P,T-DEPENDENCE OF SELF-DIFFUSION IN MIXTURES OF HEXANE ETHANOL AND HEXANE/DIMETHYLETHER/

Self-diffusion in ethanol/hexane and dimethylether/hexane mixtures of various compositions has been measured at 215-350 K and up to 200 MPa. Qualitative analysis of the results indicates that, as expected, hydr ogen bonding retards the self-diffusion of ethanol in the mixture, esp ecially at the low temperatures. Dimethylether shows a slight effect o f dipole-dipole interactions on the self-diffusion, as seen by a highe r Delta E(not equal) value than for the alkane. However there is no si gnificant difference in the pressure dependence for both mixtures. Thi s is shown by considering the ratio of the two diffusion coefficients, which suggests that, contrary to what is observed for pure alcohols, pressure has little effect upon the hydrogen bonding of ethanol in the mixture. In additon, there is surprisingly little concentration depen dence on the ratios for either mixture.