Search for isotope effects in the diffusion of methane in krypton at various densities

Abstract

Experimental measurements of the diffusion coefficient of C${\mathrm{H}}_{4}$ in Kr at $T=220\ifmmode^\circ\else\textdegree\fi{}$K in the density range $0l\ensuremath{\rho}\ensuremath{\le}2{\ensuremath{\rho}}_{c}$ are reported. The experimental data are compared with self-diffusion for Kr and C${\mathrm{H}}_{4}$ and with the data for diffusion of Kr in C${\mathrm{H}}_{4}$ at about the same reduced temperature. The behavior of the mass effect on the diffusion process is shown clearly for the first time. At $\ensuremath{\rho}\ensuremath{\le}{\ensuremath{\rho}}_{c}$ the deviation from Enskog's predictions is already marked, whereas at $\ensuremath{\rho}\ensuremath{\ge}1.5{\ensuremath{\rho}}_{c}$ the mass effect is of the same kind as for hard spheres.