Ethylenediaminetetraacetic Acid (EDTA)

Ethylenediaminetetraacetic acid is an aminopolycarboxylic acid and a colourless, water-soluble solid.It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand and chelating agent, i.e. its ability to "sequester" metal ions such as Ca2+ and Fe3+. After being bound by EDTA, metal ions remain in solution but exhibit diminished reactivity. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA. In coordination chemistry, EDTA4− is a member of the aminopolycarboxylic acid family of ligands. EDTA4− usually binds to a metal cation through its two amines and four carboxylates. Many of the resulting coordination compounds adopt octahedral geometry. Although of little consequence for its applications, these octahedral complexes are chiral. The anion [Co(EDTA)]− has been resolved into enantiomers.