REFRACTOMETRY OF WATER-ETHANOL SOLUTIONS NEAR THEIR CONTRACTION POINT

The concentration dependences of the refractive index in aqueous ethanol solutions at equilibrium have been studied experimentally. Special attention was paid to their behavior in a vicinity of the peculiar point defined as the intersection point of the concentration dependences of the contraction measured at different temperatures or as a point, at which the intensity of molecular light scattering has a maximum. The refractive index is found to noticeably deviate from its reference values in a vicinity of the peculiar point, 0.05 < x < 0.1 (x is the mole fraction of ethanol). This effect reflects the fact that the equilibrium properties of the solutions concerned are established only during a few weeks. Arguments that the system becomes microinhomogeneous in this concentration interval are presented.