Viscosity of Molten Rare Earth Metal Trichlorides I. CeCl3, NdCl3, SmCl3, DyCl3 and ErCl3

Knowledge of the viscosity of rare earth halides is important for the electrolytic production and separation of the rare earth elements [1 – 3]. However, essential difference is observed between the viscosity values of the same molten rare earth salts obtained experimentally by various researchers. As a rule, the viscosity of their halides was measured with reliable experimental methods checked repeatedly on studying other molten salts. In our opinion, there are two main reasons for the discrepancies in the results of the viscosity measurements. The first is inadequate dehydration of the salts, resulting in the formation of oxyhalide impurities. The second is a not sufficiently inert gas atmosphere over the salts during handling or measurements, leading to the same effects, especially at higher temperatures. In this study, the kinematic viscosity of molten CeCl3, NdCl3, SmCl3, DyCl3 and ErCl3 was measured, using a capillary viscometer made of quartz and a transparent electric furnace. The dynamic viscosity (η) has been calculated from the measured kinematic viscosity (ν) and density data taken from the literature.