BATTLE OF COPENHAGEN

The formation of a league between the northern powers, Russia, Prussia,

Denmark and Sweden, on the 16th of December 1800, nominally to protect

neutral trade at sea from the enforcement by Great Britain of her

belligerent claims, led to the despatch of a British fleet to the Baltic

on the 12th of March 1801. It consisted of fifty-three sail in all, of

which eighteen were of the line. Prussia possessed no fleet. The nominal

strength of the Russian fleet was eighty-three sail of the line, of the

Danish twenty-three, and of the Swedish eighteen. But this force was for

the most part only on paper. Some of the Russian ships were at

Archangel, others in the Mediterranean. Of those actually in the Baltic

and fit to go to sea, twelve were at Reval shut in by the ice, and the

others were at Kronstadt. The Swedes could equip only eleven of the line

for sea, and Denmark only seven or eight. It is highly doubtful whether

the three powers could have collected more than forty ships of the

line--and they would have been hastily manned, destitute of experience,

and without confidence. A rapid British attack would in any case

forestall the concentration of these heterogeneous squadrons. The

superior quality of the veteran British crews was more than enough to

counterbalance a mere superiority in numbers. The command of the British

fleet was given to Sir Hyde Parker, an amiable man of no energy and

little ability. He had Nelson with him as second in command--then a

junior admiral but without rival in capacity and in his hold on the

confidence of the fleet. Parker's orders were to give Denmark

twenty-four hours in which to withdraw from the coalition, and on her

refusal to destroy or neutralize her strength and then proceed against

the Russians before the breaking up of the ice allowed the ships at

Reval to join the squadron at Kronstadt.

On the 21st of March the British fleet, after a somewhat stormy passage,

was at the entrance to the Sound. Nicholas Vansittart, afterwards Lord

Bexley, the British diplomatic agent entrusted with the message to the

Danish government, was landed, and left for Copenhagen. On the 23rd he

returned with the refusal of the Danes. The British fleet then passed

the Danish fort at Cronenburg, unhurt by its distant fire, and without

being molested by the forts on the Swedish shore. Nelson urged immediate

attack, and recommended, as an alternative, that part of the British

fleet should watch the Danes while the remainder advanced up the Baltic

to prevent the junction of the Russian Reval squadron with the ships in

Kronstadt. Sir Hyde Parker was, however, unwilling to go up the Baltic

with the Danes unsubdued behind him, or to divide his force. It was

therefore resolved that an attack should be made on the Danish capital

with the whole fleet in two divisions. Copenhagen lies on the east side

of the island of Zealand; opposite it is the shoal known as the Middle

Ground. To the east of the Middle Ground is another shoal known as

Saltholm Flat, and there is a passage available for large ships between

them. The main fortification of Copenhagen was the powerful Trekroner

(Three Crown) battery at the northern end of the sea-front. Here the

Danes had placed their strongest ships. The southern part of the city

front was covered by hulks and gun-vessels or bomb-vessels. There were

in all eighteen hulks or ships of the line in the Danish defence. To

have made the attack from the northern end would in Nelson's words have

been "to take the bull by the horns." He therefore proposed that he

should be detached with ten sail of the line, and the frigates and small

craft, to pass between the Middle Ground and Saltholm Flat, and assail

the Danish line at the southern end while the remainder of the fleet

engaged the Trekroner battery from the north. Sir Hyde Parker accepted

his offer, and added two ships of the line to the ten asked for by

Nelson.

During the nights of the 30th and 31st of March the channel between the

Middle Ground and Saltholm Flat was sounded by the boats of the British

fleet, the Danes making no attempt to interfere with them. On the 1st of

April Nelson brought his ships through. He had transferred his flag from

his own ship the "St George" (98) to the "Elephant" (74), commanded by

Captain Foley, because the water was too shallow for a three-decker. On

the morning of the 2nd of April the wind was fair from the south-east,

and at 9.30 A.M. the British squadron weighed anchor, led by the

"Amazon" frigate, commanded by Captain Riou, and began to pass along the

front of the Danish line. The Danes could bring into action 375 guns in

all. Their hulks and bomb-vessels were supported by batteries on

Zealand; but, as the water is shallow for a long distance from the

shore, these defences were too far off to render them effectual aid on

the south end of their line. Nelson disposed of a greater number of

guns, 1058 in all, but some did not come into action. The "Agamemnon"

(64), commanded by Captain Fancourt, was unable to round the south point

of the Middle Ground. The "Bellona" (74), commanded by Captain Thompson,

and the "Russel" (74), commanded by Captain Cuming, ran ashore on the

Middle Ground, but within range though at too great a distance for fully

effective fire. Captain Thompson lost his leg in the battle. The other

ships passed between the "Bellona" and "Russel" and the Danes. The

leading British ship, the "Defiance" (74), carrying the flag of

Rear-Admiral Graves, anchored just south of the Trekroner. As the wind

was from the south-east Sir Hyde Parker was unable to make the proposed

attack from the north. The place opposite the Danish fort which was to

have been taken by him was occupied by Captain Riou and the frigates.

The "Elephant" anchored almost in the middle of the line. Fire was

opened about 10 A.M., and at 11.30 the action was at its height.

Until 1 o'clock there was no diminution of the Danish fire. Sir Hyde

Parker, who saw the danger of Nelson's position, became anxious, and

sent his second, Captain Robert Waller Ottway, to him with a message

authorizing him to retire if he thought fit. Before Ottway, who had to

go in a row-boat, reached the "Elephant," Sir Hyde Parker had reflected

that it would be more magnanimous in him to take the responsibility of

ordering the retreat. He therefore hoisted the signal of recall. It was

a well-meant but ill-judged order. Nelson could only have retreated

before the south-easterly wind by going past the Trekroner fort, where

the passage is narrow, and the navigation difficult. He therefore

disregarded the signal, and amused himself and the few officers about

him by putting his glass to his blind eye and saying that he could not

see it. The frigates opposite the Trekroner did retreat, Captain Riou

being slain as they drew off.

At about 2.30 the fire from the Danish hulks had been much beaten down,

but as their crews fell, fresh men were sent from the shore and the fire

was resumed. Nelson astutely and legitimately seized the opportunity to

open negotiations with the Danes. He sent a flag of truce carried by Sir

F. Thesiger ashore to the crown prince of Denmark (then regent of the

kingdom), to say that unless he was allowed to take possession of the

hulks which had surrendered he would be compelled to burn them, a course

which he deprecated on the ground of humanity and his tenderness of "the

brothers of the English the Danes." The crown prince, who was shaken by

the spectacle of the battle, allowed himself to be drawn into a reply,

and to be referred to Sir Hyde Parker. Fire was suspended by the Danes

to allow of time to receive Sir Hyde Parker's answer. Nelson with

intelligent promptitude availed himself of the interval to withdraw his

squadron past the Trekroner. The difficulty found in getting the ships

out--one of them grounded--showed how disastrous an attempt to draw off

under fire of the forts must have been.

The Danish government, which had entered the coalition largely from fear

of Russia, was not prepared to make very great sacrifices, and now

entered into negotiations for an armistice. It was the more ready to do

so because it received news of the assassination of the tsar Paul, which

had happened on the 24th of March. An armistice was made for fourteen

weeks, which left the British fleet free to proceed up the Baltic. On

the 12th of April, after lightening the three-deckers of their guns, the

fleet passed over the shallows. But its presence had now lost all

military significance. Sir Hyde Parker was assured by the Russian

minister at Copenhagen that the new tsar Alexander I. would not continue

the policy of hostility with England and alliance with France which had

proved fatal to his father. The Swedes, who like the Danes had entered

the coalition under pressure from Russia, did not send their ships to

sea. The government of the new tsar was prepared for an arrangement with

England. The date of the final settlement was in all probability delayed

by the activity of Nelson, and his belief that a British fleet was the

best negotiator in Europe. The British government learnt of the tsar's

death on the 15th of April. On the 17th it instructed Sir Hyde Parker to

agree to a suspension of hostilities, and not to take active measures

against Russia so long as the Reval squadron did not put to sea. On the

21st of April, having now received a full account of the battle at

Copenhagen, it recalled Sir Hyde Parker, whose vacillating conduct and

want of enterprise had become manifest. He received the news of his

recall on the 5th of May. Nelson, to whom the command passed, at once

put to sea, and hastened with a part of his fleet to Reval, which he

reached on the 12th of May. The Russian squadron had, however, cut a

passage through the ice in the harbour on the 3rd, and had sailed for

Kronstadt. Nelson was received with formal civility by the Russian

officers, with whom he exchanged visits. He wrote a letter to Mr

Garlike, secretary of the British embassy at St Petersburg, saying that

he had come with a small squadron as the best way of paying "the very

highest compliment" to the tsar.

The Russian government, which not unnaturally wished to avoid any

appearance of acting under dictation, and was now in no anxiety for the

Reval squadron, treated his presence as a menace. On the 13th of May

Count Pahlen answered in a most peremptory letter informing Nelson that

negotiations would be suspended while he remained at Reval. This retort

caused Nelson annoyance which he did not attempt to conceal, but he

justly concluded that he had nothing further to do at Reval, and

therefore returned down the Baltic. Nelson remained with the fleet till

he was relieved at his own request, and was able to sail for England on

the 18th of June. He gave a proof of his regard for the service of the

country by taking his passage home in a small brig rather than withdraw

a line of battle ship from the squadron, which his rank entitled him to

do, and as other admirals of the time generally did. The British sailors

and ships embargoed in Russia were released on the 17th of May. Great

Britain released her prisoners on the 4th of June, and on the 17th of

June was signed the convention which terminated the Baltic campaign.

See _Dispatches and Letters of Vice-Admiral Nelson_, by Sir N. Harris

Nicolas (1845); _Life of Nelson_, by Capt. A. T. Mahan (London, 1899).

(D. H.)

COPERNICUS (or KOPPERNIGK), NICOLAUS (1473-1543), Polish astronomer, was

born on the 19th of February 1473, at Thorn in Prussian Poland, where

his father, a native of Cracow, had settled as a wholesale trader. His

mother, Barbara Watzelrode, belonged to a family of high mercantile and

civic standing. After the death of his father in 1483, Nicolaus was

virtually adopted by his uncle Lucas Watzelrode, later (in 1489) bishop

of Ermeland. Placed at the university of Cracow in 1491, he devoted

himself, during three years, to mathematical science under Albert

Brudzewski (1445-1497), and incidentally acquired some skill in

painting. At the age of twenty-three he repaired to Bologna, and there

varied his studies of canon law by attending the astronomical lectures

of Domenico Maria Novara (1454-1504). At Rome, in the Jubilee year 1500,

he himself lectured with applause; but having been nominated in 1497

canon of the cathedral of Frauenburg, he recrossed the Alps in 1501 with

the purpose of obtaining further leave of absence for the completion of

his academic career. Late in the same year, accordingly, he entered the

medical school of Padua, where he remained until 1505, having taken

meanwhile a doctor's degree in canon law at Ferrara on the 31st of May

1503. After his return to his native country he resided at the episcopal

palace of Heilsberg as his uncle's physician until the latter's death on

the 29th of March 1512. He then retired to Frauenburg, and vigorously

attended to his capitular duties. He never took orders, but acted

continually as the representative of the chapter under harassing

conditions, administrative and political; he was besides commissary of

the diocese of Ermeland; his medical skill, always at the service of the

poor, was frequently in demand by the rich; and he laid a scheme for the

reform of the currency before the Diet of Graudenz in 1522. Yet he found

time, amid these multifarious occupations, to elaborate an entirely new

system of astronomy, by the adoption of which man's outlook on the

universe was fundamentally changed.

The main lines of his great work were laid down at Heilsberg; at

Frauenburg, from 1513, he sought, with scanty instrumental means, to

test by observation the truth of the views it embodied (see ASTRONOMY:

HISTORY). His dissatisfaction with Ptolemaic doctrines was of early

date; and he returned from Italy, where so-called Pythagorean opinions

were then freely discussed, in strong and irrevocable possession of the

heliocentric theory. The epoch-making treatise in which it was set

forth, virtually finished in 1530, began to be known through the

circulation in manuscript of a _Commentariolus_, or brief popular

account of its purport written by Copernicus in that year. Johann

Albrecht Widmanstadt lectured upon it in Rome; Clement VII. approved,

and Cardinal Schonberg transmitted to the author a formal demand for

full publication. But his assent to this was only extracted from him in

1540 by the importunities of his friends, especially of his enthusiastic

disciple George Joachim Rheticus (1514-1576), who printed, in the

_Narratio prima_ (Danzig, 1540), a preliminary account of the Copernican

theory, and simultaneously sent to the press at Nuremberg his master's

complete exposition of it in the treatise entitled _De revolutionibus

orbium coelestium_ (1543). But the first printed copy reached Frauenburg

barely in time to be laid on the writer's death-bed. Copernicus was

seized with apoplexy and paralysis towards the close of 1542, and died

on the 24th of May 1543, happily unconscious that the fine Epistle, in

which he had dedicated his life's work to Paul III., was marred of its

effect by an anonymous preface, slipt in by Andreas Osiander

(1498-1552), with a view to disarming prejudice by insisting upon the

purely hypothetical character of the reasonings it introduced. The

trigonometrical section of the book had been issued as a separate

treatise (Wittenberg, 1542) under the care of Rheticus. The only work

published by Copernicus on his own initiative was a Latin version of the

Greek Epistles of Theophylact (Cracow, 1509). His treatise _De monetae

cudendae ratione_, 1526 (first printed in 1816), written by order of

King Sigismund I., is an exposition of the principles on which it was

proposed to reform the currency of the Prussian provinces of Poland. It

advocates unity of the monetary system throughout the entire state, with

strict integrity in the quality of the coin, and the charge of a

seigniorage sufficient to cover the expenses of mintage.

AUTHORITIES.--Rheticus was the only contemporary biographer of

Copernicus, and his narrative perished irretrievably. Gassendi's

jejune Life (Paris, 1654) is thus the earliest extant of any note. It

was supplemented, during the 19th century, by the various publications

of J. Sniadecki (Warsaw, 1803-1818); of J. H. W. Westphal, J. Czynski,

M. Curtze, H. A. Wolynski, F. Hipler, and others, but their efforts

were overshadowed by Dr Leopold Prowe's exhaustive _Nicolaus

Coppernicus_ (Berlin, 1883-1884), embodying the outcome of researches

indefatigably prosecuted for over thirty years. The first volume (in

two parts) is a detailed biography of the great astronomer; the second

includes some of his minor writings and correspondence, family

records, and historical documents of local interest. The effects of

his Italian sojourn upon the nascent ideas of Copernicus may be

profitably studied in Domenico Berti's _Copernico e le vicende del

sistema Copernicano in Italia_ (Roma, 1876), and in G. V.

Schiaparelli's _I Precursori del Copernico nell' antichita_ (Milano,

1873). A centenary edition of _De revolutionibus orbium coelestium_

was issued at Thorn in 1873, and a German translation by C. L. Menzzer

in 1879. (A. M. C.)

COPIAPO, a city of northern Chile, capital of the province of Atacama,

about 35 m. from the coast on the Copiapo river, in lat. 27 deg. 36' S.,

long. 70 deg. 23' W. Pop. (1895) 9301. The Caldera & Copiapo railway

(built 1848-1851 and one of the first in South America) extends beyond

Copiapo to the Chanarcillo mines (50 m.) and other mining districts.

Copiapo stands 1300 ft. above sea-level and has a mean temperature of

about 67 deg. in summer and 51 deg. in winter. Its port, Caldera, 50 m.

distant by rail, is situated on a well-sheltered bay with good shipping

facilities about 6 m. N. of the mouth of the Copiapo river. Copiapo is

perhaps the best built and most attractive of the desert region cities.

The river brings down from the mountains enough water to supply the town

and irrigate a considerable area in its vicinity. Beyond the small

fertile valley in which it stands is the barren desert, on which rain

rarely falls and which has no economic value apart from its minerals

(especially saline compounds). Copiapo was founded in 1742 by Jose de

Manso (afterwards Conde de Superunda, viceroy of Peru) and took its name

from the Copayapu Indians who occupied that region. It was primarily a

military station and transport post on the road to Peru, but after the

discovery of the rich silver deposits near Chanarcillo by Juan Godoy in

1832 it became an important mining centre. It has a good mining school

and reduction works, and is the supply station for an extensive mining

district. For many years the Famatina mines of Argentina received

supplies from this point by way of the Come-Caballo pass.

COPING (from "cope," Lat. _capa_), in architecture, the capping or

covering of a wall. This may be made of stone, brick, tile, slate,

metal, wood or thatch. In all cases it should be weathered to throw off

the wet. In Romanesque work it was plain and flat, and projected over

the wall with a throating to form a drip. In later work a steep slope

was given to the weathering (mainly on the outer side), and began at the

top with an astragal; in the Decorated style there were two or three

sets off; and in the later Perpendicular period these assumed a wavy

section, and the coping mouldings were continued round the sides, as

well as at top and bottom, mitreing at the angles, as in many of the

colleges at Oxford. The cheapest type of coping is that which caps the

ordinary 9 in. brick wall, and consists of brick on edge above a double

tile creasing, all in cement; the creasing consisting of one or two rows

of tiles laid horizontally on the wall and projecting on each side about

2 in. to throw off the water (see also MASONRY).

COPLAND, ROBERT (fl. 1515), English printer and author, is said to have

been a servant of William Caxton, and certainly worked for Wynkyn de

Worde. The first book to which his name is affixed as a printer is _The

Boke of Justices of Peace_ (1515), at the sign of the Rose Garland, in

Fleet Street, London. Anthony a Wood supposed, on the ground that he was

more educated than was usual in his trade, that he had been a poor

scholar of Oxford. His best known works are _The hye way to the Spyttell

hous_, a dialogue in verse between Copland and the porter of St

Bartholomew's hospital, containing much information about the vagabonds

who found their way there; and _Jyl of Breyntfords Testament_, dismissed

in _Athenae Oxonienses_ (ed. Bliss) as "a poem devoid of wit or decency,

and totally unworthy of further notice." He translated from the French

the romances of _Kynge Appolyne of Thyre_ (W. de Worde, 1510), _The

History of Helyas Knyght of the Swanne_ (W. de Worde, 1513), and _The

Life of Ipomydon_ (_Hue of Rotelande_), not dated. Among his other works

is _The Complaynte of them that ben too late maryed_, an undated tract

printed by W. de Worde.

William Copland, the printer, supposed to have been his brother,

published three editions of _Howleglas_, perhaps by Robert, which in any

case represent the earliest English version of _Till Eulenspiegel_.

The _Knyght of the Swanne_ was reprinted in Thom's _Early Prose

Romances_, vol. iii., and by the Grolier Club (1901); the _Hye Way_ in

W. C. Hazlitt's _Remains of the Early Popular Poetry of England_, vol.

iv. (1866). See further the "Forewords" to Dr F. J. Furnivall's

reprint of _Jyl of Breyntford_ (for private circulation, 1871) and J.

P. Collier, _Bibliographical and Critical Account of the Rarest Books

in the English Language_, vol. i. p. 153 (1865). For the books issued

from his press see _Hand-Lists of English Printers_ (1501-1556),

printed for the Bibliographical Society in 1896.

COPLESTON, EDWARD (1776-1849), English bishop, was born at Offwell in

Devonshire, and educated at Oxford. He was elected to a tutorship at

Oriel College in 1797, and in 1800 was appointed vicar of St Mary's,

Oxford. As university professor of poetry (1802-1812) he gained a

considerable reputation by his clever literary criticism and sound

latinity. After holding the office of dean at Oriel for some years, he

succeeded to the provostship in 1814, and owing largely to his influence

the college reached a remarkable degree of prosperity during the first

quarter of the 19th century. In 1826 he was appointed dean of Chester,

and in the next year he was consecrated bishop of Llandaff. Here he gave

his support to the new movement for church restoration in Wales, and

during his occupation of the see more than twenty new churches were

built in the diocese. The political problems of the time interested him

greatly, and his writings include two able letters to Sir Robert Peel,

one dealing with the _Variable Standard of Value_, the other with the

_Increase of Pauperism_ (Oxford, 1819).

COPLEY, JOHN SINGLETON (1737-1815), English historical painter, was born

of Irish parents at Boston, Massachusetts. He was self-educated, and

commenced his career as a portrait-painter in his native city. The germ

of his reputation in England was a little picture of a boy and squirrel,

exhibited at the Society of Arts in 1760. In 1774 he went to Rome, and

thence in 1775 came to England. In 1777 he was admitted associate of the

Royal Academy; in 1783 he was made Academician on the exhibition of his

most famous picture, the "Death of Chatham," popularized immediately by

Bartolozzi's elaborate engraving; and in 1790 he was commissioned to

paint a portrait picture of the defence of Gibraltar. The "Death of

Major Pierson," in the National Gallery, also deserves mention. Copley's

powers appear to greatest advantage in his portraits. He was the father

of Lord Chancellor Lyndhurst.

COPPEE, FRANCOIS EDOUARD JOACHIM (1842-1908), French poet and novelist,

was born in Paris on the 12th of January 1842. His father held a small

post in the civil service, and he owed much to the care of an admirable

mother. After passing through the Lycee Saint-Louis he became a clerk in

the ministry of war, and soon sprang into public favour as a poet of the

young "Parnassian" school. His first printed verses date from 1864. They

were republished with others in 1866 in a collected form (_Le

Reliquaire_), followed (1867) by _Les Intimites_ and _Poemes modernes_

(1867-1869). In 1869 his first play, _Le Passant_, was received with

marked approval at the Odeon theatre, and later _Fais ce que dois_

(1871) and _Les Bijoux de la delivrance_ (1872), short metrical dramas

inspired by the war, were warmly applauded.

After filling a post in the library of the senate, Coppee was chosen in

1878 as archivist of the Comedie-Francaise, an office which he held till

1884. In that year his election to the Academy caused him to retire

altogether from his public appointments. He continued to publish volumes

of poetry at frequent intervals, including _Les Humbles_ (1872), _Le

Cahier rouge_ (1874), _Olivier_ (1875), _L'Exilee_ (1876), _Contes en

vers_, &c. (1881), _Poemes et recits_ (1886), _Arriere-saison_ (1887),

_Paroles sinceres_ (1890). In his later years his output of verse

declined, but he published two more volumes, _Dans la priere et la

lutte_ and _Vers francais_. He had established his fame as "le poete des

humbles." Besides the plays mentioned above, two others written in

collaboration with Armand d'Artois, and some light pieces of little

importance, Coppee produced _Madame de Maintenon_ (1881), _Severo

Torelli_ (1883), _Les Jacobites_ (1885), and other serious dramas in

verse, including _Pour la couronne_ (1895), which was translated into

English (_For the Crown_) by John Davidson, and produced at the Lyceum

Theatre in 1896. The performance of a short episode of the Commune, _Le

Pater_, was prohibited by the government (1889). Coppee's first story in

prose, _Une Idylle pendant le siege_, appeared in 1875. It was followed

by various volumes of short tales, by _Toute une jeunesse_ (1890)--an

attempt to reproduce the feelings, if not the actual wants, of the

writer's youth,--_Les Vrais Riches_ (1892), _Le Coupable_ (1896), &c. He

was made an officer of the Legion of Honour in 1888. A series of

reprinted short articles on miscellaneous subjects, styled _Mon Franc

Parler_, appeared from 1893 to 1896; and in 1898 was published _La Bonne

Souffrance_, the outcome of Coppee's reconversion to the Roman Catholic

Church, which gained very wide popularity. The immediate cause of his

return to the faith was a severe illness which twice brought him to the

verge of the grave. Hitherto he had taken little open interest in public

affairs, but he now joined the most violent section of Nationalist

politicians, while retaining contempt for the whole apparatus of

democracy. He took a leading part against the prisoner in the Dreyfus

case, and was one of the originators of the notorious Ligue de la Patrie

Francaise. He died on the 23rd of May 1908.

Alike in verse and prose Coppee concerned himself with the plainest

expressions of human emotion, with elemental patriotism, and the joy of

young love, and the pitifulness of the poor, bringing to bear on each a

singular gift of sympathy and insight. The lyric and idyllic poetry, by

which he will chiefly be remembered, is animated by musical charm, and

in some instances, such as _La Benediction_ and _La Greve des

forgerons_, displays a vivid, though not a sustained, power of

expression. There is force, too, in the gloomy tale, _Le Coupable_. But

he exhibits all the defects of his qualities. In prose especially, his

sentiment often degenerates into sentimentality, and he continually

approaches, and sometimes oversteps, the verge of the trivial.

Nevertheless, by neglecting that canon of contemporary art which would

reduce the deepest tragedies of life to mere subjects for dissection, he

won those common suffrages which are the prize of exquisite literature.

See M. de Lescure's _Francois Coppee, l'homme, la vie, l'oeuvre_

(1889), and G. Druilhet, _Un Poete francais_ (1902).

COPPEE, HENRY (1821-1895), American educationalist and author, was born

in Savannah, Georgia, on the 13th of October 1821, of a French family

formerly settled in Haiti. He studied at Yale for two years, worked as a

civil engineer, graduated at West Point in 1845, served in the Mexican

War as a lieutenant and was breveted captain for gallantry at Contreras

and Churubusco, was professor of English at West Point from 1850 to 1855

(when he resigned from the army), was professor of English literature

and history in the University of Pennsylvania 1855-1866, and on the 1st

of April 1866 was chosen first president of Lehigh University. In 1875

he was succeeded by John McD. Leavitt and became professor of history

and English literature, but was president pro tem. from the death of

Robert A. Lamberton (b. 1824) in September 1893 to his own death in

Bethlehem on the 22nd of March 1895. He published elementary text-books

of logic (1857), of rhetoric (1859), and of English literature (1872);

various manuals of drill; _Grant, a Military Biography_ (1866); _General

Thomas_ (1893), in the "Great Commanders" Series; _History of the

Conquest of Spain by the Arab-Moors_ (1881); and in 1862 a translation

of Marmont's _Esprit des institutions militaires_, besides editing the

Comte de Paris's _Civil War in America_.

COPPER (symbol Cu, atomic weight 63.1, H = 1, or 63.6, O = 16), a metal

which has been known to and used by the human race from the most remote

periods. Its alloy with tin (bronze) was the first metallic compound in

common use by mankind, and so extensive and characteristic was its

employment in prehistoric times that the epoch is known as the Bronze

Age. By the Greeks and Romans both the metal and its alloys were

indifferently known as [Greek: chalkos] and _aes_. As, according to

Pliny, the Roman supply was chiefly drawn from Cyprus, it came to be

termed _aes cyprium_, which was gradually shortened to _cyprium_, and

corrupted into _cuprum_, whence comes the English word copper, the

French _cuivre_, and the German _Kupfer_.

Copper is a brilliant metal of a peculiar red colour which assumes a

pinkish or yellowish tinge on a freshly fractured surface of the pure

metal, and is purplish when the metal contains cuprous oxide. Its

specific gravity varies between 8.91 and 8.95, according to the

treatment to which it may have been subjected; J. F. W. Hampe gives

8.945 (0 deg./4 deg.) for perfectly pure and compact copper. Ordinary

commercial copper is somewhat porous and has a specific gravity ranging

from 8.2 to 8.5. It takes a brilliant polish, is in a high degree

malleable and ductile, and in tenacity it only falls short of iron,

exceeding in that quality both silver and gold. By different authorities

its melting-point is stated at from 1000 deg. to 1200 deg. C.; C. T.

Heycock and F. H. Neville give 1080 deg..5; P. Dejean gives 1085 deg. as

the freezing-point. The molten metal is sea-green in colour, and at

higher temperatures (in the electric arc) it vaporizes and burns with a

green flame. G. W. A. Kahlbaum succeeded in subliming the metal in a

vacuum, and H. Moissan (_Compt. rend._, 1905, 141, p. 853) distilled it

in the electric furnace. Molten copper absorbs carbon monoxide, hydrogen

and sulphur dioxide; it also appears to decompose hydrocarbons (methane,

ethane), absorbing the hydrogen and the carbon separating out. These

occluded gases are all liberated when the copper cools, and so give rise

to porous castings, unless special precautions are taken. The gases are

also expelled from the molten metal by lead, carbon dioxide, or water

vapour. Its specific heat is 0.0899 at 0 deg. C. and 0.0942 at 100 deg.;

the coefficient of linear expansion per 1 deg. C. is 0.001869. In

electric conductivity it stands next to silver; the conducting power of

silver being equal to 100, that of perfectly pure copper is given by A.

Matthiessen as 96.4 at 13 deg. C.

Copper is not affected by exposure in dry air, but in a moist

atmosphere, containing carbonic acid, it becomes coated with a green

basic carbonate. When heated or rubbed it emits a peculiar disagreeable

odour. Sulphuric and hydrochloric acids have little or no action upon it

at ordinary temperatures, even when in a fine state of division; but on

heating, copper sulphate and sulphur dioxide are formed in the first

case, and cuprous chloride and hydrogen in the second. Concentrated

nitric acid has also very little action, but with the dilute acid a

vigorous action ensues. The first products of this reaction are copper

nitrate and nitric oxide, but, as the concentration of the copper

nitrate increases, nitrous oxide and, eventually, free nitrogen are

liberated.

Many colloidal solutions of copper have been obtained. A reddish-brown

solution is obtained from solutions of copper chloride, stannous

chloride and an alkaline tartrate (Lottermoser, _Anorganische Colloide_,

1901).

_Occurrence._--Copper is widely distributed in nature, occurring in most

soils, ferruginous mineral waters, and ores. It has been discovered in

seaweed; in the blood of certain Cephalopoda and Ascidia as haemocyanin,

a substance resembling the ferruginous haemoglobin, and of a species of

_Limulus_; in straw, hay, eggs, cheese, meat, and other food-stuffs; in

the liver and kidneys, and, in traces, in the blood of man and other

animals (as an entirely adventitious constituent, however); it has also

been shown by A. H. Church to exist to the extent of 5.9% in turacin,

the colouring-matter of the wing-feathers of the Turaco.

Native copper, sometimes termed by miners malleable or virgin copper,

occurs as a mineral having all the properties of the smelted metal. It

crystallizes in the cubic system, but the crystals are often flattened,

elongated, rounded or otherwise distorted. Twins are common. Usually the

metal is arborescent, dendritic, filiform, moss-like or laminar. Native

copper is found in most copper-mines, usually in the upper workings,

where the deposit has been exposed to atmospheric influences. The metal

seems to have been reduced from solutions of its salts, and deposits may

be formed around mine-timber or on iron objects. It often fills cracks

and fissures in the rock. It is not infrequently found in serpentine,

and in basic eruptive rocks, where it occurs as veins and in amygdales.

The largest known deposits are those in the Lake Superior region, near

Keweenaw Point, Michigan, where masses upwards of 400 tons in weight

have been discovered. The metal was formerly worked by the Indians for

implements and ornaments. It occurs in a series of amygdaloidal

dolerites or diabases, and in the associated sandstones and

conglomerates. Native silver occurs with the copper, in some cases

embedded in it, like crystals in a porphyry. The copper is also

accompanied by epidote, calcite, prehnite, analcite and other zeolitic

minerals. Pseudomorphs after calcite are known; and it is notable that

native copper occurs pseudomorphous after aragonite at Corocoro, in

Bolivia, where the copper is disseminated through sandstone.

_Ores._--The principal ores of copper are the oxides cuprite and

melaconite, the carbonates malachite and chessylite, the basic chloride

atacamite, the silicate chrysocolla, the sulphides chalcocite,

chalcopyrite, erubescite and tetrahedrite. Cuprite (q.v.) occurs in most

cupriferous mines, but never by itself in large quantities. Melaconite

(q.v.) was formerly largely worked in the Lake Superior region, and is

abundant in some of the mines of Tennessee and the Mississippi valley.

Malachite is a valuable ore containing about 56% of the metal; it is

obtained in very large quantities from South Australia, Siberia and

other localities. Frequently intermixed with the green malachite is the

blue carbonate chessylite or azurite (q.v.), an ore containing when pure

55.16% of the metal. Atacamite (q.v.) occurs chiefly in Chile and Peru.

Chrysocolla (q.v.) contains in the pure state 30% of the metal; it is an

abundant ore in Chile, Wisconsin and Missouri. The sulphur compounds of

copper are, however, the most valuable from the economic point of view.

Chalcocite, redruthite, copper-glance (q.v.) or vitreous copper (Cu2S)

contains about 80% of copper. Copper pyrites, or chalcopyrite, contains

34.6% of copper when pure; but many of the ores, such as those worked

specially by wet processes on account of the presence of a large

proportion of iron sulphide, contain less than 5% of copper. Cornish

ores are almost entirely pyritic; and indeed it is from such ores that

by far the largest proportion of copper is extracted throughout the

world. In Cornwall copper lodes usually run east and west. They occur

both in the "killas" or clay-slate, and in the "growan" or granite.

Erubescite (q.v.), bornite, or horseflesh ore is much richer in copper

than the ordinary pyrites, and contains 56 or 57% of copper.

Tetrahedrite (q.v.), fahlerz, or grey copper, contains from 30 to 48% of

copper, with arsenic, antimony, iron and sometimes zinc, silver or

mercury. Other copper minerals are percylite (PbCuCl2(OH)2), boleite

(3PbCuCl2(OH)2, AgCl), stromeyerite {(Cu, Ag)2S}, cubanite (CuS, Fe2S3),

stannite (Cu2S, FeSnS3), tennantite (3Cu2S, As2S3), emplectite (Cu2S,

Bi2S3), wolfsbergite (Cu2S, Sb2S3), famatinite (3Cu2S, Sb2S5) and

enargite (3Cu2S, As2S5). For other minerals, see COMPOUNDS OF COPPER

below.

_Metallurgy._--Copper is obtained from its ores by three principal

methods, which may be denominated--(1) the pyro-metallurgical or dry

method, (2) the hydro-metallurgical or wet method, and (3) the

electro-metallurgical method.

The methods of working vary according to the nature of the ores treated

and local circumstances. The dry method, or ordinary smelting, cannot be

profitably practised with ores containing less than 4% of copper, for

which and for still poorer ores the wet process is preferred.

_Copper Smelting._--We shall first give the general principles which

underlie the methods for the dry extraction of copper, and then proceed

to a more detailed discussion of the plant used. Since all sulphuretted

copper ores (and these are of the most economic importance) are

invariably contaminated with arsenic and antimony, it is necessary to

eliminate these impurities, as far as possible, at a very early stage.

This is effected by calcination or roasting. The roasted ore is then

smelted to a mixture of copper and iron sulphides, known as copper

"matte" or "coarse-metal," which contains little or no arsenic, antimony

or silica. The coarse-metal is now smelted, with coke and siliceous

fluxes (in order to slag off the iron), and the product, consisting of

an impure copper sulphide, is variously known as "blue-metal," when more

or less iron is still present, "pimple-metal," when free copper and more

or less copper oxide is present, or "fine" or "white-metal," which is a

fairly pure copper sulphide, containing about 75% of the metal. This

product is re-smelted to form "coarse-copper," containing about 95% of

the metal, which is then refined. Roasted ores may be smelted in

reverberatory furnaces (English process), or in blast-furnaces (German

or Swedish process). The matte is treated either in reverberatory

furnaces (English process), in blast furnaces (German process), or in

converters (Bessemer process). The "American process" or "Pyritic

smelting" consists in the direct smelting of raw ores to matte in blast

furnaces. The plant in which the operations are conducted varies in

different countries. But though this or that process takes its name from

the country in which it has been mainly developed, this does not mean

that only that process is there followed.

The "English process" is made up of the following operations: (1)

calcination; (2) smelting in reverberatory furnaces to form the matte;

(3) roasting the matte; and (4) subsequent smelting in reverberatory

furnaces to fine- or white-metal; (5) treating the fine-metal in

reverberatory furnaces to coarse- or blister-copper, either with or

without previous calcination; (6) refining of the coarse-copper. A

shorter process (the so-called "direct process") converts the fine-metal

into refined copper directly. The "Welsh process" closely resembles the

English method; the main difference consists in the enrichment of the

matte by smelting with the rich copper-bearing slags obtained in

subsequent operations. The "German or Swedish process" is characterized

by the introduction of blast-furnaces. It is made up of the following

operations: (1) calcination, (2) smelting in blast-furnaces to form the

matte, (3) roasting the matte, (4) smelting in blast-furnaces with coke

and fluxes to "black-" or "coarse-metal," (5) refining the coarse-metal.

The "Anglo-German Process" is a combination of the two preceding, and

consists in smelting the calcined ores in shaft furnaces, concentrating

the matte in reverberatory furnaces, and smelting to coarse-metal in

either.

The impurities contained in coarse-copper are mainly iron, lead, zinc,

cobalt, nickel, bismuth, arsenic, antimony, sulphur, selenium and

tellurium. These can be eliminated by an oxidizing fusion, and slagging

or volatilizing the products resulting from this operation, or by

electrolysis (see below). In the process of oxidation, a certain amount

of cuprous oxide is always formed, which melts in with the copper and

diminishes its softness and tenacity. It is, therefore, necessary to

reconvert the oxide into the metal. This is effected by stirring the

molten metal with a pole of green wood ("poling"); the products which

arise from the combustion and distillation of the wood reduce the oxide

to metal, and if the operation be properly conducted "tough-pitch"

copper, soft, malleable and exhibiting a lustrous silky fracture, is

obtained. The surface of the molten metal is protected from oxidation by

a layer of anthracite or charcoal. "Bean-shot" copper is obtained by

throwing the molten metal into hot water; if cold water be used,

"feathered-shot" copper is formed. "Rosette" copper is obtained as thin

plates of a characteristic dark-red colour, by pouring water upon the

surface of the molten metal, and removing the crust formed. "Japan"

copper is purple-red in colour, and is formed by casting into ingots,

weighing from six ounces to a pound, and rapidly cooling by immersion in

water. The colour of these two varieties is due to a layer of oxide.

"Tile" copper is an impure copper, and is obtained by refining the first

tappings. "Best-selected" copper is a purer variety.

_Calcination or Roasting and Calcining Furnaces._--The roasting should

be conducted so as to eliminate as much of the arsenic and antimony as

possible, and to leave just enough sulphur as is necessary to combine

with all the copper present when the calcined ore is smelted. The

process is effected either in heaps, stalls, shaft furnaces,

reverberatory furnaces or muffle furnaces. Stall and heap roasting

require considerable time, and can only be economically employed when

the loss of the sulphur is of no consequence; they also occupy much

space, but they have the advantage of requiring little fuel and

handling. Shaft furnaces are in use for ores rich in sulphur, and where

it is desirable to convert the waste gases into sulphuric acid.

Reverberatory roasting does not admit of the utilization of the waste

gases, and requires fine ores and much labour and fuel; it has, however,

the advantage of being rapid. Muffle furnaces are suitable for fine ores

which are liable to decrepitate or sinter. They involve high cost in

fuel and labour, but permit the utilization of the waste gases.

Reverberatory furnaces of three types are employed in calcining copper

ores: (1) fixed furnaces, with either hand or mechanical rabbling; (2)

furnaces with movable beds; (3) furnaces with rotating working chambers.

Hand rabbling in fixed furnaces has been largely superseded by

mechanical rabbling. Of mechanically rabbling furnaces we may mention

the O'Harra modified by Allen-Brown, the Hixon, the Keller-Gaylord-Cole,

the Ropp, the Spence, the Wethey, the Parkes, Pearce's "Turret" and

Brown's "Horseshoe" furnaces. Blake's and Brunton's furnaces are

reverberatory furnaces with a movable bed. Furnaces with rotating

working chambers admit of continuous working; the fuel and labour costs

are both low.

In the White-Howell revolving furnace with lifters--a modification of

the Oxland--the ore is fed and discharged in a continuous stream. The

Bruckner cylinder resembles the Elliot and Russell black ash furnace;

its cylinder tapers slightly towards each end, and is generally 18 ft.

long by 8 ft. 6 in. in its greatest diameter. Its charge of from 8 to 12

tons of ore or concentrates is slowly agitated at a rate of three

revolutions a minute, and in from 24 to 36 hours it is reduced from say

40 or 35% to 7% of sulphur. The ore is under better control than is

possible with the continuous feed and discharge, and when sufficiently

roasted can be passed red-hot to the reverberatory furnace. These

advantages compensate for the wear and tear and the cost of moving the

heavy dead-weight.

Shaft calcining furnaces are available for fine ores and permit the

recovery of the sulphur. They are square, oblong or circular in section,

and the interior is fitted with horizontal or inclined plates or prisms,

which regulate the fall of the ore. In the Gerstenhoffer and

Hasenclever-Helbig furnaces the fall is retarded by prisms and inclined

plates. In other furnaces the ore rests on a series of horizontal

plates, and either remains on the same plate throughout the operation

(Ollivier and Perret furnace), or is passed from plate to plate by hand

(Maletra), or by mechanical means (Spence and M'Dougall).

The M'Dougall furnace is turret-shaped, and consists of a series of

circular hearths, on which the ore is agitated by rakes attached to

revolving arms and made to fall from hearth to hearth. It has been

modified by Herreshoff, who uses a large hollow revolving central shaft

cooled by a current of air. The shaft is provided with sockets, into

which movable arms with their rakes are readily dropped. The Peter

Spence type of calcining furnace has been followed in a large number of

inventions. In some the rakes are attached to rigid frames, with a

reciprocating motion, in others to cross-bars moved by revolving chains.

Some of these furnaces are straight, others circular. Some have only

one hearth, others three. This and the previous type of furnace, owing

to their large capacity, are at present in greatest favour. The

M'Dougall-Herreshoff, working on ores of over 30% of sulphur, requires

no fuel; but in furnaces of the reverberatory type fuel must be used, as

an excess of air enters through the slotted sides and the hinged doors

which open and shut frequently to permit of the passage of the rakes.

The consumption of fuel, however, does not exceed 1 of coal to 10 of

ore. The quantity of ore which these large furnaces, with a hearth area

as great as 2000 ft. and over, will roast varies from 40 to 60 tons a

day. Shaft calcining furnaces like the Gerstenhoffer, Hasenclever, and

others designed for burning pyrites fines have not found favour in

modern copper works.

_The Fusion of Ores in Reverberatory and Cupola Furnaces._--After the

ore has been partially calcined, it is smelted to extract its earthy

matter and to concentrate the copper with part of its iron and sulphur

into a matte. In reverberatory furnaces it is smelted by fuel in a

fireplace, separate from the ore, and in cupolas the fuel, generally

coke, is in direct contact with the ore. When Swansea was the centre of

the copper-smelting industry in Europe, many varieties of ores from

different mines were smelted in the same furnaces, and the Welsh

reverberatory furnaces were used. To-day more than eight-tenths of the

copper ores of the world are reduced to impure copper bars or to fine

copper at the mines; and where the character of the ore permits, the

cupola furnace is found more economical in both fuel and labour than the

reverberatory.

The Welsh method finds adherents only in Wales and Chile. In America the

usual method is to roast ores or concentrates so that the matte yielded

by either the reverberatory or cupola furnace will run from 45 to 50% in

copper, and then to transfer to the Bessemer converter, which blows it

up to 99%. In Butte, Montana, reverberatories have in the past been

preferred to cupola furnaces, as the charge has consisted mainly of fine

roasted concentrates; but the cupola is gaining ground there. At the

Boston and Great Falls (Montana) works tilting reverberatories, modelled

after open hearth steel furnaces, were first erected; but they were

found to possess objectionable features. Now both these and the

egg-shaped reverberatories are being abandoned for furnaces as long as

43 ft. 6 in. from bridge to bridge and of a width of 15 ft. 9 in. heated

by gas, with regenerative checker work at each end, and fed with ore or

concentrates, red-hot from the calciners, through a line of hoppers

suspended above the roof. Furnaces of this size smelt 200 tons of charge

a day. But even when the old type of reverberatory is preferred, as at

the Argo works, at Denver, where rich gold-and silver-bearing copper

matte is made, the growth of the furnace in size has been steady.

Richard Pearce's reverberatories in 1878 had an area of hearth of 15 ft.

by 9 ft. 8 in., and smelted 12 tons of cold charge daily, with a

consumption of 1 ton of coal to 2.4 tons of ore. In 1900 the furnaces

were 35 ft. by 16 ft., and smelt 50 tons daily of hot ore, with the

consumption of 1 ton of coal to 3.7 tons of ore.

The home of cupola smelting was Germany, where it has never ceased to

make steady progress. In Mansfeld brick cupola furnaces are without a

rival in size, equipment and performance. They are round stacks,

designed on the model of iron blast furnaces, 29 ft. high, fed

mechanically, and provided with stoves to heat the blast by the furnace

gases. The low percentage of sulphur in the roasted ore is little more

than enough to produce a matte of 40 to 45%, and therefore the escaping

gases are better fitted than those of most copper cupola furnaces for

burning in a stove. But as the slag carries on an average 46% of silica,

it is only through the utmost skill that it can be made to run as low on

an average as 0.3% in copper oxide. As the matte contains on an average

0.2% of silver, it is still treated by the Ziervogel wet method of

extraction, the management dreading the loss which might occur in the

Bessemer process of concentration, applied as preliminary to

electrolytic separation. Blast furnaces of large size, built of brick,

have been constructed for treating the richest and more silicious ores

of Rio Tinto, and the Rio Tinto Company has introduced converters at

the mine. This method of extraction contrasts favourably in time with

the leaching process, which is so slow that over 10,000,000 tons of ore

are always under treatment on the immense leaching floors of the

company's works in Spain. In the United States the cupola has undergone

a radical modification in being built of water-jacketed sections. The

first water-jacketed cupola which came into general use was a circular

inverted cone, with a slight taper, of 36 inches diameter at the

tuyeres, and composed of an outer and an inner metal shell, between

which water circulated. As greater size has been demanded, oval and

rectangular furnaces--as large as 180 in. by 56 in. at the tuyeres--have

been built in sections of cast or sheet iron or steel. A single section

can be removed and replaced without entirely emptying the stack, as a

shell of congealed slag always coats the inner surface of the jacket.

The largest furnaces are those of the Boston & Montana Company at Great

Falls, Montana, which have put through 500 tons of charge daily, pouring

their melted slag and matte into large wells of 10 ft. in diameter. A

combined brick- and water-cooled furnace has been adopted by the Iron

Mountain Company at Keswick, Cal., for matte concentration. In it the

cooling is effected by water pipes, interposed horizontally between the

layers of bricks. The Mt. Lyell smelting works in Tasmania, which are of

special interest, will be referred to later. (See PYRITIC SMELTING

below.)

_Concentrating Matte to Copper in the Bessemer Converter._--As soon as

the pneumatic method of decarburizing pig iron was accepted as

practicable, experiments were made with a view to Bessemerizing copper

ores and mattes. One of the earliest and most exhaustive series of

experiments was made on Rio Tinto ores at the John Brown works by John

Hollway, with the aim of both smelting the ore and concentrating the

matte in the same furnace, by the heat evolved through the oxidation of

their sulphur and iron. Experiments along the same lines were made by

Francis Bawden at Rio Tinto and Claude Vautin in Australia. The

difficulty of effecting this double object in one operation was so great

that in subsequent experiments the aim was merely to concentrate the

matte to metallic copper in converters of the Bessemer type. The

concentration was effected without any embarrassment till metallic

copper commenced to separate and chill in the bottom tuyeres. To meet

this obstacle P. Manhes proposed elevated side tuyeres, which could be

kept clear by punching through gates in a wind box. His invention was

adopted by the Vivians, at the Eguilles works near Sargues, Vaucluse,

France, and at Leghorn in Italy. But the greatest expansion of this

method has been in the United States, where more than 400,000,000 lb.

of copper are annually made in Bessemer converters. Vessels of several

designs are used--some modelled exactly after steel converters, others

barrel-shaped, but all with side tuyeres elevated about 10 in. above the

level of the bottom lining. Practice, however, in treating copper matte

differs essentially from the treatment of pig iron, inasmuch as from 20

to 30% of iron must be eliminated as slag and an equivalent quantity of

silica must be supplied. The only practical mode of doing this, as yet

devised, is by lining the converter with a silicious mixture. This is so

rapidly consumed that the converters must be cooled and partially

relined after 3 to 6 charges, dependent on the iron contents of the

matte. When available, a silicious rock containing copper or the

precious metals is of course preferred to barren lining. The material

for lining, and the frequent replacement thereof, constitute the

principal expense of the method. The other items of cost are _labour_,

the quantity of which depends on the mechanical appliances provided for

handling the converter shells and inserting the lining; and the _blast_,

which in barrel-shaped converters is low and in vertical converters is

high, and which varies therefore from 3 to 15 lb. to the square inch.

The quantity of air consumed in a converter which will blow up about 35

tons of matte per day is about 3000 cub. ft. per minute. The operation

of raising a charge of 50% matte to copper usually consists of two

blows. The first blow occupies about 25 minutes, and oxidizes all but a

small quantity of the iron and some of the sulphur, raising the product

to white metal. The slag is then poured and skimmed, the blast turned on

and converter retilted. During the second blow the sulphur is rapidly

oxidized, and the charge reduced to metal of 99% in from 30 to 40

minutes. Little or no slag results from the second blow. That from the

first blow contains between 1% and 2% of copper, and is usually poured

from ladles operated by an electric crane into a reverberatory, or into

the settling well of the cupola. The matte also, in all economically

planned works, is conveyed, still molten, by electric cranes from the

furnace to the converters. When lead or zinc is not present in notable

quantity, the loss of the precious metals by volatilization is slight,

but more than 5% of these metals in the matte is prohibitive. Under

favourable conditions in the larger works of the United States the cost

of converting a 50% matte to metallic copper is generally understood to

be only about 5/10 to 6/10 of a cent per lb.. of refined copper.

_Pyritic Smelting._--The heat generated by the oxidation of iron and

sulphur has always been used to maintain combustion in the kilns or

stalls for roasting pyrites. Pyritic smelting is a development of the

Russian engineer Semenikov's treatment (proposed in 1866) of copper

matte in a Bessemer converter. Since John Hollway's and other early

experiments of Lawrence Austin and Robert Sticht, no serious attempts

have been made to utilize the heat escaping from a converting vessel in

smelting ore and matte either in the same apparatus or in a separate

furnace. But considerable progress has been made in smelting highly

sulphuretted ores by the heat of their own oxidizable constituents. At

Tilt Cove, Newfoundland, the Cape Copper Company smelted copper ore,

with just the proper proportion of sulphur, iron and silica,

successfully without any fuel, when once the initial charge had been

fused with coke. The furnaces used were of ordinary design and built of

brick. Lump ore alone was fed, and the resulting matte showed a

concentration of only 3 into 1. When, however, a hot blast is used on

highly sulphuretted copper ores, a concentration of 8 of ore into 1 of

matte is obtained, with a consumption of less than one-third the fuel

which would be consumed in smelting the charge had the ore been

previously calcined. A great impetus to pyritic smelting was given by

the investigations of W. L. Austin, of Denver, Colorado, and both at

Leadville and Silverton raw ores are successfully smelted with as low a

fuel consumption as 3 of coke to 100 of charge.

Two types of pyritic smelting may be distinguished: one, in which the

operation is solely sustained by the combustion of the sulphur in the

ores, without the assistance of fuel or a hot blast; the other in which

the operation is accelerated by fuel, or a hot blast, or both. The

largest establishment in which advantage is taken of the self-contained

fuel is at the smelting works of the Mt. Lyell Company, Tasmania. There

the blast is raised from 600 deg. to 700 deg. F. in stoves heated by

extraneous fuel, and the raw ore smelted with only 3% of coke. The ore

is a compact iron pyrites containing copper 2.5%, silver 3.83 oz., gold

0.139 oz. It is smelted raw with hot blast in cupola furnaces, the

largest being 210 in. by 40 in. The resulting matte runs 25%. This is

reconcentrated raw in hot-blast cupolas to 55%, and blown directly into

copper in converters. Thus these ores, as heavily charged with sulphur

as those of the Rio Tinto, are speedily reduced by three operations and

without roasting, with a saving of 97.6% of the copper, 93.2% of the

silver and 93.6% of the gold.

Pyritic smelting has met with a varying economic success. According to

Herbert Lang, its most prominent chance of success is in localities

where fuel is dear, and the ores contain precious metals and sufficient

sulphides and arsenides to render profitable dressing unnecessary.

_The Nicholls and James Process._--Nicholls and James have applied, very

ingeniously, well-known reactions to the refining of copper, raised to

the grade of white metal. This process is practised by the Cape Copper

and Elliot Metal Company. A portion of the white metal is calcined to

such a degree of oxidation that when fused with the unroasted portion,

the reaction between the oxygen in the roasted matte and the sulphur in

the raw material liberates the metallic copper. The metal is so pure

that it can be refined by a continuous operation in the same furnace.

_Wet Methods for Copper Extraction._--Wet methods are only employed for

low grade ores (under favourable circumstances ore containing from 1/4 to

1% of copper has admitted of economic treatment), and for gold and

silver bearing metallurgical products.

The fundamental principle consists in getting the ore into a solution,

from which the metal can be precipitated. The ores of any economic

importance contain the copper either as oxide, carbonate, sulphate or

sulphide. These compounds are got into solution either as chlorides or

sulphates, and from either of these salts the metal can be readily

obtained. Ores in which the copper is present as oxide or carbonate are

soluble in sulphuric or hydrochloric acids, ferrous chloride, ferric

sulphate, ammoniacal compounds and sodium thiosulphate. Of these

solvents, only the first three are of economic importance. The choice of

sulphuric or hydrochloric acid depends mainly upon the cost, both acting

with about the same rapidity; thus if a Leblanc soda factory is near at

hand, then hydrochloric acid would most certainly be employed. Ferrous

chloride is not much used; the Douglas-Hunt process uses a mixture of

salt and ferrous sulphate which involves the formation of ferrous

chloride, and the new Douglas-Hunt process employs sulphuric acid in

which ferrous chloride is added after leaching.

Sulphuric acid may be applied as such on the ores placed in lead, brick,

or stone chambers; or as a mixture of sulphur dioxide, nitrous fumes

(generated from Chile saltpetre and sulphuric acid), and steam, which

permeates the ore resting on the false bottom of a brick chamber. When

most of the copper has been converted into the sulphate, the ore is

lixiviated. Hydrochloric acid is applied in the same way as sulphuric

acid; it has certain advantages of which the most important is that it

does not admit the formation of basic salts; its chief disadvantage is

that it dissolves the oxides of iron, and accordingly must not be used

for highly ferriferous ores. The solubility of copper carbonate in

ferrous chloride solution was pointed out by Max Schaffner in 1862, and

the subsequent recognition of the solubility of the oxide in the same

solvent by James Douglas and Sterry Hunt resulted in the "Douglas-Hunt"

process for the wet extraction of copper. Ferrous chloride decomposes

the copper oxide and carbonate with the formation of cuprous and cupric

chlorides (which remain in solution), and the precipitation of ferrous

oxide, carbon dioxide being simultaneously liberated from the carbonate.

In the original form of the Douglas-Hunt process, ferrous chloride was

formed by the interaction of sodium chloride (common salt) with ferrous

sulphate (green vitriol), the sodium sulphate formed at the same time

being removed by crystallization. The ground ore was stirred with this

solution at 70 deg. C. in wooden tubs until all the copper was dissolved.

The liquor was then filtered from the iron oxides, and the filtrate

treated with scrap iron, which precipitated the copper and reformed

ferrous chloride, which could be used in the first stage of the process.

The advantage of this method rests chiefly on the small amount of iron

required; but its disadvantages are that any silver present in the ores

goes into solution, the formation of basic salts, and the difficulty of

filtering from the iron oxides. A modification of the method was

designed to remedy these defects. The ore is first treated with dilute

sulphuric acid, and then ferrous or calcium chloride added, thus forming

copper chlorides. If calcium chloride be used the precipitated calcium

sulphate must be removed by filtration. Sulphur dioxide is then blown

in, and the precipitate is treated with iron, which produces metallic

copper, or milk of lime, which produces cuprous oxide. Hot air is blown

into the filtrate, which contains ferrous or calcium chlorides, to expel

the excess of sulphur dioxide, and the liquid can then be used again. In

this process ("new Douglas-Hunt") there are no iron oxides formed, the

silver is not dissolved, and the quantity of iron necessary is

relatively small, since all the copper is in the cuprous condition. It

is not used in the treatment of ores, but finds application in the case

of calcined argentiferous lead and copper mattes.

The precipitation of the copper from the solution, in which it is

present as sulphate, or as cuprous and cupric chlorides, is generally

effected by metallic iron. Either wrought, pig, iron sponge or iron bars

are employed, and it is important to notice that the form in which the

copper is precipitated, and also the time taken for the separation,

largely depend upon the condition in which the iron is applied. Spongy

iron acts most rapidly, and after this follow iron turnings and then

sheet clippings. Other precipitants such as sulphuretted hydrogen and

solutions of sulphides, which precipitate the copper as sulphides, and

milk of lime, which gives copper oxides, have not met with commercial

success. When using iron as the precipitant, it is desirable that the

solution should be as neutral as possible, and the quantity of ferric

salts present should be reduced to a minimum; otherwise, a certain

amount of iron would be used up by the free acid and in reducing the

ferric salts. Ores in which the copper is present as sulphate are

directly lixiviated and treated with iron. Mine waters generally contain

the copper in this form, and it is extracted by conducting the waters

along troughs fitted with iron gratings.

The wet extraction of metallic copper from ores in which it occurs as

the sulphide, may be considered to involve the following operations: (1)

conversion of the copper into a soluble form, (2) dissolving out the

soluble copper salt, (3) the precipitation of the copper. Copper

sulphide may be converted either into the sulphate, which is soluble in

water; the oxide, soluble in sulphuric or hydrochloric acid; cupric

chloride, soluble in water; or cuprous chloride, which is soluble in

solutions of metallic chlorides.

The conversion into sulphate is generally effected by the oxidizing

processes of weathering, calcination, heating with iron nitrate or

ferric sulphate. It may also be accomplished by calcination with ferrous

sulphate, or other easily decomposable sulphates, such as aluminium

sulphate. Weathering is a very slow, and, therefore, an expensive

process; moreover, the entire conversion is only accomplished after a

number of years. Calcination is only advisable for ores which contain

relatively much iron pyrites and little copper pyrites. Also, however

slowly the calcination may be conducted, there is always more or less

copper sulphide left unchanged, and some copper oxide formed.

Calcination with ferrous sulphate converts all the copper sulphide into

sulphate. Heap roasting has been successfully employed at Agordo, in the

Venetian Alps, and at Majdanpek in Servia. Josef Perino's process, which

consists in heating the ore with iron nitrate to 50 deg.-150 deg. C., is

said to possess several advantages, but it has not been applied

commercially. Ferric sulphate is only used as an auxiliary to the

weathering process and in an electrolytic process.

The conversion of the sulphide into oxide is adopted where the

Douglas-Hunt process is employed, or where hydrochloric or sulphuric

acids are cheap. The calcination is effected in reverberatory furnaces,

or in muffle furnaces, if the sulphur is to be recovered. Heap, stall or

shaft furnace roasting is not very satisfactory, as it is very difficult

to transform all the sulphide into oxide.

The conversion of copper sulphide into the chlorides may be accomplished

by calcining with common salt, or by treating the ores with ferrous

chloride and hydrochloric acid or with ferric chloride. The dry way is

best; the wet way is only employed when fuel is very dear, or when it is

absolutely necessary that no noxious vapours should escape into the

atmosphere. The dry method consists in an oxidizing roasting of the

ores, and a subsequent chloridizing roasting with either common salt or

_Abraumsalz_ in reverberatory or muffle furnaces. The bulk of the copper

is thus transformed into cupric chloride, little cuprous chloride being

obtained. This method had been long proposed by William Longmaid, Max

Schaffner, Becchi and Haupt, but was only introduced into England by the

labours of William Henderson, J. A. Phillips and others. The wet method

is employed at Rio Tinto, the particular variant being known as the

"Dotsch" process. This consists in stacking the broken ore in heaps and

adding a mixture of sodium sulphate and ferric chloride in the

proportions necessary for the entire conversion of the iron into ferric

sulphate. The heaps are moistened with ferric chloride solution, and the

reaction is maintained by the liquid percolating through the heap. The

liquid is run off at the base of the heaps into the precipitating tanks,

where the copper is thrown down by means of metallic iron. The ferrous

chloride formed at the same time is converted into ferric chloride which

can be used to moisten the heaps. This conversion is effected by

allowing the ferrous chloride liquors slowly to descend a tower, filled

with pieces of wood, coke or quartz, where it meets an ascending current

of chlorine.

The sulphate, oxide or chlorides, which are obtained from the

sulphuretted ores, are lixiviated and the metal precipitated in the same

manner as we have previously described.

The metal so obtained is known as "cement" copper. If it contains more

than 55% of copper it is directly refined, while if it contains a lower

percentage it is smelted with matte or calcined copper pyrites. The

chief impurities are basic salts of iron, free iron, graphite, and

sometimes silica, antimony and iron arsenates. Washing removes some of

these impurities, but some copper always passes into the slimes. If much

carbonaceous matter be present (and this is generally so when iron

sponge is used as the precipitant) the crude product is heated to

redness in the air; this burns out the carbon, and, at the same time,

oxidizes a little of the copper, which must be subsequently reduced. A

similar operation is conducted when arsenic is present; basic-lined

reverberatory furnaces have been used for the same purpose.

_Electrolytic Refining._--The principles have long been known on which

is based the electrolytic separation of copper from the certain elements

which generally accompany it, whether these, like silver and gold, are

valuable, or, like arsenic, antimony, bismuth, selenium and tellurium,

are merely impurities. But it was not until the dynamo was improved as a

machine for generating large quantities of electricity at a very low

cost that the electrolysis of copper could be practised on a commercial

scale. To-day, by reason of other uses to which electricity is applied,

electrically deposited copper of high conductivity is in ever-increasing

demand, and commands a higher price than copper refined by fusion. This

increase in value permits of copper with not over L2 or $10 worth of the

precious metals being profitably subjected to electrolytic treatment.

Thus many million ounces of silver and a great deal of gold are

recovered which formerly were lost.

The earliest serious attempt to refine copper industrially was made by

G. R. Elkington, whose first patent is dated 1865. He cast crude copper,

as obtained from the ore, into plates which were used as anodes, sheets

of electro-deposited copper forming the cathodes. Six anodes were

suspended, alternately with four cathodes, in a saturated solution of

copper sulphate in a cylindrical fire-clay trough, all the anodes being

connected in one parallel group, and all the cathodes in another. A

hundred or more jars were coupled in series, the cathodes of one to the

anodes of the next, and were so arranged that with the aid of side-pipes

with leaden connexions and india-rubber joints the electrolyte could,

once daily, be made to circulate through them all from the top of one

jar to the bottom of the next. The current from a Wilde's dynamo was

passed, apparently with a current density of 5 or 6 amperes per sq. ft.,

until the anodes were too crippled for further use. The cathodes, when

thick enough, were either cast and rolled or sent into the market

direct. Silver and other insoluble impurities collected at the bottom of

the trough up to the level of the lower side-tube, and were then run off

through a plug in the bottom into settling tanks, from which they were

removed for metallurgical treatment. The electrolyte was used until the

accumulation of iron in it was too great, but was mixed from time to

time with a little water acidulated by sulphuric acid. This process is

of historic interest, and in principle it is identical with that now

used. The modifications introduced have been chiefly in details, in

order to economize materials and labour, to ensure purity of product,

and to increase the rate of deposition.

The chemistry of the process has been studied by Martin Kiliani

(_Berg- und Huttenmannische Zeitung_, 1885, p. 249), who found that,

using the (low) current-density of 1.8 ampere per sq. ft. of cathode,

and an electrolyte containing 1-1/2 lb. of copper sulphate and 1/2 lb.

of sulphuric acid per gallon, all the gold, platinum and silver

present in the crude copper anode remain as metals, undissolved, in

the anode slime or mud, and all the lead remains there as sulphate,

formed by the action of the sulphuric acid (or SO4 ions); he found

also that arsenic forms arsenious oxide, which dissolves until the

solution is saturated, and then remains in the slime, from which on

long standing it gradually dissolves, after conversion by secondary

reactions into arsenic oxide; antimony forms a basic sulphate which in

part dissolves; bismuth partly dissolves and partly remains, but the

dissolved portion tends slowly to separate out as a basic salt which

becomes added to the slime; cuprous oxide, sulphide and selenides

remain in the slime, and very slowly pass into solution by simple

chemical action; tin partly dissolves (but in part separates again as

basic salt) and partly remains as basic sulphate and stannic oxide;

zinc, iron, nickel and cobalt pass into solution--more readily indeed

than does the copper. Of the metals which dissolve, none (except

bismuth, which is rarely present in any quantity) deposits at the

anode so long as the solution retains its proper proportion of copper

and acid, and the current-density is not too great. Neutral solutions

are to be avoided because in them silver dissolves from the anode and,

being more electro-negative than copper, is deposited at the cathode,

while antimony and arsenic are also deposited, imparting a dark colour

to the copper. Electrolytic copper should contain at least 99.92% of

metallic copper, the balance consisting mainly of oxygen with not more

than 0.01% in all of lead, arsenic, antimony, bismuth and silver. Such

a degree of purity is, however, unattainable unless the conditions of

electrolysis are rigidly adhered to. It should be observed that the

free acid is gradually neutralized, partly by chemical action on

certain constituents of the slime, partly by local action between

different metals of the anode, both of which effect solution

independently of the current, and partly by the peroxidation (or

aeration) of ferrous sulphate formed from the iron in the anode. At

the same time there is a gradual substitution of other metals for

copper in the solution, because although copper _plus_ other (more

electro-positive) metals are constantly dissolving at the anode, only

copper is deposited at the cathode. Hence the composition and acidity

of the solution, on which so much depends, must be constantly watched.

The dependence of the mechanical qualities of the copper upon the

current-density employed is well known. A very weak current gives a

pale and brittle deposit, but as the current-density is increased up

to a certain point, the properties of the metal improve; beyond this

point they deteriorate, the colour becoming darker and the deposit

less coherent, until at last it is dark brown and spongy or

pulverulent. The presence of even a small proportion of hydrochloric

acid imparts a brown tint to the deposit. Baron H. v. Hubl (_Mittheil.

des k. k. militar-geograph. Inst._, 1886, vol. vi. p. 51) has found

that with neutral solutions a 5% solution of copper sulphate gave no

good result, while with a 20% solution the best deposit was obtained

with a current-density of 28 amperes per sq. ft.; with solutions

containing 2% of sulphuric acid, the 5% solution gave good deposits

with current-densities of 4 to 7.5 amperes, and the 20% solution with

11.5 to 37 amperes, per sq. ft. The maximum current-densities for a

_pure_ acid solution at rest were: for 15% pure copper sulphate

solutions 14 to 21 amperes, and for 20% solutions 18.5 to 28 amperes,

per sq. ft.; but when the solutions were kept in gentle motion these

maxima could be increased to 21-28 and 28-37 amperes per sq. ft.

respectively. The necessity for adjusting the current-density to the

composition and treatment of the electrolyte is thus apparent. The

advantage of keeping the solution in motion is due partly to the

renewal of solution thus effected in the neighbourhood of the

electrodes, and partly to the neutralization of the tendency of

liquids undergoing electrolysis to separate into layers, due to the

different specific gravities of the solutions flowing from the

opposing electrodes. Such an irregular distribution of the bath, with

strong copper sulphate solution from the anode at the bottom and acid

solution from the cathode at the top, not only alters the conductivity

in different strata and so causes irregular current-distribution, but

may lead to the current-density in the upper layers being too great

for the proportion of copper there present. Irregular and defective

deposits are therefore obtained. Provision for circulation of solution

is made in the systems of copper-refining now in use. Henry Wilde, in

1875, in depositing copper on iron printing-rollers, recognized this

principle and rotated the rollers during electrolysis, thereby

renewing the surfaces of metal and liquid in mutual contact, and

imparting sufficient motion to the solution to prevent stratification;

as an alternative he imparted motion to the electrolyte by means of

propeller blades. Other workers have followed more or less on the same

lines; reference may be made to the patents of F. E. and A. S. Elmore,

who sought to improve the character of the deposit by burnishing

during electrolysis, of E. Dumoulin, and Sherard Cowper-Coles

(_Engineering Review_, 1905, vol. xiii. p. 392), who prefers to rotate

the cathode at a speed that maintains a peripheral velocity of at

least 1000 ft. per minute. Certain other inventors have applied the

same principle in a different way. H. Thofehrn in America and J. C.

Graham in England have patented processes by which jets of the

electrolyte are caused to impinge with considerable force upon the

surface of the cathode, so that the renewal of the liquid at this

point takes place very rapidly, and current-densities per sq. ft. of

50 to 100 amperes are recommended by the former, and of 300 amperes by

the latter. Graham has described experiments in this direction, using

a jet of electrolyte forced (beneath the surface of the bath) through

a hole in the anode upon the surface of the cathode. Whilst the jet

was playing, a good deposit was formed with so high a current-density

as 280 amperes per sq. ft., but if the jet was checked, the deposit

(now in a still liquid) was instantaneously ruined. When two or more

jets were used side by side the deposit was good opposite the centre

of each, but bad at the point where two currents met, because the rate

of flow was reduced. By introducing perforated shields of ebonite

between the electrodes, so that the full current-density was only

attained at the centres of the jets, these ill effects could be

prevented. One of the chief troubles met with was the formation of

arborescent growths around the edges of the cathode, due to the

greater current-density in this region; this, however, was also

obviated by the use of screens. By means of a very brisk rotation of

cathode, combined with a rapid current of electrolyte, J. W. Swan has

succeeded in depositing excellent copper at current-densities

exceeding 1000 amperes per sq. ft. The methods by which such results

are to be obtained cannot, however, as yet be practised economically

on a working scale; one great difficulty in applying them to the

refining of metals is that the jets of liquid would be liable to carry

with them articles of anode mud, and Swan has shown that the presence

of solid particles in the electrolyte is one of the most fruitful

causes of the well-known nodular growths on electro-deposited copper.

Experiments on a working scale with one of the jet processes in

America have, it is reported, been given up after a full trial.

In copper-refining practice, the current-density commonly ranges from

7.5 to 12 or 15, and occasionally to 18, amperes per sq. ft. The

electrical pressure required to force a current of this intensity

through the solution, and to overcome a certain opposing electromotive

force arising from the more electro-negative impurities of the anode,

depends upon the composition of the bath and of the anodes, the

distance between the electrodes, and the temperature, but under the

usual working conditions averages 0.3 volt for every pair of

electrodes in series. In nearly all the processes now used, the

solution contains about 1-1/2 to 2 lb. of copper sulphate and from 5

to 10 oz. of sulphuric acid per gallon of water, and the space between

the electrodes is from 1-1/2 to 2 in., whilst the total area of

cathode surface in each tank may be 200 sq. ft., more or less. The

anodes are usually cast copper plates about (say) 3 ft. by 2 ft. by

3/4 or 1 in. The cathodes are frequently of electro-deposited copper,

deposited to a thickness of about 1/32 in. on black-leaded copper

plates, from which they are stripped before use. The tanks are

commonly constructed of wood lined with lead, or tarred inside, and

are placed in terrace fashion each a little higher than the next in

series, to facilitate the flow of solution through them all from a

cistern at one end to a well at the other. Gangways are left between

adjoining rows of tanks, and an overhead travelling-crane facilitates

the removal of the electrodes. The arrangement of the tanks depends

largely upon the voltage available from the electric generator

selected; commonly they are divided into groups, all the baths in each

group being in series. In the huge Anaconda plant, for example, in

which 150 tons of refined copper can be produced daily by the Thofehrn

multiple system (not the jet system alluded to above), there are 600

tanks about 8-1/4 ft. by 4-1/2 ft. by 3-1/4 ft. deep, arranged in

three groups of 200 tanks in series. The connexions are made by copper

rods, each of which, in length, is twice the width of the tank, with a

bayonet-bend in the middle, and serves to support the cathodes in the

one and the anodes in the next tank. Self-registering voltmeters

indicate at any moment the potential difference in every tank, and

therefore give notice of short circuits occurring at any part of the

installation. The chief differences between the commercial systems of

refining lie in the arrangement of the baths, in the disposition and

manner of supporting the electrodes in each, in the method of

circulating the solution, and in the current-density employed. The

various systems are often classed in two groups, known respectively as

the _Multiple_ and _Series_ systems, depending upon the arrangement of

the electrodes in each tank. Under the multiple system anodes and

cathodes are placed alternately, all the anodes in one tank being

connected to one rod, and all the cathodes to another, and the

potential difference between the terminals of each tank is that

between a single pair of plates. Under the series system only the

first anode and the last cathode are connected to the conductors;

between these are suspended, isolated from one another, a number of

intermediate bi-polar electrode plates of raw copper, each of these

plates acting on one side as a cathode, receiving a deposit of copper,

and on the other as an anode, passing into solution; the voltage

between the terminals of the tank will be as many times as great as

that between a single pair of plates as there are spaces between

electrodes in the tank. In time the original impure copper of the

plates becomes replaced by refined copper, but if the plates are

initially very impure and dissolve irregularly, it may happen that

much residual scrap may have to be remelted, or that some of the metal

may be twice refined, thus involving a waste of energy. Moreover, the

high potential difference between the terminals of the series tank

introduces a greater danger of short-circuiting through scraps of

metal at the bottom of the bath; for this reason, also, lead-lined

vats are inadmissible, and tarred slate tanks are often used instead.

A valuable comparison of the multiple and series systems has been

published by E. Keller (see _The Mineral Industry_, New York, 1899,

vol. vii. p. 229). G. Kroupa has calculated that the cost of refining

is 8s. per ton of copper higher under the series than it is under the

multiple system; but against this, it must be remembered that the new

works of the Baltimore Copper Smelting and Rolling Company, which are

as large as those of the Anaconda Copper Mining Company, are using the

Hayden process, which is the chief representative of the several

series systems. In this system rolled copper anodes are used; these,

being purer than many cast anodes, having flat surfaces, and being

held in place by guides, dissolve with great regularity and require a

space of only 5/8 in. between the electrodes, so that the potential

difference between each pair of plates may be reduced to 0.15-0.2

volt.

J. A. W. Borchers, in Germany, and A. E. Schneider and O. Szontagh, in

America, have introduced a method of circulating the solution in each

vat by forcing air into a vertical pipe communicating between the

bottom and top of a tank, with the result that the bubbling of the air

upward aspirates solution through the vertical pipe from below, at the

same time aerating it, and causing it to overflow into the top of the

tank. Obviously this slow circulation has but little effect on the

rate at which the copper may be deposited. The electrolyte, when too

impure for further use, is commonly recrystallized, or electrolysed

with insoluble anodes to recover the copper.

The yield of copper per ampere (in round numbers, 1 oz. of copper per

ampere per diem) by Faraday's law is never attained in practice; and

although 98% may with care be obtained, from 94 to 96% represents the

more usual current-efficiency. With 100% current-efficiency and a

potential difference of 0.3 volt between the electrodes, 1 lb. of

copper should require about 0.154 electrical horse-power hours as the

amount of energy to be expended in the tank for its production. In

practice the expenditure is somewhat greater than this; in large works

the gross horse-power required for the refining itself and for power

and lighting in the factory may not exceed 0.19 to 0.2 (or in smaller

works 0.25) horse-power hours per pound of copper refined.

Many attempts have been made to use crude sulphide of copper or matte

as an anode, and recover the copper at the cathode, the sulphur and

other insoluble constituents being left at the anode. The best known

of these is the Marchese process, which was tested on a working scale

at Genoa and Stolberg in Rhenish Prussia. As the operation proceeded,

it was found that the voltage had to be raised until it became

prohibitive, while the anodes rapidly became honeycombed through and,

crumbling away, filled up the space at the bottom of the vat. The

process was abandoned, but in a modified form appears to be now in use

in Nijni-Novgorod in Russia. Siemens and Halske introduced a combined

process in which the ore, after being part-roasted, is leached by

solutions from a previous electrolytic operation, and the resulting

copper solution electrolysed. In this process the anode solution had

to be kept separate from the cathode solution, and the membrane which

had in consequence to be used, was liable to become torn, and so to

cause trouble by permitting the two solutions to mix. Modifications of

the process have therefore been tried.

Modern methods in copper smelting and refining have effected enormous

economy in time, space, and labour, and have consequently increased the

world's output. With pyritic smelting a sulphuretted copper ore, fed

into a cupola in the morning, can be passed directly to the converter,

blown up to metal, and shipped as 99% bars by evening--an operation

which formerly, with heap roasting of the ore and repeated roasting of

the mattes in stalls, would have occupied not less than four months. A

large furnace and a Bessemer converter, the pair capable of making a

million pounds of copper a month from a low-grade sulphuretted ore, will

not occupy a space of more than 25ft. by 100ft.; and whereas, in making

metallic copper out of a low-grade sulphuretted ore, one day's labour

used to be expended on every ton of ore treated, to-day one day's labour

will carry at least four tons of ore through the different mechanical

and metallurgical processes necessary to reduce them to metal. About 70%

of the world's annual copper output is refined electrolytically, and

from the 461,583 tons refined in the United States in 1907, there were

recovered 13,995,436 oz. of silver and 272,150 oz. of gold. The recovery

of these valuable metals has contributed in no small degree to the

expansion of electrolytic refining.

_Production._--The sources of copper, its applications and its

metallurgy, have undergone great changes. Chile was the largest producer

in 1869 with 54,867 tons; but in 1899 her production had fallen off to

25,000 tons. Great Britain, though she had made half the world's copper

in 1830, held second place in 1860, making from native ores 15,968 tons;

in 1900 her production was 777 tons, and in 1907, 711 tons. The United

States made only 572 tons in 1850, and 12,600 tons in 1870; but she

to-day makes more than 60% of the world's total. In 1879, Spain was the

largest producer, but now ranks third.

The estimated total production for each decade of the 19th century in

metric tons is here shown:--

1801-1810 91,000

1811-1820 96,000

1821-1830 135,000

1831-1840 218,400

1841-1850 291,000

1851-1860 506,999

1861-1870 900,000

1871-1880 1,189,000

1881-1890 2,373,398

1891-1900 3,708,901

The following table gives the output of various countries and the

world's production for the years 1895, 1900, 1905, 1907:--

+---------------------+----------+----------+----------+---------+

| Country. | 1895. | 1900. | 1905. | 1907. |

+---------------------+----------+----------+----------+---------+

| United States | 175,294 | 274,933 | 397,003 | 398,736 |

| Spain and Portugal | 55,755 | 53,718 | 45,527 | 50,470 |

| Japan | 18,725 | 28,285 | 36,485 | 49,718 |

| Chile | 22,428 | 26,016 | 29,632 | 27,112 |

| Germany | 16,799 | 20,635 | 22,492 | 20,818 |

| Australasia | 10,160 | 23,368 | 34,483 | 41,910 |

| Mexico | 12,806 | 22,473 | 70,010 | 61,127 |

| Russia | 5,364 | 8,128 | 8,839 | 15,240 |

| +----------+----------+----------+---------+

| World's production | 339,994 | 496,819 | 699,514 | 723,807 |

+---------------------+----------+----------+----------+---------+