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Hydrogen cyanide

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Hydrogen cyanide
Acido cianidrico struttura modello.png
Systematic name Formonitrile
Other names

Hydrogen cyanide
hydrocyanic acid
prussic acid
Zyklon B.

Molecular formula HCN
Molar mass Molar mass:: 27.0253 g/mol.
Appearance colorless gas
or a blue-white liquid
and has a bitter almond odor.
CAS number CAS number::74-90-8
Density and phase Density::0.94g/ml
Solubility in water Miscible in water and alcohol
Soluble in both.
Melting point Melting point::-13.4 ° C
Boiling point Boiling point:: 25.7 ° C
Acidity 9.1
Viscosity 0.201 cP
Molecular shape Linear
Dipole moment 2.98 D D
MSDS Material safety data sheet
Main hazards Highly flammable.

Highly toxic.
Destructive to the environment.

NFPA 704

NFPA 704 svg.png

Flash point 18°C
R/S statement R: R: R12, R26, R27, R28, R32
S: S1, S2, S7, S9, S13, S16,

S28, S29, S45

RTECS number MW6825000
Related compounds
Other anions Hydrogen fluoride
Other cations Sodium Cyanide
Potassium Cyanide
Related compounds

Cyanogen chloride
Trimethylsilyl cyanide

Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Disclaimer and references

Hydrogen Cyanide is an extremely toxic compound that can be useful in some ways if used right. If careful, it can be used to temper metals and be an useful precursor to other special compounds. It is found naturally in some fruits and is released from certain insects, but can also be produced through chemical bonds and industrial production. It has been used in the past as a poison, chemical weapons, and explosive weapons as well because of all its special properties.


Hydrogen cyanide is a colorless and odorless gas and is an extremely flammable and toxic chemical. It has a bitter almond smell and is able to effect your respiratory system and circulatory system through the appropriate exposure. It is miscible both in water and alcohol and is also soluble in both. Hydrogen cyanide has a melting point of -13.4°C and the boiling point is 25.7°C with a density of .94g/ml. The water solution of HCN is a weak acid otherwise known as hydrocyanic acid. The salts from this compound are called cyanides and can be produced through ammonia and carbon monoxide. It also can be produced through a reaction of a strong acid with calcium cyanide. It has a linear structure with a hydrogen single bonding to carbon and triple bonding nitrogen[1].

Hydrogen cyanide is only found in nature through some vegetables like almonds, cherry stones, and sorghum. The poisonous nature of this compound allows it to be extremely dangerous and also is highly flammable. The flammability rating of HCN is a 4 which means if hydrogen cyanide is exposed to fire in anyway it has to be treated with caution through evacuations and special methods. The IUPAC name of HCN is formonitrile and has several other names like Hydrogen cyanide, methanenitrile, hydrocyanic acid, prussic acid, and Zyklon B. It is weak speaking in terms of acidity, only having a 9.1pKa acidity. Industrial production of HCN is made to be a highly useful precursor to many other chemical compounds. The poisonous properties of this compound have been used in poisons, like cyanide capsules or in a liquid form. The properties of this highly toxic compound make it extremely dangerous to be around and there are strict regulations on the health hazards and environmental precautions[2].


Occurances of hcn.jpg
  • Chemically

Hydrogen cyanide can be produced through combining cyanide salts with a strong acid or chemically bonding ammonia and carbon monoxide also works to produce this compound. Car exhausts produce trace amounts of hydrogen cyanide as well because of the carbon monoxide in the exhaust. It can also be produced by thermal decomposition of formamide. Coke from the coal can be used to make this compound as well[3].

Hydrogen cyanide is contained in any fruits that have a pit, like almonds and apples. Along with fruits it is found in some vegetable substances like peach stones, cherry leaves and sorghum. The cassava plant roots also has amounts of HCN, about 1 gram of the compound per kilogram. Some certain insects like millipedes release HCN in a defensive act against predators or threats. Wood smoke and tobacco smoke contains HCN as well as smoke from plastic fires. HCN can be seen in space, to be exact the interstellar medium. Clouds form with the compound in it that can be seen from telescopes on the ground through small atmospheric windows. These "windows" reveal destruction pathways caused by the compound in these clouds. These pathways of destruction help researchers keep tracking the clouds as they leave quite an obvious trail. HCN clouds are formed through neutral-neutral reactions and dissociative recombination of compounds. Once hydrogen cyanide is in the cloud, it starts to be destroyed. Depending on the locations of these space clouds, different mechanisms of destruction would be used, the most common being photodissociation [4].


Hydrogen cyanide is used in a variety of ways, mostly for precursors of other compounds. But different uses can consist of being used for synthesis like the production of adiponitrile, pharmaceuticals, and other chemicals that have special properties. Hydrogen cyanide can also be used as insecticides and fungicides. In metallurgy, hydrogen cyanide is used as a tempering agent for many metals. Hydrogen cyanide is also used in a various amounts of dyes, as well as engraving plates that are used for printing purposes. Another common usage is explosives and war materials because of its property of being highly flammable and explosive, which makes it an useful compound for weapons manufacturers[5]. On a darker side of the compound, in past history it has been used in gas chamber executions because of its highly toxic nature; killing a human in only about ten minutes. Electroplating is a common usage of HCN, as well as more treatment of metals.



The toxicity of hydrogen cyanide is so devastating that it can kill a human in ten minutes if ingested. Throughout history, people have used this deadly compound to poison or kill. Hitler used a cyanide capsule along with a gunshot to kill himself once Germany had lost the war. During that time, cyanide capsules were the popular thing to take if suicide was needed to avoid either an interrogation or capture. Regulations are strict on exposure either in a workplace or in nature because it is so destructive. It kills and destroys if not balanced out through some certain chemical bonds. Overall it is a destructive compound and is only useful if bonded with something or used in metals, staying away from humans, animals, and nature.