Gaseous Self-Diffusion in a Temperature Gradient

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Abstract
Deviations from the quasistationary state in diffusion have been studied experimentally by measuring self‐diffusion of gases, both isothermally and in a temperature gradient. Thermal diffusion is negligible in the cases considered. The nonisothermal measurements also serve as a check on the fundamental diffusion equation, which has not previously been tested except under isothermal conditions. The technique is convenient for obtaining diffusion coefficients over wide temperature ranges without the necessity of having all parts of the apparatus at an extreme temperature. Self‐diffusion coefficients for CO2 and Kr have been obtained over the range of about 230° to 470°K by this method. Although the corrections for nonattainment of the quasistationary state are not small in the apparatuses used, the values for CO2 are in good agreement with those from other sources and the values for Kr are in fair agreement with others, provided the temperature gradients were not too large.