54 
Book II. 
Division II. 
History. 
Purifica 
Nan. 
SALTS OF 
Sp. 1. Sulpbat of Zinc. 
CONCENTRATED sulphuric acid scarcely acts upon 
zinc without the assistance of heat ; but if it be suffi 
ciently diluted with water, it attacks the metal with 
force ; hydrogen gas is emitted, and the zinc is very 
speedily dissolved. In this case the water is decompo 
sed ; its oxygen combines with the metal, while its hy 
drogen is exhaled. When the solution is sufficiently 
concentrated by evaporation, it yields the sulphat of 
zinc in crystals. 
This salt, according to the best accounts, was disco 
vered at Rammelsberg in Germany about the middle 
of the 16th century. Many ascribe the invention to 
Julius Duke of Brunswick. Henkel and Newmann 
were the first chemists who proved that it contained 
zinc ; and Brandt first ascertained its composition com 
pletely*. It is generally formed for commercial pur 
poses from sulphurated oxide of zinc, or blende as it is 
called by mineralogists. This ore is roasted, which 
converts the sulphur into an acid ; it is then dissolved 
in water, and concentrated so much that, on cooling, it 
crystallizes very rapidly, and forms a mass not unlike 
loaf-sugar. This salt is usually called wbite vitriol, 
It is almost always contaminated with iron. Hence 
the yellow spots which are visible on it, and hence also 
the reason that its solution in water lets fall a dirty 
brown sediment; a circumstance very much complain 
ed of by surgeons when they use that solution in medi 
cine. It may be easily purified by dissolving it in 
water, and putting into the solution a quantity of zinc 
* Beckmann's History of Inventions, art. Zinc.