Liquid excess functions

We report in Table VII the signs of the excess functions reported in the literature for eight binary liquid mixtures of simple molecules the corresponding values of 8 and p for each mixture are given (first component = reference component A) as well as the temperature and TAA. These values of 8 andp have been deduced from Tables V and VI, and the reference component has been chosen in such a way that all the <5 s are positive. 

Renon, H., Prauznits, J.M., 1968, Local Compositions in Thermodynamic Excess Functions for Liquid Mixtures, AIChE Journal, 14, 135. 

Renon, H. and Prausnitz, J.M., Local composition in thermodynamic excess functions for liquid mixtures, AIChE J., 14,135,1968. 

The thermodynamic excess functions for the 2-propanol-water mixture and the effects of lithium chloride, lithium bromide, and calcium chloride on the phase equilibrium for this binary system have been studied in previous papers (2, 3). In this paper, the effects of lithium perchlorate on the vapor-liquid equilibrium at 75°, 50°, and 25°C for the 2-propanol-water system have been obtained by using a dynamic method with a modified Othmer still. This system was selected because lithium perchlorate may be more soluble in alcohol than in water (4). 

The (liquid 4- liquid) equilibria diagram for (cyclohexane + methanol) was taken from D. C. Jones and S. Amstell, The Critical Solution Temperature of the System Methyl Alcohol-Cyclohexane as a Means of Detecting and Estimating Water in Methyl Alcohol , J. Chem. Soc., 1930, 1316-1323 (1930). The G results were calculated from the (vapor 4- liquid) results of K. Strubl, V. Svoboda, R. Holub, and J. Pick, Liquid-Vapour Equilibrium. XIV. Isothermal Equilibrium and Calculation of Excess Functions in the Systems Methanol -Cyclohexane and Cyclohexane-Propanol , Collect. Czech. Chem. Commun., 35, 3004-3019 (1970). The results are from M. Dai and J.-P.Chao, Studies on Thermodynamic Properties of Binary Systems Containing Alcohols. II. Excess Enthalpies of C to C5 Normal Alcohols + 1,4-Dioxane , Fluid Phase Equilib., 23, 321-326 (1985). 

The concept of free volume varies on how it is defined and used, but is generally acknowledged to be related to the degree of thermal expansion of the molecules. When liquids with different free volumes are mixed, that difference contributes to the excess functions (Prausnitz et al., 1986). The definition of free volume used by Bondi (1968) is the difference between the hard sphere or hard core volume of the molecule (Vw= van der Waals volume) and the molar volume, V ... 

A study of the representation of liquid-fluid equilibria with the "Excess Function-Equation of State" model and the choice of a group-contribution method. Promising results were obtained here (references [3] and [4]). 

The interaction parameter Eg was first adjusted to the experimental data of the liquid-fluid and solid-fluid equilibria. The representation of both types of equilibria was very satisfactory, which proves that the "Excess Function-Equation of State" model with an adjusted parameter is well adapted to both cases ([4-6], [13]). 

Table III. Excess Functions of Liquid Systems of Small Molecules0...

The Measurement of Thermodynamic Excess Functions of Binary Liquid Mixtures... 

This chapter deals with experimental methods for determining the thermodynamic excess functions of binary liquid mixtures of non-electrolytes. Most of it is concerned with techniques suitable for measurements in the temperature range 250 to 400 K and the pressure range 0 to 100 kPa. Techniques suitable for lower temperatures will be briefly reviewed. Techniques for measuring the molar excess Gibbs function G, the molar excess enthalpy and the molar excess volume will be discussed. The molar excess entropy can only be determined indirectly from either measurements of (7 and at a specific temperature = (If — C /T], or from the temperature dependence of G m [ S m = The molar excess functions have been defined by... 

Experimental excess functions of liquid mixtures are useful in that they provide data to test theories of liquid mixtures and provide a guide for the formulation of new theories. The data are also useful in the chemical and petroleum industries. This chapter does not contain a summary of experimental data since Chapter 9 of this volume consists of a bibliography of excess function and related measurements on binary mixtures of non-electrolytes. 

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