Potassium cyanide

Structural formula
General
Surname	Potassium cyanide
other names	Potassium cyanide; Potassium cyan; Hydrogenate potassium;
Molecular formula	KCN
Brief description	colorless crystals with a smell of bitter almonds
External identifiers / databases
EC number	205-792-3
ECHA InfoCard	100.005.267
PubChem	9032
Wikidata	Q192470
properties
Molar mass	65.12 g mol −1
Physical state	firmly
density	1.55 g cm −3
Melting point	634 ° C
boiling point	1625 ° C
solubility	Easily soluble in water (716 g l −1 at 25 ° C)
safety instructions
H and P phrases	H: 290-300 + 310 + 330-370-372-410
	EUH: 032
	P: 260-264-273-280-284-301 + 310
MAK	DFG / Switzerland: 5 mg m −3 (measured as inhalable dust )
Toxicological data	2.86 mg kg −1 ( LD Lo , human , oral ) ; 8.5 mg kg −1 ( LD 50 , mouse , oral ) ; 6.5 mg kg −1 ( LD 50 , mouse , sc ) ; 5 mg kg −1 ( LD 50 , rat , oral ) ; 8 mg kg −1 ( LD 50 , rat , im ) ;
Thermodynamic properties
ΔH f 0	−113.0 kJ / mol
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium cyanide ( potassium cyanide , empirical formula KCN) is the potassium salt of hydrocyanic acid (HCN).

properties

Deadly dose of potassium cyanide

Potassium cyanide forms colorless crystals that smell like bitter almonds, have a melting point of 634 ° C, dissolve well in water , but only poorly in alcohol . Genetically, only around 20–40% of people can smell bitter almonds.

With acids (in the stomach through gastric acid or weak acids such as carbon dioxide ), hydrogen cyanide is released from potassium cyanide and other cyanides , which has the typical “bitter almond odor”. In the event of prolonged storage, potassium carbonate is formed through the absorption of carbon dioxide from the air .

Toxic effect

In humans

In an adult human weighing approx. 80 kg, the lethal dose LD _Lo (oral) is approx. 230 mg cyanide (CN ^- ). Absorption through the skin is possible. It is unclear whether this lethal dose is also possible via skin absorption. The lowest reported lethal dose of oral LD _Lo in humans was 2.86 mg / kg body weight after oral ingestion. Bright red bleeding from the mucous membrane indicates potassium cyanide in the corpse.

The active ingredient cyanide is mostly used as potassium cyanide ("potassium cyanide capsules") or as another salt of hydrogen cyanide (e.g. sodium cyanide ). When chewing and swallowing such a capsule, the toxic effect unfolds when the cyanide dissolves and the cyanide ions are released (see cyanide poisoning ).

The cyanide ion blocks the oxygen binding site of the cytochrome c oxidase (complex IV of the respiratory chain), which leads to internal suffocation . Cyanide ions are converted to thiocyanate ions by the enzyme rhodanase . These are excreted through the kidneys.

After poisoning with smaller amounts, if they are not fatal, neurological damage can occur. Such poisoning is treated u. a. with sodium thiosulphate to support the hepatic metabolism, 4-dimethylaminophenol and hydroxycobalamin .

In animals

Fish die with a cyanide concentration in the water of 1–5 µg / l. For smaller mammals such as mice or rats, the lethal dose LD ₅₀ for oral, subcutaneous or intramuscular intake is 5-8.5 milligrams per kilogram of body weight.

Manufacturing

Technical production takes place from hydrocyanic acid and potassium hydroxide ( neutralization and subsequent evaporation).

{\ displaystyle \ mathrm {HCN + KOH \ longrightarrow KCN + H_ {2} O}}

In the past, potassium cyanide was produced by the action of carbon monoxide and ammonia on potassium carbonate (potash) at high temperatures. In addition to potassium cyanide, this iron- catalyzed reaction also produces water, hydrogen and carbon dioxide:

{\ displaystyle \ mathrm {3 \ CO + 2 \ NH_ {3} + K_ {2} CO_ {3} \ longrightarrow 2 \ KCN + 2 \ H_ {2} O + H_ {2} +2 \ CO_ {2} }}

In the laboratory, it is made by heating blood liquor salts such as potassium hexacyanidoferrate (III) and sulfuric acid. The resulting hydrocyanic acid is then neutralized with potassium hydroxide, and the potassium cyanide can, for. B. be precipitated with ethanol.

Production by reducing potassium cyanate at higher temperatures is also possible:

{\ displaystyle \ mathrm {\ KOCN + C \ longrightarrow \ KCN + CO}}

use

Potassium cyanide is used in industrial manufacturing processes, where it is mainly used for gold extraction (cyanide leaching) and in galvanic baths, but also in organic synthetic chemistry (especially for the preparation of nitriles).

In medicine it is used as a component in Drabkin solutions , which are used for the spectroscopic determination of the concentration of hemoglobin.

safety instructions

storage

When storing potassium cyanide, the corresponding containers must be tightly closed. The storage must be cool and dry and under lock and key ( storage class : 6.1BS, non-flammable toxic substances, solid).

handling

It is essential to avoid inhaling dust and vapors of potassium cyanide. A protective mask must therefore be worn when handling. Potassium cyanide is absorbed by the skin . To prevent contact with the skin, rubber gloves and appropriate laboratory clothing must be worn.

disposal

For extensive detoxification, cyanides can be destroyed by oxidation, e.g. B. by means of hydrogen peroxide , see the relevant disposal information in the article cyanide .

proof

The classic analysis method for potassium cyanide consists in the detection of cyanide ions (CN ^- ): To the alkaline sample solution, a deficit of iron (II) sulfate solution is added. If cyanide ions are present, Prussian blue is formed after the addition of iron (III) salts .

literature

Entry on potassium cyanide. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.

Web links

Wiktionary: Cyanide - explanations of meanings, origins of words, synonyms, translations

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on potassium cyanide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the indicated labeling it falls under the group entry salts of hydrogen cyanide with the exception of complex cyanides such as ferrocyanides, ferricyanides and mercuric oxycyanide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 151-50-8 or potassium cyanide ), accessed on November 2, 2015.
↑ ^a ^b ^c ^d ^e ^f ^g Entry on potassium cyanide in the ChemIDplus database of the United States National Library of Medicine (NLM) .
^ ^A ^b Journal of Pharmacology and Experimental Therapeutics . Vol. 161, 1968, p. 163.
↑ ^a ^b Nippon Yakurigaku Zasshi. ( Japanese Journal of Pharmacology .) Vol. 54, 1958, p. 1057.
^ Archives of Toxicology . Vol. 54, 1983, p. 275.
^ ^A ^b C.D. Barnes, L.G. Eltherington: Drug Dosages in Laboratory Animals - A Handbook. Berkeley, Univ. of California Press, 1973, p. 209.
↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.
^ WB Deichmann: Toxicology of Drugs and Chemicals. Academic Press, New York 1969, p. 191.
↑ Axel M. Gressner, Torsten Arndt: Lexicon of Medical Laboratory Diagnostics . Springer-Verlag, 2019, ISBN 978-3-662-48986-4 ( google.de [accessed February 20, 2020]).

[GESTIS-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h Entry on potassium cyanide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[CLP_100.240.759-2] Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the indicated labeling it falls under the group entry salts of hydrogen cyanide with the exception of complex cyanides such as ferrocyanides, ferricyanides and mercuric oxycyanide and those specified elsewhere in this Annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .

[3] Swiss Accident Insurance Fund (Suva): Limit values - current MAK and BAT values (search for 151-50-8 or potassium cyanide ), accessed on November 2, 2015.

[ChemIDplus-4] ↑ ^a ^b ^c ^d ^e ^f ^g Entry on potassium cyanide in the ChemIDplus database of the United States National Library of Medicine (NLM) .

[jpet-5] A ^b Journal of Pharmacology and Experimental Therapeutics . Vol. 161, 1968, p. 163.

[nyz-6] Nippon Yakurigaku Zasshi. ( Japanese Journal of Pharmacology .) Vol. 54, 1958, p. 1057.

[aot-7] Archives of Toxicology . Vol. 54, 1983, p. 275.

[ddla-8] A ^b C.D. Barnes, L.G. Eltherington: Drug Dosages in Laboratory Animals - A Handbook. Berkeley, Univ. of California Press, 1973, p. 209.

[CRC90_5_20-9] David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.

[10] WB Deichmann: Toxicology of Drugs and Chemicals. Academic Press, New York 1969, p. 191.

[11] Axel M. Gressner, Torsten Arndt: Lexicon of Medical Laboratory Diagnostics . Springer-Verlag, 2019, ISBN 978-3-662-48986-4 ( google.de [accessed February 20, 2020]).