M. J.-M. Gaugain on Grove's Gas Battery. 467 



platinum wire immersed in water deprived of gas, developes no 

 current. M. Schonbein had observed these latter facts in the 

 year 1843, and concluded therefrom that in Grove's gas-couple 

 the oxygen serves to depolarize the positive wire. I entirely 

 assent to this explanation, and think that the function of oxygen 

 in the gas-battery is that of sulphate of copper in Daniell's 

 battery. The electromotive force of Daniell's element, 



, is represented by 193; 



Acidulated — Sulphate 

 water. of copper- 



ry r~\ 



that of a Volta's couple, — -, by 178, 



Acidulated water. 



when the two couples are at rest ; but if they are set to work 

 by joining them by a conductor offering very small resistance, 

 it is found, after a few minutes, that the electromotive force 

 of the Volta's couple falls below 70, while the Daniell's retains 

 almost all its original force. The explanation of these facts, 

 almost universally admitted, is, that the algebraic sum of the 

 electromotive forces at work is almost the same at starting in 

 each ; but, under the influence of the current, the polarization 

 of the copper developes in Volta's couple a considerable nega- 

 tive force, which diminishes the algebraic sum of the forces of 

 the couple, while in Daniell's element the sulphate of copper 

 prevents the polarization j in the same way, in Grove's element, 

 oxygen serves simply to depolarize the positive wire. 



It must, however, be remarked that the action of oxygen in 

 the gas-couple is far from being as effective as that of sulphate 

 of copper in Daniell's element. When a Daniell's element is 

 set to work by joining its poles by a short and thick copper 

 wire, the electromotive force rapidly diminishes, even when the 

 couple is arranged as Mr. Grove prescribes. I found in one 

 experiment that this force fell in a few minutes from 152 to 

 30. To establish this fact, it is necessary to measure the elec- 

 tromotive force of the couple which has been at work the 

 moment contact is broken : a few minutes' rest restores all its 

 energy. 



I have tried to find in what proportion each electrode contri- 

 buted to the enfeeblement which the couple undergoes under 

 the conditions mentioned. I found that the electromotive force 

 put in play by the wire immersed in hydrogen was lowered 

 simply by 26, and that the antagonistic force developed by the 

 wire plunged in oxygen was 96. 



In fine, it appears to me established that the electromotive 

 force put in play in Grove's element is due exclusively, or almost 

 so, to the affinity exerted between the oxygen of the water and 

 the hydrogen condensed by the electrode of platinum. 



2 112 



