Diffusion Coefficients of the Systems He—T2 and He–TH

Binary mutual diffusion coefficients have been measured for the systems He—T2 and He–TH by a radioactive tracer method at four temperatures in the range 195° to 374°K. The results, reduced to one atmosphere and normalized to the system He–H2, can be expressed within an average deviation of slightly less than 1% by the empirical relations He−T2: log10D=1.6599log10T−3.9230,He–TH: log10D=1.6960log10T−4.0140. The ratio of the normalized coefficients for He—T2 and He–TH show a small departure from unity, starting at 1.02 at the lowest temperature and decreasing smoothly to 0.996 at the highest. On the assumption that deviations from classical mechanics, contributions from internal degrees of freedom, and the effects of asymmetric force fields are the same, or negligibly small, for both systems, different sets of Lennard-Jones (12–6) potential parameters have been obtained which correlate the experimental results as well as the empirical equations.