Chloropicrin is a slightly oily, colorless or faintly yellow liquid of the formula CCl3NO2. Its freezing point is -69.2 °C and its boiling point is 112 °C, where it partially decomposes to phosgene and nitrosyl chloride. It is denser than water. It is more toxic than chlorine but less than phosgene.
Chloropicrin was used in World War I as a chemical weapon, called 'PS' by British, 'Aquinite' by French, and 'Klop' (green cross) by Germans. After WW II, however, the importance of chloropicrin for military use decreased and, today, has vanished. In the chemical industry, it is widely used for organic synthesis, in fumigants, in fungicides and insecticides, and for the extermination of rats.
Chloropicrin is a relatively stable liquid that is prepared by the reaction of picric acid with calcium hypochlorite, by the addition of nitrogen to chlorinated hydrocarbons, or by chlorinating nitromethane. In environment it undergoes photolysis.
Chloropicrin is used for fumigation, to sterilize soil and seed.
Chloropicrin vapor is highly poisonous if inhaled. As a chemical warfare agent it is a powerful irritant from the group of pulmonary agents. It causes lachrymation, vomiting, bronchitis, and pulmonary edema; the lung injury can be fatal. Very low concentrations cause burning sensation of the eyes, which may serve as a warning.