Magnesium oxide Magnesium oxide Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of and consists of a lattice of Mg ions and O ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + HO → Mg(OH)), but it can be reversed by heating it to separate moisture. Magnesium oxide was historically known as magnesia alba (literally, the white mineral from magnesia – other sources give magnesia alba as MgCO), to differentiate it from "magnesia
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