Constant finite current potentiometry

Constant current techniques often prove to be useful for redox titrations involving couples of which at least one behaves in an irreversible manner, i.e., equilibrium is not established instantaneously at the electrode surface. As a result of this the potential jump in the region of the end-point is too small to be useful. The potentials of electrodes which behave irreversibly show considerable variation in value when they pass a current. The constant current required for such titrations has to be determined in a separate determination prior to the tittation itself. In Fig. 6.8 are shown current-voltage curves for two redox couples one of which behaves reversibly, the other irreversibly. It is 

Current-potential curves for titrant and titrand. Constant current Z2 gives better separation of potentials than /i. 

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