We analyze adsorption of a multicomponent mixture at high pressures on the
basis of the potential theory of adsorption. The adsorbate is considered as
a segregated mixture in the external field produced by a solid adsorbent.
We derive an analytical equation for the thickness of a multicomponent film
close to a dew point. This equation (asymptotic adsorption equation, AAE)
is a first order approximation with regard to the distance from a phase env
elope. It can be applied to both normal and retrograde condensation. Differ
ent forms of the AAE make it possible to analyse phenomena occurring close
to a dew point. For testing of the AAE, we compare thicknesses of the adsor
bed film predicted by this equation and obtained by direct calculations. (C
) 1999 Elsevier Science B.V. All rights reserved.