PLATINUM METALS REVIEW

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

VOL. 11 OCTOBER 1967 NO. 4

Contents

Ruthenium Oxide Glaze Resistors

Cobalt-Platinum Alloy Magnets

The Platinum Metals in Fuel Cells

Further Expansion in Platinum Production

The Platinum-Molybdenum System

Electron Configuration and Crystal Structure of Platinum Metal Alloys

Brazing Graphite to Metals

The Structure of Supported Platinum Catalysts

Thc Platinum Metals in Catalysis

Iridium Coatings in Ion Engines

Carbonyl Halide Complexes of the Platinum Metals

Performance of Platinised Titanium Anodes

Abstracts

New Patents

Index to Volume 11

Communications should be addressed to The Editor, Platinum Metals Revimv Johnson, Matthey & Co., Limited, Hatton Garden, London, E.C.1 Ruthenium Oxide Glaze Resistors NEW SCREEN PRINTING PREPARATIONS FOR THICK FILM CIRCUITRY

By G. S. Iles and Miss M. E. A. Casale, B.s~. Research Laboratories, Johnson Matthey & Co Limited

many years for discrete component manu- The rapid deoelnpment of thick jlrn facture, and these are now employed in integrated circuits has created a need for thick film integrated circuit production for preparations that will provide resistor connections and interconnections. Probably Jilrns on a variety of substrates. In the the most important new requirement for decelopment of the new rangp of integrated circuits was a preparation capable rnateriuls described in this urticle of producing resistive films. This problem adimntagr has bern takpn ofthr complex has been approached by developing suspen- rnrrhanisrn of conduction through sions, usually of powdered glaze (frit) and ruthenium dioxide. powders of one or more noble metals dis- persed in an organic medium. After screening to the substrate, the preparation is fired to The past few years have witnessed mounting burn away the organic material, fuse the interest in integrated circuits and there is now glaze component and complete any other little doubt that within the next decade a reactions necessary. By varying the composi- substantial proportion of electronic equip- tion, a variety of different film resistivities can ment will be based on them. be produced but if close limits of resistance Conventional circuits are normally as- are required, they can be achieved by removal sembled from discrete components by solder- of part of the resistive film after firing. ing them on to a printed circuit board. In integrated circuits, on the other hand, the Until recently the majority of the resistive circuit elements are deposited as films on to preparations available required a temperature substrates, a number of which are often of 700°C or above, this high firing tempera- assembled together. It was first believed that ture being necessary to complete reactions vacuum deposition was the ideal technique within the preparation. This not only im- for producing these circuits, but within the posed the necessity of very close control of past year silicon integrated circuits and, to a furnace atmosphere and of the firing cycle, lesser extent, thick film circuits, have gained but also limited the choice of substrate to considerable ground. Here the elements and materials such as high-alumina ceramics their connections are applied as pastes to the capable of withstanding this firing tempera- substrate by screen printing and subsequent ture. High surface finish of the substrate is firing. While the circuits so produced are necessary for this work, and mica and most sometimes bulkier than their thin film glasses, which inherently have high surface counterparts, they have the advantage of finishes, were ruled out. simpler and well-established manufacturing Against this background the Johnson techniques, greater versatility in manufacture Matthey Research Laboratories have de- and fewer problems in making connections. veloped glaze resistor preparations based on Silver and gold preparations capable of ruthenium dioxide. The objective was an ink being screen printed have been available for incorporating a glaze based on a fully-reacted

Platinum Metals Rev., 1967, 11, (4), 126-129 126 One of the new Johnson Matthey preparations based on ruthenium oxide has been used in the production of these resistor plates by silk screening and $ring. The substrate was mica, which required no sur- face treatment. One of the assembled but unencapsulated circuits is also shown in the photograph.

preparation that would be far less dependent and his co-workers at Philips in 1950 (I). It on firing conditions than those hitherto was shown that introduction of suitable ions available. To be viable the material had to into the lattice structure of a variable oxide satisfy three other conditions : could, without deforming it, balance the ions (I) The metal/glaze system had to be of deviating valency already within the lattice capable of producing a wide range of and still maintain overall neutrality. For resistivities. example, Verwey obtained a composition (2) The films had to have acceptably low Li8+Ni2+(l-,8)Nia3-0 by calcining lithium temperature coefficients. carbonate with nickel oxide at IZOOTunder (3) The ruthenium had to be used as oxidising conditions, The product had the economically as possible. same structure as nickel oxide, but with a smaller unit cell, and the Ni3+ content was Conduction through Ruthenium broadly equivalent to the amount of lithium Dioxide oxide added. Ruthenium dioxide is a black, electrically This suggested that valency variations in conducting crystalline solid with the rutile ruthenium dioxide might be controlled by a structure. Unlike palladium oxide, it can be similar “doping” technique, leading to a heated in air to 110o”cwithout physical or better reproducibility from batch to batch, chemical change, and is almost completely together with a measure of control over both insoluble in a wide variety of frit and glass resistivity and temperature coefficient. compositions. It can seldom, if ever, be prepared as Control of Valency stoichiometric RuO,, and is usually partially The oxides of Group Va metals were defective in oxygen, with a corresponding selected for investigation. Pentavalent ions amount of Ru3+in place of Ru4+in the crystal would be necessary to balance the Ru3+ions lattice. Valency control within narrow limits in the lattice and maintain overall neutrality, was obviously necessary if stable resistors and M5+ions of Group Va metals have a based on ruthenium dioxide were to be radius within &IS per cent of that of the developed. RLP ion, which is about the limit for the Work on the control of deviating valencies entry of an ion of one species into the lattice in semiconducting oxides, in particular of another in significant quantity. It was nickel oxide, was reported by E. J. W. Verwey found that niobium pentoxide could be

Platinum Metals Rev., 1967, 11, (4) 127 introduced into the ruthenium dioxide lattice positive influence of the silver being compen- in quantities up to 50 per cent molecular, and sated by the negative influence of the niobium that the results obeyed Vegard's Law, which pentoxide on the temperature coefficient. states in effect that the extent of the change Thus silver provided an additional means of in lattice parameter of the host oxide is controlling temperature coefficient in addition proportional to the molecular percentage of to reducing the cost of the resistor preparation. added dopant. This linearity provides a useful means of monitoring the composition The Glaze Component by X-ray diffraction before processing into Investigation of the glaze component of the a resistor preparation. resistor compositions showed that this had a Moreover, since the temperature coefficient significant effect on some electrical properties. of resistance of ruthenium dioxide is metallic Glasses of the lead borosilicate type promoted in nature and strongly positive, introduction high positive temperature coefficients, often of a non-conducting oxide might be expected exceeding 500 x IO-~/"Cand 2000 x IO+/"C to exert a negative influence on the tem- respectively with doped and undoped ru- perature coefficient. Thus control of tem- thenium dioxide. Better results were obtained perature coefficient in addition to resistivity with zinc and cadmium borosilicate glasses. might be achieved. Further work showed that resistance values Electrical Properties were largely governed by the ratio of doped At present four basic ruthenium oxide ruthenium dioxide to glass, and temperature preparations are available commercially (2), coefficients by this ratio in conjunction with covering the range from 100 to 3000 ohms/ the molecular percentage of niobium pent- sq./mil., but it is expected that seven pre- oxide in the ruthenium dioxide lattice. For parations will ultimately be produced, firing example, ruthenium dioxide glaze films in a at 600°C upwards, to cover the range 5 to wide range of resistance values were found to IOO,OOO ohms/sq. /mil. Intermediate values have positive coefficients in excess of 1000 x may of course be obtained by blending the two 10 "OC. As the molecular percentage of standard compositions nearest to the desired niobium pentoxide in the calcine was in- resistance. creased the temperature coefficient decreased, Little difficulty should be experienced in reaching a negative value of IOO x IO-~//"Ccontrolling values to within &zo per cent with 20 per cent molecular content of of nominal, with the possibility of maintaining niobium pentoxide. better than AIOper cent with good machines Since the niobium and ruthenium oxides under closely controlled conditions.

are reacted by calcination before incorpora- Temperature coefficients in the range ~ 100 tion in the resistor preparation, no reaction to f~oox IO-~/"C can be expected with sheet occurs when the preparation is subsequently resistivities from 50 to 1000ohms/sq./mil. As fired on the substrate, and electrical properties resistivity increases the temperature coeffi- were not unduly affected by variations in the cient tends to become more negative, and time of firing or in the temperature and values of +50 to -250 can be expected with atmosphere in the furnace, resistivities from 1000 to 10,000 ohms/sq./mil. Silver powder was found to be a useful For even higher resistivities temperature addition to ruthenium dioxide based pre- coefficients between -zoo and -500 may be parations. Up to 60 per cent of the ruthenium expected at present, but this may be reduced dioxide could be replaced with silver without later to o to -300 x IO-~/"C. adversely affecting the temperature coefficient Ruthenium dioxide glaze resistor films provided a balance was struck between the subjected to a load of gW/in.2/mil. at 70°C niobium pentoxide and silver contents, the for 1000 hours showed a drift in resistance

Platinum Metals Rev., 1967, 11, (4) 128 value of <0.5 per cent. Short duration power used. Printing thickness was standardised at dissipation tests showed no drift in value at 0.0005 inch, using a zoo mesh stainless steel loadings of up to rooW/in2/mil. The films screen. This was considered suitable for all showed good thermal stability with a drift of circuits except those in which unusually high <0.5 per cent after ten cycles from fzo" to power dissipation is necessary, when films up rog"C, and a drift of <0.25 per cent after to 0.001inch might be preferred. 2000 hours at 105°C without load. The surface condition of the substrate was found to have an effect on the reproducibility Application to the Substrate of electrical properties of the fired films. The best results were obtained with smooth flat The organic medium in which the solid substrates such as mica, glass and high quality components are dispersed was formulated to alumina ceramics, with centre line average give a paste with rheological properties suit- values of smoothness below 5p inch. able for screen printing. This process, with close control, allows deposition of even, well References I E. J. W. Verwey, P. W. Haaijman, F. C. defined films ranging in thickness, when Romeijn and G. W. van Oosterhout, Con- fired, from 0.002 to 0.0003 inch, largely trolled-Valency Semiconductors, Philips depending on the design of the machine, the Research Report, 1950, 5, 173-187 2 G. S. Iles and 0. N. Collier, Johnson Matthey, mesh size of the screen and the type of stencils British Patent Appln 46910j66

Cobalt-Platinum Alloy Magnets TEMPERATURE DEPENDENCE OF MAGNETIC PROPERTIES

Recent studies of cobalt-platinum alloys one phase only is ferro-magnetic or that the have shown the importance of crystal struc- ordered and disordered phases have similar ture in relation to the exceptional magnetic Curie temperatures. properties which can be developed, particu- Demagnetisation curves, shown as the larly in the 50 atomic per cent alloy. relationship between intrinsic induction In work reported by Dr Hermann Dietrich (4x1) and demagnetising field (H) at of the Research Institute of Deutsche temperatures between -195" and 440"c, Edelstahlwerke, Krefeld, and reviewed in demonstrate the very high coercivity of the this journal (I), it was shown how the mag- cobalt-platinum alloy. The 'rectangular' form netic state of cobalt-platinum magnets was of the curves in the lower temperature ranges altered by heating to temperatures near the indicates high stability under large demag- Curie point. More recently, the same author netising fields of at least 2000 oersteds, and has reported the results of a further study of while residual induction reduces more rapidly the temperature dependence of various with increasing temperature, those magnets cobalt-based permanent magnets, including with a suitably high length : diameter ratio cobalt-platinum, in which temperature co- exhibit almost negligible temperature depend- efficients of saturation magnetisation and dence between -195" and +2ooCC. Above demagnetisation curves were determined (2). zoo"C the magnetic properties reduce rather From the results of tests on small cylindri- more rapidly, but can still be restored by cal cobalt-platinum magnets produced from remagnetising until changes in structure, melted and cast material, it was shown that which start to occur at about soo"C, produce variations in saturation magnetisation were permanent changes in the demagnetisation small between -zoo"C and +200"C. Within curve. this range the average saturation magnetisa- L. A. F. tion was found to be 6750 gauss and this References varied with temperature at the rate of -0.01 per cent per "C. A single Curie temperature I H.Dietrich, Cobalt, 1966, No. 30 (March), 3; was found at 530°C, despite the presence of a L. A. Ford, Platinum Metals Rev., 1966,10,84 two-phase structure, indicating either that 2 €3. Dietrich, Cobalt, 1967, No. 35 (June), 78

Platinum Metals Rev., 1967, 11, (4) 129 The Platinum Metals in Fuel Cells SECOND INTERNATIONAL CONFERENCE IN BRUSSELS

The merits of the platinum metals as electrocatalysts in a large number of fuel cell systems featured in a high proportion of the papers presented at the Second International Conference on the Study of Fuel Cells, organised by the Soci6t6 #Etudes de Recherches et d’Applications pour l’lndustrie (SERAI) and the SociBtB Commerciale d’Applications Scientijques (COMASCI)and held recently at the University of Brussels.

More than fifty papers were presented at tetrafluoroethylene, with chlorplatinic acid this meeting on all aspects of fuel cell in ethanol and reducing at 225%. The technology, ranging from considerations of novelty of this electrode is that a high degree theoretical models of the processes taking of structural cohesion and flexibility is place at working electrodes to outlines of the obtained even with very high proportions of basic economics of the manufacture and use of the conductive graphite. Excellent results fuel cells. Several instances of working cells were obtained for reactions of hydrogen and producing power in the I to z kW region were oxygen in both acid and alkaline media at described. low platinum concentrations. The superiority of platinum as an electro- Fuel cells having particular applications in catalyst has been clearly demonstrated by view were described by M. I. Gillibrand and numerous researches, particularly in those J. Gray of Electrical Power Storage, and by fuel cells designed to work at ambient C. G. Telschow and co-workers at Brown temperatures or in corrosive electrolytes, but Boveri. In the former case capacities of over the view has frequently been expressed that 10,000 ampere-hours without attention were its high cost is a disadvantage for use in large claimed from cells operating at low current scale commercial applications. C. G. Clow densities with compressed hydrogen and of Energy Conversion, presenting the results oxygen; such cells are ideal for use as power of an analysis of the basic economics of sources in navigational buoys and unattended various types of low temperature fuel cells beacons. In a buoy a life of three years using alkaline electrolytes, pointed out that between servicing would be possible, and a the cost of electricity generation comprises shore-based beacon could operate for six capital costs, maintenance and fuel, and that months without attention. Similarly the the use of the cheapest fuel and high efficiency Brown Boveri equipment had an expected six did not necessarily mean the most economic months unattended life, and could therefore generation of power. The cost of materials be used in certain areas of the world in and fabrication of the fuel cell unit depend on telephone and television relay stations. This the fuels and conditions used, and in certain cell utilises a platinum metal catalyst for the systems the cost of electrodes with platinum direct oxidation of methanol in an alkaline loadings of less than 3 mg.cm-2 did not electrolyte and is capable of producing power constitute the major item of expense. at temperatures down to - 10°C. A new type of gas diffusion electrode was Both acid and alkaline electrolytes can be described by R. G. Haldeman and his co- used in direct methanol oxidation systems, as workers of the American Cyanamid Company. was pointed out by H. H. von Dohrcn and his This is made by impregnating a conductive colleagues at Varta. Both electrolytes have graphitic carbon, bonded with fibrous poly- their advantages and Varta currently use

Platinum Metals Rev., 1967, 11, (4), 130-131 130 potassium hydroxide solutions in their experi- activity maximum now occuring at 50 atomic ments. Measurements made by this group per cent gold, sharply declining at 60 atomic indicated that below 80°C non-precious per cent gold, irrespective of the method of metals did not work very well, while of the preparation of the alloy. platinum group metals platinum, palladium, J. Bersier of Siemens has investigated the palladium-platinum alloys and platinum- diffusion of hydrogen through silver- rhodium alloys were the most active at palladium alloys, since the use of such alloys ambient temperatures. in the construction of non-porous diffusion The study of alloys of the platinum group electrodes avoids the difficulties arising from metals for fuel cell applications continues to the brittleness and cracking experienced with attract interest. Thus J. H. Fishman of pure palladium. Measurements of the Leesona Moos Laboratories had investigated diffusion coefficient of hydrogen as a function the use of palladium-gold alloys for oxygcn of hydrogen concentration and temperature in reduction in alkaline media. When a foil was the range 30 to 3oocC show that it is largely used, a maximum in the activity versus com- governed by the concentration of occluded position plot was obtained with alloys con- hydrogen, and that for the 23 per cent silver- taining 35 to 40 atomic per cent gold, and a palladium alloy a definite minimum occurs in sharp decrease in activity was observed in the concentration range 0.1 to 0.2 H/Me not alloys containing greater than 80 atomic per explicable by the existence of a two-phase cent gold. Similar behaviour was found when zone in the alloy. finely divided alloy powders were used, the D. E. W.

Further Expansion in Platinum Production A NEW REFINERY IN SOUTH AFRICA

Although a furthcr incrcase in the output of platinum to 750,000 ounces a year was announced by Rustenburg Platinum Mines as recently as October of last year, yet another step in the expansion programme has been de- cided upon. Plans to increase mining capacity to an annual equivalent of about 850,000 ounces of platinum - with corresponding amounts of the other platinum metals - have been put in hand and are expected to begin yielding thcse additional amounts of metal by the end of 1969. The capital expenditure involved in the complete expansion programme over the years 1967 to 1971will exceed 815 million. Extensions to the smelting and refining facilities are also in hand both at Matte Smelters (jointly owned by Rustenburg and Johnson Matthey) and at the Johnson Matthey plants in the United Kingdom. In addition, Johnson Matthey have decided, subject to the necessary Government authority being granted, to build a platinum refinery as an extension to the opcrations already carried out at Wadeville by Johnson Matthey & Co South Africa (Pty) Limited. This new refinery will be constructed and equipped during 1968 and will come into operation in the early part of 1969. It will take partially refined material treated by Matte Smelters at Rustenburg and produce pure platinum, palladium, rhodium, iridium, ruthenium and osmium as well as their compounds. The new Johnson Matthey refinery at Wadeville will complete the plans for handling Rustenburg’s increased output and will, for the first time, make platinum metals available in marketable forms in South Africa.

Platinum Metals Rev., 1967, 11, (4) 131 denurn The Platinum-MolvbJ SystemJ THE FORMATION OF INTERMEDIATE PHASES

By G. L. Selman, BS~. Research Laboratories, Johnson Matthey & Co Limited

Although platinum-clad molybdenum is used extensively as a material for handling molten glass, surprisingly little is known about the constitutional relationships in this refractory metal binary system. Recent work in the Johnson Matthey Research Laboratories has conjrmed that the pub- lished equilibrium diagram is incomplete and that four intermediate phases are formed at high temperatures. This work has provided a better understanding of the behaviour of platinum-clad molybdenum equipment under operating conditions in the glass industry.

Advances in glass technology, leading in 15ooOC. Such information is not generally many instances to increased handling temper- available in the literature. atures, are placing an ever-increasing burden During the course of recent diffusion upon glass handling equipment. Emphasis is studies made in these laboratories on being placed more and more on the use of molybdenum rods mechanically clad with composite materials, such as molybdenum platinum sheaths, metallographic evidence with an outer cladding of platinum, which confirming the existence of four intermediate take advantage of both the excellent high alloy phases in this complex binary system has temperature mechanical properties of the been obtained. The solubility of platinum in refractory metals and the outstanding oxi- molybdenum in the temperature range 1400' dation resistance and general chemical in- to 170oCChas also been determined by direct ertness of the platinum metals. analysis of the microstructure of two molyb- While the stirrers, mandrels and electrodes denum-rich alloys made by conventional constructed of platinum-clad molybdenum alloying techniques. The solubility has been have useful lives at temperatures of up to found to increase rapidly with temperature 12oocC,at higher temperatures, although this in this region. The results of this investiga- combination represents the most economic tion bear interesting comparison with the and technically satisfactory choice, inter- previous studies made on this system. reaction between the two metals takes place, so that the life of the platinum sheath is Previous Constitutional Work largely dictated by the rate at which molyb- The earliest reference to the platinum- denum diffuses through it and by the effect molybdenum system appears to be that due to of the intermediate alloy layers so formed Dreibholz (I) who suggested that about 16 upon its integrity. weight per cent molybdenum should be It is therefore becoming increasingly im- soluble in platinum at the eutectic temper- portant to the metallurgist concerned with ature, this figure decreasing to less than two this problem that he has at his command per cent at room temperature. Hultgren and sound information concerning the binary Jaffee (2) studied electron beam melted alloys alloys of the platinum metals with the containing up to 50 atomic per cent molyb- refractory metals at temperatures up to denum after annealing at IOOO"C.The X-ray

Platinum Metals Rev., 1967, 11, (4), 132-137 132 Fig. 1 Tentative constitutional diagram of the molybdenum- KNAPTON RAUB platinum system as proposed 0 0 Pt by Knapton (6). The present 260C A A eta, studies have confirmed that two v V E+Pt + 0 E ndditional intermediate phases b D € exist, and have also shown that B n aI the solubility of platinum in X MELTING POINTS molybdenum is considerably 220c higher than the diagram would suggest at temperatures above LIQUIDMo +\ 1400°C I U w I800 a -x-4 2) b *oa 00 4 u1Z' n a

I-3 Mo+E 1400

bb

1000 \+a;.. 0 b

OD 0

600 2r 80 I ATOMIC PER CENT PLP NUM patterns that were obtained showed a single point determinations, X-ray analyses and face centred cubic phase, with lattice con- microscopical examinations. Platinum-rich stants near to that of platinum, for all alloys were shown to form via a peritectic compositions. reaction, The first systematic investigation was Liquid f p z ci carried out by Raub (3) who studied arc and molybdenum rich alloys formed via a melted alloys. He observed very little eutectic solubility of platinum in molybdenum but Liquid 2 p + y (Mo). found that molybdenum was appreciably Nishimura ascribed the composition PtMo to soluble in platinum. He detected a tetragonal the hexagonal phase, and his diagram distortion of the face centred cubic lattice in suggests an appreciable solubility of platinum platinum-rich alloys containing more than in molybdenum at the eutectic temperature. about 25 atomic per cent (14 weight per cent) Nishimura did not account for the tetra- of molybdenum to give an axial ratio greater gonal phase in his work, and the constitutional than 1.0. This new phase, denoted al, diagram representing the best combination of separated from the terminal solid solution evidence available at that time is that due to below 14oo0C. A hexagonal close packed E Knapton (6), reproduced in Fig. I. It is phase was found to form at about Pt3M02, obvious that no attempt has been made to with a very wide composition range. Further determine the phase boundary positions references to this hexagonal phase were made accurately, and this diagram can only be by Greenfield and Beck (4) and Nishimura regarded as tentative. (5). The latter author constructed an The first suggestion that the diagram was equilibrium diagram on the basis of melting incomplete came from Kirner (7) who claimed

Platinum Metals Rev., 1967, 11, (4) 133 to have observed a new phase, stable only at in all probability PtMo,, isostructural with the high temperatures, at the molybdenum-rich P-tungsten phase previously observed in end. iridium-molybdenum alloys (9). Figure I illustrates the lack of previous experimental work in this region, and it is not Experimental Diffusion Studies at too surprising that such a phase remained High Temperatures undetected. Thc phase was very hard, and Platinum-molybdenum diffusion couples have readily observable in both arc melted alloys been examined extensively in these labora- and diffusion couples heat treated at 1400' and tories in recent times as part of a general ISOOT.It decomposed on heating for 30 investigation into the uses of platinum at high hours at 1200°C. temperatures. Pressure bonded sheets have Rooksby and Lewis (8) conducted the most been found to be unsuitable for long term recent study of this system. During their annealing above 1300"C,due to a tendency for experiments they heated fine platinum-clad the components to peel apart, and the test molybdenum wires under controlled condi- specimens which formed the basis for the tions which produced the intermediate phases major part of this work were manufactured in turn on the coating surface, from which from spectrographically pure Murex molyb- X-ray diffraction patterns were then obtained. denum rod and high temperature grade The compositions of the phases so formed platinum tubing of 0.060 inch wall thickness, were not determined directly, but were containing typically about 0.0075 per cent approximately fixcd by analogy with other total impurity. isostructural compounds from the X-ray dif- Short lengths of the molybdenum rod were fraction data. vacuum sealed into the close fitting platinum Table I, which is reproduced in part from tubes, and the two mctals were then bonded Rooksby's paper, lists the phases identified by lightly hot swaging the assemblies at and some typical heat treatments which were 1200°C.The annealing tests were conducted required to produce them at the coating in air at 1400°C. The specimens were freely surface. supported in the hot zone of a mullite tube furnace at this temperature for periods up to Table II 2000 hours, following which they were cooled Table I Electron Probe Microanalyses of in air and sectioned for metallographic Intermediate Phases in the Platinum-Molybdenumthe Four Intermediate Phases System examination. These composite specimens were difficult to etch chemically because of the Phase MoStructure Heatrt Treatment /I (Pt,Mo)Wt.yo TetragonalAt.?, Wt.:/,rooo"C At.o/b for vastly differing response of the two metals to (a, Raub) 81.0 24 hr the etching solution. The microstructures y (Pt,Mo)I 67.5 Orthorhombic31.5 r~oo"C 18.5for were revealed most clearly by cathodically I1 34.0-45.0 51.1-62.5 54.4-65.0 37.0-47.824 hr 6 (Pt,Mo,) H.C.P. 13ooOC for etching the polished sections in a stream of (E Raub) I hr I11 26.5 42.6 75.0 59.6 P (PtMo,) Cubic A15 13oo0C for low pressure argon. hr IV 28.5-24 31.6-39 77.0-81.3 62.2-67.624 Microstructure and Constitution of Rooksby and Lewis thus identified two the Diffusion Zones phases in addition to those originally pro- Diffusion couples prepared in the manner posed by Raub, the orthorhombic y and the described in the foregoing section maintained $-tungsten structure designated E. Both of their integrity throughout the annealing these phases had very narrow composition cycle, and no interfacial failures occurred. ranges, judging from the small variations Fig. 2 shows the diffusion zone formed in a observed in their lattice spacings. The platinum-clad molybdenum specimen by molybdenum-rich phase due to Kirner is thus annealing for 1100hours at 14ooOC. The

Platinum Metals Rev., 1967, 11, (4) 134 intimately convoluted nature of the inter- mediate alloy layers, which makes it difficult to isolate and follow the somewhat erratic formation of the phase adjacent to the molybdenum, was a noteworthy and fairly typical feature of the microstructures ob- served during the course of this work. Rooksby and Lewis showed from their X-ray data that the structural transitions from one phase to the next occur with the minimum of atomic movement and alteration of lattice spacings, in spite of considerable changes in Fzg. 2 A molybaknum-platinum interlace after composition. This close relationship between annealing for 1100 hours at 1400"C, showing the the phases, which resemble a series of dis- four intermediate alloy layers formed during the crete but ordered solid solutions, could well heat treatment. x 200 account for their somewhat intimate associa- 1600 tion within the microstructure. 1 On close scrutiny it was possible to resolve 11400 I four intermediate phases in the diffusion zone, t1200 in complete agreement with the findings of Rooksby. These phases are defined more - 1000 clearly in the microhardness and microprobe -HV 1500 traverses made across the diffusion zone, - 800 shown in Figs 3 and 4. I The curve of microhardness across the t 6oo diffusion zone is remarkably similar in shape to those obtained by Kirner, who studied diffusion couples annealed at 1400' and I 200 1500°C. This worker suggested that the peak

0 I00 200 300 at the molybdenum-rich end of the traverse was due to his new phase, and identified the Fig. 3 A microhardness scan made across the inter- face shown in Fig. 1. The hardness levels can be second peak with the hexagonal phase dis- readily identtfied with the mirrostruetiire covered by Raub. Comparison of the micro- hardness curve with the microprobe scan 00 strongly suggests, however, that the hexagonal 6 phase is more closely related to the mini- eo c z mum between the two peaks, and that the 60 u" second peak occurs within the orthorhombic [L w P y phase discovered by Rooksby. 4o t- I The microprobe traverse confirms Raub's !? finding that the terminal solubility of platinum 20 g in molybdenum is small at intermediate 0- temperatures, and highlights the extensive TRAVERSED LENGTH (MICRONS) composition range of the hexagonal phase. In an attempt to establish the compositions Fig. 4 Electron probe scans for molybdenum and of the intermediate alloy layers with some platinum across the interface shown in Fig. 1. The intermediate alloy layers are well dejined and can accuracy, point analyses were made at 20 kV be accurately related to hardness and microstructure on each of the four phases shown in the

Platinum Metals Rev., 1967, 11, (4) 135 Fig. 5 The substantially single Fig. 6 The 20 per cent Fig. 7 The pearlitic structure phase microstructure of a 20 platinum-molybdenum alloy formed by anneuling the 20 per ce~platinum-molybdenum quenched after annealing for per cent platinum-molybdenum alloy quenched after annealing 7 hours at 170O"C, showing the al1o.y for 165 hours at 1250°C. for 7 hours at 1850°C. x 200 typical high temperature x 750 duplex microstructure. x 200

diffusion zone. The radiations used were to the compositions PtMo3, PtMo, Pt,Mo, PtLa and MoLa. After correction for atomic and Pt,Mo, a sequence which is not well number and absorption effects the values supported by any of the previous investi- given in Table I1 were obtained. gations. The Solubility of Platinum in Molybdenum The form of the molybdenum-rich end of the binary system envisaged by Knapton Wt.yo At.?, Wt.:/, At.o/b (Fig. I) appeared from our own results, and from those of Kirner and Rooksby, to be I 67.5 81.0 31.5 18.5 seriously in error. Alloys containing 10and 20 weight per cent I11 26.5 42.6 75.0 59.6 platinum were prepared, from starting materials of similar purity to those used for IV 28.5-24 31.6-39 77.0-81.3 62.2-67.6 the diffusion studies, in an argon arc furnace. The melted buttons were turned and remelted The analyses are quoted to an estimated several times, and finally heat treated for accuracy of & 3 per cent. The composition seven hours at 1850°C to ensure homo- ranges obtained for phases I1 and IV at geneity. Samples from each ingot were then 1400°C agree remarkably well with those annealed at temperatures ranging from I IOO shown on the tentative diagram due to to 185o"C in an argon atmosphere for long Knapton (Fig, I) for the hexagonal (E) and periods, quenched and prepared for metallo- tetragonal (q)intermediate phases. graphic examination. Taken in order, however, they bear little Figs 5, 6 and 7 show microstructures resemblance to the sequence of structures typical of the 20 per cent alloy quenched from reported by Rooksby, with the possible 185o"C, 1700OC and 125oOC. Although some exception of phase I. Taken in isolation, the grain boundary precipitation has occurred in analytical results suggest that the atomic the sample quenched from 1850°C it would arrangements of the four phases correspond seem that the alloy was substantially a single

Platinum Metals Rev., 1967, 11, (4) 136 1111 26.5 42.6 75.0 59.6 IV 28.5-24 31.6-39 77.0-81.3 62.2-67.6 Fig. 8 Boundary curves for the molybdenum-rich l800, It terminal soEid sobtion and the high temperature E phase as determined by electron probe microanalysis of alloys in the duplex region

phase solid solution at the soaking tempera- ture. Untreated filings taken from this 1200 specimen gave a diffraction pattern corres- (Mo) i-& ponding to a body centred cubic structure 0 10 20 with a lattice parameter a == 3.143& a value ATOMIC PER CENT PLATINUM slightly lower than that of pure molybdenum. At lower temperatures a second phase catastrophic oxidation of the molybdenum can separated from this terminal solid solution take place without hindrance. Such failures (Fig. 6) which in turn decomposed at tempera- are rarely associated with the complete tures below about 1300OC to yield the pearlitic diffusion of molybdenum to the outer microstructure shown in Fig. 7. X-ray diffrac- platinum surface. tion showed that the high temperature duplex From laboratory experience with the manu- microstructure was composed of body centred facture of test composites it has become quite cubic and cubic @-tungsten) structures, the clear that unless special precautions are taken it is difficult to maintain a coherent interface latter corresponding to the E phase described by Rooksby. The low temperature duplex during annealing when the heat treatments are structure consisted of a body centred cubic carried out above 1300°C, and that this and a hexagonal phase corresponding to that difficulty is mainly due to high interface strains associated with the formation of the designated by Rooksby as 6. The individual phases present in specimens high temperature intermetallics in the difi- quenched from temperatures above 1300'C sion zone. The formation of these phases were fully resolvable under the electron could similarly account for the distortions ob- probe microanalyser, and their compositions served in glass handling equipment used at were determined. The analytical results have high temperatures. Further theoretical work on this and other been plotted in Fig. 8, which illustrates the refractory metal platinum systems which are very rapid increase in the solubility of plati- potentially useful at high temperatures would num in molybdenum between 1400' and 17oo0C, and the constancy of the high temp- thus be of considerable practical value to metallurgists and engineers concerned with erature E phase composition over this region. plant design and development. The E phase decomposes eutectoidally at 1325' izj"C, according to the metallographic evidence obtained on the two alloys examined. References I L. Dreibholz, Z. phys. Chem., 1924, 108, 5 Practical Significance of the High 2 R. Hultgren and R. I. Jaffee, J. Appl. Phys., 1941, 12, 501 Temperature Phase Relationships 3 E. Raub, Z. Metallk., 1954, 45, 23 When attempts are made to use the desirable 4 P. Greenfield and P. A. Beck, Trans. A.I.M.E., 1956,206, 265 properties of platinum-clad molybdenum at 5 H. Nishimura, Nippon Kinzoku Gakkai-Si, temperatures above 1300T failure tends to 1958, 22,425 take place in a characteristic manner. Large 6 A. G, Knapton, Planseeber., 1959, 7, 2 distortions of the sheath begin to occur, 7 K. Kirner, Metall, 1962, 16, (7), 672 8 H. P. Rooksby and B. Lewis,J. Less-Common giving the component a "blistered" appear- Metals, 1964, 6, 451 ance, and eventually the sheath cracks, so that 9 A. G. Knapton, 3. Inst. Metals, 1958-59,87,28

Platinum Metals Rev., 1967, 11, (4) 137 Electron Configuration and Crystal Structure of Platinum Metal Alloys INTERMEDWTE PHASE FORMATION INTERPRETED IN TERMS OF THE ENGEL-BREWER CORRELATION

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

and third long periods do not use all their The platinum metals react with some valency electrons for bonding, differing inter- of their closer neighbours in the Periodic pretations of their alloying behaviour have Table to produce intermediate phases of figured prominently in the papers referred to high stability. While this behaviour above. Before exploring the implications of tends to conjrm some of the predictions the theory so far as the platinum metals are made by protagonists of the Engel- concerned, its general background and scope Brewer theory of alloying, the general deserve a little attention. validity of this theory is still a matter of vigorous controversy. In this article Genesis of the Theory some of the conflicting opinions that The integral electron concentration theory have been advanced are reviewed and first advanced by Engel was in fact an exten- discussed. sion and generalisation of some of Hume- Rothery’s ideas on electron compounds (8,g). When considering intermediate phases con- Correlations between the electron con- taining iron, cobalt or nickel, Hume-Rothery figuration and crystal structures of the was able to correlate crystal structure and metallic elements and their alloys were first electron atom ratios only by assuming that the proposed by Engel in 1949 (I, 2), and since transition element contributed no electrons that time Brewer has enlarged and refined the to the crystal structure. Engel, however, original conception and has used it to predict concluded that the d electrons of the transition constitutional relationships in a wide range element participated in the bonding of these of alloys (3, 4, 5). Recent comments by intermediate phases, thus explaining their Hume-Rothery (6, 7) have stimulated a great high melting points. The Engel-Brewer deal of discussion; the Engel-Brewer theory theory now states that all unpaired electrons has been brought to the attention of a wide participate in crystal bonding, but that the range of metallurgical opinion and is no d electrons have no effect upon the type of longer a matter of purely academic interest. crystal symmetry adopted, which is deter- The basic point of contention is whether a mined solely by the number of s and p hypothesis, suggested originally by the electrons. valency and crystal structure sequence ex- Thus the I, z and 3 valency electrons of hibited by sodium, magnesium and alumin- sodium, magnesium and aluminium explain ium, can with justification be used to inter- why these elements crystallise respectively pret the behaviour of the transition metals in the b.c.c., h.c.p. and f.c.c. systems of and their alloys. Since the elements to the symmetry. The b.c.c. lattice is apparently right of ruthenium and osmium in the second stable from I to 1.75 electrons/atom, the

Platinum Metals Rev., 1967, 11, (4), 138-140 138 h.c.p. lattice from 1.8 to 2.2, while the f.c.c. therefore be more stable than zircomum lattice extends from 2.25 to more than three carbide. Experiments of this sort reported electrons per atom (10). by Raub (I I) several years ago used in general To thermodynamic aspects of the Engel- lower concentrations of carbide, and in most Brewer correlation Professor Hume-Rothery instances the base metal was taken into solid has so far devoted little attention. This part solution by platinum. of the theory is of great interest as it provides Zirconium carbide, although one of the a strong link between the electronic approach most stable known, has a lower free energy and metallurgical thermo-chemistry. When of formation than the refractory oxides. for example the e1ectron;atom concentration Bronger and Klemm (12)showed in 1962 that suggests hexagonal and body centred struc- zirconium oxide can be effectively reduced by tures of comparable total energy, the theory hydrogen in the presence of platinum, and predicts that the b.c.c. structure will be the this has been cited by Brewer in support of stable high temperature form, as the h.c.p. his general predictions. Aluminium oxide was structure, having a lower co-ordination would also reduced however, and the solubility of make a larger contribution to the high tem- aluminium in platinum is high. The activity perature entropy. of aluminium in this dilute solid solution must therefore have been very low. Transition Metal Compounds Bronger also reported the reduction of The theory indicates that combinations of yttrium and lanthanum oxides with hydrogen the transition elements from the left and right in the presence of platinum with the forma- of the Periodic Table should produce com- tion of the compounds Pt, Y and Pt, La. All pounds of high stability. Metals from Rb to the lanthanides between lanthanum and Tc and Cs to Re use all their valency electrons thulium have since (13) been reduced in a for bonding while the platinum metals do not. similar manner. In this series of experiments A mixture of these two types of atom pro- dry ammonia was employed as a reductant. motes, therefore, a flow of electrons from the Complete reductions were achieved at 1200°C element with an excess to that with vacant for all elements with the exception of samar- orbitals. Thus when Zr and Ir are alloyed ium and europium which required tempera- the Ir donates electrons to the Zr. The tures between I350 and 1500°C. stability of the compound Zr Ir, thus formed is according to Brewer (5) attributable to the Some Inconsistencies fact that 31 electrons contribute to the It is reported (14) that hafnium and plati- bonding process compared to the 25 bonding num, when heated together, react with ex- electrons of the uncombined atoms. plosive violence. This finding, and the other For a given base metal the number of results reported above, leave no doubt that electrons transferred on combination should the compounds between platinum and those increase as the atomic weight of the platinum base metal transition elements which form metal increases. This explains, in a qualitative refractory oxides are of quite extraordinary way, the high stability of Zr Pt, compared to stability. Zr Ir,. Brewer has attempted (5) to verify For practising metallurgists, howcver, many the prediction in a more specific manner by baffling inconsistencies remain. Platinum and heating zirconium carbide with Pt, Ir and 0s. palladium can, for example, be safely melted In all instances the carbide dissociated, under hydrogen in zirconia crucibles. Slight graphite was liberated and the zirconium contamination of the platinum metal undoubt- formed an intermetallic compound with the edly occurs under such conditions, although platinum metal. it is a minor effect and usually associated with These platinum metal compounds must silicious attack. Refractory oxide dispersants

Platinum Metals Rev., 1967, 11, (4) 139 in a solid platinum matrix are, however, 2 N. Engel, Alloys as Electron Concentration Phases, Ibid., 97, 105, 113 notoriously unstable, and this appears to 3 L. Brewer, Paper in “Electronic Structure and suggest a high affinity of solid platinum for the Alloy Chemistry of the Transition Elements”, Ed. I?. A. Beck, Interscience New York, 1963 refractory metal. 4 L. Brewer, “Predictions of High Temperature Differences in geometry could also be in- Phase Diagrams”. UCRL 10701,Univ. Cali- fornia, volved in these apparent anomalies as plati- 1963 5 L. Brewer, Acta Metall., 1967,15, 553 num, when held molten against a refractory 6 W.Hume-Rothery, Ibid., 1965,13, I039 wall, might prevent complete removal of 7 W.Hume-Rothery, Ibid., 1967, 15, 567 8 W.Hurne-Rothery “The Structure of Metals gaseous reaction products such as water and Alloys”. Monograph and Report Series vapour. No. I, Inst. Metals, London, 1936 The experimental results and interpreta- g W. Hume-Rothery, “Atomic Theory for Students of Metallurgy”. Monograph and tions given in this recent group of papers Report Series No. 3, Inst. of Metals, London, will undoubtedly lead to a great deal of I948 10 N. Engel, Acta Metall., 1967, 15, 565 further work, and should moreover encourage 11 E. Raub and G. Falkcnburg Z. Metallkunde, detailed constitutional studies on platinum 1964,559 186 metal alloys. 12 W.Bronger and W. Klemm, Z. anorg. allgem. Chem., 1962, 319, 58 References t3 W.Bronger, J. less-common Metals, 1967, 12, I N, Engel, Metals as Electron Concentration 63 Phases, Kern. Maanedsbl, 1949, 30, 53 14 J. Margrove, note to (5)

Brazing Graphite to Metals A NEW PALLADIUM-BASE BRAZING ALLOY FOR NUCLEAR ENERGY APPLICATIONS The development of advanced molten-salt as-brazed condition but also after thermal reactors posed a problem of making mechanic- cycling tests (ten cycles between 700°C and ally strong and pressure-tight joints between room temperature). A 1000 hours test in a graphite and refractory metals and alloys for molten LiF-Be,F,-ZrF,-ThF,-UF, mixture service in contact with fused fluorides at at 700°C produced only a slight surface elevated temperatures. According to a report roughening of the brazing alloy. recently released from Oak Ridge National Surprisingly, no cracking - which often Laboratory (USAEC Report ORNL-3970, occurs in graphite-metal brazed joints due to 1966), a satisfactory solution to this problem differential thermal expansion/contraction was found in brazing with a new palladium- of the metallic and non-metallic parts - was base brazing alloy. observed in this case. This was attributed to The new material, melting below IZSO”C, the fact that the thermal expansion coefficient is based on the well-known 60 per cent of molybdenum is only slightly larger than that Pd-40 per cent Ni brazing alloy to which of graphite. It is claimed, in fact, that by 5 per cent chromium was added at the expense using molybdenum inserts, or so-called of nickel. Palladium was chosen as the basis ‘transition’ pieces, crack-free joints can be of the new alloy because of its relatively low made with the Pd-Ni-Cr alloy between thermal neutron cross section (eight barns) graphite and metals with high thermal ex- and its good resistance to the corrosive action pansion coefficients. of molten salts; chromium, which is one of the Although the new alloy was developed as a carbide forming elements, was added to make special purpose material, there is no doubt the alloy capable of wetting graphite. that palladium-base alloys of this kind would As was to be expected, the 60 Pd-35Ni-5 prove useful in general engineering applica- Cr alloy exhibited good wetting properties on tions in which a high strength and good graphite, molybdenum and tungsten. Lap resistance to corrosion and oxidation at both joints made with this alloy between graphite room and elevated temperatures are important and molybdenum parts in a vacuum furnace considerations. at 1z5o”C were defect-free not only in the M.H.S.

Platinum Metals Rev., 1967, 11, (4) 140 The Structure of Supported Platinum Catalysts

EXAMINATION BY ELECTRON MICROSCOPY

By R. L. MOSS,M.Sc., Ph.D. Ministry of Technology, Warren Spring Laboratory

metal catalysts (diffusion limitations apart) Modern techniques are steadily increas- may be related not only to the metal area but ing our knowledge of the structure and to the actual size of the metal crystallites properties of the supported platinum responsible for that area. The latest standard metal catalysts so widely used in electron microscopes can resolve the smallest chemical processing. The main func- aggregates of platinum atoms which may be tion of the support, such as charcoal, described as crystallites and hence provide alumina or silica, is to increase the valuable information on the sizes and numbers surface area of the platinum metal and of crystallites present. Further, the distribu- so to enhance catalyst performance, and tion of platinum throughout the support and methods for studying the dispersion of characteristics of the support itself may be the platinum are therefore of consider- examined. able importance. This article describes the application of electron microscopy Appearance under the Electron to the problem and compares the results Microscope given by this and other methods. Suitable specimens for electron microscopy can be prepared by cutting extremely thin sections (300 to 500 A) with an ultra-micro- The study of the state of dispersion of the tome from catalyst particles embedded in, metal in supported platinum catalysts is based for example, “Araldite”. An alternative on indirect methods such as gas chemi- method is ultrasonic dispersion of the sorption, and on direct methods such as catalyst in butyl alcohol. Remembering the X-ray diffraction and electron microscopy. very small area under examination, a number The chemisorption method depends on of specimens must be prepared and surveyed finding conditions of temperature and pres- in order to obtain representative electron sure at which a gas-hydrogen or carbon micrographs. monoxide-will chemisorb to monolayer coverage on the platinum but not on the Platinum/Silica support. The volume of gas taken up shows Fig. I shows an electron micrograph of a the extent to which the platinum has been 3 per cent platinum/silica catalyst made by dispersed. For example, it was shown (I) impregnating silica gel with chloroplatinic that a freshly prepared reforming catalyst acid solution, drying at 120°C and reducing (0.6 wt. per cent platinum on ?-alumina) had in hydrogen. At a magnification of IOO,OOO X , most of the platinum atoms exposed, probably the platinum shows up as dark spots evenly as islands or as very small crystallites less than distributed as minute crystallites in the pore 10 a in size. There is, however, a growing system of the silica gel. Electron diffraction awareness that the performance of supported patterns from selected areas with a high

Platinum Metals Rev., 1967, 11, (4), 141-145 141 Fig. 1 3per centplatinunt/ silica catalyst, magnifica- tion 100,000 X, showing platinum crystallites as dark spots on grey silica background

concentration of dark spots confirm the are predominantly in sizes below about 50 A; presence of platinum. in the 10 A size crystallites most of the About 1000 platinum crystallites in this atoms (datomic=z.77 A) are “surface” atoms. electron micrograph were sized in terms of Although the 10 to 50 A crystallites account their diameters, since they appear approxi- for only one-quarter of the total weight of mately spherical, in increments of 10 A, and platinum present on the support, nevertheless Fig. z shows the number of crystalljtes they provide almost half of the available observed in each size range. The crystallites platinum area. Hence the platinum pri- marily responsible for the performance of this supported catalyst can be “seen” by electron microscopy. Electron micrographs of the silica support itself showed spherical particles of, very roughly, IOO a diameter. Assuming no loss of area when the particles contact, the cal- culated surface area is -250 m2/g. This rapid estimate agrees reasonably with the BET gas adsorption value.

Platinum/Charcoal or Alumina Fig. 3 shows an electron micrograph of a platinum on charcoal catalyst at a magnifica- tion of IOO,OOO A. Chemisorption methods showed the very high platinum area of a Johnson Matthey 5 per cent platinum/ charcoal catalyst which formed the basis of the sample examined. The catalyst was then subjected to a vigorous sintering treatment (firing at 300°C in air) to encourage crystallite growth. Nevertheless, as the electron micro- graph shows, the platinum crystallites were

Platinum Metals Rev., 1967, 11, (4) 142 Fig. 3 Sper centplatinuml charcoal catalyst, heated in air at 300”C, magni5cation 100,000 X, showing very small platinum crystallites

still very numerous and extremely small in the relation existing between the number of gas molecules adsorbed at this point and size, yielding a large catalytically-active the number of surface metal atoms. platinum surface. The equipment required however, is Fig. 4 shows an electron micrograph (2), relatively simple, for example, a conventional (35,000 X) of a catalyst with 2.5 per cent volumetric apparatus such as might be used platinum supported on a low-area alumina. for BET surface area determinations, a Measurement of the platinum area by carbon vacuum micro-balance or a flow system linked monoxide chemisorption showed that it was to a gas chromatograph. If the observed closely similar to the area of the platinum/ metal area is S, the mean crystallite size, d,, silica catalyst discussed above (Fig. I), but is calculated from dS=6/Sp where p is the the electron micrographs are in marked density of the metal; it is assumed that the contrast. Whereas the platinum crystallites crystallites are spheres or any regular poly- in the silica-supported catalyst are widely hedron except the tetrahedron. This dia- distributed, this alumina-supported catalyst meter, d,, is the surface-average diameter shows dark patches of platinum. At still defined by Cnidt/Cnid,2, where there are ni higher magnifications (IOO,OOO x ), these crystallites of diameter, di. From the crystal- patches were clearly resolved as groups of lite size distribution (Fig. 2) obtained from small platinum crystallites (Fig. 5) and the electron micrographs the diameter, d,, is platinum area is obviously higher than it readily calculated for comparison with the might at first seem. mean size obtained by chemisorption. The determination of crystallite size by Comparison with Chemisorption X-ray diffraction depends on the fact that and X-ray Diffraction below about 1000 A size, X-ray reflections The chemisorption method for measuring are broadened beyond the normal ‘‘instru- the metal area of a supported catalyst has mental” breadth. Thus the method involves already been briefly discussed. Its main measuring the breadth of one or more X-ray problems are : reflections, preferably using an X-ray counter- difiactometer which provides a chart-record- chemisorbing gas on the metal but not on the support; ing of the position, profile and intensity of choice of a criterion for monolayer coverage; each reflection. The Scherrer equation relates

Platinum Metals Rev., 1967, 11, (4) 143 Fig. 4 A 2.5 per cent platinumlalumina Fig. 5 Same catalyst, magni$cution 100,000 X , catalyst, magnification 35,000 >( ,showing plat- resolving individual platinum crystallites inum as dark patches the excess breadth to the mean crystallite done for the 3 per cent platinum/silica size, 6,which is a volume-weighted average catalyst (Figs. I and z), taking into account diameter, Cnidt/Cnidt. Again, this type of the different types of average involved, with average diameter can be calculated from the results shown in the table. Some satis- electron microscope observations for com- factory conclusions can be drawn from these parison with X-ray results. The main prob- results : lems with the X-ray diffraction method are: the assumptions involved in the chemisorption method (carbon monoxide at 25OC, COiPt the smaller platinum crystallites, perhaps ratio=^, no adsorption on silica) seem those less than 50 A, when measured with reasonably justified; standard equipment, are not detected yet provide much of the available platinum the electron microscope resolved most of the area of the catalyst. The proportion of platinum crystallites contributing to the platinum remaining undetected can, how- platinum area; ever, be estimated (3); the ‘particles’ viewed in the electron rnicro- crystallite size is measured whereas the plati- scope were also the crystallites detected by num can be present as particles, that js, X-ray diffraction. agglomerates of crystallites, with interior surfaces inaccessible to gas molecules, Relation to Catalyst Performance With the problems involved in measuring There are two important consequences, crystallite size (and platinum area) by at least, for catalyst performance arising chemisorption or X-ray diffraction, it is there- from an increase in crystallite size, perhaps fore of some interest to compare such results as a result of sintering during use. with the crystallite size distribution obtained The more obvious is the rapid loss in metal from electron micrographs. This has been area accompanying crystallite growth. The

Average Crystallite Size in 3 per cent Platinum-Silica Catalyst Mean diameter, d,, of all crystallites: by chemisorption 45 A by electron microscopy 55 A Mean diameter, d,, of crystallites 50 A size and above: by X-ray diffraction 60 A by electron microscopy 65 A

Platinum Metals Rev., 1967, 11, (4) 144 Fig. 6 Models of small platinum crystallites: left-hand represents approximately 10 A diameter with mainly (111) crystal planes ex- posed; right-hand re- presents approximately I2 A with predomi- nantly (100) planes ex- posed

left-hand model in Fig. 6 represents a very activity per unit metal area. Now a small crystallite, - 10 A diameter, containing further step forward would be to record 38 atoms ofwhich 31 are exposed (82 per cent), the structure of the catalyst, at least in excluding those which only contact the sup- part, by determining the crystallite port. The slightly larger right-hand model, size distribution from electron micro- -12 A diameter, represents 62 atoms but graphs. now only 44 (71 per cent) are present at the (ii) Apart from duofunctional reforming surface. One important factor in choosing the catalysts where both platinum and support material is the stability which it can alumina provide catalytically active impart to the crystallites against sintering sites, it is believed that the specific together. activity may sometimes be altered by Further reference to the models (Fig. 6) the nature of the support. This means shows a less obvious consequence of crystallite that, in addition to its traditional roles growth. Whereas the smaller crystallite which include extending the metal displays mainly (I I I) crystal planes, addition area, the support co-operates somehow of a single layer of atoms to.form the slightly in the catalytic process. However, larger crystallite yields a surface with pre- changing the support can alter the dominantly (100)planes exposed. As these crystallite size distribution and again small crystallites grow, other crystal planes electron micrographs may help to and atomic arrangements rapidly form and disentangle the effects of crystallite size change, each with its characteristic catalytic and support on catalyst performance. properties. For example, when n-heptane was reformed over a series of platinum/ Acknowledgement The author wishes to acknowledge the con- alumina catalysts (4, dehydrocyclisation tribution of Miss J. Holroyd who prepared the activity was decreased and isomerisation in- electron micrographs used to illustrate this article. creased as the mean crystallite size varied References from 10 to 450 A. Some applications of the electron-micro- I L. Spenadel and M. Boudart,J. Phys. Chem., 19601 64, 204 scope to supported catalyst research are 2 R. L. Moss, The Chemical Engineer, 1966, therefore apparent. (1991,(June), CE 114 3 A. Dorling and R. L. Moss, J. Catalysis, (i) When the performance of a supported T. 1966,5, 111 catalyst is being assessed, often the 4 H. J. Maat and L. Moscou, in Proceedings of metal area is measured in order to the Third International Congress on Cataly- sis, Amsterdam, 1964, p. 1277 (Amsterdam: report the specific activity, that is, North-Holland Publ. Co, 1965)

Platinum Metals Rev., 1967, 11, (4) 145 The Platinum Metals in Catalysis

PAPERS AT THE SECOND CANADIAN SYMPOSIUM

The second Symposium on Catalysis hydrocarbon in which the catalyst was sus- organised by the Canadian Institute of pended they were able to achieve complete Chemistry was held in June at McMaster substitution of all the hydrogen atoms. University, Hamilton, Ontario, and was well R. J. Harper and C. Kemball, of Queen’s attended by workers mainly from Canadian University, Belfast, compared the behaviours industries and universities. Of the twenty- of palladium and platinum with those of eight papers presented, covering a very wide nickel and tungsten in the exchange of a range of subjects, some eight or nine had series of mono-halogenated benzenes with relevance to the use of platinum metals in deuterium. The exchange rates, which heterogeneous and homogeneous catalysis, decreased in the sequence of increasing including two on electrocatalytic phenomena. atomic number of the halogen (iodobenzene The electrochemical behaviour of gold- could not however be studied), were all palladium alloys was described in a paper slower than for benzene itself. The noble by T. J. Gray, R. Rozelle, A. Schneider and metals were less poisoned by the small M. L. Soeder (Alfred University, New York amount of halogen cleaved from the ring than State); by studying alloys containing about were the base metals. 12, 26, 44, 62 and 68 per cent gold, the The development of a new PkItinUm-On- authors established that the maximum rate of alumina catalyst having high activity and hydrogen occlusion occurred with the 26 per selectivity for the isomerisation of n-hexane cent gold alloy, for which the H/Pd ratio at was described by W. J. M. Pieters and the rest potential (32 mV) was 0.042. Alloys G. C. A. Schuit, of the Technical University, containing 12 and 44 per cent gold did not Eindhoven. It is well established that treat- achieve rest potentials (indicating lower rates ment of platinum on alumina with carbon of occlusion), while the alloy having 68 per tetrachloride at elevated temperatures forms cent gold behaved similarly to pure gold. The a surface layer of aluminium chloride which observations reported by D. J. G. Ives, greatly increases the activity of the catalyst F. R. Smith, P. D. Marsden and J. B. for isomerisation. However, Pieters and Senior, of Birkbeck College, on the cathodic Schuit were able to show that selectivity activation of mercury-poisoned platinum and could also be improved by controlled poison- of gold strongly suggested that the desorption ing of the platinum by thiophene. of hydrogen atoms is retarded on these G. C. Bond (Johnson Matthey) reviewed inactive surfaces. the hydrogenation of acetylene catalysed by The mechanism of the exchange of liquid the platinum group metals. The ability of saturated hydrocarbons with deuterium cata- palladium to hydrogenate acetylene selectively lysed by supported platinum metals differs to ethylene in the presence of a large excess of substantially from the corresponding gas ethylene was attributed to its ability to become phase processes. J. G. Atkinson, M. 0. rapidly and selectively poisoned for ethylene Luke and R. S. Stuart, of Merck, Sharp and hydrogenation. The addition of deuterium to Dohme, Montreal, disclosed that in the acetylene over palladium and platinum liquid phase systems the exchange is pre- catalysts gives about 80 per cent of cis- dominantly stepwise, and by continually C,H,D,, rhodium and iridium giving a passing pure deuterium through the liquid broader distribution of deuterated ethylenes.

Platinum Metals Rev., 1967, 11, (4), 146-147 146 Two of the contributions dealt with homo- The various products obtained from the geneous catalysis by platinum metal com- reaction of disubstituted acetylenes with pounds. P. R. Rony, of Monsanto, St Louis, palladous chloride were listed by P. M. gave a theoretical treatment of supported Maitlis of McMaster University; in non- catalytic solutions, and showed that there hydroxylic solvents, hexaphenyl-benzene is should exist an optimum liquid loading for obtained almost quantitatively from diphenyl- efficient catalysis. The system had been dis- acetylene. Dimethylacetylene in methylene covered independently by workers in both the chloride solution on the other hand reacts with Monsanto Company and the Johnson Matthey palladium chloride to give only about 10 per Research Laboratories (G. J. K. Acres, cent of hexamethylbenzene, the remainder of G. C. Bond, B. J. Cooper and J. A. Dawson, the product being polymeric in nature. J. Catalysis, 1966, 6, 139). G. C. B.

Iridium Coatings in Ion Engines HIGH WORK FUNCTION AND THERMAL STABILITY In their traditional miserly role, metals cation of thin layers of iridium and rhenium with a high work function are reluctant to to porous tungsten substrates. part with electrons although when heated Iridium coatings were obtained by spraying they accept them with great alacrity from dilute solutions of iridium trichloride on to materials of lower electron affinity. As an heated tungsten compacts which were sub- electron acceptor iridium is now being sequently reduced in hydrogen. Half-micron seriously considered as an improved ioniser coatings of iridium so obtained were stable material for use in caesium ion engines. This for at least 200 hours in vacuum at 1500°C work is being carried out under the auspices and work functions of 5.28 f 0.03eV were of NASA by the Hughes Aircraft Company measured on such deposits. Research Laboratories, Malibu, California, Electroplated rhenium surfaces were also and a recent report by R. R. Turk and W. E. effective. Although the work function of McKee (I) describes some of the preliminary 5.20eV I0.03 determined for rhenium was results obtained. comparable to that of iridium, it was found Thrust is obtained in these ion engines by that rhenium, because of its high solubility the reaction of a stream of electrostatically in tungsten, provided a less stable coating accelerated caesium ions and an appreciable than iridium. un-ionised flux rapidly destroys the accelerat- Much further work will be required before ing electrodes. Although solid tungsten has the true effectiveness of these noble metal been used as an ioniser it is easily flooded by coatings can be properly assessed. It is inter- the high flow rates of caesium now normally esting to speculate, however, upon the way in employed. which osmium might behave under such Porous tungsten with its high surface area conditions. The work function of osmium has is less liable to flooding but is unfortunately been recently determined (2)as 5.93 rt 0.05eV somewhat unstable and loses its permeability a value higher than that of iridium and rhen- at the normal temperature of operation ium. Osmium also forms a carbonyl which involved in these devices. might facilitate the deposition of uniform thin Attempts to produce complete ionisers of deposits on the tungsten substrate. higher work function and improved thermal A. S. D. stability involved powder metallurgy studies on iridium and rhenium alloys. Porous com- pacts based on the 50 per cent iridium, 50 References per cent tungsten composition had the hex- I R. R. Turk and W. E. McKee, “Alloy Ioniser agonal epsilon crystal structure and a high Fabrication”, NASA Contract No. NAS 3 - 6272, Hughes Aircraft Company, Malibu, resistance to densification. Economic and California practical considerations finally indicated that z P. Zalm and A. J. A. Van Stratum, Philips Tech. better results would be obtained by the appli- Rev., 1966, 27, (3/4) 69-75

Platinum Metals Rev., 1967, 11, (4) 147 Carbonyl Halide Complexes of the Platinum Metals

By M. J. Cleare, B.s~.,A.R.C.S. Research Laboratories, Johnson Matthey & Co Limited

The many advances in the chemistry of the acid by ruthenium (11) species has been platinum metals made in recent years have studied (I) and there are reports of the been particularly evident in the field of reaction of [IrC1,I3- or [IrClJ- with formic carbonyl group-containing complexes. Im- acid to yield carbonyl halide species of un- proved methods of preparation have been certain formulae (2,3). Ruthenium complexes developed and the uses of such complexes have been prepared by the long passage of in homogeneous catalysis have been and are carbon monoxide through solutions of ruthen- being actively studied. ium (111) halogen compounds (4)and iridium The preparation of these carbonyl halide complexes by the reaction of halogen com- complexes by a variety of techniques has been pounds with carbon monoxide under pressure reported. The production of ruthenium (5). Similar osmium compounds have not, so complexes by the decarbonylation of formic far, been reported.

Carbonyl Halide Complexes of Osmium, Ruthenium and Iridium

Infra-red C - 0 Complex Colour Reactants Time Stretching Frequencies I cm-1 Cs,(Os(CO)Cl,) Orange (OsC1,)2-+H.COOH Can be found 1968~s from &5 hr Cs,(Os( CO) &1,) White (OsC1,)’-+H.COOH -8-9 hr 2014vs 189gvs or OsCl,+H.COOH (2037) (1947)

Cs 2( Os(C0) pBrp) Yellow (OsBr,)2-+H.COOH -12 hr 2005vs 189gvs Cs(0s(CO),Cl3) White (OsC1J-iH.COOH -48 hr 2125vs 2046vs OsCl,+H.COOH 2014vs 2031sh 2023sh xggzm (2128) (2039) Cs(Os(CO),Br,) White (OsBrJ-+H.COOH -60 hr z1zovs2048vs 2017vs xgg6sh Cs,(Ru(CO)(H,O)Cl,) Green (RuC1,(H,O))S-+ I hr Ig’jIVS H.COOH RuC1, +H.COOH ZOjZVS I932VS Yellow Cs,(Ru(CO),Br,) Yellow- (RuBr,(H,0))2- + -6 hr ZOjZVS I932VS Green H.COOH RuBr, +H.COOH Yellow RuCI,+H.COOH 7 hr 2076vs z018vs Pink- (IrCl,)e-+H.COOH 2-3 min 2070vs Yellow (IrCl,)a-+H.COOH Cs,(Ir(CO)BrJ Orange (1rBrJ3--l H.COOH 2-3 min 2038vs Infra-red spectra run on Nujol mulls; frequencies in parenthesis in aqueous solution

Platinum Metals Rev., 1967, 11, (41, 148-149 148 Recent investigations into the reactions of and they further react to give the mono- and platinum metal compounds with formic acid dicarbonyl species respectively. The reaction have led to the discovery of a new and con- proceeds quickly to the diformate stage and venient method of preparing carbonyl halide the monocarbonyl complex is formed in small complexes of osmium, ruthenium and iridium quantities only. by refluxing the metal halide or halo-complex Triphenylphosphine derivatives are easily with go per cent formic acid (6). The com- prepared by warming the complexes with pounds formed were initially recognised as triphenylphosphine in formic acid solution or, carbonyl rather than formate complexes by more conveniently, by treating the solutions infra-red spectroscopy in the 2000 cm-l prior to isolation of a carbonyl halide salt region. with triphenylphosphine. The complexes The complexes that have so far been pre- [OS(CO>2(PPh,)ZXZI and [OGO)3PPh3)XzI pared and the reaction conditions are set out have been prepared from Cs,[Os(CO),X,] in the table opposite; all the compounds have and Cs[Os(CO),X,] respectively, while been characterised by elemental analysis and [Ru(CO)d'Pha)&J and [Ru(CO)(PPhJ&lzI their full infra-red spectra have been deter- have been prepared from Cs2[Ru(CO),X4) mined and recorded, and Cs,[Ru(CO)(H,O)Cl,] respectively (X = To isolate salts of the anionic species it was C1, Br). found necessary to use caesium as the cation The author's thanks are due to Dr W. P. since lighter atomic weight alkali metals Griffith of Imperial College of Science and yielded salts of very high solubility. Technology for help and guidance in this The reaction between sodium hexachlor- work. osmate (IV) (used because of the low solubility References of of other [OSC~,]~-salts) and formic acid is I J. Halpern and A. W. L. Kemp,J. Am. Chem. particular interest since it takcs place much SOC.,1966, 88, 5147 more slowly than those between ruthenium 2 I. I. Chernyaev and 2. M. Novozhenynk, Russ. J. Inarg. Chem., 1966, 11, 1004 and iridium compounds and formic acid. 3 Y. Y. Kharitonov, G. J. Majo and Z. M. This has made it possible to identify by infra- Novozhenynk, Bull. Acad. Sci. U.S.S.R., 1966, red spectroscopy intermediate formato-halo 1072 4 J. Halpern, B. R. James and A. W. L. Kemp, species containing one and two monodentate J. Am. Chem. Sac., 1966, 88, 5142 formate groups. These species probably 5 L. Malatesta, L. Naldini and F. Cariati, contain formally divalent osmium, that is J, Chem. Sac. 1964,961 6 M. J. Cleare and W. P. Griffith, Chem. and [Os"(COOH)C1,]4- and [Os11(COOH),C1,]4-, Ind., in the press

Performance of Platinised Titanium Anodes The use of platinised titanium as a counter the titanium is to be avoided the anodic electrode in cathodic protection is well potential must not exceed +7.0 VSCE. established, even though a detailed mechan- Further, the authors state that at potentials ism for the excellent performance of these above +2.1 VsC~modification of the anodes is not fully documented. A recent platinum surface occurs, and studies in the investigation of this subject by P. Van Laer range $1.3 to 1.4VsCE suggest that oxidation and J. Van Muylder of CEBELCOR, pre- of platinic oxide PKO, to perplatinic oxide sented as a paper to the CITCE colloquium PtO, may take place. on Corrosion and Electrochemical Thermo- It was concluded that the long life of dynamics held in Istanbul in September, is platinised titanium anodes in sea-water is due of some considerable help in this direction. to the titanium surface being protected from Anodic polarisation studies in synthetic sea- high current densities by the platinised areas, water, using current densities in the range thus ensuring that the potential does not o to 600 mA/cm2, showed that if corrosion of exceed the threshold of danger. J. H.

Platinum Metals Rev., 1967, 11, (4) 149 ABSTRACTS of current literature on the platinum metals and their alloys PROPERTIES Wi~=piT‘-kqiT’ and WiT is the resistance ratio Ri~iRi273.15 at T”K. Accurate measure- Low-energy Electron-diffraction Study of ments were made on Pt used for resistance the Clean (loo), (lll), and (110) Faces of thermometry. The two-band model was used to Platinum correct small but significant impurity scattering. H. B. LYON and G. A. SOMORJAI, 3. Chem. Phys., The temperature dependence of the “ideal” resistivity function was compared with theory 1967, 46, (7)2 2539-2550 and previous work and some discrepancies were The (rrr) and (110) faces of a “clean” (IOO), noticed. Pt single crystal were studied as a function of temperature by LEED techniques in ultra-high Thermal Conductivity of Selected Materials vacuum. At low temperatures (111) and (100) show several ordered structures stable within a U.S. Nat. Bur. Stds NSRDS-8, 1966, (Nov.), well-defined temperature range ; the (I 10) face 9-10> 45-50 shows faceting above 600°C. Above 750°C a Among the materials reviewed are Pt and 40% new stable phase is formed irreversibly on all Rh-Pt. Curves for the variation of thermal three faces and is characterised by a ring diffrac- conductivity with temperature are derived from tion pattern which increases in intensity as the work reported in the literature. Further work is m.p. of Pt is approached and is due to domains needed to define the curves more accurately. of (I 11) surface structure. Heat-resistance of Platinum, Palladium and Surface Self-diffusion of Nickel and Platinum their Alloys A. J. MELMED, J. Appl. Phys., 1967, 38, (4), E. I. RYTVIN, v. M. KUZ’MIN and A. E. PETROVA, 1885-1892 Metulloved. term. Obrabot. MetaE., 1967, (z), 31-32 Field-electron emission spectroscopy of Pt at 25y0Pd-Pt had the greatest heat-resistance of 550450°K indicated an Arrhenius-type re- Pt, Pd, Rh-Pt and Pd-Pt samples tested at 1200- lationship between temperature and time, so that 1400°C with 0.5-X.O kg/mma axial stresses. activation energies of surface rearrangement could Time-to-failure was recorded as a measure of be derived: Qf=26.3*2.6 kcal/mole in the range heat-resistance and curves for Pd-Pt showed (27-39) x 106 V/cm for electric field build-up; sharp maxima, particularly at lower temperatures. zero field activation energy is calculated as 29.7 j3 .o kcal/mole ; Qo= 29.5 & 3 .o kcal/mole Deformation and Fracture of Gold-Platinum for surface tension (annealing). Either type of Polycrystals Strengthened by Spinodal De- measurement is satisfactory to k 10%. composition R. W. CARPENTER, Acta Metall., 1967, 15, (8), Platinum Oxidation Kinetics with Convective 1297-X308 Diffusion and Surface Reaction Study of the deformation and fracture character- R. w. BARTLETT,~. Electrochem. SOC.,1967, 114, istics of 60% and 20% Au-Pt, strengthened by (6)J 547-550 spinodal decomposition, shows that both the An analysis of the oxidation kinetics of Pt con- proportion limit and the work-hardening rate, sidered how the oxidation rate is affected by the which is initially higher than normal, increase on reversible surface reaction 02+Pt z? Pt02(g) isothermal ageing. The proposed theory for the and by transport of the oxide vapour through a work-hardening behaviour agrees well with gaseous boundary layer, and derived mass transfer the experimental results. Fractures are due to coefficients for oxide vapour diffusion, the the formation of Pt-rich and Au-rich precipitates forward and reverse specific rate constants for in the intergranular regions of the 60% and 20% steady-state surface oxidation, and oxidation rate Au-Pt alloys respectively. curves at various pressures and temperatures. Oxidisability of Alloys of Platinum with 2.5 Ideal Resistivity of Platinum below 20°K and 8.50/, Copper during Heating in Air R. J. BERRY, Can. J. Phys., 1967, 45, (5), 1693- E. A. KUZNETSOV and D. V. IGNATOV, Zh. Neorg. 1708 Khim., 1967, 12, (6), 1463-1465 The electrical resistivity of ideally pure Pt may be Samples of 2.5 and 8.5% Cu-Pt sheet were heated represented by a T2(electron-electron) scattering at 100°C intervals up to 600°C and electron term plus a second term proportional to T4*7*0*2diffraction tests showed the nature of the oxida- in the range 7-17’K and to -T4.7*0*5in the tion film. CuO was detected at 300°C and above. range 3-7”K, where the general relation is Traces of CuFe20, were detected at 500°C for

Platinum Metals Rev., 1967, 11, (4), 150-159 150 2.5:/;, Cu-Pt and at 600°C for both alloys. No 0.52 holes for Pd as opposed to the calculated oxidation was detected at IOO or 200’C. value of 0.55. The Effect of the Occlusion of Hydrogen on The Recovery Kinetics of Deformed Copper- the Characteristic Temperature of Palladium Palladium and Gold-PalladiumAlloys and the Vibration Amplitudes of its Atoms Ibid., 753-763 E. A. OWEN and E. w. EVANS, Br. J. Appl. Phys., The recovery of a range of deformed Au-Pd and 1967, 18, (5), 605-609 Cu-Pd alloys was studied by isochronal and Measurement of the fall in intensity of reflection isothermal annealing. The temperature of the of X-rays with increasing temperature in gas- annealing stages, which were similar to those free pure Pd gives a characteristic temperature of obtained for pure metals, was found to be de- -267OK compared to 270 and 275°K by specific pendent on alloy composition. heat and electrical conductivity methods. The characteristic temperature of Pd rises to 311°K Relationships between the Hydrogen Content with 0.7 at.% H, content. The r.m.s. displace- and Electrical Resistance of Palladium + ment of Pd atoms at room temperature falls Silver Alloys from 0.131 A for gas-free Pd to 0.113 A for Pd A. W. CARSON, F. A. LEWIS and W. H. SCHURTER, containing 0.7 at.% H,. Trans. Faraday Soc., 1967, 63, (6), 1447-1452 The relative electrical resistance, R/R,, and the Comparison of Hydrogen and Deuterium temperature coefficient, cc, of ro-55 at.% Ag-Pd Solubility in Palladium-rich Alloys. Gold- alloys were measured as a function of H content Palladium during the absorption and desorption cycles at A. MAELAND and T. B. FLANAGAN,?. Phys. Chem., 25°C. The rate of decrease of R/R, with H/Me, 1967, 71, (61, I95O--I952 the ratio of H atoms to the combined total of Pd Plots of electrolytic absorption of D, in a series and Ag atoms, increases with increasing silver of Pd-Au alloys were similar to those obtained for content. The variation of 01 with H/Me is des- H, except for a reduced potential for D, in the cribed in terms of the cc, phase structure of the two-phase system. Equilibrium solubilities of the alloys. two isotopes were similar. AG and AH for the reaction was found to be increasingly negative Pressure-Composition Isotherms for the with increased metal content in the two-phase Pd+Ag+H System region. A. w. CARSON and F. A. LEWIS, Ibid., r453-1457 The pressure-composition isotherms (hydride The Effect of Plastic Deformation on the vapour pressure/(H/Me)) for the absorption Resistivity and Hall Effect of Copper- of H, in 0-55 at.%, Ag-Pd electrodes at 25°C Palladium and Gold-Palladium Alloys exhibit “plateau” regions for alloys containing M. J. KIM and w. F. FLANAGAN, Acta Metall., >30% Ag where the 01- and P-phases coexist. A graph of isobaric solubility, (H/Me) against 1967, 15, (5)> 735-745 Electrical resistivity, measured as a function of at.% Ag, shows that the solubility of H, as a func- tion of the Ag content is dependent on the composition and deformation for 25, 40, 65 and H pressure at which the solubilities are measured. 95 at.”:, Pd-Au and quenched 50% Pd-Cu alloys, shows an anomalous decrease in resistivity due to a change in the electronic structure from des- Mechanical Properties at High Temperatures truction of short range order. The decrease is of Ternary Conducting Alloys on a Silver continuous for Cu-Pd which has a large short Base range order. For Au-Pd alloys, the decrease is N. L. PRAVOVEROV, A. N. BUBYREV and I. M. followed by an increase as the effect of strain LOBYNTSEVA, Metalloved. term. Obrabot. Metal., -induced defects eventually predominates. The 1967, (2), 36-37 anomalous decrease observed for the Hall effect Simultaneous addition of Pd with Cry Co or Fe is described similarly. greatly increases the mechanical strength of Ag at 20-300°C. Maximum effect occurs with An Approximate Density of States Curve Pd and Fe together; Pd plus Co and Cr gives and its Relation to the Measured Electrical almost as much effect. 0.4-0.5% Pd+o.o2%, of Resistivity of Gold-Palladium Alloys the other metal(s) are the most effective additions. Ibid., 747-752 The resistivities of the Au-Pd system, described Vaporisation Rates, Vapour Pressures and by a simple two-band model corrected for Heats of Sublimation of Rhenium, Rhodium, electron interaction, were measured by the Van Palladium and Titanium der Pauw method at 90, 195, 273, 373, 413 and H. STRASSMAIR and D. STARK, z. angew. Phys., 473°K. Density of states curves obtained from 1967, 23, (I), 40-44 published values of paramagnetic susceptibilities Results were obtained by Langmuir’s vacuum and electronic specific heat coefficients predict evaporation method for Rh at 1845-2092°K and

Platinum Metals Rev., 1967, 11, (4) 151 for Pd at 1361-1603°K and these are compared ranges were established or confirmed for four with previous work elsewhere. intermediate phases in the V-Ir system and a tentative constitution diagram is proposed. Effects of Mechanical and Thermal Treat- VJr and VIr, were known previously; a-VIr and ment on the Structure and Magnetic p-(VL-.JrX)Ir are new. Atomic volumes are Transitions in FeRh given. J. M. LOMMEL and J. s. KOWEL, J. Appl. Phys., Measurement of the Specific Magnetic 1967,38, (311 1263-1264 Well-annealed bulk FeRh samples exhibit a Susceptibility of Osmium between 80 and first-order antiferromagnetic-ferromagnetictrans- 1850°K by Means of an Improved Faraday ition at 330-K but plastic deformation converts Method the normal CsC1-type structure to disordered w. D. WEISS and R. KOHLHAAS, Z. angew. Phys., f.c.c. structure, which is only weakly magnetic 1967, 22, (6), 476-481 with no first-order transition. Annealing of the The specific magnetic susceptibility, x, of pure latter at 510°K converts it to highly-ordered Os, determined by an electronically compensated CsC1-type structure. The return of the first- microbalance with a relative resolving power of order transition occurs in three stages as perfect 0.25 pg, was found to be 0.068 emulg at room long-range order is achieved or as defects are temperature. The value of x between 80" and annealed out. 1850°K is given by x=(s~Kdx)i(2mH,S,,,), where m=mass of the probe and H, is the Magnetic Susceptibility and Specific Heat field component in the y direction. of Nearly Ferromagnetic NiRh Alloys E. BUCHER, W. F. BRINKMAN, J. P. MAITA and H. J. WILLIAMS, Phys. Rev. Letters>1967,18, (25), CHEMICAL COMPOUNDS 1125-1127 Formation of Thin Films of PdO and their Nio.6aRho.a,is just on the ferromagnetic side of Electric Properties the critical concentration and has maximum n. OKAMOTO and T. ~$0,Japan. J. appl. Phys., magnetic susceptibility at -4o"K, and an anom- 196796, (61,779 alous specific heat below 8°K. The anomaly Oxidation of evaporated Pd films in air at 973°K decreases on either side of this concentration and for 24 h formed thin PdO films. Electrical con- disappears at Nin.,5Rho.45on the paramagnetic ductivity of PdO was measured as a function side, and at Nio.,oRho.30 on the ferromagnetic of temperature at 77-560°K in various atmos- side. Plots of magnetic susceptibility and y values pheres. It decreased on heat cycling. Energy of specific heat were plotted against alloy con- gap, Hall coefficient and Hall mobility were centration and confirm that 63O6 Ni is the critical studied also. value. Phase Relations in the Systems Ti02-Ir02 The Crystal Structure of Hexagonal Rh2AI, and Sn0,-IrO, in Air L.-E. EDSHAMMAR, Acta chem. Scand., 1967, 21, c. L. MCDANIEL and s. J. SCHNEIDERJ. Res. N.B.S., (31, 647-651 Sect.A, Phys. Chem., 1967, 71A, (2), 119-123 The structure of arc-melted, hexagonal Rh,AI,, X-ray diffraction studies of the pseudobinary determined by X-ray powder photography and systems Ti0,-IrO, and Sn0,-IrO, after treat- evaluated using the least squares technique, ment in air for 18 h at 800, 900 and IOOOT belongs to the space group P6Jmrnc and has indicated similar phase diagrams with no inter- cell constants a-7.893 and c-7.854 a. It mediate phases. Maximum solid solution of is compared with the apparently isomorphous TiO, occurs with 5 mol.7" IrO, at 1040°C. Co,Al, structure. Solid solution of TiO, in IrO, extends to 12 mol.o/; TiO, at 1040"C, the dissociation tem- The Crystal Structure of IrAI, perature. Limited solid solubility of SnO, in Ibid., (4), 1104-1105 IrO, exists to 3 rno1.x SnO, at 1025OC, the Single crystal, X-ray powder diffraction studies dissociation temperature. Solid solution in of IrAl, show that it has a DO,,-type structure SnO, was not detected up to 1400°C. and belongs to the space group P 6Jmmc with cell constants a=4.246 and c-7.756 A. The Guinier Thermal Dissociation of Iridium Trichloride powder pattern data and the interatomic dis- N. I. KOLBIN and v. M. SAMOILOV, Zh. neorg. tances are tabulated. Khim., 1967, 12, (7), 1747-r750 Investigations during the thermal dissociation New Phases in the Vanadium-Iridium of P-IrCl, and of mixed a- and P-IrCI, at 810- System and a Tentative ConstitutionDiagram 1040°K showed that no mono-p or dichloride of Ir B. C. GIESSEN, P. N. DANGEL and N. J. GRANT, coexists in these conditions. During the for- J. less-common Metals, 1967, 13, (I), 6270 mation of IrC1, from its elements AH",,,,,, Crystal structures and approximate homogeneity = -242.0k6.0 kJ/mole, AS",,,.,, == -242.0i8.0

Platinum Metals Rev., 1967, 11, (4) 152 J/"K. mole. For solid 1rCl3, So288.15=127.0 HNO, mixture and a.c. is applied it dissolves JPK. mole. The dissociation pressure is I atm fairly quickly, the rate of solution increasing with at 1036°K. H,SO, concentration, but this tendency is limited by the easy formation of a passive oxide Carbon Disulphide, Carbonyl Sulphide, and film which is difficult to reduce. Pt foil samples Alkyl and Aryl Isothiocyanate and Per- were produced by electrolytic polishing in a bath fluorothioacetone Complexes of Nickel, Pal- of equal volumes of 96% H,SO,, 65% HNO, ladium, Platinum, Rhodium, and Iridium and 8004 H,PO,. The rate of polishing at 0.5 M. c. BAIRD and G. WILKINSON, J. Ckem. SOL., A/cmZwas about 3.1o-~g.crn-~s-l. A, inorg. phys. tkeor., 1967, (6), 865-872 cs, reacts with Ph,P complexes of Ni, Pd, Pt, Anodic Oxidation of Ethylene on Noble Rh and Ir in zero or +I oxidation states to form Metals and Alloys. Parametric and Isotopic complexes with the CS, ligand r;-bonded, e.g. Examination of Mechanisms (Ph,P),PtCS,. Structurally-related z-complexes occur with COS and alkyl and aryl isothiocy- A. T. KUHN, H. WROBLOWA and J. O'M. BOCKRIS, anates although the ally1 isothiocyanate-Pt com- Trans. Faraday Soc., r967, 63, (6), 149-1467 plex is best formed otherwise. Isothiocyanates The anodic oxidation of C,H4 on the platinum react with (Ph,P),RhCl to form both --bonded group metals, Au, Ag, Hg and on the alloys and donor co-ordinated complexes. Pt(PPh,), Pd-Au, Rh-Pd, Cu-Rh, Cu-Au, Pt-Rh and Pt-Ni reacts with zJ2,4,4-tetrakis(trifluoromethyl)-~,3- was determined in aqueous and deuterated dithietan and benzyl chloride to form (Ph31?),k electrolytes at 80°C. An estimate of the isotopic (C,F,CS) and (Ph3P),PtC1(COPh) respectively. effect and several reaction mechanisms are sug- RhCl,(p-FC,H4N,)(PPh,)),,o.5CHCL,is des- gested. The graph of rate of oxidation/heat of cribed, sublimation of substrate is described in terms of variable rates and rate determining steps. The Tris( triphenylphosphine)rhodium(I) treatment indicates why Pt is the superior Complexes electrocatalyst. W. KEIM, J. organometall. Chem., 1967, 8, (3), PZS-PZ~ Structure and Catalytic Activity of Platinked Synthesis of u-bonded Rh(1) complexes contain- Platinum ing a Rh-C bond, i.e. methyltris(tripheny1- D. F. A. KOCH, Extended Abstr., rgrst Nat'l Mtg., ph0sphine)rhodium and phenyltris(tripheny1phos- Electrochem. SOC.,1967, (May), abstr. I74 phine)rhodium, and of hydrotris(tripheny1phos- Studies on platinised Pt electrodes show that the phine)rhodium are described. 'The compounds, surface area of Pt measured by H, adsorption in- characterised by IR and NMR, are all air-sen- creases with increasing weight of Pt deposited, sitive, soluble in aromatic solvents and decom- indicating that pore areas are included in the pose when heated to 150~-200"C. determination, whereas capacitance measure- ments are confined to surface reactions. A On the Polymorphism of Osmium Tetra- decrease in Pt deposition potential results in a chloride decrease in surface area of Pt deposited as the P. MACHMER, Chm. Commun., 1967, (IZ), 610 H, coverage is increased, which inhibits nuclea- Elemental analysis, X-ray powder diffractometry tion and results in an increase in particle size. and magnetic measurements indicate the existence Catalytic activity below 0.5 V is oc surface area of two forms of OsC1,. A dark brown chloride, obtained by H, adsorption; at 0.67 V it is obtained from OsO, and SOCI,, appears to have area determined by capacitance measurements, a cubic lattice constant, a=9.95 A. It is para- i.e. purely a surface reaction. magnetic and has a temperature dependent susceptibility. zmole=+880 x c.g.s. units. Structural Studies of Porous Electrodes The black form, synthesised from its elements, E. Y. WEISSMAN, J. Electrockem. Soc., 1967, 114, can be represented by an orthorhombic unit cell with constants a=Iz.oS, b=11.96, and c= (7)J 658465 11.68 A. It is also paramagnetic but has a tem- Non-destructive measurements, used to deter- perature-independent susceptibility of + 1080 x mine surface area, porosity, pore size distri- bution, microporosity and polarisation curves 10-6 c.g.s. units. of Pt black-Teflon-Ta screen electrodes, show that the micropores in the radii range 25-2ooA ELECTROCHEMISTRY determine the performance. The structural geometry of the electrode was investigated with Contribution to the Electrolytic Polishing reference to electrochemical activity and can be of Platinum represented by the equation i -=a exp (bS), where J. TOUSEK, CoU. Czech. ckem. Commlm., 1967, iycurrent density, S=surface area, a and b are 32, (6),2348-2352. constants depending upon the electrode and the When a Pt electrode is immersed in a H,SO,/ experimental conditions.

Platinum Metals Rev., 1967, 11, (4) 153 Gold-Palladium Electrocatalysts showed the high wear-resistance of contacts J. H. FISHMAN and M. YARISH, Electrochim. Acta, plated in this manner. The anode of the plating bath was platinised Ti expanded sheet. 1967, 12, (S), 579-581 Homogeneous Au-Pd alloys containing 30-4Ou'h Au and 60-80% Au show significant changes LABORATORY APPARATUS in bulk characteristics due to d-band filling effect. The correlation between this effect and their AND TECHNIQUE catalytic properties is shown in the H,-0, Criteria of Soil Aggressiveness towards oxidation reaction for which there is a maximum Buried Metals. I. Experimental Methods activity at 30% Au, falling off rapidly and ap- F. H. BOOTH, A. w. COOPER, P. M. COOPER and D. S. proaching zero at -7016 Au. Addition of Au to wAKERLEY, Br. corros. J., 1967, 2, (3), 104-108 a Pd-H electrode in the presence of CO decreases the polarisation to a minimum at 40% Au; The redox potential, EH at pH-7, as a factor in above 400: Au polarisation increases, indicating the aggressiveness of soil towards buried metals, that the presence of Au increases resistance to was measured using a solid stemmed probe with CO poisoning. duplicate Pt electrodes in the tip in conjunction with a saturated calomel reference electrode Pretreatment of Pt-Au and Pd-Au Alloy inserted in the soil I ft away from the probe. The Electrodes in the Study of Oxygen Reduction mean potential of the duplicate electrodes, J?, was used to calculate EM using relationship, A. DAMJANOVIC and v. BRUSIE, J. electroanal. - Chem. interfacial Electrochem., 1967, 15, (I), E~=E+0.250+0.060[pH -71. 29-33 The effect of pretreatment of Pt-Au and Pd-Au Air Depolarised Electrolytic Oxygen electrodes in the form of wires sealed into a glass Generator tube or threaded through a small Teflon cylinder R. A. WYNVEEN and K. M. MONTGOMERY, J. Elec- were studied during 0,-reduction. 5% Au-Pt trochem. SOC.,1967, 114, (6), 589-592 has the same Vilog i relationship whether Oa in ambient air is separated from N, and treated chemically or thermally whereas elec- inert gases by reacting it at a cell cathode with trochemical pretreatment gives a high activity simultaneous evolution of pure 0, at the anode. for the reduction. Similar behaviour is observed Both electrodes are Ni grids with a uniform for 80% Au-Pt ; electrochemical pretreatment surface layer of Pt black mixed with Teflon and produces behaviour similar to that of pure Pt; the electrolyte is KOH solution. Performance thermal and chemical treatment produces be- depends on inlet air flow and pressure, and on haviour similar to that of Au. The effect of moisture balance between H,O content of the thermal pretreatment of kinetics is discussed air and the electrolyte vapour pressure. and the results are rationalised in terms of alloy composition and structure. HETEROGENEOUS CATALYSIS Studies on the Electrochemistry of Osmium The Problem of the Size of Platinum Losses J. LLOPIS and M. VAZQUEZ, Anal. R. SOC.ESP. Fis. in Nitric Acid Production Quim., Ser.B, Quim., 1967,63, (3), 273-281 H. SIKORA and E. BLASIAK, Przem. Chem., 1967, Studies of the polarisation curves and anodic and 46J (4)> 199-z00 cathodic charging curves of Os, electrodeposited The principal factors involved in the loss of on Pt from neutral solutions of Na,[OsCl,], Pt in HNO, production and some proposed show that anodic surface oxidation leads to 0s improvements are discussed. films being formed more than one molecule thick. In HCIO, electrolytes 0s is oxidised to Formation of PtO, - the Source of Platinum soluble OsO, at 0.83 V; a similar effect is observed Losses in Nitric Acid Production in HCl solution together with Cl, evolution. H. SIKORA, J. KUBICKI and E. BLASIAK, 0~0,~-has been identified in alkaline electrolytes. Zbid., (s), 257-258 The loss of Pt in HNO, manufacture is now ELECTRODEPOSITION AND believed to be due to the evolution of PtO, rather than to evaporation of Pt. Its capture by SURFACE COATINGS CaO is effected by formation of a compound of the type xCaO.yPtO,, where x and y may equal I. An Apparatus for Heavy Rhodium Plating This assumes that an essential step in the oxida- A. E. YANIV, Plating, 1967, 54, (6), 721 tion of ammonia is PtGPtO,. Bright and smooth Rh deposits on silver-plated brass electrical contacts were obtained at SOT,Study of a Pilot Unit for Catalytic Reforming I A/dm2to a thickness of IOF in H,SO, solution, P. MAURET, A. KLEIN, J.-L. ABATUT and H. KOQUES, after cleansing and activation. A jolting device Chim. Znd., Gin. chim., 1967, 97, (IO), 165~-1658 prevented adhesion of bubbles. Abrasion tests A pilot unit for the automation and optimisation

Platinum Metals Rev., 1967, 11, (4) 154 of catalytic Pt reforming using a digital computer compounds and its reactivation on contact with has been set up at Institut National des Sciences air indicates that adsorbed 0,, which appears to Appliqukes, Toulouse. Incorporated are sensors increase the number of unpaired d-electrons of developed to continuously measure octane num- the catalyst metal, is necessary to maintain high ber, catalyst activity, as well as chromatographic activity. analysis. Reported are first results of control V. Decrease in Activity of Rh-Pt Alloy techniques and of mathematical models applied Catalyst in the Hydrogenation of Benzoic to the problem. Acid K. YOSHIDA, T. OTAKI and s. KOIKE, Ibid., 295-298 Development of a Mathematical Description The decrease in activity of Rh-Pt catalyst during of Platforming for Optimisation of the the hydrogenation of C,H,COOH is shown to be Process. 11. due to the toxicity of metal ions in acid anhy- YU. M. KHOROV, G. M. PANCHENKOV, W. A. drides from the reactor and impurities in the TIRAK'YAN, s. P. ZEL'TSER and P. R. FRADKIN, C,H,COOH. A relationship between molecular Kinetika i Kataliz, 1967, 8, (3), 658-662 size and poisoning strength is discussed. X-ray The differential form of the mathematical des- diffraction studies indicate that crystalline growth scription of Platforming is independent of the is too small to be responsible for the observed dimensions of the reactors. Optimum conditions decrease in activity. were established by finding the limiting points from the mathematical relations. Nylon-Platinum Catalysts with Unusual Geometric and Selective Characteristics Structure and Activity of Noble Metal Alloy D. P. HARRISON and H. F. RASE, Ind. Engng Chem., Catalysts. I. The Activity of Supported Fund., 1967, 6, (2), 161-169 Rh-Pt Alloy Catalyst in the Hydrogenation Catalysts prepared from H,PtCl, and Nylons of Aromatic Compounds 66, 6 and 610 showed similar characteristics for C,H, hydrogenation and produced substantial K. YOSHIDA, Nippon Kagaku Zasshi, 1967, 88, amounts of the intermediate cyclohexene. Nylon 3 (2), 125-129, A9 -Pt became active at a higher temperature and The activity per unit wt. of alloy of supported, only cyclohexane was produced. Nomex-Nylon- homogeneous Rh-Pt in the hydrogenation of Pt was inactive. These differences are suggested C,H,, C,H,OH and C,H,COOH is shown to be as being due to an arrangement of Pt atoms cor- a function of the alloy composition and has a responding to the position of amide groups in the maximum value of 20-400/; Rh-Pt. Results nylon crystal. Apparent interaction between indicate that activity is dependent on electronic Pt and the amide groups increases the efficiency structure of the alloy and is independent of the of Pt compared to catalysts on inert supports. reactant. 11. State of Dispersion of Metal on the The Activity of Nylon-Platinum Hydrogena- Supported Rh-Pt Alloy Catalyst tion Catalysts as Determined by the Struc- Ibid., 220-222, A14 ture of Various Nylon Carriers Determination of the total surface area of catalyst, D. P. HARRISON, Diss. Abstr. B, 1967, 27, (8), support and free metal for Rh-Pt dispersed on 2691 carbon black or activated charcoal by N, and CO The isolation of cyclohexene over some of the adsorption at 77°K and 293"K, respectively, catalysts in the hydrogenation of C,H, over indicates that the catalyst is located in islands of several atomic layers on the carriers. This Nylon 66, 610, 6, 3 or Nomex impregnated with H,PtCI, was explained by proposing a two point agrees well with X-ray diffraction data. C,H, adsorption on the catalyst surface as sup- 111. Activity and Magnetic Susceptibility ported by kinetic evidence. Cyclohexene is not of Rh-Pt Alloy Catalysts obtained using any other Pt catalyst with similar Ibid., 222-224, A14 physical characteristics. The Pt-amide interac- Atomic susceptibility values of Rh-Pt alloys, tion between catalyst and carrier could not be measured with a Faraday balance at 25% follow confirmed due to insufficient sensitivity of the same pattern as their activities in hydrogena- apparatus. tion of aromatic compounds, indicating that activity is due to unpaired d-electrons of the Growth of Single Crystals of Cadmium alloys. Chromium Selenide by Liquid Transport IV. The Role Played by Oxygen in the Action with Platinum Catalyst of Rh-Pt Alloy Catalyst in the Hydrogenation H. VON PHILIPSBORN, J. Appl. Phys., 1967, 38, of Benzoic Acid (3), 955-956 Ibid., (3), 292-295 Pills of CdSe and CrCI, in close contact were A study of the gradual deactivation of Rh-Pt heated at -700°C for three days in a Pt boat. catalyst during the hydrogenation of aromatic Perfect octahedral single crystals of CdCr,Se,

Platinum Metals Rev., 1967, 11, (4) 155 grew in the CdSe by liquid transport, catalysed negative effect of the adsorbent is discussed and by Pt. the rate of hydrogenation is found to be dependent on the nature of both the catalysts and the un- Use of Atomic Absorption Spectrophoto- saturated compound. metry for the Study of Liquid-phase Ad- sorption Kinetics Relation between Shift of Catalyst Potential J.-M. VERGNAUD, B. REY-COQUAIS, B. BUATHIER and and Reaction Rate in Liquid-phase Hydro- R. NEYBON, Bull. SOC.chim. Fr., 1967, (6), 2194- genation Processes. IV. Correlation of 2196 Activities of Raney Ni, Pt- and Pd-black in An atomic absorption spectrophotometer coupled Liquid-phase Hydrogenations to a reaction vessel, giving a response time of v. A. DRUZ’and L. N. SADCHIKOVA, Kinetika -I sec was used to study the liquid-phase ad- i sorption kinetics of Pt/C or Pt/Al,O,. Initial Kataliz, 1967, 8, (3), 578-582 adsorption rate and the adsorption limit could be Activity of Raney Ni, Pt- and Pd-black were measured also. compared in liquid-phase hydrogenations to increase product yields and surface area of each Investigation of Liquid-phase Oxidation of catalyst. Product yield depends on the specificity Hydrocarbons on Solid Catalysts. I. Oxida- of the individual catalyst, tion of Paraffins and Cycloparaffins N. v. KLIMOVA and I. I. IOFFE, Kinetika i Kataliz, Hydrogenation of Glucose on Raney Nickel r967, 8, (31, 565-571 Catalysts. I. The catalytic activity of V,O,.WO,/Al,O, can be F. B. BIKHANOV, D. v. SOKOL’SKII,N. I. POPOV, increased by the addition of Pt and other pro- N. YA. MALKINA and A. M. KHISAMETDINOV, Ibid., moters. A heterogeneous-homogeneous mech- 620-624 anism is assumed for the liquid-phase oxidation Pd or Ru additions to Raney Ni catalysts may of the studied paraffins, cyclo-paraffins and increase the activity by 30% for the hydrogena- aromatic hydrocarbons. It may be possible to tion of glucose under pressure, with intense control the process with different combinations of agitation. Optimum additions are O.I-O.~% Ru catalysts and inhibitors. or s:,; Pd. Increased stability of the promoted catalysts was not apparent. Catalytic Properties of Platinum Catalysts. V. Effect of Alkali (KOH) on the Activity of Catalytic Activity of Reduced Noble Metal- Platinised Carbon Base Metal Mixed Oxides K. H. SCHNABEL, Ibid., 583-591 G. c. BOND and D. E. WEBSTER, Chem. Znd., 1967, Small KOH additions increase the activity of (21, May 271,878-879 Pt/C for C,-dehydrocyclisation but larger Mixed oxides of Pt and either Fe, Co, Ni or Cu, amounts poison it. Alkali gradually suppresses and of Pd and either Co or Ni, when prepared by expansion of the ring in I ,1,3-trimethylcyclopen- Adams’ method, have activities in excess of tane. Activation energies for dehydrocyclisation single oxides alone or of mechanically mixed differ significantly with KOH additions. KOH oxides. This effect was shown in hydrogenations may promote active centres on Pt. Different types of C,H,NOz (60/, v/v in CH,OH), 2-methyl- of active centre exist on Pt/C with different hut-3-yn-2-01 (7.5% v/v in CH,OH), and reactions occurring at each. cyclohexene (17% v/v in CH,OH) at 30T, I atm H,. It is suggested that on reduction of a Hydrogenation of Phenol in the Synthesis of mixed base metal-noble metal oxide part of the Caprolactam base metal forms a solid solution with the noble G. D. LYUBARSKII and M. M. STRELETS, Khim. metal. Promyshlennost’, 1967, 43, (7), 481-486 A review of the processes using Ni or Pd cat- Hydrogenation of Dimethylethynylcarbinol alysts (35 references). on Palladium/Polyacrylonit.de Catalyst D. v. SOKOL’SKII,0. A. TYURENKOVA and E. I. On the Negative Effect of Activated Carbon SELIVERSTOVA, Zh. fiz. Khim., 1967, 41, (6), during the Hydrogenation of Unsaturated 1404-1410 Compounds on Pt, Ni and Pd Catalysts The rate of hydrogenation of dimethylethynyl- D. v. SOKOL’SKII and B. 0. ZHUSUNBEKOV, Zh. carbinol on Pdipolyacrylonitrile, which is found fiz. Khim., 1967, 41, (59, 1213-1215 to increase with increasing amount of catalyst and Kinetic and potential curves were used to study reactant, is faster in CH,OH and C,H,OH the effect of mechanical mixtures of activated solutions than in aqueous solutions, but the re- C with Pt- and Pd-black and Raney Ni catalysts action ceases as the catalyst surface becomes on the H, adsorption capacity of unsaturated significantly charged with H,. The hydrogenation compounds, C,H,NO,, hept-r-ene and dimethyl- is more selective in neutral and alkaline solutions. ethynylcarbinol during hydrogenation. The An increase in acid or alkali concentration re-

Platinum Metals Rev., 1967, 11, (4) 156 duces the rate of reaction and the lateral dis- Homogeneous Hydrogenation of Methyl placement of the anode potential. Linoleate Catalysed by Platinum-Tin Com- plexes Catalytic Hydrogenation of Butyronitrile E. N. FRANKEL, E. A. EMKEN, H. ITATANI and J. C. H. GREENFIELD, Ind. Engng Chem., Product Res. BAILAR,J. org. Chem., 1967, 32, (5), 147-1452 DN.,19671 6, (2)~142-144 The relative reactivity of catalysts in the homo- Tests with Ni, Co, Pt, Pd, Rh, and Ru catalysts geneous hydrogenation of methyl linoleate is for the hydrogenation of butyronitrile to amines in the order H,PtCl,+ SnCl,>(PPh&s),PtCl,+ showed that Ni and Co appear to be best for the SnCl,>(PPh,P),PtClOH+SnCl,>SnCl,- preparation of the primary amine butylamine, (PPh,),PtOH. Rate curves for the reactions are Rh best for production of secondary amine given. Conjugated dienetrienes in trans, trans dibutylamine, and Pt and Pd best for production configuration are the major product except for of tertiary amine tributylamine. Resistance to H,PtCl, and SnCl, which gives trans-dienes. poisoning, the use of CH,OH or H,O as solvents and the effects of alkaline additives were studied. Butadiene from Vinyl Chloride. The Plati- num@) -catalysed Coupling of Vinyl Halides Kinetics of Electrodeposition and Catalytic P. N. JONES, Ibid., 1667-1668 Activity of Thin Films of Ruthenium The reductive coupling of vinyl chloride to give M. PLEISCHMANN, J. KORYTA and H. R. THIRSK, butadiene is catalysed by (C,H,),NSnCI, with Tram. Faraday SOL, 1967, 63, (5), 1261-1268 CsF and PtCl, in aqueous DMF at 25°C. The Current-time curves, used to investigate the effects of varying the reaction conditions and the electrorecrystallisation of Ru from acid RuC1, SnPt ratio are evaluated. The formation of an solutions on to a Hg electrode, show that Ru is isomer of [(SnC1,),PrC1,]2- and the role of CsF deposited in a single layer with a thickness of in the reaction are discussed. half the lattice repeat in the c, direction (2.136 A) of a h.c.p. lattice. The catalytic evolution of H, The Keaction of Rhodium Trichloride with is confined to the edges of the growth centres of D'ienes Ru and is similar to that exhibited for bulk Pt K. c. DEWHURST, J. org. Chem., 1967, 32, (9, metals. 1297-1 300 RhC1, catalyses the addition to iso-C,H, of The Catalytic Activities of Rhodium and C,H,OH to give two isomeric ethers in a ratio Ruthenium in the Hydrogenolysis of Ethane. which is temperature-dependent. On a larger Influence of the Concentrations of Hydrogen scale, the air-stable complex [(C,H,), RhCl,],, is and Ethane on the Reaction Rate formed which gives an oil containing only hydro- G. K. STAROSTENKO, T. A. SLOVOKHOTOVA, A. A. carbons after hydrogenation with RhlC. A similar reaction occurs with butadiene but the BALANDIN and K. A. EL KHATTIB, Vest. MOSkOV. Univ., Ser. IZ, Khim., 1967, (3), 63-67 oil obtained by hydrogenation of this Rh com- plex gave a C,, ether. 5% Ru/SiO, has much greater specific activity than 5 % Rhl SiO for catalysingthe hydrogenolysis Hydride Transfer Reactions Catalysed by of C,H,. Results of studies of the effects of the Metal Complexes partial pressures of H, and C,H, on the reaction H. B. CHAR~MAN,J. Chem. Soc., B, phys. org., 1967, mechanism are tabulated. (6), 629-632 Dehydrogenation of ;so-C,H,OH to (CH,),CO HOMOGENEOUS CATALYSIS is catalysed homogeneously by RhCl, in the presence of LiCl and concentrated HCI. The Homogeneous Catalysis in the Reactions of mechanism is believed to be abstraction of a Olefinic Substances. VIII. Isomerisation of hydride ion from the ctC of iso-C,H,OH by 1,5-Cyclooctadiene with Dichlorobis(tri- RhC1, with subsequent transfer of this to the proton of HCl, resulting in evolution of H,, the phenylphosphine)platinum(II) rate of which decreases as Rh metal is precipitated. K. A. TAYIM and J. c. BAILAR,~. Am. Chem. SOL, 19671 89, (141,3420-3424 Organic Syntheses by Means of Noble A study of the homogeneous isomerisation of 1~5-cyclooaadiene by [PtCl,(PPh,)2] in the Metal Compounds. Part 32. Selective De- presence of the essential cocatalyst SnCl,.zH,O carbonylation of q3-Unsaturated Aldehydes in N, or H, atmosphere is shown to proceed via Using Rhodium Complexes a stepwise mechanism of hydride addition- J. TSUJI and K. omo, Tetrahedron Lett., 1967, abstraction with the formation of 5-coordinate (23)~2173-2176 hydridoplatinum-olefin complex. The role of The decarbonylation of a-substituted cinnamal- SnC1,.2H20 is investigated and is found to dehydes in the presence of ClRh(PPh,), in function as the ligand SnC1,- which is a strong C,H, or CH,CI, yields mainly cis-olefins. A x-acceptor and prevents reduction of the Pt(I1). dimeric complex is precipitated with sterically

Platinum Metals Rev., 1967, 11, (4) 157 hindered aldehydes at high temperatures unless A Unifying Scheme for the Electrochenlical organonitrile solvents are used. A4 and Oxidation of Carbonaceous Fuels on Plati- aromatic aldehydes are readily decarbonylated num in Sulphuric Acid at 20ooCor above, in the presence of the complex J. A. SHROPSHIRE, Electrochim. Acra, 1967, 12, (3), CIRh(CO)(PPh,), which is a more selective 253-258 catalyst than PdC1,. A two-site generalised scheme is proposed for the adsorption and oxidation on Pt in aqueous Reactions and Catalytic Properties of Rho- H,SO, of the carbonaceous fuels, here represented dium Complexes in Solution by C,H,,, HCHO and CLHI. The oscillatory B. R. JAMES, Cod. Chm. Rev., 1966, I, (4), potential phenomena, observed during oxidation, 505-524 are also explained on the basis of a two-site The catalysed synthesis of Rh(II1) complexes, surface. the hydride, allylic and carbonyl complexes of Rh are reviewed, together with their reactivity Fuel Cell Oxidation of Hydrogen on Movable, as homogeneous catalysts in the hydrogenation Partially Submerged Platinum Anodes and polymerisation of olefins and acetates and H. J. DAVITT and L. F. ALBRIGHT,J. Electrochem. isomerisation of olefins. The solution chemistry SOL., 1967, 114, (6), 531-535 of Rh is also discussed. (160 references.) Potentiostatic studies of two flat Pt anodes partially immersed in I N H,SO, at 3ooC, I Catalytic Properties of Platinum Group atm showed that the electrochemical oxidation of Metal Phthalocyanines H, is affected by meniscus formation, the elec- B. D. BEREZIN and A. v. ~OsHcH~LoVA~Kinetikai trolyte film formed on the exposed parts of the Kataliz, 1967, 8, (3), 592-598 anodes, the surface roughness, and H, adsorption 0s and Ru phthalocyanines have high catalytic by exposed Pt. activity but other Pt metal phthalocyanines are inactive. (HSO,),OsPc is more active than (HSOJRuPc. Both are more active than Fe CHEMICAL TECHNOLOGY phthalocyanine. The effects of NaF, HCN and Considerations and Experiments for a NH, on their reactions were studied. The kinetic equation, rate constants and activation energies Critical Evaluation of the Platinised Titan- of these catalysts were derived from quantitative ium Anode studies and a mechanism for phthalocyanine E. ZIRNGIEBL, Chem.-leg.-Tech., 1967, 39, (IZ), catalysis is suggested. 752-756 Electrochemical comparisons of platinised Ti and Catalytic Oxidation of Ethylene to Acet- graphite electrodes show that C1, has lower aldehyde in the Presence of Complexes of potential on the former and that the anode shape Ruthenium and Other Platinum Metals and cell characteristics are also important. Amor- tisation of a cell with platinised Ti anodes is A. M. OSIPOV, K. I. MATVEEV and N. N. SHLTL'TS, Zh. ncorg. Khim., 1967, 12, (7), 1886-1892 quicker because of the reduced potential. Studies of the oxidation of CZHI to CH,CHO in The Kinetics of Metallic Activation Sin- aqueous solutions of Pt metals and of Au showed that the addition of citric acid and some other tering of Tungsten oxycarbonic acids considerably increases the I. J. Tom and N. A. LOCKINGTON, J. less-common activity of Ru(II1) chloride complexes, and that in Metals, 1967, 12, (9,353-365 solutions containing Ru(II1) complexes, citric Small amounts of Pd or Ni powerfully activate acid and Cu(I1) salts an intermediate complex the sintering to high density of W and W-2% of these three is formed. There are similarities Tho, when introduced as halide salt solution for between the mechanisms when using Pd(II), impregnation followed by reduction to metal. Ru(II1) or Pt(I1) complex catalysts. Optimum amounts, representing monoatomic layer were 0.317 wt.7; Pd and 0.130 wt."/:, Ni for FUEL CELLS 3.3~W particles. New Batteries Pack Hefty Doses of Energy GLASS TECHNOLOGY Chem. EngW, 1967, 74, (14, July 3), 38 Douglas Aircraft Co. has developed a rechargeable Preparation of Optical Quality Glass in aerospace battery with Zn anode, Pt-plated Ni Small Batches mesh cathode and novel separators. Energy A. D. PEARSON, J. R. FISHER and W. R. NORTHOVER, density is IOO w.h/lb, shelf life is two years, and J. Am. Cerarn. SOL.,1967~50, (4), 219-220 it operates at -40 to +300°F. A 5 A.h model A method is described for the preparation of has been cycled 2500 times without loss of small batches of calcium lithium borate and boro- capacity. The company has two patented methods silicate glass free of bubbles, inclusions and for electrode production. striations using a Pt crucible and strirrer.

Platinum Metals Rev., 1967, 11, (4) 158 TEMPERATURE A Precision PtRh-Pt Thermocouple for MEASURXMEYT Research and Industry M. BEDUHN and w. HEYNE, Feinger. Tech., 1967, Two-Point Comparison 16, (6), 257-260 E. W. JONES, Instrum. Control Syst., 1967, 40, Three East German research institutes have (I), 115-118 developed the "Model DAMW' Pt:Iooo Rh-Pt A two-point method for testing and calibration thermocouple instrument, which is suitable for of Pt resistance thermometers gives accuracy of both industrial and laboratory uses. Its con- --0.015"C at -1oo"C and -0.006"C at 500°C struction, characteristics and calibration are on the International Practical Temperature Scale. described.

NEW PATENTS

METALS AND ALLOYS ELECTROCHEMISTRY Heat Treatment of Platinum-CobaltMagnets Electrode Boiler INTERNATIONAL NICKEL LTD. IMPERIAL METAL INDUSTRIES (KYNOCH) LTD. Britzsh Patent 1,067,054 British Patent 1,068,732 Remarkable magnetic properties can be pro- An electrode for an electrode boiler, e.g. for duced in pure alloys containing r9.8-31.2% Co boiling H,O, has the parts immersed in the by subjecting them to a disordering treatment at a electrolyte (at least) made of Ti or its alloys coated temperature above 900°C for 30 min to I h, with Ir, Rh, Ir-Pt, Rh-Pt or Ir-Rh-Pt. cooling to 630-75o'C at a rate of 50-150"C/min, cooling to room temperature, ageing at 630700°C Production of Platinum and Palladium for 5 min - 2 h and then quenching to room Oxides temperature. JOHNSON, MATTHEY & CO. LTD. French Patent 1,458,185 Tungsten-Ruthenium Alloy Oxidation of these metals is achieved by electro- US. ATOMIC ENERGY COMMISSION lysis of a Pt or Pd anode in a bath containing British Patent 1,070,114 molten NaNO, and an alkali metal halide. This The high temperature strength of W can be corresponds to Belgian Patent 664,526. improved by adding 1.1-120,~ Ru (based on the weight of the alloy). A preferred composition is ELECTRODEPOSITION AND 1.1 wt.O: Ru and 98.97, W. SURFACE COATINGS Alloys for Strain-Gauge Elements Coating Titanium Surfaces KABUSHIKI KAISHA HITACHI SEISAKUSHO SOCIETE D'ELECTRO-CHIMIE DES ACIERIES U.S. Patents 3,305,8159 ELECTRIQUES D'UGINE British Patent 1,069,005 In strain gauges the strain element consists of a Process for coating Ti or its alloys with a metal binary alloy of 0s with 90-99'; Pt (815)~ a of the Pt group. The metal to be coated is acid ternary alloy of 20-60 at.:; Pt, 20-60 at.:/, Pd pickled and the Pt group metal deposited and and 5-30 at.% Ir (816) and a ternary alloy of then heated at 150-3oo@C. 15-80 at.16 Pt, 15-80 at.o/: Pd and 2-15 at.% Mo. Applying Designs to Metallic Bases Hydrogen Diffusion Tubes JOHNSON MATTHEY & CO. LTD. JOHNSON, MATTHEY 82 CO. LTD. French Patent 1,455,917 US.Patent 3,312,043 A decorating composition for application to a A closing plug for sealing the opcn end of Pd or noble metal base consists of a metallising paste Pd-Ag alloy H, diffusion tubes consists of containing Au, Ag, Pt, Pd or alloys thereof. material with approximately the same coefficient of thermal expansion and dimensioned to fit Palladium Plating tightly with a projecting, threaded spigot of JOHNSON, MATTHEY & CO. LTD. smaller diameter than the tube and used to form a German Patent 1,239,159 means for attachment of or for stabilising an An aqueous neutral or alkaline Pd bath contains internal support for the tube. This corresponds a Pd compound, e.g. (PdNH,),(NO,),, and a to British Patent 1,009,326. NHI salt of a weak acid which does not form an

Platinum Metals Rev., 1967, 11, (4), 159-162 159 insoluble compound with the Pd compound, e.g. Regeneration and Reactivation of Supported ammonium tartrate. Platinum Group Catalysts SHELL INTERNATIONALE RESEARCH MIJ. N.V. British Patent 1,069,057 BRAZING Reforming catalysts are regenerated by treatment with C1, or a compound which liberates C1, on Brazing Alloys for Tungsten and heating, followed by burning in a gas containing Molybdenum 0, to remove C. The catalyst is then maintained U.S. ATOMIC ENERGY COMMISSION at a temperature higher than burning temperature US,Patent 3,312,539 in a gas of higher O2 content. These metals and their alloys are brazed using alloys of 42-95 wt.O/, Mo, 5-44 wt.3; Rh and up Hydrocracking Process to 45 wt.:b Re. ESSO RESEARCH & ENGINEERING CO. Solder for Soldering Electrovacuum British Patent 1,071,467 Instruments A crystalline alumino-silicate zeolite composited with a Pt group metal is used for hydrocracking B. E. KOVALEVSKII et al. of hydrocarbons. U.S.S.R. Patent 186,836 A solder of lower melting point which has increased strength and plasticity of the soldered Production of Finely Divided Catalyst joints has composition 8-12 wt?; Ge, 2-12 wtx Layers on the Pore-free Surfaces of Hydro- Pd, balance Cu. gen-absorbing Metallic Bodies VARTA A.G. British Patent 1,071,503 A metaliic body is coated on one side with a CATALYSIS catalyst layer and subjected to H, pressure, whilst on the other side (e.g. in a tube) a solution of the Production of Saturated Aldehydes metal to be used for hydrogenation (e.g. Pd WACKER-CHEMIE G.m.b.H. (NO,),) is precipitated by diffusion of H, and British Patent 1,065,628 reduction. The partial hydrogenation of olefinically sub- stituted aliphatic aldehydes at 7G-I4O0c is Composite Catalysts catalysed by a mixture of metallic Pd and one or OFFICE NATIONAL INDUSTRIEL DE L'AZOTE more of Cu, Ni and Co. Au or Ag may also be British Patent 1,072,172 present. A catalyst comprising 0.1-2.0~6 Pt, 8-50?; Ni and/or Co and an A1,0, or MgO support. It is Silanes, their Quaternary Salts and Polymers used in the methanation of CO by H, and in the DOW CORNING CORP. British Patent 1,066,346 reforming of hydrocarbons. Haloether silanes are obtained by the Pt-catalysed co-reduction of a silane and a hydrocarbon ether. Hydrocarbon Conversion Process TEXACO DEVELOPMENT COKE'. Production of Araliphatic Dicarbinols British Patent 1,072,620 SCHOLVEN-CHEMIE A.G. British Patent 1,066,401 Mixtures of hydrocarbons (pentone, hexone, etc.) The corresponding hydrocarbons are oxidised to may be converted to highly branched hydrocarbon hydroperoxides and then reduced to dicarbinols products by using a chloride-activited Pt/Al,O, using H, and Pt/A1,0,. catalyst. Carbonylation of Olefinically Unsaturated Preparation of Aryl Thiols Compounds UNITED STATES RUBBER CO. BADISCHE ANILIN-& SODA-FABRIK A.G. British Patent 1,073,200 British Patent 1,066,772 PtS, is used as a catalyst for conversion of aryl Carbonylation is catalysed by L,PdX,, where sulphinic acids to aryl thiols by hydrogenation. L is an organic phosphine or phosphite, NH,, This obviates the use of H,S and S which are an amine, a nitrile or an unsaturated hydrocarbon, needed with prior art processes using base metal X is an anion, m is 1-4, n is 1-2 and n+m is 2-6, sulphides . e.g. Pd(PPh,),CI,. Preparing Catalysts Vinyl Acetate Production ESSO RESEARCH & ENGINEERING CO. IMPERIAL CHEMICAL INDUSTRIES LTD. British Patent 1,076,215 British Patent 1,067,850 A highly active catalyst is made by contacting a The catalyst for the reaction of CeHa with support with a salt solution of a catalytic metal, CH,COOH consists of a redox system and a Pd reducing the metal ions and subsequently remov- salt other than the fluoride. ing the support to leave a finely divided metal.

Platinum Metals Rev., 1967, 11, (4) 160 Thus Pt metals, Ag and Au can be deposited Pd and (b) a Cu chromite, Pt or Ag/Zn/Cr oxide singly or in mixtures on CaCO, which is then to introduce a formyl group on a double bond. removed. Production of 4-Halobutene-1 Dehydrogenation of Cyclo-octene E.I. DU PONT DE NEMOURS & CO. U.S. RUBBER CO. U.S. Patent 3,305,593 U.S. Patent 3,3r2,747 1,5-Cyclo-octadiene is produced by heating Commercially valuable 4-chloro- and 4-bromo- cyclo-octene and a Rh salt, e.g. RhCl,, in CH,OH, butene-1 are produced by dehydrohalogenation at 50-15o~C. of 1,3-dihalobutane at 200-385~C in the presence of Pd/Al,O,, Rh/Al,O,, ZnO or activated A1,0,. Hydro dealkylation Catalyst UNIVERSAL OIL PRODUCTS CO. Platinum Double Bond Addition Catalyst U.S. Patent 3,306,944 GENERAL ELECTRIC CO. (NEW YORK) The demethylation of alkyl aromatic hydro- U.S. Patent 3,313,773 carbons with Rh is catalysed by Rh deposited The addition of a Si compound, having at least on an alkali metal-promoted metal oxide support, one atom of H attached to the Si atom, to a e.g. Li/Al,O,. C-C unsaturated bond is catalysed by trimethyl platinum iodide or diplatinun hexamethyl. Selective Hydrogenation of Hydrocarbons MOBIL OIL CORP. U.S. Patent 3,309,307 Hydrocracking Process Dienes are selectively hydrogenated in the pre- ESSO RESEARCH & ENGINEERING CO. sence of olefines by using a Pd catalyst in the U.S. Patent 3,318,802 presence of either CS, or H,S below the de- The activity of a crystalline SO,-Al,O, zeolite sulphurisation temperature. containing a Pt group metal is increased by introducing a halogen containing compound into Catalytic Hydrogenation of Paraffin the hydrocracking zone. Hydrocarbons UNIVERSAL OIL PRODUCTS CO. Production of Metallic Oxides U.S. Patent 3,310,599 JOHNSON, MATTHEY & CO. LTD. A new composite catalyst, e.g. for producing FTench Patent 1,458,185 iso-C,H, from iso-CqH,Oy0.01-1.59, Al,O:,/Li, Oxides of Pt, Pd or mixtures of Pt andjor Pd 0.05-5% Group VIII metal and sufficient Te, with other metals are produced by electrolysing Se or their compounds to give full cracking and a molten bath of an alkali metal nitrate and isomerisation of the Group VIII metal. Pt and chloride with anodes of the requisite metals. Pd are the preferred noble metals. Oxide Catalysts for Chemical Reactions Catalyst for Combining Hydrogen and JOHNSON, MATTHEY & CO. LTD. Oxygen in Thorium Slurries French Patent 1,458,671 US. ATOMIC ENERGY COMMISSION The catalyst is a homogeneous and intimate U.S. Patent 3,312,526 mixture, not merely a physical mixture, of A catalyst for reversing the radiolytic decomposi- zo-goo:, PtO, and 1o-80% RuO, by weight. tion of H,O in Tho, slurries is produced by heating an aqueous Tho, sol and platinic acid in a Th:Pt Chemical Reaction Catalyst ratio of 2-3:r until a floculated suspension is G. WILKINSON formed. The suspended solids of platinised Tho, French Patent 1,459,643 Italian Patent 748,928 are recovered and added to Thoz slurries. A catalyst for hydrogenation, hydroformylation and carbonylation consists of a platinum metal Preparation of Butyrolactone halide or pseudohalide complexed with an PETRO-TEX CORP. U.S. Patent 3,312,718 organic isocyanate or a Group VB or VIB Succinic anhydride is hydrogenated to butyro- compound, e.g. (Ph,P),RhCl. This corresponds lactone in the presence of a suitable catalyst, e.g. a to Canadian Patent 745,663. Pt metal, and silicotungstic acid at 200-300rC and at above 500 psig. Catalyst Production JOHNSON, MATTHEY & CO. LTD. Mono-oxonation Products of Cyclic Dimers Dutch Appln. 66.17,004 and Trimers o€ Butadiene A general purpose chemical reaction catalyst is CHEMISCHE WERKE HULS A.G. an intimate homogeneous mixture of a Pt metal U.S. Patent 3,312,742 oxide and a baser metal oxide, preferably in a These butadiene-1,3 dimers and trimers are ratio of 3:r or higher. The base metal may be reacted with CO and H, in the presence of a Fe, Co, Ni, Cu, etc., e.g. a mixture of Ni and Pt catalyst mixture consisting of (a) Co carbonyls or oxides. The mixture must not be a simple salts of fatty acids, I'd halides or finely divided physical mixture.

Platinum Metals Rev., 1967, 11, (4) 161 Ole& Isomerisation made of graphite, This layer is a refractory JOHNSON, MATTHEY & CO. LTD. material comprising the elements W, Mo, Zr, Italian Patent 743,469 Hf, Ta, Ti and Ni; either singly or as mixtures An improved catalyst especially for olefine and one or more of the Pt group metals. isomerisation consists of a salt such as RhCl, or PdCl, dissolved in a virtually non-volatile Production of Pure Hydrogen hydroxylic compound, e.g. propylene glycol, J. F. MAHLER APPARARATE- 82 OFENBAU K.G. optionally dissolved on an inert porous support. German Patent 1,238,884 This corresponds to French Patent 1,445,176. NH, is decomposed, in the absence of further catalysts, on a hot membrane containing Pd FUEL CELLS which allows the nascent H, to pass through. Fuel Cells ELECTRICAL AND TOKYO SHIBAURA ELECTRIC CO. LTD. Brztish Patent 1,074,561 ELECTRONIC ENGINEERING A H, electrode consists of a non-porous Pd or Semiconductor Devices Pd alloy plate which is covered with Pd black on MULLARD LTD. British Patent 1,074,284 the surface exposed to H,, and with black mixture of Pd and Pt on the other surface. A semiconductor device is made by alloying Bi and Pt to a semiconductor body consisting of at Electrodes least two components, none of which is Bi. The amount of Pt is up to IOO; of the alloy. RODERT BOSCH G.m.b.H. British Patent 1,074,862 Porous sintered electrodes for fuel cells use Ni as Electrical Resistance Element frame metal, and Pt group metal or its Ni alloy CTS COW. Patent 3,304,199 as skeleton catalyst in which up to 20"; Ti, V, US. Cr, Co, Mo, Ru or Ta is added. Resistance elements are produced by applying to a non-conducting substrate a mixture of 2-70 Hydrogen Fuel Cell Structure wt."; of a finely divided metal oxide selected from RuO, and IrO, and 98-30°& powdered glass frit. UNION CARBIDE CORP. U.S. Patent 3,307,977 A heavy metal salt of at least one of Fe, Co, Ni, Impedance Element with Alloy Connector Mn, Cr, Cu, Ag, Au, V, Ti, Th, U and rare earth metals is used with an A1 salt to coat a layer of NYTRONICS INC. U.S. Patent 3,310,718 spinel on a porous body (e.g. C). A Pt salt is then Strong stable leads to miniaturised impedance used to deposit a catalytic layer. components are produced using connectors (such as wire) made from wrought Ag-Pd alloy, parti- Fuel Cell Electrode cularly alloys with 3-20?; Pd. AIR PRODUCTS & CHEMICALS INC. and NORTHERN NATURAL GAS CO. U.S. Patent 3,309,231 Iridium Tip Electrode It has been found that when Pt is used with a CHAMPION SPARK PLUG CO. U.S. Patent 3,315,113 Group IB or VIII noble metal in certain pro- A tip electrode, especially for a sparking plug, is portions, the noble metal acts synergistically to made from an Ir wire on which an outwardly improve the activity of the Pt metal catalyst. extending shoulder is formed by melting the centre of the length of wire and pushing the ends Activation of Electrodes Containing inwards. This avoids mechanical working in Platinum or Palladium which the metal is embrittled. UNION OIL CO. OF CALIFORNIA Platinum Electrical Contacts U.S. Patent 3,311,508 Pt or Pd bonded to a fuel cell electrode is activated INTERNATIONAL BUSINESS MACHINES CORP. French Patent 1,458,861 by exposure to a H, atmosphere at room tempera- ture. After activation the electrode must be Contacts with ohmic properties stable at high exposed to an inert atmosphere to remove H, temperatures are mixtures of 91-93 wt.O/, of a traces before use in the presence of 0,. Pt group metal and 7-9 wt."; of C. The Pt group metal is suitably Pt.

CHEMICAL TECHNOLOGY Ruthenium in a Glass Conductor AIR REDUCTION CO. INC. Process for Bonding Two Temperature- French Patent I ,463,749 resistant Members A new form of electrical resistance consists of a SOCIETE NATIONALE D'ETUDE ET DE CONSTRUCTION mixture of T1 oxide and RuO, intimately dis- DE MOTEURS D'AVIATION British Patent 1,071,179 persed in a vitreous matrix. Preferably the A bonding layer is interposed between the sur- RuO, is 0.05-80°/, of the mixture. Au, Pt or faces of the two members at least one of which is Pd may also be present.

Platinum Metals Rev., 1967, 11, (4) 162 AUTHOR INDEX TO VOLUME 11

Puge Page Puge Page Acres, G. J. K. 38, 86 Carson, A. W. 151 Frankel, E. N. 157 Kahrig, E. 78 Albright, L. F. 158 Casale, M. E. A. I 26 Freifelder, M. 77 Karakhanov, R. A. 75 Aldag, A. 35 Cashmore, P. 39 Fullenwider, M. A. 34 Karev, V. N. 74 Aldred, A. T. 1 I3 Chaikin, S. W. 56 Katsnel'son, A. A. 32 Alimov, Sh. A. 32 Chalk, A. J. 37 Allam, M. I. 1 I6 Gallaher, J. S. 10 Kawasaki, K. 112 Charman, H. B. 37,157 Galligan, J. M. 31 Kazakora, V. 1. 114 Almar-Naess, A. 39 Chasse, C. J. 120 Keim, W. 153 Anderson, J. R. 36 Gamboa, J. M. 74 Chesswass, M. 74 Gardam, G. E. 70 Kemp, A. L. W. 78 Andresen, A. F. 71 &ek, A. 70 Gault, F. G. 76, 117 Kerr, W. B. 119 Andrews, J. M. 92 Cleare, M. J. 148 Gerberich, H. R. I18 Ketley, A. D. 119 Antler, M. 115 Cockayne, B. 74 Khomenko, A. A. 36 Apel'baum, L. 0. 36 Gibb. J. G. 100 Coles, B. R. 109 Giessen, B. C. 152 Khorov, Yu. M. 155 Arajs, S. 32 Collman, J. P. 73, 114 Gileadi, E. 34 Khrushch, A. P. 77 Arkharov, V. I. 113 Colyer, J. 0. 34 Gingerich, K. A. 71 Kin, M. J. 112, 151 Armstrong, P. E. 33 Connolly, J. F. 115 Ginzburg, S. I. 73 Kirillova, M. M. 112 Arons, R. R. 72 Connor, H. 2, 60 Glemser, 0. 33 Kitchingman, W. J. 112 Aso, T. I52 Conti, F. 73 Goldberg, A. 1 I6 Kjekshus, A. 71 Attardo, M. J. 31 Cooper, A. W. 154 Golodov, V. A. 37 Kleiu, A. 154 Avery, N. R. 36 Cornet, D. 76 Gonikberg, M. G. 75 Klimova, N. V. 156 Cotton, J. B. 50 Greaves, E. 0. 33 Klyucharev, A. P. 74 Cowan, J. H. 79 Green, M. 37 Koch, D. F. A. 153 Bailar, J. C. 118, 157 Cramer, R. 37, I19 Baird, M. C. 153 Greenfield, H. 157 Kohlhdas, R. 152 Cross, R. J. 1 I4 Grinberg, A. A. 114 Kohliug, A. 57, 78, 1 I5 Balandin, A. A. 77 Cucka, P. 32 Banus, M. n. 33 Gullman, L. 0. 32 Kohll, C. F. 118 Cusumano, J. A. 35 Gurevich, M. A. 3 I Kokes, R. J. 36 Bardysbev, I. I. 38 Kolbin, N. I. 152 Barinov, N. S. 77 Konig, K. 116 Barland, P. 34 Damjanovic, A. 34, 154 Hall, J. A. 39 Koros, R. M. 117 Barron, Y. 35 Dangel, P. N. I52 Hall, W. K. 118 Koryta, J. 157 Bartlett, R. W. 150 Darby, J. B. 72 Halpern, J. 77,78 Kos, J. F. 120 Beduhn, M. 159 Darling, A. S. 94, 138 Hama, M. 76 Kouvel, J. S. 152 Belmahi, 0. 31 Davitt, H. J. 158 Hanky, J. B. 70 Kral, H. 76 Bennett, R. P. 118 Dembenski, G. W. 35 Hansen, R. S. 32 Kralina. A. A. 113 Berezin, B. D. 158 De Mourgues, L. 117 Hardy, W. B. 118 Kravtsov, V. I. 34 Berry, R. J. 150 Dent, W. U. 116 Harris, I. R. 72 Krylova, I. V. 75 Bikhanov, F. B. I56 Dewhurst. K. C. 157 Harrison, D. P. 155 Kubicki, J. 154 Binder, H. 57, 78, 115 Dey, A. 34 Harrod, J. F. 37, 78 Kubota, M. 73 Birch, A. J. 77 Dietrich, H. 129 Haszeldine, R. N. 37 Kubn, A. T. 153 Blair, J. 100 Dixon, M. 70 Hayfield, P. C. S. 115 Kupenko, 0. G. 75 Blanchard, A. 71 Donati. M. 73 Hevdinz. R. D. 114 Kutsar, A. R. 113 Blasiak, E. 116, 154 Doniach, S. 113 H&e,"'W. 159 Kutyukov, G. G. 37 Blume, H. 35 Donnelly, R. G. 140 Hightower, J. W. 74 Kuzembaev, K. K. 38 Blumenthal, J. L. 53 Doronicheva, N. 1. 3 1 Hirsch. H. 113 Kuz'min, V. M. 150 Bolotin, G. A. 112 Downey, J. W. 72 Hitzroi, H. W. 39 Kuznetsov, E. A. 150 Bond, G. C. 38,75, 156 Drnz', V. A. 35, 156 Hoare, F. E. 70 Booth, G. H. 154 Druzhinin, A. V. 79 Hoare. J. P. 33 Boronin, V. S. 117 Dubien, J. 117 Hoenig, S. A. 116 Lakey, L. T. 119 Boudart, M. 35 Dunnigan, D. A. 77 Hofer, E. M. 32 Lam, D. J. 32 Bouman, J. 72 Dwight, A. E. 72 Holland. H. B. 76 Lamarche, J. L. G. 120 Bradford, C. W. 104 Holliste;, R. G. 94 Landor. S. 79 Bradley, I). 39 Holzmann, H. 74 Lange, P. 78 Breiter, M. W. 115 Edshammar, L.-E. 152 Hopff, H. 117 Lasko, W. R. 11s Brinkman, W. F. 152 Emken, E. A. 157 Huppes, N. 119 Laubitz. M. J. 70 BrissoMeau, P. 71 Emmett, P. H. 74 Husemann, 13. 31 Lavine,'M. C. 33 Brodersen, K. 33 Entwistle. A. G. 39 Layton, A. J. 1 I4 Brodowskv. H. 3 1. 113 Eremenko, V. N. 32 lgnatov, D. V. I50 Leder. F. 34 Bronger, W. 71 Ettmayer, P. 1 I4 Tles, G. S. I26 Lee, J. B. 39 Brown, C. A. 74 Evans, E. W. 151 Imamura, S. 119 Levitskii, I. I. 75 Brown, D. W. 49 lngraham, T. R. 34 Lewis, F. A. 99, 151 Brown, H. C. 74 Lindsey, R. V. 37 Fakidov, 113 Ioffe. I. I. 156 Brown, H. L. 33 I. G. Isabekov,. A. 36 Llopis, J. 74, 154 Brusir, V. 154 Falbe, J. 119 Lockington, N. A. 158 Fasman, A. B. 36, 37,74 Itatani, H. 118 Bubyrev, A. N. 151 Ivashentsev, Ya. 1.- Lommel, J. M. 152 Bucher, E. 152 Fegan, L. V. 39 Loshchilova, A. V. 158 Buehl, W. M. 79 Ferents, V. Ya 112 Lozinskii, M. G. 112 Filonenko, A. P. 75 Iveronova, V. I. Bufferd, A. S. 112 Iwamoto, K. Lozovoi, A. V. 76 Bums, G. W. 10 Fine. T. E. 71 Idyou, H. B. 150 Burwell, R. L. 35 Firth, J. G. 36,76 Lyubarskii, G. D. 156 Butler. C. A. 115 Fishcr, A. H. 116 James, B. R. 78, 158 Butt, J. B. 34 Fisher. J. R. 158 James, W. G. 1 I6 Fisher; L. P. 119 Jardine, F. €3. 119 McCormack, J. M. 71 Fishman, J. H. 154 Jasorska-Galas, Z. 35 McDaoiel, C. L. 152 Cadenhead, D. A. 76 Flanagan, T. B. 71, 151 Jeitner, 0. I I6 McDonald, D. 18, 106 Cairns, E. J. 78 Flanagan, W. F. 15 1 Johnson. D. A. 37 Machmer, P. 153 Candlin, J. P. 73 Flannery, R. J. 115 Jones, 12. W. I59 McKee, W. E. 147 Cannon, W. A. 78 Fleischer, E. 114 Jones, F. N. 157 Maclean, A. F. 119 Carlson, C. W. 116 Fleischmann, M. 157 Jones. J. M. 140 McLean, M. 70 Carpenter, R. W. 1 50 Flid, R. M. 118 Joshi,' K. K. 73 Maeland, A. J. 113, 151

Platinum Metals Rev., 1967, 11, (4), 163-168 163 Page Pare Page Page Maire, G. 35, 117 Petrii, 0. A. li5 Sloboda, M. H. 74 Van Laer, P. 149

~Maitlis. P. M. 33 Pickwick. K. M. 112 Slovokhotova, T. A. 157 Van Reuth, E. C. 31 Markini T. I. 76 Piersma. B. J. Smirnova, E. B. 38 Van Stratum, A. J. A. Markov,'V. D. 37 Ponec, V. 75 Smith, C. P. 79 15__ Martyshkina, L. E. 117 Ponyatovskii, E. G. 1 13 Smith, G. V. 76 Vastine, F. D. 73 Marvet. R. V. 115 Porzel. W. 116 Smith, J. M. 35 Vazquez, M. 154 Masse,". G. 76 Potlova, G. A. 38 Sohn, R. L. 31 Vergnaud, J.-M. 156 Mathis, B. 1 I4 Powell, A. R. 58 Sokolova, N. P. 77 Vlugter. .I. C. 116 Matsuo, Y. 112 Powell, R. W. 70 Sokol'skaya, A. M. 38 vo& E. - 71 Matveev, I(. I. 158 Pravoverov, N. L. Sokol'skii, D. V. Volodin, Yu. A. 79 Mauret, P. 154 113, 151 36, 38, 76, 156 Von Hahn. E. A. 34 Maymo, J. A. 35 Pregaglia, G. F. 73 Somorjai, G. A. 150 Von Philipsborn, H. 155 Meibuhr, S. G. 33 Ptitsyn, B. V. 114 Spector, N. L. 38 Von Schnering, H. G. 33 Melmed, A. J. 150 Stark, D. 151 Voznesenskaya, I. I. Merck. M. 31 Starostenko, G. K. 157 35, 75 Mimeault, V. J. 32 Radyushkina, K. A. 115 Stautzenberger, L. 119 Mitchell, W. I. 70 Rase, H. G. 155 Stern, E. W. 38 Mitrofanova. A. N. 117 Raub, E. 70 Strassmair, H. 151 Walker,Walker, K.K. A.A. M.M. I777 Raynor, G. V. 72 Wang,Wang, F.F. E.E. 114114 Moiseev. I. I. 77 Strelets, M. M. 156 115 Montgomery, K. M. 154 Rennard. R. J. 36 Strel'nikova, Zh. V. 117 Warne,Warne, M.M. A.A. 115 Rey-Coquais, B. 156 Warner,Warner, T.T. B.B. 7373 Moss, R. L. 141 Sugita, T. 112 31 Mozzhukina, V. M. 36,75 Rhee, S. K. 112 Swoap, J. R. 76 Waterstrat. R. M. 31 Ritchie, A. W. 117 Webb, G. 4646 Musheuko, D. V. 77 Syutkina, V. I. 32 156 Myers, J. R. 71 Rodina, A. A, 31 Szkibik, C. 35 Webster, D. E. 156 Roesky, H. W. 33 Weiss. W. D. 152 Mykura, H. 70 I53 Myles, K. M. 32, 72 Rojkind, M. 34 Weissinan, E. Y. 153 Roschel, E. 70 Taueeva. V. G. 74 Wells, P. B. 38,7538I, 75 Roth, H. A. 115 Tankins,' E. S. 31 Wiese,Wiese. U. 114 Nagasawa, A. 112 Rotinyan, A. L. 33 Tarasevich, M. R. 115 Wikans,Wilr J. 114 Neuse, E. W. 33 Rudman, P. S. 72 Tavim. H. A. 157 Wilke, G. 72 Wilkinson, G. 1 19, 153 Nicholson, M. E. 71 Rummery, T. E. 114 Thicker, R. 33 1 19, .~I53~ Nishimura, S. 76 Rusling, R. Y. 120 Tharby, R. 34 Wilson. R. G. 72 Nixon, A. C. 117 Russell, A, D. 111 Thomson, S. J. 46 Wohlfarth, E. P. 113 Nogi, T. 38 Rytvin, E. I, 150 Timonova, R. I. 33, 114 Wolf, E. D. 72 Nowak, E. J. 117 Tokina, L. A. 77 Wroblowa,Wroblowa. H. 153 Nyholm, R. S. 114 Toth, I. J. 158 Wnyszcz,Wnyszcz,'J. J. 35 Sadasivan, N. 114 TouSek, J. 153 Wuhl, H. 72 Wynveen, R. A. 154 Odaira, Y. 37 Sadchikova, L. N. 156 Toy, M. S. 78 Wynveen, R. A. 154 Oehler, E. 71 Samoilov, V. M. 152 Treger, Ya. A. 118 Ogren, J. R. 53 Schafer, H. 114 Tribunskaya, L. A. 113 Ohno, K. 38,39, 157 Schuabel, K. H. 156 Tsuji, J. Yakovleva. E. S. 32 Oishi. T. 37 Schueider, S. J. 152 38. 39. 77. 119. 157 Yaniv, A. E. 154 Okamoto, H. 152 Schott, H. 72 Turk, R.'R.' ' ' I47 Yarish, M. 154 Osipov, A. M. 158 Sellberg, B. 72 Tye, R. P. 70 Yoshida. K. 155 Ostrovidov, E. A. 33 Selman, G. L. 132 Tyrrell, C. J. 115 Yuz'ko,'M. I. 73 Otaki, T. 155 Shashkov, A. S. 36 Tyurenkova, 0. A. Owen, E. A. 151 Shaw, B. 93 36,76, 156 Shropshire, J. A. 158 Zalm, P. 15 Shtepa, T. D. 32 Zavadskii, E. A. 113 Panchenkov, G. M. 155 Shnikin, N. I. 35,75 Utegulov, N. I. 35 Zelenskii, M. I. 34 Panetta, C. A. 37 Sikora, H. 116, 154 Zeliger, H. I. 119 Pearlman, W. M. 116 Simonite, Yu. P. 75 Zhusnnbekov, B. 0. 156 Pearson, A. D. 158 Simons, J. W. 71 Van der Meer, J. P. 70 Zirngiebl, E. 158 Pestrikov, S. V. 77 Sipes, W. A. 31 Van Heldeu, R. 118 Zwilksy, K. M. 112

SUBJECT INDEX TO VOLUME 11 a=abstract Page Catalysts (Confd.) Page Anodic Corrosion, of Ru, a 74 Adams', activity of, a 156 Bromopalladate ions, catalytic activity of, a 37 Beta 750, electrodeposit thickness gauge 13 Iridium, C,H,, oxidation of, a 153 Brazing, graphite, with Pd alloy 140 h/A1208,deuteration of CIH6on, a 75 review of alloys for, a 74 hydrogenation of C,H, on, a 38 NIIALO,, promoted with Pt and Pd, a 117 Catalysis, ,homogeneous and heterogeneous, Ni0, Pd-promoted, a 117 symposia on 16 NiO, Pt-promoted, a 117 homogeneous. Oxford Inorganic Discussion Nylon-Platinum, activity and selectivity of, a 155 on 30 hydrogenation, of C,H, on, a 155 homogeneous, transition metal complexes in, a 77 Osmium, C,H,, oxidation of, a 153 mechanism of heterogeneous, a 35 OsO,, regeneration of, in situ, a I19 Platforming, mathematical description of, a 155 homogeneous air oxidation with, a 119 Pt metals in, 2nd Canadian Symposium on 146 0sphthalocyanine, activity of, a 158 radiochemical study of 46 Palladium, acido complexes, activity of, a 37 trickle column reactors for 86 black, activity of, in liquid phase Catalysts, for HNO, production, review of, a 74 hydrogenation, a 156 preparation of, by reduction of PtIV, a 117 complexes, oxidation and reduction by 93 supported, electron microscopy of 141 complexes, oxidation of CaH, on, u 158

Platinum Metals Rev., 1967, 11, (4) 164 Catalysts (Conrd.) Page Catalysts (Confd.) Page Complexes, isomerisation of deuterio Platinum, black, activity of, in liquid phase olefins on, a 37 hydrogenation, a 156 complexes, Ph,As. hydrogenation of complexes, oxidation and reduction by 93 soybean oil methyl ester on, a 118 complexes, oxidation of C2H,on, a 158 complexes, Ph,P, hydrogenation of complexes, Ph,As, PhaP, Ph,Sb, a 118 soybean oil methyl ester on, a 118 dehydrogenation of cyclohexane on, a 35 disproportionation of cyclohexene 86 electrodeposited, activity of, a 115 C2H4.oxidation of, on, a 118, 153 C2H,,oxidation of. on, a 153 films, conversion of methyl propyl film, conversion of methyl propyl ketone ketone on, a 76 on, a 76 films hydrogenolysis and isomerisation film, H a-02reaction on, a 75 on, a 117 gauze, manufacture of HNOI and HCN 60 films, isomerisation on, a 36 hydrogenation of benzyl alcohol on, a 76 hydrogenation of butyronitrile on, a 157 hydrogenation of butyronitrile on, a 157 hydrogenation of rosin on, a 38 hydrolysis of allyl chlorides, a 118 hydrolysis of allyl chlorides, a 1 I8 hydrogenolysis and isomerisation on, a 11 7 isomerisation on, a 37 isomerisation of hexanes on, a 35 membranes, decomposition on, n 36 isomerisation on, a 36, 37 mixed oxides, activity of, a 156 losses in HNO, manufacture, a 154 potential of, a 74 mixed oxides, activity of, a I56 synthesis of caprolactam, a 156 oxidation of carbonaceous fuels on, a 158 Palladium Acetate, reaction with vinyl potential of, a 74 acetate, a 1 I8 reforming, automation of, a 154 PdCI,, carbonylation of carboxylate reforming, conversion of compounds, a 38 bicyclonaphthenes on, a 1 I6 cleavage of Si-Si bond, a 118 reforming, damage in use, a 35 dimerisation of alkenes, a 1I9 single crystal growth, of CdCr,Se,, a 155 isomerisation of butenes, a 77 S-modified 57 oxidation of n-butylamine, a 77 supported, conversion of methyl propyl production of vinyl acetate, a 118 ketone on, a 76 reactions with nucleophiles, a 37, 38 suspension of, CO adsorption on, a 74 synthesis of rr-allylic Pd complexes, a 119 PtC12,preparation of butadiene on, a 157 PdC1,-CuCI,, production of vinyl acetate, a 118 PtCI2(PPh,),, isomerisation of I ,5-cyclo- Pd-Cu, hydrogenation of C,H, on, a 76 octadiene, a 157 Palladium Cyanide, synthesis of olefinic Pt-Pb black, electrodeposited, activity of, a 115 cyanides with, a 37 Pt-Ni, CIH,, oxidation of, a 153 Pd-Au, activity of, a 154 Pt/Al20,,activation of, a 75 C,H,, hydrogenation of, on, a 76 adsorption kinetics of, a 156 CsHI, oxidation of, a 153 chemisorption of Hzand properties, a 35 CH,, oxidation of, on, a 36 conversion of dicyclopentylmethane on, a 35 conversions of spiro-(4,5)-decane and Pd-Au-H, poisoning of, with CO. a 154 -(4,4)-nonane on, a 75 Palladium Hydride, hydrogenation on, a 36 dehydrogenation of dicyclohexyl on a 117 Pd(OH)& non-pyrophoric, preparation deuteration of CIHaon, a 75 of, a 1 I6 electron microscopy of 141 Pd/AI2Os,conversion of dicyciopentyl exoelectronic emission from, a 75 methane on, a 35 H%-O reaction on, a 34 conversions of spiro-(4,5)-decane and intra-pellet heat and mass transfer, a 35 spiro-(4,4)-nonane on, a 75 isomerisation of hexanes on, a 35 deuteration of C,Ha on, a 75 specific activity of, a 35 hydrogcnation of acctophenonc 86 surface area of, a 35 hydrogenation of acctylenic compounds 86 PtjC, adsorption kinetics of, a 156 hydrogcnation of aromatic nitro adsorption of unsaturated compounds com pounds 86 on, a 156 hydrogenation of C.,H on, tz 76 conversion of dihydropyran and hydrogenation 01' olclinic cornpounds 86 propyldioxene on, a 75 oroduclion of vinvl acctate. (I 118 effect of KOH on activity of, a 156 kduction of tail &s on, a ' 116 electron microscopy of 141 Pd/BaSO,, hydrogenation of phosphatides hydrogenation of cyclohexene on, a 76 on, a 38 hydrogenation of unsaturated Pd/CaCO,, hydrogenation of phosphatides compounds on, a 156 on, a 38 preparation in sifuof, a 74 Pd/C, adsorption of unsaturated recrystallisation of, a 115 compounds on, a 156 Pt/Cr,Os, activity and electronic emission, a 36 carbonylation of carboxylate Pt/MgO, activity and electronic emission, a 36 compounds on, a 38 exoelectronic emission from, a 75 conversion of penicillins on, a 37 Pt/polyacrylonitrile,hydrogenation of allyl hydrogenation of cyclohexene on, a 76 alcohols on, a 76 hydrogenation of olefinic compounds 86 Pt/polyviuyl alcohol, properties of, a 36 hydrogenation of phosphatides on, a 38 Pt/pumice, isomerisation of hexanes on, a 35 hydrogenation of unsaturated Pt/SiO,, electron microscopy of 141 compounds on, a 156 hydrogenation of cyclohexene on, a 117 production of MAZDA with, a 76 specific activities of, a 117 selectivity and active sites of, a 76 Pt/SiO,-Al,O,, chemisorption and PdiFeCI,. synthesis of isocyanates, a 118 properties of, a 35 Pd/polyacrylouitrile, hydrogenation of isomerisation of n-butane on, a 117 ally1 alcohols on, a 76 Pt/ZrOarexoelectronic emission from, a 75 hydrogenation of PtO1,reduced, hydrogenation of cyclo- dimethylethynylcarbinol on, a 156 hexene on, a 76 PdjSiO,, hydrogenation of phosphatides Pt-Raney Ni, hydrogenation and on, a 38 oxidation on, a 36 production of vinyl acetate, a 118 hydrogenation of glucose on, a 156 Pd/zeolite, resistance to poisoning of, a 76 Pt-Rh, activity of 155 Pd-Raney Ni, hydrogenation of glucose atomic susceptibility of, a 155 on, a 156 CzH4,oxidation of, a 153 Pd-Rh, C,H,, oxidation of, on, a 153 gauze, for HNO, manufacture 2,100

Platinum Metals Rev., 1967, 11, (4) 165 Catalysts (Conrd.) Page Electrodeposition of (Contd.) Page hvdroeenation of C,H,COOH on, a 155 in chloride electrolytes, a 34 Pt-RhjC, surface area of; a 155 Platinum, electrochemical activity of, a 115 Pt-Sn complexes, hydrogenation of methyl foils, a 14 linoleate on. a 157 Platinum-lridium, a 115 Rhodium, alkyl complex, reaction with Platinum-Lead black, electrochemical CaH4, a 119 activity of, a 115 black, hydrogenation of phenyl- Platinum Metals, thickness of deposits 13 acetylene on, a 38 Rhodium, bright and smooth, a 154 complexes, isomerisation of deuterio foils, a 74 olefins on, a 37 Ruthenium, film, catalytic activity of, a 157 complexes, reactions of, a I58 Electrodes, Indium, coated, thermionic complexes, synthesis of, a 158 emission from, a 79 C,H,, oxidation of, a 153 evolution and dissolution of Oaat, a 34 films, hydrogenolysis and wire, formation and reduction of O,, on, a 1 15 isomerisation on, a 117 Osmium, coated, thermionic emission from, a 79 hydrogenation of benzyl alcohol on, a 76 Palladium-Gold, pretreatment of, a 154 hydrogenation of butyronitrile on, a 157 Platinum, adsorption and electro- hydrolysis of ally1 chlorides, [I 118 oxidation on, a 115 isomerisation on, a 37 black, area changes of, a 33 RhCOCl, (PPhs),, decarbonylation of cathodic protection by, a 39 acyl halides, a 39 coated, thermionic emission from, a 79 carbonylation of alkyl halides, a 39 electrolytic polishing of, a 153 RhCI,, dimerisation of alkenes, a 119 gauze, hydrogenation on, a 39 homogeneous and heterogeneous gauze, in 0,meter, a 116 catalysis by, a 38 ioiiisation of H, on, a 33 hydride transfer on, a 37 in fuel cells, a 78 reaction of dienes on, a 157 in measurement of soil aggressiveness, 154 RhCI(PPhs),, addition of D,, a 77 interaction of CO, with H on, a 73 decarbonylation of acyl halidcs, a 38 moveable, partially submerged, a 158 decarbonylation of +unsaturated platinised, catalytic activity of, a 153 aldehydes on, a 157 Raney, in fuel cells, a 78 hydrogenation of unsaturated aldehydes Raney, with Se and S, oxidation of on, a 119 HCOOH on, a 115 Rh-Cu, C,H,, oxidation of, a 153 Platinum-Gold, pretreatment of, a 154 Rh(OH), +Pd(OH),/C, non-pyrophoric, Platinum Metals, adsorption and electro- preparation of, a 116 oxidation on, a 115 Rh/Al,Os, deuteration of C2H,on, a 75 Pt/asbestos, in fuel cells, a 119 hydrogenation of C,H, on, a 38 Pt/Nb, anode, in electrolytic dissolver, a 119 Rh/BaSO1, hydrogenation of phenyl- Pt-02,cathodes, effect of HNO, on, a 33 acetylene on, a 38 Pt/Ti, anodes, in sea water 149 RhjC, hydrogen,ation of benzene -- corrosion of. a 115 polycarboxylic acids, a // critical evaluation, a 158 hydrogenation of phenol 86 durability of, a 115 Rh/FeCI,, synthesis of isocyanates, a 118 in sea return dc system 103 Rh/SiO?, hydrogenolyses of C,H, on, a 157 Pt-Teflon, separation of Oaby, a 154 Rh,O, in hydroformylation, a 119 Pt-Teflon-Ta, structural studies on, a 153 Rh-Pd. C,HI,oxidation of, on, a 153 Pt-plated Ni, mesh, in battery, a 158 Rh-Pt, activity of 155 Platinum-Rhodium, evolution and dissolution atomic susceptibility of, a 155 of H, at, a 34 deactivation of, a 155 Reversible 02,Pt surface of, a 33 C1H4,oxidation of, on, a 153 Rhodium, evo!ution and dissolution of O,, at a 34 gauze, for HNOJ,production 2, 100 Rh/Ti, corrosion of, a 115 hydrogenation of benzoic acid, a 155 Rhodium-Platinum, evolution and Rh-Pt/C, surface area and activity of, a 155 dissolution of H at, a 34 Ruthenium, comalexes, oxidation of Ruthenium-Platinum, adsorption and CgH40n,a . . 158 electrooxidation on, a 1 I5 C,H,, oxidation of, on, a 153 Silver-Palladium, cathode, hydrogenation

hydrogenation of butyronitrile, a 157 on 11 <,?Q thin film, electrodeposition of, a 157 Teflonrbonded Pt, a 78 RuCI?, decarbonylation of HCOOH, a 78 Tungsten, 0s-coated, in thcrmionic valves 15 hydrogenation of olefinic compound s. CI 78 RuCI,, complexes, oxidation of CzH,on, a 158 hydride transfer on, a 157 Gas Indicator, underground use of, a 34 RU(OH)~+ Pd(OH),/C, non-pyrophoric, Glass, Pt melting apparatus, 0,blisters on, u 79 preparation of, a I I6 preparation of, in Pt crucible, a 158 Ru/BaSO reduction ofp-chloronitro- benzene, a :; Hydrogen, absorption in Pd, a 71 Ru/C, hydrogenation of acetophenone on, a 157 absorption in Pd alloys, u 31 RujSiO,, hydrogenolysis ofC2H,on, a absorption in Pd-Au, a 151 Ru phthalocyaniue, activity of, a 158 detection of, in air, a 116 V,Oi,WOs/AlsOs, Pt-promoted, in Pd, internal friction of, a 72 oxidation on, a 156 Hydrogen Cyanide, production of, over Pt gauzes 67 Cathodic Protection, of drying cylinders, in paper-making, a 39 Hydrogen Diffusion, in Pd, rate of, a 31,78 platinised Ti anodes, in sea water in Pt, a 34 Hydrogenation, new laboratory technique, a 74 Coatings, Tr, in ion engines 147 Computers, memory stores Crystal Growth, sapphirc, a ;i Integrated Circuits, thick film 126 Ion Engines, Ir coatings in 147 Ionisation Detector, for H, in air, n De l’Isle, identity of 116 Deuterium, absorption in Pd-Au ,a i!f Iridium. afterheater lining of, a 74 anions, synthesis ofmetal-metal bonds via, a 73 coatings in ion engines 147 Electrical Contacts, Pd, deposits on 56 N, adsorption on, a 32 Electrodeposition of, Iridium 115 properties of, influence of purity on, a 70 Palladium, foils, a 74 vapour, electron and ion emission from, a 72

Platinum Metals Rev., 1967, 11, (4) 166 Page Palladium Alloys (Cod.) Page Iridium Alloys, Iridium-Aluminium, Palladium-Gadolinium, expansion crystal structure of, a 152 characteristics of, a 72 Iridium-Carhon, cutectic points of, a 112 Palladium-Gold, deformation of, a 112, 151 Iridium-Osmium, lattice parameters of, a 72 density of states and resistivity of, a 151 Iridium-Platinum, elastic properties of, a 33 electron diffraction study of, a 112 clectrodeposition of, a 115 Haand D,solubilityin, a 151 low-tcmperature specific heat of, a 70 ordering in, a 32, 71 Iridium-Rare Earths, Laves phases of, a 72 oxidation of CsH I on, a 118 Iridium-Rhenium, lattice parameters of, a 72 permeability for HP,a 31 Iridium-Rhodium, high-tempcrature resistivity and Hall effect of, a 151 bchaviour of 53 Palladium-Gold-Deuterium, neutron Iridium-Titanium, intermediate phases in, a 32 diffraction study of, a 112 Iridium-Vanadium, structure and constitution Palladium-Gold-Hydrogen, neutron of, a 152 diffraction study of, a 112 Iridium Complexes and Compounds, 73, 1 14, 152, 153, Palladium-Hydrogen, absorption of H,, a 71 154 internal friction in, a 72 mixing behaviour of, a 113 Johnson Matthey, 150th anniversary of 18 system 99 new refinery in S. Africa 131 Palladium-Iron, electronic structure and properties of 109 magnetic properties of, a 32, 113 Magnetic Device, for study of phase changes, N 1 16 thermoelectric power of, a 113 MAZDA, production from soybean oil, a 76 Palladium-Lead, H, absorption in, a 31 Palladium-Manganese, electronic structure Osmium,,anodic corrosion of, a 74 and properties of 109 coating of valve emitters 15 magnctic properties of, a 32 magnetic susceptibility of, a 152 thermoelectric power of, a 113 on Pt, electrochemistry of, a 154 Palladium-Nickel, electronic structure and Osmium Alloys, Osmium-Chromium, propertics of 109 nonstoichiometry of phases, a 31 Haabsorption in, a 31 Osmium-Iridium, lattice parameters of, n 72 permeability for H,, a 31 Osmium-Platinum, lattice parameters of, (2 72 Palladium-Nickel-Chromium,hrazing of Osmium-Rare Earths, Lavcs phases of, a 72 graphite to Mo by 140 Osmium-Titanium, intermediate phases in, a 32 Palladium-Phosphorus, structure of, a 32, 72 Osmium Complexes and Compounds 33,104 Palladium-Platinum, heat resistance of, a Osmium Heptafluoride, production and properties I50 of. a _.?? Palladium-Rhodium, H, absorption in, n 31 Osmium Tetrachloride, brown and black magnetic hehaviour of, a 71 speed of sound in, a forms of, n 153 31 Osmium Tetroxide, vapour, negative Palladium-Samarium, expansion staining with, a 34 characteristics of, a 72 Oxidation, by transition mctal complexes 93 Palladium-Silver, as temperature indicator, a 39 Oxygen Metcr, a 116 electrical resistance of, a 151 formation of, a 113 magnetic properties of, a 71 Pallahraze, use of, review, a 74 mixing behaviour of, a 113 Palladium, additions, sintering of W and permeability for Hp,a 31 W-Tho,, a 158 properties of, a 113 cementation of, on Cu, a 34 speed of sound in, a 31 characteristic temperature of, a 151 Palladium-Silver-Chromium, mcchan ical chromaticity coefficient and luminance of, a 70 properties of, a 151 contacts, deposits on 56 Palladium-Silvcr-Cobalt,mechanical diffusion of H, in, a 31, 78 elcctronic structure and properties of 109 properties of, a 151 Fermi surfacc of, a 112 Palladium-Silver-Hydrogen, electrical film, adsorption of CO on, a 112 resistance of, a 151 film, electrical resistance of, a 112 pressure-composition isotherm for, a 151 flake formation, reduction of, in steel, a 11 3 Palladium-Silver-Iron, mechanical foils, deposition and thickness of, a 74 properties of, a 151 grain boundaries, deposition of, a 112 Palladium-Tin, Hzabsorption in, u 31 heat resistance of, a 150 Palladium-Titanium, corrosion resistance of 50 heat ofsublimation of, a 151 Palladium-Tungsten, ordering in, a 32 mono- and diatomic cquilibrium in, a 71 Palladium-Vanadium, thermoclectrical optical properties of, a I12 power of, a 113 properties of, influence ofpurity on, a 70 Palladium-Ytterbium, expansion character- vapourisation of, a 151 wire, detection of H,, a I16 istics of, a 72 yield point of 94 Palladium-Zirconium, binary compounds Palladium Alloys, Palladium-Antimony, of, a 114 magnetic susceptibility of, a 32 Palladium Chloride, catalysis of nucleophilic thermodynamic properties of, n 72 reaction, a 37 Palladium-Cadmium, magnetic heating of, R 114 susceptibilityof, a 32 preparation of, a I14 thermodynamic proper tics of, a 72 structure and properties of Pd,CI,, 114 Palladium-Cerium, expansion Palladium Complexes and Compounds 72,73,114 characteristics of, a 72 Palladium Oxide, electrical conductivity, forma- Palladium-Chromium. thermoclectric power tion, Hail effcct of, 152 of, a 1 I3 Penicillins, conversion of, a 37 Palladium-Cohalt, electronic structure and Phase Changes, detection of, a 116 properties of 109 ordering in, a 32 Petroleum Reforming, automation of, a 154 thermoelectric power of, a 113 Platforming, mathematical description of, a 155 Palladium-Copper, deformation of, a 112, 15 1 Platinum, anodic corrosion of, a 74 formation of, a 113 apparatus for DTA 111 resistivity and Hall effect of, a 151 a paratus in glass industry, 0,reboil theory, a 79 structure and mechanical properties of, a 32 ctromaticity coefficient andluminance of, a 70

Platinum Metals Rev., 1967, 11, (4) 167 Platinum (Cuntd.) Page Rhodium-Alloys (Contd.) Page coils, dctection of phase changes with, a I 16 Rhodium-Iron, magnetic properties, a 32, 113, 152 crucible, prcparation of glass, a 158 phase transformations of, a 113 depleted zones in, a 31 structure of. a 152 dispersed, absorption of gases on, a 115 triple point, a 113 economic history of 18 Rhodium-Mercury, crystal structure of, a 114 electrical resistance of, a 70, 120 Rhodium-Nickel, magnetic susceptibility and expansion of production 9, 131 specific heat of, a 152 field ion microscopy, a 31 Rhodium-Palladium, magnetic behavionr of, a 7 I filament, in gas indicator, a 34 Rhodium-Platinum. heat resistance of. a 150 foils, deposition and thickness of, a 74 thermal conductivity of, a 150 for brazing, a 74 wire, hemispherical emittance of, a 39 heat resistance of, a I50 Rhodium-Selenium, phases of, a 114 oxidation kinetics of, a I50 Rhodium-Titanium, intermediate phases in, a 32 oxide-dispersion strengthened, a 112 Rhodium-Zirconium, binary compounds of, a 114 permeability for H2,a 34 Rhodium Chloride, hydride transfer on, a 37 properties of, influence of purity on, a 10 thermal conversion of, a 33 resistivity of, below 20"K, a 150 Rhodium Complexes, H-metal bond in 58 sheet, structure of, a 70 x-crotylrhodium(lI1)-C IH*, a 119 structure, electron diffraction study of, (I 150 reactions of. a I58 surface free energy, variation of, a 70 synthesis of, a 158 surface self-diffusion, a 150 (PFhdaRh(l), a 153 thermal conductivity of, a 70, 150 with C.H,. structure of. a 114 wire, in computer memory stores 92 with orgacometallic compounds, a 153 Platinum Alloys, Platinum-Carbon, eutectic Rhodium Porphyrins, synthesis and chemistry of, a 1 14 points of, a 112 Platinum-Chromium. nonstoichiometrv of Rustenburg Platinum Mines, production phases of, a 31 expanded at 9, 131 Platinum-Cobalt, magnetic properties of 71, 129 Ruthcnium. anodic corrosion of, a 74 Platinum-Comer. formation of. a 113 elastic properties of, a 33 magnetk'susceptibility of, a 32 oxide glaze resistors 126 oxidation in air, a 150 thermal conductivity and electrical thermodynamic properties of, a 12 resistivity, a 70 Platinum-Gold, deformation and fracture Ruthenium Alloys, Ruthenium-Rare Earths, of, a 150 Laves phases of, a 72 low-temperature specific heat of, a 70 Ruthenium-Zirconium, binary compounds Platinum-Iridium, elastic properties of, a 33 of, a 1 14 low-temperature specific heat of, a 70 Ruthenium Boron Trifluoride, structure of. (I 33 Platinum-Iron, activity of 0%in, a 31 Ruthenium Compounds, chlororuthenates, a 78 Platinum-Manganese, magnetic properties of, a 71 dodecacarbonylruthenium, reactivity of, a 73 Platinum-Molybdenum, intermediate phases 132 reaction with H,SO,, a 13 Platinum-Niobium-Uranium, phasc change RuBiSe. synthesis of, a 33 in a 112 Ruthenium Dioxide, glaze resistors 126 Platinum-Osmium, lattice parameters of, a 72 Ruthenium Sulpbate, grecn, a 73 Platinum-Palladium, heat resistance of, a 150 Ruthenium Trichloride, structure of, a 33 Platinum-Rare Earth, preparation and structure of. a 71 Ruthenium Triiodide, structure of, a 33 Laves phases of, a 72 Ruthenocene Polymers, preparation of, a 33 Platinum-Rhenium, gauzes, a 116 lattice parameters of, a 72 Platinum-Rhodium, heat rcsistancc of, a 150 Screen Printing, preparations, RuO for 126 thermal conductivity of, a 150 Sound, speed of, in Pd alloys a 31 wire, hemispherical cmittancc of, a 19 Spacecraft, stabilising of, a 31 Platinum-Silver, formation ot, a I 13 Strain Gauges, Pt-W, foil-type 55 Platinum-Tungsten, strain gauges, foil-type 55 Platinum Chloride, Pt,CI structure and propel ties of, a 114 Temperature Measurement, fifty years of, a 39 Platinum complexes 114,153 hemispherical emittance of coaled wires, a 39 Pt elcctrical resistivity below 11"K, a 120 Platinum Dioxide, formation of, in HNO, plants, a 154 Ag-Pd wire for, a 39 Platinum Metals, alloys, structure of 138 carbonyl halide complexes 148 Thermionic Valves, 0s-coated W emitter in 15 in fuel cells 12, 130 Thermocouples, Noble Metal, physical properties a 79 thermal conductivity and clectrical Platinum Metal, survey of, a 79 resistivity, a 70 P1atinum:Gold-Palladium, physical properties of, a 19 Platinum Oxygen Complexes, with PPh ?, a 72 Platinum :Platinum-Palladium-(iold, Power Sourees, 5th Int Symp. 12 physical properties of, a 79 Platinum-Platinum-Cobalt, physical ResistanceThermometers, Pt, calibration of, a I59 properties of, a 79 Pt, electrical resistivity below 11 "K, a 120 Platinum-Platinum-Copper, physical properties of, (I 79 Pt, in accurate temperature measurement, n 120 Platinum: Platinum-Iridium. ohvsical II ~ Resistors, RuO glaze 126 properties of, a 79 Rhodium, chlorination of, a 33 Platinum :Platinum-Molybdenum, physical chromaticity coefficient and luminance of, a 70 propcrtics of, a 79 dispcrsed, adsorption of gases on, a 115 Platinum: Platinum-Osmium, ..physical foils, deposition and thickness of, a 14 properties of, a 79 heat of sublimation of, a 151 Platinum :Platinum-Rhenium. ohvsical I. ~ Npadsorption on, a 32 properties of a 79 properties of, influence of purity on, a 70 Platinum :Platinum-Tungsten, physical synthesis of metal-metal bonds, a 73 properties of, a 79 vaporisation of, a 151 P1atinum:Rhodium-Platinum, for research Rhodium Alloys, Rhodium-Aluminium, crystal and industry, a 159 structure of, a 152 physical properties of, a 79 Rhodium-Hafnium, superconductivity of, a 72 Rhodium-Platinum :Rhodium-Platinum, Rhodium-Iridium, high temperature rcfcrencc table for "six-thirty" 10 behaviour of 53 selection of sheaths for 49

Platinum Metals Rev., 1967, 11, (4) 168