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I 




Uiemical Ubraq 

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/ 






HANDBOOK ^* ' 






OF 



CHEMICAL TECHNOLOGY 



BY 



RUDOLF WAGNER, PH.D., 

PROFESSOR OF CHEMICAL TECHNOLOGY AT THE UNIVERSITY OF WURT2BURG. 



Translated and Edited from the Eighth German Edition, 

with extensive additions, 

BY 

WILLIAM CROOK ES, F.R.S. 



WITH 336 ILLUSTRATIONS. 



LONDON: 
J. & A. CHURCHILL, NEW BURLINGTON STREET. 

1872. 



/ uO 37 



LONDON: 

PRINTED AT THE CHEMICAL NEWS OFFICE, 

BOY COURT, LUDOATK HILL, B.C. 



TRANSLATOR'S PREFACE. 






The several Editions of Professor Rudolf Wagner's " Handbaoh der ChemiBchen 
Technologie" have succeeded each other so rapidly that no apology is needed in 
offering a translation to the public. 

There is little to be said as to the arrangement. Improvements in Technological 
processes that have appeared since the publication of the Eighth Grerman Edition 
have been added during translation. Only when necessary have Foreign weights 
and measures been stated in English equivalents ; where the point has been one of 
comparison, the weights have been left unaltered. The Metrical System has in 
some cases been of great service in avoiding the repetition of tiresome distinctions 
between English and Prussian grain weights, English and Bavarian foot measure, 
Ac. The formulsd have been subjected to careful revision, and are molecular 
throughout Indeed, every care has been taken to merit the confidence of the 
manu£Ekcinrer and of the student. 

Under the head of Metallurgical Chemistry, the latest methods of preparing Iron, 
Cobalt, Nickel, Copper, Copper Salts, Lead and Tin and their Salts, Bismuth, Zinc, 
Zinc Salts, Cadmium* Antimony, Arsenic, Mercury, Platinum, Silver, Gold, Man- 
ganates. Aluminum, and Magnesium, are described. The various applications of 
the Voltaic Current to Electro-Metallurgy follow under this division. The Prepara- 
tion of Potash and Soda Salts, the Manufacture of Sulphuric Acid, and the Recovery 
of Sulphur from Soda- waste, of course occupy prominent places in the consideration 
of chemical manufiu^tores. It is difficult to over-estimate the mercantile value of 
Mond's process, as well as the many new and important applications of 
Bisulphide of Carbon. The Manufacture of Soap will be found to include much 
detail. The Technology of Glass, Stoneware, limes, and Mortars, will present 
much of interest to the builder and engineer. The Technology of Vegetable Fibres 
has been considered to include the preparation of Flax, Hemp, Cotton, as well 
as Paper Making ; while the applications of Vegetable Products will be found 
to include Sugar-boiling, Wine and Beer Brewing, the Distillation of Spirits, 
the Baking of Bread, the Preparation of Vinegar, the Preservation of Wood, Ac. 



iv TRANSLATOR'S PREFACE, 

Dr. Waomeb gives mnch information in reference to the production of Potash 
from Sugar residues. The use of Baryta Salts is also fully described, as well as the 
Preparation of Sugar from Beet-roots. Tanning, the Preservation of Meat, Milk, 
Ac., the Preparation of Phosphorus and Animal Charcoal, are considered as 
•belonging to the Technology of Animal Products. The Preparation of the Materials 
for Dyeing has necessarily required much space ; while the final sections of the 

• 

book have been devoted to the Technology of Heating and Illumination. 

We cannot let this work pass out of our hands without expressing the hope 
that, at no distant date. Chairs of Technology will be founded in all our Univer- 
sities, and that the subject will be included in the curriculum of every large school. 

LoHDOH, May, 1872. 



AUTHOB'S PREFACE TO THE EIGHTH EDITION. 



The Eighth Edition of mj ** Chemischen Technologie'* having followed the Seyenth 
within two years, but few words of introdaetion are necessary. 

The arrangement of the snbject-matter in former Editions has essentially been 
left unaltered, with the exceptions that I have brought the consideration of the 
materials and products of Chemical Industry, and the Technology of Glass and of 
Stoneware, in former Editions arranged as one section, under distinct headings. 
The Tarious processes of Chemical Manufeuiture have had much detail added. The 
descriptions of the Technological Preparation of Alkali and Ammoniacal Salts, 
as well as of the Tar-colours, have in consequence of the extended application 
of these products, been much enlarged. The Chemical formuha are molecular 
throughout 

Of the present Edition translations will be made into EInglish by Mr. William 
Crookes, of London, and into French by Professor L. Gautier, of Melle, Deux- 
Sevres. A translation into Dutch of part of the Seventh Edition that has reoentiy 
appeared has been made without my permission or that of my publishers. 

The First Edition of this work, written whilst I held the position of Private Tutor 

in Chemistry to the Philosophical Faculty to the High- School of Leipsic, appeared 

in September, 1850. The Second in May, 1853, and the Third Edition in July, 

1856, were presented to the puUio during my Professorship of Technological 

Chemistry in the Imperial Industrial Schools of Nuremburg. The later Editions 

appeared — 

The Fourth in May, 1859, 

Fifth in May, 1862, 

Sixth in Octobw, 1865, 

„ Seventh in Bfarch, 1868, 

during intervals in my official duties in Wurtzburg ; and in these I have been much 
assisted by the contributions and suggestions of many friends, to whom I now tender 
my sincere thanks. 

Db. RUDOLF WAGNER. 
Unitebsitt of Wubtzbubo, 
December lotht 1870. 



»» 



I* 



CONTENTS. 



DIVISION I. 

CHEMICAL METALLURGY, ALLOTS, AND PREPARATIONS MADE AND OBTAINED FROM 

METALS. 

Gkxxral Obsebtations. — Meaning of the term Metallurgy, 4. Ores, 4. Dressing of 
Ores, 5. Preparation of Ores, 5. Smelting of the Ores, 6. The Mixing of the 
Smelt, 7. Products of the Smelting Operation, 7. Slags, 7. 

Ibox. — ^Its Occurrence, 8. 

Pig OB Cbitdb Ibon. — Extraction of Iron from its Ores, 9. Theory of the Iron Extraction 
Process, 10. Blast-furnace Process, 10. Description of the Blast-furnace, 11. The 
Blowing Engine and Blast, 12. Course of the Smelting Process, 13. Chemical Pro- 
cess going on in the Interior of the Blast-furnace, 13. Temperature in the Blast- 
furnace at Different Points, 15. Blast-furnace Gases, 15. Application of these 
Oases to the Manufacture of Sal-ammoniac, 16. Crude Iron, Cast-iron, 16. White 
Cast-iron, 16. Grey Cast-iron, 16. Statistics concerning the Production of Crude 
Iron, 18. Iron Foundry Work — Be-smelting Crude Cast-iron, 18. Shaft or Cupola 
Furnace, z8. Beverberatory Furnace, 18. Making the Moulds, 19. Annealing, 
Tempering, 20. Enamelling of <3a8t-iron, 20. 

MA1.T.F.ABIJE, Bab, OB Wbouoht-Ibon. — ^Bar Iron, Refined Iron, 20. German Iron-refining 
Process, 21. Swedish Befining Process, 22. The Puddling Process, 22. Puddling 
Furnace, 22. Heating with Gases, 24. Befining of Iron by Mechanical Means, 24. 
Boiler-plate Boiling, 24. Iron Wire Manufacture, 25. Properties of Bar Iron, 26. 

Btbxl. — Steel, 26. Bough Steel, 27. Steel Making by Imparting Carbon to Wrought- 
iron, 28. Befined Steel, Shear Steel, 29. Cast-steel, 29. Steel made from Malleable 
and Crude Cast-iron, 29. Surface Steel Hardening, 29. Properties of Steel, 29. 
Tempering, 30. Steel and other Metals, 30. Damascene or Wootz Steel, 30. Sidero- 
graphy or Steel Engraving, 31. Statistics of Steel Production, 31. 

Ibom Pb^pabatioms. — Coppera8--Green Vitriol, 31. Preparation of Green Vitriol as a By- 
product in Alum Works, 32. Preparation of Green Vitriol in Beds, 32. Green 
Vitriol from the Besidues of Pyrites Distillation, 32. Green Vitriol from Metallic 
Iron and Sulphuric Acid, 32. F'rom Spathic Iron Ore, 32. Uses of Green Vitriol, 32. 
Iron Minium, 32. Yellow Prussiate of Potassa, 33. Applications of the Yellow 
Prussiate, 35. Bed Prussiate, 35. Cyanide of Potassium, 35. Berlin Blue, 36. Old 
Method of Preparing Prussian Blue, 36. Becent Methods of Preparing Berlin Blue, 
36. Tnmbull's Blue, 37. Berlin Blue as a By-product of the Manufactures of Coal- 
gas and Animal Charcoal, 37. Soluble Berlin-Blue, 37. 

Cobalt. — Metallic Cobalt, 37. Cobalt Colours, 371 Smalt, 38. Cobalt Speiss, 38. Appli- 
cations of Smalt, 38. Cobalt Ultramarine, 38. Caeruleum, 39. Binmann's or Cobalt 
Green, 39. Chemically pure Protoxide of Cobalt, 39. Nitrate of Protoxide of 
Cobalt and Potassa, 39. Cobalt Bronze, 39. 

MiCBEL. — Nickel and its Ores, 39. Preparation of Nickel from its Ores, 40. The Concen- 
tration-Smelting of the Nickel Ores, 40. Preparation of Metallic Nickel, or of Alloys 
of Nickel and Copper, 41. Properties of Nickel, 43. 

CopPBB. — Where it Occurs, and How, 43. Ores of Copper, 43. Mode of Treating the 
Copper Ores for the Purpose of Extracting the Metal, 44. The Working-up of the 
Copper Ores in the Shaft Furnace, 44. Befining the Copper, 46. Befining on the 
Hetfth, 46. Befining Copper in Large Quantities, 46. Liquation Process, 47. 
English Mode of Copper Smelting, 47. Calcining or Boasting the Ores, 48. Smelting 
the Ores, 48. Boasting or Calcining the Coarse Metal, 49. Smelting for Wbite 
Metal, 49. Blistered or Crude Copper, 49. Befining the Blistered Metal, ^9. Mode 
of Obtaining Copper from Oxidised Ores, 49. Hydro-Metallurgical Method of Prepa- 
ring Copper, 49. Copper obtained by Voltaic Electricity, 50. Properties of Copper, 
50. Alloys of Copper, 51. Bronze, 51. Brass, 52. German or Nickel Silver, 53. 
Amalgam of Copper, 54. 



▼iii • CONTENTS. 

Pbepabitionb or Ooppeb. — ^Blne Vitriol, Snlphate of Copper, 54. Preparation of Blue 
Vitriol, 54. Doable Vitriol, 55. AppHoations of Blue Vitriol, 56. Copper Pigments, 56. 
Brouswiok Chreen, 56. Bremen Blue or Bremen Green, 56. Casaelmann's Green, 57. 
Mineral Green and Bine, 57. Oil Bine, 57. Schweinfurt Green or Emerald Green, 
58. Stannate of Oxide of Copper, 58. Verdigris, 58. Applications of Verdigris, 59. 

Lead. — Occnrrenoe of Lead, 59. Method of Obtaining Lead hj Precipitation, 59. 
Obtaining Lead by Calcination, 60. Baw Lead, 61. BoTivification of Litharge, 6z. 
Properties of Lead, 62. Applications of Metallic Lead, 62. Mannfactnre of Shot, 63. 
Alloys of Lead, 62. 

Pbbpabationb of Lead. — Oxide of Lead, 63. Massicot, 63. Mininm, Bed-lead, 63. 
Superoxide of Lead, 64. Combinations of Oxide of Lead, 64. Aoetaie of Lead, 64. 
Chromate of Lead, 64. Neutral or Yellow Chromate of Potassa, 64. Applications of 
the Chromates of Potassa, 65. Chrome Yellow or Chromate of Lead, 6(5. Chrome 
Bed, 66. Chrome Oxide or Chrome Green, 67. Chrome Alum, 67. TVliite-lead, 67. 
English Method of Manufacturing White-lead, 68. French Method of Preparing White- 
lead, 69. Apparatus used in White-lead Manufacture at Clichy, 69. White-lead from. 
Sulphate of Lead, 70. Theory of Preparing White-lead, 70. White-lead from Chloride 
of Lead, 70. Basic Chloride of Lead as a Substitute for White-lead, 71. Properties of 
White-lead, 71. Adulteration of White-lead, 72. Applications of White-lead, 72. 

Tnv. — Occurrence and Mode of Obtaining the Metal, 73. Properties of Tin, 74, 
Tinning, 75. Tinning of Copper, Brass, and Malleable Iron, 75. Tinned Sheet-iron, 
75. Moir^ Metallique, 75. 

Pbepabations 07 Tin. — Aurum MusiTum, Mosaic Gold, 75. Tinsalt, 75. Nitrate of 
IHn or Physic, 76. Stannate of Soda, 76. 

BisxuTH. — Occurrence and Mode of Obtaining, 76. Bismuth Idquation-Fumaee, 76. 
Properties of Bismuth, 77. Applications of Bismuth, 77. 

Zinc. — Occurrence of Zinc, 77. Method of Extracting Zinc, 77. Distillation of Zinc in 
Muffles, 78. Distillation in Tubes, 79. Distillation of Zinc in Crucibles, 79. Mode 
of Obtaining Zinc from Sulphuret of Zinc, the Bl&ok-Jack of the English Mhiers, 79. 
Properties of Zinc, 79. Application of Zinc, 80. 

Pbepabations of Zinc. — Zinc- white, 80. White Vitriol, Sulphate of Zinc, 81. Chromate 
of Zinc, 81. Chloride of Zinc, 81. 

CADMirif, 82. 

Antimony. — Antimony, 82. Properties of Antimony, 84. 

Antikonial Pbepabations^ in Technical Use. — Oxide of Antimony, 84. Black Snlphnret 
of Antimony, 85. Neapolitan Yellow, 85. Antimony Cinnabar, 85. 

Absenio. — Arsenic, 85. Arsenious Acid, 85. Arsenic Acid, 86. Sulphurets of Arsenic, 
86. Bealgar, 87. Orpiment, 87. Busma, 87. 

QuiOKSiLyEB OB Mebctjbt. — Occurrence and Mode of Obtaining Mercury, 87. Method of 
Extracting Mercury pursued'in Idria, 87. Spanish Method of Extracting Mercury, 
89. Method of Decomposing the Ore by the Aid of other Substances, 90. Proper- 
ties of Mercury, gi. Applications of Mercury, 91. 

Pbepabations of Mebcubt. — Mercurial Compounds, 91. Chloride of Mercury, 91. Cin- 
nabar, 91. Fulminating Mercury, 92. Percussion-Caps, 93. 

Platinum. — Occurrence of Platinum, 93. Platinum Ores, 93. Wollaston's Method of 
Extracting Platinum from its Ores, 94. Method of Deville and Debray, 95. Proper- 
ties of Platinum, 95. Black Platinum, Spongy Platinum, 95. Hammered or Cast 
Platinum, and its Applications, 95. , Platinum Alloys, 96. Elayl-platino-chloride, 96. 

SiLYEB. — Silver and its Occurrence, 96. Extraction of Silver from its Ores, 96. Smelting 
for Silver directly, 97. Extraction of Silver by Amalgamation, 97. European 
Amalgamation Process, 97. American Amalgamation Process, 98. Augustin's 
Method of Silver Extraction, 99. ZiervogeVs Method, gg. Sundry Hydro-Metallur- 
gical Methods of Extracting Silver, 99. Extraction of Silver by the Dry Process, 100. 
Mode of Preparing the Lead-containing Silver, 100. Befining Process, 100. Pattin- 
8on*s Method, loi. Beduction by Means of Zinc, 102. The Ultimate Befining of 
Silver, 102. Chemically Pure Silver, 102. Properties of Silver, 102. Alloys of 
Silver, 103. Silver Alloy for Plate, <^c., 103. Silver Assay, 103. Dry Assay, 103. 
Wet Assay, 104. Hydrostatical Assay, 104. Silvering, 104. Igneous or Fire 
Silvering, 104. Silvering in the Cold, 104. Silvering by the Wet Way, 105. 
Nitrate of Silver, 105. Marking Ink, 105. 

Gold. — Occurrence and Mode of Extracting Gold, 105. Mode of Extracting Gold, 105, 
Extraction by Means of Mercury, 106. Smelting for Gold, 106. Treating with 
Alkali, 106. Extraction of Gold from other Metallic Ores, 106. Extraction of Gold 
from Poor Minerals, 106. Befining Gold, to6. By Means of Sulphuret of Antimony, 
106. By the Aid of Sulphur, 107. Cementation Process, 107. Quartation, 107. 



CONTENTS. ix 

Befimng Gold by the Aid of Snlphnrio Add, 107. ChemicftUy Pare Gt>ld, 108. Pro- 
perties of Gold, Z08. Alloys of Gold, 109. Colour of Gold, 109. Testing the Fine- 
ness of Gold, 109. Applications of Gold, no. Gilding, no. (Hiding with Gold- 
leaf, no. Gilding by the Cold Prooess, no. Gilding by the Wet Way, no. Rre- 
gilding, no. CassiuB's Pnrple, in. Salts of Gold, in. 

Manganxse A2n> rrs Pbbpabationb. — ^Manganese, in. Testing the Quality of Manganese, 
ni. 

PKSiCAjiaANATX ow PoTABSA.— Permanganate of Potassa, 112. 

AiiUKiHinif. — Preparation of Aluminium, 113. Properties of Aluminium, 113. Applica- 
tions, 114. 

Maohssium. — Magnesium, 114. 

Electbo-Mbtallubot. — ^Application of Galvanism, 114. Electrolytic Law, 114. Electro- 
typing, 115. Reproduction of Copper-plate Engravings, 115. Deposition of Metals, 
115. Electro-plating with Gold and Silver, 115. Gold Solution, 116. Silver Solu- 
tion, 116. Copper Solution, 116. Zinc and Tin Solution, 116. Etching by Gal- 
vanism, 117. MetaUochromy, 117. Electro-stereotyping, 117. Glyphography, 117. 
Galvanography, 117. 

DIVISION II. 

CBUDE MATEBIALS AND PBODUCTS OF CHEMICAL U^DUSTBT. 

Cabbokatx of Potassa. — Sources whence Potassa is Perived, 118. Potassa Salts from the 
Stassfurt Salt Minerals, 118. Mode of Obtaining Potassa from Felspar, 122. 
Potassa Salts from Sea-water, 122. Potash from the Ashes of Plants, 122. Potash 
from Molasses, 125. Potassa Salts from Sea-weeds, 129. Potassa Salts from Suint, 
132. Caustic Potassa, 133. 

Saltpktbe, Nitbate of Potassa. — Saltpetre, 134. Occurrence of Native Saltpetre, 134. 
Mode of Obtaining Saltpetre, 135. Treatment of the Bipe Saltpetre Earth, 135. 
Preparation of Baw Lye, 136. Breaking up the Baw Lye, 136. Boiling down the 
Baw Lye, 136. Befining the Crude Saltpetre, 137. Preparation of Nitrate of 
Potassa from Chili Saltpetre, 138. Testing the Saltpetre, 140. Quantitative Estima- 
tion of the Nitric Acid in Saltpetre, 140. Uses of Saltpetre, 141. Nitrate of Soda, 141. 

NiTBic AoiD. — Methods of Manufacturing Nitric Acid, 142. Bleaching Nitric Acid, 143. 
Condensation of the Nitric Acid, 144. Other Methods of Nitric Acid Manufacture, 145. 
Density of Nitric Acid, 146. Fuming Nitric Acid, 147. Uses of Nitric Acid, 147. 

TsCHNOIiOaY OF THE EXPLOSIVE COMPOUNDS — ^GUNPOWDBB, AKD THE ChEMIBTBY OF FiBEWOBXS, 

OB Pyrotechny. — On Gunpowder in General, 148. Manufacture of Gunpowder, 148. 
Mechanical Operations of Powder Manufacture, 149. Pulverising the Ingredients, 

149. Mixing the Ingredients, 149. Caking or Pressing the Powder, 150. Granula- 
tion of the Cake and Sorting the Powder, 150. Polishing the Granulated Powder, 

150. Prying the Powder, 151. Sifting the Dust from the Powder, 151. Properties 
of Gunpowder, 151. Composition of Gunpowder, 152. Products of the Combustion 
of Powder, 153. New Kinds of Blasting Powder, 154. Testing the Strength of Gun- 
powder, 154. White Gunpowder, 154. Chemical Principles of Pyrotechny, 155. 
The more commonly used Firework Mixtures, 156. Gunpowder, 156. Saltpetre and 
Sulphur Mixture, 156. Grey-coloured Mixture, 156. Chlorate of Potassa Mixtures, 
156. Friction Mixtures, Percussion Powders, 156. Mixture for Igniting the Cart- 
ridges of Needle-guns, 15^. Heat-producing Mixtures, 157. Coloured Fires, 157. 

NiTBOGLYCBBiNE. — Nitroglycennc, 158. NobePs Dynamite, 160. 

GuE-corroN. — Gun-cotton, 160. Properties of Gun-cotton, 161. Gun-cotton as a Substi- 
tute for Gunpowder, 162. Other Uses of Gun-cotton, 162. Collodion, 162. 

Common Salt.— Occurrence, 163. Method of Preparing Common Salt from Sea- water, 163. 
Method of Obtaining Common Salt in Salines, 164. By Freezing, 165. By Artificial 
Evaporation, 165. Bock-salt, 165. Mode of Working Bock-salt, 167. Mode of 
Working Salt Springs, 167. Preparation of Common Salt from Brine, 168. 
Concentrating the Brine, 168. Enriching by Gradation, 168. Faggot Gradation, 168. 
Boiling down ike Brine, 168. Properties of Conmion Salt, 169. Uses of Common 
Salt, 170. 

Mavufactube OF Soda — Native Soda. — Occurrence of Native Soda, 170. 

Soda fbom Plants ob Soda- Ash. — Soda from Soda Plants and from Beet-root, 171. 

Soda Pbepabed by Chemical Pbocessbs. — Soda from Chemical Processes,'i72. Leblanc's 
Process, 172. Sulphate or Decomposing Furnace, 172. New Decomposition Fur- 
nace, 173. Conversion of the Sulphate into Crude Soda, 174. Soda Furnace with 



X CONTENTS. 

Rotatory Hearth, 175. liziviation of the Crude Soda, 176. Evaporation of the 
Ley, 180. Theory of Leblanc's Process, 183. Utilisation of Soda Waste, 184. 
Sohaffner'B Sulphur Begeneration Process, 185. Sundry Methods of Preparing Soda 
from Sulphate of Soda, 187. Direct Conversion of Common Salt into Soda, t88. 
Soda from Cryolite, 188. Soda from Nitrate of Soda, 189. Caustic Soda, 189. New 
Methods of Caustic Soda Manufacture, 189. Bicarbonate of Soda, 190. 

pBBPiiuLTioN OF loDiNE AND Bbomine. — Preparation of Iodine, 191. Fteparation from 
Kelp, 191. Stanford and Moride^s Method of Preparing Iodine from Carbonised Sea- 
weed, 192. Preparation of Iodine ffom Chili Saltpetre, 192. Properties and Uses of 
Iodine, 193. Preparation of Bromine, 193. 

SuLPHUi. — Sulphur, 194. Smelting and Befimng Sulphur, 194. Lamy's Bcfining Appa- 
ratus, 196. Boll Sulphur, 197. Flowers of Sulphur, 197. Preparation of Sulphur 
from I^^tes, 197. Preparation of Sulphur by Boasting Copper Pyrites, 198. Sul- 
phur obtained as a By-product of Gas Manufacture, 198. Sulphur from Soda- 
Waste, 198. Production of Sulphur by the Beaction of Sulphuretted Hydrogen upon 
Sulphurous Acid, 198. Sulphur obtained by the Beaction of Sulphurous Acid on 
Charcoal, 198. By Heating of Sulphuretted Hydrogen, 198. Properties and Uses of 
Sulphur, 199. 

SiJLPHUBOus AKD Htposulphuboub Acio. — Sulphurous Acid, 199. Sulphite of Lime, 201. 
Hyposulphite of Soda, 201. 

Makufactube of Sulphubic Acm. — Sulphuric Acid, 201. Fuming Sulphuric Acid, 202. 
Ordinary or English Sulphuric Acid, 203. Present Manufacture of Sulphuric Acid, 
203. Use of Pyrites for the Preparation of Sulphurous Acid, 206. Chamber Add, 
206. Concentration of Sulphuric Acid, 206. Concentration in Leaden Pans, 207. 
Concentration in Glass Betorts, 208. Other Methods of Sulphuric. Acid Manufac- 
ture, 208. Properties of Sulphuric Acid, 209. 

Sulphide of Cabbon. — Sulphide of Carbon, 210. Carbon, 211. Chloride of Sulphur, 211. 

Htpbochlobig Acid amd Glaubbb's Salt, ob Sulphate of Soda. — Hydrochloric Acid, 211. 
Properties of Hydrochloric Acid, 213. Uses of Hydrochloric Acid, 213. Glauber's 
Salt, 2x3. Uses of Sulphate of Soda, 214. Bisulphate of Soda, 214. 

Blsachino-powdeb and Hypochlobites. — Chlorine, 214. Preparation of Bleaching- 
powder, 214. Preparation of Chlorine without Manganese, 214. Apparatus for Pre- 
paring Chlorine, 216. Condensing Apparatus, 217. Utilisation of the Chlorine 
Production Besidues, 218. Dunlop's Process, 218. Gatty's Process, 219. Hofmann*s 
Process, 219. Weldon's Process, 219. Other Methods of Utilising the Besidues, 219. 
Theory of the Formation of Bleaching-powder, 220. Properties of Bleaching- 
powder, 220. Chlorimetry, 221. Gay-Lussac's Chlorimetrio Method, 221. Perrot's 
Test, 221. Dr. Wagner's Method, 222. Chlorimetrical Degrees, 222. Alkaline 
Hypochlorites, 223. Chlorate of Potassa, 223. 

AiiKALiMETBT. — Alkalimetry, 224. Volumetric Method, 224. Mohr's Method, 225. 
Gruneberg's Method of Estimating the Value of Potash, 226. 

Ajcm GNU AKD Ammonuoal Salts. — ^Ammouia, 226. Preparation of Liquid Ammonia, 227. 
Inorganic Sources of Ammonia, 228. Organic Sources of Ammonia, 229. Ammoma 
from Gas-water, 230. Mallet's Apparatus, 230. Bose's Apparatus, 232. Lunge's 
Apparatus, 232. Ainmonia from Lant, 234. Ammonia from Bones, 235. Ammonia 
as a By-product of Beet-root Sugar Manufacture, 236. Technically Important 
Ammoniacal Salts, 236. Sulphate of Ammonia, 238. Carbonate of Ammonia, 238. 
Nitrate of Ammonia, 238. 

Soap Maeimo.— Soap, 239. Baw Materials of Soap Boiling, 239. Ley, 242. Theory of Saponi- 
fication, 242. Chief Varieties of Soap, 243. Olive Oil Soap, 244. Oleic Acid Soap, 245. 
Besin Tallow Soaps, 245. Fulling Soaps, 245. Soft Soap, 246. Various other 
Soaps, 247. Toilet Soaps, 247. Transparent Soap, 248. Uses of Soap, 248. Soap 
Tests, 248. Insoluble Soap, 249. 

BoBio oB BoBAcic AciD, AMD BoBAX. — Theory of the Formation of the Native Boracic Acid, 

250. The Production of Boracic Acid, 250. Properties and Uses of Boracic Acid, 

251. Borax, 252. Borax from Boracic Acid, 252. Purifyiog the Borax, 254. Octa- 
hedral Borax, 255. Uses of Borax, 255. Diamond Boron or Adamantine, 256. 

Pboduction of Alum, Sulphates of Alumina, and Aluminates. — Alum, 256. Material of 
Alum Manufacture, 256. Preparation of Alum from Alum-stone, 257. Preparation 
of Alum from Alum-shale and Alum-earths, 257. Alum-shale, 257. Alum-earths, 

257. Preparation of Alum, 257. Boasting the Alum-earths, 257. LizLviation, 257. 
Evaporation of the Ley, 257. Alum Flour, 258. Washing and Be-crystaUisation, 

258. Preparation of Alum from Clay, 258. Preparation of Alum from Cryolite, 258. 
Preparation of Alum from Bauxite, 259. Preparation of Alum from Blast-furnace 
Slag, 260. Alum from Felspar, 260. Properties of Alum, 260. Ammonia-alum, 260. 



CONTENTS. xi 

SodA-almn, 261. Sulphate of Alnxnina, 261. Alnminate of Soda, 262. Uses of 
Alum and of Sidphate of Alumina, 263. Acetate of Alumina, 263. 
UuTBAMABiMB. — ^Ultramarine, 26a. Native Ultramarine, 264. AriiificifJ Ultramarine, 264. 
Baw Materials, 264. MannfaotTire of Ultramarine, 265. Preparation of Soda Ultra- 
marime, 266. Preparation of Silica Ultramarine, 267. Oonstitntion of Ultramarine, 
367. Proporties of Ultramarine, 267. 



DIVISION m. 

TBCHNOLOOY OF 0LAS8, OEBAMIC WARE, OYPSUM, LIME, AND MORTAB. 

Glass I^anufaotubb. — Definition and Qeneral Properties of Glass, 268. Glassifioation 
of the Yarions Kinds of Qlass, 268. Baw Materials used in Glass Making, 269. 1 
Utilisation of Befose Glass, 270. Bleaching, 2^0. The Melting Vessel, 270. The 
Glass Oren, 271. Preparation of the Material, and Melting, 274. Drying the 
Materials, 274. Melting the Glass Material, 275. Clear-melting, 275. Gold-stoking, 

275. Defects in Glass, 276. Various Kinds of Glass« 276. Plate or Window Glass, 

276. Tools, 277. Crown Glass, 277. Sheet Glass or Cylinder Glass, 278. Plate 
Glass, 2^9. The Melting and Clearing, 280. Casting and Cooling, 281. Polishing, 
281. Silvering, 281. SUvering by Precipitation, 281. Platinising, 282. Bottle 
Glass, 282. ^ssed and Cast-glass, 283. Water-glass, 283. Stereochromy, 285. 
Crystal Glass, 285. Polishing, 286. Optical Glass, 286. Strass, 288. Coloured 
Glass and Glass Staining, 289. Glass Painting, 289. Enamel, Bone Glass, Alabaster 
Glass, 290. Cryolite Glass, 291. Ice Glass, 291. Hssmatinon Astralite, 291. Ayen- 
turin Glass, 291. Glass Belief, 291. Filigree, or Beticulated Glass, 292. Millifiore 
Work, 292. Glass Pearls, 292. Blown Pearls, 292. Hyalography, 292. 

CsBAKic OB Eabthenwabb Manxtfaotubb. — Clays and their Application — ^Felspar, 293. 
Kaolin or Porcelain Clay, 293. The Technically Important Quidities of the Clays, 293. 
Colour, 294. Plasticity, 294, Kinds of Clay, 294. Potter's Clay, 295. Walkerite, 
295. Marl, 295. Loam, 29*6. Composition of Kaolin, 296. Kinds of Clay Ware, 296. 

L Habd Pobcblain. — Grindbig and Mixing the Material, 297. Drying the Mass, 298. 
Kneading the Dried Mass, 298. The Moulding, 298. The Potter's Wheel, 298. 
Moulding in Plaster-of-Paris Forms, 299. Casting, 299. Preparation of Porcelain 
Articles without Moulds, 299. Glazing, 299. Drying the Porcelain, 299. Porcelain 
Glaze, 300. Applying the Glaze, 300. Immersion, 300. Dusting, 300. Watering, 
300. By Volatilisation or Smearing, 300. Lustres and Flowering Colours, 301. The 
Capsule or Sagger, 301. The PorcelaLi Oren, 301. Emptying the Oren and Sorting 
the Ware, 302, Faulty Ware, 302. Porcelain Painting, 302. Ornamenting the Por- 
eelain, 303. Bright Gilding, 303. Silvering and Platioicdng, 303. Lithophanie, 303. 

n. Tbbdbb Pobcblain. — ^French Fritte Poroelidn, 304. English Fritte Porcelain, 304. 
Parian and Carrara, 304. 

nL Stokewabb* — Stoneware, 305. Stoneware Ovens, 306. Lacquered Ware, 307. 

IV. Fayxnob Wabe. — ^Fayence Ware, 307. Ornamenting Fayence, 308. Flowing Colours, 
309. Lustres, 309. Etruscan Vases, 309. Clay Pipes, 309. Water Coolers, 309. 

V. Coiocoir PoTTBBY.--Common Pottery, 310. Burning, 310. 

VL Bbick AMD Tile Making, <fec. — ^Bricks, 310. Terra Cotta, 311. Brick Material, 311. 
Preparation of the Clays, 311. Moulding the Brick, 312. Brick Moulding by 
Machinery, 312. Bricks from Dried Clay, 314. The Burning of the Bricks, 315. 
Annular Kilns, 317. Field Burning, 318. Dutch Clinkers, 318. Boofing and Dutch 
Tiles, 318. I^rain and Gutter Tiles, 318. Floating Bricks, 318. Fire-bricks, 319. 
Sanitai^ Ware, 321. Crucibles, 321. 

Idxx AND LncE-BuBNnfo. — ^Lime, 322. Properties, 322. Lime-Burning, 322. Occasional 
or Periodic Kilns, 323. The Continuous Kilns, 324. Kilns for Burning' Lime and 
Bricks, 325. Properties of Lime, 325. Slaking Lime, 326. Uses of Lime, 326. 

MoBTAB. — Mortar, 326. 

A. GoMifON OB Aib-Sbttino Mobtab. — Setting of the Mortar, 327. 
' B. Htdbaulio Mobtab. — ^Hydraulic Mortar, 327. Cement, 327. Artificial Cements, 328. 
Manufacture of Axtifioial Cement in Germany, 330. The Setting of Hydraulic 
Mortars, 331. 

GiFSUM AND rrs Pbepabation.— Occurrence, 333. Nature of Gypsum, 333. The Burning 
of Gypsum, 333. Kilns or Burning Ovens, 334. Grinding the Gypsum, 335. Uses 
of Gypsum, 335. Gypsum Casts, 336. Hardening of Gypsum, 336. 



xii CONTENTS, 



DIVISION IV. 

VEGETABLS FIBRES AND THEIR TECHNICAL APPUCATION. 

The Tschnoloot of Veostablb Fibre — FLAX.~Flax, 338. Hot Water Cleansixig, 339. 
Beating or Batting the Flax, 339. Combing the Flax, 340. Tow or Tangled Fibre, 
340. Flax Spinning, 340. Weaving the linen Threads, 340. Linen, 340. 

Heup. — ^Hemp, 340. Its Snbstitntes, 340. 

Cotton. — Cotton, 342. Species of Cotton, 342. Cotton Spinning, 342. Fin& Spinning, 
343. Tarn, 343. Cotton Fabrics, 343. Sabstitntes for Cotton, 343. Detecting 
Cotton in Linen Fabrics, 343. 

Paper Masino. — Histoiy of Paper, 345. Materials of Paper Mannfaotore, 346. Sab- 
stitnte for Bags, 346. Mineral Additions to the Bags, 346. Manufacture of Paper by 
Hand, 346. Cntting and Cleaning the Bags, 347. The Separation of the Bags for 
Half-stofr and Whole-stuff, 347. Stamp Machine, 347. The Hollander, 347. 
Bleaching the Pulp, 349. Anticblore, 349. Blaeing, 350. Sizing, 350. 

A. Hand Paper. — Straining the Paper Sheets, 350. Pressing the Paper, 351. Drying the 

Paper, 351. Sizing the Paper, 351. F^eparing the Paper, 351. The Different 
Kinds of Paper, 351. 

B. Machine Paper. — Manufacture of Machine Paper, 352. Paper Cutting Machine, 353. 

C. Pasteboard and Other Paper. — Making Pasteboard, 353. Coloured Paper, 355. 

Parchment Paper, 355. 

Starch. — Nature of Starch, 356. Sources of Starch, 357. Starch from Potatoes, 357. 
Drying the Potato Starch, 358. Preparation of Wheat Starch, 358. Constituents 
and Uses of Commercial Starch, 360. Bice Starch, Chesnut Starch, Cassava Starchy 
Arrow-root, 360. Sago, 361. Dextrine, 361. 

ScoAB Manufacture. — History of Sugar, 362. Nature of Sugar, 362. 

Cane Sugar. — Sugar from the Sugar-cane, 364. Components of the Sugar-cane, 364. 
Preparing the Baw Sugar from the Sugar-cane, 365. Varieties of Sugar, 366. 
Molasses, 366. Befining the Sugar, 366. Production of Baw Sugar, 367. 

Bbbt-root Sugar. — Its Nature, 367. Species of Beet, 367. Chemical Constituents of 
the Beet, 368. Saccharimetiy, 369. Mechanical Method, 369. Chemical Method, 
369. Ferment Test, 370. Physical Method, 370. Preparation of Sugar from the 
Beet, 370. The Besidue, 372. Components of the Juice, 373. Other Methods of 
De-Liming the Juice, 374. Purifying with Baryta, 374. The Filter, 375. Dumont's 
Filter, 375, Evaporation Pans, 375. Vacuum Pans, 377. Evaporating the Juice, 
380. Draining the Crystals, 381. The Centrifugal Drier, 381. Bemoving the Sugar 
from the Form, 381. Beet Molasses, 382. Sugar-candy, 382. 

Grape Sugar. — Grape Sugar, 383. Preparation of Grape Sugar, 384. Composition of 
Starcli Sugar, 386. Uses of Grape Sugar, 386. 

Fermentation. — Fermentation, 386. Vinous Fermentation, 387. Yeast, 387. Condi- 
tiouR of Alcoholic or Vinous Fermentation, 389. 

Wine-Makdco. — ^Wine, 390. The Vine and its Cultivation, 390. Vintage, 390. The Pres- 
sing of the Grapes, 391. The Centrifugal Machine, 391. Chemical Constituents of 
the Must, 391. The Sugar of the Grape, 392. The Fermentation of the Grape 
Juice, 393. Drawing Off and Casking the Wine, 393. Constituents of Wine, 393. 
Maladies of Wines, 396. Ageing and Conservation of Wines, 397. Clearing or 
Fining the Wine, 399. The Besidue or Waste of Wine Making, 399. Effervescing 
Wines, 399. The Improving of the Wine Must, 401. 

Beer-Brewing. — Beer, 403. Materials of Beer-Brewing, 403. Hops, 404. QuaHty of the 
Hops, 404. Substitutes for Hops, 405. Water, 405. The Ferment, 405. The Pro- 
cess of Beer Brewing, 405. The Malting, 405. The Bruising of the Malt, 408. 
Mashing, 408. Decoction Method, 409. Thick Mash Boiling, 409. Augsburg 
Method, 410. Infusion Method, 410. Extractives of the Wort, 411. Boiling the 
Wort, 411. Adding the Hops, 412. Cooling the Wort, 413. The Fermentation, 414. 
Sedimentary Fermentation, 415. After-Fermentation in the Casks, 416. Surface- * 
Fermentation, 417. Steam-Brewing, 418. Constituents of Beer, 418. Beer-Testing, 
420. Balling's Saccharometrical Beer Test, 420. Fuchs's Beer Test, 422. By-pro- 
ducts of the Brewing Process, 423. 

Preparation or Distillation of Spirits. — Alcohol, 424. Alcohol and its Technically 
Important Properties, 424. Baw Materials of Spirit Manufacture, 425. 

A. Preparation of a Vinous Mash. — Vinous Mash from Cereals, 426. The Bruising, 426. 
The Mixing with Water, 426. The Cooling of the Mash, 426. The Fermentation of 



CONTENTS. xUi 

the Bfash, 427. Mash from Potatoes, 427. Mash with Snlphnrio Acid, 428. The 
Fermentation of the Potato Mash, 429. Mash from Boots, 429. Spirits from the 
Bj-prodncts of Sugar Mannfactnre, 430. Spirits from Wine and Marc, 430. 

B. DxBTiiiLATioN OF THK YiNODS Mash. — ^Distillation of the Mash, 431. The Distilling 
Apparatus, 432. Improved Distilling Apparatus, 432. Dom's Apparatus, 433. Pis- 
torius*8 Apparatus, 435. Gall's Apparatus, 433. Schwarz's Apparatus, 436. 
Siemens*8 Apparatus, 440. Continuous Distilling Apparatus, 440. Tangier'sl^Appa- 
ratuB, 443. Bemoying the Fusel Oils — ^Defuseling, 445. Yield of Alcohol, 446. 
Aleoholometry, 447. Areometer, 447. Relation of Brandy Distilling to Agriculture, 
448. The Besidue or Wash, 448. Dry Teast, 449. So-called Artificial Yeast, 450. 
Vienna Yeast, 450. Duty on Spirits, 451. 

Bbsad Bakino. — ^Modes of Bread Making, 451. The Details of Bread Baking, 451. The 
Mixing of the Dough and the Kneading, 452. Kneading, 452. Kneading Machines, 
453. The Oven, 45 a. Substitutes for the Ferments, 456. Yield of Bread, 459. 
Composition of Bread, 459. Impurities and Adulteration of Bread, 460. 

Thb Manutactubb of Yineoab. — Yinegar and its Origin, 460. 

A. Pbsfabation of Yinzgab fbom Alcoholic Fluids. — ^Yinegar from Alcohol, 461. Pheno- 

mena of Yinegar Formation, 462. The Older Method of Yinegar Making, 462. 
Quick Yinegar Making, 463. Yinegar from Sugar-beet, 466. Yinegar with the help 
of Myooderma Aceti, 466. Yinegar with the help of Platinum Black, 467. Testing 
Vinegar, 467. Aoetometry, 468. 

B. Pbipabation of Yineoab fbom Wood Yinboab. — Wood Yinegar, 469. Purifying Wood 

Vinegar, 471. Wood Spirit, 472. 

Thb Pbesebyation of Wood. — On the Durability of Wood in General, 472. Preservation 
of Wood in Particular, 474. Drying Wood, 474. Elimination of tne Constituents of 
the Sap, 474. Air Drains, 475. Chemical Alteration of the Constituents of the Sap, 
475. liOneralising Wood, 4^6. Boucherie's Method of Impregnation, 477. 

ToBAOOO. — Tobacco, 477. Chemical Composition of the Tobacco Leaf, 478. Manufacture 
of Tobacco, 478. Smoking Tobacco, 479. Snuff, 480. 

TicHNOLoaT OF EssBMTiAL OiLS AND Bbsims. — ^Essential Oils and Besins, 480. Prepara- 
tion of Essential Oils, 481. Preparation of Essential Oils by Pressure, 481. Extrac- 
tion of Essential OUb by Means of Fatty Oils, 481. Properties and Uses of 
Essential Oils, 481. Perfum^, 481. Chemical Perfumes, 482. Preparation of 
Cordials, 482. Besins, 483. Use of Besins as Sealing-wax, 483. Asphalte, 484. 
Caoutchouc, 484. Solyents of Caoutchouc, 485. Properties and Use of India-rubber, 
486. Vulcanised Caoutchouc, 486. Production and Consumption of Caoutchouc, 486. 
Gutta-percha, 486. Solyents of Gutta-percha, 487. Uses of Gutta-percha, 487. 
Mixture of Gutta-percha and Caoutchouc, ^, Yamishes, 488. Oil Varnishes, 
4S8. Gold Size, 489. Printing Ink, 489. Oil Yamishes, A89. Spirit Varnish, 489. 
Coloured . Spirit Yamishes, 490. Turpentine Oil Yamishes, 490. Polishing the 
Dried Varnish, 490. Pettenkofer's Process for Bestoring Pictures, 490. 

Cbmbmtb, Lutbs, and Puttt. — Cements, 491. Lime Cements, 491. Oil Cements, 491. 
Beam Cements, 492. Iron Cement, 493. Paste, 493. 

DIVISION V. 

ANIMAL SUBSTANCES AND THEIB INDUSTRIAL APPLICATION. 

WooLLBN Industbt. — Origin and Properties of Wool, 494. Chemical Composition of Wool, 
495. Properties of Wool, 497. Colour and Gloss, 497. Preparation of Wool, 497. 
Wool Spinning, 498. I. Washing, 498. n. Dyeing, 498. m. WiUowing or Devilling, 
498. Oiling or Greasing, 498. Y. The Carding, 498. YI. Boving,^499. Artificial 
Wool, 499. Weaving the Cloth, 499. Washing and Milling the Bough Cloth, 499, 
Teasling and Shearing the Cloth, 499. Dressing the Cloth, 499. Other doth 
Fabrics, 500. Worsted Wool, 500. 

81UL — Silk, 501. Seridoulture— Varieties of Silkworms, 501. Manipulation of the Silk, 
503. The Throwing of Silk, 504. Conditioning or Testing of Silk, 504. Scouring or 
Boiling the Gum out of Silk, 504. Weaving of Silk, 505. Means of Distinguishing 
Bilk from Wool and from Vegetable Fibre, 506. 

TAHimo. — Tanning, 508. Anatomy of Animal Skin, 508. 

L Bid- ob Babk-Tannino. — Tanning Materials, 509. Oak Bark, 509. Sumac, 510. 
Dividivi, 511. Nut Galls, 511. Valonia Nuts, 511. Chinese Galls, 511. Cutch, 512. 
Kino, 512. Estimation of the Value of the Tanning Materials, 512. The Skins, 513. 
The Bertral Operationfl, 513. Cleansing the Hides, 514. Cleansing the Flesh 



iiv CONTENTS. 

Side, 514. CleanBing the Hair Sidet 514. Stripping ofif the Hair, 515. Swelling the 
Hides, 515. The Tanning, 516. Tanning in the Bark, 516. Tanning in Liquor, 517. 
Qnick Tanning, 517. Dressing or Onrrying the Leather, 518. Sole Leather, 518. 
Upper Leather, 518. The Paring, 518. The Scraping or Smoothing, 518. Oraining 
the Leather, '519. Polishing with Prunice-stone, 519. Baising the Grain slightly 
with Pommels of Cork, 519. Smoothing with Tawer's Softening Lron, 519. Bollizig» 
519. Finishing Off, 519. Greasing, 519. Tufts, Russia Leather, 520. Morocco 
Leather, 520. Dressing Morocco Leather, 521. Cordwain, Gordoyan Leather, 521^ 
Lacquered Leather, 521. 

II. Tawing.— Tawing, Preparation of White Leather, 522. Common Tawing, 522. Hun- 
garian TawiQg Process, 524. Glove Leather, 524. Enapp's Leather, 525. 

HI. Samiam OB Oil-Tawino Process. — Samian Tawing Process, 525. Parchment, 527. 
Shagreen, 527. 

Glue Boilino. — ^General Obserrations, 528. Leather Glue, 529. Treating with Lime, 
529. Boiling the Materials, 530. Fractioned BoiUng, 530. Moulding, 531. Diyixig 
the Glue, 531. Glue from Bones, 532. Liquid Glue, 533. Test for the Quality 
of Glue, 533. Isinglass, 535. Substitutes for Glue, and New Preparations obtained 
from Glue, 536. 

MANtJFACTUBE OF PHOSPHORUS. — General Properties, 537. Preparation of Phosphorus, 
537. Burning of the Bones to Ash, 538. Decomposition of the Bone-ash by 
Sulphuric Acid, 538. Distillation of Phosphorus, 539. Befining and Purifying the 
Phosphorus, 540. Moulding the Befined Phosphorus, 541. Other Proposed MeUiods 
of Preparing Phosphorus, 543. Fleck's Process, 543. Gentele, Gerland, Minaiy, 
and Soudry's Methods of Preparing Phosphorus, 544. Properties of Phosphorus, 544. 
Amorphous or Bed Phosphorus, 545. Properties of Amorphous Phosphorus, 546. 

Requisites fob Producino Fibe. — Generalities and History, 546. Manufacture of Lucifer 
Matches, 548. The Preparation of the Wood Splints, 548. The Preparation of the 
Combustible Composition, 549. Dipping and Drying the Splints, 550. Anti- 
Phosphor Matches, 552. Wax or Vesta Matches, 553. 

Animal Charcoal. — Animal Charcoal, 553. Preparation of Bone-black, 553. Properties 
of Bone-black, 554. Testing Bone-black, 554. Beyivifioation (re-burning) of Char- 
coal, 555. Substitutes for Bone-black, 555. 

Milk. — Milk, 556. Whey, 557. Lactose, Sugar of Milk, 557. Means to Preyent Milk 
becoming Sour, 557. Testing Milk, 557. Uses of Milk, 558. Butter, 558. Chemical 
Nature of Butter, 559. Cheese, 559. 

Meat.— ^jreneralities, 562. Constituents of Meat, 562. The Cooking of Meat, 563. The 
Boiling of Meat, 564. Preservation of Meat, 564. Preservation of Meat by with- 
drawsJ of Water, 565. Salting Meat, 565. Smoking or Curing Meat, 566. 



DIVISION VI. 

DYEING AND aKLICO PRINTING. 

On Dyeing and Printing in Genebal. — ^Dyeing and Printing in General, 568. Dyes, 568. 

Lake Pigments, 569. Colouring Materials, 569. The Coal-Tar Colours : Coal- Tar, 

569. Benzol, 570. Nitro-benzol, 572. Aniline, 573. 
I. Aniline Coloubs. — ^Aniline Colours, 575. Aniline Bed, 575. Aniline Violet, 577. 

Aniline Blue, 578. Aniline Green, 578. Aniline Yellow, 579. Aniline Orange, 579. 

Aniline Black, 579. Aniline Brown, 579. 
n. Cabbolio Acid Coloubs. — Carbolic Acid Dyes, 580. Picric Acid, 580. Pheniciexme, 

581. Grenate Brown, 581. Coralline, 581. Azuline, 581. Pigment Directly |rom 

Nitro-benzol, 581. 
ni. Naphthaline Pigments. — Naphthaline, 581. Martins Yellow, 582. Magdala Bed, 

583. Naphthaline Blue and Naphthaline Violet, 583. 
rV. Anthracen Pigments. — Anthracen Pigments, 584. 
V. Pigments fbom Cinchonine. — Cinchoine Pigments, 585. 
fisD Pigments Oocdbbino in Plants and Animals. — ^Bed Dye Materials — ^Madder, 586. 

Madder Lake, 587. Flowers of Madder, 587. Azale, 587. Garanoine, 587. Ganm- 

ceux, 587. Colorine, 588. Brazil or Camwood, 588. Sandalwood, 588. Safflower, ' 

589. Cochenille or Cochineal, 589. Lac Dye, 590. Orchil and Persio, 590. Less 

Important Bed Dyes, 591. 
Blue Dte Materials.^:— Indigo, 591. Properties of Indigo, 592. Testing Indigo, 592. 

Berzelius's Indigo Test by Beduction, 593. Penny's Test, 593. Indigo Blue» 594. 

Logwood or Gampeachy, 594. Litmus, 594. 



CONTENTS. XV 

Tei<low Dyes. — Yellow-wood, Fustic, 595. Youug Fustic, French Fustet, 595. Annatto 
or Amotto, 595. Yellow Berries or Simply Berries, 596. Turmeric, 596. Weld, 
596. Quercitron Bark, 596. Brown, Green, and Black Dyes, 596. 

Blbachino. — Bleaching, 597. Bleaching of Silk, 599. 

Dtbino of Spun Y'arn and Woven Textile Fabrics. — Dyeing, 599. Mordants, 601. 
Dyeing Woollen Fabrics, 601. Dyeing Wool Blue, 601. Indigo Blue, 602. Blue 
Vats, 602. Saxony Blue, 603. Beoovering Indigo from Bags, 604. Berlin or Prussian 
Blue on Wool, 604. Dyeing Blue with Logwood and a Copper Salt, 604. Dyeing 
Yellow, 604. Dyeing Wool Red, 605. Green Dyes, 605. Mixed Shades, 605. Black 
Dyes, 605. Wlute Cloth, 606. Silk Dyeing, 606. CaHco Dyeing, 608. Turkey Bed, 
608. Dyeing Linen, 609. 

The Printing of Woven Fabrics.— Printing of Woven Fabrics, 609. Mordants, 609. 
Thickenings, 610. Resists, or Reserves, 610. Discharges, 611. Acid Discharges, 
611. Oxidising Agents as Discharges, 611. Reducing Agents as Discharges, 611. 
CiJico Printing, 612. Topical or Surface Colours, 613. Discharge Style, 614. 
Aniline Printing, 614. Hotpressing, Finishing, and Dressing, 616. Printing Linen 
Goods, 616. Printing Woollen Goods, 616. Printing Silk Goods, 616. Mandarin 
Printing, 6x6. Bandanas, 616. 



DIVISION vn. 

THE MATERIALS AND APPARATUS FOB PRODUCING ARTIFICIAL LIGHT. 

Artificial Illumination in General, 617. Flame, 618. 

I. Artificial Light from Candles. — Lignt from Candles, 620. Manufacture of Stearine 
Candles, 621. Preparation of Fatty Acids by Means of Lime, 621. Saponification 
with Less Lime, 623. Saponification by Means of Sulphuric Acid, 624. Sapo- 
nification with Water and High Pressure, 626. Manufacture of Fatty Adds by 
Means of Superheated Steam and Subsequent Distillation, 627. Candle Making, 
627. Moulding the Candles, 628. Tallow Candles, 629. ParafiSn Candles, 630. 
Candles from Fatty Adds, 631. Wax Candles, 631. Other Kinds of Wax, 632. 
The Making of Wax Candles, 633. Sperm or Spermaceti Candles, 634. Glyce- 
rine, 634. 

n. Illumination bt Means of Lamps. — Dlumination with Fluid Substances, 636. Puri- 
fying or Refining the Oils, 636. Lamps, 636. Various Kinds of Lamps, 639. 
Suction Lamps, 639. The Lamp with Constant Oil Level, 640. Pressure Lamps, 
641. Mechanical Lamps, 642. Clockwork Lamp, 642. Moderateur or Moderator 
Lamp, 642. Petroleum Oil and Paraffin Oil Lamps, 644. 

IIL Gab.— -General Introduction and Historical Notes, 645. Raw Materials of Gas 
Lighting, 646. Coal-Gas, 646. Products of the Distillation, 647. Manufacture of 
Goal-Gas, 648. Retorts, 648. Mouth-piece and Lid of Retorts, 649. Retort Fur- 
naces, 650. Charging the Retorts and Distillation, 650. The Hydraulic Main, 650. 
Cooling or Condensing Apparatus, 652. The Scrubber, 653. Exhauster, 654. 
Purifying Gas, 654. Gas Holders, 656. Distribution of Gas, 660. Hydraulic Valve, 
661. ^essure Regulator, 661. Testing Illuminating Gas, 661. Methods of 
Testing Illuminating Gas, 662. Gas Meters, 664. Burners, 665. Gas Lamps, 665. 
By-Products of Coal-Gas Manufacture, 665. Composition of Coal-Gas, 668. Wood 
Gas, 668. Method of Wood GLas Manufacture, 669. Wood Gas Burners, 670. Peat 
Gas, 670. Water Gas, 671. Gillard's Gas, Platinum Gas, 672. Carburetted Water 
Gas, 672. Whitens Hydrocarbon Process, 673. Leprince's Water Gas, Isoard's 
Gbs, 674. Baldamus and Grune's Gas, 6^4. Carburetted Gas, 674. Air Gas, 67A. 
Oil Gas, Itesin Gas, 674. Gas from Suint, 675. Gas from Petroleum Oil, or Ou 
from Bituminous Shales, 675. Petroleum Gas, 676. Resin Gas, 678. Lime-Light, 
678. Tessie du Motay's Method of Illumination, 679. Magnesium Light, 679. 
Chatham Light, 680. Electric Light, 680. 

Pa&affim and Solar or Petroleum Oils. — Paraffin Oils, 683. Manufacture of Paraffin, 
683. Preparation of Paraffin from Petroleum, 684. Paraffin from Ozokerite and 
Neftgil, 684. Paraffin from Bitumen, 685. Preparation of Paraffin by D17 Distilla- 
tion, 685. Preparation of the Tar, 685. Condensation of the Vapours of the Tar, 
686. Properties of Tar, 687. Mode of Operating with the Tar, 688. Distillation 
of the Tar, 688. Treatment of the Products of Distillation, 689. Rectification of 
the Crude Oils, 689. Refining of the Crude Paraffin, 690. Hubner's Method of 
Preparing Paraffin, 690. Yield of Paraffin, 691. Brown-coal, 691. Properties of 
Paraffin, 692. Paraffin Oil, 693. Preparation of Mineral Oil, 694. 



XTi CONTENTS. 

PsTBOLSUM.— Petroleum Oil and its Ooourrences, 695. Origin and Formation of Petro- 
leum, 695. Befining of Crude Petroleum, 696. (Constitution of Petroleum, 696. 
Technology of Petroleum, 697. 

DIVISION VIII. 

FUEL AND HEATING APPABATUS. 

A. FuKL. — ^Fuel, 698. Combustibiiity, 698. Inflammability, 698. Calorific Effect, 698. 
Determination of Combustive Power, 699. Karmarsch's Evaporation Method, 699. 
Berthier's Beduction Method, 700. Elementary Analysis, 700. Stromeyer's Test, 
701. Pyrometrical Calorific Test, 701. Mechanical Equivalent of Heat, 702. 

Wood. — ^Wood, 702. Constituents of Wood, 703. Heating Value of Wood, 704. Wood 
Charcoal, 704. Carbonisation of Wood, 705. Carbonisation in Heaps, 705. Con- 
struction of the Heap, 705. Charcoal Burning, 706. Carbonisation in Beds, 706. 
Carbonisation in Ovens or Kilns, 706. Carbonisation of Wood in Ovens, ^08. Pro- 
perties of Charcoal, 710/ Composition of Wood Charcoal, 71 x. . Combustibility and 
Heating Effect, 711. Charbon-Bouz ; Terrified Charcoal, 711. Boasted Wood; 
Bois-Boux, 712. 

PsAT — Peat, 712. Drying Peat, 713. Heating Effect of Peat, 715. New Method of 
Utilising reat, 715. 

Cabbonised Peat. — Carbonised Peat, 715. • 

Bbown-coal. — Brown-coal, 716. Brown-coal as Fuel, 717. 

Pit Coal, ob Coal. — Coal, 717. Accessory Constituents of Coal, 718. Classification of 
Coals,'^7i8. Anthracite, 719. Caking Coal, 719. Calorific Effect, 721. Evaporative 
Effect of Coals, 721. Boghead Coal, 722. 

PxTBOLBuu AS FuEL. — Pctrolcum as Fuel, 722. 

Coke. — Coke, 723. Coking in Heaps, 724. Coking in Ovens, 724. Properties of Coke, 
729. Composition of Coke and its Value as Fuel, 729. 

Abtificial Fuel. — Artificial Fuel, 729. Peras, 729. Briquettes, 730. 

Gaseous Fuel. — Gaseous Fuel, 730. Gas for Heating Purposes, 731. 

Heating Appabatus. — Warming, 731. 

Heating Dwelling Houses. — Heating' Dwelling Houses, 732. Direct Heating, 732. 
Chimney Heating, 733. Stove Heating, 733. Iron Stoves, 734. Fire-clay Stoves, 
734. Compound Stoves, 735. Air Heating, 737. Calorifiers, 738. Flue Heating, 
739. Hot Water Heating, 739. Heating with Steam, 740. Combination of Steam 
and Hot Water Heating, 740. Gas Heating, 740. Heating without Ordinary Fnel, 
740. 

BomsB Heating and Consumption of Smoke. — Boiler Heating, 740. Smoke Consuming 
Apparatus, 741. Step Grate, 742. Etage, or Stage Grate, 743. Movable Grate, 
743. Chain Grates, 743. Botating Grate, 744. Improved Fuel Supply, 744. Pnlt 
Fires, 744. Vogl's- Grate, 744. Boquillon's Grate, 744. Apparatus of Cutler and 
George, ^44. Apparatus with Unequal Distribution, 744. Consumption of Smoke 
by the Aid of Collateral Air Currents, 745. Gall's Fireplace, 745. Besom^, 745. 



/• 



INTRODUCTION. 



Man's labour, considered from an economical point of view, is of a threefold kind, being 
either productive, improving, or converting. We distinguish likewise between the 
productions obtained from the soil taken in its widest sense, and between commerce 
and manufacturing industry. 

The department of labour, the object of which is to prepare and render fit for use 
the raw materials yielded by nature, is that which, in a more restricted sense, is 
called manu&u^turing industry, and the description and elucidation of the methods 
by which this object is attained is called technology, from rkx*^ and \oyos. Taken in 
a general sense, this word would apply to all trades, arts, and manufactures what- 
soever; exclusive, however, of actual artist's work — ^notwithstanding the latter 
exceeds the industries in respect of the money -value of its productions — and exclusive, 
also, of such trades as tailoring, dress- and shoe-making, in which only certain commo- 
dities from materials that have been produced by manufacturing industry are 
worked up. 

Mining and quarrying operations, as well as commerce, do not belong to technology, 
because the former deal with the getting to hand of naturally existing materials, and 
the object of the latter is either the carrying and distributing of the products from 
various parts of the world to the wholesale consumers, or the products of different 
kinds of one and the same country to the population thereof. The position of some 
industries is somewhat difficult to define in this sense, for while metallurgy and the 
knowledge of tools and machinery are undoubtedly an integral portion of technology, 
taken in its widest sense, the construction of railways, roads, and bridges, as well 
as shipbuilding, architecture, artillery science, &c., do not come within the province of 
technology, but belong either to engineering science or are specialities to be separately 
taught and described. 

Technology is not a self-contained science which possesses its own peculiar doctrine 
and foundation; it simply borrows the principles and experience obtained by 
mechanical and natural sciences, always taking into consideration the best mode of 
applying these principles to the preparation of raw materials to become objects suitable 
for use. Technology is accordingly practical natural science, having for its object 
the reduction of manufacturing industry to the natural principles upon which it is 
based, and teaching the most advantageous methods and processes by which the raw 
materials are prepared for use. Raw products, which are either in the condition 
nature yields them, or which have already been in the hands of the manufacturer, are 

B 



2 CHEMICAL TECHNOLOGY. 

changed by the labour of men, either in their outward form only, or in their 
composition, and upon this distinction is based tlie di\dsion of technology 
mechanical and chemical ; the former division embraces such industries as h.a.ve 
for their object the changing, altering, and modifying the form and shape of tlie 
material, its inner composition remaining unaltered ; as instances we quote the jo 
and carpenter working in wood, the making of iron rails, sheath metal, and v^rire, 
casting of iron, zinc, and alloys of copper into various objects, the spinnixig 
weaving of various fibres, flax, cotton, jute, to become materials of greater value ; 
the manufacturing of paper from rags, of horn into combs, and bristles into bxxLsIi 
belong to this section. 

Chemical technology, however, deals with the operations by wliich a raw nL&tejri 
is not only changed in its form, but espeeiMy as regards its nature : such, for instctzice* 
is the case with the extraction of metals from their ores ; the conversion of lead into 
white-lead and sugar of lead (acetate of lead) ; the conversion of sulphate of baryt 
into chloride of barium and baryta white (permanent or Chinese white) ; the converHiont 
of cryolite into sulphate of alumina, alum, and soda ; the conversion of rock salt into 
sulphate and carbonate of soda ; the conversion of camallite and kainite into chloride 
and bromide of potassium, sulphate and carbonate of potassa; the conversion, of 
copper into verdigris and sulphate of copper; the manufacture of paraffine and 
paraffine or crystal oils from peat. Boghead coal, and hgnite ; the preparation of kelp 
and iodine from seaweeds ; the manufacture of stearine candles (stearic acid prox>erly I 
and soap from oils and fats ; the preparation of sugar and alcohol from starch ; the 
conversion of alcohol into vinegar ; the brewing of beer from barley and hops ; the 
manufacture of pig-iron into malleable iron (puddling process), and the conversion of 
malleable iron into steel ; the production of gas, coke, and tar from coals ; the extrac- 
tion from the tar of such substances as benzol, carbolic acid, aniline, anthracen, « 
asphalte, naphthaline ; the preparation of tar colours, as rosaniline, aniline blue, 1 
Manchester yellow, Magdala red, alizarine, iodine green, picric acid, &c. In very 
many cases, however, the preparation which the raw materials have to undergo 
before fit for use is simultaneously, or at least consecutively, a mechanical 
as well as a chemical process; for instance, in the manufacture of glass, sand, 
potash, Glauber salt (sulphate of soda)^ carbonate of soda, and hmestone, are first 
fused together to form glass (a true salt, a silicate), and the soft mass is next wrought 
in various ways to form window-glass, tumblers, bottles, &c. Another instance is the 
manufacture of beet-root sugar, in the extraction of which the sugar itself is, it is 
true, not altered or changed in any way (tliis being as much as possible avoided), hot 
the process of extraction is a combination of mechanical and chemical operations, the 
^* latter bearing chiefly upon the purification of the sugar so as to free it from adhering 
foreign substances. The same observation appUes to the manufacture of starch, to 
tanning operations, also to the various processes of dyeing and calico printing. 

The ceramic arts (that is to say, the manufacture of earthenware, pottery, china, &c.) 
are generally included in chemical technology, although, in the production of the 
objects alluded to, the mechanical operations and fine art processes predominate. 
PVrotechny (that is to say, the consideration of fuel and of its most useful and advan- 
tageous application to the production of heat, and the best mode of constructing 
furnaces, ovens, chimneys, &c.) is one of the most important parts of chemical 
technology. 

From the foregoing the reader wiH readily perceive ijiat it is scarcely possible 



intQ 
iiIt 
■aw 
aer 
the 



INTRODUCTION. 3 

to draw a sharp line of demarcation between the two divisions of technology 
(ibechanical and chemical) alluded to. We therefore define chemical technology 
best by designating it as that branch of industrial science which treats of the processes 
and methods by which the nature of raw materials is usually altered. 

In mechanical technology, machinery of various description, acting as the motive 
agent or for the exertion of great power, for the transference of movement or for the 
nd i regulation thereof, and, lastiy, as an actual implement, always plays a very prominent 
^ ; part, whilst in chemical technology its position is altogether subordinate ; the great 
^ ' aim of imfirovement being chiefly directed towards: — i. Economisation of raw 
material, and, if by any possible means, its regeneration. 2. Economy of fuel. 
3. Economy of time by improved and shortened methods of the various operations. 
The ideal of a chemical manufactory is that there should be no real waste products 
^M '• all* but only chief or main, and by-products. The better, therefore, the waste 
^ products are applied to good and advantageous use, the more nearly Uie manufactory 
^ mill approach tiie ideal, and the larger \vill be the profit. , 






n 2 



DIVISION I. 

CHEMICAL METALLURGY, ALLOYS, AND PREPARATIONS MADE AND OBTAINED FROM METALS. 



General Observations. 

'***°5ettu^^ Metallurgy, in a more restricted sense, embraces the doctrine of 
the various processes and operatiouB, some of which are purely mechanical, others 
again pui'ely chemical, by means of which metals and some preparations thereof are 
obtained on a large scale. We treat in the following pages almost exclusively of 
the chemical operations and processes by the aid of which ores are converted into 
metal or into some other product, and we shall therefore investigate the changes 
which the ore undergoes when submitted to different processes and operations re- 
sulting in the extraction of the metal. The number of the metals which belong to 
this category is not veiy large; the chief are iron, cobalt, nickel, copper, lead, 
chromium, tin, bismuth, zinc, antimony, arsenic, mercury, platinum, silver, gold. 
Excepting chromium and cobalt,* other metals are brought into the metallic state by 
means of smelting furnaces; but preparations of nickel, antimony, and arsenic are 
also obtained metallurgically. Magnesium and aluminium are as yet only prepared 
in chemical manufactories. Metallurgy, as a part of technology, treats chiefly of 
the physical and chemical principles upon which the extraction of metals from their 
ores is based; and includes, therefore, the description of the operations as based upon 
these principles. Only very few metals are found in the native, that is, metallic 
state ; most of them occur as chemical compounds in the mineral kingdom, and these 

Qroi. are termed ores ; they are partly chemical combinations of Hie metal with 
metalloids, and partly consist of rock or gaugue. Moreover, the term ore applies only 
in an industrial sense to those minerals which are worth the miner's working. 
Metals are found chiefly in combiuation with oxygen and sulphur. Metals occur in 
the ores in the following conditions: — i. In the native state, embedded in quartz, 
granite, gneiss, and other minerals, — ^gold, silver, platinum, mercury, copper, and 
bismuth. 2. Combined with sulphur, as, for instance, antimony, arsenic, and lead ; 
these combinations being — (a) single ores, as, for instance, cinnabar (sulphuret of 
mercury), HgS; galena (sulphuret of lead), PbS; speisscobalt (a compound of cobalt 
metal 'and arsenic), CoAs; {b) double ores, as, for instance, sulphuret of iron and 
copper (peacock ore), Fe2S3,3CuaS; iron and copper pyrites, FcaSj.CuaS; red silver 

* Since 1862 M. Fleitmann has prepared chromium and cobalt on the large scale by a 
metallurgical process. 



PREPARATION OF ORES, 5 

ore, SbaS3,3AgS. 3. Gombmed with oxygen, ores occur as — (a) basic oxides, as, for 
instance, hsematite iron ore, Fe203 ; tinstone, SnOa ; red copper ore, GuaO ; (b) as 
hjdrated oxides, as, for instance, bog iron ore, Fe203,3H20 ; (0) as oxysalts, as for 
instance, malachite, CuCOj+CuHaO. 4. Combined with sulphur and oxygen, 
as for instance, red antimony ore, 2SbaS3+Sb203. 5. Combined with haloids, as, for 
instance, the so-called horn silver ore, AgCl. 6. In combination with haloids and 
oxygen, as, for instance, horn lead ore, PbC03+PbCl3. 

'^'^oSf "* Since the ores are not found in a state anything approacliing to purity, 
but are mixed in the first place with what is technically termed gangue — ^rock, stone, or 
earth of any kind ; and, moreover, since very frequently the ores of different metals 
occur mixed together, they require, on being brought out of the mine, to be broken 
up and to be separated by mechanical means from the gangue and from other im- 
purities. These operations as a rule are carried out on, or near, the spot where the ores 
are raised, and are designated by the name of dressing ; the mechanical preparation 
of the ore is partly executed by hand, women and children being frequently engaged 
in picking out worthless stuff from among the minerals brought to bank ; this sorting, 
accompanied commonly by the breaking up of the ore into small lumps, an operation 
executed by men vdih suitable hammers, is usually so carried on as to separate the 
ore into three kinds. The ore thus selected is placed in separate heaps, which may be 
classed as follows: — a heap containing rich ore of sufficiently good quality to be fit to 
be directly smelted ; another heap contains ore which, previous to its being fit for 
the smelter, has to be further prepared, that is, purified from mechanically adhering 
impurities ; while the third heap is devoted to such poor ore as would not pay the 
expense of the extraction of the comparatively small quantity of metal it contains. 
The mechanical operations alluded to are frequently effected by the aid of machinery, 
stamp and dressing mills, while very often water is used in completing tlie 
operations, its use being chiefly to remove the clay and earthy matter, sand, and 
pulverised rock from the specifically heavier mineral. ' The dressing of the ores 

^"*owJ.**" ^ having been finished, they are fit for the smelting operations, but in 
majiy instances these cannot be proceeded Tvith until the ores have undergone a 
preparation, consisting in some cases of an exposure to air — ^weathering ; in otliers, 
again, in a heating of the ores, without access of air, designated calcination, or a 
heating with access of air, termed roasting. 

The object of the expo^nire to air is in some instances to effect the weathering and 
subsequent loosening and separation (mechanically) of such minerals as slate, clay, 
and marly materials, which frequently adhere to certain kinds of iron and zinc ores ; 
in other instances, again, the object of the exposure of metallic ores to air is tlie 
oxidation of iron pyrites, which is washed out by rain as sulphate of protoxide of 
iron. The object of the calcination of ores is partly to drive off water, 
carbonic acid, and bituminous materials ; partly, also, to render the ores 
softer, and thus better fitted for the metallurgical processes by which the re- 
duction to the metallic state is effected. The roasting of ores is carried on with the 
same object, but since the temperature is far higher, although not carried to 
the fusion of the ores, a more energetic chemical action takes place, and is in some 
cases promoted by the addition of common salt; moreover, the great object of the 
roasting of ores is to effect an oxidation of tlie same, accompanied in some, if not in all, 
cases bv the volatilisation of various substances. As uistances of the action of Uiis 
process, we quote wliat occihtj when magnetic iron ore, (Fea03,FeO), is roasted; 



6 CHEMICAL TECHNOLOGY, 

tlie protoxide in this case is gradually converted into peroxide. When oxidation is 
accompanied by volatilisation three different things may happen. 

1. A volatilisation of certain Bubstances attended by oxidation. The ores which are 
chiefly submitted to this process are snch as are combinations of sulphur, arsenic, and 
antimony, either jointly or siQgly, in which cases sulphurous and arsenious acids and 
oxide of antimony are volatilised, with the result that either pure metal is obtained, as is 
the case with cinnabar, which yields mercury, or the formation of metallie oxides and 
sulphates. The volatilised substances may be collected and utilised, as, for instanee, 
the arsenious acid, and the sulphurous acid for the production of sulphuric acid, Ac. 

2. Volatilisation of certain substances by reduction is a less frequently occurrizig 
operation, chiefly carried on with some sulphates and arseniates of metallic oxides by 
heating the same with coal or charcoal, the result being the volatilisation of sulphur in 
the form of sulphurous acid and of arsenic per se. 

3. Volatilisation by conversion into chlorides of metal. When an ore is roasted with the 
addition of conmion salt and free access of air, some partly volatile chlorides may be 
formed, as, for instance, in the extraction of silver from its ores by the European 
amalgamation process and M. Augustin's method. 

smoiuiigof theOxM. As soon as the ores are sufficiently prepared by the methods just 
described, they are submitted to an operation having for its object the conversion of 
the ore into metal, or into some other combination thereof; the process, which is a 
true chemical operation, is called the smelting process. It rarely happens that only 
one kind of ore is operated upon ; the more usual plan is to mingle richer and poorer 
ores together in certain quantities, so as to obtain a suitable mixture, attention also 
being paid to the various kinds of rock which accompany the ores, so as to obtain by 
the smelting process a proper slag ; but if, as is more often the oase, this end caonot 
be attained by the mixing of ores of different quality, it becomes almost always 
necessary to add other materials which either chiefly or solely act as fluxes, and 
also as reducing or converting agents, by promoting in various ways, to be presently 
more fully described, the separation of the metals from their ores. We distinguish 
accordingly between such materials as charcoal, coal and coke, lime, and common 
salt, which we term roasting materials (Rostzuschlage), and smelting or fluxing 
materials, such as quartz and various silicates, among which are hornblende, feldspar, 
augite, greenstone, chlorite-schist, slag; lime-containing minerals, as limestone, fluor- 
spar, gypsum, heavy-spar; minerals containing alumina, as, for instance, clay-slate 
and marl. Saline materials (admixtures) are also used, as potassa, borax, Glauber 
salt, and saltpetre ; likcTiise metallic admixtures, as, for instance, iron, used in the 
decomposition of cinnabar and sulphuret of lead ; zinc, for the extraction of silver 
from lead ; arsenic, in the preparation of certain nickel and cobalt ores ; protoxide 
of iron (anvil dross), haematite iron ore, and manganese, used in the puddling process ; 
certain saline admixtures, by which we understand, in this instance more especially, 
such blast furnace slags as contain a large proportion of protoxide of iron, and are 
applied in the process of puddling on account of the oxygen they contain ; or, on the 
otlier hand, are used as so-called precipitating agents, on account of the iron they 
contain, e.g.^ for the throwing down of lead from galena. The substances which act 
only as fluxes promote the separation of the metal, because the ore is more readily 
rendered fluid, thereby causing the particles of metal to unite more easily. According 
to their mode of action, fluxes can be brought under three heads, viz. : — i. Such as 
exercise no chemical action, but are only substances promoting fluidity, as, for 
instance, fluor-spar, borax, common salt, and various slags ; 2. Such as at the same 
time exert a reducing action, as, for instance, a mixture of argol and saltpetre, so- 
called black flux ; 3. Such as act as absorbents, either of acids or of bases : but this 
class belongs more properly to admixtures ah-eady alluded to above. 



SLAGS. 7 

The uixiag of the Smelt. That Operation, by which the ore and the materials required for 
the smelting process are intimately mixed together, often in previously weighed out 
quantities, is called the mixing, and the quantity which is to be used within a given 
lapse of time (generally 12 or 24 hours) is called the charge. 

8iMi3S*o5>2aaSii- '^6 following are the products which, generally speaking, are 
obtained by the smelting process : — i. Metals — ^Educts. The relative degree of the 
purity of these substances is indicated when gold or silver are alluded to by the title 
of their fineness (purity), fine gold or fine silver being understood as the perfectiy 
pure metal ; but as regards the metals not designated by the term noble, they are 
called raw or crude metal, while a higher degree of purity is indicated by refined. 
2. Such products as are not present ready formed in the ore, but are the result of 
peculiar reactions which take place during the smelting process between the various 
in^edients submitted to the operation ; these materials are, in most instances, 
ready for the market, and comprise the so-called hard lead which contains antimony, 
arsenic, and other impurities; arsenical preparations, as, for iastance, arsenious 
acid, orpiment, realgar; and black sulphuret of antimony. 3. The preparation of 
educts is often accompanied by the formation of intermediate or by-products ; if these 
happen still to contain a sufficient quantity of the metal operated upon to make it 
worth while to extract it, they are termed intermediate products ; but if the reverse is 
the case they are called — 4. Dross. Such intermediate products are often alloys ; as, 
for instance, one consisting of silver, copper, and lead — ^the so-called TellerHlber — 
silver containing lead, consisting chiefly of lead, with a smaller or larger quantity of 
copper and some silver ; so-called black copper, a mixture of copper, iron, and lead ; 
snlphurets ; arsenic alloys, so-called Speiss, as, for instance, the cobalt and nickel 
compounds obtained in smalt works, chiefly consisting of arsenical nickel ; carburetted 
metals, as, for instance, pig-iron and steel ; r)xides, as, for instance, litharge (oxide 
of lead). 

aatu. The material which usually passes by this name exhibits, when cold, an 
enamel or glass-hke appearance, and is generally made up of various combinations of 
silica with earths, such as lime, magnesia, alumina, and metallic oxides, as the 
protoxides of iron and manganese. The slags are formed during the smelting process, 
because the raw materials, and the various substances employed, contain the elements 
for their formation. The functions of the slag during the smelting process are rather 
important, servinjr to protect the particles of metal, or of sulphuret of metal, from the 
oxidising action of the blast, and promoting the adhesion and union of the particles'. 
Slags are applied in some smelting processes as a flux ; and if they should still contain 
a sufficient quantity of metal, tliey are added to another batch of ore to be operated 
upon. As regards their composition and nature, they are classified according to the 
quantity of silica they contain as sub-, mono-, hi-, and tri-silicates. The proportion 
which the oxygen of the silica beai's to tliat contained in the bases is as follows : — 

Subsilicate 3 • 6 

Monosilicate 3 • 3 

jDisiixcaie ••■ ■•• •■• ••• ■•■ «•• 0.3 
A. nsLucaie ••■ ■•• ■•• ••• ••• ■•• 3*^ 

Slags are either vitreous or crystalline. It very jfrequentiy happens that from the 
latter kind portions of silicates separate, which, as regards their chemical and mineral- 
ogical characters, agree with minerals met with in nature, such as augite, olivine, 
WoUastonite, mica, idocraso, chrysolite, feldspar, &c. Generally speaking, the . 



8 CHEMICAL TECHNOLOGY. 

mixtures of monoailicates produce slags which are very fluid, and apt to consolidate 

rapidly while cooling, while the mixtures of hi- and tri-silicates produce slags which 

have the opposite properties, heing pasty and tough. 

The following properties and constitution denote that the slags are suited to the 
smelting process : — i. The specifio gravity of the slag while molten should he less than 
that of the product (metal) it is desired to obtain, in order that the Blag may cover the 
surface of the molten metal, a. The slag should be homogeneoas throughout the duration 
of the process of smelting ; since the contrary would denote an abnormal working of the 
operation. 3. The slag should melt readily, and thus admit of the particles of metal 
readily sinking downwards as a consequence of their higher specific gravity. 4. The 
chemical composition of the slag should be so regulated as to prevent them exerting any 
decomposing action upon the metal. 

Iron. 

(Fe = 56 ; Sp. gr. = 77.) 

in>n;iuoeeiuniu». Iron is the most important and most useful of all metals. Its 
application is most intimately connected with all branches of industry, and almost all 
the wants and requirements of common daily life. The reason of this very extended 
employment of iron is due, partly to its being plentifully and even superabundantly 
met wiih. in nature, but partly, if not chiefly, in consequence of the great ease where- 
with this metal, during its reduction from the ore, assumes various modifications and 
exhibits different characters, each possessing some special feature of usefulness. 
Although the number of minerals which contain iron is very great, comparatively few 
are used in practice for the extraction of the metal. Those that are used are all 
oxygen compounds of iron, and chiefly what are technically known to ironmasters and 
the trade as ironstones. 

The follovTing is a list of the minerals termed " ironstones " : — 

1. Magnetic iron ore, (FeaO^,FeO=Fe304), the richest of all iron ores (it contains 
upwards of 72 per cent of iron), is pretty largely found, especially in Russia, Norway, and 
Sweden, in the crystalline schistose rock. The celebrated Dannemora (Sweden) iron is 
obtained from this ore. It not unfrequently happens that this mineral is more or less 
mixed with iron p^tes, galena, copper pyrites, apatite (chiefly phosphate of lime), and 
other minerals, which, by their presence, impair the good quaUties of the magnetic iron ore 
as a mineral. 

2. HsBmatite iron ore, red ironstone, (Fe^OO, contains about 69 per cent of iron. This 
mineral occurs in seams and veins in the older geological formations, often embedded 
in gneiss and granite. It is also met with in the metamorphic rocks, and is frequently 
called glassy head, owing to its external lustre; also bloodstone, on account of exhibiting, 
when scratched with a file or a knife, a deep red-coloured streak. When this ore is found 
mixed with silica, it is called siliceous ironstone ; when occurring along and mixed with 
fidumina, it is called red aluminous iron ore ; mixed with lime, the ore is known as 
ininette. The quantity of iron present in these ores varies, of course, considerably. TfaJs 
ore occurs in crystalUne state, in especially large quantities in the Island of Elba, 
and ores of the same kiud, but different in quality, are found in England and Ireland, 
Saxony, and many parts of Germany. They are, in all eases, especially as regards the 
first-named country, largely applied, e.g,y Lancashire (Dlverston and Barrow-in-Furness). 

3. Spathose iron ore, (FeCOj), with 48-3 per cent of iron. This ore, which occurs in great 
variety, is, indeed, the chief iron-stone, often containing carbonate of protoxide of manganese 
in larger or smaller quantity. This ore is often met within a globular or kidney-like shape, 
and hence called Iddney iron ; in mineralogy, spherosiderite. The ore bears a great many 
other names, derived from some peculiarities in its composition ; for instance, it is known 
and veiy largely worked in Scotland as black-band, owing to its being mixed with 
carbonaceous and bituminous matters, and alternating with seams of coal. It is known, 
also, as clay-ironstone, being then mixed with more of less argillaceous matter, and 
occurring in enormous quantities in that condition in Cleveland and Bosedale (Yorkshire), 
in Wales, and also on the Continent in various countries. 

4. When the last-named ore is acted upon by air and water containing carbonic acid, a 
secondary ore is formed, known as brown ironstone (partly FeaOs.HjO, partiy FeaO,,3HaO). 
In mineralogy this ore is named according to its varying physical properties, as follows : — 
Lepido-crocite, needle-iron ore, pyroaiderite, and stilpnosiderite. As may be expected. 



IRON. g 

thiB mineral is often mixed with carbonate of lime, gilioa, alumina ; the yellow ironstone 
being a variety of the aluminons kind. Banxite may in some instances range along with 
this kind of ore, when that substance consists of an intimate mixture of alumina and 
peroxide of iron. 

5. Pea-iron ore, in smaller or larger globular-shaped particles, formed of concentric layers, 
containing either an intimate mixture of silica, protoxide of iron, and water, or brown iron 
ore and siliceous clay. The origin and mode of formation of this ore are unknown. It 
occurs in France and in the South- West of Germany. 

6. Marsh iron ore, limonite, met with in parts of Europe, generally those which are 
only Uttle elevated above the sea level, and more especially in or near moors and marshes, 
peat bogs, Ac. ; in some parts of the Netherlands, Denmark, Sweden, and North Germany, 
and also in the United iUngdom to some extent. This ore owes its origin to the action of 
decaying vegetable matter upon water containing carbonate of protoxide of iron in solution. 
The ore is met with in irregularly shaped lumps, as hard sometimes as pebbles, but idso 
in a soft and spongy condition ; its colour is brownish, or black, and it consists of prot- 
oxide of iron, oxide of manganese, phosphoric acid, organic matter, and sand. According 
to M. Hermann, however, the ore contams hydrated peroxide of iron, hydrated oxida of 
manganese, phosphate of peroxide of iron, tribasic crenate of peroxide of iron. This 
ore is in some instances largely used for the manufacture of cast-iron objects (especially 
for domestic and ornamental uses), on account of its yielding an iron of great fluidity, 
which fills the moulds very completely,^ giving sharp-figured castings. This condition is 
due to the presence of the phosphorus in such iron ; but the presence of this element also 
causes the pig-iron made from this ore, if puddled, to yield a wrought-iron which is both 
cold- and red-short. 

7. Franklinite, (Fea03[ZnO,MnO]), containing 45 per cent of iron, 21 percent of zinc, 
and 9 per cent of manganese. This ore occurs in New Jersey, U.S., and is there employed 
both for the extraction of iron and zinc. 

Iron is also obtained from rich slags, which often contain, in the shape of protoxide of 
iron, an amount varying from 40 to 75 per cent of that metal ; they are employed in the 
puddling process. The scraps of iron resulting from various operations, old iron, and 
waste pieces of the metal, are usefully applied, either alone or with the ores, to be re-con- 
verted into metal. 

Taken from a metallurgical point of view, iron ores are distinguished as reducible easily 
or with difficulty (convertible into metal readily, or fusible with difficulty). To the former 
Class belong all those ores which, while being submitted to a preliminary roasting, become 
porous, and hence more readily penetrable by the reducing gases present in the blast- 
fomaoe ; and, as a consequence, more rapidly reduced and molten. The spathose iron 
ore and brown iron ore belong to this class ; the former because on roasting it loses 
carbonic acid, while the latter loses water. Magnetic iron ore, and hematite iron ore in all 
its varieties, are reducible with difficulty. 

a. Pio OB Crude Iron. 

^*Sj£*iuSi^ The extraction of iron from its ores is chiefly based upon the two 
foUowing . properties : — i. While particles of pure or nearly pure iron are infusible 
even by the heat produced in the blast furnace, they are possessed of the property of 
agglutination to larger masses ; in other words, the property (possessed by iron and only 
a few other metals) of welding together at a bright red heat. 

2. Iron is capable of uniting, while exposed to a high temperature, and in the 
presence of an excess of carbonaceous matter or gases containing carbon, with 
that metalloid, forming with it an easily fusible compound, viz., a carburet of iron, 
the so-called pig- or cast-iron. 

The direct manufacture of malleable iron from iron ores was in former times a very 
nsual proceeding, and is yet carried on to a small extent in some parts of Europe 
(Styria, Andorra, Sardinia, and Sicily), and far more so in Hindostan ; but this 
method, known as the Catalan process, is wasteful, and although it yields iron of 
excellent quality, it also requires ores of great richness. The process is not suited to 
meet tlie large demands now made for iron ; with these trifling exceptions aJl iron at 
the present day is obtained by the production first of pig-iron, which is afterwaida 
converted into malleable iron by the puddling process. 



lo CHEMICAL TECHNOLOGY. 

The operations by which iron is extracted from its ores are : — calcination or roasting, 
and smelting. The object of the first-named operation is the removal from the ore 
of such substances as water, carbonic acid, carbonaceous matter (as present in the 
black-band ironstone) ; also the conversion of any protoxide into peroxide, because 
the latter is less apt to become absorbed by the slag, and to promote the porosity of 
the ore. The calcined ores are next broken up to lumps of suitable size by means 
either of stamping mills or cylinders, or by macliinery specially made for the purpose 
on the principle of quartz and stone crushers ; after this has been done the ores are 
mixed, rich and poor together, in such proportions as have been found in the ex- 
perience of the workmen to jrield the best quality and largest quantity of iron. 

Theory of theLitm Bxtroction ^hc orcs having thus becu mingled, constitute a mixture made 
up chiefly of an oxide of iron and of gongue (silica) or lime ; carbonaceous matter 
is added thereto, and the mass is submitted to a strong heat, the result being the 
reduction of the iron to the metallic state, according to the following equation: — 

Fe203-J-3C=3CO-|-2Fe; 
the action, therefore, of coal is to serve as fuel and at the same time as reducing; 
agent along with carbonic oxide and carburetted hydrogen ; if, however, the operation 
were performed by simply mixing the broken up ores and coal or coke, and 
submitting this mixture to the smelting process, the iron would be obtained in a 
finely divided and spongy condition ; and in order to procure the union of the particles 
of metal so as to form a molten mass previous to the smelting operation being pro- 
ceeded with, certain substances which have the property of forming with the gangue 
a readily fusible glassy mass are added. The substance added is technically known 
as slag, and it serves not only the purpose just mentioned, but also that of with- 
drawing and absorbing from the ore such materials as might injure the quality of 
the iron ; and, lastly, the slag being by far specifically lighter tlian molten iron, floats 
on the surface and protects the metal from the oxidising action of the air blown into 
the furnace. Slag is a mixture of various silicates ; in some instances the ore itself 
contains, along witli the oxide of iron, the constituents necessary to form a good 
slag, but in most instances ores require the addition of such materials as will form, 
with the constituents (excepting the iron oxides) a proper slag ; thus, for instance, if 
silica were wanting, quartz or sand would be added ; and if bases were wanting, lime- 
stone or fluor-spar (fluoride of calcium) would be added. The . slag should become 
fluid at or about the same temperature as the metal. The mixture of ironstone aid 
slag-forming material is caUed a batch, and is so arranged as not to contain above 50 
per cent of iron. When iron in the molten condition and carbonaceous matter (coal, 
coke, or charcoal, although the latter is very rarely used) come in contact, as is the 
case during the smelting process just alluded to, the molten metal dissolves a lai^e 
proportion of carbon ; but when the metal cools a portion of the cai'bon separates in 
the crystalline form ; this is termed blast-furnace graphite : another portion of the 
carbon remains, however, in chemical combination, and it is therefore evident that 
the smelting of iron ores produces an iron — ^pig or crude iron — ^which contains 
carbon, and is, therefore, not a pure metal. 

BiMt-farnAoe proeeaa. At the prcscut day the extraction of iron from its ores (smelting) is 
chic^fly carried on eitlier in what are termed blast-furnaces or blowing-furnaces. 
Tlirse contrivances are not essentially diflerent from each other as regards their 
action, but their arrangement and construction is so far different that the slag from 
blast-furnaces, working as thoy do witli what is termed an open breast-plate, runs off" 



IHO.W 1, 

continiiously, while the eIi^ from the blowing -fiimace lina to be cleared from to time 
when tapping the metal. 
""Sln'i^JiSU!" * blast-fnmace is an oven shon-inft on the exterior a heavily made 
wall (Fig. I, A, the outer wall], having a height of from 14 t« 35 metiee; the imier 
limng ia made in the shape of two tmncaUd cones placed together at their basee ; 
the brickwork ifire bricks) which constitute this double cone-like Btructure, b, is 



Fio. 1 




"7% 



BniTound d by a cftain" m 1, le up f 1 rikm s 01 r 1 t -\ u 1 lu ! is eil 

Teloped bj the cxtcrTtal coHtin„ of heaiy mas nij the aajid is a, bad conductor of 
heat and admits also of space bemg allowed for the expansion by heat of the interior 
Blructure The portion of the mtemal rone extPn hn,, from b to c IB called the shaft, 
or chamber, while the portion which extends from d to e is named the boshes ; the 
part of B where the diameter ia greatest is called the belly or upper part of the 
bosheB. Below the bosliea at r. the space is gradually made nsirower, and called 
the throat, or tunnel hole, the lower part of which is intended for collecting the molten 
metal, and named the crucible or hearth ; this portion of tlie blnst-fumoce is lite 
most important, because the Bracltiiig process goes on in it; the crucible is pro- 
Tided with two openii^ placed opposite to each otlier. and containing conically- shaped 
lubes (see Fig. 2) called the tuyores, euding in what are termed the nozzles or nose 
pipes, or the blast pipes ; these tubes scn-e to convey tlie ah- necessary for the 
furnace. As ahown in the engraving, the admissiuu of air to the nozzles is regulated 



12 CHEMICAL TECHNOLOGY. 

by a valve. The upper open end of the furnftoe at * is caUed the mouth or furnace-top ; 
through this opening the fuel and nuKture of ore and flux are put iuto the furnace, 
which is (as also shown in Fig. i) situated on or near the slope of a hill, so as to 
have ready access to the mouth by meane of the bridge for conveying the materials 
to the furnace-top. The lower part of the hearth is prolonged towards the front, thus 
forming the breast-pan, which is enclosed by the dam-stone, m ; this stone is somewhat 
removed at one side from the wall, thereby forming a alit, which is technically called 
the tap-hole ; this is the discharge aperture ; while the smelting is going on this 
aperture is closed up with fire-clay, which is removed when it is required to with- 
draw the sl^s or tap the crucible, that is to say, discharge the molten metal. The 

Fio. 3. 




dam-stone is protected by an iron plate. Three only of the sides of the hearth are 
continued to the stone constituting tlie bottom of the arrangement : the fourth is 
merely brought to within a certain distance of the base, where it is supported by 
strong girders of caat-iron firmly fiied into the masonry of tlie walls, and on which 
rests a heavy bloch of sandstone called the tymp (see Fig. i), which is supported 
by a very heavy and stout piece of iron called the tymp iron. 

iiM^wtaBKmiM Jn order to provide the necessary quantity of air for the blast- 
furnace, a blowing engine is attached ; this is now almost exclnsively constructed 
npon what ia termed the cylinder principle, which iu one of its most convenient 
forms is delineated in Fig. 3. The cast-iron cylinder, a, contains a piston, c, which 
by means of the piston rod, a, passing air-tight through the stuffing box, e. can 
be moved upwards and downwards; at b and d the cylinder ia in commnnication n-itli 
tlie outer air, and by means of/ and g it communicates with the chest, e. The 
openings alluded to are provided with self-acting valves for regulating the flow of air, 
wliich is conveyed through i into the pipes communicating with the blast-fiimace. In 
order to regulate the blast, a large sheet-iron vessel, in construction very similar to 
the jias-holders of gas-works, and acling on the same principle, is applied. The 
application of hot air for the blast is one of the most important improvements iu the 



IRON. 13 

mannfiactare of iron, since, in this way, a decreased consumption of fael, to the 
extent on an average of 0366 (from i to |), has been obtained; while, moreover, 
the absolute gain in the production of iron amounts to about 50 per cent. It is also 
stated bj many iron-masters that the fiimace is more readily and regularly worked ; 
but this statement is discredited by others, who aver against the hot blast that dis- 
turbances arise more frequently in the regular course of working ; also, that the very 
high temperature in the crucible causes the rapid destruction of the fire-bricks, and 
consequently impairs the time of what is technically termed the campaign, that is to 
sav, the duration of the fabric of the blast-famace. The air intended for the hot blast 
is heated either by the gases given off by the blast-furnace, or by means of separate 
fire-places which heat a pipe apparatus, or lastiy by means of Siemens's regenerative 
furnace system. This system consists in first conducting the gases of the blast- 
famace through a fire-brick built space filled with fire-bricks loosely piled together, 
which becoming thoroughly red-hot are in that condition capable of heating the 
cold air previous to admitting it, care being taken to shut off the blast-furnace gases; 
by this means the air can be heated to a temperature very far exceeding that which 
is attainable by passing the air through iron tubes, these not admittiQg without serious 
injury of being heated to so high a temperature in contact with air. The hot blast 
air is heated to from 200** to 400'* C. ; blast-furnaces fed with coke as fuel require per 
minute of time from 2000 to 4000 cubic feet of air. 

s^SSi ft«J«. -^^ blast furnace is worked in the following planner : — The furnace 
is first heated by igniting in it a quantity of wood. When this has rendered the oven 
thoroughly dry, the fuel intended for use in the course of the continued process is 
put in (this fuel used to be in Germany wood charcoal, but at the present time there, 
as in England, coke is employed, or sometimes smthracite ; common coals are rarely 
used) ; the furnace is at first entirely filled with fuel, and when quite full the blast is 
turned on and a beginning made with the charging of the mixture of ore and flux, 
alternating with fresh fuel. By the burning of the fuel, and the fusing of the ore and 
flux, the layers sink downwards, the silica fuses, forming, while combuiing with the 
earths and some of the oxides present in the ore, a slag which is commonly coloured 
by the presence therein of oxide of iron, while the iron reduced to the metallic state, 
and semi-fluid at first, combines with carbon to form readily fusible pig-iron ; the molten 
metal collects in the hearth or crucible ; the fused slag floats on the top of the motal, but 
is run off over the dam-stone. The molten metal is tapped off about twice every 
24 hours, or as soon as it appears to reach the height of the dam-stone. The aperture 
here alluded to, and closed provisionally by means of fire-clay, is opened by the 
piercing of the latter, while the molten metal is conveyed through channels made in 
the sand to the moulds, also formed in the same material : during the operation of 
tapping, the blast is shut off. Crude iron cast in the shape of cakes is called lump 
iron, and when run into bars, pig-iron. The campaign, that is, the operation of 
smelting with the same furnace, often lasts many years ; it is, in fact, continued until 
the oven or blast furnace becomes worn out. 

ciwminiProcMiKoinff The chemical process which is going on in the interior of the 

onfaiUwIatatlorof the o o 

BUatFaxuM. blast fumaoe when at work (technically, while in blast) differs con- 
siderably in different portions of the vertical section. The annexed Figs. 4 and 5 repre- 
sent the interior of a blast furnace exhibited in perpendicular section, and filled with 
alternate layers of fuel and mixed ore and flux, the latter being indicated by the 
narrower, the former by tiie wider layers. Counting from the siu*facc of the fluid slag, 



14 CHEmCAL TECHNOLOGY. 

//, op to the mouth of the furnace tlie iuteiior may bu divided iut« fivu zoiiee or 
regions, viz : — 

I. The &'st heating zone, a b. 

z. The reduction zone, b c. 

3. The carburfttiou zone, d. 

4. The meltii^ zone, d e. 

5. The comboBtion zone, ef. 

In the upper part of the furnace, the first heating zone, the materialB become warmed 
and are rendered tlioroughly dry, but they hardly become hotter than a low red heal. 
The reduction zone ie the largest in extent. In the lower part of the shaft of the fumaoe, 
and especially towards the belly, the oxide of iron is, by the action of the redticiiig 
gases, first converted intoprotoxideof iron and nest into metal.- The reducing agents 
present in thia :;one are — carbonic oxide, earburetted hydrogen gas, and hydro- 
cyanic acid gas (cyanide of hydrogeni, or vapours of cyanide of potaEsium; at a certain 
part in this zone the iron is present as malleable iron. Deeper dorni in the furnace 
the oarburation zone is met witli ; liere tlie combination between the iron and carbon 




takes place, producing a more or less al«el -like and somewhat caked iron, wliich, when 
sinkii^, enters the melting zone and is saturated with carbon and entirely brought to 
the state of pig-iron. At the portion foi-ming the corabnstion or oxidation zone, which 
is, as compared with the other zones, only of very small extent, tlic air from the 
blast enters the fiimace through tlie nozzles, and meeting with iuciindcscent coke at 
the highest possible white heat, causes the formation of cai-bonic acid, but tliis gas in 
passing upwards tlirough other layers of incandescent fuel becomes reduced to 
carbonic oxide ;C0i+C=2C0i ; by the corabnstion of the hydi'ogen contained in Uie 
fuel, water is also formcil. wHclv, alonj; witli the aiineoiis vapour contained in Uic air 



IRON. 15 

of the blast (recently it has been tried to eliminate tliis aqueous vapour by passing 
the air previous to reaching the nozzles through concentrated sulphuric acid) is 
decomposed by the enormous heat of the middle portion of the furnace as well as 
by the presence of carbon, forming hydrogen and oxygen, the former of which enters 
into combination with the carbon, forming carburetted hydrogen, while the latter com- 
bining with the same element produces carbonic oxide. The nitrogen present in tlie 
coke, as well as a portion of tlie nitrogen present in the air of tlie blast, combines %vith 
the carbon, forming cyanogen (eitlier as cyanide of some metal or as cyanide of 
hydrogen).* Tlie reducing gases meeting with the ores cause the oxides present 
to be converted into metal, wlule the gases remaining (the blast furnace gases) 
escape from the mouth of the furnace. The reduced iron combines, wlule sinking 
downwards, with carbon, forming the crude metal, and fuses in so doing ; the imion of 
the particles being promoted by the slag. As soon as the iron reaches that portion of 
the furnace where the heat is strongest, the carbon contained in the metal begins to 
exercise its reducing action upon such substances as alumina, lime, silica, &c., which 
in the reduced, or metaUic, state combine with the iron. 

Becent researches have proved that the copious production of hydrocyanic acid 
generated by the process going on in the 1>last-fumace greatly and very essentially assists 
the redaction of the ores ; that compound of course combines with the edkaUes and alkaline 
earths contained in the fuel and other materials. It has been surmised that the crude 
iron is not solely a carburet of that metal, as might be produced by the decomposition 
of cyanide of iron, but, in addition to a small quantity of that body, contains also 
nitride (a nitrogen compound) of that metal. In support of this view the fact is brought 
forward, that Dr. Wdhler, of Gottingen, found many years ago that the cubical crystals 
of what was considered to be metallic titanium, and found in the blast furnace slag, turned 
ont to be a compound of nitride of titanium and cyaaide of that metal. In order to give 
some idea of the large quantity of metaUic cyanides generated by the blast fxuTiace process, 
we briefly quote from the researches made on this subject by Drs. Bunsen and L. Playfair, 
that an English blast-furnace, fed with coal as fuel, produced daily a quantity of 
225 ponnds. M. Eck, who made some researches on this subject at Eonlgshutte, in Upper 
Silesia (Prussia), discovered the formation of both cyanide and sulphooyanide of potassinm, 
and he found by calculating from the quantity of potassa contained in the ores, flux, and 
fuel, a daily production of 35 i pounds of cyanide of potassium. The reduction of alumina 
and silica to aluminium and silidum also takes place in the melting zone. 

SSJSSDiif^'pSSi! ^^' 5 exhibits the temperature prevailing at the limits of each 
zone. The temperature of the combustion-zone would be far higher than happens 
to be the case were it not that, by the conversion of carbonic acid into carbonic 
oxide — ^that is, the absorption, or more correctly vapourisation of carbon — a considerable 
lowering of temperature (in other words, absorption of heat which becomes latent) is 
produced. It should be remembered that here the volume of tlie carbonic acid is 
also doubled, while this reaction is taking place, and that process of course also 
absorbs heat. 

Taking into due consideration the fact that, under tlie most favourable conditions, 
only i6'55 P^^ ^^^ ^^ ^^ ^^^ supphed to a blast-furnace is usefully consumed, 
while no less than 83*45 P^ *^^^^ escapes from the mouth in the shape of com- 

^^■JJJJ^** bustible gases, it cannot excite any wonder that the idea arose of utilising 
these gases : this idea has actually resulted in various useful ways, as, for instance, 
for the fusion and puddling of the iron, for the refining and cleansing by welding 
of the iron, for the heating of the blast, the roasting of the ore, and the drying 
and carbonisation of the wood. 

* According to the view of M. Berthclot [1869] there is in this instance first formed 
acetylide of potasflium, GaKa* which then combines directly with nitrogen to form cyanide 
of potassinm, 2(CNK). 



i6 CHEMICAL TECHNOLOGY. 

^^toSfuanniiS^?^* ^® application of the gases to the useful purposes just mentioned 
Sia-«mmoniac. does uot exhaust the list of such appUcations. Drs. Bunsen and 

Playfair found that the gases emitted by blast-furnaces fed with coal as fuel contain such 
a large amount of ammonia that the presence of that gas in the lower parts of the blast- 
furnace is even perceptible to the smell. These eminent savants proposed to convey the 
gases previous to being used as fuel through a chamber containing hydrochloric acid gas : 
the solution of sal-ammoniac thus obtained should be run into the pan of a suitably 
constructed reverberatory furnace; and a small portion of the current of gas, after 
having been ignited, being carried over the surface of the liquid, the evaporating process 
can be regulated so as to obtain a continuous stream of a concentrated solution of sal- 
ammoniac as a metallurgical by-product. Experiments instituted at the Alfreton Iron 
Works (blast-furnace) proved that in this way about 2-44 cwts. of sal-ammoniac could be 
produced daily without any great expense and without any interference with the process 
of iron manufacture. The formation of sal-ammoniac is intimately connected with the 
formation of cyanogen just spoken of. When cyanide of potassium comes into contact with 
aqueous vapour, it is decomposed into ammonia and formiate of potassa — 

(KCN-f 2H20=NH3-fCHK02} ; 
the reverse reaction, that is to say, the withdrawal of aU oxygen in the form of water, 
from formiate of ammonia would result in the formation of cyanide of hydrogen — 

[CH(NH4) Oa ~ 2H2O = CHN] . 

^Ss^iron?* '^^ ^^^^ obtained by the blast-fttmace process is impure, and therefore 
called crude cast-iron ; it contains carbon (in the shape of graphite as well as 
in a state of intimate chemical combination witli iron as a carburet of that metal), 
silicium again as so-called silicium graphite and as a siliciuret of iron, sulphur, 
phosphorus, arsenic, and aluminium. The colour and physical properties of the iron 
are determined by the quantity of carbon it contains. Formerly the more or less 
deep colour of the crude iron was believed to be dependent upon the larger or 
smaller quantity of carbon the iron contained, and accordingly, the deepest 
coloured metal was supposed to contain the largest, and the least coloured iron the 
smallest, quantity of carbon ; investigations have, however, satis£a,ctorily proved that 
it is not so much the quantity as the manner in which the carbon (likewise the 
silicium) is present that determines the quality. The fact is, that ^dth carbon and 
silicium a portion only is chemically combined with the iron, while the largest pro- 
portion of these metalloids is only mechanically mixed with the metal, being,- as 
already stated, present in the form of graphite (graphitic carbon and silicium). 
According to the researches of M. Fr6my and others, it is probable that crude iron 
frequently contains nitrogen, and that the presence of this element influences the 
quality of the metal ; but tliis view is not endorsed by MM. Caron, Gruner, and 
Dr. Kammelsberg. There are two chief qualities of crude iron in the trade, viz., 
white and grey coloured. 

White cwt-iron. "White cast-irou is distinguished by its silvery white colour, hardness, 
brittleness, strong lustre, and higher specific gravity, which ranges from 758 to 768. 
Sometimes this kind of iron happens to contain prismatic crystals visible to the 
naked eye, and such iron is then caUed spiegeleisen, or crystalline pig (crude steel 
iron). This variety of iron may be viewed as a combination of CFes, or, more accu- 
rately stated as FeeC+FeaC, with 593 per cent of C. If the structure of the white 
cast-iron is radiated and fibrous, while the colour is bluish grey, ihe metal is known 
as white pig-iron with a granular fracture. When the white colour disappears still 
more, and the fracture becomes jagged, such a metal holds a medium between wbite 
and grey pig, and is therefore called porous white pig. 

owy Out-Iron. Grey cast-iron exhibits a bright grey to deep blackish grey colour. 
Its texture is granular or scaly ; its specific gi'avity averages about 7, consequently 
less than the white variety, and the grey iron is also less hai-d/ When pigs happen 



IRON. 17 

to contain both grey and white iron in portions only, or dispei-sed t}u'oug}i their entue 
mass, such metal is called half-and-half iron, and is specially applicable to foundry 
purposes. The chemical diJSerence between white and grey cast-iron is due to the 
fact that the former only contains chemically-combined carbon (from 4 to 5 per cent), 
while the latter contains from 05 to 2 per cent of this element in the combined 
state, with rather more than that amount mechanically mixed, viz., from 13 to 37 
per cent. As regards the melting-point of cast-iron, the white variety fuses at a 
lower temperature and more easily ; but the grey cast-iron possesses far gi'eater 
fluidity. Crude cast-iron is not malleable, and cannot be welded or forged ; when 
made red-hot, it becomes very soft — so soft that it can be cut with a saw such as is 
used for sawing wood; but when placed on an anvil and hammered, this iron 
breaks into fragments even when red hot. Grey cast-iron is the best, and, in fact, 
only suitable kind of crude iron to be used for making iron castings. The perfect 
fluidity of this metal when molten causes it to fill the moulds well, and to yield excel- 
lently sharp and well-defined forms. White cast-iron, on the contrary, is not used 
for iron-foundry purposes, because, while solidifying, it warps, and the surface 
becomes concave.' Grey cast-iron can be filed, cut with the cold chisel, turned upon 
the lathe, and planed. White cast-iron is too hard to admit of any such operations 
being performed upon it. Grey cast-iron, molten and tlien suddenly cooled, is 
converted into white cast-iron ; on the other hand, white cast-iron, molten at a very 
bigh temperature (heated far above its melting-point), and cooled very slowly, becomes 
converted into grey cast-iron. 

The quality of the iron produced by the blast-furnace process does not so much depend 
apon the ores and other materials Used. In this respect the temperature is of far greater 
importance. It would appear that after eveiy fresh charge there is at first produced white 
cast-iron, which is only converted into grey cast-iron by a very much increased tempera- 
ture. If the reduction of the ore to metal — care being of course taken to have a proper 
proportion of ore and the other materials — proceeds reg^nlarly, the furnace is said to be in 
a healthy state of working. Under such conditions, the slag, which contains only very 
little protoxide of iron, is never deeply coloured. If fuel were not snppUed in proper 
proportion and the ore to prevail, the reduction would probably be imperfect and the slag 
a deep eolonr, in consequence of the presence of a liurge quantity of protoxide of iron 
(colour of dark green bottle glass). Such a condition of working is termed irregular. 
When, in consequence of an excess of fuel, the heat in the furnace becomes very great, 
that condition of workmg is termed hot, and only grey oast-iron is formed. 

The results of the chemical analysis of some varieties of crude metal may elucidate the 
general composition of cast-iron : the under-mentioned samples are : — i. Speigol iron, made 
from 14 parts of spathose ironstone and 9 parts brown iron ore (Hammerhiitte). 2. White 
pig-iron, with a granular fracture, from Styria. 3. White pig. 4. Half-and-half pig. 
5. Grey east-iron (from brown iron ore and charcoal). 6. Grey cast-iron, from brown iron 
and spathose iron ore mixed. 7. Grey cast-iron, from ochreous brown iron ore and coke. 
The sign — indicates that no search or testing was made for the substance ; the sign o in- 
dicates that the substance was not found. 

I. 2. 3. 4. 5. 6. 7. 

Combined carbon .. 5'i4 4-920 2*91 278 0*89 i'03 0*58 

Graphite o o o 1-99 371 3*62 2*57 

Sulphur o*o2 0*017 o'oi o — — — 

Phosphorus .. .. o-o8 o o"o8 1*23 — — — 

SilicLum 0*55 o o 871 — — — 

Manganese 4*49 o 179 o — — — 

The results below are those obtained by M. Buchner, while examining the quantities of 

earbon and sUicium contained in crude iron : x, 2, 3, 4, are spiegel iron, almost or quite 
ciystaUine ; 5, 6, porous white pig. 

1. 2. 3. 4. 5. 6. 

Cy 4'i4 3«o 4*09 375 3*3i 3'03 

C/3 ^ _ _ _ - - 

Si O'oi 001 0*26 0*27 Spur 0*15 



i8 CHEMICAL TECHNOLOGY, 

7, 8, 9. White, very bright, crude iron. 10. White pig. 11. Half-and-half pig. 
12. Strongly mixed half-and-half. 

7. 8. 9. 10. II. 12. 

%:: :: :; ^1° *r 'i^ ^'^] 3-34 ^t 

Si o'i4 o*i2 0*10 0*66 o'lo 0*20 

13. Less strongly mixed half-and-half. 14, 15, 16. Qrey cast-iron. 17. Ooarse-grained 
cast-iron. 18. Over-coaled black-greyish cast-iron. 

13; 14. 15. 16. 17. 18. 

O7 2*17 i'35 i*i8 071 0*38 0*26 

C^ 2'ii 2*47 2*42 279 3*28 3*83 

Si 0*09 070 o'66 1*53 1*62 0*59 

"ttSplStaSS???* ^® present (1870) production of crude iron (pig-iron) amounts to 
crade-iron. rather more than 200 zuillions of hundred weights. Of this quantity the 
under-mentioned countries produce : — 

United Kingdom of Great Britain and Ireland 115,000,000 cwts. 

France 24,500,000 „ 

North America, U.S 20,200,000 „ 

Prussia 16,300,000 „ 

Belgium 8,900,000 „ 

Austria 6,750,000 „ 

Bussia 6,000,000 „ 

Sweden 4,500,000 „ 

Luxemburg 1,100,000 „ 

Bavaria 732,000 „ 

Saxony 280,000 „ 

Wurttemburg 138,000 „ 

Baden 16,000 „ 

Hesse 250,000 „ 

Brunswick 90,000 „ 

Thuringia 18,000 „ 

Australia 2,000,000 „ 

Italy 750,000 „ 

Spam 1,200,000 „ 

Norway 500,000 „ 

Denmark . . . . ^ 300,000 „ 

209,524,000 owts. 
EEaving a value of about 97*5 million pounds sterling. 

iron<<oiiiidry-wotk. For the manufacture of iron castings a somewhat mixed greyiron 

B«Miiing onuto oait-boD. jg employed, because its qualities best suit the purpose. Theee 
qualities are closeness of grain, strength, a capability to well fill the moulds, coupled with 
sufficient softness to admit of boring, filing, &o. Although iron castings can be made 
directly from the tapping of the blast-furnace, it is found advantageous and preferable in 
practice to re-melt the pigs. This operation is carried on in crucibles in a cupola furnace, 
or in a reverberatory furnace. Crucibles (made of plumbago or fire-clay) are only used for 
making castings of small size. The quantity of iron melted in crucibles does not usually 
exceed five or eight pounds. 

Shaft at oapoi* rnnuuM. For the purpoBCS of the iron-foundry, the shaft or cupola furnace, 
represented in Figs. 6 and 7, is more generally used. The cupola furnace is in form cylin- 
drical, and from 2*5 to 3*5 met. high. The pig-iron, previously broken up to lumps 
of suitable size, and the fuel, which may be either coke or wood charcoal, are placed m 
alternate layers in the shaft a ; the openings e and d are intended for the insertion of the 
tuyeres connected with tiie blast. The opening leading to the spout, b, is closed during 
the progress of the melting ; as soon as the molten iron reaches the orifice at a, this 
opening is closed by means of fire-clay, and the tuyere first placed in a is transferred to 
the opening d. The molten metal is either conducted by the aid of channels direct to the 
moulds, or tapped into suitable vessels and carried to the moulds. In many instances 
cranes are used to transport the molten metal. Here also the application of hot air has 
been attended with a great saving of fuel. 

B«TariMn*oi7 roinMo. In some cases pig-iron is melted in a reverberatory furnace, the iron 
being placed on the smelting-hearth, which is covered with sand ; the hearth is slightly 
inclined and narrowed towards the tapping-hole. A strong coal fire is made up, and the 
flame playing across the fire-bridge is directed over the entire length of the foniace. and 



ISON. 



>9 



thenoe into b high ohimnBy, Tha molten metal on being tapped is oondnoted to the 
■uoDlds in the Bune manner aa with the oapola fnrnaoB. Rather more than 50 owta. of 
mg-iroD oao be melted at once in a reverberatory fnmaoa ; but ainoe the air has free aooeas, 
the iron beoomea gradnally deoarboaiaed, and is thuH rendered unfit for oaatings. 

iuWb« ih> miiul The most aaBential, and also most diffionlt, part of the iron-fonnder's 
work IS the proper oonrtmctionof themouLla. Aooording to themateriaU from which the 
moiildB are oongtmctod, wo distinguieh — 1. Sand mouldmg or green-sand moulding, the 
material being a peculiar kind of aand (foundry- aand).— It ia necesaa^ for this aand to be 
«oeedmgly fine, and yet suffioiently coherent that the aharpeBt anglee and oomerB will 
TBBinn standing. This latter property ie imparted to the Band by adding as much clay aa 
will render the mass capable of being squeezed with the baud into balls when uioiBtened 
with water. A certain amount of porosity ia also requisite to enable the steam which is 
loimed whan the molten iron oomes into contact with the monhl to readily escape. This 
propatty LB oommunioated by the addition of powdered charcoal. Sand-monlda are not 
dned before the molten iron is ponied in. Such objects as platea, grates, tailinga. and 




wbeda, which are lerel on one aide, are oast in open sand-monldB ; that is to say, od the 
floor of the foundry. preTionaly covered with sand of the requiaite quality, the moold* 
being obtained by pressing the patterns into the Band. For other branchee of the work, 
as, for instance, iron-pots, the boi mould is used. a. Dry sand moulding. — The forms are 
made in MUid and oUy, or loam, care being taken to dry the monlda thoroughly before 
easting. 3. Loam -casting.— The material need for this purpose is loam, whi<£, prerioua 
to being nsed, is sifted, moistened, and mixed with horae.dong to picTent the moulds from 
oraoking during drying. 4. Oasa-hardeoing, or casting in iron moulds. — Thia mode of casting 
iron only applies to some pemliar descriptions of work, as, for, inBtanoo, the cylinders of 
roUing-millfl, aome kinds of shot and shells, and railway waggon-wheels.* Bj the nse of 
irim monlds, the casting oools and solidifies Tery rapidly, and, as a conseguenoe, the outer 
layer beoomei oonvertol into white cast-iron, which is very hard. Thus the cylinders for 
rolling-mills can be so made, that while the eurtace ia very hard, they are not brittle, and, 
therefore, fragile, heoanse the interior condsts of grey cast-iron. 

Oreen-sand casting is by far the most general mode ot casting: furnace-bars, cast-iron 
railings, grates, plates, wheels, and a Taiiety of objects, are thus made. Dry-sand 
moulding is used for the casting of iron gas- and water-pipes, and also of east-iron 
ordnance. This latter ia preferably made from such pig-iron as contains grey and white 
iron mixed ; a higher degree of tonghneia and elasticity can thus be obtained. Dry-«and 
monlding is also used tor the maUng of Bmall ornamental objects, so.called fer dt Berlin, 
■uoh as cast-iron ink-stands, candlesticks, and a peculiar kind of cast-iron pins, as well as 
brooches, ear-rings, and aimilaT things. Loam-monlding is used for the casting of large- 
■ited eaiUdrons, beUa, and other large objects for which no wooden pattern is made ; (Jio 
for the eaMing of »tMm-«ngine cylinders. We distinguish in this kmd ot monlding three 
chief parts, Tiz. : — 

e made of best 



wroaght-iron, and forged by n 



n itaam-hammeni. - 



20 CHEMICAL TECHNOLOGY, 

a. The core, or kernel, the size and shape of which corresponds to the intOTior of the 
object to be cast. 

b. The foundry-pattern. 

c. The exterior mould, also termed the case. 

The loam mouldings are verj' rapidly dried ; the casting of statues and other monumental 
work is done by loam moulding, but zinc is beginning to supersede iron for this purpose. 
Whenever objects have to be cast, the surface of which is very unequal, ».#., so shaped 
that a partial dismounting of the case is impossible, as may happen for instance with 
statues and monumental work, the shape is made on the core by means of wax : the 
pattern maker constructs a pattern, often consisting of a number of loose pieces ; into this 
the molten wax is poured, and the mould thus obtained is carefully placed on the core and 
properly joined. The wax mould is brushed over with a mixture of pulverised graphite and 
very finely divided clay, which operation is several times repeated ; after this the mould is 
covered with a layer of loam mixed with cow hair, and as soon as this layer is dry the wax is 
removed by applying a gentle heat, a channel having been left by which the wax can escape. 

Annealing. The Castings, when sufficiently cool, are deaned from adhering sand, the seams cut 

Tempering, ^ff with acoldchisel, and in many cases submitted to a series of mechanical opera- 
tions, as, for instance, cast-iron ordnance, which has to be bored, while other ohjects have to 
be worked in the lathe and planed. Frequently cast-iron objects have become as hard and 
brittle as if they had been cast from white pig-iron, and consequently are unfit for 
filing, (&c. ; such iron is restored to the requisite softness by annealing or tempering. In 
this operation the castings are submitted to a strong red heat and cooled slowly, being at 
the same time protected from the oxidising influence of the air ; the annealing is effected 
either by a physical or a chemical process. If the former is used, the castings are simply 
covered with a thick layer of clay and made red-hot, the effect being a simple rearrangement 
of the molecules of the iron, which is thus rendered soft again ; the heating to redness is 
also sometimes effected by placing the castings under a layer of dry sand or in suitably 
constructed vessels filled with charcoal or coke powder. If it is desired to impart to the 
castings somewhat of the strength and toughness possessed by steel and malleable iron, 
the tempering is so arranged, and heat appUed for a longer time, while the metal is 
surrounded by a mixture of pulverised charcoal, bone-ash, and forge scales, red oxide of 
iron, oxide of manganese, or oxida of zinc ; cast-iron which has been uniformly and 
thoroughly decarbonised, is called malleable cast-iron. A great many objects formerly 
exclusively made of wrought-iron are now cast and treated in this way, while a number of 
others, inclusive even of razors, are made of cast-iron superficially converted into steel by 
a method which will be described under the heading of Steel. In order to prevent the 
rusting of articles made of cast-iron, they are frequently covered with a varnish made from 
coal tar and powdered graphite, or boiled linseed oil and lamp-black, and when intended 
for ornamental or domestic use they are bronzed or burnished. 

Enamelling of Among the first cast-iron objects ever enamelled were the pans used in 
caat-iron. kltchens for culinary purposes, but at the present time, especially in England, 
the enamelling of cast-iron is carried on to a large extent and includes a variety of things 
made of cast- and even wrought-iron. The process in use is briefly as follows : — The 
surface of the cast-iron to be enamelled is first carefully cleaned by scouring with sand 
and dilute sulphuric acid, next a somewhat thickish magma, made of pulverised quartz, 
borax, feldspar, kaolin, and water, is brushed over the clean metallic surface as evenly as 
possible, and immediately after a finely powdered mixture of feldspar, soda, borax, and 
oxide of tin is dusted over, after which the enamel is burnt in by the heat of a muffle. 
In France an enamel is applied which consists of a mixture of 130 parts of flint glass, 
20 1 parts of carbonate of soda, and 12 parts of boracic acid fused together and afterwards 
ground to a fine powder. Enamelled iron has in some manufactured articles taken the 
place of tinned iron or zinc. 

/3. Malleable, Bar, or Wrouoht-Iron. 

BSn*.?'2on. ^ comparatively olden times the custom was to produce malleable 
iron direct from its ores by a process still in use to some extent in Styria, Illyria, Italy, 
Sweden, some parts of Asia, Andorra, and other localities. The process (a modification 
of wliich is known as tlie Catalan process) consists in the reduction of the iron ores, 
which must be very rich and pure, by means of charcoal, which serves also as fuel on 
a hearth, the combustion being aided by a blast, often simply bellows ; the lump of 
iron thus obtained is immediately submitted to the blows of a heavy forge hammer. 
Excepting in the few instances just mentioned, this process of direct extraction of iron 



from its ores has been altogether abandoned, and has given place to the production of 
malleable iron from pig-iron ; the process by which this is effected is tenned refining, 
And consiats in the removal of the greater portion of the carbon and other imporitieB 
contained in the crude meUl by oxidation. The crude metal cliiefly employed for 
refining is white pig-iron, preferably that containing the least possible quantity of 
cubon, because this kind of iron becomes soft before melting and remains for a long 
time very fluid, and therefore presents a larger surface to oxidising agents ; the chemi- 
cally combined carbon of while pig-iron bums far more readily tlian the graphite con- 
tained in the cmde grey cast-iron. The refining process is executed eitlier ; — (i) On 
hearths |the German process) ; or (2I In reverberator)- fiimaces (puddhng or English 
process) ; In the preparation of bar -iron (3) by tlie forcing of air into the molten metal 
(Bessemer and other siniilar processes). This latter process is described under Steel. 
°'™"pJSJi?''°'^ '^^ hearth on which this process is carried out is represented in 
Fig. 8. The cmde iron is placed in the cavity a of tlie hearth, 6, and the metal is 
brought to fusion in such quantity that the molten mass has a lei^th of from i to 
i'3 metre, a width of about 27 ceutims., and a thickness of from 4 to 9 centims. The 
canity, a, is hned with thick plates of fron, and the tuyere, e, supplies the necessary 
air from a blast which is directed against the molten metal. The hearth is ffrst filled 
with ignited charcoal ; next the blast is turned on. and tlien the crude metal is placed 
on the hearth, b. and becoming gradually melted, flows into the cavity, a. The action 
uf the blast causes the combustion of the carbonaceous matter of the metal, while the 







sand adhering to the pigs, thcsilicadae to the oxidation of the siUeiiuncontsiued in the 
cmdeiroD, andthesilicacontainediu theashof the fuel, airplay an important part in 
the process, because these substances combine with the protoxide of irnn which is pre- 
sent, forminjn slag,* compo^d of basic siEcate of protoxide of iron lin 100 parts, 68-84 
protoxide and3i'i6 silical. This slag protects the iron during the refining process, but 
is gradually run off. eare being taken, however, to leave a sufficient quantity to cover the 
melal. Mixed with for^n-seaiea (o mixture of prote- and peroxide of iron), the slag of 
the first refining is employed in the further refining process to decarbonise the iron. 
When crude cast-iron is heated to redness along with tliese materials, the oxygen con- 
tained in them is given off, and combining with the carbon contained in the cast-iron, 
forms carbonic oxide and leaves malleable iron. The refining process also cansee the 
moreor less complete elimination of such substances as alumininm, phosphorus, and 
manganesefrom the cmde metal, by convertiog them into alumina, phosphoric acid, and 
protoxide of manganese, all of which are taken up in the slag. As soon as all the iron 
has become fluid the slag is run off and the metal exposed to the action of the blast. 



22 CHEMICAL TECHNOLOGY, 

oare being taken to work the metal about so as to render the action nniform ; the 
somewhat thickish flnid mass becomes during decarbonisation more and more fluid, and 
the stirring up, or raising up, as the operation is termed, is continued untQ the iron is 
refined, which is shown by the iad of the slag becoming very rich in protoxide of 
iron. Towards the end of the operation, the rich slag, Si04,Fe2, is formed, which 
along with forge scales, is employed for decarbonising the metal. This rich slag is 
never crystalline in structure, but exhibits a dense tough mass of higher specific 
gravity than the raw slag. The operation, called the last breaking up of the lump, 
consists, first, in the rendering of the entire mass (the contents of the hearth) semi- 
fluid, by increased heat ; and, secondly, in the separation of the slag firom the metal. 
This end having been attained, the lump, or ball, or bloom, is removed from the fire, 
in the red-hot state, and brought under the lift-hammer, a (Fig. 9), which is set 
in motion by means of a lifter and beam. By the blows of the hammer all the 
particles of slag are squeezed out from the metal ; afterwards the lump is cut into 
smaller pieces, which are forged into bars ; 100 parts of crude cast-iron yield on an 
average 70 to 75 parts of malleable iron. 

Swedish Bdflniag proeeo. The Swedish process of iron-refining (also called Walloon-forging 
differs from the German process, inasmnch as only small quantities of crude metal are 
operated upon at a time, while no slag is added, the decarbonisation being effected by the 
action of the oxygen of the air. This process requires a great deal of fuel (in Sweden 
almost exclusively charcoal), while at the same time a not inconsiderable quantity of the 
iron is oxidised. The malleable iron obtained is, however, of far better quality, being 
denser and tougher, owing to greater purity and freedom from-slag. 

TiM Paddling proeeM. The proccBS designated by this name is carried on in a reverbera- 
tory furnace. In countries where charcoal is scarce, and hence too expensive to be 
applied to the refining of iron, coal is used, and, indeed, of later years, has be- 
come more generally employed on the Continent for this purpose. For, although 
the iron thus obtained is of inferior quality to that refined with charcoal, to the use of 
coal alone must the increase in the production of iron to the present ^lormous 
extent be attributed. Since coal contains sulphur, direct contact with iron has to 
be avoided, and the operation is carried on in a reverberatory furnace, which, in 

Paddling Foxnao*. this instance, is termed a puddling furnace, represented in vertical 
section in Fig. 10, and in horizontal section in Fig. 11. f is the fire-place, a the 
puddling-hearth, and c the flue along which the gases are carried to the chimney. 
The puddling-hearth, a, consists of a square iron box, to which air has free access 
from the fire-place. A layer of refining (puddling) slag, to which some forge-scales 
have been added, is first placed on the hearth, and heated until it begins to soften at 
the sur£Eu^. This point reached, the crude metal (by preference white cast-iron) is 
placed on the hearth in quantities of from 300 to 350 lbs. at a time and heated. 
When softened, the iron is spread evenly over the surface of the hearth by means of 
a rake or stirrer, and continually stirred about (puddled), the heat being greatly 
iucreased. d and e represent openings giving access to the hearth for the tools, 
capable of beiug readily closed. 

The soft pasty mass of metal exhibits on its surface blue flames of burning carbonic 
oxide, the metal becoming at the same time thicker and thicker ; the slag which is 
formed runs off at b, and is tapped at intervals at 0. When the iron has been 
sufficiently puddled, it is scraped together and formed into lumps or balls, which are 
submitted to the action either of heavy hammers or squeezers, to free the metal from 
slag. Grey cast-iron, when used for puddling, is first converted into white cast- 
iron by smelting in a reverberatory furnace, known as the refining process. 



ISON. 2j 

^M theoi7 of the pDddling proMK is the follawing : — The enrrent of air whioh oomes 
into oontoot with the molten iion o&nsee the formation of a aot inoonsidereble qnantitj ot 
protoparoxiile of iron, the oxygen of whioh elimtiiat«« the carbon ooniained in the pig-iron 
in the shape of eaibouic oxide, whioh boroi off with a bloiEh flune Tbe progceaa of the 
deaarbooiaation rendere the mase more and more past; ; while, in the interior, pieoea of 
mftlleable iron are gradnall; formed, whioh, being gathered together hj meant of the rake, 
become looaaly wtlded, and the iron not fnlly deoarboiueed nmi together, and being well 
ataired np soon ondecgOM the Mme ohAUge. Although this rerujut ot Uie puddling prooess 

FiQ. lo. 




is tfaeoretisally correct, in practioe the prooesa la not to limple, beeaofe — i. It Is seareelj 
possible to mix all the esrbon-oontaining iron intimately wiUi the protoperoiide, and, as a 
eonseqaence, some of that oxide remains mixed with the iron, whioh is thereby rendered 
incapable ol bejng welded (the iron loses eoheeion and becomes of a gritty nature) : this sub- 
atanee has to be, therefore, removed by the addition of coarse slag, which is thus converted 
into refined slag. The oxidation ot the iron oauses a loss of some 4 to 5 per oent. while the 
loM from tlie oombnstioD ot the oarbon amounts to a further 5 per cent. 1. The crude 




iron ajways contains more or less blast- tumaoe slag and adhering sand and dirt oentaintng 
■iliea. Daring the puddling process any free eilioa present combines with the blaat- 
tornaoe dag, and when this slag, rich in silica, comes at the end of the process into 
Mntaot with protoxide ot iron while carbon is deficient, a portion of the giUoa (or gilicic 
aoid) combines with the oxide, forming a slag which adheres to the aides and bottom of the 
hearth, while a basic, not easily fusible slog remains mixed up with tbe metal. In the 
paddling prooess the great drawback Is that the complete removal ot the slag from the 
iroa is praetioally impossible ; at least, such has been the case hitherto. That iron 
prepared in this way, which may even contain two or more per cent of such slag, is some- 
times luittle and cold-short is not to be wondered at. 



24 CIlEillCAL TECHNOLOGY. 

Hniiini with oiM. Instead of emplojing coal or coke as fnei, the reverberatorj famftoes 
arc often heated ^ith oombnutible ganes eEoaptng from the blaet-fnmaoeB or vith gas made 
for the pnrpoBO m a geDerator — on arroDgement not unlike a coke-oTon, in which aneh 
refuse fuel aa cannot be othemise ntilined, viz., waste of timber-yarda, refuse charcoal, 
peat, and small coal, ie submitted to dr; distillatioD. The generator is oonneeted to the 
ceverberatory fnmace in such a manner that the gases evolved in the former reaeh the 
latter very highly heated. Foraome jeara Siemene's regencrator-fumaoe has l>een applied 
to this purpose, and found to anrpaes all ether arrangements of the kind. When erode 
pig-iron oontaina much phosphorus, that element 
may bo eliminated daring the puddling prooeaa by 
adding to the metal a mixture of mangmeae, 
common salt, and clay,reduoed to powder. Solphiir, 
when present, may be burnt off by adding Uthlrge ; 
steam has also been used suocesafally for this latter 
purpose. 

S;^^!™,"; The metal obtained by the 
puddling procesa ia submitted to beavy hammer- 
ing or to squeezers in order to remove as mach 
mechanically adhering slag ns poaaible : aUfa 
this it is ready for the operations carried ont 
BoUiDtiraii in the rolling mill (Fig. la) which 
consists in the main of the following parts : — b b' 
and K a' are grooved rollers made of chilled cast^ 
iron : A a' are destined for shaping flat bars, and 
B B , for the shaping of square bars ; bymeana of 
the nuts, o o. the position of the rollers towards 
each other can be regulated ; the tubes, i i, carry 
water for keeping cool portions of the machinery. 
The contrivance m n serves to connect or dis- 
connect the rollers from the steam engine or 
water-wheel from which is obtained the motive 
power : the cog-wheels f and £ impart motion to 
the cog-wheels f' and c' connected with the npper 
rollers a' and a', which are thus made to move in 
Uie opposite direction to the under rollers. The 
metal to be rolled is first roughly shaped by 
means of heavy hammers (steam hammers are 
now often used), and then passed gradually 
through tlie varionsly sized grooves of the rollers. 
Fig, 13 exhibite rollers of a peculiar construction, 
viz., steel rings or discs wedged to iron shafting 
so as to form alternately large and small groovee 
for the manufacture of thin bars of iron, such as 
naU-rods, &c. 

A variety of rolled iron objects are made ; 
among these, square and flat bars, round bars. 
T-pieces, angle-iron, hoop-iron, and n&il-rods; 
railroad rails constitute an important item. 
Boii«pw.BnUia,. The rolling of boiler- and armour-plate is an isolated branch, dnce it 
requires a metal of good qaality. combining softness with toughness, and capable of being 
worked far below red heat without becoming too brittle or requiring annealing too often ; 
(or boiler- and armonr-platcs the metal is formed into slabs of proper size, which, while 
nearly white-hot. are forced through the rollers. After each succeeding passage of the 
slab, the rollers are set tighter, the oiide (forge scale) which is formed c 




1 the surface of 



inoN. 



as 



the meUl U removed by bnubicg with wet coarsdj-nutde heather brashea. Thin sheet- 
iron is rolled oat from plate-iron oDt into ansM slabn, which are at first hot, bat at a later 
it^e of the operation the rolling is performed cold, the metal 
having been prerionHly annealed in properly conetructed 
lonwcea. Under the headings of Zinc and "Kn the galvaniaiog 
and the tinning of iron ore treated of ; corrugated :' 
made bj pecnliarl; shaped and gcooved rollerB. 

iiOT wir» Thedrawingoliionintowirereqairesparticalarly , 

KuDfuUm. tou((h and fibroQS metal. In former 
wire vaa mode by drawing thin oircnlarbara, by the aid of tongs, I 
through holee made in steel plates; in the present day ir~ 
wire, if stoat, is made with rollers, while the thinner wire 
made with machinery to be presently described. The rulling- 
mili for the drawing of iron wire ap to a diameter of aboat i of 
an incb eongistE of three rollers provided with grooves which correspond to and catch a bar 
of iron when placed between, the bar being tbna sqaeened in the grooTes ; these rotlera 
make 240 revolutions a minnte, and since the diameter is 8 inches their circomferential 
Telocity is =8'37 feet, or in other words 8 feet 4J inches of wire paaa through the rollers 
in a second of time ; thinner wire is obtained by drawing, with the aid of machinery, the 
itonter kinds of wire thioagh holes made in hard and nnchangeable materials, the size 
of these holes gradually decreasing. For this pnrpose the previounly annealed wire, from 
) to ^igth of an inch diameter, is wound on the reel, « fFig. 14) ; the end ol the wire shaped 
somewhat to a point is pntthrongh the bole made in the draw-plate, b ; this hole being of a 
■lightly less diameter than that of the wire, which is next fastened to the hook, c (Fig, ij), 
of the oonically-ahaped dmm. c, which acquiies a, rotatory motion from the main shaft, d 
(Fig. 14) ,by means of conically-shaped cog-wheels, an arrangement being provided to oonneot 



1 F,o. ,3. 

i4t 




or disconnect the apparatns from the steam engine, so as to atop or set in motion the 
wire-drawing machinery without stopping the ateam engine. The ahape of the holes in 
the draw-plate la ol the highest importance for the nacceBs of tbe operation, and to obtain 
periectly round wire the holes ought to be quite true ; if, however, the holes were made 
perfect cylindera throngh the entire thickness of the draw-plates the ceanlt would be that 
the wire, instead of suddenly d T"^iniHhing in size, would break ; on that account the holes 
are boied funnel-shaped. The draw-plate is made of steel, but for very thin wire hard gems 
properly fastened and pierced are employed. Iron wire has to be repeatedly annealed 
during the process, and since hj this annealing operation, unless carried on with complete 
nclasion of air. a layer of oiide of iron is formed, tbe wire requires treatment in what is 
technically termed a scour hath, composed of dilate snlphuric acid and a certain amount 
of Bniphate of copper ; the thin layer ol copper deposited on (he wire during the immersion 
in this bath lessens the friction on the wire in passing through the holes. The thinnest 
iron wire met with in the trade baa a diameter ol only ^igtb of an inch, and is known as 
piano wire. Iron wire is rendered soft by being heated to redness, and is protected from 
ruMing by inunersioa in a bath of molten zinc, so-called galvanising. The nsee to which 
iron wire is applied are so varied that it is Bcaroely posaibU to enumerate them; this is 



26 CHEMICAL TECHNOLOGY, 

the lees naoeesary as m no oonntry in the world is iron wire so largely used as in the 
United kingdom, especially instead of hemp for rope-making. 

Prope^Mof Malleable- or bar-iron is made up of an aggregation of fibres which, 

according to the researches of Dr. Fuchs, are composed of a series of very small 

crystals. Heavy blows, continuous vibration, and sudden cooling of the metal while 

red-hot, all cause the particles to lose cohesion and alter the texture from fibrous to 

granular: a well known consequence of this change of structure, which is also 

suddenly induced by great cold, is the loss of tenacity in the iron, often attended with 

breakage, as happens frequently enough to railway wheel-tyres, axles, &c. The colour 

of malleable iron is bright grey, the firactore granular or jagged ; its specific gravity 

varies from 7*6 to 7*9 (that of chemicaQy pure iron being 7*844) ; from 0*24 to 0-84 per 

cent of carbon is present in the iron, the greater part in a state of chemical combination, 

in fact there is only a trace of graphite. 

The chemical constitution of malleable iron is shown in the following analytical 
results : — Sample I. being English iron from South Wales ; 11., soft iron from Magdespmng 
«n the Harz (Fruamsk) ; TO.,, Dannemora iron from Sweden. 

I. n. m. 

Iron 98*904 98-963 98775 

Carbon 0*411 0*400 0*843 

Silioium 0*084 0*014 0-118 

Manganese •• .. 0*043 0*303 0*054 

Ck>pper nil 0*320 0-068 

Phosphorus .. .. 0*041 nil nil 

Malleable iron of good quality does not become brittle when placed red-hot into cold water; 
it ought not to lose its malleability when thus treated : it is far softer than white and 
bright grey cast-iron, and is therefore easily filed, cut with the cold chisel, planed, and 
shaped in various ways even cold ; it melts with far more difficulty — ^requiring a much higher 
temperature — than cast-iron ; but malleable-iron is possessed of the valuable property of 
becoming, at a bright red heat (orange heat), so soft as to admit of two pieces being firmly 
welded together. The malleable-iron of commerce is often more or less mixed with foreign 
substances which in some cases impair its quality ; if sulphur, arsenic, or copper is present, 
the iron is thereby rendered red-short (breaks when hammered in the red-hot state) ; 
silioium renders iron hard and brittle ; phosphorus makes it cold-short, t.«., rather readily 
breakable when cold, although not so when red-hot ; calcium has the effect of greatty 
impairing, if not altogether destroying, the welding capability of the metal. As regards 
the choice of the different qualities of malleable iron for various uses, it is not in the scope 
of this work to enter into detail, the question being one of applied mechanics and 
engineering rather than of chemistry. Swedish bar-iron is for certain purposes in high 
repute, owing to the purity and strength of this kind of iron. 

y. Stsel. 

stML This substance diSexB from crude pig-iron and from bar-iron in the amount of 
carbon it contains; from crude iron, moreover, by being capable of welding; and again 
from bar-iron by being comparatively readily fusible : in reference to the amount of 
carbon present, steel holds a position between crude pig-iron and bar-iron. Recent 
researches have revealed the fiict that steel contains nitrogen ; but whether this 
element really contributes to the peculiar properties of steel obtained from different 
sources is not a definitely settied point. Steel is obtained of various qualities by a 
number of processes, as will be seen in the following brief reference : — 
a. DirecUy from iron ores : — 

1. By the reduction of iron ores direotiy with the aid of fuel (chiefly diarcoal), and a 
blast on the hearth, the steel hemg obtaiued in the form of lumps (so-called 
natural steel]. 

2. By the heating of certain iron ores along with coal, but without fusion (cementation 
steel from ores). 

3. By the fuaon of the iron ores along with charcoal in omoibles (oast-steel from ores). 



IRON. 27 

h. By the partial deoarboniflation of pig-iron (rongh steel, fomaoe-steel, or German-steel) : — 

4. By the refining (partial decarbonisation) of pig-iron by means of eharooal fuel on 
the hearth (shear-steel). 

By treating pig-iron in reyerberatoiy fomaees fed by ooal or blast-fnmaoe gases 
as fnel (padcUed-steel). 

6. By forcing air through molten cast-iron (Bessemer-steel). 

7. By heating oast-iron to redness along with substances which will effect decarboni- 
sation below the fasion-point of the metal ; if the sabstances employed for partial 
decarbonisation are iron ores, the steel is called iron ore steel. 

8. By melting crude oast-iron with such substances as those just mentioned. 

9. By treating crude cast-iron with sodium nitrate (Heaton-steel, Hargreave-steel). 

e. By imparting carbon to bar or malleable-iron : — 

10. By ignition with carbonaceous matter, but without fusion (cementation-steel.) 

11. By fusion with charcoal (cast-steel). 

d. By combination of methods h and e, as in fluxed steel : — 
II. By melting crude pig-iron and malleable-iron together. 

In India a kind of steel is still made directly from iron ores, and known as woots (as to 
the composition of this substance, see the ** Chemical News," vol. xzii., p. 46) ; it is possessed 
of excellent qualities. The Japanese also understand the art of malong steel of most 
excellent quidity by rather rough and primitiye means. According to the modes of 
manufacture, we distinguish the following kinds of steel : — 



This material, obtained by the partial decarbonisation of orude pig-iron, 
may be either : 

I. Bough steel made on a hearth (natural steel), chiefly obtained from the pure 
spathic iron ore, from which in Styria, Carinthia, l^rol, and various other parts, 
porous white pig-iron, or white pig-iron, with granular structure, is first obtained by 
means of charcoal and coke as fuel ; the ordinary grey cast-iron can also be used, biit 
the resulting steel is not of such good quality. The general arrangement of the 
hearths on which rough steel is made is the same as for the operatioH of iron refining ; 
the only diffiorence is in the mode of placing the metal in reference to the blast, the 
operation being so conducted as to cause only the gradual combustion of the carbon : 
the workmen take care to control the blast and place the metal in a manner which 
enables them to stop the further action of the air the momeiLt the proper amount of 
decarbonisation has been effected. 

a. Steel obtained in a reverberatory furnace, or puddled steel ; obtained from various 
kinds of cast-iron by a process akin to the puddling of crude cast-iron, the burning off 
of the carbon not being carried so far. This mode of manufacturing steel is exten- 
sively employed, and yields a material well suited for the making of various kinds of 
machinery, railway carriage-wheel tyres, and is also largely used in the manufacture 
of cast-steeL 

Syrian and Carinthian cast-steel (charcoal iron-steel) is far more expensiye than 
pad Jled steel, but the former is indispensable — at least on the Continent — ^for the manu- 
facture of all kinds of cutting-tools. 

3. Beesemer-steeL Mr. Henry Bessemer, in 1855, first applied a process of making 

steel directly from cast-iron ; the process consists in forcing large quantities of air 

through molten crude iron ; the consequence is that the conversion cf the iron into steel is 

effected in a comparatively brief space of time ; moreover, the resulting steel remains 

fluid ; the difference of the action of the air as an oxidising or decarbonising agent in 

this instance, as compared with the process of steel-making, mentioned under No. i 

and 2, is that in the case of the Bessemer method, the air thoroughly penetrates and 

comes into contact with every particle of iron ; whereas, in the other instances, the 

action of the air is only at the surface ; and since the steel obtained by methods 



28 CHEMICAL TECHNOLOGY, 

I and 2 is less fusible than the crude iron used, a second refining or smelting becomes 
necessary to render the steel uniform and homogeneous. 

The Bessemer process is executed either in diminutive shaft-ovens or in egg-shaped 
vessels made of boiler-plate converters, and lined with fire-claj ; projecting for some inches 
through the inside of the bottom, five gth inch wide fire-clay tubes are carried, through 
which powerfully compressed air can be forced. The apparatus is placed in close 
proximity to a blast-furnace, so as to admit of running the molten iron, purposely kept at 
a very high degree of heat, readily into the oven or other vessel, while at the bottom of the 
converter there is an aperture closed with a fire-clay plug, through which the molten steel 
can be discharged. As soon as the blast is turned on and the vessels half filled with 
molten iron, a very violent action ensues, the metal apparently begins to boil, flames and 
myriads of sparks burst forth from the converter (this phenomenon appears to be due to 
the fact that particles of partly -decarbonised iron and a mixture of iron and oxide are 
driven against each other). According to the duration of the action of the blast (lo to 25 
minutes), steel or bar-iron may be made, and of late, even in making steel, the action is 
carried to the highest possible pitch, and to the resulting metal a portion of molten white 
pig-iron is added. Bessemer steel is largely used for a variety of purposes ; but it is not 
suitable for the manufacture of such cutting-tools and instruments as require a keen and 
durable edge ; on the other hand, Bessemer metal is an excellent material for the manu- 
facture of boiler and armour-plates, ordnance, railroad-rails, and a great variety of heavy 
machinery. As might be expected, this method of steel-making has rapidly spread from 
England to all parts of Europe and to America ; and as a proof of the handsome profit 
earned by the inventor, whose royalty amounts to is. per cwt., we may state that the total 
quantity of Bessemer steel produced in Europe in the year 1869 amounted to 5'5 millions 
of cwts., 70 per cent thereof being produced in Great Britain. 

4. Uchatius and Martin steel are also directly prepared from crude cast-iron, by mix- 
ing granulated crude pig-iron, made from native magnetic iron ore, along with pul- 
verised spathic iron ore and fusing this mixture in plumbago crucibles. M. Martin 
replaced the use of the crucibles in this process by that of the somewhat hollow floor 
of a reverberatory furnace heated by means of a Siemens's regenerative gas-furnace. 
A quantity of crude pig-iron is melted under a layer of slag, and from time to time 
bar-iron is added until a sample taken out is found to possess the texture and good 
qualities of malleable-iron. When this stage has been reached, a certain amount of 
crude cast-iron is added, whereby the entire quantity of metal is converted into a kind 
of cast-steel, chiefly suited to the making of railroad-rails, wheel-tyres, and especially 
gun-barrels and ordnance. Tunner's steel, which dates from 1855, also known as 
malleable cast-iron, is obtained by igniting white pig-iron to bright redness with 
substances which give off oxygen (oxides of iron and zinc and peroxides of man- 
ganese) when thus treated. 

5. Heaton steel. Prepared by a process devised by Mr. Heaton, in which crude- 
iron is heated with nitrate of soda (Chili-saltpetre). By this method not only 
the carbon is eliminated, but the sulphur and phosphorus being oxidised and con- 
verted into phosphates and sulphates, find their way into the slag. Tlie principle of 
this method is the same as in Mr. Hargreaves's plan, and again identical with a pro- 
posed new method of Bessemer steel-making. 

^ou^it^^rS^SSS^ ^ The second kind of steel is that known as cementation- 
steel — a metal prepared by the ignition of bar-iron in contact with carbonaceous 
matter, preferably containing nitrogen. The bar-iron to be employed for this 
purpose should be of the very best quality, and since in Great Britain and France, 
the best iron produced is not good enough, both these countries draw largely upon 
Sweden for a supply of Danncmora iron, made from magnetic and red hsBmatite-iron 
ores mixed. The Russian iron from the Ural is of the same good quality, but the 
transport is at present far too costly. It is almost superfluous to mention that the 
chief seat of the steel manufacture in England is Sheffield. 



IRON, 29 

The process of making cementation-steel is simple enongh. The hars of lion are placed 
in fire-clay boxes, in layers alternating with the carbonaceous matter (cementation- 
powder). Two of such boxes are placed in a furnace which is heated with coal, and the 
boxes are kept at a red heat for some six or seven days, and after cooling, the bars, con- 
Terted into steel, are taken out. Each furnace contains from 300 to 350 cwts. of iron. In 
the cementation-powder such substances as will form cyanide of potassium, or ready- 
formed cyanides, ought to be present. It appears from recent researches that cyanogen 
(CN) is to be viewed as the carrier of the carbon to the metal. The crude steel (blistered- 
steei) obtained by this operation is not, as such, fit for use, but has to undergo a process 
of purifying. 
Befined-3t««L Not Only cemontatlon-steel, but also that obtained by the other methods, is 
sfacar-atML (oo coarso and not sufficiently homogeneous for immediate use, and therefore 
a process of refining has to be resorted to. This process consists, firstly, in the hammering 
out of of the steel bars, previously made red-hot, into thin rods, which are, while 
red-hot, quenched with cold water. Next a number of these are placed together in the 
form of a bundle, which is again made red-hot, well hammered, and afterwards rolled into 
bars. The method of refining here alluded to is more suited to the quality of steel 
obtained from crude pig-iron than to cementation-steel. Sfceel thus refined, on account of 
being used for making large pairs of scissors or shears, bears the name of shear-steel. 

ohM^ueL Cast-steel, in modem industry, has assumed a most enormous importance, 
as e\idenced by such gigantic works as those of M. Krupp, at Essen (Prussia). The 
eiustence of these works notwithstanding, Sheffield takes the foremost rank in the 
manufacture of cast-steel. The following is the plan pursued : — The bars of blistered- 
Bteel, cut to a convenient size, are introduced into crucibles made of Stourbridge clay, 
which are heated in furnaces similar to glass-melting ovens, fed mth coke or coal as 
fuel ; the molten metal is cast into bar-shaped moulds, and the bars are, after cooling, 
again heated to redness and hammered or rolled out in a mill. As to the uses to 
which cast-steel is applied, suffice it to say that heavy ordnance, as well as large 
bells, excellent cutting-tools and files, best cutleiy, and many surgical instruments, 
number among them. Cast-steel is homogeneous, and therefore strong and durable. 

^'tid&tt^clrtJSS!**** •^- ^ third kind of steel (varying accordiug to the mode and 
materials of production) is that called Glicenti-steel, obtained by melting together a 
peculiar white pig-iron (spiegel-iron), and bar or malleable-iron. The toughness, 
hardness, and malleability of this metal depend upon the quantity of bar-iron which 
has been added to the mixture. 

BiBfkee stMi-Hatdening. It frequently happens that for certain purposes soft iron only 
requires to be converted into steel superficially, an operation termed surface-harden- 
ing or surface-steel hardening, which is done by placing the metal) previously polished 
with emery, in a suitable vessel covered in cementation-powder (see above) ; the vessel 
and contents being next heated to redness, malleable iron tools, spanners, for instance, 
keys, and small objects, may be readily surface-hardened by being, while red-hot, 
dusted over with powdered ferrocyanide of potassium, yellow prussiate, or with pul- 
verised borax and pipe-clay. 

PnptftiMof steeL The colour of steel is bright greyish-white, its texture is imiformly 
granular, the better the quality the smaller the grain. Sound soft (that is not 
hardened) steel, never exhibits the coarse texture characteristic of crude cast-iron, nor 
the fibrous texture of bar-iron. Hardened-steel exhibits a fracture very similar to 
that of the finest silver, so close that the granular texture can hardly be detected with 
the naked eye. When red-hot, steel is nearly as readily malleable as bar-iron, and 
may be welded, but very careful management is required to prevent its becoming 
decarbonised. By inmiersing a piece of steel in dilute hydrochloric or nitric acid, the 
texture of the metal becomes apparent, and tills test may be applied to deteimine the 
quality. The specific gravity of steel varies from 762 to 7*81, and decreases in 



30 



CHEMICAL TECHNOLOGY. 



hardening (for instance, from 7*92 to 7*55) ; the quantity of carbon contained in steel 

varies from o'6 to 1*9 per cent ; the toughness, tenacity, and hardness of steel, increase 

with the quantity of carbon it contains, but good steel never contains graphite ; the 

high degree of elasticity exhibited by good steel decreases with the hardness. When 

red-hot steel is suddenly quenched with cold water, the metal becomes &r harder, but 

also brittle, and will even scratch glass and withstand the file; when brightly 

polished, if steel is gradually heated, it assumes peculiar shades of colour (annealing 

or tempering colour). This colouration is due to the formation on the surface of the 

steel of thin layers of oxide, which exhibit colours like other very thin surfaces — soap 

bubbles, for instance, or a drop of oily or tarry matter extended over water. The 

operation which causes the formation upon steel of these colours is called tempering. 

T«mp«iiag. In judging the proper temperature and the corresponding hardness these 

tints serve admirably. Since it is often rather difficult to heat a piece of steel 

uniformly, molten metallic mixtures are employed, beiDg chiefly made up of tin and 

lead ; the bright hardened steel is kept in these molten mixtures until it has assumed 

the temperature of the bath. The following tabulated form exhibits the composition 

of the metallic baths, which experience has proved to be the best for the tempering of 

cutlery : — 

Ck>mpoBition of Melting 
metallic mixture, point. 



Temperature. 



I iftfioeiio ••. ... ••• ••• 

fUkzors .•• ... ••• ••• 

Pen-knives 

Pairs of scissors 

Clasp-knives, joiners' andi 
carpenters' tools j 

Swords, cutlasses, watch- j ^ 
springs j ^ 

Stilettos, boring-tools, and 
fine saws 



Pb. 
7 



8 
8i 

19 



Sn. 

4 

4 
4 
4 



Ordinary saws 



50 2 

inboilin^\ 
linseed-ou J 



2ao* 
228° 
232° 

254^ 
265^ 

288** 

292** 
316' 



Hardly pale yellow. 
Pale-yellow to straw-yeUow. 
Straw-yellow. 
Brown. 

Purplish-coloured. 

Bright-blue. 

Deep blue. 
Blackish blue. 



Such tools as are required to work iron and other metals and hard stones are 
heated to bright-yellow ; razors, surgical-instruments, coining-dies, engravers' -tools, 
and wire-drawing plates follow next to straw-yellow ; caipenters'-tools to purphah- 
red ; while such tools and objects as are required to be elastic are heated to the violet 
or deep-blue tint; the less steel is heated the harder it remains, but also the more brittle. 
Other substances than carbon (for instance, silicon and boron) maybe capable of 
imparting to iron properties sioiilar to those we are acquainted with in steeL Some 

o£?iiSds. 0^^^ metals mixed with steel in greater or lesser quantity improve the 
quality in some respects ; for instance, for the last few years steel has been made in 
Styria, which, owing to its containing tungsten, is exceedingly tough and hard. 

^y^^Si^ ^^^^^ Bteel, specially celebrated for making swords, was first made 
at Damascus. Its name, Damascene, is appUed to the property it possesses of 
exhibiting a peculiar appearance when acted upon by an acid; but tbis appears to be 
due rather to some imperfection of the welding of the metal, since, after melting, the 
same peculiar shades of colour do not appear. We have already alluded to the recent 
researches concerning the true composition of this metal. One of the largest collec- 



IRON. 31 

tioDB of toolB, swordB, gun-barrels, and bars of this kind of steel to be found in Europe 
IB in the India Museum, Whitehall. - In order to elucidate the composition of some 
kinds of steel, the following analyses are appended: — The samples are — i. Befined 
steel, from Siegen (Prussia) ; 2. Cast-steel, from Schmalkalden (Prussia) ; 3. Puddled- 
steel ; 4. Steel from Russian cast-ordnance ; 5. Cementation- steel, Elberfeld (Prussia) ; 
6. English cementation-steel ; 7. Krupp's steel (Essen). 

|. 2. 3' 4' 5' fi' 7- 

Iron 97*91 93*154 98602 9875 99'oi 99*12 99*351 

Carboal^Sl ... 169 ^'7J° P^ ^'^ °*Jl rS? 0-532 
1C/3J ^ 0010 trace 015 o"o8j ' "oo* 

Silieium 0*03 0202 o*oo6 0*04 — cio 0*032 

Sulphur trace 0003 — — — — o'ooi 

Phosphorus — — trace — — — o'ooi 

Manganese — — o'oi2 — — — — 

Copper o'37 — — — — — — 

loo'oo loo'ooo 100*000 loo'oo 99*50 101*09 99*917 

flUemrmpiiyorstMi The eugrayiug of steel requires plates made of cast-steel, which, in 
Kagnvinc. order to be sufficiently soft for the engrayer's tools, are first superficially 
deearbonised, and after the engfaying is made, again hardened. The engraved plate is 
not employed direct for printing, but is used as a matrix for the preparation of plates to 
be printed from ; this process is carried out In the following manner : — ^A solid cast-steel 
cylmder, turned in a lathe, is superficially softened, f^d the engraved plate is placed 
imder this cylinder, so that with great pressure and a slow revolutioo of the cylinder, the 
plate moving also very slowly, a relief of the engraving is produced on the cylinder, and 
this being again hardened, is employed to reproduce the engraving on other metallic 
plates, w£dch may be either copper or soft steel. Instead of engraving the design on 
soft steel plates, etching is often resorted to, for which purpose corroding fluids, such as 
nitric ,acid (aquafortis), nitrate of silver, sulphate of copper in solution, or, lastly, a 
aolation of 2 parts of iodine, 5 of iodide of potassium, and 40 of water, are used. 

flutMiM of stMi The annual production of steel in Burope may be roughly estimated for 
^ndB^too- 1870 at 6,285,000 cwts. at 50 kilos, to the cwt. 

The imperial English crwt. is equal to 508,023 Idlos. ; of this total the undermentioned 
eonntries produce : — 

United Kingdom of Ghreat Britain and Ireland 2,300,000 

France ii35o,ooo 

Belgium 225,000 

North German Confederation 1,120,000 

Austria 900,000 

Sweden 250,000 

Russia ^ 150,000 

Italy 75»ooo 

Spain 15,000 

Total 6,285,000 

Ibon Pbxfabitions. 

aSSS^fvSca. ^^ substance called copperas and green vitriol, sulphate of protoxide 
of iron, (FeS04+7H20), is met with in the trade in the form of greenish-coloured 
crystals possessed of an inky astringent taste ; on exposure to dry air the crystals 
edfioresoe, and are gradually converted into a yellowish powder — ^basic sulphate of 
peroxide of iron. 100 parts of the chemically pure crystallised salt consist of : — 

26' 10 parts of protoxide of iron. 

2990 „ sulphuric acid. 

4400 „ water. 



32 CHEMICAL TECHNOLOGY. 

prepanuon of Gwen Since the minerals ordinarily used in the manufacture of alum — 
^'to -uii^orfci,"* the alum schists — generally contain iron pyrites, (FeSa), either as 
such or already partly converted into a hasic sulphate of the peroxide (which, on 
being treated along with the alum shale, becomes by weathering and roasting 
converted into protosulphate and peroxide of iron), green vitriol is frequently 
a by-product of alum manufacture, and is obtained by evaporating the mother-liquor 
containing iron, and leaving it to crystallise. In some localities, as, for instance, 
at Goslar (Prussia) , on the Hartz mountains, the liquor obtained by the lixiviation of 
the iron-containing minerals alluded to .is first evaporated for the separation ]of the 
green vitriol, then a potassa or ammonia salt added to the remaining acid liquid to 
obtain alum. 

^'^WSofL^BedL**" ^^^6 material sometimes rather largely found in coal pits, and 

called brass (iron pyrites), is collected and placed in layers over a somewhat 

excavated surface, which has been rendered impervious to water by puddling with 

clay, and made to incline slightly in one direction where water-tight tanks stand, 

into which scraps of old iron are placed with the view of saturating any free acid ; 

the pyrites, placed on these beds to a thickness varying from li to 3^ or 4 feet, is 

slowly oxidised by atmospheric agency, and the falling rain carries into the tanks a 

more or less strong solution of copperas, which, when sufficiently concentrated, 

is slowly evaporated, some scrap-iron being placed in the evaporating-pans. In 

Green Vitriol from couutries whcrc irou pyrites abound^, and fuel and labour are 

pyriUM Dutiuation. sufficiently chcap to make the distillati^ of sulphur from pyrites a 

profitable business, the residues are utilised in green vittiol making, a salt which 

thus made must, of necessity, contain a good deal of impurity. The brown sulx)huiic 

Green Vitriol from acid or chamber acid, also such waste sulphuric acid liquids as are 

and soiphorirAdd. obtained in the oil and petroleum refining, are sometimes used as 

solvents for scrap-iron for the preparation of green vitriol, which may also be made 

by boiling the finely pulverised puddling and iron refining sla^s with sulphuric acid. 

From spAthio Ii^ localities where spathic iron (carbonate of protoxide of iron, FeCO]) 
Iron Ore. occurs in a pure state, that mineral may be usefully applied to the preparation 
of green vitriol by treatment with sulphuric acid, and evaporating the solution thus 
obtained. The sulphate of iron (protoxide), prepared on the large scale, is often met with 
crystallised round a small thin stick of wood, which is hung up in the solution to promote 
crystaUisation ; sometimes, at least abroad, a so-called black vitriol is met with, which is 
simply green copperas superficially coloured black by means of some astringent decoction, 
such as nut galls. 

Uses of Green Vitriol. Tbls Bubstanco is employed as a disinfectant, as a mordant in dyeing 
and caUco printing for various black and brown shades, for the preparation of ink, the 
deozidation of indigo — so-called cold vat — in gas purifying, in the precipitation of gold 
from its solutions, in the preparation of Prussian blue, in the manufacture of fuming 
(Nordhausen) sulphuric acid, and for a host of other purposes. 

Iron Miniom. During the last 10 or 15 years a large number of substances under this 
name have been introduced as paints, especially for iron sea-going vessels and other 
ironwork. The late Dr. Bleekrode analysed two samples of this paint, one of which, 
made and sold by M. Cartier in Belgium, was found to consist in 100 parts of : — 

Moisture 275 

Red peroxide of iron 68'27 

Clay 27*60 

Lime 0*40 

A sample of Holland's iron minium was found to contain in 100 parts : — 

Water 6*oo 

Peroxide of iron . . 85 "57 
Clay (burnt) . . . . 8-43 



IfiO.V. 



33 



In Dr. O. J. Mnlder'B vork on the " CbemJatry of Drjiag Oils " ' — seoond or applied part 

attention is called to the fact, and supported by resnlta of aiialyties of differeut iron 
miuioiDii ubtoiaed b; the author, that aoiuo of thcae paints contain free Bolphuric aoid, 
which is always preneat in oolcothar ; this acid may eierciae an iujurioas effect on iron 
painted with snch materials. 

It is hardly neceasoi? to point ont that the uao of iron mininm aa paint is less 
eipensive than the use of red-lead, in the proportion of 20 to 30 for coating the same 
extent of surface. 

'^(TmSS™ ^* yeilow-coloured salt, generally laio(vn as yellow prussiate of 
polaesa (ferrocyanide of potassium. K,FeCy6+3HjO), is, in a technical point of view, 
a verj important substance. It crystallises in large lemon-ooloured prismatio 
rr^stals, which are not affected by exposure to air, are not poisonous, and possesa a 
nweelish bitter taste. This salt ia soluble in 4 parts of cold aud 2 of boiling wal«r, 
but is iiiDoluhle in alcohol ; in 100 parts there are : — 
37 '03 Potasaium, 



1704 Carbon, jcyanogen. 
io-Sq Nitroaen, > ' ^ 



} Nitrogen 
13-25 Iron, 
1279 Water. 
At 100° the water is driven off. The salt is prepared on a large scale by igniting 
snch carbon as contains nitrogen to a red beat with potassa- carbonate in closed 
vessels. The quantities of the materiala may be varied, the relatire proportions 
being given by some makers aa 100 parts of potassa- carbonate to 75 of the mtrogenons 
carbon, or. according to Ilunge, 100 parts of carbonate of potassa, 400 of calcined 
hum, and 10 parta of iron-filinga. 

The fusion of these ingredients is carried on either in cloaed iron vessels of a 
peculi&r shape, or in a reverberatory furnace. The iron-vessel, a, tenned a muffle 



Fio. 16. 



Fig 1 




(Fig. 16) ia egg- or pear-shaped, having a diameter of I'z metres, a width of o'8 metre, 
and vaiying from 13 tai5centiias.in thickness. As shown in tlie woodcut, the iron vessel 
is placed in the furnace in such a manner as to be exposed to the action of the flame 
and hot gases on all sides, being supported at the back by a projection about 27 centims. 
long, and resting at g on the brickwork, leaving space sufficient for the gases 
generated in the interior to pass off by c int« the chimney-flues ; m is on iron cover 
which is dosed during the operation of melting, g being an opening in the front wall 
of Uie furnace, through which tlie ingredients are put into the iron vessel, and the 

■ The original iBinDatch,and the noik Jim not been tranalalcd into any nthei Inneu.iije. 



34 CHEMICAL TECHNOLOGY. 

molten mass taken out. The shallow pan, t\ on the top of the furnace, is intended 
for the evaporation of the liquor obtained by treating the molten mass with water. 
The use of the iron vessel, however, is attended with the serious drawback that the 
iron is eaten into holes in a comparatively short space of time ; and, though this 
action is greatest on the lower part of the vessel, and it may therefore be turned 
bottom upwards, and tlie holes stopped witli fire-clay, the vessel has soon to be 
replaced by anotlier. It is on tliis account, and also owing to the fact that a larger 
quantity of raw mateiial can be operated upon at once, that instead of the apparatus 
described above, tliere has come into general use a reverberatory furnace. Fig. 17, 
arranged with a shallow cast-iron pan, a, from i to i'8 metre in diameter, vnih a rim 
about I decini. high; b is the fu'e-place; g the bridge; c a flue leading to the cbinmey. e. 
Sometimes the hot air is applied to the heating of evaporating-pans, being carried 
imder them before entering tlie cliimney. The result of the ignition is the formation 
of a black mass, technically called the metals yielding the liquor from which the crude 
salt crystallises. The salt is purified by re-crystallisation, while the black residue is 
employed as a manure. 

The theory of the formation of the ferrocyanide of potassium is as follows: — The 
carbonate and sulphate of potassa, the nitrogenous coal and the iron reacting upon 
each other, give rise to the formiition first of sulphuret of potassium, which in its turn 
converts the iron into sulphuret, while the nitrogen contained in the charcoal unites, 
under the influence of potassium, with the cyanogen of the carbon, which again in its turn 
combines with the potassium, giving rise to the formation of cyanide of potassium. When 
the fused mass is treated with water, cyanide of potassixmi and sulphuret of iron decom- 
pose each other, the result being the formation of ferrocyanide and sulphide of potassiom, 
the last-named salt remaining in the mother-liquor. M. E. Meyer states (1868) that it is 
more advantageous to employ, instead of the sulphuret of iron, the carbonate of that 
metal, for the purpose of converting cyanogen into ferrooyanogen, because the ferro- 
cyanide of potassium crystallises far more completely and freely from solutions not con- 
taining any sulphuret of potassium. Professor Dr. von Liebig has since proved that 
the fused mass only contains cyanide of potassium and metaUic iron, and not any ferro- 
cyanide of potassium, which is only formed by treating the molten mass with water, or 
more slowly by its exposure to moist air. Among the materials frequently added to the 
fueling mass are — scraps of metal, the refuse of leather, dried blood and other dry animal 
offal, because the ammonia evolved by their decomposition in the presence of an alkali 
aids the formation of cyanide of potassium. According to M. P. Havrez, the crude snint 
obtained from wool is an excellent material for the preparation of ferrocyanide of potas- 
sium, since 100 kilos, of the suint contain about 40 kilos, of carbonate of potassa, from 
I to 2 kilos, of cyanide of potassium, and about 50 kilos, of combustible hydrocarbons, the 
heating value of which is at least equal to that of 40 kilos, of coal. 

It has been tried to obtain the cyanide of potassium on a large scale, by causing a 
current of ammoniacal gas to pass through and over carbonate of potassa heated to 
redness ; and also to obtain cyanide of potassium from, or by aid of, the nitrogen of the 
atmosphere. This process was tried nearly 40 years ago at Mr. Bramwell's works near 
Newcastle-on-Tyne, but was found to be a failure commercially. The reader interested in 
a detailed account of this process may find it in the excellently-written chapter on the 
manufacture of the pmssiates, in Bichardson and Watts*s ** Chemical Technology.** 
As it has been proved by experiment that baryta, far more readily than potassa, converts 
carbon and nitrogen into cyanogen, forming cyanide of barium at a lower temperature, 
baryta might perhaps be substituted for potassa, but as yet this plan is not carried out 
commercially. According to G^hs (1861), the yellow prussiate may be prepared by the 
mutual reaction of sulphide of carbon and sulphide of ammonium, the resulting sulpho- 
oarbonate being converted into sulphocyanide of potassium by means of sulphuret of 
potassium, by which reaction sulphuret of ammonium and sulphuretted hydrogen are 
volatilised. The sulphocyanide of potassium is next converted into ferrocyanide of 
potasF-ium by being heated with metallic iron to redness, sulphuret of iron being at the 
same time formed. It is evident that this process could not be carried out commercially. 
Mr. H. Fleck described, in 1863, a plan for preparing the ferrocyanide by the action of a 
mixture of sulphate of ammonia, sulphur, and carbon, upon fusing sulphide of potassiom, 
which thus becomes sulphocyanide of potassium, one-half of the nitrogen of the sulphate 



IRON, 



35 



of azmnonia remaining in the fused metal as cyanogen, while the other half escapes 
as solphide of ammonium, which is again converted into sulphate of ammonia. The 
Bolphocyamde of potassium produced is treated with metallic iron at a red-heat, and 
thus cyanide of potassium and sulphide of iron are produced. This process is also too 
cumbrous and expensive on a large scale. 
Appu»tioiis of tiu This salt is employed in the manufacture of the red-cyanide or prussiate, 
leiiow Fmscut«. in the preparation of Berlin blue, and of cyanide of potassium (the impure 
salt as met within commerce), in dyeing and calico-printing for the production of blue and 
brown-red colours, for the purpose of surface-hardening small iron articles, and lastly as 
an ingredient of white gunpowder, and for use in chemical laboratories. 

acdPniMiatc. The 80-called red prussiate of potassa, properly ferricyanide of 

potassium, or Gmelin's salt, K3FeCy, is prepared on a large scale and extensively 

used in dyeing and calico-printing. This salt ciystallises in prismatically-shaped 

ruby-red-coloured, anhydrous crystals, which consist in loo parts of: — 

35*58 Potassium, 

21-63 Carbon, jcyanogen, 
25-54 Nitrogen, > 
17-29 Iron. 

It is prejxared by submitting either the solution of the yellow prussiate or tliat 
tialt in powder to the action of chlorine gas until a sample, when heated, yields 
no precipitate with a solution of a per-salt of iron. When the dry and pulverised 
yeUow prussiate is ftcted upon by chlorine gas, the salt is frequently placed in casks, 
closed so as only to leave a small outlet, while the vessel can be made, by means 
of machinery, to turn slowly on its axis, so as to bring all the particles of the 
salt into contact with the chlorine. Sometimes, again, the pulverised yellow prus- 
siate is placed on trays in a chamber, into the top of which chlorine gas is admitted ; 
when no more chlorine is absorbed the newly-formed salt is, if a solution of the 
yellow prussiate has been operated upon, evaporated to dryness, or in the case where 
the dry powder of the salt has been taken, the newly-formed salt is dissolved in the 
smallest possible quantity of water, and the solution left to crystallise, the mother- 
Kqiior containing chloride of potassium. This reaction is represented by — 

K+FeCye -i- CI = KCl + KaFeCy . 

, ' ^ , - 

Yellow prussiate. Bed prussiate. 

The powdered red prussiate is of an orange -yellow colour. According to 
M. E. Reichardt (1869) bromine may be successfully employed instead of chlorine for 
the preparation of this salt, which is chiefly used for dyeing woollen fabrics blue, 
And, with solutions of caustic soda or potassa, for the Mercerising process of cotton. 

cjniAt of poUsdom. This salt is obtained in an impure state — Liebig's or crude cyanide 
of potassium — by the fusion of the yellow prussiate of potassa in a porcelain crucible, 
continued as long as nitrogen escapes. Carburet of iron sinks to the bottom of the 
crucible, while the crude cyanide is poured off in a state of fusion ; 10 parts of the yellow 
prussiate of potassium yield 7 parts of crude cyanide, (K4FeCy6=4KCy-HFeC2-H2N). 
According to Liebig^s plan, the cyanide of potassium is prepared by fusing i molecule of 
ferrocyanide of potassium with i molecule of carbonate of potassa ; by this method 10 parts 
of the ferrocyanide, yielding 8-8 cyanide of potassium, mixed with 2*2 parts cyanate of 
potassa. For aU technical and industrial purposes it is far cheaper to use cyansalt, a 
mixture of the cyanides of potassium and sodium, prepared by fusing together 8 parts of 
previously dried (anhydrous) ferrocyanide of potassium and 2 parts of carbonate of soda. 
As this mixture fuses readily, the carburet of iron easily separates ; moreover, the salt thus 
obtained is less liable to decomposition on exposure to air, and its preparation requires 
less heat. The industrial applications of the crude cyanide of potassium, or of the cyan- 
**lt, are the following : — In the process of electro-gUding, for the preparation of GrSnat 
foluble^ isopurpurate of potassa, from picric acid, and in the reduction of metals. It 

P 2 



36 CHEMICAL TECHNOLOGY, 

has been mentionel, while treating of the blast-furnace process, that oyanide of potassiam 
is formed daring the reduction of iron. 

Beriin-Biua. Thls substaiice, 80 named when it was accidentally discovered at Berlin, 
in 1 710, by Diesbach, is chemically a ferrocyanide of iron, more correctly ferrous- 
ferric cyanide. A distinct variety of this substance is known as Paris-blue. Three 
different kinds of Berlin-blue are known, viz., neutral, basic, and a mixtnre of the 
two, differing in composition and prepared by different processes. 

(a). Neutral Berlin-blue, also known as Paris-blue, is obtained by pouring a solution of 
yellow prussiate into a solution of chloride of iron, or into a solution of a peroxide salt of 
iron ; the result is the formation of a larg^ quantity of a magnificently blne-ooloured 
precipitate, very difficult to wash out and always retaining a certain quantity of the yellow 
prussiate, which cannot be removed by washing. 

(b). Basic Berlin-blue is obtained by precipitating a solution of yellow prussiate with a 
solution of a salt of protoxide of iron (green copperas), the result being at first the forma- 
tion of a white precipitate of protooyanide of iron, which, either by exposure to air, or hj 
the action of oxidising substances, becomes blue ; because a portion of the iron is oxidised 
and another portion takes up the cyanogen thus liberated, converting some of the proto- 
cyanide into percyanide, wMoh in its turn combines with the unattacked protocyamde to 
form Berlin-blue, with which, however, some peroxide of iron remains mixed. It is stated 
that basic Berlin-blue is distingui^ed from neutral Berlin-blue by being soluble in water; 
but this solubility is due to the presence of some of the yellow prussiate, and is not a 
property inherent in the basic Berlin-blue in a pure state. 

(c). As the materials employed on a large scale are neither pure protoxide nor puie 
peroxide salts of iron, but a peroxide containing protosalt of iron, the ^precipitate obtained 
consists at first of a mixture of neutral Berlin-blue wi^ more or less of the white proto- 
cyanide of iron, which afterwards becomes basic Berlin-blue ; accordingly the Berlin-blue 
of commerce is a variable mixture of neutral and basic Berlin-blues. The iron salt 
employed is green copperas (sulphate of protoxide of iron), which of course should not 
contain any appreciable amount of copper, the salts of this metal, as is well known, 
yielding with yellow prussiate of potassa a chocolate-brown coloured precipitate. 
Old Method of Prepaziiig The sulphate of iron and alum are dissolved together in boiling 
Pruaaian-Biue. ram- or river-water ; the fluid, while yet hot, is decanted from any 

sediment and forthwith poured into a hot aqueous solution of yellow prussiate, oare being 
taken to stir the mixture, and to add the copperas and alum-solution as long as any preci- 
pitate is formed. The liquor is run off, and the precipitate washed with fresh water, ontQ 
all the sulphate of potassa is removed ; after which the precipitate is drained on filters 
made of coarse canvass. This haying been accomplished the substance is suspended in 
water in a boiler, and, while being heated to the boiling-point, nitric acid is added ; after 
a few minutes' boiling, the contents of the boiler are poured into a large wooden tub or 
cask, and strong sulphuric acid is added. The solution is now allowed to stand for some 
tune, during which the blue colour fully developes. The Berlin-blue is then thoroughly 
washed with water, drained on coarse canvass Mters, next dried, pressed, and cat into 
cakes ; finally it is dried in rooms heated to 80°. As Berlin-blue, when once quite dry, ia 
reduced to powder with great difficulty, and cannot be brought to the state of fine division 
as when first precipitated, it is also sent into the market in the state of paste. The 
alumina derived from the alum is so intimately mixed with the blue that the bulk of the 
mass is thereby increased without any very perceptible decrease in the intensity of the 
colour. If the quantity of alumina is very much increased, the colour, of course, becomes 
much lighter, and this variety of Berlin-blue is then Imown as mineral-blue ; a name also 
given to a preparation of copper obtained either from the native hydrated carbonate of 
copper, or artificially prepared by precipitating nitrate or diloride of copper by means of 
Ume and chalk. 

B«ccnt Methods of Among the improvements made more recently, we may briefly notice 
Propiiring Berlin-Blue, the following :— I. The mixing of the solutions of copperas and alum 
with that of yellow prussiate is effected as above described, but great care is taken to 
prevent any oxidation of the white precipitate, which is converted into an intense blue by 
being treated with nitro-hydrochloric acid, the chlorine evolved serving as an oxidising 
agent. The remaining operations, viz., washing, drying, <&c., are performed as in the 
former methods. 2. Perchloiide of iron solution is employed for the purpose of converting 
the white precipitate into blue, while the protochloride of iron thus formed serves at a 
subsequent operation instead of protosulphate of iron. 3. In some cases perchloride of 
inanganeso (Mn^Cle), is applied ; likewise a solution of chromic acid, a mixture of 
bichromate of potassa and sulphuric acid ; but it is self-evident that the application of 



COBALT. 37 

anj of those improvements is dependent as regards success in a commercial point of 
Titfw, npon local conditions, and upon the possibility of advantageously obtaining the 
▼aiiouB ingredients. 

TuntrairB-Bine. By mixing together a solution of red prussiate and of protosulphate of 
iron in such proportions as to prevent the entire saturation of the former salt, there is 
obtained a blne-coloored precipitate, known in commerce as Tumbull's-blue, consisting of 
Fe2Cy3,3FeCy, bat also oontaing some chemically-combined yellow prussiate. MM. Mallett 

BtriiiiBfa&euftBy- ^"^^ Gautier-Bouchard have proved experimentally that Berlin-blue may 
Prodnct of the be obtained as a by-product of coal-gas manufacture from the ammoniacal 
"SlSSeSi*' liquor, from the spent lime of the purifiers, and from Laming's purifying- 
Aojjua CbueoaL mixture. The spent lime contains, in addition to the cyanides of 
ealdnm and ammonium, a good deal of free ammonia, mechanically absorbed in the 
moiBt lime. Free ammonia is first removed by forcing steam through the lime, and 
eollecting the ammoniacal gas in dilute sulphuric acid. The lime is next washed with 
water, and the Uquor obtained, containing the cyanogen compounds, is employed for the 
mannfaetofie of Berlin-blue. According to M. Erafft's experiments, looo kilos, of spent 
gas-lime yield, when treated as described, from 12 to 15 kilos, of Berlin-blue, and from 
15 to 20 kilos, of sulphate of ammonia. Mr. Phipson states that i ton of Newcastle gas- 
coal yields a quantity of cyanogen which corresponds to from 5 to 8 lbs. of Berlin-blue. 
The manufacture of animed-charcoal also yields, if desired, Berlin-blue as a by-product. 

Soluble Betiin-BiiM. As ordinary Berlin-blue is quite insoluble in water, and the basic 
viriety only soluble in the presence of ferrooyanido of potassium, these pigments are only 
fit for use as paints, and the discovery of the solubility of pure Berlin -blue in oxalic acid 
is of some importance, for thereby its application as a water-colour becomes possible. 
This soluble blue is obtained by digesting the Berlin-blue of commerce for i to 2 days, 
with either strong hydrochloric acid or with strong sulphuric acid, which latter, after 
having been mixed with the Berlin-blue previously pulverised, is diluted with its own bulk 
of water. The acid is liext decanted from the sediment of blue, and the latter thoroughly 
washed and dried, and then dissolved in oxalic acid, the best proportions being 8 parts of 
Berlin-blue, treated as just mentioned, i part of oxalic acid, and 256 of water. According 
to other directions, Berlin-blue readily soluble in water can be obtained: — i. By the 
precipitation of protoiodide of iron with yellow prussiate of potassa, care being taken to 
keep the latter in excess. 2. By mixing a solution of perchloride of iron in alcoholic 
ether (tinciura fernchlorati cetherea^ Ph. Buss.) with an aqueous solution of yellow 
pnusiate. 

Pure Berlin-blue is of a very deep blue colour, with a cupreous gloss ; it is insoluble in 
water and alcohol, is decomposed by alkalies, concentrated acids, and by heat. Tho 
lighter and more spongy it is, the better is its quality ; it is employed as a pigment and in 
dyeing and calico-printing, but in the two latter instances, pigment-printing excepted, it 
is obtained on the tissues by a circuitous process. The Berlin-blue of commerce is 
frequently adulterated with alumina, pipe-clay, kaolin, magnesia, heavy-spar, and, 
according to Pohl, even with starch-paste coloured blue b.y means of tincture of iodine. 

Cobalt. 
(Co=s5g; Sp. gr. = 87). 

Xfuuk Cobalt. This metal is found native as cobalt-spoiss (CoAsa), containing from 
3 to 24 per cent of cohalt, and from o to 35 per cent of nickel ; also as cobalt-glance, 
bright white dobalt (CoAsS), containing from 30 to 34 per cent of cobalt. Cobalt is 
prepared on a large scale as a metal at Isorlohn, and at Pfannensticl, near Aue, in 
Germany. Metallic cobalt exhibits a stccl-grey colour, somewhat verging upon red, 
a strong metallic lustre, assumes a brilliant polish, is malleable and ductile, and far 
tougher than iron. It requires a very high tompcrature for fusion, is only slowly 
•cted upon by dilute acids, but readily dissolved by nitric acid and aqua regia. 

GotaitGoioon. The orcs intended for the manufacture of the cobalt colours are roasted 
for the double purpose of volatilising the sulphur and arsonir they contain, and for 
effecting tiie oxidation of the cobalt. After roasting, the orcs are known as Zaffer or 
Saphera. According to the degree of purity, the trade distinguishes the ores as 
'* coniiuon/* '* medium," and " very fine ;" they contain essentially a mixture of proto 



38 CHEMICAL TECHNOLOGY. 

peroxide of cobalt, arsenic, nickel, and traces pf the oxides of manganese and bismntb, 
and are used in the preparation of cobalt-colours. In Sweden " zaffers " are prepared 
by precipitating a solution of sulphate of protoxide of cobalt with a solution of 
carbonate of potassa. Zaffer is used for the manufacture of smalt, cobalt-ultra- 
marine, — a misnomer, for evidently ultramarine is contracted from ultra-mare, because 
the lapis lazuli was brought across the seas from India — ^OsBruleum, Rinmann's-green 
(cobalt-green or Saxony -green), and also cobalt-yellow, cobalt- violet, and cobalt- 
bronze. 

Smalt. Compounds ^f cobalt have the property of imparting a blue colour to glassy 
substances at a red-heat ; when, therefore, impure protoxide of cobalt is fused with sihca 
and carbonate of potassa, the result is the formation of an intensely blue-coloured glass, 
which, when pulverised, is known as smalt. This substance was discovered and first 
prepared by the Bohemian glass-blower, G. Schurer, who lived in the sixteenth centniy. 
Smalt is now prepared by melting the roasted cobalt ores with quartzose-dand and potash, in. 
crucibles placed in a glass-furnace. The red-hot glass produced is quenched in cold water to 
render it brittle. It is next pulverised and scoured with water, by which operation smalts 
are obtained of different degrees of fineness, not simply as regards minute state of division, 
but also depth of colour, all of which varieties abroad — where to a limited extent the 
smalt is still used, though it is almost entirely superseded by artificially-made ultramarine 
— ^bear distinctive names. It has been proved experimentally that the colouring-matter of 
smalt is potassio-siUcate of protoxide of cobalt, in which the proportion of the oxygen of 
the acid to that of the base is as 6 : i. According to M. Ludwig, loo parts of the under- 
mentioned cobalt colours contain : — 

Norwegian Smalt. German Smalt. 



Termed Coarse and 
High colour. high Eschel. pale coloured. 

Silica 70*86 66'2o 72*11 

Protoxide of cobalt . . 6*49 675 1*95 

Potassa and soda . . .. 21*41 16*31 i'8o 

Alumina 0*43 8*64 20*04 

These substances, moreover, contain small quantities of protoxide of iron, lime, prot- 
oxide of nickel, arsenic acid, carbonic acid, water, and oxides of lead and iron. Dr. Oude- 
mans lately analysed a beautifully ultramaiine-colom'ed sample of smalt, which was 
found to contain 5*7 per cent of protoxide of cobalt. As cobalt-glass obtained with soda is 
never of a pure colour, that alkali cannot replace potassa in the manufacture of smalt. 
Since the roasting of the cobalt ores is not continued long enough to oxidise the nickel 
contained in them, that and some other metals present fuse during the preparation of 
the smalt, and, settling to the bottom of the crucible, form an alloy termed Cobali-speiss. 
cobait-BpeisB. This substance is of a reddish-white hue, has a strong metallic lustre, is fine- 
grained in structure, and contains on an average from 40 to 56 per cent nickel, 26 to 44 
per cent arsenic, as well as copper, iron, bismuth, sulphur, &c. Dr. Wagner found that 
(1870) a sample of this alloy from a Saxon mine contained in 100 parts : — 

Nickel 48*20 

Cobalt 1-63 

Bismuth 2*44 

Iron 0*65 

Copper 1*93 

Arsenic 42*08 

Sulphur 3*07 



100*00 
The material is chiefly used for the preparation of nickel. 

AppucaUoni of Smalt is still employed in washing and dressing blue, and for imparting a 
Smalt. YjIjj^q tint to paper. It is not, however, very suitable for this purpose, as, 
on account of its hardness, it soon destroys the points of writing-pens. Smalt is more 
extensively used for blue-enamclUng glass, porcelain, and earthenware. 

Cobalt uitnmaiine. This Bubstance, also known as Th^nard's blue, is a pigment consisting 
of alumina and protoxide of cobalt. Curiously enough this pigment has been discovered 
and prepared at three several periods and localities by different people ; first, by Wenzel, 



NICKEL. 39 

St Freiberg, Saxony ; next by Gahn, at Fahlnn, Sweden ; and lastly, Biniultaneously at 
Paria and Vienna, by Th^nard and von Leithener. TLe pigment is prepared either by 
mixing Bolutions of alnm and a salt of protoxide of cobalt, precipitating the mixture by a 
eolation of carbonate of soda ; or by the decomposition of aluminate of eoda by meanb of 
chloride of cobalt. The ensuing precipitate, consisting of an intimate mixture of hydrate of 
alamina and hydrate of protoxide of cobalt, is first well washed, then dried and heated lor 
some time. The pigment thus produced is, when seen in daylight, of course after pulver- 
isation, vezy siihilar to ultramarine, but by artificial light its colour is a dirty riolet. It 
is, however, not acted upon by acids) as distinguished from artificial ultramarine ; neither 
is it a£feoted by alkaUes nor heat, as is copper or mineral blue. Cobalt-ultramarine, 
chiefly under the denomination of Thdnard's blue, is employed as a paint m oil- and wat^r- , 
colours, and also for staining glass and porcelain. 

cmiram. Is a pigment prepared in England, exhibiting a bright blue colour, not 
changing in artificial light, and consisting of stannate of protoxide of cobalt (Sn02,CoO), 
mixed with stannic acid and gypsum in the proportions, in loo parts, of 49*6 of oxide of 
tin, 18-6 protoxide of cobalt, 31*8 gypsum. This pigment is not affected by heat, or the 
action of dilute acids and aUcalies ; nitric acid dissolves the protoxide of cobalt, leaving 
the other ingredients, from which the gypsum may be cleared by water. 

MxuBBDii'a, or This substanco, also known as cobalt-green, zinc-green, and Saxony-green, 
cob«iv<H««n. ig a compound similar to the cobalt-ultramarine, for the alumina of which 
oxide of zinc is substituted. This green is prepared by mixing a solution of white 
vitriol with a solution of a salt of protoxide of cobalt, precipitating by carbonate of 
soda, and washing, diying, and heating the precipitate. This pigment when pure con- 
tains 88 per cent of oxide of zinc and 12 per cent of protoxide of cobalt. It is not affected 
by btroug heat, tinges the borax-bead blue, dissolves in warm hydrochloric acid, forming a 
line colour, which, upon water being added, becomes a pale red. Treated with caustic 
potassA, the oxide of zinc is dissolved, and may be detected, after previous dilution with 
water, by the addition of a solution of sulphuret of potassium. 

cheinieanT i>iii« ThiB Bubstauce is occasionally employed for the preparation of fine 
prounidc oi Cobalt, colours. It may be obtained by heating one part of previously roasted 
and finely-pulverised cobalt ore with two parts of sulphate of potassa until no more 
solphnric acid is given off. The fused mass, consisting of sulphate of potassa, sulphate 
of protoxide of cobalt, and insoluble arsenical salts, is, when cooled, first treated witii 
water, and next digested with hydrated protoxide of cobalt to precipitate any iron which 
may happen to be present, and in order to eliminate the oxide of that metal the solu- 
tion is filtered. It is next precipitated with carbonate of soda, and, finally, the precipitate 
is washed and heated. 
Kitnto of Protoxide of This doublc salt, known by its trade name of cobalt-yellow, is 
cotait sad Pouaaa. obtained by mixing a solution of protoxide of cobalt with nitrite of 
potassa ; it is a yellow crystalUne precipitate, perfectly insoluble in water. M. Saint-Evre 
first investigated this body, and struck with its beautifully yellow colour, quite like that 
of purrhee (euxanthinate of magnesia), and with the fact that cobalt-yellow resists 
oxidising and sulphurettuig infiuences, suggested its applicabihty to artistic purposeH. 
He prepares this pigment by precipitating with a slight excess of potassa the double salt 
of protoxide of cobalt and potassa, obtaining a rose-red-coloured protoxide of cobalt and 
potassa. Into tuis thickish magma deutoxide of nitrogen gas is passed. According to 
Hayes, this pigment is readily obtained by causing the vapours of hyponitric acid to pass 
into a solntion of protonitrate of cobalt, to which some potassa has been added ; the 
whole of the cobalt is then converted into cobalt-yellow. As the nitrite of protoxide 
of cobalt and potassa can be obtained even from impure solutions of protoxide of cobalt, 
so as to be quite free from any nickel, iron, dec, the use of this preparation of cobalt is 
preferable for glass and porcelain staining, when a pure blue is required. 

cobttit-BraoM. This substance, a double salt of phosphate of protoxide of cobalt and 
ammonia, prepared at Pfannenstiel, near Aue, in Saxony, hns been but lately brought into 
commerce. It is a violetrcoloured powder, very much like the \i<)lct-c<>l<>iiri'd clilorile of 
chromium, and oxhibits a strong metallic luKtrc. 

Nickel. 

(Ni = 59; Sp. jrr.=.? 07 to qzCv 

Kkkd and its oks. This mctal occurs in the Ibllnuin;^ ores: — Copper nickel or 
arsenical nickel, NiAs, containing alxmt 44 ppr cent Ni ; nntimonial nickel, NiSl), 
with about 3 14 per cent Ni; wliite arsenical nickel, NiAsj, witli iibout 28 2 per 



40 CHEMICAL TECHNOLOGY. 

cent Ni ; in some varieties of cobalt-speiss, as, for instance, the capillaiy pyrites 
(sulphuret of nickel) with 648 per cent Ni ; and the antimonial nickel-ore, 

NiS2+Ni(Sb,As2), 
with about 268 per cent Ni. There is found at llewdansk, Oural, Russia, a mineral 
known as Rewdanskite, a silicate of hydrated protoxide of nickel (i2'6 per cent Ni), 
from which the metal is obtained. Nickel is also extracted from ores which contain 
it accidentally, as, for instance, some species of iron and copper pyrites, cobalt-speiss, 
and certain copper ores known as Mansfeld ores, which yield sulphate of nickel as a by- 
product. Several varieties of manganese contain nickel and also cobalt ; and in England 
the residues arising from the manufacture of chlorine are in some instances applied 
in the production of these metals, the process yielding, according to Gerland, 2*5 Idloe, 
of nickel and 5 kilos, of cobalt for i ton of manganese. Some magnetic iron ores 
3deld nickel, a specimen of such ore from Pragaten, Tyrol, Austria, containing, 
according to M. T. Petersen, 176 per cent of NiO. 

^*"SS!tt?ora[!*^*^ ^* ^^T rarely happens that the natural ores of nickel are so pure, 
that is to say, contain the metal in such a state of combination, as to admit of the 
direct extraction of the metal, and tlierefore, as is the case \\4th copper, a preliminary 
operation is required, wliich aims at the concentration of the metal in combination 
either with sulphur, in wliich case the combined substance is termed regulus, and 
sulphuret of iron is applied as a means of concentrating tlie nickel contained in the 
ore as sulphuret ; or, if the nickel happens to be combined cliiefly with arsenic, the 
concentrated mass is termed speiss ; while in a few instances an alloy of nickel an<l 
coarse or black copper is obtained. From aU these products the metallic nickel, or 
sometimes an alloy of nickel and copper, is prepared by the dry or moist process. 

The method of obtaming nickel embraces two distinct features, viz. : — 
I. A smelting process, which aims at rendering the nickel of the ores richer, and 
concentrating the metal — 
a. fn a regulus, 
/3. In a speisB, or 
y. In alloy with coarse or black copper. 

n. In the separation of the nickel, or a definite alloy from the products obtained by 
the concentration-smelting ; this can be done — 

a. By the dry, or 

6. By the hydro-metallurgical method. 
As it is found that the preparation of an alloy of copper and nickel, for the manufac- 
ture of so-called German- silver, impairs the most valuable properties of nickel — its 
white colour and resistance to chemical action — the obtaining of pure metallic nickel is 
t)referred. 
^uieiUn'"o?So" ^' ^^® Operation is carried on (a) for regulus, when the nickel-ores are 
Niekei Ores. mixed with iron pyrites and magnetic pyrites, and consists in smelting the 
previously partly roasted ore with quartz or substances rich in sihca. During the process 
the greater portion of the oxide of iron generated is absorbed by the slag, while the nickel, 
also first oxidised, and more readily reduced than the oxide of iron, is converted to the 
metaUic state and taken up by, and concentrated in, the regulus, a mixture of undecom- 
posed sulphnrets of metals and reduced sulphates. If at the same time the ore contains 
copper, that metal is even more readily and completely incorporated with the regnlua than 
the nickel itself. If the roasted mass contains too much protoxide of iron, a portion of that 
metal is reduced, and either taken up by the regulus, or separated as containing nickel. 
The separation of the iron from the regulus frequently requires the application of a refining 
furnace provided with a blast so as to oxidise the iron. A better result is obtained by 
treating the previously roasted ore in a reverberatory furnace with quartz, heavy spar, and 
charcoal or coal; sulphuret of barium results, which, becoming converted into barj'ta, trans- 
I 1-9 its sulphur to the oxides of nickel and copper, while the baryta forms with the quartz 
mid protoxide of iron a readily fusible slag. At Dillenburg an ore which ctntains tb*» 
f.dlphurets of nickel to about 7*5 per cent, and copper, is treated in the fallowing 
iii^umer: — It is roasted in stacks, built not unlike coke-ovens; next broken up and 



NICKEL. 41 

smelted in a low blast-famace heated by means of coke, no other ingredients being added, 
as the ore contains silica, alumina, and lime in sufficient quantities, so as to obtain crude 
regains (I.) This crude regulus is next melted with slags so as to obtain concentrated 
regains (II.) It is lastly submitted to the action of a refining blast-furnace in order 
to lessen the quantity of iron, care being taken to leave enough sulphur to keep the 
refined regains (lU.) brittle; finally, the regulus is employed in the manufacture of nickel 
and alloys of nickeL Composition — 

I. II. III. 

Nickel ig 24 35 

Copper 13 39 43 

Iron 35 12 2 

Sulphur 33 25 20 

100 100 100 

This mode of operation is employed at Elefver (Sweden), and in some other localities. 

{fl). The smelting of nickel ores for the purpose of concentrating the metal in speiss is 
applied when the nickel occurs in combination with either arsenic only or with that 
metal and antimony, such compounds being occasionally obtained in the operations of 
smelting copper, lead, and silver ores, and as by-products of the smelting of metals not 
containing arsenic, as, for instance, in slags from copper-smelting, in which case there 
is added arseniuret of iron (arsenical iron pyrites, FeAs+FeSz, which when heated by 
itself splits up into As and 2FeS). When a mixture consisting of nickel, iron, and arsenic 
is first submitted to a partial calcination, and next to a simultaneously reducing and 
fnsing smelting, the iron is taken up by the slag, the nickel-oxide is reduced, and the 
arseniates are converted into arseniurets, and as the nickel has a greater affinity for 
arsenic than for sulphur, the speiss will also take up that metal. If the compound 
originally operated upon happens to contain copper, that metal is present in the speiss, 
from which it may be separated as a sulphuret by the addition of ordinary pyrites to the 
arsenical pyrites during the smelting. By frequently roasting and smelting the speiss, 
aided occasionally by an oxidising blast and the use of heavy spar and quartz as slag, the 
iron is gradually eliminated. At Birmingham, Hungarian and Spanish nickel ores are 
smelted for speiss, these minerals containing on an average from 40 to 55 per cent 
of nickel, and from 30 to 40 per cent of arsenic, as well as sulphur, bismuth, and 
copper. 

(y). Smelting for the concentration of coarse copper or nickeliferous pig-iron. When 
the quantity of nickel contained in the copper ores is very small, the nickel accumulates 
in the first portions of the refined copper in such quantities as to repay the trouble of 
extraction. M. Willo analysed some refined copper, obtained from the cupriferous slate 
of lUechelsdorf, and found it to contain from 7*8 to 13 '6 per cent of nickel ; occasionally 
the Borfaoe discs of rosette-copper contain crystals of protoxide of nickel. 

Me£S^Ktekri.°or of ^^* "^^^ ^^ eflfectcd by submitting the product of the concentra- 

AU4>y« of Miekci aad oopper. tion-smeltiug to either (a) a dry method of treatment, or (b) a 
hydro>metallurgioal process. 

(a). Preparation of nickel by the dry method. It appears that the methods hitherto 
employed have not led to very satisfactory results ; it is true that when nickel-speiss is, as 
snggeeted by M. von Qersdorf, repeatedly roasted with charcoal-powder and wood- 
afaavings, oxide of nickel is obtained, and may be reduced by means of coal, coke, or cliar- 
coal; but as this oxide is always mixed with arseniato of oxide of nickel, the metal also 
contains arsenic, and any German-silver made vdth it is brittle and turns brown on 
exposure to air ; moreover, a small quantity of iron is always present in the nickel thus 
prepared. A better result is obtained by the process proposed by the late H. Boso, in 
1863, for the preparation of the metal free from arsenic, and which consists in mixing 
the pulverised speiss with sulphur and heating this mixture, thereby forming sulphuret of 
nickel and sulphuret of arsenic, the latter being volatilised. This operation is repeated 
as often as may be necessary ; the sulphuret of nickel is roasted, and sulphate of protoxide 
of the metal is formed, which, at a high temperature, as is the case with protosulphate of 
iron, loses its sulphuric acid, leaving the oxide of nickel to be reduced to the metallic 
state by means of charcoal. At Dillenburg experiments have been made in order to 
obtain from what is termed a refined stone — a compound of nickel, copper, iron, and 
sulphur — an alloy of nickel and copper, by first coraplotoly calcining the sulphurets, and 
so driving off the free sulphur; next mixing the remainder of the substance in quantities 
of 100 lbs. with 45 lbs. of soda, and submitting this mixture to the heat of a reverberatory 
furnace in order to render the sulphur soluble in water as sulphuret of Hodium aitil 



42 CHEMICAL TECHNOLOGY. 

sulphate of soda, leaving an alloy which, of courBe, has to he refined in order to eliminate 
the last traces of iron. 

(b). Ohtaining nickel hy the wet, or hydro-metallurgical method. A preliminary 
roasting of the ores or products of metallurgical operations containing nickel is required 
in order to convert the iron into an oxide soluhle in acid, and to convert the nickcQ, 
copper, and cobalt, either into sulphates soluble in water or into oxides or basic salts, 
both of which are soluble in sulphuric and hydrochloric acids. From any such solution 
the nickel is precipitated by a suitable reagent either as oxide or as snlphuret, and from 
these materials metallic nickel or an alloy of that metal with copper is prepared. The 
preparation of nickel by the moist method consists of three different operations : — 
I. The preparation of the nickel solution. When nickeliferous metallurgical produets 
are roasted, either with or without the addition of copperas, the result is the formation of 
the sulphates of iron, copper, nickel, and cobalt, and this mixture when roasted becomes 
decomposed, the sulphuric acid being driven off first and most readily from the sulphates 
of the oxides of iron, and with greater difficulty from the sulphate of protoxide of cobalt. 
Accordingly, after roasting, the mass on being treated with water, yields the larger portion 
of the nickel and cobalt with some of the copper, while the greater part of the latter, 
with very small quantities of cobalt and nickel and the whole of the iron, remain undis- 
solved as oxides ; by the use of acids the protoxides of copper and nickel are extracted 
from this residue. If the roasted material is immediately treated with hydrochloric acid, 
the result is that more of the oxide of copper than of the protoxide of nickel is dissolved ; 
but by again treating the residue with boiling acid the oxides of iron and nickel are 
extracted. Speiss may be used for obtaining a nickel solution by first heating the previ- 
ously roasted speiss with a mixture of soda and nitrate of soda» next extracting the 
arseuiate of soda by means of water, and afterwards treating the residue with sulphuric 
acid, roasting the sulphates obtained so as to decompose only that of iron, and finally 
treating the mass again with water to obtain the sulphates of nickel and cobalt in solution. 
According to Professor Wohler's plan, the arsenic of the speiss can be removed by fusion 
with sulphuret of sodium and a subsequent treatment with water, in which it, as a sulpho- 
salt, is soluble. 2. The nickel may be precipitated from the solution in various 
ways. According to M. Stapff's plan (1858), a fractioned precipitation maybe obtained 
by means of chaXk employed at various temperatures, the result being that first iron 
and arsenic, and next copper, are separated, so that only the nickel remains in solution, 
and can be thrown down by milk of lime. According to M. Louyet (1849), iron and 
arsenic are first precipitated by milk of lime mixed with bleachmg-powder, and the 
liquid containing this precipitate filtered off. From the acid filtrate the bismuth, lead, 
and copper that may be present are removed by sulphuretted hydrogen ; the filtrate from 
these joint sulphides is next boiled with bleaching-powder, the cobalt being separated as 
a peroxide, and the nickel remaining in solution. If it is desired to obtain the cobaltie 
peroxide in a pure state, the precipitation should be so conducted as to leave a little 
cobalt with the nickel, no injury therefrom accruing to that metal. At Joachimsihal, 
Bohemia, the nickel is precipitated from the acid solution after the removal of the 
copper by sulphuretted hydrogen, by means of bisulphate of potassa as bisulphates of 
protoxide of nickel and potassa, leaving the cobalt in solution free from nickel, which iu 
its turn is thrown down by carbonate of soda. 3. The conversion of the nickeliferous 
precipitate into metal, or into an alloy with copper, may be carried out in the following 
manner. The protoxide of nickel is first separated from the liquid by filtration, then 
pressed so as to admit of its being dried by intense heat, and next ground up with water 
and washed with very dilute hydrochloric acid, in order to remove the gypsum, of which 
some 8 to 12 per cent is mixed with the oxide. The oxide is then made with beet-root sugiu-, 
molasses, and coarse rye-meal into a stiff paste, which is shaped into cubes from 
I '5 to 3 centimetres in size; these cubes are next rapidly dried, and after drying are 
placed with charcoal powder in crucibles or in perpendicular fire-clay cylinders, where 
being submitted to a very strong white heat, the metal is reduced ; an operation which, in 
the case of the alloy of copper and nickel, or of cupriferous nickel, is finished in i| hours, 
the reduction of the pure metal taking fully three hours. The copper soon becomes 
molten, but the nickel only sinters together on account of the very great infusibility of 
this metal. The small cubical pieces of nickel as met with in commerce exhibit externally 
a strong metallic lustre, produced by putting the cubes with water into casks, which are 
made to rotate. In order to ensure uniformity of composition, and hence a good sale for 
the alloy of copper and nickel, rosette-nickel, care is taken to procure the mixture of 
the two metals in the proportion of 66*67 P^^ ^^^^ copper and 33*33 per cent nickel, while 
the cubical nickel contains from 94 to 99 per cent of pure met^U. At a nickel-oven at 
Dillenburg, the metal is not made into cubes, but treated in the same way as rosette- 
copper. 



COPPER. 43 

propert'Mof KiekeL Pure nickel has a nearly silver- white colour, with a slight 
jellowish hue, is very difficult to melt, rather hard, very ductile, and easily polished ; 
sp. gr. = 8*97 to 9* 26. When quite pure this metal may be drawn into wire, rolled 
into sheets, hammered, and forged ; its tensile strength stands to that of iron as 9 : 7. 
Nickel is analogous to iron, but distinguished from it by possessing a greater power 
of resisting chemical agents ; on this account, and for its not becoming rusty in air or 
when in contact with water, nickel is used for obtaining silver-like alloys (see 
Copper). In Belgium, Switzerland, the United States, and Jamaica, small coins 
have been made of an alloy of nickel with zinc and copper, pure nickel being too 
bard to admit of readily coining. An alloy known as tiers-argent, one-third silver, 
consists in 100 parts of: — 

ouLver ••• ••• ••• ••• ••• ••• Z7 3^ 

Copper 59*0^ 

Mi\i\G ••• ••• ••• ••• ••• ••• 9 j7 

i^\C]aML»»» ••• ••• ••• ••• ••• ^ 4^ 

9961 

The total annual production of nickel on the continent of Europe amounts (1870) 
to 11,200 cwts., exclusive of what is made in England. Very pure nickel is obtained 
at Val B6noit, near Luik, Belgium, from an Italian nickel ore, the metal containing 
less than i per cent impuriticB. 

Copper. 

(Cu==63-4; Sp.gr. = 8-9.) 

*'*''**''^ tow."****^ Copper is one of the metals met with most abundantly. It has 
been known from a very remote antiquity — even before iron — and bears tlie Latin 
name Cuprum^ because it was obtained by the Romans and Greeks from the Island 
of Cyprus ; from the Latin name of this metal the English, German, Dutch, and 
French names are derived. Copper is found to some extent in a metallic state 
naturally, but it is chiefly obtained from ores, among which the oxides and sulphides 
are the chief. 

On* of Copper. Native copper is found in large quantities near Lake Superior, in North 
America; and in Chili there is known a peculiar kind of sand called copper-sand, or 
eopper-barilla, consisting of from 60 to 80 per cent of metallic copper and 20 to 40 per 
cent of quartz. This sand is imported into England and smelted, vdth other copper ores, 
at Swansea. 

Bed copper ore (suboxide, or red oxide of copper), GuaO, containing 88*8 per cent of 
copper, is met with in octahedrical-shaped crystalB, disseminated or instratiiied through 
rock in Cornwall. An intimate mixture of suboxide of copper and iron-ochre is known as 
tile-ore, or earthy red oxide of copper. Azurite, or blue copper ore, containing 55 per 
cent of copper, is a compound of carbonate of protoxide of copper and hydrated protoxide 
(2CuC0|-|-CuHa02. It occurs in beautifully blue-coloured crystals disseminated through 
rock and gangue in Cornwall, and was formerly found at Chessy, near Lyons. 

Malachite, containing 57 per cent of copper, consists of basic carbonate of hydrated 
oxide of copper (CUCO3-HCUH2O2), and occurs inrhoinbio crystals, also as stalactite and 
stalagmite, and in Atlas ore, a veined and earthy ore called copper-green os earthy 
malachite, and very frequently with azurite in Australia and Canada. 

Copper-glance, copper-glass, sesqniBulphuret of copper (CuaS), contains 80 per cent of 
the metal. Purple copper ore, variegated copper ore, a compound of copper-glance and 
sesquisulphnret of iron (sCu^S-hFeaSj), with 55 '54 per cent of copper and copper pyrites 
(Cu^S+FeaSj or CuFeSa), with 34*6 per cent of copper are the chief sulphur ores used in 
the extraction of copper. Copper pyrites is often mixed with iron pyrites, and also often 
contains silver and nickel. The mineral known as Bonmonite, although a lead ore, often 
contains as much as 1276 per cent of copper. 



44 CHEMICAL TECHNOLOGY. 

Slaty copper ore is a bitmninons marly schist belonging to the permian formation, 
through which sulphuretted copper ores are disseminated ; this ore is chiefly found in 
Germany. 

Grey or black copper ores, so called Fahl ores, are compounds consisting of electro- 
positive sulphurets, viz., ^ulphuret of copper and of silver, with electro-negative 
sulphurets, viz., those of arsenic or antimony. As these ores contain silver they are usually 
considered as silver ores, the quantity of copper contained in them amounting to about 
14 to 14*5 per cent. Atacamite is also a copper ore (3GuH202+Cu0l2)» containing 56 per 
cent of copper. This substance is chiefly met with in Chili and other parts of the Western 
Coast of South America, in Southern Australia, and in Peru, and in that country it is 
ground to powder and used instead of sand or sawdust to strew on the floors of rooms. 
It is imported in that state under the name of ArsenHlo, and is smelted with the atacamite 
in lumps at Swansea. 

Mode of Treating the Copper It is quite evident that the treatment of the ores must vary 

Ore^ for the Purpose of ■• • -i ... 

ExtrActing the Met«L according to the constitution of the metals. The ores in 
which copper is contained as oxide, or ochrey ores, are reduced readily enough by 
simple treatment with carbonaceous matter and a flux ; but these ores are by no 
means abundantly found, and are therefore usually mixed with pyritical sulphu- 
retted ores. The smelting of copper from its ores therefore embraces : — 

1. The smelting from ores containing oxides, 

2. From pyritical ores, and 

3. The hydro-metallurgical method. 

Pyritical copper ores are smelted either in a shaft, or pit-fumace, or in a reverbera- 
tory furnace, in the latter instance the reduction of the metallic regulus of copper, 
obtained from a previous roasting of the ore, is effected by the aid of sulphur, not by 
that of coal. The regulus is gradually rendered richer and richer in metal, until at 
last the decomposition of the sulphur is completed by the action of the oxygen of tlie 
air ; by this operation suboxide is plentifully formed, and as a consequence the metallic 
copper obtained is in the state technically termed '* over-reflned." When the shaft- 
furnace is employed, the first portion of the operation is similar to that alluded to, 
but the metal is reduced with coal or charcoal, and hence the copper obtained — 
leaving out of the question the presence of the foreign metals — ^is never over-refined, 
but contains carbonaceous matter, so that in order to render the copper, as it is 
technically termed, tough — ^that is to say, malleable when cold as well as when hot, 
another operation is required, which it is evident from the foregoing must differ for 
the two qualities of crude metal. 
TheWorkinu-npofthe The orcs are first roasted or calcined, and a portion of the 

Copper Ores in tha 

Shaft Furnace. sulphuT, arsenic, and the antimony they contain volatilised ; sul- 
phates of the metals as well as arscniates and antimoniatcs are at tlie same time 
formed, while a portion of the ore is not acted upon at all. Wlien the smelting 
operation is commenced, fluxes are added, and any oxide of copper present is reduced 
to the metallic state, while simultaneously the sulphates are again converted into 
sulphurets, which jointly with the metallic copper form the rather richer crude 
regulus of copper ; whUe if arsenic and antimony prevail speiss is formed. The 
more readily oxidised metals present, chiefly iron, form, as protoxides, compounds 
with the fluxes. By a repetition of this process vdOi the coarse metal regulus — ^tlie 
operation being known as a concentration- smelting — ^there are obtained tliin matt, 
and what is termed black copper, containing foreign metals, wliich are got rid of by 
a first or coarse refining, a portion of the impurities under the influence of a high 
temperature, the oxygen of the air and fluxes, being partly volatilised, pai-tly taken 
up in the slag. The copper obtained by tliis operation, rose- or disc-copper, contains. 



COPPER. 



45 



becaose the calcination is carried rather too far. suboxide of copper, which impnira 
the dnctility of the melal. This defect is remedied hy a rapid smeltiBg under a 
layer of charcoal, the suboxide being reduced and touph copper obtained. Wlien a 
rererberatoiy furnace la employed, the coarse and last refJiiinga are usually included 
in one process . 

According to the continental methods, the calcined ore is smelted and converted 
into coarse regulua in a shaft-furnace, the fuel employed being charcoal or coke, or a 
mixture of the two. Fig. iS exhibits the vertical section of the furnace ; Fig. 19 is 
a front view, the front wall being removed to show the interior construction. Fig. 20 
exhibits the lower part of this furnace; ( ( are the tuyere-holes for the blast; the 
apertures, o o, placed just above the lowest part of the breast of the hearth, communi- 
cale by means of channels with the smelting-pots, c' c', the object being to gradually 
collect the molten contents of the furnace Smco copp r ores always contom 
more or less iron, it might happen that by simph employing a reducmg smeltmg 
some of that metal would become mixed with tlie copper m order to avoid this 
fluxing materials rich m sihca are added with ^\hich the protoxide of iron forms a 

Fig. 18. 





readily fusible slag. The oxides of copper present in tlie calcined materials are 
reduced to the metallic state by the sulphuret of iron — 

3CUO + FeS = S0,+ FeO+ 3CU. 
The metal regulns. a mixture of sulphnrets of copper and iron and other metals, con- 
taining on an average 32 per cent of copper, collects in tlie lower part of the fomace, 
snd the slag formed is called crude or coarse slag. The roasting of the regulus aims 
« ita most complete oxidation, while the sulphur is eliminated. The calcined regulus 
is next smelted in a shaft furnace with the addition of a flux, a process technically 
known as concentration- smelting.* Tlie refined regulus obtained by this smelting 
eontains some 50 per cent of copper, and is next treated to obtain black -copper, coarse 
melal. But if the regulus contain a sufficient quantity of silver, that metal is 
extracted by methods which will be fully elucidated when silver is treated of; in 
Mme cases this operation is combined with the extraction of lead from the copper, 
»nd effected by what is termed Uqnation, of which more presently. 

' There are no oquitUcnt terms in English to express tho real meaning of the German 
woidg, a (act which is readily accouuted for, if we consider that these operations are 
Msentially Uciman and of very ancient ittauding. 



46 CHEMICAL TECHNOLOGY. 

The operation of Bmelting for a refined regoIuB is omitted if tolerablj pure copp«r 
ores are operated upon, and suck ores Sifter calcination are immediate!; treated in » 
low blaat-fiimoce to obtain the lila«li- copper. In addition to black-copper, a thin 
matt coutaining from 93 to 95 per cent of that metal is obtained. As an instance of 
the composition of blaok-copper, we quote Dr. Fach's analysis of a sample of that 



o parts there a 



material prodnced at Mansfeld, in 18G6 ; 

Copper 9349 

Nickel and cobalt together 

Silver 

Sulphnr 

9975 
TO". The black-copper ia next submitted to an energetic oxidising 
Iting process in older to get rid of Ibe impurities in the slag. This procCGS is 



carried on either— 




1. In a small refining furnace ; 

2. In a large refining furnace ; or 

3. In a reverberator^ furnace. 

This operation is effected in a furnace or bearth, represented 
Fig. 31, and in perspective in Fig. 32; a is a semi -globular 

Fio. 




excavation, termed the crucible ; 6 is a cast-iron bed-plate ; h represents one of the 
two tnjeres by means of which a blast is conveyed to the fuel and the suHace of the 
copper. The black or coarse copper is melted bj the heat of charcoal aided by the 
blast, the sulphur, arsenic, and antimony being volatilised, while the oxides of iron 
and of the other non-volatile metals are token up with the suboxide of copper by the 
slag, which gathers at the sur&ce of the molten metal, and is from time to time 
removed. As soon as the refining is complete, the blast is turned off and the surface 
of the copper, the metal being heated far above its melting-point, covered with 
charcool-dost. When cooled sufficiently, water is poured on, and a portirai of the 
metal thus suddenly solidified admits of being lifted off from the rest of the molten 
mass in cakes or discs, technically known as rose or rosette -copper ; this <^>eration is 
repeated until the crucible contains no more metal. 

"i£S™l!Si.'' -A* U)« refining of copper on the bearth has Ifflln found to yield but 
poor results, another contrivance, shown in vertical section in Fig. 23, ia now more 
generally employed, a is the smelting- hearth ; b the refining crucible, of which there 



COFFER. 



47 



are two; n, the opening lot the tuyere of the bloat; I, the furnace. The mode of 
operation is similar to thatjuat given. When thereliningis complete the molten metal 
is run into the cruciblea, and. after having cooled Bufflciently, water is epTinkled on and 
the discs of roBC-copper lifted off. For the reason that in this kind of reverberatory 
fnmace the copper is not, as is the case on the hearth, in contact with the fuel, the 
lefnilt is iL purer metal. 

tOflmiioB ptocm. When the copper ores contain silver, the black copper is submitted, 
before being reRned, to a process known as liquation, unless it should be preferred to 
extract the silver by the Ziervogel method (see Silver). The hquation process is 
based upon the fact that lead and copper may be melted together, hut do not remain 
alloyed on cooling, so that a compound is formed containing much more copper than 
lead, the remainder of the lead separating and, while taking up the silver, settling 
down in consequence of its specific gravity. When the molten mass is slowly cooled, 
the lead combined nith the silver runs off after the solidification of the copper ; hot 
if the molten metals are rapidly cooled, an intimate mixture of the two takes place. 
The mode of separating the silver from the lead will be referred to when treating of 
the former of these metals. 

It has been alreadj mentioned that the refined copper reBolting from the above proceBBes 
contains aaboiide of that metal, which, if amounting to a quantity of I'l per cent, renders 
the copper nnfit for use at ordinary temperatures, by impairing its ductiUty and mollea- 
hiiity; while if the quantity ot the suboxide amonnte to ti per cent, the metal la nnfit for 




oie both cold and at a red heat — that is, becomes cold- and red-short. This condition ot 
the metal is. in Germany, termed " over- cooked," and the remedy is simply to melt the 
copper and submit it to what ie, in England, technically known as poling ; that is to say, 
a snfficiently long, stont, and green piece of wood, ia lued for thoroughly stirring up the 
molten masH. The ratiomtU is that the Carbon and hydrogen contained in the wood 
deoxidise the anboiide at the high temperature, rendering the metal veiy malleable and 
dnctile. makiag it, as is technically termed, toii^A. A sample of Mansfetd refined and 
loaghened copper was found by Dr. Steinbeck (o contain in loo parts :— 

Copper 94-37 

Silver o-oi 

Niokel 0-36 

Oiygeu 058 

Snlphui 0-02 



sLujUDf. Owing chieSy to the possession of an enormous wealth of coal, the 
It suited for the reverberatory fnmacca, a method of copper- smelting peculiar 



48 CHEMICAL TECHNOLOGY. 

to England is puraiied, and b. metal obt^ued of n rery superior quali^. aJthongh not 
ao good BB tliat extracted from particulax ores in Russia and Australia, Swans(^a is 
the cliief and most important seat of this industry in the United Kingdom, and to it 
copper ores are not only carried Irom Cornwall, North Wales, Westmoreland, 
Anglesea. and other portions of the realm, Ireland included, hnt are imported from 
Chili, Peru, Cuba, Norway, Australia, and other parts of the world. The English, 
ores are mainly pyritical. 

The chief procesBes of this mode of smelting ooneist in — i. Calcination of the ore; 
2. Smelting for coaree metal; 3. Calcination of coarse metal; 4. Making of nhite metal, a 
concentration process in whieh calcined coarse metal is smelted with rich ores; 5. Prepa- 
tion of the bine metal by smelting together oolcined coarse metal and calcined ores of 
medium richness ; 6, Preparation of a red and white metal by smelting together the slaga 
of the prerioud operations ; 7. Calcination of the bine metal (5) and preparation of whlto 
extra metal ; 8. CalcinBtion of the white extra metal and preparation of the ooncentration 
metal; 9. Calcination of the ordinary white metal of ouprifeioas residues for the purpose 
of obtaining blistered ooppei. According to M. Ourlt's views, all these operations may be 
reduced to, at most, two calcinations and three smelting operations, viz. :— r. Calcioatioa 
of the previously polveriaed ores with the addition of oommun salt, or of chloride of 
calcium, to form volatile chlorides; I. The smelting of calcined ores and obtainiog a more 
hquid slag and a coarse metal; 3. The calcination of coarse metal by the aid of a blast for 
the production of blistered copper with or without the addition of chlorides; 4. Befining 
and toughening Uie blistered copper. 

caictuini.'n'niiHtiiig This operation as carried on at Swansea does not materially differ 
uwOth, from that pursned on the Continent. Mo very appreciable loss of 

weight is etpeiieneed, as the weight of the osygen taken up compensstes for the loss 
occasioned by the more or less complete volatilisation of the aulphnr, antimony, arsenic, 
iSc. The roasted ore is block, this colour being due to the oxidea of iron and oopper- 
Durin); the roasting heavy white femea ore emitted, consisting of sulphnrousand arseuious 
acids mixed with other substances ; more recently, calcining furnaces have been con- 
structed on Oorstenhofer's patent system, so as to admit of the utilisation of the snl- 
phnrous acid for the mannfaeture of snlphnric acid. 

smciuu! tho OM. This operation is Iffected at Swansea In a furnace of which Fig. 34 
eihibits a sectional view, e is a funnel intended for the introduction of the roasted ore ; 
o is on ash-pit filled with cold water. The object in view is to separate the oree from 

Fio. 24. 




the gangoe as well as from oudes other than that of copper, by cansing the sulphur of the 
BUll^urets remaining undecomposed to act apon a portion oC the oxides and snlpbates in 
SD<di a manner that theee ore either taken up by the slag, as, for instance, the oxide of 
iron, or aro again reduced to sulphide, as the oxide and sulphate of copper. At a higher 
temperature the oxide of eopjH-r is reiluci^d to the metallic state by the action of the 
sulimuretB of iron and copper, oxide of iron forming, and the metallic copper being partly 



COPPER. 49 

taken up by the regnlnB, partly converted into suboxide again by the peroxide of iron, 
which is converted into protoxide and dissolved by the siliceons matter. The prodnot of 
the first stage of the smelting is a coarse metal, regulns. 

BoMtii«orCaidiiiiw ^^^ roasting of the coarse metal is performed in the reverberatory 
a» couM MeuL furnace used for the first calcination of the ores. The objects in view 
are the oxidation of any metallic iron present, and the partial volatilisation and combus- 
tion of tiie sulphur, partial only, for otherwise the smelting for white metal would be 
impeded or not performed without serious loss of copper. 

ftTHni frrr TiTittn ^^ Operation consists in mixing the previously calcined coarse 
ZsteL metal with rich copper ores containing har^y any sulphuret of iron, 

but consisting chiefly of the sulphide and oidde of copper mixed with quartz in such pro- 
portion that the pyrites (copper) is oxidised by the oxygen of the oxides present, the result 
being that all the copper combines with the coarse metal, while the protoxide of iron 
forms with the quartz Eolicate of protoxide. The white metal, almost entirely consisting 
of (GoaS), is run into cakes in sand-moulds. 

Bitatexvd. or Gnuie The white metal obtained is converted into blistered copper by placing 
^^v«- it on the hearth of a reverberatory furnace and causing the fire to act at 
first rather gently, but afterwards so as to fuse the mass, the total duration of the 
process for each charge being 12 to 14 hours; the result is the volatilisation of the 
sulphnr in the form of sulphurous acid, and the elimination, partially by volatilisation, 
partially by their being taken up in the slag, of such impurities as arsenic, cobalt, nickel, 
tin, iron, &c. When the mass becomes fused, suboxide of copper and sulphide of copper 
mutuaUy decompose, the result being the formation of sulphurous acid and metallic 
copper, {2CuaO-hCu2S=S02+6Cu). 

The molten coarse metal, impure copper as yet, is run into moulds, and its surface 
beeoming covered with black-coloured vesicles, due to the escape of gases and vapours 
from the molten metal, it is termed blistered copper. On being broken, after cooling, it 
exhibits a honeycombed structure, due to the same cause that produces the blistered 
appearance on the surface. Blistered copper, as usually obtained, is comparatively pure. 
Bcflniagthe The Ust Operation in the English method of copper-smelting is the 

Biiatei^^etaL refining of the blistered metal in a reverberatory furnace, care being again 
taken to fire at first gently, so that the metal shall not become molten until after some 
six hours. Aa soon as the entire charge is thoroughly melted down, the slag, rich in sub- 
oxide of copper, is tapped off and the molten metal covered with charcoal-powder. The 
operation of poling (see above) is then performed, birch-wood being preferred for the 
parpose ; this done, tne copper having been run into moulds of a rectangular shape, is 
known as refined tough cake. 

*twSno^S!?8iS?'*' Copper is readily obtained from oxidised ores by smelting them 
in a ahaft-fomace with coke or coal and such flaxes as will produce a slag which docs 
not absorb copper. The crude metal obtained is refined in a low blast-furnace. The 
smelting of oxidised ores is limited to a few locaUties, among which the Oural and 
Siberian works are the most important. Large quantities of excellent and very rich 
oxidised copper ore are found, but not as yet wrought, in the Islands of Timor and 
Tunor-Laout and the adjacent islands of Polynesia. 

"'^fJSJSgJ'^JJJ.^ This method owes its existence to the application of practical 
and analytical chemistry to metallurgy. As copper is very readily obtained, even 
from ores too poor to admit of being treated by the dry process, in such a state of 
combination as to admit of its being dissolved in water, and thrown down from this 
solution by the simple presence of metallic iron, the hydrometallurgical process is 
often advantageously applied. One of the oldest of hydrometallargical methods is 
that known as the cementation-process, performed by precipitating copper from a 
solution of the sulphate of the metal by means of metallic iron. Solutions of the 
sulphate occur naturally in some mines, and are also artificially prepared by treating 
poor oxidised copper ores with sulphurous acid, or by exliausting these ores with 
hydrochloric or dilute sulphuric acids, or by roasting pyritical ores and exhausting 
them with water. The copper obtained by this process is called cementation-copper. 
^ the Island of Anglesea the cementation liquid is conducted first into large basins 
ui order that the oclirey and other suspended matters may subside, and afterwards is 

K 



50 CHEMICAL TECHNOLOGY, 

nm into the oementation-taiikB containing old sorap-iron intended to serve as a pre- 
cipitating agent. This scrap-iron is oooasionally stirred up, so as to renew the 
metallic surfiEMse presented to the solution. The muddy liquid, containing spon^ 
metallic copper and impurities, is run into reservoirs intended for the deposition of 
the spongy mass, which, after the supernatant liquid is run off, is dried in a furnace. 
The material contains on an average only 15, hut may contain from 50 to 65 per 
cent of copper. The main body is usually composed of basic sulphate of iron, which is 
effectually removed by the application of stirring-machinery, such as is used in 
breweries in the mash-tubs. At Rio Tinto, Spain, and at Schmollnitz, Hungaiy. 
cementation-copper is prepared on a very large scale. In Norway, copper solutions 
are treated, according to Sinding's plan, with sulphuretted hydrogen, and the preciju- 
tate either worked up for metallic copper or for sulphate of copper. 

Instead of sulphur, large quantities of iron pyrites containing more or less copper are 
burnt, and the sulphurous aoid obtained applied in the manufacture of sulphuric add. 
The spent pyrites is frequently treated hydrometallurgically with a solution of chloride of 
iron, the copper being precipitated by means of sulphuret of iron. Poor ochrey copper 
ores are often worked up to obtain sulphate of copper by some method suitable to the 
locality; for instance, roasting with iron pyrites or with copperas. It pays in some 
instances to roast pyritioal copper ores, and after roasting to treat them for obtaining 
cementation-copper. 
Copper obtainod by Copper clectrolytically precipitated is, provided pure materials are 
voitaiA EiMtridty. operated upon and the galvanic current not too strong, the purest 
obtainable. This method has been proposed and even tried on a large s(»le in Italy in 
order to save time and iron, and to throw down the copper of the cementation-tanks. 
It is a generally known and daUy applied fact that copper, as a coherent mass, can be 
separated from sulphate of copper electrolytioally. 

Pn>p«rtiei of oopp«r. The pecuHar and reaUy beautiful red colour of copper, the only metal 
80 distinguished, is too well known to need mention. It is, although a hard and tough 
metal, so ductile and malleable that it may be drawn out to the very finest wire and 
beaten to extremely thin leaves. Its malleability is increased by increase of temperature, 
and at a low red-heat it can be hanmiered, rolled, and beaten into any required shape. Its 
fracture is granular. Its sp. gr. is n 8'g ; one cubic metre weighs about 8900 kilos. Its 
melting-point, according to Pouillet, 1200°; to Daniell, 1400''. The latest and mof^ 
careful researches on this topic have been made by Dr. von Biemsdijk at the Utrecht Kint, 
and he has found that chemically pure copper fuses in an atmosphere of hydrogen at 
133*0° ; that is to say, at a temperature higher than the melting-point of either gold or 
silver, as simultaneously determined by an extensive series of experiments made in 
atmospheres of hydrogen. If properly poled, as the term runs, or in other words, free 
from suboxide, copper, when molten, flows readily, but when mixed with suboxide the 
flow is sluggish. While in the molten state the surface of themetal exhibits a beautiful 
sea-green colour. Copper is not suited for the making of castings, and probably this 
is due to a peculiar effect of heat upon this metal, as many of its alloys, especially those 
with tin, are very suited for casting. Molten copper suffers great expansion on cooling, 
and becomes honeycombed and internally crystalline. This defect can only be remedied by 
either keeping the metal while molten under a layer of charcoal, or by cooling it to some 
extent before casting into moulds, which should be made of a good conducting material, eo 
as to cause the rapid cooling of the metal. Iron moulds, internally coated with a layer of 
bone-ash, are the best. Small quantities, o'l per cent, of zinc, lead, potassium, and other 
metals added to the molten copper, entirely deprive it of the property of expanding and 
becoming honeycombed on cooling; the same effect is observed when copper holds in 
solution a small quantity of suboxide, but this fact is not available for any practical use, as 
such copper is cold-short. Just before cooling the vessel exhibits the phenomenon of 
spirting, the flying about of small globules of copper, accompanied, if large quantities of 
the metal are treated, by a distinctly audible report. This phenomenon appears to be 
due to a cause similar to that producing it when silver is operated upon, viz., the violent 
expulsion of previously absorbed oxygen. At a very high temperature and with free 
access of air, or under the influence of electricity, copper bums, giving a brilliant green 
flame. In countries where, as in Sweden, Bussia, and Holland, the roofs of churches and 
other large buildings are covered with copper — the most expensive at the first outlay, but 
the most lasting material for roofing purposes — tlie phenomenon of the burning of copper 
isnow and then witnessed on a very largo scale when fires accidentally occur. Copper-filings 



COPPER. 51 

are QBed in pyrotechny, for produoing a green flame. Dry air does not affect copper, 
unless sulphuretted hydrogen and other salphurous emanations are present ; but moist 
air oanses the copper to become covered vrith carbonate of hydrated suboxide of copper, 
verdigris, or rust. Experience has proved, in the case of copper roofs, that this material 
protects the snbjaoent metal and adheres to it with great tenacity. When solid masses of 
copper are heated they at first assome an iridescent rainbow hue, and next become 
oovered with a brownish-red coloured suboxide, which, if the heating is continued, becomes 
black oxide, technically known as copper-ash or copper-forge scale. In order to remove 
this oxide, when the copper is to be rolled into sheets, <&c., the metal is dipped into what 
is termed a pickle — a solution of ammonia and common salt, and on being taken out is 
brushed with a heather-broom. Copper, as usually met with in commerce, is not by any 
means pure, but contains variable quantities of other metals, among which are chiefly 
iron, antimony, arsenic, lead, tin, zinc, and sulphur ; Dr. Beischauer found in perfectly 
malleable copper no less than 1-48 per cent of impurities insoluble in nitric acid. If 
this quantity is only slightly increased, the quality of the copper is so impaired that it is 
not only nnfit for being rolled and hammered, but also for casting statues (always alloyed), 
because such copper loses its peculiar colour and does not withstand atmospheric influ- 
ences. Copper is largely used for various purposes, among which we name only a few — 
vacuum and other pans in sugar- works; distillery, brewery, and other apparatus; for 
covering wooden sea-going vessels, and for a variety of generally well-known purposes. 
Dr. Steinbeck foxmd that refined Mansfeld copper, analysed 1868, contained in 100 parts — 

Copper 99*28 

Silver .♦. 0*02 

Kickel 0*32 

Iron o'o6 

Lead 0*12 



lOO'OO 



The total annual production of copper over the entire globe amounts (1870) to 
1,300,000 cwts., of which England alone yields fully 350,000 cwts. 

Aiioyiof copp«r. There are several alloys of copper, among which bronze, brass, and 
German, or nickel silver, are the chief. 

BreoM. Alloys, consisting of copper and tin, or of copper, tin, and zinc, or of copper 
and alnmininm, all bear the name of bronze. The addition of any of these metals to 
copper renders it more fluid when molten, and hence better suited for castings, as 
well as denser and consequently more easily polished; alloys are harder, more 
sontHTOUS, and (the aluminium aUoy excepted), far cheaper tlian copper itself. 
The addition of from 012 to 050 per cent of phosphorus to these alloys renders thorn 
^ more homogeneous and malleable. The chief varieties of bronze in use are known as 
(a) bell-metal, {fi) gun metal, and (y) statuary metal. 

(a). Bell-metal consists on an average of 78 parts of copper and 22 parts of tin. It 
should be sonorous, hard, and strongly cohesive. Being a brittle alloy it cannot bo 
worked on the lathe ; hence the desired sound or musical note of a bell depends 
entirely upon the shape given in the casting and upon the constituents of the alloy. 
In order to save tin, zinc and lead are sometimes added, but too much of th(\sc 
impairs the goodness of the alloy. It is an error to mix silver with this aUoy, in 
order to render it highly sonorous ; analyses made of bell -metal cast in tlie mid<ilc 
ages in various countries, prove the absence of silver from such mptal, traces only 
being present as an impurity. 

(/^). Gun -metal consists on an average of 90 parts of copper and 9 of tin. This 
alloy should combine mechanical and chemical durability. As r(\i;ards its mediiuiical 
properties, the metal should be : — i. Tough, so as to prevent tlio piece or^uu bursting 
while the charge is being fired, during wliich operation Uie metal is exposed to a pres- 
sure of from 1200 to 1500 atmospheres. 2. Elastic, so that the f^in may be able to 
Weld to some extent to the smart shocks occaiiioned by tlie evolution of gas duiing 

K 2 



52 



CHEMICAL TECHNOLOGY. 



firing. 3. Hard, so that the motion of the ball should not cause any damage to the 
interior of the gun. As regards chemical durability, the alloy must resist the action 
of air and of the products of combustion of powder and gun-cotton at high tem- 
peratures. Gun-metal answering these requirements is unfortunately subject to i^hat 
is termed liquation ; that is to say, while in the molten state it separates into two 
qualities of alloy, one more fluid and containing more tin than the other. This separa- 
tion makes the casting of guns iu this alloy a difficult matter, because the homoge- 
neity of the mixture is uncertain. It appears, however, that the addition of from 
o'i2 to o'5 per cent of phosphorus remedies the defect. Gun-metal, however, is fast 
being superseded by steel in the manufacture of ordnance. MM. Maritz, at the 
Hague, have for several generations been renowned for the superiority of their gun- 
metal manufacture, which is still pursued by them. According to a statement in the 
" Handworterbuch der Ghemie " (Art. " Geschutz-metall,") the alloy employed hy 
them consists of 0*69 per cent Fe, 88*61 per cent Gu, and 1070 per cent Sn ; 
generally the quantity of tin amounts to from 9 to 11 per cent. 

(y.) Statuary-bronze for ornamental purposes consists of copper, tin, lead, and zinc. 
It is requisite that while molten this alloy should be very fluid, so as to fill every part 
of the mould. After cooling, the metal must admit of being chiselled, and by expo- 
sure to air it should assume what is termed patina — a peculiar greenish-black htie. 
The statue of Louis XTV. at Paris, made 1699, consists of— Gopper, 91 40 ; adnc, 553 ; 
tin, 170 ; lead, 1*37. The statue of Henri IV. on the Pont Nceuf at Pads, consists 
of — Gopper, 89*62; zinc, 4020; tin, 570; lead, 048. Aluminium-bronze (90 parts 
copper and 10 aluminium) is used for various ornamental purposes, chiefly in 
imitation of gold. 

Bom. This alloy has teen known from a very remote period. Zinc and copper 
form various alloys, but brass only is technically applied, and contains on an average 
30 per cent of zinc. The colour of the alloy is inclined to red, when the quantity of 
zinc is small, and to yellow or whitish-yellow when the quantity of zinc is increased. 
The ductility and malleability of the alloy increase with the quantity of copper. 
Brass may be hammered, rolled into sheets, or drawn to wire while cold, but cannot 
be worked hot. The so-called yellow metal, Muntz's patent, an alloy of 40 parts of 
zinc and 60 of copper, may be wrought while red-hot, rolled into sheets, and forged 
into bolts. It is chiefly used for marine purposes, including the internal lining of 
air-pumps of marine steam-engines. Brass is not so readily oxidised as copper, being 
harder, tougher, more easily fusible, and more fluid while molten. It solidifies 
without becoming honey-combed, and hence is suited for making all kinds of castings; 
while simply by the addition of from i to 2 per cent of lead, it is capable of being 
readily worked on the lathe, and may be then filed without, as it otherwise does, 
clogging the teeth of the file. 

Brass is made by any of the following methods : — i. By melting together a mixture of 
calamine stone and black or blistered copper under a layer of charcoal. 2. By simply melting 
together zinc and refined copper. The hist method is the oldest, and is still carried on 
in furnaces arranged so that they may contain from 7 to 9 fire-clay crucibles at the same 
time. These crucibles are fiUed with the necessary materials, viz., previously roasted 
zinc ore, or residues from zinc-smelting furnaces, and copper. As by the use of calamine 
stone, only some 27 to 28 per cent of zinc can be imparted to the alloy, it is usual to add, 
previously to pouring out the molten alloy, another quantity of calamine stone, rather to 
prevent any loss of zinc by ignition than to increase the quantity of that metal. In 
former times the manufacture of brass was carried on in ^o distinct operations, one 
being the preparation of an alloy containing only 20 per cent of zinc, known as aroo- 
smelting, and the other the conversion of the arco into brass by a second smelting and the 



COPPER, 53 

addition of zinc. At the present time the manufacture of brass consists in simply 
placing alternate layers of copper and zinc in fire-clay or graphite crucibles, and then 
smelting the two metals under a thick layer of charcoal. The alloy is cast in granite 
moulds Borronnded by a thick coating of clay and cow-dung, or sand-moulds. Occasion- 
aUy sheet-copper is conyerted into brass by exposing the sheets to the fumes of metaUio 
zinc. Among brass alloys we may notice the following : — Tomback, or red brass, con- 
sisting of 85 parts of copper and 15 of zinc. Butch-gold — a gross misnomer, as none of 
it is made in Holland, and as the term really applies to a very pure gold coin, the ducat, 
still made, although not current, in Holland, at the Utrecht Mnt. The brass alloy thus 
named consists of 1 1 parts of copper and 2 of zinc, and is made chiefly at Niimberg and 
Purth, Bavaria, for the purpose of beiag beaten into very thin leaves. The alloy termed 
Aich-metal, and consisting of 60 parts of copper, 38*2 parts of zinc, and 1*8 parts of iron, 
is in reality malleable brass. Sterro-metal, though very much harder, is similar to the 
foregoing in composition. 

The well-known yellow, or Muntz, metal, largely used in this ooxmtry for marine 
purposes, coating ships, <&c., is an alloy of copper and zinc in proportions varying from 
50 per cent of zinc and 63 of copper, to 39 per cent of zinc and 50 per cent of copper. 
The alloy in use for coins of small value in this country, France, and Sweden, consists of 
95 parts of copper, 4 parts of tin, and i of zinc. The alloy used for this purpose in Den- 
mark consists of 90 parts of copper, 5 of tin, and 5 of zinc. Batii-metal, or white brass, 
eonsists of 55 parts of copper and 45 of zinc. An alloy used for buttons consists of 
20 parts of copper and 80 psurts of zinc. The bronze colours (powdered alloys of copper 
and zinc), now largely used for bronzing painted surfaces, as well as for lithochromy and 
various other purposes, are obtained from scraps of metal rubbed down with oil, tallow, 
or wax, and turpentiue. The various beautiful colours, violet, copper-red, orange, gold- 
jdlow, green, are due to partial oxidation. These bronze-colours are not to be con- 
founded with a beautiful substance known as mosaic gold — aurum mvMvum — bisulphide of 
tin. Analyses show the proportions in these alloys to be — 

For bright colours |^?PP«' ;; «3 

For red or deeper colours -A^^^^^ \\ ^JZ?^ 
For copper-red colours . . 100 

Cbemical analysis has also proved the quantity of copper to amount to — 

a. In French bronzes : Copper-red colour . . . . 97*32 per cent 

Orange 94*44 

Bright yellow .. .. 81*29 

p. In English bronzes : Orange 90*82 

Deep yellow 82*37 

Bright yellow . . . . 80*42 

y. In Bavarian bronzes : Copper-red 98*92 

Violet 98-82 

Orange 95-30 

Deep yellow 81-55 

Bright yellow . . . . 82*34 

cciw^ w^Kiotoi German, or nickel silver, also called Argentan, packfong, or white 
copper, is an alloy of copper with nickel and zinc, or tin, and may be considered as a 
ij^tass to which from one-sixth to one-third of nickel has been added. This 
alloy appears to have been known in China from a very remote period ; in Europe it 
I1A8 been more generally in use during the last thirty years. The colour is nearly 
Bilver-white ; its fracture small-grained and compact ; sp. gr. » 8*4 to 8*7. It is 
harder, but yet quite as ductile as ordinary brass, and takes an excellent polish. It 
is prepared by melting together the granulated metals, zinc, copper, and nickel ; 
these metals are put into a crucible in such a manner that copper is at the bottom as 
Well as the top, while a layer of charcoal-powder covers the whole. Care is taken to 
stir the mass with an iron rod. Nickel-silver of good quality has the appearance of 
a alver aQoy, containing one-fourth of copper. Nickel-silver is capable of assuming 
uk excellent polish, and is not readily acted upon by vinegar and the ordinary acids 
m culinary use ; hence it is used for spoons and forks. 



It 
»» 
vt 
It 
tt 
ti 
ft 
tt 
tt 



54 CHEMICAL TECHNOLOGY. 

Average Gknuan-Bilver conslBts of — 

Copper 50 — 66*0 

Zinc 19 — 31*0 

Nickel 13—18*5 

At Sheffield the following yarieties of this alloy are made : — 

Copper. Nickel. Zine. 

Common 8 2 3*5 

White 8 2 35 

Electrum 8 4 3*5 

Infusible 8 6 3-5 

Tutenao 8 3 6-5 

When tried on the touchstone, nickel-silver is hardly distinguishable from the 
silver alloy just mentioned, but on applying nitric acid to the streak caused by the 
nickel alloy, it is more rapidly dissolved, and by adding a few drops of chloride of sodium 
solution no turbidity, or precipitate of chloride of silver, is produced on the stone. 
The alloy known as Alf6nide, used for making tea-pots, sugar-basins, milk-ewers, and 
similar articles, is nickel-silver, thickly electro-plated with pure silver, the quantity 
of silver amounting to about 2 per cent. The alloy, known as tiers-argent (one-third 
silver), consists, according to Dr. C. Winkler's analysis (see "Chemical News," 
vol. xxii.,p. 225), of—Copper, 59*06 ; silver, 2756; zinc, 957; nickel. 3*42. 

Since 1850 the Swiss Confederation has brought into circulation a series of small eoins 
(monnaie billon) j which contain in 1000 parts : — 

Silver. Copper. Zinc. Nickel. 

Pieces of 20 Bappen . . . . 150 500 250 100 

„ 10 „ .... 100 550 250 100 

„ 5 I, .... 50 600 250 100 

These coins are not turned red by wear, but assume a yellowish hue. In Belgium the 
5, 10, and 20 centime pieces are made of an alloy of 25 parts of nickel and 75 parts of 
copper ; while the United States' cent pieces contain 12 parts of nickel and 88 of ooppo-. 
The alloy known on the Continent as Suhler's white copper, consists of 88 parts of copper, 
8*75 parts of nickel, and 175 parts of antimony. 

Amalgam of Copper. By the name of metallic cement is understood an amalgam of 30 parts 
of copper and 70 parts of mercury. It is obtained by moistening pulverised copper, 
obtained in a spongy state, by reducing its oxide at a low red heat, by means of "hydrogen 
with nitrate of suboxide of mercury, care being taken to incorporate this saline solution 
thoroughly with the copper, while adding hot water. This cement, at first soft, bardenji 
in a few hours. It has been successfully applied in stopping decayed teeth. 

PrepaiUlTIons of Copper. 

sui^to of^iper. ^^^ ^* ^^ ^^^ ^^ naturally in kidney-shaped masses, or as an 
outer covering of minerals containing copper, as well as in solution, as referred to 
imder Cementation-copper. Sulphate of copper, blue- or Cyprus-vitriol, crystaUiaes 
in the shape of triclinohedrical blue-coloured crystals, soluble in 2 parts of hot and 
4 of cold water, and insoluble in alcohol. 100 parts of the salt contain: — 

Sulphuric add 32*14 

Oxide of copper 3179 

Water 36-07 

Formula:— CUSO4+5H2O. 

^SJvitriiL' Chemically-pure sulphate of copper is obtained by heating metallic 
copper with concentrated sulphuric acid ; the metal is oxidised by a portion of the oxygen 
of the acid, while sulphurous acid escapes, (Cu+ 2HaS04 = CUSO4+ 2H2O + SOa) . If 
the metal is previously converted into oxide of copper by exposure to a red heat, only 
half the quantity of sulphuric acid is required. Sulphate of copper is manufactored 



PREPARATIONS OF COPPER, 55 

on a large scale by any of the following processes : — i. By the evaporation of cemen- 
tation-water until crystallisation is attained. 2. By heating sheets of copper in a 
reverberatoiy furnace to the boiling-point of sulphur; a quantity of that element 
being then thrown in, and the flues and other openings closed, the effect is the forma- 
tion of sulphide of copper (GuaS), which is converted by a comparatively low heat 
and the action of the oxygen of the air into sulphate (Cu«S+50=GuS04+CuO). 
The mass is next placed in a suitable vessel, and as much sulphuric acid is added to 
it as is sufficient to saturate the oxide of copper. The clear solution, having been 
decanted from the insoluble residue, is set aside for crystallisation. 3. By treating 
the crude copper obtained by smelting the ores, and containing about 60 per cent of 
metal, with sulphuric add. The resultiog solution is evaporated in leaden vessels, 
aad the clear liquid left to crystallise in copper pans. From the mother-liquor of the 
nystals metallic copper is precipitated by means of iron, because the presence of a 
large quantity of sulphate of iron renders this mother-liquor unfit for the further 
making of blue- vitriol. This method of obtaining sulphate of copper is the least 
expensive, but the salt is not quite pure, containing, according to M. Herter's analysis 
of Mansfeld blue- vitriol, about 3 per cent of sulphate of iron, and 0083 per cent of 
metallic nickel. Veiy frequently the scraps and refuse of copper-smithies, copper- 
scale, and other residues of that metal, are used in preparing sulphate of copper. 
4- At Marseilles, malachite is dissolved in sulphuric acid to obtain blue-vitriol. 
5. In Norway, iron pyrites containing copper are roasted and treated with water, the 
copper contained being precipitated with sulphuretted hydrogen, and the sulphide of 
eopper, when dry, converted into sulphate by exposure to a gentle heat. 6. Large 
quantities of sulphate of copper are obtained as a by-product of silver -refining, espe- 
cially when silver is treated for the purpose of extracting the gold it contains, by 
boiling — ^usually silver coins, chiefly Mexican and Peruvian dollars — ^with strong 
sulphuric add; sulphate of silver and, as the coins contain some copper, the 
sulphate of that metal, are formed, while the gold is left as an insoluble substance. 
The silver is reduced to the metallic state (AgaS04+Cu=CuS04+2Ag) by means of 
sheets of copper placed in the acid solution, which is previously diluted, and which, 
^ftet having been decanted from the sediment, spongy metallic silver, yields on 
evaporation a very pure sulphate of copper. 7. Sulphate of copper is also obtained 
as a by-product of the hydrometallurgical process of extracting silver, or Ziervogel's 
process. In order to separate the sulphate of iron from the crude blue vitriol, as 
oUamed at copper-smelting works from various cupriferous refuse, the crude salt is 
roasted so as to bring about a partial decomposition. By this means the sulphate of 
inm is decomposed, and the oxide of that metal formed is insoluble in water. The 
saline mass is dissolved in water, and the clear solution, decanted from the sediment, 
evaporated to crystallisation. According to Bacco's plan, the crude blue- vitriol is 
ilissolved in water, and carbonate of copper added to the solution, to cause the preci- 
pitation as oxide of all the iron present, while an equivalent quantity of oxide of 
c^'Pper is dissolved and converted into sulphate. The purified sulphate of copper 
solution having been filtered is evaporated and left to crystallise. 

, i>o«i>i« vitrioL Under the name of donble-vitriol, a mixture of the sulphates of copper and 
^ erystalfised together, and sometimes containing white vitriol, is met with on the 
Continttit, The Salzburg vitriol, known by the brand of a double eagle, contains 
•Ixmt 76 per cent, the Admont 83 per cent, and the double Admont 80 per cent of 
"ilphate of protoxide of iron. Of later years, however, these vitriols have been less in 
demtud. 



56 CHEMICAL TECHNOLOGY. 

ApnUcadoiiB of Afl the bsse of the pigments obtainable from copper, the snlphate is very 
Biae-YitrioL frequently need, and should be pure, or at least free from the sulphates of 
iron and zinc. Blue-Tltriol also serves for the manufacture of acetate of copper, for 
bronzing iron, for bringing out the colour of alloys of gold. It is used in dyeing and 
printing in various ways, for galvano-plastic purposes, and during the last twenty years 
large quantities of tins salt have been sent to Mexico and Peru to be applied in the 
American amalgamation-process of extracting silver. 

Copper Pigments. Among Uie many pigments which owe their blue or green colour 
essentially to copper, we may treat of the following: — i. Brunswick-green. 2. Bremen- 
green and Bremen-blue. 3. Casselmann's-green. 4. Mineral-green. 5. Schweinfort- 
green, also known as emerald-green. Many of the pigments mentioned here by tlveir 
German names are known in this country by other denominations, but are not for 
tliat reason any different in composition. 

BraiiB«ick-oz«en. Under thls name several compounds of copper are applied as oil-piunie. 
The pigment now chiefly in use bearing this name is basic carbonate of oxide of copper 
rCuG03-}-0uH202), an imitation of mountain- or mineral-green, and obtained from either 
nnely pulverised malachite or the sediment often met with in cupriferous cementation- 
liquids. Brunswick-green is prepared on a large scale by the decomposition of sulphas of 
iron by means of either carbonate of soda or carbonate of lime, and in other cases by the 
decomposition of chloride of copper by means of a carbonated alkali. The ensuing preci- 
pitate is wadied with boiling water, and afterwards mixed with a smaller or larger quan- 
tity of sulphate of baryta, zinc-white, or gypsum, and frequently with Schweinfurt-green 
(aceto-arsenite of copper) in order to obtain the desired hue. Another variety of Bmna- 
wick-green, rarely met with in the present day, appears to be a kind of artiflcially -prepared 
atacamite, an oxychloride of copper, the formula of which is, according to Bitthwisen, 
CuCl2,3CuO-h3H20. 

^"SS^SSm " These substances are essentially hydrated oxide of copper, and are 

met with as a very bright blue spongy mass with a greenish hue. The value is 

greater according to the finer blue colour and loose spongy texture. When uaed with 

water, gum, or glue, this pigment yields a bright blue colour, hence its first name ; 

but when it is mixed with Hnseed-oil, the blue colour turns within twenty-four hours 

to green, in consequence of the saponification of the oxide of copper, which becomes 

oleate, paJmitate, and linoxate of that base. Bremen-green occurs in various hues 

obtained by mixing the precipitate with well-cleansed gypsum. At the present time 

the pigment is generally obtained from oxychloride of copper (CuCla,3CuO-h4H20). 

This preparation may. be made in various ways, provided care be taken that the 

light green paste — technically known as oxide — contains no protochloride of copper 

(CugCla). Gentele's method is as follows : — 

I. 112*5 Mies, of coxomon salt, and in kilos, of sulphate of copper, both free from iron, 
are ground together with sufficient w&ter to promote reaction. 2. 112*5 kilos, of old 
copper sheiBting is cut into pieces a square inch in size, and placed with water acidulated 
with sulphuric acid in rotating casks so as to remove all rust, oxide and oxychloride, from 
this metal, which is next washed with water. 3. The dean metal thus obtained is next 
placed in what is known as oxidation-closets and covered for a thickness of half-an-ineh 
with the paste mentioned above. A mutual action, aided by that of the atmosphere, is 
set up, the result being that the chloride of copper first takes up copper, beooming proto- 
chloride ; this in its turn takes up oxygen from the atmosphere and water, and thus becomes 
converted into the green-coloured insoluble basic hydrated oxide of copper, the action being 
greatly aided by the turning over of the mass with a copper spade every two or three days. 
As the treatment of protochloride of copper with alkalies or alkaline earths gives rise to the 
separation of red or yellow-coloured suboxide, the mass should not, on being tested and 
previous to further operations, yield even the faintest indication of the presence of sub- 
oxide, since the slightest trace would spoil the hue of the pigment to be obtained ; conse- 
quently in some works the pasty mass is left for years before it is used for further opera- 
tions. The action is accelerated by causing the mass to become dry before turning it over 
^ith the spade, the consequence being that the air gets thorough access, and a complete 
oxidation is obtained in about three to five months time. The mass is then cleansed with 
the smallest possible quantity of water, and is thus separated from the non-oxidised 



PREPARATIONS OF COPPER. 57 

metallio copper. 4. To Bome 6 gallons of this cleaiiBed material are added 6 kilos, of 
hydrochloric add, and this mixture is allowed to stand for abont two days. 5. Into a 
tank or tub — ^the blue tnb — are ponred some 15 gallons clear colourless potassa-lye. This 
hanng been done, the acid mixture is first diluted wrth some 6 more gaUons of water, and 
then, as rapidly and expeditiously as possible, ponrei into the bine tnb, the mixture being 
continuously stirred. The result of this last operation is that the previously basic copper 
eompound, converted by HGl into neutral cupric chloride, is, when brought in contact 
with the potassa, converted into blue-coloured oxyhydrate of copper or Bremen-blue, 
while chloride of potassium is also formed. 6. After the mass has become pasty, it is left 
to stand for a couple of days, and then thoroughly washed by decantation to remove ^e 
chloride of potassium. The cupric oxyhydrate is then put on cloth filters, kept moist, and 
exposed to the air for some time. It is next dried at a temperature of from 30° to 35*, 
smce at a higher temperature the hydrate of the oxide by losing its water becomes 
bUckish-brown coloured. It is clear that Bremen-blue can be differently obtained, but 
these differences of preparation do not bear so much upon the precipitation of the 
hjdrated oxide as upon the means of obtaining chloride of copper ; these means may of 
eourse be varied in many ways ; for instance, by causing a mixture of common salt, 
dilute sulphuric, and copper scraps to act upon each other, the mass being afterwards 
exposed to the action of the air ; by the action of hydrochloric acid upon copper and its 
oxide ; or by partly decomposing neutral nitrate of copper by means of carbonate of soda. 
In this case a precipitate of carbonate of copper is formed, which, while giving off its 
earbonic add, ^comes converted into basic nitrate of copper (OuNaOe+CuHsO^), deposited 
as a heavy green powder. A solution of zinc-oxide of potassa (solution of zinc-white in 
caustic potassa), is next added, the result being the formation of a deep blue pigment, 
TQiy spongy and very covering (a technical term in use by painters), consisting of zincate 
of copper with a small quantity of basic nitrate of copper. A magnesia Bremen-blue is 
obtained by the precipitation of a solution of the sulphates of magnesia and copper, to 
vhich some cream of tartar is added, by means of potassa, care being taken to pour the 
saline solution into the alkaline, and to keep an excess of the latter. 

'^Tfhifim'i ffrrttn In the year 1865 Dr. Gasselmann discovered this pigment, a 
beautiftil green free from arsenic. It is prepared by mixing together boiling solutions 
of sulphate of copper and an alkaline acetate; the resulting precipitate is a basic salt 
of copper (CUSO44- sCuHaOa + 4HaO) . After drying, this salt is, next to Schweinfrirt- 
green, the finest of all colours obtained from copper, and being free from arsenic, is 
highly commendable, though yet poisonous, as are most preparations of, and esped- 
ally acetates of, copper. 

Mjaenj-orean '^^^ pigment, also known as Scheele*s-green, is not so frequently used 
aad BioA. qqw as formerly. It is essentially a mixture of hydrated oxide of copper and 
urseuite of copper, and does not cover very well. It is prepared by dissolving i kilo, of 
pore sulphate of copper in 12 Jitres of water, to which is added, whUe constanUy stirred, 
s solution of 350 grms. arsenious acid and i kUo. of purified potash (carbonate) in 8 litres 
of water. The resulting grass-green coloured precipitate is washed with boiling water and 
dried. Another pigment, sometimes known as mineral-green, is obtained from pulverised 
vudachite, or basic hydrated oxide of copper. By the term mineral-blue is generally 
understood a kind of Berlin-blue, rendered less deep coloured by the addition of pix>e-clay 
or other white-coloured powders, but the term also applies to a pigment formerly obtained 
by grinding and washing the purest pieces of lazurite of copper, a mineral 

(20uC0,-|-CuHa02), 
found in the Tyrol and near Lyons. This pigment is artificially obtained in France, 
Holland, and Belgium, by precipitating a solution of nitrate of copper with caustic lime 
or caustic potassa, and afterwards mixing the previously washed precipitate with chalk, 
gypsum, or heavy spar. The pigment is sent into the trade for use chiefly as a water- 
colour. Under the name of lime-blue a similar preparation occurs in quadrangular 
lamps, obtained by precipitating a solution of 100 parts of sulphate of copper and 
i2i parts of sal-ammoniac with a milk of lime containing 30 parts of caustic-lime. The 
precipitate is a mixture of hydrated oxide of copper and sulphate of lime, according to 
the formula 2(CaS04,2HaO-f3CuHa02). This pigment exhibits a purer tint ^an 
Bremen- blue, but though it covers pretty weU as a water-colour, it is almost useless as an 
oil-colour. 

oQBiae. A pigment which, when ground with oils and varnishes, yields a beautiful 
yiolet-blue, and is essentially composed of sulphide of copper (CuS), there being applied 
in its manufacture either the native mineral, knovm as cupreous indigo, or an artificially 



58 CHEMICAL TECHNOLOGY, 

prepared sulphide, obtained byfasing finely divided metallio copper with hepar-solphniiB, 
a mixture of several sulphurets of potassium. The fused mass is treated with water, and 
the sulphide of copper remains in small blue-coloured crystals, which, after drying, are 
pulverised and mixed with oil. 

^^E^^SdS^ ""' This pigment is by far the most beautiful, but also the most 
poisonous, of aU green-coloured copper pigments. In Germany this substance is 
known under a number of aliases derived from the peculiar depth of hue as modified 
in various manufactories by means of sulphate of bar3rta, sulphate of lead, snd 
chrome-yellow. The constitution and mode of preparation of this pigment remained, 
at least on the Continent, a trade secret until the researches of MM. Braconnot and 
J.vonLiebig made the particulars known. According to Dr. Ehrmann, pure emerald- 
or Schweinfiirt-green is an aceto-arsenite of copper : — 

in 100 parts — Oxide of copper, 31*29 ; arsenious acid, 58*65 ; acetic acid, io'o6. 
Dr. R. Wagner states tliat this formula is only empirical, because a portion of the 
copper is present as suboxide, and a portion of tlie arsenic as arsenic acid. 

According to Dr. Ehrmann's statement, this pigment is prepared by first separately 
dissolving equal parts by weight of arsenious acid and neutral acetate of copper in boiling- 
water, and next mixing these solutions while boiling. There is immediately formed a 
flocculent olive-green coloured precipitate of arsenite of copper, while the supernatant 
liquid contains free acetic acid. After a while the precipitate becomes gradually crystal- 
line, at the same time forming a beautifully green pigment, which is separated from the 
liquid by filtration, and after washing and carefidly drying is ready for use. The mode 
of preparing this pigment on a large scale was originaJly devised by M. Braconnot, as 
follows : — 15 kilos, of sulphate of copper are dissolved in the smallest possible quantity of 
boiling- water and mixed with a boilhig and concentrated solution of arsenite of soda or 
potassa, so prepared as to contain 20 kilos, of arsenious acid. There is immediately 
formed a dirty greenish-coloured precipitate, which is converted into Sohweinfnrt-green 
by the addition of some 15 litres concentrated wood-vinegar. This having been done, the 
precipitate is immediately filtered off and washed. It thus appears that the preparation 
of this pigment aims first at the least expensive preparation of neutral arsenite of copper, 
which is next converted into aceto-arsenite by digesting the precipitate with acetic add. 
The pigment is available as a water- and an oil-colour, but does not cover very well in oil, 
although it dries rapidly. The colour cannot be used for mural painting, as the lime 
absorbs the acetic acid, leaving a yellowish-green arsenite of copper. The Schweinfurt- 
green consists of microscopically small crystals; if these crystals are pulverised, the 
colour, previously grass-green, becomes paler. Air and light do not affect this pigment, 
which is insoluble in water, but becoming, when boiled with it for a length of time, 
brown-coloured, probably in consequence of the loss of some acetic acid. It is a well- 
known fact that paper-hangings containing this pigment, and pasted on damp walls, 
cause the inmates of the rooms to suffer from headaches, due in all likelihood to volatile 
arsenical emanations, among which is arseniuretted hydrogen. 
stozmate of Oxide This preparation, also known as Qentele's-green, is obtained by preeipi- 
of Copper. tating a solution of sulphate of copper with stannate of soda, waeiiing and 
drying the precipitate, which forms a beautifully green, innocuous, at least as compared 
with Uie foregoing, copper pigment. 

Verdigris. Under this name we meet in commerce with a neutral and a basic acetate 

of copper ; the one, a crystalline substance is 

a salt formerly only prepared in Holland, and designated as " distilled yerdigris, ' in 
order to mislead as to its mode of manufacture. 

The basic-salt, blue verdigris, is chiefly prepared at and near Montpellier, by employing 
the marc of the grapes, the skin and stems of the bunches after the juice has been squeezed 
out, which readily forms acetic acid by fermentation. Into the marc are placed sheets ol 
copper previously moistened with a solution of acetate of copper. The metal becomes 
coated with a layer of verdigris, which is removed by scraping. It is next kneaded with 



LEAD, 59 

water, after which the paste is pat into leathern bags and pressed, so as to obtain 
reotangnlar cakes. The metal is^reated in the same manner until it is entirely oonyerted 
into baisio yerdigris, having a bine colour, and known as French-verdigris. Formula — 

A green-coloured verdigris is obtained at Grenoble and elsewhere by submitting sheets of 
eopper to the action of vapours of vinegar, or by placing the metal between pieces of 
ooane flannel soaked with that liquid. The formula of the substance thus produced is — 

(^^|^^^^^}0a,2CuHa0a. 

Neutral acetate of oopper» first made by the Saracens in Southern Spain, and since the 
middle of the fifteenth century by the Hollanders, is now obtained either by — i. Dissolving 
the bflsio salt in acetic acid. 2. Or by the double decomposition of sulphate of copper and 
acetate of lead : — 

CUSO4+ I <^f 1^^^} 02=PbS04+ I (^^^^30)a| 0^. 

By the first method the basic acetate is dissolved in 4 parts of acetum distillatum 
(punfied vinegar) or in wood-vinegar, the liquid being placed in a copper cauldron and 
heat applied. The clear liquid is decanted, and then evaporated in copper pans until a 
saline crust makes its appearance, when the fiuid is transferred to wooden vessels pro- 
vided with thin laths serving as a solid nucleus for the crystals. According to the second 
plan, the solutions of the two salts are mixed, the liquid decanted from Uie sediment of 
sulphate of lead, and next evaporated after the addition of some acetic acid, until a crust 
of the salt is formed. Instead of acetate of lead, the acetates of lime and baryta are now 
used. The neutral acetate of copper is met with in commerce in " bunches" (grappes), 
eonmnting of deep green-coloured, non-transparent crystals, soluble in 13-4 parts of cold, 
in 5 parts of hot water, and in 14 parts of boihng alcohol. This salt, like the basic acetates, 
is highly poisonous. 

AppHeaUnu of Both basic and neutral are employed as oil- and water-colours. In Russia 
Vcrucrio. verdigris, mixed with white-lead, is frequently used as an oil paint, the 
result being the formation of carbonate of copper and basic acetate of lead. The former 
of these substances yields with the undecomposed white-lead a bright blue colour, which, 
after painting, turns to a peculiarly fine green, the usual colour of the iron roofs of the 
houses in Russia, more especially in Moscow and the interior of the country. In Holland 
the same mixture is frequently applied as a paint to outdoor woodwork, of which it is an 
excellent preservative. Verdigris is sometimes further applied in the preparation of other 
copper colours, for instance, Schweinfurt-green ; also in dyeing and oalioo-printing ; in 
gilding (see Qold). The neutral salt was formerly used in the preparation of acetic add. 

Lead. 
(Pb = 207 ; Sp. gr. =- 1 1 -37.) 

oeennvaee of Lead. This metal has been known from a remote antiquity. It is only 
rarely found native; its chief ore is galena (PbS). It also occurs as Boumonite, 
ofT antimonial lead ore, consisting of — 4177 parts of lead; 1276 copper; 2601 
antimony; and 1946 sulphur; formula (3Cu2S,Sb2S3-|-2[3PbS,Sb2S3]). From this 
are copper as well as lead is extracted. The other lead ores of more or less importance 
are — cerusite or white lead ore (PbC03) ; green lead ore (pyromorphite, phosphate 
of oxide of lead, 3[P205,3PbO]+PbCla) ; mimetesite (arseniate of oxide of lead, 
3[Afla05,3PbOl+PbCla); vitriol lead ore or Anglesite, sulphate of lead (PbS04) ; 
yeUow lead ore (molybdanate of lead, PbMo04) ; and red-lead ore or krokoite, 
chromate of lead (PbCr04). 

"""^j^fteSSffiS.^*** Galena is the chief lead ore, 98*9 of the metal produced being 
extracted from it. It contains 8657 per cent of lead, and 1343 per cent of sulphur^ 
with sometimes only mere traces, sometimes an available quautily of silver. Galena 
exhibits a lead-grey colour and a strong metallic lustre, crystallises in cubes, is 
brittle, and has a sp. gr.»775. It is also employed, when finely ground, and known 
as Alqnifoux, for the purpose of glazing coarse pottery ware ; for the manufacture 
of Pattinson's white-lead ; instead of sawdust for covering the floors of rooms in some 



60 



CHEMICAL TECHNOLOGY. 



of the German minin g districts ; for onuunental purposes ; jewellery ; and of late in 
a pecoliar process of ei:tractiiig platinum from its ore^. 

Lead is obtained &om galena either by the precipitation method or by roasting. 
The former process is based upon the behavioui of metallic iron at a high temperature 
towards galena ; for if these two substances are heated together the result is the 
fonnation of sulphuret of iron and metalho lead (PbS+Fe=FeS+Pb). Accordinglj. 
the predpitation method consists in smelting the galena, previously freed from gangue. 
with granulated iron obtiuned by ponring molten cast-iron in a thin stream into cold 
water. The operation is carried on in a shaft furnace ; the result is tlie fartaaiiou 
of metallic lead, and of B lead matte consisting essentially of sulphuret of iron, 
undecomposed galena, and sulphuret of copper. Sometimes iron ores and slogs of 
ironworks are applied, in which case the oxygen of these substances aids the 
desulphuration. 

The foruoce in nee for the smelting is represented in fignies 35, 26, and 37. b is the 
shitft ; c, D, the hearth and crucible, which as exhibited by the cut is parti; outside the 
Inmace. By means of a channel the molten metal aan tie rou off from n into the tap 
cmoilile. The gases and vapours previous to their escape into the chimney, t, are mode 
to pssa throogh the flues, as indicated by the arrows, in order that any sohd particles 
oontouiiug lead, which the blast at o might carry off, may be arreated. The ore and 
iron, previoosly washed, are placed in alternate layers In the furuoee. The prodnots ol 



Pia- as. 



Fia. 36. 





the smelting eoUeeted in d, are lead, cont^iug silver, aud lead matte, the latter oontaining 
about 30 lbs. of lead to the ewt. , the former sometimes 3 lbs. of silver to the same 
quantity, while copper also may be present. This lead matte is, according to its con- 
stituents, either worked np for cementation copper, or added to other slags containing 
lead and again smelted. 

°^'^mSJ^ ""^ "^^^ process is based upon the behaviour of oxide of lead and 
the sulphate of that oxide towards galena, and is effected on a large scale in a 
ceverberatory furnace. By the action of the oxygen of the air at a high temperature 
upon galena, a portion of this mineral is converted into oxide of lead and snlphorons 
acid, while sulphate of lead is simultaneously formed. By the oxygen of the 
sulphate aud of tlie oxide the sulphur of any undecomposed galena is oxidised and 
removed (3PbO+PbS-4pb+S0,+O;PbSO,+PbS=2rb+2S0,), If there is present 
during the roasting any excess of galena, there is formed a subsulphide of lead 



LEAD. 



61 



(I%«SI, from which a Email quantity of metallic lead is obtained bj liquation, while 
the residne becomes a higlier eulphuret (2Pb3S=aPbS+aPb), 

The English proeeEB of lead Bmeltiug b; roasting and Uqaation is based upon the 
reaction joiit deBCiibed, and is aamed on in a (omace exhibited in fig. iS, The hearth, 
conBtmcted of slag and built upon a masaive wall, ie arranged to elope in all direationa 
tcarda the tap-hole, tbrontth which the lead nms oS into a oast-iron pan set in a niche. 
The Bgores, 0,0,0, indicate the opeoingH for the doors, three oa each aide of the bmlding. 
T is a funnel Uirongh which the ores are placed on the hearth. Ever; six or BOTcn honrs 
a oharge of iC cwts. ot ore is worked oET, while the oonBamption of fuel amoontB to about 
half that weight in the aame time. Care is taken to spread the ore nniforml? over the 
hearth ; thie haiing been done, the heat ia giadnaU; increased, the doors of the fumaoa 
being oloBed- Aiter a lapse ot two hours the doors are opened stifficiently to Teutilate 
Itte furnace and dissipate the smoke, and are again closed, and the heat increased until 
tbe masH, from which lead eTeryvhere exudes and runs oQ to the lowest level, becomes 
by stirring and the addition of fluor-spar, almost perfectly fluid. This point having been 
reached, the oppcr layer of slag is mn off, at once cooled with water, and thos solidifled. 

Fio. aS. 




Tia» aUg is termed white slag from its white or hght grey eolonr and containi aboat 
11 p« oent of snlpbate ol lead. Borne small coal is now oast into the hearth in order to 
solidify Che tough, pastf alag which covers the lead, after which the tap-hole is opened 
lod the raw lead ran off into the iron pan, previously heated so aa to keep the metal in 
a molten state. 

>>■ Lasd. The metallic lead obtained as described is by no means pure, osnally 
eont^iiing silver, copper, antimony, arsenic, and other metals according to the pnri^ 
of the ore. The separation of the diver, when in sofflcient quantity to repay the 
expense of extraction, will be spoken of under SUver ; but one of the by-products of 
tome of tbe methods of extracting that metal is litharge, oxide of lead, which is 
either brooght into commerce as such or reduced again to metallic lead by a process 
here described. 

"T^i;^ •* This process is pursued in a reverberatory furnace by placing on 
the hearth a mixture of litharge and small coal. The lead resulting, known as hard 
lead, in contradistinction to the soft lead obtained &om refined litharge, is nsnally 
not quite pore. In order to give some idea of the compositton of the varions kinds 
of lead as obtained at Freiberg, Germany, wo quote the following results of analyses 
by Dr. Reich :— 

AnUmonial lead. 





Bawlead 


Lead . . 


■ 9772 


Arsenic . 


136 


Antimony. 


. 07i 


Iron . . . 


007 


Copper- . 


. o-as 


SUver . . 


0*49 



Beflned lead. Hard lead. 
99' z8 8t6o 

016 790 



Hulden. 



BalsbrOek. 
8760 



62 CHEMICAL TECHNOLOGY. 

FropeztiM of Load. The oolooT and general physical properties of this metal are too well 
known to require detailed notice. Lead assumes a crystalline form with difficulty, bnt it 
is obtained in that state in a combination of cubes and ootahedra by some metcJlnrgieal 
processes, e.g., Pattinson's method of silver extraction. Lead is, when refined, a veir 
soft and tractable metal ; its absolute eohesiye strength is small. When freshly cnt it 
exhibits a strong metallic lustre, but tarnishes rapidly on exposure to air. If handled it 
dirties the skin, and -gives, when rubbed on paper, linen, or cotton, a plumbago-colonred 
mark. Its sp. gr. is 11*37 ; ^ onbie foot weighs about 600 lbs. ; i cubic metre, 11,370 kilos. 
In addition to the metallic impurities usually present in lead and already alluded to, 
some of its oxide is commonly mechanically mixed with it, impairing its midleability and 
ductility, but, on the other hand, increasing its resistance to pressure. Lead belongs to 
the most readily fusible metals, fusing far below red heat, at 332^ ; on cooling it oontraets 
and assumes a concave surface. Lead is volatilised and boils at a strong white heat, air 
being excluded. It is not well suited for being worked with files or cold chisels, the former 
becoming clogged, and the latter blunt. Sheet lead is out with knives of well-tempered 
steel, l^is metal does not take up more than about 1*5 per cent of zinc ; 0*07 per cent of 
iron, and rather more copper, but alloys readily with tm, bismuth, and antimony. 
AppUeaUoni of Lead is employed in a variety of ways in building. It is much used for 
Metoiiio Lead, the leaden chambers of sulphuric acid works, and for this purpose should 
be as free as possible from any impurities or foreign metals, all of wldoh impair the 
resistance of the sheets of lead to the acid vapours, and cause the metal to become 
gradually perforated with holes and cracks. The metal is further employed for leaden 
pans and other apparatus in chemical manufactories, for gas- and water-pipes, for rifle 
balls, and for many other purposes too numerous to be here specified. 

uaxvaiMoton of Shot This manufacture consists of five distinct operations, vis. — (z) the 
melting of the lead ; (2) the granulation of the molten metal ; ^3) the sorting of the grain of 
various sizes ; (4) separation of irregularly-shaped shot ; and (5) the polishing of the shot. 
Lead intended for this manufacture is never required to be pure, and arsenic is purposely 
added, because experience has taught that this addition improves the spherical shape of 
the shot. The quantity of arsenic depends upon the quality of the lead, but varies from 
0'3 to 0*8 per cent : too much causes an irregular shape, and too little has the same defect. 
The arsenic is added either as arsenious add, in which case the lead is melted under a 
layer of powdered charcoal, or metallic arsenic wrapped in a piece of paper is introdnoed 
under the surface of the molten lead by means of a suitable pair of foreops. The 
granulation of the lead is obtained by the use of a shallow sieve-like iron vess^ 
technically termed a card, provided with holes of regular size. The dross and scrapings 
from former smeltings are not removed, as they prevent the lead running too readily 
through the holes. The operation of granulation is carried on in shot towers, the card 
with ihe molten lead being at the top, the metal assuming a spherical shape while falling. 
The small spheres or drops are collected in water, to every 100 parts of which 0*025 puts 
of sulphide of sodium is added in order to coat the metal with a small quantity of 
sulphide of lead and prevent its oxidation. Shot is also made on an entirely different 
plan embodying the application of centrifugal force. The molten metal is forced with 
great speed through openings in a centrifugal machine, making 1000 revolutions per 
minute, the shot or particles assuming a spherical shape by reason of the great force of 
impact with the air near the machine. The sorting of the shot is effected by variously- 
sized sieves, and the separation of the imperiectly-shaped grains is obtained by causing 
the shot to run over a long slightly sloping table provided with ledges of wood to prevent 
the shot falling off sideways. Only the perfectly spherical grains of shot reach the 
lower end of the table. Lastly, the shot is polished by placing 100,000 parts by weight 
of shot and 6 parts by weight of graphite together in a cylindrical iron vessel made to 
rotate slowly on a horizontal axis. In this country some manufacturers prefer to use an 
amalgam of tin, or simply mercury, instead of graphite, for polishing. The loss of lead 
in the manufacture of shot amounts to about 2 per cent. The sizes and trade names of 
the several kinds of shot vary in different countries ; in Germany No. o is the largest and 
No. 10 the smallest size. 

AUoysot Load. THb foUowisg alloys of lead in daily use are made on a large scale : — 
Bofi lead solder as used by tinsmiths, equal paris of lead and tin ; the alloy used for 
organ pipes, usually 96 parts of lead and 4 of tin, but often more tin is added ; white 
metal alloy for domestic utensils, as coffee and teapots, consists of lead, antimony, 
and tin ; alloy for ships' nails, 3 parts tin, 2 part-s lead, i part antimony. The lecid 
used by the Chinese for lining tea-chests consists of 126 parts lead. 175 parts tin. 



LEAD. 63 

1*25 parts copper, with a trace of zinc. Other alloys, such as type metal, will be 

spoken of presently. 

Pebparations of Lead. 

oxidcof LMd. This substance is oommercially employed in two different forms, viz., 
Bs massicot or as litharge. 

li ^ wiw *. Massicot, or yellow oxide of lead, occurs as a yellow or ruddy-coloured 
powder, obtained eithw by heating carbonate or nitrate of lead, or by calcining 
metallic lead on the hearth of a* reverberatory furnace. Before chromate of lead 
was known, massicot was used as a yellow pigment. At red heat this substance 
foses and becomes glassy. In most instances it is not a pure oxide of lead, but 
mixed with silicate of lead, the fact being that oxide of lead at a red heat strongly 
attacks any material containing silica, dissolving the silica and combining with it. 
utkxcc- Litharge is a fused crystalline oxide of lead, and is obtained as a by- 
product of the separation of silver from lead in the process to be fully described under 
SOver. Litharge always contains a larger or smaller quantity of oxide of copper. 
Glide of antimony, traces of oxide of silver, and, according to Dr. Wittstein, metallic 
lead, varying in quantity from i'25 to 3* 10 per cent. The oxide of copper can be 
removed by digesting the litharge with a solution, cold of course, of carbonate of 
ammonia. Litharge absorbs carbonic acid from the atmosphere, combines at a higher 
temperature with silica, forming with it a readily fosible glass, is soluble in acetic 
and nitric, and also in very dilute hydrochloric acids, and is equally soluble in boiling 
solutions of caustic potassa and soda. It is insoluble in carbonate of ammonia and 
in the carbonates of potassa and soda. Litharge is largely used, entering into 
various compounds for glass, so-called crystal-glass, flint-glass, strass for imitating 
jewels, for glazing pottery and eartlienware, as a flux in glass and porcelain staining, 
for the preparation of boiled linseed and poppy-seed oil, for the preparations of lead- 
plaster, putty, minium, red-lead, and acetate of lead. A solution of oxide of lead in 
caiistic aoda lye is applied in the preparation of stannate of soda ; this solution Ls 
also used for imparting to combs and other toilet articles made of horn the 
appearance of tortoiseshell or of buffalo-horn. A very dilute solution is used as a 
^-dye, and again in metallochromy to produce iridescent colours on brass and 
bronze. 

WrtML Be44e«d. Rcd-lcad is a combination of oxide of lead wiih a superoxide, the 
formula being Pb304- Red-lead of excellent quality is largely manufactured near 
Newcastle-on-Tyne, by carefully heating oxide of lead in a reverberatory furnace 
expressly built for that purpose, the access of air being limited so as to prevent 
*be fusion of that portion of the oxide which cannot then be converted into 
minium. Sometimes metallic lead is oxidised in a reverberatory furnace, the process, 
as, for instance, at Shrewsbury, being so arranged that at the hotter places of the 
^^iniace massicot, and at the cooler red-lead, is produced. The finest coloured minium, 
or Paris-red, is obtained from carbonate of lead by the same method. According to 
Mr. Burton's plan, sulphate of lead is heated with Chili saltpetre, and after the mass 
^ been exhausted with water the red-lead is left, while sulphate and nitrite of 
8oda are dissolved. Red-lead is used for a variety of purposes, many similar to the 
plications of oxide of lead. Besides being applied as a cement, when mixed with 
bnseed-oil and mastic, for the flanges of steam-pipes, it chiefly enters the market as 
a pigment, being for that purpose either mixed wdth water or with linseed-oil, in both 
Mwtances covering extremely well. 



64 CHEMICAL TECHNOLOGY, 

Superoxide of Lead. When red-lead is treated with moderately strong nitric acid, there are 
formed nitrate of protoxide of lead and superoxide of that metal, PbOz, a brown oolonied 
powder largely nsed in the composition of the phosphorus mixture for lucifer matches. The 
mixture known in lucifer match works as oxidised minium, is a dried composition, con- 
sisting of nitrate of protoxide of lead, superoxide of lead, and undecomposed red-lead, and 
obtained by drying a magma of minium and nitric acid. 

co»w*^**oM I* o^*« Among the salts of lead employed industrially, the followiiig 
are the most important: — 

Acetate of LewL This Salt, 

(^^»^^*^i)0, + 3H,0) 

consists in loo parts of: — Oxide of lead, 5871 ; acetic acid, 27'o8 ; water, 14-21. 
It crystallises in four-sided columnar figures; is soluble in 1*66 parts of water and 
8 parts of alcohol. When isubmitted to dry distillation it yields neutral carbonate 
of lead and aceton, which volatilises. When heated with sulphuric acid it yields 
acetic acid, sulphate of lead remaining in the retort. Acetate of lead is prepared by 
heating litharge or massicot with rectified vinegar, or with wood vinegar in leaden 
or in tinned copper pans. The clear liquid is decanted and evaporated, and then 
left to crystallise in porcelain basins or in wooden tubs : 100 parts of litharge yield 
150 of acetate of lead. This salt is largely used in dyeing and calico printing, in 
obtaining red liquor or acetate of alumina; and for the preparation of vamishes, 
white-lead, and chrome-yellow. We shall speak of sub-acetate of lead, tribasie 
acetate of lead, when considering the manufacture of white-lead. 

chronuite of Lead. The basls of chromate of lead, and indeed the substance from which 
all chromium preparations are derived, is the chrome-iron ore, consisting mainly of 
protoxide of iron and oxide of chromium (FeO,Gr203, or Gr2Fe04). It is a magnetic 
iron ore, isomeric sesqui-, or per-oxide of chromium having been substituted for the 
peroxide of iron, but the mineral varies in composition, often containing considerable 
quantities of alumina, magnesia, and protoxide of chromium. It is met with 
interspersed through very hard metamorphic rocks in some parts of Scotland, in 
colour a steel-grey or pitchy black. Its value for industrial purposes depends upon 
the quantity of oxide of chromium it contains; and according to M. Glouets 
analysis (1869) the following chrome-iron ores contained the quoted quantities per 
cent of chromic oxide : — 



M«atzal, or TeUow Chromate 
of Potaoa. 



Chrome- 


iron 


from Baltimore 45 


»» 




if 


Norway 40 


ft 




»» 


France 37 — 51 


»» 




it 


Asia Minor 53 


>f 




ts 


Hungary 31 


i» 




»> 


Oural (RuRRia) 495 


»j 




»» 


California 425 


• This salt, 








CrO^) 


/^ Tr r^^r\ 



is prepared by heating chrome-iron ore,, previously pulverised and cleansed, with 
carbonate and nitrate of potassa on the hearth of a reverberatory furnace. The 
oxygen of the saltpetre causes the higher oxidation of the protoxide of irun and 



CHROMIUM. 65 

sesquioxide of chromium, the latter being converted into chromic aoid. The 
thoronghly sintered, not molten, mass, is, after cooling, again ground up and 
lixiviated with boiling water, and also boiled for a time to extract the neutral 
chromate of potassa. Wood vinegar is added to the solution to precipitate the 
alamina and silica, after which the clear liquid is evaporated, until a film of saline 
material begins to form, when it is left to crystallise. The crystals take a 
cdnmn-like form, and are of a lemon-yellow colour, readily soluble in water, but 
insoluble in alcohol, and having a great tendency to become converted into bichromate 
or red chromate of potassa. This conversion of the neutral salt into the hi-, or aoid 
salt, is at once effected by the addition to its solution of sulphuric or nitric aoid. 
The bichromate of potassa or acid chromate, K«0r2O7, crystallises in anhydrous, 
anrora-red coloured prismatic crystals, soluble in 10 parts of water. This solution is 
hi^y caustic and poisonous. When heated to redness the salt gives off oxygen, 
leaving oxide of chromium and neutral chromate of potassa in the retort; the 
bichromate is prepared from the neutral salt by the addition to its solution of either 
solphuric or nitric acid, preferably the latter on account of the formation of nitrate 
of potassa, which may be either sold or used in the manufacture of the neutral 
chromate. 

M. Jaoqoelain proposes that the chrome-iron should be mixed with ohalk and the 
nuxtnre heated and frequently sturred, then oooled, pulverised, and put into water, with 
the addition of enough Bulpnuxic aoid to produce a weak reaction, the result being the 
fonnation, first of chromate of lime, which, by the addition of the acid, becomes the 
Viehromate of that base. The sulphate of protoxide of iron present in this solution is 
pndpitated by means of ohalk. In order to convert the bichromate of lime into the oor- 
responding potassium salt, it is only necessary to add a solution of carbonate of potassa, 
the result being of course the precipitation of carbonate of lime and the exchange of 
the ehromic add from the lime to the potassa. According to Tilghmann's process 
ehrome-iron ore is mixed with 2 parts of lime, 2 of sulphate of potassa, and heated 
fordghteen to twenty hours in a reverberatory furnace. The same inventor suggests 
the heating of chrome-iron ore with powdered feldspar and lime. Mr. Swindells ignites 
ehiome ore witii equal parts of either chloride of sodium or chloride of potassium to the 
highest possible white heat, at the same time exposing the mixture to a constant current of 
fsperheated steam, the formation of sodium or potassium chromate resulting. The most 
hnportant improvement in the preparation of chromate of potassa is the substitution of 
ttrbonate of potassa for nitrate of potassa, and the use of a furnace so constructed as to 
>Ut of the proper access of air to the strongly heated mass, the oxygen of the air being 
made to oxid^ uie ehromic oxide to chromic acid. Another improvement is, that in using 
lime nistead of alkali, the oxidation of the chromic oxide is greatly accelerated, by reason 
that when lime is employed instead of potassa the heated materials do not become semi- 
foied or paHy, but remaining pulverulent admit of the readier access of air, as well as 
prerenting the sinking, on account of higher specific gravity, of a portion of the chrome 
ere to the bottom of tiie hearth, and there becoming withdrawn from the action of the 
heat. 

A»9ikitteMof iht Before the year 1820, the salts spoken of were only used for the pre- 
^vMiitMof PoiM«. paration of chrome-yellow; it was then a very expensive process, 
^., the ealeination of the chrome-iron ore with nitrate of potassa only. At this date, 
ILKceehlin discovered the applicability of bichromate of potassa to the obtaining of 
^hat is teehnicaJly termed " discharge** for Turkey-red — a madder colour — a discovery 
loon followed by others bearing upon the useful applications of this salt, among which are 
the fonnation of chrome-yellow and chrome-orange in calico-printing, the clu'ome-blaek 
m dyeing, the oxidation of catechu and Berlin-blue, the discharge of indigo-blue, the 
bleaching of palm-oil and other fatty substances, the preparation of mixtures for the heads 
e( Ineifer-matdies, the preparation of chromate of protoxide of mercury and chromic 
oxide as green-coloured pigments in glass- and china-painting, and for the preparation of 
Vert Qoignet, a peculiar hydrated oxide of chromium : — 

(Cra)a' 



▼I 



Oc 



66 CHEMICAL TECHNOLOGY. 

obtained by heating i part of bichromate of potassa and 3 parts of crystallised boric acid, 
and used as a pigment in calico-printing. As might be expected, all these discoTeries 
gaye a strong impulse to the mannfactnre of the chromates of potassa, which have 
recently fomid still farther asefnl applications in the obtaining of colours from coal-tar, in 
the manofaotnre of chlorine gas, in defnseling brandy and other spirits, and in ttie pnxifi- 
cation of wood- vinegar made from the cnide pyroligneoas acid. 

According to M. J. Persoz, there exist, America excepted, only six manofaotories of the 
ohromates of potassa, viz., two in Scotland, one in France, one at Trjdndhflm, Norway, and 
one at Kazan, near ^e Onral, Bnssia ; the total production of these Works amounted in 
1869 to 60,0Q0 cwts. 

^SSJ^iS! T^ere are in technical use three different compounds of lead and 
chromic add, viz., neutr^d chromate of lead or chrome-yellow, basic chromate or 
chrome-red, and a mixture of these two salts constituting chrome-orange. The first 
of these substances is obtained by two methods: — (i) By the precipitation of a 
solution of chromate of potassa with a solution of acetate of lead; or (z) by 
the use of sulphate or chloride of lead. According to the first plan, the operation 
begins with the preparation of a solution of lead, for which purpose granulated lead 
is put into wooden tubs placed one above the other, and the taps each tub is provided 
with being turned off, vinegar is poured into the upper tub. In about ten minutes 
the tap at the bottom of the tub is opened, and the contents let into the second tub. 
The operation is repeated with all the tubs, four to eight in number, the object simply 
being to moisten the lead thoroughly with the vinegar, so as to cause rapid oxida- 
tion on its subsequent exposure to air. The metal soon becomes coated with 
a bluish-white coloured film, and when this is apparent, vinegar is again poured 
into the topmost tub and left for about an hour, after which it is run off into the 
second tub, and the operation continued until there is obtained a saturated solutfon 
of basic acetate of lead. To prepare chrome-yellow enough vinegar is added ia 
obtain a reaction, and the fluid left to deposit any suspended sediment. At the same 
time, in another tub, a solution of 25 kilos, of bichromate of potassa in 500 litres of 
water is kept in readiness. The clear lead solution is next poured into the bichro- 
mate solution as long as any precipitate ensues. This precipitate is well washed, 
and usually mixed with gypsum, or sulphate of baryta, to obtain the lighter chrome 
colours ; finally it is dried. According to Liebig, chrome-yellow is obtained from 
sulphate of lead, an almost useless by-product from calico-printing- and dye-worfcBi 
by digesting it with a warm solution of neutral chromate of potassa. The depth of 
colour of die ensuing yellow pigment depends upon the quantity of sulphate of lead 
which is converted into chromate of lead. 

Dr. £[abich states that there exist two binary compounds of chromate and sulphate of 
lead, the formula of which are :— PbS04-fPbCr04 and 2PbS04+PbCr04. The former is 
obtained when a solution of bichromate of potassa, previouiuy mixed with enough sul- 
phuric aeid to cause its dissociation, is precipitated with a solution of lead ; wldle the 
second compound is formed if the quantity of sulphuric add is doubled. According to 
M. Anthon a beautdfnl chrome-yeUow is obtained by the digestion of 100 parts of txe&!^ 
predpitated chloride of lead with 47 parts of bichromate of potassium. 

chiomepited. The bflksic chromatc of lead, known as chrome-red and Austrian-cinnabar, 
PbCr04+PbH202,* is a red-coloured pigment much in demand, and obtained from the 
yellow or neutral chromate of lead, dtiier by boiling it witii a caustic potassa solution, or 
by fusing it with nitrate of potassa, the effect being that half of the chromic add is with- 
drawn from the neutral chromate. Drs. Liebig and W6hler state that chrome-red is best 
obtained by fusing together, at a very low red-heat, equal parts of potassium and sodium 
nitrates, gradually pouring into the fused salt small quantities of chemically pure ydlov 

* According to Dr. Duflos, see ** Handbuch der Angewandten Pharmaceutiseh-TeohniBcfa 
Chemische Analyse, <&o.," Breslau, 1871, p. 293, the formula of this substance is aPbO,Gr03, 
ADd the dried salt does not contain any water as a component part. 



> 



LEAD, 67 

ehromAte of lead. After oooling, the insolable chrome-red is well washed and dried. It 
is then a magnifieently-colonreid oinnabar-like orystallme powder. Professor Didong 
prepares dhrome-red by preoipitating a solution of acetate of lead with a eolation of 
ohromate of potassa to which oanstio potassa has been added. The yarious shades and 
qualities of chrome-red, from the deepest vermiUion to the palest red, are caused by the 
differenoe in size of the constituent ciystalline particles. This fact is proved by experiment, 
for when several samples are uniformly ground to a fine powder the result is the production 
of a uniformly deep-coloured hue. In preparing chrome-red of a deep eolour, everything 
nhioh might interfere with or injure the crystaUiBation has to be avoided, liie pigments 
eommercially known as the chrome-orange colours are mixtures, in varying proportions, of 
the basie and neutral ohromates of lead, and are usually made by boiling chrome-yellow 
with milk of lime. M. Anthon recommends for the preparation of a good chrome-orange 
the treatment of 100 parts of chrome-yellow with 55 parts of chromate of potassa and 
12 — 18 parts of oaustio-lime made into milk of lime, 
cbrm^ozide. or ^hls substanoe, Gr203, is used in glass- and porcelain-staining as a 

oiinaa»4ixtB. cotUew grand feu^ that is to say, it stands the most intense heat provided 
no reducing materials are allowed to affect it. It is commercially known under the name 
of chrome-green as an indelible pigment for printing, being especially employed for bank- 
notes. It is prepared in various ways, the finest being obtained by heatmg chromate of 
protoxide of mercury, but this method is far too expensive to admit of any extensive appli- 
eation« Dr. Lassaigne heats equal molecules of sulphur and yellow chromate of potassa, 
and exhausts the mixture with water, leaving the insoluble green sesquioxide behind. 
Professor Wohler prefers to mix the yellow chromate of potassa with sal-ammoniac, to heat 
that miztore, and afterwards treat it with water, leaving the insoluble chrome-green as a 
ihie powder. 

Among other methods of preparing the anhydrous sesquioxide is the heating of an 
intimate mixture of bichromate of potassa and charcoal. The hydrated oxide of chro- 
mium, aooording to the formula Gr4H60Q, is met with in the trade under a variety of 
names, and often contains boric or phospnorio acids, not, however, as an essential oonsti- 
toent (see Dr. P. Schiitzenberger's formula on p. 65 for Guignet's-green), but as a renmant 
of imperfect preparation. This hydrated oxide, the preparation of which to ensure a good 
colour is rather a difficult matter, requiring very careful manipulation, is known as 
Emerald-green, Pannetier-green, Matthieu-Plessy-green, and Amaudon-green. The pigment 
in used as an artist's colour and in calico-printing as a substitute for Sohweinfurt-green, 
but is very expensive. 

Or ) 
c i i wwM i i ii w This salt, ^^[4S04-H24H20, is obtained in rather large quantities as a 

by-product of the manufacture of aniline-violet, aniline-green, and anthracene-red. It is 
a deep violet-coloured, octahedrically crystallised substance, now used to some extent as a 
mordant in dyeing, for rendering gum and glue insoluble, for waterproofing woollen 
fabrics, and for the preparation of chromate of potassa. 
cteiak ohioite. This Compound, CraCl^, best prepared by the decomposition of sul- 
phuret of chromium by means of chlorine, constitutes a crystalline violet-coloured mica- 
like material, employed in the manufacture of coloured paper and paper-hangings. 

wuto-LMid. This very important preparation obtained from lead is the basic car- 

Ixniate of the oxide of that metal, its formula being, 

PbOOO,+«>iMHO) 

According to the method employed, white-lead is commerciaUy known as of 
Holland or Dutch, Frenoh or English manufacture. The Dutch mode of making 
^bite-lead is founded on the fSaot that when metallic lead comes in contact with 
the vapours of acetic acid, carbonic add, and oxygen, at a sufficiently high tem- 
pffiatore, the metal is converted into basic carbonate of the oxide of lead. It is 
<riite evident from this brief statement that the chief conditions being fulfilled, the 
methods of operation may be more or less yaried. In Holland, Belgium, and some 
puts of Germany, the lead — as pure as possible and free from silver, which, even in 
mudl quantities greatly impairs the good colour of the white-lead — ^is cast into 
^ strips, which are wound in a spiral and placed in coarse earthenware pots, 
^g- 29). Conmion vinegar is poured into the lower part of these pots, some beer- 
yeast being added. The lead is then placed on a perforated piece of wood, so as to 



68 CHEMICAL TECHNOLOGY. 

prereut direct contact with the vinegar. After this Qie-pote are oovered wilhlead«n- 
plat«B and buried (see Fig, 30) in a masa of horse-dung or spent-tan and dung. The 
fermentation of the dung oansea the requisite itkcrease of tempwatnre, and tbe 
vinegar evaporating, aided hy the oxygen of the air, oonverta the lead into basic 
acetate, which in its turn is oonverted into basic carbonate of lead bj the cartxKiie 
add resulting from the fenaentiiig manure. This rather clamsy prooMS h«s given 
plaoB in Oennany to the chamber method, consisting essentially in the follmring 
arrangement. Instead of the pots being made the receptacles for the lead, the Btarips 
of that metal are bent and suspended on a series of laths run laigthwise Uizoa^ tfae 
chamber, on tiie floor of which is placed a layer of spent Ian, marc of grapes, or other 
fermentable material, saturated with vinegar. Ail improvement upon this arrange- 
ment is to have the chamber constnicted with a donble flooring, one water-ti^t, the 
other a light planking perforated so as to admit of the vapours of vinegar being 
carried into the compajtment. The action upon the lead is in each case the same ; it 
is converted chiefly into whit«-lead. and this cmde product is purified fhan any 
adhering acetate of lead hy washing with water before being brought into the market- 
There is atill in Qse in this conntry a modification of the method practised by the 
Dntch, who, by-the-bje. are not the inventors of white-lead manufacture, the tme 










origiii being Saracenic, (he trade being successfully earned on by these semi-aaTagn 
in Southern Spain, whence the Dntch brought over the art in the sixteenth century to 
Eollaad. This modification consigts in the following arnmgement : — Qronulatri 
lead ia first moistened with about 15 per oeot of vinegar, the metal being previon^ 
placed on hurdles in a wooden box, the interior of whioh is heated by mean* of steam 
to 35°, some steam being introduced to keep the lead moist If oare is taken to 
supply carbonic acid, after from ten to fourteen dtye the operation is finished, and 
the product having been lixiviated with water and dried, is ready for use. 
EuuiaHMindiif According to this plan the metal is melted in a large iron eanldron, 
wuu.LwL and then made to flow on the hearth of a reverberatory furnace so 
as to convert tiie lead, by proper access of air, into lithtage, which is obtained in a 
very finely divided stale by a peculiar arrangement of the fiimace. The hearth is 
constmoted with a gutter, into which the fumng mass flows ; and the mdea or waDs 
of the gutter are perforated to admit of the passage of the molten litharge, while the 
heavier metal sinks to the bottom. The litharge is nest mixed with i-iooth of its 
weight of a solution of acetate of lead, and then placed in a series of closed troufi^ 
conununicatir^ with each other and admitting of the passage of a current of impure 
carbonic acid, obtained by the combustion of coke in a fomace provided with a blast 
to give an impulse to the gas. The litharge is coutinnally stirred 1^ machinery to 
accelerate the absorption of the carbonic acid gas. White-lead made by this prooess 



tortn reiy well, md is preferred to that prepared by the wet method. We may 
mcntioii in paasmg that it is the custom in this oonittry to bring white-lead into the 
msito ground with linseed oil to a 
tliiak paste, paeked in stioDg oaken 
logs or in iron canisters 
itaAa^dtoi This metiiod m 
wSf^ Tented by UM Thi 
Bird the elder, and Roard is not 
•Bly geuenllj adopted m France 
but in all oonntries where it is 
d«iired to cany ont a really sound 
and rational plan of white lead 
■unnfaetore. The method is as 
foUows: — LiUiarge is dissolved in 
■Mtia add to obtain a solution of 
bsiie acetate of lead, 

and through the solution a current 
•tfeaibonio add gaa is passed. Two 
mdecoles of oxide of lead are con- 
verted into irtiite-tead, while neutral 
•Mate of lead romains. Litharge 
ii i^ain added to the aolntion of 
Ibis salt, and, by digestion, more 
nbasstate of lead is obtained, which 
18 ^flied as just described. 
"VSPm'' The machmery 
'"alll?." end contrivances at 
Cliehy, near Paris, for effecting the 
xethed just explained, are exhi- 
bited in Fig. 31. In the tub, a, the 
litharge is dissolved in acetic acid, 
i c is a stirrer, moved by means of 
the shaft shown in the engraving, 
bearing at the top a pnlley for the 
rtnp. The solution of basio acetate 
<tf lead can be run off Uirough the 
t^i into the vessel e, made of copper 
and tinned inside, the object being 
to let the impurities the solution 
mi^t contiun subside. From e the fluid is led into the decomposition vessel con- 
structed with 800 tubes, which pass from the lop to a depth of 32 centims. beneath the 
kvel of the fluid. These tubes are in communication with the main-pipe, gg, which 
alio conununicatea with the washing apparatus, p, answering the porpose of purifier 
lor the carbonic acid gas generated in the small lime-ldln, o, by the ignition of a 
■nixture of 3| parts by bulk of chalk and i part by bulk of coke with sufficient access 
(rftir. The decomposition of the basic acetate of lead being finished in from twelve to 
fourteen hours, the supernatant liquor, neutral acetate of lead, is run off into the 




70 CHEMICAL TECHNOLOGY. 

vessel, t, and the semi-fluid magma of white-lead passes into o. The pnmp, b, serves 
to again convey the neutral acetate to the tank, a, and the operation is re-commenced. 
The white-lead in o is well washed — ^the first wash-water being conveyed back to the 
tank, A — and after drying is ready for use. In order ta obtain the carbonic acid 
cheaply, it has been proposed to ignite a mixture of chalk or limestone, charcoal, and 
peroxide of manganese (CaCOj-f C+3MnOj,=Mn304-f CaO+zCOa.) Where admis- 
sible, the carbonic acid resulting from the fermentation of beer- wort, or of distillezy- 
wash, may be applied. Natural sources of carbonic acid sometimes occur in the 
neighbourhood of active or extinct volcanoes ; and near Brohl, dose to the Laacher Sea 
in Bhenish Prussia, a locality well-known to tourists, a very plentiful and continuoiis 
supply of carbonic acid is naturally obtained and actually applied for the poipoae 
under consideration. 

Among the very various suggestions for improved methods of making white-leadt and 
for which an enormous number of patents have been taken out, especially in this coontiy 
and in the United States, we briefly mention the following : — MM. Button and Dyer first 
slightly moisten litharge with water, next mix it with a small quantity of a solution oi 
acetate of lead, place the mixture in a stone trough, agitating and passing hot oarbonie 
acid over it. Pallu (1859) causes finely-divided lead to be thrown with great force, fay 
means of a centrifugal machine, on an inclined plane, care being taken to moisten the lead 
with acetic acid. After the lapse of an hour, the finely-divided lead is converted into 
acetate and carbonate. A solution of acetate of lead is then poured over the mass, and 
the acetate of lead it contains is dissolved, while the white lead is carried into a tank, and 
there forms a deposit. M. 0-runeberg ^1860) prepares white-lead by submitting grann- 
laled lead to the simultaneous action 01 air, acetic, and carbonic acid, aided by Uie rapid 
motion of the metal. From private information obtained from the largest wholesale hoose 
. in London, whose connections and trade relations embrace literally the whole world, 
dealing in white-lead, we have learned that not i-ioooth part of the lead, as it is techni- 
cally termed, of good and saleable quality met with in the trade, is made by these new 
processes, since the products of most of them are deficient in some respect or other. 
wuto-Le»d from It is wcll-known that sulphate of lead (PbS04) is a by-product of 
saii^ta of Lead, yarious chcmioal operations, especially such as are carried on in connection 
with dyeing and'calico-printing. The salt of lead thus obtained is a refuse which it haa 
been sought to utilise in many ways. As it does not possess covering power, it cannot be 
used instead of white-lead as a pigment, and the difficulty of reducing it to metallic lead 
renders its metallurgical utilisation, if not impossible, at least highly objectionable. It 
has been used as a gas-purifier instead of, or in connection with, Ume, and for this purpose 
it is a very fit material, and by becoming converted into sulphuret of lead it may be 
afterwards utilised as a lead ore. It is converted into white-lead by digesting it with a 
solution of either carbonate of ammonia or of soda. The best method for converting the 
sulphate of lead into metallic lead is to mix the air-dried salt with 67 per cent of chaUc, 
12 to 16 per cent of charcoal, and 37 per cent of fluor-spar, and to smelt this mixture in a 
furnace. The result is the formation of carbonate of lead, which is reduced to the metailie 
state by carbon, the sulphate of lead and fluor-spar combiuing as a slag — 

(PbS04 -H CaCOg -f 2C -». nFlaCa =» Pb-»- 3CO4- CaS04-ffiFlaCa). 
Accordiug to Dr. Bolley, sulpliate of lead may be reduced by the moist method by pladng 
the salt with zinc into water, the result being the formation of chloride of zinc (sic) and 
metallic lead.* M. Eraflt proposes to convert sulphate of lead into acetate of lead by 
boiling the former with a solution of acetate of baryta, sulphate of that base (permanent, 
or Chmese-white) being simultaneously formed. 
Thoorr of Pnpuing Leaving out of the question the preparation of white-lead from sui- 
White-Lead. phate of lead, the preparation of the pigment as regards all the other 
methods is dependent upon : — 

1. The formation of basic acetate of lead ; 

2. The decomposition of that compound iato neutral acetate of lead and white-lead. 
Viewing white-lead for this purpose simply as a carbonate of lead, although we shall 

* It reads in the original exaotiy as above translated, but whence the chlorine for the 
chloride of zinc is to come has been left in nubibw; water, sulphate of lead, and metaDio 
zinc do not act upon each other unless some acid be present. Should dilute sulphuric be 
present there will be formed sulphate of zinc. 



LEAD, 71 

praBentl^ see that the white-lead of commeroe is not so simply constitated, the formation 
may be illustrated by the following f ormnlfe : — 

I. 2J^^^30j o + 3PbO = [(^*°^j|«]o„2PbHaOa; 

, ' s , 1 

Acetio aoid. Basic aoetate of lead. 

n. (^^^30)1 1 02,2PbHaOa + 200, + 2PbC03 + | (^^^30|a | q^, 

^ , ' >- r-. — > "^ , • — ' 

Basic aoetate of lead. Carbonate Neutral aoetate 

of lead. of lead. 

It is therefore evident that a comparatiyely very small quantity of aoetate of lead can 
produce a large quantity of white-lead, and the manufacture of that material would be 
endless but fo/the fact that white-lead retains some neutral aoetate of lead, and that the 
loss of acetic add cannot be practically avoided. 

wui«.Laad from M. Tourmentin prepares white-lead from basic chloride of lead, obtained 
oiiodfk of Lead. },y ^hc action of common salt upon litharge, by mixing that compound 
with water, passing through it a current of carbonic acid, and next boiling the fluid in a 
leaden-pan with powdered chidk until a test-sample, when filtered, does not become 
blackened by the addition of sulphide of ammonium. The white-lead thus formed is freed 
from salt by washing with water. 

*M»8SbStitli£?* ^* Pattinson, of the Felling Chemical Works, near Newcastle-on- 
widfe-LMd. Tyne, has proposed that, instead of white-lead, a basic chloride (oxy- 
ehloride) of lead should be usea, and he prepares that substance by adding to a hot solution 
of chloride of lead (PbC^), containing from 400 to 500 grammes of the salt to the cubic 
foot, an equal bulk of saturated lime-water. This addition causes the throwing down of 
the compound (PbCla+PbH^Oa), which after having been collected on a filter and washed, 
is dried and used as a pigment. The chloride of lead is obtained directly from galena, 
which is decomposed from leaden- vessels with strong hydrochloric acid. The sulphxuretted 
hydrogen thus formed is oarried by suitable tubing to a burner in the sulphuric aoid 
chamber, the resulting sulphurous aoid from the combustion being used for the produc- 
tion of sulphuric add. Pattinson*s white-lead is not so white as ordinary white-lead, its 
colour verging to yellow, but this is no objection where white-lead is to be used witti other 
paints, and the less so as Pattinson' s oxychloride of lead covers weU. 
PuMrtiM of When unadulterated and weU-made, white-lead is an exquisitely fine white- 
in&LMd. coloured powder, void of taste and smell. The white-lead of commeroe 
exhibits, according to the mode of preparation, different features ; one preparation is met 
with in flakes, having been obtained by the corrosion of thin strips of lead placed in pots. 
The lead known as Krems-lead is pure white-lead made in thin cakes by means of gum- 
water. 

The variety of white-lead known as pearl-white is blued with either a small quantity of 
indigo or Berlin-blue. The white-lead of commeroe has frequently been made the object 
of chemical analysis, especially by 1^. G. J. Mulder and M. Oriineberg. The results of 
the analyses of the under-mentioned samples prove the correctness of the formula given 
above. The numbers refer to : — i. Exems white-lead. 2. Prddpitated by the CLiohy 
method and manufactured at Magdeburg. 3. From the Harz. 4. Another sample from 
Krems. 5. A sample from a chemical laboratory by imitating the Dutch method on a 
limited scale. 6, 7. Samples from Klagenfurt, Carynthia. 8. English lead manufactured 
according to the Dutch method. 

Oride of lead 
Carbonic acid . . 
Water 



I. 


2. 


3- 


4- 


5* 


6. 


7- 


8. 


8377 


8593 


86*40 


86*25 


84-42 


86*72 


86*5 


86-5X 


15*06 


11*89 


11*53 


"•37 


14-45 


11*28 


11*3 


11*26 


I"OI 


2'OI 


2*13 


2*21 


1-36 


2*00 


2*2 


2*23 



It is certain that the covering properties of white-lead are dependent upon its state of 
aggregation, because a loose crystalline white-lead does not cover nearly as well as the 
perfectly amorphous lead prepared by the old Dutch method. It appears that the covering 
power increases with the amount of hydrated oxide of lead. This is proved by the fact that 
those who merely choose white-lead by its coveringpower are often misled, a fact lately tested 
by the translator of this work, by giving to a man, thoroughly acquainted with white-lead 
as eommerdally met with, a mixture of carefully-prepared and dried hydrated oxide of 
lead, to which white predpitate, subnitrate of bismuth, and carbonate of bismuth had 
been added. The man, after testing a series of samples of purposely-adulterated white- 
lead, all of which he detected as adulterated, was unable to speak with certainty of the 
above mixture, which he took for pure lead. 



72 CHEMICAL TECHNOLOGY. 

AdnitfltaiioB of It has been, and is still, to some extent, the custom in the mAnnfaetories 
whtte-LMd. ^ fAdi to white-lead a certain quantity of snlphate of baryta, either natiT<e 
or artificially prepared. Lead is often mixed with sulphate of lead, chalk, carbonate of 
baryta, snlphate of baryta, and pipe-day ; but these adulterations are most common in 
the retail trade. Not any of these substances ought to be present ; they possess no 
cbyering power and needlessly absorb oil. Pure white-lead ought to be perfectly soluble 
in yery dilute nitric add, and in the resulting dear solution caustic potassa should not 
produce a precipitate, for if it does chalk is present. An insoluble reddue in the dilute 
nitric acid indicates the presence of gypsum, heavy-spar, or sulphate of lead. The 
sulphate of lead may be recognised by reducing the lead with the blowpipe. Sulphate 
of baiyta can be made evident by ignition with charcoal in the blowpipe flame, treating 
the reddue with dilute hydrochloric add, and adding a solution of gypsum, which again 
yidds a predpitate of sulphate of baryta. Gypsum does not yield an ins<^uble predpitate 
with dilute nitric add, but does so with a solution of oxalate of ammonia. According to 
Dr. Stein the most simple method of estimating quantitatively a mixture of white-lead 
and sulphate of baryta, is to heat the weighed sample in a piece of combustion-tube, and 
to collect the carbonic add in a Liebig's potassa-bulb, a chloride of calcium-tube being 
fastened by a perforated cork to the combustion-tube to absorb the moisture. The 
quantity of carbonic add given off stands in direct proportion to the quantity of carbonate 
of lead present. Pure white-lead of good quality gives off about 14*5 per cent of the 
gas, and, according to Dr. Stein's researches, the undermentioned series of mixtures gave 
off the quantities of carbonic acid indicated. 

33*3 parts of white-lead and 66-6 parts of heavy-spar lost by ignition 4*5 — ^5 per cent. 
66-6 „ „ 33*3 .» ♦» »» 6-5—7 t» 

8o-o „ „ 200 „ „ „ 13-0 „ 

500 „ „ 500 „ „ „ 10—10-4 „ 

AmiiMttoosot The extensive applications of this material as a constituent of psints, 
whito-LMd. i< to give body," as the term runs, and as putty, and for various chemical 
operations, are well known. It has been experimentally proved by Dr. G. J. Mulder in bis 
treatise *' On the Ohemistry of Drying Oils and the tactical Applications to be drawn 
therefrom," that tiie quantity of white-lead used in proportion to linseed-oil for painting 
purposes is far too great, being on an average from 250—280 parts of white-lead to 100 
parte of oil, while the author found that 52 parts of unadulterated white-lead, or 44 parts 
of oxide of lead (PbO) to 100 parts of raw or boiled linseed-oil are amply suffident 
quantities. White-lead, however useful, is very sendtive to the action of sulphuretted 
hydrogen, by which it is blackened and discoloured, causing not only all the white paint 
to be spoiled, but also all pigments and paints of which white-lead is a constituent, as 
may be seen to a very large extent every summer at Amsterdam, where from the stagnant 
canals sulphuretted hydrogen is abundantiy given off. The action, however, of the sea 
air in autunm has the effect of somewhat restoring the blackened and discolotured painted 
surfooes to their primitive hue. The late Professor Th^iard suggested that pictures which 
had become blackened should be cleaned by means of peroxide of hydrogen, the oxygen 
of which present as ozone converts the blackened lead colours into white BulphAte 
of lead. 

In this country it has become an almost universal custom to sell white-lead ready 
ground with linseed-oil into a thick paste. This practice certainly saves painters a 
great deal of trouble, but is also pregnant with the difficulty of detecting adul- 
teration, while there is a chance of an inferior oil, rosin oil, being added. The 
oU almost entirely prevents the action of any acid upon the paste; even if very strong 
nitric add be taken, and heat applied, the decomposition and disintegratiosi are 
very slow and incomplete, and, besides, owing to the insolubility of nitrate of lead 
in nitric acid, the action of strong nitric acid upon oil thus mixed gives rise to a 
variety of compounds, which interfere with the usual modes of testing the white* 
lead. To remove the oil in order to test white-lead, the best plan is to thoroii^^ 
incorporate some of the sample witii a mixture of chloroform and strong alcohol in 
equal parts, and to wash the mass by decantation or on a filter with a fluid composed 
of 2 parts of chloroform and i of strong alcohol. The quantity of the oil may 
then be ascertained by the evaporation of this solvent. After washing once or twice 
with boiling alcohol and then dxying, the white-lead can be readily tested by any of 
the known methods. 



Tin. 

(Sn=ii8; Sp. gr.=7-28.) 
Tin does not occur nstnrolly in a metallic slAte; it is found as 
""uSmSZT^ oxide in tinstone, or tin ore, SnO,, containing 79 per cent of metal, 
and as sulphnret of tin in combination with other metallic snlpboiets in tin pjrit«B, 
[iCi>iS+SoSi)+2(FeS,ZnS),SnS„ with 26 to 29 per cent of tin. Tin ore occurs 
either interspersed in veins, in ajenitic and similar rooks, or in secondary formations 
depo6it«d from water, and oonaisting of Tariona detritus, when it is known as tei/fr. 
■ These ores are not as a rule simpl}' composed of pnre oxide of tin, but contain various 
other metallic oomponuds, among which are snlphnr, arsenic, zinc, iron, and copper. 
In some instances, in Cornwall, Malacca, Banca, and Klliton, tin ore is met with 
among the detritoa of ancient river-beds in a very pnre state, since the mechsnical 
separation of the ore from impurities has been performed bj nature itself, and as a 
consequence these ores yield a purer metal than the ore obtained from veins, which 
has to nndergo dressing, washing with water, and roasting, previouslj to being 
■melted, in order to eliminate the arsenic, Bolphni, and antimony. Tinstone ocours 
in Saxony in the earlier granitic formation. The ore is aooompanied by, and partly 
mixed with, wolfram, molybdeunm-glance, sulphur, and arsenical pyrites, and bears 
the name of Ziimzwitter. Fig. 33, I. and II., represent the furnace in use at 
Altenberg, Saxony, for smelting the roasted tin ore. It is built of granite upon a 
Fio. 3a. 





strong foundation of gneiss, and is about three metres in height. * is the shaft, b the 
fbre-hearth, and d the bottom-stone, consisting of one single piece of granite scooped 
ODt in tbe direction of s, B is in communication with the iron caldron, c : while the 
toyere of the blast is placed at b. The ore. mixed with coke, coal, or charcoal, and 
with slag from former smeltings, is placed in t : the reduced tin collects first on the 
Ibre-heartb, b, and runs thence into c. The metal, however, is not pnre, but contains 
iion and arsenic. It is separated from these iropnrities by a process of Uqnation ; 
8ie pore tin frising more readily, oozes out and leaves behiud an alloy of iron and 
tin fusible with greater difficulty. The metal thus oblained is very pure, containing 
hardly as mnch as O' i per cent of foreign metals ; it is known in tbe trade as refined 



74 



CHEMICAL TECHNOLOGY. 



tin. The slags, as well as the alloy remaining, are smelted separately or together 
for tin, and the result brought into the market as block-tin. In Bohemia and Saxony, 
tin is cast either in ingots or in cakes. Banca and BiUiton tin, a very pure metal, 
is cast in slabs. If tungsten ores occur with tin ores, there is great difficulty in 
obtaining pure metal. Tin ore found in Cornwall — and this county has 3rielded tin 
for at least 2000 years— has to be smelted £kccording to the ancient Stannary laws. 

t>ropertieB of Tin. Tiu, as regards it8 oolonr, approftohes the nearest to silver, caaiy 
differing by a somewhat bluish hue, and it exhibits a high metallic lustre Teiy 
Bimilar to silyer. It is next to lead the softest metal, yet is somewhat sonoroos, for if a 
rod oi tin be tree to swing, and is gently tapped, a sound is produced ; this ia not the 
-ease under similar conditions with lead, thus proving tin to be considerably harder, alio 
proved by the fact that it is not easily scratched with the naU. The bending of a rod of ' 
tin causes a creaking noise, which 13 the stronger the purer the tin. Tin is very malleable, 
and admits of being beaten to very thin foil, but it is not a very ductile metaL 'Wben 
rubbed between the fingers it imparts to them a peculiar odour. The sp. gr. of pure tin 
is 7*28, and by hammering may be increased to 7*29 ; a cubic foot of tin weighs, according 
to its purity, from 375 to 400 lbs. Tin fuses at 228*^, and becomes very brittle irhen 
heated to nearly that temperature. If the metal is intended for casting — ^it is, however, 
very rarely used in a perfectly pure state for castings, as it does not fill the moulds well- 
its metallic lustre and degree of cohesion after cooling entirely depend upon the tempera- 
ture of the tin at the time of casting. If too hot and exhibiting rainbow colours, its sur- 
face will appear striped and reddish-yeUow after cooling, and the metal will be brilUe 
if again heated to loo** to 140** ; if not sufficiently heated, though in a fluid state, it is, after 
cooling, dull and brittle. The greatest metallic lustre is obtained, and simultaneousiy the 
greatest cohesive strength, when the surface of the metal while molten exhibits a high degree 
of lustre. At a white heat tin boils and volatilises, air of course being excluded ; for 
if ihe metal be kept fused in contact with air, it becomes covered with a greyish coating 
of protoxide of tin and finely divided metal, termed tin-ash, which substance when the 
heating is continued becomes converted into a yellowish-white stannic oxide, kaowa 
as putty powder. Tin by exposure to air gradually loses its metaUic lustre, but is by no 
means so readily iCffeeted by sulphuretted hydrogen and ammoniacal vapours as silver, 
and is used to imitate that metal in the construction of lustres for gas lamps, <&e. 

AppUoatioiu of Tin. Now that chiua and earthenware have become cheap, and oUier alloys 
are used for spoons, tin is not so frequentiy in demand as in former times for domestic 
utensils. Tin, though next to silver the dearest of metals, is met with in quantities 
measured by tiie ton, which of tin varies in price from £120 to £180— copper being 
from £95 to £105 — and is largely used both as an alloy (for those wi& copper 
see under that metal), and in a pure state for various kinds of vessels for pharmaeeutieal 
and chemical operations, for worms of distUling apparatus, for the working parts 
for dry and wet gas-meters, and for block-tin pipes for conveying gas and water, te 
However, for many purposes, an alloy known in this country as pewter, of Ic^ and tin in 
varying proportions, is preferred, because this compound is harder and stands wear and 
tear bettor than these metals separately. An alloy of lead and tin is called abitnd 
two-poundly when the metals are present in equal quantities, and ihree-^^oundiy when 
consisting of 2 pounds of tin and i of lead. Tin, either pure or more or less alloyed with 
lead, may be beaten or rolled into thin sheets and foil, and applied in a great many ways ; 
among which, one of the chief, although gradually being superseded by a process of aUvering, 
is tinning or amalgamating mirrors. Tin-foil is also used for the packing of chocolate, 
soap, cheese, fruit, &c., all of which keep very well under these conditions. CSommercial 
silver-foil or leaf-silver is an alloy of tin with a little zinc ; in combination with other 
metals, viz. copper, antimony, and bismuth, in varying but small quantities, it constitutes 
a oompoation metal used for making teaspoons and other similar objects. Britannia metal 
consists of 10 parts of tin and i of antimony, its various applications are well known. 

As the specific gravity of those metals with which tin is purposely or naturally alloyed 
differs, the determination of the sp. gr. is a means of estimating the purity of the meitaL 
The undermentioned figures illustrate this in the more commonly occurring alloys of tin 
and lead. 

Parts Sn -f Parts Pb Sp. gr. 



Parts Sn + Parts Pb 


Sp.gr. 


1 + 

2 + 

1 + 

2 + 
X + 
2 + 


I 
3 

2 

5 

3 
7 


8*8640 
9*2650 

9*5530 
97700 

9-9387 
10*0734 



I 


+ 


4 


10*183 


3 


+ 


2 


8-497 


2 


•f 


I 


8*226 


5 


+ 


2 


8*109 


3 


+ 


I 


7*994 



PREPARATIONS OF TIN. 75 

The materiftl known as putty-powder and calcined tin-ash is used for polishing glass 
and metals, and for producing white enamels. 

Tianiaf. By this term we understand the covering of other metallic surfaces with a thin 
and adhesive film of tin. This operation only succeeds well when the surface of the metal 
to be tinned is quite free from oxide, and when during the operation the oxidation of the 
molten tin is preyented. The former requisite is attained by the action of dilute acids » 
rubbing and scouring with sand, pumice-stone, Ac. ; the latter condition by the use oi 
either rosin or sal-ammoniac, both of which cause the reduction of any oxide that may be 
formed. 

of coDoer. btsu, '^^^ vessels or other objects intended to be tinned are heated 



■AdHaUMiUe Iron, nearly to the melting-point of tin ; some molten tin is then poured 
iato the yessel and brushed about with a piece of hemp over which some powdered sal- 
■mmoniae is strewed. Pins, hooks and eyes, small buttons, and similar objects are tinned 
by being boiled in a tinned boiler filled with water, granulated tin, and some cream of 
tartar. The tinned objects vre dried by being rubbed with sawdust or bran. 

TiBsaisiiMi-iroii. TMs wcll-known material, from which so many useful objeeta are mad* 
by the tinman^ is not, as is frequently supposed, rolled out sheet- tin, but tinned sheet-iron. 
The iron proYiously to being covered with tin is thoroughly scoured, so as to present a 
dean metallic surface, and then immersed in baths of molten tin covered with a layer of 
molten tallow to prevent the oxidation of the metal. On being removed from the tin-bath 
the sheets are immersed in a bath of molten tallow to remove any excess of tin, wiped 
with a brush made of hemp, next cleaned with bran, and packed. In order to obtiun iron 
covered with an iJloy less easily fusible, MM. Budy and Lammatseh add about ,^^1^ ^ 
niekel to the tin. 

M«ii»]i«ui]i4iM. When tinned sheet-iron, technically termed tin-plate, is washed over 
with a mixture consisting of 3 parts of hydrochloric and i part of nitric acid diluted with 
3 parts of water, and then cleaned with pure water, there will be observed a peculiar* 
somewhat mother-of-pearl -like appearance, due to the crystalline particles of tin, produced 
by the rapid cooling, reflecting the light unequally* 

Preparations of Tin. 

^'jSS^^S^* ^® substance known under that name is in reality a faisniphide of 
tin (SuSg), prepared in the following manner : — 4 parts of pure tin, with 2 of mercuiy, 
are amalgamated by the aid of a gentle heat, and introduced with zk parts of sulphur 
and 2 of sal-ammoniac into a flask, and heated on a sand-bath, at first gently and 
then gradnallj increasing to a full red heat. First the sal-ammoniac volatilises, and 
next mereory in the shape of cinnabar mixed with a trace of the sulphide of tin ; while 
there is left the preparation known as mosaic-gold, forming the upper layer of the 
temaining contents of the flask, the lower portion being a badly-coloured sulphide. 
The ratUmale of the formation of this peculiar coloured sulphide, that is, peculiar as 
regards its physical appearance, is not quite clearly explained ; the compound, more- 
over, may be prepared without mercury. When properly prepared, it appears as a 
golden-coloured metallic substance, greasy to the touch, and soluble in the alkaline 
anlphnrets. It is chiefly used for imitating gilding on painted surfaces, but its 
employment is very much restricted from the fact that the bronze-colours are more 
satisfinctory in result, Indeed, in the English market, mosaic-gold is almost obsolete. 

TiMdt By the name of tinsalt the trade understands chloride of tin (Sn01«), but 
the commercial article, being prepared by dissolving granulated tin in hydrochloric 
acid and evaporating the solution, is really (SnCl^-faH^O). According to M. Nollner 
kydrochloric acid gas should be caused to act on granulated tin placed in earthenware 
nceivers, and the concentrated tinsalt solution thus obtained evaporated in block-tin 
veasels. The salt occurs in the trade in colourless, transparent, deliquescent 
crystals, of course very soluble in water. The aqueous solution, unless acidulated 
with more hydrochloric or tartaric acid, soon deposits a basic salt. Tinsalt is used 
chiefly in dyeing and calico-printing. 



76 CHEMICAL TECHNOLOGY. 

"^n^!^ Under this name dyew use a solution of refined block-tiii in aqtu 
regia, and uauslly this substance ia a mixture of perchloride and protochloride of tin. 
The material known as pinksalt is a double chloride of tin and Bnuoonioin — 

(SnCl^+aNH^ai. 
A couoentrated aqueous solution of this salt is not decomposed hy being boiled, bat, 
when diluted, the oxide of tin is thrown down. Pure chloride of tin is used in Fimnoe 
in the preparation of fachsine ; while as a solutioii it is used bj M. Th. Petw. at 
Ohenmitz, for dyeing in iodine-graeu. 

nuiuUDiBodi. This salt is now very lai^elj used in dyeing as well as in calioo- 
printing, and is prepared in various ways, sometimes by fusing tin-ores with caoHtic- 
Boda and lixiviating the molt«n mass with water ; oi, according to Mr. Brown, by 
boiling soda-lje with metallic tin and litharge, the effect being the formation of 
atannate of soda and metallic lead. Dr. Hafiely somewhat modifies this prooeas br 
digesting litharge with soda-lye at 2Z per cent in a metallic vessel. Into the aolatwo 
of plumbateof aoda thus obtuned, granulated tin is placed and heat applied. Some- 
times a stonnite of soda is used and made by dissolving tinsalt in an excess of caustic 
soda, but this preparation is unstable and does not answer well in dyeing and printing ; 
it is only extemporaneously used on a limited scale by small dyers. 

BiSUUTH. 

(Bi=2io; Sp.gr.=9'79). 
°*°S'n! Slft?AJ '°*' Bismuth is a rather rare metal. It occurs io Pern and Anstrslia, 
chiefly native, and with cobalt and silver ores in granite -gneiss and metamoiphie 
roclcB. It is also found as oxide, the ore being known as bismuth -ochre, BiOj, ctm- 
taiaing 89-g per cent metal : as snlphide. or bismuthine, BiS,, with SogS per oent 

Fio. 33. 




metal : and as bismuth copper ore, with 4724 bismuth. Ah bismuth is chiefly found 
in the native metallic stata. and is a readily fusible metal, its extraction from gangne 
is not a difficult matter, and consists in a process of liquation. 

""iSiiiS*'^' "^^ contrivance in use near Schneeberg. in Saxony, for the smelt- 
ing of bismuth is exhibited in Fig. 33. The ore. containing on an average from 
4 tD 12 per cent metal, separated as much as poHsible by mechanical means from the 
gangue, is broken up to the size of hazel-nuts and placed in the cast-iron tube. a. 



ZINC, 77 

Jbeatod by means of the fiimace. The fluid metal nms out into b, an iron-pot kept 
gniBciently hot by meana of charcoal to prevent the solidification of the metal, and 
partly filled with charcoal-powder to prevent the oxidation of the metal. The residue 
in the iron tube is discharged into the water which fills the box, n. By this method 
of liquation abont two-thirds of the bismuth contained in the ore is reduced. Bismuth, 
as has been stated (see Cobalt), Ib obtained as a by-product,, and from the refuse of the 
refining of certain sUver ores which are treated with dilute hydrochloric acid, the basic 
ehloride of bismuth being precipitated by water, afterwards dried, and reduced by 
means of soda. 

> iwi «u m of Btamaih. Bismuth poBBSSses a reddish-white oolour, strong metallic lustre,, 
and ciystalline texture. It is hard, but so brittle that it is readily pulTerised, yet 
with careful treatment proves to be somewhat ductile. Its fusion-point is variously 
given by different authors, the latest determination of pure metal in an atmosphere of 
hydrogen is by Dr. van Riemsd^k, who found bismuth to melt at 268*3°. On cooling 
bismuth expands very considerably. 

a is Saxony, /3 Peruvian bismuth ; composed in 100 parts : — a. Bismulh, 96-731 ; anti- 
many, 0-625; arsenic, 0*432; copper, i'682; sulphur, 0-530. /3. Bismuth, 93*372; 
sntimony, 4-570 ; copper, 2*058. 

Miatfmfloc Bismuth in the metallic state is chiefly used for certain alloys. Its oxide 
^^"^ enters with bono and silicic adds into the composition of some kinds of 
|^|sss, and is used for porcelain- and glass-staining. The basic nitrate, or magUterium 
bitmnuki, and the o/irbonate are used in medicine, and the former, under the name of 
Bkme defdrd, is employed by ladies for painting and beautifying their faces. Among the 
alloys of bismuth those with lead, tin, and eadTninm (see that metal), are the most impor- 
tant. Newton's fusible alloy is composed of bismuth, 8 parts ; tin, 3 ; lead, 5 ; and melts 
at 94*5*. Bose'B fosible metal consists of 2- parts of bismuth, i of lead, i of tin, and 
fuses at 93-75. If a small quantity of cadmium be added to these alloys they are 
randsred still more easily fusible. An alloy composed of lead 3 parts, tin 2 parts, bis- 
rnath 5 parts, fuses at 91-66, and may be used for stereotyping purposes, but is rather 
tzpenaiTe. This alloy is also used for making ihe pocket-book metaUic-penoil for writing 
on paper prepared with bone-ash. Alloys containing bismuth were used as safety-plugs 
in iteam-boilen ; these plugs were screwed into one or more of the plates exposed to the 
foree of the steam, usually in or near the steam-chest or dome, the idea being that the 
phgs would melt if the temperatore of the steam rose b^ond certain limits. Experience, 
howsver, has sufficiently proved that these pings, although carefully made, did not act as 
a real preventative to boiler-eiplosions. 

ZiNO. 

(Zn«65*2 ; Sp. gr.=7-i to 7*3) 

oocmnMocziM. Tlus metal, known only a comparatively short time, is never found 
native, but in combination with sulphur (ZnS), with 67 per cent of metal, under the 
name of Uende or black-jack, the ore sometimes containing traces of indium. It also 
oecnrs combined with oxygen as noble-calamine, carbonate of zinc, or zinc-spar 
(ZnCO}), with 52 per cent of zinc ; as ordinaiy calamine-stone, or hydrated silidate of 
zinc, with 53*8 par cent of metal; as red zinc-ore or red oxide of zinc, frequently 
containing manganese ; as Gfahnite (AlZn04) ; and farther as an admixture with other 
orea. 

ii£aSf &M. -^^ general plan is to roast the ore and then mix it with the requi- 
nte quantity of carbonaceous matter and suitable flux, care being taken that the latter 
>lutU not give rise to the formation of any oxidising material ; for instance, if the ore 
nqnires lime as flux to take up the gangue, calcined limestone, and not chalk or 
limeatone is used. The action of the fuel is aided by a blast, best of dry air. The 
products of this mode of treatment are: — i. Metallic zinc, the vapours of which 



jS CHEMICAL TECHNOLOaT. 

eondeOM in propetly constructed and cool channflls. 2. Hot gasea usoBUf applied for 
beatmg Bteam-boilarB or other pnrpoBee. 3. The non-volatile materials, gangne and 
flax, elag with some metoL 

iHitDL^m^ziu With the exception of cadmium, zinc is the moat volatile of £he 
«adily fusible metala, while its melting-point is nearly twice (he number of d^[rees of 
that of tin, the meet ftuifale of Qie commercioll? valuable metals ; this property is 
utilised in extracting the metal from its or«s. The mode of distillation vaiies in 
SDSie ptutkculort in the three chief zinc prodncing countries, SUesi^ Belgium. «nd 
England. In Silesia and Oennan]) the apparatus nsed for the distillation of zine 
connsta (see Figs. 33, 34, and 35) of a moffie-Hhaped fire-clay retort, the front or 
isoath of vMch is provided with two openings, the lower, a. being closed by a dow 



Fto. 34. 



Fto. 35. 




irluch is opened only when the residue of the distillation is taken ont. At b, tbe 
other opening, a rectangolarly bent tabe is inserted, provided with a small bole >t «. 
closed by a plug when the operation of diafUling i^ proceeding, and by ^diich the ore 
is introduced into the retort. At d Ute molten zinc rons off. The muffles are placed 
to the number of from 10 to 30 in a fnnuice (see Fig. 36) constructed inlemnUy 

Fio. 35. 




somewhat like gaa-retort furnaces, and rest on what are technically termed benches. 
The krohes of the ftamaces are so constructed as to concentrate the heat (rem th» 
hearths placed longitudinally. The metal is recaved in crucibles plaoed in the 
recesses, a. As the first portion of the metal and oxide carried over contains nearly 
aU the eadmium existing in the ore, that portion is kept separate for the ptupoae at 
wxtracting cadmium. At the outset of the distillation the condensation room, t, is so 
cool that the vapours of the zinc become solid without agglntinstioa, that is, ranaiD 
finely divided. This product, though of course containing oxide, frequenUy yields 
g8 per cent of metallic zinc. Afterwords the metal carried over is what is termed 
drop-zinc, that is to say, the liquid runs off in a molten state. This crude zine is 
refined by another smelting, and comes in the market in slabs about 2 inches thick 
by 10 long and 5 to 6 wide. 



ZINC. 79 

DMtDatisa b TibM At the cdebuted zmc-worke of VieOIe Uontagne, near Ltige, 
Belgium, zino ore is distilled in tnbea. These tol^es are placed in rows in a shnting 
peeitiDni the; aiemadeoffire-daj, i metre inlengthbjiScentims.widUiEuidscentiais. 
fliidDMS (see fig. 37) , and dosed at one end ; Uie open ends are flosh with the &ont 
biiok-w«rk of the ftunace, in order that the charge of ore, Box, aud oaibcmB«eons matter 
maj- be introduced. Fig. 38 exhibits a csst-iron conically-shapad tabe, 25 centuns. 
long, and Fig. 39 a sheet-iron tube zo oentiins. long, both of which are 6tst«cied to tli« 



F». 37. 



Fio. 38. 






Fio. 4a 



fire-elay tnbe to reoeive the volatilised metal. A vertical section of the Belgian 
fiuiuee nsed for the distiUation of zino is Hhown in Fig. 40, with the mode of placing 
Ihe tubes, the closed ends of which rest on aproJeGtion of the brick-work. The ore is 
£nt calcined in a shaft-fumace, and the charging of the tubes usuallj takes plaoe 
aretj morning at mx o'clock, when the fire ia rather low. 
'*rS3.£^''" The zinc-sraelting as carried 
en near Sheffield, Birmingham, and in Wales and 
other localitiea, is performed b; downward dis- 
tilktioB. The furnaces represented in Fig. 41 
are constructed to contain six or eight fire-clay 
erndbles, oc, access to which is obtained through 
Wee mads in the fire-arch of the furnace. The 
bottom of each crucible is perforated and fitted 
wHh a tube to carrj off the volatilised zinc • 
Bering the time of charging t.hia tube is closecl 
with a wooden-plog, which is of coarse burnt 
dunng the strong ignition. At first (he cmdUes 
tie left open, hat as soon as a bluish fiome be- 
pns to show itaelf, the covers are put on. The 
omdaiaation-tnbe is then applied over a vessel 
•mtaining water to prevent the spirting of the 
metoL The zinc is nltimatelj refined by smelt- 
ing in iron cmcibles. 

*Mii«o|M^su There are two modes of ntU- 

0? iKSl DTtba ^^"i this zino mineraL In one 
^(■■A Mtom. plan the Eiilphiuet is flrtt roaited 
■> U to aonvert it into oxide, and then treated 
u before deseribed ; or the ore is direetlj applied 
bj oddiog a qnantit? ol iron ore sufficient to desol- 
fbiirin it, Uine being need as flni. Ihe iron ore, 
d eanlsining water or carbonic acid, ought to be 
Mloinad prerionity t« being used tor this purpose ; 
M instead of iron ore metolho iron is often nsed. 
W. Bvindella haa proposed to oaloina native 
siljphnret et nna with common salt, the remit beiiu 
and «hloiide of sine. The moes being liiiTiated with 

^^ d^staUisee, the chloride of zino remain* in eolation and u precipitated b; 11 
bnu, jifllding oxide of zinc. This oxide is treated for metal in the ordiuor; manner, tli 

*y^VmttitK. The colour ol line u bluish-white or grey; its eryBtalline stmctare 
<m«i according to its purity, and according to the temperature at which it was oast and 
"» Bwra or leas rapid cooling. Whan zinc is cast and rapidly cooled the specific gravity 




Fio. 41. 




m-j^.^. 



80 CHEMICAL TECHNOLOGY. 

U 7'i7Ei bat when dowlj eoc4ed it i» 7*145, and by humnering and luninftting xavj be 
increased to 7'Z and eT«o tj. A onbic foot of zino weighs therefore, from 360 to 390 Iba. 
Zine IB alightlf harder than tilver, bnt like lead and tin it is not fitted for filing, ■■ it 

cfaokea the teeth of the filaa. When pore, £ina ie eonoroaB ; it is k brittle mstal | ■mil 

•f a tfsrj sdmU abeolnte tenadtj, bat offers a great resistance to crashing weight, wbcai 
not nibjeeted to sadden blows. Teij pore zinc maj be hammered oat at the ordinarj ' 
temperatare, bat the malleabilitv ia greatest at tempera- 
tnrea between 100* and 150°. Zmc melts at 4.11° in tli* 
open air, and perfectly pore ziim melta in an atmospbere of 
hjdn^en at 410*. Aooording to UM. Troost and E>eTiUe 
zinc Tolatilises, air or oxygen being eidnded, at 104a*, and 
m^ be distilled ; when heated in oontaot with air to son' 
zinc bams, emittiag a very strong greenish blaa-ooloared 
light and forming oxide of lino (zino-white), wMoh is not 
Tolatile. Of all the metals need on a large scale, ziim h>a 
the highest coefficient of eiponsion by heat, its longitadinal 
ezpaoBion for temperatores from 0° to ioa° beiog for oast 
zinc i|„ tor sheet zino ,i,, oonseqaently molten xino 
greatly ODatracts while oooling. The malleability, tenacity ,Biid 
coheaive force of zinc axe greatly impaired by temperBtonaa 
ranging from r50° to 100*, at which zinc maybe polTeiisad. 
Si^jerheated steam oxi^ses Kino (Ha0-(-3n — ZnO+Hi), 
and this property is made ose of In the sepuatioD of this 
metal from lead. When exposed to a moist atmospb«r« 
zino is saperfioialiy oxidised, bat as the oxide adheres 
Btmngly to the metal farther corrosion is prevented. Zinc 
is so readily oxidised and acted apon by water, weak aoidj. 
And alkalies, that it ia not at all a saitable metal for Teaaela 
intended to hold potable liqaids or moist soUdi, as thsaa 
'-■^....^■i eabatances take np zinc and become poisonoas. An addi- 
tion of o'5 pei cent of lead renders zino far more malle«ble; 
bnt if the zinc ia to be need for the pieparatioil of brass, CTen 0*15 per cent of lead is 
injarioas, and for hraaa-makiiig Kino containing lead is avoided. Zinc often oantatna 
some 0-3 per cent of iron, bnt this does not impair the good qaalily ; the iron is oaiuJlj 
derived from the iron pota need for re-meiting the crude metal ; if, however, the qaantity 
of iron incressea the zinc becomes brittle and cracks. Zinc obtained from calunine ia 
Diaally porer than that obtained bom the native salpharet. The blaek reaidae remauiiiig 
when zinc ia dissolved in acids, and often mistaken for a carbnret of zine, if a miitore in 
Tarions proportions of iron, lead, and carbon. The more impare the zinc, the more 
readily it is dissolved in aoids ; bat by oarefal distillation zinc may be almost entirely 
freed from any foreign metals. In oontaet with iron zino prevents tbe oiidatiou of that 
metal. Zino precipitates copper, silver, lead, oadmiam, arsenic, atttimoiiy, and othe>* 
from their soLationB. 

^pUHtkB ai ziu. This metal ia very largely ozed for oovering roofs, making wNtar- 
spouts, tanks for holding water, and for vaiions architectoral pnrposea. It should bs 
bome in mind that for roofing purposes sine is in so far dangerous as to greatly inoreaoa 
the intenaity of fire shoald boUdings covered with zinc become ignited ; one instanse a( 
this danger was exhibited in Uarch, 1866, when the huge wooden baiJding then itandiitg 
in Iiown Eennington Lane, and used as a floor-cloth factory caaght Ore, the buming of 
the sbeeti of zinc covering the roof prodaoing a heat so intense as to ignite no leas than 
•ixtean adjaeent bosses, althoo^ these were from 20 to 30 yards from the baming ahed. 
Zine is need in galvamc-batterieH, in varions alloys, in chemical laboratories, and for 
galvanising iron wires, as well as for the preparation of zinc-white, aad for variooa 
ornament^ castinga. whioh are made in iron moalds previonsly thoronghly heated to 
prevent a too rapid cooling and contraction of the metal. ThePmssians make nse of sitie 
for oartridges. Tbe total annnal prodnction in Eniope of this metal amomited {1870) to 
2,154,000 cwts., of which England prodnces 150,000 cwts.; in the metropolis, Viailla 
Montagne (Belgiam) zino is almost eidosiTely used. 

Prepjuutiohs op Zinc. 
ziBC'wuit. Under this name tbere has doring the last fourteen years been bronght 
into the muket anbydroue white oxide of zinc, applied instead of white-lead as a 
pigment Zinc-white is prepared for this purpose b; oxidiung metallic zinc in fire- 



PREPARATIONS OF ZINC, 8i 

cIaj retorts, placed to the nmnber of 8 to i8, in a reverberatory furnace. As soon as 
these retorts are at a bright white-heat, cakes of zinc are placed in them, and the 
Taponrs of the metal on leaving the retort are brought into contact with « current 
of air heated to 300** ; oxidation results, and the oxide, a very loose, snow-white, 
floceulent material, is carried by the current of hot air into condensing chambers, 
and gradually deposited. The oxide thus prepared is immediately fit for use ; it is 
of a pure white colour, and very light. Zinc- white is also prepared by exposing 
metallic zinc to the action of superheated steam, hydrogen being at the same time 
evolved, and used for illuminating purposes, as at Narbonne, St. Chinian, G6ret, and 
a few other places, where it is known as platinum-gas, because the flame is used 
for imparting a white heat to small coils of platinum wire, thus producing a 
veiy steady and highly pleasant light. As regards the use of zinc-white as a 
pigment, it is rather more expensive than white-lead, yet according to some is 
a hotter covering material in the surfiBkce proportion of 10 to 13, that is to say, 13 parts 
by weight of zinc-white cover as much space as 10 of white-lead ; moreover, zinc- 
white is not affected by sulphuretted hydrogen. Like white-lead, this compound may 
be mixed with other pigments. By mixing Rinmann's green with it a green colour 
nay be obtained ; blue with ultramarine ; lemon-yellow with cadmium orange- 
yellow (sulphuret of cadmium). 

wuuTibioi.sidpiiat« Zinc-vitrioI (SZnO^+yHaO), sulphate of zino or white vitriol, is 
of Zinc. found as a native nunoral, as a product of the oxidation of rinc- 

blende ; it is also prepared by disRolving zino in dilnte sulphuric acid, and by roasting 
Dative zinc sulphuret. This vitriol occnrs in white agglomerated oryetals and in small 
aeicnkr-shaped crystals, as purified sulphate of zinc ; it is used as a *' dryer" in oil paints 
and varnishes ; as a mordant in dyeing for disinfecting purposes, and sometimes as a 
aonee of oxygen, since, on being submitted to a red heat, it gives off sulphurous acid and 
oxygen, oxide of zinc remaining. 

Qraaatoof ziae. This preparation, obtained by precipitating a solution of sulphate of 
zino with bichromate of potassa, is a very fine yeUow-coloured powder, used now and 
then in pigment printing, because it is soluble in anmionia, and thrown down again as a 
powder insoluble in water when that menstruiuu is volatilised. A basic chromate of zino 
ifl nsed as a pigment in the paint trade. 

cuoddt of Zinc. This compound of zinc, ZnCljf is obtained either hj dissolving zinc in 
hydrochloric acid, or more cheaply by causing the hydrochlorio acid gas given off in 
m a n u f acturing soda to act upon native sulphuret of zinc. By this action sulphxuretted 
brdrogen is formed which can be burned to produce sulphurous acid for the sulphuric 
iotd ehambers. The solution of chloride of zinc thus obtained is evaporated to the con- 
mteney of a syrup. 

Anhydrous chloride, of zinc is obtained by heating an intimate mixture of dried 
■nlpha^ of zino and chloride of sodium ; chloride of zinc is formed which sublimes, and 
•olphateof soda which is left behind (ZnS04-f 2NaCls=NaaS04+ZnCla). "^^^^^ anhydrous 
ehloride may be sometimes advantageously used instead of strong sulphuric add, for 
instance, in rape and colza oil refining, and perhaps, although it would be more expensive 
and less manageable, in the manufacture of garancine from madder. This chloride has of 
late been applied instead of sulphuric acid in the manufacture of stearic acid, and in the 
preparations of ether and parchment paper. Chloride .of zino in a strong and crude solu- 
tion is largely and very successfully used for preserving timber ; in paper making for the 
deeomposition of bleaching powder for bleaching the half-stuff and rags, and also in 
■izing the paper. The disinfectants sold as Sir William Burnett's Fluid and Drew's 
Biiinfeotant are solutions of chloride of zinc. The salt used in soldering iron, zino, 
P^vter, dte., is a compound of the chlorides of zinc and anunonium (2NH4Cl-|-ZnQ2) ; its 
solution is obtained by dissolving 3 parts by weight of zinc in strong hydrochloric acid, 
■nd adding after the solution is complete an equal weight of sal-ammoniac. Oxychloride 
^ zmo, obtained by mixing oxide of zinc with a concentrated solution of chloride of zinc, 
^ with solutions of chlorides of iron or manganese, has been recently proposed by 
V. Borel as a plastic mass suited for stopping hollow teeth. 



82 CHEMICAL TECHNOLOGY. 

Cadmium. 
(Cd=:ii2; Sp.gr. =8-6.) 

This metal is rather rare, and as yet of very limited use ; it is a constant companion 
of zinc in varying quantities, but is only found in the Silesian zinc ores in suificiency 
to repay the trouble of extraction. It was discovered as a distmct metal by Dr. 
Stromeyer, at Hanover, and Dr. Herman, at Schonebeck, in 1817. As A^S^ 
properties, AOilminnn stands between zinc and tin ; the colour and metalLc xuhue ot 
cadmium are similar to those of tin ; it is ductile and malleable, but more readily 
acted upon by atmospheric oxygen and moisture than tin. The specific gravity of 
cadmium is 8*6 ; it melts when quite pure in an atmosphere of dry hydrogen at 320°, 
and boils and volatilises (air and oxygen being absent) at 860^ to 746'2°. The cadmium 
sold by manufacturing and operative chemists and opticians is in small round bars, 
weighing from 60 to 90 grms. Silesian calamine ore contains about 5 per cent 
cadmium ; the same ore found near Wieslock 2 per cent ; the zinc-blende found at 
the Upper Harz contains from 035 to 079 per cent cadmium ; ziac-blende from 
Przibram, Hungary, 178 per cent; and the zinc ore of Eaton, in North America, 
about 3*2 per cent cadmium. Such ores give off, while being heated in the zinc 
furnace, a brownish-coloured smoke, consisting of carbonate of zinc and metallic 
cadmium ; this smoke, condensed separately, is used as cadmium ore, and reduced 
by means of charcoal, the materials being placed in iron retorts and the metal distilled 
over, next refined, and oast in the small bars mentioned above. The annual 
production of cadmium in Belgium from Spanish zinc ores amounts to about 5 cwts. ; 
while Silesia produces some 2 cwts. annually. 

Mixed with lead, tin, and bismuth, cadmium forms the so-called Wood^s alloy or fusible 
metal, consisting of cadmium, 3 parts; tin, 4; bismuth, 15 ; and lead, 8 parts ; this alloy 
fuses at 70^, and is used for stopping teeth, and for soldering surgical instruments. M. Hofer- 
Grosjean used as stereotype metal an alloy consisting of lead 50, tin 36, and cadminm, 
22*5 parts. The only preparation of cadmium technically used to any extent is the oad- 
xxdum-jeilowy Jaune hriiliant (CdS), sulphuret of cadmium, applied as a pigment in oil 
painting, and in pyrotechny for producing blue-coloured flames. This preparation is best 
obtained by precipitating a solution of sulphate of cadmium with snlphuret of sodinin, 
and then thoroughly washing, pressing, and drying the precipitate. Dr. Van Biemsdijk of 
the Utrecht IMQnt, while experimenting with cadmium and zinc, both pure and kept fused 
in an atmosphere of pure dry hydrogen, found that these metals, though perfectly non- 
volatile at their point of fusion, and while kept fluid at that temperature, became percep- 
tibly volatilised at a few degrees above this point. 

Antimony. 
(Sb=i22; Sp. gr.=67i2.) 

Antfawmy. This metal, also named stibium, is chiefly found in combination with 
sulphur as black antimonial ore, or glass of antimony, containing 71*5 per cent of 
metallic antimony, formula (Sb2S3), in veins interspersed among granite and 
metamorphio rocks. Antimony also occurs as oxide (Sba03) in the minerals known 
as Yalentinite (rhombic) and Senarmontite (tesseral), this last variety being found in 
large quantities in Constantine, Algeria, and in Borneo. The black sulphuret of 
antimony is separated from the gangue which contains it by the application of heat, 
as the sulphuret is very fusible. 

The operation is carried on at Wolfsberg, near Harzgerode, Germany, by placing the 
broken up ore and gangue in crucibles, b (Fig. 42), perforated at the bottom, and placed 
on a smaller orudble, c, surrounded with hot sand or ash. The waUs are oi 



brickirork, lo conEtracted with openings for oaiiamg a drangbt 
beat to the, upper cmoible. Wood ' " ■- -' '- -■' 

in Honguj, the apparatuB exhibited i 
will be Been the principle Ib the same, 
bnt bet. the cmcibleB containing the 
ore, and the teoeiiing araciblea ontEide 
the fnniaoa, and comieoted i>j means 
' -' " h the inside oruoibles, are 
of ft pore ^Uy placed. The liqua- 
uoa ol lu^ ' rather fnsible antimon; 
CIS ii most readilj and conrenientl/ 
performed in the hearth of a pecnliarlj 
moBtnieted reverberator; fnmace, ex- 
hibited in Fig. 4j ; the main point of 
the arroogemeut of the hearth being 
Ihat the molten black sulphniet, col- 
lected at the lowest level, ranB thiongh 
the spoot, e, to the reeeiier, /, placed 
•mtnde the famace. At Gist a mode- 
rate heat miGoea, bat to wards the latter 
}>irt of the operation a stronger heat 
u Tsqnired to eliminate all the snl- ' — - 
Fhuet. I'he opening at / ia now 
cioaed with a ping. Not tmtil the gangne becomes sei 
vhsn the haarier enlphoiet oollected under the slag is 
«/■ 





Metallic intinlotiy ia obtained from the black sulphuret either by roasting or hy 
nnelting it with BOitable fluTes In the former inBtance th? suJphuret is placed on 
the hearth of a reverberatorj furnace and continuously etured, while a supply of air 
w Kteaa to the molten masa ; the cBlcination is continued until the bulk of the ore 
'iscoDrerted into antimoniate of antimony-oxide. This material, also known as 
■iilunDiu^ aah, is rednced to metal in crucibles, and for the reduction heat alone 



84 CHEMICAL TECHNOLOGY. 

would answer, as the calcined ore always contains nndecomposed snl^nret of 
antimony, (3 Sb408+ 481)283 »2oSb+i2S02); but as some oxide of antimony would 
be lost by volatilisation, the crude antimonial ash is mixed with crude argol or 
with charcoal-powder and carbonate of soda. A strong red heat is sufficient for the 
reduction, and it is customary to allow the metal to cool slowly under the super- 
natant slag, in order to obtain the peculiarly crystalline appearance desired in 
metallic antimony in the trade. 

By another mode of operation the sulphnr is first removed from the black solphiiret by 
means of iron, but which, if used by itself, presents a difficulty arising from tiie almost 
equal specific gravities of the metallic antimony and snlphuret of iron, rendering the sepa- 
ration of these substances too imperfect to admit of the use of iron alone ; consequent^, 
either carbonate or sulphate of soda or potassa is added, which tends also to increaae the 
fluidity of the slag. 100 parts of black sulphuret of antimony, 42 parts of maUeabb 
iron, 10 parts of dry sulphate of soda, and 3^ parts of charcoal powder are the pro- 
portions. In order to eliminate the arsenic from the metallic antimony thus obtained, 16 
parts are taken, and there are added 2 parts of protosulphuret of iron, i of solphuret of 
antimony, and 2 of dry soda; this mixture is kept fused for fully one hour's tiiDB, 
the resulting metal is next fuseid with li parts of soda, and a third time with z part 
of soda, until the supernatant slag attains a bright yellow colour. 

Properties of Antimony. The metallic antimony of commerce is never quite finee from 
arsenic, iron, copper, and sulphur ; the influence of these impuritieB on the physical 
properties of antimony is not well ascertained, as those of chemically pure antimony 
are not well known. 

Antimony may be purified by fusing it with oxide of antimony; the snlpbur 
and iron are oxidised and some of the oxide of antimony reduced to metaL For 
pharmaoeutical purposes antimony is purified by the addition to the molten metal of 
pure saltpetre, but this process is attended with a loss of antimony. Antimony pos- 
sesses a nearly silver- white but slightly yellowish colour, strong metallic lustre, and 
a foliated crystalline structure ; it crystallises like arsenic and bismuth in rhombcidio 
crystals. The specific gravity of antimony is ^6'ji2; it melts at 430^ the pura 
metal fuses at 450"*, and, according to Dr. Duflos, does not expand on cooling. 
Antimony is volatilised, air and oxygen being excluded, only at a bright white heat 
It is a very brittle metal, neither ductile nor malleable, but harder than copper. 
Antrmony forms alloys readily, imparting to them some of its own brittleness and 
hardness; it is, therefore, added to tin, lead, and pewter, in small quantities, 
to render these soft metals hard. As antimony is not readily acted upon by air, it 
has been suggested to electrotype copper with a thin layer of this metaL The 
powder sold as ironblack, and used to give to papier mache and plaster of Paris 
figures the appearance of polished steel, is finely divided antimony, obtained by preci- 
pitating that metal from its solution in an acid by means of metaUio zino; thia 
powder is also used to impart a lustre to cast zinc ornaments. The chief uae made 
of antimony is as an alloy for printing type, which usually consistB of 4 parts of 
lead and i of antimony with a small quantity of copper. Antimony also enters mio 
the hard so-called anti-friction alloys used for the bearings of machiDery. 

Antimonial Preparations in Txchnical Ubb. 

Oxide of Antimony. This substauce (Sb^OO, obtained by calcining sulphuret of antimony, 
or by the precipitation of a solution of chloride of antimony with a solution of earbonate 
of soda, finally washing and drying the precipitate, has of late been used as a subsytufee 
for white-lead, but does not cover so well and is more expensive, though it is not affeotad 
by sulphuretted hydrogen. As this oxide takes up oxygen in the presence of alkalies, and 
is converted into antimonio acid (SbaOs), it has been lately proposed for use in the prepa- 



ABSENIC. 85 

ration of anOine red and for the oonversion of nitrobensol into aniline; also for the 
pzeparation of iodide of caloixun bj keeping antimonio oxide suspended in milk of lime, 
and adding iodine as long as the latter is taken up. 

BiMk sniphnnt This oompoond (SbaSs), obtained by liquation, ooours in oommeroe in 
of AnUmaaj. ^jj^ oonical shapo it has assumed while oooling; its colour is like that 
of graphite, but it has a stronger metallic lustre, is of a deeper black colour, fibrous, 
OTstalline structure, and veiy brittle; it usually contains iron, lead, copper, and arsenic, 
and is employed for separating gold from sUyer, in yeterinary surgery, pyrotechny, and in 
the preparation of the percussion peUets used in the cartridges of ike now celebrated 
Pnusian needle-gun. 

^ HMpoWaB T«Dow. This pigment, used as an oil paint and in glass and porcelain staining, 
is of an orange-yellow colour, and very permanent. It is antimoniate of oxide of lead, 
and is prepared as follows : — i part of antimonio-tartrate of potassa (tartar emetic), 
3 parts of nitrate of lead, and 4 parts of common salt, are fused at a moderate red heat, 
and kept at that temperature for 2 hours. The molten mass is put after cooling into 
water and becomes disintegrated, the salt dissolved and the pigment precipitated. When 
required for staining glass or porcelain it is mixed with a lead-glass, and has recently 
been prepared by roasting a mixture of antimonious acid and litharge. 

iaOmeuyaaaMbu. Oxysuphuret of antimony (SbeSeOs), is a compound in colour similar 
toTermillion, and is obtained by causing dithionite of sodium or calcimn to act upon proto- 
cUoride of antimony in water, and boiling this mixture, a precipitate being readily 
deposited ; it is a soft, yelvety powder, unaltered by the action of air and light, and suited 
for either oil- or water-colour. This substance may be prepared on a large scale by the 
following process : — ^i.) Black sulphuret of antimony is calcined in a current of air and 
rteam, antimonio oxide being formed as well as sulphurous acid, which may be employed 
for the preparation of caldum-dithionite from soda waste; the antimonic oxide is 
next diflsolyed in crude hydrochloric acid. (2.) Large wooden tubs which admit of being 
internaUy heated by steam, are for }ths of their capacity fiUed with the solution of 
«Ueiimi dithionite, and the solution of protochloride of antimony is gradually added, the 
Hqnid being stirred and heated to about 60** ; the reaction soon ensues, and the precipitate 
having subsided, is thoroughly washed and dried at a temperature not exceeding 50°. 
There are prepared on a large scale, by operative pharmaceutical and manufacturing 
chemists, numerous varieties of antimonud preparations, among which are severid 
ralphurets and one oxysulphuzet, different from the preparation here mentioned. 

Absenic. 
(Afl = 75 ; Sp. gr. = 5'6.) 

AiMBk. Arsenio oocnrs in the mineral kingdom either native or in oombination 
viih sulphur. Although a few minerals are found containing arsenic in a state 
of oxidation, the quantity is so small that their technical utUisation for the obtaining 
of arsenical compounds is altogether out of the question. Metallic arsenic is a 
BoHd, crystalline, steel-grey coloured substance. It is prepared either by the subli- 
nation of the native metal, or by the ignition of arsenical iron pyrites (FeS^-f FeAss) 
tnd of arsenical pyrites (Fe4As6), or by the reduction of arsenious add 
(AstOj-f 30=:3G04-Asa). Metallic arsenic is met with in the trade in an impure 
state, often containing no less than 10 per cent of sulphuret of arsenic, in the form of 
gnyiah-bkck coloured crusts and lumps, known as fly poison. Pure metallic arsenic 
is nrdy employed ; a small quantity is used in the manufacture of shot, and in pyro- 
techny for white Bengal fire, which gives a very brilliant light, but should only be 
Ignited in the open air. Lastiy, arsenic burnt in oxygen gas is used as signal lights 
^ the Trignometrical Survey Service. 

A«"i*»MAflid. The substance known as white arsenic is really arsenious add, AS2O5, 
•iid obtained as a by-product of a great many metallurgioal operations, for instance, 
the roasting of cobalt ores for smalt, of tin and silver ores ; the volatilised add is 
condensed by conducting it through channels into wooden chambers. In some 
"^•BtieB, as in Silesia, where fuel and labour are cheap, arsenical pyrites is 
P'UT^^^ly calcined, and the crude arsenious add obtained is refined by another 



86 CHEMICAL TBCHHOLOGY. 

Bublimatioii process. For this purpose tbe cast-iron vessels, a, Fig. 46, annsed.npon 
which are placed iron rings or collars, 6, c, d, and a hood, e, conunonicating by means 
of tubes with a series of chambers, of which the first only is shown in i. Tha 
flanges of the oast-iron collars and all other joints having been thoronghly Inted, the 
fire is lighted and the heat so increased as to 
'"*■ 46' icause tha Hemi-fusion of the arsenioDs acid, 

which after cooling exhibits a peculiarly porce- 
lain-like appearance, at first being as trane^iareiit 
as glass and very pimilar h> fused anhydrona 
phosphoric acid. 

This contponnd, like nU arsenical preparationa, 
is veiy poisonous ; but it is a remarkable fact, 
proved by direct experiment, that pnre metallio 
arsenic introdoced into the stomach of rabbifs 
and other small animals in a finely divided 
state, by the aid of pure water freed from air, 
docs not act on them as a poison, being foimd in 
their ficces unaltered. The commercial ariicle is 
sometimes more or leas mised with oxide of 
antimony and eulphuret of arsenic. Aiseniooa 
acid is need in dying and calico-printing, in 
gless-maldng, for the pnrpoae of clearing the 
molten glass, for the preparation of other 
arsenical compounds and pigmeots, and farther 
in arsenioal soap for tlie preservation of stuffed 
animals. The air in muBeoms is sometimes 
poisoned by arseniuretled hydrogen being evolved 
if the arsenical compound has not been properly 
prepared; and in places where there are large 
collections of stuffed animals there should 
always be a good ventilation and a dry atmosphere. Arsenioua acid is also employed 
in the manufactnre of aniline. 

Amiaidi This add (H,As04) has become an article of large consnmption. 
It is obtained by boiling 400 Mlos. of araenions acid in 300 HIob. of nitric or nitro* 
hydrochloric acid, and evaporating the solution to dryness. Recently it has 
been prepared mora cheaply by passing chlorine gas into water wherein arsenioiUi 
acid ia suspended, and evaporating this solution. Arsenio add is aometimeB 
employed in calico-printing instead of tartaric acid, and is very largely used in the 
preporadou of rosaniliqe or fschidne. some manufacturers of these dyes annually 
consuming zooo cwta. 

The acid arseniate of soda, so-called dungsalt, now used instead of cows'-dung in 
certain oalioo-printing operations, and consisting of 2j parts of soda and 75 of 
arsenions acid, is prepared by heating for a length of time, either 36 parts of 
^Tsenions acid, and 30 parts of nitrate of soda, or a mixture of arsenile of soda and 
nitrate of soda. This salt is obtained as a by-product of the preparation of aniline 




from nitrobenzol. 
Bnipiunii Di Annb. There a 
realgar and orpiment 



i two Bulphorets of a: 



c employed indnstriaUy, vi?., 



QUICKSILVER, OR MERCURY. 87 

Bed arseme or realgar (AS2S2) is found native in a orystalline state and among 
other ores. It la artificiidly prepared oy fusing together sulphur and excess of either 
metaUie arsenic or arsenious acid, or on a large scale hy <Hstilling arsenical pyrites 
and ores containing sulphur. Bealgar is a ruhy-red coloured substance, exhibiting a 
conehoidal fracture. Its use in pyroteohny is based upon its property of yielding, when 
mixed with saltpetre and ignited, a brilliant white light. This mixture is known as 
Bengal white light, and is best prepared with 24 parts of nitrate of potassa, 7 parts 
of salphur, and 2 parts of realgar. 

oipiBCBL Auri pigmentumt yellow snlphuret of arsenic (AS3S3), is likewise found native, 
but is generally art&cially prepared by fusing together eiuier sulphur and arsenious acid 
or realgar and arsenious acid. This sulphuret is of a bright orange-colour, somewhat 
transparent; it contains, if prepared by the dry method, free arsenious acid, and 
may therefore be considered as arsenoxysulphuret. It is also prepared by pr^ipitating 
a hydrochloric acid solution of arsenious acid by means of sulphuretted hydrogen, or by 
decomposing a solution of the double sulphuret of arsenic and sulphuret of sodium with 

BoBBA. dilute sulphuric acid. Orpiment is used in dyeing to reduce indigo, and to 
prepare what is termed rusma, a paste applied in dressing slmiB in order to remove the 
bair, and which consists of 9 parts of Ume and i of orpiment mixed with water. This 
paste is also employed in the toilet to remove superfluous hair ; but instead of this very 
poisonous compound, either the spent lime from the purifiers of gasworks, or the 
sulphuret of lune solution obtained by passing a current of sulphuretted hydrogen 
through milk of lime, may be advantageously used. 

Quicksilver, ob Meboury. 
(Hg=aoo; Sp. gr.=i3-5.) 

omotmmii^ This metal is not met with so generally dispersed as silver and gold. 
v«Koi7- It occurs in the following forms: — 'i. Sparingly in the metallic state 
interspersed in globules through the gangue, and in small qiuintitids in mercury 
mines, sometimes containing sOver. 2. As a sulphuret, known as cinnabar, HgS, con- 
taining 86*29 of metallic mercury and 137 1 of sulphur. This ore is met with among 
primitive as well as metamorphic and sedimentary rocks, and is often accompanied 
by sulphuret of iron, while the gangue or matrix is generally quartz, calcareous 
spar, or spathic iron o^e. The richest mercury mines are those of Almaden 
and Almiidenejas in Spain, which were worked at a remote period of antiquity, and 
next are those of Idria, Carynthia. Cinnabar is found also in the Ehenish Palatinate, 
at Olpe in Westphalia, Horzowitz in Bohemia, in varions parts of Hungary, at 
Vall*alta in Venetia, in the Oural, in China and Japan, in Borneo, Mexico, at 
Huancavelica, in Pern, and in considerable quantities in California, where mercury ia 
largely produced. 

Among the less important mercury ores is found the so-called liver-coloured ore, a clay 
mixed with cinnabar, bitumen, paraffine, and ooaJ-slate. This ore is only met with in 
GaiynthiA. There is also the fawn-coloured mercury ore, containing 2 to 15 per oent 
of merooiy, with sulphur, copper, and other impurities, llie annual production of mer- 
eory throughout the globe amounted in 1870, to 84,500 ewts., of which California yields 
56,000 against 22,000 from Spain. 

Uercnry is extracted from its chief ore, cinnabar, by : — 

1. Calcination in shaft furnaces, the mercurial vapours being condensed in chambers con- 
stmeted either of brick-work or boiler-plate, or in earthenware vessels (Aludels) joined 
together by flanges similar to earthenware drain-pipes. 

2. By decomposing cinnabar in closed vessels, the ore being mixed with either lime or 
forge scales. This method is usual in Bohemia and the Bavarian Palatinate. 

Mrthodof Extzveunir The coutrivances in use in Idria for the extraction of mercury 

HemrTpnnaed *^ 

tn JitiM. from i\s ores are illustrated in Figures 47, 48, and 49. a is a cal- 

cination famace, which is flanked on each side by a series of condensation chambers, 
c c D, communicating with the furnace. The ore is placed in lumps on the perforated 
^ches, n n', of the furnace, and the space v completely filled. On the arch, p p\ the 



8S 



CHEMICAL TECSNOLOQY. 



smollei lumps of ore are plooed, and on r r, &e dust, pnlTernlent ore, utd reaidneB 
of former operations. This having been done the ftiel, commonly diy beechwood, is 
ignited on the Airnaoe-b&ra. The heat is gradual); raised to and kept at a dark red 
heat for lo to 12 hours. The dranght created carries into the fiimaoe enffioietit air 

Fio. 47. 




to convert the Bolphur of the Tolatjlised ore into Bnlphnnnis add and set t]ie 
mercury free iHgS-f 20=S0i4'Hg). The products of die combustion are earned 
into the chambers, c. The bottom of each chamber is made of etrongl; piesaed day, 
shaped so aa to form two planes inclined towards each oiher, and connected 
trilh gutters leading to a reservoir cut out of a solid block of porphyry in which the 
ipercury is collected. A jet of water is made to play constantly in the last conden- 
sation-chomber, in order to keep it and the adjoining smoke-chambeis, d d, quite cool, 
the last traces of mercury being condensed in d s. 



QUICKSILVER. OR MERCURY. 89 

Mil* HfH™* ■■ ^^ BRangement for oondensiiig the meronrial Taponn in tue 
•'^'■"■* ""••^- «t Almadea is exhibited in Fig. 50. It oonsiBts of a atring of pear- 
ihqied vessels open at both ends. Theae vewels, locall; known bj the Arabian t«rm, 
AhtdtU, ara made of Mtrthenware, and so constructed that the narrow end of one fits 
into the wider end of the olh«r, care being taken to Inte the joints with da;. The 
mode of arranging these rows or strings of (Judela is delineated in Fig 52, 
which represents the plan of the famace shown in Fig. 51. This fnmaoe oonsista of 






Fio. 5*. 






( — ■ — -^ 

t %^^ 


-J^"^ 




F^ 
p, 




II iiMiil \m- 


1 






Wi®/, 







• cj-lindrical shaft oven, which b; means of a perforated arch, is divided into two 
fWls. The fire is lighted in the lower part of the shaft, while on the perforated 
ttch is fint placed a layer of sandstone containing oinnabar, in qoantitiee too email 
to admit of being otherwise advantageoual; treated. He rich ore ia then placed on 
this layer of stone, and the openinga in the arch of the furnace covered with tiles 
ud tightly luted. The meronrial vapours aie first conducted into the spsoo 
«c, and thence through the twelve rows of aludels, each row having a length of from 
30 to 21 metres, and containing 44 aludels. The aludels are placed on a somewhat 
inclined plane as shown in the woodcut. At/the coudeiksed mercurj is ran off by 



90 CSEMICAL TECHNOLOOY. 

the gutter, g, into die stone cistoms, kh; the vaponrs not condensed being carried 
on to the chamber, b, where the; are completely liquefied. The smoke escapes 
through a chimney at b. As the mercuiy thus abtnined is mixed iritii Boot it has to 
be purified and cleansed ; this is effected by causing the metal to flow down an 
inclined plane, to which the soot adheres. The sooty mass and the impuritiea 
collected in the room &, are submitted to distillation for the purpose of extracting the 
last traces -of mercuiy. The quantity of ore operated upon at each calcination 
amoonts to 250 to 300 cwts. Spanish mercury is met with in the trade packed 
in wrought-iron canisters or in sheepskin bags. The apparatus above described for 
separating mercuty from its ores was invented by the Moora, who for several centu- 
ries were the only civilised inhabitants of the greater portion of southern Spain. 



>u in. Di uu ui « Method oJ meroury distillation pursued t,t Honiowitz in Bohemia. 
Hbei aubnuKca. The Bulphuret of mercury is mixed with trom 1 to | of its wei^t of 
foige-scole, and themiiture placed on the iron plates, b b. Fig. 53. These plates are fixed to an 




ifon rod, and covered by the iron oapola, e r, vhich reels in a tank filled with water. 'Hie 
onpola is removable from the furnace by means o( the frame g. The metal is oolleotad 
in the water at d. Each cupola oovers about ) cwt. of ore and i ewt. of forgo-seale, and 
there are generally sli cupulas in one furnace. The operation lasts for 30 to 36 hooTH. 

In the Bhenish Palatinate mercury baa hecn extracted from ita ores since 1410. It is 
there usual to mix the mereiuy ore with other metallic ores, that mainly worked being 
ohuabar interspersed in Bondatone. The decompoaition of the ore, which is a rather 
poor material, can lie made to pay only by Rkilfal management. The ore ia mixed with 
lime and placed in iron retorts, very aimilar to those need in gas-works, and heat having 
been applied the cinnabar is decomposed, the result being the formation of metallio 
meromy, which volatilisea and is condensed in suitably -co Dstrncted receivers, while there 
remains in the retorts a mixtnru of sulphuret of calcium and bypoaulphtte of lime. The 
operation lasts ten hours, after wbicb the contents ol the receivers are poured into 



PREPARATIONS OF MERCURY. gi 

earthenware tanks filled with water ; the mercury sipkB to the bottom and the water is 
allowed to ran off, carrying with it a blackish powder, consisting of finely-divided mercury 
mixed with a Yolatilised black snlphide, which is again snbmitted with lime to another 
distillation. 

p)rap«rtiM of Meieiiry. Mercnry is the only metal remaining fluid at ordinary temperatores. 
It freezes at — sg'S^'t and is in that state a malleable and dnctile metal. At 360'' it boils, 
and at a slightly higher temperature distils over, but is yolatilised to some extent at all 
temperatures above its freezing-point, as may be proved by suspending a piece of gold-leaf 
in the neck of a bottle containing a small quantity of mercury. Mercury readily combines 
at ordinary temperatures with various metals, forming what are termed amalgams. 
The ftTnftig«^Tng most readily formed are those of lead, bismuth, zinc, tin, silver, gold ; 
next is that with copper, while with iron, nickel, cobfdt, and platinum, mercury vdll only 
amalgamate with difficulty. The application of mercury in metiJlurgy in the extraction of 
gold and silver from their ores is based upon the property mercury possesses of readily com- 
bining with these metals. Amalgams of various lands are industrially employed, as, for 
instance, witli tin for covering mirrors and looking-glasses, vrith gold for the so-called 
process of fire gilding An amalgam of 4 parts mercury with 2 parts zinc and i part tin is 
used for the cushions of electrical machines. 

Appifcatioiu of MereniT* By far the most extensive application of mercury is in the con- 
Etraction of various physical instruments, for filling the mercurial gauges of steam-boilers, 
and on the Continent these gauges are attached to all boilers, locomotive engine-boilers 
alone excepted. Mercury is employed in the preparation of a variety of compounds, 
among which is the fulmmate of mercury ; and, further, for various purposes in chemical 
and physical laboratories. More recently, an amalgam of mercury and sodium has been 
veiy successfully used by Bir. Grookes in the metallurgical extraction of silver and gold ; 
tod a solidified amalgam of the same metals is recommended to facilitate the transport 
of mercury, the amalgam admitting of being very readily decomposed by treating with 
dilute sulphuric acid. « 

Prepajutions op Mercuby. 

Mttevtat oompoandi. The moTB important mercurial compounds which are manufac- 
tured on the large scale are the following : — 

Mamie oiiioiide. The substauce commonly known as corrosive-sublimate is the per- 
chloride of mercnry, HgCl, equivalent =135^ consisting, in 100 parts, of 73 '8 parts of 
mercury and 26' 2 parts of chlorine. It is prepared either by sublimation from a 
mixture of sulphate of peroxide (red oxide) of mercury and common salt, or by dis- 
solving the same oxide in hydrochloric acid, and also by boiling a solution of 
chloride of magnesium with the peroxide (MgCl«-(-HgO=HCl-(-MgO)'. When 
fmblimed, this salt forms a white crystalline mass, which fuses at 260°, boils at 290% 
is soluble in 13*5 parts of water at 20°, and in 1*85 parts of the same liquid at loo^ 
It is more readily dissolved by alcohol, i part of the salt requiring only 23 parts of 
cold and 1*18 parts of boiling alcohol. Mercuric-chloride has been industrially 
employed as a preservative for timber by Mr. Eyan, and is used in the manufacture of 
tniline-red, in dyeing, and calico-printing, in etching on steel-plates, and for the 
preparation of other mercurial salts. Lately, the use of the double salt, HgGla,2KGl, 
obtained by boiling chloride of potassium with peroxide of mercury, has been sug- 
gested as a preservative for timber. It should be borne in mind that this preparation 
of mercury is extremely poisonous and easily absorbed by the skin of the hands. 
oaaaim. Under this name is designated the mercuric-sulphide, HgS, which occurs 
native in crystalline or compact red-coloured masses, and was known in Pliny's 
time by the term minium.* The cinnabar, or vermillion of commerce, used as a 
pigment, is always artificially prepared either by the dry or wet way. By the former 
process 540 parts of mercury and 75 of sulphur are very intimately mixed. The 

* Bed-lead, afterwards called minium, was, as far as it appears, unknown to the 
tfkcients, being first prepared by the Arabs and Saracens. 



92 CHEMICAL TECHNOLOGY. 

eiLEniiiig blaok-oolonred powder is introduoed into iron veseels, and exposed to a 
moderate heat so as to cause the fusion of the mass, which, after cooling, is broken 
up and then introduced into earthenware and loosely closed vessels, heated on a 
sand-batii. The sublimed mass is of a cochineal-red colour, exhibits a fibrous 
fracture, and yields when pulyerised a scarlet powder, which is the more beautifal 
the purer the materials used in its preparation and the greater the care taken to avoid 
an excess of sulphur. Some chemists allege that a greatly improved veimillion is 
obtaiued if i part of sulphuret of antimony is added to the mixture of sulphur and 
mercury previously to the sublimation, and the sublimed and pulverised mass placed 
in a dark room for several months and treated with either dilute nitric acid or oaustic 
potassa. According to Dr. J. von Liebig, vermillion is obtained in the wet prooees 
by treating the white precipitate of the pharmacopoeia, or hydrargyrum amidato 
Mchloratumf according to the formula, HgGl,HgNHs, which corresponds to the term 
used, but in Dr. A. W. Hofmann's opinion, does not express the true composition of 
the compound. He considers white precipitate to be a chloride of ammonium, in the 
ammonium of which 2 equivalents of mercury have taken the place of 2 equivalents of 

TT* Other chemists, again, hold different views as to the 

constitution of this body, which has been used in medicine since, if not before, the 
time of Paracelsus. Vermillion is generally obtained by precipitating a solution of 
corrosive sublimate in ammonia with a solution of eulphiir in sulphide of ammonium ; 
or, according to Dr. von Martins, by agitating, in a suitable vessel, i part of 
sulphur, 7 of mercury, and 2 to 3 of a concentrated solution of liver of sulphixr. 
According to M. Brunner's method, by which decidedly the finest vermillion is 
obtained, 114 parts by weight of sulphur and 300 parts by weight of mercury are 
mixed, with the addition of a small quantity of caustic potassa solution, and incorpo- 
rated by being shaken by machinery. The resulting black compound is next treated 
with a solution of 75 parts caustic potassa in 400 parts of water, and heated on a 
water-bath to 45°. The mixture assumes a scarlet-colour after a few hours, and as 
soon as this is apparent the semi-liquid mass is poured iato cold water, next collected 
on filters, washed, and dried. The vemullion of commerce is often adulterated with 
red-lead, peroxide of iron, chrome-lead, and more frequently with firom 15 to 20 per 
cent of gypsum. These adulterations are, however, readily detected, as they are left 
behind when the vermillion is sublimed. Red-lead, one of the most usual adultera- 
tions of vermillion, can be readily detected either by treating a small quantity of the 
suspected sample with nitric acid, when in consequence of the formation of puce- 
coloured peroxide of lead, the mass assumes a brown colour, or by the addition of 
hydrochloric acid, when chlorine is given oflf. Pure cinnabar is completely and 
readily soluble in hydrosulphuret of sulphide of sodium (NaSH). 

FaiminAting Marearr. The oompound known as fulminating mercury is a combination of . 
fulminic acid, an acid unknown in a free state, and of oxide of mercury ; its formula may 
be written GaHgaNaOa. In 100 parte it consists of 77*06 of peroxide of mercury and 
23'94 of fulminic acid. According to the late Br. Gerhardt^s view, this body is a nitro- 
compound which may be regarded as cyan-methyl, the hydrogen of the me&yl of which 

hasbeenreplaced by hyponitrio acid and mercury ; the formulais then : C | S5* | ,CN. This 

substance was first discovered by Mr. Howard, and was known, until Dr. von Liebig gave 
the clue to its nature, as Howard^s detonating powder. It is prepared on a large scale in 
the following manner. First, 2 lbs. of mercury are dissolved, by the aid of a gentle heat, 
in ro lbs. of nitric acid (sp. gr. 1-33), and 10 lbs. more of nitric acid are then added. The 
resulting fluid is poured into six tubulated retorts, and to the contents of each retort is 



PREPARATIONS OF MERCURY. 93 

added 10 litres of alcohol (ap. gr. 0*833). I' ^^^ ixigredients are mixed by measure instead 
of weight, for every volome of mercury, there is taken 7^ volumes of nitric acid, and 
10 volumes of alcohol. After a few minutes a strong evolution of gas takes place, and at 
the same time a white precipitate, the fulminate of mercury, is formed. The retorts are 
fitted with tubulated receivers, from which glass tubes carry off the very poisonous gas 
and fumes, either to a flue or directly to the outside of the shed in which the operation is 
performed. The precipitate is collected on Alters, and washed with cold water to 
eliminate the free acid. The fulminate is next dried, filtered, and all being placed on 
plates of copper or earthenware, heated by steam to less than 100^. 100 parts of mercury 
yield in practice from 118 to 128 parts of fulminate, while, according to theory, 
142 should be obtained. The dried fulminate is, with caulious manipulation, divided into 
flnall portions, kept separately in a paper bag. The fulminate thus prepared is a crystal- 
lioe white-coloured substance, which, by being heated to 186°, or by a smart blow, explodes 
with a loud report. When placed on iron and struck with an iron instrument, the 
detonation is much increased. This substance also explodes by contact with concentrated 
sulphuric acid. When mixed with 30 per cent of its weight of water, the crystallina 
fulminate may be rubbed to powder with a wooden pestle on a marble slab. The manu- 
laoture of this substance on a large scale requires peculiar arrangements, into the particu- 
lars of which we cannot here enter. 
peRudon-OBpii. The fulminate of mercury is chiefly used for filling percussion-caps. 
For this purpose 100 parts of the fulminate are rubbed to powder with 30 parts of water, 
50 to 62-5 parts of saltpetre, and 29 of sulphur. This mixture is dried sufficiently to 
admit of being granulated, after which it is forced, by means of machinery, into the 
copper caps, and simultaneously covered with either a layer of varnish or tin-foil, to 
protect it from damp. Tin-foil being more expensive is not used for military gun-caps. 
The best varnish for the purpose is a solution of mastic in oil of turpentine. The caps 
are finally dried by a gentle heat, and packed in boxes. One kilogramme of mercury 
eonverted into fulminate suffices for the fiUing of .40,000 gun-caps of the larger or military 
size, and for 57,600 caps of the size used by sportsmen. 

Platinum. 
(Pt=i97*4; Sp. gr.=3i'o to 230). 

oecanvDeeofFifttiBim. This metal IB Only found native, and then not very abundantly, 
in platiQum ore, more especially met with in the alluvial deposits of South America 
and the Oural, in grains of a steel-grey colour and metallic lustre. More recently, 
granules of metaUic pladnum have been found among the gold- washings in Galifomia, 
the Brazils, Haiti, Australia, and Borneo. A very short time ago this metal was 
discovered in Europe, interspersed in rocks situated in the parish of Koeraas, in 
Norway, and it is reported to have been found in the lead-mines near Ibbinburen, in 
Westphalia. Dr. Pettenkofer states that a proof of the for greater dispersion of 
platiaum than is generally supposed lies in the fact that all silver contaias a 
small quantity of platinum. The metal has also been found to accompany some of 
the copper and antimony ores of Timor and New Guinea. Platinum was disoovered 
in South America by the Spaniards, who, believing it to be an inferior silver, gave it the 
diminutive j)2atina of the Spanish name for silver, plata. It was brought firom 
Jamaica and made known in Europe by a Mr. Wood in 1740, and somewhat investi- 
gated in 1767 by Dr. R. Watson, then Professor of Chemistry at Cambridge. 
Br. Scheffer, Director of the Mint at Stockholm, was the first who thoroughly inves- 
tigated the various physical and chemical properties of this metal in 1752 ; but as hia 
researches were published in the Swedish language, they remained comparatively 
unknown in this country. 

iiiiiBaiii orw. The substanoG met with in commerce under the name of platinum ore, 
or crude platinum, is a mixture of a variety of metals, among which the following 
predominate: — ^Platinum, palladium, rhodium, iridium, osmium, ruthenium, iron, 
copper, lead, and frequently granules of osm-iridium, gold, chrome-iron ore, 



94 CHEMICAL TECHNOLOGY. 

titaniTim-iron ore, spinel, zircon, and quartz. The reason why this ore is found in 
alluvial soil is, that the rocks originally containing the ore having heen disintegrated 
by water, it is carried off by the streams and water-courses. Boussingault found, 
when travelling in South America, a seam of somewhat weathered syenite containing 
the platinum ore yet in situ ; while, as regards the Oural, it has been proved by 
Pallas that the ore was originally imbedded in serpentine-rock which has been 
washed away by water, the water, however, leaving such minerals as chrome-iron 
ore, zircon, titanium-iron ore, &c. In the Island of Borneo, platinum ore is mixed 
with sesqui-sulphuret of ruthenium, a mineral which has been named by Dr. Wohler 
(1866) Laurite. 

The compoBition of some platinum ores is exhibited in the following table : — ^Analysed 
by Dr. Berzelius, a, ore from the Onral ; Dr. Svanberg, 5 and e, from Columbia and 
dhooo; Dr. Bleekxode, <2, from Borneo; Dr. Weil, e, from Calif omia. 

a. b, c. d, e. 

Platinum 86*50 84*30 86- 16 71*87 5775 

Bhodium 1*15 3*46 2*16 — 2*45 

Iridium — 1*46 I'og 7*92 3*10 

Palladium 1*10 z*o6 0*35 1*28 0*25 

Osmium — 1*03 0-97 0*48 o-8i 

Osm-iridium .. .. 1*14 — 1-91 8*43 27*65 

Copper o*45 0*74 0*40 0*43 0*20 

Iron 8*32 5*31 8*03] 

Lime -— 0*12 — • 8*40 7*70 

Quartz — o'6o — ) 

Aooording to Dr. H. Deville, the average quantity of platinum contained in the fol- 
lowing ores is: — 

Columbia 76*80 — 86*20 per cent 

Calif omia 76*50 — 85*50 

Oregon . . 50*45 

Australia 59*8o — 61*40 

Siberia 73'5o — 78*90 „ 

Borneo 5775— 70*21. „ 

The annual production of metallic platinum amounts to from 35 to 50 cwts., of which 
quantity the Oural yields 28 to 49 cwts., Columbia and the Brazils, 6 to 8 cwts. 

woiiMton's Method of The mcthod originally devised by the late Dr. Wollaston, and 
^ from iSi Ore*. still employed by the Parisian platinimi-makers, Ghapuis, Desmoutis, 
and Quennessen, is as follows : — The ore is first treated with cold aqua regia to 
dissolve any gold, and the liquid separated from the ore by filtration. The mineral 
is again treated with aqua regia in a retort, and heat applied ; the distillate contains 
osmic acid, and the insoluble residue in the retort osm-iridium, ruthenium, 
chrome-iron ore, and titanium-iron ore. The acid liquid contains palladium, 
platinum, rhodium, and some iridiimi, in solution, and the acid having been neutral- 
ised with carbonate of soda, the fluid is mixed with cya^oide of mercury, whereby 
palladium is separated as cyanide of palladium. That precipitate having been 
removed by filtration, the liquid, diluted with water, is next concentrated by evapo- 
ration, and then mixed with a concentrated solution of chloride of ammonium, the 
mixture resulting in a precipitate (PtCl4,2NH4Cl), of the double chloride of platinum 
and ammonium, containing only a trace of iridium, which, as it imparts greater 
hardness to platinum, is not injurious. The platinum sal-ammoniac, as the precipi- 
tate is industrially named, is first dried and afterwards ignited, leaving spongy 
platinum, which is forced by means of properly fitting pistons into steel tubes heated 
to redness, the operation being repeated as often as is required to obtain the metal 
in a compact coherent state. According to MM. Descotil and Hess, platinum ores 



II 



PREPARATIONS OF MERCURY. 95 

should be first fdsed with from 2 to 4 times their weight of zinc, the cooled brittle 
mass pulverised, and treated with dilute sulphuric acid to eliminate some of the iron 
and zioc ; the remaining substance is then treated with nitric acid, which dissolves 
the rest of the iron, copper, and lead. The ore is afterwards treated with aqua 
r^ia, which acts more readily on account of the fine state of division of the mineral. 
M. Jeannetty (Paris) found that platinum becomes readily fusible by the addition of 
metallic arsenic, which is afterwards volatilised. 

* mSmSS?"* '^^^ excellent method introduced by MM. Deville and Debray, in 
1859, is based upon the fact that metallic lead, while fusing with platinum ore, 
dissolves all the foreign metals, osm-iridium alone excepted. The platinum ore is conse- 
quently placed on the hearth of a reverberatory furnace, and, having been mixed 
with its own weight of galena, a regulus is ohtained, under which the osm-iridium 
is left, while a lead slag floats on the top, the iron decomposing a portion of the 
galena and producing metallic lead. The regulus is heated in a cupel furnace, 
Thereby all foreign metals are volatilised or absorbed as oxides, leaving the metallic 
phtinum, which is refined by being again melted in crucibles made of lime, which 
absorbs and eliminates all impurities, such as silicium, iron, copper, &c. The fuel 
used for this purpose is coal-gas, the combustion being kept up by means of oxygen. 
The smelting of i kilo, of platinum requires 100 litres of oxygen gas and 300 litres of 
ooal-gas. The firm of Messrs. Johnson, Matthey, and Co., the most eminent and 
extensive platinum smiths in the world, exhibited at the International Exhibition 
of 1862 an ingot of pure platinimi weighing no less than 2i cwts., valued at ^4000, 
smelted by the method of MM. Deville and Debray. The molten platinum is after- 
wards submitted to the action of a steam-hammer to render it dense, solid, and fully 
malleable. 

ftopvtiMof FiKUnnm. Thls metal is nearly as white as silver, but with a steel-grey shade. 
It exhibits considerable lustre ; is very malleable and ductile, and so soft that it readily 
admits of being cut with a pair of scissors. It may be drawn in wire thinner than a 
spiders' -web, an operation conducted by coating an already thin platinum wire with 
ttlver. The wire thus prepared is drawn out and the silver afterwards removed by nitric 
add, which dissolves that metal but leaves the platinum. The specific gravity of 
platinum varies from 21*0 to 23*0. This metal admits of being welded at a white heat, 
and may be melted by the oxyhydrogen flame, its melting-point, according to Dr. Deville, 
Wmg between 1460° to 1480**. Platinum occurs in commerce as spongy platinum, 
black platinum, forged or hanmiered and cast platinum. 

BMkrtetiniaii. Black and spongy platinum possess the property of absorbing and con- 
^ spangy PtoUnam. deusing large quantity of gases, more especially oxygen. If a jet of hydrogen 
is directed upon the spongy metal, black platinum being only an exceedingly finely divided 
•pongy platinum, the gas combines with the oxygen absorbed by the meted, forming water ; 
and this combination is attended with so great a development of heat that the platinum 
becomes red-hot and causes the ignition of the hydrogen. It is upon this property that 
the well known Ddbereiner lamp is based. Black platinum is prepared either by boiling 
solphate of platinum with carbonate of soda and sugar, when the black platinum is pre- 
cipitated as a veiy fine powder, or by melting platinum and zinc together, and treating 
the alloy with dilute sulphuric acid. Black platinum is industrially employed in the 
m a nufa cture of vinegar directly from alcohol. 
I ^23?'**' ^*iS' Platinum may be worked by hammering or by casting. The following 
^ I Ap^MiSanM. firms are platinum workers : — Heraeus, at Hanau ; Freres Chapuis ; Des- 
^ numtis and Qnennessen,Godart and Labordenave, at Paris ; and Messrs. Johnson, Matthey, 
^ and Ck)., London. The chief use of platinum is for various apparatus in chemical 
laboratories. Although this metal withstands a veiy high temperature, and is proof 
^ against a large number of chemicals which attack or destroy other materials, it requires 
^ great care in its use, as it^is readily acted upon by caustic alkalies, fusing nitrate of 
I potassa, free chlorine, alkaline sulphnrets, phosphorus, molten metals, and readily 
reducible metallic oxides. Crucibles, spoons, blowpipe points, the points of lightning con- 
EM duetors, tongs and forceps, and boilers for concentrating sulphuric acid are made of this 



g6 CHEMICAL TECHNOLOGY. 

metal. A boiler capable of concentrating dally 8 tons of snlphnric acid costs about £2500, 
while a smaller bnt similar vessel for concentrating daily 5 tons of acid costs £1640, the 
Talne of the metallic platinom for this size exceeding £1000. Platinum is also used for 
galyanic apparatus, mustard-spoons, and now and then for ornamental work in watch- 
oases, chains, &o. More recently platinum has been used in porcelain staining to produoe 
a greyish hue. In the year 1828, the Bussian Govemment commenced coining platinnxn, 
3, 6, and 12 rouble pieces ; but by a ukase of 22nd June, 1845, ^^^ coinage was dia- 
continued, and the money made, 14,250 kilos, in weight, called in. In France, pla- 
tinum is used for making medals, especially prize medals for exhibitions. The first 
platinum coin CTcr made was struck at the Paris Mint in 1799, the dies having been 
engraved by M. Duvivier with the effigy of the first Consul, afterwards Napoleon I. In the 
year 1788, there was presented to Louis XVI. a watch, some of the works of which were 
made of platinum. Small caps or cylinders woven in platinum wire, are used to emit 
light when rendered highly incandescent by the flame of burning hydrogen, the arrange- 
ment being termed a platinum gas lamp. According to M. Kraut, platinum frequently 
contains barium, or a combination of that metal. 

naUnmn Aiioyi. As before observed platinum readily alloys with other metals. Among these 
alloys, that first made by Deville, consisting of 787 platinum and 21*3 iridium, especially 
deserves notice, as it is not acted upon by nitro-muriatio acid, and is hard and malleable. 
An alloy of platinum containing 10 to 15 per cent of iridium withstands fire and reagents 
far better than platinum alone and is harder ; hence the vessels made with it are not so 
liable to be bent out of shape as those of platinum. According to M. Chapuis, an alloy of 
92 parts of platinum, with 5 parts of iridium, and 3 parts of rhodium, resists various 
reagents better than platinum alone. The aUoy of 3 parts of platinum with 13 parts 
of copper is, according to M. Bolzani, equal in all respects to gold. Dr. Percy states that 
an alloy of platinum and gold for crucibles and other small vessels applied in chemical 
operations, is best proof against alkalies. An aUoy of eqnal parts by weight of steel and 
platinnm is the best white speculum-alloy known ; its sp. gr. — 9*862. 

Biayi PiatioiHiiiiorida. This compound (PtOjH^Cla), is obtained by repeatedly dissolving 
chloride of platinum in alcohol, and evaporatmg the solution to dryness. A very dilate 
solution when heated on a sheet of glass or a porcelain slate, yields a lustrous coating of 
platinum. 

SiLVEB. 

(Ag = 108 ; Sp. gr. = 10-5 to 107.) 

siiYtf and its oocurenee. Silver is a tolerably abundant metal, and is found partly in the 
native metallic state, aJmost always containing gold; partly in combination with 
other metals, as arsenic, antimony, tellurium, mercury, or combined with sulphur and 
other Billphurets. Silver rarely occurs as oxide or combined with acids. The chief 
ores are : — The sulphuret, silver-glance (Ag^S), containing from 84 to 86 per cent of 
silver; the dark-coloured ruby ore (3AgaS-(-Sb:^S3), with 58 to 59 per cent of silver ; 
the light-coloured ruby ore (3AgaS+AsaS3), with 64 to 64*5 per cent of silver; miar- 
gyrite (AgaS-f-Sb^Ss) ; and the brittle antimonial silver ore (6AgaSb2Ss), with about 
67 to 68 per cent of silver; polybasite [(AgaS,Cu2S)9,Sb2S3], with 64 to 726 per 
cent of silver; and the white ore L(FeS,ZnS,CuaS)4,SbaS3+(PbS,AgS)4,SbaS3], with 
30 to 32*69 per cent of silver. Galena frequently contains silver, usually between 
00 1 and 0*03 per cent, and sometimes as much as c 5 to I'o per cent. . This lead ore 
is the chief source of the silver produced in the United Eongdom. Some copper ores 
contain silver to an amount varying from 0*020 to 1*101 per cent. With regard to 
line ore the reader is referred to the statements under that head. 

■xtnusUon of sfiTw ^0 metallurgical process employed in the extraction of alver may be 

tnm lU Ores. fl.ny of the following : — 

I. By the wet way. 

z. By the aid of mercury. 

a. European method of amalgamation. 
h. American method of amalgamation. 
2. By means of solution followed by precipitation, 
a. Augnstine's method. 
h, ZiervogePs method, 
e. Sundry methods. 



SILVER. 97 

n. ^y the dry way. 

z. By ooncentratiiig lead ores rich in fiilver. 
2. Separation of the silyer from the lead. 

a. Separation on the hearth. 

b. Conoentrating the BilTer in the lead by Pattinson*B method, 
e. Eliminating the ailver from the lead by means of zino. 

d. Befining the sUyer-glanoe. 

ftMittagforaiiTvDinetiy. I. It Only rarely happens that silver ores are rich enough to 
tdmit of the metal being obtained by a direct smelting process. 

***'l2ISir5Sf ^^ ^- T^® method of obtaining silver by the aid of mercury, or the 
amalgamation process, is chiefly applied to very poor ores, and to such metallurgical 
products as contain only loo to 120 grms. of silver to the metrical cwt. 

^^**'9mnJ^ajpmaatm jhig process — ^uow obsoleto — ^was conducted in four principal 
operations — ^viz., i. The roasting ; 2. Amalgamation ; 3. Separation of excess of 
meienry from the amalgam by mechanical means ; 4. Volatilisation of the mercury. 
There was first added to the ores about 10 per cent of common salt, and the mixture 
roasted to volatilise the antimony, arsenic, and other volatile minerals, the fumes 
bemg condensed in properly arranged rooms. By the reaction of the common salt 
upon the pyrites, converted by the roasting into sulphate of iron, there is formed 
solphate of soda, chloride of iron, and sulphurous add which escapes. The chloride 
of iron exchanges its chlorine with the silver, the result being the formation of per- 
oxide of iron. There are also formed sulphate of copper and persulphate of iron, 
wbieli, while oxidising any sulphuret of silver to sulphate, become reduced to proto- 
aolphates. By the further action of the common salt, chloride of silver and sul- 
pbste of soda are formed, and the other metals converted into chlorides. The 
Viown-coloured mass is next transferred to the amalgamation tuns; and after 
the addition of water, mercury, and iron, these tuns are made to rotate on their 
loDgitadinal axes for a period of 16 to 18 hours, the velocity being regulated to 20 to 
22 revolutions per minute. The iron while combining with the chlorine, causes the 
lednction of all the other metals to the metallic state, and as far as capable these 
then form an amalgam with mercury. 

In order to elucidate the amalgamation process we will, for example, take a silver ore to 
eouutof— 

(CUaS,AgB,FeB) + (AflaSa.SbaSa). 

from which the silver is to be separated, according to the method just described.* After 
the roasting with common salt (ClNa), there being taken up in this instance 30 mole. 
^ oxygen, the following substances are formed : — 

[(OuaCla^AgCl,FeCla) + 3Naa804] + [AsaOa+SbaOj+eSOa] , 

' » ' ^ , ' 

Non-volatile substances. YolatiliBed substances. 

Th« ohanges which are effected by the action of the iron, mercury, and water in the amal- 
9aiation tuns are exhibited by : — 

[(CoaCl«,AgCl,FeCla) +3NaaS04+3Pe+nHg=3NaaS04+ (Cn,Ag,nHg) +4^eOU. 

At the end of the period destined for the rotation of the tuns, the amalgam is run 
^ The excess of mercury is strained through a coarse canvas bag, and collected 
in a stone trough or tank. The real amalgam, a thick pasty mass, remains in the 

* No attention is paid in this case to the volatile chlorides of sulphmr, arsenic, and 
ntixiiQ]^ which are cdmultaneoudy formed. The reader who desires more extensive 
tafoinuition on the subject here bridly outlined, is referred to Mr. Crookes*8 ** Metallurgy,** 
'olL 



b8 chemical TECHNOLOOr. 

bag, which is next strongly pressed between planks to squeeze out taj farther 
escesB of non'OrgentiBed mercury. The solid amalgam* is then transferred to the 
iron plates, hb, |Fig. 54), &rraitged as Bhown in the woodcut, and as already described 
under the article Mercnry. By the action of the fire the mercury is separated from 
the amalgam, and being volatilised, is collected under the water contained in d, 
while the metallic silver and other metals mixed with it are left on the iron plales.t 
Fio. 54. 




At the present time instead of the above contnianee there is used an iron distil- 
ling apparatus, not unlike cylindrical iron gas retorts one end being fitted with 
a movable lid for the introdnctioB of the amalgam and the other end connected 
with an iron tube which dips into a trough filled with water to condense the 
volatiliBed mercnry Superheated steam ig also advantageously used to sepante the 
mercury from the amalgam The crude silver left after the separation of the mer- 
cury is submitted to a first refining smelting by being put into graphite cmcibles, 
and the surface covered with charcoal powder But even after this smelting the 
silver always contains a certain quantitf of copper, from which it can only be separated 
by refining in a oupel furnace. 

j-yH — Aiui(uutit>ii l^e American proaesa is chiefly naed in Meiioo, Fern, Chili, and 

Fn>°~L California. The ores to whtcli it i> generally applied are the rabj- 

silver oree and fahl ores. These aie first pnlvsrised in (tamping mills, and are neit 



* According to Dr. Earaten, the composition of the aoUd wT" i tig a 'i' is : — Silver, ii'o;' 
mercnry, S4'3 ; copper, 3'; ; lead, O'l ; lino, o'3. 

f The silver left on the plates at the Fieibrag mines oonnsts, according to Protesur 
Lampadius, of:— Silver, 75-0; mercury, 07: copper.zi'i; lead, 1-5. The reflned eilver 
of the »ame place contains, according to ProleBsor Plattner : — Silver, 71-55 ; oopper, iS'Oi. 



-». ' 



SILVEH. \ ., * 59 

• 
groimd with water nnder granite or porphyry millstoneB, to a thoroughly impalpable paste. 
Tide niaterial in placed in a yard paved with flags, which are laid with a slight inclination 
sufficient to cause the rain-water to run off. After having been kept there for some days, 
there is added from i to 3 per cent of what the miners locally designate as magistral^ 
that is to say, roasted iron and copper pyrites (FeCuS^), which is thoroughly mixed with 
the finely divided ore. Mercury is then added in quantity equivalent to about six times 
the amount of silver contained in the ore ; this operation is termed incorporation. The 
kneading of the mercury is continued on alternate days for two to five months, and after 
that time the mass is washed with water in stone cisterns in order to separate the heavy 
amalgam from the light gangue. The amalgam thus obtained is separated from any 
excess of mercury by being pressed in canvas bags ; the remainder of the mercury being 
separated by distillation. The, rationale of this amalgamation process is : — The roasted 
copper-iron pyrites is essentially made up of mixed sulphates of copper and iron, which, 
when reacting upon the common salt, are converted into chlorides of the metals and sulphate 
of soda. The chlorides acting upon the silver convert it into chloride, and this becoming 
dissolved by the excess of salt, is converted by the mercury to the metallic state. Some of 
the mercury is converted into calomel, and the excess dissolves the silver, becoming amal- 
gamated with it. This American process requires a great length of time, and, moreover, 
occasions an enormous loss of mercury, as for every mol. of silver reduced from the chloride 
of that metal there is formed i mol. of calomel (Hg2Cl2). On the other hand, this method 
admits of the extraction of silver from ores too poor to be treated in any other way, 
vhiie a great saving of fuel is obtained. 

*^'^*'bx1^J£L'*' This hydrometallurgical method, invented by M. Augastin, is 
based upon the formation of a soluble double chloride of silver and sodium when 
chloride of silver is treated with an excess of a warm solution of common salt, and 
also upon the fact that copper is capable of precipitating all tlie silver from this 
solution. The ore is first reduced to a finely divided powder, which essentially con- 
tains sulplmrets of copper, silver, and iron. This powder is roasted, first without 
tlie addition of common salt, witli the result that sulphates of the metals are formed, 
and excepting that of silver, again decomposed by a higher temperature. The mass 
is next roasted with common salt, whereby the sulphate of sUver is converted into 
chloride. The mass is then treated with a concentrated hot solution of common salt, 
which dissolves the chloride of silver, and from this solution the silver is precipitated 
by metallic copper, which becomes chloride of copper, and is, in its tmn, precipitated 
by metallic iron. 

zioTogei'B Method. This method is to some extent similar to that just described, but 
no roasting with common salt takes place. The roasted ore, chiefly containing as 
essential ingredients sulphate of copper and sulphate of silver, is treated with boiling 
water to dissolve these sulphates, and yield a solution from which metallic silver is 
precipitated bj means of copper, the sulphate of that metal being obtained as a 
by-product. When the ores happen to contain arsenic and antimony, this method is 
not applicable, as, by the roasting, arseniate and antimoniate of silver are formed, 
which are insoluble in water. If lead is present, the ore becomes fluxed and the 
roasting a far more difficult matter. 

*5jjHyjOTirt^nj!icai py. Carl Bitter von Hauer suggests the treatment of the ores 
sqt^. as in tiie European amalgamation process, and the extraction of 

the chloride of silver by means of a hyposulphite of soda solution, the metallic silver being 
next precipitated by the aid of copper or tin. Dr. Patera suggests the substitution in 
AiigQstin's method of a hyposulphite of soda solution for that of common salt, the former 
being more manageable and applicable cold. Similar suggestions have been made by 
I^. Percy, who also advocates the applicability of hypochlorite of lime, and of chlorine gas 
'or converting the silver into chloride. MM. Rivero and Gmelin were the first to suggest 
the use of ammonia for the purpose of extracting and dissolving the chloride of silver f^ter 
^ ores had been roasted with common salt ; the precipitation of the chloride from the 
ammoniacai solution by means of sulphuric acid, and the smelting of the chloride with a 
*nitable flux to obtain metallic silver. We must not omit to mention the method of 
extracting silver from copper regulus and mattes by means of hot dilute sulphurijs 

u 2 



100 CHEMICAL TECHNOLOOY. 

add, irliereby the noppv it dissolved and » residae left oontaising Oie aQver, whieli ii 
fmilier extracted in the di? vrty b? meonB of lead. 
suncum oi bu?k The method of eztiaatiug Bilyer from its ores by means of lead ia based 
bi uu eut wii)r. npon ; — ^ 

I, The propeilT of lead to deoompou fmlphimt of Hil7er,witlitltefonn«tionof m^ibiirrt 
of lead and metalUo iUTer ; ^ [ yield | ^f^ 

ABlead hardly acts at all npon the other metalUasolphidea, and least of all upon those of 
copper and iion, the prodaete of the amaltinf; are lead combined with sUtbt, and a regalnt 
conaistingof the snlphnretB of lead, copper, and iron. This method of extraction snoceads 
best with ores containing ss small a qoantity of copper as possibte. 

3. Upon the deoomposing reaction exerted by oxide of lead and solphate of lead npon 
the Bolphorat of mlrer, in oonseqaence of whiith then are'formed metallic lead oontainiog 
silTer and sulphniouB acid :- 






aPbO 



3. Upon the rednoing ^ 

aPb i ^„,, /PbO 



A&8 1 ^j |PbA«, 
PbSO«r y^" laBO, 
of lead npon oxide of silTec or upon sulphate of d]*er :— 



U 



4. upon the greater iffini^ of the silTeT tor lead than for copper. If copper that 
contains Bilver is melted with lead, the rwolt is the formation of a readily fnsiUe idloy of 
lead and a difficultly fnsilde alloy of copper and lead, the fonoer metal being separahle by 
hqaation. 
Nc^oiFnuLiiiiiihs Only genuine silTer ores are enbmitted to (lie operation of 
Haw. smelting with lead, but these ores uauallj contain TuiaUa proper- 

tions of copper, lead, cobalt, sulphur, and other anbatancea. The result of th« 



Fia. 55. 




smelting with lead is the production of a metal containing silver, to be separttted bj 
any of the following operations : — 

1. On the refining-fomace ; 

2. By I^ttinson's proeeea ; 

3. By means of zinc. 

laiBiBf n«_. This operation is as frequently carried on at laad-ore smelting- works 
as where only silTer is smelted. The ratUmaU of the operation is that lead is 
readily separated from such metals as are at a high temperature either oxidisable with 
ver; great difficult or not at .all ; whereas lead oxidiaes readily, its oxide becoming 



SILVER. tot 

ftdd. But it is requisite that the oxide of lead should be removed or absorbed by a 
snitable medinm, generally the porous substance composing the cupel or bottom of 
the hearth of the refining furnace. The operation is carried on as long as any oxide 
and metallic lead remain, so that only the silver is left. This operation is the exact 
eoimterpart on the large scale of the, well- known lead-silver assay carried on in a 
muffle with bone-ash cupels. The refining furnace, see Fig. 55, is a circular rever* 
beratoiy blast-fnmaoe. The hearth, a, is covered with a dome of stout sheet-iron, 
lined inside with fire-clay, and removable by means of a crane, d. That portion of 
the hearth upon which the smelting is earned on is constructed of a porous sub- 
stance, generally lixiviated wood-ash or marl of good quality. The cavity, 0, is 
intended for collecting the silver; b is the space for the flame. In the circular waU 
which surrounds the hearth there are : — (i). The door, not exhibited in the cut, which 
represents a vertical section intended for the discharge of the molten litharge. At 
the outset, of the smelting this door is only partly closed with fire-clay to admit of 
the litharge being run off. The furnace is charged with lead to a little above the 
level of the lower sOl of this door, and the fire-clay gradually removed as the level of 
the fiised litharge sinks. (2) . The door, p» opposite to the fire-place, and intended for 
the charging and construction of the hearth. (3). The openings, a a', admitting the 
toyeres of the blast. 

The refining operation is carried on at a gradually increased temperature until only a very 
ttun layer of oxide of lead covers the surface of the silver. This is known by the peculiar 
diqtiayof eolonrs, technically known as the brightening, more aptly expressed in German by 
a vord which means lightening, for that is really the appearance. This being observed, the 
tre ii alaekenedf and the silver having been cooled with water, is removed from the 
hearth. The litharge which runs off is, on cooling, a yellow or reddish-yellow crystalline 
(see Lead, p. 63). 

I'tMMiiod. The refining process just described is not suited, that is to say, 

does not pay, when the lead contains only o' 12 per cent of silver. Now it so happens 

that the various kinds of galena met with in England yield a lead which contains 

only 0*03 to 0*05 per cent of silver. In 1833, Mr. H. L. Pattinson, of the Felling 

Chemical Works, near Gfrateshead-on-Tyne, instituted a series of experiments relative 

to a new method, applicable on the large scale, for separating lead from silver when 

&e latter is present in small quantities. His efforts were successful, and have 

greatly benefitted his own and other countries where his process is worked. 

Pattin8on*B method essentiaUy consiBts in a concentration process, based'upon the pheno- 
nenon that when a certain quantity of lead that contains silver is melted in iron cauldrons, 
aod the fluid mass allowed to cool uniformly, there ensues a formation of small 
octahedral crystals which do not contain any silver at all, or, at any rate, are a great 
M poorer in silver than the metal originally taken, while the portion of the metal 
nmaining fluid is found to contain an increased quantity of silver. It is clear, there- 
'on, that if the crystals first obtained are again melted and cooled uniformly, another 
^oooentration will be obtained, and that the operation can be repeated until a lead is' 
obtained rich enough in silver to admit of tmdergoing a refining process. Practically, 
Mr. Pattinson's method admits of concentrating 2*5 per cent of ralver. In the execution 
of this process, the } and } systems are employed. If the first, at every operation two* 
thirds of the contents of the cauldron are removed with perforated ladles, while in the 
other ease, seven-eighths is the quantity of crystals ladled out, leaving respectively one- 
third aod one-eightii of the contents of the cauldron in the shape of fluid lead. The 
1 9item is better suited for the richer lead, the i bystem for very poor lead. M. Bondohen 
has recently modified Pattinson's process. Instead of ladling out the crystals, he 
^ffoaes them in the lead, and stirs tiiem about to prevent them enclosing any lead 
hhe^ to oontain silver. The lead is withdrawn from the cauldron by means of a tap at the 
bottom. In all cases, however, the quantity of lead operated on at one time is always 
large, geiteraUy 200 owts., to cause the cooling to proceed slowly. At the Freidrich Lead* 
Silver Works, near Tamowitz, the enriched lead contains 1*28 per cent of silver. 



102 CHEMICAL TECHNOLOGY. 

Bedtiefcionb^iieuw xhis process, Suggested by Mr. Parker, in 1850, has only recently 

been practically carried ont by M. Corduri6, at Toulouse. This method, as &r as 

we are now capable of judging, will probably supersede even Pattinson's excellent 

method. The rationale of the process is based upon the fi&cts : — i. That lead and 

zinc do not alloy together. 2. That the affinity of silver for zinc is much greater 

than for lead. 

The following is the manner of execution : — 20 owts. of lead, which may contain (pear 
ton) only 0*25 kilo, of silver, is melted, and when properly Uquefied there- is added i cwt, 
of molten zinc. The zinc having been thoroughly mixed with the lead, the molten mass 
is left to stand until the zinc, which has risen to the surface, forms a cake that is easily 
removed. The zinc is then separated from the silver by distillation. The residue of the 
distillation is melted with lead, and the alloy thus obtained refined as above described. 
The zinc obtained by the distillation is used for another operation. According to a more 
recent improvement, the zinc is separated from the silver by oxidation by passing super- 
heated steam over the red-hot zinc (Zn+H20 = ZnO + H2). The lead, which of course 
after this operation contains traces of zinc, is purified by being melted with either chloride 
of lead, or a mixture of sulphate of lead and chloride of sodium, or with chloride of potas- 
sium from Stassfurt, the result being the formation of chloride of zinc, which collects at 
the surface or may be volatilised at a low red heat. 

Tba uiumato Beftniii« ^ whatever manner silver may have been metallurgicaUy obtained, 
ofsurwr. the metal is a crude material, very far from being oent-per-cent 

silver. The impurities, foreign metals, or, more correctly, base metals, often amount to 
7 and even 8 per cent ; and in order to remove these, the silver is submitted to a process 
of ignition in, or rather on the suriace of, vessels made of an absorbent material. This 
material is, for this ultimate refining, generally bone-ash, which is pressed into iron rings 
of convenient size, care being taken to fuse some lead with the silver, if there is not already 
sufficient. As regards this ultimate refining, there can be distinguished three different 
methods. The first has just been described. The second is carried on in muffles, the 
base metals burning off slowly. The third, and most advantageous method, is carried on 
in a reverberatory furnace. 100 parts of crude silver yield 96*8 parts of refined silver at 
gg-g per cent pure fine metal, which is cast in largessized bars. The value of the annual 
production of fine silver amounts to £9,000,000. Of this, Mexico's share is the largest, 
being half of the entire production. The bulk of this silver contains some gold and 
platinum. 

Chemically Pni9 surer. When for certain purposes metallic silver is required chemically 
pure, it may be obtained by dissolving any ordinary silver coin in nitric acid, and precipi- 
tating the solution with an aqueous solution of common salt or hydrochloric acid, llie 
chloride of silver thus obtained should be reduced by ignition in a crucible with dry car- 
bonate of potassa, to which a Uttle resin may be added. But chloride of silver is now 
commonly reduced by the wet way, by causing it to be acted upon by metallic zinc and & 
dilute solution of either sulphuric or hydrochloric acid — 

(2AgCl+ Zn+C1H« ZnCl2+ Ag2+C1H). 

pn>p«itieB of snvcr. Silver obtained by smelting exhibits a pure white colour and a strong 
metalhc lustre, which is gretftly increased by polishing. Its fracture is compact rather 
than fibrous. It is softer than copper, but harder than pure gold ; when chemically pure 
its softness is greatest. It is not a sonorous metal, bearing a resemblance in this respect 
to tin and lead. Gold only excepted, silver is the most ductile of the metals, a property 
impaired by the presence of foreign metals other than copper and gold, by the latter of 
which the ductihty is slightly increased. Lead and antimony render silver brittle. "Wlien 
silver contains an excess of carburet, produced by smelting the metal with an excess of 
carbon, the metal is rendered less ductile ; but a smaU quantity of the carburet, as much 
as is found in coins of a high percentage of silver, is rather advantageous, increasing the 
hardness of the metal, and causing it to wear well. Smelting in plumbago crucibles does 
injure silver. Its specific gravity varies from 10*5 to 107. The absolute strength is far 
less than that of copper. Its expansion by heat in o*" to 100° G. is , j,th. According to 
M. Deville, the melting-point is gi6° ; but Br. van Biemsdijk states that the results of a 
series of experiments made at the Utrecht Mint, in 1868, showed the melting-point tP be 
10400, the metal being kept in a slow current of pure hydrogen. At a very high tempera- 
ture, such as can be produced only by the oxyhydropen fiame or by electricity, silver is 
volatilised. When alloyed to other metals, especially to copper, the volatility is increased, 
and even at a lower temperature than the melting-point of copper, viz., 1330"*, Dr. van 
Biemsdijk found such silver to be perceptibly volatile. M. Stas, of the Brussels Mint, in 
2869, distilled some 50 grms. of silver by means of the oxy hydrogen fiame, in order to 



SILVER. 103 

obtain the metal perfectly pnre. Molten silyer abBorbs oxygen, whioh is again expelled 
from the metal on Bolidiiication, and giyes rise to the phenomenon known by silYer- 
assayers as spirting, the escape of the gas cansing the metal to be forced asunder in small 
drops. Howeyer, when the molten silver contains even i per cent of either lead or copper, 
it BoHdifiee withont spirting. Silver is not acted npon by dilate acids, bnt is readily 
diBsoWed in the cold by nitric add. Silver is very sensitive to the action of snlphnretted 
hydrogen, by which it is readily tarnished. 

AOoTvefBOTw. 8ilver alloys readily With lead, zinc, bismuth, tin, copper, and gold ; 
but Uie moat important alloy, ia an industrial point of view, is that with copper, 
pure silver being too soft for general application. All silver, therefore, whether used 
for plate, coin, or for ornamental purposes, invariably contains a certain amount of 
copper. In most civilised countries there exist laws regulating the alloy of silver to 
be used for coin or plate. Pure silver, or fine silver, is now generally indicated 
by Jg{§. The alloy for the silver coins of Germany is indicated by ^^%% ; meaning 
that 1000 parts by weight of the coin contain 900 parts of pure silver, the remainder 
being copper. Twenty-seven Union thalers weigh i half kilo., therefore a single 
thaler weighs 18*518 grms., and contains i6'666 grms. of pure silver. By an inter- 
national treaty with France, Italy, Belgium, Portugal, Switzerland, and Spain, i kUo. 
of^VoB silver is to yield 200 franc pieces, i.e.y 222I franc pieces to i kilo, oi fine 
silver. The same alloy is employed for pieces of 2 and 5 francs, there being 200 of 
the latter to the Idlo. In the Netherlands, where, by-the-bye, gold coin is no longer 
cmrent, and silver is the standard, the alloy used is tWo* The silver coins of the 
United Kingdom are made of an alloy tVoV \ i ^' Troy, or yjyzoB grms., of this 
aDoy \b coined into 66 shilling pieces. A pound Troy of fine silver would yield 
71 H shillings. 

";j£"2^*" In nearly all European countries the laws have fixed the composition 
of the alloy of silver which, duly marked and stamped, shall be ofiered for sale as 
plate by gold- and silver- smiths, who, in Holland, Belgium, France, and Sweden, are 
not allowed to have in their workshops any electro-plated articles, or any alloys 
(^er than those fixed by law. The composition of these alloys varies ; expressed in 
miUiimes of fine metal, it is for Austria and Bavaria, 812 ; for Prussia and Saxony, 
750; for England, 925. For France, Belgium, and the Netherlands, a double alloy 
is fixed, the higher being 950, the lower 800. The alloy lately brought iuto use 
nnder the name of tiers-argent^ one-third silver, really consists of 2756 per cent 
flOver, 59 per cent copper, 9*57 per cent zinc, and 342 per cent nickel, though in the 
trade this alloy is alleged to consist of I nickel and ^ silver. Tiers-argent sells at 
^3 i2s. per kilo. This alloy is harder than silver ; its colour and polish are as good. 
It is extremely well adapted for all kinds of plate. 

wvwAMBy. If it be desured to know the quantity of fine silver contained in an alloy of 
alver—wiiich for our present purpose we will assume to contoin only silver and copper — 
there are three different methods by which this proposition can be solved, viz. :— yi. The 
•■tty by the dry way, termed cupellation. a. The assay by the wet way, or titration 
prooess. 3. The hydrostatic assay. 

Dir AiMy. Usually this assay is conducted by first testing the alloy by comparing the 
streak it makes upon touchstone — a piece of polished basalt or siliceous schist — with the 
streak produced upon the same stone by test-needles ; that is to say, small bars of silver 
of known composition. It should, however, be borne in mind that the surface of silver 
vtioles, as well as of coins, may have been hlanehed^ as the term runs ; that is to say, 
■eted upon by hot, dilute sulphuric acid, to dissolve a portion of the copper of the alloy, 
snd leave a film of alloy richer in silver. The alloy to be further assayed is next melted 
down with a piece of pure soft lead, or lead containing a known quantity of silver, in a 
e^nnle, technically €»dled cupel, made of bone-ash. The cupel is previously well heated 
in a muffle, and the lead is placed in it. As soon as the lead has become quite liquid, the 
sample of silver to be assayed is added ; the copper and lead are oxidised, and in that state 



104 CHEMICAL TECBNOLOGT. 

absorbed by the porone substanoes of the (mpd« As soon as the surface of the silTer 
button appears quite bright, the operation is finished, and the cupel slowly cooled. The 
button of silver is then weighed. It is usual to make two assays of the same sample ; 
these assays should agree in their results to within tV^i^^ to be of any value. 

Wet Amy. This method of assaying silver was devised some sixty years ago by the late 
Professor Gkty-LuBsac, at the request of the French Government, in consequence of the 
great irregularity of the results obtained by the dry method. The wet assay, having heen 
very greatly improved in detail by Dr. G. J. Mulder, M. A. W. H. van Itiemsdijk, Br. Staa, 
and M. J. Dumas, is now generally adopted, and will remain to all time a master- 
piece worthy of the ingenuity of its original inventor, who, by introducing this method, 
laid the foundation of volumetric analysis, now so usefully and completely applied. Gay- 
Lussac's wet method of silver assay is more easily executed than the dry assay, while it la 
far more correct, admitting an accuracy of judgment within ^th per cent. The method 
is based upon the property possessed by common salt of precipitating silver as chloride of 
silver from its nitric add solution. As 5*4274 grms. of pure common salt exactly convert 
I grm. of pure edlver, previously dissolved in nitric acid, into chloride of silver, it is 
evident that, from these data and with the application of suitably constructed apparatus 
for the volumetric analysis, the fineness of any alloy of silver may be asoertained readily, 
rapidly, and with great accuracy. 

Hydnwutiami am«7. Thls method is of course by no means so correct as either of the 
foregoing, and, moreover, is impaired by the fact that, although alloys of copper and 
silver expand under pressure, thiBy become denser, so that the hydrostatic weighing, that 
is to say, the estimation of the specific gravity of the alloy, is only admitted as a test of 
its relative value. With such alloys as have, like coins, to be rolled, pressed, or drawn, 

the hydrostaticalresultsrarely differ more than — from the results obtained by cupella- 

tion. The empirical rule for the estimation of the value of sUver assayed by this method 
is the following : — The number 8*814 is subtracted from the specific gravity of the alloy, 
two cyphers are added to the difference, and the figure thus formed, considered as a whole 
number, is divided by 579 ; the quotient is the fineness of the silver-alloy expressed in 
grains. For instance, let the specific gravity of the alloy be s io'o65, then the fini*n^»ftff 
is s2z6 grains, or zWo'* since — 

iO'o65-8'8i4=i'25i 

and 

125,100 

579 
somiag. The coating of metals with a film of silver can be effected by : — t, plating ; 
2, the igneous process ; 3, in the cold ; 4, the wet way ; 5, galvanically, or electro-plating. 

sttnerPiBtins. In order to coat metallic copper with a layer of silver, the sheet copper is 
first thoroughly cleansed, then treated with a moderately strong solution of nitrate of 
silver, and next covered with a sheet of silver. After having been made red-hot, the two 
metals are rolled out together. The silver then adheres so strongly to the copper as to 
admit of the metals being beaten or stamped into various shapes. Copper-wire is readily 
silvered by being covered with thin strips of silver, and passed through rollers. But this 
method of plating is almost entirely superseded by electro-plating. 

isneoos, or »!» This method of silvering is effected by the aid either of a silver-amalgam 
suTering. qj. y^y applying to the w^-deansed surface of the metal intended to be 
silvered a mixture of i purt of spongy precipitated metallic silver, 4 parts sal-ammoniao, 
4 parts common salt, and i part corrosive sublimate. The metal to be silvered is rubbed 
with this mixture, and then heated in a muffle. Buttons intended to be silvered are 
covered with a paste consisting of 48 parts of common salt, 48 parts sulphate of zinc, z part 
of mercuric chloride, and 2 t>arts of diloride of silver. 

sfltoinffintiMOoid. The metallic surface intended to be silvered, having been well 
cleaned, is rubbed by means of a smooth cork, with a mixture of equal parts of chloride of 
silver, common salt, } of chalk, and 2 of carbonate of potash, made with water into a 
creamy paste. Professor Hein recommends that i part of nitrate of silver and 3 of 
cyanide of potassium should be rubbed together in a mortar, with the addition of sufildent 
water to form a thick paste. The paste is rubbed on the metal to be silvered with a piece 
of flannel. MM. Boseleur and Lavaux recommend a mixture of 100 parts of sulphite of 
soda and 15 parts of any ealt of silver. For silvering the dial-plates of watches, Ae., 
M. Thiede recommends a mixture of spongy silver with equal parts of common salt and 
cream of tartar. In order to silver iron it is first covered with a layer of copper. 



GOLD. 105 

aanriflcwtiM This is effected by imniersmg the metal intended to be silyered in a 
w^Twsy. ' boiling aqneons solution of equal parts of cream of tartar and common 
■alt, with \ part of chloride of silver. The description of the methods of electro-plating 
will be giyen at the end of the chapter on Metals. 

oiidtawi sdtw. The small ornaments met with under the name of oxidised silyer are 
prepared with either solphnr or chlorine ; in the former case a bluish-black colour is 
in^arted, in the latter a brown. The sulphur is applied simply by dipping the object into 
a Boiution of sulphuret of potassium, while for the chlorine colour a mixture of sulphate 
of copper and sid-ammoniac is used. 

sitate of BUvw. This salt (AgN03) is now prepared on the large scale by dissolying silyer 
iwmt*mfT»g copper in nitric add, evaporating the solution to diyness, and ignitmg the 
nodue until all the nitrate of copper is decomposed. The residue is next exhausted with 
pore water, the solution filtered and left to crystallise. For medical purposes the ciystals 
are fused, and while liquid poured into moulds to form small round sticks. The most 
extensive use of nitrate of silver obtains in photography, a re-crystallised neutral and pure 
salt bdng preferred. Under the name of Sel ClSmetUy there is now in use in photography 
a mixture of fused nitrates of silver, sodium, and magnesium, recommended as preferable 
to nitrate of silver alone. It is stated that the consumption of this salt for photograpl^io 
purposes amounted, in 1870, to 1400 cwts. for Germany, France, England, and the 
United States ; the money value of this quantity being estunated at £630,000. 

xuking Ink. A large quantity of nitrate of silver is also used for the purpose of mitlriTig 
indelible ink for marking linen. This ink often consists of two different fluids, one a solution 
of pyrogallic acid in a mixture of water and alcohol, being intended to moisten the linen 
previous to writing ; the other, or writing fluid, consisting of a solution of ammoniacal 
nitrate of silver thid^ened with gum. More recently aniline black has been applied in the 
maririug of linen. 

Gold. 
(Aii=i97; Sp. gr. 195 to 19*6). 

'^'^SSS^oSl*** Gold is found only in the native metallic state, sometimes in 

veins interspersed in rocks, and accompanied by quartz, iron pyrites, and iron ore. 

More firequently gold is found finely divided in sand, mixed with larger or smaller 

nuggets, and imbedded in quartz, with various other minerals, such as mica, syenite, 

cfalorite slate, chrome-iron ore, and spineL Native gold commonly contains some 

silver and other metals, among which are palladium and platinum. According to 

lecent analyses, the composition of samples of gold obtained from several coontries is :-^ 

L IL 

Hungary. B. America. Siberia. Oalifomia. Australia. 
Ooid . . . 6477 8804 86*50 89*60 99*2 95*7 

Silver . . 35*23 11*96 13*20 io*o6 043 3*9 

Iron and other metals — — 0*30 0*34 0*28 02 

Gold is found native with tellurium and telluride of silver, and among antimony, 
zinc, arsenic, and other ores. It is also found in galena and various kinds of clay ; 
indeed, gold is, next to iron, the most widely dispersed metal. The chief gold 
yielding countries are : — ^Africa, Hungary, the Oural, Australia, and America, especially 
Uiexico, Pern, the Brazils, California, Columbia, and Victoria. 

The total value of the gold produced in the year 1869 is computed at ^860,000,000, 
one-fourth of this representing the value of the production of California. The 
▼ibie of the joint production of the Australian Colonies is a littie above another 
one-fourth. 

nad«ofxxinMCii«ooid. The mode of extracting gold is determined by the drcum- 
stances of its occurrence. By &r the largest portion of the gold in circulation 
is obtained by the washing process; that is to say, the elimination by means of water 
of the lighter minerals, the finely divided gold being left behind. This process may 
be carried on in remote districts in a very primitive manner, by simply putting the 
nad into wooden bowls, and washing it gradually away with water. The gold 



io6 CHEMICAL TECHNOLOGY. 

so obtained is not pure, but contains titanic iron and other minerals. AVfaerever 
gold washing is a regularly established business, as in some parts of the Oural, 
properly constructed contrivances are applied. 

^**^MS?iJf **""*' The application of mercury to the extraction of gold is based 
upon the fact that mercury amalgamates with gold readily and very eflfectively. The 
operation is carried on with the gold-containing sand in peculiarly constructed 
ipiUs. Mr. Grookes has shown that the addition of sodium to the mercury 
facilitates the extraction of the gold. The excess of mercury having been removed 
from the amalgam by pressure in leathern or stout linen bags, the remainder 
in amalgamation with the gold is volatilised by ignition in suitably constructed 
furnaces. 

smettiog for Gold. By a far moi^e perfect process than washing, gold is extracted from 
the gold sand by smelting with a suitable flux in a blast furnace. The object in 
view is to produce a rough or crude iron from which the gold is separated by means 
of sulphuric acid. This process yields from 25 to 30 times more gold than merely 
washing the sand. 

Treattnx ^th AikaiL Mr. Hardlugs proposcd to obtain the gold by treating the quartz 
or sand with caustic alkalies under a high pressure of steam, thereby forming 
a soluble silicate and leaving the gpld. 

"^JS^M^wiS^cfrSf™ ^ ^^^^ happens to be interspersed through copper or lead ores, 
they are roasted and then washed. When the quantity of gold is sufficient such ores 
are treated with mercury, while sometimes they are treated for coarse metal ; and 
this, containing all the gold, is smelted with litharge, which absorbs the gold, and is 
next separated from it on a refining hearth. 

*^*"po!lrMS»22i'*^'' Some minerals and metallurgical refuse containing only a very 
small quantity of gold have been treated at Beichenstein, in Silesia, by means 
of chlorine water, or an acidulated solution of bleaching powder. The gold is con- 
verted into chloride of gold (AUCI3), and is precipitated from the solution by 
sulphate of iron or sulphuretted hydrogen. This method has been severely tested by 
MM. Plattner, Th. Eichter, Georgi, and Dr. Duflos, and has been found to answer 
epcceedingly well, even with very poor ores. This plan is of course generally 
applicable to gold sand and gold quartz. According to M. Allain, pyritical ores, 
having been roasted and treated with sulphuric acid to eliminate the iron, zinc, 
and copper, can be then treated with chlorine water so as to extract the gold present, 
to an amount only of i part of gold in 10,000 of mineral. 

Beflning Gold. In Order to separate any foreign metals from the gold obtained by the 
above process, the following methods have been employed, but only the last (5.) 
is now in general use. For that reason the other methods will only be briefly 
described :-^ 

1. Refining by means of sulphuret of antimony (SbaS^). 

2. By means of sulphur and litharge. 

3. By cementation. 

4. By quartation. 

5. By means of sulphuric acid. 

By M01UIS of sniphnrtt ^^^ process Is effected by first smelting the alloy, which ought to 

of Anumony. contain at least 60 per cent of gold, in a graphite crucible. Pulverised 

black sulphuret of antimony is added in the proportion of 2 parts to i of alloy, and the 

molten mass is then poured into an iron mould, which is rubbed with oil. The mass on 

cooling will be found to consist of two separate layers — the upper, technically termed 



GOLD. J07 

plafmdt eonaiBtiiig of the Bnlphnrets of silver, copper, and antimony ; the lower, an alloy 
of antimony and gold, which is separated in a mnffle or a wind furnaoe. The remaining 
gold is fused with borax, saltpetre, and some powdered glass. 

ByUwAifiof soipfaw. This procosB does not aim at the entire separation of the gold from 
the other metals, bat rather at its concentration in a smaller quantity of silver than was 
originAlly present in the alloy, so as to render it snited for quartation. The alloy, 
previoosly granulated, is mixed with f part of powdered snlphnr, pnt into a red-hot 
graphite cmcible, and covered with charcoal powder. The crucible is kept at a low red 
heat for 2k hours, and then raised to the point of fusion. If the alloy contained gold in 
any considerable quantity, a layer of silver separates, which wiU be rich in gold ; but if the 
original alloy was rather poor in gold, litharge is added to the molten mass, the oxygen of 
the litharge causing the combustion of the sulphur of a portion of the sulphuret of 
silver, the metallio idlver combining with nearly all the gold. The reduced lead is ti^Lcn 
up hj the sulphurets of the other metals present. 

cufmution praews. The alloy containing gold having been either granulated or rolled 
into thin sheets suitably cut up, is placed in a crucible, in this instance technically termed 
a cementation box, and mixed with 4 parts of pulverised bricks, and i part each of 
common salt and dried copperas. The crucible is then gradually raised to a cherry-red 
beat. Chlorine is evolved in this operation by the action of the sulphate of iron upon the 
common salt ; there is consequently formed chloride of silver, which is absorbed by the 
polTcrised bricks, while the gold is left unattacked. After cooling, the mass is boiled in 
vater in order to obtain the gold. Here must be mentioned Mr. F. B. Miller's process of 
{wssing chlorine into molten gold in order to eliminate the base metals which render 
it brittle, while the silver, converted into chloride, floats to the surface. 

QButattoB. This process has obtained its name from an opinion that, to ensure success, 
there should be three times more silver in the alloy than gold, i.e,, the gold should amount 
to a quarter of the entire alloy. But Dr. M. von Pettenkofer has proved that if the 
amount of silver be double that of the gold, the separation of the two metals will 
be complete, provided sufficiently strong nitric acid be employed, and the boiling con- 
tinued for a length of time. Practically this method is as follows: — There is added 
to the gold a sufiicient quantity of silver, and the two metals are smelted together. The 
alloy is next granulated, placed in a platinum vessel, and boiled with nitric acid of 1*320 
sp. gr., care being taken that the acid is free from any chlorine. The sUver being dis- 
Bohed, the gold is left behind, and further refined by fusion with borax and saltpetre in a 
emcible. 

^!?Si2iJte^^* This method of refining, which has been briefly alluded to 
onder Copper, is preferable to any of the foregoing on account of its perfection, 
cheapness, and simplicity. By this method almost any aUoy containing gold in 
addition to copper and silver can be treated, but the quantity of gold should not 
exceed 20 per cent, nor that of the copper 10 per cent, while the best proportions, 
according to Dr. Pettenkofer's researches are, that in 16 parts of the alloy, the gold 
should not exceed 4 or be much less than 3 parts, and the rest copper and silver. 
Usually the alloy intended for this mode of operation is first granulated, or if 
it happens to be in the shape of silver coins — Mexican dollars, for instance — they are 
cut to pieces. Formerly, platinum vessels were employed in the boiling of the alloy 
with thoroughly concentrated sulphuric acid (sp. gr. 1848), but cast-iron vessels, or 
sometimes hard porcelain vessels, are now employed, the proportion being 2 molecules 
of acid to I molecule of the alloy. The heating is continued some twelve hours, 
Qutil the copper and silver are completely dissolved. The sulphurous acid evolved 
is employed in the manufacture of sulphuric acid, or is absorbed by a soda or 
lime solution to form sulphite or bisulphite of soda or bisulphite of lime. The solu- 
tion of mixed sulphates of silver and copper is poured into leaden pans, and 
becoming solidified on cooling, the pasty mass iJs dug out with iron spades, and put 
into leaden tanks filled with boiling water, in 88 parts of which i part of sulphate 
of silver is soluble. The silver is precipitated from this solution by strips of copper, 
and the solution of sulphate of copper obtained, having been deprived of its excess 
of free add by the addition of oxide of copper, is further treated for blue vitriol. The 



# — 

Persulphate of iron, 2Fea3S04. 
Ohloride of iron, FosClG. 



io8 CHEMICAL TECHNOLOGY. 

gold which has remained as a dark, insoluble, spongy mass, is first boiled with a 
solution of carbonate of soda, next with nitric acid, to free it from any adhering 
oxide of iron, snlphuret of copper, sulphate of lead, and other impurities ; and after 
having been dried, is melted with the addition of saltpetre. By this process it has 
become possible to extract the i-ioth to i-i2th per cent of gold contained in old silver 
coins ; therefore this method of refining has come largely into use, as within the last 
thirty years nearly all European States have recoined the silver money in circulation. 
Still Dr. von Pettenkofer has observed, that nearly all the gold obtained by this process 
contains silver and platinum, in the proportion of 97 o gold, 2*8 silver, and 0*2 
platinum. These metals are eliminated by fusion with saltpetre and bisulphate of soda. 

At Paris, Frankfort, London, and Amsterdam, this method of refining is carried on to a 
large extent by private firms. Acoording to the Paris custom, the refiners return to their 
olients aU the silver and gold, retaining only the copper, and being paid at the rate of 
from 5 to 5i francs per kHo. of refined metal ; but if the aUoy oontaLos less than i-ioth 
of gold, the refiners retain i-2oooth of that metal, paying a premium of f franc per 
kilo, of refined metal to their client. If the client desires all the gold and silver to be 
returned to him, the refiner charges 2 francs and 10 to 68 centimes per kUo., according to 
the market price of silver, and retains all the copper. Usually, however, a charge of 
5 francs per kilo, is paid to the refiner. The value of the silver annually refined for gold, 
at and near Paris, amounts to about £5,500,000. 

chsmioAUyPtaxaOou. In order to obtain perfectly pure gold, that of commerce is dissolved 
in nitro-hydroohlorio acid, the solution evaporated to dryness, the residue, chloride of gold, 
dissolved in water, and that solution precipitated by a solution of sulphate of iron : — 

Chloride of gold, 2(Au0l3) \ .^, f ^^^^' ^^''• 
Sulphate of iron, 6FeS04 J ^^^ 

According to Mr. Jackson, gold may be readily obtained in a yellow spongy mass, by 
adding carbonate of potassa and an excess of oxalic add, to a concentrated solution 
of chloride of gold, and rapidly heating tJiis solution to the boiling-point : — 

Chloride of gold, 2(AuCl3)l .,, 12^^fjn^JL« a^^ firm 

According to Mr. Reynolds, peroxide of hydrogen precipitates gold from its add solution 
in beautifully lustrous metallic spangles : — 

Chloride of goM,2(AuC10 1 ^.^^ f nSocmoric add, 6C1H. 
Peroxide of hydrogen, sHaOa J ^ ( Oxygen, 60. 

Sometimes gold is predpitated by chloride of antimony or chloride of arsenic. The 
metallic gold obtained or predpitated by any of the above processes is next fused with 
borax in a graphite crudble. 

piopattiM of ooUL The peculiar colour of gold is too well known to require description. 
The richness of that colour is very much impaired by even small quantities of other 
metals. Many of the Australian sovereigns, for instance, are of a pale greenish 
yellow, due to the presence of a small quantity of silver. A small quantity of copper 
gives a red colour to the gold. Gold assumes a very high polish ; is, when un- 
alloyed, but slightly harder than lead, and yet is the most malleable and ductile of 
all metals. Its absolute strength is equal to that of silver. The specific gravity of 
gold varies from 19*25 to 19*55, ^^^^ ^^^^ ^9'6» according to the mode of mechajiical 
treatment. Its co-efficient of expansion by heat = 682 per 100" C, and its melting- 
point, according to Dr. Deville, is 1037°. Dr. Van Riemsdgk, however, fixes the 
melting-point at 1240°, the metal being molten in quantities of several kilos, in an 
atmosphere of pure dry hydrogen. Molten gold exhibits a sea-green colour. The 
great value of gold is in a considerable measure due to its not being acted upon by 
air, water, ordinary adds, and alkalies ; but, on the other hand, even very smali 



OOLD. xog 

quantities of lead, antimony, and bismuth impair its malleability to snoh an extent 
as to render it nnfit for use either as coin or for ornamental purposes. The 
following metals have the same effect, but to a less extent: arsenic, zinc, nickel, tin, 
platinum, copper, and silver ; the two latter being the only metals suitable to alloy 
with gold to make it sufficiently hard to resist wear and tear. Gold, of all the 
metals, is most readily affected by mercury, even to such an extent that the mercury 
present in the imperceptible perspiration of such individuals as have been treated 
medicinally with calomel for some length of time, is sufficient to act very perceptibly 
upon their jewellery, while gold coins kept for some days in their pockets become 
Uanehed. Gold-leaf imparts to transmitted light a blue-green hue. 
AiioTiof oou. Pure gold is used only for certain chemical processes, and beaten into 
leaf for gilding; the Staffordshire potteries consuming for this purpose alone 
;£6o,ooo worth annually. All other gold, be it used for jewellery or for coinage, is 
always alloyed with copper or silver to produce the degree of hardness requisite for 
kammering, stamping, &c. Generally such alloys are considered as consisting of so 
many carats to the unit, the pound or half-pound being divided into 24 carats, each of 
whidi contains 12 grains. What is .termed 18 carat gold is a unit of 24 carats of alloy, 
containing 18 carats gold and 6 of silver or copper. If the latter, the alloy is termed 
red; while if silver is used, it is termed white ; and if both metaU are alloyed with 
the gold, the caratation is termed mixed. In most countries there are legally fixed 
certain standards for gold jewellery. In this country, 16, 18, and 22 carat gold is 
stamped, or as it is termed HaU marked; in France, 18, 20, and 22 carat; in 
Germany, 8, 14, and 18 carat, and also under the term of Jovjou gold, a 6 carat gold, 
used for jewellery, to be electro-gHt Among the coined gold of European states the 
tenn carat is almost everywhere replaced by the expression of so many parts fine per 

miUe. Exceptionally fine gold coins are the Austrian ducats, 23 carats 9 grains, ^^^ 

of gold; the Dutch, or more correctly Holland, ducats, /,^, or 23 carats 6 to 6*9 
grains gold. Neither of these coins are at present a legal tender in Austria or Holland, 
but they are continually made at the Utrecht Mint, having been for many years the 
dreolating medium in the North Baltic and White Sea ports, as well as in the Black 
Sea, Levant, and Egypt Originally they were coins of the Holy Boman Empire 
(Germany). The English sovereigns and half-sovereigns are coined from ^| or 
aa carat gold ; or in thousands » ^^o^ ; the Prussian Friedrich d'Or = ^^vS ; 
"Wilhehn d'Or = 21I carat ; the 20-fiunc pieces of France, Belgium, Switzerland, and 
Italy = 21 carat 7I grain, or .^^. According to the Vienna Treaty of 1857, the current 
gold coins of Germany are made in 1000 parts of 900 of gold and zoo of copper, 
the relative value of siLver to gold being taken as x : 15*3, or i : X5'5. 

cotovoc ooia. Ab all gold alloys, commercially or industrially used, exhibit colours 
different from that of pure gold, it is customary to produce superficially on such 
ftUo^ the deep yellow of fine metal by boiling in a solution of common salt, saltpetre, 
and hydrochloric acid ; the effect is the evolution of some chlorine, which dissolving 
i imall quantity of the gold, again deposits it as a film of very pure gold. Electro- 
(pUing is, however, frequently substituted for this colouring process. 

'**VooiIl'*'**" Jewellers and goldsmiths generally use touch-needles made fi^m 
buying gold alloys. The resistance of the streak made upon the touchstone to the 
action of dilute nitro-muriatic acid is the test of the fineness of the gold ; but it is 
clear that this method is only approximative, and it cannot be relied on, as jewellery 



no CHEMICAL TECHNOLOGY. 

is often snperficially coated with a film of pure gold. The most reliable test is 
afforded by cupellation, for which purpose the gold alloy to be tested is, according to 
its colour, fused with twice or three times, or an equal weight of silver, and about 
ten times its weight of lead. This compound alloy is submitted to cupellation 
in a muffle. The button which remains on the cupel is first flattened on an anvil, 
next annealed, and rolled into a thin strip, and then boiled with strong nitric acid to 
dissolve the silver, the remaining gold being washed with boiling water, dried, 
re-ignited in the muffle, and finally, when cold, weighed. 

Appucations of Gold. It is uot uecessaiy to speak of the well-known uses of gold, the 
most extensive being its application to coinage, and next that to gilding and jewellery. 
Gold in sheets I inch thick has been used to cover the large dome of Isaac's Church, 
at St. Petersburg, while three, at least, of the countless crosses on tlie domes of the 
Moscow churches are made of solid gold ; a portion of one of the domes of a ohurch 
in the Kremlin is likewise plated with gold. 

QOdinc. This is done either with gold-leaf, or by means of the cold process, the 
wet process, fire-gilding, or electro-gilding. 

oflding with Gold-leaf. Gold-leaf, applied in gilding on wood and stone, is prepared in 
the following manner : — Fine gold is molten and cast into ingots, which are hammered 
and rolled into thin sheets about an inch in width, technically termed ribbon. The 
ribbon is cut into small pieces an inch in length, which are placed between pieces of 
parchment, and beaten out to a moderate tliinness. Goldbeaters* skin— the exteiior 
membrane of the intestina crassa of oxen — ^is then substituted for the parchment 
and the hammering continued until the metal is of extreme tenuity. Tlie refuse gold 
of this operation is used for the preparation of bronze-gold for painters. The 
articles to be gilded with gold-leaf are first painted over with a suitable vaTnish or 
size, and the gold-leaves pressed on gently mth a piece of soft cotton-wool. Iron 
and steel, as, for instance, swords, gun-barrels, Ac, are first bitten, as it is termed, 
with nitric acid, next heated to about 300°, and then covered with gold-leaf. 

GUdizi£by tiu Cold For this purpose fine gold is dissolved in aqua regia ; clean linen rags 

^^"^•^^ are soaked in this solution, and then burnt to tinder, consisting of 

carbon and very finely divided gold. This tinder is rubbed on the article to be gilded 

with a cork moistened in brine ; the metallic surface to be gilded should be well polished. 

GiidinfT by the This procesB is carried out by placing the article to be gilded in either a 
Wet Way. dilute Bolution of chloride of gold in ether, which rapidly evaporates, or in 
a boiling dilute aqueous solution of the same salt, and adding to it carbonate of soda or 
potassa solution. Iron or steel should be first superficially coated with a fi^y" of copper 
by immersion in a dilute sulphate of copper solution ; or these metals, after being bitten 
with nitric acid, are painted over with a solution of chloride of gold in ether. A solution 
of chloride of gold in solution of pyrophosphate of soda Has lately been suggested as a 
suitable bath. 

Fire-giiding. Articles of bronze, brass, copper, silver, especially buttons and ornaments 
of military uniforms, are gilt with an amalgam of gold and mercury, 2 parts 
of the former and i of the latter being applied by means of a solution of nitrate of 
mercury. The articles being next heated in a muffle, the volatile metal escapes, leaving 
an adhering film of gold, which may either remain dull or be polished, the colour being 
preserved in the former case by a momentary immersion in a fused mixture of nitre, alum, 
and common salt, and immediately after in cold water. If it be desired to leave only 
some portions of the gilding dull, the portions to be afterwards polished are covered with 
a mixture of chalk, sugar, gum,- and sufficient water to form a paste. The rationale of 
the action of the fusing mixture is that chlorine gas is evolved, which, as the term nms, 
bites the gold. If it is desired to impart a red-gold colour, a paste of wax, bolus, basic 
acetate of copper, and slum is spread on the gilding, and the article held over a dear 
fire, the result being the reduction of the copper, which combines with the gold. As the 
use of the so-called quicksilver-water (nitrate of mercury) is very injurious to the 
operatives, M. Masselotte, of Paris, coats the articles with mercury, afterwards with gold, 



MANGANESE AND ITS PREPARATIONS. Iii 

ind again with meronry, by means of galvaniBm. Finally, the meronry is volatilised by 
ignition in a moifle, bo arranged that the yapours escape only in the flue. According to 
H. H. Strove, so-called lire-^t articles are not really covered with a simple film of gold, 
bat with an amalgam of gold and 13 '3 to i6'g per cent of mercury. Electro gilding will 
be treated in a separate section. 

(kHibK'kPiapie. The preparation which bears this name was discovered by Dr. Gassins, at 
Leyden, in the year 1683. ^^ ^ prepared by adding to a solution of chloride of gold a 
eertain quantity of sesquichloride of tin. Dr. Bolley prescribes the following process : — 
First, io'7 parts of the double chloride of tin and ammonium are digested with pure 
metallic tin until the metal is quite dissolved, 18 parts of water are then added, and the 
liquid mixed with the gold solution previously diluted with 36 parts of water. The result 
w the throwing down of a purple or black-coloured precipitate, about the chemical 
constitution of which nothing is certainly known. Well prepared Cassius's purple should 
contain 39*68 per cent of gold. 

saMaoiOiM. The doublo salts of chloride of gold and sodium (AuClsNaCl + zHO), and 
the corresponding potassium salt (aAuCljjKCl-i-sHO), are employed in photography and 
medicine. 

Manganese and its Prepa&ations. 

HanguiMe. Of all the OTes of manganese met with in various degrees of oxidation, 
only the peroxide, mineralogically known as pyrolnsite, polianite, and technically as 
glass-makers' soap, is industrially of mnch importance. When perfectly pure this 
mineral consists of 63 '64 per cent of manganese, and 36*36 per cent of oxygen, its 
formola being MnO^; but the ore, as met with in commerce, frequently contains 
baryta, silica, water, and sometimes oxides of iron, nickel, cobalt, and lower oxides 
of manganese^ viz., Braunite, Mns03 ; Manganite^ Mn203,HaO ; Hausmannite* 
MQ3O4 ; and various other minerals, as potassa compounds, lime, &c. In Germany, 
the ore is purified by most ingeniously contrived machinery, which might be very 
advantageouslj applied to a great many other metallic ores and phosphatic minerals. 
Manganese is industrially employed in making oxygen, the preparation of bromine and 
iodine, glass-making, colouring enamels, for producing mottled soaps, in puddling, 
iron, and in dyeing and calico-printing, for preparing permanganate of potassa ; but 
the largest consumers are the manufacturers of chlorine. The bulk of the manganese 
of commerce is derived from Germany, which supplies about 700,000 cwts. to Europe 
umoally. It is found also very largely and of excellent quality in Spain, as well 
as in Italy, Greece, Turkey, Sweden, and British India. 

'*riif^S!?'' The value of manganese for technical purposes depends — i. On 

the quantity of oxygen it is capable of yielding, or the quantity of chlorine it will 

evolve, not taking into account the O of the MuO. 2. On the nature and quantity 

of the substances soluble in acids, such as the carbonates of lime and baxyta, protoxide 

of iron, which, not yielding chlorine, saturate a certain quantity of hydrochloric 

acid. But even if these impurities are absent, it may happen that, of two samples of 

manganese, one requires more acid than the other to evolve the same bulk of chlorine 

gas, as, for instance, when one of the samples contains in addition to peroxide of 

manganese (MnOa) also the sesquioxide (Mn^Os), especially if the latter is present 

as hydrate. 3. On the quantity of water, which may amount even to 15 per cent. , 

According to the experiments of Dr. Fresenius, the most suitable temperature for drying 
a weighed sample of manganese, in order to estimate the water it contains, is 120°, no 
water of hydratation being expelled at that heat ; but for commercial analysis the drying of 
a sample at 100° is quite sufficient, provided it be kept at that heat for some hours con- 
secutively. Among the many methods proposed for testing manganese, that originally 
invented by IXrs. Thomson and Berthier, and improved upon by Drs. Will and Fresenius, 
is based on the fact that a molecule of peroxide of manganese treated with sulphuric 
acid is capable of converting, by the given o£F, i molecule of oxalic acid into 2 molecules 
of CO,. 




1X2 CHEMICAL TECHNOLOGY. 

,^ .,. %jt r\ \ /I niol. of Sulphate of protoxide of mm- 

I mol. Peroxide of mangMiese, MnOa] ^ f ganese, MnSOa. 

I mol. Sulphtirio awd, H^804 f «»v® 1 « mols. of Carbonio isid, 2C0j. * 

I moL Oxaho aoxd, 03HaO4 ) { ^ j^^^ ^^ Water, aHaO. 

From the weight of COa evolyed is determined the quantity of peroxide of manganese con- 
tained in the sample. The operation is performed in the apparatus shown in Fig. 56. The 
flasks A and b are fitted with perfectly tight-fitting corks, perforated for admitting the glius- 
tubes, as seen in the woodcut. In the flask a is placed the mixture of proTiously dried 

manganese and oxalic acid, with enough water to fill about one-third of 
the flask. The flask b is about half -filled with strong sulphuric acid; 
the end of the tube c is plugged with a piece of wax and the apparatus 
weighed. Next some air is sucked out of b, by means of the tube d, 
so as to cause a small quantity of add to run oyer into a ; thereupon the 
evolution of CO2 sets in, and the escaping gas passing through ttie add 
in B is dried. The suction having been repeated, the wax plug at e, 
as soon as the evolution of GOa ceases, is for a moment removed, and 
the suction again repeated to remove all the COa from the apparatus. 
The plug of wax is now replaced and the apparatus again weighed; 
the loss of weight gives by cedculation the quantity of peroxide of man- 
ganese contained in the sample, if one holds in view that a molecules 
GOa,(COa»88) stand to z molecule MnOa as the quantity of carbonio 
add found to x» If 2*98 grms. of dried manganese are taken, and the 
quantity of COa divided by 3, the centigrammes of COa lost express the 
proportion per cent of pure peroxide of manganese contained in the sample ; to i part of 
manganese i^ parts of neutral oxalate of potassa should be taken for the experiment. If 
the sample of manganese happens to contain carbonates, it has, previously to being tested, 
to be treated with very dilute nitric add, and of course well washed wiitt distilled water 
and afterwards dried. For other methods of testing manganese, the reader is referred to 
Mr. Grookes'B work on " Select Methods in Chemical Analysis.'* 

PeBMANGANATE of P0TA88A. 

pwmaoguutto'ofPotMM. This Salt (KMn04), used for disinfecting, bleaching, and 
other oxidising purposes, and constantly employed in chomi<al laboratories, owes its 
effidency to the fact that, in contact with dilute sulphuric acid, it yields protoxide of 
manganese and oxygen (Mna07=2MnO-|-50). The permanganate of potassa is for 
technical purposes prepared in the following manner : — 500 kilos, of caustic potassa 
solution at 45° B. (=i'44 sp. gr.) are added to 105 kilos, of chlorate of potassa 
and the mixture evaporated to dryness, there being gradually added zSo kilos, 
of powdered manganese, and the heating continued to the fusion of the mass, which is 
stirred until cold. The powder thus obtained is heated in small iron crudbles to a 
red heat, and when semi-fluid is cooled ; the mass is next broken up and put into a 
large cauldron filled with hot water, and left standing for about an hour. The dear 
liquid having been decanted from the sediment, hydrated peroxide of manganese, is 
evaporated to cryistaUisation ; 180 Idles, of manganese yield 98 to 100 kilos, of crys- 
tallised permanganate. Approximately the process may be eluddated as follows : — 

a. By the fusion of the potasdum manganate and chloride of potasdum : — 
6MnOa+2KC103-f i2K0H= (^KJiSjiO^) +KCI+6H4O ; 

fi. During the solution of the fused mass in water, the manganate of potasdum is 
converted into hydrate of potassa, hydrate of peroxide of manganese, and perman- 
ganate of potassa:— 3KaMn04-f6HaO=4KOH-faKMn04-fMnOa+4HaO. Conse- 
quently one-third of the manganic add is lost by the formation of peroxide of 
manganese. This also occurs when, according to M. Tesd6 du Motay's plan, the 
converdon of manganate of potassa into permanganic add is effected by sulphate of 
magnesia ;— 3K«Mn04-f 2MgS04=2KMn04+MnOa+2KaS04-f 2MgO. Dr.Staedeler 
therefore suggests that the manganate of potassa should be converted into perman- 



ALUMINIUM. 113 

ganate by chlorine, according to the formula : — K2Mn04+Cl=KGl-|-EMn04. For 
disinfectiDg purposes a mixed permanganate of potassa and soda, or even the latter 
alone, is nsnal ; the well-known Condy's fluid is a solution of this salt in water 
eontaining per-sulphate, not proto-sulphate of iron. Permanganate of potassa is 
mod to some extent in dyeing, and for staining wood. 

Alumuvium. 
(Al=Z7-4; Sp. gr.=2-5). 

tafcnuonof AfauniniimL Aluminium, discovered at Gottingen, in 1827, ^7 ^- Wohler, 

belongs in the shape of its oxide to the most widely dispersed as well as the most 

commonly occurring materials on our globe. The properties of this metal were more 

pirticnlarly studied in 1853 ^y ^- I^eville, who found that aluminium is far less 

readily acted upon in the molten state by oxygen, in the cold by dilute adds and by 

boiling water, than was at first thought to be the case, and this eminent author's 

researches gave rise to the production of this metal for industrial purposes, two 

manufactories existing in France, viz., at Salyndres and Amfreville, and one in 

England, at Washington, county Durham. 

Alnminium is obtained from the double chloride of aluminium and sodium by the aid 
of the latter alkaU-metal, which is prepared for this and other purposes by the ignition of 
a mixture of zoo parts of calcined so(&, 15 parts of chalk, and 45 parts of small coal. 
GUoridd of aluminium is best prepared from bauxite, native hydrate of alumina, which, 
baving been previously mixed with common salt and coal-tar, is next heated in an iron 
retort with chlorine gas, the result being the formation of carbonic oxide and the double 
diloiide of aluminium and sodium, which volatilises, and is condensed in a reservoir lined 
vith glazed tiles. The salt so obtained contains iron, and consequently the aluminium 
dfiuTed from it is alloyed with that metal. The double chloride of iduminium and sodium 
is eonverted into metallic aluminium by being heated in a reverberatory furnace with 
flodiun ; while the aluminium is set free, a slag is formed consisting of the double salt 
vith excess of chloride of sodium. Professor H. Rose, at Berlin, first used cryolite for 
ha experiments on aluminium, the mineral bearing that name being a compound of the 
double fluorides of aluminium and sodium (AlaFl^-f 6NaFl). This mineral being treated 
at a high temperature with sodium yields aluminium and fluoride of sodium, and the 
latter treated with quick-lime yields caustic soda and fluoride of calcium. 

PKpMtiea of ATliinfntnm. The colour of this metal is intermediate to those of zinc and 
tin ; its hardness exceeds that of tin, but is less than that of zinc and copper, and 
about the same as that of fine silver ; it is a very sonorous metal, rather brittle, 
naUeable to some extent, readily rolled into thin sheets, and may be beaten into leaf; 
on tbe other hand, it is not ductile. Aluminium does not rust by exposure to air, and 
it may be even heated to redness without suffering much oxidation. When fused, 
however — ^it melts at 700** — ^it oxidises so much as to necessitate the use of a flux — 
best chloride of potassium — ^to absorb the alumina which is formed. It is very 
tBadily and rapidly dissolved by hydrochloric acid and solutions of caustic potassa 
Uid soda, hydrogen being copiously evolved ; but the metal is not in the least acted 
i^pon by nitric acid. It does not amalgamate with mercury. With tin it yields an 
>Uoy of considerable hardness, yet to some extent malleable ; with copper in the 
proportion of 90 to 95 per cent of copper and 10 to 5 per cent of aluminium, it forms 
alnminium-bronze. This alloy, in colour similar to gold, is used for artificial jewel- 
lay and small ornaments. Aluminium does not alloy with lead. The aluminium of 
ocmmerce is never quite pure, always containing silicium, found by Dr. Ranunelsberg 
wan to 10-46 per cent, and frequently present to 07 to 37 per cent ; while tlie 
quantity of iron varies from i'6 to 7*5 per cent. 

1 



114 



CHEMICAL TECHNOLOGY. 



Appikations. Alnminiam is now not bo much in nse : when first introdneed alTunimnm 
jewellery waB the order of the day. The metal is at present more nsefolly employed for 
email weights, light tabes for optical instmments, and to some extent for surgioal instm- 
ments. The price, howerer, of this metal, £5 12s. per kilo., is too high to admit of ita 
extended nse; while great lightness, combined with oomparatiye strength, are its only 
prominent qualities. 

Magnesium. 
(Mg=24; Sp.gr. 1743). 

Macnednm. As an oxide, and in combination with chlorine and bromine, as well as 
with'other metalloids, magnesiom is found in very large quantities, for instance, in 
sea- water and camallite, as sulphate of magnesium, ad kieserite, shoenite, kainite, in 
rocks as a pure carbonate, and as magnesian limestone; further as a silicate in 
meerschaum. Metallic magnesium has but limited commeifcial applications. It is 
silvery- white in colour, somewhat affected by the oxygen of the air, but not more so 
than zinc ; fuses at about the same temperature as that metal, and when heated a 
little above this point, bums with an intensely brilliant white light, and in oxygen 
gas the combustion is attended with a light almost equal to bright sunlight. Magne- 
sium may be readily drawn into wire ; it is at the ordinary temperature of the air as 
malleable as zinc, and boils and distils over at about the same temperature as that 
metaL Magnesium is at present only applied to yield an intense light in photography, 
and for signals ; for this latter purpose it was extensively used in the Abyssiiiian 
campaign (1868). It has been suggested to alloy magnesium instead of zinc with 
copper. 

Magnesium is prepared by a process very similar to that of aluminium manufacture: — 
Sodium is ignited with either chloride of magnesium — ^Bunsen, Deville, and Gamm 
methods— or the double fluoride of magnesium and sodium — Tissier's plan — or the double 
chloride of magnesium and sodium — Sonstadt's method. Dr. H. Sdiwarz employs the 
double chloride of calcium and magnesium, and M. Beichardt camallite, double chloride 
of magnesium and potassimn. Several other suggestions have been made as to the mode 
of preparing this metal, but it does not appear that they are available in practice. Mag- 
nesium is manufactured on the large scide by the Magnesium Metal Company at Man- 
chester, and the American Magnesium Company at Boston, the English finn producing 
i^ut 20 cfrts. annually. 

Elbctbo-Metallurot. 

AvpHMttonoroiaTMiiim. It is one of the most prominent properties of the oontiniious 
electric current, that it is capable of decomposing compound substances in such a 
manner as to cause the constituents to be deposited on or near the place where the 
current leaves the body to be decomposed ; this property is termed deetrolytU^ the 
body decomposed being termed electrolyte^ and the places where the electric current 
enters and leaves deotrodes ; the positive pole of the battery being named anode^ and 
the negative cathode. The constituents of the body decomposed by electricily are 
termed ions (from imv, participle of ccfu, to go) ; that deposited or separated at the 
anode (-f pole) being distinguished as the anion, and that making its appearanee at 
the cathode the cation. An electric current strong enough to decompose a molecule 
of water is also capable of decomposing a molecule of a binary compound ; accordingly 
the quantities by weight of a body decomposed by the electric current are propor- 

Kieeinijtie Law. tional to the xjhemical equivalents. The main laws of electrolysis 
were discovered by Faraday, who was the first to show that the constituents 
attracted by the anode (+ pole) are electro-negative, and those by the cathode 






ELECTRO-METALLUBar. 115 

(~ pole) electro-poaitiTe. As water is a common solvent, it frequently occurs that 
dnzing electrolysis its elements are secondarily decomposed. For instance, sulphate 
of copper gives, at the anode oxygen gas, and at the cathode metallic copper, because 
the oxide of copper appearing at this pole is at once de-oxidised by the simultaneous 
appearance of hydrogen : the oxygen set free at the positive plate combines with the 
zinc, forming an oxide, converted by the acid into sulphate of zinc; so that for every 
equivalent (63*4) of copper deposited, one equivalent (65*2) of zinc is dissolved. If, 
instead of sulphate of copper, suitable solutions of gold, silver, &c., are employed, 
the electro-deposition of these metals can be .effected. 

OMtntypiiig. The following are the chief technical applications of electrolysis : — 
Electrotyping. It has just been said that the copper separated electrolytically from 
the sulphate of that metal is deposited in a coherent state, and if the operation is 
continued for some time the layer of metal may become sufficiently thick to admit of 
being detached from the form upon which it was deposited. This principle of electro- 
typing was discovered in 1839, simultaneously at St. Petersburg by Dr. Jacobi, and 
at Liverpool by Mr. Spencer; among those who have laboured to improve this art, 
are Messrs. Becquerel, Eisner, Smee, Ruolz, Elkington, and many others. The metallic 
solution applied for the preparation of casts to be electrotyped is always a saturated 
solution of sulphate of copper, and the form, technically termed the pattern or 
matrix, upon which it is desired to deposit the copper, should not consist of any 
metal, such as zinc, tin, or iron, acted upon by a solution of sulphate of copper. 
The matrix is usually, if it be a metal, made of copper ; but more frequently it 
eonaista of gypsum or gutta-percha. In order to render the electric current uniformt 
the zino plate of the battezy is amalgamated by dipping it in hydrochloric or dilute 
sulphuric add, and then rubbing mercury over the surface with a brush or piece of 
soft rag. 

■•pmdoction of Copper- The engraved oopper-plate to be reproduced is placed at the 
Plate BngnTinst. bottom o£ a wooden trough liaed "with resin or aaphalte. Above the 
plate is fixed a wooden frame, on which is strained a sheet of bladder or parchment, to 
serve as a diaphragm ; and on the top of the frame a plate of zinc is placed, and oon- 
neeied with tiie oopper-plate by a strip of lead. A saturated solution of sulphate of 
eopper is poured into the bottom of the trough, and in order to maintain the saturation a 
few oiystals are added. Above the porous diaphragm a concentrated solution of sulphate of 
aine is placed. This plan is also pursued in electrotyping woodcuts, stereotype-plates, Ae, 

Dcporiiioa of Mouia. To reproduce medals and other small objects a weak current only is 
required. The plate or object on xrhieh. it is desired to cause the deposition to take place 
ia suspended vertically from the cathode, and a plate of the metal to be deposited from 
the anode ; in proportion as the metal is precipitated at the cathode, it is dissolved at the 
anode, leaving the concentration of the fluid unchanged. Such substances as are 
non-conductors, wax, paraffine, and gypsum, are first superficially coated with some 
eonducting material, as graphite, silver, or gold-bronze. Gutta-percha is an excellent 
material for easts, owing to its becoming plastic in boiling water. According to M. von 
Kobell, a tough malleable copper is obtiuned by adding to the copper solution some 
sulphate of soda and sulphate of zinc. Unless a rather weak current is applied, the 
copper is* separated from its solution in a spongy state ; on no account should the 
eorrent be strong enough to decompose wata. 

"Sd'Sffflrw?"* ^ order to apply a coating of gold or silver to copper, brass, 
bronze, or other metallic alloy, the surface should be first very thoroughly cleaned by 
boiling in a caustic soda solution. Smee's battery — a platinised silver plate, and a 
plate of amalgamated zinc — ^is now generally used, the elements being placed in 
leaden vessels lined with asphalte. The solution of gold or silver in cyanide of 
potassium is employed as the decomposition liquid, in which the objects to be silvered 
or gilded are suspended by a wire connected with the negative pole of the battery ; 

I 2 



1x6 CHEMICAL TECHNOLOGY. 

and to another wire, oonnected to the poeitive pole of the battery, is fastened a piece 
of platinitm, which is also immersed in the liquid of the decomposition-cell. The 
whole process only lasts a few minutes, the cathode during the time being moved 
backwards and forwards by hand to render the deposit uniform. Plates of gold or 
silver are generally used instead of platinum at the anode, and become gradually 
dissolved by, and maintain, the cyanide solution at a constant strength. 

ooid Bointioii. 100 gnus. of Cyanide of potassium are dissolved in i litre of distilled 
water, and 7 grms. of very fine gold in nitro-hydrochloiic acid, this solution being 
evaporated to dryness on a water-bath, the residue dissolved in distUled water, 
and to the solution some cyanide of potassium added ; or the gold salt obtained on 
evaporation may be dissolved in distilled water, and the solution carefully precipitated 
with sulphate of iron, the finely-divided gold being collected on a filter, next washed 
with distilled water, and finally dissolved in cyanide of potassium. 

BUver Boiation. This solution is prepared by dissolving well- washed chloride of silver 
in the above solution of cyanide of potassium, so as to obtain a saturated solution of 
cyanide of silver, afterwards to be diluted with an equal bulk of water. 

Copper, bronze, brass, iron, and steel, can be eleotro-plated directly ; but poliBhed steel, 
tin, and zino, have to be first coated with a film of copper. German or nickel-silver is now 
generally eleotro-plated. The thickness of the film of silver may vaiy from i-42nd to 
1.450th, or even to i -9400th of a millimetre, corresponding to 1*240 grms. of silver, 
on I square metre of surface. Frequently the best electro-plated ware made in this 
coxmtry is afterwards coated with a very thin film of palladium to prevent the silver being 
a£Feoted by sulphuretted fumes. 

oopper Solution. For the purposo of electro-coppering, a solution of oxide of copper 
in cyanide of potassium is the most suitable fluid ; this solution is prepared by first 
decomposing a solution of sulphate of copper in water, with the aid of caustic 
potsAsa and grape sugar, so as to obtain a precipitate of suboxide (red oxide) of 
copper, which, having been collected on a filter, and well washed, is next dissolved in 
a solution of cyanide of potassium. For the purpose of electro-coppering iron and 
.steel, M. Weil, of Paris, prepares a fluid — ^350 grms. of cupiic sulphate, 1500 gnns. of 
potassio-tartrate of soda (sal seignette), and 400 to 500 grms. of caustic soda dissolved 
in 10 litres of water. 

M. Oudiy's method of depositing copper on iron eandelabras, gas lamps, fountain 
ornaments, Ac, is in some particulars quite different, the copper not being immediately 
deposited on the iron, which is first coated with an impermeable layer of a kind of red- 
lead paint, graphite being afterwards rubbed in for the purpose of rendering the surface of 
the object a conductor. To obtain a coatiog of copper i mUlim. in thickness, such articles 
as candelabra are left in the solution for 4^ days ; the ornamental fountains of the Place 
la Concorde, Paris, have been for a period of two months in the solution. 

zinc and Tin Solution. To coat irou with zuic, a solutiou of the sulphato of the latter 
metal may be used, but the so-called galvanised iron of commerce is made by a 
different process, viz., by placing the iron to be coated in a bath of molten zinc 
covered, for the purpose of preventing oxidation, with a layer of molten tallow or 
paraffin. For the purpose of electro-tinning, a solution of tin in caustic soda is 
employed, the anode being of tin. 

^ A so-called electro-steeling, really a deposit of iron on the copper plates used for engra- 
ving, is effected by M. Meidmger in the following manner : — The bath is a solution of sul- 
phate of iron and chloride of ammonium ; to the copper pole of tiie battery a plate of 
iron, and to the zinc pole the engraved copper-plate, are connected. These steeled plates 
serve for as many as 5000 to 15,000 impressions. This method has been applied to 
stereotyping with great success, and indeed the deposition of iron eleetrolytically is 
a valuable addition to technology. 



ELECTRO-METALLURGY. 117 

[ hj otifwtam. This process is based npon the fact that, under oertain conditions, the 
Ribstanoefl separated at, combine with the electrodes, the consequence being that the 
electrode is gradually corroded and destroyed. The copper-plate intended to be etched is 
nmformly covered with a mixture of 4 parts of wax, 4 of asphalte, and i of black pitch ; 
the design is then drawn or rather scratched with proper tools through this non-con- 
dneting layer, and the plate attached to the anode of a galvanic battery, and placed in 
s solution of sulphate of copper, containing also a copper-plate connected to the negative 
electrode of the battery. On this plate is deposited the copper of the solution, while the 
oxygen of the decomposed water, with the sulphuric acid, act upon the portions of metal 
not covered with the protective layer and produce the etching. 

ibwiMhniiiy, Or galvanic painting, consists in depositiDg thin films of oxide of lead in 
ft coherent state on metal plates, thus producing Nobili's colours. The oxide of lead is, for 
this purpose, best dissolved in caustic potassa or soda solutions. In England, this method 
of ornamenting is not much applied ; but at Nuremburg, where toys are largely manuf ac- 
tnred, this process is very simply carried out by placing the metallic object, previously 
connected witii the cathode of a battery, in a concentrated solution of oxide of lead in 
cftostie potassa, while to the anode is afi^ed a piece of platinum foil. 

ihrt>»8ui B 4jpius. For the purpose of reproducing printing-types by galvanic means, 
ft wax impression of the type is placed in the deposition-cell. This operation is also 
employed for the reproduction of woodcuts, gutta-percha being used as a mould. 

etnhovH»»j' By this name is understood a process for reproducing woodcuts, but it is 
now altogether obsolete, having been superseded by electro-typiog. A further disadvantage 
wis, that the glyphographic plates could not be printed from the same matrix as type. 

Oftnuogmghj. At the suggestion of Dr. von Eobell, the reproduction of some kinds of 
dnwingB and pictures has been tried. In order to enable exact copies to be printed from 
plates deotrolytically obtained from the original drawings ; but this method, of very difficult 
ftod costly execution, is superseded by photography. 



(ii8) 



DIVISION II. 
obude matxrialb and fb0du0t8 of oukmioal imdu8tby. 

Carbonate of Potassa. 

(KaG03=i38'2 ; in loo parts, 68*2 potassa and 31*8 parts oarbonio add.) 

^'^^'^^'udStlL****" ^® substance known in chemistry as carbonate of potassa is 
generally termed potash, because it was formerly obtained from wood-ash, which, 
after lixiviation with water, was evaporated to dryness in cast-iron pots. Potassa 
occurs native in considerable quantities, but never free, being combined with silica in 
many minerals, also in combination as chloride of potassium, sulphate of potassa, 
and in various plants with organic acids. The following are the sources whence 
potassa is industrially obtained. 

I. The salt minerals of Stassfrirt and Kalucz ; products — 
. . camallite, sylvin, kainite, and schoenite. 

Ittorganio sources ^ jj Feldspar and similar minerals. 

m. Sea-water, and the mother-liquor of salt works. 

IV. Native saltpetre. 

V. The ashes of several plants. 

VI. The residue of the molfiisses of beet-root sugar after 
distillation. 

VJLl. Sea- weeds, as a by-product of the manufacture of iodine. 

, Vm. The suint of the crude wool of sheep. 



of Potassa. 



B. Organic sources of 
Potassa. 



wJSSSt^sJitMSSS. ^' '^® ^®^ abundant salt-rocks near Stassfurt, in Prussia, and 
Kalucz, in Hungary, chiefly yield camallite, sylvin (CIK), and kainate, a compound 
of sulphate of potassa and magnesia with chloride of magnesium. Camallite, so 
named in honour of Camall, a Prussian mining engineer, consists, in 100 parts, 
leaving the bromine out of the question, of — 

Chloride of potassium 27 

Chloride of magnesium 34 

vva«eraa* ••• ••• ••• ••■ ••• 39 

100 
Fonnula— KCL, Mg | ^^-f 6HaO. This salt is applied in the manufacture of— 

a. Chloride of potassium. 
p. Sulphate of potassa. 
7. Potash (carbonate). 



CARBONATE OF FOTASSA. 



rrg 



•L IV«p«ntion of Chloride of Potossiimi. — Aocording to the prooess origmallj 
i»toiit«d (t86i) by Hr. A. Frank, the abrauia B&lta oie ignited in a reverberateiy 
taioaee, with or withont the aid of b. cmrrent of steam, and next lixiviated with water, 
the resulting liqnor jielding chloride of potaBsinm. The rationaU of this prooess 
is: — I. That the camsllito of the abraiuii salts is separated by the action of the water 
into chloride of potaaaiDm and chloride of magneaiom. 2. The latt«T salt on being 
ignited in a current of ateam is decomposed into hydrochloric acid, which escapes, 
and magnesia, which is practioaUj insoluble in water, and which consequently remains. 
Hiii process is not found to answer well on the large scale, because the abranin 
Mhs contain other chlorides, the chloride of sodiont and tachydrite, by the presence 
of which the deeompoaitiou of the camallite is hindered. Dr. GrQneberg. tberefore, 
mggseted that the abranm salts ahonld be first mechanically purified, that is to say, 
the different components of the abraum salts shonld be separated from each other 
■eoording to thdi liiying specific gravity, which for — 

Camallite is=r6i8 

Chloride of sodium is = a'aoo 

Kieserite i8 = 3'5i7 

The abrkinn ealt having been ground to a coarse powder is passed throngh sierea, 
tod treated as minerals are in metsUurgical processes, with the difference that, instead 
of water, which of oonrBe would dissolve tJie salts, a thoroughly ccmcentrated solution 
of chloride of magnesium is applied, this solution not acting upcm the salts, and being, 
nuir«over, obtained as a by-product in enormonsly targe quantitiea. The above- 
nenlioneci salts settle in layers according to their densities, the camallite forming 
the upper, and the kieserite the lowest layer. The camallite is at once applied to 
the pieparatioQ of chloride of potassium 1 the middle layer of common salt is so free 
from other foreign salts as to be fit for domestio nse ; the kieserite, after baring been 
•uhed with cold water t« remove any adhering chloride of sodium, is applied to the 



Fia. 57. 



Fio. jB. 





nann&ctnre of Butphate of potassa, to be presently described. However, the greater 
umber of mann&cturets at Stassfuri prefer another plan, applying the fire following 
Dperktionslo the abranm salts as delivered from the salt qnarries: — i. Lisiviation 
of the camallite with a limited qnantity of hot water, sufficient to diaaolve the 
chlorides of polassiiim and magnesiiun, leaving the bulk of the common salt """I 
1 sulphate. 1. Crystalliaing the chloride of potassium by artificially 



CHEMICAL TECmiOLOaY. 

Evaporstiug and cooling the motber-liqiior to produce a Becond jield 
of dystollised chloride of potsBsiiiiii. 4. Again evapomtiiig and oooliog the mother- 
liquor, which yieliB the double salt of the ohioridea of potaadnm and magneainm, 
01 artifici&l oaraallite, which is next treated in the same manner as the native smlt- 
5. Washing, drjing, and packing the chloride of potassium. 

I. The comftllite is pntinto out-iron liiiviationTesselBand'mixed with tbree-tonithsot 
its weight of water, preriouel; employad for the washing of ornde ohloride of polaasinm, 
and, therefore, contaimng a large ^nantity of common salt and soma ohloride ol 
potaBsintu : steam, at izo", and at a preBsare of 30 lbs. to the aqnore inch, is forced 
throogb the perforated circnlarlj' bent tube, t (Fig. 59) at the bottom of the vessel In 
Ur. Donglaa'B woilu the lixiviation vessels. Figs. 57, 
Fio. 59- 5S, and 59, have a cnbical cupaoit? of xo tons. Tb^ 

are closed with a tightly&ttiug lid, an opening being 

cut for the escape of surplns Bteam. The stirrer, c, is 
kept in motion by steam power. When the admission 
of steam and the stiniog has been oontiDned abont 
three hours, the contents of the vessels are left at rect 
tor two dajB, after which the satnrated solution has a 
density of 33° B. = i-i36 sp. gr., and is forced bj steam 
pressure Into crygtallising vesMlx; the residne in tlw 
^KiviatioD vesseb, amounting to about one-third of the 
weight of the camallite, is agun treated as described. 

a. The oi7BtaUiBation veBsels are of wood or sheet- 
iron, 1-20 meb^B diameter, by 15 to eg metres height. 
The chloride of potaasiom crjBtftiliaes in combinatioD 
with common salt, and is strongly impregnated with the 
very soluble and highly deliqueeceut ohloride of mag- 
neainm ; the salt deposited at the sides of the veeael 
oontaina npwarda of 70 per cent of chloride of potaasinm, while that collected at the 
bottom oODtainl only 55 per oent. If shallow vessels are employed, the saline solntioi) 
cools more rapidly, and a finer grained salt is obtained, mixed, bowerei, with itnpnritiea, 
and requiring more washings, au operation which, with the coarse salt, has only to be 
performed once to yield 80 per cent chloride of potassium. Most of the chloride of 
potassium sold by the manufaiiturers oontoins So, and in some cases S5 and 90, per cent 
of tfaepure salt. 

3. The eraporation of the first mother-liquor is carried on ia iron pans of Tariona 
■izes. As by the evaporation common «^t ia largely deposited, which has a tendency to 

Fio. Go. 






cake at tbe bottom of the pans, and cheek the onudnotion of heat, the pans are set so a* 
toreceiTB the action of tbe flame only on the aides (Fig. Gi), and the hquid kept conttaotly 



CARBONATE OF POTASSA. X2i 

Btimd. When fhe Hqnor has been reduced to about two-thirds of its bnlk, with a density 
of 33** B.B 1*298 sp. gr., it is run into the crystallising vessels. The mass remaining in 
the eraporating pan, consisting of 60 to 65 per cent common salt, 6 per cent chloride of 
potassiiim, and 30 per cent donble sulphates of magnesium and potassimn, is used as manure. 
Steam-heated evaporating pans, represented in Fig. 60/ are employed by some manu- 
fsetnrers ; the four steam-tubes, t, are placed parallel to the sides of the vessel, and open in 
II, the waste steam being carried off by the tube t'. As might be expected, the concen- 
tration of the liquor is more rapidly p^ormed by means of steam, but the crystallisation 
of the second crop of salt is poorer, yielding only 50 to 60 per cent chloride of potassium, 
and requiring two to three washings to accumulate 80 per cent pure potassium salt. 

4 and 5. The second mother-Uquor is again concentrated by evaporation to 35** B. 
a Bp. gr. 1*299, yielding a saline mass similar to the residue of the first evaporation, and 
to which it is added and used as a manure. On being submitted to crystallisation, this 
last liquor yields artificial carnallite, treated as the salt obtained from the native deposit, 
giTing, however, with less labour 80 to 90 per cent chloride of potassium. The chloride 
of potasflimn, after washing with pure water, is dried either in rooms heated by steam, or 
in a moderately heated reverberatory furnace. The dry salt is then packed in casks, 
each containing about 500 kilos. 

fi. The preparation of sulphate of potassa may be effected : — 

a. From chloride of potassium and sulphuiio aoid. 

b. By Longmaid's (see Soda Manufacture) roasting process, viz., the calcination 

of chloride of potassium and sulphuret of iron, and in metaUurgical 
processes where chloride of potassium is used instead of chloride of sodium. 

e. From chloride of potassium and kieserite. 

d. From kainite. 

The conversion of chloride of potassium into the sulphate of potassa by double 
decomposition with sulphate of soda is not practicable on the large scale, as the two salts 
have a tendency to form double salts ; therefore, the methods a and b are practically 
available only under certain peculiar conditions. A small quantity of chloride of potassiTmi, 
obtuned in Scotland as a by-product of the preparation of kelp, is converted into sulphate 
of potassa by the means in use for the manufacture of soda (quod vide). The leading 
points in the manufacture of sulphate of potassa by the aid of the sulphuric acid contained 
in kieserite are the following : — First schoenite and carnallite are prepared by dissolving 
ebloride of potassium and Ueserite in boiling water, and crystallising the solution thus 
obtained : — 

4 mols. Kieserite 1 =» / ^ mols. Schoenite. 

3 mols. Ohloride of potassium J ( i moL Oamallite. 

The schoenite and artificial carnallite are separated by crystallisation, and the former 
decomposed by chloride of potassium : — 

'4 mols. of Sulphate of potassa. 



4 mols. Schoenite 

3 mols. Chloride of potassium 






2 mols. of Schoenite. 
^ I mol. of Carnallite. 



The sulphate of potassa crystallises first, and is simply purified by washing with water. 
As kainite is found in very large quantities among the salme deposits near Stassfurt, it is 
also used for the preparation of sulphate of potassa ; by a simple washing with water, 
the chloride of magnesium contained in the kainite is removed, and the salt thus converted 
into schoenite : — 

-Chloride of magnesium} =* Schoenite. 

The sohoenite is then employed in the manufacture of sulphate of potassa by being 
treated witii chloride of potassium ; the sulphate of potassa thus obtained is used either 
in alum or potassa mani^acture, or as a potassa manure. 

7. Preparation of Carbonate of Potassa or Mineral Potash. — Very many suggeetions 
have been made for converting by simple means ohloride of potassiiun and sulphate 
of potassa into carbonate of potassa, industrially known as potash ; bnt most of 
the plans proposed are unfit for use on the large scale, and even the method adopted 
by Leblanc for soda manufacture has not been in every case successful when applied 
to the production of chloride of potassium. At Kalk, on the opposite bank of the 



Z2a CHEMICAL TECHNOLOOY. 

Khine to Cologne, a process, said to be based npon Leblanc's method, is snccessfblly 
in operation, but the real arrangements are carefully kept secret, no one being allowed 
to visit the works ; however, it is stated that snlphate of potassa containing schoenite 
is mixed with chalk and small coals, and calcined, the calcined mass being lixiviated 
when cool, and yielding carbonate of potassa in solution, and a residue of sulphide 
of calcium. 

""^^fro^rKo?^"* ^- Potassa-salts from feldspar. It has been found by the 
analysis of minerals entering largely into the constitution of rocks, that potassa is 
present in considerable quantities. The following may be taken as instances: — 
Orthodase, or potash feldspar, contains from lo to i6 per cent ; potash mica, 8 to lo 
per cent ; trachyte, glaukonite, phonoUthe, 7 to 8 per cent ; porphyry, granulite, and 
mica schist, 6 to 7 per cent ; granite, syenite, gneiss, 5 to 6 per cent ; dolerite, basalt, 
kaoHn, and clay, i to 2 per cent. 

Before the discoveiy of the potassa-salt deposits at Stassfurt, Ealuos, and elsewhere, 
there were many suggestions made as to the obtaining of the potassa on the large seale ; 
but at present tms branch of industry lies dormant, notwithstanding the theoretical value 
of Mr. Ward's (1857) suggestion that feldspar should be mixed with fluor-spar, both finely 
pulverised — ^the fluorine being equal in quantity to the potassa contained in the fluor-spar 
— a mixture of chalk and hydrate of lime added, the mass ignited in kilns or gas-retorts, 
and finally treated with water to yield caustic potassa and a residue, which, after another 
calcination, yields excellent hydraulic lime. 

**»^-^g,f«"» in. Dr. Usiglio found that the water of the Mediterranean contains in 

10,000 parts by weight 5*05 parts of potassa ; and after the removal of the more 

readily ciystsllisable salts left by the spontaneous evaporation of the water by the 

sun's heat, this natural mother-liquor is applied to the preparation of potassA-salts, 

according to the following method : — 

The process now in use near Aigues Mortes, and other localities in proximity to the 
Mediterranean, was invented by Professor Balard, the discoverer of bromine, and yields 
from I cub. met. of mother-liquor, equal to about 75 cub. mets. of sea-water, at 28^ B. 
B 1*226 sp. gr., 40 kilos, of sulphate of soda, 120 kilo%. of refined common salt, and 
10 kilos, of chloride of potassium. It has been found, however, that this method is rather 
costly, and the mother-liquor is generally left to spontaneous evaporation, yielding the 
three following kinds of salt:— a. The first salt separated from a liquor of 32** B. 
B 1*266 sp. gr., only impure common salt. h. The second salt separated from a fiquor, 
32** to 35^ B. B 1*266 to 1*299 Bp* gr., consisting of equal parts of common salt and Epsom- 
salt, and termed mixed salt. e. The third sidt, 35" and 37** B. « 1*299 to 1*321 sp. gr., 
termed summersalt. The second salt having been dissolved in fresh cold water, tiie 
solution is placed in Garry's ioe-making machine, and yields sulphate of soda by an 
exchange of its constituents. The third salt is dissolved in boilmg water, yielding on 
cooling half its potassa as kainite. The mother-liquor, containing camallite, common 
salt, and bitter, or Epsom-salt, yields sulphate of soda, and, when treated with chloride 
of magnesium, all its potassa as camallite, which, by being washed with water, yields 
chloride of potassium. In this way it has become possible to obtain 45 per cent of the 
potassa of the mother-liquor as chloride of potassium, and 55 per cent of schoenite, which 
is converted into sulphate of potassa. 

aS!?o?p?1^ rV. The residue left from the ignition of the organic matter, or wood, 
as it is usually termed, of plants, contains those mineral substances which the plant 
has taken from the soil, chiefly potassa, soda, lime, magnesia, smsll quantities of the 
protoxides of iron and manganese, combined with phosphoric, sulphuric, silicic, and 
carbonic acids, and also with the haloids. These combinations are not, however, the 
same as those existing in the living plant, because the high temperature of the 
ignition has the effect of changing the affinities. Plants growing near the sea gene- 
rally contain large quantities of soda, while those inland contain generally more 
potassa. The quantity of ash varies not only for different kinds of plants, but for 
various parts of the same plant, verj' succulent plants and the most succulent parts 



CARBONATE OF P0TA88A, 133 

genenDy yield the largest quantity of ash ; herbs yield more ash than shrubs, shrubs 
more than trees, and the leaves and bark of these more than the wood. It is evident 
(hat the inorganic matter, chiefly alkaline salts, being contained in the juice of 
plants in « soluble state, the quantity must of necessity be greatest in the juicy 
and succulent parts. 

Dr. B6ttg0r found the ash of beeoh-wood to contain — 

21*27 V^ <)^^t of soluble salts, 

7873 »i M of insoluble salts. 
The soluble salts were found to be — . 

Carbonate of potassa . . .. 15*40 per cent 

Sulphate of potassa . . 2*27 „ „ 

Carbonate of soda 3*40 ,, „ 

Chloride of sodium . . . . 0*20 „ „ 



21*27 per cent 

The value of an ash for the manufacture of potash is chiefly dependent, in the first 
place, upon the quantity of potassio carbonate it will yield, upon the abundance of the 
wood or other vegetable product, and the cost of labour. The undermentioned woods 
jield, on an average, for 1000 parts, the following quantities of potash — 

Pine o'45 Beech-bark 6*00 

Poplar o'75 Dried ferns 6:26 

Beech 1-45 Stems of maize (Indian com) . . . . 17*50 

Oak i'53 Bean-straw 20*00 

Box-wood 2*26 Sxmflower-stems 20*00 

Willow 2*85 Nettles 25*03 

Elm 3'go Vetch-straw 27*50 

Wheat-straw 3*go Thistles 35*37 

Bark from oak-knots 4*20 Dried wheat-plant previous to 

CotUm-grwaa{EriophoriunvaginiUuim) 5*00 blooming 47*00 

Bashes 5*08 Wormwood 73*oo 

Vine-wood 5*50 Fumitory , . 79*00 

Barley-straw 5*80 

According to M. Hoss, 1000 parts of the following kinds of wood yield — 

Ash. Potash. Ash. Potash. 

Pine 3-40 0*45 Willow 28*0 2*85 

Beech 5*80 1*27 Vine 34*0 5*50 

Ash i2'2o 0*74 Dried ferns . . . . 36*4 4*25 

Oak 13*50 1*50 Wormwood .. .. 97*4 73*00 

Ehn 25*50 3*90 Fumitory .. .. 219*0 79*90 

The preparation of potash from vegetable matter is effected in three operations, viz. : — 

a. The liziviation of the ash. 

b. The boiling down of the crude liquor. 
e. The calcination of the crude potash. 

The combustion of the vegetable matter should be so conducted as to prevent its 
becoming too violent and giving rise to the combustion of some of the reduced potassa- 
■alt ; nor should too strong a current of air be admitted for fear of the ash being mechani- 
eaUy carried off. A distinction is made abroad — ^no potash from wood or other vegetable 
inatter being produced io the United Kingdom, nor wood used as fuel in sufficient quanti- 
ties to yield ash for the preparation of potash — between the ash obtained by the com- 
biutlon of the refuse wood of forests and the ash from wood used as fuel, the f orziier 
being termed /oreft- and the latter /ueZ-ash. As ash from other fuel than wood may be 
Biixed with fuel-ash, a sample may be roughly tested by liziviation, and the density of the 
hqiior taken by the areometer, the hi^er the specific gravity the larger the quantity of 
•okble salts. Formerly ^e forest-aeh was purposely prepared, and sold to potash- 
Ixnlers. There is still known in Eastern Prussia and Sweden a material termed okras or 
oekm , holding a position intermediate to crude ash and potash. 

a* The liziviation of the ash effects the separation of the soluble from the insoluble saline 
"Batter, the former amounting to about 25 to 30 per cent of the entire weight of the ash. 
^s operation is carried on in wooden vessels shaped like an inverted truncated cone, and 
provided with a perforated false bottom, which is covered with straw ; in the real bottom 
* tap is fized for removing the liquor. If the liziviation is systematically carried on, 






134 CHEmCAL TECHNOLOGY. 

■ereral of these TeaaelB ue placed together, forming what is termed b batter]', uid nnder 
•Mh • tank to reoeive the Ui^nor. The aeh to be lijdfiated ia flrtt Bitted bom the oomm 
purtiale* ol ehaiooal, next put into a mauM sqaore water -ti^bt wooden box, and thoroaghl; 
eatorated with water lor at least twenty -fooi honis. B; this prooeediug the lixiiiatiou is - 
greatly asusted, and the eilioate ol potassa to some extent decomposed by the aotion ot 
the oorbonia add of the atmosphere. The next step is to tranafer the wet ash to the 
lillTiation Tessel, oare being taken to pieas it tightly down on to the false bottom ; oold 
vater is then ponred in, until the liqnor begins to rnn otT at the tape left open for that 
purpose. The liquor which runs oS, after the water has remained sDine little time in 
oontaot with the ash, ia foond to contain abont 30 per eent of salable salts, afterwards 
deeieasing to about 10 per cent, when hot water is employed to complete the lixiviation. 
The insoluble resldne left in the lixiTiation-tub is of volne as a mannre, on aoconnt of the 
phosphate of lima it contains, and is also med in makiog green bottle-glass, and for 
building np saltpetre-beda. 

(. Boiling down the liquor. The liqnor obtained, by liiiTiation is ot a brown ooloui, 
owing to organic matter, hmmn or nlmine, whioh the carbonate ot potasaa has dissolved 
from the small chips of imperfectl; bnmt charcoal. The evaporation is carried on in 
large shallow iron pons, fresh liqnor being from time to time added, and the operatioa 
oonCinned until a sample of the hot conoentiated hqaor exhibits on cooling a crystalline 
Bohd mass. When tble point is reached the fire is gradually extinguished, and as soop as 
the contents of the pan are sufficiently cold to handle, the solid salt mass is broken np ; 
its colour is a deep biown. This crude produo^, containing about 6 per eent water, is 
known in the trade as omde, or lump.potoshi^ It is evident that thU method of boiling 
down may eangs cousiderabie damage to the iron pans, therefore in many instancee tho 
operation is oonduoted in a somewhat 3iSerent manner. The liquid is kept stirred with 
iron rakes, and the salt, instead of forming a hard solid mass, is obtained as a graaolar 
powder, containing apwards of iz per cent water. Some manutactorerG first separate the 
sulphate of potash, which, being less soiuble, crystallises before the carbonate, a deli- 
qnesceut salt, is separated from the liquor ; in most coses, however, this operation is only 
carried on where the solphate ol potash is required for alnm-making. The pearl-ash or 
potash of oommeroe almost invariably contains a large quantity of sulphate of potash. 

c. In order to expel all the water and to destroy the organic matter, the saline maas is 
calcined, and as this operation was formerly performed in cast-iron pots, the salt has 
obtained the name of potash. A. aalclning furnace. Fig. 62, is now nsed, distingnished 
bom orditiai; reverbejatoiy furnaces by being provided wiUi a doable flre-plooe. These 

Fto. 6*. 




hearths, one of which is exhibited in section at t, Fig. 63, are placed at right ta^ee to 
each other, and the flame and smoke meeting in the oontre of the fnmaca, pass oO at o, 
the work-hole, into the chimney, K. Wood is used as fuel, and aa the heating of the 
fumaoes requires a very large quantity, they are only in use when a sufficient sopplr of 
erode potash is ready tor being operated npon. The fomaoe is (horonghly heated in 
about five to six hours, care being taken to Are gradually, and to bring the interior ot the 
tnnuuie to nearly red heat, so that the vapour due to the combustion of the wood may not 
oondense inside the furnace, bat be carried oti by the flne. The crude potash, brokem up 
to egg-siied lamps, is next plaped in such quantities at a time as ma; soit the siae of tht 
ealcining hearth ; for instance, if the hearth is roomed to contain 3 cwts., that qaantity is 
divided into three portions and put in at intervals of a few minutes. The first effeet ot 
the heat is to expel the water from the potash, the escape of the steam being promotod by 



4- 


5- 


6. 


7- 


8. 


68'0 


69-9 


386 


490 


5084 


5-8 


31 


4-3 


— 


12*14 


I5'3 


141 


38-8 


405 


17*44 


8-1 


2*1 


91 


lO'O- 


580 


— 


8-8 


5*3 


— 


io-i8 


2*3 


2-3 


3-8 


— 


3*6o 



CARBONATE OF POTASSA. 125 

■tining the mass with iron rakes. In about an honr all the water is driven off, and the 
mass takes fire in consequence of the burning of the organic matter, the salt at first being 
blackened, but gradually becoming white as the carbon bums off. As soon as this stage 
is reached, the potash is removed to the cooling-hearth, and when cold, packed in well- 
made wooden-casks, which, as this salt is very nygroscopic, are rendered as air-tight as 
poBslble. The heat of the furnace has to be well regulated to prevent the potash 
becoming semi-fused, in which case it would attack the siliceous matter of the fire- 
bricks; the workmen from time to take a small sample to test how far the oaloination is 
complete. 

We, in Europe, obtain a considerable quantity of potash from the United States and 
Canada, known as American potash, of which there are three different kinds, viz. : — 
X. Potash prepared as described. 2. Pearl-ash, or potash, purified by lixiviation, decan« 
tation from sediment, boiling down, and the calcination of the salt thus obtained. 
3. Stone-ash, a mixture of uncalcined potash (potassic carbonate), and caustic potash 
obtained by treating the crude potash liquor with caustic lime, and boiling down the mass 
to diyness ; this article has the appearance of the crude caustic soda of this country, but 
is usually coloured red by oxide of iron; the lumps, stone-hard, are from 6 to 10 
eentims. in thickness, and contain upwards of 50 per cent caustic potash. The under- 
mentioned analyses exhibit the varying composition of the potash of commerce : — Sample 
I is from Kasan (Bussia) ; analyst, M. Hermann. 2. Tuscany. 3 and 4 — the latier of 
a reddish colour — from North America. 5. Bussia. 6. Vosges ^France) ; analyst of 
2, 3, 4, 5, and 6, M. Pesier. 7. Helmstedt, in Brunswick ; analyst, M. Lmipricht. 8. Bussia ; 
anaiyst, M. Bastelaer. 

I. 2. 3. 

Carbonate of potash . . 78-0 74*1 71*4 

Carbonate of e^a . . . . — 3*0 2*3 

Sulphate of potash . . 17-0 13*5 14*4 

Chloride of potassium . . 3*0 0*9 3*6 

Water — 7*2 4*5 

Insoluble residue .. .. 0*2 o-i 2*7 

The calcined potash varies in colour, being either white, pearl-grey, or tinged with 
yellow, red, or blue. The red colour is due to oxide of iron, the blue to the manganates 
of potash, a hard, Ught porous, non-crystalline mass, never entirely sc^uble in water. 
Ponnerly, a large quantity of potash was obtained from the residues of wine-making, and 
eaUed vinasse, the semi-liquid left after the alcohol has been distilled from the wine, and 
eontaining, among other substances, argol, or crude bitartrato of potash ; it was boiled 
down, and next calcined, yielding a kilo, of very good potash for every hectolitre of vinasse. 
The large quantity of potash thus formerly produced may be judged from the fact that 
19 of the wine-produdng departments of France, those only whore largo quantities of 
iHue are converted into alcohol, technically termed trois six and cinq huit, yield annually 
about 9 to 10 million hectolitres of vinasse, at the present time employed for the prepara- 
tion on Uie large scale of cream of tartar, glycerine, and tartaric acid. 

pDtMhftomMoiMMi. V. Of late years, the manufacture of potash salts from the 
vinasse left after the distillation of fermented beet-root molasses has been added as a 
sew branch of industry by M. Dubrunfaut, and introduced into Germany by M. 
Vamhagen, in the year 1840, at Mucrena, Prussian Saxony. 

Beet-root, on being subjected to ignition, yields an ash containing a large percentage of 
potash, a fact first observed in the early part of this century by M. Mathieu de Dombasle, 
a celebrated French agriculturist, who discovered that 100 lalos. of dried beet-root leaves 
yield X0-5 kilos, of ash, containing 5*1 kilos, of potash ; but this author's idea that the 
leavee might be cut off and gathered for the purpose of potash manufacture, proved 
enoneous, in so far that the growth of the roots was greatly impeded. After the publica- 
tion of M. Dubrunfaut's researches on this subject, in 1838, the vinasse of the beet-root 
molasses distillation was evaporated to dryness, next calcined, and the calcined mass 
refiued for the production of potash and other Salts of that base, an industry which has 
obtained a great development, as may be judged from the fact that the quantity of these 
materials produced on the European continent in 1865 amounted to 240,000 cwts. 

The reader who desires details on this subject, is referred to the work, ** On the Manu- 
iftetnre of Beet-Boot Sugar in England and Irehuad," by Wm. Grookes, F.B.S., <ftc., p. 250 
etBeq. 



Soda ... . 
Liime 
Magnesia 
Carbonic acid 



2. 


3 


4767 


5038 


"•43 


8-29 


360 


312 


010 


018 


27-94 


28*70 



126 CHEMICAL TECHNOLOGY, 

The molasses from beet-root sugar consists, previous to the fermentation and dis- 
tillation, of the undermentioned substances, as recorded by the several analysts whose 

names are subjoined '.-* 

Brmmer. Fricke. Lunge. Heidenpriem. 

Water i5"2 180 18-5 190 197 

Sugar 490 480 507 469 49-8 

Salts and organic substances 358 34*0 30*8 34*1 30*5 

The following analyses by M. Heidenpriem exhibit the average composition of the 

ashes of molasses : — 

• I. 

Potassa 5172 

800 

504 
018 

28*90 

The remainder of the 100 parts consists of phosphoric and silicic acids, chlorine, 
oxide of iron, &c. The quantity of ash amounts to 10 or 12 per cent. According to 
Dubrunfaut the alkalimetrical degree of the ash of beet-root sugar molasses is a 
constant, as the ash obtained from 100 grms. of molasses neutralises on an average 
7 grms. of sulphuric acid (H2SO4). 

The molasses is generally treated in the following manner : — ^It is first diluted with 
either water or vinasse to 8* or ii** B. = 1*056 or 1*078 sp. gr., and mixed with 0*5 to 
I '5 per cent of a pure mineral acid, the object of this addition being not sunply the 
neutralisation of the alkali, but also the conversion of dextrine and such unfennentable 
sugar into fermentable sugar. Formerly, sulphuric acid was used, but upon the 
recommendation of M. Wurtz, hydrochloric acid is now generally employed, the 
advantage being the formation of readily soluble chlorides, instead of comparative 
insoluble alkaline sulphurets, the action of the organic matter present in the molaases. 

The diluted molasses is next mixed with yeast, left to ferment, and the alcohol 
distilled off; the residue is a liquid of about 4** B. density [» 1*027 ^P- S'-] containing 
undecomposed yeast, ammoniacal salts, various organic substances, and all the inorganic 
salts of the beet-root juice. The potassa is present in this liquid as nitrate chiefly, 
although by the addition of hydrochloric acid a portion of this salt is decomposed, 
red nitrous fumes sometimes being seen in the fermentation room. Evrard suggests 
that the saltpetre should be separated from the beet-root molasses by evaporation, 
and further purified by the aid of the centrifugal machine. The acidity of the 
vinasse is neutralised by chalk, and afterwards it is evaporated to dryness in an iron 
vessel, the total length of which is 20*3 metres, by an average width of 1*6 metre, 
extended at the top to 2 metres, the depth being 034 metre. Tlie vessel is muade of stout 
boiler plate, strengthened by stays and angle irons, and is divided into two-divisions, 
the larger of which has a length of 14*3 metres, and is the real evaporating pan, 
while the other is used as a calcining furnace, and covered with an arch of fire- 
bricks o'6 metre high. The fire-place is 1*3 metre wide, and the fire-box has a 
surface of 3*3 square metres. The evaporation is effected by surface heating, that 
is to say, the flame and hot gases from the burning fuel after passing across the fire- 
bridge are conducted over the surface of the vinasse, the calcining pan being nearest 
to the fire, while the evaporating pan is at its other extremity in contact with the 



CARBONATE OF POTASSA. 



"7 



floe or chimney. The viDBsse, having been run off from the still, is kept in cisterns, 
from which it is forced by means of a pump into a reaervoiT bo placed as to admit of 
the liquid nmning in a constant stream into the eraporating pan. At a first operation 
both the evaporatiiig and the calcining pan are filled with vinasse, but afterwards 
(be latter is filled regularlj with concentrated thick liquor, which is simply carbonised, 
the organic matter being only destroyed. 

The daily average of carbonised vinasse is about 5 to 5I owts. The composition 
of that substance may be gleaned from the foUowing approximative analysis : — 
Insoluble matter =23 per cent. 

Sulphate of potassa = 1107 „ 

Chloride of potassiom = 11*61 „ 

Carbonate of potaasa = 3140 „ 

Carbonate of soda = 23'26 „ 

Silicic add and hyposulphite of potassa = traces „ 

9934 ■. 
la Oennany, the calcined vinasae is generally sold to saltpetre manufacturers, but 
in Belgium and France this material is calcined, lixiviated, and the Halts it contains 
Mpuately obtained. For this purpose the vinasse is first evaporated to 38° or 40° 
B' |i 33 to 1-35 sp gr ) and next carbonised and calcmed in a &mace constructed 
u exhibited m Fig 63 v la a reservoir containing the concentrated vmasee which 
by means of a tube ts gradnally ran into the furnace of which a is the fire place, m 
the calcination qiace desbned to contam the concentrated or carbonised vinasse, 
Fia 63 




vhich is evaporated to dryneas and calcined in m; a dixir is fitted to each cora- 
partment, and at P, the end of the furnace opposite to the fire-place. The air required 
br the cftkinBtion is admitted partly through the ash-pit. partly tbrongh the 
openings, B, in the brickwork. The thiddsh liquid vinasse admitted into m' ia 
cmstantly stirred, and. as soon as it is quite dry, it is shovelled across the brickwork 
lidge, a', into the calcining E^ace, u, core being taken to again fill u' with concen- 
trated vinasse. The organic matter of the aaline masa soon takes fire, emitting 
Doiions fames. The calcination is greatly aided by the access of air at b, and also 
to some estent by the nitrate of potassa present. The temperature has to be regulated 
to prevent the aalta becoming fased and fanning a hard compact mass, in which case 
the sulphate of potassa would be reduced to sulphufet of potasainm, a salt which 



••• ••• 



a. 


6. 


c. 


d. 


26'22 


19-82 


17*47 


13*36 


12-95 


988 


2*55 


3*22 


15-87 


20-59 


18-45 


i6'62 


0-13 


0-15 


o-i8 


0"2I 


2552 


19-66 


19-22 


1654 


2340 


2990 


4213 


5005 



128 CHEMICAL TECHNOLOGY. 

conld not be removed. The calcined vinasse, technically teimed 9alint contains, 
when removed from the furnace, 10 to 25 per cent of insoluble substances, viz., 
carbonate and phosphate of lime, more or less charcoal, and in addition, 3 to 4 per 
cent moisture ; the remainder consists of carbonates of potash and soda, sulphate of 
potassa, chloride of potassium, and sometimes cyanide of potassium in considerable 
quantify. The relative quantities of potassa and soda are, of course, not at all 
constant, but vary according to the soil on which the beets have grown ; it has been 
observed in France that the molasses obtained from beets grown in the D^partement 
du Nord are less rich in potassa than those grown in the D6partements de TOise et de 
la Somme. The average composition of the salin is : — 

7 to 12 per cent of sulphate of potassa. 

18 to 20 „ of carbonate of soda. 

17 to 22 „ of chloride of potassium. 

30 to 35 „ of carbonate of potassa. 
The complete composition of the saHn may be gathered from the following 
tabulated results : — 

Water and insoluble matter ... 

Sulphate of potassa 

Chloride of potassium . . . 

Chloride of rubidium 

Carbonate of soda 

Carbonate of potassa 

lOO'OO lOQ-QO lOO'OO lOO'OO 

The method of separating the soluble salts from each other, invented by M. Kuhl- 
mann, is generally executed as foUows : — ^The saline mass is first broken up and 
granulated by the aid of grooved iron rollers, after which it is placed in lixiviation- 
tanks, each containing 264 cwts., and arranged precisely in the same manner as 
those in use in soda works. The liquor tapped from tlie tanks has a sp. gr. of 1*229 
(= 27'' B.) ; the insoluble residue is used as manure. The liquor having been col- 
lected in a large reservoir, capable of containing some 210 hectolitres, is concentrated 
by waste heat [ctbgangiger wUrme) to a density of 126 (= 30** B.) ; on cooling, the 
greater part of the sulphate of potassa crystallises, and is removed, care being taken 
to wash off the adhering mother-liquor. ' The sulphate thus obtained contains 80 per 
cent pure potassic sulphate, the rest being carbonate of potassa and organic matter : 
this material is converted into potash by Leblanc's process. The liquor at 30*^ B. is 
next poured into evaporating-pans, each capable of containing 90 hectolitres, and 
concentrated by means of heat and a steam pressure of 3 atmospheres (= 45 lbs. to 
the square inch) to a density of 42'' B. (= 1*408). By this operation a mixture of 
carbonate of soda and sulphate of potassa is separated, which frequently exhibits 
30 alkalimetrical degrees ; the liquor is transferred from the evaporating-pans to 
crystallising vessels, in which it is cooled down to not less than 30*. K, by careless- 
ness, the temperature should fall below 30**, the chloride of potassium crystals become 
mixed with a layer of carbonate of soda. The liquor at a temperature of 30**, and 
having a density of 42"" B., is again transferred to evaporating-pans, each capable of 
containing 20 hectolitres, and evaporated 

In winter to a sp. gr. of 1494 (= 48*^ B.), and 
In summer to a sp. gr. of 1*51 {= 49° B.) 



CARBONATE OF POTASSA. 129 

By this operation sodic carbonate separates, the first and purer portions of which 
are of 82 alkalimetrical degrees, and the last of 50° only. After the separation of 
the salt, the remaining liquor is poured into small crystallising vessels, each capable 
of holdiog 2i hectolitres, and, having been left standing for some time, yields in each 
vessel about 130 kilos, of a crystalline salt, mainly composed according to the 
fonnnla (EaCOs-hNaaGOj+izHaO). The remaining mother-liquor, when evapo- 
rated to dryness and calcined, yields a semi-refined potash, tinged with red by oxide 
of iron. This product is again lixiviated with water, and the liquor having been 
concentrated to 1*51 to 1*525 sp. gr. (= 49'' to 50"^ B.), deposits a large quantity of 
snlphate of potassa and carbonate of soda. The mother-liquor having been again 
evaporated and calcined, yields a potash consisting in 100 parts of — 

Carbonate of potassa 9i'5 

Carbonate of soda 5*5 

Chloride of potassium and sulphate of potassa 3*0 

lOO'O 

The carbonate of soda possessing a strength of 80 to 85 alkalimetrical degrees is 
refined by being washed with a very concentrated aqueous solution of sodic carbonate, 
and thus brought to a strength of fiilly 90 alkalimetrical degrees. 

The sulphate of potassa, chloride of potassium, and the double salt of the two 
earbonates, are purified and re-crystallised. The following analyses exhibit the com- 
position of refined potash obtained from beet-root sugar molasses : — 

a« 6. c. 

Carbonate of potassa ^73 

Carbonate of soda 644 

Sulphate of potassa 2*27 

Chloride of potassixmi 100 

Iodide of potassixmi o'02 

T¥ wHiCi ••• •■• ••• «•• ■■• ■•• JL 39 

Insoluble substances 0*12 — — 

a and fr are from Waghansel m Baden ; c is doubly refined French potash. The 
crude potash from beet-root sugar works, a product not to be confused with saJin, 
is composed as follows : — 

Carbonate of potassa ... 
Carbonate of soda 
Sulphate of potassa ... 
Chloride of potassium ... 19*6 

fi is French product ; b, from Valenciennes ; e, from Paris ; d, Belgian ; f , from 
Uagdebuig, Prussia. 

p«*-jjHjtaft«m Yi Potassa salts are obtained in large quantities from various sea- 
^^ds, as a by-product of the manufacture of bromine and iodine. The three 
following methods are employed for th's purpose : — 

0. The old calcination method, consisting in a complete reduction of the weeds to 
*^ and the methodical lixiviation of that product, so as to obtain various salts 
ty crystaUisation. 

^. The carbonisation, or Stanford's method, consisting in the dry distillation of the 
^«eds to convert them into a carbonaceous mass, afterwards lixiviated, while 



94*39 


893 


traces 


5-6 


028 


22 


2*40 


15 


01 1 


— 


176 


— 



a. 


h. 


e. 


d. 


e. 


53*9 


790 


760 


430 


329 


231 


14*3 


16*3 


17*0 


i8-5 


29 


39 


119 


47 


140 


196 


2-8 


416 


180 


160 



130 



CHEMICAL TECHNOLOGY. 



products lire simultaneously obtained, the sale of which considerably lessens the cost 
of the preparation of the potassa salts. 

e. A third mode of treatment, that of Kemp and Wallace, consisting in boiling the 
weeds with water, evaporating the solution, and carefolly incinerating the residue. 

The oldest method is still the most generally employed in France, on tiie coasts 
of Brittany and Lower Normandy, especially in the neighbourhood of Brest and 
Cherbourg, and in Scotland and Ireland. 

The process is mainly conducted as follows : — ^After drying in the air, the plants are 
incinerated, the result of which is the formation of a black semi-fused mass, which 
in France is termed Varech or Vraief and in England and Scotland is known as kdp. 
A distinction is made between the kelp obtained by the incineration of the weeds, 
Fucus 8erratu9 and Fucus nodostUt found on rocks near the sea coast, and the kelp 
obtained from the plant botanically known as Laminaria digitataf thrown upon the 
coast during the storms. The latter is richer in potassa salts, but contains much 
less iodine ; it is found plentifully on the western coast of Scotland and Ireland, 
while on the eastern coast of the British Isles the other weed is ihe chief source 
of kelp, having an average composition of : — 

Insoluble matters ... 

Sulphate of soda ... 

. Chloride of potassium 



Chloride of sodium 

Iodine 

Other salts 



57000 
10*203 

13476 
16018 

o*6oo 

2703 

lOO'OOO 



The best kelp met with in commerce is that from the island of Rathlin, the value 
at Glasgow amounting to My ids. to ^10 ids. per ton of 22 jr cwts. ; while Galway kelp 
is valued at only £2 or ^3 per ton, owing to the large quantity of salt it contains. 
22 tons of moist sea-weed yield : — 

Medium kelp i ton 

Chloride of potassium 5 to 6 cwts. 

Sulphate of potassa 3 cwts. 

The Scotch mode of treating kelp is briefly the following: — The material is 
first broken into small lumps, and put in large iron cauldrons, hot water being 
added to exhaust all the soluble matter. This operation follows the method of 
the manufiEusture of soda from common salt, to be presently considered. The water is 
first made to act upon nearly exhausted kelp, and at last with quite fresh kelp, 
until a liquid is produced mn-rlriTig 36° to 40° Twaddle = i'i8 to 1*20 sp. gr. The 
insoluble residue contains cMefly silica, sand, carbonate of Hme, carbonate of 
magnesia, its sulphates and phosphates, and particles of charcoal, and is used 
for bottle-glass manufacture. The liquor from the kelp is evaporated in large cast-iron 
semi-globular cauldrons by the direct action of a coal fire, and contains chiefly 
chloride of potassium, a comparatively small quantity of chloride of sodium, sulphate 
and carbonate of potassa, carbonate of soda, some iodide of potassium, sulphuret of 
potassium, and dithionite of potassium and sodium. The mode of separating these 
salts from each other is based upon their varying solubility in water, and is therefore 
Conducted by alternate evaporation and cooling. As the sulphate of potassa is 



CARBONATE OF POTASSA. 131 

the least soluble, it faUs to the bottom of the cauldron during the first evaporation, 
and is collected by the workmen by means of perforated ladles, and brought into the 
trade as plate sulphate. After this salt has been collected the liquid is run 
into coolers, in which the greater bulk of the chloride of potassium crystallises ; the 
mother-liquor from these crystals is again transferred to the evaporator, and by 
the continued application of heat, and consequent concentration of the liquid, the 
common salt is separated. It should be borne in mind that common salt is scarcely 
more soluble in hot than in cold water, while the solubility of most other salts 
is greatly increased by a higher temperature; it is therefore possible to push 
the evaporation and concentration to the point of incipient precipitation of the 
cUoride of potassium, the common salt being then ladled out of the cauldron, 
and the liquid again run into the coolers in order to obtain another deposit of 
chloride of potassium, always more or less contaminated with common salt. This 
operation is repeated four times ; the first crop of chloride of potassium contains 
from 86 to 90 per cent of this salt, the remainder is chiefly sulphate of potassa ; the 
second and third crop yield a very pure salt, 96 to 98 per cent of chloride of 
potassium ; the fourth crop contains some sulphate of soda mixed, with the chloride 
of potassium. The liquor left after the fourth crystallisation having a sp. gr.=i'33 to 
1-38 = 66'' to 76'' Twad., and containing among other compounds sulphate of soda, 
solphurets and hyposulphites of the alkalies, alkaline carbonates, and iodide of 
potassium, is not submitted to further evaporation, but having been poured into 
shallow vessels placed in the open air is mixed with dilute sulphuric acid, sulphu- 
retted hydrogen and carbonic acid gases being largely evolved, while in consequence 
of the decomposition of the polysulphurets and hyposulphites, a thick foam of pure 
sulphur appears on the surface of the liquid. This sulphur is ladled off, and after 
having been washed on filters and dried, is sold. Almost as soon as the evolution of 
gas ceases, there is added to the liquid more sulphuric acid and some manganese, 
and the mixture treated for the preparation of iodine {quod vide). In order to guard 
against loss of valuable substances by volatilisation during the crude and imperfect 
mode of incineration, it has been tried to simply carbonise the weeds (Stanford's 
method). The weeds are first dried and strongly pressed into the shape of peat 
Uocks ; these are submitted to dry distillation in retorts arranged similarly to those 
in gas-works. The products of the dry distillation collected in the usual manner 
contain in 100 parts of fresh Veed : — 

68*5 to 72*5 parts of Ammoniacal liquor, , 

40 „ Tar, 
70 to 75 „ Carbonised weed, or coke-weed, 
2'o to 2*5 „ Illuminating gas. 

The coke contains 33 per cent carbon, the remainder consisting of alkaline and 
earthy salts;' the volatile products of the distillation are treated for parafi&n, 
photogen, acetic acid, and ammoniacal salts, the gas being used for lighting 
purposes. Although Mr. Stanford's mode of treatment is undoubtedly rational, 
there are difficulties in its practical execution which have prevented its adoption in 
Scotland as well as in France. The quantity of potash salts obtained from sea- 
weeds in the year 1865 amounted, according to M. Joulin, to a total of 2,700,000 
kilos., of which the United Kingdom produced 1,200,000 kilos., the remainder 
being produced by France. 

Since the production of chloride of potassium at Stassfurt and Kalucz has 

K 2 



132 CHEMICAL TECHNOLOGY. 

become so extensive, the prodnction of potassa salts from sea-weeds is of little 
consequence. 

FotuflftBaiuiromBaiiit VII. The fact is Well known that sheep while browsing 
abstract a considerable amount of potassa, which, after having passed into the blood 
and tissues, is sweated through the skin, and deposited on the wool aa saint 
Professor Chevreul's researches have proved that suint constitutes nearly the third 
part of the weight of crude merino wool, while the soluble portion of the saint 
consists of the potassa salts of a fatty acid, potassic sudorate {tuintate de potaste). 
According to Messrs. Reich and Ulbricht, the fatty acids of suint are compounds of 
oleic, stearic, and probably palmitinic acids. The better wool contains more saint 
than the coarser kinds ; on an average the quautity of suint amounts to 15 per cant 
of the weight of the fleece. 

Since the year i860, and based upon the researches of MM. Maxmidne and 
Bogelet, the manufacture of potash salts frt)m the wash-water of the crude wool has 
become, in the centres of the French woollen manufacture (Kheims, Elbceuf, Fourmies) 
an industrial branch. The wash- water is valued according to its degree of concen- 
tration ; 1000 Idlos. of wool yielding a liquid which, according to M. Ohandelon, has 
a sp. gr. of 103, is paid for at the rate of 5 francs 48 cents. ; at a sp. gr. of 105, at 
the rate of 10 francs 45 cents.; sp. gr. 1*25, 18 francs 47 cents. The liquid is 
evaporated to dryness, the carbonaceous residue put into gas retorts, and heated to 
redness, the result being the formation of carburetted hydrogen gas and ammonia* 
which having been eliminated, the gas is used for illuminating purposes. The 
coke left in the retorts is lixiviated with water to obtain the soluble salts, chloride of 
potassium, carbonate and sulphate of potassa, which are separated from each other 
by methods already described. 

The residue left after the lixiviation with water contains earthy matter mixed with 
charcoal so very finely divided that it can be used as black paint. According to 
MM. Maumen6 and Rogelet, a fleece weighing 4 kilos, contains 600 grms. of suint^ 
capable of yielding 198 grms. of pure carbonate of potassa ; according to M. Fuchs, 
however, the quantity of suint only amounts to 300 grms., containing — 

Sulphate of potassa 7*5 grms. = 2*5 per cent 

Carbonate of potassa i33'5 » = 44*5 u 

Chloride of potassium 9*0 „ = 3'o 

Organic matter 1500 „ ' = 50*0 



If » 



3000 „ = 1000 „ „ 

It appears that the woollen industry of Kheims, Elboeuf , and Fourmies consomes 
annually 27 million kilos, of wool, the produce of 6,750,000 sheep. According to 
MM. Maumen6 and Rogelet this quantity of wool will yield 1,167,750 Idlos. of 
potash, representing a money value of ^80,000 to ^£90,000. According to M. P. Havrez, 
at Verviers, Belgium, suint is more advantageously worked up for the manufBu^ore of 
earbonate of potassa and yellow prussiate of potassa than for carbonate of potassa 
alone. Suint has been recently (1869) chemically investigated by MM. Marker and 
Schulze (see Joum. fiir Prakt. Chemie, voL 103, pp. 193 — 208). It is dear that 
the production of potash from the wash-water of sheep's wool can only be carried oat 
in the centres of woollen industry ; the sheep-fanners will always do better to retain 
the wash- water and potash compounds it contains to the soil from which the ftnimala 
have taken it In an industrial point of view the extensive importation of foreign 



CARBONATE OF POT ASS A. 133 

wool, especially from Australia and the Cape, is of great importance. In 1868 there 
were imported into the United Kingdom from those countries 63 million kilos, of 
wool, containing one-third of its weight of suint, from which hetween 7 and 8 kilos, 
pure potash could have been obtained, representing a money value of about £260,000. 

IVeparation of Purified Potash. — The potash formerly obtained by the lixiviation 
of wood-ash was mainly a mixture of carbonate, sulphate of potassa, and chloride of 
potassium, the value of each of these salts being of course very different. At the 
present time, in consequence of the production of pure carbonate of potassa from 
rinasse, it has become necessary to treat the crude liquor obtained by the lixiviation 
of wood-aah methodically, so as to obtain the salts separately in as pure a state as 
possible. 

The carbonate of potassa used in chemical and pharmaceutical laboratories was 
formerly obtained by the ignition of cream of tartar or a mixture of that salt with 
nitre, as well as by the ignition of acetate of potassa ; at the present time it is pre- 
pared by the careful ignition of nitrate of potassa with an excess of charcoal, or by 
the ignition of bi-carbonate of potassa. In England carbonate of potassa is manu- 
&ctared on the large scale, the pure salt being used in the Tnanufacture of flint-glass, 
tins glass owing its great superiority and perfect want of colour to the application of 
very pure materials in its manufeusture. The preparation is pure crystallised car- 
bonate of potassa, containing from 16 to 18 per cent water, equal to somewhat less 
than 2 molecules, the second molecule being partly expelled by the heat applied in the 
manufacture. This salt is met with in the trade in small cubical crystals; the raw- 
material used in its preparation is American pearl-ash, which, after having been 
mixed with sawdust for the purpose of converting the caustic alkali and sulphuret of 
potassium into carbonate of potassa, is ignited and fused in a reverberatory furnace, 
constructed like those used in the manufacture of soda. When cold the fused mass 
is treated with water, and the clear liquor having been decanted from the sediment, 
la evaporated to dryness in a reverberatory furnace ; the greyish-black mass thus 
obtained is again lixiviated with water, and the operation repeated. The white 
nline mass from the third ignition is again dissolved in water, and gently 
evaporated until the sulphate of potassa crystallises out; the mother-liquor 
left is next evaporated until a sample yields on cooling a salt of the composi- 
tion mentioned above. If this salt is further ignited all the water is expelled, and a 
^ white granular mass left. The specific gravity of carbonate of potassa solutions 
^ 15*" IB, according to Dr. Gerlach— 



Peroentage. 


Sp.gr. 


Percentage. 


Sp.gr. 


I 


I 'cog 


30000 


I '3010 


2 


1018 


35000 


1-3580 


4 


1036 


40000 


1*4180 


5 


1045 


45000 


1*4800 


10 


1092 


50000 


15440 


15 


i'i4i 


51000 


1-5570 


20 


1192 


52000 


1-5704 


25 


1245 


52024 


1-5707 



^^MittepotMn. Preparation of Caustic Potassa. — Caustic potassa, hydroxide of 
potassium, KHO, consists in 100 parts of 83*97 of potassa or dry oxide of potassium, 
*Qd 1603 of water. Caustic potassa is prepared on the large scale in England. 



134 CHEMICAL TECHNOLOGY. 

The raw material for this preparation is always a crude carbonate of potassa 
obtained from chloride of potassium, camallite from Stassfurt, vinasse, or any 
other source. The crude carbonate is lixiviated with water, and the liquor rendered 
caustic with quick-lime. A more advantageous method of preparing caustic 
potassa is to mix sulphate of potassa with limestone and small coal, in sujQiciently 
large quantities, and to ignite this mixture in a furnace. The crude material is, 
after cooHng, lixiviated with water at 50^, yielding at once raw caustic potassa 
liquor, which does not require any further addition of lime. The liquor is put into 
a steam-boiler and evaporated to a sp. gr. = 1-25 ; it is next evaporated to dryness in 
open pans, the foreign salts which separate being removed. Caustic potassa is 
employed for the conversion of soda-saltpetre into potassa-saltpetre, and with caustic 
soda for the manufacture of oxalic acid from sawdust. The following reactions, 
yielding caustic potassa, deserve a brief notice : — i. Decomposition of sulphate of 
potassa by means of caustic baryta. 2. Conversion of chloride of potassium into 
BUico-fluoride of potassium, and decomposition of that salt by means of caustic lime. 
3. Ignition of potassic nitrate with thin sheet-copper. The following table 
exhibits the quantity of potassa contained in solutions of that substance of varying 
specific gravity : — 

Sp. gr. Degrees Baum6. Percentage of potassa. 

I '06 9 47 

III 15 95 

115 19 130 

119 24 l6'2 

1 23 28 195 

1 28 32 234 

i'39 41 324 

152 50 42*9 

r6o 53 467 

1-68 57 512 

Saltfetbe, Nitrate of Potassa. 
(KN03=ioi'2. In 100 pai;^, 465 parts potassa, and 535 parts nitric add.) 

Saltpetre. TMs Salt is to somc cxtcut a native as well as a chemical product. The 

well-known flocculent substance often observable on walls, especially those of stables, 

is composed in a great measure of nitrates; a similar phenomenon is seen in 

subterraneaa excavations, and even in many localities the surface of the soil is covered 

with an efflorescent saline deposit, consisting largely of nitrate of potassa. These 

deposits are most common in Spain, Hungary, Egypt, Hindostan, on the banks 

of the Ganges, in Ceylon, and in some parts of South America, as at Tacunga in the 

State of Ecuador ; while in Chili and Peru nitrate of soda, so-called Chili saltpetre, 

is found in very large quantities under a layer of clay, the deposit extending over a 

tract of land some 150 miles in length. 

ooeamnce of NatiT* Although native saltpetre is met with under a variety of oonditions, 
saitpetK. jT^Qy ^ agree in this particular, that the salt is formed under the 
influence of organic matter. As already stated, the salt covers the soil, forming an 
efflorescence, which increases in abundance, and which if removed has its place supplied 
in a short time. In this manner saltpetre, or nitre as it is sometimes called, is obtained 
from the slimy mud deposited by the inundations of the Ganges, and in Spain from the 
liziviation of ihe soil, which can be afterwards devoted to the raising of com, or arranged 



SALTPETRE, NITRATE OF POTASSA. X35 

in saltpetre beds for the regular production of the salt. The chief and main condition 
of the formation of saltpetre, which succeeds equally in open fields exposed to strong 
Bimlight, under the shade of trees in forests, or in caverns, is the presence of organic 
matter, vias.. Humus, inducing the nitre formation by its slow combustion ; the collateral 
conditions are dry air, little or no rain, and the presence in the soil of a weathered 
erystalline rock containing feldspar, the potassa of which favours the formation of the 
nitrate of that base. All the known localities where the formation of nitre takes place 
naturally, including the soil of Tacunga, formed by the weathering of trachyte and 
tnfstone, are provided with feldspar. The nitric acid is due to the slow combustion of 
nitrogenous organic matter present in the humus, it having been proved that the nitric 
add constantly formed in the air in enormously large quantities by the action of 
electricity and ozone, as evidenced by the investigations of MM. Boussingault, Millon, 
Zabelin, Schonbein, Froehde, Bdttger, and Meissner, has nothing whatever to do with 
the formation of nitre in the soil, a fact also supported by Dr. Goppelsrdder*s discovery 
of the presence of a small quantity of nitrous add in native saltpetres. 

MaajojNWjiiitog The mode of obtaining saltpetre in the countries where it is naturally 

fonaed is very simple, consisting in a process of lixiviation with water, to which 

fi^uently some potash is added for the purpose of decomposing the nitrate of lime 

occuizing among the salts of the soil, the solution being evaporated to crystallisation. 

Soils yielding saltpetre are termed Gay earth or Gay saltpetre. The process by 

which nitrate of potassa is naturally formed is imitated in the artificial heaps 

known as saltpetre plantations, formerly far more general than at the present 

time, it having being found that the importation of Indian saltpetre, and the 

manufacture of nitrate of potassa by conversion from nitrate of soda, are cheaper 

sources. Thus, saltpetre beds are to be met with only under peculiar conditidhs, as, 

for instance, in Sweden, where all landed proprietors are required to pay a portion 

of their taxes in saltpetre. 

The mode of making these plantations may be briefly described as follows : — Materials 
eontaining much carbonate of lime — for instance, marl, old building rubbish, ashes, road 
scrapings, stable refuse, or mud from canals —is mixed with nitrogenous animal matter, 
all lands of refuse, and frequently with such vegetable substances as naturally contain 
nitrate of potassa, such as the leaves and stems of the potatoe, the leaves of the beet, 
Bunflower plants, nettles, &o. These materials are arranged in heaps of a pyramidal 
Bbape to a height of 2 to 2i metres, care being taken to make the bottom impervious to 
water by a well puddled layer of day, the heap being in all directions exposed to the 
action of the atmosphere, the circulation of which is promoted through the heap bv 
layers of straw. The heap is protected from rain by a roof, and at least once a week 
watered with lant (stale urine). The formation of saltpetre of course requires a considerable 
length of time, but, when taught by experience, the workmen suppose a heap ripe, the 
watering is disoontinued, the salt containing saltpetre soon after efflorescing over the 
nirface of the heap to 6 to 10 oentims. in thickness ; this layer is scraped oif, and the 
operation repeated from time to time until the heap becomes decayed and has to be 
entirely removed. In Switzerland saltpetre is artificially made by many of the farmers, 
nmply by causing the urine of the oattlo, while in stable in the winter time, to be 
absorbed by a calcareous soil purposely placed under the loose flooring of the stables, 
which are chiefly built on the slope of the mountains, so that only the door is level 
with the earth outside, the rest of the building hanging over the slope, and being supported 
by stout wooden poles ; thus a space is obtained, which, freely admitting air, is filled 
with marl or other suitable materiaL After two or three years this material is removed, 
lixiviated with water, mixed with caustic lime and wood ash, and boiled down. The liquor 
having been sufficiently evaporated, is decanted from the sediment and left for crystalli- 
■ation; the quantity of saltpetre varying from 50 to 200 lbs. for each stable. 

*al5j5w tiru^'' ^® crude salt from the heaps is converted into potassic nitrate 

l>y the following processes : — a. The earth is lixiviated with water, this operation 

^g known as the preparation of raw lye. b. The raw lye is broken, that is to 

tty* it is mixed with a solution of a potash salt in order to convert the nitrates of 

loagnesia and lime present into nitrate of potassa. c. Evaporation of this liquor 

^ obtain crude crystallised saltpetre, d. Refining the crude saltpetre. 



"36 



CHEMICAL TBCHNOLOOY. 



Pn^umof jiie ripe earth is lixiviated to obt&in all the valuable soluble nuitter, 
it being expedient to nae u little water as possible in order to save fuel in the 
Gubseqnent evaporation, for which the liqnor is ready when it contains &om iz U> 13 
per cent of soluble ealts. 

Bwun^op uu Jiig jf^yf lyg^ Bometimea known as soil water, contains the nitrates 
of lime, magnesia, potassa, soda, the chlorides of calcium, magneaium. and potasaiiun ; 
also ammoniacol salts and organic matter of vegetable as well as of animal orj|^. 
In order to convert the nitrates of lime and magneaia into nitrate of potassa, ths 
raw l;e is broken np as it is termed, that is to saj, there is added to it a solution 
of 1 part potossic carbonate in 2 parts water: — 

Nitrate of lime. Ca(NO})i ] fNitrate of potassa, 4KNOJ. 

Nitrate of magnesia, MgiNOjlj [■ yield | Carbonate of lime, CaCOj. 

Carbonate of potassa, 2K1CO] J ( Carbonate of magnesia, MgCOj. 

The chlorides of calcinni and magnesiam are &leo decomposed, being converted 
into carbonates, while chloride of potassium ia formed. The addition of the solatioa 
of potassa to the raw I;e is continned as long as a precipitate is formed ; in order. 
however, to have some approximative idea of the quantity of carbonate of potash 
which may be required a test experiment is made wiQi i litre of the raw lye. 

Sometimes sulphate of potassa is nsed instead of tbe carbonate, but in that case 
the magnesia salts of the raw lye have first to be decompoaed by millc of lime, tut 
operation which has to be followed by the evaporation of the finid. If, after this, 
sulphate of potassa is added, sulphate of lime is precipitated — 
[CalN0j)j+K.S04=2KN0j+CaS04] . 
Y^ien chloride of potassium is used for the decomposition of raw tye, the salts of 
magnesia are first removed by the addition of milk of lime ; and the dear supematAnt 
fluid havii^ been decanted from the sediment, there is added a mixtnre of equ&l 
molecules of chloride of potsssinm and sulphate of soda, the result being the formalioti 
of gypsum, while the sodic nitrate generated exchanges with the chloride of potassium, 
carrying over to the latter the nitric acid, and taking up the chloride to form eaaamm 
salt 
°°"K.''™'*' The clarified raw lye decanted from the precipitate of the earthy 
carbonates consists of a solution in which there are present the chlorides of 
potassium and sodium, nitrate of potaesm, 
carbonate of ammonia, excess of potasde 
carbonate, and colouring matt«r. The boiling 
down of this liquid is effected in copper 
cauldrons. Fig. 64, so set in the furnace aa 
to admit of the circulation of the hot air and 
smoke from the fire-place, passing by e 
below the heating pan, and thence by g into 
the chimney. In some works this wasta 
heat is utilised in drying the saltpetre floor. 
As the bulk of the floid in the cauldron 
decreases by evaporation, fresh lye enters by 
means of a pipe and tap from the pan, d. 
About the third day the alkaline clilorides begin to be deposited, and the workmen 
have then to take great care to prevent these salts from becomingwhal is technically 



Fio. G4. 




SALTPETRE, NITRATE OF POTASSA. 137 

termed bamt, which might give rise to serious explosions, and for this purpose the 
liqoid is stirred with stont wooden poles. After each stining the loose saline matter 
is removed from the boiling liquid by means of perforated copper ladles. However, 
aB a hard deposit is always formed, a peculiar arrangement exhibited in Fig. 64, 
consisting of a shallow vessel, m, suspended by a chain, k, and weighted with a piece 
of stone, is lowered into the middle of the cauldron to about 6 centims. from the 
bottom, the object being to catch the solid particles, which would, when aggregating, 
form an incrustation, previously to their reaching the bottom of the vessel ; and as 
no ebullition takes place at m, the particles once deposited remain there, and can be 
readily removed by raising the dish out of the cauldron, and emptying it into a box 
placed over the cauldron, the bottom of the box being perforated to admit of any 
liquor which may have been raised with the solid salt to return again to the 
cauldron. The deposit thus removed consists chiefly of gypsum and carbonate of 
lime. 

When a portion of the impurities contained in the boiling liquid have been 
removed, the raw lye still frequently contains some chloride of sodium, as this salt is 
not, as is the case with nitre, more soluble in boiling than in cold water. The 
abmidant crystallisation of the saltpetre is a sign that the lye has been sufficiently 
evaporated ; in order, however, to prove this, a small sample is taken, and if on 
cooling the nitre crystallises so that the greater part of the sample becomes a solid 
mass, the liquid is run into tanks and left for 5 or 6 hours, during which time 
impurities are deposited, and the liquid rendered quite clear. As soon as the 
temperature of the liquid has fallen to 60°, it is poured into copper crystallisation 
vessels ; after a lapse of 24 hours the crystallisation is complete, and the mother- 
liqnor being separated from the salt is employed in a subsequent operation. 
c£!^J^JS^, The crude saltpetre is yellow-coloured, and contains on an average 
some 2o per cent of impurities, consisting of deliquescent chlorides, earthy salts, and 
water. The object to be attained by the refining is the removal of these substances. 
At the present day a large portion of the refined saltpetre met with in commerce is 
obtained by the refining of the crude saltpetre imported from India. It may be noted 
that this importation is steadily increasing, there being, in i860, 16,460,300 kilos., 
and in 1868, 33,062,000 kilos, of the salt brought to England ; and, indeed, the 
production of saltpetre from natural sources in Europe is now limited to very few 
and uumportant localities. ^^^^ 

The method of refining saltpetre is based upon the fact that nitrate of potassa is 
fu more soluble in hot water than are the chlorides of sodium and potassium. 
600 litres of water are poured into a large cauldron, and 24 cwts. of the crude saltpetre 
tte added at a gradually increasing temperature; as soon as the solution boils, 
36 cwts. more crude saltpetre are added. Supposing the crude nitre to contain 
20 per cent of alkaline chlorides, the whole of the nitre will be dissolved in this 
quantity of water, while a portion of the chlorides will remain undissolved even at 
the boiling-point. The non-dissolved salt is removed by a perforated ladle, and the 
Bcnm rising to the surface of the boiling liquid by the aid of a flat strainer. The 
orgaiuc matter present in the solution is removed by the aid of a solution of glue — 
from 20 to 50 grms. of glue dissolved in 2 litres of water are taken for each hundred- 
weight of saltpetre. In order that the saltpetre may crystallise, the quantity of 
water is increased to 1000 litres, and as soon as this water is added the organic 
matter entangled in the glue rises as a scum to the surface and is removed. The 



138 CHEMICAL TECHNOLOGY. 

operation having progressed so far, and the liquid being rendered quite clear, it is 
kept at a temperature of 88^ for about twelve hours, and then carefully ladled into 
copper crystallising vessels, constructed with the bottom a little higher at one end 
than at the other. The solution would yield on cooling large crystals of saltpetre, 
but this is purposely prevented by keeping the liquid in motion by means of stirrers, 
so as to produce the so-called flour of saltpetre, which is really the salt in a finely- 
divided state. This is next transferred to wooden boxes termed wash- vessels, lo feet 
long by 4 feet wide, provided with a double bottom, the inner one being perforated ; 
between the two bottoms holes are bored through the sides of the vessel and when 
not required plugged with wooden pegs. Over the flour of saltpetre contained in 
these wooden troughs, 6o lbs. of a very concentrated solution of pure nitrate of 
potassa are poured, and allowed to remain for two to three hours, the plugs being 
left in the holes. The plugs are then removed, the liquor run off, the holes again 
plugged, and the operation twice repeated, first with a fresh 6o lbs., and next with 
24 lbs. of the solution of nitrate of potassa, followed in each case by an equal quan- 
tity of cold water. The liquors which are run off in these operations are of course 
collected, the first being added to the crude saltpetre solution, while the latter, being 
solutions of nearly pure nitre, are again employed. The saltpetre is next dried at a 
gentle heat in a shallow vessel, sifted, and packed in casks. 
preiMuvtion of Nitrate During the last twenty years the preparation of nitrate of 
Guii-Hatpetre. potassa from Chili-saltpetre has become an important branch of 
manufacturing industry. The product obtained by any of the following processes is 
called *' converted-saltpetre," to distinguish it from the preceding preparation. The 
method of procedure may be one of the following : — 

I. The nitrate of soda is decomposed by means of chloride of potassium — 

100 kilos, of sodic nitrate \ . .^ f 119*1 kilos, potassa nitrate. 

87*9 kilos, of potassium chloride/ ^ \ 68'8 kilos, common salt 

^^ MM. Longchamp, Anthon, and Euhlmann first suggested this mode of preparation, 
which is now generally used on the large scale, as the decomposition of both salts is 
very complete, and as the common salt as well as the saltpetre can be utilised. The 
chloride of potassium is obtained by the decomposition of camallite, or by means 
already mentioned. 

Equivalent quantities of nitrate of soda and of chloride of potassium are dissolved 
in water contained in a cauldron of some 4000 litres cubic capacity. As the nitrate 
of soda of commerce (Chili-saltpetre) does not, as regards purity, vary very much 
firom 96 per cent, some 7 cwts. are usually taken, while of the chloride of potassium, 
which varies in purity from 60 to 90 per cent, a quantity is taken corresponding, as 
regards the amount of pure chloride, to the quantity of nitrate of soda. The chloride 
of potassium is first dissolved, the hot solution being brought to a sp. gr. = 1*2 to 1-2 1, 
next the nitrate of soda is added, and the liquid brought, while constantiy heated, to 
a sp. gr. = 1*5. The chloride of sodium continuously deposited is removed by per- 
forated ladles, and placed on a sloping plank so that the mother-liquor may flow 
back into the cauldron, care being taken to wash this salt afterwards, so as to 
remove all nitrate of potassa, the washings being poured back into the caiddron. 
When the liquid in the cauldron has been brought to 1*5 sp. gr. — an aqueous solu- 
tion of nitrate of potassa at 15^ with a sp. gr. =i'i44, contains 21*074 percent of that 
salt — ^the fire is extinguished, the liquid left to clear, the common salt still present 
canying down all impurities, and when clear it is ladled into crystallising vessels, 



SALTPETRE, NITRATE OF POTASSA. I39 

which being vei^ shallow, the crystallisation is finished in twenty-four hours. The 
mother-liquor having been run ofi^ the crystals are thoroughly drained and covered 
with water, which is left in contact with the salt for some seven to eight hours, and 
then ran off; this operation is repeated during the next day ; the mother-liquor and 
irashings are poured back into the cauldron at a subsequent operation. 

2. Nitrate of soda is first converted into chloride of sodium by means of chloride 
of barium, nitrate of baryta being formed, and in its turn converted into nitrate of 
potassa by the aid of sulphate of potassa : — 

a. 85 kilos, of nitrate of soda \ yield | ^30*5 Iq^os. nitrate of baiyta. 
122 kilos, of chloride of barium ) ^5^*5 kilos, of common salt. 



p. 130*5 Idles, of nitrate of baryta 
require for conversion into 
nilxate of potassa 



87*2 kilos, of potassic sulphate, 

or 
692 kilos, of potassic carbonate. 

When sulphate of potassa is used, permanent- white, baryta- white, or sulphate of 
baryta is obtained as a by-product, while if carbonate of potassa is used, carbonate of 
baiyta remains, and of course may ie readily re-converted into chloride of barium. 
In order to estimate the advantages of either process, the following points must be 
kept Id view : — a. Taking into consideration that it is profitable to convert native 
carbonate of baryta into chloride of barium — for instance, by exposing witherite to 
the hydrochloric acid fumes produced in alkali works by the decomposition of salt — 
and to precipitate an aqueous solution with dilute sulphuric acid to obtain permanent- 
white, it may be inferred that it will also pay to obtain it as a by-product, b. Not- 
withstanding the complication of this process, it is advantageous as producing a fetr 
purer nitrate of potassa. 

3. Nitrate of soda is converted by means of potash into the nitrate of that base, 

pore soda being obtained as a by-product : — 

85 kilos. Chili-saltpetre ] * Id i '^''^ kilos, of potassic nitrate. 

69*2 Idlos. carbonate of potassa I ^^ 153 kilos, of soda (calcined). 

This mode of manufeMJturing saltpetre was first introduced into Germany during the 
Crimean War (1854-55) ^7 ^- Wollner, of Cologne, who established large works to 
prepare saltpetre in this way, and very soon after, during the continuance of the war, 
five other manufactories of potash-saltpetre had been established on this method. 
In 1862 the production amounted to 7,500,000 lbs. of potash -saltpetre, the carbonate 
of potassa required being obtained from beet-root molasses, the soda resulting as a 
by-product being even superior to that produced by Leblanc's process. 

4. Nitrate of soda being decomposed by caustic potassa yields potassic nitrate and 
caustic soda. 

According to M. Lunge's description, this process, first suggested by MM. Land- 
mann and Gentele, afterwards modified by M. Schnitzer, and practically applied by 
U. Kollner, is carried on in Lancashire in the following manner : — There is added to 
a caustic potash lye of 1*5 sp. gr., containing about 50 per cent of dry caustic potassa, 
an equivalent quantity of nitrate of soda, and the whole, after a short time, crystal- 
lised. The nitrate of potassa having been separated from the mother-liquor, that 
fluid, the density of which has been greatly decreased by the reaction, is by evapora- 
tion again brought to its former density, and ^delds on cooling another crop of 
crystals of potash-saltpetre. Usually there then only remains a solution containing 
caustic soda with saline impurities ; sometimes, however, a third crop of crystals is 
obtained. The deposit during the evaporation is chiefly carbonate of soda derived 



140 CHEMICAL TECHNOLOGY. 

from the chloride of sodioin contained in the potassium chloride from which the 
canstic potassa is made, this chloride heing also converted into carhonate. The 
small quantities of undecomposed chlorides of potassium and sodium and sulphate of 
lime are retained in the mother-liquor, which is evaporated to dryness and ignited, 
yielding a dry caustic soda of a hluish-colour. The crystallised nitrate of potassa 
is now carefully refined to remove all impurities to ahout o'l per cent of chloride of 
sodium, converted into saltpetre-flour, and treated as already described. Notwith- 
standing that the various operations have been carried on in iron vessels, the salt 
does not contain any of this metal, nor is the colour in any way affected. The flour 
is dried in a room 2 metres wide by 5 metres in length, built of brick- work, similarly 
to the chloride of lime rooms, and having a pointed arched roof 2 metres in height 
The saltpetre-flour is spread on a wooden floor, under which extends a series of hot- 
air pipes, keeping the temperature at 70^ and very rapidly efiecting the drying. 

Testing the saitpetn. If, whcu perfectly pure, saltpetre is carefully fused, and allowed 
to cool, it becomes a white mass, exhibiting a coarsely radiated fracture ; even so 
small a quantity as ^th of chloride of sodiimi causes the fracture to appear somewhat 
granular ; with ^th the centre is not at all radiated, and is less transparent ; and 
with ^th the radiation is only slightly perceptible at the edges of the fructure. 
Nitrate of soda has the same effect. This method of testing the purity of nitre, due 
to M. Schwartz, is employed in Sweden, where every landowner pays a portion of 
his taxes in saltpetre of a specified degree of purity. A great number of methods of 
testing saltpetre have been suggested by various authors for the purposes of the 
manu£B.cture of gunpowder, not, however, in sufficiently general use to interest the 
reader. Werther*s test for chlorine and sulphuric add is by solutions of the nitrates 
of baryta and silver; the silver solution is such that each division of the burette 
corresponds to 0004 grm. of chlorine, and with the baryta solution to 0*002 grm. of 
sulphuric acid. According to Reich's plan, 0*5 gim. of dried and pulverised saltpetre 
is ignited to a dull red heat, with from 4 to 6 times its weight of pulverised quartz ; 
the nitric acid is expelled, the loss of weight consequently indicating the quantity, 
the sulphates and chlorides not being decomposed at a duU red heat. If the loss 
= df we have 1874 d nitrate of potassa, or i'574 d nitrate of soda. 

Qnantttftttre Eitimatton This method, duo to Dr. A. Wagner, is based upon the &ct 

of the Nitric Acid in o » x- 

BaitpetzB. that when saltpetre, or any other nitrate, is ignited, access of air 

being excluded, with an excess of oxide of chromium and carbonate of soda, the nitric 
acid oxidises the chromic oxide according to the formula Cra03-f-N05=2Cr03+NOi. 
764 parts, by weight, of oxide of chromium are oxidised to chromic acid by 54 parts 
of nitric add, or of i of chromic oxide by 07068 of nitric add. The operation is 
performed by taking from 03 to 0'4 grm. of the nitrate, mixing it intimately with 
3 gims. of chromic oxide and i grm. of carbonate of soda, introducing this mixture 
into a hard German glass combustion-tube, one end of which is drawn out, and a 
vulcanised india-rubber tube attached to it, which is made to dip for about a quarter 
of an inch into water, while to the other open end, by means of a cork and glass tube 
bent at right angles, an apparatus is fitted for the evolution of carbonic add gajs, 
which is made to pass through the tube before igniting it, and kept passing through 
all the time until the tube is quite cool again after ignition. The contents of the 
tube are placed in warm water, and after filtration the chromic acid is estimated by 
Rose's method. This process of estimating nitric acid has been found to yield very 
accurate results. 



SALTPETRE, NITRATE OF POTASSA. 141 

UMocaattpatn This salt is employed for many purposes, the most important 
bemg: — i. The manufacture of gunpowder. 2. The mannfactnre of snlphuiic and 
nitric acids. 3. Glass-making, to refine the metal as it is termed. 4. As oxidant and 
flux la many metallurgical operations. By the ignition of i part of nitre and 2 of 
irgol, in some cases refined argol (cream of tartar), hlachjiux is formed consisting of 
in intimate mixture of carbonate of potassa and finely divided charcoal. The 
ignition of equal parts of saltpetre and cream of tartar gives white flux^ consisting of 
a mixture of carbonate of potassa and undecomposed saltpetre; both these 
mixtures are often used. Black flux may also be made by intimately mixing 
carbonate of potassa with lamp-black and white flux. 5. When mixed with 
common salt and some sugar in the salting and curing of meat. 6. For preparing 
floxing and detonating powders. Baum6's fluxing powder is a mixture of 3 parts of 
nitre, i of pulverised sulphur, and i of sawdust from resinous wood ; if some 
of this mixture be placed with a small copper or silver coin in a nutshell and 
ignited, the coin is melted in consequence of the formation of a readily fusible 
metallic sulphuret, while the nutshell is not injured. Detonating powder is a mix- 
ture of 3 parts saltpetre, 2 carbonate potassa, and i pulverised sulphur ; this powder 
when placed on a piece of sheet-iron, and heated over a lamp, will explode with a 
load report, yielding a large volume of gas : — 



Saltpetre, 6ENO3, 

Potassic carbonate, 2K2GO39 

Sulphur, 5S. 



' Nitrogen, 6N. 
Carbonic acid, aCOa. 
Sulphate of potassa, 5K2SO4. 



7. For manure in agriculture. 8. In many pharmaceutical preparations. 9. For 
the preparation of Heaton steel. 

iBdientaaiiL This salt, also known as cubical saltpetre. Chili-saltpetre, nitrate 
of soda, NaNOj, containing in 100 parts 36*47 soda, and 63-53 P^^^ nitric add, 
is found native in the district of Atacama and Tarapaca, near the port of Uquiqne, 
in Peru, in layers termed odUohs or terra ioUtrosa, 0*3 to I'o metre in thickness, and 
extendiug over more than 150 miles, nearly to Copiapo, in the north of Chili. The 
deposit chiefly consists of the pure, dry, hard salt, and is close to the surfSsice of the 
■oil It is also found in other parts of Peru mixed with sand, in some places close 
to the sur&ce of the soU, in others at a depth of 26 metres. Valparaiso being the 
great exportation dep6t for Peru, Bolivia, and Chili, both surface and deep soil salts 
tfe met with in the trade of that important port. The unrefined Chili-saltpetre is 
czystalline, brown or yellow, and somewhat moist ; but the salt sent to the European 
markets is commonly semi-refined by being dissolved in water and evaporated to dry- 
IM88. The composition of a sample in 100 parts is : — 

Nitrate of soda 9403 

Nitrite of soda ... o'3i 

Chloride of sodium 1*52 

Chloride of potassium 054 

Sulphate of soda 092 

Iodide of soda 0*29 

Chloride of magnesium 0*96 

Boric acid traces 

TvaMjx* ••• ••• ••• .*• ••• ••• ••• X 9^ 

lOO'OO 



Ml 



CIIE3IICAL TECHriOLOQY. 



Being deliquescent th.c salt is not employed in the raanufiicture of gunpowder, but 
may bo used for blasting powder. It is largely used for the preparation of 
sulphuric and nitiio aclda ; for piirifjing caustic soda ; for making clilorine in the 
manufacture of bleaching powders ; for the preparation of araeniate of soda ; in the 
curing of meat; glass -making; in the preparation of red-lead : in large quantities in 
the conversion of crude pig-iron into steel, by Hargreaves's and bj Heston's 
processes; for preparing nitrate of potassa ; and for the preparation of aitificitl 
manures and compoEta, it being used nnmised as a manure for grain crops. 

It may be seen from the analysis of nitrate of soda quoted above HibX that 
salt contains a small qnontitj of iodine, wliich at Tarapaca is extracted from 
the mother-liquor remaining from tlie re-crystallisation. According to M. L. Kiaflt 
the iodine amounts to o-jg grm. in i kilo, of crude nitrate ; 40 kilos, of iodine being 
prepared per day. M, NoUner thinks that the formation of the nitre deposits in 
Chili and other parts of South America has taken place nnder the influence of narioe 
plants containing iodine. In order to give some idea of the large and increasing 
exportation of Chili-saltpetre, we quote from the published statisticB, that in 1830, 
18,700 cwts., and in 1869, 2,965,000 cwte., were shipped. 



Nrrmc Acid. 
MittMyiMiMmtoaiiirtiig Tj,ig agiij iNHOj) is generally manufactured by decomposing 
nitrate of soda by sulphuric acid, and condensing the vepours set free. It is obtained 
on the large scale by placing in a cast. iron Tesael, a, Fig. 65, the nitrate to be operated 
upon, to which is added by means of a funnel strong aulphnric acid. The lid is 
replaced, and the Tessel connected by means of the clay'lined tube, b, with the glass 
tube, c, dipping into the large stoneware flask, n, which serves the purpose of a 
Fta. 65. 




rweiver This flflhk is connpcled bv means of a tubt i to a similar vessel d and 
that to a third \estel, p , and so on, m order to completely condense the vapours 
which might have escaped through the first, second, and third vessels. The iron 
vessel, *, is heated by means of the fire placed in the hearth, f, the smoke and hot 
gases being carried off by a n. At the outset of the operation the damper, d. is 
80 regulated as to shut off the lower channel, and cause the smoke and hot gases 
to pass through r, heating the ves-sela i>, n', and d ', this precaution being required to 



NITRIC ACID. 1^3 

prevent their cracking by the hot ncid vaponrs eotcring from a. Ab soon, 
however, as the distillatdon has &irlj commenced, the damper is altered to shut off e, 
and pass the hot air and gaaes through o. The nitric acid condensed in the first 
receiver is aofficientlj strong for immediate use, but to facilitate the condensatian 
■ome wBiter has been poured through the openings, b' b", into the other receivers, the 
add from nhich is weaker and known in the trade as aquafortia. 

Very frequently the distillation of nitric acid is conducted in a series of glass 
retorts placed on a sand-bath ; there are generally two rows of retorts, the heating 
^paratns being a galley oven. If the acid is to be pure, the first condensations 
ue collected in BepaiBte receivers, as the acid first condensed contains hydrochlorio 
•eid due to the chlorides contained in the nitrates under operation. 

The proportion of materials employed is : — 
30 k 

i The bianlphate of soda which remains may either be used for the preparation of 

faming sulphuric acid, or may be mixed with common salt, and ignited, to produce 
hydrochloric acid and neutral sulphate of soda, available in the preparation of sodic 
carbonate. 

The nitric add (NHO3) resolting from the above operation is a colonrless, 
transparent fluid, having a sp. gr. of i'55, and boiling at So°, When diluted with 
I water the boiling-point ie higher. An acid containing 100 parte (NHOj) and 50 
I puts of water boils at i2g°, but if the dilation with water is carried ftirther the 
boiling-point is again lowered ; conseiinently when such an acid is heated above 100'' 
I Ibe result is that at first water with only a trace of acid distils over, and if the process 
! be contdnned the boiling-point gradually increases until it reaches 130°, when there 
I distils over what is termed double aquafortis, sp- gr. = i'35 to 1*45, ordinary or single 
1 tquafortis having a sp- gr. = I'lg to 1*25. Nitric acid, when in contact with air, 

emibi fumes, owing to the absorption of water from the atmosphere. 
I ""'jldli.'""' Ths stronger acid manufactured as described is usually of a yellow 
Mlonr, due to the presence of hyponitric acid. If a colourless acid is desired, Ihe 
ernde acid mnst be snbmitled to a bleaching operation, consisting of fhe following: — 
I The coloured acid is poured into large glass vessels placed <Fig. 661 in a water- 
bath,. heated to 80° to 90°, and left in these vessels as long as any coloured vapours 

[ Fio.M. 




•re giren oK The escaping hyponittio add is eanied by means of glass or glazed 
wrthenwue tubes either into a sulphuric add chamber and there utilised, or into 
the flue of a chinmey, and thus into the aii. Any hydrochloric acid present in the 
nitric acid is also carried off as chlorine. In order to remove any sulphuric acid 



144 



CHEMICAL TECHNOLOGY. 



it is neceaBarj to distil the uitria aoii over pore nitrate of baij'ta, whUe the last 
traaea of hydrochloric acid can be remoTed bj distillAtion over pore nitrata of silver. 
ooudKuuiDDof thaNiuk. More recently improTements have been made in the matm- 
fftotu^ of nitric acid, bearing eqtecially upon the poBBibility of omitting the 
bleaching procesB, and a better mode of condensing the vaponrH of the acid. The 
first point is supplied by an arrangement introdnoed in the manniactorfof M. Chev6, 
in Paris. Every practical chemist knows that the red vapoors appear only at 
the outset and towards the end of the distillation of the nitric acid, and it is there- 
fore only reqaired to distil fractionalljto obtain on the one hand a red-coloured add, 
the addum nitroio-nitrieum or aeidum nttrumm fumam /ortittitw of the phanna- 
ceatistfi, and on the other a colonrless acid, which can be forthwith delivered to the 
consumer. In order to practically effect the fractional distillation, a tap of porcelain 
or hard-fired stoneware, conatnieted aa exhibited in Fig. 6j, is fixed by means of a, 
in commnnjcation with the iron distilling vessel, while the tubes B and b are 
connected with two different receivers. The tap is bored in such a manner, that at 



Fia. 67. 




pleasure either the communication be- 
tween A and b', or the communication 
between & and b, can be established. 

By proper management, therefore, it ia 
possible to separate the red-colonred 
acid entirely and without any addi- 
tional expense, from the colonrlesa 

A second improvement, contrived by MM. Plisson and Devers, Paris, bears upon the 
condensation apparatus, which consista in their works of a battery of ten peculiarly 




constructed bottles, uz of which are open at the bottom and fonnel- shaped, so as to Gl 
in the necks of lai^ecaruoys, o. Fig. 68. From a cylinder not shown in the engraving, 
being hidden by the wall, n, a stoneware tnbe ia connected with the bent glass tube, s. 



NITRIC ACID, 145 

which oommunioates wi£h one of the three tubnlatures of the first carboy, a, 
which serves to collect the acid, that, bj the boiling over of the mixture in the iron 
Tessel, has been rendered more or less fonl. The carboy a is provided with a small 
tube, T, arranged to act as a hydraulic valve in such a manner that, when the fluid in 
the carboy has risen to a height of some centimetres, any additional fluid entering a 
is carried off into th^ well- stoppered carboy, a'. The second tubulature of the 
carboy a is fitted with a funnel through which water flows from the bottle f into a, 
thereby aiding the condensation. The acid vapours pass through the curved glass 
tube F, into the carboy b, from which, as likewise from the carboys b' and b", the 
condensed fluid is carried by the tube t into the carboy a". Any vapours which 
escape condensation in b are carried off to c, and thence to d, a portion of the acid 
being condensed in each of the vessels, and flowing back first to b and then to a". 
Any vapour not condensed in and n is conducted by the glass tube o, first to n', 
next to c", and finally to b, where condensation takes place. Any vapours not now 
condensed are carried to b", c", n", and finally to the chimney stalk. The Mariotte 
bottles f' and f" contain water, which flows into the condensing vessels and dilutes 
the acid to 36** B. (=1*31 sp. gr.=42*2 per cent NaOs). In order to reduce any pressure 
arising in the vessels a' and a", a tube h, and a similar one not represented in the cut, 
are connected with t and t', for the purpose of carrying any non-condensed vapour 
into b", where these vapours collect. 

Although this apparatus appears complicated, the working is very readily managed. 
The acid vapours issuing from the distillatory apparatus are partly condensed in the 
vessel A, and thence carried to a', the vapours still imcondensed continuing their 
course to b, b', b", the fluid there collected flowing back to the general receiver a". 
This i^paratus when once well put together, has rarely to be repaired, saves much 
labour, and produces a larger quantity of acid than the ordinary apparatus, this 
being due to the more complete condensation ; while by the ordinary method only 
125 to 128 kilos, of nitric acid are obtained from 100 kilos, of nitrate, the quantity 
obtained by this apparatus amounts to 132 to 134 kilos. The following brief descrip- 
tion, illustrated by Figs. 69 and 70, vrill explain the internal construction of the 
bottles and of the syphon funnel. In each of the carboys of the lowest row is 
inserted a bent stoneware tube, t. Fig. 69, the opening, o, of which is outside 
the bottle ; a narrow space, l, admits the fluid to the interior of the tube, and it 
is dear that the acid can only attain a certain height in the carboy. The syphon 
fhnnel consists of a stoneware tube about 3 centims. in diameter, the side of which. 
Fig. 70, is perforated in a longitudinal direction ; any fluid therefore flowing into this 
tabe from £ can only reach to the opening o. 

otk« suthod* of nitric Add The following methods, differing from that above desoribed, 
MurateetoFe. must here be mentioned ; but the reader ahould not infer that they 

ire aotually in practice : — i. Action of chloride of manganese (chlorine preparation 
reaidiies) upon mtrate of soda. When a mixture of these salts is heated to about 230*, 
nitroos vapours (NO^+O) are evolved, and there remains oxide of manganese, which can 
be again employed in the manufacture of chlorine. 



sMnCla 

and |- yield 
xoNaNOj 



[ yi< 



(2MnO+3MnOa), 

loNaCl, 

ioNOa-J-0. 

By causing the mixture of hyponitric acid and oxygen to come into contact with water 
in the condensing apparatus nitric acid results, the excess of hyponitric acid being decom- 
posed into nitric acid and dentoxide of nitrogen. If the quantity of air in the apparatus 
is sttiSciently large to oxidise the entire bulk of the nitrogen deutoxide into nitric acid, 
this process is continuous, but if there is not enough air, the ^utoxide of nitrogen is 

L 



X46 



CHEMICAL TECHNOLOGY. 



dissolved in the nitric acid, any excess of that gas escaping. From the experiments on thid 
process by Dr. Euhlmann, who used clay retorts, it appears that 100 parts of nitrate of 
soda yield from 125 to 126 parts of nitric acid at 35° B ; this result almost agrees with 
that obtained by the ordinary process. Dr. Kuhlmann also instituted experiments with 
other chlorides, viz., those of calcium, magnesium, and zinc, the result being the forma- 
tion of nitric acid and chloride of sodium with lime, magnesia, and oxide of zinc. 

2. Action of certain sulphates upon alkaline nitrates. Dr. Euhlmann has proved by a 
series of experiments that the sulphates, including only those having no acid properties* 
decompose the idkaline nitrates. Sulphate of manganese decomposes nitrate of soda, the 
result being the formation of products similar to those when chloride of manganesft 
is employed ; similar reactions take place when sulphate of zinc, sulphate of magnesia, 
and gypsum are used for this purpose. 

3. From nitrate of soda and carbon, yielding soda and nitric add. 

4. From nitrate of soda and silica or alumina, yielding nitric acid, silicate of soda, 
and soda. 

5. From nitrate of baryta and sulphuric acid, without distillation; the nitric add 
(=sio* to 11" B.) decanted from the sulphate of baryta (permanent white) can be conoen- 
trated by boiling to 25' B. 

Dauitjof Nitric Add. Accordisg to Eolb, the specific gravity of nitric add bears to the 

quantity of concentrated acid contained the following relation : — 



100 parte 

• 


1 oontaii 
N2O5. 


1 Density. 
1 


100 parts contain 
NHO3. NaOj. 


Dendty. 

• 


NHO3. 


at o**. at 


15^0. 


ato^ 


at i5*C. 


10000 


8571 


I 559 


1-530 


5500 


47-14 


1-365 


1-346 


97-00 


8314 


1548 


1*520 


5099 


43-70 


1*341 


1323 


9400 


8057 


I 537 


1-509 


45-00 


3857 


1*300 


1*284 


9200 


7885 


1529 


1-503 


40*00 


34*28 


1*267 


1*251 


9100 


7800 


1526 


1*499 


33-86 


29*02 


1*226 


1*211 


9000 


7715 


1522 


1-495 


30*00 


2571 


1*200 


1185 


8500 


7286 


I 503 


1*478 


2571 


22*04 


1*171 


I-I57 


8000 


68*57 


1-484 


1*460 


23*00 


19*71 


1*153 


II38 


7500 


6428 


1465 


1-442 


20*00 


17*14 


1132 


I-I20 


6996 


6000 


.i'444 


1-423 


1500 


12*85 


1*099 


1089 


6507 


5577 


1*420 


1*400 


11*41 


9-77 


1-075 


1*067 


6000 


51*43 


i'393 


1*374 


4*00 


3*42 


1*026 


I-022 










2*00 


1*71 


1013 


I'OIO 


The following table exhibits comparativ 


e data of density and 


degrees accordug to 


jjaume . — 






100 parts 


contain at 


100 parts contain at 


Degrees according 
to Baum^. 


Density. 


{ 


1 




15" 


0. 




NHO3. 


N2O5. 




NHO3. 


Na05. 


6 




1044 


6*7 


57 




7*6 


6-5 


7 




1052 


80 


6-9 




9-0 


77 


9 




1*067 


10*2 


8*7 




11*4 


9-8 


10 




1075 


11*4 


9-8 




12*7 


iO'9 


15 




i-ii6 


17*6 


15-1 




19*4 


166 


20 




i-i6i 


24*2 


20*7 




26*3 


22*5 


25 




I*2IO 


31-4 


26*9 




33-8 


28*9 


30 




1*261 

• 


39-1 


33-5 




41-5 


35-6 


35 




1*321 


480 


41*1 




50*7 


43*5 


40 




1-384 


584 


500 




61 7 


529 


45 




1-454 


722 


61 '9 




78*4 


72*2 


46 




1-470 


76*1 


65*2 




830 


711 


47 




1-485 


80*2 


68*7 




87-1 


747 





NITRIC ACID. 




47° B. correspond to 96° 


Twaddle. 

• 


46° .. 


»» 


92° 


»» 


45° .. 


y* 


88° 


>» 


43° .. 




84° 


«• 


4*° .. 




80° 


M 


38° ,. 




70° 


»» 


34° .. 


ff 


60° 


»t 


89° .. 




50° 


Jt 


25° .. 




40° 


«« 


20° „ 




30° 


ff 


14° .. 




20° 


»» 


7° .. 




10° 


»> 


Titricaci 


id of 1-52 sp. gr. boils at 86" 




1-50 




99° 




1*45 




"5° 




1-42 




123° 




1-40 




"9° 




I '35 




117° 




130 




113° 




I'20 




108° 




115 




104'' 


_ ii_ - 


J.? 


_* -_«1^ 


• • * t^ 



147 



rndi«HttrieA«id. When in the preparation of nitric acid there is taken for i mole- 
cule of nitrate of potassa i molecule of snlphuric add, there is obtained by distilla- 
tion a reddish-yellow flnid, consisting of a mixture of nitric and hyponitric acids, 
kzu)wn as red fuming nitric acid. When equal molecules of nitrate of potassa and 
ndphuric acid are taken, only one-half of the quantity of nitric acid is expelled, 
while the other half is decomposed into hyponitric acid and oxygen, the former com- 
lamng with the nitric acid, and forming the fdming nitric acid. When in the prepa- 
nUion of nitric acid by the decomposition of the potassium or sodium nitrate, two 
mdecoles of sulphuric acid are employed, all the nitric acid in these salts is 
obtained, and there remains in the retort bisulphate of either base. When nitrate 
of soda is employed, it is, owing to the easier decomposition of this salt by sulphuric 
^d not necessary to use exactly 2 molecules of sulphuric acid ; 1*25 to 1*50 mole- 
cules of that acid have been found to be practically sufficient. 100 parts of Ghili- 
udtpetre yield 120 to 130 parts of nitric acid at 36° B. 

The red fuming nitric acid is now generally prepared by adding to the ordinary 
ooDcentrated nitric acid a substance which effects its decomposition. Sulphur 
Itts been employed for this purpose, but starch is generally used, and, according to 
H. G. Bmnner's recipe, in the following manner: — To 100 parts of saltpetre, 
3i parts of starch are added, and placed in a capacious retort, into which is poured 
100 parts of strong sulphuric add, sp. gr.= i 85. The distillation usually sets in with- 
out the aid of heat, but towards the end of the operation the application of a gentle 
beat is required. 100 parts of nitrate of potassa yield by this method about 60 parts 
of filming nitric add. The retort in this operation should not be filled to more than 
one-third of its capadty, owing to the very strong evolution of gas which takes place. 

ttaoc HimeAdd. The technical application of nitric acid is based on its property of 
oxidation when in contact with certain substances, the acid splitting up iuto deut- 

L 2 



148 CHEMICAL TECHNOLOGY. 

oxide of nitrogen, hyponitric acid, and ozone, the latter forming with the body 
which caused the decomposition of the acid either an oxide or a peculiar componnd, 
while the hyponitric acid, when organic substances are present capable of combining 
with it, forms the nitro-compounds, nitrobenzole, nitronaphthaline, nitroglycerine, 
nitromannite, nitrocellulose, or gun-cotton, &c. A large number of metals are 
soluble in moderately concentrated nitric acid, but the strongest add fails to 
act upon iron and lead. Proteine compounds, albumen, the skin of the hands, silk, 
horn, feathers, &c., are stained yellow by nitric acid, hence the use of this acid 
in dyeing silk. If the acid is in contact with these substances for any length of time» 
they are completely decomposed, and partly converted into picric acid. Starch, 
cellulose, and sugar, are converted by the action of nitric acid into oxalic add; 
but very dilute nitric add converts starch into dextrine, and concentrated add 
into xyloidine. Owing to the property nitric add possesses of destroying certain 
pigments — ^for instance, indigo — ^it is sometimes employed in calico printing to produce 
a yellow pattern on an indigo ground. This add is also used in dyeing woollen 
materials ; in hat-making, to prepare a mercurial solution used in dressing felt hats ; 
in the manufacture of sulphuric acid ; in the preparation of lacquers ; in the prepa- 
ration of nitrate of iron, a mordant used in dyeing silk black ; for preparing picric 
add from carbolic add, and naphthaline-yellow from naphthaline ; inthemanu&ctnre 
of nitrobenzol, nitrotoluol, and phthalic acid ; and for the preparation of nitrate 
of silver, arsenic acid, fulminate of mercury, nitroglycerine, dynamite, &c. 



Technoloot op the ExPLOsrvE Compounds. 

a. Ounpowder, and the Ch^mUtry of Fireworks, or Pyrotechny. 

ononopowddrinoeneni. The substauce kuowu as gonpowdor, or simply as powder, is 
a more or less finely granulated mechanical mixture of saltpetre, sulphur, and char- 
coal, the quantities of these materials being properly defined. It ignites at 300^ 
also when touched with a red-hot or burning body, or under certain conditions by 
friction or a sudden blow. Powder under these conditions bums off rapidly but not 
instantaneously, yielding as the products of its combustion nitrogen, carbonic add, 
or carbonic oxide, while there remains a solid substance consisting of a mixture of 
sulphate and carbonate of potassa. When the powder is ignited in a closed vessel, 
the sudden evolution of the large volume of gases causes a pressure imj^osdble to be 
withstood ; and even in guns and large ordnance, in which one dde of the vessel is 
formed by the yielding shot, the metal forming the other sides must possess great 
elasticity. In guns and artillery the pressure only lasts as long as the ball is inside 
the gun, therefore the slower the combustion of the powder through its entire mass, 
the lower is the velocity of the projectile. 

ManafMtnn of onnpowder. It is cssential that the materials employed in the manufcusture 
of powder should be very pure; the saltpetre should nof contain any chlorides; the 
sulphur should be free from sulphurous acid, hence not flowers of sulphur but 
refined roll sulphur is used ; and lastly the charcoal requires very great attention. 
The wood from which it is intended to prepare a charcoal for gunpowder should be 
such as yields the least posdble quantity of ash, while the charcoal should be soft 
like that used in pharmacy. The stems of the hemp and flax plants, espedally the 
former, yield excellent charcoal, but in oonsequence of the limited supply, the wood 
of the wild plum tree (Pruntu padus) is largely used in Germany, fVatnce, and 



EXPLOSIVE COMPOUNDS. 149 

Belginm; and in England the lime, willow, poplar, horse-chestnut, Tine, hazel, 
ehenj, alder, and other light white woods are employed for this purpose. All these 
varieties yield on being carbonised— effected in various ways, in retorts similar to 
those used in gas-works, in pits dug in the earth, by the aid of superheated steam, 
the wood being placed in boilers, &g. — ^from 35 to 40 per cent charcoal. The tempe- 
ratore during the progress of carbonisation being kept as low as possible, there is 
obtained a very soft reddish-brown chai'coal, known as charhon toujb. The charcoal 
prepared in cylindrically-shaped retorts is very inappropriately designated distilled 
charcoal. 

'JRSStoMSffiSSi These operations include :— 

I. The pulverising of the ingredients. 2. The intimate mixing of these sub- 
Btances. 3. The moistening of the mixture. 4. The caking or pressing. 5. The 
gnnnlation and sorting of the grain, as it is termed. 6. Surfacing the powder. 
7. Drying. 8. Sifting from the dust. 

pnwftriBcUM lagndienta. This Operation can be performed in three different ways : — 

a. By means of revolving drums. 

b. By mill-stones ; or 
0, In stamping-mills. 

0. The pulverisation by means of revolving drums is an invention due to the French 
rerolation, and has the advantages of being very effective, rapid in ezeoution, and of pre- 
ventmg the flying about of the ingredients in a fine dust. The drums are made of wood, 
lined with stout leather, and provided with a series of projections. The substance to be 
pulverised is put into the drum with a number of bronze baUs of about i inch diameter, 
their action aided by that of the projections, when the drum is turned on its horizontal 
ans at a moderate speed, soon effecting a reduction to a fine powder. The oharooal 
iud sulphur are separately pulverised ; the saltpetre being obtained as a flour. (See 
Saltpetre). 

h. Qrindinff by the aid of null-stones. Two heavy vertical stones, similar to those in 
use for emshing linseed, revolve on a fixed horizontal stone. This contrivance is the most 
fnqnently used. 

e. Stampers are now employed only in small powder-mills. Frequently 10 to 12 stamps 
made of hard wood are placed in a row, each stamp being fitted with a bronze shoe, the 
entire wei^t being about i cwt. The stamps are moved by machinery, and make from 
40 to 60 beats a minute. The materials to be pulverised are placed in mortar-shaped 
eanties in a solid block of oak wood, each cavity containing 16 to 20 lbs. In Switzerland 
hammers instead of the stampers are employed. 

HhfagtbaiBcndiMita. The mixing is performed by the aid of drums similar in size 
and shape to those used in the pulverisation, but made of stout leather instead of 
wood. The mixing of 100 kilos, of the ingredients, aided by the action of 150 bronze 
halls, takes folly three hours, the drum making ten revolutions a minute. It is 
Qsmd to moisten the materials with i to 2 per cent of water, supplied by fine jets 
legolated by taps. 

When stampers and mill- work are employed, the sulphur and charcoal are first 
•epsrately pulyerised by 1000 blows, and saltpetre having been mixed with these 
ingredients in the proper proportion, the machinery is again set in motion, and at 
first, after every 2000 blows, and then after every 4000 blows, the contents of the 
stamp-holes are removed from the one to the other, this operation being repeated 
some six or eight times. Where drums are used for the mixing operation, the 
moistening takes place after the mixture has been removed to a wooden trough, 
where 8 to 10 per cent of its weight of water is added, care being taken to stir with a 
Wooden spatula. 



150 CHEMICAL TECHNOLOGY, 

^^'^vi^SS!^ ^^^s operation, which in stamping-mills is the last of a continnottB 

series, is separately performed where other machinery is employed. In the French 

and German powder-mills, the compression is effected in a rolling-mill, the roQerB 

having a diameter of o'6 metre. The lower roller is made of wood, the npper of 

bronze ; between the two an endless piece of stont linen is arranged, and upon this 

the moist powder is placed. The cakes are i to 2 centims. in thickness, with the 

hardness and very much the appearance of day-slate. 

The operation of preseing is of great importance ; the stronger the pressnre the greater 
the quantity of aotive material present in a given bulk, and henoe the larger the volume 
of gas given off by the ignition of the powder. In many English powder-miUs the 
pressing is effected by very powerful hydnialic machines, because, wit^ oertain limits, 
the more the matenals are pressed, the more slowly the powder bums, when finished, 
while the temperature of ignition being lower, the expansion of the gases is less. If the 
powder were finished either without having undergone any pressure at all, or with only a 
slight pressure, it would act as a detonating-powder, the decomposition being instan- 
taneous throughout its entire mass. 

2S°s^ StofeSSS The conversion of the cake into granules is effected— 

1. By means of sieves. 

2. By means of peculiarly constructed rollers, Congreve*s method ; or 

3. According to Champy's method. 

The granulation of gunpowder by the aid of sieves is carried on in the following 
manner: — The sieves consist of a circular wooden frame, across which a piece of parch- 
ment is stretched perforated with holes ; the sieves are distinguished according to their 
uses, and by the size of these holes ; that employed for breaking up the cake having 
larger holes, and bearing a name different from the sieves used to produce the 
granules ; this sieve again being distingmshed from that employed for sorting the powder 
into the variously sized grain as commercially known. The sieves are provided with a 
so-called rummer, a lens-shaped disc made of hard wood, gnaiac, box, or oak-wood, motion 
being imparted to the sieves by hand if they are small, or by suitably arranged maohineiy 
if they are large, in which case Lefebvre's granulating-machine fitted with eight sieves in 
an octagonal wooden frame is generally employed. 

Gongreve's granulating-machine consists of three pairs of brass rollers, 0*65 metre 
in diameter, provided with diamond-shaped projections 2 millimetres high, the projec- 
tions of the upper rollers being coarser than those of the others. The broken-up cake is 
conveyed to the upper rollers by means of an endless canvas sheet. The mode of feeding 
this sheet is somewhat peculiar and ingenious : the loose bottom of a square box filled 
with coarsely pounded cake is made to rise slowly upwards, and discharge the cake uni- 
formly upon tiie sheet through an opening in the side of the box. The cake while passing 
through the rollers is granulated, and then showered upon two sets of wire-gause sieves to 
which a to-and-fro motion is imparted. Below these sieves again is a frame containing 
wire-gauze, the meshes of which are too small to admit of the passage of ordnance powder, 
while the dust and cartridge-powder readily fall through upon another wire-gauze, the 
meshes of which retain the rifle-powder but let the dust pass. Hie quantity of dust 
made by the Gongreve machine is very small, owing to the fact that the rollers do not 
crush but break the cake. Ghampy*s method, by wbioh a very round-grained powder is 
obtained, is performed in the following manner : — Throng the hollow axis of a wooden 
drum a copper tube, periorated with very small holes, is carried, and from these holes 
water spouts in a fine spray upon the broken-up powder-cake placed in the drmn, to 
which a comparatively rapid motion is imparted. Each drop of water forms the nnelens 
of a grain of powder, which is constantly increasing in size by being turned round in the 
midst of a mass of damp powder-cake; the rotation of the dram is discontinued as soon 
as the grain has attained a sufficient siee. The powder thus obtained is almost perfectly 
l^obular, but not of the same size ; the sorting is effected by means of sieves, the over- 
sized grains being returned to the drum, as weU as the undersized grains, which become 
the nuclei of proper-sized grain. According to the Berne method, round-grained powder 
is prepared by causing the angular-shaped powder to be rotated in stout linen-bags; but 
by this plan much dust is formed. 

ox«mi!!todSowd«r. ^^ ^^ ^^ ^^ Operation is to impart symmetry to the grain, and 

to separate all the dust. It is performed in drums similar to those described above: 

5 cwts. of the powder is polished at a time, the drums rotating slowly for a few hours. 



EXPLOSIVE COMPOUNDS. 151 

In some countries the pcliBhing is effected by placing the powder in casks internally 
pbyided with qnadrangnlar rods. In Holland, Dr. Wagner states that some black-lead 
is added to the powder daring this operation to prevent ignition, but this is not generally 
done. Hic^ily-poliBhed powder does not readily attract moisture, ^d is to be preferred 
in a fay damp climate. 

ikTincuiAPowdw. It is clettT that this operatioii requires very great oare in more 
than one respect. In small powder-works the powder is sometimes dried by 
exposure to the heat of the snn, being spread out on canvas sheets stretched in 
wooden frames ; or the diying-room is heated by a stove. In large powder-mills 
other methods of drying the powder are general. 

The quality of the powder very much depends on the care bestowed upon the drying. 
A too rapid drying entails the following disadvantages : — a. The powder may be very wet 
and not polic^ed ; coarse ordnance and ordinary loilitary powder is never polished, and 
hence blackens the hands ; while, although the water is driven off, the nitre is carried to 
the sor^iee of the grain, which thereby cakes together, b. By the too rapid evaporation of 
the water, channels and cracks are made in the grain, impairing its density, increasing 
its bulk, and rendering it more hygroscopic, c. Lastly, rapid drying entails a large 
unonnt of dust. For these reasons gunpowder, before being placed in the drying-rooms, 
ii exposed for some time to a gentle heat in a well- ventilated room, the heat from a waste 
steam-pipe being sufficient. 

"""SaPttSdJf.*""* Having been dried, the powder is sometimes glazed, as it is 
termed ; that is to say, again polished in the manner above described ; but generally 
this second polishing is dispensed with, and the dry powder cleansed from the dust 
which adheres to it, by being placed in bags, made of a peculiar kind of woollen 
&bric, and arranged in frame-work to which a to-and-fro motion is given by 
machinery, the fine dust passing between the threads of the fabric into a box. The 
bss thus occasioned amounts on an average to 0*143 P^^ cent, the dust consisting 
chiefly of charcoal. 

FMv«tiMofOiiiipowd«r. Good powdcr is recognised by the following properties: — 
I. Its colour should be slate-black ; when blue-black it indicates that the powder 
contains too much charcoal, while a deep black colour shows the powder to be damp. 
If the charcoal employed was the so-called charhon raux, the colour of the powder 
will be a brown-black. 2. It should not be too much polished so as to shine like 
bonushed black-lead. Small shining specks indicate that the saltpetre has crystal- 
lised on the surface. 3. The grains should be uniform in size, unless, of course, 
two differently sized powders have been mixed. 4. The grain should crack uniformly 
when strongly pressed, should withstand pressure between the fingers, and should 
not be readily crushed to powder when pressed between the hands. 5. When pul- 
verised the mass should feel soft ; hard sharp specks show that the sulphur has not 
been well pulverised. 6. Powder should not blacken the back of the hands or a 
sheet of white paper when gently rubbed. If it does so, there is either powder-dust 
or too much moisture. 7. "When a small heap of powder is ignited on paper the 
combustion should be rapid, completely consuming the powder and not setting fire to 
the paper. If black specks remain, the powder either contains too much charcoal, or 
it is an indication that that substance has been badly incorporated with the rest 
of the materials. Yellow streaks left after the ignition show the same defects for 
the sulphur. If no grains of powder remain, it is a proof that the powder was not 
well mixed ; when any remaining grains of powder cannot be separately ignited, the 
flahpetre used was impure. If the powder on being ignited sets fire to the paper, it 
is a proof that it is either damp or of very inferior quality. 



152 CHEMICAL TECHNOLOGY. 

The fact that different kinds of powder, although of the same weight to the cobio 
foot, do not have the same specific gravity, is shown hy the following table :— 

X onbio foot 
in pounds weight. Bp. gr. 

Neisse'B ordnanee powder 60 177 

„ „ „ (new mill) .. .. 60 r6j 

Berlin ordnance powder 60 X'63 

Bossian ordnance powder 60^ 1*56 

Berne ordnance powder (No. 6) 59I 1*67 

Berlin rifle powder ^ew mill) 60 1-63 

Berne rifle powder (^o. 4) 6of 1*67 

Honnslow rifle powder 59 172 

Berlin sporting powder (old mill) 62 177 

Le Bonchet*8 sporting powder 59^ 1-87 

Very coarse-grained ordinary Dutch powder.. 60^ 1-87 

Very coarse-grained ordinary Austrian powder 64 1 172 

Gunpowder can absorb more than 14 per cent of moistore from the air ; if the 
quantity of water thus taken up is not above 5 per cent, the powder, on being gently 
dried, reassumes its former activity ; but if the quantity of water absorbed exceeds that 
amount, the gunpowder will not bum off rapidly, and when dried the single grains 
become covered with an efflorescence of saltpetre, of course impairing the composition 
and active qualities of the powder. Even what is termed dry powder contains at 
least 2 per cent of hygroscopic moisture. Powder can be exploded by a heavy blow 
as well as by an increase of temperature, and as regards its explosion by a blow, 
very much depends upon the material upon which it is placed and with which the 
blow is imparted.- The following list exhibits in decreasing order the materials 
between which a blow most readily ignites powder: — Iron and iron, iron and 
brass, brass and brass, lead and lead, lead and wood, copper and copper, copper and 
bronze. For this reason gunpowder magazines are provided with doors turning 
upon bronze and copper hinges, the locks also being of copper. When dry powder 
is rapidly heated to above 300° it explodes. Even if only a very small portion of the 
powder is thus rapidly elevated in temperature, the entire quantity, be it large or 
small, is exploded ; hence a very small quantity touched by a red-hot or burning 
body is sufficient to effect an explosion. It is generally held that the charcoal is first 
ignited, and that it spreads the ignition to the otiier materials. Although Mr. Hearder 
found by experiment that powder does not ignite when touched with a red-hot 
platinum wire while under the receiver of an air-pump. Professors v. Schrotter and 
Abel proved that gunpowder so placed ignited rapidly when heated by a spirit- 
lamp. 

Composition of oonpowdtt. Gunpowdcr oonsists very nearly of 2 molecules of saltpetre, 
X molecule of sulphur, and 3 of charcoal. Accordingly 100 parts of powder contain — 

Saltpetre 74*84 

Sulphur ii-aj 

Charcoal (No. I.) 13*32 

The above figures approximately express the composition of the best kinds of sporting 
and rifle-powder. Ordinary powders, such as blasting-powder, consist of nearly eqiuJ 
molecules of nitrate of potassa and sulphur, with 6 molecules of charcoal. Accordingly 
100 parts contain— 

Saltpetre 66*03 

Solphur 10*45 

Charcoal (No. n.) 23*52 



EXPLOSIVE COMPOXrNDS. 153 

itodaiboiflM ^n* Bnnsen and Sobisehkoff found the oomposiiion of a sporting 

Otmintimtivowim. mul liflo-powder to be, in 100 parts, as follows : — 

Saltpetre 78*99 

Sulphur. 9*84 

Carbon 7*69 

Ch«o«do««£rtfagof.^J^, ;• ;: ;: ;; ;; ;; ."'^ 

^Ash traces 

The reeidoe of this powder after oombustion was found to eonsist of— 

Sulphate of potassa 56*62 

Carbonate of potassa 27*02 

Hypoenlphite of potassa 7*57 

Sulphuret of potassium 1*06 

Hydrated oxide of potassa (caustic potassa) . . ' 1*26 

Sulphooyanide of potassium 0*86 

Saltpetre 5*19 

Carbon 0*97 

Carbonate of ammonia ) ^^^^^ 

Sulphur I*'^®^ 

100*55 

It appears from this analyslB that the residue left after ignition of the gunpowder 
eonsists essentially of sulphate and carbonate of potassa, and not, as has been formerly 
stated, of sulphuret of potassium. The composition of the smoke of the powder was 
SBoertained to bo- 
Sulphate of potassa 65*29 

Carbonate of potassa 23*48 

Hyposulphite of potassa . . . . 4*90 

Sulphuret of potassium .... — 

Caustic potassa 1*33 

Sulphocyanide of potassium . . 0*55 

Saltpetre 3*48 

Carbon (charcoal) 1*86 

Sesquicarbonate of ammonia .. 0*11 

Sulphur — 



100*00 

Fnnu these figures it is clear that the smoke of gunpowder consists essentially of the 
lame substances as the residue from the combustion, the only difference being that the 
Rilphur and nitrate of potassa of the powder have been more completely converted into 
snlphate of potassa, while instead of the sulphuret of potassium, carbonate of ammonia 
makes its appearance. 100 parts by volume of the gaseous products of the combustion 
vere found to consist of — 

Carbonic add 52*67 

Nitrogen 41*12 

Oxide of carbon 3*88 

Hydrogen 1*21 

Sulphuretted hydrogen .. .. 0*60 

Oxygen. 0*52 

Protoxide of nitrogen — 

lOO'OO 

The solid residnes of combustion formed during the generation of the gases were found 
tobe— 

Sulphate of potassa 62-10 

Carbonate of potassa 18*58 

Hyposulphite of potassa . . . . 4*80 

Sulphuret of potassium . . . . 3*13 

Sulphocyanide of potassium . . 0*45 

Nitrate of potassa 5*47 

Charcoal 1*07 

Sulphur 0*20 

Sesquicarbonate of ammonia . . 4*20 

lOO'OO 



154 



CHEMICAL TECHNOLOGY. 



The deoompoBition of powder by its ignition nuiy be represented by the following 
f ormnlsd : — 



'Beddne 
o'68o 



I grm. of powder 



'Saltpetre 
Sulphur 

Charcoal 



0789' 

o'ogS 

O0076 

H 0*004 

.0 0*030, 



yields after 
combustion 



rKaS04 
KaCO, 

EaSaOs 
KaS 
KCNS 
KNO3 

S 
L (NH4)a003 




0-994 



COa 

00 

H 

SH2 





Orm. 
o'oggo 
0*2010 
0*0090 

0'0002 

o'ooiS 
0*00x4 



Grm. 
0*423 
0*126 
0*032 
0*02 X 
0*003 
0*037 
0*007 
o*oox 
0-028 

C.e. 

7940 

101*71 

749 

234 
1*16 

I -00 



19310 

According to the recent researches of Bfr. Craig, and later investigations of M. Fedorow 
(1869), the products of the combustion of powder vary according to the pressure this 
substance is subjected to while being ignited. There has not hiUierto been found any 
really effective substitute for gunpowder ; fulminates and mixtures containing ohloraie 
of potassa ignite too quickly and cause the bursting of the gun, while gun-cotton yields 
among its products of ignition water and nitrous acid, which act destructiyely on the 
metal, and also interfere with continued firing. 

M«w undg of BiMtiaf Under the name of pyronone there is sold a new kind of blasting- 
Powdw. powder, consisting of nitrate of soda 52*5 parts, sulphur 20, and 

spent tan 27*5 parts. It is, of course, far cheaper than ordinary powder, but presumably 
not very useful nor active. Captain Wynands, of Belgium, has successfully introduced 
a substance, to which he has given the name saxifragine, consisting of nitrate of baryta 
76, charcoal 22, and nitrate of potassa 2 parts. Schnitzels (1864) wood-gmipowder consists 
of granulated wood treated with a mixture of nitric and sulphuric acids, and next 
impregnated with a solution of nitrate of potassa ; this matenal is manufactured at 
Edgeworth Lodge, Hants. M. Bandisch hais invented a process by which this wood- 
gunpowder may be compressed into a solid substance exerting great power, and free 
from danger hj transport. Lithofracteur, a white blasting-powder used in Belgium, 
is a substauce sunilar to gun-cotton. The haloxylin of MM. Neumeyer and Fehleisen is 
ft mixture of charcoal, nitre, and yeUow prussiate of potassa. Callou*s blasting povder . 
is a mixture of chlorate of potassa and orpiment. Nitroleum is, in fact, nitro^yeerine, 
which, with dynamite and dualin, will be spoken of presently. Picrate of potassa is used 
in France and in England for filling shells intended for the destruction of armour-plated 
ships, and for the manufacture of picrate gunpowder. 

Testincibestnngtti ^ order to determine the strength or projectile force of gunpowder, 
ofoonpoirder. and which for equality of composition is dependent on the me^anical 
treatment the powder has undergone, the following apparatus are used: — Test mortar, 
rod testing machine, lever testing machine, baUistie pendulum, and chronosoope. The 
first of tiiese contrivances is a piece of heavy ordnance, charged with 92 grms. of powder, 
and a ball weighing 29*4 kilos., the mortar being placed at an angle of 45*. The bore of 
ihe mortar is 191 millimetres in diameter by 239 in depth. Powder of good quality should 
propel the ball a distance of 225 metres, and frequently the ball is carried a distance of 
250 to 260 metres. The rod gonpowder testing apparatus consists of a mortar plaoed 
vertically, and which, when charged with 22 to 25 grms. of powder, lifts a weight of 8 Ibe^ 
made to move between toothed rods ; by the hei^t this weight is raised, springs attached 
to the weight fastening in the notches of the rods and holding it, the quali^ of the powder 
is judged. 

White oimpowder. In the year 1849 M. Augendre brought out a new kind of gunpowder, 
whi<^, imder the the names of German white and American white gonpowder, has been 
occasionally employed. This powder consists of yellow prussiate of potassa, chlorate of 
potassa, and cane sugar. These materials, having been Uioroughly mixed in a dry state, 
can be used in powder or in grains, igniting in contact with red-hot and flaming substanees, 
but not by friction nor percussion. This white gunpowder may be preferred to the 



EXPLOSIVE COMPOUNDS. 155 

n&tikurj powder for the foUoimig reasoiiB:— -Beiiig oomposed of nnTarying snbstanees, 
this powder can always, by wei^^bing out the ]^roper quantities of eaoli ingredient, be 
obtained of uniform strengui and qua^ty. The ingredients are not hygroscopic to any 
extent, and are not acted upon by exposure to the air. The manufacture requires but a 
?eiy short time, the projectile force is far greater, and the powder need not be granulated. 
On the other hand, this powder acts, during its ignition, so very strongly upon iron and 
iteel that it can only be used in bronze ordnance, and in the filling of shells, (fee. It 
is more readily fired than ordinary gunpowder, although less so than other mixtures 
eontaimng chlorate of potassa. Fhially, its manufacture is very expensiye. According 
to the experiments of J. J. Pohl (x86i) on this subject, the following is the best recipe 
for this powder: — 

Tellow prussiate of potassa . . . . 28 parts 

lioaf sugar 23 „ 

Chlorate of potassa 49 „ 

This mixture is approximatiyely equal to— 

X molecule of Prussiate of potassa, 

1 „ Sugar, 

3 molecules of Chlorate of potassa ; 

eonesponding in 100 parts to 28*17 of prussiate of potassa, 22*78 of sugar, and 49*05 of 
chlorate of potassa. As no accurate and reliable analyses of tne products of the com- 
bustion of this powder have been made, and as these products wiU vary with respect to 
the conditions under which the ignition takes place, whether in open air or in a dose 
fesael, it can be merely calculated, that assuming complete combustion to take place, 
100 parts of this powder will yield : — 

Nitrogen 1*865 P&rts 

Carbonic oxide 11*192 „ 

Carbonic acid 17*587 m 

Water 16*788 „ 

Total gaseous products . . 47*442 „ 

The solid residue will consist of — 

Cyanide of potassium . . 17*385 psits 
Chloride of potassium . . 29*840 „ 
Carburet of iron (FeCa) . . 5*333 i> 

Total non-Yolatile products 52*558 „ 

The bulk of gaseous matter OTolTed by the ignition of 100 gnus, of this powder, taken 
at o*^ and 760 m.m. Bar., is as follows : — 

Nitrogen . . . . 1927*0 cubic cenUms. 

Carbonic oxide . . 8942*9 

Carbonic acid . . 8942*9 

Aqueous vapour 20867*9 



ft 

it 



n 



40680*4 

As the temperature of combustion is estimated at 2604*5** the quantity of the gases is 
431 162 CO. 



p'JJjJWm**' Under the name of fireworks we include certain mixtures of 
oombnstible substances employed as signals, as destructive agents (for instance, 
oongreve rockets), and for purposes of display. 

The various forms are, according to the end in view, so contrived as to bom 
off either rapidly or slowly, and veitii more or less emission of gaseous matter, heat, 
and light These mixtures are mainly distinguished as heat-produdng, ignition 
eommnnicators (technically termed a match), and light-producing. The principle 
of the rational manufacture of fireworks, applying the word in its extended sense, is 
that neither any excess of the combustible nor of the combustion promoting and 
supporting agents should be employed, and that unavoidable accessory materials, 
viz., such as are intended only to keep the essential ingredients in a certain required 
shape, the paper casings, &c., be in precisely the quantity required* The best 



i 



i5fl CHEMICAL TECHNOLOGY. 

proportions of the oombostible and combustion-supporting snbstances can bo readily 
ascertained by theoretical calculations ; for instance, it will be evident that a 
mixture of 2 equivalents of saltpetre end x equivalent of sulphur (i), or a mixture 
of 2 equivalents of saltpetre and 3 equivalents of sulphur (2), is in each instance 
wrong ; in the latter, too much of tiie combustible body is used ; and in the former 
case, too much of the supporter of combustion is employed : — 

(i). S can take up from 2KNO3 at most 3O, consequently 3O remain inactive. 

(2). 3S and 2KNO3 yield either K2S and 2SO3, or a mixture of K2SO4, E«S, 
and SO3 ; in each case some sulphur remaining unbumt. 
We have to bear in mind, however, that it is not always possible to elucidate 
theoretically the decomposition of firework mixtures, as the affinity of the substances 
which react upon each other is not well known, and depends on accessory con- 
ditions and comparatively unknown influences. It will require a more advanced 
knowledge of the products of the decomposition of the different substances and 
their specific heat before we can predict with some degree of certainty the best 
mixtures. As regards the existing mixtures, they are the result of a lengthy series 
of experiments, really made by rule of thumb, though with a certain correspondence 
with the best composition theory can give, that is to say, many of these mixtures 
have been somewhat modified and improved by modem science. 

The mora flommooiriiMd These mixtures consist mainly of saltpetre, sulphur, and charcoal, 
nnwock Miztam. either in the same proportions as those in use for gmipowder, or 
with an excess of sulphur and charcoal. Borne mixtures contain instead of saltpetre 
chlorate of potassa and other salts, not always essential to tiie combustion, but intended 
either to intenaiiy the light evolved or impart to it a distinctive colour, as in signals 
and Bengal lights. 

oonpowdcr Is used in fireworks when it is desired "that there should be projectile foroe. 
A slower combustion of the powder is obtained parUy by ^e use of the so-oaUed fiour of 
powder, that is pulverised, not granulated powder, partiy by compressing the mixture. If, 
however, it is intended to produce loud reports, granulated powder is used. 

saitpacre and Svipinur lUxkinB. This consists of 2 moleoules (75 parts by weight) of saltpetre, 
and I molecule (25 parts by weight) of sulphur, and is used as the chief constituent of 
such firework mixtures as are intended to bxum off slowly and evolve a strong light. 
However, this mixture is not used by itself for two reasons, vis., it does not derelope 
a sufficient degree of heat to support its continued combustion, and does not possess a 
sufficient projectile force, being capable of producing in the best possible condition of 
complete ignition only z molecule of sulphurous add — 

2EN03-l-S-E^804-f BOa+N ; 
that is to say, i part by bulk of this mixture omy yields 7*28 volumes of gas. For these 
reasons the saltpetre-sulphur mixture is employed with charcoal or floury gunpowder. 

ony-ooioiizMi Mixton. Suoh a mixture, sanctioned bv long use, is that known aa grey- 
coloured mixture, oorndsting of 93*46 per cent 01 saltpetre-sulphur, and 6*54 of floury 
gunpowder. This mixture is the chief constituent of other compounds intended to bum 
dowly, emitting at the same time a brilliant light, owing to the fact that the sulphate of 
potassa formed by the combustion acts similarly to a solid brought to an incandescent 
state. All mixtures intended to emit light, including coloured li^ts, are prepared upon 
the same principle, that the salt which is to give colour shall be non-volatile at the tem- 
perature of combustion. 

Ghkntoof PoUMMiuxtani. This Salt EOIO3, when in presence of combustible sub- 
stances, gives off its oxygen to the latter more readily, rapidly, and completely than salt- 
petre ; accordingly this salt is used in all mixtures in which it is desired to oombine rapid 
Ignition with combxurtion. Fonnerly a mixture of 80 parts by wdght of chlorate of 
potassa and 20 parts of sulphur, was added to intensify snd quicken the combus- 
tion of mixtures consisting of more slowly burning salts. A mixture of sulphur, ohar- 

FrisUon MixtsTM. oosl, and chlorate of potassa constitutes an active peroussion 

Pweanion Powdm. powder. A mixture of equal parts by weight of black sulphuret of 
antimony and chlorate of potassa is used for the purpose of disoharging or<uianoe by 
means of a percussion tube placed into the touchholo of the gun. Sir WUliam Armstrong 
uses for this purpose a mixture of amorphous phoBphcrus and chlorate of potassa. 



EXPLOSIVE COMPOUNDS, 157 

mxtanforznitingttw Thlfl mixtnre consists either of chlorate of potassa and black snl- 
amuf« of secdte-pma. phnret of antimony, or a componnd containing fulminate of mercury. 
The following is a good preparation : — 16 parts of chlorate of potassa, 8 parts of black 
mlphnret of antimony, 4 of floor of snlphur, i of charcoal powder, are moistened with 
either gam or sugar water, and about 5 drops of nitric acid added. A small quantity, 
teehnicaUy known as the piUf is placed in the cartridge, and ignited by the friction pro- 
duced by the sudden passage of the steel needle through it. In this country either the 
ftbove or a mixture of amorphous phosphorus and chlorate of potassa is used. Leaving 
the fulmdnates of silyer and mercury out of the question, the explosive bodies and 
their applicability to warlike purposes and war pyrotechny have not been sufficiently 
investigated. Kitromannite or fulminating mannite, the picrates of the alkalies 
and nitroglycerine, of which we shall presently treat more fuUy, especially deserve notice. 
If. Deesignolles, who suggests that instead of saltpetre, picrate of potassa should be used 
in the manufacture of gunpowder, states that quite different products are formed by the 
ignition of picrate of potassa, when effected in the open air (a), or under pressure (/3) :— 

a. 206HaK(NOa)30=KaC03+5C+2N+NO+NOa+400a+CHN. 

\ ■ ■ „ ,.--/ 

Picrate of potassa. 
p. 2C6HaK(N02)30=KaC03+6C+3N+5COa+2H2+0. 

V , f 

Herate of potassa. 
Fulminating aniline, chromate of diazobenjBol, obtained by the action of nitrons acid 
upon aniline, and the precipitation of the product by the aid of a hydrochloric acid solu- 
tion of bichromate of potassa, is, according to MM. Garo and Qriess, an efficient substitute 
for fulminating mercury. 

Baat-pRMbiciog MixtoTM. Theso couslst cMefly of floury gunpowder and grey mixtnre, 
to which are added those organic substances, as pitch, resin, tar, igniting readily, but 
ecmsumed more slowly than any firework. The heat generated by the combustion of 
fireworks is much higher than is required to ignite wood, but not of sufficient duration to 
cause the thorough burning of the wood, hence the addition of tar, Ae. 

ctkmnAtinm, llie salts employed to produce coloured flames are — ^the nitrates of 
baryta, strontia, and soda, and the ammoniacal sulphate of copper. The so-called cold 
fused mixture, composed of grey mixture, floury gunpowder, and sulphuret of antimony, 
moiBtened with brandy and then mixed, produces a white flame. The mixtures for 
coloured flres used in artillery laboratories are the xmdermentioned, calculated for 100 
parts of each mixture : — 

X. Chlorate of potassa . • 

2. Sulphur 

3. Charcoal 

4. Nitrate of baryta 

5. Nitrate of strontia .. .. — 457 — — — 

6. Nitrate of soda .... — — 9*8 — — 

7. Ammoniacal sulphate of coppe^ — — — 27*4 — 

8. Saltpetre — — 62*8 — 60 

9. Black sulphuret of antimony . . — 57 — — 5 
10. Floury gunpowder .... — — — — 15 

It is hardly necessary to mention that great care is required in mixing these mate- 
rials, and that each ingredient ought to be pulverised separately. 

According to M. IHiden a beautiful white flame edged with blue is obtained by 
the ignition of the following mixture : — 20 parts of saltpetre, 5 of sulphur, 4 of sulphuret 
of cadmium, and i part of diarcoal. Chloride of thallium with other ingredients yields a 
beautiful green flame. Magnesium was used during the Abyssinian war in various ways 
when a brilliant light was required. The chlorates of the alkaline earth bases and the 
ehbrate of soda would be preferable, were it not for the expense, and for the facts 
that these salts are rather hygroscopic and liable to spontaneous combustion. The car- 
bonates of baryta and of strontia are sometimes used instead of the nitrate. According 
to MM. Dessignolles and Oastelhaz, most hnlliant coloured flames are obtained with picrate 
of ammonia in the following proportions : — 

Tellow I ?^*^'**® ®' ammonia . . 50 



a. 


b. 


c. 


d. 


e. 


Green. 


Bed. 


Yellow. 


Blue. 


"White. 


327 


297 


— 


54'5 


— 


9-8 


17*2 


236 




20 


5-2 


17 


3-8 


x8'x 


— 


523 


— 


— 


— 


— 



Green 
Bed 



Picrate of protoxide of iron 50 

Picrate of ammonia . . 48 

Nitrate of baryta . . • • 52 

Picrate of ammonia . . 54 

Nitrate of strontia . . . . 46 



158 CHEMICAL TECHNOLOGY. 

b. Nitroglycerine. 

Nitrogiyeaiine. TluB substance, aJso known as fulminating oil» nitrolemn, trinitrine, 
glyceiyl-nitrate, glonoine, was discovered in 1847 by Dr. A. Sobrero, while a 
student in the laboratory of Professor Pelouze, at Paris. Since the year 1862, M. Alfred 
Nobel, a Swede, has manufactured this liquid on the large scale. The formula of 

nitroglycerine is C3H5N30g or /^J^^ r ^3 » consequently it consists of glycerine, 

H I ^3> ^ which 3 atoms of H have been replaced by 3 atoms of NO^. 100 parta 

of nitroglycerine yield on combustion — 

YV axer ••• •«« ••• 

Carbonic acid 

Oxygen ... ... ... 

Nitrogen 

loo'o parts. 

As the sp. gr. of nitroglycerine is 1*6, i part by bulk will yield on combustion — 

Aqueous vapour 554 volumes. 

Carbonic acid 469 ,, 

Oxygen ,- 39 ** 

Nitrogen • 236 1, 

1298 

According to experiments made in Belgium, the combustion of. nitroglycerine 
does not yield free oxygen, but a large quantity of protoxide of nitrogen ; accordingly, 
the following equation will give some idea of the mode of explosion : — 

Carbonic acid, 6OO3. 



20 ] 


parts. 


58 


»» 


3*5 


>i 


185 


It 



2 molecules of 
Nitroglycerine, C3H5N3O9 



Water, sHaO. 

Protoxide of nitrogen, NaO. 

Nitrogen, 4N. 



M. Nobel states that the heat set free by explosion causes the gases to expand to 
eight times their bulk ; accordingly, i volume of nitroglycerine will yield 10*384 
volimies of gas, while i part by bulk of powder only yields 800 volumes of gas; the 
explosive force of nitroglycerine is, therefore, to that of powder — 

By volume as 13 : i, 
By weight as 8:1. 

In order to prepare nitroglycerine, very strong nitric add, density 49° to 50** B. 
s= 1*476 to 1*49 sp. gr., is mixed with twice its weight of concentrated sulphniic 
acid. 3300 gnus, of this mixture, thoroughly cooled, are poured either into a glass flask 
or into a glazed earthenware jar, placed in a pan of cold water, and there is next 
gradually added 500 gnns. of concentrated and purified glycerine, having a density 
at least of 30'' to 31'' B. = sp. gr. 1-246 to 1*256, care been taken to stir constantly. 
According to Dr. E. Kopp*s recipe (1868) the acid mixture should consist of 3 parts 
of sulphuric add at 66** B. = 1767 sp. gr., and i part of fuming nitric add. To 
350 grms. of glycerine 2800 grms. of the add mixture are added ; and in performing 
this operation care should be taken to avoid any perceptible heating for fear of 
converting by a violent reaction the glycerine into oxalic add. The mixture is now 
left to stand for five or ten nunutes, and afterwards poured into five or six times its bulk 



EXPLOSIVE COMPOUNDS. 159 

of very cold water, to which a rotatory motion has been imparted. The newly- 
formed nitroglycerine sinks to the bottom of the vess^ as a heavy oUy Uquid, which 
ifi washed by decantation ; bat if not intended for transport — and experience has 
proyed the transport of nitroglycerine to be highly dangerous — ^the washing may be 
dispensed with, as neither any adhering acid nor water impairs the explosive 
properties. Nitroglycerine is now generally made on the spot in America and else- 
where by those whom experience in mining, quarrying, and engineering matters has 
taught the real vcdue of this very powerful agent. 

Nitroglycerine is an oily fluid of a yellow or brown colour, heavier thsm and 
insoluble in water, soluble in alcohol, ether, and other fluids; when exposed to 
continuous cold, not of great intensity, it becomes solidified, forming long needle- 
shaped crystals. The best means of exploding nitroglycerine is a well-directed 
blow, neither a spark nor a lighted body will cause the ignition, which even with a 
thin layer takes place with difficulty, only part being consumed. A glass bottle filled with 
nitroglycerine may be smashed to pieces without causing the contents to explode. Nitro- 
glycerine may even be gently heated and volatilised without decomposition or com- 
bustion, provided violent boiling is carefully prevented. When a drop of nitroglycerine 
18 caused to fidl on a moderately hot piece of cast-iron the liquid is quietly volatilised ; 
if the iron is red-hot the liquid bums off instantaneously, just as a grain of powder 
would do under the same conditions ; if, however, the iron is at Uiat heat which 
will cause the immediate boiling of the nitroglycerine, it explodes with great force. 
Nitroglycerine, especially if sour and impure, is liable to spontaneous decomposition, 
which, accompanied by the formation of gas and of oxalic acid, may have been the 
proximate cause of some of the dreadful explosions of this substance, it being 
surmised that the pressure exerted by the generated gases upon the fluid in 
hennetically closed vessels had something to do with the occurrences. On this 
account M. K. list advises that vessels containing nitroglycerine should be only 
loosely stoppered, or if being transported provided with safety-valves. Nobel 
secnrea nitroglycerine from explosion by dissolving it in pure wood-spirit, from 
which it may be again separated by tiie addition of a large quantity of water. Mr. 
Seeley on this score observes that: — i. The wood-spirit is expensive, and lost in the 
large quantity of water required for precipitating the nitroglycerine; 2. Wood-spirit, 
being volatile, may evaporate, and leave the nitroglycerine unprotected ; 3. There 
18 a change of chemical action between these bodies ; 4. The vapour of wood-spirit 
is very volatile, and forms with air an explosive mixture. Many suggestions have been 
made as to rendering nitroglycerine safe to warehouse ; among them may be noted 
the miung with pulverised glass in a manner similar to (bale's process for gun- 
powder. Wurtz recommends the mixture of nitroglycerine with equally dense 
solutions of eitiier of the nitrates of zinc, lime, or magnesia, so as to form an 
emulsion, the nitroglycerine being recovered simply by the addition of water. The 
taste of nitroglycerine is sweet, but at the same time burning and aromatic; it is a 
violent poison even in small doses, and its vapour is of course equally virulent, hence 
great care is required in working with this substance in localities where, as in mines 
and pits, the supply of fresh air is limited. Instead of manufiEtcturing nitroglycerine 
in works specially arranged for that purpose, and transporting this dangerous 
compound, it is better, as advised by and executed under the direction of Dr. E. 
Kopp, at the Saveme quarries, to have the quantity required for daily use prepared 
on the spot by intelligent workmen. Notwithstanding the very serious accidents 



i6o CHEMICAL TECHNOLOGY, 

which have been caused by the explosions of nitroglycerine in this conntry as well 
as abroad, and the consequent prohibition of its use, there is no reason iiiiy this 
powerful agent should not be employed according to Kopp's suggestion. Instead of 
the acid mixture used ia the preparation of nitroglycerine, M. Nobel suggests the 
following: — In 3! parts of strong sulphuric acid of 183 sp. gr. is dissolved i part 
of saltpetre, and the fluid cooled down ; the result is the separation of a salt consisting 
of I molecule of potassa, 4 molecules of sulphuric acid, and 6 molecules of water, 
and which at 32*" F. is altogether eliminated &om the fluid, leaving an acid which, 
by the gradual addition of glycerine, is converted into glonoine, afterwards separated 
by water, as already described. 

Nobel's Dyxuunite. Under the name of dynamite, Nobel, in 1867, brought out a new 
explosive compound, consisting of 75 parts of nitroglycerine absorbed by 25 parts 
of any porous inert matter, as finely divided charcoal, silica. As evidenced by the 
experiments of Bolley and Eundt, dynamite has the advantage over nitroglycerine 
of not being exploded even by the most violent percussion, therefore requiring a 
peculiarly arranged cartridge. The explosion is attended with such force that 
large blocks of ice are shattered to atoms. Dynamite bums off quietly in open 
air, or even when loosely packed, the combustion being accompanied by an evolution 
of some nitrous acid; but when dynamite is exploded there are generated only 
carbonic acid, nitrogen, and aqueous vapour, no smoke being formed, and only a 
white ash left. Dynamite is not affected by damp, and undoubtedly offers great 
advantages as regards its use in mining, quarrying, and similar operations, for 
although the price exceeds four times that of powder, dynamite performs eight times 
as much work with less danger, and less labour in boring blast holes. The dynamite 
is placed in cartridges of thick paper, and ignited by means of a fiisee, which passes 
through the sand serving the purpose of a wad. Dynamite can be transported 
without danger of explosion. Dittmar's dualin is a mixture of nitroglycerine with 
sawdust or wood>pulp as used in paper mills, both previously treated with nitric and 
sulphuric acids. 

c. Oun-Cotton, 

onn-ootton. This substaucc, also known as pyroxylin and falmicotton, was discovered 
in 1846, simultaneously by the late Professor Schonbein, at Basle, and by Dr. R 
Bottger, at Frankfort-on-Main. The mode of preparing this substance is as follows: — 
Equal parts of strong concentrated sulphuric acid, sp. gr.= 1*84, and fuming nitric acid 
are poured into a porcelain basin ; as much cotton- wool is steeped in the fluid as the 
acid is capable of thoroughly moistening, and the vessel covered with a glass plate, 
and left for a few minutes. The cotton-wool is then removed from the acid, 
immediately transferred to a vessel containing a large quantity of water, and washed 
with care, the water being renewed until no more acid adheres to the gun-cotton, 
which is next dried in a current of warm air, and finally combed to remove all the 
lumps. The cotton should not be left too long in the acid as it might become 
entirely dissolved. According to experiments instituted at Paris in one of the 
powder mills — for in France no one is allowed to manufacture powder or gqn-cotton 
except the Government — ^the following are the conditions under which the best results 
are obtained: — i. Equal parts of sulphuric and nitric acids and well cleansed 
cotton. 2. Time of immersion in add mixture from 10 to 15 minutes. 3. The same 
acid may be used once again, but then the time of immersion of the cotton 



GUN COTTON. 



z6i 



should be longer. 4. The gun-cotton having been thoroughly washed should be dried 

slowlj at a gentle heat. 5. Impregnating with nitre increases the strength of the 

gan-cotton. 

propartiM of onn-Gotton. In its ontward appearance gun-eotton does not differ from 
ordinary cotton, neither is any difference perceptible by microscopic investigation. It is 
insolnble in water, alcohol, and acetic acid, difficultly soluble in pure ether, but readily 
soluble in ether which contains alcohol, and in acetic ether. Gun-cotton is liable to spon- 
taneous decomposition, which may even induce its spontaneous combustion ; this decom- 
poBition is attended with the evolution of aqueous vapour and of nitrous acid fumes, the 
lemaining substance containing formic acid. As regards the temperature at which gun- 
eotton ignites statements differ; it has in some instances been dried at 90** to 100^ 
vitbont any dangerous consequences, while it has been found to ignite at 43**. Instances 
are on record of serious explosions of gun-cotton having taken place under conditions 
which leave no doubt that the greatest care is required in handling and warehousing 
this substance ; for instance, a small magazine, fiUed with gun-cotton, situated in the 
Bois de Yincennes, Paris, was exploded by the sun's rays ; and at Faversham the Le Bouchet 
drying rooms, which could not possibly be heated above 45° to 50*, exploded with great 
Tiolence. Gun-cotton explodes by percussion, leaving no residue after its ignition. Good 
Kon-ootton may be burned off when placed on dry gunpowder without igniting the latter. 
It is very hygroscopic, but may be kept for a length of time under water without affecting 
its explosive properties. 

According to the best chemical analysis, gun-cotton is trinitro-cellulose, 

C6H7(NOa)305, 

consequently it is cotton considered in a pure state as cellulose, C6HX0O5, 3 atoms of 
the hydrogen of which have been replaced by 3 atoms of hyponitric acid. 100 parts 
of gan-cotton contain — 

Carbon 24*24 

Hydrogen 2*36 

Oxygen 5926 

Nitrogen ... • '4' '4 



The conversion 
fonnnla: — 



of cotton into gan-cotton may 

C6Hxo05-f3HN03=C6H7(NOa)305-f3HaO ; 

— ' ^ " 



lOOOO 

therefore be expressed by the following 



Cotton. 



Gun-cotton. 



the sulphuric add being employed only for the purpose of absorbing water. 
Assuming that the cellulose is entirely converted into trinito-cellulose, 100 parts of 
cotton ought to yield 185 parts of gun-cotton, and when the conversion forms binitro- 
cellulose, 100 parts of cotton ought to yield 155 parts of gun-cotton. The under- 
mentioned are the results of direct investigation. For 100 parts of cotton — 

Pelonze (in ten experiments, 1849) found 168 to 170 parts of gan-cotton. 

Schmidt and Hecker (1848) „ 169 

Van Kerckhoff and Renter (1849) „ 1762 

W. Cram (1850) ,. 178 

Redtenbacher, Schrotter, and Schneider (1864) „ 178 

V. Lenk (1862) » i55 

Blondeau (1865) » 16525 

By the explosion of gan-cotton in vacuo, carbonic oxide, aqueous vapour, and 
nitrogen are evolved. The same products, with the addition of nitrous acid and 
cyanogen, are generated by the explosion of gan-cotton in closed vessels, i grm. of 

M 



>•• •■• ••< 



162 CHEMICAL TECHNOLOGY. 

gun-cotton yields, according to Schmidt, 588 c.c. gases, these gases consisting in 
100 parts by volume of — 

Carbonic oxide 30 

Carbonic acid ... 

Marsh gas 

Deutoxide of nitrogen . . . 

Nitrogen 

Aqueous vapour 



I • • • • 



20 
... 10 

9 



I • • • • 



I • *• • 



• • • 94 



>• • • • 



8 
23 



100 

I part by weight of gun-cotton is equal in projectile power to 4*5 to 5 parts of gun- 
powder. 

^^'^^StS^^i^*^*^ Gun-cotton has not yet been adopted in practice as a good 

substitute for gunpowder ; its large bulk, coupled with the fact that the explosion is 

attended with the evolution of much water and nitrous acid, render it inconvenient 

as a substitute for powder. 

ouMroMaof oon-ooHon. Gun-cctton is advantageously employed in blasting, and has been 
used as a Bubetitute for fulminating mercury in gun-caps when mixed with ohloraie of 
potassa. The experiments of Professor Abel, of Woolwich, have led to great improve- 
ments in the manufacture of gon-cotton, carried into practice l^ Messrs. Prentice, of 
Stowmarket, and consisting chiefly in mechanical operations. The cotton, either bj 
spinning and weaving, by pulping, or the aid of suitable solvents, is brought into a con- 
dition in which it has been found an excellent and cleanly substitute for gunpowder, 
having the advantages of not giving off smoke, exploding with less noise, and not fouling 
the guns. The detailed description of the method of these operations is not necessary 
here. Gun-cotton in many cases may serve the purpose of asbestos for filtering strong 
acids and other concentrated fluids which cannot be filtered through paper. 

couoiUon. Maynard employs a solution of gun-cottpn in ether as a kind of glue or 
varnish, and gives it the name of collodion. This solution has the appearance of a 
syrup, and a thin film poured on the skin, leaves, by the evaporation of the ether, a 
strongly adhesive compact layer ; hence collodion is applied in surgery, photography, 
and as a waterproof coating instead of varnish, especially to protect the compositioQ 
of ludfer-matches from the effects of damp. The film of pyroxylin, deposited after 
the evaporation of ether, is insoluble in water and alcohol, becomes highly negatively 
electric when rubbed with the dry hand, and may be obtained so thin as to exhibit 
the colours of the Newton rings. Legray prepares in the following manner a gun- 
cotton quite soluble in ether : — 80 grms. of dried and pulverised nitrate of potassa 
are mixed with 120 grms. of concentrated sulphuric acid, and in the pulpy acid mass 
are thoroughly immersed by the aid of a glass rod or porcehdn spatula 4 grms. of 
cotton, which is stirred about for a few minutes ; next the vessel containing acid and 
cotton is placed in a large quantity of water, and the converted cotton washed until 
all the acid is eliminated, when it is dried. Soluble cotton may be made with 
nitrate of soda, 17 parts; sulphuric acid, sp. gr. = 180, 33 parts; cotton, I part 
The converted cotton is soluble in acetic ether, acetate of oxide of methyl, wood- 
spirit, and aceton ; the usual solvent is a mixture of 18 parts of ether and 3 parts of 
alcohol. 



COMMON SALT. 163 

Common Salt. 

oeesR«D««. Common salt, or chloride of sodium, consists of — 

Chlorine, CI 355 60*41 

Sodium, Na 230 39'59 



585 loooo 

and is found on our globe in the solid, as rock-salt, as well as dissolved in sea- water 
is enormously large quantities. It occurs as rock-salt in extensive layers alternating 
with those of clay and gypsum at an average depth of 100 metres. The following are 
a few of the localities where rock-salt is met with in the tertiary formation : — 
Wieliczka, Poland ; the northern slopes of the Carpathian mountains, and in several 
districts of Hungary; in the chalk formation of Cardona, Spain; in the Eastern 
Alps, Bavaria, Salzburg, Styria, and the Tyrol. Among the trias formation are the 
salt deposits of the Teutoburg-wood, Germany, and a great many others, among them 
the celebrated Stassfurt deposits. In England rock-salt is found in Cheshire, this 
county being also plentifully supplied with saline springs, the water of which yields 
on evaporation an abundance of salt. Petroleum wells are found with salt in many 
parts of Asiatic Russia, in Syria, Persia, and the slopes of the Himalaya. Salt 
occurs plentifully in several districts of Africa, America, and other parts of the 
world, and mixed with clay and marl, forming salt-clay. Salt occurs secondarily by 
having been dissolved, at a depth varying in Germany from 91 to 555 metres, by 
water, which carries it again to the surface, there forming salt springs and salt lakes, 
from which the salt is obtained by evaporation. Among the salt lakes may be 
noticed the lake near Eisleben, Germany, the Elton Lake near the Wolga, Russia, the 
Dead Sea, and the Salt Lake of Utah, United States. 

There can be no doubt that the common salt met with in salt springs owes its 
origin to the solvent action of water upon rock-salt, and as rock-salt is largely met 
with in sedimentary geological formations, the prevalence of this formation in Ger- 

m 

many has there given rise to a large number of salt springs. Common salt is also 
found in sea- water, and if obtained by its evaporation is often termed sea-salt ; or if 
deposited, as is the case in the Polar regions, by intense cold on the surface of ice- 
fields, it is known as rassol. Common salt is largely obtained as a by-product of 
some chemical operations, as in the conversion of sodium-nitrate into potassium- 
nitrate by the aid of chloride of potassium. 

''•^ffrSSaSSf.te?'^" The constituent salts of sea- water do not differ in any part 
of the world ; even the difference in quantity is very small, and is generally due to 
local causes, as the dilution of the sea- water by river- water, melting icebergs, &c. 
The sp. gr. of sea- water at 17°, varies from 1*0269 ^ 10289, the sp. gr. of the water 
of the Red Sea being as high as 1*0306. One hundred parts of sea- water contain — 



Chloride of sodium . . . 
Bromide of sodium ... 
Sulphate of potassa . . . 

Sulphate of lime 

Sulphate of magnesia . . . 
Chloride of magnesium 
Chloride of potassium... 



Pacific 


Atlantic 


German 


Bed 


Ocean. 


Ocean 


Ocean. 


Sea. 


25877 


27558 


25513 


3030 


00401 


0*0326 


00373 


0064 


01359 


01715 


01529 


0*295 


01622 


02046 


01622 


0-179 


01 104 


00614 


0*0706 


0274 


04345 


0*3260 


04641 


0404 




— ^ 


— 


0288 



34708 35519 ZAZH 4534 

M 2 



i64 CHEMICAL TECHNOLOGY. 

The composition of the salt contained in the water of the several seas is shown bj 
the following table : — ^ 

i i 



i S'ss i-sj O'SS ^-s 



Q • rM «i4 CD □ — 



OQ * 



«L."S .2 9.13 ^ fi. 



rlO-*^ Cffi-*^ OO-** <X>d}-** 

lli 11^ il'-a «^l^ 



Average quantity of salt and water — 

Solid salt 0-63 177 177 3-31 337 363 2230 

Water 9937 98*23 9823 9669 9663 9637 7770 

The dissolved solid matter consists in 100 parts of — 

Chloride of sodium ... 58*25 79*39 84 70 7804 77*07 77*03 36*55 

Chloride of potassium 127 107 — 209 2*48 3*89 4*57 

Chloride of calcium ... — — — 0*20 — — 11*38 

Chloride of magnesium lo'oo 738 973 8'8i 8*76 7*86 45*20 
Bromides of sodium 

and magnesium ... — 0*03 — 0*28 0*49 1*30 0*85 

Sulphate of lime ... 778 060 0*13 3*82 2*76 4*63 0*45 

Sulphate of magnesia 19*68 832 4*96 658 834 5*29 — 
Carbonates of lime and 

magnesia 302 3*21 0*48 0*18 o*io — — 

Nitrogenous and bitu- 
minous matter ... — — — — — — 100 

One cubic metre (35*3165 cubic feet) of sea- water contains consequently abont 
28 to 31 kilos of chloride of sodium, and 5 to 6 kilos, of chloride of potassium. 
Chloride of sodium (common salt) is obtained from sea- water : — 

a. By the evaporation of the water by the aid of the sun's heat. 

b. In winter, by freezing. 

c. By artificial evaporation. 

Method cj^owigrfngooiniaon xMs mothod of obtaining common salt from sea-water is 
limited to certain of the coast-lines of Southern Europe, and is never effected 
beyond 48** N. latitude. The countries best situated for this industry are France, 
Portugal, Spain, and the coasts of the Mediterranean. The arrangement of the 
salines, or salt-gardens, is the following : — On a level sea-shore is constructed a 
large reservoir, which, by a short canal, communicates with the sea, care being 
taken to afford protection against the inroads of high tides. The depth of water in 
these reservoirs varies from 0*3 metre to 2 metres. The sea- water is kept in the 
reservoir until the suspended matter has been deposited, and is then conveyed by a 
wooden channel into smaller reservoirs, from which it is conducted by undergroond 
pipes to ditches surrounding the salines, where the salt is separated from the water. 
The salt is collected, placed in heaps on the narrow strips of land which separate the 
ditches from each other, and sheltered from rain by a covering of straw. As these 
heaps are left for some time, the deliquescent chlorides of magneaum and caldom 

* According to the experiments of Baron Sass, the water of the Baltic from the Great 
Sound between the Islands of Oesel and Moon only contains 0*666 per cent of solid matter, 
and is of a sp. gr. =s z*0O474« 



COMMON SALT. X65 

are absorbed in the soil, consequently the salt is comparatively pure. The mother- 
liquor is used in the production of chloride of potassium (see ante, p. 119), sulphate 
of soda, and magnesia salts, the process employed being that originally suggested by 
IVofessor Balard, and afterwards improved by Merle. 

lynMsfBf. This process is based upon the fact that when a solution of common 
salt is cooled to several degrees below the freezing-point, it is split up into pure water, 
which freezes, and a strong solution of salt. The solution becomes more con- 
centrated by repeated freezing and removal of the ice, until at last a solution is 
obtained which by a slight evaporation 3rields a crop of salt. In order to render the 
product purer, some lime is added to the solution before evaporation to decompose 
the magnesia salts. 

BjrAitudsiETapontion. Commou Salt ovaporatod from sea- water by the aid of fuel, 
or tel ignifire, is chiefly prepared in Normandy, in the following manner : — The sand 
impregnated with salt is employed to saturate the sea-water, which is next 
evaporated. Very frequently an embankment of sand is thrown up on the shore, so 
as to be covered at high tides only ; in the interval between two tides a portion of the 
salt dries with the sand, which in hot summer weather is collected twice or three 
times daily. The sand is lixiviated in wooden boxes, the bottoms of which are con- 
stracted of loose planks covered with layers of straw; the sand having been 
pat in the boxes sea-water is allowed to percolate through them till the specific 
gravity of the water increases to 1*14 or to i' 17, the density being observed by means 
of thiee wax balls weighted with lead. The salt boilers at Avrauchin consider that a 
solution or brine of i'i6 sp. gr. is the most suitable for evaporation. The evapora- 
tion is carried on in leaden pans, and during the process the scum is removed and 
fresh brine added until the salt begins to crystallise out, when again a small quantity 
of brine is added to produce more scum, which is at once removed, and the evapo- 
ration continued to dryness. The salt thus obtained, a finely divided but very 
impure material, is put into a conical basket suspended over the evaporating pan, 
the object being to remove by the action of the steam the deliquescent chlorides of 
calcinm and magnesium. The salt is next transferred to a warehouse, the floor 
of which is constructed of dry, well-rammed, exhausted sand, and here it is 
gradually purified by the loss of deliquescent salts, the consequent decrease in weight 
amounting to 20 to 28 per cent. 700 to 800 litres of brine yield, according to the 
quantity of salt contained in the sand, 150 to 250 kilos, of salt. A very similar 
method is in use at Ulverstone, Lancashire. 

At Lymington and the Isle of Wight, sea-water is concentrated by spontaneous 
evaporation to one-sixth of its original bulk, the brine being then evaporated by the aid 
of artificial heat In the neighbourhood of Liverpool salt is obtained by employing 
Bea-water in refining crude rock-salt ; in this way at least 23 per cent of common 
Bait results as a by-product. During a continuation of hot summer weather, salt is 
deposited from the water of many of the salt lakes in immense quantities, amounting, 
for instance, at the Elton Lake, Russia, to 20 millions of Mlos. 
BA^-Mtt. This mineral is frequently accompanied by anhydrite, clay, and marl, 
and is sometimes found in what are termed pockets of irregular shape, interspersed 
with clay. Again, in some cases saline deposits are separated by layers of marl. 
With rock-salt other minerals sometimes occur, as, for instance, brongniartine 
(Na,S04+CaSO4), near ViUarubia, in Spain, and the remarkable minerals of the 
salt deposit near Stassfurt. Above the latter deposit is a layer 65 metres thick, 
of bitter, many coloured, deliquescent salts, consisting of 55 per cent of camallite. 



i66 



CHEMICAL TECHNOLOGY. 



sylvin, and kainite ; 25 per cent of common salt ; 16 per cent of kieserite ; and 4 per 
cent of chloride of magnesium. As this saline layer contains 12 per cent of 
potassa it is an important deposit in an industrial sense. 

The composition of rock-salt is as follows : — 

I. White rock-salt from Wieliczka; U. White, and III. yellow rock-salt from 
Berchtesgaden ; IV. From Hall in the Tyrol; V. Detonating salt from Hallstadt; 
VI. From Schwabischhall. 

n. m. IV. 
9985 9992 9943 



I. 

Chloride of sodium loo'oo 

Chloride of potassium — 

Chloride of calcium — 

Chloride of magnesium traces 

Sulphate of lime — 



V. 

9814 
traces 



traces 
015 



007 



0-25 
012 

0'20 



VI. 

9963 
0*09 

028 



1-86 — 



lOOOO lOOOO lOOOO lOO'OO lOO'OO ICX>'00 

The so-called detonating salt, found at Wieliczka in crystalline-granular masses, 
has the property when being dissolved in water of giving rise to slight detonations 
accompanied by an evolution of hydrocarbon gas from microscopically small cells, 
the walls of which becoming thin when the salt is dissolved in water, give way, and 
cause the report. If the solution of the salt takes place naturally in the mine, the 
gas partly escapes, partly becomes condensed, forming petroleum, often met with in 
beds of rock-salt. The minerals of the salt deposit of Stassfurt are, according 
to MM. Bischof, Eeichardt, Zincke, and others, the following : — 



Chemical 
Formula. 



In 100 parts are 
contained : 






100 parts of 
water dis- 
solve at 

isr C. 



Synonyms 
and Obser- 
vations. 



Anhydrite 



CaS04 100 of Sulphate of lime 2*968 020 ' Karstenite. 






Boracite 



.1 



29 



Camallite 



Bed oxide of 
iron 

Kieserite ... 



26*82 Magnesia 
BieOjoCla 65 '57 Boric acid 
Mg7 10*61 Magnesium chlo 

ride j 

2676 Chloride of potas- 

KMffCl, ,, ®^^ VI I .: Q 

4-6H O 34'5° Magnesium chlo- 1 1*618 
3874 Water 

Fej03 100 of Oxide of iron 3*35 
( MffSO 4- ®7*io Sulphate of mag-' 



Almost 
insoluble J 



I Stassfortite. 



645 



Contains 
Bromine. 



Insoluble. — 



H^O' 



nesia 
12*90 Water 



• 2*517 



409 



Martinsite? 



45' 1 8 Sulphate of lime] 

2CaS04 19*93 Sulphate of mag- 1 

T> 1 1. !•*« J MgSOj nesia 1 2720 

Polyhalite ..A j^^g^^* ^g.^ Sulphate of po- 

I 2H4O tassa 

v 5*99 Water 

* According to Bammelsberg it is probable that kieserite is originally an anhydront 
mlnerid, a eonclasion which Qeems justified by the variable quantity of water found in 
different analyses. 



Is decom- 
posed while 
being dis- 
solved 



COMMON SALT. 



167 



Chemical In xoo parts are 
formula. contained : 



2 • 



& 



a 






zoo parts of 
water dis- 
solve at 
x8r 0. 



Rock-Bait ... NaCl 100 Choride of sodium 2*200 36*2 



Svlvin 



KCl 



100 Chloride of potas- 
sium 



) 



2025 



345 



Synonyms 
and Obser- 
vations. 



Tachhydrite 



Kainite 



Schonite or 
Pilcromerite 



21 50 Chloride of cal-^ 
CaCla cium 

2MgCl2 3698 Chloride of mag 
12H2O nesium 

41-52 Water 

3634 Sulphate of po-^ 
K.SO tassa 

MgSO* ^5'^ Sulphate of mag- 
nxcrC*} nesia 

^ff^Q i8'95 Magnesium chlo- 
^ ride 

19*47 Water 

43-18 Sulphate of po-^ 
K2SO4 tassa 

MgS04 29*65 Sulphate of mag- 
6H3O nesia 

26-97 Water. 



1-671 i6o*3 



Contains 
Bromine. 



Sylvin is also found in large quantities in the salt deposit near Kalucz, Qalicia. 

vodeofwoikiiigBoek-Mtt. Bock-salt, like other minerals and according to its mode of 
occurrence, is either quarried or mined. If it happens, however, that the rock-salt 
is mixed with other minerals, clay, gypsum, dolomite, &c., a solution in water is 
effected, which is pumped up from the mine as a concentrated brine. In many 
instances rock-salt is wrought in extensive and deep mines, as in the celebrated rock- 
salt mines of Wieliczka. 

vodtoiwcddiigsidt-ipdiigs. Natural salt-springs sometimes occur which have been 
imitated artificiaUy by boring to a great depth into layers of earth containing saline 
deposits. In this manner a brine may be obtained sufficiently concentrated to 
be at once boiled down. The method of working the natural salt-springs is to form 
a convenient reservoir from which the saline solution is immediately pumped up for 
the purpose of being gradated (see p. 168). The solution previous to being boiled 
down is left to allow the suspended matter to settle. The salt-springs obtained 
by boring either yield a native brine, or the borings are carried into solid rock-salt 
and water caused to descend into the salt deposit. This artificial brine is then pumped 
up, unless there is naturally an artesian formation. The brine previous to further 
operations is left for some time in reservoirs to deposit suspended insoluble matter. 

These saline solutions are not always free from impurities ; in considering their admixture 
brine may be divided into two classes ; the first containing sulphate of magnesia or soda, 
with chloride of magnesium ; the other class embraces brine containing the chlorides 
of calcium and magnesium. If the brine happens to pass through peaty soil or layers of 
hgnile, there often accrues organic matter^ humic, crenic, and apocrenic acids. 



i68 CHEMICAL TECHNOLOGY. 

^^Sifrm '^Kf**"" ^''^ operation is duplex and consists in — 

a. Concentrating the brine. 

a. By increasing the quantity of salt. 
p. By decreasing the quantity of water. 

b. The boiling down of the concentrated brine. 

ooaeoitimting the Brine. Native brines or salt-springs seldom contain enough common 
salt to make it profitable to boil them down at once ; it is consequentiy necessary to 
enrich the brine, and this may be done either (a) by dissolving in it rock-salt 
or crude sea-salt, neither being suited for culinary and many other purposes unless 
refined, or (/3) by decreasing the quantity of water without the use of fuel 

Eazioiiiiig by onMUtion. The enriching or concentration of a brine by decreasing the 
quantity of water it contains is called a gradation process, and may be proceeded 
with by freezing off the water in winter time, or more generally by evaporating the 
water by a true gradation process ; either — a. Gradation by the effect of the sun's 
rays. b. Table gradation, o. Roof gradation, d. Drop gradation. 

Gradation by means of the sun's rays is obviously the same method of procedure as 
that described under the treatment of sea-salt. Table gradation has been only experi- 
mentally tried at Beichenhall, and consists simply in causing the brine to flow slowly 
from a reservoir down a series of steps, constructed so as to give as much suriace as pos- 
sible, and thus hasten the evaporation. Boof gradation is effected by utilising the roofs 
of the large timks containing the brine as evaporation surfaces, by causing the contents of 
the tanks to flow in a thin but constant stream over the roofs, which, of course, are 
exposed to the open air. 

vegsotamdAtioa. This operation, also known as drop gradation, is carried on by 
means of the following apparatus, termed gradation house, and consisting of a frame- 
work of timber, fitted with faggots of the wood of Prunta tpinoiay which being 
thorny, presents a large surface. The entire construction is built over a water-tight 
wQoden tank, which receives the concentrated brine, and frequentiy the top of 
the gradation house is provided with a roof. Under the roof and above the faggots 
a water-tight tank is placed containing the brine to be gradated; this tank is 
provided with a number of taps, from which the brine trickles into channels provided 
with holes to admit of the brine fisdling on the faggots. These taps are placed 
on both sides of the gradation house, and are generally connected with levers to 
admit of being readily turned on and off from below. The gradation process is con- 
tinued until the brine is sufficiently concentrated to admit of being further evai>o- 
rated by the aid of fuel ; the brine may be gradated to contain 26 per cent of salt, 
but the operation is rarely carried so far. 

The gradation process not only serves the purpose of concentration, but also that 
of purifying the brine, as some of the foreign salts are deposited on the &ggots, this 
deposit of course varying in composition according to the constituents of the brine, 
but chiefly consisting of carbonate of lime, with the sulphates of potassa, soda, and 
magnesia. The deposit has in some instances been used as manure. In the tanks 
where the gradated brine is collected another slimy deposit is gradually formed, con- 
sisting of gypsum and hydrated oxide of iron. As in the present day the brine 
obtained from bored wells is generally sufficiently concentrated to be at once boiled 
down, gradation is less frequent, being a very slow process and involving a loss of 
the salt carried off by the wind. 

Boiling down the Brine. The object is to obtain witii the least possible expenditure of 
fuel the largest quantity of pure dry salt. Formerly the evaporation was carried on 



COMMON SALT. 169 

in large cauldrons, but at the present time evaporating vessels are constmcted of 
well rivetted boiler-plate, the shape being rectangular, the length 10 metres, depth 
0*6 metre, and width from 4 to 6 metres. These pans] are supported by masonry, 
which also serves to separate the flues. Over the pans a hood is fixed and con- 
nected with a tube carried to the outside of the building to afford egress to the 
steaoL The brine, concentrated to contain from 18 to 26 per cent of salt, is poured 
into the pans to a depth of 0*3 metre. 

The boiling down process is in many salt works conducted in two different opera- 
tioDs: — 

a. The evaporation of water to produce a brine saturated at the boiling-point. 

b. The boiling down of the saturated brine untU the salt crystallises out. 

The boiling down is generally carried on for several weeks, the scum being 
removed, and also the gypsum and sulphate of soda deposited at the bottom of the 
pan, with perforated ladles. As soon as a crust of salt is formed on the surface of 
the liquid, a temperature of 50" is maintained. At this stage the salt is gradually 
deposited at the bottom of the pan in small crystals, and being removed, is put into 
conical willow baskets, which are hung on a wooden support over the pan to admit of 
the mother-liquor being returned to it. Finally, the salt is dried and packed in casks. 

The quantity of mother-liquor collected after boiling for some two or three weeks is, 
compared with the quantity of brine evaporated, very small ; it was formerly thrown away 
or used for baths, but is now employed for the preparation of chloride of potassium, the 
nlpbates of soda and magnesia, artificial bitter water, and in some instances for pre- 
pazing bromine. It is evident that by the boiling down all the salt contained in the brine 
is not reduced as dry refined salt, a portion being retained among the early deposit formed 
at the bottom of the pan, another portion remaining in the mother-liquor, and finally 
some loss accmes from the nature of the operations, amounting generally from 4 to 9*25 
per cent. As in some countries salt is an article upon which an excise duty is levied, in 
order that it may be employed duty free for certain industri^ purposes, it is mixed in 
Tuioufl proportions with substances rendering it unfit for culinary use. 

rnpotiM^^oommon Chloride of sodium crystallises in cubes, the size of the crystals 
determining the varieties known in the trade as coarse, medium, and fine grained 
salt, and depending upon the rate of evaporation of the brine, a slow evaporation 
producing very coarse salt. Perfectly pure common salt is not hygroscopic, but the 
ordinary salt of conmierce contains small quantities of the chloride of magnesium 
and sodium. Usually salt contains from 25 to 5 '5 per cent water, not as a constituent, 
but as an intermixture; hence the phenomenon called decrepitation, due to the 
breaking up of the crystals by the action of the steam when salt is heated. Ignited 
to a strong red heat chloride of sodium fuses, forming an oily liquid, and at 
a strong white heat is volatilised without decomposition. Common salt is readily 
soluble in water, and is one of the few.salts almost equally soluble in cold and in hot 
water; 100 parts of water at 12^ dissolve 35*91 parts of common salt. 

In order to express the quantity of salt contained in a brine, it is usual to say the 
brine is of a particular fineness, strength, or percentage ; for instance, a brine at 
15 per cent contains in 100 parts by weight 15 parts of salt and 85 parts of water. 
The QrSdigheit or degree 9f a brine means the quantity of water which holds in solution 
I part by weight of salt ; a brine of 15*6 Grddigheit contains, therefore, i part by 
weight of conmion salt in 156 parts of water. The poundage (PJUndigkeit) of a 
brine indicates in pounds the quantity of salt 'contained in a cubic foot of brine. 
The following table shows the percentage of salt contained in brines of the several 
specific gravities: — 



lyo 



CHEMICAL TECHNOLOGY, 



Salt per oent. 


Sp.gr. 


Salt per cent. 


Sp. gr. 


Salt per oent. 


Sp.gr, 


I 


10075 


7*5 


10565 


16 


I'I206 


1*5 


10113 


8 


I 0603 


17 


I 1282 


2 


10151 


8-5 


I 0641 


18 


I 1357 


2'5 


1-0188 


9 


10679 


19 


11433 


3 


ro2z6 


9*5 


I "0716 


195 


11510 


35 


10264 


10 


10754 


20 


11593 


4 


1030a 


10*5 


I 0792 


21 


11675 


45 


10339 


II 


I 0829 


22 


11758 


5 


10377 


"•5 


10867 


23 


1*1840 


55 


10415 


12 


10905 


24 


1*1922 


6 


10452 


13 


10980 


25 


12009 


6-5 


1*0490 


14 


1*1055 


2639 


12043 


7 


10526 


15 


11131 







t7M8of Common ^* ^® ^^^ neoessary to enter into particulars on this subject. Salt is used 
Bait. as a necessary condiment to food ; a man weighing 75 kilos, contains in his 
body 0*5 kilo, of common salt, and requires annually 775 kilos, to maintain this supply. 
Common salt is used in agriculture, and is as necessai^ for cattle and horses as for man. 
It serves industrially in the preparation of soda, chlorine, sal-ammoniac, in tanning, 
in many metallurgical processes, the manufacture of aluminium and sodium. Further, 
it is employed in the glazing of the coarser kinds of pottery and earthenware, from the 
fact that when common salt is fused with a clay containing iron, the sodium is oxidised 
at the expense of the iron, and forms soda, which, combining with the alumina and silica, 
supplies a glaze, while the iron combining with the chlorine is volatilised. The uses of 
common salt for the preservation of wood, for curing meat, preserving butter, cheese, Ac, 
are too well known to require explanation. Among the salt-producing countries of 
Europe, England takes the lead, producing annually 32,400,000 cwts., while Germany 
only produces 10, and Russia 20 million cwts. 

Manufactube of Soda. 

(Soda or Sodium carbonate, Na2C03=io6. In 100 parts, 58*5 parts soda and 

41 '5 parts carbonic acid.) 

BodA. All the soda commonly used is derived from the three undermentioned 

sources : — 

a. Natural or native soda; 

p. From plants ; 

y. Chemical production. 

a. Native Soda, 
o«iu«n«Mjf NatiT. Soda is found in many mineral waters, as at Kaxlsbad, where the 
waters yield annually 133)700 cwts. of carbonate of soda, and at Burtscheid, Aix*la- 
Chapelle, Vichy, and the Geyser, in Iceland. Soda occurs as an efflorescence on 
some kinds of rocks, chiefly of volcanic origin, as trass and gneiss. Sesquicarbonate 
of soda, C308Na4-|-3H20, is met with in large quantities in the water of the so-called 
soda lakes of Egypt, Central AMca, the borders of the Caspian Sea and Black Sea, 
in California, Mexico, and elsewhere. During the hot suipmer season a portion of 
the level country of Hungary is covered with an efflorescence of carbonate of soda, 
locally known as Szikso, which is collected and brought to market. The Egyptian 
name for soda is Tro-Na, hence the Germsm term Natron. The soda locally known 
in Columbia as Urao is obtained from a lake, La Lagunilla, distant 48 miles from 
the town of Merida. During the hot season the urao crystallises from the water, 



• SODA. ryr 

and is gathered from the bottom of the lake at a depth of 3 metres by divers, with 
great risk of their lives ; the annual quantity collected amounts to 1600 cwts. When 
he Spaniards were in possession of this territory the urao was a government 
monoply, and was brought to Venezuela for the preparation of Mo or inspissated, 
tobacco juice. Very recently an inexhaustible supply of native soda has been found 
in Virginia.* 

Various theories have been proposed to explain the origin of native soda, but here 
ts in other instances it is best to bear in mind that a posse ad esse nan valet eonclusio. 
Native soda is rarely exported from the countries where it is found and collected) 
excepting the Eg3rptian Tro-Na, which is brought to Venetia for glass mnlHTig 
purposes and met with in the trade in the shape of bricks made up with sand. 

p. Soda from Plants, or Soda-ash. 

"^JldSpm'SJet w^ When treating in a former chapter of potassa we saw that the 
ash of plants, especially of those grown at a considerable distance from the sea, 
contains carbonate of potassa; likewise that plants grown near the sea-shore and in 
the localities known as salt steppes yield an ash which contains more or less soda 
in the living plant combined with sulphuric and organic acids, and which imder the 
influence of the carbonate of lime is during the tgnition of the plant converted into 
carbonate of soda. In addition to the species of Fitcus growing in the sea itself, 
the genera known as Salsola, Atriplex, Salicortiiay &c., are employed for the 
preparation of soda, and until lately were largely cultivated for this purpose. The 
process of obtaining soda from these plants simply consists in burning them in pits 
dug in the sand near the sea-shore, the heat of the combustion becoming so intense 
as to cause the ash to flux, so that after cooling the material forms a hard slag-Hke 
niass, termed in the trade crude soda or soda-ash, the quantity of carbonate of soda 
it contains varying from 3 to 36 per cent. This new material is refined by exhausting 
with water, and evaporating the liquor. From the diflerent plants and modes of 
preparation employed we obtain the following distinctions in kind: — 

a. Barilla, from Alicante, Malaga, Garthagena, the Canary Islands, and the Barilla 
soda {SaUola soda) produced on the Spanish coast ; contains on an average from 25 to 30 
per cent of carbonate of soda. 

b. Salicor, or soda from Narbonne, obtained by the ignition of the Salieomia anniui, 
planted purposely, and gathered when the seed is ripe ; contains about 14 parts of carbonate 
of soda. 

c. Blanquette, or soda from Aignes-Mortes, prepared from the plants growing wild on 
the tract of comparatively barren land lying between Aigues-Mortes and Frontignan, viz., 
the Salieomia Europeay SaUola tragus, Salsola kali. Statics limonium, AtripUx por- 
tttlaeoides. This soda only contains from 3 to 8 per cent of sodic carbonate. 

d. Araxes soda, of about the same value as the preceding, is largely used in Southern 
Bxisaia, and is obtained from plants of the mountain plateau of the Araxes in Armenia, 
where the soda is prepared. 

e. Of less value even than the preceding is the Varec soda, obtained on the coasts of 
Kormandy and Brittany from the go^non, Fitcus vesiculosus.' 

/. Kelp is obtained in Scotland and the Orkneys by the combustion of various sea- weeds, 
the Fucus serraius, F. nodosus, Laminaria digitata, and Zostera marina. Notwithstanding 
that 480 cwts. of dried plants only yield 20 owts. of kelp, containing no more than from 
50 to 100 lbs. of Bodio carbonate, 20,000 people are occupied in the Orkneys alone in the 
preparation of kelp. 

g. Among the varieties of soda derived from plants may be mentioned that obtained 
in considerable quantity from the vinasse of beet-root, but this soda, according to 
^sandier's analysis, always contains carbonate of potassa. 

■ 
• See ♦• Chemical News," vol. xri., p. 129. 



1731 CHEMICAL TECHNOLOGY. 

y. Soda prepared by Chemical Processes. 

^'^^^iSS^^ M. Leblanc, the inventor of the successful method of conyerting 
common salt into carbonate of soda, may indeed be considered as an immediate 
benefactor to his countrymen, who, until the latter half of the last century, annually 
paid 20 to 30 millions of &ancs to Spain for barilla. The war which broke out in 
1792 terminated the importation of soda, potash, and saltpetre into France, and 
hence the Oomit6 du Salut Public decreed in 1793, amongst other measures, that 
all soda manufacturers should give the fullest particulars of their mode of working, 
and the processes they imagined might be used on the large scale to obtain soda 
equally good and cheap as that from barilla without the use of that or any similar 
material. The manufacturer Leblanc was the first who sent in full particulars on 
this subject, and his process was declared by the committee to be the best and most 
suitable, the verdict standing unshaken to the present day, which witnesses the 
improvement of the recovery of the sulphur from the soda waste. 

LebiMM'i Proeeu. This now cousists in the following stages : — 

a. The preparation of sulphate of soda from salt by the aid either of sulphuric 

acid or sulphates, or by the roasting of common salt with iron pyrites or 
other native metallic sulphurets. 

b. Conversion of the sulphate iiito crude soda by roasting with a mixture of 

chalk and small coal. 

o. Conversion of the crude soda into refined soda or caustic soda by lixiviation 
and evaporation. 

d. Becoveiy of the sulphur from the soda waste. 
Deeo^^^uxwee. ^' ^® ^^^ usual mode of converting common salt into sul- 
phate of soda is by the action of sulphuric acid. The condensation of the hydro- 
chloric acid gas is generally effected by a method introduced in 1836 by Mr. Gossage, 
and consisting in tiie use of a contrivance known as coke- or condensing-towers. 
These are square buildings from 12 to 14 metres in height, by an interior width of 
1*3 to 1*6 metres, constructed of stone not acted upon by hydrochloric acid, the 
joints being cemented with a mortar made of coal-tar and fire-clay. To nearly the 
top these buildings are divided by a wall, each compartment thus formed being 
fiUed with pieces of coke resting on a perforated stone floor. Water is caused to 
flow constantiy from the top of the tower on to the coke. The hydrochloric acid gas 
resulting from the decomposition of the salt by sulphuric acid is conducted by means 
of stoneware tubes to the bottom of the first compartment of the condensing-tower, 
and there meeting with the moist coke is condensed to within 95 per cent of the 
entire quantity, the other compartment of the condensing-tower being usually in 
direct connection with the chimney -shaft of the alkali- works. The decomposition- 
fumaces at first in use were reverberatoiy furnaces so constructed that the smoke 
and gases from the combustion of the coals and the hydrochloric acid gas passed off 
together, and as a consequence the hot gases were not in the best condition 
for condensation. The furnace now in general use is that invented in 1836 by 
Gossage, and improved in 1839 by Gamble, who was the first to arrange the two 
phases or stadia of the decomposition in the separate compartments, o and k, of the 
furnace exhibited in Fig. 71. This arrangement has been used for a very long 
period, the alkali manufacturers employing a reverberatoiy furnace which could be 
put into communication at pleasure with a kind of muffle, the bottom consisting of a 
stout cast-iron plate, the flame from the furnace -grate being made to play against 



SODA. 



>73 



Ihis mnffle previously to entering the chimney. The mufQe commtmlcated with a 
(xodeiuiiig appaiSitDB, h h'. According to this plan of worldiig, &e common salt 
WW pUeed in o, and well warmed eulphuric acid made to flow over it ; a very strong 
and violent reaction took place, and half or nearly two-thirds of the hydrochloric 
acid formed was readily condensed, as it was not mixed with the hot gases of the 
combnalion. The prodnct resulting from thia mode of operation was a mixture of 
Wsiilphate of Boda and common salt, zNaCl+HiS0i=NaH80(+Naa+HCl. 
This mixture was nest shovelled into the reverheratory furnace, B, the moffle being 
»guD charged with salt and acid. By the intense heat of the reverberalory fnmace 
the mixture of hisnlphate of soda sjid common salt was converted into neutral 
sulphate, NaHS04+NaCl=Na,S04+HCl; the hydrochloric acid gas evolved in 
this operation was, however, condensed with difficulty, in conaeqnence of being 
mixed with nitrogen, carbonic acid, and carbonic oxide ; and besides the condensing- 

Fio. 71. 




towers other and complicated apparatus were required to prevent the escape of acid 
fnmes into the air. These defects have been remedied in the constrootion of an 
improved decompodtion-famace. 

Rnimnipniiini.raiua. This fomaee consists of two muffles, one of oast-iron, the 
Other of fire-bricks; the interior of the former is a segment of a hollow sphere of 
g feet or 274 metres diameter, and i foot g inches or 0*52 metre deep, resting on 
brick-work. A cast-iron lid is provided, in shape also a segment of a sphere, having 
a depth in the centre of i foot or 030 metre ; in this Lid are arranged two openings 
with suitable doors, through one of which the common salt is introduced, while the 
other communicaleB with the second mnfSe. The hearth is placed obliquely, the 
flames first playing on the lid, and then passing under the muffle ; accordingly the 
hjdrochlorio acid gas is niunixed with other gases, and its temperature being com- 
paiatiTely low, condensation is more readily efiected. The second or brickwork muffle 
CDcloaee a space of 30 feet or 9*14 metres inlength, by 9 feet or 274 metres in width; 
under the floor of this room a series of flues or channels ore built, while (he top is 
formed of a double vault to admit the circulation of the flames, which are next con- 

dncted through the channela under the floor. 



174 



CHEMICAL TECH}10L0GY. 



The mode of operation is as follova : — Into tlie iron mufSe, prerionaly well heated. 
half a ton of conunou salt is introduced, b> which isadded sulphnric acid of 17 sp.gr.. 
the qnantdty of the aeid being regulated so as to leave i to 3 per cent of salt imde- 
coniposed in order to obtain a perfectly neutral aulphato. lOo parte of salt reqoire 
for their complete decomposition 1)5 parts of an acid at 60° B. = 17 sp. gr., or 
104 parts of an acid at 55° B. = 1 '6z ep. gr. The mixture of acid and salt is occasion- 
ally well stirred, and after the lapae of i| hours has become sufficiently dry to be 
raked over into the brick-work compartment of the oven, which is kept at a bright 
red heat to assiBt the expulsion of the hydrochloric acid gas. If it is desired to 
obtain a concentrated hydrochloric acid solution, the escaping gas must be cooled 
down before entering the condensing- towers. There is generally a valve or damper, 
by which the communication between the two mufSes may be closed, in order that 
the hydrochloric acid gaa evolved in each may be separately collected and condensed. 
With these contrivances, and well constructed condensers supplied plentifully with 
water, the preparation of sulphate of soda may be carried on without any inconveul- 
enoo to the neighbourhood in wiiich the works are situated. For more than twenty 
years Messrs, Tennant, of Glasgow, have employed this iiind of fumaee,- decomposing 
500 tons of common salt per week without receiving any complaints. On the Conti- 
nent, alkah works are legnHy compelled to have the decomposition-furnaces con- 
stmoted according to a plan first brought out in Belgium, and which is very similar 
to the furnace already described. The assertion of Dr. Wagner, in his original text, 
concerning the many complaints now arising in England in reference to .the escape 
of hydrochloric acid fumes firom alkali-works, is altogether unfoonded, the fact being 
that according to the published reports of the Inspector, Dr. Angus Smith, under the 
Alkah Act, nearly all the manniacturers condense, instead of 95 per cent of the 
hydrochloric acid, as required by the Act, from 97 to 9S-5 per cent. 

""'"^ilaiSsSi?'"'* *■ ^ order to convert the sulphate of soda into crude or 
raw Bodic carbonate, the former salt is mixed with chalk, or sometimes with 
slaked lime and small coal, and this mixture, fused in a reverberatory furnace. 
According to Leblanc'a directions, the proportions are — 

Sulphate loo parts 

Cliatk 100 „ 

Slaked lime 50 „ 

fant the quantities as employed in ten diHerent works vary for 100 parts of sulphate 
firom go to 121 parts of clulk, and the quantity of small coal from 40 to 75 parts. 




In some alkali-works for a portion of the chalk is substituted the desulphnrised and 
lixiviated soda waste. The reverberatory furnace generally used in English alkali- 
works, and technically known as a h/tlUiig /i/i-iiner, is sliowu in J'ig. 72, and that 



tmplojed in Germany in Fig. 73. In England, the materiola having been first 
lieated on the npper stage of the furnace by the waste heat, only remain in ths 
tcorkitig furnace (see Fig. ^z) for about half-an-hour ; in Oennan works the mixture 
of sulphate, chalk, and small coal is strongly heated in h, see Fig. 73. nntil the ma«s 
becomes fluxed and paety, and lambent flames of burning carbonic oxide are ejected 
from the Btirface. When this is seen the semi-Snid mass is removed from the 
ftmiace throngh the openings p p. and transferred to an iron car, c, -where it is left 

It is difficult to say whether the English or Continental method is the more 
preferable ; viewed from a theoretical point of view, it would appear that the English 
method is the better of the two. As in English works, a smaller quantity of 




instenals, only about 7 cwts., while in coulinenlal works firom 30 to 70 cwta., is 
operated npoa at a time, the labour is lighter ; the materials, too. are not exposed to 
u intense heat for a long period ; thus a loss of soda by the volalilisation of the 
todinm is less likely to occur. According to Wright's investigations (18G7), the loss 
of soda by the conversion of the sulphate amounts to 20 per cent of the sodium con- 
liined in the sulphate, as shown by the following figures : — 

Undecomposed 3nlphat« 

Insoluble sodium compounds 

Volatilisation of the sodium , 

Sodium retained in the waste 

Loss occasioned hy the evaporation of the liquors 



.-. 349 



361 
656 



*imh^^Jr£ ^ 'S53 Elliot and Russell suggested a contrivance which dis- 
pensed with the gtirring of the materials by manual labour, and consisted of a cyUn- 
drical T«0sel made to rotate on a horizontal axis. Stevenson and Williamson im- 
proved apon this idea, and according to their plan of working (see Fig. 74) the 
Enixture of sulphate, chalk, and small coal is placed in the iron cylinder, a, lined 
with fire-clay. Ribs or rails, e, cast on the cylinder, nm on the wheels, c, receiving 
notion from machinery with wliich they gear, and causing the cylinder to rotate. 
The heated air of the hearth, n, flaws through the opening r into the cylinder, and 
passing through f. reaches the vaulted compartment, o, and is carried ofi' by the flue, 
X. to the chimney. The interior of the cylinder having been heated to redness, the 
"Mteriols are allowed to fall into it from the waggon, j, through the funnel H. 
After the lapse of ten minutes the cylinder is caused tomeke a half revolution. and is then 
left (or five minutes, the operation being coiitinned until the masii inside the cylinder 



176 CHEMICAL TECEHOLOQY. 

ioMSi, which takes pUce in about half -an -hoar. The cylinder is then set contina- 
ouBly in motion so as to make one revolution eveiy three minutes. The progress 
from time to time is watched through a door-way constructed in the cylinder, and 
Ks soon as the operation is complete the molten mass is run off through the opening b'. 
There can he no doubt tliat the rotat«ry furnace is a great improvement, and one 
which, besides saving labour, prevents a loss of soda by volatilisation. A cylinder 
II feet long and 75 feet in diameter converts in two hours 14 cwts. or yew kilos, of 
sulphate at an expenditure of only as. id. 



Fio. 74. 




The composition of the omde or hall soda is approiimatsly :— 
Carbonate of soda . . 
Solphnret of ealeinm 
Caustic lime 
Carbonate of lime 
Foiei^ Bubstanses . . 



[1 glass making, soap botUug. 



In thig oonntty large quantities ol soda-ash ate used i 
bleaching, and other operations. 

''''cmfcBn^*' "■ Conversion of crude into refined soda by lixiviation and 
evaporation, a. Lixiviation of the crude soda. When the cmde soda is acted upon 
by water there results a solution containing chiefly carbonate of soda, and a mass 
remaining osdissolved known as soda waste. 100 parts of raw soda yield : — 

Soluble matter 45-0 parts 

Soda waste 587 „ 

1037 .. 

As a mle English ball soda has a deeper colour, and contains more carbon t)uu> 
the soda of continental manufacture. Ball soda, previously to being lixiviated, is 
usually exposed for at least two and sometimes for ton days to the action of the air, lo 
gain in porosity, and hence be more readily acted upon by the water. 

Of the several methods of lixiviation proposed, and in more or less suooessfol dm 
on the large scale, may be mentioned the following : — The method of lixiviation by 
simple filtration is not to be recommended on account of the great labour it requires, 
but the process consists in putting the crude soda, previously broken np into lumps 
of suitable size, into tanks provided with a perforated fidse bottom, upon which the 




cnide gods is placed, water being poured on. This urongemetit ia represented in 

Kg. 75, A. B, c. D- The perforated false bottom is about 25 centdma. from the bottom 

of the tanks. The wooden channel, k, suspended from the ceilmg of the shed bj 

Ok iron bonds, t f', eonvejs water, 

vhiclib; means of the pli^, {. t', and 

1", can be let into the tanks, these 

being proTided with taps, r, r', and 

/', by which the liquid can be nm off 

into the channel, E*. To illustrate the 

mdui operandi three tanks, *, a, c, 

ire sofficieDt : A is filled with fresh 

ball Boda, B with ball soda once, 

and c with ball soda twice lixiviated. 

We then begin by filling each tank 

with the liquor which has been used 

for washing the soda waste the last 

time before throwing it aside ; this Uqnid remains in each tank for a period of eight 

hnnTB, and the alkaline ley, which then marks 30° B.. is run oS from a, and the 

operation repeated with weaker liquors in b and c, the leys bemg all conveyed to a 

Wge reservoir, the contents of which mark 35° B. Fresh liquor is poured mto a 

and B, and into d, which is filled with bail soda, B7 this arrangement a constant 

supply of ley at 25° B. is kept up. 

Desormes's lixiviatiun apparatus. Fig. 76, consists of a series of twelve to fourteen 
tanks, of which only live, a, b, c, d. e. are exhibited in the woodcut. By means of 
the bent tubes, fitted about 15 ccntima. from the bottom of each tank, the liquor 
flows into the next lower tank of the series, and so to the tanks, r f', called the 
clearing or settling tanks, of which there are sis connected together by tubes. The 
btll soda to be lixiviated ia ground to powder, and placed in the perforated sheet- 
iton vessels, e e. d d, and so on. d t the commencement the tanks are filled with 

Fio. 76. 




warm water, and two perforated vessels placed in e filled with 50 kilos, of ball soda ; 
after twentj-five minutes these vessels are removed to d, and oUiers filled with fresh 
soda placed in E. In this manner the operation proceeds, so that after eight hours, 
when fourteen lixiviation tanks are worked, there are fotmd in a perforated vessels 
which have been gradually removed from the lowest to the highest tank, a, two 



•78 



CHEMICAL TBCnSOLOOT. 



vessels. //, having been removed firam that tenli and placed apon die shelf, k, \f> 
drain, where having remained for about half-an-honr the^ are removed, the contents 
emptied, and other veasela placed to drain. Each time that two of the perforated. 
vessels filled with ball Boda are placed in the lowest tank, there is ponied into ths 
uppermost as much water as correspanda with the bnik of the fresh soda ; this water 
displaces the heavy \ej which runs through the tube from a to B, and so on, tmtil ait 
last the concentrated and nearlj saturated liquor runs from B iuto f f, where any 
suspended matter is deposited. The temperature of the liquor in these tanks shonld. 
be from 45° to 50°; but not h^her, in order to prevent anjr dectnnpoBition of the 
sulphide of calcium. The liziviatiou tanks, as well as the clearing tanks, are 
provided with steam pipes for the purpose of keeping the liquor sufficiently heated, 
and to prevent any soda ciTstallising ont by cooling. It is almost evident that this 
method of Uxiviation is the best which can be adopted, as the concenbated liqnor 
cannot adhere to the solid substance which it is intended to dissolve, because in 
consequence of its high sp. gr. the liquor sinks to the bottom of the tank. Fig. 77 
represents two liziviation tanks drawn ta a larger scale, and of a somewhat diSerent 
arrangement. Es«h tank is divided into three compartments by means of a doable 
partition wall, commnnit^tion between the two compartmenta being provided by tba 

Fio. 77. 



M33f 



V^. i^lifl 



holes a and b and the space between the partition plates reoeiving the steam pipes, 
hh. g g are the tubes for conveying the liquor, and n n the perforated vessels, to 
which are rivetted iron bars serving the pnrpose of handles. Mr, James Shanks, of 
St. Helen's, was the first to found a rational and economical plan of lixiviation, on 
what is termed methodical filtration, based upon the fact that a solution becomes more 
dense the more saline matter it has in solution, and that a colnmn of weak ley of a 
oertain height equilibrates a shorter column of a stronger ley. In accordance with 
this principle, the tanks, four or eight in number, are placed as shown in Fig. 78, 
and through them water is caused to flow, exhausting the crude soda in its passage, 
and becoming consequently denser in each consecutive tank of the series ; hence, 
the level of the Uqnid is lowered in each tank from the first, which contains pure 
water, to the last, from which a saturated ley runs off. The length of the <*iifc» is 
2*6 metres \ij 2 metres in depth ; p is a perforated false sheet-iron bottom Bapp<»ted 
by iron bars. From the bottom of each tank an open tube, t, the lower opening 
being cnt diagonally, and at the top a smaller tube, I, soldered on, connect the tanks. 
The water pipes, r r r r, fitted with taps are placed to admit of water being 
supplied to each tank ; by means of the taps, r b', the ley can he run ofiT into tba 
f. Four lixiviations as a mle suffice. The working is as fbllowa :— The 



fint tank contains boll sods already three times lixiviated; the liquor added to it is a 
verj weak soda solation from a former operation, which percolates into the second tank. 
The liquid there meeta with soda which lias been twice submitted to the lixiviation 
process, and nest flows over into the third tank, the solid contents of which have 
been only once preidously lixiviati>d. Finally, the lye arrivee in the foorth took, in 



Fio. 78. 



I I I 




*hich fresh ball soda has been placed, and &om this tank flows into a large re 
The first tank having been cleared of soda waste is now filled with fresh hall soda, 
Mid the succession of the operation reversed by the aid of taps fitted to the tnbes 
connecting the tanks. The larger the nnmber of tanks the more rapidly within 
certain limits a given weight of erode soda can be exhausted. The density of the 
ley ought to be from i'27 to i'z86, a cubic foot, or O'OzS cubic metre, containing 
from 4*5 to 495 kilos, of solid matter. The advantages of this mode of lixiviation 
ore — I. That the carriage of the crude soda from one tank to another i& dispensed 
with, and consequently much labour saved. 3. The soda being always covered with 
liquid cannot cake, 3. As the current is always downwards the most concentrated 
{■ortion of the flnid is conveyed forward, and consequently less water is required. 

4. By the continuity of the operation any reaction between the alkali and the 
insoInUe calcium snlphuret is prevented, or, in other words, the formation of soluble 
alksline and other snlphurels, entailing a loss of soda, is reduced to a minimnm. 

5. The high degree of concentration of the ley effects a considerable saving in the 
expenae of the evaporation. 

The nature of the ley, after the suBpended matter has been deposited, greatly 
depends npon the condition of the ball soda employed, the duration of the process, 
■ndthe temperature of the water; it is, therefore, difficult to make any general 
diservation. Kynaston, Schenrer-Kestner, and Kolh have proved that ball Boda 
dace not contain caustic soda, and that consequently the presence of this substance 
in the ley ie due to the action under water of the lime upon the sodic carbonate. 
Solpliuret of calcium can only be present in the dry hall soda in Tery small quantities, 
bit Bulphnret of sodium may exist in the ley to a greater extent than caustic soda, 
the quantity varying with the mode of lixiviation. Conunonly, only monosolphuret 
of sodium is present in the ley ; even if a polysulphuret were temporarily formed it 
WDold be immediately converted into monosulphuret by the presence of the caustic 
tods. The dry ball soda contains peroxide of iron, converted into sulphnret of iron 
V the action of the water ; this snlphuret dissolving in the sulphuret of sodiom 
cuses the greeu- or yellow-brown colour of the ley. The quantity of water employed 



i8o CHEMIGAL TEGHNOLOOY. 

in the lixiviation has no effect upon the causticity of the ley, but the qnantity 
of sulphuret of sodium increases with the quantity of water, the duratioQ of 
the lixiviation, the temperature, and the concentration; this is owing to the 
increased solubility of the sulphuret of calcium, which, when in contact with water, 
is converted into hydrosulphuret of calcium and hydrate of lime, the former yielding 
with caustic soda the more sulphuret of sodium the higher the concentration of the 
ley. The same reasoning holds good for carbonate of soda, which is also converted 
into sulphuret, but only in veiy dilute solutions, at a higher temperature after a 
lengthened contact. 

According to Eolb's researches, ball soda should be lixiviated rapidly, with but a 
small quantity of water, and at a low temperature. If it were possible it would be 
a great improvement to contrive an apparatus in which ball soda could be lixiviated 
in a few hours with only so much cold water as would yield a very concentrated ley ; 
the liquors obtained under such conditions would be free from sulphuret of sodium. 

The following analysis will give some idea of the composition of the crude ley. 

The sample was obtained from the alkali- works of Matthes and Weber, at Duisburg, 

the sp. gr. = 1*25, i litre containing 3139 grms. of solid saline matter, consisting in 

100 parts of — 

Carbonate of soda 71250 

Caustic soda 24*500 

Common salt 1*850 

Sulphite of soda 0*102 

Hyposulphite of soda 0369 

Sulphuret of sodium 0235 

Cyanide of sodium 0087 

ArgiQaceous earthy matter' 1*510 

OlxlOof «•« ••• •«• ••• ••• ••• ••• UX 00 

«LrCJU ••• ■•• ••• ■•• •«• ••• •■• «•• liXc&C*wD 



100*089 
Another crude ley from some works near Aix-la-Chapelle was of a sp.gr. = 1252, 
and contained 311 grms. of solid matter per litre. 

STtpontion of om Ley. /3. The clarified liquor contains essentially carbonate of soda 
and caustic soda, with common salt and other soda salts in smaller quantities. Owing 
to the presence of the double sulphuret of iron and sodium, the ley is coloured 
during the evaporation, if it be performed with the liquor immediately from the 
lixiviation tanks ; to prevent this result it is necessary that the leys should stand for 
a considerable tiii^e in the clearing reservoirs to effect a slow oxidation of the com- 
pound salt, more rapidly attained by forcing a current of air through the ley, as 
suggested by Oossage. Bleaching-powder and nitrate of soda are used as oxidising 
agents ; a lead-salt, oxide of copper, and spathose iron ore have been employed. As 
Kolb*8 researches have proved that monosulphuret of iron is insoluble in caustic and 
in carbonate of soda solutions, an addition of sulphate of iron will have the effect of 
converting the double sulphuret of iron and sodium into monosulphuret of iron and 
sulphate of soda, the former salt settling rapidly and yielding a clear coloarless 
liquid, and on evaporation a colourless salt. 

The ley is treated in either of the two following ways : — 

a. Evaporated to dr3Tie8s, tiie result being a homogeneous product which contains 
unaltered all the constituents of the ley, including the caustic soda. 



p. The ley is evaporated to a certain degree of concentration, the aapersatiirated 
solntion dcpoaiting on cooling carhonate of soda aa a crystalline powder, containing 
imolecnle of water, Na^COj+HjO; the salt is gradnally removed from the liquor 
by perforated ladles. During the evaporation fresh ley is nm into the pan from, a 
regervoir at a higher level, and in this way the operation is continued for Beveral 
aonthB. It is clear tbat by conducting the evaporation in this manner, the carbonate 
of Boda collected becomes gradually less and less pure, being mixed with chloride of 
Bodinm and solphate of soda ; at last a mother-ley is left, containing chiefly caustic 
uda uid solphnret of sodium, and in a concentrated solntiaD of these substances the 
other salts are insoluble. The crystalline carbonate of soda is first drained, anopera- 
tioii sometimes performed in centrifugal turbines, and then calcined in a reverbera- 
tory fomace to oxidise any snlphuret of sodium that might be present ; after this 
caldnstion the salt constitutes the calcined soda of conunerce. The quality of the 
(omiDertial article varies consideiablj, the difference being partly due to the care 
taken in the evaporation. The first crop of salt is always the best, that is to say, 
contains the largest percent^e of sodic carbonate, somelintes amounting to 90 per 




cent When the ley la lo 1 j rut i tu in tl 1 siti 1 is carridd on in a 

rtverberatory fnmace. Fig. jg. The hearth is floored witli fire-bricks, on to which a 
thick coating of carbonate of soda is well rammed. The fnel burning in a is coke ; 
IS soon aa the furnace has become thoronghly red-hot, ley previously evaporated to 
]]° B. in the pans n and e, is ran into the furnace, effecting a very rapid evapo- 
ntion to dryness, care being taken to stir the saline mass to keep the salt in a 
pulvemlent state. By means of the dampers, f o, and the flues, o c', the hot air and 
fiime of the burning fuel may be conducted under the pans n and b or into the 
chimney. The composition of soda thus evaporated to dryness is, according to the 
uulyais of two samples by Mr, J. Brown, as follows: — 

L n. 





. ... 68-907 


65-513 


Caustic soda 


. ... 14-433 


16072 


Sulphite of soda 


. ... 7018 


7-812 


Hyposulphite of soda ... 


2-23« 


2 '34 


Sulphuret of sodium 


. ... ran 


I-54I 


Chloride of Bodium 


3-972 


3*852 


Alnminate of soda 


. ... 1016 


1-233 


Silicate of soda 


1-030 


O'Soo 


Insoluble mattor 


0-814 


0974 



i82 CHEMICAL TECHNOLOGY, 

The salt is next calcined, and the salphoret of sodium converted into snlpfaite of aoda, 
a portion of the caustic soda being converted into carbonate of soda. The otklcined salt 
is now read; for the market ; but in some of the large alkali-works near Newcastle-on- 
Tyne it is re-dissolved in water, treated with carbonic add, and again evaporated. A 
better product results from another method, namely, evaporating the ley to a known 
degree of concentration, and obtaining small crystals of soda-salt (NaaCO^+ H^O). In 
this case, as regards the methods of evaporation employed, the two followmg are most 
general: — Heat is brought to bear on ihe surface of the liquid contained in shallow 
rectangular iron pans fitted to the hearth of a reverberatory furnace ; the liquid rapidly 
boils at the surface, and a saline crust is formed, which is constantly broken up and 
collected with iron rakes by the workmen. Now and then the salt deposited at the bottom 
is removed and placed on a sloping ledge to drain. This method of evaporation is eoono- 
mical, but attended with the disadvantage that the ley is constantly in contact with the 
carbonic and sulphurous acid gases arising from the combustion of the fuel, the conse- 
quence being that a portion of the caustic soda is converted into carbonate and sulphite 
of soda, the latter by the subsequent calcining operation being converted into sulphate. 
By the second plan of evaporation the heat is conveyed to the bottom of the pans, but 
then many precautions are required to prevent the bottom being burned in consequence of 
the settling down of a saline mass not conducting heat. Mr. Gamble, at St. Helens, 
employs a pan of a peculiar form, the section being like that of a boot ; it is heated by the 
waste heat of the soda furnace, and the inclination of the sides of the pan greatly assistB 
the removal of the salt, which, having been drained, is calcined, yielding a grey-coloured 
salt, afterwards purified by solution with the aid of steam in a small quantity of water, 
decanting the clear solution, and again evaporating it. Balston obtains a purer product 
by washmg the impure ^bonate with a cold saturated solution of pure carbonate of soda, 
the chloride and sulphuret of sodium and the sulphate being thus- removed. As already 
stated, the evaporation is not always continued to dryness, but to a degree of concentra- 
tion determined by experience. By varying the relative bulk of the Uquid a more or less 
pure product may be obtained; when, for instance, the ley of the lixiyiation tanks 
(r= 1*286 sp. gr.) is evaporated to y^^ths of its bulk and the sidt separated removed, this 
salt corresponds to a purified soda salt of 57 per cent ; by evaporating the remaining 
liquid to |ths of its bulk, a salt of 50 per cent is obtaineid. When the mother-liquor is 
evaporated to dryness, a very caustic and impure salt is obtained. Euhlmann, at Lille, 
employs pans which are graduated so that the bulk of the liquid may be readily ascer- 
tained for the purpose of fractioned evaporation. The purification of the crude ley, 
containing sulphuret of iron dissolved by sulphuret of sodium, may be effected, as 
suggested by Gossage, in 1853, by filtering the liquid through a coke-tower (one of the 
towers used for condensing hydrochloric acid), a current of air being forced upwards to 
assist in oxidising the sulphuret of sodium. 

The composition of refined soda, according to Tissandier's analyses, is: — 

I. 2. 3. 4. 5. 

Moisture 2*22 3*11 1*15 x*oo 0*40 

Insoluble matter . . . . 0-12 0*22 0*08 — 0*06 

Chloride of sodium . . .. 12*48 6*41 3'28 2*11 0*99 

Sulphate of soda . . . . 8*51 3*25 2*15 1*50 0*35 

Carbonate of soda . . . . 76*67 87*01 92'34 95*39 98*20 

100*00 100*00 xoo'oo xoo'oo 100*00 
The composition of soda, containing caustic soda, is : — 

I. a. 3- 4- 

Moisture 2*10 1*50 2*48 1*38 

Insoluble matter .. .. 0*12 cii 0*21 0*09 

Chloride of sodium .. .. 4*32 2*43 3*50 4*11 

Sulphate of soda . . . . 8'8o 1*62 2*15 2*50 

Carbonate of soda . . . . 82*47 88*09 84*54 81*67 

Caustic soda 2*11 6*25 7*12 10*25 

100*00 lOO'OO XOO'OO xoo*oo 

In order to obtain crystallised soda, Na2003-{-ioH20, with 63 per cent of water, 
a saturated solution of calcined soda in hot water is poured into large iron vessels, 
and yields crystals on cooling. The calcined soda is generally dissolved in oonical 
vessels (Fig. 80), made of boiler-plate, c is a steam-pipe, b a water-pipe, n aper- 



SODA. 



183 



(orated Teasel to eont&m the c&ldned eoda to be dissolved. The boiler is tliree- 
fbmtlia filled with water, the perforated vessel filled with soda is then lowered into the 
liquid, and the steam turned on. The soda is nipidlj diBsolved, and when the 
■dntioii marks 30° to 32° B. it is run into the crTStallieing vessels ; the crystaUiaa- 
Uon is complete in five to six days in moderately cool weather. The crjstala are 
broken up, and again dissolved in water in the vessel k (Fig. 81), heat«d by the fire 
■t c. on are fines carrying flame and heated air round the vessel ; s is a water-pipe. 
The vessel having been filled with crystals, a Email quantity of water is added, and 
■ssoonasthe salt is completely dissolved, thefireisextingnished, the liquid being left 
to settle. The clear liquid is next syphoned into a reservoir, and from this poured 

Fio. 80. 





intocast-iron ciygtallisiug vessels. After seven or eight days the mother-liquor is 
removed, and the crystals are detached from the surface of the iron by placing 
Ibe cryBtallisiiig vessels for a few moments in hot water, tbe result being that by the 
incipient fomon of the oiystals in their water of crystallisation, they are loosened 
from the metal to which they adhere. After draining, the salt is dried in rooms 
heated to 15° to 18°, and then packed in casks. Although a crystalline salt is gene- 
rally purer than a non -crystallised mass, yet the large quantity of water contained 
in ctystalUsed carbonate of soda is an impediment to its extensive use, both on 
account of expense of carriage and the weakness of the alkali. In this country, 
however, owing to the great facility of water carriage, crystallised carbonate of soda 
is very largely used. 

Tttrnitt LdiiuiyFniMa. The prooess of M. Leblanc has been best elucidated by the 
mere recent researchea of Gossage and Schenrer-Eestner. Formerly it was 
utnmed that when a mixture of snlphate of soda, carbonate of lime, and carbon 
were calcined, the carbon while yielding carbonic oxide converted the sulphate of 
aoda into solphnret of sodinm, in its turn decomposed by the carbonate of lime, the 
result being the formation of carbonate of soda, oxysulphnret of calcium, and 
•he evolution of a portion of the carbonic acid; (a) NaiS04+2C=NaiS-faC0j; 



i84 CHEMICAL TECHNOLOGY. 

08) 2Na«S+3CaC03=2NaaC03+CaO,2CaS+COa. According to Unger the car- 
bonate of lime loses its carbonic acid as soon as snlphuret of sodinm is fonned, 
there remaining a mixture of caustic lime, snlphuret of sodium, and carbon, which 
becomes converted into oxysulphuret of calcium, and caustic soda, the latter 
by taking up the carbonic oxide resulting from the combustion of the carbon 
becoming sodium-carbonate ; this view appears to be nearest the truth, but as proved 
by Scheurer-Kestner, Dubrimfaut, J. Eolb, and Th. Petersen, it is not necessary to 
assume the existence of oxysulphuret of calcium for the purpose of explaining the 
fact that the snlphuret of calcium does not act upon the sodium-carbonate, because 
snlphuret of calcium is almost insoluble in water, 12*5 parts of water dissolving at 
1 2*6° only I part of snlphuret of calcium. This view is also confirmed by the 
results of experiments made by Pelouze. During the formation of soda in the cal- 
cining furnace the carbon is only converted into carbonic acid, viz. : — 

a. 5Na2S04+ioC=5NaaS+ioCOa. 

/8. 5Na2S+7CaC03=5NaaG03+5CaS+2CaO+2COa. 

However, as there is formed during the calcination process, especially towards the 
end of this operation, a not inconsiderable quantity of carbonic oxide which bums 
off with a bluish flame, this substance, although a secondary product, has to be taken 
into account in the formula ; moreover, the formation of this gas is important, for as 
soon as it makes its appearance the chief reaction is being completed, proving 
the heat to be at its proper degree. 

The researches of Ungor have xmdoubtedly proved that when the sulphate 
is reduced by carbon there is only carbonic acid and not a trace of carbonic oxide 
formed, so that carbonic oxide is the result of the action of the excess of carbon 
upon the carbonate of lilne ; this reduction of the carbonate of lime by carbon takes 
place at a much higher temperature than that at which the sulphate is reduced, 
therefore the formation of carbonic oxide takes place after that of the carbonate 
of soda. Consequently there must be distinguished three phases in the formation of 
soda, viz. : — 

a. The reduction of the sulphate, with evolution of carbonic acid gas — 

(Na«S04+2C=NaaS+2C0a). 

/3. Double decomposition of the newly formed snlphuret of sodium and carbonate 
of lime {Na2S+CaC03=Na,C03+CaS). 

y. The reduction of the excess of carbonate of lime by the carbon — 

(2CaC03+2C=2CaO+4CO). 

During the lixiviation the presence of caustic lime aids the formation of caustic 
soda. According to theory, 100 parts of sulphate only require 20 of carbon, but it 
is the practice to employ an excess of carbon, as much as 40 to 75 per cent, to pro- 
vide against incomplete mixture, the combustion of carbon without effect, and 
because of the necessity of obtaining the reaction of the carbonic oxide in order 
that the progress of the operation may be observed, as experience has proved that the 
mass should not be removed from the furnace until this combustion is nearly over. 

utiuaation of 8od» WMte. The greater part of the soda now employed is obtained ly 
Leblanc's process, which, while it admits of lixiviating the soda readily and com- 
pletely, is defective, inasmuch as the residue, or waste as it is technically called, 
contains nearly all the 6ulx>hur used in the manufacture ; and that this is not a slight 
loss may be inferred from Oppeuheim's statement, that in the alkali works at Dieuze, 



I 



SODA. 185 

Lomdne, the accnmulated waste contains an amount of snlphnr valued at £150,000. 
For ereiy ton of alkali made there is accnmulated i| tons of waste, containing 
80 per cent of the sulphur used in the manufacture ; and this waste, until lately 
thrown on a refuse heap in some field adjacent to the works, often proved a nuisance 
in hot weather, giving rise to fumes of sulphuretted hydrogen. For the last forty 
jears much time and money have been spent in trying to recover the sulphur, 
but not until 1863 '^^^^ ^^7 attempt successful. Three different processes are now 
resorted to, viz. — Guckelberger's, modified and practised by Mond ; Schafiher's plan; 
and the process invented by M. P. W. Hofmann, at Dieuze. Since the first suc- 
ceasfol experiment the methods have been so rapidly improved that, at the Paris 
Exhibition of 1867, no fewer than nine samples of recovered sulphur were sent in. 
All the methods mentioned above are based upon the same principle — ^the conversion 
of the insoluble sulphurets of calcium contained in the waste into soluble compounds 
by the aid of the oxygen of the atmosphere ;. the lixiviation of the oxidised mass, 
and precipitation of the sulphur contained in the leys by a strong acid, practically 
hydrochloric acid. 
"^^'wSwon pt^s^*" ^- Schaffiier's plan for the regeneration of sulphur from soda 
waste involves the foUowiug operations : — 

a. Preparation of the liquor containing sulphur. 
p. Decomposition of the liquor, 
y. Preparation of the sulphur. 

a. The soda waste is submitted to a process of oxidation by the action of the air, 
and for this purpose is placed in large heaps, where heating takes place, together 
with the formation of polysulphurets and subsequently hyposulphites. After a few 
weeks the interior of the heap assumes a yeUow-green colour, when the material 
is ripe for lixiviation ; the heap is then broken up into large lumps, which remain for 
another twenty-four hours' oxidation. These lumps are next submitted to lixiviation 
with cold water, and a concentrated liquor obtained. After this process follows 
another oxidation, effected by placing the lixiviated residues in a pit dug in the soil 
to a depth of i metre, and situated close to the lixiviation tanks ; by this burying the 
heat generated by the oxidation suffers less dissipation than when the material is ex- 
posed on all sides to currents of air. The second oxidation proceeds more rapidly than 
the first in consequence of the greater porosity of the mass, so that beside poly- 
sulphurets more hyposulphites are formed. Instead of effecting the second oxida- 
tion by burying, the waste may be left in the lixiviation tanks, and the oxidation 
accelerated by forcing the hot gases from a chimney under the perforated bottom of 
the tank ; by these means both time and labour may be saved, the oxidation being 
complete in 8 to 10 hours. According to the quality of the alkali waste, this process 
of oxidation may be repeated three to four times ; the gases accompanying the smoke 
of burning fuel are exceedingly well suited for effecting the decomposition of 
the sulphuret of calcium in such a manner as to cause the formation of poly- 
sulphurets and hyposulphites. The liquors resulting from the first lixiviation con- 
tain chiefly polysulphurets and hyposulphites ; but the liquors obtained after the 
second and third oxidation contain essentially hyposulphites; all the liquors are col- 
lected in one reservoir. 

/3. The decomposition of the lixiviation liquor by means of hydrochloric acid is 
carried on in a closed apparatus of cast-iron or stone, and is based upon the fact that, 



i8S CBBKICAL TBOBSOLOaT. 

liyposnlplutea when treated nitli hydrocMorio add. evolve snlidimrotia add gig, 
salpIiiirbeiiigprecipitated(CaSi03+2HCl TieMs CaCli+SO,+^HtO), andiron 
tiiB reaction exerted bj sQlphtizoaB add apon the poljmlphimt, which, wMl« 
sulphur ia depoaited, is agam converted mto hj'posnlpHte of lima — 

(3CaSj+3SO,=3CaS,Oj+ S«). 
The liquor is teEted by titratiou to detennine the quantity of polyralphiuet and of 
hypoBolphitas contcuned, and according to the result the reddoe is more or less 
oxidised. 

The appBTBtm generally employed in the deoompontion ia shown in Fis. 81 ; & and b 
are the veHgela to oonUia the hqnor ; I ie the pipe by which the liqnor u oonveyed to 
k or fi, regolated by a piece of eiastia tabiug enteriim at c^ into 1, or q' into b. t and t* 
are euihenware tnbee by which the hydrot&lorio acid is introdaeed. c and d are glaas 




tube*, e is fitted to the top of t, and has a longer leg dipping into the fluid at a ; the revaraa 
ia the case for d, the short leg of which is fitted to b, while the longer leg dipa into the 
fluid in ±. The tap, a, is oloaed when the gasea shoiild enter throngh e into the flnid 
oontuned in a, bat tbe tap, b, is shnt, and a opened, when the gase« passing throngh d are 
to enter the flnid contained in 1. The excess of gas Is carried off by the tube a. Aa soon 
as the decomposition by the action of the hydrochloric acid is efTeoted, steam ia injected 
throngh the valves, vV, to expel the last traeea of solphnrona aoid from the liqncr. 
The liquor and finely di^ed solphni are rnn off at and o', care being taken to let Uia 
chloride of ealdnm solution ran oD by removing the wooden ping, p. In order to ascertain 
whether ^ the anlphnrons add is e^nlled, the woodem taps, k A', are opened, the imeU 
of the gaahdug a snfBoient indioatioD of itspresenoe. The taps,/ and/, are employed 
aa test cooks to ascertun the piogrcBa of the operation, and aUo to see whether the 
vesBels are properly filled with Uqnor. 

The BiQphnr obtained by this process ia flne-grained, and mixed with aome gypmim, 
ebiefly dne to the snlphnrio acid contained in the hydrochloric add. The salpbnr and 
chloride of oaldom Uqnor are oondaoted by the spout, 0, to a vessel with a false bottom, 
perforated and covered with a flannel doth, throngh which the Uqnor passea, the sulphnr 
being retained. 

y. The snlphnr is prepared for the market by a very simple procesa. It is mixed 
with anSdent water to conslitate a pasto, which ia pnt into a east-iron veasel, and 
steam at a pressure of i| atmospheres admitted to melt the salphnr, the water 
taking np ai^ adhering chloride of caldnm solution, and also the gypnim. The 
molten snlphtir collects in the bottom of the vessel, and is tqiped off into moulds; 
the supernatant liquor does not mix with the Hulphor owing to the greater apedfic 
weight of the latter. In order to perfeotlj Batnrate any &ee add which might still be 



present some nilk of lime is added ; bf this addition anoQier end is gidned, vis., 
the remoTal of suy aisenic, in the Gjllowing maimer: — If daring the melting process 
u exeeas of lime be present, aulphnret of calcium is formed, uid this enlphnret 
diwolves an; snlphoret of arsenic which is thus removed to the supernatant liquor. 
The advantages of melting and puri^di^ the snlphor b; the above process are— 
the ralphnr meed not first be oarefnll; washed and dried, foel is saved, the sulphur 
freed from arsenic, and brought to the best state for pouring into moulds. Figs. 85 
and 84 rqresent the melting vessel ; the cast-iroo cylinder, b, is snrronnded bj a 
crought-iton cylinder, a. and the whole inclined to admit of the molten enlphnr 



Fio. 83. 




collecting at the lowest part of b. The solphnr paste is kept stirred by an apparatus 
IB gearing at n with some motive power. The paste is poured into b at m ; at 
atteun ia introduced, passing at o into the inner cylinder, and let off, when the 
melting is finished through d and the valve, v ; the molten solphor is run off at z ; 
« is a safety valve. By this process 50 to 60 per cent of the snlphnr contained in 
the soda waste is recovered, for every owt. recovered 2 to 21 cwts. of hydrocblorio 
add being employed. If this acid were too expensive, the residues of chlorine 
unnofacture might be used, these residues coansting mainly of chloride of manganese, 
ftee hydrochloric acid, and chloride of iron ; the first Bl«p would then be to free 
these residaes from tbe chloride of iron by means of the lixiviated soda waste 
added ia small ^nantitieB at a time ; sulphuretted hydrogen would be ^ven o3^ and 
FeiC1« reduced to FeCU, the changed colour indicating the end of the reaction. 
The diriy grey-coloured sulphur from this reaction should be bnmt in the pyrites or 
nlphur-bnzning furnace. The prepared residue would now be fit for employment 
IS a substitute for hydrochloric add. Should, however, some monoenlphmet of 
calcium be present in the soda waste liquor — not a very likely occurrence — some 
hydrochloric acid must be added before osing the reddnes. 
■ubTiiMhodiiii Among the many methods which have been proposed for the 
^^^Dissda, preparation of soda thefollowingespeciaUydeserve notice. According 
to Eopp's methods of soda manofikctore sulphate of soda, oxide of iron, and carbon 
are snLelted together in an ordinary soda fomaee: — 



x88 CHEMICAL TECHNOLOQT. 






The crnde soda absorbs from the air water, oxygen, and carbonic acid, becoming 
converted into carbonate of soda and an insoluble residue of sulphuret of iron 
containing sodium, Fe^Na^Sa : — 






The lixiyiation is effected with warm water at 30° to 40°; the liquors yield after 
twenty-four to twenty-eight hours, without any previous concentration, a large crop 
of beautifully crystallised soda. The insoluble residue of the lixiviation is dried 
and roasted to produce sulphurous acid, employed in the manufacture of sulphuric 
add, used in its turn for the conversion of common salt into sulphate of soda. Thus 
the cycle of changes in the sulphur is complete: — 



f^if'^s,! y,^. 



faFcaO, 
Na^S04 
USOa 



The sulphate of soda present in the calcined residue is removed by liziviation. 

It cannot be denied that this process presents certain advantages. 

Diwd ooDTenion of "^ P^*° ^^' *^® direct converBion of common salt into soda has long 
Common Salt been sought, but hitherto not suocessfuly carried into practice. When 
into Soda. ^ concentrated solution of bicarbonate of ammonia is mixed ^th 
strong brine, or, better still, the pulverised bicarbonate stirred through a concentrated 
solution of salt, and this mixture left to stand, the result will be that after some hours 
bicarbonate of soda will be deposited in crystalline state, the supernatant liquid being a 
solution of sal-ammoniac. As bicarbonate of soda on being gradually heated to redness 
loses a portion of its carbonic acid, and is converted into monocarbonate of soda, this 
process has been suggested as suited for the manufacture of soda, 'and has been 
tried by Dyar and Hemming in England. SohloBsing and Bolland in 1855 took out a 
patent for some improvements on this method of soda manufacture, of which the 
foUowing is an outline: — The first operation consists in the action of ammonia and 
carbonic acid upon a concentrated salt solution ; to xoo parts of water 30 to 33 parts of 
common salt, 8i to 10 of ammonia, and carbonic acid in excess are taken. The next 
step is the separation of the bicarbonate of soda, which is effected by a centrifugal 
machine. The third stage is the calcination of the bicarbonate of soda in cylindrical 
iron vessels, the carbonic acid gas given off being collected. The fourth and fifth 
operations aim at the recovery of the carbonic add and ammonia from the liquid drained 
from the bicarbonate of soda while in the centrifugal machine. The liquid is heated in 
a boiler, the result being the escape of the ammonia and carbonic add, which are con- 
ducted to a cylinder filled with coke, through which a cold aqueous solution of car- 
bonate of ammonia trickles, causing the condensation of the ammonia, the carbonie 
acid escaping into a gasholder. Next, milk of lime is added to the liquid, and the heating 
being contiaued, all the ammonia is expelled. Lastiy, the dear supernatant liquid is 
evaporated to recover the common salt. According to Heeren's researches on this subject, 
this process is more suited for the preparation of bicarbonate of soda ; it is stated, how- 
ever, that the researches of Marguerite and Bourdiyal have resulted in improvements on 
this method which may in future lead to its being advantageously adopted in some 
localities for the manufacture of soda. 

Soto from cryouta. Cryolite (AlaFl€,6NaFl) is largely employed for the manufacture 
of soda by decomposing the mineral by ignition with lime: — 

I mol. of Cryolite ) (6 mols. of Fluoride of caldum. 

6 mols. of lime J -^ 1 1 mol. of ALuminate of soda. 

This last compound being soluble in water is decomposed by carbonic add, and 
alumina precipitated, soda remaining in solution. 100 kilos, of cryolite yield — 



SODA. iSg 

Dry caustic soda 44 kilos. 

Calcined soda 75 „ 

Ciystallised carbonate of soda ... 203 „ 
Bicarbonate of soda ii9'5 n 

Banxite (see nnder Alumina), on ignition with snlphate of soda and carbonaceous 
matter, yields in a similar manner soda and alumina. 

BodafromNitnie ^7 ^^^ oonversion of nitrate of soda into nitrate oj potassa by the aid 
of Soda. of carbonate of potassa (see under Saltpetre) not inconsiderable quantities 
of ft strong solution of soda are obtained ; the sodium of the sodium nitrate may be 
converted by any of the following means into soda or caustio soda: — 

a. By igniting nitrate of soda with carbonaceous matter. 

h. By igniting nitrate of soda with silica, and decomposing the silicate of sodium 

by carbonic acid. 
e. By igniting nitrate of soda with manganese. 
d. By the decomposition of nitrate of soda. 
a. By means of carbonate of potassa; or, 
p. By means of caustic potassa. 
In the latter case, besides nitrate of potassa, caustic soda is formed. 

cmtiesoda. This substance, sodium hydroxide (NaHO), is met with in commerco 
as a highly concentrated solution, or more frequently as a solid mass, fused hydrate 
of soda, consisting in loo parts of 77*5 parts of soda and 22*5 parts water. For 
many years a moderately strong solution of caustic soda was prepared by treating 
a carbonate of soda solution with caustic lime, but Dale was the first to use this 
solution instead of water in his boilers, and thus concentrate the lye to a sp. gr. of 
124 to 1*25, after which the ley was further evaporated in cast-iron cauldrons to a 
sp. gr. of I '9, at which point it solidifies on cooling. 

Instead of using caustic lime, caustic soda is now directly produced by simply 
increasing the quantity of small coal added to the mixture of sulphate and chalk, 
the crude soda being at once lixiviated with water at 50°. After the liquor has 
cleared, it is rapidly concentrated to 1*5 sp. gr., when carbonate, sulphate, and 
chloride of sodium are deposited, the liquor assuming a brick-red colour, due to a 
peculiar compound of double sulphuret of sodium and sulphuret of iron. The ley 
is next strongly heated in large cast-iron cauldrons, and there is added 3 to 4 kilos, 
cf Chili-saltpetre for every 100 kilos, of caustic soda required; by this operation the 
nitrate of soda reacts upon the sulphuret of sodium and cyanide of sodium present, 
causing an abundant evolution of ammonia and nitrogen. This somewhat com- 
plicated process may be elucidated by either of the two following formulsB : — 
a. 2Na2S+2NaN03+i3laO=2NaaS04+2NaHO+2NH3. 
p. 5NaaS+8NaN03+4HaO=5Na^S04H-8NaHO+8N. 

According to Pauli, the kind of reaction depends chiefly on the temperature of the 
heated ley ; at 155° ammonia is largely evolved ; above 155° and with greater con- 
centration of the ley nitrogen is given ofif. As for every ton of caustic soda produced 
this process absorbs 075 to i cwt. of nitrate of soda, the ley is in some works oxidised 
by filtering it through a colunm of coke, or by forcing air through it in minute jets. 

HewifttiuKUof ouutie Among these is the decomposition of sulphate of soda by means of 
8od« MAnaiMtiin. oaustlc baryta, a rather exi)en8ive process, baryta white or permanent 
white being a by-product. Ungerer uses caustic strontia instead of caustio baryta. Caustic 
foda may be prepared by treating cryolite for sulphate of alumina (see Alum), or by 
igniting nitrate of soda with manganese ; or by decomposing silico-fluoride of sodium 
or fluoride of sodium with caustic lime. In England very pure caustic soda is prepared 
from sodium by carefully oxidising the metal with pure water in bright iron or silver 
vessels. 



igo CHEMICAL TECHNOLOGY. 

According to Daiton's researches :*— 

A oauBtic soda liquor of the Contains percentage of canstiff 

undermentioned sp. gr. soda (NaHO.) 

2'oo 77*8 

185 636 

172 53*8 

X'63 46-6 

i'47 340 

144 310 

1*40 29*0 

1*36 26*0 

i'32 230 

I29 19*0 

1*23 160 

i'i8 13*0 

112 90 

106 4*7 

Canstio soda is largely used in soap making, paraffin and petroleum refining, and thf 
preparation of silioato of soda and artificial stone by Bansome and Sims's method. 

BicaiboiiAto of Soda. This substancc, NaHGOs, called erroneously carbonate of soda 

in many of the London shops, consists in 100 parts of 369 soda, 1073 water, and 

52*37 carbonic acid, and is prepared by passing a current of washed carbonic acid 

gas through a solution of carbonate of soda. If the solution is concentrated the 

bicarbonate is deposited as a powder, but from a dilute solution large ciystals are 

obtained. It is, however, more advantageous to cause the carbonic acid to act 

upon crystallised and effloresced carbonate of soda ; a suitable mixture consists of 

I part of crystallised and 4 parts of effloresced carbonate of soda. The sources of 

carbonic acid may differ, but in this country the gas is generally prepared by the 

action of weak hydrochloric acid upon chalk or limestone; of course the carbonic 

acid evolTed during the fermentation of wort, or must, may be applied. 

When carbonic acts upon crystallised carbonate of soda there is first formed 

sesquicarbonate of soda ; the 9 equivalents of water which are displaced from each 

equivalent of crystallised carbonate of soda are collected in a reservoir, and this 

liquid having of course dissolved a portion of the bicarbonate is employed at a 

future operation for moistening the crystallised soda carbonate. The bicarbonate 

is dried at 40^ in a current of carbonic acid gas. The preparation of the bicarbonate 

by withdrawing from the monocarbonate by the aid of an acid one-half of the soda 

it contains has been suggested; for this purpose 28 i parts of crystallised sodic 

carbonate are dissolved in twice their weight of warm water, and 4^, parts of 

sulphuric acid added, care being taken not to move the vessel. Being left to stand 

for several days the bicarbonate is deposited in crystals. It has been seen 

that when a solution of common salt is treated with bicarbonate of ammonia, the 

result is the formation of bicarbonate of soda and sal-ammoniac, which remains ib 

solution. Bicarbonate of soda crystallises in monoclinical, tabular crystals ; has a 

weak alkaline reaction ; loses its carbonic acid at 70°, and becomes monocarbonate 

of soda ; and by exposure to dry air is gradually converted into sesquicarbonate. 

The bicarbonate is employed generally in the preparation of effervescing drinks, and 






IODISE AND BBOMDIS. igi 

«ith fardxochloric or phosphoric sdd in makiiig bread withont fementatioiL Iho 
farther oacfl of this scdt are — the precipitation of the alumins from Bodinm-alnminikta 
solntiotia, for the preparation of baths, for gilding and platinising, and for puri^ring 
and cletmaing silk and wool, i grm. of the bicarbonate fields, when completel7 
decomposed bj an acid, about 270 c.c. of carbODic add gaa = 0-51 grm. by weight. 

The total prodoction of Boda in Europe amoonted in 1870 to 11,850,000 cwts., of 
which Qreat Britain produced 6,350,000 cwts. 

PnXFAnATION OF lODINB AND BbOHINE. 

PiumM a n ai loUu. This element occnrs in sea-water, from which it is taken ap by 
Tarions sea-weeds ; from these sea-weeds iodine is derived indnstTiallj. Chili-salt- 
petre and some aaline springB (for instance, the Solza, Sodiem Weimar) contain 
iodine in conaiderable quantity. Although iodine is fonnd in the mineral kingdom 
(for instance, in the iodide of lead and phoephorites of Amberg, Bavaria, and Diez on 
the I^hn), it ia not in this case indnstriallj important. The chief seat of iodine 
mannfactnre is at Glasgow, where there are twelve bctoriea ; there are two iodine 
fiKtoriea in Ireland, and two at Brest, in France. 

rnpudkn bm ittf. In Order to obtain iodine from sea-weeds, the latter are first con- 
Terted into kelp, that is to eay, they are incinerated, the prodnet broken to pieoes 
and lixiviated with water, leaving an insoluble residne of 30 to 40 per cent, and 
yielding to the liquid 60 to 70 per cent. This solntion, having a ftp. gt. at 
I'lS to i'2o, contains chlorides, sulphates, and otrbonates of alkalies, snlphuret 
of potasainm, iodide of potaaainm, and hyposulphites of alkalies ; by evaporating 
ind cooling the lienor, the sulphate of potassa and chlorides of potassiom and 
sodium are removed. To the remaining mother-liquor, previously poured into 
shallew open vessels, dilute sulphuric add is added, the result being, that while a 
strong evolution of gases, solphoretted hydrogen, and carbonic add takes place, 
there is formed a thick sewn and a deposit of snlphur at the bottom of the vessel; 
the sulphur when washed and dried is sold. When the evolution of gas has 
completely ceased, more sulphuric add ia added, and, according to Wolloston's 
nelhod, the required quantity of manganese ; this mixtnre is poured into a large 
leaden distilling apparatus, c. Fig 85. By this means the iodine is set free, carried 

Fie. S5. 




'*''' in the state of vapour to the receivers, b, b', b", and condensed as a aditl 
^fTStalline mass. In I^terson's large iodine works at Glasgow this operation & 
buried on in a cast-iron hemispherical vessel of 13 metres diameter, the cover 



rga OaSMlCAL TBCHHOLOQT. 

being a leaden dome, to which are fitted two earthenware etinheads, connected 
by meanfi of porcelain tubing with two earthenware receiTere. Fig. 85, aueh 
COiiBigting of 4 to 5 parte. At Cherboorg. iodine is obtained, according to Batraat'H 
plan, by passing clilorine gas into the mother-li(|nor; by this plan the iodine ie sepa- 
rated &om the iodide of magnesimn, the latter taking np chlorine ingtead— 

(MgI.+Cl,= MgCU+I,). 
A more recent method, by which all the iodine present in the mother-liquor is ebttuned, 
comdatB in distilling the liquor with chloride of iron — 

(2NaI+Fc,Clfi=al+2NaCl+2FeCl,).. ' 
Ab iodine ia only very elightly soluble in water, i part of iodine requiring 55Z4 puis 
of water at 10° to 12° for its solution, that ia, i grain of iodine to izonncea of water, 
it is carried over with the steam and deposited at the bottom of the receiver in the 
form of a black powder. .When it dine ia prepared by the aid of chlorine, the 
quantity of gas should be exactly aufGcient to decompose the iodide of magnesiaiii, 
for if the quantity of chlorine be too email no iodine is separated, and if too largB 
chloride of iodine is formed and free bromine, both of which being volatile escape. 
The iodine when removed from the reoeivers is drained on porons bricks or tiles, 
and dried between folds of blottu^-paper. It need hardly be said that the iodine 
Fio. 86. should not come in contact with a 

metallic snr&ce. The iodine thus 
obtained has to be purified by sub- 
limation, an operation carried on in 
the apparatos represented in Fig. 86, 
consisting of stoneware reCorta, cc, 
placed in the aand-bath, b, heated 
as ehown in the vroodciit> Each of 
these' retorts is filled with upwards 
of 40 lbs. of crude iodine, ind 
entirely surrounded by sand in order 
to prevent the sublimation of any 
iodine in the necks of the retorts. 
These are then connected with the 
a which the cTyatalline iodine ia deposited, the tubes, a ft, 
a b, being for the pnrpoae of carrying off the watery vapour. 1 ton of kelp yields 00 
an average 4*07 kilos, of iodine. 

siutDFiiuidHoiidi. In ,862 Mr. Stanford Buggasted that the Bea-weeda shonld not 

taJSc^bSSdSi.iiSi' be calcined, bat aimplj distilled with Buperheated steam, so » to 
prevent volatiliBation of the iodine, while the tarry and gOBeous produots ahonld be sep^ 
rately ntilised. This clu-boDiBed aea-weed, when aaite oold, ia liijviated with water, tui i 
the solution treated for iodine and chloride of potasaiam (see p. 130]. The yolalde pt^ 
dnctB of the diatillatjon are illununatiDg gas, acetic acid, ammonia, mmeral oil, MM 
paraffin, M. Morido, of Nantes, has modified this process; be prepares by evspoiaUng 
the liquor from the lisiviation oi the carbonised sea- weed, aulpbate and cblonde 01 
potassium, Ac The niother-Uquor ia treated with chlorine or hj-ponitrio acid, and than 
with benzine, in an apparatos so arranged that the benzine directlj gives up the "™?|J* 
has dissolved to soda or potassa, the benzine thns acting as a coiitmuons aolvent. 11" 
liquor containing iodine is treated for the aepacatiou of iodins in the naual manner. 
Pni>«tioDDM»iin.t,om Crude Cbili-aaltpetre contains on an avernHO 0-059 *" J"'" 
Chm-s.ii».ir». per cent of iodine. According to Nollner, tho iodine oo«oi» 

from the formation of the ChiK. saltpetre in tiie piesonce of deoajing sea.«e«i» 
from shallow, staKnant, inland seas, which have dried np, Tlie mother.LiiuoK, 
left after the refining of the salt, or from its UMi for the conversion of cMonde m 
potttHsinm into nitrate of potassa, and containing o-i8 to o'36 per cent of lodme, are 




IODINE AND BROMINE, 193 

treated with snlphtiroaB acid until the iodine separated begins to re-dissolye. More 
recently nitrons acid has been nsed instead of snlpliurons aoid. The iodine thus obtained is 
refined bj sublimation, while that remaining in the residual saline matter is removed ty a 
farther treatment with chlorine. 

PropddM aiid uu« of Iodine. Iodine (1=127; Sp. gr.=4-94) is a black-grey coloured 
crystalline substance, with a metallic appearance not unlike graphite. On being 
heated iodine is converted into vapours which, according to Stas, when concentrated 
exhibit .a blue colour, and a violet in a more dilute state. Iodine fuses at 115°, 
and boils above 200°. It is somewhat soluble in water, readily so in alcohol, 
ether, hydriodic acid, iodide of potassium solution, sulphide of carbon, chloroform, 
benzol, aqueous solution of sulphurous acid, and solution of hyposulphite of soda. 
A solution of iodine imparts a violet colour to starch. Adulteration of iodine 
with either pulverised charcoal or graphite may be at once detected by treating 
a sample with alcohol or a solution of hjrpdl^Jphite of soda, in ea6h of which 
the iodine, if pure, ought to dissolve completely, leaving no residue on 
sublimation. Sometimes the weight of iodine is fraudulently increased by the 
addition of water. Iodine is largely nsed in photography combined as iodide 
of potassium ; for the preparation of other iodine compounds, for instance, iodide 
of mercury ; also in the preparation of some of the tar colours, iodine violet, 
iodine green, and cyanine blue, the latter a compound from iodine and lepidin, a vola- 
tile base. The total production of iodine in Europe and Chili amounted in 1869 to 
3453 cwts., more than half, or 1829 cwts., being produced in Scotland and Ireland. 

Pdeptzation of Bromine. The element kuowu as bromine occurs to a small extent in sea- 
water, a litre containing 0061 grms. bromine. The mother-liquors, however, ,of 
many salt works (for instance, those at Schonebeck, near Magdeburg, and the 
hquors left from many of the Stassfurt salts) are so rich in bromine, that its prepara- 
tion is worth the cost and trouble. In order to avoid as much as possible the 
admixture of chlorine, there is added to the mother-liquor dilute sulphuric acid ; 
this mixture is heated to 120°, and tlie hydrochloric acid set free by the sulphuric 
uid evolved, while the less volatile hydrobromic acid is left in the liquor, from 
which, on cooling, sulphates are deposited. The decanted liquor is distilled after the 
addition of more sulphuric acid and some manganese. Two Woulfe's bottles serve 
as receivers ; in the first are condensed water, bromine, bromoform, and bromide of 
carbon, while any bromine vapours which pass over to the second bottle are 
absorbed in'the caustic soda it contains. The ley contained in this vessel is evapo- 
lated to dryness, the residue ignited in order to convert bromate of soda into 
bromide of sodium ; the saline mass being then mixed with sulphuric acid and man- 
ganese and distilled, yields pure bromine, best preserved under strong sulphuric acid. 

According to Leisler's patent (1866) bromine is separated from the mother-Uquor left by 
operations with kainite, or camallite, or from the water of the Dead Sea) containing, 
aeeording to Lartet^s analysis, in i litre, taken from a depth of 300 metres, 7*093 
gnns. =o*7 per cent of bromine) by adding bichromate of potassa and an acid ; heat being 
applied, the bromine is volatilised and collected in a condenser filled with metallic iron. 
From the bromide of iron thus formed, either the element itself or any of its compounds 
ipay be obtained. The apparatus employed by this patentee is a distilling apparatus ; the 
add is hydrochloric diluted with four times its bulk of water ; to 100 parts by bulk 
of the bromine fluid, i part by bulk of acid is added. The bichromate is added in a 
^turated aqueous solution. The bromide of iron formed becomes dissolved by the 
aqueous vapour, and condensed in the receiver. Bromine is the only metalloid 
fluid^ at ordinary temperature. Seen in thick layers its colour is a deep brown-red, 
hut in thin layers a hyadnth-red ; its odour is strong and similar to that of chlorine 
gas. The aqueous solution of bromine — i part requiring 30 parts of water for 
its solution — is of a yellow-red colour when freshly made, but like chlorine- water 



194 CHEMICAL TECUlfOLOGY, 

does not keep well, and is soon converted, especially if exposed to light, into a colourless 
solution of weak hydrobromio acid. loo parts of bromine water contain at 15^,3*226 parts 
of bromine; bromine forms with water a solid hydrate at 0°. It is readily solable 
in ether, alcohol, chloroform, and hydrobromic acid. It yields with an aqueons solution 
of sulphurous acid hydrobromic acid — 

{S02+H20+2Br=S03+2BrH). 

Bromine boils at 63°, giving off deep red vapours; at —7*3° it becomes a lead-grey 
coloured, foliated, graphite-like mass. Bromine acts upon colouring matters, dyes, and the 
colours of flowers as does chlorine, while organic matters, especially those of animal 
origin, are coloured brown. It is used in combination as bromides of potassium, 
ammonium, cadmium, and hypobromite of potassa, for photographic purposes and io 
medicine; and further as bromides of ethyl, amyl, and methyl, for the preparation 
of some of the tar colours, Hofmann's blue, and the preparation of alizarine from 
anthracen. Bromine is also used as a disinfectant, and, according to Beichardt, may with 
advantage be substituted for chlorine in the preparation of ferricyanide of potassium. 
Since the year 1866 bromine has been manufactured at Stassfurt, now the chief bromine 
producing locality. The total annual production of bromine in Europe and America 
amounts to 11 50 cwts., of which 400 cwts. are obtained at Stassfurt and 300 cwts. 
in Scotland. 

SULPHTTR. 

suiphmr. . In Combination witli coals, rock-salt, and ii'on, sulphur is tlie mainstay of 
present industrial chemistry. It is often fonnd native between gypsum, clay, and marl in 
tertiary deposits, more rarely in veins between crystalline rocks of the schistose and 
metamorphic varieties, and not unfrequently in coal and lignite deposits. Sulphur 
is an almost constant product of active volcanoes, being sublimed and deposited on 
surrounding objects. The largest sulphur deposits in Europe are met with in 
Sicily. It is also found in Egypt on the banks of the Eed Sea, especially near Suez ; 
at Corfu, one of the Ionian Islands ; near the Clear or Borax Lake in California ; on 
the slopes of the Popocatepetl, in the province of Puebla, Mexico, where yearly 
2000 cwts. of sulphur are collected. Frequently, sulphur is deposited from the sul- 
phuretted waters of mineral springs ; for instance, the waters of Aix-la-Chapelle. 
Sulphur occurs in combination with metals, as in iron pyrites, FeS2, with 533 
per cent of sulphur ; this mineral often contains thallium. The quantity of sulphur 
contained in the following minerals is, from 100 parts: — ^Iron pyrites (FeSj), 53*3; 
copper pyrites (Fe2Cu6S6), 349 ; magnetic iron pyrites, mundic (FcySg, or, according 
to Th. Petersen, FeS), 395 ; galena (PbS), 13*45 J hlack-jack (ZnS), 330; Meserite 
(MgS04-|-H20), 23-5 ; anhydrite (CaS04), 235 ; gypsum {CaS04-i-2HaO), 186 ; gas 
coal, 10. According to Dr. Wagner, the quantity of sulphur present in the coals 
used in the London gasworks annually, amounts to 200,000 cwts., equal to 612,500 
cwts. of sulphuric aoid. 

'Although sulphur occurs native as sulphuretted hydrogen and sulphurous acid, 
especially near active volcanoes, this is not of much industrial use. The regenera- 
tion of sulphur from soda- waste is decidedly one of the most important items in the 
sulphur industiy. 

*°*^*^^'Sw"**°*°* According to the comparative richness of the raw material, the 
sulphur is separated from its concomitant impurities by melting or by distil- 
lation. When the raw material is rather rich it is simply submitted to a process of 
melting in a cast-iron cauldron, b (Fig. 87), heated by a gentle coal or charcoal fire 
placed in a. During the melting the mass is stirred with an iron rod, and as soon 
as the sulphur has become quite fluid, the gangue and small stones are removed by 
means of the ladle, c. This done, the sulphur is poured into a wooden or sheet-iron 
vessel, D, thoroughly wetted with water to prevent the adhesion of the sulphur to the 



SULPHUR. 



"95 



sides. The aDlphnr when cold and solid is broken into large lumps and packed in- 
casks ready for the market. The stones and gangue are placed in heaps, or more 
coznmonly introduced into a shaft furnace (Fig, 88), and, a portion of the snlphur 
being sacrificed U) serve as fuel, the greater part of the element is eliminated by the 
following plan : — A small portion of the crude sulphur is ignited in the lower part of 
the furnace, and the shaft, f.. filled with large lumps of the earthy sulphur ore. &om 





The 



which, rapidly ignited superficiallj, the molten sulphur tncklcs donn 
openings,/// give access to the air required for the combustion of a portion of the 
snlphur. The sulphur collects in the lower part of the furnace and is tapped off 
by the channel g into wooden or sheet-iron vessels A for bftter method of pre- 
paring anlphnr from the ore is by distillation, the apparatus liemg tliat exhibited in 
Pig. 89. A is a cast-iron cauldron, which is filled with raw luatennl, and rovered 



Fio. 89. 




with a tightly-iitting iron hd Tht, ilui « aro so coustructod as to heat llie vessel 11 
geotly. The vapours of sulphur are carried by the tube m into the condenser, n. 
whence the molten snlphurruns off into the vessel k. The previously warmed ore is 
readily admitted to a by lifting the damper, p. From a suggestion made by E. and 
P. Thomas, sulphur is obtained &om its ores by the a|)plication of superheated 
*teamat 130°, this mode of working being the same as that employed by M. Schaffner 
fiir purifying the sulphur recovered from soda-waste. In passing, it may be men- 
tioned that very recently the estraction of sulphur from its ores has been attempted 



196 CHEMICAL TECHNOLOQY. 

by the aidof Bolveutg,nz.,Eulphideof carboD aud a lijjlit coal-tar oil of sp. gr. =o'SS. 
M. Mine's analyses of several samples of crude Sicilian sulphur obtained by smelting 



Sulphur (Bolnble in CSi) .. .. go-i 961 

Corbouaceoas matter .. .. r'o 05 

Sulphor {iDBolnbla in CSi) .. x-o — 

SiliceoDe atmd 3'3 l'5 

Limestone (aometimra creleslin) 4'i 1*8 

The bottom portion of (be blocks of crude sulphiu 
foreign substances. The crude sulphur is refined in 
of esjtby matter; and after this process it is brought into commerce i 
rolls or in powder. 

Limj-a BiOniif AppumiDi. Tlic apparatus for refining sulpliur, invented by Michel and 
improved by Lamy, at MarseilleB, consiata mainly of two cast-iron cjlindera, b 
(Fi<;.90l. nsed aA retorts, and a large brick -work condpnsing-room, a. The cylinder s 






3- 
913 


4- 
900 


s 

88 


7 


07 








3'3 


2'8 


5 


7 
5 


1-5 




2 


S 






0-3 


often 


contains 


25 per cent of 


order 


to pJiTti' 


nate all traces 


into 


Mmmerce in 


sticks or 




is directly beat«d by the fire, the smoke of trhicli is carried off by tbe chimnry, E. 
The flues, c, however, Eurroundn, where the crude sulphur nndergoesa partial refining' 
and wlie&ce it flows by the tobe f into the cylinder b. The cylinder b is in commn- 



SULPHUR, 197 

nication with the vaulted room, o. At the bottom of this room is placed a cast-iron 
plate in which a hole is bored, and fitted with a conical plug, j, connected with a rod, 
H, 80 as to admit of being shut and opened for the purpose of tapping sulphur into 
the cauldron, l, whence it is ladled over into the moulds placed in m. n is a box for 
the roll sulphur when it has become cold. 

BoDSBiiihiir. If it is iutended to prepare roll-sulphur, the mode of proceeding is the 
following: — ^Each of the cylinders is filled with crude sulphur, the lids firmly 
fastened, and the joints luted. Heat is at first applied to only one of the cylinders, 
and not until half of its qpntents are distilled off is the second cylinder heated. 
Gradually the heat at d increases to such an extent as to melt the crude sulphur; by 
this fusion the heavier earthy impurities settle down, while any moisture present is 
driven off. When the distillation of the contents of the cylinder first heated is 
finished, that cylinder is filled with liquid sulphur from n by means of the tube f. 
The quantity of sulphur treated iu twenty-four hours yields 1800 kilos, pure material 
collected in g. The temperature of this room being 112°, the sulphur is there kept 
in a molten state, and as soon as a sufficient quantity has collected at the Jbottom, it 
IB tapped off into l, and cast in the moulds. When it is desired to prepare flowers 

lowenof sniphnr. of sulphur, the modo of operation is the same, but the temperature of 
should be kept at or rather below 110°. This is effected by making the distillation 
intermpted instead of continuous, so that in twenty-four hours there are only two 
distillations of 150 kilos, each. As soon as a sufficient quantity of flowers of sulphur 
has been condensed in the room o, the door of the room is opened and the sulphur 
removed. 

Dujardin improved upon this apparatus in 1854. By this process of distillation 
ofsulphur a lossof 11 to 20 per cent is incurred, partly due to combustion of a 
portion of the sulphur. The residue left in the cylinders and vessel d is known as 
Bulphur-slag. The ordinary flowers of sulphur of commerce always contain some 
sulphuric and sulphurous acids, which can be removed by carefully washing with 
water. Sulphur so treated and gently dried is known in pharmacy as washed flowers 
ofsulphur, Flares sulphuris loti. 

''"TJJS'wiw?^^" Where fuel and labour are cheap, and a good quality of iron or 

other pyrites is found in abundance, sulphur may be prepared by the following 

process : — 

I. From iron pyrites, FeSa. As this mineral consists in 100 parts of 467 of iron 

^^ 53*3 of sulphur, it is clear that if half of the latter be removed by distillation, 

there will be left a compound of iron and sulphur yielding green copperas after 

oxidation. Accordingly iron pyrites might by distillation lose 2665 parts of sulphur, 

and the residue still be fit for making green copperas ; but if this quantity were to be 

driven off in practice, the temperature would require to be raised so high as to melt 

the remaining monosulphuret and lead to the destruction of the fire-clay cylinders. 

The quantity of sulphur actually distilled off on the large scale is only 13 to 14 per 

*5ent, leaving a pulverulent residue which does not attack the fixe-clay cylinders. 

The process thus briefly, outlined is carried on in the following manner : — The pyrites 
18 put into conical fire-clay vessels, a a. Fig. gi, placed in a somewhat slanting position in 
the furnace ; the lowe^ and narrower portion of these vessels is fitted with a perforated 
diaphragm preventing any pyrites falling down 6, while the volatilised or fluid sulphur 
can pass readily through the holes into a receiver, c, filled with water. After the vepsels 
AA have been filled with pyrites, the fire is kindled and the distiUatioii set in progreKs. 
The sulphur collected in the receiver has a grey-green colour, and is purified by being 
re-molted, after which it is sent into the market in coarsely broken up lumps. In order to 



198 CHE3IICAL TECHNOLOGY. 

free tbJB kind e( sulphur from sulphiiret of arsemo, it IB Hnbmitteil to distiUation, the 
reaidae being used in veterinary practice. Ilie dark colour of the aulpbnr obtained 
from pjrites is dne to an adnuitoie of thalUoni far more than to the preeeuee of 
Mr. W. Crookee found i 







sulpbnr obtained from Spanish pyriteB u 
much KB o'2g per cent of thallinm. 
PifcantisnofBiiipbiubT »■ Sulphur may b« 
BouUDf CDfpu ptium. obtained by the roMt- 
ing ol copper pyritei, and in this nj 
beoomea a by-pcodnot of emelting copper 
oree. Formerly this operation was earned 
on in peooliarly conBtrucled furnaces in 
the copper-smelting irorke of the Loirer 
Hortz, Germany ; at the present time 
golpbiu' from this sonrca ie only obtained 
at Agordo in Italy, Wicklow in Ireland, 
and at Uuhlbacb, Salzburg, Austria. 
sgp^^^^Jjij^^^jj' 3, Since Laminj'B 
'luiiiiiactiire. miilnre baa been em- 
ployed in purifying eoal-gaa, flolphni bia 
to Bome eitent been obtained ae a by. 

■ r^^^^^K . prodnct. Lamtng'a miiture Ib bydnttd, 

' ^Ij^H^Bi or any soft porous peioiide of iron miied 

^ — .' ■ '■'^''^I'lriii- 1 JK nitb aawdnst ; andin thiB miiture Bulphnr 

may ooeumulate to upwards of 40 per cent 
jFeiOj + HjS-aPeO + HiO + S). Accord- 
ing to Hill's patent the anlphnret of iron 
is calcined to obtain BOlphnronB add. 
which is employed in the preparation ol 
Bolphuric acid. 

sijpiiDriromHiidiWBiu. 4. 'WehaToalietdj 
Been, while treating of the mano&ctnre of 
soda {ride p. 185) that several procesMi 
duetoMM.Schaffner.Guckelborger.Mond, 
P. W. Hofmann, and others, are in nae for tho regeneration of sulphur from soda wisla; 
and that the quantities recuvered are not amall ma; be inferred b'om the fact that tho 
Anstrian Association for chemical and metallurgical products, under the management of 
M- SchaSner. at Ana^ig, produces annually 4;o,ooo kilos, of sulphnr in this manner. 

iht Boinll"n"A s"iRir''i"ii 5" O^^ii^" fi''»' made the obserTation that when one-third of 
H;iin>KD upnn siiirJjup>n'< '\c\i. BulphuTetted hydrogen is burned off, and the sulphurous acid 
produced conveyed with another one-third o( enlphnretted hydrogen into a leaden or bliek 
chamber, where moisCnre abounds, nearly all the sulphnr is regenerated : — 
Sulphnrong acid. BOi I ■ , . j Sulphnr, 33. 

Sulphuretted by.lrogen,jH,S( ^^'^ 1 Water, iH,0. 
By this reaction, by which, however, nearly half the snlphur is lost in the formation of 
peutatbionic acid, it boa been frequently attempted to obtain snlphur from gypanm, 
heavy spar, and soda wnate. The process is briefly as follows : — -For instance, heavy spar, 
native sulphate of baryta, is reduced to sulphuret of barinm, which is treated with hydro- 
chloric acid, sulphnrclted hydrogen and chloride of barium of ooorse being fomted. 
Either aportionof the gas iabnrnt and to the products of the combuatioti,8nlphuionB odd 
and water, the rest of the gaa added, or the sulphuretted hydrogen is conveyed into water 
to which Bnlphiirons acid is simultaneouBly conveyed from the combustion or roaBting o( 
iron pyrites, Mr. Oosaage long since proved that, by conveying snlpburetted hydrogen inW 
chloride of iron, the sulphnr of the gas ia deposited. Snipbnr may be obtained hj 
a aimilar reaction as a by-product of the manufacture of iodine and pctoeaa aalta from 
kelp. At Paterxon's iodine factory at Glasgow, 2000 cwts. of thie anlphnr ore obtained 
annually. According to E. Kopp the incomplete combnation of sulphoietted hydrogen 
yields Bolphur economically (Hi3-HO = HiO-hS). 
luS'.m'SVllh.Uii.lM ^' ^^^^ sulphuTona acid gas ia conveyed over red-hot chorooal, 
A«dDiiCbuD«i." the latter ia converted into carbonic acid, white snlphur ia set free. 
By this reaction the aniphllrons acid from the roasting of zinc orea (black-jack) is con- 
verted into sulphnr in large quantities at Burbeck, near Essen, Prussia. 
Br uaUis "I snipbuRtuj 7' When snlphnretted hydrogen is paased throngh red-hot tabes, 
Ujiiri«,^u. it ij decomposed ; but thia reaction U not industrially applicaUe to 

tho preparation o( snlphur. 



SULPHUR. 199 

piepertiamndUiM The yellow ooloux of sulphur is generally known ; at loo"* this colour 
ofsniphur. deepens and nearly disappears. At —50°, sulphur is very brittle and 
readily pnlverised, becoming by the friction, especially in warm and dry weather, so highly 
electric as to cause the particles to adhere strongly to each other. The sp. gr. of this 
element varies from 1*98 to 2-06. It melts at 115'', forming a thin yellow liquid, which, at 
160*", becomes thick and assumes an orange-yellow colour ; when heated to 220°, sulphur 
is a tough, red, semi-solid ; between 240° and 260° the colour becomes red-brown, but 
being heated aboye 340°, the sulphur is again somewhat fluid, and at last boils at 420° without 
baring lost its deep colour, which also characterises the vapours. When sulphur heated 
to 230° is suddenly poured into cold water, it remains soft and so plastic that it may be 
advantageously employed for obtaining impressions of medals, woodcuts, and engraved 
plates, these impressions as the sulphur again hardens after a few days serving as 
moulds. On being heated in contact with air, sulphur bums, forming sulphurous acid. 
It Lb insoluble in water, very slightly soluble in absolute alcohol and ether, and rather 
more soluble in warm fixed and volatile oils, forming the so-called sidphur balsam. The 
best solvents for sulphur are — sulphide of carbon, coal-tar oil, benzol, and chloride of 
Bolphur.* It also dissolves in boiling solutions of caustic soda or potassa, in hot solutions 
of Bulphurets of calcium and potassium, in the solutions of certain sulpho-salts ; for 
instance, the compound Sb2S3,Na2S, which is converted into Sb2S5,Na2S, and in solutions 
of aUudine sulphites, converted thereby into hyposulphites. 

Sulphur is used in the manufacture of sulphuric acid, gunpowder, fireworks, for sulphuring 
bops and vines as a preservative against some diseases of these plants ; the quantity of sulphur 
lued for the purpose of sulphuring vines in France, Spain, and Italy, amounted, in 1863, 
to 850,000 owts. of Sicilian sulphur, being about from 20 to 25 .per cent of the entire 
production. It is further employed in the manufacture of sulphurous acid, sulphites, and 
hyposulphites, sulphide of carbon, cinnabar, mosaic gold or bisulphide of tin, and other 
metallic sulphurets, ultramarine, various Cements, and for vulcanising and ebonising 
india-rubber and gutta-percha. 

The greater part of the total sulphur production of Europe comes from Sicily, whence, 
in 1868, 4,052,000 cwts., in value about £1,500,000, were exported. The total sulphur 
production of Europe in 1870 amounted to 7,012,500 cwts., but in this quantity the 
solphur recovered from soda waste is not included. 

SULPHUROCS AND HyPOSULPHUROUS AcIDS. 

M»inirouAeiiL Thls acid (SO^, or hydrated H2SO3) may be obtained — 

a. By oxidation of sulphur ; 

b. "By reduction of sulphuric acid ; 

e. By a combination of the processes a and b. 
The preparation of sulphurous acid by tlie oxidation of sulphur may be — a. By 
burning brimstone in the air ; /3. By roa.sting or calcining iron and copi)er pyrites, or 
the product of Laming's mixture from the purifiers of gas-works ; y. By igniting a 
mixture of manganese and sulphur. The preparation of sulphurous acid by roasting sul- 
phurets, when coupled with metallurgical operations, is, especially since Gerstenhofer's 
fomace has been more generally introduced, the most advantageous plan of obtaining 
this acid, and also where the acid is required for the manufacture of sulphuric acid. 
When, however, sulphurous acid is reqiiiied for the purpose of preserving food, 
aad as a raw material in the preparation of wines, hops, &c., it should not be 

« 

* According to Cossa (1868)— 

100 parts of sulphide of carbon dissolve at 
100 ,, ,, ,, ,, 

^00 ,, ,, ,, „ 

100 „ benzol „ „ 



»i »» It ji 



100 

100 „ ether „ „ 

100 „ chloroform „ „ 



, , «>UU.UAV> , , 



15 0* 


31*15 parts of sulphur. 


38*0° 


94*57 » 


48-5° 


146-21 „ „ 


260' 


096 „ 


yi-o" 


4*37 M 


ZS'S" 


0-97 „ 


22-0* 


1*20 ,, „ 


1300"* 


85-27 M 



100 „ aniline 

According to Pelouze — 

100 parts of coal-tar oil, sp. gr. 0*88, dissolve, at 130-0 ', 43-0 parts of sulphur. 



Sulphuric acid, 2H2SO4 
Copper, Cu 



200 CHEMICAL TECHNOLOGY. 

made from pyrites, but from sulphur, as, when obtained from pyritea, it is always 
mixed with arsenious acid. The Laming's mixture saturated with sulphur from 
gafl- works is largely used in the preparation of sulphurous acid in sulphniic acid 
works in and around London. The ignition in close vessels of metallic oxides and 
sulphur can only be advantageously used for the preparation of sulphurous add 
under certain conditions. The oxides chiefly used for this purpose are those of 
manganese and copper ; the former yields, according to the weight of the materials 
employed, either only half the weight of the sulphur in the shape of stilphuroiis acid, 
or the whole of the sulphur may be converted into acid. Sulphurous acid is some- 
times prepared by heating a mixture of sulphate of iron and sulphur — 

(FeS04-h2S=FeS+2S02). 
When sulphate of zinc is calcined it yields sulphurous acid and oxygen — 

(ZnS04=: SOa+O+ZnO) . 
Kieserite (MgS04+H20), mixed with charcoal 3delds all its sulphuric add as 
sulphurous acid. 

The preparation of sulphurous add by the reduction of sulphuric acid is very frequent ; 
sulphuric add is reduced by being strongly heated in contact with certain metals ; for 
instance, copper, mercury, and silver : — 

[Sulphate of copper, GUSO4, 
yield • Sulphurous add, SO2, 
.(Water, 2HaO. 
A small quantity of sulphuret of copper is also formed. The dilution of sulpharous 
add with carbonic acid and carbonic oxide does not interfere with its intended use. 
Sulphuric add is decomposed and reduced by being boiled with charcoal-dust, sawdust, 
wood-shavings, &c. 

[ Sulphurous add, 2SO2. 
- yield ■ Carbonic acid, CO2. 
(Water, 2HaO. 
This mode of operation may be made continuous by keeping up a supply of sulphnrie 
acid and sawdust in the glass retort, as the decomposition of both these substances is 
complete, yielding sulphurous acid, water, and carbonic add. When the vapours of 
sulphuric acid are passed through red-hot glass or porceladn tubes, the result is the 
formation of sulphurous acid, oxygen, and water (HaS04 » SOa + + H2O) . The redaction 
and decomposition of sulphuric acid by the aid of sulphur may be viewed as a combined 
process of preparing sulphurous acid by oxidation and reduction : — 

Sulphuric add, 2H2SO4) .^j f Sulphurous add, 3SO21 
Sulphur, S ; y^®^^ 1 Water, 2H2O. 

In practice, however, this operation is very difficult, owing to the fact that, long before 
the reaction begins to take place, the sulphur is molten, while as soon as the reaction sets 
in it becomes very tumultuous, and with the sulphurous acid gas vapours of sulphur are 
carried over, which solidify and obstruct the passage. At the ordinary temperature and 
pressure of the atmosphere, sulphurous add is a gas having a pungent odour, and a 
sp. gr.s=2'2i. This gas dissolves readily and in large quantity in water, i volume 
absorbing at 18^, 44 volumes of gas. It is even more soluble in alcohoL When water is 
present sdl the higher oxides of nitrogen give up some of their oxygen to the sulphurooB 
add, converting it into sulphuric acid, the oxides forming deutoxide of nitrogen. 
Chlorine also converts moist sulphurous acid gas into sulphuric add, and siimltf 
results obtain with iodine. The mixture of sulphurous add and sulphurekted hydrogen 
causes their mutual decomposition, water being formed, and sulphur deposited. Sulphu- 
rous acid is chiefly employed in preparing sulphuric acid, in the manufacture of paper, M 
so-called antichlorine, in the preparation of madder by E. Eopp's process, the prepara- 
tion of hyposulphite of soda, and the manufacture of sulphate of ammonia from 
lant (stale urine). Sulphurous add is employed according to Laminne's patent for the 
purpose of decomposing alum-shale in the manufacture of alum. 

It is further employed in some metallurgical processes, for preserving food, bleaching 
syrups, silk, wool, sponges, feathers, glue, isinglass, and other animal substances, whieh 
do not admit of being treated with chlorine, and for bleaching straw hats, willow 
and wicker baskets, gum arabic, &o. The bleaching property of sulphurous add may be 
considered as due to two entirely different causes; in some instances the pigm^it is only 



Sulphuric acid, 2H2SO4 
Charcoal, C 



SULPHUR, 20I 

masked, not deetroyed, as snlphnrons add enters with some pigments into a oolonrless 
eombination ; in other instances, howeyer, a real decomposition of the pigment takes 
place. The former condition obtains with most of the bine and red flowers and froits ; a 
red rose bleached by snlphnrons acid has its colonr restored by immersion in very dilnte 
solpbnrio acid, ^e pigments of yellow flowers are not affected by solphnrons acid ; 
it also does not at first act npon indigo and carmine and the yellow colonr of raw silk, bat 
by the combined and continned action of this acid and direct snnlight, the oxygen of the 
acid acts as ozone and determines the bleaching. The avidity of snlphnrons acid for 
oigrgen may be utilised in extingnishing fires, especially in the case of the soot of 
chimneys catching fire, which may be very readily subdued by throwing a few ounces 
of flowers of sulphur into the fireplace or stove. 

soipfaite of LioM. Neutral sulphite of lime (SGa203+H20), containing in roo parts 
41 parts of sulphurous acid, deserves attention as a cheap, commodious, and very efficient 
substance for the development of sulphurous acid, the gas being readily set free by the 
action of hydrochloric or sulphuric acid. Bisulphites of lime and soda, the former 
in solution, theiatter as a solid dry powder, are largely produced in some of the beet-root 
sugar manufacturing countries. 

Hypomipiiita of Soda. This Salt (SaNaaOs+sHaO) is largely used in photography, in 
metallnrgy, as a mordant in calico-printing, and as antichlor in paper-making. 
Hyposulphite of soda may he prepared by sevend methods. According to Anthon, 4 
parts of calcined sulphate of soda are mixed with i to li parts of charcoal powder, 
the mixture is moistened and placed in an iron crucible, and calcined at red heat for 
6 to 10 hours ; the cooled mass broken into small lumps is again moistened with 
water and then exposed to the action of sulphurous acid ; the resulting product iff 
dissolved in water, filtered, concentrated by evaporation, and left to crystallise. 
AccardiDg to £. Kemp's method, carried out industrially by Max SchajQ&ier at Aussig,. 
hyposulphite of lime is first prepared by causing stilphurous acid to act upon 
sulphuret of calcium (soda waste). The lixiviated mass is treated with sulphate of 
soda, the result being the formation of soluble hyposulphite of soda and practically 
insoluble sulphate of lime. Very recently the pentathionic acid (SsOj.HaO), 
obtained in large quantity as a by-product of the reaction between stilphuretted 
hydrogen and sulphurous acid in preparing sulphur, has been converted into hypo- 
sulphite of soda by boiling with soda lye (2S503,HaO+3HaO=5SaOa,HaO). 

As hyposulphite of soda possesses the property of readily forming with oxide of silver 
a soluble double salt, hence dissolving easily such insoluble compounds as chloride and 
iodide of silver, it is employed in photography and in the hydrometallurgical extraction of 
silver. Being a solvent for iodine it is used in chemistry for purposes of volumetrical 
analysee. A mixed solution of sulphite and hyposulphite of soda dissolves malachite and 
blue copper ore, forming hyposulphite of protoxide of copper and sodium. Stromeyer 
has applied this reaction to the hydrometallurgical extraction of copper. Hyposulphite 
of soda is also used for preparing antimonial cinnabar and aniline green ; the hyposul- 
phites of lead and copper have been proposed as a paste for lucifer matches. The 
property possessed by hyposulphite of soda of fusing at a comparatively low temperature 
in its water of crystallisation, and of readily solidifying on cooling, has been utilised by 
Fleck, in the seiding of glass tubes containing explosive compounds to be used under 
water in torpedoes. The enormous consumption of hyposulphite of soda may be readily 
inferred from the fact that the chemical factory near Aix-la-Ohapelle produces 2000 cwts., 
and the factoiy at Aussig, Austria, 6000 cwts. of this salt annually. 

Manufacture of Sulphuiuo Acid. 

Sulphuric acid, HaS04, consists in 100 parts of 81 parts of anhydrous sulphuric 

add and 18-5 parts of water, 
soipbozk Add. There are in the trade two distinct varieties of this acid : — 
a. Fuming, or Nordhausen sulphuric acid (oil of vitriol), obtained by distillation 

from sulphate of iron, bisulphate of soda, sulphate of peroxide of iron, or by the 

decomposition of sulphate of soda by means of boric acid in the preparation of 

borax. 



ao2 CHEMICAL TECHNOLOOY. 

b. Ordinarr sulphuric add, known abrotkd as l^ngli»)i eulphoric acid, prepared by 
the osidadon of sulphurous acid by moons <^ nitrous acid, or, very rarely, separated 
from native sulphates. ' 

FuiDini bdwikid ixid. At a red heat all sulphates, except those of the alkalies and 
alkaline earths, are decomposed, and therefore may be employed in the preparation 
of filming sulphuric acid; but on account of its cheapness sulphate of iron is pre- 
ferred. This salt, on eitposure to red heat, is decomposed into anhydrous snlphunc 
acid and eolphucons acid :— 

[Peroxide of iron. Fe,Oj, 
Sulphate of iron, 2E'eS04, yields J Snlphuric acid. SOj. 
(sulphurous acid, SO,. 

Anhydrous sulphuric acid would indeed be obtained from sulphate of iron if it 
were possible to procure the salt perfectly auhydioos. but as this cannot be dooe 
without decomposition, some water is always retained, the result being the compound 
Imown as fuming sulphuric acid, th&t is t^) say, a mixture of anhydrous and ordinary 
add (H1SO4), the former in very variable quaotitira. 

Fnming Bnlphnrio add ia prepared on the large scale in the following manner;— Th« 
solution of Buipfaate of iron ia flrst evaporated to drynesB, and dried in open veuali 
ai much as possible. The dry saline mass, vitriol'Stone it is termed in Oermany. ia next 
transferred to fire-clay flasks, 1, Fig. 93, placed in a g^ey furnace, the neoks paenng 
throngh the wall ol the fomaee, and being properly secored to the neclis of the recaiveis, 
BB. bito eaoh of the flasks 2'; lbs. of vitnol-stone are pnt ; on the Qrst apphoation of 
heat only snlphuioas add and weak bydrated stUphuria add oome over, and are nmaUy 




allowed to escape, the receivers not being securely luted antil white yspomfi of mnhydioDs 
aolphurio acid are seen- Into each of the receiving flasks 30 grms.ol water are poured, uid 
the distillBtian continued tor 24 to 36 hour^. The retort flasks are then agdn filled with 
raw material, and the operation repeated foui times before the oil of vitriol ia deooed 



SULPHUR. , 203 

snffidentlj strong. The residae in the retorts is red oxide fperoxide) of iron, still 
retaining some sulphuric aoid. The quantity of fuming aoid obtained amounts to 
45 to 50 per eent of the weight of the dehydrated sulphate of iron employed; at 
Davidsthal, in Bohemia, 14 cwts. of Titriol-stone yield in thirty-siz hours, 54 owts. of 
fnming sulphuric acid. 

It is preferable, however, to use sulphate of peroxide of iron instead of the dried 
protosulphate ; the sulphate of the peroxide can be readily prepared by means of the 
peroxide and ordinary sulphuric acid. Frequently the fuming acid is prepared by passing 
anhydrous sulphuric aoid, obtained by calcining perfectly dehydrated protosulphate of 
iron, or, better still, the persulphate of iron, into ordinary oil of Titriol. Fuming 
sulphuric aoid is now and then prepared from the bisulphate of soda left after the 
preparation of nitric acid from Ghili-Baltpetre. In France calcined sidphate of soda and 
boraeio acid are intimately mixed and calcined, and the yapours of anhydrous sulphuric 
add disengaged are absorbed by strong ordinary sulphuric aoid. Fuming sulphuric acid 
la an oily liquid of a brown-yellow or deep brown colour ; it emits the pungent smell of 
sulphurous add, fumes on being exposed to air, and yields on being heated vapours of 
auhydrio sulphuric aoid; the sp. gr. varies from 1*86 to 1*92. It is industrially hardly 
Qsea for any other purpose than dissolving indigo, i part of the latter requiring for its 
solution 4 parts of fuming and 8 parts of ordinary siUphurio add. 

oi^grwB^tob xhe concentrated sulphuric acid (HaS04), oil of vitriol of 

commerce, consists in 100 parts of 81*5 parts of anhydrous acid and 18*5 of water. 

The prepartion of this acid on the large scale in leaden chambers dates from the 

year 1746, when Dr. Roebuck, of Birmingham, erected the first leaden chamber at 

Prestonpans, near Edinburgh. 

The rationale of the manufacture of sulphuric acid by the chamber process, in which 
sulphurous acid, nitric or nitrous acid, and water are employed, is, according to the latest 
researchee of B. Weber (1866) and Winkler (1867), the following: — The oxidation of ihe 
solphurouB aoid to sulphuric acid takes place in the leaden chambers under the influence 
of the vapour of water at the expense of the oxygen of the nitrous acid, which is con- 
verted into deutoxide of nitrogen. It is necessary, however, that the nitrous add be &rBt 
absorbed in plenty of water, which takes up the free nitrous aoid, and decomposes the 
bypomtric acid, a process greatly promoted by the presence in the chamber of sulphurous 
acid purposely introduced. The water, usually in the form of steam, because practical 
experience proves that a certain elevation of temperature is required, acts in this process 
as ia others wherein sulphurous acid efifects reduction. By the presence of atmospheric 
air in the chamber the deutoxide of nitrogen is oxidised into hyp^tric or nitrous add, 
a&d this aoid again decomposed by sulphurous acid ; if the conditions are favourable 
the process is continuous. It occasionally happens that the nitrous add in contact with 
sulphurous acid and excess of water forms protoxide of nitrogen, of course causing a loss 
of the efficient oxides of the nitrogen. The formation of the so-called chamber crystals, 
consisting according to B. Weber of (H2S04+Na03,S03) only takes place when the 
process is not well managed, and is chiefly due to want of water. 

^*TiSptotei3£' *** Although the use of leaden chambers is due to an Englishman, 
the present mode of manufacturing sulphuric acid was invented (1774) by a calico 
printer at Bouen, and improved by the celebrated Ghaptal. The apparatus 
consists essentially of four parts, viz. — i. A furnace, f, Fig. 93, where, by the com- 
bustion of sulphur or pyrites, sulphurous acid is formed ; the sulphurous acid, 
carrying with it the nitrous vapours prepared in the sulphur burner by means of a 
peculiar contrivance, escapes from the furnace through the tube, x.* 2. An apparatus 
filled with coke through which mixed sulphuric and nitric acids percolate. 3. A 
number of leaden chambers, a, a', and a", wherein, under the influence of high 
pressure steam, the sulphuric acid is formed. 4. A large apparatus, k, known as 

* In order to convert z kilo, of sulphur into sulphuric acid, the following quantities of 
air are required: — 

When the sulphur is present in free state, 5275 litres of air, containing 4220 litres 

of nitrogan. 
When the sulphur is present as pyrites, 6595 litres of air, containing 5276 litres of 
nitrogen. 



204 CHEMICAL TBCBNOLOGY. 

Gay-Lnssac's condenseF, Med with coke, through which Bulpfauric acid x>f 66° B. 

(=i'84Bp. gr.) percolates, the ^m being to take up the nitric and hjponitric ocida, not 
the deutozide of nitrogea as was believed before Winkler elacidated this point. 




from the gases which flow into the last chamber previously to being discharged. 
The fomsce or burner, as it is technicallj caUed (see Fig. 94), is boUt of bricks : at a 
height of So centims. from the floor a stout caat.iron plate is placed so as to have 
a slight inclination towards the 
^*- 94- front. The walls are also covered 

with heavf cast-iron plates. In 
front of the burner are three or six 
large openings, p. p*. p", which can 
be closed by iron doors fitted with 
wooden handlea. On the bed or 
bottom plate three iron rails or 
ledges, each 10 centims, high, are 
placed to divide the bottom of the 
furnace into three or six compart- 
ments. At H, h', and a" are the 
holes for the necessary supply of 
air. On the top plate is firmly 
fixed the tube, t. which conveys 
the gases generated in the burner to the leaden chamber of eacli section or com- 
partment. The burner is charged with abont 50 kilos, of Riitpbur; this is kindled 
at the top, the draught of air throngb h. h'. and h" being ijt(i regulated as to GMIbc 

/ 




SULPHUR. 



205 



the snlphnr to be burnt off without becoming sublimed, for if any sulphur were 
volatilised it would cause the sulphuric acid to be turbid and mOky.* Not only 
does the burner supply sulphurous acid, but also the nitric acid or nitrous 
▼apours required in the leaden chamber; these are generated from a mixture of 
nitrate of soda and sulphuric acid at 52° B. ( = 1-56 sp. gr.) placed in the cast-iron 
pot, N, which when filled is placed on the burning sulphur. 

The construction and arrangement of the denitrificateur is shown in Fig 95. At a 
is placed an iron grating covered with thick perforated sheet lead ; the vapours and 
gases generated in the burner pass through m into the 
space immediately below o, upon which a column of ^^^' 95' 

coke is placed, and kept saturated with sulphuric 
add strongly charged with nitric acid, obtarued by the 
condensation of the gases from the last chamber. This 
add is forced by means of compressed air from the 
vessel T into the Maiiotte bottle, v, and passes thence 
through T into h, thence by t' to the coke, over which 
it is delivered in fine jets by means of a perforated 
plate fitted to the lower part of the cover a. The acid 
coming in contact with the warm gases from the 
chamber yields to them, in the state of vapour, all the 
nitrous compounds dissolved in the sulphuric acid, and 
charged with these vapours the gases pass through 
m. Fig. 93, into the leaden chambers. The denitrified 
solphuric add runs off through the tube t into a reservoir. 

The formation of sulphuric acid takes place in the leaden chambers or chamber. In many 
eftB68, especially abroad, only one large chamber is worked, which is then, as shown in Fig. 93, 
divided by the leaden plates a a', technically termed curtains, into three or more compart- 
inents, these curtains reaching to the bottom into the acid ooUeoted there. If several 
chambers are worked, communication is maintained by means of leaden tubes. The 
tubes, vv' v'\ convey steam to the chambers. The chambers are not nsnally aJl of the 
same size, one being considerably larger than the others ; in the largest most of the add is 
generated. The gases and vapours contained in the last chamber being almost free from 
solphurous add, and consisting mainly of atmospheric air and nitrous vapours, are 
conveyed through t' to the leaden reservoir, n, where the last traces of sulphuric acid are 
deposited. The action of Gay-Lussac^s condenser, k, is based upon the fact that concen- 
trated sulphuric add absorbs and combines vrith nitrous acid. The apparatus consists 
esBentially of a column of coke 8 to 10 metres in height, through which strong sul- 
phnrie add, 62** or 64° B., percolates, the flow being regulated by the apparatus shown in 
Fig. 95. The acid saturated vrith nitrous acid is conveyed by the tubes hh into a 
reservoir, o, from which it is again forced by means of the monte-add to the Mariotte 
flask, M. By the tube t'", the gases are conveyed to the chimney stalk of the works. As 
regards the cubic oapadty of the leaden chambers, each 20 kilos, of sulphur consumed in 
twenty-four hours requires 30 cubic metres (about 100 cubic feet) capacity; as this 




* Aecording to theory, i molecule of sulphur requires only 3 molecules of oxygen, viz., 
2 to form sulphurous acid, and i to convert the latter into sulphuric add ; that is to 
say, I kilo, of sulphur requires 1500 grms. =: 1055 litres of oxygen s 5275 litres of air, 
in whidi 4220 litres of nitrogen are contained. In order to regulate this supply of air 
numy contrivances have been adopted, among them the anemometer invented by Combes ; 
this is fitted to the sulphur burner by means of a tube, through which the air supplied 
has to pass. In England reliance is placed upon the skill of the workmen who regulate 
the draught, as it is termed, dmply by the slides in the doors of the burners. 

The air discharged from ^e chambers should not contain more than 2 to 3 per cent of 
oxy^n. By careful management and with good apparatus the maker may succeed in 
obtaining from 100 kilos, of sulphur 306 kilos, of strong acid at 1*84 sp. gr. ; but the 
nsnal quantity from 100 kilos, of sulphur is seldom more than 280 to 290 kilos. 



ao6 CHEMICAL TECHN0L007. 

qiuntit7 of nilphar oorregponds to Co kilos, of hydisted snlphario add, a ebunW el 
the oapacit; meatioDed yields 1-5 kiloa. ol snlphnric acid p«r boor. One btrndied paiU 
of Bolphnr require from 6 to 8 parte of nitrate of soda, bat if pyrites is employed tliis 
quantity ia often inoTeased. Also when pyrites is bnmt larger ohambers are used. Latdf 
Qay-Lnasao's condenser has, in many oases, fallen into diBose, on acoonnt of the low pdee 
of Chili- saltpetre, and the expense of keeping the apparatus in worlung order. 

"""^ ^bJSJS^ISF'"'" InBteftd of sulphur native minerals contaimsg that 
element are frequently em^jed for the preparation of eulphurons acid. Among 
these minerals, iron pyrites, biaulphuret of iron. FeSj, containing 53'5 per cent 
of sulphur, is the most largely nsed. The pyritea are calcined 
_ ° ' 0"' in peculiarly constructed kilns, built with fire-bara, the 

spaces between which may be a4iaated by means of a key, 
and the admission of the air required for combostion regn- 
' ' ' lated with great nicety. The best pyrites oven known on 

the Continent is Gerstenhofei's, invented in 1864 ; the prin- 
ciple of this oven, Fig. 0, is lliat the pyrites is made to 
foU throngh anA meet the colomn of heated air sup- 
porting the combustion. In order to prolong the faU of 
the powdered pyrit«s, terraces or banks are built at intervals 
in the shafts. The broken np pyrites falls through the 
funnels a, provided with grooved rollers to pulverise it, on to 
: the bonks e, from one terrace, aa they are termed, to 

' another. Aa the fomace has been previously made red-hot. 

^ *" , ** " the sulphur ore ignitea and bums oS, aided by a moderate 

blast at c. The sulpburous acid formed ia discharged by the channels d into the 
sulphuric acid chambers, sometimes being first conveyed to an ante-room, where 
the dtist of the pyrites mechanically mixed witli the gases is deposited. 

The nitrous acid vapours are generated in a manner similar to that used lor 
sulphur. It will be seen that when pyrites is burnt, a far larger qoantity of air is 
required for the same quantity by weight of sulphur, amounting for i kilo, of pyrites 
to 6595 litres of air. Tliis excess is due to the oxidation of the ir<m of the pyrites. 
and the large bulk of nitrogen accompanying the excess of oxygen 

(iFeSa-t-iiO=4SOj+Fej03). 
According to Fortman, the gases from the pyrites burners also contain v^wiub of 
anhydrona snlphnric acid. Among the substances found in the Bne dnst of the 
pyrites burners are selenium and thallinm. Carstanjen found thallimu to the amomit 
of 3'5 per cent in the flue dnst of a snlphuiic acid works near Berlin, where > 
pyrites from Mezzen was used. 

. ts the acid formed in the leaden chamber* has acquired a sp. gr, ol 
= 104' !rwaddle,it is run off into a reservoir, and is freqaeutly used in that state 
atton for the purpose of preparing artificial manures or superphosphates u> 
alkali works, for the preparation of nitric acid, and for other purposes. This add ma; be 
freed from arseiUD by treating with sulphuretted hydrogen. 

'sSJSSrtS'idi This operation is effected in two different stages, Ike first being car- 
ried on in leaden pans, the latter in platinum or glass retorts. Weak and cold sul- 
phnric acid does not act powerfully on lead, but as soon as the add becomes conceo' 
trated, and especially when hot, the lead is dissolved, snlphnroos acid given off, aad 
snlphate of lead formed. Many snlphnric add makers concentralo their add b> 
60° B.=i7i sp. gr., in leaden pans; others, however, concentrate in leaden pans to 
55°B.= r59 sp.gr. only. 



SULPHVB. 



ao7 



otooDtiuiaatitHAaFiiB. The pRUB employed for this purpose are rectAngnlor in 
aliape, rather shallow, bnt long ajid wide, and supported bj iron plates, so that the 
fire sbftU not strike the bottom directly. The modes of placing and conatruction are 
shown in Fig. 97 : the acid is more stronglj heated in the pan, m, while in n it ia only 




affected by the hot air The depth of the acid m the pans vanes £rom 24 to 36 
centime. As soon ks the acid is of about 171 sp gr , it is furtlier deprived of its 
excess of water in plasa porcelain or platinnm vessels 

Fiiuniim Bttcrta. Platmnm retorts are now very frequently emplojed, although it is 
dear that these vessels, considering the high pnce of platmum, are expensive, 

Pio. 98. 




Messrs. Johnson, 
among the best makers of these 



the price depending upon the weight size i 
Mfttthey, and Co., Hatton Garden, London 1 
and other platinum apparatus. 

Fig. 9S is an enlarged view of the platinum retort, represented together with the 
leaden pans in Fig. 97. The hearth communicates with a. By means of the 



attains to 310" to 320", Btrong acid ci 



i e 



ao8 . CESmCAL TECHSOLOQY. 

Hfphon, X, the acid from » crji be transferred to b ; the longer leg of x dipping iolo a 
leaden veasel, which admits of being lowered to d by the aid of the pulley. The acid then 
runs from the spnut c iuto tlie chaimel d, and thence, through the funnel-tube, iolo 
the retort, b. The head, c, comraunicateH' by meaos of tabing. not shown in the cut, 
with a worm, where the water and very weak acid mechanically carried over with 
the steam are condeiiBed. When the temperature of the acid in the plalinnin Btill 
T, and is coudeneed in the worm. 

In order to withdraw the acid froni 
the Btill. when concentrated to 178 to 
i-So ( = 63° to 66°B.}, theBroant sjThon, 
F%. 99, ia Qscd. It iaauuleof pUtinnin: 
the enter leg has a length of sbonl 
5 metiCB, and is snnoanded by a ooppa 
tube 15 centime, wide by 36ceiitiiDB. long, 
which oan bo filled at a from the tank H 
(Bee Fig, 97) with cold water, the outlet 
for the hot water being at b. Id order 
to increase the Bnrfoce the main BjpkoD 
tnbe Ib divided into fonr narrower tobn. 
The Ryphon is filled with snlphuic 
acid by d and t after dosing the tap t. 
The very hot acid oools wflle floiriiig 
through the platinum tnbes, and is oollectad in jarE, k, a', a". 
"SSntS'iSt'" When glass retorts of good quality and sufficiently large size can be 
obtained at a cheap rate, they are very frequently employed, being placed to tbe 
number of ten or more (Fig. 100) in saod-baths. The retorts are connected Ja 

Via. 





earthenware balloons, in which the acid fames are condensed. 70 per cent of tbe 
strong snlphiuic acid sold in this country is concentrated in glass retorts. Verf 
recently cast-iron vessels have been used for concentrating sulphuric add, 
onumiuiodiiitsaiptiuie Many methods of pteparjng Bulpbnrio acid have been sn^erted, 
Add Humiutan. ),□( hitiierto noue have anywhere snperseded the prooesa genenUj 
adopted. For this reason it ig oecewiary to mention a few only of the reaotiona apeD 
which these methods are baaed. Hohner oiidiseB snlphnrooB add with chlorine, care being 
taken that steam is present at the time ;~ 

SnlphuronB acid, SOj 1 (o 1 u ■ a r, an 

1 T» ^ J - . t f Snli>hunc acid. H>SO>. 



SULPHUR. 



2og 



Per80z*8 method is baaed upon the following reactions : — i. Oxidation of stilphurons 
acid by means of nitric acid, the latter being heated to ioo° and dilated with fonr to six 
times its bnlk of water. 2. The yaponrs of hyponitric acid are again converted to nitric 
acid hy the oxygen of the air and steam. In this process the leaden chambers are replaced 
by a series of large stone- ware Woolfe's bottles. Although enormous quantities of gypsum 
are found native, all attempts to prepare sulphuric acid from this mineral on an industrial 
scale have failed. Gypsum is decomposed, by superheated steam and at red heat, into sul- 
phuric acid, oxygen, and sulphurous acid, leaving caustic lime in the retort. Shanks 
mixes gypsum with chloride of lead and water at about 60°. 

f Chloride of calcium, CaCla, 
■ yield 



Gypsum, CaS04-f2H20 
Chloride of lead, PbCl^ 



Sulphate of lead, PbS04, 
Water, 2H2O. 

The chloride of calcium solution having been withdrawn from the precipitate of 
sulphate of lead, the latter is heated with hydrochloric acid : — 

Sulphate of lead, PbS04 ) .^, , ( Chloiijie of lead, PbClj, 
Hydrochloric acid, 2CIH f ^^^^ I Sulphuric acid, H2SO4. 
PropertiM of Sulphuric Acid. The most highly concentrated sulphuric acid contains 18*46 per 
C€fnt of water; its formula is H2SO4; sp. gr. = 1*848. In a perfectly pure state it is a 
eolourlees Uquid, but commonly is more or less yellow or brown, owing to the presence of 
organic matter. It destroys many organic substances, leaving a carbonaceous residue. 
This sulphuric acid does not fume on exposure to air ; it is very hygroscopic, and when 
left exposed to air, gradually absorbs fifteen times its bulk of water. When mixed with 
water great heat is evolved. The boiling-point of the most highly concentrated acid is 338°. 
The following table gives the quantity of anhydrous sulphuric acid contained in 
sulphuric acid at 15*5° C. : — 



Hydrated 




Anhydro 


Sulphuric acid. ^^' ^'' 


acid. 


100 ] 


[•8485 


81-54 


99 3 


[•8475 


80*72 


98 1 


[•8460 


79*90 


97 3 


f-8439 


7909 


96 1 


[•8410 


78*28 


95 J 


[•8376 


77*40 


94 3 


[•8336 


7665 


93 3 


t'8290 


75-83 


92 ] 


[•8233 


75*02 


91 ] 


[-8179 


74*20 


90 ] 


C-8II5 


73*39 


89 1 


f8043 


72-57 


88 ] 


[•7962 


71*75 


87 ^ 


[•7870 


70*94 


86 ] 


^7774 


70*12 


85 ] 


17673 


69-31 


84 : 


17570 


68*49 


83 ^ 


[•7465 


6768 


82 1 


C7360 


66*86 


81 ] 


[•7245 


66*05 


80 : 


t*7I20 


65*23 


79 3 


c-6993 


64*42 


78 ] 


[*6870 


63*60 


77 ^ 


[•6750 


6278 



Hydrated q^ _ 
Sulphuric acid. "P' ^• 



76 

75 

74 

73 

72 

71 
70 

69 
68 
67 
66 

65 
64 

63 
62 

61 

60 

59 
58 

57 
56 
55 
54 
53 



•6630 
•6520 

•6415 
•6321 

■6204 

*6o90 

•5975 
*5868 

•5760 
•5648 
•5503 
•5390 
•5280 

•5170 
*5o66 

'4960 

*486o 

•4760 

*466o 

-4560 

*446o 

•4360 

4265 

•4170 



Anhydrous 
acid. 

61*97 

61-15 

. 60*34 

59*55 
58-71 

57*89 
57-08 
57*26 

55*45 
54*63 
53-82 

53 'oo 
52*18 

51-37 

5055 

49-74 
48*92 

48*11 

47*29 

46-58 

45*68 

44-85 
45-03 
43*22 



ComparatiTe degrees of Baum6 and Twaddle, with the corresponding sp. gr. :- 



Degrees Banm6. 
66 

63 
60 

57 
50 

45 
40 

35 
30 

25 



Degrees Twaddle. 
168 

154 
140 

130 
104 

88 

76 

62 

52 

42 



Sp.gr. 

1*84 
1*77 
1*70 
1*65 
1*52 

1*44 
1*38 

1*31 

1*26 

1*21 



aio CHEMICAL TECHNOLOOY. 

The Tender dsBiroiis of mura inforuiatioii aa to the specifio grBvities indicated bj 
Banmi'B hydrometerB is referred to the " Chemical News," toI. ixiv., p. 28, el teq. 

The oaeB of Bnlphuric acid are so Dnmereua that it voiild be im]>osiiible to meution all 
of them, sulphuric acid being to chemical induBtr; what iron is to the meohatiica], 
Bnlphuric acid is employed in prepaiing a great many other acids, among them nitrio. 
hyi^iwhloric, Bitlphtuoua, carbouic, tartaric, citric, phosphoric, ateoiic, oleic, and palmitic. 
Fnrther, snlphmic acid is nsed ia making superphosphates, soda, Bolpbate of ammonia, 
alum, anlphatea of copper and iron, in paraffin and petrolemn refining, silier refining, 
manufacture of garnncine, garanceoi, and other madder preparations, manufacture of 
glucose from starch, to di^BoWo indigo, dc. 



Sdlphide of Caruo^. 
sniiiiiida of cuboB. This compound, consisting in loo parts of 158 ports of carbon 
and 84-2 of gutphnr, formula CSj, was discovered in 1796 by Lampadius; at Frei- 
burg. It ia obtained by canainB the vapour of sulphur to pass over red-hot coals, or 
hy distilling an intimate mixture of native metallic sulphurcts with charcoal or coke. 
The largest quantity of sulphide of carbon is obtained, according to Sidot and 
W. Stein, at not too high a red heat, that is to say, at what is termed in gas-works 
orange-red heat. 

Sulphide of carbon is best manu&ctured by means of Peroucel's apparatus 
(Fig, ioi|. A is a fire-clay gas-retort, supported on the fire-clay block b ; e and k 




lire openings, one being that of a porcelain tube firmly cemented into the cover of >, 
serving fur the introduction of sulphur ; the other opening is for the introduction of 
pieces of coke, with which, before the operation commences, the retort is filled- 
The vapours of the sulphide of carbon pass through the tubes h and 1 into tbe 
vessel J, wherein p&rt of the sulphide iscondensed and flowsthronghK into the flask, t. 
filled with wat£r, thence through m into 0, finally being runoff by the tap. k. Any 
vapours not condensed in j pass Uirough p p into the' worm, t, the condensed sulphide 
being collected in s. The crude sulpliide of carbon is rectified by re.distilWion 
over zinc or over bichloride of mercury by means of steam or a water-bath. If the 
bichloride is employcil. the crude sulphide should remain in contact with the salt for 
at least twenty-four hours before re -distillation. With the apparatus described, the 
retort being 21 metres in heiglit and 03 metre in diameter, 2 cwts. of crude sulphide 



HYDROCHLORIC ACID. 2ii 

of carbon may be prepared in twelve hours. The quantity of sulphide resulting 
from a given weight of materials is always much less than the quantity theoretically 
obtainable ; this is, of course, partly due to an unavoidable loss of liquid, and probably 
to the formation of monosulphide of carbon (GS), a compound corresponding to 
carbonic oxide. Crude sulphide of carbon contains usually lo to 12 per cent of 
sulphur in solution, and also sulphuretted hydrogen. To purify the crude sulphide, 
bleaching-powder solution is added to the liquid in the retort, into which steam at 15 lbs. 
pressure is forced to effect the reaction between the chloride of lime and the impuri- 
ties present in the sulphide of carbon. Sulphide of ccu'bon is usually kept under 
water. When pure, sulphide of carbon is a colourless liquid, strongly refractive, 
exhibiting extremely bright colours when in the sunlight. Its odour somewhat 
resembles that of chloroform; the taste is aromatic. Its sp. gr. = 1*2684; the 
boiling-point is 46' 5^, consequently the liquid is very volatile at the ordinary tempe- 
rature of the air. 

caxboD. Sulphide of carbon does not combine with water or spirits of wine. It is not 
soluble in every proportion in water (see "Chemical News," vol. xxiv., p. 34) ; in ether 
and chloroform, however, it is freely soluble. Sulphide of carbon is an excellent 
solvent for resins, essential and fixed oils, caoutchouc, gutta-percha, camphor, 
sulphur, phosphorus, and iodine. It is highly inflammable, burning with a red-blue 
flame ; the products of complete combustion are sulphurous and carbonic acids. The 
vapour of sulphide of carbon with oxygen or air constitutes an explosive mixture ; 
the light given by a mixture of deutoxide of nitrogen and sulpliide of carbon is 
very intense, and has been employed in photography. To Mr. Fisher, of Birmingham, 
is due the honour of having first prepared sulpliide of carbon for industrial 
purposes. At the present day these purposes are very varied, but consist chiefly of 
the vulcanisation of caoutchouc, the extraction of fat from bones, and oils from oil 
seeds and olives, the extraction of sulphur from its concomitant rocks, and of fat 
from crude wool. Sulphide of carbon is also used in electro-plating to obtain by its 
addition to the silver-bath a bright and polished surface. It is highly valued for 
killing vermin in corn. 

chiozidA of soiphor. Chlorido of sulphuT (CI2S3), important only in its technical use 
for the vulcanising of caoutchouc, is an oily fluid, sp. gr. i'6o, of a brown colour, 
fuming on exposure to air. It boils at 144°. On being mixed with water it is 
decomposed, yielding sulphurous and hydrochloric acids, a very small quantity of 
sulphuric acid, and sulphur. Chloride of sulphur converts rape -seed oil into a mass 
resembling caoutchouc, and linseed oil into a varnish. Chloride of sulphur is 
prepared bypassing chlorine gas over sulphur heated to 125'' to 130° ; the product is 
rectified by distillation. - 

Hydrochloric Acid and Glauber's Salt, or Sulphate of Soda. 

Hydnehiotie Add. The Commercial article known as hydrochloric or muriatic acid, 
or spirits of salt, is, as has been explained in the manufacture of soda, a solution 
of the gas given off during the decomposition of common salt by sulphuric acid. 
In order to effect this condensation, the gas is conveyed to the coke columns, or in 
many instances is prepared and condensed by the aid of the apparatus shown in 
section in Figs. 102 and 103, and in plan in Fig. 104. This apparatus consists of 
several cast-iron cylinders, 17 metres long by 07 metre diameter, closed similarly 

p 2 



Ill CHEMICAL TECHNOLOGY. 

to gas retorts by lids luted with clay. One of the lide ie prorided with ui opening, 
o, into which is fitted the stoneware or leaden pipe, a. conveying the bydrochloTte 
acid to the condensing apparatus. The other, or posterior lid, is also provided with 
an opening, d, through which is passed the tnbe of a leaden funnel, bo that afi«i 
the retort u filled with salt, sulphuric acid may be poured in. The c 




the fnmace, in which two rotorts are usunUy plated, allows the flame of the fire tt 
o to play ronnd tho cylindt^rs before rencliing the flue leading to the chimney, r, 
B is an arch covering the furnace. The first stage of the operation is to fill each 
cylinder with 15a kilos, of salt or cliloride of potassium, in locahties where the latter 
is ahundant. The lids or covers are next luted on, and the fire kindled. Ihe 




required quantity of strong sulphuric acid is now poured into the retort, and tbo 
funnel having been withilrawn from d, the hole is closed by a clay plug. As eoon 
as the reaction is over, the 180 kilos, of sulphate of soda produced are removed, and 
the operation repeated. The condensation apparatus. Figs. 102 and 104, consistB oi 



GLAUBER'S SALT. 213 

rows of Woolfe'B bottles partlj filled with water, care being taken to plfice the first 
pair of these bottles in a tank of cold water. The condensation of the last portions 




of the hydrochloric acid gas is effected either by the aid of coke columns, or in 
leaden chambers, into which fine jets of cold wat«r nre injected on all aides. 

"'"''^ oi^rdiiidiiortd Crude commercial hydrochloric acid is commonly a yellow 
liquid, this colour being dae to chloride of iron. It hoa a caustic sour taste, and 
fumes on exposure to air. At 20° water is capable of absorbing 475 times its own 
bnlk of hydrochloric acid gas : a saturated solution contains 4285 per cent of 
gas, the sp. gr. being = I'zi. The following table shows the sp. gr. of hydrochloric 
add at Tarioos degress of concenlration. and the quantity of pure acid <reat 
gas) contained 8(70°: — 

Specific Degrees 

graTiQr. Banm£. ' 



Degrees 


Peroentage 


Specific 


Degrees 


Degrees 


PercentBgfi 


Twaddle. 


or acid. 


grsTity. 


Baum£. 


Twaddle. 


of acid. 


42 


4285 




10 


'45 


2o 


20 2O 


40 


4080 




09 


12 


18 


18 18 


38 


38S8 




08 


II 


16 


1616 


36 


3636 




07 


10 


14 


1414 


34 


34*34 




06 


9 


12 


1212 


3» 


3232 




05 


8 


10 


1010 


30 


3030 




04 


6 


8 


8-o8 


28 


2828 




03 


5 


6 


606 


26 


2626 




02 


3 


4 


404 


24 


24-24 




01 


2 


2 


2-02 



155 



Vmmit H^^mjdwk HydrocUoric acid is very largely employed in the manufacture 
of chlorine, sal. ammoniac, chloride of antimony, glue, pbosphoms, in the prepara. 
tion of carbonic acid for the manufacture of artificial mineral waters, in beet. root 
sugar works, bleach works, hydro-metallurgy, and alone or mixed with nitric acid 
for dissolving various metals. 

•uutwisiut. Sulphate of soda, or Glauber's salt, consists in 100 parts of 193 soda, 
247 anlphimc acid, and 56 water ; formula, NajSOj+ioHjO; anhydrous, NoaSO^. 
in too parts — soda, 436; sulphuric acid, 56'4. It is prepared as described under 
hydrochloric acid by decomposing common salt with sulphnric acid. It is also 
found native as Thenardite (Na,S04). Brogniartine or GlanberiU {NsiSOi+CaSO^I. 
and it occurs in sea-water and some mineral waters, as in those of Pijltna and 
Carlsbad. 



214 CHEMICAL TECHNOLOGY. 

Sulphate of scMla is indirectly obtained by yarioos processes, among which are — 

1. The doable decomposition of common salt and sulphate of magnesia or Ideserite from 
the mother-hquor of sea-water, or of salines when exposed to a low temperature either 
naturally in water or artificially by the assistance of Oarr^*s ice-making machine. 

2. Longmaid's process of roasting snlphnret of iron or copper with common salt. 3. Cal- 
cination of Ideserite or magnesian sulphate with common salt. 4. Kuhlmann's process, 
the calcination of sulphate of magnesia and nitrate of soda, hyponitric add and sulphate 
of soda being formed. 5. As a by-product of paraffin and petroleum refining. The 
sulphate of soda of the alkali works contains on an average 93 to 97 per cent of the pure 
salt, the remainder being chiefly chloride of sodium. 

usM of soiphate ^^^^ ^^ ^ extensively employed in the manufactures of soda, ultra- 
of Soda. marine, and glass. In the last case the sulphate is mixed with coal and 
silica, and calcined, its sulphuric acid being reduced to sulphurous acid, which is Tolatilised, 
while a silicate of soda is formed. Sulphate of soda when thus employed should be 
purified from all traces of iron by being dissolved in water, some lime added to the 
solution, and the clear liquid evaporated to dryness. Sulphate of soda is used in 
metallurgy in the treatment of some kinds of antimonial ores, the sulphuret of antimony 
found near Bouc and Septemes, France, &q. It is also employed in certain processes of 
wool-dyeing. 

BiBniphate of Soda. ThiB Salt (NaHS04) is obtained in large crystalB when i molecule 

of sulphate of soda and i molecule of sulphuric acid are dissolved in water and 

the solution left to evaporate slowly. One of the chief uses of the bisnlphate is in 

a mixture with abramn salt containing chloride of magnesium, employed for 

removing zinc from lead. As a by-product sulphate of soda is obtained in the 

manufacture of nitric acid from nitrate of soda and sulphuric acid, and by heating 

cryolite with sulphuric acid. 

Bleachino-Powdeb and Hypochlobites. 

Chlorine. It is oue of the most valuable properties of chlorine that it destroys 
organic pigments and miasmata, and is hence useful as a bleaching agent, and as a 
disinfectant. It is also employed as an oxidising agent in the extraction of gold 
from pyritical ores. 

At the ordinary temperature and pressure of the atmosphere chlorine is a 
greenish-yellow gas, its sp. gr. = 133; it possesses a peculiarly disagreeable, 
irritating odour, and is very soluble in water, i volume absorbing 25 volumes of 
gas, forming the well-known V?^t/fi( chlorii^ or acidum muriaticum oxygenatum aqita 
solutum of the pharmaceutists, and the chlorine water of the scientific chemist. 
The bleaching property of chlorine gas, possessed also by its solution, is due to the 
great affinity of clilorine for hydrogen, so that the chlorine while seizing upon the 
hydrogen of the organic body in most instances causes the simultaneous decom- 
position of water, and by the formation of ozone destroys the organic colouring 
matter, hydrochloric acid being at the same time formed, a fact requiring attention 
in die use of chlorine as a bleaching agent. When linen, or rather flax, raw cotton, 
and paper pulp are bleached by clilorine, the fibre, really cellulose, is not acted upon, 
but only the colouring matter is oxidised by the ozone formed. Chlorine cannot be 
used to bleach animal matters, or such as contain nitrogen, these becoming yellow 
by its action. Chlorine is not suited for transport either as gas or in aqueous 
solution, therefore one of its combinations with oxygen and a base, viz., a hypo- 
chlorite, is used. Hydrated oxide of calcium or slaked lime is the chief constituent 
of bleaching-powder. Usually the alkali manufacturers prepare bleaching-powder. 

PreparaUon^o^BieacMng- Bleachiug-powdcr is prepared on the large scale in the 
following manner : — In works where soda and chloride of lime are to be manu- 
factured simultaneously, the chlorine is obtained by mixing the common salt to be 



BLEACHINQ'POWDER. 215 

converted into sulphate of soda by the action of sulphuric acid 'with perojdde of 
manganese, heat being applied. 
The process is as follows : — 



Common salt, 2NaCl, 
Peroxide of manganese, MnOs, 
Sulphuric acid, 2H2SO4 



yield 



Glauber's salt, Na^SO^, 
Sulphate of manganese, MnSO^, 
.Chlorine, 2CI, and 2H2O. 



In some 'works chlorine is prepared by the reaction of hydrochloric acid and 

manganese, and sometimes with the addition of sulphuric acid. In the first instance 

only half the chlorine contained in the hydrochloric acid is given up, because the 

other half forms chloride of manganese ; for — 

(Chlorine, CU. 
yield Manganic chloride, MnCl^, 
I Water, 2H2O. 

In the second instance all the chlorine contained in the hydrochloric acid is 
obtained — 



Manganese, MnOa, 
Hydrochloric acid, 4CIH, 



Manganese, MnO^, 
Hydrochloric acid, 2CIH, 
Sulphuric acid, H2SO4, 



Sulphate of manganese, MnS04, 
. yield \ Chlorine, Cl^, 
Water, 2HaO. 



As proposed by Clemm, a chloride of magnesium solution, as largely obtained at 
Stassfurt, may be employed by concentrating the solution to 44° B (=1-435 SP- gr). 
and adding manganese, so that to i mol. of MnO^, 2 mols. of MgCl^ are taken. The 
cooled, solid mass, when exposed to the action of superheated steam at 200° to 300°, 
yields chlorine gas. 

'*^3tSi?Mi^2SeI°* '^^ following methods are selected as being the most scientific 
and interesting: — 

1. Mac Dougal, Kawson, and Shanks's process, consisting in the decomposition of 
chromate of lime by hydrochloric acid, the result being the formation of chloride of 
chromium, chloride of calcium, and the evolution of free chlorine — 

(2CaCr04-fi6HCl=CraCl6-f2CaCl2+3H20+6Cl). 
158 parts of chromic acid 3deld 106 parts of chlorine. The chloride of chromium is 
again precipitated with carbonate of lime, and by ignition converted into chromate of 
lime. Only three-eighths of the chlorine contained in the hydrochloric acid is given 
up, while manganese yields one-half. 

2. Schlosing's method consists in acting upon manganese with a mixture of hydro- 
chloric and nitric acids, the degree of concentration of the acids being so regulated by 
the addition of water that the mixture yields only chlorine, whUe nitrate of protoxide 
of manganese is formed ; this salt being calcined yields manganese, peroxide, and 
nitric acid. The nitric acid aids the oxygen of tlie air in decomposing the hydro- 
chloric acid. The nitrate of manganese begins to decompose at 150°, and the decom- 
position is completed at 175° to 180**, yielding much peroxide, in some cases even 

93 P^' cent. 

3. Vogel's method of decomposing chloride of copper by heat. 3 mols. of 
chloride yield i mol. of chlorine ; according to Laurens the process is : — 

2CuCla=Cla+Cu2Cla. 
The chloride in crystalline state is mixed with haK its weight of sand, and heated in 
earthenware retorts to 200° to 300°, yielding chlorine gas, while the remaining proto- 
chloride of copper is re-converted into percliloride by the action of hydrochloric 
acid. Mallet has constructed a peculiar rotating apparatus for the decomposition of 



2i6 CHEMICAL TECHNOLOGY. 

this salt, the same apparatus serving to prepare oxygen. loo kHos. of capric 
chloride yield 6 to 7 cubic metres of chlorine gas. 

4. P61igot's method. When 3 parts of bichromate of potassa and 4 parts of con- 
centrated hydrochloric acid are gently heated, the fluid yields on cooling crystals of 
bichromate of chloride of potassium, KCl,0r03 ; at 100° this salt yields chlorine. 

5. Dunlop's process is followed at Mr. Tennant's works, Glasgow. Sulphuric acid 
is made to act upon a mixture of 3 mols. of common salt, and i mol. of nitrate of 
soda, the result being the formation of chlorine and hyponitric acid. The latter is 
absorbed by passing the mixed gases through strong sulphuric add. 

6. Mr. Walter Weldon's process is performed by means of an apparatus eomprising 
fiye yesselB arranged at snccesBiye eleyations, so that after haying been pimiped up to tiie 
highest of them, the liquor operated upon can afterwards descend to all the others by its 
own gravity. The lowest of these yessels is a well, which is furnished with a mechanical 
agitator. The slightly acid chloride of manganese liquor with which the process com- 
mences runs from the stills in which it is produced into this well, and is there treated with 
finely divided carbonate of Hme, the action of which is facilitated by the energetie 
agitation. When the neutralisation of the free acid which is at first contained in this 
liquor and the decomposition of the sesquichloride of iron and sesquiohloride of aluminium, 
which are also at first contained in it, are completed, the liquor is pumped up into 
settling tanks, placed nearly at the top of the apparatus, and known as the " chloride of 
manganese settlers.'* It now consists of a quite neutral mixed solution of chloride of 
manganese and chloride of calcium, containing in suspension considerable quantities of 
sulphate of lime, and small quantities of oxide of iron and alumina. These solid 
matters rapidly deposit in the chloride of manganese settlers, leaving the bulk of the 
liquor perfectly bright and clear, and of a faint rose-colour. The next step is to run off 
the clear portion of the contents of the settlers into a vessel immediately below, called 
the oxidiser. This is usually a cylindrical iron vessel about 12 feet in diameter, and about 
22 feet deep. Two pipes go down nearly to the bottom of the oxidiser, a luge one for 
conveying a blast of air from a blowing engine, and a smaller one for the injection of 
steam. The latter is for the purpose of raising the temperature of the contents of the 
oxidiser when necessary; for sometimes the chloride of manganese liquor reaches 
the oxidiser sufficiently hot — between 130° and 160° or 170° F. Immediately above the 
oxidiser is a reservoir containing milk of lime. The oxidiser having received a charge of 
clear liquor from the settlers, and this liquor having been heated up to the proper point, if 
it was not already hot enough, blowing is begun, and milk of lime is then run into 
the oxidiser as rapidly as possible, until the filtrate from a sample taken at a tap placed 
nearly at the bottom of the oxidiser, ceases to give a manganese reaction with solution of 
bleaching-powder. A certain quantity of milk of lime is then added, and the blowing 
continued until peroxidation ceases to ^vance. That point is usually attained when 
from about 80 to 85 per cent of the manganese present has become converted into 
peroxide. The contents of the oxidiser are now a thin black mud, consisting of solution 
of chloride of calcium containing in suspension about 2 lbs. of peroxide of manganese 
per cubic foot, these 2 lbs. of peroxide of manganese being combined with varying quan- 
tities of protoxide of manganese and lime. This thin mud is now run off from the 
oxidiser into one or other of a range of settling tanks or " mud settlers," placed below it, 
and is there left at rest untU it has settled as far as it will, usually until about one-half of 
its volume has become clear. The clear part is then decanted, and the remainder, 
containing about 4 lbs. of peroxide of manganese per cubic foot, is then ready to be used 
in the stills. There it reacts upon hydrochloric acid, liberating chlorine, with repro- 
duction of exactly such a residual solution as was commenced with. With that sointicai 
the round of operations is begun again ; and so on, time after time, indefinitely. 

Apparatw^fo^PrepMiiiij When hydrochloric acid and manganese are used, the apparatus 

is that delineated in Fig. 105. It consists of a large stoneware jar, a, provided with 

an opening, a, over which an air-tight cap is fitted when the apparatus is at work, and 

by which the jar is filled with manganese and acid ; h is another opening fitted with 

a leaden or cartlienware gas tube ; c is a tube serving to run oflf the spent manganese 

liquor, b is a wooden box into which steam is admitted for the purpose of heating 

A and its contents sufficiently to promote the reaction between the hydrochloric acid 

and the manganese. 



BLEACBWaPOIFDEB. 



"7 



When ahloTine ii prepured from a miitiire of common salt, gnlphorio acid, Mid man- 

gueae. the apparatiu is reqnired to withstand more heat, and is therefore oonBtmoted 
(ntireJy of metal. ao,Pig. 106, is a shallow iron pan, fitted with the tnbe 6 (or the pnrpose 
cf smptjing the oontents of the leaden cjlinder, dd. This iron Teesel serves aa the lower 
part of the leaden cylinder, dd, the top of whioh is previded with an opening for a 
fonnel sjphon-tabe for the intiodnction oi the aoid, and another opening, /, (or the jnan- 
gueH. The entire apparatna stands on a Qne leading from a (nmace. 





'>»^ a' iii « Appunui. The ehlerine passes from the generator throngh the tube, u, 
K%. 107, into a room oonstmotod of large blooks and slabs of eandstone joined b; means 
of asphalt oement, or a miitnre of coal-tar and fire-cla;. Sometimes the room is built 
of brieks laid in a similar cement, the interior being lined with asphalt ; leaden chambers 
also are nsed for thiB pnrpoBe. The room ia fitted with several ahelrea npon which slaked 
time ii plaoed in lajera o( three to (onr inches and more in thickness. The chlorine gas 







ii teadily abtorbed; best being erolTed. Care is to be taken tbat the temperature does 
not exceed 25°, because then oblorate ol lime is formed ; this is prevented by admitting 
the gas slowfy. As soon as the absorption ceases, the bleaching'powder is removed with 
rakes from the shelves, and fresh lime intrednced. Frequently the chloride o( time is 
lomewbat diluted by an admixttire of elaked lime. 

When it ia desired to prepare a aolntion of chloride of lime, the apparatna shown in 
Fig. loS is employed. Two or four earthenware vessels, i, about 2 hectohtres capacity, 
•re placed in the leaden trough, a, the bottom of whioh is protected by a cast-iron plate 
and a stoneware slab, r, from the direct action of the fire at ». " '" 



2l8 



CHEMICAL TECHNOLOOT. 



trated solation of chloride of calcium Beiring the pnrpoBeot abatli,such a BolDtion boUing 
at i79'5°. Bj the syphon Jiuinel, k, the hjdroohiorio Mid ia ponied into t. i is ■ per- 
forated cietem filled with manganese. » ia the leaden gaa tabo. The chlorine being firtt 
washed in b, pasBSB throngh n into r, filled -nitb pieces of tnanganOBe, to deeompou ui; 
Tsponrs of hydrochloric acid carried otot, and laetl;, the chlorine pasdug throngh » 
reaohes the abBorption Teasel, s. This Tesael is a lead-lined wooden cask, fitted with an 
axle bearing spokes to whieh are fastened gntta-peroha floats. The bearing and phunmer. 
blocks of the ails are made of gnaiaonni wood and ebonite. The aile, o, gears with a Bait, 
able motive power, the purpose being to keep the milk of lime in coatinnovw motion while 
the gas is being admitted. 

Fro. loS. 




The chlorine gaa enters above the level of the flmd, which is kept constantly atirred. Id 
assist in the absorptioii From the Teasel wherem the absorption tl^es plaoe a small tnbe 
leads into another yessel filled with water to a depth of iS to 24 centuns , a tnbe fitted 
to this Teasel leads into the open air to conTe; away anT onabsorbed ohlonne. &b in the 
preparation of solid chloride of lime, it is here necesaary to gnard against an incresM in 
temperature and also satoratioQ; Schlieper has proved that too oonoentrated solntions 
evolve oxygen, while too dilate solutions yield ohlorata of lime. 

""ptSf^^BrJSS?" -^ '^^ chlorine required for the preparatioii of chloride of 
lime is generallj obtained b; the aid of manganese and hydrochloric acid, the resi- 
dnes consist chiefly of free acid and protochloride of manganese. The principal 

suggeationB ae to the utilisation of these substances are : — 
a. Those aiming at the regeneration of peroxide of manganese ; and 

0. Those not proceeding with this view. The former are of course the more 

important. 
DmiiiiF'i PnmH. This process ia one of the oldest and the best, excepting perbapa, 
Batmain's, in which the chloride of manganese ia neutraliaed with the ammoniaoal nter 
of gai-works, the sapematant liqnor being employed tor preparing sal-ammoniac, irtiile 
the precipitate ia ignited in a reverberatory fomace and converted into peroride of 
manganese. Dnnlop'a process, as practiaed at Tennant'a works at Glasgow, is based upon 
the fact, first observed by Forchhammer, that carbonate of manganese, when heated la 
260°, is converted into peroride of manganese ; that is, the carbonic acid is driven off, 
and the compoond, xUsOi-i-MdO, obtained. The proceaa oonaiats in the foUowiog 
operations : — 

1. Converaion of the ohloride of manganese into carbonate of manganese. 
3. Conversion of the carbonate into peroxide of manganese. 

To the chlorine preparation residoes.when they have become clear, either chalk or milk 
of lime ia added to nentraliao the exccaa of acid and precipitate the oride of iron. Thil 
precipitate haring settled, the clear liquid, a rather pare solution of protocblorideof maa- 
ganeae, is poured into shallow troughs and intimately mixed with finely powdered etulk. 
The magma thus formed ia transferred for further deoompotitioQ to a large eOBt-iron 
tronnh, sy metres long by 3 metres wide. Parallel to the length of this vessel, a stent 



wionght-uoD axle is corned, to which a 



I fitted ci 



1 branches serving aa stiiref. 



BLEACHING-POWDER, 219 

The axle passing through stuffing boxes at each end of the trongh, gears with a motive 
power, whereby the stirrers are caused to keep the chalk constantly suspended in the 
manganese solution. High pressure steam is conveyed into the trough and aids decom- 
position. The carbonate of manganese obtained is freed by washing from chloride of 
caldum, and having been well drained, is calcined in a peculiarly constructed furnace, in 
which the carbonate is first dried on a higher stage, and then is transferred to a lower and 
hotter stage, where oxidation is commenced. The oxidation is completed at the lowest 
stage of the furnace, to which plenty of air is admitted. The fire-place is constructed to 
pdmit of the regulation of the heat with great nicety, because too high a temperature would 
cause the formation of protosesquioxide, and too low a temperature would leave the 
carbonate undecomposed. 

G«tt7^pn)O0«. In this process the residues are converted into nitrate of manganese, 
which is next decomposed by heat. The residues are evaporated to the consistency of a 
symp, and mixed with nitrate of soda : — 

To 76 kUos. of protoidOoride of manganesej ^^ ^^^ ^^ ^.^^^^^ ^, ^^ ^ ^^^ 
and to 95 kilos, of sulphate of manganese J 
The mixture is dried, and then heated to a dull red heat in an iron retort, the fumes of 
nitric acid given off being used in the manufacture of sulphuric acid. The residue in the 
retort consists, according to the salt of manganese employed, of peroxide of manganese 
and chloride of sodium or sulphate of soda ; it may be lixiviated with water to obtain the 
peroxide of manganese in a pure state if sulphate of soda is present. 

Hotnuiui'i proeeas. The procossos of regenerating manganese by the application of soda 
waste are more important than the preceding. In Hofmann's process the protochloride 
of manganese is, by tihe addition of the yellow ley obtained from the lixiviation of soda 
waste converted into sulphuret of manganese. The precipitate, consisting of — 

Sulphuret of manganese 55 'oo 

Sulphur 40*00 

Protoxide of manganese 5*00 

100*00 

is dried and calcined, the sulphurous acid given off being led into the sulphuric acid 
chambers. The remaining residue, consisting of — 

Sulphate of manganese 44*5 

Peroxide of manganese 18*9 

Protoxide of manganese 36*6 



ioo*o 

is next mixed with nitrate of soda and heated to 300^, yielding sulphate of soda and 
nitrate of manganese, the latter, however, being at once decomposed into peroxide of 
manganese and hyponitric acid : — 

a. MnS04+2NaN03=Mn(N03)2+NaaS04; 
p. Mn(N03) + MnOa+2N02. 

After the mass has cooled, the sulphate of soda is removed by lixiviation, the residue 
yielding a material free from iron, and according to the inventor, equal to native manganese. 

Wddon's Froisen. To the residue, consisting of protochloride of manganese, are first 
^ded for every molecule of that salt 2 molecules of hydrate of lime. Into this magma, con- 
sisting of hydrate of protoxide of manganese, hydrate of lime, and chloride of calcium, air 
is forced, tiie effect being that the manganese is rapidly higher oxidised, and forms 
ealciom-manganite (CaMn03, or MnOa.CaO), which, having subsided, and the supernatant 
chloride of calcium solution being run off, is ready for chlorine making by the addition of 
hydrochloric acid. The same process is repeated, and even a change of vessels is not 
required. (See p. 216.) 

oocr Methods of utuiiing /3- Utilisation of the residues without regeneration of the 
tha BMidaei. peroxide of manganese. M. Schaffner, at Aussig, precipitates the 

protochloride of manganese with lime, dries the precipitate, and calcines it in a rever- 
beratory furnace, obtaining protosesquioxide of manganese, employed with iron ore in the 
blast furnace. The solution of chloride of calcium simultaneously obtained is precipi- 
tated by sulphuric acid, yielding the material known as anruUine; that is to say, the 
gypsum used in paper manufacture. In the process of soda-making from sulphuret of 
sodium and iron, as suggested by Malcherbe and improved upon by Eopp, for the oxides 
snd carbonate of iron, the corresponding manganese compounds may be substituted. 
Carbonate of manganese may be used to convert sulphuret of sodium into soda, and may 
also serve for the preparation of permanganates. A. Leykauf suggests that the residues 



220 CHEMICAL TECHNOLOGY. 

of chlorine manofaotnre shonld be employed to form a yiolet-eolonred paint, known as 
Nuremberg- violet, a compound of ammonia, oxide of manganeee, and phosphoric add. 
In England the residues are frequently employed in tiie purification of coal-gas and as 
disinfectants. 

'^iSidSiSS^!*" When chlorine gas and slaked lime (hydrated oxide of calcium, 

CaEEsOa) are brought in contact, a portion of the oxygen of the lime combines 

with the chlorine, forming hypochlorous acid, which, combining with the nndecom- 

posed lime, forms hypochlorite of lime, while another equivalent of chlorine combines 

with the deoxidised lime (calcium) forming chloride of calcium : — 

Hydrate of lime, zCaH^Oa,! - „ {^^f""^^ of lime Ca(aO)^ 
Chlorine. 2CI,, ^ *' J 3^ jmte" 1^0 "^ ^^' 
This bleaching-powder consists in 100 parts of : — 

Hypochlorite of lime 49'3i 

Chloride of calcium 38*28 

Y*aiiei& ••• ••• ••• ••« ••• «•• ■•■ ••■ ••• 12 4' 



lOO'OO 



or of- 



v^nLo^me ••• ••• ••■ ••• ••• ••• ■•■ ••■ 40 QO 

1 Jl lIlH a, a ««a ,,, aaa ••• ••• ••• ■•■ •■• 3 ^^7 

TvaL6r**a •■• ••• ••• ••• ••• ••■ ••• ■■• 12 41 

1 0000 
A bleaching-powder of this theoretical composition does not and cannot occur in 
the trade ; a good sample, containing 26*52 per cent of active chlorine was composed 
as follows : — 

Hypochlorite of lime 2672 

Chloride of calcium 25*51 

I iiiii.e ••• ••• ••• ••• ••• ••• ••• ••■ ■•• 23 03 

Water of composition and moisture 2472 

lOO'OO 

This analysis may be more intelligible by the following arrangement : — 

Hypochlorite of lime 2672 

Active chloride of calcium 
Excess of chloride of calcium. 
Hydrate of lime 



2072 

479 
3046 



Water of composition and moisture i7'3i 

lOO'OO 

According to Dr. Fresenius (1861), bleaching-powder is a mixture of i molecule of 
Ca(C10)2 and 2 molecules of basic chloride of calcium, CaCl2,2CaHa0a+2Ha0. 

*'«»p«***^,JJ™*****^* Bleaching-powder is a white, rather moist powder, consistiBg 
of hypochlorite of lime, chloride of calcium, and excess of slaked lime. 10 parts of 
water dissolve the bleaching material, leaving the excess of lime ; the chlorine 
contained in the chloride of calcium also acts as a bleaching agent, as on adding sn 
add to the bleaching-powder the hypochlorous add set free reacts upon the hydro- 
chloric add evolved from the chloride of caldum, forming water and chlorine : — 

(glo+g|=glo+g}) 



BLEACHINQ-POWDER. 221 

The bleaching power of chloride of lime does not come immediately into play 
unless an acid is added ; this property is turned to account in the producing of white 
patterns upon fjeibrics dyed turkey-red, by printing the pattern in a thin paste of tar- 
taric acid, the fEibiic being afterwards immersed for a few minutes in a solution of 
hjpochlorite of Hme. Instead of employing acids for setting the chlorine free from 
chloride of lime, sulphate or chloride of zinc may be substituted, the result being 
that gypsum and oxide of zinc are precipitated, yrhile hypochlorous acid remains in 
solution.* The yarious industrial uses of bleaching-powder have already been men- 
tioned. Chloride of lime, as bleaching-powder is generally termed in this country, 
is sometimes used for the preparation of oxygen, i Idlo. (of the formula Ca(G10)2), 
yielding 132*2 grms.=92'4 litres of oxygen. 

cuoriBMtiy. As the value of a sample of chloride of lime depends upon the quantity 
of the really active chlorine and hypochlorous acid it contains, methods have been 
devised for ascertaining with a greater or less degree of accuracy the quantity of 
these active agents. Formerly the test was the discolouration of a certain quantity 
of indigo solution by a certain quantity of bleaching-powder solution, as compared 
with the action of chlorine upon indigo, but it is clear that this method could 
not yield accurate results. 

o«^LM«giaiflKWMtite Tj^g eminent savant makes use of the oxidising action of 
chloride of lime upon arsenious acid, a volume of dry chlorine gas dissolved in 
water being employed. The solution of chlorine is poured into a graduated tube 
divided into 100 parts, each of these divisions corresponding to one-hundredth of 
chlorine. A solution of arsenious acid in dilute hydrochloric acid is also prepared, 
the strength of the solution being such that equal bulks of the two liquids suffer 
mutual decomposition: — 

Arsenious add, Asa03,' 

. yield 



Water, 2H3O, 
Chlorine, 2CI2, 



Arsenic acid, Asa05, 
Hydrochloric acid, 4CIH. 



Water is decomposed ; its oxygen combines with the arsenious acid, forming arsenic 
acid, while the hydrogen combines with the chlorine. Usually i litre of dry chlorine 
gas is dissolved in i litre of distilled water. The normal solution of arsenious acid 
is so prepared that it is entirely decomposed by the chlorine water to arsenic acid. 
The test is carried out as follows : — Take 10 grms. of the sample, and triturate with 
distilled water, adding sufficient of the latter to make up a litre. Next take, by 
means of a graduated pipette, 10 c.c. of the arsenious acid solution, and pour it 
into a beaker, adding a drop of indigo solution to impart a faint colour ; next add, 
hy means of a burette, sufficient of the bleaching-powder solution to cause the 
colour nearly to disappear, then add more of the indigo solution, and again bleaching- 
powder solution, until the fluid becomes quite colourless. The normal arsenious 
acid solution is prepared by dissolving 44 grms. of this add in 32 grms. of hydro- 
chloric add, the liquid to be diluted to i litre. If 10 grms. of bleaching-powder con- 
tain I litre of chlorine gas, it is of 100 degrees strength. 

Pnot'B T«rt. Penot has modified Gay-Lussac's method in the following particulars : — 
For the arsenious acid solution he substitutes arsenite of soda, and for the indigo 

* Explosions have oconrred from bleaching-powder being kept in too tightly dosed 
vessels, due to spontaneous deoompodtion, (Ca(C10)2+CaCl2=2Ga0l2+02). As a pre- 
vention it is suggested that the powder should be ground, packed in casks, and strongly 
pressed into a hard mass. 



222 CHEMICAL TECHNOLOGY, 

solution a colourless iodised paper, which is turned blue by the smallest quantity of 
free acid. The paper is prepared in the following manner: — i grm. of iodine* 
7 grms of carbonate of soda, 3 grms. of starch, and \ litre of water are mixed. When 
the solution becomes colourless, it is diluted to i a litre ; in this fluid white paper is 
soaked. The arsenical fluid is prepared by dissolving 444 grms. of arsenious acid, 
and 13 grms. of crystallised carbonate of soda in i litre of water. This solution is 
poured by means of a burette into the solution of the chloride of lime intended to 
be tested (10 grms. of the sample to i litre), the completion of the reaction being 
known by the paper remaining uncoloured. Mohr, again, has modified this process, in 
not however very essential particulars. 

Dr. w»gnert Mathod. TMs test, discovered in 1859, is the so-called iodometrieal 
methodf and is based upon the fact that a solution of chloride of lime separates the 
iodine from a weak (i to 10) and slightly acidified iodide of potassium solution, the 
iodine being quantitatively estimated by means of hyposulphite of soda : — 



Iodine, 2I, 

Hyposulpliite of soda, 2NaaSa03+5H30, 



yield 



\ [Iodide of sodium, 2NaI, 

' Tetrathionate of sodium, NaaS406i 
.Water, sHaO. 

The test is thus executed : — 100 c.c. = i grm. of bleaching-powder solution* 
obtained by dissolving 10 grms. of chloride of lime in i litre of water, are mixed 
with 25 c.c. of solution of iodide of potassium acidified with dilute hydrochloric 
acid. The ensuing clear, deep brown coloured solution is treated with hypo- 
sulphite of soda solution until quite colourless. The hyposulphite of soda solution 
is composed of 24'8 grms. of that salt to i litre of water ; i c.c. of this solution neu- 
tralises 0*0127 grms. of iodine and 0003 5 5 grms. of chlorine. 

ahioromatiiiwiDagnes. The Strength of bleaching-powdcr is indicated in England, 
Russia, America, and Germany by degrees corresponding to the percentage of active 
chlorine ; but in France the degrees denote the number of litres of chlorine gas at o" 
and 760 millimetre Bar., which i kilo, of bleaching-powder can evolve. The 
following table compares the chlorometrical degrees of France and EIngland : — 

French. English. 

63 2002 

65 2065 

70 2224 

75 23-83 

80 2542 

85 2701 

90 2860 

100 31*80 

105 3336 

no 3495 

115 3654 

120 3813 

125 3972 

*i26 4004 

The percentage is calculated by multiplying the French degrees by the coefficient 
0-318, a litre of chlorine gas = 355 criths, weighing 3-18 grms. 



CHLORATE OF POTASSA. 223 

AikaUae HypoohioritM. A solution of hypochlorite of potassa is known in commerce 
under the name of Eau de Javelle, while the corresponding soda solution is known as 
£au de Laharraque\ these solutions are prepared by passing chlorine gas into a 
solution of either caustic (i), or carbonated (2) alkali: — 

(i). 2NaOH+Cla=NaOCl+NaCl+HaO: 

(2). 2NaaC03+Cla+HaO=NaOCl+NaCl+2NaHC03 ; 

or by exhausting bleaching-powder with water, and precipitating the solution with sul- 
phate or carbonate of soda solution, sulphate or carbonate of lime being thrown down, 
while the hypochlorite and chloride of the alkali remain in solution. 

Hypochlorite of alamininm, or Wilson's bleaching liquor, is obtained by miring chloride 
of lune solution with sulphate of alumina ; its action is by evolving oxygen, leaving 
chloride of aluminium in solution. Hypochlorite of magnesia (Bamsay's or Gronville's 
bleaching liquor) is obtained by adding sulphate of magnesia to a solution of bleaching- 
powder ; the result is the formation of a very energetic bleaching compound, which, espe- 
eially for the purpose of bleaching finely woven fabrics, as muslins, <&c., is preferable to 
chloride of lime on account of the absence of caustic lime. Yarrentrapp's bleaching salt, 
or hypochlorite of zinc, is another energetic bleaching compoxmd obtained by treating a 
solution of chloride of lime with sulphate of zinc, the result being the precipitation 
of sulphate of lime, while hypochlorite of zinc remains in solution ; chloride of zinc may 
be employed, but, of course, the solution then retains chloride of calcium. Hypochlorite 
of baryta is sometimes used, hypochlorous acid being obtained by the addition of 
very dilute sulphuric add. 

cbknataof potawa. TMs Salt (EGIO3) cousists in 100 parts of 38'5 of potassa and 
6i'5 of chloric acid ; its crystals are rhombic and tabular in form. It formerly was 
prepared by passing chlorine gas into a concentrated solution of carbonate of 
potassa, the result being the formation of chlorate of potassa and chloride of 
potassium. As the chlorate is the least soluble it crystallises first, while by evapo- 
ration the mother-liquor yields chloride of potassium. The chlorate is then washed 
with cold water, and purified by re-crystallisation. 100 kilos, of carbonate of 
potassa yield in this manner 9 to 10 kilos, of the chlorate. At the present day, 
however, chlorate of potassa is prepared by a method, the suggestion of the late 
Dr. Graham^ Chlorine is caused to act at a high temperature upon mKWx of lime, with 
the result of the formation of chlorate of lime and chloride of calcium, the chlorate 
of lime being afterwards decomposed by chloride of potassium. The method by 
which chlorate of potassa is prepared on the large scale according to this plan is the 
following : — i mol. of chloride of potassium and 6 mols. of hydrate of lime, having 
been mixed with water, are submitted to the action of chlorine gas ; the solution yields 
on evaporation crystallised chlorate of potassa, while chloride of calcium remains. 

This operation is carried on by the aid of the apparatus illustrated in Fig. 109. b b are 
earthenware jars, placed in a chloride of calcium bath, and filled with a mixture for 
evolving chlorine gas. This gas is conveyed through the leaden tube, f f, to the vessel, c, 
wMch is placed in cold water for the purpose of condensing any aqueous vapours. From 
the gas passes through the leaden tube g into the absorption vessel, ▲, in which the 
iniztaie of lime and water has been placed, e is an iron stirrer covered with lead ; ^, a 
portion of the tube for carrying off the non-absorbed chlorine ; d, a tube closed with 
a plug during the operation, and intended for tapping off the contents of the vesseL The 
nulk of lime is poured into the vessel at 50** to 60^ C, while sometimes steam is injected 
for the purpose of keeping up the temperature, which rises as soon as the reaction 00m- 
niences nearly to the boiling-point. A smiUl quantity of hypochlorite of lime is always 
formed. As soon as no more chlorine is absorbed the fluid is tapped off into a lead-lined 
tank, and after the suspended matter has been deposited, is syphoned over into a leaden 
^sporatin^ pan and concentrated to 35° to 30"* B., any hypocUorite of lime being thus 
<K>nverted mto chlorate. To the evaporated and concentrated solution there is added 
a hot solution of chloride of potassium, after wluch the evaporation is continued to crys- 
taUisation. According to theory, 2\ parts of Ume require i part of chloride of potassium ; 



CHEMICAL TBCHNOLOar. 



hj first preparing chlorate of lime, and boiling a Bolatiou of this eblorate, adding lo tfa« 
concentrated fluid chlorate of potasaiom to obtain chlorate of potaaaa. Chlorite of 
potaosa is not altered by eiposore to air, ia soluble in iG parts of water at IS'S", in B ptrti 
of water at 35°, and in 1-6 parts of water at 100°. On being heated to fosion, this ult 
yields oxygen ; it incantioiiHl; rabbed in a ■aortar with combuetible sabstimces, u 
solphnt or phoepboms, vioIeDt eiploEiona will euene. i kilo, of the chlorate yields, wlwa 

Flo. log. 




heated with either o 5 kilo of manganese or i kilo of onde of iron or better still, with 
k small qnantity of oiide of aopper (see ' Chemical News vol iiir p 85) 3giigniii.' 
373-5 litres of oxygen Chlorate of potasw is ohieflj employed 10 pyrotechny for the pre- 
puation of white powder aa an mgredient in the explosive mixture for the eartridgs 
of needle-guns, as an oxidising agent in cahco-printing, and in the preparation of Huhos 
black. Perehlorate of potassa fECliO^) is now more frequently nsed in pyroteehnj. 
being less dangerous to manipnlate, and owing to the targe qoaotity of oxygni, emitting 
more intense light. 

AlKALIUETRY. 

AUoJiBatiT. The poUah met with in commerce, no matter from what ■om'cs it 
is obtained, Is always a mixture of carbonate of potassa with other salts of potaffl* 
and soda ; and again the carbonate of soda of commerce is a mixtnre of the or- 
bonatA with other eoda salts, chiefly enlphate and chloride. The value of ather of 
the salts of conree depends chiefly apon the quantity of pure carbonate present is 1 
given sample. The quantitative determination may be effected by either of two rapid, 
yet sufficiently accnrate, methods : — 

a. The estimation of the qnantitr of acid required to nentralise the alkiliiw 

carbonate ; 

b. The determination of the qnantit; of caibonic add evolved by the additioD of 

a strong acid. 
It ia clear that these methods can be applied only when i 
alkaline carbonate is present. 

ToiuiHUiaiiinhMi. This method, invented by Descroizilles and ii 
Lnssac, is based npon the measurement of the quantity of sulphui' 






mproved by 0*y- 
c acid required U 



ALKALIMETRY. 225 

expel the carbonic acid from a certain quantity of carbonate of potassa,this measnre- 
xnent giving the quantity of pure salt. The best sulphuric acid is prepared by 
mxxng 100 grms. of pure sulphuric acid, sp. gr. = i'842, with 1000 grms. = 1000 c.o. 
^ I litre of distilled water; or, instead of weighing the acid, 54268 c.c. maybe 
mixed with a litre of water. 50 c.c. of this normal acid solution suffice for converting 
4807 grms. of potassa into sulphate of potassa. The burette of 50 c.c. capacity and 
graduated to half a c.c, is filled with test-acid ; next 4807 grms. of potassa are 
weighed out and dissolved in boiling water. Some litmus tincture is now added 
and the test-acid poured from the burette into the potash solution until the colour is 
a wiue-red. Supposing 60 demi-c.c. to have been used in saturating the potash, and 
deducting i c.c. for possible excess, the sample contains potash of 59 i''. The 
quantity of potassa per cent is calculated by multiplying the quantity found by 1*47. 
Potash of 50° contaioB 50 X 147 = 75 '5 per cent carbonate of potassa. 
Mdu'iUMhod. Mohr substitutes for the sulphuric acid crystallised oxalic acid — 

(CaHa04,2HaO=l26; ^ mol. = 63)! 
because: — i. It is as strong as, and similar to, sulphuric acid in its action upon 
litmus; 2. Being neither deliquesCsi|^t nor efflorescent, it can be readily weighed off 
in a dry state with accuracy; 3. Its' aqueous solution is not liable to become mouldy 
by keeping, as are the solutions of citric and tartaric acids ; 4. It is not volatile 
when in hot water. To prepare the normal acid liquor, 63 grms. of oxalic acid are 
dissolved in a litre of water ; on the other hand, there is prepared a corresponding 
Bolution of caustic potassa so titrated that, on being mixed with an equal bulk of the 
add solution, the last drop of the alkaline solution restores the blue colour of the 
previously reddened litmus, provided the liquor does not contain carbonic acid in 
solution. For alkalimetric purposes 6*911 grms. of potash or 532 grms. of soda are 
weighed out, these quantities being equal to ^a molecule, and as the test-acid contains 
in xooo C.C. i molecule of oxalic acid, icx) c.c. will exactly neutralise the quantity of 
allcali. Some litmus tincture is mixed with the alkaline solution, to which the 
oxalic acid solution is added in a slight excess (5 to 6 c.c), the solution being 
boiled to expel all the carbonic acid. There is now added by means of a pipette 
divided into tenths-cc, just sufficient caustic alkali to turn the litmus blue ; 
the number of c.c. of alkali solution employed is deducted from the number of c.c. of 
acid solution employed, the difference giving the percentage of pure carbonate of 
potassa contained in the sample. For instance, if 345 grms. of the potash = ^^o mole- 
cule, require 36 c.c. of the acid and 3 c.c of the alkaline liquor, there will be 33 c.c. 
test-add = 66 per cent carbonate of potassa, as, instead of «V mol., ^a mol. having 
been employed, the number of c.c of test- acid must be doubled. 

These instances of alkalimetric processes will suffice for the purposes of elucidation ; 
but the reader will find fuller explanations in works on volumetric analysis. However, it 
18 still to be observed that as potash is a very hygroscopic substance, it is necessary to 
estimate the water it contains, or at least to dry the sample. As 6*29 grms. of commercial 
potash and 4*84 grms. of soda contain when pure exactly 2 grms. of carbonic acid, every 
2 oentigrms. loss equals z per cent of carbonate. Supposing the loss of weight to amount 
to 164 centigrms. the sample will contain >}« = 82 per cent of carbonate of potassa ; for 
scientific purposes it would answer to say that such a sample consists in 100 parts of : — 

Carbonate of potassa 82 

Foreign salts 8 

Water 10 

100 



/ 



226 CHEMICAL TECBNOLOOr. 

For oommeroial purposes, however, at least abroad, the value {titre) of a sample 
of potash expresses the percentage of anhydrous salt ; for instance, by potash at -jVo 
is meant potash containing 60 per cent of real carbonate when in a dry state. 
But if, by having taken up moisture, 100 lbs. have increased in weight to 105 or 
109 lbs., the expression -jV^ or -1%% is equivalent to saying that the amount of money that 
would buy ^% of dry material will also buy j%% and j\°^ of the moist salt ; the purchaser, 
therefore, does not pay for water, and all that he has to do is to ascertain the quantity of 
water present in the sample. In France the quantity of soda contained in a sample ii 
usually expressed in degrees indicating the percentage of carbonate of soda, and in 
England the percentage of caustic soda ; thus, as 100 parts of carbonate of soda oontaia 
58*6 of soda and 41*4 of carbonic acid, it follows that 

80° French are equal. to 46*9" English. 
86' „ „ „ 50-5° „ 

96* » M M 52-8* „ 

SSJiSfg' thifv^? ^ ^^® preceding methods of testing potash no notice is taken of the 
of Pouah. soda contained m the samples, nor is the quality of the potassa salts 

considered. It is clear that these determinations require a full analysie, which, by 
Gruneberg's method, is executed in the following manner : — The carbonate of potassa 
is estimated by Gay-Lussac's method, the chlorine by the aid of nitrate of silver, the 
sulphuric acid by nitrate of lead, and the quantity of any free caustic potassa is deter- 
mined by means of tartaric acid. All the chlorine is calculated as chloride of potasdom, 
all the sulphuric acid as sulphate of potassa, and the rest of the potassa as carbonate; 
the quantity thus found is deducted from that found alkalimetrically, and the remainder 
is calculated to be carbonate of soda in the proportion of 69'! to 53*0. 

fl 

Ammonia and Ammoniacal Salts. 

Ammonia. Ammonia occurs in the atmosphere. Ammoniacal salts are met with in 
a few minerals and in volcanic districts. But the bulk of the ammonia and 
ammoniacal salts industrially used, is obtained from tlie dry distillation of coals, 
hones, and animal substances, also by the distillation of lant (stale urine), by the 
action of steam on some cyanogen compounds, and as a product of the blast-fomaoe 
process. 

The following sources of ammonia are technically available : — 

1. Native carbonate of ammonia, 

2. Preparation of ammoniacal salts with boracio acid, 

3. Volcanic sal-ammoniac, 

4. Ammonia from nitric acid in the purifying of caustic soda, 

5. „ „ deutoxide of nitrogen and nitrous acid, 

6. „ „ the nitrogen of the air, 
,7. „ „ certain cyanogen compounds. 

8. Coals yield ammonia : — 

a. By the dry distillation for the purpose of gas manuf^Mtuie, 

b. By the coking of coals, 
€, By the use of coals as fuel ; 

9. Ammonia from lant, 

ID. „ „ the dry distillation of bones, 

II. „ „ beet-root juice. 

Ammonia, NH3, consists of i volume of nitrogen and 3 volumes of hydrogen, con- 
densing to 2 volumes of ammonia gas, a colourless gas of a peculiar and well-known 
odour and sharp biting taste. At 15° water absorbs 727, and at 0° 1050 times its 
own bulk of this gas, the solution being known as liquid ammonia, or spirit of sal- 
ammoniac, the sp. gr. of which is 0824 (=31*3 per cent NH3). Usually, however, a 
weaker and more stable liquid ammonia is prepared for pharmaoeutical and technical 
purposes, having a sp.gr. = 0960 (= 975 per cent NH3V The following table 
shows the specific gravity* of liquid ammonia, and the percentage of ammonia 
contained : — 



A. Inorganic 
sources. 



p. Organic 
sources. 





AMMOmA, 




Bp.gr. 


NH3 per eent. 


Bp.gr, 


0-875 


3250 


0959 


o'8z4 


31-30 


o'96i 


o'qoo 


2600 


0963 


0905 


2539 


0965 


0925 


19-54 


0968 


0932 


ir52 


0970 


0*947 


1346 


0972 


0-951 


IZ'OO 


0-974 


0953 


11-50 


0976 


0955 


II'OO 


0-978 


0957 


10-50 





227 



KH5 per cent. 
100 

95 
90 

8-5 
8-0 

7'5 
70 

6-5 
6-0 

55 



Ammoma gas is very solable in alcohol. The spirittu ammoniaei eawtiei Dzondii of 
the Prussian FharmaoopoBia is a solution of ammonia gas in alcohol of o'Sao sp. gr. ; the 
ammoniaoal solution containing 10 per cent of real NH3, and having a sp. gr. of 0*808 to 
0'8io. The liquor ammonii vinosus is a mixture of i part of liquid ammonia (at 10 per 
eent NH3) and 2 parts of strong alcohol. Liquid ammonia is industrially employed for 
the extraction of the lichen (orchil) pigments, in the preparation of carmine, the manu- 
facture of snuff, the purifying of coal-gas, for the removal of carbonic acid and sulphuretted 
hydrogen, for the saponification of fats, the preparation of ferrocyanide of potassium 
according to Oelis's plan with the aid of sulphide of carbon, for the extraction of chloride 
of silver from its ores, as antichlor in bleach-works, and in the manufacture of pigments 
and dyes. As regards the use of liquid ammonia for the extraction of copper from 
pjritioal ores, Barruel stated (1852) that the copper might be dissolved by simply impreg- 
nating finely pulverised ore with liquid ammonia, and forcing air through the mixture, 
the metal being obtained as black oxide of copper after the ammonia is distilled off. 
This process, however, has not been found to answer on the large scale. The researches 
of von Hauer, Schonbein, Tuttle, and others, have proved that the oxidation of the 
ammonia is simultaneous with the oxidation of the copper, and that the nitrous acid thus 
formed is the active agent. Moreover, the experiments of Liebig and Way have proved 
that even if the operation were carried on in air-tight vessels, the ammonia could not be 
entirely recovered, owing to the fact that the ores absorb ammonia, and render it 
insoluble, thereby preventing its action on the copper. But if the copper ore be 
tolerably pure malachite or lazulite, only containing Hme or carbonate of that base, liquid 
ammonia may be successfully employed. Liquid ammonia is used in Garry's ice-making 
machine. The rationale of this machine is that ammoniacal gas being expelled by heat 
from its aqueous solution, is again condensed and liquefied by pressure and cooling ; the 
retort in which the ammoma is heated being next cooled by water, a vacuum is created, 
and as a consequence the ammonia contained in the condenser volatilised, returned to the 
retort, and again taken up by the water present. On again resuming the gaseous state, 
the ammonia absorbs a great amount of heat, causing a diminution in temperature 
sufficient to freeze water. Carry's ice-machine yields 10 kilos, of ice for every kilo, of coal 
consumed as fuel. Although Foumier has suggested that ammoniacal gas might be 
usefully employed in testing the joints of gas-fittings in houses, this is more readily 
effected by the use of a hand air-pump. The application of ammonia as a source of 
motive power has been tried, but it is not at present likely that it will supersede steam. 

PJniMttM^oMjqnid gy decomposing with canstic lime either chloride of ammonimn 
or sulphate of ammonia, ammoniacal gas is set free, and can be absorbed by water, 
carej>eing taken that the lime is in excess. When carbonate of ammonia is prepared 
on the large scale by sublimation of a mixture of chalk and sal-ammoniac, a 
large quantity of ammoniacal gas, 14 parts for each 100 parts of carbonate of 
ammonia, is obtained and may be utilised. Wagner has been the first to observe 
that the technical preparation of liquid ammonia might be combined with the 
preparation of baryta-white by precipitating a solution of sulphate of ammonia 
^th caustic baryta water ; the clear supernatant liquor will be a solution of caustic 
ammonia. 



Q2 



CHEMICAL TECHNOLOOY. 



red -lead. 



the large eaale ie effected bj mesni ef the 
-iron distilling veseel placed in a biickvoik 
ed a lid secured to the flange bj meana of 
The lid carriee an iron tnbe, m, leading to th« 



328 

The preparation ot Uqnid a 
SppaiatQB shown in Fig. i^o. 
furnace. To the neck of the vi 

bolts and nuts, an , , 

irasfa Teasel, n, of wrought-iron. This vessel is aurrounded b; cold water contained in a 
iTOodon tank, and is provided with a wide tube, o. tbrongh trhieh nt pasMB. The iFash 
vessel ia filled with only so ntuoh water as will close the tubes n and a h;draulieallj. 
as daring the operation a large quantit; of water is distilled over from k. loo paits of 
Blaked lime are mixed witb a sufficient qnaotitj of water to form a thin milk ol lime, 
which is poured into i ; the lime solution having become quite cold, there ia added loo 
ports of pulverised sal-ammoniac or snlphale of ammonia, being tJioronghlv miied bj 
stirring with an iron rod. The lid being screwed on a, the fire ig lighted in c ; tlia 




mercurial gauge, b, shows the course of the operation. The ammouiacal gas prooeeda 
from the woah veatiel, b, through the tnbe t into the condensing apparatus, a. invented 
by Bruunqnell, and highly useful for this and for similar purposes where it ia desired to 
work nnder a low pressure. This apjiaratua consists of a large tank or box in which 
four shallow boxes, a', a", a'", a"", are placed bottom upwards, the aides ot the bo»(» 
being perforated with small slits. The oatet tank is filled with water. When am- 
moniacal gaa eutera through t into a"", it forms a large babble, similar to an air babbi* 
nnder ice, and reaching one of the small slits rises into a'", and ho on, the bubbl* 
becoming smaller and smaller aa the water gradually absorbs the gas. The box or tank. 
D, ia placed in a large tank, not represented in the cut. filled with cold water constantl; 
renewed. The stiB, A, is of sufficient capacity to contain 20 kiloa. of Bolphala ot 
ammonia, and 80 litres of water. The operation is continued until the bottom o( the 
Btill becomes red-hot. The water contained in a is used at a subBeqnent operation for 
tailing with the lime. The preparation of liquid ammonia directly from gas liquor, tbe 
ammoniacal water of gas works, will be mentioned presently. The application of the 
property of chloride of calcium to abaorb ammonia and deliver it up on the application 
of heat has been atti-'nipted indastriaUy by Knab for the storing-np of ammonia. Btrcog 
liquid ammonia only contains 15 per cent NHj, and Knab's preparation 50 per cent; » 
regards transport this may not be an uninteresting fact, but chloride of calcimn i> a 
very deUqnescent salt. 

iBom^csoiiroi.oi Before proceeding to describe the preparation of ammoniacal 
salts &oni bones, coals, lant. I.e.. we must first enimierat« the inorganic sources of 
ammonia of industrial uuportiinoe. 

I. Native carbonate of ammonia, met with in brgc quantities in the goano depodti c' 
South America, was imported into Germany aa a commercial article in 1848. On being 
AoalyLicd thiij substauco waa fonud to consiBt of— Ammonia, zo'44 ; carbonic acid, 54'jJ • 



AMMONIA. 229 

▼ater, 21*54 ; and insoluble matter, 21*54 parts. It is, therefore, a bicarbonate of ammonia 
(NH4)HC03. 

2. The preparation in Tnscanj of native sulphate of ammonia as a by-produot of the 
preparation of boracio acid has reoently become important. The suffioni contain, in 
addition to boracic acid, sulphates of potassa, soda, ammonia, rubidium, &0, ; and that 
the quantity of these substances is by no means small may be inferred from Travale's 
researches, from which it appears that four suffioni yielded within twenty-four hours 
5000 kilos, of saline matter, consisting of 150 kilos, of boracic acid, 1500 kilos, of sulphate 
of ammonia, 1750 kilos, of sulphate of magnesia, 750 kilos, of the protosulphates of 
iron and manganese, &o. The ammonia is probably due to the decomposition of nitrogenous 
organic matter, occurring largely in the Tuscan mountains, the soil near the lagoons being 
impregnated with sulphate of ammonia. In combination with the sulphates of soda, 
magnesia, and iron, sulphate of ammonia forms the mineral Boussingaultite, discovered 
byBechi 

3. The ammoniacal salts due to volcanic action are of no or of little value to industry. 
Maicagnin, sulphate of ammonia, is met with on Vesuvius and Etna ; sal-ammoniac is 
sometimes also found on Etna, as in the years 1635 and 1669, in such large quantities 
as to become temporarily an article of commerce at Catania and Messina. 

4. Ammonia is formed during many inorganic chemical operations, but rarely in 
quuitities rendering its preparation or recovery commercially available. Ammonia is, 
for instance, set free in the preparation of caustic soda (see page 189), and the purifi- 
cation of caustic soda by means of nitrate of soda ; the quantity of ammonia set free in 
this case is so large that it would be commercially worth trying to condense the gas in a 
eoke scrubber or condenser. When arseniate of soda is prepared by dissolving arsenious 
acid in a caustic soda solution, evaporating this liquid to dryness, and igniting the residue 
^th nitrate of soda, ammonia is disengaged in large quantity. 

5. Under the heading '* Ammonia as a by-product of the manufacture of sulphuric 
acid,'* there is in the original German text a description of a mere suggestion, embodied in 
a provisional specification of an English patent, for the utilisation of the waste nitrous 
vapours of sulphuric acid manufacture in the preparation of ammonia, by passing these 
Tapours, with steam, through red-hot tubes or retorts filled with charcoal, the ammonia 
thus formed being absorbed by sulphuric acid. This process could never be available but 
in badly arranged sulphuric acid works, because in well managed works the escape of 
nitrous fumes is so very small that it certainly would not pay to convert them into 
Ammonia. 

6. Of the many unsuccessful attempts made to directly convert the nitrogen of the 
atmosphere into ammonia, it will only be necessary to mention Fleck's suggestion, to 
pass a mixture of nitrogen, oxide of carbon, and steam over red-hot hydrate of lime, 
whereby ammonia and carbonic acid are formed : — 

7. Perhaps the indirect application of atmospheric nitrogen for the preparation of 
ammonia is of more importance. Margueritte suggests that cyanide of barium should be 
prepared, and its nitrogen converted into ammonia by the aid of a current of superheated 
steam at 300**. According to the description of this process in an English patent, not 
however in practice, native carbonate of baryta is calcined with some 30 per cent of coal- 
tar, for the purpose of rendering the mass porous as well as more readily converted into 
caoetic baryta at a lower temperature. The carbonaceous mass is, after cooling, 
placed in a retort, and kept at a temperature of 300°, while air and aqueous vapour 
ftre forced in, the result being the formation of ammonia in considerable quantity, and 
carbonate of baryta, which is again used. Ammonia is evolved from ball soda while 
cooling, during the formation of cyanogen and cyanide of potassium in blast furnaces, 
ud thg formation of sal-anmioniao in the process of iron smelting. 

^^toilSSi?' **' Industrially speaking, the organic sources of ammonia are far 
more important than the inorganic. Among the ammonia-yielding organic sub- 
stances coal (8) takes the first place ; the average quantity of nitrogen — 075 per 
centr-contained in coal is converted into ammonia during three different processes 
employing this valuable mineral, viz. : — 

«• By the dry distillation of coals for the manufacture of illuminating gas, ammonia is 
obtained in the so-called gas-, or anmioniacal gas-water, the liquid mainly consisting of 
an aqueous solution of sesquicarbonate of ammonia. The importance of this source 



230 CHEMICAL TECHNOLOGY. 

of ammonia production may be inferred from the fact that the one million tons of Mk 
yearly carbonised by the London gas-works will vieldi supposing all the nitrogen to be 
conTerted into sal-ammoniao, 9723 tons of that salt. 

/3. Ammonia is also formed when coal is converted into ooke in coke ovaiB« Yery 
recently the utilisation of this source of ammonia has been suocessfnly carried on st the 
large coking establishment at Alais, B^partement du Gard, France, and also at the ooke 
oyens belonging to the Soeieti de CarbonUatUm de la Loire ^ near St. Etienne, whezB, ia 
oyens constructed according to Knab's method, large quantities of ammoniacal salts are 
produced. 

y. Ammonia is produced during the combustion of coal as fuel, a portion of the nitrogen 
contained in the coals being eliminated as anunonia ; but this, it should be borne in mind, 
is a consequence of imperfect combustion, and consequently of loss of fuel ; and althougit 
a series of experiments have been made, and iqpparatus devised for .collecting and con- 
densing the ammonia evolved with the smoke, tibe industrial production from this aoutee 
has hiUierto been very limited. 

^"SSSSti?* 'T^ is the most important source of ammonia production. By 
the dry distillation of coals for the purpose of gas manufacture there are formed, in 
addition to permanent gases, various vapours, some of which on cooling yield tar 
and ammoniacal liquor, consisting chiefly, as before stated, of a solution of aesqui' 
carbonate of ammonia, but containing sulphuret and cyanide of ammonium, sulpho' 
cyanide of ammonium, and sal-ammoniac, and being coloured by tony natter. 

It is obvious that the quantity of ammonia contained in this liquor is not always 
constant, but depends upon several conditions ; for instance, the quantity of nitrogen 
contained m the gas coals, the hygroscopic moisture of the coals, and the degree of 
heat applied to the retorts. The nearer the retorts are kept to a bright orange-red 
heat, and the longer the distillation is continued, the larger the quantity of amjuonia 
formed ; for at a lower temperature, of course always above red heat, there may be 
formed aniline, chinoline, lepidine, and cyanogen compounds. Taking the average 
quantity of the hygroscopic moisture of coals at 5 per cent, and the nitrogen al an 
average of 075 per cent, 100 kilos, of coal would yield, under the most fiftvourttUe 
conditions, ogi kilo, of ammonia. According to Dr. A. W. Hofinann's report (1863), 
coal yields, when distilled, only one-third of its nitrogen, two- thirds being retained in 
the coke ; but no accurate experiments have been made on this subject. It has been 
practically ascertained on the large scale,' that z cubic inetre (=220-096 gallons) of 
gas-water yields at least 50 kilos, of dry sulphate of ammonia. The ammonia of the 
gas-water may be utilised in various ways. Where fuel is cheap, and crude sulphate 
. of ammonia or crude sal-ammoniac marketable article, the gas-water may be at once 
neutralised by an acid, and the liquid thus obtained evaporated. This is done in a 
sal-ammoniae factoiy at Liverpool, where, during the colder season of the year, 
300 cwts. weekly of this salt are prepared. Generally, however, the gas-water 
is submitted to a process of distillation, and the ammonia evolved converted into sul- 
phate, as in Mallet's apparatus, or into sal-ammoniac, as in Rose's apparatos. 

xanrt'B AppuRtai. This apparatus, in use in many of the large gas-works, is shown in 
vertical section in Fig. iii. The plan of action is to force steam into large vessels 
filled with gas-water, the effect being the volatilisation of the carlxMiate of ammonis* 
Sometimes lime is added. The volatilised ammonia — of course if lime is added 
caustic anunonia is evolved — is next convey.ed into an acid liquor, and thus 
converted into sulphate of ammonia. The apparatus consists of two cylindrical 
boiler-plate vessels, a and b. a is heated directiy by the fire, and is provided with a 
leaden tube, e, dipping into the liquid contained in b, this vessel being placed 
to catch the waste heat from the fire, b and e are man-holes ; a and a stirrers. By 
means of the tube d the fluid from b can be run off into ▲. Oas- water is poured 



AMMONIA. 



»3t 



into both Teasels and lime added ; uumouia is set free, while carbonate of lime and 
lalphnret of calcium are formed, and of course remain in the vessels after the vola- 
tilisation of the ammonia. The vessel n ia alao filled with ammoniacal water, and 
when the operation ia in progress thia water, already warmed, ie riio h; the aid of 
the tube A from D into B. K is a gas-water tank, from which n is filled hy means of jr. 
The ammonia eet free in i. ia, with the steam, coureyed by the pipe e into b. 




thence through e'. into the wash-veaael, c, and thence again throng c", into the first 
condenser, n. Tlie partially condensed vapour now pasaea into the condensing 
vessel. K, the worm of which is anrroimded by cold water. The dilute ammonia is 
collected in o, and forced hj means of the pump r into c, whence it is occasionally 
syphoned into either a or B. The non-condensed unmoniacal gas is carried from o. 
through a series of WonUe'e bottles, tho first bottle, h, containing olire oil for the 



J32 



CHEMICAL TBCBNOLOar. 



purpose of absorbing an; hydrocarbons mixed with the goa ; the bottle I oantains 
csustic Boda ley, in order to purify the ammonia and retain impurities ; the bottle k 
is half-filled with distilled water. The ammoniacal gas having passed through s, 
is conveyed to tlie large lead-lined wooden tank, l, filled with dilute solpburio acid if 
it Is intended to prepare sulphate of ammonia, or with water for ma V'T' g liquid 
ammonia. The vessel l is placed in a tank of water ; t is a amaU pipe for introdn- 
cing acid ; while the tube leading to u aerres to carry off any unalsorbed wmucmia, 
u being also filled with acid. 

BsH'i ippuitu. In the monnfaotars of liquid aramonia the apparatus devised by Hr. 
Rose, and shown in Fig. :ii, may be adyaBtageoos^ employed. It oonaiBta of: — i, a 
boiler ; B and c, tvo veBsels in which the gas-water is warmed by the aid of the tubes, 
« and /, through wbiob and g the steam and ammonia gas evolved io a. pass to the 
absorption vessels, d, b, and r, tbe connection between b and i being foimed by the gas- 
filters, a and h. The ammoniaoal water can be run into & by means of the tubes, I and », 




each of which is fitted with a tap or stopcook \ ih filled two thuds with gas-water and 
one third with elaked hme The oylmdncal sheet iron gsa filters o and h are filled with 
freshly burnt charcoal to retain any empyrenmatical mattei which might be carried over 
by the gas The absorption vessel d is filled with hydrochlonc acid while pore *>tm 
IS ponred mto a snd r When a is filled and the rest of the apparatus put in working 
order, the fire is kindled, iiie ammoniacal gas evolved in i passes with the steam to b and 
c, where a portion of the steam is condensed and retained as water in e and /. Into tbe 
boiler, k, is fitted a tube, b, containing a thermometer, Bnrronnded by brass fittings lor tbe 
better conduction of the heat; when this thermometer indicates gi" to 94°, the tap A is 
opened, and the tap, t, open np to this time, shut in order to cause tbe gas to pass into the 
hydrochloric acid contuned in d, imtil the vessels and a have been filled with fresh 
charcoal, an operation which is reqnired at the beginning of the working as well ai when 
the temperature in a has risen to g6°, g8°, and 100°. This having been done, the tap A i* 
again opened. When the temperature has reached 103°, talnng the boiling-point o( 
the liquid at 100°, all the ammonia is eipelled, and the liquid is then run ofT by opening 
tbe stopcock, a. Fresh lime having been put into tbe boUer, the operation is repealed. 
When the temperature in a reaches 103', the hquid in b becomes heated to 90°, and that 
in c to from 35° to 30°. Tbe vessel i contains from 120 to 150 htres of water, which is eon- 
verted into liquid ammonia of a sp. gr. = D'gio to o'gzo. c and n are gloss safety tnbce. 

l.niiB>'> Appumtiu. This spparatns, also intended for the utilisation of gas- water, is shown 
in Fig. 113; a is the boiler ; h the gas tube connected with the worm, f, which is placed iu 
a tai^, d, fiUed with gas liquor, ran into a by means of the tube e. The tnbe / is so fitted 



Id a H to kdndt of diaohBrgiag the waste liqnor Tesdll;. Ii mpreBentB a Etirm fitted to 
the boiler bj a stuffing box, and being intended to rake np tbe lime and prevent it getting 
caked to the bottom of a ; hi, a tnbe intonded for rmmiug gBs-liqaor into d, from a tank 
pUeed at t, bigW level ; i, a tube proTided nith a tap and fitted to the Dover of J, 



to Bonve; an; gas or v^jours from d into the vorm. k represents a iruh veuel, some- 
times Sited simply irith water, at others with milk of lime. The gas and vapoors having 
pused through it, are conveyed to tbe absorption vessel, I. The tube, tn, through which 
tbe gag pwBee, is fonnel-ah^ed, and opposite to the mouth of the funnel, at tbe bottom of 
tbe tank, a thick dim of lead ia fiied, beoause at this spot the action of the gas would sooa 
f*" sway the leaden lining of the vessel, o is a smaller wooden tank, also lead-lined, 
uto whidi sulphuric acid is ponred, and whesoe it runs into I through tbe stoneware 
■Tpbou, p. Any vaponrs given off are caught by the bood, r, and tbenee conveyed by a 
tnbe into tbe ohimney, ^e saline rnatter deposited in I is removed by a leaden pail, a* 
*bown In the cat ; when this pail is filled it is drawn np by means of the chain uid 
Pii% dded by the ooonter weight, i. Tbe salt (sulphate ol ammoaia] is pUoed in the 



234 CBEMICAL TECSNOLOaV. 

boaket, u, (rom vhiali tlie mother-liquor adhering to the salt draiaa again into the tank, L 
Evaporation ia tberefoie oimeceBBary with this apparatoa. 
uunoiiii bimi LuL g. Lant, or stale urine, is a veiy important eotizce of aMmonia- 
WheneTer lutrc^enona organic bodies are decajisg, ammonia is always fonned; 
when the organic substance is a proteine compound, there is formed carbonate of 
ammonia as well as sulphnret of ammonium ; but when the organic substance con- 
taina no sulphur, onl; carbonate of ammonia is formed, as is the case witb the nrea, 
CH^NiO, contained in urine, the nrea bj taking up the elements of the water being 
converted into carbonate of ammonia. Lant is freqnentlj employed without further 
preparation for various purposes, on account of the carbonate of amipn"" it 
contains, as. far instance, in washing wool and removing the fat from flannel 
and other woollen fabrics. 

The apparatoa exhibited in Fig. T14, oontrired bjFigaera, and until lately in operation 
at a large eatabliahment for the ntiliaatioD of the contents of tlie latrines and oloaec of 
Paris, consists of a ateam -boiler, w. the steam generated in which is conveyed to two larga 
iron cyiindeiB filled with lant. The oacbonate of ammonia eipelled is, inth the steam, 
condensed in a leaden worm ; the cooled liquid ia conveyed to a tank filled with add, and 



thns converted into carbonate of ammonia. The arrangement of the apparatos ia h 
follows:— The wooden veuet, a, eontsins some 250 hectolitreB of lant, and is Blled 
by means of the tube h. and 0' are two cylindrical aheet-iron vessels of 100 heotolitrss 
capacity ; f and p* are similar veaaels, the nee of which will be presently explained. At 
the commencement of the operation the boiler, w, is filled with aboat 130 bectoiitres of 
exhausted lant, taken from the veaaela c and c'. The lant in a. warm in conaequenoe of 
having served for cofidensation, is conveyed W by a tube, and thence by the tube h" to 
<f, cold lant being poured into a.. Tbe boiler, w, ia fitted with three tabes, viz., T, 
the steam pipe, m, a safety tnbe, brought to within a few centinietres from the bottom of 
the boiler, and carried above the roof of the shed, and n a smaller safety tube; v is a tabs 
fitted with a stopcock. The steam evolved in w ia carried bv t into c', evolving from the 
liquid therein the carbonate of ammonia it holdain solution. The carbonate, with the steam 
passes through t into the veaael, p, which serveB to retain any liquid carried over from c'. 
The carbonate of anunonia vapour now passes from r through the tnbe t* to c, and 
taking up in that vessel more carbonate of ammonia, is conveyed through the tube t' into 
p* (which again serves the purpose of i). and thence tbrongh t" into the leaden wonn of 
the condensing apparatus. The condensed liquor, a more or less concentrated solution of 
carbonate of ammonia, is run through t" into a. s wooden vessel, lead lined, and fiBed 
with a sufficient quantity of aulphoric acid to aaturale the carbonate of ammonia. The 
whole operation lasts about twelve houre ; after this time the waste liquid in the boHer ii 



AMMONIA. 



335 



Btilphftte of ammoniii, and at each operstioii aoo Wloa. of that salt are obtained by tbs 

working of one of the apparatns just deeeribed. It is itated tbat, from the 8oo,oot^ 
onbio metres of nrina yearlj mn waste in Faris alone, there eoold be obtained, b; 
proper treatment, 7 to 800,000 kiloB. of Bolphate of ammonia. 

i>UKmi> iniK bohh. 10. By the destructive distilliition o£ bjuidbI substances, such es 
bonea, hoofs oF horses, refuse horn, skills, hides, decayed meat, Ac., there is obtained 
a series of products, among which carbonate of ammonia prevails, with cyanogen 
compounds, snlphnret of ammonium, ssd tarrj matter — a very complex liquid con- 
tunisg pyrrol, bases of the ethylamin series, pyridin, CJH5N, picolin, C^^N, lutidin, 
C^H,N, and colUdin, CgHuN. The organic matter of these substajices contains 
from 13 to 18 per cent nitrogen ; the organic matter of bones contains 18 per cent of 
nitrogen, and, as the organic matter amounts to about one-third of the weight of the 
bonea, these contain about 6 per cent of nitrogen. Buffalo horn contains 17, waste 
wooUen fiibrics 10, and old leather 67 per cent of nitrogen. 

It is evident that the quantity of ammonia in the products of the dry distUlation 
of aninift l substances depends upon the kind and condition of these materials, and 
upon the temperature at which the operation takes place. The carbonate of 
ammonia is obtained in the condensers as a solid saline mass, the crude ml comu 
eervi, or in aqueous solution |so called ipiritui corau eervi), floating on the surface of 
the t«r. At the present time the manufacture of ammonia and its salts from tlie pro- 
ducts of the dry distillation of animal substances is a matter of but limited indus- 
trial importance, owing to the extended coal-gas manufacture. Indeed, dry distilla- 
tion is now only carried on for the purpose of obtaining animal charcoal, and tlie occur- 
rence of anunoniacal products is rather considered aa a necessary but unavoidable 
evil. A large quantity of animal matter is used for the manufacture of phosphorus 
and of prUBsiates, and in these operations the manu&cture of anunoniacal salts 
is either altogether out of the question or effected only on a limited scale. 

_ The apparatos aeed for the deBtmctive distillation of animal matter in in some respeeta 
dniilar to a coal-gas oven. Fig. 115 exhibits the conBtraction in general nse for what is 
termed animal charcoal burning. The retorts intended to contain the bones are set in 




IniBaaei and fitted at the end farthest from the mouth with tnbes, e 
'*itb leaden chambers, b, 0, &e. In these chambers the vaponis are condensed, forming 
a soEd laline mass, which is pnrified by aublimation in tha iron vessels, d d, fitted with 
leaden oovers. If, instead of booes, other animal matters, for inatanoe, horn, woollen 
tags, hair, and leather-cuttings, are operated upon, the result is that, instead of solid 



aafi 



CBSmCAL TECBNOLOOr. 



ot BHt-Hwrt aogu 



carbonate ot unnoma, an ammoniBOal flnid of 13° to 15* B. ia obtained, wtiloti may b» 
ntiliBed in varioQB ways. Where the motheT-liqnors of aalt-works ore readily obtun&ble, 
the; may, eepedally U rich in chloride of magneaiiim, be employed lor the preparation of 
Bal-ammoniaD by naing the hartBhom-Bpirit (crade carbonate of ammonia BcJation) for tb« 
precipitation of the ohloride of magneeium Bolation. 

iS:^"* When the beet-root juice is boiled, ammonia ia evolved in 
large quaittities, and maj be utilised in the preparation of 
8nlphat« of ammonia. The ammonia jielded by tte juioe ia the prodoct of the 
decompositiou of the aapartia acid and betain present in the rooto. According tO' 
Renard, a beet- root sngar manufactory nhidi yearly consumes 200,000 cwta. of beets 
might thus obtain 887 cwts. of sulphate of ammonia. 

'SS^iSlS:" Sal-ammoniac,, chloride of ammoninm. NH/1, cmuists in 100 
parts of^ 

Ammonia, 3183 Ammonium, 3375 

Hydrochloric acid, 6822 Chlorine. 66'25 

From the thirteenlh to the middle of the eighteenth centuiy Uiis salt was imported 
into Europe exclusively from Egypt, where it was obtained by the combustion of 
camel's dtmg. The camel feeds elmoat exclosivelyupon plants containing salts, and 
the sal-ammoniac is sometimes found ready formed in the animal's stomach. The 
sal-ammoniac having sublimed with the soot from the ctanbuslion of the dung, va» 
collected and refined hy a second sublimation. 

In localities where dtmg is used as fuel, it has been tried to obtain sal-anunoniac 
by combustion with common salt. The first sal-ammoniae manufactory in Germany 
was established by Graveuhorat Brothers, at Brunswick, in 1759. We have already 
^een bow crude sal-ammoniac may be prepared horn gas-water or by other means. 

The salt, no matter whence derived, is purified hy sublimation in cast-iron caul- 
dons, w, Fig. 116, lined withfire-clay. AsHoonaathe crude sal-ammoniac is put into 



FlQ. 




these vessels and tightly rammed, heat is applied, at first gently, so as to drive ofl 
any moistDie. This effected, iron lids, f, o, h, ore luted to the cauldrons ; the Uds 
can be readily moved by means of the pulleys and chains provided with eonnter- 
weights, B. c. n. Instead of iron covers lead hoods sometimes are employed, tha 
opening of which is temporarily closed with an iron disc. The hoods or covers oie 
always securely fiistened to the cauldrons, to prevent them being forced off by the 
pressors of the vapours. The temperature has to be regulated during the proceM 
Vith great nice^, for Un low a degree of heat yields a loose salt, and with too hi^ 



a degree of heat the oiganic matter present in the cnide Bal-ammoniac is liable to 
give off empjTeninatic matter, Bpoiling the appearance of the sublimed salt and 
interfering with iia good qualitj. Experience has proved that it is expedient to 
have the sablimation veHsels of rather Urge size, 2l to 3 metres interior diameter. 
'Wb^n the anblimed sal-ammoniac cake has attained a thickness of 6 to 12 centims. 
the operation is discontinued and the cake removed. The furnace is provided with 
an oven for drying the sal-ammoniac, this oven being shut with a door, b, movable 
by meane of a chain mnning over a pnllej, and aided bj a counterpoise. At the 
present day sal-ammoniac is often sublimed in earthenware vessels or large glass 
flasks, the crude salt being first mixed with 20 to 30 per cent of its weight of 
powdered animal charcoal, then dried over a good fire, and next put into the stone- 
ware sablimation vessels, b and m, Fig. 117, placed in two rows over the fire place, o. 




ings are Biirroonded by an 

■ tnge npon which rest the 

condcnEed. When glass 

30 centims. diameter. 



Each of these vessels is 50 centima. in height; the openini 
iron plat« properly fitted to the nock and provided « 
earthenware vessels wherein the sublimed sal-a 
flasks are nsed, the height of these vesBels is 60 centims. I 
Sixteen of these flasks, each charged with 9 kilos, of the miitnre of sal-ammor 
charcoal, are placed upon a furnace in cast-iron pots, which are filled with sand. 
The cover is in this case a leaden plate. The aublimatiou is ewefullj conducted, 
and goes on slowly, lasting about iz to 16 hours. After this time, the leaden plates 
are removed, bnngs or plugs of cotton-wool inserted, and the flasks allowed to cool 
very gradually, for as the salt expands on cooling the glsaa vessels may be broken. 
Tbe cake of sal-anunoniao when quite cool is scraped clean with a knife, and after- 
wards presents a perfectly crystalline appearance. When it is desired to obtain the 
salt &ee from iron, the cmde salt shonld be mixed, befm^ the subiimaticm, with 
ftboat 5 per cent of superphosphate of lima, or with 3 per oent of phoephate of 
anunonift ; by this addition any chloride of iron is decomposed and left in the retort 
tts phosphate. Tbe sal-ammoniacof commerce is met with either in crystalline state 
or as a compact fibrous sublimed material ; in the htter case the eakes or discs have 
a meniscus shape, weigh abroad from 5 to 10, but in England usually about 50 kilos,, 
and exhibit the appearance of having been formed in layers. Crystalline sal- 
animoniac is obtained by adding to previously re-cystollised sal-ammoniac aboiling hot 
and satnrated solution of the same salt, so as to form a thickish magma, which i» 
next placed in moulds similar in shape to those in use for making loaf-sugar ; after 
draining, the loaf of sal-ammoniac is removed, dried, and packed in paper ready for 
Bal<.'. Besides the use made of sal-ammoniac in cbentical laboratories, by pharma- 



238 CHEMICAL TECHmiOGY. 

ceutists and veterinary surgeons, it is industrially in demand for turning, zincing, aid 
soldering, in calico-printing and dyeing, in the manufacture of paints and pig- 
ments, in the preparation of platinum, snufif, and yery largely in the preparation of a 
mastic — i part of sal-ammoniac, 2 of sulphur, and 50 of iron-filings — ^used in joining 
steam-pipes, the sockets and spigots of iron gas- and water-pipes, &c. Sal-ammoniac 
is also employed in the preparation of pure ammonia liquida and anmioniacal salts. 
soiphftt* of AmmoBiA. It has bceu already mentioned that sulphate of ammonia — 

iNH4)aS04, 
is met with native in small quantities in the mineral known as mascagnin, in larger 
quantities in the boracic acid of Tuscany, while it i» also found in Boussingaultite. 

The modes of preparing this salt from the ammoniaoal water of gas-works, lant, the 
produots of the dry distillation of hones, by the aid of snlphnric acid, or by doable 
decomposition by means of gypsum or sulphate of iron, have been already given. The 
concentration of the weak solution by evaporation yields the crystalline salt, which, 
however, when obtained from Uquors containing tarry matters is usually of a deep bro^m 
colour, and has therefore to be purified by being dissolved in hot water, filtered through 
animal charcoal, and then re-crystallised, the best plan being to evaporate the solution 
rapidly, and remove the salt gradually by means of perforated ladles. The salt is then 
drained by being placed in baskets, and next quickly dried on heated fire-clay slabs, in 
which operation any particles of tar are decomposed. Sulphite of ammonia obtained by 
saturating carbonate of ammonia solution with sulphurous acid gas is, when exposed to 
air, gradually converted into sulphate. Sulphate of ammonia is, industrially speaking, 
far the most important of the ammonia salts, because besides being very largely used in 
artificial manure mixtures, and by itself for the same purpose, it is extensively employed 
in alum making, and is the starting-point of the preparation of chloride of ammnTiiTim^ 
carbonate of ammonia, liquid ammonia, and other similar products. 

carboutte of Ammonia. The sslt uscd lu pharmacy and industry under this name is in 

reality sesquicarbonate of ammonia, and composed according to the formula 

(NH4)4C308, or 2([NH4]aC03)-f COa. 

It is obtained either directly fi'om the products of the distillation of bones, or by 

subliming a mixture of chalk and sal-ammoniac. 

Among the products of the dry distillation of bones is found a solid sublimate, 
essentially impure carbonate of ammonia, purified by sublimation. For pharmaceutioal 
use carbonate of ammonia is prepared by submitting a mixture of either chloride of 
ammonium or sulphate of ammonia with chalk — 4 parts of the ammonia salt, 4 of chalk, 
and I of charcoal powder — to a low red heat. The product is a perfectly pure white saU; 
during the operation a large quantity of ammoniacal gas is evolved, which is either 
absorbed br water or by coke moistened with sulphuric acid. Eunheim decomposes the 
sal-ammoniac by subliming it with carbonate of baryta, chloride of barium being obtained 
as a b^-product. When freshly prepared, carbonate of ammonia is a transparent 
crystalhne mass, which, while absorbing water from the atmosphere, and evolring 
ammonia, is superficially converted into bicarbonate of ammonia (hydrocarbonate of 

ammonia, ^^ I CO3). Owing to the penetrating odour emitted by this salt, it is known 

as smelling salts. Impure carbonate of ammonia is also used for cleaning woollen and 
other fabrics, for the removal of grease from cloth, and further, for the extraction of the 
orchil pigments. Pure carbonate of ammonia, besides its use in pharmacy, is an 
ingredient of baking and yeast powders. 

Kitnta of Ammonia. This Salt, (NH4)N03, is prepared by the double decomposition 
of solutions of sulphate of ammonia and nitrate of potassa. The sulphate of 
potassa is first separated, and the solution of ammonia nitrate having been con- 
centrated by evaporation is left to crystallise, its crystalline form being similar to 
that of saltpetre. ^Vhen dissolved in water this salt produces cold» and is therefore 
used in freezing mixtures ; while the fact that when strongly heated it is converted 
into protoxide of nitrogen and steam (N2O+2H2O) might perhaps render it of use 
in the preparation of a blasting powder. 



SOAP. 239 

SOAP-MAKINO. 

Boft^ By soap we understand the product of the action of caustic alkalies upon 
neutral £Bits, and consequently soap may to all purposes be considered to consist 
of stearate, pahnitate, and oleate of potassium or sodium. Although soap has 
been manufactured from a very remote antiquity, this industry did not attain 
its present development upon scientific and rational principles until Chevreul pub- 
lished the results of his researches on the fats, and before the discovery of Leblanc 
called the soda industry into existence. 

BawMuezteisof Soap-boiling. The raw materials used in soap-boiling, as soap manufac- 
ture is usually termed in this country, are of two kinds, viz., fatty substances and 
solutions of caustic alkalies. Among the more important fatty substances are 
the following : — Palm-oil, of vegetable origin, met with in the fruit of a palm tree, 
Avoira slats or Elais guianemis ; according to others, however, this oil is derived 
from the Cocos hutyracea, C. nricifsra, and Arsca oleraeea, trees growing wild, and 
also cultivated in Guinea and Guiana. The colour of this oil is a red -yellow, its 
consistency that of butter, while it possesses a strong but by no means disagreeable 
odour, similar somewhat to that of orris root. When fresh, this oil melts at 27^, but 
by becoming rancid as it is termed— that is, by its decomposition into glycerine 
and free fatty acids — its melting-point rises to 31° and even to 36°. It is chiefly 
composed of palmitine mixed with a small quantity of oleine. Palmitine, formerly 
confused with margarin, is saponified by the alkalies and converted into palmitate 
of potassa or soda, wliile glycerine is set free : — 

Pabnitine (tripalmitine), ^^g ^q. I O3] [Glycerine, ^3^5 jOg, 

Hydroxide of potassa, 3 KOK ~ 

(caustic potassa) 

Palmitic acid is very similar to, and has often been confused with, stearic acid ; 
the former is in a pure state a solid white crystalline mass, which fuses at 62*^. Palm- 
oil often contains one-third of its weight of this acid in free state, and the quantity 
increases with the age of the oil. The red-yellow pigment of the palm-oil not being 
destroyed by its saponification, the soap made from this oil is of yellow colour, but 
if, previous to saponification, the oil is submitted to a bleaching process, that 
is to say, the pigment destroyed by chemical agents, such as the joint action 
of bichromate of potassa and sulphuric acid, the oil becomes nearly white, and 
yields, on being saponified, a white soap. 

The illipe, or bassia-oil, very similar to palm-oil, is obtained by pressure from the 
seeds of the Bassia latlfolia, a tree growing on the slopes of the Himalaya. At first 
the colour of this oil is yellow, but by exposure to sun -light it becomes white. Its 
odour is not very strong, but rather pleasant. At the ordinary tempeiftture of the air 
this oil has the consistency of butter ; its sp. gr. is = 0958 ; its melting-point 27** 
to 30°. It is somewhat soluble in alcohol, readily in ether, and easily saponified by 
potassa and soda. In its saponification, oleic acid and two solid acids with a variable 
melting-point are formed. The galam butter produced by the Bassia hutyracec^ 
a tree met with in the interior of Africa, is sometimes confounded with palm-oil, to 
which it is veiy similar, but of a deeper red colour. Galam butter fuses at 20° to 21 '^^ 
and is in its properties very much like palm-oil. Carapa oil and vateria tallow 
belong to the same class of fatty substances ; the first, the product of the kernel of a 
species of Persoonia, a palm tree met with in Bengal and Coromandel, is a bright 



1 Palmitate of potassa, 3|^^^^3'^lo. 



240 CHEMICAL TECHNOLOGY, 

yellow colonred material, which at 18'' separates into an oil and a solid fat ; known 
as pine-tallow, Malabar tallow, and obtained from the fruits of the Vdteria indica, 
is a white-yellow waxlike-tallow, melting at 35*. Mafurra tallow is obtained by 
boiling in water the seeds or kernels of the mafurra tree found at Mozambique ; 
this seed, very rarely seen in Europe, is of the size of small cacao beans. Mafurra 
seed also occurs in the Islands of Madagascar and Isle de K6union. The fat obtained 
from this seed has a yellow colour, the smell of cacao butter, and melts more readily 
than tallow. The fat of the seeds of the Brindonia indica^ employed at Goa, instead 
of butter, also for medicinal purposes, and for use in lamps, is nearly white ; melt» 
at 40°, and is insoluble in cold, but somewhat soluble in boiling alcohol. Cocoa-nut 
oil, obtained from the kernels of the cocoa-nut (Cocoi nucifera, C. hutyracea), is 
largely used in the tropics, where the tree abounds. This oil is imported into 
Europe, and is also obtained here by pressing and by treating the kernels of 
the imported nuts with sulphide of carbon. It is white, has the consistency of 
lard, but possesses a disagreeable odour and a somewhat foliated texture; its 
melting-point is 22°. Chemically considered this fat consists of a peculiar substance 
termed cocinin, with small quantities of oleine ; by saponification the former yields 
glycerine and cocinic acid (cocoa-stearic acid), CiaH^eOa. W. Wicke obtained 
in i860, 61 '57 per cent of fed; from the kernels. During the last twenty years cocoa- 
nut oil has been largely used for soap-boiling, because it is an excellent material for 
the preparation of so-called fulling soaps. Tallow is obtained by melting the fatty 
matter deposited in the cellular tissue of the abdominal cavity of cattle and sheep. 
The hardness of the tallow depends partly upon the animals frx>m which it ift 
derived, partly upon the food they eat ; if the food be fodder, the hardest tallow i» 
produced, while if it consists of the refuse from breweries and distilleries the tallow 
is soft. Kussian tallow owes its hardness to the fact that the cattle in that country 
are for frilly eight months in the year kept on dry fodder. Generally tallow melts at 
37°, and contains 75 per cent of its weight of solid fatty matter, stearin (tristearin) 
and palmitin (tripalmitin), the remainder being olein. If previous to being melted — 
that is, separated by the application of heat from the cellular tissue and membranes 
in which it is enclosed — tallow is preserved for too long a time, it obtains a 
bad odour, removed with difficulty. The operation known as tallow-melting can 
be performed in two way», either by simply applying heat, which causes the 
cellular tissue to shrink and become dry, the fat being expelled ; or the membranes 
and cellular tissue are destroyed by chemical agents, viz., the use of either 
sulphuric or nitric acid, or caustic ley. Among these methods, that of D'Arcet, in 
which sulphuric acid is used, and the operation carried on in closed vessels, is one of 
the best; the sulphuric add decomposes the vapours which are given off and 
destroys their lietidity, while more tallow and of a better quality is obtained. The 
vapours are carried either into the furnace or into condensing apparatus. D*Arcei 
recommends that to 100 parts of cut-up tallow, i part of sulphuric acid and 50 
parts of water should be used. WMle the loss by the ordinary method of tallow- 
melting amounts to 15 per cent, it is only 5 to 8 per cent when this method i» 
employed. 

Lard, owing to its high price, is rarely used in Europe for making soap, but 
is largely employed in the United States, where, especially at Cincinnati, enormous 
quantities of lard are converted into a solid fat (42 to 44 per cent), and into a fluid oil 
(lard oil, 56 to 58 per cent). 



SOAP. * 24X 

Olive-oil is obtained from the fruit of the olive tree, Olea EuropeUy belonging 
to the natural order of the Jasminea, and largely cultivated in the whole of Southern 
Europe and the coastlands of North Africa/ 

In order to obtain an oil of good quality it is essential that the olives should 
be gathered when they are fully ripe, which happens in the months of November and 
December. Unripe olives yield an oil having a harsh bitter taste, while, again, over- 
ripe fruit yields a thick oil, readily becoming rancid. The method of oH extraction 
from olives as carried on in Southern France is the following : — The ripe olives are 
first reduced to pulp in a mill ; this pulp is put into sacks made of strong canvas, 
or, better, of horsehair, and submitted to pressure. The first portion of oil thus 
obtained is the best and is known as virgin oil, or huile vierge. In order to eliminate 
ail the oil as much as possible, the cake, after the first pressing, is treated with 
boiling water and again pressed. The oil thus obtained possesses a fine yellow 
colour, but is more liable to become rancid than the virgin oil. Notwithstanding the 
second pressure the cake retains enough oil to make it worth while to submit it to 
further operation. Some kinds of olive-oil obtained by the second pressing are 
employed, under the name of Gallipoli oil, in dyeing Turkey-red. This oil has an 
acid reaction, consequent upon its containing free fatty acids, is turbid, rancid, and 
possessed of the property of forming with carbonates of alkalies a kind of emulsion, 
which in dyeing is known as the white bath. The olive-oil used for the purpose of 
gi'easing wool in spinning is known as lampant-oil. Under the name of Huil^ dtenfer is 
understood the olive -oil deposited in the tanks, where the water used for adding to 
the olives about to be pressed is kept; it is used in the manufacture of soap. 
During the last few years it has become the custom to exhaust the olives with 
sulphide of carbon instead of pressing them. 

Fish-oil, seal-oil, obtained from tlie tliick skin of several varieties of mammalia 
inhabiting the seas, especially of tlie colder regions of the globe, and belonging to the 
cetacea and phocena, varies somewhat in its prop^Hies, according to the mode 
of preparation and the animal from wliicli it has been derived. The sp. gr. of this oil 
18 0*927 at TiQp ; when cooled to 0° it deposits solid fat ; it is readily soluble in 
alcohol, and consists of oleine, stearine, and small quantities of the glycerides 
of valerianic and similar fatty acids. Fish-oil, besides being an important material 
in Boap-makiug, is also used in tanning, ta\^dng, and leather-dressing operations. 
Hemp-oil, obtained from the hemp-seed (CanfuihU «^//tt;a), containing about 25 per 
cent of oil, is chiefly used for making black, green, or soft soap. When fresh 
pressed, hemp-oil possesses a bright green colour, which in time becomes a brown- 
7ellow. Linseed-oil, like the former a so-called drying oil, is obtained from the well- 
known linseed (Linum iisitatUsimum) containing about 22 per cent of this oil, 
the sp. gr. of which is at 12^=0*9395. This oil consists chiefly of a peculiar 
glyceride which on being saponified yields a fatty acid difierent from oleic acid ; 
moreover, linseed -oil contains some palmitin. Castor-oil, from Bieinus communis y 
^>ehave8 when sapoifified very much like cocoa-nut-oil. As yet, however, this oil is 
not used in soap-making. Rapeseed-oil, as it occurs naturally, does not yield so 
good a soap when saponified as when the oil is first converted into rapselaidifiy 
vbich, according to A. Miiller, is done in the following manner : — To i cwt. of the oil 
is added i lb. of nitric acid diluted with i J to 2 lbs. of water ; next some iron nails 
M« added, and the acid fluid is well stirred through the oil with a wooden spatula. 
By the action of the nitrous acid set free, the oil is gradually converted into a yellow 

B 



244 CHEMICAL TECHNOLOGY. 

fatty mass, which after having been left standing for some weeks in order to solidih% 
may be directly saponified with soda. The oleic acid largely obtained in the manu- 
facture of stearine candles is a very important material in soap-making. This add 
is a solution of impure stearic and palmitic acids in oleic acid. 

Colophonium. the residue of the distillation of oil of turpentine, a yellow or 
black-brown coloured material, is largely imported from the United States for the 
purpose of preparing resin soaps, for sizing paper, and for the preparation of yeUow- 
soaps, which are resin and tallow saponified together in certain proportions. 

Lo7- The other important material required for soap -making is the ley ; that is to 
say, an aqueous solution of caustic potassa or caustic soda. Ley is not so much a 
constituent of soap as the material by which the chemical process termed saponi- 
fication is brought about. Usually the soap-boiler prepares the caustic ley, and 
formerly wood-ash or potash was used for tliis purpose, but at present soda is mora 
extensively employed. The conversion of the alkaline carbonates into caustic 
alkalies is efibcted by means of quick-lime ; but abroad chemical manufacturers 
produce caustic soda, and sell it to the soap-boilers xmder the name of soap-stone. 

The preparation of soap -boilers' ley from wood-ash is carried on in the foUoving 
manner : — The sifted ash is placed on a paved floor, and moistened with enough water to 
render it somewhat pasty, ^his paste is then formed into heaps, constructed with an in- 
dentation, into which the caustic lime in quantities of one- tenth to one- twelfth of the weight 
of .the ash is placed. Over the lime is next poured sufficient water to cause it to slake, 
care being taken to cover the lune up with ash. The ash and lime having been thoroughly 
mixed, are placed in a tank, shaped like a cone from which one- fourth of the narrow 
part is cat off, and fitted near tho bottom with a tap. At a distance of some five inches 
from the bottom a false and perforated bottom is fixed, so that the ley can coUect between 
the two bottoms. Under the tap a large iron tank is placed to receive the ley. The mixture 
of ash and lime having been placed upon a layer of straw upon the perforated bottom, 
and care having been taken to squeeze the mass together, water is poured over it for 
the purpose of lixiviating the material until completely exhausted. Usually three differeDt 
kinds of ley are prepared and kept, viz. — i. Strong ley, i8 to 20 per cent of alkali; 2. 
Middling strong ley, 8 to 10 per, cent of alkali; and 3. Weak ley, containing only i to 4 
per cent of alkali. This weak liquor is commonly used instead of water for Uxiviatio^ 
a new ash and lime mixture. The sodium-alnminate obtained by the decomposition of 
cryolite is used in the United States under the name of " Natrona refined aaponijUr,^* for 
soap manufacturing purposes. Sulphuret of sodium may also be used instead of caustic 
alkali. 

Theoty of SAponifleation. Before Chcvreul published his researches, it was supposed 

that fats and oils possessed the property of combining with alkalies. Chevreul 

found, however, that fats separated from their state of combination as soaps 

possessed properties difiering from those existing before they were saponified, the 

fact being that the substances we are acquainted with as oil or fats are compounds 

of peculiar acids, stearic, palmitic, margaric, oleic, all non-volatile substances; 

while certain fats which give ojff a peculiar odour contain in addition to these adds 

volatile fatty acids, as butyric, capric, capronic, valerianic, &c. The volatile acids 

in the ordinary oils and fats are combined with a sweet material, discovered by 

Scheele, and known under the name of glycerine. 

According to Berthelot's researches it is held that all the oils and fats which are 

used in soap-making are ethers of glycerine, C3H8O3, that substance being viewed as a 

trivalent alcohol, ^ 5 I q^ Palmitin, for instance, tlie main constituent of palm- 
oil, is glycerlyl-tripalmitate, or tiipaimitin, that is to say, glycerine in which three 
atoms of hydrogen are replaced by the radical of palmitic acid, Z'A |i n I ^^' 



Tripalmitin j^^f,k3.oW3 
and Caustic soda, 3NaOH, 



SOAP, 243 

tStearine (tristearine) and oleine (trioleine) have an analogous conetitiition. Wlien 
the fats, take palm-oil for instance, are saponified with caustic alkalies, say caustic 
soda, the fat — ^that is, in chemical parlance, the ether — is decomposed into alcohol, i.e., 
glycerine, and sodium palmitate, i.e.y soap, according to the following equation: — 

^ [Glycerine, ^sHs I O3, 

•^ ' ^ rC H O) 

V» and Soap, or sodium palmitate, 3 1 ^^^ ^i I q. 

The glycerine formed during the process of saponification remains, after the 
separation of the soap, dissolved in tlie mother-liquor from wliich it is prepared. 
.It is clear that such fats as palm- and cocoa-nut oil, whic^li in their ordinary sfcite 
contain fatty acids, are more readily saponitied than the perfectly neutral fats, viz., 
olive-oil and tallow ; wliile the oleic acid derived from the stearino candle manu- 
factories is readily saponified by carbonated alkalies. This observation applies to 
colophonium (resin), which consists essentially of a peculiar acid, pinic acid, but 
in these instances no real saponification takes place, inasmuch as no glycerine is 
formed. The decomposition of ^ fat by an alkali does not take place suddenly and 
throughout the whole of the fat at once, in the manner of inorganic salts, but passes 
through several stages, the first being the formation of an emulsion of ley and fat ; 
next fat acids and fat acid salts are formed, retaining the rest of the fatty matter in 
Buspension ; gradually tlie free fatty matter is saponified, and the fat acid salts are 
converted into neutral salts, or in other words, soap. 

When caustic potassa is used, soft soaps are produced, wliile tlie hard soaps 
result from the use of caustic soda. We distinguish soaps : — 

a. As hard soaps or soda soaps. 
p. As soft soaps or potassa soaps. 

* According to the fatty substances used in soap-boiling, soaps arc distinguished as 
tallow, oU, palm-oil, oleic acid, cocoa-nut, fish -oil, and resin soaps, &c. Technically, hard 
soaps may be divided into : — 

1. Nucleus Eoaps. 

2. Smooth soaps. 

3. FuUing soaps. 

The term nucleus soap designates the soap that after having been mode and 
separated from the ley by the aid of common salt is boiled down to a unifr)rm mass, fre«» 
from air bubbles, and exhibiting after soHdification small crystalline particles. The 
portion of the soap which docs not separate in that state assumes, by becoming mixed 
with a large or smaller quantity of the impurities of the ley, a mottled appearance. Tho 
soap directly separating by the addition of salt into globules or nuclei is pure soap, free 
from any adhering ley, water, or glycerine. Smooth soop is obtained by boiling for some 
time with either water or weak ley, the soap taking up a portion of the water, and 
losing the crystalline and mottled appearance. In the preparation of this soap it is 
first separated by means of salt from the mother-liquor (in saline solutions soap is in- 
soluble), but after that separation the soap is boiled with weak ley. The only difference 
existing between the two kinds is, that the latter contains more water than the former. 
The fulling soap, at the present that chiefly met with in commerce, is essentially the 
worst kind of soap, as an insufficient quantity of salt is used, the result being that the 
entire contents of the boiling-pan are kept together. The process of boiling is con- 
tinned.until on cooling the mass solidifies. The soap is removed, cut into bars, and sold. 
Soap niade from cocoa-nut oil possesses especially the property of being hard and dry 
notwithstanding that it contains a large amount of water ; consequently the use of cocoa- 
nut oil, both alone and with other fats to which it imparts its property, is greatly on the 
increase. Soaps of this kind will produce 250 to 300 parts of soap from 100 of oil. 
chw varkdies ^he German tallow soap or curd s. ap is essentially a mixture of stearate 
of s<Mip. of sodsk and palmitate of soda, and is commonly prepared indirectly by 
first saponifying tallow with caustic potassa, and next converting, by meoiiK of common 
salt, the stearate and palmitate of potassa into the corresponding soda compound. 

R 2 



244 CHEMICAL TECHNOLOGY. 

The soap-boiling pan employed is somewhat conical in shape. It is made of oast-iron, and 
provided at the top with a high lintel or bulwark to prevent any fluid boiling over. Supposing 
it to be intended to convert lo owts. of tallow into soap: — Into the cauldron is first 
poured about 500 litres of strong lye at 20 per cent ( = 1*226 sp. gr.) ; next the tallow is added, 
and a wooden or iron lid having been fitted to the cauldron, the fire is kindled. When 
ebullition sets in, it is kept up, with occasional stirring of the contents of the cauldron, for 
five consecutive hours. The materials in the cauldron are converted into soap-glue, as it 
is termed, a gelatinous masR, which, if the operation has been well conducted, ought not, 
upon the addition of fresh ley, to become thin, while it also should not flow in drops, but 
similarly to treacle from a spatula. The production of this substance is promoted by 
.addiug oil of tallow to the ley gradually and in small portions at a time. 

Mege-Mouries recommends either yolks of eggs, bile, or albuminous compounds. As proved 
by the researches of F. Knapp, it is always advantageous to first convert the fat, with the 
requisite quantity of ley, into an emulsion, and to leave the ley either not heated at all or 
only to 50'' in contact with the fat, so as to saponify first slowly in the cold and to finish 
off with ebullition. When caustic soda ley is used it is of a density ~ 10** to 12^ B. 
(= 1*072 to i'o88 sp. gr.) When the saponification is complete the operation of fitting or 
parting is proceeded with, and consists in adding 12 to 16 lbs. of salt to 100 of tallow. 
The soap is kept boiling until the soap-glue has become a grayish mass, from which 
the mother-liquor or under-ley readily separates, the latter being let off by a tap ; or, if 
no tap is fitted to the cauldon, the soap is gradually ladled over into the cooling-tank. 
The addition of salt not only aims at the separation of the soap from the ley, but also 
at the partial conversion of the potassa into soda-soap. If the soap-glue has been 
removed, it is again put into the cauldron, and there is J^ded a moderately strong ley 
and heat again applied. The soap again becomes quite miid, but consists chiefly of soda- 
Boap glue. The ebullition is kept up, and during its continuance fresh ley and salt are 
added alternately. By continued boiling the soapy mass becomes more and more con- 
centrated ; as soon as the foaming ceases, and the whole mass is in a steady ebullition, it 
is again ladled over into the cooling-taiik, or the mother-liquor is tapped off. The object 
to be gained by this second boiling is the conversion of the material into a uniform mass 
free from air-bubbles ; another is promoted by beating with iron rods. The hot soap is 
next placed in a wooden box, so constructed that it can be taken to pieces ; upon the 
bottom of this box, which is perforated, a piece of doth is stretched, so as to allow of any 
adhermg ley running off. When the soap is cool the box is taken to pieces, the soap cut 
into bars, and these placed in a cool, dry room. The cutting of the soap into bars is now 
effected by machinery ; formerly it was performed by hand with a peculiar tool, a ooppef- 
wire with suitable handles, such as cheesemongers sometimes use. 10 cwts. of tallow yield on 
an average 16} cwts. of soap, which by drying loses some 10 per cent. As it is impossible, 
even with repeated applications of salt, to convert potassa-soap completely into 8oda-«oap, 
the German nucleus, or KernseifCy is always mixed with a considerable quantity of 
potassa-soap, to which it owes its peculiar softness. According to the re8e:u-ches of 
Dr. A. C. Oudemans (i86g) only half the potassa is converted into soda-soap. 

ouve-ou Soap. This kind of soap, also known as Marseille, Venetian, or Gastilian soap, is 
chiefly prepared in the southern parts of Europe. The olive-oil is frequently mixed with 
other kinds of oil, such as linseed, poppy-seed, cotton-seed oil, <&c. Two kinds of ley are 
•employed in the preparation of this soap : the first ley is only a caustic soda solution, 
and used for fitting or preparatory boiling ; the other ley is mixed with common salt, 
and intended to effect the separation of the soap. The preparatory boiling aims at the 
formation of an emulsion or the production of an itat globtUaire, whereby the contact of 
oU and alkali is greatly promoted, and a real soap-glue ultimately results. In order to 
remove the water from this m iterial as much as possible, a ley containing common salt is 
employed, and lastly by a third boiling the saponification is rendered complete. By the 
use of the ley containing common salt it is possible to keep the soap-glue in such a con- 
dition that it can take up alkali without combining with the water. The preparatory boiling, 
or fitting, is carried on in large copper vessels, capable of containing 250 cwts., the 
caustic soda employed for this purpose having a strength of 6° to g** B. (» 1*041 to 1*064 
6p. gr.) The ley is brought to ebullition first, and the oil to be saponified is next 
added, care beiug taken to stir the mixture in order to promote the reaction. Gradually 
the mass becomes thick, and as soon as black vapours arise, due to the decomposition of 
a small quantity of the soap-glue by coming in contact with the very hot copper, there is 
added the stronger ley of 20° B. (1*157 sp. gr.) If it is intended to produce a blue- 
white soap, some sulphate of iron is added. As soon as the mass has become sufficiently 
thick, the soda-ley mixed with salt is added. After some hours the soap entirely separates 
from the mother-liquor, which is then run off, and fresh ley added also coutainiug common 
salt. The final boiling is then proceeded with, the ley having a strength of 20"* to 28" B. 
The ebullition is continued gently until the alkali is exhausted, when the mother-liquor 



80AP» 245 

is again nin off, and fresh ley mixed with common salt again added ; this operation is 
repeated some fonr to six times, when the soap is at last quite ready. This stage is 
indicated by the absence of all smell of oil and the pecoliar grain of the mass, which is 
left to cool ; but if sulphate of iron has been added, it is necessary to stir the soap cou- 
tiuuoasly until nearly cold, in order to produce the mottled appearance due to the forma- 
tion of sulphuret of iron from the sulphate by the action of the sulphuret of sodium of the 
Boda-ley. Mottled-soap is produced in England by adding a concentrated solution of 
crude caustic soda containing sulphuret of sodium to the liquid soap, previously impreg- 
nated with sulphate of iron. When nearly cold the soap is placed in wooden boxes and 
left to completely solidify. After ten to twelve days it is ready for being cut into bars. 
64 litres of oil, = 58 to 60 kilos., yield go to 95 kilos, of soap. White-oil soap is prepared 
in a similar manner, but purer materials are employed. A good sample of Marseilles 
mottled soap should contain : — 

I. n. 

Fat adds 63 62 

Alkali 13 II 

Water 24 27 

100 zoo 

OMo Add Soap. Is obtained from crude oleic acid, a by-product of'stearine candle 
manufacture. The oleic acid produced by the distillation process is less suitable for 
803p-making pnrpoaes. Oleic acid is sapouitiei simply by being mixed with a strong 
Bolntion of carbonate of soda, or by the application of caustic soda. In the use of the 
carbonate of soda, however, there is the disadvantage of the effervescence due to the 
evolution of carbonic acid, and consequent boiling over or spiUiug of the materials. 
Pitman uses the carbonate of soda in a dry state. Heat is best applied by Morfit's 
arrangement, in which steam is passed through a system of pipes moved by machinery 
and acting as stirrers. Besin is sometimes added. As soon as the mass has acquired 
sufficient consistency, and the effervescence ceases, the soap is put into moulds to cool 
and solidify. When caustic soda is used, half the ley (sp. gr. i'i5 to 1*20 = 20° to 25° B.) 
Ib first poured into the cauldron and brought to ebullition, next the oleic acid is added, 
and as soon as the soap-glue is formed, the other half of the ley is put in, and the ebul- 
lition continued until the soap is formed. The separation from the mother-liquor is 
greatly promoted by the addition of some salt. The soap is poured into moulds to 
cool and solidify. In order to impart greater hardness to the soap, some 5 to 8 per 
<'6ut of tallow is added to the oleic acid. 100 kilos, of oleic acid yield from 150 to 
160 kiioB. of soaps, which, when weU made, consists in 100 parts of — 

Fat acids 66 

Soda 13 

Water " 21 



100 



BdiaTBiiaw 9<Mip«. Colophonlum and ordinary fir-tree resin combine at boiling heat more 
'^ftdily with alkalies thsdi fats and oils ; but the compounds obtained by treating resins 
uone with alkalies are not soaps in a chemical sense, nor have they the appearance or 
properties of soap. When tallow is saponified with a portion of resin, a true soap is 
obtained. In England resin-tallow soap is manufactured very largely by first preparing a 
tallow-soap, and when this is ready adding to it about 50 to 60 per cent of the best resm 
proriously broken into small lumps. The mass is thoroughly stirred, and after the resin 
UM become incorporated with the tallow, the mother-liquor or under-ley is run off, and 
the Boap-making finished by boiling with a quantity of fresh ley at 7° to 8'* B. The inso- 
mble alumina and iron soaps having been removed as scum from the top of the liquid, 
^ hot soap is poured into moulds made of wood or sheet-iron ; sometimes palm-oil is 
•dded in order to improve the colour, of the soap. Usually, palm-oil is not saponified 
uone, but is added to tallow ; by treating a mixture of 2 pa^s of tallow and 3 parts of 
Pum-oil with potassa or soda-ley in the ordinary manner, and by mixing this soap with a 
nnn soap prepared from i part of resin and a proper quantity of potassa-ley, the German 
pabn-oil soap is obtained. 

^oUbig'Softpi. As it is possible to incorporate soda-soaps with a certain quantity of water 
witboat impairing the appearance, the soap-boilers at the present day only prepare so- 
«jflfid fulling-Boaps, that is, such as are not completely separated from the under-ley by 
"» aid of salt. These soaps contain, in addition to water, glycerine and the salts 
ezistiiig in the nnder-ley. It is owing to the large amount of water contained that the 
Boap-boiier is enabled to sell cheap soaps notwithstanding the very greatly increased price 



346 CHEMICAL TECHNOLOGY, 

of fatty substanoes. Soap of this kind (in Germany known as Esohweger soap) appears 
when freshly made quite hard and dry, though containing such a large quantity of water. 
It is possible to make from loo kilos, of fatty matter 300 kilos, of good, bright, hard soap. 

The manufacture of cocoa-nut oil soap resembles that of the other kinds of soap. 
With a weak ley cocoa-nut oil does not form the emulsion common to other soaps, 
but swims on tlie surface as a clear fat ; when, by boiling, the ley has reached a 
proper consistence, the oil suddenly saponifies. A strong soda-ley is used in the 
preparation of this kind of soap. Cocoa-nut oil in saponifying does not separate 
from the under-ley, therefore potash-ley is never employed. To prevent the separa- 
tion of the soap from tlie mixing, the quantiiy of caustic-ley used must be accurately 
measured. Pure cocoa-nut oil soap hardens quickly. It is white, like alabaster, 
shiny, soft, and easily lathered ; it has, however, a peculiarly unpleasant smell, 
which cannot be entirely masked by any perfume. Cocoa-nut oil is seldom used 
alone, but usually as an addition to palm-oil and tallow. This kind of soap can be 
made without boiling, by merely heating to 80^ C, by means of steam, to melt the 
&t8, a strong soda-ley being added, and the mixture quickly stirred. This is known 
as the " cold method," and soap can be thus prepared in large quantities in a short 
time, and is generally hard and dry. When exposed to the air for a month or so, 
the soap loses considerably in weight, and becomes effloresced superficially. B. Unger 
(1869) prepares a soap in the following manner : — He saponifies palm-oH with soda- 
ley and salt as usual. The product is palmitate of soda. At the same time cocoa- 
nut oil is saponified by means of carbonated and caustic soda-ley; this is added to the 
palm-oil soap, and they are boiled. As a rule there are taken 2 parts of palm-oil to 
I part of cocoa-nut oil ; and to 100 parts of the latter there are added 14-3 parts of 
caustic soda (Na^O) and 12*8 parts of carbonate of soda. According to Unger s 
experiments, this soap contains 5 mols. palmitate of soda, i mol. carbonate of soda, 
and X mol. water. The " marbling " or " mottling " is eflfected in the following 
manner : — Colouring matters, oxide of iron, brown-red, Frankfort-black, are mixed 
with a small portion of soap ; this is poured into the rest of the soap, with which it 
forms layers of unequal thickness. The entire mass is now stirred, and by this 
means a marbled or grained appearance imparted. 

Soft-soap. As before-mentioned, potash forms with fats and oils only a sofi-goap, 
wliich does not dry when exposed to the air, but on the contrary absorbs water, 
remaining constantly like a jelly. As a rule, these so-called soaps are impure solu- 
tions of oleate of potash in an excess of potash-ley, mixed with the glycerine sepa- 
rated in the saponification. Soft-soaps can be prepared only with potash-le3r8, 
altliough in practice i part of soda-ley is substituted for a part of the potash to assist 
in somewhat hardening the soap. There is no separation of the soap from the 
under-ley, which contains all the impurities ; consequently these are disseminated in 
the soap. 

In consequence of tlie solubility and cleansing properties of soft-soap, its use is 
preferred to that of soda-soap in the manufacture of cloth and wooUen articles. It 
>vill have been seen that the difference in manufacturing hard- and soft-soaps 
ojnsistsin employing potash-ley for the latter, and soda for the former. Wood-ash 
is not used in prepai-ing the potash-ley, but always pure potash; the preparation 
follows the usual method with caustic lime. The fats used are mixtures of the 
vegetable and animal oils, as the fish-oil known as " Southern," with rape, hemp, and 
linseed oils. The particular oil used varies according to the time of the year and 



SOAP. 247 

Inarket price: in winter the soft oils are employed; i\\ summer the firmer oils. 
Soft-soap is generally used for falling and scouring ; but abroad it is sometimes used 
for wasliing linen, to which it imparts a most disagreeable fishy odour, hardly 
concealed by any amount of perfume. The best soft-soap is made from hemp -seed 
oil, this oil imparting a green tinge, which, however, can be imitated by adding indigo 
to inferior soaps. Summer soap, as it is termed, contains, owing to the fat employed, 
more palmitate of potash in proportion to oleate than the winter soap. Sometimes 
saponification is effected with a mixture of hemp- and pahn-oil or tallow, of train-oil 
and tallow, &c. 

The boiling of the soft-soap commences witli a strong ley containing 8 to 10 per 
cent potash, by which an emulsion is formed. The scum is dashed about with a 
stick, the beating-stick, and by this means all the alkali is caused to be taken up. A 
fresh ley is tlien added, and the boiling continued, until the soap upon cooling 
stiffens into a clear tough mass. When the soap contains too much caustic alkaU, 
which can be ascertained by the taste, more oil is added. The dear-hoiling now 
commences, during which the excess of water is removed. To avoid lengtliy evapo- 
ration a coucentrated ley is employed, and the soap, instead of bubbling up, has its 
surface covered ^vith blisters as large as the hand ; these blisters are termed leaves. 
When the boiling is finished — ascertained by placing some of tlie soap to cool on a 
glass plate, from which, if fiim, it can be separated — the soap is cooled, and stored 
in barrels. 

Soft-soap will take up a considerable quantity of water-glass solution without 
alteration. Kecently, for fulling, there has been added to the soft-soap a solution of 
sulphate of potash, or a mixture of alum and common salt, and also potato-starch. 

variom otibPr Boapi. Another Boap is prepared from hog's-lard, and when scented with oil 
of almonds or essence of mirbane (nitrobeuzol) is sold as almond-soap, and as a cosmetic. 
A soap is mode from the grease of sheep's-wool. The so-called bone-soap is nothing more 
than a mixture of the usual hard or cocoa-nut oil soap with the jelly from bones. The bones 
are first treated with muriatic acid to separate the phosphate of calcium. A variety of 
bone-Boap is the Liverpool common soap. Flint-soap is an oil- or tallow-soap with which 
nhceous earth is mixed. When powdered pumice-stone is substituted for the siliceous 
earth, the soap is called jmmic£-soap. In America as well as in England a water-glass 
solution is substituted for the siliceous earth, although according to Seeber the result is 
not BO efficacious. Cocoa-nut oil soap, however, containing 24 per cent silicate of soda 
and 50 per cent water, is very firm. In the United States water-glass is added to the soap 
when, still hot from the boiling-pan, it is poured into the moulds. The water-glass 
Bolution is of a density = 35° B. (= 1*31 sp. gr.) ; the proportion of soap is 60 per cent. 
This kind of water-glass soap generally sets hard. Recently cryolite and aluminate of soda 
have been employed. 

Toilet SMpa. On accouut of the reduction in tlie duty toilet soaps are now very 
largely in demand. They are generally made by re -melting and perfuming common 
soap. English toilet soap is considered the best, as that of France and Germany 
being perfumed while cold is not so equable a product. 
There are three modes of preparing toilet soap, viz. — 

1. By re-melting raw soap; 

2. By the cold perfuming of odourless soap ; 

3. By direct preparation. 

I. In the method of re-melting, good raw soap is scraped, into a boiling pan, and 
after melting and skimming the perfume is added. The soap is then cast in moulds 
of the required form. 2. In the method of perfuming in the cold, odourless soap is 
cut into fine shreds by a machine ; the perfume is then added, and the soap is passed 



248 CHEMICAL TECHNOLOGY. 

between rollers, the sheets or bars tlius formed being cut into tablets. Strave, of 
Leipsic, has invented a machine by means of which soap is stamped into the shape 
required. 3. The direct preparation of toilet-soap consists in colouring and scenting 
pure white common soap without an intervening cooling. The colouring materials 
are — for red, cinnabar, coralline, and fuchsine; the violet tar colour for violet; for 
blue, ultramarine ; for brown, a solution of raw sugar or carameL Windsor soap 
is prepared in the following manner: — 40 pounds of mutton tallow and 15 to 20 
pounds of olive-oU are mixed with soda-ley marking 19°, making a soap of 
15°; finaUj, with ley marking 20°, when the soap is of the consistency of marrow. 
The excess of ley is then neutralised. When the soap is set it is allowed to stand 
six to eight hours, and during this time most of the under-ley separates. It is 
then placed in a flat form, and pressed until no fluid exudes. It is scented 
with cumin oil, bergamot, oil of lavender, oil of thyme, &c. Moist sugar is used 
to impart the brown colour. Hose soap, savon h la rose, is manufactured by 
melting the ingredients of three parts of oil-soap with two parts of tallow-soap 
and sometimes water ; the perfume is attar of roses, oil of roses, or gilliflower 
water, the colouring matter being generally cinnabar. Shaving-soap must not 
contain free alkalies. It is sometimes prepared by boiling fat acids with a 
mixture of the carbonates of soda and potash. Lather-soaps have in equal 
volume only half the substance of the other soaps. Palm- or olive-oil soap is melted 
with an addition of one-third to one-eightli the volume of water, and tlie mass stirred 
imtil it has increased to double the volume. It is then placed in a mould. It 
should be remarked that the oil-soaps, and not tallow-soaps, are the true for- 
matives of the lather-soaps. 

Tnuuparent Soap. Ordinary dry tallow-soap is cut into splinters and heated 
with an equal weight of alcohol, in which the soap dissolves. The mixture is 
allowed to cool ; therewith all impurities are thrown down, and the clear fluid is 
placed in the moulds, where it has to remain three to four weeks to harden. 
Tincture of cochineal and aniline red are employed for colouring transparent 
soaps, and also Martin's yellow. The perfume is chiefly oil of dnnamon, sometLmes 
oil of thyme, oil of marjoram, and sassi£ras-oil. Glycerine-soap is prepared from 
an alcoholic solution of ordinary soap, to which glycerine is added. Or 5 cwts. of 
soap with an equal quantity of glycerine are heated by steam in a copper vesseL 
The mixture is placed in moulds, and allowed to set in the usual manner. A solution 
of soap hi an excess of glycerine (35 : 30) forms fluid glycerine-soap, which is of a 
clear honey consistency. Both varieties are perfumed with essential oils. 

um8 of Soap. Soap is used for cleansing purposes in washing, in bleaching eloth tnd 
woollen materials ; for the preparation of Uthographic tints, <tc. The cleansing proper- 
ties of soap are due to the alkaUes it contains. The alkali, although combined with the 
fat acids, loses none of these properties, which are in fact included in the combination of 
the alkali with the fatty Babstances of the dirt to be removed. The explanation of the 
action chemically, according to Chevreul, is the following : — The neutral salts formed by 
the alkalies and the fat acids, stearates, palmitates, and oleates are decomposed by the 
water, whereby insoluble double fat add salts are separated, while the alkali is set free. 
By means of the free alkaH the impurities clinging to the materials are removed, snd 
ts^en up by the fat acid salts, the suspended dirt being thus contained in the lather. 

so«p Tasta. The greater the quantity of fat adds combined in the soap, the higher is its 
value. A normal soap, besides alkaline fat acids, should only contain; free water, the 
quantity of which gives a means of estimating the value of the soap. It is in the power 
of the soap-maker to manufacture 300 parts of a good hard soap out of 100 parts of fat 
When too small a quantity of water is contained the soap becomes too hard, and 



SORACIC ACID. 240 

noflh labour ia lost in obtaming a lather. If, on the other hand, water is held in too large 
a qaantity there is a great loss of material. The degree of hardness of the soap forms, 
therefore, another means of estimating its yalue. Many soaps contain 2 to 3 per cent 
glyceiine. But the proportion of water and the hardness of a soap are not the only 
means of estimation, there still remains the estimation of the nentrekl fat acid alkalies, 
the free alkali, common salt, or unsaponified fat in the residue left after the drying of the 
soap. According to W. Stein, the presence of free alkali may be ascertained by means of 
oaiomel, or according to Nasohold, by nitrate of protoxide of meroory. Uncombined fat 
retards the formation of a lather, and after a time imparts to the soap a rancid odour. 
Bat the worth of a soap can only be accurately ascertained by means of chemical 
analysiB. 
laMiabie Soup. All soaps that havo not potash or soda for a base are insoluble in water. 
Many of the insoluble soaps are of technical importance. 

C^cium-soap plays an important part in steanne-wax manufacture. It is made either 
directly by saponifying fat with hydrate of lime, or by treating soluble soap with a solu- 
tion of a salt of lime ; this soap is formed to some extent when ordinary soap is dissolved 
in hard water. Barium- and strontium-soap are similar to calcium-soap. Magnesium- 
soap is made directly with difficulty ; it may be obtained indirectly by dissolving ordinary 
soap in sea-water. Aluminium-soap is without doubt an insoluble soap ; argillaceous 
earths will not saponify fat unless aluminate of soda or potash is present. Aluminium 
Boap is used in waterproofing. According to Jarry, wood impregnated with oleate or 
etearate of aluminium is impervious to moisture. Lately many materials have been ren- 
dered waterproof by being dipped into a solution of acetate of aluminium, and then into 
a soap solution, aluminium soap being thus formed. 

Manganese-soap is prepared by the addition of sulphate of manganese to ordinary soap, 
or by boiling carbonate of manganese with oleic acid. It is usually applied as a siccative. 
Zinc-soap is prepared by the double decomposition of sulphate of zinc and soap, or by the 
saponification of zinc- white with olive-oil or fat, forming a yellow-white mass. Zinc-soap 
is used as an oil-colour, and also as zinc-plaster. Lead-soap or lead-plaster is made by 
adding white-lead to oHve-oil, or acetate of lead to soap solution. Tin-soap is prepared 
by the double decomposition of chloride of tin with soap. Copper-soap, formed by the 
addition of sulphate of copper solution to soap, is soluble in ether and oil, less so in alcohol ; 
it is used in preparing water-colours. It may be made by boiling oleic acid with 
carbonate of copper. Mercury or quicksilver-soap is prepared from chloride of mercury 
and soap ; it is difficult to dry ; is white, but when exposed to air and light turns grey. 
Mercury-soap was formerly known as quicksilver-soap and quicksilver-plaster. Silver, 
gold, and platinum-soaps, are severally prepared by double decomposition ; but they are 
not much used. Gold-soap is employed in gilding porcelain ; and silver-soap for dark- 
ening the hair. 

Boric ob Boracic Acid, and Borax. 

Bofacic acid occurs native as sassolin, H3BO3 ; in 100 parts : — 

Anhydrous boracic acid, B2O3 56*45 

w aiier *•• .«• ... ••• ... ... «.. ... 43 5 5 



xoooo 



and further in the foUowing minerals : — 

^''^**?ji"Lf^™l,?r:t^*''''™ "^^ \ ^tJ» 62-5 per cent Boracic acid, 
cmonae 01 magnesium ) ** *^ 

Bhodicite, or borate of calcium .. 

Hayescine, Tiza, or borate of lime 

Hydroboracite 

Tincal or borax, borate of soda 

Datholite) or boro-silicate 

Botryolite ... 

Axinite 

Tourmaline 



... ... 



•.• ..• 



... ... ... ••* .*• •.• 



... ... ... ... ... ... 



... ... ... ... ... 



• »» 


30 to 45 


«> 




>f 


30 to 44 


»» 




t> 


47 


»» 




t1 


3653 


»» 




if 


18 


f» 




»> 


. 2035 


»> 




»» 


2 to 66 


91 




)l 


2 to II'8 


iy 





2y) CHEMICAL TECHNOLOGY. 

Boracic acid is found also in small quantities in many mineral waters and in sea- 
water. Larderellito, or borate of ammonia, and lagonite, or borate of iron, are both 
found in very small quantities in Tuscany, but are interesting to mineralogists only. 

Boracic acid is found as sassolin in many volcanic regions mixed with sulphur, 
and in thje hot springs of Sasso, in Tuscany, and also between Volterra and Massa 
Maritima in the clefts and rents of the volcanic formation of rock. Hofier and 
Mascagni (1776), first mentioned the occurrence of boracic acid in the waters sub- 
jected, in the clefts of the rock, to the sulphurous exhalations. The little pools 
formed in these clefts are variously known as fwnmecki^ fumaroles^ ioffiioniy and 
mofetti. The boracic acid deposits in some cases cover an extent of six miles. 
Since 18 18 artificial soffioni have been constructed, and the benefit derived by the 
country from the introduction of the industry is immense. The first artificial lake 
was situated near Monte Cerboli, and the product was ioc some time known as 
Larderellito, from the owner's name, Larderel. The production from these works 
nlone amounted in 1839 to 717,333 kilos., and in 1867 to 2,350,000 kilos. The 
increase has been greatest since 1854, owing to the energy with which Grazzeri and 
Durval entered upon the construction of the artificial soffioni. 

The soil of the natural lakes, or beds of the natural soffioni, are of a slimy 
formation, and have a peculiar seething movement due to the escape of the 
sulphurous vapours from tlie fumaroles or vents. According to Payen, this vapour 
or steam may be considered as condensed and as non-condensed, the former con- 
taining besides water, sulphate of lime, sulphate of magnesia, sulphate of ammonia, 
ddoride of iron, hydrochloric acid, organic substances, a fishy-smelling oil, day, 
sand, and a small quantity of boracic acid. The non-condensed vapour consisted of— 

Carbonic acid 0*5730 

Nitrogen 03480 

Oxygen 0*0657 

Sulphuretted hydrogen 0*0133 

Payen is of opinion that the vapours contain no boracic acid, while C. Schmidt 

tliinks otlicrwise, as tlie vapours, when condensed without contact with the water 

of tlie soffioni, yield boracic acid. The condensed vapours contain 0*1 per cent 

boracic acid. 

Theory of the Formation Dumas and Paveu fouud au explanation of the formation of 

of the , . , . . , , , , . , , . . 

Nathre Bor&do Add. volcamc boracic acid upon the hypothesis that there exists m 
the interior of the volcano or beneath the under-crust of the earth a layer of sulphide 
of boron (BaS3), which under the action of the mineral waters becomes converted 
into boracic acid and sulphuretted hydrogen. P. Bolley gives the action as similar 
to that occurring in the formation of sal-ammoniac, a very common mineral in 
volcanic regions. Professor Becchi, of Florence, found nitride of boron (BN) in 
one of the imdcr-strata, from which he prepared artificiaDy by means of steam 
ammonia and boracic acid. Also Warrington (1854) and Popp (1870) attributed the 
appearance of boracic acid and ammonia in volcanoes to the decomposition of nitride 
of boron by evaporation. Recently (1862) Becchi has obtained boracic acid by the 
decomposition of borate of calcium in a stream of superheated steam. 

"^BiS^^AdS °' T^® °^ost general method of obtaining boracic acid is by the evapoia- 
tion of the water of the natural or artificial soffioni. The water is either naturally or 



BORACIC ACID. 



251 



artificially introduced into the natursd fumaroles, as these sometimes do not re- 
supply themselves with sufficient rapidity. As soon as the water has absorbed a 
considerable quantity of the vapours it is removed and placed in a large mason- 
work cistern; this cistern is imbedded in the soil near the fumaroles, and the 
natural heat is sufficient to cause evaporation. The vapours are condensed in a 
wooden chimney. The separated impurities, gypsum, &c., remain in the cistern. As 
goon as the solution is of a sp. gr. = 107 — I'oS at 80°, it is poured into leaden 
crystallising vessels where the boracic acid crystallises out. The mother-liquor is 
evaporated to dryness. It should be remembered that the entire operation is con- 
ducted with the assistance of the natural heat of the fumaroles only. Occasionally 
the boracic acid is only present in the natural waters to 0002 of a part ; and in 
these cases fuel must be used in the evaporation, which therefore entails the expense 
of carriage, as fuel is very scarce near the soffioni. Charcoal is generally used. 
But by this means an acid is obtained, containing about 70 to 80 per cent hydrated 
boracic acid, with 10 per cent impurities. Clouet removes the impurities by treat- 
ment with 5 per cent of ordinary hydrochloric acid. Boracic acid for pharma- 
ceutical purposes may be prepared by dissolving i part of borax in 4 parts of 
boiling water, and decomposing the solution with one-third part of sulphuric, or 
better with half part of hydrochloric acid of 1*2 sp.gr. The acid separates on 
cooling, and can be purified by crystallisation. 
In 100 parts of commercial boracic acid from Tuscany, H. Vohl (1866) found : — 



!•• ••• ••• 



Boracic acid 
Water of crystallisation ... 
T I tt ler ... ^... •■* ... 

Sulphuric acid 

Sihcic acid 

omiu a*. ... •■* ... ... 

Oxide of iron 

iVotoxide of manganese... 
Alumina 

1 illl H ? ... ... ... ... ... 

Magnesia 

A OlttOn ... .a. ... ... 

Ammonia 

OUUn ... ... ... ... ... 

Chloride of sodium 

Organic substances and loss 



I. 


2. 


3- 


4- 


5- 


451996 


47 63 20 


48-2357 


452487 


48*1314 


34-8916 


356983 


37-2127 


349010 


38*0610 


45019 


2-5860 


10237 


4-4990 


1*5240 


96135 


7*9096 


8*4423 


95833 


7*8i6i 


08I2I 


1*2840 


06000 


0-2134 


o*o86i 


02991 


05000 


0*1000 


0*7722 


0-4154 


01 266 


0'i63i 


00920 


0*1030 


0-0431 


00031 


traces 


traces 


traces 


traces 


05786 


00802 


00504 


0-I359 


0*1736 


00109 


03055 


0-5178 


traces 


traces 


06080 


traces 


traces 


traces 


traces 


oi8oi 


0-2551 


0-5178 


0*6140 


0-4134 


29891 


3-5165 


35169 


37659 


3*0890 


00029 


traces 


traces 


traces 


traces 


01012 


00595 


00401 


01671 


0*032 1 


0*0918 


OOIOI 


OOIOI 


-^— 


00449 



lOO'OOOO lOO'OOOO lOOOOOO lOOOOOO lOO'OOOO 



^JiKSSc*5iS"** Pure boracic acid crystallises in mother-of-pearl-like leaves, 
which at loo"" C. lose half their water of crystallisation without melting, the other 
half being driven off at a red-heat. After cooling the anhydi*ous acid ax>pears as a 
hard, transparent, brittle glass of 183 sp. gr. i part boracic acid dissolves in 25 6 
parts water at 15"" C, and in 2*9 parts at 100° 0. At 8° a saturated solution has a 
Bp. gr. of 1*014. ^^ imparts a green colour to the flame of the spirit-lamp. In a 



25a CHEMICAL TECHNOLOGY. 

chemical point of view it is similar to silicic acid, Boracic acid is largely used in 
the preparation of borax, for glazing porcelain, and mixed in a weak aqaeons solu- 
tion witli sulphuric acid in the preparation of the wicks of stearine and paraffin 
candles. It is also used for colouring gold, for decorating iron and steel, in the 
preparation of flint-glass, and artificial precious stones. In 1859 boracic acid was 
used in the preparation of hydrated oxide of chromium, known under the name of 
Pannetier's-green, Vert-Guigtwt, &c. 

Bonx. Borax, or bi-borate of soda, when anhydrous according to the formula 
Na2B407, contains in 100 parts : — 

Anhydrous boracic acid (B2O3) 69*05 

Soda (Na^O) 30'95 



100:00 

It is found native in Alpine lakes, on the snow-capped mountains of India, China, 
Persia, in Ceylon, and Great Thibet. It is found in large quantity at Potosi in 
Bolivia, where the Borax LakSj according to Moore's analysis (1870) contains in i litre 
of its water (sp. gr. = 1*027), 3*96 grammes of borax. Pyramid Lake, Humboldt Co., 
Nevada, yields also large quantities. By the heat of the sun the water of the borax 
lakes is evaporated and the borax crystallises out. and is gathered and brought into 
commerce under the name of Tincal. It appears in small six-sided crystals, more or 
less smooth. The Clear Lake in California, to the north of San Francisco, yields 
daily 2000 kilos, of borax. 

Formerly tincal was purified by washing in water containing soda to free the 
borax from adhering fatty substances which combine with the soda to form an 
almost insoluble soap. After the borax has been well washed it is dissolved in 
boihng- water ; for each 100 parts of refined salts there are 12 parts of carbonate of 
soda. The solution is next filtered, and then evaporated to 18° to 20° B. It is now 
placed in wooden crystallising vessels lined with lead, where it is necessary to allow 
the fluid to cool gradually. Anotlier method is to place the tincal in cold water, and 
to stir in i per cent of caustic lime. The fatty substances are thus removed, com- 
bining with the lime to foi-m an insoluble calcium soap. 2 per cent of chloride of 
calcium is added to the fluid, which is next evaporated, and set to crystallise. 
Clouet recommends the powdering of the tincal, which is next mixed with 10 per 
cent nitrate of soda, and calcined in a cast-iron pan, the fatty substances being thus 
destroyed. The calcined mass is dissolved in water, and the solution evaporated to 
crystallisation. 

Borax from Borade Add. In 1818 the manufacture of borax from boracic acid was com- 
menced, and since that time borax has sunk to three-fourths its former price. Both 
according to the proportion of water and the crystalline form, there may be oonsi- 
dered two varieties of borax, i. The ordinary or prismatic borax; 2. Octahedral 
borax. The prismatic borax (NaaB407+ioH20) contains in 100 parts : — 

Boracic acid 36*6 

outiiw ••• ••• ••■ ■•• ••• (■• ••• •«• ••• 102 

Water of crystallisation 47*2 

1000 



BORACtC ACID. 

Tlie octahedral borax (NaaB^Oj+sHjO) contains in lOO parts :■ 
Boracic acid [ 



6936 
3064 



Prismatio borax is maunfaotored in the following miuiner:-'Tbere are dissolved iu a 

I lead-lined Tassel k Fig 118 26cnts of cr^'stalliBed carbonate of xodniu aboat 1300 litres 

ol aater, beated b^ meaos of Btoam to the boilinf;- point. The boiler, c, it for tbe 

pDipoae only of geoeratlng steam which is passed b; the pipe, c, and tbe rose, in, into «. 




By means of the large taps, b and r, tbe fluid may be removed from 1. Through tho 
tabs a tbe snbstanees thrown down from the Rolntion con be removed. Boracio acid is 
added in qaantities of S to 10 lbs. after the solntion has been heated to the boiling-point. 
Besides carbonic acid a small qaanlity of carbonate of ammonia is developed, and piMses 
by o into tbe vessel q, containing dilate sulphario acid, by which it is absorbed. To 
Mtnrate the solntion of 26 cwts. of eoda. 24 cwts. of crude boracic add are necessary. 
Tbe boiling saturated solution marks zi" to ix" B., and has a temperature of :04°. If 



354 



ClIF.mCAL TECIWOLOay. 



the Bolotion is -too strong. irateT in oddoil; if ton vcnk, a amall qoftnti't; of cnjo 
borax, to bring it to 21° B, The Rolution is alloweil tn nlnuJ in * until all insolnble «ab- 
Btnnoes are deposited. Tho cIkbt ley is condaoted by munua of tbe tap. r, into the crvs- 
tallisiug Teasoia, p p, th^ mud or deposit beiug received into K. The eryatailising vesa^ 
are of wood lined vitb lead. Tho crystnllinntioD ia oomplete ui two to three dayi, and 
the mother-liqnoT is driLwii off into tbo vessel a. The cry^ttiis >Lre placed to drain on ibe 
inclined plane, u. The luotber-liqaor ia rDtoinod for the dilation of a fresh qaontit; i>[ 
Boda. ^ter three or fonr oporatioas, tlie motber-UqaoT coataina Eofficient Bnlphote of 
soda to admit of proGtablo crystaUiuation ; aud the ley is allowed to cool at 30°. As tbe ^ 
eolnbility of auipbate of soda baa reached the maximum at a temperatnre of 33°, it is clear 
that the cryadUllsalion of tbo Balpbate commoncos at the completion of that of 111* 
borai. After the crj-Btalliaatioii of the aulphntii of stnia, the motber-linuor is evaporated 
to dryness, and tlie saline residue ia sold to tho glasG-iuanufactnrer. 

Purityim Urn Dom. The crude borax to be purified is placed in a lond-Unod wooden 
cistcni, A. Fig. 119, heat«d by steam. The borax is auapendud in a wire sieve 
ijiiraedia(«ly under the Hurface of the water with which a is filled. To 100 ports 
of borax, 5 parts of crystallised carbonate at soda are added, and the liquid 




IB Btrengthened horn time tb time till it muba 32° B. 'When the solution i* 
settled it is removed by the tap to the cooler, e. To prevent loss of ley, the 
floor Buder b ia stippled with waterproof cement, and sloped towards a ;;ult.'i 
Tho crystallising vessel ie of tJiick timbers, h k h, lined stonily with lend : il"* 
vessel is filled with ley to witliin nn inch of the edge, the cover l>ciii<; then pliiceil on- 
Tha steam condenses on tho cover, which when removed is found covered wiih 
small cryetalB, the larger crystals falling to the bottom of tlic veisel. To hasten Uj0 
cooling, spaces are left in timbers, e ; but the crystallisation is not effected aodiT 
16 to z8 days. After this time the ley still has a temperature of 27° to 28° C, Viben 
quite cool the foreign substances separate from tho borax. The vessel, b, contains 
tlie large borax crystals from which tbe adhering mollier-liqnor is Eepnnilcd by i 
PiHinge. If tlie crystals are not thus carefully treated, they split into thin leaves; 
for this reason also the cooling should bo gradual. The crystals are dried on 
n wooden tabic, linolly sorted, and packed.' 

In England borax is prepared from horacio acid in the following manner: — The 
crude borocic acid is mixed with half its woiglit of calcined soda and sulmiill"! 
to the action of heat in a muffle-oven. The animoiiin, wliich as sulphato i^- nn 
iuiporlant constituent of crude boracic acid, is, with carlxinic acid, given off darin;! 
tlio process, and passes through a tube to a condensing ehnnibcr. The melted mass 
is removed, and lixivi&tcd in an iron pan ; tlie suspended matter is allowed to sctit. 



BORACIC ACID. 255 

Bhd the clear liqnor is pot into smaller vessels to cool, in wliich beautiful cr}'stal9 
form. It has already been mentioned that this manufacture had its origin in 
France, where sulphuric vapours were employed. A mixture of calcined Glauber 
salts and boracic acid were placed in a retort and subjected to distillation, the 
residue on lixiviation and crystallisation yielding borax. Kohuke substitutes 
caustic soda for the carbonate of soda, tlie borax ciystallising from a very alkaline 
solution. 

Becantly borax has been obtained from native borate of oalcinm) tiza or borocalcitc, 
(formula, according to Wohler, Na2B407 + 2GaB407+i8HaO), which occurs in large quau- 
iitids at Tarapaoa in Fora, and in Western Africa. Treatment with sulphuric acid gives 
only onsatisfaotory results, and hydrochloric acid is therefore employed. The acid 
is poured upon the mineral to two'thirds of its weight with twice the quantity of water, 
and the whole heated to the boiling-point, and allowed to digest. The heat must be maiu- 
talned to the completion of the digestion, and the water lost by evaporation re-supplied. 
Tho clear hquor is then decanted, and on cooling the boracic acid cryatallises out, 
the mother-liquor retaining chloride of sodium, chloride of calcium, with a slight excesH 
of hydrochloric acid. Stassfurt boracite or Stassfurtite, is also becoming largely used in 
the preparation of borax. 

The prismatic borax is colourless and forms transparent crystals of 175 sp. gr., 
dissolved in 12 parts cold and 2 parts boiling water, the solution having a weak alkaline 
reaction upon test-paper, although borax is an acid salt. By exposure to the air it loses 
water. At a moderate heat it separates into a spongy mass known as calcined borax, and 
at a red-heat assumes a glassy appearance ; in this condition it is used as a blowpipe 
fiox. 

Octahedral Borax. Octahedral borax (NaaB40^+5HaO), is 'prepared in the following 

manner: — Prismatic borax is dissolved in boiling water till tlie solution marks 

30*' B.= i'26o sp. gr* This solution is then allowed to cool very slowly. When tlie 

temperature has fallen to 79° C, the octahedral crystals begin to form, the formation 

continuing tiU the temperature reaches 56°. After tliis the motlier-ley yields only 

prismatic crystals. Unless great care be taken, a mixed crystallisation results. 

13nran recommends the preparation of octahedral borax by evaporating a borax 

Bolntion to 32^B.=i"282 sp. gr., when it is removed to a crystallising vessel. Wlien 

10 cwts. of borax are operated upon, the process will take six days to complete. The 

prismatic and octahedral salt crystallises in distinct layers tliat can be separated 

mechanically. Indian borax and Chinese half-rciined borax sometimes contain 

octahedral crystals. Octaliedral borax is kno\\'n in French commerce under 

the names of calcined borax, jeweller's borax, surface borax, &c. It is distinguished 

from prismatic borax by its. crystalline form and the proportion of water contained, 

by its sp. gr,=i-8i, and its greater hardness. While tlie prismatic borax remains 

nnafiected in transparency by exposure to air, the octahedral borax rapidly becomes 

opaque, and absorbing five equivalents of water is converted into the prismatic salt. 

VMS of Bonx. The uses of borax are very numerous. Molten borax has the property, at 
high temperatures, of fluxing metallic oxides, vitrifying with them into coloured trauRua- 
rent glasses ; for instance, with protoxide of cobalt a blue glass is formed, and with oxide 
of chromium a green glass. This property is of great utility in chemical analysis, as the 
various metallio oxides may be thus distinguished in the blowpipe flame. It is also used 
for soldering metals; and is a constituent of Strass^ used in glass-manufacture and 
enamelling. It is used extensively in glazing the finer kinds of earthenware, and for 
separating metals from their ores. Borax forms xvith shellac in proportion of i part to 
5 parts a peculiar varnish, soluble in water, and used when mixed with aniline black 
to stiffen felt hats. With casein it gives a fluid resembling a solution of gum-arabic, for 
which it is often substituted. Borax is made into a soap for washing purposes, into 
a solution for cleansing the hair, and it is also used in various cosmetics, &c. It is 
largely employed to fix mineral mordants. According to Clouet, a mixture of boracic 
acid and nitrate of potash or soda is in many cases a better flux than borax. He recom- 
mends 100 parts boracic acid and 100 parts of the nitrate to be placed in an enamelled 



256 * CHEMICAL TECHNOLOGY. 

iron kettle with zo per eent water and heated till fluid. "When cooled, flat white <n78tais 
are formed ; those made with nitrate of potash ean be used for crystal-glass manafactnrey 
and those with nitrate of soda for enamelling. Borate of ehromiom is known in com- 
merce as Vert-GiUgnet or Pannetier's green. 
DUimond-Boron. or Wohler and H. Deville in 1857 ^^^^ ^^ ^^ ^ notice that boron 
Adamantiae. forms similarly to carbon in two allotropic conditions, namely crystalline • 
and amorphous. Diamond boron is prepared in two ways, either by the redaction of 
calcined borax with aluminium :— 



Boracic acid, B2O3, ) yi^^A^ ( Alumina, A1203, 
Aluminium, 2A, J ^ ( Boron, 2B ; 



or by convertingamorphous boron into crystalline. The latter method gives the better results 
zoo grms. of anhydrous boracic acid are mixed with 60 grms. of sodium in a sanall iron 
crucible heated to a red-heat. To this mixture 40 to 50 grms. of common salt are added, 
and the crucible is luted down. As soon as the reaction is finished, the mass, consisting 
of amorphous boron with boracic acid, borax, and common salt intermingled, is stirred 
into water acidified with hydrochloric acid. The boron is filtered out, washed with a 
weak solution of hydrochloric acid, and placed upon a porous stone to dry at the ordinary 
temperature. Molten iron, it is well known, converts amorphous carbon into crystalline 
graphitic carbon, and aluminium exercises a similar action upon boron. The erystalline 
boron is prepared in the following manner : — ^A small crucible is filled with amorphoas 
boron, in the centre of which a small bar of aluzninium weighing 4 to 6 grms. is placed. 
The crucible is submitted to a temperature sufficient to melt nickel for zi to 2 hours. 
After cooling the aluminium will be found covered with beautiful crystals of boron. The 
diamond boron is easily separated from the graphitoid. The former is a transparent 
tetragonal crystal, of a garnet-red or honey-yeflow colour, or, if perfectly pure, colourless. 
It is very brittle, hard, and lustrous ; it will scratch rubies easily. This discovery may 
in time be of great technical importance. 

Pboddction cfF Alum, Sulphates of Alumina, and AiuMrNATEs. 

Aimn. Alum is a saline substance, consisting of sulphate of alumina, sulphate 
of potash or ammoziia, and water of crystallisation. It occurs native as potash- 
alum and as ammonia-alum, being, in fact, a double salt, consisting of either snlphate 
of alumina and snlphate of potash, or sulphate of alumina and sulphate of ammonia. 

The alum known as potash-alum, ^^ \ 4SO4-I-24H2O, is found in alum-shale. But 

all natural alums are of more mineralogical than technical interest, the alums of 

commerce being always artificially prepared. We shall, therefore, pass on to the 

consideration of Uie latter. 

"^SSSiirtwe""* T^® manufacture of alum grounds itself on the formation of sulphate 

of alumina and aluminate of soda from the various alum-ores. These ores or 

earths necessitating different methods of treatment, may be divided into four 

groups, viz ; — 

z. Those which contain alumina, potassa, and sulphuric acid in such proportions that 
the addition of an alkaline salt is not requisite. To this group belongs alum-stone, and 
several varieties of alum-shale. 

2. Those in which the sulphate of alumina is alone present, necessitating the addition 
of alkali salts in large quantities. To this group belong the alum-shale and alum-earthB 
found in the brown-coal formation, 

3. Those in which alumina only is contained, and to which both sulphuric acid and 
alkali salts must be added. To this group belozig — «. Clay ; j3. Cryolite ; 7. Bauxite ; 
S. Befuse slack. 

4. To the fourth group belong those materials, such as felspar, contaizdng alnmins 
an4 potash in sufiicient quantity, but needing the addition of sulphuric acid. 



• Graphitic boron is by a later discovery of Wohler's (1867) resolved into boracic 
aluminium ; formula, AIB^p 



ALUM. 257 

'toSS^SoHlt^T ^'*« Group. — ^Alum-stone or alimite occurs only in volcanic 
regions, and is the product of the action of the sulphurous vapours upon sub- 
stances rich in felspar. It is found at Tolfia, near Civita-Vecchia, and in large 
quantities at Muszag, in Hungary. The crystallised alum-stone consists of sulphates 
of potash and alumina with hydroxide of aluminium, according to Al. Mitscherlich — 

K,S04+Ala(S04)3-f2(Ala03,3H«0). 

Alnm-stone loses its water at a red-heat, the product of the calcination being influenced 
by water, while unbornt s^om-stone is not. At a strong red-heat the sulphate of alumina 
Beparates into alumina, sulphurous acid, and oxygen, and the sulphate of potash is also 
decomposed. The mineral is calcined in lime-kilns in the ordinary manner. The calcined 
alnm-stone is lixiviated with boiling water, the supernatant liquor decanted, and the 
alom crystaUised out. Boman, rook, or roche alum is prepared in a similar manner, the 
red oolour being due to peroxide of iron. 

PnpMBtionaf Ainmtrom 2nd Oroup. — This modc of preparation yields the greatest 

•adAinm-Mrtiu. amouut of alum with as much facility as from alum-stone. 



Alum-shale or schist is a sulphurous iron pyrites, found under beds of 
clay in Upper Bavaria, in Prussia, near Diisseldorf, Saxony, Bohemia, Belgium, &c. 
Only very inferior kinds require an addition of alkali salts. 

Aiaaxartiia. Alum-earth is more or less a mixture of sulphurous iron pyrites with 
various bituminous matters. The sulphur is present partly in free state, partly as 
iron and vitriol pyrites; the iron is present partly as sulphuret, partly as iron 

hnmate. 

pvtpMmUoaof Alum. The preparation of the alum may be considered in the following 

six operations : — 

aoMUagtiMAiiiin-iiuth. I. The roasting of the alum earths is the easiest of the opera- 
tions. The greater part of the alum manufactured is produced by precipitating 
nlphate of alumina with a solution of alkali salts. It is not always necessary the schist 
should be burnt to concentrate the sulphate of alumina, a lengthy weathering being 
sufficient. The action may be explained as follows : — By the weathering the bisulphide 
of iron absorbs oxygen, to form sulphate of iron, which separates into protoxide of iron 
and sulphuric acid, the latter acting upon the alumina forming an equivalent quantity of 
sulphate of alumina. Or by roasting, the bisulphide is decomposed to monosulphide 
and sulphur, which, with the sulphur of the alum-earth, gives rise to sulphurous acid, 
and this acting upon the alumina produces sulphite of alumina and also'the sulphate. The 
roasting or mJcination, however, should not take place with earths that have been 
snbjeeted to less than a year's weathering, as there is found to be in practice a loss of 
one-sixth of the sulphate of alumina. 

UxMatioa. 2. The Uxiviatiou of the calcined alum earths is efiFected in a lixiviation 
eistem in which the earth is placed. These tanks stand in rows of Ave, the best arrange- 
ment being to build them on a slope near the calcination heaps. Each vessel has a 
length of 6 to 7 metres, is 5 metres broad, and about 1*3 metres in height. They are 
three-parts filled with the burnt earth, and completely with water ; the lixivium flows 
from the highest tank to the lowest. If the ley is not of i'i6 sp. gr. fresh shale is added. 

STtponuon of Um Ler. 3 • The concentration of the raw ley by evaporation is accomplished in 
leaden pans. These, however, deteriorate, crack, are easily melted, and their place is now 
generally supplied by cisterns of masonry. But most to be preferred is Bleibtreu's 
method of heating with gas, introduced in the alum-works on the banks of the Bhine. 
The treatment of the raw ley while being concentrated depends upon its condition and 
upon the sulphate of iron it contains. As sulphate of iron is commonly present in large 
quantities in the raw ley or Uquor, many of the German alum-works are also vitriol-workR. 
^en, however, the quantity of sulphate of iron is too small to admit of being advantage- 
ously treated for the preparation of sulphate of iron, the Uquor is at once evaporated 
until it has attained a sp. gr. of 1*40. During the ebullition basic sulphate of iron is 
deposited, the liquor becomes of yellow-red colour, assumes a somewhat slimy condi- 
tion, and has to be rendered clear before alum is obtained from it. This clearing is 
effected by pouring the liquor into large wooden water-tight tanks ; the liquor having 
deposited, the suspended matter is tapped or syphoned oft from the sediment, and trans- 
ferred to the precipitation tanks. 



258 CHEMICAL TECHNOLOGY. 

Ahiin-Fionr. 4. The precipitation of floor of alum is effected in case it is desired to 
make potash-alum by the addition to the liqnor of a potash salt, or of an ammonia salt 
if it is desired to make ammonia-alnm. The solution of the alkaline salt is called the 
precipitant ; by the combination of the sulphate of alumina contained in the liquor with 
the precipitant alum is formed, and deposited as a solid salt, care being taken to preyent 
the formation of large crystals by keeping the liquid stirred. By this means the alum^ is 
deposited as a crystalline powder or so-caJled flour of alum, which by being washed with 
cold water can be freed from any adhering mother-liquor. The precipitation was formerly 
effected by the addition of wood-ash ley or lant ; at the present day chloride of potassium 
obtained either from kelp, camallite, or beet-root molasses, and sulphate of potassa 
derived from the decomposition of kainite, are employed for this purpose. Chloride of 
potassium is useful only when the solution contains large quantities of ^sulphate of iron, 
which being converted into chloride of iron forms sulphate of potassa. * Potash can only 
be used when the ley contains enough free sulphuric acid to combine with the salt, for 
otherwise a portion of the sulphate of alumina would become precipitated as insoluble 
alumina. The ammonia salt made use of is generally sulphate of ammonia ; 100 parts of 
sulphate of alumina require for precipitation — 

Chloride of potassium . . . . , . . . 43*5 parts, 

Sulphate of potassa 50*9 „ 

Sulphate of ammonia 47*8 „ 

The liquor coTering the alum-flour is somewhat of a green colour, and contains little 
alum, but chiefly proto-perchloride of iron, sulphates of iron, sulphate of magnesia, or 
chloride of magnesiimi, dependent upon whether the precipitation was effected by 
sulphates or by chlorides. This liquor is used for m^ng impure alum, sulphate of iron, 
or is employed in the preparation of sulphate of ammonia. 

washinir and 5- The floury alum is generally waphed in the hydro-extractor or 

Re^ryBUiiiaaUon. centrifugal machine and the liquor obtained again used for preparing 
alum. The washed floury alum is (6) converted into large crystals by re-crystallisation, 
the alum at the same time being pnrifled. For this purpose the alum flour is dissolved in 
40 per cent of its weight of boiling water, the operation being carried on in wooden lead- 
tined tanks. The hot solution is run into crystallising vessels, where the crystallisation 
is finished according to the temperature of the air in eight to ten days. From this operation 
hardly any mother-Uquor remains, the vessel being almost entirely filled with alum crystals. 

^'^'SJS^SS.^"" 3r<l Group. — ^The manufacture of alum and of sulphate of alumina 

from such materials as contain only almuina, to which consequently sulphuric add 

and alkaline salts have to be added, has come largely into practice in England. The 

materials employed are : — a. Claj ; /3. Cryolite ; y. Bauxite ; 1^. Blast-furnace slag. 

a. Preparation of Alum from Clay, — The clay to be employed for this purpose should 
be as free as possible from carbonates of lime and iron. It is first gently heated in 
contact with air, partly with the view of dehydratation, partly for the purpose of converting 
any iron into oxide, -and lastly to render the clay more readily soluble in acids. By 
dehydratation the clay becomes porous and fit to take up sulphuric acid by capil- 
larity. The gently ignited and powdered clay is gradually piit into sulphuric acid of 50*" B. 
(= 1*52 sp. gr.) contained in a leaden pan, and heated nearly to the boiling-point. The 
mass effervesces and becomes thick, and is next transferred to iron tanks, where it 
solidifies. It is afterwards lixiviated with water, or better, with the liquor obtained by 
washing the alum-flour. The lixivium having become clear by standing is syphoned off 
from the sediment, and boiled with a Fufllcient quantity of bisulphate of potash or 
sulphate of ammonia from gas -liquor. The hot solution is transferred to a shallow 
leaden pan, and kept stirred for the purpose of converting the alum on solidifying into 
flour. The flour is washed, dried, and is then converted into large crystals as dei^cribed 
above. The product known in the trade as alum-cake is the result of the action of 
sulphuric acid upon clay ; it is met with in a pulverised state, is used more eBi>ecially 
ill the manufacture of inferior kinds of paper, and contains from 13 to 17 per cent of 
;ilumina. 

'^'Iromci^ou^I"" ^- Since the year 1857 ^^^"^ *"^^ sulphate of alumina have been 
l>reparcd along Tvitli soda, from the mineral known as cryolite or Greenland spar, 
AlaFlfi-f 6NaFl, and consisting in 100 parts of — 

Fluorine 54*5 

Aluminitun • 13*0 

OOvUlUll... ... ... ... •.. •«■ ••• ■«• 3 J 



ALVM, 259 

The following are fhe methods employed for this purpose :-^ 

a. DecompoHtion of Cryolite by Ignition with Carbonate of Lime according to Thomsen^s 
Method. — I moleoTile of cryolite is ignited with 6 molecules of carbonate of lime, carbonic 
add escapes, and soluble lUununate of soda and insoluble fluoride of calcium are formed 
(Al3Fl6,6KaFl)+6CaC03»Ala03,3Na30+6CaFl+6G02. From the ignited mass the 
aluminate of soda is obtained by liziviation with water, and into the solution carbonic 
acid gas is passed. The result is the precipitation of hydrated gelatinous alumina 
and carbonate of soda, which remains in solution. If it be desired to obtain the alumina 
as an earthy compact precipitate, bicarbonate of soda is used as a precipitant instead of 
carbonic acid. While the clear liquor is boiled down for the purpose of obtaining 
carbonate of soda, the precipitated alumina is dissolved in dUute sulphuric acid ; this 
■elation is eyaporated for the purpose of obtaining sulphate of alumina (so-called concen- 
trated alum), or the solution setter having been treated with a potassa or ammonia salt is 
oonverted into alum. 100 lbs. of cryolite yield 33 lbs. of alumina, which require go lbs. of 
sulphuric acid to yield a neutral solution ; 100 lbs. of oryoUte will therefore yield 305 lbs. 
of alum, and may give in addition : — 

Calcined soda 75*0 lbs., or 

Crystallised carbonate of soda . . . . 203*0 „ or 

Caustic soda 44*0 ,, or 

Bicarbonate of soda ii9'5 t« 

6. Deeomponticn of Cryolite mtk Caustic Lime by the Wet Way (Sauenoein^s Method), — 
Very fin^y ground cryolite is boiled with water and lime, the purer the better, and as free 
from iron as possible, in a leaden pan. The result is the formation of a solution of 
almoinate of soda and insoluble fluoride of calcium, 

(AlaFl6,6NaFl) + 6CaO = Ala03,3NaaO + eCaFla. 
When the fluoride of calcium has been deposited, the clear liquid is decanted, and the 
sediment washed, the first wash-water being added to the decanted liquor, and the second 
and third wash-waters being used instead of pure water at a subsequent operation. In 
order to separate the alumina from the solution of aluminate of soda, there is added to the 
liquid while being continuously stirred, very finely pulverised cryolite in excess, the result 
of the decomposition being exhibited by the following formula : — 

(Ala03,3KaaO) + (AlaFl6,6NaFl) = 2AI2O5 + i2NaFl. 
^en no more caustic soda can be detected in the liqmd — a small quantity of which 
shoold, after filtration, yield, upon the addition of a solution of sal-ammoniac and appli- 
cation of heat, a precipitate of alumina — it is left to stand for the purpose of becoming 
dear. The clarified solution of fluoride of sodium is then drawn off, and the alumina 
treated as above described. The solution of fluoride of sodium having been boiled with 
caustic lime yields a caustic soda solution which, having been decantedfromthe sediment of 
fluoride of calcium, is evaporated to dryness. Recently the fluoride of calcium obtained 
as a by-prodact of the cryolite industry is used in glass-making. 

c. The decomposition of cryolite by sulphuric acid yields sulphate of soda, convertible 
into carbonate by Leblanc's process, and sulphate of alumina free (^om iron. 238 parts 
of cryolite require for decomposition 240 parts of anhydrous or 321 parts of ordinary sul- 
phuric acid. The resulting compounds are sulphate of alumina, sulphate of soda, and 
hydrofluoric acid : — 



AlaFle.eNaFl, 
6H2SO4, 



(Ala(S0.)3. 
yield - 3Na2S04. 
1 12HFI. 

This method of decomposing cryolite is, however, by no means to be recommended, as 
owing to the liberation of hydrofluoric acid, peculiarly constructed apparatus are required ; 
while the sulphate of soda has to be converted into carbonate of soda. Persoz suggests 
that cryolite should be treated in platinum vessels with three times its weight of strong 
sulphuric acid, to be recovered with the hydrofluoric acid by distillation. The solid 
residue should be treated with cold water in order to dissolve the larger part of the 
bisulphate of soda contained in the saline mass, from which the anhydrous sulphate 
of alumina is extracted with boiling water, and converted by the addition of sulphate of 
potassa or ammonia into alum free horn. iron. The solution of bisulphate of soda having 
been evaporated to drj^ess, is employed for the preparation of fuming sulphuric acid, 
Glauber's salt remaining as a residue. 

^**SS?BJu^tJ^°™ t' ^^ some parts of Southern France, in Calabria, near Belfast, Ire- 
land, and other parts of Europe, a mineral occurs consisting essentially (60 per cent) 
of hydrated alumina of greater or less purity, termed bauxite, from the fact of 
having been first found in tlie commune of Baux, in France. In order to prepare 

8 2 - 



26o CHEMICAL TECHNOLOGY. 

alum and sulphate of alumina from this mineral it is first disintegrated hj 
being ignited with carbonate of soda, or with a mixture of sulphate of soda and 
charcoal ; in each instance the lixivdation of the ignited mass yields aluminate of 
soda, from wliich, by processes already described imder Cryolite, alum, or sulphate of 
alumina, and soda are prepared. 

£rS^ll!IIt-FamaiJ"sSig. ^' "^ ' Lurmaun recommends that the slag be decomposed by 
means of hydrochloric acid. From the resulting solution of chloride of 
aluminium the alumina is precipitated by carbonate of lime, any dissolved 
silica being precipitated at the same time. The alumina is dissolved in sulphuric 
acid, leaving the silica. loo kilos, of slag containing 25 per cent of alumina 
yield 180 Hlos. of alum and 31 kilos, of silica. 

Aimn from Felspar. ^th Group. — The manufacture of alum from minerals, (for instance, 
felspar) containing alumina and potassa, is not of any industrial importance: 
we therefore refer the reader to what has been said (see page 122) on the Prepara- 
tion of Potassa Salts from Felspar. 

proptttieB of Alum. Potash-alum, "^ I 4SO4+ a4HaO, or KaS04+ Al^ (804)3+ 24HaO, 

consists in 100 parts of : — 

Potassa ... • •• 9*95 

Alumina 10*83 

Sulphuric acid 33'7i 

\f ater..* ••• ••• ••• ... ... ••• 45 5^ 

100*00 

crystallises readily in regular octahedra, loses at 60° 18 mols. of water, and fuses at 
92° in its water of crystallisation, yielding a colourless fluid which retains its state of 
aggregation for some time after cooling before solidifying into a crystalline mass. At 
a temperature a little below red heat alum loses all its water, becoming converted 
into burnt-alum, alumen ustum, a white, porous,, readily friable mass. Wlien 
ignited with carbonaceous matter, air being excluded, potash-alum forms a pyro- 
phoric compound : — 

loo parts of water at 0° dissolve 39 parts of potash -alum. 
»» i> 20 ft 15 ^ »» »' 

„ 100'' „ 3600 „ „ 

The Bolution of almu in water (the salt is insolublo in alcohol) has an astringent swert 
taBte, and possesses an acid reaction so strong that when alum is heated with common 
Bait hydrochloric acid is evolved ; while a concentrated solution of alum deBtroys the bloe 
colour of many — not of all — artificial ultramarines. . 

AmmoniaAinm. This salt, r^^^\ 4S04-»-24H20, or (NH4)2S04+ Ala(S04)3+24HO,oon. 
sists in zoo parts of : — 

Ammonia S'Sg 

Alumina .. 11*90 

Sulphuric add 35*io 

Water 48*11 

100*00 

Ammonia-alum is now far more extensively manufactured than potash-alum. ^Vlien 
ammonia-alum is strongly heated, sulphate of ammonia, water, and sulphuric acid are 
driven off, and alumina remains. 



ALVM. 261 

100 parts of water at o^ dissolve 5*22 parts of ammoma-alafQ. 
If » 20^ „ 13-6(5 „ „ 

»» »» 4® f» 27*27 „ ,, 

„ „ ICO** „ 421-90 „ „ 

soJaAium. The formula of this salt is — 

j^} 4S04+24HaO, or NaaS04+Ala(S04)3+24HaO, 
containing in 100 parts : — 

fti^v' u& ••• ••« ••• ••• •«• ••• u o 

Alumina 11*2 

Sulphuric acid 34*9 

w auei^ •■• ••■ ••• •■■ ••> ••> 47 

lOO'O 

It is as readily prepared from sulphate of alumina and sulphate of soda as the alums 
already mentioned, but its solubility prevents tlio sf])aration from the mother-liquor, 
while its solution when boiled loses the property of crvstallising. As iron cannot be 
removed from this salt by re-crystallisation, the materials it is obtained from should be free 
from that metal. The solutions should be mixed cold, and gently evaporated at a 
temperature not exceeding 60''. 

Neutral or cubical alum (K2S04+Al203,2S03) is obtained either by adding to an alum 
solution so much carbonate of potassa or soda as will begin to separate the alumina, or a 
solution of alum is treated with gelatinous alumina. By boiling 12 parts of alum and i part 
of slaked lime in water, the same salt is obtained. This neutral salt is often preferred 
in dyeing and calico printing, as it does not affeet certain colours. When ammonia-alum 
is similarly treated, it also yields a neutral alum. Blesser (a) and Schmidt {b) found the 
following to be the composition of cubical alum in 100 parts : — 

a. h. 

Sulphuric acid 34*52 33*95 

Alumina iz'86 11*48 

Potassa 9*44 9*^4 

Water 45*27 45*6i 

101*09 100*08 

Al ) 
Insoluble, or basic alum, -^ \ 2SO4, is obtained by boUing a solution of ^um with 

hydrate of alumina ; it is a white, iuBoluble powder, and as regards its composition 
■imilftr to alum-stouc. Basic alum is soluble in acetic acid. 

SKiphflte of Aiamiiw. The activB principle of alum is evidently the sulphate of 

alnmina, not the sulphates of potassa and ammonia, the object ef the preparation of 

the doable salt being simply the obtaining of a defmite compound, wliich, while it 

readily crystallises, can be obtained in a pure state, especially free from iron, a very 

injnrioas ingredient in alum used in dyeing and calico-printing. However, at the 

present day, with improved methods of manufacture, sulphate of alumina is largely 

prepared, and of excellent quality. It is often sold under the name of concentrated 

alum ; and occurs in the trade as square cakes. It is white, somewhat transparent, 

and may be cut with a knife; is readily soluble in water, contains always free 

Bulphuric acid, and also to some extent potassa- and soda-alum. 

In the pure state this salt has the formula, Al^ (804)3+181120, and contains in 100 

part»~alumina, 1878; sulphuric acid, 38-27; water, 4295; total, 100. That 

the composition of this salt as met with in commerce varies gi-eatly may be inferred 

from the following results of Varrcntrapp's analyses of different samples of this 

Bait: — 

I. 2. 3. 4- 

Alumina 15*3 12*5 15*1 130 

Sulphuric add ... 380 30*6 380 340 



262 CHEMICAL TECHN0L007. 

According to the formula, the quantity of sulphuric acid in these samples should 
have been — 

I. 2. 3. 4. 

358 29-2 433 305 

The quantity of water even varies between 56 and 48 per cent for different 
parts of the same cake. Weygand found a sample of this salt prepared at Schwemaal 
to contain — alumina, 15*57 ; sulphuric acid, 38' 13 ; o^de of iron, 1*15 ; potassa^ 
0*62; water, 4579 parts. The sulphate of alumina prepared from cryolite at 
Harburg contains about 5 per cent of sulphate of soda. The results obtained in 
the analyses by H. Fleck of various samples of sulphate of alumina are: — 

Sulphate of alumina 47'35 ^o'So 5^*63 

Sulphate of soda 4*35 1*24 077 

Free sulphuric acid 073 0*27 — 

Water 4737 47*47 4^*94 

^ii^^_i_^__A ^^^^___^_ ^_^^__^^.a 

99-80 9978 9934 

Sulphate of alumina is prepared either from clay, cryolite, or bauxite by methods 
already described. When clay is employed, the iron has to be removed from the dilute 
solution of the sulphate of alumina by precipitation as Berlin blue by means of ferro- 
cyanide of potassium. When cryolite is used, the alumina, separated from the eoluticm 
of alnminate of soda by carbonic acid, or powdered cryolite, is put into sulphuric acid, 
contained in a wooden lead-lined tank, and heated to 80° to 90°, the addition of the alumina 
to the acid being continued until solution ceases to take place. The solution having been 
clarified by standing for some time is next evaporated in a copper vessel until the salt 
fuses ; it is then oast into moulds. With due care sulphate of idumina may be used in 
dyeing and calico-printing, but it cannot be altogether substituted for alum, owing to its 
variable composition. 

Aiami&atfl of Soda. Aluminatc of soda is now prepared on the large scale, as it has 
been found to be a useful form of soluble alumina, especially in dyeing and calico- 
printing. The preparation of this compound is based upon the solubUily of hy- 
drate of alumina in caustic potassa or soda-ley, and the ready decomposition of 
the solution by carbonic and acetic acids, bicarbonate and acetate of soda, sal- 
ammoniac, &c. 

Aluminate of soda was first brought under the notice of dyers by Macqner and 
Haussmiann in 18 19, but owing to the preparation being too expensive it did not come 
into industrial application until comparatively recently. We have already described 
the mode of manufacturing aluminate of soda from cryolite ; but in Germany — the 
chief seat of cryolite industry — ^this salt is not made on the large scale; in France 
it is manufactured by Merle and Ck>., at Alais, and in Elngland at the Washington 
Chemical Works. In France bauxite, containing 60 to 75 per cent of alumina, and 
from 12 to 20 per cent of oxide of iron, is the raw material, and is treated with 
caustic or carbonate of soda. If caustic soda is used the pulverised mineral is 
boiled with a solution of the alkali ; while if the carbonate is employed the mixture 
is ignited in a reverberatory furnace. In either case aluminate of soda is produced, 
dissolved — ^in the case of ignition the semi-fused mass is lixiviated with water-^nd 
evaporated to dr3mess. The salt met with in commerce is a white powder with a 
green-yellow hue, dry to the touch, and consisting of— 

Alumina ••• ••• ••• ••• ••• ••• ••• 4^ 

ooua ••• .•• ••• ••■ ••• ••• ••• ■.• 44 

Chloride of sodium and Glauber's salt... 8 

100 



ALUM. 263 

The formula, -^ I Oe would require : — 

Alumina 5279 

Soda 47*21 

lOOOO 

Alnmlnate of soda is equally soluble in cold and hot water. Exposed to air it absorbs 
moisture and carbonic acid, and consequently on being dissolved in water the salt so 
changed yields a turbid solution, owing to alumina being suspended. The aqueous solution 
of this salt is not stronger than 10° to 12° B., — 1*07 to 1*09 sp. gr. According to Le 
Chatellier, Deyille, and Jacquemart, sulphate of alumina is the starting-point of the 
preparation of the aluminate of soda by precipitating from the sulphate ihe alumina, 
and re-dissolving the latter in caustic soda ley. Aluminate of soda is used in dyeing 
and calico-printiag ; further, for the preparation of lake colours, induration of stone, 
and the manufacture of artificial stone, and for the saponification of fats in stearine 
candle manufacture, an alumina soap being first formed, which is decomposed by 
acetic acid into acetate of alumina and free fatty acid. Aluminate of soda is largely 
used in the preparation of an opaque, milky-looking glass, or semi-porcelain. Aluminate of 
Boda is a by-product of BsJard's method of soda manufacture from bauxite, Glauber's 
salt, and coal ; this by-product, or rather product of the second stage of the process, is 
decomposed by carbonic acid into carl)onate of soda and alumina, which is thrown down. 
The Pennsylvania Salt Manufacturing Company at Natrona, near Pittsburg, manafacture 
large quantities of aluminate of soda, which is used in soap-boiling under the name of 
natrona refined saponijier, 

c«Mof Aimnando* Owing to the great affinity of the alumina contained in alum for 
Sulphate oi AiamiiM. textile fibres, especially wool and cotton, alum is largely used as a 
mordant in dyeing, except when the tar colours are employed. Again, owing to the 
affinity of alumina for many pigments, alum is employed in the preparation of the lake 
colours, combinations of active colouring principles with alumina. It is also used in the 
melting of tallow ; for hardening gypsum ; is found in the preparation used for sizing 
hand-made paper, the alum in this case forming with the glue or size an insoluble com- 
pomid. Alum with resin is employed for the same purpose in machine-made paper, an 
almnina-pinate being formed. It is very largely used for the preparation of acetate of 
alomina, and with common salt in the tawing of leather. Alum is employed in clarifying 
turbid fluids, more especially water ; in this case the alum takes up the alumina suspended 
in the water, and forming an insoluble (basic) alum carries down organic and other 
niBpended impurities. A boiling solution of alum, common salt, and nitrate of potassa 
is used by jeweUers for the purpose of colouring gold, that is to say, to produce a film of 
pare gold on the alloy, the copper of which is dissolved by the boiling solution. 

Aeaute of AimnJaa. This Salt is prepared by double decomposition ; generally sulphate of 
alumina and acetate of lead are used, and occasionally the acetates of baryta and lime. 
The liquor, separated by filtration from sulphate of lead, is gently evaporated to dryness ; 
the dry salt is gelatinous, and does not crystallise, is very hygroscopic, and possesses a 
strongly astringent taste. When a solution of acetate of alumina is evaporated in con- 
tact with air, acetic acid is driven off, and a basic acetate, insoluble in water, formed. 
Commercially pure acetate of alumina is rarely used, as the so-called red-liquor, mordant 
fouget consists of a milture of alum, acetate of potassa, and sulphate of potassa. When 
it is desired to prepare neutral acetate of alumina from alum, to 100 parts of acetate of 
lead 62*6 parts of alum are required for complete mutual decomposition ; but it is more 
advantageous to convert a solution of alum into insoluble alumina by means of 
carbonate of soda, and to treat with acetic acid. Acetate of alumina is not an ordinary 
article of commerce, as the salt is usually prepared by the consumers. Besides being 
largely used in dyeing and calico-printing, acetate of alumina is employed for water- 
proofing woollen fabrics. Among the salts of alumina employed industrially are — hypo- 
tnlplute of alumina, suggested by E. Eopp as a mordant for cotton ; hypochlorite of 
alnmina, known as Wilson's bleaching-liquor, and used in bleaching-works ; sulphite of 
alumina, for the purpose of purifying beet-root juice ; oxalate of alumina, suggested by 
I^t and Brown for the preservation of stone, marble, dolomite, Ac. 



264 CHEMICAL TECHN0L007. 

Ultramabine. 

xTttnmaxine. Under this name is now understood an artificial blue pigment, 
formerly and still obtained in small quantities from the lapis lazuli. The qnantitr 
of artificial ultramaiine manufactured in Europe amounts to i8o»cxx> cwta. annually. 
Lapis lazuli is a scarce mineral, possessing a beautiful blue colour. The sp. gr. 
varies from 275 to 2*95. The coarser pieces of this mineral are pulverised, heated 
to redness, and immediately dipped into water, then very finely ground, and the 

NaiiTB uitmuaiine. powder treated with dilute acetic acid to eliminate carbonate of 
lime. The powder is next well incorporated with a mixture of equal parts of resin, 
wax, linseed-oil, and Burgundy -pitch ; this paste is kneaded under water until no 
more blue pigment remains suspended. The quantity of ultramarine obtained 
amounts to 2 to 3 per cent. This natural ultramarine is liighly prized for ita extreme 
beauty, softness of colour, and durability, not being affected by light, oil, and lime. 
Chemical analysis of the lapis lazuli first gave the clue to the true composition ai 
this material, and led, after many unsuccessful attempts, to the preparation of artificial 
ultramarine, not, however, by any means equal to the native pigment, although it 
has driven smalt and other blue pigments nearly out of the market. Lapis lazuli 
consists in 100 parts of — silica, 45*40 » alumiua, 31*67; soda, 9*09; sulphuric add, 
589; sulphur, 095; lime, 3*52; iron, 086; chlorine, 0*42; and water, 01 2. 

Artifidiiiuitnmwine. Gmelin first made artificial ultramarine on a very small scale in 
1822 ; but not before 1828 was ultramarine industriaUy obtained by Guimet, at 
Lyons. In Germany the first manufactories of ultramarine were established at 
WermelsMrchen, in 1836, by Dr. Leverkuss, and at Nuremberg, in 1838, by MM. 
Zeltner and Leykauf : the manufacture of artificial ultramarine in England is of 
very recent date, and is still on a very limited scale. France and Germany are the 
countries where this industiy is most developed. Of late years the process of 
manufacture has been improved by R. Hofimann, the manager of a factory at 
Marienberg, in Hessen; Wilkins, at KaiBerslautem ; Fiirstenau, at Coburg; and 
Gentele, at Stockholm. 

Bawibteriaiii. Thesc are — I. Silicate of alumina as free as possible from iron, a 
good china clay, the kaolin of Cornwall being esteemed the best; 2. Calcined sul- 
phate of soda; 3. Calcined soda; 4. Sulphuret of sodium, as a by-product of the 
manufacture ; 5. Sulphur ; 6. Pulverised charcoal, or pit-coal. 

Porcelain, or china-clay, is generally used, or a white clay, the composition of 
which is nearly the same. Small quantities of lime and magnesia have no injurious 
effect, but the oxide of iron should not exceed i per cent. The composition of the 
clay should approach as nearly as possible to the formula SiaPjAla ; the silica may 
be combined or partly free. The clay is washed with water and treated in the same 
manner as for the making of porcelain ; it is next dried, ignited, and ground to a 
very fine powder. The sulphate of soda should not contain any free acid, lead, or 
iron. If the sulphate does not possess the requisite qualities it is dissolved in 
water, milk of lime being added to neutralise the acid and to precipitate oxide of 
iron. The clear solution is left to crystallise ; and the crystals are ignited in ft 
reverberatory furnace and then pulverised by millwork. The clear solution is in 
some cases evaporated to dryness and ignited in iron vessels. Barium, but not 
potassium salts, form ultramarine (see " Chemical News," vol. xxiii.,pp. 119, 142.204). 
The calcined soda is obtained from the alkali works, and should contain at least 90 per 



VLTRAMARINM. 265 

• 

cent of carbonate of soda ; it is also finely pulverised. Very recently canstic soda 
has been snbstitated in some ultramarine works. Sulphuret of sodium (NsaS) is 
Qfinally a by-product of the process of making ultramarine, and is obtained either 
in solution or as a dry powder. The sulphur is used very finely pulverised. The 
carbonaceous matter employed is also in a very fine powder. Its use was introduced 
by Leykauf for the purpose of deoxidation. In order to have the carbon in as 
finely divided state as possible it is ground to a pulp with water under granite stones ; 
the pulp is lixiviated, and the fine powder obtained dried and passed through a sieve : 
in some cases resin $nd pitch is employed. For those ultramarines not to have their 
colour discharged by alum, pure silica, either as fine glass, sand, or pulverised 
quartz is used. Several substances are used to reduce the depth of colour of 
ultramarine, viz. — ^gypsum, sulphate of baryta, baryta-white, and flour ; the last is 
employed in making up washing-blue. 

Mairafactan oQUttnuiuriM. The mcthods of ultramariuo preparation may be classified, 
according to the crude materials employed, as the three following : — 

a. Preparation of Sulphate, or Glauber's salt ultramarine. 
/3. „ „ Soda-ultramarine. 

7. „ „ Silica-ultramarine. 

a. Preparation of SuXphate- Ultramarine. — This ultramarine is prepared according 
to the Nuremburg process from kaolin, sulphate of soda, and charcoal ; the pre^ 
paiation consisting in two distinct stages, viz : — 

a. Preparation of green ultramarine. 

h. Conversion of green into blue ultramarine. 

a. Preparation of Green Ultramarine. — ^In order to obtain a most intimate mixture of 
the dry and finely pulverised materials, small quantities are weighed off, mixed in 
wooden troughs by means of shovels, and several times passed through sieves. If solutions 
of Glauber's salt, soda, and sulphide of sodium are used instead of powders, the kaolin is 
mixed with these solutions, and the whole evaporated to dryness, gently ignited in a 
reverberatory furnace, and then pulverised and sifted. The quantities of the crude 
materials vary, but the following conditions have to be complied with : — i. Soda, whether 
sulphate or caustic, must be present in such quantity that it can saturate half of the 
silica of the clay (kaolin). 2. There must be sufficient soda remaining to form with the 
sulphur a certain quantity of polysulphuret of sodium. 3. There ought to remain 
enough sulphur and sodium to form another sodium sulphuret (NazS), i^ter deducting 
from the whole mixture as much green ultramarine as, according to its composition as 
proved by recent analysis, the silica and alumina present are capable of forming. The 
following figures will give an idea of the proportions : — 

I. n. 

Kaolin (dried) too 100 

Calcined Glauber's salt . . 83 — 1 00 41 

Calcined soda — 41 

Carbon (char- or pit-coal) 17 17 

Sulphur — 13 

For TOO parts of calcined soda 80 parts of calcined Glauber's salt, and for 100 parts of 
the latter 69 of dry sulphuret of sodium are taken. 

It is usual to have a large quantity of this mixture prepared for use. If this mixture is 
ignited without access of air, a white mass is obtained, which, having been treated with 
water, is a light, somewhat flocculent, white substance, to which Bitter has given the 
name of white ultramarine. It becomes green by exposure to air, and blue by being 
calcined in contact with air. The mixture is well rammed into fire-clay crucibles, placed 
in furnaces similar in construction to Ihose used for burning porcelain, being raised and 
maintained at a high temperature with a very limited supply of air. liiis operation lasts 
seven to ten hours, and is completed at a bright white heat. The furnace is closed and 
slowly cooled ; on removing the crucibles, the contents appear as a semi-fused grey- or 
yellow-green mass, which is repeatedly treated with water. The ultramarine thus 



266 CHEMICAL TECHNOLOGY. 

obtamed is in porons lumps, which are pnlyerised to an impalpable powder ; this is 
washed, dried, and again ground, then sifted, and finally packed in boxes or casks, and 
sent iQto the market as green ultramarine, consisting, according to Stolzel*a analysis 
{1855), in 100 parts, of — 

AlT7-minft 30*11 

Iron 0*49 (peroxide of iron, 07) 

Calcium 0*45 

Sodium 19*09 (soda, 25*73) 

Silica 37*46 

Sulphuric add 0*76 

Sulphur 6'o8 

Chlorine 0*37 

Magnesia, potassa, phosphoric acid « . traces 

94-81. 
Oxygen 5*ig 

100*00 

Green ultramarine is a pigment of comparatiyely inferior value, owing to its being less 
brilliant than the green copper pigments. 

5. Conversion of Oreen into Blue Ultramarine. — This operation may be variously effected, 
generally by roastiug the green ultramarine and sulphur at a low temperature with access 
of air, BO as to form sulphurous acid, while a portion of the sodium', is'oxidised into 
soluble sulphate and afterwards washed out ; but the sulphur originally present in the 
green ultramarine remains combined with a smaller quantity of sodium. The roasting 
may be variously carried out, but very frequently the apparatus consists of a fixed iron 
cylinder similar to a gas-retort, provided with a stirring apparatus, by means of wbich 
the mixture of green ultramarine and sulphur (25 to 30 lbs. of the former to ilb. of 
sulphur) is submitted equally to the source of heat. The addition of sulphur is 
repeated until the desired blue colour is produced ; but in some works this calcination is 
interrupted by repeated Hxiviation, the object being to produce a superior article. 
Muifle-ovens and a kind of reverberatoiy oven are also used for this operation. The 
sulphurous acid, which is evolved in large quantities, is now generally employed in 
making sulphuric acid, sometimes a co-product of ultramarine manufacture, and used 
for the preparation of the sulphate of soda required. The ultramarine, when quite blue, 
is pulverised, lixiviated, dried, and finally separated into various qualities known in 
the trade as No. oo, i, 2, 3, <!ko. 

'"^SSlrinel!*^ P' -^ manufactured in France, Belgium, and some parts of 
(Germany, this ultramarine is either pure soda-ultramarine or a mixture of soda- and 
sulphate-ultramarine. The materials and proportions are — 

I. n. m. 

Kaolin 100 100 100 

ouipnaii6 ••• ••• ••• ••• ••• ••• ^^ 4^ "" 

oocLa ••• ••• ••• ••• ■•• ••• ••• 100 4^ 9^ 

Carbon (charcoal or pit-coal) 12 17 6 

Sulphur 60 13 100 

JLM)Sin*«a ••• ••• ••■ ••• ••• ••• "^ ^'-~ O 

The ignition takes place either in crucibles, or, better, in a reverberatoiy furnace; 
the result is the formation of a brittle and porous green substance, which absorbs 
oxygen very rapidly, so that daring the cooling of the mass in the oven, the greater 
part is converted into blue ultramarine. The complete conversion, after the addition 
of sulphur, is obtained by heating in a large muffle to redness, the product being 
distinguished from the foregoing by a greater depth and beauty of colour. By 
increasing, within certain limits, the quantities of soda and sulphur, the formation 
of blue ultramarine may be at once obtained, the product containing 10 to x 2 per 
etnt of sulphur. 



ULTRAMARINE. 267 

**'»g;^2jJ["P*' . SiHea-nltxamarine is really soda-ultramarine in the prepara- 
tion of which silioa to the amount of 5 to 10 per cent of the weight of the kaolin is 
added. The calcination at once yields blue ultramarine, and further treatment with 
sulphur is therefore unnecessary. 

This ultramarine is not acted upon by a solution of alum, and may be recognised 
by its peculiar red hue, the intensity of which is increased by an increase of siHca. 
Notwithstanding the superiority of the ultramarine obtained by this process, its pre- 
paration is disadvantageous owing to the tendency of the mixture of crude materials 
to fuse during ignition. 

ooBitttiitkaof nttnmuiiM. Since 1758 the chemical constitution of ultramarine has 

been the object of a series of researches. The latest experiments are those of 

W. Stein, who comes to the condusion that ultramarine consists chiefly of a white 

mass, with which black sulphide of aluminium is most intimately and molecularly 

incorporated, the blue colour being due, not to chemical composition, but to the 

optical Telation of its component substance. Green ultramarine contains less soda 

than the blue pigment, and that again less than the white (so-called) ultramarine. 

The' quantity of sulphur contained in blue ultramarine is less than that in green. 

Propetties of xntnauuiiM. Artificial ultramarine is an impalpable powder of a fine blue 
eolonr, entirely insoluble in water, and when washed with distilled water leaving no 
residue on evaporation of the filtrate. It is not acted upon by alkalies, but is highly 
sensitive to the action of even very dilate acids and acid salts, sulphuretted hydrogen being 
evolved and the eolonr discharged. Native ultramarine obtained from lapU lazuli is not 
thus decomposed by weak acid solution. There sometimes accidentally occurs in soda 
furnaces a more or less blue ultramarine which exhibits the same resistance to adds. That 
kind of ultramarine commercially termed add proof is manufactured with the addition 
of silica, as described, but it really only.resists the action of alum-salts. Ultramarine is 
now largely used for the purposes to which smalt, litmus, and Berlin-blue were applied ; 
that is to say, ultramarine is employed as a paint, as a pigment in stereochromy, for 
paper-hangings, calico-printing with albumen as fixing material, for colouring printing- 
ink, for the bluing of Imen and cotton fabrics, paper, stearine, and paraffine-candles and 
lump-sugar. For 1000 owts. of sugar 2} lbs. of the pigment are employed, a quantity so 
small as to be perfectly innocuous ; furUier, ultramarine does not contain anyuiing inju- 
rious to health. Green ultramarine is a dTill-coloared powder used by waU-paper 
stainers, and is sometimes mixed with indigo-carmine and a yellow pigment to improve 
the colour. 

Adulterations of ultramarine with Berlin-blue, smalt, and other blue pigments do not 
now occur, as ultramarine is a cheaper material ; but to obtain lighter iants ultramarine 
is sometimes mixed with chalk, kaolin, alabaster, and chiefly with sulphate of baryta. 



DIVISION m. 

TECHROLOOY OF GLASS, CERAMIC WARE, GYPSUM, LIME, AND MOBTAS. 



Glass Manufacture. 
Definition tad G«B«ni Glass is EH amorphoiis composition of yarious sOicates obtained 

PropfltUOT ox OlMB. *■ * ^ 

by a process of siaelting, alkaline and caldQm silicates being the chief constituents. 
That which is termed water-glass — ^vi;8., a silicate of potassa or soda — of course con' 
tains no other silicates ; but real glass contains other bases in addition to soda 
and potassa, either alkaline earths, as lime, baryta, strontia, or other more or less 
basic bodies, as magnesia, alimiina, or metallic oxides, — ^those of lead, bismuth, zinc, 
thallium, protoxides of iron and manganese, while in the case of optical or fine 
crystal glass boracic acid or borax is substituted for a portion of the silica. 

Glass is generally transparent ; when opaque it is either white or coloured. Glass 
is not acted upon, in the common acceptance of the term, by either water, acids, or 
alkalies. It is, as has been said, amorphous, for as soon as it becomes crystalline it 
ceases to be glass. The amorphism of glass is due to its composition ; simple sili- 
cates have a tendency to crystallise, and are hence unfit for glass manufacture. 
Owing to its amorphism glass exhibits a conchoidal fracture. When blown to reiy 
thin laminsB or drawn into thread, glass possesses a remarkable degree of elasticity. 
As regards the chemical and physical qualities of glass, much depends upon the 
constituent silicates; the alkaline silicates render glass soft and contribute to 
its ready fusibility. Silicate of potassa glass is less bright and glossy than glass 
in which silicate of soda prevails, but the latter silicate imparts a blue-green coloor. 
Silicate of calcium renders glass harder, brighter, but less readily fosible. Silicates of 
lead and bismuth render glass very fusible, impart to it a high degree of lustre, and 
greatiy increase the re^rangibility ; they are therefore used in making glass for 
optical purposes. Silicates of zinc and baryta impart similar properties ; the fonner 
has the property of reducing the blue-green colour due to silicate of soda. Silicates 
of iron and manganese render glass readily fusible and impart colour to it Silicates 
of other metallic oxides are only of secondary importance in imparting colour 
to glass. 

^^**"**^drof'<SlZ*^"* According to its chemical composition glass may be classified 
as follows : — 

I. Potassium-calcium glass, or Bohemian crystal glass, is quite colourless, veiy 
difficultiy fusible, hard, and very difficultiy acted upon by chemicals. Abroad, 
mirrors are often made of this glass, mixed with any of the foUowing kinds. 

II. Sodium-calcium glass, French glass, window-glass, somewhat harder than the 



• • 


a-396 Sp. gr. 


• • 


2-487 




• • 


2488 




• • 


2642 




• • 


2732 




)te 


• 3'255 




• • 


377 




« • 


5*44 




• • 


5*62 





OLASS, 269 

preceding bnt more readily fusible, exhibiting, as does all soda-containing glass, 
a peculiar blue-green hue. Crown-glass is of similar composition. 

III. Potassium-lead glass, crystal glass, very readily fusible, soft to cut. has a 
higher sp. gr. than other glass, and is more refractive. Among the varieties of this 
glass are : — i. Flint-glass, optical glass, in addition to lead often containing bismuth 
and boracic acid. 2. Strass used for preparing imitation gems. 

IV. Alumiuium-calcium-alkali glass, or bottle-ghiss, always contains oxides of irou 
and manganese ; and sometimes magnesium instead of calcium. The colour varies 
from a red-yellow to a deep black-green. 

The sp. gr. of glass depends upon its composition. The alkali-calcium glass is the 
lightest, next follows aluminium-calcium-alkali glass, while thallium glass ia the 
heaviest, as may be seen in the following table : — 

Bohemian crystal glass 

V^xUWU-tUABS ••■ ••• ••■ •«• •■• •.■ •■• 

Mirror-glass 

<* mClv W-glnSS ••• ••• ••• •«• ».• ••■ ••• 

AjObiie-giass ••• ••• •«• ■•• ••• ■•• ■■• 

J^tjttU glnoo ••• •■• ••■ •■• ••• ••• •••2^ 

Flint-glass (Frauenhofer's recipe) 

,, (Faraday's „ ) 

Thallium glass • 

Slowly oooled glass possesses single, rapidly cooled doubly refractive powers ; the 
refractive index of glass differs considerably, but is never so high as that of the diamond. 
Taking the index of refraction of the vacuum of Torrioelli as unity, that of quartz is 
B 1*547; diamond, 2*506; optical glass (2*52 sp. gr.) = i'534 to 1*344; flint-glass of 
3-7 Bp, gr., 1*639; thallium glass — 1*71 to 1*965. 
BAwacatcruunsedia These are: — z. Silica, viz. quartz, for very pure glass, for other 
oiaoB-maUiig. kiiids saud of varying quality or pulverised flint stones. For very 
pore glass the silica ought to be free, or very nearly so, from iron ; in some cases the 
peroxide of iron adhering to the quartz or mixed with the sand is removed by hydro- 
chloric acid, while the sand is always first ignited and in some instances previously 
washed to remove day, marl, humus, &c. Ordinary glass is made with coarser materials, 
the sand is not required to be so pure, as when it contains limo, chalk, or clay, it renders 
the mass more fusible. 

2. Boracic acid is sometimes used as a substitute for a portion of the silica. It 
increases the fusibility of the glass, imparts to it a high polish, and prevents devitrifica- 
tion. It is employed as borax or as boro-calcite, a native boracic acid. 

3. Potassa and soda are used in a variety of forms, the former chiefly as potash 
(carbonate of potassa), or partly lixiviated wood-ash. 

Not BO large a quantity of soda is required as of potash ; 10 parts of carbonate of soda 
correspond to 13 parts of carbonate of potash. Recently the soda has been used in the form 
of Glauber's salt ; in this case, so much carbon is added to the siliceoas earth and Glauber's 
salt as will reduce the sulphuric acid of the sulphate of soda to sulphurous acid, and the 
carbon to carbonic oxide. The sihoic acid then easily decomposes the sulphurous acid of the 
sulphite. To 100 parts of Glauber's salt (imhydrous) 8 to 9 parts of coal are measured. 
An excess of carbon is detrimental, as a large quantity of sulphide of sodium is formed, 
which imparts a brown tint to the g^ss. 

4. The lime used in glass-manufacture must be free from iron. It is generally 
employed as marble or chalk, either raw or burnt. To 100 parts by weight of sand, 20 
parts by weight of lime are added. In the Bohemian manufacture the Ume is employed 
as neutral silicate of calcium, Wollastonite, Si03Ca. Instead of hme, strontia and 
baryta can be used, the former as strontianite (SrCOj), the latter as witherite (BaCOj). 
Fluor-spar (CaFls), and aluminate of soda were at one time used in making milky or 
semi-opaque glass. 

5. Oxide of lead is employed in most cases in the form of minium or peroxide, giving 
up some of its oxygon to form a lower oxide, and purif}dng the glass. The lead gives the 
glass a higher specific gravity, greater brittleness, transparency, and polish. It must be 



270 CHEMICAL TECHNOLOOY. 

Iree from oxide of copper and tin, the former imparting a green colour, and the latter 
opacity to the glass. White-lead is as e£Bloaoioiis as red-lead, provided no heavy-gpar be 
present. 

6. Oxide of zinc is always added as zinc- white. When the colour is not of importance, 
zinc-blende with sand and Glauber's salts may be used. 

7. Oxide of bismuth is only added in small quantities in the preparation of glass for 
optical instruments. Bismuth may be employed either as oxide or nitrate of the oxide. 

The natural silicates are only employed alone in the manufacture of bottle-glass ; some 
of the preceding additions are requisite in clear glass manufacture. 

BiAaohing. Coloured glass as it occurs in the first processes of manufacture may have the 
colour disguised by mechanical mixture with white glass, or the colour may be msoharged 
by chemical agents. Such agents are usually — ^braunite, arsenious acid, saltpetre, and 
minium or red-lead. 

X. Braunite, MnOat ^fts long been used as material for glass-clearing. This oxide of 
manganese is, however, used only in small quantities ; too mnch imparts a yiolet oar 
ametiliyst-red colour to the glass; while an excessiye amount renders the glass dark 
coloured and opaque. The violet-coloured glass is generally prepared with silicate of 
manganese by the addition of braunite to colourless glass. The action of braonite 
in clearing glass or rendering it colourless has been variously explained. It may be con- 
sidered that there arises in the molten glass the colours complementary to white, that is, 
the green from silicate of iron and the violet from silicate of oxide of manganese ; this view 
is supported by the experiments of Edmer, who obtained a colourless glass from a mix- 
ture of red and violet glasses ; and further by those of Luokow who obtained a colourless 
glass by the melting together of a glass strongly tinted red by protoxide of manganese 
with oxide of copper. The glass-blowers of the Bavarian Waldenses assert that a rose-red 
quartz there found is equalled by no other quartz in the production of the best czystal or 
dear glass. Yon Fuchs says that this quartz contains x to 1*5 per cent of oxide of 
titaniu|n, which similarly to braunite, effects the chromatic neutriJisation. Eohn 
employs for this purpose protoxide of nickel or oxide of antimony. Oxide of zinc has 
lately been employed to remove or mask the green colour of Glauber's salt glass, also 
imparting a higher polish. 2. Arsenious add effects the removal of colour 'by chemical 
means only from glass containing carbon or silicate of iron : in glass containing carbon — 

Arsenious acid, AS2O3 \ . ] Arsenic, Asa* 
Carbon, 3O / ^^® I Carbonic oxide, 3 GO ; 

in glass containing protoxide of iron : — 

Protoxide of iron, 6FeO, ) . f Oxide of iron, sFcaOj, 
Arsenious add, As^Oj, j ^ ( Arsenic, As^. 

The arsenious add is reduced by the carbon and protoxide of iron at a dull red heat* 
while the arsenic is volatilised. 

3. Saltpetre is added chiefly as Chili-saltpetre or nitrate of soda. In the manufaetore 
of lead-glass (flint-glass) nitrate of lead is sub