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| Names | |
|---|---|
| Preferred IUPAC name Disodium oxalate | |
| Other names Oxalic acid, disodium salt Sodium ethanedioate | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| ECHA InfoCard | 100.000.501 |
| EC Number |
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| RTECS number |
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| UNII | |
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| Properties | |
| Na2C2O4 | |
| Molar mass | 133.998 g·mol−1 |
| Appearance | White crystalline solid |
| Odor | Odorless |
| Density | 2.34 g/cm3 |
| Melting point | 260 °C (500 °F; 533 K) decomposes above 290 °C[2] |
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| Solubility | Soluble informic acid, insoluble inethanol,diethyl ether |
| Structure | |
| monoclinic | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | −1318 kJ/mol |
| Hazards | |
| GHS labelling:[3] | |
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| Warning | |
| H302,H312 | |
| P280,P301+P312,P302+P352 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 11160 mg/kg (oral, rat)[1] |
| Safety data sheet (SDS) | Oxford MSDS[unreliable source] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Sodium oxalate, ordisodium oxalate, is achemical compound with thechemical formulaNa2C2O4. It is thesodiumsalt ofoxalic acid. It contains sodiumcationsNa+ andoxalateanionsC2O2−4. It is a white, crystalline, odorless solid, that decomposes above 290°C.[2]
Sodium oxalate can act as areducing agent, and it may be used as aprimary standard for standardizingpotassium permanganate (KMnO4) solutions.
Themineral form of sodium oxalate isnatroxalate. It is only very rarely found and restricted to extremelysodic conditions of ultra-alkalinepegmatites.[4]
Sodium oxalate can be prepared through theneutralization ofoxalic acid withsodium hydroxide (NaOH) in a 1:2acid-to-basemolar ratio.Evaporation yields theanhydrous oxalate[5] that can be thoroughly dried by heating to between 200 and 250 °C.[2]
Half-neutralization can be accomplished with NaOH in a 1:1 ratio which producesNaHC2O4,monobasic sodium oxalate orsodium hydrogenoxalate.
Alternatively, it can be produced by decomposingsodium formate by heating it at a temperature exceeding 360 °C.[citation needed]
Sodium oxalate starts to decompose above 290 °C intosodium carbonate andcarbon monoxide:[2]
When heated at between 200 and 525°C withvanadium pentoxide in a 1:2 molar ratio, the above reaction is suppressed, yielding instead asodium vanadium oxibronze with release ofcarbon dioxide[6]
withx increasing up to 1 as the temperature increases.
Sodium oxalate is used to standardizepotassium permanganate solutions. It is desirable that the temperature of thetitration mixture be greater than 60 °C to ensure that all the permanganate added reacts quickly. Thekinetics of the reaction are complex, and themanganese(II)ions (Mn2+) formedcatalyze the further reaction between permanganate and oxalic acid (formedin situ by the addition of excesssulfuric acid). The final equation is as follows:[7]
Like several otheroxalates, 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 (perMSDS).
Sodium oxalate, likecitrates, can also be used to removecalciumions (Ca2+) fromblood plasma. It also prevents blood fromclotting. Note that by removing calcium ions from theblood, sodium oxalate can impairbrain function, and depositcalcium oxalate in thekidneys.
