A New Method for Testing Thermodynamic Consistency of Vapor-Liquid Equilibrium Data

Tests of thermodynamic consistency are essential tools for evaluating VLE data quality. However, there is a lack of software that offers the most commonly used testing procedures in a single application. Furthermore, currently used tests are very general and serve well to quantify experimental error but do not reveal much about its cause. In this work, a new test is proposed, called the "gamma offset test". It is designed to have a focused, limited scopeto detect inconsistency between the binary VLE data set and the corresponding vapor pressure models. The proposed testing procedure was applied to a collection of VLE data sets obtained from the literature, and the results were compared with the tests of Fredenslund and Redlich-Kister. A criterion of consistency to formally accept or reject the data was fine-tuned so that the test provides meaningful results. It was shown that this new test can be a valuable complement to the traditionally used procedures for most binary systems. Moreover, the advantages of the new test were demonstrated in systems where existing procedures are difficult to apply. The new test can be used either to assess experimental setup accuracy or to help diagnose the cause of a known experimental error. This test is part of a newly developed open-source software package called "VLizard, a VLE wizard", which also offers other well-known testing procedures. With its graphical interface, it aims to fill the gap as an easily accessible tool for both academic and industrial VLE research.