140 BLUE VITRIOL. 
The principal use of vitriol is in dyeing woollen ar- 
ticles, hats, and other manufactures, black. It is the 
basis of ink, and is used in the manufacture of Prussian 
blue. If it be reduced to powder by the action of fire 
in a crucible, and mixed with powder of galJs, it forms 
a dry portable ink. Sulphuric acid (24?) may be ob- 
tained from this kind of vitriol by distillation. The re- 
sidue, after the process is completed, is used as a red 
paint ; and when washed, is employed for the polishing 
of steel. 
SALTS OF COPPER. 
209. BLUE VITRIOL, or SULPHA T OF COPPER, 
is a blue salt formed by a combination of copper with sulphuric 
acid (24). 
This substance, though sometimes found in a state of 
concretion, or in the form of powder disseminated over 
the surface of stones that have been in contact with 
water impregnated with it, is more frequently an artifi- 
cial preparation obtained from evaporating the water 
which runs through copper mines. In the mines of 
Neussol, in Hungary, at the depth of 380 feet beneath 
the surface of the ground, are several vats, placed at dif- 
ferent distances, for the purpose of collecting the water 
impregnated with copper, and which flows into them 
through a kind of gallery above. From this water the 
vitriol is afterwards separated by evaporation. A pro- 
cess somewhat similar is pursued in our own country. 
In the principal blue vitriol manufactories established 
in France, the operation is thus carried on. Pieces of 
copper are first dipped into water, and their surface, 
while wet, is covered with a stratum of powdered sul- 
phur. The copper thus prepared is put into an oven, 
and heated to redness. After some time, it is taken out, 
and, while hot, is plunged into a vessel filled with water. 
These operations are repeated several times, till the 
whole of the copper is dissolved, and the water becomes 
loaded with vitriol. Thus saturated, the water is placed 
