Near-critical coexistence curve and critical exponent of an ionic fluid

The coexistence curve of an ionice liquid–liquid system has been obtained very close to the critical point by measuring the refractive indices of the two phases in equilibrium. The effective exponent βe remains close to the classical value of 0.5 to t=0.0005 or closer to Tc. The data are, however, not inconsistent with a limiting exponent of 0.326 provided the Wegner correction terms are very large. This behavior is qualitatively consistent with available theory and other experimental knowledge, but further theory and experiments are needed before quantitative comparisons can be made.