OF SODA. 265 



If the salts of potash exhibited above be suffi- 

 ciently numerous to entitle us to draw any con- 

 clusions, we may infer that these salts are either 

 anhydrous, or contain 1, or at most 2 atoms of 

 water. Quadroxalate of potash and sesquicar- 

 bonate constitute the only deviations from this 

 law ; and from their singular nature, we had 

 reason to look for some peculiarity in their con- 

 stitution. 



3. SALTS OF SODA. 



1. Sulphate of soda. This well known salt 

 crystallizes commonly in flat four-sided prisms, 

 the faces of which are channelled longitudinally. 

 It effloresces very speedily when exposed to the 

 air ; and loses all its water of crystallization in 

 24< hours, when confined in the exhausted receiv- 

 er of an air pump, with sulphuric acid. Its con- 

 stituents are 



1 atom sulphuric acid 5 

 I atom soda . 4- 



10 atoms water 11 '2 5 



20-25 



There is usually a minute quantity of water 

 lodged mechanically between the plates of the 

 crystals. This, in an integrant particle of the 

 .salt, may amount at a maximum to O03 parts, 

 which constitutes about jfsth part of the whole 



