(FDA) approved for use in cosmetics and is used in some tattoo inks. Iron oxide-hydroxide is also used in aquarium water treatment as a phosphate binder. Iron oxide-hydroxide nanoparticles have been studied as possible adsorbents for lead removal from aquatic media. Medication Iron polymaltose is used in treatment of iron-deficiency anemia. Production Iron(III) oxyhydroxide precipitates from solutions of iron(III) salts at pH between 6.5 and 8. Thus the oxyhydroxide can be obtained in the lab by reacting an iron(III) salt, such as ferric chloride or ferric nitrate, with sodium hydroxide: + 3 NaOH → + 3 NaCl + 3 NaOH → + 3 In fact, when dissolved in water, pure will hydrolyze to some extent, yielding the oxyhydroxide and making the solution acidic: + 2 ↔ + 3 Therefore, the compound can also be obtained by the decomposition of acidic solutions of iron(III) chloride held near the boiling point for days or weeks: + 2 → (s) + 3 (g) (The same process applied to iron(III) nitrate or perchlorate solutions yields instead particles of α-.) Another similar route is the decomposition of iron(III) nitrate dissolved in stearic acid at about 120 °C. The oxyhydroxide prepared from ferric chloride is usually the β polymorph (akaganeite), often in the form of thin needles. The oxyhydroxide can also be produced by a solid-state transformation from iron(II) chloride tetrahydrate ·4. The compound also readily forms when iron(II) hydroxide is exposed to air: 4 + → 4 + 2 The iron(II) hydroxide can also be oxidized by hydrogen peroxide in the presence of an acid: 2 + → 2 See also Rust Iron oxide Yellow boy, a yellow precipitate when acidic runoff such as mine waste, is then neutralised References Iron(III) compounds Hydroxides Transition metal oxides