Adsorption of Cl? ions on bismuth from ethanol

The specific adsorption of Cl^? ions at the bismuth-ethanol interface has been studied both in the solutions of mixed electrolytes with constant ionic strength and in the binary LiCl solutions by the method of measuring the potential dependence of differential capacity of bismuth. The charge due to specifically adsorbed anions was calculated from the experimental capacity data. It was found that in the case of specific adsorption of Cl^? ions at the bismuth—ethanol interface the conditions of undercharged as well as recharded surface of electrode could be observed experimentally. The analysis of the results obtained by fitting the charge of specifically adsorbed ions to the modified virial isotherm including the diffuse layer correction term suggests that in the conditions of recharge of the bismuth surface cations enter the inner part of the double layer and a considerable ionic association occurs in the inner layer. A procedure has been proposed for calculating the charge due to cations in the inner layer, for determining the actual value of the outer Helmholtz plane potential and for evaluating the real parameters of the adsorption isotherm. The reliability of the results of calculations was verified by comparing the data obtained by the method of mixed electrolytes both considering and neglecting the ionic association in the inner layer with the data of the method of binary electrolyte.