Oxalic acid has the chemical formula C2H2O4. It is represented as HOOC-COOH, indicating its structure with two carboxyl groups (−COOH).

Physical properties:

Appearance: Oxalic acid is a white crystalline solid that typically has no odor.

Solubility: The chemical is very soluble in water, dissolves rapidly to yield a clear solution, soluble in alcohol, but less so in ethers.

Melting point: It has a melting point of roughly 189°C (372°F).

Boiling point: Oxalic acid does not have a distinct boiling point because it decomposes at high temperatures.

Density: The estimated density for solid oxalic acid is around 1.65 g / cm³.

Hygroscopicity: Oxalic acid is hygroscopic; thus, it may directly absorb moisture from the air.

Refractive index: The refractive index is around 1.42.

Chemical properties

Acidity: Oxalic acid is a dibasic acid containing two terminal carboxyl groups. In water, it ionizes to liberate two protons and has therefore been considered strong compared with other carboxylic acids. The dissociation may be represented as

HOOC-COOH→HOOC-COO−+H+

HOOC-COO−→CO32−+H+

Reaction with bases: The reaction of oxalic acid with bases gives oxalate salts. For example, it reacts with sodium hydroxide, to form sodium oxalate and water.

HOOC-COOH+2NaOH→Na2C2O4+2H2O

Oxidation: Oxalic acid is oxidized to carbon dioxide and water. For example, during oxidation with potassium permanganate under acid conditions, oxalic acid decomposes

C2H2O4+O2→2CO2+H2O

Reduction: Oxalic acid, under appropriate conditions, can be reduced with the use of appropriate reducing agents, for instance, hydrogen gas with a catalyst, to produce ethylene glycol.

Formation of complexes: Among others, oxalic acid forms insoluble complexes with metal ions. For example, it reacts with calcium ions to form calcium oxalate, which precipitates out of solution

Ca2++C2O42−→CaC2O4

Reaction with Hypochlorites: The reaction of oxalic acid with hypochlorites, such as sodium hypochlorite, yields carbon dioxide and other by-products. It can be useful in some chemical syntheses.

HOOC-COOH+2NaOCl→CO2+Na2CO3+H2O+NaCl

Formation of Esters: Oxalic acid reacts with alcohols to form oxalate esters. This esterification reaction normally takes place in the presence of an acid catalyst.

Application

Cleaning and descaling

Rust removal: Generally, oxalic acid can be used for rust removal or metal surface staining. Generally, it forms soluble complexes with iron oxides for easy cleaning.

Household cleaners: Many household cleaners contain this compound for the removal of stubborn stains and scale buildup, especially in bathroom and kitchen cleaners.

Textile industry-dyeing: Oxalic acid is used within the textile industry for the preparation and cleaning treatments of fabrics before dyeing. It favors brighter colors with an improvement in fastness properties.

Photography-developing solutions: These are some of the photographic developing solutions containing oxalic acid, which acts as a pH controller and as such improves print quality.

Chemical synthesis:

Manufacturing of chemicals: Oxalic acid is feedstock for oxalate salts, ethylene glycol, esters, etc.

Fungicide: In agriculture, this chemical is used as a fungicide to control a class of fungal diseases in crops, particularly in organic farming.

Pharmaceutical: It also finds application in medicine where oxalic acid serves in pharmaceutical formulations and possibly in the preparation of some drugs.

Metal treatment-electroplating: The acid is also used in the electroplating of metals to prepare and clean the metal surfaces.

Water treatment-chelation agent: It is a chelation agent in water treatment processes and is valuable for use in the removal of metal ions from solutions.

Food industry-acidulant: Though less frequent, oxalic acid does find occasional use as an acidulant in the food industry to impart better acidity to certain foodstuffs and beverages.

Laboratory applications:

Reagent: Oxalic acid also serves as a reagent for several chemical analyses and experiments in the laboratory, especially in titration and complexometric assays.

These diverse areas of application reveal that oxalic acid is versatile and sometimes plays a major role in many industrial and commercial procedures.

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