Sodium cyanide

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Structural formula
Na + ion Cyanide ion
Surname Sodium cyanide
other names
  • Sodium cyanide
  • Cyan sodium
  • Prussic acid soda
  • Sodium prussic acid
Molecular formula NaCN
Brief description

colorless, crystalline powder with a slightly bitter almond odor

External identifiers / databases
CAS number 143-33-9
EC number 205-599-4
ECHA InfoCard 100.005.091
PubChem 8929
Wikidata Q410185
Molar mass 49.01 g mol −1
Physical state



1.6 g cm −3

Melting point

563 ° C

boiling point

1496 ° C

Vapor pressure
  • 1 h Pa (817 ° C)
  • 0.10 kPa (800 ° C)
  • 1.65 kPa (1000 ° C))
  • 11.98 kPa (1200 ° C))
  • 39.10 kPa (1350 ° C))

easily soluble in water (580 g l −1 at 20 ° C)

safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary
06 - Toxic or very toxic 08 - Dangerous to health 05 - Corrosive 09 - Dangerous for the environment


H and P phrases H: 290-300 + 310 + 330-372-410
EUH: 032
P: 260-273-280-301 + 310-330-302 + 352-304 + 340-310

DFG / Switzerland: 3.8 mg m −3 (measured as inhalable dust )

Toxicological data
Thermodynamic properties
ΔH f 0

−87.5 kJ / mol

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Sodium cyanide is the sodium salt of hydrocyanic acid (HCN). At room temperature it is a colorless, hygroscopic, crystalline powder that smells slightly bitter almond-like. In the presence of acids it decomposes into the highly toxic gas hydrogen cyanide :

NaCN + H 2 SO 4 → HCN + NaHSO 4


Sodium cyanide is by neutralization of hydrogen cyanide with sodium hydroxide according to the Andrussow process recovered. The starting materials for the synthesis are methane , ammonia and oxygen .

Methane, ammonia and oxygen react at ≈1500 ° C in the presence of platinum or rhodium catalysts to form hydrocyanic acid and water.

The subsequent neutralization gives sodium cyanide.

Hydrocyanic acid and sodium hydroxide solution produce sodium cyanide and water.

In the past, sodium cyanide was obtained by the Castner-Kellner process by reacting molten sodium with ammonia to form sodium amide and by calcining sodium amide with charcoal :


Sodium cyanide is very toxic. It is highly toxic to fish (see cyanide fishing ) and pollutes the ecosystem in large quantities. Sodium cyanide slowly decomposes in warm aqueous solution to sodium formate and ammonia .


Sodium cyanide is used together with potassium cyanide to extract gold , silver and other metals ( cyanide leaching ).

In electroplating technology it is used for various cyanide baths, for example cyanide copper, brass, bronze, zinc, cadmium and gold baths.

In metalworking, molten sodium cyanide is used to harden certain types of steel (case-hardening steels ).

The Organic Chemistry uses sodium cyanide for synthesis of nitrites as Decannitril

safety instructions

Make sure that sodium cyanide dust and vapors are not inhaled. Containers must be tightly closed and stored in a cool and dry place.


Since sodium cyanide has a highly toxic effect on living beings (see cyanide poisoning ), it must on no account be released into the environment via wastewater, but must be completely oxidized in a wastewater treatment plant . This can be done in the following four ways:

  1. By treatment with sodium hypochlorite (NaClO) according to the following equation:
Treatment with sodium hypochlorite has the disadvantage that the AOX value of the wastewater increases sharply.
  1. By adding hydrogen peroxide (H 2 O 2 ).
  2. By treatment with ozone (O 3 )
  3. By oxidation on carbon or platinum anodes using direct current .

The aim of detoxification is complete decomposition of the sodium cyanide into carbon dioxide and nitrogen.


Detection of cyanide ions:

Iron (II) sulphate solution is added to an alkaline cyanide solution in deficit. If cyanide ions are present, Berlin blue is formed after acidification and the addition of iron (III) chloride solution .

Individual evidence

  1. a b c d e f g h Entry on sodium cyanide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
  2. Data sheet Sodium cyanide, ACS reagent, ≥97.0% from Sigma-Aldrich , accessed on May 8, 2017 ( PDF ).
  3. a b c d E. Gail, S. Gos, R. Kulzer, J. Lorösch, A. Rubo, M. Sauer, R. Kellens, J. Reddy, N. Steier, W. Hasenpusch: Inorganic Cyano Compounds , in : Ullmann's Encyclopedia of Technical Chemistry , Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2012; doi : 10.1002 / 14356007.a08_159.pub3 .
  4. Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry Salts of hydrogen cyanide with the exception of complex cyanides, e.g. B. Cyanoferrate (II) and (III) and mercury oxide cyanide and those named in this annex in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on January 8, 2017. Manufacturers or distributors can expand the harmonized classification and labeling .
  5. Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values (search for 143-33-9 or sodium cyanide ), accessed on November 2, 2015.
  6. a b Sodium cyanide data sheet (PDF) from Merck , accessed on January 19, 2011.
  7. 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.
  8. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 912.
  9. Erwin Riedel : Inorganic Chemistry . 5th edition, de Gruyter, Berlin 2002, ISBN 3-11-017439-1 , pp. 731-732.
  10. CF Burgess, LF Richardson: The use of potassium cyanide for galvanic baths , in: Angew. Chem. , 1914 , 27 , pp. 211-212; doi: 10.1002 / anie.19140273002 .
  11. Sodium cyanide on
  12. ^ Kurt Peter C. Vollhardt, Neil Eric Schore: Organic Chemistry . John Wiley & Sons, 2011, ISBN 3-527-32754-1 , pp. 1058 ( limited preview in Google Book search).
  13. Jander, Blasius, Strähle: Introduction to the inorganic-chemical practical course , 14th edition. Hirzel, Stuttgart 1995, ISBN 978-3-7776-0672-9 , pp. 356-357.