Adsorption equilibria of binary benzene + cyclohexane liquid mixtures on silica gel, and heats of immersion of silica gel in pure liquids and in binary liquid mixtures of the two components were determined at 25°C. Liquid activity coefficients of benzene and cyclohexane were evaluated at 25°C and employed for calculating activity coefficients of the components in the adsorbed phase. The thermodynamic treatment of adsorption from solution proposed by Everett was adopted in this investigation. The heats of mixing in the surface phase appear to be much greater than that in the bulk liquid.