This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Both metal and copper oxidize when exposed to oxygen and this is a natural process. Copper that is exposed to the outside environment is more likely to turn green and that is why copper vases and decorative pieces in gardens are often green.
Copper(II) oxide can be prepared pyrometallurigically by heating copper metal above 300 deg C in air; preferably 800 deg C is employed. Molten copper is oxidized to copper(II) oxide when sprayed into an oxygen containing gas. Ignition of copper(II) nitrate trihydrate at about 100-200 deg C produces a black oxide. Basic copper(II) carbonate, when heated above 250 deg C, produces a black oxide if a dense carbonate is employed; a brown material is produced when the light and fluffy carbonate is used.