Phosphoric acid is a phosphorus oxoacid consisting of one oxo and three hydroxy groups on a central phosphorus atom. It is a colourless, odourless inorganic acid, usually handled as an 85 percent aqueous solution, and a sequestering agent that binds divalent cations such as iron, copper and calcium. It is used in fertilisers, detergents, foods and beverages, water treatment, pickling and rust-proofing of metals. Food use as E 338 is subject to the applicable food-additive specification and permitted-use conditions.