Mustard gas
Mustard gas or sulfur mustard is any of the several chemical compounds that contain the chemical structure S(CH2CH2Cl)2. In the wider sense, compounds with the substituent S(CH2CH2X)2 and N(CH2CH2X)3 are known as sulfur mustards and nitrogen mustards, respectively, where X = Cl or Br. Such compounds are potent alkylating agents, which can interfere with several biological processes. Also known as mustard agents, this family of compounds are infamous cytotoxins and blister agents with a long history of use as chemical weapons. The name mustard gas is technically incorrect: the substances, when dispersed, are often not gases but a fine mist of liquid droplets.[4] Sulfur mustards are viscous liquids at room temperature and have an odor resembling mustard plants, garlic, or horseradish, hence the name.[4] When pure, they are colorless, but when used in impure forms, such as in warfare, they are usually yellow-brown. Mustard gases form blisters on exposed skin and in the lungs, often resulting in prolonged illness ending in death. The typical mustard gas is the organosulfur compound bis(2-chloroethyl) sulfide.[5]
History as chemical weapons[edit]
Sulfur mustard is a type of chemical warfare agent. As a chemical weapon, mustard gas was first used in World War I, and has been used in several armed conflicts since then, including the Iran–Iraq War, resulting in more than 100,000 casualties.[6][7] Today, sulfur-based and nitrogen-based mustard agents are regulated under Schedule 1 of the 1993 Chemical Weapons Convention, as substances with few uses other than in chemical warfare (though since then, mustard gas has been found to be useful in cancer chemotherapy[8]). Mustard agents can be deployed by means of artillery shells, aerial bombs, rockets, or by spraying from aircraft.
In its history, various types and mixtures of mustard gas have been employed. These include:
History[edit]
Development[edit]
Mustard gases were possibly developed as early as 1822 by César-Mansuète Despretz (1798–1863).[24] Despretz described the reaction of sulfur dichloride and ethylene but never made mention of any irritating properties of the reaction product. In 1854, another French chemist, Alfred Riche (1829–1908), repeated this procedure, also without describing any adverse physiological properties. In 1860, the British scientist Frederick Guthrie synthesized and characterized the mustard agent compound and noted its irritating properties, especially in tasting.[25] Also in 1860, chemist Albert Niemann, known as a pioneer in cocaine chemistry, repeated the reaction, and recorded blister-forming properties. In 1886, Viktor Meyer published a paper describing a synthesis that produced good yields. He combined 2-chloroethanol with aqueous potassium sulfide, and then treated the resulting thiodiglycol with phosphorus trichloride. The purity of this compound was much higher and consequently the adverse health effects upon exposure were much more severe. These symptoms presented themselves in his assistant, and in order to rule out the possibility that his assistant was suffering from a mental illness (psychosomatic symptoms), Meyer had this compound tested on laboratory rabbits, most of which died. In 1913, the English chemist Hans Thacher Clarke (known for the Eschweiler-Clarke reaction) replaced the phosphorus trichloride with hydrochloric acid in Meyer's formulation while working with Emil Fischer in Berlin. Clarke was hospitalized for two months for burns after one of his flasks broke. According to Meyer, Fischer's report on this accident to the German Chemical Society sent the German Empire on the road to chemical weapons.[26]
Mustard gas can have the effect of turning a patient's skin different colors, including shades of red, orange, pink, and in unusual cases, blue. The German Empire during World War I relied on the Meyer-Clarke method because 2-chloroethanol was readily available from the German dye industry of that time.