COMBINATION OF ACIDS AND BASES. 87 



acid are probably connected with that acid's well known property of developing 

 much heat when combining with successive atoms of water. All the other acids 

 develope 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, 

 + 0°-24, and - 0°13 ; in that of soda, + 0°-26, and - 0°14 ; and in that of 

 ammonia, 4- o, 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 combining 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 1. MM. Favre and Silbermann, on the contrary, 

 have inferred from their experiments 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 mineral acids "■ — 

 among which they enumerate the nitric and hydrochloric. 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 least as much heat in combining with the bases as the hydrochloric, nitric, 

 and several other strong mineral acids. 



The experiments to be described in this paper were made some years ago, 

 but their publication has been deferred from accidental circumstances. I have, 

 however, recently repeated a few of the more important of them, with a 

 slightly modified form of apparatus. The solutions were taken in so dilute a 

 state that the heat disengaged never exceeded 3 0, 5 C. A standard solution of 

 sulphuric acid was prepared and carefully analysed, by precipitating a given 

 weight with a soluble salt of barium, and weighing the sulphate of barium. The 

 strength of the alkaline solutions was adjusted with great care by means of this 

 standard acid. The same solution of each alkali was employed in all the experi- 

 ments, and the quantity used in each experiment was determined by careful 

 weighing. The acid solution was of such a strength that, after being mixed with 

 the alkali, an excess of two or three per cent, of acid was present. The alkaline 

 solution was contained in a light glass vessel, in which a large platinum crucible 

 holding the acid was carefully floated. By giving a rapid rotation, by means of 

 a light stirrer, to the acid solution in the platinum crucible, a perfect equilibrium 

 of temperature was soon established between the two liquids. The initial tem- 

 perature of the solutions was usually about 1°5 below that of the air, and the 

 final temperature of the mixture about 1°5 above it. The corrections for the 



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



