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<u>'''Hydrogen Sulfide'''</u>
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'''Hydrogen sulfide''' (or ''hydrogen sulphide'') is a [[chemical compound]] with the [[chemical formula|formula]] [[Hydrogen|H]]<sub>2</sub>[[Sulfur|S]]. It is a colorless, highly toxic,  flammable [[gas]] with a characteristic foul odor.


Hydrogen sulfide is present in very large amounts in raw [[natural gas]] and also occurs in large amounts during the [[Petroleum refining processes|refining]] of [[petroleum crude oil]]. In fact, the vast majority of the 66,000,000 [[metric ton]]s of elemental [[sulfur]] produced worldwide in 2006 was by-product sulfur from petroleum refining and [[Natural gas processing|natural gas processing plants]].<ref>[http://minerals.usgs.gov/minerals/pubs/commodity/sulfur/sulfumcs07.pdf Sulfur production report] by the [[United States Geological Survey]]</ref> It is also present in [[volcano|volcanic gases]] and some [[water]] well sources
It also occurs in [[swamp]]s and [[sewer]]s as a result of the [[bacteria|bacterial]] breakdown of [[Organic chemistry|organic matter]] in the absence of [[oxygen]], which is known as [[anaerobic digestion]].
==Chemical properties==
{| border=0 width=325 align=right style="clear: both;"
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{| class = wikitable align=right style="font-size:90%;"
|+ <font size=3px>Properties
! width=120px|Property!! Width=185px|Value</font><ref>{{cite book|author=Carl L. Yaws|title=Matheson Gas Data Handbook|edition=7th Edition|publisher=McGraw-Hill|date=June 25, 2001|id=ISBN 0-07-135851-4}}</ref><ref>[http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=59 Air Liquide Gas Encyclopedia]</ref>
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| '''Common name'''|| hydrogen sulfide
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| '''Other names'''|| hydrogen sulphide, dihydrogen sulfide, sulfur hydride,  sewer gas
|- align=left
| '''IUPAC name''' || hydrogen sulfide
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| '''CAS number'''|| 7783-06-04
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| '''Molecular formula''' || H<sub>2</sub>S
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| '''[[Molecular mass]]''' || 34.082 g/mol
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| '''[[Melting point]]''' || −85.47 °C
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| '''[[Boiling point|Normal boiling point]]''' || −60.35 °C and 1 [[atmosphere (unit)|atm]]
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| '''[[Critical point]]''' || 100.38 °C at 88.46 atm
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| '''[[Heat of fusion]]''' ||69.74 kJ/kg at −85.47 °C and 1 atm
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| '''[[Heat of vaporization]]'''||517.87 kJ/kg at −60.35 °C and 1 atm
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| '''Liquid [[Density (chemistry)|density]]''' || 914.9 kg/m<sup>3</sup> at −60.35 °C and 1 atm
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| '''Gas [[Density (chemistry)|density]]'''||1.93 kg/m<sup>3</sup> at −60.35 °C and 1 atm,<br/>1.411kg/m<sup>3</sup> at 20°C and 1 atm
|- align=left
| ''' Gas [[specific heat]], c<sub>p</sub>''' || 1.005 kJ/(kg·K) at 25 °C and 1 atm
|- align=left
| ''' Gas [[specific heat ratio]], c<sub>p</sub>/c<sub>v</sub>''' || 1.32 at 25 °C and 1 atm
|- align=left
| '''Gas [[Viscosity]]'''||126.02 micropoise at 25 °C
|}
|}
Hydrogen sulfide is a highly [[toxic]] and flammable gas ([[flammability range]]: 4.0  to 46 volume % in air).<ref name=ChemInfo>[http://www.ccohs.ca/products/databases/samples/cheminfo.html CCOHS Chemical Name: Hydrogen sulfide] From the website of the [[Canadian Centre for Occupational Health and Safety]] (CCOHS)</ref>  It is  heavier than air and tends to accumulate at the bottom of poorly ventilated, confined spaces.
Hydrogen sulfide and oxygen burn  to form [[sulfur dioxide]] (SO<sub>2</sub>) and water. In general, hydrogen sulfide acts as a [[reducing agent]].
At high temperature (about 1000 °[[Celsius (unit)|C]]) and with the use of a [[catalyst]], sulfur dioxide will react with hydrogen sulfide to form elemental sulfur and water (in the form of [[steam]]). This is commonly accomplished by the [[Claus process]], the primary method of converting hydrogen sulfide into elemental sulfur.
Hydrogen sulfide is readily soluble in water, amounting to 4.1 grams per litre of water at 20 °C which is equivalent to 0.41 weight %.<ref>[http://www.atsdr.cdc.gov/toxprofiles/tp114.pdf Toxicological Profile for Hydrogen Sulfide] July 2006, [[U.S. Department of Health and Human Services]], [[Agency for Toxic Substances and Disease Registry]] (ATSDR)</ref>  When it is in solution in water, the H<sub>2</sub>S forms a weak acid (sometimes referred to as hydrosulfuric acid) containing hydrosulfide and sulfide [[ion]]s (HS<sup>−</sup> and S<sup>2−</sup>). The solubility is further enhanced in alkaline solutions due to increased ionization.
Hydrogen sulfide reacts with metal ions to form metal [[sulfide]]s, which may be considered the [[salt]]s of hydrogen sulfide. Some [[Mineral deposit|minerals]] are sulfides.
Hydrogen sulfide reacts with alcohols to form [[thiol]]s.
==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:<ref name=ChemInfo/><ref>[http://www.extension.iastate.edu/Publications/PM1963A.pdf Odor perception and physiological  response]</ref><ref>{{cite book|author=Peter D. Bryson|title=Comprehensive Review In Toxicology For Emergency Clinicians|edition=Third Edition|publisher=Taylor and Francis|date=September 1996|pages=p. 368|id=ISBN 1-56032-612-3}}</ref>
* 0.00047 [[parts-per notation|ppmv]] is the recognition threshold, the concentration at which 50% of humans can detect the characteristic foul odor of hydrogen sulfide.
* At 100 – 150 ppmv, the [[olfactory nerve]] is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.
* At 200 ppmv, the central nervous system is depressed.
* At 500 ppmv, the cardiovascular system is depressed.
* At 1000 ppmv, the central nervous system is paralyzed and death occurs.
==References==
{{reflist}}

Revision as of 20:52, 4 March 2011

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