Sodium hydrogenoxalate

Sodium hydrogenoxalate
Names
	Preferred IUPAC name Sodium 2-hydroxy-2-oxoacetate
	Other names Ethanedioate, hydrogen sodium salt (1:1:1); Ethanedioic acid, sodium salt (1:1); Monosodium oxalate; Sodium hydrogen ethanedioate (1:1:1); Sodium acid oxalate; Sodium binoxalate;
Identifiers
CAS Number	1186-49-8;
3D model (JSmol)	Interactive image;
ChemSpider	4953678;
ECHA InfoCard	100.013.356
EC Number	214-691-3;
PubChem CID	23684893;
UNII	2T9TH558WS;
CompTox Dashboard (EPA)	DTXSID1047499 ;
	InChI InChI=1S/C2H2O4.Na/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+1/p-1 Key: UJRAXLUXHBUNDO-UHFFFAOYSA-M;
	SMILES [Na+].[O-]C(=O)C(=O)O;
Properties
Chemical formula	NaHC2O4
Molar mass	112.016 g·mol−1
Appearance	Colorless crystalline solid
Structure
Crystal structure	Triclinic
Space group	P1
Lattice constant	a = 6.503 Å, b = 6.673 Å, c = 5.698 Å α = 85.04°, β = 110.00°, γ = 105.02°
Formula units (Z)	2
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H315, H319, H332, H335
Precautionary statements	P261, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P332+P313
NFPA 704 (fire diamond)	2 0 0
Related compounds
Other anions	Sodium bicarbonate
Other cations	Potassium hydrogenoxalate; Sodium oxalate;
Related compounds	Oxalic acid
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Sodium hydrogenoxalate or sodium hydrogen oxalate is a chemical compound with the chemical formula NaHC₂O₄. It is an ionic compound. It is a sodium salt of oxalic acid H₂C₂O₄. It is an acidic salt, because it consists of sodium cations Na⁺ and hydrogen oxalate anions HC₂O−4 or HO−C(=O)−CO−2, in which only one acidic hydrogen atom in oxalic acid is replaced by sodium atom. The hydrogen oxalate anion can be described as the result of removing one hydrogen ion H⁺ from oxalic acid, or adding one to the oxalate anion C₂O2−4.

Properties

Hydrates

The compound is commonly encountered as the anhydrous form or as the monohydrate NaHC₂O₄·H₂O. Both are colorless crystalline solids at ambient temperature.

The monohydrate can be obtained by evaporating a solution of the compound at room temperature.^[3]

Reactions

Upon being heated, sodium hydrogenoxalate converts to oxalic acid and sodium oxalate, the latter of which decomposes into sodium carbonate and carbon monoxide.^[4]

2 NaHC₂O₄ → Na₂C₂O₄ + H₂C₂O₄

Na₂C₂O₄ → Na₂CO₃ + CO

Toxicity

The health hazards posed by this compound are largely due to its acidity and to the toxic effects of oxalic acid and other oxalate or hydrogenoxalate salts, which can follow ingestion or absorption through the skin. The toxic effects include necrosis of tissues due to sequestration of calcium ions Ca²⁺, and the formation of poorly soluble calcium oxalate crystals in the kidneys that can obstruct the kidney tubules.

References

↑ Tellgren, Roland; Olovsson, Ivar (1 January 1971). "Hydrogen Bond Studies. XXXXVI. The Crystal Structures of Normal and Deuterated Sodium Hydrogen Oxalate Monohydrate NaHC₂O₄·H₂O and NaDC₂O₄·D₂O". The Journal of Chemical Physics. 54 (1): 127–134. Bibcode:1971JChPh..54..127T. doi:10.1063/1.1674582.
1 2 "SDS - Sodium acid oxalate monohydrate" (PDF). www.pfaltzandbauer.com. Pfaltz & Bauer Rare and Fine Chemicals. 26 September 2022. p. 1-2. Retrieved 22 April 2026.
↑ Ramki, C.; Ezhil Vizhi, R. (August 2017). "Growth, optical, electrical and mechanical properties of sodium hydrogen oxalate hydrate (NaHC₂O₄·H₂O) single crystal for NLO applications". Materials Chemistry and Physics. 197: 70–78. doi:10.1016/j.matchemphys.2017.04.066.
↑ W. Balcerowiak; Cz. Latocha; J. Wasilewski (1980). "Thermoanalytical investigation of mixtures containing oxalic acid, sodium hydrogen oxalate and sodium oxalate". Journal of Thermal Analysis. 18: 57–63. doi:10.1007/BF01909453. S2CID 98061114.

[1] Tellgren, Roland; Olovsson, Ivar (1 January 1971). "Hydrogen Bond Studies. XXXXVI. The Crystal Structures of Normal and Deuterated Sodium Hydrogen Oxalate Monohydrate NaHC₂O₄·H₂O and NaDC₂O₄·D₂O". The Journal of Chemical Physics. 54 (1): 127–134. Bibcode:1971JChPh..54..127T. doi:10.1063/1.1674582.

[Pfaltz-2] 1 2 "SDS - Sodium acid oxalate monohydrate" (PDF). www.pfaltzandbauer.com. Pfaltz & Bauer Rare and Fine Chemicals. 26 September 2022. p. 1-2. Retrieved 22 April 2026.

[ramk2017-3] Ramki, C.; Ezhil Vizhi, R. (August 2017). "Growth, optical, electrical and mechanical properties of sodium hydrogen oxalate hydrate (NaHC₂O₄·H₂O) single crystal for NLO applications". Materials Chemistry and Physics. 197: 70–78. doi:10.1016/j.matchemphys.2017.04.066.

[4] W. Balcerowiak; Cz. Latocha; J. Wasilewski (1980). "Thermoanalytical investigation of mixtures containing oxalic acid, sodium hydrogen oxalate and sodium oxalate". Journal of Thermal Analysis. 18: 57–63. doi:10.1007/BF01909453. S2CID 98061114.

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