Sodium oxalate

Sodium oxalate
Names

IUPAC name Sodium ethanedioate
Other names Oxalic acid, disodium salt Sodium ethanedioate
Identifiers
CAS Number	62-76-0^Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:132764^N
ChEMBL	ChEMBL182928^N
ChemSpider	5895^N
ECHA InfoCard	100.000.501
EC Number	200-550-3
PubChem	6125
RTECS number	K11750000
InChI InChI=1S/C2H2O4.2Na/c3-1(4)2(5)6;;/h(H,3,4)(H,5,6);;/q;2*+1/p-2^N Key: ZNCPFRVNHGOPAG-UHFFFAOYSA-L^N
SMILES C(=O)(C(=O)[O-])[O-].[Na+].[Na+]
Properties
Chemical formula	Na₂C₂O₄
Molar mass	133.999 g mol⁻¹
Density	2.34 g cm⁻³
Melting point	260 °C (500 °F; 533 K) decomposes
Solubility in water	2.69 g/100 mL (0 °C) 3.7 g/100 mL (20 °C) 6.25 g/100 mL (100 °C)
Solubility	soluble in formic acid insoluble in alcohol, ether
Structure
Crystal structure	monoclinic
Thermochemistry
Std enthalpy of formation (Δ_fH^o₂₉₈)	-1318 kJ/mol
Hazards
Safety data sheet	Oxford MSDS
EU classification (DSD)	Xn
NFPA 704	0 3 0
Lethal dose or concentration (LD, LC):
LD₅₀ (median dose)	11160 mg/kg (oral, rat)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is ^YN ?)
Infobox references

Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula Na₂C₂O₄. It is usually a white, crystalline, odorless powder, that decomposes at 250–270 °C.

Disodium oxalate can act as a reducing agent, and it may be used as a primary standard for standardizing potassium permanganate (KMnO₄) solutions.

The mineral form of sodium oxalate is natroxalate. It is only very rarely found and restricted to extremely sodic conditions of ultra-alkaline pegmatites.

Sodium oxalate can be prepared through the neutralization of oxalic acid with sodium hydroxide (NaOH) in a 1:2 acid-to-base molar ratio. Half-neutralization can be accomplished with NaOH in a 1:1 ratio which produces NaHC₂O₄, monobasic sodium oxalate or sodium hydrogenoxalate.

Alternatively, it can be produced by decomposing sodium formate by heating it at a temperature exceeding 360 °C.

Sodium oxalate is used to standardize potassium permanganate solutions. It is desirable that the temperature of the titration mixture is greater than 60 °C to ensure that all the permanganate added reacts quickly. The kinetics of the reaction is complex, and the manganese(II) ions formed catalyze the further reaction between permanganate and oxalic acid (formed in situ by the addition of excess sulfuric acid). The final equation is as follows:

Like several other oxalates, 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 citrates, can also be used to remove calcium ions (Ca²⁺) from blood plasma. It also prevents blood from clotting. Note that by removing calcium ions from the blood, sodium oxalate can impair brain function, and deposit calcium oxalate in the kidneys.

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