 The Freundlich adsorption isotherm is mathematically expressed as

It is also written as

or

It is also written as

where

"K" and "n" are constants for a given adsorbate and adsorbent at a particular temperature.At high pressure 1/n = 0, hence extent of adsorption becomes independent of pressure.It is used in cases where the actual identity of the solute is not known, such as adsorption of colored material from sugar, vegetable oil etc.