STRESSES AND STRAINS IN ADSORBATE–ADSORBENT SYSTEMS: IV. CONTRACTIONS OF ACTIVATED CARBON ON ADSORPTION OF GASES AND VAPORS AT LOW INITIAL PRESSURES

Abstract

When active adsorbents, such as active carbon and porous glass, adsorb relatively large quantities of vapors, normally the adsorption is accompanied by considerable swelling of the adsorbent. It has been observed by McIntosh, Yates, and others that when the quantities adsorbed are small in some cases the adsorption is accompanied by an appreciable shrinkage of the adsorbent. We have studied this phenomenon experimentally and theoretically and some of the results obtained are presented in this paper. It is suggested that the shrinkage is due to "bridging" of sites by adsorbate molecules, the "bridging" being associated with highly anisotropic forces acting on adsorbate molecules and with considerable tensile stresses along some of the bonds of the adsorbed molecules.