Structure of the MF-AlF3-Al2O3 (M = Li, Na, K) melts

Direct oxygen determination of MF-AlF3-Al2O3 (M = Li, Na, K) melts in depen dence on cryolite ratio and alumina content was performed using the LECO TC -436 Nitrogen/Oxygen analyzer. On the basis of the obtained results the dis tribution of individual oxyfluoroaluminate species was obtained. The result s have confirmed that in low alumina containing melts Al2OF62- and Al3O3F63 - species are present, while at higher alumina content: the Al2OF42- specie s become dominating. When the melt becomes more acidic the content of the A l2O2F42- species increases, while that of Al2OF62- decreases. In high alumi na melts of the KF-AlF3-Al2O3 system also the Al3O4F43- species are suggest ed. The results are in agreement with a recent Raman spectroscopic study.