APPROXIMATE ANALYTICAL EXPRESSIONS FOR THE PROPERTIES OF AN ELECTRICAL DOUBLE-LAYER WITH ASYMMETRIC ELECTROLYTES

Approximate analytical expressions for the electrostatic potential dis tribution, surface excess of co-ion, and double-layer Helmholtz energy and entropy for flat surfaces are derived. The present analysis exten ds the Gouy-Chapman formula in that asymmetric electrolytes are consid ered. The mathematical treatment of the Poisson-Boltzmann equation is based on an assumed semi-empirical fourth-order polynomial function wi th parameter k, which is a measure of the degree of asymmetry of the e lectrolytes. The results of numerical simulation reveal that the devia tion of the present approximate result from the corresponding exact va lue for the double-layer properties under consideration is ca. 5%.