BANCROFT 
 LIBRARY 
 
 <> 
 
 THE LIBRARY 
 
 OF 
 
 THE UNIVERSITY 
 OF CALIFORNIA 
 
- 
 
LEACHING 
 
 GOLD AND SILVER ORES 
 
 THE PLATTNEE AND KISS PEOCESSES. 
 
 A PRACTICAL TREATISE 
 
 -BY- 
 
 CHARLES HOWARD AARON, 
 
 ILLUSTRATED. 
 
 PUBLISHED AND SOLD BY A. J. LEARY, STATIONER, 
 
 402 k 404 Sansome Street, San Francisco. 
 
 SAN FRANCISCO: 
 
 BARRY & BAIRD, STEAM BOOK AND JOB PRINTERS, 410 SACRAMENTO ST. 
 
 1881. 
 
A 
 
 Entered according to Act of Congress, in the year 1881, 
 
 BY C. H. AARON, 
 In the Office of the Librarian of Congress, at Washington, D. C. 
 
CONTENTS. 
 
 Preface ."> 
 
 Introduction 9 
 
 Roasting 1.1 
 
 Oxidizing roast 16 
 
 Dead roast 16 
 
 Chloridizing roast 17 
 
 Apparatus -2 \ 
 
 Roasting furnaces 21 
 
 Reverberatory furnace 22 
 
 Furnace tools 30 
 
 Crosby's furnace 30 
 
 Leaching vat 31 
 
 Suction pipe 32 
 
 Vent pipe 33 
 
 Sieve 34 
 
 Precipitating vat 35 
 
 Troughs 36 
 
 Well 36 
 
 Pumps 36 
 
 Filters 36 
 
 Press 37 
 
 Chlorine Generator 37 
 
 Wash-bottle 30 
 
 Special Directions for working 
 
 A. Concentrated pyrites containing gold 41 
 
 Roasting ". 43 
 
 Charging the vat 48 
 
 Chlorination 49 
 
 Making chlorine 51 
 
 Leaching the gold 53 
 
 Precipitating the gold 57 
 
 Iron sulphate solution 59 
 
 Collecting the gold 60 
 
 Washing the gold 61 
 
 Drying the gold 62 
 
 Melting the gold 62 
 
 B. Concentrated pyrites containing gold and silver (55 
 
 Roasting 65 
 
 Leaching the silver 67 
 
 Precipitation of silver 70 
 
 Collecting the precipitate 73 
 
 Roasting the precipitate 73 
 
 Melting the silver 73 
 
 C. Concentrations containing silver, but little or no gold 75 
 
 Roasting 75 
 
 Washing the ore 77 
 
 D. Concentrations rich in gold and silver, and containing lead, &c. . 79 
 
 E. Unconcentrated ores 80 
 
 F. Ores containing coarse gold 82 
 
 Calcium polysulphide 83 
 
 Calcium hyposulphite 85 
 
 Working test 86 
 
 Change in weight 91 
 
 Loss in roasting 92 
 
 Solubility assay 93 
 
 Plan of works , 94 
 
 Assaying concentrations, &c 97 
 
CONTENTS CONTINUED. 
 
 Addenda PAGE. 
 
 Flue covering 105 
 
 Filters 105 
 
 Copper : v -. 10( ? 
 
 Means of drawing liquid from precipitating vats 106 
 
 Recovery of gold 107 
 
 Generators 108 
 
 Wash-bottles 108 
 
 Sifting ore 110 
 
 Cost of Acid 110 
 
 Salt manganese and acid Ill 
 
 Assay of salt 112 
 
 Assay of manganese 114 
 
 Surplus chlorine 117 
 
 Precipitating gold 118 
 
 Suspended gold 119 
 
 Precipitants for gold 119 
 
 Sand in gold melting 120 
 
 Drying chamber 121 
 
 Volatilization of gold 121 
 
 Solution of silver in hypo 124 
 
 Waste of sulphur 125 
 
 Recovery of sulphur 120 
 
 Matte from the silver 127 
 
 Melting furnace 128 
 
 Sodium Hyposulphite 131 
 
 The " chlorination assay " 132 
 
 Chlorination tailings 135 
 
 Value of bars 137 
 
 Chlorine 138 
 
 Plattner's process 140 
 
 The Kiss process 142 
 
 The Bruckner furnace 143 
 
 The Brunton furnace 145 
 
 The Pacific chloridizing furnace 145 
 
 The White furnace 140 
 
 The Howell White furnace 147 
 
 The Thompson-White furnace : 148 
 
 The O'Hara furnace 155 
 
 The Stetefeldt furnace 150 
 
 Remarks on furnaces 161 
 
 LIST OF ILLUSTRATIONS. 
 
 Reverberatory furnace, horizontal section 21 
 
 vertical " 21 
 
 Leaching vat 32 
 
 Suction pipe 33 
 
 Precipitating vat 36 
 
 Chlorine generator and wash-bottle 37 
 
 Generator cover ' 39 
 
 Working test apparatus 87 
 
 Plan of works 94 
 
 Flue covering 1 05 
 
 Manganese assay apparatus 114 
 
 Melting furnace 128 
 
 The Bruckner furnace 143 
 
 The Brunton furnace 145 
 
 The Thompson-White furnace 149 
 
 The Stetefeldt furnace . . . 158 
 
PREFACE. 
 
 This book is written in the endeavor to supply, in 
 some small degree, a want which is severely felt on this 
 coast, namely, that of plain, practical books on metal- 
 lurgy. In the standard works on this subject, especially 
 in regard to gold and silver, there is a great lack of 
 those practical details which are so essential to the 
 success of the operator, while some of them are char- 
 acterized by a display of scientific lore which is very 
 discouraging to those whose preliminary education does 
 not enable them to understand it. 
 
 This condition of affairs is probably due, in part, to 
 the circumstance that books are less often written by prac- 
 tical workers in this branch than by scientific gentlemen 
 who obtain such practical details as they do give us, 
 not from their own experience, but by inquiry and 
 observation, more or less extensive. It is also in part 
 owing to the fact that in Europe, where most of the 
 works alluded to were written, there are fewer men who 
 are called on to conduct metallurgical operations with- 
 out previous apprenticeship to the business. 
 
 The processes selected for description, namely, the 
 Plattner for gold, and the Kiss modification of the 
 Patera for silver, are those which seem the best adapted 
 in general to our wants; the first, for the sufficient rea- 
 son that it is the only available process for the extrac- 
 tion of gold by lixiviation; the. second, because it is more 
 convenient, and requires a less extensive plant than the 
 
6 PREFACE. 
 
 Augustin process, which depends upon dissolving silver 
 chloride by means of a hot solution of common salt, 
 while the Ziervogel process, depending on the forma- 
 tion of silver sulphate, which is extracted by means of 
 hot water, is only adapted to the treatment of matte. 
 
 The Hunt & Douglass silver copper process is a 
 method of lixiviation which has much to commend it, 
 but its mode of operation and field of adaptability are 
 so distinct that it will more properly form the subject of 
 a separate treatise. 
 
 In the arrangement of the book, the author endeav- 
 ors to make the necessary explanations and practical 
 directions as simple and straightforward as possible, 
 while matter which, however interesting or instructive, 
 is not essential, appears toward the end, in a separate 
 division. 
 
 While it is deemed necessary to give an outline of 
 the rationale of the different operations described, it is 
 also thought desirable to avoid, if possible, the use of 
 terms which might be in conflict with either the old or 
 the new systems of notation. Thus, "sodium sulphate," 
 though implying a departure from the still older binary 
 system, in which the formula for the salt was 
 Na O S O 3 , and in which it was regarded as a sulphate 
 of oxide of sodium, and called sulphate of soda, is, not- 
 withstanding, compatible with the use of the old atomic 
 weights, and represents a view of molecular constitu- 
 tion which antedates, by several years, the general 
 adoption by chemists of the new weights. 
 
 It is with this intention that the term sulphur oxide 
 is used, in preference to either sulphuric and sulphurous 
 acid, or anhydride, in speaking of the products of the 
 
PREFACE. / 
 
 combustion of sulphur, and the formation of metal sul- 
 phates; for, while strictly accurate, and sufficiently pre- 
 cise for the purpose, it is the only intermediate term 
 which could be used as applicable to either of the sys- 
 tems of notation. 
 
 The statement met with in every work on the sub- 
 ject, that "sulphuric acid," by which must, of course, 
 be understood " sulphuric anhydride," acts directly on 
 sodium chloride, with evolution of chlorine, seems, 
 while doubtless true, to require more explanation than 
 is usually given. It may be that air takes a part in the 
 reaction, by supplying the oxygen neceessary for the for- 
 mation of sodium sulphate, but it appears to the writer 
 that a clue to the true explanation is furnished by Brande's 
 statement that sulphuric anhydride is decomposed by heat 
 into sulphurous anhydride and oxygen. The decompo- 
 sition is probably assisted by the affinities of the 
 sodium in the gaseous sodium chloride. In this view 
 the reaction would be 
 
 Na Cl + 2 S 3 =Na S 4 + S 2 + C1, 
 (2 Na Cl + 2 S 8 =Na 2 S 4 + S 2 + C1 2 ) 
 
 which can take place within the roasting mass, where 
 air can have little to do with it, as well as in the atmo- 
 sphere above the ore, the sulphuric anhydride being 
 furnished by the decomposing metal sulphates, under 
 the influence of heat, and the nascent chlorine having 
 the best opportunity to act on remaining sulphides. 
 
 Chlorine which may be evolved, or may rise, above 
 the surface of the ore will, in presence of sulphurous 
 anhydride and steam, which latter must be produced 
 whenever fresh fuel (wood or coal) is introduced, 
 
8 PREFACE. 
 
 form hydrochloric acid, with reproduction of sulphuric 
 anhydride. 
 
 For valuable assistance in the literary part of the 
 work the author is indebted to his friend, Professor 
 John Calvert, of the California College of Pharmacy, 
 San Francisco. The works which have been consulted 
 comprise those of Regnault, Cooke, Abell and Bloxham, 
 Ure, and Kustel, as well as Lippincott's Encyclopedia 
 of Chemistry. 
 
 While the author has not succeeded in entirely satis- 
 fying himself, he ventures to hope that the book will 
 be found useful by those who may have occasion for it. 
 
INTRODUCTION. 
 
 1. Leaching, or lixiviation, originally meant the ex- 
 traction of alkaline salts from ashes, by pouring water 
 on them. The resulting liquid was called a leach, 
 lixivium, or lye. In metallurgy, at the present day, 
 leaching means the extraction of metal salts from ores, 
 by means of a watery solvent. The solution so ob- 
 tained is called the leach or lixivium. Leaching may 
 be done in several ways by filtration, by decantation, 
 or by flowing. 
 
 2. Filtration may be upward or downward ; the 
 solvent is passed through the prepared ore and through 
 a filter which retains all solid matter. 
 
 3. Decantation is drawing or pouring off the solu- 
 tion obtained by mixing the solvent with the ore, after 
 allowing the solid matters to subside. 
 
 4. Flowing is allowing a stream of the solvent to 
 flow continuously into the lower part, and out of the 
 upper part of a vessel containing the ore. The latter 
 is usually kept suspended in the liquid by gentle stir- 
 ring, and the vessel is so deep that only clear, or nearly 
 clear liquid rises to the outlet. 
 
 5. Ores are usually leached for gold and silver by 
 downward filtration. 
 
 6. It is necessary that the metals be combined with 
 some substance which renders them soluble in the liquid 
 used. For gold and silver, chlorine is the most suitable 
 
10 INTRODUCTION. 
 
 substance for this purpose. In order, then, to extract 
 gold and silver from ores by leaching-, these metals are 
 combined with chlorine; the resulting compounds, or 
 metal salts, are dissolved, and the leach is separated 
 from the undissolved matter by filtration. The metals 
 are then separated from the leach by precipitation. 
 
 7. Chemical combination differs from mere mixture, 
 or mechanical combination. When two or more sub- 
 stances are merely mixed, each remains the same as it 
 was before, and may be separated from the others with- 
 out having undergone any alteration of its properties; 
 but when they are chemically combined, they unite to 
 form a substance which usually differs from any one, 
 and from all of the original components a substance 
 which is the same throughout, or homogeneous, and 
 from which the components can only be recovered by 
 chemical action. Thus gold and chlorine might, under 
 certain conditions, be mixed, and again separated un- 
 changed, by a current of air; in the interval the gold 
 would remain a metal, and the chlorine a gas. If com- 
 bined, gold chloride would be formed, which is neither 
 a metal nor a gas. It bears no resemblance, in ap- 
 pearance or properties, to either gold or chlorine ; nor 
 can either of those substances be obtained from it by 
 any merely mechanical process of separation. 
 
 8. Solution also differs from mixture; the difference 
 is best explained by an example. Sand, clay, or gold 
 powder can be mixed with water, but not dissolved in 
 it. They may remain a long time suspended, but will 
 ultimately settle, or may be at once separated from the 
 water by filtering; while sugar, salt, or gold chloride 
 will dissolve in water, will not settle, and will pass with 
 
INTRODUCTION. 1 1 
 
 the water through a filter, having in the act of dissolv- 
 ing become a liquid, which the other substances, not 
 dissolving, did not. 
 
 9. Precipitation means throwing down. It is 
 effected by adding to a solution a substance, either solid 
 or liquid, which acts chemically, and causes the dis- 
 solved substance, or some of its components, to become 
 insoluble in the liquid; or, so changes the liquid as to 
 render it incapable of dissolving the substance, which 
 is therefore thrown down, or precipitated. An exam- 
 ple of the first kind of precipitation is seen when a drop 
 of muriatic acid is added to a solution of silver nitrate. 
 Silver chloride is formed, which, being insoluble in the 
 liquid, separates in the solid state. If this silver chlo- 
 ride be placed in hot brine, it will be dissolved, and will 
 be again thrown down on the addition of sulphuric acid, 
 which so changes the brine as to render it incapable of 
 dissolving silver chloride. This is the second kind of 
 precipitation. 
 
 Precipitation may also be caused by a change of 
 temperature. Thus, if the hot brine in which the silver 
 chloride was dissolved were allowed to become cool, 
 the silver chloride would, unless in very small quan- 
 tity, be precipitated, because cold brine cannot dis- 
 solve so much as when hot. Again, as any solvent can 
 only dissolve a certain quantity of a substance, it fol- 
 lows that if a saturated solution be exposed to evapo- 
 ration, the dissolved substance, not evaporating, must be 
 thrown down in proportion to the diminution in quan- 
 tity of the solvent. In the latter two cases the effect 
 is generally called crystallization, or deposition, rather 
 than precipitation. A substance which causes precipi- 
 
12 INTRODUCTION. 
 
 tation, when added to a solution, is called a precipitant. 
 
 10. Chlorine is a greenish gas, and is usually pro- 
 duced from common salt. When metals are combined 
 with chlorine, the resulting compounds are metal chlo- 
 rides, and are distinguished by the names of the respect- 
 ive metals, as gold chloride, silver chloride, and further, 
 by the prefixes sub, or di, proto, bi, ter, tetra, penta, as 
 copper chloride, copper protochloride, mercury proto- 
 chloride, and bichloride, etc., representing different 
 proportions of chlorine combined with the respective 
 metals. The terms sesqui and per, are also used to 
 designate certain ratios of combination. 
 
 11. Gold terchloride, for lixiviation, usually called 
 simply gold chloride, is made by exposing the pulver- 
 ized ore, containing the metal in small particles, to the 
 action of chlorine and moisture. It is extracted by 
 leaching with cold water, in which it dissolves readily, 
 and the gold is precipitated in the metallic state, as a 
 brown powder, by a solution of iron sulphate, known in 
 commerce as copperas, or green vitriol, which takes to 
 itself the chlorine, and leaves the gold insoluble. The 
 metal is collected, washed, dried, melted, and cast as a 
 bar or ingot. 
 
 12. If the rock, or ore containing the gold, is free 
 from opposing substances, it may be chlorinated without 
 being roasted; but in general, ores which are treated 
 by lixiviation contain the gold so combined, or mixed 
 with other substances, that a preliminary roasting is 
 necessary. 
 
 13. Silver chloride is made, for lixiviation, by means 
 of heat, in a roasting furnace, is extracted by leaching 
 the ore with a solution of calcium hyposulphite, being 
 
INTRODUCTION. 1 3 
 
 insoluble in simple water, and the silver is precipitated 
 as silver sulphide, by a solution of calcium polysulphide. 
 The precipitated sulphide, in the form of a black mud, 
 is collected, washed, dried, roasted, and melted with an 
 addition of scrap-iron, which takes the sulphur remain- 
 ing after the roasting, and sets the silver free. 
 
 14. Silver sometimes exists naturally combined with 
 chlorine, in ore, and is then soluble without roasting; 
 but in general it is combined with antimony, sulphur or 
 arsenic, or with base metal sulphides, oxides, etc., and 
 then roasting is necessary. 
 
ROASTING. 
 
 15. As a metal chloride is a compound of a metal 
 with chlorine, so a metal oxide is a compound of a metal 
 with oxygen, and a metal sulphide, or sulphuret, is a 
 metal combined with sulphur, while a metal sulphate is 
 a metal combined with both oxygen and sulphur that 
 is, a metal oxide with a sulphur oxide; the latter being 
 the same which, when combined with a certain propor- 
 tion of water, is called sulphuric acid, or oil of vitriol. 
 The metal oxides, sulphides, and sulphates are" distin- 
 guished in the same way as the chlorides. 
 
 16. The purpose and effect of roasting ore for lixi- 
 viation is, as to gold, to burn all base metals, sulphur, 
 and other substances, such as arsenic, antimony, and 
 tellurium, and either expel them by volatilization, or 
 leave them in such condition as to be harmless in the 
 chlorination of the gold, and, as to silver, to change its 
 condition in the ore, from various insoluble compounds, 
 into soluble silver chloride. 
 
 17. In order that roasting may be effective, the ore 
 must first be crushed to powder. The most suitable 
 degree of comminution must be found by trial for 
 each particular ore. The more coarsely it is crushed, 
 consistently with good roasting, the more easily is it 
 leached. A powder which will pass through wire gauze 
 of 40 meshes to the running inch is fine enough, and, 
 in some cases, a sieve of 20 meshes to the running inch 
 may be used with advantage. For crushing there is, 
 
16 ROASTING. 
 
 as yet, nothing better in the market than the stamp 
 battery. 
 
 18. Oxidizing Roast. The crushed ore is exposed 
 to heat, with abundant access of air. The metal sul- 
 phides take fire and burn, both metal and sulphur being 
 oxidized by combining with oxygen from the air. A 
 part of the oxidized sulphur flies off with the well known 
 sulphurous smell. Another part combines with a por- 
 tion of the oxidized metal, forming metal sulphate. 
 The rest of the metal remains as oxide, except silver, 
 which, if not converted into sulphate, becomes metallic. 
 In this way iron, copper, zinc, and lead sulphides are 
 changed, partly into the respective sulphates, and partly 
 into oxides. Nearly the whole of the silver is converted 
 into sulphate, or reduced to the metallic state ; gold 
 remains unchanged. Antimony and arsenic are oxidized, 
 and partly fly off, while a part remains, to combine 
 with metal oxides, forming antimonates and arsenates, 
 much in the way in which sulphur makes sulphates. An 
 oxidizing roast is a roast so conducted that the gold is 
 metallic; the silver is either metallic or in the form of 
 sulphate, and the base metals are converted into sul- 
 phates or oxides. 
 
 19. Dead Roast. Under an increase of heat, some 
 of the metal sulphates which were formed during the 
 oxidation are decomposed; sulphur oxide flies off, and 
 metal oxide remains, although some of the metal oxides 
 also volatilize to some extent. The order in which some 
 of the principal sulphates are decomposed is, iron, cop- 
 per, silver; the last requiring a very high heat. Lead 
 sulphate is not decomposed, nor is it usual to push the 
 heat so far as to decompose silver sulphate. A dead 
 
ROASTING. 17 
 
 roast is an oxidizing roast, carried forward to decompo- 
 sition of iron and copper sulphates. 
 
 20. Chloridizing Roast.- At the commencement 
 this is the same as an oxidizing roast; but salt is mixed 
 with the ore, either at the time of charging the furnace ? 
 or at a certain stage of the operation. The quantity 
 of salt used depends on circumstances, and varies from 
 one to twenty per cent, of the weight of the ore. 
 
 21. Salt is a compound of the metal sodium with 
 chlorine, and is the cheapest source of chlorine. The 
 chlorine of the salt is transferred, under the action of 
 heat, from the sodium to the other metals, by a variety 
 of agencies, chiefly by means of sulphur and oxygen, 
 for which the sodium has a greater affinity, whence it 
 happens that, when another metal sulphate is heated in 
 contact with sodium chloride, an exchange takes place, 
 the sodium takes the sulphur and oxygen, and forms 
 sodium sulphate; the other metal takes the chlorine, and 
 forms a chloride. In this way, iron, copper, zinc, lead, 
 and silver sulphates form chlorides, while a correspond- 
 ing proportion of salt forms sodium sulphate. For this 
 reason, sulphur is necessary in a chloridizing roast, 
 since without it sulphates cannot exist. 
 
 22. The higher sulphur oxide, formerly called dry 
 sulphuric acid, but now known by the name of sulphu- 
 ric anhydride, also plays a prominent part in the de- 
 composition of the salt and the evolution of chlorine. 
 The latter acts upon any remaining sulphides, and to 
 some extent on oxides, converting them into chlorides. 
 It also acts on metallic silver. 
 
 23. Among other agencies involved in the formation 
 of metal chlorides, is that of steam, from burning fuel. 
 
18 ROASTING. 
 
 Steam, in contact with salt and quartz, at a red heat, 
 produces hydrochloric acid, which assists in the work. 
 It also decomposes some of the base chlorides, es- 
 pecially the volatile ones, thus giving the silver the 
 benefit of their chlorine. For this reason, steam is some- 
 times, in the case of rich ores, admitted to the roasting 
 chamber by means of a perforated pipe laid in the fire- 
 wall, which is made hollow, with openings on the 
 side next to the ore. This, however, causes an in- 
 creased consumption of fuel. 
 
 24. As the heat still increases, the base metal chlo- 
 rides are decomposed, just as the sulphates are decom- 
 posed in the dead roast. They give off the whole, or 
 a- part of their chlorine, remaining, or volatilizing, as 
 chlorides of a lower degree, or taking oxygen from the 
 air and becoming oxychlorides, or oxides. Silver chlo- 
 ride is not decomposed by heat. 
 
 25. Iron perchloride, formed quite early in the 
 roasting, is volatile, and some of it flies away, while 
 another part, giving off chlorine, is reduced to proto- 
 chloride, and this again, losing the remaining chlorine, 
 takes oxygen from the air, and forms iron peroxide, 
 which remains in the ore. 
 
 26. Copper protochloride gives off half its chlorine, 
 becoming dichloride, which volatilizes to some extent, 
 imparting a deep blue color to the flames. 
 
 27. Lead sulphate requires a rather high heat to 
 convert it into chloride, so that it remains in part, some- 
 times wholly, unchanged. The chloride gives off some 
 chlorine and takes oxygen, becoming oxychloride. 
 
 28. Zinc volatilizes partly, in some form, and pro- 
 duces in the flues hard concretions of oxide, or carbon- 
 
ROASTING. 19 
 
 ate, which must be removed from time to time. The 
 oxide is quite stable. 
 
 29. Antimony and arsenic form volatile chlorides as 
 well as oxides, which, to a great extent, go up the 
 chimney. 
 
 30. Gold forms, at a very low heat, a peculiar chlo- 
 ride which decomposes at a higher temperature, and 
 then remains metallic, except as a portion of it may 
 be. again chloridized, in the same form, by chlprine from 
 decomposing base chlorides, during the cooling of the 
 ore, after being withdrawn from the furnace. The gold 
 chloride formed in roasting contains less chlorine than 
 that formed by the cold gas, and is not soluble in water, 
 but dissolves in the solvent used for the silver leaching. 
 The formation of this compound cannot be relied on 
 as a process for extracting gold. 
 
 31. The presence of lead is disadvantageous for 
 the roasting, because its compounds melt too easily, and 
 because the oxide and chloride volatilize, to the injury 
 of the workman's health; and for the leaching, because 
 the sulphate and chloride are soluble in the silver leach, 
 and the sulphate cannot be removed from the ore by 
 washing with water; as, however, the chloride is soluble 
 in hot water, it is preferable to the sulphate, as it can be 
 removed from the ore before the silver extraction be- 
 gins. 
 
 32. Silver chloride is not very volatile by itself, but 
 in some cases becomes so, apparently from the influence 
 of base metal chlorides, notably that of iron perchlo- 
 ride, when too much heat is used early in the roasting. 
 Antimony and zinc also tend to cause volatilization of 
 silver; so as it does not require a very high heat to 
 
20 ROASTING. 
 
 form the silver chloride, the roasting is conducted, not 
 only with a very low heat at the beginning, but without 
 an extremely high temperature at any time, and even a 
 moderately high degree is maintained for a short time 
 only towards the end. A chloridizing roast is a roast 
 which, beginning with oxidation, ends by leaving, as 
 nearly as possible, all the silver in the form of chloride 
 in the ore. 
 
Plate I. 
 
Plate II. 
 
APPARATUS. 
 
 33. ROASTING FURNACES The essential condition 
 of roasting pulverized ore is, that every particle shall be 
 exposed to the action of heated air until certain chemi- 
 cal changes are effected, after which heat alone will 
 complete the operation. This condition is fulfilled in 
 the reverberatory furnace, in which a layer of ore 
 of a certain thickness is acted on by a current of 
 heated air from a fire. The surface of the layer is 
 renewed from time to time by stirring the mass 
 by means of implements operated by hand. As stir- 
 ring by hand power is laborious and expensive, various 
 means have been devised to dispense with it, and to 
 substitute the automatic action of machinery, among 
 the best of, which are the furnaces known as the Stete- 
 feldt, Bruckner, Brunton, White, Hovvell White, Pacific, 
 and O'Hara, each of which has certain advantages over 
 the other, so that a decided preference, under all circum- 
 stances, can be given to neither, and as the reverbera- 
 tory is the original of all, as any kind of ore that is fit 
 to be roasted can be roasted in it, and as the operator 
 who knows how to use it, can easily adapt himself to 
 the others, a complete description of its construction 
 and operation will be given, but, as a work of this 
 character would be imperfect without some account of 
 the mechanical furnaces also, they will be briefly de- 
 scribed in separate articles under " Addenda." 
 
22 APPARATUS FURNACES. 
 
 34. A Reverberatory Furnace is simply an oven. 
 There is a fire-place at one end and a flue at the other, 
 and the ore to be roasted is laid on a horizontal hearth 
 between them. In the side walls are openings, which 
 admit air, and allow the workman to turn the ore over, 
 from time to time, with a long hoe, or rake. These 
 openings can be closed, when necessary, with iron doors. 
 The fuel must be such as will produce a flame; hence, 
 wood, or flaming coal is suitable. 
 
 35. Reverberatory furnaces are of several kinds; 
 the single, which has but one roasting chamber, the 
 double, in which a second roasting chamber is con- 
 structed directly over the first, and is worked with waste 
 heat; and the long furnace, which has two or more 
 chambers, either in one horizontal plane, or, which is 
 better where the ground is suitable, raised more or less 
 one above another, in step form, but not superposed. 
 
 The single hearth is wasteful of fuel; the double 
 hearth is inconvenient, so I will describe a long furnace 
 with two hearths, represented by the horizontal section, 
 Plate i, and vertical section, Plate 2. If more than 
 two hearths are required, which with concentrated sul- 
 phurets may be the case, a third or fourth can be added, 
 but it will, in general, be necessary to add also an auxil- 
 iary fire-place to aid in heating them. The capacity of 
 this furnace is three tons of average silver ore per 
 twenty-four hours, or from one to one and a half tons of 
 concentrated sulphurets in the same length of time. 
 
 36. The masonry may be built entirely of common 
 bricks; with adobes in case of necessity; but it is better 
 to make the inside of the fire-place, and the arch over 
 it, of firebrick. If convenient the outside walls can be 
 
APPARATUS- -FURNACES. 23 
 
 of any kind of stone, but, unless a good firestone can 
 be procured for the inside work, that must be of brick. 
 Lime mortar may be used with advantage for the out- 
 side work, but all parts which are exposed to much heat 
 must be laid in clay. The brickwork consists of head- 
 ers and stretchers alternately, appearances being sacri- 
 ficed for the sake of strength. The masonry below the 
 hearth is not solid, but the space inclosed by the walls 
 is filled with sand, or with earth well tamped, and on 
 this the hearth, or sole, is laid, of the hardest bricks on 
 their narrow sides, without mortar, but afterwards 
 grouted. 
 
 37. The walls are supported against the thrust of the 
 arch as follows. At the points shown in the diagram are 
 vertical backstays or "buckstays," of wrought iron, two 
 inches wide by one and a quarter inch thick, and long 
 enough to reach from below the hearth to just above the 
 arched roof. Through holes punched in the backstays, 
 near the ends, project the nutted ends of tie rods of ^ 
 inch round iron. The lower tie rods, passing through 
 the body of the furnace, below the hearth, and uniting 
 the lower ends of opposite backstays, are put in before 
 the hearth is laid. The upper ones extend across the 
 furnace above the walls, uniting the upper ends of the 
 backstays, and are not put in place till after the walls 
 and arch are laid. Usually the furnace is stayed in the 
 direction of its length, in the same manner, except that 
 the lower longitudinal tie rods do not pass entirely 
 through, but are comparatively short, being securely 
 anchored in the body of the furnace, under the hearth. 
 If the ends of the furnace are made masssive, these 
 ties may be dispensed with, especially if the ends 
 
24 APPARATUS FURNACES. 
 
 are supported by wooden posts well braced. The cross 
 ties, which are indispensable in some form, may be of 
 wood, uniting the upper ends of strong posts, the lower 
 ends of which are sunk in the ground, close to the side 
 of the furnace, and which replace the iron backstays, 
 the objection being that the posts cannot be set very 
 near the doors, both on account of being in the 
 way, and because of the heat; but near the doors is 
 precisely where they are most needed. Cast iron ribbed 
 backstays are also used, but are liable to break. 
 
 38. When all is ready for raising the walls above 
 the hearth, the cast iron door frames are set up, in the 
 middle of the thickness of the wall, which should not 
 be less than 16 inches thick, and a stirring-hoe is passed 
 through each of them in succession, and its range 
 of operation ascertained by trial, and marked on the 
 hearth. The walls are then built up along the marks, 
 cutting off the corners of the otherwise rectangular 
 hearth, and giving it the form seen in the diagram. This, 
 though entailing some loss of space within the furnace, 
 is absolutely necessary, in order that every part of the 
 hearth may be accessible with the hoe. 
 
 39. The door frames are two feet long by eight in- 
 ches high in the clear, are set two inches above the 
 hearth, and are built into the wall as solidly as possible. 
 An exception is made as to the back door on the first 
 hearth, when it is to be used for discharging the roasted 
 ore. It must then be set flush with the hearth, and is 
 two inches higher in the clear, to allow of using a large 
 hoe for discharging, but when the discharge is effected 
 through a trap in the hearth, this door frame is the same 
 as the others. The masonry is arched over the frame, 
 
APPARATUS FURNACES. 25 
 
 and as the wall at this point is liable to be rather thin, 
 it is a good plan to arch the skewback a little, in a 
 horizontal plane inwards, by which the thrust of the 
 main arch against this weak part is lessened, and to 
 some extent transferred to the points at each side, 
 where it is received by the backstays and tie-rods ; 
 notwithstanding which, it is also well to place above 
 each door frame, outside of the wall, a flat bar of iron 
 two inches wide and half an inch thick, the ends of which 
 are tucked between the adjoining backstays and the 
 wall. 
 
 40. Doors are sometimes made of cast iron, and 
 pivoted to the frames, but sheet iron doors detached 
 from the frames answer very well, and are furnished 
 with long handles, made of iron rods riveted to them at 
 right angles; when in place they rest against the rabbet 
 formed by the junction of the frames with the masonry, 
 the projecting handles being supported by the roller in 
 front. Doors sliding vertically on the outside of the 
 wall are very convenient, being counterpoised by a 
 weight attached to one end of a rope which passes over 
 a pulley, the other end being attached to the door by a 
 short chain or a link. A slot in the lower part of the 
 door allows it to be closed while the hoe rests on the 
 roller, the handle of the hoe being supported hori- 
 zontally by a hook depending from a beam above. 
 
 41. When the walls are high enough above the 
 hearth, which is 17 inches at the points opposite the 
 highest part of the arch, and not less than eight inches at 
 the lowest points, the skewback is set up with bricks on 
 end, the lower end being cut to the proper angle, and 
 then the walls are continued up, level with the top of 
 
26 APPARATUS FURNACES. 
 
 i 
 
 the arch. All openings in the walls are then tempo- 
 rarily stopped, and the enclosed space is filled with 
 moist sand, up to the skewback along the sides and 
 ends, and higher in the middle, and this is carefully 
 shaped to the required form of the furnace top. On 
 the sand, as a support, the arched roof is laid dry, the 
 bricks on end, one course thick, working from the 
 skewback all along on both sides, and keying m the 
 centre line. All openings in the arch, such as flue or 
 feed holes, are circular, formed with a course of "rollers." 
 When the arch has been well keyed, and the openings 
 filled with sand, it is wetted by pouring water on it, and 
 then grouted with a mixture of clay and sand, thinned 
 with water so as to run into and fill all the interstices 
 between the bricks. The best way to lay the bricks in 
 the arch is the style called " herring bone," but it 
 requires well porportioned bricks, of which the width is 
 just twice the thickness, otherwise straight courses are 
 to be preferred. 
 
 As soon as this . is done, the backstays and the 
 upper tie rods are placed in position, and all 
 the nuts tightly screwed to support the walls, yet 
 not so much so as to move them. The doors, 
 which were temporarily stopped with loose bricks, or 
 pieces of board to retain the sand, are opened, and the 
 sand, on which the arch was laid, is drawn out, to allow 
 the arch to settle as it dries. In a single hearth fur- 
 nace, the arch has very little spring transversely, because 
 it abuts the other way against solid end walls, but 
 in a long furnace a transverse spring is more neces- 
 sary, especially near the junction of the two hearths, 
 where the roof descends and rises again, so as in fac 
 
APPARATUS FURNACES. 27 
 
 to be an inverted arch, as to the longitudinal section, as 
 may be seen in Plate 2, but, as this is almost the nar- 
 rowest part of the furnace, there is no danger of its 
 falling, if it has a good spring crosswise. 
 
 42. In building the fireplace many masons, very 
 improperly, let the bearing bars for the grates rest on an 
 offset in the brickwork, so that though space be left for 
 the lengthening of the grates by expansion when heated, 
 yet that space is soon filled with ashes and other debris, 
 so that the grates are forced to bend or " buckle./' 
 When they become cool again they shorten but do not 
 straighten, the spaces at the end, left by their shrinkage, 
 are refilled, and, when again expanded by heat, the 
 grates buckle still more and are soon ruined. 
 
 The end walls of the ash-pit should be perpendicular, 
 without offsets; the bearing bars should be well clear of 
 them, and the ends of the grates should also clear the 
 walls by at least half an inch. The space thus left for 
 expansion is then bottomless, and remains always 
 open, and the grates remain straight. 
 
 43. The flue-holes are connected by flues in any con- 
 venient way, with a stack which is two feet square inside, 
 and 20 to 30 feet high. In some part of the flue or 
 stack is a damper, similar to that of a stovepipe, oper- 
 ated by the roaster through the agency of a cord or 
 wire. 
 
 44. It is desirable to utilize as much as possible the 
 waste heat from the furnace, and it is a good plan to carry 
 the flue in front of the stamp battery, if dry crushing is 
 done, and there enlarge it to form a dust chamber. The 
 top of the chamber is of sheet or boiler iron, which forms 
 a drier on which to dry the ore for crushing. Even 
 
28 APPARATUS FURNACES. 
 
 where only concentrated sulphides are treated, so that 
 no crushing is required, a drier is convenient, and may 
 very properly be the top of the dust chamber. The 
 walls are built two bricks high above the iron plate, and 
 topped with two-inch plank, held down by anchor bolts 
 built into the walls. If, however, there is a battery, the 
 side of the drier next to it is without a wall above 
 the plate, which, if thin, is secured by an anchor bolted 
 iron strap along the edge. 
 
 45. If silver ore is treated, a drier is necessary for 
 the precipitate. It may be made as described above, to 
 be heated by the waste heat from the roasting ore, by 
 steam, or by a special fire. A small roasting furnace is 
 also requisite for roasting the dried precipitate. It is 
 built similarly to the large furnace, except that it has 
 but a single hearth and one working door. A hearth 
 containing 36 to 40 square feet of surface, will suffice 
 for the roasting of from one to two thousand ounces of 
 silver, in the form of' precipitate, in each twenty-four 
 hours. 
 
 46. It will be observed, by those accustomed to fur- 
 naces, that there are two small innovations in the plan 
 given. Firstly, the ash-pit is open entirely across the 
 furnace. This gives the operator the choice of leaving it 
 so, or of closing either end, which is sometimes an advan- 
 tage on account of the draft. It is generally preferable, 
 though contrary to custom, to have the opening on the 
 rear side of the furnace, that is the side opposite to the 
 fire door, because the cold air, entering under the hot- 
 ter end of the fireplace, tends to equalize the heat. 
 Especially is this the case when the workman pushes 
 the half burned wood back, when introducing fresh fuel, 
 
APPARATUS FURNACES. 29 
 
 instead of drawing it forward as he should do. Secondly, 
 the doors on the first hearth are not placed in the mid- 
 dle of its length, as is usual, but a foot nearer to the 
 fireplace. Here again the object is to equalize the 
 heat, by causing the cold air which enters by the door, 
 to pass over the hotter portion of the ore near the 
 fire wall. Another advantage is that the hearth is 
 made wider near the fire wall, and narrower at the 
 other end, thus concentrating the heat toward the 
 part which is farthest from the fire. 
 
 47. When a long furnace, which may have any 
 required number of hearths, is built on a hillside, it is 
 a good plan to make each successive hearth two feet, 
 or even more, higher than the preceding one, the one 
 next to the fire-place being the lowest. By this plan 
 the cost of grading is lessened, and the dropping of 
 the ore from one hearth to the other assists greatly in 
 the oxidation. This is called a "step furnace." 
 
 48. Furnaces are often built with an arched cham- 
 ber under the first hearth, as shown by the dotted line 
 in Plate 2. This chamber is closed on the working 
 side of the furnace and open on the other, and the 
 ore is discharged into it through an opening about a 
 foot in diameter, in the hearth near the working door. 
 The opening is closed by an iron plate, which rests on 
 a rabbet a couple of inches below the level of the 
 hearth, and the depression thus formed is filled with 
 roasted ore. A small flue from the chamber, leading 
 through the wall to the interior of the furnace, removes 
 the fumes rising from the hot ore, which is not drawn 
 out of the chamber to the cooling floor for some time. 
 
30 APPARATUS FURNACES. 
 
 It is a good arrangement. The floor on each side of a 
 furnace is paved with bricks to a width of 14 feet. 
 
 49. Furnace Tools. The tools required for such a 
 furnace are: three or four hoes, each fourteen feet long; 
 a couple of smaller ones about six feet; two spades not 
 shorter than the large hoes; a poker, which, if wood 
 is the fuel, should be made like a boat-hook. The 
 shanks of the hoes and spades are of three-quarters or 
 one inch gaspipe, except some three feet next the 
 head, which is of solid round iron. The heads are of 
 one-quarter or one-half inch boiler iron. For very 
 heavy ores, containing arsenic and antimony, cast-iron 
 hoe heads are used, also rakes. These tools are repre- 
 sented in Plate 2. 
 
 50. Crosby s Furnace. At Nevada City, Professor 
 Crosby uses, in connection with a reverberatory fur- 
 nace, an inclined, rotating, unlined iron cylinder, which 
 receives the concentrated sulphides at the higher end, 
 and delivers them at the lower end, already to a great 
 extent oxidized, into a chamber where they are exposed 
 to the heat from the reverberatory hearth, to which 
 they are removed periodically, in batches, and finished 
 under hand stirring with hoes. A fire is used under 
 the cylinder, to commence the burning of the sulphides, 
 after which they continue burning without such aid, 
 combustion being supported by the air which enters 
 through the open upper end of the inclined cylinder 
 with the sulphides, the fumes being carried off at the 
 other end by the draft of the furnace, with which the 
 cylinder is in communication. 
 
 The sulphides, thus burning spontaneously, receiving 
 an abundance of fresh air, being constantly moved by 
 
APPARATUS VATS. 31 
 
 the rotation of the cylinder, and afterwards lying in the 
 furnace, exposed to a higher heat while accumulating, 
 require, when transferred to the finishing hearth, but a 
 short time to complete the roasting. Thus three tons 
 of material which requires 24 hours in an ordinary long 
 furnace, can be turned out daily by the labor of only 
 two men. Some power is consumed in turning the 
 cylinder, which however, when power is not required 
 for other purposes, might be had by applying the waste 
 heat of the furnace to a small steam or hot air engine. 
 
 51. Leaching Vat. The leaching is done in wooden 
 tubs, which are coated inside with a mixture of coal 
 tar and asphalt melted together, and applied whilst 
 hot. As the chlorination of gold is also effected in these 
 tubs, they are provided with covers when that metal is 
 present in the ore. If there is no gold, covers are not 
 needed, nor is the coating of the tubs with tar so neces- 
 sary, being in fact inadmissible if hot water is to be 
 used to wash the ore. 
 
 The side of a leaching vat is either vertical, or 
 flaired so that the top of the tub is wider than the 
 bottom. The reverse form is not suitable, because the 
 ore, in settling, draws away from the sides, and leaves 
 a space, or, at least, a greater looseness, through which 
 the chlorine can pass upward, or liquids downward, 
 without passing through the mass. The vat represented 
 in Plate 3, is suitable for the treatment of ore con- 
 taining both gold and silver. Its capacity is two and 
 three-quarter tons of roasted ore. 
 
 The vats have filters near the bottom, and rubber 
 pipes, connecting under the filters, for the solution to 
 flow through to the precipitating tubs. For the ad- 
 
32 APPARATUS VATS. 
 
 mission of chlorine a leaden nipple is inserted in the 
 side of the vat immediately below the filter. 
 
 52. In some works the vats are suspended on iron 
 gudgeons, attached to their sides, in order that they may 
 be emptied quickly by dumping. It is a convenient 
 arrangement if completed by having a stream of water 
 in a sluice below, or a tramway, for the removal of 
 tailings. In others the leaching vats themselves 
 are mounted on wheels, and can be trundled to the 
 dumping place. 
 
 53. The filter consists of a false bottom of inch 
 boards, through which half inch holes are pierced at 
 intervals of about four inches. The boards are laid 
 loosely, with open spaces a quarter of an inch wide 
 between and around them. The false bottom rests on 
 strips of wood, by which it is raised from half an inch 
 to an inch above the true bottom. As the vat is 
 slightly inclined toward the discharge side, to insure 
 complete draining, the strips are made thicker at one 
 end than at the other, so that the false bottom is hori- 
 zontal. They do not touch the sides of the vat, but 
 leave a space for the flow of solution and diffusion of 
 chlorine. On the false bottom is a layer of pebbles as 
 small as may be without falling into, or through, the 
 holes. Over the pebbles is a sheet of burlap, or a 
 layer of old grain sacks, which are cheap and good 
 enough, as they are soon destroyed by chlorine, on 
 which account some operators prefer a layer of fine 
 gravel covered with sand. 
 
 54. Suction Pipe. In cases of difficult leaching, fil- 
 tration may be facilitated by means of a suction pipe. 
 This is simply the discharge pipe of the leaching vat, 
 
Plate III. 
 
 Scale; l/zinch^lfoot. 
 
APPARATUS VATS. 
 
 33 
 
 made of stiff hose, or of wood, instead of soft rubber 
 as in other cases, and extended 
 to a vertical depth of from six to 
 twenty-five feet. The hose, near 
 its lower end, is coiled once around, 
 as in the accompanying- diagram, 
 and secured by a piece of wire; or, 
 a re-curvecl piece of lead pipe may 
 be inserted in the end of the dis- 
 charge pipe, or again, the end may 
 be immersed in a cup of water, 
 although this plan is less conven- 
 ient than the others. The object, 
 in either case, is to prevent the en- 
 trance of air. 
 
 55. Vent Pipe. Though not the 
 general practice, it is well to have a 
 vent pipe to prevent disturbance of 
 the filter by the air or gas beneath 
 it, when displaced by the entrance 
 of water, especially if the discharge 
 
 [SUCTION AND VENT PIPES.] ' > 
 
 pipe is hung up, closed as in the case of using suction, 
 or occupied by the introduction of water below the fil- 
 ter, as in commencing the washing of silver ore. There 
 are several methods of arranging a vent pipe. Perhaps 
 the simplest is the following, represented by a dotted 
 line in the preceding diagram. 
 
 When the ore vat is disconnected from the chlorine 
 pipe a short piece of rubber tube is connected at one 
 end with the nipple through which the chlorine was in- 
 troduced, and at the other with the upper part of the 
 
34 APPARATUS VATS. 
 
 vat, by being inserted tightly in a hole bored through the 
 side, just below the cover. The short tube may be 
 left permanently on the lead nipple, and connected with 
 the chlorine pipe when required, by means of a short 
 piece of lead pipe, which afterwards serves also for con- 
 necting the tube with the hole in the vat side. 
 
 Whether water be introduced from above or below 
 the ore, the air or gas beneath the filter will pass 
 through the tube, and return to the vat above the ore. 
 If the chlorine nipple is to be used thus as a vent, it 
 should be set in as high as possible, consistently with 
 the delivery of the chlorine below the filter. A 
 special vent pipe may be made by boring a one-quarter 
 inch hole lengthwise through a strip of wood, and at- 
 taching the strip to the inside of the vat by means of 
 wooden pins. It should terminate at one end im- 
 mediately below the vat cover, and at the other, beneath 
 the burlap on the gravel. The upper end must be 
 plugged, and a transverse hole bored to connect with 
 the vertical passage. This aperture must be plugged 
 during the chlorination, and opened when water is ad- 
 mitted. 
 
 56. Sieve. This is made of stout brass wire, and 
 has from four to eight meshes to the running inch. It 
 is of an oblong form, about two feet wide by three feet 
 long, and is framed with wood. The sides are six in- 
 ches high, and are prolonged so as to form handles at 
 one end, like those of a wheelbarrow, and at the other 
 points of attachment for suspension ropes from a sup- 
 port above. It is operated by hand, being swung back 
 and forth, directly over the vat which is in course of 
 being charged, into which the ore which passes through 
 
APPARATUS VATS. 35 
 
 falls, in a loose and open condition, while the lumps are 
 retained. 
 
 57. Precipitating Vat. Figure i, Plate 4 This is 
 also a wooden tub, and, if for gold, is coated inside as 
 the leaching vat. A smooth bottom is made in it, 
 either by means of a layer of tar and asphalt, melted 
 together in such proportions as to harden on cooling, 
 or by a bed of Portland cement, which can be shaped 
 as desired, to facilitate the removal of the precipitate. 
 A precipitating vat is made wider at the bottom than at 
 the top, in order that the precipitate may not settle 
 upon the staves. 
 
 58. For drawing off the waste liquor after precipi- 
 tation, the most convenient, because self-acting arrange- 
 ment is a piece of two inch hose, drawn water-tight 
 through the side of the tub near the bottom, and long 
 enough on the outside to lead to a filter, or a settling 
 tank, on a lower level, and on the inside to reach the 
 top of the tub, where it is secured, when not in use, by 
 a wooden clamp. On this end is a wooden float which 
 causes the hose, when in use, to draw always from the 
 surface; also serving to prevent its drawing too near 
 to the bottom so as to cause a loss of gold. The other 
 opening, furnished with a large wooden faucet, is only 
 used when collecting the precipitate. 
 
 The silver precipitating tubs must be larger, or 
 more numerous, than those for gold, because the 
 volume of silver solution is much the greater. The 
 size represented in Plate 4, is sufficient for the gold 
 lixivium from one vat, such as is shown in Plate 3, but 
 both for gold and for silver, extra vats are provided for 
 very weak solutions, drainings, etc. The smaller vat 
 
36 APPARATUS VATS. 
 
 Figure 2, Plate 4, is to contain a solution of iron sul- 
 phate. It is provided with a filter, and a discharge 
 pipe which reaches to the gold precipitating tub, and 
 which, when not in use, is turned up and fastened as in 
 the figure. This vat is elevated so that the precipitant 
 may be used with convenience. For silver a similar 
 vat contains the calcium polysulphide. It does not 
 require a filter, but the pipe is inserted a little highen 
 to allow room for sediment. 
 
 59. Troughs for conveying^ the lixivium from the 
 leaching vats to the precipitating tubs, are not built, 
 but hollowed out of timber. They are about five 
 inches wide and four deep, and are tarred. 
 
 60. Well. As the silver leaching solution, or "hy- 
 po," is not thrown away, but is used again continually, 
 it is usual to provide a well on a lower level than that 
 of the silver precipitating tubs. A tub or square vat 
 sunk in the ground answers the purpose. 
 
 61. Pumps. For elevating the leaching liquid from 
 the well a wooden pump is used. The small quantity 
 of metal used in its construction, for fastening the 
 valves, etc., is not injurious. In case, however, a pump 
 is used to raise weak lixivium from the gold leaching, 
 it must be constructed entirely without metal, except 
 lead, in those parts which come in contact with the 
 lixivium. Rubber ball valves are best for this pump. 
 A well may be dispensed with if desired, by having 
 the discharge pipes of the silver precipitating tubs 
 connected directly with the pump, 
 
 62. Filters. To receive the precipitate from the 
 silver tub there is a filter vat, either round or square, 
 in which it is drained and washed. The filter is made 
 
Plate 
 
Plate ~V. 
 
 Oil 
 
 I 
 
 
APPARATUS- -GENERATOR. 37 
 
 like those in the leaching vats, except that, instead of 
 burlap, cotton drilling is used. Filters for the precipi- 
 tated gold are simple pointed bags made of drilling, or 
 sheets of drilling secured over the rims of water 
 buckets which have plug holes near the bottoms, with 
 hollow plugs through which the filtrate flows to a re- 
 ceptacle beneath. A large tank, in which is a filter 
 made of sand or saw dust, is usually placed outside 
 the works. It is used for filtering the liquid drawn 
 from the gold tub after the precipitation of the gold. 
 
 63. Press. To facilitate the drying of the silver 
 precipitate it is pressed into cakes. The press is simi- 
 lar to a cheese press. It is sometimes operated by 
 means of a screw, but a weighted lever is better, be- 
 cause self-acting. A press may be dispensed with if 
 the drying facilities are ample. 
 
 64. Pipes and faucets must be provided for the con- 
 veyance of water and hypo to the points where they 
 are required. Iron pipes with brass faucets may be 
 used for the hypo. A few paper buckets will be useful. 
 
 65. Chlorine Generator. Figure i, Plate 5, is a 
 section of this apparatus. It is made almost entirely 
 of lead, sometimes heavy sheet, but better cast lead, and 
 is arranged so as to be heated from below, either by a 
 special fire, or preferably, when convenient, by steam. 
 If heated by a fire, it stands on a sand bath, which 
 forms the top of the fire place. If by steam, the gene- 
 rator itself forms the top of an iron steam chest, being 
 supported on strips of wood, which permit the steam to 
 circulate beneath it. 
 
 66. The joints of the lead work must not be soldered, 
 
 but "burned;" that is, joined with melted lead, by means 
 3 
 
38 APPARATUS GENERATOR. 
 
 of a gas blow-pipe. Very coarse solder will, however, 
 answer for repairing it. Portland cement also answers, 
 in case of necessity, for stopping a leak. 
 
 67. The apparatus consists of a leaden tub a, in 
 which the materials are put, and which is surrounded 
 by a water chamber b, also of lead, the outer wall of 
 which rises as high as the top of the cover, c, and in 
 which the curtain of the cover rests, forming what is 
 called a water joint. The water should be six inches 
 deep, or more. The pipe, d, is for the removal of spent 
 material. In the cover is a central water-joint opening, 
 through which passes the stem of a stirrer, <?, made of 
 iron, covered with lead, and to which is attached a small 
 leaden bell, or curtain, f, which, reaching near to the 
 bottom of the water chamber, closes the opening, while 
 allowing the stirrer to be turned round by means of the 
 cross bar, g. Another opening, h, which is closed either 
 by a water-joint cover, or, as shown in the figure, by a 
 wooden plug wrapped in greased cloth, serves for intro- 
 ducing material without lifting the main cover. For 
 the introduction of acid, there is a leaden pipe, z, which 
 is coiled once round, as shown in the figure, in order 
 that the lower part of the coil, remaining always full of 
 acid, may act as a valve to prevent the escape of the 
 chlorine. The pipe, k; is for the exit of the chlorine. 
 
 The subjoined diagram represents the cover in 
 a different position, showing the lugs and the chain 
 sling, by which it is raised; also a hook sustain- 
 ing the stirrer, which might otherwise injure 
 the cover. A lever or tackle is used for the lift- 
 
APPARATUS WASH BOTTLE. 
 
 39 
 
 ing. For further re- 
 marks on generators, see 
 "Addenda," near the end 
 of this volume.. 
 
 68. Wash Bottle. 
 Figure 2, Plate 5. This 
 is a bell glass, made from 
 a large bottle, the bot- 
 tom of which is cut off. 
 It is fixed air-tight, as 
 shown, in the head of 
 a keg, or the tightly fit- 
 ting cover of a small 
 tub. A piece of pure 
 rubber tube, /, which 
 is connected with the 
 leaden pipe, k, of the generator, passes through the neck 
 of the bottle, and is packed so as to be air-tight, with 
 oiled rags and putty, and terminates two or three inches 
 below the surface of the water with which the tub or 
 keg is filled. The chlorine, rising through the water 
 into the bell, escapes through the leaden pipe, ;;/, and 
 is conveyed to the chlorinating vat by the rubber tube, 
 n. The pipe, m, is passed, water-tight, through a short 
 piece of oiled rubber tube inserted in a hole bored in 
 the side of the keg, and its upper end, reaching nearly 
 to the top of the bell, and well above the water, is bent 
 downward to prevent the entrance of water, which 
 might occur in consequence of the bubbling up of the gas, 
 and which would cause an obstruction in the rubber 
 tube. 
 
 If two vats are chlorinated at once, the rubber tube, 
 
40 APPARATUS WASH BOTTLE. 
 
 n, is connected with a forked piece of lead pipe, each 
 branch of which is connected with the lead nipple of a 
 vat by a piece of rubber tube. The connections are 
 quickly made by drawing the tightly fitting oiled rub- 
 ber tubes an inch on to the pipes. 
 
 69. All rubber tubes used for chlorine should be 
 oiled on the inside. It is a valuable fact, for the knowl- 
 edge of which I am indebted to E. N. Riotte, that oil 
 is a great protection against the action of chlorine, 
 which forms with it a white, waxy substance. For this 
 reason, oil or grease is an excellent material for stopping 
 small leaks in the apparatus. 
 
 70. The wash bottle serves the double purpose of 
 washing the gas to remove any acid which may pass 
 over with it, and of showing whether or not the gene- 
 rator is operating properly, by the quantity of chlorine 
 which is passing. The chlorine should rise through 
 the water in a steady stream. If it does not, the rea- 
 son is either that it is not produced fast enough, or the 
 orifice of the pipe is too large, which may be remedied 
 by flattening the pipe more or less. Other forms of 
 wash bottle will be found described under "Addenda." 
 
SPECIAL DIRECTIONS FOR 
 WORKING. 
 
 / 71. A. Concentrated Pyrites containing gold, but 
 no silver. This material is produced in the gold quartz 
 mills, by crushing the rock in a wet stamp battery, in 
 which the free gold is amalgamated with quicksilver, 
 and passing the tailings over concentrating machines, 
 by which the sulphides are almost entirely freed from 
 rock and earth. It generally consists mainly of iron 
 bisulphide, called pyrites, but often contains copper 
 pyrites, sometimes lead and antimony sulphides, etc., 
 and in other cases consists chiefly of arsenical iron 
 pyrites. Tellurium is also met with. 
 
 72. Concentrations should be treated as soon as 
 possible after production, or kept in tanks, under water, 
 for, if allowed to lie long exposed to the weather, they 
 oxidize spontaneously to a certain extent, and form hard 
 lumps which must be repulverized for roasting, for 
 which purpose a self-feeding and discharging barrel 
 pulverizer is very suitable. 
 
 73. Ores of this class containing talc, or lime, re- 
 quire the addition, during or before the roasting, of 
 from one to five per cent, of salt, to convert those sub- 
 stances into chlorides, otherwise they would consume a 
 great deal of gas in the subsequent chlorination of the 
 gold. 
 
 74. The furnace, if new, is dried during five or six 
 days with the aid of a very small fire, after which, or 
 
42 SPECIAL DIRECTIONS GOLD. 
 
 if it has been used before, it is heated for from eight to 
 twelve hours, with a gradually increasing fire, but, for 
 this class of ore, need not be red hot before charging, 
 because there is so much sulphur in the ore that it soon 
 ignites, and assists in heating the furnace. While heat- 
 ing the furnace, a quantity of the ore is dried on the 
 drier, being turned over occasionally with a garden hoe, 
 and a charge is put into the hopper. 
 
 75. Many operators put too much ore in the fur- 
 nace, which increases the work of the roasters, without 
 any corresponding advantage, because the term of 
 roasting is nearly proportional to the thickness of the 
 bed of ore on the hearth. I have found, by repeated 
 experiments, that from ten to twelve pounds to the 
 square foot of hearth is enough. The charge for the 
 furnace described is, therefore, 1,000 pounds on each 
 hearth, or a ton in all, so the charge for the hopper is 
 half a ton. 
 
 76. When the furnace is ready, a charge of ore is 
 dropped in on the second hearth, and at once moved, 
 with hoe and spade, to the first, and there spread evenly. 
 Meanwhile, a second charge is put into the hopper, 
 dropped on the second hearth and spread. Care must 
 be taken that none of this charge falls on the first 
 hearth, for which reason the second hearth, as may be 
 seen by referring to Plates i and 2, is made a foot 
 longer, and the first foot has a slight downward inclina- 
 tion, as it is intended to be left bare of ore during the 
 roasting, and to act as a partition between the two 
 charges. 
 
 This is very important in roasting ore for chlorina- 
 tion, because the admixture of a little raw ore with 
 
SPECIAL DIRECTIONS GOLD. 43 
 
 that which is half roasted causes great delay in finish- 
 ing; or, half roasted ore mixed with that which is roasted 
 is injurious in the chlorination. Some operators build 
 the hearths on the same level, and separate them by a 
 low wall, over which the ore is lifted with the spade 
 when transferred from the second hearth to the first. 
 
 77. Roasting. When the sulphur begins to burn 
 on the first hearth, the fire is kept quite low. The 
 burning of the sulphur can be seen, even in the day 
 time, if the furnace house is dark, as it should be, with 
 no cracks or windows through which the sun can shine, 
 a point of some importance, which is not sufficiently 
 attended to. It is difficult to properly regulate the heat 
 in full day light, but it is even worse if the sun shines 
 in through chinks or windows, so that an open shed is 
 better than an imperfectly inclosed room. 
 
 78. Continuous stirring of the ore is useless, for 
 there is a certain quantity of sulphur to be burned, 
 which requires a certain quantity of air, and there is no 
 use in exposing a fresh surface until that exposed is 
 burned, as far as can be done with the moderate heat 
 allowed at this stage of roasting. The guide is, that 
 the ore must be stirred as soon as it is seen to become 
 dark on the surface. 
 
 79. The draft is regulated so as to cause as much 
 air to enter as is consistent with the required heat; hence 
 the doors on the working side are left open during all 
 the earlier part of the roasting, though it may be nec- 
 cessary to close them during the intervals of stirring, 
 at least on the first hearth, for the finishing at a high 
 heat. Even the back doors may be left ajar at the rear 
 ends, at times, with great advantage, because the ma- 
 
44' SPECIAL DIRECTIONS GOLD. 
 
 terial now under consideration, being nearly half sul- 
 phur, requires an enormous quantity of air, without 
 which it cannot possibly burn, and the more rapidly 
 this is supplied the sooner will the oxidation be com- 
 pleted, bearing in mind, of course, that the proper de- 
 gree of heat must be maintained. At the same time 
 it must be remembered that a high heat at first is an 
 actual disadvantage; the ore roasts faster and better 
 with a low heat, until oxidation is almost complete. 
 
 80. In thus starting a furnace, the roasting of the 
 charge on the second hearth will not make much pro- 
 gress until that on the first is so far advanced that a 
 higher heat may be used, when it also will begin to burn, 
 and must be stirred regularly, so that by the time the 
 first is finished, probably in twenty hours, it will be half 
 roasted, or more, and, when moved to the first hearth, 
 will bear a good heat. The roasting is continued, un- 
 der a gentle heat, as long as the sulphur burns actively, 
 and when a blue flame, or a glow, is no longer perceived 
 on stirring the ore, the heat is gradually increased until 
 it reaches a light red, approaching yellow, if the ore 
 will bear it without melting into lumps, as it will if it 
 consists chiefly of iron or arsenical pyrites. 
 
 81. From what has been said about the burning of 
 sulphur, it is evident that the stirring should be done at 
 progressively shorter intervals until oxidation is com- 
 pleted. Care must be taken to stir quite to the bottom, 
 and in every corner; and it is advantageous to clear the 
 hearth entirely, a part at a time, and leave it so for a 
 few minutes to allow of the oxidation of the thin strat- 
 um of ore which is not moved by the hoe. The stirr- 
 ing is mainly done from the front of the furnace, with 
 
SPECIAL DIRECTIONS GOLD. 45 
 
 the long hoe; but occasionally the roaster goes to the 
 back, and with a small hoe explores the sides and cor- 
 ners within his reach, raking the ore out, and pushing 
 it toward the middle of the hearth. In ceasing for a 
 time to stir the ore, it is better to leave the surface 
 ridged across by drawing the corner of the hoe over it, 
 because the wavy outline thus given exposes a larger 
 surface for. oxidation, or for heating. This, as remarked 
 by Kustel in his valuable work on this subject, is im- 
 portant enough to be attended to. 
 
 82. As the heat, in this kind of furnace, is unavoid- 
 ably greater near the fire than at other parts, the ore 
 must be changed from end to end, so that every particle 
 may, at one time or another, be brought near to the fire- 
 wall, or bridge. This is done by drawing it with the hoe 
 into a ridge along the middle of the hearth, or better, di- 
 agonally across it ; then, with the spade resting on the 
 roller bar as a fulcrum, moving that ore which is far- 
 thest from the fire, near to it, placing it on the empty 
 space on the hearth, and the reverse. As long as 
 sparks can be seen on flirting the ore with the hoe, or 
 pouring it off the spade, the roasting is not perfect, nor 
 does the ceasing of this appearance prove that it is so. 
 
 83. The roasting, under a strong heat, is continued 
 until all the iron sulphate is decomposed, which may be 
 known by taking a little of the ore on a small sampling 
 shovel, and throwing it into a cup containing a little 
 water. In a minute the water will be clear, and if, on 
 adding a few drops of solution of potassium ferridcy- 
 anide, or red prussiate of potash, a blue or green color- 
 ation is seen, the roasting is not perfect. After a little 
 practice, this test may be dispensed with, as the iron 
 
46 SPECIAL DIRECTIONS GOLD. 
 
 sulphate is very easily decomposed. The presence 
 of a little of it is not fatal to the chlorination, but 
 it causes a larger consumption of chlorine. 
 
 84. Copper sulphate, if present, remains after iron 
 sulphate disappears, requiring a long time and a high 
 heat for its complete decomposition, which, however, is 
 not absolutely necessary. It gives, with the ferrid- 
 cyanide, a brown or yellow precipitate, which, in the 
 presence of iron sulphate makes a green coloration by 
 mixing with the blue of the iron. 
 
 85. If it is desired to roast to complete decomposi- 
 tion of copper sulphate, a test is made by washing a 
 small quantity of the ore on a filter, in a glass funnel, 
 with hot water. To the water which passes through 
 the filter is added ammonia, and if even a very little 
 copper is present, a blue color is produced. It will not 
 do, in this test, tp add the ammonia without removing 
 the ore by filtration, because the blue color would then 
 be produced by copper oxide, which remains after the 
 sulphate is decomposed. 
 
 86. When the roasting is finished, a careful pan- 
 ning or horning of a little of the ore will, in general, 
 show the gold plainly ; if not, then grinding finely 
 in a mortar, and panning, should make it visible, at 
 least with a lens. But it happens with some 
 ore that very little of the gold can be seen even in this 
 way, perhaps because of its extreme fineness, causing it 
 to be lost in the most careful washing. No sulphides 
 should be visible, or only a few minute particles which 
 the grinding may have brought out. 
 
 The roasting of the first charge being completed, it 
 i s drawn from the furnace and spread on the cooling 
 
SPECIAL DIRECTIONS GOLD. 47 
 
 floor. The second charge is moved down to the first 
 hearth, and a third is put on the second hearth. The 
 charge now on the first hearth, having been all the time 
 roasting on the second, will, if it has been properly at- 
 tended to, be almost done, and, with a good heat, will 
 be finished in a few hours, while the third, having con- 
 sequently but a short time to roast on the second 
 hearth, will take longer on the first, when moved down, 
 but this irregularity will gradually disappear, and after a 
 few days the charges, if equal in quantity and properly 
 attended to, will remain an equal length of time on 
 each hearth, and the discharges will take place regularly. 
 
 87. A furnace with two hearths, or even with three, 
 does not allow of a continuous strong fire. The heat is 
 reduced each time that a charge is moved down, and 
 not until a strong smell of burning sulphur is no longer 
 evolved by the roasting ore, is the heaL, raised gradually 
 to the finishing point. The great fault of most begin- 
 ners is in using too much heat, especially in the early 
 stages of roasting. A waste of fuel and of time is 
 caused by using a higher heat than is necessary, for the 
 oxidation proceeds faster under a low heat at first, and 
 the ore assumes a better condition for the action of 
 chlorine, being more porous, and lighter. Especially is 
 this the case when lead is present. Even at the finish, 
 too high a heat may melt the gold particles together, or 
 to a spherical form, which is disadvantageous, because 
 of exposing a smaller surface than any other for the 
 chlorine to act upon. The workman must use judg- 
 ment, and acquire experience, before he can roast well, 
 and with the least consumption of fuel. 
 
 88. The roasting of concentrated sulphides, consist- 
 
48 SPECIAL DIRECTIONS GOLD. 
 
 ing chiefly of iron or arsenical pyrites, requires from 20 
 to 30 hours, in a reveberatory furnace with two or three 
 hearths. 
 
 89. The roasted and partially cooled ore is moist- 
 ened, by spraying with water from a hose, the finger 
 being placed partly over the nozzle to spread the 
 stream, or a sprinkler may be employed. To equalize 
 the moisture, the ore is mixed by means of a hoe or 
 shovel. The degree of moisture required varies. If 
 the gold is in very fine particles, the ore is made only 
 so damp as not to dust, and to cohere slightly on being 
 compressed in the hand. If the gold is coarser, more 
 moisture is required, sometimes as much as can be used 
 without making the ore so wet as to settle into a com- 
 pact mass, for it must be loose and porous in the chlo- 
 rinating vats. The use of more water than is neces- 
 sary is disadvantageous, because it causes a greater 
 consumption of chlorine. 
 
 It is beneficial to allow the ore to remain a number 
 of hours, even a day or two, in a moist heap before pro- 
 ceeding further, as this enables the moisture to pene- 
 trate and soften any lumps which may have been 
 formed in the roasting. If this is done, the surface of 
 the heap should be sprayed from time to time, to coun- 
 teract drying, and before charging a vat the ore must 
 be re-examined, to insure its being in the right condition 
 as to moisture. It is next to be placed in the vat. 
 
 90. Charging the Vat. If the filter in the vat is 
 made of sand, on the gravel, and is wet from previous, 
 use, it is advisable to dry it somewhat by laying on it a 
 few hundred pounds of dry roasted ore, which soon be- 
 comes moist by drawing the water out of the sand, 
 
SPECIAL DIRECTIONS GOLD. 49 
 
 whence it will be seen that, if the moistened ore were 
 put in it at once, it would become too wet, and, by pack- 
 ing", would obstruct the passage of the chlorine, causing 
 a back pressure which would force the gas through the 
 water joints of the generator. After the dry ore has 
 been an hour or so in the vat, and has become damp^ 
 it is removed, and the charging is proceeded with. If 
 only gravel and burlap are used on the perforated false 
 bottom, for a filter, this precaution is not needed, and 
 time is saved. 
 
 91. When charging a vat for chlorination, the dis- 
 charge pipe is stopped with an oiled plug, and hung up, 
 and the moist ore is sifted into the vat. The lumps 
 which are retained by the sieve, are removed from time 
 to time, to be afterwards recrushed, with rollers or 
 otherwise, and returned to the roasting furnace. Any 
 scraps of iron which may have found their way into the 
 ore, and which would be very detrimental to the chlori- 
 nation, are removed by the sifting. As the ore cannot 
 be spread evenly over the filter by the sifting, and as it 
 packs a little where it falls, it is distributed and loosen- 
 ed with an iron rake. The vat is filled to within four 
 inches of the top, and the ore is very slightly packed 
 around the side, by pressing it with the hand, so that 
 the chlorine cannot make its way between it and the 
 staves, but is forced to permeate the entire mass. 
 
 92. Chlorination. Time may be saved by starting 
 the chlorine generator as soon as the vat is about half 
 charged, as the filling will be completed before the gas 
 can reach the surface. 
 
 The progress of the chlorine is watched, after 'the 
 charge of ore is in, by making a few little excavation 
 
50 SPECIAL DIRECTIONS GOLD. 
 
 and holding therein a glass rod dipped in am- 
 monia, which instantly shows the presence of chlo- 
 rine by a dense white fume. The moist stopper 
 of the ammonia bottle may be used instead of a 
 glass rod. As soon as the chlorine has risen to within 
 a few inches of the surface of the ore r the holes are 
 lightly filled, and the cover is let down into its groove, 
 or rabbet, and luted with a paste made of clay and sand, 
 in such proportions as not to crack in drying; or the 
 luting is kept moist by placing wet cloths on it. The 
 plug hole in the cover is left open until the vat is quite 
 filled with chlorine, as shown by the fume when ammo- 
 nia is held to the hole, which is then tightly plugged. 
 
 If at this time the chlorine generator is not required 
 for another operation, and if the evolution of gas has 
 become so slow that it only bubbles through the wash 
 bottle at intervals of many minutes, it is well to leave it 
 connected with the vat ; otherwise it is disconnected, 
 the lead nipple in the vat is plugged, or the vent pipe 
 connected, and the chlorine pipe is either applied to 
 another vat, or the end is passed out of doors. The 
 vat is now left undisturbed for from 12 to 40 hours, to 
 allow the chlorine to act on the gold. 
 
 When two or more vats are impregnated at one time, 
 the forked lead pipe is used, the flow of chlorine to each 
 vat being controlled by a pinch-cock, for which a clothes 
 pin answers very well, applied on the rubber part of the 
 branch pipe ; or a lead pipe may be laid alongside of 
 the vats, with a nipple and lead faucet to connect with 
 each of them by a short piece of rubber tube. 
 
 93. Leaks in any part of the apparatus are easily lo- 
 cated by the aid of ammonia, as above explained, and 
 
SPECIAL DIRECTIONS GOLD. 51 
 
 the operator's nose should be excused from this duty, 
 or serious consequences may follow. Leaks in pipe- 
 joints can usually be stopped with oil or lard, and those 
 in the vat-cover with a paste of oil and sand, or earth. 
 The charging of a vat accupies from one to two hours, 
 as the sifting is very tedious. 
 
 94. Making Chlorine. To produce enough chlorine 
 for three or four tons of roasted ore, the charge for the 
 generator is about: 
 
 Manganese 30 pounds 
 
 Salt . . ." 40 
 
 Water 36 
 
 Sulphuric acid of 66 Beaume 7o " 
 
 Or the same of salt and manganese, 
 
 Water 32 
 
 Acid of 63 Beaume 74 
 
 The cleaning out pipe of the generator being securely 
 plugged, the salt, manganese, and water may be put in 
 at any time, and stirred with a wooden paddle. The 
 acid is weighed or measured, and kept at hand in a 
 vessel of lead, or enamelled iron, though the enamel 
 generally soon peels off. The naked iron does very 
 well for strong acid. The cover of the generator 
 being let down, the water joints all filled, and the pipes 
 connected, a fire is made in the fire-place, or steam is 
 turned into the heater, to warm the apparatus some time 
 before the chlorine is wanted. 
 
 When all is ready for the chlorine to enter the 
 vat, a portion of the acid is poured into the 
 generator through the funnel, and mixed by turning the 
 stirrer. Chlorine soon begins to pass, and can be seen 
 in the wash bottle by its greenish color. It must pass 
 
52 SPECIAL DIRECTIONS GOLD. 
 
 in a lively stream through the water, and when the 
 current slackens, more acid is put in until the whole is 
 used. 
 
 From time to time the stirrer is turned carefully. 
 Sometimes it must be lifted a couple of inches before 
 the impacted stuff can be loosened, and this is the 
 reason why the water joint in this part is made two 
 inches deeper than in the others ; otherwise the lifting 
 of the stirrer might cause an escape of gas which 
 would be injurious, and might be dangerous, to the 
 workman. During the operation the apparatus is 
 gradually heated, but not so as to make the contents 
 boil. 
 
 By the time the charge is exhausted the test by 
 means of ammonia should indicate an abundance of 
 chlorine issuing from the holes in the vat covers. If 
 this is not the case, more manganese and salt must 
 be put into the generator, through the opening pro- 
 vided for that purpose, but, as the workman is liable to 
 suffer serious inconvenience from the escaping gas 
 while doing this, it is better to avoid the necessity by 
 putting in enough at first. If an additional quantity of 
 the other materials is used, more acid will also be re- 
 quired, unless an excess was taken for the charge, but 
 this can be introduced without inconvenience by means 
 of the pipe and funnel. The relative proportions of the 
 materials vary according to their purity, and the quan- 
 tity of chlorine required depends much on the character, 
 and more or less perfect roasting, of the ore ; hence no 
 fixed rule can be given for either. 
 
 95. When it is desired to prepare the generator for 
 another operation, the end of the rubber tnbe leading 
 
SPECIAL DIRECTIONS GOLD. 53 
 
 from the wash bottle is passed out of doors, or con- 
 nected with a charged vat. Water is poured into the 
 water chamber, b, and passes to the interior of the 
 generator through notches cut in the lower edge of 
 the cover for that purpose, and fills it, expelling all 
 gaseous chlorine, which would otherwise escape into 
 the room on raising the cover, or removing the plug at 
 d. The water is allowed to stand for some time in the 
 generator, to dissolve the sodium sulphate formed by 
 the action of sulphuric acid on salt, which sometimes 
 forms a hard incrustation, if too much heat has been 
 applied. The plug at d is then withdrawn, and the 
 generator is emptied through the pipe, which should 
 deliver out of the room. 
 
 If there is any impacted residue which cannot be re- 
 moved by a stream of water from a hose, directed 
 through one of the openings, the main cover is raised 
 and the stuff carefully scraped off the bottom, but if 
 not, the recharging can be done by the opening, k, with- 
 out raising the cover. If the residue contains much 
 unchanged salt, the proportion used should be reduced. 
 An excess of manganese shows itself by its blackness. 
 When the ingredients have been correctly proportioned, 
 only a dark grey sediment remains with the more or 
 less acid liquid. 
 
 96. Leaching the Gold Ore. After the ore is sup- 
 posed to have remained long enough in contact with 
 chlorine that is, from 12 to 40 hours the plug hole 
 in the cover is opened, and tried with ammonia as be- 
 fore. This must still produce a dense fume ; if not, the 
 chances are that a poor result will be obtained in leach, 
 ing, unless chlorination is repeated. If appearances 
 
 4 
 
54 SPECIAL DIRECTIONS GOLD. 
 
 are satisfactory, a little ore is taken out through the 
 hole with a sampler, finely ground, and carefully washed 
 in a saucer, or a horn. Neither gold nor sulphides 
 should be visible with a lens, but, as before remarked, 
 some ores do not show the gold well, even before chlo- 
 rination, and for such this test is not conclusive. 
 
 97. At this point a difficulty arises, from the fact 
 that a large quantity of chlorine remains in the vat, the 
 escape of which into the leaching room is not desirable. 
 If the cover of the vat be raised, the gas is visible like 
 a green sea above the ore ; a pestilential sea whose 
 waves, surging forth upon the slightest disturbance of 
 the air, threaten to envelope and suffocate the work- 
 man, unless he hold his breath while hoisting the cover 
 and fastening the tackle, and then retreat in haste till 
 the storm is over ; and even then the same trouble re- 
 curs while water enters, and displaces the chlorine still 
 remaining beneath the filter, and permeating the loose 
 mass of damp ore. 
 
 To overcome this difficulty, some operators fill the 
 vat with water before lifting the cover, and, by means 
 of a rubber hose, convey the expelled gas, either out of 
 doors, or into another vat charged with ore. There 
 are two objections to this plan firstly, a great deal of 
 chlorine is absorbed by the water, which has an un- 
 favorable effect in the precipitation of gold, making it 
 more difficult to settle, as well as wasting the precipi- 
 tant ; and, secondly, the water, entering the tub in one 
 large stream, descends through the bed of ore at one 
 point, and rises through it in other parts, giving a solu- 
 tion of nearly uniform strength throughout the mass, 
 and requiring a large quantity of water to complete the 
 
SPECIAL DIRECTIONS GOLD 55 
 
 leaching, taking more time, and giving finally a weaker 
 solution than is necessary, for the precipitation takes 
 place better when the solution is strong. 
 
 The best way to apply the water is by spraying it all 
 over the surface of the ore in the vat, so that, percolat- 
 ing downward through the mass, it carries the greater 
 part of the gold chloride in the first portion of the 
 water, and a rich solution is obtained at once, while 
 less water is required to remove the whole of the gold, 
 and the stronger solution thus finally obtained gives a 
 better precipitation on addition of iron sulphate. But 
 if the spraying is undertaken by hand with a sprinkler* 
 the loose ore, settling as it becomes wet, expels chlorine 
 in such volumes as to render it impossible for a man to 
 stand near the vat. 
 
 The course I adopted was to place a coil of lead or 
 rubber pipe, in which were numerous small holes, around 
 the vat under the cover. After raising the cover, the 
 water supply pipe was connected with the perforated 
 coil, and the water, under moderate pressure, issued in 
 a number of fine jets, and showered all over the ore, 
 through which it descended gradually, dissolving the 
 gold chloride as it passed, so that the first solution which 
 passed through the filter, and filled the space under it, 
 was very rich, while that which finally remained on the 
 top was very weak. The discharge was then started, 
 and the water thenceforth admitted in the usual way, 
 keeping the surface of the ore covered until the leach- 
 ing was finished. This plan, however, is still open to 
 the objection that it gives a solution containing much 
 free chlorine, while the chlorine which is expelled is 
 not removed from the room ; hence it is very desirable 
 
56 SPECIAL DIRECTIONS GOLD. 
 
 that means should be used to abstract the surplus from 
 the vat before raising the cover, or admitting water. 
 The appliance I am about to describe will not only do 
 this, but will also save the chlorine, for use in another 
 charge of ore, with little waste. 
 
 98. Before lifting the cover, the plug-hole being 
 open, one of the lower openings, either the nipple 
 through which the gas was admitted, or the discharging 
 pipe, is connected by a rubber hose with the interior o* 
 an inverted bell of sufficient size, which is immersed in 
 a tank of water, precisely like the "gasometer" of gas- 
 works, and like it, counterpoised and suspended by 
 ropes or chains passing over rollers, so as to allow the 
 bell to rise or fall in its water tank. By adding 
 weights to the counterpoise, the bell is gradually raised, 
 and the chlorine is withdrawn from the vat and enters 
 the bell, while air, entering the vat through the open 
 plug-hole in the cover, replaces the abstracted chlorine. 
 The filling of the vat with water is then proceeded with 
 in any way that may be convenient, without annoyance 
 from escaping chlorine. The chlorine in the bell may 
 be again expelled when wanted, and caused to enter the 
 same, or another vat, by simply removing a part of the 
 counterpoise, and allowing the bell to descend by its 
 own weight. 
 
 When the ore in the vat is covered by the water, the 
 discharge pipe is let down to the trough which leads to 
 the gold tub, and the plug is removed from it. To pre- 
 vent disturbance of the ore by the water flowing into 
 the vat, the stream is received on a perforated board, 
 or on a sack laid upon the ore. The inflow and the 
 outflow must be equal, so that the ore remains sub- 
 
SPECIAL DIRECTIONS GOLD. 57 
 
 merged. If the outflow is too rapid, it is lessened by 
 simply " kinking" the pipe, which, for this reason, is of 
 pure rubber, and long enough not only to reach the 
 trough, but a foot or so more ; it can then be " kinked" 
 so as to entirely stop the flow if desired. 
 
 99. A few ounces of the strong solution of gold 
 chloride first obtained, are set aside for a purpose which 
 will shortly appear. If the ore contains no copper, 
 and has been properly roasted, the lixivium will be of 
 an amber color. A green hue indicates the presence 
 of copper, and a very dark, almost black, appearance, 
 produced by iron perchloride, shows that the ore has 
 been improperly roasted. 
 
 100. Precipitating the Gold. On beginning the 
 leaching, about a dozen gallons of the solution of iron 
 sulphate is let into the gold tub (for exceptions see 
 article on precipitating gold, under " Addenda.") The 
 gold is precipitated as a brown powder, which, how- 
 ever, requires many hours to settle. The object of 
 putting the precipitant into the gold tub in advance, is 
 to decompose the gold solution, and precipitate the 
 gold, as soon as it enters the tub, so as to lessen the loss 
 by absorption into the wood, by an accidental leak, or 
 an overflow ; also to neutralize the free chlorine in 
 the lixivium. 
 
 101. When the solution flowing from the leaching 
 vat has become colorless, or before, if much copper is 
 present, a little of it is received from the hose in a 
 glass vessel, such as a beaker, tumbler, or ore sample 
 bottle, and some solution of iron sulphate is added. If 
 gold is present, a dark cloud is produced, either instant- 
 ly or after the lapse of a few seconds. When only a 
 
58 SPECIAL DIRECTIONS GOLD. 
 
 slight discoloration is produced in the lixivium, by the 
 addition of iron sulphate, it is better to divert the 
 stream into one of the extra gold tubs, or " gold wash- 
 tubs," because the metal obtained from very weak lixiv- 
 ium is so extremely fine as to settle with difficulty, and 
 even to pass through a filter. The leaching is contin- 
 ued until not a trace of gold can be detected in the 
 lixivium coming from the vat. 
 
 102. I will here call attention to a circumstance 
 which was observed in my wwks. After the leach 
 ceased to show gold by the iron sulphate test, if the 
 discharge was stopped for a few minutes, and again 
 started, the solution would again give a considerable 
 precipitation on being tested, but in a few minutes 
 would again fail to show even a trace, and this could be 
 repeated several times. It was due to unequal percola- 
 tion, and is mentioned here in case the same might 
 occur in other works. 
 
 103. The solution in the gold tub is well stirred 
 with a wooden paddle, and, after waiting for a few min- 
 utes, to allow the gold to settle a little, a sample is taken 
 in the glass, and tested by adding some iron sulphate. 
 If any discoloration is produced, more iron sulphate is 
 needed in the tub. If none, yet, as an excess does no 
 harm, it is best to make sure that there is enough of the 
 precipitant, by emptying the glass, rinsing it once or 
 twice with the liquid from the gold tub, taking another 
 sample, and testing it by adding some of the strong 
 solution of gold, which, it will be remembered, was 
 set aside at the beginning of the leaching. If a dark 
 cloud is now produced, it is certain that enough of 
 the iron sulphate has been used in the gold tub. If 
 
SPECIAL DIRECTIONS GOLD. 59 
 
 not, 'it is safest to add another bucketful, mix thor- 
 oughly, and try again. By taking the trouble to make 
 this check test, an expensive accident may be avoided. 
 
 104. The gold settles better if the stirring is re- 
 peated after an hour or two, and it is advantageous to 
 add a few pounds of sulphuric acid. If, in stirring, a 
 circular motion is imparted to the liquid, nearly all the 
 gold will settle near the middle of the tub. The gold 
 requires from 24 to 48 hours to settle. 
 
 105. The weak leach in the wash-tub may be treated 
 with some of the iron sulphate, to throw down the small 
 quantity of gold which it contains, which must then be 
 allowed abundant time for settling; or it may be raised 
 by means of a wooden or leaden pump, and used to 
 begin the leaching of the next charge of ore. A third 
 way, which suggests itself, but has not been tried, ex- 
 cept, as will be seen hereafter, in connection with the 
 extraction of silver, is to precipitate the gold, together 
 with any remains of copper, etc., which may be present f 
 by an addition of calcium polysulphide, the preparation 
 of which will be described in its place. A great excess 
 of the precipitant should be avoided, because the gold 
 tersulphide which it produces is somewhat soluble in 
 calcium polysulphide. The precipitate obtained in this 
 way would probably settle more rapidly than the other. 
 
 106. Iron Sulphate Solution. This precipitant for 
 gold may be prepared by dissolving common copperas, 
 or green vitriol, in water. A quantity of the crystals is 
 placed in the vat prepared for it, which, it will be remem- 
 bered, contains a filter, and water is added. There should 
 always be an excess of copperas on the filter, in order 
 that the solution may be saturated. It may also be 
 
60 SPECIAL DIRECTIONS GOLD. 
 
 prepared by dissolving scrap iron in diluted sulphuric 
 acid. Several days must be allowed for the preparation 
 of the solution by this method, and an excess of iron 
 must always be present in the dissolving tub, the sup- 
 ply of solution being maintained by the addition of 
 dilute acid from day to day, and of iron as fast as it 
 disappears. 
 
 107. When the liquid in the gold tub has become 
 perfectly clear, the discharge pipe is freed, with its 
 float, and the liquid is allowed to flow through a 
 filter of sand or sawdust, because some fine gold 
 always remains in suspension, even after 48 hours' 
 settling. If a sand filter is used, it is, after a time, 
 taken up and chlorinated, like ore. If if is of saw- 
 dust, it is thrown into the furnace with ore, and burned, 
 or burned by itself and the ashes collected. 
 
 If the discharge pipe of the gold tub does not sink 
 deeply enough to draw, a piece of board is laid over it, 
 which keeps it below the surface, and follows it down. 
 If it tends to draw too deeply, by being sucked down, a 
 larger float should be used; or a cord attached to the 
 float, and turned around a nail in the side of the tub, 
 will secure it ; but it is then necessary to slacken the 
 cord from time to time. If the hose is rather stiff, and 
 well adjusted, it will give no trouble. The construction 
 of the float, encircling the end of the hose with a thick, 
 ness of two inches of wood, obviates all danger of a loss 
 of the precipitated gold by drawing too near the bot- 
 tom of the vat. Other arrangements for drawing off 
 the liquid will be found under "Addenda." 
 
 108. Collecting the Gold. Unless when working 
 very rich ore, or for special reasons, the gold is not re- 
 
SPECIAL DIRECTIONS GOLD. 61 
 
 moved from the tub until several precipitations have 
 been made. When a clean-up is desired, the liquid is 
 drawn off as closely as may be done without loss of gold 
 as described ; the remainder, with some of the gold, is 
 allowed to flow through the faucet into a small tub. 
 The greater part of the gold remains on the bottom of 
 the precipitating tub, and is taken up with a scoop, and 
 carried in a suitable vessel, such as an enamelled 
 kettle, to the filters. The bottom of the gold tub is 
 washed by means of a small stream of water from a 
 hose, and a whisk broom. The washings are added to 
 the drainings in the small tub, and are either allowed to 
 settle again, and again drawn off, or taken at once to 
 the filters. 
 
 109. Washing the Gold. When drained in the fil- 
 ters, the gold, if nearly clean, which is known by its 
 having a brown color, not too dark, may be washed at 
 once on the filter, with hot dilute sulphuric acid and 
 salt, or dilute hydrochloric acid, and afterwards with 
 hot water alone ; if very impure, it is transferred 
 to a large porcelain dish, and boiled on a sand bath 
 with slightly diluted acid. After adding water, it is 
 again thrown on the filter, drained, and washed with hot 
 water until the latter comes through tasteless. The 
 filter bags, to which some gold adheres, are kept under 
 water in a suitable vessel, to prevent rotting, until 
 wanted again. When worn out, they are lightly 
 sprinkled with powdered nitre, dried in an iron dish, 
 and touched with a live coal. They then burn like 
 touchpaper, and the ashes are added to the precipitated 
 gold. Too much nitre must not be put on the bags, 
 
62 SPECIAL DIRECTIONS GOLD. 
 
 or the combustion will be too violent, and gold may 
 be lost. 
 
 110. Drying the Gold. The washed gold is pressed 
 by hand in the filter bags, transferred to an iron dish, 
 and almost, but not completely, dried. While drying 
 it is mixed with a little powdered borax and nitre. If 
 several ounces of nitre are used, on account of impuri- 
 ties in the gold, it is advisable to add about half as much 
 clean quartz sand, to protect the crucible from the 
 action of the nitre during the subsequent melting of the 
 metal. The purpose of allowing the pulverulent metal 
 to retain a little moisture is, the prevention of loss by 
 dusting while putting it into the melting pot. 
 
 111. Melting the Gold. If the gold is very clean, 
 it may be melted in a black lead pot, but I have always 
 preferred a sand pot, on account of the tendency of 
 plumbago to cause contamination of the gold by reduc- 
 tion of the base metal compounds which may be pres- 
 ent. There is, however, some slight risk of the sand 
 pot breaking, nothwithstanding the precaution of adding 
 sand with the nitre, and well drying the pot before put- 
 ting it into a moderate fire. To guard against being 
 obliged to wash the gold out of the ashes in case of 
 breakage, with some risk of loss if the bottom of the 
 ash-pit is rough, a black lead dish, made of the lower 
 part of a crucible, is placed under the sand pot. 
 
 112. The fuel used for melting is charcoal or coke. 
 English coke is so much better than that from the gas 
 works as to compensate for the extra cost. A common 
 portable assay furnace is very suitable for the melting 
 of moderate quantities of gold, and a sand pot about 
 ten inches high is large enough for several thousand 
 
SPECIAL DIRECTIONS- -GOLD. 63 
 
 dollars worth, although a larger crucible is needed than 
 for metal which is in a more compact form. 
 
 113. When the crucible is red hot, it is taken from 
 the furnace and gently tapped, to ascertain that it is 
 sound, then filled with the gold, by means of a scoop, 
 replaced in the furnace, covered, and gradually brought 
 to a strong red heat. As the partly melted gold settles* 
 the pot is refilled, without removal from the furnace, 
 by means of the scoop, and, if required, a sheet iron 
 funnel. It is important to refill the pot before the con- 
 tents are quite fused, and while they are in a pasty condi- 
 tion; otherwise some of the gold may be thrown out of the 
 crucible. The handling and melting of the gold are 
 greatly facilitated if the precipitated metal is pressed 
 into cakes, and heated to redness in a muffle, as is done 
 in the mint with the finely divided gold from the refin- 
 ing. When the entire charge is in, a white heat is 
 maintained until the gold and slag are thoroughly 
 melted. An addition of more borax may be required 
 if the sla is not sufficiently fluid. The mass is stirred 
 
 o J 
 
 with a red-hot iron rod, which must not be kept in too 
 long, or it will make the gold base. Some metallurgists 
 use a strip of black lead for the purpose. 
 
 114. When the slag is quite liquid, it is skimmed off 
 the melted gold, by means of a piece of nail rod, which is 
 turned at one end to a flat spiral, and bent to a suitable 
 angle for convenient use. This is dipped, cold, into the 
 melted slag, quickly withdrawn, and pressed upon a cold 
 block of greased iron, so as to flatten the adhering slag, 
 then just dipped into cold water, and again into the slag, 
 repeating the routine until the latter is all removed, and 
 the melted gold is seen in the pot. 
 
64 SPECIAL DIRECTIONS GOLD. 
 
 115. It sometimes happens that the precipitated 
 gold is contaminated by lead sulphate, which cannot 
 readily be removed in the washing, and which) 
 does not mix with the slag proper. This cannot 
 be skimmed off in the manner described, but is re- 
 moved by means of a red-hot scorifier held in the tongs. 
 
 116. If the melted metal is pure, it appears greenish 
 and motionless, but if any base metal remains, colored 
 rings, or spots, are seen, moving from the center out- 
 wards. These rings are base metal oxides, and if they 
 are supposed to be caused by iron, or copper, a few 
 pieces of borax are thrown in, and allowed to melt 
 while the pot is left uncovered. After a time the new 
 slag thus formed is skimmed off, and more borax put in, 
 and, if the metal is very impure, a little nitre is added 
 to help the oxidation of the base metal, for if the opera- 
 tion takes too long a time, the pot will be cut imme- 
 diately above the gold. If the impurity consists of lead, 
 a little bone ash is better than borax to absorb the 
 oxide, as it is formed, especially when a black lead pot 
 is used. 
 
 117. When all is ready, the pot is seized by the 
 tongs and the metal is poured into a cast-iron ingot 
 mould, which has previously been warmed and smoked, 
 or oiled. A little oil is poured on the top of the bar 
 before it solidifies. Unless the gold is to be assayed 
 and stamped at the works, it is not necessary to be care- 
 ful about the shape or appearance of the bar. It is 
 then as well, and saves some trouble, to allow the metal 
 to cool in the pot, which is then broken; in any case 
 it can be used but once. But this cannot be done 
 if a black lead pot is used, because it will serve many 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 65 
 
 times. The slag and pots are preserved, and either 
 sold, or crushed and treated with quicksilver for the 
 gold which they contain. 
 
 118. B. Concentrated Pyrites Containing Gold and 
 Silver. This material is obtained in the same manner 
 as the concentrations containing gold only. The silver 
 is usually of secondary importance as to its value. 
 
 119. Roasting. - -This is conducted in the same 
 manner as that for gold, but as the chlorination of the 
 silver in the vats, by means of cold chlorine, does not 
 give satisfactory results, it is better to form the silver 
 chloride in the furnace, for which purpose an addition of 
 salt is necessary. One per cent., or 20 pounds to the 
 ton of ore, is generally enough for fifty ounces of silver. 
 In some cases the salt is mixed with the ore when 
 charged, but this is not always safe, as a very large loss 
 of gold sometimes results. 
 
 120. If it is found, by means of assays, that a loss 
 results from charging the salt with the ore, the course 
 adopted is, to roast as directed for gold, then to let the 
 ore cool somewhat in the furnace, and throw in 
 the salt through one of the doors, scattering it as 
 much as possible over .the ore. The doors are then 
 closed until the salt ceases to crackle, after which it is 
 rapidly and vigorously mixed with the ore by means of 
 the hoe, and the charge is drawn out within 20 minutes 
 after putting in the salt. The heat must be high enough 
 to cause the reaction between salt the and the metal 
 sulphates, yet not so high as to produce heavy fumes, 
 or blue flames ; nor should a yellow substance be seen 
 on the side of the furnace, where the ore is drawn out. 
 The hot ore evolves copious fumes of volatile chlorides 
 
66 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 and free chlorine. It is not spread at once, but is left 
 in the heap to be acted upon by the gases for an hour, 
 after which it is spread on the cooling floor. 
 
 121. The best results are produced by adding to 
 the ore, before roasting, a little more salt than the quan- 
 tity required by theory to chloridise the silver present ; 
 that is, for fifty ounces of silver not more than two or 
 three pounds of salt, which should be finely ground. 
 The one per cent, should be added at the finish as 
 above. The use of a little salt at the beginning in this 
 way caused no blue flames of copper chlorides, heavy 
 fumes, nor loss of gold, while it caused an increase in 
 the yield of silver amounting to three or four ounces to 
 the ton. It was not proved whether the result would 
 have been' the same if the final addition of one per cent 
 of salt had been omitted, as it could do no harm, and 
 cost almost nothing. But when no salt whatever was 
 used, the result was unsatisfactory, and considerably 
 more chlorine was required in the vats. 
 
 Ores differ much in their behavior in working, and 
 without the cause of the difference being manifest, even 
 from an analysis. Thus there are cases in which ten 
 per cent of salt has been mixed with the ore before 
 roasting, without causing a loss of gold. It therefore 
 behooves the operator not to rely solely on the instruc- 
 tions given in any book, but to watch his results carefully 
 and constantly, until he has established a satisfactory 
 mode of procedure. 
 
 122. After roasting, the work is carried on precisely 
 as directed for ore containing no silver, up to the point 
 at which the gold leaching is finished, except that it is 
 not necessary to extract the last trace of soluble gold 
 
67 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 with water, because, if a little remains, it will be ob- 
 tained with the silver. It is, however, proper to re- 
 mark that, if the ore is of such a character that much 
 salt must'not be used at the commencement of the 
 roasting, the lumps from the sifting should be washed, 
 to remove soluble chlorides, before being re-roasted. 
 
 123. Leaching the Silver. At this point some oper- 
 ators remove the ore to other leaching vats, from an 
 idea that the small quantity of the leaching liquid used 
 for silver which remains in the filter, is injurious to the 
 chlorination of the next lot of ore. I do not think it 
 worth while to take this trouble. I even found it un- 
 necessary to take any special pains to wash the filters 
 before recharging, any further than is done in washing 
 the hypo out of the ore, which is necessary in order to 
 avoid waste.- The traces of hypo remaining, if not oxi- 
 dized to harmless sulphate by the action of air, must be 
 so, instantly, on the admission of the chlorine. It is 
 true that in the latter case hydrochloric acid would be 
 formed, but in such minute quantity as to be of no im- 
 portance. At the worst the only inconvenience would 
 be a slightly increased consumption of chlorine. 
 
 When the gold leaching has been carried as far 
 as is desired, the water in the vat is allowed to subside 
 below the surface of the ore. The solution of calcium 
 hyposulphite is then admitted, and the discharge is 
 directed into one of the extra silver or wash tubs. 
 
 It is best to have a separate trough to convey the 
 silver solution to the tubs, not only because it is con- 
 venient to have the gold and silver tubs at opposite 
 ends of the set of leaching vats, but also because it is 
 often necessary, when working several vats, to run both 
 
68 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 gold and silver solution at the same time. I therefore 
 have two troughs, extending in front of and below the 
 leaching vats, side by side, but inclined in opposite 
 directions, so as to lead, the one to the gold, the other to 
 the silver tubs. 
 
 The hypo should never be allowed to flow into the 
 gold tubs, because it forms a combination from which 
 the gold cannot be precipitated by iron sulphate. As, 
 however, the precipitant used for silver throws down 
 gold also, whether dissolved in water or in hypo, there 
 is not the least danger of losing any gold which may 
 find its way to the silver tubs. 
 
 124. As the water runs out of the ore mass in the 
 vat, the hypo follows it, and as soon as- a sweet taste, 
 indicating the presence of silver, is perceptible, the 
 stream is turned into the main silver tub, because 
 the -wash water, after precipitation of any metal it 
 may contain, is thrown away, but the hypo is preserved 
 for future use. The flow is not allowed to be too rapid, 
 but is checked by "kinking" the pipe, as directed in the 
 gold leaching. There is no guide for this but experience, 
 and the strength of the silver solution coming from the 
 ore, which is known by its more or less sweet taste. 
 
 125. When a sweet taste is no longer perceived in 
 the solution coming from the vat, a test is made by 
 t aking some of it in a glass, and adding some solution 
 of calcium sulphide. If a precipitate is produced, it is 
 certain that metal of some sort is still being extracted 
 from the ore. The question then is, what metal, or 
 rather whether there is any, or much, silver, for it is 
 an unfortunate circumstance that the hypo dissolves 
 lead sulphate, and other base metal compounds, es- 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 69 
 
 pecially after the extraction of silver is finished, or when 
 the hypo is too strong. 
 
 Some idea of the nature of the metal which is 
 being extracted by the hypo, may be obtained from 
 the color of the precipitate. Silver gives a dark brown ? 
 copper a reddish brown, lead and antimony light, 
 sometimes yellowish shades. It is, however, often 
 impossible to say, from the appearance of the precip- 
 itate, whether it contains silver or not, and the sweet 
 taste, when it is no longer strong, may be masked 
 by other and less agreeable flavors. I have not been 
 able to find a very simple test for the presence of 
 silver in this case, but I will give the one I use, 
 which can be" made in ten minutes. 
 
 126. The precipitate in the glass is stirred, or 
 shaken, to make it curdle, allowed to settle for a few 
 seconds, and a portion of the liquid is poured off; the 
 remainder, with the precipitate, is heated in a small 
 porcelain dish. The precipitate blackens, shrinks, and 
 settles, so that nearly all of the liquor can be poured 
 off without much loss of precipitate. A little nitric 
 acid, and a fraction of a grain of salt, are then added, 
 and heat is again applied. The action is very rapid, 
 and in a few seconds nothing remains of the black 
 precipitate but a yellow mass, principally sulphur, but 
 possibly in part silver chloride. To prove this, ammo- 
 nia is added, very cautiously unless after cooling and 
 diluting, until the contents of the dish smell strongly 
 of it. 
 
 If copper is present, it gives a blue color; silver 
 chloride is dissolved in the ammonia, which is then 
 poured upon a filter, and to the liquid which passes 
 
70 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 through, and is received in a test tube, nitric acid is 
 added, drop by drop, while the test tube is inclined 
 away from the operator's eyes, until the smell of am- 
 monia is no longer perceptible. If there was any silver 
 in the precipitate, it now appears as a white cloud of 
 chloride, which curdles on being shaken, or, if in very 
 small quantity, as a slight milkiness in the liquid. A 
 little practice will enable the operator to judge as to 
 whether it is worth while to continue the leaching, or 
 not. 
 
 127. When the quantity of silver in the leach is incon- 
 siderable, the hypo is turned off, but, as it is not to be 
 wasted, water is again led into the vat as soon as the 
 ore is uncovered, to displace the hypo which would 
 otherwise be retained. As soon as it is found, by the 
 taste, that the hypo is almost washed out, and nearly 
 pure water begins to come, the stream is turned into 
 one of the wash-tubs, and the influx of water to the 
 vat is stopped. The ore is allowed to drain, to facili- 
 tate which it may be dug over with a shovel. It is 
 then removed. 
 
 128. The leaching of a charge occupies from eight 
 to forty-eight hours, according to the richness and 
 character of the ore, and the skill displayed in the 
 roasting. 
 
 129. Precipitation of Silver. The silver is precipi- 
 tated by means of a strong solution of calcium poly- 
 sulphide, called, in the works, simply "calcium," or 
 " sulphide," which is led into the silver tub, by a hose 
 from the elevated vat in which it is kept. It throws 
 down the silver, and other metals, as sulphides, in the 
 form of a dark brown mud, which soon turns black. 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 71 
 
 At the same time it restores the hypo, which was 
 altered in dissolving metals, so that it can be used 
 again. 
 
 It is imperative that not more of the calcium 
 sulphide be used than the quantity required to precipi- 
 tate the metals. If a little silver remains in the so- 
 lution, it is not lost, as the hypo is used again; therefore, 
 it is best to add a little less of the calcium sulphide than 
 would be required to precipitate the whole of the 
 metal. If too much is used, the excess remains un- 
 changed, and mixed with the hypo, in the re-use of 
 which it converts some . of the silver chloride in the 
 ore into sulphide, which cannot be leached out. 
 
 In practice it is not difficult to precipitate aright. A 
 circular motion is given to the solution in the silver 
 tub, the stream of calcium sulphide is turned in, and 
 allowed to run as long as it is seen to cause a distinct 
 precipitation. The liquor is then stirred, thoroughly 
 and vigorously, for a couple of minutes. The circular 
 motion is checked by a reversed movement of the 
 stirrer; a few minutes are allowed for partial settling, a 
 sample is taken in a glass, and a little calcium sulphide 
 added. If a considerable precipitate is produced, a few 
 more gallons of the precipitant are run into the tub, 
 and the stirring and testing are repeated. When the 
 calcium sulphide produces only a very slight precipita- 
 tion, the contents of the silver tub are left undisturbed 
 for a few hours. 
 
 130. If, in the test, calcium sulphide gives no pre- 
 cipitate, it may be that too much has been used in the 
 tub ; therefore another sample is taken, and tested by 
 adding a few drops of solution of iron sulphate, which 
 
72 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 instantly gives a black precipitate if there is the least 
 excess of calcium sulphide. If neither of the tests 
 gives a precipitate, all is right ; but if it is found that 
 too much calcium sulphide has been employed, it must 
 be counteracted by an addition of silver solution from 
 another vat, or, if there is none to be had, some iron 
 sulphate may be used instead. There is, however, no 
 trouble if care be used. The experienced workman 
 knows almost the exact moment when enough calcium 
 sulphide has been added, by a white cloudiness which 
 appears in the liquor. 
 
 The precipitate settles in a few hours, and the reno- 
 vated hypo is drawn off, by means of an arrangement 
 similar to that used in the gold tub, and pumped into 
 the elevated tank, whence it is again led to the leaching 
 vats as required. 
 
 131. If, when the leaching of a vat is finished, a 
 dark scum is seen on the surface of the ore, it is taken 
 off and returned to the roasting. It is caused by a 
 small quantity of metal sulphide, which remained sus- 
 pended in the hypo when it was drawn from the silver 
 tub, and is thus filtered out by the ore. It contains 
 more or less silver. 
 
 132. The metal contained in the weak solution in 
 the wash-tubs, is also precipitated by means of calcium 
 sulphide, but, after the settling, the liquid, which is little 
 more than water, is allowed to run to waste. The 
 metal should be completely precipitated, because, as 
 the liquid is not used again, any which might remain in 
 solution would be lost. An excess of the precipitant 
 can do no harm in this case. 
 
SPECIAL DIRECTIONS -GOLD AND SILVER. 73 
 
 133. Collecting the Precipitate. After several pre- 
 cipitations, or when desired, the black mud, consisting 
 of silver sulphide, mixed with free sulphur, and more 
 or less base metal sulphide, is run out through the 
 clean-up pipe, faucet, or plug-hole, to a filter, drained, 
 washed by passing hot water through it, again drained, 
 pressed into cakes or not, as desired, and dried. 
 
 134. Roasting the Precipitate. The dried precipi- 
 tate is next roasted in the small reverberatory furnace, 
 to burn off the greater part of the sulphur, beginning 
 with only the heat required to set fire to it, and 
 gradually increasing the temperature to dark redness, 
 or to such a degree as the material will bear . without 
 melting. It must be stirred while roasting, and changed 
 from end to end of the furnace, in the manner directed 
 for the roasting of ore. If but little base metal is 
 present, the roasting is continued until as little as 
 possible of the sulphur remains; otherwise a prolonged 
 roasting is avoided, on account of the formation of too 
 much base metal sulphate and oxide, which are injurious 
 to the black lead pot in the melting. 
 
 135. Melting the Silver. This is done in black 
 lead crucibles, in a wind furnace, with coke or charcoal 
 for fuel. If the precipitate, before roasting, contained 
 but little base metal sulphide, the silver is seen in the 
 form of threads traversing the roasted mass, which, 
 however, still retains a considerable quantity of sulphur. 
 The crucible, containing some scrap iron, is filled, and 
 placed in the fire, standing on a piece of firebrick; for 
 as the melting occupies a considerable time, even a 
 thick layer of the best coke does not last long enough 
 to prevent the crucible from settling down to the grate. 
 
74 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 A little borax is added, and the whole is heated till 
 there is room in the pot for more material, when it is 
 refilled by means of a scoop and funnel. As in the 
 case of gold, the refilling is done before the mass in 
 the crucible has become fluid, in order to avoid loss by 
 projection. As fast as the scrap iron disappears, more 
 is put in; but, if such addition is made after full fusion, 
 the iron is first heated. 
 
 If the roasted precipitate contains much copper 
 or iron, more borax is required, and a little clean 
 sand is useful, especially if the roasting has been exces- 
 sive. Some charcoal is also added. 
 
 When the pot is full of thoroughly melted mat- 
 ter and pieces of iron, a test is made by placing 
 the red hot end of a piece of nailrod, or thick iron wire 
 in it. If, after a few minutes, on withdrawing the rod, 
 it is found that a part of it has been melted, more time 
 must be allowed. When iron is no longer consumed, 
 the melting of that quantity of precipitate is finished, 
 and slag and matte are dipped out, by means of a red 
 hot assay crucible held with the crooked tongs, and 
 poured into a mould, or iron pan. The pot is now 
 refilled with roasted precipitate, taking the precaution 
 to add it slowly until the melted mass is somewhat 
 chilled. 
 
 When all the precipitate has been thus worked 
 up,, or the pot contains a sufficient quantity of metal, a 
 part of the slag and matte is removed as before, and 
 the remainder, with the silver, is poured into a warmed 
 and greased mould. The overflowing of the slag and 
 matte is of no consequence, if the mould is large 
 enough to contain the silver, which will go to the bot- 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 75 
 
 torn in consequence of its greater specific gravity. 
 After removal from the mould, it is usual to place the 
 bar in a tub of water, for the purpose of cooling it, but 
 when there is matte upon it this must not be done 
 until the matte also has solidified; otherwise an explo- 
 sion will occur. 
 
 If the melting has been properly conducted, 
 the matte is brittle, and separates readily from the 
 cooled bar. If it is tough, that which adheres to the 
 metal must be beaten off, and the whole remelted in 
 presence of iron, as it then contains a great deal of 
 silver. After cooling, it is broken and examined for 
 any large buttons of silver which may have been dipped 
 out with it. All the slag and matte is preserved, the 
 former to be sold, the latter to be crushed and re- 
 worked by roasting and leaching. If a handsome bar 
 is desired, it must be remelted with borax, cleaned 
 by skimming, and re-cast, covering the surface with 
 powdered charcoal before solidification. 
 
 136. C. Concentrations containing Silver, but little 
 or no Gold. These concentrations generally contain 
 less iron pyrites, and more lead, zinc, copper, antimony, 
 and arsenic, which makes them more difficult to roast. 
 They require from 5 to 20 per cent of salt, according 
 to their richness. The salt is usually charged with the 
 ore, but as some ores are more liable to melt if it is 
 added at the commencement of the roasting, than if the 
 addition is made at a later period, it is sometimes neces- 
 sary to complete the oxidation, under a moderate heat 
 before the salting. 
 
 137. The roasting is commenced with only the heat 
 required for the ignition of the sulphur. Stirring is 
 
76 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 kept up almost continuously, in order to prevent sinter- 
 ing, or partial melting. If the salt has not been mixed 
 with the ore at the time of charging, it is added as soon 
 as the smell of burning sulphur has become faint, under 
 a dull red heat. The heat is then raised cautiously, 
 the ore swells, becomes flaky, and somewhat sticky, ap- 
 pearing as though it were moist, which is caused by 
 the fusing together of the metal sulphates and the salt. 
 
 At this period the ore must not be stirred too 
 frequently, or more than is required to ensure an equal 
 heat, as it facilitates the escape of chlorine, which 
 should be retained as long as possible within the mass. 
 The furnace doors may be closed while the stirring is 
 intermitted, because what is now required is heat rather 
 than air. 
 
 It is a good plan to heap the ore near to the fire- wall, 
 and let it remain for a time, then spread it, and again 
 gather it into a heap. The roaster should be careful 
 to avoid pushing the somewhat adhesive ore against 
 the wall of the furnace with the hoe. The charge 
 
 o 
 
 on the finishing hearth must be changed from end to 
 end at least twice ; once before the heat is raised, and 
 again after. It is drawn out while still giving off an 
 abundance of chlorine and volatile chlorides, and is al- 
 lowed to remain an hour before being spread on the 
 cooling floor. 
 
 138. The degree of heat which may be used de- 
 pends on the quality of the ore. Zincblende requires 
 a high temperature for its decomposition. Iron, copper 
 and antimony sulphides, especially the latter, require a 
 low heat at first, but are not very liable to cause sinter- 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 77 
 
 ing after oxidation. Lead is troublesome, as all its 
 compounds are very fusible. 
 
 Some ores do not bear a high heat, after the ad- 
 dition of salt, without a great loss of silver; yet if 
 zincblende is present a strong heat is requisite for its 
 oxidation. Such an ore is roasted without salt until a 
 sample, ground in a mortar, and carefully horned, or 
 panned, shows no sulphides. It is then allowed to 
 cool to a moderate red heat, salted and mixed. If a 
 strong odor of chlorine is not thus developed, some 
 dried copperas, in the proportion of about sixty pounds 
 to the ton of ore, must be added and mixed. When 
 the proper smell is obtained, the charge is withdrawn. 
 
 139. Washing the Ore. The roasted and cooled 
 ore, previously sifted if lumpy, is placed in the leaching 
 vat, and cold water is passed slowly upward through 
 the mass, the discharge pipe having been connected 
 with the water supply for that purpose. When the vat 
 is full, the water is admitted above the ore, and al- 
 lowed to flow out through the discharge pipe. The 
 washings are allowed to run to waste, unless they con- 
 tain copper, in which case they are conducted to vats 
 which contain scrap iron, by which the copper is pre- 
 cipitated. 
 
 The reason for introducing the water at first in 
 the manner described is, that a certain quantity of 
 silver chloride is dissolved by the strong solution of 
 base chlorides and residual salt, which is formed on the 
 first introduction of water. By operating as described, 
 this solution is brought above the ore, and on being 
 diluted with a further quantity of water, deposits the 
 silver chloride in and upon the ore mass, where it re- 
 
78 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 mains until the hypo is admitted, while the major part 
 of the base chlorides, remaining dissolved, is removed 
 by the washing. 
 
 A portion of base metal chlorides, however, is 
 also deposited with the silver chloride, and, on this 
 account, some operators prefer to admit the water at 
 once above the ore, and to save the silver which is thus 
 carried out, by allowing the washings to flow through a 
 series of launders, together with an additional stream 
 of water. In the launders is placed a quantity of wood 
 shavings, or some similar material, on and among which 
 the silver chloride, together with base metal chlorides, 
 is deposited. The shavings, with the metal chlorides, 
 are then gathered up, and the silver is extracted, either 
 by leaching, or by a smelting operation in a crucible. 
 The flow of water through the ore is continued, until 
 a test with calcium sulphide gives no precipitate. 
 
 140. If the ore contains lead chloride, it is washed 
 with cold water until the greater part of the copper 
 and iron chlorides, and salt, are removed. It is then 
 treated with hot water, as long as any metal can be 
 extracted, after which it may be necessary to again 
 apply cold water, to cool the ore before admitting the 
 hypo, so that too much base metal may not be ex- 
 tracted with the silver. Hot water, if applied at first, 
 increases the solubility of silver chloride in the solution 
 of base chlorides and salt; but after these are in the 
 main removed, by means of cold water, it may be used 
 with advantage. If, however, it were immediately fol- 
 lowed by the hypo, more base metal would be extracted 
 than would be the case if the ore were cooled; for, as 
 before remarked, there are base metal compounds in 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 79 
 
 the roasted ore which are insoluble in both hot and 
 cold water, but which are soluble in the hypo, especially 
 if it is warm. 
 
 Lead chloride is almost insoluble in cold water, 
 but dissolves readily by the aid of heat. The sul- 
 phate is not dissolved by water, hot or cold. 
 Hence it is better that lead should be chloridized in 
 the roasting, because it can then be removed by wash- 
 ing. If lead is extracted in the silver leaching, it can- 
 not, like copper, be retained in the matte when melting, 
 but inevitably goes into the bullion, because its sulphide 
 is easily reduced by iron at a red heat, while the copper 
 sulphide is riot. 
 
 141. From this point the leaching and precipitation 
 are carried on exactly as directed, after the gold leach- 
 ing, for concentrations containing gold and silver. If 
 the ore contains a little gold, a portion of it may 
 be obtained with the silver, owing to the formation, 
 during the roasting, of the peculiar gold chloride 
 described (30). 
 
 142. D. Concentrations rich in Gold and Silver, 
 and containing much Lead, etc. It appears that certain 
 rich ores, containing much lead, and other obstructive 
 metals, do not yield the gold well when treated in the 
 ordinary way. To meet this case Ottokar Hofman 
 has devised and patented the following modification of 
 the process. 
 
 The ore is subjected to a thorough chloridizing 
 roasting, then washed with water, as described in the 
 case of silver-bearing concentrations, leached for silver, 
 and again washed to remove all hypo. It is then re- 
 moved from the vat, dried sufficiently for chlorination, 
 
80 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 returned to the vat and chlorinated. The gold is then 
 leached out, and if there still remains a considerable 
 quantity of silver, the ore is again leached with hypo 
 for its extraction. The results are said to be very sat- 
 isfactory. 
 
 143. E. Unconcentrated Ore. This material, con- 
 taining gold or silver, or both gold and silver, is treated 
 in the same way as described for concentrations of sim- 
 ilar character, except that, if it is only moderately 
 charged with sulphides, the furnace is made hotter be- 
 fore being charged, and the roasting is effected more 
 speedily, and with less draft in the furnace, the rule 
 being only to allow as much as suffices to prevent the 
 escape of fumes at the cloors. 
 
 If, as often happens, the ore contains too little 
 sulphur to effect the chloridation of silver, it is 
 necessary, if that metal is present, to add a certain 
 quantity, say four or five per cent of crushed pyritous 
 ore, one per cent of sulphur, or from two to three per 
 cent of copperas. The pyrites or sulphur must be 
 mixed with the ore before roasting, but copperas may 
 be put in later, as described in certain cases occurring 
 in the treatment of concentrations. 
 
 144. Unconcentrated ores are not often treated for 
 gold by lixiviation. They are crushed as coarsely as 
 is compatible with good roasting, but nevertheless are 
 often troublesome to leach, on account of clay, talc, etc., 
 so that, while concentrations can be leached in a bed of 
 from two to four feet in thickness, without difficulty, or 
 special appliances, Unconcentrated ores will, in many 
 cases, not admit of more than ten inches, and, in ex- 
 treme cases, they cannot be worked by leaching. 
 
SPECIAL DIRECTIONS GOLD AND SILVER. 81 
 
 This difficulty is sometimes overcome by crushing the 
 ore in a wet battery. The water removes the slimy 
 matters which impede filtration, while the heavier por- 
 tion of the ore is retained in " catchpits." This is in 
 fact a species of concentration, although a very imper- 
 fect one. As the slimes usually contain a considerable 
 quantity of silver, they must also be preserved, and, 
 since they cannot be leached, must be treated in some 
 other way. Amalgamation is usually adopted. On the 
 whole, the plan is scarcely to be recommended. In 
 cases of difficult leaching the suction pipe, (54) may 
 be used. 
 
 145. When about to begin leaching with the aid of 
 a suction pipe, it must be filled with liquid. When 
 operating on ore which is not chlorinated with gas, 
 this is done by connecting the pipe with the water supply, 
 and passing the water upward through it, and the ore 
 mass, as directed in beginning the washing of silver ore 
 (139). If a vent pipe (55) is in use, it must be plugged as 
 soon as the space below the filter is full of water. 
 If the ore has been chlorinated for gold, it is not 
 desirable to introduce the water in this way, because 
 the solution of gold would be too much diluted. It is 
 then better to let the pipe down into the trough, and 
 stop the end with a tight plug. On introducing water 
 into the vat, as described in the gold leaching, it passes 
 through the ore, and, displacing the air, fills the pipe. 
 When the water stands permanently above the ore, and 
 air bubbles have ceased to rise, the plug is removed, 
 the vent pipe stopped, and the leaching is allowed to 
 proceed, aided by the weight of the column of liquid 
 in the suction pipe, or, more correctly, by the pressure 
 
82 SPECIAL DIRECTIONS GOLD AND SILVER. 
 
 of a corresponding column of air. The suction pipe 
 may be filled before charging the vat with ore, if so 
 desired, and in the case of silver ore the water may 
 even rise to the top of the filter, thus avoiding all 
 trouble from air; but when chlorine gas is to be used, 
 the water must not cover the aperture through which 
 the chlorine is admitted. 
 
 To reduce friction, and give the best effect, the 
 the suction pipe should be large; say, for a ten foot 
 pipe, one and a half or two inches -in diameter. It is 
 impossible for it to take air at the lower end, with 
 either of the arrangments mentioned, nor can any 
 enter at the top as long as the vent pipe is closed and 
 there is liquid in the vat. I have observed that a fall 
 of six feet more than doubles the flow of liquid through 
 a bed of ore fifteen inches deep. 
 
 146. F. Ores Containing Coarse Gold, or an Alloy of 
 Gold and Silver. If the gold is too coarse, it will not be 
 entirely dissolved in a single operation by the above 
 described process of chlorination, or if it is alloyed with 
 a considerable proportion of silver, unless in very fine 
 particles, the chlorination may be obstructed by the 
 formation of a crust of silver chloride on each of the 
 particles. Gold which is too coarse is more easily col- 
 lected by amalgamation ; yet it can be dissolved by 
 leaching with chlorine water, that is, water through 
 which chlorine has been passed until no more is absorbed. 
 An alloy of gold and silver can be leached out with 
 brine of common salt, saturated with chlorine. The 
 chlorine acts on both of the metals, and the brine dis- 
 solves the chlorides as fast as they are formed. The 
 
SPECIAL DIRECTIONS CALCIUM POLYSULPHIDE. 83 
 
 dissolved metals may be precipitated together, by means 
 of plates of copper. 
 
 147. The Mears process, recently introduced, 
 seems to be well adapted to this class of ore. It is 
 conducted as follows : The roasted ore is treated in 
 rotating, lead lined, iron cylinders, with the addition of 
 water and chlorine, the latter being forced into the cylin- 
 ders under heavy pressure. The gold is said to be dis- 
 solved very rapidly, not more than two hours being 
 required. The pulp is then thrown into leaching vats, 
 and leached in the usual manner. An addition of salt 
 to the charge in the cylinder would be useful in case of 
 an alloy of gold and silver. The advantages of apply- 
 ing the chlorine, or chlorinated brine, under pressure, 
 have long been known. 
 
 148. Calcium Polystdphide. This precipitant for sil- 
 ver is made by boiling lime and sulphur together in water. 
 Lime is calcium oxide, and, when boiled with sulphur, 
 a part of it is decomposed; the calcium combines with 
 sulphur, making calcium sulphide, while the oxygen, 
 and some undecomposed lime, combines with another 
 portion of sulphur, making calcium hyposulphite, which 
 is the same as the solution used in leaching silver. 
 
 When the solution of sulphide is used for the pur- 
 pose of precipitation, the water that it contains is added 
 to the leaching solution, which would thus be gradually 
 diluted but for the hypo which the precipitant also 
 contains. This is the reason why the volume of the 
 leaching solution frequently increases, notwithstanding 
 a certain amount of waste. Not only is hypo formed 
 in making the calcium sulphide, but the sulphide itself 
 
84 SPECIAL DIRECTIONS CALCIUM POLYSULPHIDE. 
 
 absorbs oxygen from the air, and changes into hypo to 
 a certain extent. 
 
 Calcium sulphide may be made in an iron pot, over 
 a fire, with frequent stirring. A neater way is to make 
 it in a wooden tub, using a jet of steam for the heating. 
 It can thus be made in the vat in which it is kept. 
 The vat is two-thirds filled with water, and steam is 
 admitted. As soon as the water is hot, freshly slaked 
 lime is mixed with it, and flowers of sulphur added by 
 rubbing through a sieve. When the sulphide is 
 made in this way, two or three hours boiling suffices. 
 
 149. The proportions of lime and sulphur vary 
 with the quality of the lime. About 1^ pounds of 
 average lime is required for one pound of sulphur; 
 75 pounds of lime, 50 pounds of sulphur, and 120 gal- 
 lons of water will produce a solution of suitable strength, 
 and will suffice for the precipitation of from 25 to 50 
 pounds of silver, according to the quantity of base 
 metal in the lixivium. If a direct fire is used for the 
 boiling, the water which evaporates must be replaced, but 
 if steam is used, a little less water than the prescribed 
 quantity should be taken, as some will be added by the 
 condensation of steam. It is however to be observed, 
 that with an insufficient quantity of water, the-operation 
 proceeds very slowly. The proper strength of the 
 solution is indicated by a density of about 10 Beaume. 
 If below 6 it will dilute the hypo too much, when used 
 for the precipitation. 
 
 163. The chief points to be observed in making the 
 sulphide are, that the lime must be slaked before use, 
 and must not be in excess. If it is not previously 
 slaked, time and material will be wasted. If used in 
 
SPECIAL DIRECTIONS CALCIUM HYPOSULPHITE. 85 
 
 too great proportion, insoluble compounds are formed, 
 or, at least, compounds which are not sufficiently solu- 
 ble to be useful. An excess of sulphur is not injurious. 
 When the solution is properly made, with good lime, it 
 is nearly of the color of strong coffee ; it deposits, on 
 cooling, few, if any, needle-shaped, yellow crystals, and 
 the residue consists only of a small quantity of matter, 
 of a dirty greenish color. 
 
 150. Calcium Hyposulphite. This solvent may be 
 made by passing air, and the fumes from burning sul- 
 phur, or from sulphuric acid and charcoal heated in a 
 retort, through a solution of calcium polysulphide 
 until the latter is colorless. It is better to buy a barrel 
 or two of sodium hyposulphite in crystals, with which 
 to make the leaching solution to begin with. In use, 
 with calcium sulphide as the precipitant, the sodium 
 hypo soon disappears, being replaced by calcium 
 hypo through the chemical reactions which take 
 place. 
 
 151. The strength of the solution to be used for 
 leaching depends somewhat on the composition of the 
 ore. If this contains but little base metal, the solution 
 may be quite strong, and is even used warm. But, in 
 general, a strong solution would extract too much base 
 metal. It may be made by dissolving two pounds 
 of crystallized sodium hyposulphite in each cubic foot 
 of water, or about 26^2 pounds to 100 gallons. 
 If it is then found to dissolve too much base metal, 
 which may be ascertained by an examination, or 
 an assay, of some of the precipitate, the strength is re- 
 duced by an addition of water. After it has been used 
 the density cannot be relied on, as it then contains 
 
86 SPECIAL DIRECTIONS WORKING TEST. 
 
 other substances besides hyposulphite. A good guide is 
 the taste, which should be very sweet during the first 
 stage of the leaching, if the ore contains much silver. 
 The solvent power of the solution may at any time be 
 tested, thus : Dissolve 5.25 grains of pure silver in 
 fiitric acid ; precipitate as chloride, by adding a little 
 hydrochloric acid. Wash the precipitate three or four 
 times with water, to remove every trace of acid. One 
 fluid-ounce of the leaching solution should dissolve the 
 whole of the silver chloride. Some operators, when in 
 want of leaching solution for silver ores, obtain it by 
 treating with calcium polysulphide the solution of base 
 metal chlorides resulting from the preliminary washing 
 of the roasted ore. The metals are thrown down as 
 sulphides, and the solution then contains calcium chlo- 
 ride, together with the calcium hyposulphite previously 
 existing in the precipitant (148). 
 
 152. Working Test. The apparatus used is rep- 
 resented in Figure i, Plate 6. The generator and 
 wash-bottle are made of two wide-necked bottles, 
 jars, or flasks, with corks, and some glass tubes. 
 The corks should be soaked in melted paraffin, 
 and the S tube is enlarged at the upper end, so as 
 to form a small funnel, into which to pour the acid. If 
 preferred, a glass generator and two-necked wash-bottle 
 can be bought of J. Caire, in San Francisco. 
 
 A chlorinating vat is made of a common wooden 
 pail, or small tub, in the bottom of which, near the side, 
 a hole is bored and. a cork inserted. Through the cork 
 is passed a piece of J^-inch glass tube 4 inches long. 
 The cork and tube must not project above the bottom of 
 the pail inside. A wooden cover is made to fit into the 
 
Plate W. 
 
SPECIAL DIRECTIONS WORKING TEST. 87 
 
 pail half an inch below the rim, and in it is a hole, fitted 
 with a cork and tube similar to those in the bottom. 
 The pail, while dry, is thoroughly coated inside with 
 melted paraffin, which is caused to soak into the wood a 
 little by the aid of heat. A filter is made in the vat by 
 means of a layer of pebbles, covered with a piece of 
 moistened grain sack, or similar material. 
 
 A weighed quantity, from 10 to 20 pounds of the 
 pulverized ore, or concentrations, is dead roasted 
 or chloridized, in a small reverberatory furnace, 
 with the precautions indicated, according to the 
 character of the ore. When cooled, it is slightly 
 moistened, and thrown on the filter in the vat. A space 
 of not less than half an inch must be left between the 
 surface of the ore and the cover, which is now placed, and 
 luted with dough, or with a paste made from a mixture 
 of equal parts of flour and paris plaster, which will not 
 crack in drying. 
 
 Chlorine is generated from manganese and hydro- 
 chloric acid, the latter being more convenient for small 
 operations than the sulphuric acid and salt used on the 
 large scale. Three ounces of manganese are put into 
 the generator, moistened with water, and warmed on a 
 sand bath resting on a small coal-oil stove. The acid is 
 gradually added by means of the S tube. The exit 
 tube of the generator is connected with the wash-bot- 
 tle, and that with the glass tube in the bottom of the 
 vat, by rubber tubing. 
 
 When a glass rod, dipped in ammonia and held to 
 the tube in the cover of the vat, causes the formation 
 of dense fumes, indicating the escape of chlorine, the 
 
88 SPECIAL DIRECTIONS WORKING TEST. 
 
 surplus gas is conveyed out of the room by a rubber 
 tube connected with the tube in the cover. 
 
 The chlorine is allowed to pass through the ore for 
 an hour, more acid being poured into the generator 
 when required, to maintain the evolution of gas. The 
 waste pipe is then closed by a pinchcock. The wash-bot- 
 tle is disconnected from the generator, but not from the 
 vat, unless it is required for another operation, in which 
 case the glass tube in the bottom of the vat is effectu- 
 ally, and conveniently, closed by immersing its lower 
 end in melted stearin, paraffin, or tallow, contained in a 
 small cup (dry cup), which is then allowed to congeal. 
 
 After the lapse of from 20 to 40 hours, as may be re- 
 quired, the cover is removed. A rubber tube, con- 
 nected with the glass tube in the bottom of the vat, is 
 arranged to deliver into a glass, or porcelain vessel, 
 capable of containing about a gallon, and is closed by 
 a pinchcock. 
 
 Water is now sprinkled on the ore, and when the lat- 
 ter has settled, more water is poured in until it is 
 covered. After half an hour, the pinchcock on the dis- 
 charge pipe is adjusted so as to allow the leach to flow 
 in a slow stream, water being poured upon the ore from 
 time to time to keep it covered. The leaching is con- 
 tinued until a sample, received in a test tube, no longer 
 gives the slightest precipitate on addition of solution of 
 iron sulphate. A more delicate test is that with tin 
 protochloride, which, with the slightest trace of gold, 
 gives a purple coloration. 
 
 The gold is precipitated by adding to the leach a 
 strong solution of iron sulphate, which is thoroughly 
 mixed by stirring with a glass rod. To ascertain if 
 
SPECIAL DIRECTIONS WORKING TEST. 89 
 
 enough of the iron sulphate to precipitate the whole of 
 the gold has been used, a drop of the liquid is trans- 
 ferred, by means of the glass rod, to a porcelain dish, 
 or a saucer, and is brought into contact with a drop of 
 solution of potassium ferridcyanide, or "red prussiate 
 of potash." If an intense blue coloration is not pro- 
 duced, more iron sulphate is required. 
 
 The gold requires 1 2 hours to settle, after which the 
 greater part of the clear liquid may be removed by 
 means of one of the rubber tubes, applied as a siphon. 
 The remainder, with the gold, is thrown on a paper fil- 
 ter, or the whole of the liquid may be passed through 
 the filter, to insure the collection of every particle of 
 the metal. 
 
 The sides, and bottom of the vessel in which the pre- 
 cipitation was effected, and the glass rod with which the 
 stirring was performed, are carefully wiped with pieces 
 of filter paper, held in the forceps, to remove adhering 
 gold, and the paper is added to the gold on the filter. 
 The filter, with the metal, is dried in the funnel, and is 
 then placed in an assay crucible, together with an 
 ounce or more of litharge, and a little borax, and 
 smelted. The filter reduces a sufficient quantity of 
 litharge to metallic lead, for the collection of [the gold, 
 which is then separated by cupellation, weighed, and 
 the result compared with the assay of the ore. 
 
 If the ore contains silver, the gold on the r filter may 
 be washed with water, then, with the entire filter, 
 drenched with ammonia, and again washed, before 
 being dried. This will remove any silver chloride 
 which may be present, or the bead may be inquartated 
 and parted in the usual way. After the extraction of 
 
90 SPECIAL DIRECTIONS WORKING TEST. 
 
 the gold, the ore, which in this case should have been 
 roasted with salt, is leached with hypo for silver as long 
 as a precipitate is produced by the addition of a drop 
 of calcium sulphide to a sample of the leach. 
 
 The silver is then precipitated with calcium sulphide, 
 as in the large way, except that, as it is not necessary to 
 preserve the hypo, an excess of the sulphide is used, so 
 that not a trace of the metal may be lost. The precipi- 
 tate is coagulated by heating on a sanclbath, separated 
 from the liquid by filtration, dried, and dressed on the 
 filter with litharge and borax, then fused in a crucible, 
 with the addition of a little nitre to prevent the pro- 
 duction of too much lead by the action of the sulphur 
 on litharge. The lead button obtained is cupelled, and 
 the resulting silver bead, after weighing, should be SUD- 
 jected to parting, as it may contain a little gold. 
 
 The tailings are dried and weighed. The loss of 
 weight found to have been sustained by the ore in the 
 working is reduced to percentage. An assay of the 
 tailings is then made, and from the result the same per- 
 centage is deducted. The remainder is the loss per 
 ton of ore by insolubility. This is added to the 
 amount per ton extracted, and the sum deducted from 
 the assay value of the original ore. The remainder is 
 the loss per ton by volatilization, dusting, and other 
 .causes. 
 
 153. A smaller test may be made in the laboratory. 
 Half an ounce, or an ounce, of ore, is roasted in the 
 muffle, with the precautions indicated under " Assay- 
 ing Concentrations" (160), with or without salt, as re- 
 quired, and is chlorinated in the apparatus represented 
 in Fig. 2, Plate 6, formed of two glass funnels. In the 
 
SPECIAL DIRECTIONS CHANGE IN WEIGHT. 91 
 
 neck of the lower funnel some fragments of broken glass 
 are placed, and on them a filter is constructed of rather 
 coarsely powdered glass. Upon the filter the moist- 
 ened ore is placed, the upper funnel is then arranged 
 as a cover, and luted with a paste of flour and paris plaster. 
 Two ore sample bottles, fitted with corks and tubes, 
 as in Figure i, suffice for a generator and wash bottle. 
 The corks should be saturated with paraffin or tal- 
 low. 
 
 This operation has the advantage that, after the 
 precious metal has been extracted and collected, as in 
 the larger test, the whole of the ore and glass filter, 
 dried in the funnel, can be dressed as an assay and 
 smelted, so that it not only shows what can be extracted, 
 but it also gives the absolute loss by insolubility, and, 
 by difference, the loss in roasting, without complications 
 arising from a change of weight in working, 
 
 154. Change in Weight. When working on the large 
 scale by lixiviation, it must be remembered that the ore 
 not only gains or loses weight in the roasting, but also 
 loses in the leaching by the amount of soluble matter, of 
 whatever kind, extracted. The tailings assay, therefore, 
 does not represent the real loss by insolubility unless 
 corrected. The change of weight sustained in roasting 
 and leaching, is approximative^ obtained by weighing, 
 roasting, leaching, drying, and reweighing a number of 
 small samples, using the same proportion of salt, 
 and, as nearly as possible, the same heat in roast- 
 ing, as in the large way. The loss of weight thus 
 found, when reduced to percentage, gives the correc- 
 tion to be applied to the assay value of the tailings. 
 Thus, if tailings assay 2.6 oz. per ton, and the loss of 
 
92 SPECIAL DIRECTIONS LOSS IN ROASTING. 
 
 weight in roasting and leaching has been found to 
 average 22 per cent, the real loss per ton of crude ore, 
 from insolubility, is 2.6 0.57=2.03 oz. 
 
 155. Loss in Roasting. The only reliable method 
 of determining the loss of gold or silver in the roast- 
 ing of ore on the large scale is, to dry, weigh, sample, 
 and roast a quantity, say from one to ten tons; then, after 
 cooling, to weigh and sample again. It may weigh 
 more or less than before, according to the character 
 of the ore, the quantity of salt used, and the manner of 
 roasting. The assay of the un roasted ore, coupled 
 with the total weight taken, gives the quantity of 
 precious metal in the lot before roasting, and the assay 
 of the roasted ore, with its total weight, gives the quan- 
 tity remaining after roasting. The difference is the 
 loss, caused by dusting and volatilization. To make 
 the test reliable, the furnace must be thoroughly 
 cleaned, both before and after the roasting; if this is 
 neglected, the weight obtained for the roasted ore will 
 be incorrect. 
 
 As a part of the precious metal lost in the roasting 
 may be recovered from the flues and dust chamber, 
 while, besides the losses already discussed, others may 
 occur in the leaching, collecting, and melting of the 
 metal, it will be seen that a final result can only be 
 reached by means of a general and complete clean-up ; 
 yet, as this cannot be had very frequently, the investi- 
 gations described are indispensable as guides in work- 
 ing. 
 
 It is best, when any doubt is entertained as to the 
 best way of roasting a given ore, to experiment in the 
 laboratory on ounce or half ounce samples taken from 
 
SPECIAL DIRECTIONS - -SOLUBILITY ASSAY. 93 
 
 crushed lots of considerable magnitude. The method 
 employed by some metallurgists, of taking samples from 
 the furnace at intervals during the progress of the roast- 
 ing, and assaying them with the view of ascertaining the 
 loss at successive stages, is open to the objection that 
 it cannot be known exactly what correction must be 
 made for the changes of weight sustained by the ore. 
 It is, however, very proper to make such trials, because 
 a heavy loss might be thus indicated in time to alter 
 the treatment of the charge. The percentage of the 
 silver which is soluble must be considered in connec- 
 tion with the loss by volatilization, in order to arrive at 
 the most profitable manner of roasting ; for it is better 
 to make rich, rather than poor, tailings, if the difference 
 should go up the smoke stack. 
 
 156. Solubility Assay. This is commonly, but in- 
 correctly, called a " chlorination assay." It is made as 
 follows : From a quantity of the roasted ore, two 
 assays are weighed out, one of which is leached on a 
 filter with hypo as long as any metal can be detected 
 in the filtrate ; it is then washed and dried. The 
 leached and the unleached samples are then separately 
 smelted, and the resulting lead buttons cupelled and 
 parted. The result obtained from the unleached sam- 
 ple gives the assay value of the roasted ore ; that from 
 the leached sample the portion of the silver which is 
 insoluble in hypo. 
 
 If the average change of weight which the ore sus- 
 tains in roasting has been ascertained, a corresponding 
 correction, applied to these assays, will show the loss 
 in roasting, if an assay has been made of the unroasted 
 ore ; thus : 
 
94 SPECIAL DIRECTIONS SOLUBIL 
 
 Raw ore contains 56 oz. of silver per ton. 
 Loss of^ weight in roasting=5 per cent; therefore, 
 Roasted ore should contain 56 + 2.9=58.9 oz. per ton, 
 but actually contains 57-O " " " 
 
 The loss in roasting is therefore 1.9 
 
 Unleached sample contains 57 oz. per ton 
 Leached 1.5 " " '< 
 
 Soluble silver 55.5 ' " " =97-3 per 
 
 cent of the silver remaining in the ore after roasting. 
 But a ton of roasted ore which has lost 5 per cent in 
 weight corresponds to 1.052 ton of raw ore, containing 
 58.91 oz. of silver, of which we extract 55.5 oz. The 
 total loss therefore is 3.41 oz., in 58.91 oz., or 5.79 
 per cent nearly, which, however, would be a better re- 
 sult than is often obtained. 
 
 PLAN OF WORKS. 
 
 157. Plate 7 will give the reader a good idea of 
 the general arrangement of a plant for treating, per day 
 of 24 hours, from i y 2 to 3 tons of concentrations con- 
 taining gold and silver. The appended description 
 will also serve as an inventory of the principal articles 
 required : 
 
 A Two hearth roasting furnace ; A A! The same 
 extended to three hearths ; B Drier ; C Smoke 
 stack ; D Floor, level with 'top of drier, with store- 
 room beneath; E Hopper; F Boiler, for heating pur- 
 poses, set in flue; G Passage way under flue ; H 
 
Plate VTL 
 
 Plan of Works. 
 
PLAN OF WORKS. 95 
 
 Melting furnace ; k (dotted) Small roasting and dry- 
 ing furnace for precipitate inside drier ; / Sheet-iron 
 muffle for drying gold ; m Assay furnace ; n Door- 
 way to laboratory ; o Steps to lower floor ; p Tank 
 for hypo ; q q q q Leaching vats ; r r Silver precipi- 
 tating tubs ; s Calcium sulphide vat; t Well and 
 pump ; u it u Filters for precipitate ; v v Gold pre- 
 cipitating tubs; w Iron sulphate vat ; x Small tub 
 to receive washings from vv; y Filter tub for waste 
 solution ; z Gasometer, or blower ; a Chlorine 
 generator ; b Wash-bottle ; c c Cars for removing 
 tailings ; d d Tram-ways, 6 feet above floor ; e 
 Press for silver precipitate. 
 
ASSAYING CONCENTRATIONS 
 
 158. It is well known that many experienced as- 
 sayers, although generally reliable, do not obtain cor- 
 rect results from the assay of gold-bearing sulphides, 
 very rich ores of silver, or cement copper containing 
 gold, and contaminated by basic chlorides. A few 
 facts and suggestions on this subject may not be out of 
 place here. As this is not a treatise on assaying, the 
 reader is supposed to be familiar with the apparatus 
 and manipulations to be employed. 
 
 A common practice among assayers, and by some 
 deemed indispensable, is to roast the assay of gold- 
 bearing sulphides. It is better not to do so unless 
 .they contain much arsenic, and even in that case, scori- 
 fication is preferable. 
 
 When an accurate assay of an ore which is new to 
 the assayer is desired, it is best to make several assays 
 by different methods. If the assayer knows how to 
 properly clear, weigh, and part the bead, and to make 
 the necessary allowance for silver in the litharge or 
 lead employed, the presumption of correctness is in 
 favor of the highest result, because, although it is easy 
 to lose gold or silver in an assay, it is impossible to ex- 
 tract more than the ore contains. In important as- 
 says, such as those on which the purchase of a lot of 
 ore is based, the carefully taken sample should be 
 thoroughly dried at the heat of boiling water, passed 
 through a seive of at least 80 meshes to the run- 
 ning inch, and then very carefully mixed. 
 
98 ASSAYING CONCENTRATIONS. 
 
 * 
 
 It is generally assumed, and so implied in books on 
 the subject, that if two assays, made at the same time, 
 and in the same manner, give correspondiug results, 
 they are correct. This is a great mistake. Two 
 chemical operations conducted under precisely similar 
 conditions should give similar results. Their agree- 
 ment proves that no accidental loss has occurred, nor 
 any error in weighing, but it does not prove that the 
 method adopted is that by which the highest results 
 can be obtained. 
 
 159. There are two principal methods of assaying 
 ores for gold and silver by crucible, and by scorifica- 
 tion. The crucible assays may be divided into two 
 classes; firstly, that in which a thoroughly oxidized slag 
 is produced ; secondly, that in which a matte contain- 
 ing the minimum proportion of sulphur is formed. 
 
 The scorified assay is always a completely oxidized 
 assay, and is the most certain in its results, but is sub- 
 ject to certain inconveniences. Either a very small 
 quantity of ore is operated on, or, a very large quantity 
 of lead is obtained, and it usually requires more time 
 than a crucible assay. Yet it is indispensable as a 
 check, for in some cases it gives higher results than 
 can be obtained from the crucible, especially with some 
 arsenical compounds. 
 
 Each kind of assay is subject -to modifications as to 
 the quantity, kind, and respective proportions of fluxes 
 used, depending on the constituents of the ore ; whence 
 it is difficult to give rules to meet the requirements of 
 all cases. 
 
 Concentrated gold bearing sulphides, chiefly iron 
 pyrites, with or without an admixture of other sul- 
 
ASSAYING CONCENTRATIONS. 99 
 
 phides containing silver, are assayed by the different 
 methods as foilows : 
 
 160. ist Assay. Half an ounce of the finely pulver- 
 ized and dried ore is roasted in a roasting dish, in the 
 muffle. To prevent loss by decrepitation, the assay is 
 covered by another roasting dish inverted. A small 
 hole should be bored through the cover, and a few 
 notches broken in its edge, so that the arrangement 
 resembles a small reverberatory furnace. 
 
 The heat is kept very low, and after a time the dish 
 is taken from the muffle and cooled a little, to prevent 
 decrepitation, and consequent loss, on uncovering it. 
 The cover is then removed, and the ore well stirred 
 and turned over, again covered, and returned to the 
 muffle. This is repeated until it is found that the assay 
 may be uncovered and stirred within the muffle, with- 
 out danger of loss by decrepitation. The heat is then 
 increased to bright redness, and so maintained until the 
 ore is odorless. After cooling, the assay is dressed 
 thus : 
 
 Ore (roasted) 
 
 Litharge . . 2 to 4 ounces 
 
 Sodium bicarbonate ^ " 
 
 Flour 40 grains. 
 
 Mix, and place in a No. 8 French crucible, containing 
 j ounce of borax in crystals, and cover with salt. 
 Fuse quickly in a strong fire. Allow the assay to 
 remain five minutes in the fire after fusion, and pour. 
 The lead button should weigh about 300 grains. If 
 it varies much from that weight, the assay should be 
 repeated, with a larger or smaller quantity of flour as 
 
100 ASSAYING CONCENTRATIONS. 
 
 the case may be. A duplicate assay should be made, 
 with either more or less litharge, as a check. The 
 lead buttons are cupelled as usual. 
 
 161. 2d Assay: 
 
 Ore (not roasted) ^ ounce 
 
 Litharge 2 to 4 " 
 
 Sodium bicarb . j " 
 
 Dried borax y 2 " 
 
 Pulverized nitre . . . .- 420 grains. 
 
 Mix ; put into a No. 8 French crucible, and cover with 
 salt. Heat the assay very slowly until fused; raise the 
 heat to bright redness, and keep it so for five minutes 
 at least ; then pour. 
 
 The button should weigh about 300 grains, and 
 be soft. No matte should be formed. If these con- 
 ditions are not fulfilled the assay is imperfect, and must 
 be repeated with a different proportion of nitre, more 
 if the button is too large, or -if a matte is formed; less 
 if it is too small. Theoretically, 25 parts of nitre con- 
 vert 100 parts of lead into litharge; in practice the pro- 
 portion varies with the purity of the nitre. 
 
 162. jd Assay. - 
 
 Ore ^ ounce 
 
 Litharge 2 to 4 " 
 
 Sodium bicarb y 2 " 
 
 Dried borax */2 
 
 Pulverized nitre 300 grains. 
 
 Place the mixture in a No. 8 crucible ; cover with 
 salt ; fuse very slowly. When ebullition ceases, under 
 a good red heat, add 20 grains of charcoal in lumps, a 
 portion at a time. When the evolution of gas pro- 
 
ASSAYING CONCENTRATIONS. 101 
 
 cluced by the charcoal ceases, cover, and heat strongly 
 for ten minutes ; then seize the crucible with the 
 tongs and shake it, without removal from the fire. 
 Again cover, and leave it in the fire for a few minutes 
 longer, and pour. 
 
 In this assay, the quantity of nitre is sufficient for 
 the complete oxidation of even pure iron pyrites. 
 Any excess is decomposed by the heat, and after its 
 decomposition the addition of 20 grains of carbon gen- 
 erally reduces a suitable quantity of lead, which, for 120 
 grains of ore, is about 150 grains. If it does not, the 
 carbon alone is varied. The method is a little tedious, 
 but gives very good results, especially as to gold. 
 
 163. In all the preceding assays the crucible is lia- 
 ble to extensive corrosion, unless the ore contains a con- 
 siderable quantity of quartz. This may be prevented 
 by the addition of half or a whole teaspoonful of pul- 
 verized quartz, which must of course be free from 
 precious metal. Glass will answer the purpose, but 
 rather more of it is required. 
 
 164. An assay which is dressed with undried borax 
 is less liable to boil over if put at once into an intense 
 fire, than if heated by slow degrees. When nitre is 
 used rapid heating is not admissible, hence the borax 
 is dried before use. It is well to dry it in all cases. 
 Boiling over sometimes occurs in consequence of an evo- 
 lution of carbonic acid gas (carbon dioxide) produced by 
 the fusion of the alkaline carbonate, used as a flux, with 
 silica. A large proportion of litharge, and less of the 
 carbonate, will correct this, while forming an equally 
 good slag. Whenever the assay tends to boil over, it 
 may be cooled down by throwing a little dry salt into it. 
 
102 ASSAYING CONCENTRATIONS. 
 
 165. 4th Assay. 
 
 Ore 1 20 grains. 
 
 Litharge 6000 " 
 
 Cover with salt; fuse quickly, and pour as soon as 
 the assay becomes quiet. The lead button should 
 weigh about two ounces, if the ore consists chiefly of 
 iron pyrites. It must be reduced by scorification to a 
 suitable size for the cupel. 
 
 166. sth Assay.- 
 
 Ore y 2 ounce. 
 
 Sodium bicarb . . 720 grains. 
 
 Litharge 300 " 
 
 A little flour and pulverized glass will do no harm, 
 and in some cases are beneficial. Place in a No. 7 or 8 
 crucible, with a very little borax and three large nails ; 
 cover with salt. Fuse slowly; then give a white heat 
 -for half an hour or more. If, on seizing one of the 
 nails with the tongs, rinsing it in the fluid slag, and 
 tapping it against the side of the pot, it is found to be 
 free from adhering lead globules, the other nails may 
 also be removed; but if the nail shows adhering lead, 
 which cannot be washed off, more time is required. 
 
 The matte and slag should retain no lead in any 
 form; hence the weight of the button should correspond 
 with that of the litharge used, or may be in excess, if 
 the ore contained lead. It must be soft, and separate 
 well from the matte. If it does not, more soda is 
 probably required. 300 grains of pure litharge con- 
 tain 278.5 grains of lead, but five per cent may be 
 allowed for volatilization. 
 
 This is a very convenient assay, requiring but little 
 modification for the different sulphuretted ores. It is 
 
ASSAYING CONCENTRATIONS. 103 
 
 not liable to boil over, nor is it so destructive to the 
 crucible as are the other methods described. If properly 
 made, it gives as high results as can be obtained by any 
 other method, in most cases, both as to gold and silver. 
 Arsenical mattes cannot be assayed successfully by 
 this method, and, in one instance of gold and silver 
 bearing sulphides, though it gave the gold correctly, it 
 did not yield as much of the silver as the assay by 
 sconfication. 
 
 167. Oxidized coppery ores, and especially cement 
 copper contaminated with basic chlorides, may be con- 
 veniently assayed for gold and silver by a similar pro- 
 cess, as follows: 
 
 Ore or cement copper J^ ounce. 
 
 Sodium bicarb 720 grains. 
 
 Litharge 300 " 
 
 Some flour, or charcoal, borax, and enough sulphur 
 to convert all the copper, the sodium, and the lead from 
 the litharge, into sulphides. An excess of sulphur does 
 no harm. The mixture, covered as usual with salt, is 
 first fused; the nails are added, and a strong heat is 
 continued for half an hour. The copper remains in 
 the state of matte; the nails reduce the lead sulphide, 
 and take up all excess of sulphur. Massive copper, 
 and other metals, may be treated in the same way, if 
 first broken, or cut into fragments. 
 
 168. 6th Assay. Scorification. 
 
 Ore 60 grains. 
 
 Granulated lead 480 " 
 
 Mix in a scorifier, and cover with another ounce of 
 granulated lead. Place the scorifier in the muffle, under 
 a low heat, and increase the temperature gradually, until 
 
104 ASSAYING CONCENTRATIONS. 
 
 the " bull's eye " appears that is, until the surface of 
 the melted lead is clear in the centre, and the fused, or 
 partly fused, ore forms a ring around it. Keep up a 
 cupelling heat, until the slag quite covers the lead, then, 
 with the tongs, add some lumps of borax, and give a 
 strong heat. Stir with a red hot piece of stout iron 
 wire, to detach pasty lumps from the side of the 
 scorifier. Pour when the slag has become so fluid as 
 to run completely off the stirrer. If the lead button is 
 too large, return it to the scorifier, after detaching the 
 cooled slag, and oxidize it until of the proper weight. 
 
 169. Nearly clean silver glance is conveniently 
 assayed by mixing it with two or three parts of litharge, 
 melting quickly, and pouring as soon as well fused. 
 The assay No. 5 is well adapted to heavily sulphuretted 
 silver ores, containing antimony, arsenic, and zinc, as 
 well as copper. It is rarely necessary to roast silver 
 ore for assaying. 
 
 170. In assaying rich silver ores, that part of 
 the cupel which is saturated with the lead oxide must 
 be pulverized, dressed with litharge and flour, smelted, 
 and the resulting lead cupelled, as a considerable quan- 
 tity of silver is thus added to the result. This is quite 
 important. 
 
 171. Tailings of concentrated ^and roasted gold- 
 bearing sulphides are treated precisely as No. i, omit- 
 ing the roasting. The reason why as much as 40 
 grains of flour must be used in an assay of 240 
 grains of the roasted ore is, that the iron peroxide which 
 it contains consumes the carbonaceous matter, being 
 reduced to protoxide, and if only the usual quantity of 
 the reducing agent were used, little or no lead would 
 be produced. 
 
ADDENDA. 
 
 FLUE COVERING. 
 
 172. A very convenient covering for horizontal 
 flues, which can be removed and replaced easily, is 
 shown in the annexed diagram. It consists of a kind of 
 
 arched tile, made by 
 bindingtogether, with 
 an iron clamp, as many 
 bricks as may be re- 
 quired by the width of the flue, each tile, or section, 
 having the length of one brick. The flue is covered 
 with these sections, and the interstices are filled with 
 mortar, or a mixture of clay and sand. 
 
 FILTERS. 
 
 173. Filters for dumping vats are made with a bed 
 of twigs, in place of gravel, and over the twigs is a 
 piece of cloth, which is held close to the inner surface 
 of the staves by a wooden hoop. The objection to 
 burlap or other cloth is, that it is speedily destroyed by 
 chlorine gas. Attempts have been made to preserve 
 it, by soaking it in coal tar and asphalt, but without 
 much success. It occurred to me to use asbestos cloth, 
 but I found none that was not too closely woven. Clay 
 tiles, of the kind known as " biscuit ware," have been 
 suggested for filters, and it may be that basket work, 
 made of rattan, would answer, especially if soaked in 
 petroleum, or ozokerite. 
 
106 ADDENDA. 
 
 COPPER. 
 
 174. When concentrations which are to be chlori- 
 nated for gold, contain also copper, the roasting is not 
 pushed to the decomposition of copper sulphate. The 
 latter is converted into chloride by an addition of salt, 
 a short time before discharging the ore from the fur- 
 nace. The leach is then green, and, after precipitating 
 and settling the gold, it is drawn off, either through a 
 filter or not, as desired, and led into tanks containing 
 iron, where it is allowed to stand until the tanks are 
 again required. The iron goes into solution, and the 
 copper is precipitated in the form known as " cement 
 copper," which is collected periodically, washed on a 
 filter, with hot acidulated water, dried and sold. As it 
 may contain gold it should be assayed for that metal. 
 
 MEANS OF DRAWING LIQUID FROM 
 PRECIPITATING VATS. 
 
 175. Some operators use wooden faucets for this 
 purpose. One objection to faucets is, that a portion of 
 the precipitated gold lodges in the bore, and it is neces- 
 sary, on opening the faucet, to place a bucket under it 
 to receive the first liquid which flows. Faucets often 
 give trouble by leaking, especially when used for metal- 
 lic solutions, which have a tendency to cause wood to 
 shrink. Plugs are also objectionable on account of 
 their liability to leak. If used they must fit flush with 
 the inside of the tub. 
 
 A piece of rubber hose, applied as a syphon, answers 
 very well, if prevented from drawing too near the bot- 
 
ADDENDA. 107 
 
 torn of the vat, by fastening a strip of wood to it so 
 that the wood projects beyond the end of the hose. A 
 better plan is, to insert in each end of the hose a tightly 
 fitting piece of lead pipe, which is coiled once round in 
 a spiral form. The hose having been fi!led with water, 
 is laid across the side of the vat, the inner end dipping 
 beneath the surface of the liquid. 
 
 Air cannot pass the curves in the leaden portion of 
 the syphon while it is full of liquid, so that if the work- 
 man neglects to lower it as the liquid in the vat subsides, 
 no inconvenience results, and the flow is resumed as 
 soon as the inner end is lowered by drawing the hose 
 over the side of the vat. 
 
 RECOVERY OF ABSORBED GOLD. 
 
 176. The false bottoms, of perforated wood, and the 
 chlorinating vats, should be burned when no longer re- 
 quired, as they contain a considerable quantity of gold. 
 At my works at Melrose the ashes of the four false 
 bottoms yielded about $90 worth of gold and silver. 
 The vats were assayed by boring a hole in one, burn- 
 ing the chips and smelting the ashes, which gave only 
 $6 per tub, and, as they were still serviceable, it would 
 not have been profitable to burn them. I attribute the 
 fact of the vats having absorbed so much less gold than 
 the false bottoms, to the circumstance that they had 
 previously been used in the Hunt, Douglass, and Stew- 
 art copper silver process, and were quite saturated 
 with brine, etc., while the false bottoms were of new 
 lumber. Both were tarred. 
 
108 ADDENDA. 
 
 GENERATORS. 
 
 177. There are several forms of generator. That 
 described differs slightly from those in general use. In 
 Deetken's generator, with water joint cover, the wall 
 of the water chamber is not high enough to allow of 
 filling the vessel with water, to expel the chlorine. 
 Kustel describes one in which the stem of the stirrer 
 passes through a stuffing box instead of a water joint, 
 and in place of a water joint for the main cover, is a 
 shallow groove containing clay and a little water. I 
 have used this joint, and it answers very well, but 
 hardly allows of filling the generator with water. A 
 stirrer is not indispensable; at Crosby's works in Ne- 
 vada City it was not used. 
 
 I think the apparatus shown in Plate 5 has some 
 advantages over the others. Generators for chlo- 
 rine are sometimes made like a " carbonic acid gas " 
 generator, so that any required pressure can be had, 
 but much pressure is not required in the ordinary way 
 of working ores with chlorine. 
 
 WASH-BOTTLES. 
 
 178. The wash-bottle described (68) is of my own 
 contrivance. Kustel describes one, made from an 
 acid-carboy, arranged like that which I have described 
 for the working test. Dcctken used simply the bell 
 glass, standing in an open basin of water, with leaden 
 pipes for the introduction and eduction of the gas, 
 passing under the edge of the bell. This arrangement 
 would seem liable to upsetting. I used one in which 
 
ADDENDA. 109 
 
 the bell was secured vertically, in a tub of water, by 
 means of a cross board fixed in the tub, with a hole to 
 fit the bell. The gas was introduced by a leaden pipe, 
 passing under the bell, and escaped through the neck 
 of the latter, with which a rubber pipe was connected. 
 
 The objection to a bell standing in an open vessel 
 containing water is, that the water becomes saturated 
 with chlorine, which is constantly evolved from the 
 exposed surface. This, though not important in a well 
 ventilated room, may produce inconvenience in closer 
 quarters. The carboy is less convenient than the bar- 
 rel for the renewal of the water, besides being liable to 
 accidental breakage. So, on the whole, I think that my 
 contrivance is to be preferred. The barrel will be the 
 better for being tarred inside; better still if coated with 
 paraffin. 
 
 If there is any difficulty in finding a bottle which will 
 admit the chlorine pipe through the neck, it will answer 
 to pass the pipe through the head of the keg. The 
 gas will find its way to the bell, and, if the keg is full 
 of water, the bubbling of the chlorine will be as visible 
 as if it were delivered immediately under the bell, 
 which, however, must be set higher than in the figure 
 in this case, unless the pipe be of lead, and curved so 
 as to deliver under it. 
 
 It "is not essential that the gas should be seen to 
 pass, because it can always be heard bubbling through 
 the water, so that a glass bell is not absolutely re- 
 quired, but it is convenient, enabling one to see that 
 the proper quantity of water is in the keg. 
 
 The water should be renewed once in two or three 
 
110 ADDENDA. 
 
 weeks, and that which is drawn out can be utilized in 
 making the precipitant for gold from scrap iron. 
 
 SIFTING ORE. 
 
 179. The usual method of sifting the damp ore 
 into the vats, by means of a shaking sieve worked by 
 hand, is tedious. The roasted ore might be sifted dry 
 through a rotatory cylinder sieve, by hand or by power, 
 and afterwards moistened as usual; then thrown lightly 
 into the vat, by being shaken off a shovel, and dis- 
 tributed by raking. This method would admit of the 
 use of a fine sieve. 
 
 COST OF ACID. 
 
 180. Sulphuric acid of 60 Beaume, or 1.76 sp. gr., 
 containing, according to Ure, 69.31 per cent of "dry 
 acid," costs four cents per pound in San Francisco. 
 One pound of this acid is equal to i .06 pounds of acid 
 of 63 Beaume, or 1.71 sp. gr., containing 65.25 per 
 cent of dry acid, and costing 2^2 cents per pound. 
 From this it is evident that the weaker acid is the 
 cheaper to use, unless freight costs 1 5 cents per pound. 
 (Double freight is charged on acid by the Railroad 
 Companies.) For example: 
 
 i Ib. of acid of 66 4 cents. 
 
 i Ib. freight 15 
 
 ig cents. 
 
 i. 06 Ibs. of acid of 63. . . 2.65 cents. 
 1.06 Ibs. freight at 15 cts. . 15.9 
 
 18.55 " 
 
ADDENDA. Ill 
 
 Taking into consideration the freight on the carboys, 
 which must be paid both ways if they are returned, 
 thougji not equally, an addition of about 30 per cent 
 must be made to the weight on which double freight 
 must be paid, and about 20 per cent of ordinary freight, 
 or 10 per cent of the first addition, making the cost of 
 the acids respectively: 
 
 Strong acid per lb. as above. . 19. cents. 
 
 Freight on carboy going 4.5 " 
 
 " " returning. .. .0.45 
 
 23.95 cents. 
 Weak acid as above, i .06 Ibs. ..18.55 cents. 
 
 Freight on carboy going 4-77 " 
 
 " " returning. . . 0.47 
 
 23.79 cents. 
 
 The carboys are charged for at the rate of $2.25 each, 
 and if not returned their cost must be added to that of 
 the acid. This makes an inappreciable difference in 
 the relative cost of the two grades. Acid can be 
 bought and freighted more cheaply if a carload is taken 
 at once. 
 
 SALT, MANGANESE, AND ACID. 
 
 181. According to the chemical view of the pro- 
 duction of chlorine from salt and manganese, under the 
 action of sulphuric acid, 26.8 pounds of pure salt is suffi- 
 cient for 20 pounds of pure manganese binoxide. But, 
 in this connection, two points must be considered. 
 Firstly, the commercial salt and manganese are never 
 pure, the former not often containing more than 90 
 per cent of sodium chloride, while the latter is consid- 
 
112 ADDENDA. 
 
 ered to be a good article if it contains 70 per cent 
 binoxide. Secondly, the theoretical reaction is not per- 
 fectly realized in practice. 
 
 If the proportion of salt is too small, as compared 
 with that of the manganese and acid used, the latter 
 two will react, giving off oxygen, and forming man- 
 ganese sulphate, so that the subsequent addition of 
 more salt will not repair the error. A mistake in 
 the direction of an excess of salt can be rectified by 
 an addition of acid and manganese, but as salt is the 
 cheapest of the three substances, this is less important. 
 In the directions given (94) for making chlorine, the 
 proportions are those in common use, and the salt is 
 intended to be somewhat in excess of the other 
 substances. 
 
 In case the quality of the salt or manganese 
 should differ much from the assumed average, there 
 might be a considerable waste of one or the other, 
 whence it seems desirable that the reader should be 
 informed as to the manner in which these substances 
 may be assayed, in order that they may be propor- 
 tioned correctly. 
 
 182. Assay of Salt. Take a fair sample of the salt 
 to be assayed. It must not be dried, because what is 
 required is its value for the production of chlorine in 
 the condition in which it is to be weighed for working, 
 but, if too coarse, it should be crushed. Mix thor- 
 oughly. Dissolve 10 grains in about 50 grains, or 
 rather less than y% fluid-ounce, of distilled or rain water, 
 or at least water which gives no precipitate on addition 
 of a drop of solution of silver in nitric acid. Filter the 
 solution through a small wetted filter of fine bibulous 
 
\ 
 
 ADDENDA. 113 
 
 paper. The filter must be well washed with water to 
 completely remove the salt solution, and the filtrate and 
 washings received in a flask. 
 
 To the filtered solution in the flask add, drop by 
 drop, a solution of silver nitrate until no further precip- 
 itation of silver chloride takes place. Warm slightly, 
 and shake vigorously, stopping the mouth of the flask 
 with a greased cork, until the precipitate is found to set- 
 tle readily, leaving the liquid clear. Now transfer to a 
 small filter, the weight of which has been previously 
 ascertained after drying on a water bath until it no 
 longer lost weight. Wash the precipitate and the filter 
 with hot water until the washings are tasteless. Dry 
 the filter, containing the precipitate, on a water bath 
 until two successive weighings give the same result. 
 From the weight obtained deduct that of the filter ; the 
 remainder will be the weight of silver chloride produced 
 by 10 grains of the salt. 
 
 If the salt were pure and dry, 10 grains would pro- 
 duce 24.53 grains of silver chloride, but if we say 24.5 
 grains" it will be sufficiently accurate. Multiply the 
 weight of silver chloride found by 100, and divide by 
 24.5 ; the result will be the percentage of pure salt in 
 the sample. EXAMPLE: The silver chloride obtained 
 from 10 grains of the sample weighs net 19.3 grains; 
 then the sample contains 1930-4-24.5 = 78.77 per cent 
 of pure salt. 
 
 The silver chloride should be dried without much 
 exposure to light. For a water bath, the cover of a 
 vessel in which some water is boiling answers very 
 well. The pulp scales used in assaying ore are 
 sufficiently accurate for this work, if sensitive to 
 
114 
 
 ADDENDA. 
 
 183. The salt sometimes contains a considerable 
 quantity of sodium carbonate, which neutralizes an 
 equivalent quantity of acid. In the interior of the 
 country, where this is most liable to occur, acid is very 
 expensive on account of the cost of freight. Such salt 
 should therefore be purified, by dissolving it in water, 
 and exposing the solution to evaporation in shallow 
 vats, when the purified salt will be deposited. 
 
 184. Assay of Manganese. Take a short necked, 
 flat bottomed flask of three ounces capacity, and fit 
 into it a cork through which pass two glass tubes of 
 about y% inch bore. One of the tubes must extend 
 nearly to the bottom of the flask ; the other, about three 
 inches in length, is bent to a right angle about an inch 
 from one end, the shorter limb being passed through 
 the cork. Now take the barrel of a small glass syringe, 
 such as is used for medical purposes, the orifice of 
 which must be enlarged by cutting off a portion of the 
 beak. Fit a cork to the larger end, and through it pass 
 the disengaged end of the bent tube, the other end of 
 which is in communication with the flask. Place 
 in the syringe some pieces of pumice stone, and moisten 
 
 them with sulphu- 
 ric acid; attach to 
 the bent tube by 
 means of the cork. 
 A test tube sus- 
 pended from the 
 neck of the flask 
 completes the ap- 
 paratus, which is 
 represented by the 
 accompany ingcut. 
 
ADDENDA. 115 
 
 Weigb 99 grains of the finely pulverized man- 
 ganese which place in the flask. Add one ounce of 
 cold water, and then 150 to 160 grains of sulphuric 
 acid. Replace the cork in the neck, with the glass 
 tubes, and, applying the lips to the orifice of the 
 syringe, suck air through the flask. This is done for 
 the purpose of removing any gas which the acid may 
 cause to be evolved from impurities in the manganese. 
 Now weigh 150 grains of oxalic acid which place in 
 the test tube, put the entire arrangement upon the pan 
 of a balance which will indicate T V grain, and counter- 
 poise it. 
 
 Remove the apparatus from the balance, throw the 
 oxalic acicl from the test tube into the flask, cork in- 
 stantly and set aside for a short time. When efferves- 
 cence ceases, warm slightly, which will renew it, and 
 when no more p"as . is evolved draw air through the 
 
 o o 
 
 flask as before. Place the entire apparatus again on 
 the scales. It will be found to be lighter than before, 
 and the number of grains required to restore the equili- 
 brium will be the percentage of binoxide in the sample. 
 This' method, while not rigidly accurate, is sufficiently 
 so for practical purposes. It depends on the circum- 
 stance that oxalic acid, in presence of sulphuric acid 
 and manganese binoxide, is converted into water 
 and carbonic acid gas, (carbon dioxide). The 
 water remains in the apparatus. The gas escapes 
 through the tube containing pumice imbued with sul- 
 phuric acid, which retains any vapor of water which 
 might otherwise pass off, the last portion of the gas 
 being drawn out by the mouth as directed. Thus 
 nothing but the carbonic gas escapes, and as 99 grains 
 
116 ADDENDA. 
 
 of pure binoxide produce almost exactly 100 grains of 
 the gas, it follows that the weight lost corresponds to 
 the percentage of binoxide in the sample. 
 
 185. Having assayed the salt and manganese, the 
 relative proportion in which they should be used re- 
 mains to be considered. It has already been intimated 
 that practice does not conform strictly to theory, not 
 because the theory is incorrect, but because the condi- 
 tions attainable in working do not admit of its complete 
 realization. Hence it is found necessary to use sul- 
 phuric acid in excess of the chemical equivalent of the 
 manganese, and as sulphuric acid is only useful in con- 
 junction with a sufficient quantity of salt, the latter must 
 also be in excess of the manganese. 
 
 For this reason, instead of only 27 pounds of pure 
 salt to 20 pounds of manganese binoxide, we use 36 
 pounds ; these quantities usually suffice for the chlori- 
 nation of three tons of roasted ore. In order to ascer- 
 tain how many pounds of the impure materials must 
 be used, it is only necessary to divide the quantity of 
 the pure substance required by the fraction representing 
 the percentage found in the assay. 
 
 Example: Suppose the assay of the salt gave 87 
 percent, it is required to know how much of it is equal 
 to 36 pounds of pure salt, then 36 -5-. 87=4 1.37 pounds; 
 again, if the manganese is 66 */ per cent, then 
 20-^.665=30 pounds of the manganese to 41 pounds of 
 the salt, which is about the proportion generally used,, 
 but either or both of the substances may vary from this 
 supposition. 
 
 As to the acid, the quantity required depends so much 
 on the temperature of the generator, and the nature and 
 
ADDENDA. 117 
 
 quantity of the impurities in the other materials, that 
 no other rule can be given than this; it must be added 
 in small portions as long as it continues to develope a 
 useful quantity of chlorine. It will soon be discovered 
 how much is required for a given quantity of salt and 
 manganese. 
 
 The strength of the acid is indicated by its density, 
 as measured by a Beaume hydrometer, which is simply a 
 floating gauge the higher it floats the stronger is the 
 acid, and the reverse. 
 
 SURPLUS CHLORINE. 
 
 186. The gasometer, suggested for the removal of 
 surplus chlorine (98), might be made by attaching 
 a leaden curtain to a disc of wood to which the 
 suspending chains would then be fastened. A light 
 tub, with wooden hoops, thoroughly soaked with paraf- 
 fin or ozokerite, would probably answer the purpose. 
 
 The chlorine withdrawn from the vats, would, most 
 likely, be contaminated with air, and as its re-use is not 
 of great importance, the apparatus might be simply used 
 to blow air through the ore mass, from below the filter, 
 thus expelling the chlorine through a hose connecting 
 with the hole in the cover of the vat, and conducting 
 out of the room. 
 
 In this way there would be no difficulty in the con- 
 struction of the bell, as either wood or iron could be 
 used. Other methods of blowing air through the ore 
 will readily suggest themselves. 
 
 Precipitating vats for gold are sometimes made in 
 the form of rectangular tanks of wood, lined with sheet 
 
118 ADDENDA. 
 
 <, 
 
 lead. This vat, though more expensive than a wooden 
 tub, has some advantages. There is no risk of absorp- 
 tion of the gold solution, and it is not necessary to add 
 the precipitant until the vat has received its quota of 
 solution. Then, if the solution contains much free 
 chlorine, a jet of steam may be introduced and the 
 chlorine driven off, after which the precipitation of the 
 gold by means of iron sulphate proceeds better, and 
 with a smaller consumption of the precipitant. 
 
 As it is necessary to heat the solution in order to 
 drive off the chlorine in this way, it cannot be thus done 
 so thoroughly in a tarred tub, on account of the softening 
 of the tar. It could, however, be done by blowing air 
 through the solution. 
 
 , PRECIPITATING GOLD. 
 
 187. It occurred twice in my works that on collect- 
 ing the precipitated gold it was found to be brick red, 
 instead of having the usual brown color. It was also 
 deficient in quantity. On the first occasion I could not 
 account for this, but on the second I satisfied myself that 
 the workman had not thoroughly mixed the precipitant 
 with the solution, and being consequently deceived by 
 a test, he had not used iron sulphate in sufficient 
 quantity. 
 
 188. If the solution of gold contains lead chloride, 
 the iron sulphate causes a precipitation of lead sulphate, 
 which renders the subsequent washing of the. gold diffi- 
 cult. This may be prevented by precipitating the lead 
 as sulphate by means of sulphuric acid, or any soluble 
 sulphate by which the gold will not be affected, as so- 
 
ADDENDA. , 119 
 
 dium sulphate. After settling, the liquid must be 
 transferred to another vat, in which the precipitation of 
 the gold is effected as usual. 
 
 In some cases the leach contains substances the 
 character of which has not been determined, and which 
 affect the purity of the precipitated gold. I f the lixivium 
 is allowed to stand several hours, a deposit is formed on 
 the sides of the vat. The purified solution is then 
 drawn off into another vessel, and the solution of iron 
 sulphate is added. 
 
 SUSPENDED GOLD. 
 
 189. By taking some of the waste liquor from the 
 gold tub, filtering twice through Sweedish paper, and 
 then smelting the paper with litharge, I found that after 
 24 hours settling there remained gold in suspension, 
 equal to $1.00 in value for each ton of ore leached. 
 After 48 hours I still found half that quantity. The fil- 
 trates from these tests were boiled with zinc until all 
 precipitable metals were thrown down. The precipi- 
 tate contained no gold, which shows that iron perchlor- 
 ide does not dissolve gold in presence of the iron proto- 
 salts, thus setting at rest a doubt which had arisen, 
 as to whether or not the precipitated gold might be, to 
 some extent, re-dissolved by remaining for many hours 
 in contact with the solution of iron persalts, which is 
 produced when gold terchloride is decomposed by iron 
 proto-sulphate. 
 
 PRECIPITANTS FOR GOLD. 
 
 190. When the ore contains copper, the waste so- 
 
120 ADDENDA. 
 
 lution from the tanks in which the copper is precipi- 
 tated can be used for refilling the vat containing the 
 precipitant for gold, as it contains a large quantity of 
 iron protosalts, chloride and sulphate. The strength 
 must be reinforced with copperas, or acid and iron. 
 The waste liquor from the chlorine generator, consisting 
 partly of manganese proto-sulphate,is also a good precip- 
 itant for gold. In order to utilize as much as possible 
 of the chlorine which it contains, as well as any free 
 acid which may be present, it should be placed in a 
 covered tub, or small vat, with some scrap iron. 
 In a day or two the chlorine and the acid will be satur- 
 ated with iron, thus forming an additional quantity of 
 precipitant. 
 
 Other preciptants which yield the gold in the metal- 
 lic state are, oxalic acid, sulphurous acid, the antimony, 
 arsenic, and copper lower chlorides, and animal char- 
 coal. The latter is used as a filter on which the gold 
 solution is poured, when the particles of carbon become 
 covered with a film of gold. It is patented. In some 
 European works the gold is, or was, thrown down as a 
 sulphide, by means of hydrogen sulphide. This 
 method has the disadvantage of precipitating also 
 copper, and some other metals, if present. 
 
 SAND IN GOLD MELTING. 
 
 191. Many years ago I was employed as melter in 
 a bullion assaying establishment, and was often called on 
 to refine gold, which was done by granulating and 
 re-fusing with nitre and borax, in a sand pot. It often 
 
ADDENDY. 121 
 
 happened that the crucible broke in the furnace, causing 
 a great deal of trouble. 
 
 Knowing that the pots were attacked not only by 
 the metal oxides produced in the refining, but also by 
 the potassa resulting from the decomposition of the 
 nitre, it occurred to me to mix some clean quartz sand 
 with the nitre, which answered so well that I never 
 afterwards had a pot broken in the furnace. 
 
 DRYING CHAMBER. 
 
 192. For drying the gold, I suggest that a conve- 
 nient arrangement would be a sheet-iron closet, in the 
 form of a muffle, in the dust chamber, with a door 
 which could be locked. In this the dishes containing 
 the gold could be left with safety and convenience as 
 long as necessary. A similar but larger closet could 
 be used for drying the silver precipitate. Such a closet 
 is represented at /, Plate 7. 
 
 VOLATILIZATION OF GOLD. 
 
 193. It has been stated by some authors that there 
 is never much loss of gold in- roasting ores, unless the 
 roasting is performed too rapidly, and that the addition 
 of salt makes no difference in this respect. I differ with 
 them on this point, even when the statement is sup- 
 ported by so formidable a name as that of Plattner. 
 But I think that illustrious chemist would yield to the 
 logic of a pecuniary loss of three thousand dollars, es- 
 pecially when backed by other facts. 
 
 When I first entered on the business of gold chlori- 
 
122 ADDENDA. 
 
 nation on the large scale, I had a class of concentra- 
 tions to treat which, while consisting chiefly of iron 
 pyrites, and presenting no visible peculiarity, had never- 
 theless baffled many old operators, a fact of which I 
 was not at the time aware. The ore was roasted in a 
 three-hearth reverberatory furnace, with the addition 
 of from i to 2 per cent of salt, on account of the pres- 
 ence in it of a considerable quantity of silver. 
 
 I was surprised to find that although the assays of 
 the tailings were satisfactory, the gold, when collected, 
 fell alarmingly short of the results which I had guaran- 
 teed, and I was of course obliged to make up the defi- 
 cit. 
 
 Relying on the statement referred to, which I found 
 in the only handbook on the subject within my reach, 
 and being then a novice in this branch of metallurgy, I 
 did not dream that a serious loss was taking place in the 
 roasting furnace, especially as I had an expert metal- 
 lurgist in reduced circumstances employed on the roast- 
 ing, who had no more suspicion of the truth than I had. 
 
 Finding that I was sustaining some loss by inade- 
 quate tub room for the gold solution, and having con- 
 sequently to draw the liquid from the gold-tub too soon 
 after precipitation, I thought that I should find the whole 
 loss to be in the leaching and precipitating department, 
 and each time that an improvement was made, expected 
 better results, so that I was led on from trial to trial, 
 until the total loss reached the sum named. 
 
 I am not quite certain that I should ever have dis- 
 covered the truth, but for the following accident. One 
 day, I so far checked the draft of the furnace as to 
 cause some fumes to come through the airholes and 
 
ADDENDA. 123 
 
 working doors, and a yellow sublimate on the masonry 
 attracted my attention. On examination I found the 
 sublimate to be very rich in gold, although there was 
 none to be seen in it by the most careful washing. It 
 also contained iron perchloride, and copper chloride, 
 with some lead and other substances. This aroused 
 my suspicion, and I at once did what I ought to have 
 done sooner. 
 
 Knowing that the material could be roasted with lit- 
 tle or no loss, if no salt was used, because some assays 
 had been made in that way, I weighed two half ounces 
 of a sample, and roasted them in the muffle side by 
 side, under precisely the same conditions, except that 
 to one of them I added 4 per cent of salt. The roast- 
 ing was purposely pushed to an extreme as to heat and 
 time, and when the two tests were assayed, under ex- 
 actly similar conditions, that which was salted was 
 found to contain less than half as much gold as the un- 
 salted one. 
 
 I then took some light fluffy sublimate from 
 the flue of the roasting furnace, an assay of 
 which gave me a value of some $600 per ton, 
 chiefly gold. The quantity of this material was, 
 however, very small, and the bulk of the matter in 
 the dust chamber was not much richer than the aver- 
 age of the ore treated, a circumstance which indicates 
 that the gold was actually to a great extent volatilized 
 in some not easily condensable form. I also found that 
 the ore sustained a loss of weight in roasting, equal to 
 about 1 8 per cent, consequently the roasted ore ought 
 to have been more than 18 per cent richer than before 
 roasting, which was not the case. 
 
124 ADDENDA. 
 
 If this is not considered to be sufficient proof 
 that gold may be volatilized in the roasting of 
 some ores with salt, the deficiency is supplied 
 by the fact that, as soon as I made the 
 necessary change by reserving the salt until the 
 nearly dead roasting of the ore was finished, not only 
 did the roasted ore assay 20 per cent richer than when 
 raw, but the yield overran my guarantee, while the 
 tailings nevertheless contained considerably more gold 
 than before. 
 
 The moral of this is, never to neglect any precaution 
 in the way of tests and assays, nor to place implicit reli- 
 ance on rules laid down, or inferences drawn by others 
 who have worked under different conditions. 
 
 I afterwards found that a very small quantity of salt, 
 not more than three pounds to the ton, might be mixed 
 with the crude ore without detriment to the gold, and 
 
 o ' 
 
 with decided advantage to the extraction of the silver. 
 
 SOLUTION OF SILVER IN HYPO. 
 
 194. The statement that silver chloride dissolves in 
 a solution of calcium hyposulphite is not strictly accu- 
 rate. It is decomposed, exchanging constituents with 
 the calcium salt, forming calcium chloride and silver 
 hyposulphite. The latter combines with another por- 
 tion of calcium hyposulphite, and forms a double salt, 
 silver calcium hyposulphite, which is very soluble in 
 water. 
 
 If calcium pentasulphide is added to such a solution 
 in equivalent proportion, one-fifth of its sulphur com- 
 
ADDENDA. 125 
 
 bines with silver to form silver sulphide, which is pre- 
 cipitated, together with the remaining four-fifths of the 
 sulphur.. The oxygen, and so-called hyposulphurous 
 acid, which were combined with the silver, combine 
 with the calcium of the decomposed precipitant. Thus 
 the portion of the solvent which was decomposed by 
 silver chloride is reproduced. 
 
 From this it follows that, for every atom of silver 
 extracted from the ore, and precipitated by polysul- 
 phide, the solvent gains a molecule of calcium chloride, 
 without however having ultimately lost any hyposul- 
 phite, and this is the reason why the density of the so- 
 lution ceases to be an index of its solvent power. So 
 far there is neither a loss nor a gain of calcium hypo- 
 sulphite in the dissolving solution, but, as stated else- 
 where, the precipitant always contains a quantity of 
 that salt in watery solution, which being added to the 
 solvent, increases its volume without impairing its 
 strength, unless the precipitant is too much diluted. 
 
 In practice the increase or diminution in strength and 
 volume of the solvent depends on the care exercised 
 in saving as much of it, with as little addition of wash 
 water, as possible, and in having the precipitant suffi- 
 ciently concentrated. Kustel gives 6 Beaume, as a 
 minimum density for the latter. 
 
 WASTE OF SULPHUR. 
 
 195. The quantity of sulphur required for the pre- 
 cipitation of silver is really only as 16 to 108, but a 
 great waste occurs in the process described, from two 
 causes : Firstly, there is always a certain quantity of 
 
126 ADDENDA. 
 
 base metal dissolved with the silver, which also takes its 
 portion of sulphur from the calcium sulphide; sec- 
 ondly, a large proportion of the sulphur is thrown down 
 in a free state, and, in the usual course of procedure, is 
 totally wasted by being burned off in the roasting of the 
 precipitate. 
 
 The reason for this precipitation of free sulphur is 
 that the precipitant is necessarily a pentasulphide, for 
 the calcium mono sulphide is insoluble, and the bisul- 
 phide is only soluble with heat (vide Regnault\ so that 
 for our purpose we are restricted to the pentasulphide. 
 
 But in the precipitation, only one-fifth part of the sul- 
 phur of the pentasulphide can enter into combination 
 with the silver, forming silver sulphide, and as the cal- 
 cium combines with the oxygen and hyposulphurous 
 acid which were combined with the silver, the remain- 
 ing four-fifths of the sulphur are unoccupied and use- 
 less. 
 
 Base metals, when present in the solution, act simi- 
 larly, combining with only a portion of the sulphur of 
 the pentasulphide, only arsenic and antimony forming 
 pentasulphides. Gold forms tersulphide, but its quan- 
 tity is usually insignificant in the lixivium. 
 
 RECOVERY OF SULPHUR. 
 
 196. There are two methods by which the free sul- 
 phur may be recovered from the precipitate. The first, 
 introduced, it is believed, by Ottokar Hofman, consists 
 in subjecting the mass to heat, in a retort, and con- 
 densing the sublimed sulphur. The second, original 
 with myself, and which seems preferable, is as follows : 
 
ADDENDA. 127 
 
 The unwashed precipitate is placed in a vat with water, 
 boiled by means of a jet of steam, and slaked lime care- 
 fully added. 
 
 The free sulphur combines with the lime, in the 
 manner already described, producing at once the pre- 
 cipitating solution of calcium polysulphide, and much 
 more quickly than when the fresh sulphur is used. The 
 boiling can be done in a filter vat, and when finished 
 the clear solution can be drawn off. The precipitate is 
 washed by passing hot water through it, dried and 
 roasted as usual. Three-fourths or more of the sul- 
 phur is thus recovered for re-use. 
 
 MATTE FROM THE SILVER. 
 
 197. The matte obtained in melting the silver pre- 
 cipitate is usually quite rich, and it seems to be impos- 
 sible to completely desilver it by means of iron alone, 
 at least in the presence of copper. The bullion is about 
 .800 fine, even when there is a good deal of copper in 
 the precipitate, because very little, copper is reduced 
 from the sulphide by iron at a white heat. It is, however, 
 necessary that enough sulphur be left, in the roasting, to 
 convert the copper into sulphide, for if too much oxide 
 45 formed a part of it may be reduced by the blacklead 
 pot, metallic iron, or by charcoal if present, and thus 
 contaminate the silver. Antimony and arsenic, though 
 their sulphides are reduced by iron, yet volatilize, or 
 combine with a further portion of iron and remain in 
 the matte. Lead, if present in the precipitate, cannot 
 be kept out of the bullion. Gold, when melted in the 
 presence of sulphur and iron, forms a black, brittle mass r 
 
128 ADDENDA. 
 
 containing much iron, but the gold sulphide obtained 
 with the silver precipitate is mostly reduced in the 
 melting, and the metal is found alloyed with the silver. 
 
 MELTING FURNACE. 
 
 198. I have seen, in the mining regions, many bar- 
 barously constructed melting furnaces, some of which 
 were very inconvenient to work with. A description 
 of the furnace which I build for silver melting, where 
 economy is an object, and of which Figures i and 2, 
 Plate 8, are sections, will probably be useful. 
 
 This furnace is suitable for a number 30 or 35 black 
 lead pot, with charcoal as fuel. There is no heavy 
 and expensive cast-iron plate on the top, and the cover 
 may be of sheet-iron, although cast-iron is better. 
 
 The interior may be cylindrical, but is better, as 
 shown in the figures, narrowed toward the top and bot- 
 tom. The grate bars rest on an iron ring, Figure 3, 
 supported by an offset in the masonry. The latter is 
 mostly of a very rough kind, as the furnace, is sunk in 
 the ground to within a foot of the top, which, besides 
 affording great convenience in working, obviates the 
 necessity of iron bands or stay-rods to support it against 
 the expansion caused by the heat. The greater part 
 of the lining, 4 inches thick, is of good clay, very slightly 
 moistened, and beaten round a hollow wooden core, for 
 which part of a barrel of suitable size answers very 
 well. It is topped with a course of common brick, 
 and above these is a flat iron ring, Figure 4, 
 with lugs, which may be bolted down, or simply let in 
 flush with the top of the furnace. 
 
Plate VHI. 
 
 Scale; 
 
ADDENDA. 129 
 
 The grate bars are not built in, but are free to be 
 removed whenever desired. The furnace is con- 
 structed, when convenient, at the base of the main 
 smoke stack, with which it is connected by a flue; 
 otherwise a large stove-pipe will answer for a chimney. 
 When the weight of melted metal does not exceed 
 100 pounds avoirdupois, the pot is lifted out of the fur- 
 nace by hand, by means of the basket tongs, the mould 
 being placed on the platform of masonry which is seen 
 in the figure on one side of, and level with the fur- 
 nace. The melter stands on the top of the furnace to 
 lift, then steps to the ground one foot lower, to pour. 
 
 If larger quantities of metal are melted at once, a 
 lever may be employed for lifting the pot. The lever 
 is arranged like that of a blacksmith's bellows, being 
 supported by a rope, chain, or swivel, in such a man- 
 ner as to admit of a lateral as well as a vertical move- 
 ment, and at a height of not less than six feet above the 
 furnace, the center of which is directly under the 
 shorter arm. 
 
 From the longer arm of the lever a rope depends; 
 from the shorter arm a link of half-inch iron, long 
 enough to reach, when drawn downward, into the 
 Cavity of the furnace, and terminating in a hook engag- 
 ing in an eyebolt which forms the pivot connecting the 
 jaws of the tongs. 
 
 The tongs being adjusted on the pot, a ring is slip- 
 ped over the handles to hold them together; the melter 
 steadies them, while an assistant, pulling on the rope at 
 the other end of the lever, lifts the pot out of the fur- 
 nace, and swings it near to the mould, when the melter 
 pours the metal. 
 
130 ADDENDA. 
 
 The hands and arms of the melter are protected by 
 gloves, which, in some works, are elaborately made of 
 canvas and padding. To make a glove, I simply take 
 an ore sack, double it lengthwise, and sew it so as to 
 form a narrow bag, of two thicknesses of canvas, into 
 which the arm may be thrust to the shoulder. The 
 gloves may be wetted to prevent burning, but hot arti- 
 cles must not be grasped with a wet glove, because the 
 steam produced will scald the hand; yet, moisture is a 
 good protection against radiant heat, while grasping 
 the cool handles of the tongs. 
 
 In melting with charcoal, the best result is obtained, 
 not by keeping the furnace full, but by letting nearly 
 all the fuel burn away, before refilling. A little, prac- 
 tice will enable the melter so to manage that there 
 shall be but little coal in the furnace when the time for 
 pouring arrives, so that it is not in the way when seiz- 
 ing the pot with the basket tongs. The lifting must be 
 performed without delay, otherwise the tongs may be- 
 come red hot, and bend. The feet and legs of the 
 melter may be protected by woolen armor, or by wet- 
 ting the boots and trowsers ; but melters and assayers 
 must not shrink from a little scorching. 
 
 If there is much fuel left in the furnace when the 
 melting is ended, the grate is taken out, and the em- 
 bers fall into the ash pit, where they are extinguished. 
 
 Clinkers, if formed on the sides of the furnace, from 
 the melting of the lining, or from dirty fuel, are punched 
 off, while red hot, by means of an iron bar with a chisel 
 end. If they were to be removed after cooling, the 
 walls would be broken. 
 
 If making a bar of clean skimmed metal, it is proper 
 
ADDENDA. 131 
 
 to throw a little resin, or powdered charcoal into the 
 pot, a few seconds before pouring. It prevents the 
 sputtering which is often caused by the formation of 
 base oxides. As soon as such a bar is cast, the top of 
 it is covered with charcoal powder, to prevent oxida- 
 tion while solidifying When the slag or matte is 
 poured with the metal the charcoal is not required. 
 
 The addition of sand in melting an impure precipi- 
 tate, especially when, by over-roasting, a good deal of 
 base metal sulphate or oxide has been formed, is very 
 beneficial in saving the pot, by slagging the oxides by 
 which it would otherwise be attacked. 
 
 Charcoal is used to effect the deoxidation of sulphates, 
 which would otherwise take place at the expense of the 
 plumbago pot. It is also employed to prevent the 
 formation of a crust, or to reduce the same if formed, 
 on the surface of the matte. 
 
 SODIUM HYPOSULPHITE. 
 
 199. Sodium hyposulphite may be made by passing 
 sulphurous acid (sulphurous anhydride) and air through 
 a solution of sodium sulphide, produced by fusing to- 
 gether five parts of sodium sulphate (a common product 
 of the marshes in the interior) and one part of pulver- 
 ized charcoal, and extracting with water. 
 
 The sodium polysulphide may also be used. It is made 
 by boiling a solution of caustic soda on excess of sulphur, 
 or by fusing together sodium carbonate and sulphur, 
 and dissolving in water. Caustic potassa (concentrated 
 lye) may be used in place of caustic soda, making potas- 
 sium polysulphide, and then potassium hyposulphite 
 
132 ADDENDA. 
 
 with sulphurous acid and air. The potassium salt 
 answers the same purpose as that of sodium. 
 
 Sodium hyposulphite may also be made by heating 
 a solution of sodium sulphite with sulphur. The latter 
 is dissolved. The sulphite is made by passing sulphur- 
 ous acid through a solution of sodium carbonate, or by 
 exposing the latter, in a moist condition, to the fumes 
 of burning sulphur (sulphurous anhydride) in a rever- 
 beratory furnace, or in the flue of a roasting furnace. 
 
 For all the purposes mentioned, the sodium carbon- 
 ate or bicarbonate may be used indifferently. 
 
 It has been asserted, by some writers, that the solu- 
 tion of sodium hyposulphite does not dissolve any gold, 
 even in those cases in which the calcium salt does so, 
 referring to that lower gold chloride which sometimes 
 exists in ore which has been roasted with salt (30). 
 This however is a mistake, as has been proved by 
 direct experiment, more than half of the contained gold 
 having been extracted from a sample of such ore, by 
 leaching it with the solution in question. 
 
 THE CHLORINATION ASSAY. 
 
 200. The so-called chlorination assay, is so far in- 
 correct that it gives not only the silver chloride, 
 but all other silver compounds which are soluble in so- 
 lutions of the alkaline or earthy hyposulphites It may 
 seem that this is a matter of indifference, since all the 
 silver that can thus be extracted can be obtained in the 
 large operation, and this view is correct as to the silver 
 sulphate. 
 
ADDENDA. 133 
 
 But, in roasting silver ores, if all the requisites of a 
 thorough chloridation are not present, certain compounds 
 of silver are formed, which, though soluble in hypo (or 
 in hot brine), and therefore extracted in the ordinary 
 chlorination assay, are neither chloride nor simple sul- 
 phate. These compounds render the extraction of the 
 silver more difficult, and affect the purity of the result- 
 ing bullion, whether the leaching process, or amalga- 
 mation be employed. 
 
 As ammonia dissolves the chloride and sulphate, but 
 not the compounds alluded to, I suggest that compara- 
 tive assays be made, occasionally, with hypo and with 
 ammonia, as the solvents. 
 
 The following account of some investigations, made 
 in 1876, and published at the time in the Mining and 
 Scientific Press, will assist in explaining this matter: 
 
 i. Roasted ore containing silver, per ton $65.00 
 
 A. Leached with ammonia, retained per ton. . 13.20 
 
 B. Leached with solution of sodium hyposul- 
 phite, retained per ton 5.20 
 
 2. Roasted ore containing, per ton 60.00 
 
 A. Leached with ammonia (after digestion for 
 several hours in warm ammonia), retained 
 
 per ton 1 5.00 
 
 B. Leached with sodium hyposulphite, re- 
 tained per ton 3-5O 
 
 3. Sample of amalgamation tailings containing 
 
 silver, per ton 9.00 
 
 A. Washed on filter with cold water; filtrate 
 contained a chloride, but gave no precipi- 
 tate with solution of potassium sulphide. 
 
134 ADDENDA. 
 
 B. Rewashed with hot water ; filtrate con- 
 tained neither chlorine nor heavy metal. 
 
 C. Again washed, with cold solution of sodium 
 hyposulphite; filtrate tested with potassium 
 sulphide gave a copious brown precipitate 
 containing silver, lead, arsenic, iron, etc. 
 
 D. Excess of potassium sulphide was added 
 to filtrate C, and afterwards, to prevent 
 re-solution of arsenic, iron protosulphate in 
 slight excess, then nitric acid to decom- 
 pose the hyposulphites. A white precipi- 
 tate was slowly formed, which on boiling 
 became yellow (sulphur). 
 
 E. Precipitate from D, removed by filtration, 
 and filtrate treated with an acid solution 
 of silver nitrate, gave no precipitate. 
 
 The inference is, that the metal salts contained in 
 the washed tailings, and dissolved by solution of so- 
 dium hyposulphite, were not chlorides. 
 
 4. Sample of amalgamation tailings contain- 
 ing silver, per ton $4.00 
 
 A. Washed on filter with hot water; filtrate 
 tested with barium nitrate showed the 
 presence of a sulphate. . Washing contin- 
 ued until no more sulphate could be 
 detected. 
 
 B. Washing repeated with hot solution of so- 
 dium chloride (free from sulphate); a por- 
 tion of the filtrate tested with potassium 
 sulphide, gave a copious pecipitate ; the 
 
ADDENDA. 135 
 
 remainder tested with barium nitrate also 
 gave an abundant precipitate. 
 
 The inference is that the metal salts extracted by 
 sodium chloride were sulphates, and as the silver is ex- 
 tracted by hot brine about as perfectly as by sodium 
 hyposulphite, it seems probable that the metals 
 exist as a multiple sulphate, otherwise the silver sul- 
 phate would have been extracted by hot water alone. 
 The tailings gave no appreciable silver chloride by 
 treatment with ammonia. The metals extracted by 
 hot brine are very slowly reduced by metallic iron, so 
 that a good result is obtained from ore in this state, in 
 pans, only by long continued working, and a base bul- 
 lion is obtained, while the addition of lime to the pulp, 
 intended to produce finer bullion, entirely prevents the 
 reduction, causing richer tailings. With silver chlo- 
 ride, even a great excess of lime does not impede 
 reduction, nor prevent amalgamation, though the latter 
 is somewhat impeded. By longer roasting of the ore, 
 the formation of silver chloride was improved, but 
 the ore required an addition of sulphur, in some form, 
 to give the best attainable result. 
 
 CHLORINATION TAILINGS. 
 
 201. However carefully the ore may be treated, 
 a certain portion of gold remains in the tailings, 
 varying, other things being equal, according to the 
 character of the ore. In case this results, in part, from 
 the presence of particles too large to be entirely dis- 
 solved, that portion can be extracted by re-treatment, 
 
136 ADDENDA. 
 
 either with gas, by chlorine water, or by amalgamation. 
 But a portion, which is sometimes quite considerable, 
 still remains, and resists every mode of chlorination or 
 amalgamation, and can only be extracted by smelting 
 with lead. 
 
 In general, it may be said that gold which can be 
 seen by the aid of a lens, after finely grinding, and care- 
 fully washing, a sample of the tailings, can be extracted 
 by chlorination, or amalgamation; but that which can- 
 not thus be rendered visible can neither be chlorinated 
 nor amalgamated, even if the ore be re-roasted, with or 
 without re -grinding. (If re-ground it forms a pasty 
 mass, which cannot be leached, being almost impervi- 
 ous to water.) Of course the ore is supposed to be 
 properly roasted in the first instance. 
 
 Concentrated sulphides containing gold, and free 
 from lead, will frequently yield as much as 98 per cent 
 of the fire assay, if moderately rich, but the extraction 
 of 95 per cent is considered a good result, from ore 
 containing $100 worth of gold in a ton. As the mate- 
 rial loses about 24 per cent of its weight in the roasting 
 and leaching, it will readily be perceived that, if there 
 has been no sensible loss of gold in the roasting, the 
 tailings from such ore will assay about $6 per ton, and 
 for every hundred tons of ore treated, there will be 76 
 tons of tailings, containing $456 worth of gold. 
 
 Tailings of this character, consisting chiefly of iron 
 peroxide, make an excellent flux for the smelting of 
 galena. All the precious metal they contain is ex- 
 tracted, together with the lead set free from the galena 
 by the action of the iron oxide, and may be considered 
 as clear profit to the smelter, who is obliged to use 
 
ADDENDA. 137 
 
 some kind of iron flux, and can find nothing, unless it 
 be metallic iron, better adapted to his purpose than 
 these tailings. Chlorination tailings can also be util- 
 ized in the manufacture of red paint. 
 
 VALUE OF BARS. 
 
 202. Large bullion scales, and troy weights, are not 
 always at hand; yet it is often desirable to know the 
 value of a bar before sending it away from the works, 
 and as good counter scales, with advoirdupois weights, 
 are generally accessible, the following facts may be 
 found useful. 
 
 The assay value of one advoirdupois pound of pure 
 silver is $18.85; tnat of one advoirdupois ounce is $1.17 
 The pound of pure gold is worth $301.44, and the ounce 
 $18.84. Hence it is easy to calculate the value of a 
 bar of which the fineness is known, and which has been 
 weighed on common counter scales to the nearest quar- 
 ter ounce. For example: a silver bar is .969 fine, and 
 weighs 82 Ibs 3*4 ounces. 
 
 Then: $18.85 x.969 = $i8.2bx 82 = $1,497-32 
 and 1. 17 x. 969- i.i3x 3/i = 3- 6 7 
 
 Making the value of the bar $1,500.99 
 
 Each i(ioth of silver in a bar is worth 1.885 cents ? 
 and each ith of gold 30.14 cents per advoirdupois 
 pound; therefore, if in the above example the bar con- 
 tained also a little gold, say .003, and perfect accuracy 
 is not required, it would be sufficient to add to the 
 value 3 times 30.14 cents for each pound weight, or in 
 all $74.14. Again, a gold bar is .969 fine and weighs 
 
138 ADDENDA. 
 
 7 Ibs. 13^ oz., or 125 J/ oz. ; then 18.84 x .969=18.26 x 
 i25^=$2,29i.63. Or, the value of a gold bar may 
 be calculated as though it were silver, and the result 
 multiplied by 16. 
 
 The commercial or market value is different from the 
 assay value. The discount on silver varies from 10 to 
 15 per cent of the assay value, to which is added one- 
 half of one per cent for mintage, or assayer's fee. 
 Gold bars free from base metal are subject to a dis- 
 count or a premium, equal to one-tenth of one per cent 
 for every ten " points," or thousandths, above or be- 
 low the quoted par fineness; discount if above, premium 
 if below. The apparent anomaly is due to the fact 
 that, if there is no base metal in the bar, all that is not 
 gold is silver, whence at par fineness, there is just 
 enough of silver in the bar to pay parting charges, etc., 
 while in a finer bar those charges must be met by a 
 discount on the value of the gold. Conversely, a bar 
 which is below par fineness commands a premium for 
 the extra silver it contains. On account of this arrange- 
 ment, bars which are more, than half gold, are stamped 
 with the gold value only, unless they contain much base 
 metal, when both gold and silver value is stamped on 
 them. 
 
 Mixed bars in which the gold forms a large part of 
 the value, but less than half the weight, are called 
 "dore" bars, and are stamped with the value of both the 
 gold and the silver. 
 
 CHLORINE. 
 
 203. Chlorine plays such an important part in con- 
 nection with human industry, that a short sketch of its 
 
ADDENDA. 13S) 
 
 history and properties cannot but be interesting and 
 useful. 
 
 Chlorine is an elementary body, as far as is yet 
 known. It is true that this substance has been sus- 
 pected by chemists to be a compound, but although its 
 decomposition has been more than once announced, it 
 has not, within the writer's knowledge, been verified. 
 
 Chlorine was discovered by Scheele in 1774, and, in 
 accordance with the crude notions then entertained, 
 was called " depklogisticated marine air'' Sir Hum- 
 phrey Davy investigated its properties at a later date, 
 and gave it the name which it now bears, derived from 
 a Greek word signifying pale green, or yellowish green. 
 The name of the mineral " chlorite" has the same de- 
 rivation, but this substance contains no chlorine, and 
 must not be confounded with the chlorous acid salts, 
 which are also called chlorites. 
 
 Under ordinary circumstances, chlorine is a pungent 
 and suffocating gas of a yellowish green color, and is 
 2.44 times as heavy as an equal volume of air. When 
 compressed to one-fifth of its normal volume it becomes 
 liquid, and is then 1.33 times as heavy as an equal 
 volume of water. 
 
 Chlorine has powerful affinities, which cause it to 
 combine, under suitable conditions, with almost every 
 other known element. When naturally combined with 
 silver, it forms the well known mineral horn silver. It 
 is also found in nature, combined with lead, copper, and 
 other metals, especially with sodium in the compound 
 known as common salt. When it is considered that 
 the entire ocean, covering three-fourths of the surface 
 
140 ADDENDA. 
 
 of the globe, with a depth, in places, of several miles, 
 is heavily charged with salt, and that over six-tenths of 
 the weight of salt consists of chorine, it will be per- 
 ceived that a more definite statement could hardly con- 
 vey a more definite idea of the enormous quantity of 
 chlorine existing in the world. If all the chlorine in 
 the ocean could be set free at once, it would destroy 
 every vestige of life on the globe. 
 
 In combination with hydrogen, chlorine forms hydro- 
 chloric acid gas, and in this form is evolved in enor- 
 mous quantities in the manufacture of soda-ash from 
 salt, by the agency of sulphuric acid. The gas, dis- 
 solved in water, forms ordinary hydrochloric or muri- 
 atic acid. This acid, in contact with manganese binox- 
 ide, evolves chlorine, and it is in this way that chlorine is 
 produced, in countries where the acid is a waste pro- 
 duct of the soda works, for the manufacture of the 
 so-called chloride of lime, or bleaching powder. In 
 this country the use of chlorine is limited, and we gen- 
 erally make the hydrochloric acid, and develop chlorine 
 from it at the same time, by means of a mixture of salt, 
 manganese binoxide, and dilute sulphuric acid, as ex- 
 plained in the directions for the chlorination of gold 
 ores. The best remedy for the effects of an accidental 
 inhalation of chlorine is, to breathe the vapor of water 
 or alcohol, or to drink a glass of spirits. 
 
 PLATTNER'S PROCESS. 
 
 204. The process of gold extraction known as 
 Plattner's chlorination process, which is that described 
 
ADDDENA. 141 
 
 In the text, originated in Europe, and was first intro- 
 duced here by G. F. Deetken, M. E., at Grass Valley, 
 in Nevada County. 
 
 In 1866, Mr. Deetken having removed from Grass 
 Valley, the operators who succeeded him were suddenly 
 confronted by a difficulty in the treatment of the con- 
 centrations from the Eureka mine, which all at once 
 developed an amazing capacity for absorbing chlorine, 
 so that the application of Plattner's process to them 
 ^was no longer profitable. The writer, happening to 
 visit Grass Valley in that year, was applied to for a 
 remedy for the difficulty, which, not being aware of the 
 cause, nor having facilities for investigation, he was not 
 able to supply ; but the matter being made public 
 through the medium of the Mining and Scientific Press, 
 it arrested the attention of Mr. Deetken, who at once 
 repaired to the spot, and, with his well known skill, and 
 professional sagacity, detected the cause of the diffi- 
 culty and applied the remedy. 
 
 The trouble was occasioned by the presence of a 
 magnesian compound in the concentrated sulphurets. 
 By the addition of a small quantity of salt to the roast- 
 ing mass, this substance was converted into magnesium 
 chloride in the furnace, much more cheaply than it 
 could be done by means of chlorine in the vats. The 
 gold was then chloridized in the usual manner. The 
 use of salt in the furnace for this purpose was, so far as 
 is known to the writer, original with Mr. Deetken, being 
 quite distinct from its use for the purpose of chlori- 
 dizing silver, when present in the ore. To this gentle- 
 man we also owe the demonstration of the possibility of 
 conducting the process in wooden vessels. 
 
142 ADDENDA. 
 
 THE KISS PROCESS. 
 
 205. The use of alkaline or earthy hyposulphites- 
 for the extraction of silver from ores, also originated in 
 Europe, having been suggested by Dr. Percy, in 1848, 
 and first applied in practice by Von Patera, in 1858, at 
 Joachimsthal. Von Patera used the sodium hyposulphite 
 for the leaching, and the sodium polysulphide for the 
 precipitation. This method was modified by Kiss, who 
 substituted the calcium salts for those of sodium. 
 
 The Kiss process was first successfully introduced 
 on this coast by Kustel and Hofman, in Mexico, after 
 abortive attempts had been made by others in Lower 
 California. It met with such success as to supercede 
 amalgamation in the treatment of silver ores, through- 
 out the State of Sonora, and the Territory of Lower 
 California, and was even known among ill informed, 
 people as the " Mexican process." It has been gradu- 
 ally growing in public favor, the principal obstacle to 
 its extensive adoption in the silver regions of Nevada 
 being the circumstance that the ores of that State 
 usually carry more or less gold, which, while frequently 
 not justifying the application of the Plattner process, is 
 but partially, and almost by chance, extracted in the 
 Kiss silver process. 
 
 One great objection to the use of the Plattner process 
 in these cases is, the cost of acid, the transportation of 
 which is troublesome and expensive. It is therefore 
 desirable that some means of developing pure chlorine 
 from salt cheaply, without the use of acid, should be 
 devised. 
 
ADDENDA. 
 
 THE BRUCKNER FURNACE. 
 
 206. This furnace consists of a horizontal, brick- 
 lined, hollow cylinder, of boiler iron, with central open- 
 ings at the ends, through which the flames from a fixed 
 fireplace pass to a flue connecting with a dust chamber, 
 while the cylinder rotates slowly on rollers. The ore 
 is introduced and discharged, periodically, by means of 
 trapdoors in the side of the cylinder. The latter is 
 divided lengthwise by a reticulated, spiral partition, or 
 diaphragm, composed of cast-iron plates supported by 
 hollow cast-iron bars, which, passing through the walls 
 of the cylinder, admit of a circulation of air through 
 them, with the design of protecting them from too great 
 heat. 
 
 The function of the diaphragm is twofold; firstly, to 
 lift the ore, and shower it through the heated air within 
 the furnace as the latter revolves; secondly, to move 
 the ore from end to end of the cylinder, in order that 
 all portions of the ore may be equally exposed to heat. 
 
 The diaphragm is liable to rapid destruction by the 
 action of sulphur, arsenic, and antimony in the ore. It 
 is stated, on excellent authority, that the loss of the 
 diaphragm does not impair the efficiency of the furnace. 
 In some cases the furnace has been found to work bet- 
 ter without the diaphragm, forming fewer lumps in the 
 roasting of leady ores. 
 
 In this, as in all rotating cylinder furnaces, the light 
 and fine portion of the ore is carried away by the force 
 of the draft. It is therefore necessary that extensive 
 dust chambers be provided, through which the draft 
 from the furnace must pass, on its way to the chimney, 
 
144 ADDENDA. 
 
 in order that the principal part of the dust may be de- 
 posited. 
 
 The writer superintended the erection and working 
 of one of these furnaces in Inyo County, and obtained 
 satisfactory results from it. About 15 per cent of the 
 ore passed to the dust chamber, and was found to be but 
 imperfectly roasted. This dust was collected, slightly 
 moistened with a solution of salt and iron sulphate in 
 water, and then returned to the furnace, and success- 
 fully roasted. About the same percentage of it again 
 found its way to the dust chamber. 
 
 The cylinder is twelve feet long by six feet in diame- 
 ter, and a charge for it is from ij to 2*^ tons of 
 ore, with the necessary salt. The time required for 
 the roasting of a charge of ore in this furnace is from 
 four to twelve hours, including the charging and dis- 
 charging. 
 
 As the weight of the charge varies with the quality 
 of the ore, and the degree of fineness to which it is 
 crushed, and the time required for the roasting varies with 
 the same circumstances, the capacity of the furnace may 
 be said to range from four to twelve tons in 24 hours. 
 One man on a shift can do all the work, or can attend 
 to the firing of four furnaces. 
 
 This furnace has been extensively used in treating 
 the silver ores of Colorado and Mexico, and one, with- 
 out the diaphragm, is now, or was recently employed in 
 the roasting of auriferous sulphurets in Nevada County, 
 California. 
 

ADDENDA. 145 
 
 THE BRUNTON FURNACE. 
 
 207. This furnace is essentially similar to the 
 Bruckner, but has no diaphragm. In form it differs 
 slightly, being ovoid, or egg shaped, the larger end 
 toward the fire. This form must conduce to the stability 
 of the brick lining, and is said to roast the ore more 
 evenly than the cylinder. The rotation of the furnace 
 is not produced, as in the Bruckner, by means of a 
 pinion engaging in a toothed rack surrounding the shell,. 
 but simply by the traction of the rollers, two of which 
 are connected by a strong shaft, to which motion is 
 imparted by means of a screw on a transverse shaft. 
 This, with the absence of the diaphragm, a low royalty 
 for the patent right, and some other peculiarities, ren- 
 der the furnace cheaper than the Bruckner. A Brun- 
 ton furnace twelve feet long by six feet eight inches 
 in its greatest diameter, recently constructed for the 
 chlorination works at the Plumas National Mine, in 
 Plumas County, California, weighed, including gearing 
 and iron bed-plates for the rollers, in place of the wooden 
 ones formerly used, nearly 10 tons without the lining 
 bricks. 
 
 THE PACIFIC CHLORIDIZING FURNACE. 
 
 208. This is a simple brick lined rotating cylinder, 
 not differing essentially from those described. It is 
 however made of large capacity, as much as seven tons 
 of ore being treated at once. A good feature in the 
 make-up of this furnace is that the charging hoppers, 
 
146 ADDENDA. 
 
 of which there are two, are supplied by the foundry 
 already mounted on iron supports. 
 
 THE WHITE FURNACE. 
 
 209. The White furnace consists of a hollow rotatory 
 brick-lined cylinder of cast-iron, with open ends. The 
 brick lining is so arranged, in the short segments of 
 which the cylinder is composed, as to form "grooves, 
 cavities or projections," by which the ore is lifted and 
 showered through the flames, which pass through the 
 furnace from end to end. The cylinder is slightly in- 
 clined, either downward from the fireplace, or the re- 
 verse, and the pulverized ore is poured automatically and 
 continuously, together with the salt, into the higher 
 end. The rotation, aided by the lifting and dropping 
 of the ore, causes the latter to traverse the entire length 
 of the cylinder, and to fall continuously from the lower 
 end. By an ingenious arrangement, the inclination of 
 the cylinder is rendered adjustable, so that the ore may 
 occupy a longer or a shorter time in passing through it. 
 
 When the furnace is so arranged that the cylinder is 
 inclined upward from the fireplace, and the ore conse- 
 quently enters at the cooler end, it results that the 
 lighter dust does not pass through the furnace, but is 
 carried by the force of the draft in the opposite direc- 
 tion, toward the flue, and into a series of chambers in 
 which the greater part of it settles, while the smoke, 
 etc., passes on to the chimney. To effect the roasting of 
 this portion of the ore, an auxiliary fire is necessary, 
 through the flames of which the dust may pass on its 
 
ADDENDA. 147 
 
 way to the chambers. The coarser portion of the ore 
 passes along the cylinder, under continually increasing 
 heat, and, on its exit at the lower end, falls into a pit, 
 situated between the end of the cylinder and the main 
 fireplace, where it is exposed to the heat of the flames 
 passing over it. At stated periods, the accumulated ore 
 is removed from the pit and spread on the cooling floor. 
 This arrangement of the cylinder the ore entering 
 at the cooler end fulfils, better than the reverse plan, 
 the requisite conditions of a proper roasting. The 
 writer is not aware of an instance in which the inclina- 
 tion was downward from the fireplace, and the ore en- 
 tered the furnace at the hotter end, in which satisfac- 
 tory results were obtained. 
 
 THE HOWELL-WHITE FURNACE. 
 
 210. The furnace known by the above appellation, 
 is a modification of the White. The cylinder is lined 
 with bricks in only one-third of its length from the lower 
 end, adjoining the fireplace, the diameter of this por- 
 tion of the iron shell being 10 inches greater than that 
 -of the unlined portion 
 
 The ore enters the cylinder at the upper and cooler 
 end, and is lifted and showered by means of projections 
 which in the unlined portion are formed of iron, in the 
 lined portion of projecting bricks. 
 
 The inclination of the cylinder is fixed, the time oc- 
 cupied by the ore in passing through it being regulated 
 by the number of rotations per minute, which is adjust- 
 .able at will. 
 
148 ADDENDA. 
 
 The length of the cylinder is 23 feet 2 inches. The 
 internal diameter of the smaller part of the iron shell is 
 from 22 to 50 inches, that of the enlarged portion being 
 as stated 10 inches more, in order to admit of lining. 
 
 The working capacity of the furnace ranges from eight 
 to forty-five tons of ore in 24 hours, according to the 
 character of the ore and the diameter of the cylinder. 
 
 THE THOMPSON-WHITE FURNACE. 
 
 Another modification of the White furnace has been 
 made by J. M. Thompson. 
 
 This furnace differs from the Howell- White in sev- 
 eral particulars. The cylinder is of one diameter 
 throughout its length, and is lined throughout with 
 tiles, thus lessening the loss of heat by radiation, which 
 must be considerable in the unlined portion of the 
 Ho well- White furnace. The tiles are specially molded 
 for the purpose, and are so formed that the projections 
 and recesses, designed to lift the ore, are of a rounded 
 form as to their transverse section. In some cases the 
 recesses are obstructed at intervals by transverse 
 ridges. The intention of this is to prevent the ore 
 sliding along in the inclined cylinder, in consequence of 
 its low angle of stability at an early stage of the roasting. 
 In some ores this angle becomes almost nil, so that the 
 powder resembles a fluid in its action. 
 
 The further retention and equalization of heat in the 
 cylinder, is promoted by means of a layer of non-con- 
 ducting material, such as paris plaster, or asbestos, be- 
 tween the lining, of bricks or tiles, and the iron shell. 
 
ADDENDA. 149 
 
 The latter, and the supporting rollers with their bear- 
 ings, are thus, in a measure, protected from the injuri- 
 ous effects of unequal or excessive heat, by being kept 
 comparatively cool. 
 
 The furnace is arranged in either of two ways. In 
 the one, the whole of the ore enters the cylinder at the 
 higher and cooler end. In this case the lighter dusty 
 portion which is carried back by the draft, is roasted 
 by the flames from an auxiliary fire between the end 
 of the cylinder and the dust chambers, the latter being 
 constructed of masonry. In the other, the dust is sep- 
 arated from the coarser portion of the ore before enter- 
 ing the cylinder. The coarse portion then enters at 
 the upper end, while the dust enters at the lower end 
 near the fire. The main fire is thus made to serve for 
 the roasting of both portions of the ore, and the auxil- 
 iary fire is dispensed with. It is also claimed by the 
 inventor, with considerable show of reason, that the 
 heat and the chlorine, developed by the roasting of the 
 dust, mingled as it is with salt, instead of being lost, as 
 when an auxiliary fire is relied on, aids materially in 
 chloridizing the coarser portion of the ore. 
 
 A portion of the dust, impelled by the draft, traverses 
 the entire length of the cylinder, and entering the flue 
 is arrested in its flight by the ordinary means of dust 
 chambers, which, in this case, are constructed of iron 
 instead of masonry; hence they are light, portable, and 
 cheap. 
 
 The length of time occupied by the passage of the 
 coarser portion of the ore though the cylinder, is regu- 
 lated mainly by the inclination of the latter, which, as 
 in the White furnace, is adjustable, though, as the writer 
 
150 ADDENDA. 
 
 I 
 
 is informed, in a different manner. Mr. Thompson pre- 
 fers to regulate the period of transit by varying the angle 
 of inclination, rather than the speed of rotation, of 
 the cylinder, arguing that, as it is stated by eminent met- 
 allurgists that the loss of silver by volatilization is, other 
 things being equal, proportioned to the length of time dur- 
 ing which the ore is exposed to the heat, it follows that 
 the more quickly the ore is roasted the less loss it will 
 sustain. But, he continues, the greater or less rapidity 
 of the roasting depends on the greater or less exposure 
 of the particles of ore to, first oxidizing, then chloridiz- 
 ing influences, or to both simultaneously; hence the 
 more continuouslv the ore is showered through the 
 
 ' O 
 
 heated air and gases pervading the interior of the fur- 
 nace, the more quickly will the roasting be effected, 
 and consequently less loss will be caused by the volatil- 
 ization of silver. 
 
 This theory seems plausible. Let us examine it. 
 Let us suppose two furnaces in operation, receiving 
 equal quantities of the same kind of ore. They are 
 alike in every respect, rotating with equal speed, fired 
 in the same manner, and with the same amount of 
 draft. They will yield like results. 
 
 We will now suppose that both of the cylinders are 
 rotating at the highest feasible rate of speed, thus af- 
 fording the greatest exposure of the ore to the roasting 
 influences. It is desired to modify their action so that 
 'the time occupied by the passage of the ore through 
 them may be doubled. 
 
 In one, which we will call the Howell, this result is 
 attained by reducing the speed of rotation. (Owing to 
 the effect of tangential force the reduction of speed will 
 
ADDENDA. 151 
 
 be somewhat less than half.) In the other, or Thomp- 
 son, by lessening the angle of inclination. The supply 
 of ore to each is supposed to remain unchanged for the 
 present. An analysis of the effects of these alterations 
 gives the following results. 
 
 The quantity of ore passed through each furnace in 
 a given time remains unaltered. 
 
 The quantity of .fuel and air consumed by each is 
 unchanged. 
 
 o 
 
 The quantity of ore exposed to the heat at any given 
 moment in each is doubled; therefore, the time during 
 which the ore is exposed to heat in each is doubled. 
 
 The length of time during which the ore is drop- 
 ping through the air is, in the Howell, unchanged; 
 in the Thompson, doubled. 
 
 The power consumed in lifting the ore is in the 
 Howell unchanged ; in the Thompson, doubled. 
 
 In the Howell the same quantity of work is performed, 
 on the same quantity of ore, with the same expenditure 
 of power, as before the change. In the Thompson a 
 double quantity of work is performed on the same quan- 
 tity of ore, by a double expenditure of power. If the 
 ore is as well roasted in the one furnace as in the other, 
 the advantage is, so far, with the Howell. Is it proba- 
 ble that the same. result can be produced by the Howell 
 as by the Thompson, with half the work, and therefore 
 half the power ? As the result sought is a chemical one, 
 the answer to this question depends on the extent to 
 which the attainment of that result is accelerated by the 
 movement of the ore. 
 
 The time occupied by the oxidation of a single parti- 
 cle of sulphuret, exposed to heated air, other things 
 
152 ADDENDA. 
 
 being equal, is in some ratio to its mass. It matters 
 not whether an adjacent particle consists of sulphuret 
 or quartz ; the two particles of sulphuret will be oxi- 
 dized simultaneously, in the same length of time as 
 would one particle, provided the requisite quantity of 
 heated oxygen be supplied. As regards the heat, the two 
 particles will aid each other by their combustion, ren- 
 dering necessary a smaller proportionate quantity of 
 fuel than if one particle were sulphuret, and the other 
 quartz. 
 
 In a roasting cylinder there is, at any given moment, 
 a certain quantity of air, capable of oxidizing a certain 
 number of particles of sulphuret. To expose a greater 
 number of particles would be useless. To expend 
 power for that purpose would be to waste the power. 
 
 If we suppose the quantity of oxygen passing through 
 each furnace to be in excess of the quantity which can 
 be utilized, the feed may be increased in both. When 
 the quantity of air passing through the furnaces is in 
 equilibrium with the ore, so that the oxygen is utilized 
 to the utmost practicable extent, one of two things must 
 be true. Either the Thompson is wasting power in 
 lifting the ore more often than the Ho well, or, the ore 
 is remaining in it a longer time than is necessary. If 
 the former, the rate of rotation should be reduced; if 
 the latter, the inclination of the cylinder should be in- 
 creased. The latter is the most probable, because, 
 although it is not denied that oxidation proceeds to a 
 certain extent while the ore lies quiescent in the cylin- 
 der, it is proved, by all experience, to proceed faster 
 when the ore is showered through the heated air, 
 provided, as before said, that a sufficient quantity of 
 
ADDENDA. 153 
 
 free oxygen is present, which, on our hypothesis, is the 
 case in this instance. 
 
 ^4^i-**-*^-* W 
 
 If the speed of the Thompson is now increased, the 
 same quantity of ore will pass through it, but the time 
 
 ERRATUM Page 153, third line, for "speed," read, inclination. 
 
 iiij.xv~ v/i j-ycioocigv.- oiiwuji^ uv_ jua.il, v^i WUCtllCl LUC ICbLUL 
 
 would be a mean in which the diminution of volatiliza- 
 tion would compensate, or more than compensate for 
 the greater consumption of power, is a question which 
 can only be answered by experiment. 
 
 A similar view as to the chloridation, which, in this 
 class of furnace, is more or less effected by the falling 
 of the ore particles through the heated gases evolved by 
 the roasting ore and the salt, would lead to similar con- 
 clusions. But the theory of the chloridation is opposed 
 to any greater movement of the ore in this stage than 
 is necessary to ensure equal and thorough heating. 
 Hence it would perhaps be advantageous to have a 
 smaller number of lifters in the circumference of the 
 cylinder near its lower or chloridizing end, than in the 
 central and upper zones. But it is known that, in this 
 class of furnace, a considerable percentage of the chlo- 
 ridation takes place after the ore has left the cylinder, 
 and while it is accumulating in the pit into which the 
 
152 ADDENDA. 
 
 being equal, is in some ratio to its mass. It matters 
 not whether an adjacent particle consists of sulphuret 
 or quartz ; the two particles of sulphuret will be oxi- 
 dized simultaneously, in the same length of time as 
 
 wnnlrl 
 
 numoer 01 parciues wouiu ue useless. 10 expenu 
 power for that purpose would be to waste the power. 
 If we suppose the quantity of oxygen passing through 
 each furnace to be in excess of the quantity which can 
 be utilized, the feed may be increased in both. When 
 the quantity of air passing through the furnaces is in 
 equilibrium with the ore, so that the oxygen is utilized 
 to the utmost practicable extent, one of two things must 
 be true. Either the Thompson is wasting power in 
 lifting the ore more often than the Ho well, or, the ore 
 is remaining in it a longer time than is necessary. If 
 the former, the rate of rotation should be reduced; if 
 the latter, the inclination of the cylinder should be in- 
 creased. The latter is the most probable, because, 
 although it is not denied that oxidation proceeds to a 
 certain extent while the ore lies quiescent in the cylin- 
 der, it is proved, by all experience, to proceed faster 
 when the ore is showered through the heated air, 
 provided, as before said, that a sufficient quantity of 
 
ADDENDA. 153 
 
 free oxygen is present, which, on our hypothesis, is the 
 
 case in this instance. 
 
 ^ut-*'**-'*^*"***^' 
 If the speed of the Thompson is now increased, the 
 
 same quantity of ore will pass through it, but the time 
 occupied in the passage will be lessened, and the load 
 in the furnace will be reduced. Less power will now 
 be consumed in causing the cylinder to rotate, and the 
 loss of silver by volatilization will be diminished. 
 
 Whether the power required would be reduced to an 
 equality with that consumed by the Howell, which 
 would mean that the load in the furnace should be re- 
 duced to half that in the Howell, or, in other words the 
 time of passage should be half, or whether the result 
 would be a mean in which the diminution of volatiliza- 
 tion would compensate, or more than compensate for 
 the greater consumption of power, is a question which 
 can only be answered by experiment. 
 
 A similar view as to the chloridation, which, in this 
 class of furnace, is more or less effected by the falling 
 of the ore particles through the heated gases evolved by 
 the roasting ore and the salt, would lead to similar con- 
 clusions. But the theory of the chloridation is opposed 
 to any greater movement of the ore in this stage than 
 is necessary to ensure equal and thorough heating. 
 Hence it would perhaps be advantageous to have a 
 smaller number of lifters in the circumference of the 
 cylinder near its lower or chloridizing end, than in the 
 central and upper zones. But it is known that, in this 
 class of furnace, a considerable percentage of the chlo- 
 ridation takes place after the ore has left the cylinder, 
 and while it is accumulating in the pit into which the 
 
154 ADDENDA. 
 
 cylinder empties itself. Exactly how far this principle 
 may be carried in practice has not been proved. 
 
 The objection that rapid rotation of the cylinder 
 causes the separation of a larger quantity of dust from 
 the roasting ore, is too puerile to be worth refuting. 
 The only result is that the auxiliary fire has more to do, 
 and the cylinder less, a clear saving of motive power, or 
 an increase in the capacity of the furnace. One point 
 in this connection is worthy of notice; the dusting 
 almost ceases as soon as the ore begins to " sponge." 
 This is in favor of feeding the dust into the lower end 
 of the cylinder. 
 
 Another valuable feature in the Thompson furnace, 
 and which has been heretofore surprisingly overlooked 
 by inventors, is that the heat given off by the roasted 
 ore, instead of being wasted, is utilized in heating the 
 air with which the furnace is supplied ; at the same time 
 the ore is cooled sufficiently to allow of its being moist- 
 ened without loss or inconvenience from the formation 
 of a great volume of steam. 
 
 Thompson also adapts the length of the cylinder in 
 such proportion to its diameter, and to the extent of 
 grate surface in the fireplace, as that the heat at the 
 higher end shall be, as nearly as practicable, that which 
 is proper for the initial stage of the roasting. It is a 
 self-evident proposition that a large quantity of burning 
 fuel will heat a cylinder, not only of greater diameter, 
 but of greater length, than a smaller quantity. Hence, 
 if the length of the cylinder is not increased in suitable 
 proportion to the increased diameter, one of two things 
 must happen : either the larger cylinder, by being too 
 short, must waste available heat at its upper end, or, 
 
ADDDENA. 155 
 
 the smaller cylinder, being too long, is not sufficiently 
 heated throughout. As the proper initial heat varies 
 for different ores, the most advantageous length of 
 cylinder for a given diameter will also vary. The usual 
 dimensions are 21, 24, 27, and 30 feet in length, to 32, 
 40, 52, and 60 inches in diameter, respectively. 
 
 As to the question of the best manner of regulating 
 the operation of a roasting furnace of this class, the 
 writer's opinion is, that the cylinder should be adjustable 
 both as to speed of rotation and as to inclination, in 
 order that it may be adapted to the various require- 
 ments of different ores. In the White, and in Thomp 
 son's modification, this is the case. 
 
 The roasting of ores is a problem in which mechani- 
 cal and chemical factors are inextricably interwoven. 
 While it is well that theory should suggest and guide 
 experiment, yet, if the facts thus developed oppose the 
 theory, the latter, not the former, must give way. 
 
 THE O'HARA FURNACE. 
 
 212. This is a reverberatory furnace of great length, 
 the hearth being about one hundred feet long by five to 
 eight feet wide. It is traversed lengthwise by plows 
 and scrapers attached to endless chains, which, passing 
 over rollers at the ends of the furnace, carry the plows 
 back to the place of entrance, where the ore is fed in 
 continuously by a mechanical arrangement. By the ac- 
 tion of the plows the ore is not only turned over, but is 
 also progressed gradually towards the hottest part of 
 the furnace, thence to a cooling hearth, and is finally 
 
156 ADDENDA. 
 
 discharged into a suitable receptacle. In a furnace of 
 this size several fires are used on each side, at different 
 points in the length. A great advantage of this furnace 
 is, that very little of the ore is carried to the flues by the 
 draft. It can be operated by one man on a shift, and 
 has a capacity of as much as 40 tons per 24 hours. By 
 a recent improvement the furnace is built in two stories. 
 
 STETEFELDT FURNACE. 
 
 213. If any metallurgist had been told, prior to the 
 introduction of the Stetefeldt furnace, that a chlorid- 
 izing roasting of silver ore could be effected in the short 
 space of a few seconds of time, he would probably have 
 been incredulous. In the old reverberatory, the opera- 
 tion requires several hours; in the cylinder furnaces of 
 continuous action it occupies from 10 to 30 minutes, 
 but in the furnace now under consideration, the ore, if 
 not of extremely refractory character, is almost com- 
 pletely roasted while falling from a height of little more 
 than 20 feet. 
 
 The furnace consists of a stack or shaft of masonry, 
 provided with fireplaces opening into it near the base, 
 with a flue near its upper end, and with an apparatus 
 for sifting the ore and salt into it at the top. The ore 
 thus showered from the top of the stack, encounters in 
 its descent, under the most favorable conditions for 
 chemical action, the ascending flames and heated air 
 from the fireplaces, as well as the fumes of its own 
 combustion, and from the voltalization and decomposi- 
 tion of the salt. When it reaches the bottom, where a 
 
ADDENDA. 157 
 
 hopper is provided for its reception, not only is the ox- 
 idation completed, but the chloridation of the silver is 
 so far advanced as to require for its completion only 
 the further exposure to heat which the ore receives 
 while accumulating in the hopper. The latter is emp- 
 tied from time to time, by means of a slide, into iron 
 cars and the ore removed to the cooling floor. 
 
 As in all other processes in which the pulverized 
 ore is showered through the flames, the lighter portion, 
 amounting sometimes to 30 per cent of the whole, is 
 carried back by the current of air and gas. In order 
 to prevent an accumulation of dust in the flue, the 
 latter joins the stack at an acute angle, and is con- 
 ducted almost vertically downward to the base, where 
 the flames from an auxiliary fireplace enter it, and 
 effect the roasting of the dust, which then, passing into 
 a horizontal flue, settles mainly in a series of hoppers,, 
 while the hot air, smoke and gases pass through dust 
 chambers to the chimney. The construction of the 
 furnace involves many ingenious contrivances for regu- 
 lating the feed and heat, for the removal of the roasted 
 ore, the inspection of the interior, and the admission of 
 air at suitable points, and in proper quantity. 
 
 In a large furnace, capable of roasting from 30 to 70 
 tons of ore in 24 hours, the roasting tower is 25 feet 
 high and five feet square at the base. One man on a 
 shift can attend to the firing. 
 
 The following extract from the Circular of the Stete- 
 feldt Furnace Co. will assist, with the drawings,|to an 
 understanding of the arrangement : 
 
158 ADDENDA. 
 
 " Of the accompanying drawings Figure i represents 
 a vertical section of the Stetefeldt Furnace, showing 
 its latest and most improvd mode of construction, and 
 
 Figure 2 is a sketch of the Stetefeldt Feeder. 
 t> 
 
 DESCRIPTION OF THE FURNACE. 
 
 A is the shaft into which the pulverized ore is 
 showered by the feeding machine, placed on the top of 
 the cast iron frame B. The shaft is heated by two 
 fireplaces (C). The ashpits of these are closed by iron 
 doors, having an opening (E), provided with a slide, 
 so that more or less air can be admitted below the 
 grate, and, consequently, more or less heat generated. 
 In order to obtain a perfect combustion of the gases, 
 leaving the firebox through the slit (T), an airslit (U), 
 connected with the airchannel (F), is arranged above 
 the arch of the firebox. This slit also supplies the air 
 necessary for the oxidation of the sulphur and the base 
 metals. Another advantage of this construction is that 
 the arches above the firebox and firebridge are cooled 
 and prevented from burning out. The roasted ore ac- 
 mulates in the hopper (K), and is discharged into an 
 iron car by pulling the damper (L), which rests on 
 brackets with friction rollers (M). N is an observation 
 door, and also serves for cleaning the firebridges. O 
 are doors to admit tools in case the roasted ore is sticky 
 and adheres to the walls. The gases and fine ore dust, 
 which forms a considerable portion of the charge, leave 
 the shaft through the flue (G). The doors (R) are pro- 
 vided to clean this flue, which is necessary, with some 
 ores, about once a month. D is an auxiliary fireplace, 
 constructed in the same manner as the fireplaces on 
 
Fig.2. 
 
 THE STETEFELDT FURNACE . 
 
ADDENDA. 159 
 
 the shaft, which is provided to roast the ore dust, escap- 
 ing through the flue (G), in passing through the cham- 
 ber (H). P are doors for observation and cleaning. 
 The larger portion of the roasted dust settles in the 
 chamber (V). provided with discharge hoppers (I), 
 from which the charge is drawn into iron cars by moving 
 the dampers (S). The rest of the dust is collected in a 
 system of dust chambers (Q), connected with a chimney 
 which should rise from 40 to 50 feet above the top of 
 the shaft. At the end of the dust chambers is a damper 
 by which the draft of the furnace can be regulated. 
 The dry kiln can also be used as a dust chamber, and 
 the waste heat of the furnace utilized for drying the ore 
 before crushing it. The firing of the furnace is done 
 on one side, and all discharges are located on the op- 
 posite side." 
 
 DESCRIPTION OF THE FEEDING MACHINE. 
 
 " The Feeding Machine is shown in Fig. 2. The 
 castiron frame (A), which is placed on top of the shaft, 
 is provided with a damper (B), which is drawn out 
 when the furnace is in operation, but inserted when the 
 feeding machine stops for any length of time, or if 
 screens have to be replaced. C is a castiron grate, to 
 the top of which is fastened the punched screen (D). 
 The latter is made of Russian sheetiron, or of cast-steel 
 plate, with holes of one-eighth to one-tenth of an inch 
 in diameter. Above the punched screen is placed 
 a frame (E), to the bottom of which is fastened 
 a coarse wire screen (F), generally No. 3, made of extra 
 heavy iron wire. The frame (E) rests upon friction 
 rollers (G). The brackets (H) which hold the friction 
 
160 ADDENDA. 
 
 rollers can be raised or lowered by set screws, so that 
 the wire screen (F) can be brought more or less 
 close to the punched screen (D). The brackets 
 (K) carry an eccentric shaft (L), connected with 
 the shaft (M), from which the frame (E) receives 
 an oscillating motion. To the brackets (N) are 
 fastened transverse stationary blades (O), which 
 come nearly in contact with the wire screen (F), 
 and can be raised or lowered by the nuts (P). These 
 blades keep the pulp in place when the frame (E) is in 
 motion, and also act as distributors of the pulp over 
 the whole surface of the screen. The hopper (I) re- 
 ceives the ore from an elevator which draws its supply 
 from a hopper into which the pulverized ore is dis- 
 charged from the crushing machinery. The ore is gen- 
 erally pulverized through a No 40 screen. By means 
 of a set of cone pulleys the speed of the frame (E) can 
 be changed from twenty to sixty strokes per minute, 
 whereby the amount of ore fed into the furnace is regu- 
 lated. This can also be done to some extent., by 
 changing the distances between the punched screen 
 (D), the wire screen (F), and the blades (O). 
 
 The largest sized furnace, as represented in the draw- 
 ing the scale of which is i in. = 12 ft., capable of 
 roasting from 50 to 70 tons of ordinary ores, and from 
 30 to 35 tons of very base sulphuret ores in 24 hours, 
 requires the following amount of materials, from which 
 the cost of construction can be easily calculated by any 
 architect or millwright, viz: 
 
 1,500 fire-bricks, for fire boxes and arches exposed to 
 flame. 
 
ADDENDA. 161 
 
 200,000 common bricks, of good quality, for furnace, 
 large system of dust chambers, chimney, and 
 cooling floor. 
 2,500 Ibs. in bolts and nuts for anchoring furnace and 
 
 dust chambers. 
 
 4,500 Ibs. in wrought iron braces, flat iron for car- 
 guides, tools, etc. 
 16,000 Ibs. in castings. 
 
 All the castings are very plain and simple, the water- 
 jacket on top of furnace, and the water damper having 
 been discarded. Considerable work is only required 
 on the feeding-machine, feeding-machine damper, and 
 discharge damper, and some on the fire-doors, which 
 will be covered by an additional charge of about $700 
 added to the ordinary price of castings. 
 
 The cost of three iron discharge cars is $125. 
 For a furnace of 15 to 20 tons capacity, without hopper 
 discharge, and a less extensive system of dust cham- 
 bers, the amount of materials required may be esti- 
 mated at two-thirds the figures given above." 
 
 REMARKS ON FURNACES. 
 
 214. The quantity of fuel consumed in roasting 
 varies with the quality of the fuel, the character of the 
 ore, and the kind of furnace used. 
 
 In a single hearth reverberatory furnace, each ton of 
 ordinary silver ore requires from one-third to one-half 
 a cord of dry pine wood. In a long furnace the pro- 
 portion is materially reduced. 
 
162 ADDENDA. 
 
 Concentrated auriferous sulphides, when roasted for 
 chlorination, in a reverberatory furnace with three 
 hearths, require one cord of wood, or one-half ton of 
 Seattle coal, per ton of ore. In this roasting, one man 
 on a shift is sufficient for one furnace, roasting i */ 
 tons of ore in each 24 hours. The writer experimented 
 with different numbers of men employed at one time, 
 but found no advantage in more than one for all three 
 hearths, thus proving that stirring the ore beyond a 
 certain extent is useless, unless the supply of air be in- 
 creased. In the mechanical furnaces the proportionate 
 consumption of fuel is much dimished, especially in 
 those which receive the ore continuously, in which one- 
 tenth of a cord of wood to the ton of silver ore is a 
 common proportion. The mechanical furnaces de- 
 scribed are all in more or less extensive use, giving 
 satisfactory results, with great economy of fuel and 
 labor as compared with the old reverberatory furnace. 
 
 Those which receive the ore continuously are the 
 most economical in operation, but the most costly in 
 construction. They are especially adapted to the chlo- 
 ridizing roasting of large quantities of silver ore of 
 nearly uniform character. 
 
 For the roasting of gold-bearing sulphides, or excep- 
 tionally rich silver ores, for custom works in which the 
 character of different small lots of ore is liable to ex- 
 treme variation, or in small establishments, the furnaces 
 which are charged periodically are usually preferred, be- 
 cause the roasting in them is more readily controlled, 
 or because of their more moderate cost. 
 
 The furnaces which are charged continuously, as the 
 
ADDENDA. 163 
 
 Stetefeldt, and the White with its modifications, have 
 not yet been tried for the dead roasting of gold-bearing 
 sulphurets for the Plattner process, but there is no rea- 
 son to doubt that, with proper care, they might be 
 made to do the work. Possibly a modification, such as 
 that used by Mr. Crosby (50) in connection with his 
 reverberatory furnace, might be necessary on account of 
 the large quantity of sulphur which the material in 
 question contains. 
 
 One disadvantage of the continuous cylinder furnaces 
 in which the ore progresses in an opposite direction 
 to the draft is, that the heavier particles, which require 
 the longest exposure, pass through more quickly than 
 the lighter, because the force of the draft has less influ- 
 ence in retarding their horizontal progression. The 
 action of the furnace must be adjusted to the require- 
 ments of these heavy particles. Between these and 
 the dust which is completely controlled by the draft, 
 are particles of all grades, some of which are barely 
 massive enough to make headway against the current 
 of air. 
 
 As the time required for the roasting of the larger 
 particles is greater than that required for the smaller, it 
 is clear that a large proportion of the ore which passes 
 through the cylinder is detained within it longer than 
 is necessary, causing useless consumption of power and, 
 in all probability, loss of silver. This defect is obvi- 
 ated when the ore moves through the furnace in the 
 same direction as the draft. The progression of the 
 ore is then aided by the force of the draft, but in a less 
 degree as the particles are heavier. The objection to 
 this method is, that the ore in its progress encounters a 
 
164 ADDENDA. 
 
 gradually diminishing heat, and a decreased proportion 
 of oxygen, while the reverse should be the case. 
 
 Mr. White, the original inventor of the application 
 of this kind of furnace to the treatment of silver ores, 
 has been much blamed for his persistence in this man- 
 ner of working it, but it must be admitted that, if the 
 objection pointed out could be overcome, the method 
 would possess certain advantages. 
 
 In the Stetefeldt furnace, in like manner, the descent 
 of the heavier particles is less impeded by the upward 
 current of air and gas, and is therefore more rapid than 
 that of the lighter, but in this case no waste of power 
 results, because the ore is lifted, once for all, to the top 
 of the shaft by an elevator. 
 
 In the O'Hara, all portions of the ore, except a small 
 quantity of very light dust, are moved toward the hot- 
 ter end of the furnace with practical uniformity. This 
 furnace combines the advantages of the reverberatory, 
 worked by hand, with those of automatic action. It 
 probably costs more for repairs than the others. 
 
 A roasting furnace, of whatever description, should 
 be kept in operation as constantly as possible, not only 
 in order to economize fuel, but also to avoid the injuri- 
 ous effect of alternate heating and cooling. In the se- 
 lection, therefore, regard should be paid to the quantity 
 of ore to be treated daily, as well as to its character, and 
 the financial resources at command. 
 
INDEX. 
 
 PAGE. PAR 
 
 Absorbed Gold -recovery of 107 176 
 
 Acid costof 110 180 
 
 Action of chlorine on oil 40 
 
 Alloy of gold and silver 82 146 
 
 Ammonia use of 49 92 
 
 Antimony and arsenic behavior of 
 
 in roasting 16-19 18-29 
 
 Apparatus 22 
 
 Assay of concentrations 97 158 
 
 boiling over of 101 164 
 
 methods of 98 159 
 
 1st 99 160 
 
 2d 100 161 
 
 3d 100 162 
 
 4th 102 165 
 
 5th 102 166 
 
 6th 103 168 
 
 Assay chlorination, the so-called.. . .132 200 
 " copper ores, &c., of for gold 
 
 andsilver 103 167 
 
 " manganese of 114 184 
 
 " rich silver ore of precau- 
 tion in 104 170 
 
 ' salt of... 112 182 
 
 " silver glance of 104 169 
 
 " solubility, the 93 156 
 
 " tailings of / 104 171 
 
 Bar, gold casting the 64 117 
 
 Bar, silver " " 73 135 
 
 Bars value of 137 202 
 
 Bo. tie-wash see wash -bottle 
 
 Bruckner furnace, the 143 206 
 
 Brunton furnace, the 145 207 
 
 Calcium polysulphide 83 148 
 
 useof 70 129 
 
 test for excess of 71 130 
 
 Calcium hyposulphite 85 150 
 
 proper strength of 85 151 
 
 Cement-copper assay of for gold and 
 
 silver 103 167 
 
 Chemical combination 10 7 
 
 Chlorine 138 203 
 
 action of on oil 40 69 
 
 expelling of by steam 118 186 
 
 excess of 54 97 
 
 disposal of 56 98 
 
 source of 12 10 
 
 surplus 117 186 
 
 Chlorine generator 37 65 
 
 charging the 51 94 
 
 discharging the 52 95 
 
 description of 37 67 
 
 PAGB. PAR. 
 
 joints of 37 66 
 
 Chloride metal 12 10 
 
 how formed in roasting 17 21 
 
 Chloride silver how formed for 
 
 leaching 12 13 
 
 volatilization of 19 32 
 
 Chlorides base action of in roast- 
 ing.... { 18 24 
 
 Chloridizing roast 17 20 
 
 Chlorination of gold ore 49 92 
 
 Chlorination assay so-called not 
 
 correct. 132 200 
 
 Chlorination Tailings 135 201 
 
 Chlorinating (leaching) vat 31 51 
 
 charging the 48 90 
 
 Chamber drying for gold, &c 121 192 
 
 Change in weight of ore in roasting . 91 154 
 
 Clay and talc in unconcentrated ore 80 144 
 
 Combination chemical 10 7 
 
 Concentrated pyrites containing gold, 
 
 but not silver 41 71 
 
 charge of, proper 42 75 
 
 how kept 41 72 
 
 lime or talc in 41 73 
 
 roasted, chlorination of 49 92 
 
 examination of 46 86 
 
 leaching of 53 96 
 
 moistening of 48 89 
 
 roasting of 43 77 
 
 heat for 47 87 
 
 timeof 47 88 
 
 stirring of in roasting 43-45 78-81 
 
 Concentrated pyrites containing 
 
 gold and silver 65 118 
 
 leaching of for gold 66 122 
 
 for silver 67 123 
 
 roasting of 65 119 
 
 loss in to prevent 65 120 
 
 Concentrations containing silver, but 
 
 little or no gold 75 136 
 
 roasting of 75 137 
 
 loss in to prevent 76 138 
 
 washing of 77 139 
 
 leaching, &c. , of 79 141 
 
 Concentrations containing much 
 
 lead, &c., Hofman's process 79 142 
 
 Concentrations assaying see as- 
 saying concentrations 
 
 Copper saving 106 174 
 
 assay of for gold and silver 103 167 
 
 chloride, action of in roasting 18 26 
 
 sulphate test for : - 46 84 
 
 Cost of acid 110 180 
 
166 
 
 INDEX, 
 
 PA BE. PAR. 
 
 Covering-flue 105 172 
 
 Crosby's furnace 30 50 
 
 Dead roast 16 19 
 
 Directions special -for working.... 41 71 
 
 Drier ore 27 44 
 
 for precipitate 28 45 
 
 Drying the gold 62 110 
 
 Drying chamber 121 192 
 
 Dust chamber 27 44 
 
 Dumping vats 32 52 
 
 Filter in leaching vat 32 53 
 
 drying the 48 90 
 
 in dumping vat 105 173 
 
 Filters for precipitates 36 62 
 
 Filtration 9 2 
 
 Flowing (in leaching) 9 4 
 
 Flue covering 105 172 
 
 Fuel for melting 62 135 
 
 roasting 22 34 
 
 quantity required. .161 214 
 
 Furnace Bruckner, the 143 206 
 
 Brunton, the 145 207 
 
 Crosby's 30 50 
 
 Howell White, the 147 210 
 
 melting for bullion 128 198 
 
 O'Hara, the 155 212 
 
 Pacific chloridizing, the. 145 208 
 
 reverberatory 22 34 
 
 charge for 42 75 
 
 construction of 22 36 
 
 the arch 25 41 
 
 doors 25 40 
 
 door frames 24 39 
 
 fire place 27 42 
 
 stack 27 43 
 
 walls 23 ' 37 
 
 drying of 41 74 
 
 innovations in 28 46 
 
 kinds of 22 35 
 
 roasting, for silver precipitate 28 45 
 
 step. 29 47 
 
 Stetefeldt, the 156 213 
 
 Thompson White, the 148 211 
 
 White, the 146 209 
 
 Furnace tools 30 49 
 
 Furnaces roasting remarks on 161 214 
 
 Generator chlorine 37 65 
 
 different forms of 108 177 
 
 Gold -absorbed recovery of 107 176 
 
 behavior of in roasting 16-19 18-30 
 
 bar casting the 64 117 
 
 cleaning the melted 64 116 
 
 coarse, or alloyed with silver 82 146 
 
 PAGE. 
 
 ...60 
 
 FAH, 
 108 
 110 
 6 
 62 
 96 
 120 
 111 
 191 
 
 collecting the 
 
 drying the 62 
 
 extracted from ores how 9 
 
 filtei for precipitated 36 
 
 leaching of 53 
 
 loss of in roasting to prevent 65 
 
 melting the 62 
 
 sand in 120 
 
 precipitating the 57-118 1,00-187 
 
 precipitants for see precipitanta 
 
 for gold 
 
 settling of 59 104 
 
 solution color of 57 99 
 
 impurities in 118 188 
 
 suspended (in waste liquid) 119 189 
 
 terchloride 12 11 
 
 test for in leach 57 101 
 
 volatilization of 121 193 
 
 Gold tub discharge of 60 107 
 
 Hoe stirring 30 49 
 
 Hofman's process 79 142 
 
 Howell White furnace, the 147 210 
 
 Hypo pipes and faucets for 37 64 
 
 Hyposulphite calcium 86 150 
 
 solution, strength of 85 151 
 
 sodium 131 199 
 
 Introduction 9 
 
 Iron perchloride behavior of in 
 
 roasting 18 25 
 
 Iron sulphate solution 59 106 
 
 Iron use of in melting silver 12 13 
 
 Kiss process, the 142 205 
 
 Leach leaching, lixivium, lixiviation 9 1 
 
 Leaching difficulty in 80 144 
 
 mode of for gold and silver 9 5 
 
 Leachinggold ore 53 96 
 
 silver 67 123 
 
 time required for 70 128 
 
 Leaching vat 31 51 
 
 Lead chloride to remove 78 140 
 
 in gold solution 118 188 
 
 Lead in ore why troublesome 19 31 
 
 Lead sulphate action of in roasting . 18 27 
 
 Leaks of chlorine 50 93 
 
 Loss in roasting to ascertain 92 155 
 
 Manganese and salt, proportions of. 116 185 
 
 assay of 114 184 
 
 Matte from silver melting 127 197 
 
 Mears process 83 147 
 
 Melting furnace 128 198 
 
 Metal chlorides 12 10 
 
 in the furnace how formed 17 21 
 
 action of 18 24 
 
 Metal oxides, sulphide, sulphate. . . 15 15 
 
INDEX. 
 
 167 
 
 PAGE PAR. 
 
 Melting the gt>ld 62 111 
 
 use of sand in. .- 120 191 
 
 O'Hara furnace, the 155 212 
 
 Oil action of chlorine on use of.... 40 69 
 
 Ores containing coarse gold 82 146 
 
 how leached for gold and silver 9 . 5 
 
 leached scum on 72 131 
 
 preparation of for roasting 16 17 
 
 roasted chamber for 29 48 
 
 sifting of 110 179 
 
 sieve for 34 56 
 
 washingof.... 77 139 
 
 unconcentrated treatment of 80 143 
 
 clay and talc in 80 144 
 
 Oxide metal 15 15 
 
 Oxidizing roast 16 18 
 
 Pacific chloridizing furnace, the 145 208 
 
 Percolation unequal 58 102 
 
 Pipe suction 32 54 
 
 to use 81 145 
 
 vent 33 55 
 
 Pipes and faucets for hypo 37 64 
 
 Plan of works 94 157 
 
 Plattner's process 140 204 
 
 / 12 11 
 
 Precipitants for gold 4 83 146 
 
 ( 119 190 
 
 Precipitants for silver 70-83 129-146 
 
 Precipitate silver collecting the.... 73 133 
 
 dryer for the 28 45 
 
 melting the 73 136 
 
 roastingthe 73 134 
 
 fu nace for 28 45 
 
 Precipitating gold. 57-118 100-187 
 
 Precipitating vat 35-117 57-186 
 
 means of drawing liquid from 106 175 
 
 Precipitation exp'anation of 11 9 
 
 of Silver 70 129 
 
 of weak solutions gold 59 105 
 
 silver 72 132 
 
 Preface 5 
 
 Press for precipitate 37 63 
 
 Process Hofman's 79 142 
 
 Kiss, the 142 205 
 
 Hears, the 83 147 
 
 Plattner's 140 204 
 
 Pumps 36 61 
 
 Pyrites concentrated see concen- 
 trated pyrites 
 
 Recovery of sulphur 126 196 
 
 Remarks on furnaces (roasting). . . . 161 214 
 Reverberatory furnace see furnace 
 
 reverberatory 
 
 FACE. PAR. 
 
 Roast chloridizing 17 20 
 
 dead 16 19 
 
 oxidizing 16 18 
 
 Roasting ores effect and purpose of . 15 16 
 
 loss in to ascertain 92 155 
 
 Roasting furnaces 21 33 
 
 Salt action of in roasting 17 21 
 
 assay of 112 1S2 
 
 and manganese proportions of... 116 185 
 
 composition of 17 21 
 
 purification of 114 183 
 
 i 17 21 
 
 use of in roasting -\ 41 73 
 
 ( 65 120 
 
 Sand in gold melting 120 191 
 
 in silver melting 131 198 
 
 Scorification assay 103 168 
 
 Scum on leached ore 72 131 
 
 Sieve for ore 34 56 
 
 Sifting ore 110 179 
 
 Silver chloride how made for leach- 
 ing 12 '13 
 
 volatilization of 19 3ii 
 
 to prevent 76 138 
 
 Silver- extracted from ores how 9 6 
 
 leaching the 67 123 
 
 time required for 70 128 
 
 precipitation of the. ...:.. 70 129 
 
 precipitate collecting the 73 133 
 
 " dryer for 28 45 
 
 filters for 36 62 
 
 " matte from 127 197 
 
 " melting the 73 13f> 
 
 " roasting the 73 134 
 
 roasting for 65-75 119-137 
 
 solution of in hypo 124 194 
 
 test for in leach f>8 125 
 
 Silver glance assay of 104 169 
 
 Silver ore rich assay of precau- 
 tion in 104 i;0 
 
 Silver ore roasted washing the ... 77 139 
 
 Sodium hyposulphite 131 193 
 
 Solution 10 8 
 
 iron sulphate 59 106 
 
 gold chloride color of 57 99 
 
 of silver in hypo 124 194 
 
 Solubility assay ("chlorination as- 
 say") - 93 156 
 
 Steam effect of in roasting 17 23 
 
 use of to expel chlorine 118 186 
 
 Step furnace 29 47 
 
 Stetef eldt furnace, the 156 213 
 
 Suction pipe , 32 54 
 
168 
 
 INDEX, 
 
 PAGE. PAR. 
 
 to use 81 145 
 
 Sulphates metal action of in roast- 
 ing 16-17 19-21 
 
 Sulphate lead action of in roast- 
 ing 18 27 
 
 Sulphide (sulphuret) metal 15 15 
 
 Sulphur recovery of 126 196 
 
 waste of 125 195 
 
 Sulphur oxide effect of in roast- 
 ing 7-17 22 
 
 Sulphurets concentrated see con- 
 centrated pyrites 
 
 Surplus chlorine 54-117 97-186 
 
 Suspended gold (in waste liquid} .... 119 fl89 
 
 Tailings assay of 104 171 
 
 chlorination 135 201 
 
 Test for calcium sulphide 71 130 
 
 H chlorine 49 92. 
 
 " copper sulphate (in ore). .. 46 84 
 
 " goldinleach 57 101 
 
 " hypo strength of 85 151 
 
 ' iron sulphate (in ore) 45 83 
 
 silver in leach 68 125 
 
 Test working 86 152 
 
 a smaller 90 153 
 
 Thompson White furnace, the 148 211 
 
 Tools furnace , . 30 49 
 
 Troughs for solutions 36 59 
 
 arrangement of, 67 123 
 
 Tub-wash see wash-tub 
 
 PACK. PAR, 
 
 Unconcentrated ore treatment of.. . 80 143 
 
 Unequal percolation 58 102 
 
 Value of bars 137 202 
 
 Vat calcium polysulphide 36 58 
 
 charging the for chlorination 48 90 
 
 chlorination ate "sat-leach&ig . . . 
 
 dumping 32 52: 
 
 filter in 105 173" 
 
 iron sulphate 35 58> 
 
 leaching 31 51 
 
 precipitating see precipitating 
 
 vat 
 
 Vent pipe 33 55 
 
 Volatilization of gold 121 19a 
 
 " silver chloride 19 32 
 
 Wash bottle 39 68 
 
 uses of 40 70 
 
 forms of 108 178 
 
 Washing the gold 61 109 
 
 silver ore (roasted) 77 139 
 
 Waste of sulphur 125 195 
 
 Weak solution gold 59 105 
 
 " silver 72 132. 
 
 Weight change in (in roasting ore).. 91 154 
 
 Well for hypo 36 60 
 
 White furnace, the 146 209 
 
 Working special directions for. 41 71 
 
 Working test 86 152 
 
 asmaller 90 153 
 
 Zinc behavior of in roasting 17-21 18-28> 
 
JUSTINIAN CAIRE, 
 
 Importer and Dealer in 
 
 Assayers' Materials & Chemicals 
 
 MILL SUPPLIES OF EVERY KIND. 
 
 BRASS AND STEEL BATTERY SCREENS, 
 
 AGENCY OF L. OERTLING'S, London; BECKERS' & SONS, New York, 
 Assay and Bullion Balances. 
 
 Opera, Field, and Marine Glasses; Optical Goods; Aneroid and 
 Altitude pocket Barometers; Miners' Compasses of all kinds, &c. } fcc. 
 
 Makes a Specialty of everything required for Chlorination Works. 
 
 521 & 523 Market St., and 16 to 22 Stevenson Street, 
 
 CATALOGUES AND PRICE LISTS ON APPLICATION. 
 
For Quartz Mills. 
 
 Over 600 now in use, giving entire satisfaction. Awarded First 
 Premium at the Tenth and Twelfth Industrial Fairs of the Mechanics' 
 Institute. 20 per ceut. more ore crushed with 15 per cent, less wear 
 of iron than by hand feeding. 
 
 The above cut illustrates the recently introduced GRIP, and also the SPRING 
 ATTACHMENT, which replaces the Weight heretofore used, and which is an ob- 
 vious improvement. It is now fully demonstrated, after careful and long-con- 
 tinued experimentation and practical use, that the plan upon which a perfect 
 Ore-Feeder must be constructed is that of a carrier, and not that of a shakng 
 table. Uniform and accurate feeding is not possible on the latter plan. The 
 ore must be evenly carried, upon a steadily advancing plane or table, to the 
 line of discharge, and there simply dropped. Jerky or spasmodic contrivances 
 will not answer the purpose for wet, sticky ores. 
 
IMPROVED AMALGAMATOR & CONCENTRATOR 
 
 Over TOO "have been rmt in nse. 
 
 The principle upon which Henciy's Patent Concentrator is constructed is the oniy true and 
 mechanical one for the purposes of concentration. CENTRIFUGAL FORCE AND . ISA 1 1- 
 
 TATIO3T, combined as they are in this machine, cannot fail to accomplish the object sought. 
 
 Many certificates from proprietors of mills, who have this Concentrator in use, can be had, if 
 required, giving the most flattering accounts of its efficiency. A most substantial evidence of 
 iti worth is the fact that the proprietor is receiving repeated orders from those who are using 
 them, and have tested their merits. 
 
 The proprietor has recently still further improved the machine, making it stronger and still 
 more durable. He flatters himself that the added advantages leave nothing to be desired as 
 to the perfection of the Machine. Endorsed by the following Mining Companies: Grover M. 
 Co., Bunker Hill M. Co., Crown Point M. Co., Keystone Cons. M. Co., Amador Co., Cal. Plumaa 
 Eureka M. Co., Plumas Co., Cal., and very many others. 
 
"THE $1,000 CHALLENGE" 
 
 ORE CONCENTRATOR. 
 
 The Frue Ore Concentrator, 
 
 OR, 
 
 VANNING MACHINE. 
 
 Over 250 are now in use, giving entire satisfaction. 
 Awarded First Premium and Silver Medal at the Industrial Fair 
 for 1880, of the Mechanics' Institute, of San Francisco, Cal. 
 
 Saves from 50 to 100 per cant more than any other Concentrator 
 in use; and the concentrations are clean from the first working. 
 
 The wear and tear is merely nominal; the water required is less 
 than in any other wet concentrator; the power required per machine 
 is less than one-half horse power; the labor required is light, and 
 one man on a watch can attend to sixteen machines. 
 
 We challenge any other Concentrator in use for a fair and impar- 
 tial competitive trial, side by side, for stakes $1,000 each, and we 
 mean business. 
 
 ADAMS & CARTER, Agents, 
 
 Room 7, IO9 California St., San Francisco. 
 
 (SOLE AGENTS FOR THE COLMAN TAPPET.) 
 
Assay Offi ce and (Chemical Laboratory, 
 Bullion and Melting Rooms, 
 
 524 SACRAMENTO STREET, - SAN FRANCISCO. 
 
 Careful Analyses made of Ores, Metals, Soils, 
 
 Waters, Industrial Products, Foods, Medi- 
 
 cines and Poisons. 
 
 oi sultations on Chemical, Mining and Metallurgical Questions. 
 
 ASSAYS. 
 Gold and Silver ................ $3 00 
 
 Gold, Silver and Lead ......... 5 00 
 
 Gold, Silver and Copper ........ 5 00 
 
 Copper ........................ 3 00 
 
 Iron .......................... 3 00 
 
 Tin ......................... 5 00 
 
 Quicksilver ................... 5 00 
 
 Manganese .................. 5 00 
 
 Chromium . . . 5 00 
 
 ANALYSES. 
 
 Qualitative Analysis of Ores 
 
 $10 00 to $25 00 
 Qantitative Analysis of Ores 
 
 $15 00 to $50 00 
 
 Qualitative Analysis of Water. . 25 00 
 Quantitative " " ... 75 00 
 
 " " Guano.. 25 00 
 
 Proximate Analysis of Coal ____ 10 00 
 Quantitative Analysis of Coal . . 50 00 
 
 Complete Analyses, qualitative and quantitative, of complex substances at 
 
 special rates. 
 
 Deposits of Bullion Melted and Coin Returns 
 made in 24 hours. 
 
 Deposits may be forwarded to this office from 
 any part of the interior by express, and returns 
 made in the same manner, either by cheek or 
 certificate of Deposit. 
 
 Gold Bars, on all amounts below 8500 81 00 
 
 " " on all amounts from $500 to 
 
 81,600 2 00 
 
 Gold Bars, on all amounts above $1,6004 of 1 % 
 
 Silver Bars, on all amounts below $400 2 00 
 
 " "on all amounts above $400 . J of 1 % 
 
 Dore Bars for the Gold $2 00 
 
 " " forthe Silver of 1 % 
 
 Determination of Gold and Silver in 
 any Alloy 2 00 
 
 Consignments of all kinds of ore received, and prompt cash returns made. 
 
CHARLES H. AARON, 
 
 Having had eighteen years' experience in Mining, Milling and 
 Assaying, offers his services in the following branches: 
 
 EXAMINATION OF MINES, EEECT10N AND INAUGURATION OF 
 REDUCTION WORKS, 
 
 * Metallurgical Consultations, Selection of Machinery. 
 
 The Leaching Processes for the Extraction of Gold, 
 Silver and Copper a Specialty. 
 
 Address at N. W. cor. Fourth and Howard streets, San Fran- 
 cisco, Cal. 
 
"WM. IRELA1T, Jr., 
 
 (Successor to Mars & Irelan.) 
 
 & CHEMIST 
 
 ROOMS 47, 48 AtfD 49 MERCHANTS' EXCHANGE, 
 
 CALIFORNIA STREET, SAN FRANCISCO. 
 
 Analyses of Ores, Minerals, Waters, Etc. 
 
 -FOR- 
 
 MINERS AND QUARTZ MILLS. 
 
 FURNISHED TO ORDER 
 
 In any quantity and size, at lowest possible rates, 
 and Silver Plating guaranteed 
 
 -AT- 
 
 Pacific Gold, Silver, Nickel 
 
 -AND- 
 
 Copper Plating Works, 
 
 41 Geary Street, near Dupont. 
 
 SAN FRANCISCO. 
 W. E. SHEPMAN, PROPRIETOR. 
 
 ^"Table-ware and^all kinds of work Re-plated and Repaired. 
 Send for Circular. 
 
GEO. W. PRESCOTT. IRVING M. SCOTT. H. T. SCOTT. 
 
 * 
 
 Office, No. 61 FIRST STREET, P. 0. Box 2128. 
 
 COR. FIRST & MISSION STS., SAN FRANCISCO. 
 
 BUILDERS OF 
 
 Steam, Air & Hydraulic Machinery 
 
 COMPOUNDING CONDENSING ENGINES, 
 
 Automatic Cut-off Engines, Vertical and Horizontal 
 Engines and Boilers, Direct Acting and Geared Hoist- 
 ing and Pumping Engines and Reels constantly on 
 hand. Air Compressors, Quartz Mill Machinery for 
 Wet and Dry Crushing. 
 
 Pans, Settlers, Self-Feeders, Rock Breakers, Retorts, Condensers, 
 Water Jacket Smelting Furnaces, Roasting and Chloridizing Fur- 
 naces, Cornish Pumps, and Mill Irons and Castings, of every de- 
 scription, made to order. 
 
 ECLIPSE AMALGAMATING PAN, 
 
 The Best Grinder and Amalgamating Pan yet in- 
 vented. 
 
 Will save much larger percentage of gold and silver 
 than any other Pan in use. 
 
 SOLE AGENTS FOR 
 
 Cameron Steam Pumps, Stetefeldt and Brun- 
 ton Roasting Furnaces. 
 
HINCKLEY, SPIERS & HAYES. 
 
 (ESTABLISHED IN 1855.) 
 
 Works, Fremont & Howard Sts. Office, 213 Fremont Si 
 
 Hoisting Works- 
 
 Whims for prospecting small mines; Portable Hoisting Engines and Boilers, 
 with Reels suitable for wire or hemp rope, of new designs, embodying all the 
 latest improvements. 
 
 Mining Machinery- 
 Hoisting Cages, with safety attachments, Safety Hooks, Ore Cars, Ore 
 Buckets, Car Wheels and Axles, Ore Gates, with racks and pinions for ore bins, 
 Pumping Machinery, Air Compressors, Air or Water Pipe, Receivers, etc. 
 
 Milling Machinery- 
 Gold Mills, with pans or concentrators, as required; Silver Mills, either for 
 dry or wet crushing, with roasting and drying furnaces, Pans, Settlers, etc., aa 
 required; Smelting Furnaces, for either Lead, Copper, Silver or Gold, Willard 
 Roasting Furnaces, especially adapted for gold ores, Retorts, Bullion Moulds, 
 Ore Feeders, Rock Breakers, etc. 
 
 Miscellaneous Machinery- 
 saw Mills, Flour Mills, Oil Well Machinery, Water Wheels and Castings. 
 
 Engines and Boilers 
 
 For any and all purposes, adapted to the economical use of fuel 
 
 SOLE AGENTS FOR THE PACIFIC COAST FOB THE 
 
 Dectne Stecun Pvurrvp. 
 
THOMPSON'S PATENT IMPROVED 
 
 "HOWELl WHITE" BOAST1BG IWACE, 
 
 The Cylinder in this furnace is lined in Us entire length, with Fire 
 
 Brick; also, if desired, with Thompson's Patent Intermediate 
 Plaster of Paris, or Asbestos Lining, which saves heat, and 
 
 prevents excessive and unequal expansion and warping of the cylinder; thus 
 saving fuel, both for the roasting and power for rotating the cylinder, and 
 thereby making it and its supporting and rotating gear more durable. 
 
 This is the only Coasting furnace which has Thompson's Patent 
 * 'PiVOt," by which the cylinder alone can be readily inclined, more or less, 
 while working, so as to insure thorough and economical roasting of the most 
 refractory ore. 
 
 Thompson's Patent Brick Lining prevents sliding of the ore 
 in the cylinder, fits closely, is easily secured, is lighter and stronger, and, by 
 the rounded form of the "projections" and "recesses," keeps clean, and in- 
 sures constant showering of the ore through the flames. 
 
 Thompson's Patent Balanced or Adjustable "Sole 
 
 Plates " prevent breaking of the cylinder or bearings, resulting from un- 
 equal expansion of the cylinder, and consequent unequal distribution of weight; 
 also saving power. 
 
 Thompson's Ore-Cooling Pit utilizes the heat of the roasted 
 ore, causes a higher chloridization, saves once handling of the ore, and avoids 
 the nuisance and waste of "wetting down." 
 
 These patented improvements, with their completeness of detail and perfect 
 mechanical construction, render this furnace superior to all other inclined cyl- 
 inder furnaces, which, for this reason, it is rapidly superseding. The number of 
 these furnaces erected, far exceeds that of any other of the class. 
 
 The following named mining companies have, in the past five years, erected 
 furnaces containing one or more of the above mentioned features and improve- 
 ments: 
 
 Jefferson, Leopard, Ural, Martin White, Eagle, Endowment, Independence, 
 Wasou Cons. Alexander, (2), Raymond & Ely, Columbia Cons. Omega, Bristol, 
 and Paradise Valley, in Nevada. 
 
 Peck, Tiger, Bradshaw, Tombstone, Corbin, Isabella, Irene, and Arizona 
 Northern, in Arizona. 
 
 Monumental, in Oregon; South Western, in California; Silver Bow, in Mon- 
 tana; Palmetto, in Colorado; Ontario, in Utah; Cilley & Co., in Peru. 
 
 And Trinidad, Hormiguera, Plomosas, and Bajada, in Mexico. 
 
 Among the last erected, 16 have the Patent Pivot, and some of them the 
 Patent Brick, Plaster lining, &c. 
 See Engraving and description in this book. 
 
 Full plans and directions for erecting and operating furnished to purchasers- 
 
 For circular with full particulars, prices, &c., address 
 
 J. M. Thompson, 
 
 Pacific Iron Works, San Francisco, Cal. 
 
C. A. HOOPER. 
 
 GEO. W. HOOPEU. 
 
 A. M. JEWEL! ft CO. 
 
 Berry Street, between 3d and 4th, 
 
 SAN FRANCISCO, 
 
 Manufacture Wooden Tanks for Mills, Reduction 
 Works, Railroads, Etc. 
 
 Wooden Pumps and Pipe on hand and made to 
 order. Send for catalogue. 
 
 All kinds of House Finish, Mouldings, Brackets, &c. 
 furnished at short notice. 
 
 Our proximity to the Central and Southern Pacific 
 Railroad Depot gives us unusual facilities for shipping 
 goods on cars. 
 
JOHN CALVERT, 
 
 MEMBER (BY EXAMINATION) OF THE PHARMACEUTICAL SOCIETY OF 
 GREAT BRITAIN, 
 
 N. W. COR, FOURTH & HOWARD ' STS. 
 SAN FRANCISCO, CAL. 
 
 ^Dealer in Drugs and Chemicals, Pharmaceu- 
 tical Preparations, Perfumeries, Proprietary 
 Medicines, Trusses, and other Surgical Appli- 
 ances, Sponges, Vaccine, Herbs, Brushes, Combs, 
 Fancy Soaps and Toilet Requisites. 
 
 MEDICINE CHESTS 
 
 Specially fitted up for Mines and Metallurgical Works. 
 
 Physicians' Prescriptions, English and Con- 
 tinental, carefully prepared by Experienced 
 Pharmacists. 
 
 Sole Proprietor and Manufacturer of the 
 Celebrated Stock Condition Powder, Stock Lin- 
 iment and Stock Ointment, for Horses and 
 Cattle. ^ 
 
 Orders or inquiries by mail or express 
 promptly attended to. 
 

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