A numerical method, based on the integral equation of the adsorption on energy heterogeneous surfaces, is suggested for the evaluation of overall isotherm. It is shown that for the distribution of adsorption energies given by Eq. (1.11) and different models of the adsorption behaviour, the overall isotherms obey approximately the Dubinin-Radushkevich equation. The strong energy heterogeneity smears effectively the differences between the localized and mobile adsorption and leads to the same character of the overall isotherm with only a slightly changed heterogeneity parameter.
