Аннотация:Impedance spectra for ideally polarizable electrodes in mixed solutions of constant ionic strength were analyzed under the assumption that quasi equilibrium between the electric double layer and the solution is preserved during the impedance measurements. The system: Hg/[H2O + mc KBr + (1 - m)c KF], was used as the model for this analysis; in it, the specific adsorption of Br- ions and the equilibrium differential capacitance were calculated with the Grahame-Parsons theory. It was found that in systems of this kind, the frequency dispersion of measured capacitance which arises from ionic mass transport processes is more pronounced than in binary solutions having the same concentrations of the surface-active ion. For this reason, important distortions in the isotherms of specific adsorption and erroneous values of the adsorption parameters may arise when mixed electrolytes of constant ionic strength are used (in the Hurwitz-Parsons method) without due allowance for the frequency dispersion of measured electrode capacitance.