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ZIRCONIUM

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Originally appearing in Volume V28, Page 991 of the 1911 Encyclopedia Britannica.
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ZIRCONIUM [See also:

symbol Zr, atomic See also:weight 9o•6 (0=16)1, a metallic chemical See also:element. See also:Klaproth in 1789 analysed the See also:mineral See also:zircon or See also:hyacinth and found it to contain a new See also:earth, which he called " zirconia." The See also:metal was obtained by See also:Berzelius as an See also:iron-See also:grey See also:powder by See also:heating See also:potassium zirconofluoride with metallic potassium. The amorphous metal also results when the chloride is heated with See also:sodium; the See also:oxide reduced with See also:magnesium; or when fused potassium zirconofluoride is electrolysed (Wedekind, Zeit. Elektrochem., 1904, 10, p. 331). Troost produced crystallized zirconium by fusing the See also:double fluoride with See also:aluminium in a See also:graphite crucible at the temperature of melting iron, and extracting the aluminium from the melt with hydrochloric See also:acid. It is more conveniently prepared by heating the oxide with See also:carbon in the electric See also:furnace. The crystals look like See also:antimony, and are brittle, and so hard as to scratch See also:glass and rubies; their specific gravity is 4.25. The powdery metal See also:burns readily in See also:air; the crystalline metal re-quires to be heated in an oxyhydrogen See also:flame before it catches See also:fire. Mineral acids generally attack the crystallized metal very little even in the See also:heat; aqua regia, however, dissolves it readily, and so does hydrofluoric acid. In its chemical See also:affinities zirconium resembles See also:titanium, See also:cerium and See also:thorium; it occurs in See also:company with these elements, and is tetravalent in its more important salts. Zirconium oxide or zirconia, ZrO2, has become important since its application to the manufacture of mantles for incandescent See also:gas-See also:lighting.

For its extraction from zircon the mineral is heated and quenched in See also:

water to render it brittle, and then reduced to a See also:fine powder, which is fused with three to four parts of acid potassium fluoride in a See also:platinum crucible. When the See also:mass is quietly fusing, the crucible is heated for two See also:hours in a See also:wind-furnace. The See also:porcelain-like melt is powdered, boiled with water, and acidified with hydrofluoric acid, and the residual potassium fluosilicate is filtered off. The filtrate on cooling deposits crystals of potassium zirconofluoride, K2ZrFs, which are purified by See also:crystallization from hot water. The double fluoride is decomposed with hot concentrated sulphuric acid; the mixed sulphate is dissolved in water; and the zirconia is precipitated with See also:ammonia in the See also:cold. The precipitate, being difficult to See also:wash, is (after a preliminary washing) re-dissolved in hydrochloric acid and re-precipitated with ammonia. Zirconium hydroxide, Zr(OH)4, as thus obtained, is quite appreciably soluble in water and easily in mineral acids, with formation of zirconium salts, e.g. ZrC14. But, if the hydroxide is precipitated in the heat, it demands concentrated acids for its See also:solution. The hydroxide readily loses its water at a dull red heat and passes into anhydride with vivid incandescence. Zirconia can be obtained crystalline, in a See also:form isomorphous with cassiterite and See also:rutile, by fusing the amorphous modification with See also:borax, and dissolving out with sulphuric acid. The anhydrous oxide is with difficulty soluble even in hydrofluoric acid; but a mixture of two parts of concentrated sulphuric acid and one of water dissolves it on continued heating as the sulphate, Zr(504)2• Zirconia, when heated to whiteness, remains unfused, and radiates a fine See also:white See also:light, which suggested its utilization for making incandescent gas mantles; and, in the form of disks, as a substitute for the See also:lime-cylinders ordinarily employed in " limelight." Zirconia, like stannic and titanic oxides, unites not only with acids but also with basic oxides.

For instance, if it be fused with sodium carbonate, sodium zirconate, Na2ZrO3, is formed. If the carbonate be in excess, the See also:

salt Na4ZrO4 results, which when treated with water gives Na2Zr301 • 12H20, which crystallizes in hexagonal plates. When heated in a loosely covered crucible with magnesium the nitride Zr2N3 is formed (Wedekind, Zeit. anorg. Chem., 1905, 45, p. 385). Zirconium hydride, ZrH2, is supposed to be formed when zirconia is heated with magnesium in an See also:atmosphere of See also:hydrogen. Zirconium fluoride, ZrF4, is obtained as glittering See also:monoclinic tables (with 3H20) by heating zirconia with acid ammonium fluoride. It forms double salts, named zircono-fluorides, which are isomorphous with the stanni- and titani-fluorides. Zirconium chloride, ZrCla, is pre-pared as a white sublimate by igniting a mixture of zirconia and See also:charcoal in a current of See also:chlorine. It has the exact vapour-See also:density corresponding to the See also:formula. It dissolves in water with See also:evolution of heat; on evaporation a basic salt, ZrOCl2.8H20, separates out in See also:star-shaped acicular aggregates. Zirconium bromide, ZrBr4, is formed similarly to the chloride.

Water gives the oxybromide ZrOBr2. Zirconium iodide, ZrI4, was obtained as a yellow, micro-crystalline solid by acting with hydriodic acid on heated zirconium (Wedekind, See also:

Bee., 1904, 37, p. 1135). It fumes in air; with water it gives ZrOI2.8H20; and with See also:alcohol See also:ethyl iodide and zirconium hydroxide are formed. The iodide combines with liquid ammonia to form ZrI4.8NH3; and with See also:ether to give Zr14.4(C2H5)2O. Zirconium combines with See also:sulphur to form a sulphide, and with carbon to form several carbides. The sulphate, Zr(SO4)2, is a white mass obtained by dissolving the oxide or hydroxide in sulphuric acid, evaporating and heating the mass to nearly a red heat. Since it forms a See also:series of double sulphates, Ruer (Zeit. anorg. Chem., 1904, 42, p. 87) regards it as a dibasic acid, ZrOSO4•SO4H2, and that the crystalline sulphate is ZrOSO4•SO4H2.3H20 (not Zr(SO4)2.4H20). Zirconium also forms double sulphates of the type Zr203(SO4M)2•nH2O, where M=K, Rb, Cs, and n=8 for K, 15 for Rb, 11 for Cs (See also:Rosenheim and See also:Frank, Be,'., 1905, 38, p. 812).

The atomic weight was determined by See also:

Marignac to be 90.03; See also:Bailey (Prot. See also:Roy. See also:Soc., 189o, 46, p. 74) deduced the value 89.95.

End of Article: ZIRCONIUM

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