Availability of the Platinum Metals.pdf

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Availability of thePlatinum M etalsA SURVEY OF PRODUCTIVE RESOURCESIN RELATION TO INDUSTRIAL USESBy L. B. Hunt, M.SC., Ph.D., and F.J ohnsonMatthey & Co L imited

Increasing industrial uses o platinumand its associated metals - palladium,rhodium, ruthenium, iridium andosmium - have occasionally given riseto doubts as to the future availabilityof adequate supplies. This has some-times discouraged research workers fromconsidering the advantages o thesemetals in their search for new routes orfor new products i n the chemical andallied industries. This paper, pre-sented at the Symposium on thePlatinum Group Metals organised bythe American Chemical Society duringits meeting in New York in September,outlines the very substantial productiveresources now associated with thesemetals and relates them to the trendsin their applications in industry.

Every chemist is familiar with the sixmetals of the platinum group, and most willbe well aware of the chemistry of theircomplex salts upon which their separationand refining-as well as their methods ofanalysis-are based. Not so much is knownabout the extraction of these metals from theirores or about the scale upon which theseoperations are conducted to provide thechemical and other industries with theirneeds, and in consequence misconceptionshave sometimes arisen as to their availabilityfor new products or processes.

It is the intention in this paper to outlinethe chemistry of the extractive methodsemployed, to submit data on the present and

M . L ever, A.R.c.s.: Ph.D.

future supply position, and to put intoperspective some of the trends in the ap-plications of the platinum metals in theirmajor areas of growth.

Before we turn to this discussion, however,there are a few essential factors that must bemade clear:(I ) Unlike gold, platinum is not used for

monetary or speculative purposes, andonly to a limited extent for decorativeuses. We are dealing with an industrialmetal, vital to a number of chemical ormetallurgical processes which, takentogether, account for between 80 and90 per cent of the total demand.

( 2) Platinum and its allied metals are usedin industry only where their inherentproperties are essential to a successfuloperation or process. Many establisheduses of fifty or a hundred years agohave disappeared with the advent ofnew and cheaper materials, while manynewer applications have become es-tablished.

(3) By comparison with the base metals, avery high proportion of the platinummetals usedinindustry s refined and re-used repeatedly, often without changeof ownership. Figures for productiontherefore relate only to newly-minedmetals to meet increasing demandsfrom technologically advanced indus-tries. A considered estimate of thetotal amount of platinum in circulationin the world to-day would be between25 and 30 million troy ounces.

(4) There has been a great deal of dis-cussion about a shortage of platinum

PlatinumMetals Rev., 1969, 13, (4), 126-138 126


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The shallower portions ofthe Rustenburg plati nummines are worked fr ominrlined haulages such USthis, sited ubout 2,500feetapart, while the deeperareas have been opened upby means of j ke verliraEshafts runging in depthfrom 50 0 to 2,500 feet.A further shaft is nowbeing sunk to exploit theore body to a depth of3,000 feet. All togethersome eighteen mles of out-crop are being mined.Rustenburg i s the lurgestunderground mining opera-tion in South Africa. em-ploying over20,000 workers,and i s the largebt producerof platinum metals in theworld. Total reservesinthispart of South Afrira havebeen estimnted to be i n ex-cess of 200,000,000 ounresof plutinum

for industrial uses during the lastfew years. In fact there has been noabsolute shortage, and although demandhas increased very substantially, almostall industrial needs have been metby the main primary sources, SouthAfrica, Canada and Russia. Theimpression of shortage has stemmedfrom the wide disparity in the sellingprices for South African and Canadianplatinum, on the one hand, and that forthe metal coming from Russia andcertain other minor producers. Theshortage is thus one of relatively low-cost platinum only. The widely heldbelief that Russia has withdrawn as amajor supplier to the West is untrue.In fact the amounts exported year byyear have remained fairly constant,although constituting a diminishingproportion of a larger usage.(5) Increased supplies of new metal can

be made available, the only conditionbeing that responsible forecasts ofusage are provided upon which to basefurther programmes of expansion inmining and smelting facilities. At anyconceivable rate of production the orereserves available will ensure continuityof operations at the South Africanmines well into the next century.

Sources of the PlatinumMetalsPrior to World War I the greater part of

the then modest needs for the platinum metalswas met from alluvial or placer deposits inRussia and the Republic of Colombia, butthis type of primary material now representsonly a very minor part of world production,the two remaining sources today beingGoodnews Bay in Alaska and the CompaniaMinera Choco Pacific0 in Colombia.

The discovery of extensive deposits ofplatinum-bearing copper-nickel ores in

PlatinumMetals Rev., 1969, 13, (4) 127


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The ore i s j r s t crushed ina series o j aw crushers and is then ed to t h e primary and secondaryball millsCanada and South Africa some forty orfifty years ago has given rise to a majorindustry which now provides by far thegreater part of the Western worlds needs,while broadly similar deposits in the Uralsand elsewhere in Russia have been workedmore recently. I n all these three majorproducing countries the platinum content ofthe mineral runs only to a fraction of anounce per ton, and many millions of tons ofore have therefore to be mined, milled andsmelted each year. The processes of ex-traction involve basically the smelting and thenthe electro-refining of copper and nickel,followed by the recovery, separation andrefining of the platinum metals themselves.

South Africa differs, however, from Canadaand the USSR in one important respect.The Rustenburg mines in South Africa areworked primarily for the platinum metals,yielding copper and nickel as by-products,whereas the International Nickel and Fal-conbridge mines in Canada, and also theRussian deposits, are essentially sources ofcopper and nickel with the platinum metalsas by-products. This difference is of majorimportance in enabling the South African

mines to respond more quickly and effectivelyto increasing demand, and output from thissource has been increased more than fourfoldover the past five years, with further ex-pansion already in hand. Rustenburg is infact the worlds largest source of platinum,and the only major mine whose main activityis the production of the platinum metals.

For this reason, although methods ofextraction in other countries are broadlysimilar, it is the techniques adopted byRustenburg and by their refiners JohnsonMatthey that will be mainly described here.Extraction and Refining

The deposit worked by Rustenburg Plat-inum Mines forms part of the MercnskyReef of the Bushveld Igneous Complex.This reef, named after the geologist HansMerensky who was responsible for the pros-pecting programme that led to its discoveryin the 1920s, has been traced on outcrop adistance of some 75 to 80 miles along boththe eastern and western limbsof the Complex.The eighteen miles of outcrop which aremined at the two operations, the Rustenburgsection a few miles to the East of the town,

Platinum Metals Rev., 1969, 13, ( 4) 128


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and the Union section about sixty miles tothe North, are considered to contain thehighest grades of the entire Complex.

Platinum values at these two sections showa very even tenor, the platinum being partlyin the form of native metal, invariablyalloyed with iron as ferro-platinum, andpartly as the sulphide, arsenide and sulph-arsenides, these always occurring in intimateassociation with the sulphides of iron, copperand nickel. Associated with platinum, thepredominant metal, are smaller proportionsof palladium, ruthenium, rhodium, iridiumand osmium, in this descending order ofconcentration.

The platinum-bearing reef averages onlysome twenty inches in thickness, but itsregularity makes for relatively straight-forward mining. I t persists to depths beyondthe limits of practical mining, and the reservesdown to a depth of 3,000 feet are immense.

The length of strike and the comparativeshallowness of the deposit have made possiblethe rapid development of large areas of

ground whenever a greater demand forplatinum has arisen-one reason whyRustenburg has been able to follow worlddemandsoclosely. In the shallower portionsof the deposit inclined haulages are sitedabout 2,500 feet apart, while the deeperareas have been opened up by means of fivevertical shafts ranging in depth from 500 to2,500 feet. A further shaft is currently beingsunk to exploit the ore body to a depth of3,000 feet.

The ore is first crushed in a series of jawcrushers and fed to the ball mills which arein closed circuit withhydrocyclone classifiers.This stage is followed by gravity concen-tration on corduroy tables to separate thecoarse particles of platinum-bearing mineralsand the free metallic particles. The corduroyconcentrate is dressed on an elaborate systemof shaking tables up to a final high gradeconcentrate which is sent directly to theJohnson Matthey refineries in England.

The tailings from the tables are returnedto the mill circuit, the final pulp from here

F lotation concentrates are smelted to a copper-nickel-iron matte. Thi s is cast into moulds,broken up and sent to the rrjineries for extruction of copper, nickel and the sixplatinum metals



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In the electrolytic nickel re$neries pure nickel cathodes are produced whil e the plati nummetals riccumulate i n the anode residues and are removed for separation and refiningbeing treated in a series of thickeners beforegoing to the flotation plant, which recoversmost of the remaining platinum-bearingminerals. The flotation concentrates, con-sisting mainly of nickel, copper and ironsulphides with the balance of the platinummetals, are thickened, filtered, dried andpelletised, ready for the smelter.

The initial stage in the recovery of theplatinum metals is to smelt to a copper-nickel-iron matte in a series of blast furnaces.This matte is then tapped periodically intoladles, transferred to a group of convertcrs,and blown to a high-grade matte which iscast into moulds and then brokcn up in ajaw crusher. Part of this converter matteis shipped to the Johnson Matthey smelterin England, the balance being treated byMatte Smelters, a joint subsidiaryof JohnsonMatthey and Rustenburg, in a plant adjacentto the mine.

Rustenburg converter matte contains about46 per cent of nickel, 28 per cent of copper,together with small amounts of other base

metals and sulphur. The contentof platinumgroup metals is about 50 ounces troy perton (0.15 per cent). The treatment of thismaterial may be divided into two steps, firstthe removal of nickel and copper to producea rich platinum group metal concentrate,followed by chemical treatment of thisconcentrate to separate and purify theindividual metals.

Two processes are in operation to achievethe first aim. The older process, the Orfordor top-and-bottom process, involves thesmelting of the copper-nickel matte withsodium sulphide. This results in the for-mation at high temperature of two immiscibleliquids, a heavier nickel sulphide phasecontaining the platinum group metals and alighter sodium copper sulphide phase con-taining gold, silver and only minor amountsof platinum group metals. These two liquidphases are separated and allowed to solidify.The sodium coppcr sulphide is blown withair in a Bessemer converter to produceblister copper which i s further refined and



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then cast into anodes. These are electro-lytically refined to produce marketable copper,leaving an adherent anodic residue containingthe noble metals present in the copper tops.The nickel sulphide bottoms are ground,roasted, and the resultant nickel oxidereduced to metal which is cast into anodes.These are also refined electrolytically toproduce pure nickel and an anodic residuecontaining the platinum metals. Theresidues from the copper circuit and thenickel circuit are together roasted andleached with sulphuric acid to produce aconcentrate, containing about 65 per cent ofplatinum group metals.

The second process being operated toproduce a platinum group metal concentratefrom the matte involves the leaching withsulphuric acid under pressure of the finelyground matte. This results in the removal ofcopper and nickel as sulphates followed bytheir recovery by normal electro-refiningtechniques. The residue, containing theplatinum metals, is treated to remove ironoxide and to produce a concentrate suitablefor chemical refining.

Final concentration and separation of theplatinum metals is carried out in the JohnsonMatthey refinery in England, but an ad-ditional refinery is now under construction inSouth Africa to supplement supplies bytreating some part of the output of MatteSmelters.

It is only possible to outline briefly thechemical treatment of these concentrates,and this account gives only a simplifiedpicture. The concentrate is first attackedwith aqua regia to dissolve gold, platinumand palladium, the residue comprising themore insoluble metals iridium, rhodium,osmium and ruthenium. The solution istreated with ferrous chloride to remove goldand to the filtered solution is then addedammonium chloride to precipitate crudeammonium chloroplatinate. This is calcinedand the impure sponge re-dissolved. Am-monium chloride is added to precipitate thepure platinum compound, which is calcined

to pure metal. The filtrate from the crudeammonium chloroplatinate is oxidised toprecipitate ammonium chloropalladate. Thisis dissolved and decomposed by boiling withwater to produce a solution of ammoniumchloropalladite. Ammonia is added to convertthe palladium to tetramminepalladouschloride. On acidifying the solution withhydrochloric acid there is precipitated diam-minedichloropalladium which is calcined toyield pure palladium sponge.

The original insoluble residue is fused withoxidising alkaline fluxes and the cooled meltleached with water. Osmium and rutheniumare removed and separated by distillation oftheir volatile tetroxides, being subsequentlyconverted to metal by thermal decompositionof a suitable compound. The iridium andrhodium remaining in the solution afterdistillation are recovered as sodium chloro-complexes which are converted to ammoniumcompounds for calcination to metal.

All these calcinations are carried out undercarefully controlled conditions in electricallyheated muffle furnaces, to produce the metalsas sponges or powders suitable for melting.

World ProductionDeaIing first with South Africa, Rustenburg,whose output has been increased from some200,000 ouncesof platinum in1963to850,000ounces a year at present, has a further ex-pansion programme in hand to yield I , OOO, OOOounces a year by 1971, and has just announcedplans to increase production to 1,200, 000ounces by 1973.

Corresponding increases have, of course,taken place in the output of the other membersof the platinum groupof metals- alladium,rhodium, ruthenium, iridium and osmium.This has been achieved by very substantialcapital expenditures on the sinking of newshafts, the installation of additional grinding,milling and flotation equipment, and thebuilding of an additional modern smeltingplant, together, of course, with a consequentexpansion in all the facilities and services.The expenditure involved in the expansion



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The initial stage in the J ohnson Matthey met process re$nery involves digestion o theenriched concentrates with aqua regia to dissolve the platinum and palladium, leaving theiridium, rhodium, ruthenium and osmium as insoluble residues to be treated separatelyprogramme over the seven years 1967 to1973 will probably exceed $130 million.Today Rustenburg constitutes the largestunderground mining operation in the Re-public of South Africa, its two mines to-gether extending more than cighteen milesfrom one end to the other, and providingabout 60 per cent of the Western worldsneeds of platinum.

By the end of the present year there willbe a new South African producer, ImpalaPlatinum, from which can be expected anoutput of about 50,000 ounces in 1970, isingperhaps to 150,000 ounces in two years time,

The output from Canada is likely to beupwards of 200,000 ounces a year, and nosignificant change is expected from theexisting smaller producers.

There is unfortunately no real basis forestimating production from the USSR, butthis is undoubtedly geared to her growingoutputs of nickel and copper. All that can besaid is that after taking care of her internaland expanding needs of platinum, some-thing like300,000 ounces of metal ayear havebeen exported.

Thus a total annual output from theWestern world of over 1, 500, 000ounces willbe available in the early seventies, and it isreasonable to assume that this will be sup-plemented by whatever the USSR maycontribute to Western supplies.Palladium naturally follows the same trendin expanding output as platinum itself, buthere the relationship between individualproducers is somewhat different. TheCanadian ores contain more palladium thanplatinum, while in South Africa the reverseis the case. Western World production fromthese two sources together with the minorproducers is now running at around 550,oooounces a year, with the USSR over-topping this figure considerably. Lookingahead some five years or so, Rustenburg,within the framework of its present expansionplans, could produce around 500,ooo ouncesa year. To that could be added rather lessthan IOO,OOO ounces from Impala, dependingupon this producers aspirations in platinum.Canadian output should continue to providebetween 250,000 and 300,000 ounces a year,and other sources will make a modest contri-



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This section of the J ohnson Matthey re$nery - he largest of i ts kind in the world -handlestheprecipitation, re-dissolvingand re-precipitation of platinum and palladiumbution. Thus a total Western output ofsomething like 850,000 ounces a year can beexpected, whileit is likely that the substantialdeliveries of palladium made by Russia inrecent years will continue.

The remaining four platinum metals aresimilarly closely governed in terms of outputby platinum production. Currently ruthen-ium output is running at 90,000 to IOO,OOOounces a year, rhodium at around 80,000Jiridium at 25,000 ounces and osmium at13,000 ounces. Some scaling up of all theseproduction figures will of course follow fromthe expansion of platinum production.Trends in DemandPresent indications are that over the next twoyears production and demand for platinumwill be fairly well in balance. In the succeed-i ng few years the prospect is naturally not soclear, but a simple projection of presenttechnologL suggests that Western Worlddemand for new metal will lie between about1,200,000and 1, 700, 000ounces a year.

There are of course a number of imponder-ables in trying to arrive at such estimates as

this, arising mainly from the ebb and flowof competitive technological developments.During the last five years the consumptionofnewly-mined platinum has been approxi-mately 30 per cent in the chemical industry,about 25 per cent in petroleum reforming,20 per cent in electrical and allied uses, and10per cent in the glass industry, with some15per cent covering dental, medical, jewelleryand miscellaneous applications.

Thus the use of platinum is not associatedwith one or two industries, and many of itsapplications are in areas of industrial growth.What trends are discernible in these variousfields of interest ?Nitric Acid ProductionOne of the largest demands for platinumcomes from the nitric acid industry, where itis used-mainly alloyed with 10per cent ofrhodium-in the form of gauzes for theoxidationof ammonia. The Western Worldsoutput of nitric acid now exceeds 20 milliontons per annum, and it is estimated that thisoutput represents a platinum gauze inventoryof around 200,000 ounces, excluding the



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weight of gauzes that most plants carry asspares. Nitric acid manufacture representsthe largest direct platinum metal consumingprocess, in that a small but significant pro-portion of the gauzes installed is irrecover-ably lost in the high temperature oxidisingconditions encountered in the plant. Thismetal loss represents only 3 to 4 per cent ofthe total costs of manufacturing nitric acid,and the recently developed platinum recoveryprocess using gold-palladium gauze immedi-ately below the platinum gauzes should serveto reduce appreciably even this small pro-portion of the costs contributed by the use ofplatinum.

The major outlet for nitric acid is in themanufacture of nitrate fertilisers for whichthe demand is growing steadily throughoutthe world-particularly in the under-developed countries. The ammonia oxidationroute to nitric acid is now very well estab-lished and is unlikely to be superseded byalternative processes in the foreseeable nearfuture. Alternative cataIysts, using transitionmetal oxides such as cobalt oxide, have beenstudied for a number of years as possiblealternatives to platinum, but their relativelyshort operating lives makes it unlikely that

The new generation of platinum cat-alysts containing an addition of rhen-ium have given improved performancein petroleum rejorming, but thecontinual increase in severi ty ooperation is expected to require anincreasing level of platinum supply tothe petroleum industry

they will find acceptance in theindustry for the time being.

In the very long term, it ispossible that the nitric acid routeto nitrogen fixation may be re-placed by direct fixation processesusing homogeneous catalysts.The platinum metals, particu-larly ruthenium, have been inten-sively studied to provide suitable

catalysts for such a process, but at the presenttime no viable route is in sight.Atmospheric Pollution

The excellent catalytic properties ofplatinum-particularly as an oxidationcatalyst-make it likely that it will be used ina number of systems designed to oxidiseundesirable or harmful organic odours orother atmospheric pollutants. The pollutioncontrol industry is a comparatively new one,and is growing very rapidly as increasingpublic attention is focused on the problem inalmost every country, while legislative pres-sures mount to force offenders to adoptsuitable control systems. Already platinumcatalysts are used to oxidise a number ofunpleasant pollutants in several industries,for example in wire enamelling, in abattoirsand in meat or fish processing. Platinumcatalysts are also increasingly adopted by thenitric acid industry to reduce the harmful andcorrosive nitrogen oxides that are emittedwith the tail gases from most plants.

The problems resulting from the emissionof unburnt hydrocarbons, carbon monoxideand nitrogen oxides in the exhaust gases frominternal combustion engines have received a



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World production of chlorine by the electrolysis of brine i s about 25 million tons a year.Some large estimates of plati num consumption as platini sed-titanium anodes in thisindustry are now unlikely to be realised since the development of a ruthenium oxide coatingon titanium

great deal of attention. Several platinum-containing catalyst systems have already beendeveloped and await commercial exploitation.Legislation under consideration in severalcountries-notably in the USA-coulddramatically affect the future of platinumconsumption in this field in one of two ways:either the conventional petrol engines willhave to be universally fitted with catalytic orother exhaust gas purification systems, or theuse of lead additives may be increasinglycontrolled, resulting in a correspondingincrease in the need for platinum in petroleumreforming operations. Either way, it seemslikely that public pressures for the need tocontrol atmospheric pollution in the urbancentres of the worlds industrial countrieswill result in a demand for platinum usingsystems, although, of course, modificationsto engine design may also help to overcomepart of the problem.Petroleum Reforming

The recent introduction of rhenium intoreforming catalysts has a synergistic effect onthe performance of the platinum, and some

catalyst manufacturers have been able tomake use of this to give improved perform-ance while maintaining the same platinumpercentages in their products. In other casesa lowering of platinum levelshas been madepossible, at least for the time being. It is stillclear that the more platinum contained in areforming catalyst, the better is its perform-ance. The continual increase in operatingseverities coupled with the rising demandforhigh octanes and for aromatics will almostcertainly require an increasing level of supplyof platinum to the petroleum industry, butthis increase will probably be spread over anumber of years.Fuel CellsFuel cells have for a long time been underintensive development for a number of appli-cations. Among the favourite potentialapplications has been the electrically poweredmotor-cary using the fuel cell as an alternativeto the internal combustion engine. Earlywork in the deveIopment of fuel cell systemsindicated that the platinum metals weresupreme in their combination of catalyticand



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corrosion resistant properties. More recentwork, however, based on the erroneousassumption that insufficient platinum wouldbe available for their future needs, has ledresearchers to develop some potential alter-natives to platinum in certain applications.Althoughitnow seems unlikely that platinumelectrocatalysts will find applications in fuelcells for major mass market applications, it isvery probable that specialised fuel cells forselected applications will use them. Consider-able effort is being devoted towards providingplatinum electrocatalysts that make muchmore effective use of the platinum componentthan has been possible hitherto, and indi-cations are that this work will be successful.ChlorineProductionThe use of platinised-titanium anodes inthe production of chlorine and chlorates bythe electrolysis of brine has received consider-able attention in recent years, and some verylarge estimates of platinum and iridium-platinum consumption have been made. Atpresent, however, it appears likely that whileiridium-platinum deposited on titanium

anodes will be used for chlorate production,ruthenium oxide on titanium will be pre-ferred in the very much larger chlorine manu-facturing industry.Organic Electrosynthesis

The field of organic electrosynthesis isreceiving very considerable attention fromresearch workers in the universities and inindustry. Here also selective electrocatalystsare required, and it is possible that somesystems may be developed using platinummetals on suitable supports.Heterogeneous Catalysis

Other than in petroleum reforming opera-tions, platinum is not at present widely usedin industrial heterogeneous catalytic systems.Palladium is much more widely employed,particularly in liquid phase hydrogenationreactions. Hydrogenation of a wide rangeofcompounds has grown very markedly inrecent years in the general chemical, dye-stuffsand pharmaceutical industries, and thefuture application of platinum group metalcatalysts, particularly palladium, supported

The steadily increasing production of aiscose rayon calls for large quantities o platinumin the form o spinnerets in platinum-gold or rhodium-platinum alloys for the continuousextrusion of many thousands of threads



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The manufacture of glass jibre involves the rapid f l ow of glass at around 1, 400"C through a series oforijices which must retain their size and alignment. The electrically heated bushings are universallymade in rhodium-platinum alloyson a range of suitable carriers is likely toincrease significantly.Homogeneous Catalysis

Organo-metallic chemistry is the mostrapidly expanding of all branchesof chemistryand although the use of compounds andorganic complexes of the platinum metals ashomogeneous catalysts is only in its industrialinfancy at present, this isa field of applicationlikely to grow dramatically in the nextdecade. Rhodium in particular has beenfound, in its numerous complexed forms, tobe a most effective homogeneous catalyst inhydrogenation, hydroformylation, carbonyla-tion and other reactions, while rutheniumcomplexes are also showing indications ofgreat potential usefulness.Viscose Rayon

Substantial amountsof platinum are in usein the viscose rayon industry in the form ofspinnerets made from platinum-gold orrhodium-platinum alloys, but recovery andre-use are virtually complete and thisindustry does not therefore createa significantdemand for new metal.

Electrical UsesFor the electrical industry no major change

in the usage of platinum (or rhodium withwhich it is so often alloyed) is foreseen.Light duty contacts, electric furnace wind-ings, thermocouples, cobalt-platinum alloypermanent magnets, resistance thermometersand precision potentiometers represent themajor applications in this field, while metal-lising preparations based upon platinum,palladium and ruthenium are growing indemand for capacitors, resistors and otherthick film electronic components.

Some 60 per cent of the total usage ofpalladium is in the electrical industry mainlyfor telephone contacts in the cross-barswitching system adopted in the USA andJapan. This system will eventually be super-seded by the electronic exchange, but it is notexpected that the demand for palladium willfall for a further year or two.

In light duty contact applications, particu-larly for sliding surfaces such as slip-rings,electrodeposited rhodium has for many yearsbeen established and is growing in usefulness.



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Improved methods of electrodepositing bothpalladium and ruthenium have more recentlyshown the advantages of these two metals, theformer in replacing gold in electronic applica-tions and the latter as a less expensive alterna-tive to rhodium.GlassManufacture

The protection of refractories from attackby molten glass-and thus the avoidance ofcontamination-is a major problem in theglass manufacturing industry, and a large andgrowing demand for platinum arises here.Stirrers, tank blocks and other equipmentcontrolling the flow of molten glass are thusclad with platinum sheet of about 0. 25 mmin thickness, and it has been well establishedthat this practice has always resulted in theproduction of a particular type of glass at amore economic price either by the productionof a purer glass or of one with greater freedomfrom defects.

The manufacture of glass fibre-an indus-try that has grown rapidly and that is nowexpanding considerably nless well-developedcountries-involves the rapid flow of glass ataround 140o0Cthrough a series of orificeswhich must retain their size and alignment.Platinum, or more generally 10 per centrhodium-platinum, is universally employedfor t he construction of the trough-shapedbushings used in this process. The cost of theplatinum employed, including the interest onthe investment and the refining and re-manufacturing of the bushings, representsonly about 3 per cent of the selling price ofthe glass fibre.TheFuture

To sum up these trends in the demand forplatinurn and its allied metals is not a simplematter, but irrespective of the several uncer-tainties in the situation or of short-termfluctuations in consumption, the overall pic-ture remains one of growth based uponincreasing industrialisation and upon thenormal growth of the established applications.

Rustenburg has demonstrated clearly overthe years its determination to meet this grow-

ing demand. Its most recent announcementof yet another programme of increasing pro-ductive capacity to yield 1, 200,000ounces ofplatinum a year by 1973--with, of course,corresponding increases in the output of theother platinum group metals-gives any re-assurance that might still be needed on theirlong-term policy. Simply and briefly ex-pressed, this is to take all steps that might benecessary, jointly with Johnson Matthey assmelters and refiners, to ensure to industrythroughout the world adequate and con-tinuing supplies of the platinum metals.

In making this latest decision to expandstill further, the possibility has been facedthat it could conceivably give rise to someexcess of capacity and a situation of over-supply. On the other hand, should it befound that the projected output is not likelyto be adequate for the indicated demand,there will be no hesitation on the part ofRustenburg in increasing still further themines productive capacity, or on JohnsonMattheys part in extending once again theirsmelting and refining facilities.

The question then arises of how long pro-duction at this or any higher rate can becontinued. I t is difficult to assess with anyhigh degree of accuracy the amount ofplatinum contained in the South Africandeposits and so to give an indication of thepotential reserves of metal, but prospectingoperations which have been carried out byRustenburg for many years on the MerenskyReef have enabled it to build up a compre-hensive knowledgeof the potentialities of boththe very substantial areas over which it hasmining rights and of the remaining areas. Toarrive at a realistic estimate of the totalreserves, account must be taken of the gradeof ore available and the feasibility of miningoperations at increasing depths. Within thisframework, and assuming reasonable pricelevels for an arbitrarily selected period of thenext 30 years, it is estimated that the overallreserves of platinum that could be economi-cally exploited during this period amount tonot less than 200 million ounces.


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