Physical adsorption of vapors — three personae

Abstract

Some of the history of the physical chemistry of the adsorption of vapors is reviewed. The subject divides itself into three parts, each with its characteristic approach and important contributors: the multilayer region, the monolayer region and the submonolayer region. Special reference is made to the last topic as one in which the writer and Sydney Ross have overlapped in the matter of the determination of site energy distributions. Ross's contributions are noted. An important and difficult question is whether the various energy adsorption sites are distributed more or less randomly or as nearly uniform patches. An approach to the answer may be through the use of adsorbates of varying size. The role of geometric irregularity is discussed briefly, in terms of self-similar surfaces having a fractal dimension. Finally, an additional complication occurs in the case of adsorption from solution involving large raft-like molecules, where the adsorption may be irreversible, generating a paradox.