Analytical Sciences

Estimation of Molecular Diffusivity in Liquid Phase Systems on the Basis of the Absolute Rate Theory

Kanji MIYABE* and Ryo ISOGAI**

*Department of Chemistry, Faculty of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
**Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

This study was concerned about an estimation of molecular diffusivity (D_m) in liquid phase systems. An equation based on the absolute rate theory of diffusion was derived by considering the aggregation of not only solvent molecules, but also solute molecules. It was also studied how the replacement of the molar volume of a solvent with its molecular weight influences the accuracy in estimating D_m. The values of D_m estimated by the equation were compared with those experimentally measured. The mean square deviation for the estimation of D_m was calculated as being about 14% for 217 D_m data measured in aqueous solutions of methanol and acetonitrile, which is comparable to that obtained by the Wilke–Chang equation. However, D_m of some solutes in carbon tetrachloride was more accurately estimated by this equation than by the Wilke–Chang equation. It is expected that the equation proposed in this study is effective for estimating D_m in liquid phase systems.

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