3. Adsorption of a gas by a solid

A very general phenomenon, adsorption is usually defined as the enrichment of molecules, atoms or ions in the vicinity of an interface. For the gas/solid systems we're interested in here, this means an increase in gas concentration in the vicinity of, but outside, the solid surface. The term adsorption indicates that this is a surface phenomenon, and should not be confused with absorption, which would indicate that the fluid has penetrated the solid mass, deforming it.

The solid is then called the adsorbent, and the fluid likely to be retained on the surface of the solid is the adsorbable.

Desorption is the release of gases or vapors retained by adsorption on the surface...