Phosgene

Phosgene (carbonyl chloride, COCl₂) is a poison gas that was used as a chemical weapon in World War I. It is a colorless nonflammable gas that has the odor of freshly cut hay. It is a manufactured chemical, but small amounts occur naturally from the breakdown of chlorinated compounds.

Phosgene is also used in the manufacture of other chemicals such as dyestuffs, isocyanates, polycarbonates[?] and acid chlorides[?]; it is also used in the manufacture of pesticides and pharmaceuticals. Phosgene can also be used to separate ores. Phosgene is a gas at room temperature, but is sometimes stored as a liquid under pressure or refrigeration.

Phosgene was synthesized by the chemist John Davy[?] (1790-1868) in 1812. It was first used as a weapon at Verdun in 1917 when the Germans fired it over British lines in artillery shells.

Phosgene's symptoms usually appear within 24 hours but can take up to 72. The gas combines with water in the tissues of the respiratory tract to form carbon dioxide and hydrochloric acid. The acid then dissolves the membranes in the lungs and death occurs as the lungs bleed out and choke the victim. Unlike nerve agents, phosgene must be inhaled to cause harm and cannot be absorbed through the skin.