236 SALTS. 



quantity of soda required : whereas, if I were 

 obliged to employ caustic soda, it would not be 

 so easy to determine how much of it contained 

 the exact quantity of soda required. But it is 

 obvious, that no table exhibiting the composi- 

 tion of the salts can furnish us with any informa- 

 tion which will be useful in this point of view, 

 unless it tells us whether the salts are anhydrous ; 

 and, if they contain water, how many atoms 

 of that liquid enter into the integrant particle of 

 the salt. No general laws respecting the water 

 of crystallization being known, it is still necessary 

 to subject every salt to a rigid analysis in order 

 to determine whether any water be present in it, 

 and how much. 



I have made a very considerable number of 

 analyses with this object in view, and I shall 

 state the results of them in this chapter. Now, 

 salts are of two different kinds some are com- 

 posed of an acid and a base simply united to- 

 gether, with or without water: these may be 

 called simple salts. Others are formed by the 

 union of two simple salts together, and this 

 either with or without an alteration in the atomic 

 quantity of water present. These salts are 

 usually called triple salts ; but the term double 

 salts, applied to them by Berzelius, is much 

 more appropriate. These double salts are ex- 

 ceedingly numerous, though only a few of them 

 have been noticed in chemical books. It will be 



