MIXING PROPERTIES OF THE LIQUID-SYSTEM WATER PLUS 2-PROPANOL

We present results of measurements of the excess Gibbs function (from vapour-liquid equilibrium data in the literature), of the excess enthalpy (from our own calorimetric investigations), of the excess volume (from our own density data), and of the viscosity (from our own viscosimetric experiments) for the liquid system water + 2-propanol at 25-degrees-C over the entire range of compositions. Hence, we also derive the excess entropy and the entropy of mixing. The molar excess Gibbs function, as a function of composition, is positive and nearly symmetric in spite of the irregular behaviour of the other molar excess functions (''symmetry rule''). The molar excess enthalpy (molar enthalpy of mixing) is a complicated function of the composition: It is positive for low water content, passes through zero at about equimolar composition, and becomes negative for high water content. The molar excess entropy is always negative, but very asymmetric. The molar entropy of mixing is positive for most compositions, but negative for very high water content; it is also highly asymmetric. The molar excess volume is roughly proportional to the molar excess entropy (''Rehage's rule''). The viscosity exhibits an extremely irregular composition dependence. The Appendix deals with the correlation between the sign of the entropy (and enthalpy) of mixing and the type of the consolute point in a binary liquid system with phase separation.