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Diffusion of gases Cox, Kenneth Edward

Abstract

The effective diffusion coefficient of the binary gas pair, hydrogen and nitrogen, has been measured for diffusion through several types of porous solids. Electrical conductivities through the pore spaces of the same solids were also measured with a view towards testing the analogy between ordinary diffusion and electrical conductivity. The results obtained show some discrepancies (up to 25%) from exact equivalence, especially in porous solids with a mean hydraulic diameter of less than 1 micron. The diffusion apparatus was also used to determine the temperature dependence of the ordinary diffusion coefficient in the range 20 - 300°C. The results obtained show close agreement with the Hirschfelder, Bird and Spotz theoretical equation for non-polar gas pairs. The data were also compared with other values reported for this system and good agreement was found. It is therefore concluded that the flow apparatus used is satisfactory for the investigation of the temperature dependence of the binary diffusion coefficient. Calibration of the apparatus at one temperature will yield satisfactory absolute values for binary diffusion coefficients at other temperatures.

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