Diffusion in Simple Liquids

Abstract

The diffusion coefficient of various tracers (${\mathrm{H}}_2$, ${\mathrm{T}}_2$, Ne, Ar, C${\mathrm{H}}_4$) in liquid nitrogen has been determined, using the capillary technique of Anderson and Saddington, in the temperature range $70\le T\le 100$°K at constant pressure of 16 atm. The experimental results can be well described by the expression $D=A \exp (\frac{-B}{T}$). The $B$ values for the various tracers turn out to be equal within the experimental errors. The $A$ values are also independent of the mass of the tracers (absence of isotopic effect) except for a small quantum effect, and proportional to some inverse power of the molecular parameters of the tracer. The features of the present experimental results are compared with the predictions of some theories. Models which emphasize the importance of hard-core collisions or the activated process in the liquid dynamics are found in disagreement with the experimental data.