<unk>  (US) or<unk> e (UK) is the mineral form of potassium<unk> ate, KNO3, also known as saltpeter (US) or saltpetre (UK). Historically, the term "nitre" – cognate with "natrium", an old word for sodium – has been very vaguely defined, and it has been applied to a variety of other minerals and chemical compounds, including sodium<unk> ate (also "soda<unk> e" or "cubic<unk> e"), sodium carbonate and potassium carbonate. This article is about the mineral form of potassium<unk> ate, which is the usual modern meaning.<unk>  is a colorless to white mineral crystallizing in the orthorhombic crystal system. It usually is found as massive encrustations and effervescent growths on cavern walls and ceilings where solutions containing alkali potassium and<unk> ate seep into the openings. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show twinning. It is most common in arid environments. It is a soft mineral equal to gypsum on the Mohs scale and has a low specific gravity of 2.1. It has refractive indices of nα=1.332, nβ=1.504, and nγ=1.504. It readily dissolves in water.<unk>  has been known since ancient times. The name is from Hebrew<unk> , for salt derived ashes.
In<unk> ature, Edgar Allan Poe invokes the supposed Saint of<unk> e repeatedly in the short story "The Cask of Amontillado" (1846), in which the main character uses the<unk> e to his "advantages", as it slowly murders his enemy. Fortunato's health worsens, until Montresor takes his revenge in the form of immurement.
Niter
Wart
Wonder 
Sponge
Boil
Electron
Alder
Meter