The transformation of Cu(OH)2 into CuO, revisited

Copper hydroxide Cu(OH)(2) is metastable. It easily transforms into copper oxide CuO more stable, either in the solid state by a thermal dehydration or at room temperature, in aqueous basic solutions. In the solid state, the transformation is performed at a relatively low temperature, 423 K. It is a topotactic or a pseudomorphic transformation owing to clear relationships between axes of the two solids, in the three directions. The reacting process is described and the corresponding vectorial relations between crystal parameters are proposed. It is not the same case in aqueous basic solutions. Copper hydroxide gives rise to oxide through the formation of a complex anion, Cu(OH)(4)(2-), by a reconstructive transformation involving a dissolution reaction followed by a precipitation. (C) 2003 Elsevier SAS. All rights reserved.