166 On Gold Refining ly Olihrine Gas. 



addition of corrosive sublimate (bichloride of mercury) to the 

 melted gold. The two former of these plans are troublesome, 

 from the corrosive action they exert on the crucibles ; and the 

 last, namely the employment of corrosive sublimate, which is 

 that usually adopted, is most objectionable from the dense and 

 highly injurious fumes evolved. 



In Victoria, this is regarded as so serious a matter in a public 

 and sanitary point of view as to have induced the Municipal 

 Council of Melbourne to institute an action at law against the 

 Union Bank, to compel them to abate the nuisance thus created 

 by their gold melting establishment. The passage of chlorine 

 gas through the melted gold is found to effect the complete 

 toughening of the metal by the elimination as volatile chlorides 

 of the materials which render it brittle, while the evolution of 

 the deleterious mercurial fumes is avoided. 



In the metallurgic treatment of the precious metals some loss 

 is always sustained, but that incurred in the process here 

 described is not found to be excessive. 



The average loss of gold in operating hitherto has been found 

 to amount to 19 parts in every 100,000 of alloy treated, which is 

 considerably less than would be met with in toughening an equal 

 amount of gold with corrosive sublimate in the ordinary manner. 



The loss of silver has amounted to 240 parts in every 100,000 

 of alloy operated on (containing originally say 10 per cent, of 

 silver). 



There is no doubt that a considerable portion of both these 

 losses would be recovered on further treating the pots and ashes 

 remaining after the operation, and it is found that as manipula- 

 tory skill is acquired the proportional loss of silver appears to be 

 decreasing. 



In refining on the large scale gold containing 10 per cent, of 

 silver the cost of the operation in Sydney, including labour and 

 the above losses of gold and silver, but exclusive of rent of 

 premises and superintendence, is about five farthings per ounce, 

 but varying with the quantity of silver present in the alloy 

 operated on. 



In England, where hydrochloric acid is a waste product of the 

 alkali works, and all apparatus is cheaper, the cost of refining by 

 this method would be proportionally less. 



The fineness of the gold produced by this process varies from 

 991 to 997 in 1000 parts, the average, as found on a refmage of 

 many thousand ounces, being 993"5, or 23 carats 3f grains. The 

 remaining 6+ thousandths are silver, and this compares favour- 

 ably with any of the previously known practical processes, none 

 of which leave less silver than this in the resulting fine gold. 



If the refined gold be subjected to a re-finage by chlorine, the 

 amount of silver left in it can be reduced to 2-10 per cent., just 



