The surface excess and the heat of immersion in the adsorption from solutions were calorimetrically investigated for the benzene-ethanol mixtures on activated carbon powder. The surface excess and the heat of immersion, derived from the Gibbs adsorption equation and the adsorption capacity ration representing the surface areas occupied, were calculated incorporating the UNIQUAC and its two-dimensional image for the adsorbed phase, and compared with Schay's surface excess data and the heats of immersion measured with the solution calorimeter. Approximationg the localized adsorption interacting only with bulk phase and the excluded volume effect, the heats of immersion were satisfactorily calculated from the adsorption parameters optimized with the excess data.