Chap. 4.] Neutral Salts. 21 



not, like the fimple falts, communicate the faline pro- 

 perties to other bodies. Their cryftalline form is like- 

 vvife a circumftance which very generally diftinguifhes 

 the neutral from the fimple falts. The volatility of 

 the neutral falts is not in general fo great as that of the 

 fimple falts. 



Neutral falts may in many cafes be decompofed by 

 heat alone, but in general it is neceffary to have re- 

 courfe to elective attraction, or the addition of a third 

 fubftance. When the decompofition is effected by heat 

 alone, the more volatile part is forced off: but it feldom 

 fucceeds in this way, the ingredients commonly adhering 

 fo ftrongly that they rife together. It then becomes 

 neceflary to have recourfe to elective attraction. Thus, 

 if from a neutral fait we wifh to obtain the acid pure, 

 we apply another acid which has a greater attraction 

 for the alkali. If our object is to obtain the alkali 

 feparate, we apply a fubftance which has a flronger 

 attraction for the acid*. 



* I would recommend to the reader, before he proceeds further 

 in this part of the work, to look over again that part of the fourth 

 chapter of the firfl book which relates to the attraction of combi- 

 nation or chemical attraction, Vol. I. p. 18 to 24.. 



C 3 



