Thermodynamic properties of cyclohexane-methanol liquid mixture from shear viscosity measurements

摘要

The binary liquid mixture cyclohexane-methanol has an upper critical point at a mass composition of 27.5% of methanol and critical temperature T_c = 319.608±0.234 K. The shear viscosity and density of this system have been carried out as a function of temperature, under atmospheric pressure, over the composition range along the coexistence curve above the transition temperature. From these experimental data values, various thermodynamic parameters, namely, Gibbs energy (△G), enthalpy and entropy activation parameters △H and △S, the excess molar volume (V~E), excess Gibbs energy (△G~E), viscosity deviations (△η) and the activation energy (E_(av)) have been calculated and fitted to Redlish-Kister equation. Furthermore, in the one-phase region just above Tc of the critical binary fluid, the viscosity measurements yield to an enhancement as expected for Ising criticality with a crossover to regular behavior. The regular background is obtained by interpolation from the measurements at non-critical concentrations. The viscosity has been also correlated with the equation of Grunberg-Nissan, Hind et al., Katti-Chaudhri, Heric-Brewer, McAllister, Auslander and Acree-Jouyban.