An experimental investigation of the interdiffusion behavior of gases in a low permeability graphite was performed by sweeping the opposite faces of a graphite septum with helium and argon at uniform pressure and measuring the diffusive flux of both gases. The objectives were to ascertain the diffusion mechanism, to verify the applicable equations and associated theories, and to determine the parameters required to use these equations. At all experimental pressures, contributions from both normal and Knudsen diffusion effects were detectable via the pressure dependence of the diffusion fluxes. It was found that a previously proposed dusty‐gas model formed an excellent basis for correlating the results. The dusty‐gas model yielded flux equations which predicted the diffusion behavior over a wide range of pressures for particular gas concentrations at the boundaries. Only two experimentally determined parameters (characteristic of the gases and graphite) were required. These were an effective normal‐diffusion coefficient obtained by interdiffusion experiments and a Knudsen coefficient obtained using single‐gas (permeability) experiments.

Interdiffusion of Gases in a Low Permeability Graphite at Uniform Pressure. Evans, R.B., Watson, G.M., Truitt, J.: Journal of Applied Physics, 1962, 33, 2682