104 ON A METHOD OF EXTRACTING GOLD, SILVER, 
copper left was ouly 0°12 per cent. Practically, therefore, it was 
possible to remove all the copper in such 
in tals without increasing the bulk of the fluid, so that no 
evaporation would be require 
The mixed crystals of sulphate of copper and sulphate of iron 
evolve on calcination large quantities of sulphurous and sulphuric 
anhydri i 
per wat 
a tra tube, and dripping from tray to tray flowed off through 
a pipe at the bottom, whilst steam was admitted at the bottom m 
sufficient quantity to keep the lower half of the tower warm. 
alf a 
poun g cined, the copper and sulphate 
of iron was extracted with water containing sulph and 
aci residue was reduced with carbon at @ 
dull-red and the metallic powder being spread on the 
half-pound, the residue from which was treated as before, and to 
the gases from the third and so on, until the whole was operated 
dilute sulphuric acid, my parcel o 
whole of the soluble matter was then extracted with water, 
hich 
t 
sb Sgr A hag Ri as eS ER oe en - h ine: 
