Introduction in the band theory of molten salts

The electrochemical properties of molten salts are considered in the frame of band theory for ideal crystalline dielectrics. It turned out that metal impurities at low concentration in them generate the local electron levels in the wide band gap (>4 eV) of molten salt divided by 50 meV and more. They are occupied by electrons when Fermi level is approached to them from below. Then, the minor metal impurities fall out the molten salt when the electron occupation of their energy levels in the band gap achieves their solubility (<0.1 ppm) in the molten salt. At the same time, the given RedOx-potential of molten salt can be maintained without chemical additives but forced shifting of Fermi level by the electrochemical cell with one electrode strongly polarized and the other in equilibrium with this molten salt.