Composition Dependence of Physical Constants of Binary Solvent Mixtures

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)


The relative permittivity is a measure of the solvent’s ability to insulate opposite charges from each other and has a very significant effect on the strength of the interactions between ions. We have investigated the relative permittivities, εr sln, and excess relative permittivities, εr slnE, of aqueous and nonaqueous mixtures as a function of the composition at 25 ºC. Experimental data were fitted with the Redlich-Kister equation. We found the values of three coefficients (a0, a1, and a2) in the Redlich-Kister equation. We explained the deviation from the ideal solution in terms of the magnitude of the coefficient a0. a0 is a dominant factor governing the Redlich-Kister equation. The decrease in a0 made a plot of εr sln vs. x2 close to a straight line, which might correspond to the ideal solution. The cohesive forces between dissimilar components might result in the increased effective dipole moment and, consequently, in the small negative value of a0. The amount of the cooperative orientation polarization of a water (W)−2,2,2-trifluoroethanol (TFE) binary mixture was larger than that found for a W−ethanol (EtOH) binary mixture. The effective dipole moment of an ethylene carbonate (EC)dimethyl carbonate (DMC) binary mixture was increased as compared to those found for EC−ethyl methyl carbonate (EMC) and EC−diethyl carbonate (DEC) binary mixtures.