266 SALTS 



water in the salt. It amounts to only j^tti ol 

 an atom, showing clearly that it is not chemi- 

 cally combined with the salt. 



Nitrate, 2. Nitrate of soda. This salt, which crystal- 

 lizes in rhombs, resembles nitrate "of potash in 

 the absence of water of crystallization, and the 

 presence of a small quantity of that liquid lodged 

 mechanically between the plates of the crystals. 

 Its constituents are 



1 atom nitric acid . 6-?5 

 1 atom soda . 4 



10-75 



Carbonate, 3. Carbonate of soda. This salt is familiarly 

 known in this country, being manufactured to a 

 considerable extent. It may be met with in 

 commerce in beautiful crystals, seven or eight 

 inches long ; but I have never got it in a state 

 of complete purity. It usually contains about 

 2 per cent, of sulphate of soda ; and it is ex- 

 ceedingly difficult to get rid of this impurity. 

 After 12 careful crystallizations of it in my la- 

 boratory, we still could detect the presence of 

 sulphuric acid in the crystals, though in too mi- 

 nute quantity to appreciate its weight. The 

 constituents of this salt, when crystallized in oc- 

 tahedrons, with a rhombic base, the apices of 

 which are always deeply truncated, are as fol-. 

 lows : 



