ACCURACY OF EMPIRICAL CORRELATIONS FOR ESTIMATING DIFFUSION-COEFFICIENTS IN AQUEOUS-ORGANIC MIXTURES

Diffusion coefficients for a homologous series of alkylbenzenes and al kylphenones have been measured by the Aris-Taylor open tube method fro m 30 to 60 degrees C over a wide range in methanol/water and acetonitr ile/water compositions (10-100% by volume of organic). The measurement s were compared to estimates derived from five of the most common empi rical correlations, The errors for methanolic mixtures by the Wilke-Ch ang, Scheibel, and Lusis-Ratcliff correlations are usually less than 2 0%, The Scheibel, Wilke-Chang, and Hayduk-Laudie correlations work bet ter than others for acetonitrile/water mixtures. Overall, the Scheibel correlation shows the smallest errors, and we recommend its use to th at of the more widely used Wilke-Chang method for the systems studied here. We have also developed fitting equations for estimating viscosit y so that the diffusion coefficients can be easily estimated.