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Webster 1913 Edition
hafnium
haf′ni-um
(hăf′nē-ŭm or häf′nē-ŭm)
, Noun.
A metallic element of atomic number 72 present together with zirconium to the extent of 1% to 5% in zirconium minerals. It is a poisonous, ductile metal with a brilliant silver luster, has an atomic weight of 178.49, and has a high melting point (2227° C). It is used in nuclear reactors, and incandescent lamps as a scavenger of oxygen and nitrogen. See also
norium
.