Fluorine, a chemical element. It is a pale yellow gas at ordinary temperatures. Fluorine is a corrosive substance and has a strong odor. It is highly toxic to body tissues. Concentrated fluorine causes severe burns on the skin; when inhaled in large quantities it causes serious congestion of lung tissues, and in extreme cases may cause death.

Fluorine is the most chemically reactive of the nonmetallic elements. It can combine with many other elements to form simple compounds called fluorides. Such reactions usually result in the release of considerable heat. Most nonmetals burst into flame when exposed to fluorine. When certain metals, such as aluminum and nickel, are in contact with fluorine at ordinary temperatures, a protective fluoride coating forms; it protects the metal from further reaction with fluorine. At high temperatures, however, all metals burn in fluorine. Most organic compounds either burn or explode in fluorine.

Small amounts of fluorides normally occur in tooth enamel and are beneficial in reducing tooth decay. Lack of fluorides in the diet increases tooth decay and is remedied by using fluoridated water. Certain dentifrices containing fluorides also are effective in reducing tooth decay. Fluoride solutions can also be applied directly to the teeth. Dentists often use this procedure on the teeth of children in areas where the local water supply is lacking fluorides.

Some fluorine minerals give off light when exposed to ultraviolet rays or other radiation. The term fluorescence, the name for this light-emitting property, is derived from the mineral fluorite.

Fluorine was first isolated in pure form by the French chemist Henri Moissan in 1886. It is widely distributed in the earth's crust, and is always found combined with other elements. The chief source of fluorine is fluorite, commonly called fluorspar, a mineral composed of calcium and fluorine. The leading producers of fluorspar are China, Mexico, Mongolia, Russia, and South Africa. Together, they produce more than 70 per cent of the world's output. Fluorine is also obtained as a by-product in the processing of phosphate rock.

Cryolite, a mineral composed of fluorine, sodium, and aluminum, was formerly a source of fluorine. The only known commercial deposits were in Greenland; they were depleted in 1962.

Uses

Pure fluorine is used chiefly as an oxidizer in rocket fuels. Fluorine compounds and minerals have many commercial uses. The mineral fluorite has been used for various purposes for hundreds of years.

Industry. Fluorite is used as a flux in making iron and steel, and in the manufacture of fluorine compounds, glass, and enamels. Cryolite is used chiefly in separating aluminum from alumina.

Hydrofluoric acid, an extremely corrosive liquid, is used to etch glass and pottery, clean stainless steel, remove sand from metal castings, and coagulate latex in making rubber. It is also used in the manufacture of Freon and other fluorocarbons. Uranium hexafluoride is used in the gaseous diffusion process for separating isotopes of uranium. Other fluorine compounds are used in insecticides, in wood preservatives, as concrete hardeners, and as fluxes in the manufacture of glass and ceramics.

Archeology

The mineral matter of bone takes on small amounts of fluorine from ground water. Fluorine is thus accumulated by fossil remains over a long period of time. Archeologists measure the amount of fluorine in a bone to determine whether it is of the same age as other bones in the same deposit. The fluorine test does not give an age in years.

Medicine

The principal drug containing fluorine is DFP (diisopropyl fluorophosphate). DFP is used to treat glaucoma, a disease of the eye, and strabismus, a disorder of eye muscles.

Symbol: F. Atomic number: 9. Atomic weight: 18.998403. Melting point: -363.3 F. (-219.6C.). Boiling point: -306.8 F. (-188.2 C.). Specific gravity: gas, 1.69 (air = 1); liquid, 1.11 (water = 1). Fluorine has one stable isotope: F-19. Fluorine is a member of the halogen family of elements belonging to Group VIIA of the Periodic Table and has a valence of -1.