Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

Densities, kinematic viscosities, refractive indices and dielectric permittivities have been measured over the whole concentration range for the methanol + cyclohexylamine mixture at (293.15 303.15) K and 0.1 MPa. Dynamic viscosities were obtained from densities and kinematic viscosities. This set of experimental values has been used to determine, excess functions for volume, refractive index, and permittivity, as well as deviations of .eta. from the linear dependence on mole fraction. Viscosity data were correlated by the following semi-empirical equations: Grunberg-Nissan, Hind, Frenkel, Katti-Chaudhri, Teja-Ric e, McAllister, and Heric. The large and negative VEm values and the positive D.eta. values obtained reveal the existence of strong interactions between unlike molecules in the studied mixture. Such interactions become weaker in cyclohexylamine systems when the size of the alcohol increases. Values of the molar refraction determined from the Lorentz-Lorenz equation show that dispersive interactions become more relevant for the mixtures including the longer 1-alkanols. The positive aEr values indicate that dielectric polarization is strengthened along the mixing process. It has been ascribed to the mixture compounds form multimers of larger effective dipole moment than those which come from the alcohol dissociation upon mixing. The experimental data have been also used to calculate the Kirkwood's correlation factor, gK, the orientational polarization, Pm, and the corresponding excess magnitudes. From these calculations, it is concluded that the methanol mixture is more structured than those with longer 1-alkanols due to a strengthening of orientational polarization in comparison to that of the ideal solution.