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)Δ x 1 2 using Margules binary parameters, A and B, representing the VLE data, and an experimental error involved in the liquid phase composition, Δ x 1. In the present investigation, an empirical consistency test is proposed for application to polar binaries using D = 0 holding at Δ x 1 = 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 = aP b 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.