A search for multicritical points in liquid mixtures: The shield region and the three-state Potts point

In a study of the mixture, ethylene glycol + water + lauryl alcohol + nitromethane + nitroethane we have observed a region of four coexisting liquid phases between 37 and 42 °C. Analysis of the compositions of the coexisting phases provides fairly convincing evidence that they belong to a ’’shield’’ region noted previously in theoretical studies of a three-component model and a van der Waals model of binary mixtures. Such a region could be the starting point in a search for the multicritical point D2. On the other hand its presence is good evidence for the absence in this mixture of the fluid analog of the three-state Potts model multicritical point C2. This is in agreement with studies in systems with symmetry-breaking phase transitions and lends support to the hypothesis that C2 does not occur in three-dimensional systems.