Oxalation

Oxalate ion, also known as ethanedioate, has the chemical formula C2O4^2-. It is the conjugate base of oxalic acid. In aqueous solution, it exists as an anion. Oxalate is an important anion found in many plants and is also a product of metabolism in animals, including humans.

In biological systems, oxalate plays a role in calcium metabolism. When calcium and oxalate ions are present in sufficient concentrations, they can form calcium oxalate crystals. These crystals can precipitate in various tissues, most notably in the kidneys, where they can contribute to the formation of kidney stones. The accumulation of calcium oxalate crystals in the kidneys is a common cause of nephrolithiasis.

Dietary sources of oxalate include many common foods, such as spinach, rhubarb, nuts, and chocolate. The absorption of oxalate from the digestive tract can be influenced by other dietary factors, such as calcium intake. Consuming calcium-rich foods alongside oxalate-rich foods can help reduce oxalate absorption by binding to it in the gut and forming insoluble calcium oxalate, which is then excreted.

Industrially, oxalate salts have various applications. For example, potassium oxalate is used as a mordant in dyeing and printing textiles, and as a cleaning and polishing agent. Sodium oxalate is used in analytical chemistry as a primary standard for the standardization of potassium permanganate solutions. Oxalic acid itself is used as a bleaching agent and as a rust remover.