An empirical consistency test using thermodynamic consistency lines for the VLE data of 7262 constant-temperature and 5167 constant-pressure binaries

It has already been shown that the deviation in the binary VLE data from the Gibbs–Duhem equation, D, is formulated as D = 2(B − A)Δx12 using Margules binary parameters, A and B, representing the VLE data, and an experimental error involved in the liquid phase composition, Δx1. In the present investigation, an empirical consistency test is proposed for application to polar binaries using D = 0 holding at Δx1 = 0. For that purpose, a polarity exclusion factor, β = F/|B − A|, is used, in which F denotes a data deviation from A = B. Using a significant number of the A and B values from the literature reported by different authors using different equipment, it was shown that β converges to a straight line drawn on a log–log scale, which is called a thermodynamic consistency (TC) line formulated as β = aPb using the system pressure, P, of the constant-pressure data or the average vapor pressure of the constant-temperature data. The proposed empirical TC test uses the deviation from the TC line for determining the uncertainty of the data. Using the same data, it was also shown that β is a polarity-independent variable. An application of the test to ternary LLE data is demonstrated.