Equilibration in a gravitational field near the critical consolute point

Abstract

Abstract The evolution of the concentration profile in a gravitational field near the critical consolute point is studied by refractive index measurements. The dependencies of the relaxation time on the distance to the critical level and temperature change are obtained. The decreasing of equilibration time for refractive index gradient is observed, while the critical level is approached. This result contradicts with well-known “critical slowing down” due to vanishing of diffusivity coefficient at the critical consolute point. The proposed theoretical interpretation of this phenomena is based on key role of the critical layer with the highest concentration gradient and its width in gravitational field. The decreasing of the width of critical layer results in speeding up of equilibration in the nearest vicinity of the critical point. The quantitative agreement of relaxation time dependencies with this theoretical analysis is found.