Platinum Metals Review

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their applications in industry

VOL. 12 APRIL 1968 NO. 2

Contents

Lcad-Platinum Bielectrodes for Cathodic Protection 42 A Standard High Purity Platinum 45 Monolithic Ceramic Capacitors 46 Chemistry of Co-ordination Complexes 47 Platinum for Fuel Cells 48

Tcrtiary Phosphine Complexes of the Platinum Metals 50

Palladium Addition Protects Titanium in Hot Concentrated Chloride Solutions 53 Potentiometer Slidewire Materials 54 Frictional Characteristics of the Refractory Platinum Metals 61

Vapour Phase Deposition of Iridium 62

Palladium and Rhodium: Russian Reviews 63

Platinum Sales Problems in the French Revolution 64 Wollaston’s Classic Lecture on Platinum 66

Abstracts 67 New Patents 75

Communications should be addressed to The Editor, Platinum Metals Review Johnson, Matthey & Co., Limited, Hatton Garden, London, E.C.1 Lead-Platinum Bielectrodes for Cathodic Protection

ADVANTAGES IN MARINE APPLICATIONS

By L. L. Shreir, Ph.D. Department of Metallurgy, Sir John Case College, London

The insertion of small pieces of platinum into the surface of lead or lead alloy anodes causes a remarkable change in their behaviour as electrodes. Such lead-platinum bielectrodes are inexpensive, robust and easily fabricated and can be used successfully for the cathodic protection of marine structures. In this article the author describes the principles involved and reviews ten years of experience in a variety of applications.

It has been established for some years that solutions, as in sea-water, facilities the for- lead and lead alloys can be used as inert mation of PbO,, and anodes of I to 2 per anodes in electrolytic processes provided cent silver-lead and I per cent silver - 6 per that a film of lead peroxide is formed and is cent antimony-lead are used for the cathodic maintained on the surface. protection of marine structures. Lead peroxide, which is a thermodynami- It has been shown however (I), that the cally stable form of lead at elevated electrode insertion of a platinum microelectrode into potentials, can be formed by the oxidation of lead has a remarkable effect on the anodic Pb2+aq in solution at an inert electrode, behaviour of the latter, and that lead- such as platinum, or by the oxidation of lead platinum bielcctrodes can be anodically itself. The oxide is chemically stable and is polarised in chloride solutions at high current characterised by a high electronic conduct- densities (2). Chlorine evolution on platinum ivity (about 50 per cent that of lead) so that takes place at low overpotentials (3), so that lead with a film of PbO, will act as an inert this reaction occurs in preference to oxygen anode, provided the oxide remains in elec- evolution, although the latter is the thermo- trical contact with the metal and is reformed dynamically preferred process; platinum in should a discontinuity be produced in the contact with lead will therefore tend to act film. Thus anodic polarisation of lead in as a potentiostat and to limit the potential sulphuric acid results in the formation of a of the lead/solution interface to about 2.5 thin film of PbO, at the Pb/PbO,-H,SO, volts. It has been shown (4) that the PbO, reversible potential; with further passage of film thickens when anodically polarised at charge the predominant reaction is oxidation high current densities in sea-water, and since of water to oxygen and there is practically the volume ratio of PbO,/Pb is greater than no thickening of the film. unity, the film is under considerable expansive The position in chloride solutions is quite stress. This results in the formation of different, and both PbCl, and PbO, are formed blisters which eventually rupture, with simultaneously, but at low current densities subsequent formation of PbC1, and corrosion a film of the latter gradually consolidates and of the exposed lead and, at constant current the lead can then act as a relatively inert density, the potential of the electrode will electrode. The presence of SO4*-in chloride increase since the PbCI, is nonconductive.

Platinum Metals Rev., 1968, 12, (2), 4245 42 dmong the applications for aihich lead-platinum bielectrodes have been found succes.fu1 is the cathodic protertion of the structure and well cnsings of Xorth Sea driZling rigs. liere an electrode - jixed at the lrf-hand end of the steel frame is being installed on one such rig. This electrode will operate at 35 umps per square foot (Photograph by courtesy of Metal and Pipeline Endurance Limited) This can be demonstrated by forming PbO, series of tests on cast lead and lead alloys on a lead-platinum bielectrode and then and on dispersion-hardened lead have been removing the platinum microelectrode, when carried out in collaboration with D. P. the potential immediately increases. When Peplow of the Central Electricity Generating platinum is in contact with the lead this Board. The illustration overpage shows cast increase in potential cannot occur, and PbO, lead alloys (I inch long by I inch diameter) will re-form at the lead exposed at a ruptured and extruded dispersion-hardened lead (1.5 blister without excessive corrosion. inch long by 0.5 inch diameter) on test in a water box at Marchwood Power Station. Design and Construction These anodes were polarised at 50 A/sq. ft of Rielectrodes for one year in order to assess the effect of The lead-platinum bielectrode consists of the composition on the growth and spalling an extruded bar of lead or lead alloy, I to of the lead peroxide, and the results can be 1.5 inch diameter and up to 12feet in length, summarised as follows: into which are inserted platinum micro- (a)Additions of silver are beneficial, and 0.1 per cent is almost as effective as I pcr cent. electrodes at 6 to inch intervals. The micro- IZ (b) Additions of antimony, bismuth and tin electrodes consist of small wires of platinum appear to be detrimental. (with a small percentage of an alloying metal (c) Dispersion-hardened lead and lead alloys are unsatisfactory, since pronounced spall- to increase hardness) 0.5 inch long by 0.030 ing occurs in the direction of extrusion. inch diameter, inserted in the lead by drilling a 0.025 inch diameter hole, tapping in the Successful Installations wire until it is flush with the lead surface The use of lead-platinum anodes in cathodic and then peening the surrounding lead to protection installations is largely confined ensure good electrical contact. to Metal and Pipeline Endurance Limited The nature of the lead used in the bielec- (MAPEL) in England, and to Lockheed trode is important and recently an extensive Aircraft Service Corporation of Ontario, Cali-

Platinum Metals Rev., 1968, 12, (2) 43 The type of lead or lead alloy for use in platinum bielectrodes is important, and extensive tests have been rarried out with a number of alloys. The anodes shown here were in use for a year. at 50 amps per square foot. in a water box at Marchuiood Pouw Station in order to ussess the effect of composrtion on the grow& and &pallingof the lead peroxide (Photograph by courtesy of the Central Electricity Generating Board)

fornia, both of whom, on the basis of over ten Area Rapid Transit Tube, a steel tube four years’ experience, arc using them for a variety miles long and some 130 feet in circumference of marine structures. which will carry rail and road traffic under One of the earliest applications by MAPEL the Bay; this is probably the largest cathodic was for the cathodic protection of the cooling protection installation ever undertaken. water culverts in a power station in Malacca, Malaya. These anodes have now been operat- Advantages of Lead-Platinum ing satisfactorily for ten years at 25 A/sq. ft. Anodes Other examples of large structures protected Lead-platinum bielectrodes are cheap, by MAPEL are the jetties in Europort and robust and easily fabricated, and can be used North Sea gas platforms such as that shown economically in sea-water over a range of in the illustration on page 43. Here the bi- current densities, from 10 to 70 A/sq. ft; electrode is mounted on a steel frame which a large anode operating at a low current is attached to the legs of the platform so density is sometimes an advantage when a that both are protected. uniform current distribution is required on a The Lockheed Aircraft Company have used large structure. The presence of an a.c. these anodes extensively for the protection ripple on the d.c. produced by transformer- of bulk carriers, tankers, liners, offshore rectifiers causes the slow corrosion of plati- drilling rigs and oil-wells and this company num, which can be serious when the platinum has recently been awarded the contract (5) is in the form of a very thin coating on a valve for the protection of the San Francisco Bay metal. The effect of a.c. corrosion on the

Platinum Metals Rev., 1968, 12, (2) 44 relatively massive platinum microelectrode i.s References insignificant, and this has the advantage that I L.L. Shreir and A. Weinraub, Chcm. and Ind., 1958, 1326; L. L. Shreir, Platinum Metals single-phase equipment produces no problems Rev., 19~9,3, 44 when lead-platinum anodes are used in a 2 E. L. Littauer and L. L. Shreir, Proc. First Int. Congr. Metall. Corros., p. 374, Butter- cathodic protection system. worths, London, (1961); L. L. Shreir, The experience gained over the past ten Corrosion, 1961, 17, 90; E. L. Littauer and years has shown that the lead-platinum L. L. Shreir, Electrochim. Acta, 1966, 11, 465 bielectrode provides a cheap and reliable 3 E. L. Littauer and L. L. Shreir, Electrochim. anode for the cathodic protection of marine Acta, 1966, 11, 527 structures, and it is envisaged that its import- 4 D. B. Peplow and L, L. Shreir, Corrosion Technology, 1964, 11, (4)' 16 ance will increase in the future. 5 E. L. Littauer, Private communication

A Standard High Purity Platinum NEW REFERENCE MATERIAL OF CERTIFIED COMPOSITION In 1922,in the course of a study of methods with the NBS, by Johnson Matthey, Matthey for the preparation of high purity platinum, Bishop, Sigmund Cohn, Engelhard Indust- the National Bureau of Standards made a ries and RCA Laboratories, and a provisional small trial melt which was identified in a certificate of analysis has been issued by the laboratory notebook as No. 27. This was NBS giving the following impurities : found to be thermoelectrically negative to all Copper 0.1p,p.m. Gold /I other specimens of platinum observed up to Silver 0.1 Magnesium /I that time, although the temperature coefficient Palladium 0.2 Zirconium -'o.I of resistance was only 0.003922. It is re- Lead 41 Rhodium '0.2 corded that this specimen was put aside as a Iron 0.7 Iridium co.01 Nickel /I Oxygen 4 primary standard for thermoelectric purposes and was designated Pt 27. This has remained Because of a certain amount of lack of the standard of reference in the U.S.A. ever agreement among the methods used, no since, although it is extremely doubtful if any estimate of accuracy can be made at present, of the original sample exists. but it is hoped that in six months' time a At a conference in the U.S.A. in 1960 revised certificate will be issued. between the NBS and representatives of the In addition, a further sample designated platinum industry, an extensive programme SRM 681 containing substantially greater was laid down to examine the properties of quantities of impurities, has been prepared high purity platinum. In particular, it was for analytical reference, again with a provi- agreed to try to relate e.m.f. against Pt 27 at sional certificate of analysis. IZOO"~ with temperature coefficient of Both of these materials in the form of resistance and the presence of impurities. 0.020 inch diameter wire may be obtained This led to a prolonged series of tests by from the Office of Standard Reference different bodies to assess the impurities in Materials of the NBS, Washington, in lengths parts per million, by spectrographic and other of either 4 inches or I metre. means. Because the supply of Pt 27 has been totally A batch of pure platinum was prepared by exhausted, there is a need for a new standard. induction melting high purity platinum sponge The NBS is making provision for platinum of in a zirconium silicate crucible, and casting substantially the same purity as SRM 680 to into a platinum-lined water-coolcd copper be prepared, and to be designated Pt 67. This mould. The ingot was worked and drawn to will be used at NBS as the national standard wire taking the utmost care to prevent con- for the calibration of thermocouple wires. tamination. This material has been designated It is probable that the new standard will give Standard Reference Material 680. Extensive an e.m.f. against Pt 27 at IZOO'Cof about analytical programmes, as well as tests for --g microvolts and that it will have a tem- homogenity, were carried out, in co-operation perature coefficient of resistance of 0.003927. H. E. B.

Platinum Metals Rev., 1968, 12, (2) 45 Monolithic Ceramic Capacitors

PLATINUM METAL ELECTRODES IN A FIRED MULTILAYER CONSTRUCTION

There is a growing use of small monolithic the most reliable electrodes in these com- ceramic capacitor chips in integrated hybrid ponents but that they also enable an economic and thick-film circuits. They provide the production method to be employed. The miniature capacitor elements in resistance! manufacturing process first entails producing capacitance networks where the resistors may thin strips of “green” ceramic. An ink or be fired patterns of screen printed resistive paste incorporating finely divided platinum inks on an alumina substrate. group metals is screen printed on to these The ceramics used normally fall into two strips in multiple arrays of rectangular categories; “High K’ and “NPO”. High K areas. When the print is dry the strips are capacitors are those based on ceramics of di- assembled one upon the other so that the electric constants generally in the range 600 metallised areas are superimposed. The to 5000 and provide exceptionally high assembly is topped with plain ceramic, and a capacitance per unit volume. NPO capacitors light compression bonds the layers together. employ ceramics of lower dielectric constant The assembly is then diced into individual whose chief merit is that of having a tempera- “chips”, each containing one series of super- ture coefficient of capacitance very near to imposed metallic areas interleaved with zero over a wide operating temperature range. ceramic dielectric. Fired at 1300°C~these It has been established over many years chips become robust monolithic blocks. now that the platinum metals not only provide Only the use of platinum group metals

Some of the K1200 and NPO monolithic ceramic cupncitor chips from Matthey Printed Products Limited. The smallest is 2.4 x 1.3 x 1.3 mm, the largest 9.Y X 10.8 x 1.7 mm, ofering in all a capacitance range of 5.6 to 470,000 pF at a peak rating of 100 volts. The terminal areas are metallised to facilitate soft soldering.

Platinum Metals Rev., 1968, 12, (2), 4647 46 makes possible this air-fired, fully integrated per "C. The rated operating temperature range construction. The process gives reliable and for these components is -55°C to +125"C. reproducible results in quantity production In general, users of monolithic ceramic and the long-term stability of the components capacitor chips must be able to connect them in subsequent service are as good as the into or mount them on integrated hybrid and ceramics themselves allow. thick-film circuits quickly and conveniently. Matthey Printed Products Limited, of For this purpose, the chips are supplied with Burslem, have recently announced the intro- their terminal ends metallised with silver so duction of a new range of miniature mono- that they can be soft soldered with ease. lithic ceramic chips. These are their K12oo Conventional capacitors incorporating and NPO series. The type of construction monolithic ceramic chips are manufactured and the choice of ceramic produce chips with by soldering wires to the metallised terminal a capacitance density of as much as 2.5 pF ends and encapsulating the bodies in a per cms in the K12oo series, while the NPO synthetic resin that does not affect the proper- series offers chips with a temperature co- ties of the chips but provides protection efficient of capacitance of zero -L~OYIO-~against humidity. G. T.

Chemistry of Co-ordination Complexes The Chemistry of the Rarer Platinum Metals (Os, Ru, Ir and Rh), by W. P. Griffith. Pp. ix and 491. Interscience Publishers, London, New York and Sydney, E6.

To anyone concerned with the chemistry briefly considered. The following chapter of the platinum group metals the lack of texts comprises a general chemical survey in which on the subject is well known and the publica- the distinctive features of the chemistry of tion of any book would be hailed as a note- the elements are outlined. The range of worthy occasion. The appearance of this oxidation states and stereochemistries in the authoritative work by Dr Griffith, of Imperial metal complexes and the reactivities of the College, is indeed such an occasion. Over the complexes are considered. There is a survey past decade or so a vast amount of work has of the physical measurements that have been been carried out on the co-ordination made with some indication of the chemical chemistry of osmium, ruthenium, iridium and information that can be derived from them, rhodium and the literature has abounded with and a brief review of the principal ligands the resulting papers, To have now a book con- found to co-ordinate with the metals. The taining all the information that has accumu- elements are then dealt with in individual lated from the time of the discovery of these chapters, the co-ordinating ligands being metals until the end of 1966 is indeed a great arranged according to the Periodic Group to boon. which the donor atom belongs. Each of the It is not only to be hoped that the author chapters deals comprehensively and critically will continue to cover the literature so that with the subject, considering in detail further editions of thc book may be as com- molecular structure and the physical and plete as is the present one but that he, or some chemical properties of the complexes and other person prepared to undertake an equally concluding with a section on homogeneous monumental task, will producc a similar catalysis. treatise dealing with platinum and palladium. This book, if only by reason of its compre- The book is concerned primarily with the hensive coverage, is an invaluable contribu- co-ordination chemistry of the four elements tion to the literature of the platinum group and is written in the form of a reference book, metals. It makes clear the potential import- much material being presented in tabular ance of these complexes, particularly in the form. In the opening chapter such subjects as catalytic field, and should stimulate workers occurrence, physical, chemical and catalytic in this branch of chemistry to still greater properties of the elements, their analytical effort. chemistry and industrial applications are very F. M. L.

Platinum Metals Rev., 1968, 12, (2) 47 Platinum for Fuel Cells AVAILARILITY AND COST-EFFECTIVENESS

By H. Connor, BS~. Johnson Matthey Chemicals Limited

The unique combination of excellent An impression of shortage has stemmed corrosion resistance with high catalytic from the fact that there is a wide disparity activity has assured the application of the in the selling prices for South African and platinum metals, at least in some fuel cell Canadian metal, on the one hand, and that systems. In discussing the use of the for the metal coming from Russia and the platinum metals in fuel cells, however, two minor producers. Since, of course, no one questions constantly recur. Is there enough wants to use the more costly sources unless platinum available to meet the potential compelled to do so, there is a shortage of demands of the fuel cell systems under relatively low-cost platinum. development ? How can the platinum elec- And platinum for fuel cells ? Demands for trocatalyst be used at maximum cost- platinum metals for any of the numerous effectiveness ? Neither question can be specialised fuel cell systems now under answered simply, since in both cases there development are likely to grow slowly; are several interrelated complicating features. initial demands can, no doubt, be easily met There has been a good deal of talk about from current outputs. At a certain stage in a shortage of platinum for industrial uses the market development of each fuel cell, during the last few years. In fact, there has moreover, some platinum will become avail- been no absolute shortage. Although the able by the recovery from spent electrodes. demand has increased very substantially, (The design of platinum metal-containing practically all real needs have been met by electrode structures to permit economic the main primary sources - South Africa, metal recovery after use could incidentally Canada and Russia - supplemented in 1966 be the subject of fruitful collaboration between by a release of some 300,000 ounces from the fuel cell researcher and platinum refiner.) U.S. Strategic Stockpile. Large-scale, continuing supplies of platinum, The amounts available from Canada, however, can only be assured by early direct Russia and the minor producers have re- consultation with the producers. Whereas mained relatively static. The big increase in it may not be possible to equip each of ten availability has come from Rustenburg Plati- million motor-cars per annum with a fuel num Mines, for whom Johnson Matthey are cell power source containing 100 grams of the refiners and distributors. As was announc- platinum, it appears certain that the more ed last year, substantial increases in mining realistic demands for metal that may be made and refining operations are in hand to provide by fuel cells now under development for an output of 850,000 ounces of platinum a specialised applications can be met. year (I). This is more than a four-fold in- Apart from the question of availability, crease in the output of platinum since 1964, the high intrinsic value of the platinum metals with of course corresponding increases in the makes it imperative that the most effective supply of rhodium, ruthenium, palladium and use be made of them in electrode structures. iridium. Underground reserves of metal are Several approaches to this have recently been estimated to be sufficient to last well into the suggested (2). Primarily, these concentrate next century at the planned rate of output. on making catalytically available and active

Platinum Metals Rev., 1968, 12, (2), 4849 48 Operations at Rustenburg Platinum Mines have been extended many times over the last thirty yews and now prouide the largest source of the platinum metals in the iuorfd. Further expansion plans will increase output to approximately 850,000 ounces of platinum a year the highest possible proportion of metal active. With all of them, the grade of support atoms that are incorporated in an electrode selected and the technique employed in structure. For platinum metal blacks, for their preparation critically determine their example, their preparation with very high suitability in a particular fuel system. Their surface areas per unit weight is a necessary specific activities (for example R/A, where step in this direction. Such blacks, however, R=activity in appropriate units, and A- must also exhibit particular properties of metal area per unit weight of catalyst) may dispersion in the binders used to secure them differ widely when variations in catalyst to their electrodes. High surface area, preparations are introduced. Fuel cell moreover, is not a unique index of catalytic research aimed at finding the economically activity, since this depends to some extent optimum electrocatalyst for a particular sys- on the individual features of each fuel cell tem will therefore have to consider not only system. the most appropriate of the platinum metals, In order to reduce cost to a minimum or a synergistic binary mixture of these, but there is now a strong and growing trend to use also the best method of preparation. supported platinum metal catalysts in the The Johnson Matthey Research Labora- development of fuel cells for commercial tories are heavily engaged in the investigation applications. Such catalysts, containing a of catalyst preparation procedures to obtain relatively low metal concentration (for the greatest cost-effectiveness from the plati- example, 5 per cent) on an electronically num metals. Collaboration with catalyst users conductive support (for example, charcoal) and research workers operating in specific enable specific metal areas to be achieved areas, including fuel cells, is increasingly that are far higher than those of blacks. leading to the point where the factors that Even with the best catalysts that are at present govern metal utilisation may be controlled. available, however, less than 25 per cent - References more usually only 5 to 10 per cent of the - I Platinum Metals Review, 1967, 11, 131 metal atoms are catalytically accessible and 2 Platinum Metals Review, 1968, 12, 21

Platinum Metals Rev., 1968, 12, (2) 49 Tertiary Phosphine Complexes of the Platinum Metals

PRINCIPLES OF THEIR REACTION MECHANISMS AND USES IN HOMOGENEOUS CATALYSIS

By Professor Geoffrey Wilkinson, F.R.S. Inorganic Chemistry Laboratories, Imperial College, London

Complexes of transition metals with tertiary referred to as x-acids. Recent nuclear phosphines (and similar complexes with magnetic resonance studies of lS3W- 31P arsines and stibines) both non-chelating, for coupling constants in phosphine complexes example, (C,H,),P or chelating, for example, of tungsten, together with infra-red spectro- (C,H,),P(CH,),P( C,H,),( diphos), have been scopic work, have provided sound evidence studied since Hofmann's first preparation of for the reality of such metal-phosphorus triethylphosphine, arsine and stibine platinum x-bonding (2). and gold complexes in 1857. An extremely Fairly recently it was recognised that wide range of compounds of most of the certain square complexes of platinum and transition metals, often in several oxidation iridium may add neutral molecules, whereby states, is now known (I). the metal is oxidised by $2 units. Thus L. Until a few years ago, when some of the Vaska, using the complex trans-bis(tri- complexes began to be of interest as activation phenylphosphine)carbonylchloroiridium( I) for small molecules and as catalysts in organic confirmed the reaction : synthetic reactions, most of the studies concentrated on new types of complexes and especially on the use of phosphine ligands for stabilising low oxidation states of metals, 1; i- XY for example, Ni(CO),(PPh,), or Mo (diphos),, and for allowing the stabilisation of rather labile or reactive groups such as H, CH,, OC PPh C,H, bound to metals as, for example, in (Et,P),PtCl(CH,). This stabilising influence arises from the property of the phosphines to adjust energy levels in the metal atoms of complexes through the d,-d, bonding capacity of the phosphorus atom. Such R,P compounds behave not only as simple donors from electron density of the lone OC pair on phosphorus but also as acceptors of '1 Lh3 electron density from electrons in filled CI orbitals of the metal into vacant 3d orbitals of The additions of a molecule XY, examples of the phosphorus atom. Phosphines thus fall which are given below, may involve either in that class of ligands, such as carbon cis or trans addition, depending on the monoxide, which have both donor and circumstances, but isomerisation of the initial acceptor properties and which are generally complex to the most thermodynamically

Platinum Metals Rev., 1968, 12, (2), 50-53 50 stable system may occur afterwards in solution reactions (3). Such reactions, The stud? of platinum metal complexes generally now known as oxidative additions, of tertiary phosphine ligands has may proceed as in the above equation for a allowed substantial advances to be coordinatively unsaturated complex; how- made in the preparation of new classes ever, depending on the stability of a given of complexes which in turn haw coordination number in a particular oxidation contributed to a greater understanding state, loss of a ligand may occur also, Examples of the stability and reactivity of other of the latter type of oxidative additions are: ligands such as hydride and alkyl groups bound to metals. Many of (Ph3P),Pto+XY =(Ph3P),Pt1'XY+2PPh, these complexes are egectivc in horno- (Ph3P)2Ruo( CO), +XY = geneous catalyses, such as hydro- (PhJ?),Ru"( C0)xXY$. CO. genation or isomerisation of olejns, The reactions are best known for complexes and may be used for a number of of Ruo, Oso, Rh', Ir', Nio,Pdo, Pt', PdI'and other organic s.yntheses. Pt", usually though not exclusively with phosphine ligands. Further, there are two to be "activated" must have acceptor orbitals other classes of the reaction - those where available-even the hydrogen molecule has breaking of the X-Y bond occurs and those anti-bonding orbitals; the promotional energy where it does not, In both these cases, two involved in oxidising the metal from state new metal bonds, to X and Y, are formed, but n to n +z must be more than overcome through for the second class, a three-membered ring the formation of new bonds to the added is formed. Examples are: molecule. (Et,P)l't"HCl +HCl =(EtJ'),Pt1"H2C12 Of special interest are the reversible oxygen carriers discovered by Vaska, that is : IrlC1(CO)(PPh,), -lo2$Ir111C1(CO)(0,)(PPh3), These provide not only the simplest model for biological oxygen carriers but have also ,c//" provided important X-ray structural data on 0-0 bond lengths. Such data (4) and that obtained for (Ph,P),PtCS, (5) have led to the suggestion (5) that when XY is coordinated without bond breaking, the geometry of XY An extremely wide range of XY molecules can then be correlated with that determined may be added oxidatively. In the first class spectroscopically for electronic excited states we have: H,; Cl,, Brz, I,; HCl, HBr, HX; of XY. CH,I, RX; C,H,COCl, RCOCl; RS0,X; The oxidative addition reactions may be Me,SNEt,; HgX,; C1,SiH; R,SiH, etc. In important steps in many catalytic processes the second class: 0,; SO,; C,F,; CS,; employing tertiary phosphine and other metal RCGCR'; (CF,),C=O, (CF,),C = S;RNCO, complexes, where small molecules are acti- RNCS; RN=C =NR (carbodiimides); R,C = vated at a metal site prior to subsequent C=O. The criteria for oxidative addition attack by other molecules or ions. A second reactions to occur are not fully understood at very important general reaction is the so- present. Among other factors it is clear that called "insertion" reaction (6). These are now the metal atom in the complex must have considered to be transfer reactions of a unused electron density-that is, it can behave hydrido, alkyl or other ligand from the metal as a nucleophile; molecules such as H, or 0, to a second, briefly coordinated ligand;

Platinum Metals Rev., 1968, 12, (2) 51 implicit here is the fact that for a ligand to be For the hydroformylation of olefins so activated by coordination, the catalyst (olefin +CO + H,: aldehyde) there have been species must be coordinatively unsaturated patent claims that the addition of tertiary or must havc coordination sites only weakly phosphines to the cobalt carbonyl catalyst occupied by solvent molecules which can usually employed improves the yield of be competitively displaced by the ligand to straight chain relative to branch chain which a transfer is made. aldehydes simultaneously produced. Recent We can consider here in illustration only a studies using stoichiometric and well estab- few types of catalytic reactions in which the lished complexes, such as RhH(CO)(PPh,),, above principles operate and for which have shown that hydroformylation can be phosphine complexes of platinum metals achieved under abnormally mild conditions, are especially effective. even at room temperature and pressure (9). Homogeneous hydrogenation of olefins is Many platinum metal complexes, including exceedingly rapid using the complex RhCl those with phosphine ligands, can catalyse (PPh,),--or more properly, in solution, the olefin isomerisation and oligomerisation re- coordinatively unsaturated, solvated species actions-in these cases, hydrido metal RhCI(PPh,),(S) where S is a solvent molecule complexes are probably involved as well as produced by dissociation. This “activates’’ unstable alkyls derived from them by molecular hydrogen, which adds oxidatively reactions with olefins. Fairly simple systems with bond breaking in a reversible reaction: in which both the hydrido and alkyl species can be studied have been reported recently RhlllCI(PPh,),(S) 4 H,+ RhllrCl(H)(H)(PPh,),( S) (IO), for example: In presence of olefins, a coordinated oleh (Ph,P),RhCl,H t C,H,~(PhdP),RhC1,C,H, complex intermediate is postulated : (Et,P),PtCIHi C,H,e(Et,P)PtCIC,H,

€1 II

Rh Rh / /I\ Ph3 P c1 ‘ and the formation of this complex is the rate There are many other catalytic or stoichi- determining step. Hydrogen transfer rapidly ometric reactions that may be achieved OCCUTS, producing paraflin. The various using RJ complexes of platinum metals- factors and mechanism involved have been decarbonylation of aldehydes, polymerisation discussed in detail (7). Other complexes, of acetylenes, hydrosilation of olefins, oxida- such as RhH(CO)(PPh,),, IrCI(CO)(PPh,), tions using molecular oxygen and so on. One and [RuCI(PPh,),], are also effective hydro- recent example is the polymerisation of genation catalysts, which may have high allene by RuCI,(PPh,), and RhCl(PPh,), selectivity. Thus the ruthenium complex is (11). essentially specific for a-olefins, while the Finally, it may be noted that phosphine complex RhCl (PPh,), has already found species have been used in the recent prepara- extensive use for selective hydrogenation or tion of molecular nitrogen complexes of deuteration of steroids (8). cobalt (12) and that the hydrido species

Platinum Metals Rev., 1968, 12, (2) 52 (Et,P),PtClH has been found to react with 4 J. A. McGinnety, R. J. Doedens and J. A. Ibers, Znorg. Chem., 1967, 6, 2243 a diazonium salt in much the same way that 5 R. Mason, Natzire, 1968, (in the press) a reducing enzyme is thought to react with a 6 For general review see R. F. Heck, in metal complex of molecular nitrogen in “Mechanisms of Inorganic Reactions”, ACS Advances in Chemistry Series No. 45, biological systems (13). Washington, D.C., 1965 As will be seen from the reference list, 7 J. A. Osborn, F. Jardine, J. F. Young and G. this area of chemistry is currently of great Wilkinson, J. Chem. SOC.(A), 1966, 1711; F. Jardine, J. A. Osborn and G. Wilkinson, interest and it seems clear that many other J. Chem. SOC.(A), 1967, 1574 reactions of potential use in organic synthesis 8 W. Voelter and C. Djerassi, Chem. Ber., are as yet undiscovered. 1968,10,58 g P. S. Hallman, D. Evans, J. A. Osborn and G. References Wilkinson, Chem. Commun., 1967, 305 I For comprehensive reviews see: G. Booth, 10 (a) M. C. Baird, J. T. Mague, J. A. Osborn Adv. inorg. Chem. Radiochem., 1964, 6, I, and G. Wilkinson,J. Chem. SOC.(A), 1967, and, for platinum group metals, W. P. 1347; (b) J. Chatt, R. S. Coffey, A. Gough Griffith, “The Chemistry of the Rarer and D. T. Thompson, J. Chenz. SOC.(A), Platinum Metals”, Interscience, London, 1968, 190 1967. The latter contains many references 11 S. Otsuka and A. Nakamura, Polymer Letters, to catalytic uses. 19671 5,973 2 S. 0. Grim, D. A. Wheatland and W. McFar- 12 J. H. Enemark, B. R. Davis, J. A. McGinnety lane,J. Am. Chem. SOC.,1967, 89,5573 and J. A. Ibers, Chem. Commun., 1968~96 3 For examples and references see J. P. Collman 13 G. W. Parshal1,J. Am. Chem. Soc., 1967, 89, and C. T. Sears, Inorg. Chem., 1968,7, 27 1822

Palladium Addition Protects Titanium in Hot Concentrated Chloride Solutions Titanium is used widely in thc manufacture boiling chloride solutions. Although the of chemical plant because of its natural re- passivity of titanium was very stable in solu- sistance to corrosion by oxidants, such as tions of low chloride concentration it decreased boiling nitric acid, and its use has been ex- with increasing chloride and hydrogen ion tended to reducing conditions, such as with concentration. No corrosion of titanium hydrochloric and sulphuric acids, by alloying occurred in neutral 25 per cent sodium small amounts of palladium to the titanium, chloride but severe corrosion soon occurred a development due largely to Milton Stern in acidic 33 per cent aluminium chloride and his colleague at Union Carbide (I, 2). solution. Pitting corrosion arose quickly in The mechanism by which the addition of neutral solutions of 61 per cent calcium palladium affords protection to titanium has chloride and 86 per cent zinc chloride, depend- been described more recently in this journal ing on the surface condition of the speci- by J. B. Cotton of Imperial Metal Industries mens. Uniform attack took place after small (3). additions of hydrochloric acid. Akira Takamura, working at the Central No corrosion was observed with the palla- Research Laboratory of Kobe Steel Ltd in dium-titanium alloy, the superiority of which Japan, has now shown that the 0.13 per cent is attributed to palladium enrichment at palladium-titanium alloy is almost completely crevice surfaces and the consequent promo- free from corrosion by hot concentrated tion of cathodic passivation. In consequence, chloride solutions (4). Corrosion problems equipment with joints and flanges likely to had been occurring in awkward angles and have crevices is now fabricated with the alloy, crevices of titanium heat exchanger tubes, which has given more than three years suc- pipe flanges and heater tubes used in circuits cessful commercial service. carrying, for example, hot copper chloride F. J. S. and ammonium chloride solutions. References Takamura carried out corrosion and electro- I PZarinum Metals Rev., 1959, 3, (3), 88-89 2 T. P. Hoar, Zbid., 1960, 4, (2), 59-54 chemical tests on coupons of titanium and 3 J. B. Cotton, Zbid., 1967, 11, (2), 50-52 the palladium-titanium alloy in six different 4 A. Takamura, Corrosion, 1967~23,(IO), 306-3‘3

Platinum Metals Rev., 1968, 12, (2) 53 Potentiometer Slidewire Materials

METALLURGICAL CONSIDERATIONS INVOLVED IN THEIR SELECTION AND DEVELOPMENT

By A. s. Darling, Ph.D., A.M.1.Mech.E. Research Laboratories, Johnson Matthey & Co Limited

constancy frequently overrides all other The slidewire potentiometer is a device considerations. intended to produce a signal voltage Because of the obvious desirability of low uniquely related to the mechanical dis- and constant contact resistances, the use of plucements involved, and its materials noble metal alloys for precision potentio- of construction must provide therefore meters has become almost mandatory. The a reasonably accurate embodiment of contact resistance provided by a particular the desired mathematical relationships. slidewire/wiper combination is, however, de- Aoble metal alloys are usually selected pendent upon the load applied, so that we for such applications because of their can sometimes envisage the successful use of stability and freedom from corrosion. base metals in those situations where high In this paper, based on a lecture given loads and torques are possible. As heavy loads recently to the Control and Automation accentuate the rate of wear on the slidewire Division of the Institution of Electrical this solution is of rather limited application. Engineers, some general correlations A good deal of the voltage signal generated between electrical performance and across a sliding contact manifests itself as metallurgical characteristics are dis- electrical noise, and some of the traditional cussed and it is shown hozv the applica- slidewire materials are successful because of tion of these principles has led to the their ability to keep this undesirable character- deeelopment of new and improved istic within tolerable proportions. potentiometer slidewire materials. Potentiometers used in servo-mechanisms sometimes develop signals of several hundred Although it is axiomatic that resistance volts and in such instances thermo-electric wires should have a high resistivity, prevailing effects are small enough to be neglected. At circumstances will always determine the the other end of the scale, however, are those interpretation placed on this general require- slidewires used to sub-divide small fractions ment. Alloys with specific resistances ranging of a volt, where thermal potentials can intro- from 10 to 150 microhm-cm are fairly regu- duce errors comparable in magnitude to the larly employed and it is safe to say that high quantities being measured. Between these two resistivity is frequently a subordinate con- extremes can be distinguished an area in sideration when the final selection of a slide- which the main disadvantage of a high wire material comes to be made. thermo-electric force is the ‘hunting’ effect The balance finally achieved between the which it can introduce when null points are conflicting requirements of high resolution being sought by automatic methods. A low and minimum volume is generally determined thermal e.m.f. against copper is, therefore, by the qualities of electrical stability and important particularly in d.c. devices. mechanical permanence required from the Pure metals have resistivities too low and component, and the importance of resistance temperature coefficients too high to permit

Platinum Metals Rev., 1968, 12, (2), 54-61 54 There are many different types of potentiometers, each requiring individual selection of the winding material to meet the specified performance of the instrument. This illustration shows a Colvern cam-corrected single-turn precision potentiometer and its toroidal winding. The wire in this case is 20 per cent copper-platinum their effective use as slidewire materials. considering a simple practical example, such Higher resistivities and lower temperature as that afforded by the palladium-gold system, coefficients can be achieved by suitable alloy- which illustrates many of the general prin- ing procedures and the improved mechanical ciples employed. properties of the alloys facilitate winding Fig. I illustrates the effect of gold on the techniques and ensure greater resistance to electrical resistivity and temperature coeffi- abrasion in service. cient of palladium. The specific resistance of pure palladium at zo°C is 9.93 microhm-cm, Composition and Resistivity and its temperature coefficient of resistance To assist in attaining the freedom from is 0.0038 per "C. The addition of 20 per cent tarnishing necessary for low contact resist- by weight of gold increases the specific resistance, precision potentiometer alloys are ance to 18 microhm-cm, and reduces the tem- generally based on either platinum or palla- perature coefficient of resistance by a dium. A discussion of the theory of alloying corresponding amount. The peak resistivity is with respect to electrical properties is not exhibited by the alloy containing 50 per cent within the present context, but it is worth by weight of gold although this does not

Platinum Metals Rev., 1968, 12, (2) 55 Temperature coefficients calculated at 300°K from such an elementary model show roughly the same trends as those experimentally derived, although the numerical discrepancies suggest that these simple rules are not directly applicable to concentrated alloys. The alloy containing 50 per cent of gold would be the most valuable to select for a resistance slidewire as its resistivity lies at the peak of the concentration curve. Slight variations in composition would be unlikely therefore to have much influence on the electrical resistance, and slidewires of constant diameter should show few problems due to non-linearity. The maximum resistance of gold-palladium alloys is, however, rather low for many applications and they are too soft to resist abrasion. The high thermal e.m.f.s they generate against copper could moreover be undesirable in certain precise work. Silver and palladium form a continuous series of solid solutions. The peak resistivity of 42 microhm-cm is achieved with a silver content of 40 per cent by weight and this alloy has the remarkably low temperature coefficient of 0.00003 per "C. Where low correspond with the minimum temperature noise values and steady contact resistances coefficient, which occurs at rather higher gold are matters of particular concern, this alloy concentrations. is widely employed, and for really precise The gold-palladium system tends to be work its low temperature coefficient is of regarded as a classical example of one in extreme value. Its mechanical properties are which the two constituents are soluble in all unfortunately rather lower than could be proportions so that no discontinuous variation desired, and its resistance to wear and abra- of properties with composition occurs. Al- sion is not high. Since the low noise values though the slight inflexions exhibited by the appear to be a direct consequence of the low two curves in Fig. I do indicate some de- hardness, attempts to improve the mechanical parture from ideal conditions, the general properties of this valuable resistance material implications are that high resistivity corres- have usually resulted in inferior electrical ponds with low temperature coefficient and characteristics. that the resistivity rises to a maximum at the highest degree of alloying. As long ago as Platinum Alloys 1860 Matthiessen suggested (I) that the total Platinum alloys containing approximately resistance of a metal or alloy should be 70 per cent of silver were frequently used for separated into temperature-dependent and slidewires in the early days of electrical temperature-independent constituents. If we technology. Although favoured because of its imagine that the alloying constituent is low temperature coefficient and moderately temperature-independent the situation can high resistivity, this alloy was difficult to be represented graphically as in Fig. 2. make and had very variable properties.

Platinum Metals Rev., 1968, 12, (2) 56 Iridium-platinum alloys had far more reproducible characteristics and their electrical properties remained stable over long periods of time. Combined with an intermediate electrical resistivity of approximately 25 microhm-cm, the 10 per cent iridium-platinum alloy has an excellent resistance to tarnishing and corrosion and has high mechanical properties. As an alloying addition, rhodium is less effective than iridium in increasing resistivity, although binary rhodium-platinum wires are still effectively employed in some low resistance potentiometers. The electrical properties of rhodium-platinum solid solutions are considerably improved by ruthenium additions, and the platium alloy containing 5 per alloy still had a base metal content rather cent of ruthenium and 15 per cent of higher than was thought to be desirable in a rhodium is widely used for precise work precision material of this type, there appeared where low contact resistance and freedom to be considerable scope for a new noble from wear is essential. This alloy has a metal alloy of higher resistivity and freedom specific resistance of 31 microhm-cm. and a from corrosion. temperature coefficient of 0.0007 per 'C. Copper and platinum form, at temperatures Palladium Alloys below the solidus, a continuous series of solid Detailed literature and laboratory surveys solutions, the electrical resistance of quenched showed that palladium alloys tended to alloys being as indicated in Fig. 3. The peak develop higher specific resistances than those resistance of approximately 93 microhm-cm based on platinum or gold. In particular it is exhibited by the alloy containing 24.5 per was found that the highest resistances were cent by weight of copper. This corresponds obtained by alloying palladium with small to the Cu Pt equi-atomic composition and a quantities of the transition elements vana- tendency to order makes this alloy somewhat dium, chromium, niobium and molybdenum. unstable. Prolonged heat treatment of the Tungsten-palladium alloys also have very quenched alloy between ZOO' and 300°C high resistivities; 20 per cent by weight of results in ordering; the copper and platinum tungsten produces an alloy having a specific atoms line up on alternate planes and the resistance of IIO microhm-cm which can, resistance falls from 93 to 14 microhm-cm. unfortunately, be drawn into wire only with This tendency can be reduced to manageable difficulty. As the chromium-bearing alloys, proportions by moving away from the although ductile, tended to develop a coherent stoichiometric composition (2). The alloy now surface oxide skin and the reactive nature of produced contains approximately 20 per cent vanadium and niobium make these elements by weight of copper and is stable at tempera- difficult to add under production conditions, tures up to 200°C. Since this adjustment attention was therefore initially concentrated involved some sacrifice of resistivity and the upon the molybdenum-palladium system.

Platinum Metals Rev., 1968, 12, (2) 57 The effect of molybdenum upon the elec- ment. Its temperature coefficient of 0.00012 trical properties of palladium is illustrated in per "C between on and 100°Cis acceptably Fig. 4, which shows that resistivities of the low for most purposes and its high tensile order of IOO microhm-cm can be developed strength (approximately 70 tons per sq. inch in a workable alloy which contains 10 atomic in the hard drawn condition) ensures high per cent of molybdenum. Higher resistivities wear resistance and ease of winding. were obtained by adding the molybdenum to The routine production of vanadium- a gold-palladium base. The composition palladium alloys became a commercial pro- finally selected for general purposes contained position with the development of improved 5 per cent by weight of molybdenum and 40 melting and fabrication techniques. The effect per cent of gold, the balance being palladium of vanadium on the electrical resistance of (5). This material has a specific resistance of palladium is shown in Fig. 5 which illustrates IOO microhm-cm which does not change some rather serious discrepancies between appreciably either by working or heat treat- our work and that of earlier investigators

This precision potentiometer for a pressure trans- ducer, by Delta Controls, is shown jitted to a Bourdon tube pressure gauge. The winding here is in 5 per cent molybdenum - 40 per cent palladium-gold

Platinum Metals Rev., 1968, 12, (2) 58 Accurate control of temperature coeficierct of resistance is essential in the manufacture of precision resistance wires. This equipment, designed and built by Johnson Matthey, gives a continuous indication of temperature and resistance of $ne wires over the range -60' to 250°C

(3, 4). This was because work hardening the alloys of higher vanadium content had the unusual effect of reducing the specific resistance to a significant extent, Small additions of aluminium reduced this effect considerably (6). The alloy selected for commercial evaluation contains 9 per cent by weight of vanadium and I per cent of aluminium. Combined with a specific resistance of 150 microhm-cm at room temperature is a temperature coefficient of - 80 p.p.m. per "C and a tensile strength in excess of 50 tons per sq. inch in the annealed condition. Wire of this composition can be drawn down to diameters of the order of 0.0005 inch.

Contact Resistance Some typical curves indicating the effect of decreasing load. Although this behaviour is load on contact resistance are shown in Fig. 6. observed with all materials there is no doubt The wiper used for these determinations that it is less pronounced with the softer contained 62.5 per cent by weight of gold, resistance wires. the remainder being silver and copper. These Sliding contact resistances are, very ap- measurements were obtained at currents of proximately, about twice as high as the ten milliamps. At pressures below three grams, statically obtained values shown in Fig. 6. contact resistance increases rapidly with Under sliding conditions contact resistance

Platinum Metals Rev., 1968, 12, (2) 59 Typical Physical Properties of Noble Metal Resistance Wires

Specific Temperature Tensile Strength Thermal Resistance Coefficient e.m.f. Alloy of Annealed I Hard Drawn against Resistance copper pLl-cm. Q/circ. (o-iooocj tons/ tons/ tons/ at 100°C mil. ft per “C in2 in2 in2 mV

10 per cent rhodium-platinum 19 114 0.0017 30 47 75 117 -0.10 10 per cent iridium-platinum 24.5 147 0.0013 35 55 80 125 +0.55 5 per cent gold- 10 per cent rhodium-platinum 26 156 0.0011 40 63 90 42 -0.38 5 per cent ruthenium- 15 per cent rhodium-platinum 31 186 0.0007 65 101 110 173 +G.03 20 per cent iridium-platinum 32 192 0.00085 45 70 105 165 +0.61 40 per cent silver-palladium 42 252 0.00003 24 38 70 110 - 4.20 10 per cent ruthenium-platinum 42 252 0.00047 50 79 90 140 +0.14 8 per cent tungsten-platinum 62 372 0.00028 60 94 95 150 + 0.71 5 per cent molybdenum- 64 3 84 0.00024 60 94 90 140 -k 0.77 platinum 20 per cent copper-platinum 82.5 495 0.000098 I 38 I 60 I 90 I 140 I -0.67 5 per cent molybdenum- 100 40 per cent palladium-gold 600 0.0001 2 70

9 per cent vanadium-palladium 150 900 -0.00008 ~ ~ 90 40 -0.56 :: ;; I1O ~ -0.19

and noise cannot be considered independently, and detailed studies now being undertaken should lead to valuable correlations between noise, load, contact resistance, and speed of sliding. A major difficulty in this work lies in separating the behaviour characteristics of the materials under test from effects which reflect the construction and design of the testing apparatus. For purposes of comparison, contact resistance measurements were made on copper- nickel and nickel-chromium resistors. For noble metal slidewires, the relationship between load and contact resistance is well

FINE SILVER Fig. 6 E’ect of a load on the contact resistance between a gold alloy wiper and Jine silver, 40 per cent silver-palladium, 5 per cent molybdenum - I 2 3 4 s 6 7 a 9 10 II 12 I3 14 40 per cent palladium-gold and 9 per cent 2:: 2:: CONTACT LOAD IN GRAMS vanadium-palladium

Platinum Metals Rev., 1968, 12, (2) 60 tons/ in2 defined, but similar relationships are not is acceptable in certain precision applications. observed with base metal slidewires. Although Because of their high catalytic activity low contact resistances are sometimes ob- platinum and palladium alloys sometimes tained, load and contact resistance are not cause difficulty when operated in atmo- uniquely related and a very wide scatter of spheres containing high concentrations of results is obtained. This scatter is undoubt- organic vapours. A recently developed edly associated with the high noise values rhodium-platinum alloy containing 5 per cent generated between sliding contacts and base of gold does not readily promote low metal resistors. Noise and uncertainty in- temperature organic reactions and might crease rapidly as the contact load decreases therefore be of considerable help in those and it is difficult, therefore, to obtain accurate applications where the danger of polymer results from low torque potentiometers formation exists. wound with base metal wires. References Characteristics of Potentiometer I A. Matthiessen, Ann. Physik Chem. (Pogx. Folge), 1860, 110, 190; Zbid., 1864, IZZ, 10 Materials 2 Unpublished data, Johnson Matthey Research The characteristics of a few of the main Laboratories 3 W. KBster, W. Gmohling and D. Hagmann, important potentiometer wires are summar- Z. Metallkunde, 1963, 54, 325 ised in the table. Of those listed the most noble 4 E. Kudielka-Artner and B. B. Argent, Proc. Phys. Soc., 1962, 80, 1143 and resistant to corrosion is the 20 per cent 5 Johnson Matthey, B.P. 861,646 iridium-platinum alloy which unfortunately 6 Johnson Matthey, Prov. Pat. 21853/67 has a temperature coefficient rather higher than 7 Johnson Matthey, B.P. 868,259

Frictional Characteristics of the RefractorvJ Platinum Metals A recent report by D. H. Buckley of the ruthenium. No information on the frictional Lewis Research Centre (NASA Tech. Note characteristics of iridium or osmium at TN D-4152, 1967, (Sept.), 1-15) conveys at pressures above 10-* torr is given in this re- first glance the impression that osmium and port. ruthenium, the hexagonal refractory metals, Within the context of space applications have, when rubbed against themselves, lower covered by NASA, it is perhaps logical to coefficients of friction than their cubic assume that atmospheric pressures below counterparts rhodium and iridium, and are 10-8 torr constitute a perfectly normal am- therefore to be preferred for sliding electrical bient environment. Such clean conditions contacts. The author states dogmatically should certainly help when attempts are made that ‘from the results of this investigation, it to correlate surface properties such as friction would appear that ruthenium, with its with the crystallographic characteristics of hexagonal crystal structure, would certainly pure metals. It is disappointing, therefore, to be highly superior to the face centred cubic find in this report no indication of the purity metal rhodium in sliding electrical contact of the materials studied or the way in which applications’. Detailed study of the paper, the test specimens were fabricated and pre- however, shows that this conclusion is based pared for examination. In subsequent publi- entirely on experiments made under ultra cations it is hoped that fuller details will be high vacuum conditions. The superiority of supplied of the process, whereby the disc ruthenium over rhodium is only apparent at and rider specimens were ‘finished to a pressures below IO-~torr and results reported roughness of 4 to 8 micro inches and then show that at higher pressures rhodium has a fully annealed’. much lower coefficient of friction than A. S. D.

Platinum Metals Rev., 1968, 12, (2) 61 Vapour Phase Deposition of Iridium NEW TECHNIQUES FOR APPLYING COATINGS ON GRAPHITE

A reliable, easily worked process for that of graphite at temperatures up to IIOOT, depositing coherent, compact and pore-free over the range in which the metal is relatively layers of iridium could, when fully developed, unyielding. be the means of making use as never before It is with this background that the results of the outstanding and indeed unique of experiments recently reported in applying characteristics of iridium. methods of chemical vapour deposition to the Iridium has a very high melting point- formation of iridium coatings on graphite 2443OC-aIId as a platinum group metal it may be viewed. does not scale or tarnish when heated in air The process of chemical vapour deposition even to incandescence. It is true that it loses is probably best known by such examples as weight through formation of a volatile oxide the Mond process for making nickel shot or when it is heated to above about 10oo"C in powder by the decomposition of nickel car- air, but it is not difficult to contain the loss bony1 and by the Van Arkel process for within reasonable limits in most circumstances purifying such metals as titanium. In none of by controlling free circulation. these applications, however, has much con- Like the other platinum metals it does not trol been possible of the density and uniform- when solid react with carbon or graphite, but ity of the deposit. unlike platinum, palladium or rhodium it is The last decade has seen a considerable unaffected by molten tin, lead, copper or interest in expanding and controlling methods most base metals and can be heated un- of vapour deposition. In particular, the Bat- changed in contact with such refractory telle Memorial Institute and some large metals as tungsten, molybdenum, tantalum, American industrial research laboratories and zirconium. have been active in the field and have claimed In the past, however, although small success in such divergent fields as the pro- iridium crucibles are standard equipment, the duction of tungsten tubes and sheets from difficulties of fabricating iridium have often tungsten fluoride and of titanium oxide pig- restricted its wider use. Moreover, iridium ments from titanium tetrachloride. cannot be electroplated from aqueous solutions, and only limited experimental success Nucleation and Growth has been achieved with the very difficult The present state of CVD technology, as it process of electrodeposition from molten has been termed, was reviewed at a Confer- salts. ence on Chemical Vapour Deposition of More recently, the high melting point of Refractory Metals, Alloys and Compounds iridium and its compatibility with graphite at held at Gatlinburg, Tennessee, in September high temperatures have made it of special last. In general, it would appear that the interest to designers of nuclear reactors and greatest progress has been on the theoretical missile shields. It has become apparent that side, establishing the magnitudc and direction iridium coatings would be of particular value of the factors controlling nucleation and in protecting graphite from oxidation at growth of the deposits. More specifically, two around 20oocC. For this application, iridium papers at the conference were concerned with has the unexpected additional advantage that the choice of the iridium compounds most its thermal expansion is a good match with suitable for the production of iridium coat-

Platinum Metals Rev., 1968, 12, (2) 62-63 62 ings. In the first (I), B. A. Macklin and J. C. three to six times as fast as those common in Withers, of General Technologies Corpora- electrodeposition practice and has exceptional tion, Reston, Virginia, investigated the use of throwing power. Provided that conditions iridium trichloride, iridium tetrachloride, can be established which will ensure removal iridium tribromide, and the expensive iridium of the gaseous products of the reaction it hexafluoride, to produce iridium coatings on seems to offer promise of being able to pro- graphite. duce sounder and more uniform deposits on Iridium trichloride or tetrachloride can hot substrates than can be obtained by any both be decomposed thermally at 800°C or other plating process. reduced with hydrogen or carbon monoxide J. C. C. at a slightly lower temperature, 700°C. The References presence of traces of water also appears to I B. A. Macklin and J. C. Withers, “The Chemical Vapour Deposition of Iridium”, lower the decomposition temperature. It is Proceedings of the Conference on Chemical suggested that an intermediate species of the Vapour Deposition of Refractory Metals, Alloys and Compounds, 1967,161-173 form IrCl,(OH),CO, may be produced. The z J. A. Papke and R. D. Stevenson, “Evaluation best results were obtained when the graphite of Metal-Organic Compounds as Materials for Chemical Vapour Deposition”, ibid. 193-204 substrate was heated to 825’ to 975‘C using a stream of hydrogen mixed with twice to four times its volume of carbon monoxide to carry iridium trichloride vaporised at 150~to 300°C. Palladium and Rhodium : No advantages were observed through the use Russian Reviews of the tetrachloride or bromide, but by using A valuable summary of knowledge con- iridium hexachloride carried in a mixture of cerning palladium has been published re- argon, hydrogen, and carbon monoxide at a cently by the “Nauka” publishing house in low pressure, very fast rates of deposition of Moscow. This is “Splavy Palladiya” (Pal- ladium Alloys), 1967, 214 pp, by E. M. the order of 0.5 mil/hour were achieved on Savitskii, V. P. Polyakova and M. A. Tylkina graphite rods heated to 775°C. Two other of the Institute of Metallurgy named for compounds, iridium acetylacetonate and bis- A. A. Baikov. Part of the information is from cyclopentadienyl iridium hydride, have also original work by these scientists but the been considered, and may have advantages majority of it is a thorough review of international effort, fully referenced. through their freedom from halides. The book is divided into three main sec- tions: the first deals with the occurence, Organometdlic Compounds extraction and fabrication of palladium, with In the second paper (2), J. A. Papke and the physical and mechanical properties of the metal, and with its chemical reactions and R. D. Stevenson, of Ethyl Corporation Re- salts; the second part deals with the properties search Laboratories, Ferndale, Michigan, of the alloys; the third part describes the uses describe experiments with two organometallic of the metal and its alloys. compounds, acetylacetonato (1,5-cycloocta- This comprehensive study is not the first diene) iridium (I) and di-y-methoxybis (1,5- of its type. In 1966 “Nauka” published I. A. Fedorov’s “Rhodium”, which has a similar cyclooctadiene) diiridium (I). With both type of coverage but, since Fedorov works at compounds, amorphous and presumably the Institute of General and Inorganic powdery deposits were formed unless the Chemistry named for N. S. Kurnakov, puts deposition conditions were carefully con- greater emphasis on the chemical compounds trolled, but good deposits of 90 to 95 per cent of the metal. If such reviews are to be extended to the purity were obtainable on copper discs heated remaining platinum metals then a very valu- to 600 to 750cC at pressures of about 0.2 torr. able record of Russian interest in this field Generally speaking, chemical vapour depo- will be available. sition appears capable of deposition rates F. J. S.

Platinum Metals Rev., 1968, 12, (2) 63-63 63 Platinum Sales Problems in the French Revolution JANETY WRITES TO SIR JOSEPH BANKS

By W. A. Smeaton, DSC. University College, London

About 1786 Marc Etienne Janety, Master he became passionately interested in botany, Goldsmith of Paris, began to work in platinum receiving his first lessons for sixpence a at his establishment on the corner of the Rue time from countrywomen who collected de l'Arbre Sec and the Rue Bailleul, near the medicinal herbs. Instead of going on the Louvre. He perfected the arsenic process for Grand Tour of Europe he sailed in 1766 as making it malleable, and produced jewellery, naturalist on an expedition to Labrador and snuff boxes and tableware, as well as a Newfoundland, and from 1768 to 1771 he certain amount of scientific apparatus (I). led the group of scientists accompanying The beginning of the French Revolution left Captain James Cook on his first voyage round him with platinum that he could not sell, and the world (2). in an effort to find a market in England he Banks became a Fellow of the Royal Society wrote on December 13th, 1789, to Sir in 1766, when he was only twenty-three, but Joseph Banks, the President of the Royal this was not unusual at the time, for any man Society. of wealth and social standing was welcomed Though he was educated at both Harrow by the Society, and membership did not and Eton before going to Oxford, Banks did necessarily denote high scientific ability and not adopt the usual way of life of a wealthy experience. In 1778 he was elected President, young English gentleman. While at Eton and he remained in office until his death in

Sir Joseph Banks 1743-1820 As President of the Royal Soriety he dominated the scientijic world for nearly forty-two years. His correspondence shows that he was alaiiays willing to encourage closer relations between British and continental men of science. (From the portrait by Thomas Phillips in the ATational Portrait Gallery)

Platinum Metals Rev., 1968, 12, (2), 64-66 64 The secondpuge ofJanety's letter, dated December 13th, 1789, in which he hopes to enlist the help of Banks in disposing of his stock of platinum. Janety had succeeded in producing malleable platinum, but the beginning of the French Revolution lefi him with metal that he could not sell. Banlcs received the letter ten days later, and his pencilled nate on the side gives the names of those of his friends who wished to buy small quantities of pEatinum (Bycourtesy ofthe Trustees of the British Museum)

1820. A sociable as well as a rich man, Banks proposition, I shall also divulge my process to opened his house and library in Soh0 Square you. I am not sufficiently vain to believe that if you wish to turn your attention to the every morning to men of science from all subject you would need my small amount of countries, and he attended personally to his knowledge, but much patience is required, voluminous correspondence. and this would delay the full utilisation of the substance. Janety's letter of December 13th, 1789, Mr Ingenouse [Ingenhousz], who must now which is now in the Banks papers in the be in London, does me the honour of being British Museum (9,may have been written friendly towards me. As he will doubtless have at the suggestion of Jan Ingenhousz, a the honour of seeing you, he will be able to tell you whether you can have confidence in me. Dutch naturalist who sometimes travelled Here I sell an ounce of platinum for 30 between London and Paris. It can be freely Zizires tournois [about 26 shillings], but to translated as follows : dispose of a fairly large quantity I would make a reduction. Sir, I ask you to excuse the liberty that I take. . . . Without having the honour of being known Janety to you, I nevertheless take the liberty of writing. Master Goldsmith, at the corner of the By the most persistent labour I have succeeded Rue de l'Arbre Sec and the Rue Bailleul. in making platinum malleable. This discovery, Paris, 13 Xbre [December] 1789. from which at any other time I would have A botanist with no knowledge of metallurgy, greatly benefited, is of no advantage to me here, because of circumstances that are known to all Banks was probably unimpressed by Janety's Europe. flattering suggestion that, given time, he Knowing the interest, Sir, that you take in would himself discover how to work platinum. the arts and sciences, I think I may permit myself to offer you a quantity of very malleable He does not seem to have arranged to buy platinum in bars. If you are able to accept my a large amount, for in 1791 Janety was able

Platinum Metals Rev., 1968, 12, (2) 65 to supply over 400 ounces to the Paris equipped observatory. Alexander Dalrymple Academy of Sciences, but he clearly took (1737-1808)~at one time Hydrographer to the some action after receiving the letter, for it East India Company and later Hydrographer bears an endorsement in his own hand which to the Admiralty, drew up many charts of seems to show that six ounces were wanted by oriental waters. Henry Cavendish (1731- Henry Cavendish and three ounces each by I 8 10), famous for his physical and chemical Alexander Dalrymple and Alexander Aubert - researches, was also interested in astro- all Fellows of the Royal Society with whom nomical measurements; in 1790 he showed Banks was in regular contact. how the height of the aurora borealis could be Why did these three men want to buy a few calculated from observations of its position ounces of platinum ? Normally the historian at three different places (6), and in 1797 he refuses to commit himself in print to any described a method of calculating the angular statement unsupported by documentary distance between the moon and a star (7). evidence, but sometimes it is interesting to It may therefore be reasonable to suggest speculate. There is no certain proof that any that 12 ounces of Janety’s platinum was made of them used platinum for a specific purpose, into mirrors by one or other of the excellent and it is of course possible that they acquired instrument makers then working in London, it merely out of curiosity. However, it may but as a precaution this note can be concluded be significant that they were all engaged in with the words of Cavendish: “I wish it to be work where platinum might have been useful. understood, however, that I do not offer In 1786, A. M. Rochon, of the French this as a theory of which I am convinced; Naval Academy at Brest, described how he but only as an hypothesis which has some made a concave mirror for a reflecting tele- probability in it” (6). scope out of platinum, and he said that plane mirrors could also be made, for use in References navigational and astronomical instruments I D. McDonald, A History of Platinum, London, such as octants and sextants (4). At that time 1960,53 2 H. C. Cameron, Sir Joseph Banks, London, the mirrors were generally made of speculum I952 metal - a highly reflecting alloy of tin, copper 3 British Museum, Additional MS. 8097, f.323 and arsenic - but it tarnished easily, and 4 J. Physique, 1798,4,3-15 Rochon found that platinum, either pure or 5 Notices sur les objets envoyts a l’exposition des produits de l’industrie francaise, Paris, alloyed with a little speculum metal, was free 1806, 289 from this defect. His mirrors were evidently 6 Phil. Trans., 1790, 80, 101-5 popular, for he was still making them - 7 Phil. Trans., I797>87, 119-122 both concave and plane - in 1806, when they were shown at the Exhibition of National Industry in Paris (5). Rochon’s paper was not Wollaston’s Classic Lecture published until 1798, but it was originally on Platinum read in 1786at a meeting of the Paris Academy of Sciences, and knowledge of his work must As the first in a series of ‘Metallurgical Classics’ the American Society for Metals soon have reached Banks’ circle. The news has published in the December 1967 issue of that Janety was offering malleable platinum its Transactions a reproduction in facsimile for sale might have interested anyone who of W. H. Wollaston’s Bakerian Lecture of worked with astronomical and navigational 1829 to the Royal Society, ‘On a Method instruments. of Rendering Platina Malleable’. This is accompanied by an extensive commentary on Alexander Aubert (1730-1805),the wealthy Wollaston’s life and work, and on the sig- governor of the London Assurance Company, nificance of his contribution, by Professor was an amateur astronomer with a splendidly Joseph Gurland of Brown University.

Platinum Metals Rev., 1968, 12, (2) 66-66 66 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES low-temperature values of Li are parameters characteristic of each metal. A Thermodynamic Study of the Heat of Ordering CuPt Magnetic Moment of Pd to 150 kG: Limits G. W. GEIKEN, USAEC Rept UCRL-I~~T~,of Exchange Enhancement in Pd 1967, (June), 20 PP S. FONER and E. J. MCNIFF, Ibid., (25), 1438-1441 Heat of formation of Cu-Pt plotted against tem- Magnetic moment of Pd at 42°K is a linear perature at 360-1155'K indicates that the alloy function of magnetic field up to 150 kG. Experi- is disordered as it is heated. Heat of formation ments based on Wohlfarth's analysis of the high- decreases from -4010 cal/g-atom at 360°K to field enhanced paramagnetism of Pd showed the -4140 cal/g-atom at 800°K; increases to limits of exchange enhancement for Pd and an -3070 cal/g-atom at rr" IIOO~K,the critical tem- increase in the minimum field for field-induced perature, and gives a total ordering energy of ferromagnetism in Pd. rg~o*troo cal/g-atom. On the Diffusion of Hydrogen and Deuterium Atomic Structure and Ferromagnetisrn of in Palladium and Pd Alloys. I. Gas-volu- the Regular Platinum-Manganese Alloys metric Measurements S. K. SIDOROV and S. F. DUBININ, Fiz. Metall. G. BOHMHOLDT and E. WICKE, Z. phys. Chem. Metalloved., 1967, 24, (9,859-867 (FranMwt), 1967,56, (3/4), 133-154 Studies of regular zo-50 at.% Mn-Pt alloys Volumetric studies of the solubility of H, and revealed the structures of the cubic and tetragonal D, and of their diffusion rates in Pd and in up to phases and defined their limits of concentration 40% Ag-Pd foils at 20-100°C showed that more precisely. The relation of mean magnetic solubility increases with Ag content at low moment on an atom to alloy composition was pressure but decreases with increasing pressure determined and was explained by the emergence and that diffusion is hindered at higher pressure. of a complex noncollinear magnetic structure The kinetics of this hindrance were evaluated. caused by an antiferromagnetic reaction between D2 had lower activation energy than H,. neighbouring Mn atoms. 11. Electrochemical Methods G. HOLLECK and E. WICKE, Ibid., 155-172 Magnetic Properties of Intermetnllic Com- Electrochemical studies at 0-80°C gave similar pounds between the Lanthanides and Plat- results to the above. Sn-Pd alloys as well as inum Ag-Pd were considered. W. E. WALLACE and Y. G. VLASOV, Inorg. Chern., 1967~6,(IZ), 2216-2219 Viscosity of Alloys on the Basis of Palladium Magnetic properties, particularly in the para- and Silver magnetic region, were measured for LnPt, E. L. DUBININ, 0. A. ESIN, N. A. VATOLIN and A. A. compounds with Crg(MgCu,) structure, where KURANOV, Zh. neorg. Khim., 1967, 12, (II), Ln=Pr, Nd, Gd, Tb, Dy, Ho, or Er. Effective 3156-3158 movement peff for paramagnetic LnPt, is close Composition diagrams were compared with to g1/J(J$r), the value for LnS~i,but, in GdPt,, composition-viscosity relationships at various :~~ffis z(!d1 greater owing to conduction electron temperatures for the systems Pd-Ag, Pd-Cr, polarisation effects. Pt in LnPt, is nonmagnetic. Pd-Si and Ag-Si. Viscosity increases with Low moments in the ferromagnetic state indicate increasing 13 Pd in Pd-Ag alloys at 1600 and incomplete saturation. All the LnPt, compounds 1650°C. Pd-Cr alloys at 1600-1700~Cpossess become ferromagnetic at 4.z°K, except PrPt, minimum viscosity at 63 Pd, corresponding to which may be a Van Vleck paramagnet at 42°K. the eutectic point. Pd-Si alloys possess viscosity maxima at compositions corresponding to PdSi Lorenz Number of Pure Palladium at Low and Pd,Si but, as the temperature rises from Temperatures 1400 to 1600"C, these maxima are smoothed, J. T. SCHRIEMPF, Phys. Rev. Lett., 1967, 19, (19)~ which indicates partial dissociation. 1131-1133 Measurements of the ideal electrical and thermal Investigation of the -4pplication of Spinodal resistivities of Pd at z.5-ig°K yield an ideal Theory to the Palladium-Iridium System Lorenz number Li-0.7 X IO-~ Vz/deg2,which is G. WALTER, USAEC Rept UCRL - 1j470, 1967, independent of temperature below w 5°K. Com- (May), 34 PP parison with data for Re and Ni indicates that No classic spinodal decomposition occurred in

Platinum Metals Rev., 1968, 12, (2), 67-75 67 44 at.<*;Ir-Pd despite long ageing times. Hard- CsC1-type cubic PdMn is stable only at high ness, microstructure and X-ray tests studied temperatures, is homogeneous at -40 --50 existing spinodal theory for the alloy, and ageing at."/, Pd at 685"C,and is paramagnetic, whereas took place well below the predicted critical CuAuI-type tetragonal PdMn is homogeneous temperature. Modified theory is based upon at 45*I to 65.5 at."; Pd according to tem- effects of differing elastic moduli of Ir and Pd, perature, is paramagnetic above 8251 10°K for Ir has five times the modulus of I'd. for -50 at.% Pd to z9o+1oCK for 66 at.?, Pd, and is antiferromagnetic below these temperatures. Striction Susceptibility of an Alloy near the The magnetic cell structure is discussed. Fe,Pd Composition in Weak Magnetic Fields Metallurgical Problems with the Hot Work- z. I. ALIZADE, Izv. Akad. Nauk Turkm. SSR, ing of Rhodium and Iridium Ser. Fiz.-tekh. Khim. Geol. Nauk, 1967, (2), G. REINACHER, 2. Metallkunde, 1967, 58, (IZ), I 13-1 14 831-836, 839-840 Following annealing for I h at 600-8oo0C and The low ductility of Rh and Ir compared to other slow cooling to room temperature, the mag- f.c.c. noble metals makes working of them difficult netostriction susceptibility of 60 wt. "/D Fe-Pd but a review of theory and experiments to elucidate and of Ni was determined and showed maxima their brittle behaviour suggests that purification of 200 and 80 units respectively. 60 wt.% Fe-Pd to 99.999O4 and transformation of the normal has advantages over Permendur-type alloys. polygonal structure to fibrous or single crystal structure leads to enhanced ductility. However, On the Mechanism of the Antiferro- this enhancement is limited by the high shear ferromagnetic Transition in the System of modulus of Rh and Ir. Ordered Fe(Pd,Pt, x)g Alloys V. V. KLYUSHIN, V. V. KELAREV, S. K. SIDOROV, R. Z. Superconductivity and Specific Heat of ABDULOV and R. v. POSPELOVA, Dokl. Akad. Nauk Titanium-Rhodium Alloys SSSR, 1967, 176, (5) 1056-1058 G. DUMMER and E. OFTEDAL, 2. Physik, 1967, Tests confirmed that the antiferromagnetic- 208, (31,238-248 ferromagnetic transition in Fe(Pd,Pt,-,), alloys Specific heats of 0-10 at.":, Rh-Ti alloys were occurs by a complex magnetic structural change measured at 0.9-8°K and transition temperatures involving noncollinear orientation of atomic of hexagonal 0-2 at.?(, Rh-Ti and cubic 3-10 magnetic moments. The cases of FePt, and at.:/, Rh-Ti were determined by calorimetry. FePd, are discussed. Pd and Pt have opposite Both transition temperature and electronic tendencies in the ternary alloys. 0-37 at.:/, Pd specific heat increase with "2; Rh. Influence of alloys show antiferromagnetic FePt, structure, cooling rate on transition temperature was 55-75 at.?, Pd alloys show ferromagnetic FePd, studied. Unlike Hf,Rh and Zr,Rh, Ti,Rh is not structure, and 37-55 at.":, Pd alloys have the superconducting down to 1.2"K. complex structure with noncollinear orientation of the moments of the alloy components. Thermodynamic Properties of Hexagonal Close-packed (hcp) Iron and Iron-Ruthen- Neutron-diffractionStudy of Antiferro-ferro- ium Alloys magnetic Transition in a System of Ordered G. L. STEPAKOFF and L. KAUFMAN, U.S. Rept Fe(Pd,Pt,& Alloys AD 650,151, 1967, (April), 37 pp; Acta Metall., v. v. KELAREV, s. K. SIDOROV, v. v. KLYUSHIN and 1968, 16, (I), 13-22 R. 2. ABDZIZOV, Pbx. Status solidi, 1967, 24, (I), Results of measurements on h.c.p. Fe-Ru alloys 385-390 of specific heat at 60-300°K, and of vapour Studies of the antiferro-ferromagnetic transition pressure of Fe over f.c.c. and h.c.p. Fe-Ru alloys in ordered Fe(Pd,Pt,-,), alloys by analysis of the at 1600°K, were used to describe the lattice dependence of the intensity of the (100) ferro- stability of h.c.p. Fe and the thermodynamic magnetic reflexion on the average magnetic properties of the Fe-Ru system. Earlier theory moment per atom of the alloys showed that it is supported by the vibrational entropy of occurs by a set of complex magnetic structures h.c.p. Fe exceeding that of the b.c.c. form. with a noncollinear orientation of the atomic magnetic moment of the components. A New Structure Type with Octahedral Pairs for Rh,S,, Rh,Se, and IrzSe3 Equiatomic Transition Metal Alloys of E. PARTH-b, D. HOHNKE and P. HULLIGER, Acta Manganese. VI. Structural and Magnetic Cryst., 1967, 23, (9, 832-840 Properties of Pd-Mn Phases Rh& has a space group Pbcn(D2,11) and lattice A. KJEKSHUS, R. WLLERUD, A. F. ANDRESEN and constants a=8.462, b =5.985, c=6.1388. The w. B. PEARSON, Phil. Mag., 1967, 16, (143), Rh atoms possess octahedral coordination. Four 1063-1083 Rh atoms surround each S atom at the vertices of Studies of 40-66 at.:, Pd-Mn alloys show that a distorted tetrahedron. Rh,S, is isotypical with

Platinum Metals Rev., 1968, 12, (2) 68 Rh,Se, and Ir,S,. A complete range of solid showed that, whereas Rh,O, is stable at I atm.O,, solubility exists between Rh,S, and Rh,Se,. Rhoz is the stable phase at slightly higher pressures. Rho, has rutile structure with Decomposition Pressures and Enthalpies of a=4.489, C-3.0908. In the Pt-0 system, Formation of Some Transition Metal Diar- hexagonal a-PtO, appears stable at lower tem- senides and Diselenides peratures and higher 0, pressures while P-PtO, J. J. MURRAY and R. D. HEYDING, Can.J. Chem., is formed at 65o-75o0C, 2000 atm. 0,. Pt,O, 1967,453 (221,2675-2687 is formed at 68o-78o0C, 20-500 atm. and has Studies of the decomposition pressures of PtAs,, cubic NaPt,O, structure with a-5.5858 and OsAs,, Ruse,, and OsSe, as a function of tem- Na positions vacant. An intermediate phase of perature by the torsion effusion technique, and stoichiometry between PtO, and Pt,O, has also of the heats and entropies of decomposition gave been detected. The a-Pt0,- >/3-PtO, transition is unusual in involving the break up of peroxide-type as heats of formation, at 298"K, -42.0-L-3.5, 0-0 bonds. - 18.5f2.0, -3z.5f5.0, -4.qf3.5 kcal/mole respectively. Phase relationships of Pt-As, 0s-As, Ru-Se, and 0s-Se at 850-1250°C were studied. Synthesis of Thallium Platinate at High Pressure Constitution Diagrams of Plutonium with H. R. HOEKSTRA and s. SIEGEL, Znmg. Chem., Metals of Groups IIIA, IVA, VIII and IB 1968, 7, (0,141-145 V. I. KUTAITSEQ, N. T. CHEBOTAREV, M. A. AhJRIANOV, Tl,Pt,O,, prepared by reacting T1,0, with V. N. KONEV, I. G. LEBEDEV, V. I. BAGROVA, A. V. Pt or PtO, at IOOO~C,40 kbar, is a brown solid REZNOSIKOVA, A. A. KRUGLOV, P. N. PETROV and insoluble in aqua regia and thermally stable to I E. s. SMOTRITSKAYA, Atomnaya Energiya, 1967, 750°C at atm. The f.c.c. lattice has a=10.132+ o.oo&. Measured density is 11.12 g/cm3. Pt-0 23, (61, 5 11-520 and TI-0 bond lengths and structure are dis- Sixteen constitution diagrams of Pu alloys are col- cussed. The infrared spectrum has maxima at lected in this article and include those of Pu-Ir, 684, 562, 449 and 363 cm-l. Pu-Pd, Pu-Pt, Pu-Rh, and Pu-Ru. The Dissociation Energies of the Molecules CHEMICAL COMPOUNDS PtC and RhC A. VANDER AUWERA-MAHIEU and J. DROWART, Semiconducting dg Metal Complexes Found Chem. phys. Lett., 1967, I, (8), 311-313 Chem. engng News, 1967,45, (52, Dec. 11), 50-51 Mass spectrometric studies of the Pt-C and Rh-C Studies of transition metal complexes in which systems showed that the dissociation energies the metal has planar d8 configuration showed of the gaseous molecules of PtC and RhC are that single crystals of the groups of compounds respectively 145.3+ r.5 and 138.55 1.5 kcal/mole. [Ir(CO),acac] and [Rh(CO),acac], [Pt(NH3),l2+ [PtCL,I2- and [Pt(NH,),j2+[PdCI4],- are par- Structural Investigations on Rhodium ticularly suitable for electrical measurements. Halides Workers at Research Triangle Institute, Univer- K. BRODERSEN, G. THIBLE and I. RECKE, J. less- sity of North Carolina and Manchester University common Metals, 1968, 14, (I), I5X-152 have studied the structures and physical properties X-ray, magnetic and thermal studies on RhBr, of these compounds, which appear to be in- and RhI, showed that their monoclinic crystals trinsic semiconductors, leading to intermetallic have lattice structures: RhBr,, a -6.27 $0.01, polymers capable of being tailored to specific b-10.85 &o.c1,c-6.35+0.01&j3-109.0";Rh1, physical and electrical requirements. a =6.77*0.02, b == 11.72*0.02, c=6.83 *0.02A, P=109.3". Atomic positions and distances were Mass Spectrometric-Knudsen Cell Study of recorded. the Gaseous Oxides of Platinum J. H. NORMAN, H. G. STALEY and W. E. BELL, The Formation of Complexes of Molecular 3. phys. Chem., 1967, 71, (II), 3686-3689 Nitrogen with Compounds of Ruthenium These studies confirmed the species PtO,(g) and and Osmium established the existence of PtO(g). Thermo- YU. G. BOROD'KO, A. K. SHILOVA and A. E. SHILOV, dynamic data for their formation are recorded Dokl. Akad. Nauk SSSR, 1967, 176, (6), and enthalpy data for the vaporisation of Pt. 1297-1299 Infrared spectral studies showed that N, is Preliminary Investigations in the Systems coordinated to Ru and 0s atoms during the Au-0, Rh-0 and Pt-0 at High Oxygen reductions of RuCI, and RuOHCl, in tetra- Pressures hydrofuran by Zn amalgam, C,H,MgBr, or 0. MULLER and R. ROY, Extended Abstr., 1967 Fall C,H,MgBr and of OsOHCl, in similar con- Mtg, Basic Sci. Diet., Am. Ceram Sac., 5-B-67F ditions. The N, complexes are similar to Studies on the systems at up to 90oCC,3000 atm.0, [M(NH,),N,]X,, where M -Ru, 0s; X=Rr-,

Platinum Metals Rev., 1968, 12, (2) 69 I-, BF,-, produced by the action of N,H, solutions over Pt-Ru and platinised Pt electrodes hydrates on RuCl,, etc. The stability and bonding and results were plotted and compared. Graphs of these nitrogenyl complexes have been studied demonstrate the effects of the rate of electro- using I5N labelling. oxidation to the potential of the rate of oxidation to the concentration of CH,OH, of the surface Ruthenium Complexes Containing Molecular coverage of the electrodes to the potential, and Nitrogen also thc effect of stationary polarisation. A. D. ALLEN, F. BOTTOMLEY, R. 0. HARRIS, V. P. REINSALU and c. v. SENOFF, J Am. Chem. Soc., Comparison of the Properties of Compact 1967, 89, (221, 5595-5599 and Dispersed Platinum-Ruthenium Elec- [Ru(NH,),N,] 2+ complexes were prepared by the trodes action of NaHl hydrate on Ru(II1) or Ru(1V) Ibid., 1968, 4, (I), 111-114 salts, or by the action of azide ion on aquo- Further work is recorded on 10,20, 30 and 40:; pentaammineruthenium (I11). Various Ru(I I) Ru-Pt electrodes, which were tested by plotting and Ru(1II) ammine complexes could be derived. potentiostatic anodic and cathodic curves for The reported properties of [Ru(NH,)~NJ,- salts each in the compact and dispersed forms in are discussed. H,SO, solutions.

The Formation of Rn(NH,),N,2 + in Aqueous Solution by Direct Action of Molecular ELECTRODEPOSITION AND Nitrogen SURFACE COATINGS D, E. HARRISON and H. TAUBE, Ibid., 5706-5707 The preparation of [Ru(NH,),N,] is possible Protecting Refractory Metal at High Tem- between N, and [Ru(NH3),H,0l2 in aqueous perature solution at room temperature. R. E. ENGDAHL, J, R. BEDELL and C. E. KROHA, Muter. Protection, 1967, 6, (IO), 49-51 A system is described which offers 2-5 h oxidation ELECTROCHEMISTRY protection for W at 2000°C in air. The refractory metal is electroplated with Ir and sprayed with The Oxygen Electrode on Noble Metals ZrO, as a surface coating. J. P. HOARE, Advan. Electrochem. electrochem. Engng, 1967, 6, 201-288 Electrodeposition of Iridium from Fused A review of the reactions between 0, and elec- Sodium Cyanide and Aqueons Electrolytes. trodes of Pt, Au, Pd, Rh, Ir and various alloys. A Preliminary Study (327 references.) R. L. ANDREWS, C. B. KENAHAN and D. SCHLAIN, U.S. Bur. Mines RIyo23, 1967, (Sept.), 12 pp Investigation of the Adsorption of Hydrogen on Platinum Metals at Various Temperatures Metals such as W and Mo, which oxidise rapidly at high temperatures, can be protected by plating R. v. MARVET and 0. A. PETRII, Eleknokhimba, adherent and coherent deposits of Ir up to 15 1967,3, (12), 1445-1449 mils thick from a fused NaCN bath at 600°C~ Adsorption of H, on Raney 0s and Ir electrodes 10--100 mA/cm*. Pure Ir protects Mo up to surfaced with Rh and Ru was measured and IOOO"C in flowing air but above this temperature analysed by charging curves at 20-95'C using the volatility of its oxide prevents its use. Coatings IN H,SO, and IN NaOH electrolytes. up to 4 mils thick of Ir-Pt, Ir-Pd and Ir-Rh alloys may offer protection above 100o"C. The Electrochemical Activation of Platinum Aqueous electrolytes are unsuitable as they lead Electrodes to low deposition rates and cracking of heavy s. D. JAMES, J. Electrochem. SOC., 1967, 114, deposits. (II), 1113-1119 A review of mechanisms for the electrochemical activation of Pt electrodes led to experiments LABORATORY APPARATUS which showed that impurity desorption is the AND TECHNIQUE most important result of conventional brief activation. A second type of activation may How to Grow King Size Single Crystal YIGs exist, produced by prolonged preoxidation and J. R. CHABRIA, Ceram. Znd., 1967, 89, (5), 52-54 possessing very stable activity. (57 references.) Single crystals of Y,Fe,O,,, Y3Ga5012 and Y,A1,Fe5,Ol, are grown in a 3.5% Rh-Pt On the Mechanism of Methanol Oxidation on crucible by prolonged and carefully controlled a Platinum-Ruthenium Electrode heating at 2500°C. High purity oxides are the v. s. ENTINA and 0. A. PETRII, Elektrokhimiya, starting materials. The crucible is also of the 1967, 3, (IO), 1237-1240 highest purity to avoid chemical interaction and CH,OH was oxidised in both H,SO, and KOH contamination of the crystals.

Platinum Metals Rev., 1968, 12, (2) 70 Apparatus for Making Sharp Photographic Catalytic Properties of the Pt +Cu System Images with X-Rays Ibid., 353-357 H. F. SHERWOOD, Rev. iri. Insiram., 1967, 38, The activity of Pt-Cu metallic catalysts for (II), 1619-1622 CGHshydrogenation decreases with increasing The jaws of the knife-edge slit for making sharp Cu content until it is zero at 75 at.":, Cu because photographic images with X-rays are fabricated d levels in Pt are filled by electrons from Cu. from zoo/, Ir-Pt. Their manufacture and mount- ing, and the operation of the apparatus, are Study of the Adsorption and Energetic described. Properties of Metallic Catalysts. I. Specific Comparison of Tips, Thin Wires and Sharp Surface of Catalysts A. A. BALANDIN, V. I. SPITSYN, L. I. RARSOVA, A. E. as Metal Edges Emitters for Field Ionisation AGRONOMOV and N. P. DOBROSEL'SKAYA, 211. Mass Spectrometry fiz.Khim., 1967, 41, (IO), 2623-2628 H. D. BECKEY, H. KRONE and F. w. ROELLGEN, Specific surfaces of Pt, Pd, Rh and Ru blacks J. sci. Znstrum., J. Phys. E., 1968, I, (2), 118-120 are compared by the BET method with C,H, and Although tips give twice the field strength of Kr adsorption, and by the electrochemical wires, the latter are preferable for analytical methods from the capacity of the double layer purposes because of their larger emitter area region and the amount of H, adsorbed. The and give more than ten times the field strength double layer region method gives higher results of a sharp metal edge. To reduce the breakages than the H, adsorption method. There is a of wire by the mechanical forces exerted by the reciprocal relation between the mean size of the high electrical field, 2.5 pm Pt wires were crystallites in the blacks and the specific surface. strengthened by whisker growing. Uniform quality Wollaston wire of high tensile strength The Retention of Hydrogen by Supported is necessary. A compensating electrode reduces the mechanical forces on the wire. The length Metal Catalysts G. F. TAYLOR, THOMSON and G. WEBB, of etched Wollaston wire has been reduced to s. J. .7. Catalysis, 1967, 8, (4), 388-390 I. 5-2 .o mm . He treatment of Al,O,-supported catalysts does not remove all the reactive HPfrom the surface. HETEROGENEOUS CATALYSIS Less remains on Pt/Al,O, than on Pd/A1,0, or Rh/Al,O, although the total amount of 13, Noble Metal Catalysts in the Fine Chemicals retained on Pt/A1,0, is similar to that on Rh/A1,0, Industry and greater than that on Pd/Al,O,. There is less self-hydrogenation of C,H, on PdjAl,O, than on G. c. BOND, Chem. and Znd., 1967, (48, Dec. 21, 2018-2025 Rh/Al,@,. A review of the uses of Pt metals in heterogeneous and homogeneous catalysis. Topics discussed The Study of Catalysts and Adsorbents by include the choices of metal, support, and the Thermal Desorption Method. 11. Plati- conditions of reaction. Other topics include nised Alumina evaluation of catalysts, the trickle column reactor, T. s. USTINOVA, A. P. FILONENKO and I. v. KRYLOVA, and the economics of using these catalysts. (17 Zh. fiz. Khim., 1967, 41,(11), 294X-2943. references.) There exists for PtjA1,0, a direct connection between the amount of adsorbed gas and the Catalytic Conversions of Hydrocarbons intensity of exoelectronic enlission. Maxima on B. A. KAZANSKII, Kinet. Kataliz, 1967, 8, (5), curves of temperature against emission, for 977-993 Pt/Al,O,, depend on the existence of centres A review of the hydrogenolysis of C,-C,, C1, on the A1,03 surface which are activated by and CI5 cyclic hydrocarbons on Pt metal and Ni adsorption of H,O and 0,. Tests were carried catalysts, and of the dehydrocyclisation of out in the range 20-300c^C. paraffins to form aromatic and bicyclic compounds using Pt, Pd and Ni catalysts. 50 years Investigation of the State of Platinum in of work by KAZANSKII and his colleagues is Platinum Catalysts for Dehydrocyclisation reported. (69 references.) by the Extraction Method N. R. BURSIAN, S. B. KOGAN and Z. A. DAVYDOVA, Catalytic Properties of the Pt +Ag System Kinet. Kataliz, 1967, 8, (6), 1283-1289 M. A. INDZHIKYAN, Arm. Khim. Zh., 1967, 20, (5), Pt dehydrocyclisation catalysts treated by air 349-352 at 20-8oo0C and by Hz at z5o-55oCC were The activity of Pt-Ag metallic catalysts for studied by extraction methods, which showed C,H, hydrogenation decreases with increasing that, in reduced Pt/Al,O,, the Pt bonded chemi- Ag content until it is zero at 25 at.?:, Ag because cally to C1 and Also, has specific activity for the d levels in Pt are filled by electrons from Ag. formation and closing of ring compounds but

Platinum Metals Rev., 1968, 12, (2) 71 does not catalyse the dehydrogenation of cyclo- Metal Sulphide Catalysts for Hydrogenation hexane. of Halonitrobenzenes to Haloanilines H. GREENFIELD and F. S. DOVELL,J. org. Chem., Investigation of the Selectivity of Platinum 1967,32, (II), 3670-3671 Catalysts on Various Supports in the Hydro- Hydrogenations of chloro- and bromo-substituted genolysis of Methylcyclopentane nitrobenzenes over metal sulphide catalysts V. V. VORONIN, KH. M. MINACHEV and I. I. showed that Pt sulphide is probab!y best because LEVITSKII, IZV.Akad. Nazrk SSSR, Ser. Khim., of its good selectivity and commercial availability. 1967, (12), 2616-2619 SuIphides of Ni and I'd are satisfactory for H, treatment up to 550°C of Pt/zeolite, Pt/SiO, reduction of chloronitro- but not bromonitro- and PtiC catalysts does not alter their selectivity aromatic compounds. Pt sulphide was also for hydrogenation of methylcyclopentane. The suitable for quantitative hydrogenation of 2,s- C, ring is split away from the side chain. Activity dichloronitrobenzene to 2,5-dichloroaniline. is either decreased or remains constant. Similar p-Nitrochlorobenzene reacted with H, and treatment of Pt/Al,O, causes a sharp increase in CH,COCH, over Rh sulphide to form N-iso- activity and a change in selectivity so that the C, propyl-p-chloroaniline. ring is split at the bond adjacent to the CH, group. The change is caused by changes in the Liquid-phase Hydrogenation of Organic A1,0,, e.g. as a result of dehydration. Compounds on Mixed Ruthenium Catalysts. Ruthenium-Platinum Catalysts Chemisorption and Catalysis on Platinised D. v. SOKOL'SKII, K. K. DZHARDAMALIEVA, A. G. Silica. 111. Chemisorption of Oxygen SARMURZINA and T. TONMANOV, Dokl. Akad. V. S. BORONIN, V. S. NIKULINA and 0. M. POLTORAK, Nauk SSSR, 1967, 176, (9,1093-1095 Zh.fiz. Khim., 1967, 41, (lo), 2668-2674 Tests showed that two maxima occur on each Studies at 2O-47O0C, 10-3-I.5 mm Hg on the graph of catalyst activity against alloy composition sorption of 0, on Pt/SiO, with various amounts for liquid-phase hydrogenations of a number of of Pt form the basis for a method of measuring organic compounds on Ru-Pt catalysts. These the Pt surface by the chemisorption of 02. maxima are related to the nature of the reduced compound, and to the solvent used in the case Vapour-phase Hydrogenation of Benzene on of the maximum at the higher Ru concentration. Pt/Asbestos Catalyst with Control of The surface area decreases with increasing Ru Catalyst Potential content. N. I. UTEGULOV, v. s. DRUZ' and D. v. SOKOL'SKII, Zbid., (12), 3128-3131 Catalytic Reduction of Waste Nitrogen The possibility of measuring the catalyst potential Oxides during vapour-phase hydrogenation of C6H6 s. JAROS and J. diik, Chem. Prwnsyl, 1967, 17, on Pt/asbestos was studied. Equilibrium and (II), 581-586 stationary catalyst potentials, and catalyst Pt/Al,Os and Pd/A1,0, pellet or bead catalysts activity, depend on catalyst pretreatment and have the greatest activity for reduction of perhaps on processes of exchange adsoiption on nitrogen oxides, according to laboratory tests. the support. The limiting factor is activation and Gases with low ignition and operating tempera- reactivation of H, weakly bonded to the support. tures are most suitable for reduction of the oxides. The apparent order of the reaction depends on High temperature affects the catalyst adversely; the gaseous phase ratio C6H6: H,. its life is reduced and more catalyst is needed because of the lower space velocity. Results of Effect of Noble Metal Concentration upon this work form the basis for a new reactor the Isomerisation Activity of Molecular design. Sieve Zeolite Catalysts On the Catalytic Properties of Platinum M. A. LANEWALA, P. E. PICKERT and A. P. BOTTON, J. Catalysis, 1967~9,(I), 95-97 Group Metals and their Alloys Containing Tests on isomerisation of N-C,H,,showed that Palladium the optimum catalyst concentlations for methyl- R. G. DAVLESUPOVA and D. v. SOKOL'SKII, Kinet. pentane formation were 0.05 wt.yn Pd or 0.10 Kutaliz, 1967, 8, (6), 1378-1381 wt.% Pt, and for dimethylbutane formation were A study of the activity of the Pt group metals, 0.25 wt.04 Pd and -0.40 wt.7,; Pt. The metals Re, and Pd,Me-type alloys as catalysts for the are equally effective when compared on an atomic reduction of dimethylethynylcarbinol in H,O, wt.% basis. Results suggest that ion exchange 960:" C,H,OH and 0.1 N KOH in H,O or incorporation of noble metals on to zeolites C,H,OH at 10-40°C showed that the alloys gives high, almost atomic, dispersion. The possess more activity than Raney catalysts of the Pt(NH,),Cl,.H,O and Pd(NH,)&12 salts intro- individual elements. Raney Ru, Os, Re and Ir duced Pt(NH,),,+ and Pd(NH,)42+ions into the were completely inactive. The rate of the zeolite and calcining deposited the metal atoms. process was lower in alkaline solution. In the

Platinum Metals Rev., 1968, 12, (2) 72 alcoholic alkaline solution the process was Polymethylene Synthesis from Carbon Mon- checked at the semireduction stage. oxide and Hydrogen on Ruthenium Catalysts. Part 11. On the Influence of Physical Factors The Effect of Sulphur-organic Compounds on the Formation of High Molecular Weight on the Purification of Gases from Nitric Products Oxide and Acetylene by the Method of H. PICHLER and w. BURGERT, Brennstoff-chem., Catalytic Hydrogenation 1968, 49, (11, 5-9 T. A. SEMENOVA, M. I. MARKINA, T. N. LILEIKINA, Discontinuous synthesis for paraffin formation at N. B. GORBACHEVA and A. v. GERASIMOVA,K~~~.various temperatures and pressures of the re- Promyshlennost’, 1967~43,(IO), 1o-r3 acting gases showed that stirrers of special shape Thiophene, ethylmercaptan and CS, all reduce increased the exchange of gas at the double bond. the degree of hydrogenation of NO over Pd-Ru At 1000-2500~C, this exchange was pressure- catalysts. CS, has the greatest deactivation independent, unlike the molecular weight of effect. CS, also reduces the activity of Pd polymethylene. At 200,000. of hydrogenation of C,H, is reduced far more than that of C,H,, hence Pd catalyst is more selective. Mercaptans do not form between HOMOGENEOUS CATALYSIS H,S and C,H, or C,H, in N, but ethylmercaptan is formed in a H, atmosphere as the product of The Reactivity of Pt(I1) Complexes in the reaction between C,H, and CzH4 with CS, Oxidation of Carbon Monoxide in Aqueous formed by hydrogenation of S-organic compounds. Solutions N. K. EREMENKO, K. I. MATVEEV and L. N. Catalytic Conversions of Alkyl Derivatives of RACHKOVSKAYA, Kinet. Kataliz, 1967, 8, (6), the Benzene and Naphthalene Series under 1246-1251 Pressure of Hydrogen in a Flowing System K,PtX, complexes in the oxidation of CO N. G. BEKAURI, N.I. SHUIKINand T. S. SHAKARASHVILI, show decreasing reactivity in the order: Kinet. Kataliz, 1967, 8, (6), 1275-1282 PtI,2- > PtBr,,- > Pt(CNS)4z-G PtCl,,- Studies of dehydrocyclisations of N-octyl and >Pt(N0,),2-> Pt(NH,),2+ >Pt(CN),,-. dodecylbenzene, and of 2-N-butyl and 2-N-octyl- naphthalene, in the presence of 0.5% Pd/clay Application of the Mobile Equilibrium of or of activated clay at 45Ooc, 30 atm. Hz in a Isomerisation to the Polymerisation of Ole fin flowing system showed that polycyclic aromatic Mixtures. I. Prototropic Displacement by hydrocarbons with high capacity for luminescence Salts and Complexes of Noble Metals are formed. The yield rose as the molecular N. H. PHUNG, Y. CHAUVIN and G. LEFEBVRE, Bull. weight of the aromatic ring increased. SOL.chim. Fr., 1967, (10), 3618-3626 The Catalytic Activity of Rhodium in Rela- The addition of TiCl, to PdC1, produced a new catalytic system more active than PdCl, alone. tion to its State of Dispersion It encouraged different stoichiometry in the D. J. c. YATES and J. H. SINFELT, J. Catalysis, polymer. 19671 8, (4), 348-358 Studies of the catalytic activity of Rh for hydro- Olefin Oxidation with Palladium(I1) Cata- genolysis of C,H,, using Rh/SiO, and Rh as lyst in Solution catalysts, showed that the specific catalytic A. AGUIL~, Advan. organometall. Chem., 1967, activities of unsupported Rh and of severely calcined Rh/SiO, are much lower than those of 5,321-352 well-dispersed Rh crystallites 40 a or smaller. A review of process for the oxidation of C,H, and Catalytic activity ultimately falls again when the other olefins using Pd(1I) catalysts in aqueous dispersion is extremely fine. and non-aqueous solvents. The Pd-olefin complexes are considered as reaction intermediates and their structures and mechanisms are Ruthenium Catalysts for the Liquid-phase examined. (85 references.) Hydrogenation of Sulpholene N. M. SINITSYN, A. v. MASHKINA and YU. A. The Catalytic Activity of x-Complexes of SAVOSTIN, Neftekhimiya, 1967, 7, (5), 785-789 Straight-chain Olefins with Palladium Chlo- Ru catalysts, with high activity for liquid-phase hydrogenation of sulpholene and sulpholane, ride are more effective when prepared by applying G. PREGAGLIA, M. DONATI and F. CONTI, Chim. potassium ruthenate to C than RuCl, to the e Ind., ~967~49,(12), r277-1283 support. 5:); Ru catalysts were tested on a The x-complexes were synthesised by direct number of supports and are shown to enhance interaction of PdC1, with straight-chain olefins the activity of Pt/Al,O,. or by exchange between (C,H,,PdCl,), x-com-

Platinum Metals Rev., 1968, 12, (2) 73 plexes and other olefins. Exchange with 1,5- allenes to a regular structure were combinations cyclooctadiene displaces the coordinated oleiin of Rh(1) with appropriate donor ligands, e.g. with unchanged configuration. When PdCI, [RhCI(CO),],-2PPh3, Almost quantitative poly- dissolves in u-olefins the free olefin isomerises merisation is possible in 95y0 CzHsOHat 6070°C until the trans: cis ratio is greater than one, a in <5h. Studies of the reaction mechanism result due perhaps to different rates of reaction suggest insertion of x-coordinated allene monomer of the u-olefin with the cis- and tram-Tc-com- to the asymmetric z-allyl- or a---allyl-metal plexes. An intramolecular mechanism for bonding. rearrangement of the --complex of an a-olefin is inferred from the lack of isomerisation of the olefin The Catalytic Hydrogenation and Deutera- while entering or leaving the complex. tion of Steroids in Homogeneous Phase W. VOELTER and c. DJERASSI, Chem. Ber., 1968, Organic Syntheses by Means of Noble Metal 101, (I), 58-68 Compounds. XXXIII. Carbonylation of Azu- Olefin reduction by (PPh,),RhCI suggested a benzene-palladium Chloride Complexes new method for specific hydrogenation of double H. TAKAHASHI and J. TSUJI, J. organometall. bonds in steroids. The effects of the solvent, the Chern., 1967, 10, (31, 511-s~ pressure and the rate of reaction on reactions at The preparation and carbonylation of PdC1, the C=C double bonds of steroids were studied. complexes of several symmetrically and asym- D, labelling depended on the solvent and on the metrically substituted azobenzenes took place catalyst concentration. smoothly under mild conditions. Study of their structure indicared that PdCI, formed a a bond FUEL CELLS with the benzene ring by electrophilic sub- stitution, substitutes exerting inductive influences. An Intermediate Temperature Fuel Cell. The carbonylation mechanism was not clear. Operation on Hydrogen and Oxygen. Opera- tion on Dilute Hydrogen, Carbonaceous Polymerisation by Transition Metal Deri- Fuels, and Dilute Oxygen vatives. IV. Investigations on the Mechanism w. B. MATHER and A. N. WEBB, Id. engng Chem., of Butadiene Polymerisation by Rhodium Process Design Dev., 1968,7, (I), 11-15, 15-21 salts Fuel cells with BPO,-H,PO, paste electrolyte R. DAUBY, F. DAWANS and P. TEYSSI~,J. polymer and Pt'Ta or Pt,C electrodes were operated Sci., Part C, polymer Symposia, 1967, (16), continuously on H, and 0, at 200°C for up to 3 1989-2000 months and produced up to ILO mw/cm2, although 65-70 mw/cm2 was more usual. The Tests on the polymerisation of butadiene using thermally stable electrolyte rejects CO,, has high RhC1, as catalyst showed the effects of catalyst ionic conductivity and good mechanical properties concentration, different activation energies, re- and needs no regeneration with H,O. PtITa quirements in emulsifier structure and concentration, and the effects of other diolefins. Mixtures of gauze electrodes were 207b superior to Ptiporous C. Similar cells operated on dilute H,, steam- butadiene and piperylene were also polymerised. reformed CH,OH and shifted CO gave 70-90:; the performance of those on pure HB. Carbon- Rhodium Complexes for Allene Polymerisa- aceous fuels including hydrocarbons led to lower tion in Polar Media efficiency due to high activation polarisation, s. OTSUKA and A. NAKAMURA, J. polymer Sci., partly caused by oxidation of Pt anode. When Part B, polymer L,ett., 1967, 5, (IO), 973-975 operated on steam-reformed CH,OH and air, the Polyallenes are produced in high yield at cell produced 45 mw/cmz. relatively low temperatures and pressures in polar solvents using as catalysts the Rh complexes The Effect of Preoxidation and Meniscus IRhC1(CO)zI,, [RhCKCzH3zI,, [RhCI(PPh&l Shape on the Hydrogen-Platinum Anode of and [RhCI(PPh,),],. The rate of polymerisation a Molten-carbonate Fuel Cell is faster with [RhBr(CO),], than with J. T. COBB and L. F. ALLBRIGHT, J. Electrochem. [RhCI(CO),],, and [Rhacac(C,H,),] is also SOL.,1968, 115, (I), 2-6 effective in C,H,OH as solvent. Ru complexes, Studies at 723°K of a H,-0, fuel cell with Pt such as RuCl,.nH,O, RuCl,-PPh, and electrodes and molten electrolyte, composed of a RuCI,(PPh,),, catalyse allene polymerisation eutectic mixture of Li, K and Na carbonates, similarly but Pd complexes, such as Pd(PPh& showed that smooth Pt anodes are activated by and PdCl,-SnCl,, are ineffective. preoxidation to give bigger currents. Contact angle of unactivated Pt with the eutectic is 90", Polymerisation of Allene with Rhodium of activated Pt is 0' and decreases with deactiva- Complexes tion. H, diffuses to the reaction site along the S. OTSUKA, A. NAKAMURA and K. TANI, Kogyo Pt/molten carbonate interface and/or diffusion Kagaku Zasshi, 1967, 70, (II), 2007-201f, AIZI through the Pt but not appreciably through the Most active catalysts for polymerisation of molten carbonate film above the meniscus.

Platinum Metals Rev., 1968, 12, (2) 74 CHEMICAL TECHNOLOGY Experience in Industrial Determination of Glass Viscosity at a Tank Furnace Feeder The Process of Activated Sintering of M. V. OKHOTIN, E. I. RAEVSKAYA and A. I. TUZIKOV, Tungsten with Palladium Additives Steklo Keram., 1967, 24, (iz), 16-18 G. V. SAMSONOV and V. I. YAKOVLEV, Pmosh. Cylindrical Pt electrodes of diameter 10mm were Metall., 1967~7,(7), 45-49 placed 40 mm apart in the furnace and 20 mm o.og-r.o0,6 amounts of Pd in the form of aqueous deep in the molten glass. The viscosity of the PdClz solution were added to 75p W powder glass was calculated from the resistance measured and, after mixing, drying, sieving, reduction, between the electrodes. A Pt: Rh-Pt thermo- and sieving, were compressed and sintered in couple measured the temperature, whose fluaua- H,, a process which gave the highest density of tions are matched by fluctuations of viscosity. >17g/cmS at o.zo/, Pd and 1600’C. These samples had microhardness <300 kg!mm2 and compressive strength ro5 kg/mm2. The activating ELECTRICAL AND effect of Pd occurred by transfer of nonlocalised ELECTRONIC ENGINEERING electrons from Pd to W with an accompanying decrease in free energy and increase of statistical Fluorescence of Rhodium-activated Aldn- weight of the stable electron configurations of the ium Oxide Pd and W atoms. G. BLASSE and A. BRIL, J. Electrochem. .sac., 1967, 114, (IZ), 1306-1307 Fluorescence emission of 0.1-1.0 Rh- GLASS TECHNOLOGY activated A1,0, consists of a broad band in the Creep of Alloys of Platinum with Rhodium far red at 680 nm, probably due to the spin- at Temperatures 1350-1500°C forbidden 3TIg+1Ag,g transition but other Rh3+-activated aluminates had very weak I. I. NOVIKOV, S. NOVIK, E. I. RYTVIN, S. S. P. p hotoluminescence. PRAPOR and E. N. LOVINSKAYA, Ivz. Vysshikh Ucheb. Zaved., Tsvetnaya Metall., i967, (4), 132-1 35 TEMPERATURE Strip samples of 7, 10 and i5<;; Rh-Pt were examined for creep by metallography at 1350, MEASUREMENT 1400 and 15ooT and at 0.2, 0.15 and 1.3 kg/mm2 for up to 5 h. Graphs of test results Apparatus for Measuring the Hall Effect of show that creep increases with temperature. Low-mobility Samples at High Temperatures Creep was most intense at x5oo0C, 1.3 kgkmnz N. z. LUPU, N. M. TALLAN and D. s. TANNHAUSER, and 7 and Ioo& Rh-Pt alloys failed after 90 and Rev. sci. Znstrum., 1967, 38, (II), 1658-1661 240 min. in these conditions. No othe: failure A thermocouple is a more desirable sensor than a occurred at other temperatures and loadings resistance thermometer for high stability of the for any alloy. Creep decreases with greater Rh sample temperature and a Pallador I thermo- content. IOOI~ Rh-Pt is recommended for glass- couple with output BopVldeg C was found to be melting as IS”, Rh-Pt is more expensive but not suitable. The double a c measuring method uses much stronger. a c at 510 Hz with a 2 Hz magnetic field.

NEW PATENTS

METALS AND ALLOYS Treatment of Palladium and Palladium-base Alloys Tungsten-base Alloys JOHNSON, MATTHEY & CO. LTD. MALLORY METALLURGICAL PRODUCTS LTD. British Patent 1,091,051 British Patent 1,090,561 When placed under conditions of stress these Tungsten alloys with improved tensile strength materials tend to give “discontinuous yield” due and ductility are produced by incorporating to the presence of Si in the material. This 0.5-10 wt. :& Ru. Small amounts of Mo, Ni and defect is now prevented by adding an alloying Fe give another range of alloys of high strength element which more readily combines with Si and ductility. than Pd, e.g. Ca, Ba, Sr, Ti, Zr, etc.

Platinum Metals Rev., 1968, 12, (2), 75-80 75 Alloys for Pen-point Manufacture culated as Pt(OH),, o.I-lg/l N,H,, enough w. 6. HERAEUS G.m.b.H. British Patent 1,097,815 soluble alkali metal hydroxide to give a pH of The pen-points, specifically ball pen-points, at least 8 and 0-1 mole of a complexing stabiliser are made from alloys of 0-50~~Os, 20-45'0 Ir, containing a trivalent N atom, e.g. EDTA. Pt 5-20°r, Ru, ~-25:~~Pt, Pd andior Rh and 0-1500 alloys with Ir and Ru can also be deposited by of a Group VIII base metal or metals, such as Co. introducing NH, salts of the alloying metals, such as (NH,),RhCl,. Dental Gold Alloy Platinum-Iron Diffusion Alloys J. F. J~LENKO& co. INC. U.S.Patent 3,340,050 E. I. DU PONT DE NEMOURS & GO. Au alloys for dental crowns and bridges, which U.S. Patent 3,342,628 can be porcelain-enamelled, are coarse-grained and contain Ni, o.I-I", Al, 0.5-4",, A Pt-Fe alloy diffusion coating on a ferrous metal 0.1-1.1~~ article is produced by immersing the article in a Ag, I-IO", Pt, I-IOU/~ Pd and the balance (80-90 wt.*+,) Au. These alloys can withstand molten bath containing a mixture of CaCl, with 0.5-50 wt.''<, Ca and a source of Pt. The high temperatures. temperature is between 800'C (1000-1200 C) and the melting point of the alloy. The alloy Platinum Claddings for Refractory Metals coating is formed during immersion. The Pt JOHNSON, MATTHEY & 60. LTD. may be present as metal powder or an easily Belgian Patent 697,292 reducible compound. Articles comprise refractory metal cores, such as Nb, Ta, Cr, or an alloy thereof, or Mo, which Electrodeposition of the Platinum Metals do not form volatile oxides at the operating GENERAL ELECTRIC CO, (N.Y.) temperature nor form alloys with the Pt or Pt Patent 3,351,541 alloy cladding at melting points below this US. temperature. A barrier layer between core and Bright ductile coatings are obtained from 1-50 g'1 Pt metal dissolved in aqueous solution cladding consists of a compatible refractory an carbide, silicide, boride, sulphide, nitride, or of at least IOO g '1 of a Li or alkaline earth halide. oxide, e.g. a rare earth metal oxide, carbide or The bath is used at 30-11ocC and 10-zoo nitride. mA/cm?. A typical bath contains 400 gll LiCl and 9 g/l H,PtCI,. ELECTROCHEMISTRY Platinum or Platinum Alloy Coatings JOHNSON MATTHEY & CO. LTD. Electrode for Electrolysis French Patent 1,488,295 ASAHI KASEI K.K.K. British Palent 1,099,434 A Pt dispersion giving adherent coatings is Explosive bonding is used to bond Pt, Ir, Rh or produced by reducing PtO,, optionally mixed Pd (or their alloys) to a corrosion-resistant metal, with up to 50~1" of one or more other Ptmetal such as Ti, Zr, Ta and their alloys, for electrolysis oxides (except Os), while in a 2-5 C aliphatic electrode production. alcohol. Activation of Platinum Electrodeposition of Platinum or Palladium JOHNSON, MATTHEY & CO. LTD, JOHNSON, MArTHEY & CO. LTD. German Patem 1,236,302 German Patent 1,182,924 Particularly active electrodes for use in the A Pt or Pd plating bath consists of an aqueous electrolysis of brine are produced by exposing a solution of a complex nitrito-palladite compound Ti electrode plated with Pt group metal or alloy, of given general formula. Numerous examples in particular Pt, Pt-Rh or Pd-Ag, to the action of are given, the preferred bath comprising dini- Hg vapour or alkali metal amalgam vapour, the tritosulphato-platinous or -palladous acid, Hg coating being distilled off after it has been H,Pt(NO,),SO, or H,Pd(NO,),SO,. This deposited to leave the surface in a highly active corresponds to British Patent 897,690. state. This corresponds to British Patent 957,703. JOINING ELECTRODEPOSITION AND Bonding Together of Metals or Alloys SURFACE COATINGS JOHNSON, MATTHEY 82 CO. LTD. British Patent 1,093,136 Deposition of Platinum Two dissimilar metals are bonded by an inter- INTERNATIONAL NICKEL LTD. mediate layer consisting of a refractory ceramic British Patent 1,097,010 and a metal soluble only in one of the two metals. A chemical plating bath which deposits Pt in a Thus when refractory metals are bonded to a highly active catalyst form consists of an aqueous Pt metal, the bonding metal is soluble in the alkaline solution containing, 2-2ogJ Pt, cal- Pt metal and may be Au.

Platinum Metals Rev., 1968, 12, (2) 76 Metal-Ceramic Joints Production of Dienes NORTH AMERICAN PHILIPS CO. DISTILLERS CO. LTD. British Patent 1,098,697 U.S. Patent 3,339,267 A compound containing conjugated double Hermetic sealing is achieved by applying to the bonds is produced from an olefine by reaction ceramic a thin layer of Ta, Nb, or V, thenapplying with 0, over a Pt group metal deposited on a a layer of Pd or 13 by cathodic sputtering and support having a surface area greater than finally fusing the metallised surface to a metal 10m2jg. A carboxylic acid may also be present body. 3,340,025 is similar with a layer of wetting and the preferred catalyst contains Pd or Rh. metal selected from Re, Mo-Ru and Mo-Rh. Butadiene can be produced from C,H, in this way. Production of Pyridines ALBRIGHT & WILSON (MFG.) LTD. HETEROGENEOUS CATALYSIS British Patent 1,099,189 Selective Catalytic Hydrogenation of Croton- C,H,N or a substituted pyridine is produced aldehyde from a 8 valerolactam at 200-800°C in the JOHNSON, MATTHEY &! CO. LTD. presence of a catalyst causing single stage British Patent 1,089,835 dehydration and dehydrogenation. The preferred catalysts consist of a Pt metal on a SiO, and/or C,H,CHO is produced by the hydrogenation of A1,0, support. crotonaldehyde in the liquid phase using a Pd metal catalyst deposited on a support, preferably A1,0,, C or a ceramic material. Production of Esters of Unsaturated Alcohols DISTILLERS CO. LTD. British Patent 1,ioX,224 These esters are produced by oxidising a 2-6 C Improvements in Catalytic Hydrogenation olefine in the liquid phase with 0, in the presence UNIROYAL INC. British Patent 1,090,177 of a carboxylic acid and an elemental Pt group Selective hydrogenation of a conjugated diene to metal (preferably Pd) deposited on an activated the corresponding olefine is catalysed by Pt S,, C having a surface area greater than 50 mz/g. PdS, or RuS,. Their degree of selectivity is very high. Vinyl Acetate Production KNAPSACK A.G. British Patent 1,10f,726 Preparing C yclohexylhydroxylamine The vapour phase reaction of C,H,, CH,COOH ABBOTT LABORATORIES British Patent 1,092,027 and O2 or air at 12o-25o0C and 1-10 am is This compound is produced by the selective catalysed by Pd on a support; this catalyst is hydrogenation of nitrocyclohexane using Pt produced by reducing a Pd salt to metallic Pd and/or Pd in the presence of a "selectivity" in the presence of SO,, Alto,, SiO,-Al,O,, agent, i.e. an mine or related compound. Thus AlPO, and/or C. The catalyst is treated for Pd/C can be used with cyclohexylamine. at least one hour with air and/or N, at rzo-350"C and 1-10 atm gauge before use. Improvements in Hydrogenation Catalysts INVENTA A.G. British Patent 1,094,257 Urethane Production The life of Pt catalysts used in acidic media can IMPERIAL CHEMICAL INDUSTRIES LTD. be prolonged by preventing the accumulation of U.S. Patent 3,338,956 Ag or Si. These elements cause deactivation and The production of urethanes by the reaction of can be removed with HF. Si contents can be CO, an alcohol or phenol and a nitro compound reduced by eliminating all SiO, glass surfaces. is catalysed by a Group VIA, VIIA or VIIIA metal, especially Rh. Manufacture of Acetaldehyde FARBWERKE HOESCHT A.G. Hydrocarbon Hydrocracking British Patent 1,098,371 UNION OIL CO. U.S. Patent 3,342,725 CH,CHO is produced when C,H, and elementary A crystalline zeolite catalyst support is doped 0, are reacted in the presence of PdO. The with a sulphided hydrosol of Pd in NH, and then PdO may be supported on an inert support. the product heated to decompose zeolite NH, ions. The activity of the catalyst (which may Motor Fuels and Jet Fuels contain another Group VIII metal instead of TEXACO DEVELOPMENT CORP. Pd) is greatly improved. British Patent I ,098,659 A fraction boiling at 400--90o0F is cracked over a Reduced Activity Platinum Catalyst Group VI or VIII metal or oxide catalyst. When GENERAL ELECTRIC co. U.S. Patent 3,344,111 the catalyst is not sulphided a motor fuel fraction Stable mixtures of a Pt catalyst and an unsaturated is recovered while 60% or more sulphidation polysiloxane are produced by introducing an gives a jet fuel fraction. Suitable catalysts are Pt unsaturated nitrile into the mixture to reduce or Pd on an oxide support. the catalyst activity.

Platinum Metals Rev., 1968, 12, (2) 77 production of Styrene Production of Unsaturated Esters s. C. SCHUMN U.S. Patent 3,344,201 STAMICARBON N.V. The reaction of C,H, and elementary S to produce Dutch Appln 66.08,559 styrene is catalysed by a transition metal sulphide, The reaction of olefines, organic acids and 0, e.g. Ruse. is catalysed by a supported catalyst containing Pd and either Pt, Rh or Ru, preferably with a Heavy Hydrocarbon Cracking Catalyst ratio by weight of 300:1 to 3:1, Pd: second noble =SO RESEARCH & ENGINEERING CO. metal. SiO, forms a suitable support. U.S. Patent 3,346,482 A new catalyst consists of a crystalline alumino- HOMOGENEOUS CATALYSIS silicate having pore openings of 6-15 a, a SiO,-Al,O, ratio of 2.5:14 and a Na,O con- Production of Esters tent of less than 10 wt.(;/, on which is deposited IMPERIAL CHEMICAL INDUSTRIES LTD. at least I wt."; of a Pt metal, e.g. Pd. See also British Patent I,OgI,O42 3,3465 12. Esters of monocarboxylic acids are produced by Stabilisation of Platinum Group Metal Re- reacting a vinyl halide with an alkyl or cycloalkyl hydroxy compound and CO in the presence of a forming Catalysts Group VIII metal and bromide and/or iodide MOBIL OIL CORP. U.S. Patent 3,347,782 ions. PtC1, and PdCl, are suitable sources of the Supported Pt metal catalysts are stabilised, Group VIII metal. and simultaneously made more selective, by adding a N compound to the feedstock which OrganosiliconPolymers will yield NH, in the reforming conditions. DOW CORNING cow. British Patent 1,093,898 Silacyclobutanes are polymerised by a Pt catalyst, Polycyclic Aromatic Isomerisation e.g. H,PtCl,. STANDARD OIL GO. OF ILLINOIS U.S. Patent 3,349,140 Salts of Higher Alkyl Sulphates Cis isomers are produced in a higher proportion MITSUBISHI CHEMICAL INDUSTRIES LTD. when polycyclic ring compounds are hydro- British Patent 1,099,196 genated using Ru on a non-hydrogenating support Surfactants are produced by reacting a 10-24 at 2$-2oo0C and a pressure $ 3000 psig. C olefine with CO and H, in the presence of a Rh catalyst, hydrogenating the product to give DicyclohexylamineProduction higher alcohols, sulphating the alcohols and ABBOTT LABORATORIES U.S.Patent 3,351,661 neutralising the product. The Rh catalyst can Phenol and NH, are reacted with H, at an be metallic, an inorganic salt or an organic elevated temperature and pressure with at least derivative such as RhCl(CO)(PPh,), or Rh o.ozy& metallic Pd catalyst, based on the phenol. acetylacetonate. The catalyst may be supported. Methyl Alkyl Ketones Olefine Double Bond Isomerisation EASTMAN KODAK co. British Patent 1,099,348 ETHYL CORP. U.S. Patent 3,352,938 A 3-8C a-olefine is reacted with an aqueous a-Olefines are converted to p-olefines by isomeri- oxidising composition containing CuC1, and a sation in the presence of 5 wt.o/, of a mixture of catalytically active Pd compound to give a I part Ru and 5-10 parts Pd on an activated complex which hydrolyses to produce the charcoal support. 3,352,939 is similar except that required methyl alkyl ketone. Pd carboxylates, an aldehyde is used for promoting the reaction PdC1, and H,PdCl, are suitable catalysts. and the Pt metals generally (except 0s) can be used. Catalysts JOHNSON, MTTHEY & CO. LTD. Hydrogenation of Unsaturated Aldehydes British Patent 1,099,406 JOHNSON, MATTHEY & GO. LTD. Catalysts for chemical reactions such as hydro- French Patent I ,489,504 genation are an intimate homogeneous mixture of The addition of H, to these aldehydes is catalysed the oxides of Pt and Ru, e.g. made by Adam's by Pt, e.g. Pt/C, in alcobolic solution with an method and not by physical mixing, and have a alkaline base or alcoholate as initiator. Pt content of 90-20 wt.7; and a Ru content of 10-80 Wt.'?h. Vinyl Acetate Production KNAPSACK A.G. German Patent 1,252,662 Production of Ethers The reaction of C,H,, CH,COOH and molecular IFnFERIAL CHEMICAL INDUSTRIES LTD. 0, is catalysed by metallic Pd activated with British Patent 1,100,023 1-60 atom% metallic Au, based on the g. atoms Alkyl alkenyl ethers are produced by reacting a of Pd plus Au. r-olefine with a substantially anhydrous solution

Platinum Metals Rev., 1968, 12, (2) 78 of a salt or coordination compound of Pd in an FUEL CELLS alcohol and then removing the ether. The catalyst may be PdCl,, palladous acetate, lithium Fuel Cell chloropalladite or ally1 palladous chloride. ROBERT BOSCH G.m.b.H. British Patent 1,097,314 A new cell which can operate at about 100°C Oxidation of Ethylene has a known 0, electrode, a metallic Pt catalyst BRITISH CELANESE LTD. British Patent 1,100,901 fuel electrode and uses dilute H,SO, as the Acetic anhydride is produced by the reaction of electrolyte. CzHaand Oe in an CH,COOH solution of a Pd salt, a Cu or Fe salt capable of oxidising the Pd Fuel Cell Electrode metal formed, acetate ions and C1 ions, to give FUJI DENKI SEIZO K.K. British Patent 1,100,102 vinyl acetate which is then reacted with A H,-permeable membrane electrode is made CH,COOH in the presence of Pd ions and C1 from an alloy of Pd with at least one Group IB ions to give acetic anhydride and CH,CHO. element and at least one other Group VIII element. The amounts are preferably 2-39.9%, Production of Allyl Acetate Group IB element, O.I-ZO(;~~ Group VIII metal IMPERIAL CHEMICAL INDUSTRIES LTD. and at least 60';& Pd. A typical tubular alloy British Patent 1,101,055 membrane of z mm diameter and 0.06 mm Allyl acetate is produced when propylene is thickness is made from an alloy of 657" Pd, IO~;, contacted with a Pd salt in the presence of Ag, zoo,:, Au, 1% Pt, 204 Rh, 1.8% Ru and CH,COOH, an alkali, alkaline earth, or Cu 0.2%, Fe. acetate, 0, and a Cu salt. A preferred Pd salt is the acetate. See also 1,101,056. Non-porous Hydrogen Diffusion Fuel Cell Electrodes Terpene Isomerisation LEESONA CORP. U.S. Patents 3,337,368-9 INTERNATIONAL EIAVOURS & FRAGRANCES INC. The fuel cell consists of a non-porous hydrogen US.Patent 3,344,171 diffusion I'd membrane anode, a porous cathode Myrcene and related compounds are isomerised and an aqueous electrolyte. The anode can be at 60-165°C in the presence of Rh, Ir, RhCl, pure Pd and in a cell circuit, e.g. with a Pt and/or IrCl, and HCI. cathode, has unusual metering characteristics.

Tetrafluorohydrazine Preparation Fuel Cell Electrode STAhiARD OIL CO. OF ILLINOIS AEROJET-GENERAL CORP. U.S. l'atent 3,350,172 U.S. Patent 3,354,060 A liquid difluorocarbamate is oxidised to N,F, An electrode of low activation polarisation is using, among a range of possible oxidising agents, obtained by plating Pt and Cu on to a support salts of simple or complex cations containing and removing some of the Cu to give a mixed 0~81,R41, RuR1 and Ira+. porous layer of Pt/Cu. Hydroquinone Production LONZA LTD. US.Patent 3,355,503 ANODIC PROTECTION C,H,, CO and H, are reacted, at certain tem- Anodic Protection peratures and pressures in an organic solvent with trimeric Ru carbonyl as catalyst. The IMPERIAL CHEMICAL INDUSTRIES LTT). solvent must not contain mobile H atoms. British Patent 1,100,685 A cathode for an anodic protection system has a conducting base of Ag or C, etc., with a depos- Butadiene-Piperylene Copolymerisation ited layer of a metal having a low H, overvoltage, INSTITUT FRANCAIS DU PETROLE, DES CARBURANTS such as Au, Ir, Rh, Pt or Pd. ET LUBRIFIANTS French Patent r,488,982 These monomers are copolymerised in aqueous emulsion by contact with a Rh compound, e.g. CHEMICAL TECHNOLOGY chloride, nitrate, ammonium chlororhodate or sodium chlororhodate. Sintered Uranium Dioxide-Iridium Com- position Hydrogenation Catalysts U.K. ATOMIC ENERGY AUTHORITY JOHNSON, MATTHEY & CO. LTD. U.S.Patent 3,342,744 Belgian Patent 701,238 UO, ceramics which do not exhibit columnar An aqueous solution of HRh(NH,),SO, is used growth when subjected to severe temperature for hydrogenating unsaturated carboxylic acids gradients at 1600-2ooo'C are produced by adding at 60°C. Acrylic, crotonic and maleic acids may 0.1-4 wt.:;, of Ir. The Ir can be added in be hydrogenated. An advantage of this catalyst solution, e.g. as ammonium chloroiridite, to the is its solubility in H,O. UO, slurry.

Platinum Metals Rev., 1968, 12, (2) 79 Separation of Hydrogen by Permeation Sparking Plug Electrodes TYCO LABORATORIES INC. U.S.Patent 3,350,846 JOHNSON, MATTHEY & CO. LTD. A membrane permeable to H, is formed by coating British Patent 1,099,387 a Group VB metal layer on both sides with French Patent 1,490,828 non-porous films of Pd or Pd alloy. Thus a Sparking plug electrodes, without a fibrous Nb, V or Ta foil can be coated with Pd-Ag. structure and resistant to Pb and its compounds at high temperature, are made from Ru powder Diffusion Cell for Separating Hydrogen from or a Ru-Ir alloy powder of specified particle Gas Mixtures size. All particles must be in the range 1-76 p and JOHNSON, MATTHEY & GO. LTD. the 10-20 and 20-30 !L particles must represent, German Patent 1,252,186 respectively, 20-35"o and 3O-5Oouof the powder Diffusion cell for the separation of H,, consisting weight, This corresponds to U.S. Patent of flat, internally supported envelopes of Pd 3,331,685. etc. connected to a Hzcollecting tube, each such envelope being symmetrically arranged with Thermionic Valves respect to a plane containing, or normal to, the PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES LTD. axis of the collecting tube. British Patent 1,100,420 The valve cathode is a dispenser-type cathode with a porous metal surface which is coated with GLASS TECHNOLOGY Re, Ir or 0s in the areas opposite the anode grid. Metal Laminates OWENS-CORNING PIBERGLAS CORP. Electrical Resistance Composition British Patent I,IoO,g49 INTERNATIONAL BUSINESS MACHINES CORP. These laminates are especially used for orifice U.S. Patent 3,337,365 plates in glass fibre production. They consist of a The resistor is produced on a non-conductive first layer of alloy with at least 7500 Rh and less base such as glass by applying 100 parts PdO, than 25;: Pt bonded to a second layer con- 144 parts PdC1, or 86.8 parts Pd metal and taining at least 6on0Pt and less than 40°; Rh. 23.3-279 parts AgCl or an equivalent amount of AgBr or AgI, 0-400 parts finely divided glass and Alloys for Contact with Molten Glass 0-50 parts B&O, or Pb,O,. This is then fired. JOHNSON, MATTHEY & CO. LTD. French Patent r,488,455 Gold-Palladium Conductors Alloys resisting high temperatures, e.g. likely to E. I. DU PONT DE NEMOURS & CO. INC. come into contact with molten glass contain U.S. Patent 3,347,799 60-97 wt."b Pt, 2-25 wt.",, Rh and 1-10 wt.U: Conducting coatings are produced on a dielectric Au . ceramic base by firing on a mixture of 8-2500 linely divided Pd, 55-84"/, finely divided Au and Platinum Metal-coated Refractory Metals 8-37O{, finely divided vitreous binder. JOHNSON, MATTHEY & CO. LTD. Dutch Appln 67.05561 Thallium Oxide Resistor Glaze Articles which are to be used successfully at AIR REDUCTION co. INC. U.S. Patent 3,352,797 elevated temperatures, e.g. in molten glass, can The electrical noise, moisture resistance and consist of a Pt metal or alloy coating on a re- thermal stability are improved by adding RuO, fractory metal or alloy core provided that (a) to a T10, glass resistor. the core metal or alloy does not form a volatile oxide at the operating temperature and (b) the core metal or alloy does not alloy with the Pt TEMPERATURE metal or metals to give a product melting at the operating temperature. MEASUREMENT Nohle Metal Thermoelectric Wires DEUTSCHE GOLD- & SILBER- SCHEIDEANSTALT ELECTRICAL AND U.S. Patent 3,349,467 ELECTRONIC ENGINEERING Pt metal wires of high hot strength are produced by converting a Pt compound at a high tempera- Electrical Resistance Elements ture below 500°C to a powder with a particle CTS CORP. British Patent 1,091,916 size below 10,000 mesh/cm2. The powder is A film of resistance material is produced on a compressed to a compact, the compact sintered ceramic base by applying a mixture of a glass at 1300-1~00ccand then the sintered compact matrix and an Ir and,'or Ru oxide and firing cold worked to a wire without an intermediate the film. Preferably 2-70 wt.:/, metal oxide is anneal. The wire is subsequently stress relieved present. at I300-1~00c.

Platinum Metals Rev., 1968, 12, (2) 80