The adsorption of gases on plane surfaces of glass, mica and platinum

Abstract

According to the theory previously developed, gaseous molecules impinging on a solid or liquid surface do not in general rebound elastically from the surface, but condense on it, and are held or adsorbed on the surface by forces similar to those holding the atoms or group molecules of solid bodies. If these forces are weak the “life” of the adsorbed molecules on the surface is short, so that the number of molecules adsorbed at any time is relatively small. On the other hand, when the forces are strong the rate of evaporation of the molecules may be so slow that the surface becomes practically completely covered by a monomolecular layer of adsorbed molecules. In the present paper this theory is extended and is developed along quantitative lines. The theory requires that in typical cases of true adsorption the adsorbed film should not exceed one molecule in thickness. This is contrary to the usual viewpoint. The discrepancy is accounted for by the fact that nearly all investigators have worked with porous bodies in which the adsorbing surface is indeterminate or have used nearly saturated vapors so that condensation of liquid occurred in capillary spaces. Others have mistaken solution or absorption for true adsorption. © 1918, American Chemical Society. All rights reserved.