METALLURGY 



407 





trated salt solution serving for lixiviation is pre- 

 vented, if necessary, by replacing a portion of the 

 sodium hydrate with a corresponding quantity 

 of calcium hydrate. The separation of the gold, 

 silver, lead, and zinc from the iron and copper 

 in the solution is accomplished by supersaturat- 

 ing the brine with sodium hydrate. 



The method of C. Raleigh for precipitating or 

 depositing gold and silver from cyanide, chlo- 

 rine, and other solutions, without rendering the 

 same inefficient for further use, consists in filter- 

 ing the solution through granular or permeable 

 materials, such as carbon, which, while retaining 

 the precious metal, do not deteriorate the solu- 

 tion, while the latter will remain available for 

 utilization in the treatment of a fresh charge of 

 ore or compound. 



In the modified chlorination process of J. W. 

 Sut-ton, Australia, the chlorinator consists of a 

 wrought-iron barrel lined with lead, through 

 which passes axially a perforated tube lined 

 with asbestos. Attached to this barrel is a 

 smaller one, also lined with lead and fitted with 

 a steam jacket, and so arranged that both bar- 

 rels shall be rotated by the same gearing. The 

 damp ore is placed in the large barrel, and a 

 charge of manganese dioxide, salt, and sulphuric 

 acid in the smaller one before commencing oper- 

 ations. In this way the ore, as it is rotated in 

 the large barrel, is saturated with chlorine as it 

 issues from the central tube, and when the evo- 

 lution of gas becomes slow the steam is turned 

 on to the jacket, and thus insures the complete 

 decomposition of the salt. 



Experiments for using aluminum instead of 

 zinc in precipitating gold from the cyanide solu- 

 tions obtained by leaching auriferous ores have 

 been attended with satisfactory results. Among 

 the advantages claimed for this over the process 

 with zinc are, that while zinc enters into combi- 

 nation with the bound or free compound con- 

 tained in the cyanide solution, aluminum does 

 not, but simply reacts 'with the caustic alkali 

 and separates the gold very quickly from the 

 cyanogen solution, and that by the action of the 

 aluminum the cyanide of potassium employed 

 for leaching the' gold out of its ore is regen- 

 erated and may be used again. 



The merits and disadvantages of the cyanide 

 process for treating gold and silver ores are dis- 

 cussed by W. H. Virgos in the "Engineering and 

 Mining Journal." The process was introduced 

 in 1890 as a solution of the difficulties of deal- 

 ing with refractory and low-grade ores. It is 

 best adapted to low-grade ores, because the 

 strength of the cyanide solution must be in- 

 creased as the grade rises, and it finally becomes 

 too costly. The gold in the ore and concen- 

 trates must be in a fine state of division, the 

 material must be free from deleterious com- 

 pounds capable of absorbing the cyanide, and it 

 must possess good leaching properties at the size 

 of mesh required for economical extraction. The 

 manner in which the gold is carried in the mate- 

 rial is of great importance. The process is much 

 better adapted to the treatment of gold-bearing 

 than of silver-bearing ores, because silver ores 

 leach with more difficulty than gold ores in the raw 

 state ; because cyanogen, having a greater affinity 

 for gold than for silver, silver ores require long- 

 er treatment with stronger solutions ; and be- 



cause such silver ores as can be treated success- 

 fully by lixiviation methods can be more econom- 

 ically handled by some process in which cheaper 

 chemicals are used. The chlorides and bromides 

 of silver are, however, easily reduced, and good 

 extractions have been made on antimonial silver 



While admitting, on the evidence of experi- 

 ments made by himself, that a nucleus of gold 

 in an alluvial deposit, or in a vein in contact 

 with suitable solutions, would tend to increase 

 in size as long as the supply of gold in solution 

 is maintained, and that masses as large as the 

 largest known nuggets, or indefinitely larger, 

 might be so found, Prof. A. Liversidge, of the 

 University of Sydney, who has made a study of 

 the subject, is still of the opinion that the large 

 nuggets have not been so found, but have been 

 set free from veins, and have acquired their 

 rounded and mammillary surfaces by attrition. 

 Nuggets may have also received deposits of gold 

 from solution, but such deposits, the author 

 thinks, have made no material alteration in the 

 size of the larger ones. 



In the MacArthur-Forrest process for extract- 

 ing silver by means of cyanides, a soluble sul- 

 phide is formed which retards the action of the 

 cyanides on the precious metals. In an im- 

 proved process by Mr. MacArthur, C. J. Ellis, and 

 the Cassel Gold Extracting Company, a suitable 

 salt or compound of a metal is added which will 

 render the sulphur of the soluble sulphide inert 

 by forming with the sulphur a sulphide prac- 

 tically insoluble in the cyanide solution, or 

 which will diminish the action. 



Aluminum. A number of reasons are ad- 

 duced by Dr. Leonard Waldo for regarding alu- 

 minum bronze as a definite compound alumi- 

 nide of copper and that its solution in cop- 

 per gives rise to the various alloys which go under 

 that name ; and he proposes that, when it is di- 

 luted with an equal amount of copper the result- 

 ant substance be called one half aluminum 

 bronze, and so on to one quarter aluminum 

 bronze, etc. "As to the qualities of the com- 

 pound which is found in this way," the author 

 says, " it is at once evident, in view of the high 

 melting points of aluminum and copper, that if 

 we have a true aluminide of copper formed, we 

 have got a set of conditions respecting corrosion 

 which does not exist in any alloy of copper. 

 The combinations between copper and tin and 

 zinc, and the very little understood relations 

 which exist in manganese bronze and that class 

 of compounds, are very different from the action 

 between aluminum and copper, and are not 

 chemical unions at all; but in the case of alu- 

 minum bronze you have a definite compound 

 analogous in its mechanical qualities to a high- 

 grade steel. . . . 



" When the aluminum bronze has been formed, 

 and when the chemical union has been effected 

 between the aluminum and the copper, and in the 

 absence of disturbing elements, we have a metal 

 showing the fracture qualities of the highest 

 grades of steel, and equaling steel in elongation, 

 elastic limit, and tensile strength, and possessing 

 also a different class of properties. This series 

 of metals is nonmagnetic. They are very perma- 

 nent. The oftener they are rernelted the better 

 they are, providing they are kept free from oxy- 



