Volumes of mixing and theP * effect: Part I. Hexane isomers with normal and branched hexadecane

Excess compressibility in binary liquid mixtures

Brillouin scattering experiments have been carried out on some mixtures of molecular liquids. From the measurement of the hypersonic velocities we have evaluated the adiabatic compressibility as a function of the volume fraction. We show how the quadratic form of the excess compressibility dependence on the solute volume fraction can be derived by simple statistical effects and does not imply any interaction among the components of the system other than excluded volume effects. This idea is supported by the comparison of the experimental results with a well-established prototype model, consisting of a binary mixture of hard spheres with a nonadditive interaction potential. This naive model turns out to be able to produce a very wide spectrum of structural and thermodynamic features depending on values of its parameters. An attempt has made to understand what kind of structural information can be gained through the analysis of the volume fraction dependence of the compressibility.

Dependence upon temperature of the excess molar volumes of tetrahydropyran + n-alkane mixtures

Excess molar volumes VE, at 288.15 and 308.15 K and normal atmospheric pressure, are reported for the binary mixtures tetrahydropyran + n-alkanes (C7–C9). From the results, the differential coefficient (∂VE/∂T)p was estimated over the entire range of mole fractions. The Prigogine–Flory–Patterson theory and its applicability in predicting VE is tested. Keywords: Excess molar volumes, digital densimeter, tetrahydropyran, n-heptane, n-octane, n-nonane, Prigogine–Flory–Patterson theory.

Excess molar volumes of binary mixtures with 2-pentanone and 1-chloroalkanes at 298.15 and 308.15 K

Excess molar volumes υEat 298.15 and 308.15 K and normal atmospheric pressure for the binary mixtures 2-pentanone + 1-chloroalkane (from 1-chlorobutane to 1-chlorooctane) were obtained from measurements of the density with an Anton Paar densimeter. The υEvalues for all mixtures were positive, and increase as the 1-chloroalkane length increases. Excess molar volumes depend slightly on the temperature. The same characteristics were found previously for the excess molar enthalpies of the same mixtures. Experimental υEvalues are compared with theoretical results using the Prigogine–Flory–Patterson model. Keywords: thermodynamics, liquid mixtures, excess volumes, ketones, chloroalkanes.