Potassium nitrate is a chemical compound with the chemical formula KNO₃. It is an ionic salt of potassium ions K⁺ and nitrate ions NO₃⁻, and is therefore an alkali metal nitrate. It occurs in nature as a mineral, niter. It is a source of nitrogen, from which it derives its name.It is a common active ingredient in toothpaste and is also used as a constituent for several different purposes, including food preservatives, fertilizers, tree stump removal, rocket propellants, and fireworks.