THE GROWTH OF CRYSTALLINE LAYERS ON FOREIGN SURFACES

Abstract

When the bulk phase of an adsorbent is solid, it has been shown that adsorption often proceeds only to a finite limit as the pressure reaches saturation. A theory is developed for this finite limit, in terms of the excess forces at the surface and the incompatibility of the crystal lattices of the adsorbent and adsorbate. It is applied to the stepwise adsorption of krypton on graphitized carbon black. An extrapolation formula applicable to smooth isotherms at high coverages is developed and shown to be analogous to the Harkins–Jura equation. It is applied to argon adsorbed on carbon black, on xenon preadsorbed on carbon black, on silver iodide, and on anatase. The energies obtained are compared with a theoretical estimate based on the Kirkwood–Müller equation. A theory for calculating isotherms on preadsorbed layers is developed and compared with the data for argon on xenon.