318 SALTS. 



SALTS. 



Introductory Remarks. 



That the student may not be fatigued by a too frequent reiteration 

 of similar properties, the history of saline bodies will be given, in di- 

 visions, under that of the acids, which they respectively contain, in the 

 same manner as that of the principal acids is given, under combustibles. 



We shall thus dispose of the salts in convenient groups, and the 

 most important will be brought into view, as early as possible. 



As many of the salts are unimportant, the history of some of them 

 will be abridged, and that of others omitted, or included in a general 

 statement of the properties of the genus to which they belong. Some 

 of the salts are, however, eminently important and interesting, and 

 therefore the history of such salts will be developed, with all the ne- 

 cessary details. Under the head of attraction and crystallization, 

 many things have been stated respecting saline bodies, which need 

 not be repeated here, and various generalizations will be prefixed to 

 the first genus. It remains, to make a few other observations, by 

 way of introduction to the history of saline bodies generally. 



As salts consist of acids and salifiable bases ; alkalies, earths, and 

 metallic oxides, we observe that the powers of saturation differ very 

 widely among these agents ; it takes much more of some bases to satur- 

 ate a given acid than of others, and vice versa, of different acids to 

 saturate a given base. This evidently depends upon the number ex- 

 pressing the combining powers of those different bodies ; or rather 

 the formation of salts is only a mode of ascertaining and expressing 

 this very fact, in relation to acids and bases. For instance, the com- 

 bining power of nitric acid is expressed by 54, that of lime by 28, 

 and that of baryta by 78 ; to form then anhydrous nitrate of lime, 

 54 parts of nitric acid will unite with 28 of lime, and the chemical 

 equivalent of nitrate of lime will be 54+28=82; but to saturate 54 

 of nitric acid, requires 78 of baryta, and therefore the chemical 

 equivalent of nitrate of baryta will be 54+78 = 132. 



Now, suppose lime and baryta to be combined, each with two 

 acids ; say the nitric and the sulphuric ; the numbers expressing the 

 combining powers of these earths being as above stated, and that of 

 sulphuric acid being 40, the sulphate of baryta will be expressed by 

 40+78=118, and that of the sulphate of lime by 40+28 = 68, the 

 salts being supposed anhydrous. It was suggested by Berthollet, and 

 the idea was adopted, more or less, by many chemists, that the 

 strength of affinity is inversely as the saturating power ; but this idea 

 is inconsistent with facts ; e. g. 40 parts of sulphuric acid require 28 

 of lime and 78 of baryta for saturation, and therefore baryta should 

 attract sulphuric acid less powerfully than lime, which is not true. 



