Iron(II) oxide III and forms insoluble hydroxides in water. Iron(II) oxide is used as a pigment. It is FDA-approved for use in cosmetics and it is used in some tattoo inks. It can also be used as a phosphate remover from home aquaria. Iron(II) oxide Iron(II) oxide or ferrous oxide is the inorganic compound with the formula FeO. Its mineral form is known as wüstite. One of several iron oxides, it is a black-colored powder that is sometimes confused with rust, the latter of which consists of hydrated iron(III) oxide (ferric oxide). Iron(II) oxide also refers to a family of related non-stoichiometric
Copper(II) oxide from the solids. These complexes are decomposed with steam to give CuO. It can be formed by heating copper in air at around 300 – 800°C: For laboratory uses, pure copper(II) oxide is better prepared by heating copper(II) nitrate, copper(II) hydroxide or copper(II) carbonate: Copper(II) oxide dissolves in mineral acids such as hydrochloric acid, sulfuric acid or nitric acid to give the corresponding copper(II) salts: It reacts with concentrated alkali to form the corresponding cuprate salts: It can also be reduced to copper metal using hydrogen, carbon monoxide, or carbon: When cupric oxide is substituted for iron oxide in thermite