189 



COPPER. 



COPPER. 



160 





other. Saddle-bad coping is thicker in the middle than at the edges. 

 Coping-stones should project over the walls which they cover, and 

 should have a groove or throating underneath the projected part to 

 throw off the water. The coping of Gothic battlements and the walls 

 of churches, castles, and dwellings in Gothic architecture, have a deep 

 throating in the form of a bold cavetto in front, and are sometimes 

 decorated with mouldings. [BATTLEMENT.] When the ends of the 

 stones are left higher than other parts, the junctions are called water- 

 jiiints. York stone is much used for parallel coping, and also Portland, 

 but the latter is more expensive and not so durable. Bath stone coping 

 is often used for Gothic works, but it is not calculated to withstand 

 long the constant action of the weather. 



COPPER. A well-known metal. It is an element, and is repre- 

 sented by the symbol Cu, an abbreviation of its Latin name cuprum. 



Copper has been known from the earliest historical ages. It 

 derives its present name from that of the island of Cyprus (Kuirpos) 

 where it was first worked on a large scale. The alchymists called it 

 Venus, perhaps on account of the beauty of its lustre, and gave it the 



symbol jj , a compound hieroglyphic indicating that they thought it 



a mixture of gold, and a certain hypothetical substance called acri- 

 mony >J, the corrosive nature of which was symbolised by the points 

 of a Maltese cross. 



Copper occurs native, and as the base of numerous ores. Its miner- 

 alogy has already been treated of and the ores described in detail, under 

 COPPER, in NAT. HIST. Drr. The source of commercial copper is 

 principally copper pyrites, a double sulphide of copper and iron (Cu. 2 S, 

 Fe,S a ). It occurs abundantly in Cornwall, two-thirds of the copper 

 annually smelted in Great Britain, having a value of nearly one million 

 sterling, being obtained from the ore raised in that county. More 

 valuable but far less abundant ores are the red oxide (Cu a O), black oxide 

 (CuO), malachite a green carbonate, and azurite a blue carbonate. 



The metallurgy of copper or copper smelting, is a branch of manu- 

 facture extensively conducted in the neighbourhood of Swansea, South 

 Wales, a locality peculiarly fitted for the operation on account of its 

 proximity to the coal-fields, and its position as a sea-coast town ; these 

 advantages at all times insuring cheap fuel and cheap freightage to the 

 different metallurgical establishments. 



The ore of copper as raised from the mine is first cleaned from 

 adhering portions of the strata through which the vein passed, then 

 sorted according to quality, so far as appearance indicates, and placed 

 in heaps of convenient size for sale. To ascertain the value of a heap, 

 a fair average sample is taken, and about fuur hundred grains of it 

 assayed by roasting, fluxing with borax, reducing with black flux, &c., 

 according to the nature of the ore : or a weighed quantity may be 

 dissolved in nitric acid, excess of ammonia added, the mixture filtered, 

 boiled with caustic potash or soda, and the resulting oxide collected 

 on a filter, washed, dried, ignited, and weighed ; 100 parts will contain 

 79 82 of copper. As both the composition of copper ore and its richness 

 in metal are liable to great variation, the methods of smelting are 

 necessarily complicated in order that these variations may be met. The 

 process, however, on which the modifications are all based, is a very 

 simple one. It consists first in roasting the ore on the hearth of a 

 powerful reverberatory furnace ; any arsenic is thus driven off, whilst 

 a portion of the sulphur is converted into sulphurous acid and escapes, 

 oxygen taking its place. The iron present hi the ore, however, has 

 a greater affinity for oxygen than the copper has, and hence the 

 sulphide of iron will be decomposed before the sulphide of copper. 

 As soon as the sulphide of iron is thus oxidised the roasting is dis- 

 continued, and the oxide of iron removed by fusion with sand or 

 siliceous ore, and sometimes a little fluor spar. The sulphide of 

 copper is now partially roasted into oxide and then fused, when an 

 interesting reaction occurs, the sulphide and oxide mutually decompose 

 each other, sulphurous acid escapes and metallic copper remains; the 

 decomposition is expressed in the following equation : 



-CuS + 2CuO = SO, + Cu 3 



Sulphide of Oxide of Sulphurous Metallic 

 copper. copper. acid. copper. 



The metal thus produced is again roasted to remove the last traces 

 of foreign matters, and is finally thoroughly deoxidised by heating 

 with carbonaceous materials, and especially by the operation of poling ; 

 in which a pole of green wood, generally birch, is thrust into the 

 molten metal and rapidly moved about; the powerfully deoxidising 

 gases given off from the wood effectually reduce the oxide, and when a 

 small sample taken from the mass, and tested when cold by partially 

 cutting through and then breaking, presents a fine fibrous fracture and 

 4 satiny lustre, the operation is considered to be complete, and the 

 metal is at once ladled out and cant into ingots. Great care and con- 

 siderable experience are necessary to detect with certainty this latter 

 point, as a few minutes merpoling would determine the formation of 

 carburet of copper ; and this would render the whole mass brittle and 

 necessitate re- roasting. 



Such is an outline of copper smelting. For an elaborate description 

 of it uf all its details, see Muspratt's ' Chemistry, applied to the Arts 

 and Manufactures,' pp. 493 to 632. 



Perfectly pure metallic copper may be obtained on the small scale 



by decomposing a solution of sulphate of copper by means of the 

 voltaic b vttery, or by inserting strips of iron into the same solution ; 

 in the latter case the precipitated metal is called cement copper, 

 Another method consists in strongly heating six parts by weight of 

 the pure oxide with one part of finely powdered charcoal and a little 

 borax ; in this way a button is at once obtained. Copper in a state of 

 fine division results, when a current of hydrogen gas is passed through 

 the pure oxide heated to redness. 



Copper has a characteristic red colour ; very thin films of it how- 

 ever, such as are frequently obtained by the chemist in analysing 

 organic substances by the aid of black oxide of copper, appear by trans- 

 mitted light of a beautiful green colour, though by reflected light they 

 also have the usual tint. Copper is rather hard, sonorous, and ex- 

 ceedingly ductile and malleable. Its specific gravity varies from 878 

 to S'96, according to the manipulation to which it has been subjected ; 

 it is one of the best conductors of heat and electricity, and expands 

 one part in 582 on being heated from 32 Fahr. to 212 3 . Copper 

 crystallised in the form of cubes or octohedra is occasionally found 

 native. It may be obtained in the same state artificially by slow 

 voltaic action. The melting point of this metal is'under that of gold, 

 but higher than silver ; in the fused state it exhibits a bluish-green 

 colour, and at an intense white heat, such as is produced by a powerful 

 electric current, or the oxyhydrogen blowpipe, it boils, burns with a 

 green flame, and is entirely volatilised. 



Copper does not tarnish on being exposed to dry air, but in the 

 presence of moisture and carbonic acid, it gradually becomes covered 

 with a greenish coating of oxide and carbonate. Nitric acid rapidly 

 attacks and oxidises copper, forming a nitrate of copper. Sulphuric 

 acid does not act upon it when cold, but at a boiling temperature 

 oxidises it with evolution of sulphurous acid and formation of sulphate 

 of copper. Hydrochloric acid acts only on copper in the presence of 

 oxidising agents. The fixed alkalies act but little on the metal, 

 ammonia hi the presence of a small quantity of air gradually dissolves 

 it, forming a colourless solution of suboxide; more air causes the 

 formation of a deep blue solution of protoxide. Copper has a nauseous 

 styptic taste, and on being rubbed emits a peculiar disagreeable odour. 



The equivalent of copper is 31'75. 



Copper and oxygen unite in four different proportions : 



f copper . 

 Protoxide of copper 

 Binoxide of copper . 

 Cuprio acid . 



Formula. 

 , CUjO 

 . Cu O 

 . Cu O a (? 



Equivalent. 

 71-S 

 39-7 



1. Suboxide of cupper (Cu,, 0) ; cuprous o;dde, dinoxide, or red oxide of 

 copper. This oxide occurs native in the form of beautiful red crystals. 

 It is best prepared artificially by heating a solution of sulphate of 

 copper with excess of caustic potash or soda and a little honey, the 

 suboxide deposits in the form of bright red granular crystals. 



The salts of this oxide are very unstable, and consequently difficult 

 of preparation, 



tiiil/ihite uf cuprous oxide and potash is formed by gradually adding 

 solution of sulphate of copper to a hot solution of sulphite of potash ; 

 on cooling the salt deposits in crystalline needles. The principal use 

 of suboxide of copper is in the staining of glass, to which it communi- 

 cates a ruby-red colour. 



2. Protuxide of copper (CuO), black oxide, or cupric oxide, prepared 

 either by heating copper-plates and turnings in a current of air, or 

 from the nitrate of copper, by heating that salt to redness in an earthen 

 cruc.ble. By the former method it is obtained more or less massive 

 and crystalline, by the latter in the state of fine powder. In either 

 condition it is used to some extent by chemists in the analysis of 

 organic substances. [ORGANIC ANALYSIS.] It is also used to stain glass 

 of a beautiful green colour. 



The salts of protoxide of copper are numerous, well-defined, and 

 important. The following are the principal of them. 



Sulphate of copper (CuO, S0 a + 5 Aq.), equiv. 124 7, Uue vitriol. This 

 salt occurs native, see BBOCHANTITE, NAT. HIST. Div. It is obtained 

 as a by-product in silver refining; also in large quantities in the 

 roasting of copper pyrites at a temperature approaching low redness ; 

 this heat is sufficient to decompose the sulphate of iron formed at the 

 same time, but is not high enough to affect the sulphate of copper. It 

 is purified by crystallisation from a hot aqueous solution. It may also 

 be formed by boiling copper with three times its weight of strong 

 sulphuric acid, diluted with one-third its weight of water ; the copper 

 is oxidised at the expense of part of the sulphuric acid, and combines 

 with the remainder. Commercial sulphate of copper is, however, 

 principally manufactured by simply dissolving the crude oxide or scale 

 in sulphuric acid with the aid of heat. The scale is obtained by 

 roasting waste copper, and in the process of annealing copper-plates ; 

 it consists of a mixture of metallic copper with oxide. 



Sulphate of copper crystallises in large blue crystals of an oblique 

 rhombic form. It is soluble in two parts of boiling water, from which 

 solution one half of the salt crystallises out on cooling. Heated, it 

 loses its water of crystallisation, assumes a white colour, and at a 

 higher temperature is decomposed, the acid being expelled and the 

 oxide left. 



Sulphate of copper is largely used in calico-printing, and in the 



