Potassium Cyanide - KCN

What is Potassium Cyanide?

Potassium Cyanide is a chemical compound which arises due to the reaction between hydrogen cyanide (HCN) and potassium hydroxide (KOH).

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 a smell of bitter almonds and tastes like acrid with a burning sensation. It is a cyanide salt which contains an equal number of cyanide anions and potassium cations. 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
Density of of Potassium Cyanide 1.52 g/cm3
Melting Point of Potassium Cyanide 634.5 °C
Boiling point of Potassium Cyanide 1,625 °C

Structure of Potassium Cyanide (KCN)


Structure of Potassium Cyanide

Structure of Potassium Cyanide – KCN


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 and opens wounds. When it is heated to decomposition it produces toxic fumes. It is widely used for silver extraction and as an insecticide.

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. The exposure to potassium cyanide can cause nosebleed and sores in the nose and changes in the count of blood cells.

Is KCN an acid or base?

KCN is the salt with a solid base (KOH) and a weak acid (HCN), and thus the salt should have a simple pH in aqueous solution.

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 it 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.

Is CN a polar covalent bond?

When it has a net dipole a molecule would be polar. The C-H and the C-N bonds are both polar. Each N-H bond is polar since nitrogen is more electronegative than hydrogen, so that each hydrogen atom has a partial positive charge (+), and the nitrogen atom has a partial negative charge.

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

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