M. P. A. Favre's Electrolytic Investigations. 289 



be produced by a single thermoelectric element, and by the use 

 of his inductive instrument can multiply this in a measured 

 proportion until he reaches a difference of potentials measurable 

 by an ordinary electrometer. Thus it appears that his anticipa- 

 tion of all that 1 have done in my " Replenisher " is even more 

 complete than I supposed when writing the preceding. 



XXXIV. Electrolytic Investigations. By M. P. A. Favre*. 



I HAVE the honour of communicating to the Academy the 

 continuation of my thermal investigations on the battery 

 considered as a decomposing agent. I hope that the new results 

 I am about to communicate will give an idea of what may be 

 expected from attempts in this direction to elucidate the chemical 

 and dynamical theory of the battery, and that they will show that 

 the calorimeter, which has already been of such use in chemistry, 

 is destined to render even greater service. Let me hope that 

 these investigations will foreshadow the future in store for ther- 

 mal chemistry, which is now only in its infancy. I hope to con- 

 tribute to demonstrate how important is the part the battery 

 plays in the study of molecular work — a study so little advanced, 

 and which, better known, will give a more accurate idea of the 

 constitution of bodies, and of their mode of acting on each other. 



For if the balance (which in the hands of Lavoisier and his 

 successors has served to create modern chemistry, by determining 

 the relative weights of bodies which act on each other) is indis- 

 pensable to chemists, the calorimeter is no less so : it measures, 

 weighs, so to say, the force set at work in chemical reactions, 

 and gives a thermodynamic expression for the formation of bodies. 

 The same is the case with the battery, which in these reactions, 

 almost always complicated, enables us to follow and measure the 

 distribution of the motive force which it developes. 



I have already described the apparatus by means of which I 

 measure the distribution of the motive force developed by the 

 battery employed as an agent of chemical separation ; I will con- 

 tent myself with simply mentioning its principal parts. 



The first mercurial calorimeter (thermometre a calories) has 

 seven muffles, and measures the heat remaining in the battery 

 which it contains. This battery consists of five equal couples 

 (amalgamated zinc and platinum) , which are immersed in sulphuric 

 acid suitably diluted. It occupies five muffles. 



The physical resistance of the battery and of the in ter polar, which 

 includes the tangent-compass, is equal to about 50 millims. of 

 my normal platinum wire. I have endeavoured to eliminate this 

 * Translated from the Comptes Rendus, February 10, 1868. 



