Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Sodium dichromate: Difference between pages

{{short description|Inorganic compound}}

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 476993146

| Name = Sodium dichromate

| ImageFile = Na2Cr2O7.png

| ImageName =

| ImageFile1 = Dichroman sodný.JPG

| ImageName1 =

| IUPACName = Sodium dichromate

| OtherNames = Chromic acid disodium salt

| SystematicName =

| CASNo = 10588-01-9

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo1_Ref = {{cascite|correct|CAS}}

| CASNo1 = 7789-12-0

| CASNo1_Comment = (dihydrate) <!-- validated by Aldrich and ECB -->

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| Gmelin = 21597

| EINECS = 234-190-3

| PubChem = 25408

| RTECS = HX7750000<br/>HX7750000 (dihydrate)

| UNNumber = 3288

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = C9G6VY6ZZ4

| UNII1_Ref = {{fdacite|correct|FDA}}

| UNII1 = 52125XYY2A

| UNII1_Comment = (dihydrate)

| InChI = 1/2Cr.2Na.7O/q;;2*+1;;;;;;2*-1/rCr2O7.2Na/c3-1(4,5)9-2(6,7)8;;/q-2;2*+1

| InChIKey = KIEOKOFEPABQKJ-RXLKZJBDAW

| Formula = Na₂Cr₂O₇

| MolarMass = 261.97 g/mol (anhydrous)<br/>298.00 g/mol (dihydrate)

| Appearance = bright orange

| Odor = odorless

| Density = 2.52 g/cm³

| Solvent = other solvents

| Solubility = 73 g/100 mL at 25 °C<!--Ullmann's-->

| SolubleOther = soluble in [[methanol]], [[ethanol]]

| MeltingPtC = 356.7

| BoilingPtC = 400

| BoilingPt_notes = decomposes

| RefractIndex = 1.661 (dihydrate)

| Section3 =

| Section4 =

| Section5 =

| Section6 =

| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics1369.htm ICSC 1369]

| GHSPictograms = {{GHS03}}{{GHS05}}{{GHS06}}{{GHS07}}{{GHS08}}{{GHS09}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|272|301|312|314|317|330|334|340|350|360|372|410}}

| PPhrases = {{P-phrases|201|202|210|220|221|260|261|264|270|271|272|273|280|281|284|285|301+310|301+330+331|302+352|303+361+353|304+340|304+341|305+351+338|308+313|310|312|314|320|321|322|330|333+313|342+311|363|370+378|391|403+233|405|501}}

| NFPA-H = 4

| NFPA-F = 0

| NFPA-R = 1

| NFPA-S = OX <!-- validated by Fisher Sci -->

| LD50 = 50 mg/kg

| OtherAnions = [[Sodium chromate]]<br/>[[Sodium molybdate]]<br/>[[Sodium tungstate]]

| OtherCations = [[Potassium dichromate]]<br/>[[Ammonium dichromate]]

'''Sodium dichromate''' is the [[inorganic compound]] with the formula [[sodium|Na₂]][[Chromium|Cr₂]][[Oxygen|O₇]]. However, the salt is usually handled as its [[hydrate|dihydrate]] Na₂Cr₂O₇·2[[water of crystallization|H₂O]]. Virtually all [[chromium]] ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt.<ref name=Ullmann>Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. {{doi|10.1002/14356007.a07_067}}</ref> In terms of [[Reactivity (chemistry)|reactivity]] and appearance, sodium dichromate and [[potassium dichromate]] are very similar. The sodium salt is, however, around twenty times more soluble in water than the potassium salt (49 g/L at 0 °C) and its [[equivalent weight]] is also lower, which is often desirable.<ref name=eEROS>Freeman, F. "Sodium Dichromate" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289X}}.</ref>

==Preparation==

Sodium dichromate is generated on a large scale from ores containing chromium(III) oxides. The ore is fused with a base, typically [[sodium carbonate]], at around 1000 °C in the presence of air (source of oxygen):

<chem> 2Cr2O3 + 4Na2CO3 + 3O2 -> 4Na2CrO4 + 4CO2</chem>

This step solubilizes the chromium and allows it to be extracted into hot water. At this stage, other components of the ore such as aluminium and iron compounds, are poorly soluble. Acidification of the resulting aqueous extract with [[sulfuric acid]] or [[carbon dioxide]] affords the dichromate:

<chem> 2Na2CrO4 + 2CO2 + H2O -> Na2Cr2O7 + 2NaHCO3 </chem>

<chem> 2Na2CrO4 + H2SO4 -> Na2Cr2O7 + Na2SO4 + H2O </chem>

The dichromate is isolated as the dihydrate by crystallization. In this way, many millions of kilograms of sodium dichromate are produced annually.<ref name=Ullmann/>

Since chromium(VI) is toxic, especially as the dust, such factories are subject to stringent regulations. For example, effluent from such refineries is treated with reducing agents to return any chromium(VI) to chromium(III), which is less threatening to the environment.<ref name=Ullmann/> A variety of hydrates of this salt are known, ranging from the decahydrate below 19.5 °C (CAS# {{CAS|13517-17-4}}) as well as hexa-, tetra-, and dihydrates. Above 62 °C, these salts lose water spontaneously to give the anhydrous material.

It is crystallised around 30 to 35 degrees C

==Reactions==

Dichromate and chromate salts are oxidizing agents. For the [[Tanning (leather)|tanning]] of leather, sodium dichromate is first reduced with [[sulfur dioxide]].

In the area of [[organic synthesis]],<ref name=eEROS/> this compound oxidizes [[benzylic]] and [[allylic]] [[C-H bond]]s to [[carbonyl]] derivatives. For example, [[2,4,6-trinitrotoluene]] is oxidized to the corresponding carboxylic acid.<ref name="cv1p0543">{{OrgSynth | author = Clarke, H. T.; Hartman, W. W. | title = 2,4,6-Trinitrobenzoic Acid | collvol = 1 | collvolpages = 543 | year = 1941 | prep = cv1p0543}}</ref> Similarly, 2,3-dimethylnaphthalene is oxidized by Na₂Cr₂O₇ to 2,3-naphthalenedicarboxylic acid.<ref>{{OrgSynth | author = Friedman, L. | title = 2,3-Naphthalenedicarboxylic Acid | collvol = 5 | collvolpages = 810 | year = 1973 | prep = cv5p0810}}</ref>

Secondary alcohols are oxidized to the corresponding ketone, e.g. [[menthol]] to [[menthone]];<ref>{{OrgSynth |title = ''l''-Menthone | author = L. T. Sandborn | volume = 9 | pages = 59 | collvol = 1 | collvolpages = 340 | prep = cv1p0340| year = 1929}}</ref> dihydrocholesterol to cholestanone:<ref>{{OrgSynth | title = Cholestanone | author = W. F. Bruce | prep = cv2p0139 | collvol = 2 | collvolpages = 139 | year = 1941}}</ref>

:3 R₂CHOH + Cr₂O₇²⁻ + 2 H⁺ → 3 R₂C=O + Cr₂O₃ + 4 H₂O

Relative to the potassium salt, the main advantage of sodium dichromate is its greater solubility in water and polar solvents like acetic acid.

For hexavalent [[chrome plating]], chromate is converted to the so-called [[chromic acid]] (essentially [[chromium trioxide]]) by sulfuric acid.

Sodium dichromate can be used in [[fluorene]] to [[fluorenone]] conversion.

==Safety==

Like all [[hexavalent chromium]] compounds, sodium dichromate is [[carcinogen]]ic.<ref name="book100C">{{cite book

|author = IARC

|author-link = International Agency for Research on Cancer

|title = Volume 100C: Arsenic, Metals, Fibres, and Dusts

|orig-year = 17-24 March 2009

|url = https://publications.iarc.fr/_publications/media/download/3026/50ed50733f7d1152d91b30a803619022ef098d59.pdf

|access-date = 2020-01-05

|date = 2012

|isbn = 978-92-832-0135-9

|quote = There is ''sufficient evidence'' in humans for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium (VI) compounds and cancer of the nose and nasal sinuses. There is ''sufficient evidence'' in experimental animals for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds are ''carcinogenic to humans (Group 1)''.

|publisher = International Agency for Research on Cancer

|location = Lyon

|archive-date = 2020-03-17

|archive-url = https://web.archive.org/web/20200317095517/https://publications.iarc.fr/_publications/media/download/3026/50ed50733f7d1152d91b30a803619022ef098d59.pdf

|url-status = live

}}</ref> The compound is also [[corrosive]] and exposure may produce severe eye damage or blindness.<ref>{{cite web |url=http://www.inchem.org/documents/icsc/icsc/eics1369.htm |title=ILO 1369 - Sodium Dichromate |access-date=2011-07-23 |archive-date=2020-03-15 |archive-url=https://web.archive.org/web/20200315063021/http://www.inchem.org/documents/icsc/icsc/eics1369.htm |url-status=live }}</ref> Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children.

==References==

{{reflist}}

{{Sodium compounds}}

{{Chromates and dichromates}}

[[Category:Sodium compounds]]

[[Category:Dichromates]]

[[Category:Oxidizing agents]]