Adsorption of xenon on silica gel. Part 2.—Hysteresis and capillary phase transitions

Abstract

Isotherms for the adsorption of xenon on a microporous silica gel have been obtained at temperatures from 137 to 167 K. Each isotherm exhibits hysteresis, the extent of which decreases with increasing temperature. The capillary critical temperature of the smallest pores is 156 K, but exceeds 170 K for the largest pores. Our results are in accord with current theories of fluid phase transitions in small pores and also explain the absence of hysteresis for some other adsorbates on this silica gel. Based on these theories, a partial pore-size distribution is calculated which is in reasonable agreement with one derived from the Kelvin equation.