EDTA is a widely used initialism for the chemical compound ethylenediaminetetraacetic acid (which has many other names, see Table). EDTA is a polyamino carboxylic acid with the formula [CH2N(CH2CO2H)2]2. This colourless, water-soluble solid is widely used to dissolve scale. Its usefulness arises because of its role as a 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.