Light scattering studies of phase separation in isobutyric acid + water mixtures

Abstract

Measurements are reported of light scattering by isobutyric acid + water mixtures that have been quenched into the two‐phase region by a pressure‐jump technique. The conditions of the jump method are discussed in detail. Examples are given of the behavior of the scattered intensity I (k,t) as a function of the time t and scattering vector k. Power‐law expressions of the form k m =A′t −a ′ are found to represent the time dependence of the angle of maximum scattering. The intensity at the maximum can be represented by power laws as well: I (k m ) =A ″ t a ″. For mixtures of the critical composition both a′ and a ″ depend on quench depth; for other mixtures a′?0.3 and a ″?1.1. Two measurements made at the cloud point show an initial t 2 growth in I (k m ) followed by a slower growth ∝t 1/2.