Legal commercial grade chemicals are converted to illegal chemical weapons by Third World Countries. Dual-Use Chemicals of Extensive Use. Phosgene is a gas that was used as a chemical weapon during World War I. Inhalation, even of fatal concentrations, may not be noticed immediately. The main use is as an intermediate in the preparation of many organic chemicals, including agrochemicals. Cyanogene chloride and hydrogen cyanide both act by blocking cell respiration.
High concentrations can be fatal within minutes.
Both are important synthetic intermediates. Hydrogen cyanide has also been used as a pesticide. Chloropicrin is severely irritating and is a lacrymator. It is used as a soil sterilant, a grain disinfectant and an intermediate in synthesis. Schedule 3 has seven nerve agent precursors listed, including phosphorous oxychloride and phosphorous trichloride.