Reference Library: Copper
'Copper' is a chemical element in the periodic table that has the symbol 'Cu' (L.: Cuprum) and atomic number 29.
It is a ductile metal with excellent electrical conductivity, and finds extensive use as an electrical conductor, as a building material, and as a component of various alloys.
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). In oxidation is mildly basic. 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 occupies the same family of the periodic table as silver and gold, hence it shares many characteristics with these metals. All have very high thermal and electrical conductivity. All are malleable metals. Gold and copper are the only colored metallic elements besides caesium, the alkali metal of period six.
Copper is insoluble in water (HO) as well as in isopropanol, or isopropyl alcohol.
There are two stable isotopes, Cu and Cu, 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, Cu, 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. While the metal "bronze" usually refers to copper/tin alloys, it also is a generic term for any alloy of copper, such as aluminium bronze, silicon bronze, and manganese bronze.
The purity of copper is expressed as 4N for 99.9999% pure or 7N for 99.9999999% pure. The numeral gives the number of nines after the decimal point.
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.
* Roofing, guttering, and rainspouts on buildings.
* 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 suppressed by copper tubing in air-conditioning systems.
* Compounds, such as Fehling's solution, have applications in chemistry.
* Copper(II) sulfate is used as a fungicide and as algae control in domestic lakes and ponds. 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.
*U.S. Pennies are 2.5% copper by weight (Balance zinc 97.5%).
*U.S. Nickels are 75.0% copper by weight (Balance nickel 25.0%).
*U.S. Dimes are 91.67% copper by weight (Balance nickel 8.33%).
*U.S. Quarters are 91.67% copper by weight (Balance nickel 8.33%).
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 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.
left from Zakros, Crete is shaped in the form of an animal skin typical for that era.]]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. Brass, an alloy of zinc and copper, was known to the Greeks but first used extensively by the Romans.
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.
Historical copper mining
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 in the British Isles 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)
* Staffordshire (e.g. Ecton Mine)
* Isle of Man, which is between England and Northern Ireland
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 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). In addition to its enzymatic roles, copper is used for biological electron transport. The blue copper proteins that participate in electron transport include azurin and plastocyanin. The name "blue copper" comes from their intense blue color arising from a ligand-to-metal charge transfer (LMCT) absorption band around 600 nm.
Most molluscs and some arthropods such as the horseshoe crab use the copper-containing pigment hemocyanin rather than iron-containing hemoglobin for oxygen transport, so their blood is blue when oxygenated rather than red.
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.
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.
A significant portion of the toxicity of copper comes from its ability to accept and donate single electrons as it changes oxidation state. This catalyzes the production of very reactive radical ions such as hydroxyl radical in a manner similar to fenton chemistry. This catalytic activity of copper is used by the enzymes that it is associated with and is thus only toxic when unsequestered and unmediated. This increase in unmediated reactive radicals is generally termed oxidative stress and is an active area of research in a variety of diseases where copper may play an important but more subtle role than in acute toxicity.
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.
Too much copper in water has also been found to damage marine life. The observed effect of these higher concentrations on fish and other creatures is damage to gills, liver, kidneys and the nervous system.
The metal, when powdered, is a fire hazard. At concentrations higher than 1 mg/L, copper can stain clothes and items washed in water.
:See Copper extraction for the main article.
The main copper-ore producing countries are Chile, United States, Indonesia, Australia, Peru, Russia, Canada, China, Poland, Kazakhstan and Mexico.
Copper can be found as native copper in mineral form. Minerals such as the sulfides: chalcopyrite (CuFeS), bornite (CuFeS), covellite (CuS), chalcocite (CuS) are sources of copper, as are the carbonates: azurite (Cu(CO)(OH)) and malachite (CuCO(OH)) and the oxide: cuprite (CuO).
Most copper ore is mined or extracted as copper sulfides from large open pit mines in porphyry copper 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 68 ppm by mass, and 22 ppm by atoms. Native copper also forms in uneconomic placer deposits.
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.
The copper price has quintupuled since 1999, rising from $0.60 per pound in June 1999 to $3.75 per pound in May 2006 [http://www.kitcometals.com/charts/copper_historical_large.html].
Common oxidation states of copper include the less stable copper(I) state, Cu; and the more stable copper(II) state, Cu, which forms blue or blue-green salts and solutions. Under unusual conditions, a +3 state and even an extremely rare +4 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 (CuO). Copper oxides are used to make yttrium barium copper oxide (YBaCuO) 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 (III) compounds' , rare: potassium hexafluorocuprate (KCuF)
'Copper (IV) compounds' , extremely rare: caesium hexafluorocuprate (CsCuF)
Copper (I) and Copper (II) can also be referred to by their common names cuprous and cupric.
See also copper compounds.
Tests for copper ion
Add aqueous sodium hydroxide. A blue precipitate of copper(II) hydroxide should form, by the displacement of the copper ions by sodium ions.
:Cu + 2OH → Cu(OH)
Add aqeuous ammonia. A precipitate should form, which then dissolves upon adding excess ammonia, to form a deep blue ammonia complex, tetraaminecopper(II).
:Cu + 4NH → Cu(NH)
Copper band corrosion
Base for additions : band, corrosion and this copper article.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Copper".