CAS Number: 144-62-7
CAS Name: Oxalic acid
Molecular Formula: C2H2O4
Molecular Mass: 90.03

Oxalic acid is an organic acid with the IUPAC name ethanedioic acid and formula HO2C−CO2H.
Oxalic acid is the simplest dicarboxylic acid.
Oxalic acid is a white crystalline solid that forms a colorless solution in water.

Oxalic acid's main applications include cleaning or bleaching, especially for the removal of rust (iron complexing agent). 
Oxalic acids utility in rust removal agents is due to Oxalic acids forming a stable, water-soluble salt with ferric iron, ferrioxalate ion. 
The cleaning product Zud contains oxalic acid.
Oxalic acid is also widely used as a wood bleach, most often in Oxalic acids crystalline form to be mixed with water to its proper dilution for use.

Oxalic acids name comes from the fact that early investigators isolated oxalic acid from flowering plants of the genus Oxalis, commonly known as wood-sorrels.
Oxalic acid occurs naturally in many foods, but excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.
Oxalic acid has much greater acid strength than acetic acid. 
Oxalic acid is a reducing agent and Oxalic acids conjugate base, known as oxalate (C2O2−4), is a chelating agent for metal cations.

Applications of Oxalic acid:
About 25% of produced oxalic acid will be used as a mordant in dyeing processes. 
Oxalic acid is also used in bleaches, especially for pulpwood, and for rust removal and other cleaning, in baking powder, and as a third reagent in silica analysis instruments.

Extractive Oxalic acid metallurgy
Oxalic acid is an important reagent in lanthanide chemistry.
Hydrated lanthanide oxalates form readily in very strongly acidic solutions in a densely crystalline, easily filtered form, largely free of contamination by nonlanthanide elements. 
Thermal decomposition of these oxalates gives the oxides, which is the most commonly marketed form of these elements.

Oxalic acid was used in determination of oxamic acid, oxalic acid, and oxamide in hydrophobic drug substance matrix by ion-exclusion chromatography.
Oxalic acid was used in the synthesis of three-dimensionally ordered macroporous metal oxides or carbonates via templating with polystyrene spheres.
Oxalic acid was employed as supporting electrolyte during electrochemical synthesis of polyaniline-polypyrrole composite coatings.

Oxalic acid, also called ethanedioic acid, a colourless, crystalline, toxic organic compound belonging to the family of carboxylic acids. 
Oxalic acid is widely used as an acid rinse in laundries, where Oxalic acid is effective in removing rust and ink stains because Oxalic acid converts most insoluble iron compounds into a soluble complex ion. 
For the same reason, Oxalic acid is the chief constituent of many commercial preparations used for removing scale from automobile radiators.

The formula of oxalic acid is (C2H2O4); Oxalic acids usual form is that of the crystalline hydrate, (COOH)2·2H2O. 
Known as a constituent of wood sorrel as early as the 17th century, oxalic acid was first prepared synthetically in 1776. 
Oxalic acid is manufactured by heating sodium formate in the presence of an alkali catalyst, by oxidizing carbohydrates with nitric acid, by heating sawdust with caustic alkalies, or by fermentation of sugar solutions in the presence of certain molds.

Endogenous sources
Oxalate is generated mainly from the breakdown of dehydroascorbic acid and glyoxylate. 
Dehydroascorbic acid spontaneously decomposes to 2,3-ketogulonate and then to threonic acid and oxalate.
This irreversible reaction contributes about 40% of total oxalate at moderate ascorbate intake levels.

Oxalate is also produced from the oxidation of excess glyoxylate by (S)-2-hydroxy-acid oxidase in liver peroxisomes. 
L-serine, hydroxy-proline and ethanolamine contribute to glyoxylate production via glycoaldehyde and glycolate; glycolate itself is ingested with plant foods.
Another source of oxalate is glycine; a small percentage (0.1%) of the glycine pool ends up as oxalate.

might be due to a reversal of the alanine-glyoxylate pathway in liver peroxisomes whereby the pyridoxal-phosphate-dependent enzyme alanine-glyoxylate aminotransferase would then convert pyruvate and glycine into glyoxylate plus alanine.
A third potential glyoxylate precursor is ethylene glycol, though significant exposure other than from antifreeze ingestion is rare.
Since the bifunctional enzyme D-glycerate dehydrogenase/glyoxylate reductase can reduce glyoxylate to glycolate, decreased activity of this enzyme may contribute to glyoxylate accumulation.

Oxalic acid is registered under the REACH Regulation and is manufactured in and / or imported to the European Economic Area, at ≥ 10 000 to < 100 000 tonnes per annum.
Oxalic acid is used by consumers, in articles, by professional workers (widespread uses), in formulation or re-packing, at industrial sites and in manufacturing.
Oxalic acid is used in the following products: coating products, polishes and waxes and washing & cleaning products.
Other release to the environment of oxalic acid is likely to occur from: indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners) and outdoor use.

Oxalic acid Article service life
Other release to the environment of oxalic acid is likely to occur from: outdoor use in long-life materials with low release rate (e.g. metal, wooden and plastic construction and building materials) and indoor use in long-life materials with low release rate (e.g. flooring, furniture, toys, construction materials, curtains, foot-wear, leather products, paper and cardboard products, electronic equipment).
Oxalic acid can be found in products with material based on: leather (e.g. gloves, shoes, purses, furniture).

Widespread uses of Oxalic acid by professional workers
Oxalic acid is used in the following products: non-metal-surface treatment products, metal surface treatment products, washing & cleaning products, coating products, metal working fluids, polishes and waxes, laboratory chemicals and pH regulators and water

Oxalic acid treatment products.
Oxalic acid is used in the following areas: building & construction work.
Oxalic acid is used for the manufacture of: furniture, wood and wood products, pulp, paper and paper products and chemicals.
Other release to the environment of this substance is likely to occur from: indoor use (e.g. machine wash liquids/detergents, automotive care products, paints and coating or adhesives, fragrances and air fresheners) and outdoor use.

Oxalic acid Formulation or re-packing
Oxalic acid is used in the following products: pH regulators and water treatment products, washing & cleaning products, laboratory chemicals, non-metal-surface treatment products, metal surface treatment products, water softeners, water treatment chemicals and pharmaceuticals.

Release to the environment of this substance can occur from industrial use: formulation of mixtures, manufacturing of the substance, in the production of articles, as an intermediate step in further manufacturing of another substance (use of intermediates), formulation in materials, in processing aids at industrial sites and as processing aid.
Other release to the environment of oxalic acid is likely to occur from: indoor use.

Oxalic acid uses at industrial sites
Oxalic acid is used in the following products: pH regulators and water treatment products, metal surface treatment products, laboratory chemicals, non-metal-surface treatment products, leather treatment products, washing & cleaning products, textile treatment products and dyes, water softeners, water treatment chemicals and polymers.
Oxalic acid has an industrial use resulting in manufacture of another substance (use of intermediates).

Oxalic acid is used in the following areas: building & construction work, formulation of mixtures and/or re-packaging and municipal supply (e.g. electricity, steam, gas, water) and sewage treatment.
Oxalic acid is used for the manufacture of: chemicals, metals, machinery and vehicles and furniture.
Release to the environment of oxalic acid can occur from industrial use: in the production of articles, as an intermediate step in further manufacturing of another substance (use of intermediates), as processing aid, in processing aids at industrial sites, formulation of mixtures and manufacturing of the substance.

Oxalic acid Manufacture
Release to the environment of oxalic acide can occur from industrial use: manufacturing of the substance, formulation of mixtures, as an intermediate step in further manufacturing of another substance (use of intermediates), formulation in materials, in processing aids at industrial sites, in the production of articles and as processing aid.

Oxalic acid Abstract
To achieve the global goals related to renewable energy and responsible production, technologies that ensure the circular economy of metals and chemicals in recycling processes are a necessity. 
The recycling of spent Nd–Fe–B magnets typically results in rare-earth element (REE)-free wastewater that has a high ferric ion concentration as well as oxalate groups and for which there are only a few economically viable methods for disposal or reuse.
The current research provides a new approach for the effective recovery of oxalic acid, and the results suggest that during the initial oxalate group separation stage, >99% of oxalate ions can be precipitated as ferrous oxalate (FeC2O4·2H2O) by an ultrasound-assisted iron powder replacement method (Fe/Fe(III) = 2, tu/s = 5 min, T = 50 °C). 
Subsequently, almost all FeC2O4·2H2O was dissolved using 6 mol/L HCl (T = 65 °C, t = 5 min) and the dissolved oxalates were found to mainly exist in the form of H2C2O4.
Furthermore, over 80% of the oxalic acid was recovered via crystallization by cooling the oxalate containing HCl solution to 5 °C. 

After oxalic acid crystallization, the residual raffinate acid solution can then be recirculated back to the ferrous oxalate leaching stage, to decrease any oxalic acid losses. 
This treatment protocol for high-iron REE-free solution not only avoids the potential harm to the environment due to the wastewater but also significantly improves the circular economy of chemicals in the typical utilization in permanent magnet recycling processes.
Oxalic acid, one of the earliest known organic acids, was prepared in crystalline form by Scheele in 1785. 
The toxicity of this compound has long been recognized and the adverse effects of Oxalic acids administration are attributed to its chief chemical reaction, namely the formation of a highly insoluble precipitate with calcium. 
However, many of the common articles of our diet contain oxalates and, conversely, on experimental rations extremely poor in preformed oxalate, Oxalic acid continues to be present in the blood and urine. 
Oxalic acid, it has been claimed, is a product of intermediary metabolism, particularly of carbohydrate.

Oxalic acid poisoning
Oxalic acid is a poisonous, colorless substance. 
Oxalic acid is chemical known as a caustic. 
If Oxalic acid contacts tissues, Oxalic acid can cause severe damage, such as burning or ulcers, on contact.

DO NOT use Oxalic acid to treat or manage an actual poison exposure. 
If you or someone you are with has an exposure, call the local emergency number (such as 911), or the local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States.

Molecular Mass: 90.03
Boiling Point: 200 °C @ Press: 0.1 Torr
Melting Point: 189.5 °C (decomp)
Density: 1.9 g/cm3
Appearance: White crystals
Odor: Odorless
Density: 1.90 g·cm−3 (anhydrous, at 17 °C), 1.653 g·cm−3 (dihydrate)
Solubility in water: 90-100 g/L (20 °C)
Solubility: 237 g/L (15 °C) in ethanol, 14 g/L (15 °C) in diethyl ether
Vapor pressure: <0.001 mmHg (20 °C)
Acidity (pKa): 1.25, 4.14
Conjugate base: Hydrogenoxalate
XLogP3-AA: -0.3
Hydrogen Bond Donor Count: 2
Hydrogen Bond Acceptor Count: 4
Rotatable Bond Count: 1
Exact Mass: 89.99530854

History of Oxalic acid:
The preparation of salts of oxalic acid (crab acid) from plants had been known, at least since 1745, when the Dutch botanist and physician Herman Boerhaave isolated a salt from wood sorrel.
By 1773, François Pierre Savary of Fribourg, Switzerland had isolated oxalic acid from its salt in sorrel.
In 1776, Swedish chemists Carl Wilhelm Scheele and Torbern Olof Bergman produced oxalic acid by reacting sugar with concentrated nitric acid; Scheele called the acid that resulted socker-syra or såcker-syra (sugar acid).
By 1784, Scheele had shown that "sugar acid" and oxalic acid from natural sources were identical.
In 1824, the German chemist Friedrich Wöhler obtained oxalic acid by reacting cyanogen with ammonia in aqueous solution.
This experiment may represent the first synthesis of a natural product.

Monoisotopic Mass: 89.99530854
Topological Polar Surface Area: 74.6 Ų
Heavy Atom Count: 6
Formal Charge: 0
Complexity: 71.5
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
InChI: InChI=1S/C2H2O4/c3-1(4)2(5)6/h(H,3,4)(H,5,6)
Canonical SMILES: O=C(O)C(=O)O

Oxalic acid is mainly manufactured by the oxidation of carbohydrates or glucose using nitric acid or air in the presence of vanadium pentoxide.
A variety of precursors can be used including glycolic acid and ethylene glycol.
A newer method entails oxidative carbonylation of alcohols to give the diesters of oxalic acid:

4 ROH + 4 CO + O2 → 2 (CO2R)2 + 2 H2O
These diesters are subsequently hydrolyzed to oxalic acid.
Approximately 120,000 tonnes are produced annually.

Historically oxalic acid was obtained exclusively by using caustics, such as sodium or potassium hydroxide, on sawdust.
Pyrolysis of sodium formate (ultimately prepared from carbon monoxide), leads to the formation of sodium oxalate, easily converted to oxalic acid.

Laboratory methods of Oxalic acid:
Although Oxalic acid can be readily purchased, oxalic acid can be prepared in the laboratory by oxidizing sucrose using nitric acid in the presence of a small amount of vanadium pentoxide as a catalyst.
The hydrated solid can be dehydrated with heat or by azeotropic distillation.
Developed in the Netherlands, an electrocatalysis by a copper complex helps reduce carbon dioxide to oxalic acid; this conversion uses carbon dioxide as a feedstock to generate oxalic acid.

Anhydrous oxalic acid exists as two polymorphs; in one the hydrogen-bonding results in a chain-like structure whereas the hydrogen bonding pattern in the other form defines a sheet-like structure.
Because the anhydrous material is both acidic and hydrophilic (water seeking), Oxalic acid is used in esterifications.

Occurrence in foods and plants
Calcium oxalate is the most common component of kidney stones.
Early investigators isolated oxalic acid from wood-sorrel (Oxalis).
Members of the spinach family and the brassicas (cabbage, broccoli, brussels sprouts) are high in oxalates, as are sorrel and umbellifers like parsley.
Rhubarb leaves contain about 0.5% oxalic acid, and jack-in-the-pulpit (Arisaema triphyllum) contains calcium oxalate crystals.
Similarly, the Virginia creeper, a common decorative vine, produces oxalic acid in its berries as well as oxalate crystals in the sap, in the form of raphides.
Bacteria produce oxalates from oxidation of carbohydrates.

Plants of the genus Fenestraria produce optical fibers made from crystalline oxalic acid to transmit light to subterranean photosynthetic sites.
Carambola, also known as starfruit, also contains oxalic acid along with caramboxin.
Citrus juice contains small amounts of oxalic acid.
Citrus fruits produced in organic agriculture contain less oxalic acid than those produced in conventional agriculture.
The formation of naturally occurring calcium oxalate patinas on certain limestone and marble statues and monuments has been proposed to be caused by the chemical reaction of the carbonate stone with oxalic acid secreted by lichen or other microorganisms.

Oxidized bitumen or bitumen exposed to gamma rays also contains oxalic acid among its degradation products. 
Oxalic acid may increase the leaching of radionuclides conditioned in bitumen for radioactive waste disposal.

The conjugate base of oxalic acid is the hydrogenoxalate anion, and Oxalic acids conjugate base (oxalate) is a competitive inhibitor of the lactate dehydrogenase (LDH) enzyme.
LDH catalyses the conversion of pyruvate to lactic acid (end product of the fermentation (anaerobic) process) oxidising the coenzyme NADH to NAD+ and H+ concurrently.
Restoring NAD+ levels is essential to the continuation of anaerobic energy metabolism through glycolysis.
As cancer cells preferentially use anaerobic metabolism (see Warburg effect) inhibition of LDH has been shown to inhibit tumor formation and growth, thus is an interesting potential course of cancer treatment.

Other Names for Oxalic acid
Ethanedioic acid
Oxalic acid
NSC 132055
NSC 151956
NSC 62774
NSC 76990
Ultraplast Activate S 52
Acid, Oxalic
Aluminum Oxalate
Ammonium Oxalate
Chromium (2+) Oxalate
Chromium (3+) Oxalate (3:2)
Chromium Oxalate
Diammonium Oxalate
Dilithium Oxalate
Dipotassium Oxalate
Disodium Oxalate
Ferric Oxalate
Iron (2+) Oxalate (1:1)
Iron (3+) Oxalate
Iron Oxalate
Magnesium Oxalate
Magnesium Oxalate (1:1)
Manganese (2+) Oxalate (1:1)
Monoammonium Oxalate
Monohydrogen Monopotassium Oxalate
Monopotassium Oxalate
Monosodium Oxalate
Oxalate, Aluminum
Oxalate, Chromium
Oxalate, Diammonium
Oxalate, Dilithium
Oxalate, Dipotassium
Oxalate, Disodium
Oxalate, Ferric
Oxalate, Iron
Oxalate, Magnesium
Oxalate, Monoammonium
Oxalate, Monohydrogen Monopotassium
Oxalate, Monopotassium
Oxalate, Monosodium
Oxalate, Potassium
Oxalate, Potassium Chromium
Oxalate, Sodium
Oxalic Acid
Potassium Chromium Oxalate
Potassium Oxalate
Potassium Oxalate (2:1)
Sodium Oxalate

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