Volumetric behavior of molten salts

• The molar volumes of molten 1:1 salts are additive in individual ionic molar volumes portable from one salt to another.
• Vacancies in the ionic quasi-lattices of 1:2, 1:3, and 2:1 molten salts need a different treatment.
• The expansibilities of molten salts are inversely proportional to their cohesive energies.

The molar volumes of molten salts, obtained from densities reported in the literature and compared at the corresponding temperatures 1.1Tm, are correlated with individual ionic properties. For symmetrical (1:1) salts individual ionic molar volumes can be deduced, but for unsymmetrical (1:2 and 2:1) salts the quasi-lattice vacancies preclude this, but relations with the ionic radii could be established. The expansibilities of the molten salts depend inversely on their cohesive energies, irrespective of the class of ions, provided they are highly ionic.

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