A UNIFIED INTERPRETATION OF PHYSICAL ADSORPTION .2. THE EXCHANGEABILITY OF ISOTHERM EQUATIONS

The well-known Fowler-Guggenheim (FG), the Volmer (V) and the deBoer-Hill (BG) isotherm equations have been derived from the differential equation which is the basic relation of the uniform intepretation of adsorption. The FG, V and BH equations take the mobility and interactions of adsorbed molecules explicitly into account. These equations have been applied to heterogeneous surfaces. This application means that the coverage in the differential equation mentioned above is raised to power m similarly to the derivation of the T equation. In this way we have a "family" of isotherm equations describing the physical properties (mobility, interactions etc.) of layers adsorbed on heterogeneous surfaces. It has been proved that the power m in T equation takes the physical properties of adsorbed layers implicitly into account. This is the reason why the T equation can substitute all members of the "equation-family".