Tear gas
A lachrymatory agent or lachrymator (from lacrima meaning "a tear" in Latin; commonly referred to as tear gas) is a chemical compound that stimulates the corneal nerves in the eyes to cause tearing, pain, and even temporary blindness. Common lachrymators include CS, CR, CN, bromoacetone, phenacyl bromide, and xylyl bromide. Lacrymators often share the structural element Z=C-C-X, where Z = carbon or oxygen, and X = bromide or chloride.
Effects and use
Tear gas works by irritating mucous membranes in the eyes, nose, mouth and lungs, and causes crying, sneezing, coughing, hard breathing, etc. Lachrymators are thought to act by attacking sulphydryl functional groups in enzymes, but the mechanism is not well understood. First used in 1915, Xylyl bromide was a popular tearing agent since it was easily brewed.
Lachrymatory agents are commonly used as riot control agents and chemical warfare agents. For example, tear gas and pepper spray are commonly used for riot control. During World War I more toxic lachrymatory agents were used. Certain lachrymatory agents are often used by police to assist in bringing offenders under control, most notably tear gas, but also in some countries (Finland, Australia, and the USA) another issued substance is Mace, which is used as a personal attack repellent.
Other use
Although lachrymatory agents are commonly used as riot control agents, the most common use of them is in laboratory synthesis, where their lachrymatory properties are an undesirable side effect. Common examples include benzyl chloride, thionyl chloride and acetic anhydride.
Images
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Tear gas in use in France
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Exploded teargas canister on the fly
Sources
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