552 M. F. M. Raoult's Researches on the 



into the formulae is that taken at the middle of the time, d is 

 measured by the method of opposition ; f by the method of alter- 

 nate circuits*, after a sufficient number of elements have been 

 added to the battery to make the intermittent current transmitted 

 by the commutator equal to the primitive continuous current i. 



An element x, without resistance, capable of producing in the 

 voltameter the same current i as that of the battery P, would 

 give, in the sine-compass with long wire B, a current of the inten- 

 sity e —f (for the demonstration see the complete memoir) . The 

 electromotive force of the element x, compared with that of a 



e—f 

 DanielFs element, is therefore — j-. Now since the quantity of 



voltaic heat evolved in the entire circuit, for the same fraction 



Q %^ of electricity transmitted, is proportional to the electromo- 



Ol'O 



tive force, it follows that the heat evolved in the voltameter, by 

 reason of its resistance, is 



*=!=^88900x^g («) 



Such is the quantity of heat which would be evolved during the 

 experiment in a metallic conductor of equal resistance with the 

 voltameter. 



This quantity t, contrary to what has been hitherto asserted, 

 is always less than T. The difference T — t represents, for the 



fraction -Jr^ of an equivalent of electricity transmitted, the 



heat furnished to the calorimeter by a local action. The local 

 heat K, evolved in the voltameter for 1 equivalent of electricity 

 transmitted, or of substance decomposed, is therefore 



or 



K = Tx — -^.239000. ...(/?) 

 p cl 



The inverse electromotive force /of the voltameter diminishes, 

 by fx 239000 thermal units, the heat which the current i pro- 

 duces in the circuit for 1 equivalent of electricity transmitted. 

 (Comptes Rendus, 14th September, 1863 [Phil. Mag. loc.cit.]) 

 The sum X of the calorific effects, positive or negative, pro- 



* The method of opposition and that of alternate circuits, which were 

 devised by myself, were communicated to the Academie des Sciences on 

 the 2lst of February, 1859, and are described in the Annates de Chimie et 

 de Physique, 4th series, vol. ii. pp. 321 and 326. 



