THE OPEN-CIRCUIT DECAY BEHAVIOUR CHLORINE-EVOLVING ELECTRODES

Abstract-The open-circuit decay behaviour of a previously chlorine-evolving electrode, has been studied. It has been stated that the rate of the chlorine evolution on open circuit is determined by the parameters of the rate equation of the chlorine evolution and the diffusion of atomic chlorine out of the electrode. Both possible mechanisms viz. the Volmer-Tafel and the Volmer-Heyrovsky mechanism have been considered. Numerically calculated relations have been given between the overpotential on open circuit, the rate of the chlorine evolution on open circuit and time. Moreover, theoretical relations are calculated between the overpotential during the anodic polarisation and the overpotential on open circuit at the moment of, and 1 s after, switching off the polarising current, and the total quantity of chlorine evolved on open circuit, divided by the rate of the exchange reaction of the chlorine evolution. Earlier experimental results on the behaviour on open circuit, of the chlorinwhloride electrode in chloride melts and in aqueous acidic sodium chloride solutions have been compared with the calculated theoretical relations. It has been found that some earlier conclusions on the behaviour of the chlorine-chbride electrode need correction. dx, t.1 NOMENCLATURE concentration of atomic chlorine present in an electrode at a distance x at time t, after switching off the polarisation current c(x,O) at x B 0 or C(W, r,) at t,> 0 diffusion coefficient of atomic chlorine electrode potential us see Faraday constant the slope of the linear part of the qJlog t, curve real cd real exchange cd constant factor; p = O/c r f. +dt, J oh gas constant temperature time after switching off the polarisation current distance in the electrode measured from the boundary electrode surface-electrolyte Greek symbol