(2) Sulfur mustard, commonly known as mustard gas, is the organic compound with formula . It is a pale yellow, oily, highly toxic,volatile, viscous liquid alkylating compound with a sweet to garlic-like odour that evaporates to a poisonous gas. The pure compound has a melting point of 14 °C and decomposes before boiling at 218 °C. When used in impure form,such as warfare agents, they are usually yellow-brown in colour and have an odour resembling mustard plants, or garlic,hence the name.