LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class raffi 1 , m . - * ;-- HI THE CYANIDE INDUSTRY THEORETICALLY AND PRACTICALLY CONSIDERED BY E. EOBINE - M. LENGLEN CHEMICAL ENGINEER CHEMICAL ENGINEER Graduate of the School of Physics and "iomreat" of the Conservatoire National Chemistry of the City of Paris des Arts et Metiers and of the Pasteur Institute Director of Works TRANSLATED BY j. ARTHUR LECLERC PH.D., UNIV. HALLE-WITTKMBERG Physiological Chemist, Bureau of Chemistry, Department of Agriculture Washington, D. C. WITH AN APPENDIX BY C. E. MUNROE, Pn.D FIRST EDITION FIRST THOUSAND ^ UNIVERSITY OF NEW YORK JOHN WILEY & SONS : CHAPMAN & HALL, LIMITED 1906 Copyright, 1906 BY j. ARTHUR LECLEBO ROBERT DRUMMOND, PRINTRR, NKW YORK TRANSLATOR'S PREFACE. THE publication of Robine and Lenglen's "L'lndustrie des Cyanures" in the series Encyclopedic Industrielle in France is a good indication of the value of the work. The translation of this book into English makes more accessible to the American worker in Industrial Chemistry the many and various processes proposed for the production of cyanide compounds, and should be a help in stirring him to greater endeavor along these lines. The Index, rarely found in French books, has been added by the translator, and at his suggestion the publishers have appended Dr. Chas. E. Munroe's brochure on " Precious Metals Recovered by Cyanide Processes" which recently appeared as a publication of the U. S. Dept. of Commerce and Labor. The translator, being moreover interested in Agricultural Chem- istry, dares to hope that one of the results of this translation will be the successful fixation of atmospheric nitrogen on an industrial scale. WASHINGTON, January, 1906. iii TABLE OF CONTENTS. PAG INTRODUCTION PART ONE. CHEMISTRY OF CYANOGEN AND ITS DERIVATIVES. CHAPTER I. GENERAL CONSIDERATIONS ..................... . CHAPTER II. PHYSICAL AND CHEMICAL STUDY OF CYANOGEN AND ITS DERIVATIVES ...... 10 Cyanogen. .: ................................................... . 10 Paracyanogen ................................................... 13 Hydrocyanic Acid ............................................... 14 Metallic Cyanides ..... ........................................... 18 Potassium Cyanide ......................................... 20 Sodium Cyanide ........................................... 23 Ammonium Cyanide ....................................... 23- Calcium Cyanide ........................................... 24 Barium Cyanide ........................................... 24 Aluminium Cyanide ................................... ..... 24 Iron Cyanide ........................................... ... 25 Chromium Cyanide .......................... .............. 25 Manganese Cyanide ........................................ 25 Tin Cyanide ............................................... 25 Lead Cyanide ............................................. 25- Copper Cyanide ........................................... 26 Mercury Cyanide .......................................... 26 ; Silver Cyanide ............................................. 26 Cobalt Cyanide ............................ . ............... 27 Nickel Cyanide ...................... . ..................... 27 Gold Cyanide ............................................. 27 Platinum Cyanide ............. ............................ 27 Double Cyanides ................................................. 28 Ferrocyanides. Potassium Ferrocyanide ..................... 29 Ferricyanides ............................................. 32 v TABLE OF CONTENTS PAGE Cobalticyanides 34 Manganocyanides. . 34 Platinocyanides 34 Aurocyanides 35 / Nitroprussiates 35 Oxygen Compounds of Cyanogen 36 \s Cyanic Acid 36 Potassium Cyanate 36 Cyanuric Acid and Tricyanates 37 Sulphocyanides 37 Potassium Sulphocyanide 38 Organic Compounds 39 , Nitriles and Carbylamines 39 v Cyanic Esters 40 CHAPTER III. OENERAL PROPERTIES AND METHODS OF DETERMINATION OP THE VARIOUS CYANIDE COMPOUNDS 42 I. Analytical Properties 42 Hydrocyanic Acid 42 Cyanides. . . 42 Ferrocyanides 43 Ferricyanides 43 Sulphocyanides 43 Cyanates 44 II. Methods for the Analysis of the Various Cyanide Compounds. . 44 Cyanides 44 Liebig's Method 44 Fordos and Gelis' Method 45 Analysis of Commercial Potassium Cyanide 47 O. Hertig's Process 47 Determination of Medicinal Hydrocyanic Acid in Dis- tillates of Bitter Almonds and Laurel Cherry (Bui- gnet Method) 48 Ferrocyanides 49 Sulphocyanides 50 Determination of Ferrocyanides in the Purifying Materials of Illuminating-gas 50 Knublauch's Method 50 Moldenhauer and Leybold's Method. 51 Burschell's Method ^ 52 Zaloziecki's Method 52 Donath and Margosches' Method. 53 Determination of Prussian Blue in the Spent Oxids 54 Method of Nauss of the Carlsruhe Gas Works 54 Toxicological Research 54 TABLE OF CONTENTS. vii CHAPTER IV. PAGE THERMOCHEMICAL DATA OF THE CYANIDE COMPOUNDS 56 I. Cyanogen 56 II. Hydrocyanic Acid 57 III. Potassium Cyanide 58 IV. Ammonium Cyanhydrate 60 V. Potassium Ferrocyanide . . ."T 60 VI. Potassium Cyanate 66 PART TWO. PRESENT CONDITION OF THE CYANIDE INDUSTRY. CHAPTER V. COMMERCIAL AND INDUSTRIAL STUDY PART THREE. METHODS OF MANUFACTURING CYANIDE COMPOUNDS. GENERAL CONSIDERATIONS 81 CHAPTER VI. MANUFACTURE OF CYANIDES 85 I. Non-synthetic Processes 85 A. Extraction of Cyanides from Ferrocyanides 85 Old Process 85 Liebig's Process 87 Wagner's Process .88 Chaster' s Process 88 Rossler and Hasslacher's Process 89 Wichmann and Vautin's Process 90 Dalinot's Process 92 Adler's Process 93 Etard's Process .' . . 94 Bergmann's Process 94 B. Extraction of Cyanides from Sulphocyanides 95 I. By Oxidation 96 Raschen's Process 97 Beringer's Process 101 II. By Reduction 102 Playfair's Process 102 viii TABLE OF CONTENTS. PAGE Hans Luttke's Process. . . , 104 British Cyanide Co.'s Process 105 Hetherington and Musspratt's Process 106 Process of the Silesia Verein Chemische Fabrik. . . . 107 Goerlich and Wichmann's Process 107 Bower's Process 107 Conroy's Process 108 Rasfchen, Davidson, and Brock's Process 110 Etard's Process 110 Finlay's Process 110 II Synthetic Processes General Remarks Ill A. Processes Utilizing Atmospheric Nitrogen 117 Bunsen's Process 123 Possoz and Boissiere' s Process 124 Newton's Process 126 Blair's Process 126 Armengaud's Process! 126 Marguerite and Sourdeval's Process 126 Mond's Process. . 127 Weldon's Process 128 Fogarty's Process 128 Dickson's Process 129 Lambilly's Process 129 Gilmour's Process 134 Young's Process. . . 134 Mackey's Process 135 Readmann's Process 135 Mehner's Process 137 Swan and Kendall's Process 137 Pestchow's Process 137 Chipmann's Process 138 Moi'se and Mehner's Process 140 Castner's Process 141 Hornig and Schneider's Process 143 Mehner's Process 143 Frank and Caro's Process 144 Process of the Chemische Fabrik Pfersee, Augsburg 149 Berniger, Wolfram and Blackmore's Process 150 Dziuk's Process 1 50 Process of the General Electro-Chemical Co 152 B. Processes Utilizing Ammonia 1 53 Lance and Bourgade's Process 156 Mactear's Process 157 Stassfurter Chemische Fabrik' s Process 158 Moulis and Sar's Process 160 Lambilly's Process 161 Beilby's Process 162 Young and Macfarlane's Process 1 63 TABLE OF CONTENTS. ix PAGE Chaster' s Process 165 Pleger's Process 165 Roca's Process. ^ 166 Hood and Salamon's Process 169 Hornig's Process 170 Schneider's Process 171 Castner's Process 172 Process of the Deutsche Gold u. Silber Sheide Anstalt 175 Lambilly's Process 178 Martin's Process. 179 Clock's Process 179 Huntington's Process 180 Hoyermann's Process 180 Roussin Process 181 Kerp's Process 181 Kellner's Process 182 Grossmann's Process 182 III. Special Processes 183 Process of the Chemische Fabrik Aktiengesellschaft 183 Vidal's Process 184 Bueb's Process 185. Ortlieb and Miiller's Process .170 CHAPTER VII. MANUFACTURE OF FERROCYANIDES 192 I. Old Processes, Based on the Use of Nitrogenous Organic Substances 193 Calcination or Production of Metal : 197 Engler's Apparatus . 201 Theory of the Manufacture of Ferrocyanide of Potassium by the Old Process. 205 Yield 207 Lixiviation and Crystallization 210 BrunquelPs Process 210 Karmrodt's Process 211 Conroy's Process 212 Musspratt's Process 212 Goerlich and Wichmann's Process 213 Process of the Castelet Works 213 II. Extraction of Cyanide Compounds from Illuminating-gas and its Residues 214 A. Direct Extraction from Gas 229 Knublauch's Process 231 Gasch's Process 232 Rowland's Process 233 Fowlis' Process 233 Clauss and Domeier's Process 234 Schroeder's Process. . 234 X TABLE OF CONTENTS. PAGE Teichmann's Process 235 Lewis' Process 236 Bueb Process 237 Feld's process 241 B. Extraction of Cyanogen Compounds from the Ammoniacal Liquors 242 Pendrie's Process 242 Bower's Process 243 Lewis' Process 243 C. Extraction of Cyanogen Compounds from the Purifying Materials 245 Gauthier-Bouchard's Process 248 Valentin's Process 256 Harcourt's Process 257 Kunheim's Process 257 Hempel's Process 257 Wolfram's Process 257 Donath's Process 258 Richter's Process 258 Esop's Process 258 Marasse's Process 258 Holbling's Process 259 Lewis' Process 259 Mascow's Process 259 / CHAPTER VIII. MANUFACTURE OF FERRICYANIDES 261 The Chlorine Process. . . i 261 Reichardt's Process 263 Process of the Bouxvillers Mines 264 Dubosc's Process 265 Process of the Deutsche Gold und Silber Sheide Anstalt 265 Kassner's Process. 266 Carl Beck's Process 267 Williamson's Process 267 CHAPTER IX. MANUFACTURE OF SULPHOCYANIDES. 269 Geli's Process 270 Deiss and Monnier's Process 281 Hood and Salamon's Process 282 Brock's Process 282 British Cyanides Co.'s Process \ 283 Albright's Process 285 Tcherniac Process 285 Goerlich and Wichmann's Process 286 TABLE OF CONTENTS. xi CHAPTER X PAGE MANUFACTURE OF PRUSSIAN BLUE AND VARIOUS OTHER COMPOUNDS 288 Soluble Prussian Blue 292 Turnbull's Blue 292 Monthier's Blue or Ammoniacal Prussian Blue 292 Antimony Blue 293 PART FOUR. THE USE OF CYANOGEN COMPOUNDS. CONCLUSIONS 321 TABLES AND DATA 323 APPENDIX: DIGEST OF U. S. PATENTS RELATING TO CYANIDE PROCESSES FOR THE RECOVERY OF PRECIOUS METALS 331 INDEX 403 THE CYANIDE INDUSTRY. INTRODUCTION. Chemical industries are in a high degree artificial and progressive. (BERTHELOT: Opening speech at the International Congress of Chemistry, Paris, 1900.) IF the condition of chemical industry at the beginning and at the end of the nineteenth century be compared, one is immediately impressed with the immense progress which has been accomplished. Chemical industry, at the beginning, being for the most part based on a more or less crude empiricism, could not hope for better results than those brought about either through accident or through long experience. Gradually, the rational study of reactions, and the adaptation of purely scientific ideas and discoveries to manufacturing, made it necessary to have, as the basis of each modus operandi, a pro- found theoretical knowledge. From that moment advance in industrial chemistry was rapid and to-day, also, it is intimately bound to the progress of scientific research; it is the immediate result of it. Among the scientific discoveries which have had a great effect on the progress of industrial chemistry, those which especially relate to the synthesis of bodies should be mentioned. It is, in fact, due to synthesis that numerous compounds, which, till then, nature alone was thought capable of producing, have been successfully reproduced. The processes for the manufacture of certain products have been greatly simplified, and consequently the net cost con- siderably reduced through the industrial adaptation of this principle. 2 THE CYANIDE INDUSTRY. The cyanide industry, which is to be studied in this work, has not escaped this general law. The happy discovery of Scheele, who was the first to obtain Prussian blue, was the starting-point of this industry. Later, potas- sium ferrocyanide was prepared by the calcination of nitrogenous materials in the presence of alkali carbonates, and although this modus operand! was absolutely empirical, it sufficed, for a long time, for the limited demand. It is probable that this state of affairs would have existed even to-day had not the use of potassium cyanide in the metallurgy of gold given to this industry such an impetus that the manufacture of cyanide compounds has made remarkably rapid development. The application of cyanides to the treatment of auriferous mate- rials, which dates bacjc about fifteen years, is therefore the imme- diate .cause of the progress realized. Foreseeing the great role the new industry was to play, manufacturers and investigators eagerly sought out every improvement possible. It should, however, be stated that long before not altogether successful attempts had been made to modify the old processes. In the mean time, the discovery of cyanide compounds in the purifying materials used in the manufacture of illuminating-gas had likewise opened up the field of investigation toward synthetic processes, but only in individual cases, although very interesting in themselves. The early investigations were unquestionably valuable, and those which relate particularly to synthetic production were the starting-point for many researches. This is the tendency of the times; and either in the hope of a simpler manufacture or of approach- ing as close as possible to the theoretical side of the question, we shall see that the synthetic processes for the manufacture of cyanides are now preeminent. These are the processes which in all proba- bility should produce the best results, and should solve the prob- lem satisfactorily from an economical as well as an industrial point of view. The study of this special field of industrial chemistry is there- fore of great interest. Having been occupied for many years with the different questions relating thereto, we find no special works on this subject, at least in France. INTRODUCTION. 3 These reasons led us to bring together in an appropriate didactic order all the documents on this subject which we have been able to collect in the course of our researches; such is the genesis of the work which we present to the public. The work divides itself into four parts: Part I. Chemistry of cyanogen and its derivatives. Part II. The present condition of the cyanide industry. Com- mercial and industrial study. Part III. Methods for the manufacture of cyanide compounds. Part IV. Application of the various cyanide compounds. PART ONE. THE CHEMISTRY OF CYANOGEN AND ITS DERIVATIVES. CHAPTER I. GENERAL LAWS. BY cyanogen combinations is meant all compounds containing the radical CN. This radical is derived from several sources. It may arise from the direct union of carbon .and of nitrogen, which union produces cyanogen CN; or it may arise by addition or substitution from compounds, such as amides, imides, or amines, whose real radical is C or CO. The radical CN may therefore be related to two classes of com- pounds: first, to true cyanogen compounds; second, to isomers of the first class, which isomers contain the same elements in quan- titative proportions; the former differ, however, from the latter from the point of view of their chemical constitution, and are endowed with different and peculiar properties. The formation of cyanogen and of its derivatives, its constitu- tion and the determination of its valency have all been the object of much research, and although these various points have not yet been definitely solved, the results of these various studies allow the question to be thus considered: Carbon, a tetratomic element, is saturated by means of the free nitrogen valencies.- This latter is sometimes triatomic, and sometimes pentatomic. In the latter case three of its GENERAL LAWS. 5 valencies are different from the other two. It follows that the carbon may therefore satisfy three of its valencies; the compound thus formed will have three free bonds, one attached to the carbon and two to the nitrogen. The constitution of cyanogen may therefore, from these considerations, be represented by the formula -C=N = . This constitution of cyanogen allows some of its properties to be at once foreseen. If the nitrogen be replaced by elements of the same atomic value, the original compound becomes transformed into a more carbonaceous one. On the other hand, if the radical CN is connected with an alcoholic radical, the union takes place through the carbon atom. Moreover, Gautier, Wurtz, Limpricht, and Cloez admit that cyanogen is trivalent, for they succeeded in forming the union of hydrocyanic acid and of its esters with the haloid acids. The question of the formation of cyanogen and its com- pounds is far from being solved. It has been the object of much dispute, and deep study has not given sanction to one theory more than to another. The various methods by which this formation may be explained are based, rather, on probabilities than upon real data and an exact knowledge of the phenomena produced. Nevertheless, this question is worthy of attention from more than one point of view. No doubt the discovery of the true method of the formation of the cyanogen compounds would bring about, as an immediate result, the proper process of manufacturing these same compounds. Therefore it may not be useless, at the beginning of this work, to give some idea of the theory of " cyanides," and, without attempting to establish it in a definite manner, to give the pros and cons of each of the theories propounded. It is known that the radical CN cannot be formed through a direct union; it is formed, however, whenever C and N are found in the presence of an alkali at a high temperature: then there is formed a cyanogen compound in which the group CN is found united to the alkali metal. This reaction takes place according to the general formula C+N+M = CNM. This reaction, or rather the formation of the group CN, may be explained in several ways; in favor of each theory strong but 6 THE CHEMISTRY OF CYANOGEN. refutable argument may be presented. The various ways of con- sidering the subject will be treated in order. Let us take, for example, cyanide of potassium composed of the three elements C, N, K, the union of which will give the final product CNK, and let us see under which conditions this product may be formed. Three hypotheses are put forth in explaining this formation. (1) In the presence of the alkali metal the carbon unites with the nitrogen to form cyanogen CN, which, reacting on the alkali metal as fast as it is formed, would give the cyanide of this metal as end reaction (2) The nitrogen unites with the alkali metal to form a nitride, which in contact with carbon becomes transformed into cyanide. (3) First, there is a union of carbon and potassium, forming a carbide, with which nitrogen reacts to produce cyanide. The first thing noted in these three hypotheses is that in each case the final combination takes place only after an intermediary reaction, and that the fixation of nitrogen cannot take place with- out this intermediate agent, the nature of which is still undeter- mined. The first hypothesis is supported by the following facts: When cyanide of potassium is prepared by heating nitrogenous animal matter with an alkali carbonate, it is noticed that the for- mation of the cyanide takes place only at a temperature in the neighborhood of which the alkali carbonate is reduced to a metallic state. Therefore the combination C + N is due to the presence of the alkali metal. Schuetzenberger, among others, puts forth the theory that at the temperature of the experiment the carbon tends to become separated from the alkali with which it is combined. Moreover, if a current of free nitrogen or of ammonia be passed over a mixture of alkali carbonate and charcoal heated to bright redness, there is formation of cyanide. The same result is obtained if nitrogenous matter be heated in the presence of potassium or sodium. All these facts would seem, therefore, to prove that the presence of an alkali metal is necessary to effect the union of car- bon with nitrogen. Another corroboration of these observations GENERAL LAWS. 7 is the fact that cyanide of sodium is formed with much more diffi- culty than cyanide of potassium, a phenomenon which is easily explained, since carbonate of sodium is less easily reducible than carbonate of potassium. The same would be the result if caustic alkalis were used instead of carbonates. That cyanogen and oxygen can not coexist in the same medium is a known fact; on this account it is necessary first to reduce the oxygen compounds in order to permit the formation of cyanides. A third remark, no less important, to add to the two preceding ones, is the following: If a current of nitrogen be passed over car- bon, heated to redness, and the product of this operation be brought into contact with melted potassium, there will be no formation of cyanide. Against these convincing facts the following objection is brought: if a current of nitrogen be passed over a mixture of charcoal and baryta, heated to a temperature lower than that necessary for the reduction of the base, there will be formed a cyanide of barium without there having been a previous formation of metallic barium. The role played by the metal would therefore seem to be destroyed, and the statement just made leads immediately to the discussion of the two other hypotheses: formation of a nitride or of a carbide. Although experiments have not yet clearly proven that the formation of cyanides is possible by means of the intermediate passage through a nitride, yet this method of formation is ex- plicable. Moissan, who prepared nitride of calcium, was enabled, however, by bringing this body in contact with charcoal, to obtain only very small quantities of cyanide. Finally, it is a fact well known that by the action of nitrogen on the carbides of the alkaline earths, these become transformed into cyanides. This phenomenon may explain the formation of barium cyanide mentioned above. It is not at all improbable that the same reaction takes place with the carbides of the alkali metals, although thus far no real experimental data prove it. It still remains to mention Berthelot's hypothesis, a theory quite closely related to that of the carbides. This investigator, having observed that nitrogen and acetylene unite 8 THE CHEMISTRY OF CYANOGEN. directly under the influence of the electric spark, exploding in a mixture of these gases diluted with hydrogen: C 2 H 2 + N 2 = 2CNH, supposes that the formation of cyanides is preceded by that of the acetylide, C 2 K 2 , which, like acetylene, would unite with nitrogen. This question is far from being solved. It is only by means of thermochemical studies of the various phenomena which con- trol these combinations that a clear and exact idea of the conditions under which they are formed will be attained. It is to be hoped that modern investigators may solve this problem; this would be the cause of great progress for the manufacture of cyanide com- pounds. The theory of the formation of ferrocyanide is no better known. In its preparation, by means of nitrogenous substances in the presence of potassium carbonate, a cyanide would be formed according to one of the reactions mentioned above, i.e., there would be formation of cyanogen, reduction of the carbonate to a metallic state, and reaction of .the cyanogen on the metal to form cyanide of potassium. The role which iron plays is unknown; all that is known is that the ferrocyanide is formed only during lixiviation, yet it is necessary that iron be present. The reaction takes place according to the following equations : 2CNK + Fe = (CN) 2 Fe + K 2 , 4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 , or 2CNK + FeS = (CN) 2 Fe + K 2 S, 4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 . The presence of sulphide of iron is explained as follows : Commer- cial potassium carbonate always contains a certain amount of sul- phate. This sulphate being subjected to the action of charcoal and iron, at a high temperature, generates sulphide of iron according to the following equation : K 2 S0 4 +4C=K 2 S+4CO, K 2 S+Fe+2C+2N-= GENERAL LAWS 9 In his treatise on " Medicaments chimiques," Prunier puts forth another theory. According to him, nitride of carbon, which is produced by calcining animal substances, would react on potas- sium carbonate in order to form acetylene. This gas would unite with the potassium set free and with the nitrogen of the nitro- genous substance, or with nitrogen of the atmosphere, according to the following equation: C 2 H 2 + K 2 + N 2 = 2CNK + H 2 , when the iron would, in its turn, react to form cyanide of iron, which, according to the reaction above cited, would become trans- formed into ferrocyanide. It is definitely known that the ferro- cyanide is not formed during the calcination, for at that tempera- ture the ferrocyanide would be decomposed, giving off nitrogen and forming bicarbide of iron and potassium cyanide, according to Liebig's theory: Fe(CN) 6 K 4 = N 2 + 4CNK + C 2 Fe. The formation of sulphocyanides, which is readily produced, is easily understood because cyanogen remains an unsaturated body, as the following formula shows : -C-N-, the sulphur, which is bivalent, saturating two of the free atoms, while the alkali metal saturates the last. A like reasoning may explain the formation of cyanates, the bivalent oxygen of the cya- nates replacing the sulphur of the sulphocyanides. To sum up the study of the union of carbon with nitrogen is interesting from more than one point of view, because of the very difficulty which controls its formation and from the numerous bodies; to which it may give rise, bodies of which a general study will now be made. CHAPTER II. CHEMICAL AND PHYSICAL STUDY OF CYANOGEN AND ITS DERIVATIVES. CYANOGEN, C 2 N 2 = 52. ^MSifiS? 100.00 THE formula of cyanogen is N=C-C=N. It is really a nitride of carbon. double cyanide of iron and of potassium, hydroferrocyanate, yellow prussiate of potash, corresponds to the formula Fe(CN) 6 K 4 . It crystallizes with 3 molecules of water in voluminous monoclinic prisms. It has a citron-yellow color, is flexible, vitreous, and pos- sesses a salty, bitter taste. Its density is 1.833. At 60 C. it loses. its water of crystallization, which, however, does not completely disappear except at 100 C. It is then converted into a white powder. It is soluble in water, which dissolves two parts in cold and four in hot water. Its aqueous solution saturated at 15 C. has a density of 1.444. In absence of air it fuses just below red heat with the produc- tion of nitrogen, potassium cyanide, and iron carbide: Fe(CN) 6 K 4 = FeC 2 + 4CNK + N 2 . In contact with air, potassium cyanate and peroxide of iron are formed. When burned in the presence of an alkali it is entirely con- verted into cyanide of potassium: Fe(CN) 6 K 4 + K 2 C0 3 = 6CNK + FeO + C0 2 . These various reactions are of great importance and are utilized,, as will be seen more in detail later, in the industrial manufacture of cyanides Oxygen exerts no action on ferrocyanide of potassium, but ozone, the electric current, chlorine, bromine, dilute nitric acid, peroxide of lead, manganese dioxide, permanganate of potash, all transform it either wholly or in part into potassium ferricyanide. These various reactions may be expressed thus: 30 THE CHEMISTRY OF CYANOGEN. With chlorine, 2[Fe(CN) 6 K 4 ] + C1 2 = Fe 2 (CN) 12 K 6 + 2KC1. With the electric current, 2[Fe(CN) 6 K 4 ] + 2H 2 = 2KOH + H 2 + Fe 2 (CN) i 2 K 6 . These two reactions are used industrially in the preparation of ferricyanide of potassium. Sulphur converts it into sulphocyanate. When ferrocyanide of potassium is treated with dilute sulphuric acid there is formed hydroferrocyanic acid: [Fe(CN) 6 K 4 ] +2H 2 S0 4 = 2K 2 S0 4 +Fe(CN) 6 H 4 . To hydroferrocyanic acid Friedel attributes the following formula: NH II C N=C/\C=NH I | N=C\/C=:NH II NH With concentrated sulphuric acid there is formed carbon mon- oxide, sulphates of iron, potassium, and ammonium: Pe(CN) 6 K 4 + 6H 2 S0 4 + 6H 2 = 6CO + FeS0 4 + 2K 2 S0 4 + 3(NH 4 ) 2 S0 4 . This reaction is explained as follows : The sulphuric acid is com- bined with iron and potassium sulphates; hydrocyanic acid in pres- ence of moisture has yielded ammonium formate, which, acted upon by sulphuric acid, is converted into ammonia and carbon monoxide. The ammonia thus formed unites with sulphuric acid to form sulphate of ammonia, while the carbon monoxide is set free. The other alkali ferrocyanides of sodium and ammonium have similar properties. They are soluble in water, insoluble or only slightly soluble in alcohol. CHEMICAL AND PHYSICAL STUDY. 31 Ferrocyanide of sodium, Fe(CN) 6 Na 4 -f 12H 2 0, has been pro- posed as a substitute for ferrocyanide of potassium, but so far it has no^ been possible to use it industrially on account of the enor- mous quantity of water of crystallization which it contains and which renders its transportation much more expensive. The alkaline-earth ferrocyanides are white and insoluble. The other metallic ferrocyanides have various colors, which are frequently used in chemical analyses. The most interesting are those of barium, which are white and very soluble ; the cuprous salt, which is red, and the cupric, which is white; the nickel, which is greenish white, and the lead, which is white. Ferrocyanide of iron is, among these latter, very interesting; the ferriferrocyanide is more generally known under the name Prussian blue: [Fe(CN) 6 ] 3 Fe 4 + 18H 2 0. This Prussian blue is formed by the action of a ferric salt on potassium ferrocyanide : 3Fe(CN) 6 K 4 +2Fe 2 Cl 6 = (Fe(CN) 6 ) 3 Fe 4 + 12KC1. It is a dark-blue powder, odorless and insipid. Its fracture has a copper-like lustre. It loses its water of crystallization completely only when decomposed. It is insoluble in water, alcohol, ether, and weak acids. It is soluble in ammonium tartrate and in oxalic acid, giving a violet solution in the former case and a blue solution in the latter. When burned it yields carbonic acid, and water, and carbonate and cyanhydrate of ammonia. When treated with concentrated sulphuric acid it is converted into a white pitchy mass, which on the addition of water is recon- verted into Prussian blue. It is but slowly affected by hydro- chloric acid. Potassium hydroxide converts it into ferric hydrate and potassium ferrocyanide. This reaction is utilized in the manu- facture of potassium ferrocyanide extracted from the purifying materials of illuminating-gas. The alkali carbonates act in the same way, but less easily. 32 THE CHEMISTRY OF CYANOGEN. Soluble Prussian blue is the name given to the compound formed by the union of ordinary Prussian blue with f errocyanide of potassium* FERRICYANIDES. Beside the ferrocyanides is placed another class of double cyan- ides which is derived from them the ferricyanides. Ferricyanides may be considered as double ferrocyanides minus 2 atoms of metal: 2Fe(CN) 6 K 4 -K 2 = Fe 2 (CN) 12 K 6 . The tetratomic ferrocyanogen radical, Fe(CN) 6 , uniting with itself by exchanging two valences, is transformed into the hexatomic radical Fe2(CN)i2- Various authors consider the ferricyanides as double cyanides of ferric iron with another metal; others, on the other hand, think that they result from the union of a metal with the radical Fe 2 (CN)i 2 . The following ferricyanides are known: Potassium, red; silver, orange; barium and potassium, black; calcium, gold color; cobalt, red; copper, yellow; nickel, greenish yellow. The ferricyanides of the alkalis and of the alkaline earths only are soluble; the others are, as a rule, insoluble. The most interesting is ferricyanide of potassium, also called cyaniferride, red prussiate of potash. The discovery of this salt was made by Gmelin. Its percentage composition is as follows: fFe =17.02 100Fe 2 (CN) 12 K a = | CN = 47.42 [K =35.56 100.00 It occurs as red rhombic anhydrous prisms, having a density of 1.800 to 1.845 according to different investigators. It has a salty taste, is soluble in water, especially so in hot water. At 4.4 C. one part of the salt is soluble in 3.03 parts water, yielding a solution whose sp. gr. is 1.151. At 104 C. 1.22 parts water dissolve one part salt; the solution then has a density of 1.265. Dilute solutions of f errocyanide are orange-yellow; concen- trated solutions are yellowish-brown. A solution of ferricyanide is decomposed in the light and on boiling, ferrocyanide being formed. CHEMICAL AND PHYSICAL STUDY. 33 It is precipitated from its solutions of alcohol. Under the influ- ence of heat it crackles, and is converted into ferrocyanide, nitrogen, cyanogen, Prussian blue, paracyanogen, and iron carbide. When burned in the flame of a candle it emits sparks of iron. Electrolysis and reducing agents, such as hydrogen sulphide, convert it into ferrocyanide: 2Fe 2 (CN) i 2 K 6 + 2H 2 S = 3Fe(CN) 6 K 4 + Fe(CN) 6 H 4 + 2S. Nitric acid converts it into nitrate and nitroprusside of potassium. Bed prussiate peroxidizes the greater part of metallic oxides. Hydrochloric acid decomposes a solution of ferricyanide of potassium, transforming it into ferricyanide of iron. When treated with ammonia it yields ferrocyanide of potassium and of ammonium and nitrogen. It oxidizes phosphorus, sul- phur, sulphurous acid, and sulphites; it converts oxalic acid and oxalates into carbonates. Organic substances in general, and especially in the presence of ferric salts, likewise exert a reducing action on ferricyanide of potassium. All these reactions are very easily carried out if one operates in alkaline solutions. When a solution of a ferrous salt is treated with potassium ferri- cyanide a beautiful blue precipitate is obtained, which is called Turnbull's blue, Fe 5 (CN)i 2 +zH 2 0. This blue is distinguished from Prussian blue in that when it is heated with carbonate or hydrate of potassium it yields ferroferric hydrate and yellow prus- siate, while Prussian . blue under the same conditions yields ferric hydrate : Fe 5 (CN)i 2 +8KOH= 2[Fe(CN) 6 K 4 ] +Fe 3 (OH) 8 Just as there is to the ferrocyanides a corresponding acid, hydro- ferrocyanic acid, so to the ferricyanides there is a corresponding acid, hydroferricyanic acid, Fe 2 (CN)i 2 H6, which, according to Friedel, may be represented by the following formula: HN=C O=N v > N=C HN=C C=N N=CC=NH 34 THE CHEMISTRY OF CYANOGEN. Among the other interesting double cyanides must be mentioned the cobalticyanides, mangano- and manganicyanides, and finally the platino- and platinicyanides. COBALTICYANIDES. Cobaltocobalticyanide is similar to TurnbulPs blue. Hydro- cobalticyanic acid is quite energetic, capable of decomposing car- bonates, of dissolving iron and zinc, setting free hydrogen, and of neutralizing alkali bases. The most interesting of the cobalti- cyanides are those of potassium, C02(CN)i2K 6 , an anhydrous salt, pale yellow, slightly soluble in water, insoluble in alcohol; of cop- per, Co 2 (CN)i 2 Cu3 + 7H 2 0, clear blue, insoluble in water and in acids, soluble in ammonia. The cobalticyanide of nickel, Co 2 (CN)i 2 Ni 3 + 2H 2 0, blue when moist, green when dry, insoluble in water and acids, soluble in ammonia. The cobalticyanides are not toxic; they are in all respects analo- gous to ferricyanides. MANGANOCYANIDES. Manganocyanides are very unstable in air, which converts them into manganicyanides, which are likewise easily decomposable. Their solution is stable only in the presence of potassium cyanide. PLATINOCYANIDES. Platinocyanides correspond to the general formula Pt(CN) 6 M 2 . They may be considered either as combinations of cyanide of plati- num with a basic cyanide, or as the result of the union of a metal with the diatomic radical Pt(CN)e. Soluble platinocyanides are obtained by dissolving platinocy- anide hi an alkali cyanide, or else by precipitating platinous chloride with pot ssium cyanide. The other platinocyanides are obtained by double decomposition. Platinicyanides are obtained by the action of oxidizing agents on platinocyanides. Their mode of formation is doubtful; at present the best hypoth sis known is that of Hadow, who considers the platini- cyanides as a union of the platinocyanide with the oxidizing agent used in obtaining them. ' CHEMICAL AND PHYSICAL STUDY. 35 AUROCYANIDES. More stress will be laid on the double cyanides of gold, or auro- cyanides, on account of the impetus which they have given to the cyanide industry. Aurous cyanide unites easily with the cyanides of the other metals, yielding double cyanides, among which may be cited: (1) Aurosoammonium cyanide, Au(CN)2NH4, obtained by mixing saturated solutions of ammonium sulphite with auricopotassic cyanide. It is readily soluble in water and in alcohol. It is decomposed be- tween 200 and 250 C. (2) Aurosopotassic cyanide, or aurocyanide of potassium, Au(CN) 2 K, obtained by dissolving cyanide of gold, oxide of gold, or fulminating gold in potassium cyanide. It crystallizes in mother- of-pearl scales, is anhydrous, colorless, has a salty taste, is stable in air, soluble in 7 parts cold water, more soluble in boiling water, slightly soluble in alcohol, insoluble in ether. It is decomposed in a closed vessel, setting cyanogen free, and leaving ' a residue of potassium cyanide and gold. Acids break it up into aurous cyanide. Auricopotassic cyanide, or auricyanide of potassium, Au(CN)4K, occurs as large colorless, efflorescent crystals capable of being fused into a liquid which sets cyanogen free and leaves behind metallic gold. NITROPRUSSIATES Nitroprussiates, or nitroferricyanides, are obtained when nitric acid acts on the ferro- or ferricyanides. According to Gerhardt, the formation of these compounds is due rather to the action of nitrogen dioxide which is formed by the nitric acid. This author ascribes to them the following formula : Fe(CN) 5 (NO)M 2 or Fe 2 (CN)io(NO) 2 M4. They are non-saturated ferrocyanides, of which the radical CN is replaced by NO, or may be considered as ferricyanides where 2 (NO) replaces the group 2(CN)M. These salts are generally highly colored. Those of potassium, sodium, ammonium, barium, calcium, and lead are dark red, readily soluble, and distinctly cystaUine; those of copper, silver, zinc, iron, and nickel are insoluble. Alkalis decompose them, likewise does concentrated sulphuric acid; some of them dissolve Prussian blue. They give with sulphides purple color which is little stable. On heating them, nitrosulphides are produced. 36 THE CHEMISTRY OF CYANOGEN. OXYGEN COMPOUNDS OF CYANOGEN. CYANIC ACID, CNOH = 43. [ C= 27.90 100CNOH= J:gJ H- 2.33 100.00 Cyanic acid is an oxygen compound of cyanogen, which was discovered in 1818 by Vauquelin, later studied by Woehler and Liebig. Its formula is CNOH. It is monatomic. It is a colorless liquid, 'with sharp odor, the vapors of which irritate the eyes decidedly. It is soluble in water, but its solution readily breaks up into car- bonic acid and ammonia. Its solution in ether is the only one which is stable. When its alcoholic solution is heated it yields asters of allophanic acid. With metals it produces cyanates, salts which are quite stable when dry, except copper, mercury, and silver cyanates, but the presence of moisture breaks them up into carbonate and ammonia: 2CNOM + 3H 2 = M 2 C0 3 + 2NH 3 + C0 2 . They are, as a rule, soluble. The cyanates of copper, mercury, and silver are only slightly soluble. Dilute acids decompose them into cyanic acid, but quite often into carbonic acid and ammonia. With concentrated acids, cyam- elide is formed. The alkali cyanates are obtained by igniting in air the corre- sponding cyanides, especially in the presence of metallic oxides, as, e.g., oxide of lead, manganese, or copper. CYANATE OF POTASSIUM, CNOK=81. C = 14.81 100CNOK= 5:j K = 48.14 100.00 Cyanate of potassium occurs as transparent anhydrous crystals, soluble in water. It is obtained, generally, by heating manganese dioxide with potassium ferrocyanide to redness. CHEMICAL AND PHYSICAL STUDY. 37 It is gradually decomposed by moist air and by water into carbonate of potassium and ammonium. Potassium dissolves in melted cyanate, yielding cyanide and oxide. Cyanate of sodium, CNONa, has analogous properties. Cyanate of ammonium is an isomer of urea, which it yields when heated at a moderate temperature, CNOH-NH 3 . Silver cyanate is white, readily soluble in ammonia and dilute nitric acid. When heated it explodes rather violently, leaving a residue of silver carbide. CYANUEIC ACID AND TRICYANATES. Cyanuric acid was discovered by Scheele and studied successively by Serullas, Woehler, and Liebig. It is obtained in many reac- tions, but the best method of producing it is that of Wurtz, which consists in passing dry chlorine through . melted urea and treating the residue successively with cold and with boiling water. It is a solid, crystallizing in octahedrons, odorless, tasteless, readily soluble in water, alcohol, and concentrated mineral acids. It is acid in reaction. It volatilizes at 360 C., when it is converted into cyanic acid. By prolonged boiling with concentrated acids it breaks up into carbonic acid and ammonia. With metals it yields tricyanates, which are only slightly soluble. They are decomposed by strong acids which set cyanuric acid free. When the tricyanates are heated they are converted into cyanates. SULPHOCYANIDES. Sulphocyanides, or rhodanides as they are sometimes called, are really sulphocyanates. They are formed by the union of sulpho- cyanic acid with a metal. This sulphocyanic acid is really cyanic acid in which the oxygen has been replaced by sulphur: CNOH, CNSH. For a long time it was wrongly considered as a hydrazid of the com- plex sulphocyanogen radical (CN)S. The sulphocyanides have the general formula (CN)SM. Most of them are soluble in water, alcohol, and ether, especially those of the alkali metals. They easily form double salts. As to the 38 THE CHEMISTRY OF CYANOGEN. sulphocyanides of the heavy metals, they are insoluble, but are decomposed on boiling with the alkalis. Dilute acids decompose them even in the cold, with the exception of those of silver, mercury, and copper. In acid solution they are oxidized by permanganate of potash into hydrocyanic acid and sulphuric acid. Among the many sulphocyanides only the most important will be studied. SULPHOCYANIDE OF POTASSIUM, CNSK = 97. f C = 12.37 100(CN)SK- j *:JJ IK = 40.20 100.00 This is an anhydrous, extremely deliquescent salt, crystallizing in prisms or in needles, of a density 1.886 to 1.906, very soluble in water and in alcohol (100 parts water dissolve 130 parts). Its solution in water is accompanied by an appreciable lowering of temperature (150 parts of this salt dissolved in 100 parts of water at 11 C. cause a temperature of. 23 C.). It has a fresh and pun- gent taste, but it is not poisonous. According to physiologists, it occurs in the human saliva. When ignited in air it is converted into potassium sulphate, though it is capable of withstanding a dull red heat for a long time without decomposition. Its aqueous solution undergoes a slow decomposition, which may be hastened by application of heat. Ammonia is set free. Chlorine and nitric aoid decompose it. When heated with a metal, potassium cyanide and a metallic sulphide are formed: CNSK+Fe = CNK+FeS. This reaction has been used as a means of obtaining the alkali- cyanides. Sulphocyanide of sodium, (CN)SNa, has analogous properties. Sulphocyanide of ammonium, (CN)SNH 4 , occurs in the form of deliquescent prisms readily soluble in alcohol and in water (105 parts in 100 water). A mixture of 133 parts of this salt with 100 CHEMICAL AND PHYSICAL STUDY. 39 parts of water at 13 C. causes a lowering of 31 in temperature. It melts at 159 C., and when heated to 170 C. it becomes trans- formed into sulphocarbamide : NH2 or thiourea. NH 2 . When subjected to dry distillation it is decomposed, yielding hydrogen sulphide, and sulphides of carbon and ammonia, leaving a residue of melam. It is capable of dissolving salts of sulphur. Silver sulphur cyanide is a white curdy precipitate, insoluble in water and ammonia, soluble in the sulphocyanides of ammonia and of potassium. ORGANIC COMPOUNDS. By substitution of the group CN for OH hydrocyanic acid is capable with alcohols of forming hydrocyanic esters, which may be divided into two classes. In the first class, the alcoholic radical is attached to the carbon; in the second, it is attached to the nitro- gen. These are isomeric bodies; the 'former are called nitriles and correspond to the general formula R C = N; the latter are carbyl- amines or isonitriles, their formula being represented by R N = C. These are rather interesting bodies which should not be overlooked. NITRILES AND CARBYLAMINES. Nitriles are derived from amides through dehydration. Nitriles possess general analogous properties whatever may be the atomicity of the alcohols from which they are derived; they form a clearly defined class of compounds. Nitriles have the following prope ties Under the influence of nascent hydrogen they fix 4 molecules of this element and form primary amines. Under the influence of dehydrating agents nitriles fix 2 mole- cules of water and are converted into ammonia salts of acids con- taining the same number of carbon atoms as the hydrocyanic acid ester used. Thus methyl cyanide gives ammonium acetate. They fix likewise one molecule of hydrogen sulphide in pro- ducing amido-sulphides. They unite with hydracids, with negative chlorides, and with bromides. 40 THE CHEMISTRY OF CYANOGEN. The lowest member of the nitrile series is hydrocyanic acid, or formonitrile, H C=N. Among the most important may be cited: Methyl cyanide, or acetonitrile, CH 3 CN, a colorless liquid, lighter than water (sp. gr. 0.81-0.83), volatilizing at 77-78 C., having a pungent, aromatic, and ether-like odor. It is obtained by distilling ammonium acetate with anhydrous phosphoric acid. Ethyl cyanide or propionitrile, C 2 H 5 CN, is a colorless liquid having an alliaceous odor, sp. gr. 0.78, boiling-point 96.5 C. Propyl cyanide, or but yronit rile, CH 3 CH 2 CH 2 CN, having a density of 0.79 and boiling at 116 C. Butyl cyanide, C 4 H 9 CN, density 0.816, boiling-point 126 C.; amyl cyanide, C 5 HuCN; allyl cyanide, CH 2 : CH CH 2 CN, density .839, boiling-point 118 C.; cetyl cyanide, Ci 6 H 33 CN. The properties of the hydrocyanic esters of the second class, or carbylamines, are quite different from those of the nitriles. They are generally formed by the action of alkyl iodides on silver cyanide : Carbylamines are distinguished from nitriles, their isomers, by their odor, which is often disgusting, by their higher boiling-point, by their property of combining directly with acids, and finally by the action which hydrating and oxidizing agents produce upon them. In this case they yield, as do the nitriles, two products, one fixed, the other variable, according to the ester employed. But here the fixed product is no longer ammonia, and the variable product an acid more or less rich in carbon. The first is always formic acid, while the latter is an ammonium compound. Thus methylcarbyl- amine, ethylcarbylamine, amylcarbylamine yield, respectively, with hydrating agents, by fixing 2 molecules of water, methylamine, ethyl- amine, and amylamine. CYANIC ESTERS. By its union with alcohol radicals, cyanic acid also yields cyanic esters, or alcoholic carbimides. The following only will be men- (CO n TT , methyl cyanate, and butyl cyanate. ^2^15 These are mobile liquids, possessing repulsive odors and high boil- CHEMICAL AND PHYSICAL STUDY 41 ing-points. Potash converts them into primary amines. It is ta Wurtz that we owe the discovery and study of these bodies. But these are not true cyanic esters. The true yanic esters were discovered by Cloez. They are isomeric with the esters discovered by Wurtz, but with this differ- ence, that under the influence of hydrating agents they no longer yield amines a,;jd carbonic acid as do the ' carbimides, but behave themselves as ordinary esters and yield the same alcohol as was used at the start, and a cyanate or tricyanate. Their density is. also somewhat higher. CHAPTER III. GENERAL PROPERTIES AND METHODS OF DETERMINATION OF THE VARIOUS CYANIDE COMPOUNDS. I. ANALYTICAL PROPERTIES. HYDROCYANIC ACID. THE analytical properties hydrocyanic acid are the following: Silver nitrate : White precipitate soluble in ammonia and in boiling nitric acid. Iron s ts in the presence of alkalis: By adding potash and a few drops of a ferrous and a ferric salt to a hydro- cyanic acid solution there is formed a precipitate. If this be treated with hydrochloric acid, the oxide of iron dissolves, and the liquid remains dark blue, due to the Prussian blue in suspension. The following method can be used in the detection of even 1 /20ooth part of hydrocyanic acid: To the liquid to be tested, add a little potash and a small amount of copper sulphate. This produces a precipitate of cyanide and hydrate of copper. By treat- ing this precipitate with hydrochloric acid the hydrate dissolves, leaving a white residue of copper cyanide. Liebig and Taylor's method is also quite delicate. This con- sists in converting hydrocyanic acid into ammonium sulphocy- anate, by heating it with ammonium sulphide until decolorized. On adding a drop of a ferric salt to this sulphocyanate a blood- red coloration is produced. CYANIDES. Silver nitrate gives a white, curdy precipitate, soluble in excess of reagent, soluble in ammonium hydroxide, insoluble in dilute nitric acid. On igniting silver cyanide, it sets free cyanogen gas, burning with a purple flame. Ferrous-ferric salt gives a dirty-green precipitate with neutral 42 ANALYTICAL PROPERTIES. 43 solutions; a precipitate of Prussian blue and a ferrous-ferric oxide in alkaline solution. On addition of an acid the latter dissolves, leaving Prussian blue. Copper sulphide and tincture of guaiacum, if acidulated with a drop of hydrochloric acid, give an intense blue coloration. Acids give free hydrocyanic acid, recognized by its odor of bitter almonds. Calcium chloride: no precipitate. Ammonium sulphide when heated with cyanides and evaporated to dry ness, gives a red coloration on the addition of a ferric salt. FERROCYANIDES. Calcium chloride gives a precipitate in concentrated solutions. If the solution to be tested is only moderately concentrated, no precipitate occurs. Silver nitrate produces a reddish-brown pre- cipitate insoluble in nitric acid and in ammonia. ' Ferrous sulphate produces a white precipitate, which on expo- sure to the air rapidly changes to blue by oxidation. Chlorine and nitric acid oxidize this precipitate instantly. Ferric chloride gives a precipitate of Prussian blue, insoluble in hydrochloric acid, but decomposed by boiling potash. Copper sulphate gives a brownish-red precipitate insoluble in HC1. Concentrated sulphuric acid, hot, sets free pure carbon monoxide. If the acid be dilute, hydrocyanic acid is set free. FERRICYANIDES. Silver nitrate gives an orange- yellow precipitate readily soluble in ammonia, insoluble in nitric acid. Calcium chloride: no precipitate. Ferrous sulphate produces a blue precipitate insoluble in HC1. Ferric chloride yields brown coloration. Copper sulphate gives greenish-yellow precipitate insoluble in HC1. Sulphuric acid gives same reactions as with ferrocyanides. SULPHOCYANIDES. Silver nitrate gives a white flocculent precipitate, soluble in excess of the reagent, slightly soluble in ammonia. Calcium chloride: no precipitate. 44 THE CHEMISTRY OF CYANOGEN. Ferric chloride produces a blood-red coloration, stable in the pres- ence of HC1, but disappearing when exposed to heat or to the action of nitric acid, sulphurous acid, hyposulphites, or alkalis. Copper sulphate and sulphurous acid give a white precipitate of copper sulphocyanide insoluble in acids, soluble in ammonia. Lead acetate produces a crystalline precipitate which forms quite slowly. Sulphuric or hydrochloric acid produces no effect if the sulpho- cyanide solution be dilute and cold ; at the end of some time a yellow coloration takes place, and later a yellow precipitate of persulpho- cyanic acid; in warmth, carbon dioxide is set free, besides sulphide of carbon and hydrogen sulphide. Dilute nitric acid gives, in warmth, a yellow deposit of persulpho- cyanogen. Molybdic acid dissolved in HCl gives a red coloration which may be absorbed by ether. CYANATES. Silver nitrate produces a white precipitate which can be decom- posed by heat and is soluble in ammonia and in nitric acid. Lead acetate gives a white crystalline precipitate soluble in boiling water (distinct from that produced in hydrocyanic solution). Dilute and cold sulphuric acid yields carbonic acid possessing a pungent odor due to a mixture of this acid with non-decomposed cyanic acid. II. METHODS FOR THE ANALYSES OF THE VARIOUS CYANIDE COMPOUNDS. CYANIDES. Liebig's Method. This is a volumetric method based on the following reactions: If to a solution of potassium cyanide is added a solution of silver nitrate, there is formed silver cyanide soluble in the potassium cyanide still remaining in the solution. Cyanide of silver is formed permanently only when all the potassium cyanide has been converted into the double cyanide. The appearance of the slightest amount of a permanent precipitate indicates the end of the reaction: ANALYTICAL PROPERTIES. 45 CNK+AgN0 3 = CNAg+KN0 3 , (1) CNK+CNAg=(CN) 2 KAg, (2) or 2CNK+AgN0 3 = (CN) 2 KAg+KN0 3 . One molecule or 170 grams of silver nitrate requires therefore two molecules or 130 grams of potassium cyanide to form one molecule of the double cyanide of silver and potassium. A solution of silver containing 13.056 grams of pure silver nitrate per liter is prepared, and another solution containing one gram of potassium cyanide in 100 cubic centimeters of distilled water is made, of which 10 cc. are used. Several drops of a solution of sodium chloride are added, and then the solution of silver nitrate is run in drop by drop until a permanent precipitation is formed. Each tenth of a cubic centi- meter of the silver nitrate used corresponds to one milligram of potassium cyanide. Three or four titrations should be made and the average taken. This method is applicable to solutions of hydrocyanic acid, which must first be saturated with potash. If the cyanide . contains chlorides, the method is not accurate. In this case the gravimetric method is preferable. The solution of cyanide is precipitated by silver nitrate, the precipitate is filtered, washed, dried, and weighed. Then it is boiled with HC1, which converts the silver cyanide into silver chloride. This is filtered, washed, dried, and weighed again. From the increase in weight may be calculated the quantity of cyanide. 1 gram CNK should give 2.058 grams CNAg. Fordos and Gelis' Method. This method is to be recommended. It is based on the ability of potassium cyanide to decolorize a solu- tion of iodine in alcohol or in potassium iodide. The reaction is as follows: CNK+I 2 = KI + CNL That is, there is a formation of potassium iodide and of cyanogen iodide, both of which are colorless. The end of the reaction is indicated by the yellow colora- tion of iodine in excess; The iodine solution is prepared by dissolving 40 grams pure iodine in one liter alcohol of 33. Five grams of the cyanide to be analyzed are dissolved in 500 cc. distilled water. 50 cc. of this 46 THE CHEMISTRY OF CYANOGEN. solution are transferred to a 2-liter flask, to which is added 1 liter of water and 100 cc. seltzer- water. The addition of this carbonated water converts the bases and carbonates to bicarbon- ates, which do not absorb iodine. Then the iodine solution is added drop by drop, stirring constantly, till the yellow coloration char- acteristic of iodine dissolved in potassium iodide appears. From the volume of iodine solution used must be subtracted the quantity of cyanide, knowing that 254 parts of iodine are absorbed by 65 parts of potassium cyanide. If, at the end of the titration, the solution, colored by several drops of iodine in excess, has a tur- bid instead of a transparent appearance, this is an indication of the presence of alkaline sulphides. In this case it is best before titrating to remove the sulphides of the alkalis by means of a solution of lead acetate or of zinc sulphate, filtering and washing thoroughly. The following table, calculated by Fordos and Gelis, gives the percentage of cyanide directly: Iodine Absorbed. Cyanide %. Iodine Absorbed. Cyanide %. Iodine Absorbed. Cyanide % Iodine Absorbed Cyanide %. 3.896 100 2.922 75 1.948 50 0.974 25 3.857 99 2.883 74 .909 49 0.935 24 3.818 98 2.844 73 .870 48 0.896 23 3.779 97 2.805 72 .831 47 0.857 22 3.740 96 2.766 71 .792 46 0.818 21 3.701 95 2.727 70 .753 45 0.779 20 3.662 94 2.688 69 .714 44 0.740 19 3.624 93 2.649 68 .675 43 0.701 18 3.585 92 2.610 67 .636 42 0.662 17 3.546 91 2.571 66 .597 41 0.623 16 3.507 90 2.532 65 .558 40 0.584 15 3.468 89 2.493 64 .519 39 0.545 14 3.429 88 2.454 63 .480 38 0.506 13 3.390 87 2.416 62 .441 37 0.467 12 3.351 86 2.377 61 .402 36 0.428 11 3.312 85 2.338 60 .363 35 0.389 10 3.273 84 2.299 59 .324 34 0.350 9 3.234 83 2.260 58 .285 33 0.311 8 3.195 82 2.221 57 .246 32 0.272 7 3.156 81 2.182 56 .208 31 0.233 6 3.117 80 2.143 55 .169 30 0.194 5 3.078 79 2.104 54 .130 29 0.155 4 3.039 78 2.065 53 .091 28 0.116 3 3.000 77 2.026 52 .052 27 0.077 2 2.961 76 1.987 51 1.013 26 0.038 1 ANALYTICAL PROPERTIES. 47 ANALYSIS OF COMMERCIAL POTASSIUM CYANIDE. There are numerous methods, but only the most interesting and the best adapted, either in manufacturing or in gold-mining, will be cited. Commercial potassium cyanide quite often contains impuri- ties, such as the carbonate, sulphate, cyanate, formate, sulphide, ferrocyanide, sulphocyanide, and sometimes chloride of potassium. Carbonates may be detected by dissolving the salt in water and add- ing acids, which will cause effervescence, or adding lime-water, which will produce a turbidity. Cyanates may be detected in two ways: ," (1) By extracting the salt with alcohol of 84 and adding con- centrated hydrochloric acid to the alcoholic solution, when car- bonic acid will be set free; or (2) By adding ammonium chloride to the alcoholic solution and boiling urea is formed, which may be separated by evaporating to dryness on the water-bath, and taking up the residue with alcohol. When urea is acted upon by an alkaline hypobromite, nitrogen is set free. Formates may be detected by adding several drops of mercuric chloride to a boiling solution of cyanide, when, if formates are pres- ent, there will be produced a precipitate of calomel. Potassium sulphide may be detected by the aid of lead salts, which give a black precipitate. If the cyanide contains ferro- cyanide, its aqueous solution will give a precipitate of Prussian blue with a ferric salt (pure cyanide gives a greenish precipitate). Sulphocyanide may be detected by treating the solution with a slight excess of HC1 and then with ferric chloride, when a red coloration will be formed. Chlorides may be detected by precipitating the solution with a slight excess of silver nitrate, and then boiling the precipitate in nitric acid. If the precipitate completely dissolves, there are no chlorides. Analysis of Cyanates. (Method of 0. Hertig, Zt. fur angew. Chem. 1901, p. 619.) The method is based on the decomposition of cyanates by hydrochloric or sulphuric acid, with formation of an ammoniacal salt: 48 THE CHEMISTRY OF CYANOGEN. (1) CNOK+2HC1 + H 2 = KC1+NH 4 CH-C0 2 . (2) 2CNOK + 2H 2 S0 4 + 2H 2 = (NH^ 2 S0 4 4- K 2 S0 4 + 2C0 2 . Dissolve 0.2-0.5 gram cyanide in a porcelain dish in several cubic centimeters of water. Add either dilute HC1 or H 2 S0 4 and evaporate to dryness. Take up with water. The solution contains ammonia, which may be determined by boiling with soda, the ammo- nia being driven off and collected in n/5 sulphuric acid, which is afterward titrated, using fluorescein as indicator. Determination of Potassium. If this is done by means of plati- num chloride, after the cyanates have been decomposed with HC1, the presence of ammonium chloride may lead to errors. It is necessary in this case, after the cyanates have been decomposed by HC1, to drive off the ammonia at a dull red heat in a platinum dish. BUIGNET S METHOD FOR THE DETERMINATION OF HYDROCYANIC ACID IN MEDICINE, AND IN DISTILLATES FROM BITTER ALMONDS OR LAUREL- CHERRY. This method is based on the fact that when a solution of hydro- cyanic acid or an alkaline cyanide containing an excess of ammonia is treated with a solution of copper salt, there is first formed a double salt of copper and ammonium, which is colorless. When the reac- tion is complete, the ammonia acts on the copper salt added and gives the characteristic blue color. This indicates the end of the reaction, which takes place as follows: 4CNNH 4 + CuS0 4 = (NH 4 ) 2 S0 4 + Cu(CN) 2 ,2CNNH 4 . For this purpose there is used a copper-sulphate solution containing 23.102 grams of the pure crystalline salt, free from efflorescence, per liter of water. Take 1 cc. of the medicinal hydrocyanic acid, or 100 cc. of the laurel-cherry or bitter-almond extract, or 0.5 gram of alkaline cyanide dissolved in about 100 cc. water, and to such a solution add 10 cc. ammonia, and stir. Then add, drop by drop, the solution of copper sulphate, stirring constantly, till the blue color becomes permanent. Each drop of the copper solution produces ANALYTICAL PROPERTIES. 49 at first a pinkish spot, which later changes to a delicate purple when the end reaction is near completion. At this point the further addition of copper salt must be done with care. This method is scarcely applicable except for cherry water-extract. It gives results which are inexact, especially if a too large amount of water be added; because the cuproammonium cyanide may be decomposed by water. It happens sometimes that even in the titration of the cherry solu- tion there is formed, from the first, a permanent violet color, which interferes with the delicacy of the reaction, especially at the end. This may be remedied by the addition of carbonate of ammonia (10 cc. of a solution containing 1 part ammonium c rbonate, 4 parts water, and 1 part strong ammonia). FERROCYANIDES. Erlenmeyer's method is the one most generally used in the deter- mination of ferrocyanide. It is based on the precipitation of ferro- cyanide as Prussian blue. It is both rapid and 'accurate. Another method is based on the following : When an acidified solution of commercial ferrocyanide is treated with potassium per- manganate, the potassium ferrocyanide alone produces an oxidation product capable of reproducing the raw material under the influence of ferrous oxide in alkaline solution, while none of the other oxidized substances are at all affected by this same ferrous oxide. The mode of procedure is as follows : 3 grams of ferrocyanide are dissolved in water in a 500-cc. graduated flask. The solution is acidified with sulphuric acid, and then a concentrated solution of potassium permanganate is added until a permanent red coloration is obtained after several minutes 7 shaking. The solution is allowed to stand one-half hour. Caustic soda is then added in large excess, and the solution brought to the temperature of boiling water, with constant stirring. To the hot solution sulphate of iron is added till a black precipitate of magnetic iron oxide is produced. The solution is cooled, made up to 500 cc. with water, and filtered. In an aliquot of the filtrate, acidified with sulphuric acid, ferrocyanide is determined by titrating with potassium permanganate. This method requires about one hour. There is another method, based on the insolubility of potassium 50 THE CHEMISTRY OF CYANOGEN. feirocyanide in dilute alcohol, but it is applicable only when the solution contains at least 15% ferrocyanide. To 70 cc. of 95. alcohol, acidified with acetic acid, 10 cc. of the ferrocyanide solution is added. The ferrocyanide is precipitated as a crystalline powder, which may easily be separated by filtra- tion. After washing with 95 alcohol, the filter is dried at 100, the precipitate redissolved in water and titrated with permanganate. SULPHOCYANIDES. The solution of sulphocyanide is precipitated with a standard solution of silver nitrate, using a ferric salt as indicator. The blood-red color disappears as soon as there is an excess of silver solution showing the end of the reaction. Or the reverse may be done, and this latter procedure is pre- ferable: To a solution of sulphocyanide add an excess of standard silver nitrate, and titrate this excess with standard sulphocyanide. In this case the end of the reaction is indicated by the appearance of the permanent red coloration. DETERMINATION OF FERROCYANIDES IN THE PURIFYING MATERIALS OF ILLUMINATING-GAS. Knubblauch's Method (1889). This method consists in trans- forming insoluble compounds into a soluble salt, purifying this product, and titrating the ferrocyanide therein by means of a copper salt. 250 grams substance are dried at 50-60 C. for 6 hours. The dried mass is passed through a sieve (360 meshes per sq. cm.). 10 grams of the sifted material are transferred to a graduated 255 cc. flask, and 50 cc. n/10 solution of potash added. Allow the solu- tion to stand, with frequent shaking, for 15 hours. Fill the flask up to the 255-cc. mark and filter. 100 cc. of filtrate are added to an hydrochloric acid solution of ferric chloride (60- grams FeCls in 200 cc. HC1 sp. gr. 1.19, and solution made up to a liter). The precipitate is rapdily filtered through a folded filter and washed with hot water. The filter and precipitate are transferred to a 250-cc. flask and treated with 20 cc. n/10 potash in order to con- vert the Prussian blue into ferrocyanide of potassium. The solu- ANALYTICAL PROPERTIES. 51 tion is then made up to 250 cc. and filtered. If filtrate contains no hydrogen sulphide, it is acidified and then titrated with a standard copper solution. If the filtrate contains hydrogen sulphide, it is advisable to add 1-2 grams lead carbonate, shaking, and filtering. 100 cc. of this filtrate (1.6 grams original material) are acidified with 5-6 cc. n/5 sulphuric acid and then titrated with the following copper solution: Water 1000 cc. Copper sulphate 12-13 grams, which is standardized by means of a solution of potassium ferro- cyanide containing 4 grams of the pure salt per liter. The end of the reaction is noted by taking up a drop of the solution and moistening filter-paper which has been treated with ferric chloride. Moldenhader and Leybold's Method (1889). This consists in decomposing the ferrocyanides by evaporating them with sulphuric acid, and determining, by means of permanganate, the iron in the sulphate of iron remaining, after having previously converted it into the form of protoxide salt. Place 50 grams of the finely pulverized substance in a liter flask with 100 cc. of an n/10 solution of soda, containing also 2% anhy- drous sodium carbonate. Let the flask stand in a warm place for 4 or 5 hours, then make up the solution to 1030 cc. Shake, filter, and evaporate 100 cc. of the filtrate in a porcelain dish to 10 cc. Transfer these 10 cc. to a platinum dish, add 25 cc. n/10 solution of H 2 S0 4 , being careful of a too lively effervescence. Evaporate dry on a sand-bath, and heat the dish to redness. The residue in the dish is a mixture of ferric sulphate and bisulphate of sodium. Cool, and dissolve the mixture in rt/10 sulphuric acid, washing out the dish with this n/10 sulphuric acid, so that about 100 cc. in all may be used, then rinse with 50 cc. hot water. Make up the solu- tion to 250 cc., add 10 grams pure zinc and 1 cc. ?i/10 copper sul- phate solution. Heat on water-bath 3 hours; this reduces com- pletely the ferric sulphate (test with potassium sulphocyanide) . Cool, filter and dilute to 400 cc., and titrate with permanganate to a slight pink (deduct 0.4 cc., due to the same quantity of water, acid, copper, and zinc, in blank determination). From the number of cubic centimeters of permanganate used, the amount of ferrocyanide or of Prussian blue found in the spent oxide may be easily calculated. 52 THE CHEMISTRY OF CYANOGEN. Burschell's Method. Treat 20 grams of the dried and pulverized mass ; moistened with a little water, with 200 cc. of a solution of potassa (1-2). Shake and let stand several 'hours, then make up to 260 cc. (10 cc. extra due to the volume of the mass), shake and filter. Add 100 cc. of the filtrate to a solution of ferric alum dis- solved in hot sulphuric acid. Filter the Berlin-blue precipitate, wash with hot water, and then transfer paper and precipitate to a 500-cc. flask. Add a little water, 15 grams mercuric oxide, and 1 gram ammonium sulphate. Heat to boiling for about a quarter of an hour, and after cooling add 1 cc. of a saturated solution of mer- curous nitrate, Hg2(N03)2, and ammonia so long as a precipitate is formed. Make a solution up to 500 cc., shake and filter. Transfer 200 cc. of the filtrate to a 400-cc. flask, add 6 cc. ammonia (sp. gr. 0.9) and 7 grams zinc powder (the cyanogen in cyanide of mercury is thus transposed, and recombined as ammonium cyanide), shake for a few minutes, then add 2 cc. of a 30% solution of potassia and make up to 400 cc. Shake and filter. Allow 100 cc. of the filtrate ( = 0.875 gram original substance) to run into an excess of n/10 solution silver nitrate (40 cc. are gen- erally enough) contained in a 400-cc. flask. Add dilute nitric acid and make up to 400 cc. Filter and titrate 200 cc. of the filtrate with an n/20 solution of ammonium sulphocyanide after first adding 5 cc. of a saturated solution oi iron alum. The end of the reaction is indicated by a clear brown colora- tion. 1 cc. Ti/10 silver- nitrate solution corresponds to 0.007042 gram: Fe(CN) 6 K 4 +3H 2 or to 0.003832 gram Prussian blue. Zaloziecki's Method (Zt. fur angew. Chem. 1890, p. 210). 20 grams of the dry, pulverized purifying material are transferred to a 100-cc. cylinder with 20 cc. of a 10% solution of potassa. Heat on water-bath one half -hour, cool, make up to 100 cc.; take 45 cc., which corresponds to 10 grams original substance (assuming that the 20 grams occupy a volume equal to 10 cc.), and heat over free flame till no more ammonia is set free. Neutralize the solution exactly with dilute HC1 or H 2 S04, using phenolphthalein as indicator. When the solution is neutralized, add 20 cc. normal potassium carbonate and 5 grams moist zinc carbonate, heat one half-hour while passing a stream of carbonic acid through the solution. ANALYTICAL PROPERTIES. 53 After cooling, dilute to 100 cc., and titrate 50 cc. ( = 5 grams substance) with n/10 acid, using methyl orange as indicator. By deducting the amount of acid equivalent to 10 cc. potassium carbonate normal solution and multiplying the remaining number of cubic centimeters by 0.46, the per cent of potassium ferrocyanide, Ee(CN) 6 K 4 +3H 2 0, is obtained. E. Donath and B. M. Margosche's Method (Zt. fur angew. Chem. 1899, p. 345). This method is based on the fact that the ferro- cyanides and ferricyanides of the alkalis are easily decomposed, in alkaline solution, by oxidizing agents. The whole of iron separates as ferric oxide, and this element may be quite accurately determined in the precipitate, by known methods. The following is the mode of procedure: Grind the purifying material quickly in an iron mortar. Transfer 50 grams into a liter flask, add 100-150 cc. of a 15% solution of caustic potash Allow the flask to stand in a warm place for some time, shaking frequently. Complete the volume to 1030 cc. and filter through a folded filter. To an aliquot part of the filtrate add a bromated solution of caustic soda (prepared by dissolving 80 grams of sodium hydrate in water, cooling and making up to 1000 cc., and adding 20 cc. of bromine, shaking thoroughly). Heat for some time. Under these conditions there is formed an abundant, thick, pulverulent precipitate of a beautiful brick-red color, together with a lively liberation of gas. Let the precipitate settle several hours, filter and wash. It may be dissolved on the paper with hot dilute HC1 and the iron reprecipitated with ammonia. But it is preferable to dry the precipitate on the paper, then to transfer it to a small flask, to burn the paper, and fuse the ash thus obtained with potas- sium bisulphate, and to add this product to the remainder of the precipitate in the flask. The whole is then dissolved in dilute sul- phuric acid. Reduce with zinc and titrate the iron by means of potassium permanganate. The amount of iron multiplied by 7.5476 gives the quantity of crystallized salt, K 4 Fe(CN) 6 +3H 2 0, or multiplied by 6.5833 gives the amount of anhydrous salt. 54 THE CHEMISTRY OF CYANOGEN. DETERMINATION OF PRUSSIAN BLUE IN THE SPENT OXIDES. Method of Dr. Nauss of the gas-works at Carlsruhe. This is based on the decomposition of Prussian blue by alkalis, which are combined as follows: = 4Fe(OH) 3 +3Fe(CN) 6 Na 4 . Prussian blue is treated with hot caustic soda, the reaction being complete when the green coloration has disappeared. The following is the mode of procedure: Weigh 10 grams of the material and place in a 500- cc. flask con- taining 50 cc. of a 10% solution of caustic soda. Shake often, and allow the flask to stand at ordinary temperature till the whole of the blue has been decomposed by the caustic alkali. This requires about 15 hours. The formation of sodium sulphide is avoided if a dilute solution of soda be used. When the decomposition is ended make solution up to 505 cc. with water (the 5 cc. extra are for the volume of iron oxide). Shake thoroughly and filter. Take an aliquot part e.g. 50 cc. = 1 gram substance add 10-15 cc. of a hot acid solution (consisting of 200 grams ferric alum, one liter water, and 100 cc. sulphuric acid) in order to decompose the sodium ferro- cyanide contained in the Prussian blue. Heat on water-bath till the pungent odor is no longer apparent and filter through a funnel surrounded with hot water. Wash with hot water till the filtrate is free from sulphuric acid. The residue which contains all the Prussian blue is transferred to a flask to which water is added. Bring the solution to boiling, stirring continually. The quantity of blue may then be determined with a solution of sodium hydroxide. It is necessary in order to decompose the whole of the blue to add successively the required amount of n/5Q solution. The decom- position takes place rapidly if the solution be heated several moments, and the excess of the sodium hydroxide may be titrated anew against n/50 acid. The reaction is ended when the green coloration is per- manent. TOXICOLOGICAL RESEARCH. Substances in which the existence of cyanogen compounds is suspected are finely divided and diluted with distilled water so as to form a light pulpy mass. This is acidified with tartaric or ANALYTICAL PROPERTIES. 55 phosphoric acid (acids which have no action on hydrocyanic acid, but capable of setting it free from cyanides). This mixture is placed in a tubular retort provided with a straight safety-tube and connected with a bent tube which plunges to the bottom of a double tubular Woolf bottle. This latter is connected with a bulb-tube. Both of these contain a dilute solution of silver nitrate. Heat gently on the water-bath so as to produce a slow ebullition, which must be carefully watched. Under these conditions the presence of hydrocyanic acid is shown by the formation of a white precipi- tate of silver cyanide in the Woolf bottle and in the bulb-tube. When the precipitate no longer increases the distillation is stopped. Cool and unite the solutions of the bulb-tube and the bottle; filter, wash, dry at 100 C., and weigh. But as quite often substances to be analyzed contain hydro- chloric acid, which would give a perfectly analogous precipitate, it is well to make sure, by means of the ordinary reactions which we have already described, that one has really to do with cyanogen or its compounds. Moreover, it is to be noted that cyanide of mercury gives neither the reactions of mercury nor those of the cyanides. One may either precipitate the mercury with hydrogen sulphide, filter, and test for hydrocyanic acid, as indicated above, or else, and this is preferable, plunge blades of iron for a sufficient length of time into the extracted solutions of the substances suspected, which have been acidified with sulphuric acid. The mercury is precipitated by the hydrogen and the cyanogen converted into hydrocyanic acid. CHAPTER IV. THERMOCHEMICAL DATA RELATING TO THE CYANIDE COMPOUNDS. IN order to complete this general study it seems necessary to give some thermochemical information relative to the principal cyanated compounds. The following outline is taken from Berthelot's remarkable work Sur la force des matieres explosives, d'apres la thermo- chemie (t. II., p. 64, etc.): I. CYANOGEN. The heat of formation of cyanogen determined by Berthelot by ordinary combustion or by detonation is C 4 (diamond) + N 2 = C 4 N 2 -74.5 cal. 1 From this number Berthelot draws the following conclusions: " Cyanogen (C 2 N), as well as acetylene (C 2 H) and nitrogen dioxide (N0 2 ) and all substances which play the role of true compound radicals, is a body whose formation is accompanied by the absorp- tion of heat, a circumstance which seems to be of such a nature as to explain the very character of this real compound radical, mani- festing in its combinations a greater energy than in its free elements. The energy of these latter becomes stronger rather than weaker because of this absorption of heat, as is the case in combinations which give off heat, and this increase of energy renders the com- pound system comparable to the most active elements." x The same notation is used in this chapter as that used in Berthelot's work. 56 THERMOCHEMICAL DATA. 57 II. HYDROCYANIC ACID. The heat of formation of hydrocyanic acid, determined by vari- ous methods by Berthelot, may be expressed thus: C 2 (diamond) +N + H = C 2 NH (gaseous) = -29.5 cal. = C 2 NH (liquid) = -23.8 "' = C 2 NH (dissolved) =-23.8 ff " It follows from these figures/' says Berthelot, " that hydro- cyanic acid is formed from its elements with absorption of heat, which explains the readiness with which this acid forms direct combinations, polymeric compounds, and brings about complex reactions." Berthelot remarks further that " cyanogen and hydrocyanic acid, acetylene, etc., could be regarded as formed with liberation of heat, if it were admitted that carbon, when considered as diamond or charcoal, does not correspond to the real elementary carbon, which should be comparable to hydrogen and probably gaseous, while the diamond and charcoal represent its allotropic modifica- tions. In passing from its gaseous to its polymeric and condensed state, elementary carbon would liberate a considerable quantity of heat, and greater than the heat absorbed in the formations of acetylene (-30.5 cal. for C 2 = 12), and of cyanogen (-37.3 cal.)" The actual figures show that the formation of hydrocyanic gas starting with cyanogen and hydrogen is Cy + H = CyH liberates + 7.8 cal. " This formation is therefore exothermic," a circumstance which led Berthelot to foresee that it could be brought about directly; and, in fact, the illustrious savant did succeed, contrary to the negative experiments previously worked out by Gay-Lussac, in combining the two gases directly under the influence only of time and heat. The synthesis of hydrocyanic acid by means of acetylene and nitrogen, both in the free state, by the electric spark, which was discovered by Berthelot in 1868, liberates +2.1 cal. 58 THE CHEMISTRY OF CYANOGEN. III. CYANIDE OF POTASSIUM. The heat liberated by the formation, from its elements, of solid cyanide of potassium, determined by Berthelot, is as follows" C 2 + N + K = C 2 NK crystallized liberates + 30.3 cal. The direct formation of potassium cyanide, by means of the union of its elements, in the same proportion by weight as repre- sented by the equation, cannot be brought about, in fact, at the ordinary temperature. But it is admitted that it does take place at a very high temperature, if free nitrogen is made to act upon charcoal impregnated with potassium carbonate, that is, under the conditions where nascent potassium is formed. " At this temperature cyanide of potassium is a liquid, per- haps even gaseous, change of state which absorbs heat, but on the other hand the potassium is gaseous, which fact somewhat com- pensates. If the free nitrogen, carbon, and potassium really do combine, without other intermediary reaction, as, e.g., the formation of an acetylide (which has not been proved), one will have to admit that the total synthesis of cyanide of potassium liberates heat under the real conditions in which it is effected. " Whether the liberation is produced all at once or only by successive reactions, it explains the total synthesis no less. " The union of cyanogen with potassium takes place, as is known directly. This union calculated for the following states: Cy (gas) +K (solid) = KCy (crystallized) liberates + 67.6 cal. " This figure justifies the direct synthesis of cyanide of potassium by means of cyanogen, but the heat liberated is less than that liberated in the union of the same metal with the gaseous halogen elements." The latter is C1+K = KC1 = 4-105.6 cal. Br gas + K = KBr = + 100.4 rf I solid + K = KI = + 85.4 < r = KCy=+ 67.6 " Berthelot attributes to this inferiority in the amount of heat liberated the decomposition of solutions of potassium cyanide by THERMOCHEMICAL DATA. 59 the halogens, and further says that " the cyanogen which should be set free is combined moreover with one half of the halogen body, not without a slight liberation of additional heat ( + 1.6 cal. for yCl gas, +4.2 cal. for Cyl solid). Then he compares the quan- tities of heat liberated when starting with the hydracids and dilute yH (dilute) + KO - OH (dilute) = KCy dissolved + H 2 2 = + 3.0 cal., which is a quantity much less than that liberated in the formation of the chloride, bromide, or iodide of potassium ( + 13.7 cal.). With gaseous hydracids the disagreement is still greater ( + 17 cal.). Berthelot concludes from this that " hydrocyanic acid is a much weaker acid than the hydracids derived from the halogen elements, and that it is even displaced in potassium cyanide dissolved by most of the acids. " The transformation of potassium cyanide into potassium formate : C 2 NK (dissolved) +2H 2 2 = C 2 HK0 4 dissolved + NH 3 dissolved, liberates +9. 5 cal. " That is the reaction which goes on slowly in solutions of potas- sium cyanide. " The same reaction carried on on the dry salt by water- vapor produces formate, and also ammonia gas. It is much more rapid, but it also liberates twice the amount of heat, +17.7 cal. If the temperature is raised, this reaction becomes complicated because of the subsequent destruction of the formate by heat or by an excess of alkali, a reaction which takes place at about 300 and which transforms completely potassium cyanide into potassium carbonate: C 2 NK solid + KO- OH solid + 2H 2 2 gaseous = C 2 4 +2KO solid +NH 3 gas - liberates +37.4 cal. " I call attention to this because it is one of the most active causes of the destruction of potassium cyanide during its manu- facture, where one works with the fused salts, a fact which slightly modifies the figures above, without modifying the general signifi- cance of them." 60 THE CHEMISTRY OF CYANOGEN. IV. CYANHYDRATE OF AMMONIA. The formation of solid ammonium cyanide starting with gaseous hydrocyanic acid and gaseous ammonia liberates +20.5 cal. ; and starting with the elements +40. 5 cal. V. FERROCYANIDE OF POTASSIUM. Because of the difficulty in obtaining pure hydroferrocyanic acid Berthelot determined the heat of formation of this acid in an indirect way, i.e., by displacing it from its salts by a more energetic acid. " By mixing a dilute solution of potassium ferrocyanide, CysFeK^ = 4 liters, with dilute hydrochloric acid (1 equiv. = 2 liters), no change of temperature is observed; either there is no reaction, or the two acids liberate the same quantity of heat in combining with the potassa, in which case the base in the solution could be divided. The latter case is the more likely. In fact, by mixing ferrocyanide with dilute sulphuric acid a progressive separation and a displace- ment which tends to become complete, in the presence of a large excess of sulphuric acid, are observed. Thus Cy 3 FeK 2 (6 liters) +HS0 4 (1 equiv. = 2 liters) liberates +1.107 cal. Cy 3 FeK 2 (6 liters) +2HS0 4 (1 equiv. = 2 liters) liberates +0.181 cal. By continuing the gradual addition of sulphuric acid an absorption of heat is produced, due to the formation of bisulphate. "With a large excess added all at one time Cy 3 FeK 2 (4 liters) +10HS0 4 (1 equiv. = 2 liters) liberates +0.966 caL " These phenomena are comparable to the reaction of sulphuric acid on the chlorides, although the results are somewhat different. Here likewise is a progressive division of the base between the two acids. If it be admitted that the 10HS04 be sufficient to remove almost the whole of the potassa from the ferrocyanide, similar to that which is produced with the chlorides, nitrates, etc., the heat x liberated in the reaction of dissolved hydroferrocyanic acid on THERMOCHEMICAL DATA. 61 dilute potassa may be calculated. In fact, +15.7 cal. being the heat liberated in the reaction of sulphuric acid on potassa, and -1.75 cal. the heat absorbed in the reaction of dilute 4HS0 4 on dissolved potassium sulphate (formation of bisulphate), the desired reaction will be 4(Cy 3 FeH 2 =4 liters) +KO(1 equiv. = 2 liters) liberates x = + 15.71 - 1.75 -4(0.97) = + 13.5 cal. " This figure is practically the same as that which represents, the heat liberated by hydrochloric acid and nitric acid when acting on potassa, from which it follows that hydroferrocyanic acid is a strong acid comparable to the mineral acids. It is known that it displaces carbonic and acetic acids. The absence of apparent thermic reaction between HC1 and dissolved cyanoferride is in harmony with these results. " Nothing is easier than passing through that to the formation of Prussian blue; in fact i(Cy 3 FeK 2 =4 lit.)+S0 4 Fe(l eq. = 2 lit.) = -JCy 3 Fefe precipitated + KS0 4 dissolved liberates +2. 54 to 2.78 cal., the amount of heat liberated increasing with length of time, as often happens in the formation of amorphous precipitates. Likewise | (Cy 3 FeK 2 = 4 lit.) + N0 6 fe(l eq. = 2 lit.) =iCy 3 Fefe 2 precipitated + KN0 6 dissolved liberates + 0.725 cal. " From the results obtained with ferric sulphate, the substitu- tion of potassa for iron peroxide (KO for FeO) in Prussian blue liber- ates +7. 2 cal.; from the results obtained with the nitrate, +7.2 cal., a perfect agreement. " By admitting that the formation of cyanoferride of potassium, CyFeH 2 (dilute) +2KO dilute, liberates + 13.5x2 = 27.0 cal., it is thereby concluded that the formation of Prussian blue with the same acid and precipitated peroxide of iron, Cy 3 FeH 2 + 2f eO (precipitated) liberates + 6.3 X 2 = 126 cal. 62 THE CHEMISTRY OF CYANOGEN. " The value 6.3 differs but little from 5.7, which represents the union of nitric and hydrochloric acids with iron peroxide, which fact is a new proof of the analogy between hydroferrocyanic acid and the mineral acids. Nevertheless +6.3 is greater than +5.7, which fact explains why dilute hydrochloric acid does not decom- pose Prussian blue with formation of iron chloride. " Hydrocyanic acid, one of the weakest acids known, has formed therefore, by its association with iron cyanide, a powerful acid, comparable in all points to hydrochloric and nitric acids. " This is a new proof calculated to establish the fact that the best characterized acid properties, even in the hydrocarbon com- pounds, are not necessarily connected with the presence of oxygen. " The heat liberated in the formation of cyanoferride itself remains to be determined. "I found the following results: S0 4 Fe(l eq. = 2 lit.) +280^6 (1 eq. = 2 lit.)+6KO(l eq. = 2 lit.) liberates 23.2 cal. By adding to the above mixture 3CyH(l eq. = 4 lit.) a further liberation of + 39.3 cal. is observed, which represents the formation of cyano- ferride, starting with CNH and the two oxides: 3CyH (dissolved) +2KO (dissolved) + FeO (precipitated) = Cy3FeK 2 (dissolved) liberates 39.3 cal. " As a control experiment, I added to the solution 3HC1 (1 eq. = 2. lit.), which liberated +25.0 cal., with the formation of an abundant precipitate of Prussian blue, the heat liberated varying during the precipitation from 23.0 to 25.0 cal. " In short, HC1 has produced the following reactions: HC1 dilute +KO dilute = KC1 dilute + 13.6 cal. 2HC1 f( +feOppt. =2feCl " +11.4 "! 2f eCl ' '' + Cy 3 f eK 2 dissolved = Cy 3 Fef e 2 +2KC1 dilute + 1.4 "' 26.4 cal. " The agreement between 25.0 and 26.4 is as close as one may expect when working with similar precipitates, the state of which varies with the conditions. THERMOCHEMICAL DATA. 63 " From that I conclude SCyH dilute + FeO ppt . + 2f eO ppt . = Cy 3 Fef e 2 ppt . liberates + 24.9 cal. 3CyH dilute + FeO ppt. = Cy 3 FeH 2 dissolved + 12.3 cal. " I verified these values by forming Prussian blue directly by means of CNH and the two sulphates: 3CyH(l eq. = 2 lit.) +S0 4 Fe(l eq. = 2 lit.) +80*16(1 eq. = 2 lit.) = Cy 3 Fef e 2 ppt. + 3HS0 4 (dilute) liberates + 37.5 cal. " The difference between the heat of formation of alkali sul- phate and that of iron sulphate starting from the oxides being 12.5 + 11.1-47.1= -23.5 cal., and the heat of formation of 3CyK starting from potassa being +8.9 cal., from these data the heat liberated in the formation of Prussian blue from CNH is easily found: 3CyH dilute + FeO +2feO = Cy 3 Fefe 2 liberates +37.5 + 8.9-23.2= +23.2 cal., a result which shows sufficient agreement with +24.9 cal., obtained in another way, but which I regard as a little less exact. " Let us draw some general conclusions from these results. The first conclusion is in regard to the heat liberated in the formation of cyanoferride, starting with hydrocyanic acid or with potassium cyanide : SCyH (dissolved) +3KO dilute liberates +8.7 cal. SCyH (dissolved) +2KO + FeO ppt. liberates +39. 3 cal. " The substitution of ferrous oxide for potassa with formation of cyanoferride liberates a large amount of heat, i.e., +39.3 8.7 = +30.6 cal. One single equivalent of ferrous oxide contributes, moreover, to the formation of hydroferrocyanic acid. 1 This .figure explains, besides, the observed displacement^ and it corresponds to the constitution of a new molecular type, that of hydroferrocyanic acid. " In fact, we conclude from that 64 THE CHEMISTRY OF CYANOGEN. 3CyH (dissolved) +FeO ppt. liberates + 12.3 cal., a quantity greater than the heat (+9.0 cal.) liberated by 3KO (dilute) united with 3CyH. " That is because here there are two simultaneous reactions: the union of 3 mol. of CNH into a type thrice as much condensed, and the combination of ferrous oxide which enters the constitution of this new type Cy 3 FeH 2 . ", Likewise, in the case of Prussian blue, it has elsewhere been established that Cy 3 FeH 2 (dilute) +2feO ppt. liberates + 12.6 cal. = 6.3X2, i.e., practically the same number as the union of the same oxide with dilute HC1 and HN0 3 . " Starting from CNH itself we have 3CyH (dilute) +FeO+2feO = Cy 3 Fefe 2 ppt. +24.9 cal. = 8.3X3. " The magnitude of this last figure, which is three times the heat liberated when potassa unites with hydrocyanic acid, is the explanation, as above, of the formation of the new molecular type of cyanoferrides, and still more so of the formation of the double cyanides. " This superposition of effects explains, moreover, the superiority of apparent affinities which the oxide of iron shows over potassa in its union with hydrocyanic acid, which is shown by a greater liberation of heat than in the formation of ordinary oxysalts, sul- phates, nitrates, acetates, etc., starting with the dilute acids and alkaline bases corresponding to the metallic oxides. " Would it not be possible to find some analogous circumstance to explain how the oxides of silver and of mercury, besides the oxides of iron, liberate more heat than does dilute potassa in uniting with hydrocyanic acid? That is, are the cyanides of silver and of mercury really represented by the simple formulas CyAg, CyHg, salts comparable to those of CyK and CyH, or else would it not be better to regard them as a more condensed type of cyanides, such as Cy 2 Hg 2 and Cy 2 Ag 2 ? " The heat liberated by their union with cyanide of potassium THERMOCHEMICAL DATA. 65 in the formation of double cyanides, even in the state of dilute solu- tions, such as Cy2HgK, Cy2AgK (rough formulas), would support this supposition, for it would be the result of the passage from the simple type, cyanide of potassium, to the com- plex type which constitutes the double cyanides, Cy 2 Hg 2 + 2KCy = 2Cy 2 HgK ; Cy 2 Ag 2 + 2KCy = 2Cy 2 AgK " Besides, hydrocyanic acid is not the only acid which is the occasion of a general overthrowing of the ordinary affinities, inter- preted by the corresponding thermic effects between the alkaline oxides and the metallic oxides. Hydrogen sulphide is in exactly the same case. " Notwithstanding these latter considerations it remains no less a fact that the metallic oxides liberate more heat than the alka- line bases, uniting with hydrocyanic acid, a fact which explains why they displace them. Thermochemistry thus takes into account the constitution of the complex cyanides, new molecular types, which are very superior to the primitive type because of the energy of their affinities in regard to the bases, as well as because of the stability of the resultant salts I mean very superior to hydrocyanic acid, which contributes to their formation by condensation. " Hydrocyanic acid, common generant of condensed types, is distinguished, moreover, because it is formed from the elements with an absorption of heat 29.5 cal.; in other words, its formation has stored up an excess of energy which makes it specially fit for successive combinations and molecular condensations. " Let us give, finally, the heat of formation of potassium ferro- cyanide from its elements: Fe+K 2 +Cy3 = Cy 3 FeK2 (solid) liberates + 183.6 cal. or 61.2x3. From simple bodies: Fe+2K+3C+3N = C 3 N 3 FeK 2 +71.7 cal. or 23.9X3. These results are close to those which are obtained in the forma- tion of potassium cyanide, starting with cyanogen +67.6 cal., and with the elements +30.3 cal. 66 THE CHEMISTRY OF CYANOGEN. " The hydrated salt encloses 3 molecules of H 2 0(3HO), extra, whose union in the liquid form with the anhydrous salt liberated + 2.48 caL, which brings the total amount of heat liberated in the formation of the crystalline yellow prussiate from the elements and H 2 0, +94.2 cal." VI. POTASSIUM CYANATE. The formation of solid potassium cyanate from the elements is C 2 diamond + N + K + 2 = C 2 NK0 2 liberates + 102.0 cal. The dissolved salt liberates + 96.8 cal. The same formation starting with dilute KOH: C 2 + N + OKO dilute = C 2 NK0 2 (dissolved) liberates + 15.5 caL From gaseous Cy: Cy + K + 2 = CyK0 2 solid + 139 . 3 cal. Cy + + KO dilute = CyK0 2 dissolved +51.8 rr Cy 2 +2KO dilute = CyK0 4 dilute + CyK dilute + 34.2 "' All these results are greater than the heat liberated in the analo- gous reactions of the real halogen elements, e.g., C1 2 gas + 2KO dilute = C10 2 K + KC1 dissolved liberates only + 25.4 caL There is, moreover, this difference, that the complex nature of Cy and its tendency either to form polymeric and other condensed bodies, or to regenerate ammonia and its derivatives, are the cause of a number of secondary reactions, such as do not occur in the case of chlorine. These reactions are easier in proportion as the heat liberated by the direct reaction is greater and in proportion as it furnishes from that time a greater reserve of energy by other transformations. " The union of dry potassium cyanide with gaseous oxygen in the formation of solid cyanate C 2 NK (solid) + 2 (gas) = C 2 N0 2 K (solid) would liberate +102.0-30.3= +71.7 cal., a large figure, and about three fourths of the heat (+94.0) liberated by the com- bustion of the carbon contained in the cyanide. " This figure refers to bodies taken in their actual state, a fact in which, up till now, no absorption of oxygen by the cyanide of THERMOCHEMICAL DATA. 67 potassium has been observed, probably because it has not been investigated. In the fused state, on the other hand, it easily takes place, as is known. Now these figures just calculated may be approximately applied to the same bodies, under the known con- ditions of their real reaction, at a high temperature, for the fusion of the cyanide as well as of the cyanate should absorb about equal quantities of heat. " Considering the heat liberated by the oxidation of its potassium compound, cyanogen agrees more with iodine, and differs, on the contrary, with chlorine. We have in fact: KC1 + 2 = KC10 4 (solid) absorbs -ll.Ocal., KBr + 4 = KBr0 4 " " -11.1 " KI + 4 = KI0 4 " liberates + 44.1 rr = KCy0 2 "' " +71.7 a progression inverse to that which characterizes the union of a like metal, such as K, with the same series of halogen bodies, such as Cl ( + 105.0 caL), gaseous Br ( + 100.4 cal.), gaseous I (+85.4 cal.), and cyanogen (+67. 6 cal.) " From the preceding figures is explained why cyanide of potas- sium has such a great tendency to oxidation, either under the influ- ence of oxidizing agents, or even n air. " The combustible character of one of the elements of cyanogen opposes, moreover, the formation of peroxidized acids, as with chlorine, and the halogen elements such compounds would have too great a tendency to being converted into carbonic acid. " The complete combustion of solid potassium cyanate, C 2 NK0 2 + 3 = CO K+C0 2 + N, would liberate +83.9 cal. "The facility with which potassium cyanate becomes regenerated from ammonia, even from the one fact of its long contact with water, is easily explained : C 2 NK0 2 + 2H 2 2 = C0 3 K (dissolved) +C0 2 NH 3 HO dissolved liberates +20.0 cal. "That is also an amide reaction. "The well-known transformation of fused cyanate of potassium 68 THE CHEMISTRY OF CYANOGEN. by means of water-vapor into fused carbonate of potassium, car- bonic acid, and ammonia liberates about +9 cal. "'The conversion of potassium cyanide into carbonate and am- monia under the combined influence of oxygen and water-vapor at a high temperature, a conversion so pernicious in the industrial preparation of prussiates, is no less easily explained by thermo- chemistry. In fact, at the ordinary temperature we should have C 2 NK solid +0 2 +3HO gaseous = C0 3 K solid +C0 2 gas +NH 3 gas +79.3 cal. At about red heat this figure should remain likewise large, the cyanide and the carbonate being partially fused." For the thermochemical data referring to cyanogen and its com- pounds see the tables at end of the book. PART TWO. THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. CHAPTER V. COMMERCIAL AND INDUSTRIAL STUDY. THE development of the industry of the cyanated compounds is due, as was stated in the Introduction, primarily to the use of potassium cyanide in the treatment of auriferous minerals. At first the production of cyanides was, so to speak, insignificant, or at least limited. The industry was created in 1710 with the dis- covery of Prussian blue, by the dyer Diesbach, and for a long time was limited to this c mpound used in dyeing. The discovery of potassium ferrocyanide and the other cyanogen compounds came, but later, and among these the ferrocyanide alone was applied in the arts and manufactures. Cyanide of potassium did indeed have for a time a certain limited market in photography, but its poisonous properties and its relatively high price made it give place to hypo- sulphite of sodium. From that time it was a laboratory and phar- maceutical rather than an industrial product. But as a result of the remarkable researches of MacArthur and Forest, some fifteen years ago, in the extraction of gold by means of potassium cyanide, this salt became industrially important, giving to the whole industry of the cyanide compounds an impetus and a vitality which made it acquire rapidly its present development, which is still bound to increase. 70 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. The application of these methods brought about as an immediate: consequence a considerable increase in the consumption of cyanide of potassium to such an extent that in 1898 this consumption arose to 3300 tons, and in the month of August of that year the demand was S3 great that the German manufactories which produce the major part of this product were unable to fill their orders punctually, notwithstanding the price had been advanced 29% to the English buyers. In June 1899 the national bureau of foreign commerce was in possession of data from Johannesburg showing a consumption of 450,000 English pounds of cyanide per month, which amount repre- sented a value of $135,000, delivered. It is quite probable that these figures would still have increased had it not been for the war in South Africa, and the consumption in that country alone would have arisen to 10,000 tons. The result of . this development is easy to foresee. The work was undertaken most zealously; the manufacturers in England and in Germany especially sought means of producing the cyanide in sufficient quantities to supply the demand, and under the most' economical conditions, as shall be seen when the study of the various meth ds is taken up. An active s ruggle was established among the manufacturers of cyanide, the result of which has been infinite progress in this industry. Even at the present time numerous researches are being undertaken along these lines, and it is to be hoped that these efforts will not be fruitless, but rather a process will be found which will permit the production of potassium cyanide under conditions remunerative both to the producer and consumer. The industry of the cyanide compounds has been developed especially in Germany and in England; France has remained somewhat behind in this line. Several manufacturers produce some cyanide, to be sure, but they do not find such an outlet for it as they should have, because of the great competition in the market which the English and the Ge mans are making, and because of the cheaper price at which they sell their product. This condition of affairs attracted the attention of the Min- ister of Commerce and Manufactures, and in a letter of Dec. 6, 1897, addressed to the President of the Council Chamber of Chemical Products, he called to the attention of the manufactur- COMMERCIAL AND INDUSTRIAL STUDY. 71 ers the important markets reserved for this branch of chemical industry. The letter, as well as the discussion which it provoked at the meeting of the Council Chamber of Chemical Products on the 8th, of December following, are here reproduced: PARIS, December 6, 1897. MR. PRESIDENT: The export house Orosdi Back, whose headquarters are in Paris, cite- d'Hauteville, No. 9, recently called my attention to the interest which the: manufacture of potassium cyanide would offer to French industry. The use of this product in treating the wastes of gold-mines has giveir such results that all the mines are gradually making installations for putting; this method into practice. The present sales of potassium cyanide in the Transvaal and, the whole of South Africa already exceeds 3000-4000 tons per annum, and it is expected within two or three years, when the cyanide process shall have become general, that the demand for this product will exceed 10,000 tons in the Rand district alone. If to this amount be added the quantity consumed by all the gold- mines in all parts of the world, it is seen that a considerable field is open for the sale of this product, the sale of which at present is monopolized by England and Germany. According to Orosdi Back, the cyanide of potassium employed should be 98%, of a pale-yellow color. It is shipped in wooden boxes lined with zinc, holding 100 kg. The price varies from 190 to 230-240 francs per 100 kg. It seemed to me that the above data would be of interest to your association, and I have the honor of communicating them to you, giving you the care of making them knowji to the manufacturers who might be willing to use them. Yours, etc., Minister of Commerce, Industry, Post, and Telegraph. For the Minister, by authority. Director of Commerce, CHANDEZE. Council Chamber of Chemical Products, sitting of Dec. 8, 1897. MR. PRESIDENT: Before receiving this letter the Minister had already interviewed me on this question, and I explained to him that the French manufacture of potas- sium cyanide is only enough for our needs, i.e., about 30,000 kg. per year; that this amount is produced y a single firm, other manufacturers who pro- duced it formerly having abandoned it because of the unremunerative price obtained for it. The price of potassium cyanide has, in fact, suffered a considerable reduc- tion in the last few years. At present it is worth 3 francs per kg. in France, and 2.25 francs in England and Germany. 72 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. The consumption of this product is very great in the Transvaal, but the figures 3000-4000 tons, given by the firm Orosdi Back, seem somewhat ex- aggerated. From data which I have received, the sales in the Transvaal would amount to 100 tons per month, and only 1 ton in Madagascar; but the consumption of this colony is destined to increase. The company in France which manufactures potassium cyanide tried to compete with foreign firms doing business in the Transvaal, but abandoned the attempt because it was estimated that the sale price of 2.25 francs per kilogram (about 22.5 cents per Ib.) did not leave a sufficient profit. MR. GASTON POULENC: The English have found, and are now exploiting, processes for the manufacture of potassium cyanide without the use of ferro- cyanide. That is a very great advantage when the net cost is considered. And this superiority will last until our manufacturers or our chemists have analogous met hods. MR. PRESIDENT: It seems to me, finally, that the communication just presented by our fellow member fully confirms the data which I gave to the Minister, and the inability of the French industry to compete successfully ^t the present time. It is to be hoped that in the near future the discoveries of our chemists will make it possible for us to regain this industry. The effort of the inventors is i this direction, and in the last dozen years, both in France and abroad, a great number of patents for the production of this substance have been taken out. Having made these general observations, let us now examine the state of this industry in the different countries where cyanide is produced. The following table shows the production of the different coun- tries in 1899, according to L. Guillet: Country. Potassium Ferrocyanide. Potassium Ferricyanide. Potassium Cyanide. Germany Austria tons. 4,000 tons. tons. 1 500 England 3,000 __ 2 000 1,500 11 250 United States 1,500 1 500 Belgium Holland . 500 Total 10,500 11 5,250 France therefore produces l / 2 i of the total production of cyanides and 1 /7 of the ferrocyanides, while Germany and England produce more than 1 / 2 of the total of these two products. The consumption is found divided among the different countries. Ferrocyanide of potassium which is produced in France is to COMMERCIAL AND INDUSTRIAL STUDY. 73" a great extent exported to Germany and England, where it is trans- formed into the cyanide. Germany herself exports a* great quantity to the United States, where for economic reasons it is transformed into the cyanide of potassium; the remainder is us d at the manu- factory for the various needs of the industry. The cyanide is exported to gold-mines, notably to the Transvaal, where its consumption increases daily. Thus in 1897 the consumption in the Transvaal was 1710 tons; in 1898 it had increased to 2230 tons; in 1899 to 2400 tons. The other gold districts consume but little because the beds are still worked by the old method and quite often they are not in the hands of companies or manufacturers, the gold being bought from individual workers. However that may be, the cyanide method is gradually increasing. Several installations in the United States, in California and Alaska, have been noted, and one can foresee that gradually the total con- sumption wi 1 be considerably increased. The following table gives the names of the principal firms of France and other countries which manufacture or sell cyanide com- pounds: OF THE UNIVERSITY OF .74 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. Fe Cy Fe Cy Fe eaux Nancy near Bo Paris ille, nea illiers (Se Lyon Begle La Ne Gen SllltS^ ^35 g If I I ^ I ^ 3 g |"3 ^ w'S 'I :g^? i 03 i-ggg jx 02 C Jim u /^^s c3 0) t lrl i' s H 3 5 * o 5 . .H3 - . . . fl . . . . . . . 3 . . . . . j . . C . oj i ;r s o ' HH . . ^ .0 s : :.- :l a s ?! 6 -' go o !^, " COMMERCIAL AND INDUSTRIAL STUDY 75 - -b 1 11 f Q IrfS S^-iS^e3s^^^3 76 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. Manufactured. ' Manufactured. 03 O> -S 1 f Products |C 2 2 2 2 2 1 Sw ,.*, i & 13 M 1 I M o3 02 5.2255.2 7 *^J 3UCING CYANIDE COMPOUNDS- GERMANY Continued. S .s l|||l|j"l ; i||il|ll ; ENGLAND. ' London Birmingham Sheffield Leeds Birmingham London tt i i c cj 6 S o ' ' ' -g ^ ::::::::::::::: g 1 Ifil-Mi iNNN 1 "8 *o ^ :::::. 3 ^ -] Q'S^l' co S- ! 1 3 :::::: fc ^ddcS^^^li- l ~ < O-^ ^ t+-i S "S ~| "2 '. O"Q ^ S ^ ' p| j ; ^ British Cyanides Comp Cruickshank Dolbbe & Son Foster & Son Harris & Co., Limited. Hopkins & Williams. . Johnson & Sons COMMERCIAL AND INDUSTRIAL STUDY. 77 O z C" &" o S c ^ 2 ^ a <-, E t i Ng* bJO .a > 1 . 78 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. H P H- 1 'S a Si o |S ii H ? Hochstetter & Rotlingshofer. Engel und Becke S -S us 111 i w l a ^ 05 w bCP S| cc fl COMMERCIAL AND INDUSTRIAL STUDY. 79 Although it is extremely difficult to obtain data from the manu- facturers concerning the production and consumption, the net cost, etc., we have, nevertheless, been able to procure a certain num- .ber of documents bearing on these questions. The following tables give a sufficiently correct idea of the condition of the cyanide indus- tries, and show well the development of this branch of chemical industry during the past few years. FRENCH IMPORTATIONS OF POTASSIUM FERROCYANIDE IN KILOGRAMS. Exporting ' Country. Year. England. Germany. Belgium. Other Countries. Total. Value. 1887 168,669 168 79,512 248,349 347,689 1888 186 404 . 77,784 264,288 343 574 1889 150 028 % 65 66,660 216 753 303,454 1890 48086 65,317 38,777 152,180 243 488 1891 100 932 __ 28,310 15,725 144,967 260 941 1$92 69354 __ 52,185 20,018 141,557 254 803 1893 . . . 50 771 62,761 19,529 133,061 239 510 1894 . . . 40079 42,798 31,173 114050 216 695 1895 78,547 23,079 20,956 122,582 232 906 1896 48,501 49,768 4,482 142,751 228 402 1897 29,178 11,454 54,736 1,216 96,584 125 559 1898 37,266 9,153 18,457 84 64,960 87 696 1899 15,754 40,243 50 56,047 86 873 1900 1901 (10 months). 1,654 12,789 41,700 56,143 113,700 92,636 149,000 AMOUNTS CONSUMED IN EACH OF THESE EXPORTING COUNTRIES. Year. England. Germany. Belgium. Other Countries. Total. Value. 1887 89,398 141 62220 151,759 1888 104 354 52 76 699 181 105 1889 84 458 65 62 701 147 224 1890 48086 40 11 477 81 822 1891 . 69,354 353 14 212 73492 1892 50,771 . . 379 16489 83 919 1893 40,079 _ 9887 782 67,639 _ 1894 77447 27 15 705 50 478 1895 48501 6441 32 883 92 879 1896 87825 1897 28,939 8,460 29 336 33 764 49093 1898. 15,363 20,470 1899 12 022 18 634 1900 13 272 21 899 1901 (10 months). 90,200 149,000 80 THE PRESENT CONDITION OF THE CYANIDE INDUSTRY. FRENCH EXPORT OF POTASSIUM FERROCYANIDE IN KILOGRAMS FROM 1897-1900. Country. 1897 1898 1899 1900 England 45 339 115 531 87 470 71 A A A Germany 41 878 59236 miQQ 4.C1 QO/i Belgium 41 879 40 017 ioi,yo' 47 979 Switzerland 22 293 OQ OOQ Italy 17 1R^ Other countries Colonies and Protectorates United States 25,136 5,481 of which 2,189 for Algeria. 147,658 27,933 21,761 of which 20,000 for Reunion. 265,796 55,580 3,673 55 917 26,108 3,415 Spain 40 328 Total 307,371 512,550 463 124 645 697 Value in francs 403,557 697,996 717 842 1 065 400 TOTAL DRENCH AND FOREIGN EXPORTATION OF POTASSIUM FERROCYANIDE, 1887-1896. 1887 1888 1889 1890 1891 Amount in kilograms . Value in francs 122,048 177,083 90,426 118,789 85,594 122,898 127,384 215 397 188,628 363 044 1892 1893 1894 1895 1896 Amount in kilograms. . Value in francs . 120,696 230,074 184,231 361,350 198,769 406,797 107,974 216 986 139,735 232 014 FRENCH AND NATIONALIZED EXPORTATION OF POTASSIUM FERROCYANIDE, 1887-1896. 1887 1888 1889 1890 1891 117,571 235,142 Amount in kilograms. . Value in francs 24,867 41,030 6,175 9,263 15,334 24,534 57,912 104,242 ' 1892 1893 1894 1895 1896 Amount in kilograms. . Value in francs 64,092 128,184 118,938 243,823 145,682 305,932 78,907 161,759 84,383 143,451 PART THREE. METHODS OF MANUFACTURING CYANIDE COMPOUNDS. GENERAL CONSIDERATIONS. BEFORE taking up the discussion of the numerous methods for the manufacture of the cyanide compounds, it seems necessary to glance for a moment at the evolution accomplished by these methods, a very interesting evolution, since it has transformed an industry which was at first entirely subjected to the crudest empiricism to an industry based on purely scientific data. The industry of the cyanogen compounds, like that of the greater part of the chemical industries, had its origin in alchemy. It orig- inated in 1704, from the discovery of Prussian blue. This dis- covery, which was purely accidental, is due to the Berlin dyer Dies- bach, who obtained this compound by the action of alum and sul- phate of iron on the potash residues which the then celebrated alchemist Dippel had used in the rectification of an animal oil extracted from the volatile substances of blood. From this discovery, Dippel concluded that Prussian blue was formed by the action of iron on potassa which had been brought in contact with organic animal substances at a certain temperature. The discovery of Diesbach immediately became of industrial importance, and Prussian blue was prepared by calcining dried beef's blood, and later meat or horns with potassium carbonate. The product of this treatment was extracted with water, and the solution thus obtained, called blood-lye, was treated with alum and sulphate of iron, giving Prussian blue. This was for a long 81 82 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. time the only body known and prepared, and th's without knowing exactly what was its composition and its mode of formation. In 1752 Macquer, then Bergmann and Sage, showed that from Prussian blue a definite and crystallizable salt could be extracted, the nature of which they could not determine. That Prussian blue and the salt obtained from blood-lye were compounds of cyanogen was first definitely proven in 1823 by Gay- Lussac. Although this was an important discovery, yet the methods of producing these compounds were not at all changed, and for a long time the only method employed, notwithstanding its imperfec- tions, was that of igniting nitrogenous organic substances in the presence of alkaline carbonates. That method sufficed, more- over, to supply the limited demand. But, beginning with 1837, a most interesting and important series of discoveries and researches in the history of the cyanide industry attracted the attention of investigators and manufac- turers, and fixed in a clearer manner the ideas which were being formed concerning the formation of these bodies. The successive discoveries of Clark and of Redenbacher, describing the formation of efflorescences of potassium cyanide in blast-furnaces, together ' with the works of Lewis Thompson, Desf osses, Fowner, and Young, who obtained this same compound by the action, at red heat, of a current of air upon a mixture of potassium carbonate and char- coal, gave birth to the first principles of a theory which at first was disputed, but soon after acknowledged to be the true one. In fact, several -years later, Bunsen, then Playfair, and later Riecken, in their investigations established clearly the role which atmospheric nitrogen plays in the formation of cyanide compounds. It is easy to understand how this discovery attracted the atten- tion. of the manufacturers when the importance and the economic aspects of the question are considered. From that time on they exerted themselves in applying in a practical way the results ob- tained by investigators, and numbers of patents followed each other, all tending to do away with the use of nitrogenous organic matter (which is rather costly and imperfect) and approaching as much as possible to the synthetic production, which is simpler and more economical. GENERAL CONSIDERATIONS. 83 At the present time the tendency is still in the same direction, and one must not despair of seeing, in the very near future, the success of this important problem of the fixation of atmospheric nitrogen in the production of cyanide compounds on an industrial scale. The first efforts in this direction were unfortunately fruitless and therefore short lived. They were all inspired with the same idea : the passing of nitrogen over a suitably heated mixture of charcoal and an alkaline carbonate or an alkali. Such are the methods of Bunsen, Ertel, Armengaud, Possoz, and Boissiere, Lambilly. The next step was the replacing of the carbonates of the alkalis: by the alkali metal itself (Castner, MacDonald, Mackey, Hornig, Schneider). Other inventors made use of ammonia instead of nitrogen. Quite recently, in Germany, processes have been patented along this line,, and, as will be seen later, the results are thought to be satisfactory. Indirect means were also tried, such as those suggested by Gelis,. and taken up by Tcherniac and Gunzberg, which consisted in pro- ducing ammonium sulphocyanide, and this was converted into potas- sium cyanide. In the mean time the discovery of cyanide compounds in the purifying masses from the manufacture of illuminating-gas, and in sugar-beet molasses and vinasses, added a new and lively interest to this industry. One must also mention the use of metallic carbides recently praised as a means of fixing atmospheric nitrogen for the production of cyanides, a tentative method which seems to have given some results. That the question is complex may easily be seen from these general remarks. It has not yet been definitely solved, nor has the ideal process been found. Nevertheless certain modes of manufacture have already furnished appreciable results, and show a real progress.. All these will be reviewed in this portion of this work. The order in which this interesting study will be taken up follows quite naturally from the preceding remarks and will be as follows : Chapter VI. Manufacture of Cyanides. (1) Non-synthetic processes: (a) production by means of f erro- cyanides; (6) production by means of sulphocyanides. 84 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. (2) Synthetic processes : (a) the use of atmospheric nitrogen ; (6) the use of ammoniacal nitrogen. (3) Other processes. Chapter VII. Manufacture of Ferrocyanides. (1) Old processes. (2) Extraction of gas residues: (a) direct extraction of the gas; (6) extraction of ammoniacal liquors; (c) extrac- tion of the spent oxides from illuminating-gas. Chapter VIII. Manufacture of Ferricyanides. Chapter IX. Manufacture of Sulphocyanides. Chapter X. Manufacture of various other cyanide compounds : nitroprussiates, Prussian blue, Turnbull blue, etc. CHAPTER VI. MANUFACTURE OF CYANIDES. I. NON-SYNTHETIC PROCESSES. A. EXTRACTION OF CYANIDES FROM FERROCYANIDES. Old Process. The oldest method of obtaining potassium cyanide, a method which is scarcely ever used except in the manufacture of the absolutely pure salt, is that of Robiquet, modified by Geiger. It consists in igniting the dried yellow prussiate or ferrocyanide of potassium. Under the influence of heat the ferrocyanide of potassium is decomposed according to the reaction Fe(CN) 6 K 4 = 4CNK + C 2 Fe + N. It is absolutely essential that the ferrocyanide of potassium used for this purpose should be (1) perfectly free of sulphate uf potassium, which in the above reaction would become transformed into the sulphide, which would give a yellow color to the cyanide; (2) perfectly free from its water of crystallization, which would tend to retard the reaction. The method of preparation is as follows: Yellow prussiate is first carefully dried at about 100 C. upon plates of sheet iron or in cast-iron pans; thus the dried product is transferred to forged- iron crucibles capable of holding about 80 liters and covered with an iron lid. These crucibles are then placed in batteries of five or six in furnaces. Into each one are placed 80 kilograms of ferrocyanide and the whole gradually heated. Just as soon as the product is fused, the temperature is gradually raised to a dull red; the whole is stirred 85 86 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. from time to time with a long-handled iron dipper. The operation lasts about seven or eight hours, and is ended when a sample taken out and cooled has a white, dull, porcelain-like appearance. Care must be taken that the temperature does not go beyond dull redness, otherwise the cyanide formed would itself be decom- posed into potassium carbide and nitrogen. 2CNK = C 2 K 2 +N 2 .* When the operation has been carefully carried out, the result is a mixture of carbide of iron and cyanide of potassium, the former adhering to the sides of the crucible, the latter in the midst of the mass. In order to obtain the cyanide from the mixture recourse may be had to decantation followed by filtration or to lixiviation. In the first case the fused product is decanted upon cast-iron niters (A) (Fig. 1), the bottom of which is a grate which is covered to about 1 / 3 of the height of the filter with iron turnings. This filter is kept at dull redness during the time of the operation. The cya- nide is drawn from the crucibles by means of iron dippers and poured upon the filter. The first portions of the filtrate are often contaminated with carbide of iron; they are therefore fused anew in the crucibles and there refiltered. The filtrate is collected in polished and perfectly clean iron pans (C), which are set in a trough (D) filled with cold water. Too long contact of the potassium cyanide with the iron carbide formed must be avoided, for experience has shown that the ferro- cyanide was inclined to become once more formed by an inverse reaction. If recourse is had to lixiviation, the product of ignition is taken up either with water or with alcohol. The extraction with water is a cheaper but a more delicate operation. Much care must be taken and the work carried on rapidly, because water always decomposes the potassium cyanide, forming ferrocyanide. * It may be remarked that it is precisely this decomposition of potassium cyanide at a high temperature which renders it impossible to obtain the cyanide by means of the electric furnace, as was attempted by Moissan. MANUFACTURE OF CYANIDES. 87 Although the use of alcohol is quite costly, it is preferable. The extraction is carried on in the warmth; it is quite slow because of the little solubility of potassium cyanide in alcohol. In each of the above cases, the lixiviation is followed by evapora- tion and a rapid drying of the cyanide. In the case of alcohol this solvent may be recovered and so be used over and over. As may be seen this process is rather defective. During the process notable quantities of cyanogen in the form of iron carbide and nitrogen are lost, and in fact only about 2 /3 of the cyanogen used is recovered; 10 parts of ferrocyanide give only 7 parts of FIG. 1. Cyanide-filter. cyanide, i.e. 45 kg. of absolutely pure cyanide for 100 kg. ferrocy- anide used. Liebig's Process. With a view of remedying this objection,. Clemm Rodgers and later Liebig proposed igniting dry ferro- cyanide in the presence of dry potassium carbonate. This process, is still sometimes used. Clemm advised the use of a mixture of 8 parts ferrocyanide and 3 parts potassium carbonate. The reac- tion is as follows: (1) Fe(CN) 6 K 4 + C0 3 K 2 = 6CNK + FeO + C0 2 , but under the influ- ence of the iron oxide formed a smaU quantity of cyanide is trans- formed into cyanate, so that the reaction is in reality as follows: (2) Fe(CN) 6 K 4 +C0 3 K 2 = 5CNK+CNOK+Fe+C0 2 , or, better still, a combination of equations (1) and v (2). 2Fe(CN) 6 K 4 +2C0 3 K 2 = 11CNK +CNOK + FeO +Fe +2C0 2 . 88 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The product is treated with water whereby a solution is obtained consisting of cyanide and an excess of potassium carbonate. In order to separate these bodies, alcohol or acetone is added which precipitates the insoluble cyanide. The residue, consisting of iron oxide, potassium carbonate, iron, small quantities of undecomposed ferrocyanide and unprecipitated cyanide, is powdered and allowed to stand in air. Under these conditions insoluble iron peroxide is formed. The product is once more extracted, the solutions evaporated, and the residue ignited. In this way a certain part of the potassium carbonate may be recovered which may be used over again. Ten parts of ferrocyanide give 8.8 parts cyanide and 2.2 parts of cyanate. Wagner's Process. In order to avoid the formation of cyanate at the expense of cyanide, Wagner proposed igniting the mixture of ferrocyanide and alkali carbonate with a small quantity of finely pulverized wood charcoal the use of which is to reduce any cyanate formed. The following are the amounts proposed by Wagner: Ferrocyanide of potassium 8 parts. Carbonate of soda 2 Powdered wood charcoal 0.2 part. The reaction is Fe(CN) 6 K 4 + C0 3 Na 2 + C = 4CNK + 2CNNa + Fe + C0 2 + CO. Another advantage of this method would be the separation of iron, which would be easier. The mixture thus obtained is formed by 4 mol. of potassium cyanide and 2 mol. sodium cyanide. Later will be discussed the advantage which this mixture, which is richer in cyanogen, has over potassium cyanide alone. Chaster's Process. This is only a modification of Wagner's process, and consists in adding to the mixture of ferrocyanide car- bonate and charcoal a certain amount of tar, pitch, or bitumen. The yield is thus somewhat greater, the reaction being carried on in the reducing atmosphere produced by the hydrocarbons added. The following are the proportions proposed by Chaster: Anhydrous ferrocyanide 65-75 parts. Carbonate 20 " Wood charcoal. . 5 ' c MANUFACTURE OF CYANIDES. 89 The ferrocyanide and carbonate are ground together and during the grinding 5% dried wood charcoal is added, together with a quantity of tar, pitch, bitumen, or asphaltum or any other analogous substance sufficient to give the whole mass the consistency of a paste or of mortar. In case the mass may not be plastic enough a small quantity of benzine or petroleum is added. This mass is compressed into the form of briquettes, which are ignited in a furnace with a reducing flame. Notwithstanding these modifications, processes which are based on the decomposition of ferrocyanide under the influence of heat are not profitable. They are rather costly; the losses in nitrogen, in alkali, and even in cyanide by volatilization are sometimes con- siderable. Their industrial use haSv always been most limited. In trying to perfect these processes, many very ingenious modifications have been devised which have, it seems, given good results, and the industrial use of which has, latterly, been quite extensive. The Process of Rossler and Hasslacher (of New York). The type of these new modifications is that of the house of Rossler und Hass- lacher of New York, belonging to the Deutsch Gold und Silber Scheide Anstalt. This process, which was proposed by Erlenmeyer, is based upon the action of metallic sodium on potassium cyanide, according to the reaction / Fe(CN) 6 K 4 +Na 2 = Fe+4(CNK),2(CNNa). The product is then treated with water and the solution evaporated. The product thus obtained, which is sold as potassium cyanide 98-100%, is in fact but a mixture of 4 mol. of potassium cyanide with 2 mol. sodium cyanide, a product identical with that produced by Wagner's process. If the whole be assumed as potassium cyanide, it is seen that it contains 98% of the cyanogen used. Moreover, this mixture has the advantage of being richer in cyanogen than is the potassium cyanide, because the atomic weight of sodium is. less than that of potassium. Thus 109 grams of this mixture cor- responds to 106 grams of potassium cyanide. Besides having the advantage of avoiding loss of cyanogen, this method permits the use of metallic sodium, a metal which, since- 90 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Deville's process for the manufacture of aluminium was abandoned, found but little use in the arts. At present, sodium is produced on a large scale by electrochem- ical industries; it is therefore of interest to call attention to this method of application. This process is, moreover, in considerable use in England, Germany, and even in France. Wichmann and Vautin's Process. Because sodium was still rather expensive, attempts were made to replace it with alloys of alkali metals with lead. These alloys are at the present time obtained much cheaper than the alkali metals, by subjecting fused alkali chloride to electrolysis in a bath of melted lead, which acts as a cathode. In order to obtain potassium cyanide, a mixture of potassium ferrocyanide with a lead-potassium alloy is used. If the sodium cyanide be desired, sodium ferrocyanide and a lead-sodium alloy are taken. As in the Rossler and Hasslacher process, a double cyanide of sodium and potassium may be prepared, by causing an alloy of lead sodium to act upon potassium ferrocyanide, or a lead-potassium alloy to act upon sodium ferrocyanide. The dehydrated ferrocyanide is first pulverized and then mixed with the powdered alkaline alloy. The grinding of these alloys is easy enough, because they are generally brittle. Ordinarily the grinding is done in the presence of a small quantity of mineral oil, the use of which prevents oxidation. The mixture is fused in furnaces at as low a red heat as possible. This fusion should, of course, be done out of contact with air. When the reaction is finished, there remains a fused mass consisting of cyanide as well as iron and spongy lead. These two foreign substances are separated from the cyanide by decantation or by filtration. The mass may likewise be treated with water, and after filtration the solution of cyanide may be evap- orated. The lead and the iron may also be separated. In order to do this, the mixture is melted on an inclined plane, when the lead, which is more fusible, runs off first, leaving the iron behind, or else the mixture is finely divided and stirred in a bath of melted lead, which retains the lead which was mixed with the iron, thus permit- ting the iron to be collected. This iron may then serve in the prepa- MANUFACTURE OF CYANIDES. 91 ration of ferrocyanides. The lead is itself used anew in the prepa- ration of the alkaline alloy. The proportion of ferrocyanide to alloy to be used depends on the quantity of alkali metal which the alloy contains. The authors claim that, in practice, an alloy containing 10% of alkali metal is the best adapted. It is, however, always better to use a somewhat larger quantity than is theoretically sufficient in the substitution of the alkali metal for the iron of the ferrocyanide. In practice, in order to prepare a double cyanide of sodium and potassium, 10 parts by weight of the dehydrated potassium ferrocyanide and 13 parts of the 10% lead-sodium alloy may be used. A modification of this process has been proposed by Hetherington, Hurter, and Muspratt (English patent March 20, 1894, March 1895) ; it consists in melting the alkaline alloy under a certain thickness of cyanide obtained in a previous operation, and adding to this mix- ture, in small portions, the dried ferrocyanide. These inventors recommend using an alloy with 13% sodium. When the reaction is complete the final product is found in three separate layers melted lead, reduced iron, and alkalicyanide, which are easy of separation. The lead-sodium alloy may be replaced by the lead-potassium alloy, but the former is preferable. Does the use of alkaline alloys possess, as stated by the inventors of various patents on this subject, a distinct advantage over the use of alkali metals alone? This question is not so easily answered. It cannot be denied, in view of the ease with which the alloys are obtained, that the potassium-lead alloys, and more especially the sodium-lead alloys, are much cheaper, all things being equal other- wise, than the same alkali metals themselves. From this point of view the processes of Vautin and Hetherington would possess ad- vantages. But, on the other hand, one has a right to ask, What is the role played by the lead in these reactions? It is known that lead has but a slight affinity for the cyanides, and that is the reason why lead cyanide has never been prepared. The use of alkali cyanides has even been praised as a means of reducing lead carbonate to the metallic state. It becomes evident, therefore, that in the action of lead-sodium alloy on alkali ferrocya- nide, sodium alone enters into the reaction. Since the content of the alkali metal in the alloys is generally 92 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. about 13%, in order to produce the same result as 100 parts of so- dium one must use 770 parts of the lead-sodium alloy. Therefore the net cost of lead-sodium alloys containing 13% sodium should be 7.7 times less than that of metallic sodium, in order that such processes as those of Vautin and of Hetherington, etc., may possess pecu- niary advantages over those processes represented by Rossler-Hass- lacher, etc. The cost of the alloy must, indeed, be even cheaper, because in the first processes one must also reckon the expenses due to the separation of the iron and the lead in order to recover the latter. Now then, according to data on this subject, the price of lead-sodium alloys containing 12-15% sodium is not so low, in fact it is only one fifth of the price of metallic sodium, the price of sodium taken into account being that made especially to manufac- turers of cyanides. It would seem, moreover, that the advantage in using alkali alloys is rather in the case of working and manipulating the prod- ucts. In this case, one must assume that the lead is either a reduc- ing agent preventing the formation of cyanates, or simply a diluting agent (when it is considered that it forms 87% of the alloy) whose r61e would be to prevent the sodium from floating on top of the mass of melted ferrocyanide and thus not enter the reaction. In these two cases the advantage offered by the alkali alloys would be especially valuable from the point of view of the yield in cyanide. Dalinot's Process. This also depends on the action of an alkali metal on ferrocyanide, but in this case the metal is no longer used in the free state; it is produced in the nascent state during the reaction. In a suitable vessel, and at the required temperature, place dried ferrocyanide mixed with sodium hydroxide or with potas- sium hydroxide in as dry a state as possible. To this mixture add finely pulverized calcium carbide. The ingredients should be added in atomic proportions. As is well known, calcium carbide possesses remarkable reducing properties. Under the conditions just mentioned it acts upon the only body containing oxygen, that is the alkali, and sets the metal free. This reaction is the result of the well-known fact that sodium MANUFACTURE OF CYANIDES. 93 unites with oxygen, producing NaO + 100 calories, while calcium combines with oxygen, forming CaO + 135 calories. Consequently the calcium removes the oxygen from the sodium hydroxide, leaving lime and metallic sodium. The sodium is found in the mass in the molecular state. It comes in contact with the cyanogen which was united to the iron, and which has been set free in consequence of the ignition of the ferrocyanide. In accordance with the law that the most stable body is the one first formed, sodium cyanide is produced, the reaction being FeCy 6 K 4 +Na 2 0+C 2 Ca = 4KCy + 2NaCy + CaO + Fe + various carbides. During the operation an energetic stirring of the fused mass is- maintained so as to have perfect contact. When the operation is over, the fused mass is filtered through a hot filter in order to sepa- rate the residue of iron and lime. Instead of the caustic alkalis, the alkali carbonates may like- wise be used. The calcium carbides should be quite dry. For this purpose it is ground in a grinder whose interior is perfectly sheltered from the atmosphere, and is in air-tight communication with a reservoir containing sulphuric acid. This procedure does not lack in origi- nality, but its working does not seem to be very practical. It is quite difficult, in fact, to obtain an alkali completely free of water,. whence comes a loss in cyanide compounds under the form of ammo- nia. On the other hand, calcium carbide of commerce is frequently impure and gives to the cyanide a more or less intense coloration,. injuring the commercial value of this product. Adler's Process. This process was patented in July, 1900, and is: but an improvement on that of Liebig. With the object of reducing the cyanates, Adler no longer employs charcoal but alkali ferro- cyanides according to the reaction: (1) FeCy 6 K 4 +C0 3 K 2 = 4KCy+2KCyO+CO+Fe. (2) 2KCyO + 2FeCy 6 K 4 = lOKCy + 2FeO + 4C + 4N. (3) 2FeO+2C = 2CO+2Fe. 94 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. 368 parts of dry ferrocyanide of potassium are fused with 138 parts of dry potassium carbonate, and toward the end of the reac- tion 736 parts of dry ferrocyanide are added a little at a time. An abundant froth produced by the reaction of the cyanate is at first formed. When the mass is in a tranquil fusion, it is filtered in order to separate the cyanide formed from the impurities iron, oxide of iron, etc. Etard's Process. This process is connected rather with the extraction of cyanides from sulphocyanides, since it consists in removing the sulphur of the sulphocyanides by means of the iron of the ferrocyanides according to the reaction Fe(CN) 6 K 4 +CNSK = FeS+5CNR4-C 2 N 2 . In practice the perfectly dry ferrocyanide is fused with the equally dry sulphocyanide. Sulphide of iron is formed, which is deposited during quiet fusion. The cyanide formed is decanted hot; the cyanide gas which is set free is not lost, but collected in an alkaline solution. The mass may likewise be taken up by water, methyl alcohol, or ethyl alcohol. In the first case, work is carried on as rapidly as possible out of contact with air, in order to avoid the formation anew of the ferrocyanides. In order to avoid the formation of the cyanide gases and consequently to increase the yield, carbonate of potassium may be added to the mixture of ferro- cyanide and sulphocyanide. The reaction is then as follows: Fe(CN) 6 K 4 +CNKS+C0 3 K 2 =FeS + 7 368 97 138 455 In this wise, 7 molecules of cyanide of potassium are obtained instead of 5 molecules, as in the previous reaction. Bergmann's Process. This process, which is one of little prac- tical value, and which produces only the cyanides of copper and silver, is a wet method It consists in heating a solution of ferrocyanide in the presence of a copper or a silver salt, in sufficient quantity to effect the total union of the cyanide of the prussiate with the copper or the silver. MANUFACTURE OF CYANIDES. 95 The mixture should contain a certain proportion of free acid, which, producing the decomposition of the ferrocyanide, causes the formation of prussic acid, which unites with the silver or with the copper to form cyanides of these metals. In the case of the cyanide of silver the reaction is as follows: 6N0 3 Ag + FeCy 6 K 4 = GCyAg + 4N0 3 K + (N0 3 ) 2 Fe. 422 parts by weight of crystallized ferrocyanide of potassium are dissolved in 50 times its weight of water, to which is added a 2% solution of 1020 parts of nitrate of silver. After slightly acidify- ing with sulphuric acid, the solution is brought to a^boil until the whole of the precipitate of ferrocyanide of silver which is first formed is completely transformed into cyanide of silver by absorbing the whole of the silver remaining in excess. This cyanide is separated by decantation and washings. In the case of the copper cyanide the reaction may be expressed thus: 6S0 4 Cu + FeCy 6 K 4 + 3S0 2 + 6H 2 = 3CuCy 2 + 2S0 4 K 2 + S0 4 Fe + 6S0 4 H 2 . 7. In order to avoid a too excessive action of the 6 molecules of free sulphuric acid which are formed in the course of the reaction it is well to operate in very dilute solution, or to neutralize the acid as fast as it is formed by the addition of alkali. Likewise a sul- phite may be used from the beginning. At first a reddish-brown precipitate of ferrocyanide of copper is formed, which under the action of heat is gradually transformed into a white, flucculent cyanide of copper. The cyanide of copper thus obtained furnishes very interesting double cyanides when digested in the cold with an alkaline sul- phide. B. EXTRACTION OF CYANIDES FROM SULPHOCYANIDES. Sulphocyanides have but a very limited market. They consti- tute, as will be seen later, one of the most important residues in the manufacture of illuminating-gas. Moreover, for a certain time, they formed the basis of several methods of cyanide manufacture, 96 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. due to the remarkable works of Caro, Conroy, and of Playfair, who demonstrated that they could be a profitable source of cyanide production. Thus, for a long time, attempts have been made to transform these salts into cyanides or into ferrocyanides, which find a more extended application. The interest taken in this subject is well shown by the numerous studies, and the various patents taken. Theoretically, this conversion of sulphocyanides into cyanides appears quite simple. If the formula of sulphocyanide of potassium is taken, for example, one sees that its conversion into cyanide is made by the simple removal of the atom of sulphur which it con- tains : CNSK-S = CNK. There are two general methods which may be used in producing such a result. The first is one of reduction, in which case a sul- phide is formed CNSK+R=CNK+RS. The second, on the contrary, consists in removing the sulphur by oxidizing it with production of a sulphate: CNSK + R + 4 = S0 4 R + CNK. I. METHODS OF OXIDATION. This method of treatment is the oldest, but it has never been used on an industrial scale. The first attempt along this line was made by Hadow, who used permanganate of potash and peroxides of lead and manganese. In a method for the determination of sulphocyanides by means of permanganates, Erlenmeyer showed that in an acid solution the reaction takes place quantitatively: 5CNSK + 6Mn0 4 K + 4H 2 S0 4 = 5KCN + 6S0 4 Mn + 3S0 4 K 2 + 4H 2 0. This method is entirely demonstrated, but the high cost of per- manganate was a serious obstacle to its industrial application. Never- theless, this discovery of Erlenmeyer caused ' an awakening of MANUFACTURE OF CYANIDES 97 ideas. Alt showed that in the presence of barium chloride, using HNOa as oxidizing agent, the reaction is likewise quantitative. The ingenious attempts of Parker and of Robinson (1888-1889) must also be mentioned. The latter made use of electrolysis. He passed the electric- current through a solution of sulphocyanide in sulphuric acid. Prussic acid, CNH, was formed, which was collected in an alkaline solution. The causes of failure of such processes may be easily understood. The prussic acid set free was a continual source of danger to the employes on account of its great toxicity. Raschen's Methods. The next attempt was the use of nitric acid as oxidizing agent under certain fixed conditions. Such are the processes of Raschen and Brock, worked by The United Alkali Co., Limited. To the kindness of Dr. J. Raschen, Director of The United Alkali Co., Limited, we owe a complete description of his processes, which is reproduced in full. In the first of these processes the line of procedure, as indicated in the patents taken out by Brock and Raschen (1888, 1895, 1896), is as follows: A 20-30% solution of dry sodium or calcium sulphocyanide is used. A definite quantity of hot water, or, better still, of mother-liquor from a pre- vious operation, is placed in a hermetically closed boiler provided with a stirrer and the solution is heated to 96. The stirrer is then set in motion while at the same time the solution of sulphocyanide and nitric acid are added. The addition of these two solutions must be so regulated that there is always a slight excess of the acid in the mixture. The whole of the sulphur of the sulphocyanide is oxidized into sulphuric acid, while at the same time a mixture of nitrous acid, water-vapor, nitrogen , oxide carbonic acid, and hydro- cyanic acid is set free. These acids are passed through a scrubber containing water at 80 C., which absorbs the nitrous acid. After having undergone this first purification and having been cooled, the gaseous mixture passes into an absorption apparatus dividedin to two compartments. The first contains cold water, which absorbs a great portion of the hydrocyanic acid, allowing the carbonic acid and the nitrogen oxide to pass on; the second contains milk of lime, which retains the carbonic acid and the remainder of the hydrocyanic acid, so that at the outlet of the apparatus, nitrogen oxide escapes, which, mixed with air, is recovered under the form 98 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. of nitric acid, capable of being used again in the same process. The solution of calcium cyanide in the second compartment is filtered from the precipitate of the carbonate of lime and converted into alkali cyanide by double decomposition. The solution of hydro- cyanic acid in the first compartment is neutralized by means of an alkaline solution, forming an alkali cyanide. The cold water of the first compartment may equally well be replaced by an alkaline solution. It is of the utmost importance that the operation be carried on absolutely out of contact with air, otherwise the nitrogen oxide, would become oxidized with the formation of nitrogen per- oxide, which latter would be absorbed by the alkaline solution, form- ing nitrite and nitrate, which would contaminate the cyanide and so be a serious hindrance to the fusion of this compound, the mix- ture of cyanide and nitrate reacting with violence. It is likewise necessary because of the extreme toxicity of the prussic acid to work very carefully and to maintain a slight vacuum in the apparatus, so that no gas shall escape into the air if the apparatus should leak. Raschen and Brock modified this process by using mineral oxi- dizing agents, such as the nitrates, chromates, peroxides of lead or of manganese in the presence of sulphuric acid. With the water is mixed the acid and the oxidizing agent and the whole brought to a boil; then is added, little by little, the sulphocyanide dissolved in water. It is necessary to use a somewhat larger quantity of oxidizing agent and acid than the theoretical amount indicated by the following reaction, using sulphocyanide of sodium as an example: CNSNa + 3S0 4 H 2 + 3Mn0 2 - CNH + S0 4 NaH + S0 4 3Mn + 2H 2 0. Toward the end a little more heat is applied in order to drive off completely the whole of the hydrocyanic acid. The gaseous mixture is collected and purified, as before. In the Wigg works at Runcorn, which belong to The United Alkali Co., Limited* this process slightly modified is in use at the present time on a large scale. Raschen and Brock have, in fact, found that better yields (96%- 99% of theoretical) are obtained if more dilute solutions be used (170 grams per liter), and if the solution of sulphocyanide be poured MANUFACTURE OF CYANIDES. 99 slowly into the dilute and boiling nitric acid. At Runcorn sodium sulphocyanide is used, besides sodium nitrate and sulphuric acid, which latter act as oxidizing agent. The apparatus used in the decomposition consist of stoneware carboys A\, A 2 , A 3 , ... A n , placed in series, connected with each other by means of earthenware tubes starting at about mid-height of one carboy and .ending in the next at the bottom. Each one of them carries, besides, an outlet tube B and a tube C for the inlet of the steam, which latter tube serves as stirrer. First the carboys are filled with dilute sulphuric acid, then steam is let on so as to reach nearly the boiling-point. Then the solutions of sulphocyanide (170 grams per liter) and sodium nitrate are run in simultaneously. The letting in of steam and of solutions is so regulated that the temperature always remains constant, and the liquid passing from the first into the second carboy no longer contains traces of sulphocyanide, and the liquid of the last carboy is free from hydrocyanic acid. The gases which are liberated are chiefly hydrocyanic acid and nitrogen dioxide together with a little carbonic acid, nitrous acid, and considerable amounts of water- vapor. The gases pass first into the tower D, filled with quartz FIG. 2. Raschen's Apparatus. pebbles, through which they pass from bottom to top, where they meet a shower of cold water circulating in the opposite direction, 100 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. which absorbs the oxides of nitrogen, without absorbing the hydro- cyanic acid, because the temperature has not been lowered. The water- vapor is condensed in an ordinary condenser E-, it carries with it a small quantity of hydrocyanic acid, which is neutralized with caustic soda. At their outlet the gas shows 75-80 F. They are conducted into the two cast-iron absorbers CiC 2 , which are cooled on the out- side and which contain caustic alkali. The hydrocyanic acid is absorbed, and the nitrogen dioxide is set free unaltered. This latter gas is brought in contact with air in order to recover the nitric acid, The recovery of this gas is done by passing the gas mixed with an excess of air through two towers of refractory stoneware M and N, which inclose quartz pebbles, and into which falls a shower of cold water. The amount of water and the volume of air used in the reaction should be carefully regulated in order to recover an acid of uniform concentration. However, it is necessary to have an excess of air over the theoretical quantity. This excess of air carries a part of the heat liberated by the oxidation of the nitrogen dioxide and serves as a refrigerating agent. The mixture of acid thus recovered, on coming out of the second tower is conducted directly into the first decomposition carboy, where it oxidizes a new quantity of sulpho- cyanide. The whole circulation of the gases is made certain by Koerting Injectors. The last operation is the evaporation of the cyanide solution in order to have a commercial product. This procedure is easily ac- complished in the laboratory, but quite difficult on an industrial scale. In fact the evaporation of large amounts of cyanide solu- tions always causes a more or less complete transformation of cyano- gen into ammonia. This loss is chiefly due to the action of super- heated steam in the cyanide mass. This objection may be easily removed by evaporating the solution in vacuo and by keeping it constantly stirred. The product obtained under these conditions is a white powder more or less agglomerate. It is free of sulphur and therefore particularly suitable in the extraction of gold. It contains, however, several impurities, due mainly to the caustic solutions used. T. T. Conroy, who has made a thorough study of MANUFACTURE OF CYANIDES. 101 Raschen's process,* states that the precautions taken in order to avoid any liberation of such toxic gases as hydrocyanic acid and nitrogen dioxide are perfect, and the total absence of any odor in the works is a convincing proof. Beringer's Process. Having studied thoroughly the conversion of sulphocyanides into cyanides by the oxidation process, Beringer discovered that the formation of carbonic acid was due to the pres- ence of free mineral acids, and thereupon conceived a process whose object is to carry on the reaction in such a manner as to form no free acid, or at least if any be formed, its effect is not perceptible. In order to do this he uses nitric acid in sufficient quantity, but in the form of nitrate (of calcium or of barium). By causing a mineral acid, which is capable of setting free nitric acid from the nitrate, to act upon this salt ; the nitric acid will act on the sulpho- cyanide as an oxidizing agent; sulphuric acid will be formed at the same time as the oxidation is produced, but this acid will liber- ate a fresh quantity of nitric acid, which will oxidize more sulpho- cyanide, while the sulphuric acid formed will be held by the base of the sulphocyanide according to the reaction (CNS) 2 Ba + 2(N0 3 ) 2 Ba + S0 4 H 2 = 3S0 4 Ba + 2CNH + 4NO. In this way Beringer claims that the carbonic acid formed at the expense of hydrocyanic acid is reduced to a minimum, and that the yield of this latter is almost theoretical. The operation takes place in a hermetically closed receiver provided with stirrers. Into this receiver 32 kg. of barium nitrate and 700 liters of water are placed and the temperature brought to the boiling-point. Then are added slowly, either separately or mixed together in portions about equal, 37.2 kg. barium sulpho- cyanide and 31.6 kg. sulphuric acid of sp. gr. 1.84, to each of which 100 liters of water have been added. The hydrocyanic acid liberated is carried away by the watery vapor and absorbed in suitable receptacles. * Jr. Soc. Chem. Ind., 1899, May 31. 102 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. II. REDUCTION PROCESSES. The oxidation processes have never been employed industrially to any great extent. Rauschen's methods only have enjoyed some interesting developments. They are in themselves rather danger- ous, for they all set prussic acid free, an excessively poisonous gas. Moreover, there is always fear of a later oxidations, the result of which would be a greater or less loss of cyanogen. The reduction processes are much more numerous, practical, and profitable, and at the same time free from danger. They are the only ones susceptible of being used in the industry of the cyanides obtained by the conversion of sulphocyanides. The various substances proposed for the accomplishment of the reduction are quite numerous: Hydrogen, carbon, hydro- carbons, various metals, etc. Playfair's Process. Playfair has thoroughly investigated along this line, and his remarkable researches have served as a basis for the reduction processes which are used at the present time. In one of his earlier investigations Playfair attempted to heat to redness a mixture of sulphocyanide of sodium or of potassium in a current .of hydrogen, based on the following reaction: 4CNKS + 6H = K 2 S + 2CNK + 3H 2 S + 2C + 2N. He noticed an abundant liberation of hydrogen sulphide; after the reaction was completed there remained in the combustion-tube a mixture of sulphide and cyanide in almost equal proportions; from his data, only about 80% of the sulphocyanide was decom- posed. In the above equation, 110 parts of potassium sulphide corresponding to 130 parts potassium cyanide, the product of the reaction yielded 20% less cyanide than the theoretical amount. Besides, one half of the cyanogen is lost, as it is set free in the form of nitrogen, and the separation of the cyanide from the sulphide is not a very easy matter. This process was therefore quite imprac- ticable. Several years later Conroy repeated Playf air's experiments and confirmed every result. Next, Playfair tried the use of hydrocarbon vapors naphtha vapors for example as reducing agent. As in the preceding experi- ment he noted an abundant liberation of hydrogen sulphide, but at the end of the reaction he found no traces of cyanides. The residue MANUFACTURE OF CYANIDES. 103 was composed entirely of sulphides together with slight traces of formates. When he heated sulphocyanide of sodium with charcoal, he obtained no better results. In this case he obtained traces only of cyanide and a considerable quantity of sulphide. Then Playfair tried the use of metals at first lead and zinc, for these only appeared suitable. The metals decomposed the sulpho- cyanide either in fusion or in solution according to the reaction CNKS+R=RS+CNK. After many experiments, Playfair adopted the following pro- cedure : He used a receiver made of black lead, whose form is that of an inverted muffle and which is provided with a tightly fitting lid. This apparatus is placed in a furnace in such a way that the top of the receiver extends 2 to 5 centimeters above the upper border of the furnace so that it becomes heated only at the bottom and the sides. Zinc is then melted in the presence of a small quantity of pulverized charcoal, which maintains a reducing atmosphere in the crucible. When the zinc is completely fused dry sulphocyanide is added, either cold or even in a melted state. The mass is kept stirred and the reaction continued till the mass becomes quite thick and begins to redden. At this point the reaction is complete. The mass is then allowed to cool, protected from the air. When cold, the mass is easily removed from the crucible, which does not appear at all attacked. The color of the mass should be pearly gray, if the reaction has been successful, in which case its solution will be entirely free of soluble sulphides. But if the mass has been super- heated, which happens especially when too large crucibles are used, it has a brownish and sometimes even a reddish color, and the solu- tion may contain as much as 15% of alkaline sulphide. As a rule one must assume a loss of about 5%, due partly to moisture and partly to the formation of small quantities of cyanate and carbonate. One should add also to the above loss that which may result from the formation of the double cyanide of zinc and potassium or sodium in consequence of a too high temperature, but this loss may be easily avoided by the use of a slight excess of sul- phocyanide. 104 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The melted mass is subjected to a systematic lixiviation in a series of vats. The alkaline cyanide solution is separated from the insoluble zinc sulphide by decantation. This latter substance con- stitutes about 65% of the fused mass. The solutions thus obtained vary considerably in concentration; that is, from 4 grams of sodium cyanide per liter to 220-240 grams. These latter solutions are evaporated in vacuum to the consistency of a thick paste, which on cooling crystallize. The following is an analysis, made by Playfair, of one of these solutions. The figures represent the amounts per 100 cc. of solution to be evaporated. Sodium cyanide 22.00 gm. Cyanate 3.06 Double cyanide of zinc and sodium 1 . 55 Sodium carbonate 0. 71 Sodium sulphocyanide 1 . 80 The following is an analysis, made by Playfair, of the concen- trated product : Water 26.00% Cyanide of sodium 54. 70 Cyanate of sodium (contains formate) 9.45 Double cyanide of zinc and sodium 3.90 Sulphocyanide of sodium 4 . 30 Carbonate of sodium 1 . 65 Playf air's process marks a real progress; it can be applied in- dustrially, since, according to the inventor, the yield is about 70% of the theoretical amount. This result is obtained if care be taken to concentrate the solutions in a vacuum of 66 centimeters, using solutions containing at least 22% of cyanide, so as to avoid loss of cyanogen. Dr. Hans Luttke's Process. This process is based on the same principle. It consists in melting sulphocyanide with zinc powder. In an iron crucible are fused together 97 kg. sulphocyanide of potassium, 65 " zinc powder. MANUFACTURE OF CYANIDES. 105 The mass is stirred while being heated, and from the moment it fuses, the crucible is removed from the fire. The reaction then goes on by itself. When the fused mass is treated with water it yields about 60 kg, of cyanide, i.e., 90% of the theoretical amount. The sulphide of zinc which is obtained as a by-product may be profitably used as a mineral color. The reaction takes place between 360 and 400; this temperature may be lowered by an addition of 1% to 2% caustic alkali, which at the same time, increases the yield of cyanide. Various other metals have been tried. Lead, which was also recommended by Playfair, has the advantage of not forming double cyanide of lead and potassium, but on account of its high atomic weight, three times as much lead as zinc are required to perform the same work, while, at the same time, it has a tendency of falling to the bottom of the crucible without remaining mixed with the sulphocyanide. The reduction of sulphocyanide may be well carried on with the use of tin, but tin sulphide dissolves in rather appreciable quanti- ties in the alkaline cyanide. The use of copper is no more successful, for it gives rise to cupro- cyanides. Process of the British Cyanide Company. Notwithstanding the foregoing, this company has quite recently patented a process in which copper is used. This process is based on the fact that when metallic cyanide compounds are heated in a current of hydrogen at a suitable temperature, they set free the whole of their cyanogen in the form of hydrocyanic acid, which may be absorbed by alkaline solutions. The British Cyanides Company, Limited, noticed that the salt which is the best adapted for this reaction is sulphocyanide of copper. This salt, which is first thoroughly dried, is placed in a receiver provided with a stirrer and mixed with finely divided copper in considerable excess (equal quantities of sulphocyanide and of copper). Perfectly dry hydrogen is passed through the apparatus, in order to expel the air and then it is heated to 150 C., and grad- ually to 350 C. When the reaction is almost complete, the temperature is raised 106 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. to 500 C. ; the current of hydrogen being constantly kept, up. The reaction is as follows: (CNS) 2 Cu 2 + 2Cu + H 2 = 2Cu 2 S + 2CNH. The gas which is liberated is a mixture of hydrocyanic acid with hydrogen in excess. It is conducted through a strong alkaline solution which absorbs the hydrocyanic acid. The excess of hydro- gen may then be collected and used anew. The cuprous sulphide remaining behind may be treated in order to recover the copper or copper salts. In place of hydrogen may be used coal-gas or water-gas provided they be free from carbonic acid, oxygen, and moisture. Conroy tried using copper and zinc simultaneously, or copper with lead-sodium alloy, but in neither case was he able to obtain a pure product. The results obtained with iron were quite satisfactory. In his patent, No. 21,451, obtained in 1893, Conroy recommends treating the dry sulp ocyanide with finely divided reduced iron, pitch, and a, small amount of charcoal in order to prevent oxidation. The reaction takes place at about 400, but, as Conroy himself noticed it is quite irregular, and the yield may be, in consequence, quite variable. Moreover, it is rather difficult to ascertain exactly the end of the reaction, and if the operation be carried on too far, reac- tions may take place which are quite opposed to those desired. Hetherington and Musspratt's Process. This process (English patent 5830, 1894) is based on this principle: It consists in heat- ing iron filings or turnings with tar in order to reduce the oxide coating to the metallic state. The iron thus treated is mixed in the proportion of 70 to 80 parts with 20 to 40 parts tar and 100 parts alkaline sulphocyanide. This mixture is heated to 350 C., thereabouts, in a closed vessel connected by means of a tube with a retort, where the volatilized sulphocyanide is condensed. The resulting product is iron sulphide, a tar-like residue, and alkaline ferrocyanide. It is treated with hot water, and the filtered solu- tion is subjected to the action of a current of carbonic acid, which displaces the hydrogen sulphide, after which the solution is con- centrated to crystallization. MANUFACTURE OF CYANIDES. 107 Process of the Silesia Verein Chemische Fabrik. This process is in all points about the same as the foregoing. The sulphocyanide is first melted, then poured upon reduced iron filings, turnings, or shavings, and then heated to dull redness. For this purpose 1 kg. of iron may be profitably used for each kilogram of crystallized sulphocyanide. If the sulphocyanide be in solution, this is concentrated, and iron shavings added in sufficient quantity to form a pasty mass. This is then transferred to receivers of moderate dimensions which can be transported and heated at a temperature not above 800. In order to complete the decomposition properly, incan- descent bodies, such as pieces of iron, charcoal, and highly heated stones, are thrown on the mass. Then the receiver is removed from the fire and allowed to cool. In each case the product is treated either with water, in order to obtain ferrocyanide, or with alcohol, in order to obtain cyanide. Goerlich and Wichmann's Process. This process differs but little. It consists in fusing the sulphocyanide with iron, passing a moist current of air charged with carbonic acid through the fused mass and then treating it with water according to the reaction 2K 6 Cy 6 6FeS 4- 170 + 21H 2 + 2C0 2 = 2K 4 FeCy 6 3H 2 + 2C0 8 K 2 + 5Fe 2 (OH) 6 + 2S At the present time the transformation of sulphocyanides into cyanides is preferably done in the wet way. These processes originated with the patents taken out by Pitt and Bower, the object of which was the recovery of the cyanide compounds occurring in gas-liquor. Bower's Process. In Bower's first process these gas-liquors are treated with addition of metallic iron or ferric salt in sufficient quantity to convert the whole of the cyanide compounds into ferro- cyanide and iron sulphocyanide. After distilling off the ammonia in the presence of lime, the residual liquors containing the sulpho- cyanide and ferrocyanide of calcium are treated with an acid solu- tion of cuprous chloride, which precipitates the cyanide compounds as insoluble cuprous salt. While this precipitate is still moist, it is treated with finely divided iron in order to convert it into soluble 108 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. iron sulphocyanide and insoluble iron ferrocyanide. At the same time metallic copper is formed. The ferrocyanide of iron, which is separated by filtration, is treated with a strong alkaline solu- tion in order to obtain an alkali ferrocyanide. The solution of iron sulphocyanide is evaporated. Later Bower noted that when the decomposition of copper sulphocyanide is brought about by the use of iron at a high tem- perature and under pressure, the copper which is set free reacts with the sulphur of the iron sulphocyanide and forms copper sul- phide and iron ferrocyanide. Bower immediately obtained a new patent, according to which the iron sulphocyanide obtained as before stated is treated with metallic copper in an autoclave and at a high temperature under pressure. The reaction follows: 3(CNS) 2 Fe + 6Cu = Fe(CN) 2 2Fe(CN) 2 + 6CuS. The precipitate obtained is afterward treated with an alkaline or alkaline-earth solution giving a soluble ferrocyanide. Conroy's Process. Taking up Bower's work, Conroy thought of substituting another and less expensive metal for copper, and chose iron. He noted that if a solution of iron sulphocyanide be boiled under pressure with metallic iron there will be formed at Undecomposed F |de Iron Sulphocyanide. Obtained. 115-125 (after heating 13 hours). 62.0% 36.8% 150-165 " " 4 " 10.6% 88.0% 190-200 . " " 2J " 9.2% 90.5% Having settled this important point, Conroy sought to obtain a similar result with potassium sulphocyanide or other impure sulphocyanide. His first experiment along this line was with a mixture of potassium sulphocyanide with a soluble iron salt. The results were as follows: Non-decomposed Ferrocyanide Sulphocyanide. Obtained. At 160 with 1 hour's heating 38.0% 52. 6% At 160 " 2 hours' " 22.0% 67.5% At 150-160 with 5J hours' heating 95.0% MANUFACTURE OF CYANIDES. 109 The result being favorable,' Conroy determined to apply this method on an industrial scale, and in order to do this he undertook, in company with Hawliczek and Clayton, experiments bearing upon calcium sulphocyanide, the important industrial waste product in the, manufacture of gas. In a cast-iron cylindrical autoclave provided with a stirrer turn- ing at the rate of 40 revolutions per minute a mixture of (1) a solu- tion of calcium sulphocyanide, 400 g. per liter; (2) a solution of ferrous chloride, 250 gm. per liter and an excess of iron filings or shavings is heated to 135-140 C. and under a pressure of 50-60 pounds per square inch. Under these conditions he observed that the time of the decomposition of the sulphocyanide that it varies with the amount and fineness of the iron used, according to the following table Iron in Excess of Sulphocyanide Time of Theoretical Amt. Decomposed. Reaction. 12 hours Si " Si ". According to Conroy the reaction is as follows: 2CNSK+FeCl 2 +2Fe = 2KCl+Fe(CN) 2 +2FeS. The mixture of sulphide and of ferrocyanide of iron is then treated with a strong alkaline solution, there being formed soluble alkali ferrocyanide, while the sulphide of iron undecomposed re- mains insoluble: 3(CN) 2 Fe+4KOH+H 2 + = Fe(CN) 6 K 4 +Fe 2 (OH) 6 . But this treatment requires a large excess of alkali, and moreover there is an appreciable loss of this compound varying from 12%-28%. It is better to replace it by treatment with hydrochloric acid. In fact, if the mixture be treated with this acid the sulphide of iron goes into solution, while a pale-blue precipitate is formed which is insoluble in hot potassium carbonate, but which yields potassium ferrocyanide under the action of a current of air. This method presents, moreover, the great advantage of giving ferrous chloride, which may thus be used in the reaction 3(CN) 2 Fe+6KCl+FeS = Fe(CN) 6 K 4 +3FeCl 2 +K 2 S. Iron shavings Reduced iron 8 times J5.55 " [1.70 " 92.5% 94-0% 85-99 110 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. All these processes yield ferrocyanide, which product must then be reduced to cyanide. They therefore do not solve the problem completely, which is the production of the cyanide direct. Raschen, Davidson, and Brock's Process. Nevertheless there exist special processes which fulfill this purpose, among them may be cited that of Raschen, Davidson, and Brock (1894). It is based on the conversion of sulphocyanides into cyanides by ignition in the presence of an excess of alkali or of alkaline earth, together with charcoal or a hydrocarbon. The sulphocyanide used in this case is produced by the action of carbonic acid on a mixture of milk of lime, sulphide of carbon, and ammonia heated in a closed vessel. The resulting product is treated with an alkaline carbonate filtered and evaporated to dryness. Quicklime is added to the crude sulpho- cyanide together with a mixture of powdered charcoal, resin, tar, or any other such substance. The whole mass is heated as rapidly as possible to a bright-redness in a vessel provided with a stirrer. The mass is then allowed to cool, avoiding as far as possible the access of air, and then it is washed with water. In this way is obtained a solution of alkali cyanide containing a small amount of calcium sulphide, which latter product may be gotten rid of by well- known methods. Theoretically, this process seems very simple and reasonable, but unfortunately no data could be obtained concerning the yields which it furnishes and concerning its industrial application. Etard's Process. This process, which has already been mentioned (Chapter I, 1) and which consists in treating the alkali sulpho- cyanide with the ferrocryanide of the same metal either alone or mixed with a carbonate, has not, to our knowledge, been industri- ally applied. Finlay's Process. Finally may be mentioned the original process, patented in Germany by Finlay (patent 8604, 1896). It consists in producing simultaneously sulphocyanide and alkali cyanide by igniting at 1000 a mixture of alkali or of alkaline earth with charcoal in an atmosphere free from oxygen and consisting chiefly of nitrogen and sulphuric anhydride. Through the solution of the mixture thus produced a current of nitrogen and carbonic acid, in the presence of an oxidizing agent, is passed. Hydrocyanic acid MANUFACTURE OF CYANIDES. Ill is removed and passes into an alkaline solution, forming an alkali cyanide. Finlay recommends the following: A mixture of equal parts of charcoal and caustic or carbonated alkali, especially barium carbonate, is heated to about 1000. A mixture of nitrogen and sulphur dioxide obtained by direct com- bustion of sulphur in air is transmitted upon the incandescent mass. Under these conditions there is produced a mixture of cyanide and sulphocyanide of barium. When this reaction is complete, the mass is allowed to cool and is taken up with water. After a suitable addition of an oxidizing agent (of the nature and use of which Finlay gives no information) a mixture of nitrogen and carbonic acid ob- tained by the combustion of charcoal in a current of air is trans- mitted into this boiling solution. The barium separates out as an insoluble carbonate, while the hydrocyanic acid which is displaced is carried off by the gaseous current. The hydrocyanic acid is con- densed in a cooler kept at a temperature of 4-5 C. and combined with a caustic alkali. At the same time the sulphocyanide is de- composed into hydrocyanic acid and sulphur dioxide. This latter, carried off by the nitrogen, regenerates thus the initial mixture of gas used for the production of cyanide and sulphocyanide. On account of its originality, this process deserves some atten- tion, but unfortunately it is quite probable that the liberation of hydrocyanic acid will check its industrial development, as is the case in all those processes where such a liberation takes place. II. SYNTHETIC PROCESSES. GENERAL REMARKS. It is the custom to designate under " synthetic or direct proc- esses/' all those processes the essential principle of which consists in uniting by means of any energy the three fundamental bodies entering into the composition of cyanides carbon, nitrogen, and alkali metal these three bodies capable of being either in a free or nascent state or in a combined state. The. indirect processes which have just been reviewed have been able to supply the needs of the trade at a time when the use of cya- nides was very limited, but soon the requirements of industry made necessary simpler, less defective, and less expensive processes. 112 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Nitrogenous organic substances, which for a long time have been the raw materials of this industry, have in general a very high value relatively, because of their extensive use either in human or animal nutrition, or in agriculture, or in other industries. There- fore they could not be economically used for a preparation which utilizes only their carbon and nitrogen. It is consequently necessary, if it is desired to work under really economic conditions, to make use of waste or refuse products, which are necessarily insufficient, especially from the point of view of the percentage of useful products which they contain. The percentage of nitrogen in these substances is especially small in comparison with that of carbon; therefore it is always necessary to ignite them beforehand, in order to obtain a much richer nitrogenous charcoal. In this preliminary operation f of the nitrogen is lost under the form of ammonia. This loss is unfortunately not the only one, and at the time of the forming of the cyanide with the nitrogenous charcoal f and even f- of that remaining is lost, so that finally only J or ^ of the total nitrogen is utilized. If to these losses in nitrogen be added those not less important, occasioned by poor yield, from the point of view of the alkali car- bonate used, and those produced by the volatilization of the cyanide at the temperature at which it is necessary to work, it is easy to see that such processes are far from giving satisfactory results or being economical, notwithstanding the remarkable improvements which they have undergone. It is therefore quite natural to have sought to produce cyanides by the synthetic or direct way, which, besides the advantage it possesses of producing the product desired directly, allows this product to be obtained much cheaper and in a state of greater purity. Of the three substances which, in general, constitute the cyanides, carbon occurs wide-spread, is easily found, and very cheap ; the alkali metals are likewise widely distributed. As to the nitro- gen, although it occurs distributed in extensive amounts on the surface of the globe, it is quite difficult to produce in a free state. Constituting four fifths of the atmosphere which surrounds us, it is quite natural to think of utilizing the nitrogen, either in the form of air or in the free state extracted from the air. The idea of using MANUFACTURE OF CYANIDES. 113 the atmospheric air in the manufacture of cyanides is not new. It proceeds from a series of observations made by many investi- gators. In 1828 a chemist of Besanon, named Desfosses, repeating the old experiments of Scheele and Curandeau, remarked that the nitrogen unites with carbon in order to form cyanogen when a current of this gas or of air passes over a mixture of charcoal and carbonate of potash at a red heat. In 1835 Dawes discovered the existence of cyanide of potassium in the molten masses which are formed in the furnaces for the smelt- ing of iron. In 1837 the English investigator Clark made the same discovery. In examining an efflorescence which was produced at the orifice of some blast-furnaces on the Clyde, he noticed that it was made up almost entirely of potassium cyanide. In the same year, having established hot-air bellows in blast- furnaces, Neilson likewise observed the formation of masses which contained up to 43% potassium cyanide. These were confirmed by other observations, notably in the Harz, at Magdesprung, and at Zuicken by Bromeis in 1842. In 1843 Redtenbacher proved a similar phenomenon in the furnaces at Mariazell in Styria, where the production of potassium cyanide thereby became industrially important. Moreover, in 1839 Lewis Thompson demonstrated that if a mixture of coke, potassium carbonate, and iron filings be heated at a high temperature and a current of air be passed over the mass, there will be formed potassium cyanide the yield of which will be greater than that obtained by not using air even when animal charcoal rich in nitrogen be used. On account of this remarkable investigation the Society of Arts bestowed a gold medal on Lewis Thompson. In 1841 Fowner, and likewise Young, confirmed this result. But other chemists, and particularly Erdmann and Marchand in 1841, and Wohler somewhat later, disputed their assertions, and claimed that the cyanide formed was due entirely to the nitrogen of the coal and that the reaction would not take place with dry substances. In 1845 the question of the formation of cyanide in the blast- 114 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. furnaces being studied more thoroughly, Bunsen and Playfair were able to show that this product is formed in the zone situated exactly above the blast-pipes through which hot air was being blown. They experimented on this subject with the result that it received scien- tific and industrial sanction and exerted a considerable influence on the ideas concerning the role played by nitrogen. By making an opening in the wall of a blast-furnace of the iron- works at Alfreton, exactly above the orifice of the blast-pipes, they noted the formation of an abundant sublimation of potassium cyanide, which, according to their calculation, might react 188 kg. in 24 hours. From this experiment they drew the conclusion that the cyanide formed was due solely to the atmospheric nitrogen, and not to that chemically combined with the coal. Moreover, they established clearly the proba- bility of this theory by another experiment. In passing air through a tube containnig a mixture of 1 part sugar charcoal and 2 parts of perfectly pure carbonate of potash, heated to a temperature high enough to cause the reduction of the alkali carbonate, they obtained an abundant formation of potassium cyanide. In 1851 Riecken confirmed in all points the data presented by Bunsen. This investigator showed without any doubt that cyanogen may be formed in the absence of every other source of nitrogen except that of atmospheric air, provided that the latter be previously heated and transmitted in the form of a continuous current, and that the reaction be carried on at a temperature sufficiently high to reduce the potassium compounds employed to the metallic state. Some time later Delbruck's new experiments removed all doubt from the works of Bunsen and Riecken. These first principles being admitted, it was immediately planned to make it the basis of a process for the manufacture of cyanide on an industrial scale. The first practical application undertaken along this line was in 1843. This was made by Possoz and Boissiere, at first in their works at Grenelle, and the next year at Newcastle, under the direction of an English company. This process was based on the fact demonstrated by Desfosses in 1841, that if a current of nitrogen be passed over a mixture of charcoal and potassium carbonate MANUFACTURE OF CYANIDES. 115 heated to redness, there is formation of potassium cyanide. Not- withstanding unheard-of efforts, great sacrifices, and several years of struggle and in spite of their rare perseverance, the two French chemists could not hold out against competition, and were forced to abandon the exploitation of their process. That was because the yield of cyanide was small, and consequently the net cost was greatly increased. Numerous attempts followed that of Possoz and Boissiere, and among them may be c ted : In England, those of Newton in 1843, Swindel in 1844, Blairs and Bromwell in 1847. In Germany, those of Welden in 1879, and Alder in 1881. In America, those of Mond in 1882, Fogarty in 1883 and 1887, and Dickson in 1887. And, finally, in France, those of Ertel in 1846, Armengaud in 1847, and Margueritte and Sourdeval in 1862. All these processes are based on the action of atmospheric air on a mixture of charcoal and an oxide or carbonate of an alkali heated to a very high temperature. The results obtained by these various manufacturers, however encouraging they may have been, were nevertheless far from being satisfactory. Therefore these processes had a very short existence. The quantities of cyanides produced were, in fact, very small, and the net cost was consequently very great. If to this great objection be added that none the less serious of the rapid wear and tear of apparatus brought about by the extremely high temperature necessary for producing the reaction, the causes of the failure of these attempts will be readily understood. The attempt was made to overcome the difficulty by utilizing nitrogen in another form, and for this purpose ammonia-gas was suggested. This gas in fact, besides being relatively cheap, is 14 /i 7 of its weight in the form of nitrogen, and it has a greater chem- ical affinity than that of nitrogen. In fact it was proved by the experiments of Langlois and Kuhlmann that if dry ammonia- gas be passed over charcoal heated to redness there will be formed ammonium cyanide according to the reaction 4NH 3 + 3C = 2NH 4 CN + CH 4 . 116 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. This was not, indeed, a new idea. Brunnquell, later Karmrodt, and finally Lucas had already tried to utilize the ammonia produced in the ignition of nitrogenous organic matters, and which forms part of the volatile products arising from this decomposition. Toward this end these products were made to pass through retorts or cylinders charged with charcoal impregnated with potash; but notwithstanding certain advantages these processes never received industrial sanction. Laming, in 1843 and 1845, made this idea the basis of two processes for the manufacture of cyanides. But these attempts were like- wise futile. Other manufacturers and investigators studied- this question also, their results often being contradictory and their experi- ments were never taken up outside the laboratory. The weak points of the experiments undertaken along this line are (1) the difficulty of manipulating such a volatile gas as am- monia, (2) the necessity of producing a very high temperature, (3) the considerable loss due to volatilization, and (4) the rapid deterioration of the apparatus. To the above should likewise be added the fact that at such high temperatures ammonia-gas begins to undergo an appreciable decomposition, which, of course, is lost to the reaction. Another very ingenious solution of the problem had been pro- posed by Gelis, and was taken up about 25 years ago by Tcherniac and Gunzburg. It consisted in producing cyanides through the intermediary of sulphocyanides, formed by the action of ammonia on the sulphide of carbon. During the last few years this question has again become the object of numerous and important researches, but along other lines, and which permits the discovery of a real synthetic process to be foreseen in the near future, a process at once practical and of in- dustrial value. These processes are based on the action of nitrogen or of am- monia upon the alkali metals or their carbides. The reaction of ammonia oh the alkali metals was shown a long while ago by Gay-Lussac and Thenard. It is, in fact, known that if perfectly dry ammonia-gas be passed over potassium or sodium at a suitable temperature (not very high) a clearly defined compound, an alkali amide, is obtained which in MANUFACTURE OF CYANIDES. 117 contact with charcoal under suitable condition forms alkali cyanide. The low price and the facility with which large quantities of alkali metals are prepared leads to the belief that processes based upon this reaction will be put to practical use. It is evident that in this case it is no longer necessary to produce the extreme temperature required for the reaction of alkaline compounds formerly used, and from this fact losses through volatilization will be avoided while decreasing the wear and tear of the apparatus. On the other hand, it is to-day clearly proven that carbides are capable of fixing nitrogen, and, under certain conditions, of forming cyanides. These two important observations have formed the basis of numerous patents recently granted, especially in Germany. The experiments seem to be successful, and in the near future the solu- tion of this question may be met. The solution would all the more be hastened through the dis- covery of a practical and economical process of fixing the nitrogen of the air, a question which has likewise made considerable progress, and all the more through the synthetic production of ammonia by the aid of this same nitrogen. Whenever this problem is solved, that of the manufacture of cyanides will be near its solution. The synthetic processes put into operation may be divided into two large classes: (1) Processes using atmospheric nitrogen. (2) Processes using ammoniacal nitrogen. Some of these processes are capable of using either atmospheric nitrogen or the nitrogen of ammonia. Such processes will only be mentioned in the first class, but will be discussed among those processes which are based on the use of ammonia. A. PROCESSES USING ATMOSPHERIC NITROGEN. The discovery of potassium cyanide in blast-furnaces, and the remarkable investigations of Bunsen, Playfair, Riecken, and of Del- bruck, which fixed in an irrefutable manner the remarkable role played by atmospheric nitrogen in this formation, had the happy 118 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. result of inciting manufacturers and investigators to utilize atmos- pheric air, or the nitrogen contained therein for the manufacture of cyanide compounds. As is well known, the atmosphere is composed of a mixture of oxygen and nitrogen, contaminated more or less, according to circumstances, with water, carbonic acid, ammonia, etc. In reality nitrogen forms about four fifths of the air, since air is composed of 21% oxygen and 79% nitrogen by volume, or 23% and 77% by weight. Air therefore is an inexhaustible and profitable source of nitrogen for the manufacture of cyanides. At first it was attempted to use the atmospheric air, but the presence of the oxygen interfered considerably with the reactions. That is the reason why the attempt was made to use the nitrogen from which the oxygen had previously been removed. The separation o these two gases is not such an easy task as one would be led to believe, and several methods have been devised for this purpose. Therefore it may not be out of place, before taking up the study of processes for the manufacture of cyanides by the use of nitrogen of the air, to first pass in review the various means employed for the separation of these two principal constituents of air, oxygen, and nitrogen. These methods almost all depend on the following principle: If a current of air be passed over an easily oxidizable substance tinder suitable conditions, this substance will absorb the oxygen and leave the nitrogen free and pure. Most oi the metals, and even certain metalloids e.g., phosphorus or charcoal may be used for this purpose. As a rule, whenever it is desired to obtain almost chemically pure nitrogen, copper or iron is used. A current of air is passed over copper heated to redness, which absorbs the oxygen with formation of oxide of copper, while the nitrogen is left almost pure. Often passing the gas only once over the metal is not enough for the total absorption of the oxygen. This is an objection which may be easily .remedied, and thus a gas absolutely free from oxygen obtained. This operation being carried on at a high temperature, the resulting gases are like- wise hot, which fact may be of great use in certain processes. Lupton has modified this pr cess in such a way that a better MANUFACTURE OF CYANIDES. 119 yield of nitrogen is obtained, and the process is carried on con- tinuously. His process consists in passing air through an aqueous solution of ammonia before passing it over the copper; the ammonia carried away by displacement then passes over the oxide of copper formed and reduces it to metallic copper according to the reaction 3CuO+2NH 3 = 3Cu + 3H 2 0+2N, thus giving a new quantity of nitrogen. The copper thus reduced is again oxidized by the oxygen of the air setting the nitrogen free; these two reactions really take place simultaneously. The gases obtained contained greater or lesser quantities of ammonia and aqueous vapor, which may be easily gotten rid of by suitable means. The chief objection to these processes is the use of copper, which is an expensive metal, even in Lupton's process, where it is recovered, for it finally undergoes physical modifications, becoming brittle and falling to pieces, which prevents its being suitable for further use. The process of obtaining nitrogen by the combustion of char- coal in a current of air has the objection of yielding an impure gas, always contaminated with carbonic oxide, and even with a small amount of oxygen. In these various processes the oxygen is lost, as may be easily shown. It would therefore be of advantage to extract these two gases simultaneously from the atmosphere, i.e. to utilize the residue from the preparation of oxygen, a residue which consists entirely of nitrogen. The same remark may be made concerning the utilization of the residual gases of the new industry the manufacture of per- oxide of sodium. This product is obtained by passing a current of dry and pure air over heated sodium, the gaseous residue con- sisting chiefly of nitrogen. Any of the methods for the production of oxygen from air may be utilized, among which may be mentioned those of Boussingault, Tessie du Mothay and Marechal, Mallet, etc. Boussingault's process consists in fixing the oxygen by means of baryta, there being formed barium dioxide, which under the action 120 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. of A heat and reduced pressure yields one molecule of oxygen, with the re-formation of baryta. If care be taken to add certain sub- stances so as to prevent fritting, the baryta may be used almost indefinitely. This process has the advantage of being rapid, since each operation for the complete oxidation and deoxidation lasts 10 minutes, and 140 may be made per day. The process of Tessie du Mothay and Marechal utilizes a mix- ture of manganese dioxide and caustic soda. When this mixture is subjected to a red heat in a current of air, there is formed sodium manganate, Mn0 2 + 2NaOH + = MnO 4 Na 2 + H 2 0, which, when heated with superheated steam at 450, liberates oxy- gen and yields anew the original substances, Mn0 4 Na 2 + H 2 = Mn0 2 4- 2N20H + 0. The process which was brought out in 1897 by Etard is quite similar to the above, in that it also utilizes the oxygen salts of man- ganese for the absorption of oxygen; but, as Etard himself says, his process does not consist of a simple chemical cycle: it is based upon a state of equilibrium. If potassium permanganate be subjected to the action of a boil- ing alkali, there is produced, under the definite conditions of pressure and temperature, a liberation of oxygen, 2Mn0 4 K + 2KOH = 2Mn0 4 K 2 + H 2 + 0. The reaction is, moreover, a reversible one, and if the condi- tions of temperature and pressure are changed, the manganate .absorbs oxygen of the air and yields again the permanganate. The nitrogen set free may be collected by means of suitable apparatus. On account of the separation of the oxygen and the nitrogen, this process should be tried on an industrial scale. As early as 1892, Parkinson installed a similar process in Man- chester, which produced 42 cubic meters of oxygen in 24 hours. He uses a mixture of kaolin and permanganate, which is heated in retorts at a reduced pressure, and even in vacuum. Under these conditions the permanganate yields its oxygen. It reabsorbs oxygen when heated to 550 C. under pressure in a current of com- pressed and hot air. There are five retorts, one of which is used MANUFACTURE OF CYANIDES. 121 for reheating the air. This air is compressed by means of a pump in a compressor, whence it is driven to the retorts arranged in such a manner that one of them absorbs the oxygen while the other liber- ates it. The nitrogen is continually removed by means of a sniffling- valve, and the separation of the two gases is automatically regu- lated by means of a system of valves. The permanganate mixture is very stable, since it is altered neither by moist air nor by car- bonic acid. Numerous patents have been taken out in regard to the manu- facture of oxygen, but they are only more or less successful modifications of the processes brought out by Boussingault and Tessie du Mothay. Mallet's process, which is likewise much to be recommended, con- sists in using a 20% solution of cuprous chloride. This solution is placed in a retort, which is heated to 100, and a rapid current of air is passed through. The cuprous chloride is converted into the oxy chloride, which, when heated in the same retort to dull redness, loses its oxygen and becomes reconverted into the cuprous chloride. Several years ago other rather ingenious processes were shown. They are based not upon chemical reactions, but upon purely physical phenomena, especially those of dialysis and solubility. In the first case the processes are based upon the differences exist- ing between the rate of dialysis of nitrogen and oxygen. Of such is Villepigne's process, patented in 1896. This consists in causing air to pass through a series of membranes made of caoutchouc, through which the nitrogen traverses less rapidly than does the oxygen, so that at the last membrane the oxygen emerges almost pure, leaving the nitrogen behind in each membranous compartment, which is removed by special means. It is not known that such processes are successful or that they are employed on an industrial scale. Nevertheless this is not the last to be heard upon this subject, and the future will probably show us what to expect from these new methods. Finally, another very ingenious process must be mentioned, one which likewise is based upon the difference in the physical prop- erties of nitrogen and oxygen, and which seems to merit an im- portant industrial place. This is the process of Raoul Pictet, who is already well known in the scientific world through his remarkable 122 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. researches on the liquefaction of gases. From the " Bulletin de la Societe des Ingenieurs civils, " before which, on June 7, 1901, Pectet elaborated his new process, the principal features are here extracted so as to give a clear idea of this discovery. The principle of this method is as follows: The point of lique- faction of oxygen under atmospheric pressure is about - 183, whereas that of nitrogen under the same conditions is 195. Therefore the nitrogen is sensibly more volatile than the oxygen, and the difference of 12 which exists between these two boiling-points differentiates, as the theory of heat shows, at such low tempera- tures, two liquids such as 40 would differentiate at temperatures of 60 to 100. It is therefore easy to see that if a mixture of these two gases., previously liquefied, be vaporized, it will be possible to obtain, on the one hand, pure nitrogen, and, on the other hand, equally pure oxygen, by a process prefectly analogous to that upon which the system of fractional distillation depends. Nevertheless the problem is inverted, from a practical point of view, since it is necessary first to liquefy the two gases and then to vaporize them in order to collect them in the gaseous state. Thus, the inventor succeeds in separating the two gases on an industrial scale. The air is first suitably dried, then it is compressed into an apparatus completely immersed in liquid air. Under the influence of the temperature and pressure, this air is in its turn liquefied by giving up its latent heat of condensation, under the influence of which an equal quantity of the liquid air of the container becomes vaporized. In this way, with a very slight expense of energy and a definite quantity of liquid air, unlimited quantities of atmospheric nitrogen and oxygen may be set free. Now, the difference exist- ing between the points of liquefaction of these two gases being known, the more volatile nitrogen will escape before the oxygen, and it will therefore be possible to collect them separately by means of suitable apparatus. In this way three classes of gas are obtained: Nitrogen purer than 90.00% Oxygen at a purity of 50.55% Oxygen purer than 90.00% and also carbonic acid, which always exists in air, and which is collected in the solid state. MANUFACTURE OF CYANIDES. 123 As will be seen, this is a most ingenious process, practical as well as ingenious, and likewise not at all expensive; qualities which seem to warrant its coming application on an industrial scale. Having firmly established the theory of the formation of cyanides, and the remarkable role which is played by atmospheric nitrogen, it was immediately attempted to turn this discovery to account. At first view, and at least theoretically, nothing seems simpler than to combine the three elements, nitrogen, carbon, and alkali metal; but the experiments undertaken to fix the nitrogen of he ai:* on a practical scale have not always given results which would lead one to expect its fulfillment. Nitrogen has in fact quite definite nega- tive properties, and its fixation is a difficult problem which has not yet been solved satisfactorily, although remarkable progress has been made. The first attempts to fix nitrogen of the air with a view to the production of cyanides have all completely failed. Not one of them obtained the support of the manufacturer; nevertheless it is ex- tremely interesting to study them, for they are a step toward the truth, and they have had an incalculable bearing on the progress of this industry. Bunsen's Process. This first process was attempted on an industrial scale in 1845. This was shortly after the efflorescences of potassium cyanide were discovered in the blast-furnaces. Starting from the idea that the potassium cyanide formed was due to the action of air, Bunsen constructed a special blast-furnace for the production of potassium cyanide. Its shape was similar to that of ordinary blast-furnaces. It was filled with superposed layers of charcoal and potassa and heated to a high temperature by the combu tion of a portion of the charcoal. At the same time a power- ful current of air was blown through the mass by means of an air- exhauster. Under these conditions cyanide of potassium was formed, which flowed through the lower part into a receiver ad hoc. The product thus obtained was highly contaminated with such im- purities as charcoal, alkaline salts, and mineral salts, due to the ash of the combustible material, and it could be used only in the prepara- tion of yellow prussiate of potash. Besides this serious objection, there were others no less serious, such as the losses through volatilization and the difficulty of conducting such an operation, especially of regu- 124 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. lating the temperature and the draft of air, all of which caused the abandonment of this process. Possoz and Boissiere *s Process. This process, successively put into operation at Crenelle and at Newcastle, had no better success. The principle is the same as in Bunsen's process, differing from it only in the modification of the apparatus, which allowed the tem- perature and the intake of air to be regulated. Notwithstanding their patient efforts and an unceasing struggle of several years, these two French chemists were compelled to abandon their project, not being able to meet foreign competition, which sold cyanide at a lower price than theirs. Yet during the first year of their work at Grenelle, in 1843, Possoz and Boissiere succeeded in producing 15 tons of an excellent quality of ferrocyanide. But the high cost of fuel and of refractory brick -at Paris compelled them to go to Eng- land. After completing arrangements with Bramwell and Hughes, they settled at Newcastle-on-Tyne, where, in 1844, their process was established. The process was as follows: Small pieces of wood charcoal of good quality were saturated with 20 or 30% of caustic potash, or of carbonate of potash moistened with a quantity of water just sufficient to dissolve it. After desic- cation, this material was charged into vertical retorts heated on the outside in a furnace at white heat. The retorts were 3.50 meters long, 0.60 m. outside diameter and 0.492 m. inside diameter. The upper portion was of re- fractory clay and was 0.23 m. in thickness; the lower part, which served as cooling-chamber for the cyanide formed, was of iron. The height, heated to white heat, was 246 millimeters. A portion of the gases of combustion, quite rich in nitrogen, was heated to a white heat by passing it through a superheater, where it was compressed by means of a pump. On coming out of the superheater, the gases penetrated into the retorts through small lateral slits. After 10 hours' heating and action of the gases, the cyanide mixture was removed automatically and in regulated quantity from the bottom of the retort. This mixture was allowed to fall into a cooling-chamber and thence into vats containing water and sulphate of iron. By means of a similar automatic system a new charge of charcoal and potassa was added and the operation repeated. Every half hour the apparatus was charged with an amount MANUFACTURE OF CYANIDES. 125 equal to 15 kg. wood charcoal containing 25% potash, and a corre- sponding quantity of cyanided charcoal was removed. The opera- tion was in this way continuous. In 24 hours each apparatus was charged with 720 kg. dry char- coal-potash containing 460 kg. wood charcoal and 260 kg. car- bonate of potash. During the operation the mass decreased one half in volume. It contained from 30 to 50% potassium cya- nide. The number of these apparatus was twenty-four, twenty of which were in operation, two ready to be used, and two being repaired. Each one of them produced 50-70 kg. of ferrocyanide per day. The net cost at the works in Newcastle, in 1846, was 1.86 francs per kilogram, itemized as follows on the basis of 1000 kg. of ferro- cyanide of potassium: 7000 kg. wood charcoal, crushed, @2.50 fcs. per 100 kg 175 fcs. 1000 kg. potash from America @ 50 fcs. per 100 kg 500 30 tons coke @ 8 fcs 240 20 tons coal @ 2.50 fcs 50 1 ton carbonate of iron, powdered 25 120 men and children (labor) 375 Maintenance, wear, interest, etc 500 1865 fcs. Possoz and Boissiere's process was in operation at Newcastle during the three years 1844 to 1847. The works produced 1 ton of potassium ferrocyanide regularly per day. That is certainly an appreciable result, but when the process was abandoned, the company could show for this result only a very large deficit, due chiefly to the rapid wear and tear of the apparatus, which it was necessary to repair frequently, and to the losses in carbonates, which amounted to three parts for every one part of prussiate produced. Moreover, the amount of cyanided charcoal to be subjected to lixiviation was far too small in proportion to the amount of ferrocyanide obtained. Other attempts preceded or followed that of Possoz rnd Bois- siere. But, like this one, they also proved fruitless, and not one of them has, to our knowledge, succeeded in giving profitable results. 126 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The yield was too small to produce a cyanide capable of competing successfully. To understand the causes which made these processes abortive, one needs only to consider that in such innovations only 4% of the nitrogen was fixed, that the high temperatures necessary in these processes resulted in rapid wear and tear of the apparatus and in enormous losses through volatilization, and that moreover the product obtained was so impure that it was necessary to purify it .at great cost. Yet they deserve to be mentioned. Newton's Process. First comes Newton's process patented in 1843 in England. In this process the inventor causes the gas com- ing out of lead chambers to pass over a mixture of charcoal and potash, or of charcoal impregnated with 20-30% carbonate of pot- ash heated to a suitable temperature. The yield was said to be 50% of the theoretical. The process was carried on from 1840- 1847, when it was abandoned, the losses in carbonate of potash being enormous and the apparatus deteriorating rapidly. Newton noticed that wood charcoal gave better results than coke, that potash was preferable to soda, that the yield increased with increase of tem- perature, and that water-vapor exerted a detrimental action. In 1844 Sinndel passed nitrogen over charcoal in closed vessels at a high temperature. Blairs' Process. Blairs caused nitrogen to be passed over a mixture of carbon and potassa in a shaft-like furnace, which was heated by a grate placed in the exterior casing. The products of cyanide and potash were collected in chambers or in ferric solutions. The residual charcoal was treated with water and furnished a fresh amount of cyanide. Armengaud's Process. This process (1847) differs from the pre- ceding in that the inventor operated in the presence of water. All these processes, as well as those of Alder (1879) and Weldon (1881), -differ from each other only through modifications pertaining to the apparatus, with the object of the introduction of air and the produc- tion of heat. Margueritte and SourdevaPs Process. This process (1862) is I the only one which merits more attention. The inventors sub- 1 stituted baryta for potassa for many well-grounded reasons. 1 In fact, baryta is much cheaper than potassa, and is in- fusible at very high temperatures; moreover, as is well known, MANUFACTURE OF CYANIDES. 127 barium fixes nitrogen with great ease. (It would even be ideal to find masses of barium or calcium in order to fix the nitrogen of the air. Lithium has also been mentioned, but it is a rare element and too difficult to prepare.) It attacks the apparatus much less than does potash, and the wear and tear of the vessels is diminished because the temperature necessary for the formation of barium cyanide is much lower than that of potassium cyanide. This process may be operated in different ways. First a mixture is made consisting of carbonate of barium with 20 to 30 parts of tar, resin, pitch, wood charcoal or coke, which mixture is heated to high temperature under the action of a current of air. Under these conditions the baryta absorbs nitrogen with ease, with forma- tion of barium cyanide, which is converted into alkali cyanide by double decomposition by the reproduction of barium carbonate : 2C+2N + Ba = (CN) 2 Ba, (CN) 2 Ba + CO 3 K 2 = 2NCK + C0 3 Ba. This is one of the rare processes invented along this line which has given good results, and inventors have appeared to be well satisfied with its industrial practicability. Mond's Process. Margueritte and Squrdeval's process was taken up in America in 1882 by Mond, who modified it somewhat, and who obtained from it good results. Mond used a mixture consist- ing of charcoal, magnesia, and carbonate or oxide of barium pre- viously ignited out of contact with air. According to his German patent No. 21175 (1884), he operated as follows: Briquettes composed of a mixture of witherite (natural carbonate of barium), pulverized wood charcoal or coke, and pitch in the fol- lowing proportions: Carbonate of barium .............. 32 parts Wood charcoal .................... 8 " Tar .............................. 11 " These briquettes were submitted to the action of a reducing flame in such a manner as to char the pitch and to dissociate the carbonate of barium. 128 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. They were then ranged in an annular furnace, where there was directed a current of gas rich in nitrogen and as poor as possible in oxygen, carbonic acid and water-vapor; for example, that which escapes from the carbonic-acid absorption apparatus in the ammonia soda process. This gas was previously heated to a temperature about 1400. In order to do that, it passed through into the first furnace containing briquettes already cyanated, which it cooled while at the same time heating itself. On coming out of this fur- nace, it passed into a Siemens regenerator, and from there into the furnace where the reaction takes place. When the mass was thought to be sufficiently cyanated, it was drawn out of the furnace, care having first been taken to have the contents of the furnace cooled to about 300. The yield was about 40%. Weldon's Process.^Weldon (1879) made use of a revolving furnace similar to that employed in the manufacture of soda and in which at a dull-red heat he caused nitrogen to act upon a mix- ture of charcoal and alkali. Fogarty's Process. To the above must be added the processes patented in America in 1883 and 1887 by Fogarty and Dickson respectively. Fogarty begins by producing a heating gas highly superheated,, and consisting of a mixture of carbon monoxide, hydrogen, and nitrogen. Then he causes this gas to pass into retorts, into which he transmitsi n the same direction a measured volume of hydro- carbon vapors obtained from the distillation of oils. The mixture of gases comes in contact with a definite quantity of powdered incandescent lime, which falls from the top of the retort. This gas contains, therefore, no oxygen nor carbonic acid and the hydro- carbons are consequently broken up into acetylene, carbon, and hydrogen, which, in contact with lime and nitrogen, produce cal- cium cyanide. The reaction may take place in two ways: (1) Either by the combination of nitrogen and calcium with acetylene at the temperature at which this gas is formed, (2) or by the union of nascent carbon produced by the decomposition of acetylene, C2H2 = C2 + H 2 , with nitrogen and calcium. The experiments, of Fogarty justify this hypothesis, the most favorable temperature for the reaction being 2200 to 2300 F. MANUFACTURE OF CYANIDES. 129 Dickson's Processes. Dickson injected a mixture of air, water- vapor, and powdered charcoal into a chamber filled with powdered alkali and heated to a proper temperature, naturally quite high. This heat was produced by the combustion of the gases. Lambilly's Process. Not till 1889, with the appearance of the processes of Lambilly and of Chabrier, have real improvements in the manufacture of cyanides been noted. These two inventors sought first of all to produce ammonia from the nitrogen of the air by passing through cyanides. Their various patents show a deep knowledge of the phenomena of cyanuration. The first two of these patents were taken out with a view espe- cially toward the production of ammonia through the interme- diary of the cyanides. The first one (No. 199977), taken out August 8, 1889, is based on the following well-known facts: (1) The volatile hydrocarbons are decomposed at a red heat into hydrogen and more condensed carbides. (2) When nitrogen comes in contact with nascent hydrogen, it unites with it to form ammonia if the temperature is lower than that of the decomposition of this latter body. (3) The oxides of the alkalis or alkaline earths are reduced in the presence of charcoal and absorb nitrogen in order to form cya- nides at temperatures naturally varying with the kind of oxidizing agent used. The inventors proposed to operate this process on an industrial scale as follows: The hydrocarbon gas is produced by the distillation of coal, wood, peat, petroleum; the nitrogen is obtained from the atmosphere from which it is extracted by processes already known (those of Tessier du Motay, Boussingault, or Mallet). It is mixed with the carbide gas in amounts varying with the composition of the hydro- carbon. This gaseous mixture passes through a series of cylindrical retorts arranged in one or more furnaces. These retorts are charged with a mixture of charcoal and oxide of alkali or alkaline earth and the whole heated to redness. The inlet of gas is stopped when the amount already taken in is judged to be sufficient to convert the contents of the retorts into cyanide. Under these conditions the hydrocarbon gas is broken up. Its decomposition goes on 130 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. and is completed at the temperature at which it begins, if care be taken to remove the gases formed from the atmosphere in contact with the substance undergoing dissociation, in such a manner that the pressure is always less than the tension of dissociation. This condition is found fulfilled; in fact, the formation of ammonia by the union of nascent hydrogen and nitrogen takes place with con- traction. There is thus produced a partial vacuum which, together with the carrying away of the ammonia, causes a pressure inferior to the tension of dissociation. The carbon of the carbide, being in the nascent state in the presence of nitrogen and of substances capable of becoming converted into cyanides, yields this latter body. According to the inventors, if the conditions of temperature and pressure are fulfilled, it is possible to fix an amount of nitrogen corresponding theoretically to the hydrogen and to the carbon of the carbides used. An ingenious modification of the above process is that brought out by Lambilly and Chabrier in the second patent (No. 202700) , of December 21, 1889. It consists in removing the hydrogen from the mixture of hydrocarbons and nitrogen before its entrance into the cylinder where the conversion into cyanide is to take place, and for the following reasons: Illuminating-gas is composed of methane and ethylene, which are broken up at red heat into hydrogen and acetylene. In the presence of nitrogen and of bodies which may be converted into cyanides, acetylene gives rise to these latter, but the hydrogen set free with acetylene through the decomposition of the hydrocarbon places, because of its tendency to recombine with the acetylene, a serious obstacle in the way of the formation of cyanogen, which therefore takes place but slowly. It is therefore necessary to rapidly remove this hydrogen, by combining it with nitrogen under the form of ammonia, before the appearance of the mixture of acety- lene and nitrogen into the cylinder where the cyaniding is to take place. For this purpose the gas first passes through a cylinder containing oxide of copper, obtained from the process of extracting atmospheric nitrogen by the use of this metal. It reduces the oxide of copper and thus forms anew the metal, which may be used in the preparation of fresh quantities of nitrogen. The hydrogen being eliminated by this means, the gaseous mixture, which consists now MANUFACTURE OF CYANIDES. 131 of only acetylene and nitrogen, passes into the second cylinder containing the substances to be converted into cyanide. The flow- ing and the outlay of gas and of nitrogen are regulated through the result of the combinations. The inventors claim that in this way a minimum of 1 cubic meter of nitrogen may be fixed; that is, 1.25 kg. per cubic meter of illuminating-gas used. In his patent No. 210365 of December 20, 1890, Lambilly seeks only the production of cyanides. This patent is extremely inter- esting, its chief object being to produce nascent carbon, which renders its union with nitrogen all the easier. It still depends on the decomposition of illuminating-gas in an atmosphere of nitrogen and in the presence of substances capable of being converted into cyanides. But the decomposition of the gas is carried on under certain conditions which permits a gas extremely rich in acetylene (C 2 H 2 ) to be obtained, which is finally resolved into its elements. In order to carry on this dissociation, the inventor starts from the consideration that illuminating-gas is a mixture varying more or less, according to its method of preparation, in the amounts of hydrogen (a gas containing the least possible amount of this element should be prepared), and the three hydrocarbons, ethylene, methane, and acetylene, and that these three bodies are decomposable at different temperatures. In fact, acetylene is broken up into its elements only in the neigh- borhood of a white heat, while at a red heat ethylene breaks up into acetylene and hydrogen, or methane and hydrogen, or a mix- ture of these three gases according to the degree of redness and the time to which it is subjected to this temperature. Methan is decomposed at a like low temperature into acetylene and hydro- gen. From these facts the inventor concluded that if care be taken at the beginning to limit the action of the temperature, only the ethylene and methane will be decomposed, forming a mixture very rich in acetylene, which will combine with the acetylene already existing normally in the gas. Then by raising the tem- perature to a white heat, the acetylene will in its turn be dissoci- ated into its elements. The manufacture of cyanides by this method will therefore comprise four phases: (1) The preparation of nitrogen. 132 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. (2) The preparation of illuminating-gas. (3) The dehydrogenation, or, better, the carbureting of the Hatter. (4) The conversion into cyanides. The nitrogen is prepared as in the previous method, by passing air over copper heated to dull redness. The gas is prepared by the usual methods, then freed from its hydrogen by passing it over copper oxid produced in the preparation of nitrogen. The mixture which is to be converted into cyanide is composed of char- coal and oxids or carbonates of the alkalis or of barium finely powdered. This is placed in cylindrical retorts and heated to a .high temperature, which should not, however, reach a white heat. Right here Lambilly improved the methods of his predecessors in two important particulars viz., in the use of the materials for manu- facturing cyanides. Having noticed that when the alkali and charcoal .are heated there is formed a considerable amount of carbon monoxid, which prevents the intimate contact of the substances which are to be converted into cyanide with the current of nitrogenized and carbonized gas, he avoids the passing of this gas just as soon as the temperature is favorable for the formation of cyanides, and removes the carbon monoxid as fast as it is formed. For this pur- pose he makes use of the principle established by Sainte-Claire Deville 1 , that the dissociation of a body continues and ends at the temperature at which it begins provided care be taken to remove the products of dissociation. In this way Lambilly economizes fuel, for the dissociation of the alkali oxid takes place at a rela- tively moderate temperature, and, moreover, he uses the carbon monoxid in heating the furnaces in which the cyaniding process proceeds. From the moment carbon monoxid ceases to be formed, he allows the mixture of gas and nitrogen to pass. The second improvement quite naturally follows from the first. In fact, being no longer troubled by carbon monoxid, the mix- ture of gas and nitrogen may be allowed to come under pressure into the cylinder where the cyaniding process goes on, by giving to the hydrogen, which is the residue of the reaction, but a limited outlet. In this way a more intimate contact of the substances to be converted into cyanides with the reacting gases is obtained, MANUFACTURE OF CYANIDES. 133 In order to hasten the decomposition of the carbides and the foimation of the cyanides, Lambilly proposes, moreover, to add to the mixture of charcoal and alkali a certain proportion of small pieces of nickel, iron, or cobalt, which exert a decomposing action on the carbides, and which, becoming heated more easily than does the mixture which is to be converted into cyanide, yields to this mixture a part of its heat. The examination of these methods shows that the inventor strove always to produce more and more, in a state as near as pos- sible to the nascent state, substances which are to react upon one another. This is the object of the later patent dated December 31, 1900, and which allows the carbon monoxid produced in the reduction of the alkali oxids to be profitably utilized. Lambilly proposes to collect this carbon monoxid in a gasometer, then to mix it with a quantity of illuminating-gas such that the hydrogen resulting from the decomposition of the latter may com- bine with the whole of the oxygen of the carbon monoxid, the acety- lene thus formed yielding a fresh amount of carbon in the nascent state. This ingenious arrangement economizes more than half the illuminating-gas. In his German patent No. 6377 (November 14, 1890, March 14, 1892), the only new fact given by Lambilly is the manner in which he obtains the alkaline mixture which is to be converted into cyanide. In order to make caustic the alkali or alkaline earth which is to be used in producing cyanide, carbonate of potash or of barium is used, and in order to render them porous and permeable to the action of the reacting gases, there is added for each equivalent of carbonate used (69 kg. K 2 C0 3 or 98 kg. BaC0 3 ) 20 kg. of charcoal and a like amount of quicklime. The whole is worked up into a dry powder, introduced into horizontal cylinders connected with a vacuum pump, and heated under as perfect a vacuum as possible. Under these conditions the carbonate becomes caustic, and the carbonic acid produced by the reaction is reduced on contact with the charcoal into carbon monoxid, which is utilized as fuel. The inventor also states the amount of pressure under which he trans- mits the mixture of illuminating-gas and nitrogen into the cyaniding cylinders. This pressure should equal 10-15 centimeters of mer- cury. 134 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The processes of Lambilly are still far from being perfect; yet they are extremely interesting to remember. At the time of their appearance they produced certain practical results which were by no means to be despised. Besides they show a considerable progress over the first synthetic processes used, a progress obtained through a profound study of the complex reactions which take place in the formation of cyanides, and which are the result of wise observations and of the patient efforts of their inventor. One could almost affirm that they paved the way for the really synthetic processes. The following processes produce cyanides by the action of nitro- gen on a mixture of caustic alkali or carbonate of alkali and char- coal. They differ but little from one another. Gilmour's Process. First comes this process (French patent No. 233175, October 2, 1893; German patent No. 8475, September 2 y 1893). It consists in producing cyanide compounds by the action of atmospheric nitrogen on a mixture of alkali and charcoal heated to 1000. The various caustic alkalis or their carbonates may be used at will; however, the inventor prefers the use of caustic potash. These substances are mixed in about equal proportions with char- coal, the mixture is placed in suitable recipients through which nitrogen extracted from air is made to pass until the mass is more or less transformed into cyanide. The vessels are then emptied and the resulting product treated with water. The hydrocyanic acid of the cyanides in solution is displaced by means of a current of carbonic acid (this is preferably done at boiling temperature and under atmospheric pressure), and absorbed in a concentrated solution of caustic soda, where it forms sodium cyanide, which is separated. The carbonic acid is produced by the combustion of charcoal in air, an operation which allows the production of nitrogen necessary for the first reaction. Moreover, this carbonic acid pro- duces anew the alkali used for the cyaniding process. Young's Process. This process (English patent No. 24856, Dec. 27, 1893) is but slightly different. The cyanide is obtained by pass- ing a mixture of air and hydrocarbon vapors over the following mixture heated at a high temperature in iron or earthen retorts or in suitable furnaces: MANUFACTURE OF CYANIDES. 135 Caustic or carbonate of alkali 4 parts Hydrate or carbonate of alkaline earth 1 part Coke or coal 2 parts The resulting product is treated with water in order to extract the cyanide. When the temperature is too high a portion of the cyanide distils. This portion may be collected by causing the gases with which it is carried away to pass through a layer of vegetable fibres. William Donnell Mackey's Process. This process (French patent No. 243136, Nov. 25, 1894; German patent No. 87366, Nov. 28, 1894) is quite similar to that of Bunsen. It consists simply in subjecting to a powerful current of air a mixture of coal, wood charcoal, or coke, lime, potash, or any other alkaline compound which may be reduced by the charcoal. This mixture is charged in a specially constructed furnace A (Fig. 3) through the hopper E and heated to a very high temperature. The furnace is vertical and quite large. It is provided with lateral openings to which are joined two series of tuyeres. These are arranged in two series, BB and CC, one at one eighth the height of the furnace, the other at about the middle. The cyanide formed is sucked away by a machine through the opening D situated in the space included between the two series of tuyeres. Thes are worked by a powerful bellows. The cyanide is col- lected and condensed according to ordinary methods. The gases produced through combustion escape through the horizontal pipe F. Readmann's Process. Readmann's process (French patent No. 243129, Nov. 26, 1894, March 12, 1895) differs from Gilmour's process just cited only in the fact that the inventor uses the electric arc in order to produce the necessary temperature. In this way he claims that all waste and destruction of apparatus is avoided because he develops the heat in the very mass itself by means of carbon electrodes or electrodes of other suitable materials. The mixture to be con verted into cyanides is composed as follows: Carbonate of barium (perfectly dry) 50 kg. Powdered charcoal (wood charcoal or oil or coke). . . 10 " 136 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The carbonate of barium may be replaced by any other car- bonate or oxid of alkali or alkaline earth. The intimate mixture of these substances is introduced into the crucible which contains coke previously heated to incandescence. As source of nitrogen the inventor uses air more or less deoxygenized, or water-gas, whose denitrified residue may be used either as fuel or for illuminating purposes. The cyanide formed flows out through FIG. 3. Mackey's Process. a lateral opening situated on the bottom of the crucible. The volatilized portion carried off with the remaining gases passes into a receiver or condenser, where it is absorbed by well-known methods. Mehner's Process. Ch. Mehner of Charlottenburg has patented a similar process, which consists in passing a current of hot air, or MANUFACTURE OF CYANIDES. 137 of any other gas rich in nitrogen, over a mixture of coke and car- bonate of alkali or alkaline earth heated to a white heat in the vat of an electric oven. The volatilized cyanide together with the other gases are conducted into a system of condensers filled with coke placed above the level of the electrodes. Swan and Kendall's Process. In order likewise to avoid the wear and tear of the apparatus, Swan and Kendall have devised an ingenious though complicated arrangement the net cost of which must be quite high (French patent No. 252071, Nov. 24, 1895, and March 13, 1896, and German patent No. 87786, Nov. 28, 1895). It consists of an inner vessel constructed of thin sheets of nickel or cobalt, surrounded by another larger vessel made of refractory earth. This apparatus is placed in an oven which is slightly inclined. The inner vessel is provided with a platinum extension. Hydrogen circulates in the annular space between the nickel vessel and its refractory sheath; its object is to prevent the metal from being attacked. First a mixture of carbon and tungsten is prepared, consisting of 100 parts of the former to 15 parts of the latter, by moistening granular or powdered charcoal with a solution of potas- sium tungstate, drying, and igniting. This mixture is placed in the inner vessel; a current of nitrogen extracted from air is passed through and the temperature raised to redness. When this tem- perature has been attained, melted carbonate of potash in variable amounts is poured into the crucible. The cyanide formed flows out through the platinum extension as fast as it is produced. Tung- sten may be replaced by titanium, molybdenum, chromium, or manganese. Pestchow's Process. In his process, Pestchow of Dantzig (Ger- man patent No. 94114, Dec. 8, 1896) has not introduced any great modifications. It consists in causing a current of nitrogen containing or free from oxygen, mixed with or free from ammonia, and carrying a certain amount of hydrocarbon e.g. acetylene or powdered charcoal, to act on an alkali bath kept in a state of fusion. This bath is placed in a covered crucible provided with an opening through which the nitrogen gas mixed with hydrocarbons passes. The nitrogen should always be in excess, but not the carbon. To the alkali bath may be added a certain amount of cyanide from a pre- 138 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. vious operation in order to raise the temperature of the fused mass. Chipmann's Process. The latest process of this class is that of Chipmann, at Johannesburg (French patent Nos. 275570, March 4, 1898, and 275488, March 9, 1898), which produces at the same time cyanide and sulphocyanide by the action of a current of nitrogen to which sulphurous acid has been added, on a mixture of charcoal and oxid or carbonate of alkali or alkaline earth. First a mixture of equal parts of charcoal and oxid or carbo- nate is made. Preferably, carbonate of barium is used. This mixture is heated to about 1000 in suitable vessels; then a current of sulphurous acid free from oxygen is passed until the whole mass has been converted into cyanide and sulphocyanide. IVhen this result has been attained, the vessel is emptied and the product treated with water. Into the solution thus obtained, heated to boiling and after the addition of an oxidizing agent, when necessary a current of air is made to bubble under atmospheric pressure. The carbonic acid of the air precipitates the barium as carbo- nate, which is collected, dried, and used over again. The hydro- cyanic acid set free passes into condensers containing a concen- trated solution of caustic soda kept at a temperature of 40 F. The sulphurous acid produced by the decomposition of the sulphocyanide is collected with the. nitrogen and used in the next operation. Most of these processes have had but a short life industrially. That is because the circumstances which affect the yield are numer- ous, and a simple thing may change and at the same time modify the nature of the reactions. They are therefore but very imper- fect methods, to which many and serious disadvantages are inherent. The temperature necessary to carry on the reaction is in all cases very high: in some cases a white heat, in other cases a cherry- red heat. In all cases the heat must be sufficient to cause the reduc- tion of the alkali compound used, and there are few apparatus which are capable of resisting such a high temperature without wear and deterioration. Another disadvantage of this high temperature is in the loss due to volatilization either of alkali or of cyanide, loses which sometimes amount to considerable. The substances used must also be as anhydrous as possible, water converting the MANUFACTURE OF CYANIDES. 139 cyanide into ammonia. Nevertheless, Langlois, Kuhlmann, Armen- gaud, and Ertel have shown that the presence of a very small quantity of water helps along the reaction, for according to Kuhl- mann the production of cyanogen is preceded by the formation of ammonia. The mixture of substances to be converted into cyanide must be as perfect as possible, and all means must be taken to make it porous and permeable to the action of the reacting gases. The yield decreases in proportion as the cyanide is formed, for the fragments of the mass to be converted into cyanide, and especially the char- coal, becoming imbedded in the cyanide and melted alkali, come less in contact with the gases. If the contact surface of these sub- stances is too small, the same trouble is met; the apparatus should be quite large in order to present as much surface as pos- sible to the action of the nitrogenized gas. If care be not taken to remove the products as fast as they are formed, that also will impede the reaction, which will either be stopped or rendered slower. If the substances under treatment contain foreign substances without effect on the reaction, these will absorb a portion of the heat, whence comes a loss of calories. Moreover, these bodies pre- vent the intimate contact of the products of the reaction. Likewise, if the gases enclose foreign elements such as oxygen, hydrogen, carbon monoxid, or carbonic acid, they all have the disadvantage of diluting the nitrogen, which causes the reactions to go on more slowly. Moreover, each one of them exerts a detri- mental action upon the reactions. Thus it is that carbonic acid oxidizes the charcoal, and possibly also the cyanogen. As has often been demonstrated, oxygen and cyanogen cannot coexist at high temperatures. As to carbon monoxid, some investigators attribute to it an injurious action in that it prevents intimate con- tact of the cyaniding masses with the nitrogen, whereas others look upon it as favorable to the reactions because of its reducing prop- erties. The formation of cyanides in these various processes has been the subject of much controversy. Relying upon many experiments, and especially upon the fact that a mixture of acetylene and nitrogen, under the influence of the electric spark, yields hydrocyanic acid, Berthelot supposes HO METHODS OF MANUFACTURING CYANIDE COMPOUNDS. that when charcoal and potassa are strongly heated they give rise to a compound C2K 2 , which, fixing nitrogen, then yields potassium cyanide, CNK. Most of the investigators agree in saying that the union of car- bon and nitrogen can take place only at the temperature at which the alkali metal is set free. This hypothesis is confirmed by the very fact that cyanogen and oxygen cannot coexist in the same medium at a high temperature. As to the alkali metal, some investigators attribute to it a simple contact action, and its object would therefore be to fix the cyanogen just as fast as it is formed, in accordance with the law of Sainte- Claire Deville, according to which reactions are continued and finished quickly if care be taken always to remove the products formed as fast as they appear. Finally, other investigators assert that there is first a formation of an alkali nitride, which later becomes converted into cyanide through the action of carbon. This last hypothesis is just as prob- able as the preceding ones, since Center and Brieylieb obtained cyanide by heating magnesium nitride in a current of carbonic acid or carbon monoxid. Several processes have even been proposed along this line, e.g. those of Moise (French patent 246587, April 22, 1895) and of Mehner (French patent 254273, Feb. 26, 1896). Processes of Moise and Mehner. Moi'se's process consists in heating, in a rotatory oven to a dull red, a mixture of boron nitride, alkali carbonate, and charcoal in the following proportions: Boron nitride ............................. 50 kg. Carbonate of alkali (potassium) ............. 250 ' ' Charcoal .................................. 30 " The reaction is as follows: Boron nitride is obtained by heating to a bright red for one hour the following finely powdered mixture: Sodium borate ............................. 100 kg. Sal ammoniac.., , 150 " MANUFACTURE OF CYANIDES. 141 This product is treated with boiling water, then hydrochloric acid is added in excess, yielding a precipitate of boron nitride. Mehner prepares nitrides of boron, silicium, magnesium, titanium, and vanadium by reducing the oxids of these metals by means of carbon in the midst of an atmosphere of nitrogen. There is very little probability that these processes have given any practical results, and we doubt very much whether they have ever been operated industrially. Besides, the metals which these investigators used in the prepa- ration of the nitrides are too expensive to allow these processes to be used practically on an industrial scale. All these processes just described have the disadvantage that they do not produce the cyanide directly; hi fact, masses contami- nated with impurities are obtained which must be treated with water and purified, by which the net cost is increased. It has already been seen that other equally serious disadvantages are inherent to these processes. It has already been stated that the cyanide is formed only in case the alkali metal is set free. It was therefore quite natural that attempts should be made to use this metal in the free state in order to avoid the reduction of its compounds originally used and* consequently the many disadvantages resulting therefrom. These processes may really be designated as synthetic, since they start with three bodies in the free state: carbon, nitrogen, potas- sium or sodium. The low cost of the alkali metals and the ease with which they are at pres nt manufactured permit their use on an industrial scale. Moreover, the cyanide industry creates, by means of these processes, a new market for the sodium; its use became limited when it was no longer employed in the manufacture of aluminum. The experiments carried on along this line have been satisfactory. They are exceedingly interesting and they will therefore be described. Castner's Process. This, the first one of these processes, was patented by Hamilton Young Castner (No. 239643, June 28, 1894). It consists in the action of a current of nitrogen on charcoal heated to redness, upon which melted sodium or potassium flows, the reac- tion being as follows: K or Na+C+N = CNK or CNNa. 142 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The reaction is carried on in a vertical iron retort (A, Fig. 4) placed in a furnace and capable of being heated to redness. This retort is provided with an inlet tube B, an S-shaped opening at the bottom (7, and with a hopper D. FIG. 4. Castner's Apparatus. The retort is charged with wood charcoal through the hopper D, which is afterward closed. The opening at the bottom C is sealed at the elbow E by means of cyanide. The temperature is raised to redness, then a current of nitrogen, through the tube F, and melted sodium or potassium, through the inlet tube B, are let in simultaneously. The alkali metal flows gradually through the wood charcoal and meets the nitrogen, which flows in the opposite direction. The three elements combine directly and form cyanide, which flows through the opening C into the receiver G. The unab- sorbed gas escapes through the tube 77, whence it may with advantage be conducted into a second retort. Charcoal may be replaced by MANUFACTURE OF CYANIDES. 143 inert substances such as pieces of iron or of porcelain, in which case a mixture of nitrogen and hydrocarbon is conducted through the mass. The alkali metals may also be replaced by their alloys ; e.g. lead sodium. Castner has improved this process, which consists in using ammonia, and conducting the operation in two stages. This modi- fied process will be taken up at length when discussing the ammonia processes. Castner's process, properly speaking, belongs to that class of methods using atmospheric nitrogen, the only one to which the term synthetic really belongs, but to our knowledge it has never given results permitting its use industrially. Hornig and Schneider's Process. This process belongs to the same class as that of Castner. Castner's process consists in allow- ing nitrogen to act upon the vapors of the alkali metals in the pres- ence of incandescent charcoal; Hornig and Schneider's process uses' the alloys of the alkali metals and of the heavy metals. Both of these processes using nitrogen or ammonia indifferently, but preferably the latter, will be studied in detail in the chapter devoted to the ammonia processes. Mehner's Process. Mehner's process (1894-1895) belongs in some respects to that class of processes using atmospheric nitrogen It consists in electrolyzing barium cyanide in a state of igneous fusion, using a charcoal cathode and in the presence of nitrogen gas (Fig. 5). The current decomposes the barium cyanide into hydrocyanic acid, which escapes at the anode, and barium, which is set free at the cathode at a rather high temperature, close to its boiling-point. Meeting the nitrogen, which is in contact with red-hot charcoal at the cathode, this metal reproduces cyanide of barium, which flows in the bath and is thus subjected to electrolysis. In this way the process may be continued. With the same quantity of cyanide somewhat limited, it suffices to supply carbon and nitrogen and to maintain the temperature desired. The hydrocyanic acid gas formed may be conducted outside and absorbed by well-known means, or may be fixed in the electrolyzer itself by the addition of sea salt, which under the action of the current breaks up into chlorine and sodium. The hydrocyanic acid set free at the posi- tive pole in a separate cell may, by means of a suitable contrivance, 144 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. react upon the alkali metal displaced and yield cyanide of sodium directly. The last class of processes utilizing atmospheric nitrogen is based on the use of metallic carbides. It has already been stated that many investigators, especially Berthelot, explained the for- mation of cyanides through the intermediary of carbides. In Comptes Rendus, 1894, 503, Moissan reported that when nitrogen is passed over heated carbides of calcium, barium, or strontium no reaction or union takes place. Frank and Caro showed that CAzH FIG. 5. Mehner's Apparatus. the opposite was true if the nitrogen used was charged with a cer- tain amount of aqueous vapor. In this case cyanides are formed as follows: C 2 M+2N=(CN) 2 M. Based upon this reaction, these investigators have brought out a process for the manufacture of cyanides which is thought to give satisfactory results. Many other manufacturers have fol- lowed the example set by Frank and Caro, and have had similar processes patented. Frank and Caro's Process. The first patent taken out by Frank and Caro dates from 1895 (French patent No. 249539, Aug. 10, 1895). MANUFACTURE OF CYANIDES. 145 It consists practically as follows: It may be applied equally well to the carbides of the alkaline earths or alkalis, either pure or con- taining alkaline earths or alkalis, or even salts of these bases. A mixture of the carbides prepared in the usual manner may like- wise be used; but according to the opinion of the investigators, barium carbide is the most suitable. The carbide prepared in the usual way is disintegrated and introduced into a tubular retort of refractory material, preferably clay. This retort is provided with suitable tubes for the inlet and outlet of gases. The necessary nitrogen is taken from the atmosphere. Air either wholly or partly free from oxygen may be used. The air is charged with moisture by passing it through a vessel containing water. The retort is first heated almost to redness, then the current of nitrogen, charged with moisture, is admitted under a moderate pressure and at such a rate that the reaction is complete in about two hours. A change of 15 to 17 kg. barium carbide requires 2 to 2.5 cu. m. of nitrogen. The product obtained is cooled, then taken up with water. The unconverted carbide yields acetylene, which is collected separately. The solution contains barium cyanide which by double decom- position may be transformed into alkali cyanide. Carbide of calcium alone, thus treated, does not yield good results. An excellent yield is obtained, however, by using a mix- ture of calcium and barium carbides or of carbides of calcium and sodium obtained by the ordinary methods by means of soda lime and charcoal. The product of the reaction is treated as just stated i.e. treated with water the acetylene being collected separately and the solution thus obtained converted into alkali cyanide. This latter operation may be brought about either by addition of an acid or preferably by conducting carbonic acid through the solution, which displaces the hydrocyanic acid gas, which latter is brought in contact with the metallic oxid of the cyanide desired. This may likewise be effected by double decomposition by the addition to the solution of an alkali ca bonate, which transforms the cyanide of the alkaline earth into alkali cyanide, while at the same time the carbonate of the alkaline earth separates out. 146 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. The result given by the treatment of the carbides of barium or calcium may be improved by adding to the carbides or to their mixture an alkali carbonate or hydrate. When the alkali carbides, whether alone or mixed or even in the presence of an alkaline earth or its salts, are subjected to the same treatment as that indicated above in the case of the barium carbide, they yield the corresponding cyanides, which may easily be extracted with water from the product of the reaction. The most favorable temperature for these reactions is, according to the investigators, dull redness. If a lower temperature be used the action of the nitrogen takes place but slowly, while if the tem- perature be too high the yield decreases, due to a partial decom- position. In order to make the most profitable use possible of the nitrogen, several retorts may be used in a series, which allows a continuous operation . In the certificate of improvement joined to the patent just described, Frank and Caro replace nitrogen with ammonia. The investigators state that in practice the formation of cyanides depends not only on the action of free jdtrogen, in the presence of water- vapor, on the carbides, but also on the action of dry nitrogen upon impure carbides containing oxids, carbonates, and sulphates. Moreover, the chemically combined nitrogen (ammonia or the oxids of nitrogen) may likewise be used in the formation of cyanides by means of carbides if the nitrogen compounds used furnish, during their action on the carbides, the necessary nitrogen, a result which is brought about through dissociation or reduction by means of carbides. From these remarks the investigators think that the oxids, carbonates, sulphates, or other salts induce the reaction in the same manner as does water-vapor, the use of which may thus be suppressed. This action of foreign salts is shown even when the carbides contain only very small quantities of them. Likewise, with the object in view of avoiding the use of water- vapor, the inventors of this process recommend the use of ammonia, which renders the action of moisture superfluous. If ammonia be passed over a carbide or a mixture of carbides, or a mixture of carbides and alkali salts, cyanide is formed. During this formation, the ammonia becomes dissociated into its constitu- MANUFACTURE OF CYANIDES. 147 ent elements, nitrogen and hydrogen. The nitrogen becomes fixed to the metal, whereas the hydrogen escapes, and may be collected separately and used as such in the heating of the apparatus. The reaction may be thus interpreted: CaC 2 +2NH 3 = Ca(CN) 2 +3H 2 . Although the presence of moisture is useless in starting and completing this reaction, it does not modify it in any way, and exerts no perceptible action on the yield. Thus ammonia-gas, whether dry or moist, could be used equally with advantage. Continuing their researches on the manufacture of cyanides by means of carbides, Frank and Caro observed: (1) That the formation of cyanides by the processes above mentioned is however limited, and if the heating be carried on at least up to a dull redness and does not exceed a bright yellow, a large part of the nitrogen absorbed by the carbides is combined at the expense of the formation of other nitrogenous compounds. This phenomenon is, according to them, due in part to the action of cyanides already formed, and in part to the direct action of the reacting mass according to the two general equations z(2MCN) +zN = z(M 2 NCN) + (CN)s, M 2 C 2 +N 2 =M 2 NCN+C. In fact Frank and Caro discovered that the reaction masses contained appreciable amounts of metallic derivatives of cyanamid, (M 2 NCN), of paracyanogen (CN)z, and of other nitrogenous com- pounds. (2) That the formation of cyanamid in the action of nitrogen on carbides must be due to an excess of nitrogen, which condition may take place from the time that this gas comes in contact with the carbide. (3) That the formation of cyanamid may be increased, by giving the carbide a greater surface, either by powdering it or by making it very porous and allowing the nitrogen to act, at a high tempera- ture, varying from a dull red to incandescence, upon a thin layer of carbide. In this case it will be easily understood that the con- ditions will be eminently favorable for the formation of cyanamid, 148 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. a large quantity of nitrogen coming in contact with a small quantity of carbide. It is upon this series of remarkable observations that Frank and Caro have based their new patent, No. 289828, Oct. 2, 1899. Carbide, or a mixture of two or more carbides, or of a carbide with other salts of alkalis or alkaline earth, is subjected to the action of nitrogen or of ammonia under the conditions stated above, with the view of favoring the production of cyanamid and of its derivatives. The substance thus obtained is then converted into cyanide by fusing it with alkali hydrate or carbonate, which may be added to the materials of the reaction before or during fusion. If the mass does not contain sufficient carbon, set free by the preceding reactions, it is well to add suitable quantities thereof. Likewise, if the materials to be treated contain compounds of nitrogen which are not combined to a metal, e.g. paracyanogen, it is necessary to add a sufficient quantity of a base in order to com- bine the cyanogen formed. This fusion results in converting the metallic compounds of cyanamid and of paracyanogen into cyanides corresponding to the bases used, according to the equations: (1) M 2 NCN+C = 2MCN and (2) Generally the following are used: Oxid or carbonate .......................... 1 part Salt of cyanamid .......................... 2 parts It is best to treat the product of the reaction with water, then to displace the hydrocyanic acid by an acid, e.g. carbonic acid. The cyanamid remaining in solution is separated by shaking with ether or other solvent, or by other appropriate means. While studying the ammonia processes a process will be noted which, although it does not utilize the carbides, has for its object the production of cyanamid. The solution of the problem seems to be along this line. Frank and Caro's processes certainly de- serve to be kept in mind; they solve the problem quite satis- factorily and in an economic manner, seeing that the carbides are MANUFACTURE OF CYANIDES. 149 prepared with ease. We do not know whether these methods have been adopted on an industrial scale, though they were to have been tried in some Frankfort works. It was hoped that the experiments undertaken along this line would be crowned with success, since the use of carbides in the manufacture of cyanides would open, in fact, an important market for the former. Unfortunately, it would seem that the works at Frankfort have stopped operation, the results obtained not having been thought sufficiently profitable for their continuance. Other methods likewise based on the use of carbides have fol- lowed those of Frank and Caro. Process of the " Chemische Fabrik Pferse*e Augsbourg." In the first place comes this process (French patent No. 252943, Jan. 3, 1896; English patent 1022, Jan. 15, 1896). It consists in allowing free nitrogen at a red heat to act upon a mixture of calcium carbide (or barium carbide) and dry alkali carbonate. According to the investigators there would first be established a reciprocal reaction between the alkaline-earth carbide and the alkali carbonate, which in the case of calcium carbide and potassium carbonate may be thus expressed: CaC 2 +K 2 C0 3 = C 2 K 2 +CaO+C0 2 ; the carbonic acid would be immediately reduced to the state of carbon monoxid by means of a small amount of calcium carbide in excess. The potassium carbide formed would then absorb the nitrogen according to the equation C 2 K 2 +2N=2CNK. The reaction takes place still better in the presence of ammonia : C 2 K 2 +2NH 3 =2CNK+6H. The inventors propose to apply this property of the carbides to the old process of manufacture, which consists in using alkali carbonates, organic animal substances, or nitrogenized charcoal, and to ignite the whole at a high temperature. By adding a car- bide to these substances the reaction would take place at a lower 150 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. temperature than that thought necessary up to the present time and the yield which was relatively small would be increased. The advantages which would follow from the process of the Chemische Fabrik Pfersee Augsbourg would be the following: (1) An appreciable decrease in the cost of fuel, and wear and tear of the apparatus due to the relatively lower temperature of the reaction. (2) The easy and abundant absorption of nitrogen. (3) The obtaining, under the form of cyanides, of the almost theoretical quantity of ammoniacal nitrogen used. These last two points should be verified industrially. Beringer's, Wolfram's, and Blackmore's Processes. Among the other methods using carbides must be mentioned that of Beringer (German patent 20334, Feb.-Nov., 1897), which consists in passing nitrogen over carbides, noting that the conversion into cyanides is complete at 900, if dry and pure nitrogen be used, a condition which would complicate the solution of this problem from an indus- trial standpoint (the inventor claims that the reaction begins even at about 450 C.). Wolfram's method (1898) consists in causing a metallic carbide (alkaline?) and a nitrogenous compound or free nitrogen, preferably ammonia, to act upon an alkali hydrate in state of fusion. Blackmore's method (U. S. patent No. 605694, June, 1898) seems to complicate instead of simplifying matters. The inventor proposes to compress the nitrogen into a mixture of alkali sulphide and metallic carbide, preferably carbide of iron. The sulphide becomes converted into the corresponding cyanide, more or less contaminated with ferro- cyanide and sulphocyanide, according to the amounts of the charge and the conditions of the reaction, conditions which are, moreover, not stated in the patent. Besides, the complete purification of this product must be rather expensive, and the author of the patent refrains from stating what is necessary in order to bring it about. This process, which is of little value, does not deserve deep study. Dziuk's Process. Very interesting, however, is the method of Dziuk (French patent No. 286828, March 15, 1899). Dziuk of Hanover uses the alkaline-earth carbides, as do Frank and Caro, not, however, at the temperature of redness but at that of igneous fusion 01300-3000), the nitrogen also being previously MANUFACTURE OF CYANIDES. 151 heated at a high temperature. This modification is based on the* fact that nitrogen acts on the alkaline-earth metals and on mag- nesium only at a very high temperature. This fact led the author to believe that nitrogen likewise should act on the carbides only at a temperature at which their constituent elements are in a free or nascent state. And, in fact, he was able to observe that if a current of nitrogen, heated to a high temperature before coming in contact with the carbide, be made to pass over calcium carbide manufactured in an electric furnace, this latter substance is con- verted into cyanide so long as it remains in the liquid state. Here is how Dziuk in his patent explains this phenomenon. The nitrogen is first absorbed by the metal yielding a nitride which uniting with free carbon forms cyanide. In practice, Dziuk uses any kind of electric furnaces which is used in the manufacture of carbides. Into the fusion chamber f at right angles to the electrodes, opposite the charcoal tube enclosing the fusion mixture, he introduces a second charcoal tube which serves to conduct the atmospheric nitrogen which has been care- fully freed from carbonic acid, moisture, and oxygen, and which has been highly heated. Thus, a brown-colored product is obtained which is composed almost entirely of cyanide and contains but a minimum amount of unconverted carbide. It appears best to allow the mass to cool somewhat in the nitrogenous atmosphere of the furnace. Carbide in the process of formation in the electric furnace may be used or else carbide already formed, which however must first be subjected to fusion. This process is applicable to all the alka- line-earth carbides and to magnesium carbide, likewise to a mix- ture of these carbides. These gases which issue from the furnace may be used in heating the nitrogen, and the cyanides obtained may be converted into alkali cyanides by double decomposition. Dziuk comes to the same conclusion in an improvement to this patent by heating magnesium or lime in an electric furnace under the action of a current of nitrogen, then adding carbon in the form, of coke in small portions. All this without interrupting the current. Under these conditions there is first formed a nitride which the carbon converts into cyanide. 152 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Process of the General Electrochemical Co. The last process to be mentioned, which makes use of carbides, is that of the Gen- eral Electrochemical Company (French patent No. 299655, April 24, 1900). Like Dziuk's method, this process consists in causing nitrogen to pass over carbides in an electric furnace, but with this differ- C5 K-^0 rHCO O t>. (N rfi O5 O5 CO >O CO 5*; S-*3 63 ^o ' .2 oc o o 10 o o 10 10 cococo TF*O ooco w (NCOO' rHr-i ^00 O tO ^ CO ^ ^* CO *O t-J & & 1|| I>T^O >OO O L ^ O OO5iO OOO r-iCO CO OCOi^ OOO5 CSrHCO rH rH rH(N O !> 1> O <* rH CO O O5 O IO l> CD r-00 00 (N rH >O C^l O O5 O rH P 1 a 1 rH rH CO O "* ooo o ! o rH'rn'cO CO *+-, o o ^" r*. r^ o"^ "3 iJ pv^ If fj ^i O QQ Q .O 05 IO _ -4J -+J O 2 I"- -5 ^ o o co 10 ** o >^ "^^5 r ^ rH rH rH rH CD * H 1-1 . . ... j ^* I "S IO 2 -^ * a o- '_23 C o o o -4^ i IO tO "O cO *O CO Wt) w '-i!!!!!!'-"- 1 1-1 'rH 2 I 1 .0000 ! 3 O . s . ^J -J rH rH . o B fc 73 i c tt ;i ^ oo co ^3 rH rH rH . ...*'"* ... 02 rrj : : : : : :g :| : ! : i i i ! i ! i ! : j j f: j^ jl ij j : j | : : : : : :::::: :^ : : : : : : : : : : : . : ':::: :S :$ ::::; : : : : : : s^ 1 "S : -^ori g 1 S -g : |S|J|Js|1 I ^|ll fe :i ii||||.a|i -g^ **^2 i ^cx^^^fl ^Sj^J^o^ jj. I s li t -s S G^ 1- 8 i *TLIOJJ "sS'eu pu^ Jrejj uai ^arj MANUFACTURE OF FERROCYANIDES. , 197 The second raw material in the manufacture of yellow prussiate is potash. Generally commercial potassium carbonate is used, which often contains other salts such as sulphate, silicate, chloride of potassium, and sometimes sodium salts. The chlorides exert no influence; the sulphates form sulphides during the process, which attack the cast metal and rapidly puts the apparatus out of service. The silicates and earthy substances likewise exert an injurious action. One may likewise use blue potash extracted from the mother- liquors of a previous manufacture, a product which contains 40-90% potash, but 4-8% potassium sulphide, 7-16% potassium silicate, 7-13% potassium chloride. It is therefore necessary to subject these substances occasionally to purification, for their coefficient of impurities increases with the successive number of ignitions. The iron, which is often added to the ignition, may be used in the metallic form (nails, filings, wastes from tin-plate), or oxid (forge scales), which becomes reduced at the beginning of the igni- tion. The forge scales are often objectionable because they contain a large amount of combined silica, and earthy matters. The manufacture of potassium ferrocyanide Comprises three distinct stages: 1. Ignition or production of the metal. 2. Lixiviation of the metal. 3. Crystallization. i. Ignition or Production of the Metal. By the name metal is meant the crude product resulting from the ignition of the nitrog- enous organic substances in the presence of iron and alkali. The amount of these raw materials to be used is as follows: Carbonate of alkali. . 100 parts Nitrogenous substances (130-140 at a maximum, 170 with animal black) 125 "' Metallic iron r 6 or 7 " The whole mixture of these substances may be charged in retorts or ovens, but it is much better first to add the potash, then to shovel in the animal substances. In fact, under the influence of the high temperature necessary to carry on the reaction, an abundant liberation of combustible gases is produced (carbon monoxid, carbides, carbonic acid), which 198 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. remove from the mass a large amount of heat. The successive additions of animal substances to the mass restore to it the amount of heat lost. To carry on the reaction in the best way, it is necessary that the temperature be always sufficiently high that the alkali carbonate may be reduced by the charcoal, but it should not be too high, otherwise some of the cyanide formed will be volatilized. The operation takes place in iron kettles, or in specially con- structed retorts, or in reverberatory furnaces. The oldest apparatus known is pear-shape (Fig. 17). This oval or pear-shaped retort (A) is of iron and rests on one side, on FIG. 17. Pear-shaped Retort for the Manufacture of Ferrocyanide. A, retort; D, fire-grate; C, vault; E, flue for the outlet of gases; B, opening for charging and unloading; G, kettle for the evaporation of the strong solutions. the stonework of the oven, by means of a powerful trunnion, and on the other, on the facade wall of the oven by its neck. It thus presents a slight inclination backward. It is 1.20 meters long, 0.80 meter in diameter, and 0.15 meter thick. The rounded part of the retort is free, and is completely exposed to the action of the flame which arises from the grate D. The opening B, which MANUFACTURE OF FERROCYANIDES. 199 serves to load and unload the retort, is closed by a sheet-iron lid. The products of combustion, coming from the fire-grate D, are distributed on each side of the retort, and again come together in the arch C and escape by means of the flues E. The heat lost from these gases is utilized in evaporating the strong solutions in the vessel G. The retort A may be turned over from time to time in order to change the surface coming in direct contact with the flame and to avoid a too rapid wear and tear. There are two objec- FIG. 18. Reverberatory Furnace. tions to this class of apparatus: they wear out very rapidly, and the action of the heat may be exerted on the substances only through the walls of the retort. The pear-shaped retort has been replaced by the reverberatory furnace. The sole of this furnace consists of a cast-iron cupel (7 (Fig. 18) 1.1 meters in diameter and 0.10 meter thick. The fuel is put on the grate B, the products of combustion follow the conduit E in the direction indicated by the arrow, and come to the vault A, where they heat the cyaniding mixture from above, and in this way the high temperature necessary for the reaction is more easily attained. 200 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. In some works the gases of the grate pass under the cupel before coming in contact with the surface of the mixture. On com- ing out of the vault A the gases .pass through a lateral tube and thence through the chimney F, whence they are conducted under evaporating-kettles which they heat. In these furnaces 500 kg. of material may be converted at one time into yellow prussiate. The cupels wear out rapidly, but can easily be replaced; thus, after 700 tappings, a 1500 kg. cupel will weigh no more than 250 kg., and should not be used fur- ther. The wear and tear is particulary rapid in the case of fur- naces with double circulation, where the combustion gases pass above and below the cupel. These furnaces have been used quite extensively in Germany. The operation is as follows: The cupel is first heated to red- ness. When this is done, the inlet of gases is shut off and the mix- ture of potassium carbonate and blue potash is introduced into the cupel, and the cover closed. The gases are let on again and the mass brought to fusion. When this is in perfect fusion, the poker is introduced and the nitrogenous substances shovelled in, mixing them in the mass with the aid of the fire-iron. A lively reaction takes place, accompanied by effervescence and an abun- dant liberation of combustible gases which burn at the surface of the bath with flames sometimes, 2 meters in length. To prevent the fused mass from overflowing, small portions of nitrogenous substances are added whenever the reaction- becomes too lively. When about half 'of the nitrogenous substances has been added, the reaction becomes more gentle; further addition is stopped for V2- 8 /4 of an hour, during which time the mass is vigor- ously stirred with the poker until the bath is completely fluid. The rest of the organic substance is then added in 2 or 3 portions. All these operations require about 2 hours. The mass is again heated for l / 2 hour, after which it has the appearance of a thick liquid, and is run into moulds with the help of an iron spoon. After cool- ing, it has the appearance of loaves of bread. As a rule, 6 tappings of 250 kg. each may be made for each furnace every 24 hours; but, of course, the length of the operation varies according to the nature of the substances acted upon, the intensity of the fire, the experi- MANUFACTURE OF FERROCYANIDES. 201 ence of the workman using the poker, etc. In any case it varies from 4 to 6 hours. In England, preference was given to vertical cast-iron boilers, slightly narrowed at the opening and provided with a mechanical stirrer whose axle penetrated the cover, and set in motion by means of gears connected with the source of power. This arrangement allowed a good deal of manual labor to be spared. Generally these boilers were arranged in series of 24. Although this method has certain advantages, it has great dis- advantages. The greatest objection consists in the losses, which are appreciable, due to the fact that the nitrogenous substances float on the surface of the bath and there burn, the nitrogenous gases liberated thereby coming in contact with but a thin layer of potash and thus escape without being combined. Engler's process has the object in view of obviating this diffi- culty by causing the nitrogenous gases to become liberated in the very midst of the mass itself. Engler's Apparatus. This consists of a vertical boiler 60 centi- meters in diameter and 2 meters high. A piston, formed by a per- forated sheet-iron disc and moved to and fro, continually rams the nitrogenous substances into the very mass itself. First, 300 kilo- grams of potassium carbonate are placed in the boiler; when this is melted small portions at a time of nitrogenous substances are added through the hopper (the piston being lowered), till the whole of the nitrogenous substances has been added. The unload- ing is done from beneath, and the mass is collected in a suitable truck. The ammonia set free during the reaction is collected in a tower filled with pieces of coke. The product of ignition obtained in either one of the processes just described is a greenish-black mass, quite hard, porous, absorb- ing atmospheric moisture energetically, with liberation of ammonia and hydrocyanic acid. This is the mass which is commonly called metal. It yields about 16% potassium ferrocyanide. Its compo- sition varies, of course, with the composition of the substances used, the length of the operation, and the method used in carrying it on. Karmrodt, who took the average of ten tappings, produced by igniting 100 parts of potash, 100 parts nitrogenous material, and 10 of iron, gives the following figures: 202 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Cyanide of potash 8 . 20 Sulphocyanide of potassium 3 . 33 Cyanate of potassium 2 . 46 Carbonates of sodium and potassium 57. 56 Sulphate of potassium 2 . 82 Silica 3.10 Insoluble. . . * 18. 11 Undetermined. . 4.42 100.00 As may be seen, the metal does not contain any ferrocyanide. This salt is formed only on lixiviation. The metal is broken into lumps as large as one's fist and thrown into vats containing water or weak solutions from a previous opera- tion; this is heated to 60-90 for 12 to 14 hours while stirring. The temperature should not exceed 90, nor be kept at that point too long, for the cyanide might be converted into ammonia and potassium formate. When all the solid pieces have disappeared and the solution -shows about 24 B., it is allowed to stand 3 or 4 hours, after which the clear liquid is decanted. The residue is washed with fresh water, the washings being used in lixiviating the succeeding metal. The clear liquid or " blood-lye," which is greenish black in color, is concentrated in kettles by the waste heat from the ignition furnaces until the solution shows 32 B. It is finally run into wooden crys- tallizing vats, where it deposits on cooling a grayish crystalline product, called crude salt, containing about 1 / 6 of its weight of fer- rocyanide of potassium. This crude salt is withdrawn and placed in wicker-baskets in order to drip. It is purified by a second and sometimes a third * crystallization. The final product is a lemon-colored salt potassium lerrocyanide, Fe(CN 6 K 4 +3H 2 0. When th mother-liquors are concentrated to 40 B. a fresh quantity f very small crystals appears, which are purified by repeated crystallization. Gentele avoids the second crystallization by precipitating the ferrocyanide completely from its solution at the boiling-point. The lyes at 35 B. are heated to boiling. Under these conditions the MANUFACTURE OF FERROCYANIDES. 203 salt is deposited; this is withdrawn and allowed to drip. When the lyes show 50 B., the boiling is stopped and the lyes allowed to stand overnight, when the rest of the cyanide is deposited. In this way no very small or "fat" crystals are obtained; the mother- liquors are treated directly in order to obtain the blue potash. Gen- tele's method of obtaining the crude salt yields somewhat more potassium sulphate than the ordinary method. It remains but to purify the crude salt obtained by either of these two methods; to this end, it is dissolved in just enough hot water so that the solution shows 32 B. It is allowed to stand and is then drawn off or filtered in order to separate the black par- ticles of insoluble residue which detract from the appearance of the product. The clear solution is then transferred to rather deep wooden or sheet-iron crystallizing vats which are surrounded by insulating bodies, where it is left during 8-10 days. The ferro- cyanide is deposited, the mother-liquors being drawn off carefully and used to dissolve a fresh amount of crude salt, while the crys- tals are covered over with a new solution sufficiently concentrated to add to the crystals already deposited. This is repeated until the crystals obtained are 10-12 cm. in length In fact, commerce seeks rather to have large and regular crystals than pure ones. The crystals are removed, washed with a small amount of water, and dried. Sometimes the salt is crystallized in groups by suspending crystals to threads tied to wooden rods placed in the crystallizing- vats. As to the very fine crystals, they are dissolved in water, and, after concentrating the solution to 30 B., allowed to crystallize; the salt thus obtained is added to the crude salt and treated as such. The mother liquors, evaporated to 40 B., yield pearly crystals of a double salt of cyanide and chloride of potassium, much used in the manufacture of alum. The refined salt is never pure: it always contains a little potas- sium sulphate which is difficult to get rid of. Yet one may obtain it free from sulphate by dissolving the salt in water and concen- trating the solution to the density 1.31. At this point the greater part of the sulphate of potash separates out. Water is then added to bring the density to 1.27 and the solution allowed to crystallize. This is done but rarely, for the presence of potassium sulphate does OF THE UNIVERSITY OF 204 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. not in any way interfere with the industrial use of potassium ferro- cyanide, the only objection being that it reduces by just so much the amount of useful cyanogen. The manufacture of potassium ferrocyanide leaves behind two important residues: a black mass and blue potash. The black mass is made up of the residue from lixiviating the metal. It is friable and of a composition varying according to the nature of the organic substances used and the method of procedure It consists to a large extent of carbon and mineral substances- silicates, phosphates, chlorides, sulphides, soda, potash, lime, etc. In the following table Karmrodt gives the analyses of three samples of this black mass: Substance. Horn. Leather. Rags. Charcoal Per Cent. 6 10 Per Cent. 9.19 Per Cent. 4 22 Potash 12.18 10.22 16.70 Lime 16.20 19.66 18.45 Majrnesia 2 15 97 1 27 Sesquioxid and metallic iron \lumina 16.14 4 80 3.10 14 17 2.12 10 24 Manganese 0.42 72 06(?) Copper trace . 02 (?) 0.42 Silica 21 14 26 45 29 70 Sulphuric acid 1 27 1 85 16 Phosphoric acid 10 45 4 92 6 44 Residue : Sulphur, CO 2 ; chlorine, CN 9.15 8.73 10.22 100.00 100.00 100.00 The amount of the black mass varies according to the substances used. Karmrodt found the following: Using wool wastes 28. 3% " horn 18.7 " hair. 23.0 " leather scraps 35. It is sold mostly as a fertilizer, due to its high content of potash and phosphoric acid. In order to recover the potash (9%), vari- ous uses have been attempted, especially that of utilizing it in the manufacture of alum, but the experiments thus undertaken were not successful owing to the fact that the labor cost more than the value of the product. MANUFACTURE OF FERROCYANIDES. 205 Blue potash is the residue after evaporating to dryness the mother-liquors obtained from the crystallization of the crude salt. It contains potash in excess in the free state or in the form of salts not combined with cyanogen, and the salts supplied by the ash, It is used again in the process, mixed with fresh potash. Its composition varies according to the number of ignitions to which it has been subjected. It is evident that it becomes more and more impure, and ends by becoming useless. Hoffmann. Brunquell. Karmrodt. Potassium carbonate. . . ' ' silicate. . . . 44.1 to 84.0 7. 6 to 20.4 71.9 11.9 52.75 16.57 Sulphide 1.4to 8.8 4.3 6 18 Chloride 7.2to 13.1 1.15 Phosphate 2 04 Sulphate 4 34 Potash 7 22 Ferrocyanide 2 84 Sulphocyanide trace Insoluble residue Other substances Water 1 26.77 j 1.6 8.2 2 1 3.86 3.07 Theory of the Manufacture of Potassium Ferrocyanide by the Old Process. Seyeral hypotheses have been proposed on this sub- ject, the first and most probable of which is the following: Nitrogenous organic substances contain carbon, nitrogen, hydro- gen, and oxygen. After ignition, they still contain all these elements except oxygen and a large part of the nitrogen which is volatilized in the form of ammonia. Now as the amount of carbon in these sub- stances is much larger than that of nitrogen, it follows that only a part of this carbon enters into combination with the nitrogen in order to yield cyanogen, and the rest of the carbon reacts upon the carbonate of potash, which it reduces, thus setting the metal free, = C0 2 +CO+K 2 , 206 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. which metal, reacting upon the cyanogen formed, unites with it and produces potassium cyanide, CN+K = CNK. As may be seen, iron seems to take no part in this reaction, and yet it is indispensable that some be put in. In fact, carbonate of potash always contains, besides other impurities, a small amount of sulphate of potash. In contact with carbon, this salt becomes likewise reduced, yielding potassium sulphide, S0 4 K 2 + 4C = K 2 S+4CO, and this sulphide, in the presence of the cyanide formed, yields sulphocyanide. The object of the iron is, therefore, to absorb the sulphur of the potassium sulphide, forming insoluble iron sulphide, K 2 S+Fe=FeS+K 2 , or K 2 S + Fe + 2C + 2N = FeS + 2CNK, which entirely prevents the formation of sulphocyanide, the forma- tion of which must, under all circumstances, be avoided in the manufacture of potassium ferrocyanide. Therefore the product after igniting the raw materials (nitrog- enous subst nces, carbonate of potash, iron), otherwise called the metal, will be a rather complex mixture which may contain: Potassium cyanide; Alkali carbonate in excess; Undecomposed organic substances; Iron ; Iron sulphide; Carbon. It should be stated that we do not include the presence of potas- sium ferrocyanide in the said mixture. It is, in fact, admitted, according to actual data, that this salt is formed only at the time of lixiviation in the following way: MANUFACTURE OF FERROCYANIDES. 207 During lixiviation, potassium cyanide reacts with sulphide of iron, yielding potassium ferrocyanide according to either of the following reactions: 2CNK+Fe = (CN) 2 Fe+K 2 4CNK + (CN) 2 Fe = Fe(CN) 6 K 4 , or 2CNK + FeS - (CN) 2 Fe + K 2 S (CN) 2 Fe +4CNK = Fe(CN) 6 K 4 , or 6CNK + FeS = K 2 S + Fe(CN) 6 K 4 . That is precisely the reason why one should not think of extracting directly by lixiviation the potassium cyanide formed in the "metal." Still another theory is the following:* The reason for igniting organic substances is to produce a nitrogenous charcoal which would react with the potassium carbonate, yielding, in all proba- bility, acetylene. In its turn the acetylene would react with the potassium, set free from potassium carbonate, and with the ni- trogen of the organic substance, or, in case of need, with nitrogen of air, thus yielding potassium cyanide, as follows: C 2 H 2 + K 2 + N 2 = 2CNK + H 2 . It is just at this point that the presence of iron would cause the formation, first of cyanide of iron, then of potassium ferrocyanide, according to the reactions above indicated. Yield. The yield obtained by igniting nitrogenous organic substances depends on several conditions. From many experiments on a large scale made by Karmrodt, it follows that the yield may vary from 10-18% of the weight of the salt used. As an average of 459 different operations, Fleck places the yield at 11%. Hoffmann studied the various conditions which may influence the yield, the following being the result of his investigations: (1) The nature of the nitrogenous organic substances exerts a * Prunier, Medicaments chimiques, Vol. I. 208 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. considerable influence on the yield of cyanide and of sulphocyanide; it is, however, impossible to. establish a fixed relation between the yield and the nitrogenous content of the organic substances used. (2) The formation of potassium cyanide 'is quite closely pro- portional to the weight of organic substances. (3) The yield seems to increase with the purity of the alkali. (4) The yield increases especially with the temperature. (5) It increases more rapidly still if for a like quantity of potash the addition of organic substances be increased. (6) If blue potash be employed, the amount of black mass is twice as great as if pure potash had been used. (7) For the same amount of potassium ferrocyanide produced, the amount of pure potash consumed depends on the nature of the organic substances. (8) The comsumption of organic substances is greater with blue potash than with pure potash. (9) The amount of sulphocyanide formed does not vary whether iron shavings or iron turnings be added to the mixture ; but it decreases if finely divided reduced iron be used; there is almost no forma- tion if at the end of the operation forge scales be added. To these theoretical considerations should be added the following, based upon experimental data: (1) A relatively small proportion (Vs- 1 /?) of the total nitrogen of the organic substances contributes to the formation of the cyanide. The remaining 4 / 5 or 6 /7 ar e lost or volatilized as ammonia. A certain amount is, however, retained. At the beginning of ignition, the temperature being relatively low, a portion of the nitrogen escapes under the form of ammonia; but when the temperature has become raised, this ammonia coming in contact with carbon becomes converted into hydrogen and hyrdocyanic acid, which latter unites with potassium in order to form cyanide of potassium. It follows that if this high temperature could be obtained from the beginning of the operation, there would probably be formation 'of cyanide from the first. (2) Just as only a small proportion of the total nitrogen be- comes really utilized, so only a fraction of the potash used unites with the cyanogen. According to Karmrodt's experiments, this amounts to l / 7 - 1 /io. It should, however, be remarked that besides MANUFACTURE OF FERROCYANIDES. 209 'its role of absorbing the cyanogen formed, potash also acts as a flux, the effect of which is to reduce the mass to a state of liquid which is absolutely indispensable for the proper formation of potas- sium cyanide. Part of the potash is recovered in the mother-liquors, but a rather large amount is volatilized or lost in the various manipu- lations. According to Hoffmann this loss may amount to 10-20%. (3) Besides cyanide of potassium there is also formed during ignition sulphocyanide of potassium. The formation of this salt is variously explained. According to some it is due to the presence of potassium sulphate in the carbonate used. Hoffmann objects to his hypothesis because when in his experiments he used potash absolutely free from sulphate, he noticed a formation of sulpho- cyanide to about the same extent. These investigations led to a second hypothesis: the influence of the sulphur, which is present almost always in animal substances, the amount reaching sometimes 3%. A great portion of this sulphur is, however, vola- tilized, the rest being converted into sulphocyanide. In fact this formation of sulphocyanide constitutes a loss from the point of view of the yield of ferrocyanide, a loss which may amount to 1 / 5 of its weight. It is for the purpose of overcoming this objection that iron is added, which during the fusion reduces the sulphocyanide. If, however, one succeeds in the laboratory in obtaining a metal free from sulphocyanide, it is entirely different on an industrial scale, in which case a small amount of this salt is always found. N611- ner recommended the use of chalk, but the results obtained with this reagent .are not very satisfactory. Forge scales give excellent results, but they have the great objection of breaking up a portion of the potassium cyanide. All in all, iron is the best reagent; it also serves in preventing a too rapid wear and tear of the apparatus; it unites with the potassium sulphide and converts it into iron sul- phide, which does not attack the walls of the vessels. K 2 S+Fe=FeS+K 2 . (4) The reaction should not be carried on too far, otherwise the yield may decrease 9-12% (Hoffmann). (5) The substances employed should all be absolutely dry, the water-vapor set free during the reaction exerting an action which decomposes the cyanide formed. 210 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Observations Concerning Lixiviation and Crystallization. (1) The use of iron protoxid salts to convert cyanide into ferrocyanide is advantageous. The carbonate or sulphate of iron may be used, but generally in the industries the use of sulphide of iron is pre- ferred. (2) In evaporating the lyes, it is best not to bring them imme- diately to the boiling-point, otherwise the unconverted cyanide of potassium woUd be decomposed. The temperature should not exceed 70-80. Brunquell recommends macerating the metal during 24 hours at 50-60. The sum total of these various theoretical and practical considera- tions shows well that the manufacture of potassium ferrocyanide by the old process is filled with defects and requires a great deal of care if a really profitable yield is to be obtained. All in all, the losses are considerable and intimately bound to numerous circum- stances. The chief objections to this method may be thus summed up : (1) Serious losses of nitrogen through volatilization at the time of ignition. (2) Loss of potash. (3) Loss of cyanide because of the formation of sulphocyanide and cyanate. (4) Loss of cyanide due to the incomplete transformation of this salt at the time of lixiviation. (5) Rapid wear and tear of the apparatus. (6) Heavy expense for fuel. It has been sought to remedy these objections, and numerous improvements have been applied to the methods which we have just described. The object of most of them is to utilize, as much as possible, the nitrogen, which at the beginning of ignition escapes from the organic substances under the form of ammonia. Such are the processes of Brunquell and of Karmrodt. BrunquelTs Process. This process may be carried out in two different ways. In the first, two iron retorts are used connected with a vertical tube. The mixture of organic substances, potash, and iron prepared in the ordinary manner is charged into the lower retort, while the upper retort contains a mixture of animal charcoal and potash. MANUFACTURE OF FERROCYANIDES. 211 These two retorts are placed in a specially constructed furnace. First the upper retort is heated to bright redness, and then the lower retort is so heated as to bring the mass to a state of fusion. In BrunquelPs second improvement, only one cylinder is used, the lower half of which is filled with the ordinary mixture and the upper half with charcoal and potash. This cylinder is suspended by a chain and may be raised or lowered at will into a vat-like fur- nace which is provided with a grate containing a hole through which the cylinder may pass. At the beginning of the operation the cylinder is lowered deep enough so that only the upper part is sub- jected to the heat; when this part has reached the desired tempera- ture, the cylinder is raised so that it is found completely in the furnace and consequently heated on all sides. In this way, in the first as well as in the second apparatus, the gases set free by the mixture of the lower .part passed through the upper mixture. Notwithstanding these advantages Brunquell's two processes have never been adopted on an industrial scale. Still another improvement, due to Brunquell, consists in con- verting most of the nitrogen into volatile products by means of repeated distillations with lime, then to utilize the ammoniacal products thus obtained for the manufacture of ferrocyanide by passing them through a series of cylinders filled with charcoal and potash heated to bright redness. The ammonium cyanide thus formed is collected in a strong solution of sulphate of iron. Cyanide of iron is formed, which when boiled with potash is converted into potassium ferrocyanide. For a certain time this process was tried in France, with this modification, however, that the ammonium cyanide was absorbed by a strong solution of potash to which a salt of iron had been added. Karmrodt's Process. Along the same line, Karmrodt's process should also be mentioned. The object of this process is the same as that of Brunquell, and it may profitably be combined with the manufacture of animal black. The apparatus used consists of two parts, the carbonization vessel and a cylinder charged with wood charcoal impregnated with potash. The two parts are con- nected by means of a tube. The cylinder, which is vertical, is pro- vided with a fire-grate; one begins heating the cylinder by means 212 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. of this fire-grate. With the aid of a special appliance the prod- ucts of combustion are conducted either into the main chimney or into a flue joined to the carbonizing retort. When the cylinder has reached the temperature of redness, the gases of the fire-grate are conducted under the carbonizing retort. The volatile prod- ucts here liberated pass through the connecting tube into and through the cylinder. The yield is appreciably greater than by the ordinary process, but it is, nevertheless, far from the theoretical yield, which the whole of the ammoniacal products set free should give. Several processes for the conversion of sulpho cyanides into ferrocyanides have been invented, among which only two deserve to be taken into consideration. Conroy's Process. The first is that of Conroy, Hurter, and Brock (1896). It consists in treating the crude sulphocyanide with a solution of ferric or ferrous chloride. The mixture is heated to 270-280, in an autoclave provided with a stirrer, in the pres- ence of an excess of iron, preferably reduced iron. The sulphocyanide is converted into a mixture of ferrocyanide and sulphide of iron, which is collected, washed, and finally decom- posed with a caustic alkali. The residue from the treatment with alkali, consisting of a mixture of sulphide of iron and ferric and ferrous hydrate, is treated with hydrochloric acid, which forms iron chloride, which may be used anew. The hydrogen sulphide thus liberated is collected and used. Musspratt's Process. The second process is that of H. E. Hether- ington and E. K Musspratt (English patent No. 5830, March 20, 1894). It consists in treating a sulphocyanide of an alkali or alkaline earth with metallic iron. First finely divided iron (filings, turn- ings, or iron sponge) is heated with tar, the object being to reduce the oxid which always forms on the surface of these products. The iron thus prepared is mixed with sulphocyanide and tar in the follow- ing proportions: Reduced iron 70-80 parts Tar 20-40 " Sulphocyanide of potassium or sodium 100 " MANUFACTURE OF FERROCYANIDES. 213 This mixture is heated to 350 F. in a closed vessel connected by a tube to a condensation retort. This retort serves in condens- ing the sulphocyanide which might be volatilized during the opera- tion. The product of the reaction consists of a mixture of alkali ferro- cyanide, iron and alkali sulphides, and tarry residue. It is treated with hot water, the solution thus obtained being treated with car- bonic acid, which removes the hydrogen sulphide, and then concentrated to crystallization. In case of ferrocyanide of sodium, it is best to concentrate directly. Goerlich and Wichmann's Process. This process (German pat- ent No. 9139, Aug. 4, 1894, March 11, 1895) is practically the same. It consists in fusing alkali sulphocyanide with iron and treating the product of fusion, before lixiviation, with a current of moist air mixed with carbonic acid. In this way ferrocyanide, sulphur, alkali sulphide, and carbonate are obtained: 2[K 6 (CN) 6 -6FeS]+170 + 21H 2 0+2C0 2 =2K 4 Fe(CN) 6 .3H 2 0+2C0 3 K 2 +5Fe 2 (OH) 6 4-12S. By this process almost the whole of the sulphur is removed, and alkali carbonate is obtained instead of alkali sulphide. In the absence of carbonic acid, the reaction is as follows : 2K 6 (CN) 6 - 6FeS + 150+ 21H 2 =2K4Fe(CN) 6 -3H 2 0+ 2K 2 S +5Fe 2 (OH) 6 +10S. The oxidized product is treated with water, and the soluble salts are separated by fractional crystallization. The residue may be used in recovering metallic iron. Process of the Works du Castelet. Lastly, we will mention the extremely original process described in the patent No. 308808 of March 8, 1901, taken by La Societe des Usines du Castelet, and Leriche. It consists in causing a gaseous mixture of J acetylene and f ammonia to act, at a nascent red heat, upon an intimate mixture 214 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. of oxid, carbonate, or hydrate of iron and alkali oxid in a closed vessel. The reaction is as follows: 6 C 2 H 2 + 12NH 3 + 8KOH + Fe 2 3 = 2Fe(CN) 6 K 4 + HH 2 + 34H. The product is dissolved in boiling water, the clear solution being decanted, evaporated, and allowed to crystallize on cooling. II. EXTRACTION OF CYANIDE COMPOUNDS FROM ILLUMINAT- ING-GAS AND FROM THE BYPRODUCTS OF ITS MANU- FACTURE. The manufacture of illuminating-gas has made great strides in the last thirty years in England, Germany, and in France. Thus the annual consumption of gas in England reaches almost 3000 million cubic meters; in France it is about 700 million cubic meters. As will be seen later, the cyanide compounds exist already formed in the gas. It is therefore quite natural that one should think of reaping some advantage from it. To be sure, the percentage is quite small, and sometimes even trifling; but on the other hand, if one thinks of the enormous quantity of gas annually produced in the different countries, one can easily conceive how the gas industry may offer a profitable source of cyanide production. Further, it should be stated that cyanogen is an injurious product which it is necessary to remove before delivering the gas for con- sumption. It decreases the illuminating power perceptibly, and is a toxic product. Besides its being absolutely necessary to remove it from the gas, there is profit in its recovery. In England the question of cyanides in the manufacture of gas has keenly prejudiced the mind, and the manufacturers and investi- gators have foreseen the advantage to be derived in these sub- stances in a country so rich in coal and gas. Germany is not at all behind in this respect, there being few gas-works which do not recover the cyanide compounds. On the other hand, France has shown but little interest in this question, and even at the present time there seems little disposi- tion to extend this industry. MANUFACTURE OF FERROCYANIDES. 215 Moreover, it is a fact to be regretted that in France so little importance, and sometimes even not any at all, is attached to the by-products of certain manufactures. It is not a rare sight, indeed, to see numerous works neglecting such an interesting and often remunerative question as the recovery of by-products. Thus, for example, in the case of illuminating-gas, there are to our knowledge works of importance which do not even condescend to take the trouble to purify the gas, or if they are compelled to do this because of hygienic statutes, do not get any profit out of their sluice waters or from their spent oxid. And yet in most cases the recovery and utilization of by-prod- ucts (especially in the industry which we are discussing) require but slight costs of installation, costs which are repaid by the profits obtained and by a better quality of product, which is the chief ob- ject of the manufacturer. It should also be stated that the process of recovering these by-products does not generally modify the carrying on of the operations. Thus, if one considers that in France the manufacture of illu- minating-gas requires annually about 4,000,000 tons of coal, and that from each ton one can extract cyanide compounds worth 2-3 francs, it is easily seen that the illuminating-gas industry could recover, each year, a profit of 8 to 12 million francs, which is not at all an amount to be neglected. One objection may be interposed to the above remarks, and that is, that in France many gas-works are of but slight importance, and under the circumstances the recovery of these by-products seems to offer no benefit considering the small amount of product to be treated. To this objection the following reply may be made: Most of the gas-works are in the hands of powerful companies often possessing a large number of works. It would be a simple matter for each works to recover the cyanide compounds, and to obtain concentrated products (e.g., masses rich in cyanide) which might be profitably transported to a central works, which could be espe- cially occupied with the treatment of by-products furnished by all the works of the company. The expense would be slight and large profits would be assured. From all the foregoing remarks it follows that the gas industry may with advantage prove a source of production of cyanide com- 216 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. pounds, a production which would require but little expense if it were well understood, and which under these conditions would almost suffice for the demand in the cyanides. There is therefore, every reason, and it is also necessary, that the cyanide compounds should be recovered from the gas, and one should encourage every gas-manufacturer so to do. We shall now study the various ways proposed to bring about this operation profitably, but before that it seems necessary to mention briefly in what the manufacture of illuminating-gas con- sists. As is well known, illuminating-gas is a product of the distilla- tion of coal in closed vessels. Coal used in the manufacture of gas is the dry smiths' coal burning with a long flame, and contain- ing the following percentage composition (water and ash free) : 100.00 The principal types of coal most commonly used are those from Nord, Pas-de-Calais, Mons, the Sarre, Ruhr, and New- castle. This distillation takes place in retorts, formerly made of cast iron, but now of refractory brick, arranged ordinarily in a series of seven or nine, in a furnace which is heated either directly with coke or by means of combustible gases produced "by a gas-generator placed under the furnace for the recovery of the heat. These retorts, whose dimensions vary with the size of the works, are heated to a temperature of about 1100. The result- ing gas consists of a very complex mixture of different products (volatile and non-volatile hydrocarbons, ammonia, and ammoniacal salts, hydrosulphuric and hydrocyanic acids). Thus obtained, this product is unfit for domestic use, and must therefore be subjected to purification. The object of this purification is to separate the products, which on account of their easy condensation would befoul MANUFACTURE OF FERROCYANIDES. 217 and obstruct the pipes, or which on account of their own character- istics would considerably decrease the illuminating power of the gas, or would constitute a source of danger to the health of the consumers on account of their noxious properties. The purification of gas is carried on in two stages: the first is purely physical, whereas the second is based on chemical reactions. The physical purification consists in removing all the easily liquefiable or condensable products; the chemical purification consists in absorbing all the harmful substances which escape the physical by means of certain definite substances. The method of procedure is as follows: On emerging from the retorts the gas passes into a horizontal cylindrical apparatus half filled with water into which cylinder outlet tubes. from all the retorts converge. The level of the water is kept constant by means of an overflow. The gas abandons in this apparatus the less volatile products (tars) and a portion of the ammonia. From there the gas goes to a collector, a very long horizontal tube about 0.80 metre in diameter, where a great part of the light tars that have escaped the previous treatment are deposited. Then it goes into a condenser or cooler consisting of a system of inverted U tubes, joined to a rectangular box, divided into sections by partitions, into which the condensed products are collected (water-vapor, ammoniacal salts, ammonia, and the tars which have escaped the first and second treatment).. The last traces of these products are removed in the scrubber, a tall cast- iron cylinder consisting of two chambers filled with coke and into which a thin stream of water flows in a direction opposite to that of the incoming gas. Finally by passing the gas through the Pelouze and Audouin condenser the last traces of tar are removed,, and it only remains to subject the gas to the second stage for chemical purification. For this purpose the gas passes into a series of boxes filled with a mixture of sawdust, ferric oxid, lime, and sulphate of lime, which absorbs the ammonia, carbonic, hydrosulphuric, hydrocyanic, sulphocyanic acids, etc. When this mixture no longer exerts any purifying action, it is " revivified " by spreading and stirring it in the air, when it may be used again. 218 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. As may be seen by this short sketch the manufacture of gas yields many different products which may be divided as follows: I. COKE. II. AMMONIACAL LIQUORS. Principal elements Minor elements ( Ammonium carbonate (NH 4 ) 8 CO ( Gas Illuminating elements More illuminating ele- ments Elements which affect the purity of the gas Ammonium sulphide r Ammonium chlorid NH 4 C1 < Ammonium cyanide NH 4 CN ( Ammonium sulphocyanide NH 4 CNS III. ILLUMINATING-GAS. i Acetylene C 2 H 2 Ethylene C 2 H 4 Propylene C^H 6 Butylene C 4 H 8 Allylene C 3 H 4 Crotonylene C 4 H 6 Terrene C 6 H 8 Benzol C 6 H 6 Thiophene C 4 H 4 S Styrolene C 8 H 8 Naphthalene Ci H 8 Methylnaphthalene CnHi Acetylnaphthalene C, 2 Hi Fluorene CuH 10 Fluoranthane Ci 5 Hi Propyl C 3 H 7 Butyl C 4 H tt f Hydrogen H 2 | Methane CH 4 I Carbon monoxid CO Carbonic acid CO 2 Ammonia NH 8 Cyanogen CN Sulphocyanogen CNS Methylcyanide C2H 3 N Hydrogen sulphide H,S Sulphide of carbon CS 2 Sulphides of the hydrocarbons Oxysulphide of carbon COS Nitrogen N Vapors IV. TAR MANUFACTURE OF FERROCYANIDES. 21 & V. PURIFYING MATERIALS. Varying in composition according to the nature of the mixture used, but generally containing: Sulphate of ammonia, Ferrocyanide of ammonia, Sulpho cyanide of ammonia , Cyanide of ammonia, Prussian blue, Sulphide of iron, Sulphur, Oxid of iron, Sawdust, tar, etc. The amounts vary according to the kind of coal used, but, as a rule, from 100 klgm. of coal the following are obtained: I. Coke 70 klgm. =1.8 hectoliters II. Gas 30 cu. m. D = 0.4 III. Tar. '. 3J to 6 klgm. D = 1.2 IV. Ammoniacal liquors 6-9 klgm. 1 to 8 Baume (corresponding to 1-5% pure ammonia) Of these various products three only are of interest, because they contain cyanide compounds, namely: 1. Gas itself. 2. Ammoniacal liquors. 3. Purifying materials. We shall take up these three substances one after the other, in order to extract from the products of the distillation of coal the cyanide derivatives which they may contain, and which quite naturally vary according to the nature and the composition of the raw material used, and according to the methods of conducting the distillation. But before taking up the extraction of cyanides in the manu- facture of gas it would seem indispensable to review the various theories set forth concerning the formation of these compounds and the reactions which may produce them. Cyanide compounds are naturally formed in the production of illuminating-gas, and they may be found, in the various stages of the manufacture, in the following forms: Cyanogen, sulphocy- 220 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. anogen, sulphocyanic acid, hydrocyanic acid, cyanide, ferrocyanide, sulphocyanide of ammonium, etc. The nitrogen necessary for the formation of these compounds comes from the coal, which, according to the character of the coal used, contains various amounts. % Kind of Coal. Per Cent N. Analyst. FRENCH COALS. Haut-fleau ("fat ") .15 de Marsilly Escouffiaux 25 Agrappe 375 Bracquignies ("half -fat") 00 Mariemont ........ 75 Valenciennes ("fat ") 65 Bruay 875 it Noeux 525 tt Bully 34 LieVin 57 Bousquet d'Orb 40 Sables (washed) 67 Trelys " 96 Tre"lys (crude) 63 Martinet (washed) 31 Fontanes ' ' .67 Givors .65 Ch. MSne" Rouchamp, 1. . .09 Scheurer-Kestner " 2 06 i ( " 3 00 tt CHARLEROI BASIN. Poirier ("fat") 1 375 de Marsillv Carabinier (French) 1 00 it y Bois d'Heignes 40 it ENGLISH COALS. Three-quarter vein 1 65 Percy Beg vein 1 47 (Lab'y of Mines, London) Low " 2 05 Wolverhampton 1 84 Doul in (South), Wales 1 28 Newcastle 1 32 Glamorgan 1 69 Northumberland 2 05 Scheurer-Kestner 1 1 2 37 Ch Me"ne" South of Wales coal 1 65 n ii t ( it 1 49 Lancashire (uninflammable) 1 93 Scotland " 2 09 ft tt 1 33 1 1 1 1 1 57 " "speakcoal" 1 20 Cannel-coal-Wigan (Lancashire) 2 12 ' ' Tyneside (Newcastle) . . 1 85 _ Anthracite (South Wales) 83 Boghead 96 Genny tt 0.78 Matter MANUFACTURE OF FERROCYANIDES. 221 Kind of Coal. Per Cent N. Analyst. GERMAN COALS. 50 Scheurer-Kestner Alien wald ' ' 50 Hernitz " 0.50 Friedrichsthal " 50 Louisenthal 50 Konigshiitte (Prussia) 59 Schwachhof er Morgenstern ' ' 41 Hermenegilde (Low Silesia) 18 = Carolinen (Prussia) 24 Jaklowetz (Low Silesia) .... . . 20 Waterloo (Prussia) 40 Altendorf 1 00 Scheurer-Kestner" Consolidation 1 50 Boldon 1 45 __ Bohemian 1 87 Zwickau 1 20 ___ Saar 1 06 , From the foregoing table, the average content of nitrogen in coal may be seen to be 1 to 1.6%. The distillation of coal distributes this nitrogen among the vari- ous products formed, and only a small proportion passes into the state of cyanide compounds. Forster studied the migration of nitrogen produced during the distillation of coal in closed vessels (Journal of Gas Lighting, 1882). One of his experiments was made with a coal containing 1.73% nitrogen; and this he found distributed as follows: 0.251 or 14.50% passes into ammonia 0.027 or 1.56% " " cyanogen 0.863 or 49.90% remains in the coke [state 0.589 or 34.04% passes into the tars, and into the gas in a gaseous 1.73 100.00 Knublauch, who repeated the same experiment on three samples of coal, found: Total nitrogen of the coal 1 . 555 Nitrogen in the coke 0. 466 Nitrogen in the gas 0. 856 Nitrogen in the form of ammonia 0. 185 Nitrogen " " " " cyanogen 0.0268 Nitrogen in the tars 0.0212 2. 1.479 0.526 0.696 0.208 0.0278 0.0212 3. 1.176 0.751 0.189 0.187 0.018 1.555 1.479 1.17a 222 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. Or for for every 100 parts of nitrogen contained in the coal, there are i. 2. 3. JSfitrogen in the coke 30.0 35.6 63.9 " " gas 55.0 47.1 21.1 " " form of ammonia 11.9 14.1 11.6 " " " " ll cyanogen 1.8 1.8 1.8 " " tar 1.3 1.4 1.3 100.0 100.0 100.0 Leybolt (Journal fur Gasbeleuchtung, 1890) gives the following results : Coke 31. to 36. % Ammonia 10. to 14. % Cyanogen 1.5to 2. % Tar ,. l.Oto 1.3% Gas 46 . to 56 . 0% Guegen (Journal du gaz et de Pelectricite 1884) likewise studied the distribution of the nitrogen in the products of the distillation of two coals, carried on at 900 in sandstone retorts. Nitrogen in the form of ammonia Nitrogen in the form of cyanogen in the tar and in the gaseous products Nitrogen in the coke 1. Coal from Grand- Buisson, Mons, Belgium. 2. Coal from Li6vin. Distribution of 100 Parts Nitrogen. 34 27 39 100 19 29 52 100 These figures are not at all absolute: they vary with the nature of the coal, the method of operation in the works, the temperature of the distillation, etc., yet they show that the amount of cyanide compounds formed is relatively small, and that it can only become of value when large quantities of coal are treated. MANUFACTURE OF FERROCYANIDES. 223 Cyanogen is therefore always formed in very small quantities in the distillation of coal. The amount formed depends much on the temperature of the distillation, cyanogen not being formed except in brisk distillations carried on at a high temperature. In distilling coal at a higher temperature, Foulis of Glasgow found that 2831 liters of gas yielded 6.5 grams of cyanogen, while when working at a low temperature this amount was cut down to less than half. Accord- ing to Hunt, the most favorable temperature is 950 and above, while at 700 to 800 one would obtain only one twelfth as much cyanogen. This remark is, moreover, confirmed by the experi- mental fact that the greatest part of the cyanogen is formed toward the end of the distillation that is, at the moment when the temperature is the highest, and at this very moment the quantity of ammonia formed is very small. A small yield of cyanogen therefore accompanies a large yield of ammonia, and vice versa. Perthuis carried out a series of experiments which show this to be true, and that the yield of cyanogen reaches its maximum at the end of the distillation, while at the beginning it is almost nothing: Length of Hydrocyanic Acid Retained by Distillation. 100 Cu. M. of Gas. 1-2 hours trace 3-4 " 77.1 grams 5-6 " 142.1 " The form in which the cyanogen comes out of the distillation retorts has given rise to many discussions, and the opinions ex- pressed relative to this subject vary greatly. According to some investigators, cyanogen occurs in the gas in the form of cyanide and sulphocyanide of ammonium. The reaction would be that indicated by Kuhlmann: C + 2NH 3 =CN-NH 4 +H 2 . When this ammonium cyanide comes in contact with sulphur and sulphide of carbon in the highly heated retort it becomes par- tially transformed into ammonium sulphocyanide. But, on the other hand, the experiments of Bergmann clearly prove that the action of ammonia on carbon or on carbon monoxid 224 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. at a red, heat does not yield ammonium cyanide, but hydrocyanic acid, according to the reaction C+NH 8 CNH+H a . According to Lewis, and this is the most probable opinion, the cyanogen found in gas may exist therein only in the form of free cyanogen or free hydrocyanic acid. Lewis bases his views upon the following principles: (1) It is impossible that cyanogen should exist in the gas in the form of sulphocyanic acid (CNSH), for this latter in the presence of hydrogen becomes decomposed into hydro- cyanic acid and hydrogen sulphide: CNSH + 2H = CNH+H 2 S. (2) Neither can it exist under the form of ammonium cyanide f since this salt is decomposed from the time the temperature exceeds 26.6 C. (3) It is also quite improbable that it occurs therein in the state of ammonium sulphocyanide, experiments having clearly proven this. Finally, other investigators admit that ammonium cyanide is formed, but that it becomes decomposed by carbonic acid con- tained in the gas, this decomposition yielding hydrocyanic acid and ammonium carbonate. This would of course explain the absence of ammonium cyanide in the scrubbers. However that may be the formation of cyanogen compounds in gas takes place in the distillation retorts at a high temperature; it probably results from the action of ammonia on carbon or on carbon monoxid at a high temperature. This reaction in all probability causes the formation of free hydrocyanic acid, which in the course of its passage through the series of apparatus becomes transformed, as will be seen. In the ammoniacal liquors, cyanogen is found principally under two forms: as ferrocyanide and sulphocyanide of ammonium. Ammonium cyanide exists therein but rarely and in a subsidiary manner. According to Lewis, ammonium ferrocyanide will be formed by the action of free hydrocyanic acid, in the presence of ammonia. MANUFACTURE OF FERROCYANIDES. 225 on iron sulphide, which is itself formed by the action of hydrogen sulphide on the iron framework of the condenser: 6CNH + 6NH 3 +FeS=Fe(CN) 6 (NH 4 ) 4 +(NH 4 ) 2 S. The ammonium ferrocyanide cannot in any way come from the iron contained in the coal, nor be formed in the retorts because all the ferrocyanides are decomposable at temperatures much lower than those reached in the retorts. As to the ammonium sulphocyanide, its origin is a little more obscure and still requires some elucidation. And yet Lewis thinks, from experiments, that it results from the action of carbon bisulphide on ammonium sulphide, (NH 4 ) 2 S + CS 2 = 2H 2 + CNS NH 4 , this sulphide of carbon being itself produced by the action of the sulphur of pyrites contained in the coal on the carbon at the tem- perature of the distillation. The amount of ferrocyanide and of sulphocyanide of ammonium found in ammoniacal liquors is relatively very small. Lewis estimates that on an average 181 grams of ferrocyanide of ammonium, cal- culated as Prussian blue, is found in one ton of coal, and of sulpho- cyanide of ammonium he found 226 to 907 grams per ton of distilled coal. As the result of experiments carried on in certain German works at Wiesbaden, Karlsruhe, Mainz Esop gives the following figures (Chemische Industrie, 1892, page 116). Ppr PpTit Ammonia in the Ammoniacal Liquors. Sulphocyanic acid 1 .22 18.05% " 1.51 19.03% " " 2.33 36.05% Lunge claims that the quantity of sulphocyanide of ammonium contained in the ammoniacal liquors in the manufacture of gas in England amounts to 11 kilos per 454 liters; but Clayfield after numerous experiments was able to find but 0.453 kilo per 454 liters. 226 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. It is not at all surprising that the ferrocyanide and the sulpho cyanide of ammonium, both very soluble in water, should exist in such small quantities in the ammoniacal liquors; this is due simply to the action of carbonic acid which displaces the hydrocyanic and the sulpho cyanic acids from their combinations. On the other hand, in the purifying materials the cyanogen is retained almost wholly, and if we consult the following table by Lewis, it will easily be seen that immediately after passing through the first purifier the quantity of cyanogen compounds contained in the gas diminishes considerably, and that it is in this first purifier that the greater portion of the cyanogen products formed during the manufacture are collected. Hydrocyanic Acid per Cubic Meter. After the retorfs 19 . 2 to 30. 6 grams. " " condensers 18.9 to 29.0 11 " scrubbers 18.4 to 18.8 " " 1st purifier 1.2 to 14.2 " " 2d " 0.5 to 1.2 " "3d " 0.45 to 0.50 gram. " "4th " 0.30to 0.40 " Leybold had, moreover, made similar experiments, showing the progressive elimination of cyanogen, with the following results: Hydrocyanic Acid Hydrocyanic Acid, per 100 Cu. M. Per Cent. I. II. I. II. ' Conduit 265.9 203.4 5.4 14.57 After condensation 251 . 6 173 . 6 45 . 09 /' 1st purifier 131.7 '" 2d " 83.3 59.5 18.2 56.15 " 3d " 61.6 8.16 In the gasometer 41.2 19.8 15.5 9.73 The purifying materials are, as is known, composed of a mixture .of ferric hydrate and sulphate of lime, obtained by the reaction of Abime on sulphate of iron; this mixture is then made porous with sawdust. The gas, on coming into the purifying boxes, contains the follow- ing impurities: Hydrogen sulphide, ammonia and cyanogen com- MANUFACTURE OF FERROCYANIDES. 227 pounds. Rather complex reactions take place in the purifiers between the purifying materials and the impurities, there being formed notably ferrous cyanide, ferrocyanide of iron and ammonium,, carbonyl ferrocyanide of sodium, and ammonium sulphocyanide. The formation of ferrocyanide may be explained in various ways. The hydrocyanic acid would react on oxid of iron in order to form ferrous cyanide, which in the presence of oxygen of the air would become converted into Prussian blue : Fe 2 3 +4CNH = 2Fe(CN) 2 +2H 2 0+0, 9Fe(CN) 2 + 3 = Fe 2 3 + Fe 7 (CN) 18 . It follows, however, from Leybold's experiments that if a current of hydrocyanic acid mixed with hyrdogen be passed through the purifying materials no absorption takes place, while, on the other hand, if the purifying materials be first saturated with hydrogen sulphide the hydrocyanic acid becomes entirely combined, due to the previous formation of iron sulphide, according to the reaction FeS +2CNH = H 2 S +Fe(CN) 2 , the ferrous cyanide formed then becoming converted into Prussian blue under the action of atmospheric oxygen. Other investigators claim that the ferrous cyanide results from the action of ammonium cyanide on oxid or sulphide of iron. FeO +2CN NH 4 = Fe(CN) 2 + (NH 4 ) 2 or FeS + 2CN . NH 4 = Fe(CN) 2 + (NH 4 ) 2 S, and if ammonium cyanide be in excess there is formation of am- monium ferrocyanide: Fe(CN) 2 +4CN -NH 4 =Fe(CN) 6 - (NH 4 ) 4 . In every case it is to be noted that Prussian blue is not formed directly in the purifiers, but by oxidation of the ferrocyanide. Moisture or the use of steam facilitates the formation of ferrocy- anides, whereas ammonia prevents it. It is therefore of the utmost 228 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. importance, if one wishes to obtain materials rich in ferrocyanide, to wash the gas as completely as possible, in order to remove the ammonia. By removing the ammonia almost entirely, Knublauch succeeded in obtaining materials containing up to 24% of ferro- cyanide of potassium (reckoned on the dry matter). In fact ammonia, oddly enough, facilitates the formation of sulphocyanide of ammonium or of sulphocyanide of iron. Knublauch in 1877 was the first to show the close relation which exists between ammonia and sulphocyanogen, and he showed how the sulphocy- anides may be formed at the expense of ferrocyanides if the washing of the gas has been insufficient. Sulphocyanide of ammonium exists in but very small quantities in gas as it comes to the purifying boxes, but it may be formed in large amounts in these boxes, especially if ammonia or ammonium sulphide are found in the presence of finely divided sulphur such as exists in the spent oxids or in the presence of hydrogen sulphide. According to Lewis the reactions which take place on the forma- tion of sulphocyanide are as follows: NH 3 + CNH + H 2 S = CNS NH 4 + H 2 , Fe 2 S 3 + CNH = CNSH + 2FeS ; CNH + H 2 S + = CNSH -f H 2 0. Leybold studied this phenomenon and analyzed two purifying masses saturated with hydrogen sulphide which had been sub- jected to the action of a mixture (1) of hydrocyanic acid and am- monia and (2) hydrocyanic acid and ammonium sulphide: I. II. CNH + NH 3 . CNH + (NH 4 ) 2 S. Water 23.60% 33.02% Sulphur . .... 24.98% 11.39% Prussian blue 1 .70% 5.38% Ammonium sulphocyanide 3 . 03% 4 . 40% Ammonia 2.05% 0.75% It results from these analyses that, in the case of ammonia, the amount of sulphocyanide formed is, as is known, greater than that of Prussian blue, and that in the case of ammonium sulphide it is about equal. MANUFACTURE OF FERROCYANIDES. 229 The presence of an alkali in the purifying materials is likewise very favorable to the formation of the sulphocyanides. During the "revivification" of these materials, if care be not taken to avoid heating, the formation of sulphocyanides at the expense of ferrocyanides is considerable. Burschell estimates that it may sometimes amount to 30% of the weight of ferrocyanides. This transformation is due to the action of ammonia and of hydrogen sulphide found in the purifying materials, and to the moisture con- tained therein, and likewise to the action of sulphur and the alkali sulphides on the ferrocyanides. As may be seen from this rapid review of the complicated reac- tions which control the formation of cyanogen compounds in the gas itself, in the ammoniacal liquors and in the purifying materials, this formation is intimately dependent upon numerous conditions. The gas-worker who is desirous of recovering the cyanogen should strive to avoid or to produce them according as they are injurious or favorable. We shall now take up the various processes which the manu- facturer may put into operation in order to extract the cyanide compounds. A. In the illuminating-gas. B. In the ammoniacal liquors. C. In the spent oxid. A. DIRECT EXTRACTION FROM GAS. Although the presence of cyanogen compounds in gas has been known for a long time (it is mentioned in an English patent in 1850), it is only within the last few years, on account of its limited use in the arts, that any attempt has been made to derive any benefit from it. The spent purifying materials, or Laming's mixture, were considered as valueless waste products, and it was not till 1880 that a French manufacturer, Gauthier-Bouchard, thought of utiliz- ing them for the manufacture of Prussian blue and of potassium ferrocyanide. As these cyanogen compounds are formed naturally in these materials, and without care or thought on the part of the manufacturer, this process has been but little improved. But from the time that cyanides became useful in the treatment of aurifer- 230 METHODS OP MANUFACTURING CYANIDE COMPOUNDS. ous minerals, many investigators, especially in Germany, perceived the possibility of making gas a profitable source of cyanide pro- duction, and sought to extract from gas the greatest amount of cyanide possible. They soon recognized that Laming's mixture, or other similar materials, were but an imperfect and expensive source of production. In fact it is easily understood that this treatment in the dry way has the disadvantage, notwithstanding the porosity which sawdust gives to the mixture, of presenting but a small contact action to the cyanogen and its compounds, and that the absorption of these bodies is necessarily incomplete. Moreover it has already been noticed that on account of secondary reactions appreciable amounts of sulphocyanides may be formed in the materials, which are of less value than are the ferrocyanides, and their subsequent conversion into cyanides is more difficult. These are the reasons which caused the investigators to seek the extraction of the cyanogen compounds as completely as possible directly from gas. At present these processes seem to prevail among gas manufacturers who are anxious to derive some benefit from such an important by-product, while in the works which, for some groundless reason, persist in refusing to consider the impor- tance of cyanides in gas, the purifying materials are still being worked for the Prussian blue, in order to make of it a better commercial product. In other works, and they are numerous enough, they do not even try to obtain materials rich in f errocyanides ; and when these materials are spent, i.e. do not absorb any more hydrogen sulphide, they are sold to manufacturers of Prussian blue or of cyanides. In Germany and England processes for direct extraction of cyanides from gas are established on a large scale, and it is to be hoped that the French will not long remain behind their neighbors. The ideal method of direct extraction of cyanide compounds from illuminating-gas as it comes from the retorts would be to pass it through an alkaline solution, thus forming an alkali cyanide But this is quite impossible on account of the presence in gas of other acid gases, e.g. carbonic acid and sulphuric acid which could immediately displace hydrocyanic acid and therefore prevent all formation of cyanide. Therefore the idea of obtaining cyanides directly from gas must be abandoned. MANUFACTURE OF FERROCYANIDES. 231 Combinations upon which carbonic acid and hydrogen sulphide have no action must be sought. Knublauch J s Process.. Knublauch was the first investigator to become interested in this important question. Knublauch, who since 1877 had undertaken a whole series of researches on cyanogen in illuminating-gas was led during his experiments to find a method which allowed direct extraction of the cyanogen products from gas in a wet way (German patent No. 41930, Aug. 18, 1886 ; French patent No. 209770, Nov. 25, 1890). This process consists in passing the gas into purifiers, washers, or scrubbers containing in solution one or more of the substances men- tioned in the two following groups: (1) alkalis, ammonia, ammoni- acal liquors, alkaline earths, magnesia, carbonates and sulphites of" these bases ; (2) iron, manganese, zinc, oxids, hydrates, or carbon-- ates (natural or artificial) of these metals. Knublauch noticed that carbonic acid and sulphhydric acid did' not in any way interfere, and that even when these two gases were found in large quantity in the gaseous mixture, at the moment of passing through a solution containing both iron and an alkali, cyanogen forms with them ferrocyanide with so great an energy that the affinity of carbonic acid and hydrogen sulphide toward cyanogen is so weakened as to render the amount of hydrogen sul- phide absorbed insignificant. The gas should always pass through a liquid and not a solid mass,, and this liquid should be agitated during the passage of the gas, which passes through successively a series of absorption apparatus so arranged as to permit easy change of the order of succession. If, for example, a gas, such as illuminating-gas, containing, besides cyanogen, carbonic acid and hydrogen sulphide be passed into a solution containing a ferrous salt and an alkali, the precipitated ferrous hydrate, Fe(OH) 2 disappears almost wholly in the state of soluble alkali ferrocyanide, while only a small portion remains in. suspension in the liquid in the form of sulphide of iron. If an amount of iron greater than that of alkali be used, an insoluble cyanide is formed. The amount of absorbent material to be used for a definite weight of cyanogen depends on the nature of these materials, and the proportions naturally vary as one uses mono or bivalent bases, 232 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. hydrates or carbonates, natural or artificial products. In general, for every molecule of hydrocyanic acid, a molecule of alkali, of alkaline earth, hydrate or carbonate, and somewhat less than a molecule of iron compounds should be used. The quantity of liquid used should at least be sufficient to allow the gas to bubble through. Knublauch's method has received but few trials in England. Its want of success was due not to the results which it yielded but to the lack of interest shown by the manufacturers, at the time of its appearance, for the direct recovery of cyanogen. Gasch's Process. The process of Robert Gasch of Mainz (patent No. 201377, Dec. 24, 1889) consists in using recently precipitated me- tallic sulphides, which with the cyanogen of the gas form a ferrocya^ 'nide. The indispensable condition is the presence of ammonia, which condition is found in illuminating-gas. The higher the temperature the more rapid and complete is the conversion. It is instantaneous at from 50 to 60. The action of the heat may be suppressed when the reaction is well begun, and this can be done by adding a cyanide precipitate obtained from a cyanide solution coming from a previous operation. The operation is carried on by means of ordinary washers, or by the means of vertical boilers, which allow intimate contact of the gas with the absorbent materials, and this apparatus is so placed that the gas which passes through it has a temperature not exceeding 36, a temperature at which sulphocyanides begin to be formed. According to the author of this process, its advantages are as follows : (1) An increased yield in ammonium ferrocyanide. (2) High concentration and purity of the cyanide liquors under a form suitable for further treatment. (3) The only impurities are a- small amount of ammonium and potassium sulphides. Gasch recommends, moreover, the use of liquids holding in sus- pension a metallic sulphide such as iron sulphide, to which is added a milk of lime, and having in solution a soluble salt (oxalate or sulphate of alkali, an ammonia salt, sulphate of magnesia, aluminum, iron, etc.). If, for example, a solution of sodium sulphate be used to which MANUFACTURE OF FERROCYANIDES. 233 is added a milk of lime and having in suspension sulphide of iron, a weak solution of sodium ferrocyanide will be obtained contain- ing more or less sodium sulphide and a deposit of sulphate of lime and sulphide of calcium, both insoluble. Rowland's Process. This process (French patent No. 218215 r March 21, 1892) consists essentially in having the ammoniacal liquors of the scrubber absorb the whole or greater part of the cyano- gen. For this purpose Rowland adds an iron salt to the water of the scrubber in suitable quantity, but not in such quantity that iron sulphide will be formed. The optimum amount is 5.5%. Ammonium ferrocyanide is formed which remains in solution. After the addition of a fresh quantity of salt or oxid of iron, the ammo- niacal liquors are distilled, the addition of iron converting the ammo- nium ferrocyanide into double ferrocyanide of iron and ammo- nium, which is insoluble and may be separated from the liquor by adding milk of lime and filtering. The filtered solution is heated to boiling and sulphate or chloride of potassium is added, thus form- ing a double ferrocyanide of potassium and lime. The same result may be obtained by acidifying the liquor and boiling. The double ferrocyanide of potassium and lime is treated with potassium car- bonate, which on ignition converts it into alkali ferrocyanide and carbonate of lime. A strong solution is made and allowed to crys- tallize. Fowlis' Process. Fowlis of Glasgow has patented a process (English patent No. 9474, May 18, 1892) which is similar. The gas, previously freed of ammonia, is passed through a solution of potas- sium or sodium carbonate containing oxid of iron (Fe20s) or car- bonate of iron in suspension. This solution is prepared as follows: To 25 liters of a solution of ferrous chloride (FeCb), containing 150 grams Fe per liter, is added a solution of 7.5 kg. carbonate of sodium at 98 in 150 liters water. Carbonate of iron is precipitated, the solution of sodium chloride is decanted, and the carbonate of iron is put in suspension in a solution of 13.5 kg. of carbonate of sodium in 200 liters of water. The 13.5 kg. of carbonate of sodium may be replaced by 17.5 kg. carbonate of potassium. A scrubber provided with several horizontal plates is best suited for this opera- tion. These plates are perforated with numerous small holes, upon which rest tubes covered with a cap forming a hydraulic closing, 234 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. as in the distillation columns. The absorbent mixture, contained in a cylinder which is provided with stirrers, flows regularly or in ;an intermittent manner into the scrubber. It comes to the tubes, falls from one compartment to another, and finally flows through ;the lower part of the apparatus. In circulating in this way it meets the gas, which flows in the opposite direction, the cyanogen of the gas being thus removed. The ferrocyanide solution is evaporated to dryness, the tar and other impurities accompanying it being easily removed by redis- solving. The clear solution is concentrated and allowed to crys- tallize. Speaking concerning Fowlis' process before the English Gas Congress in 1896, Charles Hunt stated that he produces a solution of sodium ferrocyanide which on concentration and crystallization gives 75% sodium ferrocyanide. One must acknowledge that that is already a splendid result setting well in relief the profit which may be gained by the direct extraction of cyanogen from gas. Claus and Domeier's Process. This process (1895-96) is but a modification of Fowlis' method. These investigators first pre- pare an absorbent material by fusing a mixture of iron or oxid of iron, sulphate of sodium or potassium, and charcoal. The product of fusion, taken up with water, yields a grayish-black substance, slightly soluble, being a compound of iron and the alkali metal Fe 2 Na 2 S3. This substance is suspended in water and placed in a series of washers, into which the gas, previously freed of ammonia, passes. Ferrocyanide and sulphocyanide of sodium are formed. This process does not form much of the latter salt. Schroeder's Process. Schroeder proposes to collect all the cya- nogen compounds into the ammoniacal liquors (French patent No. 281456). To the waters which are used in absorbing the ammonia, ferrous chloride is added. When the gas passes through this solu- tion, the ammonia of the gas forms a precipitate of iron hydrate, Fe(OH)2, and ammonium chloride; then the hydrogen sulphide . converts the hydrated oxid of iron into sulphide of iron, which remains . suspended in the absorption waters with oxid of iron; these are dissolved by the ammonium cyanide of the gas, which converts ..them into ammonium ferrocyanide. The liquid is distilled in the presence of milk of lime, the ammonia MANUFACTURE OF FERROCYANIDES. 235 being thus recovered. Calcium ferrocyanide, slightly soluble, is in part precipitated. To obtain the calcium ferrocyanide still in solution a current of gas freed of ammonia and cyanogen is con- ducted through the solution, the carbonic acid precipitating the lime. The small amount of calcium ferrocyanide still remaining in solution may be precipitated as Prussian blue by means of a solution of iron perchloride. The precipitate, consisting of cal- cium ferrocyanide, Prussian blue, and carbonate of lime, is then heated to boiling and treated, with constant stirring, with potassa or potassium carbonate so as to convert the calcium ferrocyanide and the Prussian blue into potassium ferrocyanide, which, being soluble, may be separated from the insoluble carbonate of lime by filtration. The filtered solution is then concentrated and allowed to crystallize. Teichmann's Process. This process is also based on analogous reactions (French patent No. 290265, June 28, 1890), but instead -of using the chloride, this investigator uses the sulphate of iron, and in case of need he employs zinc solutions. In using iron sulphate in the washers, this salt becomes at once converted, by means of hydrogen sulphide and ammonia, into iron sulphide and ammo- nium sulphide. Then the cyanide of ammonium acts on the iron sulphide, yielding ammonium ferrocyanide. The greater portion of the cyanogen thus goes into solution, while a small part of it remains insoluble in the form of cyanide of iron. Sulphide of iron dissolves just as fast as ammonium cyanide is absorbed, and by repeated additions of a solution of iron sulphate, solutions containing a high percentage of ammonium ferrocyanide may be obtained. The absorption apparatus may be inserted between the tar extractor and the apparatus used in absorbing the ammonia. With- out fear of obstruction, the ordinary scrubbers or the standard washers may be used. But, when working on a large scale, it is best to place the iron solutions in the washers. The solutions of ammonium ferrocyanide obtained may be pre- cipitated by means of calcium chloride. The reaction is the same when zinc salts are used. The pre- cipitated zinc sulphide is converted by the ammonium cyanide into the double cyanide of ammonium and zinc and ammonium sulphide. 236 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. By the addition of other zinc salts to the solution of the double cyanide, zinc cyanide may be precipitated which may be converted directly into potassium cyanide. Lewis* Process. The last process to be mentioned in this class is that by Lewis (Moniteur Industriel, 1897, Nos. 26 and 27). This is based likewise on the affinity which cyanogen or hydrocyanic acid has for sulphide of iron held in suspension in an alkaline solution, the object of the process being to obtain a ferrocyanide. Lewis recommends that the process be carried on as follows: The sulphide of iron is produced by precipitating an iron salt by means of a. liquid prepared with the waste gases in the treatment of ammonia. The sulphide of iron is held in suspension in a specially con- structed washer, containing an alkaline solution in which is an excess of soluble iron. The washer should be so constructed as to aljow intimate contact of gas with the suspended iron, and to avoid the formation of a modified ferrocyanide, K 7 Fe(CN)i 2 , which is less stable. The ammonia should be removed as thoroughly as possible from the gas before the latter be allowed to enter the washer, since the acids of the fixed ammoniacal salts, e.g., ammonium chloride, forms, with the alkali, an alkaline chloride which contaminates the product obtained. By working carefully and with an efficient system of washers the reaction should theoretically be as follows: 2C0 3 K 2 + FeS + (CNH) 6 = K 4 Fe(CN) 6 + H 2 S + 2C0 2 + 2H 2 0. But in reality, as Lewis has stated, there are formed complicated and involved inter-reactions. That is the chief defect of all the processes which have been reviewed. Their perfect operation depends on numerous conditions chemical as well as mechanical or physical, which influence the results to a very large extent, and unless great care and many pre- cautions be taken in operating these processes, they will be far from being successful. Moreover, these processes all have the disadvan- tage of producing but very dilute solutions most of the time, and the cost of treating such large quantities of liquids is heavy. These MANUFACTURE OF FERROCYANIDES. 237 are the reasons why these methods have received but limited trials,, and have never been applied on a large scale. Bueb's Process. The process invented by J. Bueb, several years ago, is entirely different. This process, now in operation by the Deutsche Continental Gas Gesellschaft of Dessau, has thus far produced very favorable results. This method will be studied somewhat more at length, because it is at present in operation, and because of all the methods for the direct extraction of cyanogen from gas this is almost the only one which deserves to be kept in mind. In fact, the reactions utilized by Bueb are those mentioned in the processes of Knublauch and others, but with this difference, that instead of ' seeking to produce a soluble f errocyanide Bueb produces an insoluble compound. The principle of this process consists in bringing the gas, pre- viously freed of tar, into intimate contact with a saturated solution of sulphate of iron. The ammonia of the gas, playing the role of the alkalis, used in the other processes, a compound of iron, cyano- gen, and ammonium is formed, which separates in the form of a light mud. In practice, the operation takes place in an apparatus specially constructed by Bueb on the same principles as the standard washers, with this difference, that instead of flowing automatically into the apparatus the washing liquid passes, at definite intervals, from one chamber to another by means of a pump near the washer. The sulphate of iron solution, previously prepared in a special mixer ^ is pumped into the last of the four chambers, then from this one to the one preceding, and so on to the first chamber. The cyanogen muds, obtained in the first compartment of the washer, are col- lected into a forged iron reservoir or into a special vat, to be trans- ferred to suitable vessels if they are to be sold as such, or to be latertreated in the works itself, according to processes which will be mentioned further on. The first three compartments are provided with revolving discs similar to those of the standard washers, while the fourth has a stirrer, the object of which is to avoid the thickening which takes place in this chamber. As these cyanogen muds obtained by this process contain appre- ciable amounts of ammonia they may be treated for the extrac- 238 METHODS OF MANUFACTURING CYANIDE COMPOUNDS tion of this product, especially if the works have a plant for their treatment. To this end the muds are heated to boiling by means of direct steam in boilers provided with stirrers. The gas thus liberated passes into a cooler where the ammonia condenses whereas the sulphide vapors are conducted into a purifier. The residue is subjected to the action of a filter-press in order to separate the solution of ammonium sulphate from the insoluble cyanogen product. The ammonium sulphate solution which flows from the filter is concentrated and allowed to crystallize. The insoluble residue, which is a blue mass containing about 30% Prussian blue (44% ferrocyanide of potassium), and 4% ammonia, is put in tuns or sacks and sold as such. In communications made to two successive annual Congresses of the German Gas Industries (Kassel, 1899; Mainz, 1900) Bueb gives the following details concerning the working of his process: The concentrated solution of iron sulphate introduced into the last compartment should show about 20 B. (That is, should contain 28% FeS0 4 + 7H 2 0.) In this compartment, which is that of the gas outlet, the gas contains only traces of cyanogen, but contains ammonia and hydrogen sulphide, which, coming in con- tact with the iron sulphate, converts it completely in 6 to 10 hours into sulphide of iron and ammonium sulphate: FeS0 4 + H 2 S+2NH 3 =FeS + (NH 4 ) 2 S0 4 . On reaching the other compartments this solution of ammonium sulphate, holding sulphide of iron in suspension, meets the gases which are richer and richer in cyanogen and ammonia, and these two bodies reacting on the sulphide of iron form with it an insoluble double salt (NH 4 ) 2 Fe(CN) 6 , while hydrogen sulphide is set free, and is carried out of the washer, or remains in part in the product of the reaction in the form of ammonium sulphide: 2FeS+6CN.NH 4 = (NH 4 ) 2 Fe(CN) 6 +2(NH 4 ) 2 S. This reaction is finished completely in the first compartment of the washer. The reaction in its various stages may, moreover, be followed by the coloration of the absorbent material. In the last compart- ment, which contains the ir^n solution, the liquid is black; it becomes MANUFACTURE OF FERROCYANIDES. 239 lighter in the others, and in the first it is greenish yellow. The cyanogen mud which results from this operation contains an amount of cyanogen equal to 18.2% of potassium ferrocyanide (Fe(CN) 6 K 4 +3H 2 0) and to 12.2 to 13.5% of Prussian blue, besides j6 to 7% of ammonia, an amount which represents about one third of the ammonia obtained hi gas-works. If some double salt still remains in solution it may be made insoluble by simply boiling and without the addition of any reagent. The yield by this process is 95% of the cyanogen, but the results depend much on the kind of coal used. The English coals are those which contain the most cyanogen. They yield 7.4 grams of potassium ferrocyanide (Fe(CN)6K4+3Il20) per cubic meter of gas. In a plant where a mixture of English and Upper Silesian coal is used 5.3 grams are extracted per cubic meter of gas. In another works using a mixture of English and Westpha- lian coal the yield was 5.6 grams. The coals of the Saar give a yield of 4 to 4.5 grams; those of the north of France 4 to 5 grams; those of the east 4 grams; in general the minimum is 3.5 grams and the maximum is 8 grams. Furthermore, Bueb's process allows a very simple removal of hydrogen sulphide. Cyanogen possessing the property of decom- posing the sulphide of iron recently formed by setting hydrogen sulphide free, it is evident, as Bueb points out, that this property would thwart the absorption of hydrogen sulphide by the purifying materials, which, according to the old processes, should play the double role of absorbing cyanogen and hydrogen sulphide. There- fore, purifying materials are obtained containing 50-60% of sulphur. Bueb has, moreover, observed that his process gives a larger yield the warmer his gas is, that is, that the gas is cooled less before it passes through the absorption apparatus. For this purpose instead of placing the coolers, as is usual, before the cyanogen sepa- rators, Bueb places them next to these, i.e., between them and the scrubbers. In this way a smaller amount of ammonia remains in the cyanogen absorption apparatus, and because of this the yield in cyanogen compounds is again increased. Another advantage of this new arrangement is that at the high temperature at which the gas is kept the last traces of tar and naphthalene are easily 240 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. removed; and to this end Bueb places another vessel filled with: oil before the cyanogen 'absorption apparatus and connected with it. This oil, being heated by the passing gases, absorbs more easily, at this temperature, a larger amount of tar and naphthalene. Bueb's process marks a real progress in the extraction of cyanogen from gas, even considering only the results obtained: Thus in the dry way only 50-60% of the cyanogen present in gas could be extracted in well-conducted operations, while by this new process the yield is quantitative. Moreover, the cyanogen may be recovered in a very practical shape, since these products are obtained in such concentrated form as to warrant the expense of transportation, provided the gas-maker does not care to convert them into cyanide. A. Smits of Amsterdam, without knowing beforehand the inves- tigations of Bueb, in an interesting communication to the Inter- national Congress of Gas Industries in 1900, confirms the results obtained by the latter at Dessau by his own experiments made at the gas-works at Amsterdam according to a process similar to that of Bueb. Smits mentions here the reasons which led him to absorb hydro- cyanic acid in the presence of ammonia (loc. cit) instead of bring- ing the gas previously freed of ammonia in contact with a solu- tion of potassium carbonate holding a ferrous salt in suspension: "It is remarkable that generally the absence of ammonia has been considered as a condition indispensable for a good absorption of hydrocyanic acid. I suppose that we have been led into error by the following phenomenon: When illuminating-gas, coming in contact with the absorbent liquid, contains ammonia analysis shows a less amount of yellow prussiate of potash in the clarified solution, but after having again analyzed the black precipitate, which is always formed during absorption, it is easily proven that this precipitate contains a quantity of cyanogen which is proportional to the amount of ammonia which the gas contained, whence it follows that the total amount of hydrocyanic acid absorbed is in this case greater. " Now then, in this way an amount of hydrocyanic acid is obtained, which would be lost during absorption in the ammonia apparatus. " Again, the presence of ammonia helps the formation of an in- soluble cyanide, and that is the reason why a smaller amount of MANUFACTURE OF FERROCYANIDES. 241 yellow prussiate of potash ie formed in the liquid in the presence of ammonia." " Those are the reasons which led me to suppose that the place where hydrocyanic acid was being absorbed was badly chosen." Starting with these facts, Smits sought to absorb the hydro- cyanic acid by means of a ferrous sulphate solution at the exit of an apparatus where the gas still contains large quantities of am- monia, and like Bueb, he was able to prove that the yield was quant ative. Thus, as may be seen, the problem of the direct extraction of cyanogen from illuminating-gas is really simple, and at the same time profitable, since it permits the extraction of this cyanogen almost in its entirety. Feld's Process. Finally shall be mentioned the process for the direct extraction of cyanogen from gas, just recently patented by Feld (French patent No. 317382, Sept. 1901), and which certainly does not lack in originality. It consists in absorbing the cyanogen in such form that it may then be recovered by simply heating to boiling, in the state of pure hydrocyanic acid, which may then be absorbed by ordinary reagents whereas the impurities of the gas are either previously removed or are in great part unabsorbed. Feld divides the substances capable of absorbing cyanogen under these conditions into three groups : First group. Basic or carbonated compounds, which in aqueous solutions, or in suspension in water or salt solution, absorb hydro- cyanic acid, and afterwa d give it off on boiling. These are com- pounds of magnesium, aluminium, zinc, manganese, and lead. They may further be divided into three subgroups: (a) Those which absorb CNH and C0 2 and leave H 2 S. These :are basic compounds of magnesium. (6) Those which absorb CNH, but neither C0 2 nor H 2 S. These are the basic compounds of aluminium and magnesium carbonate. (c) Those which absorb CNH and H 2 S but not C0 2 . (Basic compounds of zinc, manganese, and lead.) Second group. Compounds which in basic, neutral, or acid solution, or in suspension in water or in saline or acid solution, absorb hydrocyanic acid, and give it up completely on boiling only 242 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. in the presence of acid. To this group belong the compounds of copper, mercury, and the ferric and ferrous salts. The iron com- pounds give up the hydrocyanic acid completely only when they are not intermixed. Third group. Compounds which when hot even in basic solution or in suspension in water, and in the presence of salts of the first group, do not absorb hydrocyanic acid, but decompose hydro- sulphuric acid. In this group are included ferric and ferrous salts either separate or mixed. B. EXTRACTION OF CYANOGEN COMPOUNDS FROM THE AMMONIACAL LIQUORS OF GAS. As we have seen at the beginning of this chapter, the ammoniacal liquors contain a certain amount of cyanogen in the form of ferro- cyanide and sulphocyanide of ammonium. The amount of the former varies, on an average, from 150-180 grams, calculated as Prussian blue, per ton of coal. The amount of ammonium sulpho- cyanide present in ammoniacal liquors is quite variable, and depends much on the length of time they have been stored. Thus, in the same liquors, Lewis found 1.76, 3.5, and 4 grams sulphocyanide at intervals of one month. Generally one ton of spent gas-liquors r that is, having been subjected to distillation of ammonia, yields, on. an average, 6 kg., of ammonium sulphocyanide. Formerly the operation was carried on as follows: After the gas-liquors had been distilled in the presence of lime in order to recover the ammonia, they were allowed to stand, and to the clear solution were added equal amounts of copper sulphate and iron sulphate. Copper sulphocyanide was thus formed, which was decomposed by means of ammonium sulphide with formation of ammonium sulphocyanide (Spence's process). Later the ammonium sulphide was replaced by barium sulphide. Pendrie's Process. The object of this invention (French patent No. 189648, March 28, 1888) is to recover the cyanogen compounds of the ammoniacal liquors in the form of Prussian blue. The residues, after the distillation of the ammonia, are allowed to stand until clarified and then decanted. Ordinary sulphuric acid is then added to acid reaction in order to remove any hydrogen MANUFACTURE OF FERROCYANINES. 243' sulphide contained therein. A portion of the hydrogen sulphide is set free, another portion is decomposed. The whole is allowed to stand 24 hours, during which the sulphur and sulphate of lime settle. The solution is decanted, and to the liquid is added a suit- able quantity of a ferric salt, Prussian blue being precipitated This may be converted into potassium ferrocyanide, after having first decanted the solution, and allowing the Prussian blue to stand in contact several days, with a lye made of caustic potash or potas- sium carbonate. Bower's Process. Bower (German patent of Dec. 23, 1895), recommends the precipitation of ferrocyanides and sulphocyanides, by means of a copper salt in order to form insoluble ferrocyanide and sulphocyanide of copper. A mixture of these two salts, when treated with iron, yields on the one hand insoluble ferrocyanide of iron, and on the other soluble sulphocyanide, which may there- fore be easily separated. In practice Bower recommends carrying on the process as follows: Before distilling, the ammoniacal liquors are treated with mag- netic iron either alone or with the addition of an iron salt, in suffi- cient quantity to convert all the cyanogen into the form of ferro- cyanide and sulphocyanide of iron. The liquors are then distilled in the presence of quicklime in a boiler provided with a stirrer. The residual liquors, containing* ferrocyanide and sulphocyanide of calcium, are then treated with a solution of cuprous chloride in sufficient quantity to precipitate the whole of the cyanogen compounds as insoluble salts. The precipitate is collected, washed, and, while still moist, treated with finely divided iron. The iron replaces tne copper, yielding insoluble ferrocyanide, and soluble sulphocyanide. These ara separated by filtration. The ferrocyanide of iron is then treated at the boiling-point^ with an alkali, in order to obtain a soluble alkali ferrocyanide, which is purified by crystallization. The solution of sulphocyanide is. concentrated and allowed to crystallize. Lewis' Process. Somewhat different is the process of Lewis and Cripps (English patent No. 5184, March 7, 1896), the method of procedure of which is as follows: After distilling off the ammonia by the usual method with lime, the residual liquors contain the 244 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. ferrocyanide and the sulphocyanide in the form of lime salts (CNS) 2 CaandCa 2 Fe(CN) 6 . This liquor flows from the stills into a suction reservoir whence a pump drives it to the top of a tower, filled with pieces of coke or brick, through which it filters, encounter- ing on its way down an inverse current of sulphurous acid and car- bonic acid, which is obtained by passing the waste gases of an ammo- nia distillation over a grate which burns the hydrogen sulphide and converts it into sulphurous acid. The action of this gaseous current neutralizes and acidifies the originally alkaline liquid. On emerging from the tower the acid solution flows into a long reservoir divided into two unequal compartments. The solution first comes to the larger compartment where it is treated with a solution con- taining ferrous and ferric salts in order to precipitate the ferro- cyanide as Prussian blue. The liquid passes from one compart- ment into the other, thus allowing the Prussian blue precipitate time in which to settle. The supernatant liquid then flows into a special reservoir, there to be treated with a view to the recovery of the sulphocyanides. For this purpose a copper sulphate solution is added to the liquid, there being formed an insoluble white precipitate of cuprous .sulphocyanide: Ca(CNS) 2 +S0 3 H 2 +2CuS0 4 + H 2 =Cu 2 (CNS) 2 +CaS0 4 +2H 2 S0 4 . The previous treatment with sulphurous acid is absolutely necessary, otherwise there would be formed a partially soluble black copper sulphocyanide. The cuprous sulphocyanide precipitate is separated by decanta- tion and washed. It is treated with a solution of alkali sulphydrate which forms a soluble alkali sulphocyanide and an insoluble copper sulphide. The alkali hydrosulphate is likewise obtained by utilizing the waste gas of an ammonia distillation, these gases passing through a washer filled with a strong caustic alkali solution. When the copper sulphide is exposed to air and then treated with an acid, the copper salt employed in the precipitation is "revivified/ and may be used over again. MANUFACTURE OF FERROCYANIDES. 245 C. THE EXTRACTION OF CYANOGEN COMPOUNDS FROM THE PURIFYING MATERIALS OF GAS. The purifying materials which are used for the chemical purifica- tion of gas still constitute, in the works where the direct extraction of the cyanide compounds is not in operation (arid they are the larger number) , an important source of these products. As has already been seen, these materials contain almost the whole of the cyanogen formed during the manufacture of gas, and it has likewise been shown that the other impurities, especially hydrogen sulphide, are also absorbed therein. The composition of the purifying materials varies in different works and in different countries. Generally mixtures of lime and ferrous sulphate or oxid of iron are still used. In Germany and in Belgium, purifying materials are used on a large scale, composed entirely of artificial oxids of iron, especially the brown oxid, known under the name of limonite. The hydrated and moist oxid seems to be preferable for the absorption. Below the composition of two limonites is given: I. II. Holland. Belgium. Sesquioxid of iron 51 . 30 59 . 14 Alumina 1 . 17 0. 98 Lime and magnesia 1 . 63 . 59 Silica 4.97 5.23 Organic substances 26 . 26 19 . 64 Water 14.02 15.13 Loss and undetermined 0. 63 1 . 09 These purifying materials are converted, on account of the passage of gas through them, into sulphur, sulphide of iron, ferrous ferrocyanide, sulphocyanide of iron, etc., and the moment neces- sarily arrives when they become inactive. In order to revivify them they are spread out on a flat surface, where they are constantly stirred with a shovel. The oxygen of the air converts the inactive sulphide of iron into the active oxid and sulphur, and the ferrous ferrocyanide into Prussian blue. The same mix- ture may be revivified several times, the result being that an appre- 246 METHODS OF MANUFACTURING CYANIDE COMPOUNDS. ciable part of the oxid of iron becomes converted into Prussian blue (which may be recognized by the greenish-blue color which the materials assume) and the sulphur accumulates in such quan- tities (30 to 40%) that the mixture no longer exerts any purifying action. It is hi this 'state that it is known as spent oxid, which is immedi- ately treated or more generally sold to manufacturers of Prussian blue or of prussiates. Its composition varies naturally according to a great many circumstances: kind of coal distilled, method of distillation, the composition of the purifying materials, the degree of fineness of the same, the method of revivification, etc. According to Esop, the sulphocyanic content varies from 0.39 to 4.25%, the potassium ferrocyanide from 3.02 to 4.58%, the ammonia from 0.49 to 4.38%. Below are given some analyses of purifying materials. ANALYSES OF SOME SPENT OXIDS. LAMING MIXTURE. Sulphur 41.79% Prussian blue 7.37 Sulphocyanic acid 3.01 Hydroferrocyanic acid 1.01 LUX MASS. Sulphur 40.75% Prussian blue 3.08 Ammonium sulphocyanide 5. 14 Ammonia 2. 23 NATURAL OXID OF. IRON. I. II. Sulphur 30.58% 30.03% Prussian blue 6.30 8.62 Ammonium sulphocyanide 4.08 2. 12 Ammonia 0.41 1.30 Formerly the spent oxids were considered as useless residues, but manufacturers have learned how to derive benefit therefrom, MANUFACTURE OF FERROCYANIDES. 247 CO TH 9 Tf TH *" 3 3 CN i> S R ^. rH S3 | 1C CO ^ TH rH rH CO 1-1 rH 3 3 3 3 3 3 3 3 O -r=> O 1 jo CO C5 8 8 S a s rH 8 C^ s? 10 TH & * rH H g 00 TH s S ^ (N ^ g j*s J^. Oi 0 U-i "*? co TH Q? J'a 3 3 g O -J 3 3 O +3 3 o -4-3 || 3 ^ -M - i CO S ^ M Oi Ci rh 00 !> O5 N. r-t D Ci CO CO !> CO CO O rH CO l> Tt< O5 CO O CO Ci O5 .-I I> CO CO C5 tO '*"**"* I -I ^ " I 1-1 (N iCCO COTt< T^ Oi OO 00 i-i 1 1 1 1 1 1^^^^8^^'g^ ISS \%%%% | +++++ i +++ + ++++ 00 10 CO '^^\ I II 1 1 1 1 1 1 1 1 1 1 1 I II I I + I + IO IO i-H i-l 1-H COI>i-I T H^^iOtOO5COCOi-irHOi O5rt< T* l> CO COr-H t> Oi t>i-H AV 4^^ ^, I i I T-H I O^ Oi ^H t>- ^^H0 eq CC^HOOt- i-H l-H I ' I ' I + O* CO CO CO .T}* &R is ^H CO ' i-( 1 1 r- CD O CO rt< O5 O 00 O CO 1C 00 (N O rfi CO (M O CO CO CO CO iO ' t^T-iO 1> | 00 ICOT^T-IOCCIO |lCr-*rHC^ ++++++ 1 1 1 1 1 1 1 1 1 1 1 I i ! OiOOcO ^^^' I I I I I I + I ' + 02 rr> & & & & ^>> ^o-M55^5 t S^? + ^ + + + +00 ^ + + + + + + + +,+ + + + + asal P -- i^miillli jinliiijilr ' CONCLUSIONS. 327 1 .s5 o .a- 1 1i !i 02 <- Q fc I 2 j3 ^OJ S ,O ^ >> 3 - T! ^ W) S rf I l.s l. a H *^ ^^ rH ,-g ^ fl cr -2-^ ^ :-8 ; & '- o, !llli.LJI ! ^ rj 3 (w O) B B*S O O .2 ^ ^ 'Scs s si 328 CONCLUSIONS. Fe g, -3 III! n s .| | .-.iji II 11 rdy precipi excess tB a .s l-S-9^ 5 S-e' l CONCLUSIONS. 329 DEGREE BAUME. WHICH BOILING SALT SOLUTION SHOULD INDICATE SO AS TO PRODUCE BEAUTIFUL CRYSTALS ON COOLING. Mercury cyanide 20 B. Potassium ferrocyanide 38? " Ammonium sulphocyanide 18 " COOLING MIXTURE. A mixture of Ammonium sulphocyanate 133 Water 100 produces a lowering in temperature of 31 (Ruddorf). FORMATION OF DISSOLVED SALTS, DISSOLVED ACID, DILUTE BASE. 4KOH +54.0 cal. ,, n 2BaO. +56.0 " FeCy 6 H 4 dissolved^ ^^ ; +4g g |Fe 2 3 ppt +25.2 " Fe 2 Cyi 2 H 6 dissolved +6KOH +58.0 " fKOH. .../. +14.0 " CySHdissolved + ( ^ +12 5 M HEAT OF COMBUSTION. C 2 + N 2 , 262.5 cal. C + N + H 158.0 cal. (gas) DENSITY OF SOLUTIONS. POTASSIUM FERRICYANIDE. Density. .0261 .0538 .0831 .1139 .1462 .1802 Per Cent. Potassium Ferricyanide. 5 10 15 20 25 30 POTASSIUM SULPHOCYANIDE. Density. .020 .026 .031 .034 .042 .050 .070 .077 .137 Per Cent. Potassium Sulphocyanide. 7.0' 10 11.1 12.5 14.2 16.6 20 25 33.3 330 CONCLUSIONS. DENSITY OF SOLUTIONS. HYDROCYANIC ACID. Density. Per Cent. CNH. 0.9988 1 0.9974 2 0.9958 3 0.9940 4 0.9919 5 0.9895 6 0.9869 7 0.9840 8 0.9811 9 0.9781 10 0.9716 12 0.9570 16 POTASSIUM FERROCYANIDE. Density. Per Cent. Potassium Ferrocyanide. .0116 2 .0234 4 .0356 6 .0479 8 .0605 10 1.0734 12 .0866 14 .0999 16 1.1136 18 1.1215 20 AMMONIUM SULPHOCYANIDE. Density at 15. Per Cent. CNS . NH* .020 10.0 .026 11.1 .031 12.5 .034 14.2 .042 16.6 .050 20.0 .070 25.0 1.077 33.0 1.137 50.0 APPENDIX. DIGEST OF UNITED STATES PATENTS RELATING TO CYANIDE PROCESSES FOR THE RECOVERY OF PRE- CIOUS METALS .* THIS digest covers most of the patents included in the following classes and subclasses of the United States Patent Office classification: Class 75. Metallurgy. Subclass 18. Solutions and Precipitation. Subclass 86. Solutions and Precipitation Apparatus. Subclass 185. Cyanides. Class 204. Electrolysis. Subclass 15. Aqueous Bath, Ores. Some of the patents in these categories are quite foreign to the subject under consideration, and many but indirectly related to it. It has been thought, how- ever, from the form which discussions of patent issues often take, to include the, latter. The aim in making the digest has been to give such a sketch as will indi- cate the nature of the invention and what is claimed by the inventor, this gen- erally being done by an acttial abstract from or paraphrase of the words of the letters patent, but no responsibility is assumed for the opinions, theories, or claims thus set forth. Other related patents may have been granted which do not appear in this digest, because they are not embraced in the subclasses enumerated. Thus, the patents number 229586, to Thomas C. Clark; 236424, to H. W. Faucett; and 244080, to John F. Sanders, do not appear in this digest, because the first two are classified under subclass " Reducing and Separating Disintegrating Ores," and the third under subclass " Reducing and Separating Gold and Silver J1 and neither of these subclasses is included in this digest. CLASS 75. METALLURGY. SUBCLASS 18. SOLUTIONS AND PRECIPITATION. 1551,2 August 12, 1856. W. ZIERVOGEL. Improvement in processes of separa- ting silver from the ore. The application of water or a solution of sulphate of cop- per slightly impregnated with sulphuric acid instead of lead, quicksilver, or salt, hitherto used for this purpose, to the process of separating silver from copper and other ores, rendering thereby this separation easier, shorter, less expensive, and not noxious to the health of the operator. * Reprinted from " Precious Metals Recovered by Cyanide Processes " by Charles E. Munroe, Ch. D with the kind permission of the Department of Commerce and Labor. 331 332 APPENDIX. 19991 April 20, 1858. I. GATTMAN. Improvement in the treatment of sul- phureted ores. The use of sulphuric acid in connection with the hydrate, car- bonate, or sulphate of potash or soda, or with any compound thereof, in the mode of working the native metallic sulphurets. 3584.2 July 8, 1862. J. SHAW. Improved apparatus for saving silver from waste solutions. Attaching to the waste pipe of the sink or basin into which per- sons using silver in solutions suffer them to be wasted, a vessel so arranged and constructed that the liquids passing from the sink shall run into, through, and out of said vessel, and between the time of entering said vessel and escaping there- from shall be brought into contact with such chemicals or metals as will cause the whole or any part of the silver contained in solution to be precipitated and retained in said vessel, while the worthless material is allowed to escape. (This patent was reissued as follows: Reissue 1651, April 5, 1864; reissue 3506, June 15, 1869; reissue 4030, June 14, 1870; reissue 4969, Division A, July 9, 1872; and reissue 4970, Division B, July 9, 1872.) 46875 March 21, 1865. W. BRUCKNER. Improved process for refining amal- gam. The application and use of bichloride of copper, or its equivalent, together with iron pyrites and salt, without reference to the exact proportions of each ingredient. 46983 March 28, 1865. G. W. BAKER. Improvement in treating ores. In order to produce a valuable metal or metals now almost wholly cast away in the treatment of auriferous and argentiferous pyrites, the inventor proposes to take the calcined ores as they come from the furnaces, and, having them weU pul- verized, subject them to the action of sulphurous acid in tanks located over the main discharge flues of his furnaces, whereby a sufficient heat may be obtained to assist in the reaction of the acid before mentioned. The sulphurous acid thus used is to be formed and collected by compelling the sulphurous vapors discharged from the roasting furnace to pass over, through, and in contact with water, so that sulphurous acid will be formed and collected in a properly arranged tank or tanks, from whence it may be conveyed to the ore tanks, and there mixed with the ore thoroughly by agitation in any manner most convenient. After the ore has been subjected to the action of the acid for a couple of hours the oxide of cop- per will be replaced by a sulphate soluble in water, and the oxide of iron will be partially brought into the same condition Should there be any gold or silver held in solution these metals will be reduced to the metallic state. The solution is then drawn off by siphon or otherwise and conveyed to another tank or vat for subsequent treatment, either by cementation or precipitation for the copper and evaporation for the sulphate of iron. The ore thus treated may then be lixiviated by water to wash out all the acid, and this water, which will still hold some dilute solution of the baser metals, may be conveyed to the acid tank and used for the further formation of sulphurous acid. By this means the most con- centrated solution is alone permitted to pass to the tank or vat for further treat- ment. It may be considered a well-settled fact that in all processes of calcina- tion some portion of the precious metals, if such ores are under treatment, escape mechanically or in a vaporized form. This loss, great or small, as the case may be, has heretofore been to a great degree irreclaimable. It is claimed as a part of this improvement that such loss, whether mechanical or in the form of vapor, is wholly prevented by arresting their escape and returning them, either in solu- tion or in the sediment of the liquid acid, to the ore when treated in the ore tanks. ? April 18, 1865. W. L. FABER. Improved process of working silver ores. The invention consists in a process which is divided in eight different manipu- lations, viz., smelting the ore, pulverizing, roasting at low heat, extracting sul- phates with water, roasting residue with salt, melting with soda, precipitating silver, precipitating copper. 49637 August 29, 1865. S. F. MACKIE. Improved process for treating ores. The mode of obtaining a rich gold residue from ores of gold by treating the ores by roasting and fusing, and subjecting the roast to the action of acids. 52834 February 27, 1866. J. H. ELWARD and J. L. HAYES. Improved process for separating gold and silver from ores. The process of oxidizing sulphurets con- PATENTS RELATING TO CYANIDE PROCESSES. 333, taining the precious metals and converting them into sulphates by the use of solu-. tions of nitrates. 56765 July SI, 1866. E. LAMM. Improved method of preparing gold for dentists. The use of saccharine substances to precipitate gold from its solutions, thereby forming a mass of crystal shreds extremely useful and convenient for dental and other purposes. 148356 March 10, 1874- J. DOUGLAS, Jr. Improvement in extracting silver from its ores. The process of utilizing the waste liquors of the ordinary ore-chlori- dizing process, by allowing the insoluble matters contained in said liquors to pre- cipitate, and then evaporating the clear supernatant liquid to obtain the soluble chlorides, which are reapplied in treating fresh ores. 207695 September 3, 1878. J. TUNBRIDGE. Improvement in separating metals from waste solutions. The process of separating precious metals from watery solutions, in which said metals are suspended by passing the watery solutions or puds through a bath of oil or hydrocarbon liquid. 219961 September 23, 1879. F. M. LYTE. Improvement in extracting metals from ores. In the treatment of ores containing lead, zinc, silver, and copper, the method of securing the neutralization of the solutions of soluble bases, economizing acid, and carrying over the least possible quantity of silver and lead, which con- sists in treating the raw ores with an acid solution partially saturated by previous attack on the ores, and treating the partially exhausted ore by raw acid before the latter is admitted to the raw ore, the said steps being conducted in a continu- ous, alternate, and methodical manner. 227963 May 25, 1880. W. M. DAVIS. Depositing gold from its solutions. The process of obtaining gold from its solution by bringing said solution in contact \/' with carbon, and thereby depositing the gold upon it, and of subsequently obtain- ing the gold from the carbon by calcination or other equivalent means. 287737 October 30, 1883. C. A. STETEFELDT. Process of treating sulphides. > The process of treating sulphides, such as those obtained from the lixiviation process of silver ores, said process consisting in first exposing said sulphides to the action of dilute sulphuric acid in the presence of nitrate of soda, then converting the nitric oxide which escapes into nitrous acid and nitric acid, and finally carrying on the process by means of a mixture of nitrous acid and nitric acid with dilute sulphuric acid. 288838 November 20, 1883. J. MILLER. Process of recovering metallic particles from water. The method of recovering metals in suspension in liquid, consisting, \ essentially, in forcing such liquid through a filtering medium having a capacity ^" of expansion, and resisted by a rigid inclosing vessel or medium, and then burning the filling material or otherwise separating the metal therefrom. 290258 December 18, 1883. J. MILLER. Apparatus for collecting and saving metallic particles. An apparatus for recovering metals or metallic compounds in X/" liquids, consisting of a rigid tank, perforated on one side, in combination with an entrance pipe, provided with a trap and a pressure device. 290458 December 18, 1883. J. MILLER. Method of recovering metals. The improved method for recovering metallic particles, slimes, and similar material containing metal from liquids, consisting, essentially, in conducting the liquid and metal-bearing material to a settling tank, allowing the gangue to fall to the bottom, drawing off the liquid, and forcing it under hydrostatic pressure through a filter press, and removing and drying the filtrate. 292605 January 29, 1884. C- P. WILLIAMS. Art of extracting gold by means of alkaline sulphides. In the art of extracting gold from ores and artificial gold- \f bearing products by means of alkaline sulphides, the process, which consists in mixing the gold-bearing material with carbon and an alkaline sulphate (or the equivalents of sucii carbon and alkaline sulphate), calcining said mixture in a non-oxidizing atmosphere at a temperature below the point of fusion of the charge, cooling the mass out of contact with the air, and leaching the cooled mass with water to dissolve out the soluble sulphides, and recovering the gold therefrom by- precipitation. 334 APPENDIX. 877809 February 14, 1888. T. KIDDIE. Process of separating precious metals and impurities from solutions of copper, salts, ores, mattes, etc., in acids. The process of removing precious metals and impurities from copper mattes, ores, bullion, etc., consisting in dissolving the same after desulphurization and calcination in sulphuric acid, in quantities sufficient to form a neutral solution, and in adding iron hydrates to the neutral solution, whereby the impurities are precipitated and settle with the precious metals not dissolved by the sulphuric acid, leaving a comparatively pure solution of iron and copper salts. 881809 April 84, 1888. R. OXLAND and C. OXLAND. Treatment of ores and materials containing sulphur for the extraction of metals and other constituents, The method of treating raw or unburned sulphuret ores of copper and iron to render the copper soluble in water, while leaving the iron for the most part insoluble and rendering the sulphur in the ore available for the manufacture of sulphuric acid, consisting in mixing the finely pulverized ore to a semifluid consistency with sul- phuric acid and solution of persulphate of iron, heating the mixture to a tem- perature such as to evolve sulphurous-acid vapor, and collecting and condensing isuch acid vapor. 887688 August 14, 1888. A. H. Low. Extraction of zinc from ores. The Srocess of extracting zinc from ores containing precious metals, consisting in leach- g the ore with an aqueous solution of sulphurous-acid gas to dissolve out the zinc, and then boiling the leached liquor to expel the sulphurous-acid gas and cause a precipitation of the zinc. 403615 May 21, 1889. E. H. RUSSELL. Process of leaching ores with hypo- sulphite solutions. The process of extracting metal from ores and metallurgical products, which consists in introducing into the ore or product carbonate of soda, then treating the mass with a solution of sulphate of copper, and then treating it with a hyposulphite solution. 413808 October 29, 1889. J. S. MACARTHUR. Process of leaching ores. The process of treating ores containing oxides or carbonates of earth metals, consist- ing in first subjecting such ores to the action of a proportionate quantity of a solu- tion of a ferrous salt or a bisulphate of an alkali to combine with the oxides or car- bonates of earth metals, and then treating the ores with an acid or salt to obtain the contained metals. [ February 11, 1890. R. PEARCE. Process of extracting silver from copper ores, mattes, and other copper products. The process of separating silver from ores or mattes containing base metals, which consists in mixing with the finely pulverized ore or mattes a quantity of sulphate of sodium or potassium / equal to 2 per cent., then roasting the mixture, and finally leaching out by hot water to obtain the sulphate of silver. 440143 November 11, 1890. E. DODE. Process of separating gold and plati- num from other metals in solution. The process of separating from an acid solu- tion of gold, platinum, copper, and tin the metallic constituents of said solution, which process consists in first subjecting the entire solution in the presence of ether to agitation until the ether becomes yellow, in then decanting the remaining solution from the yellow ether, in then subjecting said remaining solution to agita- tion in the presence of essence of lavender until the essential oil becomes brown, .. and in then decanting from the brown essential oil the remaining solution and e adding thereto ammonia. 442016 December 2, 1890. C. L. COFFIN. Process of treating ore containing lead, silver, and zinc. The process of treating ore containing lead, silver, and zinc to remove the zinc preparatory to smelting, consisting in first roasting the ore, then leaching the ore, filtering the leach fluid through carbon, then subject- ing the leach fluid successively to the action of metallic lead and of metallic zinc, and finally precipitating the zinc held in solution in the leaching fluid. 444997 January 20, 1891. W. WEST. Process of treating zinc ores. The process of eliminating zinc from complex ores, which consists in roasting the ore to form sulphurous-acid gas and oxidize the zinc, then cooling this gas to a tem- perature of 180 F. or below, and passing the same in gaseous form in conjunction with steam and without oxidation into sulphuric acid through a previously roasted OF THE UNIVERSITY PATENTS RELATING TO CYAN^T 335 charge to form soluble sulphite of zinc, and then immediately leaching out and separating the zinc sulphite with water at a temperature below 180 F. 449814 April 7, 1891. S. W. CRAGG. Lixiviation process of and apparatus for the extraction of gold or silver. The process of restoring the oxygen in a hypo- sulphite solution in the lixiviation process, which consists in passing a current of air through the ore pulp while the said solution is in contact therewith, and a leaching vat, a grating at the top thereof through which ore pulp and water are introduced to the interior of the vat, and a system of crossed separated bars within the vat through which the ore pulp and water pass, combined with an endless- apron filter on which the ore pulp and water fall from the said crossed bars, a,trough beneath the filter to receive the water, and a lixiviation vat into which the apron filter discharges the ore pulp. 471616 March 29, '1892. J. LEEDE. Process of treating refractory ores. The continuous process of treating refractory auriferous and argentiferous ores, which consists in subjecting the ore to the continuous action of an oxidizing blowpipe flame in direct contact with the ore at a moderate heat, intermittently subjecting the heated ore to the action of .water, agitating the ore, and then repeating the operation at a higher heat, and finally subjecting it to an oxidizing roast without chills, whereby the volatile elements are driven off, the oxidizable elements or compounds are oxidized, and the precious metals are left free and in suitable con- dition for amalgamation or chlorination. 473186 April 19, 1892. P. C. CHOATE. Method of producing metallic zinc. The process of producing metallic zinc from its ores, which consists in separating the zinc and the equally volatile and more volatile constituents from the less vola- tile constituents of the ore by the use of heat and a reducing agent, then volatiliz- ing and oxidizing the reduced metal, thereby obtaining a condensed oxidized fume, subjecting this fume to a moderate heat in order to expel its soluble con- stituents more volatile than zinc, treating the remaining product with dilute sul- phuric acid as a solvent, and finally subjecting the resulting solution to the action of an electric current to precipitate the zinc. 481499 August 28, 1892. G. T. LEWIS and C. V. PETRAEUS. Process of treating sulphide ores of zinc and lead. The process of recovering lead and zinc from sulphureted lead and zinc-lead ore, which consists in roasting the ore, then smelting the roasted mass* and exposing the fumes or volatile matter produced by said smelting to the action of the gases which are volatilized in the roasting of said ore, together with water, and then separating the zinc solution from the insoluble lead compound and recovering the zinc and lead. 483924 October 4, 1892. T. S. HUNT and J. DOUGLAS. Process of separating copper from cupriferous nickel ores. The method of separating the copper from a solution containing copper oxide and oxides of iron and nickel to produce nickel- iferous iron, which consists in first adding common salt to the said solution, then passing a stream of sulphurous-acid gas through the said solution, then precipi- tating the last traces of the copper in the form of metallic copper, and subsequently crystallizing out the nickel and iron and calcining and smelting the product to obtain nickeliferous iron. 483972 October 4, 1892. C. WHITEHEAD. Process of treating mixtures con- taining sulphides of precious metals and copper. The process of treating a mix- ture containing sulphides of the precious metals and of copper, which consists in mixing the sulphides with solution of a salt of silver, whereby a soluble salt of copper is formed and sulphide of silver is precipitated, separating the solution containing the copper from the residue containing the precious metals, roasting this residue to reduce the precious metals to the metallic state, treating the reduced metals with hot sulphuric acid to dissolve the silver, separating the silver solution from the residue, and melting the final residue. 490068 January 17, 1893. F. P. DEWEY. Process of treating mixtures con- taining sulphides : The process of treating mixtures containing sulphides of silver and copper, which consists in heating the sulphides with strong sulphuric acid to convert the sulphides into sulphates and dissolve the sulphate of silver, adding water, to bring the sulphate of copper also into solution, drawing off the resultant 336 APPENDIX. solution, precipitating the silver therefrom by metallic copper, and recovering the sulphate of copper from the remaining solution. 490193 January 17, 1893. A. FRENCH. Process of obtaining gold, silver, and copper from ores. In processes for obtaining gold, silver, and copper from ores, the treatment of the ores by pulverizing, mixing therewith small percentages of niter cake or bisulphate of soda and common salt, furnacing at a red heat, and then leaching. 497473 May 16, 1893. W. R. INGALLS and F. WYATT. Process of treating complex or sulphide ores. The process of treating complex sulphide ores, which consists, first, in subjecting the ore to a sulphatizing roasting; second, lixiviating the roasted ore with water and sulphuric acid and removing the iron therefrom if necessary; third, precipitating the zinc from said solution in the form of car- bonate or carbonate and hydroxide by the use of sodium carbonate and subse- quently converting the same into zinc oxide; fourth, evaporating the sodium sulphate obtained from the zinc sulphate solution and heating the same with sodium chloride and coal to convert it into sodium sulphide; fifth, converting the sodium sulphide into bicarbonate of soda by dissolving the same in water and treating the solution with carbonic acid gas; and lastly, converting the bicarbonate of soda into sodium carbonate by heating the same to drive off the hydrogen and car- bonic acid gas. 609058 November 21, 1893. E. WALLER and C. A. SNIFFIN. Method of concentrating ores. The method of concentrating argentiferous lead carbonate ores, which consists in dissolving out lead from the ore with the aid of acetic acid real or combined, and water, out of contact with the air whereby the lead and carbonic acid eliminated from the ore are rendered capable of utilization in the arts, and the undissolved silver is concentrated in the residue. 509633 November 28, 1893. D. K. TUTTLE and C. WHITEHEAD. Process of treating precious metal-bearing slimes. The process of treating precious metal- bearing slimes, which consists in subjecting the slimes to the action of dilute acids to dissolve the metals and oxides soluble therein and to the action of a solution of a salt of silver to remove metals more electro-positive than silver that are present in the metallic state. 509634 November 28, 1893. D. K. TUTTLE and C. WHITEHEAD. Process of refining slimes from the electrolytic refining of copper. The process of treating slimes from the electrolytic process of refining copper, which consists in removing arsenic, antimony, tellurium, bismuth, and other impurities present as oxides by treating the slimes with dilute acid and heating the purified slimes with strong hydric sulphate. 513490 January 30, 1894. S. H. EMMENS. Process of treating zinc-lead-sul- phide ores. The process of treating zinc-lead-sulphide ores carrying gold or silver or gold and silver, which said process consists in, first, finely comminuting the ore; second, roasting the same in an oxidizing atmosphere; thirdly, leaching such roasted ore with water containing ferrous sulphate; fourthly, leaching such once leached ore with an aqueous solution of ferrous and ferric sulphates; fifthly , leaching such twice leached ore with water containing ferrous sulphate; and sixthly , removing iron from the zinc sulphate solution obtained by the first and second of the said teachings by mixing such solutions together and heating them. 516016 March 6, 189 4. W. R. INGALLS and F. WYATT. Treatment of ores of zinc. The process of treating ores of zinc, which consists, first, in subjecting the ore to an oxidizing roasting; second, lixiviating the roasted ore with water and sulphuric acid; third, separating one-fourth of the zinc-sulphate solution thereby formed from the rest and precipitating the zinc from said separated por- tion by means of a sulphide of an alkaline base; fourth, evaporating the remainder of the zinc-sulphate solution to dryness and mixing the precipitated sulphide therewith; and lastly, heating the mixture in a suitable furnace whereby sul- phurous anhydride gas is evolved. 518890 April 24, 1894. L. KLOZ. Process of extracting zinc from ores. The process of treating zinc ores, which consists, first, in the preparation of a concen- trated solution of sulphurous acid; second, in leaching the ores or furnace products PATENTS RELATING TO CYANIDE PROCESSES. 337 with this solution to form a concentrated zinc sulphite solution free from sulphates; and third, scattering this solution by steam to dispel the sulphurous acid and precipitate the zinc sulphite. 527473 October 16, 1894. P. ARGALL. Cyanide and chlorination process for treating gold- or silver-bearing ores. In the process of preparing gold- and silver- bearing ores for the extraction of the precious metals, the improvement consist- ing in separating the slime from the granulated ore, preventing the forming of acid in the slime by mixing lime therewith, and then forming the mixture into lumps for burning. 541374 June 18, 1895. E. B. MIERISCH. Process of extracting gold and silver from their ores. The process of extracting gold and silver from oxidated or roasted ores, which consists in mixing the ground ores with sodium hydrate, mixed with a corresponding quantity of calcium hydrate, then subjecting the mixture to the action of chlorine, whereby the ores are acted upon by chlorates, and hydrochlorites formed "in statu nascendi," and then leaching the lye with a concentrated sodium- chloride solution, the deterioration of which is prevented by the addition of the calcium hydrate to the sodium hydrate. 541447 June 18, 1895. H. F. WATTS and A. COAN. Process of reducing zinc slimes. The process of treating zinc slimes containing the precious metals, which consists in first treating the same with dilute sulphuric acid for the pur- pose of removing metallic zinc, washing the residue to remove the soluble salts and the remaining acid, and boiling the residue thus formed with concentrated sulphuric acid to dissolve the cyanide of zinc and the other salts thereof which are insoluble in the dilute acid. 541659 June 25, 1895. J. J. CROOKE. Process of and apparatus for extracting silver from its ores. The process of extracting silver from its ores, which con- sists in roasting the ores with chloride of sodium, treating the roasted mass with a, hot aqueous solution containing chloride of sodium, nitrate of copper, and sul- phuric acid, and recovering the silver from the solution. 544499 August 13, 1895. H. BREWER. Process of utilizing waste lye. The process of treating zinciferous or cupriferous lyes resulting from the lixiviation of chlorinated roasted ores, which consists in chemically extracting the metals in the lye, except the zinc, removing the sodium chloride by concentration of the lye, extracting the zinc and chlorine from the remaining lye electrolytically, and effecting the chemical extraction in such manner that the final lye will consist essentially of a solution of calcium chloride. 544612 August 13, 1895. A. CROSSLEY. Process of manufacturing zinc. The process for the manufacture of zinc oxide, which consists in adding sulphuric acid to the metallic ores or compounds, heating the mixture and converting the lead present to an insoluble salt, and depositing any silver or gold present, then diluting with water and converting the other metals present to soluble salts, filtering off the clear liquor, then treating the clear acid liquor filtered off with an alkaline sulphi.de, precipitating the copper as copper sulphide, then filtering the liquor from the precipitate, treating with an alkali until neutral, passing chlorine into it until all manganese and iron present form manganic and ferric oxides, which are thrown down by a slight excess of alkali, adding an excess of alkali to bring the zinc oxide into solution, and then precipitating the zinc oxide, and filtering off the liquor therefrom. 547587 October 8, 1895. C. V. PETRAEUS. Method of extracting zinc from complex ores. The method of separating zinc from complex ores where it is found as a sulphate or sulphite, which consists in crushing the ore, roasting it, dissolving out the soluble zinc salts in water, adding a solution of sulphuric acid to dissolve out any zinc oxide, introducing live steam to the mixture of ore and solvents to thoroughly mix and heat them, separating the solution of sulphate of zinc from the insoluble parts of t'.e ore, adding chloride of calcium to the solution to con- vert the zinc into a chloride, separating the solution of zinc chloride from the pre- cipitated calcium sulphate and finally adding quicklime to the solution of zinc chloride to precipitate the zinc as zinc oxide. 556690 March 17, 1896. G. O. PEARCE. Process of extracting gold from solutions. The process of recovering gold and platinum metals from aqueous 338 APPENDIX. solutions of these metals, which consists in passing said solutions through a mass of vegetable carbon having associated with it sulphate of iron, oxalic acid, and tartaric acid. 559614 May 5, 1896. G. A. SCHROTER. Extraction of precious metals. The process of extracting precious metals, particularly silver, from ores and metal- lurgical products, which consists in leaching the crushed and chloridized ore with a concentrated solution of brine to which has been added a small per cent (one- half to 4 per cent, approximately) of a soluble salt of copper. 561544 June 2, 1896. F. P. DEWEY. Process of treating sulphides. The process of treating mixtures containing sulphides of silver and copper, which con- sists in heating the mixture with strong sulphuric acid, adding water, adding more mixed sulphides, separating the solution of sulphate of copper from the residue containing the sulphide of silver, and heating the sulphide of silver with strong sulphuric acid to convert it into sulphate. 561571 June 9, 1896. F. P. DEWEY. Process of treating mixtures containing sulphides. The process of treating mixtures containing sulphides of silver and copper, which consists in heating them to a temperature at which the sulphur is oxidized, in an excess of sulphuric acid sufficient to convert the sulphides of silver and copper into sulphates, and bring the sulphate of silver into solution outside of the mass of material treated, thereby oxidizing the sulphur, converting the sulphides into sulphates, and bringing the sulphate of silver into solution in the acid outside of the mass of material acted upon. 571369 November 17, 1896. B. HUNT. Process of refining gold and silver bullion. The process of refining bullion slimes by first roasting the slimes to decom- pose all cyanogen compounds and carbonaceous matters and then treating the roasted slimes with nitric acid. 586159 July 13, 1897. H. BREWER. Process of treating zinc sulphide ores. In a process of treating zinciferous sulphate lyes resulting from the lixiviation of chlorinated roasted zinc sulphide ores, adding sodium chloride to such lye to saturation or in excess, and crystallizing out the resulting sodium sulphate (Glauber salt) by refrigeration as a by-product. 587128 July 27, 1897. E. F. TURNER. Process of treating argentiferous sul- phide ores. In a process for the extraction of the metal of compound sulphide ores, disintegrating and decomposing the latter by the combined action of aqueous and gaseous hydrochloric acid, neutralizing the acid gases evolved whereby sul- phureted hydiogen is obtained, heating the disintegrated ore by means of such sulphureted hydrogen, collecting the sulphur dioxide resulting from the combus- tion, bringing this gas into contact with sodium chloride in presence of heat, whereby hydrochloric acid gas and sodium sulphate are obtained, and utilizing the former in the process of disintegration. 588476 August 17, 1897. H. A. RHODES. Process of separating gold and silver or other precious metals from their ores. In chemical processes for the separa- tion of gold or other precious metals from their ores, slimes, or compounds, the method of preparing the ores by adding thereto a self-hardening, binding mate- rial and forming a porous and rigid mass of the compound whereby the precious metals contained therein are freely acted upon by the solvent. 589959 September 14, 1897. J. J. CROOKE. Process of treating copper sul- phides. The process of recovering silver or gold and extracting copper in a metallic condition from copper sulphides associated with iron sulphides, which consists in roasting the pulverized sulphides with sodium chloride at a low heat, leaching the roasted mass with a solution whereby the iron sulphides are largely converted into oxides and the silver and gold are dissolved by and removed with the solu- tion, recovering the silver and gold from the solution, roasting the residuum or tailings, fluxing the rcasted tailings with silica and pulverized carbon, gradually melting the roasted and fluxed charge to convert the oxide of iron into metallic iron and desulphurize the copper sulphides to liberate metallic copper and form an iron silicate slag, removing the slag from the melted copper, adding a small per centum of silica to convert any remaining iron oxide or metallic iron into an iron silicate slag, and removing this slag from the copper. PATENTS RELATING TO CYANIDE PROCESSES. 339 602295 April 12, 1898. E. A. ASHCROFT. Treating solutions or ores contain- ing zinc for recovering zinc as oxides. The process of treating neutral zinc solu- tions for the production of zinc oxide, which consists in first converting the neutral zinc salt into basic zinc salt by the addition of zinc oxide and then intimately \/ mixing with said basic zinc salt, carbon in approximately the proportion of one- ' twentieth of the weight of the zinc to be recovered, and heating the mixture to a temperature approximately the melting-point of aluminum. 623154 April 18, 1899. H. HOWARD. Extraction of zinc and copper from ores. The process of extracting zinc and copper from ore or residue, which con- sists in treating the same with aqua ammonia and ammonium sulphate ; separating the copper from the resulting solution; adding sufficient soda to combine with all of the sulphuric oxide present and form sulphate of soda, and evaporating the solution to drive off ammonia, the latter being collected in water; and treating the residue with water to dissolve out the sulphate of soda, the zinc oxide remaining. 624000 May 2, 1899. J. DURIE. Method of reducing metallic sulphides. In the process of causing the solution of metallic sulphides containing lead, subjecting the sulphide ore to a solution of sulphuric acid and a nitrate of an alkali metal at a tem- perature of about 212 Fahrenheit, washing and filtering the lead sulphate obtained therefrom, dissolving the said sulphate, precipitating by carbon dioxide, wash- ing, and drying the precipitated hydrated carbonate of lead, and recovenng the sulphur. 625433 May 23, 1899. M. BODY. Process of treating sulphureted ores. In the process of treating sulphureted ores of a complex nature, comminuting and I melting the ore in presence of an alkaline salt and carbon, whereby alkaline poly- I sulphides soluble in water are formed, plunging the melted mass into water, whereby a magnetic precipitate is formed and the polysulphides dissolved in the water, separating the solution from the precipitate, subjecting the same to the action of air and sulphurous-acid gas forced thereinto, whereby monosulp hides of iron, together with the precious metals, are precipitated, maintaining the alkalinity of the solution during the operation of precipitation by addition of an alkaline substance, as lime, separating the solution from the monosulphide-of-iron pre- cipitate, extracting from the latter the copper and then the precious meatl, and separating the arsenic and antimony from the solution by precipitation 627024 June 13, 1899. R. THRELFALL. Method of treating flue dust and fume obtained from sulphide ores. In the treatment of flue dust and fume from sulphide ores, the separation of the zinc from the lead constituents by leaching out the former by means of a solution of alkali metal hydrogen sulphate, 630951 August 15, 1899. L. VANINO. Wet process of extracting silver from its haloid salts. The wet process of extracting silver from its insoluble haloid salts, which consists in mixing said haloid salts with a watering solution of alka- ** line agents, and adding formic aldehyde in the cold. 635056 October 17, 1899. D. O'KEEFE. Process of treating ore. The process of treating ore, consisting of roasting the same while being agitated, for the pui- ^ pose of mechanical disintegration, subjecting the ore to hydrogen gas under pres- sure, afterwards to chlorine gas, and then leaching the same with hot salt water. 635695 October 24, 1899. C. MARTIN. Process of chemically preparing and treating rebellious ores. The process of effecting the separation of gold, silver, tin, lead, and platinum, in pulverized rebellious ore containing arsenic and anti- mony, which consists in effecting sulphurization and disintegration of the said ore, producing a sulphide solution of the metals in said ore, and thereupon pre- cipitating the dissolved metallic compounds other than arsenic and antimony by mingling the same with an oxide of an alkali earth metal. 635793 October 31, 1899. F. W. MARTINO and F. STUBBS. Process of treat- ing ores containing pr^ious metals. The treatment of ores or tailings containing the precious metals by finely dividing the ore, mixing it with calcium carbide, ^ and moistening the mixture with water. 644770 March 6, 1900. R. W. KENNEDY. Solvent for leaching ores. A solvent for leaching ores, comprising sodium thiosulphate, ammonium carbonate, copper sulphate, and potassium cyanide in water. 340 APPENDIX 647989 April 24, 1900. T. RYAN, Jr., and N HUGHES Process of extracting vine from substances containing same. The process of extracting zinc from sub- stances containing the same, consisting in subjecting the raw material to the action of a solution of a caustic alkali, precipitating any lead present by galvanic action, securing the removal of organic matters and iron, manganese, and silicon by the addition of caustic lime and bleaching-powder, and finally precipitating the dis- solved zinc in the form of zinc oxide or zinc hydroxide by decaustifying the solu- tion by the addition of an acid. 648354 April 24, WOO. C. G. COLLINS. Process of extracting metals from their ores. The process of extracting metals from their ores, consisting in dis- solving out or extracting the metal from the powdered ore by means of a solution of ammonium salt in the presence of an alkali base capable of decomposing the ammonium salt, and then precipitating the metal by the addition of a solution of an alkali metal. 652072 June 19, 1900. G. DE BECHI. Treatment of ore. The method of treating complex ores, consisting in subjecting the ore to a chloridizing roasting, condensing the vapors and gases evolved, treating the roasted ore and the acidu- lated water containing the condensed vapors and gases with calcium chloride to precipitate soluble sulphates and sulphuric acid as insoluble calcium sulphate, then lixiviating the ore with the acidulated water to obtain a solution of zinc and copper salts and fractionally precipitating zinc and copper from the said solution as hydrated oxides by successive additions of lime. 652849 July 3, 1900. S. H. JOHNSON and H. L. SULMAN. Process of extract- ing metals from ores or slimes. The method of treating pressed slime cakes con- taining residual water, which consists in displacing the residual water with an equal volume of a solvent solution, mixing the cakes with a further quantity of solvent solution, removing the metal-bearing solvent solution by pressure, dis- placing the remaining portion of such metal-bearing solution with water and extract- ing the metal from said mteal-bearing solution, whereby all the operations may be performed with an approximately constant volume of the solvent solution. 653414 July 10, 1900. E. FINK. Process of extracting copper or other metals from tailings or ores of such metals. The process of extracting copper and other metals from tailings or ores of such metals, which consists in subjecting the tail- ings or ore to the action of a solution containing sulphuric acid and to the action of an oxide or oxides of nitrogen in the presence of air or oxygen under pressure, whereby the metal is oxidized and dissolved and the oxide or oxides of nitrogen are converted alternately into a lower and a higher oxide or oxides, and finally separating the solution from the earthy matter of the tailings or ore and sepa- rating the metal from the solution. 654804 July 31, 1900. G. RIGG. Process of obtaining oxide and carbonate of zinc from materials containing zinc. The process of producing oxide of zinc and carbonate of zinc from zinciferous material, which consists in leaching the zincifer- ous material with a solution of ammonia and carbon dioxide wherein the carbon dioxide is in such proportion to the ammonia as to impart to the latter an approxi- mately maximum zinc dissolving capacity. 656497 August 21, 1900. G. DE BECHI. Process of treating zinc-bearing com- plex ores for recovery of zinc or other metals therefrom. The method of treating com- plex zinc ores for the recovery therefrom of copper, zinc, and lead, consisting in separately roasting the ore and an alkali chloride in the presence of air and steam, conveying the sulphurous and sulphuric vapors thus derived from the ore over and in contact with the said chloride during the roasting: to obtain hydrochloric acid fumes, condensing the acid fumes, lixiviating the roasted ore with the acid liquor thus obtained to produce a solution of metallic chlorides, and successively precipitating the metals of the metallic chlorides as hydrates by successive addi- tions of alkali. 656544 August 21, 1900. H. HIRSCHING. Process of treating gold and silver ores. The process of treating copper ores, which consists in adding the com- mintued ore gradually under agitation to an ammoniated solution, and then adding a diluting liquid to the mixture to obtain a highly concentrated copper solution. PATENTS RELATING TO CYANIDE PROCESSES. 341 657955 September 18, 1900. H. PETERSEN. Process of enriching metallic sulphides. The process of enriching metallic sulphides, which are mixed with carbonates of the alkali earth metals, consisting hi dissolving out the carbonates with an aqueous solution of sulphurous acid. 659338 October 9, 1900. C. G. COLLINS. Process of extracting zinc and cop- per from their ores. The process of treating ores 'of copper and zinc, which con- sists in immersing the comminuted ore in a solution containing sodium sulphate and bisulphate (niter cake), removing the depleted ore and extracting the metal therefrom by electrolytic action, adding more comminuted ore to the remaining solution, and repeating the operation. 659339 October 9, 1900. C. G. COLLINS. Process of extracting copper and zinc from their ores. The process of treating ores of copper and zinc containing other metals soluble in any excess of solution which may be employed above that required to dissolve the copper and zinc contained therein, which consists in intro- ducing the comminuted ore into a solution of sodium sulphate containing hydro- chloric and sulphuric acid (salt-cake solution) not exceeding 5 Baume, and sub- sequently recovering these metals from the solution. . 659670 October 16, 1900. C. J. HEAD and R. C. WILD. Method of treating telluride ores. A process for the extraction of tellurium from telluride aurifer- ous ores and the preparation thereby of said ores or the better extraction of the precious metal therefrom, consisting of a lixiviation and digestion of the said ores in a solution containing about 5 per cent, of caustic potash or soda for a lengthened period of fcwo to six hours, the withdrawal of the solution after such digestion from the said ores, and the recovery of the tellurium from the solution. 660013 October 16, 1900. C. J HEAD and R. C. WILD. Method of treating telluride ores. A process for the extraction of tellurium from telluride auriferous ores and the preparation thereby of said ores for the better extraction of the precious metal therefrom, consisting of a lixiviation and digestion of the said ores in a solu- tion containing about 5 per cent, of carbonate of sodium or potassium for a lengthened period of two to six hours, the withdrawal of the filtrate, and the recovery of the tellurium from the solution. 663759 December 11, 1900. C. HOEPFNER. Process of producing solutions of zinc chloride. The process, which consists in reacting upon an oxide or insoluble salt of zinc in presence of water with sulphurous acid to form soluble zinc bisulphite converting the bisulphite into a monosulphite by suitable reagents, mixing there- with its equivalent of sodium or potassium chloride and exposing the mixture to heat and air in the presence of a contact substance, such as oxide of iron, in order to convert the monosulphite into a sulphate, separating the zinc chloride from the solution and mixing therewith a sufficient quantity of an aqueous solution of sodium chloride to dissolve the zinc chloride and leave the alkali-metal sulphate practically undissolved. 678210 July 9, 1901. J. W. WORSEY. Process of treating complex ores. Process for the treatment of complex sulphide ores, comprising, first, the reduc- tion of the combined sulphur below 15 per cent, by calcination; secondly, finely powdering the calcined ore; thirdly, adding sodium nitrate; fourthly, boiling the mixed ore and nitrate in dilute sulphuric acid; fifthly, roasting the semisolid mass in a closed furnace; sixthly, dissolving out zinc copper and other soluble salts from the said mass by weak sodium-sulphate solution; seventhly, removing any copper from the solution; eighthly, precipitating the zinc and other metals from the solution; and, ninthly, separating the zinc. 679215 July 23, 1901. H. C. BULL. Method of extracting gold from sea-water. The method of extracting gold from sea-water, which consists in mixing with a quantity of sea-water a proportion of milk of lime to react upon the iodide of gold contained in the sea-water to form iodide of calcium and to liberate the gold, then allowing the sludge formed by the reaction to settle, then drawing off the water .and then collecting the sludge and treating it to extract the metallic gold therefrom. 683325 September 24, 1901. H. J. PHILLIPS. Extraction of precious metals from their ores. The method of extracting precious metals from refractory sul- phide or telluride ores without roasting, which consists in subjecting the ore with- 342 APPENDIX. out roasting and in the form of a powder, under heat and pressure, to the action of alkaline polysulphides in solution of such weakness that same will have a selec- tive action, namely, will dissolve the elements which are combined with the gold, and for which the polysulphides have a greater affinity than for gold, without dissolving the gold itself, which latter is thus dissociated and can then be recovered by any known suitable process for recovering free gold. 684578 October 15, 1901. C. W. MERRILL. Precipitant for recovering metals from solutions. The combination with a metal capable of precipitating other metals from cyanide solutions, if a gritty, inert, non-metallic material, to increase the surface exposed per unit of weight of the precipitating metals. 689835 December 24, 1901. G. H. WATERBURY. Process of extracting copper from ores. The process of precipitating copper in solution, consisting in placing the solution in a tank or receptacle containing pieces of iron small enough to allow the solution to pass readily therethrough, and introducing hot air under pressure into the solution. 692008 January 28, 1902. O. FROLICH, M. HUTH, and A. EDELMANN. Sepa- rating process for ores. In the art of separating metals from ores containing iron among- a plurality of metals existing therein in a combined form, the process, which consists in heating the ore to a temperature below the decomposition tem- perature of the sulphate of the metal to be sulphated, but above the decomposing temperature of the sulphate of any other metal existing in the ore, and then pass- ing over it a gas mixture containing sulphur dioxide and oxygen. 693148 February 11, 1902. E. B. PARNELL. Process of treating ores. In' the treatment of refractory ores, the process, which consists in subjecting them to the action of chromic acid and then roasting them. 695306 March 11, 1902. M. M. HAFF. Separation of the constituents of com- plex sulphide ores. The process, which consists in heating mixed sulphides of zinc and lead with sulphate of an alkali metal, treating the resultant mass with a dis- solving agent to dissolve the zinc sulphate and alkali -metal sulphate, while leaving the lead sulphate undissolved, and adding barium hydrate to the mixed solu- tion of zinc sulphate and alkali-metal sulphate to precipitate zinc hydrate and barium sulphate. 699326 May 6, 1902. T. A. IRVINE. Extraction of copper by the wet method. A process for the extraction of copper, consisting in the treatment of the ore within a mixed solution of chloride of sodium and sulphuric acid, in which solution there is an excess by weight of the chloride of sodium in respect to the sulphuric acid. 700311 May 20, 1902. F. ELLERHAUSEN. Treatment of complex and refrac- tory ores. The process of treating complex and refractory ores containing lead, silver, and zinc, which consists in smelting the raw ores, churning the fumes and gases with water to condense and mix them with water, settling out the lead, sil- ver, and part of the zinc compounds from the resulting liquor, as a sludge, sepa- rating and drying the sludge and fusing the sludge with caustic alkali, thereby precipitating the lead in metallic form. 702047 June 10, 1902. C. G. COLLINS. Process of rendering metallic sul- phides soluble. The process of rendering metallic sulphides soluble, consisting m drenching the crushed sulphide ore with aqueous ammonia, draining off the excess of aqueous ammonia, treating the ore thus moistened to an excess of oxygen, leaching the ore, and repeating the operation until the metal is all extracted from the pulp. 702153 June 10, 1902. J. P. VAN DER PLOEG. Treatment of ores and mate- rials containing antimony. The method of extracting antimony from ores, mate- rials, or residues containing it, consisting in finely pulverizing the material, mixing it with a suitable quantity of powdered quicklime, and then mixing with it an adequate quantity of sulphide of an alkali-earth metal and water, so as to form a solution of the lower and most soluble double sulphides as being the best elec- trolytes, without the use of artificial heat or application of pressure. PATENTS RELATING TO CYANIDE PROCESSES. 343 702244. June 10, 1902. A. J. POLMETEER. Precipitant for treatment of cop- per-water. The precipitant for copper-water, containing in solution a sulphide and an excess of alkali. 702582 June 17, 1902. J. W. NEILL and J. H. BURFEIND. Process of recwer- ing metals from ores. The improvement in treating copper or other ores, consisting in agitating a charge of pulp containing the ore by gas from* roasting furnaces v , charged with material suitable for producing sulphurous-acid gas, separating the Vy' resultant solution, precipitating the metal from the solution thereby releasing;'/^ gas and employing the sulphurous-acid gas released by the precipitating process to enrich the gas derived from the furnace and used in leaching a charge of ore. 704640 July -15, 1902. C. HOEPFNER. Process of extracting copper and nickel from sulphide compounds. The process, which consists in oxidizing roast- ing copper and nickel sulphide ores or mattes, leaching the sulphate of copper formed, converting this into cupric chloride and then into cuprous chloride, dis- solving the nickel salts in the residue by said cuprous chloride, precipitating cup- rous chloride from the solutions formed and returning the resulting solution con- taining some cuprous chloride into the cycle of operations. 704641 July 15, 1902. C. HOEPFNER. Process of extracting zinc or other- metals from their ores. The process which consists in reacting on a material con- taining an oxygen compound of metals insoluble in water and whose chlorides- are soluble in a solution of alkali metal chloride, with sulphurous acid and an aque- ous solution of alkali metal chloride, whereby a solution is formed containing a chloride of a metal. 706302 August 5, 1902. L. B. DARLING. Means for extracting precious metals from ores. In a gold-extracting plant provided with a substantially flat treating floor of non-absorbent material, a series of longitudinally extending chan- nels formed therein, a transverse groove or end launder in direct communication with said channels, fixed screens or strainers covering the top of said channels and launder, side launders or ducts, and valved connections interposed between and uniting the said end and side launders. 707107 August 19, 1902. J. HERMAN. Process of treating ores. The process which consists in roasting sulphide of copper ore at a low heat to form sulphates of the copper and some of the iron present, and produce a large percentage of fer- rous sulphate, leaching the roasted ore, precipitating the metallic copper, and adding salt to the leaching solution before or after the precipitation of the metallic copper, whereby the ferrous salts in the solution are converted to the chloride f and a solution having an excess of salt is produced, and the said solution is adapted to dissolve copper and silver out of carbonate and oxide ores. 707506 August 19, 1902. E. FERRARIS. Method of treating mixed sulphide ores. The process of decomposing mixed sulphide ores by means of concentrated sulphuric acid without the aid of extraneous heat. 709037 September 16, 1902. W. PETHYBRIDGE. Treatment of telluride gold ores. In the decomposition of ores containing telluride of gold, the process of reducing the ore to a finely divided state and then exposing the ore to the action of a solution of ferric chloride alone to attack the tellurium. 715023 December 2, 1902. J. C. CLANCY and L. W. MARSLAND. Process of treating zinc sulphide ores. In extracting metals from zinciferous sulphide ores, roasting pulverized ores with the addition or admixture of lead sulphate obtained from a source external to the ore being treated in quantity proportional to the quantity of zinc the ore contains. 715771 December 16, 1902. F. ELLERHAUSEN and R. W. WESTERN. Treat- ment of zinc ores. The process for the treatment of zinc ores and other zinciferous matter, consisting in calcining where necessary, wetting with a dilute solution of ammonium sulphate, adding sulphuric acid, washing with ammonium sulphate , and precipitating with aqueous ammonia and heating the precipitate. 715804 December 16, 1902. H. E. HOWARD and G. HADLEY. Treatment of spent acid from galvanizing works. The treatment of spent acid from galvanizing works by adding zinc thereto, separating the solution from the precipitate, treat- 344 APPENDIX. ing with bleaching powder to transform the ferrous salts into ferric salts, then adding alkali to precipitate the iron present as ferric hydrate, and subsequently more alkali for the precipitation of the zinc salts. 71684? December 23, 1902. F. W. MARTINO. Treatment of ores containing precious metals. The process of separating gold from ores containing tellurium, r selenium, sulphur, arsenic, antimony, tin, phosphorus, or the like, consisting in grinding the mixture, heating it with powdered barium sulphocarbide in a reduc- ing (muffle) furnace, dissolving out the soluble sulphides thus formed, treating the solid residue with a gold solvent, and precipitating the gold therefrom by the employment of barium sulphocarbide. 717299 -December 30, 1902. G. C. STONE. Extraction of zinc and lead from sulphide ores. The method of separating zinc and lead from sulphide ores, which consists in smelting the sulphides, oxidizing the volatile constituents at their exit from the smelting furnace, cooling the resulting fumes and products of combus- tion to a temperature not exceeding 180 F., and passing them into contact with a solvent which will dissolve out one of the metals and not the other. 717565 January 6, 1903. A. VON GERNET. Process of extracting copper from its ores. The process of extracting copper from its ore, which consists in ^X. slowly passing the ore in the form of pulp through a current of sulphurous acid, passed in a direction opposite to that of the travel of the pulp. 7 17 86 4 January 6, 1903. J. T. JONES. Method of treating ores. The process of mixing with ore, to be treated, a leaching fluid, which consists in confining the mass of ore in a vessel with a body of leaching fluid of lesser specific gravity super- imposed upon it, carrying portions of the ore upward in said vessel and releasing it above the body of leaching fluid, to precipitate it through said body and simul- taneously convey portions of the leaching fluid below the surface of the mass of ore and releasing it and permitting it to rise through the same. 718099 January 13, 1903. S. C. C. CURRIE. Method of reducing ores. The step in the art of treating pulverized ores containing precious metals, which con- sists in subjecting the ore, in a closed vessel, to the action of hot air at a tempera- ture which reduces some of the salts in the ore from an insoluble to a soluble condition in water, , then washing ^ away the soluble salts with water and then repeating the step with air at a higher temperature. 719132 January 27, 1903. W. PAYNE, J. H. GILLIES, and A. GONDOLF. Process of treating copper^ ores. The process of treating copper ores, consisting in first roasting to an oxide, next saturating the same with a solution of ferrous sulphate or sulphate and chloride, next roasting again and meanwhile adding a small percentage of iron sulphide or sulphur, according to the percentage of cop- per present, and finally leaching the hqt ore. 719757 February 3, 1903. S. C. C. CURRIE. Process of treating ores con- Jy taining precious metals. The method of treating ore, which consists in heating the raw pulverized ore in contact with steam, and plunging the heated ore into an aqueous alkaline solution. 723787 March 24, 1903. S. TRIVICK. Process of extracting metals from ores. A process for evolving nascent chlorine and effecting the chlorination of metallic substances in order that they may be extracted from a metalliferous mass by rendering them solvent, consisting in adding to the mass a mixture in definite proportions of two substances, one being dry chloride of lime and the other ferric sulphate, the proportions being such as to result in the formation of ferric hypo- chlorite and ferric chloride which will evolve nascent chlorine. 723949 March 31, 1903. G. D. VAN ARSDALE. Process of separating copper from ores. The process of extracting copper from ores, or products containing copper, which consists in separating copper from cupric-sulphate solutions, with or without ferrous or other suitable sulphate, and of simultaneously producing free sulphuric acid, by adding to such solutions sulphur dioxide and heating with or without pressure, whereby copper or copper compounds are thrown down in the solid form to be subsequently treated, and free sulphuric acid is formed, and of adding the acid liquors thus obtained, after separation from the copper pre- cipitate, to copper ores, whereby the copper contained in them is dissolved and PATENTS RELATING TO CYANIDE PROCESSES. 345 the original solution regenerated and the process repeated and thus made con- tinuous. 724414 March 31, 1903. G. H. WATERBURY. Copper leaching process. The copper leaching process, consisting in placing the suitably pulverized ore in a leach- ing-tank, adding water, acid, common salt, and oxide of manganese in suitable quantities, heating the mass by the introduction of steam to a suitable temperature, and finally subjecting the pulp to agitation during a suitable period. 725257 April 14, 1903. T. B. JOSEPH. Gold extraction process. The process of extracting precious metals from ore containing the same, when in a suitable condition, which consists in subjecting the said ore to a leaching action of a solu- tion of water, cyanide of potassium, hydrate of calcium, carbon dioxide, and bio- mine, and subsequently precipitating the precious metals from the solution. 725548 April 14, 1903. H. R. ELLIS. Process of extracting copper from car- bonate and oxide ores. The process of extracting and recovering copper from its carbonate or oxide ores or from material carrying carbonates or oxides of copper,, which consists in subjecting the ore or other material in a crushed or powdered state to the action of a carbonate of soda or its described equivalents until the copper is dissolved and subsequently subjecting the charged solution to electrolytic action. 726802 April 28, 1903. B. T. NICHOLS. Ore-treating process. The process for treating ore preparatory to leaching, consisting first in mixing the suitably pulverized ore with lime; second, applying water to the mixture and introducing steam whereby the pulp is agitated and kept at a suitable temperature until cer- tain impurities which retard leaching are freed; third, washing the pulp by the introduction of water and continued agitation; fourth, draining on the water as far as practicable; and, finally, drying the ore. 729760 June 2, 1903. G. V. GUSMAN. Process of reducing and separating silver. The process of extracting and separating silver from its ores, which con- sists in subjecting roasted ores to the action of a preprovided aqueous solution of cupric chloride and cuprous chloride, passing the resulting solution through granulated metal, and removing and collecting the metallic silver from said metal. 729819 June 2, 1903. J. F. WEBB. Apparatus for use in extracting metals from ores. A tank for use in extracting metals by chemical process from their ores, having a filter bottom and means for discharging air within the tank and downwardly upon the said bottom, whereby the said bottom is kept free frcm clogging and air is supplied to agitate the mass within the tank and supply oxygen thereto. 734683 July 28, 1903. J. F. DUKE. Process of obtaining gold from sea-water. The process of obtaining gold from sea-water containing the same, which con- sists in precipitating the gold by carbonate of calcium. 735098 August 4, 1903. C. HOEPFNER. Process of obtaining lead or other metals from ores or mattes. The process, which consists in leaching compounds containing lead and iron with a solution of cupric chloride containing a solvent of the chlorides of said metals, supplying oxygen to produce oxychloride of cop- per whereby the iron is precipitated, and precipitating the lead as a sulphite by means of a sulphite of zinc. 735512 August 4, 1903. H. HIRSCHING. Treatment of ores containing gold r silver, copper, nickel, and zinc. The process for extracting gold, silver, copper, nickel, and zinc from substances containing the same, which consists in subject- ing said substances to the action of an acid, washing with water the substance thus treated, thereby forming solutions containing compounds of gold and base metals, and then subjecting said solutions to the action of ammonia for the pur- pose of precipitating the gold and recovering the base metals from the solution, separately, and also the ammonia. 739011 September 15, 1903. F. LAIST. Process of treating ores. The method of generating hydrogen sulphide and precipitating copper, which consists in sub- j^cting an alkaline-earth sulphide in presence of water to the action of csrbcn d'ox'de, thereby generating hydrogen sulphide and precipitating the carbonate of the alkaline-earth metal, conducting said hydrogen sulphide into the presence 346 APPENDIX. of copper in solution, thereby precipitating copper sulphide and forming a sol- vent liquid, treating copper ores with said solvent liquid, and collecting said alkaline-earth carbonate and reconverting it into sulphide. 740014 September 29, 1903. J. HERMAN. Process of treating ores. A process of extracting copper from ores, which consists in treating ore containing iron to produce ferrous chloride, utilizing the chloride and free acid to dissolve carbon- ates and oxides of copper, the free acid being adapted to neutralize interfering sub- stances and to attack the surface of the particles of copper oxide or carbonate, and regenerating the free acid by the electrolytic precipitation of copper. 740372 September 29, 1903. C. ROGERS. Process of extracting zinc from sul- phide ores, etc. The process for the extraction and recovery of zinc from zinc containing sulphide ores or tailings, which consists in subjecting the same to a partial sulphatizing roast, discharging the same while hot into water, leaching the same with said water and with dilute sulphuric acid, subjecting the leached ores or tailings to a second sulphatizing roast, releaching the same with the lix- ivium from the former leaching, and repeating said operations until sufficient zinc and sulphur are removed. 740701 October 6, 1903. A. M. G. SEBILLOT. Treatment of sulphide ores. A process for treating ores containing sulphur consisting of sulphating the ore in a closed vessel by the action of sulphuric acid upon the metallic sulphides at a temperature above its boiling-point and simultaneously recovering the sulphuric acid used, calcining the sulphated ore at a temperature of 700 Centigrade to dis- sociate the sulphate of iron to prevent dissolving of a too great quantity of sul- phate of iron in .the lixiviating liquors, and then lixiviating the calcined ore. 748662 January 5, 1904. A. M. G. SEBILLOT. Process of treating copper ores. The process for extracting pure metals from mineral ores, consisting in treating the ores with sulphuric acid at the evaporating-point of the latter, with- out roasting, to form sulphates, condensing the surplus acid fumes, and lixiviating the sulphates in successively deeper baths under constant agitation, in a current flowing in direction opposite to the progress of the ores. 749700 January 12, 1904. P- NAEF. Process of lixiviating ores. The method of lixiviating ores or other pulverulent materials, which consists in passing the ore downward in thinly divided layers through an ascending stream of leaching solution and at the same time passing a current of air or gas repeatedly through the ore layers in numerously divided jets, whereby the ore particles are agitated in the solution, and the same volume of gas acts successively as an agitating medium. 752320 February 16, 1904. J. B. DE ALZUGARAY. Extraction of metals from complex ores. In the treatment of complex ores, such, for instance, as contain copper, lead, silver, and zinc in comparatively large quantities, the process of extracting the said metals selectively, which consists in leaching the ore with a solution composed of a mixture of a chloride of an alkali or earth-alkali metal with a chloride of a metal other than those of the alkali or earth-alkali series and an acid before calcination or roasting whereby the copper is obtained in solution then washing and drying the ore, roasting the partially disintegrated ore at a low temperature, extracting the metals from the roasted ore in form of salts by means of a second and weaker leaching solution having a character consonant with the nature of the salt it is desired to obtain, and recovering the metals in the usual way. 754643 March 15, 1904- K. DANZIGER. Process of separating iron pyrites from zinc-blende. A process for separating iron pyrite from zinc-blende, which consists in exposing the zinc-blende to the action of air moisture and heat, and extracting the ferrous salt which has been formed by the oxidizing action by water. 755871 March 29, 1904. T. A. HELM. Apparatus for treating ore. An apparatus for treating pulverized auriferous ores, comprising a rotatable cylin- drical tank, radially depending blades in the tank extending the length thereof, a circular brace-frame disposed between the inner ends of the radial blades, as an air pipe leading into the tank, faucets to draw off a liquid from the tank, and means to rotate the tank. PATENTS RELATING TO CYANIDE PROCESSES. 347 CLASS 75. METALLURGY. SUBCLASS 86. SOLUTION AND PRECIPITATION APPARATUS. 108158 October 11, 1870. W. S. LAIGHTON. Improvement in apparatus for precipitating gold and silver from solutions. The invention consists in combining two vessels one to receive the solution to be precipitated and the other the pre- cipitant and connecting them by an automatic apparatus that shall deliver a certain quantity of the precipitant into the other vessel every time it is filled and provide for the discharging of the same, the quantity of the solution that receives the precipitant, measured out, being governed by a hydrometer or hydrometric float, which is used to operate the apparatus. 213382 March 18, 1879. C. C. BITNER. Improvement in apparatus for obtain- ing metallic copper from its solution. The invention relates to a novel apparatus for obtaining metallic copper from its solution; and it consists in the employ- ment of a tank or vat having a horizontal perforated diaphragm, upon which is placed a quantity of iron. This tank is filled with a solution of copper, previously prepared from the roasted ore in the usual manner. Through the top of this tank a steam pipe passes and extends below the diaphragm, so that the solution is heated by this injected steam, and, by the motion which its action gives, the deposition of the copper is hastened. By means of peculiarly arranged slides the steam is admitted above the diaphragm through holes in the steam pipe to assist the process, if desired. 234073 November 2, 1880. R. SCHULDER and E. H. RUSSELL. Ore-leacher. The invention consists of a circular frame supporting the filter and moving on a circular track above an inclined circular table; and it consists, further, of three stationary rollers, designed to elevate and depress the filter at certain points as it revolves, of a device for feeding the substance to be leached upon the filter, of a device for applying the leaching solvent, and of a precipitating tank to contain the solution passing through the filter. 248768 October 25, 1881. J. F. N. MACAY. Filter. The invention relates to improved apparatus for use in effecting the operations of dissolving solids in liquids and producing chemical reactions, and of filtering or separating liquids from solids in chemical and metallurgical processes, in which a soluble substance or substances, mixed or combined with an insoluble substance or substances, is or are to be dis- solved separately or together, wholly or partially, in a given solvent or solvents, and the solution separated by filtration from the undissolved residue. In effecting the separation of liquid from solid matters by filtration it is of importance to keep the filtering surface from being clogged by the particles of solid matter, and to present a clear and unobstructed filtering surface for effecting the rapid separtaion of the liquid from the solid matters. In the apparatus of the invention this important condition is realized in a very effective manner, the construction and operation of the apparatus being as follows: Within a cylinder of wood or other material not chemically acted on by the materials treated or the reagents employed is inclosed an inner cylinder of hard wood, or of hard earthenware or stoneware or other material not chemically acted on by the materials treated or the reagents employed, this inner cylinder being perforated with holes and lined internally or externally, but preferably inter- nally, with asbestos cloth or other suitable filtering material. Between the inner and outer cylinder there is an annular space, and the inner cylinder is kept in place by longitudinal and circumferential partitions, the former of which divide ftie annular space into a number of distinct compartments each provided with a draw-off cock for running off the liquid when separated by fil- tration. This cylinder is capable of being rotated, and is provided with doors or manholes in one of the heads by which the matters to be treated may be intro- duced and the undissolved residue removed; and the cylinder is also provided with a tubular journal or journals for the introduction of steam, water, air, or other liquids or gases, under pressure or otherwise, which may be blown, forced, or drawn into the annular space for the purpose of keeping the filtering surface 348 APPENDIX. clear and of acting chemically or mechanically upon the contents of the cylinder. I place within the inner cylinder the ore or other matter to be treated (previously ground or otherwise reduced to a pulverulent state), together with the reagents .or solvents by which it is to be treated. By imparting rotary motion to the cylinder '(the draw-off cocks and manholes being closed) the solid matters are brought into intimate contact with the solvents or reagents, and by forcing steam, water, air, or other liquids or gases into the space between the ini ^r and outer cylinders, and thence through the filtering medium into the inner cylinder, any solid mat- ters that may adhere to the filtering surface are disengaged therefrom, whereby the said surface is kept clear, the solid matters are kept in suspension in the liquid, and chemical action, which the liquid or gaseous reagents may be capable of exert- ing on the said matters, takes place under the most favorable circumstances as regards the intimate mixture of the reagents with the matters and the large sur- faces exposed to their action. The annular space between the inner and outer cylinders being divided into compartments by longitudinal divisions, the liquid which passes through into it is carried round by the rotation of the cylinder and flows back into the inner cylinder, thus helping to keep the filtering surface clear and unobstructed. When the soluble substances are dissolved or chemically acted upon, and it is desired to separate the liquid from the solid matters, the draw-off cocks are opened, and then, by giving a slow rotary motion to the appara- tus, the liquid may be decanted off from the bulk of the solid matter and at the same time filtered from any such matters which it may hold in suspension by passing through the filtering medium. By this rotary decanting action a practically clear filtering surface, unobstructed by solid matter, is constantly presented for the liquid to pass through. 251718 January 3, 1882. A. E. JONES. Apparatus for separating gold from quartz and rock tailings. The invention consists in the arrangement and applica- tion of a suitable fibrous material in combination with machinery, so that the fibrous material will unite or collect to itself the gold and carry and deposit the same to a place designated, where it may be collected and treated as desired in separating the precious metal from its sand and ore. Any fibrous matter that will form a pulp when mixed with water is used to coat a wire-cloth screen as in paper-making, and then entangle the fine gold in suspension in the water. 301460 July 1, 1884. J- L . RUSSELL. Slime filter. The invention consists of a trough' containing at intervals within it a series of double filtering boxes covered with wire gauze and filled with charcoal, sponge, or any known filtering substance, and the claims cover the trough poised over filter sections provided with adjustable partitions, as well as the combination of a sand box, a sluice pro- vided with adjustable partitions, filters composed of frames and wire gauzes, and gutters. 325835 September 8, 1885. H. C. and J. A. HENDERSON. Apparatus for con- centrating ores. The apparatus for concentrating ores, consisting of an outer tank, an inner tank provided with fabric ends, and a perforated feed-box hav- ing its lower end below the top edge of the tank, a space being left between the sides, ends, and bottom of the tanks whereby, when the water is received by the perforated feed-box, it will pass into the inner tank and slowly filter through the fabric ends thereof and flow over the top edge of the outer tank, the fabric ends preventing the formation of a current and causing the particles of ore to be precipitated. 366103 July 5, 1887. O. HOFMANN. Process of extracting silver from its ores by lixiviation. The invention relates to a certain improvement in the lixiviation process by which the ore, after having been subjected to a chloridizing roasting, is in- troduced in a series of troughs, first, together with water to dissolve the base- metal chlorides, and, sceond, together with the solution used in the ordinary lixiviation process to dissolve the silver. The ore and water are introduced either by means of a mixing-box or an agitator, and are allowed to flow in these troughs for some distance, and finally conveyed by them into settling-tanks. The water while running in the troughs dissolves the base-metal chlorides. In the settling- tanks the ore separates quickly from the liquid. The latter is drawn off and con- veyed to other tanks for the usual treatment. The ore sediment containing the PATENTS RELATING TO CYANIDE PROCESSES. 349 silver is now sluiced or charged again in a similar series of troughs with a solution which has the property of dissolving chloride of silver, like hyposulphite of lime or soda, concentrated salt solution, Russell's "extra solution" (a compound of hyposulphite of lime or soda and bluestone), etc. By passing through this second series of troughs the silver chloride dissolves. Ore and solution run into tanks which are provided with filter bottoms and allowed to separate. The tailings settle to the bottom, while the clear solution, now containing the silver, is drawn off and conveyed into the precipitation-tanks for the usual treatment. 370871 October 4, 1887. F. F. HUNT. Apparatus for agitating solutions in the leaching of metals from their ores. The invention relates to an improvement in apparatus for agitating the acid solutions formed in the leaching of copper and other ores; and the object of the same is to provide a form of rotary agitator in which the heavier portions of the charge cannot accumulate at the centre of the apparatus and escape the action of the agitating arms, which will also produce a more perfect agitation of the solutions than has heretofore been possible, and which will be more durable and economical to construct than the forms in present use. Heretofore the agitators used in leaching works have usually been made with flat bottoms and have been provided with stirring or agitating arms of conical shape at the base, arranged to rotate a slight distance above the bottom. In the invention this arrangement is reversed, and the agitating tank is constructed with a cone of small altitude placed apex upward in the centre of the bottom and covering a considerable portion thereof, and is provided with agitators, the arms of which are provided with concave shoes and are arranged to rotate in close prox- imity to the cone in the bottom of the tank. ^1 26 '10 October 8, 1889. J. B. HANNAY. Apparatus for applying chlorine to the extraction of gold from ores. This invention relates to means of extracting from ores precious metals, especially gold, in the form of chloride solution. For this purpose an apparatus is employed which consists of a chlorinating vessel, a set of circulating pumps, a filter-press, and a chlorine pump, or sets of these, with suitable communicating pipes, cocks, and valves for operating in the following manner: Having reduced the ore to a fine powder, it is mixed with water or with chlorinated water to a condition of thin sludge, which can be pumped. Then charge the chlorinating vessel with this sludge and apply the pumps to cause its circula- tion therein, drawing from the upper part and discharging into the lower part, while chlorine gas is pumped into the vessel, preferably to a pressure considerably above that of the atmosphere. After circulation has gone on for some time, until the metal in the ore is mostly dissolved by the chlorine, the sludge is pumped by the circulating pumps into the filter-press, additional pressure being given, if re- quired, by using the chlorine pump to force air into the upper part of the chlorin- ating vessel. The liquid issuing from the filter-press containing in solution the metallic chloride is treated in any of the known ways for separating the metal and recovering the chlorine. In some cases the solution discharged from the filter- press may be used in a subsequent operation to form the sludge by its admixture with a fresh quantity of pulverized ore, and this may be done repeatedly, so as to obtain finally a filtered liquor rich in chloride. As it is advantageous to charge the chlorinating vessel with an excess of chlorine above that which enters into combination with the metals, the inventor prefers to collect such excess before discharging the sludge by blowing in a little steam to warm the sludge and allowing the free chlorine thus liberated to pass either into a gasometer or into another chlorinating vessel; or an exhaust-pump may be employed to draw off the free chlorine. When metals such as silver are present, having insoluble chlorides, the blocks which are taken from the filter-press, and which contain these chlorides, may be reduced to sludge, as before mentioned, and may be subjected to the same treat- ment with a suitable solvent instead of the chlorine. 418138 -December 24, 1889. J. S. MACARTHUR. Metallurgical filter K metal- lurgical filtering apparatus for separating a precious metal from a solution containing said metals, consisting of a series of vessels, each of which has an inlet tube near its bottom, an outlet tube near its top, and a perforated false bottom above th3 inlet tube, zinc sponges disposed in the several vessels, pipes connecting the inlet 350 APPENDIX and outlet tubes of the several vessels, and a reservoir for supplying the solution to the first vessel of the series. 425025 April 8, 1890. D. DENNES and T. K ROSE. Apparatus for leaching ores. In a leaching apparatus, a movable table, having a flange or wall projecting from its upper surface to form a receptacle for filtering material, the said receptacle being of, less diameter than the upper surface of the table, whereby a packing receiving ledge projects beyond the base of the said wall or flange, combined with the leaching cylinder, the lower end of which is constructed to receive said wall or flange, while the ledge abuts against said lower end of the cylinder. 442262 December 9, 1890. S. TRIVICK. Apparatus for treating ores to obtain precious metals therefrom. This invention relates to improvements in apparatus forming a plant for treating roasted ground ores to obtain precious metals there- from, adapted for use in treating roasted ground ores of precious metals that have been roasted by any known or suitable method. The apparatus consists, essentially, of a vessel (preferably employing a pair at least of such vessels, so as to change from one to the other of the pair in working) having a porous bottom on which the ground-roasted ores rest; means of supply of leaching liquid controlled by valve; means of drawing off leached liquid, con- veyance thereof to, and means of stirring said liquid in a mixing chamber a filter vessel having a porous floor and means of pumping the filtered liquid to a reser- voir; means of evaporating the leaching liquor to recover the contained salts; also recovering the copper salts for reuse, and means of heating the leaching liquid, and also means of desiccating the product. The invention also consists in a furnace for roasting ores of precious metals, comprising, among other features, a chamber, coils of piping, a tank, reservoir, a force-pump, a system of heating pipes, leaching reservoir, tanks with porous floors, and a mixing vessel with rotating stirrers therein. 449813 April 7, 1891. J. CRAGG. Apparatus for extracting gold or silver from ares. In an apparatus for extracting gold or other metals from their ores in solu- tion, a tower and a mixer, which consists of a trough having pipes to conduct the reagents in liquid solution, which enter the same from different sides and terminate out of alignment about centrally of the trough, combined with a hopper placed over the ends of the said pipes and an overflow plate leading to the said tower. 456323 July 21, 1891. P. L. GIBBS. Ore-leaching machine. This invention has reference to ore-leaching machines in which a rotating annular series of ore receptacles pass successively under an ore vat containing the crushed ore in a solution to receive their respective contents or to be otherwise filled, and to discharge the filtrate during their transit into a suitably placed discharging con- duit or launder and at a predetermined point in their orbital movement and auto- matically discharge the residuum. The objects of this improvement are, first, to provide a suitably suspended vat to receive the ore in a solution, or dry or roasted ore, and adapted by suitable openings in the bottom thereof to optionally discharge said contents; second, to provide a series of leaching-vats to pass successively under said primary vat and respectively receive from the latter a proper quantity of its contents; third, to provide suitable mechanism for supporting and progressing said secondary vats; fourth, to provide a conduit or launder to receive and carry off the filtrate from said leaching or secondary vats; and, fifth, to afford facilities to automatically discharge the residuum from said leaching-vats preparatory to their refilling. 463120 November 10, 1891. D. DENNES. Leaching-vat for separating precious metals from their ores. An ore-leaching apparatus consisting of a closed vat or separating vessel having a removable bottom carrying a filter-bed in its upper portion and an auxiliary chamber beneath, provided with a removable bottom and a filter-bed, and a suitable pipe connection between the separating vessel and said auxiliary chamber in its bottom. 464672 -December 8, 1891. W. D. BOHM. Apparatus for separating gold and silver from ore. The inventor places the powdered or divided ore, or material to be treated for the obtainment of the gold or silver, or both, in a vessel or vat, or vessels or vats, and through it passes the leaching solution, preferably pre- PATENTS RELATING TO CYANIDE PROCESSES. 351 viously heated. By means of a force-pump, the leaching solution is forced up through the ore and through a filter at the top. The solution and the precious metal which it now contains pass into a vessel in which it is agitated with a pre- cipitating agent. From this last-named vessel the solution is forced up by a force- pump through a vessel having a filtering arrangement, such as a porous diaphragm, at the top, so that the solid matter is retained thereby, the liquid passing off to be heated again and to be restrengthened by the addition of the necessary further quantity of leaching chemicals and passed back to the leaching vat or vats for reuse. The pressure under which the liquids are forced up through the leaching- vat and precipitant vessel should be at least eighteen pounds per square inch. At intervals the solid matter retained by the last-named filter vessel is passed into a filter-press or equivalent apparatus, whereby it is deprived of the greater part of its moisture. The ore which has been leached is then drained of all solution and washed free from the last traces thereof with water, preferably hot, and then can be washed out of the vat or vats with acidulated water, and passed over zinc or alloy of zinc with other suitable metal, so that hydrogen is evolved, which reduces any precious metal still remaining in the ore to the metallic state, or such state that it is taken up when the ore is afterwards passed over mercury for instance, over amalgamated copper. 495385 April 11, 1893. F. WEBB. Method of and apparatus for extracting precious metals from their ores. The inventor claims, in means for extracting pre- cious metals from their ores, the combination of an outer vessel resting in suit- able trunnions for containing the reagent or chemical solution, and having inlet and outlet pipes communicating, respectively, with the top and bottom thereof through said trunnions, a perforated vessel in said outer chamber, and adapted to receive the crushed ore, and provided with a manhole opening extending to the \> outside of the latter, and means for reciprocating the inner vessel and for rotating / the outer vessel on its trunnions, whereby the contents of the inner vessel may be tf discharged. Also, the method of separating precious metals from their ores, con- | sisting in placing the disintegrated or crushed ore in a closed perforated vessel I and causing the latter to reciprocate in the reagent or chemical solution, whereby ' the latter is enabled to more effectually act upon the ore. 497856 May 23, 1983. C. G. BROWN. Ore-tank. In a tank for leaching or saturating ore, the combination with a false bottom and a piece of textile material laid upon the upper side of said false bottom; of a series of vertically disposed ^ perforated tubes designed and adapted to hold the pieces of ore apart and pro- mote the circulation of the leaching or saturating solution. 525970 September 11, 189 4. J. STOKER and B. T. LACY. Method of and appa- ratus for dissolving, leaching, and filtering. The inventor claims the improved method of dissolving, leaching, and filtering, consisting, essentially, in connecting a plurality of closed tanks in series, then introducing an expansible medium upon a body of non-compressible fluid contained in a terminal tank to force the said fluid under pressure into the successive tanks and through the material under treatment until it reaches the final tank, then connecting this last-named tank with the initial tank, and finally introducing pressure in the said final tank to v force the fluid therefrom so that it may be returned to said initial tank. And in an 2 apparatus for dissolving, leaching, and filtering, the combination of the tank adapted to contain the material to be treated, a tank adapted to contain a non- compressible fluid and connected with a source of steam, gas, or vapor supply, a valve-controlled pipe from said fluid tank to said material-containing tank, a final tank beyond the material-containing tank, a valve-controlled pipe connecting said material -containing tank with said final tank, whereby the fluid is forced into said final tank, a valve-controlled pipe connecting said final tank with the initial fluid tank, and means for admitting an expansive medium into said final tank to force the fluid therefrom back into the initial tank. 530397 December 4, 1894. N. H. CONE. Filter-barrel. In an apparatus of the class described, the combination with a revolvable cylinder having a hollow trunnion, and a head provided with radiating channels having independent valves of a filter arranged in said cylinder and valves for opening or closing said channels independently of each other. 352 APPENDIX. 536981 April 2, 1895. T. L. WISWALL and J. B. FRANK. Receptacle for recovering precious metals from solutions. This invention relates to apparatus wherein the recovery of the precious metals from cyanide and other solutions is effected by passing thq solutions through a filtering material, by which the precious metals are precipitated. And the inventor claims, in apparatus for the extrac- tion of precious metals from solutions, the precipitating box, having an undulating, sinuous passage from end to end, comprising a series of alternate angular depres- sions and elevations, provided with a series of retaining pins, attached to the interior of said precipitating -box, and extending into the precipitating, filtering material within said passage. 549177 November 5, 1895. T. L. WISWALL and J. B. FRANK. Apparatus for recovery of precious metals from tJieir solutions. The inventors claim in appa- ratus for the recovery of precious metals from their solutions a precipitating box adapted to contain a finely subdivided, metallic, precipitating reagent, divided into a series of compartments by removable perforated partitions, said partitions being provided with adjustable gates, controlling the flow of said solution through the perforations in said partitions for the purposes indicated. 549622 November 12, 1895. P. ARGALL. Apparatus for extraction of precious metals. The specifications set forth that in the treatment of ores by the cyanide process to extract their gold and silver contents, it is the usual practice to place the ores in open leaching-tanks and allow the cyanide solution to percolate through the mass and so dissolve and remove the precious metals in solution. This method is on the whole fairly efficient, but it occupies considerable time (forty to eighty hours) and causes a large consumption of cyanide through decomposition, owing to its long contact with the ore and atmosphere. With many classes of ore, how- ever, it is found that agitation of the ore and solution is necessary in order to obtain the best results or largest extraction of precious metals. Particularly is this the case with silver-bearing ores or ores parrying considerable value in silver. The agitators heretofore in use shorten the time necessary to dissolve the precious metals; but they invariably cause a large consumption of cyanide, due chiefly to the continuous agitation of the solution in open tanks or in partly filled barrels in the presence of an excess of air, while the ore when discharged from the agita- tors is in such a condition that very often it cannot be leached, or at best but part of the cyanide solution containing the dissolved gold can be separated from the ores. Then again, the agitators now in use are of such small capacity as to add largely to the cost of treating the ores. This invention relates to a new machine for treating ores by continuous agita- tion and continuous percolation under pressure or by means of vacuum and either with or without external or additional heat. And the inventor claims a perco- lator for treating ores by the cyanide process comprising an outer shell capable of being closed, air-tight, hollow trunnions upon which said vessel rotates, con- centric tubes extending axially through the vessel, the outer tube being covered by a filtering medium, a passage connecting the annular space between the tubes with one of the hollow trunnions, and a pipe communicating with the chamber surrounding the outer tube. The invention includes other features of a minor or subsidiary character. 552807 January 7, 1896. H. G. WILLIAMS. Method of and apparatus for extracting metals from their ores. In an apparatus for the extraction of precious metals from their ores by the wet process, the combination of one or more castings, with screw conveyers and mixers, means for feeding the solid and liquid matters thereto, and a dam placed at the discharge end of the casing for each conveyer, having its surface inclined upon the side next to the conveyer flights or blades, for the purpose of maintaining the admixture of the liquids and solids by preventing the liquid from traveling faster than the solid and still giving passage by reason of its incline to the travel of the solids over the same; and, in the extraction of precious metals from their ores by the wet process, the method of continuously and uninterruptedly precipitating and sepa- rating the metals, which consists in simultaneously introducing the precipitating agent. and an independent agitating blast of steam into the solution of metal in PATENTS RELATING TO CYANIDE PROCESSES. 353 direction as described to secure admixture and agitation by a whirling motion and the agglomeration of the precipitated particles of metal, and continuously separating the precipitate by settlement and filtration. 567144 September 8, 1896. S. B. LADD. Apparatus far leaching ores. The object of the present invention is to provide an economical and practical apparatus for the lixiviation of ores, and particularly applicable to cases where a large mass of material has to undergo treatment as, for example, in the lixiviation of low- grade gold ores by the cyanide process and where the expense of handling mate- rial becomes an important factor with respect to the commercial working of the process. The invention applies, genetically, to the lixiviation of comminuted or pulverized material of any character, but it is especially designed for the lix- iviation of ores by the cyanide process, for in the treatment of ore pulp or slimes by the cyanide and other like processes a large amount of material, often of a low grade, has to be subjected to the action of an aqueous solution of a cyanide or other solvent, or to the successive action of a series of solutions. The common course of procedure in working the cyanide process on a large scale is to run the ore pulp into large vats and then to cause the proper solutions for leaching out the precious metals to percolate therethrough, for example, first an alkaline solu- tion, when the ore is acid, then a strong solution, then a weaker solution, and finally water to wash the pulp. The vat is then emptied and refilled with fresh ore pulp; also, the solvent process is sometimes worked by agitating the pulp and leaching solution in pans or vessels. Both systems require considerable labor and are intermittent. Another object of the present invention is to provide means to make the extrac- tion process continuous, so that the ore pulp shall progressively and continuously be associated with the solutions or the washings which may be necessary for thor- oughly exhausting the values from the ore. This is accomplished by construct- ing a leaching-tank, in the form of a long trough, which may be divided by one or more fixed or removable bridges into so many trough sections as are required for the several solutions or washings when one leaching is not sufficient; or by providing a series of tanks or troughs operatively arranged with respect to each other, employing in connection therewith a conveyer for the ore pulp adapted to continuously feed the pulp with a steady movement through the several solu- tions in an uninterrupted flow through the apparatus to the point of discharge without any intermediate stoppage or handling of the same whereby the lixivia- tion of the ore is effected. For the purpose of rendering the operation continuous, provision is made for a constant drawing off of the charged solution or solutions from the leaching troughs and an inflow of fresh solution thereto. In the case of the first cyanide solution the inflow is preferably at the ore-entrance end of the trough or trough section and the current is with the ore, thus catching the fine float gold carried by the fresh pulp; but in the subsequent troughs or trough sections, and also in the first, if preferred, the inflow of the solution, (or washing water) is prefer- ably made at the ore-exit end and the outflow of the solution is at the opposite end where fresh ore or pulp is entering the trough or trough section. Thus, in this latter case, the flow of the solution is opposite to that of the ore. The fresh cyanide solution first acts upon pulp which is largely leached out, and as the solu- tion becomes more and more charged with the gold or precious metals it meets Eulp that is progressively richer in the metals, and the conditions are therefore ivorable for effecting a complete extraction of the precious metals by the sol- vent. As a preferred form of conveyer, slowly-moving blades transverse to the trough or tank are used. These blades extend across the tank with just enough room at the sides for clearance, and they reach from above the surface of the solu- tion down to and into the ore pulp on the bottom of the tank with openings or notches in or along the lower part of the blades for the underflow of the solution. These blades divide the trough or tank into a number of communicating divisions and form what may be called "traveling partitions," moving slowly through the trough from end to end thereof. The lower edges of these blades are preferably fashioned with rake teeth, and they open up and rake along the layer of ore pulp on the bottom of the tank and effect a slow and progressive movement of the mass 354 t APPENDIX. with a constant plowing therethrough and exposure of fresh portions thereof to the action of the solution, while the solution in the tank as the series of blades move forward has to flow back through the notches or openings in the bottom of the traveling blades from each of these divisions formed by the blades, re- spectively, into the adjacent rear division, and thus there is secured a constant and steady underflow of the solution in close proximity to the agitated pulp. This flow of the solution is in addition to and distinct from the flow due to the con- stant addition of fresh solvent at one end of the trough and the drawing off of the charged solution at the other end thereof; but it will be seen that the under- flow thus effected prevents a mere surface flow of the solution from one end of the trough to the other. On the contrary, as the flow from the respective divisions of the trough is from the bottom and under each traveling partition or blade, the overflow or discharge from the trough at the end is necessarily of the charged portion of the solution. It will be seen that this method of leaching ores places the ore and the solvent under perfect control, which is a very great advantage with respect to the economical leaching of ores. There is an agitation and con- stant shifting of the pulp in the solution, which very much accelerates the action of the solvent and shortens the time required therefor, and the speed of the con- veyer can be regulated so that the pulp will not remain in the tank or tanks any longer than is necessary, and -yet long enough for the extraction of all value there- from. On the other hand, the flow of the solvent through a tank can be gauged so that it will issue from the tank fully charged or charged to the degree most profitable under all the conditions of the case. 576118 February 2, 1897. W. F. HEATHMAN. Means for extracting gold and silver from sea-water. In order to extract said metals, the sea-water or salt lake- water is passed through a filter made of carbon, and the gold and sliver held in solution in the sea-water or salt lake-water are freed from the chemical combina- tions in which they occur in the water. The chlorides and bromides of gold and silver in solution when passing through the carbon filter are decomposed by the reducing power of the carbon, the liberation of chlorine, and the destruction of the bromine combination, with the result that metallic gold and silver are pre- cipitated in the carbon filter and deposited in the pores and upon the surface of the carbon. And the inventor claims a tank mounted on suitable supports and provided in its side with an inwardly opening valve or gate, said tank having a perforated bottom, and a filtering medium arranged on the bottom and comprising alternating layers of coarse and fine carbon, a layer of wire-cloth, and a perforated top covering. 584627 June 15, 1897. J. J. DEEBLE. Apparatus for extracting gold from auriferous material. This invention has been devised in order to provide a machine for use in the extraction of gold from auriferous material by the aid of chemical solvents, in order to insure the particles of auriferous material being brought into intimate contact with the cyanide or other solvent solution. It includes a vat or pan to receive the auriferous material to be treated, having at or about its cen- ter a vertical shaft or spindle with one or more agitators or stirrers attached to its lower end. Motion is imparted to this shaft or spindle by bevel gearing or other convenient mechanical contrivances, and means are* provided for reversing the rotation and controlling the speed of the agitators, as well as for raising or lowering the agitator shaft or spindle. These means may consist of a screw- threaded lifting rod with correspondingly threaded bevel wheel in gear with a bevel pinion fitted with a crank-handle, whereby it may be rotated in the required direction; or, if preferred, a rack and pinion may be used for the purpose. The inner side of the wall of this vat or pan is provided with a series of projections which produce eddies or swirls in the material under treatment as it is carried round the vat or pan. In order to drain or draw oft 7 the gold-bearing solvent from said vat, it is provided with a vertically sliding valve A waste discharge valve may also be provided in the lower part of the vat or pan for the purpose of enabling the waste material to be sluiced therefrom after the gold has been dissolved and the gold-bearing solution has been drawn off through the valve above referred to. 587408 August 8, 1897. H. L. SULMAN. Method of recovering precious metals from their solutions. This invention has for its object the recovery of precious PATENTS RELATING TO CYANIDE PROCESSES. 355 metals from solutions of the same by means of a new and improved apparatus, the apparatus being constructed to effect the deposition or " precipitation " of the precious metal or metals in solution upon a " precipitating " substance or " precipitant " which is in a solid but more or less finely divided state. The apparatus is designed to recover these metals from solutions of their haloids by means of the employment therein of dense but more or less finely divided car- bon, subsulphide of copper, or other suitable precipitant; again, also, for the recovery of the same metals from their cyanide solutions by means of the finely divided zinc product commercially known as " zinc fume," and generally for analo- gous requirements. It is necessary that whatever the nature of the precipitant used and the degree of fineness to which it is found desirable to reduce it primarily, it shall be of greater specific gravity than the liquid or solution desired to be precipitated by it, so that the precipitant shall tend to settle from the liquor by gravitation. Further, it is necessary to this invention that the solution or liquor to be precipitated shall per- colate upward through the mass of solid finely divided precipitant. In an apparatus with parallel vertical sides the upward flow of liquor would tend to carry off finely divided particles of precipitant unless special means were taken to prevent this. Filters tend to become clogged and are generally useless for this purpose, so that the inventor retains the particles of the solid precipitant, upon whose surfaces the precious metals are in course of deposition, within the apparatus by inducing the subsidence of them. This is effected by continually reducing the upward rate of liquor flow, which is secured by constantly increasing the area of the liquor column as it rises higher in the apparatus. The apparatus takes the form of a funnel. The liquor enters (under a suffi- cient pressure or "head") through the bottom orifice. It then meets with and thoroughly mixes with the mass of finely divided precipitant in a condition of suspension in the liquor. The solid, finely divided particles do not sink against the comparatively rapid inflow, or are prevented from doing so to any extent, by means of an automatic valve of ordinary type. By this intimate admixture of liquor with precipitant the deposition of the precious metals in solution in the former is effected upon the minute surfaces of the latter. It now only remains to remove the depleted liquor from the particles of the solid precipitant containing the gold, silver, etc. As the liquor continues its upward flow by virtue of the continually diverging sides of the apparatus the area of the liquor column becomes greater and greater. The rate of the vertical upflow is thereby correspondingly reduced. This continues until a point is reached at which the upflow is vertically so slow that the finest particles are able to settle or subside against it. At any point, therefore, above this limit or "zone," the absolutely clear liquid may be drawn o^ from the apparatus free from suspended particles and depleted of its precious-metal contents. If the precipitation of the precious metals be deemed to be incomplete in one apparatus, owing to the richness of the original liquor or to other causes, the outflow may be caused to pass into a second similarly arranged apparatus or through two or more such apparatus placed in series; but in general one apparatus can be made to secure practically perfect removal of the precious metals dissolved in a given liquor by the use of a suitable precipitant. If a series of two or more of such appa- ratus be employed, the first of the series may be used to enrich quantities of pre- cipitant which have only been partially used up to their fullest capacity of pre- cipitating the precious metals, while the succeeding members of the series are supplied with the necessary amounts of less rich or quite fresh precipitant in order to remove any remaining traces of gold, silver, etc., which may escape unpre- cipitated in the outflow from the first apparatus. The poorer precipitates in these last apparatus are in course of time removed through the bottom of the apparatus and transferred to the first one of the series, there to be enriched to their full capacity, while their place is taken by fresh quantities of poorer or quite unused precipitating agent, and so on. When the precipitate is deemed to be sufficiently rich, it is removed from the apparatus by a " three-way cock" at the bottom thereof, or by other suitable* 356 APPENDIX. arrangement, and the precious metal it contains finally recovered by any suitable method, such as in the case of the employment of a carbon precipitant by burning, or in the case of the use of a zinc precipitant by smelting. The apparatus is also supplied with a small central funnel for the introduction of fresh quantities of precipitant from time to time to the point of maximum pre- cipitating action in the apparatus, i.e., near the inflow. By providing this funnel with a bell-shaped or inverted funnel termination a sort of "chamber" is produced in the lower part of the apparatus having an annular space for the passage of liquors between the rim of the smaller funnel and the sides of the large one. This chamber is of considerable aid in promoting the action of the precipitant by keeping the bulk of it constantly near the liquor inflow and securing perfect admixture by means of the vortex currents, etc., it induces. It is further desirable to break up the rapid rush of inflowing liquors at their point of entry into the apparatus and to secure their subdivision and intimate admixture with the precipitant as early as possible. This is effected by capping the end of the inlet pipe with a small perforated cone or "distributer." The perforations may be from one-fourth to one- tenth the diameter of the inlet pipe, but their total area must be larger than that of the sectional area of the pipe. The holes may be bored in a direction perpendicular to the cap cone or they may be made "tangential," i.e., bored at a tangent to the internal circumference of the cone, thus securing a rotary initial flow of the inflowing liquors instead of a series of straight streams. In the major- ity of cases, however, perpendicular bore holes answer equally well. The clear precipitated liquor may be drawn off at any point above the limit of subsidence either, by a pipe, or, preferably, by allowing it to flow equally over the rim circumference of the apparatus. The latter method secures the quieter and more uniform outflow and does not disturb the top layers of liquor under- going final subsidence by establishing a quick current in one particular direction. If desired, the rim may be encircled with a filter-screen of lawn, calico, or other filtering or straining medium, so as to retain within the apparatus any particles of precipitant which may be floated or "buoyed up" by bubbles of air or other gas. The clear liquors passing over the rim and through the precautionary filter or strainer fall into and are collected by a circular trough or "launder," attached to the apparatus below the rim, whence they are conveyed away by a pipe. As before stated, this may lead into a storage-vat or into another similar apparatus, or, if deposition of the floating particles is not absolutely complete, into any suitable type of apparatus such, for example, as the slat-partitioned tank used for freeing softened water from traces of deposit where subsidence is finally rendered abso- lute. In most cases where the traces of precipitant have escaped, I have secured perfect final subsidence by allowing the liquors to flow through a shallow tank of from four to six times the area of the top of the precipitating apparatus before passing them direct to the storage liquor vats. Such an apparatus as is described is termed a " precipitating cone." It may be constructed of any suitable material, such as wood, stoneware, galvanized iron, etc., according to the nature of the liquor or precipitant it is designed to treat. Its action, until the charge of precipitant it contains is exhausted and requires renewal, is perfectly automatic and continuous. Its capacity, its height, the angle of its f'des, the ratio diameter of inflow pipe to top area of cone will naturally vary with the volume of liquor to be dealt with, the rate and head of liquor inflow, the relation of the specific gravity of the liquor to that of the finely divided precipitant, the actual coarseness or fineness of the particles of the latter, and so on. These data may be calculated or decided by preliminary experiment in any particular case. As an example, however, of the application of this in- vention to the recovery of gold bullion from cyanide solutions, the following dimen- sions of the apparatus are cited: For a flow of from 600 to 800 gallons per hour B depth of 5 feet, with a top diameter of 5 feet, is amply sufficient. The diameter of the inlet pipe is from 1-J to If inches, according to the head of the inlet liquor, Awhile the perforations of the cap cone or distributer are three-sixteenths of 1 inch PATENTS RELATING TO CYANIDE PROCESSES 357 in diameter. The charge of zinc fume in such an apparatus varies from 5 to 30 pounds, according to requirements. 587874 August 10, 1897. E. D. SLOAN. Barrel-filter. The object of this improvement is to provide a suitable filter-barrel, with a durable and highly effective filter, at comparatively low cost. With a view to securing the desired ends the usual trunnioned iron barrel is lined with lead. The framing of the filter-bed is composed wholly of suitable wood capable of fairly resist- ing the action of chlorine and acids, and which may be filled with suitable matter to enable it to better resist the destructive action of the corrosive solutions. The filtering medium is composed of material which resists the solutions, is well protected against undue abrasion due to the action of the solid matter during the rotation of the barrel, and it has its filtering area supported to enable it to safely bear the overlying contents of the barrel by an underlying floor of such metal as will practically resist the action of chlorine and sulphuric acid as, for instance, a lead floor and the latter is freely perforated to admit of the prompt discharge of the filtered liquid. The filtering surfaces are flat, and hence the body of any woven filtering medium is maintained in a condition more favorable to the passage of the liquid than would be the case if it occupied a curved line and said surfaces were concave in conformity with the interior contour of the barrel. The framing of the filter-bed involves inexpensive straight work, as distinguished from the curved or segmental work in framing, which is made to conform to the interior of the barrel as heretofore, and the filter-framing is constructed in parts which are so interlocked as to secure rigidity, but which may be readily applied to or removed from the barrel by way of the usual manhole and without deranging the lead lining or the means by which the lining is clamped to the barrel. 597372 January 11, 1898. P. J. DONOHUE and J. F. CORKER. Precipitating safe. The combination with a closed vessel or standpipe provided with a normally closed outlet at its bottom for the precipitate and having a body or column of zinc filings or like material in its upper part, adapted as corroded to fall into the lower part, of means for supplying, under pressure, the solution containing the precious metal to the lower end of said body or column of filings or like material, to cause the corrosion or oxidation thereof, whereby such corroded or oxidized portions will gradually precipitate to the bottom of the vessel or standpipe and the fresher portions of the filings or like materials be exposed to the ascending solution. 606810 July 5, 1898. J. W. PACK. Recovery of gold from waste solutions of chlorinaiion works. A means for recovering gold from waste solutions of chlorina- tion works, consisting of a tank having an inlet passage at the lower portion and an outlet passage at the upper portion and having metallic aluminum contained therein, and intermediate between the inlet and outlet passages of the tank, and a filter fixed within the tank between the metal and the outlet passage and having its lower side coated with a substance which will arrest the fine precipitated gold and prevent it from passing off with the liquid. 608554 August 2, 1898. R. MOODIE. Washing or leaching apparatus. In an apparatus for washing or leaching, a series of cells, one of which is a dry cell and the others of which contain washing or leaching liquid, means for intro- ducing the material to be washed into the dry cell, an oscillating shaft extended longitudinally of the series of cells, means operated by said shaft to transfer the material from the dry cell to the washing cell next in series, arms attached to the oscillating shaft and extending one into each washing cell, and scoops on said arms. 608945 August 9, 1898. H. B. WILLIAMS. Lixiviation apparatus In a lixiviation apparatus, the combination of a vertical series of annular tanks arranged one above another and each provided with an exit through which ore or other substances may be discharged into the tank beneath, each tank bottom being provided with an ascending incline leading to one side of the tank exit and having a descending incline on the other side, means for feeding ore into the top- most tanks, pipes for conveying leaching solution into the several tanks separately, the feed of the ore to be continuous and the feed of the solution to be continuous or intermittent, filters located in the several annular tanks, and automatic scraping 358 APPENDIX. and stirring mechanism to cause the ore and solution to be moved around each annular tank and over the filter therein. 610596 September 13, 1898. R. AYMER and D. J. NEVILL. Filter-frame. In a filter-barrel, the combination of a rubber grating having a corrugated surface in contact with the curved inner lining and periphery of said filter-barrel adapted to allow the filtering solutions to run along and down the lining of said barrel, a perforated bedplate of glass or porcelain curved concentric with the inner periphery of said barrel and resting on said rubber grating, a filtering medium on said glass bedplate, a curved glass grating resting on said filtering medium, two oppositely disposed cleats secured lengthwise of said barrel to its inner periphery adjacent to the ends of said curved glass bedplate and grating, and wedge keys between said ends and said cleats adapted to key said members against the barrel. 611515 September 27, 1898. J. P. SCHUCH, Jr. Means for extracting precious metals. In a metallurgical apparatus for treating ore by a cyanide solution, a tilt- able tank comprising a suitable support, a tank body having a discharge gate at its rear end and pivoted to a support at a point between its centre and the front end, a drain device in the bottom of the tank for drawing off the cyanide solution, holding springs mounted on the support and engaging with the tank body at points between its discharge end and the pivotal connection thereof with the support, and means for retracting the holding springs from engagement with the tank body. 611935 October 4, 1898. J. POOLE. Process of and apparatus for treating ore tailings. For the continuous treatment of pulps, slimes, tailings, and the like with cyanide and similar solvent solutions and in combination, a series of shallow tray- like baths, a rake in each bath of the series for reciprocating the rakes, an overflow chute at the end of the series, settling-tanks to receive the overflow from the chutes, means for separately discharging the solid and liquid contents of the tanks, con- veyers adapted to raise the solid contents from one tank after discharge, a launder in which such contents are received and in which they may be further treated with a solvent solution or wash, and a further settling-tank for receiving the dis- charge from the launder. 615968 December 13, 1898. T. CRANEY. Apparatus for treating ores, etc. In an apparatus for treating ores, the combination of a tank adapted to contain a body of the ore to be treated, devices for feeding ore into the top of said tank and discharging it from the bottom thereof at a point above the tank in a con- tinuous manner, a solvent supply reservoir, a receiver connections between the tank and said supply reservoir, and receiver for producing a continuous flow of the solvent through the tank in a direction opposite to that of the movement of the ore, an endless-chain carrier in proximity to the tank and having draining buckets adapted to receive the ore discharged from the tank, means for discharging a liquid upon the drainage buckets, and means for collecting the drainage from the buckets and returning it to the aforesaid supply reservoir. 617029 January 3, 1899. W. A. K 6 NEMAN and W. H. HARTLEY. Apparatus for separating liquids from solids. The method of abstracting liquid from finely pul- verized ore, ore slimes, or other solids impervious to percolation with which the liquid is mixed, which consists in subjecting the mixture to gaseous pressure ap- plied above the same, and simultaneously to the action of a partial vacuum ap- plied below the same, removing a portion of the liquid by filtration below the body during compaction of the solids, and collecting and abstracting by pressure the remaining liquid above the compacted solids. 617497 January 10, 1899. P. ARGALL. Cyanide -filter-tank. In a cyanide filter-tank, a vertical metallic side or wall, a horizontal bottom secured thereto, having a central opening, a packing ring secured to the inside of said wall, near the bottom, with a spacing, a system of level joists converging from the perimeter toward the center, upon said horizontal bottom, a plastic filling between said joists sloping downward from the packing ring regularly toward the central open- ing, a level floor with interstices laid upon said joists, permeable filtering material upon said floor, and a covering of textile fabric, the outer margin of which is packed into the crevice between the packing ring and the vertical wall. 618622 January 31, 1899. P. SOMERVILLE. Apparatus for extracting metals. An apparatus for extracting metals, consisting of parallel barrels having annular PATENTS RELATING TO CYANIDE PROCESSES. 359 disks closing one end with central inlet openings for the material, a framework and roller support for said barrels, means whereby the barrels are rotated in oppo- site directions, spiral flanges fixed to the interior of the barrels for advancing the material therethrough, devices for feeding material and fluid matter to the upper- most barrel, means for separating the coarse from the fine material and delivering them separately, and means for transferring material from the discharge end of one barrel into the inlet end of the barrel below. 619211 February 7, 1899. A. M. NICHOLAS. Filtering apparatus for separating gold- and silver-bearing solutions. This invention has been devised for the pur- pose of providing means whereby solids or insoluble material may be separated from liquids carrying same in suspension, but more particularly for the purpose of providing means whereby the separation of gold and silver-bearing solutions from tailings, slimes, pug, or pulverized ore may be carried on continuously and in such a way that a clean or partially clean filter-cloth will be continuously brought into operation without necessitating stoppages for recharging, as required with the appliances at present in use. The essential feature of the invention consists in the use of a rotating-wheel, disk, or table formed with a series of air-tight compartments covered with cloth or other filtering material supported upon a metal sqreen or perforated plate and adapted to be automatically placed in communication with a vacuum pump in turn for a sufficient time to enable the liquid to be drawn through the filtering material, leaving the solid constituents upon the filtering surface, whence they can subsequently be removed by brushes, jets of water, scrapers, or similar con- trivances, provision being made for automatically allowing air to enter into the various compartments at the desired period of the operation to facilitate the removal of the solids from the outer surface of the filtering material. 620660 March 7, 1899. J. LUCE. Apparatus for treating ores by lixivia- tion. In a tank for the treatment of ores, a lining composed of asbestos applied to the inner side of the tank, the notched or recessed boards applied inside of the asbestos, and the steam pipes placed in the notches in the boards, combined with two thicknesses of grooved perforated boards, and the layers of cloth between the boards. 623465 April 18, 1899. G. S. DUNCAN. Apparatus for separating gold- and silver-bearing solutions from ores or slimes. Hitherto upward percolation has been used for the displacement of the various gold- and silver-bearing solutions in the treatment under the cyanide or other similar processes of tailings or free leaching ores which are not in the form of slimes. With this upward percolation false bot- toms for the vats with webbing upon them have been used and the solutions have been introduced underneath these false bottoms, which have acted as distributors therefor and allowed them to pass evenly up through the free leaching ore, dis- placing the gold- and silver-bearing solution contained therein. This false bot- tom and webbing are adapted for use with free leaching ores only and cannot be employed for displacing solutions used in treating very finely crushed ores or limes which do not leach freely. /\ * The present invention has been devised in order that the various solutions may be displaced, as above described, from finely crushed ore or slimes, without the aid of any false bottom and filtering webbing. And the inventor claims, in an apparatus for separating solutions of the precious metals from residual ores and slimes, the combination with a leaching- and displacement-tank or vat and with a vat to hold said solutions, the latter being placed at a higher level than the former, of a series of pipes to convey said solutions from the higher vat, the discharge ends of said pipes entering the leaching-vat, a series of hoods having slightly arched portions which overlie the said discharge ends, and stirring arms radiating from a central shaft in said vat, the arched portions of the hoods being arranged in radial lines, or at right angles to the movement of currents set up by the stirring arms. 623772 April 25, 1899. A. F. DUEY. Apparatus for leaching ores. A device for treating pulverized ores, comprising a leaching-tank, an air-compressor, a tank for storing the leaching liquid, a perforated pipe in the bottom of the leach- 360 f APPENDIX ing-tank, connections from the air-compressor and liquid-storing tank to the per- forated pipe, a perforated drainage pipe in the bottom of the tank, and a layer of filtering material about said pipe. ? May 9] 1899. C. H. PEAD. Slime filter. The apparatus consists of a tank fitted with a hood of conical or any other convenient form. The sides of the tank project above the point of attachment of the hood, so as to form an annular space to act as a receptacle forming a launder for discharge of the clear liquid. In the center of the hood is an opening, around which is riveted or bolted a frame or seating arranged to carry a niter composed of one or more layers of niter-cloth or any other well-known filtering medium. The filter is kept in place by means of a protective gird of clamp of suitable form and strength to resist the effective pressure from the interior of the tank. A number of small distribution pipes set at such an angle as to cause the slimes to impinge on the under surface of the filter are connected to the seating of the latter, through which they pass. They are connected to a main distributer, which in turn is connected with the delivery-pipe or column of the slime-pump. One or more taper-shaped plugs or cores constructed of light steel tubes, their number varying according to the .size of the tank, pass through the hood and extend to the bottom of the tank. They taper from about 18 inches at the top to 15 inches at the bottom. They are fitted at their upper ends with a flange, to which is attached a shackle. Their lower ends are closed by means of a dished bottom riveted in place and having a strong bolt or stud fitted to its center. Each plug or core rests on a seating fitted to the outside of the hood and through which the plug or core posses. The seating is attached thereto by means of its flange. In the bottom of the tank and directly under the aperture in the hood through whi2h the plug or core passes is a discharge door of the ordinary manhole or other convenient type. The end of each plug or core passes easily into the discharge opanin^, and the discharge door is drawn up onto its seating or joint by means of the bolt or stud on bottom of the plug or core and by its nut. The plugs or cores when in place and holding up the manhole doors' afford an effectual means of resistance against internal pressure. A special pipe is arranged and fitted to the upper portion of the tank to drain the space forming a launder between the top of the tank and the upper surface of the hood and to conduct the liquid portion which has passed through the filter to the precipitation boxes or to waste. ? May 9, 1899. F. A. EDWARDES. Apparatus for use in treating metallic ores. In apparatus for use in the treatment of metallic ores, the combination with an annular vat having a stirrer moving therein and skimmers attached to and moving with the said stirrer, of means for tipping the said vat for discharging the contents. 624957 May 16, 1899. L. H. MITCHELL. Tank-bottom discharge door. A discharge apparatus for tanks provided with a hollow upper portion, a base having integral-bearing zones connected thereto at one end thereof, a casting having an upper annular supporting rim and adapted to receive said bearing zones, a ring surrounding said casting, devices connecting said rim and ring to secure the casting in position, and means supported by said casting to unseat said base. 624.958 May 16, 1899. L. H. MITCHELL. Tank-bottom discharge door. A discharge apparatus for tanks consisting of a casting secured in the bottom of the tank, a ring below the tank around the casting, and means for securing the rim and ring in position, a funnel above the casting, a base connected with the lower end of the funnel and provided with an annular offset or shoulder, a pack- ing-ring within the offset, and adapted to rest upon the rim of the casting, a plate or bar bearing against the rim of the casting, a nut-carrying screw in the plate or bar adapted to engage the base and draw the same within the casting, a brace or clamp connected to the plate or bar above the nut on the screw, and means for rotating the screw. 639540 December 19, 1899. W. DUNCAN. Means for mixing and aerating sands or tailings while under treatment by solvents. Numerous attempts have from time to time been made to secure the thorough mixing of sands and tailings, includ- PATENTS RELATING TO CYANIDE PROCESSES. 361 ing slimes, with- the solvent while under treatment and also to prevent that close packing which prevents the percolation of the solvent and wash liquors. For this purpose vertical vessels with vertical agitators, revolving barrels, and air, steam, and water jets have been used, but these means have not been as efficient as they might be. This invention relates to improved mechanical means for mixing and aerating "sands" or "tailings," by which terms are included slimes, sludges, and con- centrates, while under the action of solvents, whereby time is saved and a better extraction is obtained; and it consists of a semicircular vat provided with a re voluble agitator composed of arms arranged helically on a shaft running the length of the vat. At one end of the vat is placed the fast and loose pulleys and gear for slowing and rotating the agitator, while at the opposite end a series of taps are provided connected to the vat at various heights and to pipes, so that the liquor can be drawn off at any desired point and either run direct to the sump or through a filter to the sump. 641419 January 16, 1900, H. C. WHEELER. Agitator. In an agitator, the' combination of the vat, the track provided with the cog-rack, the carrier pro- vided with the pinion meshing with the cog-rack, the first driving-shaft provided with the driving-pinion, the driven cog-wheel meshing with the driving-pinion, the gear-wheels connecting the driven cog-wheel with the pinion meshing with the cog-rack, the agitator-frame journaled or pivoted to the carrier-frame, the second driving-shaft journaled in the agitator-frame, the agitators journaled in the agitator-frame and adapted to be operated by the second driving-shaft, inter- mediate gearing connecting the second driving-shaft with the driven cog-wheel, one of such gears being journaled with its axis in line with the axis of the pivotal support of the agitator-frame, and means for rotating the first driving-shaft. 647358 April 10, 1900. D. W. BALCH. LeacMng-tank. A tank having a bottom, a leaching false bottom above the same, and vertical filtering partitions \^> arranged in pairs within the tank, whereby spaces are left between pairs of par- titions, and other spaces are left between members of such pairs, said spaces last named all communicating with the chamber between the bottom and false bottom. 647678 April 17, 1900. C. W. MERRILL. Means for charging leaching-vcts. This invention relates to a method of charging ore or tailings to a leaching-vat, 1 which process is a step in the treatment of said ore or tailings preliminary to the application of the solvent solution in cyanide, hyposulphite, or other hydrometal- lurgical processes. It consists essentially in conveying the tailings or ore by any well-known adaptable mechanical means to a point above the center of the vat to be charged arid delivering the material there to a hopper, which feeds a revolving chute inclined at an angle greater than the natural slope of the material to be handled, and with openings adjustable both as to size and position, through which the material to/o be treated falls gently into the vat and distributes evenly, thus giving a charge'"' of minimum density and maximum homogeneity, the conditions most favorable to successful leaching and dissolution of the precious metals. The ordinary method of charging leaching-vats is from cars running on a super- imposed track. By this means the momentum of the carload of tailings or ore dropping through five or more feet to the bottom of the vat is such as to produce considerable, packing and, moreover, an uneven packing or density. For instance, in dumping from an end discharge car the resultant mass of ore or tailings will take the form of a cone in the vat and the maximum density will be in the center of the approximate circle forming the base of the cone and will decrease along" the radii toward the circumference of this circle. Furthermore, the variation in fineness of the different carloads is not equalized, and a vat charge of ore or tail- ings results, which is heterogeneous, both as regards density and as regards fine and coarse material. Now, first, the charge of ore or tailings in a vat should be of the least density possible to obtain, because experience has demonstrated that the greater the permeability, and consequently the greater the amount of lixiviant possible to percolate through the charge, the greater the extraction of the precious metals in a given time, or, from another standpoint, the greater the permeability the less the economic period for leaching, and hence the less the cost for plant 362 APPENDIX. and subsequent operation; second, the charge should be as nearly homogeneous as possible as regards both density and size of material, because in leaching ores it is necessary to follow solution with wash-water to replace and prevent the loss of the former or to follow one lixiviant with another of different strength or con- taining a different solvent, and in doing this to maintain the surface of demarca- tion between the one and the other as nearly a horizontal plane as possible in order to minimize the mixing of effluent solutions. The above conditions of minimum density and maximum homogeneity are produced by means of a revolving inclined wide chute with small openings in the bottom, adjustable as to size and position transverse to the direction of the stream of ore or tailings. By means of this method a number of very small streams of ore or tailings fall gently into the vat as the chute revolves, and by increasing the speed of revolution a carload of fine or coarse material can be spread over the whole area of the vat, thus giving the smallest possible dimension parallel with the course of the lixiviant. 653631 July 18, 1900, J. C. WALLACE. Filter barrel or tank. In a filter barrel or tank, a filtering device consisting of a series of curved metal plates, perforated, fastened to the inside wall or walls of said barrel or tank; a filter-cloth upon the upper surface of said plates, secured thereon by a series of imposed metal bars and filling strips secured in position by bolts or other fastening devices to the wall or walls of said barrel or tank. 653684 July 17, 1900. F. H. LONG! Metallurgical filter. The combination with a closed vessel having a filter septum and a regulated outlet port for the fil- trate beyond such septum, of the wash-water pipe connected in hydrostatic column with said vessel and the external centrifugal pump joined at its separate sides in closed union with the opposite ends of the vessel, the journal-box for said pump- axle being furnished with a water column pipe to counterbalance the hydrostatic pressure at the vessel. 654315 July 24, 1900. T. E. LEECE. Apparatus for working ores of valuable metals This invention relates to an apparatus which is designed for working the ores of valuable metals, and is especially useful for separating slimes from solutions in which they may occur, and also for separating heavier and lighter parts under any condition in which they may be found associated. It consists essentially of a tank and an endless traveling belt with directing rollers, by which one portion of the belt is caused to travel through the tank in close proximity with the bottom and the other part is guided back exterior to the tank by similar rollers. It also comprises a means for straining, or separating the liquid from the heavier portions. 660498. October 23, 1900. J. A. FLEMING. Apparatus for leaching ores. In an ore-leaching apparatus the combination with the leaching-tank having a pulp discharge, of the conical perforated filtering-hopper therein having the dis- charge for the pulp, means by which to maintain air pressure below the diaphragm, whereby to control the flow of solution through it, means for the introduction and withdrawal of chemicals to and from the body of the tank above the filtering dia- phragm, and devices for controlling the discharge of the pulp from the tank. 660499 October 23, 1900. J. A. FLEMING. Apparatus for leaching ores. An ore-leaching apparatus, consisting of the leaching-tank, having a filtering- hopper a solution discharge below said hopper, and a pulp discharge also below said hopper, and independent of the solution discharge, a washing-tank below the leaching-tank and in position to receive the pulp from the discharge thereof, and means for controlling the passage of the pulp from the leaching- to the washing- tank. 664059 December 18, 1900. J. P. SCHUCH, Jr. Ore-mixing machine. Heretofore, in treating gold-bearing ores by the common cyanide process, the ore is first crushed, dried, and rolled to a proper degree of fineness, and that which requires roasting is then conveyed to the roasters, while the oxidized ore, which does not require roasting, is conveyed to the bin or receptacle therefor. After the portions of the ore to be roasted have passed through this step of the process the same is conveyed to the cooling-room before being deposited in the bin or receptacle referred to which contains the ore requiring no roasting. All of the ore PATENTS RELATING TO CYANIDE PROCESSES. 363 is then removed by manual labor into the ordinary stationary cyaniding-tanks, and after these tanks are filled with the ore the cyanide solution is introduced therein. In this process the filled cyanide-tanks, with the solution and ore therein, are permitted to remain filled and unmolested for a sufficient length of time for the solution to act on the ore, after which the gold-bearing solution is drawn off and allowed to flow to the precipitation-room, while the tailings in the tank are then washed with water and shoveled out or sluiced out when this is possible. In this process, which is the one usually followed out in extracting gold and silver from their ores by the use of cyanogen containing solvents, the percentage ex- tracted rarely exceeds 80 per cent, of the ore value, and it is the purpose of the present invention to provide means whereby a larger per cent, of the value of the ores may be saved. To this end the invention contemplates an improved mixing-machine which provides for a thorough aeration of the ore and solution, while at the same time providing for a mixing of various grades of ore with the cyanide solution, so as to make one even grade out of ores of various values. And the inventor claims, in an ore-mixing machine, an open tank provided at the bottom with a solution drain, a perforated false bottom arranged within the tank above the main bottom and supporting filtering material, an ore discharge pipe communicating with the interior of the tank immediately above the plane of the false bottom, a revoluble agitator depending within the tank into close proximity with reference to the false bottom, and a plurality of air jets arranged to communicate with the tank in a plane intermediate the said false bottom and the lower end of the agitator thereabove. 664196 December 18, 1900. J. C. WALLACE. Filter-bed. In a filter-barrel, a filter-bed consisting of a series of metal plates having drain slots or perforations therethrough, a series of perforated tiles arranged as a filtering medium upon and supported by said metal plates, a series of metal-binding strips imposed upon or against said tiles; together with suitable means for fastening or confining the same together and to the inner wall of a filter-barrel or tank. 671028 April 2, 1901. J. R. PHILLIPS. Pulp agitator. This invention con- sists of an inclined or funnel-shaped tank or containing vessel into which the pulp is placed with water, cyanide solution, or other equivalent liquid, a circulating- or suction- and force-pump by which the surface liquid may be drawn from the tank, and a pipe extending centrally down to near the bottom of the cone, with a dis- charge nozzle through which the liquid is delivered with force, so as to flow upward along the sides of the funnel and through the material, whereby the latter is loosened, agitated, and prevented from packing. In conjunction with this may be used a canvas or equivalent filter lining for the funnel, with means for providing a space intermediate between it and the sides of the funnel for the filtering through of water, and a means for conducting such filtered water away from the apparatus. 680154 August 6, 1901, A. D. JANSEN. Discharge door for cyanide-tanks. In cyanide treatment the sands are subjected to the action of cyanide solution, which solution after the proper length of time has elapsed is drawn off through a filter composed of matting or some similar material situated at the bottom of the tank. This matting or filtering material does not rest directly on the bottom of the tank, but is supported by a grating or perforated false bottom in order to allow a free passage for the solution which has filtered through. That portion of the tank, therefore, which is situated over the discharge door has no grating or filtering material, and consequently a more or less vertical column of sand is left in the tank, which still contains cyanide solution with gold in solution, the result being that this portion is imperfectly treated. The object of this invention is to provide a door so constructed that a piece of matting or filtering material may be placed upon it in order that the filtration of the solution shall be just as complete over the discharge door as in the rest of the tank. This invention furthermore relates to an improved construction, whereby the door is rendered much more easily closed and also to a system of packing the same by which joint between the door and the bottom of the tank is rendered tight. 364 APPENDIX. 683412 September 24, 1901. A. J. PERRY. Ore-separator. The object of this invention is to introduce a mixture of steam and air in the pulp, whereby the precious metal receives a quick chemical action, with the result that considerable time is gained over the method heretofore employed. And the inventor claims, in a leaching apparatus, the combination of a receptacle for holding pulverized ore, an agitator mounted in said receptacle and having a series of radial horizontal pipes each provided with a series of perforations at one side thereof, a series of scrapers or blades mounted on said agitator, a pipe adapted to supply to said agitator a mixture of steam and air from a proper source, and means adapted to rotate said agitator whereby the discharge of steam and air through the perforations of said pipes is directed toward the rear while the said scrapers or blades are moving in the opposite direction. 684654 October 15, 1901. C. VOELKER. Ore-filter. The extraction of valuable metals from ores through the lixiviation processes, such as the cyanide and others, although allowing the advantageous working of low-grade ores, still has one fault, that more or less metal remains in the tailings, and thus losses occur caused by the slimy particles contained in the pulverized ores generated from clay, talc, and other minerals which clog up the meshes of the filtering-cloth, and thus pre- vent the solution from going through freely. In such apparatus the ore is intro- duced and the solution added, and where it happens that the ore lies in different grades of value inside the tank, the solution cannot dissolve the metalliferous particles in an even manner, and at the same time where it enters first it will affect the pulp more thoroughly, and as it goes down to the bottom will take the slimes forming with it, depositing them around the aperture through which the solution is drawn off, and even several after-leachings will not remove them. To over- come these drawbacks it is necessary to construct a mechanical apparatus which shall possess the condition of letting the soluble liquids needed to dissolve the metals go through the pulp in a space of time to be governed by the operator. Some ores are liable to contain chemical substances retarding the effectiveness of the soluble agent used, and where it is of great import to remove them as quickly as possible to keep them from going into chemical action with the solution used. The object of this invention, therefore, is to combine the above-mentioned conditions, and the apparatus can be used, in addition to other milling-plants, to receive the tailings direct from the mill. The filtrate can be examined in regard to the valuable mineral matter which may exist, giving the metallurgist the means of saving the valuable salts of mercury, copper, silver, gold, and the like which may form through the chemical or electrical action in the amalgamators where such are used and where the extravagant use of copper sulphate, mercury, and salt is in most cases the cause of the solubility of gold. The inventor claims: An ore-filter, comprising a funnel-shaped tank, a basket- pr filter-holder removably arranged in said tank and fitting closely against its inner wall, a filtering textile stretched over the inner surface of said basket, a top or hood for the tank, a shaft extended downward in the tank, and a screw mounted on said shaft and spaced at its inner edge therefrom, the said screw having the end of its upper turn turned downward. 687920 December 3, 1901 . A. D . JANSEN. A pparatus for charging or discharging cyanide-vats, etc. In combination, the pair of tanks situated one above the other, stirring mechanism for said upper tank, having a hollow supporting or operating mechanism, and stirring mechanism in said lower tank, having its operating mechan- ism in line with the hollow mechanism of the upper tank, and means for raising said operating mechanism of the lower tank into said hollow mechanism of the upper tank. 688085 December 3, 1901. A. G. GOLDSOBEL, W. MUTTERMILCH, and C. JABLCZYNSKI. Apparatus for the recovery of precious metals from photographic residuum. The combination with a vessel having a loose lid, a spout or outlet for the outflow of liquid and a conical bottom and with a precipitating material contained in said vessel, of a tube having a funnel-shaped end reaching within said vessel, and of a second tube provided with a cock connecting the aforesaid precipitating vessel and funnel-shaped tube with a second vessel or receiver. PATENTS RELATING TO CYANIDE PROCESSES. 365- 689799 December 24, 1901. R. L. GRAVES. Ore-leaching apparatus. The> apparatus for use in extracting ores, consisting of a plurality of tanks, a pump, a discharge-pipe leading from said pump and having a plurality of branches lead- ing to the several tanks and provided each with a discharge-pipe which may be turned axially or swung vertically, valves controlling the several branches, and a flexible supply- or suction-pipe leading to the pump and arranged to be shifted from tank to tank, levers connected with the several discharge-pipes whereby they may be turned axially, and means connected with the lower ends of the dis- charge-pipes whereby they may be swung vertically. 690375 December 31, 1901, G. RUBSCH, Jr. Agitating-machine for cyaniding An agitating-machine for the treatment of gold and silver ore by the cyanide process, comprising an agitating-tank, having a conical bottom; a heating-chamber, surrounding the conical bottom of the agitating-tank; means to heat said chamber, a rotary pump, centrally disposed in the agitating-tank, adapted to take the solution from the bottom of the tank and discharge it above the top thereof; a rotary deflector, adapted to distribute the solution over a stationary deflector; and a stationary deflector affixed to the casing of the pump, adapted to deflect the solution to near the edge of the agitating-tank. 691706 January 21, 1902. F. H. LONG. Metallurgical filter. The com- bination of a vessel having a conical filter-septum and an outlet-port for the filtrate beyond such septum, of means for establishing an end-to-end circulation of the vessel contents above said septum, a conical spreader and an oppositely facing conical baffle-plate having a projecting spiral flange successively interposed between the ends of the vessel and arranged adjacent to said conical filter-septum to in- timately direct such circulation over the surface thereof. 697178 April 8, 1902. E. L. SHARPNECK. Apparatus for the treatment of ores. As a means for facilitating the dissolving of the values in ores, the combination of a leaching-tank, a conduit leading from and discharging directly into the tank, and means in the conduit connected with the heating-medium supply for agitating, circulating, and heating the liquid contents of the tank. 698016 April 22, 1902. J. J. HERVEY. Cyanide-tank. Cyanide-tank having a tapering bottom and a central cone arranged in connection with the bottom, an annular lining arranged in the tank and open at its lower end, a filtering-screen, connecting the lower end of the lining and the central cone, the air and water- pipes, the charging- and discharging-pipes, and the forcing means connected with said pipes. 699211 May 6, 1902. DE W. C. MOSHER. Barrel-filter. The combination with the lead lining of a filter-barrel, of filter-sections or plates having projections on their outer sides and perforations through the plates between the projections, and having bent ends, whereby the plates may be united to the lining by burning. 699212 May 6, 1902. DE W. C. MOSHER. Barrel-filter. The combination with the lining of a filter-barrel, of perforated filter-sections, and means for support- ing said sections and securing them to the linings, said sections having their ad- jacent ends so constructed and arranged to form a longitudinal channel. 701239 May 27, 1902. F. D. WOOD. Means for working ores by the cyanide process. An apparatus for treating ores consisting in combination of a plurality of aligned containing-tanks, a transversely concaved endless belt passing through and returning beneath each of said tanks, and upon which the ore is carried each of said belts discharging its load upon the belt of the next succeeding tank, means for driving said belts in unison, means by which said belts are kept transversely distended, and rollers disposed at intervals in said troughs and over which the belts pass, whereby the latter are given an undulatory movement. 702064 June 10, 1902. F. H. LONG. Metallurgical filter. -In metallurgical filters, the combination with the closed perforated tank having an internal fabric- septum with stretcher-frame therefore to rest against the tank-walls of the feed- pipe leading into the tank-bottom and the separate wash-water pressure-tube united to said feed-pipe between the inlet and outlet valves thereof. 702490 June 17, 1902. R. SEEM AN. ^ Apparatus for treating copper ores. A plant for the treatment of ores, comprising a safety vessel, a mixer revolubly 366 APPENDIX. mounted, a settler revolubly mounted at a lower level than the mixer, and a still revolubly mounted at a lower level than the settler, and pipes connecting the several vessels together, the portions of the several vessels and pipes with which the ammoniacal solution of copper comes in contact being of material indestructi- ble by such solution. 705589 July 29, 1902. A. JAMES. Apparatus for precipitating gold and silver from their solutions. In the precipitation of gold and silver from cyanide and other solutions zinc is usually employed as a precipitant, and the use. of iron vessels containing the solutions has been found objectionable, because the iron being electronegative to zinc a galvanic action is set up between the vessel and the zinc, which causes the precious metal to be deposited upon the vessel instead of upon the precipitant. Owing to this difficulty the general practice has been to use vessels constructed of wood or earthenware, which are inconvenient and do not facilitate the cleaning-up operation. The object of this invention is to avoid these objections. To this end the invention consists in a metallurgical filter for separating precious metal from a solution containing it, consisting of a metallic vessel and a zinc sponge disposed therein, said vessel having an inner coating of enamel, whereby galvanic action between the metallic vessel and the zinc is prevented and deposit of precious metal on the vessel avoided. 705726 July 29, 1902. J. C. WALLACE. Filter-bed. In a filter-bed, the com- bination of a corrugated filter-sheet or blanket having numerous perforations through the lower arcs of said corrugations ; a series of transverse supporting bars formed to fit under and receive the corrugated contour of said filter-sheet; a series of superimposed binding strips or bars with transverse corrugations and slotted ends; two longtiudinal side binding strips or bars, and bolts adapted to holding the several members together and in place within a filter-barrel or tank. 706334 August 5, 1902, G. MOORE. Apparatus for leaching ores, etc. In dissolving the soluble portions of ores, furnace products, and other like materials it has always been difficult in one operation to dissolve the final traces of the soluble portions and at the same time completely utilize the dissolving power of the acid alkali. The weakening of the acid or alkali by its dissolving action makes its action less energetic toward the finish of the operation at the very time when the more difficult soluble particles needing the most energetic dissolving action are acted upon. This not only causes loss of reagent, but also further loss on account of the poor extraction of the soluble elements desired. Also, in the case of ores of a talcose or slimy nature the talcose portions in the form of slimes prevent per- colation of the solutions in tanks by clogging. These slimes should be separated and filtered separately by known methods. Then the remaining portion will easily allow percolation. The object of this invention is to provide an improved apparatus for the pur- pose of overcoming these difficulties; and with this object in view the invention consists, primarily, in a hollow truncated cone mounted to rotate about a cen- tral horizontal axial line, provided with an opening at one end to receive the mate- rial to be acted upon, an opening at the opposite end to receive the fluid solvent, means for actuating the material through the cone in one direction and means for actuating the fluid solvent through the cone in the opposite direction simultaneously with the passage of said material. 706472 August 5, 1902. A. E. JOHNSON. Filter-bed for chlorination barrels. The combination with a chlorination barrel or tank of a filter-bed placed therein and composed of a series of bars placed side by side and having grooves in their sides forming spaces for filtering material, the corners of the bars being cut away to permit insertion of the filtering material after the bars are placed side by side, and binding strips located at the ends of the bars and covering the filling open- ings, the said strips being secured to the barrel to hold the filter in place, an out- let being formed in the barrel below the filter. 708494 September 2, 1902. J. RANDALL. Apparatus for extracting metals from ores. In an apparatus for treating ores, the combination of a series of tanks PATENTS RELATING TO CYANIDE PROCESSES. 367 with a series of agitators above said tanks and discharging into the same, so arranged that the overflow of the solvent fluid from each tank discharges into the agitator over the next adjacent tank and from thence into the latter, and means for con- veying the ore from the bottom of each of said tanks into the agitator directly above the adjacent tank for discharge into the latter. 709135 September 16, 1902. J. BROWN. Ore-leaching apparatus. An appa- ratus for leaching ores, comprising a tank adapted to contain water or other liquid, a conduit connected to and extending upwardly from the tank and having the plurality of chambers, a hopper disposed above the upper chamber, ball-valves for controlling the discharges of the chambers and hoppers, electromagnets dis- posed above the valves and adapted when energized to raise the same, the hoods and deflectors arranged in the chambers and hopper above the electromagnets, an electrogenerator, a movable commutator and circuit wires connecting the magnets, generator and commutator, the said commutator being adapted to change the circuits and the condition of the magnets. 709593 September 23, 1902. D. C. BOLEY. Apparatus for treating pulverized ores of gold and silver. The difficulty which has been experienced in treating finely divided ores by filtration with a cyanide solution is well known. In the case of battery slimes, which are produced by crushing the ore in the battery in the pres- ence of either water or a cyanide solution, and equally in the case of the fine dust which is produced by dry crushing and which becomes a slime by the addition of moisture, the difficulty in all these arises when attempt is made to filter the material, so as to draw off the moisture, because the slimes collect upon the sur- face of the filter, and when this collection reaches a certain thickness the fluid will no longer pass through and the filtering surface must then be cleaned, and this difficulty begins very soon and constantly increases as the filtering "proceeds. Attempt has been made to overcome this to some extent by producing a vacuum at the delivery side of the filter, and also an attempt to facilitate the filtration by creating an air pressure on the other side of the filter; and it has been attempted to prevent the collection of this impervious coating of filtrates by stirring and agitating the contents of the filter. So far there has been no organized apparatus capable of carrying on this work of filtering slimes successfully and economically, and such an organized apparatus is the object of the present invention, which consists in a revolving filter cylinder having vacuum chambers and means for supplying air pressure, the filtering surface being arranged in cylindrical form inside of the vacuum chambers, and the mode of operation being to agitate the pulverized ore by revolving the cylinder and by the pressure of compressed air, and dissolving the gold and the silver in the presence of a solution of potassium cyanide and of the oxygen derived from the compressed air, and the removal of the solution containing the gold and silver by filtration, assisted by the vacuum, and the continuous removal of the filtrates from the surface of the filter by their own gravity in the turning of the cylinder, and the further cleaning of the filter surface by a backward blast of compressed air applied after the filtering there- through ceases. 710462 October 7, 1902. R. D. JACKSON. Settling-tank. In a settling-tank, a distributer having downwardly extending discharge outlets for pulp and liquid, 6 means for supplying material to said distributer, means for rotating said distributer, and means for raising said distributer while rotating, whereby the distributer rises steadily above the accumulating deposit. 710495 October 7, 1902. S. T. MUFFLY. Apparatus for treating ores. An apparatus for treating ores, comprising a rotary cylinder, air-inlet and outlet pipes connected therewith at opposite ends thereof, automatic valves oppositely directed and controlling the inlet and outlet pipes, means for forcing air through the said inlet pipe, means for heating the said air, a solvent container connected with the air-inlet pipe whereby the solvent is forced by and with the air into the rotary cylinder in the form of a spray, means for governing the amount and pressure of air and of the solvent, devices within the cylinder for scattering and agitating the ores as the said cylinder is revolved. 711236 October 14, 1902. H. SMITH and P. C. BROWN. Apparatus for use in extracting precious metals from their ores. In a lixiviation apparatus, a revoluble- 368 APPENDIX tank, pipes conducting a solvent air, and steam to the tank, means for rotating the tank, and a pipe in the end of the tank opposite the end containing the supply- pipe. 712963 November 4, 1902. J. J. PRINDLE. Barrel-filter. In a chlorination barrel-filter, a platform comprising a series of perforated members or sections having the end portions thereof thickened or enlarged, said enlarged portions provided on their lower sides with prolonged curved faces forming supporting heels which conform to the curvature of the barrel in which the filter-platform is adapted to be used, and bolts passing through said curved heels and co-operating therewith in holding the platform in place. 713694 November 18, 1902 J. P. SCHUCH, Jr. Ore-mixing-machine. An ore- mixing-machine, comprising the following elements: An ore-mixing-tank, a false bottom including a strainer, means for discharging air beneath the strainer to keep the meshes thereof free from any accumulation of slime or the like, air supply- pipes disposed above the strainer to effect aeration of the contents of the tank, a track carried by the upper outer portion of the tank, an agitator-shaft having its upper portion polygonal in cross-section, a spider having a hub engaging the said polygonal portion and carrying traveler-wheels at its extremities to engage 'the track, agitator-bars suspended from the spider, and beaters or stirrers carried by the bars, each set of beaters being disposed in break-joint order with relation to the adjacent set of beaters. 714822 December 2, 1902. J. RANDALL. Settling-tank or decanting vessel. A settling-tank, consisting of a body having a vertical side and a bottom formed of slopes of different inclinations and provided with a central outlet, the said side having a cutaway portion forming an overflow lip, a launder encircling said lip and provided with a discharge-spout, a baffle-plate of cylindrical form connected by strips to the upper portion of said side and extending into the tank below the top and nearly to the lower edge of said side, and a pipe leading from said central outlet. 718680 January 20,' 1903. B. TULLY. Barrel-filter. A filter, comprising a rotatable barrel, provided with a lead lining, the body of the barrel being pro- vided with apertures and the lining being perforated opposite said apertures, a lead launder arranged on the exterior of the barrel and provided with a plurality of lead branch pipes, said branch pipes at their inner ends being fitted in said aper- tures and connected to the lead lining about said perforations. 719273 January 27, 1903. Z. B. STUART. Apparatus for treating ores. A tank having an open top and a concave bottom formed of .perforated removable plates, a removable, conical plate upwardly projecting from the center of the bot- tom, a perforated box under said conical plate, a layer of coarse fabric surround- ing said perforated box, a filtering material under said perforated plates, a pump, a suction-pipe extending from said pump to and through the mixture in said tank to a point adjacent to the upper surface of the mixture, and a discharge -pipe extend- ing from said pump to a point adjacent to the conical part in said tank, a vacuum- tank, a pipe connecting said vacuum-tank to said perforated box, and a suction- pump connected to said vacuum-tank. 719664 February 3, 1903. J. B. HEFFERNAN. Chlorination barrel In a chlorination barrel a parallel series of pipes having numerous small orifices through their longitudinal walls, one or more headers adapted to receiving the ends of said pipes, a valve or valves connecting said header or headers with an outside source of fluid pressure. 719756 February 3, 1903. S. C. C. CURRIE. Mechanism for mixing and stor- ing liquids and gases for ore treatment. In combination, an alkali mixing-tank, an alkali stock-tank at a lower level and connected by a pipe thereto, a mixing- chamber at a level below the alkaline storage-tank, safd mixing-chamber having inclines leading from opposite sides, a chlorine gas supply-pipe leading from above the top of the mixing-chamber into the bottom thereof, a storage-tank for chlor- inated liquid below the level of the mixing-tank, and a gas supply-pipe leading from the top of the mixing-chamber nearly to the bottom of the storage-tank. PATENTS RELATING TO CYANIDE PROCESSES. 369 722314 March 10, 1903. L. H. MITCHELL. -Discharge means for tanks. A discharge apparatus for tanks, provided with a casting having an upwardly pro- jecting rim provided with shoulders having longitudinally inclined under faces, a funnel having a base provided with a depending offset portion, a gasket mounted in the recess formed by said offset portion and adapted to seat upon the top of the rim, lugs formed on the depending portion and provided with longitudinally curved upper faces to engage the inclined faces of the shoulders, and operating handles at the top of the funnel. 722399 March 10, 1903. H. R. CASSEL. Barrel-filter A barrel-filter com- posed of a barrel having a lead lining, and of a filter having rigid cores and sur- rounding lead casings made integral with the lining. 7255Jt9 April 14, 1903. H. R. ELLIS. Centrifugal lixiviating-machine. In a centrifugal filtering-machine, the combination of a rotary-shaft, a drum mounted thereon, a perforated partition within the drum, arranged concentrically with the periphery of the drum at such distance therefrom as to form an annular chamber < a discharge opening in the bottom of the drum, a cover therefor adapted to be held open by centrifugal force when the drum is rapidly rotated to permit dis- charge of the charged liquid, and to be held in closed position when the drum is rotated slowly, and a discharge-gate in the bottom of the drum at a point nearer the center than the discharge opening. 727230 Maij 5, 1903. F. G. UNDERWOOD. Leaching-tank filter. The appa- ratus consists of a tank having a central discharge aperture provided with a mov- able closure, an interior filter diaphragm spaced from the bottom of the tank and having a central discharge aperture registering with the tank-discharge aperture and provided with a movable closure, in combination with vertical filter members radially disposed and spaced apart between said discharge apertures and the walls of the tank and communicating with the space beneath the diaphragm. 727362 May 5, 1903. H. HIRSCHING. Apparatus for treating ores. An ore- treating apparatus including a leaching vessel, a settler, a filter, a still, a condenser containing a coil, a stock-solution-tank, and an absorption-tank, said absorption- tank consisting of an outer casing communicating with a cooling-water-tank, an \, inner casing spaced from the outer casing and communicating with the stock- "Vv / solution tank, and an innermost casing spaced from the inner casing and com- < municating with the coil of the condenser, whereby the vapors and fluid emerging from the coil, are caused to flow through the innermost casing and through the absorption water, and the absorption water is caused to flow through the inner casing to the stock-solution-tank, said parts being connected together by means of pipes. 728126 May 12, 1903. P. W. MCCAFFREY. Precipitating apparatus. In pre- cipitating apparatus, the combination of a tank having curved walls, said tank being adapted to hold the solution to be treated and being provided with a central partition around the extremities of which the liquid is free to circulate, blocks or pieces made fast to the opposite sides of the tank, their inner surfaces being parallel with the surfaces of the partition, and cylinders mounted to rotate on opposite sides of the partition and partially immersed in the solution, said cylinders being perforated and containing scrap iron, the ends of the cylinders being located as cloee to the partition and the said blocks as is practicable in order to allow perfect freedom of movement, and means for rotating the cylinders in reverse directions whereby the .liquid is set in motion in a circular current. 728746 May 19, 1903. P, W. MCCAFFREY. Means for precipitating dissolved metals. In precipitating means, the combination of a tank adapted to hold the liquor from which the precipitation is to be made, a number of perforated cylinders containing scrap metal, said cylinders being mounted to rotate in said tank which is constructed to receive solution at one end and discharge it at the opposite end above the lowest part of the cylinders, the latter being arranged in successive order from the feed to the discharge extremity of the tank and partially immersed in the solution, and suitable means for producing a current of liquid through the tank from end to end, whereby the contact of the liquid with the scrap metal in the tanks is facilitated 370 APPENDIX. 729805 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Apparatus for ex- tracting metals from ores. In an apparatus for extracting precious metals from their ores, the combination of a tank for containing a cyanide or other suitable solution, means for reducing ore to a finely divided or comminuted state, one or more conduits connected with the solution-tank and arranged to supply the ore with solution incident to the reduction thereof, means for agitating and mixing the ore and solution, arranged to receive the same from the reduction means, a filter arranged to receive the ore and solution from the agitating and mixing means, and adapted to separate the solution from the ore, one or more decant ing-tanks' arranged to receive the solution or solutions from the filter, a precipitaling-tank which receives the clear solution from the decanting-tank or tanks, and means for transferring the solution from the precipitating-tank back to the solution-tank. 729806 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Agitation-tank. The combination of a tank, a central, vertical, cylinder arranged therein, a piston movable in the cylinder and having a rod extending through the upper head thereof, a gear disposed above the tank and adapted to be connected by a driving connec- tion with a motor, a shaft stepped on the piston-rod and keyed to and adapted to move vertically through the gear, wings connected to and extending inwardly from the vertical wall of the tank, agitating means carried by the said shaft and surrounding the upper end of the cylinder, and comprising a head fixed on the shaft, blades disposed below the wings and connected together, said blades being curved in the direction of their length and inclined in the direction of their width, connections between the outer portions of the blades and the head of the shaft, connections between the inner portions of the blades and said shaft, and a pipe communicating with the cylinder below the piston and adapted to be connected with a source of fluid-pressure supply. 730195 June 2, 1903. J. STOVEKEN and L. STOVEKEN. Metallurgical filter In an apparatus for extracting precious metals from their ores, the combination of a filter comprising a frame, an endless filter-cloth, means for driving same, means for pressing pulp against the upper stretch of the cloth at different points and separate receptacles arranged below the cloth at such points, and a decanting- vat having separate tanks connected with the said separate receptacles of the filter; the said separate tanks communicating with the vat at their upper ends, and having valved discharges at their lower ends. 730384 June 9, 1903. W, H. HOTTER, Agitating apparatus. The combina- tion of a rocking platform, means for operating the same, a frame mounted to reciprocate adjacent to the platform, cylindrical tanks or vats trunnioned on the frame and engaging the platform, flexible devices connected with the opposite extremities of the frame, guides therefor, a liquid containing-tank, a piston therein, stems protruding from the opposite extremities of the tank, and a valve-controlled conduit connecting the opposite extremities of the tank, the flexible devices of the frame being connected with the piston stems. 730385 June 9, 1903. P. W. MCCAFFREY. Apparatus for the precipitation of metals from solutions. In apparatus for the precipitation of dissolved metallic values, the combination of a tank adapted to hold the solution to be treated, and a perforated receptacle containing scrap metal, the perforated walls of the said receptacle being composed entirely of the same material, said receptacle being partially immersed in said solution and mounted to rotate therein, wherehv the solution is mads to circulate through the scrap metal for the purpose set forth. 732720 July 7, 1903. H. DUNCAN and R. R. SHERRIFF. Apparatus for sepa- rating liquids from solids. A machine for separating liquids from solids, com- prising in combination a framing and gear, carrying and traversing an endless band of filter-cloth, automatic slip devices for securing the band, a vacuum-box or suction-chamber located upon the under surface of said band, and an interposed endless band of wire cloth or gauze arranged to support and travel with the filter- band. 733739 July 14, 1903. F. H. OFFICER, R. H. OFFICER, J. H. BURFEIND, and J. W. NEIL. Apparatus for use in metallurgical processes. In an apparatus for treating ores or other materials containing gold or silver or other metals by the PATENTS RELATING TO CYANIDE PROCESSES. 371 cyanide process, the combination of a treating-tank, an absorption-tank containing a caustic solution, a compressor and connections as described between the com- pressor, treating-tank and absorption-tank whereby air or gas under pressure may be forced from the compressor through the material in the treating-tank and tiie gases released or freed from said material may be passed through the absorbing solution in the regenerator-tank and thence to the compressor, so as to permit the air to be used over and over and the valuable products released in the treating- tank to be recovered, as and for the purpose described. 735206 August 4, 1903. L. P. BURROWS. Mixing and dissolving apparatus. A mixing and dissolving apparatus, comprising a containing vessel, a shaft in and movable relatively to said vessel, an inner and an outer set of stirring-plates carried by and arranged around and substantially parallel to said shaft, the ad- jacent plates of the inner and outer sets converging toward each other from their front to their rear edges, and stirring-blades secured to the rear edges of said plates and arranged in a spiral line around the shaft, the corresponding blades of the outer and inner sets being twisted in opposite directions. 735834 August 11, 1903. L. B. SKINNER. Filter. A filter-bar, consisting of a body portion and separated tongues projecting laterally therefrom and recessed for the passage of filtering fluid, each tongue with a beveled end, and beveled faces on the body between the tongues. 735835 August 11, 1903. L. B. SKINNER. Filter. The combination in a filter-bed, of bars having each a body portion and a perforated side flange with a beveled edge, and a beveled face constituting the bearing of the flange of the adjacent bar. 735960 August 11, 1903. G. S. FOSTER and S. S. D. STRINGER. Metal-extract- ing and ore-lixiviating apparatus. The combination of a solution-supply tank, a series of intercommunicating leaching-tanks adapted to receive solution from said supply-tank, drain-pipes leading from said leaching-tanks, a launder into which said drain-pipes are arranged to discharge, and a charcoal box connected to said launder, 736036 August 11, 1903. H. L. SULMAN and H. F. KIRKPATRICK-PICARD. Apparatus for the recovery of precious metals. In an apparatus for recovering precious metals, the combination of a conical vessel having an inner amalgamated copper surface, a conical body having an outer amalgamated copper surface dis- posed concentrically within the vessel and forming therewith a narrow interspace, a body of mercury charged with an electropositive metal in the interspace, an electrolytic vessel for charging the mercury, a mercury-pump, an inlet conduit to the top of the interspace from the electrolytic vessel, an outlet conduit for mercury from the bottom of the interspace to the pump, a conduit from the pump to the electrolytic vessel, an inlet conduit at the bottom of the vessel for the solution carrying the values, a non-return valve in said conduit, means for forcing the solution up through the interspace, and a launder at the top of the vessel to receive the discharged solution. 736078 August 11, 1903. H. T. DURANT. Apparatus for the treatment cf ores with solvents. A device for the treatment of ore, tailings, or other material by solvents, consisting of a tank having a conical bottom, a plug in said bottom and made conical to correspond to the angular walls thereof, a pump or forcing device discharging into the apex of the cone, and a return connection between the upper- part of the tank and the suction of the pipe. 736597 August 18, 1903. C. D. GROVE. Barrel-filter. In a barrel-strainer,, the combination with the shell thereof of a strainer the exterior surface of which^ is in contact with the barrel, its inner surface being provided with suitable straining perforations in the form of slits combined with transverse grooves beneath the interior surface and establishing communication between said slits and the: discharge opening. 737046 August 25, 1903. J. B. TRUITT, W. L. TRUITT, and W. O. TEMPLE.. Precipitating zinc box. In a precipitating; zinc box, the combination of an outer imperforate box having a valved outlet in its bottom and a valved outlet above 372 APPENDIX. its bottom, a launder at each outlet, and an inner removable zinc-holding box having a perforated bottom, and supported in the outer box above the bottom of the latter. 737533 August 25, 1903. E. L. V. NAILLEN. Apparatus for extracting gold and other metals from ores. In an apparatus for extracting metals from ores, the combination of a concentrating-tank consisting of two cone-shaped sections secured together at their largest diameter by means of suitable flanges and provided with an intermediate strip secured between said flanges and projecting outwardly, a settling-tank disposed around the concentrating-tank, a perforated diaphragm placed between the concentrating- and settling-tanks and supported upon said intermediate strip, and a suitable bracket bolted to the settling-tank and adapted to form two horizontal sections within the settling-tank. 738148 September 8, 1903. J. B. DE ALZUGARAY and W. A. MERCER. Appa- ratus for extraction of precious metals from their ores. Apparatus for treating ores, consisting of a closed containing vessel or vat provided with fixed internal blades or wings, a rotating hollow spindle provided with ball-bearings and having hollow blades or beaters set at an angle, means for raising and lowering the spindle in the vat, gearing for rotating the spindle, and means connected with the vat for supporting the gearing and steadying the spindle, all combined, arranged, and operating as shown and described and for the purpose set forth. 738329 September 8, 1903. W. E. HOLDERMAN. Device for treating slimes. In a device for treating slimes having a liquid-tight case, a discharge-pipe pro- vided with a valve in its bottom, an inclined floor in said case, spaced bars on said floor and the sides of the case, a filtering fabric covering said bars and over- lapping the upper edge of the tank, a molding to hold the fabric in operative posi- tion, and pipes provided with stoppers leading from the filter out through said case. 740193 September 29, 1903. E. D. SLOAN. Barrel-filter. In a barrel-filter", the combination with the barrel of a partial lining of porous filter-blocks fitting closely together and having grooves formed on their under sides which intercon- nect from block to block and form drain channels; means for sealing said draining channels from the inner space of the barrel, and a discharge port leading from the drains out of the barrel. 74.1189 October 13, 1903. H. H. THOMPSON. Apparatus for extracting precious metals. An apparatus for extracting precious metals, comprising a receptacle provided with an outlet, a series of bodily movable and loosely mounted agitating .arms gradually decreasing in length and adapted to be retained in their operative position when rotated in one direction and to assume an inoperative position when moved in an opposite direction, a rotatable means for suspending said arms within said receptacle, said rotatable means and arms bodily movable, a series of screened nozzles communicating with said receptacle, means for supplying a cyanide solu- tion, compressed air and water to each of said nozzles either separately or in any preferred combination, operating means for said rotatable means, and means communicating with said supply means and the said outlet for exhausting the solution from said receptacle. 741402 October 13, 1903. W. E. HOLDERMAN. Leaching-tank. In a filtering- tank having vertical slats covered with a filtering fabric, a filtering partition extended across said tank, a trough in its bottom for the filtrate, and an orifice through the filtering fabric of said tank into which the filtrate from said trough is dis- charged. 741499 October 13, 1903. A. E. JOHNSON. Barrel-filter. In a barrel-filter, the combination with a suitable barrel or cylinder, of a filter having a perforated bottom, side walls extending below the bottom and engaging the barrel on the inside, filtering material resting on the bottom and confined by the side walls, a top perforated plate, and suitable means for securing the filter in place, a channel being formed underneath the bottom of the filter to receive the filtered liquid, the barrel being provided with a valved outlet in communication with the said channel. PATENTS RELATING TO CYANIDE PROCESSES. 373 743550 November 10, 1903. J. A. OGDEN. Process of extracting metals from cyanide solutions. The process of treating gold, silver, or other metals from a cyanide or primary solution, consisting in mixing in a receptacle a given quantity of said primary solution with a given quantity of a secondary solution having a metal base and capable of liberating the metals in said primary solution; leaving said mixture in said vessel until said liberation is partially effected, then passing said mixture into a second receptacle and agitated therein so as to produce a com- plete commingling of said solutions, from thence running the mixed solution into a settling-tank and allowing it to settle, drawing off the clear solution, and then drying the precipitation and pressing and melting it into bullion. 743551 November 10, 1903. J. A. OGDEN. Apparatus for extracting precious metals from cyanide solutions. An apparatus for the purpose set forth, consisting of primary and secondary solution-tanks, each provided with discharge-pipes with controlling-cocks, and measuring-glasses; a mixing vessel adapted to receive the flow from said measuring-glasses; a barrel with rotatable blades therein and having a glass gauge on the outer face thereof, and a settling-tank adapted to receive the discharge from said barrel. 745472 December 1, 1903. W. H. ADAMS, Jr. Apparatus for treating ores. The combination of a tank, a box, a pipe at the top of the tank connecting the same with the box, a pump connected with the box, and nozzles connected with the pump and arranged to discharge liquid into the tank at intervals tangen- tially in an approximately horizontal plane. 746867 December 15, 1903. DE W. C. MOSHER. Chlorination barrel A chlorinating barrel provided with a resistant lining and with an arched channeled rib extending longitudinally, secured to said lining and having perforations between the interior -of the rib and barrel, and a discharge opening communicating with the interior of the rib. 748088 December 29,^ 1903. G. MOORE. Filtering system. In a filtering sys- tem, the combination with a tank for containing the material to be filtered and a cleansing-fluid tank, of a filter, means for introducing and removing the same into and from each of said tanks alternately, means for drawing the contents of said tanks through the filter, and means for cleansing the filter. 748217 December 29, 1903. C. H. RIDER. Apparatus for dissolving organic or inorganic substances. A device consisting of an acid-tank, a water-tank, an upper series of tanks connected with the acid-tank and the water-tank and to each other, a lower series of tanks adapted to receive the substance to be treated, connected to the upper series of tanks and to the water-tank and to each other; a retort, means for heating the retort, a pipe passing from the retort through the lower series of tanks, and a condenser into which the last-named pipe extends, substan- tially as and for the purposes specified. 748462 December 29, 1903. W. J. ARMBRUSTER. Chlorination barrel. A chlorination barrel having a pulp-chamber and a chlorine generating compart- ment rotatable therewith, a wall separating the pulp-chamber from the compart- ment, said wall having an unobstructed opening disposed about the axis of rota- tion of the barrel for freely permitting the discharge of the chlorine above the surface of the pulp in the pulp-chamber. / CLASS 75 METALLURGY. SUBCLASS 185 CYANIDES. 323222 July 28, 1885. J. W. SIMPSON. Process of extracting gold, silver, and copper from their ores. The ore is crushed to a powder, treated with a solu- tion produced by dissolving 1 pound of cyanide of potassium, 1 ounce of carbon- ate of ammonia, and ounce of chloride of sodium in 16 quarts of water when the ore contains gold and copper only; but when it is rich in silver the quantity of chloride of sodium employed is increased. After thorough agitation of the ore in the solution the mixture is allowed to stand until the solution has become 374 APPENDIX. clear, when the dissolved metals are precipitated out by means of a plate of zinc suspended in the liquid. The metal is precipitated upon the zinc and can be removed by scraping or by dissolving the zinc in sulphuric or hydrochloric acid. 403202 May 14, 1889. J. S. MACARTHUR, R. W. and WM. FORREST. Process of obtaining gold and silver from ores. The invention consists in subjecting finely-powdered argentiferous ores to the action of a solution containing a small quantity of a cyanide, the cyanide contents of the latter being proportioned to the quantity of gold or silver, or both, found, by assaying or otherwise, to be in the ore. Any cyanide soluble in water may be used, but in all cases the solution must be extremely dilute, since such a solution has a selective action in dissolving gold or silver in preference to the baser metals. The claim covers the use " of a cyanide solution containing cyanogen in the proportion not exceeding 8 parts of cyanogen to 1000 parts of water." 41 8 137 December 24, 1889. J. S. MACARTHUR, R. W. and WM. FORREST. Process of separating gold and silver from ore. This invention has for its object the preventing of loss of cyanide in the care of weathered ores by first neutraliz- ing the ore with an alkali or alkaline earth and then leaching such prepared charge with a cyanide solution. Further, the precious metal thus dissolved in the cyanide solution is precipitated out by passage through a sponge of zinc composed of fine threads or filaments of zinc formed by cutting shavings with a turning tool from a series of zinc disks held in a lathe, or by passing molten zinc at a tempera- ture just above the melting-point through a fine sieve and allowing it to fall into water. 482577 September 13, 1892. E. D. KENDALL. Composition of matter for the extraction of gold and silver from ores. Consists in extracting gold and silver from minerals, " tailings," and other matters containing one or both of these metals by an aqueous solution of one or more soluble ferricyanides and one or more soluble cyanides prepared by dissolving a ferrocyanide in one portion of water and a cyanide in another portion and mixing the two solutions, or by adding either salt in solid form to the solution of the other. 492221 February 21, 1893. C. MOLDENHAUER. Extracting gold from its ores. Consists in subjecting gold ores to the solvent action of cyanide of potassium in the presence of ferricyanide of potassium. 494054 March 21, 1893. W. A. G. BIRKIN, Process of and solvent for sepa- rating precious metals from their ores. Covers the art of separating metals from their ores by subjecting the suitable comminuted ore to the action of a menstruum composed of potassium cyanide, potassium ferricyanide, and peroxide of hydrogen in water, and separating the values from this solution by precipitation, deposition, or electrolysis. 496950 May 9, 1893. H. PARKES and J. C. MONTGOMERIE. Process of extract- ing gold or silver. Claims a process for extracting gold and silver from ores or compounds by an interrupted operation, consisting of treating the ore with cyanide of potassium in the presence of oxygen under pressure with agitation, the ore being subsequently filtered and washed and the precious metals recovered from the liquor by precipitation or other known means. 514^57 February 6, 1894- W. P. MILLER. Process of recovering precious metals. Has for its object the preservation of the cyanide solution, and consists in the treatment of the ore with the cyanide solution in air-tight vessels not only during the process of solution, but during the filtration and up to' the time of the precipitation of the precious metals from the filtered solution. 622739 July 10, 1894. C. MOLDENHAUER. Process of precipitating gold or other precious metals from their solutions Dissolves gold and other precious metals from their ores by means of acid-cyanide solutions, which consist in treating the solution with aluminum, so as to precipitate the gold from the solution, and then add a free alkali or alkaline earth for a regenerating solution. 524601 August 14, 1894. J- C. MONTGOMERIE. Process of extracting gold or silver from ores. Sodium oxide (caustic soda) or other suitable oxide of the alkalies is added to the cyanide solution before mixing the same with the ore. PATENTS RELATING TO CYANIDE PROCESSES. 375 After the precious metals have been dissolved in the solution and the liquid filtered off and the precious metals precipitated out, the remaining solution is tested to determine the quantities of potassium and sodium oxide still remaining in it, and any deficiency is supplied or the solution fortified by the addition of the necessary quantity of these agents, so as to restore the solvent solution to its original char- acter and strength. 524690 August 14, 1894, E. D. KENDALL. Method of treating gold or silver ores. Covers the treating of gold or silver ores with a composition of matter con- sisting of sodium dioxide and a suitable cyanide in solution. / 532238 January 8, 1895. C. MOLEENHAUER. Method of precipitating precious ' * metals from solutions. Consists in subjecting the ores to the action of an acid- ^ *j cyanide solution so as to dissolve the gold or other precious metal" contained in J them, then adding aluminum so as to precipitate the gold or other metal from the solution, and then regenerating the cyanide solution by means of a free alkali or alkaline earth. 532895 January 22, 1895. J. C. MONTGOMERIE. Process of extracting gold or silver from ores. Consists in adding an oxide or one of the alkaline bases to a cyanide solution, then mixing with the ore or compound the solution thus rendered alkaline, then conducting the process under pressure of oxygen, and afterwards separating from the ore the liquid containing the gold and silver in solution, then treating that liquid in any approved way for the recovery of the precious metal, 538951 May 7, 1895. S. C. CLARK. Process of treating refractory ores. Claims the process of treating a refractory ore, consisting essentially in boiling the ore I in water containing from 10 to 15 pounds of cyanide of potassium to each ton of ore for about one hour or for a sufficient length of time to enable the cyanide of potassium to dissolve the chloride, sulphide, or bromide in the ore, then allow- ing the solution to settle and finally evaporating the clear liquid so as to obtain; a residue containing metal. 540359 June 4) 1895. G. KENNAN. Process of and apparatus for treating ores. Claims the process of treating the ores of gold and silver, consisting in sub- jecting the same to the action of cyanide of potassium, agitating the same for a short period of time, discontinuing the agitation, and bringing air in contact there- with, the oxygen thereof increasing the action of the cyanide, continuing the agita- tion for a few minutes, until every particle of ore has been brought in contact with the cyanide solution in the presence of atmospheric air, and withdrawing the solution from the remaining pulp or ore. 541333 June 18, 1895. F. RINDER. Process of separating gold and silver. Consists in the treatment of cyanide solutions containing gold and silver with ^/ sulphide of iron to precipitate the silver and then with chloride of zinc to pre- /\. cipitate the gold. 543543 July 80, 1895. M. E. WALDSTEIN. Process of extracting gold or silver from ores. Consists in subjecting the ores to the action of cyanide of potas- shim, adding to the material during this action a salt or salts (such as bin oxide 1 of barium) decomposable by an acid and yielding oxygen, and sufficient acid to ' decompose this salt or salts, and subsequently adding an excessive acid to decom- pose the soluble cyanide and finally separating the precious metals as sulphides by precipitation with sulphureted hydrogen or by a soluble sulphide. 543782 July 30, 1895. M. CRAWFORD. Process of extracting precious metals from their ores, Consists first in lixiviating the ores of the precious metals with a cyanide solution to which has been added a substantially neutral substance which contains a permanent excess of oxygen; second, in subjecting the gangue and accompanying cyanide solution to an amalgamating process; and, thirdly, in withdrawing the solution from the tailings, and extracting the precious metuls therefrom. The neutral substance containing a permanent excess of oxygen may be prepared by mixing peroxide of sodium with dilute sulphuric acid and neu- tralizing with silicate of soda. 543676 July 30, 1895, M. CRAWFORD. Process of extracting precious metals from their ores. Consists in, first, lixiviating the ore with a cyanide solution to 376 APPENDIX. which has been added a small quantity of a substance prepared by agitating ether with binoxide of barium and adding thereto small quantities of very dilute hyciro- chloric acid, and neutralizing by silicate of soda, and, second, separating the precious .metal fiom this solution in which the ore has been lixiviated. 545852 September 8, 1895. P. DE WILDE. Method of extracting gold. The precipitation of gold in the iorm of a mixture of aurous cyanide and cuprous cyanide by acidulating a cyanide solution containing the gold with an acid sulphurous compound and afterwards adding a solution of copper salt. Also, specifications provide for the dissolving of gold by the use of a weak solution of potassium or sodium cyanide which has been in contact with the minimum or protoxide of lead, and for the recovery and utilization of the spent cyanide by its conversion to Prus- sian blue. 547790 -October 15, 1895. J. J. HOOD. Extracting metals. The method for the extraction of precious metals from their ores, which consists in treating the ore with a solution containing both a cyanide of potassium or sodium and a salt or compound of a baser metal in the proportion of one part at least of the former to two parts of the latter; the metallic base of the solution being displaced by the precious metal, the former being precipitated. The gold is then precipitated out by a copper-zinc couple. By " baser metal " is meant mercury, lead, and such other metals as are displaced by metallic gold from their solutions in alka- line cyanides A mixture that answers well consists of two parts, by weight, of cyanide of potassium (or its equivalent of cyanide of sodium), one part of mer- curic chloride or its equivalent of sulphate or other mercury salt, and from one- half to two parts of caustic soda. 549736 November 12, 1895. J, C. MONTGOMERIE. Extraction of gold and .silver from ores. The improved process of extracting gold and silver from ores or compounds containing the same, consisting in treating the ore in a vessel con- taining water with a cyanide, an alkaline oxide, a nitrate, and an oxidizing agent. .Sodium dioxide may be taken as a representative of the alkaline oxide and aid under pressure as an oxidizing agent, as set forth in this claim. 555463 February 25, 1896. J. S. MACARTHUR and C. J, ELLIS. Process of ^extracting gold and silver from ores: Consists in subjecting the ore to the action of a cyanide solution and precipitating, by means of a metallic compound capable of combining with sulphur any sulphur which may become soluble in the solution and thereby rendering it inert. Salts or compounds of lead, manganese, zinc, mercury, and iron are types of the metallic compound employed. By means of a salt of lead any copper present in the cyanide solution may be precipitated out. 555483 February 25, 1896. T. L. WISWALL and J. B. FRANK. Process of recovering precious metals from solutions. The process of extracting precious metals from solutions by causing said solutions to flow through a precipitating alloy, subdivided into a mass of hardened filaments, and composed of zinc, lead, and one or more other metals which impart to said filaments a tensile strength suffi- cient to withstand the compression of the flowing solution, such as arsenic, anti- mony, cadmium, or bismuth, and in which alloy there is present not more than 97 per cent, of zinc. 576173 February 2, 1897. H. L. SULMAN. Process of precipitating precious metals from their solutions. Consists in purifying zinc fumes or dust of oxides by intimately mixing with the same an ammoniacal substance, and then mixing a quantity of said fumes or dust so purified with the solution. The apparatus by which to perform the process and for the treatment of the ores is also claimed. 578089 March 2, 1897. J. F. WEBB. Process of extracting gold and silver from ores. The process or method for the extraction of gold and silver from their crushed ores, consisting in saturating the ores in a solvent solution of potassium cyanide, then applying a current of compressed air from beneath and maintaining the same throughout the leaching process, then shutting off the current, then applying a current of compressed air on top of the solution after the ore-contain- ing Vat has been closed at top and a drain at the bottom has been opened, and maintaining the same until the solution has been driven out of the ore, then shut- .ting off the current of air, then admitting water to the vat, then introducing a PATENTS RELATING TO CYANIDE PROCESSES. 377" compressed-air current at the bottom of the vat, and finally introducing a cur- rent of compressed air on top after the vat has been again closed at top and a- drain opened at bottom. 578178 March 2, 1897, D. WHITE and T. M. SIMPSON. Process of and appa- ratus for extracting precious metals from slimes, etc. In the extracting of precious metals from slimes and other auriierous and argentiferous materials, the process which consists in mixing the said material with a cyanide solution in a closed vusel,. then agitating the mixture by passing a gas under pressure through tLe s.Lrr.e, then passing "gas under pressure, together with the gases arising from tLe acilon of the cyanide solution in the said material, through another quantity oi stud material and cyanide solution in a closed vessel, then conveying the gases Lack to the source of compression and drawing off the solution, containing the precious metal and extracting said metal. The apparatus for accomplishing this purpose is also claimed. 578340 March 9, 1897. W. A. KONEMAN. Process of extracting precious metals from their ores. The process of extracting precious metal from the ore containing it, which consists in wetting the ore, in a pulverized condition, with just sufficient cyanogen-containing solution to moisten the ore and reduce the mass to the condition of mud, maintaining the saturated ore in a quiescent state for a prolonged period of time, then diluting the mass and subjecting it to agita- tion for a suitable period of time, separating the resultant solution from the ore by filtration, and finally precipitating the precious metal from said solution. 578341 March 9, 1897. W. A. KONEMAN. Process of recovering precious- metals from cyanide solutions containing them. The process of recovering, by pre- cipitation, the precious metal or metals contained in a cyanogen-containing solu- tion, which consists in subjecting said solution to contact with an alloy composed of load and zinc, and in which lead is the preponderating metal in weight, or with an alloy composed of lead, zinc, and aluminv.m. 580683 April 13, 1897. C. W. H. GCPNER and H. L. DIEHL. Recovery of gold and silver from their solutions. The process for the precipitation of gold and silver from their cyanide solutions, which consists in adding to Faid solutions a ^Jf Considerable quantity of cuprous cyanide, then adding an acid to effect precipi- tation, dissolving the latter by a fresh quantity of the cyanide solution obtained by leaching, and then adding acid to effect successive precipitations from said solution. 580948 April 20, 1897, J. C. MONTGOMERIE. Process of treating cyanide solu- tions. The process for the extraction of the precious metals from cyanide solu- tions, which consists in filtering the solution through a charcoal filter, heating the filtering material on the same becoming surcharged with cyanogen or its com- pounds, condensing the resultant gases and obtaining ammonium cyanide and ^Q/ other ammonium salts in solution, applying the regenerated charcoal (still con- taining the precious metals) in the filtration of a further charge or charges of the solution, and ultimately recovering from the charcoal the precious metals accu- mulated therein. 587179 July 27, 1897. J H. BURFEIND. Treatment of gold and silver ores. As an improvement in the extracting of precious metals from their ores, the treat -^N^ ment of the cyanide product or precipitate containing said metals, preparatory to melting the said product with sulphurous acid. 591753 October 12, 1897. E. J. FRASER. Process of obtaining precious metals by solution. The process of treating gold and silver ores by solution, which con- sists in converting the metal bases of dioxides of the alkaline metals into sulphates, by the addition of sulphuric acid, so as to produce hydrogen dioxide, preventing the decomposition of the hydrogen dioxide by an excess of acid, separating the solution from the metallic sulphate, mixing the solution with a solution of cj^anide of potassium and lime in the presence of a precious metal, and leaching the liquid holding the precious metal. 592153 October 19, 1897. J. S. MACARTHUR. Precipitating precious metals from solutions. The process of precipitating a precious metal from a cyanide solution, which consists in subjecting said solution containing a base metal to the action of a precipitant protected by a metal inert in said solution. Such a 378 . APPENDIX. precipitant is found in zinc, mercury, or copper protected by lead. When cop- per is present in the cyanide solution, this copper is removed by the precipitant prior to the removal of the precious metal. 601201 March 22, 1898. S. NEWHOUSE, A. J. BETTLES, and T. WEIR. Method or process of extracting precious metals from their ores. A method or process for the extraction of the precious metals from their ores, said method or process con- sisting, first, in neutralizing the acidity of the ore where this condition exists; second, in placing the ore in a suitable solution of cyanide of potassium and sub- jecting the mass to agitation; third, in adding a quantity of zinc to the mixture of ore and cyanide and subjecting the mass to further agitation; and, fourth, in adding quicksilver or mercury charged with sodium amalgam, and finally agitating the entire mass for purposes of amalgamation. 607719 July 19, 1898. M. E. WALDSTEIN. Process of recovering precious metals from their solutions. The process for extracting and recovering precious metals from their ores, which consists essentially of the following steps: First, subjecting the ore in a powdered state to the action of an aqueous solution of a cyanide; second, supplying to the solution charged with the precious metals that quantity of zinc dust determined to be exactly sufficient to precipitate said metals; third, agitating said solution and said zinc dust until said metals are precipitated and said zinc dust is absorbed; fourth, recovering the precious metals from the valuable precipitate of the preceding step by filtration, or other process. 610616 September 13, 1898. H. L. SULMAN and F. L. TEED. Extraction of precious metals from their ores. The essence of this invention consists in the employment of haloid compounds of cyanogen in combination with free cyanide of potassium or other suitable cyanide of the alkalies or alkaline earths as a sol- vent for precious metals in their ores, examples of such haloid compounds of cyanogen being found in cyanogen chloride, or bromide or iodide. 620100 February 28, 1899. W. A. CALDECOTT. Method of extracting gold from cyanide. An improved method for the precipitation of gold from gold-bear- ing cyanide solutions by passing such solutions over zinc shavings previously treated with a soluble salt of mercury, such as perchloride of mercury (HgCl 2 ). ) May 2, 1899. C. B. JACOBS. Process of reducing metals from their solutions'. The process of reducing metals from their solutions, consisting in sub- jecting them to the action of gaseous phosphide of hydrogen in the presence of an alkaline material, thereby precipitating the noble metals in a metallic state and the base metals as phosphides, and then separating the latter from the noble metals. 625564 May 23, 1899, E. D. KENDALL. Process of treating gold or silver ores and composition of matter for same purpose. A composition of matter to be used for extracting precious metals from ores, tailings, or other bodies, consisting of a suitable thiocyanate and a suitable ferrocyanide in watery solution. 625565 May 23, 1899. E. D. KENDALL. Process of treating gold or silver ores and composition of matter for same purpose. A composition of matter to be used for the extraction of precious metals from ores, tailings, or other bodies, con- sisting of a suitable thiocyanate and hydrogen dioxide in watery solution. 629905 August 1, 1899. J. J. HOOD. Process of extracting gold or silver. The process of extracting gold, silver, and mercury from solutions by bringing the solutions into contact with an alloy of zinc, antimony, and mercury, from time to time distilling off mercury from the alloy, and finally recovering the gold and silver from it. The precipitant used consists of an alloy of about one hundred parts of zinc, five parts of antimony, and twenty parts of mercury. 630982 August 15, 1899. W. KEMMIS-BETTY and B. SEARLE. Process of recovering gold from pulp, slimes, or similar substances. The process of extracting gold from ores, which consists of the following steps: First, dissolving the gold m the pulp in a weak solution of cyanide of potassium: second, adding a stronger solution of cyanide of potassium to the gold-bearing solution in the proportions PATENTS RELATING TO CYANIDE PROCESSES. 379 specified; third, immediately after so strengthening the solution, passing the same through a body of zinc shavings coated with lead. 635199 October 17, ,1899. J. SMITH. Process of treating gold or silver ores. The process for treating gold and silver ores, tailings, slimes, and like materials con- taining precious metals, which consists in mixing the material to be treated with caustic lime, saturating or covering the mixture entirely with water and keeping it thus until all the acid present has combined with the lime, drying the material, exposing it to the action of atmospheric air, and treating it with a cyanide. 636114 October 81, 1899. J. S. CAIN, A. SODERLING, and S. M. MACKJNIGHT. Preliminary treatment of ores or tailings before cyaniding. The method or process of treating ores containing the precious metals, which conissts in first leaching said ores or tailings in a weak solution of nitric acid, or of nitric and sulphuric acids, subsequently leaching the same in an alkaline solution, and finally leaching the same in a cyanide solution. 636288 November 7, 1899. H. DE RAASLOFF. Process of extracting precious metals from ores. The improvement in the process of separating precious metals from their ores, consisting in mixing with the ore a solution consisting of a base and a solvent for precious metals, which solvent is capable of being separated from the said base by oxygen, and adding liquid air to the ore and solution, or by evaporating the nitrogen from liquid air, and adding the oxygen which remains to the mixed ore and solution. ? December 5, 1899. M. B. ZERENER. Precipitation of precious metals from their cyanide solutions. The process of precipitating gold and silver from cyanide solutions by causing the solution to move in one direction, and during such movement passing through it, in the opposite direction and in the form of a spray, or a number of fine streams or films, mercury charged with alkali metal. 641818 January 23, 1900. C. WHITEHEAD. Process of extracting gold from ores. The process of extracting gold from ores in which the particles of free gold are enveloped in a compound of a base metal having the folio wing characteristics, to wit: non-siliceous, oxidized, practically impervious to a solvent solution, such as one of cyanide, not readily removable by washing with water, and insoluble in water, but soluble in dilute acids, consisting in first subjecting the crushed ore to the action of heat sufficient to convert the coating into a porous condition and afterwards treating the ore with a cyanide solution. 642767 February 6, 1900. G. THURNAUER. Process of separating precious metals from their mixtures with zinc. The process of treating the mixture of zinc and precious metals resulting from the treatment of cyanide solutions of the precious metals by zinc, which consists in subjecting said mixture to the action of a solu- tion containing lead and then to the action t>f acid, whereby the zinc is dissolved and the precious metals remain in admixture with metallic lead. 646006 March 27, 1900. J. C. MONTGOMERIE and H. PARKES. Treatment of gold and silver ores, etc. In the extraction of gold and silver from ores or compounds containing the same, the process consisting in treating the ore or compound with .a cyanide of an alkali metal, caustic alkali, and barium dioxide, in conjunction with ammonium sulphate. 646808 April 3, 1900. T. CRUSE. Method of extracting gold and silver from iheir ores. The process of recovering precious metals from their ores, which con- sists in first heating the ore pulp to the boiling-point, adding cyanide of potassium to the hot mass, permitting the mass to gradually cool, and while it is cooling add- ing to the mass the following: Eluestone, iron sulphate, sulphuric acid, and quick- silver. 649628 May 15, 1900. W. A. CALDECOTT. Extraction of gold or other precious metals from slimes. The method of extracting precious metals from finely divided materials, such as slimes, containing reducing substances, such as ferrous sulphide or hydrate, which consists in rendering the material alkaline, then forcing air into the pulp until the ferrous compounds are converted into ferric hydrate, then adding cyanide and continuing aeration and agitation until the precious metals are dissolved. 380 APPENDIX. 651509 June 12, 1900. F. W, MARTINO and F. STUBBS. Precipitation of precious metals from cyanide solutions. A process for the precipitation of the precious metals from their aqueous cyanide solutions, consisting in passing acetylene and atmospheric air through such solutions, or by adding calcium carbide to them, and precipitating the metals in a metallic state. 651510 June 12, 1900. F. W. MARTINO and F. STUBBS Treatment of ores and precipitation of precious metals ffom their cyanide solutions. A process for the precipitation of precious metals from their aqueous-cyanide solutions, con- sisting in treating such solutions with a hydrocarbon gas, produced when a metallic carbide is decomposed by water, and capable of precipitating the metals in a metallic state. Aluminum carbide is given as an example of such a metallic carbide. The use of methane as a precipitant is also claimed. 657181 September 4> 1900. H. DE RAASLOFF. Process of separating precious metals from their ores. The continuous process of treating ores of precious metals, consisting in mixing the finely divided ore with a suitable solvent for the precious metals, inducing the mixture to flow continuously from and back to the point of admixture, while so flowing introducing liquid oxygen or liquefied air into the mixture, then causing the mixture to flow with sudden variations of velocity to agitate it, then separating the solution from the base earthy mineral matter, and sending it continuously through an electrodepositing ,bath, where the precious metal is deposited, and thus in continuous ordered succession. 656395August 21, 1900. E. H. DICKIE. Process of leaching ores or tailings. The improvement in the process of leaching ores or tailings with a solution which dissolves the precious metals, which consists in adding to the solution an agent composed of an acetate of an alkali metal or of alkali-earth metals which is capable of readily uniting with and forming acetates of the base metals, and which has little or no affinity for the precious metals, thereby enabling the solvent to act directly upon the latter, and then leaching the ores. Calcium acetate is cited as an example of an acetate of an alkali-earth metal. 664080 December 18, 1900. J. P. SCHUCH, Jr. Process of extracting precious- metals from their ores. A method of extracting precious metals from their ores, which consists in combining the crushed ore with a cyanide solution while both are in a warm condition, mechanically mixing the ore and solution by agitation simultaneously with the commingling thereof, charging the mixture during the agitation with hot air, and finally separating the ore and slush or pulp from the metal in solution. 665105 January 1, 1901. J. C. KESSLER. Process of extracting gold and silver from ores. The process of separating precious metals from auriferous and argentiferous ores, consisting, first, in subjecting the ores to the action of an aque- ous solution, consisting of cyanide of alkali metal, yellow prussiate of potassium, and permanganate of an alkali metal in substantially the proportions of water, one thousand (1000) parts; yellow prussiate of potassium, two and one-half (2.5) parts; cyanide of alkali, two and one-half (2.5) parts; parmanganate of potas- sium, one-tenth (0.1) part, until the gold and silver contained in such ores are dissolved; second, separating the metals from their solution by the application of a soluble lead salt, by which the cyanide solution is decomposed and a non- soluble cyanide of lead is formed, at the same time a non -soluble cyanide of gold or silver is precipitated; third, by the application, to the sediment thus precipi- tated, of sodium amalgam, whereby a gold, silver, and lead amalgam is produced and at the same time a concentrated solution of cyanide and ferrocyanide of sodium is regenerated; and, fourth, diluting the concentrated cyanide solution with a quantity of water and regenerating and reenergizing the aqueous solution for reuse by the addition of permanganate of alkali. 671704 April 9, 1901. E. D. KENDALL. Process of treating ores containing 1 silver or silver and gold. The process of treating ores or other bodies for the extrac- tion of precious metals, which consists in treating them with a suitable chemical solution containing a thiocyanate and a cyanide, capable of dissolving silver and gold, and in then treating the so-dissolved silver by a suitable sulphide, such as potassium sulphide, and in so regulating; the amount of the sulphide to the silver PATENTS RELATING TO CYANIDE PROCESSES. 381 as that they shall substantially equalize each other in separating the sulphur sul- phide and in returning the thiocyanate and cyanide into subsequent operations for further treatment of the ore. 673425 May 7, 1901. G. A. DUNCAN and F. H. BEACH. Method of treating precious metal-bearing ores. The method of treatment of precious metal-bearing ores to cause the precious metal to be dissolved from the ore, and the resulting metal-bearing liquor and impoverished ore to be separated from each other, which consists in the following steps: First, maintaining a substantially continuous supply stream of mingled comminuted ore and solvent liquor; second, mechani- cally dispersing such mingled ore and liquor into the air, in a direction transverse to the onward movement of the stream, without separating the ore from the liquor; third, delivering the resultant stream of mingled metal-bearing liquor and impov- erished ore and receiving the same in mingled condition and carrying it onward; fourth, sucking the liquor from the tailings; fifth, delivering water to the impov- erished tailings remaining, and subsequently sucking such wash-water therefrom;, sixth, delivering such impoverished ore or tailings after the application cf such suction. 682612 September 17, 1901. E. L. GODBE. Method of leaching ores. The- method of leaching ores, which consists in disposing moistened ore in superim- posed strata within a containing receptacle by a continuous mechanical agitation in the lower portion of the latter to form a lower thoroughly agitated stratum of heavier portions of the ore, a stratum of lighter portions or particles next above which are agitated to a less degree, a stratum of slimes and other lighter particles next above which remain substantially immobile, and a top covering of a clear supernatant solution, introducing the ore below the upper surface of said latter solution, overflowing and carrying off the clear solution, replacing water in the charge by a cyanide of potassium solution introduced at the bottom of the recep- tacle below the lower heavier stratum and causing it to percolate upwardly through the strata above, increasing the agitation during the introduction of said cyanide solution, carrying off the metal-bearing cyanide solution which overflows from the top of the charge and precipitating the said overflow metal-bearing solution after it leaves the receptacle. 689190December 17, 1901. B. HUNT. Process of precipitating and recover- ing precious metals from their solutions. -The process of precipitating precious metajs, consisting of adding to the pulp a cyanide solution and agitating the same until the metal is extracted; then adding to the pulp, while continuing the agita- tion thereof, powdered metallic aluminum whereby the precious metal is precipi- tated, but in suspension in the pulp; then adding mercury and continuing the agitation until the metal is in the form of an amalgam, and finally recovering the precious metal by treating the amalgam. 692634- February 4> 1902. H. DAVIS. Process of extracting precious metals from their ores. A process for the extraction of the precious and other metals from ore, ore pulp, sands, slimes, tailings, mineral-bearing earths or other sub- stances containing these metals, which consists in introducing chlorine gas into the ore and afterwards wholly or partially removing the excess of chlorine by forcing air into the material and afterwards treating with a cyanide solution to- dissolve the chlorides. f March 4, 1902. B. W. BEGEER. Cyanide process of extracting pre- cious metals from ores. The process of treating material containing the precious metals, consisting in setting in motion in an endless path a solution of cyanide of potassium, introducing oxygen to the moving liquid, and finally subjecting the metal-bearing material to the action of said solution. March 25, 1902. E. SCHILZ. Cyanide process of extracting precious metals from their ores. An improved process in the art of extracting precious v v metals from their ores, said process consisting in thoroughly and intimately mix- ing peroxide of barium (BaO 2 ) with precious metal-bearing rraterial, and then subjecting the same to treatment with an alkaline-cyanide solution. 701002 May 27, 1902. J. B. DE ALZUGARAY. Method of extracting precious metals from their ores. The process for treating ores containing precious metal ,382 APPENDIX. and consisting in adding the crushed ore to a solution of sodium chloride, sodium carbonate, and potassium cyanide, then forcing through the mass a gaseous mix- ture of bromine and air and recovering the precious metals from the solution by any known means, such as electrolysis. 702305 June 10, 1902. E. D. KENDALL. Process of extracting precious metals from their ores. The process of treating ores carrying precious metals, which consists in treating such ore with a lixiviating solution, consisting of a cyanide, potassium percarbonate, and water, and finally extracting the precious metal from such lixivium. 705698 July 29, 1902. R. H. OFFICER, J. W. NEIL, J. H. BURFEIND, and F. H. OFFICER. Cyanide . process of working gold, silver, or other ores. The im- provement in treating ores by the cyanide process, consisting in agitating the pulp containing the cyanide solution by a suitable gas under pressure, passing the gas and the hydrocyanic-acid gas liberated from the solution through a regen- erating solution, and using the gas after passing through said regenerating solu- tion to agitate a fresh quantity of pulp. 708303 August 5, 1902. L. B. DARLING. Process of extracting precious metals from ores. The process of extracting precious metals from finely divided materials or ores, which consists in spreading a comparatively thin layer of the material over a substantially flat and large working surface provided with drain- age ducts or channels; then covering said material with suitable metal-dissolving or cyanide solution; then passing a heavy roll back and forth over the charge of material, etc., thereby at the same time thoroughly agitating or stirring the charge and forcing some of the solution into the drainage ducts; then discharg- ing said solution into the sump, and finally precipitating the precious metal from the solution. 707926 August 26, 1902. W. HILT and C. E. LANE. Process of extracting precious metals. The 1 process of extracting precious metals from solutions thereof, which consists in producing cyanide solutions of said metals, vaporizing metallic ^inc by means of heat, and conducting the vapor thus formed to a point beneath the surfaces of said solutions, thus producing finely divided zinc, which replaces the precious metals and thereby causes their precipitation. 708504 September 2, 1902. H. L. SULMAN and H. F. KIRKPATRICK-PICARD. Treatment of ore slimes. The process of treating ore slimes, which consists in sepa- rating, by means of a centrifugal machine, the ore slimes from the residual water with which they are mixed by adding a little lime to the charge, removing the bulk of the water, thereafter introducing into the machine an amount of leaching solution of a volume equal to that of the remaining quantity of adhering moisture and introduced into the slimes by centrifugal action, and replacing ]the moisture by the added leaching solution. 710496 October 7, 1902. S. T. MUFFLY. Process of treating ores. The process of treating ores, which consists in injecting into said ores, as they are agitated and elevated and allowed to fall by gravity in a closed chamber, a chemical solu- tion in the form of a spray, together with hot air under pressure, and allowing the elements and fumes freed by this operation to escape from said chamber. 718633 January 20, 1903. T. B. JOSEPH. Gold-extracting process. The process of extracting gold or silver from ore containing the same, when in a suit- able condition, which consists in subjecting the said ore to the leaching action of a solution of water, cyanide of potassium, hydrate of calcium, and carbonic-acid gas, and introducing an oxidizing agent into the solution, and subsequently pre- cipitating the gold from this solution. 719274 January 27, 1903. Z. B. STUART. Process of extracting metals from ores. The process of extracting precious metals from ores, consisting in agitating the pulp together with cyanide, water, and air by ebullition in one vessel, causing the mixture to assume an even consistency throughout, and passing the mixture through a mechanical agitator and combining therein a relatively smaller quantity of mixture with a relatively larger quantity of air and there forcing the PATENTS RELATING TO CYANIDE PROCESSES. 383 pulp, cyanide, water, and air into intimate contact, and circulating the mixture through the two vessels. 722455 March 10, 1903. AUGUST PRISTER Process of precipitating gold from cyanide solutions. The process for the precipitation of gold or other precious metals from cyanide solutions, such as potassium cyanide, sodium cyanide, and V/ bromine cyanide, which consists in acidifying the solution, adding a solution con- taining salts of mercury and copper, and then adding a solution containing zinc salts and a small percentage of a potassium ferrocyanide, or a small quantity of the cyanide solution discharged from the ordinary zinc-precipitation Boxes. ? March 17, 1903. J. P. SCHUCH, Jr. Process of separating precious metals from solvent solutions. The process of separating precious metals from their solvent solutions, which consists, first, in passing the solution through crushed limestone or phonolite to neutralize any free acid, then through zinc, wood ashes, asbestos wool or its equivalent, and charcoal or coke, to neutralize any free soda or carbonates, then through zinc shavings to precipitate the pre- cious metals, then through charcoal to filter the solution and effect retention of a percentage of the precious metals, then through limestone or crushed phono- lite to effect precipitation of zinc contained in the solution, and then alternately through zinc, charcoal, or coke and zinc to effect complete separation of the pre- cious metals and thorough filtration of the solution. 725895 April 21, 1903. M. V. USLAR and G. ERLWEIN. Process of extract- ing gold. The process for extracting gold from auriferous ores, which consists in x\ lixiviating the ores with a solution of potassium cyanide, rhodanides, hyposul- phites, and sodium chloride. 726294 April 28, 1903, F. J. HOYT. Method of extracting gold from ores. The method of milling gold ore, consisting of the following steps: First, pulverizing the ore; second, distributing the ore thinly over a wide, long, and open sluice- way; third, flowing the ore and propelling it forward over its bed by the action of a stream of chemical solution adapted to dissolve the ore; fourth, automatically screening and separating the solution from the tailings by the same force; and fifth, subjecting the solution to a reagent to precipitate the gold therein. 727659 May 12, 1903. F. W. MARTINO. Method of extracting noble metals. The process of recovering gold from its cyanide solution, consisting in acidify- ,, ing the solution and treating it at a raised temperature with barium sulphocar- "; bide. The latter is manufactured by fusing two parts, by weight, of barium sul- phate (baryta or heavy spar) BaSO 4 in an electric furnace with one part of carbon. 728397 May 19, 1903. T: B. JOSEPH. Gold-extracting process. The process of extracting gold and silver from ore containing the same when in a suitable con- dition, which consists in subjecting the said ore to the leaching action of a solu- tion of water, cyanide of potassium, hydrate of calcium, peroxide of barium and carbonic-acid gas, the ore being agitated by compressed air. 730835 June 9, 1903. D. MOSHER. Ammonia cyanide process of treating copper, nickel, or zinc ores containing precious metals. The process of treating refractory sulphur, tellurium, and arsenical ores containing copper, zinc, nickel, gold, and silver, consisting in first roasting such ores at a low red heat to trans- form the metals so transformable into sulphates, arsenates, or tellurates; then -N/V 1 oxidizing reducing compounds by very dilute ammonia; and subsequently extract- ' ing the metals with an ammoniacal-cyanide solution containing an excess of cupric oxide or hydroxide over and above that necessary to form metallic cyanide double salts. 731169 June 16, 1903. O. A. ELLIS. Apparatus for extracting metals from ores. An apparatus for extracting metals from ores, having in combination a receiving hopper having an inclined bottom, a discharge opening in said hopper, an inclined chute leading from said hopper and provided with a screen, a pre- cipitating box connected with said inclined chute, means for causing a flow of chemical solution through said hopper, chute, and precipitating box, and means for passing a current of electricity through said precipitating box. 384 APPENDIX. 731631 June 23, 1903. J. T. TERRY, Jr. Extracting gold or silver from, slimes. An improvement in separating precious metals from slimes with which they are mixed, consisting in forming a solution with water, spraying said solu- tion into tanks containing a cyanide solution made dense by the addition of salt, allowing the slime to settle through and into the solution, then drawing the clear liquor from the top through vertically disposed filters and discharging the sludge from the bottom into succeeding tanks containing a similar cyanide solution, allowing it to settle and again drawing off the clear liquor. 731839 -June 23, 1903. G. A. BAHN. Sulphuric acid process of extracting- precious metals from solutions. The process of . precipitating precious m3tals from solutions thereof, which consists in producing cyanide solutions of said precious metals, then acidulating with sulphuric acid said cyanide solutions, then immers- ing zinc in sheet, plate, or other form in the acidulated-cyanide solution contain- ing the precious metals; the chemical action thereupon taking place in the solu- tion, dissolving zinc and precipitating the precious metals; then recovering from the precipitate of the preceding operation the precious metals by filtering and melting, or other process. 732605 June 30, 1903. G. E. THEDE. Process of leaching ores. The proc- ess of leaching ores which consists in mixing with the ore to be treated a cyanide solution, peroxide of hydrogen, and an oxide which is reducible by said peroxide of hydrogen. 732639 June SO, 1903. T. B. JOSEPH. Gold-extracting process. The process of extracting gold and silver from ore containing the same, when in a suitable condition, which consists in subjecting said ore to the leaching action of a solution containing water, cyanide of potassium, bromine, hydrate of calcium, peroxide of barium, and carbon dioxide, said carbon dioxide being forced into the leaching solution simultaneously with compressed air. 738758 September 15, 1903. J. B. DE ALZUGARAY. Extraction of precious metals from their ores. The process for extracting precious metals from their ores, consisting in first moistening the crushed ore with an alkaline solution and afterwards agitating it in a solvent solution and blowing through it an oxidizing agent composed of gaseous bromine, and its acid and oxyacid compounds dissolved in air, and finally recovering the metals from the solvent in any well-known manner 745490 December 1, 1903. T. J. GRIER. Process of extracting precious metals. The process of extracting precious metals from slimes, consisting in directing the slimes into a settling-tank, drawing off the thicker portions of the slimes and depositing the same into a leaching-vat, of introducing a cyanide solution under pressure through perforations in* the false bottom of the vat, causing the watery portions of the slimes to be displaced by said cyanide solution, then treating the charge with an air under pressure, and afterwards introducing through the false bottom of a vat a salt solution of greater density than the cyanide solution to displace the latter. 745828 December 1, 1903. E. B. HACK. Process of extracting metals from ores. A cyanide process, consisting of the following steps in the order named: Caking the pulp by pressure under conditions allowing the moisture to escape; introducing a weak solution of the solvent simultaneously with the introduction of air under pressure; drying the pulp by passing air under pressure therethrough; introducing a stronger solution of the solvent simultaneously with the introduc- tion of air under pressure; and finally drying the cake by air pressure. 755951 March 29, 1904- J. SMITH. Process of treating ores. In the cyanide treatment of ores, the method of rendering insoluble in the cyanide solution ferrous oxide contained in a mass of moist crushed ore, which method consists in apply- ing heat to said mass in the presence of air, previous to >its treatment by the cyanide solution. PATENTS RELATING TO CYANIDE PROCESSES. 385 CLASS 204 ELECTROLYSIS. Subclass 15 Aqueous Bath, Ores. 61866 February 5, 1867. J. H. RAE. Improved mode of treating auriferous and argentiferous ores. This invention consists in treating auriferous and argen- tiferous ores with a current of electricity or galvanism for the purpose of separat- ing the precious metals from the gangue. In connection with the electric current suitable liquids or chemical preparations, such, for instance, as cyanide of potas- sium, are used, in such a manner that by the combined action of the electricity and of the chemicals, the metal contained in the ore is first reduced to a state of solution and afterwards collected and deposited in a pure state. Among the claims is one for the use of the platinum agitator as an electrode. Q2776 March 12, 1867. J. H. RAE. Improved mode of collecting gold and silver from sweepings, washings, etc. This invention consists in treating sweepings, filings, and washings containing gold or silver with a current of electricity or gal- vanism for the purpose of separating the precious metals from the impurities of foreign matter mixed with them. In connection with the electric current suitable liquids or chemical preparations, such, for instance, as cyanide of potassium, are used in such a manner that by the combined action of the electricity and chemi- cals the precious metals contained in the sweepings, filings, and washings are first reduced to a state of solution, and afterwards collected and deposited either as oxides or in a metallic state, and the operation of extracting or separating said precious metals from the sweepings, filings, or washings is attended with very little trouble and expense. During this operation the bath which contains the washings, filings, or sweepings acts as an electrode, and also as an agitator; and the third claim of the patent covers the use of this carbon electrode as an agitator. 90565 May 25, 1869. W. J. LYND. Improved process of separating iron and other metals from potters' clay. The process of removing iron, copper, and other discoloring matters from potters' clay and other argillaceous substances by subjecting the clay, when in solution, to the action of one or more magnets, or by passing through the bath containing such solution a current of electricity. 239300 March 22, 1881. A. RYDER. Apparatus for treating ores. The invention has reference to apparatus for reducing ores in which the ore, while in a heated state, is dumped suddenly into a liquid or chemical solution for the pur- pose of disintegrating the ore and separating the particles preparatory to amal- gamation. And the inventor claims, in an apparatus for disintegrating ores pre- paratory to amalgamation, the insulated vessel or non-conductor of electricity, provided with a metallic or plated hopper, in combination with an electrical gen- erator or battery and conducting wire or wires. 246201 August 23, 1881. E. REYNIER. Electrochemical treatment of ores. The method of treating ores of zinc and lead for the production of electricity and recovery of the metals by acting upon said ores in a voltaic couple with an elec- trolytic liquid haying caustic alkali as the base, and precipitating the metallic oxides from said liquid. 272391 February 13, 1883. A. THIOLLIER. Process of and apparatus for extracting metals from their ores. In combination with an electrogenerator, a recep- tacle for conductively prepared ore or other material containing metal to be recov- / ered, having attachments for the negative and positive polar conductors of the x ^ electrogenerator, arranged, as described, in electrical communication with the / mass of conductive ore by means of the electrolytic solution, whereby reduction is effected when the current is passed. 286208 October 9, 1883. L. LETRANGE. Process of and apparatus for reducing zinc ores. The process of reducing zinc ores and producing pure metallic zinc and sulphuric acid simultaneously therefrom, which consists in simultaneously roasting sulphuret ores and carbonate ores in the fame or communicating chambers, and thereby converting both ores into soluble sulnhates, then leaching these roasted ores, and then depositing the metallic zinc from a solution of the sulphates by 386 APPENDIX. electric currents on metallic plates, and drawing sulphuric acid at the same time from the solution as fast as set free by the said electric currents; and the appa- ratus for use in the process of reducing zinc ores, which consists, essentially, in a reservoir for the sulphate solution; a precipitating vessel provided with suitable anodes and cathodes; a pipe provided with a regulating cock, leading from the reservoir to near the bottom of the precipitating vessel, and an outlet pipe for the freed acid, arranged in the said vessel at the desired level of the liquid therein, whereby the strength and quantity of the sulphate solution in the precipitating vessel are maintained constant. 291670 January 8, 1884. M. BODY. Process of and apparatus for obtain- ing gold and silver from their ores by combined electrolytic and amalgamating proc- esses. The method of first subjecting gold and silver ores to the action of ferric salts, in combination with the electrolytic process, and the subsequent amalga- mation of the metals with mercury under the continued action of the electric cur- rent: and the apparatus for effecting this process. 300950 June 24, 188 '4. H. R. CASSEL. Process of and apparatus for the separation of metals from ores and alloys. The process of separating metals from ores or alloys, especially those of an auriferous character, which consists in charg- ing the ore or alloy in a powdered condition into an anode compartment, which is separated from the cathode compartment by porous material, said anode com- partment containing a solution yielding nascent chlorine under the action of an electric current, and agitating said powdered material within said solution during the passage of the electric current; and the combination in an apparatus for treat- ing ores and metals by electrolysis, of a cathode compartment, a negative pole therein, a rotary drum constituting the anode compartment, provided with por- ous material separating it from the cathode compartment, and with a series of carbon rods or plates arranged within the same, and suitable electric connections. 800951 June 24, 1884. H. R. CASSEL. Process of chloridizing ores by elec- trolysis In the process of extracting gold from rebellious or refractory gold ores, the steps which consist in subjecting the ore to the action of a solution yielding nascent chlorine under electrolytic decomposition, and adding lime or its equiv- alent, whereby acids formed by secondary action during said decomposition are neutralized. 317245 May 5, 1885. E. P. THOMPSON. Apparatus for the separation of gold from its ores by electrochlorination and deposition. The combination, with an electrolytic cell for separating chlorine from its compounds and its anode, of a battery, a cathode consisting of a pipe through which steam is admitted to the cell for the purpose of increasing the rapidity of the separating, and conduc- tors respectively connecting the same anode and cathode with the poles of said battery. 317246 May 5, 1885. E. P. THOMPSON. Apparatus for the electrodeposition of gold from its chlorides. The combination, in an electrolytic cell, of an anode formed of a series of carbon rods set in a metal ring, and a cathode formed by two thin corrugated copper plates connected electrically, which are set, respectively, within and without the circle of carbons. 332705 December 22, 1885, H. H. EAMES. Apparatus for chloridizing gold t silver, and other ores. This invention consists of an iron vessel cylindrical in shape, lined with wood, having a cast-iron cover, adjusted so as to be steam- and vapor- tight. It is also arranged with a set of stirrers, to which motion is communicated by crown- and pinion- wheels. It is also fitted with pipes, by means of which steam can be forced through the contents and held there under pressure. It is also furnished with two electrodes, by which electricity can be passed through the ore and chemicals operated upon, while the pressure is applied. The electric current is best obtained from a dynamo machine of ordinary construction used in the deposition of metals. 333815 January 5, 1886. M. BODY. Process of obtaining gold, silver, copper, nickel, and cobalt from their ores by electrolytic action. The process of separating gold, silver, copper, and other metals from chlorinated or chlorine-containing ores by electrolytic action, consisting in first roasting the ores or subjecting them PATENTS RELATING TO CYANIDE PROCESSES. 387" to an equivalent oxidizing treatment, as specified, and then subjecting the ore to the action of ferric-salt solutions, and at the same time passing an electric cur- rent through said solution, whereby the metal becomes dissolved and precipitated, and chlorine gas is generated at the positive pole, which reconverts the resulting ferrous salts into ferric salts. 351576 October 26, 1886. H. R. CASSEL. Process of extracting gold, etc.,, from ores. The process of separating metals from ores or alloys, especially those of an auriferous character, which consists in charging the ore or alloy in a pow- dered condition, into an anode compartment, which is separated from the cathode compartment by a porous partition composed of asbestos, which permits the pas- sage of the current with the metals in solution, and retains the ores within the anode compartment, said anode compartment containing a chloride solution, agitating and subjecting the charge to nascent chlorine produced from said solution during the passage of the electric current, passing the solution of metals through the asbestos partition, and depositing the metals in solution at the cathode. 357659 February 15, 1887. D. G. FITZGERALD. Obtaining chlorine by electroly- sis. The electrochemical generation of chlorine by means of an anode of per- oxide of lead in the form of dense, highly conductive layers, plates, or masses of any required form preferably obtained by the means hereinbefore described, the said anode being employed in conjunction with any suitable cathode and with an electrolyte capable of evolving chlorine. 360852 April 12, 1887. H. R. CASSEL. Apparatus for separating metals from ores or alloys. In an apparatus for separating metals from ores or alloys by electrolysis the combination of a journaled drum provided with carbon anodes, a hollow metallic shaft insulated on its exterior and extending through said drum, said shaft being perforated within the drum and separated from the interior there- of by a filter, and a screw conveyor within said hollow shaft. 360853 April 12, 1887. H. R. CASSEL. Apparatus for separating meals from ores or alloys. In an apparatus for separating metals from ores or alloys by electrolysis the combination of a rotary drum constituting the anode compart- ment and having a suitable electric connection, a rotary cathode compartment having a suitable electric connection and provided with an automatic valve, a porous diaphragm separating said anode and cathode compartments, a fixed bracket, and an arch-shaped arm attached to said bracket in the path of said valve for opening of the latter. 362022 April 26, 1887. H. LIEPMANN. Apparatus for separating metals from ores or alloys by electrolysis. In an apparatus for separating metals from ores or alloys by electrolysis the combination of an anode compartment, a cathode compartment, a filtering diaphragm separating said compartments, a dense por- ous diaphragm for separating said compartments during one step of the operation, and mechanism whereby the dense porous diaphragm may be placed in opposition with or removed from the opening between the anode and cathode compartments. 379764 March 20, 1888. C. F. CROSELMIRE. Wet process of extracting pure zinc from its ores. The process which consists in immersing roasted zinc ore in dilute acid, passing an air blast through the solution until the impurities are oxi- dized, and finally drawing off the zinc solution and depositing or precipitating the zinc. 387036 July 31, 1888. C. P. BELLOWS. Process of cleansing gold and silver where mechanically coated in ores with refractory substances. The process of cleans- ing refractory ores prior to the recovery of the precious metals therefrom, which consists in immersing said ores in a solution of a sodium chloride and caustic soda, heating said solution, and at the same time subjecting the ores to the action of the electric current, whereby the ore is rendered free milling. 391360 October 16, 1888. H. H. EAMES. Apparatus for chloridizinq ores. In a device for chloridizing metallic ores, the combination of a hermetically sealed tank, metallic plates placed inside the said tank and mounted upon insulated sup- ports, whereby they will be insulated from each other and from the tank, the said plates forming the two elements of a galvanic battery, a stirrer placed in the said 388 APPENDIX. tank and between the said plates a solution containing the ore to be treated, by which a galvanic current will be excited between the said charging steam in the said tank, whereby the said solution will be heated and a pressure maintained in said tank. 399209 March 5, 1889. J. H. RAE. Electric amalgamator. In an apparatus for working ores, a pan or tub with an internal copper ring and rotating arms or stirrers, in combination with a horizontal wooden ring suspended above the tub, a copper plate forming the upper surface of said ring and perforated to admit car- bons which pass loosely through the plates, said carbons having heads or trans- verse pins at the upper ends, and the movable elastic plates or springs pressing upon the heads of the carbons to hold them in contact with the copper plate. 407386 July 23, 1889. J C. WISWELL. Bath or solution for separating metals from their ores. The process of producing a bath or solution for the separation of metals from their ores, consisting in subjecting a solution of salt water, muriate of ammonia, and muriatic acid to a current of electricity, then placing this solution in a tank containing liquid mercury, and subjecting the whole to a current of elec- tricity, said mercury serving as the anode. 410228 September 3, 1889. J. C. WISWELL. Solution for use in separating metals from their ores. A solution or bath for use in separating metals from their ores, consisting of chlorine in solution, sodium chloride, ammonium chloride, hydrochloric acid, and bichloride of mercury. 415576 November 19, 1889. W. VON SIEMENS. Process of electrodeposition of metals. The process which consists in lixiviating ore in separate vessels with a solution containing ferric sulphate, passing the resulting ferrous sulphate succes- sively through a series of compartments containing cathode plates, and in which cells the solution is subjected to the action of an electrical current by which the metal in solution is deposited, then passing the remaining liquid successively through a second series of compartments containing anode plates of insoluble material and separated from the first-mentioned compartments by non-metallic diaphragms, whereby the ferrous sulphate is oxidized and reconverted into ferric sulphate, which solution is again used to lixiviate ores. 418134 December 24, 1889. H. F. JULIAN. Process of extracting gold and silver from their ores. The improvement in the process of extracting gold and silver from ores, which consists in agitating the pulverized ore in closed vats with chlorine, bromine, or iodine and water under pressure of a fluid forced into the vat, and aftef the gold and silver have combined with the halogen, adding mercury and again agitating under pressure of a fluid forced into the vat, next passing the ore, mercury, and solution over amalgamated copper surfaces forming the cathode of an electric circuit, and subsequently submitting the mixture to electrolytic action between cathodes of mercury below and suitable anodes above. 452125 May 12, 1891. W. VON SIEMENS. Apparatus' for extracting metals from their ores. The combination of a trough for the flow of liquid, composed of numerous sections connected at alternate ends, with an inlet at one end and an outlet at the other, with two longitudinal shafts in each section of the said trough, said shaft carrying beaters and being entirely immersed in the liquid contained in the trough, and a heating pipe located below and between the said shafts. 459023 September 8, 1891. C. SCHREIBER and H. KNUTSEN. Process of extracting antimony from ores. In the extraction of antimony from ore, the proc- ess which consists in subjecting the crushed ore to the action of a solution of sulphide of sodium and then precipitating the antimony in metallic form by electrolysis, adding hydroxide of sodium to the solution. 460354 September 29, 1891. W. VON SIEMENS. Apparatus for eUctrolytically separating metals from ores. In an electrolytical cell, the combination of a revolv- ing cathode, a trough-shaped anode situated below the said cathode, in the trough of which the cathode revolves, a screen permitting the passage of the electrolyte and of electricity and capable of preventing the passage of vibrations of the elec- trolyte situated between the said cathode and anode, and means for supplying the electrolyte above the screen and for withdrawing the oxidized liquid from the bottom of the trough of the anode. \s w<^ PATENTS RELATING TO CYANIDE PROCESSES. 389 473105 April 19, 1892. G. J. ATKINS. Electrolytic apparatus for separating gold and other metals from their ores. Electrolytic apparatus for separating gold and other metals from their ores, which consists of an upright anode compartment through which the ore is passed continuously, having within it an anode constructed to receive and retard the descent of the ore, while the ore itself forms a, more or less soluble portion of such anode pole, and an upright cathode compartment and pole, the said anode and cathode compartments communicating through an open- ing closed by a porous diaphragm and having outlets at their lower ends for the removal of the ore which has been acted upon in the anode compartment and of the metals and other substances that have been deposited or precipitated in the cathode compartment. 484869 October 25, 1892. G. J. ATKINS. Process of separating gold and other metals from their ores. The continuous process of separating gold and other metals from their ores, which consists in passing such ore through the anode com- partment of an electrolytic apparatus in contact with the anode and retarding the descent of the ore in the said anode compartment while such ore is kept in con- tact with the anode pole of such compartment, so as to form a more or less soluble portion of such anode pole, and then subjecting the ore to the process of amalga- mation. 495212 April 11, 1893. J. F. WISWELL. Process of and apparatus for treating ores. An improved process of treating ores which consists in submerging mercury in a solution of common salt connecting the mercury with the positive pole of a generator and the salt solution with the other pole, so that the current will decompose the salt solution and cause the chlorine to be attracted to the mer- cury forming calomel; ^ treating the calomel with aqua regia forming a soluble mercuric chloride, diluting the latter with water, treating undecomposed salt solu- tion with an electric current to produce sodium hypochlorite and introducing the soluble mercuric chloride and sodium hypochlorite simultaneously upon the crushed ore. 495637 April 18, 1893. J. PFLEGER. Process of extracting zinc by electrolysis. The process of obtaining zinc by electrolysis out of a zinc-containing anode, which consists in adding to the bath a basic zinc-salt solution adapted to act as electrolyte, to which basic zinc-salt solution a conducting neutral salt has been added. 495715 April 18, 1893. S. R. WHITALL. Process of lixiviating ores. The process of separating gold and silver from their ores, which consists, first, in roast- ing the ore to oxidize the base metals; and, secondly, in subjecting the roasted ore to the action of a solution of potassium cyanide and sodium hyposulphite, and subsequently precipitating the dissolved metals; and the process of separating gold and silver from siliceous ores, which consists in subjecting the ore admixed with caustic soda and potash to the action of a solution of potassium cyanide and sodium hyposulphite. 497014 May 9, 1893. F. W. CLEGHORN. Process of separating precious metals from ores. The process of separating gold and silver from ores, consisting in filtering through the ores a solution of sulphuric acid and salt, and precipitating the gold and silver in the filtrate solution by placing metallic iron in the filtrate and passing an electric current through the filtrate. 501997 July 25, 1893. S. H. EMMENS. Apparatus for the electrolytic extrac- tion of metals. In apparatus for the electrolytic extraction of metals, a vat having an anode lining on its floor and sides, in comibnation with a suitable cathode or cathodes suspended within the vat and a non-porous and non-conducting inner wall or curb located between the side linings and the cathode or cathodes and ex- tending from the upper surface of the floor lining to above the surface of the electro- lyte, and serving to support a lining of the substance to be acted upon in contact with the anode side linings and to prevent short-circuiting between said anode side linings and the cathodes. 507130 October 24, 1893. C. HOEPFNER. Electrolytic production of metals. The process of obtaining copper and silver free from other metals, which consists in forming a cuprous-chloride solution of these metals by leaching a cupriferous 390 APPENDIX. and argentiferous material with a cupric-chloride solution containing a solvent for cuprous chloride, separating from the cuprous-chloride solution so obtained such metals as arsenic, antimony, cobalt, and the like, extracting the silver by precipitation, electrolyzing the cuprous-chloride solution, preventing the solution at the anode from commingling with the solution at the cathode, mixing together the two solutions after having been acted upon by the electric current and pre- venting an accumulation of iron therein by oxidizing and removing the latter. 512361 January 9, 1894. p < C. CHOATE. Art of producing metallic zinc. The method of producing from an impure solution of zinc salts a zinc electrolyte free from depositable impurities, which consists in subjecting the solution to the action of an electric current to precipitate and deposit the depositable impurities, and at the same time preventing the resolution of such impurities in the solution by neutralizing the acid set free in the bath with a neutralizing agent which is free from any depositable impurities soluble in the solvent element of the bath. 512362 January 9, 1894. P. C. CHOATE. Process of preparing solutions carrying salts of zinc. The process of forming a solution carrying salts of zinc, which consists in forming a sulphate solution of the soluble elements of the ore and recovering the same therefrom by evaporation and crystallization, heating the crystallized product to drive off the salts of metals more volatile than zinc and convert those less volatile than zinc into compounds insoluble in water and finally treating the mass with water to dissolve the zinc element. 518732 April 24, 1894. p - C. CHOATE. Art of producing metallic zinc. The process of continuously producing metallic zinc by electrolysis, which consists in depositing the zinc from an acidulated solution of a zinc salt, drawing off from the bath the free acid liberated therein, dissolving in such acid oxidized zinc, in the state of fume, freed from its more volatile soluble impurities, and returning the solution thus formed to the bath from time to time, as required, to maintain the electrolyte. 526099 September 18, 1894. P DANCKWARDT. Apparatus for and process of extracting gold or silver from ores. The process of extracting gold and silver from ores, which consists in subjecting the same simultaneously to the action of cyanide of potassium, an alkali sulphide, and to electrolysis; and the combination of a. main apparatus consisting of a revolving outer drum having blades, an insulated inner drum and electric connections, with an auxiliary apparatus consisting of a series of communicating tanks, rotating insulated drums and electric connections. 528023 October 23, 1894. L- PELATAN and F. CLERICI. Extracting gold from its ore. The combination with a crushing mechanism and an amalgamator, of a series of vessels containing a solution of cyanide of potassium and a salt of sodium, each vessel having an amalgamated copper bottom connected to one pole of a generator of electricity and a central shaft having a zinc pipe and agitator con- nected to the other pole, a filter, a series of communicating closed vessels of lead, each containing a body of aluminum chips resting on a perforated diaphragm above the inlet and rising nearly to the outlet, and means for creating a vacuum beneath the filter to drive the fluid through and into the series of lead vessels under pressure. 531169 December 18, 1894. V- ENGELHARDT. Process of extracting metals- from sulphide ores, etc. The process of treating the sulphur compounds of metals, which compounds have combined therewith other ore compounds not soluble in a solution of an alkaline sulphydrate, which consists in extracting the sulphur compounds by treatment with an alkaline sulphydrate, thereby also generating sulphureted hydrogen, subjecting the solution thus formed to the action of an electric current in the cathode compartment of an electrolytic cell, in the anode compartment of which is an alkaline chloride, thereby obtaining the metals, reform- ing the sulphydrate, and liberating free chlorine, treating the ore residues, result- ing from the sulphydrate bath with such chlorine, and subjecting the solution thus obtained to the action of the sulphureted hydrogen first generated in the sulph- hydrate bath. 537423 April 9, 1895. F. H. LONG and D C. SKADEN. Apparatus for recover- ing precious metals from their ores. An apparatus for recovering precious metals PATENTS RELATING TO CYANIDE PROCESSES. 391 comprising a revoluble drum, a perforated metal tube opening from said drum and provided with a fabric jacket, a series of plates secured to the inner surface of the drum and having inwardly extended blades or flanges, electric connections to the plates and tube for rendering the same of opposite polarity, a rotatable conveyor located and working in said tube and a fixed vent-pipe passing axially through the drumhead and opening into the interior of the drum near the top thereof. 538522 April 30, 1895. E. D. KENDALL. Process of and reagent for recover- ing silver and gold from solutions. The process of the recovery of gold and silver from solutions, which consists of the following steps: First, the subjecting of the ore containing the precious metals to the action of a solvent, thus obtaining an aqueous solution of the solvent and the minerals contained in the ore; second, subjecting the said solution to the electrochemical action of a mercurial amalgam; third, subjecting the valuable precipitate secured by the preceding process to the action of dilute acid in the presence of carbon; fourth, the recovery of the valuable metal from the result of the preceding process. 043546 July 30, 1895. E. J. FRASER. Process of and apparatus^ for treat- ment of precious metals. The process of separating gold or other precious metal held in an electrolytic solution, which consists in passing the solution through a vessel containing "alternating porous layers of zinc and carbon, to set up a local voltaic action which tends to decompose the solution, precipitating the gold in the carbon by filtration. 543673 July 30, 1895. M. CRAWFORD. Process of extracting precious metals- from their ores. The improved process of removing precious metals from their ores which consists, first, in lixiviating the ore with a cyanide solution which has been subjected to the action of an anode separated from its corresponding cathode by a porous partition which substantially prevents the circulation of the electrolyte ; second, in withdrawing said solution and removing the precious metals there- from; third, in again subjecting the solution to the action of an anode separated from its corresponding cathode as before and using it over again in continuous rotation. 543674 July 30, 1895. M. CRAWFORD. Process of extracting precious metals from their ores. The improved process of extracting precious metals from their ores, which consists in forming a solution of a cyanide and a cyanate of the cor- responding base, the total amount of cyanate being not less than 25 per cent, of the total amount of cyanide present; lixiviating the ore therewith and extracting the dissolved precious metals from said solution. 543675 July 30, 1895. M. CRAWFORD. Apparatus for extracting precious metals from their ores. An apparatus for extracting precious metals from their ores, which consists in the combination of a tank wherein the solvent liquid is stored;, a revoluble lixiviating receptacle; a pipe running from said storage-tank to the lixiviating receptacle; an amalgamating table; means for causing the lixiviating receptacle to discharge its contents continuously upon the amalgamating table j a separating-tank; means for conducting ore which has passed over the amalga- mating table into the separating-tank; means for separating the solid contents'- of this separating-tank from its liquid contents; a third tank; connections whereby the solvent liquid thus separated is passed to said third tank; means for reclaiming the precious metals from the solution in said third tank; and connec- tions whereby the solvent liquid is run from the third tank to the storage-tank p and a separator for removing the tailings of the ores of precious metals from their- accompanying solvent solution, which consists in the combination of a tank into- which the ores and solution are discharged; a conveyor running from the bottom, of said tank to a point exterior thereto by which the solids are separated from the' liquids; a car-filter with a permeable bottom situated below the discharge end of the conveyor; and a second tank below said car-filter. 544610 August 13, 1895. E. W. CLRAK. Process of and apparatus for extract- ing ores by electrolysis. In an electric chlorinator for gold ores, the combination of the hollow cylinder constructed in longitudinal sections united by bands, and having the series of separate boxes or chambers communicating with its interior; 392 APPENDIX. the electrical connections consisting of the anode in the cylinder chamber, and the cathodes in the boxes or amalgamating chambers, the agitator-shaft provided with the spirally-arranged series of stirrer-arms and adapted to revolve in the cylinder chamber, and the stuffing boxes at the ends of the cylinder. 546873 September 24, 1895. E. A. ASHCROFT, Process of treating zinc-bearing ores. In the treatment of zinc-bearing ores and zinc-bearing products, the method of simultaneously depositing zinc from a catholyte free from iron, and raising i ferrous-salt solution to the ferric state, which consists in passing the zinc-bear- ing solution free from iron, around the metallic cathodes of an electrolytic appa- .ratus, and simultaneously passing the ferrous-salt solution around the insoluble anodes of the said electrolytic apparatus. 549907 November 19, 1895. A. L. ELTONHEAD. Apparatus for extracting gold. In an apparatus for extracting gold and other metals, the combination of a mercury receiving-box, a horizontally movable vessel therein, having its lower end open and unobstructed whereby mercury placed within the box may, in seek- ing its level, enter said vessel, a horizontally placed anode strip suspended within the latter, means for adjusting the strip vertically, a cathode connection and con- ductor wires adapted to connect the anode and cathode with a suitable dynamo or battery. 551648 December 17, 1895. L. PELATAN and F, CLERICI. Eletcrolytic process -o/ obtaining precious metals, In an apparatus for the extraction of precious metals by direct electrolytic action, the combination with an electrolytic vat having cathodes arranged at its bottom, of anode cylinders arranged above the said cathodes, anode plates alternating with said cylinders, a generator of electricity having its poles connected to said anode cylinders and plates and to the cathodes, means for rotating the anode cylinders which are provided with agitators, a force-pump having injection-pipes to discharge beneath the anode plates and cylinders, said pipes being provided at or near their mouths with interior, concentric rods having spiral ribs, or feathers, and suction-pipes having their open ends arranged above the anode plates. 552960 January 14, 1896. C. HOEPFNER. Process of producing cuprous oxides. The process which consists in leaching cupriferous materials with a cupric- chloride solution containing calcium chloride, whereby a solution containing cuprous chloride is obtained, converting the cuprous chloride in a portion of the solution into cupric chloride by means of a suitable acid as sulphurous acid in the presence of oxygen, freeing the other portion of the solution from metals other than cop- per, and converting the cuprous chloride therein into cuprous oxide by means of a suitable reagent, as caustic lime. 553816 January 28, 1896. L. PELATAN and F. CLERICI. Process of and apparatus for extracting gold from its ores. A single continuous process for the extraction of precious metals from their ores, and the amalgamation of the same whish consists in treating said ores with a comparatively weak solution of a solu- ble cyanide, such as cyanide of potassium, adding thereto a peroxide, such as hydrogen binoxide, increasing the electric conductivity of said solution by adding -chloride of sodium, increasing the solvent power of said solution by passing a relatively weak current of electricity through the same, retaining the sodium chloride in the solution practically without decomposition and continuously revolv- ing the anode in the solution over a fixed cathode of mercury. 556092 March 10, 1896. O. FROLICH. Process of extracting noble metals from ores. The process of extracting precious metals from a lye containing also inferior metals, said lye containing substantially five grains of each of the said metals to the pint, which consists in subjecting the said lye to the action of an electric current of substantially twelve amperes for each two square yards of cathode surface, whereby the gold is separated by electrolysis. 563143 June 30, 1896. J. DOUGLAS. Process of extracting copper from ores. The method of extracting copper from solid cuprous chloride, which consists in moistening said solid cuprous chloride with water, inserting both electrodes of an electric circuit in the said solid cuprous chloride, and then passing an electric cur- rent therethrough. PATENTS RELATING TO CYANIDE PROCESSES. 393 56S144 June 80, 1896. J. DOUGLAS. Process of extracting copper from ores. The process of extracting copper from the solid cuprous chloride, which consists in suspending the said solid cuprous chloride in an acidulated electrolyte, inserting the cathode of an electric circuit into the solid cuprous chloride, and the anode into the electrolyte, and passing an electric current therethrough. 566894 September 1, 1896. P. DANCKWARDT. Apparatus for extracting gold and silver from ore. The combination of a revolving barrel having an amalgamated copper lining with non-conducting bottoms, a series of inclined perforated metal strips secured to such bottoms, insulating rings that sustain the bodies of such strips, and with electric connections that communicate with the barrel and the strips. 566986 -September 1, 1896. R. KECK. Cyanide process of extracting precious metals from their ores. The process of extracting precious metals from their ores, which consists in dissolving said metals in a cyanide solution and extracting them therefrom by electrolytic precipitation effected by alternating plates of lead and aluminum, the former being anodes and the latter cathodes. 567503 September 8, 1896. L. PELATAN and F. CLERICI. Process of extracting' gold and silver from their ores. The process, which consists in submitting the ores of gold and silver to the action of a comparatively weak cyanide solution con- taining chloride of sodium, intensifying the solvent power of the solution by the passage of a continuous electric current having an electromotive force below that required for the decomposition of sodium chloride and continuously revolving the anode from which the current is supplied to the solution over a mercury cathode. 568099 September 22, 1896. L. PELATAN and F. CLERICI. Electrolytic appa- ratus for extracting gold and silver from their ores. The combination with a vat having a flat bottom, of a cathode of mercury spread thereon, an anode laving v, the form of an endless belt, rolls arranged near the ends of the vat to support and give continuous movement to said anode in parallelism with the surface of the cathode, and means for imparting continuous movement to said anode, in one direction, it being provided with stirring devices moving with it. 568724 October 6, 1896. E. ANDREOLI. Apparatus for electrodeposition of gold or silver. In an apparatus for the electrodeposition of gold and silver from a solution, a tank provided with one or more anodes and a series of amalgamated cathodes, each cathode consisting of perforated, skeleton, or network plates and a layer of mercury in the bottom of the tank into which each of the cathodes dips,, said layer of mercury being connected with the negative pole of electricity, thereby constituting a common vehicle for the current from all the cathodes while at the- esame time maintaining the said cathodes constantly amalgamated. 568741 October 6, 1896. H. R. CASSEL. Process of extracting gold frcm sub- stances containing it. The process of extracting gold from ores,_ which consists in decomposing a bromide of an alkaline base by electrolysis, dissolving the gold \(\ by the anode solution, adding the cathode solution, running the product through a mixture of iron and carbon to precipitate the gold, and redecomposing the liber- ated bromine solution by electrolysis. 568843 October 6, 1896. V. ENGELHARDT and A. NETTEL. Process of treat- ing metallic sulphides, The process of treating a metallic sulphur compound, which consists in first converting the said compound into a soluble double sulphide by treating it with any suitable reagent, such as the sulphydrate of calcium in aque- ous solution; then decomposing the resulting solution by electrolysis to produce the metal and sulphureted-hydrogen gas, then treating the spent solution with carbonic-acid gas to precipitate a carbonate of the base and liberates ulphureted- hydrogen gas, then recovering the oxide of the reagent and the carbon ir-aoid gas from the precipitate by calcination, then combining the sulphureted-ln drogen gas given off during the process with the said oxide to form more reagent, and using the recovered carbonic-acid gas to treat more spent solution. 571468 November 17, 1896. T. P. BARBOUR. Process of treating ores. The process of treating ores, which consists in first treating the raw material with copper oxide and sulphuric acid, then chlorinating the pulp thus treated, intro- ducing the chlorinated mass into a suitable agitator having zmc therein, and estab- lishing an electric current through the mass in the presence of zinc; and a chlor- ^ 394 APPENDIX. inating-tank for treating ores consisting of a revoluble cask having a single man- hole and a circular series of bungholes, copper pole disks secured within the cask at opposite ends thereof and arranged in an electric circuit, insulator bracing p_osts arranged between said disks and the outer heads of the tank, flanged guide- rings encircling said cask at an intermediate point, spur-rings encircling the cask .near its opposite ends, and a horizontal drive-shaft carrying guide-rolls engaging .said flanged guide-rings and drive-pinions engaging said spur-rings. 573233 December 15, 1896. M. NETTO. Process of precipitating precious metals from their alkali-cyanide solutions. The process of precipitating silver and gold from their alkali-cyanide solutions, which consists in acidulating the alkali- cyanide solution containing said metals with hydrochloric acid so as to precipi- tate silver chloride, separating said silver chloride by filtration, subjecting the acid filtrate to the action of the electric current so as to deposit the gold on the cathode, and regenerating the cyanide solution by the addition of caustic alkali. 578171 March 2, 1897. C. T. TURNER. Electrolijtical apparatus .An elec- trolytic apparatus, provided with an anode consisting of a non-conducting recep- tacle coated with an anti-corrosive substance and provided with an outer coat- ing of a conducting material and means for connecting said outer coating with the positive pole of a source of electrical supply. 579872 March 30, 1897. J. H. HAYCRAFT. Process of treating auriferous and argentiferous ores. The process of treating ores consisting in introducing the ore into a pan, adding thereto mercury and soluble salts capable of yielding chlorine by electrolysis, raising the ore contents of the pan to about the boiling- point of water and passing a current of electricity through the heated mass while stirring the same to secure a simultaneous electrolytic chlorination and electro- amalgamation, and maintaining the anode out of vertical alignment with the mercury cathode. 581160 April 20, 1897. H. HIRSCHING. Process of treating ores containing silver and gold. The process of treating ores, which consists in subjecting them in the presence of moisture to the action of ammonia and a nitrate, and then pre- cipitating the metal or metals from the resulting solution. 582077 May 4, 1897. E. MOTZ. Apparatus for extracting precious metals. In an apparatus for extracting precious metals, the combination of a rotative drum provided with a manhole and having a valved connection for the admission of compressed air, a core of insulating material mounted to turn in the said drum, metal plates forming the positive and negative electrodes of an electric circuit and arranged respectively on the drum and core, and an electrical connection for said plates on the core, the said connection being arranged to lock the drum and core together. 584242 June 8, 1897. P. G. SALOM. Process of making commercial lead from lead ore. The process of converting lead ore into commercial lead, without the application of heat, by subjecting the ore to the action of nascent hydrogen, electrolytically developed, producing thereby a spongy mass, and afterward, while the mass is in a non-oxidized condition, applying a consolidating pressure. 685355 June 29, 1897. C. A. BURGHARDT and G. RIGG. Process of obtain- ing metallic zinc and copper from ores. The improved process of recovering metallic zinc and metallic copper from cuprous zinc ore, which consists in treating the roasted and ground ores with an ammoniacal solution, then in freeing the resultant liquid from iron dissolved by said solution, then in depositing the metallic copper on suitable metallic plates acting as a couple, and in finally effecting the electrolytic deposition of the metallic zinc. 585492 June 29, 1897. J. F. WEBB. Method of an apparatus for separating precious metals from their solvent solutions. The improved method of separating precious metals from a solvent solution containing the same, consisting in passing the solution alternately through a body of carbon and zinc, and subjecting the same in its passage to an air current; and a metallurgical filter for this purpose vcontaining the same, consisting of a series of alternate compartments, or recep- tacles, containing, respectively, carbon and zinc, through which the. solvent solu- PATENTS RELATING TO CYANIDE PROCESSES. 395 tion is passed with an upward and downward flow, and electric circuit completing connection between the zinc and carbon. 588076 August 10, 1897. B. MOHR. Process of treating sulphide ore. The process for treating sulphide ore by acting on the pulverized ore with acid sodium or potassium sulphate, so as to obtain a solution of sulphate of zinc, depositing the zinc by electrolysis and thus recovering the acid alkali sulphate, and treating the insoluble residue obtained by the lixiviation for recovery of the other metals. 588740 August 24, 1897. B. BECKER. Apparatus for treating gold and silver ores. In apparatus for the treatment of gold and silver ores the combination of a vat provided with amalgamating plates and adapted to contain cyanide of potassium, in solution, and the ore to be treated, a vat containing the electrodes of an electrolytic apparatus and means for causing the circulation of the cyanide of potassium solution through the amalgamating vat, and for distributing it in the electrolytic vat. 590801 September 28, 1897. W. L. BROWN. Process of treating rebellious ores. The process of treating ores finely divided and mixed with water, which consists in adding a suitable compound to said ores and water, which compound contains an element which has a chemical affinity for the base constituents of the ore, then passing an electric current through said material to unite the said element chem- ically with the base constituents and to liberate the precious metals, then cir- culating the material over an amalgamated surface which is not in the electrical circuit, and finally returning the material again through the field of electrolytic action. 592055 October 19, 1897. E. C. KETCHUM. Process of treating ores. The process of treating mixed sulphide ores containing lead and zinc, which consists in first roasting the ores, then subjecting the roasted ores to the action of a solu- tion of caustic alkali in the presence of heat to remove from the ores the lead and the zinc, then subjecting the caustic solution containing the lead and zinc to electrolytic action in one or more cells to remove the lead, the anodes of which cells are immersed in a volume of pure caustic solution, which is separated by a porous medium from the electrolyte containing the lead and zinc, and then subjecting the caustic solution or electrolyte containing the zinc only to electrolytic action in one or more cells to remove the zinc. 592973 November 2, 1897. E. MOTZ. Electrolytic apparatus. In an elec- trolytic apparatus the combination with a frame or sluice of a series of convex cathode plates located in the bottom of said frame or sluice, a series of anode plates having curved under faces and disposed above said cathode plates, blocks secured to the anode plates and supported in the frame or sluice, each block having a recess in its upper edge, a series of conductors connected with said anode plates and terminating in said recesses in. the blocks, a conducting rod disposed in said recesses on the first-mentioned conductors and having a notch therein, a cross-bar passing through said notch, a conductor with which said cross-bar is electrically connected, locking devices for securing the cross-bar to the frame or sluice, and a conductor connected with the cathode plates. 594611 November 30, 1897. S. H. EMMENS. Process of and apparatus for removing^ zinc from zinciferous ores. The process of treating zinciferous ores, which consists in pulverizing and roasting the ore, leaching it in a series of vessels through which the solution flows continuously, and subjecting the contents of each vessel intermittently to electrolytic action, whereby the solution is rendered alternately acid and neutral or more acid and less acid in contact with each body of ore; and an apparatus for treating zinciferous ores, comprising a series of leaching-vats, each provided with an inlet-pipe extending to the bottom and with an exit-pipe or trough leading from the top of the vat, and each provided at bottom with an insoluble anode, a series of movable cathodes suspended above said vats, means for raising and lowering the cathodes of adjoining vats alternately, and an electric circuit to the respective poles with which said anodes and cathodes are connected. 597820 January 25, 1898. N. S. KEITH. Art of obtaining gold and silver from auriferous and argentiferous materials. The process of obtaining a precious metal from its ores, which consists first in dissolving the gold or silver in a cyanide solution containing cyanide of mercury and free cyanide of an alkaline metal, such 396 APPENDIX. as cyanide of potassium, and then passing a current of electricity through said solution to a metallic cathode, whereby an easily removable layer of the precious metal and mercury is simultaneously deposited upon said cathode. 598193 February 1, 1898. E. ANDREOLI. Apparatus for electrodeposition of gold and silver. In apparatus for the electrodeposition of gold, silver, or other metals, anodes of peroxidized lead acting in the presence of and in combination with a cyanide or cyanide-compound solution. 600351 March 8, 1898. E; A. ASHCROFT. Treatment of metalliferous ores and products. The improved process of preparing a solution suitable for leaching zinc-bearing ores of zinc-bearing products, consisting in electrolyzing a zinc-bear- ing solution successively in contact with a suitable cathode and an anode result- ing from the preliminary furnace treatment of products or ores containing cop- per and iron, and then depositing the copper from the resulting ferrous solution, and simultaneously raising the iron content of such solution to the ferric state by electrolyzing the said resulting ferrous solution successively in contact with suitable cathodes and insoluble anodes. 601068 March 22, 1898. F. W. WHITRIDGE. Method of and apparatus for extracting gold from its ores. The method of extracting gold from a weak cyanide solution, which consists in circulating the solution over anodes of iron and cathodes of lead, said cathodes being formed of thin plates arranged at short distances apart and having from 9 to 10 square meters of surface for each ton of solution in con- tact with them; and subjecting the said solution while in motion to an electric current of from 3.5 to 4 volts, and of from 0.5 to 1.5 amperes per square meter of cathode surface; and in apparatus for^ obtaining gold from a weak cyanide solution by electrolysis, the combination with a cell provided with anodes of iron and cathodes of lead formed of thin plates, said cathode plates having from 9 to 10 square meters of surface to each ton of solution in the cell; of means for cir- culating the solution in the cell, and means for subjecting the solution to a weak current of electricity. 60390 1 May 10, 1898. J. R. HEBAUS. Apparatus for extracting precious metals. An apparatus for extracting precious metals from their ores, comprising a tank having an amalgamated copper lining forming a cathode and a multiplicity of agitators, each rotating on its own axis and at the same time traveling around the tank, the said agitators forming an anode and an electric circuit. 605835 June 21, 1898. E. and G. ANDREOLI. Electrolytic production of amal- gams, etc. An apparatus for the production of amalgam, consisting of a cell pro- vided with positive and negative compartments separated by porous diaphragms, the negative compartments having a raised middle portion in the form of a table or block between the sides of which and the said partitions are narrow vertical spaces, the top of the block or table and the vertical spaces being covered and filled with a continuous body of mercury forming a cathode. 614572 November 22, 1898. J. C. McNuLTY. Method of and apparatus for treating ores. The art of extracting precious metals from their ores, consisting in mixing pulverized ore with an electrolytic fluid, causing the mixture to flow from one level to another between adjacent electrode plates of opposite polarity, passing an electric current between said plates and vibrating the electrodes in a direction substantially at right angles to the plane of said electrodes for the pur- pose of preventing the polarization thereof; and in apparatus for the electro- lytic treatment of ores the combination of a plurality of vats arranged in pairs communicating at the top, adjacent electrode plates of opposite polarity suspended within said vats and connected with a source of electricity, vibratory supports for said electrodes, means for vibrating the same at substantially right angles to their planes, a pressure conduit for pulp leading to the bottom of the first vat to provide an upward current therethrough, and an exit at the bottom of the succeeding vat providing a discharge for the downward current of pulp overflowing from the top of the vat preceding. 616891 January 3, 1899. G. D. BURTON. Electrolytic apparatus for treating metals and ores. In an electrolytic ore-treating apparatus, the combination of a tank for containing an electrolyte, an anode disposed in said tank, a cathode dis- PATENTS RELATING TO CYANIDE PROCESSES. 397 posed in said tank, a screen or deflector also disposed in said tank between the anode and cathode and adapted to distribute the ore or material being treated, said screen having a conductive surface connected to the negative pole of an elec- tric source whereby it is adapted to collect a portion of the product reduced from the ore by the action of the current and the electrolyte. 617911 January 17, 1899. E. A. SMITH and M. H. LYNG. Method of extract- ing metallic ores. The wet process of extracting copper from its ores having pre- cious metal therein, which consists in digesting the pulverized ore under action of heat and an oxidizing agent, in presence of sulphuric acid, exposing the dis- solved sulphates to metallic copper for precipitation of the silver, treating the filtrate electrolytically to deposit the copper, evaporating the lean electrolyte to concentrate the free acid, and crystallize the metallic sulphates, and finally cal- cining such crystallized sulphates to properly regenerate them as oxidizing agents for reuse. 623822 April 25, 1899. L. PELATAN. Apparatus for treating ores or the like. In apparatus, the combination with a circular vat, of a revolving anode, situated above and parallel to a mercury cathode, with an unobstructed space above the surface of the cathode, the said anode having arms which extend close to the peripheral wall of the vat and are suspended from a shaft, and are pro- vided with pins or stirrers projecting upward and downward to within a short distance of the underlying cathode, and projections or baffles extending inwardly from the inner surface of the peripheral wall of the vat. 626972 June 13, 1899. T. CRANE Y. Electrolytic apparatus for deposition of metals from solution. In an electrolytic apparatus, the combination of an outer tank provided with suitable feed and discharge connections for the liquid into the bottom and top, respectively, and an electrolytic couple, composed of sheet or analogous electrodes each folded in a fabric, with oppositely projecting mar- ginal portions and rolled together into a tight bundle and sealed in the tank, whereby the fabric inclosing the electrode forms a porous medium through which the elec- trode is compelled to flow. 627442 June 20, 1899. L. PELATAN. Process of electrolytically treating ores. The improvement in processes of treating ores electrolytically, consisting in add- ^>y* ing to a sludge, consisting of ore and water, a solvent and picric acid as an oxi- dizing agent and then passing an electric current therethrough. 631040 August 15, 1899. J. E. GREEN AWALT. Process of extracting precious metals from their ores. -A process for the treatment of gold and silver ores which consists, first, in properly roasting the pulverized ore; second, placing the ore Jf in a filtering-vat; third, washing the ore to remove soluble salts; fourth, in pass- (T) ing through the ore an electrolyzed solution consisting of a solution of chlorides chiefly sodium and ferric chlorides with a small percentage of bromides and small quantities of chlorine, bromine, and hypochlorous acid, with such other compounds as result from the electrolysis of a chloride and bromide solution; fifth, passing the solution after it leaves the ore through a precipitating-tank ; sixth, passing the solution after it leaves the precipitating-tank through the positive or onode compartment of an electrolytic cell, keeping the solution separate and distinct from the solution in the negative or cathode compartment of the cell; and, seventh, returning the solution from the regenerating cell to the ore in the vat and passing it thence to the precipitating-tank, again to the regenerating cell, arid again to the ore as often as may be required to effect the necessary saving of the values. 633544 September 19, 1899. H. S. BADGER. Electrolytic apparatus for pre- cipitating metals. A precipitating-tank comprising the tank body, having a mer- cury-coated surface in its bottom, a re voluble shaft suspended in the tank and provided with hollow arms having perforations on their lower sides to deliver air or vapor in proximity to the said surface, means for rotating the revoluble devices, means for introducing air or vapor to the hollow arms, and an electric circuit in which the shaft, agitating arms, and mercury-coated surface are located. 639766 December 26, 1899. L. E. PORTER. Apparatus for extracting precious metals from ores. The combination of a rotatable barrel adapted to form the 398 APPENDIX. cathode; a porous lining of non-conducting material arranged inside the barrel; a lining of filtering material arranged inside the non-conducting lining; anode plates arranged inside the filter lining; a source of electrical energy, having one pole connected with the barrel and the other pole connected with the anode plates. 640718 -January 2, 1900. C. P. TATRO and G. DELIUS. Process of extracting precious metals. In the process of separating precious metals from ores, the steps comprising electrolytically depositing a portion of the precious metals in the bath upon a drum cathode revolving partially immersed in the bath, at the same time scraping the said deposit from the drum, also simultaneously depositing other portions of similar precious metals in the same bath upon a cathode of sodium amalgam. 641571 January 16, 1900. W. WITTER. Process of producing solution of cyanogen halide. The process for producing a solution of cyanogen halide by electrolyzing in a bath without a diaphragm and with inert electrodes a solution containing an alkali cyanide, an alkali halide, and the salt of' a metal which forms an insoluble hydroxide. 649151 May 8, 1900. W. WRIGHT. Apparatus for extracting metals from refractory ores. An apparatus for extracting metals from refractory ores, com- prising a tank for receiving a sludge of such ores; a stationary, horizontal per- forated partition in said tank, fcrming beneath it a chamber; a cathode on the bottom of the tank within said chamber; a filtering medium carried on the par- tition; a number of pins arranged in a series of concentric circles projecting upward from said partition; a main driving-shaft; a series of radial arms supported by said shaft, and a plurality of anodes carried by said arms and working between the series of concentric pins. 650646 May 29, 1900. F. H. LONG. ^ Apparatus for electrolytic reduction of ores. An electrolytic apparatus, the combination with a reducer vessel; its bot- tom cathode and a diaphragm above said cathode, of a set of dependent anodes, each consisting of a carbon head; a copper stem extended therefrom through the vessel; an incasing iron tube carried by the vessel head to sustain the anode pole; a vulcanite sheath for said tube, and suitable elastic gaskets to expansively close the joints. 653538 July 10, 1900. N. L. TURNER. Electrolytic apparatus. An electro- lytical apparatus, comprising a tank, rotary agitators located therein eccentrically, a series of electrodes whose main portion is concentric with the tank, while the portions adjacent to the agitators are curved concentrically with the axes of said agitators, and electrodes of opposite polarity to those first named. 654437 July 24, 1900. W. A. CALDECOTT. Method of extracting gold from cyanide solutions containing the preciou.s metals. Means for extracting gold from cyanide solutions in depositing cells, consisting in a mechanical mixture of zinc shavings and lead shavings. 656305 August 21, 1900. W. STRZODA. Process of electrolytically extracting zinc from ores. The process of electrolytically extracting zinc from its ores, which consists in placing the disintegrated or pulverized ore in its natural state in an electrolytic vat containing an aqueous alkali-metal solution capable of dissolving the cre^ with production of a zincate and in direct contact with the cathode, and closing the circuit through the vat, thereby precipitating zinc and the alkali metal at the cathode, the alkali metal reacting with the water to regenerate the solvent solution. 657032 August 28, 1900. A. M. ROUSE. Apparatus for electrolyzing ores. In an apparatus of the class described having an anode and a cathode suitably arranged therein, the combination of a tank having an outer compartment, a tube located therein having an open upper end and provided at its lower end with openings forming communication from said compartment, a driving-shaft pro- jecting within said tube, an inner cup carried by said shaft, wings carried by said cup, an outer cup carried by said wings, a discharge duct, and a valve arranged to close said duct. 662286 November 20, 1900. E. MOTZ. Electrolytic apparatus. In an elec- trolytic cell having open ends, the combination with a removable cross-bar and PATENTS RELATING TO CYANIDE PROCESSES. 399 means for supporting it in position, of a metallic plate covering the bottom and two sides of the bar, and forming the anode plate of the cell, of a metallic plate arranged horizontally below and parallel with the bottom of the cross-bar, so as to form a passage between such plate and the bottom of the cross-bar, suc^i plate forming a cathode plate of the cell, and an auxiliary metallic cathode plate arranged vertically and parallel with the sides of the cross-bar and in circuit with the hori- zontal cathode plate, such vertically arranged plate extending below the plane of the bottom of the cross-bar, so as to more or less obstruct the said passage. 664537 December 25, 1900. J. DOUGLAS. Process of extracting copper. The process of reducing copper ore and matte, which consists in electrolyzing solid cuprous chloride, employing the gases evolved in the treatment of copper ore and matte, employing the electrolyte resulting from the electrolyzing of the solid cu- prous chloride as a solvent for the cuprous chloride so produced, and recovering the copper from the solution by electrolysis. 668842 February 26, 1901. A. M. ROUSE. Apparatus for electrolytically extracting and depositing gold and silver from their ores. In an apparatus, the com- bination of a series of pulp-receiving tubs, anodes and cathodes arranged in said tubs, an agitation-tube having communication with said tubs at their upper and lower ends, an agitator arranged in said tube, perforated conduits located in the upper ends of said tubs, chutes located beneath said conduits onto which the ore pulp is discharged, and deflectors located beside said conduits adapted to direct the flow of pulp onto said chutes as it passes through said conduits. 669752 March 12, 1901. P. W. KNAUF. Electrolytic apparatus. An element for an electrolytic series, consisting of a metallic receptacle having its lower por- tion of less diameter than the upper portion and having a bottom surface which is inclined upward radially from the center to the outer periphery, in combination with an exterior peripheral seat arranged below the upper edge, and an orifice adjacent to said seat. 669926 March 12, 1901. C. HOEPFNER. Process of electrolytical extraction of metals. A process which consists in placing a soluble metallic anode in a solu- tion capable of dissolving the same, placing a suitable cathode in a second similar solution containing a metal more electropositive than that of the anode, inter- posing a third similar solution of less solution pressure between the two first men- tioned, placing an auxiliary cathode therein, separating the solutions by suitable diaphragms, maintaining the solutions in motion and at a temperature above normal, passing a current, thereby dissolving the anode and precipitating the cathode metal at the cathode, and part of the diffused anode metal at the aux- iliary cathode, precipitating the anode metal from the anode and intermediate solutions and returning the resulting solution when enriched in cathode metal to the cathode cell. 678526 July 16, 1901. C. P. STEWART. Apparatus for the recovery of gold from cyanide solutions. An apparatus for recovering precious metals from flowing cyanide solutions, comprising in combination a relatively long substantially hori- zontal trough, means for supplying the solution at one end thereof, a partition near the receiving end of the trough for distributing the solution, a retaining partition at the discharge end of the trough adapted to retain the solution in the trough to the desired height, a body of quicksilver in the bottom of the trough between said partitions, a series of transverse anode supports extending substan- tially from partition to partition, a series of anodes adjustably mounted in said supports and extending down into the path of the flowing solution, and suitable electric connections. 682155 September 3, 1901. C. P. TATRO and G. DELIUS. Electrolytic appa- ratus for extracting precious metals. In apparatus for extracting precious metals, a tub: a mercurial cathode in the bottom thereof, a principal anode, means for lowering it into and raising it out of the tub, and a minor anode permanently in the tub. 689018 December 17, 1901. W. ORR. Method of recovering cyanides. The method of regenerating cyanide solutions which have become fouled by the pres- ence of zinc and copper contained in the solutions, as double cyanide of zinc and 400 APPENDIX. copper with the alkaline metals which consists, first, in passing through the solu- tion from a series of zinc anodes to a corresponding series of metallic cathodes a current of electricity; next, in introducing into such solution alkaline hydrate, being hydrate of the monovalent alkali metals and hydrate of the divalent alkali metals in the proportion of about two to one; next introducing into the solution a soluble alkali -metal sulphide, and finally removing the resulting zinc-sulphide precipitate. 689674 December ?4i 1901. A. I. IRWIN. Machine for extracting metal from ores. In a machine for the automatic and continuous extraction and deposition of metal from ores at one and the same time, a treatment-tank, an endless anode traveling in s?id tank, the upper and lower stretches of the anode being in posi- tion to be immersed in the solution in the tank, diagonally disposed blocks of insulating material attached to said anode, cathodes in the tank, one under each stretch of trie anode, and connections with a source of electricity. 689959 December 31, 1901. E. L. GRAHAM. Process of disintegrating and comm,invting minerals or ores. The process of treating ores, consisting of the fol- lowing steps: First, immersing the ores in a solution of sulphuric and hydrofluoric acids incapable of dissolving the ore; second, passing an electric current of suffi- cient strength to disintegrate the ore through the solution; and third, extracting the metal from the ore. 699964 May 13, 1902. F. H. LONG. Electrolytic converter. In electrolytic converters, the combination with the closed reducer vessel having the anode and cathode terminals and the' interposed diaphragm dividing the vessel into upper anode and lower cathode chambers, of a combined separator and vent-pipe con T nected to the cathode chamber beneath the diaphragm extending upwardiy above the level of said diaphragm and having a free outlet for the gases. 700941 May 27, 1902. N. S. KEITH. Process of treating copper or other ores for obtaining their contents of metals. The process of electrolyzing a solution of a metal; to deposit the metal therefrom, which consists in passing it as an elec- trolyte through a succession of two or more electrolytic cells, arranged so that the cells are connected in electrical series with a source of electricity; the anodes insoluble, the electrodes of each cell in electrical multiple, and having gradually increasing surfaces, whereby there is a gradual reduction of the current density as the metal of the electrolyte is deposited. 704639 July 15, 1902. C. HOEPFNER. Leaching and extraction of metals from their ores. The process of extracting metals, which consists in leaching a suitable material containing copper, lead, and silver, with a warm cupric-chloride solution containing a solvent of cuprous' chloride, in quantity less than is required for saturation, thereby dissolving lead and silver chlorides, precipitating them, reconverting the solution into cupric chloride, using the same for leaching fresh quantities of ore, leaching the residues with a similar hot solution more concen- trated in cupric chloride, thereby dissolving copper and recovering those metals therefrom, reconverting the resulting solution into cupric chloride, and returning the latter into the cycle of operations. 706436 August 5, 1902. F. T. MUMFORD. Apparatus for the electrolytical treatment of ores or sfimes. An apparatus for the extraction of metals from their ores and slimes, comprising a rotatable cylindrical metallic drum, a copper lining therein, a body of mercury in the drum to maintain the lining amalgamated, a valve-controlled inlet and outlet, and a relief- valve at one end, a plurality of con- ductive rods insulated from and passing longitudinally through the drum, a metallic ring connecting the bars, trailing electrical contact for the drum and one for said ring. 709817 September 23, 1902. C. E. DOLBEAR. Ehctrolytically treating ores. The method of reducing metals from their ores, which consists in dissolving the crushed ore in a compound containing a nitric acid radical, adding to the mix- ture sulphuric acid, and subjecting the resultant compound to the action of an electric current. 725864 April 21, 1903. W. B. MCPHERSON. Apparatus for the treatment of gold or other ores. A precipitating apparatus for d^po^iting gold and silver from PATENTS RELATING TO CYANIDE PROCESSES. 401 a cyanide of potassium solution and from other chemical solutions, comprising a precipitating-box having downward, inclined bottom with openings therein, valves located in said openings, said box provided with a series of electric con- ducting plates vertically arranged therein and connected with a source of electric supply, a gauge receptacle, a pipe communicating with said receptacle and with the precipitating-box through which the said solution passes back and forth, a float within said receptacle and adapted to reciprocate therein, a yoke secured to said float, a horizontally reciprocating valve-rod, devices for connecting said yoke with said valve-rod, means for operating said valves in connection with valve- rod, arid means for conveying said solution from said precipitating-box and return- ing the same thereto. 737554 August 25, 1903. L. P. BURROWS. Electrolytic apparatus. An electrolytic apparatus, comprising a dissolving vessel having a revoluble anode, a depositing vessel having a cathode, means for conveying an unbroken stream of liquid from the dissolving vessel, and an electric circuit including said anode and cathode, whereby the electric current is caused to transverse the stream of liquid flowing from the dissolving vessel into the depositing vessel. 741231 October 13, 1903. W. H. DAVIS. Process of treating cyanide solu- tions. The process for treating cyanide solutions during or subsequently to their contact with the ore, consisting in introducing into the solution an alkaline hydrate and then subjecting the mixture to the action of an alternating electric current, thereby raising the osmotic pressure to dissociate the double salts in the solution, causing precipitation of the hydrates of the base metals and to combine the freed cyanogen with the alkaline hydrates to cause simultaneous regeneration of the cyanide in the solution and clarifying of the latter. 741439 October 13, 1903. C. E. BAKER and A. W. BURWELL. Process of treating ores. The process of recovering copper and nickel from a solution of sul- phates of copper, nickel, and iron, which consists of electro-depositing the copper, neutralizing the solution, and electro-depositing the nickel with a current density insufficient to deposit the iron. 743668 November 10, 1903. R. SUCHY and H. SPECKE'TER, Extracting chromium from chrome-iron ore. The process of making soluble chrome-iron ore and obtaining chromium compounds, which consists in heating the ore together with sulphuric acid in excess and an oxidizing agent and separating by filtration the precipitated insoluble ferrisulphate from the chromosulpho acid. 749843 January 19, 1904. H. R. CASSEL. Process of extracting precious metals by electrolysis. The process of extracting precious metals by electrolysis, which consists in circulating the pulp between vertical electrodes, amalgamating a vertical cathode, successively deflecting the rebounding mercury back upon said cathode, removing the amalgam, neutralizing the alkali in the mercury, and returning the mercury to the cathode. 749844 January 19, 1904. H. R. CASSEL. Apparatus for extracting precious metals by electrolysis. An apparatus for extracting precious metals by electrolysis, comprising a tank, inclosed vertical electrodes, mercury deflectors, and pulp-guards at the sides of the cathode, an elevated pulp-box, communicating perforated launders, means for lifting the pulp into said box, an elevated mercury pot, communicating slidable perforated troughs, and means for lifting the mercury into said pot. 755302 March 22, 1904. E. A. LE SUEUR. Extraction of copper from com- minuted mineral mixtures, The method of obtaining metallic copper from mix- tures containing it, which consists, first in treating said mixtures with an ammo- niacal solution, containing a cupric compound or compounds, so as to dissolve the desired copper, then in removing a portion of the total copper contents of the solution, and lastly in using the partially exhausted solution over again to dissolve fresh copper as before. INDEX. Acetonitrile, 40 Adler's process, hydrocyanic acid, 93 Albright's process, sulphocyanide, 285 Alcoholic carbimides, 40 Allyl cyanide, 40 Aluminium cyanide, 24 Ammonium cyanate, 37 cyanide, 23 cyanhydrate, 60 sulphocyanate, 274 thiosulphocarbamate, 273 Ammoniacal liquors, 224 cyanogen from, 242 Prussian blue, 292 Amyl cyanide, 40 Andreoli's process, gold precipitation, 315 Antimony blue, 293 Apparatus, Bueb's, 186-8 Castner's, 142, 174 Engler's, 201 Mackey's, 136 Raschen's, 99 Stassfurter Chem. Fabrik, 159 Roca's, 167 Arnpul, Camille, works of, 248 Auriferous minerals, oxidation of, 295 Auripotassic cyanide, 35 Aurocyanide, 35 Aurosopotassic cyanide, 35 Azulmic acid, 11 Barium cyanide, 24, 169 ferricyanide, 32 Beck's process, ferricyanide, 266 Beilby's process, cyanide, 162 Bergmann's process, hydrocyanic acid, 94 cyanide, 101 results, 154 Beringer's process, cyanide, 150 Berthelot's hypothesis, 7 Black-mass, composition of, 204 Blackmore's process, cyanides, 150 Blood-lye, 81 Blue potash, 205 Bouxvillers Mines' process, ferricyanide, 264 Bower's process, cyanide, 107 ferrocyanide, 243 British Cyanide Co.'s process, cyanide, 105 sulphocya- nide, 283 Brock's process, sulphocyanide, 282 Brunquell's process, cyanide, 153 ferrocyanide, 210 Bueb's apparatus, 186 process, cyanide, 185 ferrocyanide, 237 Buignet's method, hydrocyanic acid, 48 Burchell's method, 52 Butyl cyanate, 40 cyanide, 40 Butyro nitrile, 40 Calcium cyanide, 24 ferricyanide, 32 sulphocyanate, preparation of, , 277 Carbazol, 183 Carbylamines, 39 Castner's process, cyanide, 153 Cetyl cyanide, 40 Chaster' s process, cyanide, 165 hydrocyanic acid, 88 Chem. Fabrik Aktiengesellschaft's process, cyanide, 165 Chlorides, detection of, 47 Chlorine process, ferricyanides, 261 Chromium cyanide, 25 Chryseane, 21 Clark's process, 16 Clauss and Domeier's process, ferrocya- nide, 234 Coal, nitrogen content of, 220 types of, 216 Cobalt cyanide, 27 ferricyanide, 32 Cobalticyanide of potassium, 34 sodium, 34 403" 404 INDEX. Cobaltocobalticyanide, 34 Coke, elements of, 218 Compagnie Generate des Cyanures, 273 Conroy's process, cyanide, 108 ferrocyanide, 211 Cooling-mixture, 329 Copper cyanide, 26 ferricyanide, 32 Crystallization, 210 Cyanamid, 147 Cyanate of ammonium, 37 silver, 37 sodium, 37 Cyanates, 44 detection of, 47 Hertig's method, 47 Cyanic acid, 36 esters, 40 Cyanide of aluminium, 24 ammonium, 23 barium, 24 calcium, 24 cobalt, 27 copper, 26 chromium, 25 gold, 27 iron, 25 manganese, 25 mercury, 26 nickel, 27 platinum, 27 silver, 26 sodium, 23 tin, 25 zinc, 24 'Cyanides, analysis of commercial, 47 characteristics of, 328 critical temperatures, 324 density of, 323, 329 determination of medicinal, 48 double, 28 extraction from illuminating gas, 214, 219 extraction from purifying ma- terials, 245 extraction from sulphocya- nides, 95 Fordos and Gelis' method, 45 iieat of formation, 56, 324 solution, 324 volatilization, 324 O. Hertig's method, 47 Liebig's method, 44 list of works producing, 74 methods of manufacture, 81 simple, 22 solubility of, 327 strong solution, 301 use of, 294 weak solutions, 302 Cyanides manufacturing processes* Adler's process, 93 Armengaud's process, 126 Beilby's process, 162 Bergmann's process, 94 Beringer's process, 101, 150 Blackmore's process, 150 Blairs' process, 126 Boussingault's process, 119 Bower's process, 107 British Cyanide Co.'s process, 105 Brunquell's process, 153 Bueb's process, 185 Bunsen's process, 123 Castner's process, 141, 153, 172 Chaster's process, 88, 165 Chem. Fabrik Aktiengesellschaft's, 183 Chem. Fabrik Pfersee Augsburg, 149 Chipmann's process, 138 Conroy's process, 107 Dalinot's process, 92 Deutsche Gold u. Silber Scheide Anstalt, 175 Dickson's process, 129 Dzuik's process, 150 Etard's process, 110, 120 Finlay's process, 110 Fogarty's process, 128 Frank and Caro's process, 144, 153 Gen. Elec. Chem. Co.'s process, 152 Gilmour's process, 134 Glock's process, 179 Goerlich and Wichmann's process, 107 Grossmann's process, 182 Hetherington and Musspratt's proc- ess, 106 Hood and Salamon's process, 169 Hornig's process, 170 Hornig and Schneider's process, 143 Hoyermann's process, 180 Huntington's process, 180 Karmrodt's process, 153 Kellner's process, 182 Kerp's process, 181 Lambilly's process, 129, 161, 178 Lance and Bourgade's process, 156 Liebig's process, 87, 153 Lucas' process, 153 Luttke's process, 104 Mackey's process, 135 Mactear's process, 157 Mallet's process, 121 Margueritte and SourdevaFs process, 126, 153 Martin's process, 179 Mehner's process, 137, 143 Moi'se and Mehner's process, 140 Mond's process, 127 Moulis and Sars' process, 160 Newton's process, 126 INDEX. 405 Cyanides manufacturing processes : Old processes, 85 Ortlieb and Miiller's process, 190 Parkinson's process, 120 Pestchow's process, 137 Pictet's process, 121 Pfleger's process, 165 Playf air's process, 102 Possoz and Boissiere' s process, 124 Raschen and Brock's process, 97, 110 Readmann's process, 135 Roca's process, 166 Rossler and Haaslacher's process, 89 Roussin's process, 181 Schneider's process, 171 Silesia Verein Chem. Fabrik's process, 107 Societe Anonyme de Croix's process, 190 Stassfurter Chem. Fabrick's process, 158 Swan and Kendall's process, 137 Synthetic processes, 111 Tessie' du Mothay's process, 120 Vidal's process, 184 Villepigne's process, 121 Wagner's process, 88 Weldon's process, 128 Wichmann and Vautin's process, 88 Wolfram's process, 150 Young's process, 134 Young and Macfarlane's process, 163 Cyaniding mixture, 168 Cyanogen, constitution of ,5 conversion tension, 14 formation, 12 preparation, 13 properties, 10 Cyanosulphite of potassium, 22 Dalinot's process, hydrocyanic acid, 92 Deiss and Monnier's process, sulphocya- nide, 281 Deutsche Gold u. Silber Scheide Anstalt's process, ferrocyanide, 265 DeWilde's process, 303 Donath's process, ferrocyanide, 258 Donath and Margosche's method, ferrocya- nide, 53 Double cyanides, 28 Dubosc's process, ferricyanide, 265 du Castelet Works' process, ferrocyanide, 213 Dzuik's process, cyanide, 150 En^ler's apparatus, 201 Erlenmeyer's method, ferrocyanide, 49 Esop's process, ferrocyanide, 258 Etard's process, hydrocyanic acid, 94 Ethyl cyanate, 40 cyanide, 40 Everitt's process, 16 Feld's process, ferrocyanide, 241 Ferricyanide, manufacture of, 261 of potassium, 43, 32 Ferricyanide processes : Beck's process, 267 Chlorine process, 261 Deutsche Gold u. Silber Scheide An- stalt's process, 265 Dubosc's process, 265 Kassner's process, 266 Mines at Bouxvillers, 264 Reichardt's process, 263 Williamson's process, 267 Ferricyanide, use of, 319 Ferrocyanide, 25, 43 manufacture of, 192, 205, 229 Ferrocyanide processes : Bower's process, 243 BrunquelPs process, 210 Bueb's process, 237 Glaus s and Domeier's process, 234 Conroy's process, 212 Donath's process, 258 Esop's process, 258 Feld's process, 241 Fowlis' process, 233 Gasch's process, 232 Gauthier-Bouchard's process, 248 Goerlich and Wichmann' s process, 213 Harcourt's process, 257 Hempel's process, 257 Hetherington's process, 212 Holbling's process, 259 Karmrodt's process, 211 Knublauch's process, 231 Kunheim's process, 257 Lewis' process, 236, 243, 259 Marasse's process, 258 Mascow's process, 259 Musspratt's process, 212 Pendrie's process, 242 Richter's process, 258 Rowland's process, 233 Schroeder's process, 234 Teichmann's process, 235 Valentin's process, 256 Wolfram's process, 257 Works du Castelet, 213 Ferrocyanide, detection of: Burchell's method, 52 Erlenmeyer's method, 49 Knublauch's method, 50 Moldenhauer and Leybold's method, 51 Ferrocyanide of iron, 31 potassium, 29 sodium, 31 Ferrocyanide, precipitation of, 253 use of, 316 406 INDEX. Filtering-vats, 300 Flemming's furnace, 158 Fordos and Gelis' method, 45 Formates, detection of, 47 Frank and Caro's process, cyanide, 144 Furnaces, Flemming's, 158 Gruneberg's, 158 reverberatory, 199 Siepermann's, 158, 182 Gas, composition of, 226 Gasch's process, ferrocyanide, 232 Gauthier-Bouchard's process, ferrocya- nide, 248 Gelis' process, sulphocyanide, 272 Gen. Elec.-Chem. Co.'s process, cyanide, 182 Goerlich and Wichmann's process, cyanide, 107 Goerlich and Wichmann's process, ferrocy- anide, 213 Goerlich and Wichmann's process, sulpho- cyanide, 286 Gold-bromine cyanide, formation, 297 Gold cyanide, 35 precipitation of, 298, 304, 314 solution of, 298 Grossmann's process, cyanide, 182 Gruneberg's furnace, 158 Harcourt's process, ferrocyanide, 257 HempePs process, ferrocyanide, 257 Hertig's method, cyanates, 47 Hetherington's process, ferrocyanide, 212 Hetherington and Musspratt's process, cyanide, 106 Holbling's process, ferrocyanide, 259 Hood and Salamon's process, cyanide, 169 sulphocya- nide, 282 Hornig's process, cyanide, 170 Hornig and Schneider's process, cyanide, 143 Hydrate of iron, composition, 247 Hydrocyanic acid, 14, 42 Buignet's method, 48 heat of formation, 57 Hydrocyanic acid: Adler's process, 93 Bergmann's process, 94 Chaster's process, 88 Dalinot's process, 92 Etard's process, 94 Liebig's process, 87 Rossler and Haaslacher's process, 89 Wagner's process, 88 Wichmann's and Vautin's process, 90 Illuminating-gas, composition, 226 elements of, 218 Karmrodt's process, cyanide, 153 ferrocyanide, 211 Kassner's process, ferricyanide, 266 Keith's process, gold precipitation, 314 Kellner's process, cyanide, 182 Kerp's process, cyanide, 181 Knublauch's process, ferrocyanide, 231 Kunheim's process ferrocyanide, 257 Lambilly's process, cyanide, 153, 161 Laming mixture, composition, 246 Lance and Bourgade's process,cyanide,156 Lewis' process, ferrocyanide, 236, 243, 259 Liebig's method, cyanide, 44 process, cyanide, 153 hydrocyanic acid, 87 theory, 9 Limonite, composition of, 247 Lixiviation, 210, 249 vats, 252 Lucas' process, cyanide, 153 Luttke's process, cyanide, 104 Lux mass, composition, 246 MacArthur and Forrest's method, 304 1 Mackey's process, cyanide, 135 Mactear's process, cyanide, 157 Manganese cyanides, 25, 34 Marasse's process, ferrocyanide, 258 Margueritte's process, cyanide, 153 Margueritte and SourdevaFs process, cya- nide, 126 Martin's process, cyanide, 179 Mascow's process, ferrocyanide, 258 Mehner's process, cyanide, 143 Melam, 39 Mercury cyanide, 26 Metal, production of, 197 Metallic cyanides, 18 Methyl cyanate, 46 cyanide, 40 Moise and Mehner's process, cyanides, 140* Moldenhauer and Leybold's method, 51 Mond's process, cyanide, 127 Monthier's blue, 292 Moulis and Sars' process, cyanide, 160 Mulholland's process, 303 Musspratt's process, ferrocyanide, 212 Newton's process, cyanide, 126 Nickel cyanide, 27 ferricyanide, 32 Nitriles, 39 Nitroferricyanides, 35 Nitroprussiates, 35 Non-synthetic processes, 85 Old process, cyanide, 85 ferrocyanide, 193 Organic compounds, 39 Ortlieb & Miiller's process, cyanide, 190' INDEX. 407 Oxide of iron, composition of, 247 Oxygen compounds of cyanogen, 36 Paracyanogen, 13, 147 Pendrie's process, ferrocyanide, 242 Pfleger's process, cyanide, 165 Physical study cyanogen, 10 Platinum cyanide, 27 Platino cyanides, 34 Playfair's process, cyanide, 102 Potash, determination of, 48 Potassium cyanate, 36, 60 cyanide, 20, 58 analysis of, 47 antidote, 22 heat of formation, 58 manufacture, 85 production, 72 use of, 70 cyaniferride, 32 cyanosulphite, 21 ferricyanide, 32 production, 72 ferrocyanide, 29, 43, 49 exportation, 80 heat of forma- tion, 60 importation, 79 production, 72 sulphide, detection, 47 sulphocyanide, 38 Processes utilizing ammonia, 153 atmospheric nitrogen, 117 Propionitrile, 40 Propyl cyanide, 40 Prussian blue, 31 determination, 54 discovery of, 69 manufacture, 288 use of, 319 Woodward's method, 289 Prussic acid, 14 action on system, 17 antidote, 18 Purifying materials, 50 composition, of, 219, 226, 245 revivification, 247 Raschen' s apparatus, 99 Raschen and Brock's method, 97 Raschen, Davidson and Brock's process, cyanide, 110 Readmann's process, cyanide, 135 Red prussiate of potash, 32 Reichardt's process, ferricyanides, 263 Retort, 198 Rhodanides, 37 Richter's process, ferrocyanides, 258 Roca's apparatus, 167 process, cya- Roca's process, cyanide, 166 Rossler and Haaslacher's process, hydro- cyanic acid, 89 Roussin's process, cyanides, 181 Rowland's process, ferrocyanide, 233 Schneider's process, cyanide, 171 Schroeder's process, ferrocyanide, 234 Siemens and Halske's process, gold pre- cipitation, 314 Siepermann's furnace, 158, 182 Silesia Verein Chem. Fabrik's pr nide, 107 Silver cyanate, 37 cyanide, 26 ferricyanide, 32 Simple cyanide, formation, 19 properties, 19 Socie'te' Anonyme de Croix's process, cya- nide, 190 Sodium cyanate, 37 cyanide, 23 ferrocyanide, 31 Soluble Prussian blue, 32, 292 Sourdeval's process, cyanide, 153 Spent oxide, 54 composition, 246 Stassfurter Chem. Fabrik's process, cya- nide, 158 Sulman's process, 303 Sulphate of iron, composition of, 247 Sulphocarbamide, 39 Sulphocyanates, 37 Sulphocyanide, 37, 43, 50 cost of, 271 detection of, 47 manufacture, 269 Sulphocyanide processes : Albright's process, 285 British Cyanide Co.'s process, 283' Brock's process, 282 Deiss and Monnier's process, 281 Gelis' process, 270 Goerlich and Wichmann's process, 286'- Hood and Salamon's process, 282 Tcherniac's process, 285 Sulphocyanide recovery, 56 use of, 319 Swan and Kendall's process, cyanide, 137 Synthetic processes, cyanide, 111 Tables, 294 Tar, 218 Tcherniac's process, sulphocyanide, 285 . . Teichmann's process, ferrocyanide, 235 , Tin cyanide, 25 Thomson's process, 16 Toxicological research, 54 Tricyanates, 37 i TurnbulPs blue, 33, 292 Valentin's process, ferrocyanide, 256: * 408 INDEX. Vats, filtering, 299 Vauquelin's process, 16 Vidal's process, cyanide, 184 Wagner's process, cyanide, 88 Weldon's process, cyanide, 127 Wichmann and Vautin's process, cyanide, 90 Williamson's process, ferricyanide, 267 Wolfram's process, cyanide, 150 Wolfram's process, ferrocyanide, 257 Woodward's method, 289 Young's process, cyanide, 134 Young and Macfarlane's process, cyanide, 163 Zaloziecki's method, ferrocyanide, 52 Zinc cyanide, 24 potassium cyanide, 22 SHORT-TITLE CATALOGUE OP THE PUBLICATIONS OF JOHN WILEY & SONS, NEW YORK. LONDON: CHAPMAN & HALL, LIMITED. ARRANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked with an asterisk (*) are sold at net prices only, a double asterisk (**) books sold under the rules of the American Publishers' Association at net prices subject to an extra charge for postage. All books are bound in cloth unless otherwise stated. AGRICULTURE. Armsby's Manual of Cattle-feeding xarno, Si 75 Principles of Animal Nutrition 8vo, 4 oo Budd and Hansen's American Horticultural Manual: 50 50 oo 50 oo 50 00, 50 50 50 50 Part I. Propagation, Culture, and Improvement 12 mo, Part II. Systematic Pomology i2mo, Downing's Fruits and Fruit-trees of America 8vo, Elliott's Engineering for Land Drainage I2mo, Practical Farm Drainage I2mo, Green's Principles of American Forestry i2mo, Grotenfelt's Principles of Modern Dairy Practice. (Woll.) izmo, Kemp's Landscape Gardening I2mo, Maynard's Landscape Gardening as Applied to Home Decoration i2mo, * McKay and Larsen's Principles and Practice of Butter-making 8vo, Sanderson's Insects Injurious to Staple Crops i2mo, Insects Injurious to Garden Crops. (In preparation.) Insects Injuring Fruits. (In preparation.) Stockbridge's Rocks and Soils 8vo, 2 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Woll's Handbook for Farmers and Dairymen i6mo, i 50 ARCHITECTURE. Baldwin's Steam Heating for Buildings I2mo, 2 50 Bashore's Sanitation of a Country House I2mo, i oo Berg's Buildings and Structures of American Railroads 4to, 5 oo Birkmire's Planning and Construction of American Theatres *. 8vo, 3 oo Architectural Iron and Steel 8vo, 3 50 Compound Riveted Girders as Applied in Buildings 8vo, 2 oo Planning and Construction of High Office Buildings 8vo, 3 50 Skeleton Construction in Buildings 8vo, 3 oo Brigg's Modern American School Buildings 8vo, 4 oo Carpenter's Heating and Ventilating of Buildings 8vo, 4 oo Freitag's Architectural Engineering 8vo, 3 50 Fireproofing of Steel Buildings 8vo, 2 50 French and Ives's Stereotomy 8vo, 2 50 1 Gerhard's Guide to Sanitary House-inspection i6mo, i oo Theatre Fires and Panics i2mo, i 50 Greene's Structural Mechanics 8vo, 2 50 Holly's Carpenters' and Joiners' Handbook i8mo, 75 Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 oo Kidder's Architects' and Builders' Pocket-book. Rewritten Edition. i6mo, mor., 5 oo Merrill's Stones for Building and Decoration , . . . .8vo, 5 oo Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 oo Monckton's Stair-building 4to, 4 oo Patton's Practical Treatise on Foundations 8vo, 5 oo Peabody's Naval Architecture 8vo, 7 50 Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, i 50 Snow's Principal Species of Wood 8vo, 3 50 Sondericker's Graphic Statics with Applications to Trusses, Beams, and Arches. 8vo, 2 oo Towne's Locks and Builders' Hardware i8mo, morocco, 3 oo Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo, 5 oo Sheep, 5 50 Law of Contracts. 8vo, 3 oo Wood's Rustless Coatings : Corrosion and Electrolysis of Iron and Steel . . 8vo, 4 oo Worcester and Atkinson's Small Hospitals, Establishment and Maintenance, Suggestions for Hospital Architecture, with Plans for a Small Hospital. i2mo, i 25 The World's Columbian Exposition of 1893 Large 4to, i oo ARMY AND NAVY. Bernadou's Smokeless Powder, Nitro-cellulose, and the Theory of the Cellulose Molecule i2mo, 2 50 * Bruff 's Text-book Ordnance and Gunnery 8vo, 6 oo Chase's Screw Propellers and Marine Propulsion 8vo, 3 oo Cloke's Gunner's Examiner 8vo, i 50 Craig's Azimuth 4to, 3 50 Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 oo * Davis's Elements of Law 8vo, 2 50 * Treatise on the Military Law of United States 8vo, 7 oo Sheep, 7 50 De Brack's Cavalry Outposts Duties. (Carr.) 24010, morocco, 2 oo Dietz's Soldier's First Aid Handbook i6mo, morocco, i 25 * Dredge's Modern French Artillery 4to, half morocco, 15 oo Durand's Resistance and Propulsion of Ships 8vo, 5 oo * Dyer's Handbook of Light Artillery I2mo, 3 oo Eissler's Modern High Explosives 8vo, 4 oo * Fiebeger's Text-book on Field Fortification Small 8vo, 2 oo Hamilton's The Gunner's Catechism i8mo, i oo * Hoff's Elementary Naval Tactics 8vo, i 50 Ingalls's Handbook of Problems in Direct Fire 8vo, 4 oo * Ballistic Tables 8vo, i 50 * Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. .8vo, each, 6 oo * Mahan's Permanent Fortifications. (Mercur.) 8vo, half morocco, 7 50 Manual for Courts-martial i6mo, morocco, i 50 * Mercur's Attack of Fortified Places i2mo, 2 oo * Elements of the Art of War 8vo, 4 oo 2 Metcalf's Cost of Manufactures And the Administration of Workshops. .8vo, 5 oo * Ordnance and Gunnery. 2 vols I2mo, 5 oo Murray's Infantry Drill Regulations i8mo, paper, 10 Nixon's Adjutants' Manual 24010, I oo Peabody's Naval Architecture 8vo, 7 50 * Phelps's Practical Marine Surveying. 8vo, 2 50 Powell's Army Officer's Examiner i2mo, 4 oo Sharpe's Art of Subsisting Armies in War i8mo, morocco, 50 * Walke's Lectures on Explosives 8vo, oo * \ fheeler's Siege Operations and Military Mining 8vo, oo Winthrop's Abridgment of Military Law i2mo, 50 Wcodhull's Notes on Military Hygiene i6mo, 50 Young's Simple Elements of Navigation z6mo, morocco- oo ASSAYING. Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. i2mo, morocco, i 50 Furman's Manual of Practical Assaying 8vo, 3 oo Lodge's Notes on Assaying and Metallurgical Laboratory Experiments. . . .8vo, 3 oo Low's Technical Methods of Ore Analysis 8vo, 3 oo Miller's Manual of Assaying i2mo, i oo Minet's Production of Aluminum and its Industrial Use. (Waldo.) i2mo, 2 50 O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 oo Ricketts and Miller's Notes on Assaying 8vo, 3 oo Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, Ulke's Modern Electrolytic Copper Refining 8vo, 3 oo Wilson's Cyanide Processes i2mo, i 50 Chlorination Process i2mo, i 50 ASTRONOMY. Comstock's Field Astronomy for Engineers 8vo, 2 50 Craig's Azimuth 4to, 3 30 Doolittle's Treatise on Practical Astronomy 8vo, 4 oo Gore's Elements of Geodesy 8vo, 2 50 Hayford's Text-book of Geodetic Astronomy , 8vo, 3 oo Merriman's Elements of Precise Surveying and Geodesy. 8vo, 2 50 * Michie and Harlow's Practical Astronomy 8vo, 3 oo * White's Elements of Theoretical and Descriptive Astronomy i2mo, 2 oo BOTANY. Davenport's Statistical Methods, with Special Reference to Biological Variation. i6mo, morocco, i 25 Thomd and Bennett's Structural and Physiological Botany i6mo, 2 25 Westermaier's Compendium of General Botany. (Schneider.) 8vo, 2 oo CHEMISTRY. Adriance's Laboratory Calculations and Specific Gravity Tables i2mo, i 25 Allen's Tables for Iron Analysis 8vo, 3 oo Arnold's Compendium of Chemistry. (Mandel.) Small 8vo, 3 50 Austen's Notes for Chemical Students i2mo, i 50 Bernadou's Smokeless Powder. Nitro-cellulose, and Theory of the Cellulose Molecule I2mo, 2 50 * Browning's Introduction to the Rarer Elements 8vo, i 50 3 Brush and Penfield's Manual of Determinative Mineralogy 8vo, 4 oo Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.). -8vo, 3 oo Cohn's Indicators and Test-papers lamo, 2 oo Tests and Reagents 8vo, 3 oo Crafts's Short Course in Qualitative Chemical Analysis. (Schaeffer.). . .i2mo, i 50 Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von Ende.) i2mo, 2 50 Drechsel's Chemical Reactions. (Merrill.) i2mo, i 25 Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 oo Eissler's Modern High Explosives 8vo, 4 oo Eff rent's Enzymes and their Applications. (Prescott.) 8vo, 3 oo Erdmann's Introduction to Chemical Preparations. (Dunlap.) i2mo, i 25 Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. i2mo, morocco, i 50 Fowler's Sewage Works Analyses i2mo, 2 oo Fresenius's Manual of Qualitative Chemical Analysis. (Wells.) 8vo, 5 oo Manual of Qualitative 'Chemical Analysis. Part I. Descriptive. (Wells.) 8vo, 3 oo System of Instruction in Quantitative Chemical Analysis. (Cohn.) 2 vols 8vo, 12 50 Fuertes's Water and Public Health 12010, i 50 Furman's Manual of Practical Assaying .8vo, 3 oo * Getman's Exercises in Physical Chemistry i2mo, 2 oo Gill's Gas and Fuel Analysis for Engineers 1 12mo, i 25 Grotenfelt's Principles of Modern Dairy Practice. (Woll.) 12010, 2 oo Hammarsten's Text-book of Physiological Chemistry. (Mandel.) 8vo, 4 oo Helm's Principles of Mathematical Chemistry. (Morgan.) i2mo, i 50 Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Hind's Inorganic Chemistry 8vo, 3 oo * Laboratory Manual for Students i2mo, i oo Holleman's Text-book of Inorganic Chemistry. (Cooper.) 8vo, 2 50 Text-book of Organic Chemistry. (Walker and Mott.) 8vo, 2 50 * Laboratory Manual of Organic Chemistry. (Walker.) i2mo, i oo Hopkins's Oil-chemists' Handbook 8vo, 3 oo Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, i 25 Keep's Cast Iron 8vo, 2 so Ladd's Manual of Quantitative Chemical Analysis i2mo, i oo Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 oo * Langworthy and Austen. The Occurrence of Aluminium in Vegetable Products, Animal Products, and Natural Waters 8vo, 2 oo Lassar-Cohn's Practical Urinary Analysis. (Lorenz.) i2mo, i oo Application of Some General Reactions to Investigations in Organic Chemistry. (Tingle.) 12010, i oo Leach's The Inspection and Analysis of Food with Special Reference to State Control 8vo, 7 50 Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 oo Lodge's Notes on Assaying and Metallurgical Laboratory Experiments 8vo, 3 oo Low's Technical Method of Ore Analysis 8vo, 3 oo Lunge's Techno-chemical Analysis. (Cohn.) 12010, i oo Mandel's Handbook for Bio-chemical Laboratory 12010, i 50 * Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe . . 12010, 60 Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 3d Edition, Rewritten 8vo, 4 oo Examination of Water. (Chemical and Bacteriological.) 12010, i 25 Matthew's The Textile Fibres 8vo, 3 So Meyer's Determination of Radicles in Carbon Compounds. (Tingle.). .i2mo, i oo Miller's Manual of Assaying 12010, i oo Minet's Production of Alumioum and its Industrial Use. (Waldo.) . . . . i2mo, 2 50 Mixter's Elementary Text-book of Chemistry 12010, i 50 Morgan's Elements of Physical Chemistry 12010, 3 oo * Physical Chemistry for Electrical Engineers i2mo, i 50 4 Morse's Calculations used in Cane-sugar Factories i6mo, morocco, i 50 Mulliken's General Method for the Identification of Pure Organic Compounds. Vol. I Large 8vo, 5 oo O'Brine's Laboratory Guide in Chemical Analysis 8vo, 2 oo O'DriscolTs Notes on the Treatment of Gold Ores 8vo, 2 oo Ostwald's Conversations on Chemistry. Part One. (Ramsey.) 12:010, i 50 " " " " Part Two. (Turnbull.) I2mo, 2 oo * Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 8vo, paper, 50 Pictet's The Alkaloids and their Chemical Constitution. (Biddle.) 8vo, 5 oo Pinner's Introduction to Organic Chemistry. (Austen.) i2mo, i 50 Poole's Calorific Power of Fuels 8vo, 3 oo Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- ence to Sanitary Water Analysis i2mo, i 25 * Reisig's Guide to Piece-dyeing 8vo, 25 oo Richards and Woodman's Air, Water, and Food from a Sanitary Stand- point 8vo, . 2 oo Richards's Cost of Living as Modified by Sanitary Science i2mo, i oo Cost of Food, a Study in Dietaries I2mo, i oo * Richards and Williams's The Dietary Computer 8vo, i 50 Ricketts and Russell's Skeleton Notes upon Inorganic Chemistry. (Part I. Non-metallic Elements.) 8vo, morocco, 75 Ricketts and Miller's Notes on Assaying .8vo, 3 oo Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 3 50 Disinfection and the Preservation of Food 8vo, 4 oo Rigg's Elementary Manual for the Chemical Laboratory 8vo, i 25 Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, Rostoski's Serum Diagnosis. (Bolduan.) I2mo, i oo Ruddiman's Incompatibilities in Prescriptions 8vo, 2 oo * Whys in Pharmacy I2mo, i oo Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Salkowski's Physiological and Pathological Chemistry. (Orndorff.) 8vo, 2 50 Schimpf's Text-book of Volumetric Analysis I2mo, 2 50 Essentials of Volumetric Analysis. . ." I2mo, i 25 * Qualitative Chemical Analysis 8vo, i 25 Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco, 3 oo Handbook for Cane Sugar Manufacturers i6mo, morocco, 3 oo Stockbridge's Rocks and Soils 8vo, 2 50 * Tillman's Elementary Lessons in Heat 8vo, i 50 * Descriptive General Chemistry 8vo, 3 oo Treadwell's Qualitative Analysis. (Hall.) 8vo, 3 oo Quantitative Analysis. (Hall.) 8vo, 4 oo Turneaure and Russell's Public Water-supplies 8vo, 5 oo Van Deventer's Physical Chemistry for Beginners. (Boltwood.) i2mo, i 50 * Walke's Lectures on Explosives 8vo, 4 oo Ware's Beet-sugar Manufacture and Refining Small 8vo, cloth, 4 oo Washington's Manual of the Chemical Analysis of Rocks 8vo, 2 oo Wassermann's Immune Sera : Haemolysins, Cytotoxins, and Precipitins. (Bol- duan.) i2mo, i oo Well's Laboratory Guide in Qualitative Chemical Analysis 8vo, i 50 Short Course in Inorganic Qualitative Chemical Analysis for Engineering Students I2mo, i 50 Text-book of Chemical Arithmetic I2mo, i 25 Whipple's Microscopy of Drinking-water 8vo, 3 50 Wilson's Cyanide Processes lamo, i 50 Chlorination Process I2mo, I 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Wulling's Elementary* Course in Inorganic, Pharmaceutical, and Medical Chemistry I2mo, 2 oo 5 CIVIL ENGINEERING. BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEERING RAILWAY ENGINEERING. Baker's Engineers' Surveying Instruments i2mo, 3 oo Bixby's Graphical Computing Table Paper 19^X24* inches. 25 ** Burr's Ancient and Modern Engineering and the Isthmian Canal. (Postage, 27 cents additional.) 8vo, 3 50 Comstock's Field Astronomy for Engineers 8vo, 2 50 Davis's Elevation and Stadia Tables 8vo, i oo Elliott's Engineering for Land Drainage I2mo, i 50 Practical Farm Drainage I2mo, i oo *Fiebeger's Treatise on Civil Engineering 8vo, 5 oo Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 oo Freitag's Architectural Engineering. 2d Edition, Rewritten 8vo, 3 50 French and I/es's Stereotomy 8vo, 2 50 Goodhue's Municipal Improvements I2mo, i 75 Goodrich's Economic Disposal of Towns' Refuse 8vo, 3 50 Gore's Elements of Geodesy 8vo, .2 50 Hayford's Text-book of Geodetic Astronomy 8vo, 3 oo Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Howe's Retaining Walls for Earth I2mo, i 25 Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 oo Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 oo Laplace's Philosophical Essay on Probabilities. (Truscoit and Emory.) . I2mo, 2 oo Mahan's Treatise on Civil Engineering. (1873.) (Wood.). ... 8vo, 5 oo * Descriptive Geometry 8vo, i 50 Merriman's Elements of Precise Surveying and Geodesy Svo, 2 50 Merriman and Brooks's Handbook for Surveyors i6mo, moro^ . ~. oo Nugent's Plane Surveying 8vo, 3 5^ Ogden's Sewer Design I2mo, 2 oo Patton's Treatise on Civil Engineering 8vo half leather, 7 50 Reed's Topographical Drawing and Sketching 4to, 5 oo Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 3 50 Siebert and Biggin's Modern Stone-cutting and Masonry. 8vo, i 50 Smith's Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 8vo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo * Trautwine's Civil Engineer's Pocket-book i6mo, morocco, 5 oo Wait's Engineering and Architectural Jurisprudence 8vo, 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture. . 8vo, 5 oo Sheep, 5 50 Law of Contracts 8vo, 3 oo Warren's Stereotomy Problems in Stone-cutting 8vo, 2 50 Webb's Problems in the Use and Adjustment of Engineering Instruments. i6mo, morocco, i 25 Wilson's Topographic Surveying 8vo, 3 50 BRIDGES AND ROOFS. Boiler's Practical Treatise on the Construction of Iron Highway Bridges . . 8vo, 2 oo * Thames River Bridge 4to, paper, 5 oo Burr's Course on the Stresses in Bridges and Roof Trusses, Arched Ribs, and Suspension Bridges 8vo, 3 50 6 Burr and Falk's Influence Lines for Bridge and Roof Computations. . . .8vo, 3 oo Design and Construction of Metallic Bridges 8vo, 5 oo Du Bois's Mechanics of Engineering. Vol. II Small 4to, 10 oo Foster's Treatise on Wooden Trestle Bridges 4to, 5 oo Fowler's Ordinary Foundations 8vo, 3 50 Greene's Roof Trusses 8vo, i 25 Bridge Trusses 8vo, 2 50 Arches in Wood, Iron, and Stone 8vo, 2 50 Howe's Treatise on Arches 8vo, 4 oo Design of Simple Roof-trusses in Wood and Steel 8vo, 2 oo Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of Modern Framed Structures Small 4to, 10 oo Merriman and Jacoby's Text-book on Roofs and Bridges: Part I. Stresses in Simple Trusses 8vo, 2 50 Part II. Graphic Statics 8vo, 2 50 Part III. Bridge Design 8vo, 2 50 Part IV. Higher Structures 8vo, 2 50 Morison's Memphis Bridge 4to, 10 oo WaddelFs De Pontibus, a Pocket-book for Bridge Engineers. . i6mo, morocco, 2 oo Specifications for Steel Bridges i2mo, i 25 Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50 HYDRAULICS. Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from an Orifice. (Trautwine.) 8vo, 2 oo Bovey's Treatise on Hydraulics 8vo, 5 oo Church's Mechanics of Engineering 8vo, 6 oo Diagrams of Mean Velocity of Water in Open Channels paper, i 50 Hydraulic Motors 8vo, 2 oo Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50 Flather's Dynamometers, and the Measurement of Power i2mo, 3 oo Folwell's Water-supply Engineering 8vo, 4 oo Frizell's Water-power 8vo, 5 oo Fuertes's Water and Public Health i2mo, i 50 Water-filtration Works i2mo, 2 50 Ganguillet and Kutter's General Formula for the Uniform Flow of Water in Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 oo Hazen's Filtration of Public Water-supply 8vo, 3 oo Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50 Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal Conduits 8vo, 2 oo Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 8vo, 4 oo Merriman's Treatise on Hydraulics 8vo, 5 oo * Michie's Elements of Analytical Mechanics 8vo, 4 oo Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- supply Large 8vo, 5 oo ** Thomas and Watt's Improvement of Rivers. (Post., 440. additional. ).4to, 6 oo Turneaure and Russell's Public Water-supplies 8vo, 5 oo Wegmann's Design and Construction of Dams 4to, 5 oo Water-supply of the City of New York from 1658 to 1895 4to, 10 oo Williams and Hazen's Hydraulic Tables 8vo, i 50 Wilson's Irrigation Engineering Small 8vo, 4 oo Wolff's Windmill as a Prime Mover 8vo, 3 oo Wood's Turbines 8vo, 2 50 Elements of Analytical Mechanics 8vo, 3 oo 7 MATERIALS OF ENGINEERING. Baker's Treatise on Masonry Construction 8vo, 5 oo Roads and Pavements 8vo, 5 oo Bkck's United States Public Works ; Oblong 4to, 5 oo * Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50 Byrne's Highway Construction 8vo, 5 oo Inspection of the Materials and Workmanship Employed in Construction. i6mo, 3 oo Church's Mechanics of Engineering 8vo, 6 oo Du Bois's Mechanics of Engineering. Vol. I Small 4to, 7 50 *Eckel's Cements, Limes, and Plasters 8vo, 6 oo Johnson's Materials of Construction Large 8vo, 6 oo Fowler's Ordinary Foundations 8vo, 3 50 * Greene's Structural Mechanics , 8vo, 2 50 Keep's Cast Iron 8vo, 2 50 Lanza's Applied Mechanics 8vo, 7 50 Marten's Handbook on Testing Materials. (Henning.) 2 vols 8vo, 7 50 Maurer's Technical Mechanics 8vo, 4 oo Merrill's Stones for Building and Decoration 8vo, 5 oo Merriman's Mechanics of Materials 8vo, 5 oo Strength of Materials i2mo, i oo Metcalf's Steel. A Manual for Steel-users i2mo, 2 oo Patton's Practical Treatise on Foundations 8vo, 5 oo Richardson's Modern Asphalt Pavements. . . . 8vo, 3 oo Richey's Handbook for Superintendents of Construction i6mo, mor., 4 oo Rockwell's Roads and Pavements in France 12010, i 25 Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Smith's Materials of Machines i2mo, i oo Snow's Principal Species of Wood 8vo, 3 50 Spalding's Hydraulic Cement i2mo, 2 oo Text-book on Roads and Pavements i2mo, 2 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo Thurston's Materials of Engineering. 3 Parts 8vo, 8 oo Part I. Non-metallic Materials of Engineering and Metallurgy. . ; . .8vo, 2 oo Part II. Iron and Steel 8vo, 3 50 Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their Constituents 8vo, 2 50 Thurston's Text-book of the Materials of Construction 8vo, 5 oo Tillson's Street Pavements and Paving Materials 8vo, 4 oo Waddell's De Pontibus. (A Pocket-book for Bridge Engineers.). . i6mo, mor., 2 oo Specifications for Steel Bridges i2mo, i 25 Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on the Preservation of Timber 8vo, 2 oo Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 oo Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and Steel 8vo, 4 oo RAILWAY ENGINEERING. Andrew's Handbook for Street Railway Engineers 3x5 inches, morocco, i 25 Berg's Buildings and Structures of American Railroads 4to, 5 oo Brook's Handbook of Street Railroad Location i6mo, morocco, I 50 Butt's Civil Engineer's Field-book i6mo, morocco, 2 50 Crandall's Transition Curve i6mo, morocco, i 50 Railway and Other Earthwork Tables 8vo, i 50 Dawson's "Engineering" and Electric Traction Pocket-book. . i6mo, morocco, 5 oo 3 Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 oo * Drinker's Tunnelling, Explosive Compounds, and Rock Drills. 4to, half mor., 25 oo Fisher's Table of Cubic Yards .- Cardboard, 25 Godwin's Railroad Engineers' Field-book and Explorers' Guide. . . i6mo, mor., 2 50 Howard's Transition Curve Field-book i6mo, morocco, i 50 Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- bankments 8vo, i oo Molitor and Beard's Manual for Resident Engineers i6mo, i oo Nagle's Field Manual for Railroad Engineers i6mo, morocco, 3 oo Philbrick's Field Manual for Engineers i6mo, morocco, 3 oo Searles's Field Engineering i6mo, morocco, 3 oo Railroad Spiral i6mo, morocco, i 50 Taylor's Prismoidal Formulae and Earthwork 8vo, i 50 * Trautwine's Method of Calculating the Cube Contents of Excavations and Embankments by the Aid of Diagrams 8vo, 2 oo The Field Practice of Laying Out Circular Curves for Railroads. 1 2 mo, morocco, 2 50 Cross-section Sheet Paper, 25 Webb's Railroad Construction i6mo, morocco, 5 oo Wellington's Economic Theory of the Location of Railways Small 8vo, 5 oo DRAWING. Barr's Kinematics of Machinery 8vo, 2 50 * Bartlett's Mechanical Drawing '. 8vo, 3 oo * " " " Abridged Ed 8vo, 150 Coolidge's Manual of Drawing 8vo, paper i oo Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- neers. Oblong 4to, 2 50 Durley's Kinematics of Machines 8vo, 4 oo Emch's Introduction to Projective Geometry and its Applications 8vo, 2 50 Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 oo Jamison's Elements of Mechanical Drawing 8vo, 2 50 Advanced Mechanical Drawing 8vo, 2 oo Jones's Machine Design: Part I. Kinematics of Machinery 8vo, i 50 Part EL. Form, Strength, and Proportions of Parts 8vo, 3 oo MacCord's Elements of Descriptive Geometry 8vo, 3 oo Kinematics; or, Practical Mechanism 8vo, 5 oo Mechanical Drawing 4to, 4 oo Velocity Diagrams 8vo, i 50 MacLeod's Descriptive Geometry Small 8vo, i 50 * Mahan's Descriptive Geometry and Stone-cutting 8vo, i 50 Industrial Drawing. (Thompson.) 8vo, 3 50 Meyer's Descriptive Geometry 8vo, 2 oo Reed's Topographical Drawing and Sketching 4to, 5 oo Reid's Course in Mechanical Drawing 8vo, 2 oo Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 oo Robinson's Principles of Mechanism 8vo, 3 oo Schwamb and Merrill's Elements of Mechanism 8vo, 3 co Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo, 2 50 Smith (A. W.) and Marx's Machine Design 8vo, 3 oo Warren's Elements of Plane and Solid Free-hand Geometrical Drawing. i2mo, oo Drafting Instruments and Operations I2mo, Manual of Elementary Projection Drawing i2mo, Manual of Elementary Problems in the Linear Perspective of Form and Shadow i2mo, Plane Problems in Elementary Geometry i2mo, 9 Warren's Primary Geometry I2mo, 75 Elements of Descriptive Geometry, Shadows, and Perspective 8vo, 3 50- General Problems of Shades and Shadows 8vo, 3 oo Elements of Machine Construction and Drawing 8vo, 7 $a Problems, Theorems, and Examples in Descriptive Geometry 8vo, 2 50 Weisbach's Kinematics >md Power of Transmission. (Hermann and Klein.) : 8vo, 5 o a Whelpley's Practical Instruction in the Art of Letter Engraving i2mo, 2 oo Wilson's (H. M.) Topographic Surveying 8vo, 3 50 Wilson's (V. T.) Free-hand Perspective 8vo, 2 50 Wilson's (V. T.) Free-hand Lettering 8vo, i oo Woolf' s Elementary Course in Descriptive Geometry Large 8vo,. 3 oo ELECTRICITY AND PHYSICS. Anthony and Brackett's Text-book of Physics. (Magie.) ~. . .Small 8vo, 3 oo Anthony's Lecture-notes on the Theory of Electrical Measurements. . . . i2mo, i oo Benjamin's History of Electricity 8vo, 3 oo Voltaic Cell 8vo, 3 oo Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.).8vo, 3 oo Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 oo Dawson's "Engineering" and Electric Traction Pocket-book. i6mo, morocco, 5 oo Dolezalek's Theory of the Lead Accumulator (Storage Battery). (Von Ende.) I2mo, 2 50 Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 oo Flather's Dynamometers, and the Measurement of Power i2mo, 3 oo Gilbert's De Magnete. (Mottelay.) 8vo, 2 50 Hanchett's Alternating Currents Explained I2mo, i oo Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 Holman's Precision of Measurements 8vo, 2 oo Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large 8vo, 75 Xinzbrunner's Testing of Continuous-current Machines 8vo, 2 oo Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 oo Le Chateliers High-temperature Measurements. (Boudouard Burgess.) i2mo, 3 oo Lob's Electrochemistry of Organic Compounds. (Lorenz.) 8vo, 3 oo * Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and. II. 8vo, each, 6 oo * Michie's Elements of Wave Motion Relating to Sound and Light 8vo, 4 oo Niaudet's Elementary Treatise on Electric Batteries. (Fishback.) i2mo, 2 50 * Rosenberg's Electrical Engineering. (Haldane Gee Kinzbrunner.). . .8vo, i 50 Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 2 50 Thurston's Stationary Steam-engines 8vo, 2 50 * Tillman's Elementary Lessons in Heat 8vo, i 50 Tory and Pitcher's Manual of Laboratory Physics Small 8vo, 2 oo Ulke's Modern Electrolytic Copper Refining 8vo, 3 oo LAW. * Davis's Elements of Law 8vo, 2 50 * Treatise on the Military Law of United States 8vo, 7 oo * Sheep, 7 50 Manual for Courts-martial i6mo, morocco, i 50 Wait's Engineering and Architectural Jurisprudence 8vo , 6 oo Sheep, 6 50 Law of Operations Preliminary to Construction in Engineering and Archi- tecture 8vo 5 oo Sheep, 5 50 Law of Contracts 8vo, 3 oo Winthrop's Abridgment of Military Law I2mo 2 So 10 MANUFACTURES. Bernadou's Smokeless Powder Nitro-cellulose and Theory of the Cellulose Molecule i2mo, 2 50 Holland's Iron Founder i2mo, 2 50 " The Iron Founder," Supplement 1203.0, 2 50 Encyclopedia of Founding and Dictionary of Foundry Terms Used in the Practice of Moulding I2mo, 3 oo Eissler's Modern High Explosives 8vo, 4 oo Eff rent's Enzymes and their Applications. (Prescott.) 8vo, 3 oo Fitzgerald's Boston Machinist i2mo, i oo Ford's Boiler Making for Boiler Makers i8mo, i oo Hopkin's Oil-chemists' Handbook 8vo, 3 oo Keep's Cast Iron 8vo, 2 50 Leach's The Inspection and Analysis of Food with Special Reference to State Control Large 8vo, 7 50 Matthews's The Textile Fibres 8vo, 3 50 Metcalf's Steel. A Manual for Steel-users 12 mo, 2 oo Metcalfe's Cost of Manufactures And the Administration of Workshops. 8vo, 5 oo Meyer's Modern Locomotive Construction 4to, 10 oo Morse's Calculations used in Cane-sugar Factories i6mo, morocco, i 50 * Reisig's Guide to Piece-dyeing 8vo, 25 oo Sabin's Industrial and Artistic Technology of Paints and Varnish. ... 8vo, 3 oo Smith's Press-working of Metals 8vo, 3 oo Spalding's Hydraulic Cement I2mo, 2 oo Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco, 3 oo Handbook for Cane Sugar Manufacturers i6mo, morocco, 3 oo Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 oo Thurston's Manual of Steam-boilers, their Designs, Construction and Opera- tion 8vo, 5 oo * Walke's Lectures on Explosives 8vo, 4 oo Ware's Beet-sugar Manufacture and Refining Small 8vo, 4 oo West's American Foundry Practice i2mo, 2 50 Moulder's Text-book i2mo, 2 50 Wolff's Windmill as a Prime Mover 8vo, 3 oo Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 4 oo MATHEMATICS. Baker's Elliptic Functions 8vo, I 50 * Bass's Elements of Differential Calculus i2mo, 4 oo Briggs's Elements of Plane Analytic Geometry I2mo, i oo Compton's Manual of Logarithmic Computations 12 mo, i 50 Davis's Introduction to the Logic of Algebra 8vo, i 50 * Dickson's College Algebra Large i2mo, i 50 * Introduction to the Theory of Algebraic Equations Large I2mo, i 25 Emch's Introduction to Projective Geometry and its Applications 8vo, 2 50 Halsted's Elements of Geometry 8vo, i 75 Elementary Synthetic Geometry 8vo, I 50 Rational Geometry I2mo, i 75 * Johnson's (J. B.) Three-place Logarithmic Tables: Vest-pocket size. paper, 15 100 copies for 5 oo * Mounted on heavy cardboard, 8 X TO inches, 25 10 copies for 2 OO Johnson's (W. W.) Elementary Treatise on Differential Calculus. .Small 8vo, 3 oo Johnson's (W. W.) Elementary Treatise on the Integral Calculus . Small 8vo, i 50 11 Johnson's (W. W.) Curve Tracing in Cartesian Co-ordinates i2mo, i oo Johnson's (W. 'W.) Treatise on Ordinary and Partial Differential Equations. Small 8vo, 3 50 Johnson's (W. W.) Theory of Errors and the Method of Least Squares. i2mo, i 50 * Johnson's (W. W.) Theoretical Mechanics i2mo, 3 oo Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . i2mo, 2 oo * Ludlow and Bass. Elements of Trigonometry and Logarithmic and Other Tables 8vo, 3 oo Trigonometry and Tables published separately Each, 2 oo * Ludlow's Logarithmic and Trigonometric Tables 8vo, i oo Mathematical Monographs. Edited by Mansfield Merriman and Robert S. Woodward Octavo, each i oo No. i. History of Modern Mathematics, by David Eugene Smith. No. 2. Synthetic Projective Geometry, by George Bruce Halsted. No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper- bolic Functions, by James McMahon. No. 5. Harmonic Func- tions, by William E. Byerly. No. 6. Grassmann's Space Analysis, by Edward W. Hyde. No. 7. Probability and Theory of Errors, by Robert S. Woodward. No. 8. Vector Analysis and Quaternions, by Alexander Macfarlane. No. 9. Differential Equations, by William Woolsey Johnson. No. 10. The Solution of Equations, byj Mansfield Merriman. No. 1 1. Functions of a Complex Variable, by Thomas S. Fiske. Maurer's Technical Mechanics 8vo, 4 oo Merriman and Woodward's Higher Mathematics 8vo, 5 oo Merriman's Method of Least Squares 8vo, 2 oo Rice and Johnson's Elementary Treatise on the Differential Calculus. . Sm. 8vo, 3 oo Differential and Integral Calculus. 2 vols. in one Small 8vo, 2 50 Wood's Elements of Co-ordinate Geometry. 8vo, 2 oo Trigonometry: Analytical, Plane, and Spherical i2mo, i oo MECHANICAL ENGINEERING. MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. Bacon's Forge Practice i2mo, i 50 Baldwin's Steam Heating for Buildings I2mo, 2 50 Barr's Kinematics of Machinery 8vo, 2 50 * Bartlett's Mechanical Drawing 8vo, 3 oo * " " Abridged Ed 8vo, 150 Benjamin's Wrinkles and Recipes i2mo, 2 oo Carpenter's Experimental Engineering 8vo, 6 oo Heating and Ventilating Buildings 8vo, 4 oo Gary's Smoke Suppression in Plants using Bituminous CoaL (In Prepara- tion.) Clerk's Gas and Oil Engine Small 8vo, 4 oo Coolidge's Manual of Drawing 8vo, paper, i oo Coelidge and Freeman's Elements of General Drafting for Mechanical En- gineers Oblong 4to, 2 50 Cromwell's Treatise on Toothed Gearing i2mo, i 50 Treatise on Belts and Pulleys i2mo, i 50 Durley's Kinematics of Machines 8vo, 4 oo Flather's Dynamometers and the Measurement of Power 121110, 3 oo Rope Driving i2mo, 2 oo Gill's Gas and Fuel Analysis for Engineers i2mo, i 25 Hall's Car Lubrication i2mo, i oo Bering's Ready Reference Tables (Conversion Factors) i6mo, morocco, 2 50 12 Button's The Gas Engine 8vo, 5 oo Jamison's Mechanical Drawing 8vo, 2 50 Jones's Machine Design: Part I. Kinematics of Machinery 8vo, i 50 Part II. Form, Strength, and Proportions of Parts 8vo, 3 oo Kent's Mechanical Engineers' Pocket-book i6mo, morocco, 5 oo Kerr's Power and Power Transmission 8vo, 2 oo Leonard's Machine Shop, Tools, and Methods 8vo, 4 oo * Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.) . . 8vo, 4 oo MacCord's Kinematics; or, Practical Mechanism 8vo, 5 oo Mechanical Drawing 4to, 4 oo Velocity Diagrams ' 8vo, i 50 MacFar land's Standard Reduction Factors for Gases 8vo, i 50 Mahan's Industrial Drawing. (Thompson.) 8vo, 3 50 Poole's Calorific Power of Fuels 8vo, 3 oo Reid's Course in Mechanical Drawing 8vo, 2 oo Text-book of Mechanical Drawing and Elementary Machine Design. 8 vo, 3 oo Richard's Compressed Air i2mo, i 50 Robinson's Principles of Mechanism 8vo, 3 oo Schwamb and Merrill's Elements of Mechanism 8vo, 3 oo Smith's (O.) Press-working of Metals. 8vo, 3 oo Smith (A. W.) and Marx's Machine Design 8vo, 3 oo Thurston's Treatise on Friction and Lost Work in Machinery and Mill Work 8vo, 3 oo Animal as a Machine and Prime Motor, and the Laws of Energetics. 1 2mo, i oo Warren's Elements of Machine Construction and Drawing 8vo, 7 50 Weisbach's Kinematics and the Power of Transmission. (Herrmann Klein.) 8vo, 5 oo Machinery of Transmission and Governors. (Herrmann Klein.). .8 vo, 500 Wolff's Windmill as a Prime Mover 8vo, 3 oo Wood's Turbines, 8vo, 2 50 MATERIALS OP ENGINEERING. * Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 Burr's Elasticity and Resistance of the Materials of Engineering. 6th Edition. Reset 8vo, 7 50 Church's Mechanics of Engineering 8vo, 6 oo * Greene's Structural Mechanics 8vo, 2 50 Johnson's Materials of Construction 8vo, 6 oo Keep's Cast Iron 8vo, 2 50 lanza's Applied Mechanics 8vo, 7 50 Martens's Handbook on Testing Materials. (Henning.) 8vo, 7 50 Maurer's Technical Mechanics 8vo, 4 oo Merriman's Mechanics of Materials 8vo, 5 oo Strength of Materials I2mo, i oo Metcalf's Steel. A manual for Steel-users i2mo, 2 oo Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 oo Smith's Materials of Machines. . .- i2mo, i oo Thurston's Materials of Engineering 3 vols., 8vo, 8 oo Part II. Iron and Steel 8vo, 3 50 Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their Constituents 8vo, 2 50 Text-book of the Materials of Construction 8vo, 5 oo Wood's (De V.) Treatise on the Resistance of Materials arid an Appendix on the Preservation of Timber 8vo, 2 oo 13 Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 oo Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and Steel 8vo, 4 oo STEAM-ENGINES AND BOILERS. Berry's Temperature-entropy Diagram izmo, i 25 Carnot's Reflections on the Motive Power of Heat. (Thurston.) i2mo, I 50 Dawson's "Engineering" and Electric Traction Pocket-book. . i6mo, mor., 5 oo Ford's Boiler Making for Boiler Makers i8mo, i oo Goss's Locomotive Sparks 8vo, 2 oo Hemenway's Indicator Practice and Steam-engine Economy i2mo, 2 oo Button's Mechanical Engineering of Power Plants 8vo, 5 oo Heat and Heat-engines 8vo, 5 oo Kent's Steam boiler Economy 8vo, 4 oo Kneass's Practice and Theory of the Injector 8vo, i 50 MacCord's Slide-valves 8vo, 2 oo Meyer's Modern Locomotive Construction 4to, 10 oo Peabody's Manual of the Steam-engine Indicator I2mo, i 50 Tables of the Properties of Saturated Steam and Other Vapors 8vo, i oo Thermodynamics of the Steam-engine and Other Heat-engines 8vo, 5 oo Valve-gears for Steam-engines. 8vo, 2 50 Peabody and Miller's Steam-boilers 8vo, 4 oo Pray's Twenty Years with the Indicator Large 8vo, 2 50 Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. (Osterberg.) I2mo, i 25 Reagan's Locomotives: Simple Compound, and Electric 12 mo, 2 50 Rontgen's Principles of Thermodynamics. (Du Bois.) 8vo, 5 oo Sinclair's Locomotive Engine Running and Management i2mo, 2 oo Smart's Handbook of Engineering Laboratory Practice . .i2mo, 2 50 Snow's Steam-boiler Practice 8vo, 3 oo Spangler's Valve-gears 8vo, 2 50 Notes on Thermodynamics i2mo, i oo Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 oo Thurston's Handy Tables 8vo, i 50 Manual of the Steam-engine 2 vols., 8vo, 10 oo Part I. History, Structure, and Theory 8vo, 6 oo Part II. Design, Construction, and Operation. 8vo, 6 oo Handbook of Engine and Boiler Trials, and the Use of the Indicator and the Prony Brake 8vo, 5 oo Stationary Steam-engines 8vo, 2 50 Steam-boiler Explosions in Theory and in Practice I2mo, i 50 Manual of Steam-boilers, their Designs, Construction, and Operation 8vo, 5 oo Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) 8vo, 5 oo Whitham's Steam-engine Design 8vo, 5 oo Wilson's Treatise on Steam-boilers. (Flather.) i6mo, 2 50 Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . .8vo, 4 oo MECHANICS AND MACHINERY. Barr's Kinematics of Machinery 8vo, 2 50 * Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 Chase's The Art of Pattern-making I2mo, 2 50 Church's Mechanics of Engineering 8vo, 6 oo Notes and Examples in Mechanics 8vo, 2 oo Compton's First Lessons in Metal- working i2mo, i 50 Compton and De Groodt's The Speed Lathe i2mo, i 50 14 Cromwell's Treatise on Toothed Gearing I2mo, I 50 Treatise on Belts and Pulleys i2mo, i 50 Dana's Text-book of Elementary Mechanics for Colleges and Schools. .i2mo, i 50 Dingey's Machinery Pattern Making i2mo, 2 oo Dredge's Record of the Transportation Exhibits Building of the World's Columbian Exposition of 1893 4to half morocco, 5 oo Du Bois's Elementary Principles of Mechanics: Vol. I. Kinematics 8vo, 3 50 Vol. II. Statics 8vo, 4 oo Mechanics of Engineering. Vol. I Small 4to, 7 50 VoL II Small 4to, 10 oo Durley's Kinematics of Machines 8vo, 4 oo Fitzgerald's Boston Machinist i6mo, i oo Flather's Dynamometers, and the Measurement of Power I2mo, 3 oo Rope Driving i2mo, 2 oo Goss's Locomotive Sparks 8vo, 2 oo * Greene's Structural Mechanics 8vo, 2 50 Hall's Car Lubrication i2mo, i oo Holly's Art of Saw Filing i8mo, 75 James's Kinematics of a Point and the Rational Mechanics of a Particle. Small 8vo, 2 oo * Johnson's (W. W.) Theoretical Mechanics i2mo, 3 oo Johnson's (L. J.) Statics by Graphic and Algebraic Methods 8vo, 2 oo Jones's Machine Design: Part I. Kinematics of Machinery 8vo, i 50 Part II. Form, Strength, and Proportions of Parts 8vo, 3 oo Kerr's Power and Power Transmission 8vo, 2 oo Lanza's Applied Mechanics 8vo, 7 50 Leonard's Machine Shop, Tools, and Methods 8vo, 4 oo * Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean.). 8vo, 4 oo MacCord's Kinematics; or, Practical Mechanism 8vo, 5 oo Velocity Diagrams 8vo, i 50 Maurer's Technical Mechanics 8vo, 4 oo Merriman's Mechanics of Materials . 8vo, 5 oo * Elements of Mechanics I2mo, i oo * Michie's Elements of Analytical Mechanics 8vo, 4 oo Reagan's Locomotives: Simple, Compound, and Electric i2mo, 2 50 Reid's Course in Mechanical Drawing 8vo, 2 oo Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 3 oo Richards's Compressed Air i2mo, i 50 Robinson's Principles of Mechanism 8vo, 3 oo Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 2 50 Schwamb and Merrill's Elements of Mechanism 8vo, 3 oo Sinclair's Locomotive-engine Running and Management. . i2mo, 2 oo Smith's (O.) Press-working of Metals 8vo, 3 oo Smith's (A. W.) Materials of Machines I2mo, i oo Smith (A. W.) and Marx's Machine Design 8vo, 3 oo Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 oo Thurston's Treatise on Friction and Lost Work in Machinery and Mill Work 8vo, 3 oo Animal as a Machine and Prime Motor, and the Laws of Energetics. I2mo, i oo Warren's Elements of Machine Construction and Drawing 8vo, 7 50 Weisbach's Kinematics and Power of Transmission. (Herrmann Klein.) . 8vo, 5 oo Machinery of Transmission and Governors. (Herrmann Klein. ).8vo, 5 oo Wood's Elements of Analytical Mechanics 8vo, 3 oo Principles of Elementary Mechanics i2mo, i 25 Turbines 8vo, 2 50 The World's Columbian Exposition of 1893 4to, i oo , 15 METALLURGY. Egleston's Metallurgy of Silver, Gold, and Mercury: Vol. I. Silver 8vo, 7 50 Vol. II. Gold and Mercury 8vo, 7 50 ** Iles's Lead-smelting. (Postage 9 cents additional.) i2mo, 2 50 Keep's Cast Iron .8vo, 2 50 Kunhardt's Practice of Ore Dressing in Europe 8vo, i 50 Le Chatelier's High-temperature Measurements. (Boudouard Burgess. )i2mo. 3 oo Metcalf's Steel. A Manual for Steel-users i2mo, 2 oo Minet's Production of Aluminum and its Industrial Use. (Waldo.). .. . I2mo, 2 50 Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, Smith's Materials of Machines I2mo, i oo Thurston's Materials of Engineering. In Three Parts 8vo, 8 oo Part II. Iron and Steel 8vo, 3 50 Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their Constituents 8vo, 2 50 Ulke's Modern Electrolytic Copper Refining 8vo, 3 oo MINERALOGY. Barringer's Description of Minerals of Commercial Value. Oblong, morocco, 2 50 Boyd's Resources of Southwest Virginia 8vo, 3 oo Map of Southwest Virignia Pocket-book form. 2 oo Brush's Manual of Determinative Mineralogy. (Penfield.) 8vo, 4 oo Chester's Catalogue of Minerals 8vo, paper, i oo Cloth, i 25 Dictionary of the Names of Minerals 8vo, 3 50 Dana's System of Mineralogy Large 8vo, half leather, 12 50 First Appendix to Dana's New " System of Mineralogy." Large 8vo, i oo Text-book of Mineralogy 8vo, 4 oo Minerals and How to Study Them i2mo. i 50 Catalogue of American Localities of Minerals Large 8vo, i oo Manual of Mineralogy and Petrography i2mo, 2 oo Douglas's Untechnical Addresses on Technical Subjects , . i2mo, i oo Eakle's Mineral Tables 8vo, i 25 Egleston's Catalogue of Minerals and Synonyms 8vo, 2 50 Hussak's The Determination of Rock-forming Minerals. ( Smith.). Small 8vo, 2 oo Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 oo * Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 8vo, paper, 50 Rosenbusch's Microscopical Physiography of the Rock-making Minerals. (Iddings.) 8vo, 5 oo * Tillman's Text-book of Important Minerals and Rocks 8vo, 2 oo MINING. Beard's Ventilation of Mines i2mo, 2 50 Boyd's Resources of Southwest Virginia 8vo, 3 oo . Map of Southwest Virginia Pocket-book form, 2 oo Douglas's Untechnical Addresses on Technical Subjects i2mo, i oo * Drinker's Tunneling, Explosive Compounds, and Rock Drills. -4to,hf. mor., 25 oo Eissler's Modern High Explosives 8vo, 4 oo 16 Fowler's Sewage Works Analyses i2mo, 2 oo Goodyear's Coal-mines of the Western Coast of the United States i2mo, 2 50 Ihlseng's Manual of Mining 8vo, 5 oo ** lles's Lead-smelting. (Postage QC. additional.) I2mo, 2 50 Kunhardt's Practice of Ore Dressing in Europe 8vo, i 50 O'Driscoll's Notes on the 'Treatment of Gold Ores 8vo, 2 oo Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, * Walke's Lectures on Explosives 8vo, 4 oo Wilson's Cyanide Processes ; i2mo, i 50 Chlorination Process '..... i i2mo, i 50 Hydraulic and Placer Mining i2mo, 2 oo Treatise on Practical and Theoretical Mine Ventilation i2mo, i 25 SANITARY SCIENCE. Bashore's Sanitation of a Country House i2mo, i op Folwell's Sewerage. (Designing, Construction, and Maintenance.) 8vo, 3 oo Water-supply Engineering 8vo, 4 oo Fuertes's Water and Public Health i2mo, i 50 Water-filtration Works I2mo, 2 50 Gerhard's Guide to Sanitary House-inspection i6mo, i oo Goodrich's Economic Disposal of Town's Refuse Demy 8vo, 3 50 Hazen's Filtration of Public Water-supplies 8vo, 3 oo Leach's The Inspection and Analysis of Food with Special Reference to State Control 8vo, 7 50 Mason's Water-supply. (Considered principally from a Sanitary Standpoint) 8vo, 4 oo Examination of Water. (Chemical and Bacteriological.) i2mo, i 25 Ogden's Sewer Design i2mo, 2 oo Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- ence to Sanitary Water Analysis i2mo, i 25 * Price's Handbook on Sanitation : I2mo, j 50 Richards's Cost ot Food. A Study in Dietaries i2mo, i oo Cost of Living as Modified by Sanitary Science I2mo, i oo Richards and Woodman's Air. Water, and Food from a Sanitary Stand- point 8vo, 2 oo * Richards and Williams's The Dietary Computer 8vo, i 50 Rideal's Sewage and Bacterial Purification of Sewage .8vo, 3 50 Turneaure and Russell's Public Water-supplies 8vo, 5 oo Von Behring's Suppression of Tuberculosis. (Bolduan.) . i2mo, i oo Whipple's Microscopy of Drinking-water 8vo, 3 50 Winton's Microscopy of Vegetable Foods 8vo, 7 50 Woodhull's Notes on Military Hygiene i6mo, x 50 MISCELLANEOUS. De Fursac's Manual of Psychiatry. (Rosanoff and Collins.) Large I2mo, 2 50 Emmons's Geological Guide-book of the Rocky Mountain Excursion of the International Congress of Geologists Large 8vo, i 50 Ferrel's Popular Treatise on the Winds . . . 8vo, 4 oo Haines's American Railway Management I2mo, 2 50 Mott's Fallacy of the Present Theory of Sound i6mo, I oo Ricketts's History of Rensselaer Polytechnic Institute, 1824-1 894.. Small 8vo, 3 oo Rostoski's-Serum Diagnosis. (Bolduan.) I2mo, i oo Rotherham's Emphasized New Testament Large 8vo, 2 oo 17 Steel's Treatise on the Diseases of the Dog 8vo, 3 50 The World's Columbian Exposition of 1893 4to, i oo Von Behring's Suppression ot Tuberculosis. (Bolduan.) i2mo, i oo Winslow's Elements of Applied Microscopy i2mo, i 50 Worcester and Atkinson. Small Hospitals, Establishment and Maintenance; Suggestions for Hospital Architecture : Plans for Small Hospital . 1 2mo , i 25 HEBREW AND CHALDEE TEXT-BOOKS. Green's Elementary Hebrew Grammar I2mo, i 25 Hebrew Chrestomathy 8vo, 2 oo Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures. (Tregelles.) Small 4to, half morocco, 5 oo Letteris's Hebrew Bible 8vo, 2 25 18 OF THE UNIVERSITY OF f .;:' 155402