The chemical compound ammonium nitrate, the nitrate salt of ammonium, has the chemical formula NH₄NO₃, simplified to N₂H₄O₃. It is a white crystalline solid and is highly soluble in water. It is predominantly used in agriculture as a high-nitrogen fertilizer. The compound is used as an explosive in mining, and also sometimes in improvised explosive devices. It is the main component of ANFO, a popular explosive, which accounts for 80% of explosives used in North America. It is used in some instant cold packs, as hydrating the salt is an endothermic process, though it is being phased out of use in many countries due to concerns over its potential for use in improvised explosive devices and the synthesis of illicit substances. Ammonium nitrate has also been controversially used as a cheap airbag propellant in automobile airbags, most notably by the Takata Corporation.