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_IMPERIAL INSTITUTE_
MONOGRAPHS ON MINERAL RESOURCES
WITH SPECIAL REFERENCE TO THE
BRITISH EMPIRE
PREPARED UNDER THE DIRECTION OF THE
MINERAL RESOURCES COMMITTEE WITH THE
ASSISTANCE OF THE SCIENTIFIC AND TECHNICAL
STAFF OF THE IMPERIAL INSTITUTE
THE PLATINUM METALS
BY
A. D. LUMB, A.R.S.M., F.G.S., Assoc. Inst. M.M.
LATELY OF THE SCIENTIFIC AND TECHNICAL DEPARTMENT, IMPERIAL INSTITUTE
WITH A MAP
[Illustration]
LONDON
JOHN MURRAY, ALBEMARLE STREET, W.
1920
ALL RIGHTS RESERVED
------------------------------------------------------------------------
IMPERIAL INSTITUTE
MINERAL SECTION
The Imperial Institute is a centre for the exhibition and investigation
of minerals with a view to their commercial development and for the
supply of information respecting the sources, composition and value of
minerals of all kinds.
The Imperial Institute is provided with Research Laboratories for the
investigation, analysis and assay of minerals, and undertakes reports on
the composition and value of minerals, for the information of
Governments and producing companies and firms, in communication with the
principal users in the United Kingdom and elsewhere in the Empire.
Important minerals from within the Empire are exhibited in the
respective Courts of the Public Exhibition Galleries, and also in the
Mineral Reference Collections of the Institute.
A special staff is engaged in the collection, critical revision and
arrangement of all important information respecting supplies of minerals
especially within the Empire, new methods of usage and other commercial
developments.
Articles on these and related subjects are periodically published in the
_Bulletin of the Imperial Institute_, and monographs on special subjects
are separately published under the direction of the Committee on Mineral
Resources.
IMPERIAL INSTITUTE
Advisory Committee on Mineral Resources
The Right Hon. VISCOUNT HARCOURT, D.C.L. (_Chairman_).
[A]Admiral SIR EDMOND SLADE, K.C.V.O., K.C.I.E. (nominated by the
Admiralty), (_Vice-Chairman_).
EDMUND G. DAVIS, Esq.
[A]WYNDHAM R. DUNSTAN, Esq., C.M.G., LL.D., F.R.S., Director of the
Imperial Institute.
J. F. RONCA, Esq., M.B.E., A.R.C.S., Department of Industries and
Manufactures (nominated by the Board of Trade).
[A]Professor J. W. GREGORY, F.G.S., Professor of Geology, University
of Glasgow, formerly Director of Geological Survey, Victoria,
Australia.
Sir ROBERT HADFIELD, Bart., F.R.S., Past-President Iron and Steel
Institute.
Captain A. L. ELSWORTHY, Intelligence Department, War Office
(nominated by the War Office).
W. W. MOYERS, Esq. (Messrs. A. Watson & Co.), Liverpool.
R. ALLEN, Esq., M.A., B.Sc., Imperial Institute (_Secretary_).
Footnote A:
Members of Editorial Sub-Committee
MINERAL SECTION
Principal Members of Staff
_Superintendent_
R. ALLEN, M.A. (Cantab.), B.Sc. (Lond.), M.Inst.M.M.
_Assistant Superintendent_
S. J. JOHNSTONE, B.Sc. (Lond.), A.I.C.
_Senior Assistants_
G. M. DAVIES, M.Sc. (Lond.), F.G.S.
W. O. R. WYNN, A.I.C.
_Assistants_
S. BANN.
F. H. BELL.
H. BENNETT, B.Sc. (Lond.).
A. T. FAIRCLOTH.
R. C. GROVES, M.Sc. (Birm.).
E. HALSE, A.R.S.M., M.Inst.M.M.
PREFACE
The Mineral Resources Committee of the Imperial Institute has arranged
for the issue of this series of Monographs on Mineral Resources in
amplification and extension of those which have appeared in the
_Bulletin of the Imperial Institute_ during the past fifteen years.
The Monographs are prepared either by members of the Scientific and
Technical Staff of the Imperial Institute, or by external contributors,
to whom have been available the statistical and other special
information relating to mineral resources collected and arranged at the
Imperial Institute.
The object of these Monographs is to give a general account of the
occurrences and commercial utilisation of the more important minerals,
particularly in the British Empire. No attempt has been made to give
details of mining or metallurgical processes.
HARCOURT,
_Chairman Mineral Resources Committee_.
IMPERIAL INSTITUTE, LONDON, S.W.7.
_July 1920._
CONTENTS
CHAPTER I
PAGE
=THE PLATINUM METALS: THEIR OCCURRENCES, CHARACTERS AND USES.
WORLD’S OUTPUT= 1
CHAPTER II
=SOURCES OF SUPPLY OF PLATINUM METALS=
(_a_) BRITISH EMPIRE: 16
_Europe_: United Kingdom.
_Asia_: India (Burma).
_Africa_: Rhodesia; Union of South Africa.
_America_: Canada; Newfoundland.
_Australasia_: Australia; New Zealand.
CHAPTER III
=SOURCES OF SUPPLY OF PLATINUM METALS=
(_b_) FOREIGN COUNTRIES: 32
_Europe_: France; Finland; Germany; Lapland; Russia; Spain.
_Asia_: Armenia; Borneo; China; Japan; Sumatra.
_Africa_: Congo Free State; Madagascar.
_America_: Brazil; Colombia; Ecuador; Mexico; United States.
WORLD MAP OF PLATINUM DEPOSITS 59
REFERENCES TO LITERATURE ON THE PLATINUM GROUP 60
NOTE.—_Numerals in square brackets in the text refer to the Bibliography
at the end._
THE PLATINUM METALS
CHAPTER I
PLATINUM METALS: THEIR OCCURRENCES, CHARACTERS AND USES
INTRODUCTION
The metals which comprise the Platinum group are the following:
Platinum, Palladium, Iridium, Osmium, Ruthenium and Rhodium.
Up to the year 1914 Russia produced over 90 per cent. of the world’s
supply of platinum, the Republic of Colombia, South America, ranking
next in importance with about 5 per cent. Owing, however, to the war and
to the chaotic conditions brought about by the revolution, the output of
Russia has considerably decreased, and although the Colombian production
has been steadily increasing, the increased demand in connection with
munition manufacture caused a somewhat serious shortage during the
latter stages of the war, which was especially felt in the United
States. As a result much exploratory work has recently been carried on
in an endeavour to discover new deposits of importance; but up to the
present, although several fresh occurrences have been brought to light,
results have on the whole been disappointing.
OCCURRENCES
Platinum usually occurs in nature as native metal alloyed with one or
more of its allied metals in the form of very fine grains more or less
flattened; sometimes in the form of irregular nuggets; and occasionally,
though rarely, in small cubic crystals. It is sometimes coated with a
black layer of iron oxide, which may be magnetic, in which case it is
not easily recognizable. When unrefined it is referred to as “crude”
platinum.
With the exception of a certain amount of the platinum metals, obtained
from the refining of copper and gold bullion, particularly from the
copper-nickel deposits of Sudbury, Ontario, about 99 per cent. of the
whole supply is derived from alluvial deposits. Several occurrences of
platinum _in situ_ are known, but so far few are of commercial
importance: however, in view of the indications of exhaustion shown by
some of the placer deposits, notably in Russia, the exploration of
primary ores is now receiving more attention and practical results have
already been achieved in Russia and in Spain.
The mother rocks from which the deposits are derived, in the large
majority of known cases, consist of basic and ultra-basic igneous rocks,
including peridotites, pyroxenites and dunites. The two first are
composed of iron magnesian silicates, pyroxene, augite and hornblende
with olivine, chromite, ilmenite and magnetite: the dunites consist
principally of olivine with some chromite. These rocks are often found
to have undergone more or less alteration to serpentine. In addition,
platinum has been found in quartz veins, notably at the Boss Mine,
Nevada, and in a few known cases it has been derived from formations in
schistose, or altered sedimentary rocks.
When present in serpentine, platinum is usually disseminated through the
rock in fine particles. It seldom occurs in a lode-formation. In
sedimentary rocks it usually occurs in sandstones. In cases where
alluvial deposits have been derived from the basic igneous rocks, the
associated minerals are usually chromite, magnetite, ilmenite, iridium
and osmiridium. In sedimentary deposits the metal is commonly associated
with quartz, copper, nickel, silver and palladium.
Platinum has been found in certain varieties of the copper ores
tetrahedrite and bournonite. It has occasionally been located in shales
and in coal, although not in recoverable quantities. In the latter case,
in an Australian coal, it is associated with vanadium[1] p. 992.
Several cases are known of platinum being present in meteorites, two
well-authenticated instances having been reported from Mexico. Platinum
has been shown to exist in meteoric iron from New South Wales.
Crude platinum, as recovered, contains from 70 to 90 per cent. of the
metal, and, as mentioned above, is really an alloy of platinum with one
or more of the allied metals, the chief impurities consisting
principally of iron and copper.
The table on the next page gives the analyses of typical samples of
crude platinum from the Urals, California, British Columbia, and other
places.
Platinum also occurs in combination with arsenic in the mineral
_Sperrylite_ (PtAs_{2}), in the form of minute octahedral crystals. The
colour of this mineral is tin white, its lustre is metallic and
brilliant, its hardness varies from 6 to 7, and its specific gravity is
10·6. The mineral is brittle and breaks with a conchoidal fracture. It
is very rare, and is interesting as being the only mineral of platinum
known besides the native metal. It occurs associated with sulphide
minerals of magmatic origin in gabbros and diabases, notably in the
nickeliferous pyrites of Sudbury, Canada, and in the copper ores of the
Rambler Mine, Laramie, Wyoming.
It is probable that the palladium, which is also found in these
deposits, is similarly present in the form of an arsenide, but such a
mineral has not yet been definitely proved to exist.
The following is an analysis of a sample of sperrylite: platinum, 54·47
per cent.; rhodium, 0·76 per cent.; palladium, trace; arsenic, 42·23 per
cent.; antimony, 0·54 per cent.[2] p. 69.
PROPERTIES OF THE PLATINUM METALS
_Platinum._—The colour is white with a greyish tinge. When pure it is
very malleable and ductile. Its coefficient of expansion is less than
that of all other metals. Platinum fuses at about 1750° C., but the
presence of impurities lowers the melting-point. Its specific gravity is
21·5, and its hardness is from 4 to 5. Its electric conductivity is low,
being 13·4 at 0° C.[3] p. 398.
_Composition of Native Platinum and Osmiridium_
──────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬──────┬──────────────────
Locality. │ Pt. │ Fe. │ Pd. │ Rh. │ Ir. │ Os. │ Cu. │Os-Ir.│ Remarks.
──────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼──────┼──────────────────
_Platinum_│ Per │ Per │ Per │ Per │ Per │ Per │ Per │ Per │
│cent.│cent.│cent.│cent.│cent.│cent.│cent.│cent. │
Urals 1[B]│76·22│17·13│ 1·87│ 2·50│ tr. │ │ 0·36│ 0·50│Magnetic grs.
Urals 2 │73·58│12·98│ 0·30│ 1·15│ 2·35│ tr. │ 5·20│ 2·30│Magnetic grs.
Urals 3 │81·34│11·48│ 0·32│ 2·14│ 2·42│ tr. │ 1·13│ 0·57│Non-magnetic.
Urals 4 │78·94│11·04│ 0·28│ 0·86│ 4·97│ │ 0·70│ 1·96│Non-magnetic.
Urals 5 │86·50│ 8·32│ 1·10│ 1·15│ │ tr. │ 0·45│ 1·40│Non-magnetic.
Borneo │82·60│10·67│ 0·30│ │ 0·66│ │ 0·13│ 3·80│Gold, 0·20 per
│ │ │ │ │ │ │ │ │ cent.
Brazil │72·62│ tr. │21·82│ │ 0·88│ │ │ │Sand, 0·42 per
│ │ │ │ │ │ │ │ │ cent.
Granite │68·19│ 7·87│ 8·26│ 3·10│ 1·21│ │ 3·09│ 14·62│Gangue, 1·69;
Cr., │ │ │ │ │ │ │ │ │ non-magnetic.
B.C. │ │ │ │ │ │ │ │ │
Granite │78·43│ 9·78│ 0·09│ 1·70│ 1·04│ │ 3·89│ 3·77│Gangue, 1·27;
Cr., │ │ │ │ │ │ │ │ │ magnetic.
B.C. │ │ │ │ │ │ │ │ │
Chocó, │86·20│ 7·80│ 0·50│ 1·40│ 0·85│ │ 0·60│ 0·85│Sand, 0·95.
Col. │ │ │ │ │ │ │ │ │
Chocó, │84·30│ 5·31│ 1·06│ 3·45│ 1·46│ 1·03│ 0·74│ │Gold, 1·0; sand,
Col. │ │ │ │ │ │ │ │ │ 0·61.
California│85·50│ 6·75│ 0·60│ 1·00│ 1·05│ │ 1·40│ 1·10│Gold, 0·8; sand,
│ │ │ │ │ │ │ │ │ 2·95.
California│79·85│ 4·45│ 1·95│ 0·65│ 4·20│ │ 0·75│ 4·95│Gold, 0·55; sand,
│ │ │ │ │ │ │ │ │ 2·69.
Oregon │51·45│ 4·30│ 0·15│ 0·65│ 0·40│ │ 2·15│ 37·30│Sand, 3; gold,
│ │ │ │ │ │ │ │ │ 0·85.
Fifield, │75·80│10·15│ tr. │ 1·30│ 1·30│ │ 0·41│ 9·30│Gold, nil; sand,
N.S.W. │ │ │ │ │ │ │ │ │ 1·12.
“Austra- │61·40│ 4·55│ 1·80│ 1·85│ 1·10│ │ 1·10│ 26·00│Gold, 1·2; sand,
lia” │ │ │ │ │ │ │ │ │ 1·4.
Currumbin,│26·12│27·17│ │ │ │ │ 2·51│ 40·02│Sand, 1·33.
Q. │ │ │ │ │ │ │ │ │
_Osmi- │ │ │ │ │ │ │ │ │
ridium_ │ │ │ │ │ │ │ │ │
Urals │10·08│ tr. │ tr. │ 1·51│55·24│27·23│ tr. │ │Ru, 5·85
│ │ │ │ │ │ │ │ │ (_Nevyanskite_).
Urals │ 0·14│ 0·63│ │ 1·65│43·94│48·85│ 0·11│ │Ru, 4·58
│ │ │ │ │ │ │ │ │ (_Nevyanskite_).
California│ │ │ │ 2·60│53·50│43·40│ │ │Ru, 0·50
│ │ │ │ │ │ │ │ │ (_Nevyanskite_).
“Austra- │ │ │ │ 3·04│58·13│33·46│ 0·15│ │Ru, 5·22
lia” │ │ │ │ │ │ │ │ │ (_Nevyanskite_).
Currumbin,│ 3·00│ │ │ │62·00│33·00│ │ │Sand, 2·00
Q. │ │ │ │ │ │ │ │ │ (_Nevyanskite_).
│ │ │ │ /\ │ │ │ │
Tasmania │ 0·37│ 0·30│ 0·21│ 33·80 │57·09│ tr. │ │Ru, 8·19; Au, ·04
│ │ │ │ │ │ │ │ (_Siserskite_).
_Platin- │ │ │ │ │ │ │ │ │
iridium_ │ │ │ │ │ │ │ │ │
Condado, │55·44│ 4·14│ 1·49│ 6·86│27·79│ tr. │ 3·30│ │
Brazil │ │ │ │ │ │ │ │ │
_Native │ │ │ │ │ │ │ │ │
Iridium_ │ │ │ │ │ │ │ │ │
Urals │19·64│ │ 0·89│ │76·80│ │ 1·78│ │
──────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴──────┴──────────────────
Reference—Pt., platinum; Fe., iron; Pd., palladium; Rh., rhodium; Ir.,
iridium; Os., osmium; Cu., copper; Os-Ir., osmiridium; Ru., ruthenium.
Footnote B:
Average percentage of Urals platinum is a little under 80.[4] p. 558.
Platinum is not acted upon by either nitric, sulphuric or hydrochloric
acid, but is soluble in aqua regia (1 part of nitric to 2 parts of
hydrochloric acid), or in other mixtures liberating chlorine, with the
formation of platinum tetrachloride (PtCl_{4}). It is not acted upon by
air or moisture, even at high temperatures. It is corroded by caustic
alkalis, sulphides, sulphates, phosphates and arsenides, if heated in
contact with them. It will not amalgamate with mercury unless sodium is
present, in this respect differing from gold and silver.
Platinum, in a finely-divided condition, absorbs large quantities of
hydrogen or other gases, which on occlusion become more active: hence
its value as a catalytic agent.
_Palladium._—This metal resembles platinum, but is sometimes fibrous,
the colour being between that of platinum and of silver. It possesses a
lower melting-point than platinum—about 1550° C. It is malleable, has a
hardness of from 4·5 to 5, and a specific gravity of 11·5. As already
stated, palladium, when found in copper ores, is probably present in
combination with arsenic. _Porpezite_, a rare mineral, containing gold
and up to 10 per cent. palladium, has been identified in gold-bearing
veins in Brazil [see p. 54].
Palladium is produced from the refining of copper matte and of base gold
bullion from Australia and elsewhere.
_Iridium_ is a brilliant white brittle metal, with a specific gravity of
22·4, and hardness of 6 to 7. Its fusion point is very high—about 2200°
C.—and under ordinary conditions it is not attacked by any acid. At
1100° C. it begins to oxidize to a purple oxide. Iridium usually occurs
either in crude platinum, or alloyed with osmium, as iridosmine, or as
native metal. The bulk of iridium is derived from the platinum placer
deposits of the Urals, but the Californian metal is more valuable, on
account of its better quality. It is also obtained in small amounts from
copper bullion.
_Osmium_ is a hard and brittle metal, bluish-grey in colour. Its
specific gravity is 22·5, and it has a very high melting-point, in this
respect being the most refractory of the group.
_Iridosmine_, or _Osmiridium_, an alloy of iridium and osmium, occurs as
hexagonal crystals, or flattened grains of lighter colour than platinum.
It may contain from 40 to 77 per cent. of iridium, and from 20 to 50 per
cent. of osmium. If the iridium predominates, the alloy is called
_Nevyanskite_, and _Siserskite_ if the osmium content is high. It is
distinguishable from platinum by the brittleness of the flakes.
Siserskite gives off a pungent odour, if strongly heated, caused by the
volatilization of osmium. Iridosmine has a hardness of 6 to 7, and a
specific gravity of 19 to 21.
_Ruthenium_ is a white metal, with a specific gravity of 12·1. It is
scarcely acted upon by aqua regia. Ruthenium occurs mainly in small
amounts in iridosmine. It is also found in the copper ores of Sudbury
and other places. _Laurite_ is a very rare sulphide of ruthenium
(RuS_{2}), containing a small amount of osmium, which has only been
recognized in the Borneo deposits.
_Rhodium_ is a white metal resembling aluminium, with a specific gravity
of 12·1, and a melting-point of about 2000° C. It is ductile and
malleable at red heat. In addition to its occurrence in crude platinum,
the metal is also contained in small quantities in the sperrylite found
in the copper ores of Sudbury, Canada[5] p. 779.
_Colloidal Platinum._—This has only recently been detected in ores, and
therefore its occurrence might not be detected qualitatively. By
destroying its colloidal condition, however, its presence can be
discovered in the ordinary ways[4].
METALLURGICAL TREATMENT
Crude platinum can be refined either by dry or by wet methods, the
following being brief outlines of the two processes:
By the wet method, the crude platinum is dissolved in aqua regia, with
excess of hydrochloric acid. Evaporation is continued until the whole of
the nitric acid is expelled. By addition of a solution of ammonium
chloride, the platinum is then precipitated as ammonium
platini-chloride. This precipitate is heated to redness, when chlorine
and ammonium chloride are given off, and spongy platinum remains. The
last is next granulated, after fusion by the oxy-hydrogen blowpipe in a
small lime furnace. Platinum obtained by this method may contain small
amounts of iridium, rhodium and palladium.
In the dry method, introduced by Delville and Debray, the crude platinum
is smelted with galena in a small reverberatory furnace. A portion of
the lead is reduced to the metallic state by the iron in the charge, and
forms a fusible alloy with the platinum. The osmiridium present settles
to the bottom of the furnace, and may thus be removed. Litharge is then
thrown in to form more alloy, and some glass to act as a flux. The alloy
is cupelled, and the residual platinum is then melted in a lime furnace
with the oxy-hydrogen flame. The platinum thus obtained often contains
iridium and rhodium.
A combination of these two methods is also sometimes employed[3] p. 403.
The electrolytic process of gold-refining was introduced to treat
platiniferous gold. In the gold chloride, or Wohlwill method, iridium
and osmiridium are insoluble, and remain with the anode slime. Platinum
and palladium, if nearly pure, are also insoluble, but when present
alloyed with gold and silver, pass into the solution and remain there.
In a hot bath it is stated that the platinum present should not exceed
50 gm. per litre. According to T. K. Rose, a cold bath containing only
20 gm. per litre causes a certain quantity of platinum to be deposited
with the gold[6].
H. F. Keller, in “Platinum, the Most Precious of Metals” (_Journal of
the Franklin Institute_, November 1912) deals fully with the extraction
and refining of platinum.
PLATINUM-REFINING AGENCIES
The following contains a list of the principal firms engaged in the
refining of platinum metals:
In England: Johnson, Matthey & Co., Ltd., Lees & Sanders, Warstone
Smelting Works, Sheffield Smelting Works, Johnson & Sons. (This is the
list of the Ministry of Munitions.)
In France: Legende et Cie., Compagnie Internationale du Platine, Lyon
Allemand, Lecht Lyonnais, Henrique Marrett, Bonnen, Hesse Fils.
In Germany: W. C. Heraeus, G. Siebert, F. Eisennad & Co.
In the United States: Baker & Co., American Platinum Works (N.T.),
Irvington Smelting and Refining Works, J. Bishop & Co., H. A. Wilson &
Co., Belais & Cohn, Kastenhuber & Lehrfeld, Roessler & Hasslacher
Chemical Co., Wildberg Bros., and others handling scrap.
According to Russian information about 25 per cent. of the Russian
output before the war was refined in Germany. In Russia there are
practically no platinum-refining facilities[7].
THE USES OF PLATINUM AND ITS ALLIES
_Platinum._—In the chemical industry platinum is largely used for
catalyzers in the manufacture of sulphuric, acetic and nitric acids; for
stills for the final concentration of sulphuric acid; and in the
electro-chemical industry.
In the making of “contact” sulphuric acid a “contact mass” is charged
into the chambers of the plant. This is formed by soaking asbestos, or
anhydrous magnesium sulphate, with platinic chloride solution, and
baking the mass to drive off the chlorine. The contact mass usually
contains from 7 to 8 per cent. platinum, in a very finely-divided state.
In the making of acetic acid from a mixture of air and alcohol vapour,
platinized asbestos is used. For the catalyzer used in the conversion of
ammonia into nitric acid a very fine-meshed platinum gauze is used; this
is strengthened at its edges with platinum-iridium wire. One ounce of
platinum is required for the production per annum of 25 tons of
catalytic acid, or of 40 tons of nitric acid from ammonia.
In the finely-divided state all the other metals of the platinum group,
especially palladium, have also the facility of absorbing great
quantities of certain gases, and can be used as catalysts.
Owing to its high melting-point, and to the resistance to the action of
acids at high temperatures, platinum is largely used for chemical ware
in the form of crucibles, dishes, etc. Platinum crucibles are
indispensable in the chemical analysis of rocks.
In the electrical industry platinum is largely used for contact points,
in telegraph and telephone apparatus, in magneto-contacts, and in the
construction of the thermo-couples of pyrometers. In the manufacture of
jewellery, especially in the crown-setting of diamonds, platinum has
been much used in the place of gold: alloyed with a little iridium it
can be worked into delicate designs, which are durable. During the war,
however, when platinum was largely wanted in the making of munitions,
its use in jewellery manufacture was much restricted. Platinum was
formerly largely used in dentistry. In photography potassium
platino-chloride is required for producing platinotype prints. In the
form of barium platino-cyanide it is used in X-ray photography as a
coating for the projecting screen.
Platinum is required in the manufacture of certain parts of
chronometers, theodolites and watches; also for standard weights and
measures, and for various types of self-lighting lamps[4] p. 561.
_Palladium_ has its chief value as a substitute for platinum, in
palladium-gold alloys, which are used extensively in dentistry, for
jewellery and for chemical ware. It is also utilized in the manufacture
of astronomical instruments and watches, also for plating metal ware[1]
p. 1002. The use of palladium as a catalyzer is well known.
_Iridium_, when pure, is of small value, being difficult to manipulate
on account of its brittleness. It is principally used in alloy with
platinum for hardening purposes. Jewellers’ platinum usually contains 10
per cent. iridium, and in the electrical industry an alloy composed of
from 15 to 50 per cent. iridium is usually employed. Alloys with up to
10 per cent. of iridium are ductile and malleable, but with over that
amount are hard and difficult to work.
The metal is used in the manufacture of fountain-pen points, for which
purpose the grains require careful selecting[8] p. 106; also for
standard weights and for contact points. Iridium black, an oxide, is of
value as a pigment for chinaware[1] p. 1001.
Iridium is suitable for sharp surgical instruments, and gold needles
with soldered iridium ends are employed for stitching wounds. It is also
used in photography. Iridium is of greater scarcity than platinum, hence
its greater value.
_Osmium._—There is now little or no market for osmium. It was formerly
in considerable use for the manufacture of incandescent lamps. Osmic
acid is used for staining anatomical preparations in microscopic work.
On account of the poisonous nature of its vapour the extraction of
osmium is costly and dangerous.
_Ruthenium_ is also of little or no commercial value. Both these metals
possess the disadvantages of being brittle and easily oxidized.
_Rhodium_ is of small commercial use. It is used principally in alloy
with platinum. An alloy containing 10 per cent. rhodium is used for some
thermo-couples of pyrometers, and in the making of laboratory utensils.
_Platinum Alloys._—Platinum forms alloys with a number of metals, but
only a few are of industrial importance[3] p. 400. Platinum and iridium
form a hard and elastic alloy, which is unaffected by air, and takes a
high polish. Alloyed with 10 per cent. iridium platinum is used for one
of the wires in thermo-couples of pyrometers; and with 10 to 20 per
cent. iridium for making standard measures of length and weight.
Platinum and copper form various alloys. An alloy with 18·75 per cent.
copper, called “coopers’ gold,” takes a high polish and closely
resembles 18–carat gold.
An alloy of platinum and silver containing 66 per cent. silver is used
as a standard of electrical resistance. An alloy containing 20 to 30 per
cent. silver is used in dentistry.
Platinum alloys with lead, zinc and other metals at low temperatures; it
is usually recovered from these alloys by cupellation.
Platinum alloys with steel in all proportions. With 10 per cent.
platinum, rusting is prevented. A very elastic metal is produced by
alloying platinum with from 5 to 10 per cent. gold.
The melting-point of silver is raised by alloying it with platinum, but
its thermal conductivity is lowered.
The following table gives the composition of the principal platinum and
palladium alloys[4] p. 561:
───────────────────┬──────┬──────┬──────┬──────┬──────┬──────┬─────────────
│ Pt. │ Cu. │ Ag. │ Au. │ Ni. │ Pd. │ Other
│ │ │ │ │ │ │Constituents.
───────────────────┼──────┼──────┼──────┼──────┼──────┼──────┼─────────────
│Parts.│Parts.│Parts.│Parts.│Parts.│Parts.│ Parts.
Jewellery alloys: │ │ │ │ │ │ │
Platinum alloy │ 1│ 0–1│ 2–5│ │ │ │
Platinor │ 2│ 5│ 1│ │ 1│ │Brass 2.
Palladium alloy │ │ │ │ │ │ 9│Rhodium 1.
Mock gold │ 7│ 16│ │ │ │ │Zinc 1.
Mock gold │ 1│ │ 1│ │ 6│ │Brass 1.
Mock gold │ 1│ 4│ │ │ │ │
Coopers’ pen metal:│ 4│ 1│ 3│ │ │ │
Watch alloy │ │ 13│ 11│ 18│ │ 6│
Watch alloy │ │ 25│ 4│ │ 1│ 70│
Watch alloy │ 63│ 18│ │ │ 17│ │Cadmium 1.
Platinum bronze │ 1│ │ │ │ 90│ │Tin 9.
Dentists’ alloy │ 5│ │ │ 3│ │ 4│
Dentists’ alloy │ 7│ │ 3│ 2│ │ │
Dentists’ alloy │ 6│ │ 1│ 2│ │ │
Dentists’ alloy │ │ │ │ 4│ │ 1│
Palladium alloy │ │ │ 2│ │ │ 3│
───────────────────┴──────┴──────┴──────┴──────┴──────┴──────┴─────────────
ALLOY SUBSTITUTES FOR PLATINUM
On account of the scarcity and high price of the platinum metals, much
attention has lately been directed towards the discovery of suitable
substitutes.
In the electrical industry an alloy of 3 parts of palladium and 2 parts
of silver is in use, also an alloy of nickel and chromium. _Platinite_,
an iron-nickel alloy, containing 46 per cent. nickel and 0·15 per cent.
carbon, has the same coefficient of expansion as glass, and, when coated
with copper, is used to replace the platinum connection wires of
incandescent lamps. Tungsten is sometimes used for certain ignition
devices. For cathodes an alloy of 90 per cent. gold and 10 per cent.
copper can be used to replace platinum; the same alloy, if electrically
coated with platinum, and then carefully polished and burnished, is
suitable for platinum anodes.
For platinum chemical laboratory ware, there are several substitutes,
such as fused quartz; various iron, chromium, and nickel-chromium
alloys; _palau_, a gold-iridium alloy marketed in California;
_rhotanum_, a general name for gold-palladium alloys containing from 60
to 90 per cent. of gold, which are suitable for most chemical purposes,
except for use with hot concentrated nitric acid, and for electrolytic
anodes; _amaloy_, which is a complex alloy containing nickel, chromium,
tungsten, etc., highly resistant to corrosion and to cold nitric and
sulphuric acids[9] p. 600.
In the jewellery trade platinum has been replaced by an alloy of 90 per
cent. palladium and 10 per cent. rhodium. For certain surgical work
various _stellite_ alloys, containing cobalt and chromium, and hardened
by the addition of tungsten and molybdenum, are valuable substitutes for
platinum, and are not affected by antiseptic solutions. In dental work
pins are now made of tungsten coated with palladium[10] p. 549. For most
technical purposes an alloy of tungsten and nickel with gold or silver
is used in Germany; it may be cast, rolled or forged, is acid-resisting,
and capable of taking a high polish[11]. _White gold_, another
substitute for platinum, contains fine gold, from 75 to 85 per cent.;
pure nickel, from 10 to 18 per cent.; and zinc, from 2 to 9 per cent.
_Illium_, a chromium-nickel-copper alloy reported recently as the
discovery of S. W. Parr, of Illinois, is a substitute for gold or
platinum, costing only 25 cents per ounce. It is stated to have been a
“50 per cent. standard of success.” The alloy withstands hot or cold,
strong or diluted acid, can be both cast and machined, and is already
used largely in the manufacture of calorimeter bombs[12].
The results of researches made to discover substitutes for platinum, and
undertaken by the National Dental Association of America, are described
at length by F. A. Fahrenwald, in a paper read in January 1916 before
the American Institute of Mining Engineers.
SCRAP PLATINUM
A considerable amount of platinum in the form of old and worn articles
is now collected for return to the refineries, where it is re-treated,
and sold again as new metal. The trade in scrap platinum has been
particularly active in the United States, official statistics showing
that in 1916, 49,400 oz. of refined platinum were recovered.
WORLD’S OUTPUT OF PLATINUM
According to J. L. Howe, the estimated limits of the total
world-production of crude platinum, up to January 1917, were as
follows[13]:
_In oz._ (_troy_)
Minimum. Maximum.
Russia 7,115,482 10,128,308
Colombia 700,000 735,000
Borneo 175,000 200,000
United States 10,000 12,000
Canada 9,000 10,000
Miscellaneous 9,000 10,000
————————— ——————————
Total 8,018,482 11,095,308
========= ==========
On the other hand, James M. Hill[14] states that possibly 5,000,000 oz.
was the total world’s production to June 1917, which he distributes
according to the uses made of it as follows:
Oz.
Chemical and physical apparatus 1,000,000
Electrical devices 250,000
Catalyzing 500,000
Dental uses 1,000,000
Jewellery 1,000,000
Minor uses and hoarded (balance) 1,250,000
It is difficult to obtain exact figures of the annual production of
crude platinum. This is particularly so in the case of Russia, where
there appears to have been a tendency for private enterprises to keep
their published outputs as low as possible, in order to avoid
registration. The discrepancy between the official and actual figures of
production in Russia is variously estimated at from 20 to 60 per cent.
The table on the next page is compiled from the sources considered most
reliable.
_World’s Production of Crude Platinum_
(In troy oz.)
─────────────────────┬───────┬───────┬───────┬───────┬───────
│ 1910. │ 1911. │ 1912. │ 1913. │ 1914.
─────────────────────┼───────┼───────┼───────┼───────┼───────
Borneo and Sumatra[C]│ │ │ 200│ 200│ [D]
Burma[E] │ │ 38│ 57│ 58│ 37
Canada[F] │ │ │ │ │ 18
Colombia[G] │ 10,000│ 12,000│ 12,000│ 15,000│ 17,500
Madagascar[H] │ 13│ 3│ │ │
New South Wales[I] │ 332│ 470│ 610│ 442│ 244
Russia[J] │176,334│187,008│177,596│157,735│157,182
United States[C] │ 390│ 628│ 721│ 483│ 570
Victoria[L] │ │ 184│ │ 127│
─────────────────────┴───────┴───────┴───────┴───────┴───────
─────────────────────┬───────┬───────┬─────────┬──────
│ 1915. │ 1916. │ 1917. │1918.
─────────────────────┼───────┼───────┼─────────┼──────
Borneo and Sumatra[C]│ [D]│ [D]│ [D]│
Burma[E] │ 18│ 9│ 4│
Canada[F] │ 23│ 15│ 57│ 39
Colombia[G] │ 18,000│ 25,000│ 32,000│27,030
Madagascar[H] │ │ │ │
New South Wales[I] │ 56│ 82│ 259│
Russia[J] │119,789│ 78,682│50,000[K]│
United States[C] │ 742│ 750│ 605│
Victoria[L] │ │ │ │
─────────────────────┴───────┴───────┴─────────┴──────
_Canada._—The recoveries of platinum at the works of the
International Nickel Company in New Jersey for the years 1910–1912
were 258,666 and 497 oz. respectively, chiefly from Canadian matte.
_Russia._—The _actual_ productions of platinum as quoted in _Mineral
Industry_ in oz. were: 1910, 300,000; 1911, 280,000; 1912, 300,000;
1913, 275,000; 1914, 240,000; 1915, 124,000; 1916, 90,000; 1917,
50,000.
Footnote C:
_U.S.A. Mineral Resources, 1917, Geol. Surv._
Footnote D:
Estimates not available.
Footnote E:
_Records of Geol. Survey, India._
Footnote F:
_Mineral Production_, Mines Dept., Canada. Figures are for alluvial
production only, and far below _actual_ production figures, not
including Ontario production from nickel matte, for which only
incomplete information is available. [See p. 25.]
Footnote G:
_Mining Journal_, November 30, 1918, p. 700, and _Mineral Industry_.
Footnote H:
_Mines and Quarries Reports_, Home Office.
Footnote I:
_Annual Rept. Dept. of Mines._
Footnote J:
_Mineral Industry._ These are _official_ figures for production;
_actual_ production is much greater than these.
Footnote K:
Estimated.
Footnote L:
_Dept. of Mines Reports_ (platinum obtained from copper matte).
The market value of platinum has risen considerably since 1880. In that
year the price was 12_s._ 7½_d._ per oz. troy, in 1890 it was 25_s._
3_d._, and in 1900, 63_s._ 1½_d._ The average prices in London and New
York for the years 1910–1919 were as shown on the accompanying tables:
Average price in pounds per troy oz. of refined metals of the platinum
group in London
─────────┬─────┬─────┬─────┬─────┬─────┬─────┬───────┬─────┬─────┬─────
│1910.│1911.│1912.│1913.│1914.│1915.│ 1916. │1917.│1918.│1919.
─────────┼─────┼─────┼─────┼─────┼─────┼─────┼───────┼─────┼─────┼─────
Platinum │ 9·1│ 8·6│ 9·5│ 9·5│ 8·1│ 10·9│10–14·5│ 14·5│ 20│ 24
Metals │ │ │ │ │ │ │ │ │ │
─────────┴─────┴─────┴─────┴─────┴─────┴─────┴───────┴─────┴─────┴─────
1910, 1915, 1916 and 1917—_Metal Market Year Book_. 1911, 1912, 1913
and 1914—_Mining Magazine_.
Average price in dollars per troy oz. of refined metals of the platinum
group in New York
──────────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬──────┬─────
│1910.│1911.│1912.│1913.│1914.│1915.│1916.│1917.│1918. │1919.
──────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼──────┼─────
Platinum │ 33│ 43│ 46│ 45│ 45│ 50│ 84│ 103│106[M]│ 114
Iridium │ │ │ │ │ 65│ 83│ 94│ 150│ │
Iridosmine│ │ │ │ │ 33│ 35│ 45│ 80│ │
Palladium │ │ │ │ │ 44│ 56│ 67│ 110│ │
──────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴──────┴─────
1910, 1914, 1915, 1916 and 1917—_U.S. Geol. Surv. Mineral
Resources_.
1911, 1912, 1913, 1918 and 1919—_Eng. and Min. Journ._, vol. 107,
No. 2, p. 77.
Footnote M:
The price was fixed on May 14, 1918, at $105.