Ethyldichloroarsine, sometimes abbreviated "ED", is an organoarsenic compound with the formula CH₃CH₂AsCl₂. This colourless volatile liquid is a highly toxic vesicant or blister agent

Blister agent

A blister agent, or vesicant, is a chemical compound that causes severe skin, eye and mucosal pain and irritation. They are named for their ability to cause severe chemical burns, resulting in painful water blisters on the bodies of those affected...

 that was used in chemical warfare

Chemical warfare

Chemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...

. The molecule is pyramidal with the Cl-As-Cl and C-As-Cl angles approaching 90° (see image). It is closely related to methyldichloroarsine

Methyldichloroarsine

Methyldichloroarsine, sometimes abbreviated "MD", is an organoarsenic compound with the formula CH3AsCl2. This colourless volatile liquid is a highly toxic vesicant that has been used in chemical warfare.-History:...

, which was also used in warfare.