Sodium oxalate

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Sodium oxalate
Names
IUPAC name
Sodium ethanedioate
Other names
Disodium ethanedioate
Disodium oxalate
Properties
Na2C2O4
Molar mass 133.999 g/mol
Appearance White solid
Odor Odorless
Density 2.34 g/cm3
Melting point 260 °C (500 °F; 533 K)
Boiling point 290 °C (554 °F; 563 K) (decomposes)
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
Vapor pressure ~0 mmHg
Thermochemistry
-1,318 kJ/mol
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
11,160 mg/kg (rat, oral)
Related compounds
Related compounds
Ammonium oxalate
Neodymium oxalate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula Na2C2O4.

Since oxalic acid is a dicarboxylic acid, the term "sodium oxalate" can also apply to derivate with only one sodium cation, monosodium oxalate (NaHC2O4), although the former is more often called sodium hydrogenoxalate, similar to how NaHCO3 is always called sodium hydrogen carbonate rather than sodium carbonate.

Properties

Chemical

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

Na2C2O4 → Na2CO3 + CO

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:

5 Na2C2O4 + 2 KMnO4 + 8 H2SO4 → K2SO4 + 5 Na2SO4 + 2 MnSO4 + 10 CO2 + 8 H2O

Physical

Sodium oxalate is a white solid, poorly soluble in water.

Availability

Sodium oxalate is sold in swimming pool stores as water hardness adjuster, though it's pricey.

Sodium oxalate occurs naturally as the rare mineral natroxalate.

Preparation

Sodium oxalate can be prepared through the neutralization of oxalic acid with sodium hydroxide in a 1:2 acid-to-base molar ratio. Due to the salt's low solubility in water, cooling the solution will cause to precipitate out. Further evaporation of the water will give the solid compound, that can be thoroughly dried by heating it at 200 °C.

Projects

Handling

Safety

Sodium oxalate, like other oxalate salts is toxic if consumed.

Storage

In closed bottles.

Disposal

Can be safely poured down the drain.

References

Relevant Sciencemadness threads