The measurement of coexistence curves for {x(CHCOOC2H5)2+(1−x) CH3(CH2)7CH3} in the critical region

Abstract

Coexistence curves for binary liquid mixtures of {x(CHCOOC2H5)2+(1−x)CH3(CH2)7CH3} have been determined by measurement of the refractive index. The experimental results have been used in the determination of the critical exponent β and the critical amplitudeB, and the study of the diameters of the coexistence curves. The values of the critical exponent β are found to be consistent with theoretical predictions. The coexistence curves have been successfully described by a combination of the Wegner equation and the expression for the diameter. The exponentsrandbin the relations (1−φc)/φc∝M−randBφφ−1.865c∝M−b, where φcis the critical volume fraction of (CHCOOC2H5)2, have been found to be (0.42±0.01) and (0.31±0.04), respectively, consistent with observations from experimental studies for other chain-molecule solution systems, and support the Landau–Ginsburg–Wilson type model we proposed recently.