Victim with mustard gas burns, in World War I

Sulfur mustard (HD)
General
Systematic name	Bis (2-chloroethyl) sulfide
Other names	Iprit Kampfstoff "Lost" Lost Mustard gas Senfgas Yellow Cross Liquid Yperite
Molecular formula	C4H8Cl2S
Molar mass	159 g/mol
Appearance	Colorless if pure. Normally ranges from pale yellow to dark brown. Slight garlic type odor.

Mustard gas or sulfur mustard is a chemical compound which has been used as a chemical weapon. It was used in World War I by the German Army against British and Canadian soldiers near Ypres, Belgium, in 1917. Later it was also used against the French Second Army.