The Online Encyclopedia and Dictionary






Hydrogen sulfide



Name Hydrogen sulfide
Chemical formula H2S
Appearance Colourless gas


Formula weight 34.1 amu
Melting point 187 K (-86 °C)
Boiling point 213 K (-60 °C)
Solubility 0.33 g in 100g water


ΔfH0gas -20.5 kJ/mol
ΔfH0liquid ? kJ/mol
ΔfH0solid ? kJ/mol
S0gas, 1 bar 205.77 J/mol·K
S0liquid, 1 bar ? J/mol·K
S0solid ? J/mol·K


Ingestion May cause nausea and vomiting.
Inhalation Exceedingly dangerous. Concentrations >800ppm will cause sudden death.
Skin May cause severe pain and itching.
Eyes May cause burns.
More info Hazardous Chemical Database

SI units were used where possible. Unless otherwise stated, standard conditions were used.

Disclaimer and references

For an alternative meaning for H2S, see H2S radar.

The chemical compound hydrogen sulfide (Hydrogen sulphide in British English) H2S is a sulfide compound that has an unpleasant smell; it is responsible for the smell of rotten eggs. This gas can suffocate sewer workers and is often associated with other decay smells in swamps. Hydrogen sulfide is produced by the breakdown of sulfur-containing proteins and is responsible for much of the foul odor of feces and flatulence.

Hydrogen sulfide occurs naturally in crude petroleum, natural gas, volcanic gases, and hot springs. It can also result from bacterial breakdown of organic matter. It is also produced by human and animal wastes.

Hydrogen sulfide can also result from industrial activities, such as food processing, sewage treatment, coke ovens, paper mills, tanneries, and petroleum refineries..

It is an acidic gas which reacts with alkali and metals such as silver. This is the reason why silver jewellery turns black when exposed to polluted atmosphere for a long duration. The silver sulfide resulting from the reaction is black in colour.

Health effects

Hydrogen sulfide is considered a broad-spectrum poison, meaning it can poison several different systems in the body. Breathing high levels of hydrogen sulfide may kill the olfactory nerve (making it impossible to smell the gas) and can cause death within just a few breaths. There could be loss of consciousness after one or more breaths.

Exposure to lower concentrations can result in eye irritation, a sore throat and cough, shortness of breath, and fluid in the lungs. These symptoms usually go away in a few weeks. Long-term, low-level exposure may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness.

Animal studies showed that pigs that ate food containing hydrogen sulfide had diarrhea after a few days and weight loss after about 105 days.

Last updated: 05-07-2005 12:18:51
Last updated: 05-13-2005 07:56:04