Potassium hydrogen oxalate

Crystallizes from water in large colourless prisms containing 2H2O. It is poisonous, causing paralysis of the nervous system m.p. 101 C (hydrate), 189°C (anhydrous), sublimes 157°C. It occurs as the free acid in beet leaves, and as potassium hydrogen oxalate in wood sorrel and rhubarb. Commercially, oxalic acid is made from sodium methanoate. This is obtained from anhydrous NaOH with CO at 150-200°C and 7-10 atm. At lower pressure sodium oxalate formed from the sodium salt the acid is readily liberated by sulphuric acid. Oxalic acid is also obtained as a by-product in the manufacture of citric acid and by the oxidation of carbohydrates with nitric acid in presence of V2O5. 

Potassium Hydrogen Oxalate. Potassium acid oxalate [127-95-7], KHC2O4, mol wt 146.15, exists as a monohydrate [6100-03 ]. It is of historical interest because it is the salt of sorrel found in vegetation and the first oxalate isolated. 

Potassium hydrogen oxalate (H2O) [127-95-7] M 137.1. Crystd from water by dissolving 20g in lOOmL water at 60° containing 4g of potassium oxalate, filtering and allowing to cool to 25°. The crystals, after washing three or four times with water, are allowed to dry in air. 

Klee-salz, n. salt of sorrel (potassium hydrogen oxalate), -samenol, n. cloverseed oil. kleesauer, a. of or combined with oxalic acid, oxalate of. 

Sorrelsalz, n. salt of sorrel (potassium hydrogen oxalate). 

PEROXIDES AND PEROXIDE COMPOUNDS - INORGANIC PEROXIDES] (Vol 18) Potassium hydrogen oxalate [127-95-7]... 

A solution of 67 g. (0.1 mol) of aluminum sulfate, A12(S04)3T8H20, is treated with a solution of 24 g. of sodium hydroxide. The precipitated aluminum hydroxide is filtered, washed, and boiled with a solution of 76.8 g. of potassium hydrogen oxalate (or a mixture of 55.2 g. of potassium oxalate monohydrate and 37.8 g. of oxalic acid dihydrate) in about 800 ml. of water. Any aluminum hydroxide which does not dissolve is filtered out and the filtrate is evaporated to crystallization. The yield is nearly quantitative. 

Moore FH, Power LF (1971) The crystal structure of potassium hydrogen oxalate by neutron diffraction. Inorg Nucl Chem Lett 7 873-875... 

In a fatal poisoning case, a blood concentration of 110 pg/ml of oxalic acid was reported 6 hours after the ingestion of potassium hydrogen oxalate postmortem tissue concentrations of 21 pg/g in the brain and 382 pg/g in the liver were also reported a second subject who survived the ingestion of potassium hydrogen oxalate had a blood concentration of 3.7 pg/ml after 6 hours. Postmortem blood concentrations of 18 and 77 pg/ml were reported in 2 other fatalities (P. M. Zarembski and A. Hodgkinson, 7. din. Path., 1967, 20, 283-285). 

The procedure described below represents an improvement in the synthesis of Marchi, published in an earlier volume of Inorganic Syntheses. The earlier procedure produces a product which has a C2O4 U ratio of about 3.75. An analysis of a typical preparation is Calcd. U, 28.46 C2O4, 42.08. Found U, 29.73, 29.63 C2O4, 40.76, 40.43. A purer product can be obtained by dissolving the initial product in a solution of potassium oxalate and oxalic acid, followed by precipitation with ethanol. The concentration of alcohol specified below does not cause precipitation of potassium oxalate, potassium hydrogen oxalate, or oxalic acid. 

The points lying farthest from the straight line are from 0—H.. 0 systems where a low potential barrier between the minima is expected. Those on the left side (0—H distance too small) correspond to oxalic acid dihydrate and potassium hydrogen oxalate with a symmetric double minimum (15,48), those on the right side (O—H distance too large to chromous acid with a symmetric double minimum (4,86). In all cases a delocalisation of the proton is likely (see the end of Section III). 

Fig. 16. Hydrogen-anion chains in potassium hydrogen oxalate...

Table 17. Some dimensions in potassium hydrogen oxalate (By X-rays, standard...

Figs. 19 and 20 show the infrared spectra of some acid salts and related crystalline compounds. The spectrum in Fig. 19(a) is from an acid salt of Type B, and it approximates to a superposition of the spectra of free acid and neutral salt. The other spectra are all of Hadzi s T5q>e (ii), which is shown in its starkest form in Fig. 19(c) (sodium hydrogen diacetate) with a window near 950 cm h Potassium hydrogen malonate, a Type A structure, has a similar spectrum (20 (a)). The picoline-N-oxide hemi-hydrobromide (19(d)) is a T5q>e A basic salt Cook s basic salt (Sect. XI) is of pseudo-Type A and gives the spectrum (20(b)). Sodium bicarbonate (20(c)) and potassium hydrogen oxalate (20(d)) are acid sdts of intermediate character (see Sect. XV and XVI A). 

Fig. 20 Further infrared spectra (a) potassium hydrogen malonate (b) pseudo-Type A basic salt described in section XI (c) sodium bicarbonate (d) potassium hydrogen oxalate...

The cases listed in Tables 7 and 19 give general support to this idea. We may also draw attention to three cases where failure to make use of crystal symmetry (which would be chemically feasible) is associated with hydrogen bonds that are significantly longer than those in Type A structures sodium bicarbonate (Sect. XV), potassium hydrogen oxalate (XVI B) and sodium hydrogen oxalate hydrate (XVI C). 

Potassium binoxalate KHC2O4 Essential saU of lemons potassium hydrogen oxalate salt of sorrel. 

Potassium hydrogen oxalate hemihydrate KHC303-0.6H30 127-96-7 wh cry dec 2.09 2.6 si FtOH... 

Moore, F.H. Power, L.F. The erystal stmeture of potassium hydrogen oxalate by neutron diftraetion. Inorg. Nucl. Chem. Lett. 1971. 7. 873. 

Synonyms Ethanedioic acid, monopotassium salt Monopotassium ethanedioate Monopotassium oxalate Oxalic acid, monopotassium salt Potassium binoxalate Potassium hydrogen oxalate Potassium oxalate Potassium salt of sorrel Sorrel salt... 

Potassium hydrogen oxalate. See Potassium acid oxalate... 

---