﻿the Combination of Acids and Bases, 31 



vertence, MM. Favre and Silbermann have here given an inac- 

 curate statement of my first law. It did not declare that pre- 

 cisely 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 recog- 

 nized 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 extensive, 

 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 o, 4 to o, 55 short of the same. A minute investiga- 

 tion of the influence of the disturbing sources of heat will no 

 doubt discover the causes of these discrepancies. The high 

 numbers for sulphuric acid are probably connected with that 

 acid's well-known property of developing much heat when com- 

 bining with successive atoms of water. All the other acids de- 

 velope nearly the same amount of heat in combining with the 

 same base, the greatest divergences from the mean quantity 

 being, in the case of potash, -f-0 o, 24 and — o, 13; in that of 

 soda, + o, 26 and — 0°*14; and in that of ammonia, +0°'17 

 and — 0°*05. These differences are almost within the limits of 

 the errors of experiment " *. 



But although there is a superficial agreement between my 

 original results and those of MM. Favre and Silbermann, they 

 will be found, when examined closely, to differ widely in detail, 

 and on points of great importance. I had found that the oxalic 

 acid disengages almost exactly the same amount of heat in com- 

 bining with the soluble bases as the hydrochloric, nitric, and 

 many other mineral acids ; and this observation I have always 

 regarded as one of the main foundations of Law I. MM. Favre 

 and Silbermann, on the contrary, have inferred from their expe- 

 riments that " the following organic acids — the oxalic, formic, 

 valeric, and citric — disengage sensibly the same quantity of heat, 

 but it is less (plus faible) than that given by the foregoing mi- 

 neral acids" — among which they enumerate the nitric and hydro- 

 chloric. According to my experiments, no distinction of this 

 kind can be admitted between acids derived from the mineral 

 and organic kingdom, inasmuch as the oxalic acid developes at 

 * Transactions of the Royal Irish Academy, vol. xix. p. 240. 



