Mixing properties of the liquid systems methanol plus 2-propanol and 1-propanol plus 2-propanol

We investigate the liquid systems methanol + 2-propanol and 1-propanol + 2-propanol at 25 degrees C over the entire range of compositions. We obtain the excess Gibbs function from vapour-liquid equilibrium data, the excess enthalpy from calorimetric measurements, the excess entropy from a combination of both, the excess volume from pycnometric density data, and the viscosity from experiments in an Ubbelohde viscometer. All the molar excess quantities are relatively small (as to be expected) and fairly symmetric with respect to composition. The excess Gibbs function and the excess enthalpy are negative in both systems, while the excess entropy and the excess volume are positive in the methanol system and negative in the 1-propanol system. In the plot of the viscosity against mole fraction, the deviations from linearity have signs opposite to those of the excess volume. This also holds for other binary liquid systems containing 2-propanol.