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

## TL;DR

This paper introduces a new test for checking the consistency of vapor-liquid equilibrium data, which is made available in a new open-source software tool.

## Contribution

The paper proposes a novel 'gamma offset test' for detecting inconsistencies in vapor-liquid equilibrium data.

## Key findings

- The new test complements traditional methods and is effective for most binary systems.
- The test is particularly useful in systems where existing procedures are hard to apply.

## Abstract

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.