416 COMPOUND SALTS 



salts have in most cases the same acid combined 

 in each with a different base ; though there are 

 a few examples of the union of two salts differ- 

 ing from each other both in their acids and 

 bases. There are perhaps, examples likewise of 

 two salts uniting, formed of the same base each, 

 but containing different acids, though I do not 

 at present recollect any such. It is obvious 

 from this account of their constitution, that the 

 term triple salts cannot with precision apply to 

 these bodies. The name double salts, by which 

 Berzelius distinguishes them, is more correct ; 

 though even it may probably be ultimately 

 found rather too limited to include the whole of 

 these saline bodies ; perhaps, therefore, it may 

 be better to apply to them the term compound 

 salts, by which 1 have distinguished them in the 

 title affixed to this section. 



The compound salts are extremely numerous, 

 much more so, I have reason to believe, than 

 the simple salts. In general they crystallize 

 more readily, and more regularly than the simple 

 salts ; many of them are exceedingly beautiful, 

 and such of them as act as purgatives, are both 

 more elegant and more useful medicines than 

 the simple salts from which they were formed ; 

 almost all the salts of ammonia and of potash 

 have the property of forming compounds with 

 other simple salts, and constituting compound 

 salts. Soda, and the alkaline earths, do not en- 



16 



