<Original Papers>On the Densities of Binary Molten Salts of Lithium Fluoride-Magnesium Fluoride and Lithium Fluoride-Sodium Chloride Systems

The densities of the binary molten salts of LiF-MgF_2 and LiF-NaCl systems were measured by "the double bob method" based on the Archimedes\u27 principle. 1) The densities of the molten salts in the LiF-MgF_2 binary system of an eutectic type having the solid solution on each side were measured in the composition range of 0～40 mol % MgF_2. Measured densities increased gradually with the increase in MgF_2 content. 2) The densities of the molten salts in the Lit-NaCl binary system of a simple eutectic type were measured in the whole composition range. Measured densities decreased gradually with the increase in NaCl content. 3) The molar volume isotherms were calculated for both of the systems, and the validity of the law of additivity of molar volumes was confirmed. 4) These results were analogous to those obtained for several binary fluoride systems containing LiF studied previously. It was assumed that the molar volume isotherms would be linear for lithium fluoride-alkali or alkaline earth fluoride (including sodium chloride) binary systems. 5) The fluoride and the chloride of lithium and sodium is reported to form a reciprocal system, Li, Na/F, Cl. By the X-ray diffraction analysis, the salt pair of LiF+NaCl was confirmed to be more stable than the salt pair of LiCl+NaF