A. Compostizo

Excess gibbs energy and excess volume of (cyclohexane+2-propanone) and of (cyclohexane+2-butanone)

Abstract Isothermal vapour-liquid equilibria for cyclohexane + 2-propanone and +2-butanone were obtained at 323.15 K. The results were found to be consistent. Excess molar volumes were obtained at 298.15 and 303.15 K for (cyclohexane + 2-propanone) and at 298.15, 303.15 and 323.15 K for (cyclohexane + 2-butanone). The experimental results showed that both mixtures deviate positively from ideality.

p, T, x, y data of benzene + n-hexane and cyclohexane + n-heptane systems

The isothermal vapour—liquid equilibria of the benzene + n-hexane and cyclohexane + n-heptane systems have been studied using a dynamic method. The thermodynamic consistency of the data has been tested and the prediction from several empirical and semitheoretical models have been compared with the experimental values of different excess properties.

Isothermal liquid-vapour equilibria 1. The binary systems formed by toluene + methyl ethyl ketone, + methyl propyl ketone, and + methyl isobutyl ketone

Abstract Vapour pressures at 323.15 K by a dynamic method and refractive indices at 303.15 K have been measured for several binary systems consisting of toluene + methyl ethyl ketone ( mek ), + methyl propyl ketone ( mpk ), and + methyl isobutyl ketone ( mik ). The vapour pressures have been used to calculate excess Gibbs energies.

Temperature and chain-length dependence of the volumetric properties of 1-chlorobutane–alkane mixtures

The excess volumes of 1-chlorobutane–n-alkane mixtures have been measured at several temperatures and over the entire composition range. The chain-length and the temperature dependence are non-monotonic, and might indicate the existence of structure-making and structure-breaking effects.Two generalized van der Waals equations of state using a hard convex body-repulsive contribution have been used. The equations lead to satisfactory fits of the VEvs. x curves, although they fail to predict the chain-length and temperature dependence. However, the pressure dependence of VE for nC6–nC16 at 298.15 K is predicted satisfactorily.

Activity coefficients and excess Gibbs free energies at 348.15 K in cyclohexane+chlorobenzene, +fluorobenzene, and +thiophene

Abstract Activity coefficients and excess Gibbs free energies of cyclohexane+chlorobenzene, +fluorobenzene, and +thiophene have been calculated from vapour pressures and liquid and vapour compositions. These have been measured by a dynamic method at 348.15 K over the whole range of mole fractions. Composition has been determined by refractometry. The thermodynamic consistency of the results has been checked through the Redlich-Kister equation using an iterative procedure.

Excess Gibbs free energies of mixtures of methylcyclohexane + o-xylene, + m-xylene, and + p-xylene at 348.15 K

Total vapour pressures at 348.15 K for methylcyclohexane + o-xylene, + m-xylene, and + p-xylene were measured over the whole range of mole fractions. Pressures were determined by a dynamic method. Excess Gibbs free energies, calculated from these measurements, were positive in all cases.

Excess Gibbs free energy of (n-heptane+a xylene) at 348.15 K

The Gibbs free energy GE as a function of mole fraction, was determined at 348.15 K for each of the liquid mixtures: (n-heptane, +o-xylene), (+m-xylene), and (+p-xylene). A dynamic method was used by which GE values are obtained from measurements of vapour pressure and compositions of liquid and vapour phases at a given temperature. GE values are always positive and they lie in the order: o-xylene > m-xylene > p-xylene.

Bulk modulus for some simple molecular fluids

Abstract The bulk modulus B of several molecular fluids composed of rigid molecules has been calculated from p-p-T data obtained with a high-pressure vibrating tube densitometer. The data of all the substances studied, including Ar, can be described by a single master curve when plotted versus the reduced density ϱ*, in agreement with the predictions of the Gubbins-Gray perturbation theory for fluids with the same reference system. Combination of p-p-T and C v data with the virial theorem has allowed the calculation of the exponent characterizing the repulsive branch of the intermolecular potential n . The different values of n suggest that different reference systems should be used for each substance, in contradiction with the conclusions obtained from the B versus ϱ* curves. This indicates that p-p-T data are less sensitive to the details of the intermolecular potential than their combination with other thermal properties like C v , internal energy or residual entropy.

Experimental study of the equation of state and the surface tension of water-soluble polymers: poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) + water at 298.15 K

The equation of state of poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEG–PPG–PEG) + water has been measured in the sol phase at 298.15 K and up to 40 MPa. For the sake of comparison two mixtures of (PEG + PPG) + water, with the same PEG: PPG ratio as the copolymer, have been measured. The differences found between the data of the copolymer and the blend solutions are well beyond the experimental precision, the compressibility for the copolymer mixtures being larger than for the blend one. Contrary to previous non-aqueous mixtures, the aqueous ones present deviations with respect to the corresponding states equation proposed by the group of Sanchez (I. C. Sanchez, J. Cho and W. J. Chen, Macromolecules, 1993, 26, 4234). The surface tension γ results show that both PEG–PPG–PEG and PPG are surface active, leading to a strong decrease of γ with respect to that of water even for very low polymer concentrations. The behaviour of the spinodal pressure of the system is discussed in terms of the compressibility and the surface tension data.

Thermal expansion and pressure dependence of the critical temperature near the lower-critical solution point of 2-butoxyethanol+water

Abstract A vibrating tube densitometer has been carefully calibrated using an extensive set of pure component densities measured by pycnometry. The density of a critical and a near critical mixture have been measured as a function of temperature in the vicinity of the phase separation curve. The results for the critical mixture can be described using the leading scaling term in the interval 3.6 × 10−4 ⩽t⩽ 2.9 × 10−2 where t = (T - Tc)/Tc, Tc being the critical temperature. The first correction-to-scaling term is necessary to extend the interval up to t = 7.5 × 10−2. The pressure dependence of Tc has been measured in the interval 0.1 ⩽ p/MPa ⩽ 35. The values of critical density ρc, of dTc/dp, and the critical amplitude of the thermal expansion have been combined with correlation length data, and found compatible with the two-scale factor universality hypothesis. The densities of the off-critical mixture can be described with a similar scaling-type equation with Tc substituted by T′, a pseudo-spinodal temperature.