The Workman-Reynolds effect and ionic transfer processes at the ice-solution interface

Abstract

Dilute solutions (2.5×10−4 M) of potassium fluoride, cesium fluoride, and lithium iodide were frozen at rates from approximately 1 to 20 μ/sec. A chemical analysis of the melted ice and of the supernatant liquid was made, and the electrical potentials or currents generated were measured. During the freezing, ionic transfer processes take place at the ice-solution interface which are a function of ionic species present, their concentration, and the freezing rate. These processes are ionic rejection and incorporation, ionic separation, and ionic neutralization. In all three solutions, the anion is incorporated in greater numbers than the cation, regardless of the relative ionic sizes. The difference between incorporated halogen anions and incorporated alkali cations is made up with hydrogen ions, supplied either from the freezing base (shunt case) or from the liquid (open-circuit case) or both. The relation between the rates of freezing and of ionic transfer determines the extent of this replacement. Ice samples grown from potassium- and cesium-fluoride solutions with a low-resistance external shunt show a direct-current conductivity on the average about four times greater than samples grown without a shunt. Trace impurities, growth rate, and phase-boundary conditions during growth are determining factors of the electrical bulk properties of ice.