In a binary liquid mixture,the component possessing the lowest surface tension preferentially adsorbs at the liquid-vapor surface.In the past this adsorption behavior has been extensively investigated for critical binary liquid mixtures near the mixture's critical temperature T_c.In this fluctuation-dominated regime the adsorption is described by a universal function of the dimensionless depth z/zeta where zeta is the bulk correlation length.Fewer studies have quantitatively examined adsorption for off-critical mixtures because,in this case,one must carefully account for both the bulk and surface crossover from the fluctuation-dominated regime(close to T_c)to the mean-field dominated regime(far from T_c).In this paper we compare extensive liquid-vapor ellipsometric adsorption measurements for the mixture aniline+cyclohexane at a variety of critical and noncritical compositions with the crossover theory of Kiselev and co-workers.
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