, and they do
not agree as to its physical properties.
"From our researches, trials, and experiments, we
have determined upon the following processes for pre-
paring this salt : —
" 1. The employment of a double salt of potassa
and soda, that is, a double chromate of potassa and
soda.
"2. The employment of a sulphate of zinc pre-
viously deprived of iron or copper salts, and made
sufficiently neutral by ammonia, or better still, by
carbonate of soda.
" 3. The neutralization of the mother liquors and
of the first washings of the chromate of zinc, by the
carbonate of soda. This operation is necessary for
finishing the preparation of the chromate.
" 4. Utilizing the washings of the chromate of zinc
for the production of a green which is fast and un-
alterable, by making sulphuretted hydrogen or sulphur
act upon these hot mother liquors.
" We make upon a sand bath, and in stoneware
vessels, a peculiar solution of a neutral chromate of
soda and potassa.
" We should observe that this neutral chromate of
soda and potassa is chosen on account of the economy
in its manufacture. Indeed, the neutral chromate of^
potassa is more expensive than our double chromate,
or than the bichromate of potassa, with which we
prepare our double chromate by the following
formula : —
" We take 100 kilogrammes of bichromate of po-
YELLOW COLORS. 389
tassa, which we powder and dissolve in hot water.
We then add, by portions at a time, 95 kilogrammes
of crystallized carbonate of soda, which is the equiva-
lent proportion for obtaining a neutral double chro-
mate of potassa and soda. The commercial sulphate
of zinc is dissolved in three times its weight of water,
in stoneware jars placed upon a sand bath. A stream
of chlorine is then passed through the hot solution,
and peroxidizes the iron salt present. There is also
sometimes a certain proportion of sulphate of copper.
When the solution has become turbid from a yellow
and flaky precipitate of subsulphate of sesquioxide of
iron, the stream of chlorine is interrupted, and a slight
excess of oxide of zinc is added (about 5 per cent, of
the sulphate of zinc).
"The liquor is made to boil, and the oxide of zinc
takes the place of the copper and iron, which are pre-
cipitated. An equivalent proportion of sulphate of
zinc is thus formed. As a test, a small quantity of
the liquor is filtered, and a few drops of a solution of
yellow prussiate of potassa are added to it. If the
precipitate be white, there is enough of oxide of zinc;
on the other hand, a precipitate which becomes bluish
by the contact of the air shows the presence of iron,
and the liquor is to be boiled again with a fresh addi-
tion of oxide of zinc.
" After ascertaining that the liquor no longer con-
tains iron or copper, it is filtered into tubs having
holes at different heights. Ammonia, or better still,
carbonate of soda, is added until there is formed a
slight precipitate of oxide or carbonate of zinc. This
operation is absolutely necessary if we desire to obtain
pulverulent chromate of zinc, of a fine yellow color,
and if the mother liquor is to hold a minimum quan-
390 MANUFACTURE OF COLORS.
tity of chromate of zinc and potassa. "Without this
precaution, and since the sulphate of zinc is always
acid, there is formed a bichromate of potassa which
does not react upon the sulphate of zinc.
" The proportions which we find to be the best in
the preparation of the chromate of zinc are : —
"For the above indicated quantity of chromate of
soda and potassa, we need 184.5 kilogrammes of sul-
phate of zinc. It is not possible to set down in ad-
vance the proportions of ammonia or carbonate of
soda ; they are added until there is formed a precipi-
tate of oxide or of carbonate of zinc.
"The solution of double chromate is poured into
that of zinc, as long as a precipitate takes place, and
the mixture is kept stirred with a wooden board.
After settling, the liquor is decanted and is quite
yellow. It is then evaporated to about one-third of
its former bulk, and saturated with 35.35 kilogrammes
of soda crystals. A new quantity of chromate of
zinc is obtained. The supernatant liquors are still
colored yellow, and saved for a purpose which we
shall indicate further on.
"The chromate of zinc is washed two or three
times in the tubs, by decantation, and with pure
water or rain water. The washings are mixed with
the previously saved mother liquors. The clear paste
of chromate of zinc is drained upon cloth filters, and
is there washed two or three times. "When it has
acquired the proper consistency it is moulded into
the shape of troches, which are dried in a stove-room.
" The washings and mother liquors are heated and
treated with hydrosulphuric acid, which decomposes
the chromates of potassa and zinc held in solution.
There is produced a precipitate which is a compound
YELLOW COLORS. 391
of hydrated oxide of chrome, and of oxide and sul-
phide of zinc. This compound may be used in paint-
ing as a very fast and durable pigment ; but its
nature and hue may be changed by a calcination and
washing.
" This product may be obtained directly in the an-
hydrous state by evaporating the liquors to dryness,
powdering the residuum, mixing it with 18 per cent,
of sublimed sulphur, and calcining the mixture until
the sulphur is volatilized. The hot substance is then
thrown into water, and the anhydrous pigment is
collected upon a filter.
" The neutral chromate of potassa and soda may
be replaced by the neutral chromate of soda, which
is prepared by the calcination of chrome ore with
nitrate of soda.*
2. Chromate of Baryta.
" Basing ourselves upon the processes which we
* Mr. R. Wagner has made the analysis of several samples of
chromate of zinc, and reports them as follows in his annual of
technological chemistry (1861) : —
Zinc yellow from England —
Chromic acid 14.94
Oxide of zinc ..*... 75.35
Carbonic acid '3.61
Water 6.19
100.09
The zinc yellows prepared in Germany are generally adulterated
with the carbonate or the sulphate of baryta, as is demonstrated
by the following analyses : —
a. b.
Chromic acid 11.88 9.21
Oxide of zinc 45.78 61.47
Sulphate of baryta .... 42.34 29.32
100.00 100.00
392 MANUFACTURE OF COLORS.
have indicated for the manufacture of the chromate
of zinc, and procuring a chloride of barium free from
iron, and the neutral chromate of potassa and soda,
we employ the following formula : —
" 100 kilogrammes of chloride of barium are pre-
cipitated by 82 to 84 kilogrammes of neutral chro-
mate of potassa and soda. The product is washed
by decantation, and dried in a stove-room.
" Such is the process by which we have been en-
abled to produce, in an economical manner, the chro-
mate of baryta which up to the present day had re-
mained a product of the experimental laboratory.
3. Orange-red Sulphide of Antimony.
" The preparation of this sulphide, by the processes
which we are going to describe, results in a color not
yet employed in painting, and which is not altered by
dampness, light, or sulphuretted hydrogen. This
product and its mode of preparation are new, and are
a valuable addition to the new system of painting
with zinc pigments.
" One part of natural sulphide of antimony is
powdered and dissolved with the aid of heat, in seven
parts of hydrochloric acid at 20° Be., which should
be chosen free from lead. The sulphuretted hydrogen
disengaged from the first operation is condensed in a
milk of lime ; that of subsequent operations is em-
ployed for preparing the sulphide of antimony as
follows : —
"When all the sulphide is dissolved, the solution
of acid chloride of antimony is decanted into ston<
ware vessels which have holes at different heights.
The liquor is diluted with pure water until it begins
to become turbid, and a white precipitate appears,
YELLOW COLORS. 393
The whole is then put into demijohns and submitted
to a stream of sulphuretted hydrogen.
" We must not forget to mention that the glass
tubes dipping into the antimonial solution should be
large, so as not to be obstructed by the red sulphide
of antimony, formed by the reaction of the sul-
phuretted hydrogen with the acid chloride of anti-
mony. The liquor should be stirred often with a
wooden stick, and the vases covered or communi-
cating several together, in order not to lose the sul-
phuretted hydrogen, which may injure the workmen.
On that account the last tubes dip into a milk of
lime which condenses the excess of gas. The stream
of sulphuretted hydrogen is arrested when the satu-
ration is complete, and the precipitate is allowed to
settle. The deposit of sulphide of antimony is
washed several times by decantation, poured upon
filters, and again washed until the water runs without
taste. The pigment is then dried in the stove-room
at a moderate temperature, which should not be above
40° to 50°, otherwise the sulphide will lose its com-
bined water and turn black.
"This mode of preparing the hydrated sulphide of
antimony is a new process of manufacture, since no
practical indication of the same is to be found in
works on chemistry.
4. Mixed or Compound Colors.
« We give this name to pigments of different tones
and hues obtained by the combination or mixture of
the colors here described with other usual colors, ex-
cepting those with a lead or a copper basis.
" We understand that with the chromate and the
oxide of zinc, with the chromate of baryta and the red
394 MANUFACTURE OF COLORS.
sulphide of antimony, mixed or combined with other
usual colors, it is possible to obtain a great many vari-
eties of tones and hues which will not be acted upon
by sulphuretted hydrogen. We cannot here give a
complete nomenclature ; we shall, however, mention
the following yellows : Roman yellow, bright yellow,
antimony yellow, Mars yellow, Indian yellow, Naples
yellow, mineral yellow, and several chrome yellows.
" All of these colors may be obtained by the com-
bination of our new products, and in certain cases
with the aid of raw Sienna.
" The greens known under the names of dark Eng-
lish green, light English green, Milori green, greei
earth, and verdigris, are prepared in the same manner
as the yellows, and with the addition of a greater 01
less proportion of blue.
" The colors are mixed either in the pasty state and
before being dried, or after they have been ground.
' We see that the principle of these compound
colors consists in the mixture of zinc white with the
new colors we have just described, or with other
usual colors which are not altered by sulphurette<
hydrogen. We also arrive at tones and hues whicl
formerly could not be obtained without the use oJ
pigments with bases of lead and copper, so easil;
acted upon by certain destructive agents.
"In a preceding description of the yellow chro-
mate of zinc, we said that it was obtained by th<
reaction of a neutral chromate of potassa and soda
upon a pure and neutral sulphate of zinc. The fol-
lowing are new processes for the manufacture of
basic chromate of zinc.
" About 50 kilogrammes of pure oxide of zinc an
thrown into a solution of 100 kilogrammes of bi-
YELLOW COLORS. 395
chromate of potassa in 400 kilogrammes of hot water.
After boiling, the liquor is left to cool off, and, after
decantation, the precipitate is washed and dried.
5. Lemon Yellow.
" The above decanted liquors and washings are
evaporated to two-thirds of their bulk, and receive a
solution of sulphate or of any other soluble salt of
zinc, in proportion variable with the tone desired.
The precipitate, after decanting, is washed, etc.
6. Pale Yellow.
" In order to utilize all the raw materials, the liquors
from the above operation are saved and boiled with a
sulphate of zinc, prepared with 15 kilogrammes of
zinc oxide and 7 kilogrammes of commercial sul-
phuric acid. The precipitate is treated as usual.
" We have also said that compound greens were
prepared by the action of sulphuretted hydrogen or
sulphur upon the chromate of zinc remaining soluble
in the mother liquors and washings ; and that various
tones and hues were obtained by adding to the chro-
mate of zinc a greater or a less proportion of blue.
"We also state that these greens may be obtained
from a solution of chloride of zinc to which is added
a suitable quantity of blue liquid or paste, or the ma-
terials forming Prussian blue. In this manner the
green is directly obtained."
§ 12. Basic chromate of tin, mineral lake.
Mineral lake, which is a combination of chromic
acid with the oxide of tin, possesses a fine lilac color,
and is sought for as a substitute for vegetable lakes
in the fabrication of paper hangings and for oil
painting.
396 MANUFACTURE OF COLORS.
This lake is prepared by dissolving the neutral
chromate of potassa in five or six times its weight of
water, and pouring into it a solution of bichloride of
tin as long as a precipitate is formed, which is after-
wards washed and collected upon a filter. When the
chromate of tin is well drained, but still wet, it is
ground with half of its volume of nitrate of potassa,
and the whole is allowed to dry. The mass is th<
finely pulverized and thrown by small quantities at
a time into a crucible brought to a low red heat, and
which holds already some nitrate of potassa. When
the decomposition is complete, the crucible is removed
from the fire, and left to stand a little while. The
supernatant liquid nitrate of potassa is decanted, am
the basic chromate of tin is separated from the cru-
cible by means of hot water. It is afterwards washe<
until the liquors have no alkaline reaction.
The chromate thus obtained is of a dull and pal<
yellow color, and in order to give it the desired lila<
hue it is strongly calcined for one or two hours in
luted crucible, placed in an air furnace and covei
with coke. After this calcination the substance
dense, and contains some bright spots. It is easil
powdered, and is not acted upon by air, dampness
light, or sulphuric acid.
Mr. Malaguti, to whom the discovery of this lak<
is due, prepared it by calcining at a dull-red heat an<
in a clay crucible, an intimate mixture of 100 part*
of stannic acid (binoxide of tin) and 2 parts of oxii
of chromium. After cooling, the vitrified mass was
powdered, and was of a lilac hue, but somewhat gray-
ish, as some people said.
YELLOW COLORS. 397
§ 13. Naples yellow.
Many believe that this yellow, which is a peculiar
combination of oxide of lead and antimonic acid, is
extracted from the lava of Mount Vesuvius. Fou-
geroux de Bondaroy claims that Naples yellow is a
composition known at Naples under the name of
giallolini, the secret of which is held by one indi-
vidual. He adds, that, having been unable to dis-
cover the secret during his travels in Italy, his
chemical researches proved to him that this yellow
was prepared with white lead, alum, and diaphoretic
antimony (antimoniate of potassa). In regard to
Naples yellow, Thenard says : " The preparation of
this yellow is well known only to those who make it
for the arts. It is said to be obtained by calcining, at
the proper temperature, a mixture of pure litharge,
hydrochlorate of ammonia (sal ammoniac), diapho-
retic antimony (a combination of peroxide of anti-
mony and potassa), and alum."
Naples yellow is obtained by processes differing
one from another, and which very likely furnish
different tones of color.
Fougeroux de Bondaroy has indicated the follow-
ing recipe :• —
White lead 24 parts.
Diaphoretic antimony (antimoniate of potassa) 4 parts.
Sal ammoniac ...>...! part.
Alum 1 part.
All of these substances should be finely powdered
and throughly mixed before they are placed in a cru-
cible which is kept at a red heat for three hours.
After cooling, the crucible is broken, and the mass
398 MANUFACTURE OF COLORS.
which is very dense and compact, and of a fine yel-
low color, is finely ground, and then washed several
times for the purpose of separating the soluble sub-
stances. Lastly, the powder is dried.
Naples yellow is also obtained by smelting, at a
low temperature, 3 parts of massicot and 1 part of
oxide of antimony.
Two parts of red lead may also be fused with 3
parts of powdered metallic antimony and 1 part of
calamine.
Another recipe consists in smelting 5 to 6 parts of
lead, 2 to 4 parts of antimony, and 1 part of cream
tartar (bitartrate of potassa).
Again it is said that 16 parts of lead, 16 of anti-
mony, 2 of cream tartar, and 1 of common salt, pro-
duce a Naples yellow.
Five parts of litharge, two of antimoniate of potassa,
and one of sal ammoniac, give a fine yellow.
Lastly, Mr. Guimet, of Lyons, asserts that a hand-
some yellow may be produced with two parts of re<
lead and one part of antimoniate of potassa.
A German chemist, Mr. Brunner, has made a sp<
cial study of Naples yellow, and, after a great man;
experiments, finds that the finest article is prepai
in the following manner : —
One part of tartrate of potassa and antimony 01
tartar emetic, purified by several crystallizations,
intimately mixed with two parts of nitrate of le
free from copper or iron, and four parts of commoi
salt. The homogeneous mixture is slowly brought
to a state of fusion in a Hessian crucible. After cool-
ing, the mass is detached by striking the overturn!
crucible, and then ground and washed, in order to
YELLOW COLORS. 399
remove the salt which formed the upper layer of the
melted mass.
The yellow is very fine with a properly conducted
fire, but too much heat impairs it. The color may be
brightened by washings with hydrochloric acid.
Mr. A. Hick, in the Technologiste, vol. xxi. page
72, has indicated a mode of preparing a yellow color
which resembles Naples yellow.
It is known, says he, that in refining lead the metal is
melted in a reverberatory furnace, and presents a large
surface to the action of the air. The antimony and
other metals usually accompanying lead are oxidized,
and their oxides form a sort of scoria on top of the
fused lead. These oxides are principally those of
lead, antimony, and arsenic; and in order to trans-
form them into a pigment, they are finely ground, and
calcined in a reverberatory furnace, or in any other
furnace where they are simultaneously acted upon by
air and heat. The calcination is begun at a low tem-
perature, which is slowly raised to a red heat. The
length of the operation depends on the quantity of
material operated upon, and in practice, from one to
three days are necessary to calcine 1500 kilogrammes
of pulverized oxides.
It is advantageous to mix with the powder, during
the latter period of the calcination, a certain quantity
of common salt (chloride of sodium). An accurate
proportion of salt is not very important, but practice
indicates about one-half of the weight of the oxides.
The calcined product is sometimes saturated with
sulphuric, hydrochloric, or acetic acid, or exposed to
the vapors of acetic acid in tan beds, like those used
for white lead. This treatment with common salt and
acids improves the quality of the color.
400 MANUFACTURE OF COLORS.
When the color remains constant in the furnace,
the oxides are removed, washed, ground, etc.*
The color of Naples yellow varies in tone with the
different processes of manufacture, but generally it
possesses brightness, depth, and durability. This
pigment unites readily with other colors, and enhances
the brightness of the yellow ochre with which it is
sometimes mixed. Its preparation requires peculiar
precautions; for instance, it should be ground upon a
slab of porphyry or marble, and collected with an
ivory blade, because steel turns it green. It is used
on chamois grounds, for fine yellows imitating gold,
and for carriages.
§ 14. Cadmium yellow.
This salt is of a remarkably fine orange-yellow
color, which remains unchanged by fire. It fuses at
a white heat, and by cooling, it crystallizes into trans-
lucent and micaceous laminae possessing a magnifi-
cent lemon-yellow color. On account of its beauty
and durability, this pigment is used in artistic paint-
ings, but its price is still very high.
Cadmium yellow is obtained by passing a stream
of sulphuretted hydrogen through a solution of
nitrate or sulphate of cadmium. The precipitate
of sulphide of cadmium is washed, collected upon
a filter, and dried in a stove-room. Thus prepared,
* The above described process is evidently an economical method
for obtaining a color nearly identical with Naples yellow, that is,
an antimoniate of lead, the degree of saturation of which is little
known. It is possible that the small proportion of arsenic con-
tained in the oxides, modifies the tone of the color, and causes a
certain difference between it and real Naples yellow ; but then the
pigment is poisonous, and should be used very carefully.
YELLOW COLORS. , 401
the yellow is in the state of impalpable powder which
covers very well.
This color may also be prepared in the dry way, by
heating in a crucible oxide of cadmium with an excess
of sublimed sulphur. The yellow prepared in this
manner is not so handsome as the previous one, and
does not cover so well.
Blue pigments and cadmium yellow produce very
rich and durable greens, which should not be mixed
with white lead or other lead compounds, because the
latter are decomposed and blackened by the sulphur
of the cadmium.
§ 15. Yellow of antimony and zinc.
Messrs. G. Hallett and J. Stenhouse, in 1861, took
out a patent in England, for the manufacture of colors
with an antimonial basis. The following is their
mode of operation : —
They take the native oxide of antimony, or the
mixed oxide and sulphide, often associated with the
gray sulphide of antimony. It is a combination in
variable proportions of antimony and oxygen, with
more or less sulphide of antimony, oxide of iron, silica,
water, and sometimes arsenic, and the color of which
varies from a light yellow to a yellowish-red. The
gangue is removed as far as practicable, by pick-
ing and washing, and the ore is finely ground and
sifted. The powder is introduced into large cruci-
bles, muffles, or reverberatory furnaces, where it is
carefully calcined at a dull red heat and with the
access of the air. The mass is constantly stirred in
order to prevent too great an elevation of its tempera-
ture. During the operation the powder emits steam,
sulphur, and sulphurous acid, fumes of antimony and
26
402 MANUFACTURE OF COLORS.
arsenic, and becomes less fusible. The calcination
lasts generally from two to three hours, and is com-
pleted when vapors and fumes are no longer disen-
gaged, and when all the antimony has been trans-
formed into anhydrous antimonious acid.
The impure antimonious acid thus produced, is
reduced to an impalpable powder by grinding and
levigation. After drying, it forms with oil, varnish,
etc., a new pigment for painting, which may be com-
bined with other oxides or salts, such as zinc oxide,
white lead, chromate of lead.
A yellow color is produced with eight parts of
native oxide of antimony, or of oxide mixed with sul-
phide, or the impure antimonious acid obtained by the
above process, three parts of red lead or litharge, and
one part of oxide of zinc. The whole is finely pow-
dered and thoroughly mixed, and calcined in crucibles,
muffles, or furnaces, until the combination is effected
and the yellow color has appeared. The mass is then
finely powdered, and ground in oil or in varnish.
The above proportions give good results, but they
may be made to vary. Sometimes the proportion of
oxide of lead is increased ; at other times, the oxide
of zinc is suppressed. About four parts of common
salt may be employed, in which case the product is
afterwards carefully washed. By varying the propor-
tions of the constituent parts, as seen in the examples
below, various tones and hues of Naples yellow will
be produced : —
i. ii. in.
Antimonious acid . . 4 parts 1 3
Oxide of lead ... 2 23
Oxide of zinc 1 11
YELLOW COLORS. 403
IV. V. vr.
Antimonious acid . . .1 part 1 2
Oxide of lead ... 1 1 1
Oxide of zinc . . .1
§ 16. Turner yellow. Kassler yellow. Cassel yellow.
Montpellier yellow. Verona yellow. Mineral yellow.
These various names belong to quite a number of
colors, the composition of which is not perfectly es-
tablished. Nevertheless they appear to result from
the combination of a protochloride of lead with vari-
able proportions of oxide of lead.
According to Hahneman, the mineral yellow of
Turner is prepared by mixing together twenty-one
parts of red lead, and two parts of sal ammoniac
(hydrochlorate of ammonia). After fusion in a cruci-
ble, the mass is poured upon a marble slab, and then
pulverized.
Other persons prepare this color by fusing litharge
or white lead with common salt or sal ammoniac.
The following is the method practised at Montpellier
by Chaptel, and described by him : —
Four parts of finely pulverized litharge are put into
a stoneware vessel, and mixed with a portion of a
solution of one part, of common salt in four parts of
water. The stirring is effected with . a spatula of
glass, lead, or wood, but iron is discarded. The sub-
stance swells and becomes hard ; it is then broken
and mixed with another portion of the saline solution.
The stirring is continued with fresh additions of the
solution. "When the latter is exhausted, pure water
is used as long as the substances continue to swell.
At last they sink down. The stirring is continued,
and when the mass has become perfectly white,
404 MANUFACTURE OF COLORS.
smooth, and fine, it is thoroughly washed in water.
The paste is then pressed in a cloth, and afterwards
distributed in shallow stoneware vessels which are ex-
posed to a moderate but protracted heat. The dome
of a porcelain furnace is well adapted to this last
operation. The cooling is slow, and the result is a
chamois yellow of a pure hue, but not so bright as
Naples yellow.
Mineral yellow is produced by a mixture of
English litharge and sal ammoniac ; its color is a
bright lemon-yellow without durability. It is pre-
pared with two or three parts of English litharge
(yellow protoxide slightly vitrified), and one part of
sal ammoniac, ground together in a marble mortar
with a little water. The resulting paste is put into
an unglazed clay dish, which is heated in a rever.be-
ratory furnace, slowly at first to evaporate the water.
The heat is then increased by degrees until the am-
monia has entirely escaped. The dish is removed
from the furnace, and the color is of a bright lemon-
yellow. It is employed mostly for coach painting
and theatrical scenery.
Mr. M£rimee says that a more durable mineral
yellow is prepared by grinding separately and mixing
afterwards : —
Metallic bismuth . . . .3 parts.
Sulphide of antimony 24 "
Nitrate of potassa 64 "
The mixture is introduced by degrees into a heat
crucible. After fusion, the substances are thrown
into water and stirred as long as it is necessary. The
precipitate is washed by decantation until the water
is tasteless, whence it is collected upon a filter <ind
well dried. The resulting oxide is in the shape of a
ed
YELLOW COLORS. 405
fine powder colored a dirty yellow. One-eighth of one
part of this dry oxide is mixed with one part of hydro-
chlorate of ammonia, and sixteen parts of pure lith-
arge, and the whole is fused in the manner previously
indicated. Should a given tone of color be desired,
it is necessary that the degree of temperature and the
length of operation should always be exactly the same.
There are other processes for preparing this color.
For instance, there are manufacturers who produce it
by maintaining for some time and exposed to the
access of the air, a neutral chloride of lead in fusion.
This salt is partly decomposed; chlorine is disen-
gaged, and the reduced metal combines with the un-
decomposed chloride of lead.
Others prefer melting together one part of chloride
of lead and four parts of red lead.
Lastly, some persons heat ten parts of massicot and
one part of sal ammoniac. The molten mass is divided
into two layers, the lower one being metallic lead,
and the upper one, a pure and bright mineral yellow.
This color is somewhat difficult of preparation, and
great cleanliness is necessary. Many tones and hues
are to be found in the trade depending on the pro-
portion of basic chloride. But in every case, it may
be deepened by a second fusion, or lightened by a
fusion with a small proportion of sal ammoniac.
It is employed especially for coach and theatrical
painting, and the color is deepened by an addition of
chrome yellow. It should not be placed in contact
with sulphur compounds.
The Merimee yellow is very rich of tone, and very
durable. It is sought for artistic painting, and is
sold in the trade under the names of antimony yellow
and superfine mineral yellow.
406 MANUFACTURE OF COLORS.
§ 17. Mineral straw-yellow.
This very bright color may be considered as a basic
sulphate of lead (a combination of sulphuric acid with
an excess of oxide of lead). It is obtained by melting
in a crucible a mixture of equal parts of sulphate of
lead and litharge. After fusion, the mixture is poured
out upon a slab, and when cold it is powdered.
The pure mineral straw-yellow possesses a finely
toned yellow color, is durable, and covers well. But
it should not be exposed to sulphuretted gases. That
found in the trade is very variable in tone, on account
of the large proportion of lead introduced into it.
§ 18. Mineral turbith.
The names of mineral yellow and mineral turbitJi
are given to a subsulphate of mercury, which is pre-
pared as follows : —
One part of mercury is boiled with two parts, at
least, of sulphuric acid at 66° Be., in a stoneware
retort heated in a covered furnace. There is an
abundant production of sulphurous acid, and, when
the reaction is completed, the retort is broken, and the
acid sulphate of mercury is dissolved in boiling water.
The mass becomes decomposed, and, after repeated
washings with hot water, acquires a pretty lemon-
yellow color. Lastly, it is collected upon a filter and
dried. Mineral turbith is not much used, and it is
said to become decomposed in the air. This yellow,
with Prussian blue, produces a magnificent green,
finer than that prepared with orpiment, and without a
tendency to become black. It is highly poisonous.
YELLOW COLORS. 407
§ 19. Orpin or orpiment. Yellow sulphide of arsenic.
Yellow realgar.
This mineral, which is a trisulphide of arsenic, has
a fine gold-yellow color, and is in the shape of a mass
of soft and flexible lamina, semi-translucent, and
easily separated, also in oblique prisms. It is taste-
less, odorless, and presents a lamellar fracture. More
fusible than arsenic, it burns with a blue flame and
produces a garlic smell. This mineral is composed
of—
Arsenic 63.98
Sulphur ...... 36.02
100.00
It cannot be combined with pigments holding
lead or certain other metallic compounds, because it
blackens them.
Orpiment is found in the natural state often mixed
with realgar or bisulphide of arsenic in secondary
formations, but not in sufficient quantity for the arts.
It is found in Hungary, Styria, Suabia, Bohemia,
Walachia, the East, Peru, etc.
Artificial orpiment, or yellow sulphide of arsenic,
has properties somewhat different from those of the
natural article. It appears to be a mixture of 96
parts of arsenious acid and 6 parts of sulphide of
arsenic. The following is its mode of fabrication : —
1 part sublimed sulphur, finely powdered, and
passed through a silken sieve, is thoroughly mixed
with 2 parts of powdered arsenious acid. The mix-
ture is introduced into a crucible which is covered
with another crucible, or, better still, with a condenser
for collecting the sublimate. The latter is an opaque
408
MANUFACTURE OF COLORS.
mass, the color of which varies from a clear yellow to
a red, according to the manner in which the fire has
been conducted, or the greater or less thoroughness in
the mixing of the sulphur and arsenic. By varying
the proportions of sulphur, and conducting the opera-
tion with more or less rapidity, all the intermediary
tones and hues between the extreme colors may be
obtained.
Orpiment is an extremely poisonous color, which
requires great precautions in its preparation and
handling. Moreover it is not durable. It is em-
ployed especially in oil painting, and produces with
Prussian blue a handsome green, which is, however,
liable to turn black.
The name of royal yellow is sometimes given to a
sulphide of arsenic obtained by precipitation in the
wet way.
Mr. R. "Wagner says that an extremely fine yellow
orpiment is prepared with sulphide of arsenic and
sulphate of baryta, and might replace chrome yellow
if there were no arsenic in it. This pigment is pre-
pared as follows : —
2 parts of finely-ground sulphate of baryta are
calcined with 1 part of powdered charcoal, tar, or oil
waste, etc. The calcined mass is pulverized again,
mixed with 1 part of ground orpiment, and boiled in
water. After filtration the liquor contains a sulpho-
arsenite of baryta, which may be precipitated by
diluted sulphuric acid. Chloride of barium may be
added before the addition of the acid, and in this
manner the precipitated pigment is lightened in color.
The disagreeable and unhealthy escape of sulphu-
retted hydrogen may be avoided by adding to th<
solution of chloride of barium a quantity of arseniate
YELLOW COLORS. 409
of potassa in hydrochloric acid, proportional to the
amount of sulphuretted hydrogen produced.
§ 20. Arsenite of lead.
Arsenite of lead is also a highly poisonous pigment,
which is often substituted for orpiment. Its yellow
color is equally fine with it, more durable, and with a
good body.
The arsenite of lead is obtained from an intimate
and finely powdered mixture of 10 parts of arsenious
acid and 7 parts of litharge, which is brought to a red
heat in a crucible placed in a furnace having a good
draft. "When the substances are in a quiet state of
fusion, they are poured upon a marble and afterwards
finely ground.
By varying the proportion of lead, i. e., by increas-
ing that of litharge, the arsenites become redder,
especially if the heat be more protracted.
§ 21. Massicot. Litharge.
Massicot is a pulverulent yellow protoxide of lead,
which when fused is called litharge.
If metallic lead be placed upon the hollow hearth
of a reverberatory furnace having a fireplace on two
opposite sides, it soon melts and becomes oxidized on
the surface. By removing the oxidized portions a
new quantity of oxide is formed, and so on until all
the metal is transformed into a fine yellow protoxide,
or massicot. It is sometimes employed in painting,
and it is more or less reddish according as the heat
has been more or less raised, or the lead is purer, etc.
Litharge is a protoxide of lead which has been
melted. Its yellow color often acquires a reddish
410 MANUFACTURE OF COLORS.
hue, which is due either to impurities, or to the tem-
perature, or to its more or less sudden cooling.
It is seldom that the manufacturer of pigments is
obliged to prepare his litharge, which can be had in
the trade at moderate prices, and which results from
the cupellation of lead in metallurgic works.
§ 22. Iodide of lead.
This yellow, which possesses the brightness of
orpin and of chromate of lead, is prepared by precipi-
tating a solution of nitrate or acetate of lead with a
solution of iodide of potassium. The nitrate of lead
produces a brighter article than the acetate. Iodide
of lead is soluble in 1235 parts of cold, and 192 parts
of boiling water. The latter by cooling deposits
spangles of iodide.
We are indebted to Mr. Huraut for a more practical
and economical method for the manufacture of iodide
of lead than that generally practised. The following
is a description of the process : —
Take of—
Iodine . . . . .100 parts.
Iron filings . . . 15 "
Quicklime . . . 25 "
Water sufficient,
and make with these substances a paste which it
gently heated and continually stirred. When th<
combination is effected, that is, when all the iodin<
has disappeared, more water is added. After settling
and decanting, the residuum is treated with a fr
portion of water and the mixed liquors are filtere<
They hold iodide of calcium, which is decomposed
a solution of 152 parts of neutral acetate of lead,
of 132 parts of nitrate of lead. The precipitate 'u
YELLOW COLORS. 411
washed two or three times only, and then dried at a
moderate temperature.
The above proportions give 175 parts of a micaceous
iodide of lead, which is of a magnificant orange-
yellow color.
This pigment is very bright, but is affected by the
sun and sulphurous emanations. It is also poisonous.
§ 23. Uranium yellow.
Uranium yellow is extracted from the uranium-
pech-blende or pech-urane, which was formerly dis-
carded, but which at the present time is mined with
profit in Germany, especially for furnishing glass-
makers with a pigment which colors glass a very
handsome greenish-yellow.
Mr. Patera was the first who proposed a manufac-
turing process, which may be summed up as follows :
Powdered pech-urane is mixed with chalk, and by
calcination forms a uranate of lime which is treated
by sulphuric acid. The solution is boiled with metallic
iron, in order to reduce the oxide of uranium to the
protoxide state, and is afterwards largely diluted with
water. A basic sulphate of protoxide of uranium is
precipitated, and is separated from the basic sulphate
of protoxide of iron by being dissolved in the smallest
possible quantity of sulphuric acid. An addition of
water precipitates it again. The pure basic sulphate
of protoxide of uranium, thus obtained, is used for the
preparation of other combinations of uranium.
Mr. Patera has since modified this process. The
pech-urane is calcined with lime in a reverberatory
furnace, then treated by sulphuric acid mixed with a
small proportion of nitric acid, which dissolves the
oxide of uranium. To this impure solution an excess
412 MANUFACTURE OF COLORS.
of carbonate of soda is added, which forms a soluble
carbonate of soda and of oxide of uranium. Sulphu-
ric acid separates from it an uranate of soda, which is
sold under the name of uranium yellow.
This process is said by Mr. C. F. Anthon, to fur-
nish a product which is not very well received in the
trade.
Mr. Anthon having had to work several tons of
pech-urane, with a variable yield of 10 to 70 per cent,
of uranic oxide, it is interesting to chemists to know
his process, which presents several advantageous
features.
The ore is pulverized as finely as possible, which is
difficult with the poor qualities. A clear and liquid
paste is made with the powder and water, which is
treated with a mixture of equal parts of nitric and
hydrochloric acids. These need not be pure, and
may contain a certain proportion of sulphuric acid.
The operation should take place in the open air or
under a chimney with a good draft, and the vessels
used are of varnished stoneware of a capacity of 20
litres for 12 or 13 kilogrammes of powdered pech-
urane, or of cast-iron holding from 50 to 100 kilc
grammes of ore. The materials are constantly stirn
as long as there are red vapors disengaged, especiall;
after each addition of acids.
By a previous calcination of the ore, the escaping
acid fumes will be less abundant, and there will be
sensible saving of nitric acid, since aqua regia may
then be composed of three parts of hydrochloric acid
to one part of nitric acid. The action of the aqua
regia is very energetic, even without the aid of heat,
and especially when the ore is not calcined; the pro-
YELLOW COLORS. 413
duced heat is then so great that the ore is entirely
subdivided and corroded.
The proportion of nitric acid cannot be even ap-
proximately determined ; it depends entirely on the
very variable quality of pech-blende used, and whether
the ore is in the raw state or calcined. At all events,
the end of the decomposition is ascertained by the
absence of effervescence and of red vapor.
As soon as a small addition of nitric acid fails to
produce a sensible reaction, the paste, which should
have been kept at about the same degree of consist-
ency by the addition of water if necessary, is then
evaporated and stirred until it appears dry. "When
this point is reached, the kettle is brought to about
a red heat, without reaching it, however.
The dried mass is lixiviated with water, and the
mixed liquors, which mark from 8° to 12° Be., are
treated with carbonate of soda, in slight excess, that
is, until the latter substance can be recognized by the
taste. A great excess is to be avoided.
The liquor thus obtained is not clear, and is colored
a yellowish-brown by the precipitated oxides. It is
made to boil in a cast-iron kettle, which is afterwards
allowed to cool very slowly until the next morning,
by closing the flues and covering the vessel.
The next day, the clear and yellow liquor above
the deposit is siphoned off. It is a nearly pure so-
lution of urano-sodic carbonate. The thick deposit
is drained in cloth sacks (0.80 metre long, and
0.20 to 0.22 metre wide), fixed to a wooden frame,
and which are compressed when the liquors have
ceased to run naturally. The pressed cake is boiled
again with water, and a small proportion of soda, in
order to extract what may remain in it of uranium
414 MANUFACTURE OF COLORS.
oxide. All the uranic solutions are then concentrated
into a cast-iron kettle, and the urano-sodic carbonate
which separates is "fished," that is, collected in glazed
dishes suspended in the boiling liquor. When the
deposits no longer take place, the mother liquors.,
which still hold a notable proportion of oxide of ura-
nium, are mixed with the washings of the dried mass,
after the treatment by the acids.
The collected urano-sodic carbonate forms a crys-
talline greasy powder, which is but slightly soluble
in water, and is of a bright lemon-yellow when pure.
But as this carbonate is not always of constant com-
position, or in favor with the trade, it should be changed
by a further treatment, into ammoniacal uranium
oxide, of a much deeper yellow, and which is more
eagerly sought for, on account of the greater propor-
tion of uranium oxide it yields.
The urano-sodic carbonate is slowly dissolved ii
water, and the solution is sufficiently saturated wh<
it marks from 15° to 18° Be. The impurities ai
separated, either by filtration, or by allowing tin
liquors to stand.
Although neither of these operations is difficult, ii
is preferable in practice to put the raw urano-sodi<
carbonate into small wooden tubs (5 to 6 centimetre
high, and from 20 to 25 centimetres in diameter),
through which water is made to pass until all the car-
bonate is dissolved. By this treatment, the foreigi
substances remain insoluble.
The pure solution of urano-sodic carbonate is poun
into a cast-iron kettle, and is decomposed by solution!
of sulphate or hydrochlorate of ammonia (according
to the market value of these salts), which are adde<
at intervals and in quantities to be determined
YELLOW COLORS. 415
experience. The operation is completed when effer-
vescence ceases, or when carbonate of ammonia is dis-
engaged. The yellow ammoniacal oxide is collected
(fished) in dishes, as in the preparation of the urano-
sodic carbonate, and is washed and dried.
When the boiling mother liquors, after the addition
of a small quantity of ammoniacal salt, do not give
a precipitate, or are without alkaline reaction, they
are removed from the fire and preserved for another
operation with the washings, since they yet hold a
certain proportion of oxide of uranium.
The proportion of ammoniacal salts employed is
small, because enough, and no more, is added for the
acid of the salt to saturate the soda of the carbon-
ate. As the anhydrous urano-sodic carbonate con-
tains 22.9 per cent, of soda, 100 parts of it require 49
parts of hydrochl orate of ammonia (sal ammoniac).
Moreover, if we consider that the sulphate of am-
monia may be had for about one-fourth of the price of
carbonate of ammonia, and that in other methods of
preparing the oxide of uranium the weight of car-
bonate of ammonia employed is from three to five
times that of the sulphate required by the author's
process, the superiority of the latter method is evident,
besides possessing other advantages.
While engaged in the manufacture of uranium
oxide by the method thus described, the author made
the following analysis to arrive at the composition of
the urano-sodic carbonate which he could not find
anywhere.
a. 30 grains of the compound gave 7.1 grains of
carbonic acid, that is, 23.7 per cent.
&. 30 grains were treated by a solution of sal
ammoniac, evaporated to dryness, and then gently
416 MANUFACTURE OF COLORS.
calcined to expel the excess of ammoniacal salt. The
same treatment was repeated with a small addition of
ammonia, and, after washing and heating, the residue
was 15.8 grains of oxide of uranium, that is, 52.7 per
cent.
c. The liquors and washings of the previous test,
being evaporated to dryness and gently calcined, left
a residue of 12.9 grains of chloride of sodium, corre-
sponding to 6.7 grains of soda, or 22.9 per cent.
Therefore, the urano-sodic carbonate, precipitated
in the shape of a slightly soluble and lemon-yellow
colored powder, during the evaporation of the aqueous
solutions of this carbonate, has the following compo-
sition : —
Oxide of uranium .... 52.7
Soda 22.9
Carbonic acid 23.1
Water 0.7
100.0
and its formula is 2(NaO.CO2) + IPO3.CO2, whicl
composition corresponds with that of the uran<
potassic carbonate analyzed by Ebelmen.
This compound is slowly dissolved in water, an(
the saturated solution, at the temperature of aboi
15° C., has a specific gravity of 1.161.
The urano-sodic carbonate loses a little water wh<
heated at a low temperature. By increasing th<
temperature, and even below a red heat, it loses th<
greater part of its carbonic acid, and acquires a ligl
brick-red color. It will lose more carbonic acid at
red heat, but even by maintaining it at that temper*
tare for half an hour it cannot be entirely deprived of
acid.
YELLOW COLORS. 417
§ 24. Gamboge.
Gamboge is a resin which oozes from the broken
branches, or from incisions made in the trunks of
various trees which grow in Siam, Ceylon, and Cam-
bodia. This substance is exported in the shape of
cylinders or cakes, which are yellowish-brown at the
exterior and orange-red inside, very hard, brittle, and
with a bright fracture. The powder is of a deep-
yellow color. This resin is colorless, slightly poison-
ous, and very purgative. Insoluble in water, but
soluble in ether and alcohol, it is composed of 80 per
cent, of pure resin and 20 per cent, of gum. Accord-
ing to Mr. Lefort, the yellow resin may be separated
from the gum by solution in purified essence of tur-
pentine. The greater part of the essence may be
recovered by distillation, and the residue, being
evaporated to the consistency of an extract at a low
temperature, abandons a hyacinth red resin in lump,
which is of a bright-yellow when powdered. It
mixes very well with oils.
Gamboge is employed especially in water and
miniature painting. The article purified in the above-
mentioned manner possesses more body than the raw
material, but the price is too high for extended appli-
cation.
§ 25. Jaune Indien (Indian yellow}. Purree.
We now find in the market a coloring substance,
which is known in England under the name of purree,
and in France, under that of Jaime Indien (Indian
yellow). The raw substance is in the shape of rounded
lumps, weighing from 150 to 200 grammes, brown-
green at the exterior, and of a very rich orange-yellow
27
418 MANUFACTURE OF COLORS.
inside. It emits a smell similar to that of castoreum,
is slightly soluble in cold water, but insoluble in
alcohol and ether. When pure, it burns like tinder,
and leaves a very small residuum. It may be puri-
fied by washing its powder with boiling water, and
drying at a low temperature. Purree is a handsome
yellow pigment, non-poisonous, and durable, but which
dries slowly.
Indian yellow is still sold at a high price, and is
generally adulterated with chrome yellow or other
yellow substances. Mr. Stenhouse, from an analysis
made of Indian yellow, ascertained that it was a
combination of magnesia with a peculiar organic
acid. This result gave to Mr. R. Wagner the idea of
preparing it artificially, and the following notice was
published in the Technologists, vol. xxi. page 122:—
" There is brought from the East Indies and froi
China, under the name of purree, a yellow substance
which, from the researches of MM. Erdmann am
Stenhouse, consists principally of a combination o1
magnesia with an organic acid, to which the name ol
euxanthic acid has been given. Pure purree or India]
yellow is a handsome yellow color, which is oftei
preferred in oil painting to either the chromate oi
lead or of zinc, to the royal yellow (precipitated sul-
phide of arsenic), and even to the sulphide of cad-
mium. The Indian yellow, prepared in Paris, does
not appear to be obtained by purifying the raw mate-
rial in boiling water, but by using the pure euxanthl
acid. I have also ascertained by the analysis of
Parisian sample, that the inorganic basis is nol
magnesia alone, but magnesia and alumina. A sam-
ple, dried at 100° C. and calcined, gave the following
results : —
YELLOW COLORS. 419
Organic substances and water . . . 52.3
Inorganic residuum ..... 47-7
100.0
" I have ascertained that the organic substance
is the euxanthie acid, by boiling the yellow color in
hydrochloric acid, in which it is entirely soluble. By
cooling, pale-yellow needles were deposited, which
presented all the reactions of euxanthic acid. Under
the action of heat they melted, and produced a crys-
talline sublimate (euxanthon). The calcined residue
was composed of —
Alumina . . . . . .72
Magnesia ...... 28
100
"This composition quite entirely agrees with that
of spinel (Al2O3.MgO), and gives a clue for the prepa-
ration of enxanthic yellow.
" We know from the researches of Mr. Habich that
when one equivalent of a magnesia salt is mixed
with an equivalent of an alumina salt, and when
sufficient sal ammoniac has been added to partially
prevent the precipitation of the magnesia, the pre-
cipitate of alumina caused by an addition of ammonia,
will carry with it enough magnesia to form an artifi-
cial hydrated spinel. I have also found that the
aluminous compound, equally with pure magnesia,
possesses the property of forming with the coloring
substances a lake which is remarkable for its porosity.
"We may, therefore, obtain the euxanthic yellow
in the following manner. We make a solution of —
Potassa alum 45 grammes.
Sulphate of magnesia . . . .13
Sal ammoniac ..... 6
AY uter . . 250 "
420 MANUFACTURE OF COLORS.
" We dissolve in another vessel a few grammes of
euxanthic acid in diluted ammonia, and mix this solu-
tion with the previous one. The mixture is precipi-
tated in the cold by ammonia, without any excess.
The yellow and bulky precipitate thus formed is
washed, pressed, and dried. This product, however,
is not to be compared in fineness with that manu-
factured in Paris, and the preparation of which is
kept secret."
§ 26. Aurum mussivum. Mock gold. Mosaic gold.
Cat's gold. Painter's bronze, etc.
This compound is a bisulphide of tin, which is
composed of —
Sulphur 35.3T
Tin 64.63
100.00
It is employed in oil painting for enhancing the
tones or the reflex of bronzes, for gilding wood, etc.
It is formed of bright and translucent scales, soft t<
the touch, odorless and tasteless, and insoluble in
water, alcohol, ether, and oils. The following is the
more generally employed process for the manufac-
ture of mosaic gold.
12 parts of tin are amalgamated with 6 parts ol
mercury, and the amalgam is ground with 7 parts oi
sublimed sulphur, and 6 parts of sal ammoniac. The
whole is introduced into a strong glass matrass,
which is moderately heated upon a sand-bath until
white fumes or sulphuretted hydrogen are no longer
produced. The temperature is then brought to a red
heat. After cooling, the glass vessel is broken, and
the greater part of the mosaic gold is found in the
YELLOW COLORS. 421
shape of a scaly mass, covered with other crystalline
and bright scales, which result from the sublimation
of a part of the compound. The more crystalline
portions are separated, and form a superior quality.
There are other recipes in which the proportions of
tin, mercury, and sulphur vary. But nothing proves
that they are better than the preceding one.
The amalgam of tin furnishes the finest article ; but
as the mercury is generally lost, a more economical
process has been sought for, which produces a cheaper,
but not so fine an article.
Out of many formulae, we select the following ones:
Calcine together
Sulphur 1 part
Protoxide of tin . . .2 parts
Or
Sulphur . . . . .3 parts
Protoxide of tin . . . 4 "
Sal ammoniac . . . 2 "
It results from the researches of Mr. Lefort that
all the art in the manufacture of aurum mussivum
rests on the mode of conducting the fire. Too low a
temperature gives a light-yellow product; more heat
results in a deep-yellow color; too much heat imparts
a grayish hue.
§ 27. Nankin yellow.
It is said that a fine nankin yellow color is obtained
by drying, and then calcining, a concentrated solu-
tion of nitrate of lead, in which has been mixed a
small quantity of powdered peat.
§ 28. Chlorophyl.
During recent researches on the green coloring
matter of leaves, Mr. Fremy has succeeded in sepa-
422 MANUFACTURE OF COLORS.
rating it into two principles : one, which is blue, is
called phyllocyanin ; and the other, which is yellow,
bears the name of phylloxanihin. These coloring
substances, under the influence of light, produce in-
soluble combinations, in which it has been possible to
vary the affinity of the metallic oxide for the organic
matter. The blue principle of chlorophyl is more
easily altered than the yellow one, and, under certain
circumstances, it may lose and reacquire its color.
For separating the two coloring principles which give
to chlorophyl its green coloration, 2 parts of ether are
shaken with 1 part of slightly diluted hydrochloric
acid, in a glass-stoppered bottle. If the substance re-
sulting from the decoloration of chlorophyl be shaken
a few seconds with the above liquid, a remarkable
reaction is produced: the ether is rendered yellow by
the yellow coloring principle which it has retained ;
the acid reacts upon the decolored portion of th<
chlorophyl, and reproduces a magnificent blue sul
stance. Under the influence of bases the green coloi
of leaves is transformed into a fine yellow, which
soluble in alcohol. It is this transformed yello1
which is employed for the separation of the constiti
ent blue and yellow. This substance will form ai
insoluble combination with alumina, that is, a yello^
lake which will deliver its color to neutral solvents
such as alcohol, ether, and bisulphide of carbon. W<
believe that the day will come when the arts wil
utilize the green and yellow lakes, which are so easil
prepared with chlorophyl.
RED COLORS. 423
SECTION IV.
RED COLORS.
§ 1. Red ochre.
"When considering the yellow ochres we indicated
the mode of manufacture of red ochres, and we
added that the oxide of iron which forms their basis
acquires the most varied tones and hues under the
influence of heat. The sesqui oxide of iron obtained
by the calcination in a muffle, and with the access of
the air, of the sulphate of protoxide of iron, is either
orange-red, blood-red, flesh-red, or carmine-red, ac-
cordingly as the heat has been more and more in-
creased. A white heat will give it a violet tinge, and
artists use this article under the name of violet from
iron. Some others are reddish-brown, others are
grayish. The same principle applies to the manu-
facture of the red colors employed for painting on
porcelain and glass.
Analogous colors have been used for a long time in
oil painting, and MM. Bourgeois and Colomb-Bour-
geois, Ferrand-Dosnon, and others, have successfully
manufactured certain reds, called Mars reds, browns,
and violets, which were carefully prepared from pure
copperas.
These changes in the coloration of the oxide of iron
are reproduced in the majority of substances which
contain it, especially the earths. Moreover, when,
besides the iron oxide, there are other oxides, calcina-
tion will produce different hues which may be as use-
ful as the reds and browns we have mentioned. Thus,
water, which forms with the oxide of iron a hydrated
combination of a pale-yellow color, will be replaced
424 MANUFACTURE OF COLORS.
by zinc oxide if the two oxides are calcined together,
and the resulting compound will have a fast and
durable color. Alumina produces an orange alumi-
nate. The oxides of manganese, cobalt, nickel,
copper, etc., form with the oxides of iron certain
browns possessing a depth of coloration in a ratio
with their proportion in the compound.
§ 2. Colcothar. English red or rouge.
This is a red sesqui oxide of iron, which forms a very
durable and bright color, and is obtained by the cal-
cination of the green sulphate of iron (copperas) upon
iron plates, until it has lost all its combined water
and has become white. It is then pulverized, placed
in stoneware pots, and submitted to a red heat. Dur-
ing the operation, sulphurous acid and glacial (Nord-
hausen) sulphuric acid distil over, and the residue
of the retort is a hard mass which is coarsely pow-
dered, washed, dried, finely ground, and sifted. The
finer qualities are obtained by levigation (floating).
The latter, after drying, are sometimes calcined anew,
in order to increase their brightness.
Colcothar is also produced by the wet way, in mix-
ing a solution of sulphate of iron with another of car-
bonate or, better still, bicarbonate of soda. There is
formed a soluble sulphate of soda, and a precipitate of
carbonate of protoxide of iron, which is soon trans
formed into hydrated sesquioxide of iron. This ii
washed, dried, and calcined at a red heat in clay cru-
cibles.
It is said that, when the precipitation is effected ii
hot liquors, the colcothar is finer, more velvety, an<
deeper in color.
It maybe mixed with other iron colors, or calcine<
with lampblack, for obtaining various tones of color.
RED COLORS. 425
In the latter case, there is a partial reduction of the
red oxide of iron to the black magnetic state.
§ 3. Armenian ~bole. Ochreous clay. Lemnos earth.
Oriental bole. Red bole.
These various names apply to a yellowish-red pig-
ment, which was formerly imported from the East,
but which is now prepared from certain earths found
at Meudon, in Burgundy, near Saumur, Blois, etc.,
and which contain clay, oxide of iron, silica, lime, and
magnesia.
The finest pieces are picked up, and softened in
water, then lixiviated for separating the coarse and
hard particles. The finer portions are allowed to
settle, and the deposited paste is dried in the sun, or
moulded into troches or balls. This color is durable,
but the red is somewhat yellowish.
§ 4. Iron minium.
The iron minium is a red color, prepared in Bel-
gium by Mr. de Cartret. It is a mixture of clay and
oxide of iron which is in the shape of a fine powder
having a deep red-brown color. Its composition is —
Hygroscopic water 2.75
Oxide of iron ....... 68.ii7
Clay 27.60
Alumina . 0.27
Lime . 0.40
99.29
An iron minium prepared in Holland was found
Mr. Bleekrode to be composed of —
Water 6.00
Oxide of iron 85.57
Clay 8.43
100.00
426 MANUFACTURE OF COLORS.
The difference between the iron minium and the red
ochre consists, therefore, in the proportion of peroxide
of iron. In ochres, the proportion of oxide is not over
39 per cent., and generally is much less. Colcothar or
English rouge contains sometimes not more than 40
per cent, of oxide, the remainder being sulphate of
lime. The Berlin brown-red is prepared with the
iron residue of the manufacture of alum, and always
contains free sulphuric acid.
The iron minium is, according to Mr. Wagner,
more economical than that of lead, in the ratio of 20
to 39.
§ 5. Red-brown.
Red-brown is quite a handsome reddish substance,
very durable, but little used. It is obtained by fusing •
in a clay crucible, 1 part of red oxide of iron and
10 parts of litharge or red lead, which have been
thoroughly mixed. After cooling, the mixture is
ground.
§ 6. Red lead or minium.
Red lead or minium is a very bright orange-red
powder, composed, says Mr. Dumas, of two parts of
protoxide, and one part of binoxide of lead. It is pre-
pared by pulverizing massicot (yellow litharge), and
submitting it to a red heat in a reverberatory furnace,
where a portion of the protoxide passes to the state
of binoxide. If the product be heated two or three
different times, it bears the names of two fires or three
fires red lead, and is of a very rich red color.
Red lead is also manufactured by decomposing
a high temperature white lead or carbonate of l
This salt loses its carbonic acid, and leaves a
siduum of red lead. We shall now describe
RED COLORS. 427
manner in which this pigment is manufactured at
Portillon, near Tours.
We have already seen (white colors) that the oxide
of lead produced at the works of Portillon is sepa-
rated into two parts : one for the manufacture of white
lead, the other for that of red lead.
The crude oxide is powdered and separated from
the still remaining metal (blue lead) in a small mill.
This apparatus is composed of a horizontal and cir-
cular cast-iron plate upon which rolls a cast-iron
mill-stone. Below the plate and between the cast-
iron bottom of the tub which incloses the whole,
there is the stirring apparatus proper.
The mode of working is as follows : The crude oxide
is put into the mill and ground under the stone ; the
stirring apparatus keeps the light particles in suspen-
sion in water, and they are carried with it, through
the overflow of the tub, into the various settling tanks
below. The heavy unoxidized lead remains at the
bottom of the mill tub, and is now and then removed
by a trap door, to be oxidized again in the furnaces.
The circulation of water between the head and tail of
the complete apparatus is kept up by a chain and
buckets. There are three such mills at work, one
being especially intended for the grinding of the
purest oxides for the red lead used by flint glass-
works.
When the settling tanks have received a sufficient
quantity of oxide the latter is made to flow into a
basin near the furnaces, where it loses the greater
proportion of its water.
The drained oxide is then placed in rectangular
sheet-iron trays, capable of holding 15 kilogrammes
of litharge (massicot) each. 100 filled trays make a
428 MANUFACTURE OF COLORS.
charge, and are put into the hot furnaces at the end
of each day. All the openings are closed, especially
that of the chimney, which is shut with a well-fitting
damper. The same trays are submitted three or four
times to the same treatment, after which the oxide or
massicot has become red lead. This substance is in
the shape of more or less coarse lumps, the color of
which is not the same in all the trays; but the mixing
of the whole insures a certain regularity of coloration.
The red lead is then powdered in a ventilator, the
blades of which break the pieces. The light por-
tions are carried, by the draft of air, up a sheet-iron
pipe 12 metres high, and are collected in a sheet-iron
reservoir. This mode of powdering is interesting,
and its employment should be more extended. The
red lead is prevented from falling upon the blades of
the ventilator, except in small quantities at a time,
by means of a distributing apparatus composed of a
grooved cast-iron cylinder, which turns slowly. The
grooves receive the red lead. The salubrity of the
apparatus is still further increased by a special fan,
which exhausts the air on top of the box into which
the red lead to be ground is poured. The workman
is therefore in the middle of a draught which carries
all of the dust from him. The air, exhausted by the
fan, passes through long wooden boxes, where it
leaves the greater part of the dust, and is then carried
out into the atmosphere by means of a high stack.
§ 7. Orange mineral.
Orange mineral, according to Mulder, is a definite
combination of protoxide and birioxide of lead, in
which there remains a small proportion of undecom-
posed white lead. This chemist believes that the
RED COLORS. 429
following analysis gives the correct composition of
orange mineral : —
Protoxide of lead 73
Binoxide of lead ...... 25
Carbonic acid 2
100
The greater the proportion of binoxide of lead, the
deeper is the red hue of orange mineral.
The following is the mode pursued in the manu-
facture of this pigment at the works of Portillon,
near Tours.
We know that orange mineral results from the cal-
cination of white lead. This substance is coarsely
broken and put into sheet-iron trays similar to those
employed for red lead, and with which the oxidizing
furnaces, hot from the day's work, are charged. "When
the action of the heat is completed, the orange min-
eral is removed from the fire, cooled, and then thrown
into the distributing apparatus of a grinding venti-
lator, which is similar to that used for red lead. The
powdered orange mineral falls upon a horizontal
metallic sieve, and the draft created by a special fan
prevents any dust from flying about the rooms.
§ 8. Realgar, or ruby of arsenic.
Realgar is a yellow-red bisulphide of arsenic, which
is found native in certain of the old rocks, but which
is more generally prepared by melting in a crucible
a mixture of 8 parts of arsenious acid and 4 parts of
sublimed sulphur. The hard, brittle, and opaque sub-
stance remaining in the crucible after cooling, is
powdered. This poisonous pigment is not very dura-
ble, and should not be mixed with lead or mercury
colors, which are decomposed by it.
430 MANUFACTURE OF COLORS.
§ 9. Cinnabar and vermilion.
"We find in the natural state, and we manufacture
artificially, a fine blood-red color, which is called
cinnabar, when crystalline, and vermilion, when pow-
dered. This red sulphide of mercury is found in all
mercury mines.
1. Manufacture by the Dry Way.
Cinnabar is prepared at the mercury mines of Idria,
by grinding finely in revolving tuns, 85 parts of mer-
cury and 15 of sulphur. The mixture is then heated
in cast-iron cylinders, and sublimed in condensers
made of clay. The vermilion is obtained by grind-
ing the cinnabar in water.
Mr. Ritter assures us that the renowned Holland
vermilion is prepared by grinding thoroughly a mix-
ture of 1 part of sulphur and 2 of mercury, and by
adding to 100 parts of the mixture 2.5 parts of granu-
lated lead or red lead. Each sublimation pot receives
about 100 kilogrammes of mixture, which is heat<
as shall be explained further on. After eighteen
twenty hours of cooling, the pots are broken, ai
their contents ground in a mill. The lead, in tl
state of sulphide, remains at the bottom of the vessels
Mr. Tuckert has also indicated the following diffei
ent mode of preparation, which is pursued succe*
fully in Holland : —
An intimate mixture is made of 75 kilogramme*
of sublimed sulphur (sifted) and 540 kilogrammes of
mercury (passed through a chamois skin). The
whole is moderately heated upon a shallow iron pan,
and the resulting ethiops (black sulphide) is coarsely
broken, then ground and kept in jars. Its transfer-
BED COLOKS. 431
mation into cinnabar is effected in large clay pots,
well luted, and brought to a dark-red heat in isolated
furnaces. The operation begins with the contents of
two or three jars of ethiops. The substance becomes
inflamed, and as soon as the flame diminishes in
intensity the pots are covered with a well-fitting
thick iron plate. The fire is kept up for thirty-six
hours, and is so regulated that the flame produced
by removing the iron cover will rise to about 10 or 12
centimetres above the opening of the pot. The sub-
limation is aided by stirring the mass every half hour
with an iron rod. New additions of ethiops are made
every four or five hours. The cinnabar is deposited
upon the inward surfaces of the apparatus. After
cooling, the pots are broken, and the pigment is
finely ground in a mill. The powder is afterwards
levigated in order to arrive at a greater degree of
comminution, for the finer the vermilion the greater
are its fire and brightness.
It is recommended for this manufacture to operate
on a large scale with pure materials, to heat at the
proper point, and to volatilize all the sulphur which
is not combined.
2. Manufacture by the Wet Way.
Vermilion may also be obtained by the wet way
in a state of impalpable powder. This is the method
employed by the Chinese in preparing, by scarcely
known processes, the so-called Chinese vermilion,
which is one of the finest and the most sought for in
the trade. All the processes proposed in Europe up
to the present time are based upon the employment of
| a caustic alkali, generally potassa. We shall rapidly
describe four processes : one by Mr. Kirch off, of St.
432 MANUFACTURE OF COLORS.
Petersburg; another by Mr. Brunner, of Berne; the
third by Mr. Jacquelin, of Paris ; and the fourth by
Mr. Firmenich, of Cologne.
A. Kirchoff Process.
This process is somewhat difficult of operation.
300 parts of mercury are ground in a mortar with 68
parts of sublimed sulphur, which has been moistened
with a few drops of caustic potassa. The ethiops, or
black sulphide of mercury thus formed, is mixed with
160 parts of caustic potassa dissolved in a very small
volume of water. The whole is heated upon a sand-
bath for a half hour, and water is added to make up for
that evaporated. After that time no more water is
introduced, and the substance which is kept stirred
becomes brown and gelatinous, and then red. "When
all of the mixture has turned a fine red color, it is
carried to the stove-room, and is there now and then
stirred. Lastly, the vermilion is washed several
times, drained, and dried at a low temperatur
Sometimes it is digested in caustic potassa.
B. Brunner Process.
Take 300 grammes of mercury, 114 of sulphur, 7<
of hydrated potassa, and 450 grammes of watei
Thoroughly mix and grind the mercury and sulphui
then pour upon the ethiops thus formed, by small por-
tions at a time, the solution of potassa, and stir it. Pi
the mixture into vessels of porcelain, earthenware,
cast-iron, and heat on a sand-bath at a temperature
of from 45° to 50° C. After 7 or 8 hours of sucl
heating, during which the evaporated water has beei
replaced, the product passes from a black to a browi
red, and lastly to a scarlet-red. When the vermilioi
RED COLORS. 433
has acquired its greatest degree of brightness, it is
removed from the fire, then digested for some time at
a low temperature, and lastly washed several times,
and separated from the uncombined mercury.
C. Jacquelin Process.
The proportions of the raw materials are different in
this case. Take 90 grammes of mercury, 30 of sul-
phur, 20 of hydrated potassa, and 30 grammes of
water. The mercury and the sulphur are placed in a
shallow cast-iron dish, dipping iijfto cold water, and
the solution of potassa is added by degrees while the
substances are stirred with a large pestle. When all
the potassa has been added, the dish is heated at
C. for one hour, and the evaporated water is re-
>laced. After that, the vermilion is washed in five
>r six times its weight of boiling water, and the still
hot liquor is decanted with the uncombined and sus-
pended sulphur. Other washings with cold water
remove the alkaline sulphides. Lastly, the vermilion
is collected upon a filter, drained, and dried.
We see that there is a great analogy between all of
these processes, and that, to arrive at a fine quality of
vermilion, the success appears to depend upon pure
materials, good proportions, and, especially, a proper
temperature. Indeed, we know that vermilion loses
part of its brightness when it has been overheated.
Mr. Weshle assures us that he can produce a bright
vermilion by finely pulverizing cinnabar, mixing it
with 1 per cent, of sulphide of antimony, and boiling
it several times with 3 parts of sulphide of potassium
in a cast-iron pot. The precipitate is then washed
with pure water, digested with hydrochloric acid, and
washed again. There is nothing surprising in this
28
434 MANUFACTURE OF COLORS.
process, since we know that under certain circum-
stances the sulphide of antimony acquires a fine red
color, as we shall see further on.
D. Firmenich Process.
Cinnabar, says Mr. Firmenich, is found in the
native state, either in crystals, or compact and earthy
crystalline, or fibrous, or pulverulent, etc. It is found
in pockets or in veins, or is earthy and mixed with
other rocks. It is chemically prepared either by the
dry or by the wet way.
In the manufacture of cinnabar, 7 parts of mercury
and 1 of sulphur are melted in an iron vessel, and the
resulting sulphide is then sublimed in other vases of
refractory clay. At Idria, the first mixture is effected
in rotary tuns, and the chemical combination and the
sublimation take place in heated cast-iron retorts.
A process which is less known, and which gives
better results than all of the other methods, in the
beauty of the color and the resistance to the fire, is
that with the sulphide of potassium. This mode oi
operation supposes this reagent to be in a great state
of purity. There are various methods of preparing 11
but we should discard those by which a lye of causti*
potassa is boiled with an excess of sublimed sulphui
or when potassa and sulphur are fused together, b<
cause there is also formed a hyposulphite or a sulphat
of potassa, which comes in the way of the prepan
tion of the cinnabar.
A pure sulphide of potassium is obtained by re-
ducing the sulphate of potassa* with charcoal, an<
* The author employs and repeats the words " sulphide
potassa," which we do not understand, and for which we have
substituted those of " sulphate of potassa." — TRANS.
RED COLORS. 435
saturating the lye afterwards with sulphur to the
degree required for the operation.
For instance, 20 parts of sulphate of potassa* and
6 of charcoal are finely powdered, and thoroughly
mixed. The whole is then strongly heated in a
Hessian crucible, luted and placed in an air furnace.
Although not seen, the mixture boils in a lively way,
and the crucible should not be filled to more than
two-thirds of its capacity. The melted and cooled
mass is a simple sulphide of potassium (KS), which
presents a crystalline appearance, is colored brown or
red, and attracts the dampness of the air. It is boiled
in a cast-iron kettle with pure or rain water, in the
ratio of 2 parts of substance to 7 of water, and is
then filtered. By cooling, the undecomposed sul-
phate of potassa* crystallizes on the sides of the
vessel.
Thus purified, the lye is again boiled with pow-
dered sulphur, which is added by small quantities at
a time, until saturation, which is ascertained by the
effervescence of the liquor, and the formation of bub-
bles at its surface. The simple sulphide of potassium,
by this saturation, absorbs 4 atoms of sulphur. The
contact of the air should be avoided as far as practi-
cable, because its oxygen decomposes the sulphide.
The cinnabar is manufactured as follows : Bottles
are filled with 5 kilogrammes of mercury, 1 of sul-
phur, and 2.25 of the lye of sulphide of potassium,
and, after having been moderately heated, they are
shaken, two at a time, in a basket hanging from a
spring, and striking a straw mattress in its descent.
* The author employs and repeats the words "sulphide of
potassa," which we do not understand, and for which we have
substituted those of " sulphate of potassa." — TRANS.
436 MANUFACTURE OF COLORS.
After one and a half or two hours of such motion,
the bottles become hot, and the mixture acquires a
greenish-brown color. The mercury combines with
the sulphur of the lye, while the latter keeps up its
degree of saturation from the added sulphur.
In order to keep the mixture in a greater state of
division and more porous, it is recommended now and
then to turn the bottles. After three and a half hours
the mercury is entirely combined, and the mixture is
a dark-brown. It is then left to cool off slowly. The
whole operation lasts five hours. The bottles are
next carried into a stove-room, where the temperature
is maintained at from 45° to 50° C., and where the
mixture gradually turns red. This heating continues
from two to three days, and the contents of the bottles
should be well stirred three or four times every day.
The temperature has a decisive action upon the
tone of the color ; the cooler the mixture before the
shaking operation, the lighter will be the color of the
product. For instance, a light carmine cinnabar with
a yellowish tinge is prepared by cooling the bottles
for one hour in the open air, in winter ; but in sum-
mer they are cooled in water.
It now remains to free the cinnabar from the excess
of sulphur, and this is done in the following manner :
About 6 decilitres of pure water are added to each
bottle, which is shaken and emptied upon a filter.
The clear lye runs out, and the remaining cinnabar is
put into a stoneware pot, where it is mixed with a lye
of caustic soda, which dissolves the remaining free
sulphur. Some time afterwards the lye is decanted
as completely as possible, and the deposit is washed
several times by decantation, and lastly, upon a filter.
The solution of the excess of sulphur, and the
RED COLORS.
437
washing off of the caustic lye, require a great deal of
care. Indeed, the resistance of the product to the
action of the fire entirely depends upon the first
operation; the second insures the greater or less
durability of the color. The filtration takes from two
to three days, and the drying is effected at a very
low temperature until the cinnabar can be broken to
pieces, and is dry to the touch. It is then placed in
iron basins, and is repeatedly stirred, while the tem-
perature of the stove-room is raised to 60° or 62° C.
Under the influence of too much heat the cinnabar
becomes of a darker color; this is not a defect, since
the color becomes more steady when exposed to the
fire. This last drying requires about five hours.
As we have already stated, this mode of preparing
cinnabar is to be preferred to all others, because the
product answers the requirements of beauty of color,
and is capable of withstanding fire, the latter quality
especially being wanting in most of the other cinna-
bars. Moreover, the figures prove that this method
produces a cheaper cinnabar than those prepared in
the usual manner.
Many trials have been made to brighten the color
of vermilion and increase its fire. Here are some
results : —
Desmoulins, in 1825, employed a lye of caustic
potassa. Mr. Dumas, in his Traite de Cliimie, states
that unsuccessful attempts have been made with nitric
acid to impart to French vermilion the brightness of
that of China. However, the particulars as to the
proportion and strength of the acid were not made
public. MM. Pelouze & Fremy, in their Cours de
Cliimie, indicate the use of hydrochloric acid for
washing the paste of vermilion.
438 MANUFACTURE OF COLORS.
Lastly, it appears from a recent lawsuit that Mr.
Ringault, Sr., manufacturer of colors at Paris, took
out, on the 15th of October, 1859, a patent for the
preparation of a vermilion unalterable by fire. The
process consists in a method of purifying and
brightening the cinnabar ground in water, so that
the resulting vermilion acquires a depth of color and
a durability seldom arrived at. Here are the various
operations : —
1. Treatment with nitric acid, which removes all
the excess of sulphur.
2. Treatment by a hot mixture of sulphide of potas-
sium and caustic potassa.
3. Digestion of the vermilion in hydrochloric acid.
4. Hot treatment of the paste with a solution of
caustic potassa, in order to give a more or less violet
tinge to the vermilion.
Mr. Desmottes, manufacturer of vermilion at Paris,
has tried to imitate this process as follows : The
vermilion is treated by nitric acid, with the useless
addition of acetic acid. Then comes the employment
of a hot solution of potassa, to which powdered sul-
phur is added. Lastly, the paste is digested with
hydrochloric acid. The process is the same as that
of Ringault, and produces vermilions possessing the
desired qualities of brightness and durability.
Vermilion is quite often adulterated. Its purity
may be ascertained by heating it in a closed vessel.
The pure article is entirely volatilized, whereas the
impurities, such as powdered brick, red lead, red
ochre, colcothar, etc., remain on the bottom of the
vessel. By a treatment with hot nitric acid a ver-
milion holding red lead or orange mineral becomes
RED COLORS. 439
brown. Thrown upon burning coals it emits garlic-
smelling fumes if it has been adulterated with realgar.
It is useless to say that cinnabar and vermilion are
poisonous colors.
§ 10. Iodide of mercury.
The iodide, or rather the bi-iodide of mercury, is a
salt possessing a red color of the greatest brightness,
but which is rendered yellow, and then black, by the
action of light. It is scarcely employed now-a-days,
except in water colors. Moreover, it is highly poison-
ous, and there are several other pigments, which when
mixed with it, decompose it.
The preparation of this oxide, which is called
xirlet in England, is quite easy. Two dilute solu-
tions, one of 80 parts of bichloride of mercury (corro-
sive sublimate) and the other of 100 parts of iodide
of potassium, are mixed together, and the resulting
precipitate is washed with distilled water, first in the
vessel and then upon a filter, and lastly, dried at a
low temperature. This color should be kept in black
bottles.
Heller affirms that this bi-iodide becomes more
durable if it be dissolved in a hot and concentrated
solution of sal ammoniac. By cooling, the color is
precipitated in the shape of fine purple crystals, which
are washed and finely pulverized.
§ 11. Chromates of mercury.
The combination of chromic acid with the binoxide
of mercury furnishes, according to Mr. Millon, two
chromates which differ in their composition and their
color.
The first of these chromates is obtained by pouring
440 MANUFACTURE OF COLORS.
a solution of chromate of potassa into a solution
nitrate of binoxide of mercury. A very dark brick-
red precipitate is formed, which is washed several
times by decantation, and then dried in the air and in
the dark.
The other chromate is prepared by boiling for a
long time, the red oxide of mercury with a concen-
trated solution of bichromate of potassa. The pre-
cipitate is separated by decantation, washed several
times with hot water, and dried in a dark place.
"When it has been well prepared it has a fine violet
tinge.
These colors are costly of production, and are
easily decomposed by light.
§ 12. Chromate of copper. Maroon-red.
This color is not yet very well known, and is pre-
pared with a boiling solution of sulphate of copper,
poured, drop by drop, into another boiling solution of
neutral chromate of potassa. There are formed a solu-
ble sulphate of potassa and a precipitate of chromate
of copper, which are washed by decantation with hot
water until the latter is colorless. It is afterwards
collected and drained upon a filter and dried in a
stove.
§ 13. Chromate of silver. Purple-red.
The chromate of silver is a color without much
durability, which is employed only in miniature paint-
ing. It is prepared by pouring a solution in distilled
water of 30 parts of crystallized nitrate of silver into
another solution of 30 parts of neutral chromate of
potassa, also in distilled water. The purple-red pre-
RED COLORS. 441
cipitate is washed with distilled water, then thrown
upon a filter, and dried in the dark.
§ 14. Sulphide of antimony. Vermilion of antimony.
Lampadius had already, in 1833, proposed for a
pigment, the red sulphide of antimony, which covers
well when employed with water, but which possesses
less body when ground in oil. Since then, several
chemists have examined this sulphide for a coloring
substance, but we shall mention only those experi-
ments which seem useful in practice.
Mr. E. Mathieu-Plessy has published an interest-
ing memoir on the vermilion of antimony (Bulletin
de la Societe industrielle de Mulhouse., vol. 26, p. 297),
from which we give an extract : —
" The product to which I give the name vermilion
of antimony, is the result of a new modification of
the sulphide of antimony, which I obtain from the
decomposition of hyposulphite of soda in the presence
of chloride of antimony.
" Among the phenomena of double decomposition,
so characteristic of the nature of mineral substances,
none is more striking than the production of the
orange-yellow sulphide of antimony by means of sul-
phuretted hydrogen or of an alkaline sulphide. If
the latter reagent, from long exposure to the air,
be partly transformed into hyposulphite, it may give
with a protosalt of antimony, according to its greater
or less degree of oxidization, variously colored pre-
cipitates. These variations, which may have been
observed already, will be easily explained by the re-
action which I have studied out, and which gave me
the key for obtaining a red sulphide of antimony en-
tirely distinct from the following well known ones :
442 MANUFACTURE OF COLORS.
"I refer to the orange-yellow sulphide produced
by the reaction of sulphuretted hydrogen upon the
protochloride of antimony — the black native sulphide
— and the brown-red sulphide, a modification of the
preceding one, which was observed for the first time
by Fuchs, and has recently been studied by Mr.
Rose,
"It is not sufficient, however, to put the proto-
chloride of antimony and the hyposulphide of soda
in contact with each other, to obtain the sulphide of
antimony with all the brightness which it is able to
acquire. In order always to arrive at the desired re-
sult, I have been obliged to make numerous trials,
and to vary the proportions of the reagents and the
temperature. At last I have succeeded in finding
out a process which is satisfactory in regard to the
quality of the product and the facility of its pre-
paration.
"Believing that the vermilion of antimony might
find its application in the arts, I have examined its
preparation from beginning to end, and I have, there-
fore, aimed to produce the hyposulphite of soda and
the chloride of antimony on a manufacturing scale.
In regard to the hyposulphite of soda, and in view of
avoiding the crystallizations which require a peculiar
apparatus, I followed a process which gave me this
salt in a state of sufficient purity, at a time when its
preparation was but little understood. This process
was based upon the employment of the sulphite of
soda.
" In my researches I have demonstrated that
this salt should be employed in the neutral state,
in order to avoid the reaction of the sulphurous
acid upon the hyposulphite, resulting in the Lang-
RED COLORS. 443
lois salt, which, being also decomposed, becomes
sulphate of soda. In the preparation of the sul-
phite I have followed the process of Mr. CamHle
Koechlin, which consists in burning sulphur in an
apparatus easily established. There is a sieve hold-
ing large crystals of soda, which is suspended in a
cask opened at the top. The bottom is connected by
"means of a pipe with a small clay furnace, upon which
the sulphur is thrown by small quantities at a time.
" The combustion of the sulphur is regulated by
means of a trap-door; the draft is good, and after
two or three days the crystals of soda are transformed.
Should there be portions unacted upon, the easily
crumbling sulphite is rubbed off, and the core of car-
bonate is replaced in the cask. A solution marking
25° Be., is made with the sulphite, and is afterwards
heated and saturated, with crystals of soda. When
the addition of this salt ceases to produce an effer-
vescence (litmus paper does not give sufficient in-
dications), or rather, when a diluted sample of the
liquor produces a slight disengagement of carbonic
acid by the addition of hydrochloric acid, then sub-
limed sulphur is put in, and the mixture is heated for
three hours upon a water-bath. During that time
the evaporated water is replaced, and the mass is
frequently stirred. The cold liquor is diluted with
water, so as to mark 25° Be.
"The protochloride of antimony is easily prepared
by boiling in hydrochloric acid the powdered native
black sulphide of antimony. When the disengage-
ment of hydrostilphuric acid begins to be slow, the
whole is made to boil for a few minutes. After cool-
ing, the clear liquid is decanted.
" In order to obviate the inconvenience of the pro-
444 MANUFACTURE OF COLORS.
duction of sulphuretted hydrogen, the gas is collected
in a solution of soda, or it is burned at the end of a
glass tube connected with the vessel, where the re-
action takes place. If a burning alcohol lamp be
placed at the end of the tube, the combustion of the
gas will not be arrested, even should the gas be
accompanied by a large proportion of steam. The
chloride of antimony thus obtained is diluted with
water to 25° Be.
" The two solutions of antimony and of hypo-
sulphite being prepared, we proceed as follows : We
pour into a stoneware vessel 4 litres of chloride of
antimony, 6 litres of water, and 10 litres of hypo-
sulphite of soda. The precipitate caused by the
water is rapidly dissolved, in the cold, by the hypo-
sulphite. The vessel is then placed in a hot-water
bath, where the temperature of the mixture is gradu-
ally raised. At about 30° C. the precipitate of sul-
phide begins to form ; it is orange-yellow at first and
becomes darker afterwards. At 55° C. the vessel is
removed from the water bath, and the precipitate is
allowed to settle, which it does rapidly. The mother
liquors are decanted, and the deposit is washed the
first time with water holding y1^ of hydrochloric acid,
and afterwards with ordinary water. Lastly, the
precipitate is collected upon a filter and dried. The
wet vermilion of antimony is of an exceedingly bright
red color ; after drying it loses part of its brightness.
This pigment may be prepared in the cold, but the
product is finer and more constant if we operate in
the manner just described.
"Being certain to reproduce my new sulphide
whenever it is desired, I have undertaken its analysis.
But as the determination of the antimony is very
RED COLORS. 445
difficult, and as there is no known method sufficiently
accurate for the purpose, I have determined the sul-
phur and calculated the antimony by difference. It
has also been necessary to determine the proportion
of water. Moreover, I have compared the orange-
yellow sulphide with my own, and the result is —
0.668 of orange-yellow sulphide lose 0.038 at 200° C.
0.808 of red sulphide lose . . 0.009 at 200° C.
"This proves that the vermilion of antimony is an
anhydrous substance, the above loss being evidently
due to an imperfect drying.
" There now remains to prove by analysis, that
the vermilion of antimony differs from the orange-
yellow sulphide by only one equivalent of water.
This explains the new properties of the red sulphide.
I have found by analysis —
Water 1.1
Sulphur 26.7
Antimony (by difference) . . 72.2
100.0
which composition proves that the equivalents of
sulphur and antimony are in the ratio of 3 to 1."
M. E. Kopp has also published, in the Bulletin de
la Societe Industrielle de Mulhouse, vol. 20, page 379,
a memoir on the manufacture of the vermilion of
antimony. We reproduce the following extracts : — '
" The sulphide of antimony, according to its physi-
cal state and its mode of preparation, may present
very varied colorations. It is crystalline and black-
ish-gray in the native state and melted. Kept in the
molten state for a long time, and suddenly cooled, it
becomes hyacinth-red. Precipitated by sulphuretted
hydrogen from an antimonic solution, it is of an
446 MANUFACTURE OF COLORS.
orange color more or less red. In the kermes state
it is red-brown. Lastly, obtained from the reaction
of a soluble hyposulphite upon the chloride of anti-
mony, its red color is more or less bright, and more
or less orange or crimson, in accordance with the
temperature employed, and the concentration of the
liquors.
"This latter reaction was indicated by several
chemists, who gave recipes for the regular manufac-
ture of the fine red sulphide of antimony, which was
called vermilion of antimony.
" All of these methods are based upon the employ-
ment of hyposulphite of soda and chloride of anti-
mony in quite concentrated solutions, and they present
various inconveniences.
"In the process which I have followed, the ver-
milion of antimony is obtained by the reaction of the
chloride of this metal upon a dilute solution of hypo-
sulphite of lime; and the mother liquors are used
several times, and are thrown away only after they
contain too great a proportion of chloride of calciui
"I am now going to describe successively tl
various operations in the manufacture of the red sul
phide of antimony.
" 1. Preparation of the Chloride of Antimony . — Tl
decomposition of the sulphide of antimony by hydr<
chloric acid, is very easy in experimental laboratory
but the operation presents great difficulties when
have to work upon large quantities of materials.
"After a series of experiments (employment oi
leaden vessels, heating of stoneware vessels in sand
and pitch baths, etc.), I found that it was much
better to roast the sulphide of antimony at a mode-
rate temperature, and with the contact of air and
RED COLORS. 447
steam. The greater part of the sulphide is trans-
formed into oxide of antimony, and the sulphurous
acid produced is used in the manufacture of the hypo-
sulphite of lime. The oxide of antimony is then
easily dissolved in commercial hydrochloric acid.
" If, during the oxidation of the sulphide of anti-
mony, there is produced a certain proportion of anti-
monipus acid, but slightly soluble in hydrochloric
acid, it may be saved by collecting the residues from
the treatment with hydrochloric acid, and washing
them with chloride of calcium or hyposulphite of lime,
which dissolves the adherent chloride of antimony.
They are then dried and melted with a certain pro-
portion of sulphide of antimony and of quicklime, in
order to transform the whole into antimony green.
The addition of a small quantity of quicklime is in-
tended for decomposing the small proportion of chlo-
ride of antimony which may still remain in the residues.
" 2. Preparation of the Hyposulphite of Lime. — This
salt is cheaply prepared by the action of sulphurous
acid upon the sulphide or poly sulphide of calcium, or
the oxy sulphide. The sulphurous acid is produced
by the combustion of brimstone, or the roasting of
pyrites, or of sulphide of antimony.
" The polysulphide of calcium is prepared by boil-
ing finely ground sulphur with newly slaked lime
and a sufficiency of water. It is advantageous to add
to this solution of polysulphide, a certain proportion
of powdered oxysulphide of calcium, which is the
residue of the lixiviation of crude soda. In the ab-
sence of oxysulphide, quicklime may be added.
"Sulphurous acid, in its reaction upon the sulphide
and the oxysulphide of calcium, sets sulphur free, and
forms a sulphite of lime, which, in presence of the
448 MANUFACTURE OF COLORS.
sulphur and of the undecomposed sulphide, is soon
transformed into hyposulphite of lime. The reaction
is aided by the elevation of temperature which takes
place in the apparatus.
"The liquor is examined now and then to see
whether it is alkaline, neutral, or acid. As soon as
it has become slightly acid, it is run from the appa-
ratus into a large settling tank, where it generally
becomes neutralized by a certain quantity of unde-
composed oxy sulphide of calcium held in it. If, after
stirring for some time, the liquor preserves its acid
reaction, sulphide of calcium is added until complete
neutralization, which is ordinarily made apparent by
a black precipitate of sulphide of iron.
" After settling for some time, the clear liquid is
decanted, and forms a solution of nearly pure hypo-
sulphite of lime. The same vessel is subsequently
used for neutralizing the liquors obtained during the
process of manufacture.
3. " Preparation of Vermilion of Antimony. — The
red sulphide of antimony is prepared with the above
solutions of chloride of antimony and of hyposulphite
of lime.
"The apparatus is simply composed of several
wooden tanks, holding from 20 to 30 hectolitres each,
and raised about 1 metre above the floor. These
tanks are so arranged that they may be heated by
steam, either through a copper or lead pipe, the
opening of which is about 2 decimetres from the
bottom, or, what is preferable, through a coil of
pipes, the condensed steam of which may be carried
outside, without being mixed with the liquors. In
this manner we avoid the useless dilution of the
liquors producing the vermilion of antimony.
RED COLORS. 449
" When the pressure of the boilers has reached two
or three atmospheres the tanks are filled with the
solution of hyposulphite of lime up to seven-eighths
of their height. We then pour the solution of chlo-
ride of antimony into the first tank, 2 or 3 litres at a
time. There is formed a white precipitate which is
rapidly dissolved at the beginning, but when it be-
comes glow of solution, even by stirring the liquor,
the addition of chloride of antimony is discontinued,
because there must always be a certain excess of
hyposulphite of lime.
" The liquor of the tank should be perfectly clear
and limpid, and any white precipitate should be dis-
solved by adding small quantities of hyposulphite.
" Steam is then let in, and the temperature of the
liquors is gradually raised to 50° or 60°, or even 70° C.,
while stirring goes on. The reaction soon becomes
manifest ; the liquid is successively colored a straw-
yellow, then a pure lemon-yellow, orange-yellow,
orange, reddish-orange, and lastly, a very deep and
bright orange-red. The steam is then stopped, and
the acquired heat of the liquid, aided by a slow
stirring, is sufficient to complete the reaction, and
impart to the color its maximum of intensity. Should
the heating be continued, the red-orange color would
pass successively to a pure red, then to a more or
less crimson red, which in its turn would grow darker
and darker, and become brown, blackish-brown, and,
lastly, nearly black.
" We see that by graduating the temperature it is
possible to obtain all the intermediate hues between
orange and brown-black. The tank is covered, and
the colored precipitate is allowed to deposit.
" The clear and limpid liquor, which smells strongly
29
450 MANUFACTURE OF COLORS.
of sulphurous acid, is decanted through holes bored
in the tank at different heights, and is conducted by
means of leaden pipes or wooden troughs into a large
reservoir holding a certain quantity of sulphide and
oxysulphide of calcium. The sulphurous liquor re-
generates a certain proportion of hyposulphite of
lime.
" As the solution of chloride of antimony always
contains a large proportion of chloride of iron, it be-
comes easy to watch the working of this latter ope-
ration. All the iron remains soluble in the mother
liquors of the sulphide of antimony, and as soon as
they are brought in contact with the sulphide of cal-
cium, there is a formation of insoluble sulphide of
iron. As long as the black precipitate remains, the
mother liquors charged with sulphurous acid have
not been added in excess. But when they are in ex-
cess the black precipitate disappears, since it is trans-
formed into a soluble hyposulphite of iron. The
contents of the reservoir are then well stirred, and, if
necessary, sulphide of calcium is added, until the
black precipitate of sulphide of iron reappears and
remains permanent. At the same time a certain pro-
portion of hyposulphite of iron should remain in so-
lution. This condition is easily fulfilled when we
operate upon a sufficiently large amount of materials.
After the precipitate has settled the liquor is decanted,
and is a neutral solution of hyposulphite of lime, wit]
a certain proportion of hyposulphite of iron and oi
chloride of calcium.
" We should carefully avoid, in this regeneration oi
the hyposulphite of lime, leaving in an excess of sul-
phide of calcium, which will impair the coloration ol
the vermilion by causing the formation of the ordinary
RED COLORS. 451
orange-yellow sulphide of antimony. Therefore, if
the solution of hyposulphite of lime be yellow and
alkaline, a liquor charged with sulphurous acid should
be added, until complete neutralization of the alkaline
reaction.
" This solution of hyposulphite of lime, like the
first, is employed in the preparation of a new quantity
of vermilion of antimony. The mother liquors,
charged with sulphurous acid, are again neutralized
in the large reservoir by a new proportion of sulphide
and oxysulphide of calcium, and soon, until the liquors
become so much loaded with chloride of calcium that
it becomes necessary to throw them away, or to re-
serve them for some other purpose. But this takes
lace only after twenty-five or thirty operations.
" It is even possible to save the sulphurous acid of
these worn-out mother liquors, by saturating them
with a milk of lime. There is a precipitate of oxide
of iron and of sulphite of lime, and the mother liquors
contain only chloride of calcium. The precipitate,
mixed with sulphide of calcium, is transformed by
sulphurous acid into the hyposulphites of lime and
iron. And if the proportion of iron be too great, it
may be precipitated by a slight excess of a milk of
lime.
" The precipitate of vermilion of antimony left on
the bottom of the first tank is received into a conical
cloth filter, and the drained liquors are added to those
of the reservoir. The tank is then rinsed with tepid
water, which is made to pass through the filter.
" The washing of the vermilion should be done
very carefully, and it is often necessary to empty the
contents of the filter into a large volume of pure
water, and to wash several times by decantation. The
452 MANUFACTURE OF COLORS.
red sulphide is afterwards filtered again and dried at
the ordinary temperature, or in a stove-room, the tem-
perature of which is not over 50° to 60° C.
" While the precipitate is settling in the first tank
a similar operation takes place in the second, and then
in the third. During that time the first tank has
been emptied, and its mother liquors have been re-
generated. These are then brought back into the
first tank, and another precipitation of vermilion of
antimony takes place, and so on.
" We see that by this process the expense in sul-
phur, and therefore in sulphurous acid and hyposul-
phite, is reduced to a minimum.
" 4. Properties of the Vermilion of Antimony. — The
vermilion of antimony is in the state of a very fine
powder, without taste or smell, and is insoluble in
water, alcohol, or essential oils. It is but little acted
upon by the weak acids, even concentrated ; or by the
powerful inorganic acids which have been diluted with
water. It stands the latter acids better than the ordi-
nary sulphide of antimony. Concentrated and hot
hydrochloric acid dissolves it, when sulphuretted hy-
drogen and chloride of antimony are formed. Nitric
acid oxidizes it, with production of sulphuric and
antimonic acids. The vermilion of antimony is not
sensibly acted upon by ammonia or the alkaline car-
bonates ; on the other hand, the powerful caustic
alkalies, such as potassa, soda, baryta, strontia, and
lime, decompose it and form combinations which are
colorless, or nearly so. The color is therefore de-
stroyed, and thus we see that this pigment should not
be mixed with alkaline substances. A high tempera-
ture blackens it, and should the heat be such as to
melt it, it becomes ordinary sulphide of antimony.
RED COLORS. 453
" The vermilion of antimony is an opaque color,
without much lustre or brightness, when it is mixed
with water, thickened by gummy or gelatinous sub-
stances. On the other hand, when ground in oil or
varnishes, it acquires a great intensity and brightness
of color, and has a good body or covering power,
being superior in that respect to red lead, orange
mineral, the red subchromate of lead, and cinnabar or
vermilion with a basis of mercury. A well-prepared
vermilion of antimony, ground in oil, gives possibly
the purest red color, that is to say, it is not tinged
orange, or pink, or crimson ; but it often has a
brownish hue. It is perfectly unalterable by air or
light, and may be mixed with white lead, which is not
blackened by it, even after several years. It does
not assist or hinder the drying of oil. Therefore, the
vermilion of antimony is a pigment especially fitted
for oil painting, and its low price and covering
power render it advantageous for carriage and house
painting."
§ 15. Sulpho-antimonite of barium.
Mr. R. Wagner has indicated the sulpho-antimonite
of barium, combined with the artificial sulphate of
baryta (blanc fixe), as furnishing good pigments for
painting.
The sulpho-antimonite of barium is prepared by
mixing —
Finely powdered sulphate of baryta . . 2 parts.
Native gray sulphide of antimony . . .1 part.
Powdered charcoal . . . . . . 1 "
and calcining the mixture at a red heat for several
hours in a crucible of clay or graphite. The crucible
should not be opened before it is entirely cold, because
454 MANUFACTURE OF COLORS.
the carbonaceous mixture easily becomes inflamed.
The calcined mass is then boiled in water, and, as the
insoluble residue still contains undecomposed sul-
phate of baryta and sulphide of barium, it is mixed
with the materials of another operation.
The filtered liquor is a pale-yellow, and dilute sul-
phuric acid is added to it until the orange color is
entirely precipitated. Sulphuretted hydrogen is dis-
engaged.
The color is diluted with blanc fixe. If a purer
orange hue be desired, the solution of sulpho-anti-
monite of barium is boiled with \ part of sublimed
sulphur. The sulpho-antimonite of barium is trans-
formed into sulpho-antimoniate, which has a composi-
tion analogous to Schlippe's salt. If the liquor, filtered
from the undissolved sulphur, be precipitated by sul-
phuric acid, we obtain a mixture of blanc fixe and
persulphide of antimony. As during the boiling of
the liquors a part of the sulphide of barium is trans-
formed into polysulphide, there is always in the pre-
cipitate a small proportion of sulphur, which is said
to be productive of no inconvenience.
Instead of the ordinary sulphide of antimony the
vermilion may be mixed with the sulphate of baryta.
The mixed pigment will be obtained at once by em-
ploying sulphuric acid for the decomposition of the
hyposulphite of soda, which has previously been
mixed with the chlorides of antimony and barium.
§ 16. Cobalt pink.
Cobalt pink is a mixture of the oxide of this metal
with magnesia. It is a durable color, and more or
less pink, according to the proportion of cobalt it
contains. It is an expensive pigment, which is used
RED COLORS. 455
only for fine painting. Its preparation consists in
making a paste of carbonate of magnesia with a con-
centrated solution of nitrate of cobalt. The paste is
dried in a stove, and then calcined in a porcelain
crucible.
§ 17. Arseniate of cobalt, metallic lime.
This salt is employed in oil painting, possesses a
very deep and durable red hue, and is found native in
cobalt mines combined with other substances. These
are removed by a treatment with boiling nitric acid,
which dissolves the pigment and the other impurities.
The clear liquor receives small additions of potassa
until all of the iron is precipitated as arseniate ; then,
after settling and decanting, a further addition of
potassa precipitates the arseniate of cobalt.
For preparing the artificial arseniate the sulpho-
arsenide of cobalt (gray cobalt) is powdered, mixed
with a little sand and twice its weight of potassa, and
then fused in a crucible. There is produced a kind
of cinder of sulphides, which is removed. The remain-
ing white arseniate of cobalt is pulverized and again
fused with potassa. The new cinders formed are
removed, and the button of pure arsenide is powdered
and roasted, in order to transform it into the arseniate,
the deep-red color of which is still brightened by fine
grinding.
§ 18. Purple of Cassius.
This substance, which bears the name of its inventor,
is the precipitate which takes place when solutions of
gold and chloride of tin are mixed under proper con-
ditions. The preparation of the purple of Cassius is
quite difficult, and we shall explain it in extenso, in
456 MANUFACTURE OF COLORS.
order that good results may be obtained. "We should
observe that a pure and neutral solution of proto-
chloride of tin, mixed with another solution of neutral
chloride of gold, produces maroon, brown, blue, or
green precipitates, and sometimes metallic gold,
according as the liquors are more or less concentrated.
The bichloride of tin does not produce a precipitate
with the solution of gold ; b'ut the reunion of the two
chlorides occasions a precipitate of a purple color.
Oberkamps has observed that the hue is the more
violet as the proportion of chloride of tin is greater
than that of gold ; and, conversely, that the hue is
pink if gold be in excess.
Buisson recommends the following process for
obtaining a fine purple : A neutral solution of proto-
chloride of tin is prepared by dissolving 1 part of tin
in hydrochloric acid. On the other hand, 2 parts of
granulated tin are dissolved in an aqua regia composed
of 3 parts of nitric acid and one of hydrochloric acid,
and the excess of acid removed. Lastly, 7 parts of
gold are dissolved in an aqua regia made of 1 part of
nitric acid and 6 of hydrochloric acid, and just enough,
and no more, of this mixture should be employed for
obtaining a neutral solution. The solution of gold is
diluted with 3| litres of water, receives the solution
of bichloride of tin, and then the protochloride of tin
is poured in, drop by drop, until the precipitate has
acquired the desired color. An excess of protochloride
of tin imparts a bluish hue. After settling, the pre-
cipitate is rapidly washed by decantation, and dried
in the dark.
Buisson ascertained that a sample of purple, pre-
pared by this method, was composed of —
RED COLOKS. 457
Metallic gold 285
Bioxide of tin 659
Chlorine 52
Loss 4
1000
Oberkamps has found —
In violet purple. In light purple.
Gold 0.398 0.795
Oxide of tin . . . . 0.602 0.205
Berzelius has obtained from a purple of good
quality —
Gold ...... 0.2835
Bioxide of tin . . . . 0.6400
Water 0.0765
1.0000
It is difficult from these analyses to arrive at a
conclusion as to the composition of the purple of
Cassius. In a more recent course of study Mr. L.
Fignier has demonstrated that this substance is a
stannate of protoxide of gold, which may be obtained
of a constant composition by the following process : —
The bichloride of gold is prepared by dissolving 20
grammes of gold in 100 parts of aqua regia, made
with 4 parts of hydrochloric acid and 1 of nitric acid.
The solution is evaporated to dryness in a water-bath,
in order to expel the excess of acid, and the remaining
chloride of gold is dissolved in 750 grammes of water.
Pure granulated tin is then introduced into the fil-
tered liquor, which, after some time, becomes brown
and turbid. After standing several days all the gold
is in the state of stannate of protoxide, which is sepa-
rated from the remainder of the metallic tin. The
product is collected upon a paper filter, carefully
washed, and dried at a gentle heat.
458 MANUFACTURE OF COLORS.
If the purple remains in suspension in the liquor,
it is made to settle by the addition of common salt,
and a slight heating.
The separation of the metallic tin, by decantation,
should be done carefully, because there is a black tin
powder which settles before the purple. This powder,
which contains gold, is collected apart for another
operation.
The purple of Cassius is extensively used for paint-
ing on porcelain ; it is also employed in miniature
painting.
§ 19. Madder lake.
Madder is the name of the ground root, and alizari
that of the whole root of a plant (Rubia tinctorwn),
which was formerly imported from the East and from
Holland, but which is now successfully cultivated in
several French departments.
We shall not in this work try to give all the char-
acteristics by which the madders from Holland, Avig-
non, and the East are recognized. We neither believe
that it is of advantage to indicate the various trade-
marks, because these marks have become quite illu-
sory. The best is to trust to respectable persons, well
acquainted with that product, or to learn one's self
how to recognize the characteristics, types, and quali-
ties of the various madders found in the trade.
Madder and garancin are often adulterated with
various substances, the powder of tinctorial woods,
for instance.
Among the processes generally employed for ascer-
taining the presence of the coloring substances added
to madder or garancin, there are but few which do
not require a good knowledge of chemical manipula-
BED COLORS. 459
tions. It is very difficult, sometimes, even for persons
conversant with these manipulations, to determine
with certainty the nature of the foreign substances,
especially when the adulteration consists of a mix-
ture of various coloring woods. Mr. J. Pernod, of
Avignon, has communicated to the Societe Industridle
de Mulhouse, the following simple and practical pro-
cesses : —
The vegetable powders or their extracts, employed
for the adulteration, may be divided into two classes :
the first comprises all of the tinctorial woods which
will form colored compounds with alumina and the
oxide of iron; such are the woods of Brazil, Campeachy,
Cuba, etc.
The second class comprises all of the substances
holding more or less tannin, with or without coloring
matter. These substances do not make colored com-
pounds with alumina, but they form brown or black
precipitates with the oxide of iron.
In order to detect in madder or garancin the addi-
tion of a small proportion of the various coloring
woods of the first class, a piece of white paper, from
10 to 15 centimetres square, is dipped for about one
minute into a solution of bichloride of tin.* It is
then spread upon a plate or a sheet of glass, and dusted
over, by means of a sieve, with 1 or 2 grammes of the
powdered sample. After half an hour, all the points
touched by the particles of foreign woods will present
the following colorations : crimson red spots with
Brazil wood ; violet with Campeachy ; yellow with
* This is the tin-bath of the dyers, obtained by dissolving 10
parts of tin in a mixture of 25 parts of nitric acid and 55 parts of
hydrochloric acid. This liquor, for use, should be diluted with
twice its weight of water.
460 MANUFACTURE OF COLORS.
Cuba wood, etc., while the portions of the paper in
contact with the madder will be slightly yellow.
The substances of the second class are detected in
this manner : a piece of writing paper is immersed in
an old bath of protosulphate of iron, part of which
has been peroxidized, or in a fresh one to which a few
drops of neutral nitrate of iron have been added.
After being dried, the paper is moistened uniformly
with a small quantity of alcohol (87 or 88 per cent.),
and then placed upon a sheet of glass. A. very small
quantity of the suspected powder is dusted over it by
means of a fine silk sieve, which is kept very near the
paper, in order not to lose by a current of air any par-
ticle of the foreign matters, which are generally finer
than the madder. After a quarter of an hour of con-
tact, there are blue-black spots on the points touched
by the adulterating powder, while the coloration occa-
sioned by madder is rust-like or a light-brown.
When the alcohol is entirely evaporated, the dust
adhering to the paper is rapidly removed with water,
and the blue-black spots due to the combination of
the tannin with oxide of iron, become still more appa-
rent.
Madder does not entirely abandon its red coloring
principle to cold or hot water ; but if a small propor-
tion of alum be added, an intense red solution is
obtained, which, with alumina, may produce a hand-
some red lake.
1. Eobiquet and Colin Process.
Robiquet and Colin have indicated the following
process : 2 kilogrammes of madder are macerated
several times in cold water, and pressed each time.
They are then heated for three hours upon a water-
KED COLORS. 461
bath, with a solution of 1 kilogramme of alum in 12
litres of water. After filtration, the liquor receives
gradual additions of a solution of pure carbonate of
soda, until the precipitation is complete ; but the first
portions of the precipitate are collected apart, because
they are finer. All the precipitates are washed until
the decanted liquors have no longer an acid reaction ;
they are then drained upon a filter, moulded into
troches, and dried in the open air, in a place where
there is no dust.
2. Persoz Process.
The madder is fermented or washed with water con-
taining a small quantity of sulphate of soda. It is
then treated for 15 or 20 minutes with ten times its
weight of a boiling solution of alum holding one-
tenth of alum. The liquor is strained through a
filtering bag, and when its temperature has been
lowered down to 35° or 40° C., it is neutralized with
carbonate of soda. As soon as cubic alum has been
formed in the liquors, these are brought to a boil, and
there is formed a precipitate of a tribasic sulphate of
alumina, which carries down with it all the coloring
matter. The lake thus produced is carefully washed.
This lake, in the opinion of Mr. Persoz is superior to
all others on account of not being gelatinous, and
being therefore easily deposited, washed, and col-
lected. Moreover, it possesses the great advantage
for dyeing and calico printing, of being quickly dis-
solved in acetic acid.
The madder is not entirely exhausted by this ope-
ration, and it may be treated a second and a third
time with alum. The resulting liquors are generally
reserved for working madders which have not yet
462 MANUFACTURE OF COLORS.
been submitted to the action of alum-water. But, if
lakes be precipitated from them, only one-half, or even
one-third, of the carbonate of soda necessary to satu-
rate the alum, should be added.
The liquors from which the tribasic sulphate of
alumina has become precipitated, should not be thrown
away. They are used boiling for dissolving the color-
ing matter which may remain in madder or its residue.
When charged with coloring principles, they are again
saturated and boiled, and a new quantity of colored
lake is thus obtained.
In all dye-works, the whole of the coloring princi-
ples of madder are not extracted, and there are always
valuable residua which may be worked by the Persoz
process, or by other methods. But, in such cases, it
is not necessary to ferment the madder, or to wash it
with sulphate of soda.
Mr. Persoz has also indicated another mode of pre-
paring madder lake, which has been utilized as we
shall see further on. For the saturation of the alum
liquor, he replaces the carbonate of soda by an equiva-
lent proportion of acetate of lead, the base of which
is immediately precipitated as an insoluble sulphate.
The lake thus obtained is remarkable for the purity
and the intensity of its color.
3. Lefort Process.
Mr. J. Lefort, in his Chimie des Couleurs, has de-
scribed the following process for preparing a very
fine madder lake : —
" During the year 1827, Robiquet and Colin dis-
covered that by treating madder with two-thirds of its
weight of concentrated sulphuric acid, there was pro-
duced a blackish carbonaceous substance, in which all
EED COLORS. 463
the red coloring principle remained unaltered. This
substance is now common in the market, under the
names of garancin and sulphuric charcoal of madder.
Its coloring power is three times that of the good
qualities of madder ; therefore it has been almost en-
tirely substituted for the root in print works.
" We have had occasion to employ garancin in the
manufacture of lake, and with the following results : —
" 1 kilogramme of garancin, 2 kilogrammes of alum,
and 18 litres of pure water are boiled for 15 to 20
minutes in a well-tinned kettle. After filtration, and
in the still hot liquors, a solution of carbonate of soda
is added until the decoloration is complete. By col-
lecting the precipitate at different periods, the lake
obtained at the beginning of the operation is finer
than towards the end. After a rest of several hours,
the clear liquid is decanted, and the lake is thoroughly
washed until the water runs out perfectly clear and
tasteless. The precipitate is then collected upon
cloth filters of a close texture, drained, moulded in
troches, and dried in the shade.
" We have every reason to believe that the greater
part of the fine madder lakes employed in painting
are manufactured from garancin. With ascertained,
but variable proportions of garancin, alum, and water,
we may precipitate lakes ranging in color from a light
pink to a deep red."
4. Khittel Process.
i
Mr. J. Khittel, who has made a special study of
the preparation of madder lakes, has indicated in the
Technologiste, vol. 20, p. 340, a process for the prepa-
ration of a purple madder lake, which we reproduce
here.
464
MANUFACTURE OF COLORS.
" There are many methods and recipes for preparing
lakes with madder, garancin, alizarin, etc. ; but I do
not believe that they will produce an article which
will be satisfactory in every respect, because in the
greater number of these methods, there are erroneous
manipulations, which have a disastrous influence on
the quality of the product, and diminish its value. I
have undertaken a series of experiments on this sub-
ject, and I hasten to communicate the results.
" The first condition in the preparation of a lake,
is to avoid the boiling of madder or any of its solu-
tions, because there are formed products of decompo-
sition, and the lake itself is wanting in brightness.
In the preliminary treatment of the raw material
(madder or garancin), we should also eliminate as
completely as practicable the extractive matters and
a yellow substance, which is very prejudicial. The
dissolving agent for the coloring principle is gener-
ally alum, and rightly so ; the alum solution should
be employed hot, although never boiled with madder
or garancin. I have several times treated a sample
of the latter substance with a hot solution of alum,
while another portion of the same sample was boiled
with the same alum solution. In every case, the
lake obtained by ebullition was inferior to that result-
ing from the first mode of operation.
" Another mistake in the preparation of these lakes,
is too great a proportion of alum. As the formation
of a lake is based upon the elimination of the alumina,
it naturally follows that the greater the proportion of
alumina in the liquor, the more earthy and the less
bright will be the lake. The best proportion appears
to be equal weights of alum and madder or garancin.
I entirely discard the employment of soda, potassa,
RED COLORS. 465
and alkalies, by which the alumina is precipitated in
the hydrated state. This use of alkalies will never
result in a satisfactory lake, because the alkali itself
modifies the coloring substance, and the lake always
has a violet tinge.
" Mr. Persoz has obtained a fine lake by adding to
the solution of alum a solution of subacetate of lead,
then filtering, and boiling the clear solution. I have
ascertained that this process is the best, and that,
with the proper care during the operation, satisfactory
results in quality and quantity will be obtained.
Nevertheless, I have made the following modifica-
tions : —
" Since the red coloring principle of garancin
(rubiacin and alizarin of Higgin) is scarcely soluble
in cold solutions of the alkaline sulphates, I begin to
purify the garancin with solutions of the crystallized
sulphates of potassa or of soda. The proportions
which I have found the most satisfactory are —
Garancin . . . . . .1 kilogramme.
Crystallized sulphate of soda . . . . 1 "
Water . 36 litres.
" The garancin is put into the water, and remains
there for twelve hours. It is then filtered, pressed,
and again put into pure and cold water, and these
operations are repeated until all the sulphate of soda
is expelled, that is, until the washings do not occasion
any turbidity in a solution of subacetate of lead.
" A quantity of alum corresponding with that of
the garancin to be treated, is dissolved in from ten to
twelve times its weight of water, and boiled. The
washed garancin is then introduced into the boiling
solution, which is removed from the fire. A good
proportion is 1 kilogramme of alum, 1 of garancin,
30
466 MANUFACTURE OF COLORS.
and 18 litres of water. After standing for fifteen or
twenty minutes the solution is filtered, and the resi-
due of garancin is washed with boiling water. When
the temperature of the colored extract has fallen to 45°
or 50° C., there is added to it a quantity of subacetate
of lead equal to that of the alum employed, and the
mixture is stirred until all the subacetate is trans-
formed into sulphate of lead. The colored solution
should not be allowed to become cold, because part
of the color might be precipitated. After settling,
the red and clear liquor is easily decanted from the
heavy precipitate of lead.
"But, as this lead precipitate contains always a
small proportion of coloring matter and of acetate of
alumina, it may be washed with hot water, which may
be used for dissolving the alum in a subsequent ope-
ration. In such case, the following proportions will
be used for 1 kilogramme of garancin already treated
once : —
Alum . . . . . . .1 kilogramme.
Subacetate of lead .... 1 "
Water 18 litres.
" The residue of washed garancin may be submitted
to a second similar treatment, but the proportions
should be modified as follows per kilogramme of
garancin : —
Alum 750 grammes.
Subacetate of lead 750 "
Water .15 litres.
" Should the residue of garancin, after this second
treatment, contain enough of coloring matter to cover
the expense of a third treatment, we should employ
for each kilogramme of garancin twice treated : —
RED COLORS. 467
Alum 500 grammes.
Subacetate of lead 500 "
Water 12 litres.
" By heating for some time nearly to the point of
ebullition, but without violent boiling, the red solu-
tion separated from the lead precipitate, there is sepa-
rated a purple-red lake which is much superior, in
intensity and brightness of coloration, to all the lakes
which I have prepared by the other methods. The
acetic acid of the liquors prevents the complete pre-
cipitation of the alumina and coloring matter. There-
fore, after the first lake has been collected, the clear
liquor is divided into two equal portions ; into one of
them a solution of carbonate of ammonia is poured
drop by drop, until there is formed a slight turbidity,
but not a precipitate. The two portions are then
mixed and heated as before, and another quantity of
lake is obtained, which, however, is not so bright as
the former.
" These two kinds of lake are easily collected and
washed upon a filter, and they should be dried at a
very moderate heat. An excess of alkaline lye dis-
solves the wet lake, and becomes colored a violet-red.
It is also dissolved in concentrated acetic acid, and
the residue of its calcination upon platinum foil is a
white-ash of alumina."
5. Lake of Garanceux.
By the known processes of dyeing, and when ordi-
nary madder is employed, only from 35 to 40 per cent,
of its coloring matter are utilized. The residua are
therefore very rich, and of late years have been used
for the preparation of a substance called garanceux.
Several methods have been proposed, but we shall
468 MANUFACTURE OF COLORS.
reproduce here only that published by MM. Thierry-
Mieg and Schwartz, of Mulhouse.
After dyeing, the madder-bath is mixed with dilute
sulphuric acid, and is run out into a filter. The pro-
portions are : 3 kilogrammes of sulphuric acid at 66°
Be. for 400 kilogrammes of madder used. The filter,
which may be a pit holding a layer of 20 centimetres
of gravel covered with packing cloth, retains the
coloring matter precipitated by the acid. The liquor
escapes by the bottom, which is also covered with
packing-cloth. The residua are collected and put
into a vessel with 20 parts of water, and 10 parts of
sulphuric acid at 52° Be., for 100 parts of residua.
Steam is admitted into the mixture, which is boiled
from four to six hours. After filtration, the residue
is washed five or six times consecutively by decanta-
tion. It is then saturated and macerated for one hour
with a solution of 1 to 2 kilogrammes of crystals of
soda, and poured again upon a finer filter. The satu-
ration is complete when a drop of the mixture, being
deposited upon a white cloth, produces a slightly
pink ring. The garanceux remains upon the filter,
and after being pressed, dried, and pulverized, it may
be used again in dyeing.
Should the garanceux be submitted to processes
similar to those employed for madder and garancin,
it seems easy to prepare from it madder lakes.
According to their purity, the mode of preparation,
or the adulterations, there are in the market many
kinds of madder lakes, the color of which varies from
a light pink to a purple or brown, with all the inter-
mediary hues. The substances generally employed
for adulterating madder lakes, are the lakes of car-
mine and of red woods.
RED COLORS. 469
6. Sacc Process.
Mr. Sacc has prepared very fine lakes from the
pasty alcohol extract of madder. Take —
Pasty extract 100 grammes.
and add
Caustic ammonia 50 "
Wate* 125 "
Macerate for twenty-four hours, and add the same
quantity of water as above. Pass through a silk
sieve, and add while stirring a boiling solution of 100
grammes of alum in one litre of water. This lake is
of a magnificent deep red. By substituting for the
alum 125 cubic centimetres of a solution of sulphate
of sesquioxide of iron, marking 40° Be., a deep-violet
lake is obtained.
7. Kopp Process.
Mr. E. Kopp prepared madder lakes by a process
of his invention, and which we shall describe briefly.
The root is powdered coarsely, but uniformly. A
solution of sulphurous acid is then prepared by the
combustion of brimstone or of pyrites, or by the
decomposition of sulphuric acid upon charcoal. In
the latter method from 6 to 8 kilogrammes of sul-
phuric acid produce enough of sulphurous acid for a
solution in 10 hectolitres of water.
This solution holds from four to five and a half
thousandths of sulphurous acid. If the water be pure,
from a half to one-thousandth (in volume) of commer-
cial hydrochloric acid is added to saturate the small
proportion of earthy carbonates contained in certain
kinds of madder, that of Alsace for instance. On
the other hand, calcareous waters require a larger
470 MANUFACTURE OF COLORS.
addition of hydrochloric acid in proportion to the
quantity of carbonate of lime present.
The madder is mixed with ten times its weight of
sulphurous solution, and the whole is left to macerate
from twelve to twenty-four hours in wooden tanks,
well closed. The mixture is stirred now and then.
The semi-fluid substance, with the rinsings of the tub,
is then poured into cloth filters, which, after drain-
ing, are gradually but strongly pressed. The clear
liquor is received in a closed wooden vessel. The
pressed madder powder is removed from the filter,
and again treated with ten times its weight of the
sulphurous solution. The filtered liquor is added to
that of the first treatment. Lastly, the residue of
madder is mixed for the third time with ten times its
weight of sulphurous solution ; but as the resulting
liquor is poor it is reserved for the second sulphurous
treatment of another portion of madder.
The madder is then washed with boiling water,
pressed, and dried. It then constitutes a weak " flower
of madder," which, however, will produce hues of
pure color, and will leave the body ground perfectly
white. It may be left wet and converted into a weak
garancin by processes indicated by Mr. Kopp.
In order to prepare the lakes of alizarin and purpu-
rin, which are, in the opinion of this chemist, the
only valuable coloring principles of madder, the above
sulphurous solution is employed.
By adding to this solution small quantities at a
time of acetate or hyposulphite of alumina, or of alum
neutralized by carbonate of soda, and keeping the
bath, however, with an acid reaction, and hot, we
obtain successive precipitates of aluminous lakes,
which present the following characteristics : —
RED COLORS. 471
First lake : Dark red and very bright ;
Second lake : Light red and pleasing brightness ;
Third lake : Pink, quite pure ;
Fourth lake : Pink, slightly yellowish.
The concentrated mother liquors are of a dark-
yellow color, and dye a cloth a yellow, somewhat
fawn-colored. Therefore, in the opinion of Mr. Kopp,
it results that the liquor contains the fawn-colored or
yellow principle of madder, after the precipitation of
alizarin and purpurin.
Madder lakes are employed with water or oil, and
their greatest consumption is for miniature painting
and calico printing.
8. Adulteration of Lakes.
We have already given some information as to the
manner of testing adulterated madders; but, more
recently, Mr. T. Chateau, in a memoir on the adul-
terations of madder and its derivatives, which received
a premium from the Chamber of Commerce of Avig-
non, has indicated the following processes for the
detection of the adulterations : —
" Madder lakes are falsified according to their color.
When red or pink the adulteration is effected with
lakes from Brazil woods. The violet carmine lakes are
adulterated with Prussian blue and the lakes of alka-
net and Campeachy. Black madder lakes are often
mixed with the black lakes of logwood, cochineal,
sumac, galls, etc.
A. Red and Pink Lakes.
" These lakes do not color either hot or cold water.
They color alcohol and ether very slightly, and only
after a certain length of time. By calcination they
leave a white residue of alumina.
472 MANUFACTURE OF COLORS.
" Santaline. — If the lake be dark it may contain
santaline, which is detected by the orange-red color
acquired by the ether digested with the suspected
lake. Alcohol, under the same circumstances, would
be colored red.
" If the lake be of a pink hue it may be falsified by
lakes of Brazil wood or of cochineal. But as madder
lakes, and generally all lakes, are insoluble in water,
ether, or alcohol, their coloring substance should be
insulated, and I propose the following method : —
" Every lake with alumina for base is soluble in hy-
drochloric acid, or in acetic acid to which a few drops
of the former acid have been added, or in a solution
of protochloride of tin. After the lake is dissolved
ether is added to the solution, and the whole is
shaken. All the coloring matter is dissolved in the
ether, which will acquire different colorations accord-
ing to the lakes introduced.
"Lakes of Brazil wood. — First process. Let us
suppose that a madder lake is adulterated by the
lakes of Pernambuco, Sapan, or Brazil wood, the
coloring matter will be rendered soluble in ether by
the process indicated above, and the ether will be
colored a gold-yellow.
" Venice laJce, ball shape. — Second process. A madder
lake, adulterated by Venice lake, ball shape (one of
the finest lakes of Brazil wood) will disengage am-
monia if it be heated in a test-tube with a solution of
potassa. Under the same treatment a pure madder
lake does not produce ammonia.
"Brazil lake. — Third process. A madder lake,
falsified with the lakes of Brazil wood, will be gene-
rally recognized by its effervescence with the acids,
and its blue coloration by iodine. These reactions
RED COLOES. 473
are due to the presence of chalk and starch, which
are used for thickening the lakes made with Brazil
wood.
"Carmine lake. — -Another adulteration . of madder
lakes is that with the so-called carmine lakes, of an
inferior quality. This fraud is easily detected.
"Water is not colored with madder lake, while it is
colored with carmine lake. The coloration is imme-
diate, and becomes more intense by heating. This
aqueous solution of carmine lake becomes violet by
soluble alkalies and gives a violet precipitate with
lime-water, chloride of tin, sulphate of copper, acetate
of lead, and sulphate of zinc.
"All that has been said about red and pink lakes
may be applied to the madder carmine.
B. Violet Lakes.
" The violet madder lakes, after calcination, leave
an ash of oxide of iron, which, being dissolved in
hydrochloric acid, produce an abundant precipitate
of Prussian blue by the addition of ferrocyanide of
potassium.
" These lakes, under the action of hydrochloric acid,
turn a dirty orange-yellow color.
" Campeachy lakes. — 1. If adulterated with Cam-
peachy lakes, the addition of hydrochloric acid will
produce a crimson-red coloration. After calcination,
the ash will be nankin yellow or white, whether the
Campeachy lake is partly or entirely substituted for
that of madder.
"2. After having extracted the coloring matter in
the afore-mentioned manner, the ether is colored a
gold yellow, and will give the Campeachy reaction, if
that substance be present.
474
MANUFACTURE OF COLORS.
"Alkanet. — 1. The madder lakes falsified by alkanet
lakes are easily recognized. The lake is dissolved
in acetic acid, and bisulphide of carbon is added, which,
after shaking, is colored an intense violet red if al-
kanet be present. This reaction is characteristic of
that substance.
" 2. A madder lake adulterated by alkanet disen-
gages violet fumes when heated. Moreover, such a
lake is colored blue by alkalies, baryta, and lime.
" 3. After solution of the adulterated lake in acetic
acid, and separation of the coloring matter in ether,
this is evaporated, and the residue is treated by alco-
hol, which dissolves the coloring principle of alkanet.
This alcoholic solution gives a magnificent blue pre-
cipitate by the subacetate and the acetate of lead,
if it contains anchusine.
" Orchil. — Orchil lake is dissolved in hydrochloric
acid, which becomes red. Ether, shaken with this
solution, does not dissolve a trace of coloring matter.
The same reaction takes place with bisulphide of
carbon.
"Prussian Hue — Prussian blue, added to a violet
madder lake for the purpose of deepening the hue, is
recognized by the addition of hydrochloric acid, which
changes the violet of the lake to a green. Hypo-
chlorites, and especially hypochlorous acid, turn the
violet to a blue.
C. Black Lakes.
" By calcination, these lakes give an ash of oxid<
of iron. Hydrochloric acid changes them by degrees
into a dirty orange. They turn a brown rusty coloi
by the action of protochloride of tin.
" Charcoal and lampblack. — These lakes being oJ
RED COLORS. 475
a fine black color, it is possible to falsify them with
finely ground charcoal or lampblack. This fraud
will be detected by boiling the sample with hydro-
chloric acid, which will dissolve the lake, and will
leave the charcoal or lampblack as a residue.
" Black Campeachy lakes. — Black madder lakes may
be mistaken for those of Campeachy. The latter will
redden strongly by the action of hydrochloric acid
and of the protochloride of tin. In the first case,
the red portions will stain white paper a cherry-red
color ; and in the second case, a more or less violet
red.
" Lake with cochineal basis. — In order to distinguish
a black madder lake from one with cochineal basis,
an addition of chloride of tin will turn the cochineal
lake a cherry-red, and white paper will be stained.
The madder lake presents no such reaction.
" Slack sumach lake, etc. — While the black madder
lakes are of a pure color, those manufactured from
galls, sumach, and other astringent substances are
olive-black. I do not believe that the latter can be
mixed with the former, on account of the olive hue.
Moreover, the adulteration must be considerable, in
order to be profitable."
§ 20. Violet, chocolate, brown, and red lakes of
rhamnoxanthin and elder berries.
"When the boughs of several kinds of buckthorn
(Shamnusfrangula and RJiamnus catharticus) are ma-
cerated for three or four days in bisulphide of carbon,
according to Mr. T. L. Phipson, there is obtained a
gold-yellow liquor, which, after evaporation at the
ordinary temperature, leaves a yellow residuum.
Alcohol dissolves the coloring principle of the residue,
476 MANUFACTURE OF COLORS.
and leaves behind a peculiar fatty substance, which
is of a brown color. Lastly, the alcoholic solution
being evaporated to dryness, and its residue treated
by ether, there are deposited, after spontaneous evapo-
ration, crystals of a substance called rhamnoxanthin.
In order to obtain lakes, it is not necessary to ex-
tract the rhamnoxanthin in a state of purity, although
it is the real coloring principle. The boughs of the
buckthorn are steeped in a weak ammoniacal solu-
tion, which dissolves the coloring matter, and fur-
nishes a purple-red liquor, which, after saturation of
the ammonia by citric acid, and the addition of mag-
nesia, produces a fine violet lake.
If protochloride of tin be added to the decoction in
water of the boughs, and the liquor be precipitated
by carbonate of ammonia, there is obtained a yellow-
brown lake, which becomes of a chocolate color by
the action of sulphuric acid.
With magnesia, chloride of tin, oxide of zinc,
alumina, and oxide of lead, it is possible to form with
rhamnoxanthin a number of brown, red, and yellow
lakes, with very varied hues.
It is said that MM. Depouilly and Neron have
obtained very handsome violet lakes, by treating
elder berries (Sambucus nigra and S. ebulus) in the
following manner : The berries are pressed in order
to remove the seeds and the juice, and to collect the
pellicles, which contain the greater part of the color-
ing matter. These pellicles are washed in cold water,
and when they are quite clear, they are boiled in the
same liquid, in order to obtain colored extracts, which
may be more or less concentrated, and from which
are prepared lakes for painting and for paper hangings.
RED COLORS. 477
§ 21. Madder carmine.
Madder carmine is an exceedingly bright red color,
which is as durable as that of madder lake, and may
be substituted for the same hues of cochineal. It was
discovered by Mr. Bourgeois in 1816, and is still pre-
pared by a secret process. Nevertheless, Mr. Lefort,
in his Chimie des Couleurs, asserts that from his own
researches, a very fine madder carmine may be ob-
tained by the following process : —
" Avignon madder, of the best quality, is submitted
to a kind of fermentation in a wet place. "When it is
supposed that the saccharine and bitter mucilaginous
substances have been destroyed, and that the acid
fermentation begins, the madder is disintegrated, and
thrown into four times its weight of sulphuric acid,
which has been reduced to 55° Be. by an addition of
water.
" The vessel in which the mixture is made should
be of lead, and immersed in cold water, in order to
avoid too great an elevation of temperature. The
paste thus obtained is left to stand for about three
hours. It is then diluted with 4 or 5 parts of water,
and filtered upon a layer of broken glass, placed in a
lead or glass funnel. The filtered liquor is received
in a large volume of pure water, that is, free from
lime, magnesia, or iron. The carmine is soon pre-
cipitated, and it is collected upon a paper filter, washed,
and dried in the ordinary manner."
Madder carmine is employed especially for minia-
ture and other artistic painting.
§ 22. Lakes of red woods.
The red woods of Brazil, Santa-Martha, Pernambuco,
Sapan, and Lima contain a coloring matter, of a fine
478 MANUFACTURE OF COLORS.
crimson-red color, which was by Mr. Chevreul called
Bresilin. It may be precipitated by alumina with its
natural color, but it changes to a bright pink when
a certain proportion of protochloride of tin has been
added to the solution.
These lakes are obtained by digesting the powdered
woods in water containing -^ of tartrate of potassa,
and precipitating with a solution of alum. The pre-
cipitate is collected upon a filter, washed with cold
water, and dried. Mr. Grirardin says that the results
are better, if the decoction of Pernambuco wood be
precipitated by a solution of alum, in which chalk
and starch have been put in suspension. The colored
paste obtained is washed with cold water, drained,
and formed into lumps, which are rendered firm by
small quantity of starch paste, and of rosin dissolved
in essence of turpentine.
The Venice lake, ball shape, according to the same
chemist, may be prepared by kneading a mixture oi
glue and gelatinous alumina in a concentrated decoc-
tion of Brazil wood, until the desired hue is obtained,
The coloration is brightened by alum, and a violel
reflex is imparted by soap.
The flat lake of Italy is a fine red color with but
little durability. It is said to be a combination oj
alumina and lime with the coloring substances oi
Pernambuco or Santa-Martha wood.
Mr. GL C. Habich, who paid a great deal of atten-
tion to the manufacture of certain colors, has pub-
lished, on the lakes of red woods, an article which
too important to be overlooked, and is as follows : —
" The precious coloring substances, furnished by
the woods of Pernambuco, Lima, Santa-Martha, Sapan,
etc., are all soluble in pure water. If these woods are
RED COLORS. 479
treated with boiling water, their coloring matter is
dissolved in combination with ammonia. Does am-
monia exist in these dye woods, or is it a product of
the destruction of vegetable albumen? I shall not
try to answer this question at the present time. The
presence of this ammonia, in the case of dyeing and
preparing colors, is disadvantageous, because it
facilitates the solution of certain brown substances,
similar to humin, which tarnish the brightness of the
colors. But as these humic substances are not solu-
ble in water free from ammonia, we understand that
they may be eliminated by a purification or a clarifi-
cation of the colored decoctions. On that account,
and in former times, it was usual for manufacturers
of colors to let the decoctions stand for a long time.
The small proportion of sugar held by them was, by
fermentation, transformed into alcohol ; the alcohol
was, in its turn, transformed into acetic acid, which
combined with the ammonia, and determined the pre-
cipitation of the brown matter. The red coloring
principle, useful for the preparation of red lakes,
remained therefore in solution with another deep
yellow substance, and this solution was decanted
from the deposit. This process, as we perceive, is
very slow and takes several weeks. I have arrived
at the same result by employing pure hydrochloric
acid.
" The acid, diluted with an equal volume of water,
is introduced in a stream, of the size of a straw, into
the decoction of red wood, which is kept stirred all
the while. The addition of acid is stopped when a
filtered sample of the liquor has become yellow. The
mixture is then stirred every half hour. The clarifi-
cation is generally complete in a few days. The clear
480 MANUFACTURE OF COLORS.
liquor is decanted, and the deposit is washed upon a
filter. This purified decoction is then used for the
preparation of red lake, which contains the coloring
substance combined with alumina and oxide of tin.
I shall not describe the manufacture of the aluminous
lakes, known under the names of crimson lake, lake
in ball, Vienna lake, etc., because the processes of
preparation have been often described, and because
the results are always good when the alumina salt
employed is free from iron. I prefer giving some
particulars in regard to the red Florentine lake,
which is of a bright carmine-red, and is sought for
by manufacturers of fancy and mottled papers.
"This fine color, which, unhappily, does not resist
the action of light, is a combination of the coloring
principle with the binoxide of tin. A combination
may also take place with the protoxide of tin, but it
is crimson, and without brightness. The manufac-
turer of colors should, therefore, pay great attention
to the preparation of the tin solution, which should
contain no protoxide or the corresponding chloride.
The preparation of the proper solution will be certain,
if we are guided by the following instructions : —
" The commercial tin salt is generally very impure,
and it becomes absolutely necessary to prepare the
tin solution on the spot. The purest English tin is
melted, and transformed into irregular ribbons by the
known process, that is, by letting it run from a height
of about 2 metres, into water which is being moved in
a circular direction. This tin, which presents a very
extended surface, is put into two stoneware pots, one
of which is filled with hydrochloric acid, free from
iron, and marking from 20° to 25° Be. After twenty-
four hours, the acid is decanted into the second pot,
RED COLORS. 481
and the metal remaining in the first pot is left ex-
posed to the oxidizing action of atmospheric air.
After twenty-four hours, the liquor of the second
pot is poured into the first one.
"In order to transform this protochloride of tin
into perchloride, the solution and an equal volume
of the same hydrochloric acid are poured into a
much larger vessel, holding six times as much, and
immersed in a boiling water bath. If, then, nitric
acid be added by small portions at a time, a tumult-
uous decomposition takes place, with production of
red vapors. The reaction, which requires a few
minutes, should be finished before a new quantity of
nitric acid is added; indeed, rapid additions of acid
may cause the liquor to run over. As a precaution
against such an accident, the vessels and the water
of the bath should be perfectly clean, so as to be able
to recover (in a diluted state) any liquor which may
run over.
"These additions of acid are continued as long as
there is a strong effervescence. When the reaction
shows signs of moderation, it becomes necessary to
test with reagents the exact point of transformation,
but before the tests are applied, the production of
red vapors must have ceased.
"As a reagent, we may use a solution of hydrosul-
phuric acid, which should not produce any brown
precipitate in a sample of the liquor. The precipitate
may be a light yellow with hot liquors. Sulphurous
acid should produce no precipitate whatever.
"When all the tin has been transformed into per-
chloride, the liquor is allowed to become clear, and
we proceed to the precipitation of the coloring sub-
stance. The solution of tin is added to the colored
31
482 MANUFACTURE OF COLORS.
liquor, which is kept stirred until a drop of perchlo-
ride of tin fails to produce a pink cloud in a sample
of the liquor. The mixture is then stirred for half an
hour.
" The proportion of perchloride of tin depends
naturally upon that of the coloring matter. After
having determined the amount by a preliminary trial,
an equivalent proportion of perchloride of tin is poured
into the colored liquor, and after a stirring of half an
hour, another final test is applied in order to see
whether the precipitation is complete.
"After decantation of the clear liquor, the color is
washed with pure water. Should the water employed
be calcareous, it should be rendered slightly acid with
hydrochloric acid. This precaution is necessary,
otherwise the washings may impair the brightness of
the color.
" If the color is to be sold in paste, for instance, to
manufacturers of fancy papers, there should be mixed
with it none, or very little, of earthy substance. But
if it be desired to produce a substantial color for
theatrical painting, a certain proportion of finely
ground plaster of Paris or alabaster, free from iron,
is added. Many kinds of plaster of Paris contain a
small proportion of carbonate of lime, which will im-
pair the brightness of the color; but this inconven-
ience may be remedied by a washing with dilute
hydrochloric acid."
A skilful manufacturing chemist has published in
the London Journal of Arts, a new process for the
manufacture of lakes from dye woods, which it is
interesting to reproduce here, and is as follows : —
"It is possible with the salts of antimony, and
preferably with the chloride, to precipitate the color-
EED COLORS. 483
ing matter of certain dyestuffs, such as Sapan wood,
logwood, cochineal, quercitron bark, etc., and to
obtain certain colors, known under the name of lakes,
which have been prepared, up to the present time,
with other metallic salts.
"In order to manufacture a red lake, the following
substances are employed : —
" To 5 litres of chloride of antimony, marking 80°
of the hydrometer of Twaddle, add 100 litres of a clear
decoction of Sapan or Lima wood, marking 7° Twad-
dle. The whole is carefully stirred, and allowed to
deposit for several hours, and is then filtered. The
precipitate is washed twice, each time with 20 litres
of water. After its draining, the lake is finished, and
may be dried or sold in paste. With more diluted
decoctions, the washings are not necessary.
" The proportions above indicated may vary accord-
ing to the intensity of hue desired. With a greater
proportion of chloride of antimony, the color will
have a crimson hue ; and if the proportion of the de-
coction of Sapan wood be increased, the hue will tend
towards a scarlet.
" The same processes are followed for obtaining
purple and violet lakes ; but in this case, the Sapan
wood is replaced by that of Campeachy (logwood).
The following proportions give good results ; 5 litres
of chloride of antimony, marking 80° Twaddle, and
75 litres of a well-settled decoction of Campeachy,
marking 6° Twaddle.
" In the preparation of yellow lakes, Sapan wood is
replaced by quercitron bark.
" In the same manner it is possible to obtain lakes
with all the dye drugs which form colored precipitates
with the salts of antimony."
484: MANUFACTURE OF COLORS.
§ 23. Vegetable violet.
The vegetable violet is a lake which results from
the combination of hcematoxylin, the coloring princi-
ple of logwood, with alum and acetate of lead. It
possesses a fine violet color, which, however, does not
resist the action of light, and which, in the liquid
state, should be preserved in tightly closed bottles of
black glass.
It is prepared by dissolving 300 grammes of alum
in 1 litre of hot water, and adding 250 grammes of
crystallized acetate of lead, dissolved in a small
quantity of water. Sulphate of lead is precipitated
while a portion of the acetate remains in solution
with the salt of alumina. On the other hand, a de-
coction of 600 grammes of logwood (Campeachy) is
made in 5 litres of water, which, after cooling, is fil-
tered through a cloth. To 100 parts of this decoc-
tion of logwood, 10 parts of the mixture of acetate
of lead and salt of alumina are added, and afterwards
a solution of gum Arabic, the proportion of which
varies with the hue desired.
§ 24. CartJiamus red. CartTiamin. Cartliamic acid.
Vegetable red. Spanish red. Red in plates. Por-
tuguese red. Leaf red. Chinese rouge for the face.
Carthamus red is the red coloring principle of the
flosculous flowers of a plant (Carthamus tinctorius)
called carthamus, safflower, German saffron, safra-
num, etc., which is very different from the oriental
saffron, and which is cultivated in France and
Germany.
This red coloring principle is by chemists called
carthamin or carthamic acid • it is in the plant united
RED COLORS. 485
with a yellow coloring substance, which is soluble
in water, while carthamin is insoluble.
The color of carthamus used for rendering yellow
the floors of dwellings, is a lake principally made of
the yellow coloring principle. It is prepared by boil-
ing carthamus in water holding a small quantity of
alum, and adding curcuma (turmeric) for bright-
ening the tone of the color. The yellow solution is
employed for diluting the size.
The flowers, which have been thus deprived of the
yellow principle by means of alum-water, or what is
better, by water acidulated with acetic acid, contain
only the red principle, and are ready for the extrac-
tion of the carthamus red. They are worked with
their own weight of cold water holding from 15 to 16
per cent, of carbonate of soda. The liquor is filtered
upon a cloth, and the same manipulation is repeated
two or three times. The flowers are then thrown
away. The liquors are collected in a wooden tub,
filled with pieces of woollen or cotton cloth, which
absorb the carthamin. These cloths are then well
washed in pure water, and the color is removed by a
solution holding 10 per cent, of carbonate of soda,
which dissolves it. The color is again precipitated
by a solution of pure citric acid. The flakes of pre-
cipitated carthamin are washed several times with
cold water, then collected upon a filter, and dried in
a dark place.
The dry carthamus red has a fine purple-red metallic
lustre when it is in thin layers, but a large quantity
of it appears green. Its hue may vary from a red to
a pink, according to its quality and its state of com-
minution. This color, which is always very expen-
sive, is employed by manufacturers of artificial
486
MANUFACTURE OF COLORS.
flowers, for the imitation of flesh color in colored
prints, by perfumers for the preparation of face pow-
ders, and also by dyers. It is to be regretted that it
is not fast, and that it does not unite well with the
liquid vehicles used in painting.
§ 25. Indian red.
Professor Dussauce has published in the Teclmolo-
giste, June, 1861, an article upon a new red vegetable
color, which we reproduce here.
" Painters," says he, " use but a small number of
colors of organic origin, and those employed are
generally in the state of lakes, that is, of combina-
tions of a coloring principle with a metallic oxide
or a salt. During my researches upon the coloring
principles of vegetable origin, I have obtained from
sandal wood (sanders) a substance which is nearly
equal to carmine in beauty and brightness.
" This principle is durable, of a pure red, and melts
at a temperature a little below 100° C. An increase
of heat decomposes it. It is insoluble in water and
the fixed oils, but very soluble in alcohol, ether, acetic
acid, and the essential oils. Dry chlorine has no
action upon it, but wet chlorine destroys it. Acids
do not change it, except nitric and chromic acids, and
those rich in oxygen. It stands sulphuretted hydro-
gen, light, and air well. Altogether it is a very
durable vegetable color.
"Its preparation is very simple. Powdered red
sandal wood is macerated with alcohol, and the alco-
holic solution is treated with hydrated oxide of lead
in excess. The resulting precipitate is collected upon
a filter, washed with alcohol, and dried. It is then
dissolved in acetic acid, and precipitated again by an
RED COLORS. 487
addition of water in which it is insoluble. The acetate
of lead remains in solution, and may be used for the
preparation of the hydrated oxide of lead. The pre-
cipitate is again carefully washed with water, and
dried at a low temperature.
" It would require too much space to give here all
the researches by means of which I came to the con-
clusion that this color was pure santalin. Its price
will not be over 10 francs per kilogramme, and I in-
tend to prepare for dyers and printers a santalin
compound which may be dissolved in water, a thing
not hitherto discovered."
§ 26. Cochineal carmine.
Cochineal is a small insect of the genus Hemipter,
and of the family of the gall insects, called by Linnaeus
Coccus cacti. This insect is originally from Mexico,
but it is now successfully raised in the Canaries, in
India, Spain, and Algeria. It feeds upon the nopal
Cactus coccimlifer, L.
Cochineal, from the analysis made by Pelletier and
Caventou, is composed of carmine or pure coloring
principle ; coccine or raw animal coloring material ;
stearin and olein ; phosphate and carbonate of lime ;
chloride of potassium, phosphate of potassa, and
potassa united with an organic substance.
In the trade cochineal is distinguished by the names
of the countries from which it comes, Vera Cruz,
Honduras, Canaries, and India ; and each division is
subdivided into types having each a gradation of
hues. For instance, there is the black cochineal or
zacatille, the marble or silvered cochineal, and some-
times the pinkish and wild cochineal. Each of the first
three types is subdivided into fine, good, ordinary,
488
MANUFACTURE OF COLORS.
commercial, and sometimes low commercial. Drug
brokers base themselves upon the following examina-
tions in establishing the grades of quality : 1. They
examine the size, shape, and conformation of the
insect, which is said to be hollow or filled according
as the lower face is concave or level. If the edges
are wrinkled, it is said to be curled. 2. The powder,
from the greater or less beauty of its color, is a good
index of its tinctorial value. 3. Lastly, the regu-
larity of size of the insects, the presence or absence
of foreign materials, the dust, dampness, etc., are also
considered. A cochineal is said to be greasy when it
sticks to the hands.
Several processes have been proposed for testing
the value of cochineal. Thus Robiquet made a com-
parative test by decolorizing with chlorine, the decoc-
tion of the cochineal to be tried, and that of a standard
article. Letellier based his method upon the differ-
ence of intensity in the coloration of two decoctions
made with alum, one of the sample to be tested, and
the other of a standard cochineal. Mr. Anthon has
proposed to ascertain directly the proportion of car-
mine in a sample, by decolorizing the decoction with
a solution of alum saturated with ammonia. Lastly,
Mr. Oscar Kcechlin decolorizes a decoction of cochi-
neal by chlorine, and checks the operation by another
test with a solution of alum saturated with ammonia.
None of these processes is, however, sufficiently cer-
tain and accurate.
The carmine of cochineal which is employed espe-
cially for water-color and miniature painting, for the
manufacture of artificial flowers, etc., is the most
magnificent red color we possess. Many processes
have been tried for obtaining the carmine in a state
RED COLORS. 489
of purity. Alum, cream tartar, solution of tin, caus-
tic potassa, and the carbonate, nitrate, and binoxalate
of that base, etc., have been employed. But this
operation is always extremely delicate, and requires,
to be successful, a great practice, many precautions,
pure water, perfectly clean vessels, and an intelligent
choice of raw material. We shall describe several of
these processes.
A very great variety of carmines are found in the
market, and their tone or hue is due to the process,
or to more or less care taken in the preparation.
1. Process of the old French Encyclopedia.
"Take 20 grammes of cochineal, 2 grammes of
chuan* seeds, 70 grammes of the bark of autour, ^ and
1 gramme of Roman alum. Pulverize each of these
substances separately in a clean mortar. Boil 2.33
litres of pure and clean water in a clean vessel, then
add the chuan, and give it three boils. The liquor is
constantly stirred with a wooden spatula. Filter the
liquor through a white cloth into another clean vessel
and boil. At the beginning of the ebullition, in-
troduce the cochineal and give three boils, then the
autour and another boil. Lastly, the alum is added,
and the vessel is removed from the fire. Filter the
liquor without pressing the cloth, and receive it into
a clean porcelain vessel. After standing for seven or
eight days, the clear liquor is removed, and the de-
* Chuan is a yellowish-green seed of a plant coming from the
East, and which Devaux recognized as the anabasis tamariscifolia
of Linnaeus.
t Autour is a light and spongy bark of a pale cinnamon color,
which comes from the East. The tree which produces it is still
unknown.
490
MANUFACTURE OF COLORS.
posit is allowed to dry in the sun or in a stove-room.
The precipitate is then collected with a brush or a
feather, and is a finely comminuted and colored car-
mine."
It should be remembered that carmine cannot be
made in cold weather, because it does not settle, and
forms a jelly which becomes decomposed.
The cochineal left in the cloth may be boiled again
for a carmine of second quality. A small proportion
of annotto is sometimes added to the chuan and
autour.
2. Ordinary Process.
1 kilogramme of cochineal is dissolved, at a mode-
rate temperature, in 20 litres of water holding 30
grammes of carbonate of potassa. After a few min-
utes of ebullition, the vessel is removed from the fire,
and 60 grammes of powdered alum are dissolved in
the liquor. The latter, which was of a deep red color,
becomes carmine red, and is put aside until the cochi-
neal has settled. The clear liquor is then decanted into
another vessel, and is mixed with a solution of isin-
glass, passed through a sieve. The vessel is heated, and
the carmine rises to the surface during the ebullition.
The liquor is then removed from the fire, stirred, and
allowed to settle for fifteen or twenty minutes. The
deposit of carmine is drained upon a close linen cloth
and dried. The remaining liquor is red, and is used
for the manufacture of carmine lake.
The
3. Chinese Process.
Chinese prepare the cochineal carmine by
boiling 625 grammes of cochineal and 3 or 4 grammes
of alum in 15 to 20 litres of pure river water. After
RED COLORS. 491
a few minutes of ebullition, the vessel is removed
from the fire, and the liquor is left to settle, and then
filtered. The precipitation takes place by pouring in,
drop by drop, a solution of tin made with 320 grammes
of ordinary tin salt, 500 grammes of nitric acid, and
120 grammes of granulated Malacca tin. The pre-
cipitate of carmine is separated by decantation, and
is received upon a filter, and dried in a dark place.
4. German Process.
The cochineal is boiled in alum- water. After boil-
ing for some time, more powdered alum is added, and
the boiling continued. The liquor is then removed
from the fire, decanted, filtered, and allowed to remain
in porcelain vessels, in which the carmine precipitates
slowly. After three days, the deposit is collected
and dried. The mother liquors are preserved, and
give another quantity of carmine, which is inferior to
the first.
5. Process by Cream Tartar.
Put cream tartar (bitartrate of potassa) in the water
where cochineal is being boiled, and after boiling for
some time add powdered alum. After a short boil,
remove from the fire, filter, and the carmine becomes
deposited.
6. Process with Wool, and Formation of a Lake.
Take 250 grammes of cochineal, 1 kilogramme of
alum, 250 grammes of cream tartar, and 250 grammes
of wheat bran. All these substances are ground, and
thrown into 20 litres of boiling water; 250 grammes
of white wool are then put in, which absorbs the car-
mine. The wool is removed, drained, and immersed,
492 MANUFACTURE OF COLORS.
still wet, into a solution of caustic potassa which takes
up the coloring matter. The latter is precipitated
by a solution of alum.
T. Wood Process.
Mr. Wood has recently proposed another mode of
preparation, which appears to possess real advantages.
The carmine is of a magnificent color, and is said not
to change by time or by exposure to the air.
250 grammes of pure carbonate of soda, and 225
grammes of citric acid, are dissolved in 30 litres of
water. "When the whole is boiling, 680 grammes of
powdered cochineal are aided, and the ebullition is
continued for 1 or 1.5 hour. The liquor is filtered
and allowed to cool off; and when it has become clear,
it is boiled again for 5 minutes with 250 grammes of
alum. After a second filtration, it is allowed to stand
for two or three days. The clear liquor is then care-
fully decanted from the deposit, which is washed with
cold distilled water, and dried at a low temperature
in a stove-room. The impalpable powder thus pro-
duced is, if desired, mixed with water rendered alka-
line by ammonia, and mucilaginous by gum Arabic.
By evaporation, the product may be moulded into
small blocks.
This carmine may acquire a peculiar red lustre, by
being mixed with 250 grammes of alum and a few
decigrammes of a tin salt ; for instance, the sulphate,
the nitrate of protoxide, or the chloride of this metal.
8. Grelley Process.
Mr. Grelley has proposed a method of treating
cochineal, which allows of the almost entire solution
RED COLORS. 493
of its coloring principle, and of the preparation of very
handsome red lakes.
First, the ground cochineal is digested for four or five
hours in water slightly acidulated with hydrochloric
or sulphuric acid. Second, the acid is saturated with
an excess of ammonia, and the latter is left to act for
ten to twelve hours. Third, the solution is decanted,
and the deposit is pressed, so as to lose no liquor.
Fourth, the excess of ammonia is saturated with one
of the above indicated acids, which is diluted with four
or five times its weight of water. Fifth, the useless
precipitate formed by the last treatment, is separated
by means of flannel filters. These solutions give
immediately a fine ponceau red lake, when they are
precipitated by a mixture (half and half) of the two
chlorides of tin, mixed with a small quantity of water.
The aluminous lakes are prepared by treating these
solutions, first, by alum, and then by a caustic or car-
bonated alkali.
This process is equally good for fresh cochineal,
and for that which has been already boiled.
§ 27. Carmine lake. Paris lake. Vienna lake.
Carmine lake is prepared with the mother liquors
from which the pure carmine has been extracted, and
which still contain a great deal of color. A solution
of alum is added, or a certain proportion of recently
precipitated alumina is stirred in, and the color is
brightened with a small quantity of protochloride of
tin. The precipitate is washed, moulded into troches,
and dried.
The lake is the finer as less alum or alumina is em-
ployed ; and it i s quite customary, for the inferior
494 MANUFACTURE OF COLORS.
qualities, to give them more body by an addition of
starch.
The finest kinds of lakes are prepared from fresh
cochineal, which has not been previously boiled. 20
parts of powdered cochineal are boiled in 400 parts
of water, holding in solution 10 parts of cream tartar.
The liquor is filtered, and is mixed with a solution of
300 parts of alum, and a very small quantity of pro-
tochloride of tin. The precipitate, which deposits
after a little while, is very bright, and is collected.
A solution of carbonate of potassa is then slowly
added to the liquor, which is kept stirred all the time.
The new precipitate formed is thrown upon a filter,
washed, and dried.
In this manner, a first and very handsome lake is
obtained, and those which follow are made more or
less rich in color, by adding more or less of the solu-
tion of alkaline carbonate.
§ 28. Ammoniacal cochineal.
Caustic and concentrated ammonia dissolves the
carmine of cochineal, and, at the same time, increases
the brightness of the color. This property has been
made use of for preparing what is called ammoniacal
cochineal, and which is sold in paste or in cakes.
One part of carmine is dissolved in 6 parts of com-
mercial aqua ammonia, kept in a well stoppered
glass bottle. After several days of exposure to
the sun, and with frequent shakings, the ammonia
has dissolved the carmine. The liquor is then
filtered, and precipitated with acid and alcohol. The
resulting carmine is washed with dilute alcohol and
dried.
RED COLORS. 495
§ 29. Bed and violets from archil.
A great many researches and articles on archil
have been published ; but we do not recognize in them
the exactness required by modern chemistry. We
shall therefore confine ourselves to a recent article
by M. H. Gaultier de Claubry, where the preparation
of this coloring substance is better understood and
explained.
The remarkable discovery of orcin by Robiquet
demonstrated the presence, in certain lichens, of a
colorless substance, which, under the combined action
of air and ammonia, is transformed into a fine violet
color. So is indigo, which is colorless in the plant,
but becomes blue by contact with the air. Several
natural products extracted from lichens, lecanoric
acid for instance, result, under certain circumstances,
in orcin, which may be a derived product. These
lichens are treated for obtaining archil, and this color
is always produced under the combined action of
air, ammonia, and water. Urine has, for a long time,
been used for that purpose, and Cocq proposed to
substitute for it ammonia, which has already been
employed in Germany, as seen by a memoir of
Hermbstaedt ( Magazin far Farler, I. 290). There
are several reagents which will extract from lichens
the substances which are transformed into orcin ;
for instance, water, alcohol, and alkaline solutions.
Notwithstanding the great number of researches
published on the subject, it is impossible to decide
with certainty upon the state in which these sub-
stances exist in the plants. Moreover, the latter pre-
sent great differences in their nature and in their
origin.
496 MANUFACTURE OF COLORS.
The product known under the name of archil is not
a single colored substance, but a compound of several.
Although similar in color, they vary in their resist-
ance to the action of certain agents, and, according
to their relative proportions, they give to the com-
pound peculiar qualities for dyeing.
The archil -lichens give at most 10 to 12 per cent,
of available products. If these be separated from
the mass of the plant, and then submitted alone to
the influence of the air and of the ammonia, the tinc-
torial product is obtained under conditions much more
favorable than by the ordinary processes.
During his researches upon these lichens, Sten-
house employed lime instead of ammonia, as Heeren
did, for extracting the color producing substances.
This process may be applied ; but, according to th<
mode of operation, the results may be entirely a1
variance. It is sufficient, says Stenhouse, to cut th<
lichens and to macerate them in a milk of lime, and
then to saturate the solution by hydrochloric or acetic
acid. All the available coloring product will thus be
obtained, and after a further treatment by air and
ammonia, it will be transformed into archil. The
promised result is indeed obtained, but only undei
given circumstances, that is, if the maceration b<
very short, as we shall prove further on. The won
maceration, unless accompanied by the length of time
the substance and the liquid should be in contact, is
entirely too uncertain, as upon it depends the success
or failure of the operation. A maceration is gener-
ally a long operation, lasting one, two, or several
dozens of hours, and it is therefore necessary to de-
termine accurately all of the conditions necessary to
arrive at a given result.
RED COLORS.
497
"Whatever be the time of contact of the lime with the
coloring principles, the latter will be dissolved, and
one of two cases will be presented: Either an acid will
precipitate the whole coloring matter under a small
volume, which will then be transformed into archil
by treatment with ammonia ; or the acid will produce
no precipitate, and the coloring matter will remain
entirely in solution. In the latter case, evidently all
of the advantages of the treatment by lime disappear.
The following experiments demonstrate these results
completely. 100 grammes of Madagascar lichens
were immersed in 600 grammes of a milk of lime,
holding 30 grammes of lime. After the periods of
time indicated, the insoluble parts were separated upon
a hair sieve, and washed. The liquors were treated
by hydrochloric acid in excess. Each precipitate
was collected upon a cloth, washed, and dried. The
liquors were neutralized by ammonia, and concen-
trated by evaporation ; afterwards an excess of am-
monia was added, and they were kept, a part of the
time, at the ordinary temperature, and the remainder
in a store-room heated at from 50° to 60° C.
Length of
maceration.
15 minutes.
1 hour.
Precipitate.
12 grammes, furnishing a great
deal of archil.
12.5 grammes, furnishing a great
deal of archil.
Liquors.
Scarcely any coloration.
Distinct archil coloration.
A bright color.
A brighter color.
A still brighter color.
A richer color.
Fine archil.
By repeating the experiment with double the pro-
32
2 hours. 9.3 grammes, less archil.
8
8
still less.
4
4
less again.
6
2.7
less.
8
2
very little.
12
1.1
scarcely any.
24
0.5 " scarcely any col-
48
0.5 '* oration.
498 MANUFACTURE OF COLORS.
portion of lime the precipitate was smaller from the
second hour, while, at the same time, the liquor con-
tained a great deal of archil.
These numbers cannot be given as absolute, but
they demonstrate in the most positive manner that,
by submitting lichens to the action of a milk of lime,
it is possible, in accordance with the mode of opera-
tion, to obtain the coloring material by precipitation,
or to leave it entirely in solution.
"Water alone produces a similar effect, but a great
deal more slowly. A protracted contact will render
the coloring products soluble. On the other hand,
very short contact will cause a separation.
If, instead of operating at the ordinary tempen
ture, the lime liquor be made to boil for three or foui
minutes only, the addition of an acid separates
brown material, the color of which deepens by contact
with ammonia, but which furnishes not a trace of
archil either at the ordinary temperature or with an
increase of heat.
If, instead of lime, various soluble salts be substi-
tuted, such as the phosphates of soda, potassa, or am-
monia, borax, the carbonates of potassa or soda, etc.,
the transformation of the coloring substances is very
rapid, and an ebullition of a few minutes is sufficient
to prevent the formation of any precipitate by satu-
ration with an acid.
Powerful alkalies, such as potassa, soda, baryta,
and strontia, cause the tranformation more quickly
than lime.
As I have previously stated, the product known
under the name of archil contains several coloring
principles, which unequally resist the action of various
agents. That obtained at the temperature of 60° C.
RED COLORS. 499
contains the greater proportion of the more durable
principles. On the other hand, the archil prepared at
the ordinary temperature contains a greater or less
proportion of alterable elements.
For some time past, either in France or in other
countries, the manufacture has been conducted with
the aid of heat, and the operation is more rapid and
economical.
§ 30. PercJiloride ofdiromium.
This product, according to Mr. Wohler, forms a
mass of red, bright, and micaceous laminae, which
may be ground like talc between the fingers. It will
be used as a coloring substance, especially for paper
hangings, when it becomes possible to manufacture it
at a reasonable price. The following is the mode of
preparation : —
Small balls, made of a mixture of oxide of chro-
mium, charcoal, and flour paste, are brought to a high
temperature in a covered crucible, and then put into
an apparatus composed of a large crucible, standing
upon the grate of an air furnace, and which con-
nects with a chlorine generator by means of a porcelain
tube, which is luted on to a hole made in its bottom,
and which passes through the grate. The upper part
of the tube does not project much inside of the large
crucible, and is loosely covered with a small inverted
crucible, so as to prevent the balls from falling in.
A second large crucible is inverted and luted to the
first, and has also a small hole in its bottom for the
escape of the gases.
As soon as the apparatus is filled with gaseous
chlorine, the lower crucible is raised to an intense heat,
and the fire is so conducted that the sublimed perchlo-
500 MANUFACTURE OF COLORS.
ride of chromium condenses in the upper crucible,
the temperature of which is not above a dark red heat.
As the per chloride of chromium, heated in contact
with the air, is decomposed, it is necessary to continue
the passage of chlorine during the cooling of the ap-
paratus. The operation should be conducted in the
open air, or under a chimney with a good draft. The
perchloride is then washed with water, to remove the
chloride of aluminium resulting from the clay of the
crucible. If the flow of chlorine has been weak, the
product will contain a certain quantity of simple
chloride, which, during the washings, causes the solu-
tion of a portion of the perchloride, which is thus lost.
§ 31. Chrome red.
We have already described the manufacture of this
fine product, when speaking of the preparation oi
chrome yellow, by the process of Mr. Habich.
SECTION Y.
BROWN AND BLACK COLORS.
I. BROWNS.
§ 1. Mars browns.
"While examining the preparation of ochres, we have
seen that, by calcining a Mars yellow at various tem-
peratures, and under peculiar conditions, this sub-
stance passes through a series of colors and hues,
among which there is a brown of sesquioxide of iron
which is very durable, but somewhat expensive.
We shall here indicate a process due to Mr. Salve-
tat, by which it is possible to obtain a brown, and
also a red ochre of great brightness.
A solution is made in hydrochloric acid, of 280
BROWN COLORS. 501
grammes of metallic iron, and 330 grammes of zinc.
The whole is afterwards precipitated by the carbonate
of soda, and the precipitate is carefully washed, in
order to remove all the chloride of sodium or car-
bonate of soda. The deposit, which is green at the
beginning, becomes brown ; and, when all greenish
hue has disappeared, it is drained upon sheets of fil-
tering paper spread upon cloths. Lastly, the dried
product is brought to the desired hue by calcination
upon clay dishes.
The zinc and iron may be replaced by the sulphates
of these metals, provided their composition be taken
into account.
The tone or hue of the pigment is modified by mix-
ing 1, 2, 3, . . . equivalent weights of zinc, with 2, 4,
6, ... equivalents of iron. The addition of nickel,
cobalt, or manganese produces darker hues, resembling
wood, sepia, etc.
§ 2. Iron minium.
MM. Bouchard and Clavel have made many expe-
riments for doing away with red lead in painting and
in the manufacture of mastics, and they have taken
as a substitute a Burgundy ochre.
Since then, they have taken out a patent for a new
product which they call ferrugine alumineuse, which
replaces red lead very advantageously as regards
economy, and presents none of the inconveniences of
the lead product.
A new color, preventive of rust, and which may
enter into the composition of cements, has recently
been manufactured. It is iron minium, which seems
intended to take the place of red lead in iron and
wood painting. We borrow from the Genie Indus-
triel the following paragraphs : —
502 MANUFACTURE OF COLORS.
" The new product possesses all the qualities of
red lead, without any of its inconveniences. It is of
a fine brown color, constant in price, and mixes per-
fectly well with linseed oil. Under equal volumes,
it covers more than red lead, and is a better protection
against oxidization.
" Iron minium is a very pure substance, into the
composition of which no acid enters, nor any other
combination hurtful to the painted articles. In fact,
according to Mr. Loppens, professor at the Industrial
School of Ghent, it is a composition which cannot be
altered by any of the causes generally acting upon
red lead, and which may replace the latter in all its
uses.
" Three different analyses of iron minium gave —
I. Water . . . . .' , .1.3
Clay . 25. 7
Red lead* . . .... .3.2
• Carbonate of lime 0.6
Peroxide of iron 61.7
Loss 1.5
II. Silica .
Alumina
Peroxide of iron
Lime
Water .
Magnesia
III. Peroxide of iron . ... 68.95
Aluminous earth (clay) .... 1.48
Burnt clay 29.57
100.00
* This red lead comes from the litharge employed as a dryer.
BROWN" COLORS. 503
"After experiments on painting, made under the
direction of Dutch engineers, in comparison with red
lead, the comparative weights were —
Red lead 1.4T
Iron minium ....... 3.13
" And the specific gravities, by hydrostatic pro-
cess at 22° C.—
Iron minium ....... 3.74
Red lead 8.24
" The analyses prove the absence of any kind of
acid, which, even in the smallest proportion, alters the
colors, especially when it is sulphuric or hydrochloric
acid.
" A comparison of these analyses with those made
of Oriental ~brown. Burgundy red, caput mortum, or
colcothar, shows the great superiority of iron minium.
" Colcothar always retains a trace of sulphuric acid.
Indeed, it is the residue of the manufacture of the
Nordhausen sulphuric acid, which is prepared by the
distillation of sulphate of iron. Iron, coated with this
pigment, is rusted, instead of being preserved.
" Employment of iron minium. — We know that red
lead is simply mixed with raw or boiled linseed oil,
and that the mixture dries so rapidly that it should
be prepared only a short time before its use. More-
over, its manipulation is unhealthy, and may occasion
lead colic, the same as white lead.
" The preparation of iron minium for painting is
quite like that of red lead, that is, it is simply mixed
with raw or boiled linseed oil. If thin coats are de-
sired, the mixture is ground, and a little litharge
dryer is added, preferably to essence of turpentine
which, as a general rule, does not improve colors.
504 MANUFACTURE OF COLORS.
" In painting the hulls of ships, red lead is mixed
with a certain proportion of bisulphate of mercury,
which is a virulent poison, and is intended to destroy
molluscs and wood boring insects. This poison may
be incorporated with iron minium, which is not there-
by altered.
" Mixed with one-third of white lead, iron minium
forms an excellent mastic, similar to that made with
red lead, and which is much cheaper, and becomes
very hard after drying for some time.
"As the paint made with iron minium resists a
strong heat, it may be advantageously employed for
painting the interiors of boilers, and preserving them
from incrustation.
" Mixed in certain proportions with coal tar, iron
minium forms a very firm coat, which penetrates the
pores of the wood and hardens it considerably.
" The brown color of iron minium is not altered by
the sulphides, while red lead is, and remains a long
time in its natural state. It will, therefore, be found
advantageous and economical to use this paint for
the hulls of vessels in ports where the filth of the city
is poured into the docks."
§ 3. Van Dyke brown.
Van Dyke brown is also a color derived from iron,
and is very durable.
It is prepared by the calcination of certain yellow
ochres found in the south of France. The resulting
frit is sold in lumps, in grains,, or as an impalpable
powder. Ochres, as we know, hold alumina and sand,
which combine with the oxide of iron at a high tem-
perature.
A Van Dyke brown is also manufactured by cal-
BROWJST COLOES. 505
cining sulphate of iron several times. The proper
color is arrived at by practice. We understand that
this last brown, which is entirely an oxide of iron,
and of a purer color than the preceding, is more ex-
pensive. It is often adulterated with the brown frit,
and the fraud is detected by means of concentrated
and hot acids, which easily dissolve the pure oxide of
iron, and with difficulty the ochre brown.
By mixing Van Dyke brown with variable pro-
portions of red ochre and binoxide of manganese, very
durable browns are obtained, which do not require
dryers when they are used hot.
Other durable browns may also be prepared by
mixing this pigment with lamp or ivory black.
§ 4. Manganese brown.
Mr. J. Lefort, in his Chimie des Couleurs, states that
the analyses of old Roman paintings show that the
oxide of manganese was employed as a brown pig-
ment. This chemist has, therefore, made a few ex-
periments by which he has ascertained that the bin-
oxide of manganese ground in oil, gives a very hand-
some and durable paint. He proposes to manufacture
this color as follows : —
" The protochloride of manganese resulting from
the manufacture of chlorine, or the protosulphate
obtained by the calcination of the protoxide of man-
ganese with sulphate of iron, is dissolved in water at
the temperature of 30° to 40° C. Then a solution of
hypochlorite of soda (Labarraque's liquor), or one of
hypochlorite of potassa ( Javelle's water), holding a
certain quantity of carbonate of soda, is added until
the precipitate formed does not change color. When
the oxidization is complete, the liquors are decanted
506 MANUFACTURE OF COLORS.
and the precipitate is washed first with water holding
•^ of sulphuric acid, and then with pure water until
the rinsings are tasteless. The binoxide of man-
ganese, after being dried in a stove-room, is an im-
palpable and dark-brown powder, which covers well
and is entirely innocuous."
§ 5. Brown of manganate of lead.
Take 1 part of oxide of manganese, 1 of oxide of
lead, and 1 part of sulphate of ammonia, and mix the
whole with peat, so as to form a paste which is dried
and burned. The resulting pearl-gray compound is
then mixed with 1 part of nitrate of lead and 1 part
of sulphate of iron, and the product (after calcina-
tion ?) is said to be a fine sienna earth.
§ 6. Prussian brown.
Mr. Bouvier has indicated a process for preparing
this brown, which was discovered by the painter
Toeffer.
"Heat an iron ladle upon a brisk fire until it be-
comes red, and then throw into it pieces of Prussian
blue of the size of a filbert. Each piece will soon
split, scale off, and become red. Then remove the
ladle from the fire and let it cool. A longer heating
will destroy the desired color. When the pieces are
broken, there are seen black parts mixed with others
of a yellowish-brown color, which is the proof of a
good preparation. Grind the whole together, and
there will be produced a brown resembling bistre or
a very clear asphaltum."
This process would be improved by calcining in a
closed vessel. The product would be more homo-
geneous, and the temperature more easily regulated
BROWN COLORS. 507
for a given tone of color. This pigment is very dur-
able and covers well.
§ 7. Red-brown.
We have described the preparation of this color in
Section IV., § 5, and we have seen that it is a mixture
of oxide of iron and litharge, or red lead, which is
fused in a crucible.
§ 8. Gilt-brown.
This brown is a binoxide of lead, and is prepared
as follows : —
Orange mineral, litharge or red lead, is very finely
powdered, and heated in a vessel with Javelle water
or chloride of sodium (hypochlorite of soda ?), added
by small quantities at a time. The material becomes
gradually brown, and when the desired tone of color
has been obtained, it is washed and dried.
Mr. Lefort asserts that the product is of a finer
quality when white lead is employed.
§ 9. Chicory -brown.
"When certain vegetable substances are burned in
closed vessels, the root of chicory for instance, there
is obtained a fine powder which, after boiling in
water, gives a colored solution. If the latter be
evaporated to dryness, the residue is a brown sub-
stance, soluble in water, and which is employed in
water-color painting. The color is rich, but not
durable.
§ 10. Ulmin-brown.
Dumenil recommends as a color for miniature paint-
ing, the brown deposit formed by the. action of cans-
508 MANUFACTURE OF COLORS.
tic potassa upon alcohol. Fused caustic potassa,
coarsely broken, is digested with twice its weight of
alcohol, and then filtered through a cloth.
The liquor is heated for a few hours, becomes dark-
brown, and deposits a dull-looking powder, which is
collected upon,a filter and washed with water acidu-
lated by hydrochloric acid.
By melting in a copper vessel, three parts of sugar
with one of potassa, until the mixture becomes a dark
brown, and then dissolving in water, filtering, and
precipitating with an excess of hydrochloric acid,
there is produced a brown color, which is, however,
inferior to the preceding one.
This color may also be obtained by treating peat,
cotton, lignites, etc., by alkalies ; starch, flour, etc.,
by concentrated acids ; or wood-soot, bistre, etc., by
caustic potassa.
Ulmin-brown is a fine color, which mixes well with
other pigments, and flows well under the brush.
§ 11. Bistre.
This water color is prepared from the soot which
accumulates in the flues of fireplaces in which wood
is burned. Its preparation for becoming a pigment
is as follows : —
The brightest and darkest fragments of soot, result-
ing from the combustion of beech-wood, are powdered
and passed through a silk sieve. The powder is
stirred in hot water for twenty-four hours, and again
in another water. All the liquors are collected and
allowed to settle. The precipitate is then mixed with
gum- water, and evaporated in a stove-room to the
consistency of a solid extract.
BROWIN" COLORS. 509
§ 12. Bitumens vr Asphaltum.
Such are the names given to various liquid or solid
substances, which melt at a moderate temperature,
and have a more or less pungent and peculiar smell.
They are very combustible, and leave a small charred
residue, which is very light and easily reduced to
ashes. The bitumen naphtha is abundant in Persia,
upon the shores of the Caspian Sea, near Bakou, etc.
It oozes constantly from the soil, and is accompanied
by hydrocarbon gases, which are burned by the in-
habitants for various purposes. This bitumen is also
found in Calabria, in Sicily, in America, etc.
Bitumen ofJudea or Asphaltum. — This is the kind
most generally used in painting, and it is found on
the surface of the Dead Sea. It has also been found,
under ground, in America, China, the island of Trini-
dad, France, Germany, Seyssel, Ussel, Dax, etc., and
in the Carpathian Mountains. Asphaltum is black
or brown, solid, hard, fusible, and breaking with a
smooth fracture. "When pure, it is insoluble in alco-
hol, very combustible, and leaves a residue amounting
sometimes to 15 per cent. It was employed by the
Egyptians for embalming their dead.
Bitumen or Retin asphaltum. — This substance is
of a light-brown color, with a resinous fracture, very
fusible, and partly soluble in alcohol.
Melted bitumen becomes very brown and trans-
parent. But as it destroys the drying quality of oils,
it should be dissolved in essence of turpentine. This
solution, which can be made in the cold or with very
little heat, is so thick, that in order to paint with it,
it requires to be mixed with the emplastic oil of the
Italians and with a mastic varnish.
510 MANUFACTURE OF COLORS.
A very drying bitumen may be prepared by the
following process : —
Venice turpentine 15 parts.
Gum-lac . . 60 "
Asphaltum 90 "
Drying linseed oil 240 "
White wax . . . . . . . 30 "
The gum lac is dissolved in the turpentine by por-
tions at a time, and no more is added until the pre-
vious addition is melted. The asphaltum is then
treated in the same manner. "While this operation is
going on, the linseed oil is heated nearly to the boil-
ing point, and afterwards mixed by degrees with the
melted asphaltum. Lastly, the wax is added before
cooling. The whole is poured upon a stone slab, and
worked with the muller or the knife.
Since it has become possible to employ the pure
bitumen, and to render it drying and easily ground,
Mummy and Van Dyke browns are much less em-
ployed, because these latter pigments are often adul-
terated with other coloring substances.
Bitumen or asphaltum stands the action of light
quite well ; but the tone of its color, its durability,
and its transparency vary with the nature of the bitu-
mens and the mode of preparing them. The bitumens
generally found in the trade are those of Judea,
Grenoble, and Strasbourg. When pure, they burn
and leave very little ashes, or none at all.
§13. Sepia.
Sepia is furnished by a marine cephalopod, the
cuttle-fish (Sepia ojficinalis), which is very common
on our shores. This color is extracted from a pocket
filled with a brown liquor, which the fish emits in
BROWN COLORS. 511
order to obscure the transparency of water when it is
pursued by its enemies. As soon as it has been
caught, this pocket is removed and dried in the sun.
It is then powdered, ground with a concentrated
solution of carbonate of potassa, and boiled for some
time. The solution is filtered, saturated with an acid,
and left to settle. The precipitate is washed first by
decantation, and afterwards upon a filter-, and then
dried. This pigment forms an impalpable powder of
a dark-brown color, insoluble in water or alcohol, and
is very fine and durable.
§ 14. Umber.
This earth appears to be a hydrated silicate of
iron and manganese, which is found native, and was
formerly imported from the Roman province of Um-
bria. It now comes from the island of Cyprus. The
natural article is in the state of brown lumps, adher-
ing to the tongue, staining the flesh, and falling to
powder in water. The impurities are removed by
washing, and the floated article, after settling, forms
a light-brown powder, which is employed raw or
burnt.
Powdered umber, or that which has been calcined
too much, reddens or blackens by the dehydration
of the iron or the superoxidization of the manganese.
It is rarely employed alone, and it mingles well with
other colors or with slaked lime.
§ 15. Sienna earth.
This is an earthy substance, exported from Sienna,
in Tuscany, and which owes its color to a hydrated
oxide of iron. It is used raw or burnt.
Raw sienna is a dark-yellow on the exterior, and
512 MANUFACTURE OF COLORS.
a light-yellow inside ; its powder is greenish-yellow.
Burnt sienna is either a light or dark-red when in
lumps, but its powder is of a dark-red color.
§ 16. Cologne and Cassel earths.
Cologne earth is a brown earthy substance, which
takes fire easily, and burns without flame or smoke
like decayed wood. It produces white or red ashes,
and presents all the characteristics of organic mate-
rials. It is found in the neighborhood of Cologne,
especially at Briihl and Liblar, where it forms con-
siderable deposits, as much as 12 metres in thickness,
and extending over several kilometres.
This earth is smooth to the touch, crumbles to a
fine powder, is as light as water, and of a brown-
black color. The impurities are separated by wash-
ings, and the pigment is moulded into large troches,
which, being ground in water or oil, give a very dur-
able and fine brown color.
§ 17. Puce with chr ornate of manganese.
According to Mr. Persoz, the calcined chromate of
manganese gives a handsome puce (flea) color, which
may be used for oil and porcelain painting, and for
calico printing with albumen.
II. BLACKS.
A. MINERAL BLACKS.
§ 1. Schist or shale Hack.
This black is obtained by the carbonization of
bituminous schists in closed vessels, but all kinds are
not equally good for this manufacture, and the light
BLACK COLORS. 513
schists are generally preferred, the Scotch Bog-head
for instance.
In the arts the latter schist is calcined in large
cast-iron retorts, and there are obtained essential oils
for lighting, certain gases, and a carbonaceous resi-
due which has received the name of schist black.
By a slow distillation and a moderate heat, bog-
head furnishes from 35 to 40 per cent, of crude oil,
weighing on an average 850 grammes per litre, that
is to say, a sp. gr. = 0.850. The carbonaceous resi-
due amounts to about one-half of the distilled schist,
and is directly removed from the retorts into closed
iron vessels, where it cools off without the contact of
the air. It then forms light and porous lumps, which
are easily ground.
This charred mass from bog-head contains from 30
to 35 per cent, of pure carbon, and from 70 to 65 per
cent, of alumina mixed with a small proportion of
silica, magnesia, lime, and sulphide of iron.
This material has been but recently used for paint-
ing. It combines readily with drying oils, and gives
an intense and handsome black, which is at the same
time very economical.
§ 2. Bituminous coal Hack.
Mr. P. T. Lavalleye has proposed to manufacture
a black color with bituminous coal in this manner: —
" Two pairs of ordinary millstones are necessary,
in which coal is substituted for wheat.
"Small coal (slack) is to be preferred, since it is
cheaper than the large, and saves the expense of
breakage. If, however, there are too large lumps,
they should be broken with a hammer.
" After the coal has passed through the first pair
33
514 MANUFACTURE OF COLORS.
of stones it goes through the second, the stones of
which are oije-third nearer each other than the first
set.
"The powdered pigment is then ground again as
usual with essence of turpentine, or linseed oil, or
varnish, according to the use it is intended for. It is
suitable for all kinds of oil painting, for houses, car-
riages, etc. It is also employed in distemper painting
with size and milk."
§ 3. Black of chromate of copper.
Mr. Persoz has demonstrated that the basic chro-
mate of copper contains three equivalents of oxide of
copper, and that by calcination it loses a portion of
its oxygen, and is transformed into an oxide of copper
soluble in hydrochloric acid, and into a compound
insoluble in that acid.
The calcination should take place in contact with
the air, and not in a closed crucible, because, in the
latter case, the resulting salt is different and contains
the copper in the protoxide state. This second com-
pound resembles galena, while the first is an amor-
phous black powder.
The pigment, obtained by calcining in the air the
basic chromate of copper, may also be produced by
the calcination of a mixture, in fixed proportions, of
bichromate of potassa and nitrate of copper. It is
remarkable for the intensity of its black amorphous
color, its comminution, and its unalterability. It
may be employed in oil colors, and probably also, in
porcelain painting, and calico printing with albumen.
BLACK COLORS. 515
§ 4. Elony Hack.
It is said that a fine ebony black color may be
obtained by burning nitrate of copper with peat.
B. VEGETABLE BLACKS.
§ 5. Peach-stone black.
This black is prepared by calcining in closed
vessels, the stones of peaches, apricots, and other
fruits. The calcined stones are broken in a cast-iron
mortar, and the powder, after having passed through
a silk sieve, is ground in water. The color is hand-
some, but has a reddish tinge. Ground with oil and
white lead, the color called in England old gray is
obtained.
§ 6. Fusain (spindle tree, prickle wood) black.
This black is the result of the calcination of the
prickle wood. The dry wood is divided into small
rods, which are placed in a crucible of cast-iron or of
thick sheet-iron. A layer of sand, from 8 to 10 cen-
trimetres thick, is placed between the wood and the
crucible cover, which has an opening for the escape
of the gases. The crucible is then brought to and
maintained at a red heat for two hours. After cool-
ing, the rods of charcoal are removed, and cut in the
shape of pencils.
It has been remarked that the young branches give
a lighter and a better charcoal than the old wood.
§ 7. Grape-vine Hack.
This is the product of the carbonization in closed
vessels, of the clippings of grape-vines at the prim-
516 MANUFACTURE OF COLORS.
ing time. The black is very intense and light, and
is ground by the ordinary process.
§ 8. Cork black.
This black, also called Spanish black, is prepared
by calcining in closed vessels the waste of cork
cuttings. It is very fine, and, combined with other
pigments, it produces very handsome hues.
§ 9. German black.
This black is very much employed for copperplate
printing, and is obtained by the calcination in closed
vessels, of a mixture of grape stalks, dried wine
lees, peach-stones, and bone waste. The proportions
of these various substances are not very constant, and
a very fine black may be produced from the following
proportions : 3 parts of unboiled bones, 7 of dry stalks,
5 of dry wine lees, and 6| of peach-stones from the
residue of the distillery. If the peach-stones have
not been distilled, 5 parts are sufficient.
After cooling, the charcoal is removed from the
crucible, and powdered in a mortar. The powder is
passed through a silk sieve, and then ground in water.
The paste, brought to the proper consistency, is
moulded into lumps, which are dried in a stove-room,
and constitute a German black of the first quality.
§ 10. Frankfort Hack.
Frankfort black is prepared by burning wine lees
in closed vessels, powdering and grinding the char-
coal in water, and then moulding it into cakes. The
charcoal black for printing is prepared in the same
manner. The grinding is effected between stones
kept in a kind of tub, in the bottom of which there
is an opening for removing the ground product. In
BLACK COLORS. 517
works arranged for the purpose, the motive power,
horse or steam, is generally in the centre, and drives
on one side the stamps for pulverizing, and on the
other the mills for grinding. Tubs raised somewhat
above the ground are placed along the walls, and
receive the ground black, which is allowed to settle.
After the decantation of the liquor above, the black
is drained in baskets lined with cloths, and then
moulded and dried. The moulds are 8 centimetres
in height and 10 in diameter, and are formed each of
a thin wooden ring. Several such moulds are placed
upon a board before being filled with the black paste.
These various kinds of black are employed for
painting, for copperplate printing, etc. The sticks
of fusaiii are used for sketching.
§ 11. Lampblack.
The manufacture of lampblack is quite an impor-
tant branch of trade in certain localities. This black
is obtained by the incomplete combustion of sub-
stances very rich in carbon, and which burn with a
fuliginous flame. This combustion produces a black
dust, exceedingly light, which is known in the arts
under the name of lampblack.
The substances generally employed are resins, tar,
heavy oils from tar and schists, and vegetable oils.
The latter give the finest and purest black, but its
price is higher.
There are in the trade three principal kinds of
lampblack : —
1. The resin black ;
2. The tar black ;
3. The oil or lampblack.
We shall describe the process for manufacturing
each, in the above order.
518 MANUFACTURE OF COLORS.
First Process. — Eesin Black.
As is indicated by its name, this black is obtained
by the combustion of resins. The apparatus is com-
posed of a cylindrical building A (Fig. 59), lined in-
Fig. 59.
side with hanging cloths, upon which the black con-
denses. This building is covered with a conical
roof, supporting a movable sheet-iron cone B, which
is perforated at its summit in order to permit of a
certain draft of air. This cone, the lower diameter
of which is nearly that of the building itself, hangs
by a rope passing through the pulley c, and may,
therefore, be raised or lowered at will. Lastly, the
apparatus is completed with the fireplace D, outside
of the building, and which contains a small cast-iron
kettle E, in which the resin is placed. The operation
begins by heating the kettle E, filled with resin.
When the latter is melted, it is inflamed, and the in-
complete combustion of the resinous vapors causes
the formation of a quantity of large black flakes,
which become attached to the cloths hanging in the
room. The quantity of air necessary to the combus-
BLACK COLORS. 519
tion is regulated by a small sliding damper on the
door of the fireplace. It is important to operate with
the smallest quantity of air possible, otherwise the
product will not be so abundant.
When the resin held in the kettle is burned out,
another quantity is added, and the operation is con-
tinued for several days. When the black has accu-
mulated in the room to such an extent that the ope-
ration cannot be continued, the apparatus is left to
cool off entirely, in order to prevent the black from
being inflamed by contact with the air. The cone c
is then lowered, and in its descent scrapes off the black
sticking against the sides. The black is removed
through an iron door F, which is kept tightly closed
during the operation.
The black obtained by this process is used for
marine and oil painting. It is much less pure when
rosin waste is employed, since it contains a greater
proportion of impurities which are carried over with it.
Second Process. — Tar Black.
The manufacture of lampblack by the incomplete
combustion* of coal tar, is cheaper than that we have
just described. During the distillation of bituminous
coal for making gas, there are produced considerable
quantities of tar, which has several applications in
the arts, one of which, and not the least important, is
the preparation of lampblack.
The apparatus is a furnace A (Fig. 60), lined with
firebricks, and which contains a small kettle B. A
large and thick cast-iron pipe c is fixed to the upper
part of A, and establishes a connection with a large
condensing room, built of stone or brick, and divided
520
MANUFACTURE OF COLORS.
into three compartments D, E, F, of unequal sizes.
The black settles in these compartments, which com-
municate with each other by means of holes in the
partition walls. The apparatus ends by a chimney G,
about 1 metre high, which delivers into the atmos-
phere the uncondensable gaseous products.
Fig. 60.
The mode of operation is very simple: the furnace
is first brought to a dark-red heat, and then the
kettle B is put in. The tar introduced soon becomes
inflamed, and produces an abundance of smoke which
passes through the pipe c, and is condensed in the
compartments D, E, F. A sliding register, in front
of the furnace, allows of the watching of the opera-
tion. When the combustion of the tar in the kettle
B is complete, a new quantity of material is added,
and so on for several consecutive days. In order to
render the combustion more rapid, the tar is now and
then stirred with an iron hook. When the accumu-
lation of charred residue in the kettle becomes too
considerable, the kettle is removed, and is imme-
diately replaced by a clean one filled with coal tar.
One of the most essential conditions is to conduct the
combustion with a minimum of air; otherwise, the
yield will be less, and the product will have a russet,
BLACK COLORS. 521
and sometimes a whitish tinge, which will depreciate
its market value considerably.
The solid residue left in the kettles may be em-
ployed for heating the furnace at the beginning of an
operation. It is very hard and compact, and requires
to be removed with iron tools.
We have ascertained by experiments on a large
scale, that 1000 kilogrammes of good coal tar will
give on an average 250 kilogrammes of lampblack,
that is, a yield of 25 per cent. The operation, with
this quantity of material, takes six days, with one
furnace and one man. The same man can attend to
several fires at the same time.
"When one furnace is used, the black is removed
every week through the door a, which is hermetically
closed during the operation. The packing of the 250
kilogrammes of black requires about 25 casks of 400
litres, or a cask for about 10 kilogrammes of black.
The tar should be free from earthy substances, or
the yield will be less.
The same apparatus may be used for the prepara-
tion of lampblack, with the heavy (dead) oils of tar
and schist. These oils, very rich in carbon, are very
advantageous for this manufacture, and produce a very
handsome black which is much esteemed. Lampblack
is sometimes prepared from the soft pitch left after
the incomplete distillation of coal-tar. This latter
black is not much esteemed ; but its quality may be
improved • by burning the pitch with the dead oils of
tar and schist.
Third Process. — Oil or lampblack.
This black is the lightest and finest of all, and is
obtained by burning certain kinds of oils, the vege-
522 MANUFACTURE OF COLORS.
table ones preferably, in lamps of a peculiar construc-
tion. The apparatus is represented in Fig. 61.
Fig. 61.
A, lamp, the liquid level of which remains constant.
It is fed from a reservoir B, filled with oil. At the
lower part of A there is a bent tube c, the upper
opening of which is on the same level as the oil in A.
The combustion takes place with the aid of a wick
made of cotton or amianthus. This latter substance
is preferable, because it is incombustible, and may be
used quite indefinitely. The flame burns under a cone
D, fixed to an elbow-tube opening into a large hori-
zontal pipe E. This pipe cools the smoke, and con-
denses the water, and other condensable liquid pro-
ducts, formed during the operation. From this pipe,
the smoke passes through a series of large sacks F, F,
F, six metres high, and one metre in diameter, which
are kept open at the top and bottom by funnels of
galvanized iron. The first and second sacks, and the
third and fourth, are connected together by the curved
metallic pipes H, H. The other connections at the
top and bottom are through straight pipes. The
lower funnels are closed by plugs i, i, i, which allow
BLACK COLORS. 523
of the extraction of the black after each operation.
The smoke condenses in these sacks, and the product
is the finer as the oil itself is purer. The black con-
densed in the last sacks is also purer and finer than
that in the first part of the apparatus, which is often
somewhat wet. and oily. Each series of sacks is ter-
minated by a conduit J, communicating with a draft
chimney for the escape of the uncondensable products.
A damper regulates the draft, which should not be
too strong or too weak. In the first case, the black
in the sacks might become inflamed ; in the second,
the smoke could not pass through the whole appa-
ratus.
The operation is very simple : the oil is kept at a
constant level in the lamp, by keeping the reservoir
B filled; and the damper is regulated so as to give
sufficient air for the combustion.
The black is removed when a certain quantity has
accumulated in the sacks. Receivers, barrels for
instance, are placed under each funnel I, i, i, and,
after taking off the plugs, the sacks are gently struck,
so as to detach the black. In this manner, the various
qualities of black may be collected separately, and we
have already said that the product is the finer and
the better as it is taken from the sacks further from
the lamp.
Experience has proven that the same process may
be applied to the combustion of the dead (heavy) oils
of tar and schist. These oils are substituted for the
vegetable ones, or mixed with them, in the lamps.
The operation is conducted in the same manner. Of
all the processes of manufacture we have described,
this latter gives the purest black with the least waste,
but it requires fluid materials.
524 MANUFACTURE OF COLORS.
Whateverbe^the mode of preparation, lampblack is
never entirely pure. It holds fixed and volatile salts,
fatty and oily substances, various pyrogeneous pro-
ducts, etc. It is purified by a calcination in thick
sheet-iron cylinders, into which it is tightly packed,
and which are heated in a reverberatory furnace.
The cylinders may generally open in two parts by
means of hinges, and it is then easy to remove the
calcined black. But, as, after this operation, the pro-
duct still contains various salts, it may be treated by
dilute hydrochloric acid for ten or twelve hours.
Several subsequent washings will remove the acid
and the soluble salts. The black which has been
purified in this manner contains but a trace of sili-
cious matter, upon which the acid has 110 action.
We should state that the purification of lampblack
is tedious and expensive, and that in the arts it is
generally used as it comes from the producing appa-
ratus.
§ 12. Chrome or aniline Hack.
Mr. W. H. Perkin has described a process for
obtaining a coloring matter from a solution of sul-
phate of aniline, mixed with another solution of a
bichromate. There is formed a black precipitate,
which, being purified of certain brown impurities, may
be used alone, or conjointly with lamp or ivory-black,
for the preparation of printing inks, colors, and var-
nishes. This black is much more intense than lamp-
black, which always has a brown tinge.
For incorporating this aniline or chrome black with
lampblack, Mr. J. K. Palmer uses 25 parts of chrome
black, and mixes it with 75 parts of lampblack in a
mill. The product is passed through fine copper
BLACK COLORS. 525
gauze sieves, and is received in a leather bag. What
remains upon the sieve is ground again. The chrome
black may be used alone.
§ 13. Various blacks.
We shall conclude our remarks upon vegetable
blacks by repeating that, for certain kinds of paint-
ing, a charcoal-black is employed, which results from
the calcination in closed vessels of any kind of wood.
This charcoal is very finely comminuted, and is washed
in order to remove the soluble salts. It always pos-
sesses a bluish tinge.
Mr. W. E. Newton has recently published the
details of a peculiar process for the manufacture of
vegetable blacks, which are real ulmin-blacks.
" All the blacks," says he, " met with in the trade
for painting, printing, etc., are slow in drying. This
inconvenience is remedied by mixing with the carbon
certain earthy or alkaline bases.
"The oxides of potassium, sodium, calcium, and
aluminium may be employed in the preparation of
the new blacks. The carbon is obtained from an
organic substance, coal-tar, for instance, on account
of its low price. The oxides are introduced, either
in the caustic state, or as combinations, which may
be mutually decomposed at the time of mixing.
"The following are the proportions for the mix-
tures : 100 kilogrammes of slaked lime are mixed with
80 kilogrammes of coal-tar, and then 9 kilogrammes
of alum. The whole is made into a homogeneous
paste, which is calcined in cast-iron retorts, like bone-
black. When the carbonization is complete, the fire is
removed, and the substances are left to cool in the
526 MANUFACTURE OF COLORS.
closed retorts. Lastly, the black is removed, and is
ready to be ground.
" By varying the proportions of tar and slaked
lime, all of the tones and hues of gray and brown may
be obtained."
The following is another mode of preparation of
vegetable blacks, which is described in vol. 87 of the
Brevets d* Invention, and which, notwithstanding all
it claims, will probably furnish only an ulmin-brown.
The process consists in carbonizing any kind of
vegetable matter, by the double action : first, of sul-
phuric and nitric acids, or of sulphuric acid alone ;
second, of heat. The action may be modified to suit
the nature of the substances which are to be acted
upon.
For instance, and in preference to other substances,
we take the saccharine substance resulting from the
transformation of potato starch by sulphuric acid.
This syrup is dried, and mixed in an iron kettle with
12 to 15 per cent, of nitric acid, or 14 to 18 percent,
of concentrated sulphuric acid.
The mixture is stirred all the while, and is heated
at from 100° to 110° C., which temperature is main-
tained for some time. Under the double action of the
heat and acids, the substance becomes gradually
thicker, and is converted into a black paste. The
paste is brown when the operation fails.
When, from comparative color tests upon a plate,
it is ascertained that the greatest intensity of black
has been reached, there is added to the paste from 2
to 3 per cent, of concentrated sulphuric acid. The fire
is urged more vigorously under the kettle, the contents
of which are stirred all the time, in order to prevent
them from sticking to the sides of the kettle. The
BLACK COLORS. 527
mass soon becomes granular, when the heating is
finished.
After cooling, the product is carefully washed in
draining troughs. The black, thus obtained and dried,
is of a perfect color, very light, and easily ground.
The process is also successful with ordinary flour,
potato starch, or any amylaceous substance, with any
ligneous or fibrous material, with rags, paper, wool,
cotton, the leaves of trees, the pulp of beet roots, lin-
seed cakes, etc., in fact with any carbonaceous sub-
stance. Nevertheless, we should prefer flour, potato
starch, and the syrup of glucose, which we mentioned
at the beginning.
The operator will easily ascertain, from the nature
of the substance to be worked, how he should modify
the proportions of nitric and sulphuric acids, and the
degree of heat. An increased proportion of sulphuric
acid will produce a more rapid and energetic carboni-
zation, and the particles of black will be lighter and
more divided. An excess of heat is to be avoided,
because the substance, after being completely dried in
the kettle, will become so hard that it will be difficult
to pulverize it afterwards.
When the fluid syrup of potato starch (glucose) is
employed, the acid present in it should not be neutral-
ized with carbonate of lime or any alkali. The syrup
is immediately concentrated by evaporation, and less
sulphuric acid is to be mixed with it, since it retains
that added for the saccharification.
The best substances for transformation into a fine
black, are those which make transparent solutions
with water. These substances are also those which
are the more easily pulverized, and which absorb light
528 MANUFACTURE OF COLORS.
more readily. Indeed, absorption of light, and black
coloration are the same phenomenon.
This new black replaces lampblack, and those from
ivory, bones, and charcoal. Therefore, it may be
employed for the manufacture of printing ink, of that
for copperplate printing, of blacking, of black paints,
and of any other material requiring a durable black
for a basis. *
§ 14. Inks.
Inks, generally speaking, are the liquids employed
for tracing those signs which represent human
thought ; but they are sometimes employed for dyeing
and coloring various substances, wood for instance.
Inks have not a fixed and definite composition.
They are principally, as is well known, a combination
of a solution of sulphate of iron with a solution of
nut-galls, in which the precipitate is kept in suspen-
sion by means of a gummy substance, which, more-
over, improves the fluidity of the liquid.
Besides the two elements of the black compound,
other ingredients are added in order to produce a
more intense color, or a more pleasing hue, or pecu-
liar properties, according to the uses for which it is
intended.
Thus it is that we find formulae for inks in which
there are decoctions of logwood and other dye woods,
alum, sugar, molasses, peroxide of manganese, alka-
lies or alkaline salts, acids, gelatin, soap, India ink,
lakes, indigo, lamp and other blacks, alcohol, chloride
of mercury, sulphate of copper, catechu and other
tannin materials, essential oils, resins, isinglass, mad-
der, salts of chromium, cobalt, and silver, etc. etc.
There are many other fluids of the same kind, some
BLACK COLORS. 529
of which are the so-called indelible inks, for increas-
ing the security of commercial transactions ; others
for writing with metallic pens ; and lastly, those for
marking linen, or for tracing colored signs or draw-
ings.
Typography, copperplate printing, lithography, au-
tography, etc., also use certain compositions called
inks, and which are made of oil varnish, resins, balms,
blacks, indigo, metallic salts, tallow, soap, wax, etc.
etc.
We cannot here examine at length the preparation
of these various products. Their composition, which
varies ad infinitum, would require more room than
can be had in this volume. We are, therefore, obliged
to refer the reader to our Manuel de la fabrication des
encres of the Encyclopedie-Roret, in which will be
found all the formulae which have been found advan-
tageous in practice.
The manufacturer of colors may undertake the
preparation of inks ; but, generally in large cities, it
forms a speciality.
C. ANIMAL BLACKS.
§ 15. Bone blacks.
The bones of animals are composed of water, fat,
albumen, phosphates of lime and magnesia, carbonate
of lime, and about 32 per cent, of an organic sub-
stance. When the bones are carbonized at a red heat
in a closed vessel, the organic substance is decom-
posed into gases and volatile liquids, and the residue
of carbon, mixed with the earthy salts, forms ani-
mal or bone black. Before carbonizing the bones,
they are boiled in order to remove the fat. The car-
34
530 MANUFACTURE OF COLORS.
bonization is done in closed vessels, and retorts, and
the cold product is ground and passed through silk
sieves.
Bone black has generally a reddish reflex, which is
believed to be due to the phosphate contained in it,
and which may be partly removed by a treatment
with hot and dilute hydrochloric acid. After rinsing
with water, the black is calcined a second time.
§ 16. Ivory Hack.
This black is obtained by calcining ivory scraps in
a clay crucible with its cover luted on, in such a
manner, however, that the gases may escape. The
crucible is brought to a red heat, and the operation is
complete when gases cease to burn at the junction of
the crucible and its cover. After a thorough cooling,
the black is powdered.
Thus prepared, this black is of the first quality for
painting. It is brought to a great degree of commi-
nution by grinding with water, either with a slab and
muller, or between two horizontal stones. The grind-
ing should be continued until the paste is perfectly
smooth and homogeneous. The black is then poured
into convenient moulds, and dried first at the ordinary
temperature, and afterwards in stove-rooms heated to
from 80° to 100° C.
We should state that most of the black sold as
ivory black, is only a bone black of the first quality.
§ 17. Candle Hack.
Candle black is very light and of a splendid and
intense color. It is prepared by burning candles
made of animal substances, stearin preferably, under
metallic plates or funnels. When a certain propor-
BLACK COLORS. 531
tion has accumulated, it is collected delicately, so as
not to compress it, and so as to preserve its lightness.
§ 18. Prussian blacJc.
This is the product of the calcination of Prussian
blue in closed vessels. This black is costly, but little
employed, and advantageously replaced by ivory and
lampblacks.
§ 19. China or India ink.
This is a composition, the basis of which is the
finest and purest lampblack. The calcined oil or
lampblack is that preferred for this manufacture, and
gives an ink of the first quality, which is much em-
ployed as a water color. It is used in England for
mezzotinto engravings, and the hue is heightened by
a small proportion of carmine lake. This ink was
discovered in China, and the inhabitants of that
country had for a long time the monopoly of its manu-
facture. But since the development of chemistry and
the arts, this product has been perfectly imitated.
Among the numerous formulae indicated for its prep-
aration, we find that the following one gives a pro-
duct in no way inferior to the best China ink : —
Calcined lampblack ..... 100 grammes.
Shale black (Boghead) in impalpable powder 50
Indigo carmine in cakes ..... 10 u
Carmine lake 5 "' •
Gum Arabic (first quality) . . . .10 "
Purified ox-gall 20 u
Alcoholic extract of musk .... 5 u
The gum is dissolved in 50 to 60 grammes of pure
water, and the solution filtered through a cloth. The
indigo carmine, lake, lampblack, and shale black
532 MANUFACTURE OF COLORS.
are incorporated with this liquor, and the whole is
ground upon a slab with a muller, in the same man-
ner as ordinary colors, but in this case the grinding
takes much longer. "When the paste is thoroughly
homogeneous, the ox-gall is gradually added, and
then the alcoholic extract of musk. The more the
black is ground, the finer it is. For the above quan-
tities, the grinding should last at least twelve hours.
The black is then allowed to dry in the air, until it
has acquired sufficient consistency to be moulded
into cakes, which, in their turn, are still further dried
in the air, out of the reach of dust. "When quite firm,
these cakes are compressed in bronze moulds having
appropriate designs engraved on them. The moulded
ink is then wrapped in tinfoil, with a second envelope
of gilt paper.
The ink which has been prepared in this manner
possesses all the properties of the real Chinese article.
Its grain is fine and smooth ; it flows very well, mixes
perfectly with many other colors, and becomes so
firmly fixed to the paper, that other colors may be
spread over it without washing it out.
Gum Arabic might be replaced by gelatin; but as
this latter substance is easily decomposed and putre-
fied, we prefer gum Arabic. Moreover, the ink is
better, and flows more easily upon the paper.
SECTION VI.
GREEN COLORS.
§ 1. Green Verona earth.
There are found in Italy, near Verona, in France,
Germany, Hungary, and the island of Cyprus, certain
earthy masses which are inclosed in the amygdaloid,
GREEN COLORS. 533
porphyric, and basaltic rocks, and which possess a
Celadon green color when seen in masses, and are a
light green when powdered. They are smooth to the
touch as are all magnesian earths, and smell like
clay. Such is the physical appearance of Verona
earth, which was used as a pigment by the Greeks
and Romans, and which, at the present time, is washed
and employed for landscape painting on account of
its durability.
Two kinds of Verona earth are found in the trade :
that from Verona, and that from the island of Cyprus.
The Verona article is of a purer color, and has been
analyzed by Mr. Berthier, and more recently by Mr.
Delesse. Its composition is —
Silica 51.21
Alumina 7.25
Protoxide of iron 20.72
Magnesia . . . . . . . .6.16
Soda 6.21
Water 4.49
Protoxide of manganese ..... trace.
The earth from the island of Cyprus has a color
intermediary between verdigris and apple-green. Its
analysis by Klaproth gives —
Silica 51.5
Protoxide of iron 20.5
Potassa 18.0
Magnesia ........ 1.5
Water 8.0
There are many natural green substances, which
could be employed in the arts, and which possess
tones or hues different from that of Verona earth.
For instance, Poland earth is a leek-green ; that from
Unghvar, resulting from the decomposition of tra-
534 MANUFACTURE OF COLORS.
chytes, is a grass-green. Small granules of green
earth are found disseminated in the coarse limestones
of the lower marine deposits, in the neighborhood of
Paris.
§ 2. Malachite.
This green substance is found principally in Siberia,
in the Oural Mountains, and in the Bannate, in the
Tyrol, in Saxony, Bohemia, England, etc. It is a
native hydrated carbonate of copper which possesses
different hues. It is also called mountain green and
Hungary green. Reduced to a very fine powder, this
substance gives a magnificent green, which is, 'how-
ever, too expensive to be largely used. It has been
advantageously replaced, first, by the greens of
Brunswick and of Bremen, and afterwards, by that of
Schweinfurt and by Mittis green, which are more dura-
ble than the two former. The manufacture of these
artificial greens will be described further on.
§ 3. Iris-green.
Iris-green is a color which was formerly used for
miniature painting ; but it is so fugitive that it has
been abandoned. It was prepared with the flower of
the iris, macerated in alum or gum-water. The so-
lution was filtered, and evaporated in dishes, in a dark
place.
§ 4. Sap-green.
Sap-green is a dark green mass, which is employed
only for water colors and the manufacture of pastels.
It is prepared at Nuremberg and in the south of
France. We reproduce here the improvements made
by Mr. R. de Hagen, and which are described in the
Technologists) vol. xiv. page 415.
GREEX COLORS. 535
"Sap-green, or vegetable green, is the juice of the
buckthorn berry (Ithamnus catharticus), and is pre-
pared by various processes, which do not always pro-
duce a handsome green, but often result in a greenish-
yellow color, or a dirty yellow, or a grayish-yellow.
The green-yellow coloration is generally due to the
employment of quite ripe berries, and the grayish or
dirty yellow to these same berries after they have
passed their maturity. It happens sometimes that
sap-green, when put upon a brush, is wanting in
transparency, and this is due to an addition of car-
bonate of magnesia. This color is often sticky and
viscous, because carbonate of potassa has bet i mixed
for rendering the juice green. Lastly, then *re now
to be found in the trade more or less brown sa^-greens,
because they have been evaporated at too intense a
heat.
" All of these properties of various kyids of sap-
green are often united in a greater or less degree in
the same sample of green, which is none the better
for it. For instance, there is often sold, under the
name of sap-green, a yellowish substance, rendered
opaque by the presence of magnesia. If potassa be
added, it remains shiny and yellow, and is altered when
spread with the brush. Lastly, certain peculiarities
of sap-green are due to the proportions of its con-
stituent parts.
" As I have had the opportunity of learning several
processes for the manufacture of sap-green, and of ex-
perimenting upon them, I think that it may be useful
to give some particulars as to the manner of preparing
a very fine quality of this color.
" In order to prepare a fine sap-green of a decidedly
green color and translucent, the berries employed
536 MANUFACTURE OP COLORS.
should not have reached their complete maturity.
Their juice will, therefore, not appear entirely blue,
but somewhat greenish. The boiling of the berries
and the evaporation of the juice should be done at a
moderate temperature. A charcoal lire may be em-
ployed at the beginning, but the evaporation must be
finished upon a water bath. Lastly, the green color
will be made apparent by means of the double sul-
phate of alumina and potassa (potassa alum), because
this salt produces the finest color, gives a good con-
sistency to the mass, and preserves the transparency
of the color when spread with a brush. Such are the
main conditions in the preparation of a good sap-
green ; and as it is important to know the proportions,
we give as a formula the following directions : —
"Any given quantity of buckthorn berries, not
entirely ripe, are boiled with a small proportion of
water in a clean copper kettle, and upon a moderate
charcoal fire. The mass is continually stirred, until
it has become a kind of magma, which is pressed
through cloths. The residue is washed and pressed
again. The liquors are left to settle, and are filtered
through flannel bags, before being evaporated to the
consistency of a thick extract, upon a gentle fire.
"The thickened juice is then weighed, without
pouring it out from the kettle (the weight of which
is known), and to every kilogramme of liquor, there
are added 65 grammes of alum dissolved in water,
and the mixture is thoroughly stirred all the while.
The evaporation is completed upon a water or steam
bath, and continued as long as practicable without
altering the color. The product is then poured into
calf bladders, and dried in the air.
"A sap-green, prepared in the aforesaid manner,
GREEK" COLOKS. 537
appears black when viewed in masses, and a fine
green by looking at the edges. Spread with a brush
it remains transparent, dries rapidly, and produces a
handsome leaf-green. Exposed to the air, it does not
become damp. To sum up, it presents no inconven-
iences, and is all that can be desired.
" By varying the proportions of alum, different
tones of green will be obtained. On the other hand,
should it be desired to have a yellowish-green, the
riper the berries the more yellow the color.
" Since alum gives us the means of producing the
finest qualities of sap-green, we should reject all the
other substances previously employed, such as mag-
nesia, lime, potassa, etc., because their products are
always defective for one reason or another."
§ 5. Picric acid green.
Mr. Y. Stein, Professor at the Polytechnical School
of Dresden, sends us a few particulars regarding this
color.
" The manufacture of artificial flowers has already
for some time employed a green of various tones and
hues, which equals and even surpasses the finest
Schweinfurt green. Analysis shows that the blue
and yellow elements of this green are : the first, the
blue of the sulpho-indigotate of potassa (carmine of
indigo) ; and the second or yellow, picric acid, also
called carbo-azotic, binitro-phenic acid.
" Therefore, by mixing solutions of picric acid and
of indigo carmine, there is obtained a very fine green,
in which a certain proportion of gum Arabic may be
dissolved. It is probable that, when this green is
more widely known, it will replace the Schweinfurt .
538 MANUFACTURE OF COLORS.
green in the manufacture of paper hangings, at least
of those where the cost is a secondary consideration."
§ 6. Bremen green. Bremen blue. Verditer Hue and
green.
Mr. J. C. Habich has published in the Technologiste,
vol. xvii. p. 413, very complete data on the manufac-
ture of this color, which was previously but imper-
fectly known. "We here reproduce the article.
" There is found in the market, under the names of
blue and green verditer, Bremen blue, Bremen green,
a pigment which is a hydrated oxide of copper,
more or less pure. This color, prepared for the first
time by Kulenkamp and Hoffchlaeger, of Bremen,
has been manufactured by several methods, which are
not without influence upon the principal properties
of the product.
" The hydrated oxide of copper, prepared by pre-
cipitating a neutral and soluble salt of copper, always
forms, in drying, a dense mass with a conchoid frac-
ture. On the other hand, basic and insoluble copper
salts, when treated by alkalies, furnish porous and
pulverulent colors. In accordance with the acid oi
the copper salt and the process followed, the color
presents more or less variable properties, the knowl-
edge of which is useful to the consumer, and which
should certainly be attributed to the different modes
of preparation.
" In the beginning, a basic chloride or oxychloride
of copper was always employed, and although the
preparation of this compound with metallic copper
(old ship sheathing) was done by different processes,
there was no difference in the properties of the fin-
ished color. But it is absolutely necessary that the
GREEN COLORS. 539
pale green magma should contain no subchloride of
copper. Let us now examine carefully some of these
modes of manufacture, in order thoroughly to under-
stand the importance of the condition we have just
stated.
"There are mixed in large wooden tubs, in the
construction of which there should not be a single
iron nail —
" 1. 100 parts of old copper sheathing, 99 parts of
powdered sulphate of potassa, and 100 parts of chlo-
ride of sodium (common salt). The whole is moist-
ened with pure water.
" 2. 100 parts of copper* 60 of common salt, and 30
of sulphuric acid, which latter has been diluted with
three times its volume of water.
" 3. Or there is poured upon the copper a solution
of oxide of copper (copper scales) in pure hydro-
chloric acid.
" In the first case there is obtained a chloride of
copper, which, in contact with more metal, becomes
a subchloride. This salt, by the absorption of the
oxygen of the air, is transformed into the basic green
compound called in the factories oxide.
" In the second case, the hydrochloric acid set at
liberty, and the oxygen of the air, produce the same
effects, and the same basic salt is obtained.
" The third case is explained in the same manner.
"Now, as the subchloride of copper (Cu2Cl), de-
composed by caustic alkalies, precipitates an orange-
yellow suboxide of copper (Cu2O), it is evident that
there should remain no trace of this subchloride.
" On that account, in several factories, it is cus-
tomary to prepare the magma of basic oxychloride
one year in advance, and to stir it frequently before
540 MANUFACTURE OF COLORS.
it is used. This process is expensive, since the in-
terest of the capital is lost. The same result is ob-
tained by entirely drying, now and then, the wet
mixture. In this manner atmospheric air penetrates
the mass, and oxidizes it thoroughly.
" During the transformation of this green magma
into a hydrated oxide of copper, an interesting phe-
nomenon takes place. If this magma be introduced
by degrees into a caustic lye of potassa or soda,
marking about 20° Be., the product, after a thorough
washing and drying, is highly comminuted, covers a
great deal, and becomes darker by the addition of a
very small quantity of water. If the magma be di-
luted with an equal volume of water, the mixture
then poured at once into an excess of caustic lye, and
the whole rapidly stirred and then let to rest, a few
minutes will be sufficient for the materials to form a
mass, which can scarcely be divided. After a com-
plete washing and drying, the color is much lighter
than the former one, but it covers less. Instead
turning darker by a drop of water, the wet spot b<
comes a grayish-white, which disappears on drying.
" If it be attempted to blue the precipitate of h;
drated oxide of copper, obtained by any of the above
processes, the product will not be satisfactory, since
the color will be without intensity or freshness. On
the contrary, a good result will be obtained by adding
to the magma, before its treatment with the alkaline
lye, a small proportion of a concentrated solution of
sulphate of copper. It appears that there is a highly
basic sulphate of copper, which deepens the color;
and all such colors, worked in this manner, contain
a small amount of sulphuric acid and of alkali (from
the lye used).
CffiEEN COLORS. 541
" A product, covering well, can be prepared as fol-
lows : To 100 kilogrammes of the thick magma of
basic oxychloride, add a concentrated solution of 7
kilogrammes of sulphate of copper, and then 40 kilo-
grammes of a concentrated caustic lye (32° to 36°
Be.). Stir the mixture vigorously and rapidly, and
pour it into about 150 kilogrammes of caustic lye,
marking 20° Be. The decomposition is thus com-
plete, and the precipitate is carefully washed. Before
the color is received upon the filter it is passed
through a fine hair sieve. Desiccation at a high tem-
perature should be avoided, so as not to change the
hydrated state of the copper oxide. It is no less
important that the air passing through the stove-
room should be pure and free from acid and sulphur-
etted fumes.
" The process which we have just described is,
with slight modifications, nearly everywhere followed.
But, in the following lines, I will indicate another
method, which is to be highly recommended to color
manufacturers.
" When neutral nitrate of copper is decomposed by
an insufficient proportion of a solution of carbonate
of potassa, the flocculent precipitate of carbonate of
copper formed at first is gradually transformed into
a subnitrate of copper, which precipitates in the
shape of a heavy green powder. If this basic salt
of copper be treated by a solution of oxide of zinc
in potassa, there is formed a dark blue color, which
is extremely light, and with great covering power.
It appears to be a zincate of copper, with a very
small proportion of a highly basic nitrate of copper.
" In order to render this process practical, the ope-
ration will be conducted as follows : —
542 MANUFACTURE OF COLORS.
" Copper scales are calcined in a reverberatory
furnace or a muffle, until all the suboxide (Cu2O) is
transformed into protoxide (CuO), that is to say,
until a sample dissolves in nitric acid without the pro-
duction of red nitrous vapors. If the nitric acid
contains hydrochloric acid, which is often the case,
the silver which may be present in the copper scales
will be precipitated in the form of chloride, and may
then be collected.
"The solution of nitrate of copper is heated and
decomposed by a clear solution of carbonate of potassa.
As soon as the effervescence diminishes in intensity,
the solution of carbonate of potassa is added by small
quantities at a time, until there remains but little
undecomposed copper in the solution. In order to
collect this remainder of metal, the clear liquor is
decanted, and the green precipitate is washed several
times with small quantities of water. All the liquors
are collected, and the remaining copper is precipitated
by a solution of potassa. The green carbonate of
copper is introduced into a new solution of nitrate of
copper, in which it is transformed into a basic salt.
The previous liquors are evaporated, and leave cry;
tals of nitrate of potassa.
" An economical solution of oxide of zinc is mad<
as follows : Clippings of metallic zinc are treate<
in a cast-iron vessel with a caustic solution of potass;
or soda. Hydrogen is immediately disengaged, am
the alkali becomes saturated with the oxide of zinc,
which plays the role of an acid. When the liquor is
clear, it is employed for the decomposition of th<
basic nitrate of copper. The product is a handsome
and light Bremen blue, and the evaporated liquor,
GREEN COLORS. 543
when potassa has been used, gives crystals of nitrate
of potassa.
" The advantage of this process is based principally
upon the preparation of a cheap nitrate of copper
(since nitric acid may at a moderate cost be extracted
from nitrate of soda), and upon the production of
nitrate of potassa, which is a valuable secondary
product."
§ 7. Brunswick green.
Hydrochloric acid can be had at a very low price
in certain localities,, and is used for extracting the
copper from poor oxidized ores. Nevertheless, this
acid has scarcely any effect upon those ores which
are not oxidized, and it is necessary to add now and
then a small proportion of nitric acid. A cheaper
process consists in moistening the ore with hydro-
chloric acid, and exposing it to the contact of the
atmosphere. The metal then becomes easily attacked
by chlorine, and even by solutions of chloride of am-
monium and of common salt. The subchloride pro-
duced is rapidly transformed into oxy chloride, and
forms a fine light green called Brunswick green.
§ 8. Scheele's green.
Oxide of copper, combined with various substances,
produces quite a number of green colors, which, un-
happily, are highly poisonous, but possess great
brightness. The oldest of these colors is a neutral
arsenite of copper, discovered in 1778 by Scheele.
The formula as given by the illustrious Swedish
chemist is as follows : —
Dissolve, in a copper kettle, 1 kilogramme of pure
sulphate of copper in 20 litres of water. In another
544 MANUFACTURE OF COLORS.
vessel prepare an arsenite of potassa by boiling 1
kilogramme of carbonate of potassa and 325 grammes
of arsenious acid in 6 litres of water. These two
solutions are filtered, and while they are still hot, the
arsenite of potassa is slowly poured into the solution
of sulphate of copper, which is stirred all the while.
The precipitate of arsenite of copper settles in the
liquor, which has become a solution of sulphate of
potassa. This is decanted, and the precipitate is
carefully washed with hot water, drained upon a
cloth, and dried at a low temperature. The product
is about 1200 grammes of a fine green color.
This product, we have already said, is a neutral
arsenite of copper ; but it may be rendered basic by
increasing the proportion of sulphate of copper. The
color is finer, but not so durable.
In the process actually followed by manufacturers,
a solution holding at the same time arsenious acid
and the sulphate of copper, is precipitated by one of
carbonate of potassa, which is added by small quan-
tities at a time, until the color has acquired its greatesl
brightness. The liquors are stirred during the whol<
precipitation.
Scheele's green may be used with water or oil, am
was formerly much employed especially in the manu-
facture of paper-hangings. It is now replaced
Schweinfurt green, which has more durability.
Another sort of Scheele's green, called green lake,
is prepared in this manner : A solution is made of 1
kilogramme of tartrate of potassa and 600 grammes
of arsenious acid in 8 litres of water, which, after
filtration, receives a solution of sulphate of copper
poured slowly in. The mixture is kept stirred all the
while. After settling and decantation, the precipi-
GREEN COLORS. 545
tate is washed with clear and cold water, and dried
in the stove-room.
§ 9. Schweinfurt green.
Schweinfurt green is a combination of acetate and
arsenite of copper, the color of which varies from a
dark to a pale green, and which is employed in all
kinds of painting and in the manufacture of paper-
hangings. There are several processes of manufac-
ture which we shall indicate. ,
First Process.
This process is due to Baron Liebig, and is as fol-
lows : One part of verdigris is heated in a copper kettle
with sufficient distilled vinegar to be dissolved, then
one part of arsenious acid, dissolved in water, is added.
The mixture of these substances produces a dirty
green precipitate, which is dissolved in a new quan-
tity of vinegar. After boiling for some time, a new
precipitate appears, which is granular, crystalline,
and of a magnificent green. It is separated from the
liquor, carefully washed, and drained.
If the liquor still contains copper, arsenious acid
is added ; and conversely, if arsenious acid be in ex-
cess, acetate of copper is introduced. Lastly, should
it contain an excess of acetic acid, it is used again
for dissolving verdigris.
In order to deepen and brighten the color of the
product, which is slightly bluish, it is boiled with one-
tenth of its weight of commercial potash.
Second Process.
This Schweinfurt green is prepared by mixing 10
parts of acetate of copper with a sufficient quantity
35
546 MANUFACTURE OF COLORS.
of water, heated at 50° C., to make a liquid and
homogeneous magma, to which is added a solution
of 8 parts of arsenious acid in 100 parts of boiling
water. The whole is kept boiling. It is sometimes
necessary to add a small quantity of acetic acid to
the mixture, in order to obtain a finer color with a
crystalline appearance. The precipitate is collected
upon a filter, drained, and dried.
The decanted liquor is advantageously used for
dissolving the arsenic of a new operation. The solu-
tion will be facilitated by the addition of carbonate of
potassa, which forms an arsenite of potassa.
Third Process.
This process has been described by Mr. Braconnot,
who prepares the green as follows : —
Dissolve 6 parts of sulphate of copper in a small
quantity of hot water, and prepare another solution
by boiling in water 6 parts of arsenious acid with 8
parts of commercial carbonate of potassa. When
carbonic acid is no longer disengaged, the two liquors
are mixed while being stirred. There is formed an
abundant precipitate of a dirty greenish-yellow color,
which, by the addition of a slight excess of acetic
acid, becomes crystalline and of a fine green. It i
washed with boiling water, collected, and dried.
Fourth Process.
This process is due to Mr. "Wingens, a manufac-
turer of colors. From 9 to 10 kilogrammes of arse-
nious acid are dissolved in hot and pure water, and
500 grammes of potassa are added to it. After
stirring, and settling for a few hours, the precipitate
is collected upon a cloth. (The author has omitted
I
GREEN COLORS. 547
to indicate the proportion and the kind of copper salt
necessary to produce the above precipitate. — TRANS.)
There are probably other processes for obtaining
different tones and hues of this green, which are
caused by varying the proportions of the materials,
or by other substances added fraudulently or other-
wise. A pure Schweinfurt green is entirely soluble
in nitric or hydrochloric acid.
The commercial sulphate of copper generally used
for the manufacture of arsenical greens is often con-
taminated with sulphate of iron, which considerably
impairs the purity and the brightness of these colors.
Mr. A. Bacco has indicated a simple and economical
process for removing the iron from solutions of sul-
phate of copper. A gelatinous precipitate of car-
bonate of copper is produced by decomposing a solu-
tion of sulphate of copper with one of carbonate of
soda. The precipitate is washed, and a suitable
quantity of it is added to the solution of sulphate of
copper to be purified. After stirring, the mixture
soon deposits flakes of oxide of iron, and the clear
liquor contains only a pure sulphate of copper.
§ 10. Miiiis green. Vienna green. Kircliberger green.
Mittis green is an arseniate of copper, which is
prepared by dissolving 20 parts of arseniate of potassa
in 100 parts of hot water, and mixing this solution
with another of 20 parts of sulphate of copper.
During the whole operation the mixture is stirred.
There is formed a pulverulent precipitate of a light-
green or grass-green color, which is washed and dried.
By varying the proportions, several tones and hues
are produced. But in the commercial article these
variations are generally due to the introduction of
foreign substances.
548 MANUFACTURE OF COLORS.
The arseniate of potassa is prepared by boiling
arsenious acid in concentrated nitric acid, filtering',
and saturating with carbonate of potassa, and crystal-
lizing the arseniate.
§ 11. Green asfies.
These green ashes are prepared as follows : 1 part
of caustic lime and 2 parts of arsenious acid, with a
sufficiency of water, are boiled together. This solu-
tion of arsenite of lime is decanted or filtered clear,
and, while it is still hot, it is stirred at the same time
that it receives a solution of sulphate of copper. The
precipitate is a green powder of sulphate of lime
and of arsenite of copper, which is washed and
dried.
Green ashes are used only for coloring prints, since
they do not possess sufficient body for oil colors.
§ 12. German green without arsenic.
For some time past there has been sold in Germany
a green without arsenic, which is intended as a substi-
tute for the arsenical Schweinfurt green. This coloi
is not so bright as the latter, is in the shape of lighi
and crumbling cubes, and may be applied to many
purposes, although it is poisonous.
We are not acquainted with the preparation of this
color. An analysis made by Mr. C. Struve shows its
composition to be —
Chromate of lead 13.65
Basic carbonate of copper .... 80.24
Oxide of iron 0.77
Carbonate of lime 2.65
Water 2.58
99.89
GREEN "COLORS. 549
This green is very durable, and has more body than
Schweinfurt green.
§ 13. Erlaa green.
According to Mr. Weil hem, Erlaa green is pre-
pared in the following manner, in a small town of
Saxony which bears that name.
Pure sulphate of copper and 30 per cent, of its
weight of common salt, are dissolved in water. 100
parts of this solution are poured into a milk of lime,
composed of 300 parts of water, and from 40 to 50
parts of white and well-burned lime. As soon as
the blue color appears there are added from 8 to 12
parts of a soluble chrome salt, the neutral chromate
of potassa being preferred. The color is washed
with water, and immediately pressed.
Other copper salts, or a greater or less proportion
of lime or of chromic salt, will result in a great va-
riety of hues of this color.
§ 14. Mineral green.
This color is but little used in the arts, because it
does not cover enough. It is a mixture of hydrated
oxide of copper with a greater or less proportion of
arsenite of copper. It is prepared by precipitating,
with caustic potassa, a solution of sulphate of copper
and 12 to 15 per cent, (of the weight of the sulphate)
of arsenious acid (white arsenic). If, as Mr. Habich
advises, there be added to the precipitate a solution
of zincate of potassa, prepared in the manner pre-
viously explained (see Bremen green or Verditer),
there is obtained a very bright and not too expensive
color of a light green. 100 kilogrammes of copper
550 MANUFACTURE OF COLORS.
(sulphate of?) and 15 kilogrammes of arsenious acid
and alkaline zincate, furnish 93 kilogrammes of color.
Another mineral green of an apple-green color, with
a bluish reflex, covering and drying well, but turning
black easily, is prepared from a mixture of 2 parts of
Scheele's green, 6 parts of white lead, 2 of black oxide
of copper, 3 of mountain blue, and one-half part of
neutral acetate of lead.
§ 15. Paul Veronese green.
We are not acquainted with the mode of prepara-
tion of this fine and durable color. It is another
arsenite or arseniate of copper, made in Alsace and in
England, high in price, and used either for water or
oil painting.
§ 16. English green.
English green, of which there are innumerable
varieties in the trade, is a Scheele's green mixed,
while in paste, with sulphate of baryta or sulphate of
lime, tempered with a small quantity of water. Its
hue varies from an apple-green to that of a dead leaf.
It is employed with water and oil, but generally alone,
because it alters other colors.
§ 17. Neuwied green.
A. 16 parts of sulphate of copper, dissolved in hot
water, are decomposed by a solution of arsenious
acid. On the other hand, 4 parts of well-burned lime
are slaked, and mixed with cold water, so as to mak<
a milk of lime, which is poured through a fine hail
sieve into the arsenical solution of copper, th<
latter being kept constantly stirred. The resulting
green color is washed several times. Other quuli-
GREEN COLORS. 551
•
ties of this pigment are prepared by the following
recipes : —
B. Sulphate of zinc (copper?) . 8.000 kilogrammes.
Arsenious acid .... 1.250 "
Lime 1.000 "
C. Sulphate of copper . . . 8.000 "
Arsenious acid .... 0.750 "
Lime 2.000 "
The color called picket grim in Germany is prepared
in the same manner, with a proportion of arsenious
acid equal to 3.750 to 4.000 kilogrammes.
§ 18. Milory green. Silk green. Green cinnabar.
Leaf green.
The real mode of manufacture of this fine color is
still unknown. It is found in the market in the shape
of troches, it unites with other colors well, and is em-
ployed for oil painting. It is imitated to a certain ex-
tent, by mixing together, and in certain proportions,
ferrocyanide of potassium, sulphate of iron, acetate
of lead, and chromate of potassa. A few chemists
certify that there is also some sulphate of baryta.
These greens, according to Mr. Arnaudon (Tech.no-
logiste, vol. xx. p. 519), are intimate mixtures of
chrome yellow and Prussian blue, with an addition of
alumina, or of other neutral and colorless bases or salts.
These greens possess a certain brightness and great
body, but they participate in the inconveniences of
binary colors (mixtures of two simple — primary —
colors, yellow and blue, in this case), that is, their
color changes and their brightness diminishes under
artificial light. These greens, moreover, do not resist
alkalies, which destroy the blue and produce a brown-
yellow. Acids, by the destruction of the chrome
552 MANUFACTURE OF COLORS.
yellow, render the blue predominating. They are
altered by solar light, and darken by the action of
the sulphur held in other pigments, such as vermilion,
orpiment, etc., with which they may be mixed.
Prussian green is a color which is prepared by
pouring a solution of ferrocyanide of potassium, into
one of a soluble cobalt salt (nitrate, sulphate, chlo-
ride). Its hue is very rich, but readily turns to a
reddish-gray.
Binary mineral greens, more durable than the pre-
ceding, may be prepared from mixtures of the yellows
of sulphide of cadmium, Naples yellow, and the chro-
mates of baryta, tin, and zinc, with the blues of ultra-
marine and of cobalt. They are not blackened by
sulphuretted gases.
§ 19. Green of stannate of copper.
The color of this green, in the opinion of Mr. Gen-
tele, is not inferior to that of arsenic greens. Among
the many formulae given for its preparation, the fol-
lowing is one which gives a good product : —
To a solution of 125 parts of sulphate of copper in
pure rain-water, there is added a solution of 59 parts
of tin in nitric acid. This mixture is precipitated by
an excess of caustic soda. The green color is washed
and dried.
A less handsome green is prepared as follows : —
100 parts of nitrate of soda, and 59 parts of tin, are
brought to a red heat in a Hessian crucible. When
the mass is cold, it is dissolved in a dilute caustic lye.
This solution is allowed to become clear, when it is
diluted with more water, and poured into a solution
of sulphate of copper. The reddish-yellow precipi-
GREEX COLORS. 553
tate, soon becomes of a handsome green, by washing
and drying.
§ 20. Eisner green.
This copper-green, in which there is no arsenic, is
not so bright as those of arsenic. Nevertheless, the
various hues found in Germany are good pigments,
which are not entirely devoid of brightness, and are
less dull than green ultramarine.
These green colors are prepared by pouring a de-
coction of yellow wood, clarified by gelatin, into a
solution of sulphate of copper, and adding to the
mixture from 10 to 12 per cent, of tin-salt (protochlo-
ride of tin). The whole is precipitated by an excess
of caustic potassa or soda. The deposit is thoroughly
washed, and its green color acquires a bluish tinge
by drying. A more yellowish hue is obtained by
increasing the proportion of yellow wood.
§ 21. Green cinnabar.
"We have already indicated, in the article on chrome
yellows, the preparation of a green color, which is a
mixture of chrome yellow with Paris blue. There
is sold in Germany, under the name of green cinnabar
(Griiner zinnober\ a color of the same kind and
without arsenic, the hue or tone of which varies from
a dark to a light green. Mr. L. Eisner recommends
the following mode of manufacture : —
A solution of yellow chromate of potassa is mixed
with another of ferrocyanide of potassium (yellow
prussiate of potassa). Another separate mixture is
made of neutral acetate of lead, and of proto-acetate
of iron, which is prepared by decomposing a solution
of subacetate of lead with one of sulphate of iron.
554 MANUFACTURE OF COLORS.
By the reaction, an insoluble sulphate of lead is
formed, and the proto-acetate of iron remains in the
solution. It is the clear liquor which is used; but
this acetate of iron may be prepared by other pro-
cesses.
The first mixture is poured into the second, and
there is formed a more or less dark precipitate, which
is washed and dried at a low temperature. Dark
tones are obtained by having the iron and the ferro-
cyanide predominating; and the light ones by an
excess of lead and of chromate.
§ 22. Green lakes. Vegetable green. Grass-green.
China green.
A green lake is generally a color prepared with
the lake of a yellow coloring substance, mixed with
Prussian blue. These pigments give very handsome
colors, which, however, in a majority of cases, possess
but slight durability.
The green lakes and the vegetable greens, accord-
ing to Mr. Arnaudon, may be divided into three cate-
gories.
The first of these categories comprises the com-
pound greens, formed by the mixture of a vegetable
blue and a mineral yellow, and conversely. For in-
stance, indigo-carmine with the yellows of chrome,
Naples, Cassel, Verona (oxy chloride of lead), orpi-
ment, and cadmium. These greens, especially those
in which the yellow is a chromate or a sulphide, are
easily altered by some oxidizing or reducing action.
In the converse case, that is, when the blue is of
mineral, and the yellow of vegetable origin, for in-
stance, Prussian blue, molybdenum blue, ultramarine
blue, etc., associated with gamboge, stil-de-«grain,
GREEN COLOKS. 555
woad, etc., we have still to fear the mutual alterations
of the two component colors. Thus, Prussian hlue,
in contact with an organic substance, turns by degrees
to a black, while the mixed yellow becomes brown.
Ultramarine itself becomes paler, if the yellow de-
velops any acidity. In regard to the green with
molybdenum blue, the destruction of the color is
ordinarily due to an oxidation of the molybdenum
compound.
The second category is composed of the compound
greens resulting from a mixture of vegetable yellows
and blues; for instance, indigo blue with woad yel-
low, Indian yellow, and the yellows of gardenia and
broussonetia. Although these greens cannot be con-
sidered fast colors, they are nevertheless superior to
the preceding ones from the harmony in their lighter
tones and hues. The more solid greens of this cate-
gory are those formed of indigo, associated with the
yellows of Persian berries, woad, and gardenia, and
Indian yellow.
In water color painting, it is possible to employ a
mixture of picric acid, or of picrate of ammonia
with indigo carmine. But this green is not durable,
and painting exposed to solar light for several
months becomes yellowish, then yellow, and lastly,
russet, from a mutual decomposition of the picric
acid and indigo.
In the third category of vegetable lakes we have
the green lake, made of a naturally green coloring
substance, united to a colorless metallic oxide.
For instance, grass-green is chlorophyl associated
with lime; sap-green is the coloring substance ex-
tracted from the bark or berries of the buckthorn,
and precipitated by lime or alumina. China green
556 MANUFACTURE OF COLORS.
is to be added to the list, although it is still too ex-
pensive to be used for ordinary paints.
This last green, in daylight, presents nothing
extraordinary, and its bluish-green hue makes it re-
semble green ultramarine. But, under artificial light,
it acquires a brightness and a purity of color, which,
united to its perfect solubility, renders it a precious
dye for those tissues which are intended to shine
under artificial light. This green stands quite well
the action of the air, but to a much less extent than
indigo, and does not well resist the influence of alka-
line fumes. Acids change China green to a violet-
blue.
§ 23. Mineral green lake.
This lake is a mixture of the oxides of copper and
zinc, which is prepared by precipitating with carbon-
ate of potassa a saturated solution of copper in 1 part
of nitric acid and 3 parts of hydrochloric acid, to
which is added a solution of zinc in concentrated
nitric acid. The light green precipitate of the two
carbonates is washed, dried, powdered, and heated in
a crucible, until the carbonic acid is expelled, and
the product has acquired a fine greenish hue. This
pigment, misnamed mineral lake, is ground very fine ;
and is employed for water and oil colors. It is very
durable.
§ 24. Rinmann green. Cobalt green. Zinc green.
Rinmann green is a combination of oxide of zinc
with oxide of cobalt. It is prepared by dissolving 500
grammes of cobalt ore, as pure as possible, in 4 kilo-
grammes of concentrated nitric acid, and adding a
solution of 1 kilogramme of zinc in 5 kilogrammes of
nitric acid. The mixture is diluted with water, and
GREEN COLORS. 557
then precipitated by a solution of carbonate of potassa.
The pink-white precipitate is washed upon a cloth,
dried, and calcined in a crucible at a high temperature.
The product is very durable, and of a fine green color.
Mr. R. Wagner, who has examined the preparation
of Rinmann's green, expresses himself as follows, in
a note published in the Heclinologiste, vol. xviii. page
409:—
" Rinmann green, or cobalt green, is a color dis-
covered towards the end of the last century by the
Swedish chemist Rinmann. It is obtained by the
calcination of a mixture of oxide of zinc and of oxide
of cobalt. It is not so much on account of a want of
beauty in the color, as because the constituent parts
are expensive, that this green pigment has not been
extensively employed. Even now its description is
found only in chemical books, and the color has a
place only in collections of chemical preparations.
" Of late years, since zinc has become cheap, and
a sufficiently pure oxide of cobalt may be had at a
moderate price, the conditions of the manufacture of
cobalt green are more favorable. I have, therefore,
undertaken a series of experiments on the best man-
ner of preparing this pigment, and I will now give
the results of my researches.
" The first condition, which is indispensable, is to
prepare a protoxide of cobalt as free as practicable
from foreign metals. For this purpose the oxide of
cobalt sold by certain manufacturers of blue in Sax-
ony (Oberschlemma, Pfannenstiel) is used. It is
dissolved in 3 parts of hydrochloric acid, and the so-
lution is evaporated to dryness. The residue is dis-
solved again in 6 parts of water, and a stream of
sulphuretted hydrogen is passed through the liquor
558
MANUFACTURE OF COLORS.
as long as precipitation takes place. The clear liquor,
decanted from the sulphides of the foreign metals, is
again evaporated to dryness, and the residue is dis-
solved in enough water to make 10 parts. One litre
of this solution does not contain more than 100
grammes of protoxide of cobalt ; therefore, 100 cubic
centimetres will hold 10 grammes. This liquor is
kept for use.
"If this solution be precipitated with the carbon-
ate of soda, and if, after washing, the still wet pre-
cipitate of carbonate of protoxide of cobalt be mixed
with zinc white, there is produced a reddish-violet
magma, which, after being dried and calcined, con-
stitutes a green mass, the color of which is the more
intense in proportion as the cobalt solution has been
greater.
" Cobalt green may be considered as a mixture of
oxide of zinc and of zincate of protoxide of cobalt
(corresponding with the aluminate of cobalt of the
cobaltic ultramarine or Thenard blue). Ammonia
dissolves the oxide of zinc first, and then the zinc co-
baltic combination, from the calcined cobalt green.
Melted glass is, of course, colored blue by this pig-
ment. If the cobaltic solution be employed in such
proportion that, for one equivalent of oxide of zinc,
there be one equivalent, or more, of protoxide of
cobalt, the calcined pigment will be a dirty green or
a black. The best tone of this green is obtained by
the combination of 9 to 10 parts of oxide of zinc,
with 1 to 1.5 parts of protoxide of cobalt. But, in
every case, this pigment never attains the brightness
of copper greens, or even of ultramarine green.
" Mr. Louyet, a Belgian chemist, has shown, in a
work on the preparation of oxide of cobalt and of
GREEN COLORS. 559
aluminate of protoxide of cobalt in a pure state, that
an addition of phosphoric or of arsenic acid enhances
the beauty of the color. If the addition of these acids
aids in the combination of protoxide of cobalt with
alumina, it should also act favorably in the prepara-
tion of cobalt green. Experience has confirmed this
inference. If the cobaltic solution be precipitated by
the phosphate or the arseniate of potassa, the phos-
phate or the arseniate of cobalt thus produced pos-
sesses the property of imparting- a green coloration to
zinc white, at a temperature much lower than that
necessary with the ordinary protoxide of cobalt.
Moreover, the protoxide of cobalt seems to have
gained more body. The green is also of a purer
color and brighter. The alkaline arseniates act like
phosphoric and arsenic acids. If before the calcina-
tion a small proportion of arsenious acid be added to
the ordinary mixture, the calcined mass will be of an
exceedingly bright green, and its structure being
loosened by the volatilization of the arsenious acid,
it will be easy to grind. I therefore call the atten-
tion of those who may desire to manufacture cobalt
green, to this property of arsenious acid, by which
the beauty of the color is considerably improved.
"Since boric (boracic) acid aids the combination of
the protoxide of cobalt with the oxide of zinc, it may
also possess an advantageous effect; but I have not
yet discovered the best form in which it could be
added to the mixture. The borate of protoxide of
cobalt, added to a considerable proportion of zinc
white, produces, after calcination, a bluish-green;
with a smaller proportion of zinc, the mass is blue
and compact.
"I have obtained an entirely similar result by pre-
5(30 MANUFACTURE OF COLORS.
cipitating a solution of protoxide of cobalt with solu-
ble glass (silicate of soda or of potassa), mixing the
silicate of cobalt with zinc white, and calcining.
u The oxide of antimony, which is isomorphous
with arsenious acid, and^which is obtained by the
precipitation of the perchloride of antimony with
carbonate of soda, has brought no change whatever
in the color of the cobalt green."
Mr. R. "Wagner has made analyses of Rinmann
greens manufactured in Germany. A light green
sample, from the technological cabinet of the Uni-
versity of Wiirzbourg, was composed of —
Oxide of zinc . . . . . . . 88.040
Oxide of iron . ; . . . . . 0.298
Protoxide of cobalt 11.662
100.000
Other kinds of green, prepared by himself a few
years before, were finer than the best qualities of
copper greens without arsenic. Their composition
was —
T. II.
Oxide of zine .... 71.93 71.68
Protoxide of cobalt . . . .19.15 18.93
Phosphoric acid . . . . 8.22 8.29
Soda 0.69
Messrs. Barruel and Leclaire prepare a Rinmann
green, which they call zinc green, by the following
process : 49 kilogrammes of dry and pure sulphate
of cobalt are dissolved in hot water, and this solution
is mixed with 245 kilogrammes of zinc oxide, pre-
pared in the manner given in the paragraph on yel-
low chroinate of zinc. The mixture is dried and
then calcined at a clear red heat, for three hours, in a
muffle. When the substance has cooled off a little,
it is thrown into water, washed, and dried.
GREEN" COLORS. 561
Messrs. Barruel and Leclaire have also discovered
another zinc green, in which this metal is combined,
not with cobalt, but with iron, and which appears to.
be a ferroso-zinc cyanide. The following is the mode
of preparation. Prussian blue is finely powdered and
stirred in a concentrated solution of chloride of zinc.
This magma is put aside for some time, and, when it
has acquired the desired hue it is thoroughly washed,
and the precipitate is dried in the dark. This green
is very handsome, but possesses but little durability.
§ 25. Chrome green.
Chrome green is the sesquioxide of chromium,
which is prepared in the arts by several processes
which we shall now describe.
1. The bichromate of potassa is calcined in a cru-
cible, and is transformed into chrome green and po-
tassa, the latter of which is washed out.
2. The bichromate of potassa is decomposed by
hydrochloric acid, when there is formed a soluble
chloride of potassium, and a green oxide of chromium.
3. A concentrated solution of bichromate of potassa
is heated, and while boiling, sublimed sulphur is
added to it by small quantities at a time. The mix-
ture soon becomes greenish, and the chromic acid is
transformed into a gelatinous oxide, which is washed
with boiling water, dried, and calcined at a red heat
in a crucible.
Or, by the dry way, an intimate mixture of equal
parts of bichromate of potassa and of sublimed sul-
phur is brought to a red heat in a crucible. The
product is treated by hot water, which dissolves the
sulphide of potassium and the sulphate of potassa
36
562 MANUFACTURE OF COLORS.
formed, and leaves the oxide of chromium in the
state of a green powder, finely comminuted.
4. A solution of bichromate of potassa is poured into
a neutral solution of proto-nitrate <*f mercury. There
is formed an orange precipitate, which is washed, and
dried at a gentle heat. It is then powdered, and heated
in a stoneware retort, which is provided with an
adapter dipping in cold water. The mercury distils,
and is condensed in the water. The residue in the
retort is a pulverulent oxide of chromium of a fine and
dark green.
5. A mixture of 3 parts of neutral chromate of
potassa and 2 of sal ammoniac, is heated in a cruci-
ble. The two salts are decomposed, and there is formed
an oxide of chromium mixed with chloride of potas-
sium. The latter salt is removed by several washing
of hot water. A calcination at a dark-red heat in-
creases the brightness of the product.
6. An intimate mixture of 1 part of bichromate ol
potassa, and 1 of potato starch (fecula), is calcine
at a high temperature in a crucible. The product it
washed with boiling water, in order to remove th<
carbonate of potassa formed, and a small proportioi
of undecom posed bichromate. The precipitated oxide
is filtered, dried, and calcined again to remove th<
water. It is said that this oxide is of a very hand-
some color, and that it is easily applied with th<
brush.
Mr. F. Casoria, an Italian chemist, being desiroi
of ascertaining the comparative value of the first foi
processes, made his experiments especially in view
establishing the gradation of color of the same oxide
" 1. The first process, says he, which I have tri<
twice, and which is based upon the decomposition
GREEN COLORS. 563
chromate of mercury, gave me a very comminuted
material, of a dark-green color.
"2. The sesquioxide of chromium, precipitated
from a solution of chloride of chromium by ammonia,
is a green between a gray and a blue.
" 3. The oxide of chromium, resulting from the
decomposition of the bichromate of potassa alone, at
a very high heat, is of a dark-green color and very
compact. Its hue resembles that of the oxide obtained
by the calcination of the chromate of mercury.
"4. Lastly, the decomposition of the bichromate
of potassa by sulphur, has furnished a dense oxide of
an intense green color.
" For my own satisfaction I have tried other pro-
cesses, which gave me less satisfactory results."
§ 26. Emerald green.
Emerald green is another sesquioxide of chromium,
prepared in a particular manner.
There has been in the trade for a long time, under
the names of emerald green and Pannetier green, a
handsome and durable color which was sold at a high
price. The inventor, Mr. Pannetier, has not published
his process, but communicated it to Mr. Binet alone,
as an acknowledgment of the aid given by the latter
person, in putting his pottery kilns at his disposal.
All that is known of this secret composition, is that
the green is a chromium compound, prepared in the
dry way. A few experimenters have also said that
they had found boric (boracic) acid in it.
The remarkable researches of Ebelmen upon the
artificial production of mineral compounds have shown
the advantages which may be had from boric acid as
564 MANUFACTURE OF COLORS.
a solvent. At a high temperature, boric acid acts
like a solvent, water for instance, and forms combina-
tions more or less stable with the dissolved substance.
The latter may be separated from the boric acid, either
by a higher temperature, which volatilizes the acid,
or by solution in water, alcohol, etc.
Ebelmen, when using boracic acid, employed the
method of volatilization. Mr. Guignet uses it also
as a flux ; but, instead of removing it by a high tem-
perature, he dissolves it in water. The following is
a resume of the mode of operation of Mr. Guignet.
This color may be prepared by two processes : —
First process. — There is heated, upon the bed of a
reverberatory furnace brought to a dark-red heat, a
mixture of 1 part of bichromate of potassa and 3 parts
of boric acid, moistened with enough water to make
a thick paste.* The product, while red hot, is thrown
into cold water, and washed with boiling water, in
order to remove the borate of potassa. The hydrated
oxide of chlorium is dried or kept in the pasty state.
By evaporating the liquors, and adding hydrochloric
acid, the greater part of the boracic acid is recovered.
Second process. — The bichromate of potassa of the
first process is replaced by an equal quantity of chro-
mate of soda, which is prepared by dissolving in boil-
ing water 61 parts of neutral chromate of potassa, and
53 parts of nitrate of soda. The neutral chromate of
potassa may also be replaced by a mixture of 92 parts
of bichromate of potassa, and 89 parts of crystallized
carbonate of soda, and the indicated proportion of
* The temperature should not be above a dark-red heat, other-
wise the substance will fuse entirely, instead of forming a porous
mass. The oxide will become anhydrous, the color of which is a
pale green.
GREEN COLORS. 565
nitrate of soda remains as before. In either case, the
solution, in cooling, deposits a quantity of nitrate of
potassa (saltpetre), which pays one part of the ex-
penses. The mother liquors contain the chromate of
soda, which may be crystallized ; or, what is prefer-
able in this case, the liquors are evaporated to dryness,
and the residue will be a sufficiently pure chromate
of soda, provided all the nitrate of potassa has been
separated.
By the second process of preparation of the chro-
mate of soda, the indicated proportions give twice as
much of chromate of soda as in the former case.
"When the green color is manufactured with the
chromate of soda, the liquors contain borax, which
may be sold directly as such or converted into boric
acid by the addition of hydrochloric acid. The color
prepared from the chromate of soda is of a lighter
green than that produced by the bichromate of potassa.
Still lighter colored pigments may be obtained by add-
ing to the mixture of bichromate and of boric acid,
before calcination, a certain proportion of alumina,
magnesia, blanc fixe, etc.
The chrornates of potassa or soda may also be
replaced by the chromate of lime, obtained by the
direct calcination of chromic iron and chalk, in an
oxidizing flame.
u Although the first process appears very simple, it
is however necessary, says Mr. Casoria, to indicate a
few precautions, which, if they were neglected, would
result in an inferior product. The first condition is
to avoid an excess of heat, and the best temperature
is that below a red heat. If it be attempted to de-
compose entirely the bichromate of potassa by an
increase of temperature, the colored precipitate will
566 MANUFACTURE OF COLORS.
be abundant, but of a dirty green. The very large
proportion of boracic acid has a manifest influence on
the color of the oxide, as I have repeatedly ascer-
tained by direct experiments."
In regard to the economy of the process, we should
notice that the first washings deposit, in cooling, a
large proportion of boric acid, and contain a certain
proportion of borate of potassa and of undecomposed
bichromate of potassa. It is not necessary to demon-
strate that these two residua of the process may be
used quite ad infinitum in the subsequent operations.
Thus it is that a certain quantity of boric acid is
sufficient for many operations.
This process may be tried with a very small quan-
tity of materials, in a platinum dish, and over an
alcohol lamp. The calcined substance, thrown into
boiling water, deposits a green precipitate, which
may be mistaken for the finest quality of Scheele's
green.
Mr. Arnaudon has proposed in the Technoloyiste,
vol. xx. p. 519, a different process for the preparation
of an oxide of chromium, equal in color to the finest
Schweinfurt green. The following is his process : —
Take the equivalent weights of the following salts : —
Neutral phosphate of ammonia (crystallized) 128 parts
Bichromate of potassa ..... 149 "
and mix them thoroughly, either by grinding, or by
dissolving them in a minimum of hot water, and
exaporating the solution to the consistency of a
magma, which becomes hard by cooling. This mass
is broken into small pieces, which are heated in a
shallow dish at the temperature of 170° to 180° C.
At that temperature the mixture becomes soft, then
GREEN COLORS. 567
pasty, and soon intumesces, changes its color, and
disengages a small proportion of water and ammonia.
The heat is continued for about half an hour, without
going above 200° C. Beyond that point, for in-
stance at the temperature necessary for the produc-
tion of Gruignet's emerald green, the green coloration
of the mixture disappears, and is replaced by a dark
brown color due to binoxide of chromium. By
raising the temperature still higher, at a brown-red
heat for instance, the former color changes to a blue,
which is durable in presence of water. If the tem-
perature be maintained at that point, when the mix- i
ture has become green, and if the product be washed
with hot water, to remove the soluble salts, there
will be obtained a nearly impalpable powder of oxide
of chrome, the color of which resembles that of new
leaves, and forms a near approach to the green of the
first chromatic circle of Mr. Chevreul.
The green obtained by this process, freed from
soluble salts by washings in hot water, dried at 160° C.,
ind brought to a red heat in a tube, gives off water,
and does not become dark like the bihydrate of MM.
Guignet and Salvetat. While hot, it is of a violet-
red color, which passes to a gray,* and, lastly, to a
green when entirely cold. However, the hue is different
from that presented by the green before its calcina-
tion ; and by operating with care, a green of anhy-
drous sesquioxide of chromium may be obtained,
rhich rivals that of Schweinfurt. Mr. Arnaudon is
not positive in regard to the composition of this
green, because, notwithstanding repeated washings,
* This gray coloration is due to less red and more green, which
complementary colors, by their combination, produce black.
568 MANUFACTURE OF COLORS.
it will still show the presence of phosphoric acid after
a fusion with a mixture of nitrate and carbonate of
potassa. The proportions obtained do not allow of
a certain decision as to whether this acid is combined
in definite proportions, or simply held by what Mr.
Chevreul calls capillary affinity ; that is to say, by
an affinity analogous to that of tannin for leather, or
of coloring substances for tissues.
Mr. Arnaudon, disregarding the fact of the traces
of phosphoric acid obtained, has found that this ses-
qui oxide of chromium contains about 11.70 per cent,
of water, which corresponds to the monohydrate of
sesquioxide of chromium Cr2O3.HO.
This chrome green is remarkable for its property
of preserving its brightness and purity under arti-
ficial light. It resists acids, alkalies, and sulphuretted
hydrogen. The colors resulting from its mixture
with other pigments are not altered, and it is not
poisonous. On account of all these advantages, it is
to be desired that painters should employ it in their
works. Indeed, if their pallets were entirely composed
of colors as durable as this one, their chefs d'oeuvre
would pass unaltered through ages, and with less
danger of being disfigured by unskilful restorations.
This pigment may also be used for calico-printing
with albumen, etc.
§ 27. Titanium green.
Mr. L. Eisner has proposed to prepare with titanium
a green color without arsenic or copper. The follow-
ing is the process described by this chemist : —
Several years ago, says Mr. Eisner, Lampadius
had published a few experiments he made for the pur-
GREEN COLORS. 569
pose of preparing a dark green color from rutile.*
He melted at a red heat, in a Hessian crucible, 500
parts of powdered rutile, and 1500 parts of purified
potassa. The melted mass was saturated with hydro-
chloric acid, then filtered, and the clear liquor was
precipitated with a solution of ferrocyanide of po-
tassium. The precipitate, washed and .dried, was
titanium green. "With 500 parts of rutile, Lampadius
obtained 855 parts of green. The preparation of tita-
nium green, either from washed rutile or iserine, has
been found more advantageous by the following pro-
cess : —
The clean ore is melted with twelve times its weight
of acid sulphate of potassa in a Hessian crucible. After
cooling, the melted mass is powdered, and digested
until it is dissolved in hydrochloric acid diluted with
50 per cent, of water, maintained at the temperature
of 50° C. The hot solution is separated from the in-
soluble residue by filtration, and the filtrate is evapo-
rated until a drop of the liquor, put upon a piece of
glass or porcelain, becomes of the consistency of a
magma. The whole is allowed to cool off in the
porcelain dish, and the magma, composed of nearly
pure titanic acid, is thrown upon a filter. The drain-
ings are again evaporated, and furnish a new portion
of titanic acid. "When the magma has been suffi-
ciently drained, it is mixed with a large volume of
water, holding a small proportion of ammonia, in
order to prevent the formation of a basic salt of iron.
This liquor is kept boiling for a long time, and the
* Rutile is titanic acid mixed with a greater or less proportion
of the oxides of iron and manganese, and sometimes of oxide of
chromium. Iserine or nigrine is a combination of titanic acid
with oxide of iron, and a few other substances.
570 MANUFACTURE OF COLORS.
precipitated titanic acid, after filtration and washings,
is nearly white. After several similar treatments
with the bisulphate of potassa, it may be obtained
entirely free from iron.
As iserine contains generally some carbonate of
lime, it is advisable to digest it with dilute hydro-
chloric acid, before it is treated with the acid sulphate
of potassa.
A concentrated solution of sal ammoniac is poured
upon the magma, prepared in the manner explained
above, and, after a thorough mixing, it is filtered. The
titanic acid remaining upon the filter is digested in
diluted hydrochloric acid, and kept at a temperature
of 50° to 60° C., until the solution is as complete as
practicable. The acid liquor, after the addition of
ferrocyanide of potassium, is rapidly brought to a
boil, and there is formed a precipitate of a handsome
titanium green, which is washed with water holding
a small proportion of hydrochloric acid. The solu-
tion of titanic acid must be very acid, because if pure
water be employed, and the ferrocyanide poured upon
the magma, the precipitate will be a yellowish-brown
becoming green by ebullition in dilute hydrochloric
acid. The green precipitate becomes white with
ammonia. The liquor, filtered from the green pre-
cipitate, still contains a certain quantity of titanic
acid, which ammonia will separate in the shape of a
white flocculent precipitate.
The dry titanium green, obtained either from rutile
or iserine, is a dark-green powder. It is decomposed
at the temperature of 100° C. Its desiccation should
therefore be carefully conducted.
By this method, iserine and any titaniferous iron-
ore will produce a green as handsome as that pre-
GREEN COLORS. 571
pared from rutile. Moreover, the liquor holding the
double sulphate of iron and potassa will give a
Prussian blue by the addition of ferrocyanide of
potassium. Therefore, this method will allow of the
manufacture, with iserine, of titanic acid, titanium
green, and Prussian blue.
§ 28. Green ochre.
Mr. Bouland, of Orleans, has composed a color,
called green ochre, by the following formula: 50
kilogrammes of dry ochre, in powder, are mixed into
a paste with water and 1 kilogramme of hydrochloric
acid. Twenty-four hours after, 1 kilogramme of yel-
low prussiate of potassa is also thoroughly mixed
with the above paste. Lastly, an aqueous solution
of persulphate of iron is added in order to arrive at a
given hue.
A great variety of hues may be obtained by
changing the proportions of yellow prussiate. This
green is used in the manufacture of paper-hangings.
•
§ 29. Green ultramarine.
This is a light bluish-green, having a composition
similar to that of blue ultramarine ; that is, it con-
tains sulphur, silica, alumina, soda, with traces of
iron and lime. The difference appears to be a greater
proportion of sulphur in the green ultramarine. In-
deed, with the same temperature, if air be allowed to
come in contact with the crucibles containing the
ultramarine, this substance will be blue. On the
other hand, if air does not intervene for burning the
excess of sulphur, the ultramarine will be green, but
will pass to a blue by a calcination in the air.
Green ultramarine possesses a certain brightness
572 MANUFACTURE OF COLORS.
under artificial light, resists sulphuretted hydrogen,
and is not readily attacked by alkalies ; but the weak-
est acids decompose it with production of sulphuretted
hydrogen. Mixed with other colors, or ground with
oils, gums, or varnishes, it is altered if these sub-
stances be acid, or will develop acidity.
§ 30. Verdigris.
Recent researches have shown that verdigris is a
basic hydrated acetate of copper, composed of variable
proportions of bibasic and tribasic acetates of copper.
We shall not tarry on the manufacture of this color,
which was known to the painters of antiquity, and
which forms a special trade in certain localities.
Verdigris is manufactured in France, in the depart-
ments of Aude and Herault, by oxidizing pieces of
old sheet copper from 2 to 3 millimetres thick, heated
to 80° C., with a solution of acetate of copper, and
then immersing them in the skins of pressed grapes,
which are in a state of acetic fermentation. After a
certain length of time, which is indicated by experi-
ence and various phenomena, the copper plates are
removed from the skins, dried in the air, then dipped
into water, and again laid in layers of grape skins.
When this operation has been repeated five, six, or
seven times, the verdigris has acquired a thickness
of from 2 to 3 millimetres, and is scraped off, then
kneaded in wooden troughs, and packed in leather
bags. Its desiccation is completed in the air.
Verdigris is also prepared by covering copper
plates with vinegar.
Verdigris is of a pure green, or of a bluish-green,
according to the proportion of sesquibasic acetate it
contains. When it is pure it is entirely dissolved,
GREEN COLORS. 573
and without effervescence, in diluted nitric and sul-
phuric acids. It is highly poisonous, and is not a
durable color.
§ 31. Crystallized verdet. Distilled green. Crystals
of Venus.
Verdet is a neutral acetate of copper which is
manufactured in the south of France. This salt is
of a fine green color, its taste is sweet and styptic at
the same time, and it is soluble i,n water and alcohol.
Its crystals form very regular rhombs, of a very dark
green. It is decomposed by heat, and the distilled
acid produced is colored by a small quantity of oxide
carried away mechanically. According to Yogel, a
small proportion of anhydrous acid is sublimed at
the same time in the shape of white silky crystals.
This acetate of copper is prepared by dissolving
verdigris in vinegar, filtering the solution, and letting
it crystallize.
This salt is employed for water-color painting. It
is very poisonous, and the green coating deposited
upon copper vessels is still more dangerous.
The verdet may be obtained by double decompo-
sition, and, indeed, this is the process generally fol-
lowed in the factories where acetic acid is prepared
from distilled wood. A solution of 100 kilogrammes
of acetate of lime is decomposed by one of 140 kilo-
grammes of sulphate of copper; there results an
insoluble sulphate of lime, and a solution of acetate
of copper, which is decanted, evaporated, and crys-
tallized.
The liquor known under the name of water-green,
and used as a water-color, is prepared by dissolving
the most colored crystals of verdet in a slightly
alkaline water.
574 MANUFACTURE OF COLORS.
SECTION VII.
COLORS FROM SULPHATE OF ZINC.
We shall close our remarks on colors by describing
a process for the preparation of colors with the oxide
of zinc, which has been proposed by Messrs. L. Ador
& E. Abadie.
" The oxide of zinc, which forms the basis of this
manufacture, is obtained by the decomposition of the
salts of this metal by heat, either in furnaces or in
retorts. The advantage of these colors is their salubrity
and their economy. When the oxide derives from de-
composed sulphates, monohydrated sulphuric (RTord-
hausen) acid is disengaged, and the remaining oxide,
by its combination with other metallic oxides, forms
all the colors, hues, and tones which may be desired.
" The sulphate of zinc is prepared as follows :
Metallic zinc is dissolved in sulphuric acid marking
18° to 20° Be. When the saturation is complete, the
liquor is left to stand until it is clear, and it marks
then 36° to 38° Be. The liquor is then evaporated
in leaden vessels until it forms a pasty mass, which
is spread and cooled upon zinc or lead plates. The
salt is broken as finely as practicable with a wooden
spatula.
"The mixtures of metallic salts forming with sul-
phate of zinc various colors, are as follows : —
"Delicate light yellows, called Roman yellows. —
They are obtained by a simple decomposition by
heat of the sulphate of zinc in retorts and in furnaces.
"Chamois yellows. — 100 parts of sulphate of zinc
in solution, are mixed with li parts of a solution of
sulphate of iron marking 28° to 30° Be.
" Yellow chamois. — 100 parts of sulphate of zinc in
ZINC COLORS. 575
solution, are mixed with 2| parts of a solution of
sulphate of iron marking from 28° to 30° Be.
"Dark chamois. — The proportion of iron solution
is increased to suit the hue desired.
"Gold yellows. — 100 parts of sulphate of zinc in
solution are mixed with 2| parts of a solution of
nitrate of manganese marking 12° to 14° Be.
" Dark gold yellows. — The proportion of nitrate of
manganese is increased to suit.
"Greens resembling Scheele's greens. — 100 parts of
sulphate of zinc, in solution, are mixed with 2| parts
of a solution of nitrate of cobalt marking 20° Be.
" Dark greens. — The proportion of nitrate of cobalt
is increased.
" Yellowish greens. — 100 parts of sulphate of zinc
are mixed with 2| parts of a solution of nitrate of
nickel, at 16° Be., and a few drops of a solution of
nitrate of silver.
"Grays. — 100 parts of sulphate of zinc in solution,
are mixed with 2J parts of a solution of sulphate of
copper.
"Bronzes. — 100 parts of sulphate of zinc are mixed
with 3 parts of a solution of nitrate of nickel at 15°
to 16° Be., 3 parts of a solution of nitrate of cobalt
of the same specific gravity, and from 1 to 1J per
cent, of a solution of nitrate of copper of the same
specific gravity.
"Dark bronzes. — The same materials are employed,
in the same proportions, but they are calcined longer.
"Pinks. — 100 parts of sulphate of zinc in solution,
are mixed with 2 to 3 parts of a solution of nitrate
of iron marking 20° to 25° Be.
"Dark pinks. — The proportion of nitrate of iron is
increased.
576 MANUFACTURE OF COLORS.
"Whites. — They are obtained by employing a sul-
phate of zinc very pure, especially free from iron,
which is tested with the sulphocyanide of potassium.
The greatest care should be taken to employ clean
drying vessels, and the cooling of the sulphate should
be made in stoneware pots.
"The various combinations of materials, and the
chemical reactions which produce these colors, require
a variable length of time for the transformations to
be completed, according to the apparatus employed,
the temperature, and the colors or hues desired. The
operation requires to be watched attentively, and the
fire should be removed as soon as the given hue or
tone is obtained.
" The sulphate of zinc, mixed with the other solutions
of coloring oxides, is reduced to a thick paste, which
is introduced into a furnace or into a retort. The
calcination lasts from four to eight hours in retorts,
and about one-half of this time in reverberatory fur-
naces. Side openings allow of the watching of the
operation in the furnace, and of the extraction of the
materials when the desired hue has been obtained.
"The colored oxides of zinc, after their removal
from the retorts or furnaces, are pulverized in conical
mills or under stones, and then more finely ground
and sifted.
" The nitrates, chlorides, and acetates of zinc pro-
duce similar results when they are treated in the same
manner with the same metallic salts. Every kind of
color may also be prepared by calcining carbonate of
zinc with the carbonates of the coloring metals ; but,
instead of working them by the wet way, they are
employed in powder and treated by the dry method.
It is necessary that the carbonates of zinc, iron,
DRYING AND ADHERENCE OF COLORS. 577
copper, cobalt, antimony, manganese, bismuth, nickel,
etc., should be very pure.
" The proportion of the coloring carbonates should
not be less than 6 per cent, of the weight of the car-
bonate of zinc, and the amount is increased according
to the hue desired.
"The operation requires two or three hours of
calcination. "When the color and the hue have been
obtained, the substances are removed from the
furnace, ground, and sifted in the afore-mentioned
manner."
CHAPTEE III.
DRYING AND ADHERENCE OF COLORS.
A VERY important question in applying colors is
the facility with which they dry, when they have
been ground with water, essential or fixed oils, or
varnishes. Indeed, it is necessary that these paints
should rapidly acquire a certain degree of desiccation
in order that the places where they have been applied
may be inhabited, and also for the purpose of render-
ing them resisting to friction. Until recently, colors
were made drying by the single process of mixing
them with oil boiled with litharge; but chemistry
has caused improvements to be introduced into this
part of the painter's art, on which it will be useful
for us to tarry a little while.
37
578 MANUFACTURE OF COLORS.
SECTION I.
DRYER FOR ZINC WHITE.
The colors prepared with zinc white dry more
slowly than those of white lead. Mr. Leclaire has
therefore searched for a dryer more powerful than
litharge, and has ascertained that the peroxide of
manganese is preferable to all the other metallic
oxides. The following is his process : —
Purified linseed oil is boiled for 6 or 8 hours, and
to every 100 kilogrammes of boiled oil there are
added 5 kilogrammes of powdered peroxide of man-
ganese, which may be kept in a bag, like litharge.
The liquid is boiled and stirred for 5 or 6 hours more,
and then cooled and filtered.
This drying oil is employed in the proportion of 5
to 10 per cent, of the weight of zinc white, and it is
better to add it during the grinding of the pigment
in oil, since the mixture is more thorough.
SECTION II.
DRYING OILS.
Mr. Leclaire has not confined himself to the above
process for oxidizing oils, but he has also searched
for a mode of rendering them thicker, and indicates
the following method : —
Oil oxygenized (oxidized) by the peroxide of man-
ganese, says he, may be thickened to the point of
becoming solid, when it will produce.the same effects
as litharge.
Fifteen parts of lime, made into paste with water,
are added to 100 parts of oil oxidized by the per-
oxide of manganese. The whole is boiled, or heated
DRYING AND ADHERENCE OF COLORS. 579
by steam, until the water has evaporated ; the oil
forms then with lime a thick product which is a
dryer. It is sold in lumps, or in powder, or ground
with an equal weight of oxidized oil. It may be
ground with the ordinary essence of turpentine, or
with that of Venice, but the dryer is less powerful
than when it has been mixed with 'oxidized linseed
oil. Three to five per cent, of this dryer are sufficient
for a rapid desiccation.
Other dryers may be made by combining lime with
resins and essences of turpentine, in the proportions
indicated for fixed oils.
SECTION III.
POWDERED DRYER OF GUYNEMER.
For a long time, says Mr. Guynemer in a patent
taken out for this purpose, it has been a desideratum
to find an impalpable white powder which may be
intimately incorporated with zinc white, and which
will accelerate its desiccation.
The use of litharge and acetate of lead, as dryers,
is open to the inconvenience of diminishing the
unalterability and innocuity of zinc white; and on
this account, Mr. Leclaire has proposed for zinc
white an oil rendered drying by manganese.
The employment of these oils is sometimes diffi-
cult, because their preparation is not well understood
everywhere, and because the expenses £>f transporta-
tion, the leakage, and the duties are heavy. It hap-
pens, also, in certain cases, that the brightness of
the pigment is impaired.
Mr. Leclaire, in his patents, claims the mode of
580 MANUFACTURE OF COLORS.
rendering oils drying, and the use of all the combi-
nations of manganese as dryers.
The Society of the "Vieille-Montagne, represented
by Mr. Gnynemer, has become the owner of the
patents of Mr. Leclaire, and the following formula is
a new manganese dryer, in powder : —
Take — Pure sulphate of manganese ... 1 part
Pure acetate of manganese . . 1 "
Calcined sulphate of zinc . . 1 "
White oxide of zinc . . . .97 parts.
100
The sulphates and the acetate are ground in a
mortar to an impalpable powder, which is passed
through a metallic sieve.
Three parts of this powder are dusted over the 97
parts of oxide of zinc, spread over a board or a
slab. The whole is then thoroughly mixed and
ground.
The resulting white and impalpable powder, mixed
in the proportion of | to 1 per cent, with zinc white,
will enormously increase the drying property of this
product, which will become dry in 10 to 12 hours.
SECTION IV.
VARIOUS DRYERS. ZUMATIC DRYER.
Mr. Zienkowicz is the chemist who appears to us,
in a patent described Vol. xxiv. p. 319 of the Recueil
des Brevets d* Invention, to have investigated the ques-
tion of dryers for painting the most thoroughly.
We reproduce here an extract from this work on
the preparation of the zumatic dryer.
"Since it has been tried to substitute zinc oxide
for white lead in painting, it is natural that researches
DRYING AND ADHERENCE OF COLORS. 581
should also have been made to replace litharge, as a
dryer, by a substance free from the inconveniences
which caused the abandonment of white lead. In-
deed, if sulphuretted hydrogen impairs the whiteness
of the painting done with white lead, it is not logical
to employ a lead dryer with zinc paints, because the
latter substances will lose their advantages of not be-
coming dark like white lead.
"It has been known for a long time, that several
metallic oxides and salts, especially the sulphate of
zinc, umber, and the oxide of manganese, have the
property of combining with oils, which they render
drying. But oxide of lead having been found to pos-
sess the greatest action upon oils, it has been pre-
ferred to the others, up to the present time, since its
employment in connection with white lead does not
present the same inconvenience as with zinc white.
"To the afore-named oxides, we should add the
protoxides of the metals of the third class (Thenard's
chemistry), that is to say, those of iron, cobalt, and
tin. However, as the greater number of these pro-
toxides are either difficult to prepare, or rapidly al-
tered in the air, they cannot be kept and employed in
practical operations. We have therefore searched
out as to whether these oxides, combined with cer-
tain bodies, could not be manufactured in an economi-
cal manner, and could not preserve their drying
action upon oils, from the time that they are prepared,
to that when they are employed.
" Moreover, it is acknowledged, that dryers in the
dry state are preferable in many respects to drying
oils. But the difficulty lies in their proper prepara-
tion.
" The preceding considerations caused me to search
582 MANUFACTURE OP COLORS.
for a process for producing the drying of the oil em-
ployed with zinc white, without litharge or any oxide
of lead. A similar result has been arrived at by other
persons with more or less success.
"I have therefore availed myself of the indications
furnished by various authors upon the choice of cer-
tain materials, while, on the other hand, I have made
original researches and experiments based upon a
theory which it is not necessary to explain in this
place.
"However, I should say that one of the principal
bases of my process is founded upon the combination
of the protoxides of the metals of the third class
(Thenard's chemistry), that is, those of iron, tin,
nickel, manganese, and cobalt, with benzoic, succinic,
urobenzoic, and boric acids, which, at the same time
that they preserve these oxides from the oxygen of
the air, do not prevent them from acting upon the
oils as a ferment, which causes the absorption of the
oxygen of the air by these oils, and their resinifica-
tion or drying. Any acid, combined with these pro-
toxides, with sufficient affinity to render the manu-
facture of such dryers easy and economical, and to
preserve them, is comprised in my processes. At the
same time, the affinity of the acid for the protoxide
should not be so strong as to prevent the latter from
acting upon the oils. Carbonic acid is disengaged
by the action of the air in contact with the oils mixed
with these dryers.
"I could include within these claims the above-
mentioned protoxides, although they have been indi-
cated before me ; but it is impossible to employ them
in the manner specified by the authors, especially the
pure protoxide of manganese.
DRYING AND ADHERENCE OF COLORS. 583
" The various experiments which I have made up
to this date, prove that the preference should be given
to the urobenzoate and to the borate of cobalt; but
economical considerations favor the employment of
the urobenzoate and the borate of manganese.
" I shall now explain the processes of preparation
and of manufacture, which I have followed.
1. Benzoate of Cobalt, and Benzoate of Manganese.
"Benzoic acid is dissolved in boiling water, and
the stirred liquor is gradually saturated with powdered
carbonate of cobalt, until all effervescence ceases, and
blue litmus paper does not turn red in the liquor.
" The excess of carbonate is separated by filtration,
the liquor is evaporated to dryness, and the heating
is continued until the salt has lost all its water, and
has become of a light brown color. The salt thus
prepared is an amorphous, hard, and brownish mate-
rial, which may be powdered like rosin, and which
may be kept in the pulverulent state, in any climate,
simply folded in paper.
"An experiment made by me with this drying salt
has proven that, in the proportion of 3 kilogrammes
to 1000 kilogrammes of linseed oil, mixed with about
1200 kilogrammes of zinc white, a piece of painting
was dried in from eighteen to twenty hours. The
temperature was relatively cold and wet, and between
12° and 15° C.
" The benzoate of manganese is prepared in the same
manner, by substituting the carbonate of manganese
for that of cobalt. The manganese dryer presents
nearly the same physical characteristics as the cobalt
salt. Applied under the same conditions, it dries a
little more rapidly, and a little less is needed.
584 MANUFACTURE OF COLORS.
"The high price of benzoic acid induced me to
search for a congenerate of this acid, which would
form saline combinations having the same properties,
and which would be cheaper.
"I have, therefore, tried the urobenzoic (hippuric)
acid, which my experiments have proven as effica-
cious. The urobenzoates of cobalt and of manganese
are obtained in the same manner as the benzoates of
these bases.
" The materials which I have experimented upon
are relatively too expensive for industrial uses ; but
there is every hope that it will be possible to obtain
the benzoic and urobenzoic acids in an economical
manner.
2. Borate of Cobalt.
" A soluble salt of cobalt, the sulphate for instance,
is dissolved in cold water, and this solution is precipi-
tated by a cold one of borax (biborate of soda). The
precipitate of borate of cobalt is collected upon cloth
filters, washed with cold water, and dried in the air.
" The borate of manganese is prepared in the same
manner by substituting for the cobalt salt a soluble
one of manganese, the chloride for instance, which is
cheap.
"These borates are kept and used in the same
manner as the preceding dryers.
3. Employment of Eesins.
" "With the same view, that of preparing a dryer in
the dry state, free from any foreign substance which
might impair its drying properties and render it hy-
grometric, I have tried the employment of resins,
which, from their acidity, play a part analogous to
that of the acids already mentioned.
DRYING AND ADHERENCE OF COLORS. 585
" Thus, by applying to cobalt and manganeSfe the
process hereinafter described, I have obtained a real
drying salt, containing no substance not in harmony
with the effect to be produced, and which may be
kept in the pulverulent state as the afore-mentioned
drying salt.
"An alkaline resinate of potassa or soda is dis-
solved in hot water, and this solution is precipitated
by a suitable proportion of the pure sulphates or
chlorides of cobalt or manganese. The precipitate
thus formed is a resinate of cobalt or manganese,
which is collected upon cloth filters, washed, and dried.
"These resinates are amorphous, and are powdered
and kept in the same manner as the other dryers.
They possess the same properties, and are employed
under the same conditions and in the same proportions.
4. Borate of Manganese.
" In continuing my investigations, especially on
the employment of the borate of manganese, I re-
marked that the protoxide of manganese absorbed the
oxygen of the air with great rapidity, passed to the
intermediary degree of oxidization, and at the same
time separated from the acid with which it was com-
bined. I found, also, that if more than 2 or 3 parts
of this manganese salt per 1000 parts of zinc white
were added, the paint, especially the white grounds,
would acquire a prejudicial coloration.
" In order, therefore, to remedy this inconvenience,
which may often take place from carelessness in com-
pounding the proportions, I have been obliged to find
a method for neutralizing the troublesome effects of an
excess of dryer in the paint.
" I mix in advance the borate of manganese with a
685 MANUFACTURE OF COLORS, x
certain proportion of oxide of zinc, and, in this di-
luted state, the proportion of dryer with the zinc
white paint may be in excess with less danger. I
will however remark that this arrangement does not
entirely do away with the necessity of making the
proper mixtures, but that it allows of a certain amount
of carelessness or ignorance in the compounding of
the paints.
"The following is the manner of mixing the dryer
with a certain proportion of zinc white, and how this
mixture is to be added to the white pigment and oil,
before painting : —
" A thick aqueous magma of 30 grammes of borate
of manganese is thoroughly mixed with 1 kilogramme
of recently prepared oxide of zinc, of the first
quality, and made into a thin paste with water. The
mixture is drained upon a cloth, then pressed and
dried in a stove room. It is kept in a pulverulent
state, in barrels, or in paper sacks.
" This proportion of dryer, added to 20 kilo-
grammes of zinc white, will be sufficient to dry the
paint rapidly ; and should the proportion of zinc
white be reduced one-fourth or one-fifth, or that of
the dryer increased in the same proportion, the color
of the paint will not be altered.
<• The borate of manganese as a dryer is so ener-
getic that it is proper to reduce its action in the fol-
lowing manner : —
" One kilogramme of borate of manganese is pow-
dered and mixed with 25 kilogrammes of zinc white,
first with the hands, and then in a revolving drum.
" In decoration and artistic painting, dryers, what-
ever they be, are employed only with bitumens and
lakes, for glazing, that is to say, for transparent coats.
DRYING AND ADHERENCE OF COLORS. 587
The zumatic dryer cannot conveniently be used for
such purposes, on account of the opacity and body of
the zinc white entering into its composition. I have
therefore replaced the oxide of zinc by a substance
which answers the same object as alumina in lakes,
that is, a material without opacity, and affecting in
no way the color and the transparency of the paints
with which the dryer is mixed.
" The substance employed for such an admixture
with the borate of manganese, or with the other salts
already mentioned, is the pure carbonate of zinc,
obtained by the precipitation of a soluble zinc salt
by an excess of a solution of crystallized carbonate
of soda.
"The carbonate of zinc may be replaced by the
sulphate of baryta, clay, the carbonates of lime or
magnesia ; in fact, by any substance which becomes
translucent in oil. But it is preferable to employ the
carbonate of zinc, which adds to the value of the
new article, and cannot be considered as an adulte-
ration.
" This new product has been called zumatic laJce.
It is prepared according to the following formula,
which contains about as much borate of manganese
as the zumatic dryer : —
Carbonate of zinc .... 90 parts in weight.
Borate of manganese . . .10 "
Linseed oil 90 "
"The whole is most thoroughly ground, and kept
in bladders or in tin tubes. The latter are preferable.
" Since the borate of protoxide of manganese causes
also the rapid drying of the oils employed in the pre-
paration of inks for typography, lithographic and
copperplate printing, Messrs. Barruel & Jean have
588 MANUFACTURE OF COLORS.
recommended the use of borate of manganese in the
manufacture or the employment of printing inks.
" The use of the borate of protoxide of manganese
may still be extended to the preparation or the
employment of fixed oil varnishes, since they acquire
a great tendency to dry without loss of brightness or
tenacity.
" Lastly, the borate of manganese may be very ad-
vantageously employed in the preparation of patent
leather and oil cloths."
SECTION Y.
SPREADING, DRYING, AND ADHERING PROPERTIES OF OIL PAINTS.
Mr. Chevreul published in the Annales de Physique
et de Chimie, 1857, a very important memoir on oil
painting, which is a real treatise on that art. We
should have liked to have entirely reproduced this
work of the illustrious chemist, but it is too extensive
for this volume. We shall therefore confine ourselves
to a resume and the conclusions of the author as
follows : —
"Painting is done with two objects in view, either
to change the natural color of the surfaces of various
articles, or to protect those articles by rendering their
surfaces less easily altered by air, rain, dust, etc.
"Three conditions must be fulfilled: —
" First. The paint must possess sufficient fluidity
to spread with the brush, and also be viscous enough
to adhere to the surfaces without running, and to
leave coats of equal thickness, when the surfaces are
inclined, or even vertical.
" Second. The applied paint must become hard.
" Third. After it has become hard, it must adhere
DRYING AND ADHERENCE OF COLORS. 589
strongly to the surface upon which it has been ap-
plied.
" I have proved that the hardening of white lead
or zinc white paints, is due to the absorption of the
oxygen of the atmospheric air. And since pure oil
hardens, we see that the hardening is the effect of a
primary cause, which is independent of the dryer,
white lead, or zinc white.
" Besides, my experiments demonstrate that white
lead and oxide of zinc manifest a drying property in
many cases, and that this property exists also in cer-
tain substances which are painted — lead, for instance.
" Therefore, the painter desirous to know, at least
approximately, the length of time necessary for his
painting to become dry, will have to consider all the
causes which produce that effect. Consequently, a
dryer will not be considered as the only cause of the
drying phenomenon, since this phenomenon is assisted
by several substances, having also the property of
drying under certain circumstances. Moreover, there
is this remarkable fact, that the resultante or sum of
the activities (drying powers) of each of the substances
entering into the composition of the paint, cannot be
reckoned by the sum of the activities of each sub-
stance. Thus, pure linseed oil, the activity (drying
power) of which is represented by 1.985, and oil
treated by manganese with an activity of 4.719, will,
when mixed, possess an activity of 30.828.
" If there be substances increasing the drying pro-
perty of pure linseed oil, there are others which seem
to act in the opposite direction. For instance : —
" Linseed oil, with one coat applied upon glass,
was dry after 17 days,
"The same oil, mixed with oxide of antimony, took
590 MANUFACTURE OP COLORS.
26 days to dry. In this case, the oxide of antimony
was an anti-dryer.
"Linseed oil, mixed with oxide of antimony, and
applied upon a cloth painted with white lead, was
dry after 14 days.
" The same oil, mixed with the arseniate of pro-
toxide of tin, and applied upon the same cloth, was
not hard after 60 days.
"Oak wood appears to possess the anti-drying pro-
perty to a high degree, since, in the experiment of
December 22, 1849, three coats of oil took 159 days
to dry.
"In the experiment of May 10th, 1850, a first coat
of linseed oil was dry, only on the surface, after 32
days.
" Poplar seems to be less anti-drying than oak,
and Norway fir, less than poplar.
"In the experiment of May 10th, 1850, three coats
of linseed oil took to dry : 27 days for poplar wood,
and 23 days for Norway fir.
" If there be a drying activity, and a contrary one,
in certain substances, I have no doubt that there ar
also circumstances, under which linseed oil is not in-
fluenced by the nature of the surface upon which it
has been spread. For instance, in the experiences of
May 10th, 1850, one coat of linseed oil was given upon
surfaces of copper, brass, zinc, iron, porcelain, and
glass ; and in every case the oil was dry after 48
hours.
"I hasten to say that I do not pretend to classify
all the substances in contact with linseed oil, or any
other drying oil, into drying, anti-drying, and neu-
tral or indifferent, because the circumstances under
which these substances are placed may cause varia-
DRYING AND ADHERENCE OF COLORS. 591
tions in their properties. I believe that a substance
may be drying, or ant i -dry ing, under different circum-
stances, whether it be due to the temperature, or to
the presence or absence of another substance, etc.
For instance, metallic lead is drying towards pure
linseed oil ; whereas, white lead, which is well known
as possessing drying properties, is anti-drying towards
linseed oil applied upon metallic lead.
" If painters desire to understand their operations
well they must consider the drying of their painting
in the same manner as I have just pointed out. By
so doing, and in certain determined cases differing
one from the others, they will be enabled to modify
and improve their ordinary methods. Linseed oil is
naturally drying, and this property increases almost
always by its admixture with white lead, and in cer-
tain cases, with oxide of zinc. If the mixture be not
sufficiently drying, recourse is to be had to an addi-
tion of oil boiled with litharge or manganese. At
the same time it is necessary to consider the nature of
the surface painted over, whether it be a first, second,
or third coat, the temperature of the air, the light, etc.
" From our present point of view, drying oil boiled
with litharge or manganese loses part of its impor-
tance, because it may be dispensed with for the second
and third coats, and even for the first one if the natu-
ral drying is aided by the temperature.
"Moreover, pigments themselves may act as sub-
stitutes for it, as in the case of light colors, which are
altered by yellows or browns, if the painter has de-
rived profit from some of the observations indicated
in this memoir.
" Thus, linseed oil, exposed to the air and to light,
becomes drying, and loses its color; it may therefore
592 MANUFACTURE OF COLORS.
be employed with white lead or zinc white, without
impairing the whiteness of either.
u Since by associating oxide of zinc with carbonate
of zinc, it is possible to dispense with a dryer, we
have a new way of avoiding the inconveniences of
colored dryers. At the same time, it gives a hope
that new combinations of colorless substances will
be found presenting greater advantages than those
just noticed.
"My experiments demonstrate that the processes
generally followed by color manufacturers, for render-
ing oils drying, that is, by heating them with metallic
oxides, are open to the objections of waste of fuel and
coloration of the product. Indeed, I have shown —
"1. That oil kept at the temperature of 70° C., for
eight hours, has its drying property considerably in-
creased.
"2. That, if peroxide of manganese be added to
the oil kept at this temperature, it becomes sufficiently
drying for use.
" 3. That a very drying oil will be obtained by
heating linseed oil, for three hours only, with 15 per
cent, of metallic oxide, and at the temperature gene-
rally adopted by color merchants.
" My experiments explain perfectly well the role
of linseed oil, or more generally speaking, of drying
oils, in painting. Indeed, when oleic acid is mixed
with metallic oxides which may solidify it, it passes
instantaneously from the liquid to the solid state,
and there is no uniformity in the ensemble of the
molecules of theoleate. The effect is different when
a drying oil, absorbing oxygen, passes progressively
to the solid state. The slowness with which the
change takes place allows of the symmetrical arrange-
BRONZING. 593
ment of the oily molecules, which would appear trans-
parent if there were not opaque molecules between
them. But if the latter do not predominate, the
arrangement is such that the painting is glittering,
and even brilliant, because the light is reflected by
the dry oil as by a looking-glass.
CHAPTEE IV.
BRONZING.
CERTAIN articles of plaster of Paris, wood, paper,
and pasteboard, are given a bronze color, which
varies with the kind of bronzing stuff employed,
and which more or less resembles real bronze.
1. A very brilliant bronzing is done with the
cuttings of gold-beater's foil, ground under a muller
with honey. The object to be bronzed is coated with
linseed oil, and the metallic powder is applied upon
it with a rag.
2. Mosaic gold (aurum mussivum) may be employed
for the same purpose, after having been finely ground
with 6 parts of calcined bones. A small quantity
of this mixture is taken upon a wet cloth and
applied upon the object. The bronze coat is then
rubbed with a dry rag, and afterwards burnished.
When mosaic gold is to be applied upon paper it
is not mixed with calcined bones, and the size is the
white of egg or a thin alcohol varnish. The bronze
is applied with a brush, and is afterwards burnished.
3. When a clean piece of iron is immersed in a hot
solution of sulphate of copper, it soon becomes
38
594 MANUFACTURE OF COLORS.
covered with a precipitate of metallic copper, which,
after being washed, is ground with six times its
weight of calcined bones, and may be used for
bronzing in the manner before explained.
4. Sometimes it is desired to cover articles with a
gray color, resembling that of iron, and which is
called white bronze. An agreeable appearance is
imparted by argentum mussivum; but finely-powdered
tin is also used. This powder is prepared by pour-
ing molten tin into a box, the sides of which have
been well rubbed with chalk, and shaking the metal
very rapidly and continuously until it has become cold.
This powder, passed through a silk sieve, and sized
with a solution of glue, is applied with a brush.
The coat has a dead lustre, which may be rendered
bright by burnishing.
The argentum mussivum is prepared with equal
parts of bismuth, tin, and mercury.
When plaster of Paris is to be bronzed a gray color,
it is rubbed with plumbago.
5. When cleansed and scoured cast-iron is dipped
into a weak solution of sulphate of copper, it becomes
covered with a film of metallic copper, which is quite
adhesive. In this case, the hue of the copper is
reddish, passing to a brown yellow.
SECTION I.
REAL BRONZE, COLOR WHICH IT ACQUIRES IN THE AIR.
Bronze, exposed to the air for a greater or less
length of time, becomes covered with a very thin coat
of carbonate, which imparts to it a greenish tinge, called
old bronze (patine). Various processes have been
proposed to produce this appearance in a short time;
BRONZING. 595
but however close the resemblance may be, a prac-
tised eye will discover a difference. The lovers of
antique bronzes should not complain of this result,
since they posess a means of distinguishing really old
articles from their imitations.
A color resembling more or less that of old bronze,
is given to bronze ornaments and medals, by covering
their surfaces with various mixtures.
SECTION II.
VARIOUS BRONZE COMPOSITIONS FOR METALS.
A great many compositions and pickles have been
proposed for producing a desired patine. Several of
these compositions have constantly given good
results ; but the success depends a great deal upon
the mode of operation, and different operators, using
the same composition, will often produce patines of
different hues. The following are several of these
recipes : —
The metal, turned or filed, is cleansed with nitric
acid, and then covered with the mixture, which is
uniformly applied by means of a soft brush, a rag, or
a pad.
The nature of the alloy itself has a great influence
on the bronze color obtained. Since, therefore, the
alloys of articles for ornaments vary considerably,
the same bronze composition, applied in the same
manner, will give different results.
1. Nitric acid, diluted with 2 or 3 parts of water,
is spread upon the article. The color appears gray
at first, but afterwards it passes to a greenish blue.
2. The object is wet several times with a liquor
composed of 1 part of sal-ammoniac, 3 of carbonate
596 MANUFACTURE OF COLORS.
of potassa, and 6 of common salt dissolved in 12
parts of boiling water, to which are afterwards added
8 parts of nitrate of copper. The coat is unequal
and raw at the beginning, but it soon becomes softer
and more uniform.
3. A handsome blue-green bronze may be obtained
with concentrated ammonia alone with which the
article is many times rubbed.
4. The basis of a great many compositions is vine-
gar with sal-ammoniac. Many skilful workmen never
use anything else but a solution of 60 grammes of
sal ammoniac in 1 litre of vinegar.
5. Another pickle, which gives very good results,
is a solution of 30 grammes of sal ammoniac, and 8
grammes of sorrel salt, in 10 litres of vinegar.
6. A skilful chaser of Paris uses a mixture of 15
grammes of sal ammoniac, 15 of common salt, 30 of
carbonate of ammonia, and 1 litre of vinegar.
7. Another good composition is : 15 grammes of
sal ammoniac, 15 grammes of common salt, 15 of
aqua ammonia, and 1 litre of vinegar.
A brush, dipped into this mixture, is rubbed upon
the cleansed article until it has acquired a fine bronze
color. The piece should only be moistened, and any
remaining dampness is removed with another brush.
If, after two or three days, the coat appears too
pale, the operation is begun anew. The work may
be done in the open air, which causes the color to
appear sooner. The metal never requires to be
heated.
Good effects are also obtained with the two follow-
ing compositions : —
8. Sal ammoniac and common salt, each, 8 grammes;
aqua ammonia, 16 grammes; vinegar, \ litre.
BRONZING. 597
9. Sorrel salt, 2 grammes; sal ammoniac, 8
grammes ; vinegar, ^ litre.
This mixture is applied with a slightly moist brush,
the application being continued until the desired tint
is obtained. These compositions give a better color-
ation when the operation is conducted in a clear and
aerated place, instead of a dark room.
Medals are colored in a somewhat different manner,
and the pickles also greatly vary.
10. A thick paste is made in vinegar, of an inti-
mate mixture of 500 grammes verdigris, and 333
grammes of sal ammoniac. A volume of this paste,
about equal to a walnut, is boiled and stirred in a
certain quantity of vinegar diluted with water.
After a boil of fifteen minutes the liquor is allowed
to settle, and is then decanted. The medals are boiled
for five or six minutes in the clear liquor, and are
afterwards well washed.
The same liquor cannot be used more than five or
six times, and a small quantity of vinegar is added
at each operation.
The boiling is effected in copper vessels, and the
medals are separated from the vessel and from each
other by means of small pieces of wood. The medals
should be immediately wiped off after the coloring
and washing, otherwise their hue will change. When
they are perfectly dry, a bright lustre may be given
to them by another stroke of the press.
It often happens that a portion of the medal acquires
a bad color or is spotted.
11. The operation is conducted in the same manner
with a mixture of 510 parts of verdigris, and 250
parts of sal ammoniac, ground on a slab with vinegar.
The mixture is kept in well-closed vessels. When
598 MANUFACTURE OF COLORS.
it is needed for use, a small proportion of it, as in
the previous recipe, is boiled for ten or twelve
minutes in a tumblerful of vinegar diluted with 2
litres of water.
The alloys holding lead and tin are handsomely
bronzed with a mixture of 100 parts of a neutral and
pure solution of nitrate of copper marking 18° Be.,
and 20 parts of sal ammoniac. The articles should
be barely moistened with this liquor.
As a matter of curiosity, we here give the Chinese
process for bronzing: —
The copper is washed with vinegar and wood ashes,
until it is perfectly bright. It is then dried in the
sun and smeared with the following composition : 2
parts of verdigris, 2 of cinnabar, 5 of sal ammoniac, 2
of the beak and the liver of a duck, and 5 of alum, the
whole thoroughly mixed and made into a thin paste
with water. The smeared copper article is then
heated, cooled, and wiped off. The operation is
repeated eight or ten times. The copper acquires a
handsome appearance, and the bronzing is so durable
that it loses nothing of its beauty by exposure to the
rain and air.
A fine bronze may be obtained with a mixture of
1 part of sal ammoniac, 3 parts of cream of tartar, and
3 of common salt, the whole being dissolved in 12
parts of hot water, to which are added 8 parts of a
copper solution.
By increasing the proportion of common salt, the
coloration is lighter and tending towards yellow ; by
diminishing or suppressing it entirely, the coloration
is bluish. The action is more rapid if the mixture
contains more sal ammoniac.
There are certain articles for which a red bronze is
BRONZING. 599
desirable, and which are smeared with oxide of iron.
If these pieces be rubbed nearly dry with a liquor
holding about -gV°f sulphide of potassium, and then
exposed to the fire, the* coloration turns to a greenish-
brown.
SECTION III.
RECIPE FOR THE ORDINARY BRONZE OF THE FOUNDERS.
Take-
Strong vinegar ...... 1 litre.
Sal ammoniac 30 grammes.
Alum 15 "
Arsenious acid (white arsenic) . . 8 "
Mix the whole together, and when the salts are dis-
solved, the liquor is ready for use. A good bronze
is obtained from sal ammoniac alone, in vinegar, and
many founders employ nothing else. Indeed, with a
good alloy, success is almost certain.
After the casting, the metal is polished with a fine
cut file, or upon the lathe, or with sand paper, or by
a dipping in nitric acid. It is absolutely necessary,
for the success of the operation, that the metal should
be perfectly clean, and especially free from grease.
Aqua fortis (nitric acid) is the best cleansing agent,
and it should be employed when a handsome finish is
desired. The other methods, however, are sufficient
for ordinary work.
SECTION IY.
MODE OF APPLYING THE BRONZING MIXTURES.
The bronze mixture is applied with a small brush,
and the articles should be kept constantly moist
during the operation, in order not to become green.
600 MANUFACTURE OF COLORS.
"When the desired color is obtained, which generally
requires from 25 to 30 minutes, the work is rapidly
passed through clear cold water, dried in tepid saw-
dust, and then varnished, in order to preserve the
coloration.
It happens quite often that, on account of the
quality of the alloy, the bronze composition does not
produce a sufficiently dark coloration. The follow-
ing is the best manner of remedying this inconve-
nience : —
Take about 8 grammes of the best lampblack, stir
it with about one tumblerful of rectified alcohol, and
pass the liquor through a cloth. The piece upon
which the bronze composition has been applied, should
be heated upon a metallic plate or before a clear fire,
until it can scarcely be held in the hand. Then, with
a camel's-hair brush, thin coats of the lampblack
liquor are spread upon it, so long as the desired tone
is not yet reached.
When the coats have become entirely cold, they
are polished with a very soft brush, or with a rag
dipped in very limpid green oil. The whole is then
varnished, and thus is obtained the finest bronze color
which can be imparted to an alloy of zinc and copper.
If the mixture of lampblack be not too black, and the
varnish of too light a yellow, the color of the bronzed
alloy will be of a splendid deep green. We may infer
from it, that it is possible to obtain all the tones of
green bronzes by using more or less of the lampblack
mixture, employing a varnish more or less yellow, and
giving a greater or less thickness to the coats of
black. However, the article will keep its color longer,
if the coat due to the bronze composition be made
dark enough to dispense with the lampblack. This
BRONZING. 601
can be done, but more time is required than when the
black is employed.
SECTION Y.
MODE OF GIVING THE PROPER BRONZE COLORATION WITHOUT
LAMPBLACK.
When the coat of bronze color is dry, if the tone
does not appear deep enough, the piece is placed
before a bright fire, or exposed to the rays of the sun,
and its position is now and then changed; while at the
same time, a draft is avoided. The piece is then rubbed
with a soft brush, and a very handsome bronze is thus
obtained. This method is somewhat tedious, and, in
case of hurry, lampblack is more advantageous.
SECTION VI.
BRONZING OF GUN BARRELS.
They are rubbed rapidly with melted butter of
antimony, and the operation is repeated several times.
The barrels should be moderately heated.
SECTION VII.
BRONZING PLASTER OF PARIS.
Articles of plaster of Paris may be mistaken for old
bronze (provided they are not handled), if they be
impregnated with a copper soap proposed by MM.
d'Arcet and Thenard. The following is the mode of
operation : —
Pure linseed oil is converted into a neutral soap,
by means of caustic soda. A concentrated solution
of common salt is then added, and the boiling is con-
tinued until the liquor becomes very dense, in order
602 MANUFACTURE OF COLORS.
that the grains of soap shall come to the surface.
The soap granules are collected upon a cloth, drained
and pressed, so as to deprive them, as far as practica-
ble, of the adhering lye. The soap is then dissolved
in pure water, and the solution filtered through a
cloth. Another solution is made, also in pure water,
of 80 parts of sulphate of copper, and 20 parts of sul-
phate of iron, which is filtered, and which receives
the soap water until the decomposition is complete.
A small quantity of a solution of the two sulphates
is then added, the whole is well stirred and boiled,
and, in this manner, the metallic soap is mixed with
an excess of the sulphates. The precipitate is
thoroughly washed with boiling water, and then with
cold water. It is collected upon a cloth, drained,
and dried as completely as possible.
On the other hand, 1 kilogramme of pure linseed
oil is boiled with 250 grammes of finely powdered
litharge, then filtered through a cloth, and allowed to
settle in a hot room.
A mixture is then made in a stoneware pot, placed
upon a steam or water-bath, of 300 grammes of boiled
linseed oil, 160 grammes of the metallic soap, and
100 grammes of pure white wax. The whole is kept
heated long enough to remove all dampness. The
article of plaster of Paris is also heated at from 80°
to 90° C., in a stove, and is covered with the hot mix-
ture. When the plaster has become too cold for the
mixture to penetrate, it is again heated to the same
temperature, and consecutive coats of the composition
are thus applied until the plaster of Paris no longer
absorbs it. The piece is again heated in the stove
for a few minutes, in order to absorb the composi-
tion which may remain on its surface. The natural
BRONZING. 603
porosity of plaster of Paris is such, that the mixture
will be absorbed without impairing the sharpness of
the finest parts of the cast. The mixture will pene-
trate more or less deep, according as the operation is
more or less often repeated.
When the piece has acquired the desired color, a
lustre is given by rubbing it with a pad of cotton.
In order more exactly to imitate the real old bronze,
the raised parts are touched with shell gold (ground
gold foil). This process allows of a thorough imita-
tion of medals, statuettes, vases, etc. The plaster,
which has been thus prepared, resists dampness per-
fectly well, and becomes v«ry durable.
SECTION VIII.
GREEN BRONZE.
Take—
Strong vinegar .
. . . .1 litre.
Mineral green .
15 grammes.
Umber
.15 "
Sal ammoniac .
15 "
Gum Arabic
15 "
Avignon berries
60 "
Green copperas .
15 "
And about 85 grammes of green oats, if they can be
had, but they are not absolutely necessary. Dissolve
the salts and the gum in separate portions of the
vinegar, then mix the whole in a stoneware pot. Add
the Avignon berries and the oats, and boil upon a
gentle fire. After cooling, filter through a flannel
bag. The liquor is then ready for use.
APPENDIX.
Mill for grinding colors.
THIS machine, invented by Mr. Kawlinson, is very
simple. It is intended especially for neutralizing the
dangerous effects of the dust of lead pigments, which
is produced in great quantity in the ordinary process
of grinding upon a slab.
This mill is represented in Fig. 62.
Fig. 62.
A is a solid cylinder, 45 centimetres in diameter,
and from 12 to 15 in height. It is generally made of
black marble, which is harder and more easily polished
than other stones.
B is a concave muller, of the same material as the
cylinder, which it covers for about one-third of the
circumference. It is absolutely necessary that the
curvature of this muller corresponds exactly with
MILL FOR GRINDING COLORS. 605
that of the cylinder. It is covered with a wooden
cap Z>, held by hinges i i, to the frame E.
The area of this muller, in contact with the cylinder,
is about 6 times that of an ordinary muller ; therefore
the useful effect and the economy of labor in its use
are as many times greater.
Moreover, the motion of the machine is more rapid
than that of the ordinary hand muller, and there is
less fatigue for the operator.
We should observe that the machine here described
is of the smallest pattern, and that a man of ordinary
strength may easily move a cylinder from 60 to 65
centimetres in diameter, and have his production
increased in the same proportion.
C is a bent piece of iron, firmly fixed atf. It acts
as a pressure spring upon the muller, and the pressure
is regulated by a screw c.
D is a scraper, movable around the points d d,
and inclined upon the cylinder. However, it is put
in this position only when it is desired to clean the
stone, which is then revolved in a direction opposite
to that followed during the grinding proper. This
scraper is arranged like a saw upon four pieces of
wood K K ; its blade is formed of a steel spring for
clocks.
E. Wooden frame, supporting the apparatus and
the hand crank.
F. Drawer for the cleaning knives, those knives
used by curriers being the best.
G. Sliding board upon which the color falls.
H. Metallic dish for receiving the scrapings.
No pigment is put upon this mill, unless it has
previously been powdered in a cloth-covered mortar,
or in a mill for dry grinding. This first preparation
606 APPENDIX.
is not new, and is as necessary as in the old mode of
grinding.
When the color has been mixed with water or oil,
it is carried by a spatula upon the cylinder near the
muller. More play may be given by loosening the
screw c; but this is not necessary, because paint may
be added by successive quantities, until, after several
revolutions, the cylinder is entirely covered.
When it is desired to clean the muller, the screw
c is loosened, and the wooden cap is thrown back-
wards around the hinges i i. The muller-stone may
then be removed.
A few revolutions of the cylinder, with the clean-
ing knives pressed against it, are sufficient to clean
it thoroughly.
It is impossible to state in advance the quantity
of color which should be put upon this mill, or how
long it should stay there, since the only rule is the
desired degree of comminution. But experience has
proven that as much work is done with this appara-
tus in three hours, as in a whole day wi'th the ordi-
nary flat slab and muller, and that the waste is much
less.
The author adds : —
1. That a fly-wheel, fixed at the other end of the
crank axle, will render the motion more uniform.
2. When the pigment is very hard, it is advisable
to increase the pressure of the muller, and to diminish
the velocity of the rotation of the cylinder.
3. Too great a velocity is prejudicial to the bright-
ness of delicate colors, especially when the stones
become hot.
The inventor also recommends a process for pre-
paring the bladders for oil colors. A small wooden
MILL FOR DRY INDIGO.
607
peg is inserted in the neck of the bladder, and a string
is tied upon it. 'By removing the peg and pressing
the bladder, the color runs out upon the pallet. It
will be still better to tie the bladder upon a quill, with
the point on top, because by cutting it, the color may
be squeezed out. The drying of the color remaining
in the bladder will be prevented by plugging the
quill with a small wooden pin. This method is
cleaner and more economical than that of perforating
the bladders with a knife blade.
Mill for dry indigo.
Fig. 63 represents an ordinary mortar L, made of
marble or of some other hard stone, in which revolves
a muller M, which is pear-shaped.
Fig. 63.
Fig. 64.
Its axis revolves at N" N", upon two pieces of oak
wood fastened to the wall Q. Pins are put in o o,
in order to retain the axis in its place. P is the
608 APPENDIX.
crank handle. R is a movable weight, which is
added when it is desired to increase the weight of
the muller.
Fig. 64 represents the muller and its axis removed
from the mortar. The lower curve of the muller
should correspond with that of the mortar. S is a
deep groove in the muller.
A certain quantity of coarsely broken indigo is
put into the mortar, and the rotary motion of the
muller causes the pieces to fall into the groove, and
to become finely ground. The operation will be
rendered more easy, if the lower part of the groove
be made slightly wider.
By covering the mortar with two pieces of wood
meeting in the middle, and having a hole for the
passage of the axis, no dust will escape.
In manufactories the mill is turned by steam power.
The weight R is sometimes replaced by a fly-
wheel, which renders the motion more uniform, and
which should not be more than 60 to 65 centimetres
in diameter, if made of cast-iron. If this fly-wheel
acts at the same time as a driving pulley, the strap
should be about 10 centimetres wide.
Improvements in the manufacture of oils, varnishes,
and colors, by MM. H. Bessemer and J. S. C.
Heywood.
The improvements which we are going to describe
are principally : —
1. A mechanical apparatus for extracting oils and
oleaginous substances from the materials in which
they are held.
2. A peculiar treatment of these oils and oleagi-
nous substances, still combined with the materials
OILS, VARNISHES, AND COLORS,
609
which produce them, by pure water or alkaline solu-
tion, and by hydraulic pressure in closed vessels.
3. A mode of regulating the heat applied to var-
nish vessels; by means of a metallic or air-bath ; a
method of exhausting and condensing the vapors of
resins and oils used in the manufacture of varnishes ;
and lastly, a mode of boiling oils for the preparation
of colors.
4. A process for giving more body and opacity to
colors produced by the combination of silica with an
alkali, alkaline earths, or metallic oxides, and making
vitrified colors from them.
5. An apparatus or mill for grinding these colors.
I. In regard to the mechanical apparatus for ex-
tracting oils and oleaginous substances from the
materials in which they are held ; we use the oil press
represented by the following figures : —
Fig. 65 is a side view of the apparatus.
Fig. 66 is a horizontal projection of the apparatus.
Fig. 65.
Fie. 6fi.
Fig. 67 is a longitudinal section passing through
the axis.
31)
610
APPENDIX.
Fig. 68 is, on a larger scale, a horizontal section of
part of the cylinder.
Fig. 67.
Fig. 68.
The frame a a, of one solid casting, is basin shaped
at a1 a1, in order to receive the oily substances which
run into it during the pressing; a2a? are the pedestals
and journals, in which the crank axle d revolves. On
the opposite side the pedestals a3a3 and their caps
e e, maintain the pressure cylinder jf/*1, which is made
of ordnance bronze, thick enough to resist a consider-
able internal pressure. This cylinderjf/is doubled
inside with a bronze pipe n, the outside of which is
spirally grooved like a screw, the square threads of
which are very close. Small conical holes f3 f3 are
bored in the groove, and through the whole thickness
of the pipe n. At nln\ the internal diameter of the
pipe is greater, and is filled with the steel ring it.
The other diameter nV is smaller, and is provided
with an external steel ring u u. A cylindrical sack
v v, open at both ends, and made of fustian, hair cloth,
or of any analogous permeable substance, fits the
OILS, VAKNISHES, AND COLORS. 611
inside of the pipe n, and contains another cylinder w,
of wire-cloth or of finely perforated sheet iron. All
these inside fittings are stretched and maintained
firmly by the steel rings t u. The cylinder n is then
introduced into ffl, as far as the recess # #, and the
tubular piece /?, li is brought in contact with the ring
u. The screwed plug £, acting also as a stuffing
box, maintains the whole tight.
The extremity flfl of the cylinder is of a smaller
diameter, and contains the ring jj, the diameter of
which regulates the pressure supported by the mate-
rials operated upon. A solid piston Tc fits the inside
of n, and receives its to and fro motion from the con-
necting rod Z. The parallel motion is kept up by
the small wheels m m, rolling upon the guides a4 a4, of
the bed frame, x is a hopper, bolted upon the collar
f2 of the pressure cylinder, and which delivers its
contents when the piston ~k has left the opening free.
fsf3 are holes perforated in the pressure cylinder, and
communicating with those of the doubling pipe n.
The oil escapes through them, f^f* are rings main-
taining the cylinder firmly pressed against the pedes-
tals a3 a3.
"When steam power is directly employed for giving
motion to the piston of the press, the connecting crank
placed at dl should be fixed at such an angle that,
when the piston Jc is at the end of its course, the pis-
ton of the steam engine is only halfway up, that is,
when the power of the steam admitted is the greatest.
In this manner, when the steam engine passes by its
dead points, the piston Jc is half way in its return
motion. When another motive power is applied for
turning the crank d it becomes necessary to put a
fly-wheel upon the axle dl.
612 APPENDIX.
When this apparatus is employed for the extrac-
tion of linseed oil, the seeds are ground and heated
in the ordinary manner, and then introduced into the
hopper. Each time that the piston It goes back, the
opening under the hopper is left free, and a certain
quantity of seeds fall into the tube n. When the
piston returns, it pushes these seeds towards the
narrow part of the cylinder, and, as the friction
resulting from the narrow passage through the
ring j is great, the pressure upon the seeds is also
considerable.
This ring j is movable, and may be replaced by
others having a greater or less diameter, as it is
desired. The doubling pipe n may also be entirely
removed for the necessary repair of worn-out parts.
The action of the piston Jc resembles that of the
piston of a hydraulic press ; the seeds are pumped in on
one side, and pressed out on the other. All that por-
tion of the cylinder where the seeds are held is lined
with hair-cloth or any other permeable and resisting
substance. Rents and other damages are not fre-
quent, since the cloth is protected on the outside by
the tube n, and on the inside by a metallic cloth, or
a piece of perforated sheet-iron.
The pressed oil passes through the above linings,
then through the holes of the inside tube and of the
cylinder, and lastly falls into the basin a' '. It may be
removed by the pipe y.
Although this description is that of a single pres-
sure cylinder, it is evident that several of them may
be fixed upon a common frame, and their pistons be
set in motion by the same power. In this case, the
cranks will be set at such an angle that the resistance
will be nearly uniform. We prefer a cylindrical form
OILS, VARNISHES, AND COLORS. 613
for the piston and the cylinder; but any polygonal
shape will do just as well.
In the foregoing description of the oil-press, we
have not indicated any mode of heating the oily sub-
stances ; but, as it is sometimes necessary to raise
their temperature, we will give the manner of
doing it.
A greater length and a greater diameter are given
to the pressure cylinder, and the basin a' is divided
into two distinct compartments. A strong wrought-
iron pipe is introduced into the axis of the cylinder
through the open end, and reaches about midway
towards the hopper. The extremity of the pipe inside
of the cylinder terminates in a point, while the other
rests against a framework, which gives it the power
of resisting the pressure tending to push it out of the
apparatus. ~No steam escapes into the cylinder, since
the pipe is not perforated.
The ground seeds which fall from the hopper are
pressed first in that portion of the apparatus where
the pipe does not reach, and give out a certain pro-
portion of cold oil, which is collected in the first com-
partment of a'. Being pressed further on, the seeds
are obliged to pass through the annular space between
the steam-heated pipe and the cylinder. There the
oily paste absorbs the heat rapidly, and abandons a
proportion of oil, which falls into the second com-
partment of a'. We see, therefore, that the two ope-
rations of cold and hot pressing are effected simul-
taneously.
II. Our mode of extraction of oils and oleaginous
substances still contained in the vegetable or animal
materials, by a treatment with pure water or alkaline
solutions, and with hydraulic pressure in closed
614
APPENDIX.
vessels, has been applied with the apparatus which
we shall now describe.
Fig. 69 is a longitudinal view, and Fig. 70 a lon-
gitudinal section of the apparatus.
Fief. 69.
Fig. TO.
A is a cast-iron reservoir, rounded at the ends, and
open on top. B is a cylinder with hemispherical ends,
fastened to A, and able to resist a pressure of 36
OILS, VAHNISHES, AXD COLORS. 615
atmospheres. This cylinder is kept in a vertical
position by a collar c, which forms a half circle, and
is fastened by bolts upon a similar collar cast on A.
The upper part of the vessel B forms a cup B1, the
flange of which supports a bracing iron hook D. The
neck, connecting the cup and the vessel B, is lined
with a doubled-up leather E, maintained by the ring
a. The bottom of the vessel is also provided with
another doubled-up leather H, maintained by the bolted
ring j. A stout iron rod K extends from the bottom
of B up to the top of the bracing hook D. The por-
tions K1 K2 are of a larger diameter and fit the doubled-
up leathers. The upper part of K ha?s a square thread
K3, cut upon it, which passes through D1, and is seized
by the nut N, moved by the handles p p. In this
manner the rod K may be raised or lowered.
B is a tube, through which water may be injected
into the vessel B, by means of a pressure pump, similar
to those employed for hydraulic presses, s is a stop-
cock used for letting out a part of the contents of the
vessel, or removing the pressure when it is necessary
to do so. The areas of the stoppers K1 and K2 being
equal, the pressure exerted inside of the vessel has no
tendency to push the rod either up or down, and the
doubled-up leathers make a tight joint.
After a certain portion of oil or oleaginous sub-
stances has been extracted from the vegetable or ani-
mal materials, the remaining portions are more diffi-
cult to obtain, and are treated in the following manner.
The materials are removed from the press, and then
mixed with a certain proportion of hot water, or of a
slightly alkaline lye, in order to make a semi-fluid
paste, which is introduced into the above described
apparatus. By turning the handles P P, the stopper
616 APPENDIX.
K1 is raised above the opening of the cup, whereas
the lower one K2, which is much longer, keeps the
bottom aperture closed. The semi-fluid materials are
then introduced into the cup B1, which delivers them
into the vessel B. The rod K is lowered, so as to
close the two apertures, and the hydraulic pump being
set in motion, the materials are soon submitted to the
required pressure.
The whole is allowed to stand for a few minutes,
in order to effect the reaction ; then the stopcock s
is opened, and a portion of the substances fall into
the reservoir below. By moving the handles p p,
the stoppers2 is raised high enough for the remainder
of the substances to flow out. The rod K is lowered
again, and a new charge is put into B.
The pressure exerted upon the mixture of oleagi-
nous substances and water forces the inclosed oil to
make with water a liquor of a milky appearance, from
which the oil may be separated, either by settling in
large tanks, or by evaporating the water.
When the oils are intended for the manufacture of
soap, or for certain other uses, the mixture needs not
to be separated. When seed oil is thus obtained, the
mucilaginous substances favor the combination of the
two liquids.
As soon as the materials have been removed from
the reservoir A, they are drained upon sieves, and the
solid portions are again pressed for extracting the
fluid portions. In certain cases, it is advantageous
to boil the milky liquor, in order to coagulate the
albuminous substances, and facilitate the purification
of the oil.
III. The following is the process which we use
for regulating the heat applied to varnish vessels by
OILS, VARNISHES, AND COLORS. 617
means of metallic or hot air baths ; and our method
for exhausting and condensing the vapors disengaged
from resins and oils, during the manufacture* of var-
nishes, or from boiling oils employed for the prepara-
tion of colors.
In the actual method of preparing varnishes, the
resins and gums are generally liquefied in thin copper
pots, placed directly over the fire. The temperature
may be suddenly raised so high that the gums are
seriously damaged, and often catch fire. On the
other hand, equally rapid coolings may produce other
inconveniences. Moreover, at the high temperature
required for melting copal, amber, resin anime, and
other analogous substances, their more volatile por-
tions form abundant fumes. The disengagement of
these vapors affects the men powerfully, and some-
times is the cause of dangerous explosions. On the
other hand, the value of these lost vapors is consider-
able, either for the manufacture of varnish or for other
uses. The melting pots must remain open, in order
to watch the operations, and to add fresh portions of
the materials. These considerations show how diffi-
cult it has been to prevent the losses by volatilization,
and have caused us to search for the process which
we are about to explain.
Figs. 71 and 72 are vertical and horizontal sections
of the apparatus for melting the resins or gum resins.
a is the fireplace, placed below the floor of the
work-room as usual ; & is the door of the fireplace?
and c, the ash pit. Upon this fireplace there is placed
a cast-iron kettle d, nearly filled with an alloy of
equal parts of lead and tin, because the melting point
of lead alone is too high for our purpose. The flame
passes through the flues e and f around the kettle:
618 APPENDIX.
g is the melting pot, made of thin copper, and riveted
to the collar h. The pot is held in the bath by three
iron hooks i, i, i, which pass into corresponding places
cut in the collar h ; and the fastening is effected by
partly turning the pot.
Fig. 11. Fig. 72.
On top of the pot there is a kind of hanging lip m,
occupying one-half of the circumference, and stand-
ing at about the distance of 12 millimetres from the
inward surface of the pot. The opening thus left on
the side of the pot is covered with a riveted semi-
circular conduit, which at n connects with the pipe
p pl. The pipe pl is attached to a cooling worm,
placed in a tub of cold water, and the outlet from the
worm terminates in a vertical pipe, the lower part of
which is closed with a stopcock and receives the con-
densed products, while the upper part is connected
with an exhausting apparatus, which is constantly
aspiring the vapors into the cooling worm, and de-
livers into the air the uncondensable products. The
^ following is the manner of using the apparatus.
When the fire is lighted, and the metallic bath is
OILS, VARNISHES, AND COLORS. 619
m fusion, a thermometer is introduced through the
opening r, and the temperature noted. As soon as
the required temperature is reached, the melting pot
g is put into the bath, and fastened by the hooks i,
care being taken that the tubes n and p should cor-
respond. A charge of 14 kilogrammes of amber, for
instance, is then introduced into the pot, watched,
and stirred in the ordinary manner. The exhaust
is also set in motion, and the amber oil, or volatile
portion of the amber, follows the direction of the
arrows, being drawn by suction under the lip m, and
from thence into the cooling worm, accompanied by
a certain proportion of air.
There is no great difficulty in maintaining a suitable
and uniform temperature in the metallic bath, because,
in the short time necessary for melting a charge, the
temperature of a considerable quantity of metal
does not change sensibly, even should the fire be much
urged, or allowed to die out. Besides, an excess of
heat may be reduced immediately, by introducing a
large piece of cold iron through the opening r, and
leaving it in the bath for one or two minutes. In
general, we may feel confident that the temperature
will remain constant during one operation, unless the
fire be entirely neglected.
When the resin is melted and mixed with oil, it
should be removed from the metallic bath into the
boiling pot. The contents are poured from the side
?•
Thus, in this manner of melting resins, the heat has
been easily regulated without escaping fumes, and
with a condensation of volatile products, which may
be utilized advantageously by the varnish maker.
620 APPENDIX.
Fig. 73 is a vertical section of the pot for boiling
oils, gums, and resins in the manufacture of varnishes.
The same pot may also be em-
ployed for boiling the oils em-
ployed in the preparation of
paints.-
A, copper pot of the ordinary
shape ; B, flat cast-iron pan,
which is made very thick, in or-
der to stand and retain the heat,
and thus to counterbalance rapid
changes in the temperature of the fire. This pan is
kept over the fireplace c, by means of the flange B' B',
which rests upon the brickwork D. The copper pot
is held upon the air bath, by means of the riveted
flanged ring A'. The cover of the pot is an annular
inverted gutter E, the curvature E2 of which has its
edge quite close to the sides of the pot, without, how-
ever, touching them, and is connected by means of the
tube H with a cooling worm and an exhaust. The
mode of operation is as follows: —
The heat of the fireplace c is transmitted to the
pan B, and the air contained therein communicates
its temperature to the boiling pot, which, therefore,
is not so much exposed to irregularities of temper-
ature as if it were, as usual, placed directly over the
fire. The suction exerted in the pipe H and the annu-
lar space G, carries away the vapors emitted by the
boiling oils or varnishes, and forces them to pass
through the cooling worm, where the condensable
portions are collected. At the same time, the large
aperture left in the annular cover permits of the
watching of the operation, and of the stirring of the
substances with the spatula i.
OILS, VARNISHES, AND COLORS. 621
As this shape of the air bath requires the lifting
upwards of the pot before it is removed from the fire,
it may be more handy to give to this air-bath the
shape indicated by the Figs. 74 and 75. j is a thick
Fig. 74. ' Fig. T5.
piece of cast iron with a ring and six radial ribs K K
projecting above. The spaces Q form the air-bath,
L is the fireplace ; M, the brickwork of the furnace,
and N, the bottom of the copper pan, which is level
with the top of the furnace. In this manner the pot
may be made to slide horizontally from the hot cast-
iron without lifting it.
It is evident that a metallic bath could be employed
for heating the oil pot, or an air-bath for dissolving
the resins, but we believe that the described dispo-
sitions are sufficient.
IV. Our processes for giving more body or opacity
to the colors produced by the combination of silica
with alkalies, alkaline earths, and metallic oxides, and
therefore making vitrified pigments, will be easily
understood by the following description : —
In several arts, in painting on porcelain and glass,
for instance, the colors employed are formed of the
materials we have indicated. In certain cases, it is
not absolutely necessary that the colors should be
opaque, and in glass painting, on the contrary, trans-
parency in the colors is a desideratum. The colors
formed by the combination of silica with alkalies,
622 APPENDIX.
alkaline earths, and metallic oxides, are remarkable
for their resistance to the action of air and dampness ;
therefore, it is desirable that they should be employed
in ordinary painting, but it is also absolutely necessary
that they should possess sufficient body and opacity
to cover well the materials upon which they are
applied.
It is known that several kinds of glass, especially
those which contain a great proportion of lime, will
have their molecular arrangement completely changed
by a long exposure to a not very intense red heat.
From an ordinary transparent glass, they will become
a semiopaque material, known under the names of
demtrified glass or Reaumur' s porcelain. Basing our-
selves upon this fact, we propose the following mode
of operation: —
"We introduce into an ordinary glass pot a mixture
of 250 kilogrammes of white sand, 100 kilogrammes
of dry sulphate of soda, 85 kilogrammes of phosphate
of lime, and 4 kilogrammes of charcoal, the latter
being added for decomposing and removing the acid
of the sulphate of soda. We pour the melted mix-
ture, by means of an iron ladle, into cold water, and
the suddenly cooled glass is reduced to small frag-
ments, which are immediately heated for three or
four days at from 370° to 480° C., in ordinary gas
retorts. The hot fragments are then again raked into
cold water. They become still more disintegrated,
and are so brittle that they are easily powdered
under ordinary vertical running stones.
The devitrification operated in the retorts, at alow
and protracted heat, still increases the opacity due to
the phosphate of lime. In certain cases, when an
OILS, VARNISHES, AND COLORS. 623
extreme degree of opacity is desired, a suitable pro-
portion of oxide of tin is added.
The previously indicated mixture gives a white
opaque glass which may be used as a basis for all the
desired colors.
It is well known that metallic oxides are generally
employed for coloring glass; these oxides are, there-
fore, combined with the above materials before their
fusion in the glass pots, and in proportions to suit the
desired hues or tones of color. We shall not here
examine these proportions, since our present object
is to give sufficient body and opacity to vitreous
compounds, in order to use them with water or oils
as ordinary paints.
In the proportions indicated for the formation of
the vitreous basis, it is possible, if so desired, to ef-
fect certain changes; for instance, potassa may be
substituted for the soda, as many glass manufacturers
do. We have simply given the recipe which has ap-
peared to* us the most economical, and have indicated
the sulphate of soda, which is very cheap in com-
parison with the carbonates of soda and potassa.
In order to bring the devitrified colors to the proper
degree of comminution, they are first powdered under
a vertical running stone, and then ground with oil
or water in a color mill. This grinding should be
done with the greatest care, and, in order to arrive at
this result, we propose the apparatus or mill we are
about to describe.
V. The ordinary mill for grinding colors is com-
posed of a pair of horizontal stones, the lower one of
which is stationary, while the upper one revolves on
its axis. The color is furnished from a hopper, which
delivers it into the central hole of the running stone;
624
APPENDIX.
and when this color has passed between the stones, it
is received into a gutter, fixed to the bed stone.
Each portion of the running stone traverses a space
proportional to its distance from the centre ; therefore
at each revolution, the points near the centre travel
less than those near the circumference. It follows
that the stones must wear unequally, and that their
action must become very imperfect, since the central
portions, being but slightly worn out, prevent a suffi-
cient contact of the stones near their edges. More-
over, the simple movement of rotation of the upper
stone upon the lower one produces a series of con-
centric ridges and hollows which prevent the intimate
contact and the action of the stones upon the particles
of material to be ground. The wear of the stones is
rapid, and at the same time the grinding is very im-
perfect. In order to remedy these defects we have
built the following mill: —
Fig. 70 is a side view of the principal pieces of the
apparatus, and contains also a central section of one
of the stones.
Fig. 77 is a horizontal view of the mill.
a a is a stout wooden frame, which, with the cover
a' a' forms a kind of table, upon which are bolted two
rings & Z>, with flanges c c. These rings are cast with
OILS, VARNISHES, AND COLORS. 625
a circular gutter eZ, for receiving the ground paint,
which is drawn out by the lips e e. ff are the parts
of the rings which support the bed stones g g, made
fast with a cement of plaster of Paris. At each end
Fig. 77.
of the frame a a there is a cranked axle /£, revolving
in the step i, and on top in the collar j. The cranks
of the two axles are united by the connecting rod I.
The upper extremities of the axles li li are fixed to
ordinary cranks m m, the pins of which enter conical
sockets n2 n2, of the movable frame n n, formed of
iron bars inclosing two rings n' ri. This frame acts
also like a connecting rod. The cranks & &, connected
by Z, are at right angles with the cranks m m, so as
to facilitate the passage of the dead points. The
heavy pulley o receives the motion, transmits it to the
whole apparatus by means of the connecting rod Z,
and of the rigid frame nn, and q acts as a fly-wheel.
The upper stones r r, resembling mullers, are pro-
vided with hoppers s s, and their lower surfaces are
slightly bevelled near the centre to facilitate the intro-
duction of the materials to be ground. These stones
r r are placed in the rings n' ri, where they have suffi-
cient play, and press with all their weight upon the
bed stones g g. "When the semifluid materials are
poured into the hoppers, and when the apparatus is
40
626 APPENDIX.
set in motion, these stones r r are carried by the frame
n n, and travel circles equal in diameter to that de-
scribed by the cranks m m, besides their movement
of rotation upon their own axis. It results from this
compound motion, that all the points of their surfaces
travel through equal spaces, and that the wear is
equal in all their parts. In order to cause a constant
change in the surfaces of contact, a play of 1 centi-
metre is left between the running stones and the en-
closing rings n' n'. This motion is the same as that
used in certain mills for polishing plate glass. These
stones, after being used for a certain length of time,
become perfectly level, and therefore more effective,
since no portion of the color can escape without
having been ground between perfectly fitting surfaces.
It is evident that the degree of comminution of the
particles depends upon their more or less intimate and
protracted contact with the grinding surfaces.
Description of an English mill for grinding colors.
Fig. 78, is a view of the mill on the side of the
crank handle; Fig. 79 is a front view of the same,
and Fig. 80 a horizontal view from above.
The same letters designate the same parts in the
three figures.
The frame A is of wood, strengthened by two iron
bars B B. The bed stone c c is of cast iron, and its
upper face has radial grooves like an ordinary mill-
stone. It is fixed upon the iron bars BB, and is in-
closed in a large iron ring D which prevents the color
from running out except through the opening E.
"When the paint is sufficiently ground it is received
in the vessel x placed underneath.
The running stone F is also of cast iron, and the
\
ENGLISH MILL FOE GRINDING COLORS. 627
dotted lines indicate its shape. The central hole G G
and the circumference have a raised edge, high
enough to prevent the color, inside and outside, from
getting over them.
Fig. 78.
A vertical shaft H supports the running stone F
and gives it its motion. The horizontal bevel wheel
K is of cast iron, with twenty-seven wooden cogs,
and is fixed to the top of the shaft H. Another ver-
tical bevel wheel L, with twenty-seven cogs, is placed
upon the horizontal axle M M and gears into K.
This horizontal axle M M carries at one of its ex-
tremities one crank handle N, and at the other end
a fly-wheel oo which regulates the motion. One of
628
Fig. 80.
the arms of the fly-wheel also carries a handle P,
which, if desired, may be used for turning the mill,
HERMANN'S MILL. 629
and which may be fixed at the proper radius by the
nut j.
The color to be ground is placed in the hopper R
opening into the trough s, which delivers the material
into the opening a of the running stone. A cord or
chain T is wound up around the cylinder v, and
presses the trough s against the square shaft H which
shakes it continually. At the same time the propor-
tion of material delivered is regulated by raising or
lowering s by means of the cord T. The winding
cylinder v is moved by the handle which traverses its
extremity.
A copper box x receives the ground paint, and it
is carried by the two handles z z. The paint may
also be removed from this box by the stopcock Y.
Hermann's mill.
Mr. Hermann, of Paris, well known as a con-
structor of grinding apparatus, has invented a new
machine for grinding paints in oil and in water.
Its disposition is remarkably simple, and consists
of an eccentric stone of granite which is placed in a
circular trough made of the same material or of other
hard stone. The rotation imparted to that stone pro-
duces upon the materials held in the trough a circular
and eccentric grinding, which constantly displaces
the points of contact of the rubbing parts. In this
manner colors and other products may be pulverized
and ground with great perfection.
APPENDIX.
THE METRIC SYSTEM OF WEIGHTS AND MEASURES.
THE United States being the first to introduce the decimal
system into the coinage of the country, and to demonstrate its
superior utility, it is remarkable that we have hesitated so long
in regard to the substitution of the same simple and rational
system of weights and measures for the complicated and con-
fused standards in general use.
In May, 1866, the Committee on Coinage, Weights, and Mea-
sures presented to the House of Representatives an exhaustive
report, accompanied by bills authorizing the introduction of
the metric system into the various departments of trade, and
making all contracts, based on this system of weights and
measures, valid before any court in the United States. They
said : —
"THE METRIC SYSTEM.
"It is orderly, simple, and perfectly harmonious, having use-
ful relations between all its parts. It is based on the METER,
which is the principal and only arbitrary unit. The meter is a
measure of length, and was intended to be, and is, very nearly
one ten-millionth of the distance on the earth's surface from
the equator to the pole. It is 39.37 inches, very nearly.
'The are is A surface equal to a square whose side is 10
meters. It is nearly four square rods.
"The liter is the unit for measuring capacity, and is equal to
the contents of a cube whose edge is a tenth part of the meter.
It is a little more than a wine quart.
"The gramme is the unit of weight, and is the weight of a
cube of water, each edge of the cube being one one-hundredth
of the meter. It is equal to 15.432 grains!
" The stere is the cubic meter.
"Each of these units is divided decimally, and larger units
are formed by multiples of 10, 100, &c. The successive mul-
tiples are designated by the prefixes, dtka, hecto, kilo, and myria ;
the subordinate parts by deci, centi, and milli, each having its
own numerical significance.
"The nomenclature, simple as it is in theory, and designed
632 THE METRIC SYSTEM.'
from its origin to be universal, can only become familiar by
use. Like all strange words, these will become familiar by
custom, and obtain popular abbreviations. A system which
has incorporated with itself so many different series of weights,
and such a nomenclature as 'scruples,' 'pennyweights,' 'avoir-
dupois,' and with no invariable component word, can hardly
protest against a nomenclature whose leading characteristic is a
short component word with a prefix signifying number. We
are all familiar with thermometer, barometer, diameter, gasometer,
&c., with telegram, monogram, &c., words formed in the same
manner.
"After considering every argument for a change of nomen-
clature, your committee have come to the conclusion that any
attempt to conform it to that in present use would lead to con-
fusion of weights and measures, would violate the early learned
order and simplicity of metric denomination, and would seri-
ously interfere with that universality of system so essential to
international and commercial convenience.
" When it is remembered that of the value of our exports
and imports,in the yearending June 30, 1860, in all $762,000,000,
the amount of near $700,000,000 was with nations and their de-
pendencies that have now authorized, or taken the preliminary
steps to authorize, the metric system, even denominational uni-
formity for the use of accountants in such vast transactions
assumes an important significance. In words of such universal
employment, each word should represent the identical thing in-
tended, and no other, and the law of association familiarizes it.
"Your committee unanimously recommend the passage of
the bills and joint resolutions appended to this report
The metric system is already used in some arts and trades in
this country, and is especially adapted to the wants of others.
Some of its measures are already manufactured at Bangor, in
Maine, to meet an existing demand at home and abroad. The
manufacturers of the well-known Fairbanks' scales state: 'For
many years we have had a large export demand for our scales
with French weights, and the demand and sale are constantly
increasing.' Its minute and exact divisions specially adapt it
to the use of chemists, apothecaries, the finer operations of the
artisan and to all scientific objects. It has always been and is
now used in the United States coast survey. Yet in some of
the States, owing to the phraseology of their laws, it would be
a direct violation of them to use it in the business transactions of
the community. It is, therefore, very important to legalize its use,
and to give to the people, or that portion of them desiring it, the
opportunity for its legal employment, while the knowledge of
its characteristics will be thus diffused among men."
TABLES
SHOWING THE
RELATIVE VALUES OP FRENCH AND ENGLISH WEIGHTS
AND MEASURES, &c.
Measures
of Length.
Millimetre
=
0.03937
inch.
Centimetre
=
0.393708
"
Decimetre
=
3.937079
inches.
Metre
=
39.37079
it
«
=
3.2808992
feet.
"
=
1.093633
yard.
Decametre
=
32.808992
feet.
Hectometre
=
328.08992
u
Kilometre
=
3280.8992
11
"
=
1093.633
yards.
Myriametre
=
10936.33
U
u
=
6.2138
miles.
Inch (^ yard)
=
2.539954
centimetres.
Foot (i yard)
=
3.0479449
decimetres.
Yard
=
0.91438348
metre.
Fathom (2 yards)
=
1.82876696
it
Pole or perch (5£ yards)
==
5.029109
metres.
Furlong (220 yards)
=
201.16437
"
Mile (1760 yards)
=
1609.3149
u
Nautical mile
==
1852
"
634
VALUES OF FRENCH AND ENGLISH
Superficial Measures.
Square millimetre = ^^ square inch.
centimetre :
decimetre
u
metre or centiare
u • «
Are
Hectare
ii
Square inch
« tt
" foot
« yard
" rod or perch
Rood (1210 sq. yards)
Acre (4840 sq. yards)
0.00155 " "
0.155006 " "
15.50059 " inches.
0.107643 « foot.
1550.05989 " inches.
10.764299 " feet.
1.19H033 " yard
1076.4299 " feet.
119.6033 " yards.
0.098845 rood.
11960.3326 square yards.
2.471143 acres.
645.109201 square millimetres.
6.451367
9.289968
0.836097
25.291939
10.116775 ares.
0.404671 hectare.
centimetres
decimetres,
metre,
metres.
Measures of Capacity.
Cubic millimetre = 0.000061027 cubic inch.
10 "
100 «
1000 "
Decalitre
u
Hectolitre
(I
Myrialitre
•r millilitre
== 0.061027
ti tt
or centilitre
= 0.61027
tt it
" decilitre
= 6.102705
" inches.
" litre
= 61.0270515
« it
tt it
= 1.760773
imp'l pint.
tt u
= 0.2200967
« gal'n.
= 610.270515
cubic inches.
= 2.2009668
imp. gal'ns.
= 3.531658
cubic feet.
= 22.009668
imp. gal'ns.
8 or kilolitre
= 1.30802
cubic yard.
u
= 35.3165807
" feet.
= 353.165807
« (i
WEIGHTS AND MEASURES, ETC.
635
Cubic inch
" foot
" yard
=3 16.386176 cubic centimetres.
=« 28.315312 " decimetres.
= 0.764513422 " metre.
American Measures.
Winchester or U.S. gallon (231 cub. in.) = 3.785209 litres.
" " bushel(2150.42cub.in.)= 35.23719 "
Chaldron (57.25 cubic feet) = 1621.085 "
British Imperial Measures.
Gill = 0.141983 litre.
Pint (£ gallon) = 0.567932 "
Quart (£ gallon) = 1.135864 "
Imperial gallon (277.2738 cub. in.) = 4.54345797 litres.
Peck (2 gallons) = 9.0869159 "
Bushel (8 gallons) = 36.347664 "
Sack (3 bushels) = 1.09043 hectolitre.
Quarter (8 bushels) = 2.907813 hectolitres.
Chaldron (12 sacks) = 13.08516 "
Weights.
Milligramme
=
0.015438395
troy grain.
Centigramme
=
0.15438395
u «
Decigramme
r=
1.5438395
« «
Gramme
=
15.438395
" grains.
«
=
0.643
pennyweight.
<(
=
0.0321633
oz. troy.
«
=
0.0352889
oz. avoirdupois.
Decagramme
=
154.38395
troy grains.
K
=
5.64
drachms avoirdupois
Hectogramme
=
3.21633
oz. troy.
M
=
3.52889
oz. avoirdupois.
Kilogramme
S3
2.6803
Ibs. troy.
M
r=
2.205486
Ibs. avoirdupois.
Myriagramme
=
26.803
Ibs. troy.
<(
=
22.05486
Ibs. avoirdupois.
Quintal metrique =
100
kilog. = 220.5486 Ibs. avoirdupois.
Torme =
1000
kilog. = 2205.486 " "
a
636
VALUES OF FRENCH AND ENGLISH
Different authors give the following values for the gramme : —
Gramme = 15.44402 troy grains.
" = 15.44242 "
" = 15.4402 «
" = 15.433159 "
" = 15.43234874 "
AVOIRDUPOIS.
2240 Ibs.
Long ton = 20 cwt.
Short ton (2000 Ibs.) =
Hundred weight (112 Ibs.) =
Quarter (28 Ibs.) =
Pound = 16 oz. = 7000 grs. =
Ounce — 16 dr'ms. = 437.5 grs. =
Drachm =. 27.344 grains =
kilogrammes.
1015.649
906.8296 »
50.78245
12.6956144 "
453.4148 grammes.
28.3375
1.77108 gramme.
TROY (PRECIOUS METALS).
Pound = 12 oz. = 5760 grs. == 373.096 grammes.
Ounce = 20 dwt. = 480 grs. = 31.0913 "
Pennyweight = 24 grs. = 1.55457 gramme.
Grain = 0.064773 "
APOTHECARIES' (PHARMACY).
Ounce = 8 drachms = 480 grs. = 31.0913 gramme.
Drachm = 3 scruples = 60 grs. = 3.8869
Scruple = 20 grs. = 1.29546 gramme.
CARAT WEIGHT FOR DIAMONDS.
1 carat = 4 carat grains = 64 carat parts.
" = 3.2 troy grains.
« = 3.273 "
" = 0.207264 gramme
" SB 0.212 "
" = 0.205 "
Great diversity in value.
4
WEIGHTS AND MEASUKES, ETC. 637
Proposed Symbols for Abbreviations.
M — rayria
— 10000
Mm
Mg
Ml
K— kilo
— 1000
Km
Kg
Kl
H— hecto
— 100
Hm
Hg
HI
Ha
D — deca
— 10
Dm
Dg
Dl
Da
Unit
1
metre — m
gramme — g
litre— 1
are — a
d — deci
— 0.1
dm
dg
dl
da
c — centi
— 0.01
cm
eg
cl
ca
m — milli
— 0.001
mm
mg
ml
Km = Kilometre. HI = Hectolitre. eg = centigramme,
c. cm s= <^n3 = cubic centimetre, dm2 = sq. dm = square deci-
metre. Kgm = Kilogrammetre. Kg0 = Kilogramme degree.
Celsius or Centigrade.
Fahrenheit.
Rfeauranr.
— 15°
r 5°
— 12°
— 10
- 14
— 8
— 5
- 23
— 4
0 melting
- 32
ice 0
+ 5
- 41
+ 4
-- 10
- 50
+ 8
-- 15
- 59
+ 12
-- 20
- G8
+ 16
+ 25
+ 30
- 77
- 86
+ 20
+ 24
+ 35
- 95
+ 28
-f- 40
-104
+ 32
+ 45
-113
+ 36
-f 50
-122
+ 40
+ 55
-131
+ 44
+ 60
-140
+ 48
-f (55
-149
+ 52
+ 70
4-158
+ 56
+ 75
4-167
+ 60
4- SO
4-176
+ 64
+ 85
4-185
+ 68
+ 90
4-194
+ 72
4- 95
4-203
+ 76
4-100 boiling
4-200
4-212
4-392
water + 80
+ 160
+300
4-572
+240 "
4-400
+752
+320
4-500
+932
+400
638
VALUES OF FRENCH AND ENGLISH
1° C.
1° C. = 1°.8 Ft. — f° Ft. = 0°.S R. = f° R.
| = 1°. Ft. 1° Ft. x | = 1° C. 1° R. X
=1° Ft.
1° C. x f = 1
1° Ft. x
1° R. X f =1°
Calorie (French) = unit of heat •*
= kilogramme degree } EnSlish'
It is the quantity of heat necessary to raise 1° C. the tempera-
ture of 1 kilogramme of distilled water.
Kilogrammetre = Kgm = the power necessary to raise 1 kilo-
gramme, 1 metre high, in one second. It is equal to ^ of a
French horse power. An English horse power = 550 foot pounds,
while a French horse power = 542.7 foot pounds.
Ready-made Calculations.
No.
of
units.
Inches to
centimetres.
Feet to
metres.
Yards to
metres.
Miles to
Kilometres.
Millimetres
to inches.
1
2.53995
0.3047945
0.91438348
1.6093
0.03937079
2
5.0799
0.6095890
1.82876696
3.2186
0.07874158
3
7.6199
0.9143835
2.74315044
4.8279
0.11811237
4
10.1598
1.2197680
3.65753392
6.4373
0.15748316
5
12.G998
1,5239724
4.57191740
8.0466
0.19685395
6
15.2397
1.8287669
5.48630088
9.6559
0.23622474
7
17.7797
2.1335614
6.40068436
11.2652
0.27559553
8
20.3196
2.4383559
7.31506784
12.8745
0.31496632
9
22.8596
2.7431504
8.22945132 14.4838
0.35433711
10
25.3995
3.0479450
9.14383480 16.0930
0.39370790
No.
of
nuits.
Centimetres
to incheu.
Metres to
feet.
Metros to
yards.
Kilometres
to miles.
Square inches
to square
centimetres.
1
0.3937079
3.2808992
1.093633
0.6213824
6.45136
2
0.7874158
6.5617984
2.187266
1.2427648
12.90272
3
1.1811237
9.8426976
3.280899
1.8641472
19.35408
4
1.5748316
13 1235968
4.374532
2.4855296
25.80544
5
1.9685395
16.4044960
5.468165
3.1089120
32.25680
6
2.3622474
19.6853952
6.561798
3.7282944
38.70816
7
2.7559553 '22.9662944
7.655431
4.3496768
45.15952
8
3.1496632 26.2471936
8.749064
4.9710592
51.61088
9
3.5433711 |29.5280928
9.842697
5.5924416
58.06224
10
3.9370790 32.8089920
10.936330
6.2138240
64.51360
WEIGHTS AND MEASURES, ETC.
639
No.
of
units.
Square feet to
sq. metres.
Sq. yards to
sq. metres.
Acres to
hectares.
Square
centimetres
to sq. inches.
Sq. metres
to sq. feet.
1
0.0929
0.836097
0.404671
0.155
10.7643
2
0.1858
1.672194
0.809342
0.310
21.5286
3
0.2787
2.508291
1.204013
0.465
32.2929
4
0.3716
3.344388
1.618684
0.620
43.0572
5
0.4645
4.180485
2.023355
0.775
53.8215
6
0.5574
5.016582
2.428026
0.930
64.5858
7
0.6503
5.852679
2.832697
1.085
75.3501
8
0.7432
6.688776
3.237368
1.240
86.1144
9
0.8361
7.524873
3.642039
1.395
96.8787
10
0.9290
8.360970
4.046710
1.550
107.6430
No.
of
units.
Square metres
to sq. yards.
Hectares
to acres.
Cubic inches
to cubic
centimetres.
Cubic feet to
cubic metres.
Cubic yards
to cubic
metres.
1
1.196033
2.471143
16.3855
0.02831
0.76451
2
2.392066
4.9422S6
32.7710
0.05662
1.52902
3
3.588099
7.413429
49.1565
0.08494
2.29354
4
4.784132
9.884572
65.5420
0.11325
• 3.05&05
5
5.980165
12.355715
81.9275
0.14157
3.82257
6
7.176198
14.826858
98.3130
0.16988
4.58708
7
8.372231
17.298001
114.6985
0.19819
5.35159
8
9.568264
19.769144
131.0840
0.22651
6.11611
9
10.764297
22.240287
147.4695
0.25482
6.88062
10
11.960330
24.711430
163.8550
0.28315
7.64513
No.
of
units.
Cubic
centimetres to
cubic inches.
Litres to
cubic inches.
Hectolitres to
cubic feet.
Cubic metres
to cubic feet.
Cubic metres
to cubic
yards.
1
0.06102
61.02705
3.5317
35.31659
1.3080*2
2
0.12205
122.05410
7.0634
70.63318
2.61604
3
0.18308
183.08115
10.5951
105.94977
3.92406
4
0.24411
244.10820
14.1268
141.26636
5.23208
5
0.30514
3H5.13525
17.6585
176.58295
6.54010
6
0.36617
366.16230
21.1902
211.89954
7.84812
7
0.42720
427.18935
24.7219
247.21613
9.15614
8
0.48823
488.21640
28.2536
282.53272
10.46416
9
0.54926
549.24345
31.7853
317.84931
11.77218
10 1 0.61027
i
610.27050
35.3166
353.16590
13.08020
640 FRENCH AND ENGLISH WEIGHTS, ETC.
No.
of
Quits.
Grains
to grammes.
Ounces avoir,
to grammes.
Ounces troy
to grammes.
Pounds avoir. Pounds troy
to to
kilogrammes, kilogrammes.
1
2
3
4
5
6
7
8
9
10
0.064773
0.129546
0.194319
0.259092
0.323865
0.388638
0.453411
0.518184
0.582957
0.647730
28.3375
56.6750
85.0125
113.3500
141.6871
170.0250
198.3625
226.7000
255.0375
283.3750
31.0913
62.1826
93.2739
124.3652
155.4565
186.5478
217.6391
248.7304
279.8217
310.9130
0.4534148
0.9068296
1.3602444
1.8136592
2.2670740
2.7204888
3.1739036
3.6273184
4.0807332
4.5341480
0.373096
0.746192
1.119288
1.492384
1.865480
2.238576
2.611672
2.984768
3.357864
3.730960
Pounds per
No.
Long tons to
square inch to Grammes to
Grammes to
Grammes to
of
toanes of 1000
kilogrammes grains.
ounces avoir.
ounces troy.
units.
kilog.
per square
centimetre.
1
1.015649
0.0702774 15.438395
0.0352889
0.0321633
2
2.031298
0.1405548
30.876790
0.0705778
0.0643266
3
3.046947
0.2108322
46.315185
0.1058667
0.0964899
4
4.062596
0.2811096
61.753580
0.1411556
0.1286532
5
5.078245
0.3513870
77.191975
0.1764445
0.1608165
6
6.093894
0.4216644
92.630370
0.2117334
0.1929798
7
7.109543
0.4919418
108.068765
0.2470223
0.2251431
8
8.125192
0.5622192
123.507160
0.2823112
0.2573064
9
9.140841
0.6324966
138.945555
0.3176001
0.2894697
10
10.156490
0.7027740 154.383950
0.3528890
0.3216330
Metric tonnes
Kilog. per
Kilog. per
No.
Kilogrammes
Kilogrammes
of 1000 kilog
square milli-
square centi-
of
to pounds
to pounds
to long tons of
metre to
metre to
units.
avoirdupois.
troy.
2240 pounds.
pounds per
pounds per
square inch.
square inch.
1
2.205486
2.6803
0.9845919
1422.52
14.22526
2
4.410972
5.3606
1.9691838
2845.05
28.45052
3
6.616458
8.0409
2.9537757
4267.57
42.67578
4
8.821944
10.7212
3.9383676
5690.10
56.90104
5
11.027430
13.4015
4.9229595
7112.63
71.12630
6
13.232916
16.0818
5.9075514
8535.15
85.35156
7
15.438402
18.7621
6.8921433
9957.68
99.57682
8
17.643888
21.4424
7.8767352
11380.20
113.80208
9
19.849374
24.1227
8.8613271
12802.73
128.02734
10
22.054860
26.8030
9.8459190
14225.26
142.25260
INDEX.
A BSORBED colors, 46
A Acetate of lead, 158
Ador and Abadie", colors of sulphate of
zinc by, 574-577
Adulteration of zinc white, 189, 190
of zinc yellows, 391
Adulterations of lakes, 471
Air furnace, 178
Aldobrandini wedding, blues in, 29
browns used in the, 20
greens of, 32
reds of, 22
yellows of, 21
Alexandria frit, 35
Algaroth powder, 163-164
Alizari, 458
Alkalies, effect of Prussian blue on, 202
Alkalized charcoal, preparation of, 222,
223, 224, 225
Alkanet, 474
Alumina, addition of, to chromates, 376
for artificial ultramarine, 290
Aluminous silicate, 306
Alum, resistance of ultramarine to,
333
American measures, 635
Ammonia and hydrated oxide of copper,
350
transformation of, into cyanide of
ammonium, 210
Ammoniacal cochineal, 494
sulphate of copper, 349
Analyses of Indian yellow, 418, 419
of iron minium, 502
of ultramarine, 272
of white lead, 76, 77, 132, 137
Analysis of artificial ultramarine, 296-
297
of cochineal, 487
of Cologne yellow, 377
. of copper blues, 347-349
of curcuma, 365
of green without arsenic, 548
41
Analysis —
of lazulite, 272-273
of luteolin, 370, 371
of purple of Cassius, 456-457
of Rinmann green, 560
of silicious sand, 290
of sulphide of antimony, 444-445
of ultramarines, 276, 329-339
of white lead made by Wood,
Benson, and Griineberg pro-
cesses, 102
Analytical operation with ferrocyanide
of potassium, 234
Ancients, colors employed by the, 17
Aniline or chrome black, 524
Animal blacks, 529-532
substances, ferrocyanide of potass-
ium with, 223-236
Annales des Arts et Manufactures, 165
Anthon, C. P., process for the manu-
facture of uranium yellow, 412
Antimoniate of lead, 161, 400
Antimonite of lead, 160
Antimony and zinc, yellow of, 401-403
chloride of, 446
orange-red sulphide, 392-393 .
oxide of, 161, 401
protochloride of, 443
sulphide of, 441
compound colors with, 393
vermilion of, 441
white less affected by sulphuretted
hydrogen than white lead,
164
of Bobierre, Ruolz, and Rous-
seau, 161-162
of Hallett and Stenhouse, 164
of Valid and Barreswill, 162-
164
whites, 161-164
yellow, 358, 394, 405
Antwerp blue, 256-257
red, 362
642
INDEX.
Apparatus, absorbing, 215-217
Oompton's, for white lead, 115-123
for manufacture of oxide of zinc,
169-180
for oxide of antimony, 161
Mullin's, for white lead, 106-110
of C. Schinz for ferrocyanide of
potassium, 226
of M. Ozouf for preparation of
white lead, 154
of Th. Lefevre for pulverizing
white lead, 140-145
of Yersepuy, 95-96
Sevell's, for white lead, 113-114
"Ward's, for manufacture of white
lead, 138-140
Wood's, for white lead, 98
Archil, coloring principles of, 498
-lichens, 496
red and violets from, 495
Armenian bole, 425
stone, 351
Arnaudon, Mr., process for emerald
green, 566
Arseniate of cobalt, 455
Arsenite, neutral, of copper, 543
of copper, 341
of lead, 409
Artificial flowers, green for, 537
sulphate of baryta, 193-199
ultramarine, 274-340
Ashes, blue, 341-351
manufacture of, in England,
342
green, 548
Asphaltum, 509-510
qualities of, 510
Atkinson, Mr., of Harrington, patent of,
for zinc white, in 1796, 165
Atomic sulphate, 190
Aurum mussivum, 420-421
Avignon berries, 358, 366
Azure blue, 351
inconvenience of using, 354
lazulite, 270
tint of, 185
white, 185-203
Azurite, 350
BA.CCO, A., process for removing iron
from solutions of sulphate of
copper, 547
process for testing white leads,
133-134
Baker, W., on composition of Holland
white lead, 135
Balls of wuy, 357
Bancroft, Dr. Edward, on Tyrian pur-
ple, 25
Barium, chloride of, 197
sulphide of, 197
sulpho-antimonite of, 453-454
Baroselenite, 192
Barreswill, Mr., on the value of ultra-
marine, 338, 339
Barruel and Leclaire, Rinmann green
of, 560
Baryta, chromate of, 378-379, 391-392
compound colons with, 393
in zinc yellow, 391
sulphate of, 192-199
in white lead, 132, 133
to detect in white lead, 133
white, 132
whites, 192-199
yellow, 169
Barytes, sulphates of, 192-199
Barytine, 192-199
Basic acetate, 81
chloride of lead, 158-159
chromate, 385-386
of lead, 375-376
of tin, 395
of zinc, 394
Baths of Livia, browns used in pictures
of, 20
green color in, 30
of Titus, 17, 20, 22, 23, 36
Beds for white lead, 147, 148
Benson's process for white lead, 97-
105
Berlin brown red, 406
Berzelius on the composition of indigo,
267
Besancon, M., apparatus for grinding
white lead in oil, 152
Bichromate of potassa, 388
Bi-iodide of mercury, 439
Binary colors, 48
mixed colors, 48
Bistre, 508
deep, 52
Bisulphide of arsenic, 429
Bitumen, drying, preparing, 510
naphtha, 509
of Judea, 509
qualities of, 510
Bitumens, 509-510
Bituminous coal black, 514-515
Black absorbs all colors, 37
aniline or chrome, 524
bituminous coal, 514-515
Campeachy lakes, 475
candle, 530
charcoal, 516, 525
cork, 516
Frankfort, 516
fusain, 515
German, 516
INDEX.
643
Black-
grape-vine, 515
ivory, 530
lakes, 474
of chrotnate of copper, 514
peach stone, 515
Prussian, 531
shale, 512-513
sumach lake, 475
Blacks, 512-532
animal, 529-532
artificial, of Greece, 19
bone, 529
ebony, 515
from Prussian blue ground in oil, 203
mineral, 512-514
ulmin, 525
used by the Egyptians and Romans,
19
vegetable, 515, 525, 526
Blanc fixe, 132, 193, 199
Blende, 177, 178
as a substitute for white lead and
zinc white, 191-192
Blood lye, 201, 240
use of, in manufacture of Prussian
blue, 201
Blue, ancient, analysis of, 29
arsenite of copper, 341
ashes, 341-351
for painted papers, 342
French and English, 350
in paste, 345-347
L. G. Gentele on the prepara-
tion of, 345
of the manufacturers, 341
Pelletier on the preparation
of, 341
azure, 351
Bremen, 538-543
calcareous, 345
carmine, 268-269
celestial or Marie Louise, 51
color of ultramarine, intensity of,
321
colors, 199-357
composition, 268
copper, 341-351
English sky, 356-357
from an Egyptian grave, 27
green, 345
hydrated oxide of copper, 261
in liquor, 268
lime, 341-351
made at Pozzuoli, 30
mineral or Antwerp, 256-257
Monthiers, 253
mountain, 341-351
of England, 268-269
of Holland, 268-269
Blue—
of manganate of lime, 262-264
of white earths, colored with in-
digo, 257
Paris, 244-253
PSligot, 261
Saxony, 351
sky, 203
smalt, 351
Thenard or cobalt, 257-261
tint of azure, 185
Turnbull's, 244
ultramarine, Gentele's processes for,
318-323
verditer, 538-543
Blues at Pompeii, 29
in the Aldobrandini Wedding, 29
most frequently used, 199
of the ancients, 26
ultramarine, 269-340
Bluing agent of ultramarine green, 323
Bobierre, Ruolz, and Rousseau, anti-
mony white of, 161-162
Boilers, painting with iron minium, 504
Bole, 425
Bologna stone, 192
Bolus alba, 283
Bone-blacks, 529
Bone-black, use of in manufacture of
Prussian blue, 243
Borate of cobalt, 584
of manganese, 585
Boric acid as a solvent, 563
Bouchard and Clavel, MM., experiments
on Burgundy ochre, 501
Bouland, Mr., process for green ochre,
571
Bourgeois, Mr., on purity of tones of
Prussian blue, 202
Bouton d'or yellow, 169
Boutron-Chartard, analysis of Cologne
yellow by, 377
Bouvier, Mr., process for the manu-
facture of Prussian brown, 506
Braconnot, Mr., process for Schweinfurt
green, 546
Brazil wood, lakes of, 472
Bremen blue, 345, 347, 350, 538, 543
green, 538-543
Bright yellow, 394
British imperial measures, 635
Broken or pure colors, 39
Bronze coloration without lampblack,
601
colors, 575
dark, 575
compositions for metals, 595-599
-green, 185, 563
ordinary, of the founders, 599
red, 594
644
INDEX.
Bronzing, 593-603
for gunbarrels, 601
mixtures, mode of applying, 599-
601
plaster of Paris, 601
Brown, chicory, 507
colors, 500-512
gilt, 507
manganese, 505-506
Mars, 423, 500, 501
from Mars yellow, 500
of manganate of lead, 506
of the Aldobrandini Wedding, 20
Prussian, 506
red, 507
Berlin, 406
ulmin, 507-508
Van Dyke, 504-505
Browns used by the Egyptians and Ro-
mans, 19
Brumlen, L., of New York, 188
Brunner, Mr., on the preparation of
Naples yellow, 398
on preparation of native ultra-
marine, 271
process for artificial ultramarine,
289-300
process for preparing vermilion,
432-433
Brunnquell, Mr., 230, 254
process for ferrocyanide of potass-
ium, 205-219
for Prussian blue, 205-219
Brunswick green, 543
Brussels lace, zinc white in manufacture
of, 168
Buccina, purple from, 26
Biichner, W., on testing ultramarines,
333-338
Buckthorn berries, 536
Building the beds for white lead, 147
Burgundy ochre as a substitute for red
lead, 501
CADMIUM yellow, 400-401
\J Caius Cestus, blue in the monu-
ment of, at Rome, 29
Calcareous blue, 345
Calcination, 312-313, 315, 319, 321
French, 321-322
of Prussian blue, 243
Calcining furnaces, 313-315
Calcium, chloride of, 85
hyposulphite of, 447
Calculations, ready made, 638
Calico printing, ultramarines for, 330
Campeachy black, 475
lakes, 473
Candle black, 530
Capacity, measures of, 634
Carbon, 309
Carbonate of copper, 341
of lead, condensing, 115
by the Pattinson process, 85-
92
production of, 110
of lime, 53, 54, 85, 86
in white lead, 128
of soda, for artificial ultramarine,
291
for ultramarine green, 308
washing white lead in, 115
Carbonic acid, absorption of by granu-
lated lead, 93
for manufacture of white lead,
60
for white lead, 83
production of, 112
Carbonizing furnaces, 213
Carmine, blue, 268-269
cochineal, 487-493
lake, 473, 493
madder, 473, 477
Carthannic acid, 484
Carthamin, 484
Carthamus red, 484
Cartret, Mr. de, iron minium prepared
by, 425
Cassel earth, 512
yellow, 403
Cassius, purple of, 455-458
Casting of lead, 146
Cat's gold, 420-421
Celestial blue, 51
Certeau, Mr. de, on the use of blende,
191, 192
Chalk in white lead, 128
Chalk whites, 53-54
Chamois, 185
dark, 575
hues from chrome yellows, 377
yellows, 574
Chaptal, 17
Chaptal, Mr., process for Turner yellow,
403
Chaptal's examination of the paint
found in Pompeii, 32
Charcoal, alkalized, 222, 223, 224,
225
and lampblack, 474
black, 516, 525
for artificial ultramarine, 291
Chateau, T., on madder and its deriva-
tives, 471
Chevreul, Mr., on colors, 39-49
on composition of indigo, 266
Chicory brown, 507
China green, 554-556
China or India ink, 531
INDEX.
645
Chinese process for cochineal carmine,
490
rouge, 484
Chloride of antimony, 446
of calcium, 85
of lead, 158-159
of manganese, economy of, 194
Chlorine manufacture, utilization of the
residue of, 197
Chlorophyl, 421-422
Chocolate lake, 475, 476
Chromate, basic, 385-886
of lead, 375-376
of tin, 395
of zinc, 394
dense neutral, of lead, Liebig's
process for manufacture of, 374
neutral, 373
of lead, 373-375
of soda and potassa, 388
of baryta, 378-379
compound colors with, 395
of copper, 440
black of, 514
of lime, 378
of manganese, puce color with, 512
of silver, 440
of zinc, analysis of, 391
compound colors with, 395
green from, 388
preparation of, 387-391
preparations, materials for,
390
washing, 390
Chromates of mercury, 439, 440
potassa, 373
various, 387-395
Chromatic circles of Mr. Chevreul,
39-45
Chrome green, 561-563
greens, by mixture, 386-387
or aniline black, 524
red, 382, 385-387, 500
hues of, 385
yellow, 358, 379-385, 394
hues of, 382
Jonquil, of Winterfeld, 376-
377
tones of, 383
yellows, 372-387
adulterations of, 378, 379
brightness and durability of,
377
Chromium, 372
combinations of, in the arts, 372
perchloride of, 499-500
sesquioxide, 561
Chrysocolla, 31
Cicerculum, 19
Cinnabar, 430-439
Cinnabar —
discovery of, in Rome, 23
green, 246, 386, 553
in India, 21
Classification of colors, 48-49
Clay for artificial ultramarine, 283
for ultramarine, 302
porcelain, 306
Clement and Desormes' analysis of ul-
tramarine, 272
Clichy process, 78-85
whites, 55-56
Coal black, bituminous, 514-515
Cobalt, arseniate of, 455
benzoate of, 583
blue, 257-261
borate of, 584
glass, 351
green, 556-561
ore, 351
pink, 454
subphosphate of, 257
ultramarine, 340
Cochineal, 487
ammoniacal, 494
analysis of, 487
carmine, 487-493
Cochois, Mr., preparation of ochres by,
360
Cceruleum, 354-356
advantages of, 354
composition of, 355
imitation, 356
Coke oven, 178
Colcothar, 424, 426
disadvantages of use of, on iron,
503
Cologne earth, 512
yellow, 358, 377-378
Coloring power of ultramarine, trial of,
334
principles of archil, 498
Color of smalt, 351
Colors, absorbed, 46
binary, 48
mixed, 48
classification of, 48-49
complementary, 46
contrast of, 47
employed by the ancients, 17
English millfor grinding, 626
from sulphate of zinc, 574-577
general method of preparing, 49-
52
juxtaposited and compounding
complementary, 47
mill for grinding, 604-607
mixed or compound, 393-395
mixing, 394
normal, 37
646
INDEX.
Colors —
of the rays of the solar spectrum, 46
oils, and varnishes, Bessemer and
Heywood's improvements in the
manufacture of, 608-629
origin, definition, and classification
of, 37-52.
physical effects of, 46-48
primary, 37, 46, 48
rays reflected by, 37
tertiary, 49
those in use among the ancients, 36
Combes, R., on Holland process, 64
Complementary colors, 46
Composition blue, 268
of ultramarines, 339-340
of white lead, 134-137
Compound colors, 393-395
Contrast of colors, 47
modification of, 47
nature of, 48
of tone, 46
Copper, ammoniacal sulphate of, 349
arsenite of, 341
black of chromate of, 514
blue, 341-351
hydrated oxide of, 261
carbonate of, 351
chromate of, 440
colors, L. G. Gentele on the pre-
paration of, 345
fine commercial white lead should
be free from, 104
green of stannate of, 552
hydrated oxide of, 538
and ammonia, 350
oxide, impairs colors of white lead
paints, 105
Copperas, 424
Cork black, 516
Courtois, early manufacture of zinc
white by, 165
of Dijon, mention of zinc white by,
in 1770, 164
Cream tartar process for cochineal car-
mine, 491
Crompton's apparatus for white lead,
115-123
patents, claims under, 123-125
process for white lead, 115-125
Crucibles for ultramarine, 313
Crystallized ferrocyanide of potassium,
use of, 243
verdet, 573
Crystals of Venus, 573
Curcuma longa, 364
rotunda, 364
Cyanide lye, 202, 203
of ammonium, 210, 215
of potassium, 215
DARK chamois, 185
English green, 169, 394
Davy, Sir Humphry, 17, 18, 19, 20, 21,
22, 23, 24, 25, 31, 32, 34,
36
a blue color in imitation of the
Egyptian, made by, 28
on the blue of the ancients, 28
Deep bistre color, 52
green color, 51
Definition of colors, 39-45
Desbach, of Berlin, discovery of Prus-
sian blue by, 199
Desmotte's, Mr., process for vermilion
unalterable by fire, 438
Desmoulin's process for brightening the
color of vermilion, 437
Determination and definition of colors,
39-45
of the value of the fused materials
in the manufacture of ferrocya-
nide of potassium, 230-235
Digeon, Mr., engravings of chromatic
circles of Mr. Chevreul, 41-45
Dippel, J. P., on comparing ultrama-
rines, 330
process for artificial ultramarine,
300-301
Distilled green, 573
Dryer, benzoates of cobalt and of man-
ganese, 583
borate of manganese as a, 585
for zinc white, 578
of borate of cobalt, 584
powdered, of Guynemer, 579
Dryers, Mr. Lefort on, 188, 189
resins as, 584
various, 580-588
Dry grinding scales of white lead, 149
Drying and adherence of colors, 577-
593
oils, 578
oil with peroxide of manganese,
169
rooms, 150
Dumas and le Royer on the composi-
tion of indigo, 267
Mr., on red lead, 426
Dussauce, Prof., on a new vegetable
red, 486
Dutch process, 55, 63, 78
T7BELMEN, researches of, on artificial
JLJ production of mineral compounds,
563
Ebony black, 515
Economy in the manufacture of ferro-
cyanide of potassium, 210, 218, 226,
229
INDEX.
647
Egyptian pictures, colors used in, 18
Egyptians and Romans, whites used by,
17
reds used by, 21
Elderberries, 475-476
Eisner and Varrentrapp, analysis of
ultramarine, by, 275
green, 553
L., process for green cinnabar, 553
process for titanium green, 568
Emerald green, 563-568
Enamel blue, 351
Encyclopedic me'thodique des arts et
metiers, 164
England, manufacture of blue ashes
in, 342
manufacture of white lead in, 69, 72
English green, 169, 394, 550
process for the manufacture of
Prussian blue, 239-244
red or rouge, 424
sky blue, 356-357
Erlaa green, 549
Eschel blue, 353
Euxanthic acid, 418
Extract of Saturn, 60, 78
T?ERROCYANIDE of potassium, 203
JL economy in the manufacture
of, 210, 218, 226, 229
from horn, 224, 225
furnace for, 206
manufacture of, 205-219
obtained with Karmrodt's fur-
nace, 223
Schinz's process, 226-230
testing, 234
transformation of cyanide of
potassium into, 215
value of the fused materials in
the manufacture of, 230-235
with animal substances, 223-
226
yielded by various substances,
220
Ferrugine alumineuse, 501
Firmenich process for preparing ver-
milion, 434-437
Flame receiver, Cromp ton's, 117
Flat lake of Italy, 478
Flea color, 512
Fleck, Mr., on proportions of materials
for ferrocyanide of potassium, 231
Flowers of zinc, 181
Fougeroux de Bondaroy, on the prepara-
tion of Naples yellow, 397
France, early manufacture of zinc white
in, 165
Frankfort black, 516
Fremy, Mr., researches on the green
coloring matter of leaves, 421-422
French and English weights and mea-
sure.8, 633-640
color trade, white of, composition
of, 133
encyclopedia, process for cochineal
carmine, 489
process for white lead, 78-85
Fresco paintings, ancient, 18, 21, 29
Frit, Alexandria, 35
Furnace for cyanide of potassium, 206
Karmrodt's, for cyanide of potas-
sium, 220-222
Furnaces, 178
calcining, 313-315
carbonizing, 213
for zinc, 169-175
Furstenau process for ultramarine, 323-
327
Fusain black, 515
H ALENA, heating of, 90
VJT Gamal process for white lead, 125,
126
Gamboge, 417
Gamuts, broken, of Mr. Chevreul, 44
of colors, Mr. ChevrQul, 42-45
pure, of Mr. Chevreul, 42, 44
Garanceux, lake of, 467-468
Garancin, 458, 459, 463, 465, 466
Gases from bituminous coal, purifica-
tion of, 115
Gaultier de Claubry, Mr. H. on red
and violet from archil, 495
Gelatine, trial for the proportion of for
ultramarine, 337-338
General method of preparing colors,
49-52
Gentele, L. G., on the preparation of
copper colors, 345
on the proportions of materials for
ferricyanide of potassium, 231
processes for artificial ultrama-
rine, 304-323
German black, 516
green without arsenic, 548
process for cochineal carmine, 491
Giallolini, 397
Gilt brown, 507
Girardine, Mr., analysis of an ancient
blue, 29
Glazing power of ultramarine, trial of,
337
Glue size, yellow ochre with, 361
Glycerin to prevent the efflorescence of
indigo carmine, 269
Gmelin, C. G., memoir on the produc-
tion of artificial ultramarine, 275
648
INDEX.
Gmelin's, process for artificial ultra
marine, 278-279
Gcetne, 274
Gold-button yellow, 169 »
Gold-yellow, 875
Goulard's water, 60
Grape-vine black, 515
Grass-green, 185, 554-556
Gray, pearl, 185
slate, 185
Grays, 575
Grecian or Tyrian purple, 25
Green and yellow lake from chlorophyl
422
apple color, 550
ashes, 548
blue, 345
Bremen, 538-543
bronze, 185, 603
Brunswick, 543
chrome, 561-563
cinnabar, 386, 551, 553
cinnabar from Paris green, 246
cobalt, 556-561
coloring matter of leaves, 421-422
colors, 532-573
dark English, 394
deep color, 51
distilled, «573
earth, 169, 394
Eisner, 553
emerald, 563-568
English, 550
Erlaa, 549
from chromate of zinc, 388
from mineral turbith, 406
grass, 185
Hungary, 534
iris, 534
Kirchberger, 541
lake, 544, 554-556
mineral, 556
of naturally green coloring
substance, 555
leaf, 246, 551
preparation of, 50
light leaf, 51
mineral, 549
Milori, 169, 394, 551
Mittis, 547
mountain, 534
Neuwied, 550
ochre, 571
of stannate of copper, 552
olive, 52, 185
Pannetier, 563
Paul Veronese, 550
pickle, 551
picric acid, 537
Prussian, 552
Green—
Rinmann, 556-561
sap, 534-537
Scheele's, 51
Schweinfurt, 545-547
silk, 551
silky, 387
titanium, 568-571
ultramarine, 281, 571-572
ultramarine, manufacture of, SOS-
SIS
ultramarine, transformation of into
blue, 322
verditer, 538-543
Verona earth, 532
Vienna, 547
water, 185
without arsenic, 548
zinc, 556-561
Greens, chrome, by mixtures, 386, 387
compound of mineral blue and
vegetable yellow, 554
compound of vegetable blue and
mineral yellow, 554
compound of vegetable yellows and
blues, 555
dark, 575
English, 169
from cadmium yellow, 401
from chloride of zinc, 395
from Prussian blue, 203
in baths of Titus, copper com-
pounds, 31
magnificent from chrome yellows,
378
of carmine, indigo, and chrome
yellows, 554
of the Aldobrandini wedding, 32
of the ancients, 30
resembling Scheele's green, 575
various binary mineral, 552
with copper salts, 549
yellowish, 575
Grelley process for cochineal carmine,
492
rinding colors, English mill for, 626
colors, mill for, 604, 607
white lead in oil, Mr. Bessemer's
apparatus, 152
white lead in water, 150
Griineberg's process for white lead,
97-105
Suignet, Mr., process for emerald green,
564
Guimet, Mr., on the preparation of
Naples yellow, 398
process for comparing ultrama-
rines, 329-330
production of artificial ultramarine
by, 274
INDEX.
649
Guimet —
process for artificial ultramarine,
277
Guynemer, powdered dryer of, 579
Guy ton de Morveau on invention of
zinc white, 165
memoir of, on the subject of zinc
white, 104
on the composition of lazulite, 273
Gypsum, 55
HABICH, G. C., on the lakes of red
woods, 478-482
on the preparation of Paris blue,
246
J. C., process for the manufacture
of Bremen blue, 538
Mr., on the manufacture of neutral
chrome yellow, 379
process for artificial ultramarine,
301-304
Hsematoxylin, 484
Hagen, R. de, improvements in sap-
green, 534-537
Hallet and Stenhouse, antimony wkite
of, 164
Hallett and Stenhouse's colors with an-
timonial basis, 401
Hamburg white, composition of, 132
use of baryta in, 193
Healthfulness of Schuzenbach's process
for white lead, 111
Heavy-spar, 192-199
Heeren, F., on Pattinson's white lead,
90-92
Heller on iodide of mercury, 439
Hepatite, 192-199
Hermann's mill, 629
Hick, A., on the preparation of Naples
yellow, 399
Hcofflmayer and Priickner on the pro-
portions of materials for ferrocyanide
of potassium, 231
Holland process, 55, 63-78, 98, 101,
146
process, Mr. Pelouze on, 73
white, composition of, 132
white lead, composition of, 134-
137
Hopper white, 183, 184
Horizontal tubular furnace, 178
Horn, ferrocyanide of potassium ob-
tained with, 224-225
Hues and tones, 43-45, 394
Hues of chrome red, 385
Hungary green, 534
Hydrated sulphide of antimony, 393
Hydrochloric acid, 90
loss and economy of, 194
Hydrosulphuric acid, 90
Hygiene in the manufacture of white
lead, 137-157
Hygienic -precautions in white lead
works, 72
Hyposulphate of lime, 447
IMPROVEMENTS in the manufacture
1 of oils, varnishes, and colors, 608-
629
Impurities in white lead, 127-134
India ink, 531-532
Indian blue of the ancients, 29
red, 486-487
yellow, 394, 417, 420
Indigo, 264-267
adulterations of, 267
carmine, 268-269
composition of, 266, 267
mill for dry, 607-608
platt of, 268
purple, 268
Inks, 528
Institute of France, report on zinc
white, in 1808, 165
Iodide of lead, 410-411
of mercury, 439
Iris green, 534
Iron, effect of, upon yellow from weld,
370
in ultramarine, 299
minium, 425, 501, 504
analyses of, 502
and coal tar, for wood, 504
and red lead, comparison of,
503
and red ochre, difference, 426
composition of, 425
employment of, 503-504
for painting boilers, 504
the hulls of ships, 501
mastic of, 504
oxide of, 423
removing from solutions of sul-
phate of copper, 547
sesquioxide of, 424
use of colcothar on, 503
violet-brown, 423
Italian earth, 361
raw, 358
Ivory black, 530
TA.CQUELIN process for preparing ver-
J milion, 433-434
Jaune Indien, 417-420
Jonquil chrome yellow of Winterfeld,
370-377
yellow from chrome yellows, 377
650
INDEX.
KAOLIN, 306
for artificial ultramarine, 283
Karmrodt furnace, 220-222
process for ferrocyanide of potas-
sium, 219-226
Kaseler yellow, 403
Ketzinsky, on preparing colors, 49
Khittel process for madder lake, 463-
467
Kirchberger green, 547
Kirchoff process for preparing vermilion,
432
Koechlin, Camille, 443
Kopp, M. E , memoir on the prepara-
tion of the sulphide of antimony,
445-453
process for madder lake, 469-471
Kremnitz process, 59-63
Krems or Kremnitz whites, 55, 56, 59-
63
white, analyses of, 76, 77
composition of, 132
Kuhlmann, F., of Lille, on blanc fixe,
193
on blue from manganate of lime,
262-264
LAKE, cochineal, 24, 491
mineral, 395-396
of garanceux, 467-468
zumatic, 587
Lakes, black, 474
Campeachy, 473
green, 554-556
and yellow from chlorophyl,
422
of Brazil wood, 472
of quercitron and yellow wood,
371-372
of red woods, 477-483
Paris, carmine, and Vienna, 493
testing, 471
violet, 473-474
chocolate, and red, 475-476
Lallu & Delaunay, manufacture of white
lead by, 157
Lampadius' pigment of red sulphide of
antimony, 441
Lampblack, 517-524
Languedoc, French man-of-war painted
with zinc white in 1786, 165
Lapis lazuli, 270
Laubgrun, 246
Laundry blue, 358
Lavalleye, P. T., process for manufac-
ture of a bituminous coal black, 513.
614
Lazulite, 270
analysis of, 272-273
Lazulite —
Guyton-Morveau on the composi-
*• tion of, 273
Margraff on the composition of,
273
Varrentrapp,on the composition of,
273
Lead, absorption of carbonic acid by, 93
acetate of, 158
antimoniate of, 161
antimonite of, 160
arsenite of, 409
basic chromate of, 375-376
basis, whites with, 55, 158
brown of manganate of, 506
carbonate of, 85, 110
iodide of, 410, 411
neutral chromate of, 373, 375
nitrate of, 86
oxide of, 403
picking up, 149
protochloride of, 403
white of basic chloride of, 158-159
of sulphate of, 159
tungstate of, 159-160
Leaf green, 246, 551
preparation of, 50
red, 484
Leaves, green coloring matter of, 421-
422
Leclaire, M., manufacture of zinc white
by, 166, 180
use of peroxide of manganese for
quick drying of zinc white, 187-
188
Lefevre, Th., apparatus for pulveriz-
ing white lead, 140-145
production of the white-lead works
of, 146
white lead, works of, 145-153
Lefort, J., on dryers, 188-189
on the manufacture of aurum mus-
sivum, 421
on the use of oxide of manganese
by the Romans, 505
process for madder lake, 462
process for manufacture of manga-
nese brown, 505-506
Lemnos earth, 425
Lemon color, 185
yellow, 169, 395
chromate of baryta, 379
Lengths, measures of, 633
Lenzinite, 334
Le Play on manufacture of white lead
in England, 69, 72
Lichens, archil, Stenhouse's researches
on, 496-497
liquors from, 497
precipitates from, 497
INDEX.
651
Liebig, Baron, process for manufacture
of a dense neu-
tral chromate
of lead, 374
of Schweinfurt
green, 545
Light English green, 169, 394
leaf green, 51
white, or silver white, 127
Lille, manufacture of white lead at. 66,
71, 73, 74
Lime blue, 341-351
of manganate of, 262-264
carbonate of^ 53-54
chromate of, 378
hyposulphite of, 447
in ultramarine, 299
metallic, 455
tartrate of, painting with, 165
white with basis, 58-54
Limekilns, vitreous substance produced
in, in Palermo, 274
Linseed oil, action of white lead on, 58
Litharge, 56, 115, 409, 410
commercial, 103
for gilt brown, 507
in Gruneberg's process for white
lead, 103
preparation of, in England, 84
Litmus, 356
London Journal of Arts, 231
Loppens, Mr., on iron minium, 502
Louyet, Mr., on Rinmann green, 558
Louyet's process for ascertaining the
impurities in white lead, 129-132
Ludwig, Mr., on smalt, 351
Lump white lead, powdering, 151-152
Luteolamide, 371
Luteolin, 368, 370, 371
analysis and chemical formula of,
370-371
red substance from, 371
violet substance from, 371
MACHINE of J. Poelmann for separat-
ing white lead from the metal,
154-155
Ward, for the manufacture of
white lead, 138-140
Madder carmine, 473, 477
detection of adulterations of, 458,
460
lake, 458-475
lakes, uses of, 471
various colors of, 468, 471
sulphuric charcoal of, 463
Magdeburg white lead, analysis of, 76
Malachite, 534
Manganate of lead, brown of, 506
Manganate —
of lime, blue of, 262-264
Manganese, benzoate of, 583
borate of, 585
brown, 505-506
ores, use of, by the ancients, 19
peroxide of, as a dryer of zinc white,
187-189
Margraif on the composition of lazulite,
273
Marie Louise blue, 51
Maroon red, 440
Mars browns, 423, 500, 501
reds, 423
violets, 423
yellow, 358, 362-364
Massicot, 58, 115, 358, 409-410
Mastic of iron minium, 504
zinc white in, 168
Mathieu, M., memoir on the oxide of
zinc, 1844, 166
Mathieu-Plessy, Mr., on vermilion of
antimony, 441-445
Measures, American, 635
British imperial, 635
of capacity, 634
of length, 633
superficial, 634
Mercury, chromates of, 439-440
iodide of, 439
red sulphide of, 430
Me'rime'e, 17, 18, 30
on artificial ultramarine, 277
on the eifect of the addition of
alumina to chromates, 376
on the preparation of mineral yel-
low, 404
Metallic lime, 455
Metals, bronze compositions for, 595-
599
Metric system, 631
of weights and measures, 631-
640
Meudon white in white lead, 128
Mill, English, for grinding, 626
for dry indigo, 607-608
for grinding colors, 604-607
Hermanns, 629
Millon, Mr., on chromates of mercury,
439
Milori green, 169, 394, 551
Minei'al blacks, 512-514
blue, 256-257
gamboge, 358
green, 549
lake, 556
lake, 395-396
straw-yellow, 406
turbith, 406
yellow, 358, 394, 403, 404, 405
652
nsTDEX.
Mineral, yellow —
superfine, 405
Miniature painting, ultramarine for, 282
Minium, 426-428
iron, 425, 501-504
analyses of, 502
employment of, 503-504
Mittis green, 547
Mixed or compound colors, 393-395
Mixeological principle, the, 50-52
Mixing of colors, 394
Mixture of colors, 37
Mock gold, 420-421
Modification of contrast, 47
Mollerat, manufacture of zinc white by,
in 1808, 165
Montabert, M., on the use of antimony
white, 162-164
Monthier's blue, 253
Montpellier yellow, 403
Morea berries, 366
Mosaic gold, 420-421
Mountain blue, 341-351
green, 534
Muffles, French, 321-322
Mulder, M., analyses of white leads, 76,
77
on composition of samples of white
lead, 134-137
on Holland white lead, 76
on orange mineral, 428
Mulhouse white lead, 126
Mullin's apparatus, 106-110
patent, 105
process for white lead, 105-110
Murdock's process for fabrication of
oxide of zinc, 180-182
Murex, Tyrian purple extracted from,
26
\TANKIN yellow, 421
1M Naples yellow, 358, 394, 399-400
Natural sulphate of baryta, 192
Neutral chromate of lead, 373-375
Neuwied green, 550
Newton, VV. E., process for vegetable
blacks, 525-526
Nitrate of copper, 342
Nitrate of lead, 86
basic for production of carbon-
ate of lead, 115
Nitrogen utilized, 224, 225
Normal colors, 37
0
ICFTRE, auri pigmentum of the an-
cients, 20
Burgundy, as a substitute for red
lead, 501
Ochre —
from la Berjaterie, 359
from St. George-sur-la-Pree, 359
green, 571
of Athens, 20
rut, 361
Ochres, 358-361
natural, preparation of, 362
red, 360, 423-424
used by the ancients, 19
Ochreous clay, 425
Oil, drying without lead, 168
drying with peroxide of manganese,
168
or lampblack process, 521-524
paints, spreading, drying, and ad-
hering properties of, 588-593
Oils, drying, 578
varnishes and colors, Bessemer &
Heywood's improvements in the
manufacture of, 608-629
Olive green, 52, 185
Operating the apparatus for oxide of
zinc, 177
for gilt-brown, 507
Orange mineral, 428-429
paste, 375
red sulphite of antimony, 392-
393
Orchil, 474
Orcin, 495
Ordinary process for cochineal carmine,
490
Oriental bole, 425
brown, comparison of iron minium
with, 503
Origin of colors, 37-39
Orpiment, 358, 407-408
| Orpin or orpiment, 358, 407-408
Ostrum of the Romans, 25
Oxide of antimony, 161
of copper, blue colors from, 345
of iron, 423
of lead, preparation of, 112
preparation at Portillon, 80
treatment of, by Mullin's pro-
cess, 108
of zinc, 162
compound colors with, >395
fabrication of, by the Mur-
doch process, 180-182
M. Mathieu's memoir on, in
1844, 166
process from The Technolo-
giste, 169-180
Oxidizing metals, mode of, 108
room fqr zinc, 171
Ozouf, G. H., safe apparatus for the
preparation of white lead, 154
INDEX.
653
PACKING white lead, 153
Painted papers, blue ashes for,
342
Painter's bronze, 420-421
Pale ultramarines, 298
yellow, 169, 395
Pannetier green, 563
Paper hangings, chromate of baryta
for, 379
use of weld lake for, 370
Papers, painted, blue ashes for, 342
smooth, use of zinc white in the
manufacture of, 168
Paris blue, 244-253
lake, 493
Passalaqua, colors employed in the
Egyptian collection of, 21
Patera, Mr., process for the manufac-
ture of uranium yellow, 411
Pattinson process, 85-92
Pattinson's white lead, observations on,
90-92
Paul Veronese green, 550
Peach-stone black, 515
Pearl-gray, 185
Pech-urane, 411
Peligot blue, 261
Pelletier on the preparation of blue
ashes, 341
Pelouze and Fremy on brightening the
color of vermilion, 437
Pelouze, Mr., on Holland process, 73
Perchloride of chromium, 499-500
of tin, 481-482
Perkin, W. H., process for black from
sulphate of aniline, 524
Peroxide of manganese as a dryer for
zinc white, 187-189
Persian berries, 366
coloring matter of, 368
Persoz process for madder lake, 461
Phyllocyanin, 422
Phylloxanthin, 422
Physical effects of colors, 46-48
Picking up lead, 149
Picric acid, green, 537
Pigments with zinc for basis, 169
Pink and red lakes, 471-473
cobalt, 454
Pinks, 575
and reds of madder lake, 463
dark, 575
madder, 471
Platt of indigo, 268
Pliny, 17, 18, 19, 20, 23, 26
Poelmaun, J., machine for separating
white lead from the metal, 154-155
Pohl, J. J., 269
Pompeii, blues discovered at, by Sir H.
Davy, 29
Pompeii —
Chaptal's examination of the paints
found at, 32
ochres used in paintings in, 21
Porcelain clay, 306
use of purple of Cassius for paint-
ing, 458
Potash, Russian, 224
Potassa, bichromate of, 388
chromate of, 388
chromates of, 373
yellow chromate of, for green cin-
nabar, 553
Potassium, ferrocyanide of, manufac-
ture of, 205-219
Portillon, grinding white lead in oil at,83
manufacture of orange mineral at,
429
manufacture of red lead at, 427
manufacture of white lead at, 79-84
manufacture of zinc white at, 182
Portuguese red, 484
Powder, face, zinc-white, in manufac-
ture of, 168
Powdered dryer of Guynemer, 579
Powdering lump white lead, 151-152
Pozzouli, blue made at, 30
Precautions to render manufacture of
white lead less unhealthy, 155-157
Preparing colors, general method of,
49-52
Prickle-wood black, 515
Primary colors, 37, 46, 48
Printing power of ultramarine, trial of,
336
ultramarine for, 282
Prismatic spectrum, 37
Production of the white lead works of
Mr. Lefevre, 146
Protochloride of manganese, 505
of tin, 481
Priickner, C. P., on comparing ultra-
marines, 331-333
process for artificial ultramarine,
283-288, 300
Prussian black, 531
blue, 199-244, 474
and ammonia, 253
application of, 203
by Brunnquell process, 205-
219
by the Stephens process, 235-
239
calcination of, 243
composition of, 199
discovery of, 199
effect of damp walls on, 203
effect of the alkalies on, 202
English process of manufac-
ture, 239-244
654
INDEX.
Prussian blue —
for dyeing, printing, and writ-
ing, 235, 237, 238
green lakes from, 554
greens from, 202
intensity of, 203
Karmrodt process, 219-226
manufacture of ordinary, 200
preservation of the color of, by
acid sulphate of potassa,
242
process for rendering soluble,
235, 237
pure, 200
reducing the expense of manu-
facture, 242
testing the value of, and its
adulterations, 254-256
to judge of the beauty of, 203
tones of, 202
variation in the intensity of,
200
velvety blacks from, 203
brown, 506
green, 552
Puce color, with chromate of manga-
nese, 512
Pulverizing white lead, Lefevre's ap-
paratus for, 140, 145
ordinary process of, 141
Pure or broken colors, 39
Purity of white leads, testing, 127-134
Purple, indigo, 268
madder lake, 463
of Cassius, 455-458
-red, 440
AUERCITRON and yellow wood, lakes
\l of, 371-372
bark, yellow from, 358
RAYS of the solar spectrum, colors
of, 46
reflected by colors, 37
reunion of, 46
Raw sienna, 511-512
Realgar, 429
Red and pink lakes, 471-473
and violets from archil, 495
Antwerp, 362
bole, 425
-brown, 426, 507
colors, 423-500
chrome, 382, 385-387, 500
hues of, 385
employed by the Greeks and Ro-
mans, 21
English, 424
Red-
Indian, 486-487
in plates, 484
lake, 475-476
lead, 426-428
known to the Greeks and
Romans, 23
substitute for, 501
leaf, 484
maroon, 440
ochre, 360, 423, 424
Portuguese, 484
Prof. Dussauce on a new, 486
purple, 440
sesquioxide of iron, 424
Spanish, 484
substance obtained from luteolin,
371
vegetable, 484
Venice, 362
woods, lakes of, 477-483
Reds, madder, 471
Mars, 423
used by the Egyptians, 21
Resin lampblack, 518
Resins for dryers, 584
Retin, asphaltum, 509
Retorts for zinc, 173, 175, 177
Reverberatory furnace or coke oven, 178
Rhamnin, 368
Rhamnoxanthin, 475-476
Ringault, Mr., patent for vermilion un-
alterable by fire, 438
Rinmann green, 556-561
analysis of, 560
prepared by Barruel and Lec-
laire, 560
R. Wagner on, 557-560
Ritter, H., on composition of artificial
ultramarine, 327
on the manufacture of Holland ver-
milion, 430
Robiquet and Colin process for madder
lake, 460
discovery of orcin by, 495
Robiquet's formula for artificial ultra-
marine, 296
Romans and Egyptians, white used by,
17
Roman yellow, 394, 574
Rostaing, Mr. de, 361
process for white lead, 126
Rousseau, Bobierre, and Ruolz, anti-
mony, white of, 161-162
Royal yellow, 408
Rubia tinctorum, 458
Ruby of arsenic, 429
Ruolz, Bobierre, and Rousseau, anti-
mony white of, 161-162
Rut ochre, 358, 361
INDEX.
655
SACC process for madder lake, 469
Saffron yellow, 358
Saint Cyr white, 184
Sal ammoniac and ultramarine, 323
Salvetat, Mr., process for brown, 500
Sandaraca of the Romans, 20
Santaline, 472
Sap green, 534-537, 555
Saxony blue, 268, 351
smalts of, marks of, 353
Scarlet, iodide of mercury, 439
Scheele's green, 51, 543, 545
green, green resembling, 575
Sching C., process for manufacture of
ferrocyanide of potassium, 226-230
Schist, 512-513
Schuzenbach's process for white lead,
110-111
Schweinfurt green, 545-547
Scoffern, Mr., 159
Secondary colors, 37
Seine, manufacture of white lead in
Department of, 67, 70
Separation of oxide of zinc from metal-
lic zinc, 183
white lead from the uncor-
corroded metal, 149
Sepia, 510-511
Sesquioxide of iron, 424
Sewell's apparatus for white lead, 113-
114
process for white lead, 111-115
Shale black, 512-513
Ships, hulls of, painting, 504
Sienna earth, 361, 511, 512
raw, 358
Silica for artificial ultramarine, 290
Siliceous sand, analysis of, 290
Silk green, 551
Silky green, 387
Silver, chromate of, 440
white, or light white, 127
Sky blue, 253
English, 356-357
Slate-gray, 185
Smalt, 351-354
blue, 351
color of, 351
of a magnificent blue, 353
raw materials of, 351
Smalts of Saxony, marks of, 353
Snow white, 182
Society d'Encouragement, 137
Soda, carbonate of, for ultramarine
green, 308
furnace, blue substance produced
in, 274
in ultramarine, 299
sulphate of, for ultramarine green,
307
Sodium, 309
Solar spectrum, color of rays of, 46
Sorel, Mr., process for separating oxide
of zinc from metallic zinc, 183
Spanish red, 484
white, 54
Spilsburg, Mr., 160
Spindle tree black, 515
Stannate of protoxide of gold, 457
Starch blue, 351
Stein, V., on manufacture of picric acid
green, 537
Stenhouse and Hallett, antimony white
of, 164
Stenhouse, Mr., analysis of Indian yel-
low, 418
Stephens' process for preparation of
Prussian blue, 235
Stil de grain, 358, 366, 368
preparation of, 366-367
Stinking stone, 192
Stone color, 185
Straw-yellow, 185
from chrome-yellows, 377
mineral, 406
Struve, C.y analysis of green without
arsenic, 548
Subphosphate of cobalt, 257
Sulphate, atomic, 190-191
of baryta, 192-199
in white lead, 132-133
of iron, 224
of soda for ultramarine green, 307
of zinc, colors for, 574-577
Sulphide of antimony, 441
analysis of, 444-445
compound colors with, 393
orange red, 392, 393
of sodium for ultramarine, 309
of zinc, 191-192
Sulphite of lead, white of, 159
Sulpho-antiinonite of barium, 453-454
Sulphoindigotic acid, 268
Sulphur, 309
combination with ultramarine, 323
for artificial ultramarine, 291
transformation of, into hydrosul-
phuric acid, 90
Sumach lake, 475
Superficial measures, 634
Symbols for abbreviations, 637
^TABLES of French and English weights
1 and measures, 633-640
Tar black, 518-521
Tartrate of lime, painting with, 165
Technologiste, 154, 163, 169, 205, 231,
259, 283, 289, 301, 305, 328, 345,
379, 399, 418, 463, 486,534, 538, 551,
557, 566.
656
INDEX.
Terra-merita, 358, 364-365
Terra-rosa, 312
Tertiary colors, 49
Tessart, 274
Testing madder lakes, 471
Prussian blue, 232, 254-256
the purity of white leads, 127-134
Thenard blue, 257-261
Mr., process for white lead, 78-85
on process for separating ultra-
marine from lazulite, 270
on the preparation of Naples yel-
low, 397
Theophrastes, 17, 23, 32
Thierry-Mieg and Schwartz process for
lake of garenceux, 467-468
Tin, 480
basic chromate of, 395
bath, dyers, 459
bisulphide of, 420
perchloride of, 481, 482
protochloride of, 481
white, 165
Tint of azure blue, 185
Tiremon process for artificial ultrama-
rine, 280
Tiremon' s formula for artificial ultra-
marine, 277
Titanium green, 568-571
Titrated liquor, preparation of, 234
Tone, contrast of, 46
Tones and hues, 394
Tubular furnace, horizontal, 178
Tuckert, Mr., on the manufacture of
Holland vermilion, 430
Tungstate of lead, white of, 159-160
Turbith mineral, 406
Turnbull's blue, 244
Turner yellow, 358, 403
Turkey berries, 366
Tyrian purple, 25
Tyrolese white lead, 193
ULMIN blacks, 525
brown, 507-508
Ultramarine, analysis Of, 272
and sal ammoniac, 323
artificial, 274-340
analysis of, 275, 296-297
Brunner's process, 289-300
Dippel process, 300-301
Gentele processes, 304-323
Gmelin's formula for, 276
Grmelin's process, 278-279
Guimet's process, 277-278
Habich process, 301-304
Priickner process, 283-288,
300
Robiquet's formula for, 276
Ultramarine, artificial —
Tiremon's formula for, 277
Tiremon process, 280
Weger process, 281-282
Wiriterneld process, 288-289
ash, 270
blue, fine green for, 316
Gentele's process, 318-323
real or native, 270
separation from lazulite, 270
washing, 322
blues, 269-340
cobalt, 340
combined with sulphur, 323
dark alum, composition for, 324
durability of color of, 333
for calico printing, 330
for miniature painting, 282
for printing, 282
Furstman process for, 323-327
green, 281, 571, 572
manufacture of, 305-318
proportions of raw materials,
310-311, 316-318
raw materials for, 305
lazulite, 270
method of ascertaining the quality,
288
mixture for, 291
resistance to the action of alum,
333
trial for the proportion of size, 337
of coloring power of, 334
of the glazing power of, 337
of the printing power of, 336
white, 327
yellow, 379
Ultramarines, composition of, 339-340
pale, 298
trial and analysis of, 329-339
Ultramarinometer, 335-336
Umber, 511
Uranium pech-blende, 411
yellow, 411, 416
Ure, Dr., 57
VALLE and Barreswill, antimony
white of, 162-164
Value of fused materials in the manu-
facture of ferrocyanide of potassium,
230-235
Van Dyke brown, 504-505
Varnishes, oils, and colors, Bessemer
and Heywood's improvements in the
manufacture of, 608-629
Varrentrapp on the composition of
lazulite, 273
Vauquelin, 17, 27, 274
discovery of chromium by, 372
INDEX.
657
Vegetable blacks, 515
green, 554-556
red, 484
violet, 484
Venice lake, 472, 478
red, 362
white, composition of, 132
white, use of baryta in, 193
Verdet, crystallized, 573
Verdigris, 394, 572
use of, by the ancients, 32
Verditer blue and green, 538-543
in paste, 345
Vermilion, 430-439
Brunner process, 432, 433
by the dry way, 430
by the wet way, 49, 431
Chinese method of preparing, 431
discovery of, in Rome, 23
Firmenioh process, 434-437
Holland, manufacture of, 430
Jacquelin process, 433-434
Kirchoff process, 432
of antimony, 441
preparation of, 448
properties of, 452-453
processes for brightening the color
of, 437
unalterable by fire, 438
Vernet, Horace,. 278
Verona earth, green, 532
use of, by the Romans, 31
yellow, 403
Versepuy's apparatus for white lead,
95-96
process, 93-97
Vienna green, 547
lake, 493
Violet lakes, 473-474, 475-476
from iron, 423
solution obtained from luteolin,
371
Violets, vegetable, 484
Mars, 423
Vitreous substance from lime-kilns, pro-
duced in Palermo, 274
Vitruvius, 17, 18, 20, 21, 23, 25, 27, 31
Vitry white, 184
Vlaandern, experiments on composition
of white lead, 134-137
W
AGNER, R., analysis of chromate of
zinc, 391
on economy of iron minium, 426
on Rinmann green, 557-560
on sulpho-antimonite of barium,
453
on the preparation of yellow orpi-
ment, 408
42
Wagner, R.—
process for the preparation of In-
dian yellow, 418
Ward machine for the manufacture of
white lead, 138-140
Warington, R., on the preparation of
Paris blue, 245
Washer, Crompton's, 117
Water- green, 185
Watin's process for distinguishing white
lead from chalk, 128
Weger process for artificial ultramarine,
281-282
Weights, 635
and measures, metric system of,
631-640
Weilhem, Mr., on the preparation of
Erlaa green, 549
Weld lake, 368-371
yellow from, 369
yellows, 358
Weshle, Mr., on the preparation of ver-
milion, 433
Wet way, advantages of, in preparing
colors, 49
White and gray pigments of oxide of
zinc, 168
azure, 185, 203
colors, 53-199
of basic chloride of lead, 158-159
of sulphate of lime, 55
of sulphite of lead, 159
of tungstate of lead, 159-160
Saint-Cyr, 184
snow, zinc, hopper, 183
tin, 165
ultramarine, 327-328
vitry, 184
zinc and dryers, 186-189
Whites, antimony, 161-164
baryta, 192-199
employed in painting, natural or
chemical compounds, 37
used by the Egyptians and Romans,
17
with lead bases, 55-158
with lime bases, 53-54
zinc, 576
White lead, analyses of, 76, 77
analysis of, made by Wood,
Benson, and Griiueberg, pro-
cess, 102
Bacco's process for testing,
133-134
beds for, 147, 148
by Crompton process, 1 1 5-1 25
by Gannal's process, 125-126
by Holland or Dutch process,
63-78
by Kremnitz process, 59-63
658
INDEX.
White lead-
by Mullin's process, 105-110
by Schuzenbach's process,
110-111
by the Pattinson process, 85-
92
by Versepuy process, 93-97
chalk in, 128
•composition of, 134-137
of samples of, 132-137
deaths from, 138
dry grinding scales of, 149
drying rooms, 150
fine, should be free from cop-
per, 104
French process, 78-85
grinding in water, 150
harmlessness of the manufac-
ture of, by Lallu and Delau-
nay, 157
in oil, 83
grinding of, at Portillon,
83
in powder, 82
keeping, 128
Lefevre's apparatus for pul-
verizing. 140, 145
Louyet's process for ascertain-
ing the impurities in, 129-
132
machine for separating from
the metal, 154-155
Mulhouse, 126
observations on Pattinson' s,
90-92.
packing, 153
powdering lump, 151-152
precautions to render less un-
healthy, 155-157
processes for rendering manu-
facture of, less unhealthy,
137-157
processes of Wood, Benson,
and Gruneberg, 97-105
produced in the works of M.
Lefevre, 146
Rostaing's process for, 126
testing the purity of, 127-
134
Tyrolese, 193
washing in carbonate of soda,
115
tanks for, 82
Woolrich process, 92-93
works, hygienic precautions
in, 72
Wingens, Mr., process for Schweinfurt
green, 546
Winterfield, jonquil chrome yellow of,
376-377
Winterfield process for artificial ultra-
marine, 288-289
Wobler, Mr., on perchloride of chro-
mium, 499
Wood, Benson, and Gruneberg processes
for white lead, 97-105
Wood charcoal, alkalized charcoal from,
224
painting with iron minium and coal
tar, 504
process for cochineal carmine, 492
Wood's apparatus for white lead, 98
Woolner, modification of Wood's pro-
cess for white lead by, 102
Wool process for cochineal carmine, 491
Woolrich process, 92-93
Wuy, balls of, 357
YELLOW, antimony, 394, 405
I baryta, 169
bouton d'or, 169
bright, 394
cadmium, 400-401
cassel, 403
chamois, 574
chromate of lead, neutral, composi-
tion of, 374
chromate of potash, 373
chrome, 379-385 •
Cologne, 377-378
colors, 258-422
from weld, extracting, 369
gold, 375
hues of chrome, 382
Indian, 394, 417, 420
jonquil of Winterfield, 376-377
Kessler, 403
lemon, 169, 395
lemon of chromate of baryta, 379
Mars, 362-364, 394
calcining to produce browns,
500
mineral, 403, 404
straw, 406
Montpellier, 403
Nankin, 421
Naples, 394, 397-400
tones and hues of, from anti-
mony, 402
ochre, 358, 359
with glue size or oil, 361
of antimony and zinc, 401-403
pale, 169, 395
protoxide of lead, 409
realgar, 407-408
Roman, 394
royal, 408
straw, 185
sulphide of arsenic, 407-408
INDEX.
659
Yellow-
tones of chrome, 383
Turner, 4U3
ultramarine, 379
uranium, 411—416
Verona, 403
wood, 358
lakes of, 371-372
Yellowish-greens, 575
sap-green, £37
Yellows, chamois, 574
chrome, 372-387, 394
dark gold, 575
delicate light, 574
gold, 575
in general, 358
of the Aldobrandini Wedding, 21
Roman, 574
used by the ancients, 20
zinc, of Germany, 391
7AFFER, 351
L blue, 351
Zinc, acetates, chlorides, nitrates, ox-
ides, sulphate of, 576
and iron, brown from, 501
as a basis for pigments for artists
and house painters, 169
basic chromate of, 394
charging with the retorts, 177
chromate of, 387-391
and oxide of, compound colors
with, 393
colors of sulphate of, 574-577
flowers of, 181
furnaces for, 169-175
green, 556-566
of Barruel and Leclaire, 560
Zinc —
melting, 171
ore, distillation of, 167,
operating with, 177, 178
oxide of, 162
apparatus for manufacture
of, 169-180
fabrication by the Murdoch
process, 180-182
process from the Technolo-
ffiste, 169-180
oxidizing room for, 171
retorts for, 173, 175, 177
separation of oxide of, from metal-
lic, 183
sulphide of, 191-192
white, 164, 183, 192, 576
adulteration of, 189-190
and dryers, uses of, 186-189
danger and salubrity of, 190-
191
dryer for, 578
in 1770, 164
invention of, claimed for France
in 1781, 165
manufacture of at Portillon,
182
manufacture of, by Mr. Le-
claire, 166-180
mixture of, with pigments, 168
product of, 167
uses of, 168
various pigments obtained
from, 184
various processes for the man-
ufacture of, 185-186
yellows of Germany, 391
Zumatic dryer, 580
lake, 587
TOWN AND COUNTRY
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 13
FRANKEL— HUTTER.— A Practical Treatise on the Manxi'
facture of Starch, Glucose, Starch-Sugar, and Dextrine:
Based on the German of LADISLAUS VON WAGNER, Professor in the
Royal Technical High School, Buda-Pest, Hungary, and other
authorities. By JULIUS FRANKEL, Graduate of the Polytechnic
School of Hanover. Edited by ROBERT HUTTER, Chemist, Practical
Manufacturer of Starch-Sugar. Illustrated by 58 engravings, cover-
ing every branch of the subject, including examples of the most
Recent and Best American Machinery. 8vo., 344 pp. . $3.50
GARDNER. — The Painter's Encyclopaedia:
Containing Definitions of all Important Words in the Art of Plain
and Artistic Painting, with Details of Practice in Coach, Carriage,
Railway Car, House, Sign, and Ornamental Painting, including
Graining, Marbling, Staining, Varnishing, Polishing, Lettering,
Stenciling, Gilding, Bronzing, etc. By FRANKLIN B. GARDNER.
158 Illustrations. I2mo. 427 pp. ..... $2.00
GARDNER. — Everybody's Paint Book:
A Complete Guide to the Art of Outdoor and Indoor Painting, De-
signed for the Special Use of those who wish to do their own work,
and consisting of Practical Lessons in Plain Painting, Varnishing,
Polishing, Staining, P??rr Hanging, Kalsomining, etc., as well as
Directions for Renovating Furniture, and Hints on Artistic Work for
Home Decoration. 38 Illustrations. I2mo., 183 pp. . $l.oo
GEE. — The Goldsmith's Handbook:
Containing full instructions for the Alloying and Working of Gold,
including the Art of Alloying, Melting, Reducing, Coloring, Col-
lecting, and Refining; the Processes of Manipulation, Recovery of
Waste; Chemical and Physical Properties of Gold; with a New
System of Mixing its Alloys ; Solders, Enamels, and other Useful
Rules and Recipes. By GEORGE E. GEE. I2mo. . . $i>7$
GEE. — The Silversmith's Handbook :
Containing full instructions for the Alloying and Working of Silver,
including the different modes of Refining and Melting the Metal ; its
Solders ; the Preparation of Imitation Alloys ; Methods of Manipula-
tion ; Prevention of Waste ; Instructions for Improving and Finishing
the Surface of the Work ; together with other Useful Information and
Memoranda. By GEORGE E. GEE. Illustrated. I2mo. $i«75
GOTHIC ALBUM FOR CABINET-MAKERS:
Designs for Gothic Furniture. Twenty-three plates. Oblong $2.00
GRANT. — A Handbook on the Teeth of Gears :
Their Curves, Properties, and Practical Construction. By GEORGE
B. GRANT. Illustrated. Third Edition, enlarged. 8vo. #l.oo
GREENWOOD.— Steel and Iron :
Comprising the Practice and Theory of the Several Methods Pur-
sued in their Manufacture, and of their Treatment in the Rolling.
Mills, the Forge, and the Foundry. By WILLIAM HENRY GREEN-
WOOD, F, C, S. With 97 Diagrams, 536 pages. I2mo. $2.00
HENRY CAREY BAIRD & CO.'S CATALOGUE.
GREGORY. — Mathematics for Practical Men :
Adapted to the Pursuits of Surveyors, Architects, Mechanics, and
Civil Engineers. By OLINTHUS GREGORY. 8vo., plates $3.00
GRIM SHAW.— Saws :
The History, Development, Action, Classification, and Comparison
of Saws of all kinds. With Copious Appendices. Giving the details
of Manufacture, Filing, Setting, Gumming, etc. Care and Use of
Saws; Tables of Gauges; Capacities of Saw-Mills; List of Saw-
Patents, and other valuable information. By ROBERT GRIMSHAW.
Second and greatly enlarged edition, with Supplement, and 354
Illustrations. Quarto $4-OO
GRISWOLD. — Railroad Engineer's Pocket Companion for the
Field :
Comprising Rules for Calculating Deflection Distances and Angles,
Tangential Distances and Angles, and all Necessary Tables for En-
gineers; also the Art of Levelling from Preliminary Survey to the
Construction of Railroads, intended Expressly for the Young En-
gineer, together with Numerous Valuable Rules and Examples. By
W. GRISWOLD. i2mo., tucks $I-75
GRUNER.— Studies of Blast Furnace Phenomena:
By M. L. GRUNER, President of the General Council of Mines o!
France, and lately Professor of Metallurgy at the Ecole des Mines.
Translated, with the author's sanction, with an Appendix, by L. D.
B. GORDON, F. R. S. E., F. G. S. 8vo. . . . £2.50
Hand-Book of Useful Tables for the Lumberman, Farmer and
Mechanic:
Containing Accurate Tables of Logs Reduced to Inch Board Meas*
ure, Plank, Scantling and Timber Measure ; Wages and Rent, by
Week or Month; Capacity of Granaries, Bins and Cisterns; Land
Measure, Interest Tables, with Directions for Finding the Interest on
any sum at 4, 5, 6, 7 and 8 per cent., and many other Useful Tables.
32 mo., boards. 186 pages .25
HASERICK.— The Secrets of the Art of Dyeing Wool, Cotton,
and Linen,
Including Bleaching and Coloring Wool and Cotton Hosiery and
Random Yarns. A Treatise based on Economy and Practice. By
E. C. HASERICK. Illustrated by 323 Dyed Patterns of the Yarni
or Fabrics. 8vo #7-5°
HATS AND FELTING :
A Practical Treatise on their Manufacture. By a Practical Hatter,
Illustrated by Drawings of Machinery, etc. 8vo. . . $1.25
H OFFER.— A Practical Treatise on Caoutchouc and Gulta
Percha,
Comprising the Properties of the Raw Materials, and the manner or
Mixing and Working them ; with the Fabrication of Vulcanized and
Hard Rubbers, Caoutchouc and Gutta Percha Compositions, Water.
HENRY CAREY BAIRD & CO.'S CATALOGUE. 15
proof Substances, Elastic Ttesues, the Utilization of Waste, etc., etc.
From the German of RAIMUND HOFFER. By W. T. ERANNT.
Illustrated I2mo. . $2.50
HOFMANN.— A Practical Treatise on the Manufacture of
Paper in all its Branches :
By CARL HOFMANN, Late Superintendent of Paper-Mills in Germany
and the United States ; recently Manager of the " Public Ledger "
Paper Mills, near Elkton, Maryland. Illustrated by no wood en-
gravings, and five large Folding Plates. 410., cloth; about 400
pages $3S-°°
HUGHES. — American Miller and Millwright's Assistant:
By WILLIAM CARTER HUGHES. i2mo $1.50
HULME. — Worked Examination Questions in Plane Geomet-
rical Drawing :
For the Use of Candidates for the Royal Military Academy, Wool-
wich ; the Royal Military College, Sandhurst ; the Indian Civil En.
gineering College, Cooper's Hill ; Indian Public Works and Tele-
graph Departments; Royal Marine Light Infantry; the Oxford and
Cambridge Local Examinations, etc. By F. EDWARD HULME, F. L.
S., F. S. A., Art-Master Marlborough College. Illustrated by 300
examples. Small quarto #2.50
JERVIS.— Railroad Property:
A Treatise on the Construction and Management of Railways;
designed to afford useful knowledge, in the popular style, to the
holders of this class of property ; as well as Railway Managers, Offi-
cers, ar,d Agents. By JOHN B. JERVIS, late Civil Engineer of the
Hudson River Railroad, Croton Aqueduct, etc. i2mo., cloth $2.oc
KEEN E.— A Hand-Book of Practical Gauging:
For the Use of Beginners, to which is added a Chapter on Distilla'
tion, describing the process in operation at the Custom-House for
ascertaining the Strength of Wines. By JAMES B. KEENE, of H. M.
Customs. 8vo. $1.25
KELLEY.— Speeches, Addresses, and Letters on Industrial and
Financial Questions :
By HON. WILLIAM D. KELLEY, M. C. 544 pages, 8vo. . $3.00
KELLOGG.— A New Monetary System :
The only means of Securing the respective Rights of Labor and
Property, and of Protecting the Public from Financial Revulsions.
By EDWARD KELLOGG. Revised from his work on "Labor and
other Capital." With numerous additions from his manuscript.
Edited by MARY KELLOGG PUTNAM. Fifth edition. To which u
added a Biographical Sketch of the Author. One volume, I2mo.
Paper cover $I.oo
Bound in cloth 1-5°
KEMLO.— Watch-Repairer's Hand-Book :
Being a Complete Guide to the Young Beginner, in Taking Apart,
Putting Together, and Thoroughly Cleaning the English Lever and
other Foreign Watches, and all American Wntches. By F. KEMLO,
Practical Watchmaker. With Illustrations, izmo, . Jl.2/
36 HENRY CAREY BAIRD & CO.'S CATALOGUE.
KENTISH.— A Treatise on a Box of Instruments,
And the Slide Rule ; with the Theory of Trigonometry and Log*
rithms, including Practical Geometry, Surveying, Measuring of Tim.
her, Cask and Malt Gauging, Heights, and Distances. By THOMAJ
KENTISH. In one volume. I2mo. ... fli 2j
KERL.— The Assayer's Manual:
An Abridged Treatise on the Docimastic Examination of Ores, and
Furnace and other Artificial Products. By BRUNO KERL, Professor
in the Royal School of Mines. Translated from the German l>y
WILLIAM T. BRANNT. Second American edition, edited with Ex-
tensive Additions by F. LYNWOOD GARRISON, Member of the
American Institute of Mining Engineers, etc. Illustrated by 87 en-
gravings. 8vo 13.00
KICK.— Flour Manufacture.
A Treatise on Milling Science and Practice. By FREDERICK KICK,
Imperial Regierungsrath, Professor of Mechanical Technology in the
imperial German Polytechnic Institute, Prague. Translated from
the second enlarged and revised edition with supplement by H. H.
P. PoWLES, Assoc. Memb. Institution of Civil Engineers. Illustrated
with 28 Plates, and 167 Wood-cuts. 367 pages. 8vo. . $10.00
KINGZETT.— The History, Products, and Processes of the
Alkali Trade :
Including the most Recent Improvements. By CHARLES THOMAS
KINGZETT, Consulting Chemist. With 23 illustrations. 8vo. $2.50
KINSLEY. — Self-Instructor on Lumber Surveying :
For the Use of Lumber Manufacturers, Surveyors, and Teachers,
By CHARLES KINSLEY, Practical Surveyor and Teacher of Surveying.
I2mo.
KIRK. — The Founding of Metals:
A Practical Treatise on the Melting of Iron, with a Description of the
Founding of Alloys ; also, of all the Metals and Mineral Substances
used in the Art of Founding. Collected from original sources. Bj
EDWARD KIRK, Practical Foundryman and Chemist. Illustrated.
Third edition. 8vo. $2.50
LANDRIN.— A Treatise on Steel :
Comprising its Theory, Metallurgy, Properties, Practical Working,
and Use. By M. H. C. LANDRIN, JR., Civil Engineer. Translated
from the French, with Notes, by A. A. FESQUET, Chemist and En-
gineer. With an Appendix on the Bessemer and the Martin Pro-
f^ses for Manufacturing Steel, from the Report of Abram S. Hewitt-
United States Commissioner to the Universal Exposition, Paris, 1867.
I2mo. $3-00
LARDENc— A School Course on Heat :
By W. LARDEN, M. A. 321 pp. I2mo $2.00
f-ARDNER,— The Steam-Engine:
For the Use -»f Beginners. By LH. LARDNER. Illustrated. 12010.
If
HENRY CAREV BAIRD & CO.'S CATALOGUE. 17
LARKIN. — The Practical Brass and Iron Founder's Guide:
A Concise Treatise on Brass Founding, Moulding, the Metals and
their Alloys, etc.; to which are added Recent Improvements in the
Manufacture of Iron, Steel by the Bessemer Process, etc., etc. By
TAMES LARKIN, late Conductor of the Brass Foundry Department in
Reany, Neafie & Co.'s Penn Works, Philadelphia. Fifth edition,
revised, with extensive additions. I2tno. . . . $2.25
LKROUX.— A Practical Treatise on the Manufacture of
Worsteds and Carded Yarns :
Comprising Practical Mechanics, with Rules and Calculations applied
to Spinning; Sorting, Cleaning, and Scouring Wools; the English
and French Methods of Combing, Drawing, and Spinning Worsteds,
and Manufacturing Carded Yarns. Translated from the French of
CHARLES LEROUX, Mechanical Engineer and Superintendent of a
Spinning-Mill, by HORATIO PAINE, M. D., and A. A. FESQUET,
Chemist and Engineer. Illustrated by twelve large Plates. To which
is added an Appendix, containing Extracts from the Reports of the
International Jury, and of the Artisans selected by the Committee
appointed by the Council of the Society of Arts, London, on Woolen
and Worsted Machinery and Fabrics, as exhibited in the Paris Uni-
versal Exposition, 1867. 8vo. ..... $$-o(*
LEFFEL. — The Construction of Mill-Dams :
Comprising also the Building of Race and Reservoir Embankments
and Head-Gates, the Measurement of Streams, Gauging of Water
Supply, etc. By JAMES LEFFEL & Co. Illustrated by 58 engravings.
8vo $2.50
LESLIE.— Complete Cookery:
Directions for Cookery in its Various Branches. By Miss LESLIE.
Sixtieth thousand. Thoroughly revised, with the addition of New
Receipts. I2mo £i-5°
LE VAN. — The Steam Engine and the Indicator:
Their Origin and Progressive Development; including the Most
Recent Examples of Steam and Gas Motors, together with the Indi-
cator, its Principles, its Utility, and its Application. By WILLIAM
BARNET LE VAN. Illustrated by 205 Engravings, chiefly of Indi-
cator-Cards. 469 pp. Svo • $4 ^°
MEBER.— Assayer's Guide :
Or, Practical Directions to Assayers, Miners, and Smelters, for the
Tests and Assays, by Heat and by Wet Processes, for the Ores of all
the principal Metals, of Gold and Silver Coins and Alloys, and of
Coal, etc. By OSCAR M. LIBBER. I2mo. . . . $1.25
Lockwood's Dictionary of Terms :
Used in the Practice of Mechanical Engineering, embracing those
Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turn-
ing, Smith's and Boiler Shops, etc., etc., comprising upwards of Six
Thousand Definitions. Edited by a Foreman Pattern Maker, author
of " Pattern Making." 417 pp. "mo. . . . *3-°°
i8 HENRY CAREY BAIRD & CO.'S CATALOGUE.
LUKIN.— Amongst Machines;
Embracing Descriptions of the various Mechanical Appliances used
in the Manufacture of Wood, Metal, and other Substances. J2mo.
It.ys
fcUKIN.— The Boy Engineers:
What They Did, and How They Did It. With 30 plates. i8mo.
#1-75
LUKIN.— The Young Mechanic :
Practical Carpentry. Containing Directions for the Use of all kinds
of Tools, and for Construction of Steam- Engines and Mechanical
Models, including the Art of Turning in Wood and Metal. By JOHN
LUKIN, Author of "The Lathe and Its Uses," etc. Illustrated.
I2mo $l-7S
MAIN and BROWN. — Questions on Subjects Connected with
the Marine Steam-Engine :
And Examination Papers; with Hints for their Solution. By
THOMAS J. MAIN, Professor of Mathematics, Royal Naval College,
and THOMAS BROWN, Chief Engineer, R. N. I2mo., cloth . $1.50
MAIN and BROWN.— The Indicator and Dynamometer:
With their Practical Applications to the Steam-Engine. By THOMAS
J. MAIN, M. A. F. R., Ass't S. Professor Royal Naval College,
Portsmouth, and THOMAS BROWN, Assoc. Inst. C. E., Chief Engineer
R. N., attached to the R. N. College. Illustrated. 8vo. . $1.50
MAIN and BROWN.— The Marine Steam-Engine.
By THOMAS J. MAIN, F. R. Ass't S. Mathematical Professor at the
Royal Naval College, Portsmouth, and THOMAS BROWN, Assoc.
Inst. C. E., Chief Engineer R. N. Attached to the Royal NavaJ
College. With numerous illustrations. 8vo. . . $5.00
MAKINS.— A Manual of Metallurgy:
By GEORGE HOGARTH MAKINS. 100 engravings. Second edition
rewritten and much enlarged. I2mo., 592 pages . . $3-oo
MARTIN.— Screw-Cutting Tables, for the Use of Mechanical
Engineers :
Showing the Proper Arrangement of Wheels for Cutting the Threads
of Screws of any Required Pitch ; with a Table for Making the Uni-
versal Gas-Pipe Thread and Taps. By W. A. MARTIN, Engineer.
8vo 50
UICHELL.— Mine Drainage:
Being a Complete and Practical Treatise on Direct-Acting Under-
ground Steam Pumping Machinery. With a Description of a largtf
number of the best known Engines, their General Utility and the
Special Sphere of their Action, the Mode of their Application, and
their Merits compared with other Pumping Machinery. By STEPHEN
MICHELL. Illustrated by 137 engravings. 8vo., 277 pages . $6.00
HOLESWORTH.— Pocket-Book of Useful Formulae and
Memoranda for Civil and Mechanical Engineers.
By GUILFORD L. MOLESWORTH, Member of the Institution of Civtf
Engineers, Chief Resident Engineer of the Ceylon Railway. Full-
bound in Pocket-book form . • • • • * $l.cn
HENRY CAREY BAIRD & CO.^y CATALOGUE. 19
MOORE.— The Universal Assistant and the Complete Me-
chanic :
Containing over one million Industrial Facts, Calculations, Receipts,
Processes, Trades Secrets, Rules, Business Forms, Legal Items, Etc.,
in every occupation, from the Household to the Manufactory. By
R. MOORE. Illustrated by 500 Engravings. I2mo. . $2.50
MORRIS. — Easy Rules for the Measurement of Earthworks ;
By means of the Prismoidal Formula. Illustrated with Numerom
Wood-Cuts, Problems, and Examples, and concluded by an Exten-
sive Table for finding the Solidity in cubic yards from Mean Areas.
The whole being adapted for convenient use by Engineers, Surveyors,
Contractors, and others needing Correct Measurements of Earthwork.
By ELWOOD MORRIS, C. E. 8vo $1.50
MORTON.— The System of Calculating Diameter, Circumfer-
ence, Area, and Squaring the Circle :
Together with Interest and Miscellaneous Tables, and other informa-
tion. By JAMES MORTON. Second Edition, enlarged, with the
Metric System. I2mo $1.00
NAPIER. — Manual of Electro-Metallurgy:
Including the Application of the Art to Manufacturing Processes.
By JAMES NAPIER. Fourth American, from the Fourth London
edition, revised and enlarged. Illustrated by engravings. 8vo.
NAPIER. — A System of Chemistry Applied to Dyeing.
By JAMES NAPIER, F. C. S. A New and Thoroughly Revised Edi-
tion. Completely brought up to the present state of the Science,
including the Chemistry of Coal Tar Colors, by A. A. FESQUET,
Chemist and Engineer. With an Appendix on Dyeing and Calica
Printing, as shown at the Universal Exposition, Paris, 1867. Illus-
trated. 8vo. 422 pages $3-S°
NEVILLE.— Hydraulic Tables, Coefficients, and Formulae, for
finding the Discharge of Water from Orifices, Notches,
Weirs, Pipes, and Rivers :
Third Edition, with Additions, consisting of New Formulae for the
Discharge from Tidal and Flood Sluices and Siphons ; general infor-
mation on Rainfall, Catchment-Basins, Drainage, Sewerage, Water
Supply for Towns and Mill Power. By IOHN NEVILLE, C. E. M. R.
I. A. ; Fellow of the Royal Geological Society of Ireland. Thick
I2mo 15.50
NEWBERY.— Gleanings from Ornamental Art of every
style :
Drawn from Examples in the British, South Kensington, Indian,
Crystal Palace, and other Museums, the Exhibitions of 1851 and
1862, and the best English and Foreign works. In a series of loo
exquisitely drawn Plates, containing many hundred examples. B*
ROBERT NEWBERY. 410. $12.50
KlCHOLLS.-The Theoretical and Practical Boiler-Maker and
Engineer's Reference Book:
Containing a variety of Useful Information for Employers of Labor.
Foremen and Working Boiler-Makers, Iron, Copper, and Tinsmith*
ao HENRY CAREY BAIRD & CO/S CATALOGUE.
Draughtsmen, Engineers, the General Steam-using Public, and for th«
Use of Science Schools and Classes. By SAMUEL NICHOLLS. Illus.
trated by sixteen plates, 1 2mo. $2.50
NICHOLSON.— A Manual of the Art of Bookbinding:
Containing full instructions in the different Branches of Forwarding,
Gilding, and Finishing. Also, the Art of Marbling Book-edges- and
Paper. By JAMES B. NICHOLSON. Illustrated. I2ino., cloth $2.2$
NICOLLS.— The Railway Builder:
A Hand-Book for Estimating the Probable Cost of American Rail-
way Construction and Equipment. By WILLIAM J. NiCOLLS, Civil
Engineer, illustrated, full bound, pocket-book form . $2.00
NORMANDY.— the Commercial Handbook of Chemical An-
alysis :
Or Practical Instructions for the Determination of the Intrinsic oi
Commercial Value of Substances used in Manufactures, in Trades,
and in the Arts. By A. NORMANDY. New Edition, Enlarged, and
to a great extent rewritten. By HENRY M. NOAD, Ph.D., F.R.S.,
thick I2mo. $5«oc»
NORRIS. — A Handbook for Locomotive Engineers and Ma-
chinists :
Comprising the Proportions and Calculations for Constructing Loco-
motives; Manner of Setting Valves; Tables of Squares, Cubes, Areas,
etc., etc. By SEPTIMUS NORRIS, M. E. New edition. Illustrated,
I2mo $i. $0
NYSTROM.— A New Treatise on Elements of Mechanics :
Establishing Strict Precision in the Meaning of Dynamical Terms :
accompanied with an Appendix on Duodenal Arithmetic and Me-
trology. By JOHN W. NYSTROM, C. E. Illustrated. 8vo. $2.00
KYSTROM.— On Technological Education and the Construc-
tion of Ships and Screw Propellers :
For Naval and Marine Engineers. By JOHN W. NYSTROM, late
Acting Chief Engineer, U. S. N. Second edition, revised, with addi-
tional matter. Illustrated by seven engravings. I2mo. . #1.50
O'NEILL. — A Dictionary of Dyeing and Calico Printing:
Containing a brief account of all the Substances and Processes in
use in the Art of Dyeing and Printing Textile Fabrics ; with Practical
Receipts and Scientific Information. By CHARLES O'NEILL, Analy-
tical Chemist. To which is added an Essay on Coal Tar Colors and
their application to Dyeing and Calico Printing. By A. A. FESQUET,
Chemist and Engineer. With an appendix on Dyeing and Calico
Printing, as shown at the Universal Exposition, Paris, 1867. 8vo.,
491 pages £3.50
•URTON. — Underground Treasures-.
How and Where to Find Them. A Key for the Ready Determination
of ail the Useful Minerals within the United States. By JAMES
ORTON, A.M., Late Professor of Natural History in Vassar College,
N. Y.; Cor. Mem. of the Academy of Natural Sciences, Philadelphia,
and of the Lyceum of Natural History, New York ; author of the
" Andes and the Amazon," etc. A New Edition, with Additions.
Illustrated * , . < . 11.9
HENRY CAREY BAIRD & CO.'S CATALOGUE.
OSBORN.— The Metallurgy of Iron and Steel:
Theoretical and Practical in all its Branches ; with special reff rencc
to American Materials and Processes. By H. S. O.^BORN, LL. D.,
Professor of Mining and Metallurgy in Lafayette College, Easton,
Pennsylvania. Illustrated by numerous large folding plates and
wood-engravings. 8vo. ...... $25.00
OSBORN. — A Practical Manual of Minerals, Mines and Min~
ing:
Comprising the Physical Properties, Geologic Positions, Local Occur-
rence and Associations of the Useful Minerals; their Methods of
Chemical Analysis and Assay : together with Various Systems of
Excavating and Timbering, Brick and Masonry Work, during Driv-
ing, Lining, Bracing and other Operations, etc. By Prof. H. S.
OSBORN, LL. D., Author of the " Metallurgy of Iron and Steel."
Illustrated by 171 engravings from original drawings. 8vo. $4.50
OVERMAN.— The Manufacture of Steel:
Containing the Practice and Principles of Working and Making Steel.
A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon
Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard-
ware, of Steel and Iron, and for Men of Science and Art. By
FREDERICK OVERMAN, Mining Engineer, Author of the " Manu-
facture of Iron," etc. A new, enlarged, and revised Edition. By
A. A. FESQUET, Chemist and Engineer. I2mo. . . $1.50
OVERMAN. — The Moulder's and Founder's Pocket Guide :
A Treatise on Moulding and Founding in Green-sand, Dry-sand, Loam,
and Cement; the Moulding of Machine Frames, Mill-gear, -Hollow,
ware, Ornaments, Trinkets, Bells, and Statues ; Description of Moulds
for Iron, Bronze, Brass, and other Metals ; Plaster of Paris, Sulphur,
Wax, etc. ; the Construction of Melting Furnaces, the Melting and
Founding of Metals ; the Composition of Alloys and their Nature,
etc., etc. By FREDERICK OVERMAN, M. E. A new Edition, to
which is added a Supplement on Statuary and Ornamental Moulding,
Ordnance, Malleable Iron Castings, etc. By A. A. FESQUET, Chem-
ist and Engineer. Illustrated by 44 engravings. I2mo. . $2.OO
PAINTER, GILDER, AND VARNISHER'S COMPANION;
Containing Rules and Regulations in everything relating to the Ar(S
of Painting, Gilding, Varnishing, Glass-Staining, Graining, Marbling
Sign- Writing, Gilding on Glass, and Coach Painting and Varnishing;
Tests for the Deteciion of Adulterations in Oils, Colors, etc. ; and a
Statement of the Diseases to which Painters are peculiarly liable, with
the Simplest and Best Remedies. Sixteenth Edition. Revised, witli
an Appendix. Containing Colors and Coloring — Theoretical and
Practical. Comprising descriptions of a great variety of Additional
Pigments, their Qualities and Uses, to which are added, Dryers, and
Modes and Operations of Painting, etc. Together with Chevreul's
Principles of Harmony and Contrast of Colors. I2mo. Cloth $1.50
PALLETT.— The Miller's, Millwright's, and Engineer's Guide.
By HENRY PALLETT. Illustrated. I2mo. . . . $2.00
32 HENRY CAREY BAIRD & CO.'S CATALOGUE.
PERCY. — The Manufacture of Russian Sheet-Iron.
By JOHN PERCY, M. D., F. R. S., Lecturer on Metallurgy at th«
Royal School of Mines, and to The Advance Class of Artillery
Officers at the Royal Artillery Institution, Woolwich; Author of
" Metallurgy." With Illustrations. 8vo., paper . . 50 cts,
PERKINS.— Gas and Ventilation :
Practical Treatise on Gas and Ventilation. With Special Relation
to Illuminating, Heating, and Cooking by Gas. Including Scientific
Helps to Engineer-students and others. With Illustrated Diagrams.
By E. E. PERKINS. I2mo., cloth $1.25
PERKINS AND STOWE.— A New Guide to the Sheet-iron
and Boiler Plate Roller :
Containing a Series of Tables showing the Weight of Slabs and Piles
to Produce Boiler Plates, and of the Weight of Piles and the Sizes of
Bars to produce Sheet-iron; the Thickness of the Bar Gauga
in decimals ; the Weight per foot, and the Thickness on the Bar or
Wire Gauge of the fractional parts of an inch; the Weight per
sheet, and the Thickness on the Wire Gauge of Sheet-iron of various
dimensions to weigh 1 12 Ibs. per bundle; and the conversion of
Short Weight into Long Weight, and Long Weight into Short.
Estimated and collected by G. H. PERKINS and J. G. STOWE. $2.50
POWELL— CHANCE— HARRIS.— The Principles of Glass
Making.
By HARRY J. POWELL, B. A. Together with Treatises on Crown and
Sheet Glass; by HENRY CHANCE, M. A. And Plate Glass, by H.
G. HARRIS, Asso. M. Inst. C. E. Illustrated i8mo. . $i.$Q
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HENRY CAREY BAIRD & CO.'S CATALOGUE. 29
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HENRY CAREY BAIRD & CO.'S CATALOGUE, 31
DAVIS. — A Practical Treatise on the Manufacture of Bricks.
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J2 HENRY CAREY BAIRD & CO.'S CATALOGUE.
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ROPER. — The Steam Boiler: Its Care and Management:
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ROSE. — Modern Steam- Engines.
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Giving Full Explanations of the Construction of Modern Steanv
Engines : Including Diagrams showing their Actual operation. To-
gether with Complete but Simple Explanations of the operations of
Various Kinds of Valves, Valve Motions, and Link Motions, etc.,
thereby Enabling the Ordinary Engineer to clearly Understand the
Principles Involved in their Construction and Use, and to Plot out
their Movements upon the Drawing Board. By JOSHUA ROSE. M. E.
Illustrated by 422 engravings. 410., 320 pages . . $6.00
HOSE. — Steam Boilers:
A Practical Treatise on Boiler Construction and Examination, for the
Use of Practical Boiler Makers, Boiler Users, and Inspectors; and
embracing in plain figures all the calculations necessary in Designing
or Classifying Steam Boilers. By JOSHUA ROSE, M. E. Illustrated
by 73 engravings. 250 pages. 8vo #2.<jO
SCHRJBER.— The Complete Carriage and Wagon Painter :
A Concise Compendium of the Art of Painting Carriages, Wagons,
and Sleighs, embracing Full Directions in all the Various Branches,
including Lettering, Scrolling, Ornamenting, Striping, Varnishing,
and Coloring, with numerous Recipes for Mixing Colors. 73 Illus-
trations. 177 pp. I2mo. . . . . . . $1.00
VAN CLEVE.— The English and American Mechanic :
Comprising a Collection of Over Three Thousand Receipts, Rules,
and Tables, designed for the Use of every Mechanic and Manufac-
turer. By B. FRANK VAN CLEVE. Illustrated. 500 pp. I2tno. $2.00
WAHNSCHAFFE. — Guide for the Scientific Examination of
the Soil :
By Dr. FELIX WAHNSCHAFFE. Translated from the German by
WILLIAM T. BRANNT. Illustrated by numerous Engravings. 8vc .
(In preparation.^
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Rif fault des Hetres, J.R.D. R56
A practical treatise
on the manufacture of
colors for painting.
PHYSICAL
SCIENCES
LIBRARY
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LIBRARY
UNIVERSITY OF CALIFORNIA
_ DAVIS
Rif fault des H£tres,
J.R.D.
A practical treatise
Call Number:
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R56
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