Systematic Study of Mass Transfer in a Loschmidt Cell for Binary Gas Mixtures

The present paper reports on efforts to explain discrepancies which were found in concentration-dependent binary diffusion coefficient data determined with a Loschmidt cell combined with holographic interferometry using pure gases prior to the diffusion process. While the binary diffusion coefficient data which are determined in the upper half-cell decrease with the mole fraction of the heavier component, those determined in the lower half-cell increase. The reason for such discrepancies, which can also be found in other literature data obtained with interferometric gas analysis methods, is not clear. Therefore, systematic experimental and theoretical investigations on the Loschmidt experiment and the applied evaluation procedure were performed. Furthermore, the influence of different driving forces on the particle flux was examined. Although the reason for the discrepancies between the measurement data determined in each half-cell could not been clarified, various reasons that have been debated in the literature could be excluded. Moreover, experiments using a gas mixture in one of the half-cells suggested that the evaluation procedure is most likely to be the reason for the observed discrepancies.