Comment on “Reliable Correlation for Liquid–Liquid Equilibria outside the Critical Region”

We comment on work by Ruszczyński
et al., who extended the
regression method of Cunico et al. (Fluid Phase Equilibria, 2014) and proposed certain Gibbs free energy models for binary
liquid–liquid equilibria. We find that their regression method
considers only necessary criteria for stability, and we derive constraints
to be imposed on the thermodynamic parameters during regression such
that the criteria become sufficient and the models thus become numerically
easy to use.