ZERO-POINT POTENTIALS OF METALS IN MOLTEN ALKALI-HALIDES AND THEIR BINARY-MIXTURES

The zero-point potentials of liquid bismuth, lead, and indium in molten alkali halides and their binary mixtures were determined by electrocapillary-curve method, using the same led reference electrode. They are found to grow more electropositive as temperature and alkali cation radii increase and those of halide anions decrease. Such dependence is supposed to be caused by the changing of work function as a result of capturing the emitted electrons by alkali cations and of the existence of the potential jumps to which the dipoles induced by the cations on the halide anions give rise on the interface metal/salt melt. The zero-point potential of bismuth in the binary molten mixtures with common halide anions is shown to reach the values characteristic of the heavier components when their contents in the mixtures amount to about 40 mol% and to remain nearly constant by the further increase of their concentration.s But in the mixtures with common alkali cations the zero-point potential changes fairly monotonously by substituting one halide anion for another. The difference in behaviour of these two groups of the binary mixtures gives evidence that in the molten alkali halides and their mixtures most of the halides anions are bound by the cations in (auto)complexes or associates whereas most of the alkali cations remain relatively loose among them. © 1979.