Densities and Volume Properties of the Melts of the Systems (LiF + NaF)_eut + SmF₃, (LiF + NaF)_eut + GdF₃, and (LiF + NaF)_eut + NdF₃

Based on the experimentally measured data of density (determined by the Archimedean method) of the systems (LiF (1) + NaF (2))eut + x LnF3 (3) (LnF3 = SmF3, GdF3, and NdF3; x = 0.0000–0.2500), molar volumes and partial molar volumes were calculated. Molar volumes of all three systems increase with increasing LnF3 concentration without any local extremes. The partial molar volumes of LnF3 were obtained by using two different approaches─simple polynomial regression analysis and multicomponent polynomial regression in the form of the Redlich–Kister equation. Values of the partial molar volumes of LnF3 in (LiF + NaF)eut at infinite dilution are positive and as high as V¯m,NdF3°,1073K=37.61cm3·mol−1, V¯m,SmF3°,1073K=30.55cm3·mol−1, and V¯m,GdF3°,1073K=22.19cm3·mol−1, all of them indicating volume expansion in the investigated systems. This volume expansion decreases with increasing proton number of investigated LnF3 and is generally higher at lower temperatures.