Abstraci of Fr of. Hess' s T/ierm (metrical Researches. 3 



tain group of bases, but this problem it is to be hoped will 

 soon be resolved. 



Before passing to describe the other researches of M. Hess, 

 it is proper to observe here, that the law just now announced 

 is at variance with that which Dr. Andrews has deduced from 

 his experiments, an abstract of which has been given in the 

 Phil. Mag., S. 3., vol. xix. p. 183. Dr. Andrews considers that 

 all acids evolve, when combining with the same base, the same 

 quantity of heat, but that different bases evolve different quan- 

 tities of heat. For sake of comparison, we here present in a 

 table the numbers he obtained with the same acids and bases 

 as M. Hess operated on. ^^^_ 



Base. 



Sulphuric acid. 



Potash .... 

 Soda .... 

 Ammonia 

 Lime .... 



7-32 

 7-44. 

 6-34 



Nitric acid. 



6-76 

 6-4,5 

 5-58 

 7-20 



Muriatic acid. 



6-56 

 6-74 

 5-58 

 7-08 



It is not our purpose to discuss which of these conclusions 

 is best supported by the evidence, as the respective authors 

 will probably continue the investigation of the subject until 

 the true law is obtained and recognized. 



On Thermonezdrality. — If we take two solutions of neutral 

 salts which have the same temperature, and by their mixture 

 generate two new salts, there is in general no rise of tempera- 

 ture : these saline solutions are said by M. Hess to be titer- 

 moneutral, and he explains this phaenomenon by the law and 

 the numerical results that have been just now described. Thus, 

 if the solutions contain sulphate of potash and nitrate of lime, 

 the quantities of heat absorbed by the separation and evolved 

 by the combination of the acids and bases respectively, are 

 shown to be the same, for there are by the table, — 

 Before mixture. After mixture. 



CaO.N05 = 451 CaO.S03 + 2Aq = 642 



K O . S O3 = 601 K O . N O5 = 409 



1052 1051 



These numbers are not in any way corrected. 



In some cases of double decomposition a slight change of 

 temperature occurs ; thus if chloride of calcium and sulphate 

 of potash be taken, there is 



Before mixture 

 Ca CI + 6 Aq = 436 

 KO.SO3 = 601 



1037 



After mixture. 

 Ca O . S O3 + 2 Aq = 642 

 KCl = 361 



' 1003 



B2 



