Electrical Conductivity and Density of Molten Cryolite with Additives

Abstract

The electrical conductivities at 1000°C, expressed as per cent of the cryolite value, for cryolite containing 10 weight per cent of the following substances are: sodium fluoride 112, calcium fluoride 96, aluminum fluoride 91, and alumina 83. For pure sodium fluoride at 1000°C, conductivity is 5.52 ohm−1cm−1, compared to 2.80 ohm−1cm−1 for cryolite. Molar conductance decreases linearly with mole per cent sodium fluoride, aluminum fluoride, alumina, or calcium fluoride addition to cryolite. The activation energy for conductance, calculated from a plot of the Arrhenius equation, is about 4.3 kcal/mole for the systems of cryolite with sodium fluoride, aluminum fluoride, and alumina, as well as for pure sodium fluoride, but is slightly higher for the cryolite‐calcium fluoride system. This value agrees reasonably with the 4.48 kcal/mole for pure chryolite. Densities in these systems change linearly with temperature, that for pure sodium fluoride following the equation . The stability of the complex is indicated by a density maximum.