Iron(II) hydroxide
Iron(II) hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH). It is produced when iron(II) salts, from a compound such as iron(II) sulfate, are treated with hydroxide ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidized solid is sometimes known as "green rust".
Iron(III) oxide-hydroxide
A number of chemicals are dubbed iron(III) oxide-hydroxide. These chemicals are oxide-hydroxides of iron, and may occur in anhydrous (()) or hydrated (()·"n"HO) forms. The monohydrate (()·HO) might otherwise be described as iron(III) hydroxide (()), and is also known as hydrated iron oxide or yellow iron oxide.