Abstract: In this paper, we depict the interaction between gas molecules by the Keesom, potential, and study adsorption by the application of statistical mechanics, from which we deduce the adsorption isotherm equation. We find that the theoreti cal isotherm agrees with the experimental one, and that the equation of BET is its limit form, when the interaction between gas molecules is negligible.

Key words: isotherm adsorption, real gas