The derivation of the GAB adsorption equation from the BDDT adsorption theory

The BET‐like adsorption equation, popularly known as the GAB equation, was derived from the BDDT adsorption equation without changes to the bulk liquid properties of multilayer molecules. Without these changes the third parameter K in the GAB equation cannot be said to measure changes in the bulk liquid properties of the multilayer molecules. Instead K measures the range of application of the GAB equation and differentiates multilayer adsorption, when K > 0.5, from singular layer adsorption, when K ≤ 0.5. The GAB equation, derived from and based on the BDDT theory is argued, in this paper, to provide a greater insight into the mechanism of water adsorption than the same equation derived from and based on the BET theory.