PLATINUM METALS REVIEW

A quurterly survey of reseurch on the platinum metuls urrd of dwelopments in their applications in industry

VOL. 8 JULY 1964 NO. 3

Contents

Platinum Alloy Permanent Magnets 82

Alternating Current Polarisation of Noble Metal Surfaces 90

Production of Ultra-pure Hydrogen 91

Platinum Metal Salts and Complexes as Homogeneous Catalysts 92

Electrical Resistivity of Refractories 98

Platinum Metals in Electrical Contacts 99

Carbon and the Platinum Metals at High Temperatures 101

Deformation of Zone-melted Iridium Single Crystals 102

Ethylenediamine Complexes of Ruthenium 106

Abstracts 107

New Patents 115

Communications should be addressed to The Editor, Platinum Metals Review Johnson, Mutthey & Co., Limited, Hatton Garden, London, E.C.1 Platinum Alloy Permanent Magnets

THE DESIGN OF MAGNETIC CIRCUITS FOR PLATINAX I1

By L. A. Ford, B.s~. Research Laboratories, Johnson Matthey & Co Limited

In applications of this type, it is essential Plalinax 11, fl: cobalt-platinurn allw, is for magnetic circuits to be properly designed, one of the most powerful permanent so as to ensure that effective use is made of magnet materials knwvn. Because of its the properties of the magnetic material. This high performance, its principal uppli- is particularly important when a high per- cations are in miniatwised tinits where formance material such as Platinax I1 is to size and weight considerations are ofthe be used, and necessitates redesign of the utmost importonce, or where the geo- magnetic circuit if a material of lower per- metry of de magnet excludes the use formance is to be replaced. of odier materials. It is reudib fabri- cated and machined, mabiing magnets Operating Characteristics of complex shape to be mlariufac!ured to The performance of a permanent magnet close lolerancos, and it will operate for material is shown by its demagnetisation long periods in highly corrosive environ- curve. A typical curve for Platinax I1 is ments. maximum advani- To obtain fhe given in Fig. I illustrating, together with age from its use, it is necessary to design the derived energy-product curve, the three magnetic circuits carefully so IW to properties of residual induction (BJ, coercive exploit as fully as possible thmagnetic force (H,) and maximum energy-product characteristics of the alloy. Data are @H)rnax. given in this ortick that will assisc Although these figures are valuable in engineers make the most effeccive use to making comparisons between different mater- Phtinax IT. of ials, they give only an approximate guide to the way a magnet will function in service. Final performance depends very largely upon It is some years since investigations by a the point at which the magnet works on, or Johnson Matthey research team into alloys of adjacent to, its demagnetisation curve. This is the cobalt-platinum system led to the de- governed by factors that can often be con- velopment of Platinax 11, an extremely trolled, such as magnet shape and the type powerful permanent magnet material. of external circuit in which it operates. Since then the principal applications of this For example, the working point of a magnet alloy have been for miniaturised units, such that operates free from stray magnetic fields as hearing aids and electric watches, where lies on the demagnetisation curve provided advantage is taken of the exceptionally high that the magnet is magnetised in its circuit magnetic performance of the material, and in and is not subsequently disturbed. Its instruments where powerful magnets must be magnetic performance is determined by the subjected to highly corrosive conditions, such amount of energy that it makes available, and as meters that measure and control the flow this is proportional to the product (B xH) at of corrosive liquids. the working point. The available energy

Platinum Metals Rev., 1964, 8, (3), 82-90 82 This hearing aid by Forti- phone Limited contains two Platinax 11 magnets in disc form, one .003 inch thick by -& inch and the other .005 inch thick by fc inch. By the use of Platinax II magnets tlLe combined microphone, amplifier and earphone unit has been considerably reduced in size and weight without loss of sensitivity

therefore reaches a maximum value at the The working points of four cylindrical (BH),, position and in order to obtain magnets are shown in Fig. 2 on the demagneti- maximum economy of magnetic material a sation curve for Platinax 11. Each magnet was magnet should, whenever possible, operate at measured in three separate circuits, covering this point, i.e. at BdHd in Fig. I. a wide range of self-demagnetising conditions. It can be seen that even under arduous BH PRODUCT ‘open-circuit’ conditions (Fig. za) relatively I o7 5 I06 I I 7000 short Platinax I1 magnets operate satis- 8, - 6480 factorily. The addition of a cylindrical iron extension produces some improvement in 6000 economy (Fig. zb), while still further im- provement is obtained by placing the magnets 5000 in an iron yoke (Fig. zc). The effect of the improvement is clearly shown hy comparing 4000 the sizes of magnets operating at approxi- _-. VI VI mately (BH)ma,. For an open-circuit magnet, 3000 j a length/diameter ratio of one-half is required, v m whereas for a magnet operating in the yoke - 2000

1000 Fig. 1 The high values of coerciue,force (HJ and energy-product ( BH)for Platinax 11 are indicated by the demagnetisation and energy-product curves.

r I For maximum eronomy of material a magnet - so00 -3000 -1000 should work at a point on the demagnetisation curue H (OERSTEDS) rorresponding to (BH)max,i.e. at RdHd

Platinum Metals Rev., 1964, 8, (3) 83 fB a: OPEN CIRCUIT A 6,O

c H 0 Fig. 3 The working point of a magnet subjected to a demagnetisingfield follows the curve from M to N. Whenthe$eld is removed, a partial recovery is made and the working point moves along a recoil line to the position P. The performance of the magnet undergoes a corresponding change

the ratio is reduced to one-quarter, represent- ing a saving of 50 per cent in magnet material. The overall size of the magnetic circuit is naturally increased by such measures, but this may be justifiable if space and weight limitations are not severe.

1000 Recoil Permeability A magnet that operates in a demagnetising

I' I I -5000 - 3000 - 1000 field suffers a loss in performance that is only FIELD H (OERSTEDS) partially regained when the field is removed. 7000 The extent of its recovery is determined by the recoil characteristics of the material from 6000 - which it is made. This can be appreciated v) 5000 $ by considering a magnet that operates at a -< point M on the demagnetisation curve (Fig. 3) 4000 until, on being partially demagnetised by a z field, its working point follows the curve to 3000 U the point N. In the absence of further 2000 g demagnetising forces it will remain there until the field is removed, whereupon, instead of LOO0 retracing the curve to M, it will move along a recoil line to the point P, which becomes the -5000 ' - 3000 - 1000 new working point. The performance of the FIELD H (OERSTEDS) magnet undergoes a corresponding change in magnitude. Fig. 2 A magnet's performance is governed by In order that the magnet shall have the its shape and the type of circuil in which it works. minimum reduction of performance, it is iWeaaurement of the working points of Platinax 1 I magnet systems shows that (a)high performance is necessary for the line Nl', whose slope is a obtained from short, open-circuit magnets. Greater measure of recoil permeability, to lie as economy is achieved by (b) adding a short iron close as possible to the demagnetisation extension and by (c) placing the magnet in an iron yokr curve. In the ideal case when both lines have

Platinum Metals Rev., 1964, 8, (3) 84 Fig. 4 The demagnetisa- I 16000 tion curves of various per- AVERAGE RECOIL PERMEABILITIES manent magnet materials A= ALCOMAX m 14000 are shown, together with B = ALNICO (High Coercivity) 5.2 values of average recoil per- C = 357oCOBALT STEEL l2000 meability. Unlike high- D COLUMAX E = MAGNADUR 3 (B~F~~~o,~)1.05 energy materials having 10000 more “rectangrdar” curves, F = PLATINAX II the recoil lines of Platinax G=RECO 2A H =TKONAL GX aooo 2 II lie close to the main BH 34 curve for a relatively large 6000 range, indicating high SLOPE-1.16 capacity to recover from the eflects of demagnrtising 40# .fields 2000

-5000 -4000 -3000 -2000 -1000 H (OERSTEDS) the same slope, point P would coincide with points would recover almost completely on point M, and the change in energy would removal of the field. be zero. The demagnetisation curves of some per- Platinax I1 is one of the few materials whose manent magnet materials are shown in Fig. 4, recoil lines lie very close to the main BH curve. together with published values of average Many other high-energy materials have recoil permeability. Curves for the more demagnetisation curves of more rectangular common high-energy materials, such as shape, and although these exhibit good recoil Ticonal GX and Alcomax 111, are clearly properties over the upper sections of the of a more rectangular form. curve, they are not maintained where the curves become steep. As a result, a de- The Magnetic Circuit magnetising field that causes a temporary Energy produced by a permanent magnet is lowering of working point on to the steep used in two ways. Its purpose normally is to section of the curve causes, on its removal, a provide a flux across a gap, but to do this substantial reduction of available energy. energy is also used in losses around the Comparisons, made in the table, between remainder of the circuit. In practice, wasted the slopes of the recoil lines (ur) and the energy generally far exceeds that which is demagnetisation curve for Platinax IT, show usefully employed and in order to ensure the remarkable similarity in values around the adequate performance these losses must be (BH),, point. It is evident that mignets taken fully into consideration. operating in demagnetising fields at these The losses are of two types. Those requiring least compensation are the “series” or reluctance losses Recoil Pronerties of Platinax I1 caused by inadvertent air gaps and by any associated Magnet Working Point Recoil Slope of H 6 Permeability Demagnetisation iron path. These can be (oersted) (gauss) (!4 Curve catered for by increas- ing the length of the -2000 4000 1.13 1.16 magnet by a small factor, -3000 1.14 I .34 2800 usually between 5 and 40 -3600 I900 1.16 1.66 per cent.

Platinum Metals Rev., 1964, 8, (3) 85 The second type of loss is caused by leakage Summing the magneto-motive forces around flux, that is flux which passes outside the this circuit: useful gap and therefore cannot be used. This LmHW--LgHg= 0 produces a very considerable effect on magnet performance, since it generally wastes be- or L,Hw=LgHg (1) where L,= magnet length tween 50 and 95 per cent of the total energy BW,Hw= working point of maznet produced. Its magnitude depends mainly Lg=length of air gap upon circuit geometry and this allows certain Hg==fieldin air gap measures to be taken to avoid unnecessarily high losses, for example, by ensuring that Furthermore the flux in the magnet is the same circuit components are spaced sufficiently far as that in the air gap hence: apart. Unfortunately leakage losses cannot be &Arn= BgAg (2) eliminated, and so compensation must be where Am =magnet area made for them by increasing the cross-section Ag -gap area of the magnet, generally by a factor of between &=gap flux density 2 and 20 times. ( ;Hg numerically)

From equations (I) and (2):

Am’ __BgAg BW Vm=LgHg‘Ag BwHw where V, =- magnet volume Therefore, applying the factors to correct for circuit losses : L,-=LgHg- X K, Fig. 5 A ring magnet with a short air gap HW Am’BgAgXKz- BW Whenever possible it is an advantage to Vm -LgHi2AgX K1Kz make the largest increase at the point farthest BwHw from the gap (i.e. at the neutral point) as this section must be large enough to supply the where in general K, lies between 1.05 and total of both useful and leakage flux. As the 1.4 and K2lies between 2 and 20. gap is approached, the amount of “leakage” Evaluation of the constants can sometimes to be provided for diminishes, and the re- be made, but this involves long and often quired increase in section can be progressively complex calculations. It is far more con- reduced. venient to base a design upon past experience The problem of finding suitable dimensions wherever possible, and to assist in this is approached by considering a hypothetical measurements have been made on specimen magnetic circuit in which all the energy Platinax I1 magnet systems. produced by the magnet is usefully employed. This condition is nearly achieved by the Magnetic Field Measurements simple magnet shown in Fig. 5, consisting of a Figs. 6 and 7 show flux distributions close ring having a very short air gap across which to the pole faces of cylindrical magnets all the flux is assumed to flow uniformly. operating with various degrees of self-

Platinum Metals Rev., 1964, 8, (3) 86 3000

4000

2000 3000 h ,-. ul VI 3 2 2 4 -a 0 2% v n 9 d 2000 w U LL I000

loco

, I ,817 D 0/, D D DISTANCE FROM MAGNET GAP LENGTH Fig. 6 The axial fields produced by “open- Fig. 8 An improvement on “open-circuit” circuit” Platinax magnets vary with distance from working is obtained by placing the magnet near an the magnet. The effect of the increased self- iron plate. For a magnet with an LID ratio of 1, demagnetisation of shorter magnets is illustrated this results in a 40per cent increase in the maximum by the lower j?elds they produce measured field demagnetisation. The values obtained with remained. This is illustrated in Fig. 8, which open-circuit magnets indicate that fieIds shows the field intensities at three positions diminish rapidly with distance. in a variable air gap separating a magnet Some improvement in maximum field was from an iron plate. Whereas the maximum apparent when the open circuit conditions field measured on an open circuit magnet were moderated, although the tendency for with an L/D ratio of I was 2500 gauss fields to diminish rapidly with distance still (Fig. 6), when the same magnet was placed near the iron plate the maximum field in- creased to 3500 gauss. 2000 Further improvements in performance t1 were obtained by placing the magnets between - EDGE FIELD iron cylinders of similar diameter, each having ul ... an L/D ratio of 4. The field intensities shown UI 3 I in Fig. 9 were obtained with the magnet in Q: I NS contact with one cylinder and separated by a y 1000 short air gap from the other. Using this -W LL

Fig. 7 Edge fields produced by “open circuit” Platinax II magnels vary in a similar way to thosp on the axis. However, because the magnetic field v2 D diverges to a much greater extent near the edge, the DISTANCE FROM MAGNET resultant field intensities are lower

Platinum Metals Rev., 1964, 8, (3) 87 Fig. 9 Improved performance is obtained by extending the magnetic rircuit with iron cylinders. The increase in .field over “open-circuit” jigures ranges from approximately 50 per cent for thlongest magnet (LID- 1) to nearly 250 per cent for the shortest (LID= ). The axial fields were measured at positions 1,2 and 3, and the edge Jields at positions 4, 5 and 6

demagnetising field causes it to operate on a recoil line. Further reductions in flux can occur as a result of careless handling before or during assembly.

W Although Platinax I1 is highly 1000 resistant to demagnetising forces, it is good practice to safeguard against possible loss of per-

0 D formance by magnetising after GAP LENGTH GAP LENGTH assembly whenever possible. This is particularly true for very short arrangement, the magnet having an L/D magnets in which self-dernagnetising forces ratio of I gave a maximum measured field of are high. Apart from safeguarding their approximately 4,000 gauss. performance, the likelihood of contamination from magnetic debris is reduced. Magnetic Stability Apart from the demagnetisation forces In designing a magnet for a particular job encountered before assembly, magnets fre- it is important to know how it will react when quently operate in demagnetising fields that subjected to demagnetising forces. If mag- would, in normal circumstances, cause a netisation is carried out before assembly into reduction in their performance. To provide its circuit, for example, the magnet’s own for greater stability in service a magnet can .- -.s -: 100 - 12O0C m Z x eo- ==Z, zoooc Fig. 10 Platinax ZZ magnets, in common with x Fig. 10 Platinax ZZ magnets, in common with 25OoC otherother types,types, lose lose perfurmanre performanre whenwhen heated. heated. TheThe rate rate 2 60 - \ 35OoC ofof lossloss isis high high at$rst, at$rst, bntbut diminishesdiminishes quichlyquickly until,until, ” afterafter approximatelyapproximately threethree hours,hours, aa stagestage isis reachedreached where little further change occurs. A short prelimi- $ 4o tohere little further change occurs. A short prelimi- 1 nary heat treatment toill enable u magnet to operate un$urmly at temperatures up to ut Zeust 350°C TIME AT TEMPERATURE MI NU TES

Platinum Metals Rev., 1964, 8, (3) 88 be stabilised beforehand by deliberately unless steps are taken to stabilise it. This can applying a demagnetising field slightly in be done by a preliminary heat treatment which, excess of that to be encountered later. while reducing performance, ensures that no further deterioration occurs when the magnet Temperature Effects is used at high temperature. In common with other magnetic alloys, the Often the most convenient method of fixing performance of Platinax I1 drops progressively a magnet is by soldering or welding, either of with increase in temperature, as shown in which can cause a local deterioration. If Fig. 10. Following a moderate rise in tem- magnetisation can be carried out after assembly perature, performance may be restored by the loss may not be permanent, especially in remagnetising after cooling, but at tempera- low temperature operations such as soft tures above 300 to 350°C the losses are caused soldering. by changes in alloy structure which can only be rectified by a special heat treatment. If a Magnetic Holding Power magnet is required to work at temperatures Forces of attraction between magnet poles where these changes occur it will inevitably that are in contact can be approximately suffer a gradual deterioration in performance calculated by using the formula:

(A) NEAR AN IRON PLATE (8) BETWEEN IRON KEY EXTENSIONS D SURFACES IN CONTACT Dz.53‘ m 0.0~5”AIR GAP ... - K 0.1‘‘ AIR GAP ’Oo01 N S 1l/ n0.2”Al.Q GAP

E 0 45O IRON POLE PIECE .2 2000 (SEE DIAGRAM 1 -_ i ATTACHED TO MAGNET w V AND IN CONTACT WITH a PLATE P I000 ! 1 - 0.5 I 0.5 I qD RATIO OF MAGNET Fig. 11 Forces produced by Platinax 11 magnets vary with magnet geometry and the type of circuit in use. Examples oj two basic circuits are given, showing the forces produced under a varipty of conditions

Platinum Metals Rev., 1964, 8, (3) 89 Force in dynes =B2A- Attempts to increase holding power by 87C attaching tapered iron pole pieces to the where A=area of magnet pole face in cm2 magnet have been unsuccessful, evidently B =flux density at contact in gauss because leakage is introduced which cancels It is sometimes necessary to know the the effect of possible flux concentration. forces that exist between magnetic components separated by an air gap. Specimen figures are Economics shown in Fig. 11 illustrating the changes in Platinax I1 contains 76.7 weight per cent mechanical force that occur when the magnet platinum and naturally is of high intrinsic length is altered. Throughout these tests, the value. The magnetic characteristics as out- diameters of magnets, and of extensions lined above are, however, quite exceptional when used, remained at 0.8 inch. and if due attention is paid to careful design, In general, forces produced by magnets economic circuits are feasible. Platinax I1 operating near an iron plate increase steadily obviously has its major applications for with increasing magnet length up to a length/ miniaturised circuits where it is necessary to diameter ratio of approximately three-quarters. have high flux in restricted spaces and where Beyond this point, further increases in length a small magnet can be fabricated from strip produce only small changes. A similar trend or wire. is shown by magnets operating between iron extensions, but in this case the curves begin Acknowledgment to level off at a smaller length/diameter ratio. Acknowledgment is due to the writer’s This agrees generally with the changes ob- colleagues, Dr J. C. Chaston, Mr R. A. served in working point in Fig. 9, and Mintern, Mr R. J. Newman and Mr J. A. illustrates that the effective length of the Stevenson for their considerable help in the magnet is increased by the additional iron. preparation of this article.

Alternating Current Polarisation of Noble Metal Surfaces THE FORMATION OF PLATINUM AND PALLADIUM BLACKS It has been observed that the reproducibility not occur on platinum or palladium and of a platinum electrode can be improved by a oxides were formed here also. pre-anodisation treatment. The explanation Dr Hoare deduces from his study that the of this effect has been in some doubt, and a mechanism of the formation of these blacks recent paper by Dr J. P. Hoare of the General is via the dissolution of hydrogen, since it is Motors Research Laboratories (Electrochimica well known that platinum and palladium will Acta, 19649,(s), 599-605), throws new light react readily with hydrogen, whereas gold, on the matter. iridium and rhodium will not. The break-up The effect of AC currents on small beads of the surface is attributed by the author to of noble metals was studied and it was noted the successive absorption and desorption of that whereas black films were formed on the this hydrogen. surface of platinum and palladium when Further, measurements of double layer treated in this way, no such films were capacity, a technique that can detect changes observed on gold, iridium or rhodium. Some of surface area, confirmed that the platinum oxidation did occur on the gold and iridium and palladium surfaces increased in area after and, if a DC current was superimposed on the polarisation whereas the rhodium surface did AC so that the AC swing was not centred not. The increases of area noted for the gold about a point more oxidising than that and iridium are explained by the formation originally used, then the ‘black’ formation did and reduction of oxide films. J. H.

Platinum Metals Rev., 1964, 8, (3) 90 Production of Ultra-pure Hydrogen A DISSOCIATED AMMONIA DIFFUSION PLANT

The commercial development of the diffusion cell manufactured by J. Bishop & palladium alloy diffusion process for the Co Platinum Works. production of high purity hydrogen recently The anhydrous ammonia is dissociated into moved a stage further with the installation by its constituents at high temperature and the the Drever Company of Bethayres, Penn- hydrogen-nitrogen mixture then compressed sylvania, of a complete plant operating on into the diffusion cell system. dissociated ammonia in the works of Mag- A minimum of 90 per cent of the hydrogen netics Inc. of Butler, Pennsylvania. This derived from ammonia is obtained as ultra- company manufactures magnetic alloys in the pure gas, and a substantial annual saving is form of cores and laminations, and requires achieved by comparison with the cost of the an economical source of pure hydrogen for its purified bottled hydrogen formerly used. heat treatment operations. The installation has now been in continuous The installation includes a IO,OOO gallon operation for well over a year and has led to a anhydrous ammonia storage vessel, a 2,500 significant reduction in the number of rejected cubic feet per hour ammonia dissociator, and parts as well as to a decrease in furnace a 1,500 cubic feet per hour diffusion system atmosphere consumption owing to the more designed around the silver-palladium alloy consistent quality of the gas.

This dissociated ammonia difusionplant, engineered by the Drever Co,produces 1500 cubicjeet per hour of ultra-pure hydrogen for the heat treatment of magnetic alloys. Installed in the works of Magnetics Inc. it employs the siluer-palladium alloy diffusion cells designed and produced by ,J. Bishop & Co Platinum Works

Platinum Metals Rev., 1964, 8, (3), 91-9 I 91 Platinum Metal Salts and Complexes as Homogeneous Catalysts SCOPE FOR NOVEL CHEMICAL PROCESSES

By G. c. Bond, Ph.D., F.R.I.C. Research Laboratories, Johnson Matthey & Co Limited

Olefin complexes of the platinum group metals have recently been recognised as intermediates in a number of homogeneous catalytic processes. Among the reactions undergone by co-ordinated olefins are oxidation, isomerisation, hydrogenation and polymerisation. The oxidation of olefins to aldehydes or ketones catalysed by palladium chloride is already an important commercial process, and it seems likely that many other similar reactions will achieve prominence in the future.

The first olefin complex of a platinum what unstable compounds with silver salts group metal to be discovered was Zeise’s (3). Conjugated olefins do not form salt, K[C,H, PtCl,]. For over a hundred years simple complexes with palladium salts; they after its discovery in 1827 there was little do, however, form stable compounds on further progress in this field, until the work reaction with iron and cobalt carbonyls (2). of Kharasch and of Anderson in the 1930s They also form stable compounds with (I). These olefin complexes have, however, cuprous chloride. Chelating diolefins form been the subject of intensive study during the stable and simple compounds with the past decade (2, 3), with the result that not halides of ruthenium, rhodium, palladium only are large numbers of these compounds and platinum, although the ruthenium known but the structures of many are also compound is probably polymeric : they also understood and applications for them are now form yellow compounds with silver nitrate. being discovered. No simple stable olefin complexes of iron, cobalt, nickel or copper are known: simple Classification of Olefin Complexes olefin complexes of iridium have been For the purpose of classification we may reported but not thoroughly examined (I). divide olefins into three groups: (i) mono- The elements vanadium, chromium, molyb- olefins, (ii) conjugated diolefins (e.g. buta- denum, tungsten and manganese only form diene) and (iii) non-conjugated or chelating stable olefin complexes when other strongly diolefins (e.g. cyclo-1,s-octadiene). With Tc-bonding ligands, such as the TC-cyclo- mono-olefins, the elements ruthenium, pentadienyl radical or carbon monoxide are rhodium, palladium and platinum form present in the molecule (2). These “simple” complexes which contain addition- compounds are termed “stabilised olefin ally only halogen atoms (3). Examples of complexes”. these are the I :I Ru” chloride-olefin com- Another recently discovered class of com- plexes formed with ethylene and propylene, plexes involves the Tc-ally1 (n-C,H,) group or but not isolated (4); [(C,H,), RhCl],; its analogues (2). The compound [(x-C,H,) [C2H, PdCl,],; and [C,H, PtCl,], and PdCl], results on heating palladous chloride Zeise’s salt. Mono-olefins also form some- with ally1 alcohol, and many other related

Platinum Metals Rev., 1964, 8, (3), 92-98 92 compounds can be obtained directly from techniques of infra-red, X-ray and nuclear olefins. The reaction of butadiene with a magnetic resonance spectroscopy have all palladous chloride-nitrile complex gives a been fruitfully applied. It is now established ir-ally1 compound. Compounds of the that in Zeise’s salt and in the related simple general formula (n-C,H& M are known ethylene complexes of platinum and palladium where x=2 when M is nickel or palladium, the axis of the carbon-carbon multiple bond and x=3 when M is chromium, iron or is normal to the plane in which the metal cobalt. “Stabilised” x-ally1 complexes of iron atom and halogens lie (2, 5) as shown here. cobalt and manganese are also known. The diagram summarises the types of olefin complexes formed by the metals of the transition series. The Structure of Olefin Complexes A variety of modern physical methods has been applied to the elucidation of the structure of olefin-metal complexes. The Structure ofthe [C,H,PtCI,]- ion in Zeise’s salt

Platinum Metals Rev., 1964, 8, (3) 93 The carbon-carbon bond is weakened by the The reactivity of the metal-olefin complex co-ordination : it becomes longer and the is often of first importance. The ability of a C=C vibration frequency in the infra-red metal salt to form reasonably stable but not (-1500 cm-l) is lowered. The hydrogen too stable olefin complexes is of itself no atoms, while still coplanar, are displaced away guarantee that those complexes will be from the central metal atom. reactive. The structure of Tc-ally1 palladous chloride Thus for example the silver ion forms a is also known (6): the planes of the three large number of moderately stable olefin carbon atoms comprising the ally1 groups are complexes, but as yet no method has been normal to the axis of the metal-metal bond, found of causing them to react to form any and the carbon-carbon bond lengths are all other product. The reason for this may be equal (-1.3A). that the complexed silver ion has insufficient There have been several theoretical dis- residual bonding capability towards any cussions of the nature of the bonding of further reagents, so that the necessary olefins to metal atoms. It is now generally transition state cannot be formed. agreed that the bonding involves a n-bond, There is much evidence to suggest that formed by overlap of the filled bonding an olefin molecule co-ordinated to a metal atom xz2p molecular orbital of the olefin with a has a reactivity which is different in kind from vacant s or dsp2 hybrid orbital of the metal the normal reactivity of olefins. The act of atom, and also a n-bond, by overlap of the co-ordination decreases the electron density vacant antibonding irz*zp molecular orbital between the olefinic carbon atoms, and hence of the olefin with a filled d or dp hybrid renders the olefin liable to attack by nucleo- orbital of the metal atom. This bonding philic reagents such as hydroxyl or acetate adequately accounts for all the known ions, or indeed any electron-rich species properties of metal-olefm complexes. which is seeking an electron deficient site. It is not possible to judge at the present how The Reactivity of Olefin Complexes far this hypothesis accounts for the reactions In a homogeneous catalytic reaction where undergone by co-ordinated olefins, although the net process is the conversion of an it almost certainly explains the occurrence of olefin to some other species, the original oxidation and hydrogenation processes. To platinum metal salt or complex may be what extent it explains the occurrence of regarded as the catalyst and the olefm-metal isomerisation and polymerisation remains to complex as the catalyst-substrate combination. be seen. Thus :

MXn MXIlO P MXn metal salt or -t metal-olefin +product 3- metal salt or other complex 'leiin 7complex other complex

Thus for a successful overall reaction, the (a) Oxidation and other nucleophilic metal-olefin complex must (i) be formed attacks sufficiently quickly from its components, (ii) Olefin oxidation is the most important, be sufficiently stable (i.e. must not decompose most investigated and best understood of the rapidly back to its components), and (iii) reactions of co-ordinated olefins. The yet not be so stable as to be incapable of Wacker process (7) for the oxidation of reacting to form the product. A proper olefins to aldehydes and ketones (e.g. ethylene balance between these three factors will to acetaldehyde) is accomplished by means of ensure maximum reaction velocity. palladous chloride in an acidic aqueous

Platinum Metals Rev., 1964, 8, (3) 94 medium. Unfortunately the palladous chloride yields vinyl acetate (9). Amines and amides is reduced to metallic palladium during the can also act as nucleophiles: thus the reaction reaction, and it is necessary to have an excess of acetamide with ethylene palladous chloride of cupric chloride present to re-oxidise it. yields N-ethylacetamide (10). The reaction The cupric chloride is thereby reduced to of carbon monoxide with this complex gives cuprous chloride and is re-oxidised by air. P-chloropropionyl chloride (I I) : These processes are represented by the C2H4PdCiz +CO+CH,CI-CH,-COCI+PdPd equations Transesterification of vinyl esters can be C,H,+PdCI, +H,O+CH,CHO +Pd +2HC1 accomplished without reduction of the Pd+a CuC1,+PdCl2+~CuCl palladous salt (7). 2 CuCl+2HCl+~O,-t2 CuCI, +H,O It is worth noting that in all these instances the net reaction being it is a palladium salt which has been used as CaHI-C +O,+CH&HO catalyst. Although oxidation of ethylene- The process of olefin oxidation is thus not platinum complexes does give acetaldehyde, truly catalytic, although the presence of the the rate is too slow to be useful, probably copper salts makes possible a continuous because of the greater stability of the complex. “catalytic cycle”. Higher olefins react more However, aqueous sodium hexafluoroplatinate slowly than ethylene, and temperatures of is rapidly attacked by ethylene with the about 70°C are required: propylene yields formation inter aliu of acetaldehyde: other chiefly acetone, but the yield of ketone olefins diolefins and alkynes behave decreases as the molecular weight of the analogously (12). olefin increases (7). Although there have been several kinetic (b)Isomerisation studies of the reaction (P), the mechanism is In the course of a study of olefin oxidation, still not definitely established. However, it was observed that if the reaction was most of the observations are accommodated stopped before completion the olefin had by a reaction scheme in which an hydroxyl isomerised and that an equilibrium mixture ion attacks the olefin in the complex ion of isomers was present (13). This led to the [C,H, PdCl,]- the remaining steps in the discovery that palladous chloride and its process are shown below. olefin and nitrile complexes catalysed olefin

HH

HI HH H

+Pd + 3C1-

Schematic representation of ethylene oxidation by the Wacker process

There are a number of other homogeneous isomerisation under mild conditions, e.g. at catalytic processes which may be interpreted atmospheric pressure and the normal boiling as nucleophilic attack on a co-ordinated olefin point of the olefin. Neither x-ally1 palladium molecule. If the acetate ion is used as the chloride nor platinum-olefin complexes were nucleophilic in a non-aqueous mcdium, nearly as efficient. Rhodium salts are said to reaction with ethylene palladous chloride isornerise the butenes at 50°C, but no details

Platinum Metals Rev., 1964, 8, (3) 95 are available (14). Little is known of the catalysed by platinum group metal salts and mechanisms of olefin isomerisation by metal complexes : this is the hydrogenation of mul- salts. tiple carbon-carbon bonds, especially the (c) Polymerisation olefmic bond. The first observation in this A third important class of reactions field was that ethylene platinous chloride homogeneously catalysed by platinum metal could act as the catalyst-substrate complex in salts is polymerisation. Mono-olefins, par- the hydrogenation of ethylene at low tempera- ticularly ethylene and propylene, have been tures (20). This work has twice been oligomerised (converted to low polymers, repeated (21, 22), and it appears that the mainly dimers and trimers) by palladium and process may be truly homogeneous if great platinum salts in a variety of solvents at care is taken, but if the temperature is permitted to rise colloidal platinum is about IOOOC and at 1-50 am. pressure (15): under such conditions acetylene sometimes deposited and the reaction becomes hetcro- gives quite high yields of vinyl acetylene. geneous (21). In extension of this, it has Rhodium salts in polar solvents catalyse the recently been reported that a stannous polymerisation of butadiene to almost pure chloride-platinum chloride complex is a tram-polybuta-1~4-diene (14, 16), as does more efficient and a more stable catalyst: it is also iridium chloride (r6), although less also effective for acetylene hydrogenation (23). rapidly. Rhodium chloride in alcohol gives Divalent ruthenium in an anionic form mainly oligomerisation, and butenes and in hydrochloric acid catalyses the hydro- many other products have been recognised genation of olefinic acids such as maleic and fumaric acids at about 80" (4): other com- (14). Mechanisms have not been discussed. Palladium chloride catalyses the dimerisa- pounds containing a conjugated keto-group tion of acetylenic hydrocarbons such as are also readily reduced (24). The kinetics diphenylacetylene, and the complex tetra- of some of these reactions have been studied, phenylcyclobutadiene-palladous chloride and it appears that the rate of complex results (17): on decomposition of the complex, formation is not rate-determining. A a hydrocarbon whose formula is C,,H,, mechanism has been suggested: this supposes obtained (m.p. 430°), but its structure is not the ruthenium (11) chloride species has the yet definitely established (18). The chlorides formula [RuCl,(H,O),]= and that the of palladium, ruthenium, platinum (IV) and olefin can easily displace one water molecule osmium in the presence of an hydridic to give [(olefin) RuCl, (H,O)]=. A hydrogen reducing agent such as lithium hydride molecule is then heterolytically split by this catalyse the oligomerisation of I-heptyne (19). complex, and the hydride ion attacks the complex. If this is so, this is a further (d) Hydrogenation example of a nucleophilic attack on a We come finally to the last major class of co-ordinated olefin. The mechanism is reaction capable of being homogeneously represented here schematically.

c1 c1 ,c1

Proposed schematic mechanism for the hydrogenation of olefins by RuII chloride

Platinum Metals Rev., 1964, 8, (3) 96 The chlorides of ruthenium, rhodium and A second but less widely applicable use of especially palladium in dimethylformamide olefin complexes is in the resolution of catalyse the hydrogenation of dicyclopen- optically-active olefins such as trans-cyclo- tadiene (21). The use of other olefins and octene (27). Use is made of the complex diolehs resulted in the immediate pre- [(olefin) PtC1, am] where am represents an cipitation of metal. That the reactions were optically-active amine. homogeneous was shown by adding thio- phene, which would poison any collodial Summary and Conclusions metal, but in the case of palladous chloride Two broad conclusions emerge from this the rate increased by a factor of four, perhaps survey of platinum metal salts as homogeneous as a result of the formation of a more active catalysts. First, we sense the enormous palladium-thiophene complex. scope for the development of novel chemical processes which is offered by the metal- Other Applications of the olefin system: there are without doubt many more applications awaiting discovery and Co-ordination of Olefins exploitation. It is significant and important Two other applications of olefin complexes, that homogeneous catalytic processes are often in which no net. chemical transformation more selective and specific than the corres- occurs, are worthy of mention. Very ponding heterogeneous processes would be. extensive use of the interaction of olefins and Secondly, there is a pattern of behaviour diolefins with silver ion has been made in the which may have implications in wider fields. gas-liquid chromatographic (GLC) analysis The types of complex formed depend in a of hydrocarbon mixtures (25). The use of way not yet clearly formulated on the silver nitrate dissolved in for example structure of the metal atom (see the diagram benzyl cyanide or ethylene glycol as a on page 93). The reactivity of metal-olefin stationary phase permits the rapid passage of complexes has resemblances to the reactivity saturated hydrocarbons and separation of of olefins adsorbed on metal surfaces. Thus olefins which are otherwise difficult to it is probably no coincidence that palladium separate (e.g. cis-trans isomer pairs). The salts feature largely as homogeneous catalysts use of salicylaldimines and glyoximes of for reactions of olefms, while olefins are nickel, palladium and platinum for this known to be more weakly adsorbed by purpose has also been described (26); a palladium than by platinum (28). Many triethylphosphite-palladous chloride complex details of this correlation remain to be is also effective, but the corresponding explored, but it is certain that we shall platinum compound is not. The gas- witness in the coming years a fruitful chromatographic method is a most attractive interplay between the studies of homogeneous procedure for obtaining both qualitative and and of heterogeneous catalysis. It is also quantitative information on the interaction likely that homogeneous catalytic processes of olefins with metal salts and complexes. will have an important commercial future.

References I J. Chatt, “Cationic Polymerisation”, (ed P. H. 6 J. M. Rowe, Proc. Chem. SOC.,1962, 66 Plesch), Heffer, 1953, p. 40 7 J. Smidt, W. Hafner, R. Jira, R. Sieber, J. 2 R. G. Guy and B. L. Shaw, Adv. Inorg. Chem. Sedlmeyer and A. Sabel, Angew. Chemie and Radiochem., 1962,4,78 (Eng. Edn.), 1962, I, 80 3 M. A. Bennett, Chem. Reviews, 1962, 62, 611 J. Smidt and H. Krekeler, Proceedings 6th 4 J. Halpern, J. F. Harrod and B. R. James, World Petroleum Congress, 1963 ;section 4, J. Amer. Chem. SOC., 1961, 83, 753 Paper 40 5 S. MariBC, C. R. Redpath and J. A. S. J. Smidt, Bull. Assoc. Franc. Tech. Petrole, Smith, J.Chem. SOC.,1963,4905 19631 140,467

Platinum Metals Rev., 1964, 8, (3) 97 8 I. I. Moiseev, M. N. Vargaftik and Ya. K. 17 A. T. Blomquist and P. M. Maitlis,J. Amer. Syrkin, Izvest. Akad. Nauk S.S.S.R. Chem. SOC.,1962,84,2329 Otdel. khim. Nauk, 1963, 1144: Doklady 18 R. C. Cookson and D. W.Jones, Proc. Chem. Akad. Nu& S.S.S.R., 1962, 147, 399 SOC.,1963, I 15 K. I. Matveev, A. M. Osipov, V. F. Odyakov, 19 L. B. Luttinger and E. C. Colthup, 3. Org. Yu. V. Suzdal’nitskaya, I. F. Bukhtoyarov Chem., 1962,27,3752 and 0. A. Emel’yanova, Kinetika Kataliz, i 20 J. H. Flynn and H. M. Hulburt, J. Amer. 1963, 3, 661 Chem. Soc., 1954~76,3393 T. Dozono and T. Shiba, Bull. Japan. 21 P. N. Rylander, N. Himelstein, D. R. Steele Petroleum Inst., 1963,5,8 and J. Kreidl, Engelhard Ind. Tech. Bull., 9 I. I. Moiseev, M. N. Vargaftik and Ya. K. 1962,3961 Syrkin, Doklady Akad. Nauk S.S.S.R., 22 A. S. Gow and H. Heinemann, 3. Phys. 1960,133,377 Chem., 1960,64,1574 10 E. W, Stern, Proc. Chem. SOC.,1963, 111 23 R. D. Cramer, E. L. Jenner, R. N. Lindsey and U. G. Stolberg, J. Amer. Chem. SOC., I I J. Tsuji, M. Morikawa and J. Kiji, Tetrahedron Letters, 1963, 1061 1963, 85,1961 24 G. C. Bond and D. Hawkins, unpublished 12 R. D. W. Kemmitt and D. W. A. Sharp, work J. Chem. SOC.,1963,2567 25 M. E. Bednas and D. S. Russell, Canad. J. 13 M.B. Sparke,L.TurnerandA. J. M.Wenham, Chem., 1958,36,1272 I.U.P.A.C. Conference, 1963:paper ABq-30 C. B. Barrett, M. S. J. Dallas and F. B. 14 R. E. Rinehart, H. P. Smith, H. S. Witt and Padley, Chem. and Ind., 1962,1050 H. Romeyn, J. Amer. Chem. SOC.,1962, 26 G. P. Cartoni, R. S. Lowrie, C. S. G. Phillips 84,4145.~. and L. M. Venanzi, “Gas Chromatography, 15 Consortium fiir Electrochemische Industrie, 1960”, Butterworths, 1960, p. 273 B.P. 887,362 27 A. C. Cope, C. R. Ganellin, H. W. Johnson, 16 A. J. Canale, W. A. Hewett, T. M. Shryne and T. V. van Auken and H. J. S. Winkler, E. A. Youngman, Chem. and Znd., 1962, J. Amer. Chem. Sac., 1963,853276 I054 28 P. B. Wells, Platinum Metals Rev., 1963,7, 18

Electrical Resistivity of Refractories DETERMINATION AT HIGH TEMPERATURES

In selecting suitable refractories for electric held between the two electrodes and resistance melting furnaces it is necessary to know how readings are taken, by means of a modified their resistivity varies with temperature, but Tinsley electrolytic conductivity bridge, at data on this subject are not always available. intervals during controlled cooling. To measure the resistivity of such materials at temperatures up to 15~0°Can apparatus has been designed and built at the Pilkington Brothers Research Laboratories by J. Fenerty and C. E. Smith and is described in a recent paper (Glass Technology, 1964, 5, (2), 78-81). The sample, in the form of a one-centimetre cube, is heated in a vertical muffle furnace, wound with 20 per cent rhodium-platinum wire on a fused alumina tube. This furnace is fitted with two synthetic mullite tubes, each containing a platinum :rhodium-platinum thermocouple and a platinum lead to an electrode. To ensure good electrical contact with the electrodes, two opposite faces of the sample are coated with a thin film of platinum, either by cathodic sputtering or by means of a paste consisting of metallic plat- inum in suspension in an organic medium, The furnace is heated to the maximum temperature required with the test sample

Platinum Metals Rev., 1964, 8, (3) 98 Platinum Metals in Electrical Contacts

PAPERS AT THE GRAZ INTERNATIONAL SYMPOSIUM

Platinum metals and alloys as wrought switching unit was included with the test solids, as bimetals, as powder metallurgy pieces in the cabinet and (b) that the insulation products, and as electrodeposited and on the magnet wire connections in the cabinet evaporated layers were among the contact had degraded within a year. Some hitherto materials discussed at the International unrecognised conditions certainly contributed Symposium on Electric Contact Phenomena to the unexpectedly rapid formation or de- held at Graz in May this year. The official position of poorly-conducting films on the proceedings were formidable; forty-seven metal surfaces. papers were presented to a gathering of over A type of low voltage contact which is fast 300, but fortunately there were good oppor- growing in importance is that of the minia- tunities for some lively informal discussions turised multi-blade connectors involved in the which ranged widely over the subject. inter-connection of one telephone with The types of contacts for which noble metals another. This group includes static separable and alloys have always been particularly fitted connectors which are not normally operated are those which need to remain bright and more than the few times necessary to replace free from surface films so as to provide a low- a failed component in an electronic package. resistance contact path for feeble currents. It is important to recognise, however, that as For some years now a committee of the many as 300 insertions may be required during American Society for Testing Materials has production testing prior to installation. With been conducting ‘field tests’ of crossed-rod these considerations in mind, an extensive contacts and samples of metal foils in closed series of field tests on electrodeposited noble shelters at a marine site at Kure Beach and an contact metals on a copper base have been industrial site at Newark, New Jersey. The made by the Bell Telephone Laboratories in results of exposures of up to two years, louvered cabinets similar to those used by the reported by B. E. Blake of the Components ASTM exposed in New York City, an Division of International Business Machine industrial marine location, in Kure Beach, Corp, Poughkeepsie, New York, are so surpris- North Carolina, a marine environment, and ing that further investigation is being actively at Steubenville, Ohio, a heavy industrial city. undertaken. The specimens were housed in a The results were reported by Richard B. louvered aluminium shelter, provided with a Baker. These, unlike those of the ASTM glass wool filter one inch thick to retain dust tests show no unexpected features and mainly particles and yet to permit free circuIation of bring out the point that thin gold coatings air; in these conditions palladium rapidly over thick silver coatings are not nearly as formed a brown-grey film at Kure Beach and satisfactory as thin rhodium coatings over a grey coating at New Jersey; and even gold thick silver coatings in maintaining a low surfaces developed a very high contact resis- contact resistance. The reason is that silver tance at both sites after 2S months. Tin-lead sulphide formed at the pores of a gold coating alloy surfaces, on the other hand, remained tends to migrate and spread over a large area unexpectedly clear. around each pore. With rhodium, very little It may be significant (a) that a bulky spreading is observed. The most satisfactory

Platinum Metals Rev., 1964, 8, (3), 99-100 99 composite coating so far observed is that Extensive studies on the indentation and formed by depositing first about 7.5~of deformation of contacts operated with and nickel, followed by 0.5~of rhodium and without the presence of a lubricating film were finally 0.5~of gold. This has outstanding described by Dr Alan Fairweather, D. G. M. wear-resisting properties. Shirley and R. E. Fudge, of the British Post The use of platinum metal electrodeposits Office Research Station, with particular for such applications as brush and slip rings, reference to their effect on contact resistance. plugs and sockets, and reed relays, was In a further paper from the same laboratory, described by H. C. Angus of The Inter- Fairweather, F. Lazenby and A. E. Parker national Nickel Company (Mond) Limited, examined the development of resistance and London. microphonic noise produced by vibration of Electrodeposited coatings of palladium, nominally closed contacts. Attention was rhodium and ruthenium all benefit from a given to the effects of vibration in breaking treatment in boiling distilled water after tarnish films, then piling them up and finally plating. This relieves an appreciable propor- dispersing the debris. tion of the internal stresses and removes traces Two contributions from the University of trapped electrolyte which may otherwise College of Swansea by Professor Llewellyn cause insulating films to develop in service. Jones and Dr M. R. Hopkins respectively Ruthenium plating is suggested as better reviewed our present knowledge on the wearing than rhodium for slip rings; rhodium function of the molten metal bridge in causing for semi-permanent contacts, and palladium material transfer between electrical contacts. or ruthenium for reed relays. In Dr Hopkins’ contribution a description The use of evaporated coatings of noble was given of the use of radioactive tracer metals for contacts was described by G. F. P. techniques for measuring accurately the Muller of W. C. Hereaus, Hanau. Large movement of metal from one contact electrode numbers are coated at one time, about 2.5~ to the other. being deposited per minute. The process is Progress in the development of noble metal said to be cheaper than electrodeposition for contact materials to meet specific contact re- gold and silver, and slightly more expensive quirements was described by R. F. Vines, of for the platinum metals, with their higher the Development and Research Department melting point. of The International Nickel Company Inc., A theoretical paper by J. A. Greenwood and New York. This paper showed photomicro- J. B. P. Williamson, of the Burndy Corpora- graphs of one new contact material described tion, Norwalk, Connecticut, described a as ‘ductilised ruthenium’. This consists of mathematical investigation using a computer rounded ruthenium particles bonded by a to evaluate the results of the dispersion of gold-palladium alloy, the composite being asperities on nominally flat surfaces. It was produced by liquid phase sintering. found that while the great majority of surfaces Finally, reference may be made to a paper as prepared give mainly plastic deformation by J. Spergel and E. Godwin, of the United of asperities on contact, it is easy to prepare States Army Electronic Research and Devel- surfaces which will give purely elastic contact opment Laboratories, Fort Monmouth, New the first time they are loaded together. An Jersey, and Dr Jack Anderson, of Standard interesting conclusion arising from these Research Institute, in which an organic studies is that owing to the chance distribu- monomolecular film formed from octadecyla- tion of high asperities two surfaces of large mine-hydrochloride is put forward as a new diameter will have a mean separation greater and unusually effective boundary lubricant than that between two small surfaces under for gold (and presumably other noble metal) the same load. surfaces in sliding contacts. J. C. C.

Platinum Metals Rev., 1964, 8, (3) 100 Carbon and the Platinum Metals at High Temperatures

SOME RECENT METALLOGRAPHIC INVESTIGATIONS

The melting point of the carbon platinum Platinum and palladium will, at high temp- eutectic was determined at the National eratures, decompose tungsten, tantalum and Physical Laboratory in 1934 (I) with exem- niobium carbides (4). This reaction occurs plary precision although this work was not in either the solid or liquid states. On followed up by further constitutional studies. solidification, graphite is thrown out of solu- Nadler and Kempter (2)confirmed in 1960that tion in the form of spheres or flakes, while carbon depressed the melting points of all the the refractory base metal is held in solid platinum group metals, but no attempt was solution. made to determine the composition of these A summary of the melting point determina- eutectics or whether the metals were capable tions of Nadler and Kempter (2) is presented of taking any carbon into solid solution. here. Although this table does not show the Raub and Falkenburg (3) at the Forschungs- composition of the eutectics, it illustrates very institut fur Edelmetalle, Schwabisch Gmiind, directly that the melting point depression have recently done much to remedy these caused by carbon decreases periodically with deficiencies. increasing atomic weight. In this work platinum, palladium, rhodium and ruthenium were melted with graphite, Melting Solidus Metal point temperature fitrn heated for long periods in the solid powdered t, in "C of metal/carbon ("~1 state in contact with graphite, and subjected to alloy t, in "C prolonged exposure at high temperatures to Ruthenium 2310 1941116 0.859 hydrocarbon vapours. All four metals Rhodium I960 16941. I7 0.881 dissolved large quantities of carbon when Palladium I552 15041 I6 0.974 Osmium 3050 1732122 0.90 I melted in graphite crucibles. Platinum, Iridium 1443 21961. I6 0.946 rhodium and ruthenium, on solidification, Platinum 1769 1736&13 0.984 threw out this carbon in the form of graphite flakes. Palladium precipitated spheroidal These determinations were done by the graphite particles. The graphite flakes in 'bracketing'method with an optical pyrometer. platinum codd be converted to the spheroidal The NPL value for the platinum carbon form by remelting the metal in an argon arc eutectic, corrected to conform with the 1948 furnace. International Temperature Scale, is 1730" i: X-ray diffraction studies showed that these 3°C. A. S. D. eutectiferous structures were mechanical mixtures of the metals and graphite. The References lattice parameter data indicated that the solid solubility of carbon in platinum, palladium, I L. J. Collier, T. H. Harrison and W. G. A. Taylor, J. Faraday SOC.,~g34,30, 581 rhodium and ruthenium was vanishingly 2 M. R. Nadler and C. P. Kempter, J. Phyys. small, and prolonged heat treatment at Chem., 1960, 64, 1468 temperatures just below the eutectic points 3 E. Raub and G. Falkenburg, Z. Metallkunde, 1964,559 186 failed to induce any of these metals to take up 4 E. Raub and G. Falkenburg, Z. Metallkunde, any carbon. 1964,559 190

Platinum Metals Rev., 1964, 8, (3), 101-101 101 Deformation of Zone-melted Iridium Single Crystals By H. Hieber, B. L. Mordike,* ma.,and Prof. P. Haasen Institut fiir Metallphysik der Universitat Gottingen, Germany

Iridium is known to possess properties eight times at 3.5 mm./dn. in a vacuum of which make its use at high temperatures 10-5 to 5 x IO-~torr, using a cathode current attractive despite its high cost. It has a high of IOO mA. The high thermal conductivity melting point, 2443"C, and maintains its and high density of iridium made it important strength to high temperatures. In addition, to limit the zone to a very small length, it is extremely resistant to chemical attack Before zoning, the rods were annealed at just and is consequently being increasingly used as under the melting point, usually for about a crucible material. Unfortunately iridium 30 hours, until a vacuum better than IO-~torr is very difficult to fabricate, showing a was attained. brittle behaviour characteristic of more com- The three stages of specimen preparation plex structures and completely unexpected in are illustrated in Fig. I. Photograph (a) shows a face-centred-cubic metal. Face-centred- an as-received rod; photograph (b) shows a cubic metals such as copper and aluminium rod which has been zoned once at a speed of are ductile even at low temperatures. The 3.5 mm./min. The trapped gas is, despite reason for this lack of ductility is not known prolonged previous annealing, still released but it has been suggested that it is due to rapidly during zone melting so that the surface impurities in the bulk or in grain boundaries. becomes uneven. Degassing has generally In the present investigation the characteristic ceased after three passes, when the zone be- deformation parameters of zone-relined irid- comes more stable. Before the crystal can be ium single crystals are compared with those used the unevenness must be smoothed out by of other face-centred-cubic metals. In zoning several times. During these zone passes addition a limited number of experiments on the diameter of the crystal is measured with a polycrystals are described and a comparison travelling microscope which moves at the made with single crystal behaviour. same speed as the cathode, and the diameter of the molten zone is adjusted by moving the Experimental Details upper chuck up or down. A final pass at a Iridium was obtained in the form of 4 mm. constant low speed of 1.2 mm./min. ensures diameter sintered and hot-swaged rods from uniform crystallisation conditions along the Johnson Matthey 8z Co Limited. The initial whole rod as seen in (c). The orientation did purity of the material is shown below. not change along the length of a rod by more than 4'. Since the orientations obtained were ppm by weight in the centre of the standard stereographic Pt Pd Rh A1 Ca Cu Fe Pb Mg Si Ag Na 10 I IOO 3 5 I 20 z 2 50 I 30 triangle it was not necessary to use a seed crystal. These rods were then purified and converted Spectrographic analyses of three adjacent to single crystals by the electron beam vertical sections of a typical zone-refined crystal floating zone method (I). Each rod was zoned showed only the following metallic impurities : *Now at Department of Materials Technology, Ag 0.5 ppm Mg

Platinum Metals Rev., 1964, 8, (3), 102-106 102 Fig. 1 Various stages in the production of a single crystal; (a) as receiued, (b) zoned once, (c) $final crystal ,-\

Although tensile tests would have been Shear strain a preferable it was necessary to use compression COSA, tests because of the limited amount of material J where P -load, A, =original cross-sectional available. The reproducibility of compression area, A, -initial angle between crystal axis and tests is not as good as that of tensile tests slip direction, A =angle during deformation, particularly at high strains when the specimen initial angle between crystal axis and slip deforms non-uniformly. x, plane, 1, -initial length of specimen, 1 = All experiments were carried out in an length during deformation. Instron Universal Testing Machine (Type At low strains the crystal maintained its TT-BML). The temperatures were obtained cylindrical shape but at high strains friction using oil or isopentane thermostats. A strain at the platten crystal interface prevented rate of 7.0 x 10-5sec-l was used. deformation here so that only the middle of The grown crystals were embedded in wax the crystal deformed and the crystal became on a specially designed carrier and cut into barrel-shaped. At this point a compression lengths of about 15 mm. using a paraffin test becomes unreliable. This difficulty pre- cooled, diamond impregnated wheel. The vented an evaluation of T~~~ (T, k) the stress cutting machine permitted exactly parallel at which dynamic recovery first takes place, cuts to be made so that the end surfaces needed and hence a calculation of y, the stacking only to be polished lightly before the crystal fault energy (4). was deformed. It was assumed that the same slip systems Deformation Results operate for iridium as for other face-centred- Fig. 2 shows stress-strain curves of iridium cubic metals: (111) . In a compression single crystals of the orientation indicated, test the crystal axis moves towards the normal deformed at these different temperatures, to the slip plane if the specimen is relatively 78,273 and 473°K. short compared with its diameter (2). The It is apparent that for all metals copper (s), relationships used to convert the load- silver (6), nickel (4) and iridium the stress- extension curves to shear stress-shear strain strain curves exhibit the same basic character- curves were (3): istics. An initial period of easy slide (low rate of work hardening) is followed by a period of

Shear stress T = ~ (I >'sin . cos A (1) A, 1, rapid linear work hardening. The curves

Platinum Metals Rev., 1964, 8, (3) 103 Fig. 2 Typical shear stress- shear strain curves for zone- rejined iridium single crystals of the same orientation at 473, 273 and 78°K.i=7.10-s sec-'

Effect of Annealing in Different Atmospheres The effects of various gases on iridium at high temperatures were investi- gated by annealing single t 5%* a SHEAR STRAIN crystals in these gases and noting any change in the flatten off on onset of dynamic recovery. The mechanical properties at room temperature. major inaccuracy in the evaluation of the Nitrogen, air and argon were chosen, and the parameters was due to non-uniform diameter annealing treatment was twenty hours at of the specimen along its length. Despite the goo to IOOO~C.The hardness change of such smoothing out passes a variation of & 4 per crystals is shown below: cent in the diameter could still be detected. Gas Vickers Hardness (zkg load) From the stress-strain curves the following Argon 205% 5 data were obtained: T~,critical resolved shear Nitrogen 205 & 10 stress as a function of temperature and 011, Air 207% 5 the rate of work hardening in stage 11, As zoned 203k 5 divided by the shear modulus G(T), also as a function of temperature; these data are The indentation, which was made on the plotted in Fig, 3. The values for the shear cylindrical surface, measured about 0.I to modulus were taken from Koster (7, 8). 0.15 mrn, (diagonally). The scatter of

LL 0 Fig. 3 The critical resolved g 200- w .2.1ci3 + shear stress (X), and the rate of _I a 4 LL work hardening 011 divided by 0 shear modulus G (A),asafunc- I- I / tion of temperature for zone- TEMPERATURE refined iridium single crystals.

Platinum Metals Rev., 1964, 8, (3) 104 measurements on such a surface is higher than that for flat surfaces and consequently an average of five measurements was made. All the specimens after annealing remained shiny with the exception of the specimen annealed in air which showed a hard, brittle, blue-black oxide layer (probably IrOJ. This surface layer was very thin and did not seem to affect the bulk hardness. These annealed crystals were then deformed at the same rate as the vacuum prepared crystals. The stress-strain curves for vacuum prepared and atmosphere annealed single crystals were identical in all respects. Recrystallised Specimens

The experiments described so far have all i 2 been undertaken on single crystals. Two EXTENSION techniques were used to produce poly- Fig. 4 Load-extension curves for reerystallised crystals suitable for compression testing : iridium (a) a deformed single crystal was cold-rolled to produce a rectangular rod and Discussion subsequently annealed in the electron The single crystals of iridium investigated bombardment furnace; the percentage here were ductile. Stress-strain curves over a reduction is estimated to be 30 per cent; wide range of temperature were similar to (b) a zoned rod was rotary swaged at about those of other face-centred-cubic metals. The IIOOOCin air to a smaller diameter only difference was that the absolute magni- (10per cent reduction) and recrystallised tude of the critical shear stress of iridium is in the electron bombardment furnace. somewhat larger than of, for example, copper, It would be expected that the second type of silver and gold. This can only partly be operation produced an impurer specimen accounted for by the high shear modulus. The than the first. The recrystallised specimens temperature dependence of the yield stress were coarse grained and several became was similarly small. 8,,/G was c11/3,0and single crystals despite the heavy deformation. independent of temperature as observed for Normal stress-strain curves could be other face-centred-cubic metals. This strong measured only up to the maximum permitted similarity between iridium and other face- load of the Instron machine (Fig. 4). At this centred-cubic metals rules out the suggestion point a compression of 2 per cent had been that in iridium other deformation mechanisms attained. By using a hydraulic press a much are operative. The annealing of single crystals larger load could be applied. The maxi- in air and nitrogen in an attempt to contami- mum deformation attained before cracking nate the crystals and thus influence the was 30 per cent. As can be seen the poly- mechanical properties produced no change in crystalline iridium is also reasonably ductile the properties. These impurities could, and the yield stress a,=2r, is as low as can however, produce grain boundary weakness be expected considering the values obtained and consequently two procedures were used for single crystals (Fig. 2). There was no to produce polycrystals. The polycrystals difference between the two types of poly- were, however, equally ductile at room tem- crystalline specimen. perature whether or not swaged in air at

Platinum Metals Rev., 1964, 8, (3) 105 elevated temperature in the course of pre- crystalline fracture occurred. These authors paration. The polycrystals were not as ductile were also forced to the conclusion that grain as the single crystals but withstood consider- boundary segregation of unknown impurities able deformation at low rates of deformation. is the cause of embrittlement. At high rates of deformation they showed a The authors are indebted to Johnson greater tendency to brittle behaviour but in Matthey & Co Limited for providing the any case withstood rolling 30 per cent in one iridium specimens and for carrying out the pass at a speed of 10 cmlsec. The fracture analyses. tended to be intercrystalline. The impurities present are very much References lower than those usually necessary to produce I B. L. Mordike, Z. Metallkunde, 1961, 52, 587 grain boundary weakness but it may be that 2 R. L, Fleischer,J. Mech. Phys. Solids, 1958, 6, the significant impurities are non-metallic or 301 otherwise not easily determined. 3 E. Schmid and W. Boas, Kristullplastizitat Springer Verlug, 1935, Berlin, page 66 In a similar investigation on rhodium, 4 P. Haasen, Phil. Mag, 1958, 3, 384 Calverley and Rhys (9) were able to deform 5 T. H. Blewitt, Phys. Rev., 1953, 91, 1115 zone refined single crystals by go per cent 6 M. Ahlers, Z. Metallkunde, 1962, 53, 302 without intermediate anneal and yet the 7 W. Koster, 2. Metallkunde, 1948, 39, 1 W. Koster, App. Sn'. Res. Section A, 4, annealed polycrystalline wires could only be 8 329 9 A. Calverley and D. W. Rhys, Nature, 1959, deformed to a very limited extent before inter- 183, 599

Ethylenediamine Complexes of Ruthenium By F. M. Lever, A.R.c.s., PbD., and C. W. Bradford, B.Sc. Research Laboratories, Johnson Matthey & Co Limited So far as is known, no ethylenediamine minoruthenium dichloride, [(NH&Ru]Cl, complexes of ruthenium have been isolated. and the chlorozincate [(NH,),Ru],ZnCl, by The reaction between ethylenediamine and the reduction of ruthenium chloro complexes chloro complexes of ruthenium such as with zinc dust in ammoniacal ammonium ammonium chlororuthenite or ruthenium chloride solution. It has now been shown that trichloride results in the formation of dark by cautiously adding zinc dust to a solution brown viscous solutions from which it seems of ruthenium trichloride in 25 per cent impossible to separate any crystalline deriva- ethylenediamine, boiling under reflux, filter- tives. A technique earlier discovered and ing, cooling, and carefully acidifying the used to prepare ammino derivatives of solution to pH 1-2 crystals of [en,Ru],ZnCl, ruthenium I1 has now been successfully used can be separated. (Found Ru 20.55, Zn 13.37, to produce an ethylenediamine complex of N 17.22, C1 29.10, C 14.93, H 4.93 per cent; ruthenium 11, [en,Ru],ZnCl,. This com- [en,Ru],ZnCl, requires Ru 20.69, Zn 13.39, pound should provide a suitable starting- N 17.21, C1 29.02, C 14.75, H 4.95 per cent). point for the preparation of other ethylene- It has, so far, not been possible to investi- diamine complexes, particularly of ruthenium gate fully the reactions of this compound but I11 since in its reactions it appears to be it has been found to behave similarly to the analogous to the ammino complex [(NH,),Ru] , analogous ammino complex. Thus, when it is ZnC1,. boiled with hydrochloric acid, hydrogen is In a Ph.D. Thesis (London University, evolved and a deep blue complex is formed. 1955) Lever, and at the International Con- Mercuric chloride and chloroauric acid are ference on Co-ordination Chemistry, London, both reduced indicating the powerful reducing 1959 (Special Publication of the Chemical properties of the compound. It is hoped that, Society, No. 13, 1959, 135-136) Lever and in the future, these and other reactions will be Powell described the preparation of hexam- studied andthe productsisolated and identified.

Platinum Metals Rev., 1964, 8, (3) 106 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES 1815°C is 5%, decreasing to 1.5% at 11oo"C. The Pd-rich solid solution forms periteaically from Platinum as a Thermal Conductivity Stan- liquid and a-W at 1815°C~78% Pd. W is 0.5% dard less soluble at IIOO"~.The solid solution lattice parameters have a minimum at 90% Pd. G. A. SLACK, J-APPl. PhYS., 19643 35, (21, 339-344 An evaluation of data on the thermal conductivity The System Palladium-Tungsten-Rhenium K of Pt suggests that Pt would make a reprodu- M. A. TYLKINA, v. P. POLYAKOVA and E. M. cible K standard in the range 75-2047"K. From SAVITSKII, Zh. Nemg. Khim., 1964, 9, (3), 671-673 200 to 2047"K, K conforms to within f zo/o of K=(o.64, f1.8, x Io-4T)Wjcm deg. but further Raising the Re content of Pd-rich alloys in the work, especially at higher temperatures, is re- Pd-W-Re system decreased their melting points quired before adoption of the standard. and electrical resistance but increased their hardness, resistance to deformation and tempera- Absolute and Relative Linear Thermal ture coefficient of resistivity. Microstructural Expansion Coefficients of Vitreous Silica and analysis further elucidated the structure of the system. Platinum L. P. OLDFIELD, Glass Techml., 1964, 5, (I), 41-50 Heat Capacity of Ni-Pd Alloys Work on expansion coefficients was reviewed c. A. MACKLIET and A. I. SCHINDLER, J. Phys. Chem. and standard values are recommended: for Pt:- Solids, 1963, 24, (12)~1639-1643 c~ (50-400"c) = 9.56 X IO-'/"C, a (50-35Ooc) = Measurements in the liquid He range for pure 9.50 X IW6/"C; C( (10-3500~)=9.46X 10-6/"C; Pd and 20, 40, 60 and 80 at.?& Ni-Pd alloys gave for vitreous Si0,:- c( (50--4003~)=0.60x IO-~/OC, electronic specific heat coefficients of 9.38, 10.66, (50-350"c) = 0.61 x Io-E/oc, a(to-350°C) 8.54,7.82 and 7.52 mJ/mole"KZ,respectively, and 0.60 x Io-6/"C; expansion of Pt relative to Si0,:- Debye temperatures 272, 295, 305, 330.5 and 8.88 i0.03 x IO-~/OC. 388°K. The band structure of the system is discussed. Change of Platinum Resistance by Hydrogen R. J. GALAGALI, Br. 7. Appl. Phys., 1964, 15, (z), Alloys of Thorium with Certain Transition 208-209 Metals. 111. The System Thorium-Palladium A glowing Pt filament was cooled by the presence J. R. THOMSON, J. Less-Common Metals, 1964, 6, of even a trace of H, and the resistance decreased (21, 94-99 more as PH, increased. Ar had no effect and air X-ray and metallographic studies at 1000-1500°C had only a minor effect, even at higher tempera- showed that at 10oo"C seven Th-Pd compounds tures. Ageing of Pt and electrical excitation of are stable. The solid solubility of Th in Pd is not H, modified the effect somewhat. It is suggested more than 15-17%. Th,Pd and "ThPd" that energy derived from the wire dissociated H, crystallise at 1162&12 and 1412% 12°C respect- to H at the Pt surface, hence cooling the wire. ively. ThPd, melts above 15oo"C. "ThJ'dpl' and ThJ'd, form peritectically at 1325512 and Oxidation of the Platinum Metals in Air I387f 12°C respectively. ThPd, and another w. L. PHILLIPS, Am. SOC.Met. Trans. Q., 1964, compound occur in the 79-85?! Pd range. Their 57, (11, 33-37 phase relationships are not known. A sharp Oxidation rates were measured in air over the minimum in the solidus-liquidus curve occurs at range 800-1400°C. Each metal obeyed the linear 12"& Th; 1125&12"C. weight loss law. Activation energies were: Os, 1okca1,'mole;Ru,46.1 kca1,'mole; Ir,g.zkcal/mole; New Ferromagnetic 5 :2 Compounds in the Pd, 24.2 kcal/mole; Pt, 25.4 kcal/mole; Rh, 29.6 Rare Earth-Palladium Systems kcal/mole. A. E. BERKOWITZ, F. HOLTZBERG and s. METHFESSEL, J. Appl. Phys., 1964, 35, (3 121, 1030-1031 A Constitution Diagram for the Tungsten- Magnetic data are tabulated for Gd5Pd,, Palladium System Tb5.10Pdi.90, D~,.oPd?.s and Ho,.oaPdl.ge. w. K. GOETZ and J. H. BROPHY, J. Less-Common Gd,Pd, is ferromagnetic below 335"IC. The Metab, 1964, 6, (51, 345-353 other compounds are b.c. tetragonal isostructures X-ray and metallographic studies confirmed that with para- to metamagnetic transitions at 62, 41, no intermediate phase exists in the W-Pd system 27°K. They become ferromagnetic at lower above IXOO"C. The solubility of Pd in a-W at temperatures with very high hysteresis. Energy

Platinum Metals Rev., 1964, 8, (3), 107-115 107 products (B xH)- of 20 to 26 x 10, GOe at and electrical resistivity data from 293 down to 4.2% have been observed. 2°K for a Ru rod confirmed previous results for the pure h.c.p. metal. Values obtained were po= Arsenides of the Transition Metals. VII. o.o18~, pi(9o"K) =0.9~, pi(273"K) -6.72 @cm; The Palladium-Arsenic System Wi(30"K)'0.03~~ Wi(8o"K) =0.53~cm deg wl. G. S. SAINI, L. D. CALVERT, R. D. HEYDING and J. B. TAYLOR, Canad.J. Chem., 1964, 42, (3), 620-629 Ferromagnetism and Incipient Supercon- Seven intermediate phases in the Pd-As system ductivity in a CeRu, +-7.3 GdRu, Alloy were detected by X-ray diffraction and thermal J. J. DRAUTMAN, c. J. ANDERSON and R. DEL GROSSO, analysis. J. APPl. PhW, 1964, 35, (3,:2), 974-975 Measurements between 1.3 and 20°K showed Exchange Inversion in Ternary Modifica- that this alloy is weakly ferromagnetic below tions of Iron Rhodium 4.15'K. T, for CeRu, was 5.1'K; for the alloy P. H. L. WALTER,J. Appl. Phys., 1963, 35, (3/2), was 3.2 "K. A superconducting transition reduced 938-939 the positive susceptibility. The resistance was The exchange inversion temperature T,, residual less, but did not reach zero. magnetisation and maximum magnetisation of Fe-Rh alloys are affected by the nature and Superconductivity of Solid Solutions of Ti amount of transition metal modifiers added. and Zr with Co, Rh and Ir 2 at.% Co, Ni, Cu, Nb, Mo, Ta or W is enough c. J. RAUB and G. w. HULL, Phys. Rev., 1964, 133, to eliminate the inversion. Ru, Os, Ir, or Pt (4-Q A9324934 additions raise T, and Pd, V, Mn, or Au decrease Transition temperature-composition curves for T,. For FeRhIr,, T, increases as x increases z and p-Ti and Zr solid solutions showed that T, from 0-0.25. For FeRhPd,, T, decreases as x rises with increasing valence electron concen- increases. tration n. Small Co, Rh and Ir additions to a-Ti or Zr raise T, by 2 to 4 times. T, has a 4°K Solid Solutions of Rhodium with Copper and maximum for 90 at.?& Ti in the b.c.c. region of Nickel the 8-Ti alloys. H.-L. Luo and P. DUWEZ, J. Less-Common Metals, 1964, 6, (31, 248-249 Superconductivity of Precious Metals and The Rh-Cu and Rh-Ni alloy systems form con- their Alloys tinuous series of solid solutions, as shown by c. J. RAUB, Z. Metallkunde, 1964, 55, (4, 195-199 X-ray techniques. The Rh-Cu alloys are meta- A review of the superconductivity of Au, Ag, the stable. 50 and 75 at.% Cu-Rh alloys annealed in Pt metals, and their alloys. The transition tem- vacuo at 600 and 800°C for seven to ten days peratures are very low. No solid solutions of Au decomposed into two f.c.c. solid solutions with or of Ag but of some of the Pt metals are super- 9.2 and 81.5 at.% Cu concentrations. No conducting. Noble metal additions to group V decomposition or ordering of Rh-Ni alloys was superconductors reduce T,; to group IV they observed after similar heat treatment. increase T,. General features of Pt metal com- pound superconductors are summarised. (4 The Change of Resistivity of Rh after Cold references) Work J. G. M. VAN KUIJK, Physica, 1964, 30, (z), 398-400 CHEMICAL COMPOUNDS 0.25 mm Rh wires had 20p grain size after anneal- ing at 1050"C, restivity of 4.5,uQcm at 0°C and Fluorides of the Noble Metals. Part 111. The 0.53pQcm at -196°C. Load and resistivity Fluorides of Platinum changes at - 196°C and maximum extension, 30% N. BARTLETT and D. H. LOHMANN, J. Chem. Sac., and isochronous annealing curves at -196°C 1964, (Feb.), 619-626 after pulse annealing at temperatures between Attempts to prepare and isolate PtF, and PtF, -196°C and 500°C are illustrated. were unsuccessful. Pure PtF, was shown to be Recovery of the Resistivity of Pt after diamagnetic with a structure similar to UC1,. Complex fluorides of Pt(1V) and Pt(V) have been Deformation at Low Temperature prepared and their properties are discussed. L. c. MENTING, Ibid., 407-409 PtF, is sufficiently strong an oxidising agent to Comparisons of the recoveries for Pt, Rh and Cu oxidise molecular oxygen and this property is after stretching and rolling in liquid Nz are discussed. tabulated. Carbonyl Complexes by Reaction with Resistivity of Ruthenium Alcohols R. J. TAINSH and G. K. WHITE, Canad. J. Phys., L. VASKA, Abs. Papers, 147th Meeting, Am. Chem. 1964, 42, (I), 208-209 SOC.,1964, 4L-8 Thermal resistivity data from 90 down to 2°K Carbonyl complexes including [MX,(CO)L,]

Platinum Metals Rev., 1964, 8, (3) 108 (M=Ru, Os, Rh, Ir), [MX,(CO)L,] On the Study of Mixed Potentials in Noble [MHX(CO)L,] (M=Ru, OS), [MHX,(CO)L,], Metal-Oxygen-Acid Systems [MX(CO)L,] (M=Rh, Ir) have been synthesised J. P. HOARE, Extended Abs. Theoretical Div., without using CO. Certain transition metal Electrochem. SOC.,1964, z, (May), 162-163, abs. halides reacted with some group VA donor ligands 206 (e.g. PhJ?) in alcohols and similar solvents to Rest potentials of Pt, Au, Rh, Pd and Ir electrodes form complexes with CO groups co-ordinated to in 0,-saturated H,SO, solutions were studied as the metals. The CO originated from the solvents. functions of pH, pOE,and electrode pretreatment Some Ethylenediamine Derivatives of Tetra- in order to determine the nature of the potential- valent Platinum determining reactions. If the rest potential is independent of PO,, there may be a metal-metal I. I. CHERNYAEV, N. N. ZHELIGOVSKAYA, LE TI-K'EN and D. v. KURGANOVICH, Zh. Neorg. Khim., 1964, oxide system or a mixed potential. Different polarisation curves at low current densities in 93 (3), 562-568 The following Pt complexes were isolated: 0,- and N,-stirred solutions indicated a mixed EnCl,Br,Pt, EnCl,CIOHPt, EnCl,(NO,),Pt potential. The mechanism for each noble metal was considered. EnCI,ClNO,Pt, EnCl,BrNO,Pt, EnCI,BrNO,Pt, EnCl,IOHPt, EnCl,INO$t, EnCl,NO,OHPt. A Study of Surface Oxides on Platinum They were studied by X-ray and thermal methods Electrodes and their solubilities and conductivities were J. S. MAYELL and S. H. LANGER,J. Electrochem. SOC., determined and tabulated. 1964, 111, (41,438-446. Transition Metal Complexes of Secondary Anodic oxidation and cathodic stripping tests on Phosphines. IV. Some Complexes of smooth Pt, Pt black, and Pt black-polytetra- Ruthenium, Rhodium and Palladium fluoroethylene moulded electrodes showed that R. G. HAYTER, znorg. Chem., 1964, 3, (2), 301-302 the initial oxidation sequence is Pt+Pt(OH),+ Pt(O),, which was used to determine the Pt Chloro complexes of Ru, Rh and Pd were electro-active areas, but that at higher potentials prepared and attempts were made to convert smooth Pt forms Pt(O), and PtO whereas Pt black them to P-bridged complexes, with success forms Pt(O)-,.,. A "tight" PtO structure on only with [PdCl,{HP(CH,)},] converted to smooth Pt at higher potentials may account for [PdCl{P(CH,),}{HP(CH3)z}]2.Two forms, pre- their unusual properties whereas none forms on sumed to be cis and trans, of [RhCI,{HP(C,H,),},] Pt black-perhaps because of irregular Pt atom were isolated. [RhCl{HP(C,H,),},] could only be arrangements and its catalytic behaviour. formed by the [RhCl(C,H,),] ,-di-pheny- phosphine route. Voltammetric Study of the Reduction of Mass Spectrometric Study of Gaseous Oxides Molecular Oxygen on Bright Platinum in of Rhodium and Palladium Perchloric Acid Solution J. H. NORMAN, H. G. STALEY and W. E. BELL, J. M. W. BREITER, Electrochim. Acta., 1964, 9, (4), Phys. Chem., 1964, 68, (3), 662-663 441-450 Studies on the volatility of Rh and Pd in the Cathodic reduction mechanisms for OI at bright 1g0~--2100~Krangeat IO-~-IO-~ atm. 0,pressures Pt in I b! HCIO, include neither formation of indicated the existence of Rho, Rho, and PdO. adsorbed 0 atoms as intermediates nor participa- AH",,,, values were determined for the Rh tion of adsorbed H atoms. Periodic current- oxides. potential curves at 30 mV/sec and impedance measurements at 1000 cjs showed that 0, or H, coverage of the electrode at a given potential are ELECTROCHEMISTRY the same in the presence or absence of 0, reduc- tion. O2 coverage inhibits 0, reduction and CI- Nature of Potentials Established on Some adsorption has a similar effect. Electrodes of Metals of the VIII Group A. DAMJANOVIC, M. L. B. RAO and J. O'M. BOCKRIS, hodic Formation and Cathodic Removal of Extended Abs., Theoretical Div., Electrochem. Soc., Oxides on Palladium 1964, 2, (May), 159-161, abs. 205 YU. A. MAZITOV, K. I. ROSENTAL' and v. I. Potential and poZdid not follow a simple Nernst VESELOVSKII,Z~.Fiz. Khim., 1964~38,(I), 151-155 relationship when noble metal electrodes were Kinetics of the formation and reduction of oxides immersed in solutions at o-SO'C. Electrodes on Pd in concentrated KOH solution were studied tested were Ru, Rh, Ir, Pt, Pd, Au, 13 wt."" in the -30 to +95"C range. At anodic potentials Rh-Pt, 20 wt.nO Rh-Pt and 50 wt.';" Rh-Pt. the surface was covered with an oxide of Pd (11) Coverage by 0, was related to the number of commencing at 1.05 v and at 0, evolution poten- unpaired d-electrons. A graph of 0, coverage tials with two oxides, the second of which may against at.:, Rh in Rh-Pt alloys was a straight have been a superoxide. The slope of the Tafel line. equation for cathodic reduction of both oxides

Platinum Metals Rev., 1964, 8, (3) 109 was 55 mV. An additional reduction overvoltage Rh and Ir crucibles were slightly discoloured and of the second oxide was associated with concen- corroded. Only Ru remained bright and un- tration polarisation in the oxide layer. attacked. Phosphide formation and attack are discussed. Thermogravimetric analysis indicated An Electrochemical Study of Thin Adsorbed phospham decomposition on Rh at only 650°C Oxygen Films on Rhodium in Oxygen- but stability with Ru until 850-950"c. saturated Acid Solution J. P. HOARE, J. EZectrochem. Soc., 1964, 111, (2), Ceramic Double Cell for Crystal Growth by 232-236 Fused Salt Electrolysis After determination of rest potentials of Rh w. KUNNMANN and A. FERRETTI,Rev. Scient. electrodes in 0,-saturated acid solutions as Instrum., 1964, 35, (4), 465-466 functions of time, pH, partial pressure of 0,, and A low cost cell consists of two alumina concentric electrode preparation, two electrode systems crucibles supported in a Pt safety cup. The could be distinguished; RhIRh-0 with an electrodes are a Pt strip anode and a Pt disc adsorbed layer of 0 atoms on the Rh surface cathode. Leads, inner crucible supports and (mixed rest potential 93oizo mV); Rh:Rh,O, cover are also Pt. Single crystals of Na-Mo with adsorbed oxide layer on the Rh surface bronzes were produced satisfactorily at 55o'C. (mixed rest potential 880hIo mV). These O2 films were good electronic conductors but poor catalysts for peroxide decompositions. The CATALYSIS properties of the two films differed because of different Rh to 0 bondings. Catalysts Are Made Shape-selective. Zeolitic Materials Contain Uniform Size Pores, Cat- alyse Only Moleculesof Certain Size and Shape LABORATORY APPARATUS Chern. Eng. News, 1964, 4,(6), 45 AND TECHNIQUE Ptlzeolite catalysts are shape-selective for hydro- genation of linear hydrocarbons; e.g. a 9 :I molar Determination of Oxygen in Gases ratio of H,:butene had 95"; of I-butene converted Control, 1964, 8, (70), 195-196 to alkane but less than I:!;) isobutene was hydro- genated, This was because molecules with one A brief descriptionofthe B.I.S.R.A. Pt lzrrconia Pt reversible electrochemical cell for 0, deter- side group have effective diameters greater than mination. The e.m.f. of the cell depends only on the pores of the zeolites and cannot enter the the O2 of the unknown gas if the gas at the cavities, but the linear molecules can do so. reference electrode remains constant. The ranges Particle to Particle Migration of Hydrogen are 550-1200 'C and I-IO-~O atm. Atoms on Platinum-Alumina Catalysts from A High Temperature Differential Calorimeter Particle to Neighbouring Particles c. v. THOMASSON and D. A. CUNNINGHAM,J. sci. s. KHOOBIAR,J. Phyys. Chem., 196468, (2), 411-412 Znstrum., 1964, 41, (5), 308-310 H, alone or with A1,0,, at room temperature, did The endothermic heats of reaction of raw materials not reduce yellow WO, but, with Pt :A1,0,, blue for glass making were measured by heating sam- WIOll was formed immediately. This is evidence ples and a fired alumina reference at 1o'C:min in for dissociation of H, on Pt and H atom migration 0.2 mm Pt sheet crucibles of identical heat to WOs mixed with catalyst to cause reduction. capacity, Zero temperature difference during an endothermic process was maintained by heating Kinetics of Ethylene Hydrogenation over a the sample by a 24 s.w.g. IO"/~, rhodium-platinum Platinum-Silica Catalyst element in the form of two D-shaped coils with J. H. SINFELT, J. phys. Chem., 1964, 68, (4j, 0.2 mm Pt rod leads. The crucibles were cemented 856-860 together, the sample above the reference, and ten When C,H, was hydrogenated over 0.051,) Pt:13", Rh-Pt thermocouples, five in each cru- PtiSiO, catalyst at 45-93'C in a flow reactor cible, measured the tempcrature. system, the rate of reaction was proportional to .L/PH%but as PC,H~increased the rate decreased Thermal Condensation of Polymerisations of and approached zero order dependence at suffi- Inorganic Monomers in Platinum-Metal ciently higher pressures. Apparent activation Crucibles energy was 16 kcal!mole. M. c. MILLER, D. w. RHYS and R. A. smw, Id. Chern., 1964, 40, (41, 183-187 Composition and Structure of a Catalyst The effect of the Pt-metal sintered crucibles on Used in the Synthesis of IICN from NH, and the preparation of phospham macromolecules CH, at 1150 to 1200°C from 6- and 8-membered ring aminocyclophos- F. ENDTER, Abs. Papers, 147th Meeting, Am. Chem. phazenes was studied. Pt and Pd crucibles were Soc., 1964, IOK-28 attacked severely after only one or two pyrolyses. Pt catalyst coatings on the inner walls of extern-

Platinum Metals Rev., 1964, 8, (3) 110 ally heated, sintered corundum tubes, in which studied. Oxide support surfaces behave like the synthesis takes place, became coated with C, polar solvents due to H,O, OH groups or im- which had to be burned off. After 400 hours purities. Their dielectric constants were deter- operation and 3-5 reactivations no further C mined under different conditions, including deposits or deactivation occurred. The aged temperature variation. The supports are not inert catalyst contained Pt,Al, Pt,Al and A1N. To and are heterogeneous. Pt may be very finely reduce this initial activation period finely dis- dispersed on the supports and may interact with persed A1,0, is now incorporated in the catalyst them. Kinetics due to surface migration are coating. No C deposits occur and maximum considered. HCN yields begin at once. Hydrogenolysis of Ethane over Supported On a New Method for the Investigation Platinum of Heterogeneous Catalytic Reactions. I. J. H. SINFELT, J. Pkys. Chem., 1964, 68, (2), Decomposition of Ammonia on Platinum 344-346 YA. M. FOGEL’, B. T. NADYKTO, V. F. RYBALKO, R. P. The apparent activation energies for the hydro- SLABOSPITSKII, I. E. KOROBCHANSKAYA and v. I. genolysis of C,H, over 0.6 wt.% Pt/Al,O, and SHVACHKO, Kinetika i Kataliz, 1964, 5, (I), 0.6 wt.% PtiSiO, were 31 and 54 kcal/mole 154-162. respectively, suggesting that the supports and Pt The mechanisms of the catalytic decomposition interacted, but in different ways. The rate of of NH, on Pt and of catalyst-poisoning and activa- hydrogenolysis increased with CzHs partial tion were established by a new mass-spectrometric pressure to a power in the 0.7-0.9 range but method based on simultaneous observation of the decreased with increasing H, partial pressure. intensities of primary and secondary ions. First, ‘The suggested mechanism involved extensive NH is adsorbed on the catalyst after NH, decom- surface dehydrogenation followed by a slow poses into NH and H,. Secondly, two adsorbed breaking of C-C bonds. NH molecules react to form N, and Hzmolecules. Studies of the Hydrogen Held by Solids. v‘. Reduction of Platinum Oxide by Organic Investigation of Platinum Supported on Compounds. Catalytic Self-activation in Alumina Catalysts by Exchange with Deu- Deuterium Exchange Reactions terium Gas J. L. GARNETT and w. A. SOLLICH, J. Phys. Chem., w. K. HALL and F. E. LUTINSKI, J. Catalysis, r963, 1964, 6% (z), 436-437 2, (61, 518-527 PtO, was reduced by C,H, above 90°C and then Both the Pt surface area and number of alumina catalysed isotope exchange between C,H, and hydroxyl ions were determined in the same heavy water, At IZOTequilibrium was reached investigation by D ,exchange as the temperature after 24 hr shaking. “Self-activation” of PtO, was raised. All the metal-associated H, could presumably occurred by C-H bond rupture in be exchanged at -80°C (H/Pt=o.7 to 0.9). CGH,. Aromatic compounds were more reactive Hardly any D, exchange occurred with the than aliphatic compounds for “self-activation” support below 100°C. Pt is believed to be present and isotope exchange. Tritiation without H, as submicroscopic crystallites. More than one pre-activation of catalyst is now possible. species of Hz on the support was indicated. Fluoriding increased the temperature interval of The Hydrogenation of Dihydrolanosteryl and D, exchange. Dihydroagnosteryl Acetates J. D. CHANLEY and T. MEZZETTI, J. Org. Chem., Catalytic Transformations of Cyclododecane 1964, 29, (I), 228-229 in the Presence of Platinised Charcoal Hydrogenation of these substances in acetic acid E. S. BALENKOVA, A. YU. ALYBINA, T. I. ADVEEVA, with added HCIO, using Adams’ catalyst at s. I. KHROMOV and B. A. KAZANSKII, Dokl. Akad. atmospheric pressure produced an easily separable Nauk S.S.S.R., 1964, 155, (I), 118-121 mixture of the saturated acetate 38-acetoxy-5a- Cyclododecane and H, were led over 576 Pt/C lanostane (679; yield) and the saturated ether at 3ooo0C, producing paraffins, naphthenes and 38-ethoxy-5 a-lanostane (24% yield). The re- aromatic fractions. 5076 was converted. Principal actions are slow but were previously believed not products were benzpentalane, indane, dimethyl- to occur. For 340 mg dihydroagnosteryl acetate, napthalene, benzcyclooctane and n-dodecane. 300 mg PtO, were used at first and zoo mg extra catalyst after 48 hours. Production of Benzene by Catalytic Aromat- isation of Gasoline Catalysis by Oxides and by Oxide-Supported J. VYBIHAL, Znternat. Chem. Eng., 1964, 4, (I), Metals. Kinetic, I.R. and Adsorption Studies 104-109 (Eng. trans. of Chemicky Prumysl, 1963, v. KEVORKIAN, P. J. LUCCHESI, J. H. SINFELT and (8), 393-397) D. 1. YATES, Chim. e Ind., 1964,46, (I), 46-50 Optimum conditions for preparation of C,H, Oxide (A1,0,, SO,) and Ptloxide catalysts were from gasoline derived from Romaskin crude are

Platinum Metals Rev., 1964, 8, (3) 111 reforming over a Pt catalyst at 65-1zooC, 15-20 2-octene, trans-3-octene and trans-4-octene is atm. Space velocity and catalyst properties are catalysed by sodium chloropalladate (11) in also important. The composition of the input glacial HAc at 55-65"C. N.m.r. analysis of the gasoline-C,H,,, methylcyclopentane and aro- products from ~-octene-gd, suggests that the matics content generally--affects the output. mechanism involves the stepwise migration of H Specimen fractions of wide and narrow limits are atoms along the C chain. used as examples. Physical Chemistry of Concentrated Ozone. Effect of Ultrasonics on the Genesis and XII. The Low Temperature Heterogeneous Properties of Heterogeneous Catalysts Catalytic Decomposition of Concentrated LI VEN'-CHZHOU, A. N. MAL'TSEV and N. I. KOBOZEV, Liquid Ozone Zh. Khim., r964, 38, (I), Fiz. 80-88 G. I. EMEL'YANOVA, V. P. LEBEDEV and N. I. KOBOZEV, Ultrasonic irradiation can increase or reduce the Zh. Fiz. Khim., 1964, 38, (I), 170-175 catalytic activity of Pt and Pd black depending Pt and Pd actively catalyse the decomposition of on the gaseous atmosphere and the ultrasonic 100% liquid 0, at -195.8 and --183"C. Un- frequency. Tests with N,, H,, and air showed oxidised Ag is slightly active. Fe, Cu, and oxides that the best conditions for preparing active Pt of Fe, Cu, and Ni are inactive. The third order black are N, atmosphere and high frequency kinetics are caused by poisoning of the catalyst (3000 Kcjs). surface by 0, produced in the reaction. The Activity of Pt Black Prepared in an Ultra- apparent activation energy in the range studied is sonic Field from H,PtCl, Solutions of Various 1000 cal/mole. Oxide catalysts effective at room Concentrations temperature were inactive in both liquid and gas phase ( -8x3C) catalysis. Catalyst efficiencies at (2), Ibid, 439-441 - 1958°Cwere found to be: Pt black, 4.48 x IO-, Pt black catalysts prepared in an ultrasonic field molecule. set.-' atom-'; Pd black, 7.53 x IO-~ are best produced from dilute H,PtCl, solutions molecule. sec.-l atom-l. and their activity depends upon initial Pt con- centration. 0.5, 0.25, O.X and o.o5U/, Pt concen- Improved Procedures for Converting Higher trations were studied. a-Olefins to Methyl Ketones with Palladium Promotion of Raney Palladium and Platinum Chloride Catalysts by Boron w. H. CLEMENT and C. M. SELWITZ, J. org. Chem., B. D. POLKOVNIKOV, A. A. BALANDIN and A. M. 1964,299 (I), 241-243 TABER, Izv. Akad. Nauk S.S.S.R., Ser. Khim., Hexene-1 and higher or-olefins, which do not 1964, (21,267-270 readily react with aqueous PdClz solution, may be converted to methyl ketones with 80% yield 2 and 4 wt.% B additions Raney Pd and Pt 10 by using PdC1, and CuC1, in dimethylformamide catalysts considerably increased their catalytic solvent containing 12-17:h H,O by volume. activity and stability during hydrogenation tests with cyclopentadiene, cyclohexane, cinnamalde- Results for the conversion of I-dodecene to 2- dodecanone showed that more H,O reduced the hyde, and crotonaldehyde at zo°C and atmos- pheric pressure, Results are fully tabulated and yield considerably. The method can be adapted to use p-benzoquinone instead of CuCl,. The discussed. olefin feed rate must be controlled. Other factors The Catalytic Oxidation of Olefins on Metal affecting the reaction are catalyst concentration Films and temperature. w. R. PATTERSON and c. KEMBALL, J. Catalysis, Studies of Mixed Adsorption Catalysts for 1963, 2, (61,465-478 Acyclic olefins were oxidised at Pt and Pd films Dehydrogenation. Part I. Pd/SiO, as mainly to CO, and H20. Side reactions produced Catalyst for the Dehydrogenation of Cyclo- acetone from propylene and higher olefins and, hexane over Pd, tert-butyl ethyl ketone from tert- A. A. ALCHUDZHAN, M. A. MANTIKYAN and A. M. butylethylene. C,H, oxidation over Pt from 5 to AIKAZYAN, Izv. Akad. Nauk Armyan. S.S.R., 100°Cgave results similar to those with Pd. The Khim. Nauki, 1963, 16, (4, 303-314 reaction kinetics were determined. Tests with Decreased activity of freshly-prepared Pd jSi0 , Rh, Au and W films showed that metal-0, bond in cyclohexane dehydrogenation was due not to strength governs catalytic activity. C,H, and H, produced in the process but to Hzadsorbed C,H, oxidation over Pd and the effect of HCl on while reducing the catalyst before use. Catalyst Pd film catalytic activity were also studied. treated in air had higher activity. Studies at 320, 265 and 24ooC showed that adsorption of C,H,, Palladium-catalysed Olefin Isomerisation C,H,, or dehydrogenation products reduces N. R. DAVIES, Austral. J. Chem., 1964, 17, (z), catalyst activity. Air treatment restored the 2 12-2 I 8 activity. Deactivated catalyst after 20 days The isomerisation of I-octene to cis- and trans- storage also was restored to a stable activity.

Platinum Metals Rev., 1964, 8, (3) 112 Part 11. Pd-Ag/SiO, as Catalyst for the of the deuteromethanes indicated different Dehydrogenation of Cyclohexane reaction mechanisms ; stepwise exchange for Pt, Zbid., 315-325 multiple exchange for Ru. When one mechanism Catalysts tested contained either 1.0 or 0.2 wt.'i; dominated, measurement of HD on the metal Pd and varying amounts of Ag, such that the surface gave the rate of exchange. Pd:Ag ratio varied between 32:1 and I :9. Addition of Ag to I@&PdjSiO, decreased the The Role of Supports in Catalytic Hydrogen- activity but a maximum activity was obtained ation. Part 11. Activation Effects of Various for Pd:Ag-4:1 with 0.2~:/, Pd/Si02. The degree Metallic Oxide Carriers on Palladium with of activity also depended on the number of sites relation to the Magnetic Susceptibility and on SiO, filled by Pd or Ag. A comparison was Adsorption Capacity of the Catalyst, and made with the hydrogenation of benzene. Studies on the Sintering of Palladium Catalysts Deactivation of Palladium-Alumina Catalysts E. B. MAXTED and s. I. ALI, J. Chem. SOC.,1964 D. G. MANLY and F. J. RICE, J. Phjs. Chem., 1964, (March), 1127-1132 68, (21, 420-421 Adsorption capacity and catalytic activity cannot Regeneration at 650°C for 13 hr did not restore be correlated for fast reactions, and susceptibility deactivated 0.3:h Pd!Al,O, catalyst to its original and activity only increase together up to a certain level of activity. After regeneration in vucuo, limiting quantity of Pd on the support. Where the CQ adsorption was complete but in air was only oxide has high susceptibility there is no correla- 80% and in 0, only 36q6. These effects are tion. MgOi-CeO, and MgO'ThO, give the attributed to the growth of I'd crystals accelerated greatest activities as supports. Pd catalysts with by 0,, even below 400°C. larger pores after sintering have higher activities. Decrease of activity on sintered catalyst is also Double Bond Migration and Racemisation related to Pd content, sintering temperature and during the Hydrogenation of Olefins duration of sintering. W. D. HUNTSMAN, N. L. MADISON and S. I. Catalytic Activity of Noble Metal Alloys. SCHLESINGER, 3. CataRh On the Interaction between Acetylene and with alloys showing intermediate activities. Pt Palladium Salts in Aqueous Solution and Pd exhibited stepwise exchange and Rh exhibited predominantly multiple exchange at 0. TEMKII, S. M. BRAILOVSKII, R. M. FLID, M. P. N. higher temperatures. Alloys showed mainly STRUKOVA, v. B. BELYANIN and M. G. BAITSEVA, stepwise exchange with more multiple exchange Kinetika Kataliz, 1964, 5, (I), 192-193 i at higher temperatures. An atomic radius-exchange Pd compounds and aldehydes were formed relation was observed and exchange mechanisms during the reaction of C,H, and PdCl,, according are discussed. to the acidity and temperature of the aqueous solution. Acrolein and formaldehyde were Selective Hydrogenation of Haloalkenes to formed in increasing amounts as the temperature Haloalkanes Using Rhodium Catalyst rose to IOOTby the decomposition of PdC,H,OCl G. E. HAM and P. cOKER, J. Org. Chem., 1964 formed at 20-25'C; the hydrate PdC,H,O,Cl w. formed at I-2°C. Acetaldehyde was formed by 29J (I), 194-198 the hydration of C,H, with Pd(I1) as catalyst. Rh/A1,0, successfully catalysed the hydrogena- Propionaldehyde was formed by the decompo- tion of haloalkenes to haloalkanes. 40-60~~ sition of 7:-complexes of Pd. chloroalkane yields were obtained from I- chloropropene, ally1 chloride and I, 3-dichloro- propene, and a 960" yield of 2-chlorohexane from Catalytic Exchange of Methane and Deuter- 5-chlorohexene-I. Neither Rh, Pd, nor Pt ium on Platinum, Ruthenium and Platinum- catalysed hydrogenation of chloroalkanes under Ruthenium Alloys similar conditions. Yields depended on the D. w. MCKEE and F. J. NORTON, J. Phys. Chem., solvent, on poisoning by thiophene and on the 19643 6% (3)1 481-489 catalyst support. The order of yields with Pt-rich alloys were more active catalysts than catalyst is Rh>Pd>Pt. Isomerisation of cis- Ru-rich alloys for CH,-D, exchange in the 70- or trans-dichloropropene over Rh catalyst did 200°C range. 10-z~",,Ru-Pt reached the not occur in the absence of H, but there was highest specific activity. The orders of formation some in partially dehydrogenated material.

Platinum Metals Rev., 1964, 8, (3) 113 FUEL CELLS by the Drever CO. The first commercial installa- tion by Drever is saving Magnetics, Inc. an High-performance Propane Fuel Cells estimated $50,000 per year. w. T. GRUBB, Nature, 1964, 201, (4gzo), 699-700 A complete C,H,-0, fuel cell operating at 150°C GLASS TECHNOLOGY with Pt electrodes and 85% (14.6 M) H,PO, electrolyte had a limiting current density imposed Measurement of Kinematic Viscosity at by the kinetics of electro-oxidation in excess of Elevated Temperatures 500 mApn2. The form of the e.m.f.-current density curve indicates that current density w. SKATULLA and S, SCHQNE, Silikat Technik, probably is limited by a diffusion process involv- 1964, 15, (I), 5-10 ing C,H, or COP. Electrode structure is therefore Ir-Pt alloy is used in the tube furnace and stirrer a critical factor. of a rotating viscometer used to measure the dynamic viscosity of optical glass up to 1500°C. Physical Chemistry and Construction of Fuel The temperature is measured with a Pt:Rh-Pt Cells. 11. Different Types of Electrode for thermocouple. The kinematic viscosity in stokes is then obtained by dividing the dynamic viscosity Fuel Cells in Current Use in poise by the density in g:cm3. G. FEUILLADE, La Technique Moderne, 1964, 56, (I), 16-20 Pt metals are used in many of the types of fuel ELECTRICAL ENGINEERING cells summarised. The research organisations and companies engaged on fuel cell projects are Pressed Tungstate Cathode on Iridium Base surveyed. (64 refs.) A. I. ZHADAN and B. M. TSAREV, Radiotekh. i Elektronika, 1964, 9, (z),355-356 A Simple Gas Electrode Structure for the Pressed cathodes of baria-calcia-tungstate on Ir Evaluation of Catalysts (Electrocatalysts) in bases can be used from 450 to I~~o'C,whereas Working Fuel Cells W base cathodes which have lower heat of w. T. GRUBB and c. J. MICHALSKE, J. Electrochem. vaporisation, can only be used from 550 to 1250°C. Soc.9 1964, 111, (4)3 477-478 The Ir-based cathodes emit 7A/cm2 at IOOO"~, Details are given for preparing a Pt black electrode they are activated quickly and they have good by applying an aqueous slurry to a metal mesh reproducibility. Little sublimation is noticed. screen, drying it, and treating it with hydro- Use in V.H.F. apparatus is possible. The effect carbon wax to make it hydrophobic. It can be of surface films on the emission is discussed. used in H,-0, fuel cells up to 65'C in immobilised liquids. I:I Pt blackIAg powder mixture gave similar results in alkaline electrolyte. TEMPERATURE MEASUREMENT CATHODIC PROTECTION Reference Tables for Thermocouples of Iridium-Rhodium Alloys versus Iridium Lead\Platinum Anodes for Marine Applica- G. F. BLACKBURN and P. R. CALDWELL, J. Res. Nut. tions Bur. Stds., 1964, 68C, (I), 41-59 D. B. PEPLOW and L. L. SHREW., Corrosion Technol., Temperatures from o to ZISOTare tabulated 1964, 11, (41, 16-18 against e.m.f. in mV for Ir:60°, Ir-Rh and Ir: Pb/Pt bielectrodes were tested in sea-water at 50"; Ir-Rh thermocouples. Temperature-e.m.f. 50A/ft2 for one year and appeared to offer an relationships are also given for Ir versus 10,25,75 inexpensive system of power-impressed marine and goo/o Ir-Rh alloys. 5on, Ir-Rh gives the protection. Six Pb alloys were studied. Small Te maximum thermal e.m.f. (12.2 mV at 2150°C) or Bi additions to I*(> Ag-Pb alloy reduce Pb and may provide the optimum thermocouple peroxide formation. Anode structure and electro- combination, chemical mechanism are described. Some Recent Developments in Noble Metal Thermocouples CHEMICAL TECHNOLOGY L. 0. OLSEN, SOC.Automalive Eng. Paper 750 A, 1963, (Sept.), 10 PP. Ultrapure Hydrogen in Metal Processing Empirical reference tables of temperatures versus G. L. MATLACK, Metal Progress, 1964, 85, (3), thermal e.m.f. are presented for Pd:15",, Ir-Pt, 114-117 Platinel 11, Ir:407; Ir-Rh, Ir:50°: Ir-Rh and H, derived from dissociated NH, is purified by Ir:60°: Ir-Rh. Experimental apparatus and test using the Bishop Ag-Pd alloy diffusion cell. Com- procedures are described briefly. Work on the plete units based on these cells have been designed thermoelectric stability of Platinel I1 is discussed.

Platinum Metals Rev., 1964, 8, (3) 114 A Dew Point Meter Based on Thermoelectric Thermal and Hydrostatic Behaviour of Cooling iViiniature Platinum Resistance Elements 0. G. GRIFFIN and C. M. STRINGFIELD, J. SCient. c. M. KNOBLER, w. I. HONEYWELL and c. J. PINGS, Instrum., 1964, 41, (4), 241 Rev. Sci. Instrum., 1963, 34, (IZ), 1437-1438 The dew point of a gas flowing in a tube is Glass-clad Pt wire resistance elements by measured by observing the temperature at which Degussa were calibrated against an N.B.S. Pt condensation forms on a mirror surface that is resistance thermometer from 77 to 300°K. No heated and cooled electrically. The Pallador systematic resistance deviations were observed. thermocouple is soldered into a cavity in the Pressures up to 2,000 p.s.i. at room temperature centre of the mirror. Dew points zo°C

NEW PATENTS

Rhodium Trichloride Catalyst Hydrogenation of Cycloaliphatic Compounds E. I. DU FONT DE NEMOURS & CO. BADISCHE ANILIN & SODA-FABRIK A.G. British Patent 948,041 British Patent 948,861 An acyclic hydrocarbon diene having 6 or 7 carbon Metallic Pd and heavy metal ions (Cu,Ag, Zn, atoms is made by: (I) condensing ethylene or Cd, Hg, T1, Pb Sn, Sb, Bi, V or Zr) are used in propylene with ~~g-butadienein presence of a the partial hydrogenation of cycloaliphatic com- RhC1, catalyst until the catalyst is deadvated, (2) pounds. isolating the catalyst residue, (3) mixing it with I mole of aqueous HC1 solution per mole of initial Production of Ethylene-diamine or its catalyst and, (4) using this reactivated residue as Derivatives a substitute in stage (I). THE PURE OIL co. British Patent 948,965 A Group VIII noble metal catalyst is used in the Yreparation of Dicyanogen preparation of mineral acid salts or N-acyl deriva- ROHM & HAAS G.m.b.H. British Patent 948,113 tives of ethylene diamine by reacting cyanogen A catalyst formed of an alloy of two or more Pt with hydrogen at 0”-300°C and a pressure of over metals or of one or more Pt metals with one or 50 lb/sq. in. in the presence of the catalyst. more Group VIA metals is used in preparation of Rh’A1,0, is used. dicyanogen by oxidation of HCN. 99%, Pt and I ::, Pd alloy preferred. Fuel Cell ALLIS-CHALMERS MANUFACTURING CO. Production of Aromatic Halogen Compounds British Patenrs 948,984; 948,985; 948,986 MONSANTO CHEMICALS LTD British Patent 948~8I Relate to improved liquid fuel cell of the low Pt or Pd, in the form of a halide of Pd or Pd/C, temperature catalyst-activated type, which offers may be used in a process of providing hafogeno- increased current density and in which the internal substituted aromatic compounds. resistance of the cells is reduced. The fuel electrode (948,985) carries a catalyst of a Pt group metal. Purifying Sulphuric Acid V.E.B. FARBENFABRIK WOLFEN Organosilicon Compounds British Patent 948,381 UNION CARBIDE GORP. British Patent 949,044 Concentrated H,S04 containing oxidiscd N com- Catalyst of elemental Pt on y-Al,O, is used in a pounds is purified by electrolysis at 55-8o‘C. and process of preparing organosilicon compounds by current density at anode of o.08-o.1~A/cm2 and reacting CH,C1 and a hydrogen halosilane of given at cathode of 0.20-0.~5 Alcm2 in one or more general formula in the presence of the catalyst. closed cells using a cathode of Pt and an anode of Pt or Pb oxide. Preparation of Trans-9-oxodec-2-enoic Acid Catalytic Igniters “SHELL” RESEARCH LTD. British Patent 949,319 ROLLS-ROYCE LTD. British Patent 948,578 Refers to the use of a PdiBaSO, catalyst at one A prime mover ignition device comprises a stage in the preparation of the above compound. number of cylindrical foraminate rolls of Pt or Rh or Pt-Rh alloy, supported in an annular Boron Doping Alloys formation by a mass of refractory material, having WESTINGHOUSE ELECTRIC CORP. a flow passage or passages extending through it British Patent 949,653 to lead combustion mixture to the rolls. Discloses a novel method of preparing a doping

Platinum Metals Rev., 1964, 8, (3), 115-120 115 alloy for producing P-type doping in semi- presence of the catalyst of a 4-p-(lower acylamido) conductor material, using a master alloy of 4096 B phenyl-4-oxobutyric acid dissolved in a CH,OH and 60% Pt by wt. and a sub-carrier of Pt, Cu, solution. Fe, Go, Ni, Rh, Ru, Pd, 0s or Ir. The master alloy is dissolved in the liquified carrier metal in Synthesis of 5-Chloro-2,4-bi.s-(methylsul- such proportion that the melt contains not over phamyl) -aniline 19: by wt. of the master alloy, and the melt is ABBOTT LABORATORIES INC. British Patent 952,019 maintained above melting point of the carrier A Pd hydrogenation catalyst is used in the pre- until uniform distribution of the boron is ob- paration of the above compound from 4,6- tained. dichloro-I-3-bis (methylsulphamy1)-benzene. Partial Oxidation Hydrocarbons of Treatment of Exhaust Gases NATIONAL RESEARCH & DEVELOPMENT CORP. w. R. GRACE & co British Patent 952,150 British Patent 951,100 Describes a method of preparing a Pt-containing Reference is made to the use of a combustion catalyst for use in the oxidation of exhaust gases chamber lined with a Pt-Rh alloy in a process for from an internal combustion engine. producing an unsaturated hydrocarbon by partial oxidation of a saturated hydrocarbon, e.g. pro- duction of C,H, from CH,. Electrodes and Electroplating HARSHAW CHEMICAL co. British Patent 952,171 Fuel Cells A Pt-coated anode is made by electroplating a Pt LEESONA GORP. British Patent 951,168 coating on a Ti base and then heat-treating the The fuel electrode of a fuel cell is formed of a base at 400"-800"C for 15 seconds to I hour. See non-porous plastic polymer structure surface also 95z,17z. coated with Pd, Pt, Rh or Ru. The polymer membrane may be polyethylene or a polyamide. New Quaternary Salt CHINOIN GYOGYSZER ES VEGYESZETI TERMEKEK Preparation of 2-Amino-benzophenones GYARA RT. British Patent 952,289 F. HOFFMANN-LA ROCHE & CO. J -Phenyl- I-cyclohexyl- 3-piperidino - propanol- I British Patent 951,301 is made by reacting C,H,N with I-phenyl-r- The above materials are made by hydrogenating cyclohexyl-I-hydroxypropyl-3p-toluenesulphon- the unsubstituted 5-halo-a-amino-benzo-phenone ate and reducing the pyridinium sulphonate thus with gaseous H, in the presence of a Pd catalyst, obtained. The reduction is carried out as a a halide ion acceptor and an organic solvent. The catalytic hydrogenation with a Pd catalyst. catalyst may be formed in situ. Developer for Electrostatic Images Production of Acyl-alkyl-phenols BURROUGHS CORP. British Patent 952,326 THE DISTILLERS co. LTD. British Patent 951,435 An electrically conductive powder for developing An acyl-alkyl-phenol is made by dehydrogenating electrostatic latent images consists of non-friable an alkyl-substituted acyl cyclohexenone of given powder particles of 10-80 microns diameter, the formula in the presence of a supported Pt metal particles having electrically non-conductive cores catalyst. coated with an electrically conductive metal, e.g. Pd or Rh. Glass beads may be used as the Silylated Compounds particles. DOW CORNING CORP. British Patent 951,489 Refers to the use of a solution of H,PtCI, acid Manufacture of Single Crystals in dimethylphthalate in the preparation of a THE GENERAL ELECTRIC CO. LTD. silylated polyepoxide of given general formula. British Patent 952,385 Describes an apparatus for use in a novel method Production of Fuel Gas of making single crystals which includes a source BADISCHE ANILIN & SODA-FABRIK A.G. material retainer formed of a perforated Pt disc or British Patent 951,518 sheet, or a piece of Pt gauze or a perforated Pt A supported Pd:'SiO, cracking catalyst is used in vessel. The seed crystals are supported by thin the production of fuel gas from liquid hydrocar- Pt wires. bons. Formation of Metal Coatings Manufacture of Methyl-4-p-aminophenyl- THE INTERNATIONAL NICKEL CO. (MOND) LTD. butyrate British Patent 952,493 THE WELLCOME FOUNDATION LTD A dispersion of a Pt group metal flake powder in a British Patent 951,628 liquid, which will volatilise or decompose under A catalyst of PdK is used in a method of making heat, is applied to a supporting surface and is the above compound by reduction with H, in the heated to sinter the flakes to an adherent coating.

Platinum Metals Rev., 1964, 8, (3) 116 Catalyst Cracking Process SOCONY MOBIL OIL co. INC. British Patent 952,622 FARBENFABRIKEN BAYER A.G. The following method is employed to make a British Patent 953,747 catalyst: hydrous A1,0, having a phase composi- A Pd hydrogenation catalyst is used in a process tion of 10-35:; by wt. c(-Al,O,.H,O and 65-90')~~ for pyrolysis of liquid hydrocarbon in which the of P-A1,0,.3H,O is mixed with (I) a Pt compound cracked gasoline obtained in the pyrolysis is in sufficient amount to give a content of 0.01-5"(, hydrogenated so as completely to hydrogenate by wt. of Pt in the catalyst and (2) not over 57+, the diolefines and leave the mono-olefines and by wt. of HNO, based on weight of A120,; the aromatic compounds unchanged. mixture is dried and calcined at elevated tempera- ture to convert the monohydrate to y-Al,O, and Alloy the trihydrate to q-A1,0,. The catalyst is stated AEROJET-GENERAL CORP. British Patent 953,948 to have unusual physical strength and strength An alloy for use in brazing material is formed of: retention. 96-1O:, Au, 72-1q6 Pd, 61-2% Ni, Cr and/or Co. Numerous examples given. The alloy is Production of Acetaldehyde stated to be extremely resistant to corrosion by NIPPON GOSEI KAGAKU K.K.K. hot gases, moist conditions or corrosive liquid. British Patent 952,718 A catalyst comprising a salt of Pd, Rh or Pt and a Production of Cyclohexylhydroxylamine salt of Cu, Zn, Cry Mn, Fey Co or Ni is used in COMMERCIAL SOLVENTS CORP. producing acetaldehyde by reacting CzHawith 0, British Patent 953,995 and an aliphatic alcohol, (e.g. CHaOHor C2H,0H) Cyclohexylhydroxylamhe in the presence of the catalyst at 5o0-15o0C and is made by hydro- genating nitrocyclohexene in the presence of Pd 1-100 atm. or Pt catalyst at 0-65°C and 100-2,000 p.s.i. pressure. 3-36 moles of H, are used for each mole Catalysts of nitrocyclohexene. THE BRITISH PETROLEUM CO. LTD British Patent 953,187 Selective Hydrogenation A catalyst for isomerisation of C, and higher paraffin hydrocarbons at below 400'F is made by CHEMETRON CORP. British Patent 954,203 contacting an H,-containing Al,O, with CCI,, A catalyst for use in the selective hydrogenation CHCl, or CH,Cl,, or the like, under non- of highly unsaturated hydrocarbons in a concen- reducing conditions and such that chlorine is taken trated olefin stream is formed of o.01-0.09~~,by up by the A1,0, without production of free wt. Pd, 0.01-0.09O;, Cr deposited in an A1,0, AlC1,. The catalyst includes Pt or Pd. carrier having a pore volume of surface pores of 0.0-0.4 c.c;g. Threshold diameter of surface Isomerisation of Paraffin Hydrocarbons pores is not over 800 A. THE BRITISH PETROLEUM COYLTD. British Patents 953,188; 953,189 N-substituted Nitro-phenylene Derivatives Covers processes for isomerisation of C, and BRISTOL-MYERS GO. British Patent 955,743 higher paraffin hydrocarbons using the catalyst of A Pt or Pd catalyst is used in the catalytic hydro- 953,187 above. genation of a ~~4-dinitro-phenylamineto an acid addition salt of the corresponding 2-nitro-4- Production of Noble Metal Layers amino-phenylamine or para-phenylene-diamine derivative. N. V. PHILIPS GLOEILAMPENFABRIEKEN British Patent 953,431 Manufacture of Dicyclohexylamine A noble metal layer is formed on a non-metallic, ABBOTT LABORATORIES British Patent 956,r 16 non-conductive support photographically by sub- jecting a light-sensitive layer to a minor exposure Dicyclohexylamine is made by mixing equimolar (defined), treating the layer with an aqueous germ amounts of phenol and aniline and subjecting the introduction agent including a water-soluble Hg mixture, in a low pressure hydrogenation plant, or Ag compound which reacts with the layer to to H, gas at IOO p.s.i.g. or less and at room tem- form a partly external metal germ image and perature to IOO'C in the presence of metalllc Pd physically developing this image with a non- (0.4596 by wt. of the mixture). The catalyst is stabilised intensifier. Layers of Au, Pt, Pd, Ir or supported on charcoal. Rh can be obtained. See also 953,432; 953,433. Separation of Hydrogen from Gaseous Dibenzofuran Derivatives Mixtures MONSANTO CHEMICALS LTD. JOHNSON, MATTHEY & CO. LTD. British Patent 953,661 British Patent 956,176 A Pd/C hydrogenation catalyst is used in a A H, diffusion membrane or tube is formed of an process of producing a dibenzofuran. 0.05--2 wtau0B-Pd alloy.

Platinum Metals Rev., 1964, 8, (3) 117 Manufacture of Hydrogen Cyanide Cntalysed Nitrile Production E. I. DU FONT DE NEMOURS & CO. THE PURE OIL CO. U.S. Patent 3,116,313 British Patent 956,200. The production of aromatic nitriles from the HCN is made by passing over a Pt catalyst at corresponding halides and HCN is catalysed by IOOO"-IZOO~Ca mixture, pre-heated to 400~- a Pt metal deposlted on a refractory support. 525"c, of CH, and NH, in a vol. ratio of 0.8 :I to The same supported catalyst may be used for I.Z:~, and air in amount equivalent to 25-404b aliphatic nitriles (No. 3,116,318). of that theoretically required for complete oxida- tion of the NH, and CH4. Multistage Catalytic Reforming Process STANDARD OIL co. US.Patent 3,117,073 Decontamination of Palladium Diaphragms A hydrocarbon naphtha is hydroformed in the A. 0. SMITH CORP. U.S. Patent 3,113,080 presence of a hydrogen-rich recycle gas and a Pd diaphragms for transferring atomic H to Pt/A120, catalyst in which the Also3 surface area hydrogenation cells are decontaminated and in a first stage is less than 130 ma 'g and the area in protected by applying a coating of Pd black or a second stage is 130 m*/g or more. Pt black, Mixed Platinum Reforming Catalyst Catalytic Alkyl Benzene Isomerisation STANDARD OIL co. US.Patent 3,117,096 SINCLAIR RESEARCH INC. U.S. Patent 3,113,979 New catalyst giving a high aromatic content from Positional isomerisation and isomerisation between alkyl cyclopentanes consists of 1-20 wt.O,, BN and alkyl substituents are produced in a single stage 0.1-2 wt.qu of an Al,O,-supported Pt metal. process by the use of a catalyst consisting of a Pt metal and B oxide deposited on A1,0,. Catalyst for Olefine Oxidation FARBWERKE HOECHST A.G. U.S.Patent 3,11S,001 Acetylene Selective Hydrogenation Catalyst A new catalyst system for the oxidation of olefins IMPERIAL CHEMICAL INDUSTRIES LTD. to aldehydes and ketones consists of a Pt metal, U.S. Patent 3,113,980 CuC1, and either trichloroacetic acid, dibromo- Acetylenes are selectively hydrogenated in the acetic acid or their salts or mixtures. presence of olefines by the use of a catalyst con- sisting of Pd deposited of Al,O, having pores Catalytic Nitric Acid Reduction whose mean radius lies between roo-14ooA. NATIONAL DISlILLERS & CHEMICAL CORE'. US.Patent 3,119,657 Electrode Production HNO, mixed with HCl, H,O and a Sn chloride GENERAL ELECTRIC co. (NEW YORK) is reduced to hydroxylamine (as hydrochloride) by U.S. Patent 3,114,087 H2 in the presence of Pt or Pd, e.g. Pt/C. The adherence of electrodes made of Ta to tab leads is increased by applying a layer of Pd to the Olefine Oxidation Catalyst Ta. FARBWERKE HOECHST A.G. U.S. Patent 3,119,874 Olefines are oxidised to carbonyl compounds in Inlay Metal Strip aqueous neutral to acid medium in the presence JOHNSON, MATTHEY & CO, LTD. of a catalyst consisting of a Pd salt and a redox U.S. Patent 3,1 15,702 system, e.g. PdCl, and CuCl,. No. 3,119,875 A Pt metal or alloy strip is bonded to a refractory covers the use of other Pt metal compounds. metal base element by applying to the strip and element, in contact and encascd in a metallic Promoter for Silica-Zirconia Hydrocracking sheath, heat and uniform pressure simultaneously Catalysts throughout the entire area thereof. UNION OIL CO. U.S. Patent 3,120,483 The hydrocracking activity of Si02-Zr0catalysts Fuel Cell Electrode-catalyst is promoted by small amounts of Group VIII A. J. HIPP US.Parent 3,116,165 metals, e.g. Pt, Pd, Ir, Rh. New electrode-catalyst is produced by the chemical deposition of Pd, Ir, Pt, 0s or Ru on a Dental Coping Alloy Ni plaque by heating it in a solution of the Pt NIRANIUM CORE'. U.S. Patent 3,121,629 metal at 40-7o"C and pH I or less. A non-separating alloy for use with porcelain jackets to form a durable join consists of 40-55"~ Fuel Cell Electrode Production Ni, 20-300/, Cr and 20-25:" of a Pt metal to- SHELL OIL co. U.S. Patent 3,116,170 gether with I-4°o of Be, Si andlor Mo. A conductive layer of Ag is deposited by evapora- tion on a plate of non-conducting porous poly- Catalytic Acetylene Amine Reaction vinyl chloride, then further Ag is electrodeposited PHILLIPS PETROLEUhl CO. U.S. Patent 3,121,747 and finally Pd black catalysts applied. Acetylenic amines are produced by the reaction

Platinum Metals Rev., 1964, 8, (3) 118 of a secondary amine, an acetylenic compound and substituents are hydrogenated to haloarylamines H, in the presence of Pt or Pd at 0-200°C and in the presence of an Rh catalyst activated with an 1-1000 p.s.i. alkali or alkaline earth metal hydroxide, carbonate or acetate. Graphite Bonding Method US. ATOMIC ENERGY COMMISSION Monoskeletal Silver or Platinum Metal U.S. Patent 3,122,424 Catalyst Electrode A bond is produced between graphite articles or BROWN, BOVERI & CIE. French Patent 1,337,705 between graphite and a metal by placing a Pt foil Fuel cell porous electrodes are produced by com- 2 mils or more thick between the surfaces, heating pressing and sintering a catalyst metal (e.g. Ag, in an inert atmosphere with the surfaces in con- Pt, Pd, Rh) with a non-catalyst metal (e.g. A1 or tact at 18oooC, cooling, machining away graphite Zn) and removing the latter with acid. to expose Pt and then brazing or soldering. Catalytic Hydroquinone Oxidation Catalytic Olefine Oxidation STE. DES USINES CHIMIQUES RHONE-POULENC CONSORTIUM FUR ELEKTROCHEMISCHE INDUSTRIE French Patent 1,338,462 G.m.b.H. U.S. Patent 3,122,586 The oxidation of hydroquinone to p-benzoquin- New catalyst for the oxidation of olefines to one, effected with 0, in organic medium, is aldehydes and ketones consists of a Pd, Ir, Ru, Rh catalysed by Ru or Rh on an inert support, e.g. or Pt compound and a redox system, e.g. PdC1, Rh on C black. used with CuC12. Acetylene Selective Hydrogenation Palladium-coated Containers CHEMETRON CORP. French Patent 1,338,769 THE METAL BOX CO. OF SOUTH AFRICA LTD. Acetylenic compounds mixed with dienes are U.S. Patent 3,123,491 selectively hydrogenated using a Pd-CuO catalyst, Pd is applied in finely dispersed form to the inside e.g. a catalyst containing 2o-7on,, CuO, 30-80°,, of a hermetically sealed food container, e.g. Cr,O, and 0.04-1 4, Pd. dispersed in a conventional can lacquer, and is able to remove residual 0, remaining after evacuation Fuel Cell Electrodes by catalysed combination with H,. LEESONA CORP. French Patents 1,338,755; 1,338,756; 1,338,757 Ruthenium Electrodeposition The action of electrodes for fuel cells made of, THE INTERNATIONAL NICKEL CO. LTD. inter alia, Ru, Rh, Os, Ir, Pt or Pd is improved US.Patent 3,123,544 by incorporatmg metallic Li in their surface. The The source of Ru for cathodic electroplating is an electrode surface is coated with Pt/C after Li has acid solution of at least 2.5 g,'l Ru as tetra- been introduced. (No. 1,338,756). sulphamato nitrosyl ruthenate. This aqueous solution avoids the need for molten electrolytes. Catalytic Vinyl Acetate Production STE. DES USINES CHIMIQUES RHONE-POULENC Isomerisation Catalyst Containing Palladium French Patent 1,339,614 THE PURE OIL CO. U.S. Patent 3,123,573 Vinyl esters are produced by the reaction at A S-resistant isomerisation catalyst consists of a elevated pressures and temperatures of ethylene SiO,-A1,0, support impregnated with a Pd and a fatty acid, particularly acetic acid, in the compound to give a content of 0.3-0.8 wt.OA Pd, presence of a noble metal chloride, particularly with a F compound to give a content of 1-5 wt.O,, Pd chloride, a lower fatty acid salt and benzo- combined F, and reduced with H, at 750-975"F. quinone. Catalytic Hydrocarbon Reformation Pd-Cu Oxidation Catalysts IMPERIAL CHEMICAL INDUSTRIES LTD. W. R. GRACE & CO. French Patent 1,341,068 French Patent 1,334,080 Catalysts for the treatment of exhaust gases from Hydrocarbons boiling up to 350°C (preferably at internal combustion engines by oxidation consist 30-220'C) are reformed by contact with steam at of a support containing 5-30?,, and preferably an elevated temperature in the presence of a 10-20°, CuO and 0.0025-0.4~,,Pd. A typical supported catalyst containing a Pt metal or a catalyst contains o.or'yo Pd and 107; CuO on an compound reducible to such a metal. The catalyst A1,0, support. preferably consists of 0.1-2.5 wt.Yti Rh/A1,0,. The production of the catalyst is described in Catalytic Acetaldehyde Production NIPPON GOSEI KAGAKU K.K.K. 1,334~08I * French Patent 1,341,796 Nitroaromatic Hydrogenation The oxidation of C,H, in the presence of an ali- DOW CHEMICAL co. French Patent 1,334,504 phatic lower alcohol to acetaldehyde is catalysed Aromatic compounds having nitro and halo by a noble metal, e.g. Pd or Pt.

Platinum Metals Rev., 1964, 8, (3) 119 Hydrocarbon Hydrogenation Catalyst nated with 0.002-5 wt.% of a mixture of Ag and FARBENFABRIKEN BAYER A.G. Pt containing 6090 wt.q& Pt and a 20-80 fold French Patent 1,342,470 amount of Fe oxide. Hydrocarbons boiling in the petrol range are hydrogenated over a catalyst consisting of a Catalyst for Alcohol Oxidation noble metal deposited on a porous support having ESSO RESEARCH & ENGINEERING CO. a water absorption of at least ro'!& and an internal German Patent 1,161,873 surface of less than about IOO m2!g. A typical Aldehydes or ketones are produced from saturated catalyst consists of Pd on sintered Also,. acyclic 3-8C alcohols by contact with 0, at 50- 300'C in the presence of H,PtCl,, the catalyst Catalytic Dicyclohexylamine Production being regenerated at 50-300"c in a separate zone ABBOTT LABORATORIES French Patent 1,343,391 using molecular 0,. A mixture of phenol and aniline is catalytically hydrogenated to dicyclohexylamine using H, at Produetion of 0-vinyl Compounds 7 kgkq. cm or less and 20-1ooT in the presence FARBWERKE HOECHST A.G. of at least 0.45 wt.7" metallic Pd, e.g. as Pd/C. German Patent 1,161,878 The reaction of compounds containing OH groups Cyclohexyl Hydroxylamine Catalytic Pro- and acetylene at elevated temperatures and pres- duction sures is catalysed by the presence of both (a) an COMMERCIAL SOLVENTS CORP. alkali metal, Zn or Cd compound and (b) a Group French Patent 1,343,869 VIII noble metal or a compound of such a metal, Nitrocyclohexane is hydrogenated over a Pt or Pd e.g. CdO used with Pd,'C. catalyst at 0-65°C and 7-140 kg/cm2 to form cyclohexyl hydroxylamine. Fuel Cell Electrode ELECTRIC STORAGE BATTERY CO. Catalyst for Alcohol Production German Patent 1,161,965 CONSORTIUM FUR ELEKTROCHEMISCHE INDUSTRIE Fuel cell electrode consists of a sintered mixture G.m.b.H. German Patent 1,158,960 of 1-47"/~ Ni, 3-15'?, Pd and 50-96'), Ag. The hydrogenation of u, 8-unsaturated aldehydes to the corresponding alcohols is catalysed by a Catalytic Cyclododecanonoxime Production PtO, catalyst modified by an Fe or Zn salt. BADISCHE ANILIN-& SODA-FABRIK A.G. German Patent 1,162,359 Ruthenium Hydroformylation Catalyst 2-Chloro-cyclododecanone-(1)-oxime which con- IMPERIAL CHEMICAL INDUSTRIES LTD. tains I or 2 olefinic bonds is converted to cyclo- German Patent 1,159,926 dodecanonoxime by reduction at 0-130°C in the The hydroformylation of olefines to form presence of a Group VIII noble metal catalyst, aldehydes and ketones is catalysed by the use of e.g. Pd/BaSOn. a composition containing Ru, e.g. RuCl,, supplied Catalytic Hydrogen Cyanide Production at the rate of 0.005-0.01~1~,based on the olefine. IMPERIAL CHEMICAL INDUSTRIES LTD. Catalytic Reduction of Nitroaromatics German Patent 1,163,304 GENERAL ANILINE & FILM CORP. The conversion of NH, and hydrocarbons to German Patent 1,160,445 HCN over a Pt metal or alloy catalyst is improved Aromatic monocyclic mononitro compounds are by adding small amounts of a volatile S compound reduced to the corresponding amines by reduction to the feedstock. at 25'-125"c using a noble metal catalyst having a surface area of at least 150 m2/g, e.g. Pt or Pd Catalytic Glycerol Puiification on C or Pd/A1,0,, the reaction water being dis- STE. D'ELECTRO-CHIMIE, D'ELECTRO-METALLURGIE persed as a separate liquid phase throughout the et DFS ACIERIES ELECTRIQUES D'UGINE reaction zone. German Patent 1,164,387. Glycerol produced synthetically is purified by Catalytic Carboxylate Production catalytic hydrogenation in the presence of Ru and THE DISTILLERS co. LTD. German Patent 1,160,846 an acid ion exchange resin. The production of alkyl carboxylates from option- ally substituted olefines and cuprous halocar- Production of Powdered Palladium boxylates is catalysed by Pd, e.g. metallic Pd or E. M. PROKEFEV Russian Patent 157,112 PdC12. High yields of finely dispersed powdered Pd are obtained by roasting palladosamine progressively Acetylene Hydrogenation Catalyst until the temperature reaches 650°C. The V.E.B. LEUNA-WERKE "WALTER ULBRICHT" resulting product is milled and then roasted again German Patent 1,161,555 with the temperature rising to 800°C. The Pd New catalyst consists of an inert support impreg- is then held at this temperature for about z hours.

Platinum Metals Rev., 1964, 8, (3) 120