﻿and Expansions of some Liquids, 137 



the same uniformity in the movements necessary for immersing 

 and agitating the heated thermometer in the bath. 



As each experiment could be made very rapidly, the determi- 

 nation of the specific heat of each solution was always repeated 

 at least five or six times ; and the determination was made by 

 comparing the results with those of as many alternate similar 

 experiments on water. 



In reality this does not render the determinations laborious, 

 except in appearance ; for in order to compare experiments made 

 on a solution with those made on water, several days intervening 

 between the two series, it would be necessary to compare almost 

 daily the thermometer of the calorimeter and the heated ther- 

 mometer with a standard one ; now this comparison, to attain 

 the necessary degree of precision, would take at least as much 

 time as the experiments relative to the determination of the spe- 

 cific heats. 



In short, it ought to be remarked that this mode of operating 

 not only has the advantage of rendering all correction needless, 

 and of avoiding the errors that might result from a displacement 

 of the zero in the thermometers used, but also renders insensible 

 those which might be caused by an imperfection in the gradua- 

 tion of the thermometers — an imperfection which it is impossible 

 completely to avoid in experiments where an error of t ^q of a 

 degree has a very sensible influence on the results. In compa- 

 rative experiments on water and another liquid, if the heating is 

 the same in both cases, and if the initial and final temperatures 

 are, within a few hundredths, the same in the one as in the 

 other, the determination is affected by the errors of graduation 

 of the thermometer to the exceedingly slight amount of only a 

 few hundredths of a degree. 



As the promised speedy publication of the memoir of M. 

 Thomsen on the same subject diminishes greatly the importance 

 of my own researches, I do not purpose to give in detail the 

 numbers of all my experiments, but shall merely indicate the 

 mean results. 



I will nevertheless, in order to give the means of judging the 

 course I have pursued and the agreement presented by the dif- 

 ferent observations, state in detail the experiments which refer 

 to two series of determinations. I take as examples those on the 

 specific heat of the solutions of hydrochloric acid containing, to 

 one molecule of acid (H CI = 36*5), 50 and 100 molecules of 

 water (900 and 1800) respectively. 



The study of these two solutions having taken place on two 

 consecutive days, under absolutely similar atmospheric condi- 

 tions, I have united in a single series all the experiments made 

 on water. 



