436 Prof. E. Edlund on the Thermal Phenomena of the 



periments the galvanic heat of Daniell's pile, and found that 

 it amounts to 23900 thermal units, which agrees closely with 

 M. Favre's result*. 



If the difference which is almost always found between the 

 quantities of the chemical and the galvanic heat is caused by 

 the secondary chemical processes which may take place in the 

 pile, we must assume, in accordance with what has been said 

 above, that these processes bring forth in some piles a produc- 

 tion, in others a consumption of heat. Favre thought at first 

 that the galvanic heat was exactly equal in quantity to the 

 chemical f. Subsequently he shared the view already ex- 

 pressed by others, that the cause of the difference in question 

 in Smee's pile lay in this, that the hydrogen at the negative 

 platinum disk was separated in the active state, or in statu 

 nascenti. As afterwards the hydrogen leaves the platinum 

 disk and escapes upward through the liquid, it passes over 

 into its ordinary condition, in which process heat is liberated, 

 which probably raises the temperature of the liquid, but does 

 not augment the electromotive force J. But the unexpected 

 relation shown by the cadmium-platinum and zinc-platinum 

 piles charged with hydrochloric acid finally convinced him 

 that this also could not be the true explanation §. 



In order, therefore, to explain the difference in the ordi- 

 nary Smee's pile, we must assume that heat is evolved on the 

 transition of the hydrogen from the active to the ordinary 

 state, and that this heat merely raises the temperature of the 

 liquid in the pile, without affecting the electromotive force. 

 In the two piles last mentioned, with hydrochloric acid as the 

 liquid, hydrogen separates in statu nascenti upon the negative 

 platinum disk ; but here, in order to account for the difference 

 in question, we must assume that cold is generated when the 

 hydrogen passes from the above-mentioned state into its ordi- 

 nary condition — an assumption which contradicts the prece- 

 ding one. Favre, on this account, ascribes this fact to other, 

 secondary chemical processes which may occur in the pile ; 

 but he does not specify in what those processes are to consist. 

 The fact that the galvanic heat which is developed in Smee's 

 pile by the current increases with the inserted resistance, 

 Favre has endeavoured to explain by assuming that the ratio 

 between the primary and secondary processes is, as to its mag- 

 nitude, dependent on the intensity of the current. 



* Ann. de Chim. et de Phijs. [4] t. iv. p. 392 (1865). 

 t Ibid. [3] t. xl. (1854). 



% Comptes Rendus, t. lxvii. p. 1012 (1868). Compare with this Bosscha's 

 investigation in Pogg. Ann. vol. ciii. (1858). 

 § Ibid. t. lxviii p. 1300 (1869). 



