370 MINES OF CREMNITZ. 
CHAP, in the form of scoria. Tliis is the last ope- 
IV. 
«^^ I ration. 
The gold is smelted into ingots of 12,000 
Average florins eacli. The annual produce of gold and 
Produce of . ^-^ , 
the Mines. Silver 'dii Cremnitz amounts to 800.000 marks 
of SILVER, and 3000 of gold. The nitric acid, 
of which such an immense quantity is required 
in separating the gold from the silver, is not all 
wasted during the process ; much of it is col- 
lected during its evaporation, to be used again. 
Much of this acid is made in the Laboratory, by 
distilling equal parts of sulphate of iron and 
nitrate of potass ; the product falling into the 
large glass retorts before mentioned. In the 
JiVayiiig- essaying laboratory, instead of the long process 
we have described for extracting the precious 
metals from their ores, two simple and easy 
experiments are sufficient. The first is a trial 
of the pulverized ore by cupellation. About a 
tea-spoonful of the pulverized ore, first weighed, 
is put into a small cupel, made of calcined 
bones : this being exposed to the heat of a 
powerful furnace, the lead, semi-metals, Sec. are 
either absorbed by the cupel, or they are sub- 
limed : nothing remains afterwards in the cupel, 
but a small bead of combined gold and silver; 
and by the proportion of its weight to the 
house. 
