Hydrogen sulfide
154738
226037336
2008-07-16T15:29:03Z
CarsracBot
6929011
robot Adding: [[simple:Hydrogen sulfide]]
{{Chembox new
| Name = Hydrogen sulfide
| ImageFileL1 = Hydrogen-sulfide-2D-dimensions.svg
| ImageFileR1 = Hydrogen-sulfide-3D-vdW.png
| IUPACName = Hydrogen sulfide, sulfane
| OtherNames = Sulfuretted hydrogen; sulfane; sulfur hydride; sour gas; sulfurated hydrogen; hydrosulfuric acid; sewer gas; stink damp
| Section1 = {{Chembox Identifiers
| CASNo = 7783-06-4
| RTECS = MX1225000
}}
| Section2 = {{Chembox Properties
| Formula = H<sub>2</sub>S
| MolarMass = 34.082 g/mol
| Appearance = Colorless gas.
| Density = 1.363 g/L, gas.
| Solubility = 0.25 g/100 mL (40 °C)
| MeltingPt = -82.30 °C (190.85 K)
| BoilingPt = -60.28 °C (212.87 K)
| pKa = 6.89<br />19±2 (''See Text'')
}}
| Section3 = {{Chembox Structure
| MolShape = Bent
| Dipole = 0.97 [[Debye|D]]
}}
| Section7 = {{Chembox Hazards
| MSDS= [http://msds.chem.ox.ac.uk/HY/hydrogen_sulfide.html External MSDS]
| EUClass = Corrosive('''C''') <br />Very Toxic ('''T+''') <br />Highly Flammable ('''F+''')
| {{NFPA 704}}
| NFPA-H = 4
| NFPA-F = 4
| NFPA-R =
| NFPA-O =
| FlashPt = -82.4 °C
| RPhrases = {{R12}}, {{R26}}, {{R50}}
| SPhrases = {{S1/2}}, {{S9}}, {{S16}}<br />{{S36}}, {{S38}}, {{S45}}, {{S61}}
}}
| Section8 = {{Chembox Related
| Function = hydrogen compounds
| OtherFunctn = [[water (molecule)|water]]; [[hydrogen selenide]]; [[hydrogen telluride]]
}}
}}
'''Hydrogen sulfide''' (or '''hydrogen sulphide''') is the [[chemical compound]] with the [[chemical formula|formula]] [[Hydrogen|H]]<sub>2</sub>[[Sulfur|S]]. This colorless, [[toxic]] and flammable [[gas]] is responsible for the foul odor of [[egg (biology)|rotten eggs]] and [[flatulence]].
It often results from the [[bacteria]]l break down of organic matter in the absence of [[oxygen]], such as in [[swamp]]s and sewers ([[anaerobic digestion]]). It also occurs in [[volcano|volcanic]] gases, [[natural gas]] and some well waters. The odor of H<sub>2</sub>S is commonly misattributed to elemental [[sulfur]], which is in fact odorless. Hydrogen sulfide has numerous names, some of which are archaic (see Table).
==General properties==
Hydrogen sulfide is a [[covalent]] [[hydride]] structurally related to [[water]] (H<sub>2</sub>O) since [[oxygen]] and [[sulfur]] occur in the same [[periodic table group]].
Hydrogen sulfide is weakly [[acidic]], dissociating in aqueous solution into hydrogen [[cation]]s H<sup>+</sup> and the [[hydrosulfide]] [[anion]] HS<sup>−</sup>:
::H<sub>2</sub>S → HS<sup>−</sup> + H<sup>+</sup>
:::[[Acid dissociation constant|''K''<sub>a</sub>]] = 6.9×10<sup>−7</sup> mol/L; p''K''<sub>a</sub> = 6.89.
The [[sulfide]] ion, S<sup>2−</sup>, is known in the solid state but not in aqueous solution (''[[Cf.|c.f.]]'' [[oxide]]). The second [[Acid dissociation constant|dissociation constant]] of hydrogen sulfide is often stated to be around 10<sup>−13</sup>, but it is now clear that this is an error caused by [[oxidation]] of the sulfur in alkaline solution. The current best estimate for p''K''<sub>a2</sub> is 19±2.<ref>Giggenbach, W. (1971). ''Inorg. Chem.'' 10:1333. Meyer, B.; Ward, K.; Koshlap, K.; & Peter, L. (1983). ''Inorganic Chemistry'' 22:2345. Myers, R. J. (1986). ''Journal of Chemical Education'' 63:687.</ref>
Hydrogen sulfide reacts with many [[metal]]s cations to produce the corresponding metal [[sulfide]]s. Well-known examples are [[silver sulfide]] (Ag<sub>2</sub>S), the [[tarnish]] that forms on [[silver]] when exposed to the hydrogen sulfide of the atmosphere, and [[cadmium sulfide]] (CdS), a [[pigment]] also known as cadmium yellow. [[Transition metal]] sulfides are characteristically insoluble, thus H<sub>2</sub>S is commonly used to separate metal ions from aqueous solutions. ([[Sulfide]]s should not be confused with [[sulfite]]s or [[sulfate]]s, which contain the sulfite ion SO<sub>3</sub><sup>2−</sup> and the sulfate ion SO<sub>4</sub><sup>2−</sup>, respectively.)
Hydrogen sulfide is [[corrosion|corrosive]] and renders some [[steel]]s brittle, leading to [[sulfide stress cracking]] — a concern especially for handling "[[sour gas]]" and [[sour crude oil]] in the [[oil industry]]. Hydrogen sulfide burns to give the gas [[sulfur dioxide]], which is more familiar as the odor of a burnt match.
==Occurrence==
[[Image:Deposit from hydrogen sulphide.jpg|thumb|left|300px|Deposit of sulfur on a rock, caused by volcanic gases]]
Small amounts of hydrogen sulfide occur in [[crude petroleum]] but [[natural gas]] can contain up to 90%. [[Volcano]]es and [[hot spring]]s emit some H<sub>2</sub>S, where it probably arises via the [[hydrolysis]] of sulfide minerals, i.e. MS + H<sub>2</sub>O → MO + H<sub>2</sub>S. Normal concentration in clean air is about 0.0001-0.0002 [[parts per million|ppm]].{{Fact|date=June 2007}}
[[Sulfate-reducing bacteria]] obtain energy by [[redox|oxidizing]] organic matter or hydrogen with [[sulfate]]s, producing H<sub>2</sub>S. These microorganisms are prevalent in low-oxygen environments, such as in swamps and standing waters. [[Sulfur-reducing bacteria]] (such as [[Shewanella]]) and some [[archaea]] obtain their energy by oxidizing organic matter or hydrogen with elemental [[sulfur]], also producing H<sub>2</sub>S. Other [[Anaerobic organism|anaerobic]] bacteria liberate hydrogen sulfide when they digest sulfur-containing [[amino acid]]s, for instance during the decay of organic matter. H<sub>2</sub>S-producing bacteria also operate in the human [[colon (anatomy)|colon]], and the odor of [[flatulence]] is largely due to trace amounts of the gas. Such bacterial action in the mouth may contribute to [[bad breath]]. Evidence exists that hydrogen sulfide produced by sulfate-reducing bacteria in the colon may cause or contribute to [[ulcerative colitis]].
About 10% of total global emissions of H<sub>2</sub>S are due to human activity. By far the largest industrial route to H<sub>2</sub>S occurs in [[oil refinery|petroleum refineries]]: the [[hydrodesulfurization]] process liberates sulfur from [[petroleum]] by the action of hydrogen. The resulting H<sub>2</sub>S is converted to elemental sulfur by partial combustion via the [[Claus process]], which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include [[coke (fuel)|coke]] ovens, [[paper mill]]s (using the sulfate method), and [[tanning|tanneries]]. H<sub>2</sub>S arises from virtually anywhere where elemental sulfur comes into contact with organic material, especially at high temperatures.
Hydrogen sulfide can be present naturally in well water. In such cases, [[ozone]] is often used for its removal. An alternative method uses a filter with [[manganese dioxide]]. Both methods oxidize sulfides to less toxic [[sulfate]]s.
A buildup of hydrogen sulfide in the atmosphere could have caused the [[Permian-Triassic extinction event]] 252 million years ago.<ref name="sciam">[http://www.sciam.com/article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000&sc=I100322 "Impact From the Deep"] in the October 2006 issue of Scientific American.</ref>
==Uses==
===Production of thioorganic compounds===
Several [[organosulfur compound]]s are produced using hydrogen sulfide. These include [[methanethiol]], [[ethanethiol]], and [[thioglycolic acid]].
===Alkali metal sulfides===
Upon combining with alkali metal bases, hydrogen sulfide converts to alkali hydrosulfides such as [[sodium hydrosulfide]] and [[sodium sulfide]], which are used in the degradation of biopolymers. The [[depilation]] of hides and the delignification of pulp by the [[Kraft process]] both are effected by alkali sulfides.
===In analytical chemistry===
Hydrogen sulfide used to have importance in [[analytical chemistry]] for well over a century, in the [[qualitative inorganic analysis]] of metal ions. For such small-scale laboratory use, H<sub>2</sub>S was made as needed in a [[Kipp generator]] by reaction of [[sulfuric acid]] (H<sub>2</sub>SO<sub>4</sub>) with [[ferrous sulfide]] FeS. Kipp generators were superseded by the use of [[thioacetamide]], an organic solid that converts in water to H<sub>2</sub>S. In these analyses, heavy metal (and [[nonmetal]]) ions (e.g. Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to H<sub>2</sub>S. The components of the resulting precipitate redissolve with some selectivity.
===A precursor to metal sulfides===
As indicated above, many metal ions react with hydrogen sulfide to give the corresponding metal sulfides. This conversion is widely exploited. In the purification of metal ores by [[flotation]], mineral powders are often treated with hydrogen sulfide to enhance the separation. Metal parts are sometimes passivated with hydrogen sulfide. Catalysts used in [[hydrodesulfurization]] are routinely activated with hydrogen sulfide, and the behavior of metallic catalysts used in other parts of a [[refinery]] is also modified using hydrogen sulfide.
===Miscellaneous applications===
Hydrogen sulfide is also used in the separation of deuterium oxide, i.e. [[heavy water]], from normal water via the [[Girdler Sulfide process]].
==Safety==
Hydrogen sulfide is a highly [[toxic]] and flammable gas. Being heavier than air, it tends to accumulate at the bottom of poorly ventilated spaces. Although very pungent at first, it quickly deadens the sense of smell, so potential victims may be unaware of its presence until it is too late. For more information see an [[MSDS]].
==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 H<sub>2</sub>S is comparable with that of [[hydrogen cyanide]]. It forms a complex bond with [[iron]] in the [[mitochondria]]l [[cytochrome]] [[enzyme]]s, thereby blocking oxygen from binding and stopping [[cellular respiration]]. Since hydrogen sulfide occurs naturally in the environment and the gut, enzymes exist in the body capable of detoxifying it by oxidation to (harmless) sulfate.<ref>{{cite journal| author=S. Ramasamy, S. Singh, P. Taniere, M. J. S. Langman, M. C. Eggo| title=Sulfide-detoxifying enzymes in the human colon are decreased in cancer and upregulated in differentiation| journal=Am J Physiol Gastrointest Liver Physiol| volume=291| pages=G288–G296| year=2006| url=http://ajpgi.physiology.org/cgi/content/full/291/2/G288| accessdate=2007-10-20| doi=10.1152/ajpgi.00324.2005| pmid=16500920}}</ref> Hence low levels of sulfide may be tolerated indefinitely. However, at some threshold level, the oxidative enzymes will be overwhelmed. This threshold level is believed to average around 300-350 ppm. Many personal safety gas detectors are set to alarm at as low as 5 PPM to 10 PPM and to go into high alarm at 15 ppm (utility, sewage & petrochemical workers).
An interesting diagnostic clue of extreme poisoning by H<sub>2</sub>S is the discoloration of [[copper]] coins in the pockets of the victim. Treatment involves immediate inhalation of [[amyl nitrite]], injections of [[sodium nitrite]], inhalation of pure oxygen, administration of [[bronchodilator]]s to overcome eventual [[bronchospasm]], and in some cases [[hyperbaric oxygen therapy]].
Exposure to lower concentrations can result in [[eye]] irritation, a sore throat and [[cough]], nausea, shortness of breath, and fluid in the [[lung]]s. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in [[fatigue (physical)|fatigue]], loss of appetite, [[headach]]es, irritability, poor memory, and [[dizziness]]. Chronic exposures to low level H<sub>2</sub>S (around 2 [[parts per million|ppm]]) has been implicated in increased miscarriage and reproductive health issues amongst Russian and Finnish wood pulp workers, but the reports hadn't (as of circa 1995) been replicated. Higher concentrations of 700-800 [[parts per million|ppm]] tend to be fatal.
* 0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide [http://www.extension.iastate.edu/Publications/PM1963A.pdf], normally described as resembling "a rotten egg".
* 10-20 ppm is the borderline concentration for eye irritation.
* 50-100 ppm leads to eye damage.
* At 150-250 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger,
* 320-530 ppm leads to [[pulmonary edema]] with the possibility of death.
* 530-1000 ppm causes strong stimulation of the [[central nervous system]] and rapid breathing, leading to loss of breathing;
** 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure([[LC50]]).
* Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.
A series of suicide cases in [[Japan]] in which the victims killed themselves by producing toxic hydrogen sulfide fumes by mixing household cleaning products (such as toilet cleansing liquids) with bath salts have highlighted the danger posed by such common use substances and prompted censorship of internet sites who posted advice for aspiring suicides [http://www.japantoday.com/category/kuchikomi/view/briquettes-are-out-hydrogen-sulfide-in-as-latest-suicide-method].
==Function in the body==
Hydrogen sulfide is produced in small amounts by some cells of the [[mammal]]ian body and has a number of biological functions. It is produced from [[cysteine]] by various [[enzyme]]s. It acts as a [[vasodilator]] and is also active in the [[brain]], where it increases the response of the [[NMDA receptor]] and facilitates [[long term potentiation]], which is involved in the formation of memory. Eventually the gas is converted to [[sulfite]]s and further oxidized to [[thiosulfate]] and [[sulfate]].{{Fact|date=September 2007}}
Due to its effects similar to NO (without its potential to form [[peroxides]] by interacting with [[superoxide]]), hydrogen sulfide is now recognized as a potential cardioprotective agent.<ref>[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=retrieve&db=pubmed&list_uids=17991773&dopt=AbstractPlus A new gaseous signaling molecule emerges: Cardioprotective role of hydrogen sulfide]. Since H<sub>2</sub>S is not "new", the term most likely refers to commentator's prior subjective unawareness.</ref> Vasoactivity of [[garlic]] is caused by [[catabolism]] of its [[allicin|polysulfides]] to H<sub>2</sub>S, a reaction which could depend on reduction mediated by [[glutathione]].<ref> [http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=AbstractPlus&list_uids=17951430 Hydrogen sulfide mediates the vasoactivity of garlic].</ref>
In [[trisomy 21]] (the most common form of Down syndrome) the body produces an excess of hydrogen sulfide.
==Induced hibernation==
In 2005 it was shown that [[mus musculus|mice]] can be put into a state of [[suspended animation]]-like [[hypothermia]] by applying a low dosage of hydrogen sulfide (80 [[parts per million|ppm]] H<sub>2</sub>S) in the air. The breathing rate of the animals sank from 120 to 10 breaths per minute and their temperature fell from 37 °C to just 2 °C above ambient temperature (in effect, they had become [[cold-blooded]]). The mice survived this procedure for 6 hours and afterwards showed no negative health consequences.<ref>[http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/4469793.stm Mice put in 'suspended animation'], BBC News, 21 April 2005</ref> In 2006 it was shown that the [[blood pressure]] of mice treated in this fashion with hydrogen sulfide did not significantly decrease.<ref>[http://news.bbc.co.uk/2/hi/science/nature/4469793.stm Gas induces 'suspended animation'], BBC News, 9 October 2006</ref>
Such a [[hibernation]] occurs naturally in many [[mammal]]s and also in [[toad]]s, but not in mice. (Mice can fall into a state called [[torpor|clinical torpor]] when food shortage occurs). If the H<sub>2</sub>S-induced hibernation can be made to work in humans, it could be useful in the emergency management of severely injured patients, and in the conservation of donated organs.
As mentioned above, hydrogen sulfide binds to [[Cytochrome c oxidase|cytochrome oxidase]] and thereby prevents oxygen from binding, which leads to the dramatic slowdown of [[metabolism]]. Animals and humans naturally produce some hydrogen sulfide in their body; researchers have proposed that the gas is used to regulate metabolic activity and body temperature, which would explain the above findings.<ref>Mark B. Roth and Todd Nystul. Buying Time in Suspended Animation. ''Scientific American, 1 June 2005</ref>
However, a 2008 study failed to reproduce the effect in pigs, concluding that the effects seen in mice were not present in larger mammals.<ref>{{cite journal |last=Li |first=Jia |authorlink= |coauthors=Zhang, Gencheng; Cai, Sally; Redington, Andrew N |year=2008 |month=January |title=Effect of inhaled hydrogen sulfide on metabolic responses in anesthetized, paralyzed, and mechanically ventilated piglets. |journal=Pediatric Critical Care Medicine |volume=9 |issue=1 |pages=110–112 |id= |url=http://www.pccmjournal.com/pt/re/pccm/abstract.00130478-200801000-00021.htm |accessdate= 2008-02-07 |quote=H2S does not appear to have hypometabolic effects in ambiently cooled large mammals and conversely appears to act as a hemodynamic and metabolic stimulant. |doi=10.1097/01.PCC.0000298639.08519.0C |doi_brokendate=2008-06-26 }}</ref>
==Participant in the sulfur cycle==
Hydrogen sulfide is a central participant in the [[sulfur cycle]], the [[biogeochemical cycle]] of [[sulfur]] on Earth. As mentioned above, sulfur-reducing and sulfate-reducing bacteria derive energy from [[redox|oxidizing]] hydrogen or organic molecules in the absence of oxygen by reducing sulfur or sulfate to hydrogen sulfide. Other bacteria liberate hydrogen sulfide from sulfur-containing [[amino acid]]s. Several groups of bacteria can use hydrogen sulfide as fuel, [[redox|oxidizing]] it to elemental sulfur or to sulfate by using dissolved oxygen, metal oxides (e.g. Fe oxyhyroxides and Mn oxides) or nitrate as oxidant<ref>Jørgensen, B. B. & D. C. Nelson (2004) Sulfide oxidation in marine sediments: Geochemistry meets microbiology, pp. 36-81. In J. P. Amend, K. J. Edwards, and T. W. Lyons (eds.) Sulfur Biogeochemistry - Past and Present. Geological Society of America.</ref>. The [[purple sulfur bacteria]] and the [[green sulfur bacteria]] use hydrogen sulfide as electron donor in [[photosynthesis]], thereby producing elemental sulfur. (In fact, this mode of photosynthesis is older than the mode of [[cyanobacteria]], [[algae]] and [[plant]]s which uses water as electron donor and liberates oxygen.)
==H<sub>2</sub>S implicated in mass extinctions==
Hydrogen sulfide has been implicated in some of the several mass extinctions that have occurred in the Earth's past. The [[Permian extinction|Permian mass extinction]] (sometimes known as the "Great Dying") may have been caused by hydrogen sulfide. Organic residues from these extinction boundaries indicate that the oceans were anoxic (oxygen depleted) and had species of shallow plankton that metabolized H<sub>2</sub>S. The formation of H<sub>2</sub>S may have been initiated by massive volcanic eruptions, which emitted CO<sub>2</sub> and methane into the atmosphere which warmed the oceans, lowering their capacity to absorb oxygen which would otherwise oxidize H<sub>2</sub>S. The increased levels of hydrogen sulfide could have killed oxygen-generating plants as well as depleted the ozone layer causing further stress. Small H<sub>2</sub>S blooms have been detected in modern times in the [[Dead Sea]] and in the Atlantic ocean off the coast of Namibia.<ref name="sciam"/>
==See also==
*[[Amine gas treating]]
*[[Claus process]]
*[[Induced hypothermia]]
*[[Jenkem]]
==References==
{{citations missing|article|date=December 2007}}
{{reflist}}
*"Hydrogen Sulfide", Committee on Medical and Biological Effects of Environmental Pollutants, University Park Press, 1979, Baltimore. ISBN 0-8391-0127-9
*"Girl's suicide leaves dozens ill from fumes", http://edition.cnn.com/2008/WORLD/asiapcf/04/24/detergent.suicide.ap/index.html?iref=mpstoryview
==External links==
* [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc01/icsc0165.htm International Chemical Safety Card 0165]
* [http://www.inchem.org/documents/cicads/cicads/cicad53.htm Concise International Chemical Assessment Document 53]
* [http://www.npi.gov.au/database/substance-info/profiles/49.html National Pollutant Inventory - Hydrogen sulfide fact sheet]
* [http://www.cdc.gov/niosh/npg/npgd0337.html NIOSH Pocket Guide to Chemical Hazards]
* [http://ptcl.chem.ox.ac.uk/MSDS/HY/hydrogen_sulfide.html MSDS safety data sheet]
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15329822&query_hl=7 Abstract of survey article on H<sub>2</sub>S as used by the body], by P. Kamoun
* [http://www.compchemwiki.org/index.php?title=Hydrogen_sulfide Computational Chemistry Wiki]
* NACE (National Association of Corrosion Epal) http://www.nace.org/
[[Category:Sulfur compounds]]
[[Category:Hydrogen compounds]]
[[Category:Sulfides]]
[[Category:Foul-smelling chemicals]]
[[Category:Pollutants]]
[[Category:Acids]]
[[ar:كبريتيد هيدروجين]]
[[ca:Àcid sulfhídric]]
[[cs:Sulfan]]
[[de:Schwefelwasserstoff]]
[[es:Ácido sulfhídrico]]
[[eo:Hidrogena sulfido]]
[[fa:سولفید هیدروژن]]
[[fr:Sulfure d'hydrogène]]
[[ko:황화 수소]]
[[id:Hidrogen sulfida]]
[[is:Brennisteinsvetni]]
[[it:Acido solfidrico]]
[[he:מימן גופרתי]]
[[hu:Kénhidrogén]]
[[ms:Hidrogen sulfida]]
[[nl:Waterstofsulfide]]
[[ja:硫化水素]]
[[no:Hydrogensulfid]]
[[pl:Siarkowodór]]
[[pt:Sulfeto de hidrogênio]]
[[ro:Hidrogen sulfurat]]
[[ru:Сероводород]]
[[simple:Hydrogen sulfide]]
[[sk:Sírovodík]]
[[sr:Водоник-сулфид]]
[[fi:Rikkivety]]
[[sv:Svavelväte]]
[[vi:Hyđro sulfua]]
[[tr:Hidrojen sülfür]]
[[uk:Сірководень]]
[[zh:硫化氫]]