Oxalic acid

The oxalic acid or according to the nomenclature the éthanedioïque acid or salt of sorrel is a Carboxylic acid of structure HOOC-COOH. Thanks to the connection between the two groups carboxyl, it is one of the organic acids strongest (pK_A1 = 1,27 and pK_A2 = 4,27). The anions of the oxalic acid as well as the salt S and Ester S are known under the name of oxalates.

He was discovered in 1776 by the Swedish chemist Carl Wilhelm Scheele in the oxidation of sugar.

__TOC

Production

The oxalic acid and the oxalates are substances toxic that one finds in many plants. One finds among food having a strong acid content oxalic the Cacao, the Chocolat, the Noix and Noisette S, the bay S, the Rhubarbe, the Haricot S and of course the Oseille and the spinach S. Présent at the natural state, primarily in the form of potassium or calcium oxalate in the root S and Rhizome S of plants such as the sorrel, rhubarb or beet, it intervenes in the constitution of certain minerals (flint kidney).

In an industrial way (Rhône-Poulenc), the oxalic acid is obtained by two successive oxidations: Acid nitric, then Oxygen of the air in the presence of a Catalyst.

Biology

This acid can irritate the ways œsophagienne or gastric at the time of its ingestion and cause renal damage (calculations, Oligurie, Albuminurie, Hématurie). It is mortal with strong amount, the precipitates of calcium oxalate which can block the renal channels. It appears in the animal and human urine in the form of oxalate of calcium and oxaluric acid (H₂N-CO-NH-CO-CO₂H). The individuals in good health can without problem eat such food but one recommends to the people reached renal calculus, of drop or Arthrite to avoid their consumption.

Food

Because of its capacity to be bound to certain minerals such as the Calcium, the Iron, the Sodium, the Potassium or the Magnesium, the food consumption with strong amount in oxalic acid can cause food Carence S.

The oxalic acid is present in the wine at the ferric state of complex, when the wine is bottled, the reduction of the ferri-iron releases the oxalic acid and precipitated calcium oxalate.

Uses

Sold out of crystals, (under the name of lemon salt sometimes) to dilute in water, it is very effective to remove the rust and the traces of rust on the tiling, the linen…

The oxalic acid is used in the following fields:

surface treatment of metals
derusting and the polishing of the Marble
agent of Bleaching (textile, paper, cork, leather, wood)
corrosive agent for the Dyeing of the Wool
initator in the Polymeric manufacture of S
Monomeric for the preparation of Fiber S and plastic films - poly (ethylene oxalate) - presenting a mechanical resistance and a good behavior with heat.
allows the extraction of Rare earths (Lanthanide S)
preparation of magnetic media of the tapes for recording.
reducing in certain photographic processes of development.
in Bee-keeping, it is used to fight against the Varroa.

Notes and references of the article

Random links: