﻿30 Dr. T. Andrews on the Heat Developed in 



The law deduced from this inquiry is implicitly involved in the 

 foregoing, of which it may indeed be regarded as a necessary 

 consequence. It was enunciated in the following terms : — 



Law 4. — When one base displaces another from any of its 

 neutral combinations, the heat evolved or abstracted is always 

 the same, whatever the acid element may be, provided the bases 

 are the same*. 



Finally, the law of metallic substitutions, first announced in 

 the Philosophical Magazine for August 1844, was thus stated in 

 a paper published in the Philosophical Transactions for 1848. 



Law 5. — When an equivalent of one and the same metal re- 

 places another in a solution of any of its salts of the same order, 

 the heat developed is always the same ; but a change in either 

 of the metals produces a different development of heat. 



In 1845 [1844] a paper appeared by Graham on the heat dis- 

 engaged in combinations, the second part of which refers to the 

 heat produced when hydrate of potash is neutralized by different 

 acids f. The results arrived at by this distinguished chemist 

 exhibit a close agreement with those contained in my first com- 

 munication to the Royal Irish Academy. 



The concluding part of the elaborate memoir of MM. Favre 

 and Silbermann on the heat disengaged in chemical actions is 

 chiefly devoted to the same subject. A large number of experi- 

 ments 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 1841 ; but they widely differ in the 

 details. The authors of this able memoir fully recognize the 

 accuracy of my fourth law, which asserts the equality of thermal 

 effect when one base is substituted for another. " M. Andrews," 

 they observe, " avait en effet etabli que, quel que soitl'acide d'un 

 sel, la quantite de chaleur degagee par la substitution d'une base 

 a une autre pour former un nouveau sel est la meme, lorsque 

 Fon considere les deux memes bases" J. 



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 per- 

 mitted to quote the passage in the original language. " Ses con- 

 clusions, savoir : que la chaleur degagee par F equivalent d'une 

 meme base combinee aux divers acides est la meme, ne s'ac- 

 cordent pas avec les resultats de nos recherches, et ne nous pa- 

 raissent pas pouvoir etre admises." No doubt, through inad- 



* Philosophical Transactions for 1844, p. 21. 



f Memoirs of the Chemical Society, vol. ii. p. 51. [Phil. Mag. June 

 1844, p. 401.] 

 % Ann, de Chim. et de Phys. S. 3. vol. xxxvii. p. 497 (1853). 



