The adsorption behaviour of benzene (A), toluene (A), p-xylene (A), and o-xylene (A) in their binary mixtures with o-chlorotoluene (B) on silica gel has been studied at 308.15 K. The data have been analysed in terms of a model that assumes that partition and surface reactions play an important role in the adsorption process, and have revealed that while both partition and surface reactions dictate the adsorption (U-shaped isotherms) of o-chlorotoluene (OCTE) (B) from benzene (A) or toluene (A) + OCTE (B) mixtures, the adsorption of A and B entities of p-xylene (A) or o-xylene (A) + OCTE (B) mixtures (S-shaped isotherms) onto the silica gel surface is governed primarily by the distribution process and secondarily by the surface reaction.