certain Sulphates, and particularly Sulphate of Copper. 355 
its pulverulent texture, and is converted into a mass of silky 
pale green crystals: on the heated portions of tube, points of 
a chocolate brown matter are produced. The current of gas 
being continued until all action ceased, and the tube and its 
contents had cooled to the ordinary temperature of the room, 
the apparatus was weighed, and the bluestone was found to 
have absorbed rather more than one atom of muriatic acid, 
the excess being attributed to the quantity absorbed by the 
water disengaged. 
The mass of green crystals thus obtained is very delique- 
scent, excessively acid, and gives fumes, arising probably from 
some muriatic acid in excess. Dissolved in water it yields 
by crystallization the hydrated chloride of copper in long 
needles. 
When there is used sulphate of copper, either quite dry, or 
retaining one atom of water, the effect is so nearly similar as 
to allow of the same description serving for both. 
S Cu or S Cu H absorb muriatic acid rapidly, and assume 
a dark chocolate brown colour. The mass becomes slightly 
coherent as if some water became free; but the second desic- 
cating tube does not increase in weight in any perceptible de- 
gree. The process is accompanied by the evolution of so 
much heat as occasionally to crack the tubes; but the passage 
of the gas must be continued for a long time after the whole 
has become cold. The amount of gas absorbed then approxi- 
mates very closely to one atom, but it seldom absolutely at- 
tains the theoretical quantity; it can approach, however, 
within one per cent., and we may consequently consider that 
one atom is the quantity absorbed. 
This brown matter is possessed of interesting properties. 
When heated it gradually and readily parts with its muriatic 
acid gas, leaving behind the sulphate of copper unaltered. 
Exposed to the air it rapidly absorbs water, with the evolution 
of heat, and becomes apple green, a change which occurs 
instantaneously if a few drops of water be allowed to fall upon 
it. Dissolved in water it forms an apple green solution ; and 
by crystallization gives the crystallized chloride of copper, 
sulphuric acid remaining in the liquor. 
Two theories may be conceived of the nature of the body 
thus formed: One, that the chloride of hydrogen is absorbed 
by the sulphate of copper and combines with it as water would 
do,—that, in fact, the so-called muriatic acid is capable of re- 
placing the water of crystallization of salts as ammonia and 
phosphuretted hydrogen have been shown to do by Rose and 
Graham: The other, that the chloride of hydrogen reacting 
on the oxide of copper forms water and chloride of copper, 
2N 2 
