Mustard Gas:

Mustard gas is the common name for 1,1-thiobis(2-chloroethane) and is a chemical weapon classified as a vesicant (blistering) agent. The chemical formula is C₄H₈Cl₂S.  Other names for it include HD, Sulfur Mustard, and Yperite.

    Mustard gas does not occur naturally in the environment; all sources are completely anthropogenic.  Mustard gas was first manufactured in 1822 by Frederick Guthrie when he reacted ethylene and Cl₂.  It was commonly used by the 1880’s as a pesticide and to treat minor tumors.  Mustard Gas’ first application as a chemical weapon was during World War I by the Germans against the British at Ypres, Belgium on July 12, 1917.  Early gas warfare substances of WWI were primarily inhalation hazards such as chlorine gas and were non-persistent.  Soldiers armed with a gas mask were fully protected from these early gas attacks.  However, Mustard gas soon became the most lethal poisonous chemical used due in part to its low volatility (900 mg/m³ at 25º C) making it rather persistent.  It has a 5.4 fold greater density than air allowing its vapors to settle near to the ground by soldier in trenches. Mustard agents are three times more toxic than the same concentration of cyanide gas.  Plus, mustard gas was capable of penetrating rubber and textiles, consequently protective masks used at the time were rendered ineffective.  It wasn’t until much later that it was discovered that urethane is resilient to mustard gas. 

Since WWI it has been employed in the following wars:

• Spain against Morocco in 1923-26;
• Italy against Ethiopia in 1935-40;
• the Soviet Union in a province of China in 1930;
• Japan against China in 1937-45;
• Egypt against Yemen in 1963-67;
• Iraq against Iran in 1983-88, resulting in as many as 16,000 deaths;
• and possibly by Iraq on a small scale against U.S.-led coalition troops in the Gulf War.

Despite its name Mustard Gas is a thick viscous liquid at ambient temperatures, reminiscent of motor oil.  It has a freezing point of 14º C and a boiling point of 217º C.  The name ‘mustard’ gas is derived from its odor akin to that of mustard, garlic, or horseradish.  Mustard gas is very lipophillic, meaning it is highly soluble in fats, oils, and organic solvents, allowing it to penetrate the skin and cell membranes with ease.  Plus, due to its low solubility in water and quick penetrating nature, it is difficult to wash off.

***See reference page for background information.

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