Electric Smelting and Refining ... Being the second edition of 'Elektro-Metallurgie' ... Translated, with additions, by Walter G. M'Millan, etc

Front matter

ELECTRIC SMELTING AND REFINING. GRIFFIN'S SCIENTIFIC TEXT-BOOKS. ELECTROMETALLURGY (A Treatise on) : Embracing the Application of Electrolysis to the Plating, Depositing, Smelting, and Refining of various Metals, and to the Reproduction ol Printing Surfaces and Art Work, &e. By WALTER G McMillan, F.I.C, F.C.S., Lecturer on Metallurgy, Mason College, Birmingham. With numerous Illustrations. Large Crown 8vo. Cloth, 10s. 6d. "One of the best and most complete manuals hitherto published on Electro- Metallurgy." — Electrical Review. ELEMENTS OF METALLURGY : A General Treatise on the Art of Extracting Metals from their Ores. By J. Arthur Phillips, C.E., F.C.S., F.G.S., and H. Bauerman, F.G.S. Third Edition. In Royal 8vo. With numerous Illustrations, 36s. " The value of this work is almost INESTIMABLE." — Mining Journal.

METALLURGY (An Elementary Text-Book of). By Prof. Humboldt Sexton, F.I.C, Glasgow and West of Scotland Technical College. With numerous Illustrations, 6s. "For Engineers in practice ... a handt work of reference."— Practical Engineer. ASSAYING (A Text-Book of). By J. J. Beringer, F.C.S., F.I.C, Lecturer to the Mining Association of Cornwall, &c. ; and C. BERINGER, F.C.S. Fourth Edition, ios. 6d. " A really Meritorious Work, that may be safely depended upon."— Nature. MINE-SURVEYING : For the Use of Managers of Mines, Collieries, <ftc. By "H. H. Brough, F.G.S., formerly Instructor of Mine Surveying, Royal School of Mines. Fifth Edition, Illustrated, 7s. 6d. "No English-speaking Mine Agent or Mining Student will consider his technical library complete without it." — Nature. ELECTRICAL RULES AND TABLES FOR THE USE OF ELEC- TRICIANS AND ENGINEERS.

By J. Munro, C.E., and Professor A. JAMIESON, F.R.S.E., M.Inst.CE., M.Inst.E.E. Twelfth Edition, Leather, 8s. 6d. "Wonderfully perfect. . . . Worthy of the highest commendation we can give it." — Electrician. GRIFFIN'S METALLURGICAL SERIES. Edited by W. C. ROBERTS-AUSTEN, C.B., F.R.S., Cftemist and Assayer of the Royal Mint ; Professor of Metallurgy in the Royal College of Science. In Large Svo, Handsome Cloth. With Illustrations.

Introduction

TO THE STUDY OF METALLURGY. By the Editor. Fourth Edition. Large 8vo. Shortly. GOLD (The Metallurgy of). By Thomas Kirke Rose, Assoc.R.S.M., D.Sc, Assistant- Assayer of the Royal Mint. Second Edition, 21s. IRON (The Metallurgy of). By Thomas Turner, Assoc.R.S.M., F.I.C. 16s. STEEL (The Metallurgy of). By F. W. Harbord, F. I. C. , Assoc. R. S. M. fcILVER AND LEAD (The Metallurgy of). By Henry F. Collins, Assoc.R.S.M., Assoc. Mem. Inst.CE. ALLOYS. By the Editor. *„* Other Volumes in Preparation. LONDON: CHARLES GRIFFIN & CO., LTD., EXETER STREET, STRAND. ELECTRIC SMELTING AND EEFINING: THE EXTRACTION AND TREATMENT OF METALS BY MEANS OF THE ELECTRIC CURRENT. BEING THE SECOND EDITION OF "ELEKTRO-METALLURGIE." by DR. W. BORCHERS. Translated, with additions, by WALTER G. MCMILLAN, LECTURER ON METALLURGY IN MASON COLLEGE, BIRMINGHAM; AUTHOR OF A "TREATISE ON ELECTRO-METALLURGY."

TKHitb 3 plates an& IRumcrous Jllustrations in tbe Œejt. LONDON: CHARLES GRIFFIN AND COMPANY, LIMITED; EXETER STREET, STRAND. 1897. [All Rights Reserved.]

Preface

. In bringing before English readers an English version of a manual so well known as that of Dr. Borchers — on a subject which has so rapidly attained to the prominent position now held by Electro -Metallurgy — but little by way of introduction is needed. The Author, in his preface to the Second German Edition (that of 1896, from which the present volume has been translated), refers to his twelve years' practical work in chemical and metallurgical industries, and states that in preparing the first edition he had hoped to be of service to his fellow-labourers by laying before them the results of the experience with electro - metallurgical processes which he had gained in conducting experimental tests on a scale sufficiently large to enable him to form a trustworthy opinion as to their practical value.

During the four years which elapsed before the appearance of the Second Edition, electro - technology had made enormous progress ; and at the end of that time the Author found himself at liberty to publish much information which pre viously, owing to personal considerations and business obligations, he had been prevented from giving to the world. He, therefore, re-wrote and greatly extended the work in the edition from which this version is taken. A short sketch only is given of the newer electro-chemical theories, and the student is referred for fuller and more elaborate explanations to the works of Ostwald on General Chemistry and Electro-Chemistry, and to that of Nernst * * Nernst's Theoretical Chemistry from the Standpoint of A vogadro's Rule and Thermodynamics. Translated by C. S. Palmer. VI

PREFACE.

. on Theoretical Chemistry. Those who are engaged in scientific or technical research are recommended to consult Ostwald's Handund Hulfsbuch zur Ausfuhrung pkysiko chemischen Messungen* and Oettel's Anleitung zu Eleldro chemischen Versuchen. In the present volume, all those metals in the extrac tion and working of which the electric current has found any application are treated of; but electrolytic analysis, electro-plating, and electro-typing have not been touched upon. From the mass of material accumulated in journal and patent-office literature, only those papers or processes which are capable of practical application have, usually, been selected for reference. A short survey of the purely metallurgical methods of treating the metals has been added to each chapter, so that the reader may be in a position to compare such methods with electro-metallurgical processes, and to see how the two may be used in conjunction.

During the few months that have passed since the publication of the German Edition, progress has been made in many directions. The Translator has, therefore, ventured to add notes here and there in the hope of bringing the work more nearly up to date. He has also added accounts of the practical working of certain processes which have been developed since the German work was placed before the public. Extra references to English patents and the British equivalents of the metrical measurements quoted in the text have also been given. All these additions, whether in the text or in footnotes, are enclosed within square brackets, [ ], so that the reader may distinguish between the orio-inal and the supplementary matter. Tables for the conversion of certain Continental into the corresponding British units nave also been added in an appendix.

Whenever possible quotations from the French have been translated direct * Ostwald's Manual of Physiro - Chemical Measurements. Translated by J. Walker.

PREFACE.

. VII from the French text, instead of fromthe German version, and those from English sources have been reprinted ver batim from the original. In arranging the additional matter, the Translator has kept in view the industrial aspect of the question, and has introduced one or two short supplementary notes referring to actual applications of processes not otherwise referred to in the text. It is believed, therefore, that under each of the various metals, separately, enough has been stated to give a good general idea of the present industrial position of that branch of the subject. The practical applications of Electro-Metallurgy are advancing with phenomenal rapidity, especially on the Continent and in America, and there is little doubt that, if England is to hold her own in Metallurgy, she also must give more and more attention to the electro-metallurgical smelting and refining processes, which are cheapening and simplifying the work of producing high-class products abroad.

In conclusion, the translator's thanks are due to Mr. A. E. Hunt and the Institution of Civil Engineers, to the Electrician, and to Industries and Iron, for the use of the blocks employed in Figures 82a, 101a, and 50a and 50b respectively. WALTER G. MCMILLAN. Metallurgical Department. Mason College, Birmingham, June S, 1S97. CONTENTS. PAGE Introduction, . 1-15 Electrolysis, ......•••• 1 Osmotic Pressure, ........ Electrolytic Dissociation, ...-••• Theory of Electrolysis, 3 Conditions of Electrolysis, ....... Relation of Current Strength to Weight of Deposit, . 8 Valency, ......•■•• ™ Relation of Work expended to Weight of Deposit, . 10 Current Density, .....••• lu Calculation of Potential, ....••• 1 1 Electro-thermic Work, ..,.■•■• '" Cost of Electro-Metallurgical Work, . . . . ■ 13 9

Part I

— ALKALIES AND ALKALINE EARTH METALS. Chapter I.— Magnesium. PAGE PAGE Properties of the Metal, . . 16 Occurrence in Nature, . . 17 Early Experiments in Reduction, 17 Bunsen's Electrolytic Reduction Process, . . . .17 Matthiessen's Double Chloride Process, .... 19 Berthaut's Process, ... 19 Small-scale Apparatus, . . 20 Fischer's Apparatus, . . 20 Graetzel's „ 22 Napier's Electrolytic Vessel, . 27 Borchers' Magnesium Process, 28 Melting of Electro-deposited Magnesium, . . .31 Electro - thermic Reduction of Magnesium, ... 31 Applications of Magnesium, . 32 Chapter H.— Lithium. Properties, .... 33 Occurrence in Nature, . . 33 Extraction, .... 33 Troost's Process, . . .34 Hiller's Apparatus, . . 35 Grabau's Apparatus, . . 37 Guntz's Process, . . .38 Treatment of Lithium Minerals, 38 Uses of Lithium, ... 39 Chapter III.— Beryllium.

Properties, .... 40 Occurrence in Nature, . . 40 Extraction, .... X CONTENTS. Chapter IV. -Sodium. PAGE PAGE 61 Properties, . . 42 Reduction Process, . . . 4-. Electrolysis, .... 43 Davy's Experiments, . 43 Watt's Process, ... 44 Jablochkoffs Process, . . 45 Hoepfner's „ * . . 46 Rogers' ,, . . 47 Omholt's Apparatus, . . 49 Fischer's Process, . . 53 Hornung and Kasemeyer's Plant, .... 53 Grabau's Apparatus, . . 55 Borchers' ,, 57 Grabau's later Apparatus, . 59 Borchers' Sodium-Extraction Plant 60 Castner's Process, . ■ °1 Manufacture of Sodium by Electrolysis, ' ' " S Disposition of Plant, . • -.. Cost of Electrolytic Sodium- Extraction, ■ * ■ £5 Sodium Alloys, ... 67 Use 67 Early Apparatus for decomposition of Alloys, . 68 Castner' s Caustic Soda Plant, 69 Later Amalgam-forming Processes, . • • . *0 Borchers' Plant for Sodium Alloys, .... 72 Chapter V.— Potassium.

Properties, .... 75 Extraction Processes, . . 76 Occurrence in Nature, . . 75 Uses, ..... 76 Chapter VI— Calcium, Strontium, Barium. Extraction on a large Scale, . 82 Borchers' Modified Apparatus, 85 Properties of the Group, . . 77 Occurrence in Nature, . . 77 Extraction, .... 78 Reduction of the Alkaline Earths by Carbon, . 86 Uses of the Alkaline Earth Matthiessen's Experiments, . 79 Extraction of Calcium, . . SO of Strontium, . 81 Metals 87 Chapter VII.— The Carbides of the Alkaline Earth Metals. Willson's Process, ... 93 The Production of Carbides, . 87 Methods of Production, . . The Calcium Carbide Plant at Spray 94 Borchers' Electric - Smelting Furnace, . . . . !S9 Estimated Cost of Producing Calcium Carbide, ... 96 Early Experiments in Carbide Production, .... 92 Use of the Carbides, . . 98 Bullier's Specification, . . 92

Part II

— THE EARTH METALS. Chapter I. Aluminium. Properties, .... 101 Occurrence in Nature, . . 101 Precipitation Processes of Extraction, . . . .102 The Reduction Process, . . 103 The Cowles Process, . . 105 Theory 109 Thermal Reduction of Alumina by Carbon, . . .110 Modified Borchers' Resistance Furnace, . HI The Electrolytic Methods oi Reducing Aluminium, . 114 Early Experiments, . . IIS Deville's Process. 119 Practical Obstacles to the Electrolysis of the Chlorides, . ]21 CONTENTS, XI PAGE PAGE The Teaching of Deville's and Bunsen's Experiments, . 122 Impracticable Processes, . 123 Successful Reduction Processes, 129 Decomposition of Aluminium Compounds by the Electric Arc 129 Johnson's Process, . . 130 The Siemens Electric Furnace, 131 The Menges Electric Furnace, 134 The Kleiner-Fiertz Electric Furnace, .... 135 The Grabau Electric Furnace, 135 The Gerard Lescuyer Furnace, 135 The Electric Construction Corporation Furnace, . 136 The Willson Furnace, . . 137 Electrolysis of fused Aluminium Compounds, . . 138 The Heroult Process, . .

K.8 The Hall Process, . . 142 The Minet-Bernard Process, 152 The Nenhausen-Froges Process, ..... 156 Borchers' Aluminium Extraction Apparatus, . . 157 The KiliaDi Aluminium Extraction Apparatus, . . 159 The Grabau Patent, . . 160 The J. B. Hall Process, . 161 Electrolysis of Aluminium Sulphides, . . .161 Summary of Conditions to be Observed in the Extraction of Aluminium, . . . 163 Relative Specific Gravities of Metal and Electrolyte, . 164 Chapter IL— Cerium, Lanthanum, Didymium. Preparation of the Cerite Metals, 166 Properties of the Cerite Metals, 165 Cerium, 166 Electrolytic Deposition of the Cerite Metals, . . . 166 Applications of the Cerite Metals, 169 Lanthanum, . . . .166 Didymium, . . . .166

Part III

— THE HEAVY METALS. Chapter I.— Copper. Properties, . . . .171 Occurrence in Nature, . . 172 The Roasting Processes, . . 172 The Reduction Process, . . . 174 Leaching of Copper from Ores and Furnace Products, . 175 Refining Processes for Nature and Crude Copper, . . 176 Electrolytic Methods, . . 177 Electrolytic Refining, . . 177 Early attempts in the Electro- Deposition of Copper, . 177 Patera's Process. . . • 178 The Elkington Patents, . 178 Theory of Electrolytic Copper Refining, . .' 182 Kiliani's Experiments, . .183 The Siemens- Halske Copper Refinery Process, . .189 Limitations, . . . 190 The Siemens-Halske Installation at Goslar, . .191 Borchers' Improvements, . 194 Details of the Siemens- Borchers Installation, . 197 Purification of Old Liquors from Bismuth and Anti- • mony, . . . .198 Reduction in Cost, . . 198 Schneider and Szontagh System, 200 The Thofehrn Process, . 201 Thofehrn's New Process, . 206 Modified System of Deposition, 207 The Stalmann Process, . 207 The Hayden, Smith, and Randolf Processes, . . 209 The Multiple and the Series Systems, . . . .210 Refining of Argentiferous Copper, . . . .211 Treatment of Sulphide Ores and Mattes, . . .211 The Marchese Process, . 212 The Stolberg Installation, . 219 Use of Depolarisers, . . 222 Body's Process, . . . 223 The Siemens-Halske Matte- Refinery Process, . . 225 Modified Siemens - Halske Process 227 The Hoepfner Process, . . 231 The Schwarzenberg Experiments, .... 234 The Cohen Process, . . 234 Applications of Copper, . .

CONTENTS. Chapter II.— Silver. PAGE PAGE Properties, .... 236 Occurrence in Nature, . . 237 Extraction by solution of Silver in another metal, . . 237 Separation by processes of Chemical Solution, . . 239 The Ziervogel Process, . . 239 The Augustin, Patera, and Kiss Processes, . . 239 The Russell Process, . . 240 Sulphuric Acid Processes, . 240 Electrolysis — Early Experiments, . . 240 Process depending on the Insolubility of Silver at the Anode, . . . 242 Processes involving Solution of Silver at the Anode, . 242 Moebius Process, . . • 243 The Pennsylvania Lead Co. _ Plant, .... 248 Later form of Moebius Apparatus, .... 249 The Perth-Amboy Installation, 250 The House-Symon Process, . 251 The Separation of Copper - Silver-Gold Alloys, . . 251 Borchers' Apparatus, . . 253 The Dietzel Apparatus, . 256 Chapter III— Gold.

Properties, .... 259 Occurrence in Nature, . . 260 Mechanical Treatment, . . 260 Washing, .... 260 Solution in other Metals, . 261 Chemical Extraction Processes, 262 Chlori nation, . . . 262 Cyanide Extraction Processes, 262 Removal of the Impurities by Fusion, . . . 263 Solution of the Impurities in Acids, .... 263 Electrolysis — Without Solution, . . 263 With Solution, . . . 264 Treatment of Gold containing Platinum, . . 264 Electrolysis of Ores, . . 265 Bonnet's Process, . . 268 Body's Process, . . 268 Molloy's ,, . .268 Modified Forms of Apparatus, . . . .269 Gmehling's Experiments, 271 Electrolysis of ores without the aid of Mercury, . 272 Causes of Failure, . . 274 Jory's Process, . . . 275 Solution of Gold by Chemical Method followed by Electrolytic Precipitation, .... 275 Siemens-Halske Process, . 276 Comparison of Electrolytic and Chemical Precipitation Processes, . . 280 Later Processes, . . 281 Uses, 282 Chapter IV.— Zine and Cadmium.

Zinc 282 Properties, .... 2S2 Occurrence in Nature, . . 283 Extraction, .... 2_3 The Roasting and Reduction Process, . . . 283 Electrolysis, . . . 285 Zinc Salts Solutions with Anodes of Zinc Ore, . 285 Zinc Salts Solutions with Anodes of Zinc or Zinc Alloys 286 Treatment of Zinc Crusts, 287 Electrolytic Refining of Zinc ogg Kiliani's Experiments, . 2S9 Mylius and Fromm's Experiments, . . .290 Dissolved or Fused Zinc Salts with Insoluble Anodes, . *'Qsi Luckow's Process," . 296 The L_ .range ,, 097 Other Patented Processes, 298 Use of Deoxidisino- Agents, . _ ° CONTENTS. XIII PAGE PAGE Use of Depolarising Agents, . . . 300 Lindemann's Process, . 301 Nahnsen's Experiments, 303 Coehn's Process, . . 306 Covvper-Coles' Process, . 306 Hoepfner's ,, . 306 The Ashcroft, ,, .307 Modern Industrial Developments, . . . 308 Conditions for the Electrolytic Extraction of Zinc, 308 The Solution of Zinc, . 309 Purification of the Solutions, . . . .309 The Apparatus and Conditions for Electrolysis, . 310 Electromotive Force and Current Density, . . 315 The Prevention of Spongy Zinc, . . . .315 Utilisation of the Anode Reactions, . . . 315 Cost of Zinc Extraction, . 316 Uses, 316 Cadmium — Properties 316 Extraction, .... 317 Electrolysis, . . .317 Uses, 317 Chapter V.— Mercury.

Properties and Occurrence, . 317 Extraction, .... 318 Uses, 318 Extraction, Chapter VI— Tin. Properties and Occurrence, . 319 I Extraction, .... 319 I Electrolysis 320 ! Tin Ores, .... 320 Tin-plate Scrap, . . ' 300 Uses, ... 304 Chapter VII— Lead. Properties and Occurrence, . 325 Extraction, .... 326 The Reaction Process of Smelting, . . . .326 The Reduction or Roasting and Reduction Process, . 328 The Precipitation Process, . 330 Refining of Lead, . . 330 Electrolysis 331 Chemical Solution and Electrolytic Separation, . 331 Becquerel's Process, . . 331 Lyte's Process, . . . 333 Lead Salt Solutions with Lead Ore Anodes, . . . 333 Dissolved or Fused Lead Compounds with Crude Lead Anodes, . . 333 The Keith Process, . . 333 Use of Organic Depolarising Agents, . . .336 The Tommasi Process, . 337 Uses of Spongy Lead, . . 338 Electrolysis of Fused Lead Salts, . . . .338 Borchers' Apparatus, . 339 Applications, .... 342 Chapter VIII.— Bismuth.

Properties and Occurrence, . 342 Extraction, .... 343 Eliquation 343 The Reduction Process, . 343 The Precipitation „ . .343 Chemical Solution and Precipitation, . . . 344 The Refining Process, . . 344 Electrolytic Methods, . . 345 Applications, .... CONTENTS. XIV Chapter IX.— Antimony. PAGE PAGE Conditions Suitable to Electrolytic Refining, . • 351 Practical Working, . . 352 Sanderson's Process, . . -_8 Kopp's ,, • ■ 359 Siemens-Halske Process, . 359 Treatment, .... 360 Applications, .... 360 Properties, .... 346 Occurrence in Nature, . . 347 The Precipitation Process, . 347 The Reduction or Roasting and Reduction Process, . . 347 Electrolytic Processes, . . 348 Methods Available, . . 348 Borchers' Experiments, . 348 Chapter X.— Chromium, Molybdenum, Tungsten, Uranium, Manganese. Chromium, .... 360 Properties, .... 360 Occurrence in Nature, . 360 The Reduction Process, . 361 Moissan's Furnace, . . 362 Chaplet's „ . . 363 Refining, .... 364 The Precipitation Process, . 364 Electrolysis, . . . 364 Dissolved or Fused Chromium Compounds, with Insoluble Anodes, . 364 Bunsen's Experiments, . 365 Borchers' „ .366 The Placet-Bonnet Process, .... 366 Fused Salts, with Crude Chromium or Ferro- Chrome Anodes, . . 368 Application, . . . 368 Molybdenum, . . . 368 Properties and Occurrence, . 368 Production, . . .369 Tungsten, . . • . .369 Properties, . . . .369 Extraction, .... 369 Uranium, .... 370 Properties, .... 370 Manganese, .... 371 Properties, .... 371 Occurrence in Nature, . . 371 Reduction, . . . .372 The Precipitation Process, . 372 Electrolysis, . . . 372 Dissolved or Fused Manganese Compounds, with Insoluble Anodes, . 372 Fused Manganese Compounds with Soluble Anodes, . . . 374 Applications, . . . 374 Chapter XL— Iron.

Properties, .... 374 Occurrence in Nature, . . 376 Preparation of the Raw Materials, .... 376 Magnetic Separation, . . 376 Smelting, .... 378 Production, .... 378 De Laval's Smelting Furnace, . . . . . 378 The Production of Malleable Iron, 379 The Working of Iron, . . 383 Thomson's Electric Welding Process, .... 383 Local Softening of Quenched Steel 3S5 The Benardos Electric Welding Process, . , , 386 The Slavianoff Process, . 3S9 The Lagrange and Hoho System, . . _ ggg The Burton Liquid Forge, '. 390 The Zerener Process, , ' CONTENTS. XV Chapter XII.— Nickel and Cobalt. PAGE PAGE Properties of Nickel, . . 393 Occurrence, .... 393 Extraction, .... 394 Andrews Process, . . . 395 Farmer's ,, . . 396 The Basse-Selve Process, . 398 The Hoepfner „ . 398 The Rickets Process, . . 399 Deposition of Pure Nickel and Cobalt, . . .399 Summary, .... 401 Application of Nickel, . . 402 Cobalt, 402 Chapter XIII.-The Platinum Group.

Electrolysis, ........... 402 ADDENDA. Table I. — Value of Equal Current Volumes, ..... 404 II. — Thermometer Scales, ........ 405 Index, LIST OF ILLUSTRATIONS. Plate I. Plan of electrolytic sodium works with gas motor, to face p. , 65 ,, II. Copper refinery, Siemens' system, . . . „ 194 ,, III. „ Siemens-Borchers-Brothers' system, ,, 197 PIG. PAGE 1. Osmotic pressure, ....... 2 2. Bunsen's electrolyte cell, ...... 18 3. ,, carbon electrode ...... 18 4. Gorup -Besanez apparatus, ...... 19 5. Fischer's earliest magnesium reduction apparatus, . . 20 6. ,, continuous electrolysis apparatus, . . .20 7. ,, later apparatus, ...... 21 8, 9. Graetzel's apparatus, ...... 23 10, 11. „ „ 24 12. Borchers' flanged crucible for electrolytic reduction, . . 27 13. „ experimental furnace for the electrolysis of fused salts, 28 14. ,, furnace for the manufacture of magnesium, . . 30 15.

Troost's apparatus for the electrolysis of fused lithium chloride, 34 16. Hiller's apparatus for the extraction of strontium, . . 36 17, IS. Grabau's electrode cell for use with light metals, . . 37 19. Watt's apparatus for the extraction of sodium, . . .44 20. Jablochkofi's ,, ,, ,, ,, 46 21, 22. Rogers' „ „ „ ,, . . .48 23, 24, 25. Omholt's sodium plant, - . . . . .50 26. Omholt's modified sodium plant, . . . . .51 27. Fischer's apparatus, ...... 53 28, 29. Hornung and Kasemeyer's apparatus, . . . .54 30. Grabau's apparatus for the reduction of alkali metals, . . 56 31. Borchers' apparatus for reducing the alkali metals, . . 58 32. Grabau's modified cathode cell, . . . . .59 33, 34. Borchers' sodium-extraction plant, . . . .60 35. Castner's electrolytic sodium-extraction plant, . . .62 36.

Borchers' sodium-reduction plant, . . . . .65 37. Plate I., ...... to face 65 38. Sinding-Larsen's electrolyte cell, . . . . .69 39. Castner's electrolyte cell for the manufacture of caustic soda, . 69 40. Vautin's apparatus, ...... 72 b LIST OF ILLUSTRATIONS. FIG. PA£5 41. Borchers' apparatus for the production of sodium alloys, . 73 42. ,, improved apparatus for the production of sodium alloys, . . . . . . • .74 43. Borchers' experimental apparatus for alkaline earth metal reduction, .....•• 8* 44. Borchers' calcium reducing furnace, . ■ • .85 45. „ experimental electric furnace, . . . .88 46. ,, electric-smelting furnace (longitudinal section), . S9 47. ,, ,, ,, (transverse section), . . 89 48. „ „ „ (plan),. ... 90 49. Cowles' electric furnace, ...... 91 50. The Willson „ ...... 93 50a and u. The King furnace for calcium carbide, . . .95 51.

Cowles' plant for manufacture of aluminium alloys, . . 107 52. The Cowdes" furnace (longitudinal section), . . . 108 53. „ ,, (cross section), .... 108 54. Arrangement to show direct reduction of alumina by carbon, . 110 55. Modified experimental Borchers' furnace, . . . 112 56, 57. ,, ,, (in section and plan), . 112 5S. Borchers' support for crucibles of different diameters, . .113 59. Deville's apparatus for reducing aluminium, . . . 120 60. Graetzel's aluminium electrolysing vessel, . . . 124 61. Grabau's cooled cell apparatus, ..... 126 62. Henderson's apparatus (aluminium), .... 127 63. Cowles' ore-smelting furnace, ... . 130 64. Pichou's smelting furnace, ...... 131 65. Siemens' electric furnace, .... . 132 66. ,, modified electric furnace, .... 133 67. Menges' electric furnace, . ... 134 68, 69.

The Kleiner-Fiertz furnace, ..... 134 70. Gerard-Lescuyer's electric furnace, .... 136 71. The Electric Construction Corporation furnace, . . . 136 72. The Willson furnace, ..... 137 73, 74. The He'roult aluminium furnace in longitudinal section and in plan 139 75. He'roult aluminium furnace for small installations, . 141 76. The Hall furnace, U.S.A. patent, No. 400,766, . . .143 77. Modified apparatus, Hall patent, 400,766, . . 145 7S, 79, SO. The Hall furnace, American patent, No. -100,664 145 81- >> .. ». 400,665, . 146 82- '• >• .. 400,666, 148 82a. The Pittsburg Co.'s Hall furnace, . 14g 83,84. Bernard (Minet) aluminium furnace, . . -r, 85. Aluminium reduction. Apparatus used at Neuhausen ir;c S6. Borchers' aluminium extraction apparatus, . --„ 87. Kiliani's electrode mechanism, ... LIST OF ILLUSTRATIONS.

XIX ma. page 88. Section of copper-refining vat, showing anode, . . . 191 89. Mould for casting anode plates, ..... 192 90. Cross-section of copper-vat (Siemens), showing cathode, . 192 91. Longitudinal section of copper vat (Siemens), . . . 193 92, 93, 94. Plate II. , ..... . to face 194 95. Scheme of electrical connections in copper vats (Siemens), . 194 96. Siemens-Borchers' copper vats (longitudinal section), . . 195 97. ,, ,, (cross-section), . . . 196 98, 99, 100. Plate III., .... . to face 197 101. The electrical connections of Thofehrn's apparatus, . . 201 101a. The Anaconda Thofehrn installation, .... 204 102, 103, 104. Stalmann's electrode connections, . . . 20S 105. Stalmann's copper vat (cross-section), .... 208 106. Scheme of electrical connections in Stalmann's vat, . . 208 107.

Scheme of electrical connections in Hayden's vat, . . 209 108-111. Moulds for casting anodes of matte at Casarza, . . 213 112, 113. Connections of anode-strip with main conductor at Casarza, 214 114. Scheme of electrical connections at Casarza, . . . 214 115, 116. Method of attaching the lead linings to the vats (Casarza), 215 117. Section of vats, showing method of circulating the electrolyte (Casarza), ....... 215 118. Plan of vats, showing method of circulating the electrolyte (Casarza), ....... 215 119. Plan of the Casarza installation, ..... 216 120. Cross-section of the Casarza depositing-room, . . . 216 121. Interior of the Casarza depositing-room, .... 217 122. General scheme of the Marchese process, . . . 218 123, 124. Body's apparatus, . . . ■ • .224 125. Siemens & Halske electrolytic cell for treating copper ore, . 226 126.

Arrangement of vats in the Siemens-Halske process, . . 227 127, 128, 129. Siemens _ Halske's electrolyte cell (1889), . . 228 130. New form of anode (Siemens-Halske), .... 230 131. Newer form of tank ( ), . . • • 230 132. Cohen's single-compartment electrolyte cell, . . . 235 133. The Moebius apparatus, showing anode compartment in half section, ........ 243 134. The Moebius apparatus — section showing cathode, . . 244 135. „ ,, section through A RCE (Fig. 136), . 244 136. ,, ,, plan, • • • • .245 137. scheme of electrical connections, . 246 138, 139. The Moebius process— later form of apparatus, . . 249 140. The Moebius anode connection (new form), . . . 249 141, 142. Borchers' electrolytic cell for the treatment of alloys, . 253 143 144. ,, modified electrolytic cell for the treatment of alloys, 255 145.

Dietzel's alloy-separating vat, ..... 258 146, 147, 148. Barker's gold-extraction plant, . . . XX LIST OF ILLUSTRATIONS. FIG. '"J 149. The Molloy amalgamating pan, . 150. Stolp's gold-extraction apparatus, . *"• 151. ,, modified apparatus, . 152. Connections with subsidiary electrodes in zinc deposition, . -95 153-156. Apparatus for electrolysis of zinc solutions, . . • 311 157. Borchers' zinc-extraction apparatus (experimental), . • 313 158. ,, ,, ,, for use on a large scale, . 313 159. Shape of zinc plate to be cut for use as cathode, . . 314 160-162. Keith's plant, . ...... 334 163, 164. ,, lead-refining vat, ..... 334 165, 166, 167. Borchers' lead-refining plant, .... 340 168. Antimony extraction plant (section), .... 354 169. „ „ ,, (plan), . . . .355 170. ,, electrolytic tank (section), .... 357 171. „ „ „ (plan), . . . .357 172.

Borchers' electric furnace, ..... 362 173. Moissan's ,, ..... 363 174. Chaplet's ,, ..... 363 175. ,, modified electric furnace, .... 363 176. Borchers' electric furnace, ..... 373 177, 178, 179. De Laval's electric furnace, .... 379 180, 181, 182. Elihu Thomson electric welding process, . . 384 1S3. Benardos' method of electrical heating, .... 387 184, 185. Lagrange and Hoho electrical heating method, . . 390 1S6. Zerener's apparatus, ...... 392 1S7, 1SS. Farmer's nickel depositing plant, ....

INTRODUCTION.

. In the study of electro-metallurgy we are concerned with the electrolytic and electro-thermic, rather than with the electro magnetic, relations of electricity ; and only the former two will, therefore, be treated of in this work. ELECTROLYSIS. Until quite recently the idea of electrolysis was associated only with those changes in the constitution of substances that could be effected by the action of electric currents generated externally. But this conception is now greatly enlarged ; and the newer electro-chemistry, together with the whole fabric of chemical science, is placed upon a broader foundation, strengthened both by experimental and by mathematical investigation. A full exposition of the modern electro-chemical theories would be out of place here, and the reader is referred for this to standard treatises, such as those of Ostwald and Nernst.

A short sketch, however, of the now classical work and theories of these two writers, and those of Van't Hoff and Arrhenius, will be given before passing to the consideration of electro-metallurgical practice. The observations of these investigators have started a new era in the science of chemistry. The fact that they, for example, afford a full explanation of the action of the voltaic cell and of the electric circuit, towards which goal science has been striving for nearly a century, points to the solidity of the basis upon which these modern theories have been founded. Osmotic Pressure. — As the starting point for the sketch, reference may be made to the simple machine illustrated in Fig. 1, which represents a cylinder, 0, partly filled with steam. The steam-chamber, D, is closed by a piston, which is capable of sliding freely in the cylinder; and above the piston is a space free from vapour.