A collection. Each instance is a portion of a toxic substance. agent orange is an herbicide sprayed on plants as a defoliant. It has been used mainly in modern guerilla conflicts, notably in the VietnamWar. Although agent orange is not used against troops like NerveGas, it is classified as a chemical weapon because it's used to gain strategic advantage, either by reducing the amount of vegetation enemy troops can use for cover or by destroying an enemy's civilian crops. The name is a US military code name which comes from the color of the containers used for this chemical weapon in the VietnamWar.