Density and viscosity of several molten fluoride mixtures

Using a dilatometric method, densities were determined for the following molten salts: LiF-- BeF/sub 2/ (66-34 mole%), LiF-- BeF/sub 2/-ThF/sub 4/ (70.1-- 23.9--6.0, 70--18--12, 70--15--15 mole%), LiF--BeF/sub 2/-ZrF/sub 4/ (64.7--30.1-- 5.2 mole%), LiF--BeF/sub 2/--ZrF/sub 4/--UF/sub 4/ (64.7 For the fluorides, molar volumes obtained from the density meaaurements agreed within 2% with volumes calculated from additive contributions of the components. The expansivities of three LiF-BeF/sub 2/-- ThF/sub 4/ mixtures were practically identical, 2.5 x 10/ sup -4// EC. Density--temperature curves from 25 to 700 deg C for LiF--BeF/sub 2/ -ThF/sub 4/ (72--16--12 mole%) and for NaBF/sub 4/--NaF (92--8 mole %) were derived from room-temperature pycnometric determinations and from estimated expansivities of the solid salts. Viscosities of three salt mixtures were determined by oscillating-cup methods: mole%) and NaBF/sub 4/--NaF (92--8 mole%). The viscosities of the LiF--BeF/sub 2/-ThF/sub 4/ melts were analogous to viscosities of similar mixtures containing UF/sub 4/ instead of ThF/sub 4/. (auth)