Isotopic thermal diffusion factors of Ne, Ar, Kr, and Xe from column measurements

Abstract

The isotopic thermal diffusion factors of Ne, Ar, Kr, and Xe were determined as a function of temperature from separation measurements carried out at low temperature differences in a precisely constructed thermal diffusion column. The apparatus and techniques were similar to those used in previous work with Ne–Xe mixtures. The results, which were obtained for average temperatures in the range from 323 to 438°K, were in good agreement with the data of other investigators for Ne and Ar. Partial agreement was obtained for Kr, but for Xe the column results are substantially lower than published values derived from swing separator experiments. The Dymond‐Alder and the Bobetic‐Barker intermolecular potential energy models for argon were applied in reduced form to neon, krypton, and xenon. It was found that the thermal diffusion factors calculated on the basis of either potential were in good agreement with the experimental results. The data appear to follow a unique corresponding‐state relationship between the reduced thermal diffusion factor and the reduced temperature. This relationship, in turn, is closely predicted from calculations based on the Dymond‐Alder potential.