Oxalic acidis anorganic compoundwith theformulaC2H2O4. It is a colorless crystalline solid that forms a colorless solution in water. Itscondensed formulais HOOCCOOH, reflecting its classification as the simplestdicarboxylic acid. Its acid strength is much greater than that ofacetic acid. Oxalic acid is areducing agentand itsconjugate base, known asoxalate(C 2O2 4), is achelating agentfor metal cations. Typically, oxalic acid occurs as thedihydratewith the formula C2H2O42H2O. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous
About 25% of produced oxalic acid is used as amordantin dyeing processes. It is used inbleaches, especially forpulpwood. It is also used in baking powderand as a third reagent in silica analysis instruments.
Oxalic acid's main applications include cleaning or bleaching, especially for the removal of rust (iron complexing agent).Bar Keepers Friendis an example of a household cleaner containing oxalic acid. Its utility in rust removal agents is due to its forming a stable, water-soluble salt with ferric iron,ferrioxalateion.
Oxalic acid is an important reagent inlanthanidechemistry. Hydrated lanthanide oxalates form readily in very strongly acidic solutions in a denselycrystalline, easily filtered form, largely free of contamination by nonlanthanide elements. Thermal decomposition of these oxalate gives theoxides, which is the most commonly marketed form of these elements.
Honeybee coated with oxalic acid crystals
Vaporized oxalic acid, or a 3.2% solution of oxalic acid in sugar syrup, is used by somebeekeepersas amiticideagainst the parasiticvarroa mite.
Oxalic acid is rubbed onto completed marble sculptures to seal the surface and introduce a shine. Oxalic acid is also used to clean iron and manganese deposits fromquartzcrystals.
Oxalic acid is used as a bleach for wood, removing black stains caused by water penetration.