The Freundlich adsorption isotherm is the mathematical representation for the variation of the extent of adsorption (x∕m) with pressure (p) at a given temperature. x∕m=k⋅p1∕n(n>l) where ' x ' is the mass of the gas adsorbed on mass ' m ' of the adsorbent at pressure ' p '. ' k ' and ' n ' are constants that depend on the nature of the adsorbent and the gas at a particular temperature. Experimentally, it was determined that the extent of gas adsorption varies with pressure raised to the power 1∕n until saturation pressure ps is reached. At high pressure, x∕m becomes independent of pressure. Hence, Freundlich equation becomes x∕m=k⋅p0⇒x∕m=k Thus, the Freundlich adsorption isotherm fails at higher pressure.
