IMPEDANCE SPECTRA FOR IDEALLY POLARIZABLE ELECTRODES IN THE HG [H2O+MCKBR+( 1-M)CKF]MODEL SYSTEM/

Impedance spectra for ideally polarizable electrodes in mixed solution s of constant ionic strength were analyzed under the assumption that q uasi 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, t he specific adsorption of Br- ions and the equilibrium differential ca pacitance were calculated with the Grahame-Parsons theory. It was foun d that in systems of this kind, the frequency dispersion of measured c apacitance which arises from ionic mass transport processes is more pr onounced than in binary solutions having the same concentrations of th e surface-active ion. For this reason, important distortions in the is otherms of specific adsorption and erroneous values of the adsorption parameters may arise when mixed electrolytes of constant ionic strengt h are used (in the Hurwitz-Parsons method) without due allowance for t he frequency dispersion of measured electrode capacitance.