178 Serentific Intelligence. 
ed. It was collected, washed, dried, and then melted with saltpetre. 
The acid liquids united, were placed in contact with plates of copper, 
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 employed 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 was 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 washed, dried and melted with a little saltpetre and borax. 
The solution of sulphate of copper is saturated by, adding oxide of 
copper, then evaporated and crystallized. In this process much labor 
is saved, and less expense incurred in saltpetre, acid, crucibles and 
charcoal ; 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 most easily refined by sulphuric acid, ought, in general, 
to consist of gold, silyer and Copper, in nearly the following pro- 
portions. ; é 
Silver, - < 
EDA oe 98h 
Gold, Ber an te eee 200 
Copper, —- - - - . “ 75 
1000 
If the proportion of copper be much greater than the above, an- 
hydrous sulphate of copper, will be held in suspension in the solutions 
which prevents the gold from separating easily ; and if the gold be in 
_ Breater quantity, the alloy is not easily attacked by boiling sulphuric 
acid ; the r should therefore previously analyze a small portion 
