Gas-Solid Interaction

In physical adsorption the interaction of adsorbed molecules with solids is mainly due to induction forces acting between the surface electric field and permanent or induced dipoles in the adsorbate, and to L O N D O N dispersion forces, these prevailing, for example, in adsorption of apolar molecules In the last years it has been shown that the dielectric behaviour of the heterogeneous adsorbentadsorbate systems is deeply affected by the predominant type of interaction; it became also apparent that, while dielectric data relating to polar adsorbed phases can generally be treated in terms of hindered or restricted rotation of dipoles close to the adsorbing surface, greater difficulties are involved when dealing with apolar adsorbed phases 2. In the latter case, e. g. some characteristic discontinuities of dielectric isotherms have not been clearly and uniquely explained. In this work the dielectric behaviour of cyclohexane, carbon tetrachloride and benzene, respectively, adsorbed on y-alumina was experimentally investigated at 25 °C. The adsorption isotherms of these systems had been reported in a previous paper 3.