Phenomenological interpretation of the systems exhibiting a closed-loop liquid-liquid phase diagram by using a simple g ^e-model

A simple phenomenological g^E-model based on the Flory-Huggins lattice theory was used to interpret critical behavior, excess properties and liquid-liquid equilibria of three aqueous systems that exhibit a closed-loop phase diagram: (2-butoxyethanol + water), (2,6-dimethylpyridine + water) and (tetrahydrofuran (THF) + water). The model showed flexibility in application and good performance in all the aforementioned properties. Since it describes with a very good accuracy both binodal (coexistence) curves and excess enthalpies, it was used to calculate the molar excess enthalpies of the phases in equilibrium which may be a useful task in practice.