Zirconium
. Zirconium, symbol Zr, metallic element with an atomic number of 40. Zirconium is one of the transition elements of the periodic table . The element was discovered in 1789 by the German chemist Martin Heinrich Klaproth and isolated 1824 by the Swedish chemist Baron Jöns Jacob Berzelius . 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 qua