About Oxalates

Structure of an Oxalate Anion

Oxalate is an anion with the formula C2O2-4, also written [(COO)2]2-. The ion forms salts or coordination complexes with many metals. The oxalate salts of alkali earth metals, such as calcium oxalate, a major component of human kidney stones that is also found in some plants as sharp crystals known as raphides, are insoluble in water and irritating to the skin and digestive tract. Calcium oxalate is used in the production of ceramics, while strontium oxalate and barium oxalate are used as reducing agents in laboratory chemistry and pyrotechnics.

Other oxalates used as chemical reagents include potassium hydrogenoxalate, also known as salt of sorrel, due to its occurrence in the sorrel plant. It is used in photography and for the removal of ink stains. Ferric oxalate is a chemical compound used in platinum printmaking, while cobalt oxalate is used in the production of cobalt catalysts. Oxalates may also be used in some instances as sources of the metals they contain.