adhesion of the molecules of gases, liquids, or dissolved substances to a solid surface, resulting in relatively high concentration of the molecules at the place of contact; e.g., the plating out of an anti-wear-additive on metal surfaces. Also, any refining process in which a gas or a liquid is contacted with a solid, causing some compounds of the gas or liquid to adhere to the solid; e.g., contacting of lube oils with activated clay to improve color.

Also see absorption, clay filtration, hydroscopic.