Oxalic acid is typically manufactured in industries by the oxidation of precursors such as glycolic acid, ethylene glycol, propylene and other carbohydrates using air or nitric acid in the presence of vanadium pentoxide. First, the precursor chemical is dissolved in strong nitric acid and the solution is then heated to 45-100 °C. The oxalic acid can be recovered and concentrated by distillation. Although this is the most common process being adopted for the manufacture of oxalic acid, its several inherent disadvantages have prompted research into alternative preparation methods. An alternative method involves the oxidative carbonylation of alcohols to produce oxalic acid diesters, which can be hydrolyzed to give oxalic acid. This process produces significantly higher yields of oxalic acid and is hence more appropriate for industrial manufacture of oxalic acid.
As a bleaching and cleaning agent:
One of the primary applications of oxalic acid is as a bleaching agent for the removal of rust from metallic articles. Its ability to form stable, water-soluble ferrioxalate ions allows oxalic acid to clean the surface of metal objects of rust without causing damage to the product. It is also used to lighten heavily stained areas of furniture prior to refinishing and can be used for restoring whiteness to stone floors and articles as well. Since oxalic acid is a gentle bleaching agent, it is also used to remove ink, food stains and surface grime on brick, linoleum, wood and vinyl surfaces.
Oxalic acid has a diverse range of niche uses in various industries. About a quarter of the global amount of oxalic acid produced is used as a mordant in dyeing processes. It is used as a reagent in lanthanide chemistry and is highly important for the manufacture of lanthanide oxides. It is also used as a miticide by beekeepers to protect bee colonies against parasitic mites without causing any harm to bees. It is also used in the aluminum anodizing process because the coatings obtained in this manner are thinner and exhibit lower roughness. It also used as a reagent in silica analysis instruments and it is used in the manufacture of baking powder.