Lutetium: Fluoride Reduced by Calcium in Tantalum under Argon, Remelted under Half an Atmosphere of Argon (Spedding and Daane, 1954)

How Ames Laboratory first made lutetium metal. Calcium takes the fluorine from lutetium fluoride at high heat in a tantalum crucible under argon, leaving the metal under a slag of calcium fluoride. It is then remelted to drive off the leftover calcium, under half an atmosphere of argon because lutetium itself evaporates at its melting point. Result: lutetium metal holding less than 150 ppm calcium. The paper puts lutetium's melting point at about 1650-1750 °C. Source: F. H. Spedding and A. H. Daane, The Rare Earth Metals, Journal of Metals 6 (1954), pp. 504-507: lutetium was reduced under the same conditions the paper gives for yttrium. Not given: the lutetium charge and calcium excess, heating times, and how the 1550 °C of the yttrium run was matched to lutetium's higher melting point. Picture: Wikimedia Commons.