Adsorption of Mixed Gases on a Pyrex Glass Surface at Very Low Pressures

Abstract

The physical adsorption of mixed gases, N2–CO, Kr–CO, and Kr–Xe, on a Pyrex glass surface was studied at the pressure range of 10−6–10−8 Torr and at the temperature of 77.4 K. The amounts of adsorption for component gases were obtained from the partial pressure variation after rapid cooling of the adsorbent. The amounts were also measured using the thermal desorption method. The component gases with lower activation energy of desorption seem to be replaced by the gases with higher activation energy of desorption. The replacement of gases physisorbed at 77.4 K and low coverages suggests the existence of heterogeneity on a Pyrex glass surface. The accuracy of residual gas analysis by the physical desorption spectrometer is likely to be limited by the replacement phenomena of physisorbed gases.