Atomic test of the Stokes-Einstein law. II. Diffusion of Xe through liquid hydrocarbons

The diffusion coefficient D has been measured for ${}_{}{}^{133}{}_{}{}^{}\mathrm{Xe}$ atoms diffusing through 12 liquid n-alkanes, n-pentane through n-hexadecane, at 20.0 °C. The dependence of D (${\mathrm{cm}}^2$/sec) on the viscosity η (P) was found to be D=(1.26±0.06)×${10}^{\mathrm{-}6}$ ${\eta }^{\mathrm{-}0}$ ${}_{}{}^{686\pm 0.011}{}_{}{}^{}$ where ${\eta }_{20.0}$ ${}_{°\mathrm{C}}{}^{}{}_{}{}^{}$ varies monotonically in these solvents from 0.235 cP (for n-${\mathrm{C}}_5$ ${\mathrm{H}}_{12}$) to 3.48 cP (for n-${\mathrm{C}}_{16}$ ${\mathrm{H}}_{34}$). The observation that D is proportional to η to a negative power of magnitude near (2/3) is in agreement with other work on several different solute-solvent systems. Some ramifications of this dependence are suggested.