Copper(II) Oxide

OVERVIEW

Copper(II) oxide (KOPP-er two OK-side) occurs in nature in the minerals tenorite, melaconite, and paramelaconite. In pure form, it is a black to brownish powder or crystalline material. Like copper(I) oxide, copper(II) oxide is a semiconductor, a material that conducts an electric current, although not nearly as well as conductors such as gold, silver, and aluminum.

HOW IT IS MADE

Copper(II) oxide forms naturally in the Earth as a result of the weathering of copper sulfides (Cu₂S and CuS). It is prepared synthetically by heating copper metal in air to about 800°C (1,500°F) or, more commonly, by heating copper(II) carbonate (CuCO₃) or copper(II) nitrate [Cu(NO₃)₂] to red heat.

KEY FACTS

OTHER NAMES:

Cupric oxide; copper monoxide; black copper oxide

FORMULA:

CuO

ELEMENTS:

Copper, oxygen

COMPOUND TYPE:

Metallic oxide

STATE:

Solid

MOLECULAR WEIGHT:

79.54 g/mol

MELTING POINT:

1,446°C (2,670°F)

BOILING POINT:

Not applicable; decomposes

SOLUBILITY:

Insoluble in water and organic solvents; soluble in dilute acids and ammonium hydroxide

COMMON USES AND POTENTIAL HAZARDS

Throughout recorded history, copper(II) oxide has been used as a pigment to color ceramics, enamels, porcelain glazes, and artificial gems, applications that continue to the present day. The oxide adds a bluish to greenish tint to such materials. Copper(II) oxide also finds use as an insecticide and fumigant. It is used primarily in the treatment of potato plants and as an antifouling agent on boat hulls. An antifouling agent is a material that prevents the formation of barnacles and other organisms on the bottom of a boat. When such organisms grow on a boat's hull, they increase the friction produced when the boat rides through the water, thus reducing its speed. The compound is also used as a wood preservative, to protect fence posts, pilings, decking, roofing, shingles, sea walls, and other freshwater and marine structures from insects and fungi.

Other uses to which copper(II) oxide is put including the following:

• In the preparation of superconducting materials, materials that have essentially no resistance to the flow of an electric current;
• In the manufacture of batteries and electrodes;
• As a welding flux for use with bronze objects and materials;
• For polishing of optical glass, glass used in telescopes, microscopes, and similar instruments;
• In the preparation of phosphors, materials that glow in the dark after being exposed to light;

• For the removal of sulfur and sulfur compounds for petroleum;
• In the manufacture of rayon; and
• As a catalyst in many industrial and commercial chemical reactions.

Interesting Facts

• The ancient Greeks used a mixture of copper(II) oxide and copper(II) sulfate to treat wounds.
• U.S. pennies sometimes develop a black coating that is caused by copper(II) oxide. The coating can be removed by cleaning the penny in a solution of vinegar, lemon juice, and salt. Coca Cola™ can also be used because it contains phosphoric acid (H₃PO₄), which dissolves copper(II) oxide.
• Some fingerprinting powders contain copper(II) oxide.

Words to Know

CATALYST

A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.

FLUX

A material that lowers the melting point of another substance or mixture of substances or that is used in cleaning a metal.

Inhaling copper(II) oxide fumes may result in a condition known as metal fume fever, with irritation of the throat, coughing, shortness of breath, nausea, and fever. Excessive exposure may result in chronic lung disease. Ingesting large amounts of copper(II) oxide may cause vomiting, diarrhea, nausea, excessive salivation, and intense abdominal pain. The compound is also an eye irritant.

FOR FURTHER INFORMATION

"Copper Oxide 99.99+%." Louisiana State University. http://www.camd.lsu.edu/msds/c/copperII_oxide.htm#Synonyms (accessed on October 5, 2005).

"Cupric Oxide." J. T. Baker. http://www.jtbaker.com/msds/englishhtml/c5885.htm (accessed on October 5, 2005).

Richardson, H. W., ed. Handbook of Copper Compounds and Applications. New York: Marcel Dekker, 1997.