Chloropicrin
The next gas to be introduced was chloropicrin, trichloronitromethane or “vomiting gas.” It has been stated that a mixture of chloropicrin (25 per cent) and chlorine (75 per cent) has been used in cloud attacks, but the high boiling point of chloropicrin (112° C.) makes its considerable use for this purpose very unlikely. The gas is moderately toxic and somewhat lachrymatory, but it was mainly used because of its peculiar property of causing vomiting when inhaled. Its value was further increased at first because it was particularly difficult to prepare a charcoal which would absorb it. Its peculiar properties are apt to cause it to be used for a long time.