Nitrosyl chloride

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Nitrosyl chloride
IUPAC name
Nitrosyl chloride
Other names
Nitrogen chloride oxide
Nitrogen oxychloride
Nitrosonium chloride
Tildens Reagent
Molar mass 65.459 g/mol
Appearance Yellow or reddish gas
Odor Choking
Density 2.872 g/cm3
1.36 g/cm3 (-5.7 °C)
Melting point −59.4 °C (−74.9 °F; 213.8 K)
Boiling point −5.55 °C (22.01 °F; 267.60 K)
Solubility Reacts with alcohols
Soluble in oleum
Vapor pressure 2,409 mmHg at 25 °C
261.68 J·K−1·mol−1
51.71 kJ/mol
Safety data sheet Matheson
Flash point Non-flammable
Related compounds
Related compounds
Nitryl chloride
Nitrogen dioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Nitrosyl chloride is a yellow gas, commonly encountered as a decomposition product of aqua regia, very corrosive and toxic. It has the chemical formula NOCl.

Due to its hazards, nitrosyl chloride doesn't have many uses in amateur chemistry, and most of the time it's encountered as unwanted side-product in chemical reactions, such as the preparation of aqua regia.



Nitrosyl chloride reacts with water to give hydrochloric acid and nitrogen oxides.


Nitrosyl chloride is a yellowish gas, which reacts with water.


Nitrosyl chloride is sold by industrial suppliers, but they will not sell it to individuals due to its hazards. Not even big chemical suppliers have it in their stock.


There are several routes to nitrosyl chloride:

The most common route involves the reaction between nitric oxide and chlorine, below 100 °C. Above this temperature, the reaction reverses.

2 NO + Cl2 → 2 NOCl

Dehydration of nitrous acid by using hydrochloric acid will give nitrosyl chloride:

HNO2 + HCl → NOCl + H2O

Nitrosyl chloride is an unwanted side product in the preparation of aqua regia.


  • Make nitrosylsulfuric acid
  • Make N-nitroso compounds



Nitrosyl chloride is a toxic and corrosive gas. Work should be performed in a well ventilated area or outside.

Nitrosyl chloride reacts violently and may even explode in contact with ethers or ketones in the presence of trace metal salts.[1]


Nitrosyl chloride should not be stored unless you have gas cylinders specially designed to store this compound.

It's best to use this compound as soon as you made it.


Nitrosyl chloride can be neutralized by bubbling it in an aqueous alkaline solution.



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