Natron
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225528550
2008-07-14T04:15:17Z
Gwen Gale
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[[WP:UNDO|Undid]] revision 225524204 by [[Special:Contributions/71.188.155.39|71.188.155.39]] ([[User talk:71.188.155.39|talk]])
{{Refimprove|date=July 2008}}
'''Natron''' is a naturally occurring mixture of [[sodium carbonate]] decahydrate ([[sodium|Na]]<sub>2</sub>[[carbon|C]][[oxygen|O]]<sub>3</sub>'''·'''10[[water|H<sub>2</sub>O]], a naturally occurring form of [[soda ash]]) and about 17% [[sodium bicarbonate]] (also called [[nahcolite]]<ref>''webmineral.com'', [http://webmineral.com/data/Nahcolite.shtml "Nahcolite"], retrieved 5 July 2008</ref> or [[baking soda]], Na[[hydrogen|H]]CO<sub>3</sub>) along with small quantities of household [[salt]] ([[halite]], [[sodium chloride]]) and [[sodium sulfate]]. Natron is white to colorless when pure, varying to gray or yellow with impurities. Natron deposits occur naturally as a part of saline lake beds in arid environments. Throughout history, natron has had many practical applications, which still resonate in the wide range of modern uses of its constituent mineral components.
In modern [[mineralogy]] the term ''natron'' has come to mean only the ''sodium carbonate decahydrate'' (hydrated soda ash) which makes up most of the historical salt.
==Etymology==
The [[English language|English]] word ''natron'' is a [[French language|French]] [[cognate]] derived from the [[Spanish language|Spanish]] ''natrón'' through the [[Arabic language|Arabic]] ''natrun'' from [[Greek language|Greek]] ''nitron'', which derived from the [[Ancient Egyptian]] word ''netjeri'', stemming from [[Wadi El Natrun]], [[Egypt]]. The modern chemical symbol for [[sodium]], '''Na''', is an abbreviation of that element's new [[Latin]] name ''natrium'', which was derived from ''natron''.
==Importance in antiquity==
Historical natron was harvested directly as a salt mixture from dry lake beds in [[History of Egypt|ancient Egypt]] and has been used for thousands of years as a cleaning product for both the home and body. Blended with oil, it was an early form of [[soap]]. It [[Water softening|softens water]] whilst removing oil and grease. Undiluted, natron was a cleanser for the teeth and an early [[mouthwash]]. The mineral was mixed into early [[antiseptics]] for wounds and minor cuts. Natron can be used to dry and preserve fish and meat. It was also an ancient household insecticide, was used for making leather and as a bleach for clothing.
The mineral was used in Egyptian [[mummy|mummification]] because it absorbs water and behaves as a drying agent. Moreover, when exposed to moisture the carbonate in natron increases pH, which creates a hostile environment for bacteria. In some cultures, natron was thought to enhance spiritual safety for both the living and the dead. Natron was added to [[castor oil]] to make a smokeless fuel, which allowed Egyptian artisans to paint elaborate artworks inside ancient tombs without staining them with soot.
Natron is an ingredient for the making of a distinct color called ''Egyptian blue''. It was used along with [[sand]] and [[lime (mineral)|lime]] in ceramic and glass-making by the Romans and others at least until [[640]] CE. The mineral was also employed as a [[flux (metallurgy)|flux]] to solder precious metals together.
===Declining use===
Most of natron's uses both in the home and by industry were gradually replaced with closely related sodium compounds and minerals. Natron's [[detergent]] properties are now commercially supplied by [[soda ash]], the mixture's chief compound ingredient, along with other chemicals. Soda ash also replaced natron in glass-making. Some of its ancient household roles are also now filled by ordinary [[baking soda]], natron's other meaningful ingredient.
==Chemistry of hydrated sodium carbonate==
Natron is also the mineralogical name for the compound sodium carbonate decahydrate (Na<sub>2</sub>CO<sub>3</sub>'''·'''10H<sub>2</sub>O), which is the main component in historical natron.<ref>''webmineral.com'', [http://webmineral.com/data/Natron.shtml "Natron"], retrieved 5 July 2008</ref> Sodium carbonate decahydrate has a [[specific gravity]] of 1.42 to 1.47 and a [[Mohs hardness]] of 1. It crystallizes in the [[monoclinic]]-domatic [[crystal system]], typically forming efflorescences and encrustations.
The term ''hydrated sodium carbonate'' is commonly used to encompass the monohydrate (Na<sub>2</sub>CO<sub>3</sub>'''·'''H<sub>2</sub>O), the decahydrate and the heptahydrate (Na<sub>2</sub>CO<sub>3</sub>'''·'''7H<sub>2</sub>O), but is often used in industry to refer to the decahydrate only. Both the hepta- and the decahydrate effloresce (loose water) in dry air and are partially transformed into the monohydrate [[thermonatrite]] Na<sub>2</sub>CO<sub>3</sub>'''·'''H<sub>2</sub>O.
===As a source of soda ash===
Sodium carbonate decahydrate is stable at room temperature but recrystallizes at only 32°C (90°F) to sodium carbonate heptahydrate, Na<sub>2</sub>CO<sub>3</sub>'''·'''7H<sub>2</sub>O, then above 37-38°C (98-100°F) to sodium carbonate monohydrate, Na<sub>2</sub>CO<sub>3</sub>'''·'''H<sub>2</sub>O. This recrystallization from decahydrate to monohydrate releases much crystal water in a mostly clear, colorless salt solution with little solid [[thermonatrite]]. The mineral natron is often found in association with [[thermonatrite]], [[nahcolite]], [[trona]], [[halite]], [[mirabilite]], [[gaylussite]], [[gypsum]], and [[calcite]].
Most industrially produced sodium carbonate is soda ash, sodium carbonate anhydrate Na<sub>2</sub>CO<sub>3</sub>, which is obtained by calcination (dry heating at temperatures of 150 to 200°C) of sodium bicarbonate, sodium carbonate monohydrate, or [[trona]].
==Geological occurrence==
Geologically, the mineral natron as well as the historical natron are formed as transpiro-[[evaporite]] minerals, i.e. crystallizing during the drying up of salt lakes rich in sodium carbonate. The sodium carbonate is usually formed by absorption of [[carbon dioxide]] from the atmosphere by a highly alkaline, sodium-rich lake [[brine]], according to the following reaction scheme:
NaOH<sub>(aq)</sub> + CO<sub>2</sub> -> NaHCO<sub>3(aq)</sub>
NaHCO<sub>3(aq)</sub> + NaOH<sub>(aq)</sub> -> Na<sub>2</sub>CO<sub>3(aq)</sub> + H<sub>2</sub>O
Pure deposits of sodium carbonate decahydrate are rare, due to the limited temperature stability of this compound and due to the fact, that the absorption of [[carbon dioxide]] usually produces mixtures of [[bicarbonate]] and [[carbonate]] in solution. From such mixtures, the mineral natron (and also the historical one) will only be formed, if the [[brine]] temperature during evaporation is maximally ca. 20°C (68°F) - or the [[alkalinity]] of the lake is so high, that little [[bicarbonate]] is present in solution (see reaction scheme above) - in which case the maximum temperature is increased to ca. 30°C (86°F). In most cases the mineral natron will form together with some amount of [[nahcolite]] ([[sodium bicarbonate]]), resulting in salt mixtures like the historical natron.
Otherwise, the minerals [[trona]][http://webmineral.com/data/Trona.shtml] or [[thermonatrite]] and [[nahcolite]] are commonly formed. As the evaporation of a salt lake will occur over geological time spans, during which also part or all of the salt beds might redissolve and recrystallize, deposits of sodium carbonate can be composed of layers of all these minerals.
The following list may include geographical sources of either natron or other hydrated sodium carbonate minerals:
*[[Quebec, Canada]]
**[[Rouville|Rouville County]]
**[[Mont-Saint-Hilaire, Quebec|Mont-Saint-Hilaire]]
*Interior British Columbia, Canada
*[[Wadi El Natrun]], [[Egypt]]
*[[Shewa|Showa Province]], [[Ethiopia]]
*[[Hungary]]
**[[Bács-Kiskun|Bács-Kiskun County]], (Great Hungarian Plain)
**[[Szabolcs-Szatmár-Bereg|Szabolcs-Szatmár-Bereg County]] (Great Hungarian Plain)
*[[Campania|Campania, Italy]]
**[[Province of Naples]]
**[[Somma-Vesuvius]] Complex
*[[Russia]] (Northern Region)
**[[Murmanskaja Oblast]]
**[[Kola Peninsula]]
**[[Khibiny Massif]]
**[[Lovozero]] [[Massif]]
**[[Alluaiv Mountain]]
**[[Umbozero]] Mine
**[[Kedykverpakhk Mountain]]
*[[England, UK]]
**[[Cornwall]]
**[[St Just in Penwith|St Just District]]
**[[Botallack]] - [[Pendeen]] Area
**Botallack, and Botallack Mine
*[[California, USA]]
**[[Inyo County, California|Inyo County]]
*[[Nevada|Nevada, USA]]
**[[Churchill County, Nevada|Churchill County]] ([[Soda Lake|Soda Lake District]])
**[[Humboldt County, Nevada|Humboldt County]]
**[[Mineral County, Nevada|Mineral County]]
*[[Oregon, USA]]
**[[Lake County, Oregon|Lake County]]
*[[Washington|Washington, USA]]
**[[Okanogan County, Washington|Okanogan County]]
==References==
{{reflist}}
==External links==
* [http://www.balashon.com/2008/07/neter-and-nitrogen.html Etymology of "natron"]
==See also==
[[Sodium nitrate|Saltpeter]]
[[Category:Sodium compounds]]
[[Category:Desiccants]]
[[Category:Antiseptics]]
[[Category:Sodium minerals]]
[[Category:Carbonate minerals]]
[[Category:Alchemical substances]]
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