w hot3 the we? Symbol: Atomic number: Atomic weight: Melting point: Boiling polnt: Density:
Nitrogen, the lighest element of group VA (15), is a colorless, odorless gas with two stable isotopes (I4Nand15N). I t is isolated from the air by three techniques, with cryogenic distillation being the method that produces high purity nitrogen most economically. The element was first reported by Daniel Rutherford in 1772, although Cavendish, Lavoisier, and Scheele were apparently working with "dephlogisticated" air during that year. Lavoisier dubbed the gas azotewithout life-as a result of the gas's inability to support life, and such prefixes as azo, azide, and diazo still convey Lavoisier's stamp. In 1790 the name nitrogen was suggested by Jean-Antoine-Claude Chaotal to recomize its presence in nitrates (GI., nitron, native soda;genrs, to form). Comprising approximately 78%(by volumeJ of our atmosphere, nitrogen does not react with air, water, acids, or bases at 25 O C . Indeed nitrogen is used as an inert blanketing medium in theelectronirs industry, the ironand steel industry, and the glaas industry. Other applications attributable to its inert nature include use as a filling material for light bulbsand inflatable rubber tiresand asa pressurizinggas for teleohone cables. Additionallv the oil industrv use8 nitrocen " as a pressurizinggas to enhance oilrecovery. Liquid nitrogen
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plays a very important role in operations involving freezing and maintaining food, preserving biological samples (e.g., blood, tissues, and semen), and providing low-temperature environmentn for superconductivity research. The importance of nitrogen in many compounds cannot he overlooked. Com~oundsof nitroeen have been known since antiquity. ~ h e ~ ~ i s t oofr i~ae r i d o t u s(Fifth Century B.C.) mentions the compound ammonium chloride as existing". .. in large lumps on the hills of Libyaand the Ammonians who live there worship the god Ammon. . . ". The ammonia industry is the largest consumer of nitrogen, primarily in the preparation of fertilizers. Ammonia, urea, nitric &id, and &monium nitrate are four of the most important nitrogen-containing industrial chemicals, with all of these being in the top 15of the "Top 50"chemicals. Finally, even a terse listing of important compounds of nitrogen would be incomplete without a mention of the most biologically important compounds of nitrogen, the proteins-compounds essential to all life. Some of these applications are shown on "The Periodic Table Videodisc" in frames 96381-36398.
Sources "KC? Discoverer: Exploring the Properties of the Chemical Element-.": JCE: Soft. 1988.
S.,Ed.: McGrawHill: NeuYork,1984:p 1157. Greenwood,N. N.: Earnshsw. A,; Chemistry o/thsElemsnfs: Pergamon:NewYork, 1984: p 467. Chrm. En& N e w 1988,66(25), 38. Banks, A. J.: "The Periodic Table Videadise: JCE:Soft. 1989, Specid Issue I . MeGrou-Hill Concise Encwiopedia of Science & Technology; Parker.
Number 3 March 1990