Carbonyl sulfide is a colorless gas with the chemical formula COS, structurally similar to carbon dioxide but with one oxygen atom replaced by sulfur. As the most abundant sulfur compound in Earth’s atmosphere, COS plays a crucial role in the global sulfur cycle and contributes to the formation of atmospheric aerosols that influence climate patterns. First synthesized in 1841, this linear molecule is produced both naturally through ocean processes, volcanic activity, and wetlands, as well as industrially as a byproduct of petroleum refining and coal combustion. While less well-known than its relatives CO₂ and CS₂, carbonyl sulfide serves important industrial purposes including grain fumigation and as a chemical intermediate, though its ability to penetrate deep into stored products and its toxicity at high concentrations require careful handling and monitoring.

Find a review of the 50 most important industrial gases here.

20 Fun Facts About Carbonyl Sulfide

Beyond the basics above, what else should we know about Carbonyl Sulfide? Check out the 20 fun facts below!

1. COS is the only atmospheric gas that can penetrate the stratosphere intact and contribute to the stratospheric sulfate layer that affects climate.
2. The molecule vibrates asymmetrically 2079 times per second, creating a unique infrared signature used to track it from satellites.
3. Carbonyl sulfide was a popular grain fumigant in Australia until they discovered it turns silver coins black in stored wheat.
4. Deep-sea hydrothermal vents emit COS at concentrations 10,000 times higher than surface seawater, supporting unique ecosystems.
5. The gas has an extremely faint rotten egg odor only detectable above 10 ppm, well into the toxic range for humans.
6. Plants accidentally absorb COS while taking in CO₂, making vegetation a major global sink removing 1 million tons annually.
7. Carbonyl sulfide forms explosive mixtures with air between 12% and 29%, but decomposes before accumulating to dangerous levels.
8. The compound exists on Venus, Jupiter, and in interstellar space, suggesting it forms easily under various cosmic conditions.
9. Industrial catalysts containing COS-resistant materials cost 10 times more than standard versions due to its corrosive sulfur content.
10. Forensic scientists can detect COS in blood years after exposure because it forms stable compounds with hemoglobin proteins.
11. The molecule is exactly linear with a C-S bond length of 1.56 Angstroms and C-O bond of 1.16 Angstroms.
12. Termites produce measurable amounts of COS when digesting wood, contributing about 1% of natural atmospheric emissions.
13. COS breaks down into CO and sulfur in UV light, which is why it doesn’t accumulate despite continuous production.
14. Antarctic ice cores show COS levels have increased by 25% since 1850, tracking closely with industrial development.
15. The gas liquefies at -50°C but forms unusual crystal structures when frozen that are still being studied.
16. Some metal-organic frameworks can selectively capture COS from gas streams with 99.9% efficiency for sulfur recovery.
17. Carbonyl sulfide was tested as a potato sprout inhibitor but abandoned when it made the potatoes taste slightly metallic.
18. The compound can substitute for CO₂ in certain photosynthesis studies because plants process both molecules similarly.
19. Natural gas wells in China‘s Sichuan Basin produce up to 1% COS, requiring special processing before pipeline transport.
20. Astronomers use COS emissions to map dense molecular clouds where stars form, as it survives longer than other sulfur compounds.

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