En las fronteras de la Materia Condensada

In recent years, there was abundant discussion regarding the critical behaviour of ionic systems. Theoretical and experimental studies have finally established that electrolyte solutions belong to the Ising-3d class. Lately, computer simulation results [1] and integral equation theories [2] have predicted that charged systems may exhibit a phase transition between ordered-non ordered states with appearance of tricritical behaviour. The ordered, antiferromagnetic-like phase was located at high ionic concentrations for solvents with intermediate dielectric constant, and emerges as a consequence of high non-coulombic attractions between ions bearing the same charge, compared to those of opposite charge. In the present work we report the results of an experimental study on several ionic systems, with intermediate dielectric constants (between 10 and 20). The refractive index and electrical conductivity in the 2-phase region and the turbidity of the homogeneous phase have been measured for ternary liquids containing water, an organic liquid and an inorganic salt. All the investigated systems were previously [3,4] studied and its phase behaviour was signaled out as possibly related to multicritical behaviour. Our results do not confirm multicritical phenomena in any of these systems.