Galvanic Pile, and Electromotive Forces. 429 



vanic, and that which arises from the chemical processes in the 

 pile the chemical heat. Then it has heen inferred, from the 

 experiments which have been made, that, under the presuppo- 

 sition mentioned, the chemical is equal in amount to the gal- 

 vanic heat. Calling the galvanic heat gw, according to Joule's 

 law giv — Mi 2 lt, where M is a constant, i denotes the current- 

 intensity, I the resistance of the conduction and the pile toge- 

 ther, and t the time during which the current is in action. 

 Therefore, if E denotes the electromotive force of the pile, we 

 can also write gw = 'M.'Eit f from which, in consequence of the 

 inference drawn, we obtain kw = MJElit y if kw signifies the heat 

 evolved by the primary chemical processes in the pile. Jf n 

 denotes the number of chemical equivalents decomposed by the 

 action of the current at the positive-pole plate of the pile, ac- 

 cording to the law of electrolysis n=zmit, m denoting a constant 

 which is independent of the nature of the electrolytic liquid. 



tvt 

 Hence we conclude that kw= E, and therefore that, for 



M m . 



one equivalent, kw= — E, from which it follows that the quan- 

 tity of heat which is produced in the pile by the primary che- 

 mical processes while one equivalent is decomposed at the 

 positive pole is a measure of the electromotive force of the 

 pile. 



If the galvanic is in reality precisely as great as the primary 

 chemical heat, we may consequently say that the whole effi- 

 cacy of the current consists only in this, that it conducts the 

 chemical heat to all parts of the closed circuit, and deposits at 

 each place exactly as much as corresponds to the resistance at 

 the same place — although of course it is very difficult to form 

 a clear conception of the actual physical processes that take 

 place in this conduction. If by direct measurement of the 

 heat produced in the pile itself it were to be found that its 

 amount is greater than that of the galvanic heat occasioned 

 by the passage of the current, or, in other words, exceeds 

 the heat which the current calls forth in a metallic conduc- 

 tor whose resistance is equal to that of the pile, we should 

 have to admit that this excess was derived from the secon- 

 dary processes which may take place in the pile and have 

 nothing in common with the formation of the current. In 

 this way also it has been attempted to explain such surplus 

 heat in the cases in which it has been observed : — If a chemi- 

 cal-decomposition cell or a voltameter be inserted in the circuit, 

 so that the current has opportunity to decompose water, for 

 example between platinum poles, then, according to the way 

 of regarding it now presented, all the primary chemical heat 



