NaF-BaCl₂2元系溶融塩の反応について

アルミニウムの電解精製に関する研究 (第8報)

抄録

Gadeau's bath, one of the electrolytes of the aluminum refining, is composed of the ternary molten salt mixtures of sodium fluoride, barium fluoride, and aluminum fluoride.
We have experimented the thermal analysis and the X-ray diffraction for the binary sodium fluoride-barium chloride system, which is one side of the above-mentioned ternary system, and discussed these, results applying the treatment of the reciprocal ternary system.
1) At first. we calculated the free energy change of the next reactions.
2NaF+ BaCl₂=2NaCl+ BaF₂ΔG°1000°C=-5kcal/mol (1)
NaF+ BaCl₂=NaCl+ BaFClΔG°1000°C -5kcal/mol (2)
As a result, we think that the displacement reaction (1) has priority to the reaction (2).
2) In the binary barium fluoride-barium chloride system, the composition of BaF₂ 45.8% (BaF₂: BaCl₂=1: 1 in mole ratio) shows the maximum melting temperature 1, 005°C, and this is assumed to be the melting point of the compound BaFCl (barium fluochloride) which is formed in this system
This binary system gives two minimum melting temperatures (e. g. 840°C at BaF₂ 13.6% and 930°C at BaF₂ 70%). The former is the eutectic temperature of BaCl₂-BaFCl system and the latter is that of BaFCl-BaF₂system.
3) As the results of the thermal analysis and X-ray diffraction, we concluded that the square of the Na, Ba/F, Cl reciprocal ternary system is divided into three triangles, i. e. NaF-BaF₂-BaFCl system, NaF-BaFCl-NaCl system and NaCl-BaFCl-BaCl₂system.
And then sodium fluoride-barium chloride system corresponds to the diagonal of the above-mentioned square, i. e. the pseudobinary system extending over three ternary systems.