Nitre, also known as saltpeter or potassium nitrate, is an odorless, colorless crystalline solid that has been used in various applications since ancient times. It is a naturally occurring mineral found in soil and sediment, and is also produced synthetically. Nitre has been used as a fertilizer, a food preservative, a propellant for fireworks, and in the manufacture of gunpowder. It is also used in the production of glass, ceramics, and enamels.