DIFFUSION OF XENON IN LIQUID ALKANES - TEMPERATURE-DEPENDENCE MEASUREMENTS WITH A NEW METHOD - STOKES-EINSTEIN AND HARD-SPHERE THEORIES

Measurements are reported of the diffusion constant D(T) for xenon gas, in the form of the radioisotope 133Xe, through liquid n-octane, n-decane, and n-tetradecane, in the range 10-40°C. The values range from D (10.0°C, Xe→n-C14H30) = 1.32×10 -5 cm2/s to D (40.0°C, Xe→n-C8H 18) = 6.02×10-5 cm2/s. A new experimental method is used in which D is obtained by monitoring the decrease in concentration as gas diffuses into the liquid in an effectively one-dimensional geometry. As expected, the results do not agree with the Stokes-Einstein law. They do follow the usual correlation Dηp = AT, with p = 0.708 and A = 9.80×10-8, where η is the liquid viscosity in centipoises and T is in K. Application to these results of the rough-hard-sphere theory of diffusion is discussed. A quantitative analysis cannot be made until molecular dynamics results for smooth-hard-sphere diffusion are available. © 1990 American Institute of Physics.