312 Mr Granam on Water as a Constituent of Salts. 
Sulphate of Magnesia with Saline Water : MgSH-+H‘’. Sulphate 
of Magnesia. 
One atom of water is retained by sulphate of magnesia at 
460°, but the other six are not entirely expelled under 270° in 
open air. Indeed this sulphate is remarkable for a disposition 
to retain two atoms of water, in which respect it resembles the 
sulphate of lime. Dried at 212° in open air, the crystals of sul- 
phate of magnesia were found in several experiments to retain 
somewhat more than two atomic proportions of water. When 
dried at the same temperature in vacuo over sulphuric acid, the 
water was reduced to two proportions. Crystals placed over sul- 
phuric acid in vacuo, without heat, were found to retain only 
two and a quarter atomic proportions of water. 
Anhydrous Anhydrous] ¥ 
Salt. Water. Salt. Water. 
Crystallized salt, dried in vacuo at 70° for six} jo 34 
days, or till it ceased to lose, ; , 
Do. in vacuo at 212, . .. . cnet Seales : 28.62 
Do. heated between 410° and 460° for one \ 49 
hour, being previously dried at 238°, : 
Relative composition of the anhydrous salt 
with one atom of water (by theory), 
The sulphate of magnesia and ammonia lost its six atoms of 
water of crystallization and became anhydrous, when exposed to 
a temperature not exceeding 270°, for one hour, having pre- 
viously been dried at 212°. It retained of course the atom of 
water which is essential to the ammoniacal salts. A somewhat 
higher temperature was required to deprive the sulphate of mag- 
nesia and potash of its whole water of crystallization. 
Hydrated Sulphate of Lime: CaSH+H. 
The only crystalline hydrate of sulphate of lime, which is 
