Most sulfur mustards are viscous (squishy) liquids with no color and no smell when they are at room temperature. When used in warfare, they are yellowish or brown. Some of them smell like culinary mustard (the type used for food), horseradish or garlic. They got their name from the smell, but are completely unrelated to culinary mustard.
Sulfur mustard (in its form mustard gas) was synthesized by Frederick Guthrie in 1860. It may have been discovered as early as the 1820s by M. Depretz.
Later, in 1993, the Chemical Weapons Convention also made it illegal to produce or stockpile (collect) poison gases. Despite these prohibitions, mustard gas has been used in several wars.
