Properties of capillary-condensed benzene

Abstract

Isotherms for the adsorption of benzene on a microporous silica gel have been determined at integer temperatures from 280 to 294 K. At relative pressures > ca. 0.2 the adsorbed benzene behaves as a capillary liquid. Several thermophysical properties have been determined, including thermal expansivity, isothermal compressibility, heat capacity and the enthalpy and entropy of expansion of the capillary liquid. The volume available to the centres of the molecules, within the pore space, is less than the total pore volume by an amount proportional to the adsorbent surface area and the collision diameter of the adsorbed molecules. This excluded volume, and hence the adsorbent surface area, can be estimated from the isotherms when the isothermal compressibility of the capillary liquid is the same as that of the bulk liquid.