Verification of protonic conduction

in the same cell as described above, when steam is supplied to 

However, when each gas of the above cell is moistened, a stable e.m.f. 

A stable e.m.f. is also observed when air with different humidities is suppUed to the electrode compartments (cell 3). In this case, the electrode with the higher humidity is the negative pole. This is a type of steam concentration cell using a proton conducting electrolyte. The principle of the steam concentration cell is shown in Fig. 8.6 . The difference in water vapour partial pressure between the electrodes can be a driving force for the following electrode reactions. 

Electrode with higher water vapour pressure  

H2O 2H + I/2O2 + 2e-Electrode with lower water vapour pressure  

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