Element Copper, Cu, Transition Metal

Between the metals of the new group, which is called after copper, and those of the former groups, many points of relationship exist. The circumstance that most of the heavy metals can form several series of compounds, i.e. ions of different valency, causes a crossing and interweaving of these mutual relationships which render it impossible to draw up a simple list of the elements in such a way that the most nearly related always stand together. For indeed, on following out one of the existing series, other ones must be interrupted; for the sum of these mutual relationships cannot be represented by means of a straight line, but only as a much-branched river system, or still better perhaps, as an arterial system exhibiting manifold anastomosis.

Thus in copper we have, on the one hand, a metal which in certain compounds shows itself to be related to the elements of the magnesium and iron series, while other compounds exhibit close relationships to silver and mercury. We have already frequently met with such ambiguity of behaviour, e.g. in the case of iron, and especially of manganese; it points to the fact that a systematisation of the chemical elements according to a single scheme is impossible, for a really exhaustive system must necessarily contain all the existing relationships, and must, therefore, be of such a form that these diversities receive adequate expression. The satisfactory solution of this problem has not as yet been attained, and we must at the present time get over the difficulty by pointing out, when necessary, the various relationships existing.

Of the heavy metals already discussed, copper is the first that is found in any considerable quantity in the metallic state on the earth, and it belongs, therefore, together with silver and gold, to the metallic elements which have been longest known. It is distinguished from all other metals by its bright red colour, which, however, is seen only on fresh surfaces. Even in a very short time these become covered with a dark coating of oxygen or sulphur compounds, which although it does not destroy the metallic lustre, changes the rose-red colour of the pure metal into the brown-red, which is usually called copper-red.

Copper melts at 1050°, has the density 8.9, and is, at the ordinary temperature, a tenacious metal which can be mechanically moulded, and which resists well the influences of the atmosphere and of moisture. On being exposed for a lengthened period to moist air, it is true, it becomes covered with a layer of oxygen compounds this, however, remains very thin, and effectually protects the metal underneath. At a red heat copper combines fairly rapidly with oxygen to form a black, brittle oxide, which readily breaks off in scales and exposes the underlying metal to fresh attack.

On account of its chemical resistibility, its good mechanical properties, and its melting point, copper is largely employed for utensils of all kinds. Another very extended sphere of application of copper depends on its great conductivity for the electric current. In this respect it is superior to all other accessible metals (silver is alone superior to it), and very large quantities of it are therefore employed in electro-technics. For this purpose it must be very pure, since the conductivity is greatly lowered even by very small amounts of foreign metals.

Besides being used in the pure state, copper is also extensively employed for alloys. Brass has already been mentioned; others will be given later.

Pure copper, or an alloy with tin in the form of bronze, appears to have been known for at least 7000 years. The metal was probably familiar to the Chaldeans before the year 5000 b.c., and seems to have been worked by the Egyptians about the same period, since Egyptian copper tools supposed to date from about the year 4400 b.c. have been discovered. The copper mines of the Sinai Peninsula were extensively worked by the Egyptians about the year 3700 b.c.

About the year 1500 b.c. bronze containing between 5 and 16 per cent, of tin was without doubt extensively employed in Egypt. Copper vases of Cyprian origin dating from the same period have been found in Egypt. The metal employed in their manufacture was free from tin. The great metallurgical skill possessed by the makers of these vessels proves that copper must have been known in Cyprus for many centuries previous to their production.

Copper daggers found in Northern Italy probably date from about the year 2100 b.c. Keith gives the date 2000 b.c. for the beginning of the Bronze Age in Britain, five centuries later than the date suggested by Montelius. Copper was probably known in China about the year 3000 b.c. There is evidence of its having been worked in India at an early period.

The association of the ores of copper with those of other metals is probably the cause of the production of alloys of varying composition by the prehistoric smelters. The earliest copper tools of Britain contain tin; those of Hungary up to 4.5 per cent, of antimony.

Chinese and Japanese bronze mirrors dating from the first, fifth, seventh, eleventh, and twelfth centuries have been found to contain between 62 and 74 per cent, of copper associated with other metals. A Corean mirror of the tenth century contains 73 per cent, of copper, and considerable proportions have been found in ancient coins, arrow-heads, and water-pots from these lands.

Copper deposits in Britain are said to have been known to the Phoenicians about the year 1000 b.c. In 1581 mining was being carried on at Keswick, in Cumberland, the ore being probably a sulphide. The Mines Royal Society established a works for copper-smelting at Neath, in Wales, in 1584. Various other works were started in Wales at different times, notably those erected by Lane and Pollard at Swansea in 1717.

The production of copper in Cornwall and Devon continued from the time of Queen Elizabeth to the end of the nineteenth century. In Ireland the industry was carried on from the beginning of the eighteenth century until 1880. The copper of Anglesey was known to the Romans, and the mines of the island were worked during the eighteenth and nineteenth centuries.

Reverberatory furnaces were constructed by Lambert in Chile in 1842, and the first blast furnace was erected by him in that country in 1857. So successful was the development of this enterprise, that Chile became the world's largest producer in the years 1861 to 1870, and furnished about half the total output. The decline of the Welsh industry dates from this period, and also the development of the manufacture in the United States of America, Calumet, in the Lake Superior district, becoming an important centre. The next decade is noted for the inception of copper-mining in Spain and Portugal, the chief centres being the Andalusian, San Domingo, Tharsis, and Rio Tinto mines.

Between 1881 and 1890 the United States of America became the greatest producer, manufacturing one-third of the world's output. In

addition to the Lake mines, works were begun in Montana and Arizona.

Spain and Portugal continued to prosper, and under Gowland's influence Japan also entered the field of competition. Simultaneously, the Chilean output began to decline.

In 1800, 75 per cent, of the world's production of copper came from Great Britain. In 1913 the British output had fallen to 6 per cent., and that of the United States of America had risen to 55 per cent. During the same period the total annual production increased a hundredfold, from 10,000 to 1,000,000 tons.

The last ten years of the nineteenth century witnessed the establishment of complete supremacy by the United States of America, more than half the total output being produced there. During the present century that country has further improved its position, the production for the year 1916 being estimated at 865,000 long tons.

The name of the metal is derived from the Latin cyprium, Cyprus, that island having constituted the chief source of the copper employed by the Romans. Later, the name changed to cuprum, from which the word copper is derived.

Copper is contained in liver in significant amounts 0.0004 mg per 100 g of body weight; and the blood of a grown-up human being contains 0.001 mg/l of copper. Copper plays essential role in haematogenesis and enzymatic oxidation. It is a constituent part of some enzyme molecules such as lactase and oxygen in the blood of most mollusks, and some arthropods such as the horseshoe crab, and are responsible for oxygenation causing a color change, contain 0.15 - 0.26% copper.

Plants also need copper. It is one of the most important microelements; copper plays significant roles in photosynthesis process and it is necessary for nitrogen fixation. The copper deficiency in soils causes plants sterility. Copper fertilizers contribute to the processes of aluminium and only one 600^th of iron's. Native copper is one of the few metals to naturally occur as an uncompounded mineral. However it is a constituent part of 200 minerals, some of which have bright vivid colours. Bornite Cu₅FeS₄ and azurite Cu₃(OH)₂CO₃ are blue, chalcopyrite CuFeS₂ has a golden yellow color; the Malachite Room in the Hermitage in St. Petersburg in Russia which features malachite decorations and, especially, malachite coupe and malachite vases.

Great quantities of minerals with a large proportion of combined copper are widely distributed over the earth's surface. Examples are cuprite or ruby copper, Cu₂O (United States and Australia); melaconite or tenorite, CuO (United States); malachite, CuCO₃,Cu(OH)₂ (North and South America, Australia, and the Urals); azurite or chessylite, 2CuCO₃,Cu(OH)₂ (Chessy in France, the Urals, Siberia, and North America); chalcopyrite or copper pyrites, Cu₂Fe₂S₄ (Cornwall, Devonshire, Wales, Ireland, Canada, Newfoundland, Australia, United States, France, Germany, Austria, Hungary, Sweden, Norway, and South America); bornite, horse-flesh ore, or peacock ore, Cu₃FeS₃ (Cornwall, Montana, Saxony, and Chile); chalcocite or copper glance, Cu₂S (United States); covellite or indigo copper, CuS (Serbia and Chile); atacamite, CuCl₂,3Cu(OH)₂ (Chile and Peru); chrysocolla, CuSiO₃,2H₂O (Chile and the Urals).

Sulphide ores and copper sandstones are the main sources of copper production. However all rich deposits are already exhausted. Nowadays copper is recovered from low-quality rocks which contain less than 1% of the metal.