PLATINUM METALS REVIEW

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

VOL. 10 APRIL 1966 NO. 2

Contents

Recent Advances in Industrial Platinum Resistance Thermometry 42

Petrochemicals by Platinum Reforming 47

Prevention of Corrosion in Paper Making Machines 48

Expansion in Platinum Production 52

Platinum-wound Furnaces in the Manufacture of Semiconductors 53

The Wetting of Platinum and its Alloys by Glass 54

Electrodeposition of Iridium 59

The Reaction between Hydrogen and Oxygen on Platinum 60

Catalysis of Olefin-to-Olefin Addition 65

Abstracts 66

New Patents 73

Communications should be addressed to The Editor, Platinum Metals Review Johnson, Matthey & Co Limited, Hatton Garden, London ECI Recent Advances in Industrial Platinum Resistance Thermometry

By J. S. Johnston, B.s~.,A.R.C.S. Rosemount Engineering Company Limited, Bognor Regis

The modern platinum resistance thermometer provides the most accurate and versatile method of industrial temperature measurement and control. This article gives details of a new design of platinum resistance thermo- meter element of small dimensions and good stability. It also describes a range of complete thermometers based on these elements together with a resistance-bridge system used for signal conditioning when the thermo- meters are used in data-logging or computer controlled systems.

Two principal factors have contributed to a thermometer confers the advantages of better recent large increase in the use of platinum reproducibility and larger output signal resistance thermometers in industry. On the coupled with the ability to scale the output one hand new techniques of manufxture to fit the requirements of the instrumentation. have produced thermometers that are smaller and more robust than was possible in the Thermometer Designs past so that it becomes feasible to specify Modern methods of refining platinum resistance thermometers for applications have put materials of extreme and dependable which have hitherto been the province of the purity at the disposal of the manufacturer of thermocouple. On the other hand the con- resistance thermometers in a wide range of tinual striving after improved accuracy of wire diameters down to 0.0004 inch or even measurement and control has received an smaller. These small diameters were often, in additional impetus with the introduction of the past, associated with high impurity central data-logging and computing equip- content as a result of material picked up from ment. For these applications the resistance the drawing dies; this problem has now been

Platinum Metals Rev., 1966, 10, (2),4247 42 Fig. 2 A range of modern industrial platinum resistance thermometers suitable either for direct immersion or for use in pockets largely overcome, although some surface problem is usually solved by some sort of etching is still normally necessary to achieve compromise since, in general, higher vibra- the highest temperature coefficients. tion levels will require greater degrees of The problem facing the thermometer manu- support, with inevitably poorer electrical facturer is to maintain the high temperature stability. At one extreme are found inter- coefficient and good stability inherent in the polation standard thermometers with almost pure platinum, while at the same time unsupported coils, since the ultimate in providing the mechanical support needed to stability is required under conditions of enable the element to survive the vibration careful laboratory handling, while at the other and shock conditions of military and industrial extreme thermometers for use in aircraft use. This support is the more necessary in engines may have the platinum encapsulated that pure annealed platinum is extremely over the whole length. Many compromise con- soft and hence mechanically weak. This structions between these extremes have been

Platinum Metals Rev., 1966, 10, (2), 43 Fig. 4 The resistance thermometer shown on the left is suitable for measuring the temperature of metal bodies such as bearings by insertion into an oversize hole in the metal so as to be tip-sensitive. That on the right has a sensitive portion mrresponding in length to the threaded part of the thermometer

firmly attached to withstand the levels of vibration normally en- countered in industrial processes. The fact that part of the coil is en- capsulated necessarily means that there is some reduction in tempera- ture coefficient and degradation in stability as compared with the proposed; for example in some aircraft unsupported platinum wire. It might be thermometers the platinum coil is wound on somewhat naive to suppose that the charac- an insulated platinum tube to avoid differen- teristics should fall roughly one-sixth of the tial expansion effects (an example of this is way between those of the unsupported and shown in Fig. I), but the construction des- the fully encapsulated thermometer, but the cribed below (I) has proved extrcrnely value obtained for a) the mean temperature useful and versatile in a very wide range of coefficient between oo and IOO~C,of 0.003916 industrial applications. is in approximately this relationship with the The main features of the construction may typical figures of 0.003925 for unsupported be appreciated from Fig. 3. The helical wire and 0.003850 to 0.003880 for fully element is embedded in a glazing compound encapsulated constructions. Stability figures which attaches it to the high-alumina do not admit of such facile juggling, but these ceramic over approximately one-sixth of the also lie closer to those of unsupported than circumference of each turn. The result of those of encapsulated wires. This stability is this is that the greater part of the coil is illustrated by the following figures obtained free to expand and contract, but is sufficiently on a sample batch of four thermometers:

Stability Tests on a Batch of Four Thermometers R"=Resistance in ohms at 0°C;R,,,=Resistance in ohms at 100°C

Thermometer 1 2 3 4

Ro R,,, R, Rtoo Ro RlOO Initial Values 99.998 139.1 33 99.988 139.1 29 99.988 139.1 07 100.004 139.1 52

After 10 cycles I from 20°C to 400°C, and 250 99.995 139.126 99.982 139.109 99.985 139.104 100.008 139.142 hours at 400°C

Platinum Metals Rev., 1966, 10, (2), 44 Fig. 5 The large unit on the lef, incorporating the basic element construction shown in Fig. 3, is used for sucface temperature sensing in wing- skin temperature measurements in an aircraft anti-icing SYS- tem. The two small units, although not using exactly the same element design, retain the concept of a partially ronstrained platinum helix

The wide range of shapes and sizes of left a sensor incorporating the same basic platinum thermometers that these and other element construction for surface temperature techniques have made possible means that sensing in wing-skin temperature measure- an ever-increasing number of temperature ments in an aircraft anti-icing system, and measuring systems now use resistance tem- on the right two small surface temperature perature sensors. Some of the special shapes sensors which, though not using exactly the of resistance thermometer that have been same element construction, retain the concept produced for a variety of industrial, aircraft of an only partially constrained platinum and medical applications are shown in the illus- helix. Fig. 6 shows thermometers designed trations. Fig. 2 shows a range of industrial for medical and pathological work and based immersion thermometers, some suitable for on the standard range of hypodermic needles. direct insertion and some for use in pockets (thermo-wells). These thermometers all use Bridge Designs elements having the construction shown in When resistance thermometers are used Fig. 3 and can be produced in sheath in systems requiring the high accuracy diameters down to 0.093 inch. Fig. 4 shows called for in computer control, some of the thermometers for metal or bearing tempera- precautions normally associated only with ture sensing. The latter unit has found wide appli- cation in metal temperature sensing because of the ex- treme ease of installation and the wide temperature- range (up to 650°C) cov- ered. Fig. 5 shows on the

Fig. 6 Two platinum resist- ance thermometers, for use in medical and pathological work, lased on the standard range of hypodermic needles

Platinum Metals Rev., 1966, 10, (2), 45 The basic principle is that the leads in- corporated in the bridge arms are in series with fixed resistors having values very large compared to the lead resistances so that moderate changes in lead resistance have negligible effects on the total series resistance value. Thus N and J are large compared with L, and L, respectively, and L, is in the output circuit in series with the recordcr or indicator, which has a large input irn- pedance. The bridge is designed so that very little current flows through L, when lead resistances are at the design values and, when lead resistances vary, L, tends to equalise the voltage across the top of the bridge. This configuration makes it feasible to locate the sensor several thousand feet from the bridge and recorder or indicator. A particularly versatile conditioning unit of this type is shown in Fig. 8; this is a IO- channel bridge chassis to which the resistance thermometers are connected and which can precision laboratory measurements become accept up to ten plug-in Kelvin double necessary. The most important is the elimina- bridge modules. These are arranged to tion of lead resistance effects; this has, over convert the resistance change of the sensor, the years, received considerable attention and over a specified temperature range, to a systems using compensating loops and three- o to IoomV d.c. output signal. This standard wire connections have been widely used in signal is suitable for most data-loggers and industry, while four-wire, current and poten- computers and demonstrates one of the ad- tial lcad connections have normally only vantages of resistance thermometry; this been employed in standards work. This signal can be made to represent a different last connection scheme, however, has the temperature range using the same sensor by capability of providing the highest possible plugging in a different resistance bridge. measurement accuracy and its use is gradually Systems of this sort have been accepted becoming essential to obtain the accuracies for use in data-logging applications in power envisaged, for example, by the recent stations, nuclear plants and chemical in- British Standard BS1goq:1964. stallations to give system accuracies of better When resistance thermometers are used in than 0.25 per cent overall in the temperature association with an analogue-to-digital con- range o to 600°C with a wide variety of verter or computer it is convenient to provide thermometer shapes and configurations. a voltage output representing the temperature. One of the first large scale applications of This is normally achieved by using some this system in computer control will be at variant of the Wheatstone bridge fed from Fawley Power Station, near Southampton, a stable power supply and reading the out- which will employ resistance thermometers of-balance voltage. The Kelvin double in approximately zoo0 temperature measuring bridge answers both the requirements for channels, some 1000 of which will be used a voltage output and for a current and potential with these plug-in bridge units to provide lead connection; it is shown in Fig. 7. information to the computer.

Platirum Metals Rev., 1966, 10, (2), 46 Fzg, 8 A versatile 10-channel bridge chassis to which resistance thermometers can be con- nerted. The plug-in double bridge modules convert the resistance change of thp sensor to a d.c. output signal suitable for most types of data-loggers and computers

The modern platinum resistance thermo- -2oo0C to +5oo"C are a matter of routine. meter has overcome virtually all the obstacles Above this range to +750°C some extra that have hitherto prevented its widespread precautions are needed, while special units use and now provides the most accurate and are being introduced to cover temperatures up versatile method of precise industrial tem- to approximately IOOOT. perature measurement and control over the greater part of the normal spectrum of Reference process temperatures. Temperatures from I B.P. 959,368; 959,369; U.S.P. 3,114,125

Petrochemicals by Platinum Reforming WORLD'S LARGEST AROMATICS PLANT The world's largest aromatics petro- chemical plant recently began production in Puerto Rico. Operated by Commonwealth Petrochemicals Inc., a subsidiary of Common- wealth Oil Refining Company, the plant receives raw naphtha feedstock both from the parent company's refinery and by tanker from Venezuela. The naphtha is fed to a Unifining process unit where it is catalytically desulphurised, and thence to a Platforming unit where it is reformed over a platinum catalyst to produce a high yield of aromatics. These are separated in a Sulfolane unit and finally produced as high purity benzene, toluene, ortho-xylene and mixed xylenes. The total annual capacity of the plant is 172 million gallons of aromatics. Five of the plant's major units were designed by Universal Oil Products Company.

The aromatics complex at the new Puertu Rico plant of Commonwealth Petrochemicals Inc.

Platinum Metals Rev., 1966, 10, (2),4747 47 Prevention of Corrosion in Paper Making Machines

CATHODIC POLARISATION WITH PLATINUM-TITANIUM ANODES

By Professor A. Almar-Naess and J. M. Drugli Department of Metallurgy and Metals Working, Technical University of Norway, Trondheim

tected against corrosion and by which other Corrosion problems can become severe advantages can also be obtained. in paper-making machines in which the After laboratory studies had been carried pulp is dried over steam-heated cast- out the polarisation unit shown in Fig. I was iron cylinders. Paper with a smooth designed. It consists of an anode plate bright surface will be produced pro- z to 5 cm wide and as long as the cylinder to vided that the cylinder remains smooth be protected. It is embedded in a body of and bright, but corrosive media in the glass fibre epoxy, this being fastened by pulp attack the surface. This article screws to a rigid beam of steel. The anode describes the successful application of plate is made of 10 mm thick titanium to cathodic polarisation, using platinum- which a foil of 50 pm platinum has been spot- titanium anodes, to a large paper- welded. The distance between the cylinder drying cylinder to give it complete pro- and the anode plate is a few tenths of a centi- tection from corrosion metre, and electrolyte is pressed through the gap. Fabric water may be used as electrolyte In paper-making machines the paper pulp if the electrical conductivity is sufficient. The is dried over cast iron cylinders heated with cylinder and the anode plate are connected to steam. One machine of this type, known as a a suitable current source, giving a total Yankee machine, consists of only one big current of 2 to 4 amp per square metre of dryer. The cylinder may be 5 metres in cylinder surface. diameter and 5 metres in length, and have a When a surface element of the cylinder time of revolution of 2 to 15 seconds. Such passes the anode plate it is cathodically machines are normally in continuous opera- polarised. The electrolytic double layer is tion day and night. A Yankee machine charged and hydrogen develops according to produces a paper with a smooth and bright the reactions : surface, provided the cylinder is smooth and zH+ +2€I&H2 bright. However, this is a great problem for a 2 H,O I 28 z H, I 20H- great number of paper mills, because the sur- After the element has passed the polarisa- face is broken down by corrosive agents in the tion unit, the charge of the double layer pulp. It seems clear that C1 ions are respon- keeps it cathodically protected for a few sible for the main part of this corrosion, and tenths of a second. But when the double paper mills situated near the sea therefore layer has lost its charge the element is still have the most trouble. The present paper protected against corrosion for a considerable describes an equipment for cathodic polarisa- period of time because a strong basic layer tion now in use at some paper mills, by which was formed on the surface during polarisation the cast-iron cylinder can be completely pro- according to the chemical reactions referred to.

Platinum Metals Rev., 1966, 10, (2),48-51 48 Fig. 1 The design ofplatinum- clad titanium anode adopted for the cathodic polarisation of the cast-iron cylinder of a paper-making machine

Just after polarisation this layer has a thickness of approximately one-hund- redth of a centimetre and a pH of 10 to 11. It adheres to the cylinder on its rotation and, in the basic

layer, a protective film of PRESSURE HOSE Fe,O, or Fe,O, is formed. The pH of the basic layer decreases because OH ions / CAST IRON CYLINDER (CAT~ODE) PLATINUM-TITANIUM ANODE diffuse out in the paper 5 METRES D1A.X 5 METRES LONG 10 MM X 50 MM X 5 METRES pulp, and subsequently the protective film dissolves. The polarisation At this current density the consumption of current is adjusted so that the protective layer platinum is considerable when the electrolyte is intact a little longer than is the time of contains C1 ions. The amount is also depend- revolution of the cylinder. ent on the temperature and on the concenrra- tion of the electrolyte. Anode Design From the point of view of practical anode- Generally that part of the cylinder not cylinder distance and maximum cell voltage, covered by paper is small and therefore the the electrolyte to be circulated through the space which can be allowed for the anode polarisation unit should have an electrical unit is rather limited. It can be seen in Fig. I conductivity of 6 to 8.10 ohm-l cm-l. that the breadth of the unit is partly governed This corresponds to a solution of z g NaC1/1 by the width of the anode ?J plate, which consequently SOLUTIONS ,\\\ 0.70 NaCI+1;1gNa2SO4lLlTRE H20 must be made as small as - 0.035 N 029 8, +2.29 I - 11- possible. This results in a ////309 I -8,- I)0,505 N high current density on the anode, generally of 2 5- 0 the order of 0.2 amp/cm?. I ;4- \ E“

Fig. 2 Eflict of current density on platinum losses in chloride solutions. The anode consisted of rolled and recrystallised platinum with an exposed surface of 0.785 crn2

Platinum Metals Rev., 1966, 10, (2), 49 platinum, as can be appreciated from the platinum-titanium equilibrium diagram. Such metals are generally difficult to weld together because of cracking in the hard and brittle weld zone. However, when the weld- ing time is kept as short as 3 to 6 msec the diffusion zone is narrow and very satisfactory spot welds can be obtained between platinum and titanium, Small cracks can be seen in the weld zones, but they cause no practical in- convenience. The anodic properties of platinum are made inferior by alloying it with titanium, and a very thin weld zone such as is Fig. 3 A satisfactory spot welded joint between platinum and titanium ( x 100) shown in Fig. 3 is most desirable, since only a small amount of titanium has diffused into the platinum layer. Further study of the spot at 70‘6, or generally for Cay Nay SO,, C1, welding mechanism has been carried out, and NO, ions to a 0.035 N solution. If the paper the results will be published elsewhere. mill is situated near the sea the fabric water As is well known, the “break through” contains NaCl, but generally not in the voltage of titanium oxide formed in sea- required quantity, and therefore NaCl or water is 12 to 15 volts, and it is not much another inexpensive salt such as Na,SO different in dilute NaCl solutions. In sulphate must be added. solutions the oxide is stable up to 90 to IOO The platinum loss has been measured in different solutions at 70T at different current densities and the results are shown in Fig. 2. In dilute solutions of 0.035 N con- taining NaCl and Na,SO,, it is seen to vary between 0.05 and 0.20 pm/24 hours at 0.2 amp/cm . In stronger solutions the loss is smaller, but for many practical reasons such solutions are not desirable. No measurable platinum loss occurs when the solution is free of C1 ions, but unfortunately this is a rare situation in practice.

A platinum loss of 0.1 pm/24 hours means that the platinum thickness must be at least 30 pm in order that the anode shall have a life of one year. Thus platinised titanium cannot be used, as the thickness of the platinum layer is generally limited to I to 2 pm. Instead the anodes were madc by spot weld- ing 50 pm platinum foil to the titanium base. The distance between the spots was approxi- mately 0.4 cm, and each spot had a diameter of 0.05 to 0.1 cm. Titanium is known to form intermetallic compounds with most other metals, including

Platinum Metals Rev., 1966, 10, (2), so Fig. 6 The platinum-clad titanium anode structure in position on a relatively small machine making tissue paper volts and in mixtures of sulphates and usual way. It can be seen in Fig. 4 that the chlorides the stability can be noticeably in- titanium oxide will keep stable at a cell creased compared with pure NaCl solutions. voltage of 40, if the flaw in the platinum layer Suppose that the oxide is stable up to 15 volts. is not wider than one-half of the anode- What is the effect of a scratch in the platinum cathode distance. In Fig. s, A represents a foil or of an area of uncovered titanium local dissolution of the platinum at one of the formed, for instance, by excessive platinum anode edges. It is seen to be without any dissolution? If the cell voltage does not harmful consequence. exceed 15 volts there is no harmful effect The polarisation unit was originally apart from the corresponding reduction of designed for a Norwegian paper mill which the anode surface, as only a small current can for many years had had corrosion trouble. It pass through the titanium oxide. This is was set into operation early in 1963 and since generally the situation when platinised then it has worked successfully in that the titanium anodes are used for cathodic pro- drying cylinder is still metallically clean with- tection. out any trace of rust. It has also proved to be In the polarisation unit described above, a a very effective cylinder cleaner, probably cell voltage of 40 to 50 was necessary in order because the hydrogen development strips to avoid excessive salt content in the electro- fibre and paper remnants off the surface. lyte. In such circumstances the voltage across This has a favourable influence on the paper the titanium oxide layer might exceed 15 quality and on the speed of production. volts. A closer investigation was performed In Fig. 6 the anode unit is shown mounted on in a plane model of the anode-cathode space a machine for making tissue paper and made of electrically conducting paper, in wadding. The surface of the cylinder has which the equipotentials were drawn in the remained clean and mirror-like.

Platinum Metals Rev., 1966, 10, (2), 51 Expansion in Platinum Production SHORT AND LONG TERM PLANS AT RUSTENBURG

Over the past two years successive pro- long period either at the presently designed grammes of expansion have been announced rate or at a substantially increased rate of by Rustenburg Platinum Mines Limited, each milling. designed to maintain output in balance with Consideration has also been given, says demand and to give effect to the declared Mr Watson, to the advisability of increasing policy of the mining company and its sole the rate of production still further and to the refiners and marketing agents Johnson most rapid means of so doing. As an imme- Matthey & Co Limited to ensure to the best diate short-term measure, steps are being of their ability that platinum shall always be taken to increase rapidly, and for as long as available for use by industrial consumers, and may be necessary, the company’s output of that it shall be available at reasonably steady platinum beyond the designed capacity of the prices. plants. This additional increase will be achieved In a statement published in February, Mr by relatively inefficient technical measures, by D. A. B. Watson, Chairman of Rustenburg, increasing the tonnage of ore delivered to the confirms that the programme to expand mine crusher station and there sorting out the lower production is proceeding satisfactorily and is grade fraction, while at the same time opera- on schedule. Output has increased steadily ting the reduction plants beyond their and substantially and is still increasing, and designed capacities. These expedients, which the full designed milling rate will by now have will become fully effective in terms of mine been reached. Reserves of ore at the mine are production towards the end of the present amply sufficient to provide the tonnage of ore year, will produce more metal but will be required to maintain production over a very expensive; if it is found that this additional

Platinum ore loaded into hopper trains at Rusten- burg. Very large tonnages of ore are available, and for many years ahead expansion can be effected here more rapidly and more eficiently than in other areas in which mineral rights are held by the mining company

Platinum Metals Rev., 1966, 10, (2),52-53 52 Ore is carried by conveyor belt to the sorting station in the reduction plant output is likely to be required for several the present year events indicate that addi- years then steps will be taken to introduce tional capacity might be needed ahead of the more efficient mcthods of achieving this end. date originally contemplated, then immediate At the same time the company has recon- steps will be taken to provide this even though sidered whether the next major expansion a part of such capacity might in due course should be initiated at an earlier date than had and in certain circumstances prove to be in previously been thought necessary. If during excess of requirements from time to time.

PLATINUM-WOUND FURNACES IN THE MANU FACT URE 0F SE M I C0 ND UCTO RS

For the diffusion heat treatment of semiconductor materials the advantages of rhodium-platinum wound tubular furnaces include long life at the high temperatures involved, compactness, and high rates of heating and cooling. Each of the units in this battery of Johnson Matthey furnaces in the Lincoln factory of Associated Electrical Industries Limited is maintained at a closely controlled temperature to carry out one of the many diffusion processes required by the wide range of devices produced by AEI.

Platinum Metals Rev., 1966, 10, (2),53-53 53 The Wetting of Platinum and its Alloys by Glass

I11 - MICROSTRUCTURE AND MECHANICAL PROPERTIES OF GOLD-RHODIUM-PLATINUM ALLOYS

By G. L. Selman, B.s~.,M. R. Spender, B.s~., and A. s. Darling, Ph.D., A.M.1.Mech.E. Research Laboratories, Johnson Matthey & Co Limited

determinations in 1964. The 800T isotherm, In the concluding part of this stzdy of taken from this work, is shown in Fig. I. At platinum alloys for use in the glass this temperature level I per cent by weight industry, correlations between structure, of rhodium completely eliminates the single- composition ad high temperature phase region at the gold-rich end of the mechanical properties have been ob- diagram. Although gold also reduces the tained in the platinum-rich corner of solubility of rhodium in platinum, the effect the gold - rhodium - platinum system. is not so pronounced and the platinum-based Although gold additions decrease the solid solutions extend in an unbroken line melting point of rhodium-platinum over a considerable area of the diagram. alloys, the effect is notpronounced. The The present investigation has extended the alloy containing 5 per cent gold and 10 field of study to higher temperature levels. per cent rhodium which was shown in Although attention has been confined largely the previous parts of the paper to be par- to those platinum-rich alloys, described in an iicularly resistant to wetting has a earlier paper (s), which are reluctantly solidus between 1730°C and 1760'C. wetted by molten borosilicate glass, a great This alloy is single phased at tempera- deal of basic information has come to light. tures above 1JOO"C and is more rssis- The creep properties have been related to tant to creep than the 10 per cent composition, and it has been shown that high rhodium-platinum solid solution. Some temperature strength is not incompatible with of these improved high temperature resistance to wetting by molten glass. properties are sacrifcced if the gold content is reduced to 3 per cent. Alloy Preparation Platinum and rhodium sponges, and gold Small additions of rhodium to gold- grain, all of the highest available purity, were platinum alloys are known to broaden the induction melted, in air, in alumina crucibles miscibility gap (I), which eventually inter- before being chill cast into thick copper acts with the solidus to produce a system of moulds. The ingots were homogenised at the peritectic type (2, 3). The only informa- 1250°C for periods up to 64 hours, slowly tion on alloys containing substantial quantities cooled to 800°C and held at this temperature of rhodium comes from Raub and Falkenburg for 16 hours before quenching into water. (4), who published the results of their X-ray After this treatment all the alloys studied

Platinum Metals Rev.,1966, 10, (2),54-59 54 Fig. 2 3 per cent gold-12 per Fig. 3 5 per cent gold-1 0 per Fig. 4 13 per cent gold-2 per rent rho d ium-p1 at inum cent rho d i u m-p1 at i n u m rent rho d ium-p1 at inum quenched ufer unnealing for quenched after annealing for quenched after annealing for 48 hours at 90OOC ( X 500) 24 hours at 900°C ( X 500) 24 hours at 900'C ( X 500) could be cold worked into sheet or wire, Samples of homogenised and rolled sheet although it was noted that the ease of working were rapidly heated, in intimate contact with declined rapidly when the gold content ex- this thermocouple, to a temperature zo°C ceeded 5 per cent. below the desired level, held constant for one The total base metal impurity content of hour and then taken up to the quenching the alloys was of the order of 0.005 per cent. temperature at a rate of 20°C per hour. Cold rolled sheet examined after the final Quenching was accomplishcd in water from a stage of fabrication contained typically the vertical furnace, and the quenching tempera- following impurities : ture was increased by increments of ZO'C until signs of fusion became apparent in Cu O.OOI"~, Ca 0.0005°0,Cr o.oo~O0, Fe 0.002~~,Mgo.o002~~, Pd o.ooruo polished and etched microsections. Attempts were also made to determine by Metallographic Studies metallographic methods the boundary be- Solidus determinations were undertaken by tween the homogeneous and two-phase the "bracketing" method, a 20 per cent regions. This was found to bc rather an rhodium-platinum : 40 per cent rhodium- approximate technique in view of the steeply platinum thermocouple being employed be- sloping nature of the boundary curve. Alloys cause of the high temperatures involved. containing more than 7 per cent of gold were, Au moreover, very highly stressed by rapid quenching. Grain boundary precipitation was not completely suppressed and this led to what might almost be described as stress corrosion. In some instances etching removed

Fig. 1 Isothermal section through the gold-rhodium-platinum constitutional diagram at 800°C (after Raub and Rh Pt Falkenburg (4)) 20 40 60 80 WEIGHT % PLATINUM

Platinum Metals Rev., 1966, 10, (2), 55 Fig. 5 5 per cent gold-10 per cent Fig. 6 13 per cent gold-2 per cent rhodium-platinum quenched after anneal- rhodium-platinum quenched after anneal- ing for 24 hours at 1200°C ( x 500) ing for 24 hours at 1200°C ( X 500). Note incompletely suppressedprecipitate round the grain boundaries and the cavity left by a grain detached by etching complete grains from the surface of polished boundary evidently occurs between 3 and 5 microsections, and this behaviour complicated per cent of gold. Duplex structures are the search for small quantities of a second shown in Figs. 3 and 4. Globular precipitates phase at the grain boundaries. of the gold-rich phase can be distinguished Figs. 2, 3 and 4 show typical micro- round the grain boundaries of these micro- structures of the alloys containing 3, 5 and 13 sections, while the constituent in the body of per cent by weight of gold after quenching the grains is too fine for complete resolution. from 900°C. At this temperature the phase The gold denuded zones round the grain boundaries and the tendency towards sub- grain formation are characteristic features of the structure of alloys heat treated at this SINGLE- temperature level. PHASE tLL0YS MINOR PHASE Au RICH The homogeneous structures shown in ++ Figs. 5 and 6 were obtained by quenching + + Q(2 + from IZOO'C.The well-defined cavity shown in Fig. 6 occurred when a complete grain fell out of the surface during the process of etching. X-ray Diffraction Work Filings taken from homogenised alloys were sealed in silica quills and heat treated at the MAJOR PHASE Pt RICH + same time as the metallographic specimens. t After rapid quenching, these filings were +++@I 0 used for X-ray diffraction studies with Cu Ka 0 radiation and a Phillips powder camera. The C TWO PHASE ALLOYS patterns obtained were those of either a

Fig. 7 Lattice parameters of the phases present in 2 4 b 8 10 12 14 ternary gold-rhodium-platinum alloys quenched WEIGHT o/o AU IN 85% ~h pt ALLOY- after annealing for 24 hours at 850°C

Platinum Metals Rev., 1966, 10, (21, 56 homogeneous face centred cubic solid soh- tion or of a mixture of two such phases. The lattice parameters of the phases present in alloys quenched from 850°C are plotted in lloo PHASE CHANGE DUE TO 3% Au 10% RhPt Fig. 7. These results confirmed the sudden emergence of the gold-rich phase when the gold content exceeded 3 per cent by weight. PI 000 They agreed closely with values obtained by W a 3 Raub and Falkenburg (4) at Soo’C, but they 5 a did not permit an accurate determination of w the whole phase boundary. !?j900 Resistometric Studies PHASE CHANGE DUE TC The boundary between the single- and two- 3%Au 10% Rh Pt phase regions was fmally determined by 79OoC electrical resistance methods. The differential resistance bridge employed was first described 700 0.I I 2 by Stockdale (6), with modifications by DIFFERENTIAL EMF MILLIVOLTS Haughton (7). Two test specimens of very Fig. 8 Typical curve obtained with the differential similar temperature/resistance characteristics bridge were connected in opposition, the platinum leads having resistances which were low involved within limits of +203C. Support compared to those of the test specimens. for the accuracy of these resistometric deter- In general, the “standards” used for this minations was provided by the close agree- work were the 15 per cent gold-platinum ment between the value of 1028OC determined alloy and the 3 per cent gold, 12 per cent for the 15 per cent gold-platinum alloy and rhodium-platinum alloy. The test specimen the established value of 1030°C(8). Similarly, and an appropriate “standard” were placed the value of 790°C determined by the resist- in a horizontal tube furnace, in a region of ance bridge on the 3 per cent gold, 12per cent uniform temperature which was adjusted to rhodium-platinum alloy is close to the 80o”C about 700°C. The bridge was then balanced obtainable from the X-ray work of Raub and as closely as possible, and the furnace tem- Falkenburg (4). perature changed by increments of 30°C at half-hourly intervals. The out of balance Section through the Diagram at e.m.f. corresponding to each temperature level 85 per cent of Platinum was carefully measured with a vernier The results obtained by application of the potentiometer. A typical example of the previously described techniques made it graphs obtained by plotting these millivolt possible to construct the vertical section readings as a function of temperature is pro- shown in Fig. 9. It is obvious from this vided in Fig. 8. The lower inflection on this diagram that alloys used in contact with curve is caused by the 3 per cent gold, 12 per molten borosilicate glass will all be working cent rhodium-platinum alloy “standard” in the single-phase condition. Differences in entering the single-phase region. The upper contact angle behaviour cannot therefore be inflection is attributable to the test specimen attributed to discontinuous microstructural undergoing the same transformation. changes and must therefore be caused by At least three sets of determinations were fundamental modifications in the nature of made on each alloy, and the results obtained the solid solution induced by increasing defined the position of the phase boundaries quantities of gold.

Platinum Metals Rev., 1966, 10, (2), 57 2000 V 10. These tests were made on specimens A METALLOGRAPHIC EXAMINATION machined out of rolled sheet 0.060 inch thick and 0.25 inch wide. The gauge length was 1.5 inch. When stressed in tension at 700 I800 p.s.i. at 1400°C the 5 per cent gold, 10 per cent rhodium, 85 per cent platinum alloy resists failure for approximately 150 hours. I600 This compares with 60 hours for the binary 10 per cent rhodium-platinum alloy and 0.5 hour for pure platinum tested under the same u conditions. The 3 per cent gold, 10per cent 2 1400 rhodium, 87 per cent platinum alloy has a 3 G 0 DIFFERENTIAL slightly shorter test life than the 10 per cent a RESISTANCE W a rhodium-platinum alloy although the differ- 5 ence is not pronounced. As shown by the 1200 elongation curves on Fig. I I, the gold-bearing alloy creeps less rapidly than the binary rhodium-platinum alloy, and although it has 1000 a lower elongation at fracture, this is unlikely to have an adverse effect upon its performance in service. All the gold-bearing alloys were found to 800 fail at the grain boundaries after high tem- perature stressing. This behaviour occurred 2 4 6 8 10 12 14 at all stress levels, although rhodium- O/o Au IN 85% Pt Rh ALLOYS platinum is perfectly ductile at stresses above Fig. Y Vertical section through the gold-rhodium- 400 p.s.i. at 1400°C. At lower temperatures, platinurn constitutional diagram on a parallel however, the 10 per cent rhodium-platinum traverse ut 85 per cent of platinum alloy frequently exhibits intercrystalline failure and this has not imposed any restrictions High Temperatiire upon its industrial employment. Mechanical Properties Components in the glass industry are in- Stress-rupture data for the alloys containing variably taken out of service when distortions 3 and 5 per cent of gold are presented in Fig. prevent efficient operation of the process. As

-3000 w I J a :: 2000 Solo Au 10% Rh Pt u -3 1500- z 0 y 1000- m J Fig. I0 Stress-rupture data 700- for two gold-rhodizim-platinum W a alloys tested at 1400°C. The + broken line represents the * 500- performance of the binary 10 per cent rhodium-platinum I I 4 10 40 100 400 1000 alloy at the same temperature TIME TO FAILURE IN HOURS ILOG SCALE I

Platinum Metals Rev., 1966, 10, (2), 58 indicated by the table, the fracture 50% 77% 27% elongations of the gold-bearing alloys at 1400°C are high enough to ensure appreciable ductility under industrial conditions. Fracture Elongations of Gold-Rhodium- Platinum AUoys at 14QO"C

Stress Level 3% Au- 5y0Au- Ib./sq. in. 10% Rh-Pt 10% Rh-Pt I

750 27% 25% 1025 19% 27% 1167 50% 42% 1500 53% 45%

References I E. Grafried, K. Protzmann, K. Ruthard and H. Speidel, Heraeus Festschrift, r951 2 H. Schmid, Metall, 1958, 12, (7), 612-619 3 D.B.P. 940,188 Degussa 4 E. Raub and G. Falkenburg, Z. Metallkunde, 1964, 55, (7), 392- 3 97 5 G. L. Selman, M. R. Spender and A. S. Darling, Platinum Metals Rev., 1965, 9, (41, 130-135 3 6 D. Stockdale,J. Inst. Metals, 1931, 45, 127 7 J. L. Haughton, Ibid., 1931, 45, 140 8 A. S. Darling, R. A. Mintern and Fig. 11 Creep curves of the 3 per cent gold-10 per cent J. C. Chaston, J. Inst. Metals, rhodium-platinum alloy and of the binary 10 per cent 1952-53, 81, 125 rhodium-platinum alloy tested at 1400°C

Electrodeposition of Iridium PROGRESS IN DEPOSITION FROM AQUEOUS SOLUTIONS A recent paper by C. J. Tyrrell of Inter- G. A. Conn of Westinghouse Electric national Nickel Limited (Trans. Inst. Metal (Plating, 1965, 52, (12), 1258). This author Finishing, 1965~43,161-6)proposed a bromide has found that the cathode efficiency of an electrolyte for the deposition of iridium from iridium chloride electrolyte is markedly aqueous solution. The electrolyte contains improved by increased anodic current density, 5 gjl of iridium as the bromide and 8 g/1 and also by the introduction of auxiliary of hydrogen bromide. It is operated at 75OC a.c. electrodes. When these electrodes were at a cathode current densityof 0.15 amp/sq.dm operating at a current density of 50 amp/sq.dm to give deposits which are crack-free to a ax. the cathode efficiency improved from 2 to thickness of I p. Further dcposition will 30 per cent. The maximum thickness obtained produce cracked deposits, but nevertheless in these tests was 25 p, and again cracking the coating remains smooth and bright to a occurred with the heavier deposits. thickness of 10 p. Thus, while it appears that for thick Dr Tyrrell also reports on his experiences crack-free deposits the fused cyanide elec- with iridium chloride electrolytes, where he trolyte is still the only practical plating was unable to confirm the cathode efficiencies system, progress is being made with aqueous obtained by earlier workers. However, these electrolytes, and thin coatings are now possible variations may be explained by the work of from stable aqueous electrolytes. J. H.

Platinum Metals Rev., 1966, 10, (2),59-59 59 The Reaction between Hydrogen and Oxygen on Platinum PROGRESS IN ESTABLISHING KINETICS AND MECHANISMS

By G. J. K. Acres, M.SC., Pm. Research Laboratories, Johnson Matthey & Co Limited

Nothing certain is understood concerning the mechanism of what is the oldest known, and the simplest, catalytic oxidation. Recent work in the Johnson Matthey Research Laboratories has partly explained some of the inconsistencies found in previous work, and has established the best con- ditions for studying the kinetics of this reaction. In this article new suggestions are put forward on possible reaction mechanisms.

The formation of water when platinum (a) Simultaneous adsorption of hydrogen sponge or strip is exposed to a mixture of and oxygen on the catalyst surface hydrogen and oxygen was one of the first with subsequent reaction and desorp- catalytic reactions to be discovered and tion of water (5). recognised as such (I), but in spite of numerous k cc [0,lo-' [H,]n-l subsequent investigations there exists no accepted mechanism for this reaction. There (b) Reaction between adsorbed oxygen and are two related reasons for this gap in our hydrogen molecules in a van der catalytic knowledge: (i) in no instance arc Waals layer (6). two sets of kinetic results identical (see k GC [O,]"' [H,]' table), and (ii) the activity of platinum catalysts has not been reproducible. Much (c) Reaction between adsorbed hydrogen more is known about the mechanism of and oxygen molecules in a van der catalytic exchange and hydrogenation reac- Waals layer (3). tions than about this, the simplest oxidation k 01 [O,]' [Helo-l reaction. (d) Complex two site and alternate reac- Some Tentative Mechanisms tion mechanisms (7, 8). As with many other catalytic reactions, a classical kinetic approach has not yielded k cc [Osl" [H2IY where x and y can range from -I to + I sufficient information for the development of a satisfactory reaction mechanism, and Any one of these mechanisms will explain hence additional information has been sought. some but not all of the kinetic equations Isotopes have been used to determine the given in the table. None will apparently composition of the activated complex formed explain the observed phenomena of catalyst in the rate determining step (2, 3), and the activation by adsorbed oxygen and deactiva- phenomenon of catalyst activation by adsorbed tion by adsorbed hydrogen unless the forma- oxygen has received considerable attention. tion of an active oxide layer on the surface From these and the kinetic results, four of platinum is postulated. Roginsky indeed possible mechanisms have emerged : claims to have detected this oxide layer

Platinum Metals Rev., 1966, 10, (2),60-64 60 Fig. 1 The apparatus used for studying the oxidation of hydrogen on platinum wires

(PtaO,) on a platinum catalyst after it has been exposed to a hydrogen/ oxygen mixture (4). With so much information about this reaction already available, it should be possible to derive a mechanism without having to resort to any more practical work. How- ever, although the special features of this reaction such as catalyst activa- tion by adsorbed oxygen (4), de- activation by adsorbed hydrogen (9) and surface rearrangement of the catalyst are now well known, their effect on the kinetics of the reaction has not been established. Recent work in these laboratories enables us to account for some of the discrepancies in the system to less than 10-"mm Hg. The between previous studies of the reaction and catalyst was a platinum wire, 99.999 Pt, to throw some new light on possible reaction 0.203 mm in diameter and 15 cm long, rigidly mechanisms. fixed along the longitudinal axis of a cylind- rical reaction vessel, and electrically ther- Experimental Procedure mostated. Adsorbed gases were removed The reaction was studied in an all-glass from the wire by standard ion bombardment static system attached to a conventional techniques (10). In a typical experiment, the vacuum line capable of lowering the pressure reaction vessel was immersed in a bath of

Rate Equations for the Reaction between Hydrogen and Oxygen on Platinum Rate Equation Reference Comments ru Po, PH~-' Langmuir (I 5) Catalyst irreproducible

r tl Po,'+o Pn: Donnelly and Hinshelwood (5) ra Po, PH,O Boreskov, Slin'ko and Chesalova (16)

rcr Po, Or PH* Tanner and Taylor (6) Wire heated in air at white heat

rtl PO, pHa-f Krylov and Roginsky (4) Oxygen covered surface

Platinum Metals Rev., 1966, 10, (2), 61 sumably associated with changes in the heats of adsorption of oxygen and hydrogen on platinum after activation (11). Our results lend support to the hypothesis (4, 6) that a layer of adsorbed oxygen causes an enhanced activity, but this effect is only shown when gas mixtures containing an excess of hydrogen are used. It is probable that activation by adsorbed oxygen is an integral part of the reaction mechanism and should not be confused with activation caused by surface rearrangement. Effect of Water Vapour on the Reaction The pressure of the water vapour produced during the reaction increases progressively unless it is either condensed or swept out of the system; we have found that the reaction is retarded by water vapour. The vapour pressure of water was controlled by varying the temperature of the walls of the vessel using suitable constant temperature baths. The effect of the “wall temperature” on the rate is shown in Fig. 2: this effect also occurs

liquid nitrogen and a hydrogen- oxygen mixture of known composi- tion admitted; the rate was deter- mined by following the change in pressure in the system. The appa- ratus is shown in Fig. I. Catalyst Activation Activation of the catalyst by oxygen or the reacting gases is the probable cause of catalyst irrepro- ducibility and is often accompanied by a change in surface structure (4). If an increase in surface area were solely responsible for the activity increase, no change in the activation energy of the reaction is expected: such a change has, however, been observed in our work and is pre-

Platinum Metals Rev., 1966, 10, (2), 62 with silver and gold catalysts (12, 13). Wc If both are added simultaneously to a clean have also found that the diameter of the surface, moderate rates are found, pressure- reaction vessel affects the rate as shown in time curves are linear and the reaction is Fig. 3; the magnitude of the effect varies first order in oxygen and of negative order with the pressure of gas in the reaction vessel. in hydrogen above about I cm pressure. When pre-adsorbed oxygen is present before Effect of Pressure on the Reaction the mixture is added, rates are faster, but The effects of the pressures of hydrogen pressure-time curves are still linear although and of oxygen on the rate were investigated the reaction is now zero order in hydrogen. by varying one pressure while keeping the Very slow rates are found when pre- other constant at I cm : because of the adsorbed hydrogen is present. The import- activation effects mentioned above, a new ance of pre-adsorbed gases has not been wire was used for each gas mixture studied. clearly appreciated before. The vessel diameter was 22 mm and the wall An unusual feature of this system is that temperature -196°C. The total pressure the surface seems reluctant to change from and thermal conductivity of the gas mixture the conditions obtaining at the start of an were kept constant by the addition of an experiment. Dcspite the well-established inert gas, which was helium when hydrogen fact that oxygen is more strongly chemisorbed pressure was varied and nitrogen when oxygen than hydrogen (14) pre-adsorbed hydrogen is pressure was varied. Under these conditions, not rapidly displaced by oxygen nor does an pressure-time curves arc linear and the extensive oxygen layer seem to accumulate zero order rate constant is directly propor- in the presence of hydrogen. This point also tional to oxygen pressure and to a negative has not been clearly stated before. power of the hydrogen pressure above I cm Many years ago Donnelly and Hinshelwood (Fig. 4). If, however,the catalyst is “activated” (5) obtained orders similar to those we find by the reacting gases or by pre-adsorbed when no pre-adsorbed gas is present. The oxygen, the reaction is not retarded by high interpretation must be that the reactive hydrogen pressures (see also Fig. 4). The oxygen is adsorbed only weakly or not at activation energy does not change with gas all, and that vacant sites (progressively composition at constant total pressure. filled at higher hydrogen pressures) are required for reaction. The linear pressure- The Reaction Mechanism time curve could result from the opposite It is clear from our results that the reaction signs of the reaction orders, but this cannot between hydrogen and oxygen is strongly be so at hydrogen pressures below about I cm poisoned by the water vapour which is and some additional form of explanation produced: to obtain reasonable rates, it is may be required. essential to keep the prcssure of the water Different conditions exist when pre- vapour low and to encourage its transport adsorbed oxygen is present. Work on the away from the catalyst surface by keeping the adsorption of oxygen on platinum films has walls of the reaction vessel at a low tem- shown that only 63 per cent of the surface perature. Meaningful orders of reaction are can be covered, at which time the heat has obtained when the water vapour pressure is fallen from 70 kcal/mole-l at zero coverage less than 0.004 mm and when precautions to 30 kcal/mole-l(14). The limit is apparently are taken to keep the temperature gradient set by geometric rather than energetic between the wire and the wall approximately factors. The remaining surface is pre- constant. Even under these conditions, both sumably covered by adsorbed hydrogen and the rate and the orders of reaction vary the reaction is then zero order in hydrogen. with the sequence of addition of the reactants. It is difficult to see why rates under these

Platinum Metals Rev., 1966, 10, (2), 63 conditions are faster than those found when closely the variables that need to be con- no pre-adsorbed oxygen is present. A trolled if worth-while kinetic measurements possible explanation is that between the are to be obtained. pre-adsorbed oxygen atoms there are sites References prohibited to oxygen atoms but available to I D. McDonald, Platinum Metals Rev., 1965, 9, weakly adsorbed oxygen molecules and 136 2 S. Z. Roginsky, Proc. 3rd International Congr. hydrogen atoms. on Catalysis, Amsterdam, 1964, (North- The effect of vessel diameter on rate Holland Publishing Co, 1965)~p. 939 (Fig. 3) is complex and its form varies with 3 E. N. Khar’kovskaya, G. K. Boreskov and M. G. Slin’ko, Doklady Akad. Nauk S.S.S.R., the composition of the gas mixture. This 1959,1273 I45 effect is connected with the retarding effect 4 0. K. Krylov and S. Z. Roginsky, ibid., 1953, of water vapour which is interpreted as 88, 293 5 R. P. Donnelly and C. N. Hinshelwood, follows. The reaction of hydrogen atoms J. Chem. SOL.,1929, 132, I727 with oxygen molecules or weakly adsorbed 6 H. G. Tanner and G. R. Taylor, 3. Amer. Chem. Soc., 1931, 53, 1289 oxygen atoms leads 10 adsorbed hydroxyl 7 D, L. Chapman and G. Gregory, Proc. Roy. radicals: the slow step is the reaction SoC., 1934, A1479 69 H f OH d H,O 8 G. K. Boreskov, J. Chim. phys., 1954, 51, x # 759 9 D. L. Chapman, Proc. Roy. Soc., 1936, (asterisks indicate bonding to the surface), A156,284 and hence if the water formed is not efficiently 10 A. Couper and D. D. Eley, Discussions removed the reverse reaction will occur with Faraday SOL.,1950, 8, 172 11 J. G. Aston, J. Phys. Chem., 1963,67,2042 consequent retardation of the reaction (see 12 A. F. Benton and J. C. Elgin,.?. Amer. Chem. Fig. 2). ~OC.,1926, 48, 3027 13 Idem ibid., 1927, 49, 2426 Conclusion 14 D. Brennan, D. 0. Hayward and B. M. W. Trapnell, Proc. Roy. SOL.,1960, A256, 81 The present work has by no means resolved 15 I. Langmuir, Trans. Faraday Soc,, 1922, 17, all the outstanding problems of the mechanism 62 I of the reaction of hydrogen with oxygen on 16 G. K. Boreskov, M. G. Slin’ko and V. S. Chesalova, Zhur. Fiz. Khim., 1956, 30, platinum, but it has served to define more 2787

Platinum Metals Rev., 1966, 10, (2), 64 Catalysis of Olefin- t o=OlefinAddition by Rhodium Chloride A NEW HOMOGENEOUS REACTION

Much interest has recently been shown in The mechanism of the ethylene dimerisa- homogeneously catalysed reactions of oleiins. tion reaction catalysed by ethanolic solutions These reactions include isomerisation, poly- of rhodium chloride containing hydrochloric merisation, hydrogenation, oxidation and acid has been studied by Cramer (3). An carbonylation, and are catalysed with par- induction period of about 30 minutes is ticular efficiency by salts and complexes of observed, during which time ethylene is rhodium and palladium (I). Their homo- absorbed only slowly : the catalytically geneous performance has the potential ad- active species then formed is believed to be vantages over their heterogeneous catalysis the anion [(C,H,), Rh' Cl,]- (A). This ion of greater selectivity and more economic is also obtained when [(C,H,), Rh' Cl], is use of metal atoms. An important develop- dissolved in ethanolic HCI, and when this ment in this field is the reaction recently solution is used as a catalyst no induction disclosed by workers in the Du Pont Research period is found. Laboratories of olefin self-addition catalysed The ion A is oxidised by HCl to by rhodium chloride (2, 3). This will be of [C,H,(C,H,)Rhll'C1, s]- (B) where s may particular interest in the petrochemical be water, ethanol or conceivably C1-. This industry as a possible means of upgrading latter species is of interest because it is the the large quantities of ethylene now or first example of an olefin coordinated to shortly to be available. RhI" : however at -15"C, where no dimeri- Ethylene is dimerised to the equilibrium sation occurs, this ion is unstable and liberates mixture of n-butenes by rhodium chloride in ethylene, and from the solution the salt methanol or ethanol at 45" to 150°C with Cs [C,H, Rh Cl,(H,O)] has been isolated. ethylene at atmospheric pressure or above: Dimerisation occurs when the coordinated the presence of the solvent is not essential, ethylene molecule in B inserts itself between and it is believed that the primary product the ethyl group and the rhodium atom, is I-butene which subsequently is isomerised. giving the ion [C,H,Rh"'CI, s]-: this rapidly Ethylene also combines with propylene loses HC1 giving [(C,H,)Rh' C1, s]- from to give equal amounts of C,, C, and C6 which butene and s are quickly displaced products, the hydrogenated C, fraction con- by ethylene, regenerating the ion A. This taining both n-pentane and 2-methylbutane. is a consequence of ethylene being much more The addition of ethylene to butadiene strongly coordinated to Rh' than butene. proceeds with great facility with rhodium Dimerisation only occurs when the ligands chloride at 50T, giving no dimers but chiefly are C1-, Br- or I- : other anions and ligands I ,4-hexadiene which is partly isomerised to do not allow the reaction to proceed. the zJ4-isomer. The reaction of ethylene with I ,3-pentadiene is even faster, giving 3-methyl- References 1,4-hexadiene. No doubt a general reaction I G. C. Bond, Platinum Metals Rev., 1964, 8, 92 z T. Alderson, E. L. Jenner and R. V. Lindsey, of considerable importance has been dis- 3. Am. Chem. SOC.,1965, 87, 5638 covered, and many more examples will soon 3 R. Cramer, ibid., p. 4717 be added to those listed above. G. C. B.

Platinum Metals Rev., 1966, 10, (2),65-65 65 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES W and Mo oxidation the rate is controlled by 0, diffusion through the boundary-layer towards the Electron Density and Electronic Properties metal. This difference results from the much in Noble-Metal Transition Elements lower oxidation rate of Pt. M. A. JENSEN, B. T. MATTHIAS and K. AND~S, Science, 1965, 150, (3702), 1448-1450 Thermal Diffusivity of Platinum It is shown empirically that, for the Pt group J. J. MARTIN, P. H. SIDLES and G. c. DANIELSON, metals and their alloys, the superconducting U.S.A.E.C. Rept. IS-1261, 1965, (Oct.), 11 pp transition temperature, the magnetic susceptibility Values for the thermal conductivity of Pt were and the electronic specific heat are adequately calculated from diffusivity measurements. They described as universal functions of the valence agree with other studies at room temperature but electron density. not at high temperature and the use of Pt as a conductivity standard will need additional Surface Energy and the Secondary Re- measurements by absolute methods. Four Pt crystallisation of Platinum Sheet samples with resistivity ratios of 34, 100, goo and M. MCLEAN and H. MYKURA, Acta Met., 1965, 13, 5000 were studied at 300-1200~K. Thermal (n), 1291-1297 diffusivity values were insensitive to Small When growth rates of secondary crystals in thin amounts of impurities. Pt sheet at 1500°C were measured, only crystals with orientations close to {111} were observed Magnetic Moments in the Ordered Fez.8 Ptlz to grow. They grew through the polycrystalline Alloy matrix at rates dependent on the specimen thick- E. KR~Nand P. SZABQ, Solid State Commun., 1965, ness and their own orientation. Impurities may 3, (II), 371-372 cause the reduced grain boundary mobility. Neutron diffraction measurements on Fe,., Ptl.z, Contributions to driving pressure for 0.01 cm Pt which has Cu,Au-type structure, give pFe=3.3 sheet are: surface, sgY/o; grain boundary, 62q0; 10.2 p~ and ppt=1.5*o.2 p~. impurity drag, -21%. No secondary recrystal- lisation is predicted for Pt sheet thicker than Investigation of the Recovery of Atomic 0.027 cm. More possible orientations occur with thinner specimens. Defects in Palladium and Copper-Palladium Alloys The Wetting of Gold and Platinum by Water w. KOSTER and H.-P. KEHRER, Z. Metallkunde, K. w. BEWIG and w. A. ZISMAN,~. Phys. Chem., 1965, 56, (111, 760-767 1965,693 (121,4238-442 Studies of the recovery of cold-worked and A sessile drop of pure H,O placed on pure, quenched Pd and Cu-Pd alloys by resistivity polished Au or Pt spreads spontaneously over the measurements at -40 to 300°C showed that Pd clean surface with zero contact angle but if the recovers in stages 111 and IV with activation surfaces have been contaminated by hydrophobic energies of 1.03 fo.02 eV (stage 111 after cold traces then white heat in a stream of high-purity working only), due to recovery of interstitial gas is required previously. Similar traces in the atoms, and 1.5o&o.o7 eV (stage IV after quench- gas may be adsorbed and keep the surfaces non- ing), due to annihilation of vacancies. Activation wetting but, if they are removed in an adsorbent energies of the alloys increased with Pd content. cold trap, the Au and Pt specimens can be wetted completely. On the Change in the Thermoelectric Power and the Electrical Resistance of Alloys of the The Pressure Dependency in the Oxidation Palladium-Silver System in a Transverse of Platinum Explained by a Boundary- Magnetic Field layer Diffusion Mechanism T. RICKER and R. LUCK, Ibid., 799-802 G. c. FRYBURG, Trans. Met. soc. A.I.M.B., 1965, Studies were made on Pd-Ag, Pd-Rh and Ag-Cd 233, (111, 1986-1989 alloys. A cryomagnet for the measurement of Evidence indicates a boundary-layer diffusion galvanomagnetic properties at low temperatures mechanism for Pt oxidation above 800°C except is described. The changes depend on both the at the lowest pressures. The oxidation rate magnetic induction and resistivity according to depends on the rate of diffusion of oxide through the second power although this is not strictly true the boundary-layer away from the Pt, whereas for in pure metals and in stronger fields.

Platinum Metals Rev., 1966, 10, (2),66-73 66 The Temperature Dependence of the Resist- The Plastic Deformation of Iridium Single ance and Other Electrical Properties of Crystals Palladium-Silver and Palladium-Rhodium R. HAASEN, H. HIEBER and B. L. MORDIKE, Z. Alloys Metallkunde, 1965, 56, (12), 832-841 T. RICKER and E. PFLUGER, Ibid., 1966, 57, (I) The critical shear stress of zone-refined Ir single 39-45 crystals has temperature dependence similar to Results for the temperature dependence of the that of impure Cu and Ag. Activation energy is resistance of Pd-Ag and Pd-Rh alloys at 80- 1.2 eV and initial activation volume is 2.5.10-l9 ~roo"K,for the Hall effect in Pd-Ag alloys at cm3. Stacking fault energy is estimated to be 80-400°K and for the Nernst effect in Pd-Ag, .,I -296i59- erg/cm2, i.e. more than other noble Pd-Rh and Pd-Ma alloys at room temperature metals and comparable to that of Ni, i.e. disloca- agree well with an extended model of quasi-free tions are practically undissociated. Elastic and electrons combined with Mott's picture of elec- plastic parameters of Ir show quantitative agree- tron structure of transition metals. Ag-rich ment of mechanical properties with other f.c.c. alloys show effects due to change of Debye metals if the characteristic deformation stresses temperature. The model enables temperature are related to shear modulus, which for Ir is very dependence of resistance, thermoelectric power high and limits its range of plasticity. The in- and Nernst effect to be derived from the same fluence of impurities is still apparent and yet density of states function. The concentration more so in polycrystalline Ir. dependence of these effects is due essentially to scattering of electrons into the incompletely Establishment of Two New Compounds filled d-band. IrBi, and IrBi, in the System Bismuth- Iridium Ordered Alloys of Gold-Palladium System. N. N. ZHURAVLEV and E. M. SMIRNOVA, Kristallo- I. Electron Diffraction Study of Evaporated grafya, 1965, 10, (6), 828-832 Au3Pd Films IrBi, has rhombic crystals isomorphous with A. NAGASAWA, Y. MATSUO and J. KAKINOKI, J. Phys. NiBi,. IrBi, has monocyclic crystals isomorphous Soc.Japan, 1965, 20, (IO), 1881-1885 with rx-RhBi, and possesses arsenopyrite structure. Electron diffraction study of evaporated single crystal films of 10-60 at."L Pd-Au alloys revealed The Reaction of Niobium with Ruthenium an ordered phase with Cu,Au-type structure at L. PANTALEIMONOV, 0. NESTEROVA, 2. A. GUTS, 25 at."" Pd-Au with an order-disorder trans- A. P. K. G. AKHMETZYANOV and I. G. SOKOLOVA, formation which occurs at 850'C. vat. Moskov. Univ., Ser. 11, Khirn., 1965, (6), 57-62 Plastic Deformation of Pal-H Alloys NbRu melts at ~goo"C,the eutectic point occurs at s. TAKAGI and T. SUGENO,~~~~~J. Appl. Phys., 1760°C~66 at.46 Ru and there is a minimum in 1965, 4, (Io), 772-777 thc solidus curve at 1800°C, 40 at.% Ru. This minimum and that of lensile tests on Pd-H alloys were carried out at the isotherm of electrical resistivity and of the temperature coefficient of various temperatures and strain rates. Hardening of Pd due to H-charging was more pronounced in resistance, the maximum of the hardness curve and the b.c.c. lattice to tetragonal lattice transition than in (3-phase. In polycrystalline d-alloys a- all occur at -400; Ru. the temperature and concentration dependence of yield stress were measured at -80 to +13o"C and indicated that hardening was dominated by The Reaction of Ruthenium with Tantalum the chemical interaction. Low H,-concentration L. A. PANTALEIMONOV, 0. F. NESTEROVA, K. G. specimens at liquid Hztemperatures had serrated AKHMETZYANOV and I. G. SOKOLOVA, Ibid., 63-68 stress-strain curves (the Portevin-Le Chatelier The Ru-Ta system has a eutectic point at 1950°C~ effect) but why is not known. 70 at.";; Ru, a minimum in the solidus curve at 197o'C, 44-45 at.? Ru and RuTa melts at Absorption Isotherms of Hydrogen in the 2050°C. The maximum in the hardness curve %-Phaseof the Hydrogen-Palladium System and the b.c.c. to tetragonal lattice transition also J. W. SIMONS and T. B. FLANAGAN,~. l'hys. Chem., occur at 44-45 at.06 Ru. 1965, 69, (II), 3773-3781 Absorption isotherms were determined at o-go"C On the Occurrence of Some U,X Compounds from variations in the electrode potential and of Uranium with Transition Metals electrical resistivity of Pd wires during slow A. F. BERNDT and A. E. DWIGHT, Trans. Met. SOC. absorption of H, from dilute HCl solutions, and A.I.M.E., 1965, 233, (IZ), 2075-2078 represent equilibrium data. Average isosteric The stoichiometrically prepared compounds heat of absorption is 4780j,100 cal/mole of H, U,Tc, U,Rh, U,Os and UJr, formed by peri- from H-Pd=o.o02 to 0.014. Statistical analysis tectic or peritectoid reactions, are isostructural of the isotherms is based on interacting absorbed with U,Ru. Lattice parameters and miscibility protons. relationships are listed.

Platinum Metals Rev., 1966, 10, (2), 67 New T,B, Compounds C,,H,,RhCl,B, where B is monodentate basic F. HULLIGER, Nature, 1966, 209, (5OZZ), 500-501 ligand. New compounds synthesised include Ir,Ga,Ge,, IrJnlSn,, Ir,Ga,Ge,, Ir,Ga,Sn,, Ir,In,Ge,, Ionisation and Dissociation of Ruthenium Ir,In,Sn,, Mo,Sb,, OsIr,Sn,, Tc~As,, Re,As,. and Osmium Tetroxides J. G. DILLARD and R. w. KISER, J. Phys. Chem., The Occurrence of Superconductivity in 1965>69,(111,3893-3897 Sulphides, Selenides, Tellurides of Pt-group Principal ions from ionisation and dissociation of Metals RuO, and OsO, by electron impact were deter- mined by mass spectrometry and their heats of C. J. RAUB, V. B. COMPTON, T. H. GEBALLE, B. T. formation were obtained. M0,- is formed by MATTHIAS, J. P. MAITA and G. W. HULL,J. Phys. dissociative electron attachment; MO- and M0,- Chem. Solids, 1965, 26, (IZ), 2051-zo57 are produced by ion-pair formation processes. Superconductivity occurs in Pd-Se and Pd-Te I(RuO,)= 12.3,&0.2,eV, I(Os0,) =12.9,& compounds, in IrTe, and in PtTe. 85-87 at.OL o.12eV, D(O-RuO,) =104 kcaljrnole and Pd-Se alloys have TC=o.66"K, which is unusually D(0-OsO,) = 108 kcaljmole. high for its valence-electron concentration. Homogeneity ranges exist for hexagonal B8-type PdTe and for trigonal C6-type PdTe,. Low ELECTROCHEMISTRY temperature heat capacity measurements for Nature of the Surface of a Platinum- PdTe and PdTe,.,, show that large changes of T, with composition are accompanied by large Rhodium Alloy in Electrocatalysis changes in linear heat capacity coefficient y. A. DAMJANOVIC, A. DEY and J. O'M. BOCKRIS, J. Catalysis, 1965, 4, (6), 721-724 Steady state potential-log rate relationships for CHEMICAL COMPOUNDS the electrochemical oxidation of H,O to 0, and Platinum Carbonyls Substituted by Tertiary for the cathodic reduction of 0, to H,O in I N HClO, and in I N KOH, plotted for Rh, Pt and Phosphines 40~1~Rh-Pt, show that the reactions on the alloy G. BOOTH, J. CHATT and P. CHINI, Chem. Commun., follow the kinetic characteristics of whichever 1965, (241, 639440 pure metal has the faster rate at a given electrode A series of quite stable trinuclear Pt carbonyl potential, indicating the possibility that the homo- derivatives was produced by substitution of geneous alloy substrate has become a hetero- tertiary phosphines and also a less well-defined geneous mixture of the metal oxides and therefore polymeric dicarbonyl [Ptn(CO,),]. Ease of prepa- a type of polyelectrode. ration fell when methyl groups replaced phenyl groups. Structures, melting points and some Anodic Corrosion of Rhodium in Hydro. other properties are tabulated. Those derivatives chloric Acid Solutions which contain triangles of Pt atoms are the first J, LLOPIS, I. M. TORDESILLAS and M. MUI~IZ, to be reported. Electrochim. Acta, 1965, LO, (11), I045-IOSs Anodic corrosion of Rh in HCl by action of dc Rhodium Sirlphate Complexes occurs with high overpotential and Rh(II1) S. I. GINSBURG and N. N. CHALISOVA, zh. Neorg. complex formation (yellow solutions) and it is Khim., 1965, LO, (11), 2411--2417 enhanced by increasing temperature and HC1 Thermogravimetric, polarographic and potentio- concentration. Superimposed ac increases the metric studies of the synthesis of Rh sulphates attack and at low overpotentials raspberry-red show that the mononuclear aquohydroxysulphate RhjIII) solutions are obtained; ac effect increases is formed at room temperature with single bonds as frequency decreases. For a given dc value no which readily split in aqueous solution. At IOC- apparent corrosion occurs until a threshold 125°C the sulphate is more complex with double i,,%idc is reached. Order of corrosion resistance bonds and Rh:SO,=a:3. At z50-3z5'C the is Rh

Platinum Metals Rev., 1966, 10, (2), 68 PdOz to PdO and 0,. 0, was reduced from Hydrocarbon-leak-detectorTool Contributes adsorbed 0, molecules on a Pd cathode. to Cleaner Air On the Adsorption Properties of Rhodium Oil GasJ., 1965,63, (48),65 and Ruthenium Electrodes in Relation to Esso Research and Engineering Co have developed a leak detector for hydrocarbons with a sensing Electrolytes head containing shielded and unshielded Pt G. P. KHOMCHENKO, A. F. LUNEV and K. N. wires. When gaseous fumes reach the less- BOGDANOVSKAYA, Elektrokhimiya, 1965, I, (11) shielded wire the Pt catalytically raises the burn- 1352- 1 35 5 ing of the gases and also changes the circuit Adsorption properties of Rh and Ru electrodes resistance to alert the operators. Use of the depend on the electrolytes in relation to the device at Humble's Bayway Refinery, Linden, potential. Comparison of their properties of gas N.J., has reduced hydrocarbon leakage to the adsorption and retention demonstrates the roles sewers, and air and water pollution. of the ionic double layer and of the potential drop at the metal-solution grain boundary. Just as the Pt surface is fully degasified in the double layer CATALYSIS potential region so on Rh is an insignificant Platinum-based Reforming Catalysts amount of gas present, whose atoms have dipole J. TOMASIK and J. WRZYSZCZ, Chem. Stosowana, bonding with the metals. 196539, (ZA), 205-216 New Method of Dissolving Ruthenium Tests on catalysts containing 0.1-1.0 at.:/, Pt for A. A. GORYUNOV and A. N. RYABOV, Zh. Neorg. both low and high pressure reforming show that the amount of Pt does not affect the isomerisa- Khim., 1965, 10, (IZ), 2596-2601 tion activity but that it affects the degree of The anodic dissolution of Ru powder in an alka- conversion and the aromatisation. These data can line medium to obtain a concentrated solution of be used in optimising Pt content of industrial ruthenates and perruthenates of the alkaline contact catalysts. metals, free from extraneous salts, occurs effi- ciently and relatively quickly in a described cell. Changes of the Aromatisation Property of Platinum-Alumina Catalyst in Relation to ELECTRODEPOSITION AND the Content in it of Platinum and Sodium SURFACE COATINGS N. R. BURSIAN, s. B. KOGAN and z. A. DAVYDOVA, Kinetika i Kataliz., 1965, 6, (6), 1046-1051 Investigation of Electrolytic Mixed Deposits The aromatisation of N-hexane at 545", atm. of Platinum and Palladium with Ruthenium pressure over Pt/A1,0, catalysts with 0.01-1.2 0. A. PETRII and v. E. KAZARINOV, Elektrokhimya, wt.:; Pt and 0.02-1.6 wt.O/;, Na and the conver- 19651 1, (1111 1389-1391 sion of N-hexene-1 over A1,0, were studied in Ru-Pt and Ru-Pd deposits on Pt from 1% the same conditions. Possible mechanisms for [xH,PtCl,+yK,RuNOC1,] and I % [xPdCI, alkylaromatic hydrocarbon formation were +yK,RuNOCl,] solutions were checked for examined. A scheme for conversion of N-hexane thickness and composition by radioactive over Pt/Al,O, with parallel formation of aromatic labelling of K,RuNOCl,. The amount of Ru is hydrocarbons on Pt and acid centres is proposed. proportional to the amount in solution until Optimum Na concentration depended on the Pt secondary factors cause its value to pass through content of the catalyst. a maximum. Mixed electrolytic deposits contain- ing 5-80% Ru have high chemical stability and Development of a Mathematical Description are more active for catalytic and electrochemical of Platforming for Optimisation of the processes than the metallic alloys. Process. I. YU. M. KHOROV, G. M. PANCHENKOV, s. P. ZEL'TSER LABORATORY APPARATUS and W. A. TIRAK'YAN, Ibid., 1092-1097 This mathematical model of platforming takes AND TECHNIQUE account of the catalyst and of the composition of Diffusion-Sorption Pumping the input material and its fractions. Determina- P. L. READ and H. H. GLASCOCK, 3. vacuum sci. tions of the reaction parameters show good agree- Technol., r965, 2, (6), 307-308 ment betwccn calculation and experiment. Pressure in a small system was reduced from 760 Torr to I XIO-* Torr by using Ha diffusion The Production of High Octane Petrol by through a 25"; Ag-Pd foil combined with the Catalytic Reforming sorption of gas on liquid-N,-chilled synthetic G. N. MASLYANSKII, R. F. PANNIKOVA and G. D. zeolite. This is a useful technique for a forepump KAMUSHER, Khim. i Tekhnol., Topliv i Masel, 1965, in getter-ion-pumped ultra-high vacuum systems. (12), 1-6 Ag-Pd alloy is used because pure Pd might crack Catalytic reforming of a wide range of petroleum during the& cycling. fractions can be carried out at 20 atm without

Platinum Metals Rev., 1966, 10, (2), 69 regeneration of the catalyst for many months. Catalytic Conversions of 1,P-Endomethylene- The use of Pt catalysts with high selectivity in- spiro-(5,5)-undecane on Platinum Catalyst creases the yields of high-octane petrol and of N. V. ELAGINA, A. K. MIRZAEVA, KH. E. STERIN, A. V. H,. Fractions evaporating in the ranges 85-140, BOBROV and B. A. KAZANSKII, Neftekhimiya, 1965, 85-180, 105-140 and 105-18o’C,which contain 5, (51, 671-675 60:/” paraffins can be reformed to 95 octane petrol Final products (wt.7,) of the catalytic conversion with a yield between 78.7:0 and 85.70/;compared with Pt/C at 320°C are 2,3-benzbicyclo-[1,2,3]- to the original composition. H, yield is 1.5-1.80:. octane and 2,~-benzbicyclo-[o,3,3]-octaneJ(SO); 1-methyl-3-phenylcyclopentane, (11); benzyl- Catalytic Oxidation of Ammonia on Platinum cyclopentane, (9); monoalkylbenzenes, (7). E. J. NOWAK, Chem. Engng. Sci., 1966, 21, (I), 14-27 Hydrogenation of 2-Methyl-5-acetylfuranon The kinetics and mechanism of NHs oxidation on Platinised Carbon in a Flow System under Pt or Pt alloy screens and gauzes are discussed Pressure with respect to new data on heat and mass trans- N. I. SHUIKIN, G. K. VASILEVSKAYA and I. F. port compared with those for a single infinite cir- BEL’SKII, Izv. Akad. Nauk S.S.S.R., Ser. Khim., cular cylinder. The adequacy of mass transport 1965, (11),2029-2032 for a solely heterogeneous mechanism is indicated. Effects of catalyst shape and roughness together The reaction was studied at 200-2207C. Changing with analysis of earlier data suggest that catalyst pH, from I to 50 atm. did not affect the reduction losses during commercial oxidation are due to of the carbonyl group nor hydrogenolysis of the oxidative volatilisation of Pt. furan ring but increased the degree of hydro- genisation of the hydrogenolysis products. The Mechanisms of Hydrogenolysis and Kinetic Regularity of the Isomerisation Isomerisation of Hydrocarbons on Metals. Reaction of n-Pentane on Platinum Catalysts I. Hydrogenolysis of Cyclic Hydrocarbons N. R. BURSIAN and N. K. VOLNUKHINA, Zh. Priklad- G. MAIRE, G, PLOUIDY, J. c. PRUDHOMME and F. G. noi Khim., 1965,38, ( 10), 2273-2278 GAULT, Catalysis, 4, J. 1965, (51, 556-559 The rate of n-C,H,, isomerisation is directly pro- Product distribution for hydrogenolysis of portional to pcaH,*up to 10 atm when pH2 is methylcyclobutane and of various substituted atm from to atm. The rate is inversely cyclobutanes and cyclopentanes on metal films 30 15 75 proportional to pHI from to 75 atm when depends on the metal, on the temperature and on 15 pCaH,2is atm, and from to atm when pHe;on the corresponding metal/Al,O, it depends I 60 90 PC.H,~ is 10 atrn. Changes of working pressures on metal concentration. At high temperatures on between and atm do not affect the rate of Pt and Pd films and on low content Pt/Al,O, and 15 IOO n-C,H,, isomerisation if pCIHLZdoes not exceed Pd/A1,0, it is typical, denoting equal chances of 10 atm. Studies establish that adequate activity breaking the cyclic bonds ; z-allylic triadsorbed and stability of the PtISi0,-Al,O, catalyst for the species are involved in the inferred mechanisms. industrial process occur at: working pressure, On IOO/; Pt/A1,0, or Pt film, or on Ni, only di- 35-40 atm; pC5H,z,10 atm; pH2,25-30 atm, which secondary CH,-CH, cyclic bonds of cyclobutanes are the optimum conditions. and cyclopentanes are broken; oc,cc,p,g-tetra- sorbed species are involved in the suggested mechanism. Distributions from methylcyclo- The Conversion of cis-8-Methylhydrindane pentane on Pt/A1,0, and the pHa dependency in the Presence of Platinised Carbon of methylcyclobutane hydrogenolysis on Pt films E. S. BALENKOVA, N. A. KHAFIZOVAand S. I. KHROMOV, point to another mechanism. Similar distribu- Neftekhimiya, 1965, 5, (6),797-800 tions on films to those on supported catalysts Pt/C catalysed the conversion at 300°C of cis-8- indicate no catalytic effect by the carrier. methylhydrindane with the formation of o-xylene, a-methylethylbenzene, o-methylpropylbenzene, The Effect of Deformation on Catalytic indane, and I- and 4-methylindane. This shows Activity of Platinum in the Decomposition that some methyl groups were split off during of Hydrogen Peroxide aromatisation and that methyl radicals also ex- changed positions with neighbouring C atoms. K. B. KEATING, A. G. ROZNER and J. L. YOUNGBLOOD, Ibid., 608-619 The decomposition of 0.3:; H,O, on annealed Activation Energy of Crystalline Catalysts and cold-worked Pt foils is first order. The rate LI VEN’-CHZHOU, A. N. MAL’TSEV and N. I. KOBOZEV, constant increases with cold working. The Zh. Fiz.Khim., 1965,39,(11), 2704-2707 catalytic activity of Pt and its deformation are Pt black is 140 times more active than thin Pt related directly. Increased activity seems due layers for the strongly exothermic oxidation of directly to deformation since possible effects of C,H,OH to CH,COOH (Qp-117 kcal/mol). preferred orientation and of increased surface Moderately exothermic reactions exhibit less were proved negligible. activation of Pt atoms in the lattice. Results con-

Platinum Metals Rev., 1966, 10, (2), 70 firm that the Pt crystals account for the energy of XVII. Reaction of 7-Allylpalladium Chloride the reaction by the way in which catalyst atoms with Nucleophiles act as acceptors of energy when the reaction J. TSUJI, H. TAKAHASHI and M. MORIKAWA, Zbid., occurs at active centres. (491,4387-4388 n-Allylpalladium chloride reacts smoothly with Effect of Exposure on the Catalytic Activity ethyl malonate and acetoacetate to form ethyl of Platinum during Hydrogenation allylmalonate and ethyl diallylmalonate. I. v. KRYLOVA, A. P. PILONENKO and N. I. KOBOZEV, Enamines react similarly with the complex. Thus Ibid., 2742-2744 carbanions can attack the C atom of the Pd com- Exposure of Pt catalysts to light from mercury- plex to give allyl derivatives in high yield. quartz lamps caused increased activity for hydro- Acetate and alcoholate anions react with the com- genation of cyclohexene but preliminary illumina- plex to give allyl acetate and ether in low yield. tion decreased activity for reduction of nitro XX. Decarbonylation of Acyl Chloride and groups (e.g. in nitropheno!) and for H,O, Aldehyde Catalysed by Palladium and its decomposition. Tested were Pt/SiO, and Pt black. Relationship with the Rosenmund Reduction J. TSUJI,K. QHNO and T. KAJIMOTO, Zbid., (so), The Oxidative Coupling of Aromatic Com- 4565-4568 pounds with Palladium Salts Olefin was formed from acyl chloride with evo- R, VAN HELDEN and G. VERBERG, Rec. Trav. Chim., lution of CO and HC1 in the presence of metallic 1965, 841 (9-101, 1263-1273 Pd from PdCl, decomposed by heating, e.g. C,H,, PdCI, and CH,COONa react in CH,COOH decanoyl chloride treated thus formed nonene to produce biphenyl in high yield but no reaction isomers. Thus Pd catalyses both carbonylation of occurs in the absence of CH,COONa. A mixture olefin to acyl halide and dearbonylation of acyl of isomeric biphenyls is obtained from mono- halide to olefin. Decarbonylation of aliphatic substituted benzenes. Steric effects affect the aldehyde to form a mixture of olefin and the reaction with disubstituted benzenes, e.g. 3,4,3‘,4‘,- corresponding paraffin also occurred, e.g. decanal and 2,3,3’,4’-tetramethylbiphenyl were obtained to nonane and nonene. A mechanism for the from o-xylene in ratio 2.7:1. The assumed olefin-CO reaction in the presence of Pd is pro- mechanism involves complex formation between posed; connection with the Rosenmund reduction the aromatic compound and PdCl,, then x-cyclo- (acyl halide into aldehyde) is established. hexadienyl-PdC1, formation by reaction between the complex and acetate ions, and decomposition XXI. Decarbonylation of Aldehyde Using to biphenyl and Pd metal. Rhodium Complex J. TSUJI and K. OHNO, Zbid., (44), 3969-3971 The Oxidation of Propylene by Palladium Chlorotris(tripheny1phosphine)rhodium was con- Chloride in Acetic Acid verted into chlorocarbonylbis(tripheny1phos- A. P. BELOV, G. YU. PEK and I. I. MOISEEV, ZZV. phine)rhodium by reaction with aldehydes even Akad. Nauk S.SS.R., Ser. Khim., 1965, (12), at room temperature and thus aldehydes were 2204-2206 decarbonylated smoothly into corresponding paraffins. C,H, oxidised by PdCI, in glacial CH,COOH forms iso-, cis-n- and trans-n-propenylacetates, the respective alkylidenediacetates and small The Transannular Addition of Carbon Mon- amounts of allylacetate. oxide to Cyclo-octa-1-5-diene s. BREWIS and P. R. HUGHES, Chem. Commun., 1966, Organic Syntheses by means of Noble Metai (I), 6-7 Compounds. XI. Copolymerisation of Carbon Pd complexes catalyse this reaction, e.g. cyclo- Monoxide and Norbornadiene octa-1,s-diene in tetrahydrofuran reacted with J. TSUJI and s. HOSAKA, J. Polymer Sci., Part B, CO at ISO‘C, 1000atm in the presence of I:$ di- Polymer Letters, 1965, 3, (9), 703-707 iodobis(tributylphosphine)palladium(II) to give Norbornadiene and CO react in C,H, to form a 40-457; yield after 8 h of bicyclo-[3,3,1]-non-a- I:I copolymer in the presence of a catalytic en-pone. Some 45-509/0 cyclo-octa-1,3-diene was amount of PdCl,, which is the first copolymerisa- obtained. tion of CO and olefins catalysed by a transition metal compound to be reported. Homogeneous Catalytic Hydrogenation of XVI. Carbonylation of Allene-Palladium Ethylene and Acetylene with Four-Co- Chloride Complexes ordinated Iridium and Rhodium Complexes. J. TSUJI and T. SUSUKI, Tetrahedron Letters, 1965, Reversible Catalyst-Substrate Adducts (34h 3027-3031 L. vmm and R. E. MODES, J. Am. Ckem. Sac., Structures of substances prepared by carbonyla- 1965,87, (211,4970-4971 tion of allene-PdC1, were identified and the The trans-[MX(CO)(Ph,P,] complexes, where mechanisms are discussed. M =Ir, Rh and X =halogen, catalyse reactions of

Platinum Metals Rev., 1966, 10, (2), 71 CaH4, C,Hs and CzHnwith H, in CGHGor studied during liquid phase hydrogenation of C,H,CH, solutions at subatmospheric pressure aromatic amines under pressure. Conditions for and 40-60°C. These systems combine the stereospecificity during the hydrogenation of features of: catalyst complexes with known com- 1,4-phenylenediamine to trans-1,4-diaminocyclo- positions, properties and structures; Ir complexes hexane with high yield over RuO, were estab- reacting reversibly with I rnol.H,icomplex; the lished. H, adducts [H,IrX(CO) (Ph,P),], which have been isolated, characterised, and their molecular Oxidation of Sugars with RutheniumDioxide- consfigurations established; Ir complexes react- Sodium Periodate: A Simple Method for the ing reversibly with C,H,, C,H, etc. at ambient Preparation of Substituted Keto Sugars conditions. v. M. PARIKH and J. K. N. JONES, Canad. J. chenz., 1965, 43, (1213 3452-3453 The Isomerisation of Cyclo-octadienes Cata- Substituted keto sugars as intermediates in the lysed by Rhodium, Iridium and Platinum synthesis of antibiotic agents are prepared by Complexes combining the two steps of the previous method J. K. NICHOLSON and B. L. SHAW, Tetrahedron into one, whereby RuO, oxidant is formed from Lettws, 1965, (3911 3533-3535 RuO, and then oxidises the alcohol to the sugar. During the preparation of [RhCI(C,H, ,)I , from Advantages include nearly quantitative sugar cycloocta-1,5-diene and RhCl, all the uncom- yields, use of only trace quantities of RuO,, time- plexed olefin is converted to the 1,3-isomer and saving and destruction of impurities in the much of the 1,4-isomer is formed as an inter- starting material. mediate. In the reaction of chloroiridic acid with 1,5-C,H1, to give [IrHCl,(C8Hl,)]n all the Homogeneous Hydrogenation and Hydro- uncomplexed olefin is converted into 1,3-C8H,,. formylation Using Ruthenium Complexes Tertiary phosphine complexes also isomerise D. EVANS, J. A. OSBORN, F. H. JARDINE and G. I,s-C,H,, to 1,3-C,Hl,, e.g. [Ir HCl,(PEt,Ph),] WILKINSON, i\'ature, 1965,208, (5016), 1203-1204 at 130°C gives 90y0 conversion after 120 min. The Ru(I1) complexes RuCl,(PPh,), and RuCI, [Ir Cl,(PEt,Ph),] is five times less effective. Di- (PPh,), dissociate in C,H, solutions. Olefines ethylphenylphosphine inhibits the isomerisation. and acetylenes such as hept-I-ene and hex-1-yne [RhCl,(PEt,Ph),] is also a good catalyst but trans- are hydrogenated rapidly by the complexes at [PtHCl(PEt,),] and trans-[PdI,(PMe,Ph),] are 25"C, I atm in C,H,/C,H,OH solution. poor. A high yield of catalyst can be recovered Ru(CO),(PPh,), in 10-' M CGH,at IOO atm of from 1,3-C8H,,. CO:H,(I: I) gives 80"; yield of hexaldehydes from pent-1-ene in 15 h, and is the first case of a The Isomerisation of Octenes Catalysed by Ru complex hydroformylation. Phosphine Complexes of Iridium(II1) R. S. COPPEY, Zbid., (43), 3809-3811 Similar work to the preceding abstract has been FUEL CELLS carried out with Ir complexes on octene isomerisa- The Electrochemical Oxidation of Hydro- tion. carbons on a Tantalum-supported Platinum Polymerisation by the Derivatives of Transi- Catalyst R. THACKER, Electrochem. Technol., 1965, 3, tion Metals. 111. Competitive Action of (11-IZ), 312-316 Different Ligands on the Stereospecific Teflon-bonded Pt/Ta cathodes with 9 mg Ptjcmz Polymerisation of Butadiene by Rhodium were used in the oxidation of CZHG, C,H,, C,H,, Salts in Aqueous Emulsion CsHG and n-C,H,, gases, and n-C,H,, and P. TEYSSIE and R. DAUBY, Bull. Soc. Chim. France., CH,OH vapours, with 14.6 M H,PO, electrolyte 1965, (10),2842-2848 immobilised on an asbestos matrix, at 150°C. Rh salts catalyse the steraspecific polymerisation Cells with higher Pt content on the cathode had of butadiene in aqueous emulsion to give only the been preferred for oxidation of CGH,. Rest poly-trans-1,4 isomer. The reaction is co- potential and polarisation behaviour is discussed. ordinated polymerisation. Very active catalyst systems (Rh-cyclohexadiene) were discovered and Electrochemical Energy Conversion in a the possibility of polymerising butadiene and Palladium Hydrogen Diffusion Electrode piperylene simultaneously. H. J. CLEARY and N. D. GREENE, Electrochim. Acta, 1965, 10, (II), 1107-1115 Hydrogenation of Aromatic Amines on Current densities of 165 mAicm3 were achieved Ruthenium Catalysts at 30°C on Pd-H diffusion wall electrodes after A. S. CHEGOLYA, N. S. SMIRNOVA, B.I. ZHIZDYUK, pretreatment by abrading and oxidising in air at L. M. RYSHENKO, G. I. GOLUB and A. A. PONOMAREV, 800°C. H, transport is governed by solid-state Zh. Org. Khini., 1965, I, (IO), 1868-1871 diffusion. H, diffusion in P-Pd is expressed by The activity and stability of Ru catalysts were Dg=3.8 x 104- exp (-2930,'RT).

Platinum Metals Rev., 1966, 10, (2), 72 CATHODIC PROTECTION TEMPERATURE MEASUREMENT Anode Design for Shipboard Cathodic Pro- Reference Tables for Platinum-40% Rho- tection dium/Platinum-200/o Rhodium Thermo- R. L. BENEDICT, Materials Protection, 1965,4, (I2), couples 36-38 R. E. BEDFORD, Rev. Sci. Instrum., 1965, 36, (II), Effective protection depends on the shape and 1571-1580 voltage of the anodes and on their area. They Tables in the range 0-1880°C are based on cali- should be located where mechanical abrasion of brations in air of ten thermocouples from four paint is unlikely to occur. Platinised Ti, and Pb wire lots at the freezing points of Zn, Sb, Ag and anodes with Pt micro-electrodes are most effective Au; the melting points of Pd and Pt by the wire and should last the life of the ship. method, and from comparison with standard Pt:IoO/;Rh-Pt and 5~&h-Pt:zoO//,Rh-Ptthermo- GLASS TECHNOLOGY couples at 0-1750T. Test thermocouples are intercompared at 0-1850°C. A.P.H. Report No. A Wide Range (up to 10IOP) Rotating 1292gives more detailed tables. Cylinder Viscometer A. NAPOLITANO, P. B. MACEDO and E. G. HAWKINS, J. Res. N.B.S.,Sect. A, Phys. Chem., 1965, 69A, Measurement and Control of Gas Tempera- (5)s 449-455 ture in the FINGAL Process Three techniques enable the range of this vis- M. N. ELLIOTT and J. R. GROVER, Br. Chem. Engng., cometer (described in Platinum Metals Rev., 1963, 19659 10, (12),846-849 7, (2), 54-55) to be extended up to 10l"P. At The design of a bare wire Pt:13:& Rh-Pt IO~-IO~Pthe outer Pt cylinder is rotated at con- thermocouple is described for measurement of off- stant speed and the torque measured on the inner gas temperatures in the FINGAL process, devel- Pt bob. From 104'5 to 107.Tthe bob is rotated oped at Harwell for the incorporation of highly through an angle and timed as it returns to its radioactive fission product wastes in glass. A zero position. From 105.5to lolDPthe bob is similar thermocouple is used with a suction-type driven through an angle at constant torque and pyrometer for gas temperatures in the process is timed as it does so. vessel.

NEW PATENTS METALS AND ALLOYS Silver Oxide-Palladium Electrode GENERAL MOTORS CORP. U.S. Patent 3,212,934 Hydrogen Diffusion Tubes An electrochemical secondary battery cell com- JOHNSON, MATTHEY & CO LTD. prises a Zn cathode, an alkaline electrolyte and an British Patent 1,009,326 Ag anode having 1-1.5 wt.94 Pd alloyed with it, A closing plug for sealing the open end of Pd or PdiAg alloy H, diffusion tube comprises a body formed of a material having approximately ELECTRODEPOSITION the same coefficient of thermal expansion and is dimensioned to give a tight fit and has a pro- AND SURFACE COATINGS jecting, threaded spigot of smaller diameter than Electrodeposition of Palladium the tube and used to form a means for attachment TECHNIC INC. British Patent of or for stablising an internal support for the 1,014,045 tube. Heavy, clean stress-free and bright electroplated Pd films are formed by using an aqueous elec- trolyte bath containing 2-10 g:1 Pd as its chelate with N,N'-cycloalkane diamine tetraacetic acid ELECTROCHEMISTRY and a buffer maintaining a pH 4-12. Activated Platinum Electrodes Improved Method of Coating Graphite or J. BISHOP & CO. US.Patent 3,202,594 Like Elements and Products Obtained by The overvoltage of electrodes coated with a Pt group metal, in particular Pt, is lowered by con- Such Method tacting the coating with an alkali metal amalgam, STE. NATIONALE D'ETUDE ET DE CONSTRUCTION DE removing the alkali metal from the Hg film and MOTEURS D'AVIATION heating the electrode so that Hg and Pt metal British Patent 1,016,309 react and finally Hg is distilled off leaving an C elements, e.g. graphite, are protected against activated Pt group metal coating. thermal shock by applying on them a fixative

Platinum Metals Rev.,1966, 10, (2),73-76 73 CATHODIC PROTECTION TEMPERATURE MEASUREMENT Anode Design for Shipboard Cathodic Pro- Reference Tables for Platinum-40% Rho- tection dium/Platinum-200/o Rhodium Thermo- R. L. BENEDICT, Materials Protection, 1965,4, (I2), couples 36-38 R. E. BEDFORD, Rev. Sci. Instrum., 1965, 36, (II), Effective protection depends on the shape and 1571-1580 voltage of the anodes and on their area. They Tables in the range 0-1880°C are based on cali- should be located where mechanical abrasion of brations in air of ten thermocouples from four paint is unlikely to occur. Platinised Ti, and Pb wire lots at the freezing points of Zn, Sb, Ag and anodes with Pt micro-electrodes are most effective Au; the melting points of Pd and Pt by the wire and should last the life of the ship. method, and from comparison with standard Pt:IoO/;Rh-Pt and 5~&h-Pt:zoO//,Rh-Ptthermo- GLASS TECHNOLOGY couples at 0-1750T. Test thermocouples are intercompared at 0-1850°C. A.P.H. Report No. A Wide Range (up to 10IOP) Rotating 1292gives more detailed tables. Cylinder Viscometer A. NAPOLITANO, P. B. MACEDO and E. G. HAWKINS, J. Res. N.B.S.,Sect. A, Phys. Chem., 1965, 69A, Measurement and Control of Gas Tempera- (5)s 449-455 ture in the FINGAL Process Three techniques enable the range of this vis- M. N. ELLIOTT and J. R. GROVER, Br. Chem. Engng., cometer (described in Platinum Metals Rev., 1963, 19659 10, (12),846-849 7, (2), 54-55) to be extended up to 10l"P. At The design of a bare wire Pt:13:& Rh-Pt IO~-IO~Pthe outer Pt cylinder is rotated at con- thermocouple is described for measurement of off- stant speed and the torque measured on the inner gas temperatures in the FINGAL process, devel- Pt bob. From 104'5 to 107.Tthe bob is rotated oped at Harwell for the incorporation of highly through an angle and timed as it returns to its radioactive fission product wastes in glass. A zero position. From 105.5to lolDPthe bob is similar thermocouple is used with a suction-type driven through an angle at constant torque and pyrometer for gas temperatures in the process is timed as it does so. vessel.

NEW PATENTS METALS AND ALLOYS Silver Oxide-Palladium Electrode GENERAL MOTORS CORP. U.S. Patent 3,212,934 Hydrogen Diffusion Tubes An electrochemical secondary battery cell com- JOHNSON, MATTHEY & CO LTD. prises a Zn cathode, an alkaline electrolyte and an British Patent 1,009,326 Ag anode having 1-1.5 wt.94 Pd alloyed with it, A closing plug for sealing the open end of Pd or PdiAg alloy H, diffusion tube comprises a body formed of a material having approximately ELECTRODEPOSITION the same coefficient of thermal expansion and is dimensioned to give a tight fit and has a pro- AND SURFACE COATINGS jecting, threaded spigot of smaller diameter than Electrodeposition of Palladium the tube and used to form a means for attachment TECHNIC INC. British Patent of or for stablising an internal support for the 1,014,045 tube. Heavy, clean stress-free and bright electroplated Pd films are formed by using an aqueous elec- trolyte bath containing 2-10 g:1 Pd as its chelate with N,N'-cycloalkane diamine tetraacetic acid ELECTROCHEMISTRY and a buffer maintaining a pH 4-12. Activated Platinum Electrodes Improved Method of Coating Graphite or J. BISHOP & CO. US.Patent 3,202,594 Like Elements and Products Obtained by The overvoltage of electrodes coated with a Pt group metal, in particular Pt, is lowered by con- Such Method tacting the coating with an alkali metal amalgam, STE. NATIONALE D'ETUDE ET DE CONSTRUCTION DE removing the alkali metal from the Hg film and MOTEURS D'AVIATION heating the electrode so that Hg and Pt metal British Patent 1,016,309 react and finally Hg is distilled off leaving an C elements, e.g. graphite, are protected against activated Pt group metal coating. thermal shock by applying on them a fixative

Platinum Metals Rev.,1966, 10, (2),73-76 73 intermediate layer of Ta, Zr, 1-0, Hf, Nb, Ti, W suspension of C in an aqueous solution of a Pd or their carbides, nitrides or borides and 1-50 salt at least an equimolar amount of an aqueous wt.96 Ru, Rh, Pd, Os, Ir or Pt and then depositing solution of an alkaline hydroxide and then by plasma jet spraying a coating of a selected reducing the precipitated hydroxide to Pd metal refractory material. by treating it with an excess of H, at 50-100°C.

Method of Electroplating Palladium Unsaturated Carboxylic Acids WESTERN ELECTRIC CO. INC. IMPERIAL CHEMICAL INDUSTRIES LTD. British Patent 1,017,950 British Patent 1,007,707 Pd films are electrodeposited by using an aqueous An unsaturated carboxylic acid is produced by solution having a pH 7-9 and containing 30-60 g/l reacting a x-allylic complex of PdCI, with CO dichlorodiamine Pd(H), 0.1-1.0g;l selenous acid at io-150°C and 200-1000 atm and then and NH, for pH adjustment and operating at hydrolysing the product at 100°C or above. 15-160 A/ft2 cathodic current density. Fluidised Bed Plating with Noble Metals Process for Preparing Aminophenols UNIVERSAL OIL PRODUCTS CO. ETHYL CORP. U.S. Patent 3,202,537 British Patent 1,009,024 Metal or ceramic substrates are coated with Pt group and other transition metals by contacting Aminophenols are produced by reacting a the substrate with a fluidised bed of solid, heat- nitro-substituted phenol with H, in an aqueous decomposable, C-containing compound of the alkaline medium at 25-1oo0C, 1-35 atm and in plating metal and ensuring that the temperature the presence of Pt, Pd, Rh, Pt or Pd black or Pt of the substrate is sufficient to decompose the or Pd oxide supported on a porous material. plating metal compound. Catalytic Production of Hydrogen Cyanide Electrodeposition of Platinum and Palladium E. I. DU PONT DE NEMOURS & CO. JOHNSON, MATTHEY & CO. LTD. British Patent 1,009,137 U.S. Patent 3,206,382 HCN is produced by reacting NH,, 0, and an A bath for the electrodeposition of Pt or Pd on hydrocarbon gas at 1000-1200°C in the presence to Au, Ag, Cu, Ni, Ti, etc., has a pH below 2, of Pt gauze catalyst at least partially insulated is operated at 3070°C and 5-25 A/fP and against heat losses by a refractory fibre of Al,O,- contains 5-20 g/1 Ma (M'(NO,),%-,) or Ma SO,, modified SiO, or K titanate and positioned (M1(NO,), R1 (4-a)/z), where M is H, NH,, upstream of the catalyst. alkali or alkaline earth metal, M' is Pt or Pd, R is OH or monovalent acid radical, R is a divalent Process for the Preparation of Ketene acid radical and a is r-3. Polymers SHELL INTERNATIONALE RESEARCH MI J. N.V. Electrodeposition of Iridium British Patent 1,009,910 U.S. SECRETARY OF THE ARMY Polymeric ketenes are produced by contacting U.S. Patent 3,207,680 the monomer at ro-15"C with a catalytic amount An excellent electrodeposited film of Ir is formed of PdC1, or (Ar,X),PdCl,, where Ar is aryl on a Cu, Ni, Nb or Mo substrate by connecting and X is P, As or Sb. the substrate as a cathode in an electrolytic bath maintained at 25-9O0C and containing X,IrY,, where X is H, Na or K and Y is C1, Br or I and Production of Unsaturated Organic Esters passing a current of 20-120 Aift,. THE DISTILLERS CO. LTD. British Patent 1,010,548 Esters of unsaturated alcohols are produced Deposition of Palladium by reacting at 30-2o0°C and 2-100 atm an olefine JOHNSON, MATTHEY & CO. LTD. and a gas containing molecular 0, with a solution Canadian Patent 722,528 containing an amine carboxylate, a carboxylic A plating bath for the immersion of electroless acid and 0.1-4 wt.% Pt group metal compound, deposition of Pd on a metal base comprises an e.g. PdCl, or PdAc,, in the absence of a redox aqueous solution of a complex nitrito-palladite system. compound. Selective Hydrogenation Procedure and Catalyst therefor CATALYSIS CHEMETRON CORP. British Patent I,OI 1,270 A catalyst for the selective hydrogenation of Preparation of Palladium Catalysts and acetylenic and diolefinic hydrocarbons comprises Catalysts Obtained thereby 0.01-0.5 wt.*: each of Pd and Cr taken in 2:1 to SNIA VISCOSA S.P.A. British Patent i,oo7,359 2:3 wt. ratio on an A1,0, carrier having a pore Pd/C catalysts are produced by adding to a volume of surface pores of 0.0-0.4 cm3/gand the

Platinum Metals Rev., 1966, 10, (2), I1 surface pores having a threshold diameter of less Palladium-on-Carbon Hydrogenation than 8001% Catalyst U.S. SECRETARY OF AGRICULTURE Production of Phenol U.S. Patent 3,206,440 HALCON INTERNATIONAL INC. Vinyl estors of maleic anhydride adducts have British Patent I,OI 1,432 been characterised by reduction in glacial A catalyst for the production of phenol by vapour CH,COOH in the presence of PdjC as hydro- phase dehydrogenation of a fraction containing genation catalyst. cyclohexanol, cyclohexanone, their lower alkyl derivatives or mixtures, comprises up to 5 wt.u/O Platinum Group Metal Isomerisation Pt and an active C support which has been treated with o.I-I~'/~aqueous HCI, and then Catalysts washed until the washings have a pH 5.3-7.0. SINCLAIR REFINING CO. U.S. Patent 3,206,525 4-9 C paraffins are isomerised by contacting them Production of Aldehydes and Alcohols at 5oo-750°F and an elevated pressure with H, and activated A1,0, supporting 0.1-2 wt.?, Pt THE DISTILLERS CO. LTD. group metal and NH,BF, taken in an British Patent I,oIz,orr 0.001- 0.3 :I molar ratio with respect to A1,0,. Saturated aldehydes and/or alcohols are produced by reacting at 90-30O0C, 25-300 atm and in the liquid phase, an olefine, Co and H, in the Noble Metal Hydrogenation Catalysts presence of a catalyst comprising a synthetic UNION OIL COMPANY OF CALIFORNIA molecular sieve zeolite supporting a Pt group U.S. Patent 3,208,931 metal, preferably Rh or Ru. Wax of desired colour stability is produced from wax bottoms or petrolatum by contacting Dehydrogenation Process and Catalyst for them with H, at 700-775"F, 500-1500 psig and in the presence of a supported Group VIB and/or Use therein VIII metal, metal oxide or sulphide and then HALCON INTERNATIONAL INC. hydrogenating the product at 450-600°F in the British Patent 1,013,115 presence of a supported Pt, Pd, Rh, Ir or Ru A dehydrogenation catalyst particularly suitable catalyst. for phenol production is produced by dissolving 0.5-5 wt. parts Pt compound in H,O, mixing the Platinum Catalysts for Reductive Alkylation solution with IOO wt. parts activated C, re- fluxing for at least min., separating the catalyst UNIVERSAL OIL PRODUCTS CO. 10 U.S. Patent 3,209,030 and drymg it. A catalyst for the reductive alkylation of organic compounds having an amino or nitro substituent Production of Aminophenols comprises a suitable support, preferably A120a, MONSANTO CHEMICALS LTD. 0.01-25 wt.:/, Pt, 0-8 wt.o/, halogen and 0.05-5 British Patent 1,014,968 mol. 7, S. Aminophenol or aminophenate is produced by contacting an aqueous solution of an alkali metal Gas Oil Hydrocracking Process nitrosophenate with H,, at 5--120"C, 200-400 psig SINCLAIR RESEARCH INC. U.S. Patent 3,210,264 and in the presence of a Pt or Pd catalyst. A combined process for hydrocracking gas oil boiling at 460-650OF and reforming naphtha has, A Treatment Process for Silicon Compounds as its first stage, contacting the naphtha with TEXAS INSTRUMENTS LTD. a supported Pt metal reforming catalyst at British Patent 1,015,604 80o-1000"F and 150-250 psig in the presence PC1, is removed from halogen substituted of H,. derivatives of silane by contacting the latter for over I h with adsorbent A1,0, coated with 0.1-25 wt.O; PtCI,. Supported Noble Metal Catalyst PHILLIPS PETROLEUM CO. U.S. Patent 3,210,296 Oxidation, Reduction Catalysts A high surface area active catalyst is produced by impregnating A1,0, with a i-so wt.OU solution JOHNSON, MATTHEY & CO. LTD. of PtCl, in ether, draining, drying and calcining 1,016,058 British Patent at 200-400°C in the presence of H, to give a Pt Catalysts for oxidation, reduction and electro- metal content of 0.05-1 wt.o/,. chemical processes are produced by forming a mixture of Pt and Ru compounds, fusing it with NaNO, to form an intimate mixture of 9-9 Platinum Group Metal Catalysts wt.q$ Pt oxide and 1-10 wt.% Ru oxide and then PHILLIPS PETROLEUM co. U.S. Patent 3,213,150 applying it on a suitable catalyst carrier or porous Os, Ir, Ru, Rh, Pd or Pt supported on the usual electrode matrix. carriers are used as catalysts for the demethylation

Platinum Metals Rev., 1966, 10, (2), 75 of a H, stream, e.g. a reformer off-gas stream, GLASS TECHNOLOGY and subsequent hydrogenation reactions. Mica-Metal Bonds Palladium Catalysts in the Production OWENS-ILLINOIS INC. U.S. Patent 3,206,355 of Unsymmetrical Hydrazines An integral bond is formed between mica or AEROJET-GENERAL CORP. US.Patent 3,214,474 glass-bonded mica and steel or I:I Pt:Pd alloy Unsymmetrical lower alkyl hydrazines are by bringing them in contact with powdered, produced by reducing a nitroso amine with H, in devitrifiable glass, fusing the glass and then aqueous solution in the presence of colloidal cooling slowly to cause devitrification and bonding. Pd or finely divided Pd on usual carriers, e.g. SO,, CaCO,, BaSO,, C, etc. A Platinum Liner for a Glass Furnace BAUSCH & LOMB INC. U.S. Patent 3,206,295 Platinum Gauze Catalyst in the Production A glass furnace with refractory-lined melting of Hydrogen Cyanide and fining chambers has the interconnecting E. I. DU PONT DE NEMOURS & CO. throat and the fining chamber lined with Pt. US.Patent 3,215,495 An improved process for the production of HCN Platinum Articles for Glass Furnaces is operated at rooo-~~oo"Cand utilizes NH,, COMPTOIR LYON-ALEMAND LOUYOT & CIE. 0, and hydrocarbon gas reacted in a bed con- US.Patent 3,210,167 taining a Pt gauze catalyst. Articles which come into contact with molten materials at high temperatures, e.g. molten glass, comprise a layer of Pt in contact with the FUEL CELLS material, a layer of an alloy of Pt with Ir, Ru or Process and Apparatus for the Generation 0s and a layer of Pt-Rh alloy. of Electrical Power VARTA A.G. British Patent 1,010,635 ELECTRICAL AND A cell for the production of electrical energy comprises loose heaps of Ag, Pt or Pd catalysts or ELECTRONIC ENGINEERING such catalyst impregnating a support and placed between screens or sieves. The partial oxidation Electrode Structures for Use in Electric products of a saturated or unsaturated aliphatic Discharge Devices hydrocarbon are then fed to a 10 wt.D/, Pd fuel THE M-o VALVE co. LTD. British Patent 1,007,860 cell electrode, whilst the 0, electrode is composed A wire for the manufacture of grid electrodes for of Raney Ag. electric discharge devices has a refractory metal core which is coated with a layer of small Pt Improvements Relating to Fuel Cells particles of dull grey appearance and a second COMMONWEALTH SCIENTIFIC AND INDUSTRIAL layer of partly reduced TiO,. RESEARCH ORGANISATION British Patent 1,013,703 An ion exchange membrane for a fuel cell is Electrolytic Capacitors produced by treating the membrane with a PHILIPS ELECTRONIC AND ASSOCIATED INDUSTRIES reducing agent, and then with an aqueous Britixh Patent 1,010,096 solution of one or more noble metal salt, prefer- An electrolytic capacitor is manufacturcd by ably Pt, thus forming a film of finely divided and assembling a Ta or Nb anode provided with a catalytically active metal. dielectric oxide film formed by electrolytic oxidation, a Ag container cathode and an elec- Palladium Paste-form Fuel Cell Electrode trolyte containing 0.05-2 wt.:& of at least one AIR PRODUCTS AND CHEMICALS INC. and NORTHERN Pt group metal salt, whereby a spongy layer of NATURAL GAS CO. U.S. Patent 3,212,936 such Pt group metal is deposited as a coating A fuel cell electrode is produced by impregnating upon the cathode. activated C powder with a Pd salt optionally mixed with a transition metal, ageing the paste, Noble Metals in Resistor Compositions treating it with KOH and using a solid C electrode E. I. DU PONT DE NEMOURS & CO. to support the paste. See also 3,212,937. U.S. Patent 3,207,706 A resistor composition consists of (i) 35-85% Platinum-coated Screen Electrodes of a frit having z4-34yn ZnO, 18-250/~ SiO,, AIR PRODUCTS AND CHEMICALS INC. and NORTHERN 22-30% B,O,, 3-716 A1,0,, 4-10:;; Na,O, NATURAL GAS CO. U.S. Patent 3,215,562 4-604 ZrO,, c-4oi;, CaO, 0-4v0 P,O,, more than Fuel cell electrodes comprise a number of inter- 1% and less than 2% total of PbO, Sb,O,, connected, conductive mesh screens made of a TiO,, NiO and Fe,O, and less than 0.1% other corrosion-resistant alloy and coated with cataly- alkali metal oxides and (ii) 15-659 Ag and Pd tically active Pt. or PdO so that the Ag:Pd ratio is 3:2 to 2:3.

Platinum Metals Rev., 1966, 10, (2), 76