In physical chemistry, the Polanyi potential theory, also called Polanyi's potential theory of adsorption or Eucken–Polanyi potential theory, is a model of adsorption proposed independently by Michael Polanyi and Arnold Eucken. Under this model, adsorption can be measured through the equilibrium between the chemical potential of a gas near the surface and the chemical potential of the gas from a large distance away.
In this model, the attraction largely due to Van der Waals forces of the gas to the surface is determined by the position of the gas particle from the surface, and that the gas behaves as an ideal gas until condensation where the gas exceeds its equilibrium vapor pressure. While the adsorption theory of William Henry is more applicable in low pressure and the adsorption isotherm equation from Brunauer–Emmett–Teller (BET) theory is more useful at from 0.05 to 0.35 P/P0, the Polanyi potential theory has much more application at higher P/P0 (≈ 0.1–0.8).