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The inverse gas chromatographic method of reversed-flow gas chromatography is extended to the measurement of the probability density function f( ) for the adsorption energies on heterogeneous surfaces, as a function of the experimental time. The values of f( ) are not found from the solution of an integral equation, but by their direct calculation from experimental data in a very simple way. The method is applied to the adsorption of (CH 3 ) 2 S on CaCO 3 and CaCO 3 + C, in the presence and in the absence of NO 2 , at two temperatures around 303 and 323 K. The kinetic physicochemical parameters for the adsorption/desorption phenomena are also calculated for the above systems. The normalization of the f( ) found, with respect to time, is easily done.

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If the internal wall of the diffusion column used in the reversed-flow gas chromatography (RFGC) technique is covered with an adsorbent material or a supported liquid, then isotherm determination becomes much simpler.Diffusion and resistance to mass transfer are not neglected, the sorption effect is non-existent and the pressure gradients are negligible along the bed. The method leads directly to independent experimental isotherms over a wide range of concentrations, without specifying a priori an isotherm equation. The isotherm can also be determined in the presence of a surface reaction of the adsorbate. The necessary theoretical analysis has been developed, and the equations derived were applied to benzene and cyclohexane adsorbed on graphitized carbon black, to ethene, ethyne, propene and sulfur dioxide on marble powder, and to propene on silica gel.

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