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>Comments on classical and nonclassical representations of critical demixing in liquidndash;liquid binary solutions
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Comments on classical and nonclassical representations of critical demixing in liquidndash;liquid binary solutions
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机译：Comments on classical and nonclassical representations of critical demixing in liquidndash;liquid binary solutions
Classical expressions for the free energy of binary mixtures do not agree with observed behavior near critical points (Tc,Xc) for liquidndash;liquid demixing. Very near (Tc,Xc) longhyphen;range concentration fluctuations produce logarithmic discontinuities in certain of the derivatives of the free energy and this necessitates an alternate description in terms of scaling laws. Arguments are presented that, for mixtures of small molecules, the range of such nonclassical effects is approximately (0t10minus;3);t=1minus;T/Tc. This is about the same as the range of nonclassical effects for other kinds of critical phenomena. Although it has been claimed that nonclassical effects in liquidndash;liquid equilibria extend tot=10minus;1, or even further, experiments in the regiont10minus;3are as well or better described by classical thermodynamics as they are by scaling expressions. Classical thermodynamics also permits an accurate description of the pressure dependence ofTcandXc, and suggests that the equal volume criterion used to locateXcis not generally correct.
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