Characterization of Gases by the Reversed-Flow GC Technique

Abstract

A new method is presented for characterizing gases in terms of their mutual diffusion coefficient, molecular diameter, critical volume, and relative molar response to the thermal conductivity detector. This is the reversed-flow gas chromatography method, based on perturbations imposed on the carrier gas flow. In previous work the method was applied for the determination of mutual diffusion coefficients in gases. It is now shown that, in the same experiment, one can determine, together with the diffusion coefficient of a gas A into another gas B, its relative molar response to the thermal conductivity detector. Because this depends on the molecular diameter σ, and the latter is immediately related to the critical volume Vc, the σ and Vc values of a substance may be estimated. The method has been applied to the gases ethane, ethene, propane, propene, 1-butene, 2-methylpropene, cis-2-butene, trans-2- butene, oxygen, nitrogen, air, argon, and carbon dioxide. The values determined for diffusion coefficient, relative molar response, molecular diameter, and critical volume are in good agreement with those calculated theoretically or found in the literature.