Bromine, a chemical element. It is a heavy, reddish-brown liquid with a choking odor. (The name bromine comes from the Greek for "stench.") Bromine gives off a brown vapor that is extremely corrosive. The vapor is very irritating to the mucous membranes of the eyes, nose, and throat, and the liquid causes severe burns if spilled on the skin. Bromine belongs to the halogen family, which includes chlorine, fluorine, and iodine. It is the only nonmetallic element that is a liquid at ordinary temperatures and pressures.

Bromine is very active chemically and is never found free in nature. It occurs primarily in the form of bromide salts, which are generally found together with common salt. Bromine was discovered in 1826 by the French scientist Antoine Balard.

Bromine is obtained commercially from seawater, underground brines, and brines from saline lakes. These solutions are treated with chlorine and with steam or air. The chlorine frees the bromine from its compounds by oxidation; the steam or air vaporizes the element and carries it from the solution. The vapor is then distilled to obtain pure bromine. In the United States, most bromine is produced in Arkansas; a small amount comes from Michigan.

Bromine and its compounds are used as flameproofing agents in fabrics, carpets, and plastics and, in agriculture, as fumigants and soil sterilants. They are also used in certain dyes, inks, photographic papers and films, disinfectants, bleaches, and tear gases.

Ethylene dibromide is a bromine compound used in leaded gasoline to prevent deposits of lead from forming in engines. Until the mid-1970's, when unleaded gasoline came into use, it was the most commercially important compound of bromine. Some bromides, including potassium bromide, were once widely used in medicine as sedatives. They have been largely replaced, however, by less toxic drugs.

Symbol: Br. Atomic number: 35. Atomic weight: 79.904. Melting point: 19.0 F. (-7.2 C.). Boiling point: 137.8 F. (58.8 C.). Specific gravity: 3.12. Bromine belongs to Group VII-A of the Periodic Table and may have a valence of +1, 3, 5, or 7. There are 17 isotopes, ranging from Br-74 to Br-90. Ethylene dibromide is C2H4Br2.