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.

Thermodynamic studies have been made on various fractions of polyoxypropylene glycols of molecular weights from 150 to 3350 in methanol. Vapor pressures of the solvent and the relative lowering of vapor pressure of the solvent by the polymer have been determined in a special differential manometer over the temperature range −30°C. to 28°C. Heats of mixing for the systems have been determined in an isothermal phase‐change calorimeter empolying diphenyl ether as the dilatometric fluid. The relative partial molar free energies are derived for the solvent and solute.

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The effects of some changes of ambients on the dimensions of an activated carbon rod are presented. The emphasis is on the regions where anomalous contractions occur. It is suggested that dimensional changes can be used to estimate adsorption potentials of liquids of very low vapor pressures where adsorption isotherms cannot be measured by the usual methods.

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