Density of LiCl-NaCl-AlCl₃ Ternary Melt

Abstract

Density of LiCl-NaCl-AlCl₃ ternary melt has been measured over the composition range of less than 50 mol%AlCl₃ and the temperature range of 800∼1200 K by means of the manometric method using a special electric furnace whose inside can be seen through. The results obtained are summarized as follows :
The density of the ternary melt was expressed as a function of temperature and composition on the basis of the data measured. The density decreases with an increase in LiCl or AlCl₃ content, and the degree of the decrease depends largely on the change in AlCl₃ rather than LiCl content.
The ternary melt of the composition range of less than 50 mol%AlCl₃ was regarded as a reciprocal melt of (Li⁺,Na || Cl⁻,AlCl₄⁻) because most of the aluminum chloride exists as AlCl₄⁻ anionic species in this composition range. The molar volume and the expansion coefficient of the reciprocal melt, and the partial molar volumes of the compounds LiC1, NaCl, LiAlCl₄, NaAlCl₄ were calculated. The molar volume increases with an increase in either the cationic fraction of Na⁺ or the anionic fraction of AlCl₄⁻. The expansion coefficient depends on the anionic fraction rather than the cationic fraction. The partial molar volume of each compound slightly increases with the change of the cationic fraction, and decreases with the change of the anionic fraction.
These results could be explained in terms of the size and the electrical charge density of ionic species and the hole volume of the compounds.