Yellow Cross (chemical warfare)

Yellow Cross (Gelbkreuz) is a German World War I chemical warfare agent usually based on mustard gas (also known as sulfur mustard, HS, Yperite, or Lost, among other names). The original Gelbkreuz was a composition of 80–90% of sulfur mustard and 10–20% of tetrachloromethane or chlorobenzene as a solvent which lowered its viscosity and acted as an antifreeze, or, alternatively, 80% sulfur mustard, 10% bis(chloromethyl) ether, and 10% tetrachloromethane.

Source: Wikipedia — Yellow Cross (chemical warfare) (CC BY-SA 4.0)