Potassium hydrogenoxalate

Potassium hydrogenoxalate is a salt with formula KHC2O4 or K+·HO2C-CO2−. It is one of the most common salts of the hydrogenoxalate anion, and can be obtained by reacting potassium hydroxide with oxalic acid in 1:1 mole ratio.

Potassium hydrogenoxalate
Names
IUPAC name
Potassium 2-hydroxy-2-oxoacetate
Other names
Potassium bioxalate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.004.431
UNII
Properties
C2HKO4
Molar mass 128.124 g·mol−1
Appearance White crystalline solid
Odor odorless
Density 2.0 g/cm3
2.5 g/100 g
Solubility slightly soluble in alcohol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

The salt is also known as: potassium hydrogen oxalate, potassium bioxalate, acid potassium oxalate, or monobasic potassium oxalate. In older literature, it was also called: Salt of sorrel,[1] sorrel salt, sel d'oseille,[2][3] sal acetosella; or, inaccurately, salt of lemon (due to the similar acidic “lemony” taste of the edible common sorrel or garden sorrel; see sorrel below).[4]

Potassium hydrogenoxalate occurs in some plants, notably sorrel. It is a commercial product used in photography, marble grinding, and removing ink stains.

Properties

The anhydrous product is a white, odorless, crystalline solid, hygroscopic and soluble in water (2.5 g/100 g at room temperature). The solutions are basic. Below 50 °C the much less soluble "potassium tetraoxalate" K+[C
2HO
4]−•C
2H
2O
4 forms and precipitates out of solution.[5]

The monohydrate KHC2O4·H2O starts losing the water at 100 °C.[6]

The anhydrous salt was found to have remarkable elastic anisotropy, due to its crystal structure that consists of relatively rigid columns of hydrogen-bonded hydrogenoxalate anions, joined into sheets by ionic K–O bonds.[7]

Toxicity

Potassium hydrogenoxalate is strongly irritating to eyes, mucoses and gastrointestinal tract. It may cause cardiac failure and death.[5]

See also

References
  1. "Die Net Dictionary: "Salt of Sorrel"". Archived from the original on 19 May 2012. Retrieved 19 May 2012. (retrieved via Internet Archive)
  2. "Selency: Old bottle at pharmacy—'Salt of Sorrel'". Salt of Sorrel labelled “sel d'oseille”.
  3. "Salt of Sorrel: labelled 'sel d'oseille'". Old dark-amber glass vial marked “sel d'oseille” with protective leaden cap.
  4. "kitchn™ It's Fresh, Green, and Super Tangy: Sorrel Is In Season!". “This fresh, “lemony” sourness has been highly prized in cuisines all over the world.”
  5. ChemicalBook (2007) Potassium binoxalate Product Description
  6. Mark Dugan (2009) Potassium binoxalate product data sheet. Hummel Croton Inc.
  7. H. Koppers (1973), 'The Elastic Constants of Monoclinic Potassium Hydrogen Oxalate Acta Crystallographica,volume A29, p. 415.
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