NaF-NaCl-BaCl₂-AlF₃系溶融塩の密度と融点について

アルミニウムの電解精製に関する研究 (第10報)

抄録

It is reported that the Gadeau's bath (molten salts of sodium fluoride-barium fluoride-aluminum fluoride system) is more suitable for the aluminum refining when a small amount of sodium chloride is added.
In this paper, the densities and the melting temperatures of some compositions of the quaternary molten salts, sodium fluoride-sodium chloride-barium chloride-aluminum fluoride system, were determined.
(1) The values of the densities of this quaternary system ranged 2.2-2.5g/cc at 800°C. These values decreased with the increase in the content of sodium chloride and increased with the increase of the content of barium chloride.
When the contents of sodium chloride and barium chloride are kept constant, the maximum density is observed at the point where the mole ratio of sodium fluoride to aluminum fluoride corresponds to 3: 1 (3NaFE·AlF₃).
(2) In this quaternary system, assuming the additivity of the density to be applicable and the following displacement
NaF+BaCl₂=NaCl+BaFCl
to occur in the melt, it seems that the calculated densities are accord well with the measured ones.
(3) Isothermal liquidus line of this quaternary system has a likeness to that of sodium fluoride-barium chloride-aluminum fluoride ternary system when the content of sodium chloride is kept constant, but the melting temperatures are lower than the latter on the whole.
And the melting temperatures of some composition ranges are about 650°C.
(4) It is preferred that when this quaternary molten salts are used as an electrolyte of aluminum refining, the contents of sodium chloride must be less than 10% as far as densities are concerned.