sneeze gas, poison gas used in riot control and chemical warfare. It is highly irritating to the nose and throat; inhalation of the substance causes sneezing and coughing, but rarely causes permanent injury. Mixed with CN (common tear gas, chloroacetophenone), it is used by police for dispersing crowds. Chemically, it is diphenylamine chloroarsine; sneeze gas is prepared by heating diphenylamine with arsenic trichloride.
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