304 Mr Granamon Water as a Constituent of Salts. 
pressure in blotting paper, are apt to undergo the same decom- 
position, if the air is damp, and frequently impart a large quan- 
tity of their sulphate of water to the paper in the course of 
twenty-four hours. This circumstance must be kept in view in 
preparing bisulphates for analysis. The facility with which these 
salts are decomposed by water, accords well with their relation 
to sulphate of water with ‘saline water, which we have supposed 
to exist. Sulphate of zinc, sulphate of magnesia, &c. are capable 
of separating the sulphate of water from these salts, at a temper- 
ature approaching ‘to redness, and take its place. 
I have observed that the bisulphate of soda is more prone to 
decomposition, when dissolved in water, than the bisulphate of 
potash. The double salts of sulphate of soda with sulphate of 
magnesia, &c., are also much less stable than the corresponding 
double salts containing sulphate of potash. Indeed, I believe 
that the former are uniformly decomposed when dissolved in 
water. 
Sulphate of Potash, Sulphate of Soda. KS,NS. 
These salts differ from other sulphates in having no saline 
water. Of the ten atoms water with which sulphate of soda 
crystallizes, none is essential to its constitution. The whole 
were lost, even at a temperature not exceeding 47° Fahrenheit, 
when the crystals of the salt were exposed over sulphuric acid 
in vacuo for five days. From the regular progress of the desic- 
cation of the salt, which was observed by occasionally weighing 
it, it was evident that no portion of the water was more strongly 
retained than the rest. It is well known that sulphate of soda 
crystallizes in an anhydrous condition from a hot solution. 
Sulphate of Zinc with Saline Water : ZnSH-++H’. © Sulphate of 
Zine. 
‘In the sulphate of zinc, we have the basic atom of water con- 
tained in sulphate of water displaced by oxide of zine, while the 
