Potassium nitrate Potassium nitrate Potassium nitrate is a chemical compound with the chemical formula KNO. It is an ionic salt of potassium ions K and nitrate ions NO, 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. Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpeter or saltpetre. Major uses of potassium nitrate are in fertilizers, tree stump removal, rocket propellants and fireworks. It is one of the major constituents of gunpowder (black powder) and has been used since the
Chemical element plants, the calcium in mollusc shells, or the iron in the hemoglobin in vertebrate animals' red blood cells. The concept of an "element" as an undivisible substance has developed through three major historical phases: Classical definitions (such as those of the ancient Greeks), chemical definitions, and atomic definitions. Ancient philosophy posited a set of classical elements to explain observed patterns in nature. These "elements" originally referred to "earth", "water", "air" and "fire" rather than the chemical elements of modern science. The term 'elements' ("stoicheia") was first used by the Greek philosopher Plato in about 360 BCE in his dialogue Timaeus,