Thermal Diffusion and Diffusion in Hydrogen-Krypton Mixtures

Abstract

Experimental measurements of thermal diffusion and diffusion over a temperature range of about 195° to 580°K are reported for the systems H₂−⁸⁵Kr, D₂−⁸⁵Kr, and T₂−Kr, and are analyzed to obtain information on intermolecular forces. The measurements are discussed from three separate points of view: (1) their internal consistency within the framework of the Chapman‐Enskog kinetic theory, without reference to any specific model of intermolecular forces; (2) the applicability of the 12–6 and exp‐6 models of the intermolecular potential; (3) the accuracy of various combination rules used to estimate forces between pairs of unlike molecules. The measurements are shown to be theoretically consistent, but an unresolved discrepancy in the thermal diffusion of H₂−⁸⁵Kr between our work and that of Ghozlan prevents any firm conclusion being drawn on (2). The discrepancy is not too large to prevent some conclusions on (3), and it is found that the exp‐6 combination rules work somewhat better than the 12–6 rules.