174 
Proceedings of the Pcoycd Society 
2. On the Heat Disengaged in the Combination of Acids 
o O 
and Bases. Second Memoir. By Thomas Andrews, M.D., 
F.B.S., Hon. F.B.S.E. 
( Abstract .) 
In the beginning of this paper the author recapitulates the five 
fundamental laws of the heat of combination, which he had de¬ 
duced from his previous researches, and which form the subject of 
several memoirs published in the Transactions of the Boyal Irish 
Academy and of the Royal Society of London, from 1841 to 1848. 
They are as follows :— 
Law 1.—The heat disengaged in the union of acids and bases is 
determined by the base, and not by the acid; the same base pro¬ 
ducing, when combined with an equivalent of different acids, nearly 
the same quantity of heat; but different bases, different quantities. 
Law 2 .—When a neutral is converted into an acid salt by com¬ 
bining with one or more atoms of acid, no change of temperature 
occurs. 
Law 3.—When a neutral is converted into a basic salt by com¬ 
bining with an additional proportion of base, the combination is 
accompanied with the evolution of heat. 
Laio 4.—When one base displaces another from any of its 
neutral combinations, the heat evolved or abstracted is alwavs the 
same, whatever the acid element maybe, provided the bases are the 
same. 
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 disengaged is always the same, but a change in either of 
the metals produces a different disengagement of heat. 
The concluding part of the elaborate memoir of MM. Favre and 
Silbermann, on the heat disengaged in chemical actions, which ap¬ 
peared a few years later, is chiefly devoted to a repetition of the 
experiments already published b}^ the author. They state that 
they consider the fourth law, which asserts the equality of thermal 
effect in basic substitutions, to be fully established; but they 
dissent from what they consider to be the enunciation of the first 
law, and infer from their own experiments that- the organic acids— 
