86 DR ANDREWS ON THE HEAT DEVELOPED IN THE 



potash is neutralised by different acids. 4 ' The results arrived at by this distin- 

 guished chemist exhibit a close agreement with those contained in my first 

 communication to the Royal Irish Academy. 



The concluding part of the elaborate memoir of MM. Favre and Silber- 

 mann on the heat disengaged in chemical actions is chiefly devoted to the same 

 subject. A large number of experiments are described, which are nearly a 

 repetition of those I had previously published. Their results bear a general 

 resemblance to those given by myself in 184i ; but they widely differ in the 

 details. The authors of this able memoir fully recognise the accuracy of my 

 fourth law, which asserts the equality of thermal effect when one base is sub- 

 stituted for another. " M. Andrews," they observe, " avait en effet etabli que, 

 quelque soit l'acide d'un sel, la quantity de chaleur degagee par la substitution 

 d'une base a une autre pour former un nouveau sel est la meme, lorsque Ton 

 considere les deux memes bases, "t 



In a preceding paragraph of the same memoir, the authors object to what 

 they conceive to be my first law, and state that it is not in accordance with the 

 results of their investigations. As the question is one of some importance, I 

 may perhaps be permitted to quote the passage in the original language. " Ses 

 conclusions, savoir : que la chaleur degagee par l'equivalent d'une meme base 

 combinee aux divers acides est la meme, ne s'accordent pas avec les resultats 

 de nos recherches, et ne nous paraissent pas pouvoiretre admises." No doubt, 

 through inadvertence, MM. Favre and Silbermann have here given an inaccurate 

 statement of my first law. It did not declare that precisely the same amount 

 of heat is disengaged by all the acids in combining with the same base, but 

 that the heat is determined by the base, "the same base producing, when 

 combined with an equivalent of different acids, nearly the same quantity of 

 heat." A comparison of the results of MM. Favre and Silbermann with those 

 in my original memoir will show that I had fully recognised and described the 

 deviations from the other acids, exhibited, on the one hand, in excess, by 

 the sulphuric acid, and on the other, in deficiency, by the tartaric, citric, 

 and succinic acids. " If we refer," I remarked, in the original memoir of 

 1841, "to the first, second, and fourth tables, as being the most exten- 

 sive, from the large number of soluble compounds formed by potash, soda, 

 and ammonia, it will be observed that the sulphuric acid developes from o- 8 to 

 nearly 1° more than the mean heat given by the other acids; while the tartaric, 

 citric, and succinic acids fall from 0°4 to o, 55 short of the same. A minute 

 investigation of the influence of the disturbing sources of heat will no doubt 

 discover the causes of these discrepancies. The high numbers for sulphuric 



* Memoirs of the Chemical Society, vol. ii. p. 51. 



f Annales de Chimie et de Physique 3 feme serie xxxvii. p. 497 (1853). 



