Sodium oxalate

Preparation

Sodium oxalate can be prepared through the neutralization of oxalic acid with sodium hydroxide (NaOH) in a 1:2 acid-to-base molar ratio. Evaporation yields the anhydrous oxalate that can be thoroughly dried by heating to between 200 and 250 °C.

Half-neutralization can be accomplished with NaOH in a 1:1 ratio which produces , monobasic sodium oxalate or sodium hydrogenoxalate.

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

Reactions

Sodium oxalate starts to decompose above 290 °C into sodium carbonate and carbon monoxide:

:

When heated at between 200 and 525°C with vanadium pentoxide in a 1:2 molar ratio, the above reaction is suppressed, yielding instead a sodium vanadium oxibronze with release of carbon dioxide

:

with x increasing up to 1 as the temperature increases.

Sodium oxalate is used to standardize potassium permanganate solutions. It is desirable that the temperature of the titration mixture be greater than 60 °C to ensure that all the permanganate added reacts quickly. The kinetics of the reaction are 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:

:

Biological activity

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 () 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.

References

References

1. "ChemIDplus - 62-76-0 - ZNCPFRVNHGOPAG-UHFFFAOYSA-L - Disodium oxalate - Similar structures search, synonyms, formulas, resource links, and other chemical information.". NIH.
2. GHS: [https://gestis.dguv.de/data?name=570199 GESTIS 570199]
3. "Natroxolate". Mineral Data Publishing.
4. (1933). "The system; sodium iodate, sodium oxalate, water". American Journal of Science.
5. (1978). "Investigation on the drying and decomposition of sodium oxalate". Talanta.
6. (1994). "Thermal decomposition of sodium oxalate in the presence of V2O5". Thermochimica Acta.
7. Mcbride, R. S.. (1912). "The standardization of potassium permanganate solution by sodium oxalate". [[J. Am. Chem. Soc.]].