Potassium cyanide

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Template:Chembox ECNumberTemplate:Chembox E numberTemplate:Chembox Lethal amounts (set)
Potassium cyanide
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RTECS number TS8750000
Molar mass 65.12 g/mol
Melting point
Solubility in other solvents 71.6 g/100 ml (25°C)
Std enthalpy of
−131.5 kJ/mol
Standard molar
127.8 J.K–1.mol–1
EU classification {{{value}}}
R-phrases R26/27/28, R32
S-phrases (S1/2), S7, S28, S29
S45, S60, S61
Related compounds
Other cations {{{value}}}
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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Potassium cyanide is an inorganic compound with the formula KCN. This colorless crystalline compound, similar in appearance to sugar, is highly soluble in water. The vast majority of KCN is used in gold mining followed by use in organic synthesis, and electroplating. Smaller applications include jewelry for chemical gilding and buffing.[2]

Highly toxic, KCN is odorless but due to hydrolysis, the moist solid emits small amounts of hydrogen cyanide, which smells like bitter almonds (not everyone can smell it—the ability thereof is due to a genetic trait[3]). It is also used by entomologists as a killing agent in collecting jars, as most insects succumb within seconds, minimizing damage of even the most fragile types.


KCN is produced by treating hydrogen cyanide with potassium hydroxide.[2] Approximately 50,000 tons are produced yearly (the production of sodium cyanide is 10x that amount). It is detoxified most efficiently with hydrogen peroxide:[2]

KCN + H2O2 → KOCN + H2O


In gold mining, KCN and NaCN form water-soluble salts from gold metal in the presence of air:

4 Au + 8 KCN + O2 + 2 H2O → [Au(CN)2]- + 4 OH-

Very few methods exist for this extraction process.

KCN and the related NaCN are widely used in organic synthesis for the preparation of nitriles and carboxylic acids. Illustrative is the Von Richter reaction.


Cyanide is a potent inhibitor of cellular respiration, acting on mitochondrial cytochrome c oxidase and hence blocking oxidative phosphorylation. This prevents the body from oxidising food to produce useful energy. Lactic acidosis then occurs as a consequence of anaerobic metabolism. Initially, acute cyanide poisoning causes a red or ruddy complexion in the victim because the tissues are not able to use the oxygen in the blood. The effects of potassium cyanide are virtually identical to sodium cyanide. The person may die within two hours if not treated medically. During this period, convulsions may occur. Death occurs mainly by cardiac arrest.

A number of prominent Nazis, including Hermann Göring and Heinrich Himmler, committed suicide using lethal pills which contained potassium cyanide.[4] The substance was also used in the 1978 mass murder/suicide of over 900 people at Jonestown, Guyana.[5]

In fiction

Potassium cyanide (and other forms of cyanide) often appear in fiction. In crime fiction it is a popular choice as a murder weapon.


  1. Bernard Martel. Chemical Risk Analysis: A Practical Handbook. Kogan, 2004, page 361. ISBN 1903996651.
  2. 2.0 2.1 2.2 Andreas Rubo, Raf Kellens, Jay Reddy, Norbert Steier, Wolfgang Hasenpusch "Alkali Metal Cyanides" in Ullmann's Encyclopedia of Industrial Chemistry 2006 Wiley-VCH Verlag GmbH, Weinheim, Germany.ISBN: 10.1002/14356007.i01 i01
  3. Online Mendelian Inheritance in Man (OMIM) 304300
  4. "Anderson Cooper 360 Degrees: Police Continue Search for Child Pornographer; Hermann Goering's Suicide Solved?; Atlanta Bride-to-be Still Missing; Massachusetts Money Find a Hoax?" (Transcript). CNN.com. 29 April 2005. Retrieved 2007-11-09.
  5. http://www.opb.org/radio/archives/2007/04/there_was_no_ch_1.php Text and first-hand account audio recording #4 indicate it was cyanide and bitter, respectively.

External links

bg:Цианкалий cs:Kyanid draselný da:Cyankalium de:Kaliumcyanid ko:사이안화 칼륨 lv:Kālija cianīds nl:Kaliumcyanide no:Kaliumcyanid sk:Kyanid draselný sr:Калијум цијанид fi:Kaliumsyanidi sv:Kaliumcyanid