9470. Titanium

Nomenclature

CAS number: 7440-32-6

Description and references

Ti; at. wt 47.867; at. no. 22; valence 2, 3, 4 (mostly tetravalent). Group IVB (4). Five naturally occurring isotopes (mass numbers): 48 (73.94%); 46 (7.93%); 47 (7.28%); 49 (5.51%); 50 (5.34%). Artificial isotopes: 43-45; 51. Ninth most abundant element in earth's crust; 0.63% by wt. Occurs as the oxide in the minerals rutile, ilmenite, perovskite, anatase, or octahedrite and brookite; other minerals include sphene or titanite (CaTiSiO5) and benitoite (BaTiSi3O9). Discovered by Gregor in 1789; investigated and named by Klaproth in 1795; isolated by Berzelius in 1825. Prepn: de Boer, Ind. Eng. Chem. 19, 1256 (1927); Fast, Z. Anorg. Chem. 241, 42 (1939); Ehrlich in Handbook of Preparative Inorganic Chemistry vol. 2, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) pp 1161-1172. Reviews: Gmelins, Titanium (8th ed.) 41 (1951); Everhart, Titanium and Titanium Alloys (Reinhold, New York, 1954); Brophy et al., Titanium Bibliography 1900-1951 + suppl (Washington, 1954); McQuillan & McQuillan, Titanium (Butterworth's, London, 1956); Barksdale, Titanium, Its Occurrence, Chemistry and Technology (Ronald Press, New York, 2nd ed, 1966); Clark, “Titanium” in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 355-417.

Properties

Dark gray, lustrous metal. Dimorphic; α-form: hexagonal structure below 882.5°; β-form: body-centered cubic crystals above 882.5°. Brittle when cold; malleable when hot. Ductile only when free of oxygen; traces of oxygen or nitrogen increase strength. mp 1677°. bp 3277°. Calculated d (α- form): 4.506 (25°); (β-form): 4.400 (900°). Specific heat (25°): 5.98 cal/g-atom/°C. Decomposes steam at 700-800°. Combines with oxygen at a red heat. Can burn in an atm of oxygen under certain conditions: Chem. Eng. News 36, 36 (Aug. 4, 1958). Attacked by acids only on heating; oxidized by nitric acid to the dioxide. Reacts with fluorine at 150°, with chlorine at 300°, with bromine at 360°, with iodine above 360°. Combines with nitrogen at 800°. Forms alloys with aluminum, chromium, cobalt, copper, iron, lead, nickel, tin.

Use

As alloy with copper and iron in titanium bronze; as addition to steel to impart great tensile strength; to aluminum to impart resistance to attack by salt solns and by organic acids; to remove traces of oxygen and nitrogen from incandescent lamps. Surgical aid (fracture fixation).