British Anti Lewisite, often referred to by its acronym BAL, is a compound developed by the British biochemists of Oxford University during World War II . It was developed secretly as an antidote for Lewisite poisoning, which is a now-obsolete chemical warfare agent. It is also known by its structural name 2,3-dimercaptopropanol, as well as 1,2-dithioglycerol, mercaprol, dimercaprol, dicaptol, or sulfactin. It is a colorless, oily liquid. It converts Lewisite into a non-toxic cyclic compound and also forms protective complexes with arsenic within the body of an Lewisite-exposed victim.
Today, it is used extensively in medical practice for the treatment of heavy metal poisoning by arsenic, mercury and lead, acting as a chelating agent. In addition, it is used for the treatment of Wilson's disease, a genetic disorder in which the body tends to retain copper.