52 Copper. 
Preparation of sulphat of Copper , or blue vitriol oj com- 
merce . 
The sulphat of copper, as an article of importance in 
several of the arts, merits our attention* For the purposes 
of commerce this salt has been prepared by different me- 
thods, which are, 
1st® The vitriolization of the native sulphur ets of cop- 
per, (copper pyrites)* 
2dly. The formation and vitriolization of artificial sul- 
phur ets of copper. 
Sdly. The evaporation of cupreous waters, and 
4thly. By dissolving metallic copper in the sulphuric 
acid. 
The first mode is practised on a large scale, particu- 
larly in Germany. That the sulphurets of copper are 
more difficult to vitriolize than those of iron is evident 
from the circumstance of the latter frequently undergoing 
a decomposition in consequence of exposure to atmosphe- 
ric air ; on this account some particular treatment is 
required to fit those of copper for our present purpose® 
Copper pyrites are broken into small pieces, alternate stra- 
ta are formed with these and combustible matter ; when 
the heap is finished it is set fire to ; the fire should be 
Moderate, and long continued ; by this means the opera- 
tion will be more easily managed, and more salt will be 
formed by the process. This roating generally lasts for 
24 hours, the matter remaining is, whilst hot, thrown into 
tubs containing water : here it continues during 48 hours 
the water should be agitated whilst it is acting on the 
roasted ore. The ore is now taken from the water and is 
roasted a second time, and is treated with water as before. 
We continue throwing roasted ore into the water until 
this last receives a fine blue colour. The solution must 
then be sufficiently evaporated in boilers of lead or 
