The measurements of coexistence curves and light scattering for 2,6-dimethypyridine + H2O in the critical region

The coexistence curves and light scattering data for the critical solution of 2,6-dimethypyridine (2,6-DMP) + H2O have been reported. The critical exponents β, γ, and ν have been deduced. The experimental results of the coexistence curves have also been analyzed to examine the Wegner correction terms and the behavior of the diameter of the coexistence curves. The light scattering data are well described by the crossover model proposed by Anisimov and Sengers, and the effective critical exponents γ and ν show nonmonotonic crossovers from the 3D-Ising values to the mean-field ones as the temperature departures from the critical point. Furthermore, as the distance from the critical point increases, the values of effective critical exponents of the refractive-index and the volume fraction decrease while that of the mole fraction increases, however after the regular terms are subtracted, the nonmonotonic crossovers from Ising to mean-field critical behavior are exhibited.