Arsenical vesicants

Lewisite (L) (A-243) is an organoarsenic compound. It was once manufactured in the United States, Japan, Germany and the Soviet Union for use as a chemical weapon, acting as a vesicant (blister agent) and lung irritant. Although colorless and odorless in its pure form, impure samples of lewisite are a yellow, brown, violet-black, green, or amber oily liquid with a distinctive odor that has been described as similar to geraniums.

Ethyldichloroarsine, also known as ED, CY, and ethyl Dick, is an organoarsenic compound with the formula CH3CH2AsCl2. This colourless volatile liquid is a highly toxic vesicant (blister agent) that was used during World War I in chemical warfare. The molecule is pyramidal with the Cl–As–Cl and C–As–Cl angles approaching 90° (see image). Ethyldichloroarsine has high chronic toxicity, similar to lewisite.

Methyldichloroarsine, sometimes abbreviated "MD" and also known as methyl Dick, is an organoarsenic compound with the formula CH3AsCl2. This colourless volatile liquid is a highly toxic vesicant that has been used in chemical warfare.

Phenyldichloroarsine, also known by its wartime name phenyl Dick and its NATO abbreviation PD, is an organic arsenical vesicant and vomiting agent developed by Germany and France for use as a chemical warfare agent during World War I. The agent is known by multiple synonyms and is technically classified as a vesicant, or blister agent.