Copper

Background

Copper is one of the basic chemical elements. In its nearly pure state, copper is a reddish-orange metal known for its high thermal and electrical conductivity. It is commonly used to produce a wide variety of products, including electrical wire, cooking pots and pans, pipes and tubes, automobile radiators, and many others. Copper is also used as a pigment and preservative for paper, paint, textiles, and wood. It is combined with zinc to produce brass and with tin to produce bronze.

Copper was first used as early as 10,000 years ago. A copper pendant from about 8700 b.c. was found in what is now northern Iraq. There is evidence that by about 6400 b.c. copper was being melted and cast into objects in the area now known as Turkey. By 4500 b.c., this technology was being practiced in Egypt as well. Most of the copper used before 4000 b.c. came from the random discovery of isolated outcroppings of native copper or from meteorites that had impacted Earth. The first mention of the systematic extraction of copper ore comes from about 3800 b.c. when an Egyptian reference describes mining operations on the Sinai Peninsula.

In about 3000 b.c., large deposits of copper ore were found on the island of Cyprus in the Mediterranean Sea. When the Romans conquered Cyprus, they gave the metal the Latin name aes cyprium, which was often shortened to cyprium. Later this was corrupted to cuprum, from which the English word copper and the chemical symbol Cu are derived.

In South America, copper objects were being produced along the northern coast of Peru as early as 500 b.c., and the development of copper metallurgy was well advanced by the time the Inca empire fell to the conquering Spanish soldiers in the 1500s.

In the United States, the first copper mine was opened in Branby, Connecticut, in 1705, followed by one in Lancaster, Pennsylvania, in 1732. Despite this early production, most copper used in the United States was imported from Chile until 1844, when mining of large deposits of high-grade copper ore around Lake Superior began. The development of more efficient processing techniques in the late-1800s allowed the mining of lower-grade copper ores from huge open-pit mines in the western United States.

Today, the United States and Chile are the world's top two copper producing countries, followed by Russia, Canada, and China.

Raw Materials

Pure copper is rarely found in nature, but is usually combined with other chemicals in the form of copper ores. There are about 15 copper ores mined commercially in 40 countries around the world. The most common are known as sulfide ores in which the copper is chemically bonded with sulfur. Others are known as oxide ores, carbonate ores, or mixed ores depending on the chemicals present. Many copper ores also contain significant quantities of gold, silver, nickel, and other valuable metals, as well as large quantities of commercially useless material. Most of the copper ores mined in the United States contain only about 1.2-1.6% copper by weight.

The most common sulfide ore is chalcopyrite, CuFeS₂, also known as copper pyrite or yellow copper ore. Chalcocite, Cu₂S, is another sulfide ore.

Cuprite, or red copper ore, Cu₂O, is an oxide ore. Malachite, or green copper ore, Cu(OH)₂•CuCO₃, is an important carbonate ore, as is azurite, or blue copper carbonate, Cu(OH)₂•2CuCO₃.

Other ores include tennantite, boronite, chrysocolla, and atacamite.

In addition to the ores themselves, several other chemicals are often used to process and refine copper. These include sulfuric acid, oxygen, iron, silica, and various organic compounds, depending on the process used.

The Manufacturing
Process

The process of extracting copper from copper ore varies according to the type of ore and the desired purity of the final product. Each process consists of several steps in which unwanted materials are physically or chemically removed, and the concentration of copper is progressively increased. Some of these steps are conducted at the mine site itself, while others may be conducted at separate facilities.

Here are the steps used to process the sulfide ores commonly found in the western United States.

Mining

• 1 Most sulfide ores are taken from huge open-pit mines by drilling and blasting with explosives. In this type of mining, the material located above the ore, called the overburden, is first removed to expose the buried ore deposit. This produces an open pit that may grow to be a mile or more across. A road to allow access for equipment spirals down the interior slopes of the pit.
• 2 The exposed ore is scooped up by large power shovels capable of loading 500-900 cubic feet (15-25 cubic meters) in a single bite. The ore is loaded into giant dump trucks, called haul trucks, and is transported up and out of the pit.

Concentrating

The copper ore usually contains a large amount of dirt, clay, and a variety of non-copper bearing minerals. The first step is to remove some of this waste material. This process is called concentrating and is usually done by the flotation method.

• 3 The ore is crushed in a series of cone crushers. A cone crusher consists of an interior grinding cone that rotates on an eccentric vertical axis inside a fixed outer cone. As the ore is fed into the top of the crusher, it is squeezed between the two cones and broken into smaller pieces.
• 4 The crushed ore is then ground even smaller by a series of mills. First, it is mixed with water and placed in a rod mill, which consists of a large cylindrical container filled with numerous short lengths of steel rod. As the cylinder rotates on its horizontal axis, the steel rods tumble and break up the ore into pieces about 0.13 in (3 mm) in diameter. The mixture of ore and water is further broken up in two ball mills, which are like a rod mill except steel balls are used instead of rods. The slurry of finely ground ore that emerges from the final ball mill contains particles about 0.01 in (0.25 mm) in diameter.
• 5 The slurry is mixed with various chemical reagents, which coat the copper particles. A liquid, called a frother, is also added. Pine oil or long-chain alcohol are often used as frothers. This mixture is pumped into rectangular tanks, called flotation cells, where air is injected into the slurry through the bottom of the tanks. The chemical reagents make the copper particles cling to the bubbles as they rise to the surface. The frother forms a thick layer of bubbles, which overflows the tanks and is collected in troughs. The bubbles are allowed to condense and the water is drained off. The resulting mixture, called a copper concentrate, contains about 25-35% copper along with various sulfides of copper and iron, plus smaller concentrations of gold, silver, and other materials. The remaining materials in the tank are called the gangue or tailings. They are pumped into settling ponds and allowed to dry.

Smelting

Once the waste materials have been physically removed from the ore, the remaining copper concentrate must undergo several chemical reactions to remove the iron and sulfur. This process is called smelting and traditionally involves two furnaces as described below. Some modern plants utilize a single furnace, which combines both operations.

• 6 The copper concentrate is fed into a furnace along with a silica material, called a flux. Most copper smelters utilize oxygen-enriched flash furnaces in which preheated, oxygen-enriched air is forced into the furnace to combust with fuel oil. The copper concentrate and flux melt, and collect in the bottom of the furnace. Much of the iron in the concentrate chemically combines with the flux to form a slag, which is skimmed off the surface of the molten material. Much of the sulfur in the concentrate combines with the oxygen to form sulfur dioxide, which is exhausted from the furnace as a gas and is further treated in an acid plant to produce sulfuric acid. The remaining molten material in the bottom of the furnace is called the matte. It is a mixture of copper sulfides and iron sulfides and contains about 60% copper by weight.
• 7 The molten matte is drawn from the furnace and poured into a second furnace called a converter. Additional silica flux is added and oxygen is blown through the molten material. The chemical reactions in the converter are similar to those in the flash furnace. The silica flux reacts with the remaining iron to form a slag, and the oxygen reacts with the remaining sulfur to form sulfur dioxide. The slag may be fed back into the flash furnace to act as a flux, and the sulfur dioxide is processed through the acid plant. After the slag is removed, a final injection of oxygen removes all but a trace of sulfur. The resulting molten material is called the blister and contains about 99% copper by weight.

Refining

Even though copper blister is 99% pure copper, it still contains high enough levels of sulfur, oxygen, and other impurities to hamper further refining. To remove or adjust the levels of these materials, the blister copper is first fire refined before it is sent to the final electrorefining process.

• 8 The blister copper is heated in a refining furnace, which is similar to a converter described above. Air is blown into the molten blister to oxidize some impurities. A sodium carbonate flux may be added to remove traces of arsenic and antimony. A sample of the molten material is drawn and an experienced operator determines when the impurities have reached an acceptable level. The molten copper, which is about 99.5% pure, is then poured into molds to form large electrical anodes, which act as the positive terminals for the electrorefining process.
• 9 Each copper anode is placed in an individual tank, or cell, made of polymer-concrete. There may be as many as 1,250 tanks in operation at one time. A sheet of copper is placed on the opposite end of the tank to act as the cathode, or negative terminal. The tanks are filled with an acidic copper sulfate solution, which acts as an electrical conductor between the anode and cathode. When an electrical current is passed through each tank, the copper is stripped off the anode and is deposited on the cathode. Most of the remaining impurities fall out of the copper sulfate solution and form a slime at the bottom of the tank. After about 9-15 days, the current is turned off and the cathodes are removed. The cathodes now weigh about 300 lb (136 kg) and are 99.95-99.99% pure copper.
• 10 The slime that collects at the bottom of the tank contains gold, silver, selenium, and tellurium. It is collected and processed to recover these precious metals.

Casting

• 11 After refining, the copper cathodes are melted and cast into ingots, cakes, billets, or rods depending on the final application. Ingots are rectangular or trapezoidal bricks, which are remelted along with other metals to make brass and bronze products. Cakes are rectangular slabs about 8 in (20 cm) thick and up to 28 ft (8.5 m) long. They are rolled to make copper plate, strip, sheet, and foil products. Billets are cylindrical logs about 8 in (20 cm) in diameter and several feet (meters) long. They are extruded or drawn to make copper tubing and pipe. Rods have a round cross-section about 0.5 in (1.3 cm) in diameter. They are usually cast into very long lengths, which are coiled. This coiled material is then drawn down further to make copper wire.

Quality Control

Because electrical applications require a very low level of impurities, copper is one of the few common metals that are refined to almost 100% purity. The process described above has been proven to produce copper of very high purity. To ensure this purity, samples are analyzed at various steps to determine whether any adjustment to the process is required.

Byproducts/Waste

The recovery of sulfuric acid from the copper smelting process not only provides a profitable byproduct, but also significantly reduces the air pollution caused by the furnace exhaust. Gold, silver, and other precious metals are also important byproducts.

Waste products include the overburden from the mining operation, the tailings from the concentrating operation, and the slag from the smelting operation. This waste may contain significant concentrations of arsenic, lead, and other chemicals, which pose a potential health hazard to the surrounding area. In the United States, the Environmental Protection Agency (EPA) regulates the storage of such wastes and the remediation of the area once mining and processing operations have ceased. The sheer volume of the material involved—in some cases, billions of tons of waste—makes this a formidable task, but it also presents some potentially profitable opportunities to recover the useable materials contained in this waste.

The Future

Demand for copper is expected to remain high, especially in the electrical and electronics industries. The current trends in copper processing are towards methods and equipment that use less energy and produce less air pollution and solid waste. In the United States, this is a difficult assignment because of the stringent environmental controls and the very low-concentration copper ores that are available. In some cases, the production costs may increase significantly.

One encouraging trend is the increased use of recycled copper. Currently over half the copper being produced in the United States comes from recycled copper. Fifty-five percent of the recycled copper comes from copper machining operations, such as screw forming, and 45% comes from the recovery of used copper products, such as electrical wire and automobile radiators. The percentage of recycled copper is expected to grow as the costs of new copper processing increase.

Where to Learn More

Books

Brady, George S., Henry R. Clauser, and John A. Vaccari. Materials Handbook. McGraw-Hill, 1997.

Heiserman, David L. Exploring Chemical Elements and Their Compounds. TAB Books, 1992.

Hombostel, Caleb. Construction Materials. John Wiley and Sons, Inc., 1991.

Kroschwitz, Jacqueline I. and Mary Howe-Grant, ed. Encyclopedia of Chemical Technology. John Wiley and Sons, Inc., 1993.

Stwertka, Albert. A Guide to the Elements. Oxford University Press, 1996.

Periodicals

Baum, Dan and Margaret L. Knox. "We want people who have a problem with mine wastes to think of Butte." Smithsonian (November 1992): 46-52, 54-57.

Shimada, Izumi and John F. Merkel. "Copper-Alloy Metallurgy in Ancient Peru." Scientific American (July 1991): 80-86.

Other

http://www.copper.org.

http://www.intercorr.com/periodic/29.htm.

http://innovations.copper.org/innovations.html.

—Chris Cavette

COPPER (REVISED)

Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.

Overview

Copper was one of the earliest elements known to man. At one time, it could be found lying on the ground in its native state or uncombined state. Copper's distinctive red color made it easy to identify. Early humans used copper for many purposes, including jewelry, tools, and weapons.

Copper is a transition metal, one of several elements found in rows 4 through 7 between Groups 2 and 13 in the periodic table. The periodic table is a chart that shows how chemical elements are related to each other.

SYMBOL
Cu

ATOMIC NUMBER
29

ATOMIC MASS
63.546

FAMILY
Group 11 (IB)
Transition metal

PRONUNCIATION
COP-per

Copper and its compounds have many important uses in modern society. Most electrical equipment has copper wiring. Copper is also used to make many alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. The most familiar alloys of copper are probably brass and bronze. Many compounds of copper are commercially important, too. They are used as coloring agents in paints, ceramics, inks, varnishes, and enamels.

Discovery and naming

The oldest objects made of copper are beads found in northern Iraq, which date to about 9000 b.c. Tools for working with copper, made in about 5000 b.c., have also been found. In the New World, Native Americans used copper objects as early as 2000 b.c.

The symbol for copper, Cu, comes from the Latin word cuprum. Cuprum is the ancient name of the island of Cyprus. The Romans obtained much of their copper from Cyprus.

Bronze was one of the first alloys produced. It is primarily copper and tin. The two metals can be melted together rather easily. Humans discovered methods for making the alloy as early as 4000 b.c. Over the next thousand years, bronze was used for a great variety of tools, weapons, jewelry, and other objects. It was such an important metal that the period from 4000 to 3000 b.c. is now known as the Bronze Age. The Iron Age followed the Bronze Age when iron began to replace bronze in tools and weapons.

Physical properties

An important physical property of copper is its color. In fact, people often refer to anything with a reddish-brown tint as being copper colored.

Copper metal is fairly soft and ductile. Ductile means capable of being drawn into wires. Both heat and electricity pass through copper very easily. The high electrical conductivity makes it ideal for many electrical purposes.

Copper has a melting point of 1,083°C (1,982°F) and a boiling point of 2,595°C (4,703°F). Its density is 8.96 grams per cubic centimeter.

Chemical properties

Copper is a moderately active metal. It dissolves in most adds and in alkalis. An alkali is a chemical with properties opposite those of an acid. Sodium hydroxide, commonly found in bleach and drain cleaners like Drano, is an example of an alkali. An important chemical property of copper is the way it reacts with oxygen. In moist air, it combines with water and carbon dioxide. The product of this reaction is called hydrated copper carbonate (Cu₂(OH)₂CO₃). This compound has a beautiful greenish color, called a patina. Copper roofs eventually develop this color.

Occurrence in nature

The abundance of copper in the Earth's crust is estimated to be about 70 parts per million. It ranks in the upper quarter among elements present in the Earth's crust. Small amounts (about 1 part per billion) also occur in seawater.

At one time, it was not unusual to find copper lying on the ground. However, this is no longer true. Today, copper is obtained from minerals such as azurite, or basic copper carbonate (Cu₂(OH)₂CO₃); chalcocite, or copper glance or copper sulfide (Cu₂S); chalcopyrite, or copper pyrites or copper iron sulfide (CuFeS₂); cuprite, or copper oxide (Cu₂O); and malachite, or basic copper carbonate (Cu₂(OH)₂CO₃).

Bronze, a copper alloy, was such an important metal from 4000 to 3000 b.c. that the era is now known as the Bronze Age.

Copper is mined in more than 50 nations, from Albania and Argentina to Zambia and Zimbabwe. The leading producers are Chile and the United States. Nearly half of the world's copper comes from these two countries. The next largest producers are Canada, Peru, Australia, Russia, and Indonesia. About 98 percent of copper mined in the United States comes from Arizona, Utah, New Mexico, Nevada, and Montana.

Isotopes

There are two naturally occurring isotopes of copper, copper-63 and copper-65. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.

Nine radioactive isotopes of copper are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.

The color of the Statue of Liberty

A n important physical property of copper is the element's color—reddish-brown. An important chemical property is the way copper reacts with oxygen. It turns the reddish-brown tint green. This change of color is a result of the copper combining with water and carbon dioxide in moist air. The product of this reaction is called hydrated copper carbonate.

Perhaps the most famous and dramatic example of this phenomenon is the Statue of Liberty on Ellis Island near New York City. The Statue, or Lady Liberty as it is often called, was a gift to the United States from France. It was dedicated on October 28, 1886. It symbolizes political freedom and democracy.

The Statue of Liberty is covered with copper plates. When it was new, Lady Liberty was copper in color. Over time, the plates slowly turned green. The statue was given a thorough cleaning for its 100th birthday party on July 4, 1986. But the color stayed green. It would take a lot of elbow grease to return the Lady to its original copper color!

Two radioactive isotopes of copper are used in medicine. One is copper-64. This isotope is used to study brain function and to detect Wilson's disease. This disease is the inability to eliminate copper from one's body. The second isotope is copper-67. This isotope can be used to treat cancer. The isotope is injected into the body. It then goes to cells that have become cancerous. In these cells, the isotope gives off radiation that can kill the cancerous cells.

Extraction

Converting copper ore to copper metal often involves many steps. First, the ore is crushed into small pieces. Then the crushed pieces are mixed with water to form a slurry, a soup-like mixture of crushed ore and water. The slurry is spun around in large vats with steel balls to crush/the ore to an even finer powder.

Next, blasts of air are passed through the slurry. Impure copper rises to the top of the mixture and unwanted earthy materials sink to the bottom. The copper mixture is skimmed off the top of the slurry and dissolved in sulfuric acid (H₂SO₄).

Bars of iron are added to the copper/sulfuric acid mixture. Iron is a more active metal than copper. It replaces the copper from the sulfuric acid solution. Copper deposits on the surface of the iron bar where it is easily scraped off.

The copper is still not pure enough for most purposes. The most common method for copper purification relies on electrolysis, which is the process by which an electrical current is used to cause a chemical change, usually the breakdown of some substance. The copper is dissolved in sulfuric acid again and an electric current is passed through the solution. Pure copper metal is deposited on one of the metal electrodes. By repeating this process, the copper is 99.9 percent pure.

Other methods are also used to remove copper from its ores. The method chosen depends on the kind of ore used.

People often refer to anything with a reddish-brown tint as being copper colored.

Uses

The most important application of copper metal is electrical wiring. Nearly every electrical device relies on copper wiring because copper metal is highly conductive and inexpensive. These devices include electric clocks, stoves, portable CD players, and transmission wires that carry electricity. A large skyscraper contains miles of copper wiring for all its electrical needs. Older telephone lines are thick bundles of copper wires. And computers depend on circuit boards imprinted with minute copper pathways.

Alloys of copper, such as bronze and brass, are also used in construction. These alloys find their way into roofs, heating and plumbing systems, and the skeleton of the building itself.

A number of copper alloys have been developed for special purposes. For example, gun metal is an alloy used to make guns. It contains about 90 percent copper and 10 percent tin. Monel metal is an alloy of nickel and copper that is resistant to corrosion (rusting). Coinage metal is a copper alloy from which U.S. coins are made.

How much is a penny worth?

The core of a penny used to be copper. From its introduction in 1909 to 1982, the penny was 95 percent copper. Depending on the year, the other 5 percent was either all zinc or a combination of zinc and tin (bronze). In 1943—during World War II (1939-45)—the penny consisted of zinc-plated steel. This penny was a failure. The steel was magnetic (so it got stuck in vending machines), the zinc corroded easily, and the public often confused it with a dime.

By the 1980s, copper had become more valuable than the one cent that the penny was worth. So in 1982, the U.S. mint switched the penny's core to art inexpensive zinc coated with copper. The rest of that pocket change—dimes, nickels, and quarters—have a core of coinage metal with a thin coating of a silvery metal. Coinage metal is a copper alloy.

A large skyscraper contains miles of copper wiring for all its electrical needs.

Compounds

A number of copper compounds are used as pesticides, chemicals that kill insects and rodents like rats and mice:

basic copper acetate (Cu₂O(C₂H₃O₂)₂): insecticide (kills insects) and fungicide (kills fungi)

copper chromate (CuCrO₄ ○ 2CuO): fungicide for the treatment of seeds

copper fluorosilicate (CuSiF₆): grapevine fungicide

copper methane arsenate (CuCH₃AsO₃): algicide (kills algae)

copper-8-quinolinolate (Cu(C₉H₆ON)₂): protects fabric from mildew

copper oxalate (CuC₂O₄): seed coating to repel rats

copper oxychloride (3CuO ○ CuCl₂): grapevine fungicide

tribasic copper sulfate (CuSO₄ ○ 3Cu(OH)₂): fungicide, used as a spray or dust on crops

Other copper compounds are found in battery fluid; fabric dye; fire retardants; food additives for farm animals; fireworks (bright emerald color); manufacture of ceramics and enamels; photographic film; pigments (coloring agents) in paints, metal preservatives, and marine paints; water purification; and wood preservatives.

Turquoise and malachite are semi-precious gemstones made up of copper compounds. Turquoise ranges in color from green to blue.

The color of blood

In humans, the blood that comes from the lungs to the cells is bright red. The red color is caused by oxyhemoglobin (the compound hemoglobin combined with oxygen). Hemoglobin carries oxygen through the blood and is red because of the iron it carries. Compounds of iron are often red or reddish-brown. Blood returning from cells to the lungs (which flows through the veins) is purplish-red because the hemoglobin has lost its oxygen.

Some animals, however, do not have hemoglobin to carry oxygen through the blood. For example, crustaceans (shellfish like lobsters, shrimps, and crabs) use a compound called hemocyanin. Hemocyanin is similar to hemoglobin but contains copper instead of iron. Many copper compounds, including hemocyanin, are blue. Therefore, the blood of a crustacean is blue, not red.

Health effects

Copper is an essential micronutrient for both plants and animals. A micronutrient is an element needed in minute amounts to maintain good health in an organism. A healthy human has no more than about 2 milligrams of copper for every kilogram of body weight.

Copper is critical to enzyme production. An enzyme is a substance that stimulates certain chemical reactions in the body. Without enzymes, the reactions would be too slow. Copper enzymes function in the production of blood vessels, tendons, bones, and nerves. Animals seldom become ill from a lack of copper, but copper-deficiency disorders (problems because of lack of copper) can occur with animals who live on land that lacks copper.

Large amounts of copper in the human body are usually not a problem either. One exception is the condition known as Wilson's disease. Some people are born without the ability to eliminate copper from their bodies. The amount of copper they retain increases. The copper level can become so great it begins to affect a person's brain, liver, or kidneys. Mental illness and death can result. Fortunately, this problem can be treated. The person is given a chemical that combines with the copper. The copper's damaging effects on the body are reduced or eliminated.

Copper

Description

Copper is an essential mineral that plays an important role in iron absorption and transport. It is considered a trace mineral because it is needed in very small amounts. Only 70–80 mg of copper are found in the body of a normal healthy person. Even though the body needs very little, copper is an important nutrient that holds many vital functions in the body.

Copper is essential for normal development of the body because it:

• Participates in a wide variety of important enzymatic reactions in the body.
• Is a component of or a cofactor for approximately 50 different enzymes. These enzymes need copper to function properly.
• Is essential for iron absorption and transport. Iron is needed to make hemoglobin, a main component of red blood cells. Therefore, copper deficiency is often linked to iron-deficiency anemia.
• Is required to build elastin and collagen, which are an important components of bones and connective tissues. Therefore, copper is believed to protect the bones and joints against degeneration and osteoporosis .
• Is required for melanin production. People with copper deficiency may have pale skin and hair.
• Is a key mineral for the immune system. Copper promotes wound healing. Studies show that premature infants or children with genetic copper defects are at high risk of getting infections and would significantly improve with copper supplementation.
• Attacks free radicals. Copper is a strong antioxidant. It works by attaching itself to the enzyme Superoxide dismutase (SOD). Copper also binds to a protein to form ceruloplasmin, which is an antioxidant.
• Helps the body produce energy. Copper participates in many oxidative reactions that break down fats in fat tissue to produce much needed energy. Copper deficiency has been associated with high cholesterol levels.
• Is necessary for normal functioning of insulin. Copper deficiency is also associated with poor blood glucose control.
• Is needed for normal functioning of the cardiovascular system.
• Protects the structure and function of the nervous system, including the brain. Copper protects nerve fiber by maintaining myelin, the insulating sheath that surrounds nerve cells. It also aids the transmission of nerve signals in the brains.

General use

Copper supplements may be beneficial in treating or preventing copper deficiency. Copper deficiency used to be relatively rare because the body requires so little of it, only about 2 mg per day. In addition, it is available naturally in a variety of foods such as whole grains, shellfish, nuts, beans, and leafy vegetables. Additional sources of copper are the copper water pipes that run through homes or the copper cookware in the kitchen. These sources leach copper into the water we drink and the food we eat. The level of copper in drinking water is sometimes so high that it becomes a public concern. However, scientists now realize that copper deficiency, especially borderline cases, is more common than once thought. Copper deficiency is currently on the rise due to a decrease of whole foods in the diet and high consumption of fatty and processed foods.

It was discovered in 2001 that vegetarian diets generally contain more copper, but that the absorption efficiency was lower for lactoovo vegetarians than for nonvegetarians. The study also showed that the increased amounts of copper in the vegetarian diets allow for greater copper content.

Besides dietary causes, certain diseases or conditions may reduce copper absorption, transport or increase its requirements, resulting in abnormally low copper blood levels. Increased copper intake through diet or supplementation may be necessary in the following conditions:

• premature infants fed only cow's milk
• pregnant women
• malnutrition
• celiac disease, sprue, cystic fibrosis, or short-bowel syndrome (these diseases cause poor absorption of dietary copper)

• kidney disease
• high consumption of zinc or iron (these minerals interfere with copper absorption)
• highly processed foods (copper is stripped away during food processing)
• Menkes syndrome (copper deficiency is caused by genetic defects of copper transport; Menkes syndrome patients cannot use copper supplied by the diet efficiently)

Symptoms of copper deficiency include:

• anemia
• malnourished infants
• prominently dilated veins
• pale hair or skin
• poorly formed bones
• nervous system disorders
• high cholesterol levels
• heart disease
• loss of taste
• increased susceptibility to infections
• infertility
• birth defects

Exceeding the daily requirement is dangerous, however, because copper toxicity commonly occurs. Copper toxicity is a very serious medical problem. Acute toxicity due to ingestion of too much supplement, for example, may cause nausea, vomiting , abdominal pain, diarrhea, dizziness, headache , and a metallic taste in the mouth. Chronic toxicity is often caused by genetic defects of copper metabolism, such as Wilson's disease. In this disease, copper is not eliminated properly and is allowed to accumulate to toxic levels. Copper is therefore present at high concentration where it should not be, such as in the liver, the lens of the eye, kidneys, or brain.

Disease prevention

Copper is a good antioxidant. It works together with an antioxidant enzyme, superoxide dismutase (SOD), to protect cell membranes from being destroyed by free radicals. Free radicals are any molecules that are missing one electron. Because this is an unbalanced and unstable state, a radical is desperately finding ways to complete its pair. Therefore, it reacts to any nearby molecules to either steal an electron or give away the unpaired one. In the process, free radicals initiate chain reactions that destroy cell structures. Like other antioxidants , copper scavenges or cleans up these highly reactive radicals and changes them into inactive, less harmful compounds. Therefore, it can help prevent cancer . In 2001, a study reported that concentrations of copper sulfate and ascorbate may inhibit breast cancer growth. With further study, the combination may even prove useful as a chemotherapy agent for certain breast cancer patients.

Copper may also help prevent degenerative diseases or conditions such as premature aging , heart disease, autoimmune diseases, arthritis, cataracts, Alzheimer's disease , or diabetes.

Osteoporosis

Copper may play a role in preventing osteoporosis. Calcium and vitamin D have long been considered the mainstay of osteoporosis treatment and prevention. However, a recent study has shown that they can be even more effective in increasing bone density and preventing osteoporosis if they are used in combination with copper and two other trace minerals, zinc and manganese .

Rheumatoid arthritis

Copper has been a folklore remedy for rheumatoid arthritis since 1500 b.c. in ancient Egypt. Some people believe that wearing jewelry made of copper may relieve arthritic symptoms. To evaluate the effect of copper for the treatment of rheumatoid arthritis, Dr. Walker and his colleagues conducted a study of 77 arthritic patients. Patients were divided into two groups: treatment group wearing copper jewelry and placebo group wearing nothing or aluminum jewelry. In this study, patients who wore copper bracelets felt significantly better than those in the placebo group. In addition, patients in the treatment group reported recurrences of symptoms after the bracelets were removed. To explain the effects of the copper bracelets, these researchers suggested that copper contained in the bracelets was dissolved in sweat and then absorbed through the skin. They suspected that copper's effectiveness may be related to its role as an antioxidant. They also believe that copper may function as both an anti-inflammatory agent and as an antioxidant. Thus, it is possibly effective in reducing inflammatory response to such conditions as rheumatoid arthritis.

Preparations

Copper is contained in many multivitamin/mineral preparations. It is also available as a single ingredient in the form of tablets. These tablets should be swallowed whole with a cup of water, preferably with meals, to avoid stomach upset. A person may choose any of the following preparations: copper gluconate, copper sulfate, or copper citrate. However, copper gluconate may be the least irritating to the stomach.

Zinc and copper compete with each other for absorption in the gastrointestinal tract. As a result, excessive copper intake may cause zinc deficiency, and vice versa. Therefore, a person should take zinc and copper supplements together in ratios of 10:1 or 15:1.

Precautions

Those adding copper supplements to their diets should consider:

• Informing their doctors for proper instruction and monitoring of side effects. Copper toxicity due to excessive doses of copper supplements has been reported.
• Although there currently is no recommended daily allowance (RDA) established for copper, 2 mg of copper per day is considered sufficient and safe. Nausea and vomiting may occur in persons taking more than 20 mg of copper daily.
• It is not known if copper supplementation may harm a growing fetus. However, as with any drugs, pregnant or nursing women should not take copper or any other supplements or drugs without first consulting their doctors.
• In certain areas, drinking water may contain high levels of copper. Periodic checks of copper levels in drinking water may be necessary.
• Because individual antioxidants often work together as a team to defend the body against free radicals, the balance between copper, zinc, and iron must be maintained. Excessive intake of one nutrient might result in a deficiency of other minerals and decreased resistance to infections and increased risk of heart disease, diabetes, arthritis, and other diseases.

Side effects

A person should stop taking copper supplements and seek medical help immediately if having the following signs or symptoms:

• anemia
• nausea
• vomiting
• abdominal pain

Interactions

Factors that increase copper concentrations

Certain disorders have been known to increase copper levels. Persons with these conditions should not take copper supplements as they may cause copper toxicity.

• recent heart attacks
• lupus erythematosus
• cirrhosis of the liver
• schizophrenia
• leukemia and some other forms of cancer
• viral infections
• ulcerative colitis (This inflammatory bowel disease may cause accumulation of copper in the body. Excessive amount of copper may worsen many symptoms of this disease by increasing susceptibility to infections and inhibiting wound healing.)
• Wilson's disease (This disease causes accumulation of copper in the tissues. As a result, patients have liver disease, mental retardation, tremor and poor muscle coordination. They also have copper deposits in the cornea of the eye. To manage this disease, patients are put on a low-copper diet and given penicillamine, a drug that attaches itself to copper and increases its excretion.)

Resources

BOOKS

Lieberman,, Shari and Nancy Bruning. "Copper." In The Real Vitamin & Mineral Book: Using Supplements for Optimum Health Garden City Park, NY: Avery Publishing Group, 1997.

Passwater, Richard A. All About Antioxidants. Garden City Park, NY: Avery Publishing Group, 1998.

PERIODICALS

Gonzalez, M. J, et al. "Inhibition of Human Breast Carcinoma Cell Proliferation by Ascorbate and Copper."The Journal of Nutrition 131, no. 11 (November 2001): 3142S.

Hunt, Janet R., and Richard A. Vanderpool. "Apparent Copper Absorption from a Vegetarian Diet."American Journal of Clinical Nutrition 74, no. 6 (December 2001): 803–805.

Reginster, Jean-Yves, Anne Noel Taquet, and Christiane Gosset. "Therapy for Osteoporosis: Miscellaneous and Experimental Agents."Endocrinology and Metabolism Clinics (June 1998): 453–463.

Uauy, Ricardo, Manuel Olivarez, and Mauricio Gonzales. "Essentiality of Copper in Humans."American Journal of Clinical Nutrition 67 suppl (1998): 952S–959S.

OTHER

"Copper" The Merck Manual of Diagnosis and Therapy. [cited October 2002]. <http://www.merck.com>. Rosenstein, Elliot D., and Jacques R. Caldwell. "Therapies: Trace Elements in the Treatment of Rheumatic Conditions." In Rheumatic Diseases Clinics of North America. Part II. [cited May 2000]. <http://www.mdconsult.com>.

Mai Tran

Teresa G. Odle

Copper

melting point: 1,084.62°C
boiling point: 2,927°C
density: 8.96 g/cm³
most common ions: Cu⁺, Cu²⁺

Copper was first used by humans more than 10,000 years ago. A copper pendant discovered in what is now northern Iraq has been dated to about 8700 b.c.e. For nearly five millennia copper was the only metal known to humans. Early copper artifacts—first decorative, then utilitarian—were undoubtedly hammered out from "native copper," pure copper found in conjunction with copper-bearing ores in a few places around the world. By 5000 b.c.e., the dawn of metallurgy had arrived, as evidence exists of the smelting of simple copper oxide ores such as malachite and azurite.

Known worldwide copper resources are estimated at nearly 2.6 trillion kilograms (5.8 trillion pounds), of which only about 12 percent (300 billion kilograms; 804 billion pounds) has been mined throughout history. Nearly all of this mined copper is still in circulation, as copper's recycling rate is higher than that of any other engineering metal.

As a molten liquid, copper may be poured to form cake or slabs from which plate, sheet, strip, and foil are rolled; billet or logs from which tube, rod, bar, and forgings are extruded; wire rod from which wire is drawn; and ingot or bricks from which copper may be alloyed with other metals or used by foundries for casting.

There are more than 450 copper alloys , including brasses, bronzes, copper-nickels, nickel-silvers, and other specialty alloys. Copper is naturally a salmon color and may oxidize or patinate to gradually become dark brown or a greenish blue. Its alloys may range from pink to brown to gold to silver in color.

Copper is used extensively for its high thermal and electrical conductivity and corrosion resistance. In the United States, the most predominant of thousands of copper and copper alloy applications include building construction (largely sheet, tube, building wire, and hardware), 45 percent; electrical and electronic products, 26 percent; transportation equipment, 9 percent; industrial machinery and equipment, 10 percent; and consumer products, 10 percent.

see also Electrochemistry.

Ken Geremia

Internet Resources

Copper in Your Home. Available from <http://www.copper.org/copperhome/homepage.html>.

The Copper Page. Available from <http://www.copper.org/>.

The Standards & Properties for Copper and Copper Alloys. Available from <http://properties.copper.org/>.

copper mines, existing from the Bronze Age, in Schull and Derrycahon, Co. Cork, and Killarney, Co. Kerry, have been radio‐carbon dated to 1500 bc. In modern times, due to rising demand in the late 18th and 19th centuries, there were highly productive copper mines at Allihies, Co. Cork, Bunmahon, Co. Waterford, and Avoca and Ballymurtagh, Co. Wicklow. The price peaked, in the mid‐19th century, at £100 a ton, falling to a low of £90 in 1875. By 1899, due to both overseas competition and falling demand, the output for the whole of Ireland had dropped to only 533 tons annually. Production remained low until the start of the Second World War. Following the Minerals Development Act (1940), the state mining company, Minrai Teoranta, began general exploration. Post‐war copper deposits have been found at Avoca, Tynagh, Co. Galway, Gortdrum, Aherlow, Mallow, Ballyvergin, and Silvermines in Munster, and Navan, Co. Meath.

Peter Collins

copper (symbol Cu) Metallic element, one of the transition metals. Reddish copper occurs native (free or uncombined) and in several ores including cuprite (an oxide) and chalcopyrite (a sulphide). The metal is extracted by smelting and is purified by electrolysis. It is malleable, a good thermal and electrical conductor, second only to silver, and is extensively used in boilers, pipes, electrical equipment and alloys, such as brass and bronze. Copper tarnishes in air, oxidizes at high temperatures and is attacked only by oxidizing acids. Properties: at.no. 29; r.a.m. 63.546; r.d. 8.96; m.p. 1.083°C (1981°F); b.p. 2567°C (4653°F); most common isotope Cu⁶³ (69.09%).

cop·per¹ / ˈkäpər/ • n. 1. a red-brown metal, the chemical element of atomic number 29. A ductile metal, it is a very good conductor of heat and electricity and is used esp. for electrical wiring. (Symbol: Cu) 2. dated a copper coin, esp. a penny. 3. a reddish-brown color like that of copper. 4. a small, typically orange or purple butterfly (genus Lycaena, family Lycaenidae) of North America and Eurasia. Its numerous species include the American copper (L. phlaeas). • v. [tr.] cover or coat (something) with copper. cop·per² • n. inf. a police officer.

Copper river, c.300 mi (480 km) long, rising in the Wrangell Mts., SE Alaska, and flowing S through the Chugach Mts. to the Gulf of Alaska. Copper deposits near the upper river, long mined by natives, attracted the attention of Russians and later Americans, but exploration was difficult because of the river's currents and the glaciers near its mouth. The great Kennecott mine (discovered 1898; abandoned 1938) was made reachable by the building of the Copper River and Northwestern RR from Cordova, which followed the river along part of its lower valley. Today the Copper is noted for its salmon.

copper metallic chemical element; symbol Cu [Lat. cuprum =copper]; at. no. 29; at. wt. 63.546; m.p. 1,083.4°C; b.p. 2,567°C; sp. gr. 8.96 at 20°C; valence +1 or +2. Copper and some of its alloys have been used by humanity since the Bronze Age . One of the first metals known to humans, free copper was probably mined in the Tigris-Euphrates valley as long ago as the 5th cent. BC Cyprus, from which the metal's name originally comes, was the primary source of copper in the ancient world.

Properties

Copper is a reddish metal with a face-centered cubic crystalline structure. It is malleable, ductile, and an extremely good conductor of both heat and electricity. It is softer than iron but harder than zinc and can be polished to a bright finish. It is found in Group 11 of the periodic table , together with silver and gold. Copper has low chemical reactivity. In moist air it slowly forms a greenish surface film (usually a mixture of carbonate, sulfate, hydroxide, and oxide) called patina ; this coating protects the metal from further attack. Copper dissolves in hot concentrated hydrochloric or sulfuric acid but is little affected by cold solutions of these acids; it also dissolves in nitric acid. Salt water corrodes copper, forming a chloride.

Compounds

The most important chemical compound of copper is copper sulfate pentahydrate, also called bluestone or blue vitriol. Other compounds include Paris green , Bordeaux mixture , a cyanide, a chloride, oxides, and a basic carbonate. Verdigris is basic copper acetate.

Sources and Ores

Small amounts of copper are found uncombined, particularly near Lake Superior in Michigan. Copper ores are found in various parts of the world. In the United States (the chief producer of copper) ores are mined in Arizona, Utah, Montana, New Mexico, Nevada, and Michigan. Copper ores are also found in Canada, South America (in Chile and Peru), S central Africa, Russia (in the Ural Mts.), and to a limited extent in Europe and the British Isles.

The principal ore of copper is chalcopyrite , a sulfide of copper and iron, also called copper pyrite. Other important ores are chalcocite, or copper glance, a shiny lead-gray copper sulfide; bornite, a lustrous reddish-brown sulfide of copper and iron; cuprite, a red cuprous oxide ore; and malachite , a bright green carbonate ore. Azurite is a blue crystalline basic carbonate of copper found with other copper ores. Chrysocolla is a bluish-green copper silicate ore. Another important source of copper is secondary (scrap) copper, which is produced from discarded copper and copper alloys.

Commercial Preparation

Copper metal is prepared commercially in various ways. Copper sulfide ores, usually containing only 1% to 2% copper, are concentrated to 20% to 40% copper by the flotation process . They are then usually roasted to remove some of the sulfur and other impurities, and then smelted with iron oxide in either a blast furnace or a reverberatory furnace to produce copper matte, a molten solution of copper sulfide mixed with small amounts of iron sulfide. The matte is transferred to a converter, where it is treated by blowing air through it to remove the sulfur (as sulfur dioxide, a gas) and the iron (as a slag of ferrous oxide). The resulting copper is 98% to 99% pure; it is called blister copper because its surface is blistered by escaping gases when it solidifies during casting.

Most copper is further purified by electrolysis . The blister copper is refined in a furnace and cast into anodes. Thin sheets of pure copper are used as cathodes. A solution of copper sulfate and sulfuric acid is used as the electrolyte. When the anode and cathode are immersed in the electrolyte and an electric current is passed, the anode is dissolved in the electrolyte and pure copper metal is deposited on the cathode. Soluble impurities, usually nickel and arsenic, remain dissolved in the electrolyte. Insoluble impurities, often including silver, gold, and other valuable metals, settle out of the electrolyte; they may be collected and purified.

Copper oxide ores are usually treated by a different process, called leaching, in which the copper in the ore is dissolved in a leaching solution (usually dilute sulfuric acid); pure copper is recovered by electrolysis. Alternatively, the solution is treated with iron to precipitate the so-called cement copper, which is impure.

Importance and Uses

Copper is present in minute amounts in the animal body and is essential to normal metabolism. It is a component of hemocyanin, the blue, oxygen-carrying blood pigment of lobsters and other large crustaceans. It is needed in the synthesis of hemoglobin, the red, oxygen-carrying pigment found in the blood of humans, although it is not a component of hemoglobin.

The chief commercial use of copper is based on its electrical conductivity (second only to that of silver); about half the total annual output of copper is employed in the manufacture of electrical apparatus and wire. Copper is also used extensively as roofing, in making copper utensils, and for coins and metalwork. Copper tubing is used in plumbing, and, because of its high heat conductivity, in heat-exchanging devices such as refrigerator and air-conditioner coils. Powdered copper is sometimes used as a pigment in paints. An important use of copper is in alloys such as brass , bronze , gunmetal , Monel metal, and German silver . Compounds of copper are widely used as insecticides and fungicides; as pigments in paints; as mordants (fixatives) in dyeing; and in electroplating.

copper the earliest metal to be used by humans; the Copper Age is the Chalcolithic period, especially in SE Europe, when weapons were made of copper. Copper was also associated by alchemists with the planet Venus.

Recorded from Old English (in form copor, coper), the word is ultimately based on late Latin cuprum, from Latin cyprium aes ‘Cyprus metal’, so named because Cyprus was the chief source.
copper-bottomed thoroughly reliable, certain not to fail; figuratively, from earlier usage referring to the copper sheathing of the bottom of a ship.

copper (Cu) An element that is required in small amounts by plants, although high concentrations of it can be toxic. It is found bound to proteins and is involved in oxidation-reduction reactions, especially those involving molecular oxygen. The signs of copper deficiency can be very varied: leaves may become chlorotic (see CHLOROSIS) or dark green; the bark of trees may blister; shrubs may become very bushy.

copper(Cu) An element that is required in small amounts by plants, although high concentrations of it can be toxic. It is found bound to proteins and is involved in oxidation-reduction reactions, especially those involving molecular oxygen. The signs of copper deficiency can be very varied: leaves may become chlorotic (see chlorosis) or dark green; the bark of trees may blister; shrubs may become very bushy.

copper A dietary essential trace metal, which forms the prosthetic group of a number of enzymes. The Reference Nutrient Intake is 1.2 mg/day. Toxic in excess, and it is recommended that not more than 2–10 mg/day should be consumed habitually. Rich sources include: meat, poultry, game, fish and shellfish, avocado, nuts, pulses, bread, chocolate, beer, cider, coconut, mushrooms.

copper 1 metal of reddish colour OE.; vessel made of this XVII; copper money XVIII. OE. copor, coper, corr. to MDu. coper (Du. koper), ON. koparr (cf. MLG. kopper, OHG. kupfar (G. kupfer)) — late L. cuprum, for L. cyprium (æs) ‘(metal) of Cyprus’, so named from its most noted ancient source.

copper 2 see COP.

copper •Agrippa, chipper, clipper, dipper, equipper, flipper, gripper, hipper, kipper, nipper, Pippa, ripper, shipper, sipper, skipper, slipper, stripper, tipper, tripper, whipper, zipper •crimper, shrimper, simper, whimper, Whymper •crisper, whisper •mudskipper • caliper • Philippa •juniper • gossiper •worshipper (US worshiper) •griper, piper, sniper, swiper, viper, wiper •bagpiper • sandpiper •bopper, chopper, copper, cropper, Dopper, dropper, hopper, improper, Joppa, poppa, popper, proper, shopper, stopper, swapper, topper, whopper •stomper • prosper • bebopper •teenybopper • grasshopper •clodhopper • sharecropper •name-dropper • eavesdropper •window-shopper • doorstopper •show-stopper •gawper, pauper, torpor, warper