Zirconium, symbol Zr, metallic element with an atomic
number of 40. Zirconium is one of the transition elements
of the periodic table.
Properties and Occurrence
In its pure state zirconium exists in two forms: the
crystalline form, a soft, white, ductile metal; and the amorphous form, a
bluish-black powder. Both forms are insoluble in water, slightly soluble
in alcohol, and completely soluble in hydrofluoric acid. The metal burns
in air at 500° C (932° F).
Zirconium ranks 18th in abundance among the elements in
the crust of the earth. Zirconium melts at about 1852° C (about 3362° F),
boils at about 4377° C (about 7911° F), the atomic weight the element is
91.22.
Zirconium is never found free in nature; it occurs chiefly
as a silicate in the mineral zircon
and as an oxide in the mineral baddeleyite, which is found in commercial
quantities in Brazil. Zirconium ores also contain the element hafnium,
a metal with properties similar to those of zirconium.
