The potential, φ{symbol}0, of the diffuse electric layer was determined by the equilibrium liquid film method (1). The method is based on calculating the φ{symbol}0-potential by means of the DLVO theory of the electrostatic disjoining pressure at known concentration, Cel of the solution forming the microscopic liquid film and at known thickness, hr of the film. The thickness of the film was measured by the microinterferometric method (7, 8). The calculation of the potential was carrried out by means of the more general eqs. [2] and [3], valid for a wide range of Cel and φ{symbol}0. The dependence of the potential of the diffuse electric layer on the concentration of surface activ agent (surfactant) stabilizing the liquid film was found. It was established that ionogenic SAS show a higher potential than the non-ionogenic ones. The potential of SAS-free solutions was determined - ca. 30 mV. The dependence of the potential of the diffuse electric layer on concentration and kind of electrolyte was also found. A strong effect of pH on φ{symbol}0-potential was observed and the isoelectric points were found. An analysis is made of the φ{symbol}0-potential values obtained by the method of equilibrium liquid film with respect to their similarity to those on the boundary of the bulk liquid. © 1969 Dr. Dietrich Steinkopff Verlag.
