User:Milton Beychok/Sandbox: Difference between revisions

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Hydrogen sulfide is a highly [[toxic]] and flammable gas ([[Flammability range]]: 4.3 % - 46 % volume % in air).  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 safe handling procedures, a hydrogen sulfide [[MSDS|material safety data sheet]] (MSDS) should be consulted.<ref>[http://avogadro.chem.iastate.edu/MSDS/hydrogen_sulfide.pdf Hydrogen Sulfide Material Safety Data Sheet (MSDS)] [[Iowa State University]], Department of Chemistry</ref>
Hydrogen sulfide is a highly [[toxic]] and flammable gas ([[flammability range]]: 4.3 to 46 volume % in air).  It is  heavier than air and tends to accumulate at the bottom of poorly ventilated spaces.  


Hydrogen sulfide and [[oxygen]] burn with a blue flame to form [[sulfur dioxide]] (SO<sub>2</sub>) and [|water]]. In general, hydrogen sulfide acts as a [[reducing agent]].
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 and in the presence of [[catalyst]]s, sulfur dioxide can be made to react with hydrogen sulfide to form elemental sulfur and water. This is exploited in the [[Claus process]], the main way to convert hydrogen sulfide into elemental sulfur.
At high temperature (about 1000 °C) and with the use of a [[catalyst]], sulfur dioxide will react with hydrogen sulfide to form elemental sulfur and water. This is exploited in the [[Claus process]], the main way to convert hydrogen sulfide into elemental sulfur and water (in the form of [[steam]]).


Hydrogen sulfide is slightly soluble in water and acts as a [[weak acid]], giving the hydrosulfide ion HS<sup>&minus;</sup> ([[Acid dissociation constant|pK<sub>a</sub>]]=6.9 in 0.01-0.1&nbsp;mol/litre solutions at 18°C) and the [[sulfide]] ion S<sup>2&minus;</sup> (pK<sub>a</sub>=11.96).  
Hydrogen sulfide is slightly soluble in water and acts as a [[weak acid]], giving the hydrosulfide ion HS<sup>&minus;</sup> ([[Acid dissociation constant|pK<sub>a</sub>]]=6.9 in 0.01-0.1&nbsp;mol/litre solutions at 18 °C) and the [[sulfide]] ion S<sup>2&minus;</sup> (pK<sub>a</sub>=11.96).  


Hydrogen sulfide reacts with metal ions to form metal [[sulfide]]s, which may be considered the [[salt]]s of hydrogen sulfide. Some [[ore]]s are sulfides. Metal sulfides often have a dark color.  
Hydrogen sulfide reacts with metal ions to form metal [[sulfide]]s, which may be considered the [[salt]]s of hydrogen sulfide. Some [[ore]]s are sulfides. Metal sulfides often have a dark color.  
If gaseous hydrogen sulfide is put into contact with concentrated [[nitric acid]], it explodes.


Hydrogen sulfide reacts with alcohols to form [[thiol]]s.
Hydrogen sulfide reacts with alcohols to form [[thiol]]s.

Revision as of 14:12, 2 March 2011

Hydrogen Sulfide

Hydrogen sulfide (or hydrogen sulphide) is a chemical compound with the formula H2S. 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 refining of petroleum crude oil. In fact, the vast majority of the 66,000,000 metric tons of sulfur produced worldwide in 2006 was by-product sulfur from petroleum refining and natural gas processing plants.[1] It is also present in volcanic gases and some water well sources

It also occurs in swamps and sewers as a result of the bacterial breakdown of organic matter in the absence of oxygen, which is known as anaerobic digestion.

Chemical properties

Properties
Property Value[2][3]
Common name hydrogen sulfide
Other names hydrogen sulphide, dihydrogen sulfide, sulfur hydride, sewer gas
IUPAC name hydrogen sulfide
CAS number 7783-06-04
Molecular formula H2S
Molecular mass 34.082 g/mol
Melting point -85.47 °C
Normal boiling point -60.35 °C and 1 atm
Critical point 100.38 °C at 88.46 atm
Heat of fusion 69.74 kJ/kg at -85.47 °C and 1 atm
Heat of vaporization 517.87 kJ/kg at -60.35 °C and 1 atm
Liquid density 914.9 kg/m3 at -60.35 °C and 1 atm
Gas density 1.93 kg/m3 at -60.35 °C and 1 atm,
1.411kg/m3 at 20°C and 1 atm
Gas specific heat, cp 1.005 kJ/(kg·K) at 25 °C and 1 atm
Gas specific heat ratio, cp/cv 1.32 at 25 °C and 1 atm
Gas Viscosity 126.02 micropoise at 25 °C

Hydrogen sulfide is a highly toxic and flammable gas (flammability range: 4.3 to 46 volume % in air). It is heavier than air and tends to accumulate at the bottom of poorly ventilated spaces.

Hydrogen sulfide and oxygen burn to form sulfur dioxide (SO2) and [|water]]. In general, hydrogen sulfide acts as a reducing agent.

At high temperature (about 1000 °C) and with the use of a catalyst, sulfur dioxide will react with hydrogen sulfide to form elemental sulfur and water. This is exploited in the Claus process, the main way to convert hydrogen sulfide into elemental sulfur and water (in the form of steam).

Hydrogen sulfide is slightly soluble in water and acts as a weak acid, giving the hydrosulfide ion HS− (pKa=6.9 in 0.01-0.1 mol/litre solutions at 18 °C) and the sulfide ion S2− (pKa=11.96).

Hydrogen sulfide reacts with metal ions to form metal sulfides, which may be considered the salts of hydrogen sulfide. Some ores are sulfides. Metal sulfides often have a dark color.

Hydrogen sulfide reacts with alcohols to form thiols.

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.

  • 0.00047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic foul odor of hydrogen sulfide.[4]
  • At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.[5][6]
  • 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.

References

  1. ↑ Sulfur production report by the United States Geological Survey
  2. ↑ Carl L. Yaws (June 25, 2001). Matheson Gas Data Handbook, 7th Edition. McGraw-Hill. ISBN 0-07-135851-4. 
  3. ↑ Air Liquide Gas Encyclopedia
  4. ↑ Odor perception and physiological response
  5. ↑ USEPA; Health and Environmental Effects Profile for Hydrogen Sulfide p.118-8 (1980) ECAO-CIN-026A  ???
  6. ↑ Zenz, C., O.B. Dickerson, E.P. Horvath. Occupational Medicine. 3rd ed. St. Louis, MO., 1994, p.886 /publisher.ISBN???
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