Binary systems regular solution theory

If the mutual solubilities of the solvents A and B are small, and the systems are dilute in C, the ratio ni can be estimated from the activity coefficients at infinite dilution. The infinite dilution activity coefficients of many organic systems have been correlated in terms of stmctural contributions (24), a method recommended by others (5). In the more general case of nondilute systems where there is significant mutual solubiUty between the two solvents, regular solution theory must be appHed. Several methods of correlation and prediction have been reviewed (23). The universal quasichemical (UNIQUAC) equation has been recommended (25), which uses binary parameters to predict multicomponent equihbria (see Eengineering, chemical DATA correlation). 

The corresponding monomer/micelle equilibria can be dealt with by the regular solution theory (RST), as shown in particular by Rubingh in 1979 (1). The application of this theory to numerous binary surfactant systems (2 - 4) has followed and led to a set of coherent results (5). 

I-f the interactions between sur-factants in the mixed micelle can be described by regular solution theory, the -following equations apply -for a binary system ... 

Regular Solution Theory. I-F the sur-Factant mixing in the micelle obeys regular solution theory, the -Following relationships are valid -For a binary sur-Factant system (45) ... 

The heat of mixing term can be obtained from various theories. One valid possibility for nonpolar systems is the regular solution theory, introduced by Joel Hildebrand, which employs the concept of the solubility parameter. For a binary solvent(l)-polymer(2) system, the heat of mixing is given according to the regular solution theory ... 

The surface composition Xj can be foimd by equating the two expressions in Equation 1.80 and the resulting value can then be used to calculate the surface tension y. We note that the basic method can be extended to predict the interfacial tension between liquid phases in a binary system described by regular solution theory (Defay et al., 1966). 

The regular solution theory is not limited to binary systems. It can directly be applied for the calculation of activity coefficients in multicomponent systems ... 

Examine with the help of the regular solution theory, UNIFAC and modified UNIFAC if the binary systems benzene-cyclohexane and benzene-n-hexane show an azeotropic point at 80 C. In case of the regular solution theory, calculate the solubility parameter from the saturated liquid density and the heat of vaporization using Eq. (5.70). All required data are given in Appendices A, H, and 1. 

To a first approximation, the deviations from ideality may be expressed by regular solution theory (Guggenheim, 1952, p. 29), in which the activity coefficient of a component in a binary system is given by the simple expression ... 

LIQUID-LIQUID CURVE AND CRITICAL SOLUTION POINT. In the now classical theory of regular solutions developed by Scatchard (10) and Hildebrand (5) with the nonideal entropy correction given by Flory and Huggins (5), the activities of the components of a binary system are given by... 

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