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Autoren: Hans-Jürgen [[Benutzer:Hschwarz|Schwarz ]], Nils Mainusch, NN....
<br>zurück zu [[SalzWiki:Carbonate |Carbonate]] 
{{Infobox_Salt
|Footnote=<ref>
http://webmineral.com/data/Thermonatrite.shtml</ref><ref>http://www.mindat.org/min-3938.html</ref><ref>http://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Thermonatrit</ref>
|bild =  <!--[[Image:"Name der Bilddatei"|300px]] -->
|mineralogischerName=Thermonatrit
|chemischerName =Natriumcarbonathydrat
|Trivialname =Natriumcarbonat
|chemFormel =Na<sub>2</sub>CO<sub>3</sub>•H<sub>2</sub>O<sub></sub>
|Hydratformen =Natrit (Na<sub>2</sub>CO<sub>3</sub>)<br>Natriumcarbonatheptahydrat (Na<sub>2</sub>CO<sub>3</sub>•7H<sub>2</sub>O)<br>Natriumcarbonatdecahydrat - [[Natron]](Na<sub>2</sub>CO<sub>3</sub>•10H<sub>2</sub>O)
|Kristallsystem =orthorhombisch
|Deliqueszenzfeuchte =71% (35°C)
|Löslichkeit=330 g/l
|Dichte =2,255 g/cm<sup>3</sup>
|Molvolumen =55,11 cm<sup>3</sup>/mol
|Molgewicht =124,01 g/mol
|Transparenz =durchsichtig bis durchscheinend
|Spaltbarkeit =undeutlich
|Kristallhabitus =
|Zwillingsbildung =
|Brechungsindices =n<sub>x</sub> = 1,420<br>n<sub>y</sub>= 1,509<br>n<sub>z</sub> = 1,525
|Doppelbrechung =Δ = 0,105
|optOrientierung=zweiachsig negativ
|Pleochroismus =
|Dispersion =
|Phasenübergang =
|chemVerhalten =
|Bemerkungen =in wässriger Lösung alkalisch,<br> pH ≈ 12
}}
<!--
== Abstract  ==


== Introduction  == -->
== N.B. ==
General information on transition reaction, hydrate pressures and occurrence are available on [[Natrite|Sodium carbonate – natrite]].
=== Hygroscopicity ===
Estimating the hygroscopicity of sodium carbonates in situ is difficult, because the situation of the sorption point and saturation value varies greatly, due to the influence of local circumstances (i.e. foreign ions, hydrate stages present, temperature conditions).
In the following section, values for the deliquescence humidity of thermonatrite and [[natrite]] as a function of the ambient air temperature are listed (see also table [[Gleichgewichtsfeuchte in Abhängigkeit von Temperatur]]):
<br>
{|border="2" cellspacing="0" cellpadding="4" width="30%" align="left" class="wikitable"
|+''Table 1: Deliquescence humidity of thermonatrite''                 
|-
|bgcolor = "#F0F0F0" align=center| '''35°C'''
|-
|bgcolor = "#FFFFEO" align=center| 71,0% RH
|}
{|border="2" cellspacing="0" cellpadding="4" width="40%" align="left" class="wikitable"
|+''Table 2: Deliquescence humidity of natrite [Arnold/Zehnder, 1991]''
|-
|bgcolor = "#F0F0F0" align=center| '''15°C'''
|bgcolor = "#F0F0F0" align=center| '''20°C'''
|bgcolor = "#F0F0F0" align=center| '''25°C'''
|bgcolor = "#F0F0F0" align=center| '''30°C'''
|-
|bgcolor = "#FFFFEO" align=center| 96,5% RH
|bgcolor = "#FFFFEO" align=center| 97,9% RH
|bgcolor = "#FFFFEO" align=center| 88,2% RH
|bgcolor = "#FFFFEO" align=center| 83,2% RH
|}
<br clear="all">
== Analytical detection  ==
The identification of thermonatrite and natrite can be carried out in situ using simple solvent tests and by measuring the pH: According to Bläuer/ Böhm, natrite is the only efflorescent salt known to date, that is alkaline (pH clearly greater than 8) and has the property to dissolve in its chemically bound water at slight warming. The solubility in water is good. Thermonatrite is not soluble in anhydrous ethanol.
=== Microscopy<br>  ===
'''Laboratory investigation:'''<br>
Good solubility in water and low solubility in ethanol can be checked using microscopy. Thermonatrite and natrite<br> have a marked tendency towards the formation of acicular or dendritic crystal shapes, when re-crystallizing. If gypsum is present in the sample material, a rapid precipitation of calcium carbonate takes place, which becomes apparent through a whitish precipitate.<br>
<br> '''Refractive indices:'''&nbsp; n<sub>x</sub> = 1.420;&nbsp; n<sub>y</sub> = 1.509; n<sub>z</sub> =&nbsp;1,525; <br>'''Birefringence''':&nbsp;&nbsp;&nbsp; Δ&nbsp; = max. 0,105<br>'''Crystal class'''e:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; orthorhombic<br>
<br> '''Examination with the polarization microscope:'''<br>
As a function of the prevailing relative humidity and temperature conditions, the crystals of the starting sample material and the re-crystallized specimen change in content of chemically bound water. In dry air (&lt; ca. 60% RH) predominantly thermonatrite will be present after a short time.<br>The assignment of the refractive indices of thermonatrite is carried out according to the immersion method. Single particles that have been embedded in standard immersion oil with a refractive index of n<sub>D</sub> = 1,518, show strong relief changes on rotation under polarized transmitted light <bib id="Blaeuer-Boehm:1994"/>"/>, a.a.O., S. 86 ff. Due to high birefringence, thermonatrite crystals have lively interference colors. These are a clear differentiating factor from natrite, having a much lower maximum birefringence. <br> Thermonatrite belongs to the orthorhombic crystal order. This association is connected with the occurrence of parallel and/or symmetrical extinction. Large crystal needles are usually completely extinct. The extinction occurs '''in focus???scharf?????'''.
<br> '''Possible mistakes:'''
Thermonatrite is clearly assignable, if the following examination criteria have been clarified.
*high pH-value
*good solubility in water<br>
*characteristic habit
*all refractive indices below n<sub>D</sub>=1,53
*high birefringence
*parallel/symmetrical extinction<br>
{|border="2" cellspacing="0" cellpadding="4" width="80%" align="left" class="wikitable"
|+''Table 3: Salt phases with similar characteristics and the possibility to be confused''                 
|-
|bgcolor = "#F0F0F0"| '''Salt phase'''
|bgcolor = "#F0F0F0"| '''Distinguishing features to thermonatrite'''
|-
|bgcolor = "#F7F7F7"| '''Nesquehonite''' MgCO<sub>3</sub> •<sub>&nbsp; </sub>3H<sub>2</sub>O;
|bgcolor = "#FFFFEO"| slightly water soluble/ oblique extinction
|-
|bgcolor = "#F7F7F7"| '''Lansfordite''' MgCO<sub>3</sub> • 5H<sub>2</sub>O
|bgcolor = "#FFFFEO"| slightly water soluble / oblique extinction / low birefringence
|-
|bgcolor = "#F7F7F7"| '''Trona''' Na<sub>3</sub>H(CO<sub>3</sub>)<sub>2</sub> • 2H<sub>2</sub>O
|bgcolor = "#FFFFEO"| mainly observed index &gt; 1,53 / oblique extinction
|-
|bgcolor = "#F7F7F7"| '''Potash''' K<sub>2</sub>CO<sub>3</sub>
|bgcolor = "#FFFFEO"| mainly observed index &gt; 1,53 / oblique extinction / strongly hygroscopic
|}
<br clear=all>
<!--
== X- Ray diffraction  ==
== Raman-Spectroscopy  ==
== DTA / TG  ==
== IR-Spectroscopie  ==
== Umgang mit Thermonatritschäden  ==
== Thermonatrit im Bild  ==
=== Am Objekt  ===
=== Unter dem Polarisationsmikrokop  ===
<br>
<br>
== Unter dem Rasterelektronenmikroskop  ==
-->
== Weblinks  ==
<references/><br>
== Literatur  ==


[[User:SLeithaeuser|SLeithaeuser]] 12:07, 22 June 2012 (CEST)
[[User:SLeithaeuser|SLeithaeuser]] 12:07, 22 June 2012 (CEST)

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SLeithaeuser 12:07, 22 June 2012 (CEST)

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