Solid Solutions of Ice and NH4F and Their Dielectric Properties

Abstract

The solidus curve for the system H₂O–NH₄F was partly determined by means of chemical analyses, heating curves and a dilatometric method, and partly estimated from the liquidus curve using a thermodynamic relation. The solubility limit thus estimated is roughly 10%. The dielectric relaxation times, τ, of solid solutions of ice containing 0.002 to 10 weight percent NH₄F were measured at temperatures of about —60° to —10°C. The activation energies for dipole rotation were only about 4 kcal/mole as compared with 13 kcal/mole in pure ice. At low concentrations the frequency factor increases with increasing concentration of NH₄F. At high concentrations of NH₄F this trend is reversed.