The coexistence curve of the binary fluid mixture perfluoromethylcyclohexan-isopropyl alcohol was determined by precisely measuring the refractive index both above and below its upper critical consolute point. Sixty-seven two-phase data points were obtained over a wide range of reduced temperatures, 10 -5<t<2.5x1O-1, to determine the location of the critical point: critical temperature=89.901 oC, and critical composition=62.2% by volume perfluoromethylcyclohexane. These data were analyzed to determine the critical exponent 6 close to the critical point, the amplitude B, and the anomaly in the diameter. The volume-fraction coexistence curve is found to be as symmetric as any compositionlike variable. Correction to scaling is investigated as well as the need for a crossover theory. A model is proposed that describes the asymptotic approach to zero of the effective exponent B, which allows an estimation of the temperature regime free of crossover effects.
Jacobs, D.T., Kuhl, D.E., Selby, C.E., Coexistence Curve of Perfluoromethylcyclohexane-Isopropyl Alcohol, J. Chem. Phys., American Institute of Physics, College Park, MD, Vol. 105 (2), pp. 588-597, July 8, 1996.