Nitrogen Dioxide
Title: Nitrogen Dioxide
CAS Registry Number: 10102-44-0
Molecular Formula: NO2
Molecular Weight: 46.01
Percent Composition: N 30.44%, O 69.55%
Literature References: Damaging component of photochemical smog. Prepd industrially from nitric oxide and air. Convenient lab prepn from lead nitrate: Schenk in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 1963) pp 488-489. Ultrapure NO2 from N2O5: Hackspill, Besson, Bull. Soc. Chim. Fr. Mem. [5] 16, 479 (1949). Reviews: Beattie, "Nitrogen Dioxide and Dinitrogen Tetroxide" in Mellor's Vol. VIII, supplement II, Nitrogen (part 2) 246-268 (1967); Jones in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 340-356. Symposium on chemistry and toxicology: Toxicology 89, 1-312 (1994).
Properties: Reddish-brown gas. Liquid below 21.15°. Irritating odor. Deadly poison! The commercial brown liq under pressure is called nitrogen tetroxide. Actually this is an equilibrium mixture of NO2 and the colorless N2O4. d420 (liq) 1.448; d (gas) 1.58 (air = 1); dgas21.3 3.3 g/liter. mp -9.3°. bp 21.15°. Crit temp 158.2°. Crit press. 99.96 atm. Heat of vaporization (bp) 9.110 kcal/mole. Does not burn, but supports the combustion of carbon, phosphorus, sulfur. Sol in concd sulfuric and nitric acids. Dec in water forming nitric acid and nitric oxide, reacts with alkalies to form nitrates and nitrites. Corrosive to steel when wet, but may be stored in steel cylinders when moisture content is 0.1% or less.
Melting point: mp -9.3°
Boiling point: bp 21.15°
Density: d420 (liq) 1.448; d (gas) 1.58 (air = 1); dgas21.3 3.3 g/liter
CAUTION: Potential symptoms of overexposure are coughing, mucoid frothy sputum, decreased pulmonary function, chronic bronchitis, dyspnea; chest pain; pulmonary edema, cyanosis, tachypnea and tachycardia; eye, nose and throat irritation. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 228. One of the most insidious gases. Inflammation of lungs may cause only slight pain or pass unnoticed, but the resulting edema several days later may cause death. 100 ppm is dangerous for even a short exposure, and 200 ppm may be fatal: Y. Henderson, H. W. Haggard, Noxious Gases, A.C.S. Monograph Series, no. 35 (Reinhold, New York, 2nd ed., 1943) pp 134-137, 141. See also Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section III, pp 319-326.
Use: Intermediate in nitric and sulfuric acid production. Used in the nitration of organic compds and explosives, in the manuf of oxidized cellulose compds (hemostatic cotton). Has been used to bleach flour. Proposed as oxidizing agent in rocket propulsion. See also: Sisler, "Reactions in Liquid Dinitrogen Tetroxide," J. Chem. Educ. 34, 555 (1957).

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