On Temperature Dependence of Excess Gibbs Energy

Temperature dependence of GE is discussed for three widely used equations linear and nonlinear in parameters. It is shown that the Wilson equation predicts always positive excess heat capacity regardless of values of its parameters. Several temperature modifications of the Redlich-Kister, Wilson and NRTL equations are discussed with respect to the sign of the excess Gibbs energy, excess enthalpy and excess heat capacity.

Vapour-liquid equilibrium in the binary systems formed by ethylene glycol, diethylene glycol, and N-methylpyrrolidone

Vapour-liquid equilibrium data are given for the binary systems ethylene glycol (EG)-N-methylpyrrolidone (NMP), ethylene glycol-diethylene glycol (DEG), and N-methylpyrrolidone-diethylene glycol at 50°C. The measurement of vapour-liquid equilibrium was carried out in a modified version of semimicrostill from foregoing paper. This still makes it possible to measure even at the pressures of the order 101 Pa. The dependence of the excess Gibbs energy on composition was expressed by the 4th order Redlich-Kister, Wilson, and NRTL equations. The systems EG-NMP and DEG-NMP exhibit negative deviations from ideal behaviour, EG with DEG form practically ideal solution.