Thermodynamic and Physical Behaviour of Binary Mixtures Involving Sulfolane Viscosity, Dielectric Constant and Solid + Liquid Phase Diagram of Mixtures of Dioxane + Sulfolane

Abstract Excess functions, H ≠E , S ≠E , G ≠E for activation of viscous flow, as well as the dielectric constants of dioxane (1) - sulfolane (2) mixtures were determined: slight negative deviations from ideality were observed in both cases, with a minimum at x ≈ 0.5. Solid-liquid equilibrium temperatures were also measured over the entire composition range. Solid solutions were observed in the region in which mesomorphic sulfolane is in equilibrium with the liquid. Two phase diagrams may be drawn, in the region 0.33 ≦ x 2 ≦ 0.98: one is of the simple eutectic type and the other exhibits two eutectis and a flat maximum corresponding to a 1:2 molecular compound, the occurrence of which is supposed to be caused by weak electrostatic attractions in a system of favorable crystal geometry rather than by bonding. A lessening of these interactions, with increasing temperature, would result in the liquid solution regular behaviour.