Thermodynamic properties of thulium and ytterbium in fused NaCl–KCl–CsCl eutectic

This work presents the results of a study of the Tm3+/Tm2+ and Yb3+/Yb2+ couple redox potentials vs. Cl–/Cl2 reference electrode at the temperature range (823 to 973) K in fused NaCl–KCl–CsCl eutectic by direct potentiometric method. Initial concentrations of TmCl3 and YbCl3 in solvents did not exceed 5.0 mol%. Basic thermodynamic properties of the reactions TmCl2(l) + ½ Cl2(g) ⇔ TmCl3(l) and YbCl2(l) + ½ Cl2(g) ⇔ YbCl3(l) were calculated using the temperature dependencies of apparent standard potentials of the couples ETm3+/Tm2+∗ and EYb3+/Yb2+∗.

Research highlights
► Tm and Yb chloride compounds as fission products.
► The investigation of electrochemical properties of lanthanides.
► Determination of the apparent standard redox potentials of the couple Ln(III)/Ln(II) in fused NaCl–KCl–CsCl eutectic at (823 to 973) K.
► The calculation of the basic thermodynamic properties of redox reaction in molten salt.