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[1] | |
| Other names |
|
| Identifiers | |
| CAS number | |
| PubChem | |
| EC number | 231-977-3 |
| KEGG | C00283 |
| MeSH | |
| 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 ΔfH |
−21 kJ mol−1[5] |
| Standard molar entropy S |
206 J mol−1 K−1[5] |
| Specific heat capacity, C | 1.003 J K−1 g−1 |
| Hazards | |
| EU classification |  F+  T+  N
|
| Main hazards | Flammable and highly toxic |
| NFPA 704 |
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
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
Process flow diagram of a typical amine treating process used in petroleum refineries, natural gas processing plants and other industrial facilities
Sludge from a pond; the black color is due to metal sulfides
A hydrogen sulfide bloom (green) stretching for about 150km along the coast of Namibia. As oxygen-poor water reaches the coast, bacteria in the organic-matter rich sediment produce hydrogen sulfide, which is toxic to fish.
References
- ↑ "Hydrogen Sulfide - PubChem Public Chemical Database". The PubChem Project. USA: National Center for Biotechnology Information.
- ↑ Perrin, D.D. (1982). Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution (2nd ed.). Oxford: Pergamon Press.
- ↑ 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.
- ↑ Patnaik, Pradyot (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
- ↑ 5.0 5.1 Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin Company. p. A23. ISBN 978-0-618-94690-7.
- ↑ "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
Other websites
- International Chemical Safety Card 0165
- Concise International Chemical Assessment Document 53
- National Pollutant Inventory - Hydrogen sulfide fact sheet Archived 2006-03-09 at the Wayback Machine
- NIOSH Pocket Guide to Chemical Hazards
- MSDS safety data sheet Archived 2007-05-15 at the Wayback Machine
- Abstract of survey article on H2S as used by the body, by P. Kamoun
- Computational Chemistry Wiki Archived 2008-12-07 at the Wayback Machine