Redlich-Kister test

From Figures 5 and 6, the Redlich-Kister test apparently will not suffice for this system since the integrated areas of the curves are not zero. Retaining Equation 24, values of Ah /RT2 were calculated using the procedure outlined above. The results are presented in Table I, along with values of... 

The consistency test (Redlich-Kister test) is performed by plotting the logarithmic value of the ratio of the activity coefficients as a function of the mole fraction xi. If the VLE data are thermodynamically consistent the area above and below the x-axis should be equal. 

A lot has been written about consistency tests [2, 8- TO]. The Redlich-Kister test has already been described in Section 5.4.1. However, for testing the consistency, it has the serious disadvantage that the pressure cancels out. At low pressures, where... 

Modified Redlich—Kister Consistency Test Results... 

Experimental values of excess molar volume and change of refractive index of binary mixtures were correlated by Redlich-Kister equation (Ottani and Comelli, 2005). The binary contribution was used to correlate the experimental ternary results with the Cibulka equation (Al-Jimaz et al., 2004). Several methods to predict density and refractive index of mixtures were applied to test their validity in the systems studied. 

The authors mention similarity between the Legendre polynomials and the Redhch-Kister expansion. This similarity is not that striking if we realize that the Legendre polynomials are orthogonal on interval ( — 1 1) while each even order term in the Redlich-Kister expansion is orthogonal to each odd order term on interval (0 1). Possibility of testing consistency of isobaric data is also mentioned. 

A consistency test described by Chueh and Muirbrook (C4) extends to isothermal high-pressure data the integral (area) test given by Redlich and Kister (Rl) and Herington (H2) for isothermal low-pressure data. [A similar extension has been given by Thompson and Edmister (T2)]. For a binary system at constant temperature, the Gibbs-Duhem equation is written... 

The equal-area consistency test, proposed independently by Coulson and Herington and Redlich and Kister, involves plotting ln (l — y)xp%j [y(l - against x and if the areas above and below the x axis are equal,... 

In the case of isobaric data the excess enthalpy part has to be taken into account. This can be done if the excess enthalpies for the system investigated are known. Since the excess enthalpies are usually not known, in the area test the contribution is taken into account empirically using the quantity J as suggested by Redlich and Kister [25] ... 

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