|Jmol-3D images||Image 1|
|Molar mass||128.13 g mol−1|
|Appearance||White crystalline solid|
|Solubility in water||2.5 g/100 g|
|Solubility||slightly soluble in alcohol|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Potassium hydrogenoxalate, also known as potassium bioxalate, 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.
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 sorrel salt, sal acetosella, or (rather improperly) salt of lemon
Potassium hydrogenoxalate occurs in some plants, notably sorrel. It is a commercial product, used in photography, marble grinding, and to remove ink stains.
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 forms and precipitates out of solution.
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.
Potassium hydrogenoxalate is strongly irritating to eyes, mucoses and gastrointestinal tract. It may cause cardiac failure and death.
In Popular Culture
During season one, episode one, of the television series Downton Abbey, the cook, Mrs. Patmore, has a pot of "salt of sorrel" on the kitchen preparation table that one of the servants uses to clean the brass and copper pots. An inexperienced kitchen maid, Daisy, accidentally gives the pot to William, the footman, to serve upstairs to the aristocratic Crawley family. William comes back downstairs unsure what meal the contents of the ceramic pot go with. Daisy realizes she gave him the wrong pot (salt of sorrel), and Daisy frantically gives William the correct ceramic pot for the meal.