n. Symbol Hf A brilliant, silvery, metallic element separated from ores of zirconium and used in nuclear reactor control rods, as a getter for oxygen and nitrogen, and in tungsten filament alloys. Atomic number 72; atomic weight 178.49; melting point 2,233°C; boiling point 4,603°C; specific gravity 13.31; valence 4. See Periodic Table. [After Hafnia, Medieval Latin name for Copenhagen, Denmark.] |
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