Hydrogen sulfide
Colorless, toxic gas with a rotten-egg odor.
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Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless, toxic, and flammable hydrogen chalcogenide gas, known for its characteristic foul odor of rotten eggs at trace levels. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
Quick Facts
- Formula
- H2S
- Discovered by
- Carl Wilhelm Scheele
- Discovery year
- 1777
- State at room temperature
- Gas
- Key property
- Toxic
- flammable
- weak acid
Facts from the source article.
Lore & Background
Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers, a process known as anaerobic digestion carried out by sulfate-reducing microorganisms. It also occurs in volcanic gases, natural gas deposits, and sometimes in well-drawn water. The gas is slightly denser than air, and a mixture of H2S and air can be explosive.
Reader's Guide
Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule. H2S is involved in vasodilation in animals, as well as in increasing seed germination and stress responses in plants. The field of H2S biology has advanced from environmental toxicology to investigate the roles of endogenously produced H2S in physiological conditions and in various pathophysiological states, including cancer, Down syndrome, and vascular disease. At lower concentrations, it stimulates mitochondrial function; at higher concentrations, it inhibits Complex IV of the mitochondrial electron transport chain, reducing ATP generation.
Did You Know?
- It acts as a reducing agent and burns in oxygen with a blue flame to form sulfur dioxide and water.
- At pressures above 90 GPa, hydrogen sulfide becomes a metallic conductor and exhibits superconductivity when cooled.
- Lead(II) acetate paper is used to detect hydrogen sulfide because it readily converts to black lead(II) sulfide.
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Frequently Asked Questions
Who is Hydrogen sulfide?
Hydrogen sulfide (H2S) is a colorless hydrogen chalcogenide gas best recognized by its unmistakable rotten-egg stench, even at trace concentrations. It is a weak acid that is both toxic and flammable, making it one of the most dangerous small molecules you can encounter.
What is Hydrogen sulfide known for?
As a weak acid, H2S can donate protons in solution, and its flammability lets it serve as a fuel in certain industrial reactions. Its severe toxicity is what makes it a notorious hazard in mines, sewage systems, and volcanic gas plumes.
How was Hydrogen sulfide discovered?
Swedish chemist Carl Wilhelm Scheele is credited with pinning down the true chemical composition of purified hydrogen sulfide in 1777. Prior to that work, the gas was encountered in various impure mixtures but its identity as a distinct compound had not been established.
What state is Hydrogen sulfide in at room temperature?
At ordinary conditions it exists as a colorless gas, so it is invisible to the eye. The rotten-egg odor is your primary warning, though at high enough concentrations it actually paralyses the olfactory nerve and the smell vanishes—a dangerously misleading sign.
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