Adsorption of xenon on silica gel. Part 1.—Thermophysical properties of the adsorbate

Isotherms for the adsorption of xenon on a microporous silica gel have been measured at temperatures from 137 to 167 K. At higher coverages the adsorbate is a capillary liquid and at lower coverages a capillary gas. The transition region is denoted by a small hysteresis loop in each isotherm. The enthalpy of desorption, heat capacity, isothermal compressibility and thermal expansivity of the adsorbed xenon are calculated. Simple hard-sphere equations of state are shown to provide a satisfactory description of xenon adsorbed as a capillary liquid. These equations allow the calculation of the capillary-liquid surface tension. The surface tension of capillary-liquid xenon is found to be less than that of bulk liquid.