Hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
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| Names | |||
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| Systematic IUPAC name
Hydrogen sulfide | |||
Other names
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| Identifiers | |||
3D model (JSmol) |
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| 3DMet | |||
| 3535004 | |||
| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.029.070 | ||
| EC Number |
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| 303 | |||
| KEGG | |||
| MeSH | Hydrogen+sulfide | ||
PubChem CID |
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| RTECS number |
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| UNII | |||
| UN number | 1053 | ||
CompTox Dashboard (EPA) |
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SMILES
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| Properties | |||
| H2S | |||
| Molar mass | 34.08 g·mol−1 | ||
| Appearance | Colorless gas | ||
| Odor | Foul, pungent, like that of rotten eggs | ||
| Density | 1.539 g.L−1 (0°C) | ||
| Melting point | −85.5 °C (−121.9 °F; 187.7 K) | ||
| Boiling point | −59.55 °C (−75.19 °F; 213.60 K) | ||
| 3.980 g dm−3 (at 20 °C) | |||
| Vapor pressure | 1740 kPa (at 21 °C) | ||
| Acidity (pKa) | 7.0 | ||
| Conjugate acid | Sulfonium | ||
| Conjugate base | Bisulfide | ||
Magnetic susceptibility (χ) |
−25.5·10−6 cm3/mol | ||
Refractive index (nD) |
1.000644 (0 °C) | ||
| Structure | |||
Point group |
C2v | ||
Molecular shape |
Bent | ||
| 0.97 D | |||
| Thermochemistry | |||
Heat capacity (C) |
1.003 J K−1 g−1 | ||
Std molar entropy (S⦵298) |
206 J mol−1 K−1 | ||
Std enthalpy of formation (ΔfH⦵298) |
−21 kJ mol−1 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards |
Flammable and highly toxic | ||
| GHS labelling: | |||
| Danger | |||
| H220, H330, H400 | |||
| P210, P260, P271, P273, P284, P304+P340, P310, P320, P377, P381, P391, P403, P403+P233, P405, P501 | |||
| NFPA 704 (fire diamond) |
4
4
0 | ||
| Flash point | −82.4 °C (−116.3 °F; 190.8 K) | ||
| 232 °C (450 °F; 505 K) | |||
| Explosive limits | 4.3–46% | ||
| Lethal dose or concentration (LD, LC): | |||
LC50 (median concentration) |
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LCLo (lowest published) |
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| NIOSH (US health exposure limits): | |||
PEL (Permissible) |
C 20 ppm; 50 ppm [10-minute maximum peak] | ||
REL (Recommended) |
C 10 ppm (15 mg/m3) [10-minute] | ||
IDLH (Immediate danger) |
100 ppm | ||
| Related compounds | |||
Related hydrogen chalcogenides |
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Related compounds |
Phosphine | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |||
Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.
Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion, which is done by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water.