SURFACE AMPLITUDE RATIOS NEAR A CRITICAL END-POINT

We provide the first experimental test of the universality of a surface amplitude ratio near a critical end point by measuring the modified critical adsorption amplitude ratio, R(MA), for the liquid mixtures aniline + cyclohexane and isobutyric acid + water. Our results thus far support the universality hypothesis with R(MA) = 1.3 +/- 0.1. The universality of R(MA) would imply that the surface tension amplitude ratio Q is universal in agreement with the predictions of Fisher and Upton; however, a precise connection relating R(MA) to Q is not currently available.