Structure of the electrolyte surface near the critical point

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Abstract
An electrolyte near the critical point for a pure solvent is considered. The short-range interaction between the ions and molecules of the solvent is investigated by the free-energy-formalism method. A set of non-linear differential equations that are modifications of Ginzburg-Landau and Poisson-Boltzmann equations is obtained. In the region adjacent to the boundary of the electrolyte, macroscopic non-uniform distributions of the densities of the solvent and of the ions are investigated. The authors predict that if an external electrostatic potential is applied to the boundary, a first-order phase transition between surface phases with different distribution of the order parameter will appear. The surface capacitance of the electrolyte will be discontinuous at this phase transition point. The values of both the critical external potential and the capacitance jump are estimated. The temperature and concentration dependences of these quantities are obtained.