PLATINUM METALS REVIEW

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

VOL. 19 OCTOBER 1975 NO. 4

Contents

Small Particles of the Platinum Metals

The Oxidation of the Platinum Metals

Lead Poisoning of Automobile Emission Control Catalysts

Palladium Flakes for Hydrogen Solid Storage Applications

High Tensile Strength Thick-Film Silver-Palladium Metallisations

Advances in Platinum-Silver Thick-Film Conductors

A Platinum Bowl by Janety

The Melting of Iridium

Abstracts

New Patents

Index to Volume 19

Communications should be addrmsed to The Editor, Pkrtinum Met& R&w Johnson Matthey & Co Limited, Hatton Garden, London ECl N 8EE Small Particles of the Platinum Metals THEIR PREPARATION, CHARACTERISATION AND USE IN CATALYSIS By Geoffrey C. Bond School of Chemistry, Brunel University, Uxbridge, Middlesex

The economic use of noble metals as catalysts usually requires them to be in the form of extremely small particles, typically less than 100 A in sire. This article reviews methods for the preparation and characterisation of such particles, and their importance in catalysis. For certain limited classes of reaction, activity per unit of surface area is itself a function of particle size; possible bases for explaining this effect are discussed.

When using noble metals as catalysts, it is area on particle size. We do this by a simple naturally desirable to employ them in a form model in which we consider I g of metal in such that the largest possible fraction of the the form of small spheres of uniform radius v; atoms are at the surface and hence available then using well-known formulae the surface to the reactants. This can only be achieved area and volume of a single sphere are readily by converting them into very small particles calculated as a function of r. Assuming the having a high surface to volume ratio. particles to have. the normal density of the Fortunately this can readily be done by the metal, the volume is converted into a mass, well-known techniques for preparing sup- and hence the number of particles per g of ported metal catalysts, which typically con- metal is derived. Using the relations tain metal particles between 10 and IOO A in n, =m/m, =mN/p size. Reasons for being able to make small where na is the number of atoms of mass m, particles in this way will be given later. There in a particle of mass myand N is Avogadro’s are two other methods which have been used constant and p the atomic mass relative to for preparing particles in this size range. lZC,the number of atoms in a single particle (i) It is quite easy to make colloidal can be calculated. Finally the total surface dispersions of metal particles, and area per g is obtained as the product of the these have some limited practical uses area of each individual particle and the num- as catalysts. ber present. (ii) Small particles can also be made by The results of calculations made for evaporation of metal atoms from heated palladium and platinum using this Uniform wires, and allowing them to condense Sphere Model are shown in Figs. I and 2. on a cold surface: the technique has The area per particle naturally increases as been used in fundamental catalytic the square of the diameter, and the number of studies (I). atoms per particle as its cube. The number of particles per g is therefore an inverse cubic Uniform Sphere Model relation, and the total area per g varies as the It is helpful to begin by establishing simple reciprocal of the diameter. Because quantitatively the dependence of surface of the nearly twofold difference in density

Platinum Metals Rev., 1975, 19, (4), 126-134 126 00 50C

30 400 ) 10P (%lo'')

167 0 (X .-. +

tPx x30C 30; METAL - w 1 5-d wIT /PARTICLE w 2 z /PARTICLE Ln 9 \ ATOMS PARTlCLES/g 9 20c 10 e AREA IT a OF OF 4 ’” W 9 SURFACE NUMBER NUMBER 3 A o

0 1 oc ?O

20 40 60 80 1C PARTICLE DIAMETER (i) PARTICLE DIAMETER A1 Fig. 2 The surface area per gram of metal Fig. 1 The number of particles per gram of metal, the number of atoms per particle and and the degree of dispersion as a function of ihe surface area per particle as a function of particle diameter according to the Ungorm particle diameter according to the Uniform Sphere Model Sphere Model

and in atomic mass between the two metals, sometimes used is the percentage of atoms palladium particles of a given size are much present on the surface: this is termed the lighter than platinum particles of the same degree of dispersion D, and its dependence on size; I g of palladium therefore produces particle size is shown in Fig. 2. To estimate almost twice as many particles of a given size the number of atoms at the surface of a as does platinum, with a consequently particle, it is necessary to assume what area a greater surface area. Such calculations are single atom would occupy. We suppose that useful in a semiquantitative way, but they the whole surface comprises the closely- make no assumptions concerning crystal packed (111) plane, in which the area of a geometry and therefore lose significance for single platinum atom would be 6.55 Az. extremely small particles. It is also of course Since the atomic radii of palladium and quite unrealistic to suppose that in real cata- platinum are very similar, the dependence of lysts all the particles would have the same dispersion on size is almost exactly the same size; to assume that they are approximately for the two metals. The relevant relations are spherical may be more reasonable. D =ns/na=a/na x 6.55 Another measure of the effectiveness of where n, is the number of atoms at the surface subdividing metal into small particles which is of a particle of surface area a.

Platinum Metals Rev., 1975, 19, (4), 127 a b Fig. 3 Diagramnzatic representation of the formation of platinum particles in preparing a I%/SiO, catalyst (a) Pores of various sizes Jilled with H2PtCl, solution (b) Crystallites oj IIzPtCl, after drying, and also platinum particles after reduction, in those pores

Preparation of Small Metal Fig. 3. In such systems the average metal Particles particle size can be altered by changing the As noted above, conventional methods for pore characteristics, by changing the metal making supported metal catalysts frequently Ioading and by sintering. lead to metal particles smaller than about When a reactive support is used in con- IOO A in size (2). We may distinguish be- junction with a suitable metal-containing tween two different ways in which they can species (e.g. activated carbon and PdCl;), a arise. When the support is quite unreactive chemical reaction takes place whose nature is towards the metal compound employed (e.g. poorly understood but is probably a kind of silica gel and chloroplatinic acid), impreg- hydrolysis. Small particles of metal are nation of the support with a solution of the obtained on reduction (4) because the exist- metal compound, followed by drying, gives ence of a large number of reactive centres on microcrystals of the compound in each the support, acting as nuclei, and the limited physically separate pore. The size of these amount of metal-containing species available, microcrystals will thus depend on the volume means that each nucleus cannot grow to be of the pore in which they are formed on large. Chemical pretreatment of the support, evaporation of water during drying, and on as well as the concentration of the solution the concentration of the solution used. Thus used, can thus affect average particle size. with an amorphous support such as silica gel, Ion exchange procedures also lead to highly the presence of a wide distribution of pore dispersed metals (3, 5). sizes naturally leads to a wide distribution of A similar principle applies to the prepara- metal particle sizes on reduction of the tion of metal sols containing very small microcrystals of the metal compound (3). particles. Success depends on forming a large The effect is illustrated schematically in number of nuclei in the nucleation phase, and

Platinum Metals Rev., 1975, 19, (4), 128 subsequently allowing these to grow in the presence of a limited supply of metal salt. Colloidal platinum having an avcrage size of about 20 A (Fig. 4) is readily prepared by reduction of a dilute solution of chloroplatinic acid with sodium citrate at 100°C (6). Colloidal palladium has also been made and deposited on boehmite (AlO(0H)) filaments for catalytic use (7). There is much interest in the preparation of extremely small metal particles, where it is more meaningful to speak in terms of a cluster of a relatively few atoms than of a particle size. Thus the careful reduction of Fig. 4 Electron micrograph of colloidal platinurn the chloroplatinate ion confined within a prepared by reduction of I12PtC1, solution with sodium citrate (6). I mrn=50 A zeolite cage gives platinum clusters con- taining only about six atoms: they have high catalytic activity more reminiscent of iridium than of platinum, and hence are thought to be X-ray methods are also widely used, but the electron-deficient (8). Another approach line broadening method is limited in scope which is receiving attention is the use of since particles smaller than 40 to 50 A are polynuclear metal carbonyls for the prepara- essentially amorphous to X-rays. Small-angle tion of catalysts (9). scattering of X-rays is a more promising technique, but the apparatus is costly and not yet widely available (I I), Characterisation The selective chemisorption method has A number of experimental methods are also been widely practised (8). Its success available to give an estimate of the average depends, in the case of a supported metal size of small metal particles (IO), but com- catalyst, on being able to remove pre-adsorbed paratively few give information on the size gases, especially oxygen, from the surface of distribution. By far the best and most direct the metal particles without causing sintering, method is transmission electron microscopy, and then treating a gas whose molecules since this is the only technique to yield the chemisorb selectively on the metal but not on images of the particles in a visible form (2). the support. Measuring of the monolayer The method, which is fairly simple, involves volume, and assuming what number of dispersing a supported metal catalyst in a surface atoms each adsorbed molecule covers, thermosetting resin, and then cutting with a allows an estimate of surface area and hence microtome to give slices of about 1000 A of average particle size. Hydrogen, oxygen thickness. Metal colloids may be examined and carbon monoxide have been successfully just by allowing a drop to evaporate on to a used. Unlike the physical methods men- film of suitable material placed on the grid tioned above, this chemical method becomes which goes into the sample holder. To obtain increasingly sensitive with decrease in particle clear images of very small particles is not size, but residual uncertainty concerning the easy: good voltage stability and minimal stoichiometry of the chemisorption especially instrumental vibration are required. In for very small particles is an undoubted principle a size distribution is obtained by limitation. However, as Fig. 5 shows, careful measuring a statistically significant number of work can yield surprisingly good agreement particles (2, 3). between results given by chemical and

Platinum Metals Rev., 1975, 19, (4), 129 has been undertaken in recent years to look for specific particle size effects. All catalysts and all reactions need not behave in the same

r way, and Fig. 6 illustrates a number of sO 200- possible ways in which specific activity might E vary with particle size. The predicted basis Q for such effects is to be found in a careful L 150. examination of the surface topography of Q

-I minute particles having one of the crystal w2 habits appropriate to the face-centred cubic I100 structure in which palladium and platinum crystallise (19). Let us consider first a small

I octahedron (Fig. 7): the surface atoms are of 1 2 3 4 PLATINUM CONTENT PER CENT three quite distinct kinds, viz. corner atoms having four near neighbours (CJ, edge atoms Fig. 5 Comparison of measurements of with seven (C,) and atoms within the (111) platinum surface area made by different methods on Pt/AE,O, catalysts having planes having nine near neighbours (C9). It is various platinum contents (11) evident that the fraction of surface atoms 0 H, chemisorption being at corners will decline rapidly as the size A Low-angle X-ray scattering of the octahedron is increased, since the + Electron microscopy 0 CO chemisorption number of corner atoms (six) does not change. Similarly the fraction of edge atoms on the surface decreases with increasing size, but physical methods, especially when the metal content is relatively large (I I). Consideration is also being given to gas titration methods. The first to be developed I was the hydrogen-oxygen titration (12, 13, 14): the reaction monitored is basically: *0 +3/2 H,-tH@ +H* which gives a “magnification factor” of three compared with hydrogen chemisorption, but there has been much debate (15, 16) on the O/H ratio per site and on its variation with particle size. More recently adsorbed oxygen has been titrated with carbon monoxide (17), and adsorbed hydrogen with an olefin (IS), the latter yielding added information on the time-dependence of the process. PARTICLE SIZE - Specific Particle Size Effects : Fig. 6 Possible forms of specijc particle Topographical Basis size effect It has long been thought likely that catalytic 1 :structure-insensitive reaction 2 and 3: structure sensitive reactions activity expressed per unit surface area 4 and 5: the sense of the structure sensitivity (termed the speciJic activity) might itself be is itself a function of particle size dependent on particle size, and much work

Platinum Metals Rev., 1975, 19, (4), 130 Fig. 7 A face-centred cubic octahedron containing 44 atoms: the coordination numbers of apical, edge andplane atoms are Fig. 8 A regular face-centred cubic cubo-octahedron indicated containing 38 atoms

Much em- less rapidly; and the proportion of atoms with surface of perfect crystallites. phasis has been laid on two particular kinds the (111) planes increases. One only has to of site comprising five atoms and occurring at ascribe different catalytic properties to each steps on (100)and planes respectively; kind of surface atom to have a basis for specific (111) they have been strongly indicated as the sites particle size effects. for strong physical adsorption Several groups of workers have calculated of nitrogen the proportion of surface atoms having a given (24). B, sitcs at steps on a (110) plane are shown in close-up in Fig. Somorjai (25) coordination number C, as a function of 11. has also produced a great deal of clear particle size for regular crystals of various experimental evidence for the extraordinary geometries (octahedra, cubo-octahedra (see activity of atoms at steps on single crystal Fig. 8), tetrahedra, etc.) (20-23): the results surfaces. Now the maximum surface density for fcc octahedra, shown in Fig. 9, take the expected form. The range of particle size from 8 to 40 A has been termed the rnitohedri- cal region (23) for it is in this range that the

proportions of atoms having low coordination R HAVING

number changes most rapidly with particle BE

size. It is, however, quite improbable that a NUM ATOMS real catalyst particle will contain exactly the N- I0 number of atoms required for a regular T A

crystallite of any geometry; the average real N SURFACE particle will doubtless possess an incomplete DI OF

outer shell of atoms. Fig. 10 illustrates a COOR

cubo-octahedron with an incomplete outer N layer. Under these circumstances, atoms FRACTION GIVE having coordination numbers other than those PARTICLE DIAMETER ( A) found in the perfect body will exist, and Fig.Fig. 9 9 DependenceDependence ofof the the fraction fraction of of surfacesurface moreover special groupings of atoms or sites atomsatoms inin regular regular face-centred face-centred cubic cubic octahedra octahedra hawing co-ordination nuders of 4, 7 and 9 will occur which are not to be found at the

Platinum Metals Rev., 1975, 19, (4), 131 show the symmetry expected from the bulk structure. Calculations have indicated that particles based on fivefold symmetry (icosahedra) are more stable than other forms, and indeed such forms have been observed. There is nothing inherently improbable in this notion, for five-coordinate complexes of the platinum metals are certainly known. It seems likely that fivefold symmetry particles are most easily formed under conditions of supersaturation, for example, in the hot wire evaporation method, and do not necessarily arise in the preparation of supported catalysts. Clusters of five rhodium atoms on silica have however been directly observed by electron microscopy Fig. 10 An incomplete face-centred cubic cubo- (28). octahedron showing B, sites at the junctions of (110) and (111) planes (courtesy of Dutch State Physical Properties Mines) Since in very small particles a large fraction of B, sites arises just before each outer layer of the atoms are superficial and hence lack of atoms is completed (see Fig. 10). Calcula- their proper complement of neighbours, it is tions on incomplete cubo-octahedra (22, 24) reasonable to expect measurable differences in having maximal numbers of B5 sites, and of physical properties from those of the bulk various sizes, have shown that the proportion solid. There is both theoretical and experi- of surface atoms comprising B, sites passes mental evidence to show that melting point through a maximum when the particle size falls as particle size decreases, and a 10 A is between 20 and 25 A, that is, in the middle particle may have a melting point of only half of the mitohedrical region. Thus it is still that of the bulk metal (27). Surface atoms possible to have a basis for specific particle size are also calculated to have a much larger effects evenwith real (i,e.incomplete) particles. vibrational amplitude than sub-surface atoms, It has recently been claimed (26, 27) that notwithstanding the fact that interatomic very small metal particles may not necessarily distances are shorter in the surface, by about

Fig. 11 B, sites at a step on u (110) surface: the atoms forming the nearest B, site are marked

Platinum Metals Rev., 1975, 19, (4), I32 3 per cent for a 10 A particle. Surface pre- - 20, I melting may also occur, and the molten surface skin on quenching may afford an FOR amorphous outer layer. Such has indeed been observed recently for supported platinum ACTIVITY

particles examined by the radial electron HYDROGENOLYSIS distribution technique (29). Specific particle size effects may therefore well have an SPECIFIC energetic as well as a topographical basis. ETHANE Spec& Particle Size Effects: Fig. 12 Specijic activity of RhlSiO, Experimental Evidence catalysts for ethane hydrogenolysis as a To obtain accurate experimental evidence function of average particle size (32). Specijic activity is expressed as millimoles on the existence or otherwise of a dependence h-l per m2 of rhodium surface at 253°C. of specific activity on particle size is a matter The solid point is for unsupported rhodium of great difficulty, a major stumbling block powder whose averageparticle size is 2560 A being that supported metal catalysts normally contain a wide distribution of particle sizes. Furthermore it may be necessary to go to sizes larger with increasing particle size (33). This below 20 A to reveal the existence of such may however be associated with changes in effects, and this has not always been done. the chemisorption strength or stoichiometry To facilitate further discussion, it is desirable with changing particle size. The exchange of to introduce Boudart’s terminology (30) : a benzene with deuterium over iridium catalysts system exhibiting no dependence of specific is also depcndent on particle size (22). activity on particle size is termed structure- insensitive (line I in Fig. 6); one exhibiting a Fundamental Calculations on dependence in either sense (curves 2 and 3 of Metal Clusters Fig. 6) is referred to as structure-sensitive. Apart from the practical importance of It is possible to summarise a large body of using the platinum metals in a highly dis- experimental work by saying that surprisingly persed state, and of knowing whether or not a few systems show structure sensitivity (30); particular system is structure-sensitive so that the reason for this is not at the moment clear. particle size can be optimised for the envisaged One general class of reactions does however application, there is lively current interest frequently reveal structure sensitivity, this in this field because it is now possible to carry being where carbon-carbon single bonds are out fundamental quantum-mechanical cal- broken in the presence of hydrogen, viz. culations on small clusters of metal atoms. hydrogenolysis or skeletal isomerisation. This is an advance of great potential sig- Specific activity usually increases with de- nificance, as for the first time it may prove creasing size (31)~but the results obtained (32) possible to relate catalytic behaviour to basic for the hydrogenolysis of ethane over rhodium electronic characteristics of the solid. Ex- catalysts is of particular interest in that a tended Huckel calculations on clusters of up maximum specific activity was observed for to 55 atoms of palladium, silver, gold and particles of about 10 to 20 A in size, thus palladium-silver have been reported (34), replicating the form of curve 5 in Fig. 6 (see and the use of the self-consistent field Xcc Fig. 12). It has also been shown recently method for eight-atom clusters of nickel and that the oxidation of ammonia on supported copper have also been described (35). Rapid platinum catalysts shows structure sensitivity and useful developments in this area are in the sense of specific activity becoming confidently to be expected.

Platinum Metals Rev., 1975, 19, (4), 133 Conclusion for demanding reactions. It needs to be The absence of widespread structure- emphasized that the methods currently used sensitivity for many systems of practical for catalyst preparation are still relatively importance is in fact a great blessing to the crude, and the performance of resulting practitioner of catalysis, for it means that catalysts still somewhat uncertain. We have apart from simply maximising surface area much to learn from enzymes, whose specific there are no other factors to worry about in activity and selectivity are vastly greater. connection with particle size control. At the If catalysis is to fulfd the hopes which are same time, the number of systems as yet being placed on it, we must strive more investigated thoroughly is quite small, and effectively to emulate nature. further work may reveal more examples of Future advances will depend much on structure-sensitivity : their advent would per- our ability to prepare catalysts having much mit not only more rapid progress to be made narrower particle size distributions than have in our understanding of heterogeneous hitherto been available: their advent would catalysis, but also the manufacture of cata- enable rapid progress to be made in our lysts optimised with respect to particle size understanding of catalysis.

References I J. R. Anderson and Y. Shimoyama, Proc. 5th 17 P. Wentrcek, K. Kimoto and H. Wise, Internat. Congr. Catalysis, ed. J. W. J. Catalysis, 1974,34, 132 Hightower, North Holland, 1973, I, 695 18 G. C. Bond and P. A. Sermon, Reaction 2 R. L. Moss, Platinum Metals Rev., 1967, 11, Kinetics and Catalysis Letters, 1974, I, 3 141 19 W. Romanowski, Surf. Sci., 1969, 18, 373 3 T. A. Darling and R. L. MOSS, J- catalysis, 20 G. C. Bond, Proc. 4th Internat. Congr. 1967, 7, 378; T. A. €3. w.J. LPch Catalysis, Akademiai KiadB, Budapest, 1971, and R. L. Moss,J. Catalysis, 1971, 20, Kg0 2,266 4 D. Pope, W. L. Smith, M. J. Eastlake and 21 E. G. Schlosser, Proc. 4th Internat. Congr. R. L. Moss,J. Catalysis, I971,22, 72 Catalysis, Akademiai KiadB, Budapest, 1971, 5 D. L. Hanson, J. R. Katzer, B. C. Gates, 2, 312 G. c. A. Schuit and H. F- Harnsberger, zz R. van Hardeveld and F. Hartog, Swf. Sci., J. Catalysis, 1974, 32, 204; H. A. Benesi, 1969,15, 189; Adv. Catalysis, 1972,22,75 R. M. Curtis and H. p. Studer, J. catalysis, 23 0. M. poltorak and v. s. ~~~~~i~,Boronin R~~.J. 1968, 10, 328 Phys. Chem., 1966,40, 1436 6 6G. G* C. c* Bond,Bond, Trans.Trans. Faraday Farday Soc., 1956,I9S6J 52, S2J 24 R. van Hardeveld and A. van Montfoort, I2351235 Surf. Sci., 1966, 4, 396 7 Turkevich and GWan Kim, 7 J.J. Turkevich and G\nm Kim, Science, 1970,'97OJ 25 G. A. Somorjai, Cata&sis Reviews, 1973, 7, 169,169,873 873 9rr 8 R. A. Dalla Betta and M. Boudart, Proc. 5th "I Internat. Congr. Catalysis, ed. J. W. 26 Y. Fukano and C. M. Wayman, J. Appl. Hightower, North Holland, 1973, I329 Physics, 1969, 40, 1656 2, 27 J. J. Burton, Catalysis Reviews, 1974,4,209 9 J. R. Anderson and D. E. Mainwaring, J. Catalysis, 1974, 35, 162 28 E. B. Prestridge and D. J. C. Yates, Nature, 10 T. E. Whyte, Catalysis Rev., 1974, 8, 117; 1971,134,345 A. D. O'Cmneide and J. K. A. Clarke, 29 P. Ratnasamy, A. J. Leonard, L. Rodrique Catalysis Rev., 1973, 7,214 and J. J. Fripiat,J. Catalysis, 1973,29,374 11 A. Renouprez, C. Hoang-Van and P. A. 30 M. Boudart, A. Aldag, J. E. Benson, N. A. Compagnon, J. Catalysis, 1974, 34,411 Dougharty and C. G. Hawkins, J. Catalysis, 12 J. E. Benson and M. Boudart,J. Catalysis, 1966, 6, 92 Ig65, 4J 7'4 31 J. H. Sinfelt, Catalysis Reviews, 1970, 3, 175 13 J. E. Benson, H. S. Hwang and M. Boudart, 32 D. J. C. Yates and J. H. Sinfelt,J. Catalysis, J. Catalysis, 1973, 30, 146 19671 8,348 14 J. M. Basset, A. Theolier, M. Primer and 33 J. J. Ostermaier, J. R. Katzer and W. H. M. Prettre, Proc. 5th Internat. Congr. Manope, J. Catalysis, 1974, 33, 457; R. J. Catalysis, ed. J. W. Hightower, North Holland, Pusateri, J. R. Katzer and W. H. Manogue, I973,% 91.5 AlChE Journal, 1974, 20,219 15 D. E. Meares and R, C. Hansford,J. Catalysis, 34 R. C. Baetzold and R. E. Mack,J, Chem. Phys., I967,9, 125 I975 62,1513 16 G. R. Wilson and W. K. Hall, J. Catalysis, 35 J. C. Slater and K. H. Johnson, Physics Today, 1970~17~190; 1972,249 306 19743 27, 34

Platinum Metals Rev., 1975, 19, (4), 134 The Oxidation of the Platinum Metals

A DESCRIPTIVE SURVEY OF THE REACTIONS INVOLVED

By J. C. Chaston Johnson Matthey & Co Limited

journal a little over ten years ago (I). Not a On gentle heating in air or in oxygen great many observations have been recorded all six of the platinum metals develop since then, but in the intervening years some thin tarnish films, visible or invisible, of the uncertainties in the original papers on their surfaces. On exceeding in- have been clarified. The present paper is an dividual critical temperatures these attempt to give a unified account of the jlms disappear, exposing clean metal, reactions involved. the change having the characteristics When platinum is heated in air or oxygen of a low-energy phase transformation. up to a temperature at which it glows with a The mechanisms involued are examined dull-red colour it, like gold, undergoes no in this survey and their effects on the visible change, The alchemists would have stability, strength and surface reactivity said that it remains noble. Nevertheless, it is of the platinum metals and their alloys not difficult to show that a very thin film of are discussed. transparent solid oxide can form on its surface-probably having the composition Pt0,-and that this thickens as the temper- It is little short of a hundred years ago that ature is raised. Thomas Alva Edison first reported (in 1879) The chief evidence for the existence of this that heated platinum wires lost weight many film derives from electrochemical observa- times more rapidly in air than in vacuum. tions. The film, which can be thickened by Ever inventive, he suggested that the effect anodic oxidation in many electrolytes, can be was the result of “air washing” by convected stripped in a solution of hydrochloric acid currents of air which mechanically carried and sodium chloride and its composition away particles from the soft glowing surface. determined. Moreover, the existence of this Today it is well established that the higher film makes possible the dissolution in the losses in air are bound up with the formation same electrolyte of electrodes of platinum of an oxide of platinum which is very much and many of its alloys by the application of an more volatile than is the metal at high alternating potential. During one half- temperatures. The mechanisms involved in cycle an oxide film is formed on the surface by the reaction are, however, complex and nascent oxygen; during the other half-cycle continue to be a fascinating and sometjFs a the oxide is dissolved. rewarding study for the user of platinum. When polished specimens of palladium, The experimental data available on the iridium, rhodium or ruthenium are similarly oxidation behaviour of platinum and the other heated the solid oxide films form dark platinum group metals were reviewed by brown or black colorations on the surface, the present writer in three articles in this like the temper colours on iron. The oxide

Platinum Metals Rev., 1975, 19, (4), 135-140 135 Heavy crystalline deposits of platinum on the hotter surfaces of a refractory brick that had seen long service in a position close to the rhodium-platinum heating elements of a furnace

coatings are still very thin and adherent and of this change. Sometimes the solid oxide once formed have every appearance of being film is said to evaporate; at other times it is protective in character against continuing said to dissociate. Many find it difficult to growth on long heating. reconcile thermal dissociation of a solid It may thus be said that the behaviour of oxide with the increase in affinity between some of the platinum metals on heating in air platinum and oxygen which is known to take or oxygen to temperatures of around 400 to place as the temperature is raised. 500°C is not so very different in kind from This mental block may perhaps be removed that of certain of the base metals. simply by considering that within the critical At higher temperatures, however, the temperature range the oxide experiences a difference is dramatic. For each of the phase change-from PtO, solid direct to platinum metals there is a critical temperature PtO, gas. or range of temperatures above which the In addition, it is necessary to appreciate oxide film, instead of continuing to thicken, that at atmospheric pressures the increase in completely disappears; and if the metal is energy involved in this solid-gas phase then quenched rapidly it is seen to be bright change is extremely small; so that the partial and oxide-free. The exact temperatures of vapour pressure of the PtO, gas formed is also the transformations are difficult to determine very low. Thus there will be little driving and exact values have yet to be established. force available to disperse the newly-liberated In the literature there are signs of much gaseous molecules throughout the surround- confusion of thought in describing the nature ing oxygen.

Platinum Metals Rev., 1975, 19, (4), 136 The consequences of the phase change will must appear paradoxical that a molecule of depend on the freedom of the newly formed PtO, formed at the hot Pt surface should be molecules of PtO, gas to escape from the decomposed on its return. It would appear vicinity of the metal surface. If the original more acceptable to consider that returning film of solid oxide is very thin and the heating molecules, projected into the saturated region rate through the transformation slow, the of the boundary layer, produce such a state partial vapour pressure of the gas may be of supersaturation that the excess molecules sufficient to disperse the molecules through- are forced to deposit their platinum. It out a quiescent surrounding atmosphere of follows from this that it is not necessarily the oxygen. In a turbulent atmosphere, greater returning molecule that is decomposed; it may amounts would be swept away. In these very well be another which is already close conditions the effect is as if the solid oxide had to the hot wire. As the temperature is raised evaporated. above the critical point, reaction becomes If the oxide films are thicker, and molecules more vigorous, larger quantities of PtO, gas of PtO, may be unable to disperse, then the will be formed, and its equilibrium partial partial vapour pressure of PtO, gas above the vapour pressure will increase, and provide surface will exceed the equilibrium value. an increased driving force for dispersion of The layer will be super-saturated in PtO, gas. the gas molecules. Evaporation will eventually Since PtO, solid cannot exist above the replace decomposition. critical temperature, the only way in which Now consider what happens if the current equilibrium can be restored is for some through an electrically heated platinum wire platinum metal to be deposited. The effect is reduced. As the temperature falls, the gas in these conditions is as if the solid oxide had layer near the wire becomes immediately dissociated. supersaturated with PtO, gas; and as long as The mechanisms which govern the rate at the temperature of the wire or surrounding which the gaseous oxides form and diffuse refractories remains above about 40ocC, then away from an electrically heated wire or platinum metal will be deposited. On raising ribbon of platinum have been studied by the current again the small amount of de- several investigators. In particular George C. posited platinum on the wire will quickly be Freyburg, of NASA Lewis Research Center, oxidised and re-evaporated; but after repeated Cleveland, Ohio, has examined the losses of cycles of temperature platinum will generally weight of ribbons or wires of various sizes build up slowly on any cooler refractory and when heated by the passage of an electric will eventually form the familiar spangles with current in oxygen at pressures of 0.025 to 1000 well-defined crystal faces which are observed Torr (2). He has shown that the rate of in old platinum-wound furnaces. oxidation is determined by the rate of escape Fluctuations in temperature may thus be of oxide molecules through the boundary an important, if often unconsidered, cause of layer away from the platinum, and not by migration of platinum in such diverse diffusion of oxygen through the layer towards industrial applications as catalyst surfaces, hot the metal. crucibles and containers, and heating ele- In his discussion, Freyburg points that as ments. the pressure of oxygen increases the gaseous oxide molecules formed at the wire surface Rhodium suffer collisions at distances closer and closer Of the other platinum metals, rhodium to the ribbon and . . , “any oxide molecule most closely resembles platinum in its that is back-reflected is decomposed on the behaviour at high temperature. On platinum, hot ribbon; the platinum is redeposited on the the thin solid oxide film persists at tempera- platinum surface”. Stated in this way, it tures up to about 450°C in oxygen at a

Platinum Metals Rev., 1975, 19, (4), 137 pressure of I atmosphere (values ranging until a temperature of 1540 to 1580°C is from 280 to 750°C have been suggested in reached in I atmosphere of oxygen or about the literature), and perhaps up to rather lower 1405Oc in air. temperatures in atmospheric air. On rhodium, The formation of solid RuO, is, however, as was mentioned earlier, the oxide film only an intermediate stage in the oxidation of thickens sufficiently to be visible as a tarnish ruthenium metal. The weight-losses observed after heating. The transformation tempera- when ruthenium is heated are not the result ture is much higher than for platinum of volatisation of the solid oxide but of the and has been reported to be about 1030°C formation by its further oxidation of new in air and 1040°Cin oxygen at a pressure of volatile species. one atmosphere. For it appears that RuO, cannot itself Since the solid oxide remains the stable exist as a gaseous molecule. The coating of phase up to such a high temperature, a very solid RuO, therefore reacts with the sur- small amount of evaporation of Rho, can rounding oxygen and forms new gaseous occur below its transformation temperature. compounds-Ru04 in small quantities at Every solid, as Robert Boyle expressed it, temperatures up to about 72ooC,and RuO, at has its own “little atmosphere”; and al- higher temperatures. though “no man has yet tried whether gold It is significant that the reactivity of RuO, (or any other solid) may not in time lose its with oxygen is exceptionally high. Even at weight” at room temperature, when a solid 1000°C the vapour pressure of RuO, gas becomes white hot the losses com- mence to become measurable. 16‘ Thus at IOOO’Cthe partial vapour pressure of Rho, above a solid Rho, film in air is probably a little over IO-’ atm and only a little less than that of PtO, above platinum. Above the transformation temper- ature the partial vapour pressure probably suddenly increases; for it is lrnown that above about IIOO’Cit Aim is higher than that of PtO, and then increases with temperature at very

much the same rate or only very PRESSURE- slightly more rapidly.

Ruthenium and Osmium VAPOUR With the more reactive platinum

metals, ruthenium and osmium, PARTIAL their reactions with oxygen are more complicated. On heating ruthenium in air, a thin film of RuO, forms on the

surface and becomes visible as a lo’, 7~- , ~- ,A 1000 1160 1260 1300 1400 1500 1600 1700 brown coloration above about 400°C. TEMPERATURE ‘C It is the only solid oxide that exists Partial vapour pressures of some of the platinum in equilibrium with the metal and metal oxides in 1 atmosphere of oxygen with oxygen, and does not transform

Platinum Metals Rev., 1975, 19, (4), 138 formed from RuO, is about zoo times as up to about 1450°C and is probably the great as PtO, gas at the same temperature and controlling factor in determining the loss of at 1300T it is about 1000 times as great. weight of the metal when heated in air or Osmium is much more reactive. Even at oxygen. Reactions probably take place room temperatures it is covered with a layer between Pd vapour and oxygen at high of solid OsO, which reacts with the air to temperatures with the formation of PdO gas, form the poisonous OsO,. This has a but surprisingly little is known quantitatively remarkably high vapour pressure, so that about their mechanisms. finely divided osmium powder loses weight at a measurable rate. Oxidation of the Alloys Industrially, the oxidation of the pure Iridium platinum metals rhodium, ruthenium, osmium and even palladium at high temperatures is of Not a great deal of experimental evidence is little concern; it is the performance of their available on the exact mechanism of the generally rather dilute alloys with platinum oxidation of iridium. Like ruthenium, that needs to be considered. Typically, the iridium becomes covered with a layer of the industrial alIoys contain about go per cent of dioxide, but this seems to be a little less platinum and per cent of the second stable than RuO,. There are indications that 10 platinum metal. IrO, may start to decompose with formation The first question that arises concerns the of an oxygen-deficient non-stoichiometric structure and composition of the oxide layers compound at a temperature above about that form as the temperature is raised. Thcy 1050°C; and it transforms to IrO, at about are almost certainly solid solutions of the 1115'C under a pressure of oxygen of I oxides of the alloy components-double atmosphere or at about 10zo"C in air. oxides of the platinum metals involved. With The formation of IrO, may well involve rhodium-platinum alloys, the proportions of an appreciable energy change, since the platinum and rhodium in the double oxide partial vapour pressure of IrO, gas at the is probably about the same as in the alloy. temperature of its formation is remarkably With alloys of platinum with iridium, high-of the order of IO-~atm. It has for rhodium, or osmium the oxide films may long, indeed, been recognised that iridium contain more of the reactive alloying metal loses weight at a measurable rate when it is than is present in the underlying alloy, and heated in air to temperatures in excess of about thc composition may vary with temperature, II00"C. but little experimental work on this has been reported. Palladium The second question has to do with the At temperatures up to about 85ooC, transformation temperature of the alloy palladium is very similar to rhodium in its oxide film. The oxide film persists on the reactions with oxygen. A dark brown oxide surface of all these alloys to an appreciably film develops on its surface, and this vanishes higher temperature than on pure platinum, suddenly when the transition temperature is and transformation takes place, not at one exceeded. definite temperature, but over a temperature The vapour pressure of the PdO gas formed range. is relatively low, but at above about iooo0C a The answers to both these hitherto largely new factor calls for consideration-the neglected questions may well have a bearing vapour pressure of the metal palladium itself. on the behaviour of platinum and the The valuc of this increases with rise in tem- platinum alloys in catalytic oxidising reac- perature as fast as that of rhodium oxide gas tions, since they determine the nature of the

Platinum Metals Rev., 1975, 19, (4), 139 catalytic surface-whether it is bright metal When these alloys are first heated, selective or an oxide film; and if an oxide film, its volatilisation will start from the surface. The composition. extent and rate of the loss depends, as has At high temperatures at which the alloy been discussed earlier, on the ease by which surface is free from solid oxide coatings in the volatile oxides can escape from the hot air or oxygen there is, of course, a loss of surface, and in any given environment it weight due to the formation of volatile is reasonable to expect that it is largely a oxides. Rhodium-platinum alloys volatilise function of the partial vapour pressure of almost unchanged in composition at temper- the oxide. Furthermore, the partial pressures atures from about I 100' to 1800°C or higher. produced by each constituent are initially in Over this range of temperatures the partial the ratio of their atomic proportions in the vapour pressure of Rhoz is slightly higher alloy. than that of PtO,; but the difference is not As heating continues, however, the surface great and there is little experimental evidence will be depleted of the most volatile com- of any preferential loss of rhodium. The ponents and a diffusion gradient will be set up crystalline deposits on refractories close to within the alloy which will control the rhodium-platinum furnace windings are subsequent progress of evaporation. One usually very close indeed in composition to consequence of this outwards diffusion is the that of the heating elements. generation of vacancies which may lead to The behaviour of alloys of platinum with cracking and premature failure if the material the more readily oxidisable metals iridium, is under stress. ruthenium and osmium is, however, very The consequences of the selective oxidation different. As long ago as 1886 Le Chatelier of these alloys may well influence their observed that platinum thermocouples having behaviour as catalysts. The steady depletion as one leg a 10 per cent iridium-platinum of the surface in the alloying metal would be alloy were prone to change their calibration in expected to result in a drift in its selectivity or service at about 10oo"C and over, and activity; although in conditions of fluctuating attributed this to a loss of iridium from the temperature the effect may to some extent be alloy. His recommendation that rhodium- masked by selective re-deposition from the platinum alloys were to be preferred as being vapour phase. more stable in air at high temperatures has In this connection, it is of interest to been followed ever since. speculate on the possibility of using a com- At above about 1200°C the differences be- posite structure formed from a platinum- tween the partial vapour pressures in air of clad core of iridium, ruthenium or osmium. the oxides IrO,, RuO, and OsO, amount to In operation, a diffusion gradient would be many orders of magnitude and the differences set up and by proper choice of platinum increase rapidly as the temperature is raised. thickness a steady state might be achieved, The table gives approximate values at 13oo0C the loss of alloy at the surface being balanced and 1500°C. by material diffusing outwards from the core. Thus, at constant working temperatures, it might be possible to provide an oxide-free surface of constant composition. Partial Vapour Pressures, atm. 1300°C 15000c 0.513000c x 10-5 References PtO2 I 1.8 x 10- 5 I J. C. Chaston, Platinum Metals Rev., 8, IrO, 110~10-5 130x10-5 1964, (21, 50-59; 1965,9, (2), 51-56, (41, 126-129 RuOs 500 x 10-5 4000 x 10-5 2 G. C. Freyburg, Trans. Met. SOC.A.I.M.E., , 1986-1989

Platinum Metals Rev., 1975, 19, (4), 140 Lead Poisoning of Automobile Emission Control Catalysts THE INFLUENCE OF EMISSION SYSTEM DESIGN

By B. J. Cooper Group Research Centre, Johnson Matthey & Co Limited

In a paper presented to the American Chemical Society Symposium on Auto Emission Catalysts, held in Chicago in August, an investigation was described in which it was shown that, by careful selection of the position of the catakst in the exhaust train and of the operating tempera- ture, deterioration due to lead poisoning can be minimised. This article summarises the jindings reported in the paper.

The installation of platinum catalysts in coupled with the engine tune (amount of an automobile’s exhaust train to control CO/HC being burnt over the catalyst) will carbon monoxide (CO) and hydrocarbon affect the running temperature of the con- (HC) emissions over a period of 50,000 miles verter. It will also affect the nature and dis- calls for a catalyst system capable of with- tribution of lead species deposited on the standing the many rigours of such a hostile catalyst surface. The presence of lead environment. The progressive tightening of scavengers which lead to formation of various U.S. emission standards has caused catalytic lead halide - lead oxyhalide species with a researchers to investigate methods of im- range of volatilities will also affect the lead proving catalyst systems for greater control deposition process. of CO and HC tailpipe emissions. Two In an effort to explore these effects, and to factors which control the life of a catalyst resolve the controversy over poisoning rates system are its ability to withstand high in the presence and absence of the halide operating temperatures and to withstand scavenger, Johnson Matthey have conducted poisoning by lead compounds originating a series of tests using monolithic platinum from the fuel. exhaust catalyst described previously (6). A controversy has recently arisen regarding These tests determined the relative rates of poisoning by lead, notably from Chrysler thermal sintering, and lead poisoning by (I, 2) who claimed that lead did not poison comparing catalyst performance after 300 catalysts if the halide scavenger ethylene hours operation at different engine tune- dibromide was omitted from the fuel. This exhaust position combinations. The aged claim has been refuted by other workers at catalysts were then compared to catalysts Ford (3, 4) and at General Motors (5). poisoned under controlled conditions by a However, since the siting of the catalyst in known quantity of lead using an exhaust gas the exhaust train will control the subsequent simulator. environment in which the catalyst operates, elucidation of the poisoning process will be Engine Tests dependent on the installation of the catalyst. Four EWz/1zC/4o catalyst units 4 inches Thus the distance from the exhaust manifold, diameter by 6 inches long were aged for

Platinum Metals Rev., 1975, 19, (4), 141-145 141 Fig. 1 A static engine test bed for the evaluation of catalyst performance. The rig is equipped with a cycle pro- grammer for durability tests on the cutulyst and its reactor system

300 hours in the exhaust train of a 1.8 1 The catalysts were evaluated after ageing Triumph Dolomite Engine. The engine for 300 hours by installing them on a slave dynamometer shown in Figure I is similar to test car and a slave test engine. The test car that used for this trial, when fuel containing was driven over the 1975 Federal Test Pro- 0.03 to 0.05 g Pb1U.S. gallon was used. cedure used in the U.S.A. for evaluation of Conditions experienced by the catalysts in automobile exhaust emissions, and the test the four positions were as follows : engine was used to determine the catalysts I. 11 inches from manifold- conversion efficiency at 3600 r.p.m. Both sets outlet temperature 695 to 770°C of results show similar trends when expressed 2. 11 inches from manifold- as percentage residual hydrocarbon emission outlet temperature 590 to 660°C (Fig. 2). All results show an increasing loss in 3. 102 inches from manifold- performance as the running temperature outlet temperature 615 to 650'C increases; however, under similar operating 4. 102 inches from manifold- temperatures the remote catalyst, 3, shows outlet temperature 480 to 490°C. worse performance. The relative effects of

Platinum Metals Rev., 1975, 19, (4), 142 Fig. 3 The laboratory reactor system used as an exhaust gas simulator in investigating the poisonous characteristics of oxidation catalysts

Platinum Metals Rev., 1975, 19, (4), 143 lead and sintering can be seen from the was greatly accelerated by exposing the repeat test in position I using lead free fuel. catalyst to a feed containing the equivalent of The basic reason for the pattern of results 1.5g Pb/U.S. gallon. The effect of thermal observed has been explored using an exhaust ageing on lead poison resistance is shown in gas simulator (Fig. 3), in which the poisoning Figure 4, and demonstrates the faster

Platinum Metals Rev., 1975, 19, (4), 144 poisoning of the sintered catalyst. The poison- catalyst is highly lead poison resistant, and ing process is also accelerated by the presence can also act as an effective lead filter. of halide scavenger, as shown in Figure 5. The Design studies such as these have enabled greater toxicity in the presence of scavenger Johnson Matthey to achieve emission levels is reflected by the lower performance, even below the United States Statutory Standards though the amount of lead deposited on the recommended for 1982 for over 50,000 miles catalyst is reduced by the scavenging action. vehicle operation. Comparison of the performance of the engine aged catalyst and the simulator results Acknowledgements shows good agreement for the samples run The author would like to thank the staff of the at similar operating temperature (-600°C) Johnson Marthey Catalyst Research Group and Ricardo Engineering for their assistance in this (Fig. 6). Further, the simulator has enabled work. Particular thanks are due to Mr A. J. us to deduce that the superior performance Wilkins who supervised the engine test pro- gramme. of the catalysts run in position 2 close to the manifold is due to the deposition of the less References toxic lead oxide in this position, whereas in I Chern. &J Engng. News, 1954, 52, (IS), 5 z D. M. Teague and A. N. Speca, Letter to the remote position the more toxic lead halides J. Dekany, Director, Emission Control Tech- and lead oxyhalides are deposited leading to nology Division, EPA May 3oth, 1974 greater catalyst degredation. 3 D. A. Jensen, Letter to John Dekany, June The good performance position z was 7th, I974 in 4 M. Shelaf, et al., ‘Poisoning of Monolithic achieved even though the amount of lead Noble Metal Oxidation Catalysts in Automobile Exhaust Environments’. 74th National Meeting deposited was the highest observed and of A.1.Ch.E. New Orleans, March 1973 approached nearly half the ingoing lead to the 5 G. J. Barnes, K. Baron and J. C. Summers, engine. Thus by judicious selection of the S.A.E. Paper 741062, Automobile Engineering Meeting, Toronto, Canada, October 1974 catalyst position and operating temperature 6 G. J. K. Acres and B. J. Cooper, Plat. Metals. catalyst deterioration can be minimised, the Rev., 1972,16, (3h74

Palladium Flakes for Hydrogen Solid Storage Applications

Hydrogen appears capable of playing an tive for hydrogen solid storage applications. important role in the provision of energy for On account of their hydride properties the future. Whether it will provide all the palladium and erbium were selected for in- answers to the world’s fuel problems, as some vestigation. In the case of the palladium, believe, is open to discussion but it is certainly where pure sponge was the starting material, unlikely that it will quickly realise its full the process was carried out in ethyl alcohol potential unless the problems which its using argon as a cover gas in an attrition mill exploitation will produce are anticipated and containing 0.6 cm diameter hardened steel solutions to these problems found. Forward balls and running at a reduced speed of looking organisations throughout the world 60 r.p.m., which was found to minimise the are now investigating many different aspects disintegration of the flakes. Palladium has the of hydrogen energy. A recent article by R. M. advantage of flaking more readily than German and V. Ham, of the Sandia Labora- erbium and giving a considerably higher tories, Livermore, California (Internat. J. aspect ratio. Flakes having short diffusion Powder Metall. Powder Technol., 1975, 11, paths, but without the handling properties (2), 97-100) outlines and discusses a tech- generally associated with ultrafine powders, nique for the production of submicron thick produced by this process have now been pro- metal flakes which appear potentially attrac- vided for hydrogen solid storage studies.

Platinum Metals Rev., 1975, 19, (4), 145-145 145 High Tensile Strength Thick-Film Silver-Palladium Met allisat ions

IMPROVED COMPOSITIONS FOR SCREEN-PRINTED CIRCUITS

By T. H. Lemon Group Research Centre, Johnson Matthey & Co Limited

Thick-jilm, silver-palladium conductor compositions with improved mechanical properties have been developed in the Johnson Matthey Research Laboratories. These conductors are capable of retaining high adhesion strengths using tin-lead solder after prolonged storage at elevated temperature. This article is based upon a contribution to the Institution of Electronic and Radio Engineers' Conference held at the University of Technology, Loughborough, in September.

The rate of progress in the level of com- connections between thick-film conductors plexity that any electronic technology is and lead-out wires or frames, and also at capable of accommodating is limited in- areas of attachment for discrete devices. evitably by the nature and quality of the Interactions at these interfaces during opera- materials used. At present, this is nowhere tion account for the principal cause of more true than in thick-film microelectronics, limited life-times of high-density hybrid with advances in recent years made possible circuits. by considerable improvements in both the Of all conductor compositions encountered physical and electrical properties of com- in thick-film networks, those containing positions suitable for screen-printing applica- silver and palladium are the most widely used tions. Much of this progress has been (I), offering circuit manufacturers potentially concentrated on further miniaturisation of the most attractive compromise between hybrid circuits, not only as space-saving cost and performance. Screen printed exercises when both weight and size are at a silver-palladium films are readily wetted by a premium, but also to minimise path lengths range of soft solders, and this property is among devices in order to obtain shortest exploited frequently by circuit manufacturers over-all response times from the circuit. In as a convenient means of overcoming turn, however, these smaller, more compact problems associated with multi-device at- assemblies, operating at somewhat higher tachment (2). This asset is used with full temperatures, place increasing demands on awareness of limitations in using tin-contain- thick-film materials used in hybrid micro- ing solders with silver-palladium conductors electronics, particularly those which form -limitations which were recognised nearly interfaces or junctions of dissimilar metals in ten years ago and subsequently characterised the circuit. These areas, frequently lying in in an elegant investigation by Crossland and natural, thermal drain paths, represent sites Hailes (3). These workers found that above of metallurgical activity potentially detri- 125°C there is a rapid diffusion of tin from the mental to over-all electrical performances. solder into palladium-containing metallisa- Such active sites exist at most inter- tions forming brittle intermetallics based

Platinum Metals Rev., 1975, 19, (4), 146-153 146 A selection of thick-jilm networks forming the basis of hybrid amplijication circuits and showing the exten- sive use of screen-printed silver-palladium conductors. The $red conductors readily accept solder, and recent modi$cations to paste compositions have enabled silver-palladium jilms to give high bond strengths at elevated temperatures upon PdSn,. The formation of this phase is materials viewpoint. It is admitted at the considered to account for the dramatic loss in outset that the complex nature of this system adhesion when soldered conductors contain- has not yet allowed a complete understanding ing palladium are stored at high temperatures. of the interactions occurring in solder-coated The purpose of this article is to re-examine silver-palladium metallisations. Some of silver-palladium conductors from the these shortcomings are discussed in greater detail in subsequent sections. It will be demonstrated, however, that, providing cer- tain important chemical aspects of the silver- palladium system are recognised, and appropriate action taken, tin-soldered silver- palladium films may be used with renewed confidence in compact circuitry operating at elevated temperatures.

Thick-Film Silver -Palladium Conductors The system which will be discussed in the following sections may be best considered with reference to Figure I showing a simpli- fied cross-section of a soldered assembly. In this assembly the glass and bismuth oxide

Platinum Metals Rev., 1975, 19, (4), 147 spite of this, however, the two metals alloy with appreciable heats of reaction reaching a maximum of -5.7 kJ g/atom at around 60 atomic per cent silver for the solid reaction:

Integral thermodynamic properties of this system were established by Chan and Hultgren (4) using tin-solution calorimetry. It was noted in the course of their work that the reaction of solid palladium with liquid tin was accompanied by a large negative enthalpy of solution. This behaviour was unexpected not only because of the magnitude of the exothermicity (-109 kJ g/atom; 430"c), but also because silver, with physical similarities to palladium already noted, dissolved endo- thermically in tin (16.7 kJ g/atom). It appears, therefore, that in the liquid phase at least the formation of palladium-tin internietallics from the two elements is favoured thermo- dynamically. Alloy formation in metallisations containing the parent metals, silver and palladium is complete well below the peak temperature of standard king schedules (850°C). This is shown both by suitable X-ray investigation and by thermogravimetric analyses (TGA) of (layer D) have concentrated at the substrate the metal powders when heated singly and in surface, forming a bond between the ceramic combination. Little weight change is ob- and the silver-palladium layer (C) above. A served when silver metal is heated alone under wire (A) is attached orthogonally to the metal normal atmospheric conditions because of the film using a tin-lead solder (B). Of course, low stability of AgzO (5). On the other under real conditions there has to be a hand, thermal analyses of palladium metal considerable amount of inter-diffusion among when heated under similar conditions showed these layers in order for the solder assembly weight changes as recorded in Fig. 2. The to retain integrity. The model shown in initial weight gain, due to metal oxidation: Figure I will, however, be used as a basis of discussions when reviewing failure modes of Pd + i02--+ PdO (ii) soldered silver-palladium conductors under is complete at 640°C, and the PdO formed is tensile stress. stable up to 8~0°C;beyond this point the oxide is unstable and rapidly reduces to the The Silver-Palladium System metal. In the presence of silver, the redox Silver and palladium form a continuous behaviour of palladium is quite different, as series of face-centred cubic solid solutions can be seen from the thermogram reproduced displaying a simple phase diagram-a feature in Figure 3. Here, under similar oxidising expected from the similar electronegativities conditions, a mixture containing 69.7 atomic and atomic radii of the two elements. In per cent silver-palladium shows two interest-

Platinum Metals Rev., 1975, 19, (4), 148 ing points when compared with the thermo- glass must be allowed to permeate and gram for palladium. First, in the presence of “key-in” with the lower regions of the metal silver, the oxidation of palladium is incomplete layer so that the latter is bound physically to with a discrepancy between theoretical and the substrate material. That these predomin- observed weight gains amounting to 1.5 per antly physical bonds in silver-palladium cent; and, second, that reduction of PdO, metallisations are inherently strong is sup- initiated at -500°C, is near complete in the ported by observations on unaged soldered presence of silver at 700°C. The latter samples. Here, using conventional silver- temperature, considerably lower than that palladium compositions, the over-all tensile observed for the reverse of reaction (ii) is, of strengths of soldered assemblies are limited by course, a direct result of this reaction being in the strength of alumina substrates, which competition with the alloying mechanism frequently rupture with increasing load represented by equation (i). Thus, when leaving intact the soldered assembly. This palladium is alloyed with a less easily generally occurs at around 3-4 kN/cmZ. oxidised metal such as silver, any oxide After thermal ageing these samples, however, formed (PdO) is itself more readily reduced. bond strengths fall rapidly with time, with This is demonstrated by direct comparison of the plane of fracture shifting to that between the thermograms shown in Figures I and 2 the metallising layer (C in Fig. I) and the and indicates that alloy formation in an glass layer (D in Fig. I). Electron probe intimate silver/palladium mix is complete analyses on both the substrate and corres- substantially by 500°C. ponding pulled pad have shown (a) that very Identification of the reduction temperature little metal deposit associated with the for PdO in the presence of silver gave rise to a metallisation remained on the substrate, and model intended to offer novel interpretations (b) that the substrate retained a very large of phenomena occurring at the glass-metal proportion of the glass phase from the paste interface on firing metallised layers. If these composition. Hence, in order to obtain ideas are well-founded, they will require a increased strength in thermally aged soldered glass with physical characteristics quite metallisations it is necessary to fortify different from those used currently in order bonding between the glass and silver- to improve the mechanical properties of palladium metal layers. This may be achieved, soldered metallisations. These requirements of course, by increasing the quantity of glass are explored more fully in the following used in metallisations so that a greater section. degree of interlock is formed between the vitreous and metal phases. Results to be Interplay between Silver-Palladium described will show the extent of improve- and Glass-Bismuth Oxide Phases ments in tensile strengths gained using this The major role of the glass and bismuth approach. oxide in metallising compositions is to Yet another way considered capable of provide a means of binding the metal layer to increasing the efficiency of physical bonding ceramic substrates. For this process to be between these two phases arises from recog- accomplished in an efficient manner it is nition of the redox behaviour of silver- necessary to ensure that the contact angle palladium alloys, as discussed above. It is between glass and substrate is lower than that assumed here that in high glass-containing between glass and metallisation. In this way metallisations the efficiency of metal “wetting” the glass is concentrated at the substrate is dependent not only on relative contact surface which it “wets” efficiently-a process angles and mobilities of the vitreous com- assisted by inclusion of bismuth oxide acting ponents, but also on the extent that the as a fluxing agent. At,the same time, the interface between glass and metal remains

Platinum Metals Rev., 1975, 19, (4), 149 free of physical disturbanccs during standard palladium films were measured on tracks processing cycles. Incompatibilities will be 0.75 mm wide with an aspect ratio of 60 present in metallisations if the glass is re- squares. Adhesive strengths of the soldered quired to form a coherent bond with a films were assessed using 1.5 mm square material subject to dissociation under normal pads to which tinned copper wires (22 swg) firing conditions. Such a situation, it is having plane butt ends were attached. The postulated, is likely to occur in silver- wires were attached orthogonally to the palladium metallisations with oxygen from substrate using LMP solder (62 Sn-36 Pb-2 reduction of PdO not allowing as complete Ag). All traces of solder flux were removed bonding as would otherwise be possible. It from the substrate by rinsing the assembly in is conceivable that this reduction process boiling ‘Arklone I<’ before placing samples on could prise apart the glass and metal layers, life-test. creating minute fissures or channels through Tensile strengths of soldered assemblies which metallic diffusion may proceed at a were evaluated using an Instron tensometer rapid rate. Attempts have been made, with the crosshead speed set at 8 x IO-~m/s. therefore, to avoid these incompatibilities as The wires were pulled in a plane perpendicular far as possiblc by selecting a glass with a to the substrate surface containing the solder softening point lying above the temperature assembly ensuring that at all times the wires for reduction of PdO but below the peak remained kink-free. firing temperature of standard processing Thermal ageing of the soldered assemblies schedules. In this way, the mobility and was carried out in an oven with a fan- “wetting” characteristics of the vitreous assisted circulating atmosphere; the tempera- component are retarded until after complete ture was held within Is0&5°c during test reduction of PdO has been accomplished. The runs. After thermal ageing a number of glass subsequently softens and wets the samples were withdrawn from the test reduced alloy, binding the latter to the environment at pre-determined times, allowed ceramic substrate. The degree of success to cool to room temperature for at least four that this innovation has achieved in improv- hours, and the strengths of solder assemblies ing high temperature strengths of soldered evaluated as outlined above. assemblies is discussed below. Returning now to earlier comments, it was necessary as a first exercise, to determine the Experimental Procedure and level to which glass has to be incorporated in Results silver-palladium metallisations before signi- All pastes were produced by sieve-mixing ficant improvements are observed in the silver, palladium, glass and Bi,O, powders in tensile strengths of soldered and aged correct proportions and dispersing the pre- samples. Looking at this problem from a mixed powders in an organic medium by slightly differcnt viewpoint, the question may triple-roll-milling. The pastes, containing be re-phrased: to what extent may the 80 weight per cent solids with a silver- vitreous component be included in silver- palladium ratio of 4:1 by weight, were palladium compositions before other as-fired applied to “Alsimag” 614 substrates using a physical and electrical properties of the DEK 1200 screen printer. Substrates were films become unacceptable ? cleaned under reflux with trichlorethylene and To provide an answer, a range of silver- dried in dust-proof containers before being palladium compositions was investigated used for printing. The printed patterns were containing varying amounts of glass and dried under infra-red and fired in a belt Bi,O,. The fired fdms were assessed both furnace to 850°C under atmospheric con- electrically and for the readiness with which ditions. Resistivities of the fired silver- these metallisations accepted LMP solder at

Platinum Metals Rev., 1975, 19, (4), 150 215°C. Results of these investigations, in temperatures. Even so, soldered films with which a low softening point (-450°C) around 30 volume per cent of glass and borosilicate glass was used in the silver- Bi,O,, which represents somewhere near the palladium compositions, are shown in Figure upper practical limit, display a continuous 4. Here electrical data for fired films are downward trend in tensile strengths to IOO plotted against volume contents of the glass hours with adhesions levelling off at -2 and Bi,O, expressed as a percentage of total kN/cm2. At this stage, the major fracture (volume) content of the solids in the metal- mode was identified as again occurring lisation. Those compositions which yielded predominantly at the interface between glass films with poor soldering characteristics are and metallisation (layers D and C, respectively marked by an asterisk. Not surprisingly, one in Figure I), with the substrate retaining only of the features to emerge fist from Figure 4 small deposits of metallic phase after the is that the quantity of glass which may be soldered assembly had been tested to des- included in silver-palladium films and, at the truction. same time, produce acceptable fired electrical The mode of failure in thermally aged results, is dependent on the quantity of soldered assemblies changes dramatically if Bi,03 with which the vitreous component is the “soft” borosilicate glass used in the associated. Thus, if compositions are re- metallising composition is replaced by one quired with volume contents of glass and with a higher softening point. A borosilicate Bi,03 in excess of 20 per cent, and this will glass was selected having a softening point be shown to be the case later, then the (-800°C) lying in the quiescent range be- volume ratios of Bi,O, to glass should not be tween the reduction temperature of Ag-PdO less than I :I. and the peak firing temperature (850°C). The initial and thermally aged tensile Using the same volume content of this glass strengths of soldered assemblies using silver- as before (30 volume per cent), silver- palladium compositions given by curve D of palladium metallisations were produced Figure 4 have been evaluated and the results which, after soldering and thermal ageing, reproduced in Figure 5. Here it is seen that yielded over-all tensile strengths shown in the composition containing -30 volume per Figure 6. The improved adhesions, with cent of glass and Bi,O, yield films which mean values at no time during the test run showed the greatest resistance to the de- falling below 3 kN/cmZ, are reflected in a gradation of adhesion when stored at elevated shift in the plane of failure from the glass/

Platinum Metals Rev., 1975, 19, (4), 151 metal interface found with softer glasses to one occurring generally (90 per cent rate) in the metallic deposit (interdiffusion of layers B and C in Figure I). As a result, after rupturing the soldered joints, a substantial metallic deposit was retained by the substrate. Electron probe studies of these deposits showed that they contained all four metallic elements (Ag, Pd, Pb, Sn) originally present in the metallising composition. The presence of lead could, of course, originate either from the glass or from the solder; no quantitative evaluations have so far been undertaken on these deposits. Tensile strengths of the remaining 10 per cent of thermally aged samples were limited by substrate ‘rshell-out”. This behaviour, much slower bulk diffusion predominates. also observed in soldered samples which had Only limited success was achieved in at- undergone thermal cycling tests (6), was tempts to identify by diffraction techniques characterised by the solder joint remaining intermetallic formations between lead and tin intact and parting from the substrate with a from the solder and silver and palladium in portion of the latter attached immediately the metallisation. It has not been possible, so below the joint; a feature quite remarkable in far, to obtain evidence supporting the forma- the light of reported tensile strengths of tion of any well-defined Pd-Sn intermetallic. 17.5 kN/cm2 (7) for as-processed alumina Furthermore, attempts to identify significant substrates. increases in conductor layer thickness after soldering and thermal ageing proved unfruit- Conclusion ful. In this context, however, it is worth It has been demonstrated that if the redox noting that the formation of voluminous behaviour of silver-palladium alloys is taken Pd-Sn intermetallics has found some support into account, then fired metallisations may be from studies of soldered, palladium-plated obtained which not only readily accept solder components (S), although in this work the but also retain high tensile strengths even authors conclude that the alloy most likely to after prolonged thermal ageing. This was be formed (PdSn,) is not expected to be achieved by selecting a glass with a softening brittle. As discussed earlier, the observation point in the quiescent range between that of that palladium dissolved exothermically in the reduction temperature of Ag-PdO and the liquid tin has to be considered with caution peak temperature of standard firing pro- when reviewing the solid-solid reaction cesses. In this manner, it is postulated between tin (from a lead-tin alloy) and that the glass-metal interface will be sub- palladium (from a silver-palladium alloy). jected to the minimum of physical disturbance None the less, such strong chemical attractions and that in the long-term the absence of would supply the potential necessary for the these local disruptions produces the observed rapid adhesion degradation found in con- over-all increase in tensile strengths of ventional silver-palladium compositions. soldered and aged metallisations. The dif- If these attractions play a dominant role, fusion rate of the active species has been then it is anticipated that the formation of retarded by ensuring that surface-diffusion Pd-Sn intermetallics will be accompanied by mechanisms are minimised and that the an over-all contraction in atomic volume, in

Platinum Metals Rev., 1975, 19, (4), 152 keeping with thermodynamic properties of W. A. Crossland and L. Hailes, Solid Stare other alloy systems (9). Clearly, more Tech%.,1971, 14,(2),42 fundamental investigations are required if J. P. Chan and R. Hultgren, J. Chem. Tlzermo- dYnam.3 1969, (I), 45 mechanisms occurring in such complex I, 0. Kubaschewski, E. Evans and C. B. Alcock, assemblies are to be better understood. It “Metallurgical Thermochemistry”, Pergamon, is through this more complete knowledge London, 1967, 304 that improvements in physical properties A. C. Buckthorpe, “Degradation of Thick Film of thick-film materials may be presented in Conductor Adhesion”, IERE Conf. Hybrid Microelectronics, 1973, 57 a rational form, appreciated and accepted by Amcrica Lava Corpn., Alsimag Ceramic Chart a market not renowned for its credulity. No. 711 References J. Whitfield and A. J. Cubbin, A.T.E. Journal, I G. K. Boyce, Electron. Produc., 1975, 4, 50 1965, 21, (I), 2; see also Platinum Metals Rev., 1965, 9, (31, go 2 D. W. Hamer and J. V. Biggers, “Thick Film Hybrid Microcircuit Technology”, Wiley, 9 R. A. Swalin, “Thermodynamics of Solids”, London, 1972,238 Wiley, London, 1972, 85 Advances in Platinum-Silver Thick-Film Conductors Two new series of platinum-silver con- no major discrepancies in adhesion values ductors, described in a recent article by after thermal ageing. S. J. Stein, C. Huang, L. Chang and Ultrasonic bonding of aluminium (I per G. Schultz of Electro-Science Laboratories, cent silicon) wire was considered to be more New Jersey (Solid State Technology, 1975, efficient with fritless platinum-silver com- IS, 25-33), are intended to supplant pal- positions than with the glass-containing ladium-silver compositions in a number of counterparts, presumably because in the microelectronic applications where tradition- former case there is no danger of the vitreous ally the latter have been considered to offer component residing on the conductor surface the most attractive compromise between cost thereby impeding the bonding operation, and performance. The electrical and physical Highest platinum content fritless materials performances of six compositions were appear to show least degradation in adhesion evaluated; three of these compositions used a on thermal ageing. On the other hand, vitreous component (fritted systems) to bind fritted platinum-silver pastes appear ideal for the film to alumina substrates, while the thermal compression bonding of gold wires. remainder (fritless systems) relied upon Compatibilities of both fritted and fritless copper oxides to form a chemical bond with platinum-silver conductors were assessed the substrate material on firing. The three using three dielectric materials and a number compositions belonging to each of the two of thick-film resistor pastes from three systems form a series in which the metal different systems. Fewer compatibility ratio of silver to platinum progressively varied problems were encountered with dielectric up to 2:1. materials when glass-containing platinum- As anticipated, electrical resistivities of silver conductors replaced the fritless elec- platinum-silver films fired at 930°C increased trode materials. All platinum-silver fdms in with platinum content, although films con- the pre-fied form were found to be com- taining equivalent quantities of platinum patible with resistor pastes from the three had near identical electrical properties irres- systems. pective of whether the compositions con- These two platinum-silver thick-film con- tained glass or not. Similarly, little difference ductor systems thus appear to offer some was found in initial peel strengths of soldered advantages over conventional, glass contain- samples based on either fritted or fritless ing palladium-silver compositions particularly platinum-silver compositions. Soldered where the complete absence of oxidation samples from both the fritted and fritless on the surface of films would significantly platinum-silver compositions again showed improve methods of circuit fabrication.

Platinum Metals Rev., 1975, 19, (4), 153-153 153 A Platinum Bowl by Janety

By Clare Le Corbeiller Metropolitan Museum of Art, New York

Marc Etienne Janety (c. 1750 - c. 1823) is Lavoisier to the Academy in 1790 (2). So known to readers of this journal for his far, however, familiarity with Janety’s work mastery of the arsenic process by which he in platinum has been based entirely on written made platinum malleable, and thus useful evidence. The sugar bowl illustrated here is to the artist-metalworker as well as to the now in the Metropolitan Museum of Art and instrument maker (I). Received into the is, to our knowledge, the only example by him Paris Guild in 1777, Janety practised as a to have survived. One other, a coffeepot, was silversmith for several years. But in 1788 he in existence as recently as 1933 (3), but was described as having “busied himself for disappeared during World War 11. more than two years” with platinum which- The sugar bowl is 7 inches long and is except in pre-Columbian South America- fitted with a dark blue glass liner against had never been used in such a context. His which the white brilliance of the metal is contemporaries mention snuff boxes, watch particularly effective. It is signed and dated, chains and similar trinkets among his pro- along the base rim, PLATINA JANETY FECIT ductions, and a coffeepot was shown by 1786, and thus establishes Janety’s control

Platinum Metals Rev., 1975, 19, (4), 154-155 154 of the new material by that year. In addition, material, and the ease and inexpense of it bears the French import mark for platinum producing the same articles in cast or stamped introduced in 1926. silver combined to prevent its general use in It has not been possible to trace the history the decorative arts. The sugar bowl is thus of of the bowl beyond the 1890s when it was interest both as a document and as an example in the collection of Baron JCr6me Pichon, the of the extraordinary quality of design and skill first of the modern connoisseurs and col- that could be achieved in platinum. lectors of French silver. In 1900 it was lent by an unidentified owner to the International References Exhibition in Paris, and lately it was owned I Platinum Metals Rev., 1960, 4, (2), 68-69; 1968,IzJ (21,6446; I973,17~(3), 102-104 by the late David David-Weill from whose 2 Donald McDonald, “A History of Platinum”, collection it was sold in 1971. Johnson Matthey, London, 1960, 53, 55 Janety appears to have been the only 3 “Exhibition of Old French Gold and Silver Plate”, New York, Arnold Seligman Rey and French silversmith to substitute platinum for Co, December 1933, No. 45. This is the same silver in the manufacture of objects for piece as shown in a line drawing in H. Nocq, Le poinGon de Paris, I1 (1927), 353. It is domestic use. The difficulty of working the conceivably the same shown by Lavoisicr

The Melting of Iridium

A HISTORICAL NOTE Recent developments in the application of to iron by phosphorus, he tried the effect of iridium as an electrode in high-duty sparking phosphorus additions to iridium and, accord- plugs lend interest to a little-known paper ing to the paper, “made half an ounce at the published over ninety years ago entitled “The first go”. Fusion, Casting, Dephosphorising, and Plat- On May 10th~1881, Holland patented in ing of Iridium, together with a Bibliography America the fusion of iridium with phosphorus of the Subject”. This was written by Nelson and about this time formed the American W. Pevry, and was published in three parts in Iridium Company of Cincinnati, with Pro- issues of Chemical News, commencing on fessor w. D. D. Dudley as general manager. January znd, 1885. The method used for making pen points was The paper records efforts made by a to fuse iridium with phosphorus and pour the succession of inventors in America over a alloy between two hinged iron plates which period of more than 40 years to develop were closed to give a slab & inch thick. This melted iridium as a substitute for the natural- was broken up and the pieces soldered to a occurring mineral iridosmine (or osmiridium) brass strip for grinding to shape with corun- for the hard-wearing tips of gold nibs for dum or diamond, countersinking with a fountain pens. These were known as diamond drill, and piercing. Later, Pro- McKinnon nibs. fessor Dudley suggested that the phosphorus The earliest experimenter in this field is be removed by heating the alloy on a bed of said to have been G. W. Sheppard, who died lime. in 1862, when his business was taken over by This account of activities in the New John Holland. Six years later Holland ac- World brought a curt letter from Johnson cepted a contract to supply tips for a new Matthey & Co Ltd of London in reply, type of nib which required a centre-drilled commenting that some of their staff carried a “iridium” tip. Being unable to secure suffi- record of preparing iridium-phosphorus as cient grains of iridosmine of the size needed, far back as 1837. And the editor, Sir William and under a threat of being sued for breach of Crookes, added a footnote that in April 1882 contract, Holland offered 1000dollars in 1868 Mr Sellon, the Chairman of Johnson Matthey, to anyone who would fuse for him a mass of I had presented him with a beautiful specimen ounce of iridium. With no solution forth- of iridium sheet. coming, and observing the fluidity impartcd J. C. C.

Platinum Metals Rev., 1975, 19, (4), 155-155 155 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES On the Constitution of the Mixture Nickel- Platinum-Gallium On the Chemisorption of Oxygen on Plati- A. A. GADALLA and K. SCHUBERT, z. Metallkunde, num (111) Surfaces ‘975, 661 (51, 3’7-3’’ J. A. JOEBSTL,.Y. vacuum sci. Technol., 1975, 12, The intermediate phases Ni,PtGa and NiPt,Ga (I), 347-350 were found on the section with 25at.x Ga. The Chemisorption of 0,on clean Pt (111) surfaces phases Pt,Ga, and PtGa had an extended solu- was studied at room temperature by a (2 x 2)- bility for Ni, while Pt,Ga, and PtGaehad a small 0 LEED pattern with CO content of the residual solubility for Ni, and Ni,Ga, had a small gas less than 0.50/0. The (2 x 2)-0 pattern dis- solubility for Pt. Pt3Ga,(Ru,Sn, type) formed a appears during re-evacuation of the surface system, continuous mixed crystal with the isotypic phase showing that a critical ratio of po,/pco is of the Ni-Ga mixture. required for the formation of an absorbed layer of 0,. The results show that similar “clean-off” Crystal Structure of Pd&eq reactions occur in the Pt-0, chemisorption W. WOPERSNOW and K. SCHUBERT, 3. Less-common system like those recently observed for the Ag-0, Metals, 1975, 41, (1),97-103 and Cu-0, system. Studies of the Pd,,Ge, phase showed that it crystallises in a hexagonal structure with 34 Magnetic Structure of Ordered FePt and atoms in the elementary cell. The structure is Fe,Pt Alloys characterised by interaction of the valence- electron spatial corrclation and by two vacancies A. MENSHIKOV, T. TARN~CZI and E. KR~N,Phys. in a cell which produces a system of displace- Status Solidi A, Appl. Res., 1975, 28, (I), K85- ments. K87 Neutron diffraction and magnetic studies of the of magnetic structure of the FePt and Fe,Pt phases Constitution the Mixture Pd-Ga-Ge with tetragonal CuAu-I and cubic Cu,Au-I s. HEINRICH and K. SCHUBERT, z. Metallkunde, crystal structures, respectively, showed both 1975,661 (61,353-355 (100)and (110) type super-reflections in FeJt The extension of the marginal phases into the but in FePt the reflection (100)is absent indicating ternary mixture at 700°C was studied. The that the magnetic moments lie along the c-axis of phase Pd,,Ga,Ge, does not occur in one of the the tetragonal unit cell. The temperature hys- marginal mixtures; its homogeneity range is teresis of the magnetisation measured in a extended at constant I’d-content. 6kOe field is explained by ferrimagnetic ordering in FePt. Some Mechanical Properties of Phase Se- perated Pd0.74 Auo.08 Sio.18 Metallic Glasses Magnetic Properties of Ordered and Dis- c.--F. P. CHOU and F. SPAEPEN, Acta Metall., 1975, ordered Nil -J?eXPt 23, (51,609-613 Studies were made of the effect of phase separa- N. KAWAMIYA and K. ADACHI, Trans. Japan. tion and crystallisation of glassy Pd,.7,Au,.,, Inst. Met., 1975,16, (64 327-332 Si,.,8 on its tensile behaviour, fracture strength, The magnetic properties of the ordered and dis- hardness and fracture morphology. The results ordered phases of NiPt and Fe-doped Ni,-,Fe, were discussed in terms of the dilatation mech- Pt(o

Platinum Metals Rev., 1975, 19, (4), 156-162 156 of the E and 9 phases within the N/P miscibility Co at 1.6-300 K. At low concentrations the gaps was determined. The lattice expansion at system has been previously described as an the p min boundary exhibited a linear variation enhanced band paramagnet, however it is found with the electron concentration, and the lattice that local moments are stabilised in alloys with expansion at the N max boundary was thought to Co-concentrations below the critical level for long- be influenced by the solid-solution strengthening range ferromagnetism, and it is the local moments of the particular alloy system. which are the dominating influence in the initial stages of magnetic order. Two stages of order are The Physical Properties of Some Palladium distinguished in those samples which contain Alloy Hydrogen Diffusion Membrane Mater- local moments. Alloys with concentrations up to ials 42 ”/, have magnetic characteristics commonly D. FORT and I. R. HARRIS, J. Less-common Metals, associated with spin glasses. There are indications that samples with concentrations in excess of 1975,41, (2), 313-327 The hydrogen solubility as well as magnetic, ~36%are ferromagnetic at low temperatures. The magnetic properties are distinctly different dilatometric and electrical-resistivity of solid- at 44 :/;. solution alloys 25% Ag-Pd, 8% Y-Pd and 9:4 Y-Pd have been measured as a function of temperature in both hydrogenated and non- Structural Transformation of Near- hydrogenated conditions. The results show an equiatomic V-Ru Compounds at High increascd solubility of hydrogen in 974 Y-Pd Pressure alloy compared with 25q/o Ag-Pd alloy, and a C. W. CHU, S. HUANG, T. F. SMITH and E. CORENZWIT, large increase in the room temperature resistivity Phys. Rev. B., 1975,11, (s), 1866-1869 shown by this alloy upon hydrogenation. The structural transformation of near-equiatomic V-Ru compounds was studied resistively under Magnetic Properties of Ni-Rh Alloys near hydrostatic pressure up to -21 kbar. The rate of the Critical Composition for Ferromagnetism suppression increases the critical concentration w. c. MUELLNER and J. s. KOUVEL, Phys. Rev. B., for the occurrence of the transformation. 1975, 11, (1111 4552-4559 The magnetisation of 65-51 at.:<> Ni-Rh alloys Displacive Transformations in Near- on either side of the critical composition for equiatomic Niobium-Ruthenium AUoys-I. ferromagnetism (Ccritz 63 at.‘!& Ni) were Morphology and Crystallography measured at 4.2-250 K in the fields up to 56 KOe. B. K. DAS and D. s. LIEBERMAN, Acta Metall., 1975, The average moment a cluster is deduced to be 235 (5),579-585 ~(20--24)p~ and the concentration of magnetic Displacive phase transformations in near- clusters increases rapidly as ccrit is approached equiatomic Nb-Ru alloys were studied using from the paramagnetic side. Pertinent aspects of electrical resistivity measurements, optical metal- the weakly ferromagnetic alloy Ni,,Rh,, is also lography and X-ray diffraction. Alloys con- discussed. taining 41-45 at.?; Ru undergo a CsCI(p) to tetragonal (B’) transformation on cooling from Some Anomalies of the Thermodynamics of 15oo’C to room temperature. Alloys with more Antiferromagnetism to Ferromagnetism than 46 at.?,:, Ru exhibit a two step CsCl(p) to Transition in Iron-Rhodium Alloys tetragonal (3’) to orthorhombic ((3”) transforma- V. M. POLOVOV, B. K. PONOMAREV and V. E. tion on cooling to room temperature. ANTONOV, Fiz. Metal. Metallovcd., 1975, 39, (s), 977-986 The heat capacity, critical magnetic field and CHEMICAL COMPOUNDS critical pressure of Fe,.,,Rh,.,, were measured at temperatures close to the antiferromagnetic to Hydrogen-Deuterium Exchange at a ferromagnetic transition. It was found that the SaturatedCarbon Atom in Tertiary Phosphine thermodynamic characteristics of the transition Complexes of Platinum(I1) were different for quenched and slowly cooled A. A. KIFFEN, c. MASTERS and L. RAYNAND, J. samples. The entropy changes on transition as Chew. Soc., Dalton Trans., 1975, (10), 853-857 measured in calorimetric, magnetic and high Chloro-bridged di-Pt(I1) complexes of the type pressure experiments show considerable dis- [Pt,Cl,L,] (L =PPr3, PBu,, PBuPr,, PBu,Pr, crepancies, apparently due to the metastable PPrPh,, PPr,Ph, or PBuPh,), undergo a regio- character of the antiferromagnetic phase. specific H-D exchange in acetic acid (CH,CO,D) medium to give complexes containing D in the The Approach to Magnetic Order in alkyl groups of the tertiary phosphine moiety. Rhodium-Cobalt Alloys The results show that in internal-metallation H. c. JAMIESON,~. Phys. F: Metal Phys., 1975, 5, reactions of Pt, the ease of ring formation de- (s), 1021-1036 creases in the order five membered > six mem- Magnetic data are presented for Rh-28 to 44 at.:/, bered > four membered rings.

Platinum Metals Rev., 1975, 19, (4), 157 The Crystal and Molecular Structures of Hydroxoplatinates(1V) of Calcium, Stron- cis-Dichloroethylenedianheplatinim(I1) tium and Barium and Palladiurn(II) M. TRO‘MEL and E. LUPPRICH, Z. Anorg. Allgem. J. IBALL, M. MACDOUGALL and S. SCRIMGEOUR, Che% 1975, 414, (2), 169-175 Acta Cryst. B., 1975, 31, (6), 1672-1674 CaPt(OH),, CaPtO,(OH),, SrPt(OH),.zH,O and The structures of cis-M(en)Cl,(M ==Pt,Pd) were BaPt(OH), were prepared by precipitation from studied using diffractometer data and refined by alkali hydroxoplatinate(1V) solution with alkali least-squares calculations; R =0.073 for Pt(en)Cl, earth salt solutions. These salts are characterised and 0.057 for Pd(en)Cl,. The compounds are by X-ray diffraction and chemical analysis. The isomorphous, space groups Czaz, with Z-4. The crystal structure of CaPt(0H), was determined. metal atoms have a square-planar configuration Probable H positions are calculated and H- and the ethylenediamine rings are puckered, bonding is discussed. intermolecular Pt-Pt and Pd-Pd distances being 3.381 and 3.3698, respectively. Reductive Syntheses of Transition Metal Fluoride Compounds. Synthesis of Rhenium, Possible Mode of Action of Anti-Tumour Osmium and Iridium Pentafluorides and Platinum Drugs: X-ray Evidence for cis Tetrafluorides Binding by Platinum of Two Inosine 5’- R. T. PAINE and L. s. ASPREY, Inorg. Chem., 1975, Monophosphate Molecules via the N(7) 14,(5),1111-1113 Positions Two simple syntheses of third-row transition D. M. L. GOODGAME, I. JEEVES, F. L. PHILLIPS and series MF5 and MF,(M=Re, Os, Ir) reduced by A. C. SKAPSKI, Biochim. Biophys. Acta, 1975, 378, H, or Si metal in anhydrous HF at room tempera- (I), 153-157 ture are described. The MF, and MF, are The ion [Pt(NH,)2(5’-IMP),]2- was obtained by characterised and the data are discussed in terms the reaction of cis-[Pt(NH,),(H,O),1,’ on the of known properties of similar compounds. disodium salt of inosine 5’-monophosphate. X- ray diffraction studies showed that Pt was bonded Alkynyl Compounds of Transition Metals. to the N(7) atoms of two 5’-ILMP moieties. XXIX. Alkynyl [ethylenebis(diphenyIphos- Possible modes of anti-tumour action of platinum phine)] Complexes of Platinum(I1) compounds are discussed. R. NAST, J. voss and R. KRAMOLOWSKY, Chem. Ber., Organometallic Compounds with Metal- 1975, 108, (5), 15II--I517 Metal Bonds. V. New Heteronuclear Cis-[PtCl,(dpe)] reacts with alkali acetylides in of liquid NH, or liquid methylamine to yield Tetrametallic Clusters Platinum with nonionic monomers of the type cis-[Pt(C-CR), Cobalt or Molybdenum and a New Homo- (dpe), where dpe =(C ,H,),P[CH2] J’(C ; trimetallic Platinum Cluster R=H, CH, or C,H,. The analogous reaction P. BRAUNSTEIN, J. DEHAND and J. F. hTNNIG, r. BRAUNSTEIN, J. DEHAND and J. F. ~TNNIG, with the divalent anion of o-diethynylbenzene, J. Organometal. Chem., 1975~92,(I), 117-123 J. Organomctal. Chem., 1975,92, (I), 117-123 however, gives the polymeric cis-[pt(C rC),C6H4 Two new heteronuclear tetrametallic complexes (dpe)],. With an excess of acetylide polymeric complexes of the type [K,Pt(C =CR),(dpe)], are (CO),Coz(CO)zPt,(CO)(PPh,)z,(C0)5Co~(C~)~Pt2(C0)(P~h3)~, (?-C5HJ2- (CO),Mo,(CO)aPtz(PPh3)z(CO)2Mo,(CO)4Pt,(PPh3)z and a new homo- precipitated. nuclear trimetallic complex Pt,(CO),(PPPh3),Pt,(CO),(PPh,) % were synthesised by reaction between Na[Co(CO),] or Oxidative Addition Reactions of Halogens Na[(q-C,H,)Mo(CO),] and cis- or trans- PtCI,PtCl, to Rh(1) Complexes (PPh,),. They appear to have a tetrahedral M. R. GAJENDRAGAD and u. AGARWALA, J. Inoyg. arrangement of the metallic atoms in a butterfly- arrangement of the metallic atoms in a butterfly- Nucl. Chem., 1975, 37, (7/8), 1834-1835 type structure. Studies on oxidative addition reactions of com- Diolefiuic Complexes of Rhodiurn(1) and plexes of metal ions of the d8 system are reported Iridium(1) with Nitrogen-containingLigands for phosphine complexes of Ir(1) and dihalo- dicarbonyl complexes of Ir(1). Complexes of G. ZASSINOVICH, G. MESTRONI and A. CAMUS, 2. Rh(1) are also potential species for such reactions. Organometal. Chem., 1975, 91, (3), 379-388 The synthesis and the substitution and oxidation Metal-Olefin Complexes: Synthesis and reactions of the series of Rh(1) and Ir(1) com- plexes iM(L-L)(B)Cl, [M(L-L)(B),]X and Molecular Structure of trans-Chloro [M(L-L)(chel)]X, where L-L =cis-, cis-cycloocta- (ethylene) bis (tripheny1phospUne)iridium I, 5-diene, cycloocta-I, 3, 5, 7-tetraene, bicyclo (I), IrC1(C,H,)(PPh,), [z.z.I] hepta-z, 5-diene; chel=8-aminoquino- R. J. RESTIVO, G. FERGUSON, T. L. KELLY and c. v. line, phenylendiamine, dipyridylketone, sub- SENOFF, J. Organometal. Chem., 1975, go, (I), stituted phenanthrolines, and X=Cl-, PF,-, 101-109 C10,- are described. The use of these complexes The complex trans-IrC1(C,H,)(PPh,)2 was isolated as anti-tumour agents is considered. and its structure determined in the solid state.

Platinum Metals Rev., 1975, 19, (4), 158 The crystals are monoclinic Pzlk, with a= was studied. Pd or Pt diffusion from the coating 12.334, b=zz.957, c=14.039& p=125.54” and into the ceramics during sintering lowers the high Z--4. The molecule has a trans-square planar permittivity of laminated ceramics to that of configuration. The coordinated CzHl is TC- the permittivity of the original BaTiO,, which is bonded to the Ir atom and is essentially per- smaller by an order of magnitude. pendicular to the P,IrCl plane with a very short C =C distance of I .375A. Electrodeposition of a Palladium-Bismuth Alloy s. N. VINOGRADOV, L. M. PIRYULINA and L. N. ELECTROCHEMISTRY KHZTRTOVA, Zushchita Metal., 1975, 11, (3), Interaction of Acetone and Isopropyl Alcohol 380-383 with Platinum-Black The electrodeposition of a Bi-Pd alloy on electrical L. V. RUSALINA, A. D. SEMENOVA and ZH. V. contacts, from an electrolyte containing Pd and Bi STRELNIKOVA, Zh. Fiz. Khim., 1975, 49, (6), in a complex form was studied. The deposits are characterised by low internal stresses and ease of 1570-1571 soldering, in comparison with pure Pd deposits. Chemisorption behaviour of acetone and iso- propyl alcohol on Pt-black in IN H,SO, was studied using electrochemical and gas chromato- graphy methods. The results show that partial LABORATORY APPARATUS dehydrogenation and breaking down of molecules AND TECHNIQUE occurred during chemisorption. Cyclic Voltammetric Studies on Platinum Electrochemical Generation and Reactivity Electrodes in Aqueous Electrolytes of Organo-Cobalt(1V) and -Rhodium(IV) K. A. NATARAJAN and I. IWASAKI, J. Electrochem. Chelates SOC. In&@,1975, 24, (I), 1-6 I. LEVITIN, A. L. SIGAN and M. E. VOL’PIN, J. The experimental techniques involved in cyclic Chem. SOC.,Chem. Commun., 1975, (IZ), 469-470 voltammetry are discussed with respect to the The electro-oxidation of organo-cobalt(II1) and electrochemical behaviour of Pt electrodes in -rhodium(III) chelates was investigated. It is inorganic electrolytes. The behaviour of the found that the reactivity and ease of formation of electrode is studied with reference to the effect of organometallic cations [RMIb’(chel)J+, where R O,, electrode pretreatment, scan rate, solution is a primary or secondary alkyl group, depends on pH and ionic strength of the electrolytes. the nature of the u bonded organic ligand which behaves as a carbonium ion and contributes significantly to the structure. HETEROGENEOUS CATALYSIS

Study of the Hydrogen Adsorption on Hydrogen Adsorption by Alumina-supported Ruthenium Catalysts. I. The Effect of Platinum Medium Acidity on the Strength of Hydrogen I.. T. DIXON, R. EARTH, R. J. KOKES and J. w. Adsorption on Ruthenium Black Studied by GRYDER, J. CatabSi3, 1975,37, (2), 376-382 Electrochemical Methods Isotherms at 295 and 77 K for Ha adsorbed on wet or dry Pt /Al,O, were used to study five kinds A. A. VEDENYAPIN, N. D. ZUBAREVA, E. I. of H, adsorption. Type I is reversible at 77 K, KLABUNOVSKII, I. P. GODYASHCHEVA and I. A. type I1 is irreversibly bound at 77 K and type 111 RUBTSOV, Zh. Fiz. Khim., 1975,49, (6), 1480-1485 is an activated chemisorption with i.r. band at Charging curves of H, adsorption in IN H,SO, 206o/cm. Type IV has i.r. band at zrzokm and and IN KOH on Ru-black showed that the its binding energy is lower than that for type 111. adsorption capacity as well as the strength and Type V H, is irreversibly bound at room tempera- heat of adsorption were higher in the alkaline ture and is necessary for the adsorption of type IV than in the acidic solutions. It is suggested that at 77 K. 0, atoms present on the surface of Ru in alkaline solutions can act as additional centres for H2 Toluene Dealkylation on Platinum Group adsorption. Metals in the Presence of Water Vapours G. L. WINOVICH and v. N. MOMAIKO, Neftekhimiya, ELECTRODEPOSITION AND 1975, 15, (3)~373-378 SURFACE COATINGS Studies of toluene dealkylation over catalysts containing Pt group metals on y-A1203 in the Interpolation of Pd and Pt in n-doped presence of water vapours at 350-~IOocshowed BaTiO, Ceramics that the catalytic activity changed in the following H. SCHMELZ, Keram Z., 1975, 27, (4), 198-199 manner: Rh, Ir>Pt> Pd> Ru>-Os, whereas the The influence of Pd and Pt containing coatings selectivity was highest for Pt and Pd followed by on the conductivity of n-doped BaTiOs ceramics Ir, Os, Rh and Ru.

Platinum Metals Rev., 1975, 19, (4), 159 Study of the Mechanism of Isomerisation of Hydrogenation of Acetone and Isopropyl 2,2-Dimethylbutane on Platinum/Alumina Alcohol on Platinum Black in Hydrogen Catalyst in a Pulsed Regime Adsorbed Bed YU. N. usov, N. I. KWSHINOVA and E. D. A. D. SEMENOVA, ZH. v. STRELNIKOVA and L. v. CHEKUROVSKAYA, Neftekhimiya, 1975, 15, (z), RUSALINA,~~.Fiz. Khim., 1975,49, (6), 1572-1573 224-230 The hydrogenation of acetone and isopropyl The isomerisation of 2,a-dimethylbutane was alcohol on a Pt-black electrode in IN HzSO4 at carried out on an industrial (0.5% Pt-AIzO, 25°C was studied. The presence of propane and -0.3:/0F) platinumlfluorated y-Al,03 catalyst. It ethane in the reaction products suggest that the was shown that the isomerisation process took hydrogenation is accompanied by chemisorption place on both the y-Al,O, and metallic Pt followed by dehydrogenation and the subsequent surfaces. The mechanism was explained in terms breakdown of the reactants molecules. of intcrrnediate carbonium-ion formation on the y-Al,O, surface and the electron exchange of between Pt atoms and the hydrocarbon resulting Interaction Acetone with the Surface of Skeleton Platinum-Iridium Catalysts Free in the formation of 5 and T: complexes. from Chemisorption Products Infra-red Active Species of Hydrogen -4d- s. v. KROPOTOVA, A. D. SEMENOVA and G. D. sorbed by Alumina-supported Platinum VOVCHENKO, Zh. Fiz. Khim., 1975, 49, (6), 1430- L. T. DIXON, R. nmw and J. w. GRYDER, J. Cataly- I433 sis, 19753 37r (2), 368-375 The rate of dehydrogenation of acetone on Studies were made of two i.r. active H species Ir-o-IooO/b Pt skeleton catalysts was studied. For adsorbed on Pt/AI,O, with bands at 2120 and a Ir-75°(1 Pt catalyst the rate of dehydrogenation zo60/cm. Corresponding bands for D at 1520 at zo°C was higher than for pure Pt and Ir and 148okm were also observed. The results catalysts. This is attributed to the presence of an show that the species with i.r. band at 206o/cm increased number of unpaired d-electrons on its is a stronger form with increased intensity in the surface. The activation energy of dehydrogena- presence of H,O and an activated adsorption tion for the Ir-754/, Pt catalyst is Z~Ikcal/mol, occurring only above 130 K. The species with a whereas for all the other compositions it is band at zIzo/cm adsorbs irreversibly at 77 K 951 kcal/mol. if the sample has been exposed to H, at 300 K. Reactions of Hexanes, Unlabelled and Activity of Metallic Catalysts. IV. Influence Labelled with I3C, on Alumina-supported of the Nature of the Support and Effect of Palladium-Gold and Platinum-Gold Alloys Sulphur-containing Poisons on Two Ex- A. O’CINNEIDEand F. G. GAULT,~. Catalysis, 1975, amples of “Demanding Reactions” 37, (21, 311-323 R. hum, G. LECLERCQand J. BARBIER,?. Cata- Studies of isomerisation and hydrocracking of lysis, 19751 37, (21, 324-331 unlabelled and labelled hexanes over Au-Pd and The activity of various Pt/AI,O, in crystallised or Au-Pt alloys (10% of metal/Al,O,) showed the amorphous form with various amounts of sul- “cyclic mechanism” on Au-I~~Pt alloys but phate ions, was studied during the hydrogenolysis mostly “bond-shift’’ mechanism on Pt catalyst. of cyclopentane at 300°C and the reactions of A nonselective ring opening of methylcyclopen- benzene with D, at 85’C, in addition and ex- tane also occurred on Au-Pt alloy, but on Pt, change. The results show that the nonpropor- only the CH,-CH, secondary-secondary bonds tionality of activity to metallic surface area of the were broken. The Au-I~:/~Pt alloy was active support are caused by a selective poisoning, S only after pretreatment by air and was deactivated being a selective poison, whereas SOz and H,S in the presence of H2. at 300°C are nonselective poisons,

On the Differences in the Mechanisms of On the Stability of Palladium/Zeolite Cata- Cg- and C6-Dehydrocyclisation of Alkanes lysts during Storage in the Presence of PtjC D. v. SOKOL’SKII, N. A. GOGOL’,N. L. SHLIOMENZON 0. V. BRAGIN, A. V. PREOBRAZHENSKII, A. L. and L. D. ZHUBANOVA,Zh. Fiz. Khim., 1975,49, (4), LIBERMAN and n. A. KAZANSKII, Kinet. Kataliz, 896-899 ‘975, 16, (21,472-475 The activities of freshly prepared Pd/zeolite Studies of rates of C,- dehydrocyclisation of 2- CaA, CaX, NaY(SiOz/Al,0,=r.3; 1.5 and 8.9) and 3- methylpentanes alone and with -2oq4 of catalysts were compared with those stored for up the corresponding olefins on 20% Pt/C at 300°C to 4 years. The CaA and CaX catalysts containing showed that the olefins retard the reaction and 0.27( Pd showed high initial activities as measured cannot, therefore, be reaction intermediates. in the hydrogenation of dimethylethynylcarbinol. Similarly the yield of C,H, from hexene-1 is After storage the CaX catalyst decreased in ac- higher than from n-hexene. tivity while the CaA remained unchanged.

Platinum Metals Rev., 1975, 19, (4), 160 Reduction of Nitric Oxide by Monolithic A Palladium-Catalysed Conjugated Diene Supported Palladium-Nickel and Palladium- Synthesis from Vinylic Halides and Olefinic Ruthenium Alloys Compounds C. H. BARTHOLOMEW, Ind. Engng. Chem. Prod. H. A. DIECK and R. F. HECK,J. org. Chem., 1975, Rex- Dm.3 I975,14, (1),29-33 40, (S), 1083-1090 The effect of reaction parameters such as tempera- The reaction of vinylic bromides or iodides with ture, space velocity and pollutant concentration olefin compounds at 100-150°C in the presencc of was studied in a laboratory reactor. Freshly pre- a trialkylamine and a catalytic amount of pared Pd-Ni and Pd-Ru catalysts convert roo"4 Pd[P(C,H,5),] ,(OAc), produced conjugated NO (1000 p.p,m.) with less than 54; NH, dienes. These showed appreciable stereospecifi- formation in a 0.40; 0, (15h CO and 250 p.p.m. city when (2)- or (E)- vinylic halides were C,H,) mixture at 600 and 480°C, respectively. treated. Conversions of NO, CO and C3Ho decrease slightly with increasing space velocity. The Group VIII Metal Complexes as Catalysts for effect of dynamic exposure to IOO p.p.m. of SO, Halogen Exchange between Alkyl Halides is to lower slightly but reversibly the NO and J. E. LYONS,~. Chem. sac., Chem. Commun., 1975, C,H, conversions while significantly and irre- (111,418-419 versibly lowering conversion of CO. Chromatographic studies were made of alkyl halide exchange reactions catalysed by CO- Catalytic Reduction of Nitric Oxide on ordinatively unsaturated group VIII metal Ruthenium complexes [MX(CO)(Ph,P),1 (M=Rh, Ir; X=Cl, R. L. KLIMISCH and K. C. TAYLOR, Id. Engng. Br, I) at rooT and under 150 lb/in2 of either Ar Chem. Prod. Res. Dev., 1975,14, (I), 26-29 or CO. The results showed formation of acyl Rh The details of NO catalytic reduction by CO and complexes under CO pressure. H, over a supported Ru catalyst were investigated. The feed stream used in these studies resembled Selective Hydrogenation of Mesityl Oxide automotive exhaust. The effect of space velocity to Methylisobutylketone with the Catalyst and various reactant concentrations on the NH,/N, product distribution were studied along RhCI(PPh,), with the effect of these various parameters on the w. STROHMEIER and E. HITZEL, 3. Organometal. rate of NO removal. Chem., I9751 9'J (3), 373-377 Mesityl oxide dissolved in toluene is selectively Kinetic Study and Catalyst Structural Analy- hydrogenated to methylisobutylketone in the sis for the Dehydrogenation-Hydrogenolysis presence of RhCl(PPh,) ,. After 70% conversion the catalyst is deactivated. Without solvent, of n-Pentane over Ru-AI,O, Catalysts distilled but not degassed mesityl oxide is com- v. RAGAINI, L. FORNI and L. v. MAO,~.Catalysis, pletely and selectively hydrogenated to methyl- I975, 37, (2)J 339-347 isobutylketone. Turnover numbers are 4400. Studies were made of the reaction of n-pentane Under these hydrogenation conditions the cata- over 0.034-1.49zqb Ru/y-Al,O, at I atm, lyst is active for > Iooh. 45~~490°Cand molar feed ratio of 5-20. The catalyst activity was strongly dependent on sur- Homogeneous Catalytic Hydrogenolysis of face topography and a maximum specific activity was at 0.085 wt.o/b Ru. The results also show the C-0 Bond: the Selective Reduction of that the number of Ru atoms constituting the Cyclic Carboxylic Acid Anhydrides to y- active centre for dehydrogenation is 2-3. Lactones Catalysed by [RuCI,(Ph,P),] J. E. LYONS,?. Chem. soc., Chem. Commun., 1975, (II)i 412-413 HOMOGENEOUS CATALYSIS [RuCI,(Ph,P),] efficiently catalyses the selective homogeneous hydrogenolysis of carboxylic acid Fixation of Molecular Nitrogen in Aqueous anhydrides at roo"C and 150 lb:in2 H,. The results Solution. Catalysis by Platinum Group show that when the C-0 bond of the anhydride is Metal Ions cleared, y-lactone is formed. M. M. T. KHAN and A. E. MARTELL, Inurg. Chem., 19751 14, (411 938-939 Ruthenium Promoted Oxidation of Amines Isotopic studies of the fixation of N, in aqueous s. E. DIAMOND, G. M. TOM and H. TAU BE,^. Am. solution catalysed by Ru(11)-, Ru(II1)-, Rh(II1)-, Chem. SOC.,1975, 97, (IO), 2661-2664 Ir(IlI)-, Os(11)-, and Os(111)- chloro complexes at Studies of the oxidation of benzylaminepentaam- I atm showed prominent peaks of N,O at mass mineruthenium(II1) showed a high yield of the numbers 44 and 45 which established Nzfixation nitrite bound to the ion with the imine as a in catalyst systems Ru(I1) j-TiCl, and Rh(II1) -t recognisable intermediate stage. The formal SnCl,. These were the systems which gave the reduction potentials for the pentaammine- highest yields of NH,. ruthenium(II1)-(11) couples are given.

Platinum Metals Rev., 1975, 19, (4), 161 Reactions of (q -AUyl)tricarbonylchlororuth- CHEMICAL TECHNOLOGY enium(I1) with Hydrogen and Unsaturated Substrates: Catalytic Hydrogenation and Interaction of 0s (IV) Halogen Complexes Isomerisation of Alkenes with TrialkylphosphineOxides in Extraction Processes G. SBRANA, G. BRACA and E. BENEDETTI, J. them. SOC.,Dalton Trans., 1975, (g), 754-761 K. A. BOLSHAKOY, N. M. SINITSYN, N. M. BODNAR Studies were made of the reactions of and M. N. SHAKHOVA, Zh. Neorg. Khim., 1975, 20, (6), 1641-1646 [RuCl(C,H,)(CO),], with unsaturated substrates such as acrylonitrile (acn), alkynes, butadiene, Extraction of 0s in the form of [OsCI,]" and and acetylenic esters using i.r. and n.m.r. tech- [OsBr,12- complexes in HCI medium was carried niques. The solids [{RuCl(a-C,H,)(CO) 2(acn)},], out using tri-n-butylphosphine oxide and tri-n- [ {RuC1(OC.CR:CR'.C3H5)(CO!2},](R =R' =H ; octylphosphine oxide. The extent of 0srecovery R=H, R'=Ph; and R=R'=Rh), and [RuCl measured in terms of coefficient of distribution D {(C,H,),.C,H,](CO),] were isolated. In the case increases with increasing HCI concentration and of diethyl acetylenedicarboxylate an alkenyl attains a maximum at "4 mol HC1. The influence complex of formula [RuCI{C(CO,Et) :CH. of different extracting reagents, ligands and dil- C(OEt)O}(CO),] was obtained. uents on the recovery process as well as on the structure and properties of the complexes ob- Asymmetric Synthesis by Chiral Ruthenium tained was also investigated. Complexes. I : Enantioselective Hydrogena- tion of Kctones and Ketoximes Catalysed by ELECTRICAL AND H4RU4(CO)* [(-)-DIOPI, ELECTRONIC ENGINEERING C. BOTTEGHI, M. BIANCHI, E. BENDETTI and U. MATTEOLI, Chimia, 1975, 29, (6), 256-258 I-V Characteristics of PtSi-Si Contacts Made H,Ru,(CO),[( -)-DIOP] catalyses asymmetric from CVD Platinum hydrogenation of C-0 and C-N double bonds at M. J. RAND, J. Electrochem. Soc., 1975, 122, (6>, high temperature and pressure. In the case of 811-815 t-butylphenylketoxim the degree of asymmetric The use of CVD Pt to make PtSi contacts was induction reaches 14.5 74. studied. With heavily doped Si and sintering at 450-7OOoc no electrical anomalies appear. With Acid-dependent Selectivity in the Homo- light doping there is still no problem provided a gencous Hydrogenation of Mono- and Di- relatively low (-450°C) is used. CVD Pt reliably enes by Acetatotriphenylphosphine Com- forms PtSi at this temperature. The effects of plexes of Ruthenium and Rhodium higher contact formation temperatures are dis- cussed. A. SPENCER, J. Organometal. Chem., 1975, 93, (3), 389-395 The hydrogenation of mono- and di-enes by TEMPERATUREMEASUREMENT catalysts derived from protonation of Ru(CO,Me), (PPh,), and Rh(CO,Me)(PPh,), in methanolic Rh-Ir Thermocouples Operate at 2100°C solution with p-toluenesulphonic acid was studied. L. R. THOMAS, MetalProg., 1975,107, (6), 55 The rate of hydrogenation is highly dependent on The new Feussner thermocouples, Ir :40% the acidity. Rapid highly selective reduction of Ir-Rh, are recommended for applications where cyclic dienes to monoenes occurs. This selectivity continuous temperatures exceed 1700OC up to is attributed principally to the superior coordinat- 21oooC. Accuracy is&IO"C. Below ISOOOC, Pt ing power of the dienes. is preferred.

NEW PATENTS

CHEMICAL COMPOUNDS ELECTROCHEMISTRY New Rhodium Carbonyl Salts Electrolytic Electrodes UNION CARBIDE CORP. U.S. Patent 3,878,290 ELECTRONOR CORF. Brirish Patent 1,398,21 I New salts have the formula M Rh,,(CO),, where Electrolytic electrodes are provided with more M is divalent Be, Mg, Ca, Sr, Ra, Sc, Y,Mn, Fe, stable coatings by depositing a mixture of a Pt-Ir Ru, Re, Co, Ni, Pd, Pt, Zn, Cd, Hg, Ce and Eu. alloy and 2.5-20:/~ of a valve metal oxide on their

Platinum Metals Rev., 1975, 19, (4), 162-166 162 surfaces. The preferred coatings consist of a contains a Au chloride, Pd chloride or other 70% Pt-Ir alloy and Ti02. noble metal-Sn salt complex modified with a lower alkanol. Electrowinning of Metals DIAMOND SHAMROCK CORP. Metallised Macromolecular Material British Patent 1,398,378 HOECHST A.G. US.Patent 3,871,903 An electrode for the recovery of metals by A shaped body consists of a solid support therm- electrolysis has a surface coating containing ally resistant at 25c-40Ooc, a sintered film on the I.o-Io~/, Sb,O,, 30-900/0 SnO, 1-50"/0 of one or surface of the support of polytetrafluoroethylene more Pt group metal oxides and 0.5-30% of Ti having a noble metal salt dispersed in it and a or Ta oxide. metal coating on the surface of the polytetra- fluoroethylene film. The noble metal salt is Diaphragm Cells for Electrolysis preferably Pd chloride, Pt chloride or Ag nitrate ORONZIO DE NORA IMPIANTI ELETTROCHIMICI S.P.A. and the metal of the coating may be Ni or Cu. British Patent 1,400,053 Diaphragm cells stacked horizontally for electro- lysis have a number of horizontal planar anodes LABORATORY APPARATUS made from a valve metal coated with a catalytic AND TECHNIQUE layer containing a Pt group metal or its oxide. Gas Concentration Cells Electrode Having a Silicide Surface BAILEY METER CO. British Patent 1,400,579 P.P.G. INDUSTRIES INC. U.S. Patent 3,862,023 A solid electrolyte concentration cell has two An electrode with a valve metal substrate has a electrodes and is used for O2 detection on a coating consisting of a Pt group metal silicide porous Pt electrode. The amount of 0, is indi- chosen from Pd,Si, Pt,Si and Ru,Si,. cated by the electrode temperature which is measured by a Au-Pt thick film thermocouple, ELECTRODEPOSITION AND Potentiometric CO Detector EXXON RESEARCH & ENGINEERING CO. SURFACE COATINGS U.S. Patent 3,880,722 Ruthenium/Osmium in Cutting Tools In an instrument for the detection and measure- ment of the CO content of gases, particularly in INTERNATIONAL NICKEL LTD. British Patent 1,393,115 ICE exhaust gases, GO is reacted with H,O to form CO, and H+ and to produce a voltage A new cutting tool, e.g. a carbide tool, has a change which is proportional to the CO content coating of Ru and/or 0son the surfaces adjacent of the gas under suitable conditions. The reaction to the cutting edge. In one example the tips of a takes place in an aqueous solution and employs tool containing 83y0 W carbide, 12% Ti carbide suitable oxidising agents and a Pd salt catalyst. and 5% Co is given a flash coating of Au and then is electroplated with Ru.

Platinum and/or Iridium Electroplating JOINING RHONE-PROGIL British Patent 1,399,500 Binder for Carbide Tools The mechanical and chemical resistance of Pt INTERNATIONAL NICKEL LTD. and/or In deposits are improved by using a bath British Patent 1,393,116 containing bromoplatinic and/or bromoiridic The carbide particles constituting the tool are anions and HNO,, H,SO,, HC10, and/or held together by a binder containing Co and a HBrO,. A typical plating bath contains 0.75 g/l lesser or equal amount of Ru and/or Os, e.g. ammonium bromoplatinate in 0.35N HClO,. 70y0 C0-3oiy0 Ru. Siloxane Coating Composition IMPERIAL CHEMICAL INDUSTRIES LTD. HETEROGENEOUS CATALYSIS British Patent 1,399,885 Organopolysiloxane coatings are cured by the ICE Exhaust Gas Treatment presence of O.I?; of a Pt group metal halide KALI-CHEMIE A.G. British Patent 1,392,528 catalyst complexed with a suitable ligand, e.g. In a two bed reduction-oxidation catalyst system, cyclooctadiene or tripropyl phosphine complexes the first bed is used in oxidising conditions during of PtCl,. cold starts to generate heat before reverting to the reduction-oxidation operation. The first bed Activator Solution for Chemical Plating contains a calcined support carrying (a) 0.02- ENTHONE INC. U.S. Patent 3,871,889 0.1% Kh with 0.05-0.20/0 Pd or (b) o.005-0.5% The solution for activating non-metallic surfaces Rh with 0.005-0.5 :h Ir.

Platinum Metals Rev., 1975, 19, (4), 163 Hydrogenation Processes Pt group metal. Thus Pt may be used with DIAMOND SHAMROCK COW. niobium oxide or vanadium oxide. British Patent 1,393,659 An unsaturated carbocyclic or heterocyclic Hydrocarbon Conversion with a Multimetal compound, such as benzene, pyridine but Catalyst especially a a,5-dialkyl-pyrrole, is converted to a UNIVERSAL OIL PRODUCTS CO. corresponding saturated compound in the pres- US.Patent 3,859,201 ence of a mixture of a H,O soluble unreduccd Ru In a process for converting a hydrocarbon charge salt and Al,O,. In the examples, A1,0, and Ru stock, the stock is contacted with a catalytic chloride are milled togethcr. composite consisting of a porous carrier material containing 0.01-2'); Pt group metal, O.OI--Z<,!(, Re, Hydrogen Isotope Exchange Catalyst 0.1-3.5% halogen and Bi in an amount sufficient ATOMIC ENERGY OF CANADA LTD. to result in an atomic ratio of Bi to Pt group metal British Patent 1,394,089 of about O.I:I to about I:I. A longer life Pt group metal catalyst for exchange reactions is obtained by hydrophobing the Ruthenium-Promoted Fluorided Alumina support, e.g. with a polyolefin or polyacrylate. PHILLIPS PETROLEUM CO. U.S. Patent 3,864,425 Thus a Pt/A1,0, catalyst may be replaced by apt/ A method of isomerising paraffin hydrocarbons polystyrene catalyst. containing 4-8 C uses a catalytic composition consisting of a Ru-promoted fluorided Al,Os Platinum Group Metal Catalysts catalyst containing SbF,-HF. BRITISH PETROLEUM CO. LTD. British Patent 1,397,293 Reforming with Promoted Platinum-Iridium Small amounts of an alkali or alkaline earth metal, Catalysts when added to a C-supported Pt catalyst, g,ive a EXXON RESEARCH & ENGINEERING CO. marked increase in its dehydrocyclisation activity. US.Patent 3,867,280 The additive such as sodium is present in an A process for improving the octane quality of amount of 5-100 at. based on the 0.01-5:* Pt naphtha consists of contacting the naphtha in an on the support. on-oil porrion of an operating cycle at reforming conditions with a catalyst composite including a Platinum-Coated Catalysts porous inorganic oxide support, 0.1-2 :(, halogen, JOHNSON, MATTHEY & CO. LTD. 0.05-3:," Pt, 0.05-3'& Ir and 0.5-';,;5 Fe or Bi British Patent 1,399,453 based on the total weight of the catalyst, and in a A heterogeneous catalyst for use at high tem- subsequent portion of an operating cycle, burning peratures in reducing or non-oxidising conditions of deposited coke with an 0,-containing gas. has a refractory carbide, nitride, sulphide or silicide support which is coated with magnesia, Nuclear Hydrogenation of N-Aryl Poly- preferably in a thickness of 0.0004-0.5 inches amides depending on its intended use, before the Pt UNIROYAL INC. U.S. Patent 3,867,443 group metal or alloy is deposited on it. The A method for nuclear hydrogenation of an N-aryl magnesia layer acts as a heat barrier, e.g. in ICE polyamide to an N-alicyclic polyamide consists of exhaust gas catalytic converters. contacting the N-aryl polyamide with H, in the presence of an acid-treated Rh hydrogenation Hydrocarbon Conversion Catalysts catalyst at 5-25OCc. STE FRANCAISE DES PRODUITS POUR CATALYSE British Patent 1,400,345 Catalyst Production of Nitric Acid A catalyst for use in hydrocarbon conversion, e.g. DEUTSME GOLD- & SILBER-SCHEIDEANSTALT naphtha reforming, of long life and improved US.Patent 3,873,675 mechanical properties consists of an Al,O, In a process of forming NO, by the gas phase support carrying Pt, Ir and Nb. Preferably the oxidation of NH, with air in the presence of a Pt- catalyst contains 0.005-1~/u Pt, O.OO~-I~(, Ir and containing catalyst, an improved catalyst consists 0.005-5 7; Nb. of 55-70:'o Pd, 1-6% Rh and/or Ru and the balance Pt. Hydrocarbon Reforming Catalyst AIR PRODUCTS & CHEMICALS INC. Platinum-Tin Catalyst Regeneration British Patent 1,400,491 CHEVRON RESEARCH co. US.Patent 3,875,049 A reforming catalyst of improved life consists of Hydrocarbons are hydroconverted over a catalyst an AlzOs support having a surface area of at least consisting of 0.01-5 Pt group metal, 0.01-5~;(~Sn zoo m2/g a content of 25-50% y. type A1,0,, and 0.1-3% of a halogen on aporous solid support, less than 5% q type and the balance y type and a such as SiO,;Al,O,, and the spent catalyst is bulk density of less than 0.55 kg/l which carries regenerated by heating it with a gas containing 0.05-0.5% Group VB metal oxide and 0.2-1.5:; oxygen and a halogen.

Platinum Metals Rev., 1975, 19, (4), 164 Three Metal Hydroconversion Catalyst by repeatedly impregnating an A1,0, support UNIVERSAL OIL PRODUCTS CO. with a solution containing Ir and 0ssalts and then U.S. Patent 3,878,089 reducing the salts. A new hydroconversion catalyst has a spinel, SiO,, A1,0, or other known support carrying Coated Support for a Catalyst 0.01-2% Pt or Pd, 0.01-2% Ir, Bi in an amount JOHNSON, MATTHEY & CO. LTD. giving an atomic ratio of Bi to Pt or Pd of 0.1- German Offen.2,450,664 I :I and o.1-3.5% halogen. A catalyst, e.g. for NO, removal in spent gases from a HNO, plant, consists of (a) an elongated Support for a Three Metal Conversion metal support made from a refractory steel alloy Catalyst of 3-40% Cr, I-IOO/, Al, at least 5% Co and/or UNIVERSAL. OIL PRODUCTS CO. at least 72% Ni with at least 0.5% C, remainder U.S. Patent 3,878,125 Fe coated with (b) an oxide layer and (c) a Pt A mixture of Al,Os and a zeolite is used to group metal, Ag, Au or their alloys in a catalytic support a catalytic mixture of Pt or Pd, Ir and a layer. Thus Kanthal D foil may be coated with Group IVA metal such as Pb or Ge. Typically Al,Os and then with Pt. 0.1-20% zeolite is used with Ala03to support 0.0~2%of Pt or Pd, 0.01-2% Ir and 0.01-50/0 Group IVA metal. HOMOGENEOUS CATALYSIS

Four Component Dehydrogenation Catalyst Production of 2-Methyl-1,P-Butanediol I. DU PONT DE NEMOURS & CO. UXIVERSAL OIL PRODUCTS CO. E. U.S. Parent 3,878,131 U.S. Patent 3$59,369 A dehydrogenation catalyst consists of or A process for the production of a-methyI-1,4- Al,O, butanediol consists of (I) hydroformylating another support carrying 0.01-2% Pt group metal 1,4-butenediol with CO and He at a HJCO (Pt or Pd), o.o1-5% Sn, O.OI-~?/,Ge and 0.01- 5% of an alkali or alkaline earth metal. In one molar ratio of at least 0.1,50-2SO0c and at an example isobutylene is obtained from isobutane elevated pressure in the presence of a catalytic amount of a phosphine complex of Rh, Co, Ir, or using a catalyst containing 0.75% Pt, 0.2% Ge, 0.20/, Sn, 0.60/, Li and less than chloride. Ru and (2) hydrogenating the hydroformylation 0.15% reaction product using a conventional hydrogena- tion procedure. The preferred catalyst for high Platinum-Indium-Molybdenum Reforming yields of 2-methyl-1~4-butanediolis a phosphine Catalysts complex of rhodium, such as RhHCO(PPh,),. EXXON RESEARCH &? ENGINEERING CO. U.S. Patent 3,880,748 Condensation of Alcohols The octane quality of naphthas is improved by CONTINENTAL OIL co. U.S. Patent 3,860,664 reforming them over a mixture of 0.05-2% Pt, High molecular weight hydrocarbon alcohols 0.01-2% Mo and 0.05-2% In on A1,0, or another inorganic oxide support. are formed by condensing a reaction mixture consisting of at least one lower molecular weight alkanol having a methylene group adjacent to the Platinum Catalyst for Hydrocarbon Con- hydroxylated C atom, an alkali catalyst and a version catalytic amount of a Pd(I1) halide or (Y)$d(X), STE FRANCAISE DES PRODUITS POUR CATALYSE where Y is ammonium or an alkali metal and X French Appl. 2,234,922 is a halogen. A new catalyst, for hydrocarbon conversion reactions, has a support, preferably A1,0,, Palladium Catalyst for Condensation of carrying o.oog-~.o% Pt, 0.005-1.076 Ru and Alcohols o.o0~-5~~Mn or Re. CONTINENTAL OIL CO. US.Patent 3,862,994 A process of producing higher molecular weight Platinum-Containing Catalyst hydrocarbon alcohols consists of condensing at STE FRANCAISE DES PRODUITS POUR CATALYSE least one lower molecular weight alkanol having a French Appl. 2,234,923 methylene group adjacent to the hydroxylated A new catalyst, for hydrocarbon reforming and C in the liquid phase at 8o-3oo0C in the presence other conversion reactions, has a support, of an alkali catalyst and a catalytic amount of a I’d preferably A1,0,, carrying o.oo5-1.0% Pt, salt while simultaneously removing H,O as it o.oo5-1.0% Ru and o.oo~-~.oo/oof Ge, Sn, Pb, forms, The alkali catalyst is an alkali metal, Ti, Zr or Hf. alkali metal hydroxide, alkali metal oxide, alkali metal bisulphite or alkali metal hydrocarbon Iridium-Osmium Catalyst alcoholate and the Pd salt has the formula KALI-CHEMIE A.G. German Offen. 2,341,363 Pd(RCOCH=CRO), where each R is a I-IOC A hydrazine decomposition catalyst is obtained hydrocarbon group.

Platinum Metals Rev., 1975, 19, (4), 165 Stereospecific Hydrogenation Process tertiary amine or quaternary ammonium com- DIAMOND SHAMROCK CORP. pound, (c) removing Pt as its complex with the U.S. Patent 3,864,361 amine by organic extraction, (d) reoxidising the A process for hydrogenating 2,s-dimethylpyrrole Ir(II1) to Ir(1V) with the Rh remaining in solu- to z,5-dimethylpyrrolidine consists of contacting tion, (e) adding fresh nitrogen compound to the dimethylpyrrole at 75-160°C and under pH2 complex the iridium present and (f) extracting the of 200-1,ooo p.s.i.g. with 0.2-0.80/, of an un- iridium complex. General Mills's Alamine 336 is a supported RuOzas the sole hydrogenation catalyst suitable amine for both extractions which give a the RuO, having an average crystallite size up to 99% + purity. 1,oooA. Catalysts for Siloxanes GLASS TECHNOLOGY IMPERIAL CHEMICAL. INDUSTRIES LTD. Wired Glass Production U.S. Patent 3,867,343 PILKINGTON BROS. LTD. British Patent 1,394,428 An elastomer composition consists of an organo- As float glass is made, a reinforcing wire, e.g. hydrogenpolysiloxane, an cc-w-dihydroxydi- mild steel wire web, is introduced into the ribbon organopolysiloxane and an organic Pt complex of glass as it passes under a Pt, Pd, Ru, Ir or other catalyst in which the ligand or donor groups are refractory metal flow regulating member which is selected from As, P, S or N and olefins, the groups electrically heated. being capable of donating electrons to form a bond with Pt and a N compound selected from NHs and derivatives of NH, in which the three valences ELECTRICAL AND ELECTRONIC are satisfied by bonding to an atom selected from, C, H, 0, N and Si provided that not more than ENGINEERING one 0 atom is bonded to the ammonia N atom. Copper in Noble Metal Metallisation Metal Rhodium Carbonyl Salts E. I. DU PONT DE NEMOURS & GO. UNION CARBIDE CORP. U.S. Patent 3,878,214 British Patent 1,393,646 New salts, claimed per se, have the formula Me- A balance between cost and performance is struck RhIz(CO),, where M is Al, Ga, Ir, Sc, Y or Re in in printed circuit production by the use of a glass- a trivalent state. They may be produced by three free mixture of noble metal and/or noble metal different methods from Rh carbonyls and are oxide with Cu, Cu,O or their precursors. The useful as catalysts in the reaction of CO and H, to noble metal must be at least 50°6 Pd, and at produce methanol, ethylene glycol, glycerol and least 90% of the particles of both components propylene glycol. must be 5 pm in size or smaller. Electrical Connectors CHEMICAL TECHNOLOGY KAYCHEM CORP. British Patent 1,395,601 A connector consists of a member pressed against Purification of Iridium a heat recoverable member which may be made of U.S. ATOMIC ENERGY COMMISSION a Au-Cd alloy, ZrPd,Rh,,, etc. The recoverable U.S. Patent 3,867,137 member is deformed while cold but recovers its A method for purifying Ir consists of oxidising shape on heating. impure Ir to form volatile Ir03, decomposing the IrO, to condense IrO, as a solid at a point away Resistive Glaze and Paste Compositions from the oxidising step and reducing the IrO, AIRCO INC. U.S. Patent 3,868,334 to Ir metal. A composition for firing into a resistive glaze consists of finely divided RuO,, a glass frit Recovery of Metals from Catalysts consisting of 5575% PbO, z-10% ZnO, 2-100,; JOHNSON, MATTHEY & CO. LTD. MnO, 5-z0% SO,, 5-20% BeO, and 0-5"/0 German Offen. 2,443,146 ZrOa and a temporary liquid binder. The metal content of catalysts, e.g. Pt on a cordierite support, is recovered by stripping off a layer containing the metal from the catalyst TEMPERATURE surface and then processing the product. MEASUREMENT Separation and Purification of Metals Platinum Probe for a Thermometer MATTHEY RUSTENBURGREFINERS (PROPRIETARY) LTD. J. M. BRUYERE German Offen. 2,459,623 German Offen. 2,457,672 An amplifying circuit is used with a thermometer Pt, Rh and Ir, present as salts in an acidic solution having a Pt probe and a recoupling stage is fitted are separated and purified by (a) reducing the to the amplifier to compensate for the non-linear Ir(1V) to Ir(III), (b) introducing a secondary or change of Pt resistance values with temperature.

Platinum Metals Rev., 1975, 19, (4), 166 AUTHOR INDEX TO VOLUME 19

iPage Page Page I Page Abou-Zahra, A. A. 115 Caulton, K. G. 116 Fort, D. 114, 157 Itagaki, T. 31 Adachi, K. 156 Chaston, J. C. 135 Foster, A. J. 117 Ivashchenko, Yu. N. 31 Agarwala, U. 158 Chattopadhyay, T. 70 Foster, T. E. 77 Iwasaki, I. 159 Ahmad, N. 32 Chen, H. S. 31, 71 Frankel, E. N. 76 Aika, K.-I. 75 Chepaikin, E. G. 76 Freidlin, L. Kh. 35 Alcazar, H. B. S. 33 Chernova, G. P. 76 Furukawa, G. T. 48 Jackson, J. S. 71 Aleem, A. 74 Chernysbkova, A. 35 M. F. Jaklevic, R. C. 32 Alekhin, A. P. 72 Chcrnyshova, T. A. 95 Jamieson, H. C. 157 Allard, K. D. 71 Chisholm, M. H. 100 Gadalla, A. A. 156 Jasinski, R. 72 Alter, E. 32 Chou, C.-P. P. 156 Gajendragad, M. R. 158 Jeeves, I. 158 Anderson, H. U. 70 Christoe, C. W. 30 Gallagher, J. S. 48 Jeitschko, W. 72 Anderson, J. R. 72 Cbristou, A. 37 Garipov, Z. V. 73 Jelinek, F. J. 70 Andersson, Y. 72 Chu, C. W. 157 Garnett, J. L. 119 Joebstl, J. A. 156 Appel, M. 116 Chudinov, M. G. 114 Gasser, R. 117 Jonsson, L. 76 Appleby, J. 116 Clarke, J. K. A. 75, 114 Gault, F. G. 160 Arajs, S. I15 Cochrane, R. W. 115 George, A. M. 117 Asprey, L. S. I58 Compagnon, P. A. 33 German, R. M. 145 Avilov, V. A. 76 Contour, J. P. 75 Kaewchansilp, V. 72 Gillespie, G. R. 117 Avramenko, M. V. 116 Cooper, B. 141 Kajiwara, S. 30 J. Given, R. 36 Corollenr, S. 74 garpinski, Z. 114 Gogol’, N. A. 1 18, 160 Katzer, J. R. 34 Goodgame, D. M. L. 158 Kavathekar, B. J. 116 Baboian, R. 32 Gopalakrishnan, I. K. Kawamiya, N. 156 Danyluk, S. 70 117 33 Kawakami, M. 72 Bakulin, R. A. Das, B. K. 157 Goto, K. S. 72 Bambakidis, G. 114 Khalaff, K, 70 Dawson, P. T. 116 Griffith, W. P. 60 Banks, R. L. 76 Khan, A. A. 92 Davis, K. P. 119 Grigor’ev, L. S. 119 Bard, J. E. 77 Khan, M. M. T. 161 Day, H. M. 37 Grishina, T. M. 34 Khor’kova, N. N. 75 Barletti, R. 77 Dedushev, N. F. 72 Gryaznov, M. 34 V. Khrapova, E. V. 34 Barth, R. 159, 160 Dehand, J. 158 Guai, L. 118 Kiffen, A. A. 157 Bartholomew, C. H. 161 Deiseroth, H. 32 J. 118 Diamond, 161 Kinoshita, K. 74, Bartoletti, I. 76 S. E. 32 Dieck, H. A. 161 Kmchner, S. Bass, J. 114 Hajek, M. 74 115 Dixon, L. T. 159, 160 Kleykamp, H. Becker, J. 115 Ham, V. 145 Klimisch, R. L. 161 Dobroserdova, N. B. 117 Beille, J. 31 Hammad, F. H. 115 119 Dorofeev, Yn. A. 30 Kobozev, N. I. Hamann, C. 118 34 Beketaeva, L. A. 75 Drosdziok, S. I16 Kobylinski, T. P. Belluco, U. 11 Harris, I. R. 157 Kogan, S. B. 73 Duncan, D. M. 74 Harrison, J. A. 33 Berents, A. D. 75 Komarov, V. S. 33 Dydykina, G. V. 33 Hausch, G. 70 31 Bett, J. A. 74 Dyrin, V. G. 33 Koshy, J. Hawthorne, M. F. 36 Kouvel, J. S. 157 Betteridge, W. 50 Heck, R. F. 76, 161 Kozlov, N. S. 33, 117 Bianchi, M. 162 Hedgcock, F. T. 115 31 Eberson, L. 76 Kraus, H. G. Bingham, D. 36 Heinrich, S. 156 71 Egan, C. J. 118 Krause, J. T. Bolshakov, K. A. 162 Hershkowitz, M. 75 160 Ernst, R. 35 Kropotova, N. V. Bol’shakov, P. P. 73 Hirota, K. 119 31 Evans, M. J. B. 30 Kuprina, V. V. 126 Hitzel, E. 161 31 Bond, G. C. 117, Evdokimova, 0. I. 71 Kupyachaya, G. I. Borunova, N. V. 35 Hoang-Van, C. 33 Kuvshinova, N. I. 160 Hoare, J. P. 116 Botteghi, C. 162 Kuznetsova. T. V. 37 Hod, E. L. 36 Bozon-Verduraz, 115 F. Farooq, 0. 32 Hoeschele, J. D. 32 Braca, G. 162 Farr, J. P. G. 114, 156 Hojabri, F. 35 Lazcano, R. L. 35 Bragin, 0. V. 73, 160 Feldstein, N. 33 Hojo, J.-I. 119 Leclere, C. 75 Braunstein, P. 158 Ferguson, G. 158 Hope, J. 50 Leclercq, G. 160 32 Ficalora, P. J. 33 Hoppe, R. 32 Breiter, M. W. Le Corbeiller, C. 154 Firynlina, L. M. 159 Huang, S. 157 Brieger, G. 35 Lemmetti, P. 77 Fischer, 0. 71 Hudson. B. 36 Bronnikov, 0. D. 74 Fischer, R. G. 32 Lemon, T. H. 146, 153 Burch, R. 114 Flanagan, T. B. 116 Leonova, A. I. 117 Bnrnett, M. G. 37 Foley, R. J. 70 Iball, J. 158 Levinter, M. E. 33 Bursian, N. R. 73 Fornasini, M. L. 31 Iles, G. S. 42 Levitin, I. 159 Buss, R. G. 114 Forni, L. 161 Ismail, S. M. 74 Lieberman, D. S. 157

Platinum Metals Rev., 1975, 19, (4),167-168 167 Page Page Page Page Liederman, D. 34,72 Oates, W. A. 116 Sadykov, F. F. 73 Tardy, M. 115 Loewenstein, K. L. 82 O’cinneide, A, 160 Sagert, N. H. 16 Tarudczi, T. 156 Logacheva, L. I. 34 O’Leary, K. J, 37 Saillant, R. B. 32 Taylor, B. W. 34 LOW, J. 31 Ostermaier, J. J. 34 Salvi, G. 73 Taylor, K. C. 75, 161 Lou, s. s. 71 Otterson, D. A. 30 Shrkiny, A. 118 Taylor, R. 14 Lupprich, E. 158 Oudeman, A. 76 Sasovskaya, I. I. 114 Terry, L. E. 115 Lyashenko, A. I. 35 Owen, W. S. 30 Shrana, G. 162 Thomas, F. L. 76 Lynch, J. F. 71 Ozaki, A. 75 Schifter, I. 76 Thomas, L. R. 162 Lyons, J. E. 161 Schirber, J. E. 70 Thomas, S. 115 Schlesinger, M. 33 Thomson, A. J. 71 Paez-Pedroza, M. 76 Schmelz, H. 159 Thompson, D. T. 88 McGuire, G. E. 70 Paine, R. 158 Schoenberg, A. 76 Tmdall, R. F. 42 Macdougall, M. 158 T. Palenzona, A. 31 Schubert, K. 156 Tkachenko, I. B. 70 Mackliet, C. A. 14 Pavlikhin, B. M. 73 Schulz, H. 32 Tolle, H. J. 21 Markov, S. S. 119 Pavlov, A. I. 73 Searles, R. A. 49 Tom, G. M. 161 Martell, A. E. 161 Paxson, T. 36 Sedriks, A. J. 119 Tomashov, N. D. 76 Martsenyuk, P. S. 31 E. Pedrosa, M. P. 35 Semenova, A. D. Treyvaud, A. 71 Martynyuk, T. G. 34 159, 160 Peng, Y. K. 116 Tromel, M. 158 Mashchenko, A. I. 74 Sercombe, E. J. 2, 118 Pennella, F. 76 Tsintsevich, V. M. 1 16 Masters, C. 157 Sermon, A. 117 Peresie, H. J. 32 I?. Maurel, R. I60 Seryshev, G. A. 119 Perona, J. J. 14 Maurer, A. 32 Seville, A. H. 96 Ualikhanova, A. 74 Petersen, L. 72 Medovoi, I,. A. 47 J. Shalaev, V. I. 70 Urisson, N. A. 34 Petr6, 76 Meier, J. S. 30 J. Sbekhobalova, V. I. 34 Usov, Yu. N. 160 Pierce, R. W. 117 Menshikov, A. 156 Shestakov, G. K, 35 Plunkett, T. J. 75 Men’shikov, A. 2. 30 Van Rantwijk, F. 76 Polovov, V. M. 157 Shimamura, T. 75 Merker, P. 115 Shimomura, K. 72 Vasil’ev, A. M. 35 Polyhnszky, 6. 76 Sbirinskaya, L. P. 33 Vedenyapin, A. A. 159 Mestroni, G. 158 Ponec, I14 V. Shliomenzon, N. L. 118 Vinogradov, S. N. Meyer, C. D. 36 Ponomarev, B. K. 157 Siebert, H. 116 72, 159 Miller, R. F. 31 Pouteau, R. M. L. 16 Sigan, A. L. 159 Visser, C. 74 Milova, L. P. 73 Preobrazhenskii, A. V. Sigurd, D. 71 Voloshinskaya, N. M. Mokrousov, L. N. 34 73, 160 Simbirskii, D. F. 119 114 Volponi, L. 115 Mijllers, F. 21 Sindellari, L. 115 Voltz, S. E. 34, 72 Morrison, R. J. 37 Siaitsyn, N. M. 162 Rahinovich, G. L. Voorhoeve, R. J. H. 75 Mostovaya, L. Ya. 33 Sinkevitch, R. M. 75 33, 117, 159 Voss, J. 158 Mozhaiko, V. N. Skrigan, E. A. 117 117, 159 Ragaini, V. 161 Ramakrishnan, S. 116 Smirnova, A. L. 74 Muellner, W. C. 157 E. Waldron, M. B. 115 Smith, F. J. 93 Mukhedkar, V. A. 116 Rand, D. A. J. 32 Warren, R. 71, 115 Murabayashi, M. 115 Rand, M. J. 162 Smith, R. J. 30, 114 Webster, D. E. 36 Rao, V. 115 Murahashi, S.-I. 75 IC. Snider, J. W. 74 Weise, M. 116 Rasadkina, E. N. 37 Sokol’skaya, A. M. Murani, A. P. 30 Williams, G. 30 Ravdel’, M. P. 71 34, 35, 74 Murarka, S. P. 59 Williams, J. M. 72 Reed, J. 36 Sokol’skii, D. V. Wimber, R. Murav’eva, G. P. 3 1 T. 31 Reiff, K. H. 29 118, 160 Wise, M. L. H. 156 Mushenko, D. V. 35 Reilly, M. L. 48 Sorokin, I. N. 72 Wiskiak, J. 75 Remeika, J. P. 75 Spaepen, F. 156 Wolf, G. 115 Woods, R. 32 Nadykto, B. T. I18 Restivo, R. J. 158 Spencer, A. 162 Wopersnow, W. 156 Narayana, K. L. 71 Richards, P. J. 30 Sreedharan, 0.M. 116 Nast, R. 158 Roberts, D. 117 Srikrishnan, V. 33 Yoda, R. 31 Natarajan, K. A. 159 Robertson, A. J. B. 64 Stepanov, V. V. 95 Roos, I. A. G. 71 Stephan, J. J. 114 Yoshida, N. 119 Navin, T. J. 37 Yuasa, S. 119 Root, G. S. 70 Strathdee, G. 36 Nemoshkalenko, V. V. Yurtaeva, V. K. 31 114 Roshko, R. M. 30 Strel’nikova, Zh. V. Nestrick, T. J. 35 Ross, P. N. 118 119, 160 Nicholson, M. E. 70 Roth, J. F. 12 Stretzker, B. 14, 115 Zaidman, N. M. 73 Zakumhaeva, G. D. 75 Nixon, J. F. 22 Ronlet, R. 35 Strohmeier, W. 161 Zanella, E. 73 Norikov, Yu. D. 74 Rusalina, L. V. 159 Sturm, w. 116 Zassinovich, G. 158 Northrup, C. J. M. 70 Rusby, R. L. 71 Swain, J. R. 22 Zetts, J. S. 114 Norton, P. R. 30 Russell, T. W. 74 Swamy, K. M. 71 Znbareva, N. D. 159 Nurgozhaev, K. Kh. 34 Rytvin, E. I. 47 Swindells, B. 110 Zuidwijk, J. G. P. 74

Platinum Metals Rev., 1975, 19, (4), 168 SUBJECT INDEX TO VOLUME 19 a = abstract Page Ca talysts (eontd) Page Acetic Acid, Rh complexes in methanol Palladium-Nickel, monolithic support, carbonylation 12 reduction of NOx by, a 161 Azelaic Acid, catalyst for the synthesis of 88 Palladium-Rhodium, dehydrogenation of cyclohexane on, a 34 Palladium-Ruthenium, monolithic support, Catalysis, history of 64 reduction of NO, by, a 161 Catalysts, Iridium, complexes, buta-l,3-diene Palladium Sulphide, hydrogenation of hydrogenated to butenes and butane by, a 37 2-methylpentene-2 over, a 75 complexes, isomerisation of pent-1-ene Pd/Ala03,hydrogenation and isomerisation to pent-2-ene over, a 36 of hexanes on, a 74 complexes, oxidation of benzaldehyde Pd/y-AI,O s, hydrodealkylation of toluene on, catalytic activity of, a 119 over, activity of, a 117 hydrogenation activity of, excess free Pd/AlaOa,ionising radiation on, a 118 surface energy of, a 76 Pd/AlaOs,liquid-phase oxidation of cumene hydrogenation of methylacetylene on, over, a 74 selectivity of, a 119 Pd/AlaO,, packed-bed reactor, hydrogenation metal-polymer, CoH, hydrogenation of u-methylstyrene over, a 74 over, a 37 Pd/A120,, toluene dealkylation on, a 159 Iridium-Gold, films, conversion of n-hexane Pd-Au/A120,, reaction of hexane on, a 160 and n-butane on, a 75 Pdtresin, hydrogenation of acetylene Ir/y-AllOs, toluene, reaction on, a 117 compounds on, a 76 Ir/v-AIs03,interaction between, hydrazine Pd/SiOa,liquid-phase oxidation of cumene decomposition over, a 75 over, a 74 Ir/AlaOs,toluene dealkylation on, a 159 Pd/SiOl-AlaO,activity of, hydrogenation of Osmium, complexes, OsClH(PPh,) 3, butylbenzenes and benzene on, a 118 hydrogenation of 1-alkenes over, a 76 Pd/zeolite, activity of, a 118 Os/y-Al10 I, hydrodealkylation of toluene Pd/zeolite (CaA and CaX), hydrogenation of over, activity of, a 117 dimethylethynyl-carbinol on, a 118 Os/AI2Os,toluene dealkylation on, a 159 Pd/zeolite, stability of, storage of, a 160 Palladium, black, hydrogenation of olefins over, a 117 Pd-Ru/monolithicsupport, reduction of NOx black, liquid-phase oxidation of cumene on, a 118 over, a 74 Platinum, black, hydrogenation of acetone borohydride reduced, hydrogenation of and isopropyl alcohol on, a unsaturated compounds over, a 74 black, hydrogenation of hexyne-1 on, a '42 chloro-complexes, selectivity of, a 35 black, hydrogenolysis of butanes on, a 118 complexes, acetoxylation of aromatic black, interaction of acetone and isopropyl compounds, a 76 alcohol with, a 159 complexes, amidation of aryl, black, liquid-phase oxidation of cumene heterocyclic and vinylic halides over, a 76 over, a 74 complexes, hydrogenation of CaHa and complexes, PtH(SnCI,)(PPh&, CIHl over, a 35 isomerisation of pent-1-ene to complexes, oxidation of benzaldehyde pent-2-ene over, a 36 on, catalytic activity of, a 119 complexes, oxidation of benzaldehyde on complexes, PdClaPh,P, carboxylation catalytic activity of, a 119 of fats over, a 76 deactivation of, a 34 complexes, PdPh,P, carboalkoxylation diesel exhaust purifiers 2 of aryl, benzyl and vinyl halides over, a 76 films, hexane and methylcyclopentane conversion of alcohols into unsymmetrical reactions over, a 72 secondary or tertiary amines over, a 75 gauzes of, a 118 -x-complexes, polymerisation of hydrogenation activity of, excess free cycloolefins with, a 35 surface energy of, a 76 hydrogenation of epoxycyclododecadiene complexes, PdCla(C,HsCH) z, isomerisation of pent-I-ene to over, a 35 cis- and trans- pent-2-ene, a 36 hydrogenation of methylacetylene on, hydrogenation activity of, excess free the selectivity of, a 119 surface energy of, a 76 hydrogenation of olefins over, activity hydrogenation of epoxycyclododecadiene and selectivity of, a 117 over, a 35 isotope orientation in, exchange of hydrogenation of methylacetylene on, polyphenyls on, a 119 the select!vity of, a 119 metal-polymer, CeH(I hydrogenation hydrogenation of xylose over, a 75 over, a 37 metal-polymer, COHOhydrogenation "- monolithic, thermal deactivation of, a 72 over, a 51 NH3 oxidation on, a 117 rare earth activation of, hydrogenation NH3oxidation, crystallite size effects of cyclohexane over, a 74 on, a 34 reaction of hydrocarbons on, a 74 odour and fume control by 49 reduction of NO over, production of production of D1O over 16 NHs over, a 34 reduction of NO over, a 34 resin complexes, hydrogenation of ally1 skeleton, effect of temperature, alcohol over, a 35 adsorption of H, by, a. 34 synthesis of conjugated dienes on, a 161 skeleton, heat of adsorption of H a on, a 34 transfer hydrogenation over, a 35 Platinum Metals, auto emission, Pb poisoning Palladium-Gold, reaction of hydrocarbons I, of 141 on, a 14 fixation of N, over, a 161 Palladium-Iron, activity of, synthesis of halogen exchange between alkyl azelaic acid over 88 halides over, a 161

Platinum Metals Rev., 1975, 19, (4), 169-172 169 Catalysts (conld) Page Catalysts, Rhodium (conrd) Page in pollution control, a 118 hydrogenation of epoxycyclododecadiene on y-Al,Os. demethvlation of toluene over, a 35 on, a 33 hydrogenation of methylacetylene on, on y-A1,OJ, hydrodealkylation of the selectivity of, a 119 toluene over, activity of, a 117 hydrogenation of xylose over, a 75 preparation of, small particles 126 metal-polymer, C,He hydrogenation Platinum-Iridium, skeleton, interaction of over, a 37 acetone with, a 160 reduction of NO over, a 34 PlatinumYRhodium, electrochemical skeleton, effect of temperaturc, oxidation of Haon, a 118 adsorption of Haby, a 34 gauzes of, a 118 skeleton, heat of adsorption of HZon, a 34 skeleton effect of temperature, Rh/AI1O,, toluene dealkylation on, a 159 adsorition of HIby, a, 34 Rhodium-Palladium, dehydrogenation of skeleton, heat of adsorption of Hnon, a 34 cyclohexane on, a 34 Platinum-Tin, complexes, hydrogenation of Rhodium-Platinum, electrochemical acetylene hydrocarbons over, a 35 oxidation of HIon, a 118 Pt/AlaOs,activity of, the effect of gauzes of, production of, a 118 S-containing poisons on, a 160 on v-AlP08,hydrodealkylation of characterisation of by alkene toluene over, activity of, a 117 titration, a 117 skeleton, effect of temperature on, chemisorption of H, on, dispersion of adsorption of Haby, a 34 Pt for, a 73 skeleton, heat of adsorption of H, on, a 34 conversion of cyclic hydrocarbons on, a 33 Ruthenium, activity and the exccss free cyclotrimerisation of C,H, into benzene surface energy of, a 76 over, a 73 complexes, hydro enation and dehydrogenation of cyclohexane over, a 117 isomerisation 0%alkenes over, a 162 effect of pore diameter on activity, complexes, hydrogenation of ketones stability and selectivitv of. a 33 and kctoximcs over, a 162 flameless-heaters, a . . 73 complexes, hydrogenation of mono- and formation of cyclopentanes on, a 73 di-enes on, a 162 hydrogen adsorption by, a 159 complexes, isomerisation of pent-1-ene i.r. active H species adsorbed on, a 160 to pent-2-ene over, a 36 Ir addition to, dehydrogenation of complexcs, oxidation of amines on, a 161 cyclohexane on, a 33 complexes, (PPh,)RuHCl, specific ortho isomerisation of 2,2-dimethylbutane deuteration of triphenylphosphine on, a 160 over, a 36 liquid-phase oxidation of cumene over, a 74 complexes, RuCI,(PhaP),, hydrogenolysis preparation and composition of, a 33 of carboxylic acid anhydrides on, a 161 Re additions, aromatisation of complcxe!, RuH,O\T d(PPh 3) n-heptane over, a 73 isomensation of 1 -pentene over, a 76 toluene dealkylation on, a 159 dual state behaviopr of, a 75 vapour-phasc-. hydrogenation .- of C,H. hydrogen adsorption on, a 159 over, a 73 hydrogenation of epoxycyclododecadiene Pt-Au/AllO,, reaction of liexane on, a 160 over, a 35 PtjC, C.- and C,-dchydrocyclisation of hydrogenation of methylacetylene on, alkanes on, a 160 selectivity of, a 119 crystdllite growth of, a 74 hydrogenation of xylose over, a 75 surface of dispersed, a 34 perovskites, NO reduction over, a 75 Pt-Pd/SiO,, crystal phases in, a 73 reduction of NO over, a 34 Pt/SiOl, adsorption, hydrogenation of supported, reduction of NO on, a 161 cyclohexene on, a 119 Rn/Al,O,, dehydrogenation-hydrogenolysis characterisation, of alkene titration, a 117 of n-pentane over, a 161 group 11-IV additions to, aromatisations toluene dealkylation on, a 159 of hydrocarbons over, a 73 Ru/y-Al,O,, hydrodealkylation of toluene liquid-phase oxidation of cumene over, a 74 over, activity of, a 117 Pt/zeolites, activity of, a 33 hydrogenation of aliphatic ketones adsorption of Haon, a 34 over, a 35 formation of, high dispersed metals, (I 74 Ru/C, alkali metal-promoted, adsorption of Rhodium adsorption and catalytic Nzand Hzby, a 75 proper'ties of, a 75 Ruthenium-Palladium,monolithic support, black, hydrogenation of ally1 alcohol reduction of NOx by, a 161 on, a 34 complexes, anion radicals of Corrosive Environments, Pt alloys in 47 indigosulphonic acid, hydrogenation of olefins over, a 76 Electrical Conductors, Palladium-Silver, thick film, complexes, carbonylation of CH,OH on 12 for screen-printed circuits 146 complexes, hydrogenation.~ of mono- and Platinum-Silver, thick film, physical and diIenes on, a 162 electrical properties of 153 comolexes. hvdroformvlation of olefins Electrical Contacts, Platinum, Gold, Titanium, on, 0x0 prbcess pIa6ts 93 complexes, oxidation of benzaldehyde utilising thin layers of, a 119 on, catalytic activity of, a 119 Platinum Silicon-Silicon, made from CVD complexes, rcduction of NO by CO Pt, a 162 over a 36 Rhodium plating for 92 complixes, RhC1(PhsP)s, D1-CIH,OH Electrodeposition of, Palladium, kinetics of, a 33 exchange in CcH,-C2HsOHover, a 36 Palladium, SnCI,/PdCI,/HCl.for, a 33 complexes, RhCI(PPh B)3 hydrogenation Palladium-Bismuth, on electrical contacts, a 159 of mesityl oxide on, a 161 Rhodium, for electrical contacts 92 hydridometallocarboranes, preparation Electr*es,,Palladium, Pd hydride, pH, stability of, a 36 and lifetime of, a 72

Platinum Metals Rev., 1975, 19, (4), 170 Electrodea (conrdj Page Palladium (contd) Page Platinum, clad anodes of, a 32 diffuse reflectance study of, oxidation of, a 115 cyclic voltammetric studies on, a 159 flakes, for H solid storage 145 Hzadsorption on, effect of CO on, a 32 H separation by 50 rotating disc, a 72 interpolation of, in n-doped BaTiO, Platinum-Oxygen, 0,reduction on, ceramcs, a 159 ring-disc. a 116 ions, photoreduction of 21 reduction of 0,on, a 1I14 powder, sintering of, a 70 Platinum-Rhodium chemisorptive and pressure-composition isotherms of Hain, a 30 catalytic properiies of, a 32 reaction of H with, a 116 Rhodium-Platinum, chemisorptive and Palladium Alloys, age-hardenable for springs 29 catalytic properties of, a 32 glassy, formation and stability of, a 71 Rhodium-Zirconium. skeleton. adsorption of glassy, thermal cxpansion and density of, a 71 HZon, a 116 glassy, transition temperature of, a 31 Ruthenium, dimensionally stable anodes, a 37 Palladium-Chromium-Tungsten, sintering Electrolytes, Palladium, powder, dissolution in, a 72 and oxidation behaviour of, a 31 Electroplating of, Platinum group metals, practical Palladium-Cobalt, Curie temperature of, a 30 aooroach to. a 117 Palladium-Copper, adsorption of H by, a 114 Platinum,’on refractory metals from molten valence band structure in, a 114 salt bath I5 Palladium-Gallium-Germanium, constitution of, a 156 Palladium-Germanium, crystal structure of, a 156 Fire-resistance, rubber, Pt in 109 Palladium-Gold, mechanical properties of, a 70 Palladium-Gold-Silicon, mechanical properties Glass, manufacture of fibres 82 of, metallic glasses, a 156 Palladium-Hydrogen, concentration dependence of, supcrconducting Hallmarking of platinum 63 transition temperature in, a 70 Heavy Water, production of 16 ajP miscibility gaps of, a 156 Hydroformylation, new technology for 93 superconductivity in 14 Hydrogen, separation of, from gas mixtures 50 superconductivity in, ion implantation solid storage 145 in, a 115 Palladium-Hydrogen-Silver, electrical resistivity of, a 114 Indium, complexes, dimethyl( I-naphthy1)arsine Palladium-Iron, Curie temperature of, a 30 with, a 115 heat capacity of, ordered and complexes, diolefinic, a 158 disordercd state of, a 115 complexes, trans- IrCl(CeHa)(PPha)8, Palladium-Lead, absorption of H, by, a 71 preparation of, molecular structure of, a 158 Palladium-Manganese, strengthening of, a 71 compounds, fluoride, reductive syntheses Palladium-Nickel, magnetic properties of, a 3 1 of, a 158 optical and magnetooptical properties density of, melting point, a 31 of, a 114 melting of, history of 155 Palladium-Platinum, high temperature oxidation of, a 31 resistancc to molten glass, air 47 Iridium Alloys, Iridium-Iron-Molybdenum, Palladium-Rare Earths, crystal structure of, a 31 magnetic and superconducting propertics of, a 71 Palladium-Rhodium-Nickel, field dependent Iridium-Platinum, low temperature properties susceptibility in, spin fluctuations in, a 115 of, a 70 Palladium-Ruthenium, cemented carbides manufacture of international standards with, sintering of, a 71 in 110 tensile properties of, a 70 Palladium-Silicon, glassy, defects in, a 31 Iridium-Zirconium, intermediate phases of, a 3 1 Palladium-Silver, H, diffusion membranes of, Iridium Oxide, free energy of formation of, a 116 comparison of, a 114 Hadiffusion membrane of, physical properties of, a 157 Laboratory Apparatus, H permeable Pd metal low-temperature electrical resistivity membranes. detection of airborne S-compound of, a 30 by, a 117 mechanical properties of, a 70 Palladium-Silver-Hydrogen, electrical resistivity of, a 30 Metre, centenary of the convention of 110 Palladium-Tin, electrodeposition of, microhardness and contact resistance of, a 72 Osmium, compounds, fluoride, reductive Palladium-Titanium, metal ceramic, corrosion syntheses of, a 158 properties of, a 76 extraction of, with trialkylphosphine Palladium-Yttrium, H2diffusion membranes oxides, a 162 of, comparison of, a 114 compounds, Os(1Vj-amino acids, Hgdiffusion membrane of, physical composition and stability of, a 32 properties of, a 157 Process, rhodium based catalyst for 93 Palladium Silicide, films, spectroscopy analysis 0x0 of, a 115 structure of. formed on Si. a 71 Palladium, complexes, antitumour, preparation Platinum, chemisorption of 0 on, a 156 of, a 32 complexes, alkynyl, a 158 complexes, crystal and molecular structure complexes, antitumour, &-binding by, a 158 of, a 158 complexes, antitumour, interaction with complexes, dimethyl(1-naphthy1)arsine dinucleotides, a 71 with, a 115 complexes, antitumour, new major classes compound, PdoP,crystal structure of, a 72 of, a 32 compound, PdPS, crystal structure of, a 72 complexes, antitumour, preparation of, a 32 compounds, fluoropalladates(II), complexes, coloured, formation of, a 32 preparation of, a 32 complexes, dimethyl( 1-naphthylj arsine density of, melting point, a 31 with, a 115

Platinum Metals Rev., 1975, 19, (4), 171 Platinum (contd) 1'age Platinum Metals-(conrd) 1'age complexes, H-D exchange at a saturated C oxidation of a descriptive survey of 135 in, a 157 thermodynahic properties of 48 complexes, homotrimetallic cluster of, a 158 trifluorophosphine complexes of, recent complexes, one-dimensional conductor, developments in 22 thermal expansion coefficient of, a 116 complexes, stabilisation of C ions in the Platinum Silicide, Pt-PtSi interface, formation organic chemistry by 100 of, a 70 complexes, vinyl rearrangement of, a 116 Pollution Control, automobile emission, compounds, crystal and molecular structure influence of design 141 of, a 158 diesel exhaust gases, Pt catalyst for 2 compounds, for the production of fire- industrial processcs, Pt catalyst systems for 49 resistant silicone rubber 109 compounds, Kz[Pt(CN),]CI,.i*3Ha0, crystal structure of, a 32 Resistance thermometers, Platinum, dew point compounds, KaPt(CN)4Bra.r,3Ha0. hygrometer incorporating, a 117 electromagnetic resonance in, a 32 easily calibrated, versatile, a 71 compounds, KaPt(CN)&Bra.a.3H 10, thick film 42 neutron diffraction study of, a 72 Rhodium, chelates, organometallic, reactivity of, a 159 coordination polymer, preparation of. a 116 complexes, dimethyl(1-naphthy1)arsine density of, melting point, a 31 with, a 115 effects of vacancies in, physical properties of 96 complexes, diolefinic, a 158 films, deposition of, radio-frequency complexes, oxidative reaction of halogens sputtering for 59 to, a 158 films, thermal desorption of H from, a 114 films, growth and structure of, a 31 Haand DIadsorption on, exchange and equilibration on, a 116 Rhodium Alloys, Rhodium-Cobalt, magnetic hallmark 63 order in, a 157 heat of adsorption of Haon, a 30 Rhodium-Nickel, thermodynamics of hydroxoplatinates(IV), preparation of, a 158 antiferromagnetism to ferromagnetic interpolation of, in n-doped BaTiOs transition in. a 157 ceramics, a 159 magnetic properties of, a 157 Janety, M. E., history of 154 Rhodium-Palladium-Nickel, field dependent organometallic chemistry of, review of susceptibility in, spin fluctuations in, a 115 book on 11 Rhodium-Platinum, films, reaction of alkanes physical properties of 96 on, a 114 plating from molten salt bath 15 four point-probe cell of, a 117 stabilised carbonium ions in the organic high temperature creep of, a 70 chemistry of 100 high temperature resistance to molten vacancy formation energy in, a 1 I4 glass, air A7 in manufacture of glass fibres 82 Platinum Alloys, Platinum-Chromium, electrical intercrystalline rupture of 95 resistivity of, antiferro-magnetism of, a 115 Rhodium-Thorium, thermodynamic in, electric resistivity of, temperature intermetallic phases in, a 115 dependence of, a 30 Platinum-Cobalt, Curie temperature of, a 30 Ruthenium, cemented carbides with, sintering of, a 71 70 V-Ru compounds, high pressure structural Platinum-Gallium,phases of, a transformation of, a 157 Platinum-Gallium-Gernium, phases of, a 70 Ruthenium Alloys, Ruthenium-Iron, low Platinum-Gallium-Nickel, constitution of, a 156 temperature resistivity of, a 71

Platinum-Gold.I, &ns. thermal desorution of Ruthenium-Niobium, displacive H from, a 114 transformations in near-equiatomic, a 151 Platinum-Hafnium, coatings of, a 33 Ruthenium-Palladium, cemented carbides Platinum-Iridium, low temperature properties with, sintering of, a 71 of, a 70 Ruthenium-TiC, sintering behaviour of, manufacture of international standards microstructure of, a 115 in 110 Ruthenium-Titanium, corrosion resistance tensile properties of, a 70 of, a 119 Platinum-Iron, Curie temperature of, a 30 Ruthenium-Uranium, thermal expansion of, elastic constants of, a 70 density and microhardness of, a 115 magnetic structure of, a 30, 156 Ruthenium-Vanadium,fault formation in, a 31 ordering of the Y phase in, a 30 Ruthenium Trichloride, properties, preparation Platinum-Iron-Nickel,magnetic properties and applications of 60 of, ordered and disordered, a 156 Platinum-Palladium, high temperature resistance to molten glass, air 47 Silicone Rubber, Pt in fire-resistant 109 Platinum-Rhodium, high temperature creep Spring Alloy, age-hardenablc 29 of, a 70 Superconductivityin Palladium-Hydrogen alloys 14 high temperature resistance to molten glass, air 47 films, reaction of alkanes on, a 1i4 Temperature Measurement, Pt resistance four point-probe cell of, a 117 thermometer for 42 in manufacture of glass fibres 82 Pt wire temperature sensor. a 17 intercrystalline rupture of 95.. Thermocouples, Ir :Ir-Rh, for high temperature Platinum-Tin, films, reaction of alkanes on, a 114 measurements (1700-210OoC)~a 162 Platinum-Titanium, contacts, corrosion Platinum-refractory materials, for high behaviour of, a 119 temgerature measurement, a 119 Platinum-Zirconium, coatings of, a 33 Pt:13 ARh-Pt, stabilisation of metal- Platinum Metals, Debye temperature in, a 71 sheathed, a 77 introducing the nitrosyl functionality Transistors microwave power, PtSi-Ta-Au, into, a 116 metallisation system for, reliability of, a 37

Platinum Metals Rev., 1975, 19, (4), 172