in Chemical Combinations. 485 



nitude of the resistance to conduction and the square of the 

 quantity of transmitted electricity. 



2nd. That the resistance to electrolysis presented by water does 

 not occasion the evolution of heat in the decomposing cell. At 

 the same time, the heat evolved by the whole circuit, for a given 

 quantity of transmitted electricity, is diminished on account of 

 the decreased electromotive force of the current, owing to the 

 resistance to electrolysis. It is reasonable to infer that this di- 

 minution of the heat evolved by the circuit is occasioued by the 

 absorption of heat in the decomposing cell. 



And 3rd. That the resistance occasioned by the polarization of 

 Ritter occasions the evolution of heat at the surfaces on which 

 this phenomenon takes place; and thus it happens that the 

 diminution of the heat evolved by the circuit, in consequence of 

 the diminished intensity of the pile, is exactly compensated for ; 

 so that the heat evolved by the whole circuit may be estimated 

 by the chemical changes occurring in the pile, just as if no such 

 polarization existed. 



I have already given theoretical results* for the heat of com- 

 bustion agreeing so well with the experiments of Dulong, as to 

 convince me of the accuracy of the principles above advanced. 

 My method was to ascertain how much of the intensity of a pile 

 is spent in overcoming the affinity of the combustible for oxygen, 

 and then to calculate the heat due to such an intensity, which 

 heat ought, on our principles, to be equal to the heat occasioned 

 by the recombination of the elements in combustion. I hope in 

 the present paper to be able to show that still more accurate 

 results may be attained by the use of a method, founded upon 

 the same principles, but of greater simplicity. Previously, how- 

 ever, to the description of the new experiments, I intend to bring 

 forward some new proofs of the correctness of the law upon 

 which their accuracy entirely depends. 



I am aware that M. Ed. Becquerelf andM. Lenz J have sepa- 

 rately, and by numerous and skilfully performed experiments, 

 made it abundantly clear that the heat evolved by voltaic elec- 

 tricity is proportional to the resistance to conduction and the 

 square of the current. Nevertheless I have made new experi- 

 ments upon the subject, thinking it impossible to demonstrate 

 too completely the accuracy of a law upon which all theriuo- 

 chemical phenomena depend. I have endeavoured to make the 

 results of these experiments worthy of confidence by the employ- 

 ment of a galvanometer and thermometers of great delicacy and 

 accuracy. 



* Phil. Mag., S. 3. vol. xix. p. 2/o' ; and vol. xxii. p. 205, &c. 

 t Annates de Chimie et de Physique, L843, vol. i.\. p. 21. 

 X Annalen der Physik unit C hemic, vol. lxi. p. 18. 



