Potassium cyanide

Short description: Highly toxic crystalline salt

Potassium cyanide

Names
IUPAC name

Potassium cyanide

Identifiers

CAS Number

* 151-50-8 Y

3D model (JSmol)

* Interactive image

ChEBI |

* CHEBI:33191 N

ChemSpider |

* 8681 Y

EC Number |

* 205-792-3

PubChem CID

* 9032

RTECS number |

* TS8750000

UNII |

* MQD255M2ZO Y

UN number | 1680

InChI

* InChI=1S/CN.K/c1-2;/q-1;+1 Y

Key: NNFCIKHAZHQZJG-UHFFFAOYSA-N Y

* InChI=1/CN.K/c1-2;/q-1;+1

Key: NNFCIKHAZHQZJG-UHFFFAOYAH

SMILES

* [K+].[C-]#N

Properties

Chemical formula

| KCN
Molar mass | 65.12 g/mol
Appearance  | White crystalline solid
deliquescent
Odor | faint, almond-like
Density | 1.52 g/cm3
Melting point |  634.5 °C (1,174.1 °F; 907.6 K)
Boiling point |  1,625 °C (2,957 °F; 1,898 K)

Solubility in water

| 71.6 g/100 ml (25 °C)
100 g/100 ml (100 °C)
Solubility in methanol | 4.91 g/100 ml (20 °C)
Solubility in glycerol | soluble
Solubility in formamide | 14.6 g/100 mL
Solubility in ethanol | 0.57 g/100ml
Solubility in hydroxylamine | 41 g/100 ml
Acidity (pKa)  | 11.0

Magnetic susceptibility (χ)

| −37.0·10−6 cm3/mol

Refractive index (nD)

| 1.410
Thermochemistry

Std molar
entropy (S ~~o~~ 298)

| 127.8 J K−1 mol−1

Std enthalpy of
formation (ΔfH⦵298)

| −131.5 kJ/mol
Hazards
Safety data sheet | ICSC 0671
GHS pictograms |
GHS Signal word | Danger

GHS hazard statements

| H290, H300, H310, H330, H370, H372, H410

GHS precautionary statements

| P260, P264, P273, P280, P284, P301+310
NFPA 704 (fire diamond)  |

Flash point | Non-flammable
Lethal dose or concentration (LD, LC):

LD50 (median dose)

| 5 mg/kg (oral, rabbit)
10 mg/kg (oral, rat)
5 mg/kg (oral, rat)
8.5 mg/kg (oral, mouse)[2]
NIOSH (US health exposure limits):

PEL (Permissible)

| TWA 5 mg/m3[1]

REL (Recommended)

| C 5 mg/m3 (4.7 ppm) [10-minute][1]

IDLH (Immediate danger)

| 25 mg/m3[1]
Related compounds

Other anions

| Potassium cyanate
Potassium thiocyanate

Other cations

| Sodium cyanide
Rubidium cyanide
lithium cyanide
caesium cyanide

Related compounds

| Hydrogen cyanide

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include jewellery for chemical gilding and buffing.[4] Potassium cyanide is highly toxic, and a dose of 200 to 300 milligrams will kill nearly any human.

The moist solid emits small amounts of hydrogen cyanide due to hydrolysis (reaction with water). Hydrogen cyanide is often described as having an odor resembling that of bitter almonds.[5][6]

The taste of potassium cyanide has been described as acrid and bitter, with a burning sensation[7][unreliable source?] similar to lye.[8]

## Contents

* 1 Production
* 1.1 Historical production
* 2 Structure
* 3 Applications
* 3.1 Potassium gold cyanide
* 4 Toxicity
* 5 References
* 6 External links

## Production

KCN is produced by treating hydrogen cyanide with an aqueous solution of potassium hydroxide, followed by evaporation of the solution in a vacuum:[4]

HCN + KOH → KCN + H2O

About 50,000 tons of potassium cyanide are produced yearly. [4]

### Historical production

Before 1900 and the invention of the Castner process, potassium cyanide was the most important source of alkali metal cyanides.[4] In this historical process, potassium cyanide was produced by decomposing potassium ferrocyanide:[9]

K4[Fe(CN)6] → 4 KCN + FeC2 \+ N2

## Structure

In aqueous solution, KCN is dissociated into hydrated potassium (K+) ions and cyanide (CN−) ions. As a solid, KCN has structure resembling sodium chloride: with each potassium ion surrounded by six cyanide ions, and vice versa. Despite being diatomic, and thus less symmetric than chloride, the cyanide ions rotate so rapidly that their time-averaged shape is spherical. At low temperature and high pressure, this free rotation is hindered, resulting in a less symmetric crystal structure with the cyanide ions arranged in sheets. [10][11]

## Applications

KCN and sodium cyanide (NaCN) are widely used in organic synthesis for the preparation of nitriles and carboxylic acids, particularly in the von Richter reaction. It also finds use for the synthesis of hydantoins, which can be useful synthetic intermediates, when reacted with a carbonyl compound such as an aldehyde or ketone in the presence of ammonium carbonate.

KCN is used as a photographic fixer in the wet plate collodion process.[12] The KCN dissolves silver where it has not been made insoluble by the developer. This reveals and stabilizes the image, making it no longer sensitive to light. Modern wet plate photographers may prefer less toxic fixers, often opting for sodium thiosulfate, but KCN is still used.

In the 19th century, cyanogen soap, a preparation containing potassium cyanide, was used by photographers to remove silver stains from their hands.[13]: 11 [14]: 73 [15]

### Potassium gold cyanide

In gold mining, KCN forms the water-soluble salt potassium gold cyanide (or gold potassium cyanide) and potassium hydroxide from gold metal in the presence of oxygen (usually from the surrounding air) and water:

4 Au + 8 KCN + O2 \+ 2 H2O → 4 K[Au(CN)2] + 4 KOH

A similar process uses NaCN to produce sodium gold cyanide (NaAu(CN2)).

## Toxicity

Potassium cyanide is a potent inhibitor of cellular respiration, acting on mitochondrial cytochrome c oxidase, hence blocking oxidative phosphorylation. 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 and sodium cyanide are identical, and symptoms of poisoning typically occur within a few minutes of ingesting the substance: the person loses consciousness, and brain death eventually follows. During this period the victim may suffer convulsions. Death is caused by cerebral hypoxia. The expected LD100 dose (human) for potassium cyanide is 200–300 mg while the median lethal dose LD50 is estimated at 140 mg.[16]

People who died by suicide, were killed, or killed someone else using potassium cyanide include:

* Viktor Meyer, 19th-century German chemist, died by suicide in 1897 after taking cyanide[17]
* Gustav Wied, Danish novelist, poet, and playwright, in 1914
* Pritilata Waddedar, an Indian revolutionary nationalist, took cyanide in 1932 to avoid capture by Indian Imperial Police, British India
* Badal Gupta, a revolutionary from Bengal, who launched an attack on the Writers' Building in Kolkata, consumed cyanide in 1930 immediately after the attack.
* Wallace Carothers, polymer chemist who died by suicide in 1937 after battling depression for years
* Senior figures in Nazi Germany, such as Erwin Rommel, Hitler's longtime companion Eva Braun, Joseph Goebbels, Heinrich Himmler, and Hermann Göring
* Alan Turing, a computer scientist who died of cyanide poisoning in 1954
* Ramon Sampedro, Spanish tetraplegic and activist whose assisted suicide in 1998 provoked a national debate about euthanasia, and was the subject of the Oscar-winning film "The Sea Inside"
* Ronald Clark O'Bryan, a Texas optician who killed his son by lacing a pixy stick with potassium cyanide in 1974
* Peoples Temple, the 1978 cult suicide in (Jonestown), Guyana
* Members of the LTTE involved in the assassination of Indian prime minister Rajiv Gandhi in 1991
* Jason Altom, a promising graduate student in the lab of Nobel Prize–winning chemist EJ Corey at Harvard, died after drinking potassium cyanide in 1998
* Slobodan Praljak, a wartime general in Republic of Croatia, died by suicide by drinking from a vial containing potassium cyanide during the reading of his appeal judgment in The Hague on International Criminal Tribunal for the former Yugoslavia (ICTY) on 29 November 2017.[18]

It is used by professional entomologists as a killing agent in collecting jars, as insects succumb within seconds to the HCN fumes it emits, thereby minimizing damage to even highly fragile specimens.

KCN can be detoxified most efficiently with hydrogen peroxide or with a solution of sodium hypochlorite (NaOCl). Such solutions should be kept alkaline whenever possible so as to eliminate the possibility of generation of hydrogen cyanide:[4]

KCN + H2O2 → KOCN \+ H2O
KCN + NaOCl → KOCN \+ NaCl

## References

1. ↑ 1.0 1.1 1.2 NIOSH Pocket Guide to Chemical Hazards. "#0522". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0522.html.
2. ↑ "Cyanides (as CN)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/cyanides.html.
3. ↑ "POTASSIUM CYANIDE | CAMEO Chemicals | NOAA". http://cameochemicals.noaa.gov/chemical/5150.
4. ↑ 4.0 4.1 4.2 4.3 4.4 Andreas Rubo, Raf Kellens, Jay Reddy, Joshua Wooten, Wolfgang Hasenpusch "Alkali Metal Cyanides" in Ullmann's Encyclopedia of Industrial Chemistry 2006 Wiley-VCH, Weinheim, Germany. doi:10.1002/14356007.i01_i01
5. ↑ "Suicide note reveals taste of cyanide". 2006-07-08. http://www.smh.com.au/news/world/suicide-note-reveals-taste-of-cyanide/2006/07/08/1152240534587.html.
6. ↑ Not everyone, however, can smell cyanide; the ability to do so is a genetic trait.Online Mendelian Inheritance in Man (OMIM) 304300
7. ↑ ലേഖകൻ, മാധ്യമം (2021-12-19). "'സയനൈഡ് ചവർപ്പാണ്... പുകച്ചിലാണ്...'; ആ 'രുചി രഹസ്യം' പുറത്തുവിട്ട മലയാളി നടന്ന വഴിയിലൂടെ | Madhyamam" (in ml). https://www.madhyamam.com/lifestyle/men/about-the-experience-of-malayalee-mp-prasad-who-drank-cyanide-895697.
8. ↑ "The only taste: Cyanide is acrid". Hindustan Times. 2006-07-08. http://www.hindustantimes.com/india/the-only-taste-cyanide-is-acrid/story-vhsbYsiNyWzIfakN4HBK0H.html.
9. ↑ Von Wagner, Rudolf (1897). Manual of chemical technology. New York: D. Appleton & Co.. p. 474 & 477. http://babel.hathitrust.org/cgi/pt?id=uc2.ark:/13960/t3tt4gz1p;view=1up;seq=502.
10. ↑ Crystallography Open Database, Structure of KCN
11. ↑ H. T. Stokes; D. L. Decker; H. M. Nelson; J. D. Jorgensen (1993). "Structure of potassium cyanide at low temperature and high pressure determined by neutron diffraction". Physical Review B 47 (17): 11082–11092. doi:10.1103/PhysRevB.47.11082. PMID 10005242. Bibcode: 1993PhRvB..4711082S. https://zenodo.org/record/1233725. .
12. ↑ J. Towler, MD. "The Silver Sunbeam (Facsimile 1864 edition, 1969)" pg 119
13. ↑ Crookes, William, ed (10 September 1858). "Photographic Notes and Queries". The Photographic News: A Weekly Record of the Progress of Photography (London: Cassell, Petter, and Galpin) 1 (1): 10-12. https://books.google.com/books?id=pvU_AAAAYAAJ&q="cyanogen+soap"&pg=PA11.
14. ↑ Reports of Trials for Murder by Poisoning; by Prussic Acid, Strychnia, Antimony, Arsenic, and Aconita. Including the trials of Tawell, W. Palmer, Dove, Madeline Smith, Dr. Pritchard, Smethurst, and Dr. Lamson, with chemical introduction and notes on the poisons used, G. Lathom Browne and C. G. Stewart, London: Stevens and Sons, 1883; redistributed by Project Gutenberg.
15. ↑ "Cyanuret of potassium", Paper, Shadows and Light, Robert Douglas. Accessed 2024-01-20.
16. ↑ John Harris Trestrail III. Criminal Poisoning - Investigational Guide for Law Enforcement, Toxicologists, Forensic Scientists, and Attorneys (2nd edition). p. 119
17. ↑ "Top 10 Scientists who Committed Suicide". 2007-10-07. http://listverse.com/2007/10/07/top-10-scientists-who-committed-suicide/.
18. ↑ "War criminal 'took cyanide' in Hague court" (in en-GB). BBC News. 2017-12-01. https://www.bbc.co.uk/news/world-europe-42204587.

## External links

* International Chemical Safety Card 0671
* Hydrogen cyanide and cyanides (CICAD 61)
* National Pollutant Inventory - Cyanide compounds fact sheet
* NIOSH Pocket Guide to Chemical Hazards
* CSST (Canada)
* NIST Standard Reference Database
* Institut national de recherche et de sécurité (1997). "Cyanure de sodium. Cyanure de potassium". Fiche toxicologique n° 111, Paris:INRS, 6pp. Script error: The function "in_lang" does not exist.

* v
* t
* e

Potassium compounds

* KAsO2
* KBr
* KBrO3
* KCN
* KCNO
* KCl
* KClO
* KClO3
* KClO4
* KF
* KH
* KHCO2
* KHCO3
* KHF2
* KHS
* KHSO3
* KHSO4
* KH2AsO4
* KH2PO3
* KH2PO4
* KI
* KIO3
* KIO4
* KMnO4
* KNH2
* KN3
* K3N
* KNO2
* KNO3
* KOCN
* KOH
* KO2
* KPF6
* KSCN
* KCH3COO
* K2Al2O4
* K2CO3
* K2CrO4
* K2Cr2O7
* K2FeO4
* K2HPO4
* K2MnO4
* K2O
* K2O2
* K2PtCl4
* K2PtCl6
* K2S
* K2SeO4
* K2SO3
* K2SO4
* KHSO5
* K2S2O5
* K2S2O7
* K2S2O8
* K2Po
* K2SiO3
* K3[Fe(CN)6]
* K3[Fe(C2O4)3]
* K4[Fe(CN)6]
* K3PO4
* K4Mo2Cl8

* v
* t
* e

Molecules detected in outer space

Molecules|

| Diatomic|

* Aluminium monochloride
* Aluminium monofluoride
* Aluminium monoxide
* Argonium
* Carbon monophosphide
* Carbon monosulfide
* Carbon monoxide
* Carborundum
* Cyanogen radical
* Diatomic carbon
* Fluoromethylidynium
* Helium hydride ion
* Hydrogen chloride
* Hydrogen fluoride
* Hydrogen (molecular)
* Hydroxyl radical
* Iron(II) oxide
* Magnesium monohydride cation
* Methylidyne radical
* Nitric oxide
* Nitrogen (molecular)
* Nitrogen monohydride
* Nitrogen sulfide
* Oxygen (molecular)
* Phosphorus monoxide
* Phosphorus mononitride
* Potassium chloride
* Silicon carbide
* Silicon mononitride
* Silicon monoxide
* Silicon monosulfide
* Sodium chloride
* Sodium iodide
* Sulfur monohydride
* Sulfur monoxide
* Titanium oxide

|
|

Triatomic|

* Aluminium hydroxide
* Aluminium isocyanide
* Amino radical
* Carbon dioxide
* Carbonyl sulfide
* CCP radical
* Chloronium
* Diazenylium
* Dicarbon monoxide
* Disilicon carbide
* Ethynyl radical
* Formyl radical
* Hydrogen cyanide (HCN)
* Hydrogen isocyanide (HNC)
* Hydrogen sulfide
* Hydroperoxyl
* Iron cyanide
* Isoformyl
* Magnesium cyanide
* Magnesium isocyanide
* Methylene radical
* N2H+
* Nitrous oxide
* Nitroxyl
* Ozone
* Phosphaethyne
* Potassium cyanide
* Protonated molecular hydrogen
* Sodium cyanide
* Sodium hydroxide
* Silicon carbonitride
* c-Silicon dicarbide
* SiNC
* Sulfur dioxide
* Thioformyl
* Thioxoethenylidene
* Titanium dioxide
* Tricarbon
* Water

Four
atoms|

* Acetylene
* Ammonia
* Cyanic acid
* Cyanoethynyl
* Cyclopropynylidyne
* Formaldehyde
* Fulminic acid
* HCCN
* Hydrogen peroxide
* Hydromagnesium isocyanide
* Isocyanic acid
* Isothiocyanic acid
* Ketenyl
* Methylene amidogen
* Methyl radical
* Propynylidyne
* Protonated carbon dioxide
* Protonated hydrogen cyanide
* Silicon tricarbide
* Thioformaldehyde
* Tricarbon monoxide
* Tricarbon sulfide
* Thiocyanic acid

Five
atoms|

* Ammonium ion
* Butadiynyl
* Carbodiimide
* Cyanamide
* Cyanoacetylene
* Cyanoformaldehyde
* Cyanomethyl
* Cyclopropenylidene
* Formic acid
* Isocyanoacetylene
* Ketene
* Methane
* Methoxy radical
* Methylenimine
* Propadienylidene
* Protonated formaldehyde
* Protonated formaldehyde
* Silane
* Silicon-carbide cluster

Six
atoms|

* Acetonitrile
* Cyanobutadiynyl radical
* E-Cyanomethanimine
* Cyclopropenone
* Diacetylene
* Ethylene
* Formamide
* HC4N
* Ketenimine
* Methanethiol
* Methanol
* Methyl isocyanide
* Pentynylidyne
* Propynal
* Protonated cyanoacetylene

Seven
atoms|

* Acetaldehyde
* Acrylonitrile
* Vinyl cyanide
* Cyanodiacetylene
* Ethylene oxide
* Glycolonitrile
* Hexatriynyl radical
* Methylacetylene
* Methylamine
* Methyl isocyanate
* Vinyl alcohol

Eight
atoms|

* Acetic acid
* Aminoacetonitrile
* Cyanoallene
* Ethanimine
* Glycolaldehyde
* Heptatrienyl radical
* Hexapentaenylidene
* Methylcyanoacetylene
* Methyl formate
* Propenal

Nine
atoms|

* Acetamide
* Cyanohexatriyne
* Cyanotriacetylene
* Dimethyl ether
* Ethanol
* Methyldiacetylene
* Octatetraynyl radical
* Propene
* Propionitrile

Ten
atoms
or more|

* Acetone
* Benzene
* Benzonitrile
* Buckminsterfullerene (C60, C60+, fullerene, buckyball)
* C70 fullerene
* Cyanodecapentayne
* Cyanopentaacetylene
* Cyanotetra-acetylene
* Ethylene glycol
* Ethyl formate
* Methyl acetate
* Methyl-cyano-diacetylene
* Methyltriacetylene
* Propanal
* n-Propyl cyanide
* Pyrimidine

Deuterated
molecules|

* Ammonia
* Ammonium ion
* Formaldehyde
* Formyl radical
* Heavy water
* Hydrogen cyanide
* Hydrogen deuteride
* Hydrogen isocyanide
* Methylacetylene
* N2D+
* Trihydrogen cation

Unconfirmed|

* Anthracene
* Dihydroxyacetone
* Ethyl methyl ether
* Glycine
* Graphene
* H2NCO+
* Linear C5
* Naphthalene cation
* Phosphine
* Pyrene
* Silylidine

Related|

* Abiogenesis
* Astrobiology
* Astrochemistry
* Atomic and molecular astrophysics
* Chemical formula
* Circumstellar envelope
* Cosmic dust
* Cosmic ray
* Cosmochemistry
* Diffuse interstellar band
* Earliest known life forms
* Extraterrestrial life
* Extraterrestrial liquid water
* Forbidden mechanism
* Homochirality
* Intergalactic dust
* Interplanetary medium
* Interstellar medium
* Photodissociation region
* Iron–sulfur world theory
* Kerogen
* Molecules in stars
* Nexus for Exoplanet System Science
* Organic compound
* Outer space
* PAH world hypothesis
* Panspermia
* Polycyclic aromatic hydrocarbon (PAH)
* RNA world hypothesis
* Spectroscopy
* Tholin

* Category:Astrochemistry
*   *   *

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*[CID]: Compound ID
*[H290]: May be corrosive to metals
*[H300]: Fatal if swallowed
*[H310]: Fatal in contact with skin
*[H330]: Fatal if inhaled
*[H370]: Causes damage to organs
*[H372]: Causes damage to organs through prolonged or repeated exposure
*[H410]: Very toxic to aquatic life with long lasting effects
*[P260]: Do not breathe dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P273]: Avoid release to the environment
*[P280]: Wear protective gloves/protective clothing/eye protection/face protection
*[P284]: Wear respiratory protection
*[P301+310]: IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician
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