Hydrogen Cyanide

Hydrogen cyanide is a chemical compound with chemical formula HCN. Hydrogen cyanide is a colorless, extremely poisonous liquid that boils slightly above room temperature at 26°C.
Hydrogen Cyanide has a faint, bitter, almond-like odor that some people are unable to detect due to a genetic trait. The volatile compound has been used as inhalation rodenticide and human poison.
HCN is produced on an industrial scale, and is a highly valuable precursor to many chemical compounds, ranging from polymers to pharmaceuticals.
Air-Met has a wide range of portable and fixed gas detectors as well as detection tubes available for detection of HCN. Our product selector can guide you towards to right instrument for your application. For more information, please contact one of our sales representatives.
Hydrogen Cyanide Characteristics
Synonyms Hydrocyanic acid, Methanenitrile, Prussic acid
CAS No. 74-90-8
Chemical formula HCN
Vapour density 0.90 (air = 1)
Safe Work Australia ES TWA 10 ppm peak limitation
STEL ---
Flammable limits LEL 5.4 % by volume
UEL 46.0 % by volume
Equipment group IIB
Temperature classification T1
Chemical/physical properties Hydrogen cyanide is a colourless, volatile liquid, readily forming a colourless, flammable vapour at room temperature. It has a characteristic, but not always detectable, bitter almonds odour.
Hazardous properties Hydrogen cyanide, like other cyanide salts (sodium cyanide, potassium cyanide etc.), is extremely toxic due to the solubility of the cyanide ion (CN-) and the inhibitory effect it has on critical respiratory enzymes preventing the uptake of oxygen by the tissues and leading to asphyxiation and death. It has been reported that exposure to a concentration of 3,500 ppm can be fatal after 1 minute.
As well as the risk due to inhalation, it is readily absorbed through the skin.
Although it is flammable, the risk of explosion is far outweighed by its toxicity – everyone in the vicinity would be dead long before it reached the LEL!
Occurrence/Uses Hydrogen cyanide has been used as fumigant but its main application is in the extraction of mineral ores (e.g. gold and silver). It is also a by-product of combustion and is found in vehicle exhaust, tobacco smoke, wood smoke and smoke from burning nitrogen containing plastics (e.g. ABS – acrylonitrile butadiene styrene).
Detectors available Electrochemical (0 – 30 ppm)
Colorimetric paper tape (0 – 2,500 ppb)
Gas detector tube (0.3 ppm – 3.0 % by volume)
Suggested alarm levels Lo: 5 ppm
Hi: 10 ppm


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