1889.] 



A new Form of Gas Battery. 



303 



In the hope of throwing some light upon the question of the 

 disappearance of energy in the gas battery, we have determined the 

 E.M.F. of the following combinations by means of a block of plaster 

 of Paris impregnated with sulphuric acid, one end of which was 

 covered with platinum foil and platinum black and arranged so that 

 it could be exposed to H or 0, while the other end was plunged into 

 a beaker which contained the liquid electrolyte and the electrode 

 which we wished to examine. 



Found. 



PtH,HoS0 4 .PtO = 0-97 volt 

 Zn,H 3 S0 4 ,PtO = 177 voltj 



Cd,H 2 S0 4 ,PtO = 1-425 volt* 



Cu,H 2 S0 4 ,PtO = 0-70 volt| 



PtH,H 2 S0 4 ,CuS0 4 ,Cu = 0-31 volt 

 PtH,H 2 S0 4 HN0 3 ,C = 1*19 volt 

 PtO,H 2 S0 4 ,HN0 3 ,C = 0-22 volt. 



Theory. Difference. 

 = 22,512 cal* instead of 34,178 cal.f- 11,666. 

 = 41,078 cal. instead of 53,043 cal. - 11,965. 

 = 33,171 cal. instead of 44,928 cal. -11,767. 

 = 16,245 cal. instead of 27,978 cal. -11,733. 

 = 7,194 cal. instead of 6,200 cal. +994. 

 = 27,617 cal. instead of 29,175 cal. -1,553. 



These figures show that the loss of energy is very nearly the same 

 per equivalent of O consumed, when PtO is used as the negative 

 electrode, whether PtH, zinc, cadmium, or copper is used as positive 

 electrode, and also that PtH with copper in copper sulphate, or 

 carbon in nitric acid, as negative electrodes, gives nearly the theo- 

 retical E.M.F. It would thus seem as if the loss of energy in the 

 gas battery occurred on the PtO electrode ; but the question is 

 undoubtedly a complicated one, and requires further study before an 

 explanation of it can be attempted. 



This battery differs from all other gas batteries in showing all the 

 characteristics of polarisation after it has been at work for some 

 length of time. It loses within an hour from 4 to 10 per cent, of its 

 E.M.F. As the chemical processes taking place at the electrodes 

 could not explain this, we had to look out for its cause in another 

 direction, and found it to be the transport of the sulphuric acid from 

 the O to the H electrode, resulting in the acid becoming gradually 

 more concentrated on the positive side and weaker on the other, 

 which we have established by analysing the gypsum scraped off below 

 the platinum leaf at both sides. Probably this difference of concen- 

 tration of the acid sets upa counter- current. In order to counteract 

 this disturbing influence and to keep the current constant, we inter- 

 change the gases in the battery from time to time, say once an hour, 

 so that the current goes in an opposite way through the porous 

 diaphragm, and transports the sulphuric acid back. This necessitates, 



* 1 Daniell = 25,065 cal. = 1 -08 volts. 



t Calculated from Thornsen's data (' Thermochemische Untersuchungen ') divided 

 by 2, so as to refer to O = 8. 



+ Wright and Thompson found 1'75, 1*5, and 0"78 respectively (' Eoy. Soc. Proc.,' 

 vol. 44, 1888, p. 182). 



VOL. XLVI. z 



