Hydrogen sulfide

Hydrogen sulfide (British English: hydrogen sulphide) is the chemical compound with the formula H2S, 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 if there is no oxygen. This happens in swamps, and sewers (alongside the process of anaerobic digestion). It also happens 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
Hydrogen-sulfide-2D-dimensions.svg
Hydrogen-sulfide-3D-balls.png
Hydrogen-sulfide-3D-vdW.svg
Other names
  • Dihydrogen monosulfide
  • Dihydrogen sulfide
  • Sewer gas
  • Sulfane
  • Sulfurated hydrogen
  • Sulfureted hydrogen
  • Sulfuretted hydrogen
  • Sulfur hydride
  • Hydrosulfuric acid
  • Hydrothionic acid
  • Thiohydroxic acid
  • Sulfhydric acid
Identifiers
CAS number 7783-06-4
PubChem 402
EC number 231-977-3
KEGG C00283
MeSH Hydrogen+sulfide
ChEBI CHEBI:16136
RTECS number MX1225000
SMILES [H]S[H]
Beilstein Reference 3535004
Gmelin Reference 303
3DMet B01206
Properties
Molecular formula H2S
Molar mass 34.08 g mol-1
Appearance Colorless gas
Odor Rotten eggs
Density 1.363 g dm−3
Melting point

−82 °C, 191 K, -116 °F

Boiling point
Solubility in water 4 g dm−3 (at 20 °C)
Vapor pressure 1740 kPa (at 21 °C)
Acidity (pKa) 7.0[2][3]
−25.5·10−6 cm3/mol
Refractive index (nD) 1.000644 (0 °C)[4]
Structure
C2v
Molecular shape Bent
Dipole moment 0.97 D
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−21 kJ mol−1[5]
Standard molar
entropy
So298
206 J mol−1 K−1[5]
Specific heat capacity, C 1.003 J K−1 g−1
Hazards
EU classification Flammable F+ Very Toxic T+ Dangerous for the Environment (Nature) N
Main hazards Flammable and highly toxic
NFPA 704

NFPA 704.svg

4
4
0
 
R-phrases R12, R26, R50
S-phrases (S1/2), S9, S16, S36, S38, S45, S61
Explosive limits 4.3–46%
U.S. Permissible
exposure limit (PEL)
C 20 ppm; 50 ppm [10-minute maximum peak]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

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".

Occurrence

 
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.

Safety

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.

Toxicity

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.

Hydrogen Sulfide Media

References

  1. "Hydrogen Sulfide - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
  2. Perrin, D.D. (1982). Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution (2nd ed.). Oxford: Pergamon Press.
  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. Patnaik, Pradyot (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
  5. 5.0 5.1 Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. p. A23. ISBN 978-0-618-94690-7.
  6. "Southern Natural Gas Company Tariff, General Terms and Conditions Section 3.1(b)". Archived from the original on March 5, 2016. Retrieved October 18, 2011.
  • "Hydrogen Sulfide", Committee on Medical and Biological Effects of Environmental Pollutants, University Park Press, 1979, Baltimore. ISBN 0-8391-0127-9

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