Phase Equilibria Of Binary Systems Research Articles

Phase equilibria for strongly nonideal mixtures from an equation of state with density-dependent mixing rules

Abstract An equation of state of the van der Waals form represents vapor—liquid and liquid—liquid equilibria in binary, particularly aqueous, mixtures. The Mansoori—Carnahan—Starling expression is used for the repulsive part of the equation of state while the attractive part uses a simple van der Waals form. For a mixture, the usual (density-independent) quadratic mixing rule is used for the leading attractive term but a density-dependent correction is added to allow for noncentral intermolecular forces of disimilar components at high densities. This procedure gives the necessary quadratic dependence of the second virial coefficient at low densities but includes also cubic terms for representation of phase equilibria at liquid-like densities. Good results are obtained for vapor—liquid and liquid—liquid equilibria in binary systems containing water, hydrocarbons, phenol, pyridine and methanol. However, extension to liquid—liquid equilibria in ternary systems is not successful because the equation of state is not able properly to represent phase equilibria of binary systems at conditions only slightly removed from binary liquid-phase instability; at these conditions, the equation of state erroneously predicts a two-liquid region. For further progress toward application of equations of state to ternary liquid—liquid equilibria, it will be necessary to introduce some fundamental modifications toward better representation of phase behavior in the critical region.

Phase equilibria of binary systems containing ethylene carbonate and an aromatic compound

Boiling temperature data for binary systems of ethylene carbonate with benzene, toluene and p-xylene were measured at 500 mmHg. At lower temperatures ( T < 348 K) the system ethylene carbonate- p-xylene exhibits a liquid phase splitting and the liquid-liquid equilibrium was measured in the range 303-348 K. Phase equilibria data were used to obtain the activity coefficients. Solubility of solid ethylene carbonate in p-xylene was also measured at temperatures lower than the melting point of ethylene carbonate. These data were correlated by using an experimental value of enthalpy of fusion and activity coefficients obtained from liquid-liquid data.

Phase equilibria of binary systems containing crystalline inclusion compounds. Part 1. The perhydrotriphenylene–n-heptane system

The vapour pressure of saturated solutions containing the perhydrotriphenylene (PHTP)–n-heptane inclusion compound as a solid phase shows a maximum at ca. 10 °C below the m.p. of the crystalline adduct. A second pressure maximum coincident with a eutectic point, is observed in the case of mixtures very rich in PHTP. Moreover, a sudden increase in pressure is observed in the case of pure or nearly pure inclusion compound in the close vicinity of the m.p. Such a behaviour is consistent with that predicted on the basis of the phase rule. The experimental values agree with those calculated by assuming the complete dissociation of the adduct in the liquid phase.

Phase equilibria in binary systems containing acetaldehyde

The vapour-liquid equilibrium in binary acetaldehyde-diethyl ether, acetaldehyde-ethanol and acetaldehyde-water systems was measured at the pressure of 101.32 kPa. The experimental data were correlated by the two- and three-constant Redlich-Kister equation.

Gas—gas equilibrium and the two-component lattice-gas model

A two-component lattice-gas model is developed to explain the phase equilibria in binary systems.