AN ELECTROMOTIVE FORCE STUDY OF MOLTEN LITHIUM FLUORIDE-BERYLLIUM FLUORIDE SOLUTIONS

The potential of the cell [formula ommitted] was measured over a composition range of 0.30-0.90 mol fraction of BeF2 and a temperature range of 500-900°. cell potential was related to the activity of BeF2 in the solutions by [formula ommitted] activity coefficients could be derived for BeF2 (and by a Gibbs-Duhem integration for LiF). Usefully accurate measurements could not be made with pure BeF2 in the cell; hence values of E° were calculated using values for αBeF derived from the phase diagram and a previously reported heat of fusion (1.13 kcal/mol) giving E° = 2.4430. 0.0007952 V. This comparison of the emf data with the LiF-BeF2 phase diagram also indicated that the heat of fusion for BeF2 is <2.0 kcal/ mol. A power series in xLAF was assumed for log γBeF and the coefficients were determined by a least-squares fit to the data. This gave [formula ommitted] Formation free energies and heats for BeF2 and BeO were also calculated by combining the results of the present study with available thermochemical data. The Be2+∣Be0 and HF, H2∣F- electrodes performed acceptably for use as reference electrodes, both being stable and reproducible. © 1969, American Chemical Society. All rights reserved.