Diffusion Coefficients of Hydrogen Isotopes

Abstract

Binary mutual diffusion coefficients have been measured by a radioactive tracer method for the following systems: H₂−T₂ and D₂−T₂ at 195°, 273°, and 353°K; H₂–TH and D₂−TH, at 195° and 273°K. The ratios of the normalized coefficients for H₂−T₂ relative to H₂–TH and for D₂−T₂ relative to D₂−TH show the same trend as that previously reported for He–T₂ relative to He–TH. In the present case both ratios are slightly greater than unity at 195° and slightly less than unity at 273°K. A larger isotope effect, produced by the substitution of D₂ for H₂, is reflected in the normalized coefficients for D₂−T₂ relative to H₂−T₂ and for D₂−TH relative to H₂–TH. The average values of these ratios are about 2% greater than unity at the lowest temperature and about 5% greater than unity at the higher temperatures.