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
Few hydroxo complexes of germanium have been characterized. Tin(II) hydroxide Sn(OH) was prepared in anhydrous media. When tin(II) oxide is treated with alkali the pyramidal hydroxo complex is formed. When solutions containing this ion are acidified, the ion [Sn(OH)] is formed together with some basic hydroxo complexes. The structure of [Sn(OH)] has a triangle of tin atoms connected by bridging hydroxide groups. Tin(IV) hydroxide is unknown but can be regarded as the hypothetical acid from which stannates, with a formula [Sn(OH)], are derived by reaction with the (Lewis) basic hydroxide ion.