Copper

Copper is a chemical element in the periodic table that has the symbol Cu and atomic number 29.

Notable characteristics

Copper is a reddish-colored metal, with a high electrical and thermal conductivity (among pure metals at room temperature, only silver has a higher electrical conductivity). Copper has its characteristic color because it reflects red and orange light and absorbs other frequencies in the visible spectrum, due to its band structure. Contrast this with the optical properties of silver, gold and aluminium.

Copper is insoluble in water (H₂O) as well as isopropanol, or isopropyl alcohol.

There are two stable isotopes, ⁶³Cu and ⁶⁵Cu, along with a couple of dozen radioisotopes. The vast majority of radioisotopes have half lives on the order of minutes or less; the longest lived, ⁶⁴Cu, has a half life of 12.7 hours, with two decay modes, leading to two separate products.

There are numerous alloys of copper—speculum metal is a copper/tin alloy, brass is a copper/zinc alloy, and bronze is a copper/tin alloy. Monel metal is a copper/nickel alloy, also called cupronickel.

Applications

Copper is malleable and ductile, and is used extensively, in products such as:

Copper wire.
Copper plumbing.
Doorknobs and other fixtures in houses.
Statuary: The Statue of Liberty, for example, contains 179,200 pounds (81.3 tonnes) of copper.
Electromagnets.
Electrical machines, especially electromagnetic motors and generators.
Watt's steam engine.
Electrical relays, electrical busbars and electrical switches.
Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
Wave guides for microwave radiation.
There is increasing use of copper in integrated circuits, replacing aluminium because of its superior conductivity.
Alloyed with nickel, e.g. cupronickel and Monel, used as corrosive resistant materials in shipbuilding.
As a component of coins, often as cupronickel alloy.
In cookware, such as frying pans.
Most flatware (knives, forks, spoons) contains some copper (nickel silver).
Sterling silver, if it is to be used in dinnerware, must contain a few percent copper.
As a component in ceramic glazes, and to color glass.
Musical instruments, especially brass instruments.
As a biostatic surface in hospitals, and to line parts of ships to protect against barnacles and mussels, originally used pure, but superseded by Muntz Metal. Bacteria will not grow on a copper surface because it is biostatic. Copper doorknobs are used by hospitals to reduce the transfer of disease, and Legionnaire's Disease is supressed by copper tubing in air-conditioning systems.
Compounds, such as Fehling's solution, have applications in chemistry.
Copper(II) sulfate is used as a poison and a water purifier. It is used in gardening powders and sprays to kill mildew.
As a material in the manufacture of computer heatsinks, as a result of its superior heat dissipation capacity to aluminium.
Copper was sometimes used by the Inuit to make the cutting blade for ulu's.

History

In Greek times, the metal was known by the name chalkos (χαλκός). Copper was a very important resource for the Romans and Greeks. In Roman times, it became known as aes Cyprium (aes being the generic Latin term for copper alloys such as bronze and other metals, and Cyprium because so much of it was mined in Cyprus). From this, the phrase was simplified to cuprum and then eventually Anglicized into the English copper.

Copper was known to some of the oldest civilizations on record, and has a history of use that is at least 10,000 years old. A copper pendant was found in what is now northern Iraq that dates to 8700 BC. By 5000 BC, there are signs of copper smelting, the refining of copper from simple copper oxides such as malachite or azurite. The earliest signs of gold use, by contrast, appear around 4000 BC.

There are copper and bronze artifacts from Sumerian cities that date to 3000 BC, and Egyptian artifacts in copper and copper alloyed with tin nearly as old. In one pyramid, a copper plumbing system was found that is 5000 years old.

The Egyptians found that adding a small amount of tin made the metal easier to cast, so bronze alloys were found in Egypt almost as soon as copper was found. Use of copper in ancient China dates to at least 2000 BC. By 1200 BC excellent bronzes were being made in China. Note that these dates are affected by wars and conquest, as copper is easily melted down and reused. In Europe, Oetzi the Iceman, a well-preserved male dated to 3200 BC, was found with a copper-tipped axe whose metal was 99.7% pure. High levels of arsenic in his hair suggests he was involved in copper smelting.

The use of bronze was so pervasive in a certain era of civilization that it has been named the Bronze Age. The transitional period in certain regions between the preceding Neolithic period and the Bronze Age is termed the Chalcolithic, with some high-purity copper tools being used alongside stone tools.

Brass, an alloy of zinc and copper, was known to the Greeks but first used extensively by the Romans.

Copper was associated with the goddess Aphrodite/Venus in mythology and alchemy, owing to its lustrous beauty, its ancient use in producing mirrors, and its association with Cyprus, which was sacred to the goddess.

In alchemy the symbol for copper was also the symbol for the planet Venus.

Copper mining

The main copper-ore producing coutries are Australia, Canada, Chile, China, Mexico, Russia, Peru, Indonesia and the United States.^[1]

Copper has been mined for many centuries. By 2000 BC, Europe was using copper-tin alloys or ‘bronze’. The Bronze Age is taken as 2500 BC to 600 BC. During the Bronze age, copper was mined mainly in the following locations:

South West County Cork
West Wales (e.g. Cwmwystwyth)
North Wales (e.g. Great Orme)
Anglesey (Parys Mountain)
Cheshire (Alderley Edge)
Derbyshire (e.g. Ecton Mine)
Isle of Man.

At Great Orme in North Wales, such working extended for a depth of 70 metres (ref: O’Brien, W., Bronze Age Copper Mining in Britain and Ireland) At Alderley Edge in Cheshire, carbon dates have established mining at around 2280 - 1890 BC (at 95% probability) (ref: Timberlake and Prag, 2005).

Copper Mining in Ireland

Copper Mining in Ireland can be traced back to 1700 BC at Mount Gabriel in County Cork. As with all mining in Ireland, deposits were worked intermittently, two primary factors determining the extent of working:

the price obtainable for ore,
the development of processes that would make previously uneconomic rock to be mined for ore extraction.

The last active copper mining in Ireland took place at Avoca in County Wicklow, ending in 1982.

Biological role

Copper is essential in all higher plants and animals. Copper is carried mostly in the bloodstream on a plasma protein called ceruloplasmin. When copper is first absorbed in the gut it is transported to the liver bound to albumin. Copper is found in a variety of enzymes, including the copper centers of cytochrome c oxidase and the enzyme superoxide dismutase (containing copper and zinc), and is the central metal in the oxygen-carrying pigment hemocyanin. The blood of the horseshoe crab, Limulus polyphemus, uses copper rather than iron for oxygen transport. [1]

It is believed that zinc and copper compete for absorption in the digestive tract so that a diet that is excessive in one of these minerals may result in a deficiency in the other. The RDA for copper in normal healthy adults is 0.9 mg/day.

Toxicity

All copper compounds, unless otherwise known, should be treated as if they were toxic. Thirty grams of copper sulfate is potentially lethal in humans. The suggested safe level of copper in drinking water for humans varies depending on the source, but tends to be pegged at 1.5 to 2 mg/L. The DRI Tolerable Upper Intake Level for adults of dietary copper from all sources is 10 mg/day. In toxicity, copper can inhibit the enzyme dihydrophil hydratase, an enzyme involved in haemopoiesis.

An inherited condition called Wilson's disease causes the body to retain copper, since it is not excreted by the liver into the bile. This disease, if untreated, can lead to brain and liver damage. In addition, studies have found that people with mental illnesses such as schizophrenia had heightened levels of copper in their systems. However it is unknown at this stage whether the copper contributes to the mental illness, whether the body attempts to store more copper in response to the illness, or whether the high levels of copper are the result of the mental illness.

Miscellaneous hazards

The metal, when powdered, is a fire hazard. At concentrations higher than 1 mg/L, copper can stain clothes and items washed in water.

Occurrence

See Copper extraction for the main article.

Copper can be found as native copper in mineral form. Minerals such as the carbonates azurite (Cu₃(CO₃)₂(OH)₂) and malachite (Cu₂CO₃(OH)₂) are sources of copper, as are sulfides such as chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), covellite (CuS), chalcocite (Cu₂S) and oxides like cuprite (Cu₂O).

Most copper ore is mined or extracted as copper sulfides from large open pit mines in copper porphyry deposits that contain 0.4 to 1.0 percent copper. Examples include: Chuquicamata in Chile and El Chino mine in New Mexico. The average abundance of copper found within crustal rocks is approximately 68000 parts per billion by mass, and 22000 parts per billion by atoms.

The Intergovernmental Council of Copper Exporting Countries (CIPEC), defunct since 1992, once tried to play a similar role for copper as OPEC does for oil, but never achieved the same influence, not least because the second-largest producer, the United States, was never a member. Formed in 1967, its principal members were Chile, Peru, Zaire, and Zambia.

A recent news paper article (January 2006) stated that the earths crust now contains only a few more years of copper at it current rate of extraction.

Compounds

Common oxidation states of copper include the less stable copper(I) state, Cu⁺¹; and the more stable copper(II) state, Cu⁺², which forms blue or blue-green salts. Under unusual conditions, a +3 state can be obtained.

Copper(II) carbonate is green from which arises the unique appearance of copper-clad roofs or domes on some buildings. Copper(II) sulfate forms a blue crystalline pentahydrate which is perhaps the most familiar copper compound in the laboratory. It is used as a fungicide, known as Bordeaux mixture.

There are two stable copper oxides, copper(II) oxide (CuO) and copper(I) oxide (Cu₂O). Copper oxides are used to make yttrium barium copper oxide (YBa₂Cu₃O_7-δ) or YBCO which forms the basis of many unconventional superconductors.

Copper (I) compounds : copper(I) chloride, copper(I) oxide.

Copper (II) compounds : copper(II) carbonate, copper(II) chloride, copper(II) hydroxide, copper(II) nitrate, copper(II) oxide, copper(II) sulfate, copper(II) sulfide.

Copper (I) and Copper (II) can also be referred to by their common names cuprous and cupric.

Tests for copper²⁺ ion

Add aqueous sodium hydroxide. A blue precipitate of copper(II) hydroxide should form, by the displacement of the copper ions by sodium ions.

Ionic equation:

Cu²⁺_(aq) + 2OH^-_(aq) -> Cu(OH)_{2 (s)}

Add aqeuous ammonia. A precipitate should form, which then dissolves upon adding excess ammonia, to form an ammonia complex, tetraaminecopper(II).