Hydrogen sulfide

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Hydrogen sulfide

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CAS Number	Template:Chembox CASNo/format Template:Chembox CASNo/format Template:Chembox CASNo/format Template:Chembox CASNo/format Template:Chembox CASNo/format Template:Chembox CASNo/format
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Beilstein Reference	3535004
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DrugBank	Template:Chembox DrugBank/format Template:Chembox DrugBank/format Template:Chembox DrugBank/format Template:Chembox DrugBank/format Template:Chembox DrugBank/format Template:Chembox DrugBank/format
Gmelin Reference	303
KEGG	Template:Chembox KEGG/format Template:Chembox KEGG/format Template:Chembox KEGG/format Template:Chembox KEGG/format Template:Chembox KEGG/format Template:Chembox KEGG/format
MeSH	{{{value}}}
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RTECS number	MX1225000
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Chemical formula	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
Refractive index (nD)	1.000644 (0 °C)
Molecular shape	Bent
Dipole moment	0.97 D
Thermochemistry
Std enthalpy of formation ΔfHo298	−21 kJ mol−1
Standard molar entropy So298	206 J mol−1 K−1
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	75px 4 4 0
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 HS, 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".

Occurrence

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. 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.

References

• "Hydrogen Sulfide", Committee on Medical and Biological Effects of Environmental Pollutants, University Park Press, 1979, Baltimore. Template:Catalog lookup link

Other websites

• International Chemical Safety Card 0165
• Concise International Chemical Assessment Document 53
• National Pollutant Inventory - Hydrogen sulfide fact sheet
• NIOSH Pocket Guide to Chemical Hazards
• MSDS safety data sheet
• Abstract of survey article on H₂S as used by the body, by P. Kamoun
• Computational Chemistry Wiki