View source for Chemistry:Sodium oxalate

{{chembox
|Verifiedfields = changed
|Watchedfields = changed
|verifiedrevid = 408853766
|Name = Sodium oxalate
|ImageFile = Sodium-oxalate-2D.png
|ImageName = Disodium oxalate
|PIN = Disodium oxalate
|OtherNames = Oxalic acid, disodium salt<br />Sodium ethanedioate
|Section1={{Chembox Identifiers
|CASNo = 62-76-0
|CASNo_Ref = {{cascite|correct|CAS}}<ref name="ChemIDplus">{{cite web |title=ChemIDplus - 62-76-0 - ZNCPFRVNHGOPAG-UHFFFAOYSA-L - Disodium oxalate - Similar structures search, synonyms, formulas, resource links, and other chemical information. |url=https://chem.nlm.nih.gov/chemidplus/rn/62-76-0 |website=chem.nlm.nih.gov |publisher=NIH |access-date=7 January 2019 |language=en}}</ref>
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = 7U0V68LT9X
|PubChem = 6125
|ChEMBL_Ref = {{ebicite|changed|EBI}}
|ChEMBL = 182928
|ChEBI_Ref = {{ebicite|changed|EBI}} 
|ChEBI = 132764
|RTECS = K11750000
|EINECS = 200-550-3
|SMILES = C(=O)(C(=O)[O-])[O-].[Na+].[Na+]
|ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
|ChemSpiderID = 5895
|StdInChI_Ref = {{stdinchicite|changed|chemspider}}
|StdInChI = 1S/C2H2O4.2Na/c3-1(4)2(5)6;;/h(H,3,4)(H,5,6);;/q;2*+1/p-2
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
|StdInChIKey = ZNCPFRVNHGOPAG-UHFFFAOYSA-L
}}
|Section2={{Chembox Properties
|Formula = {{chem2|Na2C2O4}}
|Na=2|C=2|O=4
|Appearance = White crystalline solid
|Odor = Odorless
|Density = 2.34 g/cm<sup>3</sup>
|Solubility = {{ubl|2.69 g/(100 mL) (0 °C)|3.7 g/(100 mL) (20 °C)|6.25 g/(100 mL) (100 °C)}}
|SolubleOther = Soluble in [[Chemistry:Formic acid|formic acid]], insoluble in [[Chemistry:Ethanol|ethanol]], [[Chemistry:Diethyl ether|diethyl ether]] 
|MeltingPtC = 260
|MeltingPt_notes = decomposes above 290 °C<ref name=yoshi/>
}}
|Section3={{Chembox Structure
|CrystalStruct = monoclinic
}}
|Section4={{Chembox Thermochemistry
|DeltaHf = −1318 kJ/mol
}}
|Section7={{Chembox Hazards
| ExternalSDS = [http://msds.chem.ox.ac.uk/SO/sodium_oxalate.html Oxford MSDS] {{Unreliable source|sure=y|reason=The webpage has been deprecated and is advising users to not use it as a reference.|date=May 2020}}
|GHSPictograms = {{GHS07}}
|GHSSignalWord = warning
|GHS_ref = <ref>GHS: [https://gestis.dguv.de/data?name=570199 GESTIS 570199]</ref>
|NFPA-H = 1
|NFPA-F = 0
|NFPA-R = 0
|LD50 = 11160 mg/kg (oral, rat)<ref name="ChemIDplus" />
}}
}}
'''Sodium oxalate''', or '''disodium oxalate''', is a [[Chemistry:Chemical compound|chemical compound]] with the [[Chemistry:Chemical formula|chemical formula]] {{chem2|Na2C2O4|auto=1}}. It is the [[Chemistry:Sodium|sodium]] [[Chemistry:Salt|salt]] of [[Chemistry:Oxalic acid|oxalic acid]]. It contains sodium [[Physics:Cations|cations]] {{chem2|Na+}} and [[Chemistry:Oxalate|oxalate]] anions {{chem2|C2O4(2−)}}. It is a white, crystalline, odorless solid, that decomposes above 290 °C.<ref name=yoshi/>

Sodium oxalate can act as a [[Chemistry:Reducing agent|reducing agent]], and it may be used as a [[Chemistry:Primary standard|primary standard]] for standardizing [[Chemistry:Potassium permanganate|potassium permanganate]] ({{chem2|KMnO4}}) solutions.

The [[Earth:Mineral|mineral]] form of sodium oxalate is natroxalate. It is only very rarely found and restricted to extremely [[Physics:Soil salinity#Sodic soils|sodic conditions]] of ultra-[[Chemistry:Alkaline|alkaline]] [[Earth:Pegmatite|pegmatite]]s.<ref name="RRUFF">{{cite web |title=Natroxolate |url=http://rruff.geo.arizona.edu/doclib/hom/natroxalate.pdf |website=RRUFF |publisher=Mineral Data Publishing |access-date=7 January 2019}}</ref>

==Preparation==
Sodium oxalate can be prepared through the [[Chemistry:Neutralization|neutralization]] of [[Chemistry:Oxalic acid|oxalic acid]] with [[Chemistry:Sodium hydroxide|sodium hydroxide]] (NaOH) in a 1:2 [[Chemistry:Acid|acid]]-to-[[Chemistry:Base|base]] [[Mole (unit)|molar]] ratio. [[Physics:Evaporation|Evaporation]] yields the [[Chemistry:Anhydrous|anhydrous]] oxalate<ref name=foote>H. W. Foote and John E. Vance (1933), "The system; sodium iodate, sodium oxalate, water". ''American Journal of Science'', series 5, volume 26, issue 151, pages 16-18. {{doi|10.2475/ajs.s5-26.151.16}}</ref> that can be thoroughly dried by heating to between 200 and 250 °C.<ref name=yoshi/>

Half-neutralization can be accomplished with NaOH in a 1:1 ratio which produces {{chem2|NaHC2O4}}, [[Chemistry:Acid salt|monobasic]] sodium oxalate or [[Chemistry:Sodium hydrogenoxalate|sodium hydrogenoxalate]].

Alternatively, it can be produced by decomposing [[Chemistry:Sodium formate|sodium formate]] by heating it at a temperature exceeding 360 °C.{{citation needed|date=April 2017}}

==Reactions==
Sodium oxalate starts to decompose above 290 °C into [[Chemistry:Sodium carbonate|sodium carbonate]] and [[Chemistry:Carbon monoxide|carbon monoxide]]:<ref name=yoshi>Yoshimori T1, Asano Y, Toriumi Y, Shiota T. (1978) "Investigation on the drying and decomposition of sodium oxalate". ''Talanta'', volume 25, issue 10, pages 603-605. {{doi|10.1016/0039-9140(78)80158-1}}</ref>

:{{chem2|Na2C2O4 → Na2CO3 + CO}}

When heated at between 200 and 525°C with [[Chemistry:Vanadium pentoxide|vanadium pentoxide]] in a 1:2 molar ratio, the above reaction is suppressed, yielding instead a sodium vanadium oxibronze with release of [[Chemistry:Carbon dioxide|carbon dioxide]]<ref name=balli>D. Ballivet-Tkatchenko, J. Galy, -M. Savariault (1994): "Thermal decomposition of sodium oxalate in the presence of V2O5: Mechanistic approach of sodium oxibronzes formation". ''Thermochimica Acta'', volume 232, issue 2, pages 215-223. {{doi|10.1016/0040-6031(94)80061-8}}</ref>

:{{chem2|''x'' Na2C2O4 + 2 V2O5 → 2 Na_{''x''}V2O5 + 2''x'' CO2}}

with ''x'' increasing up to 1 as the temperature increases.

Sodium oxalate is used to standardize [[Chemistry:Potassium permanganate|potassium permanganate]] solutions. It is desirable that the temperature of the [[Chemistry:Titration|titration]] mixture be greater than 60 °C to ensure that all the permanganate added reacts quickly. The [[Chemistry:Chemical kinetics|kinetics of the reaction]] are complex, and the [[Chemistry:Manganese|manganese]](II) ions ({{chem2|Mn(2+)}}) formed catalyze the further reaction between permanganate and oxalic acid (formed ''in situ'' by the addition of excess [[Chemistry:Sulfuric acid|sulfuric acid]]). The final equation is as follows:<ref>{{cite journal | doi = 10.1021/ja02205a009 | year = 1912 | author = Mcbride, R. S. | journal = J. Am. Chem. Soc. | title = The standardization of potassium permanganate solution by sodium oxalate | volume = 34 | issue = 4 | pages = 393–416| url = https://zenodo.org/record/1429003}}</ref>

:{{chem2|5 Na2C2O4 + 2 KMnO4 + 8 H2SO4 → [[Chemistry:Potassium sulfate|K2SO4]] + 5 [[Chemistry:Sodium sulfate|Na2SO4]] + 2 [[Chemistry:Manganese(II) sulfate|MnSO4]] + 10 CO2 + 8 H2O}}

==Biological activity==
Like several other [[Chemistry:Oxalate|oxalate]]s, sodium oxalate is toxic to humans. It can cause burning pain in the mouth, throat and stomach, bloody vomiting, headache, muscle cramps, cramps and convulsions, drop in blood pressure, heart failure, shock, coma, and possible death. Mean lethal dose by ingestion of oxalates is 10-15 grams/kilogram of body weight (per MSDS).

Sodium oxalate, like [[Chemistry:Citrate|citrate]]s, can also be used to remove [[Chemistry:Calcium|calcium]] ions ({{chem2|Ca(2+)}}) from [[Biology:Blood plasma|blood plasma]]. It also prevents blood from clotting. Note that by removing calcium ions from the [[Biology:Blood|blood]], sodium oxalate can impair [[Biology:Brain|brain]] function, and deposit [[Chemistry:Calcium oxalate|calcium oxalate]] in the kidneys.

==References==
{{Reflist}}

{{Sodium compounds}}
{{Oxalates}}
[[Category:Oxalates]]
[[Category:Sodium compounds]]

{{Sourceattribution|Sodium oxalate}}