Redox reactions in molten electrolytes containing chlorides of rare-earth metals

Solutions of rare-earth metals (REM, Ln) in molten chlorides, including mixtures MCl + LnCl₃, where M stands for an alkali metal, are studied by methods of potentiometry, voltammetry, and conductimetry in broad intervals of concentration and temperature. The results that had been obtained give sufficiently comprehensive and reliable enough information concerning the valence state of rare-earth metals, as well as the structure and composition of complex ions that make a substantial impact on the properties of electrolytes. It is demonstrated that the co-existence of ions of rare-earth metals in different oxidation states, which form as a result of possible redox reactions 2Ln³⁺ + Ln ? 3Ln²⁺, Ln²⁺ + Ln ? 2Ln⁺, and nM⁺ + Ln ? nM + Lnⁿ⁺, clearly manifests itself in the thermodynamic and transport properties of molten systems Ln-LnCl₃ and Ln-LnCl₃-MCl.