Complete scaling theory applied to light scattering measurements of nitrobenzene + alkane liquid–liquid phase separation behaviors

Abstract

Complete scaling theory expresses universal critical scaling fields as analytical combinations of all relevant experimental fields, both independent and dependent. Its utility has been demonstrated in the analysis of asymmetric liquid–liquid coexistence curves. Here, applications of complete scaling theory are extended to two other physical observables in liquid–liquid systems: light scattering and wetting properties. Coexistence curves for the nitrobenzene + n-hexane, +n-decane, and +n-tetradecane systems were measured using a synthetic method approach. Critical compositions ZC for these systems were determined from 90° light scattering data using three different choices of experimental composition coordinate. For each system, the ZC values became independent of composition choice when the nonanalytic complete scaling coefficients D2, found from fitting the coexistence curves, were incorporated into the analyses of the light scattering data through a transformation of the experimental composition coordinate. In addition, divergent wetting layer formation at the liquid/vapor interface on the nitrobenzene-rich side of the coexistence curve was observed in all three systems. After making the complete scaling correction to the composition coordinate, the growth behaviors of the wetting layers were identical to each other and to those seen in other systems. Values of the critical mole fraction xC, the critical temperature TC, and the complete scaling field mixing coefficient a1 for the three systems are reported and compared with the literature.