A thermodynamic study of polar and non-polar fluid mixtures : n-alkanenitrile and n-alkane systems.

This work consists of a thermodynamic study of liquid binary mixtures of the type polar + non-polar. The polar components were chosen to be members of the n-a1kanenitrile series of compounds whereas the non-polar components are members of the n-alkane series. The experimental part of the work includes: a) the determination of upper critical solution temperatures of binary mixtures of ethanenitri1e, propanenitri1e, and n-butanenitrile with n-a1kanes in order to establish the limits of liquid-liquid miscibility; b) the measurement of the gas-liquid critical locus (pc_Tc_X) for the six mixtures ethanenitrile + n-pentane to n-decane. c) measurement of excess enthalpies of mixing at 298.15 K for propanenitrile + n-pentane to n-heptane; n-butanenitrile + n-hexane, + n_octane, + n-dodecane, and + n-tetradecane. d) and the measurement at 303.15 K of excess volumes of mixing for propanenitri1e + n-pentane to n-octane; n-butanenitrile + n-pentane, + n-hexane, +n-octane, +n-decane, + n-dodecane, +n-tetradecane; and n-hexanenitrile + n-hexane. Although the experimental results are readily related to the molecular size of the studied substances statistical theories of fluids are used for a more formal interpretation. The Scatchard - Hildebrand theory with a modification is used to predict upper critical solution temperatures. The now widely used van der Waals' one and two-fluid theories are used here to predict excess enthalpies and volumes of mixing. The gas-liquid critical properties are interpreted using a first-order theory together with the Van der Waa1s' equation of state. The predicted results show in each case satisfactory agreement with experiment, furthermore, information is obtained on the relative strength of the unlike interaction between the molecules of the mixtures studied.