Ethylenediaminetetraacetic acid, widely abbreviated as EDTA, 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.
| ITEM | STANDARD |
| Appearance | White crystalline powder |
| Identification | Pass test |
| Assay (C10H14N2Na2O8.2H2O) | 99.0% ~ 101.0% |
| Chloride (Cl) | =< 0.01% |
| Sulphate (SO4) | =< 0.1% |
| pH (1%) | 4.0- 5.0 |
| Nitrilotriacetic acid | =< 0.1% |
| Calcium (Ca) | Negative |
| Ferrum (Fe) | =< 10 mg/kg |
| Lead (Pb) | =< 5 mg/kg |
| Arsenic (As) | =< 3 mg/kg |
| Mercury (Hg) | =< 1 mg/kg |
| Heavy metals (as Pb) | =< 10 mg/kg |