Phosgene oxime

Phosgene oxime, also known as CX, is a chemical weapon, specifically a nettle agent. It was first produced in 1929. As a solid, it is colorless; as a liquid, it is yellow-brown. It has a strong, irritating odor. The chemical formula for phosgene oxime is CHCl₂NO.

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Symptoms of phosgene oxime poisoning

Phosgene oxime can be toxic if inhaled, ingested, or absorbed by the skin and the effects of the poisoning occur almost immediately. If inhaled, it irritates the airway and may eventually lead to pulmonary edema, or, literally, drowning in one's own fluids. The effects on the skin include weals, hives, itching, and necrosis of the skin, which scabs and falls off. Absorption through the skin can also lead to pulmonary edema. It also causes lacrimation in the eyes and even blindness. There is no antidote for phosgene oxime poisoning. Generally, any treatment is supportive. The standard decontamination process for humans exposed to CX is to irrigate the eyes and gently wash affected skin with water. If shower facilities are available, these can also be used.

Typical physical symptoms are as follows:

• Skin: Blanching surrounded by an erythematous ring can be observed within 30 seconds of exposure. A weal develops on exposed skin within 30 minutes. The original blanched area acquires a brown pigmentation by 24 hours. An eschar forms in the pigmented area by 1 week and sloughs after approximately 3 weeks. Initially, the effects of CX can easily be misidentified as mustard gas exposure. However, the onset of skin irritation resulting from CX exposure is a great deal faster than mustard gas, which typically takes several hours or more to cause skin irritation.

• Eyes: Eye examination typically demonstrates conjunctivitis, lacrimation, lid edema, and blepharospasm after even minute exposures. More severe exposures can result in keratitis, iritis, corneal perforation, and blindness.

• Respiratory: Irritation of the mucous membranes may be observed on examination of the oropharynx and nose. Evidence of pulmonary edema, including rales and wheezes, may be noted on auscultation. Pulmonary thromboses are prominent features of severe CX exposure.

• Gastrointestinal: Some animal data suggest that CX may cause hemorrhagic inflammatory changes in the GI tract.

This chemical has no useful industrial applications, so accidental exposure is extremely unlikely to occur. Therefore, any exposure to CX is almost certainly the result of its deliberate use as a chemical warfare agent.

Chemical properties

Phosgene oxime is about 70% soluble in water. The boiling point is 128° Celsius (262° Fahrenheit), its melting point is between 35-40° C (95-104°F) Its vapor density is greater than air, which mean it tends to settle in low lying areas. It is corrosive on metals and also decomposes on contact with metals.