The compound
2-chlorobenzalmalononitrile (also called o-chlorobenzylidene malononitrile) (chemical formula: C
10H
5ClN
2), a
cyanocarbon, is the defining component of a
tear gas commonly referred to as
CS gas, which is used as a
riot control agent. Exposure causes a burning sensation and tearing of the eyes to the extent that the subject cannot keep their eyes open, and a burning irritation of the nose, mouth and throat mucous membranes causing profuse coughing, mucous nasal discharge, disorientation, and difficulty breathing, partially incapacitating the subject. CS gas is an
aerosol of a
volatile solvent (a substance that dissolves other active substances and that easily evaporates) and 2-chlorobenzalmalononitrile, which is a solid compound at room temperature. CS gas is generally accepted as being
non-lethal. It was discovered by two Americans, Ben Corson and Roger Stoughton, at
Middlebury College in 1928, and the chemical's name is derived from the first letters of the scientists' surnames.