Cyanic acid

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Cyanic acid
IUPAC name cyanic acid
CAS number 420-05-3
Molecular formula CHNO
Molar mass 43.02 g/mol
Appearance Colorless liquid or gas (b.p. near room temperature)
Melting point

-81 °C

Boiling point

23.5 °C

Main hazards Poisonous
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references


Cyanic acid is a colourless poisonous liquid with a boiling point of 23.5°C and a melting point of -81°C. At 0°C cyanic acid is converted to cyamelide.

In water, cyanic acid hydrolyses to carbon dioxide and ammonia.

Cyanic acid (H-O-C≡N) is an isomer of fulminic acid (H-C=N-O).

A tautomer exists for cyanic acid, H-N=C=O, isocyanic acid.

It forms in a reaction between potassium cyanate and formic acid.

The trimer of cyanic acid is cyanuric acid.

Cyanic acid is the simplest stable chemical compound that contains carbon, hydrogen, nitrogen, and oxygen, the four most commonly-found atoms in organic chemistry (fulminic acid is not stable).

See also


  • Handbook of Chemistry and Physics, 65th. Edition, CRC Press (1984)
  • Cyanic acid from NIST Chemistry Webbook (accessed 090906)

ar:حمض سيانيك de:Cyansäure