COPPER, in the arts, seems to have been known in the remotest periods of antiquity. It is among the first me tals which was employed by the early nations of the world; it is not one of the scarce metals, is easily extracted from its ores, and not difficult to work. The Egyptians applied it to a great variety of uses, as it appears from the earliest pe riod of their history. The Greeks were acquainted with the mode of working cop per, and employed it in many of the arts. It was the basis of the celebrated Corin thian metal. The Romans knew the uses of this metal, and it is generally supposed that of it they fabricated the greatest number of their utensils. The alloys which they made with copper, after the example of the Egyptians and Greeks, were very numerous, and applied to a great variety of uses. Copper exists in considerable abundance in nature ; it is found native, alloyed with other metals, combined with sulphur, in the state of oxide, and in. that of salt. It is not un frequently met with in the native state, sometimes crystallized in an arborescent form, and sometimes in more regular figures. Copper exists native, alloyed with gold and silver. The most abundant ores of copper are the sulphurets, and of these there is a considerable variety, ex hibiting various colours and various forms of crystals. In the state of oxide it has been found in Peru, of a greenish colour, mixed with white sand. In the state of salt, copper is combined with the sulphu ric and carbonic acids, forming native sul phates and carbonates of copper. The latter present many varieties, but may chiefly be referred to the blue and green carbonates. The extraction of the ores of copper is to be conducted according to the nature of the combination in which they exist. The following process is recommended for the treatment of the sulphurets of copper. The ore is first reduced to powder, and then boiled with five parts of concentrated sulphuric acid. The solution is evaporated to dryness, and the residuum well washed with warm water, to remove all soluble matters. The solution being sufficiently diluted, a plate of copper is immersed in it, which precipi tates the silver, and afterwards a plate of iron to precipitate the copper. It is boil ed with the plate of iron till no farther precipitate takes place. The copper which is thus obtained is dried with a gentle heat, so that it may not undergo oxidation. It is supposed that the cop per is mixed with iron ; the whole may be dissolved in nitric acid ; and the pro cess is again repeated by introducing the plate of iron. In this way it is easy to discover the quantity of copper in the sulphurets of this metal.
Copper is a very brilliant metal, of a fine red colour, differing from every other metallic substance. The specific gravity of copper is 8.58.. When it is hammered it acquires a greater density. It posses ses a considerable degree of hardness and some elasticity. It is extremely mal leable, and may be reduced to leaves so fine, that they may be carried about by the wind. It has also a considerable de gree of ductility, intermediate, according to Guyton, between tin and lead. The tenacity of copper is also very great. A wire .078 of an inch in diameter will sup port a weight, without breaking, equal to more than 30016s. avoirdupois. Copper
has a peculiarly astringent and disagree able taste. It is extremely deleterious, when taken internally, to the animal economy, and indeed may be considered as a poison. It is distinguished by a peculiarly disagreeable odour, which it communicates to the hands by the slight est friction. Copper does not melt till the temperature is elevated to a red heat, which is about 27° Wedgwood, or by estimation 1450° Fahrenheit. When it is rapidly cooled after fusion, it assumes a granulated and porous texture ; but if it be cooled slowly, it affords crystals in quadrangular pyramids, or in octahe drons, which proceed from the cube, its primitive form. When the temperature is raised beyond what is necessary for its fusion, it is sublimed in the form of visible fumes. When copper is exposed to the air, especially if it be humid, it is soon deprived of its lustre. It tarnishes, becomes of a dull brown colour, 'which gradually deepens till it is converted into that of the antique bronze, and at last is covered with a shining green crust, which is well known under the name of verdi gris. This process is the oxydation of the metal by the absorption of oxygen from the atmosphere ; and it is promoted and accelerated, either by being moistened with water, or by the water which ex ists in the atmosphere. As this oxide is formed, the carbonic acid of the at mosphere combines with it, so that it is to be considered as a mixture of oxide and carbonate of copper. But when copper is subjected to a strong heat, the oxida tion proceeds more rapidly. If a plate of copper be made red hot in the open air, it loses its brilliancy, becomes of a deep brown colour, and the external layer, which is of this colour, may be detached from the metal. This is the brown oxide of copper. This oxide may be obtained by immersing a plate of red-hot copper into cold water. The scales which are formed on the surface fall off by the sud den contraction of the heated copper. This may be repeated till the whole is converted into this oxide. The copper in this state is in the highest degree of oxidation. The component parts of this oxide are, Oxygen . . . . 25 Copper . . . . 75 100 There are, however, different oxides ; copper combines with a smaller propor tion of oxygen, forming an oxide of an orange colour. This is the oxide of cop per with the smaller proportion of oxy gen. The component parts of this oxide, according to Mr. Chenevix, are, Oxygen . . . ,11.5 Copper . . . 88.5 100.0 This oxide changes colour the moment it is exposed to the air, by the absorption of oxygen, for which it has a very strong affinity. There is no action between azote, hydrogen, or carbon, and copper, Phosphorus readily combines with cop per, and forms with it a phosphuret, which is prepared by fusing equal parts of cop per and phosphoric gas, with nth of the whole of charcoal in powder Copper combines with sulphur by different pro cesses. if sulphur in powder and filings of copper are mixed together, and form ed into a paste with a little water, when they are exposed to the air, the mass swells up, becomes hot, and is convert ed into a brown matter, which efflores ces slowly in the air, and is converted into sulphate of copper.