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".
Hydroxide
When bound to a strongly electron-withdrawing metal centre, hydroxide ligands tend to ionise into oxide ligands. For example, the bichromate ion [HCrO] dissociates according to
with a p"K" of about 5.9.