Potassium Cyanide - KCN

What is Potassium Cyanide?

Potassium cyanide is a form of cyanide salt which contains equal numbers of potassium cations(K+) and cyanide anions(CN-).

Potassium cyanide is also called cyanide of potassium or cyanopotassium. The chemical formula of Potassium cyanide is KCN.

It is a crystalline salt which has no colour and is highly toxic and soluble in water. It has the smell of bitter almonds and tastes acrid with a burning sensation. It is a cyanide salt, potassium salt, and a one-carbon compound.

Properties of Potassium Cyanide – KCN

Potassium Cyanide KCN
Molecular Weight of Potassium Cyanide 65.12 g/mol
The density of Potassium Cyanide 1.52 g/cm3
Melting Point of Potassium Cyanide 634 °C
The boiling point of Potassium Cyanide 1625 °C

Structure of Potassium Cyanide (KCN)

Structure of Potassium Cyanide 1

Uses of Potassium Cyanide (KCN)

  • Potassium Cyanide is used in the extraction of silver and gold from ores.
  • It is used in the electroplating process.
  • Used as a reagent in analytical chemistry.
  • It is widely used in the preparation of carboxylic acids and nitriles.
  • It is used in the wet plate collodion process as a photographic fixer.
  • It is used in gold mining.
  • Used in warehouses.

Preparation of Potassium Cyanide

It is obtained by the treatment of hydrogen cyanide (HCN) with a solution of potassium hydroxide (KOH). Further, it is evaporated in a vacuum:


Approximately 50,000 tons of potassium cyanide (KCN) is produced annually.

Historically Production of KCN

Potassium cyanide (KCN) was an important source of alkali metal cyanides before the invention of the Castner process. It was produced by the decomposition of potassium ferrocyanide. The reaction is as follows:

K4[Fe(CN)6] → 4 KCN + FeC2 + N2

Effects on Health

It is a highly poisonous compound which acts as an inhibitor for many metabolic processes. It is toxic by skin absorption through opened wounds. When it is heated to decomposition it produces toxic fumes. High exposure of KCN fumes can cause headache, nausea, dizziness, anxiety, heart racing, and even death and unconsciousness

Frequently Asked Questions


What are the hazards of using KCN?

High exposure can cause headache, nausea, dizziness, anxiety, heart racing, and even death and unconsciousness. Exposure to potassium cyanide can cause nosebleeds and sores in the nose and changes in the count of blood cells.


Is KCN an acid or base?

Since there is a considerable electronegative difference between the N and H across the linear molecule, HCN, or hydrogen cyanide, thus HCN is a polar molecule. It is made up of two polar bonds with polarities that are aligned in the same direction.


How is KCN made?

KCN is formed by the treatment of hydrogen cyanide with aqueous potassium hydroxide solution, followed by the vacuum evaporation of the solution: HCN + KOH KCN + H2O. It produces about 50,000 tons of potassium cyanide annually.


Is HCN polar or nonpolar molecule?

Yes, it is polar to HCN. The composition is H-C underground. The electronegative of nitrogen is not only inherently but also toggles on three pairs of electrons in its triple carbon bond. It makes the molecule polar with a dipole moment to the N, in comparison to the single bond of hydrogen on the other hand.


Does CN have polar bonds?

When a molecule has a net dipole moment then it would be polar. The C-N bond is a polar bond since nitrogen is more electronegative than carbon. This gives a partial positive charge on carbon and a partial negative charge on nitrogen. Hence CN has a net dipole moment.

Learn more about the physical and chemical properties of Potassium Cyanide (KCN) from the experts at BYJU’S.

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