Points in Electrolysis. 3 



to produce the chemical work. This must be liberated as 

 heat, aud some of this must be available ; the cell must there- 

 fore not only have a Peltier effect at the higher temperature, 

 but though the chemical work done at that temperature is less, 

 the electromotive force must actually be greater. By taking 

 a cell whose E c varies with the temperature round the usual 

 Carnot cycle, we get 



d& _ Eft cm c 

 old ~ 6 6 ' 



which shows that the temperature-coefficient of the cell is not 

 affected by the variation of chemical work with the tempera- 

 ture. The term — dE c /6 is the remains of the extra work 

 that had to be allowed in compensating for the reduction of 

 the chemical work in the example just taken. Cutting it out 

 we get 



or 



which is HelmhohVs equation again. Writing the equation 

 in full, with separate terms for the poles, we have 



E. + E, = E.. + E F . + ^ + ^. 



The cell may be made up with the plates in separate vessels 

 with a tube of electrolyte to connect them ; and the vessels 

 can be heated to different temperatures. As E„ ? E nc; and 



-T?? depend on the temperature of their vessel, the last 



equation can be split up into two : — 



E, l = E„ e + # 7— or J<j nh = 6—jQ, 

 and 



Fj p = E pc + d-j^ or E ph = d-^; 



and, as the temperature-coefficient of each contact can be 

 found, the Peltier effect at each contact can be obtained 

 separately. 



The hypothetical cell discussed has only one fluid, and is 

 reversible. It might be difficult to find such a cell. If two 

 fluids are used, their junction can be arranged in a third 



B 2 



