Editing Natron

{{Short description|Carbonate mineral}}
{{Other uses}}
{{More citations needed|date=August 2022}}

{{Infobox mineral
| name        = Natron
| category    = [[Carbonate mineral]]
| boxwidth    = 
| boxbgcolor  = 
| image       = Emi Koussi crater natron.jpg
| imagesize   = 
| alt         = 
| caption     = Natron deposits in the Era Kohor crater in the [[Tibesti Mountains]], [[Chad]]
| formula     = Na<sub>2</sub>CO<sub>3</sub>·10H<sub>2</sub>O
| IMAsymbol   = Nt<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}</ref>
| molweight   = 
| strunz      = 5.CB.10
| dana        = 15.01.02.01
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''2/m
| unit cell   = a = 12.75 Å, b = 9 Å, c = 12.6 Å<br>β = 115.85°
| colour      = Colourless to white, greyish, yellowish; colourless in transmitted light.
| habit       = crystalline, granular, and columnar crusts
| twinning    = on {001}
| cleavage    = On {001} distinct; on {010} imperfect; on {110} in traces.
| fracture    = Conchoidal
| tenacity    = Brittle
| mohs        = 1 – 1.5
| lustre      = Vitreous
| streak      = White
| diaphaneity = Transparent to translucent
| gravity     = 1.478
| density     = 
| polish      = 
| opticalprop = Biaxial (−)
| refractive  = n<sub>α</sub> = 1.405 n<sub>β</sub> = 1.425 n<sub>γ</sub> = 1.440
| birefringence = δ = 0.035
| pleochroism = 
| 2V          = Measured: 71° , Calculated: 80°
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence= 
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = Soluble in water
| other       = 
| alteration  = 
| references  = <ref name=Mindat>{{Cite web|title=Natron Mindat|url=https://www.mindat.org/min-2858.html|access-date=2022-11-28|website=mindat.org}}</ref><ref name=Handbook>{{Cite web|title=Natron Handbook|url=http://rruff.info/doclib/hom/natron.pdf|access-date=2022-11-28}}</ref><ref name=Webmin>{{Cite web |title=Natron Mineral Data |url=https://webmineral.com/data/Natron.shtml |access-date=2022-11-26 |website=webmineral.com}}</ref>
}}
'''Natron''' is a naturally occurring mixture of [[sodium carbonate]] decahydrate ([[sodium carbonate|Na<sub>2</sub>CO<sub>3</sub>]]·10H<sub>2</sub>O, a kind of [[soda ash]]) and around 17% [[sodium bicarbonate]] (also called baking soda, NaHCO<sub>3</sub>) along with small quantities of [[sodium chloride]] and [[sodium sulfate]]. Natron is white to colourless when pure, varying to gray or yellow with impurities. Natron deposits are sometimes found in saline lake beds which arose in arid environments. Throughout history natron has had many practical applications that continue today 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) that makes up most of the historical salt.

[[File:Natron deposits, Trou au Natron, Chad.jpg|thumb|Natron deposits, Trou au Natron, Tibesti, Chad]]

== Etymology ==
The [[English language|English]] and [[German language|German]] word ''natron'' is a [[French language|French]] [[cognate]] derived through the [[Spanish language|Spanish]] ''natrón'' from [[Latin language|Latin]] ''natrium'' and [[Greek language|Greek]] ''nitron'' ({{lang|el|νίτρον}}). This derives from the [[Ancient Egyptian]] word [[wikt:nṯrj#Egyptian|''nṯrj'']]. ''Natron'' refers to [[Wadi El Natrun]] or Natron Valley in Egypt, from which natron was mined by the ancient Egyptians for use in burial rites. The modern chemical symbol for [[sodium]], ''Na'', is an abbreviation of that element's [[Neo-Latin]] name ''natrium'', which was derived from ''natron''. The name of the chemical element [[Nitrogen]] is also a cognate to natron, it derives from Greek ''nitron'' and ''-gen (''a producer of something, in this case [[Nitric acid]], which was produced from [[niter]] (potassium nitrate)). Niter was also an obsolete name for natron because in earlier times, both minerals used to be confused with each other.

== Importance in antiquity ==
[[File:Egyptian - "Malqata Kateriskos" Vessel - Walters 4732 - Profile.jpg|thumb|upright|A [[Egyptian faience|faience]] vase fabricated in part from natron, dating to the [[New Kingdom of Egypt]] (c. 1450–1350 BC)]]

Historical natron was harvested directly as a salt mixture from dry lake beds in [[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]] while 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, and was used for making leather as well as a bleach for clothing.

The mineral was used during [[mummy|mummification]] ceremonies in ancient Egypt because it absorbs water and behaves as a drying agent. Moreover, when exposed to moisture, the [[carbonate]] in natron increases [[pH]] (raises [[alkalinity]]), 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.

The Pyramid Texts describe how natron pellets were used as funerary offerings in the rites for the deceased pharaoh, "N". The ceremony required two kinds of natron, one sourced from northern (Lower) and one from southern (Upper) Egypt.

{{poemquote|''Smin'', ''smin'' opens thy mouth. One pellet of natron.
O N., thou shalt taste its taste in front of the ''sḥ-ntr-''chapels. One pellet of natron.
That which Horus spits out is ''smin''. One pellet of natron.
That which Set spits out is ''smin''. One pellet of natron.
That which the two harmonious gods (spit out) is ''smin''. One pellet of natron.
To say four times: Thou hast purified thyself with natron, together with Horus (and) the Followers of Horus. Five pellets of natron from Nekheb, Upper Egypt.
Thou purifiest (thyself); Horus purifies (himself). One pellet of natron. Thou purifiest (thyself); Set purifies (himself). One pellet of natron.
Thou purifiest (thyself); Thot purifies (himself). One pellet of natron. Thou purifiest (thyself); the god purifies (himself). One pellet of natron.
Thou also purifiest (thyself)—thou who art among them. One pellet of natron.
Thy mouth is the mouth of a sucking calf on the day of his birth.
Five pellets of natron of the North, Wadi Natrûn (''št-p.t'')<ref>[http://www.sacred-texts.com/egy/pyt/pyt05.htm www.sacred-texts.com/egy/pyt/pyt05.htm ''The Pyramid Texts''], Utterance 35. Translated by Samuel A. B. Mercer, 1952. Accessed 9 April 2020.</ref>}}

Natron is an ingredient for making a distinct color called ''[[Egyptian blue]]'', and also as the [[flux (metallurgy)|flux]] in [[Egyptian faience]]. It was used along with [[sand]] and [[lime (mineral)|lime]] in ceramic and glass-making by the Romans and others at least until AD 640. The mineral was also employed as a flux to solder precious metals together.

=== Decline in 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]] (pure sodium carbonate), the mixture's chief compound ingredient, along with other chemicals. Soda ash also replaced natron in [[Ancient glass trade|glass-making]]. Some of its ancient household roles are also now filled by ordinary [[baking soda]], which is [[sodium bicarbonate]], natron's other key 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 name="Webmin"/>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 (lose 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 {{convert|32|°C|°F|abbr=on}} to sodium carbonate heptahydrate, Na<sub>2</sub>CO<sub>3</sub>'''·'''7H<sub>2</sub>O, then above {{convert|37|-|38|C|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&nbsp;°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:

{{block indent|NaOH<sub>(aq)</sub> + CO<sub>2</sub> → NaHCO<sub>3(aq)</sub>}}
{{block indent|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 be formed only if the [[brine]] temperature during evaporation is maximally about {{convert|20|°C|°F|abbr=on}}&nbsp;– or the [[alkalinity]] of the lake is so high, that little [[bicarbonate]] is present in solution (see reaction scheme above)&nbsp;– in which case the maximum temperature is increased to about {{convert|30|°C|°F|abbr=on}}. 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]]<ref>{{cite web|url= http://webmineral.com/data/Trona.shtml|title= Trona Mineral Data}}</ref> 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:

* Africa
** [[Chad]]
*** shores of [[Lake Chad]]
***[[Trou au Natron]]
***Era Kohor crater on [[Emi Koussi]]
** [[Egypt]]
*** [[Wadi El Natrun]] (Natron Valley)
** [[Ethiopia]]
*** [[Shewa|Showa Province]]
** [[Niger]]
*** [[Bilma]]
** [[Tanzania]], [[Kenya]]
*** [[Lake Natron]]
* Europe
** [[Hungary]]
*** [[Bács-Kiskun|Bács-Kiskun County]], (Great Hungarian Plain)
*** [[Szabolcs-Szatmár-Bereg|Szabolcs-Szatmár-Bereg County]] (Great Hungarian Plain)
** [[Italy]]
*** [[Campania]]
*** [[Province of Naples]]
*** [[Somma-Vesuvius]] Complex
** [[Kola Peninsula]], northern [[Russia]]
*** [[Khibiny Massif]]
*** [[Lovozero Massif]]
**** [[Alluaiv]] Mountain
**** [[Kedykverpakhk]] Mountain
*** [[Umbozero]] Mine
** [[England]], UK
*** [[St Just in Penwith|St Just District]]
*** [[Botallack]]&nbsp;– [[Pendeen]] Area
* North America
** [[Canada]]
*** [[Quebec]]
**** [[Rouville Regional County Municipality|Rouville County]]
**** [[Mont-Saint-Hilaire, Quebec|Mont-Saint-Hilaire]]
*** Interior [[British Columbia]]
** [[United States]]
*** [[California]]
**** [[Inyo County, California|Inyo County]]
*** [[Nevada]]
**** [[Churchill County, Nevada|Churchill County]] ([[Soda Lakes|Soda Lake District]])
**** [[Humboldt County, Nevada|Humboldt County]]
**** [[Mineral County, Nevada|Mineral County]]
*** [[Oregon]]
**** [[Lake County, Oregon|Lake County]]
*** [[Pennsylvania]]
**** [[Karns, Pennsylvania|Karns]]
**** [[Natrona, Pennsylvania|Natrona]]
*** [[Washington (state)|Washington]]
**** [[Okanogan County, Washington|Okanogan County]]
*** [[Wyoming]]
**** [[Natrona County, Wyoming|Natrona County]]

== See also ==
* [[Nahcolite]]
* [[Niter]] 
* [[Potassium nitrate]]
* [[Shortite]]
* [[Soda (disambiguation)]]
* [[Sodium sesquicarbonate]]
* [[Thermonatrite]]
* [[Trona]]

== References ==
{{reflist}}

== External links ==
{{wiktionary|natron|νίτρον|natrium}}
{{Commons category}}
* [http://www.balashon.com/2008/07/neter-and-nitrogen.html Etymology of "natron"]

[[Category:Carbonate minerals]]
[[Category:Sodium minerals]]
[[Category:Desiccants]]
[[Category:Antiseptics]]
[[Category:Alchemical substances]]
[[Category:Monoclinic minerals]]
[[Category:Industrial minerals]]