Occurrence and preparation [change]
It is found in very dry areas. If it was wet, then the sodium nitrate would dissolve. But it is normally made artificially by reacting sodium hydroxide and nitric acid. Chile used to have much sodium nitrate naturally in the very dry Atacama Desert. It is found in small amounts in leafy green vegetables.
It is used to supply nitrogen to the soil. It is also used in making gunpowder. Some other explosives use it. It can be used to make nitric acid by reaction with sulfuric acid. It is used in rockets and smoke bombs. Sometimes it can be a food preservative.