Discovered | Name | Characteristics | Found | Prepared | Reactions | Uses | Minerals

Titanium is a transition metal in Group IVB and the 4th period. It has oxidation numbers ranging from 0 to +4, with +4 most common. Other members of the group are zirconium (Zr) and hafnium (Hf).

Titanium was discovered by William Gregor, an English clergyman, in 1791. Klaproth rediscovered titanium in 1795 and gave the new element its name. Impure titanium was first prepared by Nilson and Pettersson in 1887. The pure metal (99.9%) was not made until 1910 by Hunter by heating titanium tetrachloride with sodium in a steel bomb.

TiCl4(liq) + 4 Na(s) Ti(s) + 4 NaCl(s)

The name is derived from Latin, Titans, the first sons of the Earth according to mythology. The symbol Ti is an abbreviation of the name.

The element is the ninth most abundant in the earth's crust (and second in the transition element series). Titanium, when pure, is a lustrous, white metal. It has a low density, good strength, is easily fabricated, and has excellent corrosion resistance. It is ductile only when it is free of oxygen. In the solid state the metal has a hexagonal closest packed structure.

Titanium is almost always present in igneous rocks and in the sediments derived from them. It occurs in the minerals rutile or anatase (TiO2), ilmenite (FeTiO2), and sphene (CaTiSiO5), and is present in titanates and in many iron ores. Titanium is present in the ash of coal, in plants, and in the human body.

The metal was a laboratory curiosity until Kroll, in 1946, showed that titanium could be produced commercially by reducing titanium tetrachloride with magnesium. The metal cannot be produced by reduction of the dioxide, because titanium reacts with both oxygen and nitrogen at high temperatures.

One method of preparing the metal consists in passing chlorine over ilmenite or rutile, heated to redness with carbon.

TiO2(s) + 2 Cl2(g) + 2 C(s) TiCl4(g) + 2 CO(g)

Titanium tetrachloride, which is formed, is condensed, purified by fractional distillation, and then reduced with molten magnesium.

The metal burns in air and is the only element that burns in nitrogen. Titanium is resistant to dilute sulfuric and hydrochloric acid, most organic acids, moist chlorine gas, and chloride solutions. The metal combines with oxygen at red heat (To give TiO2), and with chlorine at 500°C (to give TiCl4). The metal is dimorphic, that is, the hexagonal form changes to the cubic form very slowly at about 880°C.

The metal is used to form alloys with other metals for use in medical applications, and aircraft parts.

Titanium is important as an alloying agent with aluminum, molybdenum, manganese, iron, and other metals. Alloys of titanium are principally used for aircraft and missiles where light weight, strength, and ability to withstand extremes of temperature are important. The metal has excellent resistance to sea water and is used for propeller shafts, rigging, and other parts of ships exposed to salt water. A titanium anode coated with platinum has been used to provide cathodic protection from corrosion by salt water.

The mineral rutile is titanium dioxide, TiO2. When pure, titanium dioxide is relatively clear and has an extremely high index of refraction with an optical dispersion higher than diamond. It is produced artificially for use as a gemstone, but it is relatively soft. Star sapphires and rubies exhibit their star-like inclusions as a result of the presence of titanium dioxide in aluminum oxide. Since TiO2 does not absorb visible light, is inert, and has good covering power, it has become the predominant white pigment around the world. It is used not only in paints but in paper coatings. (And it is used to mark the white lines on grass tennis courts and football fields.)

Titanium tetrachloride, a liquid, fumes in moist air forming titanium dioxide and hydrogen chloride and is used for smoke screens and in skywriting. It is an important catalyst in the polymerization of ethylene. Titanium esters, formed by the reaction of the tetrachloride with alcohols, are used as waterproofing agents on fabrics.