4S 



lents of difFerent bases. To take, as an example, the nitric 

 acid, which also produces very nearly the mean quantity 

 of heat given by all the acids, the following numbers ex- 

 press the increments of temperature obtained on combining 

 the same quantity of it with each base : magnesia, 8* 1° ; lime, 

 7'2°; barytes, 6-9°; potash, 6-8° ; soda, 6-5° ; ammonia, 5'6° ; 

 oxide of zinc, 4*8° ; oxide of lead, 4-2° ; oxide of silver, 3-2°. 

 The numbers for barytes, potash, soda, and ammonia, are 

 strictly comparable with one another (except a slight correc- 

 tion for differences in the specific heats of the solutions ;) but 

 in the case of the other bases, an absorption of heat, unknown 

 in amount, takes place in consequence of their conversion 

 from the solid to the fluid state. Hence the numbers for 

 these bases are all below the truth. 



Two singular anomalies are described as occurring in the 

 combinations of the peroxide of mercury with the hydracids, 

 and in those of the hydrocyanic acid with the bases. 



In confirmation of the second law the author adduces a 

 series of experiments, which prove, that during the conver- 

 sion of a neutral into a supersalt no heat is produced. Thus 

 while the normal development of heat occurs when a solution 

 of caustic potash is neutralized by oxalic acid, the subsequent 

 additions, first of one, and afterwards of two more atoms of 

 the same acid, so as to convert the neutral oxalate into the 

 binoxalate, and the latter again into the quadroxalate of 

 potash, is not accompanied by any change of temperature in 

 the solutions. In testing the accuracy of this law, it is neces- 

 sary to select examples where all the compounds are soluble 

 in water, otherwise the heat arising from the formation of 

 precipitates would interfere with and complicate the result. 



The second law does not extend to the case of the conver- 

 sion of neutral into basic compounds, — a part of the subject 

 which the author has carefully investigated. 



