37S Scientific Intetligenct. 



ed. It was collected, v/ashed, dried, and then melted with saltpetre^ 

 The acid liquids united^ were placed in contact with plates of coppery 

 which separated the silver entirely, which being washed, was melted; 

 with saltpetre and borax. The liquid uitrate of copper was evapo- 

 rated, and then exposed to a heat capable of decomposing it. The 

 oxide of copper was reduced by charcoal in an air furnace. In this- 

 operation the nitric acid, which is very expensive, was almost entirely 

 lost — a great deal of saltpetre was used — the vessels en:iployed were 

 often broken, as they were unfit to resist the great variations of tem- 

 perature to which they were exposed — deleterious gases and vapors. 

 were copiously produced — ^the waste was very great- — and consider- 

 able expense v^as incurred in reducing the copper. 



In the new process, nearly all these inconveniences are avoided.- 

 The ingot is melted and granulated without saltpetre— the grains are 

 treated with sulphuric acid in large vessels of platina, at a high tem- 

 perature, by which the silver and copper are dissolved.^ The gold 

 being thus separated from the silver, is treated with fresh acid, then; 

 washed, dried and melted with a little saltpetre. The sulphate of 

 silver is decomposed by plates of copper aided by heat^ and the 

 silver is v/ashed, dried and melted ivith a little saltpetre and borax.^ 

 The solution of sulphate of copper is saturated by adding oxide of 

 Gopper, then evaporated and crystallized. In this process much labor 

 is saved, and less expense incurred in saltpetre^ acid, crucibles and- 

 eharcoal ; there is less waste, and the amount of saleable products 

 is greater, — while, no other gases being disengaged than sulphurous 

 acid with a little sulphuric, the operations are performed with less 

 injury to the workmen. 



The alloy m.ost easily refined by sulphuric acid, ought, in generaL 

 to consist of gold, silver and copper, in nearly the following pro- 

 portions^ 



Silver, -.----. 725 



Gold, .-„-„- 200' 



Copper, „ - ™ - « ~ 7& 



1000 

 If the proportion of copper be much greater tiaan the above, an'- 

 hydrous sulphate of copper, will be held in suspension in the solution? 

 which prevents the gold from separating easily ; and if the gold be in 

 greater quantity, the alloy is not easily attacked by boiling sulphuric 

 acid ; the refiner should therefore previously analyze a small portioE; 



