A highly toxic colourless liquid, C4H10FO2P; r.d. 1.09; m.p. –56°C; b.p. 158°C. It is an organophosphorus compound, O-isopropyl methylphosphonofluoridate. Sarin was discovered in 1938 and belongs to the G-series of nerve agents (GB). It was used by Iraq in the Iran-Iraq war (1980–88). In 1988, sarin was also used by Iraq in a poison gas attack on the Kurd city of Halabja in the north of Iraq. About 5000 people died. In 1994, a Japanese religious sect released sarin in Matsumoto and in 1995 released it in the Tokyo subway.