lewisite

Lewisite[1]
IUPAC name	2-chloroethenyldichloroarsine
Identifiers
CAS number	541-25-3
PubChem	5372798
MeSH	lewisite
SMILES	C(=C[As](Cl)Cl)Cl
Properties
Molecular formula	C2H2AsCl3
Molar mass	207.32 g/mol
Density	1.89 g/cm3
Melting point	–18 °C
Boiling point	190 °C
Hazards
NFPA 704	1 4 1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Lewisite is an organoarsenic compound, specifically an arsine. It was once manufactured in the U.S. and Japan as a chemical weapon, acting as a vesicant (blister agent) and lung irritant. Although chlorovinyl dichloroarsine is colorless and odorless, the impure samples in lewisite are yellow or brown liquid with a distinctive odor that has been described as similar to scented geraniums.^[2]

Chemical reactions

The compound is prepared by the addition of arsenic trichloride to acetylene:

AsCl₃ + C₂H₂ → ClCHCHAsCl₂

lewisite, like other arsenous chlorides, hydrolyses in water to form hydrochloric acid:

ClCHCHAsCl₂ + 2 H₂O → "ClCHCHAs(OH)₂" + 2 HCl

This reaction is accelerated in alkaline solutions, poisonous (but non-volatile) sodium arsenite being the coproduct.

Mode of action as chemical weapon

It can easily penetrate ordinary clothing and even rubber; upon skin contact it causes immediate pain and itching with a rash and swelling. Large, fluid-filled blisters (similar to those caused by mustard gas exposure) develop after approximately 12 hours.^[2] These are severe chemical burns. Sufficient absorption can cause systemic poisoning leading to liver necrosis or death.

Inhalation causes a burning pain, sneezing, coughing, vomiting, and possibly pulmonary edema.^[2] Ingestion results in severe pain, nausea, vomiting, and tissue damage.^[2] The results of eye exposure can range from stinging and strong irritation to blistering and scarring of the cornea.^[3] Generalised symptoms also include restlessness, weakness, subnormal temperature and low blood pressure.

Chemical composition

Lewisite is usually found as a mixture, of 2-chlorovinylarsonous dichloride as well as bis(2-chloroethenyl)arsinous chloride ("lewisite 2"), and tris(2-chlorovinyl)arsine ("lewisite 3").

History

Lewisite is named after the US chemist and soldier Winford Lee Lewis (1878-1943). In 1918 he found the thesis of Julius Arthur Nieuwland at Maloney Hall, a chemical laboratory at The Catholic University of America, Washington DC in which Nieuwland detailed the synthesis by the combination of allowing arsenic trichloride to react with acetylene in the presence of a hydrochloric acid solution of mercuric chloride.

It was developed into a secret weapon at Nela Park (a facility located in Cleveland, Ohio at East 131st Street and Taft Avenue^[4]) and given the name "the new G-34" to confuse its development with mustard gas.^{[citation needed]} It was not used in World War I, but experimented with in the 1920s as the "Dew of Death."^[5]

After World War I, the US became interested in lewisite because it was not flammable. It had the military symbol of M1 up into World War II, when it was changed to L. Field trials with lewisite during the World War II demonstrated that casualty concentrations were not achievable under high humidity due to its rate of hydrolysis and its charactistic odor and lacrymation forced troops to don masks and avoid contaminated areas. The United States produced about 20,000 tons of lewisite, keeping it on hand primarily as an antifreeze for mustard gas or to penetrate protective clothing in special situations. It was replaced by the mustard gas variant HT (a 60:40 mixture of sulfur mustard and O Mustard), and declared obsolete in the 1950s. It is effectively treated with British anti-lewisite (dimercaprol). Most stockpiles of lewisite were neutralized with bleach and dumped into the Gulf of Mexico,^[6] but some remain at the Deseret Chemical Depot.

Controversy over Japanese depots of lewisite in China

In mid 2006, China and Japan were negotiating disposal of stocks of lewisite in northeastern China, left by Japanese military during World War II. Residents of China have died over the past twenty years from accidental exposure to these stockpiles.^[7]

References

External links