11. Toxicological Information
3794-83-0 PHOSPHONIC ACID, (1-HYDROXYETHYLIDINE)BIS-, TETRASODIUM SALT

Phosphonates are effective chelating agents that bind tightly to di- and trivalent metal ions, preventing them from forming insoluble precipitates (scale) and suppressing their catalytic properties. They are stable under harsh conditions. An important industrial use of phosphonates is in cooling waters, desalination systems, and in oil fields to inhibit scale formation. In pulp and paper manufacturing and in textile industry they serve as "peroxide bleach stabilizers," by chelating metals that could inactivate the peroxide. In detergents they are used as a combination of chelating agent, scale inhibitor, and bleach stabilizer.

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." In similar manner, 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.