ingredient information
Edetate Disodium
AAA
EDTA is a widely used acronym 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. In industry, EDTA is mainly used to sequester metal ions in aqueous solution. In the textile industry, it prevents metal ion impurities from modifying colours of dyed products. In the pulp and paper industry, EDTA inhibits the ability of metal ions, especially Mn2+, from catalyzing the disproportionation of hydrogen peroxide, which is used in "chlorine-free bleaching." Similarly, EDTA is added to some food as a preservative or stabilizer to prevent catalytic oxidative decolouration which is catalyzed by metal ions.[8] In personal care products, it is added to cosmetics to improve their stability toward air.[9] In Soft drinks containing ascorbic acid and sodium benzoate, EDTA mitigates formation of benzene (a carcinogen).[10] The reduction of water hardness in laundry applications and the dissolution of scale in boilers both rely on EDTA and related complexants to bind Ca2+ and Mg2+ ions as well as other metal ions. Once bound to EDTA, these metal centers tend not to form precipitates or to interfere with the action of the detergents. For similar reasons, cleaning solutions often contain EDTA. The solubilization of ferric ions near neutral pH is accomplished using EDTA. This property is useful in agriculture including hydroponics, especially in calcareous soils. Otherwise, at near neutral pH, iron(III) forms insoluble salts, which are less bioavailable. Aqueous [Fe(edta)]- is used for removing ("scrubbing") hydrogen sulfide from gas streams. This conversion is achieved by oxidizing the hydrogen sulfur to elemental sulfur, which is non-volatile: 2 [Fe(edta)]- + H2S ? 2 [Fe(edta)]2- + S + 2 H+ In this application the ferric center is reduced to its ferrous derivative, which can then be reoxidized by air. Similarly, nitrogen oxides are removed from gas streams using [Fe(edta)]2-. The oxidizing properties of [Fe(edta)]- are also exploited in photography where it is used to solubilize silver particles.[4] EDTA was an most important chelating agents used in the separation of the lanthanide metals by ion-exchange chromatography. Perfected by F.H. Spedding et al. in 1954, the method relies on the steady increase in stability constant of the lanthanide EDTA complexes with atomic number. Using sulfonated polystyrene beads and copper(II) as a retaining ion, EDTA causes the lanthanides to migrate down the column of resin while separating into bands of pure lanthanide. The lanthanides elute in order of decreasing atomic number. Due to the expense of this method, relative to counter-current solvent extraction, ion-exchange is now used only to obtain the highest purities of lanthanide (typically greater than 4N, 99.99%