Oxalic acid is a dicarboxilic acid found in many plants. Oxalic acid is also known as Ethanedioic acid with chemical formula of HOOC-COOH. The commercial and technical grade of oxalic acid usually comes in dihydrate fine white crystals that are fully soluble in water. The CAS Number for oxalic acid dihydrate crystals is6153-56-6.
Historically oxalic acid has been extracted from wood (saw dust). The process usually involved reacting saw dust with a strong base such as Sodium Hydroxide or Potassium Hydroxide. Modern production methods of oxalic acid is mainly by oxidation of sucrose or by reducing carbon dioxide gas.in water.

Uses of Oxalic Acid
Mordant in Dying
About 25% of produced oxalic acid is being used as a mordant in dyeing processes. It is used in bleaches, especially for pulpwood. It is also used in baking powder[13] 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.
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.[30]
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.[31][32]
Oxalic acid is used as a bleach for wood, removing black stains caused by dissolved iron that binds to the wood during water penetration.
Oxalic acid is sometimes used in the aluminum anodizing process, with or without sulfuric acid. Compared to sulfuric acid anodizing, the coatings obtained are thinner and exhibit lower surface roughness.

A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in cell or tissue preparations.
Oxalic acid acts as a reducing agent for metal oxides to remove tarnish as well as rust or ink stains. It is used commercially as a laundry rinse, wood-bleaching agent, and calcium remover. Oxalic acid can remove some paints and varnishes. It is also used as a mordant in dyeing textiles and in the manufacture of ink.

or beekeepers who treat for varroa mites, oxalic acid has become the default favorite miticide. It is inexpensive, a natural component of honey, safe for bees when used as directed, and is drop-dead effective. But being beekeepers, we can’t agree on anything, so the disagreement about how to apply oxalic acid rages on.
Oxalic acid is a naturally-occurring organic compound. In its pure form, it is a colorless crystalline solid that dissolves in water. Many foods contain oxalic acid, including buckwheat, parsley, rhubarb, spinach, beets, cocoa, nuts, berries, and beans. In industry, oxalic acid is often used as a cleaning or bleaching agent.