LIQUID MASS-TRANSPORT THEORIES APPLIED TO MOLECULAR-DIFFUSION IN BINARY AND TERNARY SUPERCRITICAL FLUID MIXTURES

Diffusion coefficients for benzene and m-cresol in supercritical fluids containing polar modifiers were determined by using the chromatographic band-broadening technique. The addition of low proportions of modifiers had a profound effect on the diffusion coefficient of the solutes. The data were compared to diffusion coefficients predicted from several different theories of mass transport. Significant deviations were found between the experimental and theoretical diffusion coefficients. For the binary supercritical solvents, the Stokes-Einstein expression was most applicable. The dense-gas Enskog hard-sphere theory showed considerable promise for prediction of binary diffusion coefficients in neat supercritical fluids.