Diffusion of xenon in liquid alkanes: Temperature dependence measurements with a new method. Stokes–Einstein and hard sphere theories

Abstract

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-C8H18)=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.

Use of Taylor dispersion for the measurement of probe diffusion in polymer solutions

“…These theories introduce a friction factor f into the denominator of the Stokes-Einstein equation, thus reducing the Stokes drag to account for the failure of continuum hydrodynamics at molecular dimensions. Additionally, roughhardsphere theories have been successful in modeling the tracer diffusion of spherically-shaped solutes (Chen et al, 1981(Chen et al, , 1983Pollack et al, 1990).…”

Diffusion of aromatic compounds in nonaqueous solvents: A study of solute, solvent, and temperature dependences

“…For example, different values of 0.563, 3 0.598, 71 0.708, 64 and 0.941 68 have been reported for Xe; the values 49 of 0.943 (in n-alkanes) and 0.982 (in cyclohexane) for rubrene are very much different from that of 0.722 for the same solute. 75 Also, values of 0.717, 0.755, and 1.01 for CCl 4 as well as 0.472, 0.538, and 0.91 for CH 4 have been published.…”

“…Except for macromolecules, however, numerous experimental studies 3,[57][58][59][60][61][62][63][64][65][66] have shown that tracer diffusivity is inversely proportional to a fractional power of the viscosity of the solvent instead. This fractional power dependence of viscosity on diffusion is often referred to in the literature as the fractional Stokes-Einstein (FSE) relation, (D 12 /T) ∝ η −t , where t is known to be normally less than unity and generally around 2/3.…”

Solubility of noble gases and nitrogen in n-alkanes at 298.15 K and atmospheric pressure. Correlation analysis

“…[37][38][39][40] In order to test the validity of Eq. (22) in a wide inter val of gas pressures, the results of calculation of nitrogen solubility in n heptane at 298 K and the total pressure in the gaseous phase from 10.22 MPa to 69.02 MPa are com pared with experimental data ( 42 The molar volumes of n heptane and molar concentrations of nitrogen in the gaseous phase at the corresponding pressures were calculated from the tabulated 22 values of specific volumes of these substances in wide intervals of temperatures and pressures.…”