The Temperature Dependence of the Mutual Diffusion Coefficient for Four Gaseous Systems

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Abstract
Diffusion coefficients have been measured for the systems He—A, H2—A, H2—nC4H10, and H2–SF6 over the temperature range 13°C to 150°C. The values were determined by a point concentration analysis, while diffusion proceeded at one end of a Loschmidt‐type cell. The analysis was made with a hot‐wire technique and utilized the large difference in thermal conductivity to indicate concentration. The generalized equations for calculating D from an experiment with a Loschmidt‐type cell are given as well as an analysis of the errors involved in calculating D from these data. The data were used to calculate binary force constants for the Lennard‐Jones 6–12 potential. In the system SF6–H2 these are ε/k=320°K and (r0)12=3.25A. The other three systems fit the theory very poorly. The middle temperature value was about 5 percent low relative to the theoretical curve through the high and low data point. The difficulties of calculating Lennard‐Jones force constants from experimental viscosity or diffusion data are discussed.

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