METALLURGY. 



443 



milk, butter. h<>m>y. prepare! fruiN. 

 potable water, 1 pT cent, tartiirie acid, acetic 

 arid..') |i.-r cent, boraeic acid, carbolic acid and 

 salicylic acid, and 1 per cent, soda solution, 

 ling to the collected results, the action 

 of the Milistauce.s on the aluminum articles was 

 so very insignificant as to leave hardly any 

 question as to the insolubility of aluminum in 

 i with alimentary substances. The ex- 

 periments of llerren Lubbert and Roscher, 

 which led to opposite results, were conducted 

 with leaf aluminum, which has some different 

 qualities from solid aluminum. While the metal 

 in a finely divided condition leaf aluminum 

 uxidiy.es in boiling under development of hydro- 

 gen. >oiid aluminum under the same conditions 

 remain* unaltered. But aluminum vessels are 

 not adapted to contact with alkaline fluids. 



The use of aluminum tokens as a substitute 

 for the I'l Hank of England notes which it is 

 proposed to issue is suggested by Sir Henry Bes- 

 semer. After mentioning the advantages of a 

 hard, permanent substance over a perishable ma- 

 terial for such purpose, the author speaks of its 

 extreme lightness as a recommendation, making 

 it possible to distinguish it from any other coin, 

 even in the dark, and as effectually preventing 

 its imitation in plated base metal like lead and 

 pewter alloys. 



Mr. Alfred E. Hunt names as among the 

 properties of aluminum which will probably give 

 it the most availability in the arts its relative 

 lightness, its nontarnishing quality as compared 

 with many other metals, its extreme mallea- 

 bility, its easy casting qualities, its influence in 

 vaiintis alloys, its nigh tensile strength and 

 elasticity when weight for weight of it is com- 

 pared with other metals, and its high specific 

 heat and heat conductivity. He regards the ex- 

 periments on the ground of which it has been de- 

 clared not suitable for certain domestic uses not 

 satisfactory, because the tests to which it has 

 -objected in them never occur in practical 

 housekeeping, while other metals that have been 

 long in domestic use without suspicion suffer as 

 badly, or worse, than it, under such tests; and 

 however much it maybe acted upon, it. never 

 forms a poisonous compound. 



Gold and Silver. The principal distinction 

 of the matte-smelting process for the extraction 

 of gold and silver from their ores is. according to 

 Herbert Lang, of Mineral, Idaho, that it is pre- 

 eminently suited for the treatment of base ore, 

 partieiilarlysulphureted varieties, and. generally 

 speaking, all such ores as are. or were, classified as 

 refractory or rebellious. Nothing is too difficult 

 for matte smelting, and such substances as sul- 

 phur, antimony, arsenic, etc., which give great 

 trouble in other modes of treatment, are of no 

 detriment, and sometimes of great use, in the 

 process. The valuable metals that can be ex- 

 tracted by matte smelting are gold, silver, plat- 

 inum, copper, nickel, cobalt, and. less perfectly, 

 lead. A large number of the "rare" metals also 

 come down. The percentage saved is rarely less 

 than !H), and is usually somewhat more. Two 

 substances, the slag and the matte, are formed 

 in matting. The latter contains the valuable 

 metals united in a homogeneous mass, with sul- 

 phur and with more or less iron, lead, etc.. accord- 

 ing to the composition of the ore. The slag 



contains silica united with various oxides of the 

 ore, or flux, principally oxide of iron or man- 

 ganese, which we do not want to save. The sim- 

 plest ore or mixtureof ores that wecould treat in 

 a blast furnace would have to contain, besides t In- 

 valuable metal to be extracted, sulphur, oxide of 

 iron, and silica. . Some of the iron would be re- 

 duced in the furnace, and would then join t he- 

 sulphur and form the matte, taking down the 

 values. The remaining oxide of iron would 

 combine with the silica and form sing. Arsenic 

 and antimony serve the same purpose as sulphur, 

 and manganese acts the same as iron ; so neit her 

 iron nor sulphur is indispensable, though prac- 

 tically they are both present and perform, with 

 silica, the most important part in the reactions. 

 It is evident that the matting process has a 

 great range of adaptability. Almost every com- 

 bustible can be used in it. No ore or complica- 

 tion of ores is too difficult for it ; and, further- 

 more, we are not obliged to expend any time or 

 money tp find out how to work any proposed 

 combination; a simple chemical analysis of the 

 ore will tell us. Leaching, while it is a failure as 

 applied to raw silver ore, is a useful auxiliary in 

 matte smelting. 



The Bartlett zinc-lead process of treating sil- 

 ver ores is based on the fact that when ores con- 

 taining silver and zinc are burned in the pres- 

 ence of sulphur, the zinc is volatilized, and 

 takes out a small part of the silver with it. Two 

 methods of treating the ores are adopted, ac- 

 cording to the amount of zinc and gangne they 

 contain. In the first method, the ores contain- 

 ing stronger proportions of zinc are mixed with 

 hydrocarbon, sulphur is added till a proper pro- 

 portion is obtained, and the whole is burned in 

 the presence of an air blast and with free air 

 above to prevent with the hydrocarbon flame 

 the formation of sulphuric acid. The zinc and 

 lead are volatilized, and pass off as a fume, leav- 

 ing the silver and nonvolatile metals. In the 

 second method, for ores less rich in zinc, the ore 

 is continuously charged, without previous burn- 

 ing, in a thin layer, into a special furnace. 



An electrolytic process for the decomposition 

 of common salt and its conversion into chlorine 

 gas and caustic soda, applied by Mr. James 

 Greenwood to the manufacture of soda and 

 bleaching powder, is also capable of application 

 to the production of sodium amalgam and chlo- 

 rine for the extraction of gold and other metals. 



The new process of Areas silver plating is 

 performed with an alloy of silver and cadmium. 

 The preparatory steps are the same as for ordi- 

 nary silver plating, and the only essential dif- 

 ferences in the process are in the alloy and the 

 use of certain chemicals which are employed in 

 the baths. The new alloy is said by those who 

 have used it to wear well, to show greater resist- 

 ance than ordinary silver-plating material to 

 abrasion, and to resist tarnishing better. It is. 

 moreover, said to be 10 per cent, cheaper than 

 the old process. The superiority of cadmium 

 over copper in an alloy with silver sugg- 

 wider application of it than in this process. The 

 alloy appears to be suitable for use in manufac- 

 t tiring processes requiring stamping, rolling, cast- 

 ing, or engraving, and in coining. 



Copper. As shown by Mr. G. C. V. Holmes, 

 the manufacture of copper goods by electrical 



