IN MEMORIAM FLOR1AN CAJOR1 THE ART OF ELECTROLYTIC SEPARATION OF METALS, ETC. (THEORETICAL AND PRACTICAL.) G. GORE, LL.D., F.R.S., \ A uthor of 'The Art of Electro-Metallurgy," "The Theory and Practice of Electro- Deposition," "Electro-Chemistry," "The Art of Scientific Discovery," "The Scientific Basis of National Progress," etc., etc. SECOND EDITION NEW YORK : THE D. VAN NOSTRAND COMPANY, 23, MURRAY STREET, AND 27 WARREN STREET. LONDON : 'THE ELECTRICIAN" PRINTING AND PUBLISHING COMPANY, LIMITED, SALISBURY COURT, FLEET STREET, E.C. 1894. [All Rights Reserved.] *-?'?. Printed and Published by 1 THE ELECTRICIAN " PRINTING AND PUBLISHING CO., LIMITED, 1, 2, and 3, Salisbury Court, Fleet Street, London, E.G. PREFACE. THIS volume is written to supply a want No book entirely devoted to the Electrolytic Separation and Refining of Metals exists at present in any lan- guage ; those hitherto written on the subject of Electro- metallurgy are more or less devoted to electro-//^//^; or the processes of coating articles with thin layers of gold, silver, copper, nickel, and other metals ; the mould- ing and copying of works of art, of printers' type, of engraved wooden blocks, and metal plates, &c., by electro-deposition. Much of the information hitherto published on the subject lies scattered about in short articles and frag- mentary accounts, in periodicals and books ; and state- ments, more or less inaccurate, have been made, owing to the writers not having had access to the manufac- tories the processes in which they have attempted to describe. M. Kiliani* and others have observed the privacy with which electrolytic refining works are con- ducted ; he says that " its effect has been to some extent to make people believe that the operations carried on are based upon discoveries known only to a few, and are surrounded by difficulties of a very special and complicated nature." He writes with "the object of dissipating this wrong impression, and of convincing * "On the Electrolytic Refining of Copper," in the Berg und Hutten- mannische Zeitung, 1885. 918308 IV. PREFACE. all those interested in the subject, that whatever is done inside these works can be done by anybody who gives a little attention and study to the subject, the only 'secrets* being slight and immaterial details of practice." The probable explanation of this is, that each electro- refiner, in consequence of being imperfectly acquainted with the literature of the subject, and of how his fellow- refiners were working, has been obliged to ascertain by means of experiments in his own works the practical details of the process ; and has thus independently arrived at the same general plan of operating as other refiners, whilst considering his own method a secret. The author of the present book, having been kindly permitted by some of the largest electro-refiners of copper and makers of electro-metallurgical dynamos in this country, to unreservedly inspect their manufactories, processes, and dynamo-electric machines, is thereby better enabled to avoid inaccurate statements. At the same time, whilst being at liberty to publish all information already open respecting the general processes employed by electro-refiners of metal, he carefully avoids making known any private communi- cations. His object is not to describe the arrangements employed in particular works, but only to supply such information as will be useful to students, and to those who are engaged in practically establishing and' working electrolytic processes. Manufacturers' secrets nearly always leak out, and the idea that any of importance remain relating to this subject is an illusion. A perusal of this book will show that whilst all the methods of working the electrolytic process employed in different works are substantially the same, and are based upon and conform to well-known principles of PREFACE. V. chemistry, thermo-chemistry, voltaic action, and elec- trolysis, very expensive experiments upon a large scale have been made in electrolytic refineries, especially the earliest established ones, in order to determine the con- ditions of practical and commercial success, under which the process could be conducted in the most economical manner and with pecuniary profit, more particularly as regards the most suitable number and dimensions of vats. Great expense has also been incurred by makers of dyna- mos in improving those machines, and by electrolytic refiners in substituting one kind of dynamo for another in order to obtain the most suitable.* As nearly every inventor wishes his invention to be quickly published and used ; nearly as fast as those improvements in refin- ing and in dynamos have been made, information respect- ing them has been published in various periodicals, and all that is suitable of it has been condensed and arranged in a systematic order in this work. The present book contains both the Science and the Art of the subject, i.e., both the Theoretical Principles upon which the art is based, and the Practical" Rules and details of technical application on a commercial scale, in order thereby to render it suitable both for students and manufacturers. Whilst the fundamental principles of the art are fully described, it is not intended to supply a treatise containing information respecting chemistry of the metals, because the reader is supposed to be already acquainted with that subject as a necessary preliminary to enable him to understand electrolytic processes. Nor is it intended to furnish full information respecting dynamo -electric machines, because that is * More than thirty dynamos have been thrown aside for improved ones in a single refinery. A2 Vl. PREFACE. largely a separate and preliminary matter ; sufficient, however, is said respecting the chemical relations of electrolysis, and respecting dynamos, to afford general guidance in the art of electrolytic refining. Only those portions of the subjects are included, a knowledge of which is indispensable to the successful working of the process. The special subjects required to be previously . known in order to fully understand this one are chemistry,, voltaic electricity, magnetism, and electrical measure- ment ; the necessary preliminary knowledge of these .the reader is supposed to already possess. As the process has not yet been extended as a com- mercial success greatly beyond the separation and refining of copper, not much can be said respecting its attempted application to other metals ; what has been done on a commercially successful scale is, however,, briefly described. Many commercially unsuccessful processes are omitted. The subject of the book is treated throughout in a thoroughly systematic manner. First is given a brief historical sketch of the origin and development of the sciences of voltaic and magneto electricity, the dynamo- electric machine, and of electrolysis and its application to the refining of copper. Next comes the Theoretical Division, treating of, in succession in separate sections,, the chief electrical, thermal, chemical, voltaic, electrolytic,, magneto and dynamo electric facts and principles of the subject. Of these sections the one on electrolysis is the most full and complete, omitting no known truth of importance relating to the subject ; it also includes some useful tables of the rates of corrosion of various metals at different temperatures, the amounts of electric energy and horse-power expended in electrolysing PREFACE. VI i. various substances, the amount lost in heating the conductors, &c. Then follows the Practical Division, containing valuable information respecting the mode of establishing an electrolytic refinery, the amount of space necessary, the number and size of the vats, the amount of electric energy and horse-power required ; the preparation of the electrolyte, arrangement of the vats, electrodes and main conductors ; the mode of conducting the process, &c., so as to obtain pure copper at the least cost ; brief descriptions are also given of various pro- cesses adopted or attempted for refining other metals than copper, and for operating upon cupreous minerals without previously smelting them ; also for recovering gold from auriferous earths ; concluding with an account of Cowles's electric smelting furnace ; and an appendix of data, &c., useful in electrolytic refining. As various alterations and improvements are con- tinually being made in dynamo-electric machines, in electrolytic processes, &c., in electrolytic refining works, and accounts of these alterations are not always imme- diately published, some of the statements given neces- sarily represent the circumstances that existed a short time ago ; nevertheless, no trouble has been spared to bring the descriptions generally well up to date. Some of the previously published statements, especially the numerical ones, are so inaccurate that they have had to be omitted, but all that could be have been corrected and inserted. Many of the data have been obtained direct from electrolytic refiners and dynamo makers. Several points of useful information respecting dynamo-electric machines the author has obtained from the valuable works on " Dynamo-electric Ma- chinery," by S. P. Thompson, and " Magneto and Vlii. PREFACE. Dynamo Electric Machines," by W. B. Esson. To various manufacturers of those machines also who have afforded him information respecting their own particular kinds of dynamo, and to proprietors of electrolytic refineries who have freely answered his enquiries, he has to offer his thanks. To several correspondents in America he is especially indebted for information of the state of the art in that country. A number of points of practical information the Author has extracted from " Electrolyse," by M. Fon- taine ; M. Kiliani's Pap2r in the Berg und Hiitten- mdnnische Zeitnng, 1885, and M. Badia's Papers in La Lumiere Electrique, 1884 ; also from numerous articles in The Electrician, Dinglcr's Polylechmsches Journal, the Proceedings of the Institute of Civil Engineers, Industries, Engineering, The Scientific A merican Supplement, The Electrical Review, &c. The Author has also to acknowledge the loan of several of the illustrations appearing in the book. CONTENTS. PAQB PREFACE. iii.-viii. Historical Sketch ~ 1 Discovery of Voltaic and Magneto-Electricity 2 First Application of Electrolysis to the Refining of Copper ... 3 Development of the Dynamo-Electric Machine ... 5 Localities at which the Electrolytic Refining of Copper is carried on 6 1. THEORETICAL DIVISION. Energy 8 Fundamental Units of Quantity 9 Chief Phenomena in the Electrolytic Refining of Metals 9 SECTION A. Chief Electrical Facts and Principles of the Subject 11 Electric Polarity and Induction ... 11 Electric Quantity and Capacity 12 Electric Potential 13 Electromotive Force ... ... ... 14 Measurement of Electromotive Force 15 Electric Current 18 Strength of Current (Ohm's Law) 18 Measurement of Strength of Current 19 Density of Current 20 Circuit ... 20 Shunt, Switch 21 Electric Energy 23 Conduction and Insulation 23 Leakage of Electricity 24 Electric Conduction-Resistance 24 Resistance of Liquids ... 25 Electric-Conducting Powers of Metals 26 Relative Conductivity of Alloys ... 27 Resistance of Pure Copper 27 Measurement of Resistance... ... 29 Resistance of Dilute Sulphuric Acid _ 30 X. CONTENTS. SECTION A. (continued). Electric Conduction Resistance PAGE Specific Resistance of Solutions of Sulphate of Copper ... 30 Influence of Temperature on Resistance ... ... 31 Relative Resistances of Pure Copper at Different Temperatures 32 Resistance of Solution of Cupric Sulphate 32 Sulphuric Acid 33 Conduction Resistance of Minerals. &c 33 Internal and External Resistance 34 "Transfer-Resistance" 34 SECTION B. Chief Thermal Phenomena of the Electrolytic Separation of Metals 36 Heat of Conduction Resistance ... ... ... ... ... 36 Mechanical Equivalent of Heat ... ... 37 Thermal Units or Calories ... ... 37 Heat of Chemical Union and Decomposition ... ... ... 37 Thermal Symbols and Formulae .. ... ... 38 Table of Amounts of Heat of Chemical Union ... 39 Heat of Formation of Chlorides ... ... ... ... ... 41 Oxides 42 SECTION C. Chief Chemical Facts, and Principles of the Subject ... ... 43 Explanation of Chemical Terms ... ... ... ... ... 43 Definition of Chemical Affinity ... ... ... 43 Elementary Substance, Atom, Molecule, Mass, Atomic-weight ... 43 Symbols and Atomic-weights of Elementary Substances ... 44 Molecular Weight 45 Chemical Formulae and Molecular- weights of Substances ... 45 Equivalent Weight ... ... ... ... ... ... ... 46 , Valency, Atomicity, Atom-fixing Power ... ... ... ... 47 Monads, Dyads, Triads, &c 47 Metal, Metalloid, Alloy, Acid, Alkali, Base, Salt, Anhydride, &c. . . . 47 Chemical Potentiality 48 Relation of Heat to Chemical Action 49 SECTION D. Chief Facts of Chemico-Electric or Voltaic Action 50 Definition of Voltaic Action 50 Chemico-Electric or Volta-Tension Series ... 50 Electrical Theory of Chemistry 51 Order of Voltaic Potentiality 51 Relation of Chemical Heat to Volta-Electromotive Force 52 Table of Volta-Electromotive Forces 54 CONTENTS. Xi. SECTION D. (continued). PAGE Volta-Electric Relations of Metals, &c., in Electrolytes . ... 56 Voltaic Batteries 58 Electromotive Forces of Voltaic Batteries 59 Influence of Strength of Liquid on Voltaic Order of Metals ... 62 Temperature ... 62 Relative Amounts of Voltaic Current produced by Different Metals 64 Table of Voltaic Equivalents of Elementary Substances ... 64 Influence of Ordinary Chemical Corrosion ... 65 External Resistance ... 67 ., Kind of Substance on Chemical Corrosion ... 67 Temperature ... 67 Unequal Temperatures of the Metals 68 Tables of Chemical Corrosion at 60 and 160 Fahr. ... 69 Theory of Voltaic Action and Source of the Current ... . 70 SECTION E. Chief Facts of Electro-Chemical Action 72 Definition of Electrolysis 72 Distinction between Electroly tic and Voltaic Action ... ... 72 Connection ... ... 72 Chemical and Voltaic Action 73 Arrangements for Producing Electrolysis 73 "With one Metal and one Liquid. Simple Immersion Process ... 74 two 74 two one 75 two . Single Cell Process 76 separate Electric Current. Battery Process ... ... 76 a Series of Electrolysis Vessels 77 Self-Deposition of Metals 77 Modes of Preparing Solutions for Electrolysis ... 78 The Chemical Method 78 The Electro-Chemical Method 78 Nomenclature of Electrolysis 78 Electrodes, Anode, Cathode, Anion, Cation 78 Locality of Electrolysis ... 79 Distribution of Current in Electrolytes ... 80 Conduction in Electrolytes without Electrolysis s 81 Alternate-current Electrolysis 81 Transport of Ions in Electrolysis ... 82 Order of Velocity of Migration of Ions 83 Electrolytic Osmose and Diffusion of Liquids 83 Influence of Liquid Diffusion on Electrolysis. Decharme's Experi- ments ... ... 83 Polarisation of Electrodes, Counter-Electromotive Force ... 86 Unequal Electrolytic Action at Electrodes 86 XH. CONTENTS. SECTION E. (continued). PAGB Influence of Chemical Composition of the Liquid on Electrolysis... 87 Effects of Alcoholic and Etherial Solutions, &c 87 Influence of Water, Free Acid, &c. ... ... 88 Influence of Temperature on Electrolysis 89 Thermal Phenomena attending Electrolysis 89 Electrolysis of Fused Compounds ... 91 Influence of the Kind of Electrodes 92 Metallic Sulphides as Anodes. Badia's Experiments 92 Influence of Solubility of Anodes 95 Tables of .Retardation at Electrodes 96 Insoluble Coatings on Electrodes 98 Influence of Density of Current 98 Separation of Difficultly reducible Metals 99 Physical Structure of Electro-deposited Metals ... 99 Necessary Rate of Deposition to yield Reguline Metal 105 Electrolytic Separation of Elementary Substances ... 106 Deposition of Compounds, Mixtures, and Alloys ... 106 Secondary Effects of Electrolysis 106 Incidental Phenomena attending Electrolysis ... ... 107 Diysolving of Anodes,- Disintegration of -Anodes, &c. ... ... 108 Contraction of Deposited Metals, Electrolytic Sounds, Absorption of Hydrogen, &c. ... ... ... ... ... 109 Explosive Deposited Antimony ... ... ... 110 Purity of Electrolytic Deposits 110 Influence of Various Circumstances upon Purity of Deposits ... 110 Decomposability of Electrolytes ... ... ... ... ... ... 112 Minimum Electromotive Force necessary to Decompose Com- pounds. Berthelot's Experiments ... 113 Order of Decomposability of Electrolytes ... 114 Heats of Formation of Salts of Copper ... 115 Order of Solubility of Anodes, and Separation of Ions 115 Divided Electrolysis 116 Quantity of Electro-chemical Action ... ... 117 E. Becquerel's Experiments ... ... ... ... .. ... 118 Co-existence of Chemical and Electro-chemical Action . ... 120 Differences of Loss of Anode and Gain of Cathode 121 Effects of Stirring the Liquid 122 Temperature of the Liquid ... ... 123 Losses of Copper by Chemical Corrosion without Electrolysis ... 123 Amounts of Copper Deposited in Hot and Cold Liquids ... 124 Electrolytic Balance of Chemical and Electro -chemical Action 124 Chemical Corrosion of Cathodes ... ... 125 Electro-chemical Equivalents of Substances ^ ... 125 Elementary Substances ... ., 126 Secondary Products of Electrolysis ... 127 Electro-chemical Equivalents of Compound Substances 127 Table of ditto , 128 CONTENTS. Xiii. SECTION E. (continued). PAGE Consumption of Electric Energy in Electrolysis 129 Minimum Amounts of Electric Energy necessary to Decompose Compounds 131 Table of ditto 131 Energy Expended in Electrolysing Fused Cryolite 133 Total Consumption of Electric Energy in Electrolysis 134 Loss of Energy as Heat of Conduction-resistance 134 Table of ditto , 135 Theories of Electrolysis 134 SECTION F. The Generation of Electric Currents by Dynamo Machines 138 Definition of a Dynamo, and of a Magnetic Field. Lines of Force. 138 Curve of Strength of Magnetisation 139 Electro-magnetic Induction. Oersted's Discovery ... 140 Electromotive Force of Magneto-electric Induction 140 Lines of Magnetic Force ... ... 141 Variation of Magneto-electric Induction ... 142 Conversion of Alternately-opposite into Uniform-direction Currents 144 Pacinotti's Magneto-electric Machine 145 Efficiency of Dynamos 148 Heating 148 2. PRACTICAL DIVISION. SECTION G. Establishing and Working an Electrolytic Copper Refinery ... 149 Advantages and Disadvantages of the Process 149 Magnitude of the Establishment 149 Daily Output of Refined Copper 149 Amount of Space Required 149 Total Amount of Depositing Surface Necessary 150 Gramme's Experiments 151 Number and General Magnitude of the Vats 152 Electromotive Force and Strength of Current Required 153 Kinds of Dynamo Employed at Different Electrolytic Refineries 153 Electrolytic Dynamos of Different Makers 155 Wilde's 155 Siemens and Halske's ... 156 Gramme's .. ... 159 iv. CONTENTS. SECTION G. (continued). Electrolytic Dynamos of Different Makers PAGE Brush's 162 Edison-Hopkinson's ... 164 Hookham and Chamberlain's ... ... 167 Elwell-rarker's 169 Giilcher's 371 Oerlikon ... ... 173 Hochhausen's 174 Mather's 175 Crompton's ... 176 Elmore's -> 176 Source and Amount of Motive-Power Necessary... ... ... 177 Choice of Dynamo ... ... ... ... ... ... ... 177 Care and Management of Dynamo... ... ... 179 The Depositing Room 180 Construction of the Vats 180 Insulation ... ... ... ... 181 Arrangement ... ... ... ... ... ... 182 General Arrangement of the Electrodes ... ... ... ... 184 The Anodes 186 Composition of Crude Copper, "Black," "Pimple," "Blister" Copper 188 The Cathodes . 189 Amount of Cathode Surface in each Vat ... 191 The Main Conductors 192 Preparation of Depositing Solution ... ... ... ... 194 Circulating the Solution in the Vats 194 Inspection of the Vats, Electrodes, etc 196 Expenditure of Mechanical- Power ... ... ... ... ... 198 Electric Energy ... ... ... ... ... 200 Sources of Loss of Energy ... ... ... ... 201 Resistance of the Solution ... ... ... 203 . Examination of the Current ... ... ... ... ... 204 Detection of Resistances and Leakages... ... ... ... 204 Limit of Rate of Deposition ... ... ... 207 Density of Current and Rate, of Deposition ... ... ... 208 Thickness of Deposit 209 Economy of Working ... ... 209 Influence of Impure Anodes upon the Liquid ... ... ... 210 Influence of Arsenic 211 Antimony, Bismuth, Tin, and Lead 212 Iron, Manganese, Suboxide of Copper ... ... 212 Influence of the Impurities of the Anode upon the Current ... 213 Effect of Impurities of the Liquid upon Purity of the Deposit... 214 the Current 215 Chemical Examination of the Solution 216 Purity of the Deposited Copper ... 217 CONTENTS. XV. SECTION G. (continued). Expenditure of Mechanical- Power PAGB Composition of the Mud ... ... 219 Chemical Analysis of the Mud ... . 220 Effects of the Mud upon the Solution 220 Treatment of the Mud 221 Cost of Electrolytic Refining 221 Recapitulation ... * 224 SECTION H. OTHER APPLICATIONS OF ELECTROLYSIS IN SEPARATING AND REFINING METALS. Electrolytic Refining of Copper by other Methods ... ... ... 225 M. Andre's Process for Separating Metals from Coins 225 Keith's Process , 225 Extraction of Copper from Minerals, and Mineral Waters 226 The " Cementation " Process ... 226 Becquerel's Experiments ... 227 Dechaud and Gaultier's Process 227 Deligny's Process 228 Bias and Miest's. Process 229 Marchese's Process at Casarza... ... 229 Stolberg 235 Siemens and Halske's Process .. 237 Electrolytic Refining of Silver Bullion 210 Moebius's Process 240 Cassel's 242 At the North Dutch Refinery 242 Electrolytic Refining of Lead 244 Keith's Process ... 24* Separation of Antimony 247 Borcher's Process 247 Separation of Tin ... "V. 248 Smith's Process 248 Separation of Aluminium ... ... ... 251 Kleiner's Process ... ... ... ... ... ... ... 251 Heroult's ^55 Minet's 259 Hall's 259 Diehl's ... 260 Other Processes... . 260 Separation of Zinc 261 Letrange's Process ,.. 261 Lambotte and Doucet's Process 264 Lalande's Process 264 Burghardt's 265 Watt's 265 Rosing's Process. Refining of Argentiferous Zinc-Lead, "Zinc-scum" 265 XVI. CONTENTS. SECTION H. (continued). PAGE Separation of Magnesium .. ., 266 Gratzel's Process 266 Rogers's 268 Separation of Sodium and Potassium 270 Hopner's Process 270 Jablochoff's 270 Rogers's ... ,.. 271 Beketov's 273 Greenwood's,, 273 Separation of Gold, etc., from Auriferous Earths 273 Werdermann's Process... ... ... ... ... ... ... 273 Barker's 274 Lambert's 275 Molloy's 275 Cassel's 276 Fischer and Weber's Process 279 Other Processes , 280 Electrolytic Refining of Nickel ... 280 Hermite's Process 280 Electric Smelting 281 Cowles's Process 281 Hampe's Experiments 285 APPENDIX. Decimal Equivalents of Inches and Feet .... 286 Areas of Circles ... 286 English Measures of Capacity ... 287 Weights, Avoirdupois, Troy ... ... ... 287 French Measures, Length, Weight, Capacity ... ... 288 Conversion of French and English Measures, Length, Surface, Capacity, Weight 288 Table of Specific Gravities of Liquids 289 Metals 290 Relations of Thermometric Scales 290 Table of Fusibility of Metals ... , ... 290 Centigrade and Fahrenheit Degrees 2S1 Useful Data 291 Mechanical Units ... 291 Electrical Units.: 292 Thermal Units 292 Miscellaneous Data ,293 THE ART OF ELECTROLYTIC SEPARATION AND REFINING OF METALS, HISTORICAL SKETCH. MORE than thirteen hundred years ago Zosimus mentioned the earliest known fact respecting the electrolytic separation of metals, viz., that by immersing a piece of iron in a cupreous solution it acquired a coating of copper. Ever since that time the same fact has been commonly observed by workers in copper mines, that their tools of iron or steel became coated with a film of copper by contact with the water percolating through the mines ; the water holding in solution blue vitriol derived from oxidation of mineral sulphides of copper contained in the rocks. Paracelsus in the years 1493 to 1541, and even Stisser, the professor of chemistry in Helmstadt, as late as 1690, believed that by this process the iron was changed into copper. The discovery of chemical electricity by Volta and the invention of the voltaic battery as an instrument for producing it did not occur until about the year 1799. Wollaston soon afterwards observed that " if a piece of silver in connection with a more positive metal be put into a solution of copper, the silver is coated over with copper, which coating will stand the operation of burnishing " (Philosophical Transactions of the Royal Society, 1801). About the same time Mr. Cruickshank 2 HISTORICAL SKETCH. passed an electric current from his voltaic battery through a solution of sulphate of copper, and found that the copper attached itself to the wire connected with the zinc end of the battery, and stated that the metal was " revived completely " {Wilkinson's "Elements of Galvanism," Vol. II., 1804, p. 54). In 1805 Bruguatelli also observed that when the current entered the liquid by means of a piece of copper, the copper was dissolved and then deposited upon the negative pole (" Annals of Chemistry "). In 1831 Faraday discovered magneto-electricity, or the pro- duction of electric currents by means of mechanical power act- ing through the medium of magnets, a discovery which enabled all the subsequent inventions and improvements in dynamo- electric machines to be made, and the refining of metals by electrolysis to become commercially possible on a large scale. When he made this discovery the electric current he obtained was so very feeble that he was barely able to detect it, and he remarked : "I have rather, however, been desirous of discover- ing new facts and new relations dependent on magneto-electric induction than of exalting the force of those already obtained, being assured that the latter would find their full development hereafter" ("Experimental Researches," para. 158). This prediction has since been abundantly verified. . In 1836 De la Rue observed that the copper deposited by the voltaic current in a Daniell's battery cell gradually became thicker, and might be stripped off in the form of a separate sheet of metal from the surface upon which it had been depo- sited. About the year 1839 Jacobi, of St. Petersburg, and soon afterwards Jordan, Sp ;ncer, and others, made and published their experiments on electrotyping in copper, and thus made the process of depositing that metal familiar to the public. From that time until the present, copper has been constantly deposited on a commercial scale as a coating upon various articles of iron, &c., in order to protect them ; the electrolytic process has also gradually extended and been employed to form orna- ments and othe- articles, until at length copper of more than one inch in thickness has been deposited, and copper statues weighing several tons have been formed by the process. Electro- HISTORICAL SKETCH. 3 deposited copper has also been frequently analysed and found to be extremely pure so much so, that it has been employed in the Royal Mint to alloy with gold in making the standard coins of this realm. Its deposition on a large scale and great degree of purity, thus foreshadowed the electrolytic refining process. The first actual commercial application of electrolysis to the refining of copper is to be found in a patent (No. 2,838) granted to James B. Elkington (son of the late G. R. Elkington, the original patentee of commercial electro-silvering and gilding), Nov. 3rd, 1865, entitled "Manufacture of Copper from Copper Ore." In this process plates of crude copper are used as anodes, suspended in " troughs charged with a nearly saturated solu- tion of sulphate of copper," the cathodes or negative plates being formed "of pure copper, rolled very thin." As the crude copper dissolves, pure copper is deposited upon the nega- tive sheets. The patentee proposed to use a series of depositing troughs, each containing a set of properly connected anodes and cathodes, the electrolysis being effected by a current obtained from a magneto-electric machine. The insoluble residue which falls from the anodes to the bottom of the liquid frequently contains " silver, some gold, and also tin and antimony." In a second patent (No. 3,120), taken out by the same patentee, Oct. 27th, 1869, for the "manufacture of copper, and separating other metals therefrom," impure copper, and espe- cially that which contains much silver, is cast with a " T-shaped head of wrought copper," to enable it to be conveniently sus- pended as a dissolving plate in the depositing vessel. " These plates are placed in fireclay jars, ranged longitudinally in troughs on a slightly-inclined, pitched, and otherwise prepared wooden floor, in the dissolving-house. Each jar has a hole in the bottom, closed by a wooden plug, and two holes in the sides, one low down and the other on the opposite side near the top, each jar being connected with the next lower one by a pipe or tube passing from the higher hole of the one to the lower hole of the other jar. The liquid current thus established between the solutions effects mixture of the layers of different density, maintaining all the liquids in the series of jars practically alike 4 HISTORICAL SKETCH. at top and bottom, notwithstanding the disturbing influence- of the electro-deposition, which constantly tends to produce- inequalities of density. " The solution made use of is water saturated with sulphate- of copper, a store of which is kept in a tank at the upper part of the depositing-room, whence it is admitted into the upper- most jars, and runs from jar to jar till all are filled. A solution may also be used obtained by boiling the deposit formed in the culvert or long flue by which the smoke from the copper furnaces- is led to the high chimney. " The tubes connecting the jars have clips attached to their india-rubber portions, acting as stop-cocks. When needful the clips are removed, so as to cause the solutions to mix, the dense- layer from the bottom of one jar displacing the lighter portion from the top of another, until the density throughout becomes equalised. The outflow is received in a tank at the lower end' of the room, from which it is pumped back to the upper reser- voir. The plugged holes at the bottom of the jars enable the- latter to be emptied on to the inclined floor, the liquid then- flowing into the lower tank. The T-shaped heads attached to the plates enable them to be suspended in the jar, from hori- zontal copper bars having forks upon them. Interposed between- the copper plates to be dissolved are suitably-suspended receiving plates for the deposit of the electrolytic copper. The receiving plates of one jar are connected by a conducting strip of copper with the cast plates of the next jar, and so on throughout. The series being coupled up into a circuit, the terminals are con- nected with one or more magneto-electric machines. The silver originally contained in the copper of the plates set for solution separates as a sediment, and ultimately accumulates as a deposit in the tank below, after the repeated workings and emptyings- of the jars. " Ores rich in silver are preferred as the source of cast copper for this treatment, since the silver is obtained as a bye product, without increasing the cost of obtaining pure copper from the impure metal." These two patents of Mr. James Elkington contain the essential parts of the process of purifying copper by means of HISTORICAL SKETCH. 5 electrolysis, viz., employing slabs or thick plates of the crude metal as anodes ; a series of depositing vessels with the solution flowing slowly through the whole of them, in order to keep it uniform in composition ; the use of electric currents generated by means of mechanical energy, and the collection of the valuable impurities in the form of a sediment at the bottom of the vessels. The only other essential circumstance remaining is that of the occasional purification of the electrolyte by evapo- rating it, and crystallising out of it the sulphate of iron and other soluble salts which gradually accumulate. This process was developed and carried out on a large scale at Pembrey, near Swansea. The works at Pembrey formerly belonged to Messrs. Elkington, Mason and Co., but have since passed into the possession of the Elliott Metal Company (Limited), Selly Oak, near Birmingham, and at the present time this refinery is one of the largest and most perfect existing. Meanwhile, i.e., during the gradual extension of electro- deposition of copper, the originally minute, but, nevertheless, extremely important fact and phenomenon, of the production of an electric current by mechanical energy acting through the medium of magnetism, was developing slowly. This phenomenon when first discovered by Faraday in 1831 was so small as scarcely to be perceptible, and was first observed by him as " a sudden and very slight effect at the galvanometer " (Faraday's "Experimental Researches," Vol. I., p. 3). No sooner had Faraday published this seemingly unimportant effect than various experimentalists endeavoured to obtain it upon a larger scale. Prof. Forbes, of Edinburgh, Nobili, Ritchie, and others, as well as Faraday himself, quickly succeeded in obtaining electric sparks by means of the magneto-electric current. In 1832 H. Pixii invented and exhibited at Paris the first magneto-electric machine, and decomposed water by means of the current from it; this was followed in 1833 by Saxton's improved machine, and by that of Clarke in 1836 ; and on August 1st, 1842, was granted to J. S. Woolrich the first patent, No. 9,431, for a magneto-electric machine for commercial pur- poses. Woolrich's machine was for a long time used by Messrs. Prime, of Birmingham, for electro-silverplating. 6 HISTORICAL SKETCH. Since that time the improvements in producing magneto- electricity have been numerous. In 1857 Werner Siemens in- vented his shuttle- wound armature; in 1860 Pacinotti developed his ring armature machine for yielding a continuous current, which formed the basis of Gramme's and other direct-current machines. In 1866 H. Wilde further increased the power of the apparatus by using a soft iron electro-magnet instead of an ordinary steel one to produce the currents; in 1867 Siemens,. Wheatstone and Ladd each separately observed the fact of self- excitation by mechanical power, and developed the self-exciting machine; and in 1871 M. Gramme produced the first prac- tical continuous-current machine for commercial purposes. Alterations and improvements have since that time succeeded each other so rapidly that there exists now quite a large variety of machines for converting mechanical energy into electric current. The magnitude, weight, and speed of the machines have also increased, until there are some which require several hundred horse-power to drive them ; others which weigh as much as forty-five tons each, and some with armatures revolv- ing at a speed of nine thousand revolutions a minute. The efficiency of the machine has also been increased until as much as 96 per cent, of mechanical energy imparted to the armature is converted into electric power. With a single dynamo as much as thirty tons of copper are now deposited per week. Even now the limit has not been attained, or even conceived, to the magnitude and uses of the machine, and dynamos will probably yet be constructed equal in amount of energy to the largest steam engines, and their power be applied to a great variety of purposes, mechanical, thermal, and chemical.* At the present time the process of electrolytic separation and refining of metals is extending rapidly ; it is carried on at Pembrey, Widnes, Swansea, Tyldesley (Lancashire), St. Helens (Lancashire), Milton (near Stoke-upon-Trent), Paris, Marseilles, St. Denis, Angouleme, Biache (Pas de Calais), Froges (near Grenoble), Hamburg, Stolberg, Berlin, Moabit (near * Dynamos of "10,000 electric horse-power each," weighing "500 tons,''" and having armatures "45 feet over all, "are being constructed (see The Electrician, Vol. XXI., p. 737). HISTORICAL SKETCH. 7 Berlin), Oker (in the Hartz), Eisleben, Burbach (near Siegen), Frankfort-on-the-Maine, Schaffhausen, Stattbergerhutte (near Cologne), the Koenigshiitte (in Silesia), Witkowitz (in Moravia), Stephanshiitte (in Upper Hungary), Brixlegg (in the Tyrol), Ponte St. Martino (in Piedmont), Casarza (near Genoa), Pitts- burg (Pennsylvania), Milwaukee (Wisconsin), Bridgeport (Con- necticut), Omaha (Nebraska), Ansonia (Connecticut), St. Louis (Missouri), Newark (New Jersey), Cleveland (Ohio), Longport (near New York), Santiago (Chili), Chihuahua (Mexico), &c. At Messrs. Balbach's Works, Newark (New Jersey), sixty tons of copper are deposited and refined per week. "Messrs. Bolton, at Widnes, and Messrs. Vivian, as well as Messrs. Lambert, at Swansea, are each depositing from forty to fifty tons per week, by currents from 5,000 to 10,000 amperes" (Nature, January 26th, 1888, p. 303). The "daily quantity refined at Oker is two and a-half tons ; and the total amount in Germany and Austria is about six tons daily." Messrs. Elliott and Co., of Pembrey (near Swansea), deposit nearly the largest amount, forty-five to sixty tons per week, in this country. I am informed from a direct source that the Bridgeport Copper Company, of Bridgeport (Connecticut), electrolytically refine " one million pounds of copper per month," or about 108 tons per week, u by means of three dynamos." THEORETICAL DIVISION. CHIEF FACTS AND PRINCIPLES UPON WHICH THE PROCESS IS BASED. THE very foundation of electrolysis and dynamo-electric action consists of the principles of energy, conservation of energy, transmutation, correlation and equivalency of different forms of energy, and indestructibility of matter and motion. Energy may be denned as motion, and that of any given substance or system of bodies is the total amount of motive power which it possesses or can impart. It is either potential or active; potential when stored up in an unchanging con- dition, ready to produce, but not producing, any dynamic effect, and active when producing some change. Energy may be changed in form, but not altered in total amount, i.e., not created, nor destroyed ; mechanical energy may be transformed into heat, electric current, &c., equivalent in amount to that which disappears ; heat may be converted into electric current, chemical action, and so on. Work done is resistance overcome, and is often attended by transformation of energy. Every act and change which occurs in the dynamo-electric machine and in the electrolysis vat involves energy and change of form of energy. The mechanical power of the motor driving the machine disappears, whilst electric current appears in the conducting circuit ; and the amount of the former ex- pended is proportionate to that of the latter which is produced, the one being in a large degree equivalent to the other. If the conducting circuit is broken, so that no current passes, the amount of mechanical power consumed to drive the dynamo is small, and is only about equal to that required to overcome the friction of the moving parts, but directly the circuit is com- pleted, and a copious current is generated, the mechanical energy consumed is very great. The total effect produced is . in all cases equivalent to the amount of energy expended. In THEORETICAL DIVISION. 9 the electrolysis vessel the electric current produces chemical action, and the amount of potential chemical energy of the substances separated in that vessel is equivalent to that of electrical energy required to separate them. The following are the fundamental units upon which all calculations of energy expended and effects produced (or work performed) in all dynamo-electric and electrolytic actions are based : FUNDAMENTAL UNITS OP QUANTITY. Length = 1-0 centimetre ( = -3937 inch). Mass =1'0 gramme ( = 15'43 2 grains). Time = 1'0 second. The centimetre-gramme-second (or C.-G.-S.) unit of force is called a DYNE, and is the force which, acting on a muss weighing one gramme during one second, produces in it a velocity of one centimetre per second. The force of one dyne is nearly equal to a weight of 1-02 milligramme on the earth's surface. The C.-G.-S. unit of work is called an ERG, and is the amount of work done by one dyne acting through a distance of one centimetre, i.e., it is the product of the unit of force by the unit of length. The C.-G.-S. unit rate of working, or unit of power, is one erg per second; power is the rate of working, and not the amount of work done. Both the dyne and the erg are quantities much too small for ordinary use in technical calculations. For the sake of greater convenience, therefore, what are called "practical units," derived from and quanti- tatively related to the C.-G.-S. or absolute ones, are usually employed. The practical units are given in the Appendix, for greater convenience of reference. HIEF PHENOMENA IN THE ELECTROLYTIC SEPARATION AND REFINING OF METALS. Some of the chief subjects involved in the electrolytic separation and purification of metals by means of dynamo- electric currents are, electric conduction and insulation; electric- conduction resistance ; decomposability of electrolytes, polarisa- tion of electrodes; resistance at electrodes; chemical action; thermo-chemical action; atomic and molecular weights, valency; 10 THEORETICAL DIVISION. chemico-electric or voltaic action; definite electro-chemical change ; magnetic induction ; magneto-electric action ; electro- magnetic action ; electro-dynamic induction, &c. Conduction and insulation are involved, because the current has to pass through the electric generator, the conductors, the plates, and solutions in the vats, and must be prevented leak- ing or passing in wrong directions. Conduction resistance, and the heat due to it, have to be considered, because of the attendant waste of mechanical and electric energy. The fact that the same amount of current is able to separate and purify the metal in the solutions of either a few or a large number of vats at the same time, without the expenditure of an increased amount of energy, depends upon the laws of conduction resist- ance. The decomposability of electrolytes is also a matter of importance, because a difference in its degree involves a change- in the amount of power required to be expended. Thermo- chemical action and thermo-chemical equivalents also throw great light upon the amounts of energy necessary to decom- pose different substances. Upon the atomic weights and chemical valencies of the elements depend the quantities of different metals which a given amount of current will separate and purify. The molecular weights of the acids in the solu- tions affect the quantity of metal with which they will combine. Upon the law of definite electro-chemical action depends the circumstance that the amount of metal deposited by the same electric current is the same in each of any number of vessels placed in successive connection. Chemico-electric action affects the process, by generating voltaic currents, which may assist or oppose the working current. And magnetic and magneto- electric, electro-magnetic and electro-dynamic action take place in all the different kinds of dynamo-electric machines now em- ployed for the electrolytic separation of metals. All these chief facts and principles, therefore, require to be sufficiently known and understood by every person engaged in superintending; such processes. SECTION A. CHIEF ELECTRICAL FACTS AND PRINCIPLES OF THE SUBJECT. Electric Polarity and Induction. Electric polarity is an electro-static condition of a body which is electrified, and upon FIG. 1. Polarity and Induction. the surface of which a charge of electricity exists; the kind of charge and of polarity being either positive or negative, plus or minus. In consequence of the self-repellent power of electricity, a charged body is in a state of electric tension or potential tending to discharge and assume the electric state of the earth; the latter is assumed to be at zero. Electric- induction is an action of an electrified body upon neighbouring ones through a non-conducting or dielectric medium. Electric- polarity tends to produce by induction an opposite state of charge and polarity upon the surfaces of all neighbouring bodies. Thus the insulated charged metallic ball, A (Fig. 1), induces a negatively charged state upon the nearest end of the insulated metallic cylinder B. Polarity and induction 12 ELECTRICAL PRINCIPLES. precede conduction at the first moment of flow or passage of a current. Electric Quantity. Electric quantity is either static or dynamic, i.e., quantity of electricity in a state of rest or of motion. The C.-G.-S. (or centigrade-gramme-second) electro- static unit of quantity is that amount of accumulated elec- tricity which at a distance of one centimetre repels an equal quantity of similar electricity with a force of one dyne. The C.-G.-S. unit of quantity is the amount of electricity which is conveyed by unit current in unit time i.e., in one second ; it is about 3 x 10 10 times the electro-static unit. The practical unit of quantity of electricity is termed a COULOMB (formerly a weber), and is equal to one-tenth of the C.-G.-S. electro-magnetic unit of quantity. FIG. 2. Condenser. Electric Capacity. The electric capacity of a body is the quantity of electricity it can hold when charged to one unit of potential. This amount varies with the magnitude of the body and with its shape. The best form to retain a charge is that of a smooth sphere, and the worst is that of an elongated body terminated by points. The C.-G.-S. unit of capacity of a conducting body is that which requires a charge of one unit of static electricity to raise it from an uncharged state to one unit of potential, and is equal to that of a smooth metal sphere of one centimetre radius. The capacity of a condenser which holds one coulomb when charged to unit potential of one volt is called a FARAD ; but the practical unit of capacity employed is one-millionth part of this, and is termed a MICROFARAD. Commonly a third of a microfarad is used as the most con- venient. A condenser has a capacity of one farad when a ELECTRICAL PRINCIPLES. 13- difference of potential of one volt between its two sets of platen charges each set with one coulomb. According to the single fluid theory of electricity, a condenser is not a store of electric energy, because in the act of charging as much electricity is taken out of one set of its plates as is put into the other. A condenser (see Fig. 2) is usually formed of a pile of alter- nate circular sheets of tinfoil and of mica or paraffined tissue paper very carefully insulated, every alternate sheet of foil being connected with one terminal of the instrument, and every other alternate sheet with the other, and is provided with a brass plug for connecting the two sets together when required to discharge the instrument by enabling its two electricities to- unite. Electric Potential is electric capability of doing work. We call that condition electric potential which isolated bodies are in when electrically charged, and which in some sense may be likened to the expansive tendency of gases, the hydrostatic pressure of liquids, or the temperature of substances. It is in consequence of its potential that free accumulated electricity tends to discharge and diffuse into electrically neutral bodies and into those of lower potential. As electricity is not known separate from matter, it is more correct to speak of degree of electrification than of amount of electric charge. Electrostatic potential at any point is defined to be " the work that must be expended upon a unit of positive electricity in bringing it up to that point from an infinite distance." Potential (or difference of potential) has also been defined as " the quotient of quantity of electricity by distance." Two bodies having the same posi- tive or the same negative potential produce no current when connected together by a wire. The potential of a conductor depends partly upon the quantity of its electric charge and partly upon the size and shape of the body ; the potential at all parts of a charged isolated conducting sphere on which elec- tricity is at rest is equal. With a non-spherical charged con- ductor the density of the charge and the tendency to discharge are greatest at the parts of greatest diameter and at the most sharp-pointed projections. Potential differences may be measured by weighing. The practical unit of difference of potential and of electromotive 14 ELECTRICAL PRINCIPLES. force is termed a VOLT. According to Exner, the earth is at a negative potential of 4-1 volts, ready to discharge its electricity with that degree of pressure into an electrically neutral body ; it is, however, usually treated as if it was at zero. The potential of an isolated electrified body, but not the amount of charge, varies on the approach of another body. Electromotive Force is that power which produces current or which moves, or tends to move, electricity from one place to another, and is, in some sense, analogous to pressure. Dif- ference of electromotive force is considered to be due to difference of potential, and varies with it. That of a current FIG. 3. Tripod Galvanometer. generator is equal to the degree of inequality of potentials at its poles when the latter are disconnected and no current is circulating. A unit of electromotive force (or of potential) exists between two points when one erg of work has to be done in order to urge one unit of positive electricity from the point which is at the lower to that which is at the higher potential. The practical unit of electromotive force, termed a volt, is equal to '9268 of that of a Daniell cell, and is the differ- ence of potential which must be maintained at the ends of a conductor having a resistance of one ohm in order that a current of one ampere may flow through it. ELECTRICAL PRINCIPLES. 15 Measurement of Electromotive Force. There are various ways of effecting this object. It may be done with the aid of an electric condenser, with a suitable galvanometer, a quadrant electrometer, a standard voltaic cell, a thermo-electric pile, a voltmeter, tire. By successively and separately charging a condenser (see p. 12) from two generators of current, and separately discharg- ing it successively through a suitable galvanometer and ob- serving the amounts of swing of the needle, the relative elec- tromotive forces of the two generators may be easily and quickly FIG. 4. Quadrant Electrometer. determined; a Thomson's reflecting galvanometer (Fig. 3) of high resistance may be employed for the purpose. By connecting the terminals of two generators in succession with the poles of a quadrant electrometer (Fig. 4) and observ- ing the amounts of steady deflection of the needle. When the electromotive force is thus measured directly as a difference of potential the circuit is never closed, and no current passes. The difference of potential at the ends of a current-producer of constant electromotive force, when no current is circulating, is 16 ELECTRICAL PRINCIPLES. equal to the electromotive force, and is very nearly so when a very small current is passing The relative electromotive forces of the currents from genera- tors of unchanging electromotive force may be measured by ascertaining the amounts of resistance through which they ELECTRICAL PRINCIPLES. 17 respectively force equal strengths of current. In using this method the law of the galvanometer employed need not be known. The relative electromotive forces of currents from two such sources may also be found, either (1) by connecting them together in series, with a suitable galvanometer in the circuit, so that their currents are in the same direction and assist each other ; or (2) so that they oppose each other. We may oppose the current from a generator to that of such a number of standard voltaic cells in single series that no current passes, as shown by a galvanometer in the circuit ; the electromotive forces of the two sources are then equal. In using this method neither the resistances of the generators nor that of the galvano- meter need be known. As standard cells we may employ either Clark's, the electromotive force of which is equal to 1 -438 legal volts, or Daniell's constant battery, a single cell of which has an electromotive force of 1-074 volt (see pp. 59 61). If the electromotive force of the current to be measured is constant, and does not much exceed one volt, we may oppose to it that of a current from a thermo-electric pile of many pairs of iron and German silver wires (Figs. 5 and 6) (see Proceedings of the Birmingham Philosophical Society, Vol. IV., Part I., p. 130; The Electrician, March 15, 1884, Vol. XII., p. 414).* By this method, using a small magnesium-platinum couple in distilled water, I have detected the change of electromotive force caused by add- ing one part of chlorine to 500,000 million parts of water (Pro- ceedings of the Royal Society, Vol. XLIV., 1888, p. 151). One advantage of the method of opposition is that it is a null one, being made when no current is passing in either generator, and therefore no polarisation is produced ; it is also a delicate method if the galvanometer employed is a sensitive one. For details of the methods of measurement the reader is referred to special works on the subject. t * The Electrician is a weekly illustrated journal devoted to the Practical and Theoretical Applications of Electricity, and is published at 1, 2, and 3, Salisbury Court, Fleet Street, London. The pile referred to is manufac- tured by Messrs. Nalder Bros, and Co fKempe's "Handbook of Electric Testing," Ayrton's "Practical Elec- tricity," Latimer Clark's " Electric Measurement." All books on Electrical and allied subjects can be obtained at The Electrician Office. 18 ELECTRICAL PRINCIPLES. Electric Current. An electric current is said to be a flow of electricity from one point to another, but we do not actually know whether it is a flow or not, nor what its real direction is ; it has, however, no existence in the absence of a conductor. Its direction in a voltaic cell is said to be from the zinc through the liquid to the copper, and in an electrolytic one, from the metal which dissolves or evolves oxygen to that which receives a deposit or evolves hydrogen. According to modern theory, the transfer of electric energy is not along the conductor at all, but in the surrounding dielectric, the presence of the con- ductor, however, being a necessary condition of the transfer- ence. An electric current differs in several fundamental respects from .accumulated electricity or an electric charge. Whilst a charge resides chiefly on the surface, a steady current permeates the mass of a substance. A current possesses direction and exhibits magnetism, but electricity at rest does neither ; a charged body, however, when rapidly rotated in a circle is magnetic, like a circular electric current. An electric current, however small, heats a conductor, and decomposes an electrolyte, but a static charge of electricity does not. The practical unit of quantity of current is called a COULOMB, .and is the amount of electricity which passes through a con- ductor in one second when the strength of current is one ampere, or that which electrolytically deposits '01725 grain of silver, Strength of Current. This is the quantity of electricity which flows through any cross-section of a circuit in one second of time. It has been frequently called "intensity" of current; it depends upon the electromotive force and the total resistance. By 'using a sufficient electromotive force, and an adequate quantity of electricity, any strength of current may be sent through a conductor until the latter melts or volatilises. No difference has hitherto been proved to exist between any two currents of ^qual strength. The practical unit of strength of current is called an AMPERE (formerly "weber per second"), and is produced when an electromotive force of one volt acts through a resistance of one ohm, and conveys one coulomb in one second. It is equal to one-tenth of the C.-G.-S., or absolute unit of quantity. A ELECTRICAL PRINCIPLES. 19 milliampere is one-thousandth of an ampere. According to Ohm's law, the strength of a current is equal to the electro- motive force divided by the resistance E.M.F. If a current is passing through a wire, and the resistance remains the same but the electromotive force varies, the strength of current or number of amperes varies directly with that of volts ; a galvanometer, therefore, which measures strength of current may be used to measure electromotive force. A current can only be constant in strength whilst the proportion of electro- motive force (or difference of potential) to resistance remains unchanged. Generally if V be the potential difference in volts at the ends of a conductor whose resistance is R ohms, and if A y be the current in amperes passing through it, then A = - . Ohm's R law shows that the strength of current passing through any circuit is inversely proportional to the resistance if a constant potential difference is maintained at the ends of that circuit. A unit current in amperes is that strength of current which -deposits -001118 gramme or -01725 grain of silver per second from an aqueous solution containing fifteen to thirty per cent. of argentic nitrate, or '0003296 gramme or -00508 grain of copper from a solution of blue vitriol per second. Measurement of Strength of Current. Strength of current is usually ascertained, cither (1) by means of its chemical effect, -as in a voltameter (Fig. 7), by finding how much hydrogen, silver, or copper is set free by electrolysis in a given time (see p. 105) ; (2) by its magnetic influence, as in a galvano- meter (Figs. 8 and 9), by observing the amount of deflection of a magnetised needle or to what extent a coil conveying the current is deflected by a permanent magnet; or, as in an electro-dynamometer (Fig. 10), by noting through what angle of deflection a coil of wire conveying one portion of the current is moved by the influence of a second coil conveying another portion ; or (3) by the rate of production of its heat of conduc- tion resistance. This latter method, as well as that in which c2 20 ELECTRICAL PRINCIPLES. an electro-dynamometer is employed, is used in measuring the- strength of alternating currents. It is only when the current is sufficiently strong to quickly raise the temperature of the liquid of a calorimeter several degrees that method "3" can be- employed. For particulars respecting the methods of measure- ment consult the works already referred to on p. 17. FIG 7. Hofmann's Voltameter. FIG. 8. Torsion Galvanometer. Density of Current. By this is meant the strength of current passing at a given moment through a given cross- sectional area of a conductor, or into or out of a given sized, surface of an electrode in an electrolyte. Circuit. The entire path of the current is termed tW circuit. The amounts of steady current passing at the same- moment through all cross-sections of a circuit are equal, and. ELECTRICAL PRINCIPLES. 21 arc independent of the composition, shape, size, or number of pieces of the conductor. In many cases it is only after the first instant of flow that the current is of the same strength throughout the circuit; this is due to self-inductive action, which precedes conduction. A SHUNT is a divided circuit, one portion of the current being shunted or turned aside from the main circuit into a side one (Fig. 11). When a portion of a main current is shunted, the FIG. 9. D'Arsonval's Galvanometer. strength of the main current parallel with the shunt is decreased, whilst that before and behind the shunt is increased, because the total resistance in the circuit is diminished by adding the shunt conductor, this addition being equivalent to increasing the thickness of that portion of the main conductor. The sum of the strengths of current in the divided part of the circuit equals the strength of the main current ; and the 22 ELECTRICAL PRINCIPLES. relative strengths in the divided part are inversely as the relative resistances of the two parallel conductors. The conductors in a circuit may be arranged either in single series, i.e, one after another, thus ; in parallel, i.e., side by side = ; or in combined series and parallel, thus == = == or = ==. Practically in all cases where a current from a generator of very small internal resistance is employed, the currents in parallel circuits supplied by it are largely independent of each FIG. 10. Siemens's Electro-Dynamometer. other. The strength of current in any one of the circuits depends upon the resistance of the particular circuit and the potential difference at the poles of the generator. By " short-circuiting" is meant the cutting-out of a portion or the whole of the external resistance by means of a conductor of less or very small resistance, so that the circuit is greatly diminished in resistance and usually shortened. A SWITCH is a contrivance, either worked by hand or automatically, for diverting the current into a separate course,, generally when the current in the usual circuit is from some* cause altered or interrupted. An automatic one is generally operated by the magnetic influence of the current itself, which, ELECTRICAL PRINCIPLES. 23 when the latter becomes too strong or too weak, liberates a mechanism and makes a fresh contact. A CUT-OUT is a similar contrivance for breaking the circuit, either when the current becomes too weak, too strong, or is reversed in direction; it is either automatic or not. In an auto- matic one, an electro-magnet breaks the circuit. An automatic cut-out is sometimes formed of a fusible wire or wires, usually of lead about two or three inches long, inserted in the main circuit on either side of the generator, so that when from any cause the current becomes too strong the wire melts and breaks the circuit. S html- . FIG. 11. Shunt Conductor. Electrical Energy. This includes electromotive force and strength of current. The practical unit of electric energy is termed a WATT, and is the work done per second by one ampere passing between two points, between which the difference of electric potential is one volt. It is = 10 7 ergs ; also *7375 foot- pound, or -r^th of a hone-power (or ^^ French horse- power), one horse-power being = 550 foot-pounds per second.. To find the amount of electric energy of a current in watts r multiply the number of its amperes by that of its volts. The- number of watts or volt-amperes being expended in any circuit may be measured directly by means of a wattmeter. N Conduction and Insulation. The conducting and insulating powers, or the capacities of substances to permit and to hinder electric flow, differ in degree in every different substance ; all substances permit and all hinder in different degrees, and the difference of degree of these properties in extreme cases is enormous. The best insulators (called also dielectrics) are ebonite, shellac, india-rubber, gutta-percha, resins, wax, asphalte, gases, glass, f a centimetre cube at 0C. Resistance in epalohmsof a wire 1 metre ong, weighing 1 gramme. Silver annealed 1-000 1 504 1527 1-063 1 598 1424 Silver hard drawn 1-086 1-634 1662 1-086 1-634 1453 Gold annealed 1 369 2 -058 4035 1-393 2-094 4104 1-935 2 912 0749 Zinc, pressed 3*741 5 626 4023 Platinum, annealed 6-022 9057 1-938 Iron ,, 6-460 9716 757 Alloy, gold 2 pts., silver 11 pt., hard or annealed / 7 228 8 '285 10-87 12-47 1-650 Tin, pressed 8784 13-21 9632 Lead 13-05 19-63 2-232 German silver, hard or an- \ riealed j" 13-92 2093 1-830 Alloy, silver 2 pts., platinum 1 1 pt., hard or annealed ... J Antimony, pressed . . . 16-21 23-60 24-39 35 50 2924 2-384 6273 94-32 12-91 Bismuth . . 87-23 131-20 12-88 ELECTRICAL PRINCIPLES. 27 Relative Conductivity of Alloys. The following is from a table given by L. Weiller : Pure silver 100' Silicon bronze telegraph wire.... 98' Copper and silver alloy of 50 per cent 86*65 Silicon copper with 4 per cent, of silicon 75* 12 , 547 Tin containing 12 per cent, of sodium 46 '9 Silicon bronze telephone wire 35'0 Plumbic copper, with 10 per cent, lend 30* Phosphor bronze telephone wire 29* Silicon brass, with 25 per cent, of zinc 26 49 Brass, with 25 per cent, of zinc 21'15 Phosphide of tin 177 Gold and silver alloy 50 per cent 16'12 Antimonic copper 127 Aluminium bronze 10 per cent 12'6 Siemens's steel 12*0 Cadmium amalgam, with 15 per cent, of cadmium. 10'2 Mercurial bronze 10'14 Arsenical copper, with 10 per cent, of arsenic. ... X>'1 Bronze, with 20 per cent, of tin 8'4 Phosphor bronze, with 10 per cent, of tin 6 '5 Phosphide of copper, with 9 percent, of phosphorus 4'9 Antimony 3'88 An alloy called "platinoid," consisting of nickel silver with about 1 or 2 per cent, of tungsten, has been found by Mr. Bot- tomley to possess a resistance of about 60 per cent, higher than that of German silver. Relative Conductivities of Alloys of Copper (Mattb iessen). Pure Copper = 100. Temperature in Conductivity. Centigrade dt-grees. 5 per cent, of carbon 77*87 at 183 18 sulphur 92 08 19 4 13 phosphorus 70'34 20'0 '95 2416 22-1 25 7-52 17-5 With traces of arsenic 6008 197 28 percent. 13'66 19'3 5-4 6-42 16-8 With traces of zinc 88*41 19'0 1-6 per cent, of zinc 7937 16'8 3-2 59 23 10-3 48 iron 3592 11 "2 1-06 ,, 2801 13-1 1-33 ,, tin 5044 16'8 2-52 3393 17'1 4-90 ,, , 2024 14-4 1-22 silver 90'34 207 23 ELECTRICAL PRINCIPLES. Relative Conductivities of Alloys of Copper (Matthiessen), continued. Pure Copper = 100. Temperature in Conductivity. Centigrade degrees. at 197 2'45 per cent, of silver 82'52 3-5 gold 67-94 10*0 ,, ,, aluminium 12'68 31 antimony 1 64>5 29 lead f 18-1 14-C 12-0 Resistance of Pure Diameter in Metres per millimeters. ohm. 5 12-305 1-0 4887 1-5 10975 2-0 19515 2-5 308-6 3-0 . 439-1 3-5 4-0 4'5 5-0 6-0 7'0 8-0 605- 777- 989- 1231' 1756- 2420- 3008- Copper Wire at 0C. 1 Diameter in Metres per millimetres. ohm. 9-0 3956- 10-0 4878- 11-0 5854- 12-0 7025- 13-0 8293' 14-0 9680- 15-0 10975- 16-0 12032- 17'0 14450- 18-0 15824- 19-0 17561- 20-0 .. . 19515* Electric Resistance of Metals. (Benoit, Comptes Rcndus, Paris, 1873, Vol. LXXVI., p. 342.) (Journal of the Society of Telegraph -Engineers, Vol. I., p. 443.) 1 metre long x 1* sq. mm. section at 0C. Conduc- tivity. Silver, pure, annealed 0154 100- Copper 0171 90- Silver (<&&) 0193 80- Gold, pure ,, 0217 71- Aluminium, pure, annealed 0309 497 Magnesium, hammered 0423 36-4 Zinc, pure, annealed at 350C 0565 27'5 ,, ,, hammered 0594 25-9 Cadmium, pure, hammered 0685 22-5 Brass, annealed 0691 22-3 Steel 1099 14-0 Tin, pure 1161 13-3 Aluminium bronze, annealed 1189 13-0 Iron, annealed . . 1216 127 Palladium, annealed . . 1384 ll'l Platinum ,, 1575 977 Thallium 1831 8-41 Lead, pure 1985 776 Maillechort, annealed 2654 5-80 Mercury, pure 9564 1-61 ELECTRICAL PRINCIPLES. 29 For a given length and weight, aluminium has the least resistance of all metals, but for a given length and diameter annealed silver has the least. The order of conductivity of metals for electricity is nearly the same as that for heat ; but with less conducting substances the conductivity for electricity diminishes very much more rapidly than that for heat; conse- quently the insulation of electricity is vastly less difficult than that of heat. The resistance of atmospheric air and gases is usually much greater than that of liquids. Liquids conduct, according to Ohm's law, the same as solids (Journal of Chemical Society, 2nd Series, Vol. X., p. 208). The resistance of dilute hydro- chloric acid, and of a solution of zinc sulphate, is said to be increased by a pressure of five hundred atmospheres (Nature, Vol. XXXIII., 1886, p. 356). According to Dr. Overbeck, the conduction resistance of ether is 102 times larger than that of water, and that of bisulphide of carbon is still greater. FIG. 12. Wheatstone's Bridge. The amount of resistance of a wire, A, may be conveniently measured by dividing a current from a very small Daniell's cell, so that one portion passes through A and on through one wire B of a differential galvanometer, and the other portion through another wire C of known amount of resistance, such as a British Association standard unit of electrical resistance, and on through the other wire D of the galvanometer in the opposite direction to that through B, and then altering the length of A, until the needles of the instrument stay at zero; the resistance of A and C are then equal, provided the resist- ances and the lengths of the two wire coils of the galvanometer are alike. For more accurate measurements a Wheatstone's bridge should be employed (Fig. 12). Various other methods are described in books devoted to the subject (see foot note, p. 17). 30 ELECTRICAL PRINCIPLES. Resistance of Solutions of Sulphuric Acid (H 2 S0 4 ) (Matthiessen). Specific Gravity of Liquid. Percentage of H-SO* by weight. Resistance. Temperature in Centigrade degrees. 1-003 5 16-01 16-1 1-018 2-2 5-47 15-2 1-053 7-9 1-88 137 1-080 12-0 1-37 12-8 1-147 20-8 96 13-6 1-190 26-4 87 13-0 1-215 29-6 83 12-3 1-225 30-9 86 13-6 1-252 34-3 87 13-5 1-277 37-3 93 1-348 45-4 97 17-9 1-393 50-5 1-09 14-5 1-493 60-6 1-55 13-8 1-638 737 2-79 14-3 1-726 81-2 4-34 16-3 1-827 927 5-32 14-3 Resistance of Solutions of Cupric Sulphate (CuSO 4 + 5 H 2 0) at 14C. (Wiedemami). Grammes per litre of water. Ohms. 124-68 457 15585 39-9 Grammes p*=r litre of water. Ohms. 31-17 1243 62-34 70-2 7792 599 93-51 548 187-02 36-3 The resistance of solutions of sulphate of copper and sulphate of zinc increases regularly by dilution of the liquids from their points of saturation, but that of a solution of chloride of sodium has the least resistance when the liquid contains about 24 per cent of the salt. Specific Resistance of Solutions of Sulphate of Copper at 10C. (Ewing and MacGregor). Specific Gravity. Resistance. 1-0167 164-4 1-0236 134-8 1-0318 98-7 1-0622 59-0 1-0858 . 47-3 1-1174 38-1 Specific Gravity. Resistance. 1-1386 35-0 1-1432 34-1 1-1679 317 1-1823 30-6 1-2051 (saturated) 29 '3 The measurement of resistance of an electrolyte is much less easy than that of a wire, in consequence of the varying degree ELECTRICAL PRINCIPLES. 31 of polarisation and counter electromotive force produced at the electrodes by the passage of the current. It may, however, be approximately effected in a somewhat similar manner (see p. 29) by making two measurements with a very feeble current after the polarisation has become sufficiently steady, one when the electrodes are near together, and the other when they are farther asunder; using in each case a narrow trough filled with the liquid, with two immersed porous cells containing electrodes as large as the transverse section of the electrolyte, and usually of the same metal as that of the salt of the liquid. The difference of resistance in the two measurements is that of the difference in length of the liquid in the two cases. The liquids in the porous cells should be rapidly stirred in order to diminish or prevent polarisation whilst making the measurements. Influence of Temperature on Resistance. Usually, by rise of temperature, the conduction resistance of metals is increased, and that of electrolytes and gases is decreased ; with carbon and mercury it is decreased. That of copper increases about 1 per cent, by a rise of 2 '57 centigrade degrees. According to E. Weston, an. alloy, composed of 65 to 70 parts of copper, 25 to 30 of ferro-mauganese, and 2^ .to. 10 of nickel, has its resistance lowered by rise of temperature (The Electrician, Vol. XXI., 'August 10th, 1888, p. 448). For the resistance of metals at high temperatures, consult Benoit's research in the Comptes JRendus of the Paris Academy of Sciences, January to June, 1873, p. 342. According to Matthiessen and Benoit, the coefficient of electric conduction resistance is about ^i^rd of the absolute resistance for each centigrade degree rise of tempera- ture between 0C. and 100C. According to Clausius, the resistance of copper is proportional to the absolute temperature ; therefore, at the absolute zero of heat, or 273C., the conducting power of that metal would be infinite. Cailletet and Bouty have experimented in this direction down to - 123C. with copper and other metals, and conclude as probable, that with certain ductile metals the resistance below - 200C. would be very small. Wroblewski has also made similar experiments, and found that whilst the resistance of copper at + 100C. was 5*174 Siemens's units, at - 200C. it was only -414. 32 ELECTRICAL PRINCIPLES. Relative Resistances of Pure Copper at Different Temperatures. Temp, in C. Resist. 21 1-0816 22 1-0855 23 1-0895 24 ......... 1-0936 25 1-0976 26 1-1016 27 1-1057 28 1-1197 29 1-1238 30 . . 1-1278 The following table embodies some results obtained by the late Dr. Matthiessen on the influence of temperature on resistance : Percentage Variation per 1C. Degree at about 20C. Alloy, platinum 2 pts., silver 1 pt., hard or annealed, about "037 Temp, in C. o Resist. 1-0000 Temp, in C. 10 Resist. . 1-0382 1 1-0038 11 . 1-0420 2 1 -0076 12 . 1-0460 3 1-0114 13 1-0500 4 1-0152 14 . 1-0541 5 1-0190 15 . 1-0577 6 1-0228 16 . 1-0617 7 1-0266 17 . 1-0656 8 1-0305 18 . 1-0696 9 1-0344 19 . 1-0736 20 . 1-0774 German silver, hard or annealed Alloy, gold 2 pts., silver 1 pt., hard or annealed Mercury Bismuth, pressed Gold, annealed Zinc, pressed Tin ,, Silver, annealed Lead, pressed Copper, annealed Antimony Iron... 044 065 072 354 365 365 365 '377 387 388 389 500 The alloy termed platinoid (see p. 27) has a percentage varia- tion of only about '021 per 1 centigrade degree, or about half that of German silver, and as its conduction resistance is higher by 60 per cent, than that of that alloy, it may prove suitable for resistance coils if it does not change by lapse of time. Resistance in Ohms of a Cubic Centimetre of Various Solutions of Cupric Sulphate at Different Temperatures (Centigrade). (Computed by Fleeming Jenkin.) Percentage of Dis- Specific Gravity at At 14C. 16. 18. 20. 24. 28. 30. solved Salt 18C. 8 1-0516 45-7 43-7 41-9 40-2 37-1 34-2 32-9 12 1-0785 36-3 34-9 33-5 32-2 29-9 27'9 27'0 16 1-1063 31-2 30-0 28-9 27'9 26-1 24-6 24-0 20 1-1354 28-5 27'5 26-5 25-6 24-1 22-7 22-2 24 1-1659 26-9 25-9 24-8 23-9 22-2 20-7 20-0 28 1-1980 24-7 23-4 22-1 21-0 18-8 16-9 16-0 ELECTRICAL PRINCIPLES. 33 Resistance in Ohms of a Cubic Centimetre of Solutions of Sul phuric Acid at Different Temperatures (Centigrade). (Com- puted by Fleeming Jenkin.) Specific Gravity of Containing per cei.t. AtO. 4*. 8*. 12. 16. 20. 24. 28. Liquid at 15* C. of H* SO*. 1-10 15' 1-37 1-17 1-04 925 845 786 737 709 1-20 27' 1-33 111 926 792 666 567 486 411 1-25 33- 1-31 1-09 896 743 624 509 434 358 1-30 40- 1-36 113 94 79 662; -561 472 394 1-40 50- 1-69 1-47 1-30 116 1-05 964 896 839 1-50 60- 2-74 2-41 213 1-89 1-72 1-61 1-52 1-43 1-60 68- 4-82 416 3-62 311 275 2-46 2-21 202 170 77- 9-41 7-67 6-25 512 4-23 3-57 3-07 271 According to the computation of the same writer, the resist- ance of one cubic centimetre of a solution of zinc sulphate, containing 96 grammes of the salt in 100 c.c. of solution, was = 22-7 at 10C., and decreased regularly to 15'6 at 24C. And when the same solution was diluted with an equal bulk of water, the resistance at 14'0C. was 211 ohms, and decreased regularly to 17 '3 ohms at 24C. For further information respecting the conduction resistance of a large variety of electrolytes, see tables compiled from the researches of F. and W. Kohlrausch, Grotian, Long, and others, in Landolt and Bernstein's " Physikalische-Chemische Tabellen," 1886, pp. 100-107. Conduction Resistance of Minerals, &c. In consequence of the great variations of density and of physical structure in different specimens of the same compound, the usual difficulty of obtaining suitable specimens for measurement, and other cir- cumstances, minerals and solid chemical compounds can only at present be crudely classified into inferior conductors and rela- tively non-conductors. To the former group belong magnetic iron ore, tinstone, peroxide of lead, arsenical silver, red silver, galena, arsenical cobalt, copper glance, cubical iron pyrites, arsenical iron pyrites, magnetic pyrites, peroxide of manganese, sulphide of bismuth; the sulphides of mercury, copper, nickel and cobalt; mispickel, tin pyrites, subsulphide of copper, mag- D 34 ELECTRICAL PRINCIPLES. netic iron ore, graphitic tellurium, oxide of zinc, also nltro- cyanide of titanium and titanic iron ore. In the latter group are included zinc blende, sulphide of molybdenum, crystallised stihnite, compact variety of crystallised cinnabar, orpiment, bouranite, manganese blende, proustite, pyrargite, silver-glance, horn-silver, calamine, crystallised chrome ore, crystallised black carbonate of iron, crystallised tungstate of iron, rutile, braunite, crystallised specular iron ore, iserine, crystallised tin ore, sub- oxide and protoxide of copper, sulphide of silver, oxychloride of copper, &c. Whilst cupreous sulphide is a very bad conductor, cupric sulphide is a relatively good one. The latter fact is important in certain practical electrolytic processes (see pp. 228-237). Internal and External Resistance. The total resistance in .an electrolytic circuit is usually classed into internal, or that in the electric generator, and external, or that in the electrolysis -vessel and the remainder of the circuit. " Transfer Resistance." By this term is meant a retardation at the surfaces of electrodes in electrolytes, different from that due to polarisation or other counter electromotive force (see p. 95). Evidence respecting it may be found in the following published researches by the author: "On ' Transfer-resistance' in Electro- lytic and Voltaic Cells" (Abstract, Proc. Roy. Soc., Vol. XXXVIII. March, 1885, p. 209). "On 'Resistance' at the Surfaces of Electrodes in Electrolytic Cells" (Proc. Birm. Phil. Soc., Vol. V., p. 45; Phil. Mag., Vol. XXI., 1886, p. 249). "Relation of ' Transfer-resistance ' to the Molecular Weight and Chemical Composition of Electrolytes" (Abstract, Proc. Roy. Soc., 1886, :p. 380; full paper, Proc. Birm. Phil. Soc., Vol. V., 1887, p. 426). " Evidence respecting the Reality of ' Transfer-resist- ance ' in Electrolytic Cells " (Proc. Birm. Phil. Soc., Vol. V., p. 26; Phil. Mag., 1886, Vol. XXL, p. 130). "Relation of Surface-resistance at Electrodes to Various Electrical Pheno- mena" (Proc. Birm. Phil. Soc., Vol. V., p. 36; Phil. Mag., 1886, Vol. XXI., p. 45). "Influence of External Resistance on Internal Resistance in Voltaic Cells " (Proc. Birm. Phil. So$., Vol. IV., p. 417 ; The Electrician, Vol. XV., p. 279). W. Peddie lias also investigated this phenomenon. He states " conclusively ELECTRICAL PRINCIPLES. 35 that a transition resistance exists," and that with platinum plates in dilute sulphuric acid it " is due to condensed films of gas " upon the surface of the electrode, and is not removed by hard rubbing. He also found that " the resistance is inversely proportional to the area of the plates," and that " the order of the specific resistance is the same as that of ordinary dielectrics " ("On Transition-resistance at the Surface of Platinum Elec- trodes, and the Action of Condensed Gaseous Films," Proc. Roy. Soc. Edinburgh, 1886-1887, No. 124). I have verified the fact that the gas absorbed by a platinum cathode in water is not wholly removed by hard rubbing, but is expelled by heating to redness. It is not improbable that this gas offers resistance to the passage of the current, independently of that due to its well-known counter electromotive force. The physical actions which occur at the surfaces of electrodes in electrolytes are more complex than is sometimes assumed. J. Monckman, Proc. Roy. Soc., May 31st, 1888, pp. 223-226, has shown that pla- tinum and iron, by absorbing hydrogen when employed as cathodes, increase in conduction-resistance. These circum- stances are sufficient to account for the "resistance" I observed. D2 SECTION R CHIEF THERMAL PHENOMENA OF THE SEPARATION OF METALS BY MEANS OF DYNAMO ELECTRIC CURRENTS. The chief thermal phenomena taking place in dynamo-electric machines are : 1. Heat evolved by conduction resistance in the conducting wires surrounding the armature and field-mag- nets. 2. Heat generated by Foucault or eddy induction currents in the metallic portions of the magnet and armature. 3. Heat produced by friction of the axles of the armatures in their bearings. The chief source of thermal changes in the electrolysis vessel appear to be : 1. Heat evolved or absorbed by chemical and electro-chemical changes at each of the electrodes. 2. Heat produced by conduction resistance of the electrolyte. 3. By conduction resistance of gaseous, liquid or solid films, formed upon the anode or cathode. 4. By resistance due to polarisa- tion at each of the electrodes. 5. By " transfer resistance " at those electrodes. 6. By chemical action in any sediment at the bottom of the vessel. Heat of Conduction Resistance. Whenever a current passes through a resistance it evolves heat, and as the best of con- ducting substances offers resistance, the passage of a current is always attended by evolution of heat. The amount of heat thus produced by a current in a conductor in a given time is- directly proportional to the product of the square of the strength of the current into the resistance. This is known as Joule's- law. If the composition and diameter of a wire are unifcirm throughout its length, with the same strength of current passing through its entire length, and uniform cooling influences, the increase of temperature is the same in all parts of the wire. CHIEF THERMAL PHENOMENA. 37 The electro-thermal unit of conduction resistance, termed a joule, is the amount of heat produced in one second by a current of one ampere flowing through a resistance of one ohm, and is the quantity necessary to raise the temperature of *239 gramme of water one centigrade degree. One joule is equal to '7375 foot-pound, or to 1 watt of power exerted during one second ; it is only *24 of an ordinary heat unit or centigrade-gramme calorie (see below). Mechanical Equivalent of Heat. Joule's mechanical equiva- lent of heat is the amount of energy required to raise 772 P 55 Ibs. one foot high, and is equal to the quantity of heat necessary to increase the temperature of one pound of water at 60 Fahrenheit one Fahrenheit degree. The quantity of heat required to raise the temperature of one gramme of water at 0C. one centigrade degree is equal to the energy necessary to lift 423*55 grammes or -42355 kilogramme weight one metre high, or to that of 3*0636 foot-pounds. (One kilograrnmetre = 7'233 foot-pounds or 9-807 joules.) Thermal Units. The unit of quantity of heat is termed a calorie, and is that amount which will raise the temperature of a unit mass of water, at some assumed standard temperature, through one thermometric degree. The unit of mass employed is usually either one gramme, pound or kilogramme. If it is a gramme raised one centigrade degree it is called a centigrade gramme calorie ; and if a kilogramme, it is a centigrade kilo- gramme calorie. One gramme of water at about 18C. raised one centigrade degree is a commonly used unit, and is equal to 0098 joule or electro-thermal unit (see Appendix).* Heat of Chemical Union and Decomposition. In every chemical action, and in every voltaic and electrolytic one, there is a transformation of energy, an evolution or absorption oi heat, and a change of physical condition of the substances. In every voltaic and electrolytic action substances either unite * The centigrade-gramme calorie is now called a THERM, and the term JOULE is used to indicate the work done by one watt in one second ; 4 '2 joules =1 therm (O. J. Lodge, The Electrician, Vol. XXL, September 28th, 18*8, p. 661). 38 CHIEF THERMAL PHENOMENA. together chemically to form compounds, or compounds are chemically decomposed. Chemical combination very usually evolves, and decomposition nearly always absorbs heat. What- ever amount of heat two substances evolve when combining, that same amount do they absorb when separating. The amounts of heat liberated by the elementary substances when chemically combining vary in substantially the same order as the degrees of chemical potential of the substances (see p. 48), and as the position of the substances in the volta-tension series (see p. 50). The amount of heat or thermal energy necessary to decompose a given compound is equal to that produced by the separated substances when uniting together to form that compound in the same physical state. This agrees with the principle of con- servation of energy, which affirms that in any substance or system of substances the total amount of heat or energy in it i& a fixed quantity, and is unaffected by any intervening changes which occur, provided the substance or system is in exactly the same physical and chemical condition after the changes that it was in before they occurred. Thermal Symbols and Formulae. The thermal changes which take place in chemical and electro-chemical actions are repre- sented by symbols and formula}, very much like those used to- represent ordinary chemical changes. Thermo-chemical formulae are generally enclosed in a small bracket; a comma, or sometimes a colon, being placed between the two formulae of the substances which react upon each other. The plus or negative signs pre- fixed or affixed to the numbers representing heat of formation,, of solution, or of decomposition, indicate whether the action- evolves or absorbs heat ; if no sign is given plus is meant. For instance (H 2 , 0) = + 68360 means that when two atomic weights of hydrogen in grammes unite with one atomic weight of oxy- gen in grammes at a temperature of 18 to 20C., and form 18 grammes of water at that temperature, sufficient heat is set free to raise the temperature of 68360 grammes of water at about 18C. one centigrade degree. Substances whose sym- bols are not separated by a comma or colon have already united together chemically and evolved (or absorbed) heat. The symbol Aq indicates an unlimited amount of water. CHIEF THERMAL PHENOMENA. The following tables give the relative quantities of heat, in centigrade-gramme units, evolved by the chemical union of various substances with each other, in the proportions of their equivalent weights in grammes as represented by the formuls& given. The numbers are those given by Thomsen in hia " Thermo-Chemical Memoirs," and are results of his laborious investigations : Heat of Chemical Union. Chemical Reaction. Centigrade-Gramme Calories. llrnt tf SoliiH-n in Abundance ol Water. (H 2 , 0) + 68360 (H 2 , S) 4740 4560 (H 2 , S, Aq) 9300 (H, Cl) 22000 17315 (H, 01, Aq) 39315 (H, Br) 8440 19940 (H, I) (H 3 , N) - 6040 11890 19210 8340 (0,0) 29000 (0, O 2 ) 96960 S, O 2 ) 71080 8,05) 103240 (S, O 3 ', H 2 0) 124560 (S, O 3 , Aq) 142410 (P 2 , 0*) 369000 (As, Cl 3 ) 71390 17580 As 2 , O 3 ) As 2 , O 6 ) 154670 219380 - 7550 6000 As 2 , O 5 , 3H 2 0) 226180 Sb, Cl 3 ) 91390 Sb, Cl 3 , Aq) 7730 So 2 , O 3 , 3H 2 0) 167420 Enthsly decomposed. Sb 2 , O 5 , 3H 2 O) 228780 Bi, Cl 3 ) 90630 Bi, 0, Cl, H 2 0) 88180 Bi 2 , O 3 , 3H 2 O) 137740 (Au, Cl 3 ) 22820 4450 (Au, Cl 3 , 2H 2 0) 28960 - 1690 (Ag 2 , 0) (Ag 2 , Cl 2 ) 5900 58760 (Ag 2 , 02, SO 2 ) 96200 - 4480 (Hg, 0) (Hg 2 , 0) 30670 42200 (Hg, Cl 2 ) 63160 - 3300 (Hg 2 , Cl*) 82550 (Cu, O) (Cu 2 , 0) 37160 40810 40 CHIEF THERMAL PHENOMENA. Heat of Chemical Union (continued). Chemical Reaction. Centigrade-Gramme Calories. Heat of Solution in Abundance of Water. (Cu 2 , O, H*O) 37520 (Cu, Cl 2 ) 61630 11080 (Cu, Br 2 ) 32586 8250 (Cu, O 2 , SO 2 ) 111490 15800 (Cu, O 2 , SO 2 , 5H 2 O) 130040 - 2750 (Cu, O 2 , N 2 0*, 6 H 2 0) 96950 -10710 (Ni, Cl 2 ) 74530 19170 (Ni, 0, H 2 0) 60840 (Ni, O 2 , SO 2 , 7H 2 0) . 162530 - 4250 (Co, Cl 2 ) 76480 18340 (Co, O, H 2 O) 63400 (Co, O 2 , SO 2 , 7H 2 O) 162970 - 3570 (Fe, Cl 2 ) 82050 17900 (Fe, Cl 2 , 4H 2 O) 97200 2750 (Fe 2 , Cl 6 ) 192080 63360 (Fe, O, H 2 0) 68280 (Fe, O 2 , SO 2 , 7H 2 0) 169040 - 4510 (Mn, Cl 2 ) 111990 16010 (Mn, O, H 2 O) 94770 (Mn, O 2 , H 2 0) 116330 (Mn, O 2 , SO 2 ) 178790 13790 (Al 2 , Cl 6 ) 321960 (Tl 2 , O 2 , SO 2 ) 149900 - 8280 (Pb, Cl 2 ) 82770 - 6800 (Pb, 0) 50300 (Pb 2 , O 3 , 3H 2 O) 250320 (Pb, O 2 , SO 2 ) 145130 (Sn, Cl 2 ) 80790 350 (Sn, Cl 2 , 2H 2 0) 86560 - 5370 (Sn, 0, H 2 0) 68090 (Sn, O 2 , H 2 O) 133500 (Cd, Cl 2 ) 93240 3010 (Cd, 0, H 2 0) 65680 (Cd, O 2 , SO 2 ) 150470 10740 (Zn, Cl 2 ) 97210 15630 (Zn, O, H 2 O) 82680 (Zn, O 2 , SO 2 ) 158990 18430 (Mg, Cl 2 ) 151010 35920 (Mg, Cl 2 , 6H 2 0) 183980 2950 (Mg, O 2 , SO 2 ) 231230 20280 (Sr, Cl 2 ) 184550 11140 (Ba, Cl 2 ) 194770 2070 (Na 2 , 2 ,S0 2 ) 257510 460 (Na 2 , Cl 2 ) 195380 - 2360 (K 2 , 2 ,S0 2 ) 273560 - 6380 (K 2 , Cl 2 ,) 211220 - 8880 (K 2 , Cy 2 ) 130700 - 6020 CHIEF THERMAL PHENOMENA. 41 The approximate general order of the metallic elementary substances, in which they evolve the most heat by chemical union with fluorine, oxygen, chlorine, bromine, acids, &c., is usually as follows: Cs, Kb, K, Na, Li, Al, Ca, Ba, Sr, Mg, Zn, Tl, Cd, Sn, Pb, Fe, Co, Ni, Cu, Sb, Ag, As, Au, Pt. The following is their order when uniting with chlorine : Heat of Formation of Anhydrous Chlorides. Metallic Element. Compound formed. Centigrade-Gramme Calories. K (K 2 , Cl 2 ) 211220 Na (Na 2 , Cl 2 ) 195380 Ba (Ba, Cl 2 ) 194740 Li (Li 2 , Cl 2 ) 187620 Sr (Sr, Cl 2 ) 184550 Ca (Ca, Cl 2 ) 169820 Mg (Ma, Cl 2 ) 151010 Mn (Mn, Cl 2 ) 111990 Al (Al 2 , Cl fi )x-333 107320 Zii (Zn, Cl 2 ) 97210 Tl (Tl 2 , Cl 2 ) 97160 Cd (Cd, Cl 2 ) 93240 Pb (Pb, Cl 2 ) 82770 Fe (Fe, Cl 2 ) 82050 Co (Co, C! 2 ) 76480 Ni (Ni, Cl 2 ) 74530 Fe (Fe 2 , Cl)x-333 64027 Sn (Sn, Cl 4 )x-5 63625 Hg (H Phosphorus p2Q5 5964-5 ) Carbon CO 2473- Favre and Silbermann Sulphur SO 2 2221-3 Thomsen Manganese MnO 2 2113-0 ) Iron Fe 2 O 3 2028- Favre and Silbermann Potassium K 2 O 1745- Woods Manganese MnO 1724- Thomsen Iron FeO 1352-6 Favre and Silbermann Zinc ZnO 1314-3 Thomsen Tin SnO 2 1147- Andrews SnO 573-6 Lead PbO 243- Thomsen Mercury HgO 153-5 * j Hg 2 105-5 , 9 Bismuth Bi 2 O 3 95-5 Woods Silver Ag 2 27-3 Thomsen SECTION C. THIEF CHEMICAL FACTS AND PRINCIPLES OF THE SUBJECT. As in every electrolytic and voltaic action, substances either unite together chemically to form compounds, or compounds are chemically decomposed, it is manifest that every student of electro-metallurgy, and every person who superintends the electrolytic separation and refining of metals, requires some train- ing in chemistry. He might with great advantage have previous experience in chemical and electrical manipulation, and possess a knowledge of the leading physical and chemical properties of the common elementary substances and their chief compounds ; of metals and metalloids, alkalies, bases and salts ; of chemical nomenclature, the use of chemical symbols, notation, formulae, equations, and schemes of decomposition ; the meaning of the terms chemical affinity, elementary substance, atom, molecule, atomic, molecular and equivalent weight, valency, specific gravity, &c. ; and be able to perform chemical analyses and make chemical calculations. Knowledge of the meanings of the terms monobasic, bibasic, and tribasic is also necessary in order to be able to judge respecting the true electrolytic equivalents of compounds, and the relative amounts of substances decom- posed by a current. As the reader is supposed to have already received sufficient preliminary training to enable him to under- stand the subject of this book, only a very brief and incomplete outline will be given of the chief points of chemical knowledge relating to electro-metallurgy. EXPLANATION OP CHEMICAL TERMS. By chemical affinity is meant the kind of energy which causes two dissimilar sub- stances to unite together in certain definite proportions by weight, and produce a third homogeneous substance, widely different in its properties from the originals ; its action is nearly always attended by evolution of heat. The proportions in which they chemically unite are usually those of their atomic or molecular weights, or some simple multiple of these. An elementary body is a substance which we have never yet been able to decompose or separate into two substances. Ac atom is the smallest particle of an elementary substance which CHEMICAL FACTS AND PRINCIPLES. can exist in a chemically combined state. A molecule is a group of two or more atoms chemically united together, and is the smallest particle of an elementary or compound substance which can exist in a chemically free state ; a molecule of an elementary substance in the gaseous state is usually composed of two atoms. A mass is a collection of molecules; its amount is usually denned by its weight, but more accurately by the amount of its mecha- nical energy when moving at a given velocity. By atomic weight is meant the relative weight of an atom, that of hydrogen being the unit. Of the actual weight of atoms we know but little; it is, however, extremely small. The following is a tfible of atomic weights : Symbols and Atomic Weights of Elementary Substances. Name. Symbol. Atomic Weight. Name. Symbol. Atomic Weight. Aluminium Al 27-3 Mercury Hg 199-8 Antimony Sb 122-0 Molybdenum Mo 95-6 Arsenic As 74-9 Nickel Ni 58-6 Barium Ba 136-8 Niobium Nb 94-0 Beryllium Be 9-0 Nitrogen N 14-01 Bismuth Bi 210-0 Osmium Os 198-6 Boron Bo 11-0 Oxygen O 15-96 Bromine Br 79-75 Palladium Pd 106-2 Cadmium Cd 111-6 Phosphorus P 30-96 Caesium Cs 133-0 Platinum Pt 1967 Calcium Ca 39-9 Potassium K 39-04 Carbon C 11-97 Rhodium Ro 104-5 Chlorine Cl 35-37 Rubidium Rb 85-2 Cerium Ce 141-2 Ruthenium Ru 103-5 Chromium Cr 52-4 Selenium Se 78-0 Cobalt Co 58-6 Silver As 107-66 Copper Cu 63-0 Silicon Si 28-0 Didymium Di 1470 Sodium Na 22-99 Erbium Er 169-0 Strontium Sr 87-2 Fluorine F 19-1 Sulphur S 31-98 Gallium Ga 69-7 Tantalum Ta 182-0 Gold Au 196-2 Tellurium Te 128-0 Hydrogen H 1-0 Thallium Tl 2036 Indium In 113-4 Thorium Th 231-5 Iodine I 126-53 Tin Sn 117'8 Iridium Ir 1967 Titanium Ti 48-0 Iron Fe 55-9 Tui'gsten W 184-0 Lanthanum La 139-0 Uranium Ur 240-0 Lead Pb 206-4 Vanadium Va 51-2 Lithium L 7-01 Yttrium Yt 93-0 Magnesium Mg 23-94 Zinc Zn 64-9 Manganese Mn 54-8 Zirconium Zr 90-0 CHEMICAL FACTS AND PRINCIPLES. 45 The molecular weight of a substance is the sum of the relative weights of the atoms composing a molecule of it. The following are the relative molecular weights of some of the common sub- stances, including those which are the most likely to be useful to the electrolytic chemist : Chemical Formulae and Molecular Weights of Substances. Substance. Formulae. Molecular Weight. Hydrogen H 2 2-0 Oxygen O 2 32-0 Fluorine F 2 38-0 Chlorine Cl 2 71-0 Bromine Br- 160-0 Iodine I 2 254-0 Sulphur S 2 64-0 Water H 2 O 17-96 Hydrofluoric acid HF 20-0 Hydrochloric ,, HC1 365 Carbonic ,, CO 2 43-9 Nitric ,, HNO 3 62-88 Hydrosulphuric ,, H 2 S 33-98 Sulphurous ,, H 2 SO 3 81-86 Sulphuric ,, H 2 SO 4 97-82 Phosphoric ,, H 3 PO 4 97-8 Arsenic us ,, As 2 O 3 197-68 Arsenic ,, As 2 5 2296 Terchloride of Antimony SbCl 3 228-5 ,, Bismuth Bid 3 316-5 Nitrate ,, Bi3NO 3 + 5H 2 O 485-44 Chloride of Platinum PtCl 4 339-0 Gold AuCl 3 303-0 Nitrate of Silver AgNO 3 169-54 Fluoride ,, AgF 126-66 Chloride ,, AgCl 143-16 Iodide Agl 234-19 Mercuric chloride HgCl 2 2700 Cupric nitrate Cu2NO 3 + 6H 2 O 294-52 chloride CuCl 2 13374 ,, sulphate CuS0 4 + 5H 2 249-5 Chloride of Nickel NiCl 2 130-0 Sulphate ,, NiSO 4 +7H 2 O 281-0 Nitrate of Cobalt Co2NO 3 +6H 2 O 291-0 Chloride CoCl 2 130-0 Sulphate CoS0 4 +7H 2 281-0 Ferrous chloride FeCl 2 127-0 Ferric ,, Fe 2 Cl 6 325-0 Ferrous sulphate FeSO 4 +7H 2 O 278-0 Manganous chloride ,, sulphate MnCl 2 +4H 2 O MnSO 4 + 5H 2 O 198-0 241-0 \ 46 CHEMICAL FACTS AND PRINCIPLES. Chemical Formula, &c. (continued). Substance. Formula?. Molecular Weight. Nitrate of Lead Pb2NO 3 331-0 Sulphate of Thallium Stannous chloride Tl-SO 4 SnCl 2 504-0 189-0 Chloride of Cadmium CdCl 2 + 2H 2 O 219-0 Zinc ZiiCl 2 136-0 Sulphate of Zinc Chloride of Magnesium ZnSO 4 + 7H 2 O MgCl 2 287-0 95-0 Sulphate ,, Cryolite Chloride of Aluminium 6NaF, A1 2 F 6 A1 2 C1 6 226*0 421- 268- Sodio-chloride ,, Potash alum 2NaCl, A1 2 C1 6 KA12SO 4 + 12H 2 O 382- 473-7 Chloride of Calcium CaCl 2 no- Caustic Lime CaO 56- Soda NaHO 39-86 Chloride of Sodium NaCl 58-4 Sulphate ,, Na 2 SO 4 + 10H 2 O 321-44 Carbonate ,, Na 2 CO :! + 10H 2 O 285-48 Phosphate ,, Na 2 HP0 4 + 12H 2 29336 Caustic Potash KHO 56-1 Nitrate of Potassium KNO 3 101- Chloride ,, KC1 74-6 Chlorate ,, KC10 3 122-5 Bromide ,, KBr 119-1 Iodide KI 166- Sulphate K 2 SO 4 174- Carbonate K 2 CO 3 138- Ammonia H 3 N 17- Nitrate of Ammonium H 4 N, NO 3 80- Chloride ,, H 4 N, Cl 53*5 Sulphate ,, (2H 4 N)SO* 132- Cyanogen Hydrocyanic acid C 2 N HC 2 N 26- 27' Cyanide of Potassium KC 2 N 65- Oxalic acid H 2 C 2 4 + 2H 2 126- An equivalent weight of a simple substance is either the .atomic weight or some simple proportion of it, and is that weight which contains the same amount of chemical energy, or some simple proportion thereof, as the substance it is to com- bine with or decompose. An equivalent weight of a compound .substance is either the molecular weight or some simple pr(% portion of it. A substance may have several equivalent pro- portions, but can have only one atomic or molecular weight. CHEMICAL FACTS AND PRINCIPLES. 47 By atomicity, valency, or atom-fixing power, is meant the number of atoms of hydrogen or other monad element with which one atom of the elementary substance can combine, or which it can displace. A monad is an elementary substance, an atomic weight of which can combine with or displace one atom of a monad element ; a dyad is one, an atomic weight of which can combine with or displace 2; a triad, 3; a tetrad, 4; a pentad, 5 ; and a hexad, 6. Degrees of valency always correspond to equivalent weights or combining proportions, whether these are the same as the atomic weights or not. As, however, there are instances in which the same elementary substance combines in several definite proportions with another, as in the case of nitrogen uniting with oxygen, chlorine with antimony, &c., difficulties have arisen in determining the true valencies of substances, and the following classification is therefore largely an arbitrary one: Monads. Dyads. Triads. Tetrads. Pentads. Hexads. Hydrogen Oxygen Boron Carbon Nitrogen Molybde- Fluorine Sulphur Rhodium Silicon Phosphorus num Chlorine Selenium Gold Titanium Arsenic Vanadium Bromine Tellurium Bismuth Tin Antimony Tungsten Iodine Barium Aluminium Zirconium Osmium Caesium Strontium Indium Thorium Chromium Rubidium Calcium Cerium Manganese Potassium Lanthanum Nickel Sodium Didymium Cobalt Lithium Glucinum Uranium Thallium Magnesium Lead Silver Zinc Ruthenium Cadmium Iridium Iron Palladium Copper Platinum Mercury A metal is an elementary substance which conducts heat and electricity freely, and unites chemically with metalloids ; a metalloid is one of the opposite properties to these, and unites chemically with metals. An alloy is a homogeneous mixture or compound of metals. An acid is a compound substance, which chemically combines with and neutralises an alkali, tastes sour, and turns blue litmus-paper red ; it is usually soluble in water, and is an oxide of a metalloid or a peroxide of a metal. An alkali is a compound body, which chemically combines with neutralises an acid, tastes soapy, and turns red litmus- 46 CHEMICAL FACTS AND PRINCIPLES. paper blue ; it is soluble in water, and is usually an oxide of a metal. A base is a compound substance, which by chemically uniting with an acid forms a salt ; it is usually a metallic oxide, sometimes an alkali. A salt is a chemical compound, either of a metal and metalloid or of an acid and a base. An anhy- dride is a compound substance which by uniting with water forms an acid ; it is usually an oxide of a metalloid. Anhydrous means destitute of water. Hydrated means containing water combined in definite proportions by weight. Chemical Potentiality. By this term is meant the amount of chemical energy stored up in a static or inactive state in substances under certain conditions, and ready to become dynamic or active under other circumstances, and converted into some other form of energy, such as heat, electric current, 5 M | !S S;^0 O 02 i S 5 - - o o o 8 O ?7 i o p p p p fc-e - : ^ ^ S ( xZpH Q Q < PH' 4 ^ =sy|| I g g |1 . ^ BC TJ S r - S S o ; P^^r? 9 8 8 ;8 2 - NO^S^I PH S 6 S?.*?,?, S S!S SSS888 8 8 i pp55 o 5 o T3 S fi ft <4 - iHOCO-^O t- CO I O C<1 00 O lit 'T 5^ i I 10 P- *? 2 *2 if5 "-2 o co 20 i ' C O ;O i ^sji ( i OOOOO ONO g S 3 'P 9 =P 9 9 r 1 r *f- TI ' x r: rfp^l^^-lrHrHpp' ppt.pt. OT-iM 70 CHEMICO-ELECTRIC OR VOLTAIC ACTION. that if two pieces of the same metal are connected with a gal- vanometer, their free ends immersed in an electrolyte, and heat applied to one of the junctions of the metal with the liquid, an electric current is produced. I have investigated this pheno- menon in several researches (see Phil. Mag. Jan., 1857 ; Proc. Roy. Soc., 1871, Vol. XIX., p. 234; ibid., 1878, Vol. XXVIL, pp. 272 and 513 ; 1879, Vol. XXIX., p. 472 ; 1880, Vol. XXXL, p. 244; 1883, Vol. XXXVI., p. 50; and 1884, Vol. XXXVIL, pp. 251-290), and have found that it is due to two chief causes, viz., 1st, to ordinary thermo-electric action in those cases where neither of the pieces of metal is at all corroded ; and, 2nd, to an alteration of ordinary voltaic potential in those where the metal is corroded. The most usual effect observed was, that in alkaline liquids the hot metal was often positive and in acid ones often negative ; the latter effect occurs with copper in an acidulated solution of cupric sulphate. In a large majority of cases the hot piece of metal became positive. The effect of heating both pieces was largely composed of the sum of the effects of heating each singly, Theory of Voltaic Action and Source of Current. Two distinct and different theories of the source of the voltaic cur- rent have long been entertained ; first, that of Volta and many Continental investigators, that the current is due to contact of dissimilar conductors of electricity ; and, second, that of Faraday and other English experimentalists, that it is due to chemical action. Neither of these views, however, is alone com- pletely satisfactory or has been universally accepted, and the most general one held at present is that the current is due both to contact and to chemical action. If we adopt the theory that the molecules of substances those of chemically energetic bodies in particular are in a state of ceaseless motion (that of frictionless bodies in a frictionless medium, such as the universal ether), and that when they chemically unite the amount of their motion is diminished, an efficient cause of chemical action and of voltaic current becomes much more clear. According to this view, which has been gradually developed by the labours of many eminent investigators, neither contact nor chemical action is the primary cause of the current, but the CHEM I CO-ELECTRIC OR VOLTAIC ACTION. 71 essential cause is the stored up and ceaseless molecular energy of the corroded metal and of the corroding element of liquid with which it unites, whilst contact is only a static condition, and chemical action is the process or mode by which the molecular motions of those substances are more or less trans- formed into heat and current. Both the heat and electric current produced by chemical corrosion of metals in electrolytes are recognised forms of energy, and as motion or energy cannot be created it must come from the original substances, and these must, after the action, have lost some of their vis viva and power of producing further heat or current. SECTION E. CHIEF FACTS OF ELECTRO-CHEMICAL ACTION. Definition of Electrolysis. Electrolysis, or electro-chemical action, is the decomposition of liquids by means of electric currents. The fundamental basis of electrolysis is the fact, that when a current of electricity passes through a suitable liquid the liquid is decomposed. The only essential conditions necessary are that the substance be a liquid, a definite chemical compound, and a conductor of electricity. Liquid alloys, such as that of sodium and potassium, tin and mercury, &c., are not decomposed by the current, and liquid compounds of two non-metallic elements, such as bisulphide of carbon, chloride of sulphur, c., are also not usually capable of electrolysis. Electrolysis is commonly distinguished from ordinary chemical action By not taking place with non-conducting substances (pp. 51 and 87). Distinction between Electrolytic and Voltaic Action. Electrolysis, or electro-chemical action, is the converse of voltaic or chemico-electric action ; whilst electrolysis is che- mical change produced by electric current, voltaic action con- sists of electric current produced by chemical change. Voltaic action is essentially a producer, and electrolysis usually a con- sumer, of molecular energy. In a voltaic cell substances are usually burned ; whilst in an electrolytic one they are usually unburned. In a voltaic cell elementary substances unite to- gether, and their molecular energy assumes a free and active state ; in an electrolytic one, elementary substances are libe- rated at the poles, and absorb and render latent molecular energy. The one kind of action converts potential energy into active, and the other converts active energy into potential. Connection between Electrolytic and Voltaic Action. ^.s in nearly every voltaic cell the current produced by the union of bodies at the positive plate decomposes the liquid at the negative one, and in nearly every electrolytic cell, voltaic action ELECTRO-CHEMICAL ACTION. 73 is produced by the substances set free at the electrodes, nearly every voltaic action produces electrolytic ones, and nearly every electrolytic action produces voltaic ones. According to these views pure voltaic action is essentially a case of chemical union, and pure electrolysis essentially consists of chemical separation. Connection between Electrolytic, Chemical, and Voltaic Action. The various phenomena of electrolysis are produced, not only by electric currents proceeding from an external source, but also by those originated in the electrolyte itself, and not only by currents flowing in circuits of measurable mag- nitude in that liquid, but also by others in circuits so small that they cannot be measured. In the case of an ordinary electrolysis vessel (or in a voltaic cell) the positive and nega- tive surfaces are sufficiently far apart to enable us to perceive and distinguish the action at each ; but in that of " deposition by simple immersion," or the chemical precipitation of one metal by another, as when iron becomes coated with copper by simply immersing it in a solution of cupric sulphate, the positive and negative surfaces of each circuit are so extremely small, so exceedingly near together, and the circuits so very numerous, that they cannot be separately observed, and the entire immersed surface of the metal is covered with inse- parable voltaic, chemical, and electrolytic actions. The substances also set free by electrolysis do not always appear; the instant they are liberated they are subject to ordinary chemical action by contact with the liquid and the atmosphere. Thus when potassium is set free by electrolysis at the cathode from a solution of any of its salts, it is instantly oxidised into potash, or when oxygen is liberated at an anode in a solution of argentic nitrate, it at once combines with the silver of that salt. With rapidly reversed currents, the pro- ducts do not always appear. These facts show the intimate connection between elec- trolytic, chemical, and voltaic action, and the necessity of the student possessing a previous knowledge of chemistry and of voltaic electricity. Arrangements for Producing Electrolysis. Various com- binations have been employed in which voltaic or other electric 74 ELECTRO-CHEMICAL ACTION. currents produce chemical changes, and these have been classi- fied as follows : 1. Electrolysis by simple contact of one metal with one liquid. 2. By contact of one metal with two liquids. 3. By contact of two metals with one liquid. 4. By contact of two metals with two liquids. 5. By a separate electric current. And, 6. By a separate current and a series of electrolysis vessels. In Nos. 1, 2 and 3, the source of the electric current is voltaic, and exists in the metals and liquids themselves, whilst in 4 and 5 the current is generated separately by any convenient voltaic or other method. FIG. 21. Simple Immersion Cell. FIG. 22. Two Liquids and One Metal Cell. No. 1 arrangement is termed the "simple immersion process," and consists simply of immersing a piece of suitable metal in a suitable liquid (Fig. 21). The most familiar example of it is the coating of iron with copper by simply dipping it into a solution of blue vitriol. In this process the voltaic currents kre generated by chemical action of the liquid upon the iron; they are excessively minute, and produced in immense numbers at points inconceivably small all over the immersed surface of the ELECTRO-CHEMICAL ACTION. 75 metal, and re-enter all over that surface ; where they leave iron is dissolved, and where they enter copper or hydrogen is deposited. The method is extensively used for separating copper from solutions by means of scrap iron. By this method the electrolyte rapidly becomes impure. No. 2 consists in either carefully placing a lighter liquid upon a heavier one in a tall narrow vessel, and standing a rod of metal vertically in the two strata (Fig. 22), or dividing a glass vessel into two parts by means of a vertical porous partition, placing the two liquids in the two divisions and immersing the two ends of the bent rod of metal in the two solutions (Fig. 24). The one end of the rod then dissolves and produces a voltaic current which re-enters the rod at its other end and deposits the metal. FIG. 23. Two Metals and One Liquid Cell. FIG. 24. T\vo Metals and Two Liquids Cell. By this contrivance the negative end of a piece of metal may be caused to receive an electrolytic deposit in a liquid which the metal itself is unable to decompose by simple immersion. Copper in dilute sulphuric acid, and in a saturated solution of cupric sulphate, is an example of this method. No. 3 consists in bringing two metals into electrical contact at their upper ends, either direct or through a wire, and immersing their lower ends in a suitable liquid, or allowing the metals to touch each other in the solution (Fig. 23). A current then passes from the positive metal through the liquid into the negative one, producing deposition, and returns by the point of metallic contact; the positive metal also acts simultaneously by the " simple immersion process," and deposits metal upon itself. This contrivance, like the second one, enables a metal to 76 ELECTRO-CHEMICAL ACTION. receive a deposit in a liquid which it does not decompose by " simple immersion." Zinc in contact with copper, in a solu- tion of cupric sulphate, is an example of this method. Under this arrangement may be classed the "two metal couples" of Gladstone and Tribe, in which the resistance to conduction is greatly diminished, and therefore the strength of current much increased, by making the voltaic circuits extremely small and numerous. This is effected by electrolytically depo- siting copper, silver, or platinum, in a porous, spongy state, upon the surface of zinc or magnesium, washing the plate so prepared, and immersing it in the liquid to be electrolysed. No. 4 is termed the " single cell process," and consists of two liquids separated by a porous partition, the two metals being FIG. 25. Separate Cell Process. partly immersed, one in each liquid, and either in immediate contact or connected together at their upper ends by means of a wire (Fig. 24). This method also enables a metallic deposit to be produced upon a metal in a liquid which it does not itself decompose by simple immersion. In this arrangement, and in the second one, deposition by simple immersion is obviated by keeping the liquids apart by means of a porous partition; they, however, slowly diffuse through the partition, and the positive metal then becomes wasted by " simple immersion process." No. 5 is the most convenient arrangement, and the most com- monly used ; it consists of a vessel containing the electrolyte and two electrodes, neither of which decomposes the soliibion by simple contact, the electrodes being connected by means of wires with a voltaic battery or other source of current. It is ELECTRO-CHEMICAL ACTION. 77 known as the "battery process" or "separate current process" (Fig. 25). By this method the strength of the current to produce electrolysis may be increased to any extent by means of additional voltaic cells, the most incorrodible metals may be employed as anodes, and by using a sufficiently powerful current even the alkali metals may be deposited. It was by this pro- cess that Davy first isolated potassium and sodium. No. 6 consists merely of a series of such depositing vessels and electrodes as those in No. 5, with an undivided current passing through the whole of them (Fig. 26). It is now much used in copper refining. Self-Deposition of Metals. In addition to the cases in which a metal in contact with one liquid causes the deposition of the same metal upon itself in another liquid (see " No. 2," p. 74), instances have been observed by Kaoult, Gladstone and Tribe, FJG. 26. Series of Cells Process. in which a metal deposits itself upon another less positive than itself, by a modified " simple immersion process." Raoult states that when two plates, one being of copper and the other of cadmium, are completely immersed in a solution of sulphate of cadmium deprived of air, and covered with a layer of oil, as long as they do not touch each other a very slight escape of hydrogen is observed on the cadmium plate, whilst the copper shows no visible change. When, however, the plates are caused to touch each other, cadmium begins at once to be deposited on the copper. Couples formed of gold-iron, gold-nickel, gold- antimony, gold-lead, gold-copper, gold-silver, immersed either in cold or hot, acid or neutral, solutions of salts of the more positive of the two metals, yielded, however, no deposit of that metal (Comptes Rendus, Vol. LXXV., p. 1,103; Jour. Chem. Soc., 2nd Series, Vol. XL, p. 464). Gladstone and Tribe also noticed that a copper zinc couple separated metallic zinc from a 1*5 per cent, solution of zinc sulphate (ibid., p. 453). 78 ELECTRO-CHEMICAL ACTION. Modes of Preparing Solutions for Electrolysis. The special methods of preparing particular substances for making solu- tions differ in nearly every different case, and a description of them belongs to a work on chemistry. There are, however, two general ones for preparing the solutions, viz., the chemical and the electro-chemical process, the former being used for large operations and the latter for small ones. In the former the usual chemical processes of oxidation, solution in acids, crystal- lisation, &c., are employed ; in the latter we take the particular solvent, usually a dilute acid, solution of potassic cyanide, &c., suspend in it a large anode of the particular metal to be depo- sited, and a smaller cathode, the latter being either in the solution itself or in a small porous cell filled with the liquid and placed in the bath, and pass a strong current until a sufficient quantity of the metal is dissolved, and the outer bulk of liquid yields a proper deposit with a current of suitable strength. The two processes, however, do not always yield liquids of exactly the same composition, because in the electrolytic one chemical changes occur at the cathode, and yield new products ; for instance, with a solution of potassic cyanide, potassium is .set free at the cathode, and is instantly oxidised by the water, .and forms potash which dissolves in the liquid, and this potash gradually absorbs carbonic acid from the atmosphere and becomes carbonate of potash. Nomenclature of Electrolysis. The liquid undergoing elec- trolysis is termed an electrolyte. The immersed surfaces of metal or other conductor, by which the current enters and leaves the liquid, are called electrodes, or poles ; the one by which it enters is called the anode, or positive pole, and that by which it leaves is the cathode, or negative pole. The substances into which the liquid is decomposed are called ions, those which separate at the anode being called anions, and those at the cathode cations. Anions are what are called electro-negative bodies, such as metalloids (fluorine, oxygen, chlorine, bromine, iodine, sulphur, phosphorus, &c.), acids, peroxide. &c. ; and cations are electro- positive ones, such as hydrogen, the metals, alkalies, and basic oxides. Hydrogen is the only known gaseous cation. As tl^ conditions of positive and negative are not absolute, but only relative ones, the relatively negative constituents of the elec- ELECTRO-CHEMICAL ACTION. 79 trolyte are set free at the positive electrode, and the relatively positive ones at the negative electrode, and it sometimes hap- pens that the same substance IB separated at the anode in one liquid and at the cathode in another, according to the electric nature of the body with which it is united. Thus, sulphur, when united to a positive substance, such as a metal, as in sulphide of potassium, is separated at the anode, but when united with a more negative one than itself, such as oxygen, as in a solution of sulphurous anhydride, it is separated at the cathode ; in a similar manner, iodine sometimes behaves as an anion and sometimes as a cation, as in the instances of potassic iodide and iodic acid. In the case of electrolysis of two liquids, separated by a porous partition, it is sometimes convenient to call the liquid containing the anode the anolyte, and that containing the cathode the catholyte (see p. 93). Locality of Electrolysis. The chemical changes directly produced by the current do not take place in the mass or body of the liquid, but at the immersed surfaces of the conductors by which the current enters and leaves the solution, and are strictly limited to the extremely thin layers of metal and liquid in immediate contact with each other. Faraday proved that the decomposing action of an electric current upon an electrolyte is not necessarily limited to the con- tact surfaces of the solid or metallic conductor with the liquid, but may also occur at the mutual contact surfaces of two different electrolytes. Thus, by placing a concentrated solution of sulphate of magnesia of some depth below a deep stratum of distilled water, and passing an electric current from a platinum anode at the bottom of the magnesium solution upwards through the two liquids into a platinum cathode in the upper part of the water, magnesia was separated, not at the cathode, but at the surfaces of mutual contact of the two liquids. The water remained quite clear, no alkali was set free at the cathode, but plenty of acid was liberated at the anode. Daniell also subsequently, in a research on the " Electrolysis of Secon- dary Compounds" (Phil. Trans. Roy. Soc., 1840, pp. 209-224), passed an upward electric current through solutions of various easily-reducible metallic salts into a supernatant dilute one of caustic potash, the two liquids being separated from each other 80 ELECTRO-CHEMICAL ACTION. by a thin horizontal film of bladder. Oxygen was separated at the upper, and the respective metals and oxides of metals at the lower surface of the bladder. From a number of results obtained in a series of experi- ments on the " Influence of Voltaic Currents on the Diffusion of Liquids" (Proc. Roy. Soc., Vol. XXXII., 1881, pp. 83 and 84), in which the effect of a vertical electric current passing through the horizontal surfaces of mutual contact of dissimilar electro- lytes in a large number of instances was examined, the author concluded that " ions are probably liberated at every surface of junction of electrolytes, of sufficiently different composition, through which the current passes," and " that every inequality of composition or of internal structure of the liquid in the path of current, must also act to some extent as an electrode." Distribution of Current in an Electrolyte. With an elec- trolyte of perfectly homogeneous composition and temperature, FIG. 27. Equipotential Lines. and two narrow vertical electrodes placed symmetrically in it, the current from the anode spreads out in curves of equi- potential lines, not unlike those of magnetism diverging from the poles of a magnet, and converge in similar lines to the cathode, the densest portion of the current and the greatest number of lines being in the central axis of the liquid, and joining the centres of the electrodes (Fig. 27). Its distribution has been experimentally examined by Tribe, who suspended small pieces of sheet metal in different parts of the liquid between the electrodes, and ascertained it by the amounts of electro- lytic action produced upon them by the same current during the same period of time (Proc. Roy. Soc., Vol. XXXL, p. 32Q, Vol. XXXIL, p. 435; Phil. Mag., June, 1881, p. 446; October, ELECTROCHEMICAL ACTION. 81 1881, p. 299; June, 1883, p. 391; August, 1883, p. 90; and October, 1883, p. 269). Conduction in Electrolytes without Electrolysis? The ques- tion whether electrolytes conduct in some minute degree with- out undergoing decomposition has been an unsettled one during many years. If they conducted in this manner freely the re- sults would be serious in electro-metallurgical processes on a large scale, because there would be great waste of current. That each electrolyte requires a certain electromotive force to decompose it is true, and that it transmits by some means even the feeblest current is also true. " A single Daniell cell con- nected with platinum electrodes in sulphuric acid produces only polarisation, no visible decomposition, the voltameter acting as a condenser of immense capacity " (Jour. Chem. Soc., 2nd Series, Vol. X., p. 463). It is well known that an electro- motive force of about 1'47 volts is necessary in order to elec- trolytically decompose water; nevertheless, much below this difference of potential a current passes, and is easily detected by means of a galvanometer. Different views are held as to the mode of transmission of this current. One is that it is trans- mitted by convection of the liquid particles, like that which occurs when an electrically-charged body discharges itself by attraction and repulsion of particles of dust in the air ; in this case the liquid is not decomposed. Another is that within these extremely minute limits the solution conducts like a metal ; in this case also the liquid is not decomposed. A third is that at first the liquid is decomposed, but that the ions are not liberated but are occluded by the electrodes, and by their subsequent very gradual diffusion and reunion produce a very feeble current. And a fourth is that it is due to air dissolved in the liquid. There are also other views on the subject. Melted fluoride of silver appears to transmit a very much larger current than agrees with the amount of visible electrolysis. Alternate-Current Electrolysis. Various investigators have observed that when an electric current, the direction of which is continually and rapidly being reversed, passes through an electrolyte, products of electrolysis sometimes appear at the electrodes, whilst at other times they do not (see The Electrician, Vol. XXI, p. 403 ; Nature, Vol. XXXVIIL, p. 555 ; Phil. Mag., June, 1853, p. 392). 82 ELECTRO-CHEMICAL ACTION. The explanation of this is simple, and the liberation of the products of electrolysis in such a case depends upon two con- ditions: first, the degree of frequency of reversal of the current; and second, upon the density of the current at the electrodes. If the reversals are sufficiently slow, or the quantity of ions separated per unit of surface is sufficiently large, there is set free at each electrode a mixture of positive and negative sub- stances. It is manifest that if the reversals are very slow, the products of the portion of current from A to B electrode will have time to separate and get away from the electrodes before those of the succeeding portion of current from B to A can be liberated and recombine with them. It is also clear that with a given rate of reversal, if the density of the current is sufficiently great, the quantity of the products of the current from A to B will be so large that they will be produced so fast as to push each other away from the electrodes more rapidly, and thus get away from the electrodes before those of the succeeding current from B to A can be liberated and recombine with them. In each of these cases, also, the products will have lost their nascent state to a greater or less degree before those of the opposite kinds can come into contact with them, and therefore will have lost to a corresponding extent their power of spontaneously recombining. Transport of Ions in Electrolysis. According to the results of experiments made by Hittorf and F. Kohlrausch, " in very dilute solutions of various salts, of strengths proportional to the chemical equivalents of the salts, the specific conductivities of the solutions are all of the same order of magnitude. In very dilute solutions, acted upon by a current of given electro- motive force, each of the ions moves through the solution with a fixed velocity dependent upon its own chemical action, and independent of the velocity of the other ion, i.e., the migra- tions of the different ions arc independent of each other. The following is the order of velocity of cations, the first named being the fastest : Hydrogen, potassium, ammonium, barium, copper, strontium, magnesium, zinc, lithium; and of anions, hydroxyl, iodine, bromine, cyanogen, chlorine, NO 3 , CIO 3 , fend the halogen of acetic acid." The quickest is "about four inches per hour " (see The Electrician, Vol. XXI., pp. 466 and 622). ELECTRO-CHEMICAL ACTION. 83 According to 0. Lodge ("Modern Views of Electricity," 1889, p. 87), " The following are the rates at which atoms of various kinds can make their way through nearly pure water when urged by a slope of. potential of one volt per lineal centimetre": Centimetre per hour. Hydrogen T08 Potassium '205 Sodium -126 Lithium . . '094 Centimetre per hour. Silver '106 Chlorine "213 Iodine "216 NO 3 .... -174 Electrolytic Osmose and Diffusion of Liquids. In the year 1807, Reuss of Moscow discovered electric osmose ; and in 1817, Porrett extended the discovery and modified the experi- ment, and showed that if an electrolyte is divided into two portions by means of a porous partition, and an electric current is passed from one portion to the other, the liquid flows slowly through the partition in the direction of the current, and increases in bulk on the negative side. In a research on the same subject (Proc. Roy. Soc., Vol. XXXI., 1880, p. 253) I have shown that the direction of flow is occasionally affected by the nature of the liquid, and that in a saturated alcoholic solution of bromide of barium it was opposite to that of the current. This was the only exceptional case in a series of sixty-eight different liquids of varied composition and strength. For addi- tional experiments on the influence of electric currents on the diffusion of electrolytes, see Proc. Roy. Soc., Vol. XXXII., 1881, pp. 56-85. Influence of Liquid Diffusion on Electrolysis. Diffusion exercises very great influence upon electrolysis ; if there was no diffusion or motion of the liquid, there could be no continued electro-deposition of metal, because the solution near the cathode would become exhausted of that substance, and that near the anode would be wholly deprived of free acid. The rate of electrolysis is largely limited by that of diffusion; if the electro-deposition of metal proceeds faster than the metallic salt diffuses from the mass of the liquid to the surface of the cathode, the current begins to decompose the other compounds present, usually the saline impurities and the water ; if, also, it proceeds faster than acid can diffuse to the anode, the latter becomes coated with oxide, or faster than water can diffuse to 84 ELECTRO-CHEMICAL ACTION. it, it becomes encrusted with salt (see p. 88). When the speed of diffusion is deficient in relation to that of electrolysis, some of the products of electrolysis are themselves liable to be electrolysed. With a viscous liquid the quality #f the depo- sited metal soon deteriorates during electrolysis, because of deficiency of supply of metallic salt to the cathode ; such a solution can only yield reguline metal very slowly. Long has observed that in almost every case the best con- ducting aqueous saline electrolytes are those composed of salts which have the fastest rate of diffusion, and those are usually the ones which have the largest molecular volume, and which absorb the most heat in dissolving. He also arrived at the conclusion that the "rate of diffusion of a salt is proportional FIG. 28. Decharme's Experiments. to the sum of the velocities with which its component atoms move during electrolysis" (Phil. Mag., 1880, Vol. IX., p. 425). Directly a dense current enters the cathode in a sulphate of copper solution the layer of liquid next the cathode is deprived of nearly all its metal, and is thereby not only rendered speci- fically lighter, but also less viscous and more diffusible, and tends to pass away from the cathode faster than the denser liquid tends to approach. This is rendered manifest by the fol- lowing experiments made by M. Decharme, who, however, gives a different explanation of the phenomenon. If we place a small disc of copper upon a film of solution of argentic nitrate cover- ing a clean plate of glass, the liquid at once draws back from the edge of the disc as if it was strongly repelled, and in less than a minute a nearly dry annular space is produced all round KLECTRO-CHEMICAL ACTION. 85 the disc. In a few minutes the liquid gradually returns to- wards the disc. The first portion of silver separated is brown, and looks like imperfectly reduced amorphous oxide, in the form of an Annular layer ; succeeding this is a zone of white semi-crystalline spongy silver. Soon after this rapid action is FIG. 29. Decharme's Experiments. over, and the silver solution has returned to the disc, the arborisations or tree-like formations of definite crystals of silver begin to form at the outer edge of the white deposit (see Fig. 28). If a disc of zinc was placed upon a film of pure water of the same thickness it produced around it merely the ordinary ascending meniscus. M. Decharme attributes the centrifugal motion of FIG. 30. Decharme's Experiments. the silver solution to " electric repulsion," but to me it appears to be due to the inner ring of liquid being deprived of its silver, and thereby rendered more readily diffusible. Figs. 29 and 30 are illustrations of the "repulsion" of silver arborisations (see La Lumiere Electrique, 1887). 86 ELECTRO-CHEMICAL ACTION. Polarisation of Electrodes, Counter Electromotive Force. Immediately an electric current passes through an electrolyte products of electrolysis begin to be liberated, and accumulate at the surfaces of the electrodes, and directly this occurs voltaic action is produced, because the two electrodes are no longer alike in composition and no longer in contact with layers of liquid of the same nature. This dissimilarity of con- ditions excites a counter electromotive force, tending to stop the original current, and to produce a voltaic one in the oppo- site direction. The substances which produce this effect differ in almost every different case. They usually consist of thin films of either solids, liquids or gases adhering to the surfaces of the electrodes, and in many cases may be largely or entirely removed by rapid stirring, but they sometimes consist of gases absorbed by the electrodes. With a cathode of sheet platinum in distilled water I have found the resistance and counter electromotive force, due to the gas absorbed by the platinum, and not removable by rubbing, sometimes amount to as much as 18 per cent, of the total electromotive force of the current. (See p. 34.) Unequal Electrolytic Action at Electrodes. By the elec- trolysis of a solution of a metallic salt with vertical corrodible electrodes, the liquid about the anode usually becomes more saturated with metallic salt, and being rendered specifically heavier descends and forms a layer at the bottom of the vessel, whilst that about the cathode becomes deprived of metal, acquires less specific gravity, ascends and spreads over the surface of the electrolyte. In consequence of these differences of specific gravity and chemical composition of the upper and lower parts of the electrolyte, the distribution and direction of the electric current in it are affected. At the commencement, whilst the liquid is uniform in composition the current is uni- formly distributed, and equal strengths of it pass horizontally through equal cross-sections of the liquid in every part ; but if the current is sufficiently strong, and produces the above inequalities of composition faster than diffusion or other motion corrects them, after a time it passes unequally, the greater portion of it going in an oblique direction from the upper part of the anode to the lower part of the cathode. In consequence ELECTRO-CHEMICAL ACTION. 87 of this the upper part of the anode becomes the most corroded, and the lower part of the cathode receives the greatest amount of deposit. These changes in composition of the liquid also give rise to local electric currents quite distinct from the general one ; for instance, as the upper part of each elec- trode is in contact with a more acid liquid, and the lower part with liquid containing more metallic salt, the upper part is continually being corroded and generating an electric current, which continually re-enters the lower part and deposits metal, and thus an anode sometimes actually increases in thickness at its lower end instead of becoming thinner, and is gradually cut off at the surface of the liquid and falls to the bottom. With horizontal electrodes and the anode above, these effects do not occur. Influence of Chemical Composition of the Liquid on Electrolysis. The chemical nature of the liquid is a matter of fundamental importance ; it determines whether electrolysis takes place at all, and the kind of effects it produces. Some fused salts, such as melted boracic acid, sulphide of arsenic, iodide of sulphur, and sulphide of phosphorus, scarcely conduct or suffer electrolysis at all. Some liquid compounds behave similarly; for instance, bisulphide of carbon, the chlorides of sulphur, phosphorus and arsenic, tetrachloride of tin, penta- chloride of antimony, the chlorides of titanium and silicon, &c. Even some aqueous solutions of chemical compounds offer con- siderable resistance to conduction and electrolysis ; amongst these are boracic acid, cyanide of mercury, ammonia, sugar, the various fatty acids, rate at which the lines are included by or excluded from the .coil. The identity of the above forms of stating the con- .ditions of magneto-electric induction is not always obvious. For instance, if we take the case of a magnet having very large flat pole-pieces over which the magnetic density is practically uniform, we may then consider the greater part of the field crossing the air-gap to be also uniform, and if a very small coil were moved across the lines of this field there would be no change in the number of lines passing through it during the .major part of its journey ; there would, therefore, be no rate of inclusion or exclusion of lines during this period and no elec- tromotive force. Still, it might be argued that the lines were being cut by the circuit, and this is true, only since both the forward and hinder parts of the coil are cutting the lines simul- taneously and at the same rate, equal electromotive forces are generated in both these portions, and, meeting together, neutralise one another. In the example we are taking, the fluctuations of electromotive force would probably be of a very complicated character, being influenced primarily by the shape of the coil together with the shape and distribution of the field, and secondarily by certain reactions due to the corresponding fluctuations in the induced current. It is important to observe that what is primarily induced in .a circuit by the increase or decrease in the number of magnetic lines embraced by it is electromotive force. The flow of a cur- rent must necessarily follow the generation of such a force in a closed circuit, but it is a secondary effect, and may be reduced indefinitely by increasing the resistance of the circuit. When the current does flow, however, the coil is for the time 'being converted into an electro-magnet, and, if provided with an GENERATION OF ELECTRIC CURRENTS. 143 iron core to assist the passage of magnetic lines, into perhaps a very strong electro-magnet. It was stated by Lenz, as a general law, that in all cases of magneto-electric induction the induced current was in a direc- tion such as to offer opposition to the operation which caused it. We may, therefore, test the effect of this self-magnetisation of the coil by the application of Lenz's law. During the approach of the coil to the position of maximum magnetic induction its faces must be so magnetised as to be repelled, and during its recession in such a way as to be attracted by the adjacent poles of the magnet. The polarity of the faces of the coil is therefore changed at the moment when it begins to exclude the lines after passing through zero E.M.F. at the period of maximum induction. Thus, during the approach, when the effect of the operation is to include more lines within the em- brace of the coil, the effect of its own current is to generate lines in the contrary sense, and so to neutralise some of the lines of the initial field. During the recession, when the operation is to exclude the lines, the effect of the reversed current is to add more lines to the initial field. The effect of current induction is thus not only to reduce the net value of the induced electromotive force, but also to delay its rise and to prolong its fall. The above reaction of a current on the electromotive force is called self-induction. It is often convenient to speak of the electromotive force or of the magnetic field as it would be without the disturbing in- fluences of self-induction, and it is then usual to speak of the impressed electromotive force and the impressed magnetisation. The first attempts to obtain currents of electricity by electro- magnetic induction were made on the lines of the elementary experiment which we have been discussing. Two coils were mounted upon a spindle, and were made to rotate before the poles of a steel horseshoe magnet. This form of apparatus fur- nished currents continually alternating in direction, and is still retained for medical purposes, and also, when separately excited electro-magnets are substituted for the permanent steel mag- net, to generate alternating currents for electric lighting on a large scale at the present day. For many purposes, however, and notably for all electrolytic processes, an alternating current is useless, and some arrange- 144 GENERATION OF ELECTRIC CURRENTS. ment must be made in order to rectify the alternations in the external circuit. In the elementary form of machine above described a very simple commuting device was adopted for this- purpose. In the original form of the machine the free ends of the rotating coils were connected to two independently insu- lated rings of metal rotating with the coils. From these rings the alternating current could be collected by stationary springs or brushes making a rubbing contact on the rings. The free ends of the external circuit wire were then connected to these contact brushes. In order to correct the alternating character of the current from brush to brush in the external circuit, a single ring. FIG. 45. Commutator and Brushes. divided across its diameter was substituted for the two complete rings, and the free ends of the rotating coils were joined one to each half of the divided ring. The position of the fixed springs was now so adjusted as to change their contacts with the two separate portions of the rings at the moment when the direction of the induced current was reversed in the rotating coils. The effect of this arrangement was to furnish in the external circuit a current pulsating in waves between zero and its maximum value, but always in one direction. This form of direct current, although capable of effecting electro-chemical decomposition, was still very objectionable for many purposes on the ground of its pulsating character, and a much nearer approach to the truly continuous currents furnished by primary batteries was needed. In 1864 Pacinotti described a machine in which a number of small bobbins or coils were wound side by side upon a circular GENERATION OF ELECTRIC CURRENTS. 145 iron ring, which was mounted upon a vertical spindle, and was capable of rotation between the poles of a horseshoe electro- magnet. The iron ring thus formed an armature or keeper to the magnet, whose poles were very near the rim. This circumferential rim was provided with radial projections of iron, which served to define the angular spaces in which the coils were wound, and were also of value in reducing the air- gap between the poles of the electro-magnet and the surface of the iron ring. The free ends of the coils were so joined as to form a continuous closed winding in one direction round the FIG. 46. Pacinotti's Machine. ring. At every junction between adjacent coils an electrical attachment was made to a strip of metal which was fixed longi- tudinally on a wooden cylinder; there were thus the same number of metal strips as there were coils or sections in the armature. The width of these strips was so chosen that although perfectly isolated from each other, the space between adjacent strips was very small. Two contact springs were arranged to press upon opposite points of a diameter on this cylindrical collector, the diameter being chosen so that con- tact was made by the springs to ai_y pair of junctions on the L 146 GENERATION OF ELECTRIC CURRENTS. armature winding at the moment when these were midway between the true poles of the magnet. Fig. 46 indicates the general arrangement of the machine. The presence of the iron ring between the poles of the magnet induces the lines of force, which would naturally pass in the most direct manner from pole to pole, to complete their course through the coils by which the ring is overwound. To apprehend the action of the machine, we will first consider the revolution of a single coil from one magnet pole to the other. In its position immediately over one pole the lines of force diverge through it on either side, and, passing through the iron armature core, enter the magnet at the other pole. The impressed lines of force undergo no disturbance, nor do they take part in the movement of the ring during its revolution. The effect, then, of turning a coil on the armature from a posi- tion of rest over one pole, through 180 degrees, or half a revolu- tion, to the other pole, is similar to that which followed the operation of moving a coil through a straight-line magnetic field from a point at which the magnetic induction was zero through the point of maximum induction and out again to zero. In this latter instance we saw that the direction of the induced E.M.F. and current was reversed on passing through the point of maximum magnetic induction. Thus in Pacinotti's ring the reversal occurs in each coil as it passes through the space midway between the poles. In working such a machine, however, the coil does not start from a position of rest above one pole of the magnet, but, on the contrary, this point in its revolution is that in which the rate of change in the number of lines included in its embrace is at its maximum, the rate of change being zero midway between the poles where the induced E.M.F. passes through zero in its reversal. The E.M.F. is therefore in one direction during the half revolution of the coil, on one side between the neutral zones, and in the reverse direction during the completion of its revolution on the other side, and attains its maximum values as the coil passes the poles. If now we consider all the coils on one side the neutral diameter simultaneously, we shall perceive that at any anj every instant an induced E.M.F. in the same direction, but of different values, exists in each one of them, and that these GENERATION OF ELECTRIC CURRENTS. 147 E.M.F.s are summed owing to the fact of the coils being joined in series to form one continuous bobbin. At the same time a similar summation of the E.M.F.s is being continually effected in an opposite direction within the coils on the other side of the neutral line. These two equal and opposite forces collide at the neutral zones, and would there neutralise each other were it not for the connections to the external circuit which are made by the contact of the brushes on opposite strips of the collector on that diameter. As it is, a current is sent through the external circuit between those two points of contact, which is the more nearly continuous as the subdivision of the armature into sections is increased, each section being connected to a separate strip on the collector. This beautiful machine was not recognised by Pacinotti as a generator of current electricity, but was called by him an electric motor. In 1870, however, the machine was re- invented by Gramme for the purpose of generating current by the application of mechanical power. Used as a motor, mechanical power was developed by the rotating ring upon the application of electrical power in the form of current from a large battery. Viewed in this way, it is easy to see that all the coils on either side of the neutral diameter under the influence of magnetic induction resulting from the flow of a current through them would be repelled from one pole of the electro-magnet and attracted by the other, and that, being rigidly connected together by the body of the ring, their respective mechanical moments would be summed and would result in a definite tortional couple about the axis. Thus the dynamo machine is entirely reversible, and may be used with qual advantage as a motor. In 1872, von Alteneck, improving upon an original form of machine invented by Dr. Werner Siemens, produced the so-called Siemens drum winding, in which the coils are wound longitudinally over an iron drum core, and connected together in series and severally to the segments of a col- lector, as in Pacinotti's ring. The principle of this form of machine is identical with that of Pacinotti. In both, the E.M.F.s generated in all the conductors on either side of the neutral line are summed and are directed in parallel through the external circuit. In recent years the design and construc- L2 148 GENERATION OF ELECTRIC CURRENTS. tion of dynamo machinery has reached such perfection that this form of apparatus for the conversion of energy may be truly instanced as the most efficient in existence. The best dynamos to-day are capable of converting from 90 to 95 per cent, of the mechanical energy with which they are supplied into its equivalent useful electrical energy. Such economy in working must naturally demand the almost total absence of local currents in any part of the machine. By far the greatest source of wasteful heating in the dynamos of former years could be traced to the imperfect lamination of the armature cores. When any solid mass of metal rotates in a strong magnetic field local currents are generated in it by the same mechanism as that which induces the main current in the coils of wire wound upon it. The outer portions of the mass of metal which are perpendicular to the lines of force may be looked upon as closed coils cutting the lines in their revolu- tion, and thus becoming the seat of an E.M.F., sending cur- rents eddying round and round in the mass. The heat which might in this way be produced in iron revolving in a strong field is enormous and quite sufficient to destroy the insulation of any wire wound upon its surface. Several devices for over- coming these inherent faults were devised by unscientific makers, such as directing a cold blast upon the armature, making the armature hollow, and providing for a cold water circulation through it, &c. These remedies only removed the worst effects of the fault, but in no way touched the cause thereof. The only effectual way of avoiding this objectionable feature is to build up the armature core of very thin iron plates or wire, so as to ensure electrical discontinuity in directions perpen- dicular to the lines of force. A further condition of high effi- ciency is in working with a very strong magnetic field. It is obvious that the number of coils necessary to produce a certain E.M.F. will be diminished as the density of the field is in- creased, and this consideration lends a still greater import to that of efficient lamination, since the demand for effective lami- nation increases with the strength of the field. The same remarks apply to the speed of driving. An increased speed reduces thf amount of copper on the machine, but it increases the chances of local heating. PRACTICAL DIVISION. SECTION G. ESTABLISHING AND WORKING AN ELECTROLYTIC COPPER REFINERY. THE chief disadvantages of the electrolytic process of refining copper are the great cost of the plant, the continuous period of time during which a large stock of metal remains unproductive of interest, the constant attention required to be paid to the process, and the comparatively large amount of covered space necessary. But notwithstanding these drawbacks, the method is rapidly extending for the refining of argentiferous and auri- ferous copper, because it enables the precious metals in the ore to be completely recovered, w r hilst by the ordinary fusion pro- cess they pass into the refined metal and are partly lost ; the copper also resulting from the electrolytic process may be obtained extremely pure and of high conductivity for electrical purposes, and commands a high price. In planning an electrolytic copper refinery, some of the first questions to be settled are the probable rate of output of refined metal, the quality of the raw copper, and the cost of the me- chanical power, because upon these depend the magnitude of the plant and of all the arrangements. As the proportional amounts of horse-power, of space employed, and the number, arrangement, and size of vats, for a given daily output, differ considerably in different works, only a very crude outline of a general plan can be given (for a brief outline, see p. 224). Amount of Space. A comparatively large covered space is necessary for the refining of a moderate amount of metal. The room occupied at the North Dutch Refinery, Hamburg, for 150 WORKING AN ELECTROLYTIC COPPER REFINERY. refining " 330 tons a year," is stated to be about " 660 square- metres." That of a plant of 40 vats, worked by a "C 18 " dynamo of Siemens and Halske's, at Oker, and depositing " about 350 kilogrammes daily," or 125 tons per annum, "occupies SO 1 square metres," and at Marseilles " 300 square metres " are re- quired to refine 89 tons yearly. At the "Bridgeport Company's" Works, Connecticut, the depositing room is 100 x 120 feet, and is only one-half occupied by vats, in which " one million pounds of copper per month," = 110 tons per week, is deposited. At Stol- berg, to deposit " 10 to 12 cwts. a day," the surface allowed i& "324 square metres." In some works for instance, those at Casarza, near Sestri Levante, Italy the dynamos are in the same room with the vats. In these two latter cases there are- various additional chemical and other processes, which require much extra space (see pp. 230-232). Total Amount of Depositing Surface. The first considera- tion is the total amount of active cathode surface necessary to yield the intended amount of good refined copper in the given time. This depends essentially upon the kind and amount of impurity in the solution (and consequently also upon the kind raw copper which supplies the impurity). It further depends- essentially upon the commercial or economic condition, the rela- ' tive cost of motive-power to that of copper ; where motive- power or fuel is dear or copper is cheap, the total amount of cathode surface employed is large. If the solution contains freely metals which, like bismuth and antimony, are easily thrown down along with the copper, the total cathode surface must be much larger, and the rate of deposition much slower, in order to deposit the given amount of copper in a pure state in the given time. The rate of deposition which enables this result to be obtained, and which is usually employed in different copper-refining works, varies from about 1 to 8 or 10 ounces per square foot in 24 hours (see pp. 207-209). In order to refine about l,8001b. of copper in that period of time, by a rate of deposition of 5 ounces of copper per square foot per 24 hours, 5,760 square feet of active cathode surface would be required. The more impure the solution, especially as regards the above metals, the less must be the rate of deposition per square foot of cathode surface. im of WORKING AN ELECTROLYTIC COPPER REFINERY. 151 With regard to the cost of motive-power, some experiments of M. Gramme's which bear upon the question, confirmed the theoretical conclusion that if we increase the number of vats in series, and at the same time keep the total amount of resistance and strength of current in them constant by en- larging the surfaces of the electrodes in each, the total quantity of copper dissolved and deposited by the expenditure of the same amount of electric energy (and consequently of motive- power) increases directly as the number of vats in series. The following table shows the conditions and results of his experi- ments : Gramme's Experiments, "Third Series" Copper anodes ; Baths in series ; Strength of current constant ; Variable surface of anodes. Number of Experi- ment. Section of Bath in Square Decimetres. Number of Baths. Deflection of Galvano- meter. Kilo- grammes of active Solution. Gramme Weight of Copper Deposited. Toal per hour. Per Bath. 1 8-26 3 7-5 19-8 1575 5-25 2 16-52 5 7-5 33-0 29-00 5-80 3 33-04 7 7'5 92-4 37-38 5-34 4 49-56 9 7-5 178-2 48-00 5-33 5 66-08 11 7-5 280-4 61-6 5-60 The resistance and strength of current were kept constant, as shown by the deflection of the galvanometer, whilst the number of baths in series was increased. The speed of the dynamo and the electromotive force of the current did not vary, and the electric energy expended was unchanged. In order to keep the resistance constant, it was found necessary to increase the section of the liquid and size of the electrodes in a greater ratio than the number of vats joined in series. The total quantity of copper deposited was directly propor- tional to the number of baths. From this it may be concluded that with electrodes of unlimited surface, in an unlimited num- ber of vats in series, a constant and limited amount of current energy would deposit a comparatively unlimited amount of cop- per. " The results show that with soluble anodes the expendi- ture of energy in the act of electrolysis is nil." M. Theuard 152 WORKING AN ELECTROLYTIC COPPER REFIXERY. has made somewhat similar experiments, and obtained similar results. In some cases, therefore, where motive-power is ex- pensive, as in those where coal is dear and water-power is not available, a larger total surface of anode and cathode and slower rate of deposition have been employed (see pp. 188, 191, 208). We must, however, remember that whilst by doubling the number of vats in series and doubling their size, we nearly double the quantity of copper deposited by the same amount of energy in the same time, we simultaneously quadruple the out- lay in solution, copper, and vats, and soon arrive at a point at which the increased loss of interest upon that outlay balances or even exceeds the saving of cost of motive-power required to produce the electric current. Number and General Magnitude of Vats. Having decided upon the total amount of receiving surface, we now require to determine its mode of distribution, i.e., into how many portions the cathode surface shall be divided 1 into many small vats or a few large ones ? and whether the vats shall be in single series or parallel ? So long as the total amount of cathode surface and same density of current per square foot are maintained, the same amount of electric energy (and therefore of horse-power) will deposit the same quantity of copper per day, whether the vats be few and large or many and small ; in the former case, however, the current employed has great strength with low elec- tromotive force, and in the latter the reverse. The number and size are largely decided by the risk of accidental short-circuiting in any one of them, and in case it occurred the number should be such that not more than 1 or 2 per cent, of the electric energy would be wasted ; in some works two sets of vats of 20 each, in others a single series of 60, and in others two series of 120 each, have been used to deposit from 1,600 to 2,0001b. of copper every 24 hours. The two latter only of these arrange- ments fulfil the above condition. Large vats and electrodes are very inconvenient both to manage and inspect (see also pp. 187, 191). With a small number of large vats in series it is difficult to detect losses of current due to leakages and short circuits ; and with a large number the loss of interest uponl capital is too great unless it is compensated by greater saving in cost of motive-power or fuel. WORKING AN ELECTROLYTIC COPPER REFINERY. 153 From the total amount of active cathode surface and the total number of vats is determined the amount of surface of anodes and cathodes in each vat, and from the latter and the distance asunder of the electrodes the general magnitude of each vat is arrived at. If the number decided upon is 60, and the rate of deposition 5 ounces per square foot per 24 hours, then the total amount of active cathode surface in each vat to give the 1,800 Ibs. is . = 96'0 square feet; if the number of vats is 60 doubled the amount of surface in each must be halved. Electromotive Force and Strength of Current Required. From the numberof vats in succession (or alternations in the series if a double row of vats in parallel is used), and the amount of re- sistance in each, including that due to polarisation or counter- electromotive force, the difference of potential required at the terminals of the dynamo is found ; and from the number in series and the weight of copper to be deposited daily in each, the strength of current necessary is ascertained. The amount of electromotive force allowed for the resistance in each vat or alternation in the series varies in different works, but to provide for the maximum of occasional and variable counter-electro- motive force of voltaic polarisation, and for producing the maximum density of current required for quick working, a total of "3 to 1 volt per vat is allowed in some refineries. As an example : at Pembrey, to deposit 4,0001bs. of copper each 24 hours; in a single series of 200 vats, a dynamo yielding 350 amperes at an electromotive force of 110 volts is employed, and is driven by about 65 indicated horse-power from a steam- engine. Kinds of Dynamos Employed. In different electrolytic metal refineries, dynamos of the following kinds are or have been used : At Messrs. Elliotts' (late Elkington's), Pembrey, near Swansea, formerly Wilde's magneto, then Gramme's and Wilde's improved machines, but recently only those of Messrs. Chamberlain and Hookham ; at Messrs. Bolton's, Mersey Cop- per Works, Widnes, Siemens's and El well-Parker's ; at Messrs. Vivian's, Swansea, Elmore's, Gulcher's, Cromptou's, also Edison- Hopkinson's, made by Mather and Platt, Manchester; at 154 WORKING AN ELECTROLYTIC COPPER REFINERY. Williams, Foster and Co.'s, Swansea, Elmore's, and subsequently Crompton's; at C. Lambert and Co.'s, Swansea, Siemens and Halske's, Gulcher's, also Edison-Hopkinson's ; at Messrs. Seaver and Kleiner's, Tyldesley, Lancashire, for separating aluminium from cryolite, Edison-Hopkinson's, also Siemens's ; at the Cowles Syndicate Company's Works, at Milton, near Stoke-upon-Trent, Brush, made by Crompton ; at M. Letrange's, and MM. Lyon Allemand's, Paris, and M. Secretan's, St. Denis, Gramme's ; at M. Hilarion Roux's Works, Marseilles, Gramme's, made by Mather, Hartford, Connecticut, U.S.A. ; at M. Weiller's, Angouleme, and MM. Oeschger, Mesdach and Co., Biache, Saint Waast (Pas de Calais), Gramme's ; at the North Dutch Refinery, Hamburg, Gramme's ; at the Stolberg Company's, Stolberg, Westphalia, Siemens and Halske's; at Messrs. Heckrnan's, Berlin, and Kayser and Co.'s, Moabit, near Berlin, Siemens and Halske's ; at the " Kommunion Hiittenwerke," at Oker in the Hartz, Siemens's ; at the Mansfeld Mining Company's, Eisleben, and Messrs. Stern and Co.'s, Oker, Wilde's ; at Messrs. Schrieber and Co.'s, Burbach, near Siegen, Siemens's ; at M. Andre's,, Frankfort-on-the-Maine, Gramme's ; at the Aluminium Com- pany's Works, Schaffhausen, for preparing aluminium bronze by M. Heroult's process, Oerlikon dynamos ; at Stattbergerhiitte,, near Cologne, the Koenigshiitte, in Silesia, the Hiittenwerke, Witkowitz, in Moravia, Stephanshiitte, in Upper Hungary, and at the Royal Hiittenwerke, Brixlegg, in the Tyrol, Siemens and Halske's ; at the works of the Electro-Metallurgical Society of Turin, Ponte St. Martino, Piedmont, Oerlikon dynamos ; at those oi the Electro-Metallurgical Society of Genoa, Casarza,. near Sestri Ponente, Italy, Siemens and Halske's ; at the Penn- sylvania Lead Company's Works, Pittsburgh, U.S.A., Brush dynamos; by the "American Aluminium Company of Mil- waukee," Wisconsin, Gramme's, made by Mather of Hartford, Connecticut ; at the St. Louis Smelting and Refining Company's Works, Cheltenham, St. Louis, Mo., Hochhausen's ; at Messrs. E. Balbach's Refinery, Newark, New Jersey, Hochhausen's, made by the " Excelsior Electric Company," of Brooklyn ; at the Electrolytic Copper Company's Works, Ansonia, Connecticut, Mather's, made by the "Eddy Manufacturing Company" of Hartford, Connecticut; at the "Omaha and Grant Smelting IVorks," Omaha, Nebraska, Hochhausen's ; at the " Bridgeport WORKING AN ELECTROLYTIC COPPER REFINERY. 155" Copper Company's Works," Bridgeport, Connecticut, Mather's ;. at the "Cowles' Electric Smelting Works," Cleveland, Ohio, and Longport, near New York, Brush dynamos; at M. Logger's Works, Santiago, Chili, Gramme's ; at M. Moebius's, Chihuahua, Mexico, Siemens and Halske's. In a large electrolytic refinery a considerable number of dynamos are usually employed ; for instance, at the Casarza establishment, there are no less than 30 of Siemens and Halske's, and at the works at Pembrey 32 of Wilde's were formerly used. In nearly all the works, changes in the kind of dynamo used have had to be made in consequence of im- provements in those machines. A single dynamo now deposits/ 7 15 tons of copper per week at Pembrey, and one at Bridgeport Connecticut, deposits more than 30 tons per week. Dynamos of Different Makers. The following are some of the chief kinds which have been used for the commercial refin- ing of metals : Wilde's. A number of Wilde's separately-excited small ones of the magneto kind were originally employed at Messrs. Elking- ton's works at Pembrey. The armatures of the exciter rotated 2,400 and of the dynamo 1,500 times a minute. They gave alternate currents, which were rectified by means of a commu- tator. These machines became much heated after a few hours' working, and had to be cooled by circulating cold water through them, and by switching on cool ones in their stead at intervals of time. They did much work, but with considerable waste of energy, and are now quite out of date. An improved machine was brought out by Wilde in 1867. It consisted of two circular sets, each of 16 soft iron field- magnets, with their free ends facing each other, each set being attached at their outer ends to a fixed soft iron ring. Between these rotated a circle of 16 bobbins of wire with soft iron cores, constituting the armature, the coils of one or two of these being used to excite the field-magnets, and the remainder connected in parallel to generate the external current which worked the vats. It was provided with two separate commu- tators, one for rectifying the currents of the field-magnets, and the other for correcting those of the armature. There were five of these machines at Pembrey, and five series of vats, each. 156 WORKING AN ELECTROLYTIC COPPER REFINERY. of 48 in single order, each dynamo working one series, and de- positing "324 kilogrammes of copper daily." This machine was a great improvement upon the previous type, and did good -service, but still produced much heat ; Chamberlain and Hook- ham's dynamos, a description of which is given on page 167, are now used at these works. Wilde's machines have also been employed by the Mansfeld Mining Company at Eisleben, 'Germany, and at Messrs. Stern and Co.'s, Oker. According to a statement of the Electric Engineering Com- pany, of Manchester (successor to H. Wilde), his 32-magnet dynamo is capable of depositing in 138 vats in single series >each vat having 40 square feet of active cathode surface, and 'the same amount of anode surface a total of 9001bs. of copper per 24 hours, with a consumption of 12 to 13 horse-power. The Siemens and Halske Dynamo. One of these, of the '"C 1 " type (see Fig. 47) series-wound, with specially thick con- ductors, has been in use in the Kommunion Huttenwerke at Oker, in the Hartz, since about the year 1878, and two have been ^added since. The armature is a cylinder, with the Hcfner- Alteneck system of winding (see Proc. Institution Civil En- .gineers, 1878, Vol. LIL, p. 39, Plate 1 ; also S. P. Thompson's "Dynamo-Electric Machinery," second edition, pp. 152, 238). It has a single layer of conductors of thick bars of copper laid lon- gitudinally upon its outer surface only, insulated by means of asbestos, and with air-spaces between them for ventilation and -cooling. Each of the four rectangular limbs of the two field- magnets is formed of seven square bars of soft iron, bolted to a thick yoke of iron at the back, and has coiled upon it a single layer of seven turns of insulated thick copper conductor, each turn having a section of 13 square centimetres. The junctions of all the conductors are bolted, and soldered together with -silver solder. The collecting brushes are very solidly mounted. The internal resistance is only -00075 ohm, the electromotive -force is about 3 '5 volts, and the strength of current about 1,000 amperes. The machines become much heated, but are not in- jured by the heat, after running day and night for 10 years. Notwithstanding the dynamos are close to the vats, and the conductors are 25 square centimetres in section, the latter become sensibly warm. Each dynamo supplies 12 large vats, arranged in series, and refines about 1 "2 kilogramme per hour per vat, or WORKING AN ELECTROLYTIC COPPER REFINERY. 157 \ 158 WORKING AN ELECTROLYTIC COPPER REFINERY. 350 kilogrammes ( = 7711bs.) of copper per 24 hours, with an expenditure of 5 horse-power. The total resistance of the baths and conductors is -0035 ohm. These machines are still in use, and the commutator of the first machine is not yet worn out. FIG. 48. The Siemens " H C " Type Dynamo. At the Casarza Works 30 of Siemens' "C 18 " vertical direct- current dynamos, shunt-wound, are used for separating copper from crude matte of iron and copper pyrites. The armature of each of these rotates about 1,000 times a minute, and yields either 30 volts and 120 amperes, or 15 volts and * 240 amperes, and in the latter case, with 12 vats in single series, and an external resistance of *0625 ohm, deposits about 1801bs. of copper every 24 hours, some of the power being WORKING AN ELECTROLYTIC COPPER REFINERY. 159 wasted in deoxidising persalt of iron in solution. This im- proved kind of dynamo is also employed at the " Koenigs- hiitte," in Silesia, and in the "Hiittenwerke," at Witkowitz, Moravia, and is now used in preference to the " C 1 " type, in the Hiittenwerke, at Oker, where it deposits in 40 vats in single series "about 350 kilogrammes ( = 77 libs.) of copper every 24 hours." Messrs. Siemens and Halske's "C 1 " dynamo is also used by Kayser and Co., Moabit, near Berlin, and their 4 ' C 2 " machine by M. Schrieber, at Burbach, near Sicgen, Prussia ; others also for refining black and red copper of 90 per cent., at Stephanshiitte, Upper Hungary, and for refining 300 kilogrammes of silver daily at the works of Messrs. Moebius, at Chihuahua, Mexico (see p. 241). The following is a list of the most recent shunt -wound dynamos made by Siemens Bros, and Co. for electro-deposition. Fig. 48 shows their " H C " type : Type of Machine. Maximum C itTeilt ill amperes. Difference of potential iu volts. Number of revolutions per minute. Horse-power required. c c c 150 6 1,200 H CN 75 15 920 o C 7 300 8 1,180 4 C 8 240 25 850 9| HC 300 50 750 21 HC 10 500 GO 700 47 HC 11 1,000 CO 050 93 The Gramme Dynamo. The only works in which Gramme machines are used upon a large scale for the refining of copper are those of the North Dutch Company, at Hamburg; M. Mesdach, at Btache ; and M. Leggers, at Santiago, Chili. They have, in addition, been experimentally employed for separating or refining metals, by M. Letrange in Paris, M. Roux at Mar- seilles, M. Secretan at St. Denis, M. Weiller at Angouleme, M. Heroult at Schaffhausen, and others. At the North Dutch Refinery, Hamburg, there are six of the "No. 1 " type (see Fig. 49), working at a maximum speed of 1,500 revolutions a minute, and giving a maximum current of 300 am- peres at 27 volts. The motive energy is derived from a " 40 horse- power steam-engine." When used for refining copper they are 160 WORKING AN ELECTROLYTIC COPPER REFINERY. provided with a special armature of cylindrical shape, having a single layer of thick copper rod conductors upon its outer surface only. "Two of these dynamos, connected in tension, operate upon two sets of vats of 120 each, each set being in single series, joined in tension, and deposit a total of 900 kilogrammes in 24 hours; the mechanical energy expended being 12 horse- power, which equals 80,000 kilogrammetres per kilogramme of copper deposited." FIG. 49. The Gramme "No. 1" Type Dynamo. There is also used at those works a larger and much more powerful machine of the same kind, constructed specially for Dr. Wohlwill in the year 1873 (Fig. 50). It is 1-5 metre long, 1 metre high, '75 metre wide, and weighs about 2,500 kilo- grammes, of which 735 are copper, and the remainder iron. It has four single cylindrical horizontal iron bars of 12 centimetres diameter, bolted to the massive iron end-plates of the machine ^ these form eight electro-magnets, each 41 centimetres long. On each of these magnets is wound, in 32 turns, a ribbon of WORKUNG AN ELECTROLYTIC COPPER REFINERY. 161 162 WORKING AN ELECTROLYTIC COPPER REFINERY. sheet copper, !! millimetre thick, and of the same width as the length of the magnet, the eight coils being connected in series with the main circuit, and offering a total resistance of '00142 ohm. The " ring " armature is in the form of a short cylinder. The conductors upon it are divided into 40 sections or partial coils, each section being composed of seven strips of copper, 10 millimetres wide and 3 millimetres thick. The machine has two collectors, with brushes, one at each end of the armature, each collector having 20 sections. Twenty of the partial coils are connected to the right-hand collector, and the other 20 to the left-hand one. The total resistance of the armature con- ductors when connected in series is '0004 ohm, and when in parallel '0001 ohm ; in the former case, with a speed of 500 revolutions a minute, the electromotive force is 8 volts and strength of current 1,500 amperes, and in the latter 4 volts and 3,000 amperes. It supplies 40 baths, in two parallel series of 20 each, and deposits 800 kilogrammes of copper every 24 hours, with a consumption of 16 horse-power. This result is inferior to that obtained with the smaller dynamos. It is stated that at this refinery 500 tons of copper are elec- trolytically refined each year, and that the deposited copper is exceptionally pure. (United States Geological Survey, " Mineral Resources of the United States," by A. Williams, 1883, pp. 225, 644, and 1884, p. 369, published at the Government Printing Office, Washington.) At M. Hilarion Roux's works, Marseilles, "a Gramme 'No. 1* dynamo, with its armature revolving 850 times a minute, yielded a current of 300 amperes and an electromotive force of 8 volts, .and with 40 vats deposited 10'4 kilogrammes of copper per hour, with an expenditure cf 5 horse-power and a daily consump- tion of 240 kilogrammes of coal." Several Gramme machines were formerly used at Pembrey. The Brush Dynamo. Used by the Pennsylvania Lead Com- pany, Pittsburgh, U.S.A., for refining lead ; also by Messrs. Cowles and Co. for separating aluminium, silicon, &c., in the form of alloys. An enormous one has recently been employed for this purpose at Longport, near New York. It is 15 feet long, 5 feet high, and 4 feet wide, and weighs about 9J tons (Fig. 51). ft is compound-wound, and yields direct currents. It has eight iield-magnets, each with a cylindrical core of cast iron 16in. WORKING AN ELECTROLYTIC COPPER REFINERY. 163 Ufiiiiih I, 164 WORKING AN ELECTROLYTIC COPPER REFINERY. long and 11 in. diameter, and wound with 30 layers of 102 turns each of single copper wire *134in. ( = 3*404 millimetres) dia- meter; all the eight wires are coupled in multiple arc, and have, when thus combined, a total resistance of 1 ohm when cold. The magnet coils take a current of 80 amperes, or about 2'5 per cent, of the total current. The armature is 42in. diameter, contains 1,600 pounds of wrought iron, and has 16 bobbins ; each bobbin has 21 turns of copper wire, 65ft. long and *35in. diameter, in two parallel strands, wound upon it ; the bobbins are all in multiple arc. Sixteen copper bars convey the currents from the bobbins to the commutators. The weight of copper on the magnets is 5,4241b., and upon the armature 8251b. It is stated to yield, at a speed of 450 revolutions a minute, and with an expenditure of nearly 400 indicated horse -power, an electromotive force of 80 volts, and a strength of current of 3,200 amperes, or 249,000 watts of energy, and to be capable of yielding 300,000 watts. It is driven by two 30in. turbines^ and absorbs 355 horse-power. (See The Electrician, Oct. 15th, 1886.) More recently, Messrs. Crompton and Co., of Chelmsford, have constructed for the Cowles Syndicate, at Milton, near Stoke-upon-Trent, another of these colossal machines (Fig. 52), yielding 5,000 amperes, having a gua.ranteed minimum working capacity of 300,000 watts, and intended for separating the above refractory metals. (The Electrician, Vol. XXI., p. 590.) The Edison-Hopkinson Dynamo. A 50-unit machine made by Mather and Platt, Salford Ironworks, Manchester. In use by Messrs. Vivian and by C. Lambert and Co., Swansea. Two of 90 horse-power and one of 60 were in use at Dr. Kleiner's Aluminium Works, Tyldesley, for separating aluminium (Fig. 53). The bar armature type machine weighs about 5J tons, and its magnets and pole-pieces are solid forgings of specially high quality of soft iron. The core of the armature is composed of about 1,000 discs of very thin charcoal iron, insulated from each other by thin sheets of paraffined paper. The machine is shunt-wound; the conductors on the field-magnets consist of 520 pounds of copper wire, and have a resistance of 3*74 ohms. Those on the armature are formed of 74 wedge-shaped bars of drawn copper, each of '338 square inch sectional area, insulated from each other by "a special tape," and having a total resistance of 166 WORKING AN ELECTROLYTIC COPPER REFINERY. 0-016 ohm at 13'5C. The commutator is formed of copper bars, insulated with mica, and has five separately adjustable FIG. 53. The Edison-Hopkinson Dynamo. spring brushes on each side. At a speed of 400 revolutions a minute the machine gives 50 volts and 1,000 amperes. The electrical efficiency of the machine is between 95 and 96 per WORKING AN ELECTROLYTIC COPPER REFINERY. 167 cent., and the commercial efficiency " between 93 and 94 per cent.," meaning by the term " commercial efficiency " the ratio of the electrical power in the external circuit available for use- ful work, to the mechanical power absorbed by the machine. The Chamberlain and Hookham Dynamo (Fig. 54). A num- ber of these machines are used by Messrs. Elliott and Co., Pem- brey. "The 30-unit machine (or 25-unit nominal) weighs 25 cwts.; it is shunt-wound and its armature and pole-pieces are magnetically well isolated from the iron framework. The field magnets have a cross-sectional area of 42 square inches, with yokes and pole-pieces of cast iron ; they are wound with 2,856 turns of -109in. copper wire, having a total resistance of 8 ohms when hot; the amount of current shunted through this wire is 7*13 amperes. The armature is cylindrical, 13in. long and lOin. diameter, and built up of notched discs of very thin sheet iron and paraffined paper. It has 35 longitudinal slots and projections (like those of the Pacinotti ring), each slot being slightly oblique to the axis, in order to diminish singing vibrations, and containing 12 insulated wires in parallel, having a total resistance of *003 ohm when hot. The entire length of wire on it is about 53 yards, or 32ins. per volt generated. At a speed of rotation of 900 per minute, the machine yields a cur- rent of 450 amperes at 57 volts. The total amount of energy converted is 26,635 watts, equal to 9'5 watts per pound weight of material in the machine; 610 watts are absorbed in the arma- ture conductors, thus giving a loss of 2'28 per cent. ; there is also a loss of 373 watts, or 1*4 percent., in the wires of the magnets. The electrical efficiency is 96 '3 per cent., and the commercial efficiency is about 94 per cent. The total weight of the machine is in the proportion of 82 pounds per electrical horse-power developed in the external circuit." " The 60-unit machine for electro-depositing has an armature 25in. long and lOin. diameter. At 820 revolutions a minute, it yields 110 volts and 350 amperes, and deposits 4,000 pounds of copper per day of 24 hours, or 20 pounds per vat in 200 vats. The 30-unit machine at 900 revolutions gives 55 volts and 350 amperes, and deposits 2,000 pounds of copper per day of 24 hours, or 20 pounds per vat in 100 vats." One of the 60- unit machines is stated to have deposited 18 tons per week. These machines are only worked up to 70 per cent, of their full WORKING AN ELECTROLYTIC COPPER REFINERY. WORKING AN ELECTROLYTIC COPPER REFINERY. 169 capacity, in order to obviate undue heating. One of the former and five of the latter, including a spare one, are used at a single works. The Elwell-Parker Dynamo. The largest machine of this type hitherto made is a 75-unit machine, with four poles and two horizontal wro light-iron magnets (Fig. 55). It is plain shunt- wound, and has an armature of the drum type 22in. diameter and 20in. long, having a core of thin sheet-iron discs mounted upon the shaft, and 80 parallel copper wires on its surface, each of *2 square inch area of section, and having a total active length of 1,600 inches, or about 47 per cent, of the total length. The resistance of these wires is '0008 ohm when cold, and of those upon the magnets 1'25 ohm. The loss of energy in the armature is 1,800 watts, and in the magnets 2,000 watts, vlt is stated by the makers to yield a current of 1,500 amperes, and a difference of potential of 50 volts, when revolving at a peripheral speed of 2,500ft., or 500 times a minute, by an expenditure of 94 approximate belt horse-power, and to have an electrical efficiency of 95'1 per cent., and a commercial efficiency of over 90 per cent., without sparking at full load. The density of current in the armature wire with this load is equal to 1,880 amperes per square inch sectional area of wire. Its general dimensions are, 8ft. 2in. long, 6ft. wide, and 3ft. Sin. high. Its weight is about six tons, equal to about ISOlbs. per horse-power of electrical energy developed in the outer circuit. Three of them are in continual use, run- ning day and night, usually about 160 hours per week, at the Mersey Copper Works, Widnes, Lancashire. (The Electrician, Vol. XXI., p. 183. Esson's " Dynamo-Electric Machines," 1887, p. 288.) It should deposit 11-44 tons of copper per 156 hours, in a single series of sixty vats, when running at the above speed. The 50-unit machine is a two-pole one, with vertical electro- magnet, and a drum armature, giving " 50 volts and 1,000 amperes." "The resistance of its armature coils is -0023 ohm, and of the magnet coils 3-72 ohms. The loss of energy in its armature is 2,300 watts, and in the magnet 675 watts. Its electrical efficiency is 9 4 -3 per cent., and its commercial efficiency over 90 per cent.; length 9ft., width 2ft. lOin., height 3ft. 4in." 170 WORKING AN ELECTROLYTIC COPPER REFINERY. WORKING AN ELECTROLYTIC COPPER REFINERY. 171 The Giilcher Dynamo. Several of these are used at C. Lambenj and Co.'s., and Messrs. Vivian's works, Swansea. The machine (Fig. 56) is composed of two sets each of four soft-iron field-mag- nets, each set being arranged in a circle and fixed at their outer ends to a cast-iron end-plate forming the yoke, with their inner ends facing each other, and having hollow box-shaped pole- pieces of cast iron fixed upon their ends, within which the arma- ture revolves. Each alternate bar has opposite polarity, and each opposing magnet similar poles, and they are all shunt- wound. The armature has the appearance of a flat ring or disc, and is formed of a gun-metal wheel, having a JL-shaped rim, in the angles of which are wound two continuous ribbons of soft iron insulated by asbestos paper. This composite ring is turned true and its angles rounded, and the insulated conductor wound at right angles upon it in one or two layers of continuous sec- tional coil (as in a Gramme ring) covering its entire surface. It thus forms a kind of fly-wheel revolving between the two circles of magnets, and within their hollow pole-pieces, and from its form, construction, &c., is well ventilated. Its axle has massive bearings. The collector, and its connections with the armature coil, are like those in a Gramme machine ; it is very substan- tially formed of hard-drawn copper bars, insulated with talc. 4- Pole Giilcher Dynamos. Units. Amperes. Volts. Vats in series. Square feet of cathode surface per vat. Brake at pulley. Horse- power. Pound? of copper deposited per hour. Revolu- tions per minute. 2 3 5 200 300 500 10 10 10 20 20 20 20 30 50 ? H 10 15 25 1,500 1,200 1,000 10 12 15 20 25 500 500 500 500 500 20 24 30 40 50 40 48 60 80 100 50 50 50 50 50 17 20 25 35 40 50 60 75 100 125 800 750 600 550 450 " These machines are made of two types, viz., No. 4, yielding a current of 700 to 800 amperes at a difference of potential of 20 volts, with an electrical efficiency of 93 per cent., and com- mercial efficiency of 87 per cent., and No. 6, giving 500 to 600 WORKING AN ELECTROLYTIC COPPER REFINERY. 173 amperes at 50 volts, with an electrical efficiency of 94 per cent., and commercial 89 per cent. The latter size is designed to work 100 vats in single series, each vat being 3Jft. long, 3ft. wide, and 3ft. deep, and containing 50 square feet of cathode surface, equal to a density of current of 10 amperes per square foot of depositing surface." The foregoing table is the maker's list of these machines ; the five larger sizes only are used for refining, and the smaller ones for plating. The Oerlikon Dynamo (Fig. 57). Made at Oerlikon, Switzer- land. This is a shunt-wound machine, and has a capacity of FIG. 57. The Oerlikon Dynamo. 50,000 watts ; five similar ones are employed by the Societa Elettro-Metallurgica of Turin in their refinery at Ponte St. Martino, Piedmont. Its total weight is 14,7001bs., its electrical efficiency 95 per cent., and it yields a current of 400 amperes at a potential of 120 volts. The resistance of the field-magnet coils is 11-1 ohms, and of the armature coils -0075 ohm. A current of 10 '36 amperes flows through the coils of the field-magnets. After 14 hours continuous running with full load, the following fixed temperatures were attained: Armature, 140 Fahr.;. field-magnets, 85 Fahr. (The Electrician, 1887, Vol. XIX:, 174 WORKING AN ELECTROLYTIC COPPER REFINERY". pp. 291, 306). Two more, each yielding 6,000 amperes at 16 volts, are constructed for separating aluminium at Schafifhausen by M. Heroult's process (p. 258). The Jfochhausen Dynamo (Fig. 58). This dynamo has a closed-coil armature in the form of an elongated ring, made of four separate curved frames of iron, carrying the previously FIG. 58. The Hochhausen Dynamo. wound coils, and bolted to massive end-plates. It nas two ver- tical field-magnets, one above and the other below the armature, the upper end of the former being bolted to and supported by two vertical curved frames of iron, one on each side, fixed to the bed-plate of the machine. The segments of the collector are very massive, with air-spaces between them, and are bolted t<^ a thick disc of slate (Fig. 59). This dynamo is made by the "Excelsior Electric Company " of New York city, and is stated WORKING AN ELECTROLYTIC COPPER REFINERY. 175 by its inventor to have a commercial efficiency of " about 85 per cent." " Five of these machines, viz., three * No. 7 ' and two 'No. 6,' are used at the works of Messrs. Edward Balbach and Sons, Newark, New Jersey, and deposit altogether 60 tons of copper per week, running day and night, Sundays included. Each 'No. 7' dynamo deposits 2'1 tons per day in 48 vats in series. Each * No. 6 ' deposits 1 ton per day, one of them working 12 large vats and the other 60 small ones. At the St. Louis Smelting and Refining Company's works, Chel- tenham, St. Louis, Missouri, a 'No. 7' deposits 14 tons of copper per week in 48 vats ; and at the Omaha and Grant FIG. 59. Hochhausen Collector. Smelting Works, Omaha, Nebraska, a 'No. 6' operates 48 small vats, and has a capacity of depositing 7 tons of copper per week. Each ' No. 6 ' is driven by a 25 horse-power high speed Westinghouse steam-engine, and each 'No. 7' by a 50 horse power engine of the same kind." The Mather Dynamo (Fig. 60). This dynamo, as con- structed by " The Eddy Electric Manufacturing Company," of Windsor, Connecticut, has been made up to a size of 65 horse- power, for the purpose of refining copper, WORKING AN ELECTROLYTIC COPPER REFINERY. Tats, connected in single series, arranged in two double rows of 25 each, each set being worked by a 30-unit dynamo ; and .a separate 50 vats in single series, worked by a 5-unit dynamo, for making cathodes. At Biache there were " 40 vats in single series." In the North Dutch Refinery at Hamburg '240 tanks in two series of 120 each," worked by the current -from two dynamos connected for tension ; also 40 vats in two series of 20 each, worked by a single dynamo (see p. 160). At Casarza each dynamo works 12 vats in single series (see Fig. 62). At Oker, with the " C 1 " type of Siemens and Halske's dynamo {see p. 157), there are 12 large vats in series, and with the ti QIS dynamo, 40 vats in single series. One writer (Dr. Higgs) .-speaks of as many as " 1,500 depositing cells " being used, by which, with one dynamo, " as much as three tons of copper Lave been deposited daily;" also of "one set of 327, placed 109 in series and 3 in multiple arc." The Ansonia Copper Company work from 30 to 75 (usually from 50 to 60) vats in single series, with each dynamo of 30,000 watts, yielding -300 amperes at 100 volts, and " are under contract to deposit 400,0001bs. of copper per month." The Electrodes. The sizes of anodes and cathodes are chiefly determined by convenience in handling, and as the anodes are thick and heavy, they are in some refineries much smaller than the cathodes. The number of electrodes in each vat varies greatly in different refineries; a usual number in this country is eight anodes and nine cathodes. At Pembrey each vat contained "16 anodes and 10 cathodes;" at present there are in each vat practically five anodes and four cathodes, each anode being formed of four separate pieces about eight inches wide and two feet deep, suspended edge to edge. In the establishment at Biache as many as 88 anodes and 69 larger cathodes were employed in each vat, the anodes and cathodes having about an equal total amount of active surface, and in other works only 10 cathodes per vat. At Casarza each vat contains 15 anodes and 16 cathodes ; at Marseilles "115 plates in each vat." In some works the anodes are numerous and narrow, about '15 to '175 metre wide; whilst in others they '.are '5 metre or more. At Biache there were 22 rows of anodes 4 in a row, and 23 of cathodes 3 in a row. One difficulty, both WORKING AN ELECTROLYTIC COPPER REFINERY. 185 with single wide electrodes and with several narrow ones suspended side by side, is to keep the anodes and cathodes sufficiently parallel to each other, which is one of the chief conditions for obtaining deposits of uniform thickness. The average distance of the electrodes asunder varies in different refineries from 5 to 9 centimetres; at Biache it is 7 centimetres, at Hamburg 6*3, at Pembrey 6*0, at Marseilles 5 centimetres, and it should not be less because of impurities from the anodes getting upon the cathodes, also because of the risk of mutual contact and short-circuiting. These effects occur, sometimes by fragments of the anodes falling over, at other times by rapid growth of nodules of copper upon the cathode, especially when the current is extra dense. The general arrangement of the electrodes is shown in the annexed sketches working day and night, when depositing thirty tons of copper per week, to manipulate the electrodes, examine the vats, and attend to the steam-engine and dynamo, melt and cast anodes, wash dirty ones, tfcc. A chemical analyst is also em- ployed to analyse the copper and the electrolyte. As stoppages in the process do not often occur, they are not a large element of expense ; there is, however, the cost of occasional emptying the vats, evaporating and purifying the solution, collecting and treating the mud, s -4 Su2phtite of Residues of of sulphur \ of Gre&n/ V?_^7"7./?Z' FIG. 78. Diagram Plan of Marchese's Process. of effectual current ; some of the excess of current is expended in reducing persalt of iron. Each vat contains 15 anodes and 16 cathodes. Each anode is 32in. long, 32in. wide, 1^-in. thick, and weighs 1761bs. The anodes rest upon two wooden bars fixed upon the bottom of the vat. Each cathode is 28in. long, 28in. wide, and ^ T in. thick% The total amount of active cathode service in each vat is 163-33 square feet, or 19,600 square feet in 12 vats ; and the EXTRACTION OF METALS FROM MINERALS. 233 density of current is nearly 1'84 ampere per square foot. " For a good circulation the vats must be arranged in the form of a cascade, the fall of each being about *15 per cent. They are arranged in series of six." Every anode is cast with two strips of sheet copper to serve as connectors, which are inserted in the fused liquid matte at its upper end and become fixed on cooling. Many anodes break during the cooling : the best means of preventing this is by using a matte containing from 20 to 25 per cent, of copper, and cooling the mass very gradually and uniformly, sheltering it from the air. The anodes contain metallic iron, and consequently acquire a coating of copper when immersed in the electrolyte. The presence of this iron makes them electro-positive to copper, and assists the current, so that only about 1-0 volt per vat has to be provided. In order to protect the suspending strips from corrosion, the upper ends of the anodes are kept about three- quarters of an inch above the liquid. All the sulphur of the anodes is either recovered in the elementary state or is used for making sulphuric acid. The electrolytic action corrodes the anodes freely, and external layers of impurity (sulphur, oxides, sulphides, tkc.), which can be easily separated, gradually accumulate all over their immersed surfaces. Analysis has shown that the outer- most layers contain as much as 85 per cent, of sulphur, and are the richest in that ingredient. -The separated sulphur, being very porous, does not much increase the resistance. The remains of the anodes are either treated for separation of their sulphur, or they are put into the reverberatory furnace again. The cathodes are changed when the deposit upon them has become " '5 centimetre " thick : this requires about 12 weeks, equal to a rate of deposition of 1'84 ampere per square foot. The free sulphuric acid in the electrolyte prevents iron being deposited along with the copper, the proto-salt of iron in solu- tion prevents liberation of oxygen at the anode, and the persalt of iron, of which there is always some present, prevents evolution of hydrogen ; the reduction of this persalt however costs energy. The deposited metal is stated to be " chemically pure." By washing the roasted matte with dilute sulphuric acid, " a solution was formed containing as much cupric sulphate as was required to render the ferrous sulphide of the anode useful for 234 EXTRACTION OF METALS FROM MINERALS. the electro-deposition of the copper salt." The electroiyt* when newly made, contains about 4 to 5 per cent, of copper, and the copper which is continually extracted by electrolysis from it is constantly renewed by the circulation of the liquid over the rich regulus ; but as it also continually takes up iron from that regulus, the sulphate of iron in it gradually accumu- lates, until, after having been used about two or three months, the quality of the deposited copper begins to deteriorate ; the copper in it is then reduced by deposition to about *1 per cent., and the liquid removed. The impure liquid contains a large amount of ferrous and ferric sulphate and free sulphuric acid. The residue of copper in it is precipitated by sulphuretted hydrogen, as already described. The mud which settles to the bottom of the electrolysing vats contains sulphur, oxides and sulphides of iron, lead, and copper ; also the silver. If it contains much copper it is roasted over again. According to Badia, " If the sulphides in the anode contain as much copper as iron, half the current will pass through the copper, and half through the iron (see pp. 92-94). The half that passes through the copper sulphide will operate without any loss, and deposit its equivalent of copper; but the other half, which traverses the iron sulphide, operates at first only upon the copper salt, and finally in reducing the iron persalt : so that, with the same number of coulombs, no more than half the amount of copper is deposited. Consequently, with anodes in which the copper and iron are of equal weight, we may calculate upon a rendering of 75 per cent, of the electric energy expended. If the copper increases, the rendering will be greater, and, on the contrary, less if it diminishes. It cannot, however, get below the 50 per cent, that is obtained when there is no longer any copper in the anodes." " By employing anodes composed of iron, copper, and sulphur, such as result from a first ordinary fusion of the ore, we may always extract the copper with an electric rendering, which is comprised between 50 per cent., in cases where there is no longer any copper in the anodes, and 100 per cent, when, on the contrary, there is no more iron." "If the baths are properly arranged, and the electrolyte kept at proper strength * a maximum yield of 44 pounds of copper per horse-power may be obtained daily " (nee p. 199). EXTRACTION OF METALS FROM MINERALS. 235 It was found necessary to continually ascertain what varia- tions of potential and strength of current were occurring, in order to know the conditions of the baths, resistances, &c. To determine these a Siemens' torsion galvanometer was employed. The dimensions and arrangement of the depositing vats, and the mode of circulating the electrolyte in them, have been already described (pp. 184, 185, 191, and 195). The pro- cess is best adapted for places where water-power is abundant and fuel is dear. For further particulars see a Paper by G. Badia in La Lumiere Electrique, 1884, Nos. 40, 41, 42; also Scientific American Supplement, 1885, Vol. XIX., Nos. 478, 479. Since the establishment of these works the system has been adopted at the large establishment of the Stolberg and West- phaliau Company at Stolberg, Prussia. At this place a large quantity of regulus, containing 7 to 8 per cent, of copper, is produced in the lead furnaces. This is calcined and re-smelted in order to recover as much lead and silver as possible, the calcination yielding a regulus containing from 15 to 25 per cent, of copper. In some experiments made at Stolberg (with the experimental apparatus used at the International Electrical Exhibition at Turin), for the purpose of testing the process, the material used was this regulus : it contained copper 15 to 16, lead 14, iron 41 to 44, and sulphur 25 per cent. ; also 16 ounces 7 penny- weights of silver per ton. The electrolyte was the acidulated wash- water of a richer regulus containing copper 53, lead 14'4, iron 7-65, and sulphur 15 '8 per cent. ; also 18 ounces 6 penny- weights of silver per ton. The quantity of copper in the elec- trolyte varied from 3 to 4 per cent. The dynamo employed was a Siemens and Halske's "C G ," and, running at an average speed of 1,118 revolutions a minute, gave an average current of 89 amperes at a difference of poten- tial of 5 -6 5 volts, the total external resistance being about 033 ohm, and the counter-electromotive force in each vat, due to chemical reaction, being computed to be from '4 to '45 volt. The main conductors were of copper I'O centimetre diameter = "882 square millimetre per ampere, and there were six vats in single series. 236 EXTRACTION OP METALS FROM MINERALS. The vats were of wood, lined with lead, each of the same dimensions, viz. : Length. Breadth. Height. Inside 1,000mm 680mm 800mm. Outside ... 1,160 920 ,, 920 ,, Each contained 7 anodes and 8 cathodes. The anodes were 620 to 640 millimetres long, 600 millimetres broad, and 55 millimetres (usually 30 millimetres) thick ; and the cathodes were 600 millimetres long, 600 millimetres wide, and -5 milli- metre thick. The vats were all on the same level, and were filled to within 10 millimetres of the top of the cathodes, at which level the sulphate solution ran off from each vat into a common gutter to a storage tank, and from that to a clarifying tank, from which a pump lifted it back to a pipe placed opposite to the overflow and supplying the vats. The rate of flow through the vats was 800 to 1,000 litres per hour. The total amount of copper deposited each 24 hours was 13-322 kilogrammes, or 2-261 kilogrammes per vat = 450 grammes per square metre in 24 hours, or 1-482 ampere per square foot. The theoretical deposit by 89 amperes was 2-5 kilogrammes per vat in 24 hours ; the amount actually obtained was " 90 to 95 per cent." of this. The deficiency represents energy used in reducing ferric to ferrous sulphate. "A similar percentage of duty has been realised in the works at Casarza, when the solution contained not less than 1 per cent, of copper." The deposited copper was perfectly free from lead and silver, and gave 99-92 and 99 -95 per cent, of copper in two analyses (Proc. Institution Civil Engineers, 1885, Vol. LXXXIL, p. 446). The plant was worked continuously during two months, and "it is certain that less than 1 horse-power was consumed in the experiments." The dissolved salt of iron continually increased, but did not become so large in amount as to require removal during the two months of working. " The works (at Stolberg) constructed upon the above data are arranged to produce 10 to 12cwts. of refined copper a day, corresponding to a consumption of 12 tons of 1st (i.e., 7 to 8 per cent.), or 3 tons of 2nd (15 to 20 per cent.) regulus, and EXTRACTION OP METALS FROM MINERALS. 237 cover an area of 324 square metres. The number of vats is 58, arranged as series of six in terraces. Each vat contains about 25 square metres of anodes, and the same surface of cathodes. The corresponding weights of regulus No. 2 are 2J tons for each yat, or a total of 145 tons for the 58, repre- senting a value of 14,500 francs (580) at the works. Of this, one-half may be considered as being locked up." " The corresponding lock-up of copper in the cathodes, which require about three months to acquire a saleable thickness, may also be taken at one-half, or 45 days at 580 kilogrammes = 26,100 kilogrammes, worth at present price about 32,000 francs (1,280). The total value of stock rendered idle will, therefore, be about 1,600 for a production of 210 tons of refined copper per annum." "The loss of interest will (according to M. Marchese) be more than compensated by th& extra price obtained for the product, which is worth from, 5 to 5. 12s. more per ton than the best selected copper" (ibid., p. 444; Dingler's Polytechnisches Journal, 1885, Vol. CCLV., pp. 199-532; also "Traitement ^lectrolytique des Mattes Cuivreuses au Stolberg," par E. Marchese, p. 64 : Genoa, 1885). Siemens and Halske's Process. According to this more- recent (1887) method, instead of using soluble anodes of sul- phide, the casting of which is attended by great waste of ma- terial and labour, and which crumble in the electrolyte and interfere greatly with the process, insoluble ones of carbon are employed, with cathodes of sheet copper, and porous diaphragms between them. In this arrangement the solution of the sulphates of iron and copper, containing free sulphuric acid, is caused to flow slowly upward against the cathode, by which, means it is partly deprived of copper, and the persalt of iron in it partly reduced to ferrous salt ; and then to flow downwards against the anode, during which time it absorbs the electrolytic oxygen, and is partly converted into ferric sulphate. The solution of feme sulphate thus produced has the property of converting cupreous sulphide, cupric sulphide, and cupric oxide into sulphate of copper and rendering them soluble. In order to again impart sufficient sulphate of copper to- the weakened electrolyte, powdered cupreous pyrites is roasted 238 EXTRACTION OF METALS FROM MINERALS. at a low temperature, so as to chiefly convert it into cupreous sulphide and cupric sulphate, and the iron almost entirely into oxide. It is then washed in a series of troughs, with the acidulated and peroxidised liquid from the depositing vats, the liquid being caused to pass first through the trough contain- ing nearly exhausted powder, and finally through the one last charged with fresh ore. During this flow through the troughs the acid ferric sulphate energetically attacks and dissolves the FIG. 79. Siemens and Halske's Process. cupreous sulphide, converting it into sulphate, and is itself reduced to ferrous sulphate. If the copper in the ore is wholly in the form of cupreous sulphide, the renovated liquid will contain " exactly the same amount of sulphate of copper, sulphate of iron, and free sulphuric acid as before the electrolysis ; but if it exists partly as oxides, the liquid will be richer in copper, but poorer in iron and free sulphuric acid." % The processes are based upon the fact that the protosalt of iron in contact with the anode prevents polarisation at that EXTRACTION OP METALS FROM MINERALS. 239 electrode by absorbing the electrolytic oxygen and becoming ferric salt. And as the renovated solution contains no ferric salt, none of the electric energy is expended in reducing it to the ferrous state at the cathode. " As it is generally more convenient to use electric currents of high tension, which require a considerable number of decom- posing vats in series, it is necessary to arrange so that the renovated liquid flows consecutively through all the cathode FIG. 80. Siemens and Halske's Process. cells, then through all the anode ones, and lastly through the troughs containing the roasted ore." "The same portion of solution is used repeatedly until it becomes too impure for the process." The vats are arranged in single series and cascade fashion, so that the liquid flows from one vat to another throughout by the action of gravity, as shown in Figs. 79 and 80. The anodes consist of rows of bars of carbon. 240 ELECTROLYTIC REFINING OF SILVER. ELECTROLYTIC REFINING OF SILVER. Moebius's Process. This consists essentially of a mechanical arrangement of brushes for continually keeping the cathodes- free from loose crystals of electro-deposited silver, and of muslin bags enclosing the anodes to collect the separated insoluble substances. Beneath the cathodes are trays for catching the silver, and these are lifted out occasionally and the silver removed. The process is specially suitable for copper bullion containing large proportions of silver and gold, with small quantities of lead, platinum, and other metals. The vats are made of wood, coated inside with graphite paint, and may be arranged either in series or multiple arc as may be- desired. The electrolyte consists of dilute nitric acid, contain- ing not more than one per cent, of the acid, and is continually stirred by means of blades hung upon the anode conductors.. The bullion anodes are in the form of plates half an inch thick and 14in. square, and the cathodes are made of sheet silver slightly oiled, to prevent adhesion of the deposited metal. By passage of the current, the copper and silver dissolve and form. a solution of nitrate of copper, nitrate of silver, and free dilute nitric acid ; the silver alone is electro-deposited as powder and as crystals, leaving the copper in solution; the nitrate of copper is necessary in order to ensure that all the lead is converted into insoluble peroxide at the anode. The peroxide of lead, the gold, platinum, antimony, and some peroxide of silver, separate at the anodes and fall into the bags. The bags are saturated with coal oil, linseed oil, and paraffin, to protect them from the acid, and are very little affected. No porous cells or partitions are employed. The current must have an electromotive force of one to three volts for each vat. The copper is not deposited provided the liquid is not too poor in silver or too rich in copper ; if a little happens to be deposited, it falls into the trays with the silver,, and is then gradually re-dissolved by the liquid. The sediment from the anodes is removed, dried, and melted ; the peroxide of lead then changes to lower oxide, the base metals are oxidised, and the noble ones separate as metal. If platinum or indium are present, they are subsequently separated by means of bromine. ELECTROLYTIC REFINING OP SILVER. 241 When too much copper lias accumulated in solution, carbon anodes are substituted for the bullion ones, and a feeble current passed until all the silver is deposited. The silver cathodes are then removed, and copper ones substituted. A powerful current is then passed so as to deposit the copper rapidly as a loose powder, which falls into a copper box placed to receive it ; and when so much acid is set free as to corrode the box and its contents, the former is connected as a cathode. The liquid thus regenerated is used again, partly for making new electro- lyte, and partly for replacing water evaporated from the baths. If the base bullion contains as much copper as one-third of the silver in it, it must first be treated as follows : Plates of the alloy must be used as anodes, and sheets of copper as cathodes, in an acidulated solution of cupric nitrate ; or if the alloy is poor in silver, a solution of cupric sulphate may be employed. By now passing a current of low electromotive force the copper dissolves, and the silver, gold, platinum, also at Miask, in the Ural. It melts at a red heat, and is very slightly soluble in water. It has Hitherto been used for making caustic soda, aluminate of soda, to render glass opales- cent, and for other purposes. The process of separating the metal consists essentially in reducing the purest quality of the mineral to powder, immersing in it two rods of carbon in mutual contact at their extremities, passing a copious electric current of high electromotive force, and then slowly separating the ends of the rods until a suffi- ciency of the powder between them has become fused, and continuing the action for a sufficient time to separate the metal. The arrangement actually used is as follows : An iron box is lined with powdered bauxite, rendered compact by being forced in under hydraulic pressure. Through a hole in the bottom of the vessel is introduced a vertical rod of carbon, to act as the cathode. Dry cryolite powder is then placed in the 252 SEPARATION OF ALUMINIUM. cavity until the cathode is covered. A vertical rod of carbon, supported by a bracket above, and used as a temporary anode, is now lowered into momentary contact with the cathode, so as to produce an electric arc, the electromotive force of the current being about "80 to 100 volts, and the strength 60 to 80 amperes." The anode is then slowly separated, the arc ceases, and the melted substance transmits the current. As the powder melts more is added, and the anode farther separated. FIG. 81. Kleiner's Apparatus. Hollow horizontal cylinders of pure carbon, attached to pro- jecting ears through the sides of the vessel, and on a level with the top of the cathode, constitute the permanent anodes ; they are covered with alumina in powder, to prevent their combus- tion, and are gradual ly submerged by the melted cryolite. After about ten minutes' action, when sufficient liquid i| formed to cover these cylinders, the latter are used as the anode, the temporary one is withdrawn, and the electromotive SEPARATION OF ALUMINIUM. 253- force is reduced to " 50 volts." Gentle fusion is maintained by the current for about three to six hours, and then the process is stopped, and the current switched on to another electrolysing vessel. No fluorine is set free, and no hydro- fluoric acid is evolved unless the cryolite powder is damp. Fig. 82 shows the vessel, and Fig. 83 the annular anodes. By the electrolytic action due to passage of the current, the metal separates at the negative electrode in the form of minute globules, which gradually increase in size to several centimetres diameter, and then fall to the bottom. After sufficient of the metal has been separated, the fused residue is cooled, broken up FIG. 82. Kleiner's Improved Crucible. and washed, and the metal removed. The soluble residue is preserved for conversion into caustic soda, whilst the insoluble unreduced portion is dried and replaced in the bath. There are several chief features in this process : 1st. The salt itself is employed alone, and not an aqueous or other solution of it. 2nd. It is reduced to a liquid state by fusion. 3rd. The fusion is effected, not by an external fire or furnace, but by the current itself, i.e., by the heat of conduction resistance. The current therefore performs two functions it not only electrolyses the saline substance, but also melts it. As the heat is applied only to the interior of the mass and not from 254 SEPARATION OF ALUMINIUM. the outside, and as the powdered mineral is an inferior con- ductor of heat, the process may be conducted in a wooden box .or other combustible vessel. No more of the substance need foe melted than is absolutely required for the electrolysis. The electrical energy required in the process is considerable, .and for the following reasons : 1st. The current has not only to melt the salt as well as electrolyse it, but also to continually make good the loss of heat by radiation and conduction. 2nd. Owing to the powerful chemical affinity of aluminium and .fluorine, the electromotive force required to separate the two is FIG. 83. Carbon Electrodes. large. 3rd. As the anode is insoluble the loss of energy at the cathode is not compensated (as in the case of electrolytic purification of copper) by a corresponding gain at the anode ; and 4th. The electro-chemical equivalent of aluminium being less than one-third that of copper, the same strength of current separates less than one-third the weight of the former than of the latter metal (see p. 126). In accordance with this, in an experiment made by Dr. \ Hopkinson, with a mean current of 100-2 amperes, mean poten- tial = 57"43 volts, or a mean energy of 5604-2 watts, during SEPARATION OF ALUMINIUM. 255 10380 seconds ( = 173 minutes, or 2 hours 58 minutes) = 21-6 horse -hours, the amount of aluminium separated was 60 grammes, the theoretically equivalent amount of the strength of current passed being 93*09 grammes of the metal. From these results " it appears that 3 grammes of metal per horse- power per hour are already attainable when working on a very moderate scale, and a dynamo giving 100 electric horse-power, and working 20 hours a day, would produce 80 pounds of aluminium per week of six days," the theoretical result obtained by an amount of electric energy of one horse- power per hour being 3 grammes, or T J^th Ib. It has been calculated that the cost of horse-power or mechanical energy required is about "Six shillings and fourpence per pound of aluminium." The cost of purest cryolite is stated to be from 30 to 60 a ton. Recently (1889) several dynamos, constructed by Messrs. Mather and Platt, Salford, Manchester, and by Messrs. Siemens Brothers, each requiring about 90 horse-power, and yielding 1,000 amperes at 55 volts, and one consuming 60 horse-power, yielding a higher electromotive force, were working at Tyldesley, near Manchester, to test the process on a commercial scale for " The Aluminium Syndicate" of London (see Fig. 61). Patents in connection with the process have been taken out by Major R. Seaver, in England, No. 8,531, June 29, 1886, and by Dr. Kleiner, No. 15,322, November 24, 1886. (See also Jour. Chem. Soc., Vol. VIL, pp. 517, 518.) Heroult's Process. English patents, No. 7,426, May 21, and 16,853, December 7, 1887. This is a method for producing aluminium and aluminium-bronze, 1884, Vol. XLIX., p. 69). For the electrolytic separation of zinc from cadmium, see Jour. Soc. Chem. Industry, 1886, Vol. V., p. 41 Vol. VIII., p. 639. SEPARATION OF MAGNESIUM. Various attempts have been made to separate magnesium by electrolysis on a commercial scale. E. Reichardt, also F. Fischer, employed carnallite and tachyhydrite for this purpose (see Dingler's Polytechnisches Journal, 1865, Vol. CLXXVL, p. 141 ; 1868, VoLCLXXXVIIL, p. 74; and 1882, Vol. CCXLVL, p.27). R. Gratzel, of Hemelingen, near Bremen (ibid., 1884, Vol. CCLIIL, p. 34), used carnallite and the apparatus shown in Figs. 89, 90 and 91. In the furnace Q are always, according to the strength of the electric current, two to five melting pots, arranged in a row, each SEPARATION OP MAGNESIUM. 267 one in a separate hearth. The crucible-shaped vessel A is com- posed of cast steel, and forms the negative electrode : it stands FIG. 89. Gratzel's Magnesium Process. upon a refractory fire-brick plate. Each crucible is clusod with a cover, e t of similar material. Fio. 90. Gratzel's Magnesium Process. The reducing gas arrives through the common supply pipe and the tube o into the crucible, and goes back by means of the tube z in the conduit Z. 268 SEPARATION OF MAGNESIUM. The positive carbon electrode k is suspended through an opening in the fire-clay cover of G. The vessel G is cylindrical and formed of fire-clay, which is an electrically insulating sub- stance : it has openings, c, c, on each side for access of the melted substance. Chlorine gas escapes through the common pipe P from each vessel G. For the recovery of aluminium, the apparatus shown in Fig. 91 is employed : r is connected with the negative electrode. mfm P t ! J 1 \ 6 c a - 2 S\ o \ \ 1 PlG. 91. Gratzel's Aluminium Process. For further particulars the reader is referred to the German patent, No. 26962, of October 9, 1883. Rogers' Process. A. J. Rogers, of Milwaukee, U.S.A., took out an American patent, No. 296,357, for the separation of magnesium from carnallite. He used sheet-iron crucibles, coated inside with asbestos paste (see Fig. 92). a and b are two cylinders, 13 and 17 centimetres wide respectively, connected below by three strong wires, and supported by three legs. The cover of this furnace is coated on its under side with asbestos paste, and has an opening through which the crucible passes. The bottom of the crucible rests upon thick iron wires. Heat is applied to the crucible by means of three gas flames beneath; and the products of combustion from them, after heating the cruci'.lc, pass down- SEPARATION OF MAGNESIUM. 269 wards between the two cylinders in the direction ot the arrows and escape. The material employed for yielding the mag- nesium was heated to fusion. When the substance was melted, an annular asbestos plate was put upon the crucible, and by means of a heavy iron ring, /, fixed by pressure upon the edge of that vessel. The asbestos plate held a clay tube, o, in the side of which small holes were 9** FIG. 92. Rogers's Process. bored for the passage of gas. In this tube was supported, by the help of small asbestos rings, the positive carbon elec- trode + ; also the joined mouth-pipe r, for the escape of evolved chlorine, having a vertical branch through which the pipe might be cleared of stoppage. The negative electrode- consisted of an iron wire 5 mm. thick, its lower end being in the form of a ring surrounding the carbon. Instead of this ring a carbon plate may be employed. "270 SEPARATION OP POTASSIUM AND SODIUM. A current of reducing or indifferent gas, previously dried by means of calcium chloride, was introduced through the tube g. This gas passed through the small holes in the clay tube, and together with the chlorine evolved at the anode, escaped by the tube r. A motor of 1 horse-power, and a dynamo giving 50 amperes -at 9 to 10 volts, were employed, and 10 grammes of metallic magnesium per hour in a spongy state obtained. Above a red heat balls of magnesium of the size of a hazel-nut were formed, and floated upon the surface a long time. The patent specification contains also a description of a method for electrolytically separating sodium from its melted chloride, and distilling it out of contact with air (see next page). M. de Monglas has described a process for electro-depositing an alloy of magnesium and zinc from a strong aqueous solution -of the mixed chlorides of the two metals, and obtaining the magnesium from the alloy by distilling away the zinc (see The .Electrician, August 3, 1888, p. 401). SEPARATION OF POTASSIUM AND SODIUM. Hbpner's Process. Hopner took out a German patent, No. 30,414, March 21, 1884, for obtaining sodium by elec- trolysis. Common salt was melted in a crucible containing .at the bottom a layer of silver or copper to serve as the anode, -connection with which was made by means of a rod of iron or copper. A suitable resisting cathode of metal was suspended in the melted chloride. No precaution appears to have been taken for securing the separated sodium, to prevent its oxida- tion, or its reunion with the chlorine (Dingler's Polytech- nisches Journal, 1885, Vol. CCLVL, p. 28). JablochofFs Process. According to this plan the chloride of potassium or of sodium is melted in a covered iron pot, A, over a fire (Fig. 93). Supported by a central hole in the lid is a conical iron funnel, D, with its lower end dipping into the liquid the funnel being for the purpose of introducing^ a -supply of fragments of the chloride. On opposite sides of the funnel, supported by the lid, are two vertical wide iron pipes, SEPARATION OF POTASSIUM AND SODIUM. 271 c and c', closed at their upper ends, but with their lower ends open and dipping into the liquid. These tubes enclose two vertical electrodes, a and 6, which are supported by the tops of the pipes, and their lower ends dip into the liquid. Exit tubes of iron branch from the upper ends of the pipes, and convey away the evolved chlorine from the positive pole a, FIG. 93. Jablochoff's Process. and vapour of alkali metal from the negative one 6 (Dingler's Polytechnisches Journal, Vol. CCLL, p. 422 ; Jour. Soc. Chem. Industry, 1884, Vol. III., p. 260). Eogers's Process. The apparatus employed consists essen- tially of three vessels, A, B, and C (Fig. 94). A and B are set in a furnace and heated to redness. A is for melting common salt ; B is for electrolysing the melted substance, and contains two carbon plates as electrodes, separated by a porous partition of nnglazed earthenware; and C is a vessel for condensing the vapour of sodium, which then flows in a liquid state into vessels, D, beneath containing non-volatile oil of petroleum. A is a cast-iron vessel, covered with an air-tight iron lid, which has a funnel for supplying the perfectly dry salt in powder, and is provided with a small valve opening out- wards to prevent accidents from explosions. The lower end of the funnel has a hinged valve, which is closed by a floating 272 SEPARATION OP POTASSIUM AND SODIUM. metal ball, G, when the liquid rises sufficiently high. The melted salt flows through the pipe H and stop-cock I, until it rises in the vessel B to the same height as in the one A. FIG. 94. Rogers's Process B is a rectangular vessel of iron divided vertically into two equal parts by the porous partition, which extends from the top or lid nearly to the bottom of the vessel, and is fixed air- tight at its upper and side edges, so that the vapours rising from the two electrodes are prevented from mixing. The electrodes J, K (Fig. 95), rest upon non-conducting supports of earthenware, and their conducting wires pass through short FIG. 95. Rogers's Process, fire clay protecting tubes to the outside of the vassol and furnace, and on to the dynamo. Above the two chambers of the vessel, and formed ja one piece with the iron lid, are two bent tubes or retort necks, L, for conveying away the vapours of chlorine and SEPARATION OF POTASSIUM AND SODIUM. 27$ sodium respectively. The lid has two manholes, which can be opened when necessary. It has also a pipe and stop-cock M, through which a current of hydrogen can he passed inta the chamber containing the cathode until all the air is expelled. Beketov's Process. According to the Moscow Technik, M. Beketov, of Charkotf, has obtained metallic sodium economically by the electrolysis of common salt. The salt is fused at 500 C., in a horizontal tube of earthenware, and fresh salt is added from time to time through an opening in the middle of the tube. The electrodes are introduced at the opposite ends of the tube, and pass through porcelain tubes which extend beyond the electrodes at their inner ends. The anode is of carbon, and the cathode is a tube of iron through which the liquid sodium continually flows away. "With a current of 16,000 amperes, and an electromotive force of 5 volts ( = about 120 horse-power), about 1,800 pounds of salt, yielding 720 pounds of sodium and 1,080 pounds of chlorine, can be de- composed in 24 hours." (The Electrician, Vol. XXII., p. 97 ; Engineering, December 14, 1888, p. 588.) Greenwood's Process. Mr. James Greenwood, of Queen Victoria-street, London, has recently patented an improved process for the same object, and has used it on a commercial scale for obtaining sodium and chlorine at the works of the "Alliance Aluminium Company," at Wallsend, Newcastle-on- Tyne. SEPARATION OF GOLD AND SILVER FROM AURIFEROUS EARTH, &c. Werdennann's Process. The ores, in a state of fine powder, containing gold, silver, antimony, arsenic, sulphur, &c., are first oxidised by means of ozone, then washed with water, and the silver deposited from the solution by means of electrolysis. The ore is then wetted throughout with a solution of caustic alkali, and the residuary silver, together with the gold, amalgamated with mercury by stirring the mixture with a cathode, the amalgamating vessel being the anode. 274 SEPARATION OF GOLD AND SILVER. Barker's Process. Patented June 28, 1882, No. 3,046, for " abstracting gold and silver from their ores by means of electricity and mercury," especially those containing pyrites, arsenic, black sand, or other heavy substances. This invention consists essentially of a long and narrow slightly inclined plane of wood, iron, or earthenware, Industries, Sept. 7, 1888, p. 237. . According to W. Hampe, the reduction of alumina to metal by means of carbon, even at the temperature of the electric furnace is, on thermo-chemical data, impossible ; and the effect of the electric current in the Cowles process, is in the first place electro-thermic in melting the alumina by the heat of electric conduction-resistance, and then electrolytic in decom- posing the fused substance. He electrolysed a melted mixture of cryolite, common salt, and chloride of calcium with a carbon anode and a cathode of fused copper. Chlorine separated at the anode, and sodium at the cathode. The sodium rose to- the top of the melted mixture in fused globules and burned,, but scarcely a trace of aluminium was separated (Jour. Soc. Chem. Industry, Vol. VII., p. 236). It has been stated that the radiation of heat and light from the electric furnaces at Creusot blinds the workmen, and causes the skin to peel off their neoks and faces. APPENDIX. Decimal Equivalents of Indies and Feet. Frac- Decimals Decimals Frac- Decimals Decimals tions of of an of a tions of of an of a an inch. inch. foot. au inch. inch. foot. A = -0625 = -00521 T0 = -5625 = -04688 , * = -125 = -01041 s i? = -625 = -05208 ft = -1875 = -01562 H = '0875 = -05729 i = -25 = -02083 1 - -75 = -06250 n Iff = -3125 = -02604 = -8125 = -06771 f = -375 = -03125 i = '875 = -07291 A = "4375 . = -03645 M = -9375 = -07812 i = -5 = -04166 1 = 10 = -08333 Area of Circles. Diam. Area. Diam. Area. Diam. Area. Diam. Area. 1 007854 1-625 2-074 425 14186 7-25 41-261 125 012246 1-75 2-404 4-5 15-9 7'5 44-156 25 049 1-92 2-894 4-75 1772 775 47-147 375 11 2- 3-14 5- 19'63 8- 50-266 5 196 2-25 3-974 5-25 21-649 8-25 53-456 625 306 2-5 4-906 5-5 2376 8-5 56 745 75 4418 2-75 5-939 5-75 25-967 875 60-099 875 6013 3- 7-668 6- 28-274 9- 63617 1- 7854 3-25 8-295 6-25 30-63 9-25 67'2 1-1 95 3-5 9-62 6-5 33-183 9-5 70-846 1-25 1-227 3-75 11-045 6-75 35785 975 74-622 1-5 1-767 4- 12-566 7- 38-485 10- 78-540 To find the area of a circle, multiply the diameter by itself, and the nroduct by '7854. AITEXDIX. 287 English Measures of Capacity. Cubic Inches. Tints. Fluid Ounces. Fluid Drachms. Minims. Imperial Gallon . 277276 8 160 1,280 76,800 Quart . 69 318 2 40 320 19,200 Pint ... 34 650 20 160 9,600 Fluid Ounce .... 1733 ... ... 8 480 Fluid Drachm ... ... ... 60 1 One cubic foot equals 6 '232 gallons or 1,728 cubic inches. One cubic yard equals 168*264 gallons. English Weights. AVOIRDUPOIS. Grains. Drachms. Ounces. Pounds. Drachm '27-3 437-5 7,000- 196,000- 784,000- 15,680,000- 16 256 7,108 28,672 573,440 16 448 1,792 35,840 28 112 2,210 Ounce Pound Quarter Hundredweight . Ton Grains. Ounces. Pounds. Fluid drachm of w ounce Imperial pint ,, ater 547 437-5 8,750- 17,500- 70,000- 252-5 20 40 160 1-25 25 10- quart gallon One cubic inch ,, TROY. Grains. Pennyweights. Ounces. Pennyweight 24 Ounce 480 20 Pound . 5760 240 12 288 APPENDIX. French Measures. Length. Millimetres. Millimetre Centimetre equals 10 Decimetre ,, 100 Metre ,, 1,000 Kilometre 1,000 metres Weight. Milligrammes. Milligramme Centigramme equals 10 Decigramme ,, 100 Gramme ,, 1,000 Decagramme ,, 10,000 Hectogramme ,, 100,000 Kilogramme ,, 1,000,000 (equals 1,000 grammes) Capacity. Millilitre equals 1' Gramme, or 1 cubic centimetre of water at 4C. Centilitre ,, 1* Decagramme. Decilitre ,, 1' Hectogramme. Litre ,, 1' Kilogram tne = l cubic decimetre of water at 4C. ,, 1000- Grammes. Conversion of French and English Measures. Capacity. Cubic Centimetre equals '061027 cubic inches. Metre ,, 35'36 ,, feet. Litre ,, Gl'027 inches. , ,, 35*2155 fluid ounces. ,, 176077 pints. ,, ,, -2201 gallon. Cubic Inch 16*386 cubic centimetres Fluid Ounce ,, 28'3966 ,, Pint -5679 litres. Gallon 4-54346 1 Cubic Metre ,, 220-41 gallons. Weight. Milligramme equals '01543 grains. Gramme ,, 15*432 ,, Kilogramme ,, 15,432- ,, , 35-274 ounces. ,, 2-2046 pounds. Litre ,, 15,432- grains. Grain ,, -0648 grammes. Ounce 28-3495 ,, Pound ,, '45359 kilogrammes. Hundredweight ,, 50'8024 APPENDIX. 289 Length. Millimetre equals -03939m. Centimetre *3939in. Metre 3'2809ft. =3ft. Sin. and Kilometre 1093 6 yards. Inch ,, 25 '3995 millimetres. Foot . -304795 metre. Surface. 1 square metre = 10*78 square feet = 1,552 '36 square inches. 1 foot = '0929 ,, metre = 92,900 millimetres. 1 ,, inch =645* ,, millimetres. 1 circle I'O inch diameter =506 7 square millimetres. 1 'I =126-677 1 ,, 1*0 centimetre = '12186 square inch. Specific Gravities of Liquids corresponding to degrees of Baume'i Hydrometer. (Poggiale.) Deg. Sp. Gr. Deg. Sp. Gr. Deg. Sp. Gr. Deg. Sp. Gr. Deg. Sp. Gr. 1000 15 1116 30 1264 45 1453 59 1691 1 1007 16 1125 31 1275 46 1468 60 1711 2 1014 17 1134 32 1286 47 1483 61 1732 3 1022 18 1143 33 1297 48 1498 62 1753 4 1029 19 1152 34 1309 49 1514 63 1774 5 1036 20 1161 35 1320 50 1530 64 1796 6 1044 21 1171 36 1332 51 1546 65 1819 7 1052 22 1180 37 1345 52 1563 66 1846 8 1060 23 1190 38 1357 53 1580 67 1872 9 1067 24 1199 39 1370 54 1597 68 1897 10 1075 25 1210 40 1383 55 1615 69 1921 11 1083 26 1221 41 1397 56 1634 70 1946 12 1091 27 1231 42 1410 57 1652 71 1974 13 1100 28 1242 43 1424 58 1671 72 2000 14 110S 29 1253 44 1438 TwaddelVs Hydrometer. To convert degrees of this hydrometer into specific gravities, multiply them by 5 and add 1,000. u 290 APPENDIX. Specific Gravities of Metals. Metal. Sp Gr. Metal. Sp. Gr. Metal. Sp Gr. 21 '53 Cobalt 8-95 Tellurium G'25 1' rid i urn 21-15 Copper 8-95 Arsenic . 5-97 Gold 19 34 Nickel 8-82 Aluminium... 2-60 Mercury . . 13-60 Cadmium ... 8-70 Strontium ... 2-54 Thallium ... Palladium 11-90 11-80 Manganese... Iron 8'01 7'84 Magnesium .. Calcium . . 1-75 1-58 Lead 11-30 Tin 7-29 Sodium 97 Silver 10-53 7'15 Potassium ... 87 Bismuth 9-80 Antimony ... 6-71 Lithium 59 One cubic inch of Copper weighs 2257 '35 grains. Relations of Thennometric Scales. 9 Fahrenheit degrees = 5 Centrigade degrees = 4 Reaumur degrees. To convert Fahrenheit to Centigrade, subtiact 32, multiply by 5, and divide by 9. Reaumur, ,, 32, 4, ,, ,, 9. Centigrade to Fahrenheit, multiply by 9, divide by 5, and add 32. ,, ,, Reaumur, ,, 4, ,, ,, 5. Reaumur to Fahrenheit, ,, ,,9, ,, ,, 4, and add 32. ,, ,, Centigrade, ,, ,, 5, ,, ,, 4. Example: 212 Fahrenheit to Centigrade, 212 - 32 = 180 x 5-r 9 = 100 Centigrade. Fusibility of Metals. Metal. Fusibility Deg. C. Metal. i Fusibility Deg-. C. IVtercury . . -39-4 Aluminium "1 Above a red Potassium + 62-5 Calcium . J heat 97 '6 Silver 1023- Lithium ISO- Conner . 1091- Tin 228- Gold 1102- Cadmium 228- Cast iron 1503- Bismuth 264- Cobalt ~) Thallium 294' Nickel I The highest Lead 325- Manganese }- heat y^inc . 412- Silicon j of a forge. Antimony about... Magnesium a little below G20- 800- Wrought iron . . . J Palladium ^ Platinum \ Require the oxyhydrogeix flame. APPENDIX. 291 Table of Centigrade and Fahrenheit Degrees. D c eg ' r . S> Deg. w y D t TEMP. 67 .. ii ,, tt KIND OF SUBSTANCE ON ; 67 CORROSION OF CATHODES 125 ENERGY, UNIT OF 292 EQUIVALENTS 46 ,, EXAMINATION OF THE COPPER SOLUTION 216 ,, FACTSAND PRINCIPLES OF ELECTROLYTIC REFINING 43 ,. FORMULAE OF SUBSTANCES 45 HEAT, RELATION OF, TO ELECTRO-MO- TIVE FORCE 52-54 POTENTIALITY 48 TERMS 43"47-48 UNIT 292 CHILI BARS OF COPPER AS ANODES 186 CHOICE OF DYNAMO FOR ELECTROLYTIC PURPOSES 177 CHLORIDES, HEAT OF FORMATION OF 41 CIRCLF.S, AREAS OF 286 CIRCUIT, MEANING OF TERM 20 CIRCULATING COPPER SOLUTION, MODE OF .. 194-195 CLARK'S STANDARD CELL 17-61 CLAUSIUS'S THEORY OF ELECTROLYSIS 136 COATINGS UPON ELECTRODES, INSOLUBLE 98 COMMERCIAL EFFICIENCY OF DYNAMOS 178 COMMUTATION OF ALTERNATE CURRENTS 143 COMMUTATOR AND BRUSHES 144 COMPOSITION OF ANODES IN COPPER REFINING.. 188 MUD 219 SOLUTION ,, 194 COMPOUNDS, ELECTRO-DEPOSITION OF 106 ELMCTROLYTIC EQUIVALENTS OF 127 ENERGY NECESSARY TO DECOMPOSE 113-131 INDEX. PAGE CONDENSER, ELECTRIC 12 CONDUCTION AND INSULATION 23 CONDUCTION IN ELECTROLYTES WITHOUT ELEC- TROLYSIS ? 81 RESISTANCE, CAILLETET'S EXPERI- MENTS ON 31 ~~ ., ,, ELECTRIC 24 ,, HEAT OF 36 KOHLRAUSCH'SEXPERI- MENTS ON 31 M ,, MATTHIESSEN'S EX- PERIMENTS ON 26-30 ,, ., WROBLEWSKI'S EXPERI- MENTS ON 31 M , OF LIQUIDS 25-30 ,, OF MINERALS 33 ,. ,, UNIT OF 292 CONDUCTING POWERS OF METALS AND ALLOYS 26-27-32 CONDUCTOR, THE MAIN 192 ,, ,, CHEAPEST SIZE OF 193 CONNECTION BETWEEN ELECTROLYTIC, CHEMICAL, AND VOLTAIC ACTION 71-72 CONNECTIONS OF CATHODES IN COPPER REFINING 190-191 CONSTRUCTION OF VATS FOR KEFINING COPPER.. 180 CONSUMPTION OF ELECTRIC ENERGY IN ELEC- TROLYSIS 129-134-151 CONVERSION OF ENGLISH AND FRENCH MEASURES 288-289 COPPER, COMPOSITION OF " BLACK " 189 ,, "BLISTER" 189 ,, ,, ,, "PIMPLE" 189 n CRYSTALS, ELECTRO-DHPOSITED 104 ,, FIRST ELECTROLYTIC SEPARATION OF .. i IN SOLUTION, FINDING AMOUNT OF 2:6 ,, Loss OF, BY CHEMICAL COKROSION 69-123-124 ,,. NODULES, ELECTROLYTIC FORMATION OF 100 RATE OF ELECTRO-DEPOSITION OF 207 REFINERIES, LIST OF ELECTROLYTIC 6 H REFINKRY, ESTABLISHING AN ,, 149-224 ,, REKINING, ADVANTAC;ES OF ELECTRO- LYTIC 149 ,, AMOUNT OF CATHODE SURFACE NECESSARY IN 150 ,, COST OF ELECTROLYTIC . . 152-221 EXPENDITURE OF ELECTRIC POWER IN 198 ,, ,, EXPENDITURE OF MECHANICAL POWER IN 200 SOLUTION, CHEMICAL EXAMINATION OF 216 ., RESISTANCE OF, IN COPPER REFINING 203 THICKNESS OF, DEPOSITED PER HOUR . . 293 ,, WEIGHT ,, ,, ,, AMPERE HOUR 293 SURFACES OF DIFFERENT THICKNESS 293 CORROSION, INFLUENCE OF CIRCUMSTANCES ON CHEMICAL 64-67-69-123 SERIES OF METALS 69 COST OF DYNAMOS AND VATS IN COPPER REFINING 223 ELECTROLYTIC COPPER REFINING 221 MOTIVE POWER AND PLANT IN DITTO.. 152 COULOMB, MEANING OF TERM 12-18-292 COUNTER ELECTROMOTIVE FORCE 86 COWLES'S PROCESS OF ELECTRIC SMELTING 281 CROMPTON-BRUSH DYNAMO 176 CRYOLITE, ENERGY CONSUMED IN DECOMPOSING.. 133 KLEINER'S PROCESS OF ,, .. 251 CRYSTALS OF METALS, ELECTROLYTIC FORMATION OF 104 CURRENT, ELECTRIC 18 ,, DENSITY OF 20 USED IN RE- FINING COPPER 208 ,, ,, DISTRIBUTION OF, IN AN ELECTROLYTE 80 it ,, EXAMINATION OF, IN COPPER REFINING 204 ,, INFLUENCE OF DENSITY OF 98 > DISSOLVED IMPURITIES UPON 215 PAGE CURRENT, ELECTRIC, RETARDATION OF, AT ELEC- TRODES 96 ,, STRENGTH OF 18-292 " CUT-OUT " 23-205 DANIELL'S BATTERY 60 ,, " ELECTROLYSIS OF SECONDARY COM- POUNDS " .T. 79 DATA, MISCELLANEOUS 293 DAVY, ISOLATION OF POTASSIUM AND SODIUM BY 77 DECHARME'S EXPERIMENTS 84 DECHAUD'S PROCESS OF TREATING MINERALS .. 227 DECIMAL EQUIVALENTS OF INCHES AND FEET .. 286 DECOMPOSABILITY OF ELECTROLYTES 112-114 DECOMPOSE COMPOUNDS, ENERGY REQUIRED TO 131 ,, CRYOLITE ,, ,. ,, 133 DEFINITE ELECTRO CHEMICAL ACTION, LAW OF 117 DEI.IGNY'S METHOD OF TREATING MINERALS 228 DENSITY OF CURRENT, INFLUENCE OF, ON ELEC- TROLYSIS 98 ,, ,, ,, MEANING OF THE TERM.. 20 ,, ,, USED IN REFINING COPPER 208 DEPOSITS, PURITY OF ELECTRO- no ,, RATE OF INCREASE OF THICKNESS OF COPPER 209-293 DEPOSITED ANTIMONY, EXPLOSIVE no ,, COPPER, DEGREE OF PURITY OF 217 DEPOSITING COPPER, USUAL RATE OF .. 105-207-208 ROOM, THE 180 ,, SOLUTION, ANALYSIS OF COPPER 217 ,, COMPOSITION OF COPPER 194 ,, SURFACE, AMOUNT REQUIRED IN COPPER REFINING 150-191 DEPOSITION, NECESSARY RATE OF 105 ,, OFCOMPOUNDS,MlXTURESANDALLOYS IO6 DETECTION OF RESISTANCES AND LEAKAGES OF CURRENT 204 DIEHL'S PROCESS OF SEPARATING ALUMINIUM .. 260 DIFFUSION EXPERIMENTS OF M. DECHARME .... 84 OF LIQUIDS, ELECTROLYTIC 83 ,, ,, ,, INFLUENCE OF VOLTAIC CURRENT ON 8c DISCOVERY OF ELECTROLYTIC SEPARATION OF METALS i ELECTRO-MAGNETIC INDUCTION 140 ,, ,, MAGNETO-ELECTRIC ,, 2-5 ,, ,, VOLTAIC ELECTRICITY i DISTANCE APART OF ELECTRODES IN COPPER REFINING 185 DISTRIBUTION OF CURRENT IN AN ELECTROLYTE 80 DIVIDED CIRCUIT 21 ,, ELECTROLYSIS 116 DYAD, MEANING CF TERM 47 DYNAMO-ELECTRIC CURRENTS, PRODUCTION OF.. 141 ,, MACHINE, CAKE OF 179 ,, ,, ,, DEFINITION OF 138 ,, EFFICIENCY OF 148 ,, ,, ,, GENERATION OF CURRENTS BY .. 138 ,, BRUSH'S 162-165 ,, CHAMBERLAIN AND HOOKHAM'S 167 CHOICE OF, FOR ELECTROLYTIC PURPOSES 177 ,, CROMPTON'S 176 ,, EDISON-HOPKINSON'S 164-166 ,, ELECTROLYTIC, OF DIFFERENT MAKERS 155 ,, KI.MOKE'S 176 , , ELWELL- PARKER'S 169 ,, GRAMME'S 147-159 ,, GULCHEK'S 171 ,, HEATING OF, DURING WORKING 148 ,, HOCHHAUSEN'S 174 ,, KINDS EMPLOYED IN ELECTROLYTIC RE- FINING ( 6-153 ,, MANAGEMENT OF 179 ,, MATHER'S 175 ,, SIEMENS' 147-156 ,, THE OERLIKON .- 173 ,, USEFUL QUALITIES OF, FOR ELECTRO- LYSIS 178 ,, WILDE'S 155 INDEX. 297 H PACE EARLIEST ELECTROLYTIC REFINING OF COPPER.. 3 ,, KNOWN FACT OF ELECTRIC SEPARATION OF METALS i ECONOMIC RATE OF REFINING COPPER, THE MOST 208 ECONOMY, LIMITS OF, IN ELECTROLYTIC REFINING OF COITKR 209 EDISON-HOJ'KINSON DYNAMO 164-165 EFFECTS OF STIKRING THE ELECTROLYTE 122 TEMPERATURE ON CORROSION OF METALS 69-123-124 VAT SEDIMENT ON THE COPPER SOLU- TION 220 EFFICIENCY OF DYNAMOS, COMMERCIAL 148-178 ELECTRIC CAPACITY 12 CONDENSER 12 CONDUCTION RESISTANCE 24 CURRENT 18 ENERGY 23 AMOUNT OF, USED IN REFINING COPPER 200 ,, CONSUMPTION OF, IN ELEC- TROLYSIS 129 UNIT OF 292 POLARITY AND INDUCTION u POTENTIAL 13 QUANTITY 12 SMELTING, COWLES'S PROCESS OF...... 281 ,, WORKS AT MILTON 164 ,, WORK, UNIT OF 292 ELECTRICAL THEORY OF CHEMISTRY 51 ,, UNITS 292 ELECTKO-CHEMICAL ACTION, CHIEF FACTS OF .. 71 QUANTITY OF 117 DEPOSITED ANTIMONY, EXPLOSIVE no CRYSTALS OF METAL .. 101-104 ,, METALS, PHYSICAL STRUC- TURE OF 99 NODULES OF COPPER :oo DEPOSITION, BATTERY METHOD 76 METHODS OF 74 PREPARING SOLUTIONS FOR 78 SERIES MR-SHOD 74 ,, SINGLE CELL METHOD 76 ,, NECESSARY RATE OF 105 ELECTRODES, MEANING OF THE TERM 78 USED IN COPPER REFINING 184 CONNEC- TIONS OF 186 ,, ,, DISTANCE APART OF 185 INSOLUBLE COATINGS ON 98 INSPECTION OF, IN COPPER REFINING 196 METALLIC SULPHIDES AS 92 POLARISATION OF 86-204-208 RETARDATION op CURRENT AT .... 96 SUSPENDING COPPER, MODE OF .... 185 UNEQUAL ACTION AT 86 ELECTRO-DYNAMOMETER, SIEMENS' 19-206 ELECTROLYSIS, ARRANGEMENTS FOR PRODUCING . . 73 ,, BY ALTERNATING CURRENT 81 CHIEF FACTS OF 71 CONDUCTION IN ELECTROLYTES WITHOUT? 81 DIVIDED 116 OF FUSED COMPOUNDS 91 INCIDENTAL PHENOMENA OF 107 INFLUENCE OF COMPOSITION OF THE LIQUID UPON CUR- DENSITY OF RENT UPON ...... KIND OF ELEC- TRODES UPON ____ LIQUID DIFFUSION UPON ............ SOLUBIUTYOF ANODE UPON ............ 95 TEMPERATURE UPON 89 WATER AND FREE ACID UPON ...... 88 83 PAGH ELECTROLYSIS, CONSUMPTION OF ELECTRIC ENERGY IN 129-134 LOCALITY OF 79 NOMENCLATURE OF 78 QUANTITY OF n 7 SECONDARY PRODUCTS OF 127 SECONDARY EFFECTS OF 106 THEORIES OF i 34 IHERMAL PHENOMENA ATTENDING 89 TRANSPORT OF IONS IN 82 ELECTROLYTE, MEANING OF THE TERM 78 ELECTROLYTES, ORDER OF DECOMPOSABILITY OF 112-114 VOLTA-TENSION SERIES OF 52 ELECTROLYTIC AND VOLTAIC ACTION, DISTINCTION BETWEEN 71 BALANCK OF CHEMICAL CORROSION 124 COPPER REFINERIES, LOCALITIES OF 6 REFINERY, PLANNING AN.. 149 DEPOSITION OF MIXED METALS .. 106 ,, CRYSTALS 101 DEPOSITS, PURITY OF no DIFFUSION OF LIQUIDS 83 EQUIVALENTS OF SUBSTANCES 125-127 PROCESS OF TREATING MINERALS 227-237 REFINERY, ESTABLISHING AN.. 149-224 REFINING, CHIEF FACTS AND PRIN- CIPLES OF 9 OF METALS, THERMAL PHENOMENA OF 36 M OF COPPER, EARLIEST PROCESS OF 4 n CHEMICAL FACTS AND PRINCIPLES OF 43 ELECTRICAL FACTS AND PRINCIPLES OF n THERMAL FACTS AND PRINCIPLES OF 36 t CHOICE OF DYNAMO FOR 178 PROCESS, ADVANTAGES OF THE 149 ., OF COPPER, COST OF .. 221 .. GOLD 242 ,, NICKEL 280 SILVER 940 . ZINC 261 SEPARATION OF ELEMENTARY SUB- STANCES 106 ALUMINIUM .. 251-259 ANTI MON Y 247 LEA D 244 MAGNESIUM 266 POTASSIUM 271 SODIUM 271 . TIN 248 ,, ,, ZINC 261 WORK, UNIT OF 292 ELECTRO-MAGNETIC INDUCTION 140 ELECTROMETER, QUADRANT 15 ELECTROMOTIVE FORCE 14 COUNTER 86 DEGREE NECESSARY IN REFINING COPPER .... 153 lf ,, MEASUREMENT OF 15 ,, RELATION OF CHEMICAL HEAT TO 52 ,, ,, STANDARD OF 17 UNIT OP 292 ELECTRO-THERMAL UNIT 37-292 ELEMENTARY SUBSTANCES 43 ATOMIC WEIGHTS OF.. 44 ,, ELECTROLYTIC EQUIVA- LENTS OF 126 ELECTROLYTIC SEPARA- TION OF 106 VOLTAIC EQUIVALENTS OF 64 VOLTA TENSION SERIES OF 50 ELKINGTON'S FIRST ELECTROLYTIC REFINING PROCESS 4 2 9 8 INDEX. PAGE ELMORE'S DYNAMO 176 ELWELL- PARKER'S DYNAMO 169 ENERGY, ELECTRIC 23 ,, ,, CONSUMED IN REFINING OF COPPER 200 ,. CONSUMPTION OF, IN ELEC- TROLYSIS 129-151 ' ,, GRAMME'S EXPERIMENTS ON 151 ,. ,, LOST IN OVERCOMING RESIST- ANCE 134 . ,, MECHANICAL, CONSUMED IN REFINING OF COPPER 198 ENGLISH WEIGHTS AND MEASURES 287 EQUIPOTENTIAL LINES 80 EQUIVALENT OF HEAT, MECHANICAL 37-292 ,, WEIGHTS OF SUBSTANCES, CHEMICAL 46 EQUIVALENTS OF SUBSTANCES, ELECTROLYTIC 125 ESTABLISHMENT OF AN ELECTROLYTIC COPPER REFINERY 149-224 EXAMINATION OF THE COPPER SOLUTION, CHEMICAL 216 ,, ,, ELECTRIC CURRENT IN COPPER REFINING 200 EXPENDITURE OF ELECTRIC ENERGY IN COPPER REFINING 120 ,, ,, ,, GRAMME'S EXPERIMENTS 151 ,, ,, MECHANICAL ENERGY IN COPPER REFINING 198 EXPLOSIVE-DEPOSITED ANTIMONY no EXTERNAL RESISTANCE 34 EXTRACTION OF METALS FROM MINERALS BY ELECTROLYSIS 226 FARAD, MEANING OF THE TERM 12 FARADAY'S DISCOVERY OF MAGNETO-ELECTRICITY 2-5-140 ,, LAW OF DEFINITE ELECTROLYTIC ACTION 117 THEORY OF ELECTROLYSIS 134 FAVRE'S EXPERIMENTS ON DIVIDED ELECTROLYSIS 136 MEASUREMENTS OF CHEMICAL HEAT .. 42 FISCHER'S PROCESS OF TREATING AURIFEROUS EARTHS 279 FOOT-POUND, MEANING OF THE TERM 293 FORMATION OF CATHODES IN COPPER REFINING 189 FORMULA OF SUBSTANCES, CHEMICAL 45 ,, AND SYMBOLS, THERMAL 38 FREE ACID IN COPPER SOLUTION, TESTING AMOUNT OF 216 FRENCH MEASURES OF LENGTH, ETC 288 FUSED COMPOUNDS, ELECTROLYSIS OF 91 FUSIBILITY OF METALS, TABLE OF 289 GALVANOMETER 19 GLADSTONE'S EXPERIMENTS ON ELECTROLYSIS 77-91-104 GOLD, ELECTRO-DEPOSITED CRYSTALS OF 103 ,, AND SILVER BULLION, REFINING OF 240 SEPARATION OF, FROM AURIFEROUS EARTHS 273 GRAMME'S DYNAMO 6-147-159 ,, EXPERIMENTS ON ELECTRIC ENERGY .. 151 GRATZEL'S PROCESS OF OBTAINING MAGNESIUM.. 266 GREENWOOD'S PROCESS OF OBTAINING SODIUM, ETC. 273 GROVE'S BATTERY 61 GULCHER'S DYNAMO 171 HALL'S PROCESS OF OBTAINING ALUMINIUM 259 HAMBURG, ELECTROLYTIC REFINING OF BULLION AT 2 4 2 HAMMERL'S EXPERIMENTS ON MEASUREMENT OF CURRENT 126 HAMPE'S EXPERIMENTS ON ELECTRIC SMELTING 285 M ,, ELECTROLYSIS 88-91 HEAT, ABSOLUTE ZERO OF 294 HEAT OF CHEMICAL UNION 37.42 CONDUCTION-RESISTANCE 36 ,i >, ,, ENERGY LOST AS 134 it M M UNIT OF ..37-292 FORMATION OF CHLORIDES 41 FORMATION OF OXIDES 42 PACK HEAT OF FORMATION AND SOLUTION OF SALTS OF COPPER 115 HEAT, MECHANICAL EQUIVALENT OF 37-292 HEAT ATTENDING ELECTROLYSIS 89 HEAT, RELATION OF, TO ELECTRO-MOTIVE FORCE 52-54 HEATING OF DYNAMOS 148 HERMITE'S PROCESS OF REFINING NICKEL 280 HERAULT'S PROCESS OF OBTAINING ALUMINIUM 255 HEXAD, MEANING OF THE TERM 47 HITTORF'S EXPERIMENTS ON TRANSPORT OF IONS 82 HOCHHAUSEN'S DYNAMO 174 HOPKINSON'S EXPERIMENTS OF ELECTROLYSING CRYOLITE 133 HOPNER'S PROCESS OF OBTAINING SODIUM AND POTASSIUM 270 HORSE-POWER, MEANING OF THE TERM 293 HYDROMETER SCALES, RELATIONS OF. 289 IMPURE ANODES IN COPPER REFINING, INFLU- ENCE OF 210-214 IMPURITIES IN COPPER ANODES 210 ,, ELECTRO-DEPOSITED COPPER 217 IMPURITIES, INFLUENCE OF, ON THE ELECTRIC CURRENT 213 INCIDENTAL PHENOMENA ATTENDING ELECTRO- DEPOSITION 107 INDICATORS, CURRENT 206 INDUCTION, ELECTRO-STATIC n ,, ELECTRO-MAGNETIC 140 ,, MAGNETO-ELECTRIC 140 INJECTOR, KORTING'S 197 INSOLUBLE COATINGS ON ELECTRODES 98 INSPECTION OF THE VATS, ELECTRODES, ETC. .. 196 INSULATION 23 OF THE VATS IN COPPER REFINING 181 INTERNAL RESISTANCE 34 IONS, MEANING OF THE TERM 78 ,, ORDER OF SEPARATION OF 113 ,, TRANSPORT OF IN ELECTROLYSIS 82 IRON PYRITES, TREATMENT OF, FOR OBTAINING COPPER 226 JABLOCHOFF'S PROCESS FOR OBTAINING SODIUM, ETC 270 JOULE, MEANING OF THE TERM 37-292 KEITH'S PROCESS OF REFINING LEAD 244 ,, ,. ,, SEPARATING COPPER 225 KLEINER'S PROCESS FOR OBTAINING ALUMINIUM 133-251 KOHI.RAUSCH'S EXPERIMENTS ON CONDUCTION- RESISTANCE 331 KOHLRAUSCH'S EXPERIMENTS ON TRANSPORT OF IONS 82 KORTING'S INJECTOR 197 LALANDE'S PROCESS FOR REFINING ZINC 264 LAMBERT'S PROCESS FOR TREATING AURIFEROUS EARTH 275 LAMBOTTE DOUCET s PROCESS FOR SEPARATING ZINC 264 LAW OF DEFINITE ELECTRO-CHEMICAL ACTION.. 117 ,, ,, MAGNETO-ELECTRIC INDUCTION .... 143 LEAD, COMPOSITION OF ELECTROLYTICALLY RE- FINED 246 LEAD CRYSTALS, ELECTRO-DEPOSITED 104 LEAD, KEITH'S PROCESS OF REFINING 244 LEAKAGES OF CURRENT IN THE REFINING OF COPPER .. 202-204 LEAKAGES OF ELECTRIC CURRENT 24 LECLANCHE'S BATTERY i. 60 LETRANGE'S PROCESS FOR SEPARATING ZINC 261 LENZ'S LAW OF MAGNETO-ELECTRIC INDUCTION 143 LIMITS OF ELECTROLYSIS, BERTHELOT'S EXPERI- MENTS ON 114 LIMITS OF RATE OF DEPOSITION OF COPPER 207 LINES OF EQUIPOTENTIAL FORCE 80 ,, ,, MAGNETIC FORCE 13$ INDEX. PAGE LIQUID DIFFUSION, EXPERIMENTS OF M. DB- CHARME 84 ,, INFLUENCE OF, UPON ELEC- TROLYSIS 83 LIQUIDS, ELECTRIC CONDUCTION RESISTANCE OF 25-30 LIQUIDS. SPECIFIC GRAVITY OF 289 LONG'S EXPERIMENTS ON RATES OF LIQUID DIF- FUSION 84 Loss OF ANODE AND GAIN OF CATHODE, DIF- FERENCE OF lai COPPER BY CHEMICAL CORROSION 69-123 ,, ,, ENERGY AS HEAT OF CONDUCTION RE- SISTANCE 134 ,, ENERGY IN COPPER REFINING, SOURCES OF 201 MAGNESIUM, SEPARATION OF 266 MAGNETIC CURVES 139 ,, FIELD, DEFINITION OF A 138 ,, FORCE, LINES OF 138-140 MAGNETISM., INFLUENCE OF, ON VOLTAIC ACTION 64 MAGNETO-ELECTRICITY, DISCOVERY OF 2-5-140 ,, ELECTRIC MACHINES 5-6-144-147 MAGNITUDE AND NUMBER OF VATS 152 MAIN CONDUCTORS, THE 192 MAINTENANCE OF THE COPPER SOLUTION 216 MANAGEMENT OF DYNAMOS 179 MARCHESE'S PROCESS OF TREATING MINERALS .. 239 MATHER'S DYNAMO 175 MATHIESSEN'S EXPERIMENTS ON CONDUCTION RESISTANCE 26-30 MEANING OF TERMS .. 12-14-18-20-23-34-43-47-78-292 MEASUREMENTS, ELECTRICAL, IN REFINERIES .. 206 OF CURRENT, HAMMERL'S EX- PERIMENTS ON 126 ,, ELECTROMOTIVE FORCE .... 15 ,, STRENGTH OF CURRENT 19 MEASURES OF CAPACITY AND WEIGHT, ENGLISH 287 ,, ., ,, FRENCH 288 MECHANICAL EQUIVALENT OF HEAT 37-292 POWER EXPENDED IN COPPER RE- FINING 198 MOST ECONOMICAL PROPOR- TION OF 199 ,, UNITS 291 METAL, DEFINITION OF THE TERM 47 METALLIC SULPHIDES AS ELECTRODES 92 METALLOID, DEFINITION OF THE TERM 47 METALS, ELECTRIC CONDUCTION RESISTANCE OF 26-27 CORROSION SEFIES OF 69-123 FROM MlNEKALS, SEPARATION OF.. 226-273 PHYSICAL STRUCTURE OF ELECTRO-DE- POSITED 99 SELF DEPOSITION OF 77 SPECIFIC GRAVITIES OF 290 TABLE OF FUSIBILITY OF 290 MILTON. COWLES'S ELECTRIC SMELTING PROCESS AT 164 MINERALS, PROCESSES OF TREATING 227 M >t i, M AT CASARZA 229 ,, CONDUCTION RESISTANCE OF 33 ,, SULPHIDES AS ANODES 234 MINET'S PROCESS OF SEPARATING ALUMINIUM .. 259 MINIMUM ENERGY REQUIRED TO DECOMPOSE COMPOUNDS 131 MINIMUM E. M. F. REQUIRED TO DECOMPOSE COMPOUNDS 1 13 MISCELLANEOUS DATA 293 MIXTURES AND ALLOYS, ELECTRO POSITION OF.. 106 MOEBIUS'S PROCESS OF REFINING BULLION 240 MOLECULE, MEANING OF THE TERM 44 MOLECULAR WEIGHTS OF SUBSTANCES 45 MOLLOY'S PROCESS OF TREATING AURIFEROUS EARTHS 275 MONAD, MEANING OF THE TFRM 47 MOTIVE POWER, RELATIVE COST TO THAT OF PLANT 152 SOURCE AND AMOUNT OF IN REFINING COPPER 177 PAGE MUD FROM COPPER SOLUTIONS, COMPOSITION OF 219 ,, EFFECTS OF ____ 220 M >i M ,, TREATMENT OF 221 ,, ., ,, VALUE OF ..... , 221 NECESSARY RATE OF ELECTRO DEPOSITION OF COPPER .................................... 105 NEUHAUSEN, SEPARATION OF ALUMINIUM AT .. 255 NICKEL, ELECTROLYTIC REFINING OF .......... 280 NOMENCLATURE OF ELECTROLYSIS .............. 78 NORTH D;TCH ELECTROLYTIC REFINERY AT HAMBURG .............................. 159-24* NUMBER AND SIZE OF VATS FOR COPPER RE- FINING .................................... 15* NUMBER AND SIZE OF ELECTRODES FOR COPPER REFINING .................................. : R* OERLIKON DYNAMO, THE ...................... 173 OERSTEDT'S DISCOVERY OF ELECTRO-MAGNETISM 140- OHM, MEANING OF THE TERM .............. 25-292 OHMS LAW .................................. 19, OHM METERS .................................. 206 ORDER OF DECOMPOSABILITY OF ELECTROLYTES 114 SOLUTION OF ANODES AND SEPARA- TION OF IONS .................... 115 ORDER OF VOLTAIC POTENTIALITY .............. 51 OSMOSE, ELECTROLYTIC ........................ 83 OXIDES, HEAT OF FORMATION OF .............. 42- PABST'S VOLTAIC BATTERY .................... 59 PACINOTTI'S ARMATURE AND DYNAMO ........ 6-144 PENTAD, MEANING OF THE TERM .............. 47 PERSALTS OF IRON IN THE SOLUTION, INFLUENCE OF .................................. 93-118-214 PHENOMENA, INCIDENTAL ...................... 107 PHYSICAL STRUCTURE OF ELECTRO DEPOSITED METALS .................................... 99 " PIMPLE COPPER," COMPOS.TION OF .......... 189. PIXII'S MAGNETO-ELECTRIC MACHINE .......... 5 PLANNING AN ELECTROLYTIC COPPER REFINERY 149 PLATINOID, CONDUCTION RESISTANCE OF ...... 27-31 POGGENDORFF'S BATTERY ...................... 59, POLARI rv, ELECTRIC ............................ 1 1 POLARISATION OF ELECTRODES .................. 86 IN COPPER DEPOSITING VATS .. 204-208 PORRETT'S EXPERIMENTS ON ELECTRIC OSMOSE.. 83. POTASSIUM, ELECTROLYTIC SEPARATION OF ...... 270- POTENTIAL, ELECTRIC .......................... 13 POTENTIALITY, CHEMICAL ...................... 48 PRACTICAL DIVISION OF THE SUBJECT .......... 149 PREPARING SOLUTIONS FOR DEPOSITING ....... 78 ,, ,, COPPER REFINING .. 194 PRINCIPLES OF ELECTROLYTIC REFINING ........ 8 PROCESSES, ELECTRO-DEPOSITION .............. 74 ,, FOR SEPARATING ALUMINIUM ........ 251 ,, ,. ANTIMONY ........ 247 ,, ., ,. COPPER ........ 225-239. ,, ,, ,, GOLD AND SILVER ,, ,, ,. LEAD .............. 244 MAGNESIUM ...... 266 ., ,, NICKEL ............ 280- ,, ,, ,, POTASSIUM AND SO- DIUM .......... 271 TIN .............. 248 ZINC .............. 261 PRODUCTS, SECONDARY OF ELECTROLYSIS ...... 127 PURITY OF ELECTRO DEPOSITS .................. x jo ,, ,, DEPOSITED COPPER .... 214, 217 PYRITES, TREATMENT OF, FOR OBTAINING COPPER 225-23$ QUANTITY, MEANING OF THE TERM ELECTRIC., i* OF ELECTRIC CURRENT .............. 18 UNIT OF .. 18-29* QUANTITY OF ELECTRO CHEMICAL ACTION ____ 117 ,, HEAT, UNIT OK .............. 37-292 QUINCKE'S EXPERIMENTS ON DENSITY OF CURRENT 98 300 INDEX. '1 PAGE RAOULT'S EXPERIMENTS ON SELF-DEPOSITIONS OF METALS 77 RATE OF DEPOSITION NECESSARY . . 105 USUAL IN COPPER REFINING 150-207 ,, ,, ,, OF COPPER, LIMIT OF.. 126-207 ,, FLOW OF ELECTRIC CURRENT, UNIT OF 292 RECAPITULATION OF THE MODE OF ESTABLISH- ING A COPPER REFINERY 234 REFINERY, PLANNING AN ELECTROLYTIC COPPER 149 AMOUNT OF SPACE NECESSARY IN A COPPER REFINERIES, LIST OF ELECTROLYTIC REFINING OF COPPER, COST OF ELECTROLYTE .. 221 ,, ,, AMOUNT OF ELECTRIC ENERGY NECESSARY 153 ,, ,, NICKEI 280 ZINC AND " ZINC SCUM" 265 RELATION OF CHEMICAL HEAT TO ELECTRO- MOTIVE FORCE 52-54 ,, HEAT TO CHEMICAL ACTION .... 49 REMOVAL OF SEDIMENT FROM COPPER REFINING SOLUTIONS 221 RESISTANCE, ELECTRIC CONDUCTION 24 EXTERNAL AND INTERNAL 34 TRANSFER 34 OF MINERALS, CONDUCTION 33 HEAT OF CONDUCTION 36 INFLUENCE OF TEMPERATURE ON .. 31 OF COPPEK REFINING SOLUTION.... 203 REGULATOR OF 207 RETARDATION OF CURRENT AT ELECTRODES .. 34-96 REUSS'S DISCOVERY OF ELECTRIC OSMOSE 83 REVOLUTION OF DYNAMOS, SPEED OF 179 ROGERS'S PROCESS OF SEPARATING MAGNESIUM 268 ,, ,, ,, ,, SODIUM AND POTASSIUM 271 ROSING'S PROCESS OF REFINING "ZINC SCUM".. 265 SALT, MEANING OF THE TERM 48 SALTS OF GOITER, HEAT OF FORMATION OF.... 115 SAXTON'S MAGNETO-ELECTRIC MACHINE 5 SECONDAKY EFFECTS OF ELECTROLYSIS 106 PRODUCTS OF ELECTROLYSIS 127 SEDIMENT FROM VATS, COMPOSITION, VALUE, AND TREATMENT OF 219-221 SELF-DEPOSITION OF METALS 77 SEPARATE CURRENT METHOD OF DEPOSITION .. 74 SEPARATION OF METAI.S, EARLIEST KNOWN FACT OF ELECTROLYTIC i ,, ELEMENTARY SUBSTANCES, ELEC- TROLYTIC 106 COMPOUNDS, ELECTROLYTIC .... 106 IONS, ORDER OF 115 ALUMINIUM 251 ANTIMONY 247 COPPER 225-239 GOLD AND SILVER 2^0-273-280 LEAD 244 MAGNESIUM 266 NICKEL 280 POTASSIUM AND SODIUM 77-271 TIN 248 ZJNC 261 METALS FROM COINS, ETC 225 ,, MINERALS AND EARTHS 226-273 "SHORT CIRCUITING 22 r SHUNTS 21-205 SIEMENS'S ARMATURE AND DYNAMO.... 6-147-156-235 ,, ELECTRO- DYNAMOMETER 22 SILVER CRYSTALS, ELECTRO-DEPOSITED 101 ELECTROLYTIC REFINING OF 240 WEIGHT OF, DEPOSITED PER AMPERE HOUR 293 SIMPLE IMMERSION PROCESS OF DEPOSITION 74 SINGLE CELL .... 76 SMEE'S BATTERY 59 SMELTING, ELECTRIC 281 SODIUM AND POTASSIUM, SEPARATION OF 270 PAGB SOLUBILITY OF ANODES, INFLUENCE OF 95 SOLUTION, PREPARING THE COPPER i v4 CIRCULATING THE COPPER 194 ,, RESISTANCE OF THE COPPER 203 TEMPERATURE OF THE COPPER 194 SOLUTIONS FOR ELECTRO-DEPOSITION, PREPARING 78 SPACE, AMOUNT OF, REQUIRED FOR ELECTROLYTIC REFINING 149 SPECIFIC GRAVITIES OF LIQUIDS 289 ,, ,, METALS 290 SPEED OF REVOLUTION OF ELECTROLYTIC Dv- NAMOS 179 STANDARD OF ELECTRO- MOTIVE FORCE 17 ,, VOLTAIC CELL 17 STIRRING THE ELECTROLYTE, EFFECTS OF 122 STOLBERG, ELECTROLYTIC REFINERY AT 235 STRENGTH OF CURRENT 18 ,, ,, ,, MEASUREMENT OF 19-153 ,, LIQUID, INFLUENCE OF, ON VOL- TAIC ACTION 6a STRUCTURE, PHYSICAL, OF ELECTRO - DEPOSITED METALS 99 SUBSTANCES, CHEMICAL FORMULAE OF 45 ELECTROLYTIC SEPARATION OF ELE- MENTARY 106 . CHEMICAL EQUIVALENT WEIGHTS OF 46 ,> MOLECULAR WEIGHTS OF 45 SULPHATE OF COPPER SOLUTION, RESISTANCE OF 30 SULPHIDES, METALLIC, AS ANODES 92-234 SURFACE OF CATHODES, AMOUNT REQUIRED IN REFINING COPPER 150-191 SWITCH 205 SYMBOLS AND FORMULAE, CHEMICAL 44, 45 ,, ,, ,, THERMAL 38 TABLE OF AMOUNTS OF COPPER DEPOSITED IN HOT AND COLD LIQUIDS 124 ,, ,, ,, ,, ENERGY REQUIRED TO DECOMPOSE COMPOUNDS 131 ,, ,, ,, ,, CURRENT FROM DIFFER- ENT METALS 64-66 ,, ,, ANALYSES OF MUD FROM VATS 218 ,, ,, AREAS OK CIRCLES 286 ,, ,, ATOMIC WEIGHTS , 44 , t ,, CENTIGRADE AND FAHRENHEIT DE- GREES 291 ,, ,, CORROSION SERIES OF METALS AT 60 AND 160 FAHR 69 ,, DECIMAL EQUIVALENTS OF INCHES AND FEET a86 ,, ,, ELECTRO-MOTIVE FORCE OF VOLTAIC CELLS 59 ,, ELECTROLYTIC EQUIVALENTS OF SUB- STANCES 126-128 ,, ,, ELECTRO-MOTIVE FORCES CALCULATED FROM CHEMICAL HEAT 54 ,, ,, ENGLISH WEIGHTS AND MEASURES .. 287 ,, ,, FRENCH ,, ,, ,, .. 288 ,, FUNDAMENTAL UNITS OF QUANTITY.. 9 ,, ,, DEGREES OF FUSIBILITY OF METALS 289 ,, HEAT OF CHEMICAL UNION 39 ,, ,, FORMATION OF CHLORIDES 41 , ii . >i n OXIDES .... 42 ii n n n n ji SALTS OF COPPER .. 115 ,, ,, Loss OF ANODE AND GAIN OF CATHODE 121 ,, ,, COPPER BY CHEMICAL COR- ROSION 123 ,, ,, ,, ENERGY AS HEAT IN COPPER CONDUCTORS 135 ,, ,, MOLECULAR WEIGHTS AND FORMULA 45 RESISTANCE OF ALLOYS. . . t aj ,, ,, LIQUIDS ..\ 26-28-38 METALS 25-30-32-33 ,, RETARDATION AT ELECTRODES 34-96 ,, SPECIFIC GRAVITIES OF METALS 289 ,, USEFUL DENSITIES OF CURRENT IN DEPOSITING METALS 105 VALENCIES OF ELEMENTARY SUB- STANCES 47 ,, VELOCITIES OF MIGRATION OF IONS.. 83 INDEX. 301 PAGE TABLE OK VOLTAIC EQUIVALENTS OF ELEMEN- TARY SUBSTANCES 64 i. it SERIES 50-56 TEMPERATURE, INFLUENCE OF, ON CHEMICAL CORROSION 67-69-123 ., ELECTROLYSIS 89 M i. ,, RESISTANCE 31-33 6= VOLTAIC AC- TION FOR COPPER RE- ,. OF SOLUTION FINING 194 TKRMS, MEANINGS OF.. 12-14-18-20-23-34-43-47-48-292 TETRAD, MEANING OF THE TERM 47 THEORY OF CHEMISTRY, ELECTRICAL 51 ,, VOLTAIC ACTION 70 THEORIES OF ELECTROLYSIS ,, 134 THERMAL DEPOSITION OF METALS 01 PHENOMENA ATTENDING ELECTROLYSIS 89 ELECTROLYTIC REFINING 36 SYMBOLS AND FORMULAE 38 UNITS 37-292 THERMO-ELECTRIC PILE 16 THERMOMETRIC SCALES, RELATIONS OF 290 THICKNESS OF COPPER DEPOSITED PER HOUR 209-293 '1 HOMSEN'S MEASUREMENTS OF CHEMICAL HEAT 39 THOMSON'S MODE OF CALCULATING ELECTRO- MOTIVE FORCE 52 TIN CRYSTALS, ELECTRO-DEPOSITED 103 ELECTROLYTIC SEPARATION OF 248 TORSION GALVANOMETER 206 TOTAL CONSUMPTION OF ELECTRIC ENERGY IN ELECTROLYSIS 134 "TRANSFER- RESISTANCE" 34 TRANSPORT OF IONS IN ELECTROLYSIS 82 TREATMENT OF PYRITES FOR RECOVERY OF COPPER 226 ,, MUD FROM THE VATS 221 TRIAD, MEANING OF THE TERM 47 TWADDELL'S HYDROMETER SCALE 289 UNEQUAL ACTION AT ELECTRODES 86 UNITS, OF CHEMICAL ENERGY 292 ELECTRICAL 292 CONDUCTION-RESISTANCE 25-292 ENERGY 23-292 STRENGTH OF CURRENT . . 19-292 THERMAL 37-292 OF QUANTITY, SPACE, TIME, FORCE, WORK, ETC 9-291 USEFUL DATA 291 VALENCY, MEANING OF THE TERM 47 VALUE OF THE MUD FROM COPPER REFINING .. 221 ,, ,, ,, STOCK OF COPI-F.R AT STOLBERG 237 VATS AT CASARZA AND STOLBERG 232-237 ,, ARRANGEMENT OF, AT CASARZA 184 PEMBREY 182 CONSTRUCTION OF THE 180 FREQUENCY OF EMPTYING THE 198 ,, INCONVENIENCE OF LARGE 153-182-191 rM^ VATS, INSPECTION OF THE 196 ,, INSULATION OF THE 181 METHOD OF CIRCULATING THE LIQUID IN THE 194 ,, SIZE AND NUMBER OF THE 152-181 VOLT, MEANING OF THE TERM 14-292 VOLT-COULOMB, MEANING OF THE TERM 29* VOLTAMETER 19, VOLTMETER 206 VOLTA'S DISCOVERY OF CHEMICAL ELECTRICITY x VOLTA-TENSION, SERIES OF ELEMENTARY SUB- STANCF.S 50 VOLTA-TENSION SERIES OF ELECTROLYTES 5* ,, ,, ,, METALS IN ELEC- TROLYTES 56, 63 VOLTAIC ACTION, CHIEF FACTS OF 50 CHEMICAL ACTION AND ELEC- TROLYSIS, MUTUAL RELA- TIONS OF 72,73 INFLUENCE OF MAGNETISM UPON 63 THEORY OF 7 <> INFLUENCE OF STRENGTH OF LIQUID UPON 6 INFLUENCE OF TEMPERATURE OF LIQUID UPON 6a ,, BALANCE, THE 53, BATTERIES 58 CURRENT, AMOUNTS OF, PRODUCED BY DIFFERENT METALS 64, 66 ,, ,, INFLUENCE OF EXTERNAL RE- SISTANCE UPON 67 ,i UNEQUAL TEM- PERATURE OF METALS UPON 68- ELECTRICITY, DISCOVERY OF x EQUIVALENTS OF ELEMENTARY SUB- STANCES 64. POTENTIALITY, ORDER OF 51 ,, RELATIONS OF METALS IN ELECTRO- LYTES 56-63. WATER UPON ELECTROLYSIS, INFLUENCE OF .... 88- WATT, MEANING OF THE TERM 23-292 WATT'S PROCESS OF SEPARATING ZINC 264 WEIGHT OK COPPER DEPOSITED PER HOUR 19-128-293. SILVER 19-128-293. SQUARE FEET OF COPPER OF DIFFE- RENT THICKNESS 209-293 WERDERMANN'S METHOD OF TREATING AURI- FEROUS EARTHS 273 WHEATSTONE'S BRIDGE 29. AND LADD'S DYNAMO 6 WILDE'S DYNAMO 155 WOLLASTON'S BATTERY 59, WOOLRICH'S MAGNETO-ELECTRIC MACHINE 5 WORK DONE IN ELECTROLYSIS 130-134-151 WROBLEWSKI'S EXPERIMENTS ON CONDUCTION RESISTANCE 31 ZINC, ELECTROLYTIC PROCESSES OF REFINING 364. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewals only: Tel. No. 642-3405 Renewals may be made 4 days prior to date due. Renewed books are subject to immediate recall. 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