302 



Messrs. L. Mond and C. L anger. [June 20, 



abnormal voltaic batteries have lately been explained by Chroustchoff 

 and Sitnikoff,* viz., by the Peltier effect, which would probably not 

 be different for the combinations HPt,S0 4 H 3 and S0 4 H 2 ,PtO ; nor 

 do the causes by which Herrounf explains this deviation appear to 

 us to be applicable to the gas battery. It seems more probable — and 

 what we have stated above respecting the rapid loss of the E.M.F. when 

 taking out larger currents favours this view — that this loss of energy 

 is to some extent due to the heat given out in the condensation of the 

 gases by the platinum black. 



FavreJ found the heat given out by the condensation of 1 gram of 

 H by platinum to vary from 23,000 to 13,000 calories, and concluded 

 that this condensation was analogous to the condensation of carbonic 

 acid by carbon, a purely capillary action. He did not determine the 

 heat of condensation of oxygen. 



Berthelot§ found the heat of condensation of H by platinum to vary 

 per gram of H condensed from 17,000 to 8700 cal., and concluded 

 that the H formed two distinct combinations with the platinum, the 

 first takiug place with a disengagement of 17,000 cal., and then com- 

 bining with another equivalent of H with a disengagement of 8700 cal. 



Berthelot also attempted to determine the heat given out by the 

 absorption of O by platinum, which gas he found to be absorbed only 

 in very small quantities, so that he could not determine the caloric 

 effect with any amount of certainty ; but he calculates it from the 

 figures he obtained at at least 17,000 cal. for 8 grams of O. But these 

 figures would lead to a much larger loss of energy than we find actually 

 to take place. According to Berthelot, the condensation by platinum 

 of 1 gram of H and 8 grams of O produces 25,700 to 34,000 cal. We 

 obtain in the battery out of 34,187 cal. (resulting from the combina- 

 tion of 1 gram of H with 8 grams of O) 23,512 cal. as electricity, thus 

 losing 11,666 cal. We are engaged upon an investigation of this rather 

 difficult subject, with a view to further elucidating its effect upon 

 the gas battery. 



The fact that PdH, which, according to Favre,|| is formed with an 

 evolution of only 4150 cal. per 1 gram of H (a figure which agrees 

 fairly well with that obtained by calculation from the tension of PdH), 

 produces, if opposed to PtO, a smaller E.M.F. than PtH, has also to 

 be considered in studying this question. 



Using Pd black on gold foil opposed to Pt black on Pt foil in our 

 battery, we found the E.M.F. PdH,H 2 S0 4 ,PtO = 0'91 volt, as com- 

 pared to 0-97 volt for PtH,H 2 S0 4 ,PtO. 



* ' Comptes Kendus,' vol. 108, 1889, p. 987. 

 f 1 Phil. Mag.,' vol. 27, 1889, p. 209. 

 X 1 Comptes Kendus,' vol. 77, 1873, p. 649. 

 § ' Annales de Ckhnie,' vol. 30, 1883, p. 519. 

 || * Comptes Kendus,' vol. 68, 1869, p. 1525. 



