mustard agents (class) History Development Mustard gases were possibly developed as early as 1822 by César-Mansuète Despretz (1798–1863). 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. 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. 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. Use Mustard gas was first used in World War I by the German army against British and Canadian soldiers near Ypres, Belgium, "on the night of July 12, 1917." Later also against the French Second Army. Yperite is "a name used by the French, because the compound was first used at Ypres." The Allies did not use mustard gas until November 1917 at Cambrai, France, after the armies had captured a stockpile of German mustard shells. It took the British more than a year to develop their own mustard agent weapon, with production of the chemicals centred