Аннотация:ne conception of a supporting electrolyte has been analyzed in reference to the adsorption impedance. It has been shown that the Frumkin-Melik-Gaikazyan impedance actually has the form of an intermediate asymptote. An examination of a model system suggests that in the general case the use of the assumption of constancy of the chemical potential of the supporting electrolyte under the conditions of impedance measurements can result in errors exceeding 10% unless an excessively large excess of the supporting electrolyte is present.