6601. Nitrogen

Nomenclature

CAS number: 7727-37-9

Description and references

N; at. wt 14.00674; at. no. 7; valences 3, 5; elemental state: N2. Group VA (15). Two naturally occurring isotopes: 14 (99.635%); 15 (0.365%); five short-lived, artificial, radioactive isotopes: 12; 13; 16-18. Discovered in 1772 by Daniel Rutherford and independently by Scheele and Cavendish. Constitutes about 75.5% by weight or 78.06% by volume of the atmosphere; found frequently in volcanic or mine gases, gases from springs and gases occluded in minerals and rocks; an essential constituent of all living organisms; fixed or combined nitrogen is present in many mineral deposits. Prepn from sodium (and alkaline earth) azides by heating the azide: Tiede, Ber. 46, 4100 (1913); 49, 1745 (1916); Justi, Ann. Phys. [5] 10, 985 (1931). Prepd industrially by fractional distln of liquid air; by removal of oxygen by combustion; by reduction of ammonia. Purification of nitrogen furnished in steel cylinders: Kautsky, Thiele, Z. Anorg. Allg. Chem. 152, 342 (1926); Kendall, Science 73, 395 (1931); Schenk in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 458-460. Review of nitrogen and nitrogen compounds: Jones in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 147-388; R. W. Schroeder in Kirk-Othmer Encyclopedia of Chemical Technology vol. 15 (Wiley-Interscience, New York, 3rd ed., 1981) pp 932-941. Books: W. L. Jolly, The Inorganic Chemistry of Nitrogen (Benjamin, New York, 1964) 124 pp; Mellor's Vol. VIII, Supplements I, II, Nitrogen, part 1 (1964) 619 pp; part 2 (1967) 676 pp; M. Sittig, Nitrogen in Industry (Van Nostrand, Princeton, 1965) 278 pp.

Properties

Odorless gas; condenses to a liquid, bp -195.79° (77.36 K); solidifies to a snow-white mass, mp -210.01° (63.14 K). dgas (0°, 1 atm) 1.25046 g/l. Critical temp: -147.1°; critical press: 33.5 atm; critical density: 0.311 g/cm3. Sparingly sol in water: 100 volumes of water absorbs 2.4 volumes of gas at 0°, 1.6 volumes at 20°. Soly in water at 50, 75 and 100° from 25 to 1000 atmospheres: Wiebe et al., J. Am. Chem. Soc. 55, 947 (1933). Soly in liquid ammonia: Wiebe et al., ibid. 975. Soly in alc: one volume of alcohol dissolves 0.1124 volume of nitrogen at 20°. Liquid oxygen at -195.5° absorbs 50.7% of its weight of gaseous nitrogen. Heat of dissociation of the nitrogen molecule (N2): 225.1 kcal/mole. Combines with oxygen and hydrogen on sparking, forming nitric oxide and ammonia, respectively. Combines directly with lithium, and at a red heat with calcium, strontium, and barium to form nitrides. Forms cyanides when heated with carbon in presence of alkalies or barium oxide.

Caution

In high concns it is a simple asphyxiant.

Use

In manuf of ammonia, nitric acid, nitrates, cyanides, etc.; in manuf explosives; in filling high-temp thermometers, incandescent bulbs; to form an inert atm for preservation of materials, for use in dry boxes or glove bags. Liquid nitrogen in food-freezing processes; in the laboratory as a coolant. Pharmaceutic aid (air displacement).