Oxalic acid descriptions and applications

oxalic acid appearance

Oxalic acid is an organic compound with the formula C2H2O4. It’s a colorless crystalline solid that forms a colorless solution in water. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid. Its acid strength is much greater than that of acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate (C2O2−4), is a chelating agent for metal cations. Oxalic acid occurs as the dihydrate with the formula C2H2O4·2H2O. Excessive ingestion of oxalic acid or prolonged skin contact can be dangerous.

oxalic acid 3d balls b

Oxalic acid Applications

About 25% of produced oxalic acid is used as a mordant in dyeing processes. It is used in bleaches, especially for pulpwood. It is also used in baking powde and 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 Friend is 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, ferrioxalate ion.

Extractive 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 oxalate gives the oxides, which is the most commonly marketed form of these elements.

Niche uses

Honeybee coated with oxalic acid crystals Vaporized oxalic acid, or a 3.2% solution of oxalic acid in sugar syrup, is used by some beekeepers as a miticide against the parasitic varroa 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 from quartz crystals.

Oxalic acid is used as bleach for wood, removing black stains caused by water penetration.


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