Hydrogen sulfide

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Hydrogen sulfide
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3DMet {{{value}}}
Beilstein Reference 3535004
Gmelin Reference 303
MeSH {{{value}}}
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RTECS number MX1225000
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Template:Chembox Elements/molecular formula
Molar mass Template:Chem molar mass
Appearance Colorless gas
Odor Rotten eggs
Density 1.363 g dm−3
Melting point Template:Chembox CalcTemperatures
Boiling point Template:Chembox CalcTemperatures
Vapor pressure 1740 kPa (at 21 °C)
Acidity (pKa) 7.0[2][3]
1.000644 (0 °C)[4]
0.97 D
Std enthalpy of
−21 kJ mol−1[5]
Standard molar
206 J mol−1 K−1[5]
Specific heat capacity, C 1.003 J K−1 g−1
EU classification Flammable F+ Very Toxic T+ Dangerous for the Environment (Nature) N
Main hazards Flammable and highly toxic
NFPA 704
R-phrases Template:R12, Template:R26, R50
S-phrases (S1/2), Template:S9, Template:S16, S36, Template:S38, S45, S61
Explosive limits 4.3–46%
U.S. Permissible
exposure limit (PEL)
C 20 ppm; 50 ppm [10-minute maximum peak]
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Hydrogen sulfide (British English: hydrogen sulphide) is the chemical compound with the formula HScript error: No such module "Su".S, is a colorless, toxic, flammable gas that is responsible for the foul smell of rotten eggs and flatulence. It often results when bacteria break down organic matter in the absence of oxygen. This happens in swamps, and sewers (alongside the process of anaerobic digestion). It also occurs in volcanic gases, natural gas and some well waters. This is the smell that people often think to be that of sulfur. But sulfur itself does not smell.

Hydrogen sulfide is also known as sulfane, sulfur hydride, sour gas, sulfurated hydrogen, hydrosulfuric acid, sewer gas and stink damp. IUPAC accepts the names "hydrogen sulfide" and "sulfane". When people speak of more complicated compounds they always use the term "sulfane".


File:Deposit from hydrogen sulphide.jpg
Deposit of sulfur on a rock, caused by volcanic gases containing hydrogen sulfide

Small amounts of hydrogen sulfide can be found in crude petroleum. Sour natural gas can contain up to 28%. But, sour natural gas must be cleaned before it can enter a long distance pipeline. Pipelines limit hydrogen sulfide to 3 grains per thousand cubic feet of natural gas.[6] Volcanoes and hot springs give off some H2S, where it probably is made by the hydrolysis of sulfide minerals, i.e. MS + H2O to give MO + H2S.

Normal average concentration in clean air is about 0.0001-0.0002 ppm.


Hydrogen sulfide is a highly toxic and flammable gas. Because it is heavier than air it tends to accumulate at the bottom of poorly ventilated spaces.


Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected. The toxicity of H2S is comparable with that of hydrogen cyanide.


  1. "Hydrogen Sulfide - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
  2. Template:Cite book
  3. Bruckenstein, S.; Kolthoff, I.M., in Kolthoff, I.M.; Elving, P.J. Treatise on Analytical Chemistry, Vol. 1, pt. 1; Wiley, NY, 1959, pp. 432–433.
  4. Template:Cite book
  5. 5.0 5.1 Template:Cite book
  6. "Southern Natural Gas Company Tariff, General Terms and Conditions Section 3.1(b)". Retrieved October 18, 2011.
  • "Hydrogen Sulfide", Committee on Medical and Biological Effects of Environmental Pollutants, University Park Press, 1979, Baltimore. Template:Catalog lookup linkScript error: No such module "check isxn".

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