Coexistence curves for binary liquid mixtures of {x(CHCOOC2H5)(2) + (1 - x)CH3(CH2)(7)CH3} have been determined by measurement of the refractive index. The experimental results have been used in the determination of the critical exponent beta and the critical amplitude B, and the study of the diameters of the coexistence curves. The values of the critical exponent beta 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 exponents r and b in the relations (1 - phi(c))/phi(c) proportional to M-r and B(phi)phi(c)(-1.865) proportional to M-b, where phi(c) is 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. (C) 1998 Academic Press.