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da. Hearth or body of furnace. Jist istab Bridge.

c. Fire place.

d. Flue,
aspidi loe. Stack, or chimney.
Poult f. Tapping hole.

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The processes are conducted in the following order :
1. The
copper

calcined.
2. Calcined ore melted.
3. Coarse * metal from Process 2, calcined.
4. Calcined coarse metal melted.
5. Finet metal from Process 4 calcined.
6. Calcined fine metal melted.
7. Copper from Process 6 roasted.
8. Coarse or blistered copper

refined.

ore

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Metal, means sulphuret when thus used ; and coarse metal, sulphuret of copper and

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+ Fine metal, ditto with larger proportion of copper.

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PROCESS I.--The Calcination of the Ore. The copper ores, when discharged from the vessels in which they are brought from Cornwall, are wheeled into yards or plots contiguous to the works, and there deposited, one cargo over the other, so that, when cut down perpendicularly to be carried to the furnaces, a tolerably general mixture is formed of the ores of the county. This is always desirable in a smelting work, as, the ores being of different qualities and component parts, the one acts as a flux for the other. A more accurate mixture, calculated from the chemical analysis of each parcel of ore, might be preferable; but this on a large scale cannot be practised, as it would be impossible to keep the ores separate, on the different whàrfs in Cornwall, to ship them separately, and to have sufficient space on the wharfs at the works to receive them.

The ore in the yard is weighed over to the calciner-men in boxes, containing each one hundred weight. These are carried on men's shoulders to the calciners, and emptied into iron bins or hoppers, formed by four plates of cast iron tapering to the bottom, placed over the roof of the furnace, and supported by wrought iron frames resting on its sides. From these bins, the ore is passed into the calciner through a hole in the roof immediately below the bottom of the hopper. Two of these bins are usually placed over each calciner, and nearly opposite the side doors, so that the charge of ore, when let into the furnace, may be conveniently spread, which is done by means of long iron tools, called stirring rabbles.

This charge of ore usually consists of three to three and a half tons. It is distributed equally over the bottom of the calciner, which is made of fire bricks or square tiles. The fire is then gradually increased: so that towards the end of the

process, which lasts 12 hours, the heat is as great as the ore will bear without being fused or baked together. To prevent this taking place, and to assist the disengagement of the sulphur, the.ore is frequently stirred during the operation, and fresh surfaces exposed. At the expiration of the 12 hours, the charge is drawn out through holes in the bottom of the calciner, of which there is one opposite to each door, and, falling under the arch of the furnace, remains there till it is sufficiently cool to be removed, when water is thrown over it to prevent the escape of the finer particles ; it is then put into barrows, and wheeled to the proper depots. In this state it is called calcined ore.

If the process has been well conducted, the ore is black and powdery. The dark colour is no doubt owing to a portion of the iron being oxidized during the process, by which the ores acquire an increased degree of fusibility. The quantity of iron oxidized during the first caloination is, however, small in proportion to the contents in the ore, as the metal is protected from the action of the air by the mass of earthy matter with which it is combined, and by the sulphur

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and other volatile substances. The sulphur that is expelled is in no part sublimed as flowers of sulphur, but is all acidified, and the process being conducted with admission of atmospheric air is properly a roasting.

Process II.-The Melting of the Calcined Ore. The calcined ore is delivered, as in the raw state, to the work. men in boxes containing 1 cwt. each. The charge is deposited in the same manner in a bin placed on the top of the furnace, and from thence passed into the interior as required. When the charge is let down and spread over the bottom, the door of the furnace is put up, and well luted. Some slags from the fusion of the coarse metal or sulphuret are added, not only on account of the copper they contain, but to assist the fusion of the ore, being chiefly composed of oxide of iron. These are thrown into the furnace through the front door.

After the furnace is charged, the fire is made up, and the main object of the smelter is to bring the substances into fusión : it is, therefore, in this respect different from the calcining process. When the ore is melted, the door of the furnace is taken down, and the liquid mass well rabbled, or stirred, so as to allow of the complete separation of the metallic particles from the slags or earthy matters, and to get the charge clear of the bottom of the furnace, which is made of sand, and soon becomes impregnated with metal. The furnace being ready; that is, the substances being in perfect fusion, the smelter takes an iron rabble, and skims off, through the front door, the sand or slags consisting of the earthy matters contained in the ore, and

any metallic oxides that may have been formed, which, being specifically lighter than the metals in the state of sulphuret, Hoat on the surface. When the metal in the furnace is freed from slags, the smelter lets down a second charge of ore, and proceeds with it in the same manner as with the first; ard this he repeats, until the metal collected in the bottom of the furnace is as high as the furnace will admit of without flowing out at the door, which is usually after the third charge; he then opens a hole, called the tapping hole, in the side of the furnace, through which the metal flows into an adjoining pit filled with water. It thus becomes granulated, and collects in a pan at the bottom of the cistern, which is raised by means of a crane. It is then filled into barrows, and wheeled to the place appointed for its reception."

The slags received into moulds made in sand in the front of the furnace, are removed after each charge, and wheeled out of the work to the slag bank, where they are broken, and carefully examined; any pieces found to contain particles of metal, are returned to the smelter to be remelted; and unless the slag is very thick and tenacious, the copper which they may contain is found at the bottom. What is clean or free of metal is rejected. These slags are composed of the earthy matters contained in the ore

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and the oxides of iron and other metals that were mixed with

copper. The oxide of iron gives them a black colour. The silex or quartz remains in part unfused, and gives the slags a porphyritic appearance.

In this process, the copper is concentrated, and a mass of stuff with which it was combined in the ore got rid of. The granulated metal usually contains about one-third of copper. It is thus four times as rich as the ore, and must consequently þave diminished in bulk in the same proportion. Its chief conaponent parts are sulphur, copper, and iron.:::

The most important point to be attended to in this process is to make a fluid good mixture of earths and metals, so that the copper which is combined with the sulphur, may from its greater specific gravity, settle at the bottom, and yield clean slags. This object is effected chiefly by means of metallic oxides, the slags from Process 4, which are melted with the ore, being almost wholly black oxide of iron. When the ores are very stubborn or difficult to melt, a box of fluor spar is added to the change, but it is not desirable to increase the bulk of matter in the furnace unless required.

The men work round the 24 hours, and commonly melt in this time five charges. Under favourable circumstances, as fusible ore, strong coal, furnace in good repair, they even do six charges. They are paid by the ton. Process III.-Calcination of the Coarse Metal, the Product of

the first Fusion. This is conducted in precisely a similar manner to the calcining of the ore · The charge is nearly of the same weight; but as it is desirable to oxidize the iron, which is more readily effected in this process than in the ore calciners, where it is protected from the action of the air by the earthy matters with which it is combined, the charge remains 24 hours in the furnace, and during that time is repeatedly stirred and turned. The heat during the first six hours should be moderate, and from that time gradually increased to the end of the operation. Process IV.-Melting of the Coarse Metal after it has under:

gone Calcination. This is performed in furnaces precisely similar in construction to those in which the ore is melted; and with the calcined metal are melted some slags from the last operations in the works which contain some oxide of copper, as likewise pieces of furnace bottoms impregnated with metal, the proportion of each varying 'according to the stock or to the quality of the calcined metal

. The chemical effect which takes place is, that the oxide of copperin the slags becomes reduced by a portion of the sulphur which combines with the oxygen, and passes off as sulphurous acid gas, while the metal thus reduced enters into combination with the sal

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phuret. That there may be a sufficient quantity of sulphur in

. the furnace to promote these charges, it is sometimes necessary, when the calcined metal is in a forward state, to carry a small quantity of raw or uncalcined metal, so that a clean slag may ba obtained. Stor

The slags from this operation are skimmed off through the ftont door, as in the ore furnaces. They have a high specific gravity, and should be sharp, well melted, and free from metal in the body of slag. Such particles of metal as are drawn off, which, from the thinness of the slags, will commonly happen, should sink to the bottom of the slag while it is in the liquid state. These slags, as, has been before observed, are melted with the ore, not only for the purpose of extracting the copper they may contain, but on account of their great fusibility, as, being composed chiefly of the black oxide of iron, they fuse readily, and act as solvents for other substances, earthy mat. ters, &c. In some cases, the slags from the metal furnaces are melted in a distinct furnace with some small coal or carbonaceous matter, and in this case, the slags resulting therefrom are even sharper than those from the metal furnaces, they have a crystalline splendent appearance, and crystals are frequently to be observed in the interior.

D The metal in the metal furnace, after the slag is skimmed off, is either tapped into water, as from the ore furnaces, or into sand beds, according to the mode of treatment it is to be subjected to in subsequent operations. In the granulated state, it is called fine metal; in the solid form, blue metal, from the colour of its surface. The former is practised when the metal is to be

forward by calcination. Its produce in fine copper is about 60 per cent.

Tips vivo Process VCalcination of the Fire Metal. (017 - "This is performed in the same manner as the calcination of the coarse metal.

me sot, silti Process VI.-Melting of the calcined Fine Metal. Ils This is performed in the same manner as the melting of the coarse inetal ; "the resulting product is a coarse copper from: 180 to 90 per cent. of pure metal. PROCESS VII.-Roasting, solo

bolt 5. This is chiefly an oxidizing process. It is performed in furnaces of the same descriptîon as the melting furnaces,

although distinguished by the appellation of roasters. 1. The pigs of coarse copper from the last process are filled the furnace, and exposed to the action of the air, which draws through the furnace at a great heat; the temperature is gradually increased to the melting point, and the expulsion of the volatile substances, that remained is thus completed, and the riron or

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