Structure of electrical double layer between mercury and dimethyl sulfoxide in the presence of chloride ions

Abstract

The adsorption of the chloride ion on a mercury electrode from solutions of lithium chloride in dimethyl sulfoxide (DMSO) has been studied by measuring the interfacial tension of the electrode as a function of potential and concentration at 25°. The adsorption could be described by a virial isotherm in which the free energy of adsorption varied linearly with electrode charge, and in which the second virial coefficient (ion-ion repulsion term) is large. Specific adsorption of chloride ions is stronger from DMSO than from water. The inner layer capacity is analyzed into its components and the relative distances from the surface to the inner and outer Helmholtz planes (xi and x2, respectively) are deduced. (x2 -Xi)/x2 is larger for adsorption of Clĩ ons from DMSO than from water.