4025. Ferric Hydroxide

Nomenclature

CAS number: 20344-49-4
Ferric hydroxide oxide; hydrated ferric oxide.
FeHO2; mol wt 88.85.
Fe 62.85%, H 1.13%, O 36.01%.
FeO(OH).

Description and references

Occurs in nature as the minerals goethite [α-FeO(OH)], lepidocrocite [γ-FeO(OH)], and limonite [FeO(OH).nH2O]. Other known allomorphic forms: β-FeO(OH); δ-FeO(OH). The hydroxide Fe(OH)3 is not known. Prepn: Lux in Handbook of Preparative Inorganic Chemistry vol 2, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1965) p 1499. Crystal structure of α-FeO(OH): Sampson, Acta Crystallogr. 25B, 1683 (1969). Review: Bernal et al., Clay Miner. Bull. 4, 15-30 (1959).

Properties

Red to brown powder or crystals. Loses H2O to form Fe2O3. d 3.4-3.9. Practically insol in water, alcohol. Sol in mineral acids.

Use

In purifying water; as absorbent in chemical processing; as pigment; as catalyst.