Turbidity very near the critical point of methanol-cyclohexane mixtures

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We have measured the turbidity of a critical mixture of methanol and cyclohexane extremely close to the consolute point. The data span the reduced-temperature range 10-7 < t < 10-3, which is two decades closer to Tc than previous measurements. In this temperature range the turbidity varies approximately as lnt, as expected from the integrated form for Ornstein-Zernike scattering. A thin cell (200-μm optical path) with a very small volume (0.08 ml) was used to avoid multiple scattering. A carefully controlled temperature history was used to mix the sample and to minimize the effects of critical wetting layers. The data are consistent with a correlation-length amplitude ξ0=3.9±1.0 , in agreement with the value 3.5 calculated from two-scale-factor universality and heat-capacity data from the literature. © 1984 The American Physical Society.

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Physical Review A