Titanium

Titanium is a transition metal , one of the elements found in Rows 4, 5, and 6 of the periodic table . It has an atomic number of 22, an atomic mass of 47.88, and a chemical symbol of Ti.

Properties

Titanium exists in two allotropic forms, one of which is a dark gray, shiny metal. The other allotrope is a dark gray amorphous powder. The metal has a melting point of 3,051°F (1,677°C), a boiling point of 5,931°F (3,277°C), and a density of 4.6 g/cm3. At room temperature , titanium tends to be brittle, although it becomes malleable and ductile at higher temperatures. Chemically, titanium is relatively inactive. At moderate temperatures, it resists attack by oxygen , most acids, chlorine , and other corrosive agents.

Occurrence and extraction

Titanium is the ninth most abundant element in the earth's crust with an abundance estimated at about 0.63%. The most common sources of titanium are ilmenite, rutile, and titanite. The metal is often obtained commercially as a byproduct of the refining of iron ore . It can be produced from its ores by electrolyzing molten titanium chloride (TiCl4): TiCl4 —electric current ? Ti + 2Cl2, or by treating hot titanium chloride with magnesium metal: 2Mg + TiCl4 ? Ti + 2MgCl2.

Discovery and naming

Titanium was discovered in 1791 by the English clergyman William Gregor (1761-1817). Gregor was not a professional scientist, but studied minerals as a hobby. On one occasion, he attempted a chemical analysis of the mineral ilmenite and found a portion that he was unable to classify as one of the existing elements. He wrote a report on his work, suggesting that the unidentified material was a new element. But he went no further with his own research. It was not until four years later that German chemist Martin Heinrich Klaproth returned to an investigation of ilmenite and isolated the new element. He suggested the name of titanium for the element in honor of the Titans, mythical giants who ruled the Earth until they were overthrown by the Greek gods.

Uses

By far the most important use of titanium is in making alloys. It is the element most commonly added to steel because it increases the strength and resistance to corrosion of steel. Titanium provides another desirable property to alloys: lightness. Its density is less than half that of steel, so a titanium-steel alloy weighs less than pure steel and is more durable and stronger.

These properties make titanium-steel alloys particularly useful in spacecraft and aircraft applications, which account for about 65% of all titanium sold. These alloys are used in airframes and engines and in a host of other applications, including armored vehicles, armored vests and helmets; in jewelry and eyeglasses; in bicycles, golf clubs, and other sports equipment; in specialized dental implants; in power-generating plants and other types of factories; and in roofs, faces, columns, walls, ceilings and other parts of buildings. Titanium alloys have also become popular in body implants, such as artificial hips and knees, because they are light, strong, long-lasting, and compatible with body tissues and fluids.

The most important compound of titanium commercially is titanium dioxide (TiO2), whose primary application is in the manufacture of white paint. About half the titanium dioxide made in the United States annually goes to this application. Another 40% of all titanium dioxide produced is used in the manufacture of various types of paper and plastic materials. The compound gives "body" to paper and makes it opaque. Other uses for the compound are in floor coverings, fabrics and textiles , ceramics , ink, roofing materials, and catalysts used in industrial operations.

Yet another titanium compound of interest is titanium tetrachloride (TiCl4), a clear colorless liquid when kept in a sealed container. When the compound is exposed to air, it combines with water vapor to form a dense white cloud. This property make it useful for skywriting, in the production of smokescreens, and in motion picture and television programs where smoke effects are needed.