THE DENSITY AND SURFACE TENSION OF MOLTEN FLUORIDES

Abstract The densities and surface tensions of the liquid eutectics KF-NaF, NaF-LiF, NaF-LiF-CaF 2 and KF-NaF-LiF, the system KF-LiF (0–100 per cent KF) and the ternary system KF-LiF (eutectic composition) containing 0—80 mole per cent ZrF 4 have been measured over a temperature range from just above the liquidus to about 900°C. The plots of surface tension versus temperatures are in all cases linear, d γ/ d T being negative as is customary. Plots of surface tension vs. logarithm of composition, while smooth in alkali fluoride systems, show discontinuities in the ZrF 4 -containing melts. The existence and stoichiometry of complex compounds in the liquid were inferred from the compositions at which these discontinuities occurred. Calculations of surface content and of excess surface heat content were made but structural conclusions could not be derived from the latter.