Absorption
Ability of a porous solid material to hold, within its body, relatively large quantities of gases or liquids.

Absorption coefficient
The volume of gas in cubic centimeters at 00C and 760 mm pressure which dissolves in 1 cc water.

Absorption line
Refers to a minute range of wavelength or frequency in the electromagnetic spectrum within which radiant energy is absorbed by the medium through which it is passing.

Acid anhydride
An oxide of a non-metallic element of an organic radical which is capable of forming an acid when treated with water, or which can be formed by the abstraction of water from the acid molecule, or which can react with basic oxides to form salts.

Acid electrolyte
A compound, such as Sulphuric acid, that dissociates into ions when dissolved, forming an acidic solution that conducts an electric current.