Interaction between Lead Difluoride and LiF-BeF2 Melt

The equilibrium of the Pb2+/Pb0 pair in the LiF-BeF2 melt was studied by the potentiometric method depending on the temperature and lead fluoride concentrations. The empiric equations of isotherms and polytherms of lead equilibrium potentials have been obtained. The cathode polarization of lead fluoride in the molten mixture of lithium and beryllium fluorides was measured by the method of current switch-off from the stationary state. Within the studied temperature and lead fluoride concentration ranges lead ions were found to have a predominantly two-valence state in the LiF-BeF2 electrolyte. The experimentally obtained values of the lead electrode equilibrium potentials in the LiF-BeF2-PbF2 melt were used to calculated the standard lead potentials in the molten lithium and beryllium fluoride mixture relative to the fluorine reference electrode. Conditional standard values of Gibbs energy changes, enthalpy and entropy were determined at the formation of lead difluoride from the elements in the form of dilute solutions with the 0.66LiF-0.34BeF2 melt.