(including its alloy brass) and iron are the first metals named in the most ancient authentic history of the world, as having been made use of by man. Tubal-cain was "an instructor of every artificer in brass and iron." The words *ἀσης* and *χάλκος* (usually translated brass) of the ancient Romans and Greeks were used indifferently to apply to the pure metal copper (as when they spoke of their money) and to its alloys with other metals, as when they spoke of their brazen statues, or of their defensive and offensive armour, in which case the copper was alloyed with tin. The enormous statue of the Sun, known by the name of the Colossus of Rhodes, was composed entirely of bronze (see COLOSSUS); and many others are mentioned, which prove that the ancients were at least as well acquainted with the difficult art of working in brass as we are at the present day.

In a pure state, copper is a very brilliant metal, and susceptible of a high polish. It is of a fine red colour, differing in this respect from every other metal except titanium. Its specific gravity varies, according to its density, from 8·584 to 8·9. According to Brard, the cubic foot of melted copper weighs ................................................. 545 lb. Of native metal .................................................. 600 lb. Of copper medals .................................................. 620 lb. In a native state, it is not an uncommon mineral. It occurs in arborescent groups, very beautifully crystallized, in Siberia, imbedded in limestone, and in very considerable masses. In the cabinet of Ajuda, near Lisbon, a mass of native copper is said to be preserved, of the enormous weight of 2617 pounds (Brard). In Cornwall it occurs in many of the mines, and also in the island of Anglesea; and in the island of Nalsoc, one of the Perce group, it occurs very beautifully crystallized, along with zeolite, imbedded in amygdaloidal trap.

Metallic copper is used for culinary vessels in many parts of Europe; but for this purpose the inner surface of the vessel should be tinned. Large vessels for distilling, brewing, dyeing, and the like processes, are made of copper. The making of these vessels constitutes the ordinary business of the coppersmith.

Copper rolled into sheets is employed for covering the wooden work of the roofs of churches and large edifices in Germany, Sweden, and other countries. It is a costly covering, and does not possess any commensurate advantage over lead. A modern, and now a very extensive use of sheet-copper, is for the sheathing of ships. That part of the hull of a ship that is in the water is covered with sheet-copper. This covering preserves the wood from the attacks of the teredo, and thereby gives the ship the advantage of passing more rapidly through the water, as the copper bottom remains always smooth; for sea-weed and shells will not take root and attach themselves to copper, as they do to bare planks, owing to the galvanic effect produced by the action of sea water. As this action, however, produces a rapid decay of copper, it was proposed by Sir Humphry Davy to neutralize it by applying metallic protectors—an object which he accomplished; but as this also deprived the copper of the effect it was intended to produce, and allowed the molluscous tribes to attach themselves, the protecting process was abandoned.

Its malleability and ductility are very considerable. A wire of 0·078 of an inch diameter will support 302 pounds avoirdupois.

Copper bolts are used for fastening the planks and timbers of ships. This is a great improvement in ship-building. A copper-fastened ship or boat is preferable to one with iron fastenings, because the copper bolts remain unaltered by rust, and endure longer than the wood which they hold together, particularly when used in the state of alloy, which preserves it from waste by neutralizing the galvanic action.

For the frames of delicate dipping needles and magnetic compasses, copper is employed; as it has been found that the brass generally used in philosophical instruments sometimes contains iron, which of course might affect the magnetic needle.

Copper is drawn into wire, used for the communication with the bells in houses, and for other purposes.

Small pipes for conveying coal-gas from the level of the street to the aperture by which the gas issues, were formerly made of copper or of brass, till superseded by tin. These pipes were fitted on an iron cylindrical mandril, and a cylindrical ring drawn over the outside. By this means copper and brass tubes are drawn out. The brass tubes for telescopes are drawn out in the same manner.

Copper may be plated; that is, its surface may be covered with a layer of silver, by rubbing the surface with a mixture of nitrate of silver, nitrate of soda, and acidulous tartrate of potass (cream of tartar). But the method practised at Birmingham is the most permanent and effectual. A plate of copper, with a plate of silver applied to it, and borax placed in the interstice, is heated to a particular degree, which it requires the skill of the workman to know; a degree of heat, in short, near that at which copper and silver melt. The two metals thus heated, and in contact, are then taken out of the furnace and passed through rollers. There is a fusion and combination of the adjacent surfaces; and their adhesion is perfected by the pressure of the rollers. Copper thus plated is manufactured at Birmingham into candlesticks, teapots, buttons, buckles, and a variety of other articles.

Standard silver coins contain a small proportion of copper, for the purpose of giving them hardness. This proportion is regulated by government in the several countries of Europe, and varies in different states. The combination of gold and copper in various proportions is used for making rings and other trinkets.

Copper is gilded by applying on its surface an amalgam of gold with mercury. Bronze ornaments are gilded in the same way.

Copper united with zinc forms brass: when alloyed with tin it forms bronze. This combination is hard and brittle if the proportion of tin be great; but when the proportion of tin is small, the bronze is soft, and possesses tenacity so as not to be easily broken. The ancients employed hard bronze, containing much tin, in making sword blades, spear heads, hatchets, and cutting instruments. Bronze cramps are found in ancient buildings in Egypt. Statues and bas-reliefs, culinary vessels, and a variety of other articles of soft bronze, are to be seen in different collections of antiquities. In modern times soft bronze is used for casting cannon and statues.

Copper melted with a large proportion of tin constitutes bell-metal, which is hard and brittle. The metal of which the Chinese gongs are made is composed of the same ingredients; and it has the property of being in some degree malleable at a certain stage of its cooling, for their gongs are covered with marks of the hammer.

The most common ore of copper, from which the chief supplies of that metal are derived, is the yellow copper ore, or copper pyrites, essentially a combination of copper with sulphur and iron. There are, however, numerous other ores of copper in which the metal is in combination with oxygen, carbonic acid, various other metals, &c.

Copper in its varied artificial combinations, as in that of verdigris (acetate of copper), blue vitriol (sulphate of copper), Scheel's green (arsenate of copper), verditer (carbonate of copper), &c., is largely used in the arts of dyeing, painting, enamelling, glass and porcelain colouring, &c.

The salts of copper are poisonous; and from the facility with which copper utensils become oxidated, their use should be as prescribed as possible. One or two of the salts of copper are occasionally used in medicine; and the sulphate of copper has been found to be one of the most efficacious emetics in croup, checking the disease and preventing the effusion of the fibrinous matter into the trachea. This salt is also used as a lotion in the treatment of ulcers, &c.

Quantities of Copper Ore imported into the United Kingdom for home consumption in 1851, with the Duties charged thereon.

| Countries | Quantities | Duties | |----------------------------|------------|--------| | Holland | 202 8 0 | 10 2 | | France | 1,029 11 | 51 6 | | Spain | 1,085 11 | 54 5 | | Italy | 3 0 0 | 0 3 | | Algeria | 89 12 0 | 41 11 | | West Coast of Africa | 11 13 2 | 0 11 | | British Possessions in S. Africa | 144 0 0 | 7 4 | | British Territories in E. Indies | 87 3 24 | 4 7 | | South Australia | 4,157 10 | 207 17 | | New South Wales | 991 2 10 | 49 11 | | Victoria | 664 13 | 33 4 | | Van Diemen's Land | 199 4 0 | 9 19 | | New Zealand | 209 18 | 10 9 | | British N. America & Colonies | 728 11 | 36 8 | | Cuba | 20,871 2 | 1,043 11 | | Chile | 3,154 15 | 157 15 | | Bolivia | 245 0 0 | 12 5 | | Peru | 1,054 0 13 | 52 14 | | Other Parts | 54 18 0 | 2 15 |

Deduct quantities exported subsequently to the payment of duty and over-entered, 280 11 0 19 Repaid, 29 6 4

Total, 35,493 11 2 20 Ll,1,759 18 6

In 1853 the duty on copper ores and on wrought copper was repealed.

Copper, as a mineral. See Mineralogy.

Copper-Smelting. Copper seems to have been known from the earliest times. The great beauty which copper ores in general possess, and the ease with which the metal is obtained from these by fire, may have brought it early into notice. That the metal was obtained by fusion at a very early period, is indicated by the following sentence in the Book of Job (xxviii. 2)—"Copper is molten out of the stone." Copper is often found in nature in the metallic state, and occasionally in considerable quantity, such as the masses recently found at Lake Superior; but the principal source is from ores; the metal in them being in combination with other matters, such as oxygen, sulphur, carbonic acid, &c., forming an extensive variety of minerals of distinct forms and character, and of great scientific interest.

The principal sources of copper ore in this country are Cornwall and Devonshire; great quantities, however, are imported from Ireland, Cuba, Chile, and Australia. The average quantity of ore raised in this country during these last five years is about 155,000 tons, yielding about 12,000 tons of metal; and the quantity imported about 60,000 tons, yielding about 10,000 tons of metal. The ores are mostly all taken to Swansea and neighbourhood, where the principal smelting-works are situated.

The ores are divided by the smelter into two general classes—those containing sulphur, and those having little or no sulphur. The former are subdivided according to certain qualities which they are known to possess, such as having much silica, iron pyrites, tin, arsenic, &c.; some consideration is also given to the quantity of copper they contain. The object of these arrangements and classifications of ores in the yard is to enable the operative smelter to select from and make up a constant working mixture, having the following characters:

1. That the copper in the mixture be not under 9 nor above 13 per cent.: if under the former, it is unprofitably poor; if over the latter, the slags have a tendency to contain copper, creating a loss.

2. That after being calcined for an ordinary length of time, it will fuse easily without the necessity of adding flux, giving a clean and easily fused slag.

3. That the mat or coarse metal obtained from fusion contain as nearly as possible 30 per cent. of copper. And

4. That the mixture do not contain ores having impurities calculated to make the copper of a lower quality than is desired. There is no definite or fixed rule to guide the smelter in these classifications, except a practised eye in distinguishing the character of ores, and the report of the assayer.

The mixture of ores being selected according to these rules, it is carried to hoppers on the top of a large reverberatory furnace, termed the calcining furnace, and then let down into the hearth, where, after drying a little, it is spread equally over the bottom, and covered to a depth of from six to eight inches. The quantity of ore put in varies, according to the size of the furnace, from three tons to six tons. The fire of the furnace is kept low at first: after two or three hours the ore on the surface becomes visibly red, the heat is gradually increased to a yellow red; but this heat only penetrates to the depth of about two inches, consequently the ore has to be stirred and turned over by means of long iron paddles every hour, so as to expose a new surface to the action of the air and fire. This calcination lasts generally nine hours; but when ores are known to be stiff, containing much silica and sulphuret of iron, twelve hours are allowed. The following changes and chemical actions take place: the sulphur is partly burned off by combining with oxygen and forming sulphurous and sulphuric acids, and partly volatilized as sulphur uncombined; arsenic is volatilized either as metal or oxide; the copper and iron lose a part of their sulphur and combine with oxygen, forming oxides.

When the ore is sufficiently calcined, it is let down into the cubs or vaults beneath, by openings in the floor. Water is added to the hot ore in the cubs to prevent dust and assist further oxidation; the ore is then removed to a yard, and there stored up, ready for the fusing furnace. The following analysis of ore, before and after calcining, will give an idea of the changes that have taken place.

| Before Calcination | After Calcination | |-------------------|------------------| | Copper | 12·3 | | Iron | 32·7 | | Sulphur | 31·0 | | Silica | 24·0 | | Copper | 12·2 | | Iron | 22·7 | | Oxide of Iron | 18·5 | | Sulphur | 16·2 | | Silica | 30·4 |

The next operation is the fusing of the calcined ore, which is done in a reverberatory furnace, termed an ore-fusing furnace, fitted also with a hopper on the top for charging it. The charge consists of

From 25 to 30 cwt. of calcined ore. From 7 to 9 cwt. of sharp slag from more advanced operations. From 2 to 3 cwt. cobbling.

When the charge is let down into the furnace it is spread equally over the bottom, the doors are all closed, every air-hole is stopped with clay, and the heat of the furnace increased as rapidly as possible.

After about five hours' firing, when the furnace has reached a white heat, the door-plate is removed and a long iron rake passed through the fused contents to make sure that the whole is perfectly fused. This being the case, the workman begins the operation of skimming, that is, drawing off the scoriae or slag, which from its less specific gravity floats on the surface of the mat: this is effected by means of a long rake, the scoriae being drawn out at the front door. When the surface is skimmed, the common practice is to let down a second charge of ore, and to fuse and skim in the same manner, before tapping the furnace to let out the metal or mat, which is generally tapped into a large pit of water which granulates it. These pits are from 6 to 8 feet deep, and from 4 to 5 feet square, and into them a perforated box is lowered which receives the charge of metal, and is raised by a crane or pulley. The metal is then removed to a yard for the next operation. This mat is termed granulated coarse metal.

The average composition of good coarse metal is

| Copper | 31·4 | |--------|------| | Sulphur| 27·3 | | Iron | 41·3 |

and the slag or scoriae, as

| Silica | 71 | |--------|------| | Protoxide of Iron | 27 | | Lime, &c. | 2 |

The next operation is the calcination of the granulated coarse metal. This is done in the same manner as the calcination of the ore. The charge of metal covers the bottom of the hearth to the depth of about 4 inches, making about 4 tons to the charge, which is put in through the hoppers fitted upon the top of the furnace, as described for the ore.

The coarse metal being easily fused, great care is required not to raise the heat of the furnace too high, otherwise the metal will cake, and by adhering to the bricks will prove prejudicial both to the calcination and the furnace. When the charge is let into the furnace, it is slowly brought to a visible red, and the fire is gradually and cautiously increased until the metal acquires a bright red heat, which should take about fourteen hours. This temperature is continued until the charge has been altogether twenty-four hours in the furnace, when it is let down through the bottom into the cubs or vaults beneath, and a quantity of water is thrown upon it to prevent dust, &c., from accumulating above it.

1 Cobbling is a term given to old bricks and bottoms of furnaces that have absorbed copper, and are broken down into pieces. The following analysis gives an average result of the changes effected in this operation:

| Metal put into calciner. | Metal after calcination. | |-------------------------|--------------------------| | Copper | Copper | | Iron | Iron | | Sulphur | Sulphur | | Other matters and loss | Oxygen, &c. |

100

The next operation is fusing the calcined coarse metal. The charge for an ordinary-sized furnace of 8 feet by 13 feet is—

- 25 cwt. of calcined metal, - 6 to 7 cwt. slags from the roasters, - 2 to 3 cwt. of cobbings.

In this mixture the oxide of iron is in excess in relation to the silica, and it is therefore much more easily fused than the ore; but the reactions which take place are similar: the silica and oxide of iron combine to form slag, which floats upon the surface of the mat and has to be skimmed off; after which the mat is tapped out into sand-moulds. Two charges are generally fused before the metal is tapped out. This mat is termed blue metal, from its being of a slate-blue colour; the scoria is termed sharp slag, from its containing an excess of oxide of iron, and being consequently used as a flux for fusing the ore.

The following is the composition of good blue metal and sharp slag.

| Blue Metal | Sharp Slag | |------------|------------| | Copper | 58-8 | | Sulphur | 20-5 | | Iron | 12-6 | | Insoluble | 4-2 | | Oxygen and loss | 3-9 |

Should there be no ores such as carbonates or oxides on hand to smelt, the blue metal, instead of being tapped into sand-beds as described, is run into pits of water in the same manner as coarse metal, and subjected to another calcination and fusion.

When oxides and carbonates, such as the Australian ores, are on hand, they are generally fused with the calcined coarse metal, by which means a double advantage is obtained; the excess of oxide of iron in the calcined metal fluxes the silica of the ore which has little iron, and the copper in the ore is converted into subsulphuret—a condition necessary for reduction by the present method of smelting. The produce of this fusion is a mat termed pimpled metal, from its having small rough granules on the surface of the ingots. The average composition of this metal is—

| Copper | Sulphur | Iron | Silica | |--------|---------|------|--------| | 78 | 18 | 2 | 2 |

The composition of this slag is very irregular: it always contains copper, and has to be remelted.

The next operation is roasting—a process generally identified in books on chemistry with calcining, but which is distinct. The roasting furnace differs from the fusing furnace by having a large opening in the side for putting in the charge, and is furnished with more air-holes in the bridge. The charge for an ordinary-sized furnace is three tons. When the metal is brought to fusion, the air-holes of the furnace are all opened, and a free current is allowed to pass over the surface of the fused mass: the heat of the fire is then regulated so as to keep the charge in a sort of semifluid state. This is continued for about twenty-four hours, during which a great portion of the sulphur is driven off with the whole of the iron, which, with silica and other matters, forms scoria, and is from time to time skimmed off. When all these impurities are removed, and when the composition of the mat or regulus is a subsulphuret of copper Cu₂S, then begins what may be termed roasting proper; and which, unless when the regulus has been very rich, constitutes another operation termed the second roasting, requiring other 24 hours. In this last roasting, when the air-holes are opened a brisk effervescence ensues over the surface of the fluid mass.

The chemical reactions which take place during this effervescence may be explained thus: if we take 1 equivalent of subsulphuret of copper, which is composed of 16 sulphur and 64 copper, and 2 equivalents of oxide of copper, which is composed of 16 oxygen and 64 copper—incidentally equal weights,—mix them together in a crucible, and expose them to a heat sufficient to melt copper, the whole of the copper will be reduced, and the sulphur evolved as sulphurous acid, Cu₂S + 2 CuO = SO₂ + 4 Cu.

The reactions which occur in the process of roasting are the same. The oxygen of the air combines in the first place with a portion of the sulphur, forming sulphurous acid. A portion of the copper is also oxidized, and instantly reacts upon another portion of the subsulphuret, reducing the metal, as shown above. The process is a very beautiful one, and exhibits a nice adaptation of principles to practice. The sponge regulus has a specific gravity of 5, the reduced copper of about 8; so that the copper sinks to the bottom where it is protected, and a new surface of regulus becomes exposed to the action of the air.

If the ore be pure, or if no select copper be required, the operation of roasting is continued until the whole of the copper is reduced; when it is tapped out into sand-moulds, forming coarse copper, bed copper, pimpled copper, or blistered copper, according to quality. The term coarse copper is applied occasionally to all these kinds except the blistered. If the ingot sets with contraction with a smooth hollow surface, it is termed bed, and generally indicates the presence of other metals, as tin. When the surface of the ingot is covered with pimples, it is termed pimpled copper, and indicates the presence of sulphur. When covered with large scales or blisters of oxide of copper, it is termed blistered; which only takes place when the copper is good and ready for refining. When making select copper, the roasting is carried on until about one-fourth of the copper in the regulus is reduced; the furnace is then tapped, and the reduced metal is obtained at the bottom of the first and second ingots or pigs, as copper bottoms which contain most of the metallic impurities. The regulus is collected and again roasted, which produces the purest metal the ordinary process of smelting can give: it is termed best select.

The reader will not have failed to remark that the reduction and purifying of the copper are effected without the aid of carbonaceous matters of any sort, contrary to what is stated in all chemical books in reference to the reduction of copper; indeed, the addition of carbonaceous matters would be detrimental.

The next operation is that of refining—bringing the metal into a state fit for the market. The refining-furnace is similar in form to a roasting-furnace, but a little smaller, and the bottom is made to incline a little to the front door, where a small well is made. The copper being ladled from the furnace, this well allows of the ladles being dipped into the metal when the quantity in the furnace is small, so that the last portions of the metal can be taken out.

About six tons of copper from the roasting-furnace are put into the refining furnace, the doors and air-holes of which are closed, and the heat raised until the metal is in fusion, when the air-holes are opened. A short roasting is generally required, which is done in the manner we have described, and the scoria which collects is carefully skimmed off. The separation of impurities is facilitated by occasionally stirring the metal with a rake. Some refiners throw pieces of green wood upon the surface, under the impression that it assists the escape of sulphur. The roasting is con- tinued until a ladleful of the metal taken out sets with contraction. If the metal be very coarse, it will set with a surface having a frothy appearance; if finer, it sets with expansion, first round the edge, then swelling towards the centre, forming a little mound or cone, and occasionally boiling over and throwing up jets of metal, forming a miniature volcano. These phenomena are caused, no doubt, by the presence of gases in the copper. Several metals when in fusion absorb oxygen; but the fact that copper, when it sets in this way, does not refine well by the operation of poling, which would soon take away oxygen, is presumptive that the gas which escapes is not oxygen, and renders probable the prevailing idea that it is caused by the presence of sulphur or sulphurous acid.

When the setting of the metal in the ladle is favourable, the charge is ready for the operation of poling. A quantity of charcoal or anthracite coal is first thrown upon the metal to prevent oxidation by the air, and then the end of a large pole of green wood, generally of birch or oak, is inserted into the melted copper, and kept pressed down to the bottom of the metal, which occasions violent ebullition, the metal spurting and boiling with loud noise. The action which takes place during this operation will be apparent to every one slightly versed in chemistry—the reduction of any oxide or suboxide. But the reason why such an operation as poling is required is, that oxide of copper dissolves in metallic copper as a salt dissolves in water and makes it brittle. To put pieces of wood or charcoal upon the surface would not remove the oxygen; hence the necessity of poling, in order to bring the carbonaceous matters into contact with the dissolved oxide. As the poling proceeds the refiner takes from time to time small samples called assays, which he hammers and breaks for examination. When the copper is in the proper pitch the assay bends without breaking, and if cut and broken the fracture presents a fibrous silky lustre. When this pitch is attained the pole is withdrawn, and a quantity of charcoal thrown upon the surface; and, if the copper is for rolling or hammering, a little lead is added to the charges, to insure toughness.

When the copper is brought to the proper pitch by the refining operation, it is ladled out into moulds. A ladle holds about 30 lb. of fluid metal, three of which form a cake, the ordinary size of which is $14 \times 10$ inches. Twenty moulds are set round the floor in front of the furnace, three ladlefuls are poured together into each mould, going over the whole, by which time the cake first poured is set, and the mould is ready to receive another charge. Each mould holds five such charges or cakes. During the ladling out the refiner takes an assay at short intervals, as the metal is liable to get out of pitch, or become dry, as underpoled copper is termed; in which case poling has to be resumed. So much depends upon refining, that the best copper by a defect in this operation will be rendered unmarketable.

In making what is termed best select copper, the refining is performed in the manner described, but no lead is added. This quality of copper is used for the manufacture of fine alloys, such as Muntz's yellow metal. Copper a little overpoled is generally preferred for these purposes.

A great variety of improvements have been proposed and patented for copper-smelting. One or two have been usefully applied, but the greater portion of them exhibit a want of practical knowledge of the processes in use, and consequently of the requirements of the trade, and a few of them an entire want of principle to effect the objects sought after.