Sodium hydrogenoxalate

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.

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) Oxalic acid sodium salt Oxalic acid, sodium salt Sodium acid oxalate Sodium and hydrogen and oxalate Sodium bioxalate[1]
Identifiers[2][1]
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	112.0167 g/mol[3]
Appearance	Colorless crystalline solid
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312
Precautionary statements	P264, P270, P280, P301+P312, P302+P352, P312, P322, P330, P363, P501
Related compounds
Other anions	Sodium bicarbonate (oxalate replaced with carbonate)
Other cations	Potassium hydrogenoxalate (potassium instead of sodium) Oxalic acid (hydrogen instead of sodium) Sodium oxalate (sodium instead of hydrogen)
Related compounds	Hydrogenoxalate (sodium ion removed) Oxalate (sodium and hydrogen ions removed)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[4]

The crystal structure of NaHC₂O₄·H₂O is triclinic normal (pinacoidal, space group P1). The lattice parameters are a = 650.3 pm, b = 667.3 pm, c = 569.8 pm, α = 85.04°, β = 110.00°, γ = 105.02°, and Z = 2. The hydrogen oxalate ions are linked end to end in infinite chains by hydrogen bonds (257.1 pm). The chains are cross linked to form layers by both O−H···O bonds from the water molecules (280.8 pm, 282.6 pm) and by ionic bonds Na⁺···O. These layers are in turn held together by Na⁺···O bonds. The oxalate group is non-planar with an angle of twist about the C−C bond of 12.9°.^[5]

Reactions

Upon being heated, sodium hydrogenoxalate converts to oxalic acid and sodium oxalate, the latter of which decomposes into sodium carbonate and carbon monoxide.^[6]

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 stones in the kidneys that can obstruct the kidney tubules.^[2]