Lewisite
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Lewisite_structure.PNG
Lewisite is a chemical compound from a chemical family called arsines. While it is a colourless and odourless liquid when pure it is usually found as a oily, brown liquid with a distinct odour similar to geraniums. It is a chemical weapon, acting as a vesicant and lung irritant, and can be used in combination as mustard-lewisite.
It can easily penetrate ordinary clothing and even rubber; upon skin contact it causes immediate pain and itching with a rash and swelling. Blisters develop after 12 hours, and discomfort lasts for 2 to 3 days. Sufficient absorption can cause systemic poisoning leading to liver necrosis or death.
Inhalation causes a burning pain, sneezing, coughing, vomiting, and possibly lung oedema. Ingestion results in severe pain, nausea, vomiting, and tissue damage. Generalised symptoms also include restlessnesss, weakness, subnormal temperature and low blood pressure.
Lewisite is usually found as a mixture of isomers, 2-chlorovinylarsonous dichloride should predominate but often bis(2-chloroethenyl)arsinous dichloride and tris(2-chlorovinyl) arsine are present. Lewisite can be given any of the preceding names and is also sometimes described as 2-chlorovinyldichloroarsine, (2-chloroethenyl)arsinous dichloride or dichloro- (2-chlorovinyl) arsine. Its empirical formula is C2H2AsCl3 and can be represented as ClCHCHAsCl2. Its molecular mass is 207.32, melting point -18°C, boiling point 190°C, at 20°C its vapour pressure is 0.35 mm Hg and its density is 1.89 g/cm³. Lewisite hydrolyses in water to form hydrochloric acid, and in contact with alkaline solutions can form poisonous trisodium arsenate.
It is named after the US chemist and soldier Winford Lee Lewis. He discovered it at the Catholic University of America, Washington DC in 1918 by the combination of acetylene and arsenic trichloride, based on the 1904 work of Nieuwland. It was widely experimented with in the 1920s.
After World War I, the US became interested in Lewisite because it was not flammable. Thus, the US created a large stockpile of the substance. After BAL, British anti-Lewisite, was discovered, rendering Lewisite obsolete, the US neutralized its stockpile of Lewisite with bleach and dumped it into the Gulf of Mexico.zh:路易斯毒气