1887.] Contributions to the Metallurgy of Bismuth. 



91 



most satisfactory results. It will only be necessary to take the figures 

 of one operation as an illustration. 



A quantity of 9483 lbs. of bismuth, holding about one per cent, of 

 impurity, and 12*5 ounces of gold per ton (equal to 53*5 ounces in 

 the bulk), was so treated, and of this nearly 9000 lbs. was imme- 

 diately rendered available for commercial use, the skimmings, which 

 amounted to 658 lbs. (7'30 per cent, of the bulk), containing the whole 

 of the gold. 



These skimmings I oxidised by means of nitric acid, thus obtain- 

 ing the greater proportion of the bismuth and what little copper there 

 was in solution, from which the bismuth was precipitated by the 

 ordinary method, care being taken to saturate the nitric acid by ex- 

 tracting the greater portion of the bismuth as nitrate, so as to leave 

 a portion of the bismuth as oxide with the gold in order to refine 

 it from the impurities existing as oxides when fused with it. This 

 residue, collected and dried, was, when dried, fused in clay crucibles, 

 with a small quantity of borax, yielding the full amount of gold shown 

 by assay. 



As before stated, in these fusions the metallic gold separates from 

 the bismuth litharges, and descends to the bottom of the crucible by 

 its own gravity. The liquid and supernatant bismuth litharge floats 

 upon it and breaks away readily when cold, the gold so obtained being 

 associated only with silver, both metals being in fact refined by the 

 action of the bismuth litharge. 



§ 2. Separation of Bismuth from Lead. — The difficulty surrounding 

 the treatment of bismuth associated with other metals by any rapid 

 or comprehensive process is well known to the metallurgical chemist. 

 I believe I am correct in stating that hitherto the only process 

 employed for the refining of bismuth on the Continent — notably in 

 Saxony, the chief continental source of this metal — has been that of 

 chlorination and subsequent precipitation, a process tedious in itself 

 and involving much plant and labour in comparison with the quanti- 

 ties of metal operated upon. 



Rapidity of production with a minimum margin of loss, in order 

 to free the metal from its impurities and render it marketable as 

 quickly as possible, being a great desideratum, induced me to turn 

 my attention to its refining by dry processes. In carrying this out I 

 have found present most of the metals which are easily seized by and 

 become associated with the bismuth itself during the process of reduc- 

 tion from its ores,* such as antimony, arsenic, tellurium, lead, copper, 

 &c, &c, all of which I have successively and successfully dealt with. 



It is not my intention in this paper to describe the processes 

 adopted for the elimination of these several metals, but to confine 



* See Table of Analyses herewith. 



