Chapter I: Preface (1)

The lectures on “Modern Copper Smelting” embodied in this volume were delivered at the University of Birmingham to the Senior Students in the School of Metallurgy and to others interested in the subject.

They are based largely upon the results of a study of the practice as conducted at a number of the best organised smelters and refineries in the United States of America, at which the author has had the opportunity of spending some considerable time, and it has been felt that there exists a scope, particularly on this side of the Atlantic, for a compact volume dealing broadly with the principles underlying Modern Copper Smelting, illustrated with such examples of working practice from personal observation. The subject-matter of the Lectures has been extended by the addition of an Introduction on the History, Uses, and General Metallurgy of Copper as applied to Modern Practice.

The Copper Industry is already fortunate in the literature at its disposal. It possesses standard works of reference through the publication of Dr. Peters’ classical volumes on the _Principles of Copper Smelting_, and more recently (during the preparation of the present work) of the volume on the _Practice of Copper Smelting_—works which have done much to raise copper smelting to a science. The industry is being rendered invaluable service by the Technical Societies and Technical Press, whose publications furnish an admirable record of the constant advance in the theory and practice of the art. Use has been made of these sources of information in the present work, and lists of such references are appended to each of the Lectures.

Grateful acknowledgment is made to several authors and editors who have given permission for the reproduction of illustrations or for the inclusion of references:—Dr. Peters, Professor Gowland, Mr. Hughes, the Editors of the _Engineering and Mining Journal_, _Mineral Industry_, _Mines and Minerals_, and others. The Institution of Mining and Metallurgy, Messrs. Chambers Bros., The Traylor Engineering Co., and the Power and Mining Machinery Co. have very kindly provided blocks for several of the illustrations; the Anaconda Copper Mining Co. furnished a set of photographs, whilst Figs. 8, 37, and 76 have been reproduced by permission of the American Institution of Mining Engineers.

To the Superintendents and Staffs of the several smelters where opportunities were so freely given for studying modern practice, and particularly to Mr. E. P. Mathewson at Anaconda, Montana, to Mr. J. Parke Channing at the Tennessee Copper Company’s Smelter, and to Mr. W. H. Freeland at Ducktown, Tennessee, the author desires to express his appreciation for much valued information and many other kind services. The frequent references made in this book to the organisation and the methods employed at these works is not only a tribute to the useful information freely imparted, but is also due to the fact that such features are so thoroughly representative of the most advanced practice in copper smelting upon a large scale and of the direction in which all modern work is undoubtedly tending.

The author further thanks Professor Turner of Birmingham University for his interest in this volume, Mr. Frank Levy for reading the proofs, and the publishers, Messrs. Charles Griffin & Co., Ltd., for the care taken in the preparation and production of the work.

UNIVERSITY OF BIRMINGHAM,
_May_, 1912.

CONTENTS.

LECTURE I. PAGES
History of Copper — Development of the
Copper Industry — Progress of Smelting
Practice — Price and Cost of Production of
Copper — Copper Statistics, 1–17

LECTURE II.
The Uses of Copper: as Metal and as
Alloy — The Physical Properties of
Copper — Effects of Impurities — Mechanical
Properties — Chemical Properties, 18–34

LECTURE III.
Compounds of Copper — Copper Mattes — The
Varieties of Commercial Copper — Ores
of Copper — Preliminary Treatment of
Ores — Sampling, 35–50

LECTURE IV.
Modern Copper Smelting Practice — Preliminary
Treatment of Ores: Concentration, Briquetting,
Sintering — The Principles of Copper Smelting
— Roasting, 51–80

LECTURE V.
Reverberatory Smelting Practice: — Functions
of the Reverberatory Furnace — Requirements
for Successful Working — Principles of Modern
Reverberatory Practice — Operation of Modern
Large Furnaces — Fuels for Reverberatory Work;
Oil Fuel; Analysis of Costs — Condition of the
Charge, 81–112

LECTURE VI.
Blast-Furnace Practice: — Functions of the
Furnace — Reduction Smelting — Oxidation
in the Furnace — The Pyritic Principle
— Features of Modern Working: Water-Jacketing,
Increase in Furnace Size, External Settling
— Constructional Details of the Furnace, 113–145

LECTURE VII.
Modern Blast-Furnace Practice
(_continued_): — Charge Calculations
— Working — Disposal of Products — Pyritic
Smelting — Sulphuric Acid Manufacture from
Smelter Gases, 146–191

LECTURE VIII.
The Bessemerising of Copper
Mattes: — Development of the Process — The
Converter — Converter Linings — Grade of
Matte — Operation of the Process — Systems
of Working, 192–216

LECTURE IX.
The Purification and Refining of Crude
Copper: — Preliminary Refining and
Casting into Anodes — Electrolytic
Refining — Bringing to Pitch, and Casting
of Merchant Copper, 217–243

INDEX, 245–259

LIST OF ILLUSTRATIONS.

FRONTISPIECE—The Colour of the Converter Flame during
the Bessemerising of Copper Matte.

PAGE
Fig. 1.—Fluctuations in the Price of Best Select Copper, 12
" 2.—Annual Production of Copper, 16
" 3.—Equilibrium Diagram, Cu-Zn Series, 22
" 4.—Influence of Arsenic and Antimony on the
Electrical Conductivity of Copper, 25
" 5.—Relations of Copper and Oxygen, 27
" 6.—Microstructure of Copper containing Oxygen
(Heyn), _Plate to face_ 28
" 7.—Relations of Copper and Arsenic, 29
" 8.—Freezing-Point Curve of Iron-Copper Sulphides
(Mattes), 38
" 9.—Outline of Sampling Scheme, Anaconda, 48
" 10.—Section through Sampling Mill, 48
" 11.—Brunton Sampler, 49
" 12.—Outline of Smelting Scheme at the Anaconda
Smelter, Montana, U. S. A., 54
" 13.—Sketch Plan of Briquetting Plant, 56
" 14.—Section through Auger-Former, showing
Briquetting Mechanism of Chambers’ Machine, 56
" 15.—Chambers’ Briquette-making Machine,
_Plate to face_ 57
" 16.—Dwight-Lloyd Sintering Machine, 60
" 17.—O’Harra Furnace (Fraser-Chalmers), illustrating
Principle of Mechanical Rabbling by Travelling
Ploughs, 71
" 18.—Section through Mechanically Rabbled Roaster
Furnace (illustrating Improvements for Protecting
Driving Mechanism), 71
" 19.—MacDougal Roaster—Vertical Section, 74
" 20.—Herreshof Furnace—Section indicating
Connections for Cooling Rabbles and Spindles, 74
" 21.—Spindle Connections and Guide Shields of
Evans-Klepetko Roasters, 76
" 22.—Rabble-blades and Bases, 77
" 23.—Development of the Reverberatory Furnace
(Gowland), 90
" 24.—Draft Pressure Record of Anaconda Reverberatory
Furnace, 94
" 25.—Skimming Reverberatory Furnace, Anaconda,
_Plate to face_ 96
" 26.—Transverse Section of Modern Reverberatory
Furnace, Anaconda, indicating Foundations,
Hearth, and Bracing, 96
" 27.—Reverberatory Furnace under Construction,
_Plate to face_ 96
" 28.—Sectional Plan and Elevation of Reverberatory
Furnace at Anaconda, 98
" 29.—Fire-box End of Reverberatory Furnace, showing
massive Bracing, Charge Bins, and Charging Levers,
Anaconda, _Plate to face_ 100
" 30.—Interior of Reverberatory Furnace (looking
towards Skimming Door), showing Expansion Spaces
in Roof, and Charging Holes, Anaconda,
_Plate to face_ 100
" 31.—Shelby Oil-Burner for Reverberatory Furnace Use, 106
" 32.—Modern Blast-Furnace Shell of Sectioned Jackets
(P. & M. M. Co.), _Plate to face_ 122
" 33.—Blast-Furnaces under Construction, showing
Fixing of Jackets, Bottom Plate, Method of
Support, Sectioning, etc. (T. E. Co.),
_Plate to face_ 124
" 34.—Development of the Blast Furnace (Gowland), 126
" 35.—Plan of 51-foot Blast Furnace, Anaconda,
indicating Position of Crucibles, Spouts, and
Connecting Bridge between Old Furnaces, 128
" 36.—Longitudinal Section and Part Elevation of
87-foot Blast-Furnace, Anaconda, indicating
Crucibles of Old Furnaces, Bridge, and Jacketing, 128
" 37.—Copper Contents in the Slags accompanying Mattes
of Various Grades, 132
" 38.—Water-Jacketed Blast Furnace, lower portion
indicating Air and Water Connections, Bottom
Supports, End Slag Spouts, etc.
(P. & M. M. Co.), _Plate to face_ 134
" 39.—Tapping Breast of Blast Furnace, Cananea, 136
" 40.—Rivetted Steel Water-Jacket, showing Tuyere
Holes and Water Inlets, etc. (P. & M. M. Co.), 137
" 41.—Transverse Section through Modern Blast Furnace,
showing Arrangements of Boshed Lower Jackets,
Upper Jackets, and Plates, Stays and Supports,
etc., 138
" 42.—Interior of Anaconda Blast Furnace, showing
Jacketing, Tuyere Holes, and Bridge,
_Plate to face_ 138
" 43.—Showing Upper Jackets, Apron and Mantle Plates
and Superstructure of Blast Furnace, Anaconda,
_Plate to face_ 140
" 44.—Charging Blast Furnaces, Anaconda,
_Plate to face_ 140
" 45.—Blast-Furnace Shell, with Air Connections
(P. & M. M. Co.), 142
" 46.—Details of Tuyere, Cananea Blast Furnace, 142
" 47.—=V=-Shaped Charging Car, indicating Mechanism
for Release and Tilting, 153
" 48.—End View of Blast Furnace, showing Tilting of
Charge Car, Anaconda, 155
" 49.—Hodge’s Charging Car, 155
" 50.—Freeland Charging Machine (D. S. C. & I. Co.), 157
" 51.—Freeland Charger-Details, 157
" 52.—Slag Spout, showing Method of Trapping Blast,
also Replaceable Nose-Piece of Spout (A), 159
" 53.—Details of Slag Spout, Cananea, 161
" 54.—Slag Spout, showing Method of Support, 161
" 55.—General View of Settler (T. E. Co.), 163
" 56.—Method of Lining Settler, Cananea, 163
" 57.—Arrangement for Matte and Slag Discharge from
Settlers (T. C. C.), 164
" 58.—Tap-hole Casting and Detail for Settlers, 165
" 59.—Anaconda Blast Furnace (51 feet long), showing
Settlers, _Plate to face_ 166
" 60.—Hoppers of Flue-Dust Chambers and Tracks for
Cars underneath, 167
" 61.—Slotted Tuyeres, 12 inches by 4 inches
(T. C. C.), 185
" 62.—Sectional Elevation and Plan of Barrel-Shaped
Silica-Lined Converter (Peters), 196
" 63.—Latest Form of Silica-Lined Barrel Converter, 197
" 64.—Longitudinal Section of Basic-Lined Converter, 198
" 65.—Basic-Lined Converter, indicating Tuyeres,
Lining, &c., 199
" 66.—Composition of a Charge during Bessemerising
Operation, 208
" 67.—Pouring Slag, Anaconda, 209
" 68.—General View of Converter Shop, Anaconda,
_Plate to face_ 214
" 69.—Sectional Plan, Elevation, and Transverse
Sections of Refining and Anode-Casting Furnace,
Anaconda (Peters), 220
" 70.—Indicating Tilting and Pouring Mechanism of
Ladle of Casting and Refining Furnaces, 225
" 71.—Walker’s Anode-Casting Machine,
_Plate to face_ 226
" 72.—General View of Tank-room of Electrolytic
Refinery (Perth Amboy, N.J.),
_Plate to face_ 226
" 73.—Indicating Methods of Suspending and Connecting
Electrodes (Perth Amboy, N.J.), 234
" 74.—Indicating Connections for Circulation of
Electrolyte (Barnett), 235
" 75.—Tank-house, showing Anode Crane (Ulke), 237
" 76.—Microstructure of Commercial Copper containing
Oxygen (Hofman), _Plate to face_ 242

TABLES.

TABLE PAGE
I. The Production of Copper, 15
II. North American Production of Copper, 17
III. Influence of Impurities on the Electrical Conductivity
of Copper, 23
IV. Analysis of Various Commercial Coppers, 44
V. Development in Size of the Reverberatory Furnace, 89
VI. Daily Reports. Reverberatory Furnaces, 102
VII. Daily Assay Report. Reverberatory Furnaces, 103
VIII. Monthly Report. Reverberatory Furnaces, 104
IX. Effect on Coke Consumption of Increased Sulphur in
the Furnace Charge, 120
X. Blast-Furnace Charge Calculations, 151
XI. Typical Charging Tables at Pyritic Smelter, 187
XII. Changes in Composition during Bessemerising, 206

COPPER SMELTING.

LECTURE I.

History of Copper — Development of the Copper
Industry — Progress of Smelting Practice — Price and
Cost of Production of Copper — Copper Statistics.

=The History of Copper.=—Copper was probably the earliest metal commonly employed by mankind. It occurs in the native condition in various parts of the world, and the natural product thus required no metallurgical treatment prior to use. Its malleability and the property of being readily toughened by simple mechanical treatment were also factors which account for the discovery of its general usefulness in such primitive times.

Although silver and gold were possibly known even earlier, these metals appear to have been employed chiefly for ornamental purposes, and as tokens, rather than for general service.

The alloy of copper and tin, known as bronze, was the first metallic combination in common use by man; its employment was so characteristic in prehistoric times, that archæologists assign to one of the epochs the name of the Bronze Age. As is well known, archæological time is marked by a series of ages, in which the use, first of stone, then of bronze, and ultimately of iron for the manufacture of tools and implements, indicate the development of industrial culture. The dates which can be assigned to those periods vary with the locality; the races in the more Northerly latitudes being later in their development. In our own country, the Stone Ages may be said to date from 3000 B.C. down to 1000 B.C., and the Early and Late Bronze Ages from 1000 B.C. to 500 B.C., and from 500 B.C. to the commencement of the present era, respectively.

It is not unlikely that in many places copper was largely used during the Stone Ages and before the Bronze epoch, since it was only after the art of making fire had been discovered that it became possible to manufacture bronze, whilst native copper could be fashioned without the aid of heat. Metallic relics of the Bronze Age, in the form of arms, ornaments, and domestic implements have been found in widely distributed localities.

The mention of copper occurs in the Hebrew Scriptures, the metal being termed _Nehosheth_, from the root _Nahásh_, to glisten. This was translated as χαλκὸς (_chalcos_) in the Septuagint, and _Aes_ in the Vulgate; the Greeks and Romans using the terms, however, both for copper and for the alloys brass and bronze.

According to Pliny, the Roman supply was derived chiefly from Cyprus, and the metal thus came to be known as _Aes Cyprium_, which was gradually shortened to _Cyprium_, a name afterwards corrupted to _Cuprum_, from which are derived our modern terms _Copper_, the German _Kupfer_, and the French _Cuivre_.

Copper was well known to the alchemists, and inasmuch as it was largely obtained from Cyprus, an island dedicated to Venus, it was considered to be the metal specially sacred to the Goddess, and was generally known by that name in their writings, and symbolised by the sign [symbol: circle with plus sign underneath]. The production of metallic copper on iron by the action of certain liquors from the Hungarian mines and other localities, was likewise known to the alchemists, and was a constant source of inspiration to them; the changes were regarded for some hundreds of years as examples of the transmutation of the elements, until Boyle showed that it was necessary to introduce copper into such solutions before that metal could be precipitated from them.

=The Development of the Copper Industry.=—The mining and smelting of copper ores on a primitive scale have been carried on from time immemorial; these operations were certainly practised in Greek and Roman days, and the deposits of Britain are said to have been known to the Phœnicians so far back as 1000 B.C. Percy refers to the finding of lumps of copper weighing 42 lbs., carrying a Roman inscription; this metal was found in close proximity to mines in North Wales, which yielded an easily reducible ore, and he concluded that this was smelted _in situ_ by the Romans.

There are undoubted records of copper mining in this country in the time of Edward III., and in that of Elizabeth; whilst the first authentic accounts of copper smelting date also from the latter period, relating to South Wales. It appears that one of the earliest establishments was situated at Neath—a fact recorded in a publication of 1602. The works probably existed for a century before that date, and the copper smelters at Swansea were established about 120 years afterwards.

The processes employed for the primitive smelting of copper ores were, to a large extent, of the same nature as the crude operations practised generally for the extraction of metals in remote ages and by primitive races, as recorded from time to time by travellers and explorers. The furnace-hearth was a hole in the ground, working usually on oxide ores with charcoal or wood as fuel. This primitive furnace was later developed, by the addition of walls for enclosing the charge, until the “shaft furnace” provided with an air blast of some kind was attained. The sulphide ores presented rather more difficulty in their treatment, but the production of metallic copper from sulphide materials by super-oxidation, in a process akin to the bessemerising of to-day, was developed in Japan centuries ago, and has been described by Professor Gowland.

It would appear that during the middle ages, the art of reducing copper ores to metal on a comparatively large scale was practised simultaneously in Britain and in Central Europe; first by primitive methods similar to those indicated above, developing later by successive improvements into the employment of small blast furnaces. By about 1700, however, the methods diverged, and it is interesting to note that the different styles of working then introduced have persisted, until recent years, as the methods typical of these two parts of the world. In Wales, where the well-known furnace coal was one of the characteristics of the locality, as it still remains to-day, the smelting processes developed along the lines of reverberatory practice, for which such fuel is eminently suited, and this resulted in the establishing of the representative Welsh process. On the other hand, the enormous forests of Central Europe furnished wood suitable for the making of charcoal, a type of fuel which necessitates close proximity with the furnace charge, so that in these localities smelting was carried out in the shaft furnace, which gradually developed into the small blast furnace. At the present time, the solid fuel suitable for reverberatory practice is only obtainable in very small quantities in Central Europe, and the characteristic method employed there for copper smelting is that in which small blast furnaces are used, except that charcoal has been largely replaced by coke as the fuel.

It is probable that the early ore furnaces of the primitive blast-furnace type in Britain were worked by Germans experienced in that class of work, just as at a later period in the history of the industry, Swansea coppermen were to be found in all parts of the world teaching other nations their art. Gowland reproduces a letter, dated January, 1583, protesting against the introduction of this foreign labour, whilst a second letter, dated July, 1585, which is also quoted, is of particular interest, as it gives evidence of a remarkable knowledge of the art of smelting, and, whilst illustrating an important feature of modern practice, indicates also the manner in which an astute smelterman was able to work profitably with difficult material so long ago as three and a quarter centuries.

The letter is to the following effect:—

“ULRICKE FROSSE to ROBERT DENHAM. _4th July, 1585_.

“To his loving friend, Robert Denham.

“Friend Denham,—I have me heartily commended unto
you, you shall understand it we did lack ore more than
14 days ago, for we have found out a way to smelt 24
cwts. of ore every day with one furnace, the Lord be
thanked, and if we may have ore enough from your side
we may, with God’s help, melt with two furnaces in 40
weeks 560 tons of ore, having reasonable provision
made for it, desiring you from hence-forward to send
such ores as you have with as much speed as maybe, not
caring what ore it is. Your ore of St. Dines is very
hard to melt it, hoping we will overcome it what St.
Ust ores will do, we long to see it.

“This I rest, the Lord send you good success with
your mines. And so I commit you to God. From Neath, the
4th of July, 1585.
“Your friend,
“ULRICKE FROSSE.

“When you do send any more ore, if you can, send
of all sorts, the better it will melt and with more
profit.”

The sound principle of obtaining, when possible, one class of copper ore for the purpose of fluxing off the gangue from ore of another class, was thus recognised as a profitable feature of practice from comparatively early times.

Copper mining and smelting in Staffordshire dates back a considerable time, certainly prior to 1686; the mines were situated at Ecton, and the smelter was at Elleston, near Ashbourne, where small blast furnaces were employed. Copper smelting in Lancashire, which is nowadays conducted on a comparatively extensive scale, appears to have commenced in 1720 with Cornish ores and smaller importations from the West Indian and American Colonies. During the 18th century, the chief supply of the world’s copper ore came from the Cornish mines, which even at that time, were deep and extensive. It seems, however, that for some peculiar reason, the Cornishmen were unable to smelt these ores with profit, nor indeed, to do more with them than to send the material to South Wales to be treated. There are numerous explanations for their failure, which have been discussed exhaustively by Percy.

The centre of the copper smelting industry thus came to be located in the South Wales (Swansea) district, where circumstances were very favourable. The study of local conditions is one of great importance for metallurgists, and since this case affords a good example, it will be of value to refer briefly to those circumstances which rendered the Swansea district such an excellent centre for the industry.

The extensive collieries in the locality rendered available an abundant supply of suitable fuel at a low price, and many of the smelters held a financial interest in them. The large coal was profitably used for home consumption or export, and the small, which, though dirty, still gave the long flame required, was very suitable for smelting work, and was reserved for that purpose.

Further, Swansea was an excellent seaport, situated at a short distance only from Cornwall, the chief source of ore, and was also readily accessible to vessels carrying cupriferous ores and products from South America, Australia, and other parts of the world. This was a great advantage, in that the Swansea copper smelters, having a large variety of ores at their disposal, some with basic gangue, others with siliceous gangue, were in a position to make up furnace charges which were more or less self-fluxing, and thus avoided the necessity for purchasing and using barren fluxes. The finished products were also in a most convenient centre for distribution, at the seaport of Swansea.

At the end of the 18th century, Great Britain was producing 75 per cent. of the world’s copper, the Cornish mines supplying most of the copper ore, and the Swansea smelters extracting most of the world’s supply of metal. Stevens has summarised the position for 1799, showing that “from the Cornish ores 4,923 tons of refined copper were produced, and from the Welsh ores of Anglesea 2,000 tons. The great Mansfeld mine in Germany produced only 372 tons in that year, Spain’s output was insignificant, and in the United States only a few tons were made. Russia and Japan probably ranked next to Great Britain as producers, small amounts of ore from Austria, Scandinavia, and Italy made up the remainder. Thus at the commencement of the 19th century, the copper resources of the United States, Spain, Chili, Mexico, Australia, Tasmania, Canada, and South Africa, which now supply over 90 per cent. of the world’s metal, were either undeveloped, or only yielded a few tons each; Great Britain, which produced nearly 7,000 tons of copper at that time, extracted from its own ore supplies, a hundred years later, only 550 tons.”

It will be remembered that it was in connection with the development of Cornish copper mining that the use of steam power in engineering was introduced and successfully worked out. On account of the increasing depth and extension of the Cornwall mines, the problem of disposing of the underground water became urgent, and led to the introduction of steam engines for driving the pumps, the Newcomen engine being installed on the Wheal Fortune Mine in 1720. The success of this engine led to increase both in depth and in extent of the workings, until it became impossible to cope with the pumping requirements by this means. At the right moment Watt brought out the modern steam engine, and the first Watt engine was erected in 1777 at Chasewater, in Cornwall. It was the introduction of these improved methods of pumping which have made possible the successful development of present-day mining. Not only has the steam engine thus led to an increase in the supply of copper, by enabling the opening up of vaster deposits to be undertaken, but the development of engineering science which it has brought about, has caused a further consumption of the increasing quantity of copper which it has helped to render available for use.

During the first half of the 19th century Great Britain retained its position as the chief copper producer of the world, and the Swansea smelters possessed advantages such as have been rarely enjoyed by any other body of manufacturers. They were able to impose what conditions they pleased on the producers and sellers of copper ore, as well as on the consumers of the metal, and as business men, were not slow to avail themselves of their opportunities to the greatest possible extent, strengthening their position by the formation of a combination known as the Associated Copper Smelters of Swansea, which controlled the price of the metal from 1850 to 1860. Percy gives an interesting account of the terms imposed by them under the name of returning charges, etc., as well as of the conditions of sampling, analysis, and sale, which were strongly in their favour.

During these years of monopoly, the smelters were, on the whole, conservative in tendency from the metallurgical point of view, and few great developments in either processes or methods were devised: nevertheless, they enjoyed great prosperity, and their business attained such dimensions that Swansea remains one of the greatest centres of smelting industry in the world. The Welsh smeltermen had, moreover, acquired such proficiency in furnace management, and such knowledge of the working and control of copper charges, that their reputation had spread to all quarters of the world.

Though from 1840 onward, the British copper mining industry commenced to decline, still for 20 years longer the Swansea smelting works prospered more and more as new mines were being opened abroad and thus furnished a constantly increasing supply of rich copper ore, cheap to purchase and easy to smelt.

It was this development of foreign copper resources, and the unsatisfactory conditions which the producers received at the hands of the smelters, which was the cause of the eventual displacement of Swansea from its position as the leading seat of copper manufacture.

In 1830, the production of copper ore in Chili had commenced and developed rapidly, Chili soon becoming one of the chief suppliers of ore to the Welsh smelters, whose independent attitude led to the first introduction of the copper-smelting industry on any large scale in America. Owing to the sailing conditions of the time, the simultaneous coming into port of several ships laden with ore, instead of their arrival at regular intervals, enabled purchases to be made by the smelters at a remarkably low figure, the standard price of the metal being subsequently raised. Mine-owners commenced to seek for a remedy, their ultimate endeavour being to substitute, for the exportation of their ores, smelting operations at or near the mines themselves. In 1842 Lambert introduced reverberatory furnaces into Chili, and so great was his success, that in a short time they were in use throughout that country. In 1857 he erected the first blast furnace in Chili, and the smelting industry thereupon grew so rapidly that, whilst from 1856 to 1865 the copper exports from Chili were in the proportions of ore 21 per cent., regulus 38 per cent., and bars 40 per cent., they subsequently became ore 1½ per cent., regulus 3½ per cent., and bars 95 per cent. The ultimate effect was a widening of the market for the finished Chilian product, so that Continental purchasers were enabled to obtain their supplies of metal direct, instead of being obliged to purchase from the Welsh smelters on the unsatisfactory terms then prevalent.

In 1842 the first large copper mines of Australia (Kapunda and later Burra Burra) were discovered, but developed slowly; and in 1844 the first copper mines of the Lake Superior district began work—on oxide ore, not on native metal.

In 1850 an enormous development in the Chilian mines commenced, half the world’s copper being produced from this source; in 1859–60 the Spanish mines at St. Domingo (Mason and Barry) were re-opened, as well as the Portuguese mine, the Tharsis. These mines were in reality operated in order to supply the wants of the sulphuric acid industry, the ore residues being subsequently smelted for copper at Swansea. In 1862, however, the Henderson wet process for copper was introduced, for which these materials were very suitable, and the Spanish and Portuguese supplies became of considerable importance, soon afterwards coming under the control of a Scottish company.

The competition from these new and abundant supplies of rich ores from Chili, Spain, and Portugal severely injured the production from the British mines; increasing supplies led to a fall in the price, and one native mine after another shut down, the British supply diminishing with considerable rapidity.

In 1866 the great Calumet and Hecla mine at Lake Superior commenced operations, and speedily became one of the most important sources of copper in the world; the Moonta and Wallaroo mines in Australia opened about the same time, and in 1873 the Arizona mines started producing. In 1876 the enormous Spanish mines at Rio Tinto were re-opened, and soon rendered available large quantities of ore. Later, the Tasmanian supplies entered the markets.

In 1880 a remarkable development in copper mining occurred with the discovery of the Butte camp in Montana; this is now the greatest producer in the world.

The later extensions of the copper mining industry occurred in Utah, Tennessee, and Queensland, whilst within recent years the most important work on a large scale has been commenced in Tanganyika, in Nevada, and in Siberia.

The developments in the smelting industry in most of these localities have proceeded, until the last few years, on very similar lines. During the first periods following the opening up of mines and works, ore was shipped to the custom smelters, most often to Swansea; where, in the early days, many of those connected with the smelting works had some sort of financial interest in the foreign mines. Later, the ore underwent its first smelting to matte in the mining district itself, the matte product being then shipped East for treatment, thus saving much of the freight-charge on useless gangue, as well as smelters’ heavy returning charges, etc. At a later period the smelting operation was carried to a still further stage in the mining district, crude blister copper only being sent to Swansea or elsewhere to be refined.

Gradually, electrolytic refineries were established somewhat nearer to the mining districts, and in the natural course of events, and where local conditions are not prohibitive, the probability is that the whole cycle of operations from mining to the production of refined market metal will be carried out at the great camps themselves.

At present, however, this is not generally the case, since the conditions under which the enormous refineries in the Eastern States of New York, New Jersey, and in Baltimore, etc., operate, allow of the cheaper production of electrolytic copper at points nearer to the distributing markets. At Anaconda, indeed, the fully-equipped electrolytic plant was shut down, owing to the commercial conditions such as have just been indicated, having rendered the refining of the anode copper at the Eastern refineries more profitable than electrolytic treatment on the spot.

=The Chief Features in the Development of Modern Copper Smelting Practice.=—In the early days of copper smelting, the reduction of the oxidised ores, which were then chiefly available, was not a problem of very great difficulty, although losses in slag were likely to be very high, and the operation generally wasteful. When, however, mines became deeper and sulphide ores had to be smelted, the problem became rather more complicated. In the first stages of development, such ores were probably roasted until as much sulphur as possible had been driven off, leaving practically an oxide charge to be treated by the older reduction methods involving the attendant extravagance in fuel consumption and large losses of copper in the slag.

From these crude and wasteful methods the Welsh process was gradually worked out, and it will ever rank as one of the finest examples of highly developed smelting practice in the history of metallurgy, particularly when the times and working conditions are borne in mind. The process having received such full treatment from most of the common text-books, it is not proposed to review it in detail here, since, moreover, it has been largely superseded by more modern processes.

As will be explained later, copper smelting of sulphide ores is essentially a fractional oxidation—chiefly of iron and sulphur—followed by the slagging or elimination of extraneous constituents of the ore. The Welsh process embodied a series of roastings and slaggings which, though most admirably adjusted for a substantial concentration of the copper in each succeeding product, allowed of the formation of slags in the first stages which carried but comparatively little copper, on account of the low tenor of the matte; whilst the slags in the later stages of the process, containing more copper on account of their association with higher grade matte, were made in such relatively small quantity that their re-treatment for the recovery of these values did not involve very much loss of efficiency in the furnace operations.

Later modifications of the process were chiefly devised with the view to reducing the number of operations, by eliminating the successive roasting stages, for which purpose oxidised materials, such as roasted or oxidised ores, were added to the charge.

The Best-Selecting process, and the Nicholl and James process are likewise valuable and ingenious modifications of the Swansea method for special work.

In general, however, up to 1880, there had taken place but little change in principle from the older methods of smelting. The chief improvements involved a slow change in furnace size, and progress in several details in practice. The more important of these advances were—

(_a_) _In Roasting Practice._—=1865.= Introduction
of the mechanically driven furnace (the Brückner cylinder);
not, however, adopted for copper smelting till many years
afterwards. Later—Arrangements for using roaster gases for
sulphuric acid manufacture.
(_b_) _In Reverberatory Furnace Smelting._—=1861.=
Gas firing introduced, but with very little success for
copper smelting, even at the present day.
(_c_) _In Blast-Furnace Smelting._—Several very important
changes were introduced in the construction of furnaces.

=1863.= Elongation of the furnace.

Rachette in Germany introduced the elliptical blast furnace. (Intended first for lead smelting; rapidly adopted for copper matte smelting.)

=1875.= The water-jacketing of blast furnaces.

The Piltz water-jacketed furnace was likewise first employed in lead smelting, and subsequently introduced into copper smelting practice. The principle had, indeed, been utilised in certain branches of iron smelting before this date, but for non-ferrous work the idea was new.

Although the method of water-jacketing was recognised as leading to great improvement in the working of the furnace, its use was at first somewhat restricted, owing to various practical difficulties, and the ultimate great success was effected when in American practice, the plan of working the two principles of elongated furnaces and water-jacketing in conjunction, was adopted.

Commencing from 1880, and onwards, however, when production in the Far West began, enormous advances have been made, both in connection with the principles of working as well as in practical operation. These include—

(1) Enormous increase in the size and capacity of furnaces
of both the reverberatory and the blast-furnace type.
(2) The application of the Bessemer process to copper mattes.
(3) The development of the pyritic smelting principle.
(4) The adoption of electrolytic refining.
(5) The use of mechanically rabbled roaster furnaces.
(6) The manufacture of sulphuric acid from blast-furnace gases.
(7) The blast-roasting and sintering of sulphide fines.

With an increased output of ore from the mines, and with increased consumption, stimulated by the growth of the electrical industry, the demand for metal increased so quickly that developments naturally followed with a view to an augmented and rapid production by more efficient and scientific processes; especially since increased competition and poorer ore supplies necessitated a very decided lowering of the costs of production. To meet the enormous present-day demand for metal with the older methods and furnaces would have been impossible. The greatest stimulus to the adoption of these new or modified processes was the shifting of the chief producing centres from the older and more conservative influences to districts like the then newly awakening West, where, with ever-increasing—almost limitless—supplies of ore available, and free from the necessity of considering the capital invested in old plants, the men in charge of the work, untrammelled by old smelting customs which might stand in the way of rapid progress, were in a position to develop their ideas with originality and vigour.

There may, nevertheless, be recalled the important share which British, and especially Swansea, workmen had in this great development of the industry. At many of the greater smelters in these new districts, Welsh furnacemen are still to be found, and large numbers went abroad in former days to take charge of such work, especially during the critical early stages. The principles underlying these modern improvements were, in many cases, first worked out by scientists in Europe.

=The Price and Cost of Production of Copper.=—The price of copper has been influenced to an enormous extent by financial speculation, so that until recent times it has fluctuated very considerably from year to year, the curve in fig. 1 relating to Best Select copper, indicating this variation over a considerable period. The price of the other qualities of commercial copper follows this line fairly closely, electrolytic copper being from £2 to £4 per ton lower, and standard copper £3 to £6 per ton. The average value of the standard refined metal at the present time (December, 1911) is about £56 per ton in London, and about 12 cents per pound in New York.

On three occasions during the past century, and once at least during the past decade, the market price of copper has been directly affected by more or less artificial conditions consequent on financial manipulation. The first of these instances was the 1850–1860 period, when the Welsh smelters held the monopoly of the copper trade, and were in a position to fix their own price; the second was during the French combination of Secretan during 1887–9, which, as a result of mere market speculation, caused fluctuations of price which amounted on one occasion to no less than £35 per ton within twenty-four hours. The third instance was created by the American combine.

In 1899 the Amalgamated Copper Company was formed in the United States. This corporation was established in view of the enormously increasing production of the West, and of the extensive development of electrical industry which involved a greatly increased consumption of copper; and it was probably designed to control the world’s copper industry. Prices were raised gradually for some time, but in 1901 the Trust, as then constituted, failed, owing largely to trade depression in Europe. Heavy losses resulted, as well as expensive law suits, and the price of the metal dropped again with great rapidity. Trade subsequently revived and expanded, the consumption of copper increased and appeared to overtake the rate of production, whilst stocks diminished and the price advanced, until, in 1907, copper was sold at well over £100 per ton. The American financial panic in the autumn of that year again reduced prices to a comparatively low figure, and they have, on the whole, remained fairly steady since, though showing a tendency to decrease. Production has, meanwhile, increased very largely, and a steady price of 12 to 13½ cents per pound yields handsome profits to most of the larger concerns. The present situation in the copper market is such that the enhanced production has again resulted in an accumulation of stocks, which has occasioned restricted output on the part of many of the principal smelters until briskness of trade development shall call forth increased consumption and more satisfactory prices.

The question of price is one involving certain considerations to which attention may be drawn. The present conditions and the comparative steadiness in the copper market have been shown in a recent review to result in part from:—

(1) The concentration of the copper industry in a few
strong hands, which, whilst maintaining healthy competition,
keeps the market free from such outside pressure as would
reduce the price too much, and by restricting unprofitable
output, brings production and consumption into equilibrium,
making for stability.

(2) The comparative cheapness of money, which has allowed
of the financing for large production, with the prospect of
absorption not being long delayed.

At the same time, some of the richer and more cheaply worked mines of former times are gradually approaching exhaustion—recent instances of this will be readily recalled, whilst the disadvantages of having to work lower-grade deposits at greater depth have also tended to increase the price of metal. These conditions, on the other hand, have been counterbalanced by improvements in the mining and metallurgical processes concerned, by the opening up of new districts, and by the economies resulting from amalgamation of interests, involving closer organisation and enormous outputs of material.

Apart from finance, two of the factors most likely to affect the price of the metal considerably are the possible replacement of copper for electrical transmission purposes by conductors of other metals; and further, the enormous prospective production in the newer districts, such as Utah, Nevada, and Tanganyika, in the course of a few years.

The cost of production of the metal is so dependent on local and general circumstances as not to admit of analysis in this place. Questions of locality, transport facilities, proximity to supplies of every kind, problems of labour, capitalisation, bye-products, and numerous similar considerations have such an important bearing on each individual case as to convey a definite meaning only to the man on the spot. In the same way, detail costs of each stage of the copper smelting processes are influenced by similar circumstances.

Broadly speaking, the average total cost of production and marketing at present may be taken as being somewhere about 10 cents per pound of copper; in certain specially favoured cases, 9, 8, or even 7 cents per pound. The newly opened low-grade “porphyry” camps at Utah and elsewhere, which have been commenced under an enormous capitalisation, anticipate a production at a cost of about 6 cents per pound when steady and normal running is in progress.

A recent analysis gives interesting information with regard to the cost of production estimated at different plants. Of the American output of about 480,000 tons in 1909—

Almost 3·5 per cent.
was produced
at a cost of 7·14 cents per lb. (Nevada).
1·8 " 7·98 " (Baltic, Superior).
10·5 " 8–9 " (Utah, etc.).
48·3 " 9–10 " (Boston and Montana,
Calumet and Hecla, etc.).
9·0 " 10–11 " (Utah Consolidated,
Tennessee, etc.).
20·0 " 11–12 " (Anaconda, Arizona, Cananea).
1·8 " 12–13 "
1·1 " 13–14 "
1·4 " 14–15 " (Tamarack).
1·1 " 15–16 "
1·1 " 16–17 "
0·1 " 17·09 "

=Copper Statistics.=—The outstanding features which attract attention in the statistics of copper production will be most readily seen from the curves of fig. 2. The enormous increase within recent years in the total output of metal, and the overwhelming proportion produced by the United States of America, is clearly indicated. The curves also show the practical extinction of the native supply of Great Britain and the steady output of Spain and Germany.

An analysis of the total production for the year 1910 is given in the following Table I.:—

TABLE I.—THE PRODUCTION OF COPPER (Short Tons of 2,000 lbs.).

1909. 1910.
─┐
U. S. A., 549,114 543,125 │
Canada, 26,998 28,801 │ 1909. 1910.
Newfoundland, 1,546 1,210 ├─ North America,
Mexico, 63,085 68,899 │ 644,058 645,927
Cuba, 3,315 3,892 │
─┘
─┐
Argentina, 672 336 │
Bolivia, 2,240 2,800 ├─ South America,
Chili, 40,079 39,463 │ 60,911 63,101
Peru, 17,920 20,502 │
─┘
─┐
Spain and Portugal, 58,447 56,386 │
Germany, 25,150 27,675 │
Russia, 19,880 24,987 │
Norway, 10,170 11,676 │
Hungary, 5,152 5,550 ├─ Europe, 127,283 135,738
Sweden, 2,240 2,240 │
Italy, 3,052 3,606 │
Austria, 1,809 2,386 │
Turkey, 896 672 │
Great Britain, 487 560 │
─┘
Japan, 52,640 51,520
Africa, 16,738 17,030
Australasia, 38,528 45,153
_______ _______

Total, 940,158 958,469
═══════ ═══════

In Table II. is indicated the distribution of the American production among the various States.

TABLE II.—NORTH AMERICAN PRODUCTION OF COPPER (in Short Tons of 2,000 lbs.).

1909. 1910.
Alaska, 2,028 2,504
Arizona, 146,021 149,803
California, 26,679 22,897
Colorado, 5,244 5,063
Idaho, 3,885 3,108
Michigan, 113,624 110,700
Montana, 156,918 143,121
Nevada, 25,917 31,944 (about 6,000 tons in 1908)
New Mexico, 2,567 1,816
Utah, 50,219 62,521 (about 35,000 tons in 1908)
Wyoming, 44 90
South and East, 11,409 9,098
Other States, 1,973 463
———- —-———-
Totals, 546,538 543,125

There will be noticed a decline in the production of the United States during the year 1910, resulting from the present movement to restrict output whilst the large accumulated stocks of metal are being absorbed. The movement is probably more or less temporary, and is being largely directed by American financiers who are endeavouring to bring about an international agreement on the subject.

Regarding the American output, the marked movement for curtailment in Montana has reduced the output of that State to such an extent, that the position it gained in 1909, of being the greatest producing State once more reverts to Arizona. The increases from Nevada and Utah, in which developments on a large scale are commencing, may be noted.

References.

Percy, John, “Metallurgy (Copper).”
Gowland, William, Presidential Address,
_Trans. Inst. Mining and Metallurgy_,
vol. xvi., 1906–7, pp. 265–291.
Stevens, H. J., “The Copper Handbook.”
Brown, N., and Turnbull, C. C., “A Century of Copper.”
_Engineering and Mining Journal_, “Copper Production.”
May 6th, 1910, p. 891.
_Mineral Statistics of the United Kingdom._
_Mineral Industry._

LECTURE II.

The Uses of Copper: as Metal and as Alloy — The
Physical Properties of Copper — Effects of
Impurities — Mechanical Properties — Chemical
Properties.

=The Uses of Copper.=—Generally speaking, the industrial applications of copper involve its employment in two forms:—

(1) As metal.
(2) As a constituent of alloys.

The more limited use in the form of copper salts is of chemical rather than of metallurgical interest.

Copper in the metallic form is employed for three classes of work:—

(_a_) For electrical purposes.
(_b_) For engineering purposes.
(_c_) General industrial uses.

(_a_) _Electrical Uses._—Of late years the marked growth in the consumption of copper has arisen very largely from its usefulness as a conductor of electricity; the increased demand for the metal with the development of electrical enterprise being a well-marked feature in industrial progress. It is estimated that from 60 to 70 per cent. of all the copper produced is utilised for this purpose, and metal is specially prepared and sold under the designation of “high-conductivity copper.” The demand has, to a large extent, increased irrespective of price up to recent years, owing to the necessity of employing copper for such purposes, though the natural economic factor that an enhanced price of the metal tends to some discouragement of expansion and of fresh electrical enterprise, has exerted considerable effect in checking consumption.

It is merely necessary to enumerate some few of the present aspects of electrical industry in order to realise the enormous absorption of copper in this connection, as, for instance, electrical traction, lighting, and power, the telegraph, and the telephone. With reference to the use of the metal for this work, it is important that certain mechanical as well as electrical requirements should be fulfilled, for in many branches, considerable strength of the material is also requisite. The demand of the electrical engineer is that as a conductor, the copper shall offer a minimum of resistance to the passage of the current, and for this requirement the metal must be in a condition of very great purity. With but few exceptions, this necessitates the purification of the copper by electro-deposition. Electro-deposited metal as produced at the refineries is, however, not immediately suitable for drawing into wire, owing to the weakness and porosity inherent in the material prepared by this method. It must, therefore, be melted, brought to pitch, cast into bars, and these bars transformed into wire, which operations require to be conducted with much care in order to keep the metal in as pure a condition as possible for its work. It may be noted that within recent years, several processes, notably those of Cowper-Coles and Elmore, have been put into operation for the direct manufacture for electrical purposes, of electrolytic-copper wire of the requisite strength.

The mechanical qualities demanded of the metal for such purposes as telegraph work may be indicated by the two specifications of wire for the British Post Office, which are appended:—

A. _Post Office Specification._
=Weight=, 150 lbs. per mile.
=Minimum diameter=, ·95½".
=Maximum diameter=, ·98".[1]
=Minimum breaking strain=, 490 lbs.
=Minimum number of twists=, 25 in 3 inches.
=Wraps required=, 6 times round wire of its
own diameter, unwrapped, and again wrapped without breaking.
=Maximum resistance per mile at= 60° =F.=, 5·857 ω.

B. _Post Office Specification._
=Weight=, 500 lbs. per mile.
=Minimum diameter=, ·135¼".
=Maximum diameter=, ·138¾".
=Minimum breaking strain=, 950 lbs.
=Minimum number of twists=, 30 in 6 inches.
=Wraps required=, 6 times round wire of its
own diameter, unwrapped, and again wrapped without breaking.
=Maximum resistance per mile at= 60° =F.=, 2·928 ω.

The following figures afford some indication of the increasing demand for copper in two branches only of electrical industry:—

1902. 1907.
Mileage of wire for telegraph purposes, 3·9 5·3
" " telephone purposes, 10·9 28·2
(in million of miles)

(_b_) _Engineering Uses._—Metallic copper finds application in marine shipbuilding and engine work, as well as in railway and locomotive work, where the metal is particularly employed for steam pipes, and for fire-box plates and stays, sometimes also for boiler tubes, on account of its high conductivity for heat, combined with toughness. The questions of suitable composition, and the other requirements of the metal intended for these purposes, has been a subject for discussion by some of the leading marine and locomotive engineers. Useful information on the subject will be found in the reports of some of these discussions at the Institution of Mechanical Engineers.

The following tests are required for copper plate (best quality) intended for locomotive fire-boxes on the Lancashire and Yorkshire Railway, taken from standard specifications given by their Chief Mechanical Engineer at the Institute of Metals:—

_Bending Test._—Pieces of the plate shall be tested both
cold and at a red heat by being doubled over on themselves—
that is, bent through an angle of 180°—without showing
either crack or flaw on the outside of the bend.
_Flanging._—Plates must not show any defects in flanging.
_Tensile Test._—Ultimate breaking load, 14 tons per square
inch; Elongation, 35 per cent. in 8 inches.
_Analytical Test._—To be made at contractor’s expense.

The copper upon analysis to give the following results:—Arsenic, not less than 0·35 per cent. nor more than 0·55 per cent.; other foreign elements, exclusive of combined oxygen, not to exceed 0·25 per cent.

Clauses are also inserted as to stamping, inspection, and the giving of testing facilities.

Typical analysis of such plates show—

Copper, 99·30 per cent.
Arsenic, 0·43 to 0·51 per cent.
Oxygen, 0·1 per cent.

Impurities, chiefly antimony, lead, iron, nickel, tin, and sulphur, not exceeding 0·25 per cent.

The average test on a number of plates gave—

Tensile strength, 14·66 tons per square inch.
Elongation on 8 inches, 43·36 per cent. of original length.
Contraction of area, 45·9 per cent.
Close bend test, Double.

The effect of temperature and the influence of impurities on the mechanical properties of the metal intended for engineering purposes are of very great importance, and much attention has been devoted to researches in this subject, particularly by Milton and Le Chatelier, whose published experience gives important information of much practical value. The main conclusions arrived at from practice have had reference to the general effects of impurities in hardening the metal, and the general tendency of heat to soften it and to increase the ductility. The diverse effects of different impurities on strength and ductility will be reviewed in detail at a later stage.

(_c_) _General Industrial Uses._—Copper as metal is also employed to a considerable extent in certain important industries, as in textile manufacture, where it is used for the rollers in calico-printing; and it is in general industrial use in the form of copper heaters, vats, coils, pans, and the like, and occasionally also for roofing and sheathing.

=Uses of Copper Alloys.=—Between 20 and 30 per cent. of the copper produced is employed in the form of alloys. The more important of these are:—

=Brasses=; alloys of copper and zinc.
=Bronzes=; chiefly alloys of copper and tin.
=Coinage Alloys=; of gold and silver with copper.
=German Silver=; alloys of copper, nickel, and zinc.
=Special Bronzes=; alloys of copper with such metals
as aluminium and manganese.

It is further not unlikely that several classes of ternary alloys, at present still under investigation, may have important industrial application in the future. Among such alloys may be mentioned the copper-aluminium series alloyed with other metals, Monel metal and the Monel steel series, etc.

Of the above alloys, the brasses are by far the most widely used. It may be recalled that the advantages possessed by alloys of copper and zinc are in large measure due to their increased strength and hardness; to the fact that they are more fusible, and more fluid when melted, and so give good castings; that they are characterised by a good colour and high lustre, as well as by the factor of cheapness resulting from the addition of a less costly metal—zinc—in their manufacture.