tear gas, gas that causes temporary blindness through the excessive flow of tears resulting from irritation of the eyes. The gas is used in chemical warfare and as a means for dispersing mobs. Compounds that cause lacrimation (watering of the eyes) include bromoacetone, benzyl bromide, chloroacetophenone, ethyl iodoacetate, chloropicrin bromobenzyl cyanide, and bromine-substituted xylenes. In warfare a lacrimating compound in liquid form is placed in bombs, shells, or grenades; when the device explodes, the liquid is dispersed as an aerosol.