during the Combination of Acids and Bases. 247 



I. NaO + iP,0„ . . . 

 (NaO + ^PA+F^OJ . 



II. NaO + ^AsA. • 



(NaO + ^AsA) + MsA. • 



III. KO + ^AsA 



(KO + ^AsA)+iAsA . 



58. Had the evolutions of heat corresponded with the additions of acid the 

 second numbers would have been one-half of the first in each set of experiments. 

 Hence, the increments of temperature for equal portions of acid are nearly as 

 2.5 : 1, before and after the formation of the subsalt. The pyrophosphoric acid, 

 on the contrary, presents no similar irregularity, developing equal increments of 

 heat, for equal additions of acid, till the pyrophosphate of soda (NaO -{- i|PyrA) 

 is formed. 



59. It may, perhaps, be prematnre, from such imperfect and limited data, to 

 offer any general observations on the preceding experiments ; but I shall, never- 

 theless, venture to show the accordance of laws second and third, with those 

 general views of the constitution of the salts which have been so ably illustrated 

 by Graham. The conversion of a neutral into an acid salt being in reality the 

 formation of a double salt, is not accompanied by any disengagement of heat ; 

 because such combinations as the latter do not evolve heat. No caloric is 

 extricated when the tartrates of potash and soda unite ; and, consequently, none 

 ought to be given off, when the tartrate of soda is combined with the tartrate of 

 water. But, on the other hand, heat is disengaged when the base in the tartrate 

 of water is replaced by soda; because soda, in its combinations with the acids, 

 evolves much more heat than water. How far the heat evolved in the formation 

 of the different hydrated acids may be the same, is an interesting question not 

 yet determined ; but there can be little doubt that water holds a very low rank 

 among the bases, in reference to its power of generating heat when combining 

 with the acids. On the same principles, and again referring to the observations 

 of Graham, we can understand the cause of the evolution of heat during the 



