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Monographs on Industrial Chemistry 



THE ZINC INDUSTRY 



ERNEST A, SMITH 



MONOGRAPHS ON INDUSTRIAL 
CHEMISTRY 

Edited by Sir EDWARD THORPE, C.B., LL.D., F.R.S. 

Emeritus Professor of General Chemistry in the Imperial College of Science and Technology, 
South Kensington ; and formerly Principal of the Government Laboratory, London. 

INTRODUCTION 

TOURING the last four or five decades the Appli- 
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Sheffield. io.y. 6d. net. 
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WATSON, M.A., D.Sc., Dacca College, Bengal. 
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F.R.S., The Dyeing Department, The University, Leeds; and 

A. E. EVEREST, D.Sc., PH.D., Technical College, H udders field. 
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MORGAN, D.Sc., A.R.C.S., F.R.S., Finsbury Technical College, 
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Utilisation of Atmospheric Nitrogen : Synthetical Production 
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The Electric Arc in Chemical Industry. By J. N. PRING, D.Sc., 
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By-Product Coking Practice. By ERNEST BURY, M.Sc. 

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Imperial College of Science and Technology, South Kensington. 



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MONOGRAPHS ON INDUSTRIAL CHEMISTRY 
EDITED BY SIR EDWARD THORPE, C.B., LL.D., F.R S. 



THE ZINC INDUSTRY 



THE ZINC INDUSTRY 



BY 

ERNEST A. SMITH, Assoc.R.S.M., 

Deputy Assay- Master \ Sheffield ; Formerly of the Metallurgical 

Department of the Royal School of Mines, London : 

Member of the Institution of Mining and 

Metallurgy ; Member of the Institute 

of Metals ; Member of the 

Society of Chemical 

Industry 



WITH 4 PLATES, AND DIAGRAMS IN THE TEXT 



LONGMANS, GREEN AND CO 
39 PATERNOSTER ROW, LONDON 

FOURTH AVENUE AND JOTH STREET, NEW YORK 
BO ( MBAY, CALCUTTA, AND MADRAS 



PREFACE 

ALTHOUGH the art of zinc extraction has been practised in 
this country for more than a century, comparatively little has 
been written relative to its development since the publication 
of the classical work of Dr. John Percy, which appeared in 1861. 

It is probably this absence of a special literature dealing with 
the position of the zinc industry in recent years that partly 
accounts for the lack of interest hitherto shown in this branch 
of British metallurgy. 

At the present time, however, the importance of the production 
of zinc and other non-ferrous metals is, fortunately for this country, 
becoming more generally recognised ; it is, therefore, in the 
highest degree desirable that there should be available treatises 
suitable for the use of those interested in non-ferrous metals, 
whether they are manufacturers, users of metals, scientific 
investigators, or students of metallurgy. 

In this work the author has endeavoured to give a general 
survey of the development of the zinc industry, and its present 
and possible future position in relation to the various metal 
industries of this country. 

In its preparation the author has freely availed him- 
self of the current literature on the subject. He would more 
particularly express his indebtedness to the papers by J. C. 
Moulden, on " Zinc, its Production and Industrial Applications " 
(Royal Society of Arts, 1916) ; H. M. Ridge, " The Utilisation 
of the Sulphur Contents of Zinc Ore " ; and also to the Bulletin 
of the Imperial Institute, 1915-1916, for useful information on 
the zinc ore resources. 

v 



384941 



PREFACE 

Thanks are also due to Mr. Ridge for valuable information 
and for kindly providing the illustrations of the roasting furnaces, 
and to Dr. F. C. Thompson for preparing the photomicrographs. 

With regard to statistics the figures for the year 1913 have 
been given purposely in preference to those of subsequent years, 
as being more representative of the zinc industry under normal 
conditions. In many cases later figures are not procurable, some 
of the belligerent nations having ceased to issue them since 1914. 
Due consideration has, however, been given to the very marked 
influence of the war on the zinc industry. 

A bibliography of some of the more important publications 
relating to the subject is appended. 



VI 



CONTENTS 



PAGE 

PREFACE v 

INTRODUCTION i 

Position of Zinc in Commerce and in the Arts ... . . 4 

CHAPTER I. 
THE HISTORY OF ZINC 7 



CHAPTER II. 

THE RISE AND PROGRESS OF THE PRODUCTION OF ZINC . . 10 

The Establishment of Zinc Smelting Centres 10 

The Development of the British Zinc Industry 18 

British Empire Centres of Zinc Production 29 

The Development of the European Zinc Industry .... 33 

The Development of the American Zinc Industry .... 40 

Zinc Production in Asia 43 

CHAPTER III. 

ZINC ORES AND THEIR SOURCES OF SUPPLY 46 

Zinc Ores : Their Nature, Occurrence and Distribution . . . 46 

Zinc Ores in the British Empire 51 

European Sources of Zinc Ores 55 

American Sources of Zinc Ores 61 

Asiatic Sources of Zinc Ores 67 

CHAPTER IV. 

THE MARKETING OF ZINC ORES 70 

The Concentration of Zinc Ores 70 

The Valuation of Zinc Ores 73 

The European Ore Trade 77 

CHAPTER V. 

THE SMELTING OF ZINC ORES 79 

Recent Advances in Zinc Smelting 104 

CHAPTER VI. 

ZINC SMELTING (Continued) in 

By-products in the Smelting of Zinc in 

Sulphuric Acid in 

The Cost of Zinc Production 119 

The Conditions of Labour in Zinc Smelting 122 

CHAPTER VII. 

OTHER METHODS OF ZINC PRODUCTION 124 

The Electric Smelting of Zinc Ores . . . * . . . 124 
Hydro-metallurgical Processes of Zinc Production . . . .130 

vii 



CONTENTS 



CHAPTER VIII. 

PAGE 

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC . . . 137 
The Micro-structure of Zinc ......... 14 

Impurities in Commercial Zinc ........ M5 

CHAPTER IX. 

THE MARKETING OF ZINC . . . ...... *4& 

Grades of Commercial Zinc . ........ M 8 

The Price of Zinc ........... X 5* 

The World's Zinc Markets . ........ *54 

The Spelter Convention *; J .' | .> : X * S * ^H* ' X 55 
The Production and Consumption of Zinc ...... 157 

CHAPTER X. 

THE INDUSTRIAL APPLICATIONS OF ZINC ...... 161 

Rolled or Sheet Zinc . ........ 166 

ZincCastings . ... . 5 ^* . . ,. . .> ....... 167 

Other Uses of Zinc . ... ''"..' . , . . - 

Zinc Dust (Blue Powder) . .... . . 

CHAPTER XI. 
INDUSTRIAL ZINC ALLOYS ; M . . . ': ' . . 



CHAPTER XII. 
COMMERCIAL COMPOUNDS OF ZINC: ZINC PIGMENTS .... 19* 

CHAPTER XIII. 

THE FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN . .198 

BIBLIOGRAPHY . . . i. . .^ . . . . 213 

INDEX . . . . . . ^ . . ^ . . - 223 



LIST OF PLATES 

PLATE To face page 

I. PHOTOMICROGRAPH OF CAST ZINC . ., ;. . .| x . 2 

DITTO, SHOWING TWINING . ., . . , : > ./ 
II. PHOTOMICROGRAPH OF CAST ZINC WITH 30% OF LEAD 144 

III. BRASS (70% COPPER, 30% ZINC) AS CAST, SHOWINGN 

CORD STRUCTURE . . Bei ween pp.. 

IV. BRASS (70% COPPER, 30% ZINC) AFTER ANNEALING)- 144-145 

FOR ONE HOUR AT 750 C., SHOWING CRYSTAL- 
LINE STRUCTURE / 

viii 



THE ZINC INDUSTRY 



INTRODUCTION 

THERE is considerable truth in the statement, made more than 
sixty years ago by Dr. John Percy, 1 the father of British metal- 
lurgy, that " in proportion to the success with which the metal- 
lurgic art is practised in this country will the interests of the 
whole population, directly or indirectly, in no inconsiderable 
degree be promoted." This is true, not only of the United 
Kingdom, but also of the British Empire. 

Had the importance of this fact been more fully recog- 
nised during the past three or four decades by the Government 
and by those engaged in the mining and metallurgical industries, 
there can be little doubt that the valuable mineral resources 
of the Empire would have been more fully developed and 
utilised, and adequate provision would have been made for smelt- 
ing the ores within the Empire in the interests of the metal 
industries of this country and the Colonies. The crisis through 
which we are passing has revealed to what an extent our lack 
of metallurgical enterprise has enabled Teutonic influence to 
gain control of the mineral and metal resources of the British 
Empire, and made the United Kingdom largely dependent on 
foreign supplies to meet her increasing demands for industrial 
metals. 

" Before the war the world's markets for the majority of the 
non-ferrous metals were very largely controlled by a group of 

1 Inaugural lecture to students of the Royal School of Mines, London, 
1851. 

I B 



NDUSTR Y 



German metal companies engaged primarily in buying metals 
and acting as selling agents for producers. 

" How complete this control was few people knew. 
" The outbreak of war disclosed it in all its formidableness. 
"The most important of these concerns was the Metallgesell- 
schaft of Frankfort-on-the-Main. This place was the centre of 
certain German financial interests which had combined to 
establish the Metall Bank and the Metallurgische Gesellschaft. 
In one way or another this great organisation had established 
financial interests in metal undertakings, not only in Germany 
and Austria, but also in the United States of America, the United 
Kingdom, and various parts of the British Empire. 

" This enormously powerful group of companies controlled the 
world's metal markets, of which Frankfort became the centre. 

'* Their connections with other undertakings and their ramifica- 
tions were exceedingly complicated and difficult to control. 
In some instances there was a direct financial connection ; in 
others the connection was established by some form of agree- 
ment. But whatever the method, there was no doubt about 
the ascendency acquired by the Germans." 1 

In no case was this control more stringent than in that 
of zinc. Before the war the Germans, by means of the so-called 
Zinc Convention which they organised, were placed very 
largely in control of the zinc trade of the world, and were also 
able to enter into long-date contracts for the supply of large 
quantities of ore mined within the British Empire, thus placing 
British consumers of zinc in an unwarrantable position of in- 
security. 

This control was a source of great embarrassment to the 
British Government at the outbreak of war, and for quite two 
years afterwards the cause of this country and its Allies was 
severely handicapped because we were without the necessary 
metal supplies, and many trades were in jeopardy. With the 
view of preventing this control in the future, the Government 
has recently passed the " Non-ferrous Metals Bill," which is a 
measure designed to keep the control of the supply of these 
essential metals in British hands. 

For many years the United Kingdom has had to depend on 
imported metal to the extent of more than 70 per cent, of her 
zinc requirements. 

1 H. C. H. Carpenter, Nature, 1917, vol. c., p. 284. 
2 



INTRODUCTION 

Before the war the bulk of the British supply of zinc was 
obtained from Germany and Belgium. Each country was a 
large producer of the metal, and each also a large importer 
of zinc ore from the most important zinc mine in the British 
Empire, that at Broken Hill, in Australia. 

The outbreak of war led to a remarkable situation in the 
British and Colonial zinc markets, owing to the sudden cutting 
off of pre-war supplies of the metal, and the loss to Australia 
of nearly all her markets for zinc ore (concentrates). The 
demand for the metal increased enormously, zinc as a con- 
stituent of cartridge brass being an indispensable munition metal. 
But whilst there were enormous quantities of zinc ore await- 
ing shipment in New South Wales, most of the British smelters 
were unable to treat it, as their furnaces were not adapted to 
this particular class of ore. 

Consequently, at the outbreak of war Great Britain found 
herself in the anomalous position of having command of the 
seas, and with an immense supply of zinc ore within the Empire, 
but with smelting plant quite inadequate to convert this ore into 
metal. 

The serious shortage of spelter was temporarily met by exports 
from the United States, the world's largest producer of zinc, but 
as the production in that country is usually only about equal to 
the consumption, the result was a rapid rise in the price of the 
metal, the selling price appreciating to more than five times its 
pre-war figure. 

These conditions led to an inquiry into the position of the 
British zinc industry, and also to a consideration of the possi- 
bilities of so increasing the future output of metal that it shall 
at least be sufficient to meet all home requirements. Such a 
situation as that in which Great Britain found herself at the 
beginning of hostilities should never have been allowed to arise, 
and it is satisfactory to know that steps are being taken to make 
its recurrence impossible. There is every reason why the supplies 
of zinc concentrates which have hitherto been largely shipped 
to the Continent, should be treated within the British Empire, 
and it is to be hoped that in the future this will be done. 
Legislation has decided that the resources of the Empire are 
not, in the future, to be left to be exploited by Germans. 

As showing the great importance of the Broken Hill zinc ore 
deposits it may be stated that the output would be more than 

3 B 2 



THE ZINC INDUSTRY 

sufficient to supply the entire demand of the United Kingdom 
for metallic zinc. 

With the view of relieving the zinc situation and rendering 
the United Kingdom less dependent on foreign supplies, important 
schemes, which are dealt with later in this monograph, have been 
taken in hand, and there seems to be some prospect that the 
British zinc smelting industry will, in the near future, take the 
position that its importance demands. 

Steady progress has already been made, and the movement is 
progressing at an accelerated rate, largely through the impetus 
given to it by the crisis through which the country is now passing. 

When the rank this country holds among nations as regards 
her metal industries is taken into consideration, it must be 
a matter of surprise that in the past so little attempt appears 
to have been made to develop the zinc smelting industry 
so that the production of this important industrial metal shall 
be commensurate with the needs of the country. 

The Position of Zinc in Commerce and in the Arts 

Although zinc was extracted from its ores on a commercial 
scale in Europe in the middle of the eighteenth century, it did 
not begin to take a prominent place in the arts until a 
century later, so that, from an industrial point of view, it is 
regarded as a comparatively modern metal when compared with 
metals such as lead and copper that have been in common use 
for centuries. 

Zinc, or spelter, as it is termed commercially, possesses physical 
and chemical properties that render it extremely useful, and 
when these properties were fully recognised the metal rose, 
somewhat rapidly, to a position of considerable importance. 
It now occupies the third place in the list of non-ferrous base 
metals of value in the metal industries, only being surpassed in 
this respect by lead and copper. 

The rapidity with which zinc has grown in industrial importance 
may be judged from the fact that the world's output has almost 
quadrupled itself in the past thirty years, and in that time the 
British production has increased tenfold. The world's produc- 
tion of the three non-ferrous metals in most common use in the 
years 1911-1913 the latest figures available under normal 
conditions was as follows : 



INTRODUCTION 

WORLD'S OUTPUT OF NON-FERROUS METALS. l 
(In metric tons. 2204-6 Ib.) 





Production. Consumption. 
Metric tons. Metric tons. 


Average 
Price. 


1911. 
Lead 
Copper 
Zinc 


1,136,000 
893,800 
902,100 


1,149,200 
954,100 
911,400 


s- d. 
13 9 2 

56 i 9 
25 3 2 


1912. 
Lead 
Copper 
Zinc 


1,181,800 
1,018,600 
977,900 


1,201,800 
1,038,700 
996,900 


17 15 10 
73 i 2 
26 3 4 


1913- 
Lead 
Copper 
Zinc 


1,186,700 
1,005,900 
997,900 


1,196,200 
1,044,500 
1,012,700 


18 6 2 

68 5 9 
22 14 3 



From the figures for the production in 1913 it will be seen 
that for every 1,000 tons of lead produced there were 921 tons of 
copper and 920 tons of zinc. 

This close coincidence between the figures for copper and zinc 
shows that the relative position occupied by zinc in the arts and 
commerce was, at the outbreak of war, practically the same as 
that of copper, a metal which has been in use for industrial 
purposes for a very much longer period. 

Owing to the disturbance caused by the war, it is doubtful 
how far this ratio is to-day strictly preserved. 

Zinc owes its important position largely to its valuable pro- 
perty of preventing the corrosion or rusting of iron when this 
metal is coated superficially with it, and also to the fact that 
it is a valuable constituent of brass, now one of the most 
widely used industrial alloys. 

It may be well here to point out that the nomenclature of zinc 
is a little confusing. The British usage, and also to a certain 
extent the American, is to apply the term " spelter " to designate 
the ordinary ingot zinc of commerce, the word " zinc " being 
usually reserved for the rolled metal and for chemical and 
mineralogical terminology. 

1 Statistics issued by the Metall Gesellschaft and the Metall Bank of 
Frankf ort-on-the-Main . 



THE ZINC INDUSTRY 

The miner sells ore to the smelter on the basis of its zinc 
content, and the latter markets the extracted metal as spelter, 
which is not " a metal " in sensu stricto, but a commercial 
alloy produced by the smelting of zinc ores, and, although 
consisting mainly of zinc, usually contains sensible proportions 
of lead and other metals. 

Recent usage, so far as Great Britain is concerned, has inclined 
towards the use of the word spelter for all grades of metal up to 
those containing 99-8 per cent, of zinc or thereabouts, those of 
higher quality than this being designated " fine-zinc." l Although 
arbitrary, there are commercial reasons for the distinction. 

The crude zinc obtained direct from ores by smelting is usually 
known in the trade as " virgin spelter " in this country, and as 
" primary zinc " in America, whereas metal that has been in use 
and then remelted is termed " remelted spelter " in this country 
and " secondary zinc " in America. 

The term " hard spelter " is given to a cheap and common 
brand of metal, consisting of zinc contaminated with iron, 
resulting from the galvanising process. 

1 " Zinc, its Production and Industrial Applications," F. C. Moulden. 
Journ. Roy. Soc. of Arts, 1916, vol. Ixiv, p. 500. 



CHAPTER I 

THE HISTORY OF ZINC 

IN turning to the history of zinc it is difficult to determine 
when, and by whom, the metal was first isolated in the metallic 
state. Primitive metallurgical processes are referred to in the 
oldest known historical records, but none of the descriptions 
of ores and processes used, and of metals obtained, can be applied 
with any degree of certainty to metallic zinc. Undoubtedly 
zinc as a distinct metal was unknown in early times, in fact as 
late as the sixteenth century it was not known in Europe ; but 
there are strong reasons for the belief that the Chinese were 
acquainted with it as metal at least several centuries earlier. 1 

In Roman times it was known in the alloyed state as a con- 
stituent of brass, an alloy of zinc and copper. 

Zinc first appears in the coins of the Republic as an impurity ; 
as an intentional addition, however, it only dates from the time 
of Augustus (20 B.C. to 14 A.D.), when brass was made for the 
first time in the world's history. 

The Romans were the first makers of brass. Although they 
were unacquainted with the essential constituent, zinc, yet they 
had discovered that, by melting copper together with a certain 
ore (calamine, the natural zinc carbonate) by the process known 
as " cementation," a yellow alloy of a more golden colour than 
bronze could be obtained, the alloy being known subsequently 
as " calamine brass." That the Romans were the first inventors 
of brass is, according to Prof. Gowland, 2 without doubt, as the 
alloy is not found in Greece or the Greek colonies or elsewhere 
until the time of the Roman Empire. 

1 W. Gowland, Presidential Address, Journ. Inst. of Metals, 1912, 
vol. vii, p. 42. 

2 Loc. cit., p. 46. 

7 



THE ZINC INDUSTRY 

The first mention of zinc as a distinct metal is usually ascribed 
to the alchemist Paracelsus (1493-1541), but there appears to 
be little doubt that it was first actually recognised in the metallic 
state in Europe by his contemporary, Georgius Agricola, the 
renowned metallurgical writer, who about the middle of the 
sixteenth century accidentally discovered it in the wall crevices 
of a smelting furnace treating zinciferous lead and copper ores 
at Goslar in the Hartz. 1 

As, however, Agricola only describes the metal and makes no 
mention of the extraction of zinc from its ores in his well known 
work " De Re Metallica," 1556, it may be concluded that the 
metal was not generally known in his time. 

The discovery of zinc in Europe seems to have been quite 
independent of any knowledge of the metal in the Far East, 
where, as previously stated, it was undoubtedly known prior to 
the sixteenth century. 

There is also some evidence that zinc was known and extracted 
in India prior to the sixteenth century. 

The localities of Eastern production have never been 
adequately investigated. Nevertheless, it is well known that 
the Chinese have, from very early times, possessed considerable 
metallurgical knowledge, and it is not improbable that when 
the early history of the metallurgy of this ancient people 
comes to be written it will be found that the first separa- 
tion of metallic zinc from its ores must be attributed to the 
Chinese. 

There is evidence that the greater part of the zinc produced 
in the sixteenth and the seventeenth centuries came from China. 
The metal was imported from China into Europe by Portuguese 
and Dutch merchants under such names as tutinag, and spiauter, 
or spialter ; hence the word speltrum, introduced by Boyle, 
and the English word spelter, which is almost the only term for 
crude zinc in the works at the present day. 

The importation of zinc from China has continued to the 
present day, and quite a substantial quantity of Chinese zinc 
of very good quality has found its way to England since the war 
began . 

The earliest certain descriptions of zinc production in India 

1 For full discussion of the early history of zinc, see Agricola's " DeRe 
Metallica," transited by H. C. and L. H. Hoover, London, 1912, 
pp. 408-410. 

8 



THE HISTORY OF ZINC 

appear to be some recipes for its extraction dating from the 
eleventh to the fourteenth centuries quoted by Praphulla Chandra 
Ray in his " History of Hindu Chemistry," London, 1902, p. 39. 
The crude distillation of zinc was conducted in Rajputana as 
late as the beginning of the nineteenth century, and the remains 
of such smelting, in this and other districts of India, are said to 
be very ancient. 



CHAPTER II 

THE RISE AND PROGRESS OF THE PRODUCTION 

The Establishment of Zinc Smelting Centres 

WHATEVER uncertainty there may be as to the antiquity of the 
discovery of metallic zinc, there appears to be little doubt that 
the art of extracting it from its ores by distillation was acquired 
from the Far East and was introduced into Europe in the latter 
part of the eighteenth century. 

There is a tradition, recorded by Bergman, that an Englishman 
visited China in the eighteenth century expressly to learn the 
method of making zinc ; that he attained his object and returned 
home in safety with the secret ; and that some time afterwards 
works were erected at Bristol for the extraction of zinc in large 
crucibles by distillation per descensum} This tradition is sup- 
ported by the fact that zinc works were established at Bristol 
about 1740, by John Champion, who was, so far as is known, 
the founder of the British spelter industry, and also the first 
metallurgist in Europe to extract zinc from its ores commer- 
cially. Exactly what circumstances led Champion to start the 
spelter industry at Bristol must be more or less a matter of 
conjecture, but probably it was due to the fact that a calamine- 
brass industry had been in existence in England for about a 
century previously. 

Formerly calamine, an important ore of zinc, was fairly 
abundant in England and was employed in brass-making, and 
was also exported as ballast to the Continent to be used for the 
same purpose. It is recorded that calamine-brass works were 
erected in Surrey about the middle of the seventeenth century. 
Works were also established in Bristol about 1702, and after- 

1 Quoted by J. Percy, " Metallurgy of Copper and Zinc," London, 1861, 
p. 520. 

10 



THE RISE AND PROGRESS OF THE PRODUCTION 

wards at Cheadle, in Staffordshire, about 1720. Later, works 
were erected for the manufacture of ingot-brass at Smethwick, 
Swansea, and Llanelly. 

The smelting of zinc ores was continued at Bristol for nearly 
one hundred years, when it was transferred to Swansea, which 
possessing greater natural facilities for the development of the 
industry, gradually became the most important centre of zinc 
production in the United Kingdom. 

The manufacture of brass by cementation was also carried 
on in Europe in the eighteenth century, notably at Moresnet 
in Belgium, and at Beuthen in Poland, at which places important 
deposits of calamine (zinc carbonate) were worked. As the art 
of zinc smelting gradually became known, it necessarily followed 
that in course of time it should be introduced at these noted 
European centres of brass-making. It was not, however, until 
some fifty years after the establishment of the industry in 
England that it was introduced on the Continent. 

The manufacture was started in Germany about 1798 by 
Johann Christian Ruberg, who probably learned it in England, 
and began zinc distillation at the glass works of Wessola, near 
Pless, in Poland. 

Ruberg first adopted the method of distillation per descensum 
as practised at Bristol, but he soon found that it was very 
defective, and devised the system of treatment in horizontal 
muffles of large capacity, known as the Silesian method. Ruberg 
thus laid the foundation of what became, in later times, the 
important Silesian zinc industry. 

About the same time, zinc distillation from calamine was 
also started at Dollach, in Carinthia, by Dillinger, by the method 
practised at Bristol, but the works^ only remained in operation 
for a comparatively few years. 

The calamine deposits at Moresnet, in Belgium, passed in 
1795 under the suzerainty of France, and it is stated that the 
Government in granting a concession of mining rights to the 
Abbe Dony, imposed on him the obligation to make such experi- 
ments as would enable the calamine to be reduced to the metallic 
state. Whatever truth there may be in this story, the introduc- 
tion of zinc smelting into Belgium is to be credited to the Abbe 
Dony, who, after many years of experimental work, appears 
to have made the independent discovery of a method of zinc 
distillation and to have established works at Liege in 1807. 

ii 



THE ZINC INDUSTRY 

These works formed the corner-stone of what became in later 
times the world-famed Belgian zinc industry. They have for 
many decades outlived the native supply of zinc ores on which, 
with the presence of coal of the district, the industry originally 
depended. 

Subsequently, works were established at Moresnet, near 
Aix-la-Chapelle, to smelt the important deposits occurring at 
La Vieille Montagne, La Nouvelle Montagne, and Corfalie. 

Dony's method of zinc extraction differed from that employed 
in Great Britain and in Silesia. He distilled the calamine in a 
number of small retorts set in a single furnace, thus constituting 
the Belgian method, adopted by all the Beigian zinc works 
erected later, and subsequently in England and elsewhere. 
Dony reaped little benefit from his discovery ; he died a ruined 
man in 1819, and his successor, M. Dominique Mosselmann, 
who was admitted as Dony's partner in 1816, took over the 
works. Although a man of great energy and capability, 
Mosselmann had not brought about any noteworthy progress 
in the zinc industry when he died in 1837, possibly because 
up to that time no regular demand had been found for the 
increasing output of this new commercial metal. 

Mosselmann carried on the works until his death, when his 
successors, in order to realise his estate, founded the celebrated 
Societe de la Vieille Montagne, with a capital of 7,000,000 francs 
(280,000) .* 

The growth of the company was at first very slow, and it was 
only when Saint Paul de Sincay took over the management that 
the works began to prosper rapidly. 

By the middle of the nineteenth century the Belgian industry 
had become firmly established, and was a formidable rival to 
that of Germany in the amount of zinc produced annually. 
Both Belgium and Germany adopted the method of zinc distil- 
lation per ascensum, which proved to be more economical and 
more satisfactory than distillation per descensum as used in 
England. 

The latter method, which was also carried on to a limited 
extent in Carinthia and Hungary, was discarded in England 
in favour of the former method about the year 1850. 

Towards the latter half of the last century zinc smelting was 
also started in Austria, Holland, Spain and France, but the 

1 J. Gilbert, The Mining Journal, London, 1916, vol. cxiv, p. 480, 

12 



THE RISE AND PROGRESS OF THE PRODUCTION 

industry in these countries has never grown to very large 
proportions, the production, even at the present time, being 
insufficient to satisfy their own requirements. 

During the eighteenth century the growth of the European 
zinc industry was comparatively slow, owing most probably to 
the somewhat limited use of the metal at that time in the manu- 
facture of brass. Although Emerson used metallic zinc for the 
manufacture of brass in England as early as 1781, its use for 
this purpose extended very slowly owing to the indifference, 
and even hostility, displayed by the calamine-brass makers, who 
averred that the metal produced brass inferior in quality to 
that produced by cementation. 

The long survival of this ancient process, after the discovery 
of metallic zinc, and its production on a commercial scale, afford 
a striking example of the conservatism characteristic of early 
British metallurgy. 

At the beginning of the nineteenth century it was found 
to be possible to convert zinc into sheets by heating it to a 
temperature between 100 C. and 150 C. and rolling it while 
hot, thus breaking down the crystalline structure of the metal, 
and rendering it malleable and ductile. 

The credit of this discovery is due to Hobson and Sylvester, 
of Sheffield, who in 1805 obtained a patent for "a method of 
manufacturing the metal called zinc into wire and into vessels." 
This discovery was of no little importance, as it enabled the 
metal to be used for the manufacture of sheets for roofing 
purposes, for which the higher priced metal, copper, had hitherto 
been employed. 

Very little advantage appears to have been taken of the 
patent in this country. The Abbe Dony, however, laid down the 
first rolling mills for sheet zinc production at Liege in 1812, and 
since that time the manufacture of zinc sheets has been a very 
important branch of the Belgian zinc industry. 

The initial difficulties of finding a suitable outlet for the 
increasing quantities of the zinc produced at the different 
centres of production lasted over several decades. 

As late as 1825 the association for fostering the Prussian 
industry offered a prize for the discovery of a useful employment 
of zinc, and this led to its use for ornamental purposes, as imitation 
bronze for statues, lamps, pedestals, and for architectural 
pieces, etc. 

13 



THE ZINC INDUSTRY 

Further impetus was given to the zinc industry by the 
employment of the metal for the manufacture of the so-called 
11 galvanised " iron, the name given to sheet iron coated super- 
ficially with zinc to prevent its corrosion when exposed to 
atmospheric influences. 

The term " galvanised " is said to have been first used, 
improperly, in France and subsequently adopted in this country. 

The galvanising process is effected by dipping the iron articles 
into a bath of melted zinc, a patent for zincing iron in this way 
being granted to H. W. Crawford in 1837. 

The application of these two valuable properties of zinc 
greatly extended its use for industrial purposes when once their 
importance was fully realised. 

It was not, however, until the middle of the nineteenth century 
that the zinc industry began to be established on a sure footing 
in Europe. In 1830, the total production of spelter in Europe 
was less than 5,ooo tons, and in 1840, ten years later, the total 
output had only reached a little more than 17,000 tons. 

From this time onwards, however, there was a steady increase 
in the production of the metal, until it eventually occupied third 
place in the list of non-ferrous metals of industrial importance. 
A notable increase in output occurred from about 1873, due to 
the progress of galvanising. 

Zinc smelting was not introduced into America until 1838, 
in which year the metal was first produced experimentally in 
the United States. Between the years 1841 and 1850 various 
attempts were made to smelt the red oxide ore of New Jersey, 
which is contaminated with willemite and franklinite in such a 
way that a clean separation could not at that time be economi- 
cally effected. 

The attempts to produce metallic zinc were unsuccessful, 
and attention was then directed to the recovery of the zinc as 
oxide, and works for the manufacture of zinc oxide on a com- 
mercial scale were erected in Jersey City in 1854. 

The regular production of metallic zinc was not undertaken 
until 1859, when J. Wharton started zinc smelting in muffle fur- 
naces of the Belgian type, with Pennsylvanian anthracite as fuel. 

By 1870, six works were producing zinc in the United States 
at the rate of approximately 4,500 tons per annum, while the 
works in New Jersey produced in addition about 13,000 tons of 
zinc oxide. 

14 



THE RISE AND PROGRESS OF THE PRODUCTION 



While at this time the American industry was only just becom- 
ing established, the European industry had made considerable 
progress, as shown by the following figures giving the approxi- 
mate zinc output for the various countries of Europe in 1870 : 

Long tons. 

Germany . . . . . . . . . . . . 56,000 

Austria . . . . . . . . . . . . 3,ooo 

Belgium . . . . . . . . . . . . 46,000 

Great Britain (estimated) . . . . . . 10,000 

France ,, . . . . . . . . 6,500 

Spain ,, . . . . . . . . 6,500 



Total European zinc production in 1870 



128,000 



This amount, with 4,500 tons of spelter produced in the United 
States, makes a total of approximately 133,000 tons as the 
world's zinc production in 1870. The production of the indi- 
vidual countries in recent years is dealt with on page 158. 

Attention must be directed to the fact that although domestic 
ores were mined and smelted in Europe at this time, a by no 
means inconsiderable quantity of imported zinc ore was also 
smelted. Thus, the total annual production of the famous zinc 
ore in the island of Sardinia was, in 1870, about 49,200 tons, 
representing 16,900 tons of zinc ; this ore was chiefly exported 
to Germany, Belgium, and the United Kingdom. 

The enormous increase in the rate of production, and in the 
demand for zinc since the year 1870, is well shown in the follow- 
ing figures, which give the approximate output and consumption 
of zinc, in English tons from 1870 to the outbreak of war, in 
intervals of ten years. 





European 


American. 


World's 


World's 




production. 


production. 


production. 


consumption. 


Year. 












English tons, 2,240 Ib. 


1870 . ; 


128,000 4,500 


133,000 


, 


1880 . 


207,000 21,000 


228,000 


230,000 


1890 . . 


343.ooo 


345,000 


1900 


310,000 58,000 


368,000 


474,000 


1910 


557,000* 


247,000 


804,000 


820,000 


1913 


663,000* 


315,000 


982,000 


997,000 



Includes small amounts produced in Australia. 
15 



THE ZINC INDUSTRY 

It will be seen that not only has there been an enormous 
increase of production, especially during the present century, 
but the ratio between the European and the American produc- 
tion has altered, implying far-reaching economic changes in 
regard to the supply and demand for zinc. 

The increase in the world's supply of zinc from 1845 
to 1913, in English tons, has been plotted graphically by 
J. C. Moulden in the accompanying curve (page 17). Prior 
to 1845, the statistics are not very trustworthy, and in any 
case the tonnage was so small as to have little bearing upon the 
metal in relation to the part it plays to-day in our commerce. 
The curve indicates in a striking manner the ever-increasing 
relative rate of production, a considerable advance being noted 
about 1873, due to the progress of galvanising. With the 
exception of a decrease in 1900 and 1908, there has been pro- 
gressive output, the increase for 1900 to 1913 being very remark- 
able. In the relatively short space of sixty-eight years the 
world's output has increased about 3400 per cent. (Moulden). 
The actual figures compiled by Moulden for the world's zinc 
production for the period included in the curve 1845-1913 are 
as follows (in English tons) : 

THE WORLD'S PRODUCTION OF ZiNC. 1 
From 1845 to 1913. 



Year. 


English tons of 
2,240 Ib. 


Year. 


English tons of 
2,240 Ib. 


i845 


29,000 


1904 


612,687 


i855 


70,000 


1905 


643,906 


1865 98,000 


1906 688,321 


1875 166,000 


1907 725,616 


1885 294,000 


1908 711,514 


1890 342,000 


1909 762,559 


1895 406,000 


1910 797336 


1900 471,460 


1911 880,411 


1901 508,422 
1902 544, 1 93 


1912 
1913 


955,398 
985,142 


1903 561,547 







A significant feature of the zinc industry is its limitation to 
the comparatively few smelting centres in Europe and America 

1 Compiled by J. C. Moulden, Journal of the Royal Society of Arts, 1916, 
vol. Ixiv, p. 527. 

16 



i 

THE RISE AND PROGRESS OF THE PRODUCTION 





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Long tons (in Thousands) 



THE ZINC INDUSTRY 

already mentioned, viz. : Silesia, Westphalia and Belgium on 
the Continent ; Swansea, Birmingham, and more recently Durham 
in England ; Kansas, Illinois and New Jersey in the United States. 
In recent years, a zinc smelting plant, to which reference will 
be made later, has been erected at Port Pirie in Australia. 
These are the more important smelting centres contributing to 
the world's supply of zinc, and to one or other of these centres 
practically all zinc ores have, hitherto, been shipped for treat- 
ment. 

This localisation of the zinc industry is due to the necessity 
for cheap fuel, the occurrence of good quality fireclay required 
for the retorts used in smelting, and to the necessity of skilled 
labour, whilst the climatic conditions must be suitable to the 
trying conditions of the workers. 

It has been found very difficult to install zinc smelting works 
without close regard to these somewhat narrow factors ; in 
regard to labour especially, it takes many years to train the 
workers, whose skill and practical knowledge may be said to 
result from environment and in this branch of operative metal- 
lurgy to become almost hereditary. 1 

The main strength of the great centres of zinc production 
to-day may be said to be their force of skilled labour. 

It may not be without interest to trace briefly the development 
of the zinc industry in each of the different centres of produc- 
tion. This will conduce to a more thorough appreciation of the 
relative positions of the individual localities in contributing to 
the world's supply of zinc. 

The Development of the British Zinc Industry 

As the enterprise at Bristol that marked the beginning of zinc 
production, not only in Great Britain, but also in Europe, was 
unsupported by any important domestic deposits of zinc ore, 
and was handicapped by methods of smelting inferior to those of 
Belgium and Silesia, it gradually languished and eventually died 
out about 1860. 

Meanwhile, the well-known firm of Vivians had, in 1835, 
erected zinc smelting works at Swansea in South Wales, around 
which, as a nucleus, gradually grew the British zinc smelting 
industry. 

1 H. L. Sulman, Presidential Address. Transactions of the Institute of 
Mining and Metallurgy, 1910-1911, vol. xx. 

18 



THE RISE AND PROGRESS OF THE PRODUCTION 

As already indicated, the process of extracting the metal 
first practised in this country differed very materially from 
that adopted later in Belgium and Silesia. In the English 
method of distillation per descensum, the zinc vapour was 
drawn downwards from the bottom of the pot or crucible to 
the condensing apparatus, whilst in the process per ascensum 
as practised on the Continent the vapour of the metal passed 
from the uppermost point of the retort or muffle to the con- 
densing apparatus. The English method was conducted in 
large crucibles heated in a furnace in many respects similar to 
those used in glass works for the fusion and preparation of 
glass. The method is said to have entailed only a comparatively 
small expenditure of manual labour, but it involved a much 
larger consumption of fuel than in either the Belgian or the 
Silesian process, and on that account the English process 
was superseded by the Continental methods of smelting 
about 1850. 

The extensive zinc smelting works erected near Swansea by 
Mr. Hussey Vivian in 1835 are stated to have contained English, 
Silesian and Belgian zinc furnaces, from which it would appear 
that British zinc metallurgists were giving attention to the 
Continental methods of zinc production some years before they 
finally abandoned the English method in favour of the Belgian 
and Silesian processes. 

Percy states that in 1861 both the Silesian and Belgian methods 
of distillation were in use at a large zinc smelting works in this 
country producing about 100 tons of zinc weekly. 

With the growth of the zinc industry, works for the pro- 
duction of the metal were established at Llanelly, Wigan, 
Wrexham, Sheffield, Birmingham and Bristol, but Swansea has 
always been the principal centre of zinc production in Great 
Britain and is still responsible for a large proportion of the 
metal annually produced in this country. 

The early statistics of zinc output in Great Britain are not 
very trustworthy, but it would appear that prior to 1880 the 
annual production was under 10,000 tons (English, 2,240 lb.). 
Four years later the output was 30,000 tons, showing that the 
production of the metal had increased threefold, due to the 
progress of the galvanising industry. 

Between 1884 and 1887 the output fell to 20,000 tons, and 
then rose again rapidly to about 31,000 tons in 1889. 

19 C 2 



THE ZINC INDUSTRY 

With the exception of a fall to 24,000 tons in 1896, the annual 
production averaged about 30,000 tons between the years 1889 
and 1901, from which date the output rapidly increased until 
it reached approximately 50,000 tons in 1905. Since that 
time the British production of zinc has fluctuated between 50,000 
and 60,000 English tons annually. 

The accompanying curve shows the approximate annual 
output of zinc in Great Britain from 1875 to 1915 in metric 
tons. 

The growth of the British zinc industry is largely due to the 
rapid progress in the manufacture of galvanised or zinc covered 
sheets, which soon became an important branch of British 
metallurgical industry, and created a demand for zinc which 
became so considerable that the smelters in this country could 
not keep pace with its constantly increasing requirements. This 
presented the opportunity for the importation of foreign zinc, 
an opportunity of which Continental smelters readily availed 
themselves, with the result that very considerable quantities of 
metal have for some years been shipped to this country annually, 
chiefly from Belgium and Germany, a condition of things that 
must have been very helpful to the development of the zinc 
industry in those countries. The extent of this importation of 
foreign zinc to meet British demands may be realised when it is 
stated that"5 for some years prior to the war the imports of 
crude zinc into the United Kingdom averaged about 100,000 
tons annually. 

The bulk of the imported metal, as shown by the table on 
p. 26, came from Germany and Belgium, whilst other countries 
also contributed smaller amounts. It will be seen that the 
cost of this imported metal amounted to the enormous sum of 
3>5oo,ooo annually, a fact which shows how important an 
adequate supply of the metal is to British industries, even under 
normal conditions. 

In addition, however, to the imports of crude zinc, about 
20,000 tons of manufactured zinc, largely sheet metal, and valued 
at about 600,000, was imported annually into the United 
Kingdom in the few years immediately preceding the war. 

It will be seen that in 1913 the zinc imports amounted to as 
much as 145,000 tons, whilst the zinc produced in the country 
in 1913 totalled only 58,298 tons, representing 5-9 per cent, 
of the world's production of zinc for that year, which was 

20 



THE RISE AND PROGRESS OF THE PRODUCTION 
BRITISH PRODUCTION OF ZINC 1875-1915 




20,000 



15,000 



0.000 



1875 '860 



THE ZINC INDUSTRY 

985,142 tons. It must, however, be pointed out that of the 
total metal produced in Great Britain in 1913 probably not more 
than 31,290 tons were " primary " zinc in the sense of being 
extracted from ores, the balance of 27,008 tons being the result 
of treatment of by-products, galvanisers ashes, hard-zinc, etc. 1 

It will be seen, therefore, that this country in the year before 
the outbreak of war was producing even including "secondary " 
metal only about 26*0 per cent, of its zinc requirements. 

For many years the galvanising industry has been by far the 
largest consumer of zinc in this country, probably requiring 
at the present time nearly 70 per cent, of the total zinc con- 
sumed in Great Britain. 

With this very important field of zinc consumption so close 
at hand, it is difficult to explain why British zinc smelters have 
made so little progress and have allowed the output of metal 
to fall so far short of the demand that prior to the war fully 
two-thirds of the British zinc requirements were imported from 
the Continent and to a small extent from America. 

There is doubtless some justification for the assertion that, 
as the ores of zinc which are to be found within the limits of the 
British Isles do not equal in importance those of some of the 
foreign zinc producing countries, the home production of the 
metal has had to struggle against the superior advantages of 
some of the foreign sources of supply. But, as pointed out by 
J. Gilbert, 2 more than one half of the zinc imports to the United 
Kingdom have hitherto come from Belgium and the Rhine dis- 
trict, where for some years fully 33 per cent, of the European 
production of zinc has been produced almost exclusively from ore 
imported from all parts of the world ; consequently the above 
assertion loses much of its weight. One must therefore look for 
other causes in order to explain the apparent neglect of the 
zinc industry in Great Britain, and the principal one will be found 
in the fact that the British smelters have scarcely availed them- 
selves to any great extent of the enormous progress made by 
the Continental smelters in the improvement of their furnaces, 
whereby they have been enabled to reduce the former considerable 
loss in smelting by from 33 to 50 per cent. This source of economy 
became of special importance when the old supplies of the rich 
and comparatively easily smelted carbonate of zinc (calamine) 

1 Rudolf Wolff & Co., published statistics for 1913. 
? The Mining Journal, 1916, vol. cxiv, p. 480. 
22 



THE RISE AND PROGRESS OF THE PRODUCTION 

were gradually diminishing, and the treatment of the originally 
neglected sulphide of zinc (blende) had to be resorted to. 

The experiments in that direction, started in Germany and 
Belgium some twenty years ago, have gradually led to such 
important improvements in the old type of furnaces, chiefly in 
reducing the ruinous loss in smelting and in the saving of 
fuel, retorts, and labour, that these factors may be considered 
as the principal sources of prosperity of the Continental " Lohn- 
huetten " (" customs ") works, that purchase ores for treat- 
ment, in contradistinction to " Grubenhuetten " works, which 
treat ores produced by their own mines. Most of the " Lohn- 
huetten " companies, during the last ten to twenty years, have 
equipped their works with modern furnaces. 

As J. Gilbert remarks, " Unfortunately, the British zinc 
smelters and consumers have not watched the rapid development 
of the industry on the Continent, which went hand in hand with 
some enormous contracts for ore, chiefly from mines situated in 
the British Colonies, with sufficient alertness to enable them to 
participate in the financial results realised during the last decades, 
to such an extent as their position as principal consumers of 
zinc in Europe might entitle them. 

" The smaller British zinc companies shrank from the responsi- 
bility which the outlay for the comparatively expensive modern 
plant would involve, and the larger companies most likely had 
sufficiently profitable employment for their capital and labour 
in other metallurgical enterprises, that the prospects of zinc 
might have appeared to them as a quantite negligeable. Thus, 
generally speaking, very little progress has been made by British 
zinc makers during the last thirty to forty years, which fact is 
also shown by a comparison of the values of British zinc shares 
with, for instance, Belgian shares." 

Although economic reasons have had something to do with the 
lack of enterprise in the British zinc industry, it would appear 
that a certain amount of conservatism, and perhaps an undue 
regard for local tradition on the part of the zinc metallurgists 
and the natural desire of our financiers to see a fair return on 
their capital, such as they have hitherto more readily obtained 
elsewhere, are mainly responsible. 

Two important circumstances which also appear to have 
retarded the development of the British zinc smelting industry 
are lack of scientific control and want of co-operation between 

23 



THE ZINC INDUSTRY 

the different smelting companies, in which respects the British 
industry compares unfavourably with that of the Continent. 

The increasing cost of production during the past few years 
has emphasised the necessity for scientific control. 

Whilst there are instances where individual firms keep them- 
selves informed regarding scientific developments in zinc metal- 
lurgy and make efforts to improve working methods, there is 
little doubt that a fuller appreciation of the value of the scien- 
tifically trained metallurgist and of co-operative action is 
needed in order to produce general increased efficiency. This 
statement should not, however, lead to the erroneous conclusion 
which some persons are inclined to draw, that British metallurgists 
are too ignorant of chemical knowledge to understand the theory 
of the processes under their direction. It is not too much to 
affirm that with respect to knowledge, both of the theory and 
practice of the special departments of the art in which they 
are engaged, the zinc smelters of this country are in many 
cases not excelled by any metallurgists in Europe. But while 
progress, although slow, has been made in the past, much more 
will have to be done in the future, since the unprecedented times 
through which we are now passing demand a long step forward 
in knowledge, equipment, and organisation. The advantages 
of co-operation are too self-evident to need emphasising here. 

As has been well said, 1 " the spirit of co-operation is not a 
mere sentiment or theory. It has been as much a scientific 
necessity for the winning of this war as the provision of guns 
and ammunition, and it will be equally a scientific necessity to 
success in the arts of peace." Co-operation will be secured as 
the result of confidence between individual firms engaged in the 
same industry and between employer and employed. The 
value of co-operation has long been recognised by the zinc smel- 
ters on the Continent. Some years ago a society was started in 
Germany in the interests of the producers of non-ferrous metals, 
and sections were formed to deal with special branches of industry, 
including a zinc section consisting of the managers and higher 
technical officials of the zinc smelting works. 2 They met at the 
same time as the half-yearly meetings of the society, and 

1 Prof. W. Ripper, " Works Organisation and Efficiency," Journal of 
Royal Society of Arts, 1917, vol. Ixv, p. 461. 

2 H. M. Ridge, Journal of the Society of Chemical Industry, 1915, 
vol. xxxiv, p. 764. 

2 4 



THE RISE AND PROGRESS OF THE PRODUCTION 

exchanged experiences confidentially. No reports of the sectional 
meetings were published, since they were only for the mutual 
benefit of the members and for the promotion of German 
industry, but the system has given excellent results. Some 
such system might with advantage be adopted in this country. 
The first step would be to consider the means needed to 
overcome the hindrances which have occasioned the lack of 
co-operation in the past. 

Probably an amalgamation of various zinc smelting works 
would be the easiest means of attaining the desired end. 

It is necessary to realise that the industry must move forward 
as a whole if the greatest advantage is to be gained, and this 
can only occur by the loyal co-operation of those engaged in 
it and by the cultivation of a spirit of confidence in each 
other. 

It is much to be regretted that the schemes so far suggested 
will not increase the British output of zinc sufficiently to 
relieve entirely consumers of their dependence on foreign 
supplies. 

The proposals that have been made for the development of 
the zinc industry are dealt with in Chapter XIII (p. 198). 

Speaking generally, it may be said that the British zinc in- 
dustry has always been dependent on imported ores. Almost 
as soon as the industry became firmly established important 
zinc mines in Sardinia were operated by British zinc smelting 
companies, the ore being shipped to Swansea for treatment. As 
early even as 1870 the small production of zinc ore in Great 
Britain was decreasing, the output for that year amounting to 
only 18,500 tons, equivalent to approximately 5,000 tons of 
metallic zinc, whilst a considerable tonnage of zinc ore was 
exported from Sardinia to Swansea in that year. From that 
time forward the British smelters have imported increasing 
quantities of zinc ore annually. 

For many years the zinc mines in the United Kingdom have 
yielded only an average output of some 17,000 tons, the bulk of 
which was mined by the Vieille Montagne Zinc Company of 
Belgium, and exported to that country for treatment. The 
small quantity of British ores smelted in this country produce 
about 2,500 tons of zinc annually, the remainder of the metal 
produced in the United Kingdom being obtained from imported 
ores as already stated. 

25 



THE ZINC INDUSTRY 





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26 



THE RISE AND PROGRESS OF THE PRODUCTION 

The quantity and the sources of zinc ore imported into the 
United Kingdom for the three years 1912 to 1914 are shown in 
the table on p. 26. 

There are almost unlimited supplies of high grade zinc ore 
within the British Empire that have long been available for 
zinc smelters, but it is only within quite recent years that any 
quantity of the ore has found its way to this country for the 
extraction of the metal. 

It will be seen from the table on p. 26 that in 1914 there was 
a very large increase in the quantity of ore imported from Australia. 
Prior to the war a very considerable proportion of the Australian 
output of zinc ore was controlled by German firms and shipped 
to the Continent for smelting. Further reference to this question 
will be found on p. 152. 

It is very regrettable that so much of the work done by 
Englishmen in devising means of dressing the vast supplies of 
zinc-lead ores of Broken Hill, Australia, should have merely 
resulted in our becoming suppliers to the Continental smelter 
firms who readily treated such ores, because our smelters were 
not prepared to pay a price which would induce the sellers to 
send them to this country, or to adapt their furnaces for their 
special treatment. 

There are now seventeen works producing zinc and remelting 
scrap zinc, etc., in Great Britain, seven being situated in the 
Swansea Valley, the chief centre of production, and the remainder 
in different parts of the country. 

In the selection of a locality for the erection of zinc works, 
it is requisite not only that the ore should be delivered 
at a reasonable price, but also that good coal and very 
superior fireclay should be readily obtainable. These con- 
ditions are well met in Swansea, and on that account 
this district was early selected as the chief seat of the British 
industry. 

About ten works produce zinc direct from ores to the extent 
of approximately 31,000 tons, while the remaining seven works 
produce " secondary " zinc amounting to approximately 
27,000 tons, thus making the total output 58,000 tons for 1913. 
The bulk of the secondary zinc is extracted from the by-products 
of the galvanising works, and the zinc works for the treatment of 
this material are therefore usually situated near the centres 
of the galvanising industry. 

27 



THE ZINC INDUSTRY 



The actual position of the works producing zinc in the 
United Kingdom is shown in the following list : 

LIST OF ZINC SMELTERS AND ZINC EXTRACTORS IN THE UNITED KINGDOM. 



County. 
Cheshire . . 

Durham . . 
Glamorganshire . 



Lancashire 

Middlesex 
Somersetshire 

Warwickshire 
Worcestershire 

Ayrshire . . 



Owner of Works. 

Brunner, Mond & Co., 
Ltd. 

Central Zinc Co., Ltd. 

British Metals Extrac- 
tion Co., Ltd. (Villiers 
Smelting Works). 

Dillwyn & Co., Ltd. 

Down & Co., Ltd. 

English Crown Spelter 
Co., Ltd. 

Williams, Foster & Co., 
and Pascoe, Grenfell 
& Sons, Ltd. (Upper 
Bank Spelter Works) 

Swansea Vale Spelter 
Co., Ltd. 

Vivian & Sons (Morris- 
ton Spelter Works). 

New Delaville Spelter 
Co., Ltd. 

The British Electro- 
lytic Zinc Co. 

Thos. W. Ward, Ltd. 

John Lysaght, Ltd. 
New Delaville Spelter 

Co., Ltd. 
New Delaville Spelter 

Co., Ltd. 
Stewarts & Lloyds, 

Ltd. (Coombs Wood 

Tube Works). 
Brands Pure Spelter 

Co., Ltd. 



Situation of Works. 
North wich. 

Seaton Carew. 
Llansamlet. 



Llansamlet. 

Swansea. 

Swansea (Port Ten- 

nant). 
Swansea. 



Llansamlet. 
Swansea. 
Warrington. 
Widnes. 

Silvertown, 

London, E. 
Bristol. 
Bloxwich. 

Birmingham. 

Halesowen, near Bir- 
mingham. 

Irvine (Glasgow). 



Previous to the war the Swansea Vale works belonged to an 
influential German firm, who had installed a modern smelting 
plant capable of producing 10,000 tons of spelter per annum. 
Practically all the shares in the company are now held by the 
Share Guarantee Trust, Limited, and the works, which are now 
the largest in Swansea, are being further enlarged. 

The works at Seaton Carew, Durham, which are modern and 
well equipped, are operated by the Sulphide Corporation, and 
before the outbreak of war were treating annually some 10,000 

28 



THE RISE AND PROGRESS OF THE PRODUCTION 

to 12,000 tons of zinc concentrates from the Broken Hill mines ; 
since the war the works have been enlarged, and a considerable 
increase in output of zinc from these ores will result in future. 

Formerly the whole of the zinc produced in Great Britain 
was extracted by distillation, but within recent years the deposi- 
tion of zinc from solution by electrolysis has been introduced 
by Messrs. Brunner, Mond & Co., Ltd., Northwich, and zinc of 
very high grade is now being produced by this method. Since 
the beginning of the war Messrs. Chance and Hunt, of Oldbury, 
and the British Electrolytic Zinc Company, of Widnes, have also 
commenced the production of electrolytic zinc, for which there 
is an increasing demand on account of its freedom from impurities. 

British Empire Centres of Zinc Production 

In addition to the old-established zinc smelting centre of 
Swansea, various plants have been erected in modern times 
to deal more particularly with zinc ores occurring within the 
British Empire. 

Many of these ores are of a complex nature, and in connection 
with their treatment there has been a very important 
development in the field of electrolytic methods of zinc extrac- 
tion. 

Australia. Foremost amongst the newer smelting plants are 
those erected at Port Pirie and at Cockle Creek, near Newcastle, 
New South Wales, to smelt the lead ore product from the vast 
deposits of complex lead-zinc sulphides mined at Broken Hill. 
The nature of these ores is dealt with later (see p. 53). 

The satisfactory treatment of these ores for the recovery of 
both lead and zinc has presented considerable difficulties to the 
metallurgist, and it is only within quite recent years that the 
profitable extraction of zinc has been rendered possible. The 
modern methods of dressing the ore yield two products, one of 
which is rich in lead and is smelted for that metal, and the other 
rich in zinc, which is smelted for its zinc content. 

( The Port Pirie smeltery takes the lead concentrate and the 
zinc concentrate from the Broken Hill Proprietary, Zinc Corpora- 
tion, Junction, Junction North and Amalgamated Zinc Companies. 
The Sulphide Corporation smelts its lead ore at Cockle Creek, 
together with the lead ore from Block 14 Mine. In the earlier 
working of the Broken Hill deposits for lead and silver, the zinc 

29 



THE ZINC INDUSTRY 

was neglected and enormous quantities of zinciferous tailings 
and slimes accumulated from the concentrating plants. 

In addition to these, some of the slags from the lead smelting 
contained from 16 to 20 per cent, of zinc oxide. It was 
estimated by the New South Wales Department of Mines that 
in 1903 there had accumulated zinc residues and tailings amount- 
ing to 5,687,400 tons, and these contained 18-6 per cent, of zinc. 
Numerous processes were tried in order to produce a marketable 
grade of ore from these residues, and it was finally decided that 
flotation processes were the most suitable. 

The importance of these residues at the present time is well 
illustrated by reference to the operations of only one company, 
the Amalgamated Zinc Company, which in 1913 treated 498,289 
tons of tailings which contained zinc, 17-1 per cent. ; lead, 37 
per cent., and silver, 4-4 oz. per ton. 1 

From these residues there were obtained 140,098 tons of zinc 
concentrates carrying zinc, 48-9 per cent. ; lead, 5-9 per cent., 
and silver, 8-5 oz. per ton. The lead concentrates also produced 
amounted to 1,584 tons and contained lead, 57-1 per cent. ; 
zinc, 15 per cent., and silver 35-2 oz. per ton. The lead and 
zinc concentrates together were valued at 392,182. In 1913, 
the total value of the products obtained by the companies 
engaged in treating zinc-bearing tailings was 776,228. 
Most of the " dumps/' or reserves of tailings, have now been 
treated. 

The annual output of crude ore from the Broken Hill district 
amounts to about 1,700,000 tons, and employment is found for 
about 8,800 men. These figures give some idea of the great 
importance of the deposits as a potential source of lead, zinc 
and silver. 

The annual output of zinc concentrate in normal times is 
approximately 500,000 tons, valued at about 1,500,000. Prior 
to the war, about 41-5 per cent, of the lead concentrates produced 
at Broken Hill was smelted at Port Pirie, and 8-5 per cent, at 
Cockle Creek, while the remaining 50 per cent, was dispatched 
to Belgium, Germany, France and Austria, where it was handled 
almost entirely by German firms. Of the zinc concentrates, 
only about 2-5 per cent, was smelted annually at Port Pirie, 
and with the exception of some 20,000 tons which is exported 

1 Bulletin of the Imperial Institute, 1915, vol. xiii, p. 621. 

30 



THE RISE AND PROGRESS OF THE PRODUCTION 

to the United Kingdom and smelted at the works of the 
Sulphide Corporation at Seaton Carew and other works, the 
bulk of the remainder was dispatched to smelters in Belgium 
and Germany under long term contracts. 

The disposal of the lead concentrates was on very different 
lines, at least onejialf of the ore being smelted locally, as stated 
above, and the remainder sold under short-date contracts, 
chiefly to German firms. 

The output of zinc from the Australian smelting plant has, 
up to the present, been too small to have any effect on the world's 
production, owing to the large amount of zinc concentrate 
shipped before the war to Europe, but which, in view of the 
proposal to enlarge the Port Pirie smelting plant, may become more 
important in the near future. This extension forms part of the 
scheme that has been proposed since the outbreak of war with 
a view to increase the output of zinc within the British Empire. 

Tasmania. Some experimental plants are in course of erection 
in Tasmania for the treatment of the complex zinc-bearing ores 
of the Mount Read district by electrolytic methods. Reference 
to the processes to be used will be found on p. 134. 

This enterprise, which has been discussed for some ten years, 
embraces, not only a large plant which is being erected by the 
Australian Electrolytic Zinc Company, with a suggested capacity 
of 45,000 tons of zinc per annum, and Gillie's works at Hobart, 
but all the fresh range of output from the Tasmanian West 
Coast ores. 

Canada. Although zinc ores have been mined in Canada for 
some years, it is only quite recently that attempts have been 
made to treat them in the country. Formerly the ore was 
shipped to the United States for treatment, but since the outbreak 
of war considerable attention has been given to the question of 
treating the ore in Canada. 

To encourage the erection of zinc extraction plants, the 
Canadian Government recently agreed to grant bounties on a 
sliding scale, not exceeding 2 cents (i^.) perlb., on the production 
of zinc in Canada from Canadian ores when the standard price 
of zinc in London (England) falls below 33 per ton of 2,000 Ib. 
Such zinc must not contain more than 2 per cent, of impurities. 

There are deposits of low grade and leady zinc ores in Canada 
that can only with difficulty be concentrated so as to produce 
high grade lead and zinc concentrate respectively. 

31 



THE ZINC INDUSTRY 

In the past there has been a moderate production of zinc 
concentrates for export to American smelters, the treatment 
charges and high freight rates serving to prevent any very 
extensive development in this direction. Some 7,000 to 9,000 
tons of zinc ores and concentrates, containing about 3,000 to 
4,000 tons of zinc, have been shipped annually in recent years. 
At the beginning of the war the smelters in the United States 
declined to take further shipments of zinc ores from British 
Columbia, and there was at that time in Canada a shortage of 
zinc for use in manufacturing ammunition and a quantity of 
zinc ore that could not be disposed of. A Commission was 
appointed by the Minister of Militia and Defence to look into 
the matter on behalf of the Government. 1 It was found to be 
impossible to obtain the pure zinc for use in the manufacture of 
cartridge brass from the British Columbia ores by an}' distillation 
process, whether in the Belgian retort or in the electric furnace. 
It was therefore necessary to turn to hydro-metallurgy, and after 
a large amount of experimental work a process has been developed 
at the works of the Consolidated Mining and Smelting Company 
at Trail, B.C., and at some other smelters, which is a modification 
of the well-known Letrange process, the ore being roasted, 
leached with sulphuric acid, and the resulting zinc sulphate 
solution electrolysed with insoluble anodes. During 1916 a 
large plant was built at Trail, costing perhaps 1,000,000 dollars, 
and capable of producing 30 or 40 tons of electrolytic zinc per 
day, which should meet in large measure the present requirements 
for cartridge brass in Canada. 

Similar work is going on at Welland in Ontario, at a large 
plant owned by the Weedon Mining Company. Prof. Stansfield, 
of McGill University, considers that " this development was 
undoubtedly the best under the existing circumstances, but it 
must not be supposed that it disposes of the possibility of smelting 
these ores in the electric furnace." The works at Welland will 
be supplied with ore from the mines owned by the company 
at Welland and at Nottingham, Quebec. 

According to a recently issued report of the Canadian Depart- 
ment of Mines, Ottawa, the shipments of zinc ores to America 
in 1915 amounted to 14,895 tons, valued at 554,938 dollars, 
and containing 12,231,439 lb. of zinc. 

1 A. Stansfield, Journal of the Institute of Metals, 1916, No. i, vol. xv, 
p. 292. 

32 



THE RISE AND PROGRESS OF THE PRODUCTION 

Assuming a probable recovery of 80 per cent, of the metal, 
the production of zinc in 1915 from Canadian ores may be put 
at 9,785,151 Ib. (approximately 5,000 short tons), valued at 
1,294,575 dollars. Adding to the result of a similar estimate for 
1916 the actual output of zinc at Trail, it would appear that the 
production of zinc from Canadian ores in that year was 23,515,030 
Ib. (approximately 12,000 short tons), valued at 3,010,864 dollars. 
According to the Report for 1916 of the British Columbian 
Minister of Mines, the output of zinc from the smelter at Trail in 
that year was approximately 15,000,000 Ib. (7,500 short tons). 
At the beginning of 1917 the output of the smelter was stated 
to be from 25 to 30 tons per day. 

The Development of the European Zinc Industry 

The position taken by Europe as the largest contributor to 
the world's supply of zinc has been maintained until the present 
time. In 1913 Europe's share of the world's output of zinc was 
673,900 metric tons, or 67-5 per cent, of the world's total output 
for that year. 

The bulk of the metal was produced in Germany and Belgium. 
Thus, in 1913, Germany's output was nearly 42 per cent, of 
Europe's production and about 28-4 per cent, of the world's 
total for that year, whilst Belgium contributed about 40 per 
cent, of the European production. 

The zinc production of the remaining European countries is 
much smaller than that of Germany and Belgium. 

The British output hardly exceeds 10 to 12 per cent, of the 
European production, whilst British consumers of zinc absorb 
about 40 per cent, of the European output. 

Next in importance as producers in Europe are France, 
Holland, Austria-Hungary, Norway and Sweden. 

Compared with the old-established British, German and 
Belgian industries, zinc production in the other European 
countries must be regarded as of comparatively modern origin. 

As the result of the ever-increasing demand for zinc, the 
European zinc industry made rapid progress, notably in Ger- 
many and Belgium, during the latter part of the nineteenth 
century. 

Germany. Taking advantage of her extensive natural resources 
in zinc ore and coal, Germany early took the lead as the largest 

33 D 



THE ZINC INDUSTRY 



producer not only in Europe, but in the world, a lead which she 
maintained for many years ; but in recent years the first place 
in the world's zinc producers has been taken by America. 

The growth of the zinc industry in the German Empire is 
shown by the following figures : In 1862 the output was about 
55,000 metric tons ; in 1872 it amounted to 58,400 tons ; ten years 
later the output had nearly doubled, the total for 1882 being 
about 106,000 tons, while in 1892 it had reached a total of 
approximately 140,000 tons, thus showing an increase of about 
139 per cent, in twenty years, equivalent to an advance of about 
8 per cent, per annum since 1885. 

A further ten years saw a considerable augmentation of output, 
the total for 1902 being about 190,000 tons, which had increased 
to approximately 271,000 tons in 1912. 

The production for 1913 was 283,113 tons, showing an enor- 
mous increase on the output of ten years previously. 

The chief zinc producing centre of Germany is Silesia, the 
output from this district being about two-thirds of the total 
production of the German Empire, the remainder coming chiefly 
from the Rhine district and Westphalia. 

The actual production of zinc, in metric tons, from these two 
districts in recent years is shown in the following table l : 

PRODUCTION OF GERMAN ZINC IN METRIC TONS (2,204-6 LB.) 



District. 


1909. 


1910. 


1911. 


1912. 


1913- 


Silesia 
Rhine District and 
Westphalia 


139,690 
75,173 


140,249 
78,765 


156,174 
81,458 


169,088 
86,619 


170,119 
92,852 



The Silesian zinc industry is confined to the extreme south- 
eastern part of Prussia, in a somewhat narrow strip of territory 
between Russia and the Austrian frontier. 

Established, as already stated, in the latter part of the 
eighteenth century, it was prior to the war an industry of 
considerable magnitude, taking a very prominent part in supply- 
ing the European markets with zinc. 

Formerly the metal was produced entirely from domestic 

1 Compiled by Henry R. Merton & Co., London. 

34 



THE RISE AND PROGRESS OF THE PRODUCTION 

ores, but in more recent years considerable amounts of ore have 
been imported. 

For some years Germany has adopted the policy of conserving 
national resources for the future, and of buying ore in foreign 
markets when this could be done on terms which would permit 
of a good profit on the smelting. 

It has been stated recently 1 that several of the mines in 
Silesia, particularly those of Hohenlohe and Giesche, have 
milling and concentrating plants which are only being worked 
to something between 30 and 40 per cent, of their possible 
capacity. The Von Giesches Erben is reported to possess ore 
reserves which at the rate of mining in 1914 are estimated to 
last for more than 100 years. 

From the reports which have reached this country since the 
war commenced, it would appear that Germany has suffered no 
shortage of zinc, her domestic ores and established smelting in- 
dustries having supplied all demands and enabled the metal 
to be sold at very little above the pre-war average price. 

The zinc smelting industry of Upper Silesia is in the hands 
of several large firms, the metallurgists of which stand at the 
head of their profession and have brought the industry to a 
high state of perfection. 

The works are divided into two main classes (i) the " Gruben- 
huetten " or " Erzhuetten " companies, which smelt ore produced 
by their own mines, and (2) the " Lohnhuetten " companies, 
which buy ore in the market. 

These latter have yielded good profits in recent years, being 
supported by the leading wealthy metal and mineral trading 
companies, who have large interests in the zinc industry. 
Nothing has been spared to develop the dominant position 
taken by the German zinc industry, and during the past ten years 
most of the works have been reconstructed and supplied with 
modern gas-fired furnaces, and many improvements have been 
introduced into botn the roasting and smelting processes. 

Although the number of smelting concerns engaged in the 
zinc industry in 1870 was 35, the number had been reduced to 
29 in 1890, but the capacity of these works was increased so that 
the output of metal was augmented. Since 1890, a few new 
works have been added to enable the output to be brought to 
the large figure which represents the modern production. 

1 H. M. Ridge, Journal of the Institute of Metals, 1916, vol. xvi, p. 187. 

35 D2 



THE ZINC INDUSTRY 



The German output of zinc, in metric tons, for the ten years 
ending 1913 is as follows : 



GERMAN OUTPUT OF ZINC. 



Year. 


Metric tons. 


Year. 


Metric tons. 


1904 


191,060 


1909 


220,080 


1905 


197,184 


1910 


227,747 


1906 


205,023 


1911 


250,393 


1907 


208,707 


1912 


271,064 


1908 


216,876 


1913 


283,113 



Since the production has for many years been in excess of 
the consumption of zinc in Germany, the surplus metal has 
been exported, chiefly to the United Kingdom. 

The smelting of sulphide zinc ores in Germany led to the 
establishment of very complete arrangements for utilising the 
sulphurous acid generated in the roasting of the ore, the first 
practical results in this direction being obtained by Hasenclever 
as early as 1855. 

Most of the works are now equipped with special roasting 
furnaces, which permit of the roast gases being used for the 
manufacture of sulphuric acid, and there is little doubt that the 
utilisation of the sulphur in zinc ores for this purpose has con- 
tributed very materially to the success of the Continental zinc 
smelting industry. 

Sulphuric acid is a by-product of considerable commercial 
value, and consequently a source of additional profit to zinc 
production. The question of roasting blende for sulphuric acid 
production is more fully discussed when dealing with the by- 
products from zinc smelting on p. in. 

In addition to the production of zinc and sulphuric acid, the 
Silesian industry includes a number of zinc-rolling mills which 
contribute a considerable quantity of sheet metal to the world's 
requirements. Prior to the war, eight mills were producing about 
50,000 tons of sheet metal per annum. 

Austria- Hungary. The zinc production from these countries is 
comparatively small, although the output has gradually increased 
in recent years. The output rose from 19,600 metric tons in 
1912 to 21,700 tons in 1913. The larger proportion of the metal 

36 



THE RISE AND PROGRESS OF THE PRODUCTION 



is produced at the works in Galicia, whilst rather less than 50 
per cent, is obtained at the works at Steiermark. 

Belgium. As already stated, Belgium early became the second 
largest zinc producer in Europe, producing about two-thirds 
of the European output in 1890, but so rapid has been the 
increase in later years that prior to the war the output almost 
equalled that of Germany. 

The Belgian zinc production in recent years is shown in metric 
tons in the following table : 

BELGIAN OUTPUT OF ZINC. 



Year. 


Metric tons. 


Year. 


Metric tons. 


1904 


139,982 


1909 


167,100 


1905 


145.592 


1910 


172.578 


1906 


152,461 


1911 


195,092 


1907 


154.492 


1912 


200,198 


1908 


165,019 


1913 


I97.7 3 



Zinc rolling also forms an important branch of the industry, 
the production of sheet metal in 1913 being 51,500 metric tons, 
as against 49,100 tons in 1912. 

A small proportion of the output of crude zinc is utilised 
for the production of zinc oxide (zinc white) by burning the 
metal in air as described later (p. 192). 

The Belgian industry was founded to utilise the important 
deposits of ore in the country, but since 1856 the yield of native 
zinc ore has been comparatively small, so that it has been neces- 
sary to import increasing quantities of foreign ores to maintain 
the large production of metal in modern times. Within recent years 
considerable quantities of zinc concentrates from Broken Hill, 
Australia, have been smelted in the country. The Belgian zinc 
smelting works are situated in the neighbourhood of Liege and 
are owned by the well-known Vieille Montagne Spelter Company , 
but are largely under German control. 

The company has works, or mines, not only in Belgium, but 
also in France, Germany, Sweden, England, Algeria and Italy. 

Much that has been said regarding the German zinc smelting 
works applies equally to those in Belgium. 

The works are well equipped with modern plant, including 
gas-fired furnaces and roasting furnaces which permit of the 

37 



THE ZINC INDUSTRY 



utilisation of the sulphur gases for the production of sulphuric 
acid. Prior to the war there was a considerable surplus in the 
production of this commodity in Belgium in consequence of the 
enormous quantities of zinc blende roasted in that country. 

The future of the Belgian zinc industry is very uncertain, 
as there is some doubt as to the fate of the works when the 
enemy are obliged to evacuate the country. 

It is reported that the Germans are keeping together the 
skilled labour of the Belgian zinc works, and that they are 
assisting in the running of some of the works, but since the 
available supplies of ore are limited it is doubtful whether the 
yield can be very large. 

The German control of the Belgian zinc industry is not likely 
to continue after the war. 

France. The production of zinc in France is very little in 
excess of that required for home consumption. Although a 
moderate producer of zinc ore, much of the ore smelted is of 
foreign origin. The smelting works are situated at Pontgiband, 
and in recent years the metal produced has been of high grade. 
In 1912 France contributed 64,300 metric tons of zinc to Europe's 
supply, and 61,100 tons in 1913, thus showing a small decrease. 
In each of these years about 5,000 tons were exported to the 
United Kingdom. 

The consumption of zinc in France amounted to 82,000 tons 
in 1912, and 81,000 tons in 1913, thus showing a falling off. 

Holland. Zinc production in Holland has shown a steady 
increase in recent years, the production for the ten years ending 
1913 being as follows : 

PRODUCTION OF ZINC IN HOLLAND. 



Year. 


Metric tons. 


Year. 


Metric tons. 


1904 


I3. 99 


1909 


i9,54 8 


1905 


13.767 


1910 


20,975 


1906 


14.650 


1911 


22,733 


1907 


14,990 


1912 


23,932 


1908 I7 2 57 


1913 


24.323 



Spain. Only a small proportion of the zinc ore raised in 
Spain is smelted in the country, the bulk being treated in France 
and other centres of production. 

38 



THE RISE AND PROGRESS OF THE PRODUCTION 



The leading Spanish zinc works are those of Penarroyain 
Cordoba and Arnao in Oviedo. The output amounted to 8,000 
metric tons in 1912 and 10,000 tons in 1913. In April, 1915, 
the export of zinc in cakes was embargoed, and on January I, 
1916, an export tax equal to 375. 6d. was placed on zinc in pigs, 
blocks and waste articles, and the import duty was removed. 

Norway. Within recent years Norway has become a small 
producer of zinc, the output in 1911 being 6,680 metric tons, 
that of 1912, 8,128 tons, and 9,287 tons in 1913. 

Sweden. A special feature of zinc production in Sweden is 
the application of electric smelting processes to which reference 
is made later (p. 124). The development of these processes 
has been rendered possible by the plentiful supply of water 
power in the country, which has been utilised for generating the 
necessary electrical power. 

Sweden produced, in 1913, 6,900 tons of ordinary zinc and 
2,000 tons of fine zinc. 

Russia. Up to the present the production of zinc in Russia has 
been small, the zinc smelting industry being of comparatively 
recent introduction. There are good deposits of zinc ore in the 
country, more especially in Poland, the chief sources of the ore 
smelted being the mines at Ulisses and Boleslaw, near Olkusch. 
Prior to the war the annual output of zinc in Russia was 
between 8,000 and 9,000 metric tons, whilst the average con- 
sumption was more than three times this amount. 

The production, in metric tons, for the ten years ending 
1913 was as follows * : 

PRODUCTION OF ZINC IN RUSSIA. 



Year. Metric tons. 


Year. 


Metric tons. 


1904 


10,606 


1909 


7,945 


1905 


7,642 


1910 


8,631 


1906 


9,610 


1911 


9,936 


1907 


9,738 


1912 


8,763 


1908 


8,839 


1913 


7,610 



Owing to heavy requirements in roofing sheets, Russia con- 
sumed 33,300 tons of zinc in 1913, as compared with approxi- 
mately 28,000 tons in 1912. On the other hand Russia's 
1 Compiled by Henry R. Merton & Co. 

39 



THE ZINC INDUSTRY 

production declined in 1913 to the extent of 1,200 tons, as 
shown, which was made up for by the increase of 6,600 tons in 
her imports of zinc in cakes and sheet metal. To meet home 
requirements Russia has hitherto been obliged to import over 
20,000 tons of zinc annually, most of which was obtained from 
Germany. 

It would appear that attempts are now being made to develop 
the Russian zinc smelting, as, according to the United States of 
America Consular Report for 1916, a large zinc smelting works 
is being erected at Hikoshuna, in the Shimonoseki Straits, by 
the Su uki Shoten of Kobe. It is proposed to treat at these 
works ore derived chiefly from Asiatic Russia and Australia. 

The Development of the American Zinc Industry 

Although started more than half a century later than that 
of Europe, the American zinc industry has made such rapid 
progress, especially during the past few decades, that the United 
States have since 1906 held the premier position as a producer 
of zinc. 

In 1913 the United States contributed 32*1 per cent, of the 
world's supply of zinc, whereas Germany, formerly the largest 
producer, contributed 28*4 per cent. 

This rapid growth of zinc production in the United States 
has been rendered possible by the possession of very large 
quantities of raw material in the form of zinc ore. and of coal, 
and more particularly of large supplies of natural gas, which, 
in some localities, is used as the source of heat in smelting the 
ore, and has proved to be of considerable importance in the 
economic production of the metal. 

The remarkable progress of the American zinc industry 
affords a striking illustration of the speed with which industrial 
enterprises develop under the combined influence of great 
natural resources and of modern smelting plant used with in- 
telligence and skill. 

This progress can best be seen by comparing the data of 
production thirty years ago with those of the present time. 

In 1885 the total production of zinc in the United States 
amounted to only 40,000 metric tons, whilst the production 
in 1905, twenty years later, had increased five-fold, being more 
than 200,000 tons. By 1913 the output had increased more 

40 



THE RISE AND PROGRESS OF THE PRODUCTION 



than 50 per cent., and since the outbreak of war the production 
of zinc in America has reached nearly twice the pre-war figure, 
as shown by the following returns : 

ZINC PRODUCTION IN THE UNITED STATES IN METRIC TONS. 



Year. 


Metric tons. 


Year. 


Metric tons. 


1907 
1908 
1909 
1910 
1911 


226,838 
189,941 
240,446 
250,627 
267.472 


1912 
1913 
1914 
1915 
1916 


314.512 
320,283 
328,731 
446,788 
609,906 



With the growth of the industry, zinc smelting works were 
established in the States of Illinois, Kansas and Missouri, which 
in pre-war days produced about two-thirds of the total output 
of American zinc, the remainder being produced in a few Eastern 
and Southern States. 

In consequence of a falling-off in the yield of the natural 
gas springs of Kansas and Oklahoma in recent years, it became 
necessary to transfer the works to Illinois and other places where 
coal or oil could be obtained in sufficient quantity and at a cheap 
rate. At the end of 1914 there were 33 zinc smelting plants in 
operation in the United States, their disposition being as follows : 
Illinois 10, Kansas 9, Oklahoma 6, and the remaining 8 in the 
States of West Virginia, Missouri, Pennsylvania and Colorado. 

The works are independent of each other, so that the com- 
petition for ore is keen. 

The American zinc industry has always been independent of 
the European industry, and it is generally agreed that in normal 
times America is not favourably situated to compete with the 
European markets, and the shipment of zinc to the United 
Kingdom only becomes possible when the zinc market is abnor- 
mally high, as it has been since the outbreak of war. American 
smelters have the advantage of being entirely independent of 
foreign ore, as they have enormous native deposits on which to 
draw. 

The supplies of rich ores from the older districts, such as the 
famous Joplin district, on which the smelters formerly depended, 
have been considerably augmented in recent years by con- 
centrates from the complex ores from the Western States. The 



THE ZINC INDUSTRY 

greatest impetus was given to the production and utilisation 
of the Western ores by the development of the methods for 
dressing and separating the complex zinc ores by the aid of 
electricity, to which reference is made on p. 70. 

Previous to the war, the production of zinc in the United States 
was about equal to the consumption in that country ; thus in 
1913 they produced 320,283 metric tons of zinc, and consumed 
313,300 tons. The balance available for export was therefore 
only 6,983 tons. 

The cutting off of the European supplies of zinc at the outbreak 
of war resulted in the Allies with one accord turning to the 
United States, the largest producer of zinc in the world, for 
supplies, and the response made by the American smelters 
considerably eased the serious situation in which this country 
and her Allies found themselves owing to shortage of zinc for 
munition purposes. 

The limited supply of zinc available for export, however, led 
to a rapid rise in the price of the metal, and the American zinc 
smelters have been very highly paid for their services. 

The deficiency in the world's supply of zinc has been met by 
the rapid erection of additional works in the United States, 
and an increase of production has resulted which as the figures 
given below show, is unprecedented in the history of the zinc 
industry. 

As Professor Carpenter remarks, " What these figures mean 
can be adequately appreciated only by those who know what 
is involved in the expansion of an industry where mining and 
ore-dressing operations, transport and assemblage of materials, 
erection and operation of furnaces, and, most difficult of all, 
the training of the necessary labour are concerned." 

Taking the individual States in the order of their zinc output, 
Illinois comes first, then Oklahoma, and Kansas third. As 
shown by the following figures, these three States are now 
producing collectively nearly three-fourths of the total output 

of zinc in the United States. 

1915. 1916. 

State. Metric tons. Metric tons. 

Illinois ,1. .. .. 145,105 163,612 

Oklahoma ..' .. .. 99,073 148,859 

Kansas . . . . . . 92,010 127,475 

Other States .. .. .. 107,892 157,429 



Total ,v - .. .. 444,080 597.375 




THE RISE AND PROGRESS OF THE PRODUCTION 

Considerable additions are still being made to the smelting 
plants, so that the future output of zinc will be greater even 
than that for 1916. The full capacity of the furnaces was not 
utilised in smelting ore at any time during the past three years ; 
a large number of the retorts were occupied in redistilling crude 
zinc for the production of high grade metal for munition purposes, 
much of which was exported to this country. 

In 1916 two new smelteries, with large graphite retorts, were 
erected for this purpose. The high prices of zinc ruling during 
the past few years have greatly stimulated research in the 
treatment of low grade complex zinc ores, and America is now 
producing appreciable quantities of high grade zinc from such 
ores by electrolytic methods which are described on p. 124. 

The enormous increase in zinc production will no doubt make 
America a formidable competitor of this country after the war. 
The zinc smelters have been making very large profits, and these 
have been used wisely in improving the plant, so as to make 
it as efficient as possible, and in accumulating great financial 
reserves. 

In view of the large ore reserves in America, there is no reason 
to suppose that there will be any failure to realise the enormous 
output expected through smelting plant being in excess of the 
capacity of the mines. 

Zinc Production in Asia 

The Asiatic centres of zinc production, although at present 
contributing but little to the world's supply, are by no means 
unimportant, especially in view of recent developments in Japan. 

China. As previously stated, China has for several centuries 
been a producer of zinc by crude distillation in pots by native 
methods, and small quantities of metal made in this manner 
have found their way to the European market for very many 
years. No details are available as to the amount of metal 
produced annually, but the amount of metal exported to Europe 
in recent years is stated to be as follows. In 1911, 710 metric 
tons ; in 1912, 760 tons, and in 1913, 908 tons. The metal, which 
is produced chiefly at Kweichow, probably from carbonate ores, 
is of good quality, containing 99-56 per cent, of zinc with a little 
lead and iron. 

China possesses vast deposits of zinc ores, which in the past 

43 



THE ZINC INDUSTRY 



have been largely worked by foreign concerns, and the ore exported 
for treatment, but the erection of smelting works for the treat- 
ment of the ore in the country has been proposed, and possibly 
in the future a zinc smelting industry on modern lines will be 
established. 

Japan. Zinc smelting in Japan appears to be of recent 
origin, although zinc ores have been mined in the country for 
many years and exported to European smelting centres for 
treatment. The war has, however, given considerable impetus 
to the Japanese zinc smelting industry, and plant is being erected 
capable of supplying sufficient metal to meet home requirements 
and reduce imports of zinc. 

The chief smelting works are situated at Osaka and Ohmuta, 
the former works producing about twice as much zinc as the 
latter. 

The Japanese Bureau of Mines reports the quantity of zinc 
produced in Japan in recent years as follows : 

PRODUCTION OF ZINC IN JAPAN IN METRIC TONS. 



Quality. 


1914. 


1915- 


1916. 


Refined zinc 


5,966 


21,306 


39,3^6 


Unrefined 


zinc 


14,138 


6,121 


2,187 




Total .. .; 


20,104 


27,427 


41,503 



In 1913 the zinc imported into Japan, in the form of ingots 
and sheet metal, amounted to nearly 11,000 tons, whereas in 1914 
it was less than 6,000 tons. 

The future of the zinc industry in Japan is generally con- 
sidered to be exceedingly good, and it is expected that a large 
export trade will be carried on after the war. One company 
is manufacturing zinc for the export trade. Much of the 
Japanese zinc ore contains other metals, such as gold, silver 
and copper, and the refining of these metals is carried on in 
conjunction with the treatment of the ore. Five new companies, 
with a total combined capital of 760,000, have been organised 
and operate six works for the treatment of zinc ore produced 
in the country. 1 

1 Report of H.M. Vice-Consul at Tokio. See Journal of the Society 
of Chemical Industry, 1917, vol. xxxvi, p. 1119. 

44 



THE RISE AND PROGRESS OF THE PRODUCTION 

According to the Board of Trade Journal,' 1 the supply of ore 
for the Japanese zinc smelting works is by no means assured. 
The production of zinc ore in Japan does not exceed 50,000 
tons per annum, whilst the existing Japanese works need about 
three times this quantity if they are to be kept working at their 
full capacity. Further, if all the projects for new works and 
additional plant are realised, the requirements of the industry 
in the near future for zinc ore will exceed 300,000 tons. This 
being so, the important question of ensuring a regular supply 
of ore is now engaging the attention of the zinc smelters and 
the Japanese Government. 

During the past two years zinc ore and zinc concentrates 
have been imported into Japan from Australia (Broken Hill), 
China, Burma, Indo-China and Vladivostok, but no contracts 
for future deliveries of zinc ore appear to have been made. 

One important Japanese firm secured during 1916 about 
11,000 tons of zinc ore from the Schwai-Ko-Schan mine in 
China, and recently negotiations have been begun between 
these two concerns with a view to contracts for the supply of 
large quantities of ore in the future. 

Before the war the cost of zinc production in Japan was 
nearly 25 per cent, higher than the cost of production in Ger- 
many and Belgium, Japan's chief competitors in the zinc 
industry, and to this cost must be added the cost of transport 
from those countries to Japan. The total Japanese demand 
for zinc is estimated at about 29,000 tons yearly, against which 
Japanese smelting works have a present productive capacity 
of about 45,000 tons per annum. In the near future, when all 
the schemes for new undertakings and extensions are completed, 
Japanese zinc smelting works will have a productive capacity of 
about 100,000 tons, or 70,000 tons in excess of the requirements 
of the country. It is stated that schemes are in hand for the 
establishment of a galvanising industry on a considerable scale, 
which will absorb some of this excess metal. 

1 October, 1917. 



45 



CHAPTER III 

ZINC ORES AND THEIR SOURCES OF SUPPLY 

Zinc Ores ; Their Nature, Occurrence and Distribution 

ZINC-BEARING minerals are geographically very widely distri- 
buted so widely, indeed, that they are found in almost all metal 
mining districts. 

The extent of their distribution is well shown in the accom- 
panying map of the world, in which the more important zinc ore 
producing districts have been marked. 

The map was prepared by J. C. Moulden, for his paper before 
the Royal Society of Arts, and is reproduced here by his kind 
permission. 

The ores of zinc are found more particularly associated with 
ores of lead, copper and silver, often forming extensive deposits 
of considerable complexity which present problems to the 
metallurgist, for the practical solution of which a large number 
of processes have been devised. 

Whilst zinc occurs as a constituent of a very large number 
of the ores of other metals, minerals containing the metal in 
sufficiently large quantity, and occurring in sufficient abund- 
ance to constitute ores of zinc, are comparatively very few. 

The metallurgy of zinc necessitates the employment of ores 
relatively high in zinc content ; it is, therefore, frequently 
necessary to submit the ores to some preliminary process of 
concentration to separate the zinc mineral from the other 
minerals and gangue, or worthless material, before a product 
sufficiently high in zinc content can be obtained for use by the 
zinc smelter. 

The percentage of zinc in the ore mined is frequently very 
low, and often averages not more than 3 per cent., but this is 
increased by concentration to 40 per cent, of zinc or more. 



ZINC ORES AND THEIR SOURCES OF SUPPLY 




47 



THE ZINC INDUSTRY 



Of all the minerals containing zinc, three only are of much 
importance to the metallurgist ; these are the sulphide (blende) , 
the carbonate and the oxidised compounds usually designated 
under the generic term of calamine, and the silicates of zinc. 

Two systems of mineralogical classification are in use for 
zinc minerals. In this country the carbonate is generally known 
as calamine, and the silicate as smithsonite or hemimorphite. 
In America the carbonate is known as smithsonite and the 
silicate as calamine, whilst the sulphide is commonly called 
sphalerite. This double classification frequently leads to con- 
fusion, especially amongst students. 

The American nomenclature of zinc minerals is, however, 
gradually being adopted by British metallurgists. 

The principal zinc-bearing minerals and their respective content 
of zinc when pure are as follows : 



Mineral. 


Composition. 


Zinc. 


Blende or sphalerite . 
Calamine or smithsonite . 


Zinc sulphide 
Zinc carbonate . , 


Per cent. 
67-15 

C2-OO 


Hydrozincite .... 
Willemite 


Hydrous basic zinc carbonate . 
Zinc silicate 


57-10 
58-10 


Hemimorphite 
Zincite 


Hydrous zinc silicate .... 
Zinc oxide 


53'7 
80-25 


Franklinite . . ... 


Oxide of iron, zinc and manganese . 


16 to 21 



Zincite and franklinite, the composition of which is variable, 
are important as ores of zinc in the United States of America 
only and are utilised for the production of zinc oxide. 

Although formerly calamine was the most important ore of 
zinc, blende is, at the present time, the chief source of the metal. 

Zinc blende, sphalerite, termed by miners " Black Jack," 
when pure, contains 67-15 per cent of zinc. It is, however, 
usually contaminated with iron pyrites and other metallic 
sulphides, and with gangue minerals, so that as received at the 
smelting works it usually contains only from 35 to 55 per cent, 
of zinc. 

Regarding its association with galena (lead sulphide), it maybe 
said that most lead mines are also blende producers, and, similarly, 
nearly every zinc deposit carries lead. The two minerals are 
frequently mined simultaneously, the blende as a subsidiary 
source of income to the lead mine. 

48 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

Dressing operations suffice in many cases to yield the greater 
part of the lead as a galena concentrate, suitable for the lead 
smelter, and the zinc blende as a concentrate carrying from 45 
to 50 per cent, of zinc. 

The lead mines of Cardigan and Cumberland in this country 
and of Joplin in America, and Broken Hill in New South Wales 
are familiar examples. 

Lead and silver are sometimes present, in the more complex 
ores, in sufficient quantity to permit of profitable extraction from 
the residues, after extraction of the zinc. 

Germanium has been found to occur in zinc blende from 
Missouri and Wisconsin. 1 The oxide of zinc prepared from zinc 
residues from the zinc distillation furnaces in which these ores 
had been treated was found to contain as much as 0-25 per cent, 
of GeO 2 . 

Zinc blende is very widely distributed and occurs in large 
quantity in Europe, America, and Australia. 

Calamine, smithsonite of the Americans, the carbonate of zinc, 
is decreasing in importance as an ore of zinc since the deposits in 
many localities are more or less exhausted. 

The present supplies are largely derived from Upper Silesia, 
Austria, Italy, Greece and Algeria. 

When pure, calamine contains 52 per cent, of zinc, but it is 
usually accompanied by oxide of iron, carbonate of lime, etc., 
which depreciate its commercial value, since these substances 
give trouble in smelting if present in appreciable quantities. 
Before smelting, calamine is usually calcined to expel the bulk 
of the carbon dioxide, thereby decreasing the weight of the ore 
and relatively increasing the zinc content. 

Hydrozincite is a basic hydrated carbonate of zinc, the only 
important deposits of which occur in Spain. Metallurgically 
speaking, it differs little from smithsonite. 

Willemite is anhydrous silicate of zinc, the best known deposits 
of which occur in Franklin, New Jersey, U.S.A., where it is 
associated with zincite, franklinite, and calcite, the willemite 
forming about 25 per cent, of the deposit. It contains, when 
pure, 58-10 per cent, of zinc, but it is usually accompanied by 
manganese and other constituents that lower its value materially. 

Hemimorphite, electric calamine (calamine of the Americans), 

1 " The Occurrence of Germanium in Missouri and Wisconsin Blendes," 
G. H. Buchanan, American Chemical Society, 1917. 

49 E 



THE ZINC INDUSTRY 

a basic hydrated silicate of zinc, occurs associated with the 
ordinary calamine or zinc carbonate, with lead ores and with 
blende. It is a valuable ore of zinc, although not of such economic 
importance as blende or calamine. 

It was formerly mined extensively at Aix-la-Chapelle and 
Moresnet, in Belgium, but these deposits are now practically 
exhausted. Extensive deposits of exceptional purity occur in 
Virginia and Missouri, in the United States of America, and 
provide the source of one of the purest brands of zinc in the 
world obtained by ordinary distillation methods direct. 

Zincite, the native oxide of zinc, known as red oxide of zinc, 
in a pure condition contains 80*2 per cent, of zinc. It usually 
contains oxides of manganese, to which the red colour is con- 
sidered to be due, since chemically pure oxide of zinc is white. 

Zincite occurs to a limited extent in the extensive ore deposit 
at Franklin, New Jersey, forming about 5 per cent, of the 
deposit. 

Franklinite is a mixture of oxides of iron, zinc and man- 
ganese, of variable composition, but containing as a rule from 
12 to 18 per cent, of zinc. 

It constitutes about 50 per cent, of the deposit at Franklin, 
New Jersey. The zinc minerals in this deposit occur as 
rounded grains in a crystalline limestone, and are probably the 
result of metamorphism. The willemite associated with the 
franklinite is separated by a magnetic process and is then treated 
for the extraction of the zinc. 

The franklinite is treated for the production of zinc white 
(commercial zinc oxide), leaving a highly manganiferous residue, 
which is smelted in blast furnaces for the production of spiegel- 
eisen, a rich manganese-iron alloy used in the manufacture of 
steel. 

Goslarite, white vitriol, is hydrated zinc sulphate, found chiefly 
at Goslar in the Harz, and also sparingly in some of the 
Cornish mines and at Holywell, in Flintshire. The mineral 
is not, however, sufficiently plentiful to be of much, if of any, 
commercial importance. 

Zinc minerals in small quantity also frequently accompany 
ores of iron and manganese, especially the latter, from which 
the zinc, varying from 6 to 10 per cent., is recovered as oxide, 
in chambers at the top of the blast furnace, when the ores are 
smelted, thus forming a valuable by-product. 

50 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

The zinciferous flue dust frequently contains as much as 
75 per cent, of zinc, and is sold to paintmakers or to zinc 
smelters. The production of zinc from such sources is by 
no means inconsiderable. 

Zinc Ores in the British Empire 

Australia is the premier producer of zinc ore within the British 
Empire, and in recent years immense quantities have been 
obtained from this source. 

Ores of zinc are also worked in Canada and in the British Isles, 
and deposits of complex ore in Burma and in Rhodesia are already 
being actively developed and give promise of becoming a great 
national asset and of influencing the world's supply of zinc in a 
marked degree in the near future. Zinc ore is found also in 
Queensland, Tasmania, New Zealand, Newfoundland, Egypt, 
Nigeria, South Africa and, associated with copper ore and 
galena, at Tsumeb, in the former German colony of South- West 
Africa. 

United Kingdom. The occurrence of zinc ores in the United 
Kingdom cannot be considered as extensive, although ores of 
zinc, generally associated with lead ores, are found in the 
Palaeozoic rocks of Wales, the Isle of Man, the North of England 
and the South of Scotland, some of which have been worked 
since Roman times. 

The best known deposits are those in Flintshire, Cardiganshire, 
Durham, Cumberland, Derbyshire, the Isle of Man, Dumfries- 
shire and Lanarkshire. The mines are worked for both zinc 
and lead, and the ores are subjected to crushing, concentration 
and separation to obtain a concentrate suitable for smelting. 

Formerly calamine was the chief ore mined in the United 
Kingdom, but at the present time the zinc ore is almost entirely 
blende, the largest producers being the Nenthead and Nentsbury 
Mines at Alston, in Cumberland, and the Carshield Mine in 
Northumberland. Prior to the war the output of dressed zinc 
ore for the United Kingdom amounted to between 17,000 and 
18,000 long tons per annum. 

The output in 1913 was 17,294 tons, of which amount England 
produced 12,730 tons, Wales 2,601 tons, Scotland (Dumfries) 
1,010 tons, and the Isle of Man (Great Laxey Mine) 953 tons. 

The Alston mines in Cumberland have for some years been 

51 E 2 



THE ZINC INDUSTRY 

owned and worked by the Vieille Montagne Spelter Company of 
Belgium, who have installed a very complete up-to-date ore- 
dressing plant. The ore produced at these mines, and at one 
or two other North Country mines, is shipped chiefly to Belgium 
for treatment. The total weight of British zinc ore exported 
from the United Kingdom in 1913 was 13,378 tons, of which 
amount 11,260 tons were consigned to Belgium and approxi- 
mately 2,000 tons to France. 

In 1912 the total export of zinc ore was 11,139 tons. The 
ownership and working of the British mines by foreign companies, 
and the exportation of the ore to foreign smelting centres, are not 
very creditable to the British mining industry, especially when 
it is remembered that practically all the zinc ore smelted in this 
country is imported from abroad. Thus in 1913 the total 
imports of zinc ores by British smelters amounted approximately 
to 65,000 long tons, which were derived mainly from Australia, 
Italy, Algeria, Germany, Spain and France. 

Attention is now being directed to the possibility of developing 
the sources of zinc ore in the British Isles, which, with the applica- 
tion of modern methods of dressing and bold development, aided 
by adequate financial support, may yet be profitably worked. 
The Development of Mineral Resources Department, recently 
appointed by the Government, is making a move in this direction. 

Canada. Deposits of zinc ore occur in many parts of Canada 
and British Columbia, but at present the output is not large. 
Recent proposals for fostering, by the Government, the zinc 
industry in the Dominion of Canada will doubtless facilitate 
the exploitation of known deposits and the search for new 
deposits. 

Practically the whole output in the past has come from British 
Columbia, mainly from the Kootenay district. 

The deposits are numerous, but the ores, which consist of 
mixtures of argentiferous galena and blende, with or without 
iron and copper pyrites, are complex and difficult to utilise. 
Up to the present the zinc concentrates resulting from the 
treatment of the ores have been shipped to the United States 
for smelting. 

There are prospects, however, that in the near future the 
ores will be treated in Canada, since the investigations carried 
out by the Dominion Government on their treatment by electro- 
lytic and other methods have met with some success. 

52 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

During 1913 Canada produced approximately 11,000 tons of 
zinc ore, almost all of which was raised in British Columbia. 

In 1914 the output was approximately 13,000 tons, and in 
view of the increased mining activity the present output is 
probably greater. 

Australia. The well-known deposits at Broken Hill, New 
South Wales, are the most important sources of zinc ore in the 
British Empire. The ore, which is highly argentiferous, consists 
of a complex association of galena and blende, with a gangue 
mainly composed of rhodonite, quartz and garnet. 

The ore is crushed and submitted to concentration and separa- 
tion processes which give two main products, viz., a lead ore 
concentrate containing 65 per cent, of lead, 6 per cent, of zinc, 
with varying quantities of silver, and a zinc concentrate con- 
taining about 46 per cent, of zinc and 8 per cent, of lead with 
some 15 ounces of silver per ton. Except for the ore smelted at 
the plant of the Broken Hill Proprietary Company at Port Pirie, 
South Australia, and about 20,000 tons annually exported prior 
to the war to England for treatment, the whole of the zinc 
concentrates in the past have been sold under long-term contracts 
to smelters on the Continent. Formerly the ore was worked 
only for lead and silver, the zinc being neglected, and, as pre- 
viously stated, it was estimated that in 1903 zinc residues and 
tailings, containing i8'6 per cent, of zinc, and amounting approxi- 
mately to 6,000,000 tons, had accumulated at Broken Hill, 
besides large quantities which had been used for stope fillings 
in the mines. 

After many experiments, these accumulated tailings have, 
through the application of flotation processes of concentration, 
become a very substantial source of supply for the world's zinc. 
The first effect of the introduction of flotation processes on the 
world's supply of spelter was felt in 1904, and in 1906 the 
great rise in Broken Hill zinc production began. Between the 
years 1906 and 1911 the production rose from 100,000 tons of 
zinc concentrate to roughly 500,000 tons, at about which figure 
the annual output has since remained. Owing mainly to the 
high price and scarcity of skilled labour, it has not hitherto paid 
to smelt these concentrates to any extent locally, or even in the 
country ; they have been bought by European smelters and 
mainly shipped to Belgium, Germany and France for 
treatment. 

53 



THE ZINC INDUSTRY 

The ascertained life of the chief Broken Hill producing mines 
is such as to assure the future production, although on a gradually 
reduced scale, for some years to come probably ten as a 
minimum even if no further ore bodies be developed. 1 

Since the outbreak of war the shipments of concentrates has 
been largely suspended, and the mine owners have had to seek 
new markets for that very considerable portion of ore that was 
formerly shipped to the Continent, the contracts with the German 
firms having been cancelled. Further reference to this matter 
will be found on p. 200. As stated above, in normal times the 
output of zinc concentrates is approximately 500,000 tons 
annually, sufficient to satisfy approximately one-fifth of the zinc 
requirements of the world in pre-war times. In 1914 the 
output amounted to only 359,310 tons, being 147,350 tons less 
than that of the previous year and representing a fall in 
value of more than 500,000. 

Tasmania. Lead-zinc sulphide ores occur in the Mount Read 
district on the West Coast of Tasmania, and although somewhat 
complex in nature the deposits are being developed with a view 
to the extraction of the zinc by electrolytic methods, experiments 
on a commercial scale having proved the feasibility of such 
treatment. Mount Read is about 17 miles by rail from Zeehan 
and about 71 miles from the port of Burnie. The zinc-lead 
sulphide deposits occur over a length of 7 miles and contain from 
24 to 43 per cent, of zinc. 

Tasmania is expected to play an important part in future 
development in Australian zinc production. 

India. Large and very promising deposits of silver-lead-zinc 
ores of the sulphide class occur in Upper Burma. They are 
situated at Bawdwin in the Northern Shan States, some sixty 
miles from the Chinese province of Yunnan. The deposits are 
remarkable for their high silver ratio, and were long ago worked 
for that metal by the Chinese. 

The ore is complex and consists of galena, blende and pyrites 
with occasional chalcopyrite. The crude ore, as mined, is remark- 
ably free from gangue and frequently contains, as much zinc as 
the Broken Hill concentrates, with substantially greater 
quantities of lead and silver. 

The deposits are being actively developed, and although up 
to the present they have had little influence on the world's supply 
1 J. C. Moulden, op. cit., p. 502. 

54 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

of zinc, there is a prospect of this district becoming an important 
producer in the near future. 

South Africa. A lead-zinc deposit the Rhodesian Broken 
Hill which is reported to be of great prospective importance 
has been discovered in North- Western Rhodesia. The rich 
oxidised surface ore consists of a mixture of carbonate of lead 
with carbonate and silicate of zinc. 

The separation of the oxidised ore minerals from one another 
presents difficulties which have not yet been overcome. But 
when a commercial process has been worked out and transport 
facilities have been improved, this, like the Bawdwin deposit, 
promises to become a valuable addition to the Imperial lead-zinc 
resources. The deposit is being developed, and a smeltery for 
lead and zinc is reported to be in course of erection. 

The production and value of zinc ore in the British Empire 
and in foreign countries for the three years 1911 to 1913 are 
shown in the table on p. 56. 

European Sources of Zinc Ores 1 

The working of zinc ore in Europe in modern times dates 
from the introduction of the use of brass, and there are records 
extant which show that in 1439 the calamine mines of Vieille 
Montagne had been worked for a considerable time by the men 
of Aix-la-Chapelle. 

In the past Europe has contributed very considerable amounts 
to the world's supply of zinc ores, and although the supply is 
less than formerly the output is still very large. The bulk of the 
ore is mined in Germany, and for many years past this country 
has ranked second only to the United States as a producer not 
only of zinc ore, but also of spelter. The zinc ore-producing 
countries of Europe are here referred to in alphabetical order. 

Austria-Hungary. The more important zinc ore deposits 
are situated in Southern Carinthia, Styria and Tyrol. 

The Carinthia deposits are distributed over a wide area, and 
consist mainly of blende and galena, although large masses of 
zinc carbonates occur in certain localities, notably at Schneeberg. 

In Tyrol, zinc blende has been mined since 1866, prior to which 
the mines were worked for lead only. 

In 1913 the total output of zinc ore in Austria amounted to 

1 The author is indebted to the Bulletin of the Imperial Institute, 1915, 
vol. xiii. for useful information contained in this section. 

55 



INDUSTRY 













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56 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

31,000 long tons ; of which about one-half was devoted to 
Government use. The annual output has remained about the 
same for the past five years. 

Hungary cannot be classed as a zinc ore producer, as mining 
for the metal is almost unknown. 

Belgium. In the early days of the zinc industry Belgium was 
an important producer of zinc ore, but since 1856 the output has 
been comparatively insignificant, owing to the gradual exhaustion 
of the rich deposits. 

The most important zinc mines are at Bleyberg, and near 
Verviers and Liege, whilst the famous deposits worked by the 
Societe de la Vieille Montagne are, as previously stated, situated 
in Moresnet. 

The Bleyberg ore consisted chiefly of zinc blende and galena 
in nearly equal amounts, whereas the deposits of Vieille Montagne 
consist chiefly of smithsonite and hemimorphite, but large masses 
of the silicate, willemite, are also occasionally found. Very little 
zinc blende accompanies these ores. Zinc ore has also been 
mined at Welkenrodt near Altenberg, Nouvelle Montagne, 
Corphalie near Liege, and Philippeville, from which districts 
large quantities of ore have been mined in the past. 

The present output of zinc ores (entirely blende) from the 
Belgian mines is about 11,000 long tons per annum. 

Bulgaria. This country is a small zinc ore producer, the chief 
source being the Sedmolchisleniza Mine, about six miles south- 
west of Vratza. The crude ore contains about 18 per cent, of 
zinc, but by hand-picking the zinc content can be raised to 28 
per cent. 

Ores are also worked at Roupio and at the Blagodat Mine near 
Kustendil. 

France. This country first became a zinc ore producer about 
1870, the ore consisting chiefly of carbonate, being obtained 
from the country between the Alps and the Pyrenees. Within 
recent years the supply of zinc ores has fallen considerably. 
The largest producing mines at present are those of Malines 
(Gard), where zinc ores have been worked since 1883. Both 
oxidised ores and blende are worked. 

In the Pyrenees, zinc ores occur in many localities. Argenti- 
ferous sulphides and carbonates of zinc and lead are produced 
at the Sentein mines in Ariege, and important deposits also 
occur in both the Hautes and Basses Pyrenees. Deposits of 

57 



THE ZINC INDUSTRY 

zinc carbonate, silicate, and blende occur in the department of 
Var, the chief mine being the Bormettes, which produces zinc 
blende. The total output in 1913 amounted to only about 
45,000 long tons, compared with 95,000 long tons in 1909, 
more than one-third coming from the mines at Malines. 

The French colonies Algeria and Tunis are also important 
zinc ore producers and may be conveniently considered here. 
In Algeria, both zinc carbonate and blende are worked in the 
department of Constantine. The chief mines are the Hammam 
N 'Bails and Ain Arko. Ore is also mined at several places near 
the Atlas Mountains. In 1913 Algeria produced 81,000 long 
tons of zinc ore, chiefly calamine, compared with 83,000 long 
tons for the previous year. 

Tunis produces about 35,000 long tons of zinc ore annually, 
consisting chiefly of carbonate and silicate, derived from a 
number of localities. The ore is usually calcined locally before 
being exported in order to save freight. 

In the past, most of the ore produced in Algeria and Tunis 
was shipped from the ports of Bona and Sousse, and found its 
way to smelters in Belgium, France and Germany. 

Germany. This country is the chief producer of zinc ore in 
Europe, the most important deposits being situated in Upper 
Silesia, whilst ore in smaller quantities is obtained in Rhineland, 
Westphalia, Nassau, the Harz, etc. Although mined for cen- 
turies, the German zinc deposits still produce a considerable 
amount of high grade ore. 

The well-known deposits of Upper Silesia occur in the south- 
eastern corner of the province, on the borders of Austria and 
Russia. The ores of this district are principally calamine and 
blende. The latter occurs in the deeper workings, consequently 
as the mine workings increase in depth the proportion of calamine 
as compared with blende has gradually declined. 

The calamine occurs rarely in the condition of pure zinc 
carbonate ; the bulk of the ore is in the form of a dolomitic 
calamine, often more or less argillaceous. The deposits are very 
irregular, and occur in the form of more or less extensive pockets, 
whilst the blende deposits show great continuity. 

Oxidised ores were treated exclusively in the Silesian district 
until about 1860, but since that time blende has been worked in 
increasing quantity and is now by far the more important ore 
smelted in the district. 

58 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

The crude zinc blende, as sent to the dressing plants, contains, 
on the average, about 10 per cent, of zinc, but dressing gives a 
high-grade smelting concentrate. 

The calamine produced in Upper Silesia is usually ferruginous 
and of high grade, containing from 28 to 35 per cent, of zinc ; 
cadmium in appreciable quantity is usually present. Ores 
containing as little as 13 per cent, of zinc are worked in Silesia 
by local smelters, such ore being of too low grade to bear the cost 
of transport. As a general rule, the zinc ores smelted in Silesia 
are of very low grade. 

In Westphalia, the ore is mainly blende, the chief deposits 
occurring at Iserlohn and Brilon. 

In the Upper Harz and Hanover, zinc blende is recovered in 
the dressing of argentiferous lead ore mined near Clausenthal 
and Laurenthal. 

In the Lahn Valley, Nassau, important deposits of more or 
less complex sulphide ores occur, carrying about 3 per cent, of 
zinc, 4 per cent, of lead, and 2 oz. of silver per ton. 

The crude ore is concentrated at the Laurenberg, Silberau and 
Friedrichssegen works, and yields a blende concentrate containing 
44 per cent, of zinc, and a galena concentrate with 36 per cent, of 
lead and n oz. of silver per ton. 

The Lower Harz deposits occur chiefly at Rammelsberg, near 
Oker. The ore is an intimate mixture of zinc blende with other 
metallic sulphides, and yields on concentration a product carrying 
25 per cent, of zinc. 

Special processes have been devised for the treatment of the 
Rammelsberg ore body (see p. no). 

At the present time, the larger proportion of the zinc ore 
mined hi Germany comes from the Silesian district, the output, 
which has steadily declined in recent years, amounting to 
between 650,000 and 700,000 long tons per annum. In 1913 
the production amounted to 627,000 long tons, a decline of about 
10,000 tons on the previous year. This decrease in output is, 
however, most probably intentional, since Germany, as previously 
stated, has for some years adopted the policy, which is being 
strictly followed, of conserving national resources of ore. It is 
due to this fact that Germany has been able to maintain a 
considerable output of zinc during the war, in spite of the cutting 
off of imported ores. 

Greece. The most important zinc mines are those of the 

59 



THE ZINC INDUSTRY 

Laurium district, where both zinc blende and carbonate occur. 
The mines are of great antiquity and still yield a considerable 
amount of ore. The carbonate ore is usually calcined before 
export, and then contains about 60 per cent, of zinc. The 
production in 1913 consisted of about 30,000 long tons of blende 
and 20,000 long tons of calcined calamme a total of 50,000 
long tons, showing a decrease of some 17,000 long tons on the 
previous year. 

Italy. Zinc carbonate ore is mined chiefly in Sardinia, the 
carbonate of which has long been famous. The mines now 
worked are amongst the most productive in Europe. Less im- 
portant deposits occur in Lombardy, Piedmont and Tuscany. 
The richest mines in Sardinia are probably those of the Inglesias 
district, which yield zinc carbonate and silicate near the surface, 
whilst zinc blende is found at the lower depths. 

The output was approximately 151,000 long tons in 1913. 

The ore has hitherto been exported chiefly to Germany, Belgium 
and the United Kingdom. Important zinc mines in Sardinia 
have long been operated by the English Crown Spelter Company, 
of Swansea, to which port the ore is shipped for treatment. 

Norway. Small amounts of zinc ore have been mined at 
Hadeland, Modum, and Ranen. Extensive deposits of low- 
grade ore occur near Christiania, but their concentration has 
presented considerable difficulty. 

Russia. Russian Poland, in the districts bordering on Silesia, 
produces calamine from deposits which are probably an exten- 
sion of the Silesian deposits in Germany. At one time the zinc 
deposits of Poland were amongst the most productive in 
Europe. 

Several deposits of complex ore containing zinc occur in the 
Nerchinsk district of Eastern Siberia, and in the Altai Mountains, 
Siberia, in the Irtish River district. These districts are being 
developed, with the aid of British capital, and promise to 
become of importance in the future. 

In the Northern Caucasus, rich deposits occur at Sadon and 
Primorsk, the latter being mined by the Tetysch Company. 

The output of the district in 1910 was about 20,000 tons. 

Spain. The most important zinc ore deposits are found in 
the provinces of Murcia and Santander, which produce about 
80 per cent, of the total Spanish output. 

Small amounts are obtained from deposits in the provinces 

60 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

of Teruel and Cordoba. About 175,000 long tons of ore, both 
cal-amine and blende, are mined annually in Spain, a small portion 
only of which is smelted in Spain, the remainder being shipped 
to Belgium, Germany and France. 

Sweden. The only important mines appear to be those at 
Ammeberg, in the Nerike province. The mines, which are 
controlled and worked by the Vieille Montagne Company, are 
situated about eight miles from Ammeberg, at the northern end 
of Lake Wetter. The ore consists of zinc blende, associated 
with pyrites and galena, and after hand-sorting carries about 20 
per cent, of zinc and i per cent, of lead. 

In order to facilitate the removal of the pyrites the ore is slightly 
roasted before being crushed and concentrated. The concentrates, 
as shipped, contain about 42 per cent, of zinc, and have hitherto 
been treated in Belgium. 

The output in 1913 was 50,840 long tons, practically the whole 
being blende. 

Moulden has stated that many of the iron mines yield also no 
small amounts of zinc blende, and under favourable conditions 
the potentialities of this country are undoubtedly considerable. 

American Sources of Zinc Ore 

The United States of America is the greatest producer of zinc 
ores in the world, the output at the present time far exceeding 
that of any other country. 

The output in 1913 approximated to no fewer than 790,000 
long tons, exclusive of ore exported or used for the manufac- 
ture of zinc oxide. Since the outbreak of war the output has 
increased enormously. 

Both calamine and blende are extensively worked, in addition 
to the zincite and franklinite deposits. There exist also great 
reserves of the more complex low-grade lead-zinc ores, which, 
owing to the abundance of richer and purer ores, have not 
yet been exploited to any considerable extent. 

Of the recoverable zinc content of the ores mined in 1913, 
more than 77 per cent, was contained in zinc ores proper, the 
remainder, with the exception of 0-8 per cent., being from zinc- 
lead ores. 

The chief ore-producing States in order of importance are 
Missouri, Wisconsin, Idaho, Kansas, Oklahoma, Colorado and 

61 



THE ZINC INDUSTRY 



Montana, but there are in addition some twelve other States 
that produce smaller quantities of zinc ore and collectively 
considerably augment the output for the United States. 

The mine production of zinc-yielding ores in 1913 from the 
more important States is shown in short tons (2,000 Ib.) in the 
following table : 

ZINC ORE PRODUCTION IN THE UNITED STATES, IN SHORT 
TONS (2,000 LB.), IN 1913. x 





Zinc Ore. 


Zinc-lead Ore. 




State. 


Crude 


Zinc 


Crude 


Zinc 


Total. 




Ore. 


Content. 


Ore. 


Content. 






Short tons. 


Per cent. 


Short tons. 


Per cent. 


Short tons. 


Missouri 


8,049,300 


1-6 


, 





8,049,300 


Wisconsin 


1,406,000 


2-1 


. 


, 


1,406,000 


Idaho 


2,719 


42-2 


646,080 


1-6 


648,799 


Kansas 


590,300 


1-7 


. 


, 


590,300 


Oklahoma 


581,000 


2-0 


, 


, 


581,000 


New Jersey 


490,434 


17-2 


, 


- 


490,434 


Colorado 


141,295 


23-5 


203,367 


11-4 


344,662 


Montana 


3,840 


9-8 


307,615 


I4'3 


3H,455 


'~tTtah . . 


16,322 


29-2 


211,609 


2-1 


227,931 


Tennessee 


171,392 


3'3 


. 


, 


171,392 


New Mexico 


40,439 


17-0 


8,735 


16-1 


49,174 


Arizona 


14,554 


17-2 


29,700 


7'3 


44,254 


Nevada 


10,208 


31-1 


16,749 


24-1 


26,957 


Totals . . 


11,517,803 




1,423,855 




12,941,658 



These figures show that the zinc content of the ores as mined 
varied from as little as 1-6 per cent, to 42 per cent., these figures 
being the average for Missouri and Idaho respectively ; the 
average for the whole of the crude zinc ore mined in 1913 was 
2-8 per cent. 

The low-grade ores are submitted to concentration processes, 
and so far, in the United States, the greatest tonnage of zinc 
concentrates has been produced by magnetic separators, without 
including the enormous separating plant at Franklin Furnace, 
New Jersey, with its capacity of nearly one thousand tons 
daily, for the separation of franklinite from willemite. Flotation 
processes are, however, now being introduced for the treatment 

1 United States Geological Survey and Department of Mines Report, 
1914. 

62 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

of complex ores in America . Detailed reference must be restricted 
to the more important zinc ore-producing States in their order 
of quantity of ore mined. 

Missouri. Output 8,049,300 short tons. Although the zinc 
deposits of Missouri consist of some of the lowest grades of zinc 
ores worked in the country, the enormous output enables the 
State to hold the first place as regards zinc production. The 
ore mined is mainly zinc blende with small quantities of galena 
and marcasite. 

About three-quarters of the celebrated Joplin district is in 
Missouri, the remainder being in Kansas (Cherokee County) 
and Oklahoma (Ottawa County). 

The zinc-bearing deposits of the Joplin district consist of large 
pockets from which ore can be removed cheaply and in a more 
or less crude manner. 

The character of the ore is such that, in practically all cases, 
it breaks away from the gangue material easily with coarse 
crushing, and makes an ideal jig product, any lead contained 
in the crude ore being saved by the jig as a separate product, 
which is sent to the lead smelter. The bulk of the ore now mined 
in this district is blende, calamine forming about one-tenth only 
of the total output. 

Important deposits of " silicate ore " (a mixture of hemimor- 
phite and smithsonite) occur in the Aurora and Granby districts ; 
in many cases the ore contains from 40 to 45 per cent, of zinc, 
and is therefore of sufficiently high grade to ship in lump form. 

Wisconsin. Output 1,406,000 short tons. As a zinc ore 
producer this State ranks second, but occupies fourth place as 
regards zinc output. The most important ore-producing counties 
are Grant, Iowa, and Lafayette. 

The ores, which consist of galena, zinc blende, and smithsonite, 
contain a large amount of marcasite, and much difficulty was at 
first experienced in concentrating the ore, but this has been 
overcome by slightly roasting the ore to render the marcasite 
non-magnetic. 

By this means magnetic separation of the blende from its 
associated iron sulphide is rendered possible, thus giving a shipping 
ore of sufficiently high grade suitable for distillation. In 1914 
there were 46 ore dressing mills and five magnetic separating 
plants in operation in various places in the Wisconsin district. 

Zinc carbonate ore also occurs in Wisconsin, mainly in the 

63 



THE ZINC INDUSTRY 

Highland and Mineral Point districts, and it is chiefly used for 
the production of zinc oxide. 

Idaho. Output 648,799 short tons. Zinc-lead ore is chiefly 
mined in this State and is obtained from the Beaver, Hunter and 
Placer Center districts of Shoshone County. 

The zinc content of the ore as mined is about 2 per cent., but 
concentration yields a product containing on an average 34 per 
cent, of zinc and small amounts of gold and silver, which enhance 
the value of the ore. 

A small quantity of crude ore of good quality and containing 
about 42 per cent, of zinc was shipped from the Beaver, Summit 
and Lelande districts in 1913. 

Kansas. Output 590,300 short tons. Practically the only 
deposits at present being worked in this State are those of 
Cherokee, in the south-eastern part of the State, which forms 
the western portion of the Joplin district. 

Both carbonate and sulphide of lead occur with the zinc ores, 
which are of low grade and contain on an average about 1-7 per 
cent, of zinc only. 

Oklahoma. Output 581,000 short tons. The zinc ore deposits 
in Ottawa County in this State form the south-western portion 
of the Joplin district. The Miami district is responsible for 
about 95 per cent, of the total output in Oklahoma. The crude 
ore as mined contains a little more than 2 per cent, of zinc, but 
yields a concentrate suitable for smelting. 

New Jersey. Output 490,434 short tons. This State is of 
considerable interest on account of the special nature of the 
zinc minerals in the ore. 

Practically the whole of the output is obtained from two 
deposits that occur in Franklin Furnace and Stirling Hill, in 
Sussex County, both of which are mined by the New Jersey 
Zinc Company. Enormous quantities of the ore are consumed 
annually in the manufacture of zinc oxide direct from the ore, 
so that in 1913 New Jersey only attained fifth place on the 
basis of zinc produced. 

The ore comprises zincite, willemite and franklinite, but the 
relative amounts of the minerals vary considerably. The 
franklinite is usually closely associated with the other zinc 
minerals, from which it is separated by magnetic treatment, first 
devised by Samuel Wetherill, who also developed and applied 
the blowing-up grate furnace for the economic production of 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

zinc oxide direct from these ores. The name of Wetherill thus 
became intimately associated with the history and success of the 
district. 

Colorado. Output 344,662 short tons. Zinc ore is mined in 
many localities in this State. About 80 per cent, of the zinc 
ore produced in the State is derived from the Leadville mines 
in Lake County. The deposits yield galena, zinc blende, and 
iron pyrites, the crude ore containing 19 per cent, of zinc. 
Considerable amounts of zinc carbonate and silicate are also 
mined in this district. In 1913 the output consisted of approxi- 
mately 98,000 tons of crude sulphide ore and 136,000 short 
tons of carbonate and silicate ore. 

The next largest producing counties are Eagle and Summit, 
their total output in 1913 being about 8 per cent, of that of the 
whole State. In Summit County zinc blende is associated with 
galena, but usually the quantity of galena is small. The ore as 
shipped is stated to contain 42 per cent, of zinc. 

Other zinc ore-producing counties are San Miguel, Dolores 
and Chaff ee. 

Montana. Output 311,455 short tons. The zinc ore produced 
in this State comes largely from the celebrated copper district 
of Butte, the chief mines being the Butte and Superior. The 
Butte district, which has very rapidly come into prominence as 
a zinc ore producer, promises to become one of the largest zinc- 
producing areas in the United States. 

The ore is chiefly zinc blende and carries about 20 per cent, 
of zinc, but by concentration a product is obtained carrying 
49 per cent, of zinc and about 24 oz. of silver per ton and a little 
gold. In 1913 Montana was third as a zinc produces*^ 

Utah. Output 227,931 short tons. The ore produced in 1913 
was derived chiefly from Beaver County, whilst important out- 
puts were made from the counties of Salt Lake, Utah, Wasatch, 
Summit, Tooele and Juab. 

The zinc-lead ores contained on an average about 27 per cent, 
of zinc and 0-06 oz. of silver per ton, but concentration yielded 
a product containing about 33 per cent, of zinc and nearly 2 oz. 
of silver per ton. 

Tennessee. Output 171,392 short tons. During the past few 
years there has been considerable activity in prospecting zinc- 
bearing deposits in Eastern Tennessee, and several large bodies 
of ore have been located. 

65 F I 



THE ZINC INDUSTRY 

Zinc blende is mined in Knox County, the zinc content of the 
crude ore being from 3 to 5 per cent ; the concentrate obtained 
from this carrying about 60 per cent, of zinc. 

New Mexico. Output 49,174 short tons. The production in 
1913 was chiefly from mines in the Socorro, Luna and Grant 
Counties. The ore shipped in 1913 consisted of 12,000 short 
tons of zinc blende and concentrates containing 42 per cent, 
of zinc, and 13,000 short tons of carbonate ore containing 34 
per cent, of zinc. 

Arizona. Output 44,254 short tons. Most of the ore mined in 
this State is obtained from Mohave and Pima Counties. Small 
amounts are also produced in Yavapai and Cochise Counties. 
Both zinc and zinc-lead ores are produced, the latter forming 
about two-thirds of the total output. 

Nevada. Output 26,957 short tons. The ore raised in this 
State in 1913 consisted of zinc-lead ore and of silicate and 
carbonate ; it was chiefly produced in Clarke and Lincoln 
Counties. The ore as sold to the smelter averaged about 30 per 
cent, of zinc. 

Mexico. Zinc ore occurs in a number of localities in Mexico, 
but many of the deposits cannot be utilised owing to transport 
and other difficulties. 

The chief producing States are Coahuila, Chihuahua, San Luis 
Potosi, Tamaulipas and Nuevo Leon. 

The bulk of the ore mined in the past has been exported to 
America and to Europe, but in recent years the unfortunate 
political disturbances prevailing in the country have prevented ore 
producers from taking advantage of the more favourable import 
duties on ores entering the United States. 

Conditions limiting the shipment of zinc ore from Mexico have 
now improved somewhat, so that a larger output of ore than in 
past years is to be expected. 

In 1909 the ore imported by America from Mexico amounted 
to 105,000 short tons, but since that time the output has fallen 
considerably, amounting to only 18,000 short tons in 1913 and 
21,000 short tons in 1914. 

The ore shipped usually contains from 30 to 40 per cent, of 
zinc and varying amounts of silver. 

South America. This continent is at present a very small zinc 
ore producer, Bolivia and Peru alone making small contributions. 

Bolivia. The present output is derived chiefly from the 

66 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

Huanchaca district, but zinc ores have been found in a number 
of other localities in Bolivia. 

Owing to shortage of water for concentrating the ore and to 
other difficulties, the output has decreased in recent years. The 
production in 1913 was 7,500 short tons, and in 1914 it had 
decreased to approximately 4,000 short tons. 

An estimate of the total production of zinc ore in the United 
States is given in the report of the zinc smelters, who are stated 
to have smelted in 1914 approximately 

629,000 short tons of blende. 
227,000 ,, ,, of calamine. 

Total . . 856,000 short tons. 

This total will probably include some 21,000 short tons of ore 
imported from Mexico and 11,000 short tons from Canada. 

On the other hand, a small quantity of ore, amounting to 
11,000 short tons, was exported to Europe. 

The very considerable increase of zinc ore production in America 
since the outbreak of war is shown by the following figures, which 
give the recoverable zinc content of the ore mined in the United 
States for the past four years. 1 In 1913 it was 406,000 short 
tons ; in 1914, 407,000 short tons; in 1915, 605,915 short tons, 
and in 1916, about 708,000 short tons. The large increase in 
output in 1915 and 1916 was due to the demand for zinc from 
Great Britain and the Allies. 

The largest increase in output was made by the Joplin region, 
which in 1916 had an increase of more than 40,000 short tons. 
Montana made a notable increase and from the return available 
appears to have taken second place. Substantial increases were 
also made in the zinc mining districts of the Upper Mississippi, 
Valley, Colorado, Tennessee, Idaho, Nevada, New Mexico, New 
York, Arkansas and Washington. 

Of the total output of zinc in the ore mined, the Eastern States 
produced 148,000 short tons, or 21 per cent. ; the Central 
States 274,000 short tons, or 39 per cent. ; and the Western 
States 286,000 short tons, or 40 per cent. 

Asiatic Sources of Zinc Ores 

Little accurate information appears to be available regarding 
the nature and extent of many of the zinc deposits in Asia. 
1 United States Geological Survey Report. 

67 F 2 



THE ZINC INDUSTRY 

Actual figures of output are also very difficult to ascertain. 
China has long been the largest zinc ore producer in Asia, but in 
recent years considerable attention has also been given to zinc 
deposits in Japan and Siberia. 

China. 'This country appears to have been the world's earliest 
producer of zinc ores, and also of metallic zinc produced by 
crude methods of native smelting. 

The most important deposits worked are situated in the Pre- 
fecture of Changlin, in Hunan province, and consist of argenti- 
ferous galena, associated with blende, iron pyrites and calcite. 
The deposit has been exploited by means of surface workings 
for about two centuries, and has been considerably developed 
during recent years as the result of German influence. The 
chief mines are the Shui K'ou Shan, worked by the Hunan 
Board of Mines. 

A considerable portion of the ore mined is first submitted to a 
preliminary dressing at the mine. The dressed blende and mixed 
zinc-lead sulphides are then sold to a German firm having an 
ore-dressing plant at Woo Chang, where the material is further 
concentrated to yield a zinc concentrate carrying from 30 to 35 
per cent, of zinc, which prior to the war was exported to Germany 
to be smelted. 

It is stated that before the outbreak of war the German 
company was considering the desirability of erecting a smeltery 
in China. The output of zinc ore in 1914 was approximately 
21,500 long tons. 

Numerous deposits of zinc ore are known to occur also in 
South-Western China, and in Kweichow province appreciable 
quantities of metallic zinc have been produced by native 
smelting. 

Japan. Zinc blende, usually associated with ores of copper 
and lead, has been found in a number of localities in Japan, but 
up to the present most of the marketable ore has been obtained 
from the Kamioka Mines in the province of Hida, the output 
of crude ore being normally about 10,000 long tons annually. 
The crude ore, consisting of zinc blende and argentiferous galena 
carrying from 10 to 16 per cent, of zinc, is treated at two dressing 
works at Shikama and Mozumi, where wet concentration and 
flotation methods are employed. The greater part of the zinc 
concentrates produced have in the past been exported, chiefly 
to Belgium. 

68 



ZINC ORES AND THEIR SOURCES OF SUPPLY 

The lead concentrates are smelted in blast furnaces about 
35 miles from Toyama. 

Zinc mines of less importance occur in the provinces of Tsu- 
shima, Etchu, Echizen, Bizen and Mimasaka. 

The output of zinc ore within the Japanese Empire has shown 
a very marked increase during recent years, practically the whole 
of which has been exported to foreign smelting centres for treat- 
ment. Thus the exports amounted to approximately 18,000 
long tons in 1909, to 22,000 long tons in 1910, and 23,000 long 
tons in 1911. The annual production at the present time is 
said to be about 50,000 long tons. 

Japanese zinc ore amounting to 1,200 long tons was imported 
into the United Kingdom in 1913 and more than 5,000 long tons 
in 1914. 

In view of the great activity in the Japanese zinc industry 
since the outbreak of war, and the erection of smelting plant to 
smelt the zinc ores mined in the country, the mine-owners would 
appear to have a very hopeful future before them. 

Siberia. Important deposits are worked at the Ridder Mine 
in the Altai Mountains, Siberia. Since the mine was acquired 
by the Irtish Corporation, Ltd., in 1915, considerable develop- 
ment has taken place. The ore produced is said to consist of 
two qualities, about one half being high-grade ore containing 
27 per cent, of zinc, 18 per cent, of lead, and I oz. of gold per ton. 
whilst the remainder is of lower grade, carrying about 9 per cent, 
only of zinc and 5 per cent, of lead. As previously stated, the 
Irtish Corporation are building a large zinc-and-lead smelting 
plant at Ekibastus for the treatment of the ore of the Ridder 
Mine. Part of this plant began operations in May, 1916. 



CHAPTER IV 

THE MARKETING OF ZINC ORES 

The Concentration of Zinc Ores 

ORES of zinc as mined are seldom of sufficiently high grade 
to be sent direct to the smelter for immediate conversion into 
metal without previous concentration. Especially is this the 
case with ores containing zinc blende, which is by far the most 
important source of zinc at the present time. 

The gradual exhaustion of the deposits of rich calamine ores 
has led, during the past few decades, to a considerable develop- 
ment in the concentration of zinc blende ores to meet the demand 
of the smelters for high-grade ores. 

During the past twenty years the zinc ore market has been 
considerably augmented by the supply of thousands of tons of 
" zinc concentrate," a high-grade zinc blende product resulting 
from the mechanical treatment of low-grade ores, and so-called 
complex ores, in which the zinc is intimately associated with other 
metals, such as lead, copper and silver. 

The preliminary treatment of zinc ores has for its object not 
only the enrichment of the ore by removal of the minerals of 
comparatively low specific gravity which compose the gangue, 
but also the elimination, as far as possible, of heavy minerals, 
such as those containing lead, iron and manganese, which are 
objectionable in smelting. 

In many cases these heavy minerals are of market value and 
are recovered in sufficient quantity to be a source of profit. 

The methods of concentration employed include hand sorting 
and separation by gravity (wet dressing), electromagnetic and 
oil flotation processes, or combinations of these. The process 
adopted varies with the nature of the ore. 

Where ores are sufficiently high in zinc blende and lead 

70 



THE MARKETING OF ZINC ORES 

(galena) and carry little or no iron pyrites, or chalcopyrite, the 
ordinary methods of water concentration in jigs, and upon tables, 
such as are employed at Joplin and some of the Leadville mines 
in the United States, give satisfactory separation, but magnetic 
separation or flotation methods are usually employed for more 
complex ores. In favourable circumstances, and if worked on a 
sufficiently large scale, ore containing as little as 3 per cent, of 
zinc may be worked at a profit, and will on concentration yield 
a zinc product suitable for smelting ; but in such cases the lead 
and copper, and small amounts of silver and gold which often 
accompany the zinc in the ore, are recoverable, and are usually 
the determining factors of commercial success in the treatment of 
low-grade ores. 

In this connection, the more modern system of concentration 
known as " flotation," which is applicable to the treatment of 
the sulphide ores of most metals, has in recent years been widely 
adopted for concentrating those of zinc. 

Magnetic concentration has been successfully applied to the 
separation of the zinc minerals comprising the well-known 
franklinite ores of New Jersey. 

Following the pioneer work of Wetherill's high intensity 
magnetic separator, considerable progress has been made in the 
magnetic concentration of ores, and many machines have been 
introduced. Electrostatic methods for the separation, by 
electric repulsion, of good conductors (such as certain metallic 
sulphides, magnetite, haematite, etc.) from poor conductors 
(such as silicates, carbonates, oxides and sulphates, and including 
zinc blende) were first applied in practice by Blake and Mecher- 
nich, and followed by Sutton and Steele, Huff and others. 

Magnetic separation of blende and pyrites may be accomplished 
without preliminary roasting by the use of high intensity mag- 
netic separators of the Wetherill type, the zinc mineral being 
lifted out of the mass. 

The more usual practice, however, is to give the mineral a 
magnetic or " flash " roast, rendering the iron magnetic, after 
which it is separated from the mass by separators of the low 
intensity type, such as that of Dings. 

The main objection to electric separators appears to be their 
inability to handle fine powders, and their liability to dust 
trouble unless the dust be first removed. 

The flotation processes of concentration have come rapidly 



THE ZINC INDUSTRY 

to the front since their introduction some fifteen years ago by 
the Messrs. Elmore. Their work, which resulted in" the filing of 
Frank Elmore's patent in 1898, focussed the attention of 
metallurgists upon the great possibilities of these methods. 

Many new systems of concentration by flotation have been 
introduced within recent years. 

In these processes advantage is taken of the property possessed 
by metallic sulphides, when in a fine condition, of floating in 
water, hence their term of " flotation " processes. When 
for example, a mixture of such sulphides and waste mineral 
(gangue), in a finely crushed condition, is gently brought on to 
the surface of moving water, it will be found that the sulphide 
particles will float, whilst those of the gangue will break through 
the surface and sink. This different behaviour will be aug- 
mented if the water be very slightly acidulated, and still more 
so if the surface of the sulphide particles is oiled or greased. 
Since metallic sulphides possess also the property of absorbing 
oil, or being " wetted " by oil, while particles of gangue do not, 
a separation can be effected by agitating the finely crushed ore 
with water containing a small proportion of oil, whereby the 
sulphide particles will gradually collect in the floating film of oil, 
whilst the rock particles remain sunken. 

Neither of the above phenomena alone suffices for a practical 
working method ; other principles equally important have been 
drawn upon (such as the modification of the surface-tension of 
water, factors of absorption, aeration, fine subdivision of the 
mineral, eto.) and blended into one or other of these processes, 
which reverse the operations of " wet " concentration inasmuch 
as they save the heavier mineral by floating it to the surface 
whilst causing the specifically lighter material to sink. 

In the Elmore oil vacuum process separation is assisted by the 
partial exhaustion of a large metal receiver into which the oiled 
slimes and water enter. The air films surrounding the oiled 
particles are thus expanded, and the separation is much improved. 
In other cases diluted acid is employed, and with suitable ores 
gas bubbles are produced which cause the sulphide particles to 
rise to the surface of the liquid. 

One of the most widely used and successful of the flotation 
methods of concentration is that known as the " Froth Flotation 
Process," wherein the mineral is recovered in a more or less thick 
and coherent bubble-froth which is skimmed or run off from 

72 



THE MARKETING OF ZINC ORES 

the pulp, thus effecting a separation of the mineral from the 
gangue. 1 

The success of flotation methods has been very marked in 
the treatment of large quantities of slimes and complex ores 
that had previously defied all known methods of treatment. 

They proved to be very suitable for the treatment of 
the complex ores obtained from Broken Hill, New South 
Wales, in which zinc blende and galena are very intimately 
associated, and enormous quantities of these and similar ores 
are now treated by flotation. 

By gravity concentration it was possible to market only about 
60 per cent, of the lead in the Broken Hill deposits, and less of 
the silver, leaving the bulk of the zinc associated with the heavy 
waste as a middle product, whilst the finest and lightest portion 
of the crushed material was often allowed to flow away. 

So successful has been the application of flotation methods to 
the treatment of the Broken Hill ores that now the whole range 
of zinc products is treated by flotation, and zinc concentrate to 
the extent of about 500,000 tons per annum is being recovered. 

Owing principally to improved methods of mechanical separa- 
tion, large deposits of zinc-lead sulphides are being opened up 
in America, Burma and Siberia, in addition to those in Australia 
and elsewhere. 

In view of the fact that the supply of flotation and other zinc 
concentrates is bound to increase, metallurgists are giving special 
attention to their treatment, since in many cases their very fine 
state of division renders some modification of the ordinary 
Smelting processes necessary. 

The Valuation of Zinc Ores 

For technical purposes, zinc ores are divided into two classes : 
( i) zinc blende, and (2) calamine, the latter including the common 
carbonates and silicates. 

A large proportion of the zinc ore now marketed consists 
of zinc blende concentrates, which usually contain from 35 to 
55 per cent, of zinc. 

The market value of an ore is based on the price of the metal 
content, less the total cost of extraction ; in other words, the 
net return to the proprietors. 

The zinc content is determined by wet analysis, usually 

1 " Copper, " H. K. Picard, London, 1916, p. 24. 
73 



THE ZINC INDUSTRY 

volumetrically by sodium sulphide (Schaffner's method) or by 
ferrocyanide. 

The value of a zinc ore depends chiefly upon its content of 
zinc and the absence of objectionable impurities such as iron, 
manganese and lime (calcium carbonate), which form fusible 
slags and increase the corrosion of the retorts ; and lead, cad- 
mium, arsenic and antimony, which contaminate the spelter 
and therefore lower its market value. Lead, however, is present 
in almost all zinc ores. 

The total percentage of iron and manganese should not exceed 
10 per cent., and if lead is present the metallic zinc produced by 
distillation will be contaminated with lead unless special precau- 
tions are taken. 

Fluorite (calcium fluoride) is sometimes present and is a very 
undesirable constituent, as it forms a very fusible slag, and when 
present in appreciable quantity in zinc blende causes deterioration 
in the lead chambers used in the manufacture of sulphuric acid 
as a by-product from the roasting of the ore. 

The value of the ore is also affected by its character, whether 
oxidised or sulphide, or a mixture of both ; the sulphide ore 
must be roasted, but yields a diminished weight for the subsequent 
treatment, which is the most expensive part of the process ; the 
calamine ores seldom require preliminary treatment by the 
smelter, as the economy in freightage between mine and smelter 
is usually sufficient to warrant calcination to expel carbon 
dioxide and combined water prior to shipment, this saving being 
more important where the mine is widely distant from the smelting 
worksi 

The value of an ore is, moreover, affected by its physical 
condition. Lump ore is subject to an additional expense for 
crushing : fine concentrates are more expensive and troublesome 
to treat than coarse concentrates. 

Some ores roast and distil easily, others with more difficulty. 
All these factors are considered by the zinc smelter in purchasing 
ores. 

It will be observed, therefore, that whilst the chemical com- 
position of ores is the most important factor in determining 
their value, the price does not depend solely on the metallic 
content and on the presence of other compounds, but also on 
certain physical properties governing the suitability of the ore 
for smelting purposes or for other methods of treatment. 

74 



THE MARKETING OF ZINC ORES 

Several schedules are employed in Europe for calculating the 
value of zinc ores, all of which embody at least three factors : 
(i) the current price of spelter, (2) the zinc content of the ore, 
(3) a " returning charge " per ton of ore. 

The last named is the cost of smelting a ton of ore, and is 
affected by the mineralogical nature of the ore and its physical 
condition. The treatment charges necessarily vary in different 
smelting centres, as, in addition to the above factors, they are 
also affected by local conditions, such as fuel supply, cost of 
labour, freight, etc. 

A general type of formula used for calculating the value of 
zinc ores is as follows : 



Where V is the value in per ton, 

P the price of spelter (G.O.B.) in London, 
T the percentage of zinc in the ore, 
R the " returning charge." 

The selling price basis for London spelter (G.O.B. = good 
ordinary brands) is usually the average of the daily prices for the 
month previous to arrival, and is usually taken as London Public 
Ledger quotation less 5 per cent., which is, of course, 0-95 P 
of the formula. Thus on a 20 average quotation basis the ore 
unitage paid for (T - 8) is based on 95 per cent, of 20, which is 
19, or 3-8 shillings per unit. 

As an example of the use of the above formula, if an ore which 
contains 48 per cent, of zinc and spelter is 30 per ton in London, 
and if a returning charge of 3 55. be assumed, then the market 
value of the ore per ton will be : 

0-95 x 3o(^ 8 ) -& 5 o = 8 3 o. 



When silver is present in the ore in sufficient quantity to permit 
of profitable extraction, it is usually paid for at the price based 
on the current price of standard silver after allowing for smelting 
loss and for cost of working. 

In determining the treatment charge on the ore purchased, 
the zinc smelter starts with the cost of smelting a ton of the ore 
of average composition, that is to say, the mixture on which he 
proposes to operate his furnaces. 

75 



THE ZINC INDUSTRY 

For various reasons it is aimed to have all the furnaces on the 
same ore-mixture. To this smelting charge he adds the profit 
that he ought to make to obtain a proper interest on his invest- 
ment, allowing for the necessary amortisation of his outlay in 
plant. The further addition of the freight on the ore to his 
works, and on the spelter product to its market, with allowances 
for the expenses incurred in buying the ore and selling the spelter, 
gives the returning charge which he must make against the ore 
in buying it on the basis of f.o.b. (free on board at port of ship- 
ment) or f.o.r. (free on rail) at the mine or concentrating mill 
where produced. 

Within recent years a marked change has taken place in the 
quality of the ores supplied to the zinc smelter. As the result 
of the gradual exhaustion of the high-grade calamine supplies, 
and even of the richer blende ores, and also the increasing 
demand for zinc, sulphide ores are now readily purchased which 
earlier would have found a poor market. It is not long since 
50 per cent, of zinc in a blende product was a standard which 
admitted of little reduction, particularly amongst smelters in this 
country. 

For several years prior to the war, however, it was possible 
to market ore containing only 35 per cent, of zinc, but as the 
price of spelter has advanced considerably since the outbreak of 
war, many smelters have refused to buy ores carrying less than 
40 per cent, of zinc, in order to secure as large an output of metal 
as possible from their furnaces. As a general rule, zinc smelters 
consider low-grade ores only if they contain other metals, such 
as lead and silver, in sufficient amounts to render the residues, 
after extraction of the zinc, profitable commercial sources of 
those metals, and thus to recoup the loss due to the decreased 
zinc content of the ore. Such foreign metals are, however, 
naturally paid for at a low price owing to the incompleteness of 
their recovery. 

That these secondary sources of profit may nevertheless become 
substantial is shown by the fact that, whereas zinc concen- 
trates were formerly subject to a deduction or " penalty " by 
the smelter for shortage of zinc below a certain figure, and the 
ore producer, therefore, did his best to increase the zinc tenor 
and to decrease that of lead and silver, he is now subject to a 
penalty if the zinc content is above a certain limit when this 
involves what the smelters consider to be an undue absence of 



THE MARKETING OF ZINC ORES 

silver or lead in connection with a given smelting charge. This 
applies more particularly to the Broken Hill and similar zinc 
concentrates. These zinc blende concentrates contain a payable 
quantity of silver, to recover which a certain amount of lead 
must be present. Thus the Continental smelters, who formerly 
treated large quantities of the Broken Hill concentrate, called 
for a product containing not less than 8 per cent, of lead, which 
metal they required for collecting the silver when smelting the 
residues, although the flotation process is capable of producing 
a zinc concentrate much lower in lead if desired. 



The European Ore Trade 

Owing to the growing shortage of the supply of domestic zinc 
ores and the ever increasing demand for zinc during the past 30 
years, the European smelters have had to rely more and more 
on imported ores, and this resulted in a European ore trade that, 
at the outbreak of the war, had grown to considerable dimensions. 

For many years, large quantities of zinc ore have been shipped 
to Antwerp and to Swansea from Sardinia, Algeria, and Spain, 
and also in more recent years from Australia and America. 
Despite the growing disposition of the American smelters to 
adapt their works to the handling of all classes of ores, the ship- 
ment of zinc ores from America to Europe has in the past been 
important, and the tendency before the war appeared to be for 
the shipments to increase rather than to decline. The American 
ore was shipped from Colorado via the Gulf ports of Galveston 
and New Orleans, cheap ocean freights being secured on the 
steamers carrying cotton to Europe. 

The ores were shipped to Antwerp and to Swansea in bulk, 
as no sacks appear to be proof against the acid nature of the ore. 
The ore arrived in the condition of fines, having generally been 
calcined, if calamine, and roasted, if blende, except in the case 
of Australian concentrates. 

The cargo was sampled by reserving one basket in twenty-five 
during unloading, the sample basket being chosen at random 
by agreement between the representatives of the buyer and 
seller, or, more commonly, the agent to whom both parties had 
entrusted their interests in this part of the business. The ore 
reserved for sample was reduced in quantity either by machinery 
or mixed and quartered down by hand to obtain a small repre- 

77 



THE ZINC INDUSTRY 

sentative quantity for assay to determine the zinc content and 
the presence of objectionable impurities. 

Settlements were made in Antwerp and Swansea on the results 
of the assay. The ores were bought on different formulae, of 
which an example has been given on p. 75. 

The formula quoted was used for ores containing 46 per cent, 
of zinc or more, and was quoted only on consignments c.i.f. 
Antwerp (costs, insurance, and freight paid to Antwerp) . 

As already stated, this formula is based on payment for the 
metallic content of the ore, less 8 units, 95 per cent, of the London 
price of spelter, G.O.B., less a returning charge. 

The following approximate figures, making a total of nearly 
900,000 tons, show the extent of the European ore trade in 
1913 : 

Zinc ore imported into English tons, 2,240 Ib. 

Germany . . . . . . . . . . 308,000 

Austria-Hungary . . . . . . . . 50,000 

Belgium . . . . . . . . . . 300,000 

France . . . . . . . . . . 173,000 

United Kingdom . . . . . . . . 65,000 

To what extent the European zinc ore trade will be resumed 
after the war is very difficult to predict. 



CHAPTER V 

, THE SMELTING OF ZINC ORES 

PRACTICALLY the whole of the world's supply of zinc is obtained 
by the distillation method in retorts in which advantage is 
taken of the volatility of the metal at a bright red heat. 
Until quite recent years this was the only method of zinc 
production, but at the present time appreciable and increasing 
amounts of the metal are being produced by wet processes, and 
by electrothermic smelting. 

Preliminary Treatment. For the distillation method the first 
clearly-defined stage is the conversion of the zinc compounds 
present in the ore into oxide by calcination or by roasting, and 
this is followed by the reduction of the oxide to metal by means 
of carbon at a temperature which is higher than the boiling 
point of zinc, i.e., about 940 C. (Moissan). 

These two operations are so distinct that they may be, and 
often are, carried out for commercial reasons in establishments 
widely distant from one another. 

The processes of calcination and roasting are different in their 
operation, but both aim at the same type of product, i.e., zinc 
oxide that is reducible under the conditions of distillation. 

Calcination. Calcination is used for the expulsion of carbon 
dioxide and water from carbonate ores, and of water from 
hemimorphite ; it also renders the ore more porous, and therefore 
more readily acted upon by the carbonaceous matter employed 
for its reduction. 

Although it is possible to reduce zinc carbonate without 
previous treatment, this practice is seldom adopted, as it has been 
found more economical to calcine the ore first. Apart from any 
other reason, the economy in freightage between mine and 
smelter, as previously stated, is usually sufficient to warrant 

79 



THE ZINC INDUSTRY 

calcination, the saving thus effected being of increasing im- 
portance the more widely apart the two are situated. 

Calcination is a simple operation, and analogous to the burning 
of limestone for lime, being carried out in practically the same 
manner, usually in kilns, in the presence of excess of air and also 
of moisture, the two latter points being important for the attain- 
ment of a good product. 

The use of kilns is restricted to lump ore, or to a mixture of 
lump and fines, usually in alternate layers, whereas for finely 
crushed ore furnaces either of the reverberatory type, or revolving 
cylindrical furnaces with a continuous discharge, of the Oxland 
type, are used. 

The method of calcination employed in Sardinia, where some 
of the most important deposits of calamine exist, may be taken 
as typical of the best practice in Europe. The lump ore is charged 
into slightly conical, circular shaft furnaces, 6-5 ft. in diameter 
at the bottom and varying from 12 to 18 ft. in height. The 
heat is supplied either from external grates, or by charging the 
furnace with alternate layers of coal and ore. The former 
method is preferable, as it avoids the contamination of the ore 
with ash from the fuel. The complete dehydration of the 
hydrated zinc minerals is readily effected by heating to the 
dullest perceptible red heat, but when other carbonates are 
present a higher temperature is necessary. 

The chief carbonates associated with calamine and the approxi- 
mate temperatures required for the expulsion of their carbon 
dioxide are as follows T : 

Zinc carbonate . . . . . . 300 C. 

Magnesium carbonate . . . . 650 C. 

Iron carbonate . . . . x . . 800 C. 

Calcium carbonate . . . . . . 812 C. 

Owing to the comparatively high temperature required to 
decompose calcium carbonate, calamine ores containing a high 
proportion of this carbonate are the most difficult to calcine 
completely, and they usually retain a sensible proportion of their 
original carbon dioxide content. 

The calcination of calamine is seldom complete, and when 
the ores are contaminated with much calcium carbonate or 
magnesium carbonate as much as 15 per cent, of carbon dioxide 
may be retained. 

1 Ingalls, " Metallurgy of Zinc." 
80 



THE SMELTING OF ZINC ORES 

Roasting. The desulphurisation of zinc blende is a more 
difficult matter than the process of calcination as described above. 

It is usually effected on the crushed ore by roasting in the 
presence of an excess of air, in shelf furnaces of two or more 
shelves. The particles of ore should not exceed 2 millimetres 
in diameter. Numerous difficulties are encountered in the pro- 
cess, which requires considerable experience on the part of the 
man supervising the work. Especially is care necessary to 
transform the sulphide as completely as possible into oxide and 
at the same time to avoid its passage into the sulphate, as the 
latter is reduced to sulphide by carbon, instead of to the metal. 

Of all the metallic sulphides with which the metallurgist has 
to deal, zinc sulphide is one of the most troublesome to roast 
" sweet," i.e., to expel all the sulphur. 

It has, however, the advantage of not sintering by heat, so 
that in the process of roasting it may from the first be exposed 
to a higher temperature than most other metallic sulphides. 
The roasting is considerably complicated by the presence of other 
metallic sulphides, such as those of iron and lead, and by the 
presence of manganese, lime, strontia and barytes. The first 
effect of the elevation of the temperature in roasting is to distil 
off sulphur, reducing the sulphides -to a lower stage of sulphurisa- 
tion. This sulphur burns in the furnace to sulphur dioxide 
(sulphurous anhydride, SO 2 ) part of which coming into contact 
with the hot ore and hot walls of the furnace, and the oxidising 
furnace gases, is converted into sulphur trioxide (sulphuric 
anhydride, SO 8 ). On raising the temperature the decomposition 
of zinc sulphate and other metallic sulphates is effected, leaving 
oxide of zinc contaminated with the oxides of other metals 
present. For the expulsion of the sulphur trioxide from the 
zinc sulphate, however, a very high temperature is required, 
especially from the basic sulphates, which remain towards the 
end of the process, and it is this fact which makes the perfect 
roasting of zinc blende difficult. 

The oxidation of both the zinc and the sulphur in zinc blende 
by atmospheric oxygen during the roasting operation may be 
represented by the following equations : 



ZnS + 30 = ZnO + SO 2 . 
2ZnS + 70 = ZnO + ZnSO 4 + SO 
At a higher temperature, ZnSO 4 = ZnO -f SO 8 . 



THE ZINC INDUSTRY 

The reactions in blende roasting being exothermic, the ore, 
when once sufficiently heated, is self-roasting until the total 
sulphur contents are reduced to about 8 per cent. Beyond 
this stage the further application of heat becomes necessary in 
order to decompose the sulphates, so that the final reactions 
are strongly endo thermic, and the temperature of the ore when 
roasting is complete is about 900 to 950 C. The amount of 
sulphur to be expelled is dependent on the amount of metallic 
sulphides associated with the blende. Pure zinc sulphide contains 
32-92 per cent, of sulphur, but the ores of commerce are usually 
contaminated with iron pyrites (FeS 2 ) and other metallic sulph- 
ides and gangue materials, so that the sulphur content is usually 
between 21 and 35 per cent. 

When roasting has been successfully conducted, the final 
product does not contain on the average more than i per cent, 
of sulphur. Thus, in the case of certain of the purer ores the 
desulphurisation is so complete that no more than 0-5 to 0-8 
per cent, total sulphur remains, whilst others equally carefully 
dealt with retain from 2 '5 to 3 per cent., and even more in special 
cases, particularly those ores containing lime and baryta. Follow- 
ing modern Continental practice, however, the sulphur combined 
with lime, magnesia, strontia and baryta should be considered 
separately from that otherwise present in the roasted ore. 

The loss of zinc in roasting is very small and averages only 
about O'5 per cent. Probably highly ferruginous blende is the 
most difficult ore to roast. 

Zinc ores are rarely absolutely free from lead, and the trouble 
introduced in the operations of roasting and distillation by the 
presence of this metal in substantial amounts prevented to a 
large extent the smelting of zinc-lead ores until about 1890, 
when they were first smelted on a large scale on the Continent. 

Broken Hill ore, containing from 17 to 33 per cent, of lead and 
from 28 to 34 per cent, of zinc, was treated in Belgium and 
Germany in 1897, the ore being roasted in hand furnaces and the 
zinc distilled, after which the residues were treated for the silver 
and lead. 

Zinc concentrates from the dressing of the Broken Hill ore 
were first shipped to the Continent in 1899, and contained from 
12 to 15 per cent, of lead and from 38 to 40 per cent, of zinc. 
They were first smelted in Belgium and Holland and a little 
later in Germany. 

82 



THE SMELTING OF ZINC ORES 

The treatment of Broken Hill concentrates in this country was 
first commenced in 1905 by Mr. H. M. Ridge, who in 19071908 
built and started the works at Seaton Carew, Durham, where 
large quantities of this ore are now treated. 

Roasting converts lead sulphide (galena) into lead oxide, and to 
lead sulphate, a stable compound very difficult to decompose 
even at a high temperature. In the presence of free silica lead 
silicate is formed, and since this compound is readily fusible 
there is a risk of the ore agglomerating during roasting if it 
contains much quartz. Considerable success has attended the 
attempts to roast zinc-lead ores, and now excellent desulphurisa- 
tion of Broken Hill concentrates, containing about 45 per cent, 
of zinc and as much as 10 per cent, or more of lead, is daily 
achieved by well-designed muffle roasting furnaces. 

It has been found in practice that the rhodonite (mainly 
manganese silicate) which is mechanically mixed with the zinc 
ore in Broken Hill concentrates has a peculiar beneficent 
effect in the roasting, but the reasons for this are not clear, 
and the matter requires investigation. 

The reactions peculiar to the roasting of Broken Hill concen- 
trates appear to reach their maximum effect in muffle roasters, 
and are not nearly so noticeable when the roasting is carried out 
in furnaces of the "open" type. 1 In fact it may be said that 
the successful treatment of zinc-lead ores is due largely to the 
improvements in the design of modern roasting furnaces of the 
muffle type. 

The surmounting of the difficulties which at first attended 
the roasting and subsequent distilling of the Broken Hill and 
similar zinc concentrates is a matter of far-reaching importance, 
as it renders available vast additional sources of ore for augment- 
ing the world's supply of zinc. 

Many types of furnaces are in use for roasting zinc blende ; 
they may be classified under four heads, viz. : 

(r) Hand-raked reverberatory furnaces with one or more 
hearths, or with shelf burners. 

(2) Mechanically-raked reverberatory furnaces. 

(3) Multiple-hearth hand-raked furnaces. 

(4) Mechanical multiple-hearth muffle furnaces. 

The work of stirring in zinc ore-roasting furnaces is most 

1 J. C. Moulden, op. cit., p. 508. 

83 G 2 



THE ZINC INDUSTRY 

laborious, and even on the Continent, where labour is com- 
paratively cheap, continuous efforts have been made, since the 
beginning of the industry, to replace hand labour by machinery. 
The first attempt was made by the Societe de la Vieille Montagne, 
who succeeded in carrying out the first part of the operation in a 
circular furnace with several hearths, 8 feet in diameter, in which 
the ore was stirred by means of rotating rabbles. The ore, after 
passing over three or, in some of the furnaces, four hearths, 
dropped to two hand-rabbled hearths similar to those used in 
the Rhenania furnaces described later. In America, where 
hand labour was even more difficult to obtain, it was impossible 
to use hand furnaces. 

Roasting furnaces of the muffle type are employed when it is 
desired to utilise the sulphur dioxide for the manufacture 
of sulphuric acid, as the fuel gases never come into direct 
contact with the ore, the sulphur gases from which are led by 
an independent flue system to the sulphuric acid plant. The 
gases that pass to the acid maker contain on an average between 
5-5 per cent, and 6-5 per cent, (by volume) of sulphur dioxide. 
If below 5 per cent., the acid-chamber reactions are retarded, 
while if sensibly above 8 per cent, the roasting is retarded. 

Further reference is made to the manufacture of sulphuric 
acid from blende roasting on page in. 

The utilisation of the sulphur contents of zinc ore has received 
considerable attention within recent years on the Continent and 
in America, with the result that furnaces of the muffle type, 
either hand or mechanically raked, are now largely employed 
for roasting blende. 

Representative furnaces of this type now in use are (i) the 
Hasenclever or Rhenania furnace, (2) the Delplace furnace. 
(3) the Hegeler furnace, and (4) the Ridge furnace. 

The first two named are hand-worked muffle furnaces and are 
almost exclusively used in Europe ; and the third is a mechanical 
furnace in general use in the United States. Hasenclever built 
his first furnace at the Rhenania Works in Germany in 1855, 
and since that time many modifications have been introduced. 
In the later modifications, the Rhenania furnace consists of three 
superimposed muffles, the fire gases travelling beneath and above 
the bottom muffle. 

The furnace is 47-5 ft. long and 17-5 ft. wide, so that the ore 
travels a distance of 118 ft. along the hearths. With a 12-hour 

84 



THE SMELTING OF ZINC ORES 




THE ZINC INDUSTRY 




86 



THE SMELTING OF ZINC ORES 

shift a total of 8 men is required for the production of 6 tons of 
roasted ore per 24 hours. 1 

By working with 8-hour shifts only 12 men were required, and 
the production per man per shift slightly decreased. 

The coal consumption is about 25 per cent. 

These furnaces have been generally built together in blocks 
of four and have been more largely used on the Continent than 
any other type of furnace. 

Owing to the high price of fuel, " Delplace " furnaces have, 
since 1895, been largely built in Belgium. Figures I and 2 
show the details of this furnace. 

The travel of the ore on the seven superimposed hearths in 
this furnace is only 40 ft., but the ore is exposed thoroughly to 
the air because the arches are low, and only a thin bed of ore is 
maintained on each hearth. Only 16 per cent, of coal is required 
for heating. It is stated that with good labour, and if carefully 
built, these furnaces give satisfactory results. In addition to 
those erected in Belgium, some have been built in France, and a 
few have been erected in this country and in Germany. 

Experienced labour is required to work them satisfactorily, 
and the men prefer to work on the Rhenania furnaces, in which 
the ore is rabbled sideways, instead of being alternately pushed 
from and drawn towards the worker as in the Delplace furnace. 

As previously stated, work on zinc ore-roasting furnaces is 
most laborious, and continuous efforts have been made to replace 
hand labour by machinery, especially in furnaces in which the 
gases are used for sulphuric acid production. The mechanical 
operation of the muffle furnace, however, presents considerable 
difficulty, and although much progress has been made in recent 
years, it does not appear to have reached the development and 
application which every zinc metallurgist hopes it may do.. 

The Hegeler furnace, so largely used in America, is a mechani- 
cally worked multiple-muffle furnace, in which seven muffles 
are placed one above the other, two furnaces being built to form 
one block. Figures 3 and 4 illustrate the general design of 
the Hegeler furnace. 

The three lowest muffles are heated by producer gas, the flame 
passing first under and then over them. The ore is rabbled 
mechanically by rakes attached to iron rods, so that it travels 

1 " The Utilisation of the Sulphur Contents of Zinc Ore," H. M. Ridge, 
Journal of the Society of Chemical Industry, 1917, vol; xxxvi, pp. 676-685, 

8 7 



THE ZINC INDUSTRY 

from shelf to shelf, finally being discharged through an opening 
in the lowest shelf. The rakes are drawn through the furnace 
by chains, and after passing through the furnace in one direction 
are moved to the level of the next shelf, and then drawn 
through this in the opposite direction. This allows of cooling 
the stirring mechanism whilst outside the furnace. 

These furnaces occupy a very large floor area, and the capital 




FIG. 3. HEGELER ROASTING FURNACE. SECTIONAL ELEVATION. 
H=MUFFLES. C = GAS FLUES. 



outlay is large. They have been adopted in America on account 
of the scarcity and dearness of skilled labour and because coal 
is cheap. It is stated that the repair bill of the Hegeler furnaces 
working on the Continent is such that there is no appreciable 
saving in cost of roasting as compared with hand-rabbled 
furnaces. With 8-hour shifts 17 men are required per shift, so 

88 



THE SMELTING OF ZINC ORES 



that there is no reduction in the 
actual number of men as compared 
with hand furnaces, but, with the 
exception of a few mechanics, the 
men can be of the unskilled labour 
class. 

A 75-ft. furnace roasts 48 tons of 
ore to a sulphur content of 1-25 per 
cent, in 24 hours, with a consumption 
of coal of about 30 per cent, of the 
raw ore. The gases from the roasting 
contain 4-75 per cent, by volume of 
sulphur dioxide and are utilised for 
the manufacture of sulphuric acid. 

The improvements in the Hegeler 
furnace since its introduction about 
thirty years ago have been only in 
structural features and mechanical 
details. Most of the new zinc- 
smelting plants in the eastern coal- 
fields of the United States are 
designed to make sulphuric acid, 
and are equipped with mammoth 
Hegeler furnaces capable of roasting 
about 50 tons of blende per day. 

Another muffle furnace operated 
mechanically which is being experi- 
mented with in Europe, and to a 
certain extent in America, is the De 
Spirlet furnace, invented by a 
Belgian engineer of that name. This 
is a multiple-hearth turret furnace, 
in which the alternate hearths rotate 
and the ore is stirred by means of 
special bricks projecting downwards 
from the hearth above. 

In consequence of there being no 
metal parts inside the furnace in 
contact with the ore, the fuel con- 
sumption is low. The capacity of 
the furnace is 3 to 3-5 tons per 24 





J 



i \ 

'=. 

~ 




_i 



THE ZINC INDUSTRY 

hours. Good results are stated to have been obtained, but the 
campaign is short, and as soon as one or two of the projecting 
bricks which stir the ore wear or break off, the furnace chokes 
and has to be cooled. 

In this country several Merton roasting furnaces have been in 
use in South Wales for some years. This furnace, which is of 
the open-hearth reverberatory type, has three superposed hearths 
and a special finishing hearth, the ore being stirred by means of 
revolving iron rabbles attached to vertical shafts which pass 
through the top of the furnace and through all three hearths and 
are supported in sockets below the lowest hearth. There are 
four sets of rabbles for the main hearths, and one or sometimes 
two water-cooled rabbles for the finishing hearth. The motion 
of the rabbles gives a circular rabbling to the ore, and produces a 
slow forward movement of the ore owing to the paths of the 
rabbles slightly overlapping. The hearths are level and com- 
municate with one another by short vertical channels. The 
crushed ore is fed in at the coolest part of the uppermost 
hearth, is gradually drawn by means of the rabbles along each 
hearth, and finally discharged through an opening in the finish- 
ing hearth into a truck below it. The necessary heat is supplied 
by a fire-place at the end of the finishing hearth near the discharge 
opening. The furnace in use at one of the Swansea works has 
four hearths 10 ft. wide, with four sets of rabbles. The finishing 
hearth is 6 feet wider than the others, and has two rabbles 
cooled by circulating water in the usual way. 1 

The latest type of mechanical-rabbled furnace used in this 
country for roasting zinc blende is the Ridge furnace illustrated 
in Figs. 5 and 6, which appears to be gaining favour. 

It consists of three muffles placed one above the other, and is 
gas fired, the gas being burned only under the bottom muffle or 
hearth, experience having shown that it is not necessary, with 
proper design, to pass the fire gases both beneath and then above 
the bottom muffle as is frequently done. The general design 
of the furnace is shown in the illustrations. The ore is 
stirred by means of iron rabbles attached to four vertical iron 
shafts passing through all the roasting hearths and made to 
revolve by suitable mechanism beneath the furnace. The 
shafts are each made in one piece and are water-cooled ; about 
15,000 gallons of cooling water are passed through the shafts in 

1 Gowland, " Metallurgy of Non-ferrous Metals," London, 1914, p. 29. 

90 




%, i 




THE ZINC INDUSTRY 

24 hours to prevent overheating. The rabbles which stir the 
ore are easily and quickly renewed and the part to be replaced 
weighs only 5 Ib. The ore is fed continuously to the drying 
hearth on top of the furnace and passes over three roasting 
hearths and finally to the cooling hearth, where it serves to 
preheat the air required for the oxidation. The mechanism 
of each furnace is driven by a separate electric motor of from 
8 to 10 horse-power. The motor and all the gearing are on a 
solid foundation beneath the furnace and fully accessible. The 
discharge opening is separated from the gearing by a brick wall 
to keep out all dust. The furnace runs noiselessly, the only 
sound being the hum of the motor. In this furnace Broken Hill 
zinc concentrates are roasted down to 0-75 per cent, total sulphur 
with a feed of 12 tons of ore per day of 24 hours and a coal 
consumption of 10 per cent. The sulphur fumes leave the furnace 
with 6J to 8J per cent, sulphur dioxide and at a temperature 
of 380 C. so that they can be used satisfactorily for sulphuric 
acid production in the lead chamber process. One man per shift 
can attend to the furnace and the producer. 

Zinc concentrates with 14 per cent, lead have been satisfactorily 
treated, and also concentrates with 17 per cent, iron ; when roast- 
ing an ore, high in lead or iron, it is essential that a mechanical 
furnace be kept working continuously, because half an hour's 
stoppage means that the ore on the hearths sets hard and forms 
lumps which have to be broken up. It has been found possible 
in this furnace to use the rabbles for breaking up the lumps, and 
the gearing can, if necessary, be run alternately backwards and 
forwards till the hearths are free. 

Reduction and Distillation. The extraction of the zinc from 
the calcined or roasted ore is effected by mixing it with crushed 
coal or coke and exposing it to a high temperature in fire-clay 
vessels or retorts so as to reduce the zinc oxide. The carbonaceous 
matter must be in excess to prevent the formation of carbon 
dioxide, which acts as an oxidising agent on zinc vapour, in 
which condition the reduced metal is obtained. 

The vapour distils off and is condensed to liquid metal in 
clay receivers attached to the retorts, and a continuous stream of 
carbon monoxide issues from the retorts. 

Owing to the chemical and physical characteristics of the 
metal, the extraction of zinc from its oxide by distillation is by 
no means as simple as the reduction of most other metallic 

92 



THE SMELTING OF ZINC ORES 

oxides. The reaction between zinc oxide and carbon is highly 
endothermic, and cannot therefore take place without external 
heat. Whether, and to what extent, zinc oxide is reduced 
by carbon monoxide is still a question of much controversy. 
The oxide is not sensibly reduced by carbon below a 
temperature of 1125 C., and in modern practice the retorts 
require to be heated to 1400 C. to effect the reduction. 
At this temperature the reduced metal is in the condition of 
vapour, and is not only extraordinarily susceptible to ordinary 
oxidising influences, such as air and water vapour, but is capable 
even of being oxidised by carbon dioxide. In ordinary distilla- 
tion practice so small an amount as 0-25 per cent, of carbon 
dioxide in the retort is quite inadmissible, hence the great impor- 
tance of keeping excess of carbon in the retorts. 

Under these conditions the condensation of the zinc vapour 
to liquid metal is a matter of considerable difficulty, as it can 
only be effected within a limited range of temperature, viz., 
between 415 and 550 C. Below 415 C. it condenses to a powder 
called zinc fume or powder, which consists of finely divided 
metallic zinc mixed with zinc oxide to the extent of 6 to 10 per 
cent. If the temperature is much above 550 C. the vapour is 
not condensed at all. 

Another difficulty also attends the condensation. If the zinc 
vapour is much diluted with other gases, it will not condense to 
fluid zinc, but only as zinc fume. 

The facility with which zinc oxide is reduced is also affected 
by the temperature at which it has been produced in the pre- 
liminary roasting of the ore. The oxide obtained by roasting 
zinc blende requires a higher temperature for reduction than that 
from the calcination of the carbonate. Also, the higher the 
temperature at which zinc blende has been roasted, the higher is 
the temperature required for the reduction of the resulting 
oxide. 

According to W. Me A. Johnson, 1 pure zinc oxide is reduced by 
charcoal at 1022 C., and by soft coke at 1029 C. When, 
however, the zinc oxide is roasted at 1100 C., reduction with 
soft coke only takes place at 1048 C., and on roasting the zinc 
oxide at a temperature of 1300 C., reduction is not effected 
until a temperature of 1061 C. is reached. In actual practice 

1 American Electrochemical Society, see Electrochemical Industry 
Journal, 1904, ii, pp. 185-187. 

93 



THE ZINC INDUSTRY 

it does not appear to be an invariable rule that the reduction 
temperature is dependent on the temperature at which the zinc 
oxide has been produced, and further investigation on this point 
appears to be necessary. 

It is customary among smelters of other metals to speak of 
the metallurgy of zinc as behindhand and lacking in the care and 
completeness which characterise their own practice. When, 
however, the inherent difficulties attached to the art of extracting 
zinc, as outlined above, are appraised at their proper value, this 
reproach is unmerited. Much as it leaves to be desired, the 
modern metallurgy of zinc is not substantially inferior in its 
methods and practice to that of the other metals in common use. 
The difficult and peculiar conditions attending the reduction 
and distillation of zinc render it necessary to adopt special 
methods of extraction, since owing to these conditions the metal 
cannot be extracted in large quantities in blast or reverberatory 
furnaces, as is the common practice with other industrial metals. 
In zinc extraction the ore charges, which are necessarily kept 
in the condition of coarse powder throughout the operation, are 
very poor conductors of heat, and to extract the metal it is 
necessary to supply heat energy continually by external heating 
of the retorts. This imposes a maximum charge thickness of 
about 8 in., a 24 hours' reduction period (from charging to re- 
charging), the provision of small-sized retorts of specialised con- 
struction, and with only about six weeks' life, and generally the 
handling of large bulks of raw material in very small quantities. 
Also/ it does not pay to carry the extraction of the zinc below a 
certain limit, consequently the residues are dumped when still 
carrying several units of zinc. Nevertheless, viewing the present 
status of the practice in zinc smelting, one cannot but be 
impressed by the high extraction results, the low consumption 
of fuel made possible by modern methods of gaseous firing and 
the reduction of labour involved in the process. 

The methods of distillation now in use may be conveniently 
classified into (i) Belgian, (2) Silesian and (3) Rhenish or Belgo- 
Silesian. The chief differences in these methods are in the shape, 
size and arrangement of the retorts in the furnace. 

The retorts in the Belgian process are circular or slightly 
elliptical in cross section, about 8 in. in diameter, 4 to 4^ ft. 
average length and arranged in the furnace in from two to seven 
rows. 

94 



THE SMELTING OF ZINC ORES 

In the Silesian process there is, as a rule, one row of large, 
narrow, muffle-shaped retorts to each furnace, although occasion- 
ally two rows are used. On an average the retorts are 5j ft. 
long, 2j ft. high and 6 to 8 in. in breadth. The Rhenish process 
employs retorts somewhat larger than those used in the Silesian 
process ; they are muffle-shaped or elliptical, and arranged in 
two or three rows. This type is a combination of the best features 
of the Belgian and Silesian types, and is the one now very gener- 
ally adopted in erecting new plant. The retorts are about 5 ft. 
long, 13 in. high and 6 in. wide. A modern type of Rhenish 
retort is shown in Fig. 7. 



13 ns 
i 







5 2 ft *> Cross 

Longitudinal Section of Retort. Section. 




Retort with Condenser attached. 
FIG. 7. RHENISH RETORT FOR ZINC DISTILLATION. SECTION. 

The Belgian and Silesian furnaces formerly in extensive use 
are being replaced on the Continent and in England by the 
Rhenish type of furnace. The Belgian type of furnace is 
however, still in use in the United States, although here 
also in the more recently erected plants the furnaces have 
been so modified that they may be classified as Rhenish. The 
type of retort used in the United States is practically the same 
for all plants. The length of the retorts varies from 4 ft. to 
4-5 ft. in length, according to the size of the furnace, with a 
circular interior of from 7*5 to 8-5 in. in diameter. 

To the mouth of each retort is luted a simple fire-clay nozzle 
or condenser, in which the zinc accumulates, and again fitted 
over the mouth of the condenser is a conical sheet-iron tube or 
prolong, which serves to condense and collect the " fume " 

95 



THE ZINC INDUSTRY 

which passes over along with the zinc during the distillation, and 
which is detached by the workmen and returned to the retorts 
with a subsequent charge. The condensers vary in form according 
to the retort capacity, type of furnace and system of distillation. 
They may be plain clay cones, conical-bellied to act as a metal 
receptacle, or Q -shaped. They are made of less refractory clay 
than the retorts, and are sometimes coated with limewash, to 
facilitate the removal of adherent material. 

Manufacture of Retorts and Condensers. The manufacture of 
retorts and condensers is always carried out in close proximity 
to the smelting works, and forms a most important branch of 
the art of zinc extraction, since owing to the nature of the process 
of distillation there is a constant destruction of retorts, their 
life in modern practice being usually from forty to forty-five 
days. 

The retorts were formerly made by hand, but in modern practice 
they are shaped by means of a hydraulic press capable of making 
250 in a nine-hour shift. Machine-made retorts are greatly 
superior to those made by hand, as they are denser and on this 
account more durable and less permeable by zinc vapour. The 
material used for the manufacture of the retorts must be 
extremely refractory, and considerable difficulty is frequently 
experienced in obtaining clay suitable for the purpose. The raw 
clay needs careful weathering and pugging before use. Usually 
retorts are made of a mixture composed of burnt clay, or chamotte 
and sufficient raw clay to act as an efficient binding agent. In 
modern practice, finely-divided coke is often used to replace 
part of the chamotte, as it assists in retaining the shape of the 
retort under great heat and gives density and impermeability. 

A typical retort mixture would consist of l : 

Crushed burnt clay (chamotte) . . . . 50 parts. 

Raw clay .. .... ... .. 40 ,, 

Finely-ground coke .'. ' v. '.'. . . 10 ,, 

The retorts are dried very gradually by standing upright in 
rows in chambers heated to a moderate temperature, and before 
being placed in the distillation furnace they are tempered by 
gradually heating in kilns until they attain a full red, in which 
condition they are transferred to the furnace and luted in position. 
An old zinc retort shows a great alteration of texture, zinc oxide 

1 J. C. Moulden, op. cit., p. 510. 

96 



THE SMELTING OF ZINC ORES 

reacting with the alumina of the clay to form zinc spinel, 
ZnO.Al 2 O 3 , silica being liberated. 

In modern plants, the condensers are moulded by means of 
a machine capable of producing from 1,000 to 1,200 per shift 
of nine hours. The mixture used consists of crushed old retorts 
and raw clay, and after leaving the moulding machine they are 
carefully dried and burnt before use. 

The question of refractories for use in connection with zinc 
furnaces has recently received considerable attention, and the 
Ceramic Society has appointed a sub-committee to prepare a 
report on the subject. 

A modern distillation furnace consists of an arched chamber 
containing a large number of retorts arranged nearly horizontally 
in two or three superimposed rows, one above another, and 
supported only at both ends in order that they may be sur- 
rounded by flame. Usually the retorts are arranged in two sets, 
back to back, with an intervening space for the gas and air- 
ports, the furnace being heated by producer-gas firing. The 
substructure of the furnace is usually arranged for preheating 
the air, or the air and the producer-gas, by a transference of 
heat from the waste gases of the furnace. Formerly reversing 
regenerative furnaces on the Siemens system were used, but 
in recent years counter-current recuperative furnaces have come 
into favour. The laboratory part of a zinc furnace, with retorts, 
without condensers attached, is shown in Figs. 8 and 9. 

The older zinc furnaces were direct-fired by coal, but all modern 
furnaces are gas-fired. This results in economy in labour, fuel 
and repairs. The gas producers are built either in, or near, the 
furnaces, or in some cases entirely independent of them. 

The ordinary life of a zinc furnace is about six years, but some 
regenerative furnaces have given good results even after eight 
to ten years. 1 

The zinc furnaces on the Continent hold from 100 to 240 
retorts ; the weight charged per retort is, according to its size, 
from 35 to 50 kg. of ore, plus 40 per cent, reduction coal, or a 
total of 47 to 70 kg., with 17 to 25 kg. of zinc. 

The zinc dust produced varies, with the character of furnace 

and ore, between 4 and 10 per cent, of the spelter produced. The 

loss in metal varies between 10 and 15 per cent, according to the 

class of furnace and quality of ore. The durability of the retorts 

1 J. Gilbert, Mining Journal (London), 1916, vol. cxiv, p. 496. 

97 H 



THE ZINC INDUSTRY 

varies from thirty to forty-two days or more with three tier 
furnaces ; that of the tubes varies between eight and twelve 




FIG. 8. ZINC DISTILLATION FURNACE. CROSS SECTION. 




FIG. 9.' ZINC DISTILLATION FURNACE. FRONT ELEVATION. 

days. The cost of retorts of 1,800 mm. length is about 45., and 
that of the tubes from $d. to 6d. each. 

The German zinc smelters have closely watched the develop- 
ments in gaseous firing, and in recent years the furnaces of the 

98 



THE SMELTING OF ZINC ORES 

regenerative type have been replaced by counter-current or 
recuperative furnaces. This development was being carried out 
very quickly in Silesia in the last two years before the war in 
consequence of the rapid increase in the price of coal, which made 
it imperative for the smelters to economise in fuel. By replacing 
the regenerative furnaces by counter-current recuperative 
furnaces the German smelters reduced their fuel consumption 
appreciably and got higher extraction results in the distillation. 
The type of furnace which is in most general use in this country 
is the reversible regenerative gas-fired, but some of the newer 
plants have recuperative furnaces. 

In America, natural gas has been extensively used for heating 
distillation furnaces, and has become a very important 
factor in the economic production of zinc in that country. 
The utilisation of these natural gas resources has permitted 
of the establishment of zinc distilleries in districts which 
otherwise offer no special advantage, the capital required 
and the working costs being so lowered thereby as to offset any 
disability attaching to transport of ore, clays, reducing material 
and finished product. 1 

The process of distillation is not continuous, but consists 
of a well-defined cycle of operations repeated every twenty-four 
hours. 

The reduction of the zinc oxide in the roasted ore is effected 
by mixing it with about 40 per cent, of its weight of reducing 
material, in the form of coke, coal or anthracite. This propor- 
tion is about 2\ times the quantity of reducing material required 
theoretically, but it is necessary in order to maintain a reducing 
atmosphere in the retorts, which is of vital importance for the 
reasons already stated. 

As an example of the method of working, a brief account of 
the smelting of Broken Hill concentrates at the Port Pirie works, 
New South Wales, may be given. 2 The distillation plant com- 
prises 10 furnaces of the Rhenish type, having two tiers of retorts, 
back to back, with three rows of 24 retorts in each tier, i.e., 
1,440 retorts in all. The retorts are elliptical in cross-section, 
and measure 5j ft. in length and 13^ in. in height. The heating 
is effected by means of producer-gas, the air required for combus- 
tion being pre-heated by a counter-current system. The burners 

1 Moulden, he. cit. p. 510. 

2 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 65. 

99 H 2 



THE ZINC INDUSTRY 

are of the Bunsen type, 18 in. in diameter, with a gas inlet of 
9 in. set in the hearth of the furnace between the two tiers of 
retorts. Each row of 24 retorts requires the attention of one 
man. The charge consists of about 10,000 Ib. of roasted ore 
concentrates, 3,000 Ib. of coke, and 1,500 Ib. of coal. This is 
thoroughly mixed on the furnace floor and fed into the retorts 
through the condensers. 

Usually the top and middle rows of retorts receive this charge, 
but the lower row, which does not get so strongly heated as the 
others, is charged with coke and material scraped from the 
condensers during tapping, consisting of zinc oxide and waste 
zinc. 

The ends of the condensers are next partly stopped by luting 
on to them cast-iron tiles which have an inner lining of fire-clay 
and a hole for the passage of the evolved gases. This hole has a 
small projecting collar, into which is fitted the small end of a 
conical " prolong." These iron prolongs serve to collect the zinc 
dust not retained by the condensers. The temperature of the 
retorts is slowly raised until it reaches 1325 to 1350 C. The 
workman judges of the progress of the operation by the colour 
of the flame or vapour which is evolved. 

When the distillation is complete, the prolong is removed, 
and, on releasing the iron tile, the molten zinc flows out and is 
caught in an iron ladle. The condenser is next scraped to 
remove all zinc and dross. The residue in the retort is removed 
by pulling down counterbalanced sheet iron aprons in front of 
the furnace to screen the men from the heat, and raking through 
holes. The residues fall out and are deflected by the apron 
into trucks below, whence they are sent to the lead blast furnace 
for the recovery of the lead and silver they contain. 

Damaged retorts are next located, and after these have been 
replaced charging is recommenced. The whole series of opera- 
tions occupies twenty-four hours. The recovery of zinc as 
spelter and zinc dust is stated to amount to about 80 to 85 per 
cent, of the quantity present in the ore. 

The zinc dust collected amounts to about 12 per cent, of the 
total zinc obtained and contains about 92 per cent, of metallic 
zinc. This is sometimes returned to the furnace for recovery 
as spelter. The spelter contains from 2 to 3 per cent, of lead and 
is refined by being melted in a reverberatory furnace. 

In modern works large condensers are used and the metal is 

100 



THE SMELTIN^ g 

tapped once only into a mechanical ladle running along the 
furnace front, but with the ordinary small condensers the metal 
is tapped three or four times during distillation, and hand ladles 
are used for conveying the molten metal to the ingot moulds. 
The formation of some zinc powder is inseparable from distilla- 
tion, but the proportion varies according to the method of working 
and may be deliberately controlled by placing common salt or 
other haloid salt at the mouth of the retort or even in the con- 
denser. 

This method has been very successful and is the subject of 
a patent by H. W. Webster and J. C. Moulden (British Patent 
No. 26788, 1910). In Belgium, salt is added to the charge for 
the same purpose. The amount of zinc dust produced varies 
in Continental works from 4 to 10 per cent., according to the 
class of ore and furnace employed. 

The exhausted residues drawn from the retorts in the case 
of clean ores are usually thrown away. The composition of 
the residues naturally depends on the composition of the ores 
treated, and with average ores they may be said to contain 
as a rule from 4 to 8 per cent, of zinc. Residues containing 
lead and silver constitute an important by-product in zinc 
smelting and have been considered on p. 118. 

In European practice, the amount of metal extracted by the 
distillation process is very generally referred to in terms of the 
percentage calculated upon the metal content of the roasted ore, 
since the smelter generally buys roasted ore and has no knowledge 
of the zinc content of the original sulphide ore. 

The extraction of the zinc under modern European methods 
is given in broad terms as between 80 and 90 per cent., calculated 
on the roasted ore contents. 

Thus the loss of zinc during smelting is large in comparison 
with the losses sustained in the different metallurgical opera- 
tions employed for the production of other industrial metals. 
The zinc losses are subject to wide variations, according to the 
grade of ore, the impurities present and the care exercised in 
working. In the treatment of high grade ore carrying from 
45 to 50 per cent, of zinc, as smelted in the best operated plants 
in Europe and in America, the loss is between 10 and 15 per cent. 

A very sensible proportion of the total amount of zinc extracted 
from the ore is derived from the treatment of by-products, 
consisting of crusts of metal and oxide chipped off the con- 

101 



J&DUSTRY 

densers, condenser scrapings, oxide and dross from the metal 
ladles, all of which are recharged into the retorts. 

Refining of Crude Zinc. When pure ores have been employed, 
the zinc obtained by the distillation process is generally sufficiently 
pure for industrial purposes, but to ensure uniformity of product 
as far as possible it was formerly usual to remelt it in large kettles 
and recast it. The metal is poured into open iron moulds so as 
to produce slabs or cakes about 17 in. by 8 \ in. by 2 \ in., weighing 
from 45 to 5 lb., an d bearing the name of the smelting 
company. 

Metal containing impurities such as lead is first submitted to 
a refining process known as liquation. This consists in melting 
the impure metal in large reverberatory furnaces with sloping 
hearths, holding from 20 to 30 tons. 

As the slabs melt the metal runs down and collects in the well, 
or sump, situated at one end of the furnace bed, where it is 
kept molten at as low a temperature as possible. 

The bulk of the lead separates by gravity and accumulates 
at the bottom of the bath, while the zinc, largely freed from lead, 
forms an upper layer from which the metal is ladled and cast 
into slabs as it collects. 

With the exercise of every care, however, it is seldom that by 
this means the amount of lead can, in ordinary practice, be 
reduced below 1-4 per cent. 

Several methods have been proposed in recent years for elimin- 
ating the lead in zinc-lead concentrates during the distillation 
process. One of these in use at Irvine, on the Firth of Clyde, 
consists in placing a filter of carbon, fire-brick, or other crushed 
and porous material in the mouth of the ordinary retort. This 
filter retains the lead while the zinc vapour passes through and 
is condensed. 

Both filters and darns are in use in America and are effective 
in reducing the lead and iron content of the zinc, but have no 
apparent influence on the cadmium. Their effect is shown in the 
figures on p. 103 which give the lead content for different 
tappings of zinc. 1 

Their use has also reduced the iron content of the zinc from 
0-07 to 0*02 per cent. Dams, however, have not found favour 
in the works, as they tend to reduce the yield of spelter. 

1 " Zinc Refining," L. E. Wemple, American Institute of Mining Engi- 
neers, 1917. 

IO2 



THE SMELTING OF ZINC ORES 





First draw 


Second draw 




of zinc. 


of zinc. 




Lead 


Lead 




per cent. 


per cent. 


Condenser without dam 


0-58 


1-48 


Condenser with dam 


0-28 


0-36 


Condenser without filter 


0-66 


1-28 


Condenser with filter 


0-14 


0-15 



Another method, devised by Sulman and Picard, consists in 
briquet ting the material with bituminous coal and pitch, and 
distilling the briquettes in an ordinary distillation furnace, 
when the carbonaceous residue is found to retain most of the 
lead in the metallic state, and is suitable for lead smelting. In 
this process the filtration of the lead takes place in the pores of 
the briquette itself. 

The highest grades of zinc have to be produced either by the 
distillation of pure ores, by the redistillation of commercial spelter, 
or by special methods, such as electrolytic separation. The 
redistillation of ordinary spelter is responsible for considerable 
quantities of the high-grade zinc on the market. It has been 
largely used in America, especially since the outbreak of war, 
large graphite retorts being used for the purpose. Redistilla- 
tion has also been carried out in electric furnaces in Norway and 
Sweden and has been very successful. It seems probable that 
the electric furnace will find extended application for this purpose 
in the future. 

According to Juretzka, 1 " electrically heated furnaces are 
much more advantageous for the redistillation of zinc than the 
ordinary gas-heated muffle furnaces, as the temperature can be 
closely adjusted. A central condensing system is more eco- 
nomical than muffles fitted with condensers, and enables the 
process to be carried out under reduced pressure. High-grade 
zinc containing 997 to 99-8 per cent, of zinc is obtained from 
refined metal containing lead i-o per cent, and iron 0*03 per 
cent, by distillation at low temperatures in electric furnaces. 
The yield of pure metal is from 70 to 75 per cent." 

1 " Manufacture of Pure Spelter," F. Juretzka, Chem. Zeit., 1916, xl, 
pp. 885-886, 894-896. (Abstract, Journal of Society of Chemical Industry, 
1916, xxxv, p. 1263.) 

103 



THE ZINC INDUSTRY 

Redistillation is essentially a fractional distillation process, 
the more readily volatile zinc being distilled and condensed, 
leaving behind the lead and iron in the distillation vessel. When, 
however, much lead is present in the crude zinc, the separation 
of this metal is never complete by redistillation. The process 
still leaves more than 0-25 per cent, of lead in the redistilled metal, 
and cadmium when present is also carried over with the zinc. 

The electrolytic process, where available, produces a higher grade 
of spelter from impure ores than does the distillation process ; 
a large portion of these impurities in the ore, which by the 
distillation process would be carried into the spelter, is removed 
in the leaching of the ore and the purification of the zinc solution. 

Recent Advances in Zinc Smelting 

Whilst progress has been made in the metallurgy of zinc of 
late years, it has not been characterised by any great change 
in method, or by the discovery of new principles, but rather by 
a continuous and steady improvement in detail, an increase in 
the productive capacity of the existing works, and by the installa- 
tion of new plants. Nevertheless, the minor changes have been 
important, and have been directed mainly towards higher extrac- 
tion results and the reduction of labour. Whilst several new 
processes of zinc extraction are being experimented with on a 
comparatively small scale, these are not yet sufficiently developed 
to determine their influence on the future methods of metallur- 
gical treatment of zinc ores. 

The principal changes in zinc smelting in recent years are 
in the method of firing, first by the introduction of gas 
producers and reversing regenerative furnaces, and then by the 
adoption of counter-current regenerative furnaces, the use 
of machine-made retorts, the increase in the size, shape and 
dimensions of retort, from the Belgian to the Rhenish type, 
the use of improved condensers, large ladles for tapping, 
refining the metal without remelting, and mechanical mixing 
and transport of materials. 

By these means the cost of production has been reduced and 
the yield of metal increased. 

In the old direct-fired furnaces the coal consumption was over 
two tons per ton of ore smelted, whereas in modern gas-fired Bel- 
gian furnaces the consumption of coal for fuel is about 1-6 tons per 

104 



THE SMELTING OF ZINC ORES 

ton of ore smelted. For Rhenish gas-fired furnaces the average 
has been about i-i to 1-2 tons, but at present it is i ton 
of coal per ton of ore ; much necessarily depends, however, on 
the quality of the coal. With a view to the reduction of the 
cost of labour, mechanical appliances for charging and cleaning 
the retorts have been introduced in several European works, 
and more recently in American works, but they have not yet 
come into general use. 

The ore charged into the retorts generally contains about 45 to 
50 per cent, of zinc. The weight of the charge varies with the 
size of the retorts, the Belgian retorts in the United States taking 
about 60 Ib. plus a small quantity of by-products, exclusive of 
reduction material, whilst for Rhenish retorts in Europe it is 
from 85 to no Ib. Although the Saeger charging machine is 
now in regular use at the works of the National Zinc Company 
at Bartlesville, Oklahoma, 1 where it was introduced in 1913, the 
common arrangement of the distillation furnaces in American 
works is unfavourable to the use of a charging machine, American 
practice being to set the furnaces in parallel, whereas in modern 
European practice they are commonly set in series, i.e., in a 
single row, thus allowing more room for manipulation. Machine 
charging takes one hour, as compared with three hours for hand 
charging, and the ore is charged more densely, enabling 2,000 Ib. 
more ore to be charged into each furnace. 

Two difficulties, however, attend machine charging when 
applied to the excessively fine flotation concentrates now coming 
to the zinc smelters. This very fine ore sticks to the augers, 
necessitating frequent cleaning during charging, and also tends 
to " blow out " with considerable force, sometimes only twenty 
minutes after they have been charged. 

The method of removing the residue from the retorts generally 
employed in Europe is to rake them by hand into a pit in front 
of the furnace ; in America the common practice appears 
to be to use a long iron pipe, with water flowing from the end, 
which is pushed to the back of the hot retort, where the water is 
converted into steam by the heat, throwing the charge forward. 

By this method a considerable amount of fine material is blown 
away, causing loss of any silver or lead contained in the residue. 

A retort-discharging machine has recently been patented by 
J. J. Simmonds, of lola, Kansas, which in the opinion of some 
1 " Mineral Industry," 1915. 
105 



THE ZINC INDUSTRY 

distinguished American zinc metallurgists has solved the problem 
of mechanically discharging retort residues. It is stated that 
the machine has been installed at three zinc-smelting works in 
America. It consists essentially of a truck carrying a series 
of bars, or plungers, with sprockets at each end of the bar, 
over which travels an endless chain of scrapers. The machine 
is run up facing a tier of retorts, into which the scrapers are 
introduced and set in motion, the mechanical arrangements being 
very ingenious. The scraper chains are sprayed with water to 
keep them cool. 

Careful attention is also given in America to the gangue con- 
stituents of the ore and the composition of the ash from the 
reducing agent employed, with the view of reducing the amount 
of slagging in the retorts. Iron, lime and manganese are the 
most objectionable impurities. Few American smelters care to 
have more than 2j per cent, of iron present, but in Europe 7 
to 8 per cent, is allowed, whilst ore with even as much as 22 
per cent, has been successfully smelted. 

The utilisation of the unburnt coal in retort residues is another 
matter claiming the attention of American zinc smelters. 
The residues, which contain a good deal of unburnt coal, are 
screened, and all material over J in. in diameter is mixed with 
about 20 per cent, of fresh coal and used as fuel under steam 
boilers. So far this mixture has proved serviceable at the works 
of the Edgar Zinc Company, and ten boilers are now fired in 
this way. 

In modern German and Belgian practice a 90 to 94 per cent, 
yield of spelter is constantly reached with roasted blende carrying 
50 per cent, of zinc. In the Western States of America the yield 
from a 40 per cent, ore is stated to be about 75 to 80 per cent., 
but in the newest plants efforts have been made to bring the 
yield up to that in Continental works. 

Before the outbreak of war the English zinc smelters could not 
claim equality with the better Continental practice, the yield 
in this country in the past having been generally nearer 85 per 
cent. Although progress has been made in British works during 
the past decade, and gas-fired furnaces have almost completely 
replaced the older Welsh-Belgian type, much remains to 
be done in the older works to bring British practice up to the 
level attained in several Continental centres. During the past 
four years, however, there has been a considerable advance in 

106 



THE SMELTING OF ZINC ORES 

the methods of British zinc works, and wherever new plant has 
been erected it has been of modern type, and should be productive 
of results equal to those obtained on the Continent. 

In the past many attempts have been made to use vertical 
retorts in the distillation process, with the view of reducing 
the labour of charging and discharging the retorts, which is the 
principal part of that required in distillation. Hitherto such 
attempts have not been successful, mainly owing to the charge 
hanging in the retorts and preventing the gases and zinc vapour 
from escaping properly. More recently, however, the question of 
vertical retorts has been taken up on the Continent, and as the 
result of experiment it is now claimed that the old difficulties 
have been overcome. The reduction of the charge has been 
made a continuous process by the employment of vertical retorts 
in the Roitzheim-Remy furnace installed at Hamborn in West- 
phalia. In this process, " continuous reduction is obtained by 
feeding the preheated charge of ore into the top of a vertical 
retort, and discharging the cooled residue mechanically from 
the bottom of a cast-iron cooling chamber. 

" The retort is open, top and bottom, but is sealed from the 
atmosphere by the charge and ashes. The clay condenser is 
arranged perpendicularly to the retort in a niche suitably heated, 
the front end being connected to a tube leading to the ' prolong ' 
catching the zinc dust, and the escaping carbon monoxide is 
burnt to ascertain if uncondensed zinc is present, the gases being 
passed into the main chimney. The furnaces are heated by 
gaseous fuel on the regenerative principle, and require little 
attention beyond superintendence of the machinery and tapping 
of the zinc once in twenty-four hours. Zinc of 98-6 to 99-0 per 
cent, purity is obtained, and is fairly free from lead. Several 
advantages over the Rhenish smelting system are claimed for 
the process, including the reduction, by 40 per cent., of the 
labour required, the lessened consumption of refractory materials 
in muffles and condensers equal to about 45 per cent., and a 
saving in tools, machine work, heating coal and general costs, 
but against these economies must be set the greater use of power 
for driving the discharging machinery, pumping cooling water, 
etc. 

"The net result is stated to be, in the production of 15,700 metric 
tons, a saving of about 20,000 (407,000 marks). 

" There are also the advantages of increased extraction, smaller 

107 



THE ZINC INDUSTRY 

mechanical losses of ore and metal, the furnaces have much less 
dead space, are easier to regulate and superintend, and the furnace 
room is free from fumes. 

"The costs of installation of both systems, without the dis- 
charging machinery, are stated to be about the same, though the 
wear and tear on the parts of the machinery are so small that their 
ultimate cost is negligible." l 

In commenting on this process, Mr. W. R. Ingalls, 2 a well- 
known American authority on zinc smelting, states that it may 
be accepted from Hr. Liebig's description, given above, that the 
continuous smelting of zinc ore in a vertical retort is an accom- 
plished fact, and the development of the Roitzheim-Remy 
furnace "should be watched carefully. 

In 1916 application was made by the Swansea Vale Spelter 
Company for the transfer of German patents relating to the 
smelting of zinc ore in vertical retorts, and the employment of 
machinery for scraping the lower part of the furnace, with the 
object of erecting vertical retorts in this country to test the 
feasibility of the process as a commercial method of zinc pro- 
duction. 

With a view to economise fuel and labour, and to render the 
process of zinc production continuous, numerous attempts 
have been made to smelt zinc ores in the blast furnace. All 
such attempts have failed, however, owing to inability to control 
the percentage of carbon dioxide which so readily oxidises zinc 
vapour at a red heat. 

The small size, confined character and presence of an excess 
of carbon in the charge are conditions which in the ordinary 
retort process result in the carbon dioxide being kept within 
the necessary limits. 

In the blast furnace the zinc can be reduced and separated from 
the ore as vapour, but owing to the conditions of working the 
vaporised zinc, which has to travel by the same outlet as the 
waste furnace gases, is much diluted with carbon monoxide and 
nitrogen, and is oxidised by the carbon dioxide invariably present, 

1 " The Roitzheim-Remy Continuous Zinc Distillation Process," by 
M. Liebig, Metall und Erz, 1916, xiii, pp. 143-156 ; also Metallurgical 
and Chemical Engineer , New York, 1916, xiv, pp. 625-629. The abstract 
quoted is from the Journal of the Society of Chemical Industry, 1916, xxxv, 
p. 846. 

a Engineering and Mining Journal, New York, 1916, cii, p. 623. 

108 



THE SMELTING OF ZINC ORES 



so that only zinc oxide is produced. Apart from the fact that 
the condensation of vaporised zinc can only be effected within a 
limited range of temperature, it has been found that the zinc can 
be oxidised by as little as 0-5 per cent, of carbon dioxide in the 
furnace gases or by water vapour. 

By rapid cooling of the furnace gases and other methods, it 
has been found largely possible to overcome this oxidation, but 
so far the process does not appear to have been generally employed 
on a commercial scale. 1 

Attention has already been drawn to the zinciferous dust 
which collects in the flues of the blast furnaces in which iron and 
manganese ores containing small quantities of zinc have been 
smelted. The percentage of zinc in the ores is very small, and 
its recovery affords an interesting metallurgical example of how 
the treatment of an iron ore, valueless as such from the point of 
view of zinc, results in a by-product containing often as much as 
75 per cent, of zinc and correspondingly valuable. 2 It is produced 
by many of the iron blast furnaces in this country and in Sweden, 
and in the works at New Jersey, in the United States of America. 
It is a most important by-product in smelting franklinite residues 
for ferro-manganese. 

Blast furnace smelting also implies the production of a fluid 
slag that will flow readily from the furnace, a condition pro- 
hibiting any excess of carbonaceous material, and one that is 
difficult to attain in view of the tendency of zinc to pass into 
the slag and render it pasty unless a high temperature is attained. 
It has been shown, however, that this difficulty may be overcome. 

In ordinary blast furnace practice a temperature of 1400 C. 
was once considered high ; but now a temperature of 1500 C. 
and upwards is reported. The conditions for low zinc retention 
in the residuum are, according to W. R. Ingalls, 3 a high tempera- 
ture and a highly calcareous slag. Slags of this nature con- 
taining less than i per cent, of zinc have been made. 

The smelting of complex zinc-lead ores in the blast furnace in 
the ordinary way suffers from two main disadvantages ; upon 
the one hand the ores contain too much lead for the ordinary 
distillation process of zinc extraction, and on the other they 
contain too much zinc for lead smelting, their reduction in the 

1 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 70. 
3 J. C. Moulden, loc. cit. p. 501. 
3 Experiments at McGill University, 1912. 
109 



THE ZINC INDUSTRY 



blast furnace being hindered by the excess of zinc, which requires 
special amounts of flux, and thus is slagged off and lost unless 
the slag is specially treated to recover the zinc. 

The recovery of zinc from slags containing large quantities 
of the metal has been carried out by H. Pape's process at several 
places on the Continent, notably at the Oker Smelting Works 
in the Lower Harz district, where it has been applied to the 
treatment of the various complex ores from the Rammelsberg 
deposits, the main varieties of which are lead ores with 9 per 
cent, of lead and 20 per cent, of zinc, and copper ores with from 
i to 15 per cent, of copper and i to 20 per cent, of zinc. The 
ores are first subjected to a sulphurising roast and leached to 
remove some of the zinc ; the residual ore is then smelted with 
fluxes in the ordinary way in blast furnaces. 

The slags, containing from 22 to 27 per cent, of zinc oxide, 
are crushed to 50 mesh, mixed with coke screenings, and the 
mixture made into briquettes by means of pitch. The briquettes 
are then raised to a high temperature in a continuous rever- 
beratory furnace, where the zinc after volatilisation as metal is 
carried off as oxide by the flue gases. After dilution with cold air, 
the gases are passed through bag-house plant to collect the oxide. 
The better quality caught in the bags is sold as a pigment, the 
rest is sent to a local zinc works, where it is used for enriching 
poor zinc ores, in order that they may be treated by the Belgian 
process. 

Under conditions of forced oxidation, such as in the blast 
furnace or blowing hearth, lead is as freely volatilised in the 
form of oxide as is zinc, a fact which has been utilised in Germany, 
where the blowing of oxidised low grade zinc-lead ores has been 
practised, bag-house plant being employed to collect the mixed 
oxide fume. This fume is then treated with sulphuric acid for 
the production of crystallised zinc sulphate, the residual lead 
sulphate being sold to the smelter. 



no 



CHAPTER VI 
, ZINC SMELTING (continued) 
By-products in the Smelting of Zinc 
Sulphuric Acid 

NOT the least important of the varied problems that present 
themselves in the extraction of zinc from its ores is the disposal 
of the sulphur dioxide resulting from the roasting of blende. 
Not only has this to be considered on the ground of health 
and the preservation of vegetation, but there is the further 
important economic consideration of utilising the sulphur 
gases for the manufacture of sulphuric acid, and thus securing 
a valuable product that is not only essential to chemical industry, 
but one that also plays an important part in many other 
industries. 

As previously pointed out, where the manufacture of sulphuric 
acid is one of the objectives, certain conditions are imposed 
upon the roasting of blende, the most important of which is the 
conducting of the operation in muffle furnaces, as the sulphur 
fumes must not be contaminated and diluted with fire gases. 

Most zinc ores are free from arsenic, consequently the sulphuric 
acid made from blende roasting usually commands a higher price 
than that made from iron pyrites, which almost invariably 
contains arsenic. On the other hand, zinc ores frequently contain 
fluorine, as calcium fluoride (fluor spar), which flotation and other 
concentrating methods have, unfortunately, not, up to the 
present, been able to separate effectively. Calcium fluoride is 
decomposed in the roasting furnace in the presence of silica and 
forms silicon fluoride, which is subsequently decomposed and 
causes the brickwork in the furnace to be appreciably attacked 
unless special precautions are adopted. 

in 



THE ZINC_ IND USTR Y 

When the sulphur dioxide from blende roasting is converted 
into strong sulphuric acid of 60 Be*, the yield from i ton of 
40 per cent, zinc blende amounts, on the average, to 80 to 90 per 
cent. Whilst the old-established English lead chamber method 
of sulphuric acid manufacture has to meet the increasing 
competition of the newer contact processes, these up to the 
present have found but little application in this country in 
connection with zinc ore roasting, although contact processes are 
in use in America and in Germany. 

The lead chamber process, when working with hand-rabbled 
roasting furnaces, has to be carefully watched because of the 
irregular evolution of sulphur dioxide in consequence of inter- 
mittent rabbling of the ore. In Germany it has been usual to 
reduce this difficulty by arranging for the furnace hands working 
on the different furnaces to start their shifts at different times, 
but, in spite of this, it is not possible to obtain a continuous 
current of uniform gas throughout the twenty-four hours, and, 
unless the process is watched carefully, loss of nitre will result. 1 

With modern mechanical furnaces this difficulty is completely 
overcome. Apart from some increase in the manufacture of 
sulphuric acid from blende roasting, there has been a large 
increase in the operation of contact plants for sulphuric acid 
production in this country since the outbreak of war, both as 
regards extension of existing works and the erection of new 
ones. Acid production was considerably increased in 1915 and 
1916, and further small increase is in prospect. The import- 
ance of contact processes is therefore claiming the attention of 
British sulphuric acid manufacturers. 

The contact process consists essentially in bringing about the 
combination of sulphur dioxide and oxygen by contact with 
heated finely divided platinum (hence the name " Contact 
process ") and hydrating the sulphur trioxide so produced in 
the presence of strong sulphuric acid. 

Hitherto the recovery of the sulphur from blende roasting 
has not received in this country the attention its great importance 
demands, and in this respect the British smelters are behind those 
on the Continent and in America, who have for some years given 
considerable attention to the production of sulphuric acid as a 
valuable secondary product of zinc smelting. As recently 

1 H. M. Ridge, " The Utilisation of the Sulphur Contents of Zinc Ore," 
Journal of the Society of Chemical Industry, 1917, vol. xxxvi, pp. 676-684. 

112 



ZINC SMELTING 



pointed out by Moulden, it is now the practice in most European 
and many American works to carry on the blende roasting in 
conjunction with the manufacture of sulphuric acid, and this 
for two main reasons : (i) the restriction imposed by legislation 
in most thickly populated districts upon the discharge of 
sulphurous gases into the atmosphere, and (2) the value of 
sulphuric acid in such localities, due to the fact that they are 
consumers of the acid, and it therefore pays to utilise the 
sulphur. 

It is not uncommon in Europe to find the roasting and the 
manufacture of sulphuric acid carried on in one district where the 
call for the acid is considerable, and the roasted ore distilled in 
another where conditions as to fuel, clay and labour are the more 
favourable. Economic considerations govern, of course, each 
individual case, and this system has reached its greatest 
development in Belgium and Germany, largely owing to the 
abundant and cheap facilities for transport afforded by the 
various canal systems. 

SULPHURIC ACID PRODUCTION IN UPPER SILESIA. 



Year. 


Raw 
blende 
roasted. 


Sulphuric 
acid 
reduced 
to 50 Be. 


Sale A 


ralue. 




Metric 
tons. 


Metric 
tons. 


Total 
marks. 


Metric ton of 
50 B6. acid. 


1887 
1891 

1895 
1899 
1903 
1907 
1911 
1912 


53,882 
66,236 

84,857 
123,602 
187,596 
421,006 
411,352 


21,013 
32,676 
33.229 
64,029 
104,268 
139,840 

213,317 
254,008 


479,000 
746,000 
778,000 
1,074,000 
1,728,000 
2,187,000 
3,025,000 


Marks. 
22-81 
22-85 
23-43 
l6 /77 
16-62 

15-65 
14-18 



To illustrate the importance of the utilisation of the sulphur 
of zinc ores, Ridge gives the above figures for the output 
for Upper Silesia prior to the war. In normal times this 
district produces about 60 per cent, of the spelter made in 
Germany, but a considerable amount of calamine ore is still 

113 i 



THE ZINC INDUSTRY 

available there, so that the maximum production of sul- 
phuric acid from blende has not yet been reached ; the 
tonnage of calamine treated is, however, steadily decreasing, 
but this is compensated for by an increase in the amount of 
blende treated, and permits of an increasing spelter and acid 
production. The last figures available are for 1912, and the 
table on page 113 shows the results for every fourth year 
since 1887. 

The rapid annual increase in the production of sulphuric acid 
in the Upper Silesia district in recent years is shown by the 
following statement. In 1900 the production of sulphuric acid 
per ton of crude zinc produced amounted to only 0-08 metric 
ton ; in 1905 it had increased tenfold to 0-85 metric ton, and in 
1913 it still further increased to 1-34 metric tons. 

" Prior to the war six works in Silesia still used their old 
reverberatory furnaces, so that not all the sulphur could be 
utilised, but for some years factory legislation has prohibited the 
emission of noxious fumes, and as the plants become worn out 
they have to be replaced by modern installations. The fumes 
from the reverberatory furnaces are scrubbed with milk of lime 
which is sent to waste. Five plants have lead chambers and 
make acid of 50-55 Be. ; this is generally concentrated in 
cascades or Kessler apparatus and in recent years largely in 
Gaillard towers. Three works have contact plants as well as 
lead chambers. There was in 1912 a total of 48 lead chambers. 

" Of the total production of acid, 

41,055 metric tons was sold as acid of 50 Be. 
114,346 metric tons was sold as acid of 5o-6o Be. 
42,349 metric tons was sold as acid with 98-100 per cent. H 2 SO 4 . 
216 metric tons was sold as oleum with 20 per cent. SO S , 
4,774 metric tons was sold as SO 3 ., 
and in addition 2,855 metric tons of liquid SO 2 was made. 

" The acid is used for making superphosphates, sulphate of 
ammonia, dynamite, and guncotton, and for refining mineral 
oil. It is distributed by rail over a wide area, some going into 
Russian Poland, Austria-Hungary, and even to Roumania. 

" The position in the zinc smelting districts in Western Germany 
is analogous, but the make of acid there is larger in proportion 
to the production of spelter, because there is no local supply 
of calamine. The newer smelting works have been placed on 
navigable waterways so that freights on raw materials and 
finished products are low. The chamber process is used in all 

114 



ZINC SMELTING 



the works except one, which has a contact plant ; there is also 
one installation making liquid sulphur dioxide. 

" In 1913 in Germany 554,760 metric tons of blende was 
roasted for making sulphuric acid ; of this 87,439 tons was 
imported from Australia and 56,181 tons from other countries. 

" In Belgium blende is mainly roasted by the chemical manu- 
facturers, who retain the sulphur and receive from the zinc 
smelter in addition a payment of 6 to 8 francs per 1,000 kilos, 
for roasting the ore. This was facilitated by the low freights 
on the canals, which reduced transit charges to a very low figure. 
In Belgium 65 per cent, of the total production of sulphuric acid 
is made from blende ;' the amount of zinc acid is nearly 400,000 
tons." x 

In America, fourteen zinc smelters make sulphuric acid, 
mainly by the contact process. With the movement of the 
zinc smelting industry to the eastward, which has taken place 
in recent years in America, the separation of blende roasting and 
zinc distillation has become more pronounced, as it has been for 
a long time in Europe. 

It is now regarded as good practice to roast the blende at some 
convenient centre for the distribution of the sulphuric acid, and 
then to reship the roasted ore to a suitable place for zinc distilla- 
tion. This is now being done by many of the larger concerns. 

The American production of sulphuric acid from blende, 
calculated as 60 Be. acid, in modern times is as follows 2 : 



Year. 
1911 
1912 

1913 
1914 

1915 



Production 
in short tons 

(2,000 lb.). 
230,643 
292,917 
296,218 
411,911 
484,942 



The average price realised in 1915 was 8-85 dollars per short 
ton. The use of the contact process for the treatment of the 
sulphur fumes from blende has made its biggest strides in the 
United States because the smelters are largely able to rely for 
their ore supplies upon the produce of one or more home mines, 
and are not dependent upon small lots of ore shipped from various 
parts of the world, as has been the case in this country and on 
the Continent. Consequently, the American smelters have been 

1 Ridge. 2 ibid., loc. cit. p. 683. 

115 I 2 



THE ZINC INDUSTRY 

able to make provision for eliminating any harmful ingredients 
which may be present in the ore which they expected to be treating 
over a long period. The American smelters also have the advan- 
tage of having practically no hand-rabbled furnaces, all the 
blende roasting being done in the Hegeler furnace. 

In the United Kingdom, sulphuric acid has hitherto only 
been made from zinc ore roasting in three plants, and it is 
estimated by Ridge that their combined output of acid does not 
exceed 25,000 tons of 140 Tw. acid a year. This amount 
corresponds with a production of about 10,000 tons of virgin 
spelter, which is approximately one-third the production of 
spelter in this country in 1913. Part of this metal was made 
from calamine, but since the available supplies of this ore are 
steadily decreasing, it is only a question of a comparatively 
short time before the whole of the virgin spelter will have 
to be smelted from zinc blende. This country has suffered 
badly in the past from the existence of wasteful and harmful 
metallurgical processes in certain areas, and especially in 
the treatment of zinc ores it has been customary to roast the 
sulphide ore in reverberatory furnaces from which the sulphur 
fumes cannot be used, so that the sulphur is wasted and the 
atmosphere polluted. While it is true that there has been 
some increase in recent years in the utilisation of the gases from 
blende roasting for the manufacture of sulphuric acid, it is much 
to be regretted that the Inspector of Alkali Works has had to 
report that considerable extensions of roasting plants for zinc 
ores were erected during 1915, and that arrangements had 
actually been made for further extensions in 1916, in which 
no provision whatever had been made for the recovery of the 
sulphur. 

It is very desirable that such a procedure should be prohibited 
by legislation. That the matter is, however, receiving some 
attention is evident from the Inspector's latest report, in which 
it is stated that further progress has been made in the utilisa- 
tion of the sulphur fumes from blende roasting for producing 
sulphuric acid, in spite of difficulties connected with the working 
of mechanical roasting furnaces and the scarcity of suitable 
labour for working the necessary hand furnaces. In the newest 
installations, the mechanical reverberatory Ridge furnaces 
have been adopted with satisfactory results. 

It is necessary to remember that in 1913 the total consumption 

116 



ZINC SMELTING 

of zinc in this country amounted to no fewer than 224,000 tons, 
of which 74 per cent, was imported. 

After allowing for the metal produced by the British smelters, 
the imported metal was about 166,000 tons of spelter in addition 
to zinc in other forms. If, as pointed out by Ridge, this quantity 
were all made from blende, the roasting fumes could be used to 
produce annually 400,000 tons of 140 Tw. acid. There is no 
reason why this should not be done and the corresponding 
quantity of brimstone and non-cupreous pyrites, and pyrites 
with small copper content, now used for sulphuric acid produc- 
tion, displaced. Before the war the cost of making 140 Tw. 
acid from zinc ore roast gases in this country was only between 
Ss. and 95. per ton, so that the operation is remunerative. 
Zinc ore must be heated because spelter is required, and if the 
roasting is not done here it will be done elsewhere. Cheap 
sulphuric acid has always been an important factor in the 
chemical industries, and the resources of the Empire should be 
used for its production within the Empire. 

Although the main commercial use for the sulphur fumes from 
blende roasting is the manufacture of sulphuric acid, they are 
also utilised to a limited extent for making sulphites and liquid 
sulphur dioxide. 

" Aluminium sulphate has been made at Flone in Belgium by 
passing the roaster gases into large chambers excavated in the 
hill-side and filled with alum shale. 1 At Ampsin this method 
was also used for making alum with gas from reverberatory 
furnaces ; it seems that sulphite is first formed, and this readily 
oxidises to sulphate. 

" The manufacture of liquid sulphur dioxide was started by 
Grillo at Hamborn in Westphalia, because the fumes from the 
roasting furnaces were low in sulphur dioxide, and it was, at 
that time, considered impossible to utilise them for making 
sulphuric acid. The furnace gases pass to a scrubbing tower 
sprayed with water, which dissolves the sulphur dioxide, and 
the liquor gravitates to a series of pans, which are placed over 
the burners, the heat of which is sufficient to drive off the sulphur 
dioxide gas, which, after being cooled, is compressed and liquefied 
at a pressure of 7 atmos. In Germany two plants are in opera- 
tion, viz., one at Hamborn and another at Lipine in Silesia, but, 
in this country, the method has not been employed on the 
1 Ridge/oc. cit. p. 682. 
117 



THE ZINC INDUSTRY 

fumes from zinc ore. The demand for liquid SO 2 is 
limited." 

Lead and Silver. These metals form important by-products 
in the smelting of zinc-lead ores, such as the Broken Hill concen- 
trates, to which reference has already been made (p. 53). 

When the ores contain much lead and silver, practically the 
whole of the silver and most of the lead will be found in the 
residues, which in this case are of commercial value. 

They are usually concentrated, after grinding, by simple 
water-concentration in jigs and on tables, and the enriched 
material sold to lead smelters. The presence of lead is necessary 
in residues containing silver, as it acts as a collecting agent for 
the silver, consequently the lead content, as well as the silver, 
is taken into account when determining the price to be paid for 
the zinc blende. A deficiency of lead reduces the value of the 
ore because it causes loss of silver. 

Zinc Fume. This is another important by-product in zinc 
smelting, and consists of a mixture of finely divided zinc and 
zinc oxide. In America, zinc fume is called " blue powder." 
This product has increasing commercial value and its utilisation 
is dealt with later (p. 171). 

Cadmium. This metal is also obtained as a by-product. 
Cadmium occurs in small quantities, usually less than 0-5 per 
cent., in many zinc ores, such as the sulphide and carbonate, 
and practically all the cadmium of commerce is obtained from 
such ores. The metal is reduced by carbon and carbon monoxide 
at a lower temperature than zinc ; consequently, in the process 
of extracting zinc from its ores, the cadmium, is obtained in the 
first portions of the product of the distillation, partly as metal 
and partly as oxide. It collects in the condensers and prolongs 
during the first two hours, and the product may contain from 
5 to 8 per cent, of cadmium. This is submitted to redistillation 
to obtain the metal of commerce. Upper Silesia is the chief 
centre of cadmium production ; some is produced in Great 
Britain, and a small quantity in the United States. The amount 
capable of being produced in Upper Silesia is comparatively 
large, but there has never been an important demand for the 
metal, and consequently its recovery has been undertaken by 
only a few concerns, and in limited quantity, most of the 
product from which it might be obtained being permitted to 
remain in the spelter. The consumption of the metal is small. 

118 



ZINC SMELTING 

Its chief use is in the preparation of certain " fusible " alloys, 
in which advantage is taken of its low melting point. It is 
also used to a limited extent in electroplating. The metal 
possesses some very useful properties, and its electro deposition 
may in the future find a more extended application. Compounds 
of cadmium are used in photography and also as pigments. 

Owing to the limited demand, the metal is comparatively 
high in price, but as it occurs fairly abundantly in nature, this 
would doubtless be reduced if the demand increased. 

Residues from Retorts. The exhausted residues drawn from 
the retorts are, in the case of clean ores, usually sufficiently free 
from zinc to be thrown away. The composition of these 
residues naturally depends, of course, on the composition of 
the ores, and with average ores they may be said to contain 
as a rule from 4 to 8 per cent, of zinc. They contain carbon- 
aceous matter in sufficient quantity to permit of profitable utilisa- 
tion, and attention has already been drawn to the attempts that 
have been made in America to turn them to account. 

When the ores contain much lead and silver, practically the 
whole of the silver and most of the lead will be found in the 
residues, which in this case are of commercial value. 

They are usually concentrated after grinding by simple water- 
concentration in jigs and on tables, and the enriched material 
is sold to lead smelters, who also value them for the iron they 
contain, which acts as a flux in smelting. 

The carbon content in the lead residues or slack is also a 
cheap reduction material. 



The Cost of Zinc Production 

The combined cost of roasting and distilling zinc ore 
necessarily varies in different smelting centres, as such con- 
ditions as character of ore, cost of raw materials, labour, fuel, 
distance from market, etc., differ with locality. The output, 
or works capacity, also has an important bearing on the cost of 
the metal produced. Practically two and a half tons of ore give 
one ton of spelter. 

Pre-war British practice was to roast blende in reverberatory 
hand-rabbled furnaces at a cost of 115. to 125. 6d. per ton of ore. 

This figure compares very favourably with Continental practice 

119 



THE ZINC INDUSTRY 

in modern mechanical furnaces, as shown by the working costs 
given below. 

In the larger installations in the Swansea district the pre-war 
smelting charge of 2 155. od. to 3 os. od. may be taken as the 
inclusive cost, and as covering the roasting of the ore. 

The following approximate figures have been given by J. 
Gilbert, 1 as the average cost of smelting one ton of ore at modern 
works on the Continent. 

The cost of roasting one ton of blende is : 



Superintendence 
Rolling, &c. 
Roasting furnace work 
Coal 


Per ton of 
unroasted 
blende. 
s. d. 
9 
3 
. . 4 10 

2 Q 


Repairs 
Sundries 


2 

Q 


Various contributions 
Crushing, &c. 


6 



Total cost . . . . . . 10 7 

Details. From 2,300 to 2,500 tons of crude blende produced 
2,000 to 2,200 tons of roasted ore. Fuel consumption was 23 to 
25 per cent, of furnace coal per ton of roasted blende. The cost 
of one ton of coal was 125. on the basis price given below. Loss 
of metal in roasting, 0*95 to i-o per cent. Maximum value of 
sulphuric acid realised 95. Actual cost of roasting, per ton, 
15. yd. 

The above figures refer to Rhenish roasting furnaces producing 
about 8 to 8-5 tons of roasted blende when working normally. 
With crude ore containing from 23 to 25 per cent, of sulphur 
and about 0-5 per cent, of lime, and retaining after roasting about 
i -i per cent, of sulphur, the yield of sulphuric acid from the 
extractable sulphur is from 85 to 92 per cent., normally about 
90 per cent. 

Cost of distillation of zinc ore at a modern Rhenish works 
with a producing capacity of 10,000 to 12,000 tons per 
annum : 

1 " Costs and Profits of an up-to-date Spelter Works," J. Gilbert, The 
Mining Journal, London, 1916, vol. cxiv, pp. 480-481, 496-498. (Very 
complete details of costs are given in this article.) 

120 



ZINC SMELTING 



Per ton of 


ore treated. 


s. d. 


Management, office, &c. 




9 6 


Generators (wages, coal), reductive coal 




17 6 


Repairs of furnace 




3 


Fireproof material, tempering 
Zinc stores and sieving of zinc dust 




5 o 
6 


Various contributions to funds, &c. 




I 


Sundries (water, light, &c.) 




2 9 




General expenses . . . . ..36 



Each ton of ore treated : total actual costs . . 40 9 

Details. Ore treated, 2,000 to 3,000 tons per month. Produc- 
tion, 1,000 to 1,400 tons of spelter and 100 to 140 tons of zinc 
dust monthly. Percentage of zinc contained in the roasted ore, 
50 to 51 per cent. Loss in smelting (ore poor in lead), 12 per 
cent. Durability of retorts, forty to forty-five days. Coal, 
furnace, and tempering, 115 to 120 per cent, on ore weight, at 
IQS. 6d. to IQS. yd. per ton delivered at works. Basis price main 
coal, 135. <}d. delivered at works. Reduction coal, 40 to 45 per 
cent, of weight of ore. 

The ordinary life of a zinc furnace is about six years, but some 
regenerative furnaces have given good results, even after eight 
or ten years. 

The costs of repairs vary from 150 to 300. 

Considerable discussion has taken place since the outbreak of 
war as to the possibility of smelting a large proportion of the 
Broken Hill zinc concentrates in the United Kingdom. 

Without entering into the many problems involved, the 
following estimate for the treatment of the concentrates in 
Swansea recently put forward may prove to be of interest; 
an allowance, equivalent to one-half of the cost of roasting, 
is made in this estimate for the recovery of the sulphur as 
sulphuric acid. 1 

The estimate is based on a recovery of 85 per cent, of the 
zinc, 60 per cent, of the lead, and 50 per cent, of the silver from 
concentrates containing zinc 47 per cent., lead 8 per cent., and 
silver 10-5 oz. per ton. On this basis, the spelter recovered 
would be 0-4 ton for each ton of concentrate treated. 

1 Quoted in the Bulletin of the Imperial Institute, 1916, vol. xiv, 
p. 68, but original source not given. 

121 



THE ZINC INDUSTRY 



Roasting 

Furnace labour 

Fuel and reducing coal 

Retorts and condensers 

Repairs 

Administration and overhead charges 



Cost of concentrates at works 



Total 

Deduct value of residue less treatment costs . 




Net total 6 7 



The Conditions of Labour in Zinc Smelting 

The work connected with the distillation of zinc is very arduous, 
and considerable skill is required in conducting the process, 
especially in charging the retorts, an operation which needs 
great dexterity. 

In the chief zinc-smelting centres the workmen are specially 
trained, and in many cases the knowledge required for the more 
important parts of the process has been handed on from 
father to son through several generations of workers. On the 
Continent, special provision has been made to train the men 
required so that the output shall not suffer from lack of skilled 
workers. 

There is a general agreement that the labour conditions in 
this country, as compared with the Continent, are detrimental 
to output. It is not, however, suggested that this is due to 
inferiority of the men individually. 

Unquestionably the most difficult part of the problem con- 
nected with the development of the British industry is the 
training and organisation of the labour required for the smelting 
process. Difficult though these are, they should be undertaken 
without delay, for America has shown that they can be done, 
and done rapidly when necessary. 

The system of payment of wages adopted in this country 
differs from that in use on the Continent. In the British spelter 
works the Datal system is in use, a fixed rate of wage being given 
per shift, according to the duties to be performed. 

122 



ZINC SMELTING 

On the Continent the system of giving premiums has been 
attended with marked success. 

At the great Belgian zinc works of La Vieille Montagne, the 
smelters and mill men receive, in addition to a fixed wage, a 
premium calculated on the output, and a special premium is 
also given for unusual energy. In some cases the firemen receive 
a similar premium, based on the time their furnace lasts without 
repair. In other cases, the workmen receive a premium when 
they obtain from the ores a greater amount of metal than that 
which they are calculated to yield. Two-thirds of this premium 
is paid periodically with the regular wage. The remaining third 
is retained until the end of the year, and it is not paid then unless 
the workmen have worked regularly throughout the year. 

In some of the German works additional premiums are paid on 
the production of zinc dust, of metallic lead recovered from the 
distilling furnace, and the life of the retorts. 

The tendency of zinc smelters within recent years has been 
to substitute, as far as possible, mechanical labour for manual 
labour. Especially is this the case in regard to roasting furnaces, 
but in the case of the distillation process, although mechanical 
charging and discharging appliances have been introduced, they 
have only been adopted to a very limited extent. The various 
operations connected with the distillation process do not lend 
themselves readily to mechanical devices. However, attention 
is being given to the possible application of mechanical appliances 
to the manipulation of zinc distillation furnaces, and a certain 
amount of success has been attained, more particularly on the 
Continent and in America. 

As previously stated, machine-made retorts have now very 
largely replaced those made by hand, thus effecting a considerable 
saving in manual labour. 



123 



CHAPTER VII 

OTHER METHODS OF ZINC PRODUCTION 

The Electric Smelting of Zinc Ores 

WHILST practically the whole of the zinc of commerce is pro- 
duced by distillation, great efforts have been made in recent 
years, and large sums of money spent, in the endeavour to 
simplify, expedite, and cheapen extraction, and in particular to 
render the process of zinc production continuous. 

It is recognised that the distillation process leaves much to 
be desired, because the heat is applied uneconomically, as it 
has to pass through the walls of the retorts, and in consequence 
these retorts must be relatively small, restricting the output of 
metal, and much hand labour is required in treating the ore. 

Of all the various newer processes that have been devised and 
experimented with for the extraction of zinc from its ores only 
two may be said to have approached commercial success, viz. : 
(i) electro-thermal methods, or electric smelting, and (2) hydro- 
metallurgical methods. In the electro -thermal methods the 
distillation is continuous, the reduction and distillation being 
effected by heat produced within the reducing vessel or furnace 
itself ; and in hydro-metallurgical, or wet methods, the zinc is 
first dissolved and then recovered from solution by electrolysis. 

Both these methods have been applied to the recovery 
of the metal in low grade ores and in ores which cannot be 
satisfactorily treated by the usual distillation method. The 
electro-thermic production of zinc in the electric furnace 
was first attempted, in 1883, by the Brothers Cowles, who 
developed the resistance type of furnace originated by Despretz 
in 1849, m which a core of carbonaceous material in the charge 
itself carries the current in a horizontal direction. In 1901 
C. P. G. De Laval erected the first electric furnace for smelting 

124 



OTHER METHODS OF ZINC PRODUCTION 

zinc on a commercial scale, and four years later works were 
erected in Sweden to carry out his process. Since that time 
a considerable amount of attention has been given to electric 
furnaces for smelting zinc ores. 

As pointed out by Professor Gowland, 1 " the chief drawbacks 
that impede the commercial success of the application of the 
electric furnace to the smelting of zinc ores are the cost of the 
current and of the electrodes, the loss of metal and the difficulty 
of obtaining a fair proportion of the zinc as metal and not as 
oxide, which has to be re-treated." 

In spite of these drawbacks, the electric smelting of zinc ores 
has held the attention of metallurgists for a long time, and 
during recent years a large amount of work has been done on 
the problem of treating, not merely the high grade ores that are 
easily distilled in the ordinary retort furnaces, but also the low 
grade and complex ores that can hardly be treated at all by 
existing methods. 

In discussing the electric smelting of zinc ores, Prof. A. Stans- 
field 2 considers that the first point to make clear is the great differ- 
ence between the old practice and the methods attempted by the 
electro-metallurgist. In the usual retort, the charge of roasted 
ore and coal is heated gradually for a number of hours, driving 
off first the moisture and the hydrocarbons from the coal, then 
the carbon dioxide resulting from the reduction of easily reducible 
metals such as iron and lead, and finally, when a temperature of 
more than 1000 C. has been reached, the zinc vapour itself with 
its equivalent of carbon monoxide. 

Under these conditions the condensation of the zinc vapour 
is satisfactory, and a large proportion of the metal is obtained 
in the molten condition. This operation could no doubt be 
reproduced in an electric furnace, and would have the advantage 
that somewhat larger retorts could be employed ; but the electric 
furnace inventor is not content with so moderate an attainment ; 
he wishes to change the whole process from the present step by 
step method to a continuous smelting operation in which the ore 
and reducing carbon shall be fed into the furnace at one point, 
the zinc flow out of the condenser, in the molten state, at another 
point, the slag be tapped off from a third point, and lead bullion, 

1 " Metallurgy of Non-Ferrous Metals," ist. Edit., London. 1914, p. 396- 

2 A. Stansfield, " Electric Furnaces as Applied to Non-Ferrous Metal- 
lurgy," Journal of the Institute of Metals, 1916, vol. xv, p. 289. 

125 



THE ZINC INDUSTRY 

carrying any gold and silver values, shall flow out at a fourth 
opening in the furnace. 

The task thus set is by no means easy ; if the ore mixture 
goes without preparation into the smelting chamber, the moisture, 
hydrocarbons and carbon dioxide will come off in admixture with 
the zinc vapour and carbon monoxide, and the zinc will condense 
from this mixture mostly in the form of a blue powder. By a 
preliminary heating of the ore mixture in a separate chamber 
the moisture, hydrocarbons and carbon dioxide can be removed 
to a large extent, but it is difficult to effect their complete removal. 

Thus it appears that there are considerable difficulties to be 
overcome before a successful electric furnace process can be 
developed. 

One difficulty, inseparable from the ordinary process of zinc 
smelting, is the need for an almost perfect roast of the sulphide 
ore, as a preparation for the distillation process. 

Stansfield considers that the electric furnace process, on the 
other hand, holds out the hope that this roasting operation can 
be dispensed with, or at least that it need not be nearly so 
thorough. This possibility depends on the removal of the 
sulphur in the electric furnace in combination with metallic 
iron, or more cheaply with calcium supplied in the form of lime. 

This latter reaction has been studied by O. W. Brown and 
W. F. Oesterle, 1 who find that it takes place very completely, 
in the electric furnace, according to the equation 

ZnS + CaO + C = Zn + CaS + CO. 

Early experimental work by W. R. Ingalls at the McGill 
University confirmed the opinion that, if electric smelting is to 
offer any advantages over distillation in retorts, the process 
must be continuous, and all modern furnaces are constructed 
on this principle. In many of the electric furnaces now in use 
the energy is applied with great ingenuity and high efficiency 
is obtained, whilst efforts are made to reduce the electrode 
consumption to a minimum. 

The reduction in the electric furnace seems to take place more 
rapidly than in retort smelting, but the reaction between the 
carbon and carbon dioxide does not appear to occur to such an 
extent in the former as in the retort. Hence the electric furnace 

1 " The Electric Smelting of Zinc," Transactions of the American 
Electrochemical Society, 1905, vol. viii, p. 171. 

126 



OTHER METHODS OF ZINC PRODUCTION 

contains an atmosphere comparatively rich in carbon dioxide, 
so that a larger amount of fume (blue powder) is formed than 
when the retort furnace is employed. 

Cote and Pierron, Johnson and others have attempted, with 
some success, to solve the carbon dioxide problem by such means 
as passing the gases through columns of incandescent carbon. 
But while progress has been made, the discovery of how to 
avoid oxidation of the zinc deposits, as formed under the 
conditions prevailing in electric smelting, is still the problem 
which metallurgists have to solve in connection with this method 
of zinc smelting. 

The continuity of operation in the electric furnace implies 
discharging the residue as a slag that will flow, and there has 
been a tendency for inventors of electric zinc furnaces to render 
the charge fusible, so that fluid slags may be tapped as from 
cupolas. This condition, however, prohibits any great excess 
of carbonaceous material in the charge, and accounts for the 
higher percentage of carbon dioxide frequently found in con- 
tinuously operated furnaces. 

Among the various types of electric furnace now in use, those 
of De Laval, Cote and Pierron, and Johnson may be mentioned. 
The first two may be selected as typical, and as involving the 
two types of electric furnace ; De Laval employs the electric 
arc, and Cote and Pierron slag resistance, as means for converting 
electric energy into heat. 

The De Laval process, which has been carried out commercially 
for some years at Trollhattan and Sarpsborg, in Sweden, develops 
heat by means of the arc, current being generated from water 
power at prices variously given as from 385. to 505. per electrical 
h.p.-year. 1 The works are equipped for 18,000 electrical horse- 
power and produce over 6,000 tons of refined zinc annually. 

The process is conducted in two operations, the first being the 
smelting of the roasted ore in an arc furnace for the production 
of a coarse metal containing zinc, lead and other metals, and the 
second the refining of this coarse metal by distillation in another 
arc furnace. 

Much of the zinc is obtained as fume or dust. 

The furnaces are of the resistance type, with one large vertical 
carbon electrode passing through the roof, the other electrode 
being a carbon block in the bottom of the furnace. Each furnace 

1 Sulman, loc. cit. 
127 



THE ZINC INDUSTRY 

has a capacity of about 3 metric tons and smelts nearly 3 tons 
of ore in twenty-four hours. 

The complex argentiferous zinc-lead sulphide ore is first roasted 
to expel most of the sulphur. The roasted ore containing about 
7 per cent, to 8 per cent, sulphur is then mixed with anthracite 
or coke and flux and charged through a hopper into a closed 
electric " melting " furnace, where most of the zinc and some of 
the lead are volatilised, and condense chiefly as crude spelter 
high in lead, and partly as blue powder, which has to be re-treated. 
The other part of the lead is reduced to metal and is tapped 
out with the slag. It contains a considerable proportion of the 
silver present in the ore. Some matte (fused sulphides) is 
formed, and this and the slag contain some of the lead, zinc and 
silver. The crude spelter containing lead passes to the electric 
refining furnace, where the zinc is distilled, producing, on con- 
densation, spelter of high grade, and a further quantity of zinc 
dust, leaving the remainder of the lead and silver as base bullion. 
Two melting furnaces supply one refining furnace. 

The company owning these Swedish works reported recently 
that its smelting operations have not yet proved commer- 
cially profitable ; considerable progress has, however, been 
made and it is hoped that things will eventually turn out well. 
About half the cost of smelting is for electric current, and it is 
thus evident that very cheap electric power is essential for the 
commercial success of the process. 

It would appear that the solution of the difficulties connected 
with the condensation of the zinc are to be sought, not in the 
condenser proper, but in the character of the gas delivered to it. 
The attempt to condense a commercial proportion of the vapour 
resulting from the reduction of zinc oxide has so far failed, this 
being the crucial point of electric zinc ore smelting. 

On the basis of ore alone the consumption of power at Troll- 
hattan, according to report, was 2,078 kilowatt-hours per 100 kilo- 
grammes of ore, but for every ton of ore smelted about two tons of 
zinc powder had to be resmelted. 

The smelting of 1,000 kilogrammes of ordinary zinc ore 
( 2 5-3 o per cent, zinc) is reckoned to require from 900 to 1,000 
kilowatt-hours. Each furnace smelts about 2,800 kilogrammes 
of ore in twenty-four hours. 

The Cote and Pierron process is carried out on a small scale in 
France, notably at the Arundy Works in the Pyrenees, which 

128 



OTHER METHODS OF ZINC PRODUCTION 

have been in operation since 1904 ; experimental work with this 
process has also been carried on since 1914 at Ugine and Iperre, 
in Savoy, and at Quenean in Belgium. 

An important feature of the process is the smelting of blende 
in the raw state, that is, without previous roasting to remove 
sulphur. Whilst simplifying the metallurgy of the process, this 
method increases the difficulties of operation of the electric 
furnace. The Cote and Pierron process is ba^ed on the fact that 
iron replaces lead in lead sulphide at a comparatively low tempera- 
ture, and zinc in zinc sulphide when the temperature is increased. 
It is claimed that the process effects a complete separation of 
the zinc and lead. The furnace is a combined arc and resistance 
furnace. It is circular, with sides and bottom lined with 
graphite, thus giving a conducting lining ; the roof is a low dome 
of fire brick. A carbon electrode, which can be raised or lowered, 
passes through an opening in the centre of the roof ; the other 
electrode, a cone of graphite, projects from the hearth. The 
furnace is charged through the roof, and the lead, slag, and 
iron sulphides are tapped through an aperture in the side. 
The volatilised zinc passes through an outlet in the upper part 
of the furnace to the condenser, which consists of a cylindrical, 
shaft-like chamber of fire brick filled with coke or anthracite, 
and provided with a taphole at its base for the discharge of the 
condensed zinc. 

The charge, consisting of a mixture of 200 kilogrammes of ore 
with iron turnings, and lime as flux, is introduced into the hot 
furnace, and the first reaction of iron on lead sulphide is effected 
at a relatively low temperature. The resulting lead is then 
tapped. The temperature is now raised and the decom- 
position of the zinc sulphide by the iron brought about. 
The zinc distils over, and is condensed in the condenser, 
the carbon in the upper part of which is kept at a red 
heat, to prevent as far as possible the formation of zinc fume. 
Finally, the iron sulphide and the slag are run out. At the 
Arundy Works a furnace of 350 kilowatts, with alternating- 
current at 55 volts, treats one ton of blende (35 per cent, zinc) per 
95 to 100 horse-power-days. 

It is claimed that not more than 2 per cent, of zinc remains 
in the slags. 

In America a considerable amount of experimental work has 
been done with W. McA. Johnson's electric furnace at Hartford, 

129 K 



THE ZINC INDUSTRY 

Connecticut, and it is stated that arrangements have been made 
to erect a loo-ton commercial plant at Keokuk, Iowa, for the 
treatment of very complex ores. This is a continuous process 
with furnace of the resistance type, in which the charge carries 
the current. 

The charge is heated to about 900 C. in a continuous pre- 
heater before reaching the furnace. 1 To prevent the formation of 
blue powder, the carbon dioxide formed in the smelting zone is 
rendered innocuous by passing the gases from the furnace through 
an electrically-heated carbon filter, whereby the carbon dioxide 
is converted into harmless monoxide. 

This process has been investigated by the Dominion Govern- 
ment with a view to its application in British Columbia, but 
apparently complete success has not yet been reached. 

Another process that is claiming attention is the Snyder process, 
which has been applied to the treatment of argentiferous zinc- 
lead ores. The ore is roasted to oxide, and fluxes added so that 
the mixture will melt at about 1000 C. The molten mixture 
is then treated in an electric furnace and results in the reduction 
of the metals present. The lead, alloyed with the silver, collects 
below the slag, and is tapped off, and the zinc which is oxidised 
and volatilised is condensed in brick chambers. 

Although electric zinc smelting has now passed beyond the 
experimental stage and become a commercial process, it is being 
continually investigated by those especially interested in this 
method of smelting zinc ores. An expert on zinc production, 
J. C. Moulden, 2 has recently expressed the opinion that, given 
favourable primary conditions and the inevitable improvement 
to be brought about by experience, the electrothermic method 
of distillation will in the future substantially influence the pro- 
duction of zinc. 



Hydro-metallurgical Processes of Zinc Production 

Since Parnell took up the question of treating complex zinc- 
lead ores at Swansea in 1881, many wet methods of zinc extrac- 
tion have been suggested and experimented upon, but until quite 
recently none have met with commercial success owing to their 
inability to produce metallic zinc. 

1 Journal of the Royal Society of Arts, 1916, vol. Ixiv, p. 513. 
* Ibid. 

130 



OTHER METHODS OF ZINC PRODUCTION 

Unlike most metals, zinc cannot be precipitated from its 
solutions by common metals, and if other precipitants are used 
and it is obtained as oxide, this must be mixed with carbon and 
treated by a distillation process in order to obtain the zinc as 
metal. Thus Parnell's process consisted in roasting the ore to 
sulphate, leaching with water, evaporating the purified zinc 
sulphate solution to a paste and adding powdered zinc blende. 
This mixture was then heated to produce zinc oxide, which was 
reduced in retorts and distilled. The argentiferous lead residue 
left in the vats was sold to lead smelters for the extraction of the 
lead and silver. 

The difficulty of obtaining the zinc in the metallic state has 
been the main reason for the slow development of wet methods 
of zinc production. However, where formerly it did not pay to 
leach out zinc in the form of sulphate, owing to the limited market 
for the salt and the prohibitive cost of converting it into oxide, 
the growing demand for white pigments free from lead has made 
it possible to avoid the necessity of extracting the zinc as metal 
by crystallising the dissolved zinc as sulphate. 

Thus, as the result of the increasing demand for zinc sulphate 
for the production of " lithopone," to which reference is made on 
p. IQ3, the unit of zinc in crystalline sulphate has a con- 
siderably higher market value at present than a unit of zinc in 
the form of oxide for smelting purposes. 

More recently, hydro-metallurgical processes have been devised 
in which the zinc after having been obtained in solution, either 
as sulphate or chloride, is precipitated in the metallic state by 
electrolysis ; but while the difficulties which formerly attended 
the precipitation of electrolytic zinc have so far been overcome 
as to form the basis of recent methods, the high cost of electric 
power has operated against the commercial success of most of 
these processes. 

Letrange was one of the earliest workers in the production of 
zinc by electro-deposition ; in his process the crushed blende was 
carefully roasted at a low temperature to produce zinc sulphate, 
which was dissolved with dilute sulphuric acid. The solution 
was then electrolysed, using an anode of lead (or carbon) and a 
cathode of zinc. 

Electrolytes of zinc chloride solution are said to be more 
economical in electric current than solutions of zinc sulphate, 
the electromotive force necessary for the decomposition of the 

131 K 2 



THE ZINC INDUSTRY 

former being less than for the latter. In practice, however, it 
has been found to be more satisfactory to extract the zinc as 
sulphate than as chloride, and in most of the wet processes now 
in use the electrolyte consists of zinc sulphate. 

Considerable attention has been given during the past few 
years to the electrolytic separation of zinc from its ores, especially 
so-called complex ores, and a specially pure zinc is now being 
satisfactorily produced by this process. 

Compared, however, with smelting, the amount of zinc produced 
by electrolytic separation is very small, though the importance 
of the latter process is gradually increasing in districts where the 
special nature of the ore renders the application of hydro-metal- 
lurgical processes on a commercial scale possible. There is, 
however, little prospect that wet methods of zinc production 
will be sufficiently successful on a commercial scale to enable 
them to compete with the distillation processes. 

The only commercial processes in the electro-metallurgy of 
zinc by direct wet methods appear to be those of Nahnsen, of 
Hoepfner, and of Dieffenbach. 1 

The Nahnsen process has been employed at Lipine, Silesia, 
since 1893, the electrolyte used being a solution of the double 
sulphate of zinc and magnesium. The Hoepfner process is in 
operation at Duisburg, in Germany, and two plants were erected 
in 1914 at Kristiania and Balestrand, in Norway, for the treat- 
ment of Broken Hill flotation concentrates. 

A modification of the method originally devised by Hoepfner 
has been employed with considerable success in the United 
Kingdom at the works of Messrs. Brunner, Mond and Co., near 
Northwich, Cheshire, where considerable quantities of zinc of 
high grade are now made and employed for the manufacture of 
brass for cartridge cases and other articles requiring a highly 
ductile alloy. 

The ore is roasted to convert the zinc into oxide, which is 
then transformed into zinc chloride by carbon dioxide and a 
solution of calcium chloride, waste calcium chloride liquors from 
the Solway ammonia-soda process being used for the purpose. 
This results in the solution of the zinc as chloride and the pre- 
cipitation of calcium carbonate. The zinc solution is purified by 
a series of operations analogous to those devised by Hoepfner. 

1 Abstract of paper by R. Sylvany, Journal of the Institute of Metals, 
1914, vol. xii, p, 318. 

132 



OTHER METHODS OF ZINC PRODUCTION 

The iron and any manganese are precipitated by means of 
chloride of lime and calcium carbonate, and the other metals, 
copper, lead, etc., by the addition of zinc fume to the clear 
solution. The purified solution is electrolysed, using revolving 
iron disks as cathodes and carbon anodes enclosed in cloth 
diaphragms, a current density of 30 amperes per square foot of 
cathode surface being employed. The solution for electrolysis 
should contain from 0-08 to 0-12 per cent, of free hydrochloric 
acid. 

The products of electrolysis are metallic zinc and chlorine, 
the latter being subsequently converted into bleaching powder. 
The recovery of such a valuable by-product as chlorine from a 
waste material is a very important factor in the economic success 
of this process at Messrs. Brunner Mond's works. The zinc 
produced has a purity of about 99-96 per cent. 

The Dieffenbach process is applied to a Westphalian iron 
pyrites, containing 8 per cent, of zinc, which is converted 
into chloride by roasting with sodium chloride, and extracted 
by leaching with water. The residue, which is said to contain 
only 0-5 per cent, of zinc, is smelted for iron, whilst the aqueous 
solution of zinc chloride is electrolysed in double-compartment 
vats, the anode compartments being completely closed. The 
liberated chlorine is employed in the manufacture of calcium 
hypochlorite. 

Since the outbreak of war there has been a very important 
development in the electrolytic production of zinc in America, 
especially at Anaconda and Trail. The processes being used in 
American plants are based on sulphuric acid leaching, and sub- 
sequent electrolysis of the zinc solution, using lead anodes. 
The largest American plant for electrolytic zinc production is 
that of the Anaconda Company, at Great Falls, Butte, which 
when complete will produce 35,000 tons of electrolytic zinc 
annually. 1 The ore is concentrated, chiefly by flotation, and 
is then roasted until the sulphur content is 2 or 3 per cent., 
mostly as sulphate. 

The temperature must not exceed 732 C., in order to avoid 
the formation of zinc ferrite. The roasted residue is leached with 
spent electrolyte to which a sufficient quantity of sulphuric acid 
has been added. A little manganese dioxide, followed by 

1 W. R. Ingalls, Transactions of the American Electrochemical Society, 
1916, vol. xxix, p. 347. 

133 



THE ZINC INDUSTRY 

powdered limestone, is added to remove iron, arsenic and anti- 
mony. Lead, silver and gold remain in the residue, and the 
only impurities in the filtrate are copper and cadmium, which 
are precipitated by metallic zinc. Formerly zinc fume was used 
to precipitate the cadmium, but difficulties were encountered, 
and the plan now adopted consists in running the clear solution 
through tube mills containing zinc balls. 

After filter-pressing, the solution is electrolysed with lead 
anodes and aluminium cathodes. The current density is 20 to 
30 amperes per square foot of cathode surface (220 to 330 per 
sq. m.), and the current efficiency 93 to 94 per cent. The 
cathodes, which are stripped every forty-eight hours, are melted 
and cast into ingots. The process is said to be particularly 
suitable for the fine concentrates obtained by flotation, which 
are troublesome to treat in retorts. 

At the Welland plant, Ontario, recently erected by the Weedon 
Mining Company, the solution of the zinc and electrolysis of the 
solution are performed in the same vat, the cathodes being enclosed 
in canvas bags. Other works adopt the arrangements at 
Anaconda. 

It is proposed to use the method employed by the Anaconda 
Copper Company, described above, for the treatment of the 
complex zinc-lead sulphide ores which occur in large quantities 
in the Mount Read district of Tasmania. In these ores the 
metals are found in such an intimate state of fine division 
as to render concentration almost impossible. After much ex- 
periment, chemical treatment has been found to be the only 
feasible and economic method of dealing with such ores, and 
after trying several methods of wet extraction it is proposed 
to use the Anaconda method as stated. This has been 
rendered possible by the electric power scheme of the Tasmanian 
Government which has been in operation since May, 1915. The 
main water-storage basin is the Great Lake, and the present 
output is about 10,000 horse-power, but this can be very con- 
siderably increased in the future. The probable consumption 
of hydro-electric power in Tasmania in the near future for zinc 
ore reduction processes is estimated as 2,500 horse-power. 1 The 
electrolytic production of zinc is proposed by several companies. 

1 " Tasmanian Hydro-electric Power and Chemical Industry," F. H. 
Campbell, Proceedings of the Society of Chemical Industry of Victoria, 
1916, pp. 419-429- 

134 



OTHER METHODS OF ZINC PRODUCTION 

In the Gillies process, the zinc sulphate is electrolysed between 
a rotating cylindrical zinc sheet as cathode and lead anodes, with 
a woollen diaphragm for separating the gases. 

The bisulphate process is another wet method of zinc extrac- 
tion which has been tried in several localities, including Tasmania, 
for the treatment of complex sulphide ores containing zinc. 
In this process the roasted ore is pulped with water and 
sulphur dioxide gas passed through the mass, resulting in the 
zinc passing into solution as the soluble bisulphite, ZnH 2 (SO 8 ) 2 . 1 
This solution is pumped into another tank where the mono- 
sulphite of zinc is precipitated, and this yields the oxide on roasting 
in a muffle furnace. 

The sulphur dioxide evolved at two stages in the above process 
is added to the roaster gases, which are in turn employed as 
the source of the sulphur dioxide used in the initial leaching 
process. A certain quantity of sulphate of zinc collects in the 
leaching solution, and this is periodically recovered by crystallisa- 
tion. 

The " French " process of zinc recovery, which is in operation 
at Silverton, British Columbia, has several points of interest. 
Roasted zinc blende is treated with a solution of sodium bisulphate 
(nitre cake) containing a small quantity of a manganese com- 
pound, usually manganese sulphate. After about an hour the 
solution has extracted almost the whole of the zinc, whilst the 
iron, lead and silver remain in the insoluble sludge. 

The liquor from the first extraction is run on to a second 
charge of ore in order to neutralise its acidity, and when this has 
taken place the clear solution is run into vats and the zinc re- 
covered elect rolytically, using lead and zinc electrodes. Any 
manganese present is deposited on the lead as manganese dioxide, 
which is redissolved and used over again, whilst the zinc is 
deposited on the zinc electrode. As the zinc is electrolytically 
deposited, the sodium bisulphate is regenerated, and when all 
the zinc has been removed the solution is again ready for use 
and is employed in re-treating the charge of ore previously used 
to complete the neutralisation of the solution. It is stated that 
the process can be employed equally well for low or high grade 
ore, although in the former case the cost of treatment is somewhat 
higher. 

In the opinion of W. R. Ingalls, 2 the electrolytic refining of 

1 Bulletin of the Imperial Institute, 1916, vol. xiv, p. 69. 2 Loc. cit. 

135 



THE ZINC INDUSTRY 

zinc is only practicable where power is very cheap, or where other 
conditions are exceptionally favourable, such as a readily soluble 
ore, as at Anaconda, or one high in silver. 

The crude zinc ore at Anaconda lends itself very successfully 
to treatment by the flotation process, which gives a high-grade 
concentrate. This is of such a nature that by roasting and 
leaching with weak sulphuric acid the percentage of zinc extracted 
as sulphate is unusually high. 

This is not often the case with ordinary ores, which very 
frequently contain sensible quantities of iron and manganese 
which form troublesome compounds in roasting and lower the 
percentage of zinc recoverable by lixiviation. 

The recovery of silver from zinc ores, which is only 65 per cent, 
in the distillation process, amounts to 90 or even 95 per cent, in 
the electrolytic process. 

The concentrated ore at Anaconda contains 20 oz. of silver 
per ton. 

The zinc produced is of high purity, and in view of the increasing 
demand for pure metal for alloying purposes the electrolytic 
methods of zinc extraction are receiving renewed attention, 
especially in connection with the recovery of the metal from 
by-products and residues, etc., containing zinc. The prospects 
of electrolytic zinc in relation to distillation methods of zinc 
extraction have been very ably dealt with by W. R. Ingalls 
in a recent paper on " Electrolytic Zinc," l to which all interested 
in the subject are referred. 

1 W. R. Ingalls, " Electrolytic Zinc," Engineering and Mining Journal 
(New York), March 4th, 1916, vol. ci, pp. 425-428. 



136 



CHAPTER VIII 

THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 

ZINC is a bluish- white metal possessing a bright metallic lustre 
and is capable of taking a high polish. As usually met with in 
commerce and used, the metal is impure, and seldom contains 
more than 99 per cent, of zinc. Zinc in a chemically pure con- 
dition may be prepared by the electrolysis of a chemically pure 
solution of the sulphate or chloride, and if effected with scrupulous 
care in every particular will afford zinc of 99-998 per cent, purity. 
The pure metal is comparatively soft, being softer than copper, 
but harder than tin and silver. 

The hardness of cast zinc measured by Brinell's method is 
38'!, compared with copper 40-0, and silver 24-8. 

Pure zinc is appreciably hardened by quenching in water after 
casting. The pure metal is malleable and may be rolled into 
thin sheets at the ordinary temperature, but commercial cast 
zinc is moderately hard and brittle at the ordinary temperature, 
a flat ingot, or cake, of the metal being fairly easily broken across 
under a blow from a heavy hammer. Although commercial 
zinc is very much less brittle than antimony or bismuth, the 
crystalline structure of the metal causes it to split and break 
up if hammered or rolled cold. The fracture exhibits large 
crystal faces of high metallic lustre, especially when the metal is 
free from iron. The appearance of the fracture is characteristic 
and affords an indication of the purity of the metal. The fracture 
is more largely crystalline the higher the temperature of casting 
is above the melting point of the metal. When bent, the cast 
metal emits a sound resembling the " cry of tin," but somewhat 
more feeble. 

The commercial metal becomes malleable and ductile if heated 

137 



THE ZINC INDUSTRY 

to a temperature of from 100 C. to 150 C., after which treatment 
it retains its malleability when cold sufficiently to admit of being 
rolled into thin sheet or drawn into wire. On a large scale, 
however, the metal is rolled hot. At a temperature above 
205 C. zinc again becomes so brittle that it may be pulverised 
in an iron mortar. In common with other metals, zinc is 
hardened by mechanical treatment, such as rolling, and requires 
annealing at a low temperature to restore its malleability. It 
has been shown by T. K. Rose 1 that, in the case of pure sheet 
zinc 1*25 millimetres thick, softening is nearly completed in about 
half an hour at a temperature of 125 C. 

Zinc is less tenacious than most metals in common use, its 
tenacity, according to Karmarsch, being 2,809 Ib. per square inch 
when cast, and between 18,703 Ib. and 22,188 Ib. when in sheets 
or wire. 

Measurements of the tensile strength of rolled zinc have been 
made by H. F. Moore, 2 which show that zinc, either in the cast 
or rolled state, has no definite yielding point. The breaking load 
of thin rolled zinc (not more than 0*05 inch thick) was found by 
Moore to be about 24,000 Ib. per square inch, and its tensional 
modulus of elasticity 11,500,000 Ib. per square inch. Rolled 
zinc is somewhat stronger in tension across than with the grain. 
The stress developed in punching or shearing the rolled plates is 
about 40 per cent, of that developed with mild steel plates. 

The sheets are more ductile with the grain than across it. 
Results obtained by T. K. Rose 3 show that zinc hardened by 
rolling is in an unstable condition at the ordinary temperature 
and undergoes a gradual change to the soft state. Thus the 
scleroscope hardness of rolled zinc was found to be 36, and after 
ninety-seven days the hardness had fallen to 31*0. Zinc may 
be granulated by pouring the molten metal into water. In hot 
water it is obtained in the form of small globules, known as 
bean-shot, and in cold water flakes are produced, known as 
feathered-shot metal. Both these forms of granulated zinc are 
prepared commercially. 

The density, or specific gravity, of cast zinc ranges from 
6-9 to 7*2, according to the temperature at which it has been 

1 Journal of the Institute of Metals, 1912, vol. viii, p. 114. 

2 University of Illinois Bulletin, 1911, vol. ix, No. 9. (Abstract Journal 
of the Institute of Metals, 1915, No. 2, vol. xiv, p. 230.) 

3 Journal of the Institute of Metals, 1912, No. 2, vol. viii, pp. 86-114. 

138 



THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 

cast and the manner in which it has been cooled. By rolling the 
metal its specific gravity is increased to about 7-25. 

The electrical conductivity of zinc is 25*6 to 29*9, according to 
the determinations of several observers, and its thermal conduc- 
tivity 28-1, compared in both cases with silver as 100. 

The atomic weight of zinc is 65*37 (taking O = 16), and its 
symbol is Zn. 

Zinc melts at a comparatively low temperature, its melting 
point being 419 C. ; it boils at 950 C., the vapour burning 
in air with a characteristic brilliant bluish-green flame, and 
the production of zinc oxide, a soft, white, flocculent substance 
resembling wool, and formerly known as philosopher's wool, or 
" flowers of zinc." According to Ingalls, zinc burns in the air 
at a temperature as low as 500 C. It can be distilled in quantity 
at a bright red heat, and on cooling condenses in globules which 
coalesce, when a reducing atmosphere is maintained. 

When it passes from the cold solid to the molten condition 
zinc increases in volume n-i per cent. It contracts but slightly 
on cooling from the molten state, and is thus well adapted for 
castings. The molten metal retains a small quantity of zinc 
oxide, which separates on solidification, presenting very thick 
crystal boundaries when examined under the microscope. 

Zinc expands T3 ^th of its length by heating from o C. to 100 C. 

The metal is not affected by pure dry air or by oxygen at the 
ordinary temperature, but under ordinary moist atmospheric 
conditions it gradually acquires a coating of the greyish-white 
basic carbonate which protects the metal from further corrosion. 
In consequence of this property, zinc is used in the form of sheets 
for roofing purposes, and is also employed as a protective covering 
for iron, which when thus coated is said to be galvanised, a term 
that is somewhat misleading, since the iron is not ordinarily 
coated by electrical deposition, but by dipping the iron into a 
bath of molten zinc. The industrial value of zinc is largely due 
to this protective property. 

Pure zinc is scarcely acted upon by pure sulphuric or hydro- 
chloric acid, either dilute or strong. The presence of small 
quantities of impurities, however, determines the rate of solu- 
tion of the metal, hence ordinary commercial zinc is readily 
attacked by these acids with rapid evolution of hydrogen, and 
on this account the metal is used as the positive element in 
el ect ricjoa.it eries . 

139 



THE ZINC INDUSTRY 

When zinc is brought into contact with mercury, zinc amalgams 
are formed which are only very slowly acted upon by dilute 
sulphuric acid ; therefore, by the superficial amalgamation of 
the zinc plates used for electric batteries, the same result is 
obtained as though the zinc were perfectly pure, and no solution 
of zinc takes place until the electric circuit is closed. Amalga- 
mation protects zinc from corrosion by acids, because the 
discharge potential of hydrogen on mercury exceeds the 
potential of zinc. 

Sulphuric acid dissolves zinc appreciably more slowly than 
hydrochloric acid with an equal concentration of hydrogen ions. 

Owing to the differences in the crystalline structure of the 
metal, cast zinc is less easily acted upon than rolled zinc by dilute 
acids. The dark grey residue obtained on treating the com- 
mercial metal with acids consists chiefly of lead. 

Both pure and commercial zinc are dissolved readily by alkalis. 

Water has no action on zinc at the ordinary temperature, if 
air is excluded, but at a red heat the metal readily decomposes 
the vapour of water and is converted into oxide. 

Carbon dioxide very readily oxidises zinc vapour with the 
production of carbon monoxide and zinc oxide. This reaction, 
as previously pointed out, is of considerable importance as it 
constitutes a decisive factor in the metallurgy of zinc, and confines 
within very narrow limits the methods that are applicable, on 
a commercial scale, to the extraction of the metal from its ores. 

Zinc is strongly electro-positive and readily precipitates most 
other metals from their solutions. In this connection it finds 
industrial application ; e.g. it is in- extensive use for precipitating 
gold from cyanide solutions in the cyanide process of gold extrac- 
tion. 

Zinc unites with most of the common metals to form a number 
of useful alloys, the most important of which are the various forms 
of brass. The zinc alloys, and also a number of zinc compounds, 
of value in the industries, are discussed under the " Industrial 
Applications of Zinc " (see p. 161). 

The Micro-structure of Zinc 

The evidence afforded by the microscope, in relation to the 
constitution of metals and alloys, has been of such value that 
the systematic study of the micro-structure of commercial 

140 



THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 

samples of zinc and its alloys is now very generally undertaken. 
In particular, the systematic study of brass and of nickel silver 
as revealed by the microscope has claimed a considerable amount 
of attention in recent years. 

The rapid growth of this new science of metallography, 
and the attention paid to it by both manufacturers and users 
of metals, is a cause for much satisfaction, as it evidently 
indicates that those connected with the British metal industries 
are beginning to recognise the fact that any advance in purely 
scientific knowledge of metals is capable of being turned to 
practical advantage. 

The chief points ascertainable by the use of the microscope 
are the crystalline state of the metal or alloy, and changes in 
the general structure due to varying mechanical or heat treat- 
ment, and the constitution of the material, that is to say, the 
differentiation of the various constituents which enter into the 
composition of the alloys. This is one of the most important 
points connected with the modern study of alloys, and much 
valuable information has now been obtained by this method of 
investigation. 

As regards crystalline structure, attention may be directed 
to the distinction between the grains of which a mass of metal 
is usually composed and the crystallites which compose each 
grain, the latter constituting the true crystalline structure. In 
each grain the crystallites are arranged in a definite direction or 
orientation. When, therefore, the surface of any pure metal, 
after having been carefully polished, is lightly etched with a 
weak acid or other reagent and examined under the microscope, 
it is seen to be composed of a number of separate grains, irregular 
in size and shape. If the etching be made deeper it is found that 
the grains, besides differing in size, differ also in texture, reflecting 
at different angles light thrown upon them. 

Examination of the strongly etched surface under a higher 
power shows that this difference in texture is due to a number of 
small facets in each grain. The facets are oriented, but in any 
one grain they are similarly oriented, so that the general surface 
of the grain reflects light in a particular direction. Each of 
these grains has the uniformity of internal structure character- 
istic of a crystal and is, in fact, a crystal. With this fundamental 
fact established, the cause of the behaviour of metals under 
different conditions, under strain, for example, can be explained, 

141 



THE ZINC INDUSTRY 

but much remains yet to be investigated. In particular, no 
completely satisfactory explanation of the manner in which the 
individual crystalline grains are cemented together has yet been 
obtained. 

Well-defined or idiomorphic crystals are seldom found in the 
structure of cast metals, while crystallites or the incipient forms 
of crystals are predominant. On annealing, however, this 
crystallitic structure is replaced by a well-defined crystalline 
structure. 

Various etching reagents are in use for developing the structure 
of zinc and its alloys. For etching the surface of zinc Timofeef l 
recommends a mixture of 94 per cent, nitric acid and 6 per cent, 
chromic acid, a few drops of this mixture being added to 
50 or 100 cubic centimetres of water before use. This reagent 
is also recommended by Desch, and has been found satisfac- 
tory in practice. 

Iodine is found by Gulliver to be most suitable for alloys rich 
in zinc or cadmium. 2 He uses a solution of I part iodine and 
3 parts potassium iodide in 10 parts of water. 

Caustic potash and caustic soda are used for zinc and aluminium 
and alloys rich in these metals. When caustic soda is used for 
etching alloys of aluminium with zinc, a black deposit is often left 
on the etched surface. This can be very satisfactorily removed 
by dipping the specimen in a solution of chromic acid in water. 

The strength of the caustic soda reagent varies from 5 to 
20 per cent. A 10 per cent, solution of chromic acid etches zinc, 
cadmium and many alloys of these metals, whilst a highly con- 
centrated solution of chromic acid is, according to Czochralski, 3 
suitable for developing the internal crystalline structure of zinc. 

The micro-structure of pure cast zinc consists of comparatively 
large grains, often showing a cross-hatching upon their surfaces, 
presenting a structure analogous to that of martensitic steel. 
A photomicrograph of cast zinc, etched with very dilute nitric 
acid, and magnified 100 diameters, is shown in Plate I. 4 Another 

1 " Revue de M6tallurgie," 1914, No. I, p. 127. 

2 O. F. Hudson, "Etching Reagents," Journal of the Institute of Metals, 
1915, No. i, vol. xiii, p. 193. 

3 " Stahl und Eisen," 1915, vol. xxv, pp. 1073, 1129. Abstract Journal 
of the Institute of Metals, 1916, No. 2, vol. xvi, p. 245. 

4 Photomicrographs taken for the author by Dr. F. C. Thompson, 
University of Sheffield. 

142 








Photomicrograph of cast zinc 
Magnified 100 diameters. 




Photomicrograph of cast zinc (showing twinning). 
Magnified 100 diameters 

PLATE i. 



THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 

photomicrograph of the same metal, treated as before, is also shown 
in Plate I . In this latter case the structure consists of allotrio- 
morphic crystals with twinning, which is of somewhat rare 
occurrence in metals in the cast state. 

When the zinc is contaminated with zinc oxide, which is 
usually the case with commercial samples, the oxide tends to 
separate at the crystal boundaries, giving rise to very thick 
boundary lines. 

The changes in structure of hard worked zinc on annealing 
are discussed by G. Timofeef. Cast specimens of zinc were 
prepared and strained in compression. The micro-structure of 
zinc crushed in a vice becomes homogeneous, no crystals being 
visible under very high magnifications. The hardness increases 
considerably. Recrystallisation takes place, however, very 
readily on annealing the metal, a very slight rise in tempera- 
ture effecting a noticeable change in the micro-structure of the 
strained metal. The etching of the samples was effected with 
Timofeef's reagent given above. The strained specimens were 
annealed at different temperatures ranging from 65 C. to 
360 C. 

The photomicrographs showed that the average size of the 
crystal grain in the annealed specimens increases uniformly 
with the annealing temperature, the hardness suffering a corre- 
sponding decrease in value, until it finally reaches the same 
figure as that found for the cast metal. It was found in all 
cases that the size of the grains was greater at the edges than 
in the middle of the specimens ; this is ascribed to the greater 
amount of plastic strain at the edges of the specimens during 
deformation by compression. 

It is concluded that the velocity of recrystallisation depends 
both upon the temperature of annealing and upon the severity 
of plastic strain ; the final size of the crystalline grains when 
annealing at a given temperature is limited by the duration of 
heating. Under slight shock the large individual crystals 
composing cast zinc became striated, this effect being produced 
even by removing the ingots from moulds, if special care is not 
taken. 

The micro-structure of zinc containing lead indicates that at 
the freezing point of zinc the still molten lead is rejected and 
forms minute globules occupying often the cleavage cracks 
caused by the contraction of the crystalline zinc during solidifica- 

143 



THE ZINC INDUSTRY 

tion. This separation of lead is well shown in Plate 2, which in 
the lead appears as isolated dots within the zinc crystals. The 
cast zinc contained about 3 per cent, of lead, and the structure 
was developed by etching with very dilute hydrochloric acid 
with the addition of a few drops of a solution of zinc chloride. 
The magnification is 100 diameters. 

Iron is a frequent constituent of commercial zinc, and when 
present above o-i per cent, it forms distinct crystallites which 
are readily discernible under the microscope, and, as already 
stated, are doubtless the cause of the light specks on the crystal 
faces of fractured spelter. Hard zinc, containing about 10 per 
cent, of iron, presents a characteristic structure in which the 
crystals are well defined even at a low magnification of about 30 
diameters. 

The microscope affords a very ready means of controlling the 
annealing process for brass and other zinc alloys, and has been 
adopted for that purpose in several large works. After every 
stage of the process samples are taken, rapidly polished, etched 
and examined under the microscope. From the size of the 
crystals it is easy to determine whether the alloy has been in- 
sufficiently, correctly, or over annealed. 

The accompanying photomicrographs of brass, containing 
60 per cent, of copper and 40 per cent, of zinc, are given as 
illustrations of the study of the constitution of brasses by means 
of the microscope. 

Plate 3 represents the brass (copper 70, zinc 30) as cast, 
while Plate 4 shows the appearance of the metal after annealing 
for one hour at 750 C. The magnification in each case is 80 
diameters. 

The etching-agent was a 10 per cent, solution of ammonium 
persulphate. 

For further examples of the micro-structure of brass and other 
alloys containing zinc reference must be made to the researches 
on the subject that have been published in the Proceedings 
of the scientific societies, notably in the Journal of the Institute of 
Metals, and several of which have been mentioned in the Biblio- 
graphy appended. 



144 




Photomicrograph of cast zinc with 3 % of lead. 
Magnified 100 diameters. 



PLATE 2. 




Brass (70 % copper, 30 % zinc) as cast ; showing cored 

structure. Magnified 80 diameters. Etched with 

10 % solution of ammonium persulphate. 

Photomicrograph by Dr. F. C. Thompson, 
University of Sheffield. 



PLATE 3. 




Brass (70 % copper, 30 % zinc) after annealing for 

one hour at 750 C. ; showing crystalline structure. 

Magnified 80 diameters. Etched with 10 % solution of 

ammonium persulphate. 

Photomicrograph by Dr. F. C. Thompson, 
University of Sheffield. 



PLATE 



THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 



Impurities in Commercial Zinc 

Owing to the fact that zinc possesses so powerful an alloying 
affinity for other metals, and even metalloids, e.g., arsenic, the 
commercial metal produced by distillation is invariably con- 
taminated with impurities, the amount of which varies according 
to the composition of the ore from which the spelter is produced. 

The most frequent impurities in spelter are lead, iron, cadmium 
and arsenic. From the table of typical analyses given on p. 149 
it will be seen that the chief impurities to be guarded against are 
lead and iron. 

The variations in the lead and iron content in different brands 
of spelter examined by R. T. Rolfe x during the years 1913-1916 
were as follows : 



Brand of Spelter. 


Lead per cent. 


Iron per cent. 


Crown 






1-52 


0-08 


De Boom 






0-31 


trace 


Nouvelle Montagne 








0-94 0-03 


Revil 








0-46-1-73 


0-07-0-19 


S.S 








0-32-3-43 


trace 


Ste. de Boom 


_ 






1-65 2-03 


trace 


Vieille Montagne 








1-47-1-49 


0-04-0-07 


Vivian & Co. 









0-83-1-32 


0-08-0-12 



Lead. The lead does not usually exceed 2 per cent., although 
some spelters are placed on the market containing as much as 
3 per cent. It is usual, however, to refine such impure metal 
before marketing, since, as already stated, the quantity of lead 
present very largely determines the market value of the spelter. 

In spelter intended for rolling, a small percentage of lead is 
desirable, and up to I-Q per cent, it has no injurious effects on 
the malleability or ductility of the metal. 

When, however, the spelter has to be used for making brass 
which has to undergo severe mechanical treatment, as, for 
example, the manufacture of cartridge cases, the presence of 
lead exceeding o-i per cent, is very undesirable, the metal being 
often somewhat brittle and liable to crack. When present in 
quantities greater than 07 per cent., lead tends to produce 
bad cracking in spelter castings. 

1 Journal of the Institute of Metals, 1916, vol. xvi, p. 201. 
145 L 



THE ZINC INDUSTRY 

Any cheap and readily applicable method for the elimination 
of lead from spelter, short of redistillation, would, in the opinion 
of Moulden, find both world-wide application and substantial 
remuneration. 

Iron. Iron is a very frequent impurity, the amount passing 
into the spelter depending more on the method of smelting than 
on the ore employed. 

When over o-i per cent., its presence is indicated by the grey 
appearance, and by the presence of a number of black specks 
(crystallites) on the crystal faces of the fractured spelter, while 
the pure metal exhibits clear, brilliant crystal faces on fracture. 

The zinc may be freed from this impurity by redistillation, 
the use of iron tools and appliances being avoided. The effects 
of iron are to increase the hardness and brittleness of zinc and 
reduce its malleability, but when the refining by liquation has 
been properly conducted there is insufficient present to affect 
these properties. 

For spelter intended for the manufacture of brass 0-05 per 
cent, of iron is often specified as the limit, but less than this 
amount is preferable for brass of high ductility and malleability. 

Cadmium. Cadmium, being more volatile than zinc, is more 
difficult to condense, and is rarely present in spelter in injurious 
proportions. 

Spelter may, however, contain as much as 2-0 per cent, of 
cadmium, but usually the quantity is under 0-2 per cent. Spelter 
free from cadmium can only be obtained by single smelting when 
the ore is free from cadmium, but by redistilling common spelter 
with proper control of the temperature, and separating the first 
distillate, a high-grade spelter, low in cadmium, is easily produced. 

Cadmium has a pronounced hardening effect on spelter and 
tends to increase its brittleness, but its effect on zinc to be used 
for the production of alloys requires further investigation. As 
the result of practical experience many metallurgists consider 
that cadmium up to 0-5 per cent, has no injurious effect on zinc 
used in the manufacture of cartridge brass, nickel silver, and similar 
alloys. 

The specification of military engineers for high-grade spelter 
for the production of cartridge brass permits a maximum of 
only O'i5 per cent, of cadmium. 

Season cracking in brass, which was formerly attributed solely 
to cadmium, is now recognised to be the result of internal strains 

146 



THE PHYSICAL AND CHEMICAL PROPERTIES OF ZINC 

due to improper heat treatment or the entire lack of heat treat- 
ment. On the other hand, cadmium if present beyond 0-5 per 
cent, is considered to be injurious when the spelter is used for 
sheet rolling, for galvanising, and for making slush (ornamental) 
castings. Its presence in galvanising is very important, as 
brittleness due to cadmium causes the coating to peel off. This 
is of particular importance in galvanised wires for telephone and 
telegraph purposes, which are sharply bent in making splices. 

Cadmium has a strong tendency to make castings crack. In 
brass cadmium tends to act like lead, and is also said to make the 
metal more sensitive to heat treatment. The amount present 
in brass is, however, seldom large, since it *readily volatilises 
during melting. 

Arsenic, Antimony, Copper, Sulphur and Carbon. These 
elements are seldom present in sufficient quantities in spelter to 
affect its properties for the uses for which the metal is usually 
employed. Arsenic, however, should be absent in zinc used for 
generating hydrogen for use in lead burning, or autogenous 
welding, otherwise it is often impossible to burn a strong seam. 
It should also be absent in zinc intended for the precipitation of 
gold in the cyanide process, as in treating the precipitate with 
acid arseniuretted hydrogen is given off, and this has resulted in 
several fatal accidents. 

Tin and Aluminium should always be looked for in remelted 
spelter. Tin tends to make zinc very hard and brittle in rolling. 
Some brands of remelted spelter contain aluminium, usually 
to the extent of about 0*3 per cent. 

Small quantities of copper are not infrequently present in 
remelted spelter. 



147 L 2 



CHAPTER IX 

THE MARKETING OF ZINC 

Grades of Commercial Zinc 

THE quality of commercial zinc varies considerably according 
to the method of production, but in many cases the sole practical 
difference between ordinary commercial spelter and the much 
more valuable fine-zinc is represented by the lead content. For 
some industrial uses zinc is required in a state of fairly high 
purity, consequently there is a good demand for high-grade 
metal. 

The brands of zinc produced by remelting scrap metal, &c., 
usually contain impurities and are of inferior quality. 

The slab zinc is marketed under various names, which are 
used by the different smelting companies to denote their products, 
the quality of which is known to the users of zinc. 

A large number of brands of spelter are made on the Continent. 
Many of the works make two or three different brands, varying 
in quality and price mainly according to the lead contents, 
but in some cases dependent upon whether the metal is 
higher or lower in iron. The grading of commercial zinc 
according to the amount of impurity, especially lead, is 
most desirable, and, as shown below, has been generally adopted 
in America in recent years. In this country, however, a hard 
and fast classification does not appear to obtain, and what are 
described as good ordinary brands show a very large variation 
in the proportion of lead. Furthermore, different consignments 
of spelter of the same brand will often vary in this manner 
to an undesirable degree. 

In good ordinary brands (G.O.B.) of British spelter the lead 
usually varies from 0-8 to 1-8 per cent, and the iron from 0-02 to 

148 



THE MARKETING OF ZINC 



0-04 per cent. In Silesian unrefined spelter, as tapped in hand 
ladles, the lead is usually higher, reaching over 2 per cent. In 
some brands of American high-grade zinc lead is absent or does 
not exceed 0-02 and the iron o-oi to 0-02 per cent. The brands 
of electrolytic zinc seldom show higher purity than is obtainable 
by modern fire refining. The purity in both cases is usually 
guaranteed 99-95 per cent, of zinc. 

The following analyses of British, Continental and American 
brands of spelter may be taken as typical : 

ANALYSES OF COMMERCIAL ZINC. 







Cad- 








Zinc. 


Lead. 


Iron. 


mium. 


Tin. 


Copper. 


Brand. 


Per 


Per 


Per 


Per 


Per 


Per 




cent. 


cent. 


cent. 


cent. 


cent. 


cent. 


Central Zinc Co. (British) 1 . . 


98-642 j 1-205 


0-06 


0-089 


_ 


0-004 


V.M.G. (Belgium) 2 
Vieille Montagne (Belgium) 2 . . 


99-05 0-66 
97-89 2-00 


0-26 
0-04 


0-07 


0-03 





Freiberg (Saxony) 2 


98-84 


1-03 


0-04 


0-02 


0-07 


. 


Lazyhutte (Upper Silesia) 2 . . 


97-85 I-I2 


O'O2 


0-017 





. 


Lipine Electrolytic (Upper 












Silesia) 2 


99.905 


0-06 


O-OI 


0-005 


0-02 


- 


Font-d'art (France) 8 


99.718 


o-i35 


O-2O 


0-123 





trace 


Scrap 3 . . . . . . . . 96-447 


2-05 


0-03 


0-003 


I-4I 


0-06 











The virgin spelter produced by the Central Zinc Company, at 
Seaton Carew, Durham, is from Broken Hill ore. 

The American Society for Testing Materials suggested in 1911 
the following four grades for commercial spelter. 





Grade. 


Lead. 
Per cent. 


Iron. 
Per cent. 


Copper. 
, Per cent. 


Total 
not over 
per cent. 


A. 

B. 


High grade . . 
Intermediate . . 


0-07 

O-2O 


0-03 

0-03 


| 
0-05 
0-05 


O-IO 

0-50 


c. 


Brass special . . 


0-75 


0-04 


0-75 


I-2O 


D. 


Prime Western 


1-50 


0-08 







1 Moulden, Journal of Royal Society of Arts, 1916, vol. Ixiv, p. 512. 
- Primrose, Journal of Institute of Metals, 1909, vol. ii, p. 234. 
3 Jones, Journal of American Institute of Metals, 1915. 

149 



THE ZINC INDUSTRY 

The figures represent the maximum percentage of impurities 
allowable. This classification corresponds substantially with 
the understanding among American zinc smelters. 

The following table gives the analysis of typical commercial 
samples of the various grades of American spelter l : 



Zinc. 
Per cent. 


Lead. 
Per cent. 


Iron. 
Per cent. 


Cadmium. 
Per cent. 


High grade 




99-960 


010 


026 


040 


,, ,, 




99-945 


041 


014 





,, ,, 




99-951 


35 


-014 


- - 


Intermediate 




99-896 


095 


009 


. 


,, 




99-793 


190 


-017 


. 


Jf 




99-746 


123 


Oil -I2O 


Brass special 




99-631 


343 


026 


. 




99-5I3 


'474 


013 


i 




99-036 


680 


oio -274 


Prime Western 




99-045 


870 


062 -023 


, ,, 




98-253 


-644 


013 1-090 


. > 




98-641 


1-270 


oio -079 


2 




98-503 


1-448 


024 -024 


Willemite (Eastern Penn- 






sylvania) 2 . . . . 99-955 


039 


003 -ooi 






and copper 


and copper 


' 




OOI 


002 



The " Prime Western " brand corresponds with " good ordinary 
brands " in European quotations and includes the bulk of 
American spelter. 

The grade produced in largest amount in America is " Prime 
Western," a considerable part of which is used for galvanising 
iron and steel wire and sheet. " Brass special " is used chiefly in 
the manufacture of brass. The price of " high-grade " spelter is 
usually 2 to 4 cents per Ib. more than that of " Prime Western." 
The "high-grade" and "intermediate spelters" are made by 
only a few smelters, but the "brass special" and "Prime 
Western " are made by many concerns. 

Sampling Zinc. Slabs of spelter as supplied by the smelter 
are not of exactly uniform composition, as the kettle into which 
the metal is received from the furnace holds a relatively small 
quantity, and the impurities passing over with the zinc vary in 

1 G. C. Stone, Transactions of the American Institute of Metals, 1915, 
vol. ix. 

2 J. L, Jones, ibid. 

150 



THE MARKETING OF ZINC 

amount in different parts of the furnace, according to the tempera- 
ture of the retort. To ensure uniformity as far as possible, the 
zinc should be tapped into large ladles or remelted in large pots 
or furnaces before being cast into slabs for delivery. 

Segregation of the impurities, however, invariably takes place, 
and slabs of commercial zinc are rarely uniform in composition. 
Under these conditions the sampling of the slabs is a matter of 
considerable importance, although it does not always receive 
the attention it deserves. 

One slab out of every ten should be taken for sampling to 
secure a trustworthy average of the shipment or consignment, 
but this practice is not always carried out. American brass- 
makers follow a time-honoured practice of sampling a carload 
(about 50,000 Ib. of spelter in 820 to 960 slabs) by drawing 10 slabs 
at random, and that practice has recently received the endorse- 
ment of t.,e American Society of Testing Materials. 

The sample for analysis is taken from the selected slabs either 
by breaking a small piece off one corner of each slab or by 
drilling right through each slab. 

The latter method is the more satisfactory, provided proper 
precautions are taken to prevent contamination of the sample 
with iron from the drill. A twist drill, about f inch, is very 
suitable for the purpose. It must be kept sharp and be 
fed slowly enough to enable it to clear itself of all drillings. 
If this is not done, the drillings are liable to pick up iron from 
the drill in such a firmly adhering form that removal by means 
of the magnet or otherwise is out of the question. Sampling by 
sawing the slab completely through with a band saw, as is 
frequently done in sampling pigs of lead, has been adopted in a 
few cases with satisfactory results. 

The Price of Zinc 

When viewed over a considerable period of years, the market 
value of spelter has, not unnaturally, fluctuated considerably. 
When first produced it realised a high price, which rapidly fell 
as production increased and no new output for its consumption 
opened out. 

In renewing the price of zinc Moulden points out that in 1807 l 

1 The prices quoted, 1807 to 1850, are based upon figures as given by 
Liebig : " Zink und Cadmium," Leipzig, 1913 (per J. C. Moulden). 



THE ZINC INDUSTRY 

it was about 40 per ton, rose in 1808 to 84 per ton, and then 
fell steadily as production overtook demand, until in 1820 it 
stood at no more than n. 

The extension of sheet rolling caused the price to rise until 
in 1825 it reached 30 ; it fell again as production increased, and 
between 1830 and 1836 fluctuated between 10 and 19. It 
again fell to 10 in Breslau (the Silesian centre) in 1848. In 
1850 it was quoted at about 16, and from that time onward 
to 1913 the yearly average fluctuated between 13 195. nd. 
(the lowest touched in 1885) and 27 is. $d. in 1906. 

Moulden remarks that the general tendency of late years has 
been towards a distinctly higher average level. For a very long 
time low wages and easily won and treated ores kept the price 
low. As wages increased and difficulties of treatment arose the 
improvements in metallurgical efficiency and extraction kept 
pace up to a certain point and compensated the producer. Beyond 
this point there was bound to be a rise in average value, and this 
is clearly reflected in the fact that only twice since 1898 has 
the average price been below 20, and never since the close of 
1902. Prior to the war industrial conditions had reached such 
a point that, broadly viewed, a 20 market was considered by 
smelters to be unremunerative and distinctly unprofitable in 
particular for those concerns which did not themselves possess 
mines. 

The establishment of the Zinc Conventions (see p. 155) and 
the German control of Australian concentrates, not unnaturally, 
had some influence in regulating the price of spelter. 

" The Metallgesellschaft, acting on behalf of the German 
Group, purchased for a number of years the whole supply of 
Australian zinc concentrates, and the price was regulated by 
the average of the mean daily quotations made on the London 
Metal Exchange. The Metallgesellschaft, through its Australian 
connection, the Australian Metal Company, and Hirsch & Com- 
pany, through their Australian representative, arranged the 
contract with the Broken Hill Groups. 

" The contract was made so that if the price of spelter rose 
above 22 or 23 a ton, any excess above that price was divided 
equally between the buyer and the seller. That contract having 
been signed, the European Spelter Convention was formed about 
the middle of January, 1909. Spelter at that time was 21 IQS. 
a ton, and it is now common knowledge that it was forced up to 

152 



THE MARKETING OF ZINC 



more than 27 a ton. The higher price brought a remarkable 
increase in production, so that the price, after touching more 
than 27 a ton in 1911 and 1912, fell during the first half of 1913 
to 22 a ton, and during July and August of the same year to 
about 20 IDS. a ton." 1 Thus the successful negotiations and 
contracts for the Australian was a mere question of s. d. or 
who would pay the highest price. 

Owing to the conditions that prevailed consequent upon the 
outbreak of war, the selling price of spelter appreciated to more 
than five times its pre-war figure. During 1915 the price of the 
metal was subject to more violent fluctuations than have been 
recorded during the past fifty years. 

THE HIGHEST, LOWEST, AND AVERAGE PRICE PER TON OF COMMERCIAL 
METALLIC ZINC IN THE LONDON MARKET FROM THE YEAR 1900 

TO 1917. 







English 
spelter. 


Foreign 
spelter. 


Year. j 








Highest. 


Lowest. 


Average. 


Average. 




s. d. 


s. d. 


s. d. 


s. d. 


1900 


22 15 


18 10 o 


20 16 o 


20 13 5 


1901 


18 18 9 


16 o o 


17 14 5 


17 7 6 


1902 


19 17 6 


16 7 6 


19 3 8 


18 14 8 


1903 .. . . 


23 18 9 


19 15 o 


21 12 


21 4 8 


1904 


25 10 o 


21 2 6 


23 2 II 


22 l8 


1905 


29 2 6 


23 5 o 


26 


2 5 15 2 


1906 


29 10 o 


24 o o 


27 12 4 


27 8 o 


1907 


28 2 6 


19 10 o 


24 II I 


24 9 6 


1908 


21 17 6 


18 o o 


21 II 


20 17 i 


1909 . . 


23 6 3 


21 I 3 


22 16 6 


22 13 


1910 


24 5 o 


21 12 6 


23 19 o 


23 12 


1911 


27 17 6 


22 17 6 


25 3 9 


25 16 7 


1912 


27 12 6 


25 o o 


26 3 4 


27 4 2 


1913 


. . 


1 


22 14 3 


23 15 6 


1914 


34 o o 


21 6 3 






1915 


I2O O O 


28 o o 


Average 


66 13 8 


1916 


110 


44 o o 






1917 


57 o o 


44 o o 







It rose gradually from 28 per ton in January of that year to 
120 in June ; then a reaction occurred, and by August the price 
had fallen to 55 a ton. Thence up to November there was 

1 H. Kaye, Journal of the Institute of Metals, 1916, vol. xvi, p. 186. 

153 



THE ZINC INDUSTRY 

another increase until the price was again more than -fioo. In 
1916 the highest price reached was 110, and the lowest 44, 
while in 1917 the price rose to 57 and went as low as 44. The 
year closed with zinc at about 52 per ton. 

The yearly and monthly average prices of spelter for the ten 
years prior to the war are given in the table on p. 153. 

In normal times the prices of metals reflect, in a large measure, 
the relation between production and consumption, but for some 
time past such cannot be said to be the case, as the metal industry 
is now controlled by the Government, almost all the available 
supply being devoted to the purposes of war, the ordinary trade 
requirements having, naturally, to be left unfilled. 



The World's Zinc Markets 

London is the principal European zinc market, the price of 
the metal being quoted in s. d., according to the prevailing 
prices for G.O.B. (" Good ordinary brands " or " Good ordin- 
aries "), and a slightly higher quotation for " Specials," the purer 
quality of zinc. As previously stated, many of the smelters, 
both in this country and abroad, make two or three different 
brands of zinc, varying in quality mainly according to the lead 
contents, but in some cases dependent on the iron content. 
They are sold at various prices, the better grades of metal natu- 
rally commanding higher prices. British spelter is usually quoted 
under the heads of " Ordinary brands/' " Special brands," and 
" English Swansea." 

The several selling centres for zinc in the German Empire 
are Breslau, Cologne, and Frankfort-on-Main. The price is 
always quoted in marks per ton, the difference in price between 
each brand being usually I or 2 marks. 

The American zinc market is entirely independent of that of 
the rest of the world, as, under normal conditions, America is 
not favourably situated to compete with the British and Conti- 
nental markets. The conditions relating to the marketing of 
zinc in America have been summarised recently by C. H. Fulton 1 
as follows : 

1 Technical Paper 83, Bureau of Mines, Washington, 1915, p. 38. 

154 



THE MARKETING OF ZINC 

" The main market or basing point for spelter is St. Louis, 
Missouri, for the reason that the great zinc fields and a large 
number of the smelting plants for zinc are situated not far from 
St. Louis. However, the large consumption of spelter is at places 
between St. Louis and New York, and it is sold in New York 
on a St. Louis basis, the quotations being given in cents per Ib. 
The New York price is the St. Louis price plus 15 cents per 
100 Ib., which is the freight rate on spelter from St. Louis to New 
York. The American market is in part independent of the 
European market, because spelter is protected by an import duty 
of 15 per cent, and zinc in ore by a duty of 10 per cent, ad 
valorem. 

" In the marketing of zinc, it is customary for the producer 
to sell direct to the manufacturer. This policy, however, in 
view of the large number of producers, is not nearly so closely 
followed as in the selling of copper, and some of the producers, 
particularly the smaller ones, sell to anyone who cares to purchase. 
This condition of course gives rise to more speculation in zinc 
than in copper. The real spelter market is established by the 
private transactions of producer and consumer, and any informa- 
tion as to the state of the market can come only from them. 
The facilities for exchanging information in the spelter market 
are not as good as those in the copper market, and hence transac- 
tions between producer and manufacturer often show considerable 
difference in price." The four brands of spelter on the American 
market, with their names and permissible proportions of impuri- 
ties, have been given on p. 149. 



The Spelter Convention 

Prior to the outbreak of war the spelter market was very 
largely controlled by the Spelter Convention, an association 
of zinc smelters formed in 1909 and elaborated in 1910. Separate 
syndicates were formed for each zinc-producing country, and 
included all the German, most of the Austrian, Belgian and 
French, and many of the British smelters. The Convention 
consisted of three groups : 

Group A, known as the Verband, or German Syndicate, com- 

155 



THE ZINC INDUSTRY 

prised the associated German and Belgian makers, whose output 
was disposed of by a joint selling office. 

Group B comprised certain Belgian and French producers. 

Group C comprised the British producers. 

The two latter groups constituted the International Spelter 
Syndicate, which on December i8th, 1913, was, with slight 
changes, renewed on the old conditions until April 3oth, 1916. 
The German Syndicate was also prolonged until the same date. 

The object of the Convention was to control output by fixing, 
within certain limits, the individual production of its members, 
and to ensure a uniform mode of selling, and, if the market 
showed that the demand was not keeping pace with the output, 
to restrict the latter. 

On the Continent, the sale of the metal was in the hands of 
the leading trading companies in metals and minerals, who, 
jointly with the producers, fixed the selling prices and the 
quantities to be produced by each works. Over-production 
above the quantities fixed by the board of management was 
subject to heavy penalties. The total of the amounts realised, 
after deduction of selling and administration expenses, was 
distributed amongst the various works in accordance with the 
deliveries made by them, and in taking into consideration certain 
geographical positions and superior qualities of spelter produced, 
various premiums were admitted. The smelters with their own 
mines (" Erzhuetten "), on the other hand, paid a certain amount 
for each ton of ore produced and treated by them to make up 
for the advantage they had against the " Lohnhuetten," or 
customs works, who bought their ore in the market. 1 

Restriction of output came into force when the average price 
of spelter in the London market had remained at 22 or under 
for two months, and when the unsold stocks, which were taken 
quarterly, amounted to 50,000 tons. 

The British and French smelters were bound to a joint restric- 
tion of output in certain circumstances, but they had more 
liberty of action than the other members, being free from selling 
restrictions. The German smelters were under the most stringent 
rules as regards production, prices and agencies through which 
sales could be made. 

1 J. Gilbert, Mining Journal, London, 1916, vol. cxiv, p. 497. 

156 



THE MARKETING OF ZINC 

American smelters were not included in the Convention, as 
the home consumption at that time equalled the production, 
and it was therefore unlikely that they could influence the 
European market. 

Pursuant to the above provisions the International Syndicate 
on May 26th, 1913, reduced prices by 505. per ton, and the London 
quotation went down to 23. On October ist, 1913, the Conven- 
tion ordered a reduction in output of 8 per cent. 

" On the whole," according to J. Gilbert, 1 " the Spelter Syndicate 
may be said to have served the interests of European producers 
to some considerable extent by regulating the uniformity of 
the supply, which has permitted a steady progress of the industry, 
with fairly uniform remuneration of capital and labour, and with- 
out unduly exposing it to the inveterate risk of speculation, which 
very frequently most radically interferes with the interests of 
both producers and consumers of certain commodities. Unfortu- 
nately, however, so far as British interests are concerned, one 
all-important feature has been overlooked, and that is the fact 
that, whilst British consumers of spelter absorb about 40 per 
cent, of the European production, the British production of 
spelter hardly exceeds 10 to 12 per cent, of the European output." 



The Production and Consumption of Zinc 

Production. Owing to the complications introduced by primary 
and secondary and redistilled hard spelter, &c., it is very difficult 
to ascertain with accuracy the world's yearly production of zinc. 
The bulk of the metal will, however, have been produced direct 
from ore, possibly about 75 per cent., leaving 25 per cent, for 
remelted metal recovered from scrap metal, galvanisers, ashes, 
&c. The world's output of spelter from the early days of the 
industry to modern times has been given previously. The 
quantities of spelter produced by the chief countries for the ten 
years ending 1913 are shown in the following table. 

1 J. Gilbert, Mining Journal, London, 1916, vol. cxiv, p. 487. 



157 



THE ZINC INDUSTRY 









MON-^-C^OHOO MOO 

M t^. co M O t^vo N ON N 



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oo ON N 

C/4 M 



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t-N 
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vO ON co rovO O <O N 



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VN 



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vO CO 



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CO O^ t^ ON C/ 00 ONVO 

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III 






THE MARKETING OF ZINC 



From the figures on p. 158 it will be seen that the absolute and 
relative contributions of Europe and the United States to the 
world's production of spelter for the years 1910-1913 are as 
follows : 





Europe. 


United States. 


Year 












Per cent, of 




Per cent, of 




Metric tons. 


world's 


Metric tons. 


world's 






output. 




output. 


IQIO 


565.500 


69-3 


250,600 


30-7 


IQII 


632,900 


70-2 267,500 


29-7 


1912 


661,100 


67-6 3I4.5 00 


32-2 


1913 


673,900 


67-5 


320,300 


32-1 



Consumption. One of the difficulties in estimating the amount 
of zinc used in the Arts is that variable proportions of old material 
are used with new material, and in consequence the consumption 
sometimes exceeds the total production for the year. The esti- 
mates of consumption take no account of any stocks which may 
exist, and hence, theoretically, the total consumption should 
yield the same figures as the total production. 

Taking into account stocks at German works, the actual con- 
sumption of spelter in Germany during 1911 was about 217,900 
tons, in 1912 about 220,800 tons, and in 1913 about 221,800 tons. 
When the stocks of other countries are taken into account, the 
returns show that prior to the war the production for the years 
named was in excess of the consumption. 

The following table shows the absolute and relative contribu- 
tions of Europe and the United States to the world's consumption 
of spelter for the years 1910-1913. 



Europe. 



United States. 



Year. 


















Per cent, of 


Per cent, of 




Metric tons. 


world's 


Metric tons. world's 






output. 




output. 


1910 . . 


599,4 


73'4 


244,500 


29-9 


1911 


652,400 


72-3 


251,600 


27-8 


1912 


667,700 


68-2 


312,900 31-9 


1913 


675,000 


67.7 


313,300 31-4 



159 



THE ZINC INDUSTRY 



The world's consumption of spelter during the ten years imme- 
diately preceding the war is shown in the following table. 

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III It II I 

160 



CHAPTER X 

THE INDUSTRIAL APPLICATIONS OF ZINC 

THE most important use of metallic zinc is in galvanising, which 
probably consumes more than 70 per cent, of the total output. 
The manufacture of brass probably utilises another 20 per cent., 
while the remaining 10 per cent, is used for conversion into 
sheets and for minor purposes, such as the production of alloys 
other than brass. 

Galvanising. The process of zincing, or, as it is termed, 
galvanising, which was discovered by Crawford in 1837, consists 
in depositing a very thin coat of zinc on iron, whereby the latter 
is preserved from oxidation by the atmosphere. In the United 
Kingdom galvanising has become an important branch of metal- 
lurgical industry and is very extensively practised, the chief 
centres of production being the Birmingham, Wolverhampton 
and South Wales districts. 

Galvanising may be effected by the method known as hot 
galvanising (immersion in molten zinc), by the electrolytic pro- 
cess, by Sherardising, or by Schoop's metal-spraying process. 

The hot galvanising process was, however, responsible for the 
production of practically all the 850,000 tons of galvanised sheets 
and wire exported from the United Kingdom in 1913. 

In this process the iron is first freed from scale by immersing 
(" pickling ") in hydrochloric acid, then washing well and scouring 
with sand. After cleaning, the plates or other articles are 
immersed in the galvanising bath, which is contained in a 
wrought iron pot, and consists of molten zinc covered with a 
layer of ammonium chloride. 

The strength of acid used for pickling varies with the nature 
of the work. In the United Kingdom a 20 per cent, solution of 

161 M 



THE ZINC INDUSTRY 

hydrochloric acid is generally used for iron sheets, and acid of 
12 per cent, strength for iron wire and tubes. The pickle is 
used cold, or nearly cold, and the operation is complete in a few 
minutes. At some works, particularly on the Continent, dilute 
sulphuric acid is used in place of hydrochloric acid for reasons of 
economy, but in this case a longer immersion is necessary. The 
temperature of the galvanising bath determines the thickness of 
the zinc coating ; the hotter the bath the thinner the deposit. The 
solvent action of zinc on iron, according to Diegel, 1 increases 
gradually up to about 490 C., above which temperature it rises 
very rapidly, being thirty times greater at 530 C. than below 
490 C. 

The iron sheets may be passed, after their passage through 
the bath, between rolls or wire brushes to remove superfluous 
zinc, and thus reduce the consumption of zinc. This treat- 
ment considerably improves the surface of the sheets. 
Zinc of good quality should be used for the galvanising bath, 
as the presence of lead exceeding 2 or 2-5 per cent, renders the 
zinc unsuitable for galvanising, the lead being easily dissolved 
by most soft waters, thus exposing the surface of the galvanised 
metal and hastening corrosion. Galvanised sheets often exhibit 
a beautiful moirt-metallique surface, due to the crystallisation of 
the zinc. When it is especially desired that the finished articles 
shall have a spangled appearance, from 2 to 3 per cent, of tin is 
sometimes added to the zinc bath. The addition of aluminium 
is said to increase the fluidity of the galvanising bath, owing 
to its deoxidising action, and also to its influence in effecting 
the separation and precipitation of the iron that accumu- 
lates in the bath. The aluminium should be added in 
the form of a zinc-aluminium alloy with a melting point 
below 480 C. Corrugated iron sheets form a considerable portion 
of the galvanising trade ; these are often galvanised plain and 
then passed through the corrugating machine. The galvanising 
of iron wire, such as is employed for fencing, signal wires, &c., 
is performed with great rapidity, the coiled wire being annealed 
at the same operation. For this purpose the coiled wire is 
drawn through a furnace of such length that the wire in its 
passage through it is heated to redness, whilst the heated wire, 
as it passes out from the furnace, is directed by guide pulleys 
through a reservoir of dilute sulphuric acid (pickle), which has 

1 Journal of the Society of Chemical Industry, 1915, vol. xxxiv, p. 1147. 

162 



THE INDUSTRIAL APPLICATIONS OF ZINC 

the effect of cleaning off any scale. On leaving the pickle it 
passes through a quantity of sand, whereby the wire acquires a 
clean metallic surface before it enters the bath of molten zinc. 
In this manner, whilst one end of the wire is still passing 
through the annealing furnace, the other extremity is being 
wound on to a drum in its galvanised state. 

Owing to the great ease with which zinc is attacked by acids, 
galvanised iron is not adapted as a constructive material where 
it would be exposed to acid vapours. 

In addition to sheets and wire, the process of galvanising is 
applied to chains, links, and many other articles requiring to 
be protected from corrosion. 

The hot galvanising process yields two by-products : (i) hard 
zinc and (2) flux skimmings. The former is an alloy of zinc 
and iron, containing from 2 to 5 per cent, of iron, resulting 
from the gradual contamination of the zinc bath with iron. 
Being heavier than zinc, this alloy sinks to the bottom of the 
bath in pasty masses, and is removed from time to time by means 
of a perforated iron ladle, and cast into plates, which, when 
broken, exhibit a close-grained fracture with black spots character- 
istic of zinc containing iron. Part of this alloy passes into 
commerce for use where a zinc-iron alloy is required, and the 
remainder is liquated to separate as much zinc as possible. 
For this purpose the alloy is usually remelted at a high tem- 
perature, when it separates into two layers, the top layer 
consisting of tolerably pure zinc, which is carefully ladled off. 
The bottom layer is much less fusible, and forms a hard 
crystalline or granular material of the colour of zinc, but less 
lustrous. This ferriferous zinc is very friable, and frequently 
exhibits surface colorations of great beauty ; it contains about 
7*5 to 9 per cent, of iron, and is sold to the zinc smelters, who 
recover the zinc by a special redistillation. 

The scum that accumulates on the surface of the galvanising 
bath and known as " flux skimmings " is removed from time to 
time. It consists of chloride and oxide of zinc together with 
some ammonium chloride and dirt. It is sold to the smelters, 
who treat it, usually by distillation, for the recovery of the zinc. 

The disposal of the waste pickling liquors, which contain 
about 15 per cent, of hydrochloric acid and 10 per cent, of iron, 
chiefly as ferrous chloride, has caused considerable trouble in 
many localities where galvanising is carried on, and special 

163 M 2 



THE ZINC INDUSTRY 

processes have been devised to deal with them. Hitherto the 
usual system has been to neutralise the acid with lime and 
subsequently to roast the precipitate of ferrous hydroxide so 
obtained in order to convert it into red oxide of iron, which is 
sold. 

The great increase in the price of zinc since the outbreak of war 
seriously affected the galvanising industry and led to the 
adoption of other methods and of substitutes, such as electro- 
galvanising, which consume much less zinc, and galvanising with 
lead, either by the hot process or by electro-deposition. Although 
it is not easy to disturb the settled demand for a world-wide 
commodity such as galvanised sheets, there are obvious possi- 
bilities in substitutes, once the buyer is familiarised with them 
and finds them cheaper. Experience shows that substitutes 
for zinc will probably hold some of the ground they have 
temporarily acquired. 

The electro-galvanising process has gained considerable favour 
in recent years, and its use is rapidly extending for certain classes 
of work, as it possesses several important advantages over hot 
galvanising. These may be summarised as follows : (i) greater 
economy in the use of zinc, as a much thinner deposit than that 
afforded by hot galvanising is sufficient to prevent rusting ; 
(2) more complete control of the thickness of the coating on 
various surfaces ; and (3) suitability for articles, such as steel 
springs, which have been subjected to special heat treatment 
and must not be heated to the temperature of molten zinc. 
Another advantage claimed for electrolytic galvanising is that it 
reveals defects, such as fine cracks, &c., in the iron, which 
would be concealed by hot galvanising. On the other hand, 
the electro-galvanised surface is dull or " dead " and not so 
pleasing in appearance as that produced by the older method. 

Although a large number of solutions have been tried for 
electro-zincing, the general opinion amongst practical operators is 
that solutions of the sulphate, either alone or with other salts, 
give for general purposes the most trustworthy results, with the 
minimum of trouble in working. 1 In practice, the zinc is usually 
employed either in the form of a neutral solution of the sulphate 
or dissolved in excess of caustic soda. 

" Sherardising." In the process of coating iron and steel with 
zinc, introduced by Sherard Cowper Cowles, and known as 

1 " Electro-Plating," Barclay and Hainsworth, London, 1912, p. 312. 

164 



THE INDUSTRIAL APPLICATIONS OF ZINC 

" Sherardising," the articles, after being thoroughly cleaned by 
pickling, &c., are heated in metal drums, or boxes, in contact 
with zinc dust at a temperature of from 260 C. to 425 C. 
Vaporisation of the zinc dust takes place, the metal vapour then 
condensing on the surface of the iron articles. A zinc dust 
having a high metallic content will give the best coating. The 
condensed zinc slowly combines with the iron, giving a coherent 
protective coating that is highly resistant to corrosion. 

The iron content of the Sherardised coating is a function of 
the temperature. The process is therefore carried out at the 
lowest temperature that is economically possible to secure a low 
iron content in the coating, since a high iron content is detri- 
mental to the weathering properties of the coating. 

The Sherardised surface is light grey in colour, with a dull or 
matte finish, but it is capable of receiving a high polish and 
made to resemble nickel plate. The process is economical and 
yields a superior product, and will doubtless receive more atten- 
tion in the future than has been hitherto accorded to it. It is 
specially adapted for coating articles having a pattern or design 
on the surface which would become filled up and obliterated if 
the ordinary galvanising process were employed. Iron screws 
which have been galvanised by Sherardising are ready for use 
without further treatment. Narrow tubes can be galvanised 
inside by Sherardising, and this process has been used for coating 
with zinc the iron 5 pfennig pieces recently introduced in the 
coinage system of Germany. 

The process of galvanising, patented by Schoop, of Zurich, 
consists in projecting a spray of pulverised zinc on to the goods, 
previously cleaned and warmed, until a zinc deposit about 
o-i mm. thick is produced. The adherence of the deposit is 
said to be perfect. In the latest development of the spray pro- 
cess the zinc in the form of strip or wire is fed at a uniform rate 
into an oxy-hydrogen or other flame (or even an electric arc) 
sufficient to melt it readily. As fast as the metal melts a stream 
of compressed gas directed on it carries it away in a state of 
fine subdivision on to the surface to be coated. In practice, a 
specially constructed " metal spray pistol " is used for producing 
the spray. Very promising results are said to have been obtained 
by this process in Belgium and France, where it is in use on a 
large scale. 

165 



THE ZINC INDUSTRY 



Rolled or Sheet Zinc 

Zinc lends itself well to rolling into sheets when the operation 
is carried out at a temperature between 100 C. and 150 C., 
within which range the metal is most malleable and ductile. In 
spelter intended for rolling, a small percentage of lead is desirable, 
as it improves the rolling qualities of the zinc, but the amount 
should not exceed i per cent. The rolled zinc of commerce 
is therefore a nearly saturated solution of lead in zinc, 
since it usually contains I per cent, of lead. Iron increases 
the hardness and impairs the malleability of zinc and should not 
exceed 0-15 per cent. In practice, it is usual partially to refine 
the spelter by liquation, so as to reduce the lead and iron 
to the minimum practicable by such methods, and when the 
refining has been properly conducted these amounts have little 
or no effect upon the malleability and ductility of the zinc. 
The metal to be used for rolling into sheets is cast in open moulds 
into flat ingots or plates which, whilst still hot and at the proper 
temperature, are rapidly passed through the rolls until the 
correct gauge is attained. For convenience, the ingot moulds 
are sometimes arranged in a circle on a rotating table. 

Most of the zinc rolling is done on the Continent in Silesia and 
Belgium. The output of sheet zinc in Belgium in 1913 was 
51,500 metric tons. A small quantity is rolled in the United 
Kingdom, chiefly at Birmingham, where zinc was first rolled 
early in the last century. There are also zinc rolling mills in 
the United States. 

Prior to the war it was usual to import Continental zinc for 
rolling in this country, as it contained more lead than most of 
the British brands, which after refining are relatively free from 
lead, and are mainly employed for the production of alloys. It is 
customary when rolling Continental zinc to remove the excess of 
lead by liquation, as previously stated. In addition to the small 
amount of zinc rolled in this country, more than 20,000 long tons of 
foreign sheet zinc are annually imported into the United Kingdom. 
It would thus appear that there is ample scope for the extension 
of the British zinc rolling industry. A very large proportion of 
the zinc sheeting annually produced is employed for roofing 
purposes, mainly on the Continent. The metal is used either 
in the original sheets, or in the form of ornamental stamped 

166 



THE INDUSTRIAL APPLICATIONS OF ZINC 

tiles, which are nailed to the roof in an inclined position in the 
same way as slates. As a roofing material, sheet zinc is durable, 
light and efficient. Although up to the present it has found little 
application in the United Kingdom for roofing, its uses for this 
purpose have become so extensive in Continental countries that 
the spelter market is very materially influenced by the pros- 
perity or otherwise of the general building trade. 1 

Thin sheet zinc finds application for a variety of purposes. 
In this form it lends itself readily to stamping in dies, 
and stamped ornaments in zinc were first produced in 1852. 
Within recent years it has found very considerable use for 
ceilings, the metal being stamped with varied ornamental designs 
in relief. It finds employment in the manufacture of many 
articles in ordinary domestic use, such as bath-tubs, pails, toys, 
c. Metal of thinner gauge is used for the lining of air-tight 
wooden cases, hermetically sealed by soldering, for export to 
tropical countries. When perforated, sheet zinc is used for 
screens, sieves and other purposes. Rolled zinc plates of specially 
high quality find important use in the photographic reproduction 
process known as photo-zincography and in photo-etching. 

Hot zinc sheets with a fine smooth polished surface are employed 
for producing the satinised surface finish on the better-class 
papers. 

Thick rolled zinc plates, sawn to suitable sizes and drilled for 
bolting, are used to a considerable extent in marine boiler work 
to prevent corrosion of the boiler plates. For this purpose the 
zinc is bolted into position in different parts of the boiler, and 
owing to its being highly electro-positive it is first attacked by the 
corrosive influences and can be renewed when necessary. It is 
essential, however, that thorough metallic contact between the 
surfaces should be made to obtain full advantage of the pro- 
tective influence of the zinc. 



Zinc Castings 

The use of zinc in the foundry is somewhat limited, the demand 
for the cast metal being very small. It contracts but slightly 
on solidification, and. is thus well adapted for castings. The 
castings made at a high temperature are brittle and largely 

1 J. C. Moulden, loc. cit., p. 522. 

167 



THE ZINC INDUSTRY 

crystalline ; but when cast near the solidifying point they are 
more malleable. Overheating of the metal, with its attendant 
losses, should be carefully avoided. Ammonium chloride (sal 
ammoniac) is recommended as the best flux, its action being to 
convert the floating dross from a pasty mass to a " dry 
dust." 

Aluminium is recommended as the best deoxidiser, to be added 
after skimming, in the proportion of o-ooi per cent., and in the 
form of thin sheet clippings ; the fluidity of the molten zinc is 
thus increased. 1 

Owing to the facility with which lead segregates, especially 
if the metal is poured at a high temperature, no brand of zinc 
containing more than 0-5 per cent, of lead should be used in the 
foundry. 

Dies or blocks upon which hats are shaped are made of cast 
zinc. Cast zinc dies are used in the dental laboratory for swaging 
artificial metal-dentures. It is also employed for monuments, 
statues and tombstones, under the name of white bronze. 

Spelter is also largely used for the production of " slush " 
castings for ornamental purposes. 

In these, the metal in the mould is poured back into the 
ladle as soon as a thin layer has solidified on the face of the 
mould. These hollow castings must be sound, not merely 
for strength, but because they are all ornamental in character, 
and are usually required to be subsequently plated. The 
moulds are usually made of bronze, and many of the shapes 
are such as to cause excessive strains in the solidified zinc. The 
castings are polished and plated or otherwise finished. Makers 
of intricate slush zinc castings find it necessary to use 
metal of high grade, otherwise the castings are very liable to 
crack. Indeed so much is this liability to crack an indication of 
the quality of the metal that a number of the makers of high- 
grade zinc in America use the slush mould as a means of testing 
their product. 

Cast zinc rods find extensive application in battery cells for 
electrical work. Rods are also prepared for this purpose by 
rolling, or by extruding the metal. Zinc of high grade should 
be used in their manufacture, as the life of such rods is much 
longer than of rods made from ordinary brands of spelter. 

The employment of zinc for the manufacture of seamless pipes 
1 The Foundry, 1915. vol. xliii, p. 233. 

168 



THE INDUSTRIAL APPLICATIONS OF ZINC 

for water supply has been advocated in recent years. 1 The pipes 
are made from pure " hard " zinc and have a diameter up to 
80 millimetres. They can be tin-lined if required. Two pipes 
can be joined in the usual manner by widening the end of one 
and inserting the end of the other, or by covering the adjacent 
ends with a sleeve, and soldering. Tin solder is used, preferably 
with a stearine flux. The manufacture of the pipes is simple, 
and their bending easy. The pipes are as useful for water supply 
as lead pipes, and have the advantage of being much safer from 
a hygienic point of view, as no injury has been found to a rise from 
the traces of zinc which are dissolved by water. Zinc is cheaper 
than lead for this purpose, and on account of its lightness the 
pipes do not require such strong wall supports. A pressure of 
500 atmospheres is required to burst the pipes. These pipes 
cannot, however, be used for a hot water supply on account of 
the great expansion of zinc. In some recent tests by Rinck 2 
tap water of medium hardness was sealed up in large zinc pipes 
with air excluded. After a year the amount of dissolved zinc 
was 2 to 3 milligrammes per litre. Physiological tests over a 
long period with water containing 7 to 8 milligrammes of zinc 
per litre gave no indications of injurious results. 



Other Uses of Zinc 

Metallic zinc plays an important part in several metallurgical 
operations, notably in the precipitation of gold and silver in 
the cyanide process, the desilverisation of argentiferous lead 
by the Parkes process, and the reduction of silver chloride in 
gold refining. 

Large quantities of zinc are used annually in South Africa 
and elsewhere for precipitating gold from cyanide solutions by 
means of zinc shavings. The precipitation is usually effected 
in wooden or steel troughs (known as zinc boxes) containing 
shavings of zinc coated with precipitated lead, formed by dipping 
the shavings into a strong solution of lead acetate. The zinc 
shavings are very thin and light, and are carried on iron gratings 

1 Wittus, Jour. Gasbeleucht. 1913, vol. Ivi, pp. 936-937. Abstract, 
Journal of the Society of Chemical Industry, 1913, vol. xxxii, p. 957. 

2 A. Rinck, Zeit. Untersuch. Nahr. Genussm., 1914, vol. xxviii, pp. 99-103. 
Abstract, Journal of the Societv of Chemical Industry, 1914, vol. xxxiii, 

P. 88 3 . 

169 



THE ZINC INDUSTRY 

through which the auriferous solution passes. The gold is 
precipitated on the zinc as a black mud, and is recovered by 
dissolving out the excess of zinc with acid. After drying, the 
gold mud is melted with fluxes and the resulting metal refined. 
From 5 oz. to 16 oz. of zinc shavings are generally needed for each 
ounce of gold recovered. The consumption of zinc in South 
Africa, chiefly for this purpose, amounted to 4,867 tons in 
1914. 

The employment of zinc in the desilverisation of lead is based 
on the fact that when molten zinc is stirred with a bath of 
argentiferous lead, which is afterwards allowed to cool, a crust 
forms on the surface consisting of zinc alloyed with silver and 
any gold and copper that may be present. 

In the Parkes process, the solid zinc in slabs is thrown on the 
surface of the molten lead, and when it is melted the mixture is 
well stirred and then allowed to cool. The total amount of 
zinc added varies according to the content of silver, but is usually 
from ij to 2 per cent, of the weight of the argentiferous lead, 
and it is added in two or three lots, as several treatments with 
zinc are necessary to remove all the silver. The zinc crusts 
that form on the surface are removed by means of perforated 
ladles, the crusts being kept separate. 

Fresh additions of zinc are made until the lead contains only 
about one-sixth of an ounce (0-0005 P er cent.) of silver per ton. 
The zinc crusts, which are largely contaminated with lead, are 
submitted to liquation, whereby the lead separates and flows 
away, leaving the enriched scum behind. 

The rich scums are distilled so that a large proportion of the 
zinc is recovered and is available for further use. The residue 
consists chiefly of lead, and contains from 5 to 10 per cent, of 
silver, which is recovered by cupellation. It is essential that 
fairly high-grade zinc be used for the Parkes process, as certain 
impurities, particularly iron, cause a much larger consumption 
of zinc. The process is carried out in large cast iron pots holding 
as much as 50 tons. 

Zinc plates are used to a limited extent for the reduction of 
silver chloride resulting from the refining of gold. For this 
purpose the silver chloride is melted and cast into slabs, which 
are encased in flannel bags and boiled in water to remove base 
metals. The slabs are then arranged alternately with zinc plates 
in a tank of acidulated water, whereby the silver is reduced by 

170 



THE INDUSTRIAL APPLICATIONS OF ZINC 

electrolytic action. In modern practice, however, iron plates 
have been substituted for those of zinc. 

Attention has already been directed to the use of zinc balls 
for the precipitation of impurities in solutions that are to be 
submitted to electrolysis. Recently the use of zinc balls for the 
precipitation of gold in cyanide solutions in place of zinc shavings 
has been suggested and introduced at several mines. 

Metallic zinc has also been used for coinage. A new coin 
consisting of pure zinc, and representing in value the ^-^th part 
of a piastre, was legalised in 1905 for circulation in Indo-China. 1 
In that year 60,000,000 pieces, valued at 21,600, were struck 
at the Paris Mint. 



Zinc Dust (Blue Powder) 

There is a limited market for zinc dust, which, as previously 
pointed out, is a by-product from the distillation process. When 
zinc vapour is cooled too rapidly after distillation, or if it becomes 
too largely diluted with other gases, it condenses, not as fluid 
metal, but in the form of a fine bluish-coloured powder, consisting 
of an infinite number of minute globules coated with oxide, which 
prevent it from coalescing by ordinary means. Some of this 
substance, which is known as " Zinc Dust," " Blue Powder," or 
" Poussiere," is always formed during the process of distillation, 
and is usually found in the " prolongs " beyond the condensers. 

The amount produced varies from 3 to 10 per cent, of the total 
zinc present when retort smelting is used, but with electro- 
thermic processes the quantity is usually much larger. 

The commercial value of zinc dust depends upon its content 
of metallic zinc, and the best grades contain from 86 to 92 per 
cent, of zinc in the metallic state. 2 

The commercial standard is that it shall pass a loo-mesh 
sieve and not contain more than 10 per cent, of zinc oxide. 

Zinc dust is considerably more active chemically than spelter, 
being oxidised readily, and having the power to absorb hydrogen. 
On this account it finds many uses in chemical industries, being 
used to discharge locally the colour of dyed cotton goods and in 
the preparation of the indigo vat. It is used as a precipitant for 

1 Thirty-sixth Mint Report, 1906, p. 31. 

2 J. C. Moulden, loc. cit., p. 524. 



THE ZINC INDUSTRY 

the removal of copper, antimony, arsenic, &c., from electrolytic 
solutions containing these and other metals. 

It has also been used for the recovery of gold and silver from 
cyanide solutions of these metals, for which purpose it has been 
stated to be more efficient than zinc shavings. Latterly it has 
found increasing favour for this purpose, as the small amount 
of lead it usually contains acts beneficially in promoting more 
rapid and complete precipitation of the gold and silver. 

Reference has already been made to its use in the Sherardising 
process. 

Care has to be exercised in the storage of zinc dust, owing to 
the readiness with which it will fire if exposed to moist air, or 
wetted, when in bulk. Serious fires and even explosions have 
been caused in this manner. 



172 



CHAPTER XI 

INDUSTRIAL ZINC ALLOYS 

ZINC enters into the composition of a number of important 
alloys, to which, when present in certain proportions, it com- 
municates hardness without impairing the malleability of the 
alloy. In larger proportions it often renders the alloy 
brittle. 

Owing to the comparatively low melting point and volatility 
of zinc, the preparation of its alloys requires considerable care 
to prevent unnecessary loss of the metal. 

Modern research has shown that the mechanical properties of 
metals and alloys are materially influenced by the presence of 
small quantities of impurities, and has emphasised the necessity 
of employing pure metals in the preparation of alloys. This has 
led, in the case of zinc alloys, to an increasing demand for zinc 
containing less lead and other impurities than are usually present 
in commercial spelter. 

The economy and other advantages resulting from the use of 
high-grade zinc for alloying purposes are so great that brass and 
other alloy makers who have once employed it will never resort 
to ordinary spelter if they can help it. To meet this demand 
various works in the United Kingdom are producing a consider- 
able amount of high-grade metal by distillation, and also by 
electrolytic processes. 

There are but few alloys in which zinc is the main constituent, 
the chief being the so-called anti-friction metals, but in smaller 
proportion zinc is a valuable constituent in several very useful 
alloys. 

The alloys of industrial importance in which zinc is a con- 
stituent are (i) those consisting of.zinc and copper, constituting 

:I 73 



THE ZINC INDUSTRY 

the numerous varieties of brass ; (2) those consisting of copper, 
zinc, nickel, forming the so-called " German or Nickel Silvers " ; 
and (3) zinc with tin and other metals known as " anti-friction 
metals." 

Brass. Brass was first made by the Romans shortly before 
the Christian era, and was used both for coins and orna- 
ments. The ancient name of the alloy was latten, which 
is still retained in the French word laiton. In the Middle 
Ages the Germans were famous for the production of brass, 
which was imported into this country, principally from 
Cologne, chiefly in the form of rectangular pieces known 
as Cullen plates ; this was employed for the so-called 
" brasses " of churches, particularly in the Eastern Counties. 
More than 4,000 such brasses are known to exist in various 
churches, &c., in the United Kingdom, which is far richer in 
this respect than any other country. The first works for the 
production of brass in England are stated to have been erected 
by a German, at Esher in Surrey, about the middle of the seven- 
teenth century, copper being imported from Sweden for its manu- 
facture. Its manufacture was started in Bristol in 1702, and 
brass works were erected in Birmingham about 1740 by the 
Turner family. Birmingham is now the principal seat of the 
brass industry of this country, and so rapid has been the develop- 
ment within recent years, that in Birmingham alone prior to the 
war more than 35,ooo persons (male and female) were employed 
in the brass trade, the value of the metal consumed amounting 
to four millions sterling. 

Considerable impetus was given to the brass industry in the 
early part of the eighteenth century by the introduction of 
rolling mills, with the subsequent application of powerful stamping 
machinery, in 1769, which enabled articles to be produced in sheet 
metal more rapidly, with better finish and with less metal than 
by the process of casting hitherto exclusively employed. 

Among the more important factors that have contributed to 
the enormous development of the zinc industry in more modern 
times must be mentioned the introduction of gas fittings, in the 
early part of the nineteenth century ; the use of brass tubes in 
locomotives and marine engines ; the introduction of yellow 
metal sheathing ; the extended uses of brass for engineer's work, 
and for water fittings, &c. ; and more recently the very extensive 
employment of the metal for electrical fittings. 

174 



INDUSTRIAL ZINC ALLOYS 

Until the middle of last century, brass was exclusively made 
by the old process of " cementation," in which metallic copper 
was heated in crucibles in contact with calamine (zinc ore) and 
carbon, whereby zinc was liberated and combined with the copper 
to form the alloy known as " calamine brass." This ancient 
process was superseded by the direct preparation of brass which 
is now exclusively employed. This is effected by melting together 
a mixture of copper and zinc, either in crucibles, or when very 
heavy castings are required in a reverberatory furnace. 

When prepared in crucibles the zinc is added to the copper 
immediately after the latter is completely melted, the ingots 
of copper having been heated to redness prior to their intro- 
duction into the pots. In making castings, and in the remelting 
of brass, there is always a considerable loss of zinc through 
volatilisation, for which allowance must be made when arranging 
the mixture. 

The clay or graphite crucibles usually hold about 90 Ib. of 
metal, but much larger pots are sometimes employed. The 
crucibles are heated in small wind furnaces burning coke as 
fuel, or in furnaces heated by gas or oil. 

Zinc and copper alloy in all proportions, the resulting products 
being of uniform composition throughout, as the metals do not 
segregate. The colour and properties of the alloys vary with the 
relative proportions of the metals. When the alloys are of a 
decidedly yellow colour they are known industrially by the 
general term " brass," although many special names have 
been introduced by different makers to represent one and the 
same alloy, thus giving rise to considerable confusion. 

The term white brass is given to alloys in which zinc pre- 
dominates, giving a white alloy. As a result of the work carried 
out by modern methods of research, our knowledge of the consti- 
tution of alloys of the zinc-copper series has advanced consider- 
ably of late years. The constitution of alloys rich in zinc is 
very complex, but these alloys are of little industrial value ; on 
the other hand, the constitution of the alloys rich in copper 
which constitute the brasses proper is comparatively simple. With 
a few exceptions the zinc-copper alloys of industrial importance 
may be said to contain from 50 to 70 per cent, of copper, and 
within this range there are three constituents or phases, which 
are respectively designated by the Greek letters a, /?, 
and y. 



THE ZINC INDUSTRY 

Research has shown that in certain mixtures of metals there 
is obtained one or more classes of crystal formation, dependirg 
on the mutual solubility of the two metals. Thus iron and nickel 
dissolve in one another in all proportions and give only one type 
of crystals, no matter what the proportions. On the other hand, 
zinc and copper are not mutually soluble in all proportions. 
Starting with pure copper and adding zinc, the limit of solu- 
bility is reached with 36 per cent, of the latter metal. Up to 
this point only a-crystals are observed under the microscope, 
beyond it ^-crystals appear with the a-crystals, and later 
y-crystals appear. The Alpha-constituent consists of a solid 
solution of zinc in copper, the maximum content of zinc being 
as stated, about 36 per cent, at 400 C. The Gamma-phase was 
regarded by Shepherd as a solid solution, but as the result 
of more recent research there is evidence to show that the 
Gamma-phase contains a definite compound, Cu 2 Zn 3 , con- 
taining about 40 per cent, of copper. The Beta-constituent 
contains about 52 per cent, of copper and has the pro- 
perties of a solid solution. According to Carpenter, 1 however, 
the so-called Beta-constituent splits up into an intimate mixture 
of Alpha and Gamma on cooling from a critical temperature of 
470 C. On heating above this temperature the reverse change 
takes place. This critical temperature is found in all alloys 
containing from 60 per cent, of zinc down to 28 per cent., and 
probably less. 

The Alpha-phase is relatively soft and ductile, and the Beta- 
phase is harder and less ductile, while the Gamma-phase is still 
harder and very brittle, and can be readily powdered in a mortar. 
As the Gamma constituent is very brittle, the fact that the stable 
phase above 470 C. is Beta, and below this temperature Alpha 
plus Gamma, has an important bearing on the cause of the 
brittleness and decay of many brasses in engineering work 
(Carpenter) 

The brasses containing more than 64 per cent, of copper 
consist of a single homogeneous solid solution, while those con- 
taining from 55 to 64 per cent, of copper are composed of two 
constituents, each of which is a solid solution. Rapid cooling 
from a suitably high temperature is capable of profoundly 
modifying the structure and constitution, and consequently the 
properties, of the zinc-copper alloys. 

1 Journal of the Institute of Metals, 1911. i, vol. v, p. 127. 

176 



INDUSTRIAL ZINC ALLOYS 

The constitution of the chief commercial brasses has been 
classified by Hudson 1 as follows : 



Copper per cent. 



Nature of Constituent. 



100-71 
71-64 



Consists entirely of Alpha-phase at all temperatures. 
Alpha-phase below 400 C., Alpha plus Beta above. 



64-63 j Alpha plus Beta at all temperatures. 

Alpha plus Beta at low temperatures, Beta only at 
some higher temperature. 



53*1-51 
51-40 



Consists entirely of Beta at all temperatures. 
Beta plus Gamma at low temperatures, Beta only 
at higher temperature. 



It will be noted that the proportion of the Beta-constituent 
increases as the temperature rises, and this fact has important 
bearings on the heat treatment of brasses. As shown by Charpy, 
the effect of adding zinc to copper is to increase the tenacity and 
to diminish the ductility. 

With more than 40 per cent, of zinc, however, the tenacity 
very rapidly decreases, whereas the ductility is diminished after 
the addition of 30 per cent, of zinc. 

Consequently, for ductile brasses the limit of zinc is usually 
about 30 per cent., and in cases where a combination of ductility 
and strength is required, as with brass for cold-drawn tubes, or 
for cartridge cases, an alloy of about 70 per cent, of copper and 
30 per cent, of zinc is preferred. 

The industrial brasses may be conveniently considered under 
three heads, viz. : (i) Cast brass, (2) low brass (i.e., low copper- 
content) for hot rolling, and (3) high brass (i.e., high copper- 
content) for cold rolling. 

(1) Cast brass is very .variable in composition, but with the 
exception of a few alloys rich in copper used in the manufacture 
of cheap jewellery, &c., the usual composition of cast brass is 
about 66 per cent, of copper and 34 per cent, of zinc, which is 
known as English standard brass. It casts well, and is capable 
of being rolled and hammered and even drawn into wire if so 
required. 

(2) Low brasses suitable for hot rolling contain from 55 to 
63 per cent, of copper. The commonest of these yellow brasses 
is that known as Muntz metal, patented by G. F. Muntz in 1832, 

1 Journal of the Society of Chemical Industry, 1906, vol. xxv, p. 503. 

177 N 



THE ZINC INDUSTRY 

and consisting of 60 per cent, of copper and 40 per cent, of zinc. 
Although Muntz metal was originally introduced for sheathing 
wooden ships, it is now chiefly used, either under the name of 
Muntz metal or " yellow brass," for the cheaper varieties of 
brass tube, wire and sheet. 

Muntz metal is hardened by quenching, and the explanation 
of this is readily seen from its structure. With increasing 
temperature the Alpha-constituent is dissolved by the harder 
Beta-constituent until, at 720 C., the alloy containing 60 per 
cent, of copper .consists entirely of the Beta-constituent. If, 
now, the alloy is quenched from this temperature the separation 
of the Alpha-constituent is hindered, and the alloy will be found 
to be stronger but less ductile than before. 1 

(3) High brasses, suitable for cold rolling, usually contain more 
than 60 per cent, of copper. Whereas these alloys are readily 
workable in the cold, they are quite brittle when hot, and, there- 
fore, cannot be subjected to hot working. The best alloy of this 
class is the brass used for tubes and wire drawing, which contains 
70 per cent, of copper and 30 per cent, of zinc. This alloy 
possesses the maximum elongation of the copper-zinc series 
combined with a considerable degree of strength. On this 
account it is used for the production of cartridge cases, alike for 
rifle, machine-gun and the lighter types of artillery, and is fre- 
quently referred to as " Cartridge " brass. 

As it is subject to the severest of treatment, cartridge brass 
requires that both the copper and zinc shall be as pure as 
possible, 99*8 per cent, of zinc being a minimum, with o-i per 
cent, of lead and o-i per cent, of iron as maxima. 

The annealing of brass is carried out in reverberatory furnaces, 
the temperature employed varying with the composition of the 
brass. In the case of cartridge brass, the maximum effect of 
annealing is reached at 600 C., whilst there is a very marked 
softening of the alloy at 420 C. 

Industrial brass is capable of withstanding very drastic treat- 
ment, and in addition to rolling, drawing, stamping and spinning, 
it is capable of being extruded or forced through dies at tempera- 
tures somewhat below the melting point of the alloy. Great 
advances have been made within the last few years in the extru- 
sion of brass, and complicated sections which it would be im- 
possible, to produce by rolling are now regularly manufactured by 
1 " Alloys," E. F. Law, London, 2nd edition, 1914, p. 179. 

178 



INDUSTRIAL ZINC ALLOYS 

this process (Law). The alloys used for this purpose usually 
contain about 40 per cent, of zinc. 

Brasses containing Iron. The addition of iron to brass, first 
suggested by Kier in 1779, imparts special hardness, toughness, 
tenacity and wearing properties, whilst the alloy can be rolled 
either hot or cold. In more modern times brasses containing 
iron as an essential constituent have been introduced under 
special names, such as " Sterro-metal," or " Gedge's alloy," 
" Aich's metal " and " Delta metal," which may be taken as 
representative of the class. 

These alloys, which are now largely used, consist essentially 
of yellow brass, containing from 55 to 60 per cent, of copper 
and 38 to 41 per cent, of zinc, with the addition of iron, which 
varies from 1-5 to 4-5 per cent. In addition to iron, small 
quantities of other metals are frequently added. 

Sterro-metal contains 60 per cent, of copper, 38 per cent, of 
zinc, and 1-5 to 2 per cent, of iron, and Aich's metal is practically 
the same, although various analyses show that the percentage 
of iron present varies within somewhat wide limits, and tin is 
sometimes present. Sterro-metal can be made very hard and 
dense by suitable mechanical treatment, which has as great an 
influence in modifying its properties as its chemical composition. 
In rolling or hammering this alloy when hot, special care is 
requisite in regulating the temperature to which it is raised, as 
it becomes brittle when overheated, and cracks under the hammer 
or between the rolls. 

Delta metal, introduced by Alexander Dick in 1883, varies 
in composition, an average composition consisting of approxi- 
mately copper 55 per cent., zinc 42 per cent., with i to 2 per cent, 
of iron. In some cases small amounts of manganese, aluminium, 
tin or lead are added to the alloy to impart special properties to 
it. 

Delta metal is stronger, harder and tougher than brass. It is 
easily cast, forged or stamped, and is capable of beirg rolled hct 
and drawn cold. In addition, it has a much greater power cf 
resisting corrosion than ordinary brass, which enables it to te 
used for many purposes where such brass is inadmissible, mere 
especially for shipbuilding, marine engineering and sanitary we rk. 
The maximum stress of Delta metal varies frem 27-8 to 35-4 tens 
per square inch, according to the treatment to \vhich it has heen 
subjected. The constitution of the ircn brasses dees ret appear 

179 N 2 



THE ZINC INDUSTRY 

to have been sufficiently investigated ; when present in small 
amounts the iron appears to enter into the alloy as a solid solution 
and does not form definite chemical compounds (Law). When 
more than about 2 per cent, of iron is present, the iron and zinc 
would seem to combine. Formerly the iron was added to these 
alloys in the form of a copper-iron alloy, but this was not found 
to be entirely satisfactory, the metals in all probability not 
being properly alloyed. Dick, when he patented Delta metal, 
suggested the introduction of the iron in the form of an alloy of 
iron and zinc, which can be obtained of reliable composition, 
and is also relatively cheap as a by-product from the galvanising 
process. Since that time iron-zinc alloys have been largely used. 
The preparation of iron-zinc alloys for this purpose is dealt with 
subsequently. 

Brasses containing Lead. A small addition of lead is beneficial 
ia brasses intended for turning, the best alloy, and that which 
is most commonly used, containing about 60 per cent, of copper, 
38 per cent, of zinc, and 2 per cent, of lead ; it is sometimes 
termed " clock brass." The lead is usually added after the zinc, 
and while the crucible is still in the fire, the temperature being 
kept as low as possible. Lead does not alloy with brass, but 
separates out in the form of globules and films between the 
crystals of the brass, a condition which necessarily weakens the 
metal, so that the addition of lead is only permissible where 
strength is of secondary importance. The fracture of brass 
containing lead is distinctly grey in colour, owing to the fact that 
the line of fracture passes through the lead. 

The beneficial effect of lead in brasses intended for turning was 
known long before the nature of its influence was understood. 
Ordinary brass is difficult to turn owing to the character of the 
turnings, which are long and tenacious, and tend to foul the 
tools ; a slow speed has also to be employed. On the other 
hand, the presence of lead in a free state in the brass renders the 
alloy less tenacious, and the turnings break off through the lines 
of weakness caused by the lead, so that chips are produced instead 
of spiral turnings. The lead also appears to act as a lubricant, 
with the result that a much higher speed can be employed and a 
better finish given to the work. Brass containing not more than 
2 per cent, of lead can be rolled, but the alloy is rolled cold, on 
account of its liability to crack if rolled hot. 
- Brass containing Tin. A small percentage of tin renders brass, 

180 



INDUSTRIAL ZINC ALLOYS 

and more especially low brasses of the Muntz metal type, less 
liable to corrosion by sea- water when in contact with gun-metal. 
On this account brasses containing tin are employed in naval 
construction, the alloys being known as " naval " brasses. They 
contain approximately 62 per cent, of copper, 37 per cent, of 
zinc and I per cent, of tin. The mechanical properties of brass 
are not seriously affected by the addition of I per cent, of tin, 
but beyond this amount there is a rapid increase in brittleness 
and hardness, whilst with more than 2 per cent, the alloys lose 
their useful properties. 

Many of the more important of the copper-zinc alloys are those 
containing about 60 per cent, or less of copper in which part of 
the zinc is replaced by small quantities of one or more other 
metals, such as those mentioned above. The number of such 
special brasses is now increased by the so-called vanadium 
bronzes, in which cupro-vanadium is used as one of the in- 
gredients. The actual effect of vanadium in alloys does not 
appear to be very great. 

Alloys of Zinc and Iron. With iron zinc forms a series of 
alloys which are generally white, hard and brittle. When the 
iron does not exceed about 5 per cent, the alloys are less crystalline 
and darker in colour than pure zinc ; such alloys are produced 
in the process of galvanising, and are known as " hard zinc." 
The alloys become greyer, harder and more brittle as the iron 
content is increased. The alloy obtained by saturating zinc 
near to its temperature of volatilisation with iron is not attracted 
by a magnet ; it does not rust, nor give sparks by friction or 
blows. It is dense in structure, but is only semi-metallic in 
fracture, and contains about 22 per cent, of iron. 

The zinc-iron alloys have a somewhat important application 
in the preparation of the special yellow brasses, such as Delta 
metal, which contain from 1-5 to 4-5 per cent, of iron, and to 
which reference has been previously made. 

The necessary zinc-iron alloy is prepared commercially either 
(i) by direct union of the constituent metals, or (2) by the treat- 
ment of hard zinc from galvanising. The alloys actually used 
in practice generally contain from 7 to nearly 30 per cent, of 
metallic iron. 

The production of the zinc-iron alloys by direct fusion of the 
metals is difficult owing to the high melting point of iron and 
the volatile character of zinc. When prepared by this method, 

181 



THE ZINC INDUSTRY 

clean iron wire, or sheet, is added to a bath of molten zinc heated 
to near its boiling point. The union of the metals is facilitated 
by the addition of a little charcoal and some solid ammonium 
chloride. This method of preparation is usually accompanied 
by a considerable loss of zinc. 

Alloys rich in iron are usually obtained commercially by 
liquating the hard zinc from galvanising works to remove part 
of the zinc, and then strongly heating the residue, which is rich 
in iron, in a closed crucible. 

The excess of zinc is thus volatilised, leaving a zinc-iron alloy 
in which the content of iron increases with an increase in the 
temperature employed. 

Nickel Silver or German Silver. The white alloys manufactured 
under these names consist essentially of nickel, copper and zinc. 
An alloy composed of these three metals was known in early 
times in China, and was exported to Europe in the eighteenth 
century under the name of " pack-fong," or white copper. 
Pack-fong seems to have been recognised as a triple alloy of 
nickel-copper-zinc in 1776, when Engestrom published what 
appears to have been the first analysis. The manufacture of a 
white alloy composed of these metals was first started on a 
commercial scale at Berlin, about the year 1824, and was subse- 
quently exported to the United Kingdom as a cheap substitute 
for silver, and it is probably owing .to this fact that the alloy 
became known as " German silver." 

Although alloys of nickel-copper-zinc are now usually known 
in the trade under the general term of nickel silver, they probably 
exist under a greater number of special names than any other 
alloy, since different manufacturers employ fanciful names to 
denote alloys containing different proportions of the constituent 
metals which they consider best suited to produce an alloy of 
good white colour and possessing satisfactory working qualities. 
Thus Nevada silver, Virginia silver, Potosi silver, Silveroid, 
Arguzoid, &c., may be given as examples. 

The term nickel silver is somewhat misleading, as the alloy 
does not contain silver. If a nomenclature which indicates 
the true nature of the alloy be adopted, it would be described as 
a zinc-cupro nickel, but it is probably more convenient to call 
it a nickel brass, and this term is now usually adopted by research 
workers on these alloys, although this name has to a certain extent 
unfortunately become associated with the alloys of the copper- 

182 



INDUSTRIAL ZINC ALLOYS 

nickel series containing no zinc and used for coinage pur- 
poses. 

The nickel silver alloys are now prepared largely as a basis 
metal for electro-plating upon, and as a substitute for silver for 
the manufacture of table forks, spoons, &c., the chief centres 
of production being Sheffield and Birmingham. 

In the form of wire they are used for electrical resistances. 
The percentage of zinc in the industrial alloys varies from 20 to 
35 per cent., and it is added as a substitute for the more expensive 
metal nickel. 

The various grades of nickel silver in general use in the United 
Kingdom are known in trade circles as firsts, seconds, thirds and 
fifths, which contain approximately the following percentages 
of nickel : firsts, 20 per cent. ; seconds, 16 per cent. ; thirds, 
12 per cent. ; fifths, 7 per cent. ; the content of copper appears 
to vary between 56 and 59 per cent. 

The alloy known as seconds is used by many firms as the basis 
metal for electro-plate wares of best " A I " quality, although an 
alloy of higher nickel content is preferred by others. The seconds 
alloy is also largely used for the manufacture of best quality 
nickel silver spoons, forks, &c., that are sold as such and not 
plated. 

The character of the silver deposit in relation to the composi- 
tion of the basis metal has been studied by McWilliam and 
Barclay, 1 who conclude that when the proportion of nickel 
exceeds 14 per cent, the silver is more liable to strip off irregularly 
in actual use. It seems advisable, therefore, to avoid too high 
a percentage of nickel in the basis metal for high-grade electro- 
plate which has to endure rough usage. Although the alloys 
poor in nickel are not so white and not so strong as the richer 
alloys, the importance of the colour is not so great where there 
is a heavy deposit of silver. 

Owing to the high temperature required for the fusion of the 
nickel, and the low melting point and ready oxidisability of 
zinc, the preparation of nickel silvers is attended with a loss of 
zinc, and special care is accordingly required in their production. 
To overcome this difficulty the alloys are made by melting together 
an alloy of copper and nickel (usually containing 50 per cent, of 
each metal) and brass. The copper-nickel alloy has a lower 
melting point than pure nickel, whilst the brass has a higher 

1 Journal of the Institute of Metals, 1911, vol. v, p. 214. 

183 



THE ZINC INDUSTRY 

melting point than zinc, and the melting points being thus more 
nearly alike, the metals are more readily alloyed and the loss 
of zinc by volatilisation is very materially reduced. This 
method answers the double purpose of lessening the oxidation 
of the zinc and of more readily producing a homogeneous 
alloy. The alloys are made by melting the metals in the usual 
way in graphite crucibles. Shortly before pouring the metal 
a small quantity of manganese is usually added to ensure thorough 
deoxidation of the alloy. The metal is cast in iron moulds similar 
to those used in brass casting, but of different sizes. 

In constitution the nickel-silver alloys, when cast, exhibit the 
characteristic structure of quickly-cooled solid solutions, but, on 
annealing, the crystallites undergo gradual absorption and are 
replaced by the regular crystalline structure of simple metals 
and homogeneous solid solutions, the addition of zinc to the 
copper-nickel alloys not being attended with the formation of 
compounds. They may be regarded either as brasses containing 
nickel in solution, or as copper-nickel alloys containing zinc in 
solution. The nickel silvers are greyer in colour and harder than 
silver, and are capable of receiving a high polish ; their fracture 
after casting is strongly crystalline, and the alloys require, in the 
first instance, careful annealing before rolling or hammering ; but 
after the crystalline character has been thus overcome, the metal 
may be hammered, rolled or stamped into a variety of forms, whilst 
some specimens possess considerable elasticity. The alloysof nickel, 
zinc and copper become brittle when hot and are therefore always 
rolled and drawn in the cold. Most of the alloys acquire a yellow 
tarnish when exposed to the atmosphere, and in acid solutions, 
such as vinegar, with access of air, they become coated with a 
layer of verdigris, the rate of corrosion varying with the nickel 
content of the alloy. 

As in the case of most solid solutions, the alloys are softened 
by annealing. This is effected in reverberatory furnaces so 
constructed that a reducing atmosphere is, as far as possible, 
maintained and oxidation kept at the minimum. 

The temperature of annealing, which is of great importance, 
has been found by recent research to vary from 700 C. to 900 C., 
according to the composition of the alloy, the higher temperature 
being employed for the alloys of high zinc content. In works 
practice annealing from twenty minutes to an hour, according 
to the thickness of the sheets, at a temperature of about 

184 



INDUSTRIAL ZINC ALLOYS 

750 C. is sufficient to render the metal soft enough for all pur- 
poses. 

For ornamental castings, nickel silver containing i or 2 per 
cent, of tin is frequently used ; the presence of tin, however, 
even in small quantity, makes the alloy decidedly yellow in 
colour ; it also renders it brittle and unfit for rolling. 

It has been frequently asserted that the brass and nickel silver 
made in Germany and America, and imported into the United King- 
dom prior to the war, is superior in working qualities to that pro- 
duced in this country. Whilst there is undoubtedly some truth in 
this assertion, it is well to bear in mind that this superiority of 
product has only been attained by the use of pure metals, and the 
application of scientific knowledge to the melting, casting and 
heat treatment of the alloys, and also to scrupulous cleanliness in 
all the processes through which the metal passes during manu- 
facture. All these conditions for the production of high-grade 
metal are equally available to British manufacturers, and it is 
gratifying to know that within recent years many firms 
have availed themselves of the rapid advancement of scientific 
knowledge in the preparation and treatment of metals and alloys, 
and are now producing metal equal in quality to any supplied 
from foreign sources. On the other hand, it is unfortunately 
true that there is still a considerable number of manufacturers 
who appear to have inherited a certain conservatism, and a 
tendency to cling to " rule of thumb " methods which may 
produce alloys suitable for certain classes of work, but they 
frequently fail to produce the high quality metal required to 
withstand the severe mechanical treatment to which brass and 
other non-ferrous alloys are now subjected in modern manu- 
facturing processes, as in the production of cartridge cases. 

Anti-friction Metals. Zinc enters into the composition of a 
number of so-called anti-friction alloys, or white metals, used 
for bearings. Bearing linings of white metal are indispensable 
for certain purposes, as they are soft and enable the axle to adapt 
itself to the condition of the bearing and run with much less 
friction than in the case of harder alloys. This tendency of white 
metal to reduce friction has given rise to the term " anti-friction " 
metal, which is now generally used for such alloys. One great 
advantage of white metal alloys for this purpose is their low 
melting point, which permits of a worn-out bearing being readily 
melted out and replaced by a new one. The white metal is 

185 



THE ZINC INDUSTRY 

generally melted in an ordinary ladle, and when the journal or 
mandril is wiped dry and chalked, the molten metal is poured in. 
Since the introduction of white-metal bearings an immense 
number of so-called anti-friction metals have been placed upon 
the market. The composition of these varies very considerably, 
and they may contain copper, tin, zinc, antimony and lead ; 
but seldom more than three of these metals are used in any one 
alloy. 

Whilst zinc in small proportions enters into the composition of 
many anti-friction metals, the alloys in which the percentage of 
zinc preponderates form a comparatively small class. 

The composition of a number of white metals in which zinc is 
the chief constituent is given in the table on p. 190. 

From these figures it will be seen that the zinc content may 
reach 90 per cent. The alloys of zinc, tin and antimony possess 
a high compressive strength, and they are employed for bearings 
of machinery, such as rock-breakers, where strength is of more 
importance than perfect anti-frictional qualities. 

Zinc Alloys for Die-casting. Within recent years white metal 
alloys containing zinc have found extensive application in the 
production of die-casting or casting under pressure in steel moulds. 
In this process the molten metal is forced into the die or mould 
under a pressure of 100 to 400 Ib. per square inch, the pressure 
being transmitted by a mechanically or hand-operated plunger, 
actuated by compressed air or by centrifugal force. The alloys 
used for the production of die-castings are generally white metals 
of low melting points. The shrinkage of the alloys is an impor- 
tant consideration, and involves special provision in making the 
moulds. The shrinkage of zinc-base alloys, that is, those in 
which zinc is the main constituent, is said to be about twice as 
great as that of tin-base and lead-base alloys and about one-third 
that of aluminium-base alloys. In a zinc-base alloy the shrinkage 
is given as 0-004 inch per inch of dimension, thus indicating the 
care required in making the dies, which are made of special alloy 
machinery steel. The cost of the dies is very considerable, but 
upwards of 100,000 duplicate castings, each accurate, may be 
made from a properly constructed die, thus making the die-cost 
per casting small. 

In ordinary practice, die castings are made to dimensions of 
plus or minus o-ooi inch to each inch of dimension. 

The temperature of the dies and of the metal varies with the 

186 



INDUSTRIAL ZINC ALLOYS 



different alloys used, so as to assist in controlling shrinkage. 
The zinc-base alloys may contain zinc 50-80, tin 5-30, copper 
2-20, aluminium 2-6, and antimony 1-5 per cent. A considerable 
range of alloys is thus available in this series. The following 
alloys may be given as representative of zinc-base white metal for 
die-casting. 1 Nos. i and 2 are stated to be suitable for ordinary 
work in place of brass, No. 3 is harder and No. 4 harder still. 

ZINC-BASE DIE-CASTING ALLOYS. 





No. i. 


No. 2. 


No. 3. 


No. 4. 




Per cent. 


Per cent. 


Per cent. 


Per cent. 


Zinc 


73-75 


72-7 73-8 


46-2 


Tin 


!4'75 


ig-O I2-O 


30-8 


Copper 


5-25 


5-0 10-6 


20-4 


Aluminium 


6-25 


i-o 3-4 


2-6 


Lead 




2-0 


. 


Antimony 





0-3 


' 



Gas furnaces may be used for melting the metal, the pot being 
covered to prevent oxidation, and the metal forced through a 
tube and nozzle into the moulds. 

The advantages of die-casting are low cost of production and 
interchangeability, together with greater degree of accuracy 
in the case of small castings than is possible by machinery. 
The introduction of die-castings has done much to facilitate the 
work of the foundry, as the process is adopted for making intricate 
parts which would be expensive to cast in sand, to stamp in dies, 
or to machine. The accuracy of die-castings having holes, screw 
threads, teeth, &c., is as great as with ordinary machined parts. 
Owing to technical difficulties the limit in weight of average die- 
castings is given as 5 lb., although in special cases the weight may 
be as high as n lb. Some of the uses of die-castings are as 
bearing magneto parts, electric lighting and starting systems, 
speedometer housings, &c., in automobile work, and as parts 
in automatic machines, cash registers, &c. 

Alloys of Aluminium and Zinc. The importance of alloys of 
aluminium and zinc has long been recognised, but it is only 
within recent years that the price of aluminium has enabled its 
alloys to be used on a large scale. Zinc forms solid solutions with 
aluminium, and the alloys of these metals, either alone or more 
1 Engineering, 1914, vol. xcvii, pp. 144-145. 

187 



THE ZINC INDUSTRY 

often with small additions of other metals such as copper or 
magnesium, are practically the only aluminium alloys of industrial 
importance. 

The alloys are largely used in connection with munitions of 
war, as in certain parts of shells, in aeroplane construction, in 
the motor industry and for many other purposes where strength 
and lightness are desired. 

Only the aluminium-zinc alloys containing less than 40 per 
cent, of zinc are single homogeneous solid solutions, and they 
are therefore the only ones of practical value. Those containing 
up to 15 per cent, of zinc are soft enough to be rolled or drawn, 
whereas beyond this amount the alloys are hard and more suitable 
for castings, as they are easily worked. In practice the alloys 
usually contain from 10 to 20 per cent, of zinc, with the addition 
of a small quantity of copper. The properties of the aluminium- 
zinc alloys have been investigated by Rosenhain and Archbutt, 1 
whose mechanical tests indicate that alloys containing frcm 
15 to 25 per cent, of zinc (with or without addition of copper) 
would be more serviceable than alloys containing less than 
15 per cent, of zinc, which are much more widely used in present 
practice. If dynamic as well as tensile tests be taken into con- 
sideration, the alloy containing 20 per cent, of zinc appears to 
be the most useful of the binary alloys. A characteristic feature of 
the alloys is the very large effect produced upon them by hot work. 

When the alloys are heated, the tensile strength falls rapidly, 
but the hot alloys exhibit a considerable amount of ductility, 
so that it is possible to roll into bars alloys which are brittle in 
the cast state. The alloys containing respectively 25 and 20 per 
cent, of zinc attain their maximum tensile strength when in the 
form of rolled bar i J in. diam., the figures for the two alloys being : 
ultimate stress, 27-5 and 22-64 tons per square inch ; yield point, 
25 and 17*3 tons per square inch ; elongation on 2 in., 16*5 and 
20-5 per cent, respectively. The alloys, with and without 
addition of copper, differ from most non-ferrous alloys in that 
in the rolled condition they exhibit a definite and well-marked 
yield point. All the alloys containing from 10 to 30 per cent, of 
zinc are very easily machined. Corrosion tests in sea-water 
showed that the loss of weight increases with increasing zinc 
content. The rapid corrosion (especially in moist air) frequently 
observed with commercial aluminium-zinc alloys is attributed 
1 Tenth Report to the Alloys Research Committee, Inst. Mech. Eng., 1912. 

188 



INDUSTRIAL ZINC ALLOYS 

to the presence of impurities derived from the spelter employed 
in their production. 

The alloys are now very generally melted by means of coal- 
gas as a fuel. Melting is performed either in graphite crucibles 
or very commonly in cast iron pots, which are preferably pro- 
tected by a wash of inert material. 

Miscellaneous Zinc Alloys.- The Biddery ware manufactured 
at Bidar in India usually contains about 90 per cent, of zinc 
together with copper, lead, and tin in different proportions. 
Two analyses of Biddery metal are given in the table on p. 190. 

Zinc alloys readily with silver, the alloys rich in silver presenting 
some resemblances to the corresponding silver-copper alloys, 
although somewhat whiter in colour. They are malleable and 
ductile and take a high polish. 

Silver-zinc alloys have long been used by native silversmiths in 
India for the production of silver wares. Fcr this purpose the 
silver is usually alloyed with about 10 per cent, of zinc. 

Zinc in small proportions also enters into the composition of 
a number of important industrial alloys. 

The addition of a small quantity of zinc to certain alloys 
increases their wearing power, and for this reason it is added to 
the bronze used for coinage, which contains I per cent, of zinc, 
4 per cent, of tin and 95 per cent, of copper. This alloy was 
first used in England in 1861. 

A standard Admiralty bronze consists of 88 per cent, of copper, 
10 per cent, of tin and 2 per cent, of zinc, whilst in some alloys 
of this class the percentage of zinc reaches 10 or even 15 per 
cent. Statuary bronze usually contains from 2 to 10 per cent, 
of zinc. The alloys used for this purpose lie midway between the 
bronzes and the brasses and usually contain a considerable 
percentage of lead. 

The addition of zinc renders the alloy more fluid and greatly 
facilitates the operation of casting. Too much zinc, however, 
has to be avoided or the metal will have a brassy colour, and will 
not assume a pleasing " patina " on exposure to the atmosphere. 

The class of alloys known under the name of Britannia metal, 
consisting of tin and antimony together with small quantities of 
other metals, not infrequently contains zinc. 

The percentage of zinc is, however, usually under 5 per cent., 
as it increases the hardness and brittleness of the alloy, and is 
therefore not a desirable constituent if present in large amounts. 



THE ZINC INDUSTRY 



The composition of typical industrial alloys in which zinc is 
an important constituent is shown in the accompanying table. 

Typical Zinc Alloys. 1 



Alloy. 


Composition per cent. 


Remarks. 


i 

N 


| 


& 


3 


1 


i*\ 

c 

< 


j 


Aluminium. 


Anti-friction Metals 
Anti-friction metal . 
Babbits' metal (so 
called) .... 
Bearing metal 
hard . 
Bearing metal medium 
hard 
Bearing metal . . 
Lumen bearing metal 
Special 
Vaucher's alloy . 
Brasses 
Aluminium brass . . 
Best yellow brass 

Brass 

,, to be machined 
Cast brass (so called), 
very variable . 
Naval brass . 
Ordinary brass 
Aich's metal . . 
Delta metal (average 
composition) 
Muntz metal . . 
Parson's white "brass" 
Sterro metal . . 
Brazing solder 
Bronzes 
Coinage bron ze 
(British) 
Gun metal . . . 

Manganese bronze . 
Parson's white bronze 
White bronze . . . 
' German Silvers " (so 
called) 
Firsts . . . , . 
Seconds . . 
Thirds . . . . i 
Fourths . . . . 
Fifths 
Miscellaneous 
Admiralty metal . 
Ashberry metal . 
Biddery ware . 

Motor alloy . . . 
White button metal . 


85 'o 

69-0 
8'o 

2'0 

6-0 
20*0 
85-0 
82-0 
75 'o 

38 o 
30-0 

S'o 
2g'o 

38-0 

43-0 
37' 
33 '3 
38-0 

36*0 
40-0 
30*0 
55'5 
50*0 

I'O 
2'0 
1*0 

42-0 
38-5 

29 'o 

28-0 
24-0 
32'0 

35 'o 
36'o 

28-5 

I'O 

84-3 
93 '4 

lO'O 

8o'o 


S'o 

4'o 
82*0 
82*0 

67-5 
76 'o 

lO'O 
I2'C 

60 'o 

70'0 

94 '5 
70*0 

60 'o 

57-o 
62 'o 
66-6 
6o'o 

60 -o 
60 'o 
S'o 
42-0 
50-0 

95 'o 
88-0 
86-0 

54'5 

2*5 

4'5 

56-0 
62*0 
56-0 
55 'o 
57 'o 

i '5 
2*0 
11-4 
3'5 

2'0 
20 


19-0 

lO'O 

i6'o 

21*5 

3'o 


S'o 


... 


lO'O 

3'o 


... 




For locomotive axles. 

Daimler motor-bus bearings. 
For journal lining. 

Sheet, wire, tubes, cartridges, 
&c. 
High-pressure turbine blades. 
Condenser tubes. Admiralty 
specification. 

Admiralty specification. 
Wires, sheets, &c. 

Sheafhing. 

Admiralty No. i. 
Admiralty No. 2A to resist 
high pressure, 
o's Mn (composition varies). 

For work under water. 
Other metals 3 per cent. 
Manufactured in India. 

Light alloy for motoi-car 
work. 




















I'O 
















S'o 
6'o 

2'0 












iS'o 


4 '5 




2 '5 




















o'S 


I'O 






























I'O 




























2'0 
I'O 




2'O 

65*0 


I'O 


... 


... 








" 














40 

lO'O 

13-0 

r 

05 'o 






















o'S 




i '5 


I 'O 


'5 
o'S 


... 


i6'o 






... 










70 'o 
8o'o 
i'4 




10 '0 

7-0 


'.'.'. 


... 




2-9 
3 'i 




14-0 


... 


... 
















S8'o 























1 Compiled from tables in Law's Alloys, and other sources. 
IQO 



CHAPTER XII 

COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS 

OF the various compounds of zinc of commercial value zinc 
oxide is by far the most important. It is largely used as a pigment 
under the name of zinc white, and is valued for its permanency, 
as it is not blackened by sulphuretted hydrogen like white lead, 
for which it is a substitute. Although it lacks the body and 
opacity of white lead, it has good covering power, and is non- 
poisonous. 

The zinc oxide of commerce is prepared either (i) direct from 
zinc ore or (2) by the combustion of crude spelter. One of the 
best known direct methods is the Wetherill process, which is 
largely used in the United States, especially in New Jersey 
and Pennsylvania. The ore treated is obtained from the mines of 
Franklin Furnace, New Jersey, where it is crushed and con- 
centrated, first by magnetic separators and then by jigs, giving 
four products. 1 

The first, franklinite, consists mainly of oxides of zinc, iron 
and manganese, with practically no injurious impurities. 

This ore is worked by itself, making the best qualities of oxide. 
The manganiferous residue remaining in the furnace after removal 
of the zinc is treated in blast furnaces for the manufacture of 
spiegeleisen. The second product contains about the same 
amount of zinc as franklinite, but less iron and manganese, and 
does not make quite so good an oxide. It is used, like franklinite, 
for the manufacture of oxide, and the residues are thrown 
away. 

The third product is willemite, anhydrous zinc silicate, which 
is used for the production of high-grade zinc. The fourth 

1 Plant of the New Jersey Zinc Company. Oil, Paint, and Drug Report, 
Nov. 2nd, 1914. 



THE ZINC INDUSTRY 

product consists of limestone tailings. The ore is shipped to 
Palmerton, where a very extensive plant produces enormous 
quantities of zinc oxide annually. The plant comprises 54 blocks 
of furnaces with a total grate surface of about one-half acre. 
Each furnace, known as a " Wetherill grate," consists of a 
brick chamber with an arched roof and a flat grate, under which 
is a closed ashpit. The ore is mixed with the quantity of 
powdered anthracite necessary for its reduction, and then spread 
over a layer of burning anthracite on the perforated grate of the 
furnace, through which a low blast from a fan is forced, produc- 
ing an underdraught. The zinc is volatilised and burned to 
oxide by the excess of air above the charge. The zinc oxide 
so produced and the products of combustion are drawn from 
the furnace by large exhaust fans which draw them over to 
the bag-rooms. These are provided, at the top, with distributing 
pipes, from which hang muslin bags about 45 feet long and 6 feet 
in circumference. The combustion gases pass out through the 
bags and the oxide is collected in them. The bags are con- 
nected with hoppers at the bottom, from which the finished 
oxide is drawn to be taken to the packing room. The six bag- 
rooms contain nearly 71 miles of bags, with a total surface of 
51 J acres of muslin. The oxide is first sifted through wire screens, 
and then fed into a packer which forces the oxide into barrels 
or bags. The barrels are made at the works and contain 300 Ib. 
of oxide each. For smaller quantities paper bags, containing 50 
Ib. each, are used. 

The Wetherill process is also carried out at Liege and other 
places, but the ore used is generally zinc blende, which is first 
converted to oxide by roasting. 

Leclair's process of making zinc oxide by distilling and burning 
metallic zinc, started between 1840 and 1850, is still in use in 
Europe and also at the Florence works of the New Jersey Zinc 
Company of Pennsylvania. 

In the Silesian method, the spelter is heated to its boiling 
point in retorts, and the vaporised metal is conveyed into 
chambers through which air is kept in circulation, when the 
metal burns, and the oxide, with more cr less metallic zinc, 
is deposited in a series of condensing chambers. As the 
crude spelter always contains some lead, which in this process 
would be converted to oxide and impart a yellowish tint 
to the zinc white, impairing its commercial value, a small quantity 

192 



COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS 

of gas containing carbon dioxide is introduced into the retort. 
By this means the lead is converted into carbonate, which is 
considerably heavier than the zinc white, and therefore settles 
first in the condensers. 

In Belgium, zinc white is also made by burning spelter in the 
manner described, but the final product is purified by levigation. 
The spelter used in Belgium contains up to 2 per cent, of lead, 
but the purified product contains under 0-2 per cent, of lead, 
with very small amounts of iron, and zinc oxide from 99*69 to 

99*99 P er cen t- 

Commercial zinc oxide nearly always contains lead compounds 
(carbonate or basic sulphate), the presence of which affects its 
market value. It has been claimed that zinc white made direct 
from the ore is a more durable pigment than that obtained by 
burning spelter. 

Zinc oxide is prepared for pharmaceutical purposes by pre- 
cipitating a solution of zinc sulphate with sodium carbonate 
and igniting the basic carbonate thus thrown down. Zinc oxide 
is a pure white, amorphous powder, which when heated becomes 
yellow, but again becomes white on cooling. When ignited at a 
high temperature it shrinks and becomes hard and gritty. It is 
infusible at all ordinary temperatures, but distinctly volatile at 
a white heat. The oxide does not fuse in the oxy-hydrogen 
flame, but, like lime, in these circumstances becomes intensely 
incandescent ; for some time after being so heated it appears 
phosphorescent in the dark. 

The oxide prepared by burning the metal has a specific gravity 
of 5-6. It is insoluble in water, and does not combine 
directly with water to form the hydroxide. It dissolves in 
acids, producing the different zinc salts. 

Commercial zinc oxide is not infrequently adulterated with 
barium sulphate (barytes) , which is cheap and blends well with 
the oxide. 

An impure zinc oxide, known as zinc grey, is obtained as a 
by-product in the manufacture of zinc white. It is used as a 
silver-grey paint, and, when made into a paste with wood oil, 
as a cement for steam joints. 

Lithopone. The important zinc pigment known as lithopone, 
or Orr's zinc white, was first produced by T. B. Orr in 1874 
(English patent of Feb. 10). Theoretically it is a mixture in 
molecular proportions of zinc sulphide and barium sulphate, but 

193 o 



THE ZINC INDUSTRY 

the products on the market contain other substances as well. 1 
The advantages claimed for it are that it is not affected by 
sulphides and has high covering power, and its disadvantages, 
due to particular methods of manufacture, are that on exposure 
to sunlight it often turns grey and becomes chalky. It is prepared 
by mixing solutions containing equivalent quantities of barium 
sulphide and zinc sulphate. As in the case of other white pig- 
ments, purity of raw materials is essential, iron compounds being 
very objectionable. 

Barium sulphide is obtained by roasting ground barytes 
(barium sulphate) with coal or other carbonaceous material in a 
reducing atmosphere, either in a flat bedded reverberatory 
furnace or in a rotary kiln of the Bruckner type. Lixiviation 
of the product of the roasting gives a solution of sufficient purity 
for the purpose. 

For the zinc sulphate solution any zinc-bearing material may 
be used. Spelter and dross, when treated with sulphuric acid, 
leave little or no zinc in the insoluble residue, but zinc ashes 
usually leave so much mud in the solution tanks that the unit 
of zinc in this material is not so valuable. Iron and manganese 
when present are usually removed by boiling with bleaching 
powder. The two solutions in proportionate quantities are then 
mixed to produce the mixed precipitate, which is filter- 
pressed and dried. In some cases about 0-5 to i-o per cent, of 
a mixture of freshly prepared magnesia and common salt is 
added to the precipitate before filtration. The dried precipitate 
is mixed with 3 per cent, of ammonium chloride, and the whole 
heated to dull redness to give it body, which it lacks if not 
sufficiently heated. Excessive heating converts some of the 
zinc sulphide into oxide. Some oxide is always found in litho- 
pone, but it should not exceed 2 per cent. ; it ranges, however, 
in commercial samples from 0-5 per cent, to as much as 12 per 
cent. After burning, the red-hot pigment is at once quenched 
and ground fine, after which it is thoroughly washed, dried, dis- 
integrated, usually in pebble mills, and then packed. 

Ordinary lithopone contains about 29-5 per cent, of zinc 
sulphide. A higher grade, containing from 45 per cent, to 48 
per cent, of sulphide, is produced by replacing part of the barium 
sulphide by sodium sulphide, and washing out the resulting 

1 " Lithopone," H. S. Riederer, Journal of the Society of Chemical 
Industry, 1909, vol. xxviii, p. 403. 

194 



COMMERCIAL COMPOUNDS OF ZINC : ZINC PIGMENTS 

sodium sulphate. Lower grades are also made by replacing part 
of the zinc sulphate by sodium sulphate. When used for outside 
painting, lithopone is frequently mixed with other pigments, so 
as to prevent the darkening which takes place when it is exposed 
to sunlight. Unlike ordinary zinc white, lithopone is free 
from lead. 

Lithopone is chiefly made in the United States, and the 
quantity made has increased considerably within recent 
years. The amount produced in the United States in 1912 was 
24,220 short tons ; in 1913 the output was 29,685 short 
tons. 

Zinc-lead pigment, or leady zinc oxide, consists of a mixture of 
zinc oxide and sulphate, lead oxide and sulphate, with some 
sulphurous acid and water. Commercial samples contain lead 
up to about 25 per cent. The output of this pigment has been 
rapidly increasing. It is usually produced by the treatment of 
zinc-lead concentrates, or residues containing these metals. 

Zinc oxide also finds limited application in the glass industry 
for the production of opal glass, and also in the preparation of 
crystalline glazes for pottery and stoneware, as such glazes are 
less liable to " craze " than lead glazes. 

Zinc chloride, ZnQ 2 , is formed by the direct combination of 
zinc with chlorine, or by the action of hydrochloric acid upon the 
metal. The latter method is adopted for the production of zinc 
chloride on a large scale. For this purpose scrap zinc is placed 
in hydrochloric acid contained in a stone, cast iron or wooden 
vessel. The solution so obtained is neutralised with sodium 
carbonate, warmed to 40 or 50 C. and bleaching powder added 
to precipitate iron and manganese. When the precipitate has 
settled, the clear solution of zinc chloride is siphoned off and 
boiled down in enamelled iron pots. The evaporation is continued 
until the temperature of the liquor is 230 or 240 C., a little 
potassium chlorate is added to oxidise any organic matter, and 
some pure hydrochloric acid carefully poured into the hot solu- 
tion to dissolve any basic salt. The mass is then allowed to 
solidify, and while still warm is packed in iron drums of from 
30 to 50 kilos, capacity, which are at once closed air-tight. 

When the aqueous solution of zinc chloride is evaporated, 
partial decomposition takes place, hydrochloric acid being evolved 
and basic compounds precipitated, consisting of combinations 
of the chloride and oxide. Hence, during the concentration of 

195 O 2 



THE ZINC INDUSTRY 

the liquid in the preparation of zinc chloride, hydrochloric acid 
is added to re-dissolve this compound. 

The anhydrous chloride is a greyish-white, soft, waxy-looking 
substance, which is readily fusible, melting at 262 C. to a clear, 
mobile, highly refractive liquid ; at a higher temperature it 
volatilises and distils without decomposition, with the produc- 
tion of peculiarly irritating fumes. It deliquesces rapidly on 
exposure to moist air, and is very soluble in water or alcohol, 
its solution being powerfully caustic. 

From a strong aqueous solution, deliquescent crystals are 
deposited on evaporation, having the composition ZnCl 2 ,H 2 O. 

A concentrated solution attacks and dissolves vegetable fibre, 
consequently it cannot be filtered through paper ; it should be 
filtered through asbestos or glass wool. When a solution of 
zinc chloride is electrolysed, chlorine is evolved and crystalline 
zinc deposited. 

Zinc chloride is extensively used as a preservative of timber, 
and it acts as a powerful dehydrant. It is much used for railway 
sleepers, either alone or in combination with creosote. American 
railroad companies buy sleepers specified to contain J Ib. of zinc 
chloride per cubic foot, equal to about 0-5 per cent, of zinc. The 
textile industry absorbs considerable amounts, and it is used in 
" mercerising " or giving the appearance of silk to cotton goods. 

In dilute aqueous solution it is employed as an antiseptic, 
acting as a powerful disinfectant and germicide. 

Zinc chloride for medical purposes is usually cast in the form 
of small rods or tablets. A paste made by moistening zinc 
oxide with zinc chloride rapidly sets to a hard mass ; this 
mixture, under the name of oxychloride of zinc, is employed 
in dentistry as a filling or stopping for teeth. Many of the 
oxychloride cements used for this purpose contain small 
amounts of other ingredients, such as powdered glass or silica, 
to confer greater hardness on the mass when set. Other zinc 
compounds used as cements by dentists are oxy-phosphate and 
oxy-sulphate. The former consists of zinc oxide mixed with 
one of the forms of phosphoric acid ; and the latter is a mixture 
of zinc oxide and calcined zinc sulphate made into a paste 
with a solution of gum arabic. Compared with metal fillings 
these cements usually lack hardness, but they are non-irritating 
and set fairly rapidly. They are all more or less readily acted 
upon by the fluids of the mouth. 

196 



COMMERCIAL COMPOUNDS OF ZINC: ZINC PIGMENTS 

Zinc oxychlorides are also used as pigments. 

Zinc Sulphate, or White Vitriol, known also as zinc vitriol, 
is prepared on the large scale either by the action of sulphuric 
acid on zinc or by the treatment of zinc sulphide ore (blende). 
In the former case commercial zinc scrap or zinc waste is 
dissolved in sulphuric acid, and the solution evaporated to the 
crystallising point. When produced from ores containing blende, 
these are carefully roasted to produce zinc sulphate, which is 
extracted with water, and the salt crystallised from its aqueous 
solution by evaporation. It was obtained, on a manufacturing 
scale, by this method as far back as the sixteenth century. The 
water from zinc mines is frequently charged with zinc sulphate 
which is extracted by crystallisation. 

The salt crystallises with seven molecules of water in colourless 
rhombic prisms, which on heating fuse readily in their water 
of crystallisation. Commercial zinc vitriol is made to assume 
the shape of a sugar-loaf by stirring the fused salt in wooden 
troughs with wooden shovels until crystallisation takes place, 
and subsequently pressing the mass into moulds. 

In common with all the soluble salts of zinc, zinc sulphate has 
an astringent taste, and is poisonous. It dissolves in less than 
its own weight of water at the ordinary temperature. When 
exposed to the air, the crystals slowly effloresce ; if heated 
to 100 C. they lose six molecules of water, leaving the 
monohydrated salt, ZnSO 4 ,H 2 O. At ja. temperature of about 
300 C. this is converted into the anhydrous compound, and at 
a white heat it gives off sulphur dioxide and oxygen, leaving the 
oxide. 

Zinc sulphate is used as a mordant in calico printing, and is 
employed as a clarifying agent and preservative in the manu- 
facture of glue. In medicine it is employed as an astringent, and 
a very weak solution forms a common eye lotion. It, however, 
finds its greatest application in the manufacture of lithopone, to 
which reference has already been made. 



197 



CHAPTER XIII 

THE FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

THE question of the future supply of zinc in sufficient quantity 
for the maintenance and development of the metal industries of 
this country, without the importation of foreign metal, has been 
brought into special prominence by the exceptional circumstances 
arising out of the world-war. The conditions which gave rise to 
the very serious position in which this country was placed at the 
outbreak of war in regard to her zinc supplies have already 
been referred to. It has been shown that during the past 
few decades the zinc market was becoming increasingly a 
German monopoly. The war has, however, fortunately brought 
about the beginning of a new epoch in the development of this 
important branch of non-ferrous metallurgy, and if certain 
comprehensive schemes, which have recently been formulated, 
for the treatment of Imperial zinc ores in the United Kingdom 
come to fruition, the increase in zinc production may be con- 
siderable. 

The first essential in the development of any industry is a 
regular and ample supply of raw material, and where this is 
lacking progress is invariably retarded. Undoubtedly one of the 
obstacles to the expansion of the British zinc industry in the past 
lies in the fact that for many years the smelters have relied for 
raw materials chiefly upon the rich ores which have been shipped 
in comparatively small lots from foreign sources. 

Before the war there was little difficulty in obtaining all the 
ore required to sustain the comparatively small output of metal 
hitherto produced in this country, the ore itself being moderate 
in price, whilst freights were low. Now the cost has greatly in- 
creased, and the expenses of ocean transport have advanced 
enormously and are likely to remain high for some time to come. 

108 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

In respect to ore supply the British zinc smelters have always 
been at a disadvantage compared with Continental and American 
smelters, both of whom have sufficient domestic supplies of ore 
available to augment that obtained from foreign sources, 
and to ensure a steady and plentiful supply of raw material. 
If Great Britain is going to produce all the zinc needed for 
home consumption, the pre-war output of metal will have to 
be increased at least five-fold, and this entails a corresponding 
increase in ore supply and the building of much new plant. 

But, as already pointed out, the available supplies of the rich 
calamine ores, upon which British smelters have relied so much 
in the past, are steadily decreasing, and there is little doubt that 
in the near future the whole of the zinc of commerce will have 
to be smelted from zinc blende. In these circumstances it is 
very important that the supplies of this ore within the Empire 
should be utilised for the development of the Empire zinc in- 
dustries, and not left to the exploitation of foreign concerns. 

As it has not infrequently been asserted that the superior 
acumen and metallurgical knowledge of the Germans enabled 
them to obtain control of the Broken Hill concentrates and treat 
them successfully, it may be well to state, on the authority of 
Moulden, 1 that although the Germans obtained control of a large 
proportion of the huge output of Australian zinc concentrates, 
they did not treat them except in relatively small quantities. 
They utilised this control to make money, in which they were 
most successful, passing the major part of the concentrates on to 
the Belgian works for smelting. Of the total Australian output 
Belgium smelted at least 75 per cent, and Germany only 14 per 
cent. The Germans had placed themselves in a position to force 
this on the Belgian works by acquiring at the outset a controlling 
interest in a number of them. 

In this connection it is well to remember that the export of 
Empire raw material to foreign countries for the recovery of 
the commercial products is most undesirable in the interests 
of this country. Not only is the benefit in wages, skilled 
employment and greater profits involved in the working up of 
the raw material to a refined metal lost to this country, but the 
art of producing the finished metal and its alloys, and the 
control of it, pass into alien hands. In this way supplies of 
indispensable metals, such as zinc, can only be obtained by paying 
1 Moulden, op. cit., p. 528. 
199 



THE ZINC INDUSTRY 

enhanced prices, or may be cut off altogether in times of urgent 
need, as experience has unfortunately proved. 

It may be well to repeat that the extensive deposits of zinc 
ore at Broken Hill, New South Wales, afford an ample supply of 
ore, sufficient to meet all the zinc requirements of the United 
Kingdom for some years to come, and now that the difficulties 
which at first attended the treatment of the ore have been 
successfully overcome, there is every reason why this ore 
should be smelted in preference to ores from foreign sources. 
The importance of treating Broken Hill zinc concentrates within 
the Empire, and more particularly in this country, becomes more 
apparent on reviewing the situation as created by the war. The 
effect of the outbreak of war on the zinc industry was felt more 
quickly in Australia than in Great Britain. The mines, deprived 
of the greater part of their market, had to curtail production very 
considerably, and it is to their credit that, in order to minimise 
hardships among their labouring population, they continued to 
produce considerably more ore than they could for the time being 
dispose of. Certain considerations bearing on the question of 
the future markets for Broken Hill concentrates have been 
enumerated as follows. 1 

(1) Australian legislation has been passed cancelling the 
contracts for the sale of Australian ores to alien firms and 
prohibiting them for the future, so that no zinc concentrates 
will be henceforth shipped to Germany. The Australian mine- 
owners will therefore have to find fresh markets for that 
considerable proportion of their ore which previously went to 
Germany or to the German smelters in Belgium. 

(2) Germany, in spite of the length of time that her own ore 
deposits have been worked, has still large reserves. She has 
also considerable zinc-mining interests in China, and before the 
war shipped zinc concentrates from that country. She will 
not fail to develop her trade in this direction as far as she is able 
to do so after the war, and will continue to be an important 
producer of spelter. 

(3) The United States zinc smelters will be formidable com- 
petitors after the war so long as high prices are maintained. They 
have used their large profits wisely in making their plants efficient 
and up to date, and in accumulating large financial reserves. 
Their present rate of production is sufficient for more than 70 per 

1 H. C. H. Carpenter, Nature, 1916, vol. xcviii, p. 129. 
200 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

cent, of the world's peace requirements before the war. They 
will have considerable tonnages of the metal available 
for export. They have very large ore supplies, not only of 
" straight " zinc ores, but of the complex ores in which zinc blende 
is associated with galena and other metallic sulphides, and which 
now constitute an increasingly important source of spelter. It 
is very unlikely, therefore quite apart from the 10 per cent. 
ad valorem tariff to which zinc ores imported into the United States 
are liable -that Australian zinc concentrates will find a market 
in America. 

(4) The Canadian Government is encouraging zinc extraction 
by granting bounties on zinc produced in Canada from Canadian 
ores. Australian concentrates are therefore not likely to enter 
Canada to any great extent. 

(5) The future of the Belgian industry is quite uncertain, but 
it is much to be hoped that it will be re-established and the 
smelting works rebuilt after the war, and in this case, as it will 
depend largely on imported ores, there may be a renewal of the 
contracts with the Broken Hill mine-owners. 

(6) By virtue of the magnitude of its population, its transport 
facilities, markets and the raw materials necessary for zinc 
smelting apart from the ore itself Great Britain is the most 
suitable country for the treatment of Broken Hill concentrates 
exported from Australia. The future development of the British 
zinc industry is largely dependent on the facilities that will be 
afforded for their treatment, by the adaptation and enlarging of 
existing works, and the erection of new works for the extraction 
of the zinc and other metals, &c., by distillation, or by electrolytic 
or other processes. 

The Australian Government has dealt with the situation 
created there, and a scheme has been drawn up affecting the 
future of the zinc mining and smelting industry, and one in which 
Australia and Great Britain are immediately concerned. It does 
not appear probable that America will be able to compete in the 
supply of spelter at a reasonable price on the English market 
after the war. 

A new company, known as the Zinc Producers' Association 
Proprietary, Limited, has recently been formed to handle all 
zinc concentrates produced within the Commonwealth. This 
is the largest and most powerful metal combination in the 
Southern Hemisphere, and one of the most important in the 

201 



THE ZINC INDUSTRY 

world. 1 The Commonwealth's annual output of zinc ores and 
concentrates amounts to 450,000 tons, and the gross value of 
metal is not less than 5,000,000. All the zinc-producing 
companies of Australia are members. The Association will act 
for all Australian producers of zinc ores who belong to it during 
the next fifty years, on a co-operative basis, the companies under- 
taking to have all their smelting done through it. One of the 
fundamental principles is " equality of treatment " of all 
members, irrespective of the tonnage of output. The Common- 
wealth Government is represented on the board, thus safeguard- 
ing the interests of the general community. 

In spite of the Commonwealth Prime Minister's efforts in 
England, the spelter question has not yet been definitely settled 
so far as Great Britain is concerned. A contract has been 
entered into for a large supply of zinc concentrates per annum 
for Great Britain during the continuation of the war, with the 
option of increasing the quantity. The British Government has 
entered into a definite agreement for a term of ten years to 
take a minimum of 100,000 tons of Australian concentrates at 
satisfactory prices. 

As to the remainder, arrangements have been suggested 
whereby Australia will treat locally 40 per cent, of the whole 
of the zinc concentrates produced in the Commonwealth. 

The British Government has further contracted to take up to 
45,000 tons per annum of spelter and electrolytic zinc produced 
in Australia for a period of ten years. The post-war require- 
ments of France, Belgium and the other Allies are being 
considered. 

In order to deal with some of the zinc concentrates reserved to 
Australia under the scheme, a company, called the Australian 
Electrolytic Zinc Company, has been formed, and will, it is 
hoped, be successful. 

Contracts for power have been arranged with the Tasmanian 

Government ; technical experts have been engaged in America, 

and the company promises to be one of the foremost industrial 

concerns in the Commonwealth. Towards securing capital for 

Australian zinc industries the Imperial Government undertakes 

to advance a substantial sum at the same rate of interest as is 

paid by the Imperial Government, if required, to finance 

Australian zinc works until war restrictions are removed. ' The 

1 Chamber of Commerce Journal, March, 1917. 

202 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

Mount Lyell Company is embarking upon a new venture, and 
promises to be a large producer of electrolytic zinc. The enlarge- 
ment of the Port Pirie zinc distillery is receiving attention. Zinc 
specialists have been engaged to undertake the modernisation 
of the zinc distilling plants in Australia, and also to install and 
work the electrolytic zinc processes. All the above provisions 
will, however, only permit of the treatment of a portion of 
the zinc concentrates which can be produced in Australia for 
which concentrating plant is already in existence. What is to 
become of the balance of the concentrates available for smelting 
is uncertain, but Japan has already made offers for purchasing 
considerable quantities. 

With regard to the development of the British zinc industry 
there has been much discussion ; it has been proposed to erect 
large smelting works in this country under Government subsidy, 
in addition to the extension of existing works, with a view to 
largely increase the output and render this country less dependent 
on foreign supplies. A special committee has been appointed 
by the Secretary of State for the Colonies and the President of 
the Board of Trade to elaborate a scheme. What is involved 
in this proposition is best seen by reference to the figures repre- 
senting the output and consumption of zinc in the United 
Kingdom under normal conditions. From the few available 
statistics it would appear that the maximum production of 
spelter in this country in any year before the war was approxi- 
mately 58,000 English tons, whereas the consumption was 
approximately 200,000 tons, the difference between production 
and consumption being 142,000 tons. 

The actual production for 1913 was 58,298 tons, of which, as 
previously stated, probably not more than 31,290 tons was 
" primary " spelter, produced direct from ores, the balance of 
27,008 tons being " secondary," or remelted metal from the 
treatment of by-products, &c. Thus secondary zinc forms an 
exceptionally abnormal proportion of the total British output. 

Practically the whole of the primary spelter was produced 
from imported ores, the metal produced from British ores being 
comparatively insignificant and probably amounting to not more 
than 2,500 tons. 

The consumption of virgin zinc in 1913 was 203,302 tons, of 
which no less than 145,004 tons was imported. 

The actual consumption of spelter in 1913, after allowing for 

203 



THE ZINC INDUSTRY 

imports of zinc wire and sheet, and that present in imported 
brass, was 224,000 tons, but even this does not include the zinc 
contained in zinc dust, zinc oxide, lithopone and salts of zinc 
(chloride and sulphate), figures for the import of which are difficult 
to obtain, but the quantities are by no means inconsiderable. 

The imports of drawn and rolled zinc in 1913 were 18,768 tons. 
With regard to these imports it is of interest to note that in 
1913 Germany imported 313,269 tons of zinc ore, 57,641 tons of 
spelter and 725 tons of drawn or rolled zinc, and exported in the 
same year 44,731 tons, 109,606 tons, and 24,965 tons of these 
materials respectively. It should be noted also that the British 
statistics refer only to the United Kingdom, and take no account 
of the imports of crude or manufactured zinc into Canada, 
Australia, South Africa and India, which were large. 

From the above figures it will be evident that in order to render 
this country independent of foreign supplies of zinc it will be 
necessary to smelt sufficient ore to produce annually at least 
140,000 tons more spelter than has been produced in the past. 

Apart from the provisions that have been made recently for 
an adequate supply of zinc ore for British smelters there is very 
little information available as to what steps are being taken to 
increase the output of metal in this country. According to the 
latent report of the Inspector of Alkali Works, extensive additions 
were made to registered zinc works in 1916, but no new works 
were added. In 1916 the Sulphide Corporation acquired the 
smelting works of the Central Zinc Company at Seaton Carew, 
and in 1917 they purchased the sulphuric acid works constructed 
by that company for 52,000. These works utilised the 
sulphurous gases coming from the zinc-roasting furnaces, The 
smelting works are to be doubled, and when this is accom- 
plished they are expected to be able to treat 30,000 tons of Broken 
Hill concentrates yearly, equal to an annual output of zinc of 
about 12,000 tons. This tonnage amounts to one-half the 
Sulphide Corporation's output of zinc concentrates. 

Considerable additions are also being made to the Swansea 
Vale Spelter Works, the largest works in the Swansea district. 
Good progress has been made with the extensions, which, when 
completed, will give an output of 15,000 to 20,000 tons of spelter 
per annum. Extensions are in progress, or completed, in other 
works, and according to a recent estimate when all the new 
plant is erected the total capacity of the British smelting 

204 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

works will be about 78,000 tons of primary spelter, made up as 
follows : * 

Works. Capacity. 

Swansea Vale . . . . . . . . 20,000 English tons. 

English Crown Spelter . . . . 18,000 

Vivians . . . . . . . . . . 10,000 

Seaton Carew . . . . . . . . 10,000 

Dillwyn . . . . . . . . . . 8,000 

Williams Foster . . . . . . 6,000 

Sundry lesser plants . . . . . . 6,000 

Total . . . . . . 78,000 English tons. 

This estimate is based on the theoretical capacity of the 
respective plant extensions when finished ; the actual produc- 
tion would naturally be lower. According to this estimate 
the total production of zinc from ores will be approximately 
50,000 tons more than the pre-war output of virgin metal, or, 
including secondary zinc, an increase of nearly twice the pre- 
war annual output. 

To encourage the smelting of Broken Hill concentrates by 
British smelters the Government, in connection with the British- 
Australian scheme, has guaranteed the minimum price of 23 
for ordinary spelter and 28 for high-grade spelter. 

An agreement has also been reached between the spelter 
producers in this country and the Ministry of Munitions on the 
subject of new works. The producing companies are to be 
allowed to deduct from their excess profits the difference between 
the cost of new production during the war and before the war ; 
they are also to receive from the Ministry of Munitions a 
" reward " for extending their works, in that they will be allowed 
to deduct from their excess profits, before taxation, 50 per 
cent, of the pre-war cost of construction. 

Before the war it was agreed by producers generally that it 
did not pay to produce permanently under 22 per ton. With 
existing methods and conditions of production, the cost for 
some time to come must be considerably more. 

In these circumstances it is considered by many that the 

margin of profit is not sufficient to stimulate private enterprise. 

In this connection it may be permitted to quote the opinion of 

Mr. J. C. Moulden, who has had a wide experience in zinc smelting. 

Compared with the production of other metals in common use, 

he considers " that there is no branch of the metallurgical industry 

1 Mining Journal, London, 1917, vol. cxvi, p. 66. 

205 



THE ZINC INDUSTRY 

in which, considering the difficulties and risks involved, the 
invested capital has been so ill-requited as that of zinc. 
What profits there have been were made largely by the ore 
and metal-dealing firms, and those who, in addition to smelting, 
turned out rolled and stamped zinc together with lead and silver 
from complex ores and possibly also zinc oxide." That zinc 
smelting can, however, be profitably undertaken, under favour- 
able conditions, and by the utilisation of all the valuable by- 
products, with good management and if equipped with labour- 
saving appliances, is evident from the fact that the Continental 
zinc-smelting companies have in recent pre-war days paid divi- 
dends of 20 to 25 per cent, and over. Under the conditions 
that obtain in this country it seems obvious that the Government 
must undertake the cost of erecting new works if they want to 
see the position much further advanced, and it is the uncertainty 
of what they are going to do which makes an estimate of the 
outlook for home production so much a matter of hypothesis, 
and which prevents private capitalists from embarking. The 
problem is obviously a very different one for the Government in 
contrast to private enterprise. They have not merely to 
consider the question from the point of view of the price of 
spelter after the war. Beyond economic factors there is the 
consideration of the public safety in view of possible restric- 
tions on the necessary supplies of sulphuric acid and spelter. 

Assuming that the above estimate of increased production is 
substantially correct, it will be evident that something like another 
100,000 tons of metal will be required to bring up the spelter 
production to correspond with the pre-war consumption, and it 
is to supply this extra output that the construction of smelting 
works by the Government has been suggested. The erection of 
smelting works at Avonmouth, capable of producing 24,000 tons 
of zinc per annum from Australian ore, has been proposed, and 
in this connection the Bristol City Council recently sanctioned the 
preparation of schemes for extending the accommodation of the 
Royal Edward Dock to meet the traffic incidental to the proposed 
shipment of zinc concentrates from Australia. Negotiations for 
the treatment of further quantities of these concentrates at 
Widnes, and possibly elsewhere, are also in progress. But after 
allowing for the carrying out of the present programme for the 
expansion of the productive capacity of existing works, even in- 
cluding the 24,000 tons per annum for the proposed new works at 

206 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

Avonmouth, it would appear that the possible output will be only 
about one-half the pre-war consumption. It is most unfortunate, 
in the future interests of the zinc industry in this country, and 
in the interests of the metal industries dependent on metallic 
zinc as raw material of first importance, that the Government 
has not, up to the present, taken any steps to begin the erection 
of new zinc-smelting plant. Moreover, it cannot be too strongly 
urged that the provision for increased zinc output so far suggested 
is inadequate to meet the situation, and the erection of large 
works would be one of the greatest factors in supplementing the 
zinc deficiency, and would help to keep the production in our 
own hands and remove our dependency on metal from foreign 
sources. 

In addition to the home output, there is the proposed spelter 
production from Australia, which, as stated above, is to be 
imported to the extent of 45,000 tons per annum, and which 
would be of great assistance in making the total output approxi- 
mately equal to the demand. 

Climatic and labour conditions are, however, against any 
large extension of zinc distilling in Australia, and up to the 
present only the erection of small plant has been started there, 
and for a long time to come no appreciable tonnage of metal can 
be expected. 

The Government has bought supplies of Broken Hill zinc 
concentrates, and many tons have been shipped to this country, 
but they are of no value to the country until they are turned into 
metal. The erection of works to effect this with all possible 
speed becomes imperative. It may be well to emphasise the 
fact that the complete treatment of these concentrates involves 
not only the production of zinc, they are also a potential source 
of sulphuric acid, and of lead and silver, and for economic reasons 
they should be worked to produce all these. The general method 
of treating the concentrates is shown in the accompanying flow 
sheet, (p. 208.) 

To erect new zinc-smelting plant without proper provision for 
the utilisation of so valuable a product as the sulphur would 
undoubtedly be a serious mistake, and would greatly hinder the 
future development of the British zinc industry which is so 
urgently necessary, because it would not only waste a product of 
considerable value to the chemical industries, but would also 
deprive the zinc industry of a source of profit and increase the 

207 



FLOW SHEET SHOWING THE GENERAL METHOD OF TREATING AUSTRALIAN 
ZINC CONCENTRATES. 



Zinc Concentrates. 



Roasting to expel 
Sulphur. 



Sulphur fumes. 



Roasted Concen- 
trates mixed with 
Coal. 



4 



Sulphuric Acid 
Works 



Market. 





Distillation. 










i 


N , 


| 


Zinc Powder. 


Spelter. 


Furnace Residues 
(containing Lead 
and Silver.) 




i 




Sifted through 
70-mesh Screen. 


Market. 


Concentrated 
in jigs. 


N , 






Packed in Drums 
or Barrels. 




Argentiferous 
Lead Concentrate. 


I 




^ ' 


Market. 




Lead Smelter. 



b.ead ^k 
ilver) 



To Market. 



208 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

difficulty of meeting foreign competition. It is just the fact that 
this ore is a potential source of sulphuric acid which renders it 
necessary for the bulk of the concentrates to be shipped from 
Australia, where the market for acid is limited, to a country like 
Great Britain, with nine times the population of Australia and 
highly developed industries which can absorb the acid. 

Probably one of the most difficult problems in connection with 
the utilisation of the sulphur is to decide on the most suitable 
location of the plant for roasting the ore. The Swansea district 
is one of the most favourably situated places in the world for 
the production of zinc and is the chief seat of the British industry, 
but it does not follow that the roasting of the ore for acid should 
necessarily be effected at the same place as the smelting of 
the roasted material for the metals. As already pointed out, it 
is not uncommon to find the roasting and the manufacture of 
sulphuric acid carried on in one district and the roasted ore 
smelted in another district where economic considerations render 
this course desirable. In treating the Australian concentrates 
in this country, therefore, it may be found, after a due con- 
sideration of all the circumstances, to be more suitable to roast 
the ore for acid at some centre connected with the chemical or 
galvanising industries, and to treat the roasted ore for zinc and 
its allied metals at Swansea or some other zinc-smelting centre, 
or even to extract the zinc in the same locality as that in 
which the sulphuric acid is made. 

In adopting this latter course a considerable quantity of by- 
products from galvanisers' works would be available in the 
immediate proximity of the projected smelting works, and the 
saving in freight alone on this material would probably be 
considerable. A most important element in favour of a scheme 
for the production of sulphuric acid from the roasting of concen- 
trates is the keen interest shown by the leading manufacturers 
of sulphuric acid, who have been longing for an opportunity 
to adopt the Belgian blende roasting system in preference to the 
roasting of pyrites, which have been advancing in price con- 
siderably of late. 

There is always an increasing demand for sulphuric acid in 
this country, especially for non-arsenical acid, as produced from 
zinc ores. 

The whole question of the treatment of the Broken Hill zinc 
concentrates is, in view of the commercial and military 

209 P 



THE ZINC INDUSTRY 

value of zinc, of great importance, and the Government 
authorities have rightly decided that the handling of what is 
undoubtedly a great Imperial asset requires careful consideration. 
At the same time, there seems to be no reason why that con- 
sideration should be indefinitely deferred, and why, under proper 
safeguards to retain the control of this asset of the Empire, the 
treatment of the ore for its zinc and other valuable constituents 
should not be proceeded with without further delay, so that the 
country may be relieved of the necessity of importing spelter. 
The shortage of domestic zinc is bound to continue unless works 
are built capable of dealing with the zinc concentrates from 
Broken Hill. The war may yet last a long time, and it will 
scarcely be possible to hold up all trade and development 
questions until peace arrives. 

The establishment in this country of a zinc-smelting industry 
on a scale commensurate with its needs is most urgently required. 

There is no reason, if there is a proper application of organising 
ability, technical knowledge, perseverance and resourcefulness, 
why success should not be achieved. 

We have in the country metallurgists with knowledge and 
experience of the very best Continental zinc-smelting plants and 
methods ; we have the raw materials in ample quantity in the 
Empire ; we have the demand for the metal, but we have not yet 
availed ourselves of these. 

As Professor H. C. H. Carpenter 1 has well said, " the establish- 
ment in this country of a zinc industry on a scale commensurate 
with its needs would be an industrial victory of the first magnitude 
and it would remove a peril in which this country was placed 
by the outbreak of war, a peril which has been all too imperfectly 
realised, and should never be allowed to recur." 

The urgent need is to make provision for the reconstruction 
that must follow on the declaration of peace, and in that recon- 
struction the development of the zinc industry holds an important 
place. There can be no doubt that further to neglect to respond 
to the urgent demands for a largely augmented output of zinc 
in this country will very seriously interfere with the progress of 
the non-ferrous metal industries, which have hitherto played so 
important a part in the industrial development, not only of this 
country, but of the British Empire, and are destined to be of 
much greater importance in the near future. 

1 Nature, 1916, vol. xcviii, p. 131. 
210 



FUTURE OF THE ZINC INDUSTRY IN GREAT BRITAIN 

The question as to what is going to be the future of the zinc 
industry in this country is one which has been exercising the 
mind of those who have the welfare of this industry at heart ever 
since the lamentable and dangerous situation at the outbreak of 
war was revealed. One cannot refrain from comparing the long 
delay in dealing with the question of the future development of 
the British zinc industry with the very expeditious manner in 
which the Royal Ontario Nickel Commission, appointed by the 
Ontario Government in September, 1915, dealt with the question 
of the nickel industry. Although many countries were visited, 
the Commissioners have, after a lapse of only eighteen months, 
presented their valuable and exhaustive report, which deals very 
fully with the nickel question, especially in relation to industry 
and trade, and will form a standard work of reference on nickel 
for many years to come. As the result of the recommendations 
of the Commissioners, extensive works are now being erected in 
Ontario for the treatment of the large quantities of ore found in 
the district, which have hitherto been mainly treated in the 
United States. 



2ir P 2 



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r ./ " - v r '"** _ " ' "^ 

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F. Johnson. " A Note on the Annealing of Brass," Journal of 
Institute of Metals, 1914, vol. xii, pp. 111-115. 

W. E. Thorneycroft and T. Turner. " Behaviour of Copper-Zinc 
Alloys when Heated in a Vacuum," Journal of Institute 
of Metals, 1914, vol. xii, pp. 214-229. 

S. Whyte. " The Micro-Chemistry of Corrosion. Part III. 
The a/3- Alloys of Copper and Zinc," Journal of Institute 
of Metals, 1915, vol. xiii, pp. 80-99. 

O. F. Hudson and R. M. Jones. " The Constitution of Brasses 
containing Small Percentages of Tin : A Contribution 
to the Ternary System Copper-Zinc-Tin," Journal of 
Institute of Metals, 1915, vol. xiv, pp. 98-115. 

D. Meneghini. " Structural Changes in Industrial Brasses," 

Journal of Institute of Metals, 1915, vol. xiv, pp. 154- 

159- 
" The Hardness of Copper-Zinc Alloys," Journal of 

Institute of Metals, 1915, vol. xiv, pp. 160-167. 
S. L. Hoyt. " The Grey Constituent which forms by adding Tin 
to the Brasses," Journal of Institute of Metals, 1915, 
vol. xiv, p. 188. 

219 



BIBLIOGRAPHY 

C. H. Mathewson and E. M. Thalheimer. " The Annealing of 
Arsenical Brass containing 61 and 62-5 per cent, of 
Copper : A Study of the Structure and Properties 
developed by Varying the Rate of Cooling within the 
Transformation Range/' Journal of Institute of Metals, 
1916, vol. xvi, pp. 18-83. 

C. H. Mathewson and A. Philips. "The Recrystallization of 
tf-brass after Cold-working," Bulletin of the American 
Institute of Mining Engineers, 1916, p. I. 

P. D. Merica and R. W. Woodward. " The Failure of Brass. I. 
Microstructure and Initial Stress in Wrought Brasses of 
the Type Copper 60, Zinc 40 per Cent/' United 
States Bureau of Standards, Technical Paper No. 82, 
1916. 

O. W. Ellis. " The General Properties of Stampings and Chill 
Castings in Brass of approximately 60 : 40 Composi- 
tion/' Journal of Institute of Metals, 1917, vol. xvii, 
pp. 25-43. 

" Note on the Machining Properties of Brass," 

Journal of Institute of Metals, 1917, vol. xvii, pp. 44-64. 

H. M. Thornton and H. Hartley. " The Melting of Brass and 
Copper in a Crucible Furnace with Coal-gas Fuel," 
Journal of Institute of Metals, 1917, vol. xvii, pp. 213-230. 

R. A. Wood. " Brass Rolling Mill Alloys," Journal of American 
Institute of Metals, 1917, vol. xi, pp. 181-192. 

O. Smalley. " The Influence of Arsenic on Brass," Journal of 
Society of Chemical Industry, 1917, vol. xxxvi, pp. 

429-439- 
H. W. Brownsdon. " Cartridge Brass," Journal of Society of 

Chemical Industry, 1917, vol. xxxvi, pp. 794-796. 
B. P. Haigh. " Experiments on the Fatigue of Brasses," 

Journal of Institute of Metals, 1917, vol. xviii, pp. 55-86. 
O. W. Ellis. " A Comparison Screen for Brass," Journal of 

Institute of Metals, 1917, vol. xviii, p. 171. 
L. C. Harvey. " Fuel Economy Possibilities in Brass Melting 

Furnaces," Journal of Institute of Metals, 1917, vol. xviii, 

pp. 213-241. 
W. R. Webster. "The Cold Working of Brass," Journal of 

the American Society for Testing Materials, 1917, 

vol. xvii. 



230 



BIBLIOGRAPHY 



Zinc Alloys : Nickel-Silver (so called). 

O. F. Hudson. " The Microstructure of German Silver," Journal 

of Institute of Metals, 1913, vol. ix, pp. 109-119. 
F. C. Thompson. " Nickel-Brass/' Transactions of the Chemical 

Society, 1914, vol. cv, p. 2342. 
" The Annealing of Nickel-Silver. Part I," Journal 

of Institute of Metals, 1916, vol. xv, pp. 230-263. 
" The Annealing of Nickel-Silver. Part II," Journal of 

Institute of Metals, 1917, vol. xvii, pp. 119-140. 
C. C. Karr. " The Casting of Nickel-Silver," Journal of the 

American Institute of Metals, 1917. 



Zinc-Aluminium and other Zinc Alloys. 

E. S. Shepherd. " Aluminium-Zinc Alloys/' Journal of Physical 

Chemistry, 1905, vol. ix, pp. 504-512. 
W. Rosenhain and S. L. Archbutt. " The Alloys of Aluminium 

and Zinc," Journal of Institute of Metals, 1911, vol. vi, 

pp. 236-258. 
" The Alloys of Aluminium and Zinc" (Tenth Report of 

the Alloys Research Committee of the Institution of 

Mechanical Engineers. Collected Researches of the 

National Physical Laboratory), 1913, vol.x, pp. 1-90. 

E. F. Lake. " Zinc-base Alloys used for Die-moulded Castings/' 

Mechanical World, 1914, vol. Ivi, p. 64. 
O. Bauer and O. Vogel. " Aluminium-Zinc Alloys," International 

Journal of Metallography, 1916, vol. viii, p. 101. 



221 



INDEX 



Aich's metal, 179 
Alloys of zinc, 173, 190 
Aluminium and zinc, 187 
American zinc industry, 14, 40, 106 
Annealing of zinc, 138, 143 
Anti-friction metals, 185 
Australian concentrates, 29, 99, 208 

Belgian zinc industry, u, 37 
Bibliography : alloys of zinc, 217 

metallurgy of zinc, 213 
Blue powder, 171 
Brass, constitution, 175 

early production, 7 

history of, 7, 174 

industrial, 175 

Brasses, composition of, 175, 190 
British zinc industry, 10, 18, 106, 198 
British zinc works, 28 
By-products, in 

Cadmium, 118, 146 
Calamine brass, 7, 175 
Calcination, 79 
Casting of zinc, 139, 167 
Chamber process, 112 
Charging machine, 105 
Chemical properties of zinc, 137 
Complex zinc ores, 70, 109 
Compounds of zinc, 191 
Condensers, 95 
Consumption of zinc, 157 

world's, 1 60 
Contact process, 112 
Convention, 2, 155 
Cost of zinc production, 119 

Delta metal, 179 
Die-casting, 186 
Distillation, methods of, 94 
process, 92 



Electric smelting of zinc, 1 24 
Electro-deposition of zinc, 131, 137 
Etching reagents for zinc, 142 
Europe : production of zinc, 159 
of zinc ore, 56 

Filters, 102 

Fine zinc, 6 

" Flotation," 72 

" Flux skimmings," 163 

Fracture of zinc, 137 

Fume, 118 

Furnace, distillation, 95 

Furnaces, Delplace, 84 

electric, 124 

Hegeler, 87 

Merton, 90 

Ridge, 90 
Future of zinc industry, 198 

Galvanising, 14, 161 

centres, 161 
" German silver," 182 
German zinc industry, n, 33 
Grades of zinc, 6, 103, 148 
Granulated zinc, 138 

Hardness of zinc, 137 
Hard zinc, 181 
History of zinc, 7 
Hydro-metallurgical processes, 130 

Imports of zinc, 26 

of zinc ore, 26 
Impurities in zinc, 145 
Industrial applications, 161 
Iron and zinc, 181 

Labour in zinc works, 18, 122 
Lead in zinc, 102, 145 
Liquation, 102, 146 



INDEX 



Lithopone, 193 
Losses in smelting, 101 

Malleability of zinc, 137 
Melting point of zinc, 139 
Microphotographs of brass, 144 

of zinc, 143 

Micro-structure of zinc, 140 
Miscellaneous zinc alloys, 189 
Muffle furnaces, 84, in 

" Nickel-silver," 182 
Non-ferrous Metals Bill, 2 

Ores of zinc, 46 
America, 61 
Australia, 53 
Belgium, 57 
China, 68 

concentration of, 70 
France, 57 
Germany, 58 
Greece, 59 
India, 54 
Italy, 60 
Japan, 68 
marketing of, 70 
roasting of, 81 
Russia, 60 
Siberia, 69 
Spain, 60 
Sweden, 61 
Tasmania, 54, 134 
United Kingdom, 51 
valuation of, 73 

Physical properties of zinc, 137 
Pigments, 191, 195 
Price of zinc, 3, 151 
Production of zinc, America, 41 

Belgium, 37 

British, 20 

China, 8, 43 

France, 38 

Germany, 34 

Holland, 38 

Japan, 44 

Norway and Sweden, 39 

Russia, 39 

World's, 15, 1 6 

Re-distillation, 103 
Reduction and distillation, 92 
Refining, 102 
Residues from retorts, n8, 119 



Retorts, graphite, 103 

manufacture of, 96 

types of, 95 

vertical, 108 
Roasting, 81 

furnaces, classified, 83 
Rolled zinc, 13, 138, 166 

Sampling zinc, 150 

zinc ore, 77 
Schoop's process, 165 
Sheet zinc, 13, 138, 166 
Sherardising, 164 
Silver in zinc ores, 75 
Silver-zinc alloys, 189 
Smelting losses, 101 
Solubility of zinc, 140 
Spelter, definition, 5, 8 
Sterro-metal, 179 
Sulphur fumes, 84, in 
Sulphuric acid, in, 207 

Tensile strength of zinc, 138 
Typical zinc alloys, 190 

United States, zinc production, 41, 

158 
zinc ore production, 62 

Wet methods, 130 

World's consumption of zinc, 160 

World's production of zinc, 16, 158 

zinc ore, 56 
World's zinc markets, 154 

Zinc alloys, composition, 190 
Zinc castings, 167 
Zinc chloride, 195 
Zinc Convention, 2, 155 
Zinc dust, 97, 100 
Zinc-lead pigment, 195 
Zinc ore trade, 77 
Zinc oxide, 139, 191 

reduction of, 93, 99 
Zinc smelting centres, 18, 28, 34, 37, 

38>4i 
Zinc smelting in America, 40 

Australia, 29, 99 

Belgium, n, 37 

blast furnace, 108 

Canada, 31 

Germany, 33 

Great Britain, 18, 198 

Tasmania, 31, 134 
Zinc sulphate, 197 
Zinc white, 191 



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