Organic Reagents

Oxalic acid gets its name from the fact that early researchers isolated it from flowering plants of the genus Oxalis. It is the simplest dicarboxylic acid, a colorless monoclinic flaky or prismatic crystal or white powder, which dissolves in water to form a colorless solution. Oxalic acid produced by oxidation is odorless, while synthetic oxalic acid has a taste. It sublimates at 150-160°C and can weather in hot dry air. 1 g of oxalic acid dissolves in 7 mL of water, 2 mL of boiling water, 2.5 mL of ethanol, 1.8 mL of boiling ethanol, 100 mL of ether, and 5.5 mL of glycerol, and is insoluble in benzene, chloroform, and petroleum ether. The pH of a 0.1 mol/L solution is 1.3, the chemical formula is H₂C₂O₄, the relative density is 1.653, and the melting point is 189.5°C. It is present in many foods and is a naturally occurring compound in many fruits, vegetables, nuts, and whole grains. Although small amounts of oxalic acid are harmless, this compound can inhibit the absorption of other important nutrients. Excessive intake of oxalic acid or prolonged skin contact can be dangerous. It easily forms calcium oxalate with calcium ions in the human body, leading to kidney stones, so oxalic acid is often considered an antagonist of mineral absorption and utilization.