A process in which molecules of gas,
of dissolved substances in liquids, or of
liquids adhere (see adhesion) in an extremely
thin layer to surfaces of solid bodies with
which they are in contact. The degree of absorption depends on temperature,
pressure, and the surface area. The forces
binding the absorbate to the absorbent (solid surface) may be physical or
chemical; chemical adsorption is specific, and is used to separate mixtures
(see chromatography). Adsorption
is used in gas masks and to purify and decolorize liquids.
| Adsorption on the surface of activated
Adsorption, which involves a usually weak and reversible binding, is different
than absorption, in which the pores of
a solid are filled. The commonest industrial adsorbents are activated charcoal,
silica gel, and alumina, because they have
extremely large surface areas per unit mass.