Cyanogen Chloride (CK) 1916

Ck One Choke, a Breath Taking Fragrance

Historical background of cyanogen chloride

Cyanogen chlorine was synthesized for the first time in 1802 by the French chemist Claude Louis Berthollet, although the correct chemical format was established by his compatriot Louis-Joseph Gay-Lussac in 1815. Cyanides have been used for their toxic potential since ancient Roman times.

The use of cyanides in warfare was not implemented until World War I. France combined hydrocyanic chloride acid with cyanogen chloride and used it for the first time against German in October 1916. The use of cyanogen chloride in this mixture had the ability to penetrate German masks and cause irritation, making soldiers remove their mask, and exposing themselves to these very toxic gases. Cyanogen chloride was also combined with arsenic trichloride later in the war. France was the only country that used cyanogen chloride in the battlefield. They used about 4000 tons without notable military success, because the used small munitions could not deliver the large amounts needed to cause effects. Other factors were that, cyanogen chloride has high volatility and high dispersion ability, which reduce the agent’s effects below the lethal concentration (“all or nothing biological effects”).

The U.S. maintained a small number of cyanide munitions during World War II. Japan allegedly used cyanide against China before and during WWII, and Iraq may have used cyanide against the Kurds in the 1980’s.

Commercial uses of chemical or precursor chemicals

Cyanogen chloride is currently used in nylon and synthetic rubber production, pigments and dyes manufacturing, in printing and photography, in metal cleaning and core hardening of metals. It is also used in chemical synthesis and fumigation. Cyanogen chloride is typically stored and transported as a compressed liquefied gas.


Cyanogen chloride, also known as CK, is a highly toxic Blood agent (military chemical warfare classification). In commercial use, this chemical is also known as CNCl. It is one of the most rapidly acting poisons.

CK is a colourless liquid with lower boiling point and, therefore, very volatile, whereas the water-solubility is lower.
Its vapours are extremely irritating and corrosive. The pungent odour, that is very irritant to the mucous membranes, nearly completely hides the bitter almond aroma and causes a severe tear flow. CK quickly affects the respiratory systems preventing oxygen transportation to the cells.

Immediate signs and symptoms of CK exposure can be lachrymation, severe irritation on the eyes, skin, and respiratory track, effects on the cellular respiration, convulsions, unconsciousness, lung oedema, and death. Rapid evaporation of the liquid may cause frostbite on unprotected skin.


Leave the area and evacuate the exposed people into fresh air and stay upwind. CK vapours may be heavier than air. They will spread along the ground, collect and stay in poorly-ventilated, low-lying, or confined areas. 
For first responders’ the protection level in an unknown situation is the highest level.  In a small spill or leak (less than 200 litres) the initial isolation distance in all directions is 800 metres (300 metres in stabilized) and the protection distance during day is 5,4 kilometers (1,8 kilometers in stabilized) changing to 11+ kilometers (6,2 kilometers in stabilized) at night.  In large a spill/leak (more than 200 liters) the isolation area is 1000 meters in all directions, and the protection distance in day is 11+ kilometers (9,4 kilometers in stabilized) changing to 11+ kilometers at night.

Cyanogen Chloride decomposes on heating, producing toxic and corrosive fumes of hydrogen cyanide, hydrochloric acid, and nitrogen oxides. When in contact with water or water vapour it reacts slowly and as a result of that reaction it produces hydrogen chloride.

Did you know that chemist Berthollet also discovered sodium hypochlorite, which can be used as chemical warfare agents’ decontamination solvent?

Published by Toni Leikas

CBRN Officer (CPT.ret), CBRN Specialist. I'm always wondering, why so many makes and thinks that CBRN is rocket science? It's simple following few basic rules and common sense.

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