631 



935 



1176 



1341 



412 M. J. Thomsen's Thermo -chemical Researches. 



one equivalent of the base and acid were* : — 



Silbermaim. 

 Sulphuric acid . . 15689 15810 



Nitric acid . . . 13617 15283 



Hydrochloric acid . 13740 15128 



Supersaturation of soda by sulphuric acid- — One equivalent of 

 sulphate of soda gives rise, by the addition of sulphuric acid, 

 to a very remarkable absorption of heat, which increases with 

 the proportion of the acid, as the following numbers show : — 



Thermal units. 

 For £ equivalent of acid ... — 396 

 i 

 2 >> 



i 



2 



4 



For intermediate proportions, the thermic effect may be cal- 

 culated with sufficient approximation by the formula 



^1650, 



Ti + 0-8 ' 



n denoting the number of equivalents of acid added to one equi- 

 valent of sulphate of soda. 



Supersaturation of soda by nitric acid and by hydrochloric acid. 

 — These reactions occasion a scarcely perceptible absorption 

 of heat. We have found, for one equivalent of nitrate of soda and 

 one equivalent of nitric acid, —36 thermal units ; for one equiva- 

 lent of chloride of sodium and one equivalent of hydrochloric acid, 

 — 32 thermal units. Hence, in calculating complicated reactions^ 

 we might neglect the thermic effects due to these causes ; and so 

 it appeared useless to repeat these determinations for other rela- 

 tive proportions of acid and salt. 



Decomposition of sulphate of soda by nitric acid. — We first stu- 

 died the decomposition of neutral sulphate of soda by various quan- 

 tities of nitric acid. The sulphate was always dissolved in 200 

 equivalents of water; the nitric acid varied from NO 5 +100 aq 

 to NO 5 + 300 aq. Experiment had shown that the addition 

 of 100 equivalents of water to 1 of nitric acid which already con- 

 tained 100 equivalents of it, disengages so small a quantity of 

 heat that it may be completely neglected f. For one equivalent 



* [We have placed the results obtained by the author side by side with 

 those obtained by Messrs. Favre and Silbermann. 



t This remark of the author's seems to indicate that he attributes no 

 influence to the degree of dilution of the solutions, except in proportion to 

 the thermic effect developed in their preparation. That would be, we 

 think, to neglect the most important cause of the variations which that di- 



