PLATINUM METALS REVIEW

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

VOL. 5 OCTOBER 1961 NO. 4

Contents

PaUadium-on-Charcoal Catalysts 122

Continuous Melting of Optical Glass 126

Removal of Chloride Contaminants from Nitric Acid 128

Synthesis of Penicillin Derivatives 131

The Contamination of Platinum Metal Thermocouples 132

The Gaseous Oxides of the Platinum Metals 134

A High Temperature Research Microscope 139

Internal Nucleation of Glass I 4'3

Corrosion Resistance of Chromium 141

Miniature Moving Coil Relay 143

Creep Tests on Platinum Alloys 144

The Discovery of Iridium and Osmium 1466

Abstracts 149

New Patents

Index to Volume 5 159

Communications should be addressed to The Editor, Platinum Metals Review Johnson, Rlutthey & Co., Limited, Hatton Garden, London, E.C.1 Palladium-on-Charcoal Catalysts

SOME EFFECTS OF VARIABLES ON HYDROGENATION ACTnTITY

By J. C. Chaston, Ph.D., and E. J. Sercombe, B.SC.

Research Laboratories, Johnson Matthey & Co Limited

The performance of charcoal-based catalysts cannot be described simply in terms of their mesh site and noble metal content, as many factors can cause wide variations in activity, selectivity and resistance to poisoning. It is possible, however, by close collaboration between catalyst manufac- turer and user, and by suitable choice of base and production technique, to provide a range of such catalysts tailored to meet the needs of a particular industrial reaction.

Catalysts of the type commonly described tion catalysts, in their selectivity and in their as palladium-on-charcoal find extensive use resistance to particular forms of poisoning in in the chemical and pharmaceutical manufac- use. It cannot be emphasised too strongly turing industries as hydrogenation catalysts that the activity of any palladium hydrogena- for a wide variety of reactions. tion catalyst cannot be expressed generally Basically, charcoal supported catalysts are but only as it is related to specific hydro- comprised of powdered activated charcoal genation reactions or groups of reactions. having a particle size of the order of ZOO mesh impregnated with a solution of a palladium Nature of Charcoal Base salt which is subsequently reduced to metallic Charcoal bases for catalysts are nearly form. always selected from the group known as Since charcoal is essentially a natural pro- “activated” charcoals. The raw material from duct, wide variations in its physical structure, which “activated” charcoal is made is a care- in its purity, in its content of trace elements, fully selected natural product which may be and indeed in its properties generally are to be hard wood, nutshells, peat, or a blend of par- expected. More than this, the activity of ticular grades of coal and anthracite. After palladium-on-charcoal catalysts is, somewhat carbonising by heating in retorts to about surprisingly, susceptible to extraordinarily 600”C,the charcoal is “activated” to develop wide variation according to the method chosen the required pore structure by heating again to introduce palladium into the structure and in a controlled atmosphere, usually of steam. to absorb it on the surface of the charcoal The control of this stage is normally by means particles. In addition, the resistance of a of an absorption or decolourising test using a palladium-on-charcoal catalyst to certain suitable dyestuff such as methylene blue. types of poisoning can be influenced both by The extent to which the activity of pal- method of manufacture and by various after- ladium-on-charcoal catalysts in specific re- treatments. actions is dependent on the nature of the It thus becomes possible, by suitable choice charcoal base may be illustrated by a simple of charcoal and by the use of appropriate example I manufacturing techniques, to make palladium- Two charcoals, impregnated with the same on-charcoal catalysts that differ widely in their proportion of palladium by the same tech- performance, in their activity as hydrogena- nique, were used as catalysts in two well-

Platinum Metals Rev., 1961, 5, (4), 122-125 122 Determining the activity of a palladium-on-charcoal catalyst in the Johnson Matthey research laboratories by measuring the rate of hydrogen absorption in a hydrogenation reaction at room temperature

known hydrogenation reactions-one of cro- this means is well shown by the following test tonic acid and the other of nitrobenzene- results, all relating to catalysts containing 3 both at room temperature and atmospheric per cent of palladium on the same type of pressure. The relative rates of uptake of charcoal. hydrogen were found to be as follows: Relative Activity in Activity in an Industrial Hydro- Hydro- Crotonic Acid Nitrobenzene genation of genation Charcoal A I00 55 Nitrobenzene Reaction Charcoal B I05 3 Made by Procedure A 100 Good ,, B 46 Poor It is clear that these two charcoals are ,, C 24 Good fundamentally different in their performance ,, D 118 Good as catalyst bases. A catalyst made with Charcoal B is slightly more active than one Percentage of Palladium made with Charcoal A in promoting the The amount of palladium incorporated in hydrogenation of crotonic acid, yet it is very a catalyst mass of the type under discussion is, nearly inactive for the hydrogenation of in general, of less importance than the way in nitrobenzene, for which the catalyst made which it is applied or the nature of the char- with Charcoal A is over 17 times more active. coal base. Provided that more than a mini- Similar wide variations in the character- mum amount is present, the actual palladium istics of palladium-on-charcoal catalysts may content is generally not very critical. be deliberately achieved by modifying the The effect of varying the palladium content procedure by which the charcoal is impreg- on the properties of one type of palladium-on- nated with palladium. The extent to which charcoal catalyst (all other factors being kept activity can be varied in different reactions by constant) is shown in the table over page.

Platinum Metals Rev., 1961, 5, (4) 123 vigorous interaction between the catalyst, the Effects of Variations in Palladium Conten! liquid and the gaseous hydrogen) that it is on the Activity of a Charcoal-base Catalys! not possible to compensate for a low pal- Relative Rates of ladium content simply by using more cata- Hydrogenation of lyst. The activity of the catalyst in this and in Nitrobenzene many other reactions appears to rise sharply Using Using constant sufficient to a maximum corresponding to around 4 to 5 Per cent weight of catalyst to per cent of palladium and then to remain pal lad ium catalyst contain in catalyst (I .Dog.) 0.03 g. Pd constant or to decline slowly as the palladium content is increased. This conclusion applies 0.5 22 44 equally whether activity is judged in terms of I .o 59 84 the weight of catalyst or of the weight of 2.0 88 88 palladium in the circuit. 3.0 I00 I00 Poisoning of Catalysts 4.0 I12 I10 General poisoning of charcoal-base cata- 5.0 I I6 I I5 lysts, resulting in an overall loss of activity, 6.5 I I8 97 may of course often occur in scrvice. It is not 8.0 I I8 96 so generally appreciated that poisoning may occur during storage in industrial atmo- It follows from these results (at least under spheres. Traces of sulphur dioxide, in par- the test conditions employed, in which a ticular, may render an active catalyst mechanical shaker was used to maintain completely inactive in the course of a few minutes, and for this reason the protection of catalysts in storage needs particular care and considera- tion to ensure that their initial high activity is maintained until the time comes for their use. Charcoal- base catalysts are accordingly packed in airtight containers and these should be stored in clean, dry and uncontaminated surround- ings. The original packings should not be opened until immediately

A constant temperature autoclave for the investigation of hydrogenation reactions over charcoal-base catalysts at elevated temperatures and pressures

Platinum Metals Rev., 1961, 5, (4) 124 Equipment for the impregna- tion of charcoal supports in the production of Johnson Matthey catalysts to meet special require- ments in the pharmaceutical industry

before the catalyst is required for use. to poisoning in service increased, by selec- In some instances it is of advantage to tively pre-poisoning it during manufacture. supply the catalyst as a damp paste rather The original activity is by this treatment than as a dry powder, for ease in transport and somewhat reduced, but an appreciably more handling. stable catalyst is produced. It is sometimes possible to develop charcoal- The examples quoted above have been con- base catalysts which will selectively promote fined to palladium-on-charcoal catalysts, but one of two or more possible hydrogenation the discussion applies with equal force to reactions in certain systems. This may be platinum-on-charcoal and to charcoal-base achieved by selectively poisoning the catalyst, catalysts impregnated with ruthenium or other presumably thereby occupying those active platinum metals. The performance of none sites on the catalyst surface which would of these is to be described simply in such normally be responsible for the unwanted general terms as mesh size of the charcoal and hydrogenation reactions. Controlled quan- the noble metal content. There is an almost tities of base metal salts, of quinoline or of unlimited field for the development of an certain sulphur compounds, added during immense range of catalysts differing in catalyst manufacture, are examples of selec- activity, selectivity, and service life, and one tive poisons which have been used for the which can be explored only by the closest control of industrial hydrogenation processes. collaboration between the manufacturer of Finally, the active life of a charcoal-base catalysts on the one hand and the user- catalyst in some hydrogenation reactions has whether research chemist, development sometimes been prolonged, and its resistance engineer or plant operator-on the other.

Platinum Metals Rev., 1961, 5, (4) 125 Continuous Melting of Optical Glass

PRODUCTION IN PLATINUM FWRNACES AT JENA GLASSWORKS

The development during the last few years method must not only improve the actual of greatly improved optical glasses has melting technique but must also, by permit- necessitated the solution of several problems ting the manufacture of lenses direct from the in their manufacture. Most of these newer melting furnace, replace as far as possible glasses cannot be produced by melting in the the very expensive method of producing semi- traditional refractory crucibles since they are finished products from a cast glass. liable to attack the refractory material quite These considerations led to the continuous actively, and while platinum was the obvious melting of optical glass in a furnace com- choice for a containing vessel it could not pletely lined with platinum. simply be substituted as a crucible material Continuous glass melting units of this on account of its relatively low mechanical kind are naturally not of the size normally strength at the high melting temperatures associated with the manufacture of window involved. Further, the greater cost of melting and bottle glasses, but neither are they smaller in small platinum crucibles made this tech- versions of such large units; the use of nique uneconomical, and a new approach platinum was found to allow of completely to the manufacturing method had to be new constructional possibilities. adopted. High Frequency Heating Direct Manufacture of Lenses The method of heating had also to be The successful development of new indus- changed from the normal gas firing to an elect- trial melting processes for these high quality rical method. Radiation, induction and resis- glasses at the Jena Glassworks at Mainz has tance heating were all investigated, and a most recently been described by their director of interesting study was made of the effect of research, Dr Carsten Eden [(Glastechnische increasing frequency of the alternating current Berichte, 1961,34, (3), IZO).] The investigation used for the last method. When normal 50 began from the requirement that any new cycle current is passed through a glass melt

0.7

06 SA'cm2 \ $ 0.5 2.5A/crn -I4 0 0.4 E 3 0.3 m The colloidal dispersion of plat- E inum in a heavy crownglass as a 0-2 function of frequency for various IA/crn current densities. Temperature 0.1 1290"C, duration of test 30 min- utes. At 10 kilocycles per second 0 measurable dispersion ofplatinum 4 from the electrodes ceases. FREQUENCY C/S

Platinum Metals Rev., 1961, 5, (4), 126-127 126 An automatic machine in the Jena Glassworks at Mainz for the manufucture of tens blanks direct from the platinum.furnace from platinum electrodes, a colloidal disper- means an extremely good cord-free quality is sion of platinum is produced, causing an obtained. After homogenising, the glass is unacceptable contamination of the glass. cooled to working temperature as evenly as Research into the physico-chemical processes possible and again in contact only with occurring at the platinum-glass interface platinum. An automatic machine, shown showed that this colloidal dispersion is depen- in the photograph, can then be used to press dent on the migration velocity of the ions in lenses, having a uniform weight and diameter, the melt. This made it possible to influence direct from the platinum furnace. In addi- the dispersion by using higher frequencies for tion, the continuous production of glass bars the heating current. The results of this study has proved of value where larger pieces of are given in the graph, which shows the optical glass are required. amount of platinum dispersed in the glass as a function of frequency for various current Improved QuaIity of Glass densities with a melt of a heavy crown type This continuous method of melting was having a barium oxide content of more than developed initially for the newer glasses of 25 per cent. It will be seen that the colloidal very high optical quality, but it soon became dispersion decreases sharply as the frequency evident that with this method substantial increases, so that at 10 kilocycles per second, improvements could be obtained in the quality even with a high current density, measurable of a great many types of glass previously dispersion of platinum ceases. At this order melted in refractory crucibles. The use of of frequency, furthermore, bubble formation platinum eliminates all reactions between at the electrodes is also eliminated. refractory and the glass melt that give rise Attention was also given to achieving to bubbles and cord, while manufacture be- perfect homogenisation of the glass by inten- comes more economical, especially in the sive stirring with platinum paddles. By this production of large quantities.

Platinum Metals Rev., 1961, 5, (4) 127 Removal of Chloride Contaminants from Nitric Acid

ELECTROLYTIC PROCESS USES PLATINUM ANODES

By R. G. Wilkinson Eldorado Mining and Refining Limited, Port Hope, Ontario

Eldorado’s refinery at Port Hope separates removal of chlorides by oxidation to chlorine. uranium from other components of the The third method offers the greatest economic chemical concentrate feeds by a nitric acid advantage for the refinery. Chemical oxidants digestion/solvent extraction technique. The adapt themselves quite readily to the removal waste liquid from extraction is high in free of chlorides from nitric acid, while in most nitric acid impurities, and a plant process for instances chemicals such as potassium per- the recovery of nitric acid from the extracted manganate, potassiumpersulphate and sodium acid raffinate stream is used to effect a saving bismuthate are soluble in either water or in nitric acid costs. nitric acid and are, therefore, conveniently In this process, the acid railinate is mixed handled. If ozone is considered, its gaseous with sulphuric acid to liberate the metal state makes it extremely convenient. The nitrates and the liquid is evaporated. The choice of proper oxidants is dependent resulting metal sulphates are relatively easy largely upon economic considerations. to handle, and the ultimate disposal problem The use of ozone requires a relatively large is simple. The path of the chlorides through capital outlay for generating equipment. On the processing equipment is such that all the the other hand, the use of other chemical volatile chlorides ultimately enter the stainless oxidants requires little capital expenditure, steel fractionation column where nitric acid is but high chemical costs are inherent with concentrated. It has been found that during these processes. Where a particular chemical the extraction process nearly all of the chlo- oxidant is available at a low cost, this may rides present in the uranium concentrates show that method of chloride removal to follow the metallic impurities into the nitric advantage. acid raffinate. From vapour-liquid equilibrium data on Experimental Cells the HCl-HNO,-H,O system, it is indicated Ozone oxidation equipment was installed that the HC1 concentration of the dilute during the original construction at the refin- nitric acid increases during continuous ery. Subsequent years of operation have operation of the nitric acid concentrator. This indicated the major disadvantages to be: accumulation of chlorides in nitric acid, (I) high maintenance costs, (2) high capital resulting from inadequate removal facilities, costs for the initial operation, and (3) lack of causes rapid acceleration of the corrosion rate flexibility for treating a variable chloride load. of the stainless steel concentrator. Consideration of these disadvantages, along There are three general methods of remov- with the possibility of higher chloride levels ing chlorides from nitric acid : (I) discard of a in the refinery feed, prompted investigation of chloride-contaminated acid stream, (2) re- electrolysis as an alternative to ozonation. moval of chlorides by precipitation, and (3) The first experimental cell was constructed

Platinum Metals Rev., 1961, 5, (4), 128-131 128 on the chlorine-caustic bell jar design, using wide range of chloride strengths. The current a carbon rod anode and a cylindrical stainless efficiency was increased only slightly with an cathode, and was contained in a one-litre increase in chloride concentration. An increase beaker. Nine volts were necessary to produce in the nitric acid strength decreased the chlor- a reaction. The carbon anode began to flake ide removal efficiency. The removal decreased and darken the acid with fine colloidal carbon. from 80 to 70 per cent as the nitric acid The reaction of this simple cell was suf€icient strength increased from 20 to 30 per cent. to indicate that further development was From a plot of the results of a beaker cell worth while and platinum electrodes were the test, it was found that, at a given current obvious choice. A second beaker cell was density, the chloride concentration of the constructed with platinum electrodcs; one electrolysed solutions was an exponential side of each was imbedded in clear acrylic function of the average retention time of the resin to eliminate the effect of the back of electrolyte between the electrode faces. each electrode. With this cell, the effect of log (C1-) = -kt electrode spacing, current density, chloride where t = residence time in minutes concentration, nitric concentration and reten- (C1-) = chloride concentration (mg/l) tion time were studied with respect to k = reaction rate constant reaction rate. Solution agitation was important to the effi- At electrode spacings of less than one inch, ciency of the process, as electrode polarisation a severe heating effect was noted and the nitric and the eventual chloride solubility were acid decomposed. At spacings of greater than minimised by good agitation. one inch, the resistance of the solution became an important factor and the voltage efficicncy Anode and Cathode MateriaIs was poor. The chloride removal efficiency of a Platinum was a satisfactory electrode metal cell operated at a fixed retention time and electrochemically, but had the disadvantage current density was relatively constant over a of being expensive. No other material would

One of the anodes used in the final design of the production unit. Coristructcd in Unimesh platinum by Johnson Matthey & MalEory Ltd., the anode is twentyfour inches in width by six inches in depth

Platinum Metals Rev., 1961, 5, (4) 129 The continuous $ow cell, with six platinum anodes and jive copper cathodes, for the removal of chlorides from nitric acid

serve as an anode, but there were several num cathode to act as a baffle to the acid flow. possibilities for cathodes. The impressed The removal rate of the smallest cell was potential should make the cathode passive 0.30 lb. chlorine per day per square foot. The and an investigation of cathode materials low efficiency compared to a batch operated indicated as possible alternatives gold, carbon cell was assumed to be due to the flow short- and copper. circuiting the cathode and baffle. A larger cell, Operations of batch cells with diffused air containing 24 square inches of electrode, was agitation removed 1.25 lb. of chlorine per day then constructed. This cell, operated at 175 per square foot of anode at all acid strengths. amp per square inch, removed 0.48 lb. chlor- The electrodes of continuous batch cells were ine per square foot of anode per day. The constructed in a similar way to a storage platinum cathodes were changed to solid battery and were connected in parallel with copper. The cell removal of chlorides was every other electrode an anode, each spaced increased to 0.65 lb. chlorine per square foot one inch apart. per day and the improvement was attributed to the copper cathode reducing the hydrogen Continuous Flow Cells polarisation voltage. At a temperature of I 2o°F Three sizes of flow cells were constructed, and 30 per cent acid, the copper sheet was one containing electrodes totalling 16 square attacked by the acid solution. The heat build- inches, another of 24, and a semi-industrial up was minimised by the cooling produced by cell of 3.75 square feet to observe the scale-up the air agitators and was not considered a effect on the design of much larger cells. The problem in the design of larger cells. small continuous flow cell contained platinum Flow-cell tests indicate that a better rate of anodes of perforated sheet and a solid plati- chloride removal is possible if the electrodes

Platinum Metals Rev., 1961, 5, (4) 130 are positioned with their longer dimension in sufficient to construct a large industrial model. the horizontal plane. Bubble resistance seems This cell was composed of six anodes, each to increase if the vertical dimension is longer 24 inches wide by 6 inches deep, constructed than the horizontal; the electrode width to in platinum Unimesh by Johnson Matthey & height ratio should be at least 2 to I. Mallory Ltd., Toronto, and five copper The semi-industrial cell containing 3.89 cathodes of similar size. square feet of electrode surface was made up Water cooling tubes were necessary to of five copper cathodes and six platinum mesh operate the cell with nitric acid strengths up anodes each spaced one inch apart. Cell to 35 per cent. The current efficiency of a operation on acid strengths up to 23 per cent large cell was 30 per cent and the power cost nitric removed 0.75 lb. chloride per square was $1.60 per pound of chlorine removed, foot of anode. With acid strengths greater than compared with $7.00 for the ozone process. 23 per cent the coppcr cathodes were attacked. The industrial cell has been operated three This occurred at a temperature of 120°F and months without requiring maintenance. it was assumed the energy going into heat In any plant concentrating a nitric acid was too great to be removed by air diffusion. contaminated with chlorides by a fractiona- Water tubes were placed between each of the tion process, electrolysis is competitive with electrodes in vertical banks of five tubes. ozone oxidation for the removal of the Cooling water passed through the tubes chlorides. The capital expenditure is $1,000 removed sufficient heat to allow copper per pound of chlorine removed per day, or cathodes to operate in 35 per cent acid without about 30 per cent of the cost of the ozone attack. process, and the operating cost is about 25 Design data obtained from the operation of per cent. The amortisation period is estimated three sizes of continuous flow cells were to be 10years.

Synthesis of Penicillin Derivatives HYDROGENATION WITH PALLADIUM CATALYST

An important advance in medical treatment, of derivatives, some of which possess activities made possible by the synthesis of penicillin against a wider range of infections than did derivatives of greater antibiotic activity than earlier preparations. Others of the range are those produced naturally, has recently been either more readily absorbed orally than the announced by Beecham Research Labora- older penicillins or are lethal to certain tories Ltd. strains of staphylococci that have hitherto The first major step in a long programme destroyed penicillins by producing a substance of research was the isolation of the common called penicillinase. nucleus of the penicillin compounds, 6-amino In the course of preparing these synthetic penicillanic acid, which has the simple basic penicillins, the 6-amino penicillanic acid is structure of the penicillins without any side- coupled with the desircd amino-substituted chain other than one hydrogen atom. From carboxylic acid having its amino group this compound it bccame possible to produce protected, and the protective group is then an immense number of penicillins that could removed by catalytic hydrogenation. This not be obtained from the natural mould by last procedure must be carried out under the introduction of substituent groups into conditions sufficiently mild to avoid attack the side-chain of existing penicillins, or in on the penicillin nuclcus with subsequent other words, into the amino group of 6-amino loss of antibiotic activity, and it has been penicillanic acid. Very broadly, the replace- found that, with a palladium catalyst on an ment of one hydrogen in the simple side-chain inert support such as barium carbonate, this of the penicillin nucleus by one of a wide reaction can successfully be carried out at range of aminoacyl groups can yield a variety room temperature and atmospheric pressure.

Platinum Metals Rev., 1961, 5, (4) 131 The Contamination of Platinum Metal Thermocouples CAUSES OF FAILURE IN HYDROGEN ATMOSPHERES

By H. E. Bennett, F.I.M. Research Laboratories, Johnson Matthey & Co Limited

The attractive features of platinum metal always the liability of contaminating the wires thermocouples include their resistance to at the bare junction and where the ends of corrosion by the common acids and alkalis and the insulators meet. their freedom from oxidation at all operating From time to time platinum : rhodium- temperatures. On the other hand, unlike some platinum thermocouples heated in hydrogen base metal thermocouples upon which a become embrittled and break. There is no protective oxide skin is formed, platinum is reaction between the platinum metals and readily contaminated by contact at high tem- hydrogen, and therefore any failures associated peratures with such elements as lead, zinc, with changes in structure must be due to phosphorus, arsenic and silicon, and adequate contamination. It is well known that platinum protection must be given where such con- heated in hydrogen in contact with a siliceous taminants might be encountered. refractory becomes embrittled owing to In an oxidising or neutral atmosphere, the the reduction of silica in these conditions, the use of an impervious refractory sheath that will subsequent diffusion of silicon into the withstand the operating temperature is platinum forming platinum silicide which generally adequate protection even against segregates at the grain boundaries. metal vapours, while in extremely contaminat- It is essential, therefore, that thermocouples ing atmospheres it is possible to employ an employed for high temperature measurement additional metal sheath. Where twin-bore in a hydrogen atmosphere be insulated and insulators are used and a sheath is not em- sheathed with refractories free from silica. ployed in order to obtain the maximum For this purpose alumina is commonly used, response to temperature changes, there is but it has occasionally been found that when

Fig. 1 Platinum wire showing Fig. 2 A 40 per cent iridium- Fig. 3 A 13 per cent rhodium- grain boundary embriitlernent rhodium wire embrittled after plutinum wire after 1 hour at after 15 hours in hydrogen in 96 hours at 1400°C in hydrogen 1400°C in hydrogen with alu- an alumina tube x 144 in an alumina tube x 320 mina insulators x 320

Platinum Metals Rev., 1961, 5, (4), 132-133 132 Fig. 4 The cast structure of a 0.3per cent Fig. 5 The cast structure of a 0.6 per cent silicon-platinum alloy x 320 silicon-rhodium alloy x 320 using alumina insulators the thermocouple in this furnace periodically, but had been in has failed by embrittlement. Some expcri- the furnace for an estimated total time of not mlents carried out in this laboratory have more than an hour, was also embrittled. As shown that the small amount of silica present frequently happens, the embrittled areas in commercially pure alumina refractories, of occurred in the wire at the junctions between the order of 0.2 per cent of SiO,, is quite the alumina insulators where the hydrogen sufficient to lead to the formation of em- flow had greatest access. The grain-boundary brittling silicides. silicide can be seen in Fig. 3. A platinum wire was heated to 1400OC for As a check on these microstructures, a 15 hours in an alumina tube in an atmosphere sample of platinum was melted in an argon- of cracker gas. On removal, the wire would arc furnace with 0.3 per cent of silicon. The not withstand bending but broke into small microstructure of this alloy in the cast condi- pieces. Fig. I shows the microstructure of tion is shown in Fig. 4. It is stated in the this wire after heat treatment, with intergranu- literature that the solubility of silicon in lar platinum silicide clearly visible. rhodium is less than 0.5 per cent, so a sample A Feussner thermocouple (iridium : 40 per of rhodium was argon-arc melted with 0.6 per cent iridium-rhodium) insulated with alumina cent of silicon. The cast structure of this alloy tubes was placed in an alumina tube furnace, is shown in Fig. 5. These photomicrographs in cracker gas, and heated at 1400°C. The illustrate the effect on the structure of plati- thermocouple was removed for inspection num and rhodium of small additions of silicon after 24 hours but after a total of 96 hours at and give some idea of the small amount of temperature the wires broke on removal. The silicon pick-up that will embrittle platinum 40 per cent iridium-rhodium wire was very alloys. brittle, and the microstructure, showing grain These experiments show that where hydro- boundary rhodium-silicide, is seen in Fig. 2. gen is present in contact with commercially In the iridium wire there was no second phase pure alumina and platinum or rhodium alloys, present, but the wire had become embrittled embrittlement can occur through the diffusion through recrystallisation and grain growth, of silicon and the formation of grain boundary which occurs when the wire is heated in any silicides from the reduction of silica present in atmosphere. If there was any pick-up of small amounts in the alumina. Experience has silicon it was within the limits of solid shown, however, that an alumina sheath solubility. impervious to hydrogen, or one containing no The 13 per cent rhodium-platinum wire of silica, will protect a platinum : rhodium- a platinum : rhodium-platinum thermocouple platinum thermocouple in a hydrogen atmo- that had been used to check the temperature sphere at around 1400OC for a year or more.

Platinum Metals Rev., 1961, 5, (4) 133 The Gaseous Oxides of the Platinum Metals

By c. B. Alcock, Ph.D., A.R.c.s. Department of Metallurgy, Royal School of Mines, London

This paper reviews the experimental techniques used in the elucidation of the thermodynamics of the volatile oxides of the platinum metals in the temperature range 1200 to 18OO0C. It is shown how the molecular formulae of the gases were obtained, and free energy equations of the two- term type are given for PtO,, Rho,, IrO,, RuO, and OsO,. At other temperatures oxides of different compositions may predominate, and approximate methods for calculating the thermodynamics of these from the present data are given.

The platinum metals all show an increased mation has recently been advanced to a stage volatility when heated in oxidising atmo- where it can reasonably be said that we now spheres, compared with the volatility due to have a practically complete knowledge of both evaporation as metal atoms that occurs in the molecular composition and the free vacuum or inert gas atmospheres. The study energies of formation of all of the important of the thermodynamics of volatile oxide for- species. Therefore the calculation of the maximum rates of volatilisation of the elements,

7 both as a function of temperature and of oxygen partial pressure, can be made with a high degree of accuracy, both over pure b metals and over alloys where the activities of the noble metals are known. m Q The experimental techniques that have x5 L yielded these results are best described by W dealing with the individual elements, and we t14 will first discuss the oxide of platinum, rr PtO,(I). o. I3 2 Platinum I SI- If platinum forms the gaseous oxide PtxO, !22 B then the equilibrium constant for the forma- tion of the oxide from metal and oxygen at a I temperature, T, is expressed by

C 0 02 04 06 08 P p2) ATMOSPHERES In the case of the oxidation of pure platinum The weight loss of platinum, under equilibrium conditions at 1400"C, for unit volume of transport- (apt= I) the pressure of the oxide will depend ing gas, as a function of oxygen pressure on the Y/ath power of the oxygen pressure

Platinum Metals Rev., 1961, 5, (4), 134-139 134 only. Thus if we compare the weight losses into intimate contact with all of the oxygen of a piece of platinum which is brought suc- passing through the apparatus, thus assuring cessively to equilibrium with gases of known the attainment of equilibrium. This was oxygen partial pressure passing at a known achieved by passing the metered mixture of flow rate for a known time, and at a constant oxygen and nitrogen through a narrow bore temperature, then a plot of the weight loss of refractory tube which ended at the thermal platinum per litre of gas passing over the centre of the furnace. At the open end of this sample against pOz will be linear when the tube a weighed roll of gauze was inserted so correct choice of y has been made. A typical as nearly to fill the tube. It was found, by result at 1400°C with y -2 is shown in the varying the flow rate of the gas, that the graph on page 134. weight loss of platinum per litre of gas passed The weight loss of the sample has here at constant temperature was independent of been used as a measure of the partial pressure gas flow rate over a wide range of flow rates, of the gaseous oxide. Of course the pressure thus clearly indicating that equilibrium had of a species containing two atoms of platinum been achieved. Details of the transportation per molecule would be half that of one con- apparatus are shown in the diagram above. taining one atom per molecule, but although The next part of the research was to estab- this would affect the scale on the ordinate, it lish the number of platinum atoms in the would not affect the linearity test. molecule by measuring the weight losses, at The transportation method used in these constant temperature and oxygen pressures, experiments was arranged so that the metal, of platinum alloys. The choice of an alloying in the form of 80 mesh gauze, was brought element was very restricted here since the

Platinum Metals Rev., 1961, 5, (4) 135 alloying element must have the following ing gas and the same alloys were then properties. oxidised in pure oxygen at the same tempera- (I) It must not form a volatile oxide or a ture in the apparatus. The weight losses condensed oxide under the conditions under nitrogen were used to calculate the of the experiments. difference in platinum activities, and the (2) The metal must have a measurable, weight losses in oxygen minus those in nitro- although not too high, vapour pressure gen were used to fix x as having the value one. so that its thermodynamic activity in Finally now that the composition of the the alloys could be measured and from volatile oxide was known, the heat and these the platinum activities could be entropy of formation of PtO, were obtained calculated. With the low vapour pres- by measuring the weight loss of platinum in sure and chemical inertness of platinum pure oxygen as a function of temperature since it was clearly necessary to be able to d Ind+ p PtO, measure the activity of the alloying ---=( ) R element in order to arrive at the other- PO, wise unmeasurable activity of platinum and AG" = -RT In p PtO,; by means of the Gibbs-Duhem relation. -ASo =z (AGO-AHo)/T (3) It must form alloys with platinum over a reasonable range of compositions. under these conditions with the standard Fortunately gold has all of these properties. states of pure solid platinum, and oxygen It was not necessary to know the absolute and platinum dioxide at one atmosphere values of the platinum activities since the pressure. value of x: could be obtained from experiments where the difference in platinum activities was Rhodium known at two atom fractions Nand N. Exactly similar studies of the dependence of the weight loss of a spool of rhodium wire Thus as a function of oxygen pressure at constant temperature served to establish the number of oxygen atoms in this molecule as two. from equation (i) at constant T and PO,. Alloying with gold was not useful, due to Hence log p'pt,O, -log p Pt,O, ==x (log the very narrow range of gold-rich alloys u'rt -log art) (ii) which are formed at about 15oo0C, as a But by the Gibbs-Duhem relationship means for establishing the number of rhodium atoms. A less rigorous method was used rely- log a'p, - log apt = -INf&hu d In aAu ing on the established knowledge of PtO,. N NPt The platinum-rhodium phase diagram (iii) shows a continuous range of solid solutions Thus combining (ii) and (iii) and noting that together with a narrow solidus-liquidus lens. 1% P'ptxOZ -1% Ppt,o, is equal to log W'pc This suggested that the alloys were approxi- -log W,, where W is the weight loss/litre mately ideal in the Raoult sense, that is that of gas the activity of each component was equal to its atom fraction in the alloy. Weight loss W'Pt log- = -x d In aAu studies in pure oxygen at were there- wrt 1400'C fore made on a series of platinum-rhodium Therefore gold partial pressures over a alloys and from these, after deduction of a range of liquid compositions at a temperature PtO, pressure which was calculated assuming of ISSOTwere measured in the transporta- ideality for platinum in the alloys, the weight tion apparatus using nitrogen as the transport- loss assuming X=I and x=2 in Rh,O, were

Platinum Metals Rev., 1961, 5, (4) 136 calculated and compared with the measured tures the species OsO, and OsO, are formed. ones. It was found that close agreement In these experiments a sample of osmium was could be obtained if X=I and aRh'N~l,, but heated in a refractory Knudsen cell in which if x=z there would have to be large positive a low pressure of oxygen could be maintained. deviations from ideality in the platinum- The vapour effusing from the cell was rhodium alloys. Thus the molecule was Rho,. analysed mass spectrographically and found to contain ions derived from OsO, and OsO, Iridium molecules. The oxygen dependence measurements From the results given in this letter, the gave three atoms per molecule for the gaseous following equation was obtained oxide of this element, and the number of oSo,(g)-+ oSo,(g) f*O2 iridium atoms was found by an interesting 4Gc=I 1,800 +o.qTcal. method devised by Schafer (2). and using data given by Kubaschewski and Iridium forms a solid oxide in air which is Evans (6) stable up to about 12oo~C.If one studies the OS(S)t2OZ-t OsO*(g) weight loss, under saturation conditions, of 4G" = -80,000f38.5 T-1. IrO, samples as a function of oxygen pressure then this should depend on p*02for IrO, and Palladium p-*O, for Ir,03 thus This metal has a far higher vapour pressure IrOds) +go,+IrOdg) than the other members of the series, and zIrO,(s)+ Ir,O,(g) t 40,. consequently the metal volatility interfered The former dependence was established by with attempts to measure the volatility due to Schafer and Heitland (2). gaseous oxide formation by the transportation method. An increase in weight loss of about Ruthenium 20 per cent was found at ISOO'Cwhen oxygen In preliminary studies, it was shown that was substituted for nitrogen. the weight loss of a ruthenium sample heated in oxygen-nitrogen mixtures at 1280°C varied Summary of the Results as p*Oo,. Schafer, Gerhardt and Tebben (3) The results of all of these measurements have subsequently shown that the solid oxide can now be collected together to give free RuO, is stable at this temperature and oxygen energy of formation equations. These are: pressures and thus it may be concluded that PtO, AG" = 39,270 - 0.93Tcal/mole the gaseous molecule is RuO,. The stability Rho, AGO= 45,140- 4.9T of RuO, is confirmed by the recent work of Shchubarov and Ryabov (4), who have IrO, AGO = 4,150 + 10.8T shown, calorimetrically, that the heat of RuO, AGO= -~0,700+18.6T formation of RuO, is -73+1 Kcal/mole 0~0,4G" = -668,200+39.0T. and not -52.5 Kcal as previously thought. The standard states for these equations are Hence by combining this result with an the pure solid metal, and oxygen and the estimated entropy content of RuO, of 14.5 volatile oxide at one atmosphere pressure. e.u. at 298"K, and using the results for the Thus the pressure of the volatile oxide over volatility of RuO, in oxygen, the equation the metal in pure oxygen at a temperature T given below for the formation of RuO, was is given by calculated. -4G"7-

pMO, =antilog ~ in atmospheres. Osmium 4.576T Recent studies using the mass spectro- In surveying the results of these measure- graph (5) have shown that at high tempera- ments, one is led to ask why the particular

Platinum Metals Rev., 1961, 5, (4) 137 species have been found to be stable in the the formation of one mole of MO, MO,, experimental temperature region. Thus why MO,, MO, from metal and oxygen (0,)gas. PtO, rather than PtO or PtO,? (We shall Therefore at low temperatures MO, is pre- neglect the possibility of polymer formation, dominant, but at the highest temperatures e.g. Pt,O,.) The answer to this question can MO must predominate. Hence we see that it be indicated by the following considerations. is untrue to speak of one molecular species of The bond energies in a series of gaseous gaseous oxide being formed by a metal, and oxides of a given element, that is the energy it is better to say that there is a temperature evolved when the separated atoms are brought range in which one species will be pre- together to form the molecule divided by the dominant. number of linkages which are formed, usually Applying these considerations to platinum, follows thus we know that for the reaction EM-0MO > EM&MO > EMLOMO > EE?o Pt(s)+O,+PtO,(g) AH"= 39 Kcal. and so on, thus as each extra bond is formed and 0% + 20 AH" = 120 Kcal. the extra amount of energy which is gained Pt(s) -Pt(g) AH =rzg Kcal. decreases, excepting possibly when going Therefore from one oxygen atom bonded to two atoms bonded. If this value were constant, then the Pt(g)+zO-PtO,(g) AH= -210 Kcal. energy of formation of MO, from metal M PtO, ~ -105 Kcal. and oxygen gas would be given by EPt -0 AE=n (EM-o --Eo-o)+AE evap. Then where Eo-0 is half the dissociation energy AHopto -(-105+60-t129) = 85 Kcal. of oxygen gas, 0,, and AE evap. is the vapor- AGopto -85,000 -zoT cal. isation energy of the metal M. AH0pt~,-( -315 + 180+ 129)= -6 Kcal. Summing up, we would expect the heat of formation from metal and oxygen gas (0,)to AGoptO,- -6,000 SzoTcal. be the greatest, that is most negative, for the These equations clearly apply to the forma- species involving the greatest number of tion of the gaseous oxide from metal and oxygen atoms. Thus for example, OsO,(g) diatomic oxygen gas. should have a greater heat of formation than One of the most useful applications of these OsO,(g), and so on. However the entropy results is in the calculation of the weight changes of formation will be, very approxi- losses of the elements in various atmospheres mately, +20, 0, -20, -40 entropy units for over a range of temperatures. The calculated

I Weight Losses of the Platinum Metals in Grams of Metal per Litre of Gas T= 1500°K (I 223°C) T=2000°K (1723°C)

Inert Metal Atmosphere POz= PO*= I Atmosphere PO2= PO2= I Inert I - I - Palladium 5~ 10-7 - ca 7x lo-' 4~ 10-3 Platinum v. small 3x lo-* 3~ 10-5 9x lo-? 2x 7x

Rhodium v. small 2x 10-8 2x 10-5 5x lo-' 10-0 7~ 10-4 I

~ Ruthenium v. small 10-6 4x 10-1 v. small 10-6 7x lo-* I

~ Iridium v. small 4x 10-8 9~ 10-3 v. small 5x 10-8 10-3

Platinum Metals Rev., 1961, 5, (4) 138 losses will, of course, be the maximum losses, per litre of gas. (The values have been assuming that equilibrium is reached. The rounded to the nearest integer.) table shows some results for temperatures The weight losses fo the elements were of 1500 and 2000°K, and for atmospheres calculated by using Brewer’s estimates (7) for of an inert gas, a rough vacuum, p0,=10-~ the vapour pressures, except in the case of atmospheres, and I atmosphere of pure palladium for which results have been oxygen, in grams of platinum-group metal reported by Alcock and Hooper (8).

References C. €3. Alcock and G. W. Hooper . . Proc. Roy. Sac., A., 1960,254, 557 H. Schafer and H. J. Heitland . . Zeit. anorg. u. aZlgemeine Chemie, 1960,304,249 H. Schafer, W. Gerhardt and A. Tebben Angew. chew., 1961,73,27 S. A. Shchubarov and A. N. Ryabov. . Zhur. neorg. Khim., 1960, 5, I931 R. T. Grimley, R. P. Burns and M. G. Inghram ...... J. Chem. Phys., 1960~33,308 0. Kubaschewski and E. L1. Evans . . Metallurgical Thermochemistry, Pergamon Press (3rd Edn. 1958) 7 L. Brewer ...... National Nuclear Energy Series. Paper 3, 1950, 19~ 8 C. B. Alcock and G. W. Hooper . . Metallurgical Society Conferences, 7, Physical Chemistry of Process Metallurgy, (I), p. 325; Interscience Publishers, 1961

A High Temperature Research Microscope

NEW DESIGN OF PLATINUM MICRO-FURNACE

For the study of crystallisation phenomena tained very quickly, and can be measured in glass and for the construction of phase accurately by means of a 0.012 mm diameter diagrams a high temperature polarising micro- platinum thermocouple accurately located in scope is needed capable of examining speci- contact with the specimen. mens at temperatures up to 1400°C. A new type of micro-furnace for use in this way on a microscope stage has recently been designed by N. Murphy, of Pilkington Brothers Research Laboratories. This con- sists of a 3 mm diameter vertical open-ended tube in 10 per cent rhodium-platinum, partitioned about its centre by a foil diaphragm which serves as a support for a cone- shaped rhodium-platinum crucible. The current leads are of 3 mm square section rhodium-platinum. Equilibrium temperatures are at-

The platinum micro-furnace unit mounted on the stags of the microscope

Platinum Metals Rev., 1961, 5, (4) 139 Internal Nucleation of Glass ROLE OF THE PLATINUM METALS IN CONTROLLED CRYSTALLISATION

Glass normally devitrifies by the growth of glasses containing neither titania nor photo- crystals nucleated either at the surface or at sensitive elements can be effectively nucleated some internal imperfections such as inclusions by any member of the platinum group of or bubbles. The crystals so formed are coarse metals. Examples are alkaline phosphate and and possess a distinct orientation which results silicate glasses which are aided to form fine in a marked deterioration of mechanical and crystals by the presence of collodial platinum physical properties. liberated from platinum chloride added to the Recent work has shown that crystallisation melt. of certain glasses can be closely controlled No special heat treatment is required to produce a fine, uniform grain size and a to develop these nuclei since the suspension completely random orientation. The resulting forms during melting. Crystal growth occurs materials, known as “glass-ceramics”, possess when the glass is reheated to about 600°C. remarkably enhanced mechanical and elec- In a paper given in Toronto on “Crystal trical properties when compared to the normal Orientation as Influenced by Platinum Nuc- glasses of the same chemical composition leation” Rindone described the effect of and their development has opened up an platinum nucleation on the orientation of interesting new field. This interest was lithium disilicate crystals forrr.ed from lithium acknowledged by the American Ceramic silicate glasses. The normal devitrification Society during its April meeting in Toronto, process of this glass produces crystals with a when a symposium was held on “Nucleation marked orientation relative to the surface. and Crystallisation”. When the glass is inoculated with platinum To obtain the fine grain structure it is during melting this tendency towards orienta- necessary to have present in the glass a large tion in the surface layers is greatly decreased number of nuclei around which crystal growth and is completely eliminated a few microns can develop. The first glasses examined were below the surface. those containing titania. It was found that Patents recently granted to Corning Glass after suitable heat treatment a dispersed Works in the name of S. D. Stookey, the precipitate of a titania-rich phase was formed pioneer of this type of glass-ceramic material, which then acted as nuclei for subsequent describe the inoculation with platinum group crystal growth. metals of a number of types of glass. The Several papers at the symposium dealt inoculant is added to the melt as a compound with the formation of these nuclei, but which on dissociation gives a free metal it is apparent that many problems remain content of between 0.001 and 0.01 per cent unsolved. in the glass. The desired fine crystal size Other glasses containing small amounts along with improvements in properties are of copper, gold, silver or cerium were found then attained by heat treating in the range to be photosensitive, nuclei being formed by 580” to 650T. subjecting the glasses to ultra-violet radiation. It is evident that platinum group metal Heat treatment then produced the fine crystal inoculants can be used in a wide variety of growth. glasses because of their ability to form an It had also been shown by G. E. Rindone, insoluble colloidal suspension capable of of the Pennsylvania State University, that acting as crystal nuclei. J. A. S.

Platinum Metals Rev., 1961, 5, (4), 140-140 140 Corrosion Resistance of Chromium

EFFECTS OF ADDITIONS OF PLATINUM METALS

By T. P. Hoar, s~.D.,F.R.I.c., F.I.M. Department of Metallurgy, University of Cambridge

The addition of small percentages of paper presented to the Detroit meeting of the platinum, palladium or other noble metal to Electrochemical Society, have reported the readily passivated metals such as titanium extension of the work to chromium, a metal and stainless steel has been shown to be in which considerably greater interest is being capable of greatly improving their corrosion taken than was formerly the case. resistance towards non-oxidising acids. A Noble metal additions appear to have two series of papers by Tomashov and co- main actions: first, by providing points of workers on stainless steel and one by Stern low hydrogen overpotential they induce a and co-workers on titanium were reviewed high anode current density at a high potential and summarised in this journal (rJ 2). over the bulk of the alloy surface, so leading Now Greene, Bishop and Stern (3), in a to passivation, and secondly, by somewhat

TABLE I Effect of Alloy Additions on the Corrosion Resistance of Chromium CORROSION RATE IN MILSjYEAR

Boil I ng Addition Boiling H,SO, Boiling HCI 10% 20% 30% 40% 50% 60% 90% Conc. 5% 10% 15%

Pure Cr DDD D 3

0.5y0 lr 43 100 D D 34

0.5% Rh 68 66 970 D 5

0.5% Ru 83 7,100 - D I00

0.570 Pt 175 120 36 D 200

0.5% Pd ieo 1,500 1,300 D 15

0.5y00s - - -_ D 8

0.5% Au - - - I20

0.5y0 Re - - - - 5

2% cu D- - D 70

0.5yoAg - - - - 4

D -Dissolved during test [ )-Samples activated with an iron wire for at least one minute (a)-Corrosion rate- 100,000 mpy (0.5 hr. test) (b)-Corrosion rate-240,000 rnpy (0.5 hr. test)

Platinum Metals Rev., 1961, 5, (4), 141-143 141 r TABLE II Effect of Platinum and Palladium Alloy Content on the Corrosion Resistance of Chromium CORROSION RATE IN MILSlYEAR

Boiling65% Addition Boiling H,SO, Boiling HCI 20% 30% 40% 50% 60% 70% 5% 10% 15% HNO,

Pure Cr D D D D D D D 3

0. I yo Pt 5 22 I00 840 D 9 D 9 (1 1) (1,400) 0.S0% Pt 12 28 I75 I20 36 a D 200 (16) (25) 1.0yo Pt 6 22 210 68 21 140 D 500 (3) 2.0y0 Pt 6 18 I30 28 9 3 D 300 (18) (51) 5.0% Pt I 18 51 12 - 490 (4) 0.05% Pd 0-22 57 - D D 6 (56) 0. I yo Pd 620 31 I30 1,600 D D - 5 (20) 0.2% Pd 0-13 23 I50 1,400 D 044 D - 7 (13) (915) 0.3% Pd 1-12 21 370 1.400 300 0-36 D - 5 (13) (94) 0.5% Pd 8 22 I80 1,500 1,300

Platinum Metals Rev., 1961, 5, (4) 142 The results generally confirm and extend colleagues on the effect of noble metal the theory of Tomashov and of Stern on the additions on high chromium alloys is mechanism of the action of platinum metal promised. All in all, the principle of noble additions. Experimentally, Tomashov has metal additions for increasing the acid resist- recently reported (4) full confirmation of the ance of easily passivated metals appears to Stern school’s findings concerning titanium. be now very well established and worthy of A further publication by Greene and his extended practical trial.

References I T. P. Hoar ...... Platinum Metals Rev., 1958, 2, 117 z T. P. Hoar ...... Platinum Metals Rev., 1960, 4, 59 3 N. D. Greene, C. R. Bishop and M. Paper presented to Electrochem. SOC., Detroit, Stern October 1961 4 N. D. Tomashov ...... Lecture to Gordon Conference on Corrosion, August 1960

Miniature Moving Coil Relay IRIDIUM-PLATINUM CONTACT ASSEMBLY

In order to take the fullest possible advan- normally keeps the blade in the central or tage of the extremely limited operating power ‘‘off) position. available, moving-coil construction is em- Provided that spark-quenching is em- ployed for very high sensitivity relays. The ployed, the contacts will handle powers of type S.I 15 relay by Sangamo Weston Limited up to one watt, a.c. or d.c. (substantially is an example of miniature moving-coil non-inductive) and provided that the circuit construction, the unit measuring only 51 x voltage does not exceed 50 or the circuit 19.5 ~21.5mm. It can be wound to operate current IOO microamp. on a current of only 50 microamp. Iridium-platinum provides the combina- The contact arrangement comprises a blade tion of hardness and complete freedom from of 20 per cent iridium-platinum attached to tarnish that is essential in this application. the lower end of the moving coil, this moving between the two dimpled iridium-platinum strip contacts in the base assembly shown on the right of the illustration. The hairspring of the relay

A sensitive moving-coil relay of miniature construction by Sangamo Weston Ltd. Both $xed and moving contacts are in 20 per cent iridium-platinum.

Platinum Metals Rev., 1961, 5, (4) 143 Creep Tests on Platinum Alloys A NEW METHOD OF ASSESSING HIGH-TEMPERATURE PROPERTIES

In a recent paper on the tensile creep At IIOOOC,the maximum temperature at properties of platinum and a number of its which a complete range of data was available, alloys (I), Dr G. Reinacher of Degussa, the 10 per cent rhodium-platinum alloy was Hanau, has extended the information presen- the strongest material tested. This was closely tedin two earlier papers (2, 3), and has ad- followed by the 10per cent iridium and 4 per vanced intriguing explanations for some of the cent ruthenium-platinum alloys which had anomalously low elongation values that have very similar characteristics. The physically been observed. pure platinum had a IOO hour loading capacity The behaviour of physically pure (as approximately half that of the ruthenium opposed to commercially pure) platinum was alloy and slightly higher than that of the compared with that of platinum alloyed with 4 per cent palladium alloy. At temperatures 4 per cent of palladium, 5 per cent of below 500°C the iridium-platinum alloys rhodium, 10 per cent rhodium, 5 per cent were superior to rhodium-platinum alloys. iridium, 10 per cent iridium, 5 per cent of As opposed to the pure platinum and the gold, and 4 per cent of ruthenium over the 4 per cent palladium-platinum alloy, both of temperature range 20 to 125oOC. Tensile which displayed considerable ductility over creep tests were carried out in air for periods the whole temperature range studied, inter- extending up to IOO hours. The specimens crystalline failures within the intermediate were in the form of 2 mm diameter wire and temperature ranges occurred with the iridium elongations were determined over a gauge and rhodium-platinum alloys, and elongation length of 50 mm. Wires were selected from minima were observed in the range 900 to standard production batches, and although IIOO"~. Elongation values as low as 3 and no purity figures are quoted, all the 7 per cent at 500" and 700°C occurred with the specimens were pre-annealed at temperatures 5 per cent gold alloy, and the 4 per cent comparable to those at which they were to be ruthenium alloy had a sharply defined tested so as to stabilise the grain structure. ductility minimum at 1100°C. At goo"C, where the rhodium and iridium-platinum An Index of Resistance alloys had elongation minima, the ruthenium- to Creep platinum alloy showed its highest elongation Some of the more important results are values. summarised in the table, which compares the tensile stress fioo each material was capable of Boundaries of Low withstanding for IOO hours with the stress fo Ductility Regions which caused instantaneous failure at the Dr Reinacher concludes that the boundary same temperature. The ratio of these two of the high temperature ductility region values affords a valuable index of the resistance corresponds with the temperature at which to creep, and the rapid rate at which this index rapid grain growth occurs and the microscopic decreases with rising temperature should be evidence confirms that the fine-grained observed. The concept of a "temperature materials are much less ductile than those in coefficient of creep resistance" is introduced which grains extend across the specimen. at this stage and used to compare the relative In order to confirm a suspicion that atmos- behaviour of the various test materials. pheric oxidation contributed to the ultimate

Platinum Metals Rev., 1961, 5, (4), 144-145 144 Creep Resistance of Platinum and Platinum Alloys at Temperatures up to 1250°C (Tons per square inch)

Temp. Pure Pt 4% Pd-Pt 5% Rh-Pt 10% Rh-Pt "C fl,, f0 fi00 f, fl,, f, fl,,

20 8.57 7.87 14.1 13.02 14.28 12.95 18.2 16.8 300 6.40 5.14 11.37 10.17 10.78 9.57 16.5 13.0 500 4.86 2.92 9.27 6.35 8.70 6.92 11.6 9.39 700 4.1 I I .46 6.80 3.30 6.54 3.18 9.54 4.7 900 2.13 0.76 4.37 1.19 4.50 I .08 6.8 I.74 I100 1.14 0.32 1.50 0.32 2.28 0.49 3.78 0.76 I250 0.89 0.25 0.96 0.18 1.90 0.36 - -

Temp. 5% Ir-Pt 10% Ir-Pt 5% Au-Pt 4% Ru-Pt "C fll fmo fo f,,, fo fl,, fo fioo

20 15.5 13.85 22.86 21.25 22.4 20.3 28.0 25.4 300 13.9 10.6 17.15 16.2 19.6 - 19.55 - 500 10. I 5.7 13.7 9.26 19.05 8.15 18.7 14.3 700 6.73 2.80 9.72 3.75 13.3 3.62 12.6 6.66 900 4.25 0.81 5.65 I .27 7.42 I .40 8.05 2.10 I100 2.06 0.44 3.20 0.61 2.98 0.41 3.59 0.60 I250 1.36 0.30 2.38 0.32 1.84 0.24 - -

f,=stress required to cause instantaneous failure f,,,=stress required to cause failure in 100 hours failure of the rhodium and iridium-platinum temperatures suggests that a simple "tem- alloys, special platinum-sheathed test speci- perature co-efficient of creep resistance" is mens were produced but the results obtained not applicable over wide temperature ranges, were unfortunately not reported. although it may be of considerable value in The value of the index floo~o which, at comparing the properties of the various room temperature, was approximately 0.9 for platinum alloys between goo" and 125oOC. all the materials tested, decreased rapidly Interesting speculations on the influence as the temperature increased above soo"C, of miscibility gaps on creep behaviour are reaching 0.2 at IIOO"~and in some instances advanced by the author, who suggests that the 0.15 at 1250°C. At IIOO'C the IOO hour intermediate-temperature brittleness exhibi- loading capacity of the 10 per cent rhodium ted by the gold and iridium-platinum alloys alloy is only 20 per cent of its hot tensile might be associated with a type of precipita- strength, while that of physically pure plati- tion which is accelerated under the influence num, surprisingly enough, is 28 per cent of of a tensile stress. This mechanism might also its hot tensile strength. The high temperature be operative in the rhodium-platinum system, properties of pure platinum, therefore, where Raub (4) has postulated by analogy the although inferior to those of its alloys, do not existence of a miscibility gap. decrease so rapidly with temperature. A. S. D. The data in the table indicate the existence of what might be termed a plateau of creep References resistance, extending with some alloys up to I G. Reinacher, Metall, 1961,15, 657-665 5oo°C, over which the mechanical properties z G. Reinacher, Metall, 1958, 12, 622-628 deteriorate only to a limited extent. The 3 G. Reinacher, Metall, 1956, 10, 597-607 rapid deterioration which occurs at higher 4 E. Raub,J. Less Common Metals, 1959, I, 3-18

Platinum Metals Rev., 1961, 5, (4) 145 The Discovery of Iridium and Osmium

BICENTENARY OF SMITHSON TENNANT

By Donald McDonald, B.Sc., M.I.Chem.E., F.R.I.C.

The various men and the one exceptional when only 23, he was elected a Fellow of the woman who are credited with the discoveries Royal Society with an imposing body of of the hundred or so chemical elements form Cambridge support. In December 1786 he a remarkable pattern of dedicated scientists, moved from Christ’s to Emmanucl, where he high-minded divines and happy-go-lucky ex- took his degree as Bachelor of Physic in 1788. perimenters, among whom Smithson Tennant Soon after that he left Cambridge for stands out as one of the most human and London. likeable. In 1791 he presented a paper to the Royal He was a good Yorkshireman, only child Society demonstrating the composition of of the vicar of Selby, where he was born on “fixed air” (carbon dioxide), which attracted November 3oth, 1761. His father died when considerable notice. In 1792-1793, being he was nine and his mother a few years later. very disturbed by the state of affairs in His education was sketchy, but from the France, he made another extended foreign beginning he was interested in science. This tour. On returning to London he took up did not prevent him from acquiring “a com- residence in the Temple and resumed attend- petent knowledge of Greek” and becoming ance at the hospitals. In 1796 he took his “well versed in the Latin language”, but doctor’s degree at Cambridge, but before directed his attention, when the time came to long abandoned any idea of entering the choose a profession, to that of medicine. medical profession; he was really not fitted With this in view he went to Edinburgh temperamentally for such work and already and came under Joseph Black, an event had ample private means. He was now “well calculated to stimulate and direct his therefore free to follow his scientific tastes curiosity”. in his own time. In 1796 he sent to the Royal In October 1782 he entered Christ’s Society his paper on the nature of the diamond, College, Cambridge, where he was most in which he confirmed and systematised fortunate in both circumstances and com- Lavoisier’s opinion that it consisted of carbon. panions, and where he devoted his principal It was in the course of this work, in which a attention to chemistry and botany. At the platinum tube was used, that he became inter- same time he read widely and with a catholic ested in that metal, and was assisted by taste, helped by “extraordinary powers of another budding young doctor from Cam- memory and understanding” and by a re- bridge, William Hyde Wollaston. markable power of getting to the heart of a He was now able to travel, but the war with book in little more than a cursory inspection. France and a proneness to sea-sickness de- In 1784 he travelled in Denmark and terred him and he sought a new interest in Sweden, where he met and talked to Scheele, agriculture. He bought land in Lincolnshire and a year or two later to Paris to meet the and later in Somerset, and proceeded to study great French chemists. In January 1785~ the scientific bases of farming. The first

Platinum Metals Rev., 1961, 5, (4), 146-148 146 4x6 Mi. TENRANT~JRtwo Metals,folrnd kt the Powder some kinds of pfatina may contain that substance, besides the other bodies usually mixed with it. When the alkaline solution is first formed, by adding water to the dry alkaline mass in the crucible, a pungent and peculiar smell is i~m~iatelyperceived. l‘his smell, as I afterwards discovered, arises from the extrica- tion of a very volatile metaIIic oxide; and, as this smell is one of its most distin~ui~~~ngcharacters, I should on that account incline to call the mezd Ilsmirm,

The passage from Smithson Tennant’spaper, read to the Royal Society on June 21st 1804, describing the discooery and nurning of osmium result of this was a paper sent to the Royal obtained by means of ammonium chloride Society in 1799 on the bad effects of dolomitic from the solution in aqua regia of native lime on germination, his conclusions being platinum; in 1803 he published his view that supported by goniometrical researches by these were due to the presence of an unknown Wollaston. metal. About the same time his master This continued association of the two Vauquelin, having treated the black powder men now had a very important result. Both with alkali, obtained a volatile oxide which were interested in platinum and, some time he thought to belong to the same unknown in 1799 or 1800, they entered into a partner- metal. ship for the thorough investigation of the Tennant continued his work during the native metal, for which Tennant undertook winter and later studied carefully the papers to provide the finance. Towards the end of of Collet-Descostils and of Fourcroy and 1800 they bought nearly 6,000 ounces of Vauquelin. He soon realised, however, that material and extraction commenced shortly whereas they suspected the presence of only after. It was already known that when this one new metal in the black powder, in fact mineral was treated with aqua regia there there were two. For breaking up the material remained insoluble a small quantity of a he used a method similar to that employed black powder, which J. L. Proust in 1801 by Vauquelin, namely the alternate action of described as “nothing else than graphite or caustic alkali and of acid. The second metal plumbago”. he found in the alkaline solution which had In the summer of 1803 Tennant undertook been suspected by Vauquelin to contain the examination of this material, while chromium. Tennant was unable to confirm Wollaston devoted his attention to the main this latter conclusion, but further examina- aqua regia solution. The results of the latter tion showed that the solution contained a work are well known, and Tennant’s led him volatile oxide which could be separated by to the discovery of iridium and osmium. acidification and distillation. This was a In the early stages of the work he mentioned colourless body, condensing first to an oily it to Sir Joseph Banks, and this establishes liquid and then solidifying into a semi- his priority over certain work going on at the transparent mass. In all stages it had a strong same time in France. There Descostils had and very characteristic smell. It was this that been examining the curious variations from caused him to confer on the metal the name orange to red of the colour of the precipitates of osmium, from a Greek word meaning smell.

Platinum Metals Rev., 1961, 5, (4) 147 As it is necessary to give some name to bodies which have not been known before, and most ~onv~nj~~tto indicate by it some characteristic property, J should illcline to call this metal Iridium, from the striking variety of colours which it gives, while dissolving in marine acid.

The naming of iridium - a later passage from the same paper

With regard to the other metal, Tennant’s the changes that had taken place. He moved work confirmed and extended the observations leisurely to the south, to Montpellier and of Fourcroy and Vauquelin on the subject, Marseilles, and then back to Boulogne, where and this one he named iridium “from the he arrived on February 20th, 1815. On the striking variety of colours which it gives while 22nd he embarked for home, but rough dissolving in marine acid”. Tennant pub- weather delayed the sailing of the ship. To lished this work to the Royal Society on pass the time Tennant suggested to a German June zrst, 1804, in a paper entitled “On two officer, whom he had met on board, a visit on Metals, found in the black Powder remaining horseback to Napoleon’s column. On the after the Solution of Platina”. This is a way back they came to a drawbridge at the masterpiece of clarity and conciseness, and side of a small fort. Unfortunately, the bolt it is a tribute to it and to him that the French securing this had been stolen a fortnight workers accepted the priority of his discovery before and both men were thrown into the without question. In 1814 Vauquelin pub- ditch beneath. The German escaped with lished a paper confirming and extending his bruises, but Tennant fell under his horse work. and his skull was badly fractured. He died For his discoveries Tennant was awarded shortly after in the Civil Hospital at Boulogne the Copley Medal for 1804 by the Royal and was buried in the public cemetery there. Society, to whom he had also communicated So passed a man of the highest intellectual in 1802 a paper on the nature of emery, character, marked especially by “a prompt identifying it with corundum and as princi- and intuitive perception of truth, both upon pally of alumina. those questions in which certainty is attain- In 1805 and 1806 Tennant travelled in able, and those which must be determined by Scotland and Ireland, where he met Wollaston the nicer results of moral evidence”. That is by chance at the Giant’s Causeway. He always his epitaph as a man; as a scientist his achieve- had the urge to travel, but was no longer ments still speak for themselves. physically strong. In 1813his friends induced him to become References a candidate for the vacant Professorship of Most of the information given above is derived from a rare pamphlet in the library of Johnson, Chemistry at Cambridge, to which he was Matthey & Co., Limited, called “Some Account elected in May. In the spring of 1814 he of the late Smithson Tennant, F.R.s.” and pub- delivered his first and only series of lectures, lished in 1815 by some of his friends, the matter which made a great impression. In June of having appeared in substantially the same form in Thomson’s Annals of Philosophy for that year. that year he read his last two papers to the Reference has also been made to the late L. F. Royal Society, one on an easier method of Gilbert’s article on the Wollaston MSS at obtaining potassium and the other on “pro- Cambridge (Notes and Records of the Royal curing a double distillation by the same heat”. Society, May 1952). The appropriate section in Mary Elvira Weeks’ admirable book on “The In September 1814 Tennant went to Discovery of the Elements” has also been most France and travelled widely there to observe profitably consulted.

Platinum Metals Rev., 1961, 5, (4) 148 ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES those with single-crystalline Pt is interpreted in terms of an extra diffusion transport along the The Zirconium-Platinum Alloy System grain boundaries in polycrystalline Pt. Porosity and dimensional and structural changes were also E. G. KENDALL, C. HAYS and R. E. SWIFT, Trans. studied. Met. SOC.A.I.M.E., 1961, 221, (3), 445-452 Phase relationships in the region 0-50 at.); 11. The Concentration Penetration Curves (68.2 wt.",) Pt were investigated by metallogra- and the Diffusion Coefficients phic, incipient melting, and X-ray diffraction Ibid., 643-652 techniques. Phase fields in the Pt-rich region were outlined. The maximum solubility of Pt in pZr Concentration penetration curves were determined is 13.5-tr wt.7, and the minimum solubility in and the overall diffusion coefficient was calculated according to the graphical method of Matano. aZr is < 1.0 wt.";. Zr solubility in pure Pt is Partial diffusion coefficients may be calculated < 1.0 wt.o/,. A eutectic exists between pZr and Zr,Pt at 36&1 wt.% and 1185"C, and a eutectoid from the observed Kirkendall displacement and reaction between pZr and aZr+Zr,Pt occurs at data concerning the concentration gradient and the 8.551 wt.% Pt and 826°C. Zr,Pt is formed concentration in the marker interface. A method peritectically at about 51.7 wt.74 Pt and rp5"C. of expressing an observed Kirkendall effect in a ZrPt and ZrPt, occur at 68.2 and 86.5 wt.O/, Pt, numerical value between I and o is given. respectively, with melting points at 21oo~Cand >21zoCC,respectively. An Investigation of the Ageing of Platinum- Rich Alloys of Platinum with Silver A. A. RUDNITSKII and N. A. BIRUN, Zhhw. Neorg. Constitution Diagrams of the Palladium- Khim., 1961, 6, (6), 1342-1346 Tungsten System Vickers hardness measurements were made on M. A. TYLKINA, v. P. POLYAKOVA and E. M. SAVITSKII, alloys containing 5,1o, 15~20~25and 30 wt.% Ag Zhur. Neorg. Khim., 1961,6, (6),1471-1474 which had been aged for various periods in the The system was investigated by thermal analysis, range 10 min-33 h at 400', 500°, 600" and 700°C. microscopic and X-ray analysis, and measurement The alloys were also aged at 500'C for periods of hardness, microhardness and absolute thermal in the range 11-75 h and then hardness-tested. e.m.f. No chemical compounds were observed in Alloys containing 15-30 wt.% Ag show the great- the system. A peritectic reaction occurs at est ageing effect which is obtained by soaking at 2175fz5~C. a solid solution of W in Pd extends 500°C for 10-20 h. up to 28 wt.% W and its melting point increases steadily from 1552'C to ZIOOOCfor the alloy Ternary Carbon Alloys of Palladium and containing 25 wt.yo W. A narrow P-phase solid Platinum with Magnesium, Aluminium, solution based on W extends up to 2 wt.:,; Pd. Zinc, Gallium, Germanium, Cadmium, In- Between the w- and P-solid solutions there is a dium, Tin, Mercury, Thallium and Lead two-phase (a+p) region. H. H. STADELMAIER and W. K. HARDY, z.Metall- kunde, 1961,5z, (6),391-396 Kirkendall Effect and Diffusion in the Gold- The crystal structure of 22 ternary alloy systems Platinum System was examined. True ternary phases of the A1 and I. The Kirkendall Effect related structures were found in the Pd-In-C, A. BOLK, Acta Met., 1961, 9, (7), 632-642 Pd-Sn-C, Pd-Pb-C, Pt-Mg-C, Pt-AI-C, Sandwich-type diffusion couples of pure Au and Pt-Ga-C, Pt-In-C, Pt-Sn-C and Pt-Pb-C pure Pt (poly- and single-crystalline), and of pure systems. The structures of PdMg, Pd,Zn, Pd,Tl, Au and a 73.5 at.O; Au-Pt alloy were prepared by Pt,Mg, PtMg, Pt,Al, PtJn and Pt,Hg were also welding platelets of Au on both sides of a platelet determined. of Pt or the Au-rich alloy. Diffusion took place in a furnace and the Kirkendall effect was Metal-Optical Investigations on Silver- measured as a function of temperature and time. Palladium and Nickel-Chromium Alloys A displacement of the marker interface in the H.-E. SCHMIDT and R. E. HUMMEL, z.Metallkunde, direction of the highest Au concentration was 1961, 52, (51, 337-343 observed. A difference in the magnitude of the Optical constants of mechanically polished effect in couples with polycrystalline Pt and in samples were determined using incident visible

Platinum Metals Rev., 1961, 5, (4), 149-157 149 light of different wave-lengths. Reflected intensity was measured and a term proportional to para- and phase of the originally plane polarised light magnetic magnetisation proposed. were observed and the refractive coefficient and absorption coefficient were calculated as a func- Crystallography of the Ru-B and 0s-B tion of intensity ratio and principal angle of Systems incidence. Data obtained are used to study the C. P. KHMPTER and R. J. FRIES,?. Chew. Phys., 1961, application of the free conduction electron model 34, (61,1994-1995 to the alloys studied. The systems were studied by X-ray powder diffraction. The existence of the hexagonal Ferromagnetism in Dilute Solutions of Cobalt Ru7B, phase was confirmed and the hexagonal in Palladium phases RUB,, Ru,B,, OsB, and Os,B, were found. Crystallographic data are given. R. M. BOZORTH, P. A. WOLPF, D. D. DAVIS, V. B. COMPTON and J. H. WERNIK, Phys. Rev., 1961,122, (4>11157-1160 Arsenides of the Transitinn Metals W. A Note on the Platinum Metal Arsenides Magnetic moments were measured in fields up to Izk oersteds at temperatures down to 1.3%. R. D. HEYDING and L. D. CALVERT, Canad. J. Chem., Ferromagnetism exists in the 0.1 at.?; Co-Pd 1961, 39, (4L 955-957 alloy even though the Co atoms are about 10 at. Binary alloys corresponding to M,As, M,As, diameters apart. The Curie point of this alloy is MAS, MAS, and MAS, (M=Ru, Rh, Pd, Os, Ir, 7°K. It was found that the moment associated or Pt) were prepared and their structures were with one Co atom increases from 1.7 Bohr units examined by X-ray powder diffraction techniques. The compounds Pd,As, Rh,As, RhAs. in pure Co to 9 to 10 units in the maximum RuAs, dilution. The onset of ferromagnetism at about RuAs,, OsAs,, PdAs,, PtAs,, RhAs,, and 10 at.% Co was indicated by measurement of IrAs, were detected and their structures are lattice constants. discussed. Ruthenium Hexafluoride Magnetic Coupling in Palladium-Dilute Iron H. H. CLAASSEN, H. SELIG, J. G. MALM, C. L. Group Alloys CHERNICK and B. WEINSTOCK, J. Amer. Chem. E. 0. WOLLAN, Phys. Rev., 1961, 122, (6), 1710- sot., 1961, 83, (IO), 2390-2391 1713 RuF, was prepared by heating the metal powder The magnetic properties of Pd and its alloys with in a F atmosphere at 300 mm pressure. The Fe group metals is discussed in terms of the split- resultant dark brown solid melts at 54°C and ting of the d orbitals. Data already obtained for decomposes at 200°C according to the reaction: the Curie point temperatures of Pd-Fe alloys RuF,+RuF, ++Fz. and ferromagnetic saturation moments of Pd-Fe and Pd-Ni alloys are shown graphically. Experimental Study of Intermetallic Dif- fusion in Large Temperature Gradients c. J. MEECHAN, J. Appl. Phys., 1961, 32, (5), NCel Temperatures and Thermoremanent 954-950 Magnetisation of MnxPd,,,-x Alloys (34

Platinum Metals Rev., 1961, 5, (4) 150 gas molecules is thought to cause a decrease in oxygen and gas-phase oxygen was examined with the oxidation rate with increased pressure. the 0l8 mass spectrometer. Pt and Ni, compared with Fe, have a much slower sorption rate. The atmospheric behaviour of the coatings was Vaporisation of Iridium and Rhodium observed during several months. M. B. PANISH and L. REIF, J. Chem. Phys., 1961, 34, (61, 1915-1918 Some Specific Chemical Reactions at the Knudsen effusion and Langmuir evaporation Surfaces of Noble Metals techniques were used in the study. The vapour A. KEIL, Metall, 1961, 15, (7), 655-657 pressure of Ir over the temperature range Reactions which occur at room temperature 2100°-2600"K is represented by the equation: include the formation of Ag,S and diffusion of log p-= 10.46 -(33980jT), and that for Rh over Ag,S on Au surfaces. Conditions for the occur- the temperature range 2050°-22000K by the rence of this phenomenon are discussed. Adsorp- equation: log p-= 10.28-(28300/T). Heats of tion and polymerisation reactions of organic vaporisation calculated are: Ir, AHzg8= 158.4i vapours on Pt metal surfaces are described. The 0.5 kcal,/mole, and Rh, AHzgs= 132.8 A0.3 kcall atmospheric oxidation of Ag, Au, and the Pt mole. Boiling points are estimated for Ir and Rh metals at high temperatures is discussed. (14 as 4800°K and 3980"K, respectively. references)

Heat Capacity and Resistivity Anomalies in Rates of Chemisorption of Hydrogen on Palladium Hydride Hydrogen-Covered Ruthenium Surfaces P. MITACEK and J. G. ASTON, Nature, 1961, 191, M. J. D. Low,J. Phys. Chem., 196r, 65, (9,887-888 (Ju~.151, 271 Hydrogen was pre-adsorbed on a 0.57; Ru/Al,O, Slow exothermal processes were observed near catalyst at 257'C. The rate of hydrogen uptake on 150°K and above 200°K on cooling solutions of the pre-adsorbed gas was then measured at 257°C. hydrogen in polycrystalline I'd. Heat capacity Data obtained for the chemisorption kinetics measurements with HjPd ratios of 0.25 and 0.125 indicate that the chemisorption mechanism re- show a maximum at 55°K coinciding with that quires a surface which changes in character during previously reported for a HjPd ratio of 0.50. A adsorption. migration of hydrogen from the cc- to @-phaseat low temperatures is suggested. Resistivity and heat capacity data are compared. ELECTROCHEMISTRY The Fundamental Behaviour of Passive The Electrical Resistance of Alpha Alloys Hydrogen-Palladium H. H. UHLIG, Werkstoffe u. Korrosion, 1961, 12, w. T. LINDSAY and F. w. PEMENT, Bull. Amer. Phys. (7), 413-416 Sac., Series ZI, 1961,6, (4), 353 (Abstract of paper The mechanism of passivation of a base metal by presented at the 1961 Summer Meeting, Mexico alloying, as in the addition of Cr to Fe, is dis- City, June 1961) cussed. Passivation achieved by the addition of Resistance measurements were made on gas- alloying constituents of lower overvoltage, exemp- chargcd alloys in the range 100"-400"C. The lified by the addition of 0.1% Pd to Ti and 18/8 increase of resistance of Pd resulting from hydro- stainless steel, is also described. Critical alloy gen addition is proportional to the hydrogen compositions for Cr-Fe and Ni-Cu alloys are concentration, and the proportionality constant discussed. is independent of temperature. Results obtained combined with those obtained previously may be Possibilities of Protecting Titanium from represented in the range 75"-400"c by the Corrosion equation (R/R")-I =(2.41fo.o4)m, where R= W. R. FISCHER, Techn. Mitt. Krupp, 1961, 19, (2), resistance of crH-Pd, R" =resistance of H-free Pd, 16-72 and m=H:Pd atom ratio. The possible corrosion protection of Ti is predic- ted from a study of potential-pH (Pourbaix) diagrams for the Ti-Ti0,-H,O system and of The Kinetics of Oxygen Absorption at current-voltage curves for Ti in aqueous solutions. Vaponr-Coated Fe, Ni or Pt Layers and Cathodic and anodic methods of protection in Alloys aqueous solutions are described. Methods of C. WEISSMANTEL, K. SCHWABE and G. HECHT, anodic protection include the addition of oxidising Werhtofle u. Korrosion, 1961, 12, (6), 353-359 substances to the corrosive medium, the applica- The rate of oxygen sorption on layers of metal tion of impressed currents, and galvanic contact about SOOAthick was measured manometrically of the Ti with Pt metals by coupling or coating. in the temperature range 25°-450"c. The effect of The corrosion resistance of Ti in HC1 and H2S04 the simultaneous addition of H,O vapour was is greatly improved by alloying with small amounts studied. The exchange rate between combined of Pt or Pd; the addition of 0.2% Pd is sufficient.

Platinum Metals Rev., 1961, 5, (4) 151 Alloying with base metals such as Mo, Ta, V, and layer of chemisorbed oxygen is formed on the Pt Zr is also mentioned. The corrosion properties electrode by oxygen separated from the H20. of Ti in non-aqueous solutions and gases are also This passivating oxygen layer may be removed discussed. either by cathodic reduction or by reduction by the H,C,O,. It is suggested that the anodic An Investigation of the Mechanism of the oxidation of H,C,O, is effected by intermediate Electrochemical Corrosion of Titanium active oxygen. 111. The Corrosion and Electrochemical Behaviour of Titanium and of its Platinum Mechanisms for the Evolution and Ionisa- and Palladium Alloys in Sulphuric and tion of Oxygen at Platinum Electrodes A. c. RIDDIFORD, Electrochim. Acta, 1961, 4, Hydrochloric Acid Solutions (2-41, I7O--I78 N. D. TOMASHOV, G. P. CHEFNOVA and R. M. Observations by other workers on the oxygen AL'TOVSKII, Zhur. Fiz. Khim., 1961, 35, (5), 1068-1077 (English summary) electrode process support the suggestion that it follows the same path in both acid and alkaline The polarisation in H2S04and HC1 solutions of solution. The path is identified. anodes and cathodes of Ti and its alloys with 19; and 2% Pt and Pd was investigated by of potentiostatic methods. It was shown that Effect Adsorption of Anions on the increases in both acid concentration and tem- Discharge of Hydrogen on Palladium and perature cause an increase in the passivation the Ionisation of Hydrogen Dissolved in current and a shift of the total passivation potential Palladium in the positive direction. Alloying of Ti with Pt L. T. SHANINA, Proc. Acad. Sci. U.S.S.R., Phys. or Pd lowers the cathodic hydrogen overvoltage Chem. .Section, 1960, 133, (I-6), 647-649 with a positive shift of the steady state potential. (Transl. of Doklady Akad. Nauk S.S.S.R., 1960, Consequently the corrosion resistance of the '33, (2)Y 417-419) alloys is increased. Polarisation measurements on a palladised Pt electrode were made inHCl,HBr, KI + IN H,SO,, Electrochemical Properties of Anodically and KI + IN NaOH at ZOT,and anode charging Prepared Oxide Layers on Platinum curves were plotted. Charging curves plotted in K. NAGEL and H. DIETZ, Electrochim. Acta, 1961, HCl (o.IN, o.gN and zN) differ little from those plotted in IN H,S04. The reversibility of the 4, (11, 1-11 Conditions for the formation of thick oxide layers process is disrupted in the presence of Br- and on Pt by anodic treatment with pure d.c. or with there is an even greater deviation in the presence superposed a.c. were investigated. Cathodic of I-. charging curves obtained with the Pt oxide electrodes thus produced show a plateau region. Effect of Surface Oxidation on the Behaviour Rest values obtained with intermittent current of Platinum Electrodes. The Fe(II1)-Fe(I1) indicate that the equilibrium potential of the Couple in Sulphuric Acid and Perchloric Acid PtO, electrode should be close to UH=0.80 V, F. c. ANSON, Analyt. Chem., 1961~33,(7), 934-939 the rest value measured with thin layers. An Chronopotentiometric studies showed that a film explanation of the electrochemical behaviour of of platinised Pt is formed on the surface of an the Pt oxide electrode is given. electrode which has been oxidised and reduced electrolytically. The behaviour of the electrode is Potential-Activity Diagram for Important influenced by the presence of this film as well as Electrode Reactions in the System Platinum/ by that of a Pt oxide film. The oxide film is chemi- Platinum Oxide/Solution cally reduced rapidly by Fe(I1) in IM H,SO,, but in rM HC10, solutions of Fe(II1) and Fe(I1) it K. NAGEL and H. DIETZ, Electrochim. Acta, 1961, persists on the electrode and causes decreases 4, (2-4), 141-154 in the reversibility of the reduction and oxidation The dependence of UH values for electrode of Fe(II1) and Fe(I1). reactions in the system on the activity ai of dis- solved reactants is shown graphically in a V(a) The Problem of Hydrogen Overpotential on diagram. The possibilities of determining equilib- rium values of the Pt oxide electrode are discussed. Platinum YA. M. KOLOTYRKIN and A. N. CHEMODANOV, Proc. Acad. Sci. U.S.S.R., Phys. Chem. Section, 1960, The Anodic Oxidation of Oxalic Acid on 134, (I-6), 819-822 (Transl. of Doklady Akad. Platinum. I. Passivation Effect of a Bright Nauk S.S.S.R., 1960, 134, (I), 128-131) Platinum Electrode Determination of the hydrogen concentration in J. GINER, Electrochim. Acta, 196r, 4, (I), 42-54 the vicinity of a functioning Pt microcathode by The mechanism of the anodic passivation of a means of oscillographic polarography was used bright Pt electrode in IN H,SO, for the reaction to examine the theory that, for low potentials, the H,C,O,+zCO,i-zH++ze- was studied. A rate of evolution of hydrogen in acid media is

Platinum Metals Rev., 1961, 5, (4) 152 controlled by the rate of diffusion of molecular chloride or ruthenium sulphamate. Plating solu- hydrogen from the cathode surface into the tions containing 5 g metal11 and 250 ml HCl liquid. (32%,)/1 are recommended with operating tem- peratures of zs0C for Rh and Pd and 95°C and Intermediate Temperature Fuel Cells 65°C for Ru and Pt, respectively. Deposits of G. v. ELMORE and H. A. TANNER, J. Electrochem. Pd, Rh, Pt, and Ru up to thicknesses of 50,30,65, Sac., 1961, 108, (7), 669-671 and IOO pin., respectively, may be obtained. The The construction and performance of two types of coatings are sealed by immersion in a replacement gas cell operating from 125* to 200T is described. Au solution, in boiling H,O, or in NH,OH. The A Pd foil, 0.0005 in. thick, hydrogen electrode adhesion, tarnish and corrosion resistance, and and Teflon-treated Ag powder oxygen electrode solderability of the deposits are discussed. are used in an alkaline cell with a NaOH-KOH- Ca(OH), electrolyte. In a H,PO,-SiO, electrolyte, Barrel Plating by Means of Electroless carbon coated with Teflon and Pt or Pd is used Palladium for both the hydrogen and oxygen electrodes. R. N. RHODA,~.Electrochem. SOC.,1961, 108, (7), Current densities up to about rnajcm, have IOO 707-708 been attained. Experimental work was carried out using a bath of composition: Pd (as chloride of tetrammine Electrochemical Corrosion of Platinum in amine complex) 2.5-20 g/l, Na,EDTA 8 g/l, and Hydrochloric Acid Solutions NH,OH 280 g/l. The effect on plating rates of J. LLoPis and A. SANCHO, J. Electrochem. Sac., variations in temperature (Z~~-~SOC),addition 1961, 108, (8), 720726 rates of the N,H, reducer, and Pd concentration Anodic corrosion of Pt by d.c. (i,) is increased by were studied. The maximum rate (0.1 mil Pd increasing temperature, high C1- concentration, deposited in Iih) is obtained at 45°C with the high acidity and by superimposing a.c. (ia). addition of 0.096 g N,H,/15 min and log Pd/l. Corrosion by a.c. at frequencies below 50 CIS Operating techniques for long and short runs, was studied. Using a 10 cis square wave, intense storage of the baths, and pretreatment of sub- corrosion is increased by increasing acidity and strates are discussed. temperature. Corrosion is nil until i, reaches a critical value above which it increases, and with solutions of low acidity, it goes through a maxi- Crack-free Rhodium Deposits mum with increasing i,. Oscillographic cathodic F. H. REID, Metalloberfldche, 196r, 15, (2), 33-37 and anodic charging curves were studied and Two modified plating baths have been developed. interpreted. Rh deposits containing A1 and Mg, which are practically crack-free, are suitable for applications Electrochemical Applications of Platinised where corrosion resistance is most important and Titanium surface quality is of less importance. These coat- C. E. TIRRELL, Crucible Titanium Rev., 1961, 9, ings must be polished for applications in electrical (21, engineering. Rh deposits containing Se have good 2-6 surface quality and, though not truly crack-free, The electrochemical properties of Ti and Pt- have enhanced protective properties. coated Ti anodes are discussed, and methods of applying Pt to Ti are outlined. Applications in which Pt/Ti anodes have been used include fuel LABORATORY APPARATUS cells, impressed current cathodic protection systems, electrodialysis cells, and caustic-chlorine AND TECHNIQUE cells. In chlorine production, Pt/Ti anodes may be used in concentrated brine cells with current Induction Heated Pressure Vessel for Grow- densities ranging from IOO to 300 A/sq. ft. A ing Oxide Single Crystals fifteen-month plant-sale test with a diaphragm A. FERRETTI, D. G. WICKHAM and A. WOLD, Rev. Sci. cell has resulted in reduced power consumption, Imtr., 1961, 32, (5), 566-568 increased diaphragm life and improved chlorine The pressure vessel consists basically of a water- and NaOH quality. cooled stainless steel tube. This contains an A1,0, tube which surrounds a radio frequency load coil. The heating chamber, located in the ELECTRODEPOSITION cylindrical space enclosed by the load coil, con- Immersion Plating of the Platinum Group sists of a 20% Rh-Pt crucible sheathed by fused A1,0, and heated by Rh-Pt-Al,O, ring elements Metals the whole assembly being contained in a fused R. w. JOHNSON,J. Electrochem. SOC.,1961, 108, A1,0, crucible. Two Pt:Io:,b Rh-Pt thermo- (71, 632-635 couples are mounted in the heating chamber. The Pd, Rh, and Pt may be deposited on Cu from furnace, which operates at 1600°C and 75 atm chloride solutions, while Ru is deposited from oxygen pressure, has been used to grow ferrite solutions based on ammonium nitroso ruthenium crystals.

Platinum Metals Rev., 1961, 5, (4) 153 Oxygen Gauge and in some cases complete hydrogenation to J. WEISSBART and R. RUKA, Rm. Sci. Instr., 1961, butane was found. The optimum yield of buta- 3% (51, 593-595 diene (69O/,), given with a Pd/BaSO, catalyst, was A galvanic cell which measures oxygen partial accompanied by 21% butene-1, 5.5"/0 trans- pressure and oxygen pressures in vacuum systems, butene-2, 3.5% cis-butene-2 and 1Yn butane. both at high temperatures, is described. The gauge Further hydrogenation of butadiene-(I, 2) and consists of a $ in. diameter tube of Ca stabilised -(I, 3), butine-(I) and butine-(a) was investi- ZrO, sealed to a Kovar metal flange through a gated in the liquid- and gas-phases. Hydrocarbons graded glass seal. The flat bottom of the tube, with 12-16 C atoms are produced in the gas coated on both sides with a porous Pt film, acts phase. as the electrolyte. The electrodes are connected by k wire leads to a potentiometer. A Pt:Io:6 Catalytic Reforming Rh-Pt thermocouple measures the cell tempera- P. G. -CIAPETTA, Petrkeum Eng., 1961, 33, (s), ture. CIg-C31 The history of the development of the catalytic reforming process is outlined. Various reactions CATALYSIS which occur in the reforming of petroleum naphthas are discussed and the functions of the Plants Tests on the Decomposition of Nitrous constituents of PtiSiO,, Ft/Al,O,/SiO, and other Oxide over a Heated Rhodium Catalyst reforming catalysts in these processes are des- L. T. LAKEY, U.S.A.E.C. Report JDO-14545, cribed. Factors which affect the activity, selec- 11 PP. tivity and life of Pt catalysts are discussed in Dissolver off gases containing 14.2 to 19.8 vol.o/, detail. These include boiling range of the feed, feed N,O were passed over a 0.5% Rh/Al,O, catalyst composition, the presence of catalyst poisons, and bed in a stainless steel reactor. It was found that, variations in operating temperature, pressure, with outlet temperatures maintained between space velocity and hydrogen recycle rate. (88 1300"and 15oo0F,the N,O content of the off gases references) may be reduced to < 0.05 vol.o/,. Suggestions for the design of a single, double-pass reactor are Alumina: Catalyst and Support. VI. Aro- given. matisation of 1,l-Dimethylcyclohexane, Metbylcycloheptane, and Related Hydro- Reaction of Ethane with a Clean Rhodium carbons over Platinum/Alumina Catalysts Film H. PINES and T. W. GREENLEE, 3. erg. Chem., R. W. ROBERTS, Nature, 1961, 191, (Jul. 8), 170 1961, 26, (41, 1052--I057 C,H, at low pressure was brought into contact Catalysts prepared by impregnating aluminas of with a Rh film 3oA thick at 27°C and 100°C. At various intrinsic acidities with a solution of 27OC the CzHs decomposed to yield gaseous Pt(NH,N0,)2 were used in the investigation. CH, and an adsorbed residue with the composi- Aromatisation of I,I -dimethylcyclohexane (I), tion CH,.,. It was found that the rate of reaction 4,4-dimethylcyclohexene (11), methylcyclo- is a function of the surface temperature and of heptane (111), and 5,5-dimethylcyclohexadiene surface cleanliness. was studied at 35o*C. The composition of the aromatiscd product is affected by the relative The Selective Hydrogenation of Linolenic acidities of the aluminas and the method of platinising them. Absorption of the Pt complex Acid probably neutralises the acid sites of the A1,0,. J. G. WILLARD and M. L. MARTINEZ, Amer. J. Oil. Isomerisation, with the production of xylenes, SOL.,196r, 38, (6), 282-286 Chem. accompanies the aromatisation of I and I1 and Methyl linoleate was hydrogenated in the presence the extent of isomerisation is related to the intrin- of Rufert Ni, reduced NiO, Cu chromite, or sic acidity of the A1,0,. Aromatisation of (111) Pd-Pb catalysts. It was found that variation of gives C,H,CH,, C,H,C,H, and xylenes. catalyst, catalyst concentration, solvent, tempera- ture, and pressure had little influence on the Ethylene Oxidation: Low-Cost Route to selectivity. Differences in relative reactivity of the Acetaldehyde Manufacture 9, 12, and 15 double bonds of the methyl lino- ANON., Chem. Eng., 196r,68, (Io), 66-68 leate were found. The Aldehyd G.m.b.H. process is described. An aqueous solution of CuCl, containing a small The Hydrogenation of Monovinylacetylene amount of PdCl, acts as the oxygen-carrier in the A. RIECHE, A. GRIMM and H. ALBRECHT, Brennstoff- conversion of C,H, to CH,CHO. In a one-stage Chem., 1961, 42, (6), 177-185 oxidation, C,H,, oxygen, and recycle gas are Known methods of partial hydrogenation of boiled together with the catalytic solution under monovinylacetylene to butadiene are reviewed. slight pressure, the gaseous effluent is scrubbed A number of Pd, Pt, and Ni catalysts on various with H,O and the resulting aqueous CH,CHO bases were used in the hydrogenation reactions solution is distilled. When air is used instead of

Platinum Metals Rev., 1961, 5, (4) 154 oxygen, the spent catalyst is regenerated in a ~,[H,][Ru~~~],where k,=4.o x 1014exp [-23,800/ separate reactor before recycling. Operating costs RTIM-' sec-I. Mechanisms of the reduction for the one- and two-stage processes are given. reactions are discussed. Preparation of Some Condensed Ring Carb- Adsorption of Hydrogen on Low Percentage azole Derivatives Pt/Al,O, and Pd/Al,O, Catalysts in the H. M. GROTTA, c. 3. RIGGLE and A. E. BEARSE,~.Org. Liquid Phase Chem., 1961,26, (s), 1509-1511 D. v. SOKOL'SKII and E. I. GIL'DEBRAND, proc. A Pt/MgO catalyst was used in the vapour phase Acad. Sci. U.S.S.R., Chem. Section, 1960, 133, cyclodehydrogenation of N,N'-diphenylphenyl- (I-6), 855-857 (Transl. of Dokludy Akad. Nauk enediamines. Indolo [3,2--b] carbazole and indolo S.S.S.R., 1960, 133, (3), 609-612) [2, 3-bJ carbazole were prepared from N,N'- Catalysts containing 0.05 to 3.479; of the metal diphenyl-p-phenylenediamine and N,N'- di- were prepared, suspended in a buffer solution phenyl-m-phenylenediamine, respectively. Benzo- (CH,COOH/NaOH), and saturated with hydro- carbazoles were prepared from phenylnaphthyl- gen by shaking. The adsorbed hydrogen was amines by a similar method. determined by shaking the catalyst with quinone and determining the hydroquinone formed. It Catalytic Fission of the Carbon-Halogen was found that as the concentration of Pt and Pd Bond in the catalyst is increased, their adsorption capaci- Part 1. Reactions of Ethyl Chloride and ties decrease sharply at first and then more slowly. Ethyl Bromide with Hydrogen on Evaporated The adsorption capacity of Pd is less than that of Metal Films Pt. The phenomenon of excess paramagnetism developed by the Pt and Pd during hydrogenation J. s. CAMPBELL and c. KEMBALL, Trans. Faraday reactions is discussed. Sot., 1961, 57, (9,809-820 Evaporated films of Pd, Pt, Ni, Fe, W and Rh Annual Review of U.S.A. Patents on were used as catalysts in a study of the hydro- genolysis of the ethyl halides. The principal Petroleum Refining and Processing reaction observed was: C,H,X$H,+C,H,+HX, H. HEINEMANN and P. A. LEFRANCOIS, World but with Ni and Fe, C2H4was also formed. Some Petroleum, 1961, 32, (8), 53-59, IIZ CH, was formed over Rh. No exchange of the 183 patents are reviewed. The processes covered alkyl halides with deuterium was found up to by the patents include catalytic reforming and 450°C. The distributions of isotopic ethanes petrochemical production, hydrocracking, cataly- formed by deuterolysis of the halides was observed. tic cracking, hydrogenation, dehydrogenation, Kinetic results and reaction mechanisms are alkylation, dealkylation, isomerisation, and desul- discussed. phurisation. Pt metal catalysts are employed in many of the processes. A Study of the Catalytic Hydrogenation of Hydroxybenzenes over Platinum and Reforming the 60"-140" Benzine Fraction Rhodium Catalysts and Standard B-70 Benzine of Bakinski H. A. SMITH and B. I.. STUMP,J. Amer. Chem. soc., Petroleum on a Platinum Catalyst 1961, 839 (I2), 2739-2743 N. I. SHUIKIN, KH. M. MINACHEV, V. S. ALIEV, I. I. Adams' Pt and 57; Rh/Al,O, were used in the SIDORCHUK and M. A. RYASHENTSEVA, Zhur. hydrogenation of phenol, catechol, resorcinol, Priklad. Khzm., 1961, 34, (2), 461-463 hydroquinone, phloroglucinol and pyrogallol. Reforming was carried out at 48o0-5oo0C, 40-50 Reduction rates were found to be of the same atm hydrogen pressure, and space velocity 2-3:h order as those for corresponding methyl- and in the presence of a o.s"L Pt/AI,O, catalyst. Under methoxybenzenes. It is suggested that, in the the given conditions, 45.8-57.9": aromatic reduction of the phenols, cyclohexenolsare formed hydrocarbons were produced from the 60"-140" as intermediates and that these are reduced to benzine fraction and 38.6:~ from the B-70 form cyclohexanols, isomerised to form cyclo- benzine. Five-membered ring compounds and hexanones or cleaved to form cyclohexanes. alkanes were also present in the catalysate. Kinetic data are given. Catalytic Isomerisation of n-Pentane on a Catalytic Activation of Molecular Hydrogen Platinum Catalyst by Ruthenium (111) Chloride Complexes N. R. BURSIAN and G. N. MASLYANSKII, Khim. J. F. HARROD, s. CICCONE and J. HALPERN, Canad. J. Prom., 1961, (3), 18-20 Chem., 1961,39, (6), 1372-1376 A supported 0.6~~Pt catalyst was used in the Ru (111) in aqueous HC1 solution was found to isomerisation process which was carried out under catalyse the homogeneous reduction by hydrogen pressure. The effect of variations in the hydrogen: of Ru'" and of Fe"'. Rul" itself is resistant n-pentane ratio, pressure, temperature, and to reduction by hydrogen. The rate law for the volumetric flow rate was studied. Optimum reduction of RuIV and FeX1I is -d[H,]/dt= parameters found were: temperature, 4oo-4z0°C;

Platinum Metals Rev., 1961, 5, (4) 155 molar ratio of hydrogenx-pentane, 3:1; the rate Mechanics of Electrical-Contact Failure of addition of n-pentane, I volume/volume of Caused by Surface Contamination catalyst/h. The yield of iso-pentane under these s. w. CHAIKIN, Electro-Technol., 1961, 68, (2), conditions was 50%, and that of C,-C, gases 70-75 below 1.5%. Methods of examining sealed relays contaminated by base metals and organic material are described, Non-conducting deposits may be formed on GLASS TECHNOLOGY contact surfaces, either spontaneously or during friction, by the polymerisation of organic vapours Galvanic Corrosion of Glass Tank Refrac- evolved by insulating materials. The contamina- tories tion of Pd and Au contacts under static conditions F. J. SHONEBARGER, Glass Technol., 1961, 2, (2), was studied, and frictional polymers formed on 53-59 Au, Ag, I'd and Au alloy contacts were also Cells consisting of molten glass as the electrolyte examined. It is concluded that the latter are and a refractory bar and coiled Pt wire as elec- produced by the combined effects of catalysis trodes were used to investigate the corrosion and electron emission. Contamination may be of refractories by molten glass. The refractory controlled by chemical and ultrasonic cleaning, bars were supported by Pt tie wires. It was selection of insulating and contact materials, and found that the corrosion of refractories may be the use of carbon pellet "getters". accelerated by the electrical potentials established by refractory combinations exposed to molten ELECTRONICS AND glass. TELECOMMUNICATIONS New Plant Features Latest Look in Making The Selection of Contact Materials for Glass Fibres Telephone Switching N. r. CHOPEY, Chem. Eng., 1961,68, (IO), 136-139 L. BORCHERT, Nachrichtentech. 2. (N.T.Z.), 1961, The processes operated at the Aiken, S. C., Owens- 14, (411 175-179 Coming plant are described briefly and a flow- The suitability of Ag, Pd, Pd-Ag, Ni-Au, Ni-Pt, sheet is given. Glass filaments are drawn directly and W-Pt contact materials is discussed. Pd-Ag from the forehearths of recuperative furnaces alloys containing 30-50°/~, Pd are recommended through Rh-Pt bushings, treated with a binder for use in relays and selectors. Their satisfactory material, and wound on spindles. New features performance in the presence of HzS, organic of the winding process are mentioned. vapours, and under various climatic conditions, is described. (20 references) Mechanical Strength of Polycrystalline Materials Produced from Glasses Containing TEMPERATURE Platinum MEASUREMENT M. TASHIRO, S. SAKKA and M. WADA, YOgyO Kyokai Calibration of Platinum Resistance Ther- Shi, 1960, 68, 223 (Br. Ceram. Abs., 196r, 60, mometers (5),215A) ANON., Nat. Bur. Stds. Tech. News Bull., 1961, The effect of the addition of Pt on the bend- 45, (411 62-65 strength of glasses containing Li 20, MgO, The calibration of long stem-, capsule-, and Al,O, and SiO, was investigated. o.019~Pt is calorimetric-type resisrance thermometers is sufficient to cause complete devitrification of some described. Stem-type thermometers are calibrated glasses. The bend-strength of devitrified glass at the boiling points of oxygen ( ~ 182.97'C), increases with increasing Pt content and is water, and sulphur (444.6'C), and at the triple influenced by the LizO content. point of water (o.o~"C). The calorimetric-type are calibrated at the triple point, steam point, and near 50°C. Capsule-type thermometers are ELECTRICAL ENGINEERING calibrated over the range - 263" to -183°C in a hydrogen bath against N.B.S. standard resistance The Transfer of Material between Contacts thermometers. Resistance measurements are of Precious Metal Alloys and Its Dependence made using a Mueller-type bridge. on Heat Treatment W. ME=, Metall, 1961, 15, (7), 672-674 Accurate Recording of Fast-Changing Tem- Contact materials used in the investigation were peratures 400/;Cu-Pd, 3:.; Co-Au, 10% Ni-Au and 16:(, D. H. NALLE, I.S.A.J., 1961, 8, (6), 58-59 Ni-Au alloys. The electrical and thermal conduc- A system consisting of a Pt resistance ther- tivities of these alloys may be increased by lattice mometer, a Wheatstone bridge, a carrier- changes (Cu-Pd) or precipitation processes amplifier and a direct-recording oscillograph is (Co-Au, Ni-Au). The mechanisms of bridge described. Applications include the measure- transfer and coarse transfer are discussed. ment of average and differential temperatures.

Platinum Metals Rev., 1961, 5, (4) 156 High Temperature Black Body Radiation A Pt:IoO/b Rh-Pt thermocouple is embedded in Source the counterbore of the cone close to its apex. The H. P. BEERMAN, Bull. Amer. Ceram. Soc., 1961, core is insulated by bubble A1,0, and diatoma- 4% (5)j 308-309 ceous earth. The operating range may be extended A standard radiation source consists of 40:/0 from 1650" to 1850°C by using a Rh winding, an Rh-Pt wire wound on an AlzOacore which has a Ir:400/~ Rh-Ir thermocouple, and different core conical cavity, blackened with a fired-on Pt paste. and insulating materials.

NEW PATENTS

Hydrogenation of Nitrosamines Beryllium Brazing FOOD MACHINERY & CHEMICAL CORP. British Patent ASSOCIATED ELECTRICAL INDUSTRIES LTD. British 868,147 Patent 870,780 An N, N - disubstituted hydrazine is prepared by Beryllium is brazed to another metal by inter- reacting a dialkyl or substituted dialkyl nitros- posing between the parts a palladium-containing amine or a heterocyclic nitrosamine with hydrogen solder, heating the assembly to below the solidus in the presence of a palladium catalyst and an of the solder but high enough to cause inter- iron salt in the proportion of about 0.5 millimole diffusion between the beryllium and the solder, of iron per g of catalyst. The catalyst consists of and holding this temperature long enough to 5 parts palladium and 95 parts of active carbon. cause limited interdiffusion and then raising the temperature above the liquidus to effect brazing. Brazing of Beryllium Solder alloy preferably 55-700,& Ag, 20-300/& Cu and IO-ZO~~Pd. ASSOCIATED ELECTRICAL INDUSTRIES LTD. British Patent 869,607 Beryllium is brazed to a metal base by the use of Electric Switch Contacts palladium in the brazed joint. The palladium may DEUTSCHE GOLD-UND SILBER-SCHEIDEANSTALT be present in the brazing alloy, i.e. an alloy of British Patent 871,660 silver, copper and palladium may be used or the Elecrric switch contacts, e.g. circuit-breaker con- palladium may be electrodeposited on the tacts in the weak current field, are formed of an beryllium after the latter has been copper plated. alloy of 1-20q, rhenium and remainder palladium. Suitable for brazing a beryllium window to an Up to 507, of the rhenium may be replaced by X-ray tube. tungsten.

Anode for Cathodic Protection Electrochemical Diode Rectifiers ENGELHARD INDUSTRIES INC. British Patent UNION CARBIDE CORP. British Patent 871,675 8 70~086 An electrochemical diode rectifier comprises a An anode assembly for cathodically protecting vessel containing an electrolyte (reversible redox pipes, the walls of which come into contact with system in solution) and in which are mounted a an electrolyte, is formed of a flexible wire anode pair of platinum electrodes, one of which is sub- surrounding one end part of a rod of insulating stantially greater in active surface area than the material, an inner conductive wire being pro- other. vided for connecting the anode wire to a positive potential. The anode may be in the form of a helix or a wire mesh sleeve of platinum or other Purification of Nitrogen platinum group metal. ENGELHARD INDUSTRIES INC. British Patent 8711755 Nitrogen, containing oxides of nitrogen as Electrolytic Anodes impurities, is purified by adding hydrogen to the METAL & PIPELINE ENDURANCE LTD. British Patent gas and contacting the mixture with palladium 870J277 metal or other palladium-containing catalyst at An anode, primarily for cathodic protection of reaction temperature (5Oo-700"F). steel structures, consists of a body of lead or lead alloy (10-160/; silver-lead alloy) in intimate con- tact with a platinum group metal, part or all of Hydrogenation of Acetylene which is on the outside of the lead body and BADISCHE ANILIN- & SODA-FABRIK A.G. exposed to the electrolyte in use. The platinum British Patent 871,804 group metal is preferably in the form of a wire Acetylene compounds are partially hydrogenated embedded in the lead. in the presence of a palladium catalyst which has

Platinum Metals Rev., 1961, 5, (4), 157-158 157 been treated with an aqueous or organic solution carbon, the proportion of platinum to carbon of a salt of a metal of group IIb andlor IIIb of the being from 3: I to 5:1 by wt. Periodic System. Isomerisation of Paraffin Hydrocarbons Corrosion- and Oxidation-resistant Surfaces ESSO RESEARCH & ENGINEERING co. U.S. Patent NORTON GRINDING WHEEL CO. LTD. British Patent 2,9851699 872,445 Normal paraffin hydrocarbons of from 4 to 7 The corrosion and oxidation resistant properties of carbon atoms are converted to the corresponding articles made of platinum or an alloy thereof, branched chain isomers by contacting the hydro- such as crucibles, furnace parts, feed nozzles, carbons at 4o"-r2o"F with a supported bifunc- subjected to contact with high temperature molten tional catalyst formed of an aluminium halide material are increased by first flame-spraying (bromide or bromide-chloride mixture) and a thereon a coating of ceramic material and then a support carrying 0.01-5 wt.% of platinum in the coating of platinum or an alloy thereof. form of a sulphide compound.

Electric Furnace Element Catalyst Preparation THE ATLANTIC REFINING CO. U.S. Patent 2,989,488 JOHNSON, MATTHEY & CO. LTD. British Patent A catalyst is made by impregnating an acidic 873,946 metal oxide component with an aqueous solution The electric furnace heater element claimed in of platinous tetrammino-hydroxide, ageing for at Patent No. is made in the form of a sheet 849,507 least 3 h at ZIO'-ZIZ"F, drying and converting or panel of a platinum group metal or alloy there- the platinum compound to the metal in an of, instead of in the form of a wire or strip. amount of 0.1-2.504 by wt. of the catalyst. Vitreous Enamel Catal'yst E. I. DU PONT DE NEMOURS & CO. British Patent THE Evl. W. KELLOGG CO. U.S. Patent 2,989,489 874,157 A hydrocarbon conversion catalyst is made by A vitreous enamel composition for firing on to a combining water, an acyclic polyhydric alcohol ceramic dielectric to form a resistor is composed in amount of 1-50% by wt. based on wt. of water, of 8-2774 of finely divided palladium and 92-7304 a carrier material, and a water soluble compound of enamel flux (30-9594 Bi,O, or PbO and 70-5% selected from a chloroacid and an ammine com- of glass frit). plex of platinum or palladium in sufficient amount to provide o.or-zo% by wt. of the metal Manufacture of Semi-crystalline Ceramic in the catalyst, and heating the mixture to form Bodies the catalyst. CORNING GLASS WORKS Belgian Patent 586,153 Alloy A semi-crystalline ceramic body is made by heat THE INTERNATIONAL NICKEL co. INC. US.Patent treating a moulded glass formed from a molten batch of the type R,O, BaO, SiO, (R,O=Li,O, 2,992499 Na,O and K,O), or of the type Li,O, Al,O,, An alloy is composed of 0.05-2o/b selenium and SiO,, containing one or more platinum group balance essentially rhodium. metals in sufficient amount to produce Hydroforming of a Naphtha O.OOI-CJ,IO~~ metal, at 580-650T for a time varying from 8 h at about 580°C to about g h at UNION OIL CO. OF CALIFORNIA U.S. Patent about 650°C. 2,992,985 Gasoline is hydroformed by contacting it, mixed with 500-10,000 s.c.f. of hydrogen per barrel of Platinum Plating feed, with a catalyst composed of an activated gel- SEL-REX CORP. U.S. Patent 2,984,604 type alumina carrier and a minor amount of Thick layers of stress-free platinum are obtained rhodium at 7oo"-rooo"F, a pressure of 0-2000 by electrolysing a solution formed by dissolving p.s.i.g. and a feed rate of 0.2-10 liquid vols. per platinum diamminodinitrite in an aqueous solu- vol. of catalyst per h. tion of sulphamic acid containing sufficient acid to dissolve the dinitrite and adding water to form a Electrolytic Bath for Deposition of Iridium solution containing at least 6 gj1 of platinum N. v. IGNATOVA and B. I. VASSERMAN U.S.S.R. metal. Patent 136,056 A high quality dark-grey deposit of iridium on Rods for Electron Microscope Technique metals, particularly copper, is obtained by use of METROPOLITAN-VICKERS ELECTRICAL GO. LTD. U.S. a plating bath containing, per litre of distilled Patent 2,985,599 water, 6.1g of ammonium chloroiridate, 14 g of A carbonaceous electrode is formed of a com- ammonium fluoride, 23 ml of 98:j; sulphuric acid pressed mixture of finely divided platinum and and 20 ml of 20X sodium hydroxide.

Platinum Metals Rev., 1961, 5, (4) 158 AUTHOR INDEX TO VOLUME 5

Puge Page Puge Page Abraham, K. P. 71 Calvert, L. D. 150 Fletcher, P. C. 76 Hume-Rothery, W. 71 Adkins, E. F. 109 Campbell, J. S. 155 Fletcher, W. 37 Hnmmel, R. E. 149 Aladzhalova, N. A. 111 Carson, A. W. 30, 33 Fraker, A. C. 32 Hurlbert, R. C. I1 1 Alcock, C. B. I34 Castellan, G. W-. 110 Francis, R. C. 77 Hnrwitz, H. 37,77 Alizade, Z. I. 32 Chaikin, S. W. 156 Freifelder, M. 115 Allen, C. C. 101 Chaston, J. C. 122 Fries, R. J. 150 Altovskii, R. M. 73, 11 1 Chemodanov, A. N. 152 Fryburg, G. C. 150 Andersen, H. C. Chernova, G. P. 152 Funston, E. S. 56 Ionov, N. I. 72 75, 115, 116 Chopey, N. P. 156 Ito, A. 109 Anderson, I). R. 71 Chopoorian, .I. A. I10 Anderson, E. 71 Ciapetta, F. G. I54 Anson, F. C. 152 Ciccone, S. 155 Galwey, A. K. 116 Jaffee, R. I. 19 Arje, K. 51 Claassen, H. H. 150 Garrison, M. C. 110 Jankowska, H. 14 Aronsson, B. 93 Clement, W. 38 Gerassimow, J. I. 71 Joachim, E. 76 Ash, R. 72 Cohn, G. 115 Germain, J. E. Johnson, A. 2 76, 115, 117 Aston, J. G. 151 Connor, H. 9 Johnson, R. W. 153 Gibson, J. G. 117 Austin, D. T. 116 Cook, C. F. 74 Juchniewicz, R. 112 Gil’debrand, E. I. 155 Cope, R. G. 113 Giner, .I. 152 Cousins, E. R. 35 Gochaliev, G. Z. 1 12 Cox, E. G. 32 Raker, R. H. 76 Godtfredscn, W. 0. 36 Kamimura, H. 31 Bal’yan, Kh. V. 34, 35 Graves, B. B. 34 Kaswan t 38 Barber, C. R. 77 Green, A. W. 35 Kataev, G. I. 72 Barrer, R. 72 Green, W. J. 116 M. Darling, A. S. 58, 97 Keely, W. M. 35 Greenberg, J. 34 Barton, J. C. 112 Davies, M. W. 71 Keil, A. 151 Greene, N. D. 141 Beath, C. B. 102 De Jong, B. C. 72 Kemball, C. 35, 155 Beerman, H. P. 157 Deportes, C. 74 Greenlee, T. W. 154 Kempter, C. P. Grigor’ev, A. T. 109 Bell, W. E. I10 De Rosset, A. J. 37 70, 117, 150 Bel’skii, I. F. 36 Dietz, H. 152 Grimley, R. T. 31 Kendall, E. G. 149 Grimm, A. 154 Belyakov, Yu. N. 72 Doh, P. I. 112 Khar’kovskaya, E. N. 36 Gronwold, F. 71 Khotinskaya, A. N. 109 Benham, R. R. 13 Dorgelo, G. J. H. 31 Grotta, H. M. 155 Kimura, H. 30, 109 Bennett, H. E. 132 Douglass, R. W. 30, 109 Grubitsch, H. 34 Berger, C. V. 37 Downey, J. W. 110 Knapton, A, G. 32 Besson, J. 74 Dreesen, J. A. 70 Knight, B. 73 Betteridge, W. 31, 110 Dreger, L. H. 32 Knorr, C. A. 33 Birnbanm, L. S. 77 Kobozev, N. I. 114, 115 Dwight, A. E. 72 Haley, A. J. 75 Birun, N. A. Kocharov, E. P. 51 109, 110, 149 Hallgren, L. J. 34 Koide, S. 31 Bishop, C. R. 74, 141 Halpern, J. 88 Kojima, H. 110 Blake, J. C. 113 Edeleanu, C. 117 Haraldsen, H. 71 Kokoulina, D. V. 112 Blanke, W. W. 77 Eden, C. 126 Haranij, Y. 36 Kolesnikov, I. M. 35 Boffe, M. 33 Elmore, G. V. 153 Hardy, W. K. 149 Kolotyrkin, Ya. M. 152 Bolk, A. 149 Emmett, P. H. 114 Harrod, J. F. 88, 155 Kondrat’ev, D. A. 37 Bond, G. C. 75 Enke, C. G. 33 Hawthorne, J. 0. 117 Konecny, J. 0. 11 1 Borchert, L. 156 Erkelens, J. 116 Hays, C. 149 Krasna, A. I. 116 Boreskov, G. K. 36 Euler, J. 71 Hearle, J. W. S. 2 Krause, A. 115 Borovikova, N. A. 34, 35 Everett. D. H. 72 Heckel, K. 34 Bourgeois, Y. 76, 117 Heinemann, H. 116, 155 Boyden, P. M. 77 Heitland, H. J. 31 Henny, V. E. 75 Lacroix, R. 78 Boaorth, R. M. 70, 150 Faraday, M. 26 Laitincn, H. A. 33, 73 Bradbury, J. T. 35 Farr, J. D. 71 Heyding, R. D. 150 Lakey, T. 154 Breiter, M. 33 Fcates, F. 73 Hickling, A. 73 L. S. Lang, W. H. 115 Brennan, D. 76 153 Hoar, T. P. 117, 141 Ferretti, A. Lebedev, P. 76 Brown, M. L. 35 32 Hoare, F. E. 31 V. Ferro, R. Lee, W. T. 113 Budworth, D. W. 31 Feuge, R. 0. 35 Hoare, J. P. 33, 73 Lefrancois,P.A. 116,155 Bundy, F. P. 118 12 Hockings, E. F. 30 Fischer, H. C. Leger, L. 33 Burger, J.-P. 70, 150 Fischer, W. R. 151 Hoffmann, K. 33 F. Leonhard, F. 74 Burns, R. P. 31 Flanagan, T. B. Holden, C. 30 Bursian, N. R. 155 30, 33, 111, 113 Hoppin, G. S. 114 Levin, A. I. 34

Platirzum MetalsReu., 1961, 5, (4), 159-160 159 Page Page Page Page Lewartowicz, E. 74 Newham, J. 75 Rundqvist, S. 93, 109 Tebhle, R. S. I10 Lewis, F. A. Nicholson, M. E. 111 Russell-Wood, J. 66 Tiedema, T. J. 70, 72 21, 111, 112, 113 Nicolescu, I. V. 37 Rylander, P. N. 1 J 4 Tirrell, C. E. 153 Lewis, J. 110 Nikol’skii, B. P. 32 Toda, G. 113 Liisberg, S. 36 Nishimura, S. 116 Tomashov, N. D. Lindsay, W. T. 151 Noble, L. A. 34 32, 73, 111, 152 Lipke, H. 38 72 Sachtler, W. M. H. 31 Tomassi, W. 74 Nordon, P. Sagel, K. 32 Littauer, E. L. 113 Noser. W. P. 77 Trosman, E. A. 76 Little, L. H. 75 Sagoschen, J. 78, 116 Trusov, G. N. 111 Llopis, J. 153 Sain, W. H. 34 Tshchernova, G. P. 32 Low, M. J. D. 151 Sakka, S. 156 Tsiplyakova, V. A. 31 Lnttinger, L. B. 35 Obayashi, T. 74, 112 Sancho, A. 153 Tylkina, M. A. 149 Onoda, T. 116 Sauvage, J.-F. 76 Oranskaya, M. A. 71 Savill, J. 32 Ostroumov, V. V. 72 Schafer, H. 31, 71 Uhlig, H. H. 151 McBride, J. P. 36 Schindler, A. I. 30, 73 McDonald, D. 18, 146 Schmidt, H.-E. 149 McCurty, J. A. 56 Schuldiner, S. 113 Panish, M. B. 151 Macartney, E. 77 Schwahe, I(. 151 Van der Toorn, L. J. 70 Macnichol, E. F. 74 Pankratov, B. A. 34 Scott, C. D. 115 Vargaftik, M.N. 36, 1 14 Mal’tsev, A. N. 114 Panteleimonov, L. A. Selig, H. 150 Vielstich, W. 76 Margrave, J. I. 32 109, 110 Sercombe, E. J. 122 Martinez, M. L. 154 Parsons, R. 34 Shanina, L. T. 152 Pask, J. .4. 117 Maslyanskii, G. N. 155 Sheppard, N. 75 Want, J. G. 42 Pement, F. W. 151 Maurel, R. 155 Shibata, S. 112 Weissbart, J. 154 Petrus, H. M. 150 Maykuth, D. .I. 19 Shkol’rikov, Ya. A. 51 Weissmantel, C. 151 Pichler, H. 37 Meechan, C. J. 150 Shock, D. A. 117 Wendling, R. 150 Pines, H. 154 Merl, W. 156 Shonebarger, F. J. 156 West, E. D. 38 Plate, W. 30 Merten, U. 110 Shreir, L. L. I 12, 113 Westwood, R. J. 102 Polyakova, V. P. 149 Metson, G. H. 77 Shuikin, N. I. 36, 37, I55 Wetscher, A. A. 71 Popescu, A. 37 Migal’, P. K. 31 Siegcl, S. 76 Whetten, N. R. 74 Pospelova, T. A. 115 Mikhailova, N. A. 71 Sinfelt, J. H. 37, 77 30 Prior, A. C. 118 White, J. G. Miller, H. S. 75 Singer, J. M. 110 Wickham, D. G. 153 Minachev, Kh. M. Pugh, E. M. 70 Sirota, 2. D. 72 37; 155 Wilkinsou, R. G. 128 Sloan, J. G. 54, 116 Mintem, R. A. 82 Will, F. G. 33 Smith, G. V. 76 154 Mitacek, P. 151 Willard, J. G. Smith, H. A. 155 Mitani, K. 36 Rambaldi, G. 32 Wilt, M. H. 117 Smith, M. F. 110 Mituya, A. 74, 112 Happerport, E. J. 110 Wittum, M. 38 Ranb, E. 30 Smith, R. J. 30, 73 Mdger, D. 115 Wolbarsht, M. L. 74 Rayne, J. A. 32 Sokol’skii, D. V. Wolff, P. A. i 50 Moiseev, I. I. 36, 114 111,155 Morse, L. E. 36 Reid, F. H. 113, 153 Wollan, E. 0. 150 Reif, L. 151 Spiro, M. 36 Mortlock, A. J. 71 Wucher, J. 70 Reinacher, G. 144 Staats, H. C. 54 Mosevich, A. N. 32 Stadelmaier, H. H. Miiller, K. 51 Rhoda, R. N. 153 32, 149 Khodes, D. W. 71 Munster, A. 32 Steele, D. R. 75 Yanagihara, T. 30 Rhys,D. W. 31,110,113 Murphy, N. 139 Stern, M. 74 Yao, H.-C. 114 Riddiford, A. C. 152 Myers, C. G. 115 Stevenson, J. A. 77 Yazliev, S. I09 Kiecbe, A. 154 Stone, G. R. 11s Young, J. R. 74 Kiggle, C. J. 155 Stump, B. L. 155 Rindone, C. E. 117, 140 Sudbury, J. D. 117 Nadler, M. R. 70, 117 Roberts, R. W. 154 Nagel, K. 152 Roe, D. K. 73 Zajcew, M. 35 Nagy, F. 115 Rowe, A. H. 71 Zakumbdeva, G. D. 11 I Nalle, D. H. 156 Rudnitskii, A. A. Tanner, H. A. 153 Zalkind, Ts. 1. 112 Nash, C. P. 77 109, 149 Tashiro, M. 156 Zufall, J. H. 75 Nevitt, M. V. 72, 110 Kuka, R. 154 Tebben, A. 31 Zwicker, U. 72

Platinum Metals Rev., 1961, 5, (4) 160 SUBJECT INDEX TO VOLUME 5

a = abstract Page Catalysts (conrd.) Page Acetaldehyde, manufacture, a 154 reduction of HNOa plant tail gas, a 116 Anodic Protection, reforming 9, 101 of iron and alloy steels, a 117 Pt/AI,O,, activity & physical properties, a 37 theory of, a 117 aromatisation of hydrocarbons, a 154 decomposition of N,O, a 75 dehydrogenation of methylcyclohexdne, a 77 hydrogen adsorption on, liquid phase, a 155 Bushings, Rh-Pt, for glass fibre manufacture 51 isomerisation of n-pentane, a 37 reforming, aging of, a 115 in Y.S.S.R., a 155 poisoning by thiophene, n 37 Pt/Al,O,/SiO,, hydrogenation of n-nonane, a 37 Catalysis, hydrogenation of saturated bicyclic heterogeneous, a study, a 35 hydrocarbons, a 115 homogeneous, using Ru complexes 88 reforming, a 115, 154 Catalysts, 76 in petroleum industry, new U.S.A. patents, a Pt/Cd, decomposition of HL02,a 116, 155 Pt/C, hydrogenation of furans, a 36 in hydrogen-oxygen fuel cells, a 76 Palladium, black, synthesis of H,O,, a 115 colloidal, hydrogenation of Pt/MgO, cyclodehydrogenation of alkylacetylenes & phenylacetylene, a 35 N,N’-diphenylphenylencdiamines,a I55 hydrogenation of vinylacetylene, a 34 Pt/pumice, hydrogenation of methylene- film, deuteration of cyclohexene, a 116 cyclopropane & methylenecyclobutane, a 75 hydrogenolysis of ethyl halides, a 155 Pt/SiO,, hydrogenation of C,H,, a 76, 117 heterogeneous reactions with hydrogenation of hydrocarbons, a 114 dcutcrium & hydrogen, a 35 reforming, a 115, 154 hydrogcnation of C,H,, a 35 reduction of HNO, plant tail gas, a 116 PtCI,, activation of molecular hydrogen, a 116 Pd/AI,O,, decomposition of N,O, a 15 PtO, hydrogenation of CeH,NO, hydrogen adsorption on, liquid phase, a 155 & CH3N02,a 114 hydrogenation of cycloolefins, a 76 Pt02,activation of molecular hydrogen, a 116 hydrogenation of C,H, in C2H, plant, a 75 hydrogenation of cyclohexenes, a 76 synthesis of H,O,, a 115 hydrogenation of cycloolefins, a 76 Pd/BaCO,, synthesis of penicillin derivatives 131 hydrogenation of hydroxybenzenes, a 155 Pd/BaSO,, hydrogenation of monovinyl- Pt-Li, colloidal, hydrogenation of acetylene, a 1 54 cyclohexene, a 77 Pd/C, decarbonylation of aromatic Platinum Metals, electron-transfer reactions aldehydes, a 117 in solution, a 36 hydrogenation activity of 122 hydrogenation & dehydrogenation, a 35 hydrogenation of cycloolefins, a 76 in organic chemistry, a 114 hydrogenation of fatty oils, a 35 on pumice, hydrogenation of cyclo- hydrogenation of methyl oleate, a 35 propane & methylcyclopropanc, a 75 synthesis of a 115 petroleum refining, review, a 37 H201. polymerisation of acetytenic Pd/SiO,, hydrogenation of CaH, & C2H,, a 75 compounds, a 35 synthesis of H,O,, a 115 reduction of HNO, plant tail gas, a 37, 116 Pd/SrCO,, hydrogenolysis of ketosteroids, a 36 oxidcs, hydrogenation of organic Pd/Th02,hydrogen-oxygen recombination, a 36 compounds, a 116 Pd/WO,, synthesis of H,O,, a 115 Rhodium, film, decomposition of C,H,, u 154 hydrogenolysis of ethyl halides, a 155 PdCI,, CH,CHO manufacture, a 154 heterogcncous reactions with deuterium oxidation of olefins, a 114 & hydrogen, a 35 reactions with olefins, a 36 oxidation of CO in hydrogen, a 35 PdO/A1,O3/SiOz,effect of irradiation on, a 115 reduction of HNO, plant tail gas, u 116 Pd-Pb, hydrogenation of linolenic acid, a 154 Rh/AI,O,, decomposition of N,O, a 75, 154 Pd-Ru, hydrogenation of C,H,, NO & COS hydrogenation of hydroxybenzenes, a 155 in coke oven gas, a 75 Rh/C, hydrogenation of furans, a 36 Platinum, colloidal, hydrogenation of Rh-Pt, oxidation of CO in hydrogen, a 35 nitrocompounds, a 114 gauze, in HNO, manufacture, a 116 dissociation of hydrogen & oxygen, a 76 film, hydrogenolysis of ethyl halides, a 155 Rh-Pt Oxide, hydrogenation of organic deuteration of cyclohexene, N 116 compounds, a 116 gauze, for HNOI manufacture 54 Ruthenium, oxidation of CO in hydrogen, a 35 heterogeneous reactions with deuterium & hydrogen, a 35 RuCI, Complexes, hydrogen rcduction of hydrogen-oxygen reaction, a 36 Rurv & FelII, a 155 isomerisation of n-pentane, a 155 Ru Complexes, hydrogenation of olefinic oxidation of CO in hydrogen, a 35 compounds 88 oxidation of hydrogen, CO & CH,, a 1 15 platinised, in liquid phase RuO,, hydrogenation of pyridines, a 115 hydrogenation, a 115 Cathodic Protection, reaction between NH, & NO, a 115 impressed current anodes for, a 71 reaction with N,O, a 36 Pt-Pd anodes for, a 77

Platinum Metals Rev., 1961, 5, (4), 161-164 161 Cathodic Protection (contd.) Page Electrodes (contd.) Page theory of, a 117 Pt-Au, exchange current in redox solutions, a 74 of water heatcrs 12 Pt-Pd, absorption &evolution of hydrogen, a 1 13 Cermets, rare carth-Pd, fabrication of 56 anodcs, for cathodic protection, a 77 Pt-Ti, behaviour in H2S0, & HCI electrolytes, a 152 Rhodium, hydrogen evolution on, a 113 Deuterium, absorption by Pd, a 111 Rh-Pd-H, catalytic activity & electronic Diodes, lr-Pt wirc 95 structure, a 33 Electroless Plating of Palladium, a 153 Electrical Contacts, Platinum, a 153 Ir-Pt, in moving coil relay 143 Rhodium, a 153 mechanism of matcrial transfer, a 156 Ruthenium, a 153 Pd, effcct of other materials on, a 38 Pd-Ag, effect of other matcrials on, a 38 Pt metals, light duty 42 surfacc contamination of, a 156 tclephone switching, a 156 Fuel Cells, intermediate temperature, a 153 Electrodeposition of, Furnace, platinum, for production of optical glass 126 in powdcr camera 96 Palladium, survey, a 113 Pt-lincd, fluorination 92 Platinum, a 34, 113 Rh-Pt wound, in microscopc I39 Rhodium, addition of Al, Mg & Se, a 153 with Rh-Pt-Al,Os ring elements, a 153 survey, a 113 to specification 13 Ruthenium, a 113 Electrodes, Gas Recombination, catalytic, hydrogen-oxygen, a 36 Ir-Pt, microclectrode, a 74 Glass, effect of Pt metals on crystallisation 117, 140 Palladium, absorption & evolution of fibre manufacture 51, 156 hydrogen by, a 113 optical, continuous melting of 126 effcct of adsorbed anions on behaviour Pt-to-Pyrex scals, a 34 of, a 152 uses of Pt in production of, a 38 wetting of Pt by, a 1 I7 Pd-H, electrical phenomena of, a 1 I3 proton transfer with Pd-Pt-H elcctrodes, a 33 Pd-H-H 1, impcdance of, a 112 Pd-Pt-H, proton transfer with Pd-H Hydrogen, adsorption on Pt black, a 111 electrodcs, a 33 diffusion through Pd, a 74,111 Pd-Ti, bchaviour in H,SOn and HCI isotopes, exchange on Pd, a 111 electrolytes, a I52 Hydrogenation, Platinum, anodes, for cathodic protection, a 77 of C2H,, a 15 anodcs, in rcmoval of chloridc of alkylacetylenes & phenylacetylene, a 35 contaminants from HNO, I28 of C&, a 35, 76, 117 anodic bchaviour in HrSOn,a 112 of cyclohexenes, a 76, 17 bchaviour in HCI, a 74 of cvclooletins. a 76 bright, anodic passivation of, a 152 of &lopropane, a 75 disc, determination of diffusion of CkIn, U 75 coefficients, a 33 of fattv oils. a 35 double laycr capacity in molten of hydroxybenzencs, a 155 LiCI-KCI, a 73 of linolenic acid, a 154 effect of a.c. on corrosion of, a 112 of methyl olcate, a 35 cffect of irradiation on, a I12 of monovinylacetylene, a 154 cffects of anodic elcctrolysis on, a 112 of nitrocompounds, liquid phase, a 114 effects of y-radiation on, a 73 of n-nonane, a 37 e.m.f. measuremcnt at glass-refractory of olefinic compounds 88 intcrfacc, a 33, 156 of pyridines, a 115 exchange current in rcdox solutions, a 74 of saturated bicyclic hydrocarbons, a 115 hydrogen cvolution 011, a 34, 1 I3 of vinylacetylene, a 34 hydrogen overpotential on, R I52 Hydrogen Peroxide, synthesis, a 115 in the solion, a 77 oxide films on, 61 33 potential in an irradialed HISOn solution, a 112 surfxe changes, a 34 Iridium, surface oxidation of, R 152 adsorption of hydrogen & oxygen, a 33 use in baths of oxygenated salts, a 74 discovery of 146 high-temperature oxidation, a 110 Pt-clad brass, in anodic protection, a 1 I7 magnetic susceptibility, a 110 Pt oxide, electrochemical reactions at, a 152 vaporisation of, a I51 Pt/Pb, bielectrodes, in chloride solutions, a Iridium Alloys, 112, 113 Iridium-Platinum, tensile creep propertics 144 Pt/Ta/Ti, anodes, for cathodic protection 12 thcrmal & magnetic properties, a 31 Pt/Ti, effect of a.c. on corrosion of, a 112 potentiometer windings in artificial electrochemical applicatious, a 153 horizons 57 in chlorine cell, a I12 Iridium-Tellurium, constitution, a 30 Pt/C/Cl, potential of, a 74 Iridium Trioxide, thermodynamic data, a 31

Platinum Metals Rev., 1961, 5, (4) 162 Page Palladium Alloys (conrd.) Page Lithium-Rhodium Hydryls, preparation of Li ,RhH, Palladium-Iron, intermetallic diffusion of & Li,RhH,, a 71 Y Fe & Pd. a 150 ’ magnetic properties, u 32, 150 Palladium-Iron-Nickel, melting points, a 110 Magnets, permanent Co-Pt, processing & Palladium-Iron-Silver, constitution, a 109 properties 82 Palladium-Manganese, magnetic properties, a 150 Palladium-Molybdenum-Titanium, corrosion resistance, a 111 Nitric Acid Manufacture, dual pressure process at Palladium-Nickel, electrical resistivity, a 109 Ardcer, a 116 Hall effect .& resistivity, a 70 intcrmediate pressure NH, oxidation 54 intermetallic diffusion of Ni & Pd, a 150 tail gas reduction, a 37 magnetic properties, a 32, 150 use of Pt metal catalysts, a 116 thermoelectric properties, a 109 PalladinmrNickel-Hydrogen, electrical properties, low temperature, a 30 Palladium-Platinum, hydrogen Osmium, absorption by, a 30, 113 discovery of 146 hydrogen evolution by, a 113 melting point, a 32, 109 tcnsile creep properties 144 a 109 spcctral cmissivity, Palladium-Rhodium, thermal & magnetic Osmium Alloys, properties, a 31 Osmium-Boron, crystal structure, a 150 PalladiumyRhodium-GoId, constitution & Osmium-Tantalum, constitution, a 110 properties, a 109 Osmium Carbide, preparation &crystal structure, a 70 Palladium-Samarium, use in cermet production 56 Osmium Oxides, mass spectrometric study of, a 31 Palladium-Silicon-Chromium, use in high Oxidation, temperature brazing, a 114 of hydrogen, CO & CH,, a 115 Palladium-Silver, brushes in artificial horizons, 57 of olefins, a 114 optical properties, a 149 Oxygen Gauge, construction, a 154 use for electrical contacts, a 156 Palladium-Silver-Hydrogen, pressure- concentration-temperature relationships 21 Palladium-Titanium, constitution & Palladium, properties, a 109 absorption of deuterium by, a 111 corrosion resistance, a 32, 72, 11 I, 151,152 absorption of hydrogen by, a 72, 73, 113 Palladium-Tungsten, constitution, a 149 addition to Ti 8~stainless steel, a 151 adsorption of hydrogen & oxygen, a 33 Palladium Chlorides, at high temperature, a 71, 110 anodic oxidation, a 73 Palladium Complexes, magnetic properties, a 3 I dehydrogenated, excess free energy, a 110 Palladium Nitrides, structure, a 32 desorption of hydrogen & deuterium from, a 72 diffusion of hydrogen through, a 34, 74, 11 1 Penicillins, synthesis of 131 elastic constants, a 32 Petroleum Refining, heterogeneous catalysis exchangc of hydrogen isotopes, a 111 processes, review, a 37 high tempcraturc oxidation of, a 110 Platforming Saharan naphthas, a 75 magnetic susceptibility, a 110 reforming, in China 101 on SiOI glass, adsorption of C,H2 & C,H,, (I 75 reforming of Bakinski gasolinc, a 155 prevention of hydrogen cmbrittlement of Ta, a 74 reforming, review, a 37, 154 vapour pressure, a 32 Platinised Carbon, adsorption of Cs & Br, a 32 Palladium Alloys, Platinum, Palladium-Carbon, with Mg, AI, Zn, Ga, activities of Mn in, a 71 Ge, Cd, In, Sn, Hg, TI & Pb, crystal adsorption of hydrogen & oxygen, a 31 structure, a 149 atomic diffusion in Au, a 71 Palladium-Chromium-Hydrogen, magnetic black, adsorption of hydrogen, a 11 1 properties, a 70 Brownrigg’s investigations, 18th century 66 Palladium-Chromium-Titanium, corrosion chemical plant, a 38 resistance, a 111 chemical reactions at surface of, a 151 complex hydrides, a 110 Palladium-Cobalt, magnetic properties, a 1 50 contamination by fission products, a 30 Palladium-Cobalt-Hydrogen, Hall effect in, a 150 cores for oxide cathodes, a 77 Palladium-Copper, thermodynamic effect on crystallisation of glass, a 117, 156 properties, a 71 effect on strength of devitrified glass, a 156 electrochemical corrosion of, a 153 Palladium-Copper-Nickel, solid solubility of Faraday’s lecture 26 C in, a Ill films, oxygen absorption at, a 151 Palladium-Copper-Silver, solid solubility of high temperature oxidation, a 110 C in, a 111 history of 18 Palladium-Hydrogen, u-Pd-H, electrical magnetic susceptibility, a 110 resistance, a 151 mining at Rustenburg 102 desorbed, electrical resistivity & oxidation of, a 150 thermoelectric power, u 73 prevention of hydrogen embrittlement of Ta, a 74 diffusion of hydrogen, a 72 seals for Pyrex glass, a 34 electrical properties, a 302 111, 113 screen, support for fused salts, a 34 heat capacity & resistivity anomalies, a 151 specific heat, a 31 hysteresis, a 72 structural chemistry, (I 32 optical properties, a 72 tensile creep properties 144 physical properties & constitution 21 use in passivation of Ti in HCI, a 73

Platinum Metals Rev., 1961, 5, (4) 163 Platinum ironfa’.) Pane Rhodium Alloys, Page vapour prcssure, a 32 Rhodium-Palladium, thermal & magnetic wetting by glass, a I I7 properties, a 31 Platinum AUoys, Rhodium-Palladium-Gold, constitution & propertics, a 109 Platinum-Carbon, with Mg, AI, Zn, Ga, Ge, Cd, In, Sn, Hg, TI, & Pb, crystal Rhodium-Platinum, constitution L structure. a 149 properties 58, 97 Platinum-Cobalt, Platinax 11, properties & tensile creep properties I44 applications 82 Ruthenium, Platinum-Gold, Kirkendall effect & diffusion chemisorption of hydrogen on surface, a I51 in, a 149 high temperature oxidation, a I10 miscibility & critical point, a 32 magnetic susceptibility, a 110 precipitation in, a 70 melting point & spectral emissivity, a 109 tensile creep properties 144 powder metallurgy of, a 113 thermal & magnetic properties, a 31 Ruthenium Alloys, Platinum-Hydrogen, electrical resistance, a 3 1 Ruthenium-Boron, crystal structure, a 150 Platinum-Iridium, tensile creep properties 144 Ruthenium-Gadolinium, magnetic properties, a 70 thermal & magnetic properties, a 31 Ruthenium-Gadolinium-Cerium, magnetic Platinum-Iron, magnetic properties, a 32 properties, a 70 modulus of elasticity & internal friction in Fe,Pt, a 72 Ruthenium-Iron, constitution, a 30 Platinum-Magnesium, constitution, a 32 Ruthenium-Molybdenum, constitution, a 7 1 Platinum Niobium, Constitution, a 109 Ruthenium-Platinum, tensile creep properties 144 Platinum;Palladium, hydrogen absorption by, a 30 Ruthenium-Tantalum, constitution, a 110 tensile creep properties 144 Ruthenium-Tungsten, constitution, u 110 Platinum-Rhodium, constitution & Ruthenium Carbide, preparation & crystal properties 58, 97 structure, a 70 film,, preshadowing in electron Ruthenium Chlorides, gaseous, thermodynamic microscopy, a 74 properties, a 110 tensile creep properties 144 Ruthenium Hexafluoride, preparation of, a 150 Platinum-Ruthenium, tensile creep properties 144 Ruthenium Phosphide, structure, a 109 Platinum-Silver, ageing of, a 149 Ruthenium Tctroxidc, adsorption on SiO, gel, a 71 Platinum-Titanium, corrosion Ruthenium Trioxide, preparation, a 71 resistance, a 32, 151, 152 Platinum-Zirconium, constitution, a 149 Platinum Complexes, magnetic properties, a 3 1 Platinum Compounds, sulphides, selenides & tellurides, a 71 Solion, operating principles & applications, a 77 Platinum Nitrides, structure, a 32 Spinnerets, Pt alloy, viscose rayon production 2 Platinum . Oxide, anodic, electrochemical properties, a 152 thermodynamic data, a 31 Platinum Metals, arsenides of, structures, a 150 boridcs of, properties & structure 93 Tantalum, prevention of hydrogen embrittle- in chemical plant construction, a 77 ment by Pt metals, a 74 effect on crystallisation of glass I40 Temperature Measurement, Fourth Symposium, gaseous oxides of, thermodynamics of 134 review 89 industrial uses, a 31 in C atmospheres, a 117 intermediate phases with rare earths, Sc, Y, in vacuum radiation furnace, a 118 Hf, & Th, a 72 of average & differential temperatures, a 156 phosphides of, properties & structure 93 a 78 production & uses 101 with Pt metal thermoelements, refractory, properties of 19 Thermocouples, silicides of, properties & structure 93 Gold-Palladium-Platum:Gold-Palladium 89 tensile properties, a 30 Iridium:graphite, use in C atmospheres, a 117 Platinum Metal Alloys, high temperature 1ridium:Iridium-Rhodium, for high oxidation, a 110 temperaturcs 89 with C, solidus temperatures, a 70 contamination of 132 with Cr, corrosion resistance 141 with Ti, Zr or Hf, constitution, a 110 Palladium-Go1d:Rhodium-Platinum,in calorimetry, a 38 P1atinum:Rhodium-Platinum, calibration of, a 118 contamination of 132 effect of pressure on e.m.f. of, a 1 I8 Radiation Source, high temperature, a 157 effects of radiation on 89 properties & applications, a 78 Resistance Thermometers, platinum 89 platinum, calibration of, a 156 Rhodium-Platinum :Rhodium-Platinum, a 1 18 platinum, for use at high temperatures, a 77 Platinum Metals, properties & applications, platinum, measurement of fast-changing review, a 78 temperatures, a 156 Titanium, corrosion & passivation of, a 73 Rhodium, adsorption of hydrogen & oxygen, a 33 high temperature oxidation, a 110 magnetic susceptibility, a 110 specific heat, a 31 vaporisation of, a 151 Viscose Rayon, production of 2

Platinum Metals Rev., 1961, 5, (4) 164