Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Systematic measurements of density, viscosity, and electrical conductivity on the ternary system water + ethanol + lithium chloride over entire ranges of solvent composition and LiCl solubility from (-5 to +50) !aC have been carried out. The temperature-independent aquamolality scale, m (LiCl moles per 55.5 moles of solvent) has been used to justify data comparison not only at different temperatures but also for the solutions in various solvent mixtures. Density isotherms (fitted to second-order polynomials in m) provided a composition-dependent density index, g(x1), which can conveniently be used to determine the density at any desired LiCl concentration, mixture composition, and temperature. Excess molar volumes (VE) of the solvent mixtures have been calculated over the whole temperature range, and minima of all the VE isotherms at the same water mole fraction, x1 ) 0.6, suggest that no significant structural rearrangement takes place in the solvent mixtures upon temperature variation. From the density data, the !deg temperature average coefficient of thermal expansion!+- ( ) is also determined for all the samples. Fitting the viscosity (|C) isotherms to an extended Jones-Dole-type cubic equation in m provided coefficients related to various interactions taking place in the solutions. The temperature dependence of the entire |C data can well be explained by the Arrheniustype equation involving single flow activation energies (Ea) that always increased with LiCl concentration for a given solvent but exhibited a sharper rise for the ethanol-rich mixtures; Ea values tend to pass through maxima at x1 !O 0.6. In all the cases, electrical conductivity (|E) plotted against m exhibits maxima which shift from 4.5m to !less thanless than6m in the water-rich mixtures, and exhibition of the |E-maxima has been explained with a simple model according to which |E at any given m is comprised of two sets of the oppositely acting terms, namely |Eup and |Edown. Since all the |E plots fit very well to third-order polynomials in m with negligibly small coefficients of the cubic terms, the other two terms involving m and m2 can be compared with |Eup and |Edown, respectively. From temperature variation of molar conductivity, activation energies have been determined and compared with those of viscous flow.