Various Aqueous Solutions Crystallizing from the Side

Abstract

Crystallization of a solution or melt at a side boundary can lead to vertical differentiation of the liquid. Residual fluid from crystallization flows up the solidifying wall in a compositional boundary layer and, when ejected into the environment, stratifies the liquid. The nature and extent of the stratification depends on the structure of the boundary layer which in turn depends on the morphology of the crystal-liquid interface.

A series of experiments using five different chemicals in aqueous solutions was carried out to investigate the influence of increasing interface roughness on the rate and shape of the stratification. It was found that a rough interface enhanced the crystal growth over a smooth one and that the stratification rate increased with the roughness. All the rough interfaces produced a stratification with the same characteristic shape: a steepening compositional gradient in the direction of flow of the boundary layer. One chemical, which formed a porous interface, produced a qualitatively different stratification.