Copper

Copper is a chemical element with atomic number 29, symbol Cu. The simple copper body is metal.

Position in the periodic table
Symbol	Cu
Name	Copper
Atomic number	29
Group	11
Period	4th period
Block	block d
Element family	Transition metal
Electronic configuration	[Ar] 3d10 4s1
Electrons by energy level	2, 8, 18, 1
Atomic properties of the element
Atomic mass	63.546 ± 0.003 u
Atomic radius (calc)	135 pm (145 pm)
Covalence radius	132 ± 4 pm
Van der Waals radius	140 pm
oxidation state	2, 1
Electronegativity (Pauling)	1.9
Oxide	Weakly basic
Ionization Energies
1st: 7.726 38 eV	2nd: 20.292 4 eV
3rd 36.841 eV	4th: 57.38 eV
5th: 79.8 eV	6th: 103 eV
7th: 139 eV	8th: 166 eV
9th: 199 eV	10th: 232 eV
11th: 265.3 eV	12th: 369 eV
13th: 401 eV	14th: 435 eV
15th: 484 eV	16th: 520 eV
17th: 557 eV	18th: 633 eV
19th: 670.588 eV	20th: 1,697 eV
21st: 1 804 eV	22nd: 1,916 eV
23rd: 2,060 eV	24th: 2,182 eV
25th: 2,308 eV	26th: 2,478 eV
27th: 2,587.5 eV	28th: 11,062.38 eV
29th: 11,567.617 eV
Most stable isotopes
Iso AN Period MD Ed PD MeV 63Cu 69.17% stable with 34 neutrons 64Cu synthetic radioisotope 12.70 h ~42.7% ε ~38.9% β– ~17.9% β+ ~0.5% γ/CI 1,675 0.578 0.653 1,354 64Ni 64Zn 64Ni 64Cu 65Cu 30.83% stable with 36 neutrons 67Cu synthetic radioisotope 2.58 h β- 0.6 67Zn
Physical properties of the simple body
Ordinary state	Solid
Density	8.96 g·cm-3 (20 °C)
Crystal system	Face-centered cubic
Mohs	3
Color	Red-brown
Melting Point	1,084.62 °C (freezing)
Boiling Point	2 562 °C
Fusion energy	13,05 kJ· mol-1
Vaporization energy	300,3 kJ· mol-1
Molar volume	7,11×10-6 m3·· mol-1
Vapor pressure	0.050 5 Pa at 1 084.45 °C
Speed of sound	3 570 m·s-1 at 20 °C
Mass heat	380 J· kg-1· K-1
Electrical conductivity	59,6×106 S· m-1
Thermal conductivity	401 W· m-1· K-1
Solubility	soluble in HNO3,HCl + H2O2, H2SO4 dilute + Hg(II), NH4OH + H2O2
Miscellaneous
No CAS	7440-50-8
No ECHA	100.028.326
No CE	231-159-6
Precautions
WHMIS
Uncontrolled product This product is not controlled according to WHMIS classification criteria. Disclosure at 1.0% according to the ingredient disclosure list Comments: The chemical identity and concentration of this ingredient must be disclosed on the material safety data sheet if it is present at a concentration equal to or greater than 1.0% in a controlled product. This product is not controlled according to WHMIS. Disclosure at 1.0% according to the ingredient disclosure list Comments: The chemical identity and concentration of this ingredient must be disclosed on the material safety data sheet if it is present at a concentration equal to or greater than 1.0% in a controlled product.
SI Units & CNTP, unless otherwise indicated.

General and simple body

Copper is an element of group 11, period 4, an element of the chalcophilous transition metal block.

In the periodic table of elements, copper is of the same family as silver and gold, because all have orbital s occupied by a single electron on fully filled p and d subshells, which allows the formation of metal bonds (electronic configuration Ar 3d¹⁰ 4s¹). The three metals of this “copper group” have a character of nobility and increased rarity, from semi-noble copper to truly noble gold, the first character being explained by their low atomic radius and atomic stacking compactness, their greater ionization potential because of the d subshells, their relatively high melting point and their low reactivity or relative chemical inertness.

Naturally present in the earth’s crust, copper (in low doses) is essential for the development of all life. It is mainly used by humans in the form of metal. Pure copper is one of the only metals colored along with gold and cesium. It presents on its fresh surfaces a salmon pink metallic hue or sheen: this “red metal” appreciated in goldsmithing and jewelry, for example as a support for enameled or rare enamel pieces, was dedicated to the goddess of beauty Aphrodite and artists. It is sometimes referred to as red copper as opposed to brasses (alloys of copper and zinc) incorrectly called “yellow copper”. A ductile metal, it has particularly high electrical and thermal conductivities that give it various uses. It is also used as a building material and is used in the composition of many alloys, cupro-alloys.

Copper, now a common metal, is the oldest metal used by man. The melting point is not too high, and the ease of reducing copper oxide, often by a simple wood fire, is remarkable.

The oldest traces of copper smelting in wind furnaces were discovered in the Iranian plateau at the archaeological site of Sialk III dated to the first half of the V^th millennium BC — so nearly seven thousand years ago. 6,000 years ago the extraction of ore to extract copper is common in some places of Eurasia and Africa, like the malachite of Sinai for ancient Egypt whose mines are exploited around 4500 BC.

The ancient Mediterranean history of copper is intimately linked to the island of Cyprus which is called late in ancient Greek Κύπρος / Kýpros: it is indeed on this island that the mines of copper and native copper were exploited, which allowed little-known human civilizations to flourish, long before the Minoan, Mycenaean and Phoenician civilizations. These various civilizations from the Eastern Mediterranean organized the ancient trade of the red metal in the Mediterranean, so much so that the Romans generically called copper and various alloys aes cyprium (literally “Cyprus metal”), cyprium (Ancient Greek Κύπρος) designating the island. The term has changed over time to become “cuprum” in Latin to give the word “copper” in French.

Allied mainly with tin and sometimes other metals, it gave rise to a technological revolution, the “Bronze Age”, around 2,300 years before our era. Bronzes are harder, more easily fusible and suitable for casting in a mold, more resistant to atmospheric corrosion than native or purified copper. The manufacture of utensils and weapons, objects of art and massive statues, bells or bells, stamps or cymbals, candlesticks or large vessels possibly sacred or offerings, medals and coins can develop. The mastery of this allied metallic material is such that it allows the erection of the Colossus of Rhodes, a flagship statue of Helios-Apollo 32 m high in the III^rd century BC.

A series of articles in the journal Science in April 1996, of a transdisciplinary nature, bringing together teams of historians, archaeologists, physical chemists and glaciologists, made it possible to place globally in relation to variations in artisanal and proto-industrial production, spectrometric analyses of particles and dusts of copper metal and its derivatives, trapped in ice samples extracted from the Greenland ice sheet.

Historical peaks in copper production, for example, the introduction of coinage, the wars of the Republic and the Roman Empire, the opening of the Swedish mine of Falun could be roughly traced, taking a base at -5000 BC and considering atmospheric losses of the order of 15% at the beginning of generalized metallurgy in the Œkoumenes around -2500 BC, reduced only to 0.25% around 1750 by the progress of chemical processes.

The world’s annual copper production, stimulated by coinage, is said to have reached a long-standing high of 15 kt at the beginning of I^st the Christian era. The average figure of annual copper production estimated year after year in Western and Central Europe from the end of the Roman Empire to the dawn of the eighteenth century is of the order of 2 kt in this way. The rise of Chinese metallurgy would justify production of 13 kt/year in the XII^th century and XIII^th century.

The adjectives “coppery” and “coppery” generically describe copper-based materials or copper-containing materials. The first adjective remains ambiguous in wide use, since it designates precisely for chemists copper at the degree of oxidation (I), while the second is commonly used, especially in geosciences.

The adjective “copper”, in addition to an extended meaning analogous to “coppery”, referred mainly to the oxidation state II of copper most common, especially in aqueous solution. The adjectives “cupric” and “cuprous” are the scholarly equivalents of copper and copper. The Latin radical cupro- or cupr- designating copper is found in many technical or chemical names.

Copper isotopes

Copper has 29 known isotopes, with mass numbers ranging from 52 to 80, as well as seven nuclear isomers. Of these isotopes, two are stable, ⁶³Cu and ⁶⁵Cu, and constitute the total natural copper in a proportion of about 70/30. They both have a nuclear spin of 3/2. The standard atomic mass of copper is 63.546(3) u.

The other 27 isotopes are radioactive and produced only artificially. The most stable of these radioisotopes is ⁶⁷Cu with a half-life of 61.83 hours. The least stable is ⁵⁴Cu with a half-life of about 75 ns. Most others have a half-life of less than one minute.

Occurrences in natural environments, mineralogy and geology, deposits and deposits

Copper is an element with a clarke of 55 to 70 g/t. It is sometimes abundant in some mining sites.

Copper is one of the few metals that exist in its native state, making it one of the first metals used by humans. However, it appears mainly in minerals, especially in the form of sulfide, because of its chalcophile character (attraction to the element sulfur).

In its native state, it is presented as a polycrystal of cubic structure with centered faces. It is also sometimes found in the form of a single crystal, the largest measuring about 4.4 × 3.2 × 3.2 cm. Well-formed crystals are rare. In the few sites where it can be observed (its native occurrence is low), it is found in the form of dentritic threads, leaf assemblies or more or less massive impregnation covers. In the Neolithic, the recovered metal was then easily shaped by light hammering.

In mineral form, copper appears most frequently as sulfide or sulfosalt in minerals such as chalcopyrite (CuFeS₂), bornite (Cu₅FeS₄), cubanite (CuFe₂S₃) and especially covelline (CuS) and chalcosine (Cu₂S). It is also found in carbonates such as azurite (Cu₃(CO₃)₂(OH)₂) and malachite (Cu₂CO₃(OH)₂), as well as in an oxide, cuprite (Cu₂O).

Minerals containing the element copper often have a beautiful colored appearance, such as Eilat stone.

Native copper

Native copper deposits most often attest to very active hydrothermalism and basic magmatic rocks.

We find native copper:

• in porous basalt zones: reactions between hydrothermal solution and iron ore generate copper from the main deposits of this mineral. In the Keweenaw peninsula in the United States, basalt layers alternate with sandstones and conglomerates, cavities are filled with copper associated with calcite, epidote, copper minerals, zeolites, some silver; large masses of native copper up to about 500,000 kg have been found there, particularly in the state of Michigan, where geologists estimate among high-power clusters on the shores of Lake Superior a block with an internal and external fractal character at least 420 kg of copper;
• in sandstones and shales, where copper was probably of hydrothermal origin;
• in small amounts in meteorites.

Some notable deposits of native copper are:

• in Bolivia: Coro-Coro, Pacajes Province, La Paz Department;
• in Canada: Rouyn-Noranda, Normandy Mine, Saint-Joseph-de-Coleraine, Les Appalaches RCM, Chaudière-Appalaches, Quebec;
• in the United States: Keenawa Peninsula, and Lake Superior, Keweenaw County, Michigan
• en France:
  • Les Clausis, Saint-Véran, Hautes-Alpes,
  • Pélites Permians du Dôme de Barrot, Alpes-Maritimes,
  • Chessy, Rhône,
  • Saint-Jean-de-Jeannes, Mont Roc, and le Burc, Tarn;
• in Poland: Lubin Basin (Lower Silesia).

Minerals

Sulfides

• Chalcopyrite: CuFeS₂: (Cu₂S, Fe₂S₃).
• Bornite: Cu₅FeS₄: (5Cu₂S, Fe₂S₃).
• The covelline or covellite: CuS.
• Chalcocite: α Cu₂S.

• Carrollite: Cu (Co,Ni)₂S₄.
• stannite: Cu₂FeSnS₄.
• Germanite: Cu₁₃Fe₂Ge₂S₁₆.
• Keterite: Cu₂ (Zn, Fe)Sn S₄.

Grey Copper

Grey coppers are complex sulfides where copper accompanies arsenic and/or antimony… Thus tennantite, tetrahedrite, freibergite.

Sulfo-salt

• Enargite: Cu₃AsS₄ or (3Cu₂S, As₂S₅).
• Meneghinite: Pb₁₃CuSb₇S₂₄.
• Lengenbachite: (Ag,Cu)₂Pb₆As₄S₁₃.

Oxides

Copper oxidizes:

• copper ion Cu⁺, or Cu(I) ion:
  • cuprite Cu₂O;
• cupric ion Cu²⁺, or Cu(II) ion:
  • tenorite CuO.

The standard potentials of the main half-reactions are:

Cu₂O_(s) + H₂O + 2 e⁻ ⇄ 2 Cu_(s) + 2 HO⁻;

Cu2+ + e− ⇄ Cu+	E0 = +0.159 V;
Cu2+ + 2 e− ⇄ Cu(s)	E0 = +0.340 V;
Cu+ + e− ⇄ Cu(s)	E0 = +0.522 V.

carbonates

• Azurite: Cu₃(CO₃)₂(OH)₂: (2CuCO₃, Cu(OH) ₂).
• Malachite: Cu₂(CO₃)(OH)₂: (CuCO₃, Cu(OH) ₂).
• Aurichalcite : (Zn,Cu)₅(CO₃)₂(OH)₆.

Silicates

• Chrysocolla: (Cu, Al)₂H₂(Si₂O₅)(OH)₄* n(H₂O).
• Dioptase CuSiO₃ • H₂O.
• Kinoite: Ca₂Cu₂Si₃O₁₀,2H₂O.
• Plancheite Cu₈Si₈O₂₂(OH)₄,H₂O.
• Macquartite: Pb₃Cu²⁺(CrO₄)SiO₃(OH)₄,2H₂O.
• Cuprosklodowskite : Cu(UO₂)₂(HSiO₄)₂·6(H₂O).

Chlorides (and other halides)

• Atacamite: Cu₂Cl(OH)₃.
• Boleite: KPb₂₆Ag₉Cu₂₄Cl₆₂(OH)₄₈.
• Cumengeite: Pb₂₁Cu₂₀Cl₄₂(OH)₄₀·6H₂O.
• Mitscherlichite: K₂CuCl₄·2H₂O.
• Botallackite: Cu₂Cl(OH)₃.

Sulfates

• Brochantite: Cu₄(SO₄)(OH)₆.
• Langite: Cu₄ (SO₄)(OH)₆ 2H₂O.
• Kröhnkite: Na₂Cu(SO₄)₂·2 H₂O.
• Connellite Cu₁₉ Cl₄ (SO₄) (OH)₃₂ 3H₂O.
• Cyanotrichite: Cu₄Al₂[(OH)₁₂/SO₄].2H₂O.
• Antlerite: Cu₃(OH)₄SO₄.
• Linarite: PbCu [(OH)₂/SO₄.
• Liroconite: Cu₂Al(AsO₄)(OH)₄·4 H₂O.

Phosphates

Reichenbachite, cornetite and libethenite are copper hydroxyphosphates of the respective formulas Cu₅(PO₄)₂(OH)₄, Cu₃(PO₄)(OH)₃ and Cu ₂PO₄(OH).

Torbernite is a uranium copper phosphate Cu(UO₂)₂(PO₄)₂ · 12 H₂O.

Other rare minerals

Rickardite is a copper telluride. Berzelianite or berzelin is a copper selenide Cu₂Se. Quetzalcoatlite is a complex mineral, an intimate combination of a copper and zinc hydroxy-tellurite, and a lead-silver chloride Zn₆Cu₃(TeO₆)₂ (OH)₆· Ag_xPb_yCl_x+2y.

Szenicsite is a copper hydroxy-molybdate with the formula Cu₃(MoO₄)(OH)₄.

Stranskiite is a copper-zinc arsenate with the formula Zn₂Cu^II(AsO₄)₂.
Olivenite, euchroite and cornubite are copper hydroxyarsenates, Cu₂AsO₄(OH), Cu₂(AsO₄)(OH) ·3H₂O and Cu₅(AsO₄) ₂(OH)₄· H₂O.

Bayldonite is a hydrated lead copper hydroxy arsenate PbCu₃(AsO₄)₂(OH)₂H₂O.

Mixite is a copper bismuth hydroxy arsenate trihydrate BiCu₆(AsO₄)₃(OH)₆•3(H₂O).

Deposits

Since ancient times, copper has been mined in significant quantities on the island of Cyprus, nicknamed the island of a thousand mines.

During Antiquity and sometimes locally until the Middle Ages, grey copper deposits were exploited.

Most copper ore is mined as sulfides or chalcopyrite-based rocks in large open-pit mines in copper porphyry veins with a copper content of 0.4 to 1.0 percent. On the surface, ores with large amounts of waste rock are more oxygenated, but remain sulfur in deep layers. In the 1990s, an exploitable ore had to never fall below 0.5% by mass, and ensure a grade of the order of 1% or more. The mines in Kennecott, Alaska, operated until the 1940s, were the purest on the planet.

Examples: Chuquicamata, Chile; Bingham Canyon Mine, Utah and El Chino Mine, New Mexico, USA. In 2005, Chile was the world’s largest copper producer with at least one-third of world production, followed by the United States, Indonesia and Peru, according to the British Geological Survey.

The exploitation of polymetallic nodules, based on Cu, Mn, Co, Ni, etc., from the seabed, another potential source of copper, remains confidential.

Simple body, chemistry and chemical combinations of copper

Physical and chemical properties of the simple body

A reddish, red or orange-red metal, copper has exceptional thermal and electrical conductivity. The very pure metal is resistant to atmospheric and marine corrosion, but also very malleable, tenacious and ductile, relatively soft.

• Identification
  • hardness (Mohs): 3
  • Density: 8.93
  • cleavage: absent
  • Line: lighter copper red, pale metallic red, pinkish red
  • Fracture: scaly, shredded, difficult
  • Rupture: ductile (few impurities or insoluble impurities) or brittle (soluble impurities such as phosphorus)
  • Color: copper red, or orange, yellow-red, red-brown metallic
  • Crystal system: face-centered cubic
  • Crystal parameter: a_Cu = 3.62 Å
  • Crystal class and space group: hexakisoctahedral – m3m

• • Bravais lattice: face-centered cubic
  • Macle: very common on {111} by attachment or penetration
  • Solubility: insoluble in water, but soluble in nitric acid, concentrated and hot sulfuric acid, ammonia
• Optical properties
  • Transparency: opaque
  • Brilliance: salmon red metallic (“red metal”)
  • Obtaining a very nice polish
  • Birefringence: low after deformation
  • Fluorescence: none

Copper is among the most ductile and malleable metals. Relatively soft, the metal can easily be stretched, rolled and drawn.

Rubbed, its surfaces emit a particular and unpleasant odor, an indirect effect of the density of free electrons within the metallic crystal lattice.

The metal can deteriorate superficially after long exposure to air in a thin layer of basic copper carbonates of a beautiful green or green-grey, which forms the “patina” of some copper-covered roofs. This layer can sometimes contain malachite and azurite.

Mechanical and optical properties

Like silver and gold, copper is easy to work, being ductile and malleable. The ease with which it can be given the shape of wires, as well as its excellent electrical conductivity make it very useful in electricity.
Copper, like most metals for industrial or commercial use, is usually found in a fine-grained polycrystalline form. Polycrystalline metals have better strength than those in monocrystalline form, and the smaller the grains, the greater the difference.

Tensile strength is low and elongation before failure is important. After iron, copper is the most tenacious common metal. The mechanical properties of copper confirm the ancient techniques of forming this metal, common cold and hot, rarer. Its malleability partly explains the manufacture of vases or shapes by hammering at the repoussé.

The practical density of molten copper is in the range of 8.8 to 8.9. It increases significantly with rolling to 8.95. Work hardening makes copper both hard and elastic.

Copper has a reddish, orange or brown color due to a thin layer on the surface (including oxides). Pure copper is salmon pink in color. Copper, osmium (blue), cesium and gold (yellow) are the only four pure metals with a color other than gray or silver.
The characteristic color of copper results from its electronic structure: copper is an exception to Madelung’s law, having only one electron in the 4s subshell instead of two. The energy of a photon of blue or violet light is sufficient for an electron in the d-shell to absorb it and transition to the half-occupied s-layer. Thus, the light reflected by copper does not have certain blue/violet wavelengths and appears red. This phenomenon is also present for gold, which has a corresponding 5s/4d structure. Liquid copper appears greenish, a characteristic it shares with gold when light is low.

Electrical and thermal properties

The similarity of their electronic structure makes copper, silver and gold analogous in many respects: all three have high thermal and electrical conductivity, and all three are malleable. Among pure metals and at room temperature, copper has the second highest conductivity (59.6 × 10⁶ S/m), just after silver. This high value is explained by the fact that, virtually, all valence electrons (one per atom) take part in conduction.

The resulting free electrons give copper a huge charge density of 13.6 × 10⁹ C/m³. This high charge density is responsible for the low sliding speed of currents in a copper cable (the sliding speed is calculated as the ratio of current density to charge density). For example, for a current density of 5 × 10⁶ A· m^-2 (which is normally the maximum current density present in domestic circuits and transport networks), the sliding speed is just slightly higher than ¹⁄₃ mm/s.

However, the resistivity of copper is sensitive to traces of impurities, it increases sharply with low foreign contents, unlike that of iron. Also, pure copper has been and is used extensively as an electric wire, to make submarine cables and overhead lines.

Electrical conductivity or its inverse resistivity, that of a pure copper wire in the control annealed state named IACS or International Annealed Copper Standard, which, measured at 20 °C, is 1.724 × 10⁻⁸ Ωm serves as a measurement standard in physics. Conductivity is expressed as a percentage of IACS.

This metal is a very good conductor of heat, less so than silver. This is partly why copper is used as a cook’s utensil, brewery refrigerant, in evaporative boilers, from stills to sugar factories. Another reason for choosing this metal was the catalytic capabilities of copper in a large number of thermal reactions.

Copper melts around 1,085°C. It vaporizes at a higher temperature, boiling around 2,562°C. Its vapor burns with an intense green flame, which allows its quantitative detection in flame spectrometry or qualitative by simple flame test.

Chemical properties

Copper is not altered in dry air or oxygen gas. Only traces of water and especially the essential presence of carbon dioxide or carbon dioxide initiate a reaction. Copper does not react with water, but reacts slowly with oxygen in the air, forming a layer of brown-black copper oxide, passivating in nature. Unlike iron oxidation by a humid atmosphere, this oxide layer prevents mass corrosion.

In the absence of carbon dioxide, oxidation of copper in air begins only at 120°C. It is easy to understand that the action of water is observable especially in the state of water vapor and at high temperatures.

2Cu _solid + 1/2 O_{2 gas} → Cu₂O _{suboxide solid red.}
Cu₂O + 1/2 O_{2 gas} → CuO _{black solid.}

Copper is on the contrary altered in contact with air and acidulated water, air accelerating the oxidation initiated. Vinegar thus forms soluble copper oxides. Similarly traces of fatty substances by their acid or oxidizing function. The dietary toxicity of the oxides formed justified the traditional tinning (addition of a protective layer of tin) of copper culinary instruments and containers. Former breeders or cheese makers, distillers, cooks or jam makers ensured that copper surfaces were kept clean after use during heating.

However, moist air plays a limited role. A green layer of copper carbonate or basic copper hydroxycarbonate Cu₂CO₃· Cu(OH)₂, called green-grey, is often noticed on old copper constructions or on bronze structures in urban areas (the presence of carbon dioxide and moisture), such as copper roofs or the Statue of Liberty. This layer partly plays the role of patina protective. But in marine or saline environments (presence of chlorides brought by drizzles) or in industrial environments (presence of sulfates), other compounds are formed, respectively hydroxy chloride Cu₂Cl₂· Cu(OH)₂ and hydroxy sulfate Cu₂SO₄· Cu(OH)₂.

Copper reacts with hydrogen sulfide — and all sulfide-containing solutions, forming various copper sulfides on its surface. In solutions containing sulfides, copper, exhibiting potential debasement relative to hydrogen, will corrode. This can be observed in everyday life, where the surfaces of copper objects tarnish after exposure to sulfide-containing air.

The typical reaction to obtain copper sulfides in black precipitates can be used to detect copper, it is very slow at 20 °C, more efficient at 100 °C and especially very fast at 550 °C, where it is written simply:

2 Cu _solid + H₂S _gas → Cu₂S _{solid black} + H_2gas.

The reaction with hydrochloric acid is very slow.

Cu _solid + HCl _gas → CuCl _{solid black} + 1/2H_2gas.

Thus copper is not really attacked at room temperature by hydrochloric acid concentrated in an aqueous medium. It is very poorly soluble. Copper, on the other hand, dissolves in other hydro-halogenic acids, such as HBr or HI.

Generally speaking, it is oxidizing acids or other acids in the presence of dissolved oxygen gases that can attack copper. Yet copper is not attacked by cold-concentrated sulfuric acid, but only by this highly concentrated and hot acid. Copper oxide sulfates and sulfurous acid are formed in the gas phase.

Nitric acid is the solvent par excellence of copper. The chemical reaction is active even with the dilute acid. It explains the graphic possibilities of copper etchings. Here are the two basic reactions, the first in concentrated medium, the second in diluted medium.

Cu _{solid metal} + 4 HNO_{3 aqueous, concentrated} → Cu(NO₃)_{2 aqueous} + 2 NO_{2 gas} + 2 H₂ O _water.

3 Cu _{solid metal} + 8 HNO_{3 aqueous, diluted} → 3 Cu(NO₃)_{2 aqueous} + 2 NO _gas + 4 H₂O< sub>water.

Copper reacts with a combination of oxygen and hydrochloric acid to form a range of copper chlorides. Blue/green copper(II) chloride, when boiled in the presence of metallic copper, undergoes a back dismutation reaction producing white copper(I) chloride.

Copper reacts with an acidic solution of hydrogen peroxide which produces the corresponding salt:

Cu + 2 HCl + H₂O₂ → CuCl₂ + 2 H₂O.

Ammonia oxidizes copper metal on contact with air. It is formed from soluble copper oxide and ammonium nitrate, with excess ammonia.
Copper dissolves slowly in aqueous ammonia solutions containing oxygen because ammonia forms water-soluble compounds with copper. Concentrated ammonia dissolves it easily by giving a blue solution, traditionally called “Schweitzer liquor”, based on the complexed cation Cu(NH₃)₄²⁺ or better in basic medium Cu(NH₃)₄(H₂0))²⁺. This liquor can dissolve cellulose and cellulosic fibers, such as cotton or textile lint from rag pickers. This is how ammoniacal copper rayon is made.

Copper powdered copper has various catalytic properties. For example, it is a catalyst for the synthesis of cyclopropene.

When copper is in contact with metals with different electrochemical potentials (e.g. iron), especially in the presence of moisture, closing an electrical circuit will cause the junction to behave like an electrochemical cell. In the case, for example, of a copper pipe connected to an iron pipe, the electrochemical reaction causes the iron to be transformed into other compounds and can possibly damage the fitting.

During the twentieth century in the United States, the temporary popularity of aluminum for domestic electrical wiring meant that the circuits of many homes consisted partly of copper wires and partly of aluminum wires. The contact between the two metals has caused problems for users and manufacturers.

Smelters never place aluminum and copper stocks nearby. Even if there are specific cupro-aluminum alloys, traces of aluminum in a copper alloy cause serious technical drawbacks. Knowing, on the other hand, the properties of pure copper, men of the art have developed alloyed coppers, for example, coppers with about 1% chromium, this one allowing to harden the metal obtained.

Metallurgy and refining

Copper, 99.95% pure metal

The primary sulfur ores, already described, account for more than 80% of production, this is copper pyrometallurgy.
Copper is accompanied by the other metallic elements Fe, Co, Ni, Zn, Mo, Pb, etc., and sometimes the precious Ag, Au, Pt and PGMs that are interesting to recover in anode sludge, but also Ge, Se, Te, As, etc.

Copper ore, of the order of 2% copper, is concentrated into copper after mechanized technical steps of sieving, crushing, grinding and sorting, including flotation separation with selective and hydrophobic surfactants such as potassium amylxanthate. This “concentrated ore” containing 20% to 40% copper is roasted in the presence of silica, to obtain a supernatant slag based on sterile minerals and mattes based on iron and copper sulfides containing about 40 to 75% copper depending on the process.

The liquid matte is oxidized in the presence of silica in a converter. Here is the overall reaction, requiring almost no heating because it brings together two strongly exothermic reactions, which takes into account only copper and abandons the technical phases concerning matte, slag and slag (slag or grime).

3 Cu₂S _liquid + 3 O_{2 gas} → 6 Cu _{metal liquid} + 3 SO_{2 gas}.

Everything happens as if matte is converted into impure copper, which is cast in blisters (copper material cast with characteristic surface blisters, called blisters in technical English, with less than 2% impurities) of 140 to 150 kg.

Secondary oxygenated ores (malachite, azurite, cuprite) pave the way for copper hydrometallurgy. The sorting step is associated with sulfuric acid leaching or liquid-liquid extraction. The cupric ion dissolves into an organic solvent, kerosene-type, thanks to extractants of the hydroxy oxime or hydroxyquinoline type, a stripping step makes it possible to obtain concentrated solutions of cupric ions, which can be separated by electroplating or carburizing using steel waste. The first electrolytic process collects “red copper”, sometimes almost pure in the order of 99.9% copper. The second process gives copper polluted by iron, it requires electrolytic refining.

Refining can in principle be thermal or electrolytic.
Impure copper can be purified in part by melting. But this ancient thermal process involving oxidation and then “perching” in the liquid metal bath to remove the remaining oxygen charge, in the form of volatile oxide molecules, remains expensive. For example, the melting of the blister makes it possible to oxidize impurities As, Sb, S in the form of volatile oxides. Perching uses trunks or poles of green wood or, increasingly, gaseous or liquid hydrocarbons, it allows by stirring to remove the oxygen present in the metal in the form of carbon monoxide and water vapor.

Industrial refining of copper today is mainly carried out by electrolysis of raw copper anodes or blister (containing iron, sometimes silver, etc.) in a solution of copper sulfate and sulfuric acid.

Cu²⁺ + 2 e⁻ → Cu⁰ _metal with a normal electrode potential ε⁰ of the order of 0.34 V.

Copper ions migrate to the cathode, noble metals such as silver are trapped in the anode sludge at the bottom of the anode compartment, and impurities, e.g. iron oxidized to ferrous ions, remain in the electrolysis bath. This process makes it possible to obtain pure metal from 99.9% to 99.95%. But this cathode or technical copper is sometimes porous or has inclusions or pockets of electrolytes. It must be remelted in the furnace under various controlled atmospheres (e.g. with phosphorus P deoxidation) or in air to obtain billets castings, copper plates or wires. These materials are then transformed into semi-finished products.

The fact remains that for specialists, there are different grades of copper according to national standards (for example standard NF A50-050), in particular various categories: without oxygen, with oxygen, deoxygenated with deoxygenating remainder, deoxygenated without traces of deoxygenates.

Copper may be distributed, in addition to cylinders, tubes or wires of specific uses, by sheets (solid or perforated) or plates, solid bars which may be flat, square, round, by perforated bars, by tapped bars, by insulated flexible bars, by trolley wires, by strips, by lightning rod strips, by specific strips for cables or transformers, by discs (stamping), etc.

Recycled copper can be resold as a shot of various qualities (purity) and particle sizes.

Copper has a much softer appearance around 830°C and melts around 1,085°C.

Copper is not suitable for foundry casting. If the temperature of the casting is too low, therefore close to the melting point, cooling too fast is not controlled, the cast metal does not take the impression of the molds. If the casting is too hot, the copper after cooling has blows. Also in the arts and industries, there have been since distant times different practical alloys.

Notable alloys

Very early on, alloys that were more fusible, harder than purified copper and above all suitable for quality casting, were developed by trial and error, without knowing their true chemical nature. Sometimes they were made directly from ores, and considered as singular metals apart, such as ancient bronzes obtained with tin ores and ancient brasses with those of zinc…

There are a large number of ancient and modern copper alloys. Here are the main ones:

Brass, AlNiCo (sometimes a little copper), alfenid or white metal (copper with Zn, Ni, Fe), Aluminum alloy for 2000 series grinding, Devarda alloy (Al with a little Zn), copper amalgam (mercury), argenton (Ni, Sn), avional (aluminum, Mg, Si), billon (alloy) (silver alloyed copper), britannium (Sn, Sb), bronze (tin), arsenic bronze (tin and arsenic), beryllium bronze (beryllium), phosphorous bronze (same with a little P), constantan (nickel), cuproaluminum (aluminum), cunife (Ni, Fe), cuprochrome, cupronickel (nickel), Dural or duralium, brass (zinc), red brass (a little Zn), maillechort (nickel and zinc), moldamax (beryllium), Orichalque, Mu-metal type (NiFe₁₅Cu₅Mo₃, Nordic gold (a little Zn, Al and Sn), gossip (tin and lead), ruolz (Ni, Ag), shakudō (with a little gold), tumbaga (gold), tombac (a little Zn), virenium (a little Zn, Ni), zamak (zinc, aluminum and magnesium)

Copper is used in shape memory alloys.

Roman brass is a variety of bronze, used to make weapons and utensils and objects very diverse. Modern bronzes, designed as alloys with a specific composition of copper and tin, cover an even wider field of application, from coins and medals to valves and taps, from heavy bases to components of various objects of art, statuettes or statues, supports for enameled pieces or jewelry enamels, etc. Bronzes with up to 3% phosphorus (P) greatly increase their hardness. Phosphorous bronze at 7% Sn and 0.5% P has reduced oxidation, better behavior during melting.

The brasses, malleable and cold ductile, have a color all the more golden the higher the copper content. This beautiful color justifies its use as a filling of lamps and torch furniture, but also inspires the creation of false jewelry, formerly based on “chrysocolla” or “Mannheim gold”. Brasses, however, leave a bad smell at the tips of the fingers that handle them. They have been and sometimes still are used in piping, taps and screws, as household utensils, physical instruments (obsolete), buttons, pins and wires, knife trim, guns, springs, gears and sprockets, heat exchangers, radiators. Marine instrument holders were made of yellow brass at 20-40% Zn, while sextants were made of white brass at 80% Zn.

The addition of zinc and nickel makes it possible to obtain mesh, for example at 20-28% Zn and 9-26% Ni. They are suitable for the manufacture of cutlery, crockery and cups, teapots, upholstery parts and spurs because of their great hardness, optical instruments and precision mechanics, for example, parts for watch movements, because of their low alterability in air. They are also monetary alloys.

Copper and nickel alloys are called cupronickels. Monel metal at 65-70% Ni is used as currency. At lower levels, cupronickels are used for laboratory and chemical equipment in general, as well as precision resistors. The constantan at 40% Ni is characterized by a value of the electrical resistance, independent of the temperature.

In addition to Zn, Ni and Sn, copper alloys may be based on lead Pb, silver Ag or gold Au, or low in Al or Si.

The addition of lead makes it possible to design anti-friction alloys, for example at 10-30% Pb and 7% Sn.
Copper, gold and silver are miscible in all proportions, these relatively expensive alloys give rise to English gold. These include silver-based solder alloys of the type Ag 20% Zn 30% Cu 45% Cd 5% by mass which melts around 615 °C or Ag 35% Zn 21% Cu 26% Cd 18% by mass which melts even lower around 607 °C.

Aluminum bronze is a 5-10% Al alloy, used as a coin or material for marine corrosion-resistant instruments, valves and pumps.

There are also silicon alloys, with contents of 1-2% Si.

Tellude copper, as well as sulfur copper to a lesser extent, is an ideal metallic material for fast and precise turning or manufacturing of parts by machining or even hot forging. Tellurium copper can also be used in plasma nozzle welding, for electrical connections of batteries and bolting.

Chemistry and major copper compounds

Copper compounds occur in several oxidation states, usually +2, by which they impart a blue or green color due to the minerals they constitute, such as turquoise. This property of Cu²⁺ means that they have been widely used throughout history in the manufacture of pigments. The architectural elements and copper statues corrode and acquire a characteristic green patina. Copper is found significantly in the decorative arts, both in metallic form and in the form of colored salts.

Copper compounds have four oxidation states:

• copper(I), often referred to as copper;
• copper(II), often called copper;
• copper(III);
• copper(IV).

The first two and especially the second in aqueous solution are the most frequent.

Before presenting the different states of copper, note the existence of a range of complex ions characterized by the geometry of the three series of copper coordination compounds. Thus according to the coordination number n:

• if n = 2, it is linear as in [Cu^I (NH₃)₂](SCN);
• if n = 4, it forms a square plane as for the dark blue cuproammonium ion [Cu^II(NH₃)₄]²⁺ for example, present in the chemical body [Cu^II (NH₃)₄](SO₄), obtained from cupric sulfate and ammonia in an aqueous medium;
• if n = 6, the symmetry is octahedral as for the compound [Cu^II(NH₃)₆](Br)₂.

Copper(I)

Copper(I) is the main form found in its deposits.

Copper oxide Cu₂O, insoluble in water, is red. Anhydrous copper salts are white.

The Cu⁺ ion is colorless and diamagnetic. It is characterized by a fairly large ionic radius of 0.91 Å, it does not give stable hydrates, it is mainly present in the form of complexes that are not all stable.

Cu⁺ + e⁻ → Cu⁰ _metal with a normal electrode potential ε⁰ of the order of 0.52 V

Yet it is rare or practically non-existent in an aqueous solution because this cation is subjected to dismutation or oxidized easily in solution.

2 Cu⁺ → Cu²⁺ + Cu _metal with K_s ≈ 1.6 × 10⁻⁶ and Δε⁰ ≈ 0.18 V

Let us give a concrete example of this global reaction in equilibrium, first in an aqueous solution brought to a boil in a concentrated chloride medium:

Cu²⁺ + Cu _{metal in excess} + 4 Cl⁻ _{chloride in excess} → 2 Cu₂Cl⁻ _{copper complex in aqueous medium}

Then, by the dilution effect of chloride ions, occurs the precipitation of cuprous chloride of simplified formula CuCl.

Cu₂Cl⁻ _aqueous + H₂O → CuCl_{precipitated solid} + Cl⁻ with K_s ≈ 6.5 × 10⁻²

Its compounds, with the exception of a number of complexes, are very often non-stoichiometric, unstable and poorly soluble, or almost insoluble in water. The copper ion is similar in some properties to the cations Ag⁺ Tl⁺ Hg₂²⁺.

Cu₂O is a red base oxide, which reacts with halogenated acids HX, with X = Cl, Br, I. Copper halides, insoluble or poorly soluble in water, precipitate.

Copper halides, white anhydrous salts with crystalline structure displaying a coordination number 4, typical of the crystal of the blende, very poorly soluble or dissociable in water, easily fusible and semiconductors CuCl, CuBr, CuI are well known, except fluoride. In reality, chloride is as much in the solid state a dimer Cu₂Cl₂ as a monomer, in solution HCl in (neo) precipitated form CuCl or in the form of complex ion CuCl₂⁻, in the vapor state a mixture of monomer, dimer and trimer. The complex ion CuCl₂⁻ explains the association with carbon monoxide gas CO and the absorption of this gas.

sugars are often detected by their ability to convert blue copper(II) compounds into copper(I) oxide compounds (Cu₂O), such as Benedict’s reagent. The principle is the same for Fehling’s liquor, whose cuprous ions are reduced by sugars to Cu₂O, brick red oxide.

The qualitative and quantitative search for copper in the urine (cupremia) is carried out in a concentrated basic medium by causing the characteristic deposition of cuprous oxide, for example:

2 Cu²⁺ + 4 HO⁻ → Cu^I₂O _{precipitated copper (I) oxide} + 2 H₂O + 1/2 O_{2 gas}

Cuprous sulfide Cu₂S as well as oxide Cu₂O, can be obtained by chemical reaction at high temperatures of copper and the respective simple bodies, sulfur and oxygen gas.

There are copper acetylide, copper(I) thiophene-2-carboxylate, copper(I) acetylacetonate, white copper cyanide, orange-yellow copper hydroxide, copper thiocyanate, etc.

The cuprous thiocyanate precipitate, insoluble in water, is used for the gravimetric determination of cupric ions in an aqueous solution.

2 Cu²⁺ + 2 SCN²⁻ + SO₃²⁻ + H₂O → Cu^ISCN_{precipitate copper (I) thiocyanate} + 2 H⁺ + SO₄²⁻.

Copper(II)

The divalent copper cation Cu²⁺, of configuration ⁹, is colored and paramagnetic because of its unpaired electron. It presents a large number of analogies with the divalent cations of transition metals. Together with electron donor bodies, it forms many stable complexes.

It is characterized in fundamental analytical chemistry by its precipitation by H₂S at pH 0.5 in an aqueous medium. The group of cations Hg²⁺ Cd²⁺ Bi³⁺, etc., to which it belongs, have soluble chlorides and its sulfides insoluble in ammonium sulfide.

Copper(II) is very commonly found in our everyday lives. Many of its salts do not have the same aspects of coloration in light if they are anhydrous or hydrated, in concentrated or diluted solutions. However, dilute solutions of cupric salts in water are usually blue or sometimes blue-green.

Copper(II) carbonate is the green deposit that gives copper-covered roofs or cupolas of old buildings their specific appearance.

Copper(II) sulfate consists of a crystalline blue pentahydrate that is perhaps the most common copper compound in the laboratory. Anhydrous copper sulfate is white, hydrated copper sulfate (especially pentahydrate) is blue, aqueous copper sulfate is blue in concentrated solution. This sulfate can thus be used as a test for the presence of water. It is also used as a fungicide, under the name of Bordeaux mixture.
By adding a basic aqueous solution of sodium hydroxide, the precipitation of copper(II), blue, solid hydroxide is obtained. The simplified equation of the reaction is:

Cu²⁺ + 2 HO⁻ → Cu(OH)_{2 precipitated copper hydroxide}.

A finer equation shows that the reaction involves two hydroxide ions with deprotonation of the copper(II) compound 6-hydrated:

Cu(H₂O)₆²⁺ _aqueous + 2 HO⁻ → Cu(H₂O)₄(OH)₂ + 2 H₂ O.

Copper hydroxide is soluble in acids, and also in an excess base at some point, because of the complex species Cu(OH)_4²⁻.

An aqueous solution of ammonium hydroxide (NH₄⁺ + HO⁻) causes the formation of the same precipitate. When an excess of this solution is added, the precipitate redissolves, forming a dark blue ammonia compound, copper(II) tetraamine:

Cu(H₂O)₄(OH)₂ + 4 NH₃ → Cu(H₂O)₂(NH₃)₄²⁺ + 2 H₂O + 2 HO⁻.

This compound was once important in the processing of cellulose. It is still used in ammoniacal copper rayon processes.

Other well-known copper(II) compounds, often anhydrous or hydrated, include copper(II) acetate, formate, oxalate, copper(II) tartrate, copper(II) carbonate, copper(II) chloride, copper(II) nitrate, phosphate, chromate, arsenate, sulfide, and copper(II) oxide. These include the brown color of anhydrous copper chloride, the green color of hydrated copper chlorides, the yellow-green color of their concentrated solutions, as well as the green color of anhydrous copper acetate, the blue-green color of hydrated copper acetates, the green-blue color of concentrated solutions.

The biuret method is a colorimetric determination of proteins.

Copper ions are oxidizing, they oxidize aldehydes according to the Fehling reaction in a basic medium, detect reducing dares, coumarins or flavonoids according to the Benedict test reaction. Bertrand’s method makes it possible to measure milk sugars. The Barfoed reaction is a test for detecting oses with cupric acetate in an acidic medium, whereas Fehling’s liquor operates in this case only in a basic medium.

The action of aldehydes or sugars on Fehling’s liquor reduces Cu²⁺ eventually to copper oxide Cu₂O, leaving a brick-red precipitate. Recall that this detection liqueur based on the copper complex is used fresh (freshly prepared) and with a light thermal heating.

CuF₂ cupric fluoride is characterized by a crystalline ionic lattice, analogous to fluorite.

Copper chloride or anhydrous cupric bromide form chains that are in principle unlimited (CuCl₂)_n or (CuBr₂)_n where the two potential electron-donating chlorine atoms appear to chelate or pinch the accepting copper atom. These linear polymers are hydrolyzed by dissolution in water.

Copper metal can be extracted from its salt solutions by metals, necessarily less noble or non-noble, such as iron and magnesium. This carburizing reaction is written for example with iron Fe.

Cu²⁺ _aqueous + Fe⁰ _{filings or metal powder iron} → Cu⁰ _metal + Fe²⁺ _{aqueous (ferrous ions)}.

There are many methods for detecting copper ions, one involving potassium ferrocyanide, which gives a brown precipitate and copper salts. The medium soda NaOH_aq of cupric salts, for example, the copper sulfate ion, chloride or copper acetate, previously described, leaves a blue precipitate. Similarly, the ammonia medium NH₄OH_aq generates a blue liquor, the addition of potassium ferrocyanide a brown precipitate, the reaction by bubbling hydrogen sulfide H₂S_gas a characteristic black precipitate.

Ammoniacal solutions of cupric salts are often dark blue, this deep coloration is provided by the complex ions Cu(NH₃)_n²⁺ involving n ammonia molecules. These complex ions explain the absorption of carbon monoxide CO.

Copper complexes are generally very stable. They are also paramagnetic when they have a single electron and a coordinated structure in dsp³.

Copper tartrate diluted in an alkaline solution based on NaOH_aq and caustic potash KOH_aq gives an intense blue liquor.

Copper tartrate is readily converted by H₂S into CuS copper sulfide, forming a black precipitate.

The formula of copper sulfide is misleading because there are concatenations of sulfur in the crystal lattice, a copper Cu^I with tetrahedral coordination and a copper Cu^II at the center of the equilateral triangle of S, hence the formula of crystallographers Cu^I₄Cu^II₂(S₂)₂S₂

Double copper potassium cyanide in an aqueous medium does not exhibit any transformation or alteration, as it is a complex structure.

Cyanides are both reducing cupric ion and especially complexing agents in large quantities or excess.

Cu²⁺ _aqueous + 2 CN⁻ _aqueous → (CN)_{2 cyanogenic gas} + Cu⁺ _aqueous.

Cu²⁺ _aqueous + 4 CN⁻ _aqueous → Cu(CN)₄ ³⁻

The reduction of the cupric ion by iodide ions I⁻ allows the volumetric determination of copper, because iodine is titrated in return by sodium thiosulfate. The basic reaction in an aqueous medium is written:

Cu²⁺ + 2 I⁻ → CuI _{copper iodide} + 1/2 I_{2 iodine}.

Copper(II) acetylacetonate catalyzes carbene coupling and transfer reactions. Copper(II) triflate or trifluoromethyl sulfonate is also a catalyst.

Mixed copper yttrium barium oxide is among the first superconducting ceramic materials at liquid nitrogen temperature.

Copper(III)

The Cu³⁺ cation is unstable and exists only by stabilization in the form of complexes. There are Cu₂O₃

A representative compound of copper(III) is CuF₆³⁻. There are also K₃CuF₆, KCuO₂, etc.

Copper(III) compounds are uncommon but are involved in a wide variety of reactions in non-organic biochemistry and homogeneous catalysis. Superconducting cuprates contain copper(III), such as YBa₂Cu₃O_7-δ.

Copper(IV)

Copper(IV) compounds, such as CuF₆²⁻ salts, are very rare.

Dosage

The amount of copper in different media is quantifiable by different analytical methods. To dissociate copper from the matrix of its medium, it is necessary, most of the time, to perform digestion using an acid (usually nitric acid and/or hydrochloric acid). The Centre of Expertise in Environmental Analysis of Quebec uses coupled techniques, namely ICP-MS for analyses in the flesh of fish and small invertebrates, and ICP-OES for analyses in water that must first be acidified.

Simple body, alloy and compound uses and applications

About 98% of the element copper is used in the form of a simple metallic body or its alloys, taking advantage of its specific physical properties – malleability and ductility, good thermal and electrical conductivity and the fact that it is resistant to corrosion. Copper is often too soft for some applications, so it is incorporated into many alloys. These include brass, an alloy of copper and zinc, or bronze, an alloy of copper and tin.
Copper can be machined, although an alloy is often required for complex parts, such as threaded parts, to maintain satisfactory machinability characteristics. Its good thermal conductivity allows it to be used for radiators and heat exchangers, as in the past boilers and stills.

The properties of copper (high electrical and thermal conductivity, corrosion resistance, recyclability) make this metal a widely used natural resource. It is used to make electrical conduction equipment (bar, cables, electrical wires, telephone wires, radio sheaths), copper plates and sheets for roofing, kitchen utensils, decorative objects, plates for electroplating and plate making on copper.

It is thus used in the electricity sector, electronics, telecommunications (cable networks, microprocessors, batteries), in construction (water piping, roof covering), in architecture, transport (electromechanical components, oil coolers, tanks, propellers), machine tools, equipment products (oil platforms) and consumer products (kitchen utensils, sometimes by doubling vessels into thin sheets, formerly bakery utensils) but also coins such as the euro. Copper is frequently used in electroplating, usually as a substrate for the deposition of other metals, such as nickel.

The one-euro coin (The Star Tree designed by Joaquin Jimenez for the euros minted in France) consists of a “white” cupronickel center (75% Cu 25% Ni) on a nickel core and a “yellow” crown in maillechort (75% Cu 20% Zn 5% Ni). The alloys (center and crown) are reversed for the two-euro coin.

Mechanical and electrical industries

Copper is found in a large number of contemporary applications and in many different industries: telecommunications, construction, transport, energy and renewable energy. Due to its very good electrical and thermal conductivity, copper is used in many applications. It is the best electrical conductor among all non-precious metals. For example, the electrical conductivity of copper (59.6 × 10⁶ S.m⁻¹) is 58% higher than that of aluminum (37.7× 10⁶ S.m⁻¹).

Electrical and electronic equipment contains up to 20% of its weight in copper. However, due to its high density (8.94 g/cm³), it cannot be used in overhead high-voltage lines where aluminum is required due to its lightness. Its electrical properties are widely exploited, and its use as a conductor, in electromagnets, relays, distribution bars and switches. Integrated circuits are increasingly using copper instead of aluminum because of its higher electrical conductivity, as are printed circuit boards. It is also used as a material for the manufacture of computer heaters, due to its better thermal conductivity than aluminum. Vacuum tubes, cathode ray tubes and magnetrons in microwave ovens use copper, as do waveguides for microwave emission.

In some thermal applications (automotive radiators for example), for economic reasons, it is sometimes replaced by materials that perform less efficiently (aluminum, synthetic materials). Copper is rarely used pure, except for electrical conductors and in the case where high thermal conductivity is desired, because pure copper is very ductile (high elongation capacity without breaking).
It is shown that the thermal and electrical conductivities of copper are very strongly related. This results from the mode of transmission of heat and electricity in metals, which is mainly done by moving electrons. It should be noted that the copper used in this field must be extremely pure (minimum 99.90% according to international standards). Impurities soluble in the copper matrix such as phosphorus (even in very small proportions) greatly decrease conductivity.
Copper is commonly used in the laboratory as a target in X-ray tubes for powder diffraction. The K line of copper has an average wavelength of 1.541 82 Å.

Architecture and industry

While unoxidized copper is used for electrical applications, copper used in architecture is deoxidized phosphorous copper (also known as Cu-DHP).
Since ancient times, copper has been used as a waterproof roofing material, which gives many old buildings the green appearance of their roofs and cupolas. At first copper oxide is formed, soon replaced by copper and copper sulfide, and finally by copper carbonate. The final patina of copper sulfate (called “green-grey”) is highly resistant to corrosion.

• Statuary: The Statue of Liberty, for example, has 179,220 pounds (81.29 metric tons) of copper.
• Alloyed with nickel, for example in cupronickel and monel, it is used in shipbuilding as a corrosion-resistant material.
• Due to its excellent heat dissipation, it is used for the firebox of Watt.
• Copper compounds in liquid form are used to preserve wood from dry rot damage, especially when processing the original parts of structures being restored.
• Copper wires can be placed on non-conductive roofing materials to limit foam development (zinc can also be used for this purpose.)
• Copper is also used to prevent lightning from hitting a building directly. Placed high above the roof, copper spikes (lightning rods) are connected to a copper cable of the strong section itself connected to a large buried metal plate. The charge is dispersed in the soil, instead of destroying the main structure.

Copper has good corrosion resistance, but is lower than gold. It has excellent welding and brazing properties and can also be arc welded, although the results obtained are better with the neutral gas arc welding technique, with the addition of metal.

Copper alloys

Copper alloys are very widely used in many fields. The most famous alloys are certainly brass (copper-zinc) and bronze (copper-tin) which were developed long before the first castings of pure copper were made. The baptismal font of the collegiate church of Saint-Barthélemy in Liège has fascinated researchers at this level. It had to be realized that brass is much easier to implement than pure copper and pure zinc separated.

• Conductive parts: e.g. for electrotechnical use, in particular in red brass or tombac.
• Mechanical parts: pure or slightly alloyed copper has satisfactory mechanical properties but is generally not used due to its high density.
• Friction and wear parts.
• Parts that must resist corrosion, copper oxide is stable at room temperature and usually covers copper parts with a thin insulating layer.
• Musical instruments, in particular tombac or red brass with 20% zinc, brass, but also cymbals, timpani, bells or bells in different bronzes with 20 to 25% tin.
• Pièces de bijouterie.
• Piece of cartridges, e.g. tombac.

Applications of copper compounds

About 2% of copper production is used to produce chemical compounds. The main applications are food supplements and fungicides for agriculture.

Copper sulfate, like other copper salts, can be used as a green pigment for paints, fungicides and algaecides. It is found in the Bordeaux mixture.

Copper carboxylates are used as fungicides and catalysts.

The uses of copper salts are also diverse:

• as a component of glazes for ceramics and for coloring glass;
• extinguishing product Class D used in powder form to extinguish lithium fires by smothering burning metal and acting as a heat sink;
• textile fibres, to make antimicrobial protective fabrics.

Other specific applications

Armament

• Warheads (“bullets”) of so-called “armored” ammunition for long or handguns commonly consist of a copper jacket surrounding a core usually made of lead.
• Copper, in the form of brass, is often used to make cases.
• Copper is also used in so-called hollow-charge munitions for piercing armor, as well as in explosives used in demolition (blade).

Pyrotechnics

In pyrotechnics, copper compounds or formerly fine copper powder color a shower of fireworks blue.

Superconductivity

Cupric oxide CuO associated with yttrium oxide Y₂O₃, barium oxide BaO, strontium oxide SrO, bismuth oxide Bi₂O₃ can form superconducting ceramics or nano-assemblies at −140 °C.

Similarly, but at lower temperatures, CuS. CuS₂ and CuSe₂ are notable for their superconductivity.

Interest in cuprates in this field was initiated by the work of two perovskite specialists Georg Bednorz and Alex Müller published in 1986 who initially assumed superconductivity at −238 °C for BaLaCuO.

Biomedical applications

• Copper(II) sulfate is used as a fungicide and to limit algae blooms in domestic ponds and pools. It is used in powder and spray form, in gardening, to control late blight.
• Copper-62 PTSM, a compound containing radioactive copper-62, is used as a radioactive marker in positron emission tomography (PET) for measuring blood flow in the heart.
• Copper-64 as a radioactive marker in positron emission tomography (PET) in medical imaging. Combined in a chelated complex, it can be used for the treatment of cancer by radiotherapy.

Applications in aquaculture

Copper alloys have taken an important place as materials used in nets in the aquaculture industry. What sets copper alloys apart from other materials is that they are antimicrobial. In a marine environment, the antimicrobial and algaecidal properties of copper alloys prevent biofouling. In addition to their antifouling properties, copper alloys exhibit structural and corrosion resistance properties in the marine environment. It is the combination of all these properties – antifouling, high mechanical and corrosion resistance – that make copper alloys materials of choice for nets and as structural materials in large-scale commercial fish farms.

Toxicology and role of trace elements in biology

Copper and especially its soluble salts are recognized as toxic and poisonous in consistent or high doses. At very low doses, it is a well-known trace element. The human body contains about 150 mg of copper in various forms, and the daily requirement is about 2 mg for a 75 kg person.

Food should not be stored in copper vessels or containers. Ancient wisdom reserved this metal with a clean surface for heating or heat transfer operations with sometimes catalytic effects sought, because operators knew the dangerousness of soluble and poisonous salts. A possible technical solution was tinning, i.e. the application of a thin layer of hot tin, for example to certain kitchen utensils. But in this case, the protected surfaces lose their catalytic properties.

The cupric ion Cu²⁺ is soluble in water, its aqueous solutions are a violent poison for microorganisms and even at low concentrations, it has a bacteriostatic and fungicidal effect, quite ephemeral, rarely multiannual. In some applications, this property is used to prevent the development of germs and fungi (sanitary water pipes, vine cultivation, boat hulls and woodwork, etc.).

It is also a vital trace element for all higher plants and animals. It is naturally present in the human body and essential for the proper functioning of many physiological functions: nervous and cardiovascular system, iron absorption, bone growth, proper functioning of immune functions and cholesterol regulation.

Toxicological study and precautions

Ecotoxicology

Copper, when present in the form of ions or certain bioavailable compounds can be ecotoxic even at low doses, especially for certain aquatic organisms, and on land for mosses and lichens, which is why it is used in many antifoulings and wood treatment agents used outdoors.

Risks to agriculture and livestock

Due to its algaecidal, bactericidal and antifungal properties, copper is also used as a pesticide for agriculture. In accordance with European Directive 2092/91, it can be used in organic farming in the form of copper hydroxide, copper oxychloride, copper sulfate and copper oxide. It is particularly used in organic viticulture in the form of a Bordeaux mixture to fight against late blight. This ancestral technique is effective, but must be reasoned: too intensive application can lead to an accumulation of copper in the soil and – in the long term – deteriorate its quality. For example, toxic effects have been observed in sheep grazing near vines. This mammal is one of the most sensitive to copper – among those whose reactions to copper have been studied: 15 mg of Cu per kg of food is the lethal threshold. The European Union has set the maximum copper content of organic soil at 150 mg/kg.

Grape must from organic viticulture may contain copper. This is removed from the wines by treatment with potassium ferrocyanide or sodium monosulfide which precipitates it to the state of sulfides eliminated with yeasts and lees.

Other problems related to the use of copper in too large quantities exist, for example in pig farming, where copper is sometimes used as a food supplement. The growth factor for the piglet in post-weaning, it is sometimes incorporated at levels up to thirty times higher than the needs of the animal. Such practices lead to an excessive concentration of copper in manure, which after spreading can then pose environmental problems (phytotoxicity phenomena could appear in the medium term in certain regions of intensive farming). Reducing copper intake in pork feed would be one way to reduce these environmental risks.

Risks to humans

For humans, copper ingested in very high doses, especially in its oxidized forms (green-grey, cuprous oxide, cupric oxide) or in often chronic forms of copper compound dust can be harmful. A few cases of prolonged exposure to copper resulting in health disorders have been observed. The INERIS Toxicological and Environmental Data Sheet for Chemical Substances on copper and its derivatives is freely available.

Acute poisoning is rare, as ingestion of large amounts causes violent reactions in the body, including vomiting. The old laboratory chemists, who could be confronted with some accidents, proposed counter-poisons more or less effective, such as the regulated ingestion of albumin (egg white diluted in water), zinc filings [sic] or iron powder reduced by hydrogen as a reducer, for metallic copper was not considered poisonous.

Contamination with copper dust and its compounds can cause a feverish malaise close to a viral disease or small flu, formerly known as “foundry fever”. With rest, the discomfort disappears in two days.

Long-term daily exposure to copper can cause irritation of the affected areas for particles or dust, mucous membranes, nasal cavity and mouth, not to mention the eyes. It causes headaches, stomach aches, dizziness, as well as vomiting and diarrhea. Voluntary intake of high doses of copper can cause irreversible damage to the kidneys and liver and lead to death.

It is an essential trace element for spermatogenesis (an abnormally low level of copper in seminal plasma is associated with oligospermia and azoospermia), but it can, like other metals, have an inhibitory effect on sperm motility. This is revealed by a study conducted in the 1970s on the following metals: copper, brass, nickel, palladium, platinum, silver, gold, zinc and cadmium).

Further work conducted in vitro in rats showed in the 1980s that prolonged inhalation of copper chloride could lead to non-reversible sperm immobilization in rats. The authors, from the Department of Veterinary Studies at the University of Sydney, note that this effect could explain the contraceptive efficacy of copper IUDs, in addition to the mechanical effect of the IUD that inhibits the contraceptive process in a human uterine environment. Another study shows that it is phagocytosis activated by leukocytes of the uterine cavity that would explain the effectiveness of copper IUDs.

A trace element essential for life

Copper is a trace element essential to life (humans, plants, animals, and microorganisms). The human body normally contains copper at a concentration of about 1.4 to 2.1 mg/kg. Copper is found in the liver, muscles and bones. Copper is transported through the bloodstream using a protein called ceruloplasmin. After absorption of copper in the intestine, it is transported to the liver, bound to albumin. The metabolism and excretion of copper is controlled by the supply of ceruloplasmin to the liver, and copper is excreted in the bile.

At the cellular level, copper is present in many enzymes and proteins, including cytochrome c oxidase and some superoxide dismutases (SODs). Copper is used for the biological transport of electrons, for example, the proteins “copper blue”, azurin and plastocyanin. The name “copper blue” comes from their intense blue color due to an absorption band (around 600 nm) by coordinated charge transfer/metal (LMCT). Many mollusks and some arthropods, such as horseshoe crab, use a copper-based pigment, hemocyanin, rather than hemoglobin, which has an iron core, for oxygen transport, and their blood is blue, not red, when oxygenated.

Various health agencies around the world have set daily nutritional standards. Researchers in microbiology, toxicology, nutrition and health risk assessment work together to precisely define the amounts of copper required by the body, avoiding copper deficits or overdoses. In France, the recommended dietary allowances (RDA) by the French Food Safety Agency are 1 mg/day for children up to 9 years of age, 1.5 mg/day for adolescents up to 19 years, and 2 mg/day for adults.

Excess and lack of copper

In humans and mammals, copper is particularly necessary for the formation of hemoglobin, it intervenes in immune function and against oxidative stress. Because it facilitates iron assimilation, copper deficiency can often give rise to symptoms similar to anemia. In some species, it even replaces iron for oxygen transport. This is the case of horseshoe crabs (arthropods) whose blood is blue, or some chironomids that are green.

Copper deficiency is also associated with decreased blood cell counts (cytopenia) and myelopathy. The deficiency is mainly seen after digestive surgery (including bariatric surgery and zinc overloads (zinc being absorbed competitively with copper by the digestive tract).

Conversely, an accumulation of copper in tissues can cause Wilson’s disease in humans.

Antibacterial properties

Since ancient times, the red metal has been used by humans for its health benefits, especially to treat infections and prevent diseases. Even before the discovery of microorganisms, the Egyptians, Greeks, Romans and Aztecs used copper-based preparations for their sore throats, rashes and for daily hygiene. In the nineteenth century, after the discovery of the causal link between the development of pathogenic germs and the declaration of diseases, many scientists became interested in exploiting the antibacterial properties of copper. Currently, copper is used by the pharmaceutical industry, in applications ranging from antiseptics and antimycotics to care and hygiene products (creams, ampoules of trace elements, etc.).

Although beneficial at low doses, Cu²⁺ can, however, like most chemical elements, be toxic to certain organisms at very high concentrations (cases of contamination were identified in the Bronze Age on human or animal skeletons near the old copper mines of present-day Jordan) or when combined with other materials such as lead (a such an association may increase the risk of Parkinson’s disease).

In March 2008, the U.S. Environmental Protection Agency (EPA) registered copper and its alloys as antibacterial agents capable of fighting the growth of certain bacteria responsible for life-threatening infections. Copper, bronze and brass are the first materials officially authorized to claim sanitary properties in the United States. This recognition is an important step for the use of copper as an antibacterial agent.

Construction

In the field of construction, the bacteriostatic and antifungal properties of copper, its corrosion resistance and impermeability also justify its use in water pipes, and in some countries, for roofs and gutters (neither moss nor plants settle there). Copper is the most widely used material worldwide for the distribution of sanitary water, and the one for which we have the most feedback, covering several decades of use. Copper pipes help prevent and limit the risk of contamination of water systems by certain bacteria such as legionella, which causes legionellosis, a fatal lung disease in 10% of cases. According to Professor Yves Lévi, Director of the Public Health and Environment Laboratory, Paris-Sud 11 University: “While no material can guarantee the total absence of bacteria in networks, copper nevertheless makes it possible to limit the risks.”

Antifouling paints

The antibacterial properties are at the origin of another application: the so-called “antifouling” paints, or anti-fouling, which are covered on the hulls of boats. This prevents the proliferation and attachment of algae and marine microorganisms that slow down boats and increase the risk of corrosion. Pure copper is the main active component of these paints (up to two kilograms of copper powder per liter). Now used for most ships, they have replaced the copper foils that were once nailed to the submerged parts of ships’ hulls and had the same effect. Invented by the Phoenicians, this technique had been generalized at the end of the eighteenth century by all shipyards. In the navy, copper and its alloys (bronze or brass) are also used for their corrosion resistance (nails, portholes, fittings, propellers).
The same principle is sometimes applied to protect roofs: a simple copper wire stretched on the ridge of a roof prevents the appearance of mosses or algae that could grow there.

Contact surfaces

Since 2007, a new application of the future has emerged in several countries around the world: the use of copper contact surfaces (door handles, flush pulls, bed bars) in hospitals to reduce the risk of nosocomial infections.

In January 2010, St Francis’ Private Hospital in Ireland was fitted with copper door handles in an effort to limit the risk of hospital-acquired infections. This is the first time that a healthcare facility will exploit the antibacterial properties of copper to guard against this type of infection and increase patient safety. The very promising results of laboratory and field studies conducted in Great Britain since 2007 on the antibacterial potential of the red metal are at the origin of the decision of the hospital’s leaders. The results of the Birmingham Hospital experiment show that copper surfaces can eradicate 90 to 100% of microorganisms such as methicillin-resistant Staphylococcus aureus (MRSA) in hospitals.

In France, it was the intensive care and pediatrics department of the Rambouillet public hospital that first tested this metal to fight against nosocomial diseases (on door handles, bed bars, handrails, cleanliness plates).

At the 25^th Congress of the French Society of Hospital Hygiene, the Amiens Hospital Center publicly revealed the results of an experiment confirming the effectiveness of copper against bacteria in hospitals. According to the results of this experiment, copper significantly reduced the presence of bacteria in the neonatal department of the University Hospital of Amiens.

The Arago Clinic, a Parisian health facility specializing in orthopedic care, located within the walls of the Saint-Joseph Hospital in Paris, has installed door handles and handrails in copper to prevent nosocomial diseases.

But the high cost of raw materials quickly becomes a brake for health facilities. The French company MétalSkin then developed a coating process made of recycled copper powder mixed with resin. A test, carried out in 2013 at the Saint-Roch clinic in Montpellier, proved conclusive. This coating can divide the number of bacteria by 3,000 in an hour. The soluble shape of this coating makes it possible to widen the supports on which it can be applied. Thus, computer keyboards or mice, laptop cases and all surfaces potentially spreading bacteria can be treated to become self-decontaminating.

Antibacterial standards

Initially, ISO 22196 (the international version of Japan’s JIS Z 2801) defined the measurement of antibacterial action on plastic and other non-porous surfaces. But very quickly, the measurement protocol found itself too far from the real conditions of the field.

In 2016, a study on the normative reference system is conducted and Afnor creates a standardization commission, bringing together various experts, such as the National Agency for Food, Environmental and Occupational Health and Safety, microbiologists or specialists in regulations and materials. In May 2019, the NF S90-700 standard was created. The S90-700 standard on the measurement of the basic activity of non-porous surfaces requires that, on four distinct strains, a mortality of 99% be observed in one hour (division by 100 or 2 logs) with each of them.

Copper production and economy

Copper is the third most used metal in the world after iron and aluminum. It is the second most important non-ferrous metal, far ahead of zinc, lead, nickel or tin.

Copper mine production increased twentyfold between 1900 and 1990, then doubled again between 1990 and 2019, reaching 20.3 Mt. World production of refined copper exceeds 18 Mt. Total global consumption of copper (refined primary copper plus recycled copper) more than doubled between the early 1970s and 2008 to 23.5 Mt. In 1990, for a recorded annual world consumption of 8.5 Mt, 470 kt in France. About 70% of the copper metal marketed at that time was in its pure state in the form of electrical wires, tubes, laminates, and the rest in the form of alloys.

The strong correlation of copper with industrial conditions makes the copper market study an excellent leading indicator of the state of the economy.

Mining production

Annual copper mine production has increased sharply since the beginning of the twentieth century, from 0.5 Mt in 1900 to 11 Mt in 1990, then 15 Mt in 2008, and 20.3 Mt in 2019.

The top eleven producing countries in 2019 accounted for 73.7% of this production: Chile, Peru, China, the United States, the Democratic Republic of Congo, Australia, Zambia, Mexico, Russia, Kazakhstan and Indonesia. Four of the ten largest copper mines in the world were located in Chile (Escondida, Collahuasi, El Teniente, Chuquicamata) and three in Peru (Cerro Verde II, Antamina and Las Bambas).

According to the webzine Illuminem, the top producers are companies incorporated in the UK, followed by companies incorporated in Chile, the US and Mexico, while China ranks fifth in economic control of copper mines.

Copper production
Rang	Country	Production 2020 (kt)	% global
1	Chile	5,700	28.5
2	Peru	2 200	11.0
3	China	1,700	8.5
4	USA	1 200	6.0
5	Democratic Republic of the Congo	1 300	6.5
6	Australia	870	4.4
7	Zambia	830	4.2
8	Mexico	690	3.5
9	Russia	850	4.3
10	Kazakhstan	580	2.9
11	Canada	570	2.9
12	Indonesia	380	1.7
	autres	370	18.5
World		20 000	100

Production is struggling to keep up with the strong growth in demand, due to the needs of the energy transition. The first obstacle is the structural decline in grades: according to a report by the “Bureau de Recherches géologiques et minières (BRGM)”, the average concentration of copper in operating mines is 0.62%. In recently opened sites, it does not exceed 0.53% and for projects under study, it falls to 0.43%. The second challenge is the impact of mines on the environment, particularly due to water use, which has become highly problematic for many mines located in areas of high water stress. The opposition of local populations is growing: it is one of the causes of the victory in 2021 of the left-wing parties in Peru or Chile.

Russia began in 2022 to exploit the Novaya Chara copper mine, in northern eastern Siberia, which would be the third largest deposit in the world, with reserves of 26 Mt and a high grade (more than 1%), according to its operator Udokan Copper, which plans to start by producing 160 kt of copper per year to rise, Eventually, at 400 kt.

Copper has been used for at least 10,000 years, but more than 95% of all copper ever mined and smelted has been mined since 1900. As with many natural resources, the total amount of copper on earth is significant (about 10¹⁴ t in the first kilometer of the earth’s crust, corresponding to about five million years of the reserve at the current rate of extraction). However, only a small part of these reserves are economically viable, given current prices and technologies. Various estimates of copper reserves available for mining range from 25 to 60 years, depending on initial assumptions, such as copper demand.

The price of copper, one of the measures of the availability of copper supply in relation to world demand, has increased fivefold over the past sixty years; low in 1999, from USD 0.60 per pound (USD 1.32/kg) in June 1999 to USD 3.75 per pound (USD 8.27/kg) in May 2006, and falling from that date to USD 2.40 per pound (USD 5.29/kg) in February 2007; it then rose to USD 3.50 per pound (USD 7.71/kg = £3.89 = €5) in April 2007.
In early February 2009, however, weakening global demand and a sharp drop in commodity prices from the previous year’s high values brought copper prices down to USD 1.51 per pound.

The Intergovernmental Council of Copper Exporting Countries (CIPEC), which has been defunct since 1992, once tried to play the same role as OPEC for oil, but it has never wielded the same influence, especially because the second largest producer, the United States, has never been part of it. Established in 1967, its main members were Chile, Peru, Zaire and Zambia.

World reserves

The world’s estimated copper reserves amounted to 2.1 billion tonnes in 2019, with an additional 3.5 billion tonnes undiscovered (average estimate) spread across eleven regions of the world. Thirteen countries account for 75% of the identified reserves: 23% in Chile, 10% in Peru, 10% in Australia, 7% in Russia, 6% in the United States, 6% in Mexico, 3% in China, 3% in Kazakhstan, 3% in Indonesia, 2% in Zambia, 2% in the Democratic Republic of Congo.

The largest copper reserves in the world in 2020
Country	Million tons
Chile	200
Australia	93
Peru	77
Russia	62
Mexico	53
USA	48
Democratic Republic of the Congo	31
Indonesia	24
China	26
Zambia	21
Other countries	180

Major copper mines

The twenty largest mines account for more than 40% of world production. The Escondida mine in Chile, in particular, alone produces more than 1.2 million tonnes of copper per year. Of these 20 mines, 14 entered production in the twentieth century, including 6 before 1975.

The twenty largest copper mines
No	Name	Country	Overture	Scheduled shutdown	Owner
1	Escondida Mine	Chile	1990	2076	BHP Group, Rio Tinto, Mitsubishi
2	Collahuasi mine	Chile	1989	2081	Glencore, Anglo-American, Mitsui
3	Grasberg Mine	Indonesia	1972	2041	Freeport-McMoRan, Government of Indonesia
4	Rudna mine	Poland	1966	2040	KGHM Polska Miedź
5	Cerro Verde mine	Peru	1976	2053	Freeport-McMoRan, Sumitomo
6	El Teniente mine	Chile	1917	2083	Codelco
7	Antamina mine	Peru	2001	2028	Glencore, BHP Group, Teck Resources, Mitsubishi
8	Morenci mine	USA	1987	2045	Freeport-McMoRan, Sumitomo
9	Buenavista mine	Mexico	1991	20??	Southern Copper, a subsidiary of Grupo México
10	Las Bambas Mine	Peru	2015	2036	MMG Limited
11	Los Bronces Mine	Chile	1925	2048	Anglo American plc,Mitsubishi
12	Los Pelambres mine	Chile	1999	2038	Antofagasta PLC
13	Norilsk mine	Russia	1939	2037	Nornickel
14	Radomiro Tomic mine	Chile	1998	2044	Codelco
15	Chuquicamata Mine	Chile	1915	2057	Codelco
16	Kansanshi Mine	Zambia	2005	2042	First Quantum Minerals
17	Sentinel Mine	Zambia	2015	2034	First Quantum Minerals
18	Mount Isa mine	Australia	1990	2026	Glencore
19	Antapaccay Mine	Peru	2012	2029	Glencore
20	Toromocho mine	Peru	2015	2051	Aluminium Corporation of China

Request

Due to its multiple properties (thermal and electrical conductivities, corrosion resistance), copper has become an essential metal in modern societies. It is commonly used in the manufacture of electrical cables and wires, in plumbing, in electronic equipment (printed circuit boards, electronic chips), in the transportation sector (braking systems, injection systems, etc.), in buildings and for the manufacture of coins. Its demand is set to grow strongly as an essential material in the context of the energy transition. Electric vehicles consume nearly four times more copper than those with internal combustion engines and copper requirements per megawatt are much higher for hydroelectricity, solar and wind than for nuclear or fossil fuel plants: an onshore wind turbine requires nearly 5 t/MW of copper and rooftop photovoltaic panels nearly 11 t/MW compared to about 1.5 t/MW for nuclear and 1 t/MW for a gas-fired power plant.

Recycling

In the modern world, recycling is one of the main sources of copper. As a result, as well as other factors, the future of copper production and supply is the subject of much debate, including the concept of peak copper, analogous to peak oil.

Copper, because of its chemical stability, lends itself particularly well to recycling, because unlike many other raw materials, it is infinitely recyclable, without alteration or loss of performance. The recycling process saves up to 85% of energy compared to the production of copper via its waste. On the other hand, recycling emits fewer greenhouse gases. “The production of cathodes from recycled copper alone saves nearly 700,000 tonnes of CO₂ each year.”

In 2008, 2.5 million tonnes of recycled copper were used in Europe, or 43% of the total use over the period according to the ICSG. In the early 1990s, one-third of the copper consumed in Western Europe already came from recycled copper, either through the refining stage or through the direct manufacture of semi-finished products (rolled or copper tubes, brass bar, etc.).

Recycling comes from two sources:

• the revalorization of “secondary copper” from products that have reached the end of their life cycle, which are recovered, sorted and whose copper can be remelted;
• the direct reintroduction of factory scraps into the production process (also known as “redesign of new scraps”).

Applications with the highest proportions of copper and the highest recycling potential include cables, piping, valves and fittings, copper roofing and cladding, industrial engines, household equipment, and computer and electronic equipment.

The steady increase in demand, up 134% since 1970, combined with significant fluctuations in the price of the raw material, make copper recycling an indispensable complement to primary production. In addition to the environmental argument, the availability of recycled copper at competitive prices is now an economic necessity and an essential part of the copper value chain.

Some economic data

• At the beginning of 2022, the price of copper was around €9,000/t, up sharply compared to 2020, with its price oscillating between €4500 and €6500/t between 2012 and 2020.
• The most important copper-producing companies are the Chilean national company Codelco, then the American Freeport-McMoRan, the Anglo-Australian Rio Tinto and the Anglo-Swiss Xstrata.
• Copper, its futures and options are traded on three metal exchanges around the world: the London Metal Exchange (LME), the Comex, the New York Mercantile Exchange, and the Shanghai Metal Exchange (SHME). In London, copper is traded in 25 t lots and quoted in US dollars per tonne. In New York, it is traded in lots of 25,000 pounds and quoted in U.S. cents per pound. In Shanghai, it is traded in lots of 5 t and quoted in yuan per tonne.
• Following the 2008-2009 crisis, copper, which was trading at $9,000/t in July 2008 in London, plunged to a low of $2,800/t in late 2008, then recovered 140% in 2009 and reached $8,501/t in October 2010.
• Primary recycling gained 20% in five years worldwide, then fell by 2.6% following the 2008 crisis (compared to 2007), due to a smaller overhaul of “new scraps”.
• Secondary recycling increased by 3% in 2008 worldwide (+49% from 2002 to 2008) (for 23.5 Mt used worldwide in 2008, which corresponds to consumption that has increased by 140% since 1976, the need has increased by 140%. 2 Mt were recycled in 2005, i.e. 13% of the total production of this metal.
• Scrap dealers participate fully in recycling by buying old metals and scrap metals from individuals and businesses. In 2015, the price of copper on redemption varies from 4 to 5 € / kg in France.
• Europe (including Russia) would be the world’s largest user of recycled copper, with more than 40% of its consumption, and would be the region where the proportion of recycled copper increased (from 41.3% in 2007 to 43% in 2008), with 2.5 Mt of recycled copper used in 2008.
• The latest figures indicate, according to the ICSG, that more than a third of global needs and 42% of European needs came from recycling in 2009. This rate even reaches 70% in construction. China is the largest producer of secondary recycling copper.
• From 1967 to 1988, the major copper-producing countries formed a consortium: CIPEC. Created and dissolved at the initiative of Chile, the Intergovernmental Council of Copper Exporting Countries (CIPEC) accounted for about 30% of the world copper market, and more than 50% of the world’s known reserves.
• In 2020, Europe is an exporter of copper, according to the Directorate General of Customs and Indirect Taxes; The average export and import price was €2,232 and €5,598/t.
• In May 2021, the price of copper reached a record high with a tonne trading at more than $10,300 on the London Metal Exchange (LME), driven by the recovery from the Covid-19 pandemic in 2020.

History of Copper

Neolithic

Copper is, along with gold, the first metal to have been used by man, as early as the V^th millennium BC, because it is one of the few metals that are naturally found as a pure mineral, in a native form. It is likely that gold and meteoric iron were the only metals used by humans before the discovery of copper. As such, he is widely studied in archaeometallurgy.

At the site of Tell Qaramel in Syria, a polished copper nugget transformed into an ornamental pearl dating from the X^th millennium BC, was found and is the oldest copper coin known to archaeologists.

In the Balkans, archaeologists commonly find pingen or mining pits 20 to 25 m deep to extract copper whose excavation from the surface can be dated before the IV^th millennium BC The grain of a copper necklace, unearthed in Greece, dates back to 4700 BC. But objects from the surroundings of ancient Mesopotamia or present-day Iraq dating from the IX^th millennium BC have also been uncovered.

Traces of copper smelting have been found, due to the refining of copper from simple compounds such as azurite and malachite, dating from about 5,000 BC. Among the archaeological sites in Anatolia, Çatal Höyük (circa 6000 BC) contains copper artifacts and layers of molten lead, but not molten copper. The oldest molten copper artifact discovered (a copper chisel from the Chalcolithic site of Prokuplje, Serbia) dates from 5500 BC A little later, the people of Can Hasan (about 5000 BC) left traces of the use of molten copper.

The metallurgical sites of the Balkans seem to have been more advanced than those of Anatolia. It is therefore quite likely that the copper smelting technique originated in the Balkans.

Lost wax casting was also used around 4500 to 4000 BC in South-East Asia.

As for the beginnings of mining, mining sites at Alderley Edge in Cheshire, UK, have been carbon-14 dated back to 2280 and 1890 BC.

Copper metallurgy seems to have developed independently in several parts of the world. In addition to its development in the Balkans around 5500 BC, it had developed in China before 2800 BC, in the Andes around 2000 BC, in Central America around 600 BC and in West Africa around 900 BC. It is found systematically in the Indus Valley civilization during the III^rd millennium BC. In Europe, Ötzi, a well-preserved male mummy dating from the Chalcolithic period (4,546 ± 15 years BP before calibration) was found accompanied by an axe iron made of 99.7% pure copper. High concentrations of arsenic found in his hair suggest that he was working on copper smelting. Over the centuries, the experience gained in copper metallurgy has helped the development of that of other metals; For example, knowledge of copper smelting techniques led to the discovery of iron smelting techniques.

On the American continent, production in the Old Copper Complex, located in present-day Michigan and Wisconsin, dates from about 6000 to 3000 BC. Some books claim that ancient American civilizations, such as the Mound Builders, knew a method of copper quenching that has still not been rediscovered. According to historian Gerard Fowke, there is no evidence of such “lost know-how” and the best-known technique for hardening copper at that time was threshing.

Copper Age

The distant surroundings of the island of Cyprus attest before this period to an important trade in copper extracted from the island.

In Western Europe, the Copper Age or Chalcolithic, between about 3200 and 2000 BC, is located, depending on the region (Italy, Switzerland, Alps, Cevennes, Spain and Portugal). This technological period is much older in the eastern Mediterranean. Copper objects dating back to 8700 BC were found in the Middle East. This is the case of a copper pendant found in the north of present-day Iraq.

The transition period, in some areas, between the previous period (Neolithic) and the Bronze Age has been named “Chalcolithic” (“copper-stone”), with some very pure copper tools being used at the same time as stone tools.

Bronze Age

The artificially alloying of copper with tin or zinc, first by processing their intimately associated ores, then by processing a refined mixture of selected ores, then by smelting metals already previously obtained and weighed, to obtain, according to our modern conception, bronze or brass is practiced 2,300 years after the discovery of copper itself. This brought early the peoples of Central Europe to a mastered art of hammering large bronze leaf.

Copper and bronze artifacts from Sumerian cities date back to 3000 BC, and Egyptian copper and copper-tin alloy objects are about as old. The use of bronze spread so much in Europe around 2500 to 600 BC that this period has been called the “Bronze Age”. Bronze ingots are probably used as monetary units in the Mediterranean world. As copper ore, although not abundant, but sometimes concentrated in certain sites, is not uncommon, the control of tin resources, which are much rarer and with restrictive places of exploitation, has become crucial. Hence the search by merchants and sailors-negotiators for legendary lands or islands called Cassiterides.

In the thirteenth, merchant ships, not devoid of watertight decks, often transported more than two hundred bronze ingots to the eastern Mediterranean.

Antiquity and Middle Ages

In Greece, the name given to this metal was chalkos (χαλκός); according to Pliny the Elder according to Theophrastus, casting copper and soaking it are inventions of a Phrygian named Delas. Copper was an important resource for the Romans, Greeks and other ancient peoples. In Roman times, it was known as aes Cyprium (aes being the generic Latin term for copper alloys such as bronze and other metals, and cyprium because, since most of it came from Cyprus, The Hellenic world thus designated this reddish metal and its notable compounds.

Then, this term was simplified to cuprum, hence the English name copper. In mythology and alchemy, copper was associated with the goddess Aphrodite (Venus), because of its brilliant brilliance, its ancient use for the production of mirrors, and its association with Cyprus, an island dedicated to the goddess. In astrology and alchemy, the seven celestial bodies known to the ancients were associated with seven metals also known in antiquity, and Venus was associated with copper.

Brass

Brass (copper-zinc alloy) was also known nominally to the Greeks, but only significantly supplemented bronze during the Roman Empire. The first known use of brass in Britain dates from the III^rd to the II^nd century BC In North America, copper mining began with marginal metallurgy practiced among Native Americans. It is known that native copper was mined from sites on Isle Royale using primitive stone tools between 800 and 1600. The copper industry was flourishing in South America, especially Peru, around the beginning of the first millennium AD.

Copper technology has progressed more slowly on other continents. The largest copper reserves in Africa are located in Zambia. Copper funerary ornaments dating from the fifteen century have been discovered, but commercial production of this metal did not begin until the early twentieth century. There are Australian copper artifacts, but they do not appear until after the arrival of Europeans; Aboriginal culture does not seem to have developed its metallurgy. Vital to the metallurgical and technological world, copper has also played an important cultural role, especially in currency.

The Romans, between the VI^th and the III^rd century BC, used pieces of copper as currency. At first, only the value of copper itself was taken into account, but gradually, the shape and appearance of copper money became preponderant. Julius Caesar had his own coin, made of a copper-zinc alloy, while the coins of Octavian were made of Cu-Pb-Sn alloy. With an estimated annual production of about 15,000 tons, Roman activities in terms of copper mining and metallurgy had reached a scale that was only exceeded at the time of the Industrial Revolution; the provinces with the highest mining activity were Hispania, Cyprus and Central Europe.

The doors of the Temple in Jerusalem were made of Corinthian bronze, obtained by gilding by impoverishment. Corinthian bronze was prized in Alexandria, where some believe alchemy originated. In ancient India (before 1000 BC), copper was used in Ayurvedic holistic medicine for the manufacture of surgical instruments and other medical equipment. The ancient Egyptians (circa 2400 BC) used copper to sterilize wounds and drinking water, and later (circa 1500 BC) to treat headaches, burns, and pruritus. Hippocrates (circa 400 BC) used copper to treat varicose leg ulcers. The ancient Aztecs fought throat damage by gargling composed of various copper-based mixtures.

Copper is also present in some legends and stories, such as that of the “Baghdad Pile”. Lead-soldered copper cylinders dating back to 248 BC by 226 AD, look like battery elements, leading some people to speculate that it may have been the first pile. This claim has not yet been confirmed.

The Bible also alludes to the importance of copper: “There are mines for silver, for gold, places where it is purified. Iron is drawn from the ground, molten stone delivers copper. (Job 28:1–2) [Jerusalem Bible translation].

A bronze statue of a temple in Nara, Japan, representing a large Buddha, would represent a casting fabrication, in 749, almost 16 meters high and involving 400 tons of material.

In 922, the copper mines of Saxony, especially the Frankenberg sector, made the prosperity of the line of Henry, Saxon ruler of the Kingdom of East Francia.

The carburizing manufacturing, known since Antiquity, was maintained in the Middle Ages.

Modern era

Falun Great Copper Mountain was a mine located in Sweden, which operated for a millennium, from the X^th century to 1992. In the seventeenth century, it produced about two-thirds of European needs and at that time made it possible to finance part of the wars led by Sweden. Copper was considered a national treasure; Sweden had a (paper) currency backed by copper.

Throughout history, the use of copper in art extended far beyond money. It was used by Renaissance sculptors, in the pre-photographic technique known as daguerreotype, and for the Statue of Liberty. Copper plating and lining of ship hulls was widespread. Christopher Columbus’ ships were among the first to benefit from this protection. The Norddeutsche Refinery in Hamburg was the first electroplating plant, whose production began in 1876. The German scientist Gottfried Osann invented powder metallurgy and applied it to copper in 1830 by determining the atomic weight of this metal. In addition, it was also discovered that the type and amount of alloy metal (e.g. tin) affected the sound of the bells, resulting in the casting of bells. Flash melting was developed by Outokumpu in Finland and was first applied at the Harjavalta plant in 1949. This energy-efficient process provides 50% of the world’s raw copper production.

A fraction of rural communities, often at the origin of the Gallo-Roman fundi, specialized in metalworking, especially for copper cauldrons and utensils sold at the spring and autumn fair. Thus, the Museum of Durfort in the Black Mountain recalls this activity.

Fugger bankers and financiers built a market monopoly on copper resources around the 1500s. At that time the guns were mainly cast in bronze.

Contemporary era

At the end of the nineteenth century, the suboxide Cu₂O and the carbonate CuCO₃ are minerals massively exported to Europe by Peru, Chile and the Russian Urals. France in the movement of the Anglo-Saxon maritime economy prefers to import from Latin America, Peru and Chile. These ores are processed in the vicinity of the receiving ports, by smelting with coal in tank furnaces. The reaction to obtain more or less impure copper metal, sometimes called “rosette copper”, involves the release of carbon dioxide.

Cu(CO₃· Cu(OH)_{2 ore or green-grey} + C _charcoal → 2 Cu _{impure metal} + 2 CO_{2 gas} + H₂O _{water vapor}

This is an easy way, because the other category of very abundant and even less expensive ores, such as chalcosine Cu₂S or chalcopyrite or copper pyrite based on double sulfide of copper and iron, Cu₂S.Fe₂S₃ requires a long treatment due to the persistence of S and Fe (sometimes Ag) Il

Partial oxidation of the chalcosine ore stock is required.

Cu₂S _{sulphide ore} + O_{2 gas of air} → 2 Cu₂O _{cuprous oxide}

A high-temperature melting of the mixture is then required, requiring heavy heating.

2 Cu₂O _{copper oxide} + Cu₂S _{sulfide ore} → 6 Cu _{impure black copper (Fe, Ag) (partly sulfide)} + SO_{2 gas}

The exporting countries of these sulfur copper ores are England, Germany, Mexico, Chile, China and Japan. The mines of Chessy and Saint-Bel, near Lyon, in the Rhône department, extract this type of ore.

Le sou de 1900, a twenty-cent coin of the French Republic, is a copper coin with holes. Even in 1990, the US cent or the coin of one or two pfennigs is based on copper.

In the sociological and economic world, copper has proved to be a crucial element, mainly because of conflicts involving copper mines. The Cananea strike of 1906 in Mexico City was about the problems of a world organization. The Teniente copper mine (1904–1951) highlighted the political problems of capitalism and class structure. Japan’s largest copper mine, the Ashio Mine, was the scene of a riot in 1907. The Arizona miners’ strike in 1938 was triggered by American labor problems, including the right to strike.

The industrialist Eugène Secrétan is an actor-inventor and witness of the evolution of industrial copper techniques.

The French term for a factory of copper and common copper alloys, such as maillechort, is “cuivrerie”. For example, the Cerdon copper works in Ain.

In the XXI^th century

In the twentieth century, copper is used in different industries, including electrical cables, plumbing pipes and superconductors.

Alchemical symbolism

Traditionally, copper is associated with the planet Venus. Alchemists used the symbol ♀ to represent it. It is therefore a metal associated with femininity, youth and love. Ancient mirrors, a symbol of narcissism, were made of copper.

Regionalism

• In Quebec, a commonly used term for copper is coppe, a francization of English copper. The industrial past of this province of Canada has led factory workers to appropriate certain industrial terms. Richard Desjardins, Quebec singer, refers to it in the song Et j’ai couché dans mon char. He then highlights the variations in the price of copper in the years 1970-1980 in North America: the gang is splitted, it was only a time. Its value has fallen, as has the price of the coppe.
• In the Hispanic world and especially in South America, the expression “sin un cobre” (literally “without copper”) is used. The use of the expression is found in some coins of little value that were made of copper.

Calendar

In the Republican calendar, Copper was the name given to the 24th day of the month of Nivôse.

References (sources)

USGS National Minerals Information Center, « Mineral Commodity Summaries 2020 »; Jaiser S.R. et Winston G.P., Copper deficiency myelopathy, J. Neurol., 2010; Cuivre, Wikipedia; Cuprum Copper; « En pleine Sibérie, le cuivre promet d’être le « nouveau pétrole » russe », Les Échos, 2022.