EXCESS GIBBS ENERGIES AND EXCESS-ENTHALPIES OF LIQUID BINARY-MIXTURES CONTAINING NITROALKANES

A head-space gas chromatographic technique was used to determine vapour phase equilibria for binary mixtures of 1-nitroalkanes (1-nitropropane, 1-nitrobutane, 1-nitropentane) + n-heptane or cyclohexane. Excess molar Gibbs energies, G(E), for the mixtures investigated were obtained. All systems exhibit positive deviations. The G(E) values decrease with increasing nitroalkane chain length. Activity coefficients at infinite dilution, gamma(i)infinity were also evaluated. A flow microcalorimeter, Model 2277-LKB, was used to determine excess enthalpies, H(E), as a function of concentration at atmospheric pressure and 298.15 K, for binary liquid mixtures containing the same 1-nitroalkanes with tetrachloromethane. A tentative approach, based on an additivity scheme of surface interactions combined with the scaled particle theory, is presented to estimate and analyse group contributions to DELTAG(solv)0 and DELTAH(solv)0, the energy and the enthalpy of solvation respectively.