RECENT EXPERIMENTAL WORK ON SOLUTE REDISTRIBUTION AT THE ICE/WATER INTERFACE. IMPLICATIONS FOR ELECTRICAL PROPERTIES AND INTERFACE PROCESSES

Abstract

Redistribution of NaF, HC1, NaC1, NH4F, and AFGP at the ice/water interface have been investigated under near-equilibrium constrained growth conditions. The distribution coefficient of NaF-declined from 2 x 10 (at 1 0 9 initial liquid concentration) to 3 x (at 10 N). By contrast, the distribution coefficient of the two chlorides was 3 x and invariant wirh initial liquid concentrations in the range 5 x N to 5 x 10'~ N. At 10 N concentration of the mother solution, the distribution coefficient of NH,F was found to be strongly pH dependent. AFGP is the most highly soluble of known impurities in ice, with a distribution coefficient close to unity. In unstirred solutions, traces of AFGP in the mother solution caused an increase in the distribution coefficient of HC1 due to instabilities in the flux fields of heat and solute. We report on new measurements of redistribution of trace amounts of ionic solutes (NaF, HC1, NaC1, NH4F) and of AFGP (antifreeze glycoprotein) at the ice/water interface under near-equilibrium conditions of phase transformation. Concentration dependence of the distribution coefficient was of primary concern because it reflects solute interactions with the ice lattice, such as formation of point defects [I], microstructures [ 2 ] , dislocations [3], and vacancies [ 4 ] . Conductivity and dielectric relaxation spectrum of ice are controlled by these phenomena 151.