Niter
| Niter | |
|---|---|
| General | |
| Category | Nitrate minerals |
| Chemical formula | KNO3 |
| Strunz classification | 05.NA.10 |
| Dana classification | 18.1.2.1 |
| Crystal symmetry | 2/m 2/m 2/m |
| Identification | |
| Color | white |
| Crystal habit | encrustations |
| Crystal system | orthorhombic |
| Cleavage | very good on {001}; good on {010} |
| Fracture | brittle |
| Mohs scale hardness | 2 |
| Luster | vitreous |
| Streak | white |
| Diaphaneity | transparent |
| Specific gravity | 2.10 (calc.) |
| Refractive index | nα = 1.332 nβ = 1.504 nγ = 1.504 |
| Solubility | soluble |
| References | [1][2][3] |
Niter (US) or nitre (UK) is the mineral form of potassium nitrate, KNO3, also known as saltpeter (US) or saltpetre (UK). Historically, the term "nitre" – cognate with "natrium", a Latin 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.
Because of its ready solubility in water, niter is most often found in arid environments. A major source is the Atacama desert in Chile.Potassium and other nitrates are of great importance for use in fertilisers, and, historically, gunpowder. Much of the world's demand is now met by synthetically produced nitrates, though the natural mineral is still mined and is still of significant commercial value: as of 2007, Chilean niter was reportedly trading at around US$1000 per tonne.
Description
Niter is a colourless 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 nitrate seep into the openings. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show twinning.
History
Niter has been known since ancient times. The name is from Hebrew néter, for salt-derived ashes. It may have been used as, or in conjunction with soap, as implied by Jeremiah 2:22, "For though thou wash me with nitre, and take thee much sope…" However, it is not certain which substance (or substances) the Biblical "neter" refers to, with some suggesting sodium carbonate. A term (ἀφρόνιτρον) which translates as "foam of nitre" was a regular purchase in a fourth-century AD series of financial accounts, and since it was expressed as being "for the baths" was probably used as soap.[4]
See also
References
- ↑ Niter, <http://webmineral.com/data/Niter.shtml> (accessed 4 December 2009), WebMineral.com.
- ↑ Niter, <http://www.mindat.org/show.php?id=2917> (accessed 4 December 2009), MinDat.org.
- ↑ Adiwidjaja, G.; Pohl, D. Superstructure of α-phase potassium nitrate. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2003, 59, 1139–40.
- ↑ More conventional soap also appears in the accounts but was more expensive: John Matthews, The Journey of Theophanes, Yale UP 2006
External links
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