Elastic Scattering of Light by Binary Mixtures above and below the Critical Solution Temperature. I. Methanol Cyclohexane

摘要

An investigation was made of the lighthyphen;scattering properties of the methanolndash;cyclohexane binary system in the onehyphen;phase region above the critical solution temperatureTcand in the twohyphen;phase region belowTc. Measurements were made down the critical isochore forTthinsp;thinsp;Tcand along the methanolhyphen;rich side of the coexistence curve forTthinsp;thinsp;Tc. A modification of the Ornsteinndash;Zernikendash;Debye theory of light scattering was found to be in reasonable agreement with the results forTthinsp;thinsp;Tc. The Debye parameter ldquo;lrdquo; was 14.5thinsp;plusmn;thinsp;0.5 Aring; aboveTcand 14.0thinsp;plusmn;thinsp;1.3 Aring; belowTc. The ratio of the extrapolated zerohyphen;angle inverse intensity at anyDgr;TbelowTcto that quantity at the sameDgr;TaboveTcwas 3.6. The persistence length for fluctuations belowTcas determined by the Debye theory was of the same order of magnitude as the thickness of the binary interface.