Competition of liquid components for silica gel surface was tested for binary liquid mixtures: methanol + benzene and 2-propanol + n-heptane. The adsorption isotherms were measured using silica gels for column chromatography Si-40 and Si-100 from Merck. On the basis of specific surface excess isotherms the surface layer capacities were calculated. Taking into account the properties of the bulk solutions, the influence of geometrical structure of silicas on the composition of the surface phase is discussed.