Mustard gas

Mustard gas refers to a family of potentially lethal but primarily casualty-producing chemical weapons, introduced in the First World War and with improved versions in WWII. The first version was impure dichloroethyl sulfide, and code-named "Yellow Cross" by the Germans and "H" in the modern U.S. system.

Originally produced by the Lowenstein reaction, it could be purified by distillation into the more potent "HD".

In WWII, the U.S. developed a family of much more toxic nitrogen mustards, in the "HN" series. After their declassification at the end of the war, they proved to be the basis of some of the first effective antineoplastic agents for cancer chemotherapy.