Densities of a dissolving mixture of molten (AgI + NaCl)

• The density in the 0.5 AgI + 0.5 NaCl melt is measured as a function of the temperature.
• The system is biphasic between the melting point and 1063.5 K.
• The densities for the coexisting phases converge when the temperature increases.
• The temperature coefficient of the reduced density difference is lower than that for the alkali halide melts.

The densities of a molten mixture of (0.5 AgI + 0.5 NaCl) were measured along the saturation line over a wide temperature range by the hydrostatic weight method to establish the peculiarities of the mixing of salts with different chemical bonds. We showed that the difference between the magnitudes of the densities for the coexisting phases decreases with increasing temperature and becomes equal to zero at 1063.5 K. This temperature corresponds to the critical phase transition point, Tc. The temperature dependence of the difference in densities, Δρ, is described by equation Δρ/ρc ≈ Tc-TTcβ, where ρc is the density at Tc. The index β = 0.476 occurs at a lower value than that found for alkali halide melts (β = 0.52) where long-range Coulombic forces between ions prevail.