Self-Consistent Calculation of Activity Coefficients and the Diffusion Layer Capacitance in Asymmetric Electrolytes

It is shown that substituting activities of individual ions for their concentrations in the equation for the ionic strength of solution substantially extends application of the first approximation of the Debye–Hückel theory for electrolytes of different valence. The obtained relationship predicts a changeover from the square root law in the charge region where the average distance between ions lis smaller than the ionic-atmosphere thickness 1/, to the cube root law, at l> 1/. The increasing deviation from experimental data upon going from LaCl₃solutions to La₂(SO₄)₃is attributed to the formation of ionic pairs LaSO₄ ⁺.