Ethylenediaminetetraacetic acid, widely abbreviated as EDTA (for other names, see Table), is an aminopolycarboxylic acid and a colourless,
water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because
of its role as a hexadentate ("six-toothed") 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.
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