The Structure of the Mercury-Solution. Electrical Double Layer in the Presence of Adsorbed Oxyanions

The unusual adsorption characteristics of oxyanions are described with special reference to the adsorption of nitrate ions from solutions. The adsorption energy is shown to be linearly dependent on the charge in contrast to the behavior previously found for mixed solutions of (and also ) with at constant ionic strength where the dependence is approximately quadratic. The reasons for the differences are discussed in terms of the structure of the inner region of the double layer. The capacity of the inner region of the double layer is analyzed and related to the form of the adsorption isotherm and the Esin and Markov coefficient. Arguments are advanced in favor of using the mean ionic activity rather than the salt activity in the isotherm.