The thermal behaviour of the water-vein system in polycrystalline ice

Abstract

AbstractExperimental studies are reported concerning the thermal behaviour of the water-vein system in ice grown in the laboratory from dilute solutions. The temperature versus vein-size behaviour of these samples is determined. The measurements show that the solute, which is concentrated in the veins, remains in the liquid phase during a temperature change. The mass of the solute per unit length of veinMis found to be of the order ofM≈ 10−8mol m−1for samples grown from singly-distilled water.Mis seen to vary with temperature only because of the volume expansion (contraction) on freezing (melting) which causes the liquid to flow along the veins. The effect of these flows on the sample is studied. They are found to provide a mechanism for the transport of impurities along the veins and to and from the sample surface. Samples grown from doubly-distilled water doped with small amounts of NaCl or H2SO4are studied and are found to display the same general behaviour. However,Mis an order of magnitude higher in the H2SO4-doped samples than in either the NaCl-doped samples or the samples grown from singly-distilled water. The approach to equilibrium of distortions in the vein-system geometry is studied. It is suggested that these distortions are due to variations inMalong the length of the veins and that equilibration is therefore governed by diffusion of the solutes.