Graphical analysis of the phase equilibria diagram

Abstract

The complexity and variety of possible behaviours of the quaternary liquid-liquid, liquid-liquid-solid equilibrium at constant temperature and pressure and the ternary isobaric or isothermal liquid-liquid-vapor equilibria are very high and, sometimes, the phase equilibria diagrams appear incomplete and not clearly explained. It is not difficult to find references in the literature where important misinterpretation and mistakes are committed as a consequence of applying a non-adequate experimental methodology and a lack of the spatial point of view. Thus, the objective of the present paper is to show some examples where special behaviours are selected to clarify some aspects concerning the experimental determination and graphical representation of liquid-liquid-solid and liquid-liquid-vapor equilibrium data, and remark on the importance of the knowledge and consideration of the qualitative expected behaviour of the system under study, obtained from the binaries.