View source for Niter



==Overview==
'''Niter''' (US) or '''nitre''' (UK) is the mineral form of [[potassium nitrate]], KNO<sub>3</sub>, 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 nitrate]] (also "soda nitre" or "cubic nitre"), [[sodium carbonate]] and [[potassium carbonate]]. This article is about the mineral form of potassium nitrate, which is the usual modern meaning.

Niter is a colorless to white mineral crystallizing in the [[orthorhombic]] [[crystal system]]. It usually is found as massive encrustations and effervescent growths on [[cave|cavern]] walls and ceilings where solutions containing alkali potassium and nitrate seep into the openings. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show [[crystal twinning|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 index|refractive indices]] of nα=1.332, nβ=1.504, and nγ=1.504. It readily dissolves in water. 

Niter has been known since ancient times. The name is from Hebrew ''néter'', for salt derived ashes.

In literature, [[Edgar Allan Poe]] invokes the supposed Saint of Nitre repeatedly in the short story "[[The Cask of Amontillado]]" (1846), in which the main character uses the nitre to his "advantages", as it slowly murders his enemy. Fortunato's health worsens, until Montresor takes his revenge in the form of [[immurement]]. 

==References==
* [http://www.mindat.org/min-2917.html Niter page on mindat.org]
* [http://www.webmineral.com/data/Niter.shtml Niter page on webmineral.com]
* [http://mineral.galleries.com/minerals/carbonat/niter/niter.htm Mineral galleries]
* [http://bau2.uibk.ac.at/sg/poe/works/cask_amo.html Poe's ''The Cask of Amontillado'']

{{mineral-stub}}

[[Category:Nitrate minerals]]
[[Category:Potassium minerals]]

[[de:Salpeter]]
[[it:Niter]]
[[ja:硝石]]
[[pl:Nitrokalit]]
[[zh:硝石]]
{{WH}}
{{WS}}