Mr Graham on Water as a Constituent of Salts. 301 



alkali or true base. The function of the first atom is basic, but 

 a new term is required to distinguish the function of the second 

 atom of water, or of the essential atom of water in the sulphate 

 of zinc. The application of the epithet saline to that atom of 

 water, may, perhaps, be permitted, to indicate that it stands in 

 the place of a salt. The hydrate of sulphuric acid in question 

 contains, therefore, an atom of basic, and an atom of saline water. 

 It is " a sulphate of water with saline water," as the hydrous 

 sulphate of zinc is " a sulphate of zinc with saline water." The 

 bisulphate of potash also is " a sulphate of water with sulphate 

 of potash," and corresponds with the sulphate of zinc and potash ; 

 which last is " a sulphate of zinc with sulphate of potash." 



A reason could now be given why there exist no supersul- 

 phates (or indeed any supersalts) of magnesia, zinc, &c. A bi- 

 sulphate of magnesia would be a compound of sulphate of water 

 with sulphate of magnesia, on our view of supersulphates. Now 

 sulphate of magnesia, and sulphate of water, are bodies of analo- 

 gous constitution, or of the same category, and should have as 

 little disposition to combine together, as sulphate of zinc and 

 sulphate of magnesia have. 



1 . Sulphate of Water with Saline Water ; HSH. Sulphuric Acid 



ofsp.gr. 1.78. 



It appears, then, that in an exposition of the relations of the 

 sulphates, we may set out from this body as our primary sulphate. 

 Of the two atoms of water which it contains, that atom which is 

 basic cannot be separated from the acid, unless by the agency of a 

 stronger base. The second, or saline atom of water, may be separ- 

 ated by heat, but not by any degree of heat, under 400° Fahren- 

 heit, and is re-absorbed with great avidity. 



A diluted sulphuric acid may, I find, be concentrated at a 

 temperature not exceeding 380°, without the loss of a particle of 

 acid ; and the quantity of water retained is reduced to two atoms 



