Hydrogen Sulfide
Title: Hydrogen Sulfide
CAS Registry Number: 7783-06-4
Additional Names: Sulfureted hydrogen; "hydrosulfuric acid"
Molecular Formula: H2S
Molecular Weight: 34.08
Percent Composition: H 5.92%, S 94.09%
Literature References: Evolved from numerous environmental natural sources such as bacterial decomposition of vegetable and animal proteinaceous material. Occurs naturally as a component of crude petroleum, natural gas, volcanic gas and sulfur springs. Also a pollutant released into the environment as a by-product of a variety of industrial operations. Lab prepn: Bickford, Wilkinson, Inorg. Synth. 1, 111 (1939). Purification: Ward et al., ibid. 3, 14 (1950). Toxicity studies: E. H. Vernot et al., Toxicol. Appl. Pharmacol. 42, 417 (1977); M. F. Tansy et al., J. Toxicol. Environ. Health 8, 71-88 (1981). Review of toxicity and properties: R. O. Beauchamp, Jr., et al., Crit. Rev. Toxicol. 13, 25-97 (1984); of toxicology: R. J. Reiffenstein et al., Annu. Rev. Pharmacol. Toxicol. 32, 109-134 (1992); and human exposure: Toxicological Profile for Hydrogen Sulfide (PB99-166696, 1999) 217 pp.
Properties: Gas with characteristic odor of rotten eggs, perceptible in air at concns of 0.02-0.13 ppm, sweetish taste. Flammable, poisonous. Burns in air with pale blue flame. Ignition temp 260°. Explosive limits when mixed with air: lower limit 4.3% by vol, upper limit 46% by vol. mp -85.49°; bp -60.33°: Giauque, Blue, J. Am. Chem. Soc. 58, 831 (1936). Heavier than air; 1.5392 g/l (0°; 760 mm). dgas 1.19 (air = 1.00). Vapor pressure 18.75 ´ 105 Pa. One gram H2S dissolves in 187 ml water at 10°, in 242 ml water at 20°, in 314 ml water at 30°; in 94.3 ml abs alcohol at 20°; in 48.5 ml ether at 20°. Sol in glycerol, gasoline, kerosene, carbon disulfide, crude oil. Water solns of H2S are not stable, absorbed oxygen causes the formation of elemental sulfur, and the solns become turbid rapidly. In a 50:50 v/v mixture of glycerol and water the precipitation of sulfur is retarded considerably. pH of freshly prepd satd water soln 4.5. pKa1 7.04; pKa2 11.96. LC50 in mice, rats (ppm): 634, 712 (1 hr inhalation) (Vernot). LC50 in rats (ppm): 444 (4 hr inhalation) (Tansy).
Melting point: mp -85.49°
Boiling point: bp -60.33°: Giauque, Blue, J. Am. Chem. Soc. 58, 831 (1936)
pKa: pKa1 7.04; pKa2 11.96
Density: dgas 1.19 (air = 1.00)
Toxicity data: LC50 in mice, rats (ppm): 634, 712 (1 hr inhalation) (Vernot); LC50 in rats (ppm): 444 (4 hr inhalation) (Tansy)
CAUTION: Highly toxic irritant and chemical asphyxiant; overexposure can be fatal. Insidious poison, since sense of smell may be fatigued and fail to give warning of high concns. Direct contact with gas may cause irritation of eyes and respiratory tract resulting in keratoconjunctivitis, photophobia, lacrimation, corneal opacity; rhinitis, laryngitis, cough, bronchopneumonia. Direct contact with solution may cause skin irritation, erythema. Potential symptoms of overexposure by inhalation include salivation, GI disturbances; giddiness, headache, vertigo, confusion, unconsciousness; tachypnea, tachycardia, sweating, fatigue. Exposure to very high vapor concentrations may result in systemic intoxication leading to paralysis of respiratory center of brain, apnea and sudden collapse. See Clinical Toxicology of Commercial Products, R. E. Gosselin et al., Eds. (Williams & Wilkins, Baltimore, 5th ed., 1984) Section III, pp 198-202; NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 170.
Use: To produce elemental sulfur and sulfuric acid; in manuf of heavy water and other chemicals; in metallurgy; as analytical reagent.

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