Nomenclature
CAS number: 10102-44-0
Nitrogen oxide (NO
2).
NO
2; mol wt 46.01.
N 30.44%, O 69.55%.
Description and references
Oxidizing free radical; 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). Equilibrium
constant with N2O4 and determn methods in the
polar stratosphere: H. K. Roscoe, A. K. Hind, J. Atmos. Chem. 16, 257 (1993). Review of
structure and reactivity: P. Gray, A. D. Yoffe, Chem. Rev. 55, 1069-1154 (1955). Symposium
on chemistry and toxicology: Toxicology 89, 1-312 (1994). Review of pathobiochemistry: M. Kirsch et al., Biol. Chem. 383, 389-399 (2002).
Properties
Reddish-brown paramagnetic gas. Irritating odor.
Poisonous. Exists in equilibrium
with
dinitrogen tetroxide (N2O4),
q.v. At high temperatures, the gas
phase is predominantly NO
2. Liquid and solid phases are
almost entirely pure N
2O
4. Colorless solid
at low temp; pale lemon-yellow from -20° to -30°; honey colored at mp -11.2°. bp 21.15°. d
420 (liq) 1.448; d (gas) 1.58 (air = 1); d
gas21.3 3.3 g/liter. d
-40 (solid) 1.95. 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.
Caution
Potential symptoms of overexposure
are eye, nose and throat irritation, cough, mucoid frothy sputum,
decreased pulmonary function, chronic bronchitis, dyspnea, chest pain,
pulmonary edema, cyanosis, tachypnea and tachycardia. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 2005-149) 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.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. Oxidizing agent in rocket propulsion.