PLATINUM METALS REVIEW · pressure an orange peel effect tends to develop ... By the accurate addition of minor quanti- ties of other noble metals to platinum it is possible to produce

PLATINUM METALS REVIEW

A quurterly survey of reseurch o n the platinum metuls urrd of developments in their applications in industry

V O L . 6 A P R I L 1 9 6 2 NO. 2

Contents

Platinum Bursting Discs

Rhodium as a Polymerisation Catalyst

Palladium Alloy Diffusion Process for Hydrogen Purification

Surface Phenomena at Platinum Electrodes

Apparatus for Crystal Growth Studies in Glass

Palladium Plating on Telephone Plugs and Sockets

Cobalt-Platinum Magnets Resist Corrosion

Cathodic Protection Against Cavitation Damage

High-Temperature Properties of Platinum Metals

A New Glass Tubing Machine

Gold-Platinum Alloys

Platinum Mining in Alaska

Abstracts

New Patents

42

46

47

48

49

52

56

57

58

59

60

68

75

82

Communications should be addressed to The Editor, Platinum Metals Review

Johnson, Mutthey & Co., Limited, Hatton Garden, London, E.C.1

Platinum Bursting Discs APPLICATIONS IN THE PROTECTION OF CHEMICAL PLANT

By J . E. Philpott, B . s ~ . Industrial Division, Johnson Matthey & Co Limited

In any closed system under pressure the use of a safety device to protect the vessel against excessive internal pressure is essential. For many years the only method available was the use of a safety valve.

By far the most commonly used device of this kind has an escape vent normally closed by a conically seated plug held in place either by a spring or a dead weight. When the internal pressure is sufficient to overcome the retaining force the valve plug is lifted allowing pressure relief.

While simple and robust, the safety valve has its limitations. I t is difficult to obtain a leak-proof seating between the conical plug and the vent; the working parts are difficult to protect against corrosion, the seat may be stuck to the vent by resinous material, while its small relieving area and high inertia make it ineffective against explosions.

Other devices have been suggested and many attempts have been made to produce designed weak spots in equipment by accurately machining grooves or slots in the walls of the pressure vessel. These methods relied on delicate precision machining and were often extremely difficult to execute. While in principle sound, in practice no reliable pre- diction could be made about the pressure at which the weak spot would yield.

The idea of using a thin breakable membrane to ensure the safe relief of pressure in a closed vessel is simple, direct and therefore attractive. The maior difficulty that hindered the adoption of the method lay in ensuring that discs fitted successively into the same holder would always break at the same pressure. Attempts to produce foils that would answer this requirement were always unsuccessful

until a technique was developed for rolling very thin foil of uniform and reproducible quality. Once this difficulty was overcome, a method of protecting pressure vessels was available that suffered from none of the above disadvantages, and the wide use of bursting discs throughout the chemical and petroleum industries nou7 points to its established success.

As a protection device, a bursting disc must successfully perform two functions; it must burst when the pressure in the system reaches a certain value, and it must withstand without rupture all lower pressures to which it may be subject during working.

The mathematical relationship between the fluid pressurc exerted on one face of a circular disc and the spheroidal form the disc asslimes has been expressed by Lake and Inglis (I) .

Since the bursting pressure of a disc in a given orifice at constant temperature is dependent upon its thickness and the metallurgical condition of the foil, it is possible to make discs with a predictable bursting pressure from foil of precise thickness provided only that careful attention is directed to reproducing the exact composition and metallurgical condition of the foil. By close production control and special rolling techniques discs can be manufactured to burst with a tolerance of 5 per cent on the bursting pressure.

The use of a bursting disc to protect systems operated under pressure ensures that the system is leak-proof and that any abnormal working conditions or incorrect assembly will cause the disc to “fail safe”.

Although some non-metals, notably graphite, have been used for bursting discs, the vast majority of discs have been made from

Platinum Metals Rev., 1962, 6, (2), 4 2 4 6 42

and most certain form ofprotection against the eJect of excess pressure in a closed vessel. They cannot f a d to operate, thpy have very loto inertia, and they open immediately to provide an unobstructed passage for the relief of pressure. For corrosive conditions, platinum bursting discs are simple to install, inexpensive to replace, and can be used at relatively high temperatures. The illustration shows an eight-inrh diameter narrowface capsule type holder with platinum bursting disc and stainless steel vacuum support, the h t e r serving toprevent collapse of the disc under vacuum conditions.

metal foils. The most commonly used metals fall roughly into two groups which approximately reflect their individual tensile strengths. Metals such as aluminium, copper, silver, palladium and gold form a group that are particularly useful for low pressure applications. A second group including nickel, Monel and stainless steel are employed for high bursting pressure requirements and are especially useful for discs which are exposed to elevated temperatures.

Platinum, by virtue of two alloys specially developed by Johnson Matthey, spans both groups and the high melting point, high annealing temperature and excellent resistance to creep of both alloys allow their safe use up to 450%. Coupled with these advantages thc pre-eminent resistance of both alloys to corrosion makes platinum the most versatile material available.

The use of pure metals is preferred for the manufacture of bursting disc foils because they can be obtained in a high state of purity.

Extremely pure platinum can be prepared, but foil rolled from this material possesses a coarse grain structure and when subject to pressure an orange peel effect tends to develop on the spherical surface, destroying the cohesion of the foil.

By the accurate addition of minor quantities of other noble metals to platinum it is possible to produce thin platinum alloy foils with a fine grain structure in the annealed condition. Two such alloys have been developed known as “C” Platinum and “D” Platinum and each fits neatly into one of the two groups described above. The development of these two alloys permits the use of platinum over a very wide field of application.

The relationship between bursting pressure and thickness of various metals in a one inch diameter orifice is shown in the graph overpage; this also illustrates the grouping of the metals into two classes.

If a bursting disc is to operate successfully it must be mounted in a correctly designed

Platinum Metals Rev., 1962, 6, ( 2 ) 43

holder. The disc must be clamped between two smoothly machined flanges with an accurately machined radius on the edge of the orifice against which the disc bears.

The narrow face capsule type holder shown on page 43 is the one most commonly used. This assembly includes a vacuum support which fits into the locating recess, and the outside diameter of the capsule is such that the assembly will fit neatly within the bolt circles of standard flanges as defined in British, European and American standard specifications. For high pressure applications, and especially for laboratory scale autoclave work, a plug type assembly is used similar to that described in British Standard 2915: 1959, “Domed Metallic Bursting Discs and Bursting Disc Assemblies”.

The thickness used for bursting disc foils lies in the range 0.001 to 0.010 inch. Slow corrosion rates that may be acceptable for thick-walled vessels obviously cannot be tolerated for bursting disc materials, while it

can be easily understood that quite minor chemical attack causing pits in the bursting disc foil would rapidly develop into pinholes rendering the disc useless. The complete corrosion resistance offered by platinum makes for its frequent selection as a bursting disc for corrosive media. Initially the cost of a platinum bursting disc may appear high, but it should be remembered that after the disc has burst the metal of the fractured dome is still attached to the disc periphery. Thus all the original metal can be recovered and returned for refining and credit. The loss of production time and of product through failure of a disc due to corrosion often proves that an alternative material to platinum cannot be afforded in the long run.

The excellent corrosion resistance of platinum favours its selection for bursting discs to protect autoclaves used for laboratory work, and the advantages of using one disc for different chemical conditions do not need to be stressed. The same reasons lead to the


A platinum bursting disc is installed in the ethyl chloride plant of the Associated Octel Co Ltd at Ellesmere Port. It is Eocated in the pipeline near to the lower end of the ribbed ducting

choice for autoclaves used in small scale production of expensive or uncommon chemical Compounds.

Numerous applications occur in the field of industrial organic chemistry. Platinum discs are used on vessels digesting wood under pressure with sodium bisulphite and solium hydroxide, and on vessels used in the manufacture of the sulpha drugs when the highly corrosive materials employed subject the system to constant attack.

Many applications for platinum bursting discs are found in the petroleum industry, and a particular application is illustrated here. The photograph shows a narrowface capsule type assembly, containing a platinum disc, clamped between the faces of two standard flanges, and located next to the lower end of the ribbed ducting. The disc is installed on a run-down tank used for chlorinated hydrocarbons and is normally in contact with ethyl chloride. This latter compound is an intermediate in the preparation of tetraethyl lead used in the production of the anti-knock compounds manufactured by the Associated Octel Co Limited at Ellesmere Port.

Platinum discs are also employed on storage vessels for hydrocarbons where they remove the possibility of slow corrosion arising from the presence of miscellaneous impurities. Their resistance to inorganic acids also permits their use on systems handling these fluids. A system in which platinum discs are used to protect a plant containing superheated water has been described by Patrick (2).

Some of the largest platinum bursting discs in use at the present time serve to protect the

carboniser at the National Coal Board's Birch Coppice Colliery. The discs are eighteen inches in diameter and weigh approximately twenty ounces troy each. Platinum discs are employed because this is the only material which would withstand the corrosion products from coal dust and superheated steam.

An interesting application of platinum bursting discs is found in the Graviner fire extinguishing equipment used in modern jet aircraft. The extinguisher is generally installed in the whg of the aircraft and contains a liquid of relatively low boiling point. The platinum disc is fitted to relieve the internal pressure arising from volatisation due to inadvertent overheating. Without this safeguard the container could explode and so endanger the aircraft.

Various alternative methods of protecting the container were tried before a platinum bursting disc was selected. Experiments were


I n th.e Graviner $re extinguishing equipment used in jet aircraft a platinum bursting disc is Jitted at the three-way junction to relieve internal pressure due to hdver tent overheating

carried out using a soft metal plug in the side of the vessel. This was designed to melt if the vessel temperature rose above a dangerous level, but unfortunately the time lag between heat transfer to the plug and the build-up of internal pressure was too great and the vessels burst before the plug had time to melt.

Platinum was found to have complete resistance to seepage of fluid, and its corrosion resistance was excellent. The bursting pressure can be accurately predicted and a life of over five years can be expected.

References

Eng., 1939,142,265-375 I

z

G. F. Lake and N. P. Inglis, Proc. Imt. Mech.

E. A. K. Patrick, Trans. Insr. Chew. Eng., 1953, 31, 114-119

Rhodium as a Polymerisation Catalyst PREPARATION OF POLYBUTADIENE

In the production of synthetic rubbers from polymers and co-polymers of a series of dienes, notably butadiene, the properties and utility of the resulting polymer depend to a very great extent on the conditions of polymerisation and on the nature of the catalyst employed. Diene polymers and co-polymers are mixtures of 1,2 and 1,4 additions - each in the cis- and transform. Different methods of polymerisation cause certain structures to predominate and yield polymers of widely differing properties.

The stereo-specific activity of trivalent rhodium when used as a catalyst in the emulsion-polymerisation of 1,4 butadiene has recently been reported by R. E. Rinehart, H. P. Smith, H. S. Witt and H. Romeyn, of the United States Rubber Company (J.A.C.S. 1961, 83, (23), 4864-4865). The chloride, nitrate and some other salts of trivalent rhodium were employed in dilute solution in

water or ethanol and yielded polymers containing more than 98 per cent of the trans- structure. 'This form of the polymer is hard, brittle and crystalline, compared with the usual rubbery material which consists largely of the cis- structure. The novelty of this finding lies in the fact that stereo-specific polymerisa- tions of dienes had not previously been possible by the commonly-used emulsion polymerisation technique, as catalysts which could be employed are affected by water.

Applications of this technique for the production of cis-polybutadiene offers very interesting commercial possibilities. This type of rubber is said to have considerable advantages over natural and styrene-butadiene rubbers in the manufacture of heavy-duty tyres, in that it exhibits higher recovery rates from load strains and better resistance to undesirable temperature rises.

H. C.


Palladium Alloy Diffusion Process for Hydrogen Purification FIRST COMMERCIAL-SCALE PLANT IN OPERATION

The development of a silver-palladium alloy having a hydrogen diffusion rate more than twice that of pure palladium, as well as a high degree of stability on heating and cooling in hydrogen, was described in Platinum Metals Review, 1960, 4, 130-131, by Dr J. B. Hunter, of J. Bishop & Co Platinum Works, Malvern, Pennsylvania. In the course of this article the author also outlined the design of a range of diffusion cells based upon this alloy suitable for laboratory, pilot plant and full- scale operation in the separation and purification of hydrogen. Since that time further design and engineering work have been carried out, and a number of relatively small- scale units have been put into service. Now

Dr J . B. Hunter, ofJ. Bishop & Co Platinum Works, exam- ining a single silver-palladium alloy diffusion cell in its test rig. Unit cells of this type are assembled in multiples to build commercial-scale plants such as the installation ltow on stream at the National Cylin- der Gas Los Angeles plant

the first commercial-scale plant for volume production of high purity hydrogen has been put on stream. This is at the Los Angeles plant of the National Cylinder Gas Division of the Chemetron Corporation, where the installation is producing 115,000 cubic feet a day of hydrogen with an impurity level as low as 0.1 part per million.

The basic unit of the system consists of a bundle of thin-walled small diameter silver- palladium alloy tubes, manifolded together into a header, and assembled into an outer envelope. This construction provides a thin membrane for diffusion, coupled with high surface area in a small volume and adequate mechanical strength. Multiples of this unit

Platinum Metals Rev., 1962, 6, (2), 4 7 4 8 47

can of course be assembled to provide the throughput required.

In the National Cylinder Gas plant the feed hydrogen, more than 99.7 per cent pure, is preheated to around 315”C, while the diffusion cells are maintained at the same temperature. The diffusion rate depends upon the partial pressure of hydrogen in the gas stream and the rate of circulation of the feed gas. The temperature of around 315°C is the minimum at which the rate of diffusion through the alloy becomes a practical proposition, but the hydrogen pressure differential across the alloy tube walls and the rate of bleed-off from the cells are factors which influence the econo- mics of operating a diffusion unit.

The National Cylinder Gas installation employs electrolytic hydrogen, the 0.3 per cent of impurities consisting primarily of

oxygen, with some nitrogen, methane and water. Hydrogen produced from hydrocarbon reforming processes would of course contain also carbon monoxide and carbon dioxide, but these would not affect performance. The only impurities that do in fact interfere with diffusion are unsaturated hydrocarbons and sulphur, but the former can be removed by a hot air purge of the cells, while the latter can readily be removed by normal methods before beingallowed to reach the diffusionunit.

The factors that led National Cylinder Gas to install their diffusion plant were mainly the safety, simplicity and ease of operation of the Bishop system. The unit has no moving parts, and the capital cost represents almost the total expense. Control of the process is simple, consisting only of analysis of the output stream.

Surface Phenomena at Platinum Electrodes ADSORPTION OF CATIONS AT ANODIC POTENTIALS

When platinum electrodes are used for the anodic formation of persulphuric acid, the nature of the cations present has long been known to have a marked influence on the kinetics of the anodic oxidation; at any given potential, the rate of persulphate formation is diminished by the presence of alkali metal ions, the effect increasing in the order Li+ <Na+ tK+. Experiments on the anodic evolution of oxygen from perchloric acid, which is also influenced by the nature and concentration of the cations present, have shown that the platinum surface changes with time, chemisorbed oxygen being produced.

In a review paper recently published (Electrochimica Acta, 1961,s~ 265 -in French) Professor A. N. Frumkin, of the Institute of Physical Chemistry, Moscow, draws together a number of phenomena concerned with the surface of platinum anodes, and puts forward the view that the dipolar nature of the platinum-oxygen bond promotes the adsorption of cations. At high anodic polarisations, definite oxide films are formed, as indicated by earlier work. Cation adsorption has been directly demonstrated by the use of caesium ions labelled with Cs13*.

Both the adsorption of cations and the oxidation of the surface inhibit anodic oxida- tions such as persulphate formation and oxygen evolution. With the alkali metal ions, the cation effect increases in the order Lit <Na‘ tK+ <Cs+, undoubtedly the order of increasing specific adsorbability, when platinum is polarised anodically in 6N sulphuric acid and in electrolytes such as 5N H,SO,, IN Li,S04. Even o . o ~ N Cs+ has an appreciable influence. A similar although smaller effect of Csf can be found on the evolution of oxygen from the oxide-covered surface of passive iron.

In this important paper Professor Frumkin gives sixty-six references to earlier work in his own and other laboratories on the platinum anode. In view of the importance of platinum as a so-called “inert” electrode in electrolytic processes, in cathodic protection and in fundamental investigations, it is surprising that its actual “reactivity” has been relatively little studied; the paper is valuable in drawing attention to many points urgently needing further examination, as well as being an excellent summary of what is known to date.

T.F.H.


Apparatus for Crystal Growth Studies in Glass A PLATINUM-WOUND DEVITRIF’ICATION F”ACE

By D. A. Richardson, B . s ~ . Research Laboratories, Pilkington Brothers Limited, Lathom

The absence of crystals is normally considered essential for a glass, but the crystalline state is a more stable one than the liquid one. The vitreous state is, therefore, to some extent an artificial condition since all glasses pass through an unstable condition with respect to one or more crystalline compounds on cooling from the melting temperature. It is because a glass has a relatively high viscosity in the crystallising region that complete crystallisation is inhibited and, by passing through this temperature zone as quickly as possible, a glass is produced in the form that is generally known. The temperature at which crystals first appear is designated the “liquidus temperature” and, on cooling the melt below this temperature, the rate of crysral growth rises to a maximum and then falls as the viscosity increases until it is completely inhibited at very high viscosities by the rigidity of the structure. Data on the liquidus temperature and the rate of crystal growth at various temperatures are obviously of great importance to the glassmaker because of the limitations they impose on the manu- facturing processes involved in melting, forming and annealing.

Glass devitrification studies are often made by using the platinum boat method described by Silverman (I) and Preston (2). The glass being examined is placed in a platinum boat about 6 inches long and this is then put into a furnace which has a temperature gradient along its length. It is desirable that the boat should be so positioned in relation to this temperature gradient that the expected liquidus temperature comes at about the

centre of the boat. The sample is left under the action of the heat treatment for such a time as to make certain that crystals are formed; the soaking time may be minutes, hours or even weeks as it is dependent on the ease with which devitrification occurs. After the heat treatment, the boat is removed and examined by means of a microscope to establish the highest temperature at which crystals have begun to grow. The temperature gradient of the furnace, as well as its level of temperature, must be accurately controlled for the whole of the heat treatment period and may be measured by either a sliding platinum : rhodium-platinum thermocouple or by a series of fixed thermocouples.

Because of the comparatively massive sample involved in this method, the heat treatment time is not precisely defined due to the necessary heating-up and cooling-down periods.

For studies of the rate of crystal growth, very small samples are used so that the glass is brought rapidly into equilibrium with the temperature of treatment and is as quickly quenched when it is removed from the furnace. The condition of the crystals grown is, therefore, frozen in to the sample and they are then examined under the microscope. The rate of growth of the largest crystal obtaining in the sample is calculated from the time of heat treatment assuming the nucleation time to be zero and the rate of growth to be linear. Swift (3) has shown that the latter assumption is correct provided that there is no interaction between crystalline zones.

Platinum Metals Rev., 1962, 6, (2), 49-51 49

This demonstration model of the apparatus for investigating the rate of crystal growth in glass shows the rhodium-platinum furnace element with its centre tapping, the twelve platinum- clad thermocouples for determining the temperature gradient, and the control thermocouple

The method used in this laboratory is shown in the photograph, which is of a demonstration model of the apparatus. A small horizontal electric furnace is wound with 10 per cent rhodium-platinum wire 1.2 mm in diameter, and the winding is provided with a centre tapping so that the power supplied to the two halves of the furnace can be changed. This enables a variable temperature gradient to be established along the centre section with the temperature level of the whole furnace adjusted to cover the devitrilication zone of the glass sample. A sensitive and accurate temperature controller is used to maintain the desired condition over a long period of time. The temperature gradient along the furnace is obtained by means of twelve I .6 mm diameter JMC platinum-clad platinum : rhodium-platinum thermocouples as shown

in the illustration although the arrangement in practice differs slightly in detail from this.

Each sheathed thermocouple is cemented through a separate hole in a refractory tile at I cm intervals so that the thermocouples occupy the centre section of the furnace and extend over the length of the sample holder, with their thermojunctions just above it. A continuous record of their output and hence of the temperature gradient is given by connecting them to a twelve-point electronic potentiometric recorder. A separate thermocouple, placed outside the furnace winding and adjacent to it, is used as the sensing element for the temperature controller. I t has been found preferable to employ this separate element in close proximity to the winding to reduce hunting of the temperature about the desired level.

The sample holder consists of a strip of


25 mesh platinum gauze welded to a framework made of 20 per cent rhodium-platinum rectangular strip.

The glass to be examined is crushed, and pieces passing a 20 mesh sieve but retained by the 25 mesh gauze are placed along the top of strip to fill most of the cells formed by the mesh.

Thus we have in effect a large number of separate crucibles in which the glass is retained by surface tension when it is heated.

The sample holder is inserted into the furnace and pushed up against a stop cemented to the refractory tile so that it is in a known position in relation to the thermocouples. Because of the relatively low thermal capacity, the holder quickly attains

25 MESH PLATINUM

in holes in the end members of the gauze supporting frame to locate the sample holder in a definite position relative to the microscope scales. The positions of individual crystals on the sample holder are obtained from the readings of these vernier scales and can be correlated with the known temperature gradient.

The sample can be returned to the furnace and the increase in size of particular crystals can be measured after given times of heat treatment to eliminate errors due to finite nucleation times. If the temperature level of the furnace is changed so that, on re- inserting the holder, some of the crystals are above their liquidus temperature, they will begin to dissolve and the rate of solution can be measured.

The advantages of this method are as follows:

(a) the relatively large amount of sample material of large surface area is useful in a glass which provides few nucleation centres ;

(b) iixed thermocouples enable a continuous record to be made and any faults in temperature reading immediately be-

The sample holder used in studying crystal growth come obvious; phenomena consists of a strip of platinum gauze welded to a framework of rhodium-platinum. (c) the glass is prevented from flowing Measuring Jive"inches in Zenith, the holder provides a large number of "crucibles" in which the glass is

retained bv surface tension

laterally by surface tension; this is of value when studying glasses of low

i "

viscosity ;

equilibrium with the temperature regime in the furnace. After it has been in the furnace long enough for crystals to have grown to a measurable size, the sample is removed and undergoes rapid cooling. I t is then placed in a specially constructed cell attached to the stage of a travelling microscope which is equipped with scales for two directions of movement.

The cell is provided with pins which locate

(d) the sample is available for direct microscopic examination and can also be subjected to further heat treatment if required;

( e ) an adjustable temperature gradient makes possible exploratory measurements when the devitrification range is unknown since a steep gradient can be used; in normal operation a gradient of about Io"C/cm is used.

References I W. B. Silverman .. . . . . J . Amer. Cer. SOC., 1939,zz, 378 z E. Preston .. . I . . . . J. SOC. Glass Tech., 1940, 24, 101 3 H. R. Swift .. . . . . . . J . Amer. Cer. SOC., 1947, 30, 165


FRAME OF 2O0/oRH0DIUM- PL ATINUL

Palladium Plating on Telephone Plugs and Sockets By R. W. Beattie Automatic Telephone & Electric Co. Ltd., Liverpool

This article describes the performance of electrodeposited palladium on a typical telephone two-motion selector plug and socket employing contact forces in the range 100 to 300 grammes. The conclusions are based on environmental tests and electrical measurements which indicate that palladium forms a reliable contact finish in this application.

The plug and socket (or more correctly- unitor) employed for connecting two-motion selectors or relay groups to their associated racks in telephone exchanges is illustrated here. It employs nickel silver springs and operates with contact forces of from IOO to 300 grammes. Although these forces are insufficient to disrupt the naturally occurring tarnish film mechanically (I), the practice of imposing 50 V d.c. in telephone circuits is sufficient to disrupt the film electrically. Where 50 V d.c. is not available there is a need for improved contact performance. Silver plating was employed for this purpose but has been abandoned due to silver migration (2). An improved non-tarnishing palladium finish has therefore been developed for these contacts and is considered to be a praaicd proposition satisfying a wide range of environmental test requirements in low voltage circuits.

Plating Considerations Barrel plating (electrolytic) was used for

this investigation as it provides excellent agitation, gas bubble detachment, uniform deposition and is a convenient means of handling large quantities of contacts. It was found that solution purity, current density, barrel loading (to provide adequate tumbling) and temperature, required reasonably critical control during plating to produce a bright


non-porous coating 0.0002 to 0.0003 inch thick. This was achieved by using de-ionised distilled water in the rinsing and palladium solutions and by thorough washing, and scrupulously avoiding transfer of base metals to the palladium bath.

Pre-treatment of the contacts comprised polymotion barrel deburring, chemical clean- ing and the application of an acid copper flash. The latter was found to improve adhes- ion and to show low diffusivity in palladium.

In keeping with most electrodeposits, due to their initial high surface activity immediately after plating, the palladium was prone to fingermark. This is overcome by a hot water rinse which provides a slight measure of passivity.

By barrel plating, the soldering tag terminations of the contacts were coated with 0.0002 to 0.0003 inch palladium. These tags were found to solder very readily with 60/40 tin lead resin-cored solder using a small electric soldering iron. There was no evidence of plating detachment or blistering on a trial of 5,000 contacts.

Contact Resistance Total contact resistances of the mated

plugs and sockets were measured at a maximum open circuit voltage of 50 mV a.c. 1,000 C.P.S. with a current of 50 mA through the contacts. For practical purposes, this

x

voltage is considered insufficient to disrupt tarnish films at the contact interface.

The pole resistance due to the contact springs was measured separately by welding a typical contact by the discharge of a 32 microfarad capacitor at 230 V. By subtracting pole resistance from the total contact resistance the true contact resistance was deduced.

Gas Exposure Tests To produce by accelerated environmental

testing the actual tarnishing of contacts that occurs in practice is virtually impossible.

An accelerated test has, however, been devised that produces copious tarnish on base metals and readily detects weaknesses in precious metal deposits. The test has been applied to more than forty commercial plugs and sockets and has consistently discriminated between reliable and unreliable contact.

The actual conditions were as follows: 24 hours in I per cent SOz in air at 2ooC at high humidity followed by 24 hours in I per cent H,S in air at 2ooC at high humidity.

The separated plugs and sockets were submitted to these conditions and contact

Table I Contact Resistance (Milliohms)

(Pole resistance - 7.8 milliohms)

Before Gas Exposure After Gas Exposure Before Gas Exposure After Gas Exposure


Plain nickel silver

Palladium plated

Plain nickel silver

Palladium plated

Minimum Average Maximum Minimum Average Maximum I

A typical telephone twa motion seleclor plug and socket

Palladium plated and plain nickel silver contacts before and after the gas exposure test Top -palladium plated (left) and nickel silver (right) before exposure Bottom -palladium plated ( lef t ) and nickel silver (right) after exposure

resistance measurements were made before exposure and on the first insertion after exposure. The results in milliohms are shown in Table I for 192 plain nickel silver and 192 palladium plated contacts.

The results indicated the effectiveness of the palladium plating in preventing the formation of insulating tarnish films. An idea of the severity of the test can be obtained from the photograph which shows palladium plated and plain nickel silver contacts before and after gas exposure.

Constriction Heating This phenomenon (3, 4) is due to the

heating of contact asperities by the passage of current. It may reach a value, characteristic upon the contact metal, at which the voltage drop at the contact interface will produce a softening (softening voltage) or melting (melting voltage) of the asperities.

In the case of base metal contacts, constriction heating accelerates corrosion of the asperities. When plain nickel silver contacts were employed the plug and socket under discussion has developed occasional dis-


connections in industrial atmospheres due to the passage of I A from a 6 V a.c. source. On the other hand, similar adjacent contacts not carrying current continuously, remained unaffected. The mechanism of the former failure has been postulated as follows:

(a) Asperities heated slightly by continuous current

(b ) This accelerates atmospheric corrosion dependent upon the environ- ment

( c ) Contact resistance and heating increases as the asperities become progressively corroded

(d ) Eventually the melting voltage is reached at which the asperities melt and the contacts may then either collapse together or become insulated by the corrosion products.

This phenomenon was investigated by passing a maximum current of I A from a 6 V a.c. source for three months through nickel silver plugs and sockets having (a) plain nickel silver contact surfaces and (b) palladium plated contact surfaces. The plugs and sockets were placed in an atmosphere of

Table I I Contact Resistance (Milliohms)

Plain nickel silver . . . .

10 ppm SO, in air throughout this test. In each case 32 contacts were employed.

It was observed that the current could not be maintained through the nickel silver contacts due to contact resistance fluctuations. The current through the palladium plated contacts remained constant. Low voltage contact resistance measurements before and after this treatment are shown in Table 11.

Influence of Dust New plugs and sockets were wired to carry

I A through ten connections from a 6 V ax. source. Dusts of fuller’s earth, barium titanate and powdered glass were liberally applied while the plugs and sockets were inserted and withdrawn S t y times. With both nickel silver and palladium plated contacts no disconnections occurred during this test.

The contact springs were then oiled with a light mineral oil and the test repeated. Barium titanate and fuller’s earth produced one disconnection in twenty operations on nickel silver and one in thirty on palladium. Powdered glass produced one disconnection in three operations on nickel silver and one in five on palladium.

Wear As a realistic mechanical life test, new plugs

and sockets were submitted to 500 insertions and withdrawals at 20°C and a frequency of five insertions per minute. Contact resistance measurements were made as before and are shown below in Table I11 for ninety-six contacts in each finish. The contact surfaces in both cases were burnished, but did not show visible wear.

Friction Polymers To investigate the possibility of organic

friction polymer interference (5) on the palladium finish, one 32-contact assembly with palladium plated contacts was submitted to 500 insertions and withdrawals in benzene vapour in air. The closed assembly was then vibrated IOO,OOO times in this vapour. Contact resistances and appearances are given overpage in Table IV. The brown deposit after IOO,OOO vibrations conformed to the description of a friction polymer. I t did not influence the contact resistance appreciably and apparently had been displaced by the normal contact forces and is not considered detrimental in this application.


Palladium plated nickel silver

Table Contact Resistance (Millioh ohms) after 500 Insertions

Nickel silver contacts

Palladium plated contacts

Minimum Average Maxi mu rn

Minimum Average Maximum Minimum Average Maximum

After 3 months i n 10 ppm SO, a t I A 6 V a.c. Initially

Tdeposit around the con-

After 100,000 vibrations; closed assembly in benzene vapour .. ..

References

I A. Fairweather . . . . . . . . Proc. Z m t . Elec. Eng., Part I 1953,100, (124)~ 174-182 2 G. T. Kohman, H. W. Hermance and

G. H. Downes . . . . . . Bell Sysrem Tech. J., 1955, 34, (6), 1115-1147 3 R.Holm . . . . .. . . . . Electric Contacts Handbook, Springer-Verlag, Berlin,

4 F. Llewel lyn Jones . . .. . . The Physics of Electrical Contacts, Clarendon Press,

5

1958

Oxford, 1957 H. W. Hermance and T. F. Egan . . Bell System Tech. J., 1958, 37, (3), 739-776

COBALT-PLAT1 NU M MAGNETS RESIST CORROSION The combination of outstanding magnetic properties and resistance t o chemical attack has made possible the use of Platinax II cobalt-platinum alloy magnets in conditions where ferrous magnets would suffer severe corrosion. The photograph shows an apparatus developed by Thorn-A.E.I. Radio Valves & Tubes Ltd for the electrolytic polishing of nickel radio valve components. In this equipment are eight Platinax I I magnets, each 0.375 inch in diameter by 0.2 inch long, attached t o the positive electrode. The nickel components, which have to be highly polished both internally and externally w i th no contact marks beyond the closed end, are held in position by these magnets. W i t h a high current density in a strongly acidic electrolyte operating at 60 t o 70°C there have been no apparent burns o r marks at the point of contact between the nickel parts and the magnets, which have been in use for over a year without showing any sign of attack o r of loss in magnetic strength.

Platinum Metals Rev., 1962, 6 , (2) 56

Table IV

Contact Resistance Milliohrns

Appearance of Contact Surface

Minimum Averane Maximum

After 500 closures benzene vapour

Bright and clean

Bright and clean

Initially

Bright with a little browi deposit around the con tactinn area

Cathodic Protection Against Cavitation Damage AN INVESTIGATION WITH PLATINUM-CLAD ANODES

The vapour cavities that form in very rapidly flowing or vibrating liquids may collapse on metal or other surfaces in the liquid and cause localised deterioration, known as cavitation damage. This type of damage may occur on marine propellers, and it is common to find all forms of corrosion or erosion damage on propellers referred to as “cavitation”. This unfortunately loose application of the term is partly responsible for the wide discrepancy in results that have been reported for the effectiveness of cathodic protection in preventing cavitation damage.

The principle underlying the use of cathodic protection to prevent corrosion is to apply a cathodic current to the metal concerned sufficient to depress its potential below the minimum at which it is thermo- dynamically possible for the metal to pass into solution in the medium in which it is situated. The forces developed by collapse of vapour cavities in experiments using magnetostriction apparatus and at the blade roots and certain other areas on propellers of some design are, however, sufficient to cause direct mechanical removal of metal and one would not expect this type of attack to be affected by normal cathodic protection. Much of the damage that occurs on propeller blades in service - particularly near the tips - is probably due to impingement attack rather than cavitation and this, being largely an electrochemical corrosion process, can be prevented by cathodic protection.

A recent paper by H. S . Preiser and B. H. Tytell (I) provides an excellent discussion of the types of cavitation damage that can occur and describes experiments on the application of cathodic protection, using a platinum-clad tantalum anode, to mild steel and manganese

bronze specimens fixed to a propeller boss and rotated at 1,250 r.p.m. 10 ft. below the surface in open sea water. In most of these experiments the specimens were rods, I in. diameter x 6 t in. long, screwed into the propeller boss. Cavitation damage was severe on the trailing half of each specimen when no cathodic protection was applied, but became progressively less with increasing applied cathodic current densities between 150 and 500 ma/ft2.

Preiser and Tytell distinguish three types of cavitation damage : (a) cavitation deformation or fracture in which the forces developed by the collapsing cavities are sufficient to remove particles of the material from the surface on which cavitation is taking place, (b) cavitation fatigue in which the stresses due to cavity collapse are below the proof stress of the material but sufficient to cause fatigue cracking as well as removing protective surface films and exposing the metal to the corrosive action of the surrounding medium, and (c) cavitation corrosion in which the forces are sufficient only to damage the protective film and the actual removal of the metal is entirely electrochemical. This differs from impingement attack only in the nature of the forces causing breakdown of the protective film.

The type of cavitation that is occuring is indicated by the cathodic current density that is necessary to prevent it. The relatively small currents that were found sufficient to prevent damage in Preiser and Tytell’s experiments show that the type of cavitation concerned was cavitation corrosion. Similarly, in cases where cathodic protection at low current densities has been found effective in preventing cavitation damage to propellers in service

Platinum Metals Rev., 1962, 6, ( 2 ) 57-58 57

this damage may also be considered to have been due to cavitation corrosion. Impinge- ment attack would equally be suppressed by cathodic protection and Preiser and Tytell do not discuss how cavitation corrosion in service can be distinguished from impingement attack. They do differentiate between the two and note that since the attack on their rotated rod specimens occurred on the trailing half rather than the leading half the damage to the film was caused by cavitation rather than impingement forces in these experiments.

Cathodic protection at low current densities has practically no effect on cavitation deformation or fracture since the damage is almost entirely due to mechanical forces. The damage can be reduced or prevented, however, if very high currents are used. Current densities of the order of 250 amps/fta have been found by other workers to be necessary to prevent damage by cavitation in experiments using magnetostriction apparatus. The hydrogen that is freely evolved from the protected metal at these current densities is believed to act as a resilient gas cushion between the collapsing vapour cavities and

References I H. S. Preiser and B. H. Tytell

2 H. S. Preiser and B. H. Tytell

. . The Electrochemical Approach to Cavitation Damage and Its Prevention, Corrosion, 1961, 17 (II), 535T

Some Platinum Anode Designs for Cathodic Protec- tion of Active Ships, Corrosion, 1959, 15 (11), 596T

. .

the metal surface. Entrained air has a similar effect in reducing cavitation damage and is sometimes introduced into hydraulic systems to prevent cavitation.

In cavitation fatigue metal is not removed directly by mechanical forces and electrochemical corrosion consequently plays an important part. In this case cathodic protection at low current densities greatly reduces the severity of attack since it prevents removal of metal by corrosion, but it does not prevent damage completely since the repeated collapse of cavities on thc same part of the metal surface can still cause fatigue cracking. To prevent this requires, as in the case of cavitation deformation or fracture, a current density sufficient to give hydrogen evolution.

To provide a controlled range of current densities in their experiments Preiser and Tytell used impressed current cathodic protection with a platinum-clad tantalum anode. The advantages of platinum-clad tantalum over other anode materials for cathodic protection in sea water have been discussed in a previous paper by the same authors (2).

H. S. C.

High-Temperature Properties of Platinum Metals STRENGTH AND DEFORMATION CHARACTERISTICS

Some two years ago the Battelle Memorial Institute submitted to the U.S. Office of Naval Research a report on “High-Tem- perature Properties and Alloying Behaviour of the Refractory Platinum-Group Metals”, designed to survey the literature and thence to reveal areas in which investigation is needed. A further report, by R. W. Douglas, C. A. Krier and R. I. Jaffee, has now been issued, under the same title, describing the results of three years of study. The experimental work now reported was based largely on the results of the earlier literature survey.

Much of the report, running to 170 pages, is concerned with the strength properties of the more refractory platinum metals at high temperatures, and includes studies of strength- temperature relationships, deformation characteristics, strain and structure sensitivity and fracture initiation and propagation characteristics. At high temperatures the mechanical strengths of rhodium and iridium are shown to be superior to those of tungsten, molybdenum, tantalum and niobium.

Other sections of this report deal with fabrication, alloying behaviour and oxidation.


A New Glass Tubing Machine DOWN-DRAWING OVER A PLATINUM'-CLAD MANDREL

A new vertical down-draw tubing machine installed at James A. Jobling & Company's Wear Glass Works, Sunderland, is producing tubing in Pyrex glass from about I$ to 8 inches in external diameter, while its range will eventually be extended to tube of 10 inches diameter. The machine was developed by the Corning Glass Works of America, with whom Joblings are associated, and will in due course replace a Woods up-draw machine. The down-draw machine gives a fifty per cent greater output and greater dimensional accuracy. It also extends Jobling's range of machine-made tubing, as hitherto all tubing from 4; to IS inches external diameter has had to be hand-blown.

The new machine draws molten glass, from a reservoir supplied through a forehearth, downwards over a rhodium-platinum sheathed base metal mandrel. Beneath the mandrel is a vacuum chamber through which the tube passes. The external diameter of the tube is determined partly by the size of the mandrel and partly by the degree of vacuum induced in the chamber. Tubing is produced at a maximum rate of approximately fifty feet per minute. On leaving the machine the tubing descends at a speed controlled by pulling units into a pit beneath the level of the work- shop floor, where it is cut into lengths. The smaller sizes of tubing will continue to be made on a Vello horizontal-draw machine.

The new down-draw tubing machine at James A. Jobling & Company's Wear Glass Works. Pyrex tubing is produced by drawing molten glass over a platinum-

clad mandrel.


Gold-Platinum Alloys A CRITICAL REVIEW OF THEIR CONSTITUTION AND PROPERTIES

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

The alloying characteristics of gold and platinum were described in 1796 by Lampadius (I) and by Morveau in 1803 (2). Percival Norton Johnson’s first paper, published in 1812 (3), dealt with the action of nitric acid upon platinum alloyed with gold and with silver, and dental applications involving the use of gold-platinum alloys were well established by 1845 (4). When platinum was cheap it was used as a convenient hardener for gold. At a later date gold could be regarded as a relatively cheap and corrosion resistant hardener for platinum (5). The gold-rich alloys have, for many years, been used as spinning jets for synthetic fibre production and to a lesser extent as electrical contacts.

The Constitutional Diagram Crude melting point determinations on the

alloys were first undertaken in 1879 by Erhard and Schertel (6) and ten years later Silow (7) attempted to interpret the very meagre temperature data in terms of van’t Hoff’s recently developed theory. In 1907 Doerinckel (8) carried out thermal analysis on six gold-rich alloys and concluded that the system comprised a continuous series of solid solutions. A more detailed study by Grigorjew, published in 1928 (9), involved cooling curves on eighteen alloys covering the range o to 61 per cent of platinum and led to the proposal of B simple peritectic type diagram. As the age-hardening Characteristics of the alloys were well known at this time, Grigorjew’s diagram appeared more plausible than that of Doerinckel.

Platinum Metals Rev., 1962, 6, (2), 60-67

Johansson and Linde (10) concluded in I930 that although a continuous series of solid solutions existed just below the solidus, decreased mutual solubility at lower temperatures resulted in the formation of a two-phase field which at 800°C was shown to extend from 25 to 92 atomic per cent of platinum. More precise X-ray diffraction studies by Stenzel and Weerts (11) confirmed quali- tatively the general shape of the miscibility loop. Theoretical interest aroused by the unusual nature of the system led Wictorin (12) to confirm the shape of the loop by resistometric methods.

Quenched samples had been used for the phase boundary determinations reported in the latter three investigations (10, 11, 12).

Further work by Wictorin (13) involved continuous resistance measurements at the actual temperature of precipitation, thus avoiding the uncertainties associated with quenched specimens. The results, published in 1947, showed that the peak of the miscibility loop extended to temperatures above IZOOOC. Solidus determinations, also by resistance methods, were found to be in agreement with the theoretical distances between solidus and liquidus calculated in accordance with the thermodynamic theory of H. Jones (14).

In spite of Wictorin’s confirmation the diagram advanced by Johansson and Linde was, at this period, by no means generally accepted. Nemilow, Vidusova, Rudnitsky, and Putsykina reported in 1946 (IS) that the system was of the simple peritectic type as suggested by Grigorjew almost twenty years previously. Similar conclusions were arrived

60

I 8 0 0 - 4 RESISTANCE MEASUREMENTS

COOLING CURVES

v MICROSCOPIC WORK

o X-RAY DATA

I 6 0 0 -

2 1400-

W K 3 I- < 0: W a I F 1200-

1000-

\ LIOUID + a

N

800 4

I \ I I

0 2 0 4 0 6 0 8 0 I

WEIGHT PER CENT GOLD

Fig. 1 Constitutional diagram of the gold-platinum system

)O

at by Grube, Schneider and Esch (16). The pronounced thermal arrests observed when heating alloys containing 10 to 70 atomic per cent of platinum led these workers to an implicit belief in the existence of a peritectic reaction at 13ooOC. The results of resistance- temperature measurements on alloys containing 5 to 40 per cent of platinum appeared to support this hypothesis.

Very accurate solidus determinations were required to establish the true nature of the diagram. Darling, Mintern and Chaston reported in 1952 (17) the results of solidus determinations by microscopic methods. The results are shown in Fig. I which gives the revised equilibrium diagram plotted on a weight basis because of the similar atomic weights of gold and platinum. Between 30 and 45 per cent of gold the solidus is a gently sloping line having upper limits of 1315°C

Platinum Metals Rev., 1962, 6, ( 2 )

at 30 per cent and 1305°C at 45 per cent of gold. Microscopic examination confirmed the existence of a single phase area immediately below the solidus. Fig. 2 shows the well-defined duplex structure of the 42 per cent gold alloy quenched from 1220°C. Small pockets of the second phase, shown in Fig. 3, still persist at 124ooC, while Fig. 4 illustrates that the structure at 12yj’C is that of a typical solid solution.

The lattice parameters of the single phase alloys fall on a smooth curve not far from the straight line predicted by Vegard’s law, and phase boundary determinations made by electrical resistivity measurements were in agreement with those arrived at from the plotted X-ray diffraction data. High temperature X-ray work confirmed the upper boundary of the duplex region determined by measurements of electrical resistivity.

61

2 3 4

Microstructures of the 4% per cent gold alloy Fig. 2 Quenched from 1220°C Fig. 3 Quenched f r o m 1240°C Fig. 4 Quenched f r o m 129S'C

In order to account for discontinuities in curves illustrating the change of electrical resistance during the process of precipitation, Johansson and Linde (10) postulated the existence of intermediate, possibly ordered phases, within the miscibility gap at temperatures below 400°C. No evidence of these phases was found by Grube, Schneider and Esch, who reported, however, that alloys containing up to 40 atomic per cent of platinum began to order when heat-treated below goo"C. A second phase, having a lattice parameter rather lower than that of the platinum solid solution, appeared after heat treatments of up to forty-two days with intermediate deformation by grinding.

Tiedema, Bouman and Burgers (IS) repeated these experiments but were unable to detect a second phase even after sixty-six days of heat treatment. No other investigators have detected an intermediate phase in the gold-rich solid solution, and it is difficult to account for the observations of Grube, Schneider and Esch.

The accuracy of the diagram of Fig. I was confirmed in 1955 by Raub and Worwag (19) and in 1957 by Bouman and Burgers (IS). Kanebetskaya in 1957 (20) used the system as illustration of the way in which a relatively small increase in the free energy of mixing could transform a solid solution diagram into one of the peritectic type.

The metallographic preparation of the alloys presents little difficulty. Suitable techniques have been described by Darling, et al. (17) and by Reinacher (51).

Thermodynamics of the System In 1930, when Johansson and Linde ad-

vanced their diagram, gold-nickel alloys afforded the only other example of a metallurgical system having a closed miscibility loop below the solidus (21). The solidus and liquidus curves of gold-nickel alloys were almost coincident above the miscibility loop, whereas those of gold-platinum alloys were widely separated. The system was thus of considerable interest, and attempts were soon made to apply thermodynamic analysis to the solubility and melting point data.

Scatchard and Hamer (22, 23) used in 1935 a regular solution model modified to allow for the effect of a net volume change upon the entropy of mixing. The expressions derived described the solubility data fairly accurately and indicated that the solidus, the liquidus and the solid solubility curves of Johansson and Linde's diagram were self- consistent and in agreement with a positive heat of solution in solid and liquid phases. The free energy expression derived predicted a solidus curve which, although considerably lower than the present accepted values, fitted Doerinckel's data quite closely. It had a


fairly flat inflexion over the range 50 to 70 per cent of gold, which, it was suggested, could have explained the thermal arrests wrongly interpreted by Grigorjcw as evidence of a peritectic reaction.

Wictorin (13) used his solubility data to devise an expression in which the integral molar free energy of solution was represented by a four-constant exponential function of concentration. In developing this expression it was assumed that the molar entropy of mixing was ideal. Although fairly good agreement with the experimental data was achieved above g o o T the situation at lower temperatures was less satisfactory.

Hardy (24, 25) found that the shape of the miscibility loop was more accurately described by a Lcsub-regular” solution model in which the exchange interaction energy was allowed to vary with composition in a linear manner. The excess molar heat of solution was given by the expression

H = A, x‘y + A2xyL x andy being the atomic fractions. By apply- ing this expression to the solubility data of Wictorin (13) and of Darling, Mintern and Chaston (17) the quantity (A,-A,) was found to be sensibly independent of temperature over the range 1250” to 900°C.

Weiss and Tauer (26) advanced in 1958 a six-termed expression for the total free energy of the system, in which the magnitudes of dominant components such as electronic, lattice and mixing free energies were inde- pendently computed. These authors attributed the asymmetrical distribution of the miscibility loop to the rapid filling of the “8’ band, indicated by a rapid increase in the electronic specific heat coefficient over the range 10 to 30 atomic per cent of platinum. At the upper critical point the third derivative with respect to composition of any free energy expression should be zero. This criterion, when applied to Weiss and Tauer’s expression, displaces the top of the miscibility loop to the equi-atomic composition, thus suggesting some inaccuracy in their basic assumptions.

In their recent paper L. J. van der Toorn and T. J. Tiedema (27) reverted to the classical approach and evolved an expression in which the excess free energy of solution was represented by the first three terms of a power series in x divisible by xy, x and y being the atomic fractions. The integral molar heat of solution was only positive for platinum contents higher than 20 per cent. The solubility limits calculated from this expression agree closely with all the recent experimental data (13, 17, 18, 19) and this analytical approach seems likely to supersede that of earlier workers.

The Mechanisms of Precipitation Because of its unusual simplicity the gold-

platinum system was the first to be studied by Borelius and his colleagues during the development of their thermodynamic potential barrier theorem (28, 29, 30). The rate of precipitation, according to this theory, depended greatly upon the curvature of the free energy composition curve. The spinodal, being the locus of the inflexion points of the isothermal free energy composition curves, forms a lower limit of metastable equilibrium. Between the spinodal and the two-phase field boundary exists a thermodynamic potential barrier which must be overcome before nucleation can OCCUT, with the result that precipitation is retarded in this area.

Resistometric studies on the 70 : 30 gold- platinum alloy were reported by Johansson and Hagsten in 1937 (29). Up to 550” the velocity of precipitation increased with temperature owing to increased atomic mobility. Above this temperature a retardation set in, which at IOOO below the solubility limit became so pronounced that no appreciable change in resistance occurred after thirty-five hours of heat treatment. Wictorin (12) followed the rate of precipitation by plotting the relative decrease in resistance which occurred in ten minutes against the reciprocal of the absolute temperature. The curves obtained showed well defined retardation limits in agreement with the predictions of


... . . .... . PHASE B O U N D A R Y i d n n - VAN DER TOORN L T I E D E M A I

I W ICTOR I N __-- ’--- I - -’ H A R D Y

A T O M I C PER CENT GOLD

Fig. 5 Comparison of the spinodal curves calculated by Wictorin (23), Hardy (24) , and van der

Toom (27)

Eorelius. In his later work (13) the boundary of the two-phase region was carefully re- determined, and an expression for the free energy of solution advanced. The spinodal calculated from this expression coincided with the limits of retardation found during precipitation experiments. In Fig. 5 the spinodal curves calculated by Wictorin (13), Hardy (25), and van der Toorn (27) have been contrasted. Increasingly refined methods of calculation have displaced the curve further and further from the gold-rich phase boundary. These results might possibly explain the frequent reluctance of the 70 : 30 gold- platinum alloy to age harden (37).

X-ray diffraction studies show that during the early stages of precipitation the normal reflections from the super-cooled solid solution are accompanied by “side bands” which appear on each side of the Debye- Scherrer lines before any movement of the lines occurs and before emergence of the diffraction pattern of the precipitated phase, A characteristic feature is that bands on either side of a diffraction line are of different intensity. Tiedema, Bouman and Burgers (18) studied these bands using wire and single crystal specimens. A modification of Har- greaves’ lattice modulation model was advanced to account for the experimental data.

Periodic disturbances in lattice parameter were, it was suggested, responsible for the “side bands”, which arose from the alternation of two crystal lattices having differing dimensions in one cube dimension only, thus initiating a lattice disturbance of regular period. During the pre-precipitation period the two lattices were present in the same proportions as the two equilibrium phases, accounting thereby for the differing intensities of the two side bands.

Diffusion Processes Early studies by Jedele (31) and Jost (32)

suggested that platinum diffused into gold faster than gold diffused into platinum. Bolk‘s recent investigation (33), which contra- dicted this belief, was deliberately made under conditions in which a phase boundary was formed during an experiment. The progress of diffusion with time was measured by X-ray techniques and the results analysed by procedures evolved by Matano (34) and Darken (35).

The phase boundary formed by diffusion bctween pure gold and platinum results from the shape of the diagram. Once the equilibrium phases are formed diffusion occurs across the interface between the gold

I 400

VI v) W z

< 300

r

a

v

Lo

; 200 >

I00

l O 0 O ~ C

20 40 60 ao loo WEIGHT PER CENT GOLD

Fig. 6 Hardness of gold-platinum alloys quenched from temperatures up to 1250°C, ajter previous

soaking at 1150°Cfor twelve days


TE

MP

ER

AT

UR

E

and platinum solid solutions, each of which is constantly replenished from the reservoirs of pure gold and platinum. Because the partial diffusion coefficient of gold in the gold-rich solid solution is approximately seventy-five times that of platinum, a pronounced Kirkendaal effect is observed and the marker interface moves considerable distances towards the gold-rich side of the couple.

Hardness and Mechanical Properties

Fig. 6 shows that alloys containing 20 to 60 per cent of gold are greatly hardened by quenching from temperatures above I 100'.

Precipitation is not completely suppressed by quenching within this composition range, and partial decomposition of the two solid solutions is primarily responsible for the high hardness values attained. Alloys containing 25 to 50 per cent of gold have very variable hardnesses when quenched from IZOO to 1280°C, and the intercrystalline cracking which frequently occurs can be reasonably attributed to partly suppressed grain boundary precipitation.

Fig. 7J based upon unpublished data (37)J illustrates the tensile properties of commercially prepared solution-treated alloys. Small additions of gold rapidly increase the ultimate tensile strength of platinum at the expense of elongation. Gold increases the mechanical properties of platinum more rapidly than platinum increases the mechanical properties of gold. Although the informa- tion on this graph is in fair agreement with that presented by other investigators (36, 38, 39, 40) details of prior thermal treatment influence considerably the mechanical properties of individual specimens, and the tensile data presented should be used for guidance purposes only.

The softest and most ductile material is obtained by quenching from 850°C. Fig. 8 illustrates the effect of cold rolling upon the hardness of material treated in this manner. The greatest proportional increase in hardness is exhibited by alloys containing approxi-

Platinum Metals Rev., 1962, 6, ( 2 )

WEIGHT PER CENT GOLD

Fig. 7 Tensile properties of commercially prepared solution-treated gold-platinum alloys

mately 70 per cent of gold. Even in the cold rolled condition such alloys exhibit a sur- prisingly high ductility, as indicated by the elongation data in Table I (37).

Considerable hardening results when duplex alloys, quenched from above IIOO'C, are reheated to temperatures ranging from 400 to 600°C. Fig. 9 illustrates the hardness of several alloys after ageing at 550°C for periods up to five hours. These alloys were quenched after solution treatment for half an hour at temperatures of 1100 to 1200OC. Their quenched hardnesses are lower than

250 1

0 10 2 0 3 0 4 0 5 0 P E R C E N T REDUCTION IN THICKNESS

Fig. 8 Effect of cold-rolling upon the properties of four quewhed gold-platinum alloys

65

UL

TIM

AT

E

TE

NS

ILE

S

TR

EN

GT

H

LIM

IT O

F P

RO

PO

RT

ION

AL

ITY

V

ICK

ER

S

HA

RD

NE

SS

EL

ON

GA

TIO

N P

ER

CE

NT

ELONGATlOh

ELONGATlOh

TABLE I

Effect of Cold Rolling upon the Tensile Properties of Two Gold-Platinum Alloys

Per cent reduction

in thickness

U.T.S. Tons/sq. in

0

10

20

30 1 ;; 37.2

23.2

26.5

28.8

30.3

sequent response to age- hardening. Fig. 10, taken from Schmid (36), illustrates the effect of homogenisation upon the response to age-hardening of a 50 per cent gold-platinum alloy. The material solution treated for 170 hours was at all stages of ageing approximately 70 points harder than material solution treated for thirty minutes only. The effect illustrates the slow rate of approach to equilibrium during normal solution treatment processes.

Fig. 9 indicates that the 70 per cent gold alloy age-

the corresponding values indicated in Fig. 6, hardens while the 80 per cent gold alloy, which is based upon the behaviour of speci- being within the single phase region, does mens homogenised for twelve days at 1150'C not respond to heat-treatment. Although before quenching. This increase in hardness the 70 per cent gold alloy is well within the value with length of solution treatment is duplex region its response to age-hardening characteristic of the behaviour of gold- is rather erratic, being critically dependent platinum alloys and reflects itself in the sub- upon composition (37).

400

ul ul w

300 a 4 I ul

t 200 2 >

80'loAu 'oorI Iz

4 5 0

40 0

In 3 3 5 0 z 0

4

v)

w

a 300

a

5" 25C

20c

I5C

HOMOGENISED AGED 5 0 0 C

HOMOGENISED AGED 6 0 O 0 c

HETEROGENEOUS AGED 5OO0C

HETEROGENEOUS AGED 6 0 O 0 c

I0 I0 I , I TlME OF AGEING HOURS

0 . . .

1 2 3 4 5 6 TIME OF AGEING HOURS Fig. 10 Effect of homogenisation upon the response

to age-hardening of a 50 per cent gold-pEatinum Fig. 9 E$ect ofprecipitation-hardening upon gold- alloy. (After Schmid (36)) The homogenised platinum alloys aged at 550°C ufter solution material was solution treated for 170 hours, the

treatment for thirty minutes at 1 100-2 200' C heterogeneous material for thirty minutes only


Gold-platinum

Gold-platinum

L.O.P. Tonslsq. in.

Elongation per cent

100

5oooc

0. I 10 10 100 TIME OF AGEING HOURS

Fig. 11 Effect of precipitation upon the tensile properties of a 50 per cent gold-platinum alloy

The effects of precipitation upon the tensile properties of the 50/50 alloy are illustrated in Fig. I I . Although ultimate tensile strengths of the order of go tons per square inch can be attained, the corresponding elongations may be as low as 2 per cent. Over-ageing does not improve the ductility (36).

The concluding part of Dr Darling’s article will be published in the July issue of ‘Platinum Metals Review’.

References

I W. A. Lampadius, Chem. Ann., 1796, I, 219 2 G. de Morveau, Ann. de Chim., 1803, 47, 300 3 P. N. Johnson, Phil. Mag., 1812, 40, 3 4 J. Weiger, London J . Arrs, 1845, 26, 398

6 T. Erhard and A. Schertel, Jahr. Berg -U Huttenwes in Sachsen, 1879, 17, 163

7 P. Silow, Z. Physik. Chem., 1889, 3, 605-607 8 F. Doerinckel, Z. anorg. Chem., 1907, 34,

5 A. Cohn, B.P. 144, 119 (1919)

345-349

9 A. T. Grigorjew, Ann. Inst. Platine, 1928, 6,

10 G. H. Johansson and I. 0. Linde, Ann. Phys.,

11 W. Stenzel and J. Weerts, Siebert Festschrift, Hanau, 1931,300-308. Also Z. Metallkunde,

I Z C. G. Wictorin, Ann. Physik., 1938 (v), 33, 509-516

13 C. G. Wictorin, Ivar Hoeggstroms Boktry- cherei, Stockholm, 1947. Also Arkiv. Mat., Asaon. Fysik., 1949, (B), 36, (9)

14 H. Jones, Proc. Phys. SOL, 1937, 49, 243 15 V. A. Nemilow, T. A. Vidusova, A. A.

Rudnitsky and M. M. Putsykina, Izvestia Instituta Platiny, Akad Nauk, S.S.S.R.,

16 G. Grube, A. Schneider and E. Esch, Heraeus Festschrift, 1951, 20-42

17 A. S. Darling, R. A. Mintern and J. C. Chaston, J. Inst. Metals, 1952-53, 81, 125

18 T. J. Tiedema, J. Bouman and W. G. Burgers, Acta Met., 1957, 5, 310-321

19 E. Raub and G. Worwag, Z . Metallkunde,

20 A. K. Gorbatenko and D. S . Kanebetskaya, Zhur. Fiz. Khimii, 1957, 31, (2), 481-484

21 W. Fraenkel and A. Stern, Z. anorg. Chem., 1927, 166, 160-170

22 G. Scatchard and W. J. Hamer, J . Amer. Chem. Sac., 1935, 57, 1805-1809

23 G. Scatchard and W. J. Hamer, J. Amer. Chem. SOL., 1935, 57, 1809-1811

24 H. K. Hardy, Acta Met., 1953, I, 202-209 25 H. K. Hardy, J. Inst. Metals, 1952-53, 81,

26 R. J. Weiss and W. J. Tauer, J. Phys. Chem.

27 L. J. van der Toorn and T. J. Tiedema, Acta

28 G. Borelius, Proc. Phys. SOC., 1937, 49,

29 C. H. Johansson and 0. Hagsten, Ann.

30 G. Borelius, Ann. Physik., 1934, (5) , 20, 57;

184-194

1930, 5, 762-792

1932, 24, 138-141

1946, 20,176

I955J q63 5’3

599-560

Solids, 1958, 7, (2/3), 249-251

Metallurgica, 1960, 8, 711 and 715

Extra Part 77-95

Physik., 1937, v, 28, 520-527

1934, (5)> 20, 650; 1935, (51, 24J 4’9; 1936-37, (5),28,507; 1938, (5h33, 517-531

31 A. Jedele, Z . Electrochem., 1933, 39, 691-695 32 W. Jost, Z . Phys. Chem., 1933, B ~ I , 158 33 A. Bolk, Acta Met., 1958, 6,5942 34 C. Matano, Proc. Phys. Math. SOL. Japan,

35 L. S . Darken, Trans. Amer. Inst. Min. (Metall.)

36 H. Schmid, Metall, 1958, 12, (7% 612-619 37 Johnson Matthey Research Laboratories,

38 R. F. Vines, Platinum Metals and their Alloys,

39 D, B. P. 940,188, Degussa

1933, 15405-6

Engrs., 194% 175, 184

Unpublished data

New York, 1941


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Platinum Mining in Alaska DREDGE AND DRAGLINE OPERATIONS AT GOODNEWS BAY

By Charles Johnston Goodnews Bay Mining Company

The only primary production of platinum metals in the United States occurs on the Bering Sea coast of Alaska. Goodnews Bay indents the mainland coast of western Alaska just south of the mouth of the Kuskokwim River. The Goodnews Bay Mining Company and its predecessor, Northland Development Company, have been mining a placer deposit of platinum metals in this remote area since 1934.

Goodnews Bay, from which the Mining Company derived its name, was originally called Imagpiguak, “Little Ocean”, by the Eskimos. It owes its present name to the

Russian explorers Ustiugof and Korsakcf. In reporting their land expedition of 1818-1819 they called the inlet Dobriek Vestei. Sarichef continued the name in 1826, as did the Frenchman Lutke who came later. However, his use of Bonnes Nouvelles Baie must have been reluctant as he added the disillusioned comment that “Bay of False Reports” would have been more appropriate.

The discovery of platinum in the Goodnews Bay area was made in 1926, when Walter Smith, an Eskimo from the village of Kana- kanagamute on Chagvan Bay, led Henry Wuya, an Eskimo, and Charlie Thorsen, a

The Yuba diesel-electric dredge of the Goodneuis Bay Mining Company. Before dredging can begin each season some eight to ten thousand tons of ice have to be removed from the pond


Goodnettis Bay and the township of Platinum l ie on the coast of Alaska just south of the Kuskokwim River. In this remote and inaccessible region, with only two or three ships calling during the few months in which the Bering Sea is navigable, the mining company maintains a complete and self-

suficient undertaking, the only primary producer of platinum in the United States

white prospector, both from the village of Mumtrak, to a place on Platinum Creek where Smith had earlier panned some of the heavy metal which he termed “black gold”. Thorsen persuaded Joe Jean, the French Canadian trader at Mumtrak, to send a sample of the metal to the College of Mines at Fairbanks for assay, and in the winter of 1927 came confirmation of the fact that the heavy grey metal was platinum.

Hand-mining operations began in the summer of 1927 in the relatively shallow gravels of Clara Creek, Squirrel Creek, Fox Gulch and Platinum Creek. All of these streams are right-limit tributaries of Salmon River, and all cut the eastern flank of Red Mountain, a rust coloured ridge of rock that rises two thousand feet from the Bering Sea.

From 1927 until 1933 hand mining produced a scant 3,000 ounces of crude platinum, or less than 500 ounces a year. As eight or ten individual miners were involved, it was

clear that little profit or progress could be made in developing the deposit.

In 1933 an Anchorage prospector, Walter Culver, obtained leases and options on most of the mining claims in the area, and turned them over in the fall of that year to a group of successful pioneer goldminers headed by Andrew Olson, who with his partners operated the Northland Development Com- pany and Olson & Company in the Flat- Iditarod section of interior Alaska.

In 1934 the Northland Development Company shipped into Goodnews Bay a dragline excavator, trestle sluice box, cater- pillar tractor and the rest of the equipment and supplies necessary to set up a complete and self-sufficient modern mining camp. The boat carrying the equipment from Seattle arrived at Goodnews Bay on July 10th. The equipment and supplies were hauled approximately twenty-five miles around the western flank of Red Mountain and up Salmon River


When a post ofice laas established on the sand spit at the mouth of Goodnews Bay i n 1935 an o@cial name had to be found for the settlement and ‘Platinurn’ was chosen. The photograph shows the post ofice and

the general store

to Squirrel Creek, the mining camp site. Equipment was assembled, buildings completed and mining operations began on August I Ith and have continued without interruption, except for the annual seasonal shutdown, to the present day.

Early in 1935 the Goodnews Bay Mining Company was incorporated under the laws of the Territory of Alaska to consolidate the holdings of the predecessor company in the Goodnews area. This company, with relatively few changes in management and stock ownership, has continued to operate the mine.

From 1934 to 1936, mining was limited to the dragline operation. An intensive drilling and exploration programme in 1934 and 1935 indicated a substantial yardage of deeper ground on Salmon River which provided the

Walter Smith, the Eskimo who discovered the placer deposit of platinum in 1926 while panning f i r gold


The Bucyrus- Erie wafking dragline, with a six-cubic- yard bucket, s t r i p the overbrLrden to permit the dredge to reach bedrock

basis of a $600,000 loan from the Reconstruction Finance Corporation for the purchase of a dredge. In 1937 a Yuba diesel-electric dredge with eight-cubic-foot buckets was purchased, shipped from San Francisco, lightered, hauled to the erection site on Salmon River and assembled. The dredge started digging on November Ioth, perilously close to the date of the usual freeze- up. A benign providence provided mild weather, which not only made possible the completion of the required thirty- day trial run to prove the mechanical performance of the dredge and the platinum values in the ground, but as an added and most welcome bonus, permitted dredging until December 2znd - almost a full month later than dredging has been possible in subsequent years.

The bare factual statements that a mining camp and dragline operation wcre established in 1934 and that a dredge was erected in 1937 are deceptively simple. Because of the isolation of Goodnews Bay and the extremely limited transportation facilities then available, both were substantial undertakings.

In 1934 the present settlement of Platinum consisted of a single log cabin and a few Eskimo sod huts. The log cabin housed the small trading post that had been established the year before. A somewhat larger trading

post was located at Mumtrak at the head of Goodnews Bay, some ten miles from Platinum by boat or native kayak and a longer distance by foot or dogsled in the winter. The next nearest source of supply was Bethel, on the Kuskokwim River and about one hundred and thirty-five air miles from Platinum. Bethel could provide staple groceries, fresh meat, clothing and a few simple hardware items. Some repair parts could be obtained from Anchorage or Fairbanks, five hundred to six hundred miles away by bush plane, but the cost of air freight from this distance was prohibitive for all except the direst emergen- cies. Almost all supplies were shipped by boat from Seattle, a distance of over two thousand miles. During the four summer months - June to September -when the Bering Sea is


open to commercial navigation not more than two or three ships could be expected. In July orders were placed for August shipment for all the equipment and supplies that the mine and the community would require until the following June. As is usual in isolated mines, the problem of ordering for the mine was far more simple than ordering for the community.

In 1934, the first year of operations, the Mining Company produced approximately 2,575 ounces troy of crude platinum; production increased to almost 8,000 ounces in 1935. A production decline in 1936 and 1937 was partly attributable to the preparation for and the erection of the dredge. In 1938, the first full season of operation for both dredge and dragline, production rose to approximately 37,000 ounces.

In subsequent years operating methods

have not changed materially, although a number of mining problems have been met and solved, and several ingenious modifica- tions and additions to equipment have been introduced. The successful solution of mining and mechanical problems in large part has been due to the inventive minds of the two Olson Brothers: Andrew Olson, the President of the Mining Company since its inception, and Edward Olson, Vice-president and General Manager since 1937.

The mining season extends from about May 1st to November 15th each year. How- ever, the first of the crew start work about April Ist, overhauling equipment and pre- paring for mining. Onc of the first tasks each spring is the removal of ice from the dredge pond. The ice, which averages about three feet in thickness, is first cut into blocks roughly

The digging ladder of the dredge carries a line of ninetyfour buckets. each of eight-cubic-feet capacity. The dredge is rapable of digging fifty feet below water leuel to reach the platinum-bearing gravel


Working twenty-four hours a day at a speed of thirty-one buckets a minute, the dredge digs over a million cubic yards of p a y gravel in a mining season to yield about 15,000 ounces of platinum

five feet wide and ten feet long with a power chain saw. The blocks of ice are hoisted from the pond by the dragline and piled on shore. With an average dredge pond surface area of two to two and one-half acres, the weight of ice to be removed is formidable - running from eight to ten thousand tons,

The dragline operation utilised two Bucyrus-Erie machines of a yard and a quarter bucket capacity, bulldozers, and hydraulic water. Sometimes an elevated trestle was used for the sluice boxes; at other times, the boxes were placed on bedrock. The dragline season was shorter than the dredge season, running from May 15th to October 15th~ an average season involving the handling of about 200,ooo cubic yards of gravel and bedrock. Dragline mining operations were discontinued in 1957 when the shallow gravels suitable for this method of mining were exhausted.

The Yuba dredge is capable of digging fifty

feet below pond water level and frequently does so, as the depth of the ground has varied from fifteen to sixty feet. The actual thickness of the pay gravel, lying on a bedrock of altered dunite, serpentine, and some extremely hard sedimentary rock, ranges from two to six feet. The dredge, which originally weighed about fourteen hundred tons, now totals nearly two thousand tons as the result of subsequent equipment additions. The added weight has required the addition of four more pontoons to the original thirty-three pontoons that constitute the steel hull. The digging ladder carries a line of ninety-four buckets, each of eight cubic feet capacity, running at a speed of thirty-one buckets a minute. Working twenty-four hours a day, the dredge has averaged a little over a million cubic yards each mining season.

In recent years the dredge has been operating in deep ground that required the stripping of up to forty feet of overburderl

Platinum Metals Rev., 1962, 6, ( 2 ) 7 3

platinum and some gold with considerable quantities of black sands of magnetite, chromite and ilmenite, are processed further in a cleanup house on shore where they are passed over a four by eight foot Wilfley table. Further concentration is effected after drying by screening and magnetic separation. Finally, air is blown through the concentrates as they drop from a vibrating hopper, the heavier platinum metals falling through the air into a sectionalised box, while the lighter impurities are blown away into different sections. This method has been found successful in yielding a go per cent concentrate.

The crude platinum is shipped in moose-hide or calfskin bags called “pokes” which are double- sacked in canvas and sent by air to Johnson, Matthey & Company, Inc. in New York for weighing and sampling. The crude is then shipped to the J. Bishop & Com- pany plant in Malvern, Pennsyl-

Packing the platinum concentrates into moose-hide bags for despatch to .Johnson, Matthey & Company, Inc. in New York

to permit the dredge to reach bedrock. Stripping this ground was accomplished by a Bucyrus-Erie walking dragline with a six cubic yard bucket.

Material dumped by the dredge buckets into the main hopper feeds through a 7+ foot diameter revolving trommel screen, thirty-six feet long with perforations ranging from # to ; inch in diameter. Undersize material passing through the screen flows on to a bank of tables fitted with rubber covered riffles, from which the major part of the platinum concentrates are recovered. Overflow from the tables passes through a series of jigs, the concentrates from which are collected on expanded metal and coconut matting in a cleanup sluice. Oversize material from the trommel screen discharges on to the 140-foot long stacker belt at the stern end of the dredge.

Dredge concentrates, consisting of crude

vania, for assaying and refining. After refining, the six platinum metals are returned to Johnson, Matthey & Company, Inc. for marketing. Since the discontinuance of the dragline operations in 1957, the dredge has produced an average of IS,M)O troy ounces of crude platinum each season.

An interesting characteristic of the Good- news platinum deposit is the wide variation in the percentage of iridium. Clara Creek, which is the northernmost of the creeks cutting Red Mountain, yielded a crude that contained 4 per cent iridium. The iridium percentage increased progressively in each creek to the south, reaching a high of 33 per cent in Fox Gulch, the southernmost of the creeks cutting the mineralised section of Red Mountain. The Salmon River deposit, which is a mixture of mineral from its northerly right limit tributaries, has averaged an iridium content of 10 per cent over the years.


ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES The Phase Diagram and Properties of Palladium-Iridium-Silver Alloys A. A. RUDNITSKII and V. r. POLYAKOVA, Zhur. Neorg. Khim., 1962, 7, (I), 251-256 The microstructure and properties of the ternary alloys containing up to 50 wt.% Pd were studied and the phase diagram of that part of the system was constructed. Changes in the properties of the alloys in the solid solution region indicate the possibility of ageing. Additions of I wt.% Ag to Pd-Ir alloys impairs their mechanical working. Up to 2 wt.% Ir added to Pd-Ag alloys increases their strength and hardness with practically no change in electrical resistivity and its temperature coefficient.

The Constitution Diagram of the Palladium- Tellurium System

and s. N. ANDREEvA, Zhur. Neorg. Khim., 1961, 6, (71, 1737-1739 The system was investigated by thermal and X-ray analysis, examination of microstructure, and by measurement of microhardness and electrical conductivity. A phase diagram was constructed for the region from o to 80 at.% Pd. The intermediate compounds PdTe, and PdTe melt at 740°C and 720°C, respectively, while Pd,Te, Pd,.,Te, Pd,Te and Pd,Te are formed by peritectic reactions at 590", 760", 820° and -IOOO~C, respectively. In the Te-PdTe, region there are two-phase alloys which form a eutectic at 440°C near pure Te. Alloys representing an uninterrupted series of unstable solid solutions are formed in the PdTe2- PdTe region in the temperature range 64o0-69o0C.

Z. S. MEDVEDEVA, M. A. KLOCHKO, V. G. KUZNETSOV

The Constitution Diagram of the Niobium- Palladium System E. M. SAVITSKII, v. v. BARON and A. N. KHOTINSKAYA, Zhw. Neorg. Khim., 1961, 6, (11), 2603-2605 Physico-chemical analysis methods were used to construct the phase diagram. Two chemical compounds found in the system are: Nb,Pd, with tetragonal crystal structure, which is formed by a peritectic reaction at 1650"C, and the Kurnakov compound, Pd,Nb, which is formed at 1700'C. Nb and Pd are mutually soluble over a wide region in the solid state. Small additions of Nb increase the hardness and strength of Pd alloys and reduce the temperature coefficient of electrical resistivity, but have little effect on the magni- tude of the electrical resistivity.

Phase Relationships in Tantalum-Rich Tan- talum-Ruthenium Alloys at 1500°C C. S. HARTLEY, W. L. BAUN, D. W. FISHER and E. J. RAPPERPORT, Wright Air Development Division Technical Note WADD-TN-60-288, Mar. 1961, 18 pp., PB I71823 Alloys containing 10,20, 30, 40, 45 and 50 at.?* Ru were heat-treated for 168 h at 15oo'C and quenched. The structure and lattice parameters of the alloys were determined. The solubility of Ru in Ta at 1500°C lies between 20 and 30 at.?". An intermediate phase TaRu exists from between 20 and 30 at.% Ru to 48*2 at.O/, Ru. The 50 Ru alloy is two-phase.

The Constitution Diagram of the Ruthenium- Chromium System

Zhur. Neorg. Khim., 1961, 6, (8), 1960-1962 The system was investigated by various methods of physico-chemical analysis and the constitution diagram was constructed. Two peritectic reactions occur: liq. +P*c at 160o0C, and liq. + ofa at 1470°C. The a-phase coincides with the compound Cr,Ru, u represents the solid solution of Ru in Cr, and p represents the solid solution of Cr in Ru. Cr,Ru is formed at low temperatures from a solid solution and a-phase. The solid solubility of Ru in Cr extends from about 42 wt. Ru at room temperature to about 47 wt.So Ru at the melting temperature. Hardness and crystal- lographic data are given for some of the alloys.

The Order-Disorder Transformation in Iron- Cobalt-Palladium Alloys A. T. GRIGOR'EV and v. v. KUPRINA, Zhw, Neorg. Khim., 1961, 6, (8), 1891-1901 Phase changes in Fe-Co-Pd alloys were studied at temperatures below IOOO"C. Alloys in the following sections of the system were studied: Pd,Fe-Coy Pd,Fe-FeCo, PdFe-Co, PdFe-FeCo, and FeCo-Pd. Hardness measurements were made on numerous samples in the annealed and quenched states and electrical resistivity data were also obtained. A ternary phase diagram of the systems investigated is given. The microstructure of various alloys is described.

Nickel-Ruthenium Alloys E. RAUB and D. MENZEL, Z. Metallkunde, 1961, 52, (121, 831-833 The system was studied by thermal analysis and by X-ray and microscopic methods. A peritectic reaction occurs at 1490°C and there is a wide

E. M. SAVITSKII, V. F. TEREKHOVA and N. A. BIRUN,

1


region of solid solution at this temperature. Between 1490°C and 600'C, the solubility of Ru in Ni decreases from 29.7 at.O/, to 3.1 at.?;, and the solubility of Ni in Ru decreases from 48.7 at.o& to 7.2 at.Oo. Hardness increases with increasing Ru content in the Ni-rich solid solution. Alloys with up to 30 Ru are easily worked by cold-rolling and cold-forging.

Mechanism of the Interaction of Oxygen with Surfaces of Noble Metals v. v. ANDREEVA and N. A. SHISHAKOV, J . Appl. Chem., 1961, 11, (IO), 388-389 In this review the nature of the oxide film formed on Pt, Pd, Au and Ag is discussed. In the case of Pt, the formation of Pt,(02)4 on the surface is proposed. (r4 references)

Adsorption Properties of Hydrogen and Oxygen on Platinum Black and Carbon- Supported Platinum from 20 to 300 Degrees Kelvin

Oxygen and hydrogen adsorbed on Pt black were removed by a thermally indicated titration using hydrogen and oxygen, respectively. The cleaned Pt black sintered easily at 7o-10o0C, but the oxygen covered surface showed no sintering at 200°C. Hydrogen chemisorbs on carbon-supported Pt, but chemisorption of oxygen on the same material is not appreciable at 280°K. A carbon-Pt bond which prevents formation of an oxygen-Pt bond is postulated in this latter case.

The Preparation and Some Properties of Platinum Hexafluoride B. WEINSTOCK, J. G. MALM and E. E. WEAVER, 3. Amer. Chem. SOC., 1961,83, ( 2 1 ) ~ 431-4317 PtF, was prepared by burning a Pt wire at about roooT in a fluorine atmosphere and condensing the vapour on a Pyrex flask cooled by liquid nitrogen. Yields of up to 70Yo were obtained. Heats of transition and of fusion were calculated and vapour pressures of the two solid phases were determined. Pt has two triple points, one corresponding to a solid transformation at 3.0"C, and the other to fusion at 61.3"C. The boiling point is 69.14T. PtF, is the most reactive and least stable of the known hexafluorides.

Kurnakov Phases in the Palladium-Silver System E. M. SAVITSKII and N. L. FRAVOVEROV, Russ. J. Inorg. Chem., 1961, 6, (2), 253-254 (Transl. of Zhur. Neorg. Khim., 1961, 6, (2), 499-500) Alloys of the system were examined by thermal analysis, microstructural analysis, hardness and resistivity measurements. The effect of quenching temperature on resistivity was studied. At high temperatures the Pd-Ag alloys are a continuous series of solid solutions. Changes in physical properties with composition of annealed and quen-

R. A. FISHER, Dass. Ah., 1961, 22, (Z), 441

ched alloys indicate the formation of Kurnakov compounds with the compositions Ag,Pd, and AgPd.

The Crystal Structure of Ru,Si B. ARONSSON and J , ASELIUS, Acta Chem. Scand.,

Alloys were prepared by arc-melting or sintering mixtures of pure Ru and Si. The crystal structure was elucidated from single crystal data and unit cell dimensions are a=5.27,8, b=4.005A and c=7.4r8A.

1961, 1.52 (7 )~ 1571-1574

Conductivity and Hall Constant XVI. Solid Solutions of Palladium with (its) Neighbouring Elements in the Periodic System w. KOSTER and D. HAGMANN, Z . Metallkunde, 1961, 5% (II), 721-727 Measurements of susceptibility, electrical resistance, Hall coefficient and thermo-e.m.f. were made on binary alloys of Pd with Ag, Au, Cd, In, Rh, Ru, Mo, Nb and Zr. Small additions of the alloying element result in increases in resistance and the absolute value of the negative Hall coefficient, and, with the exception of Rh, in decreased susceptibility. In some cases the thermo-e.m.f. is increased by these small additions, and in others it is decreased. The changes in resistance, Hall coefficient and susceptibility are explained by the simple band model concept.

XVII. Application of the Two-Band Model to the Electrical Properties of Palladium D. HAGMANN, Ibid., 727735 The parameters for Pd were determined by measurements of electrical resistance, Hall coefficient, susceptibility, thermo-electric power and the Ettinghausen-Nernst coefficient. Data obtained for both bands differ from previous measurements and calculations. These deviations may be due to neglect of interaction of the over- lapping bands in use of the A. H. Wilson formula. The influence of scattering by foreign atoms is shown by alloys.

Surface Tension of Molten Platinum at 1800°C P. KOZAKEVITCH and G. URBAIN, Compt. rend.,

The surface tension, measured by the drop method on an A1 support, was found to be 1699&20 dynes/cm at r8oo"C. The density of Pt at 18oo~C, previously determined, is 18.82&0.02 g1c.c.

The Density of Silver, Copper, Palladium and Platinum in the Liquid State L.-D. LUCAS, Compt. rend., 1961, 253, (22), 2526-2528 Density values were studied as a function of temperature at temperatures above the melting

196r, 253, (20), 2229-2231


point of each metal and the results obtained are shown graphically.

Deviations from Matthiessen's Rule for Platinum P. G. KLEMENS and G. C. LOWENTHAL, Austral. J .

An investigation of the resistivity-temperature relationship of seventeen Pt resistors at temperatures down to 50'K indicates that the observed deviations from Matthiessen's rule may be due to the presence of small concentrations of impurities. Thus the behaviour of a resistor depends on the nature as well as the total amount of impurities and imperfections.

Determination of the Emissivity, for Total Radiation, of Small Diameter Platinum - 10% Rhodium Wires in the Temperature Range 600 - 1450°C D. BRADLEY and A. G. ENTWISTLE, Brit. 3. Appl. Phys., 1961, 12, (12), 708-711 Two lengths of 0.00057 in. diameter 10% rhodium- platinum wire, 1 . 4 2 5 in. and 1.064 in. long, were heated electrically in vacuo. The net rate of radiant energy loss from the wires, and thus the emissivity of the wire, was obtained by measurement ofwire resistance and current. The resistance- temperature relationship was found for wire immersed in a horizontal electric furnace, the tcmperature being measured by a sheathed Pt : 13 yo Rh-Pt thermocouple. Emissivity values are compared with those for pure R.

The Reversible Temperature Coefficient of Remanence of a Pt-Co Permanent Magnet w . L. ZINGERY and T. M. WIRT, Canad. J. Phys.,

50 : 50 at.:/, Pt-Co magnets, operating at a per- meance coefficient of 20, were temperature-cycled five times from 100°C to -60°C. Measurements then made gave a reversible temperature coefficient of --0.042 7 o.

Vapour Pressures of Platinum Metals. 11. Rhodium L. H. DREGER and J. L. WGRAVE,~ . Phys. Chem., 1961, 65, (II), 2106-2107 Values found for the heat of sublimation of Rh at 298°K and for the normal boiling point are 134.2h0.8 Kcallmole and 39oof IOO"K, respectively.

Resistance and Hall Constant. XXI. Gold- Palladium Alloys w . KSSTER and T. HALPERN, Z . Metallkunde, 1961, 52, (12)~ 821-825 The dependence of resistance and Hall coefficient of the alloys on mechanical and thermal pre- treatment was measured. Changes of state were followed by this temperature dependence, and the effective mobility was also calculated. Short-

P~YS~CSJ 1961, 14, (31, 352-358

1961, 39, ( 9 ) ~ 1384-1385

range order resulting from slow cooling or annealing of quenched and deformed samples is associated with an increase of resistance and Hall coefficient. Cold-working causes a decrease in resistance and Hall coefficient. The temperature coefficient of the Hall constant is negative for alloys with 12-95 at.% Pd.

ELECTROCHEMISTRY The Effect of Organic Molecules on the Adsorptive Properties of Platinum Electrodes M. w . BREITER, J . Electrochem. soc., 1962,109, (I),

42-48 Impedance measurements and quasistationary potentiostatic current potential curves were used in the study of the effect of addition of amyl alcohol, caprylic acid and diphenylamine to I M HClO, on the adsorption of hydrogen and oxygcn by a Pt wire electrode. Hydrogen adsorption decreases with increasing amyl alcohol concentration in the potential range +o.r to +0.4 V. In the double layer region, $0.4 to $0.8 V, capacity decreases with increasing amyl alcohol concentration at constant potential. Adsorbed organic molecules are oxidised at potentials at which oxygen is adsorbed simultaneously.

Hydrogen Overvoltage at Cathodes of 77 per cent Palladium and 23 per cent Rhodium J. C. BARTON and P. A. LEWIS, Nature, 1961, 192,

23% Rh-Pd wire cathodes were used in the investigation in which R/Ro (R,=resistance in the hydrogen-free alloy) was recorded and plotted against electrode potential. Measurements were made in 0.002 N and 0.01 N HCI. The electrodes were preactivated by (i) preflaming near white heat, (ii) plating Pd black, or (iii) plating bright Pd.

I I), 549-55O

Performance of Fractional Watt Ion Ex- change Membrane Fuel Cells E. J. CAIRNS, D. L. DOUGLAS and L. w. NIEDRACH, Amer. Inst. Chem. Engrs. J. , 1961~7, (4), 551-558 The performance of about IOO hydrogen-oxygen cells with electrode areas of 11.4 sq. cm was studied. Two basic cell designs, one with a bonded Pt gauze current collector and the other with external collectors in contact with the Pt or Pd catalyst electrode layer, were investigated. Pt, Pd, Ir and Rh are suitable electrode materials for room temperature operation. Characteristic open circuit voltages are 1.07 for Pt and 0.97 for Pd electrodes. The typical current density at 0.5 V is about 30 mA/sq. cm. In the load range 8.5 to 230 ohm/sq. cm at room temperature, about 40 amp-hr.jsq. cm of active area may be expected before failure due to pinhole formation in the resin electrolyte. In the temperature range on to 85"C, cell performance shows a maximum at 55°C.


ELECTRODEPOSITION The Electrodeposition of Iridium E. L. MaCNAMAFL4, 3. Electrochem. soc., 1962,

Deposits of Ir were obtained from an aqueous solution of chloriridic acid throughout a concentration range of 1-120 g Ir/l and a current density range of 2.2 - 10.8 amp/dm2. The deposition is temperature dependent, and, depending on the temperature, the appearance of the deposits is markedly affected by the current density. Optimum operating conditions were found to be: metal concentration, 10 g/l; bath temperature, 60°C; current density, 6.6 amp/dm2; pH, approximately 2. These conditions produce a cathode efficiency of 6%, while decreasing the current density to 2.2 amp/dma increases it to 14"~. Deposits may also be obtained from sodium and potassium chloroiri- dates and bromoiridates. A Pt anode-& cathode system was used predominantly in the experimental work.

Io9J (I), 61-63

Palladium Plating J . E. FHILFOTT, Electroplating 69 Metal Finishing,

The properties of Pd electrodeposits obtained from a tetrammino palladium nitrate bath are described. Details are given of hardness, specific gravity, specific resistance, electrical and thermal conductivity, and thermal e.m.f. against Pt.

1962, 1.5, (I), 20

Rhodium Plating Thickness Measurements L. MAISEL, Metal Finishing, 1961, 59, (12), 50-52, 56 Methods of measurement at present used depend on metallographic mounting of a plated sample or on determination of the cathode efficiency of the plating bath at the operating current density. Suggested methods involve the use of eddy currents, X-ray fluorescence, or radioisotopes (20 references)

LABORATORY APPARATUS AND TECHNIQUE A Hot-Stage Petrographic Microscope for Glass Research T. w. B R O C K , ~ . Amer. Chem. Soc., 1962, 45, (I),

5 7 The construction and operation of the microscope are described in detail. The magnification is x 70 and the maximum operating temperature is 2000'F. Two pieces of 10% Rh-Pt foil welded at two opposite ends to toy& Rh-Pt bars form the heating element which is suspended within a carbon block on the microscope stage. The instrument is of particular value in the measurement of glass crystal growth rates.

CATALYSIS

Studies on the Silk-Platinum Catalyst. I. Its Preparation and Activity A. AKAMATSU, Y. IZUMI and s. AKABORI, Bull. Chem. SOC. Japan, 1961, 34, (8), 1067-1072 A silk-Pt chelate was prepared by boiling silk fibroin with an aqueous 0.75"'; K,PtCI, solution for 14 to 20 min. The most active catalyst was obtained by reduction of the chelate in IO/O

CH,COOH with 90 kg/cm* of hydrogen at 160°C. Activity is affected by the solvent, temperature and time of activation. The catalyst may be stored in the dry state for several weeks without loss of activity. In the hydrogenation of C,H,NO,, the catalyst is about 250 times as active as a PtO, catalyst with the same Pt content.

11. General Properties

The catalyst was found to be less active in the hydrogenation of some aldehydes, unconjugated aliphatic ketones, C=C double bonds, and aliphatic nitro groups than in the hydrogenation of aromatic nitro groups. It is poisoned by CO, benzyl mercaptan, and the cupric ion. Differences in the behaviour of the catalyst from that of other Pt catalysts are attributed to the spacing of the active centres due to the structure of the silk fibroin protein.

Ibid., 1302-1306


Catalysis of the Hydration of Acetylenie Compoiinds by Ruthenium (111) Chloride J. HALPERN, B. R. JAMES and A. L. W. KEMP, 7. Amer. Chem. SOC., 1961, 83, (IS), 4097-4098 An aqueous Ru(II1) chloride solution was used to catalyse the hydration of C,H, and several mono- and di- substituted acetylenes under mild conditions. The rate law for the conversion of C,H,to CH,CHOis -d[C,H,]/dt-k[C,H,][Ru (III)]. k varies with HCl concentration, showing a maximum value at about 4 M HCI, and depends on C1- concentration. A reaction mechanism involving the formation of an intermediate r-complex is proposed.

Reactions of Cyclanes and Alkanes in the Presence of Metals of Group VIII of the Periodic System under Hydrogen Pressure N. I. SHUIKIN, Ind. 3. Appl. Chem., 1961, 24, (I),

7-13 A study was made of the performance of supported Pt, Pd, Rh and Ru catalysts in the conversion of the ethylcyclopentane, methylcyclohexane and n-heptane constituents of the methylcyclohexane fraction of straight-run gasolines. A1,0, and SiO, gel were used as catalyst supports. Experiments were carried out at 460°C and 20 a m hydrogen pressure with rapid flow rates and a 1:5 molal hydrocarbon-hydrogen ratio. The products of the processes of aromatisation, isomerisation and

hydrogenolysis were analysed and the properties of the various catalysts was compared. It is concluded that under these conditions the direc- tion of the reactions may be influenced by the choice of catalyst.

Valence State of Platinum/Alumina Catalysts R. J. BERTOLACINI, Nature, 1961, 192, (Dec. 23), 1179-1180 Ultra-violet and reflectance spectrophotometric measurements made on Pt/A1,0, catalysts indicated that Pt in the soluble form is present in the octahedral plus-four valence state.

Isotope Exchange between Hydrogen and Liquid Ammonia in the Presence of Platinum Catalysts R. HAUL and D. BLENNEMANN, Naturwiss., 1961, 48, @o), 644 PtiC and PtlSiO, catalysts were used in experiments to measure the exchange velocity. Measure- ments were made in the temperature range -7oT to + 2 5 T and at hydrogen pressures up to 150 atm. Results obtained were compared with those obtained in the gaseous state.

Catalytic Exchange of n-Hexane and Deuter- ium and Some Allied Reactions on Films of Palladium and Rhodium F. G. GAULT and c. KEMBALL, Trans. Faraday SOC.,

Mass spectrometric analysis was used to study the exchange of deuterium with C,H,, n-C,H,, and n-C6HI4 on Pd films and with n-C6HI4 on Rh films. It is suggested that =By- triadsorbed alkanes, in addition to monoadsorbed and uf3- diadsorbed species, are involved as intermediates in the mechanism. An alternative mechanism of exchange on Rh involves the direct formation of diadsorbed hexane. Self-poisioning of the exchange by dissociated hydrocarbons occurs above 100°C on Pd, and at 0°C or above on Rh. Both oxygen and diethyl ether poison the exchange reactions on Pd and Rh. The experimental results are discussed in detail.

1961, 57, (Io), 178r-1794

Oxidation of Olefins with Palladium Chloride Catalysts J. SMIDT, Chem. G. Id , 1962, (Jan. 13), 54-61 The history of the discovery of the reaction: CzH4 +PdCl,+H,O +C,H40 +Pd+2HClis outlined. Complex formation and complex hydrolysis, the two main steps of the reaction, are discussed. Their mechanism involves the formation of a x-complex between the olefin and PdCl,. Non- oxidative reactions between Pd salts and unsaturated compounds, including transesterification and saponification, are also described. For the continuous direct oxidation of olefins to carbonyl compounds, CuC1, is added to the PdC1, to accelerate the reoxidation of the precipitated Pd. In the continuous oxidation of C,H4 either a one-

step or a two-step process may be carried out. The commercial application of the two-step process is described.

The Role of Supports in Catalytic Hydro- genation. Part I. Activation Effects of Various Oxide Carriers on Palladium E. B. -TED and s. I. ALI, J . Chem. Soc., 1961,

A study was made of the activation effects of ZrO,, Tho, , Also3, TiO,, Cr,03, MgO, and V a 0 5 as supports for 6 mg Pd in the hydrogenation of I ml cyclohexene in alcohol at 20°C. In all cases the activity of the supported catalysts increases to a maximum and subsequently falls as the amount of the support is increased. The peak activities occur at different catalyst : support ratio for each support and vary for different specimens of the same support. Surface areas and total pore volumes of the oxide supports were measured.

Part 11. Further Effects of Various Oxide Supports on the Activity of Platinum E. B. MAXTED and J. s. ELKINS, J . Chem. SOC., 1961, (Dec.), 5086-5090 Catalysts consisting of 6.25 mg Pt supported on various amounts of A1,0,, ZrO,, and Cr,O, were used in the liquid-phase hydrogenation of I ml cyclohexene (or 1.5 ml. ethyl crotonate) dissolved in C,H,OH. ZrO, and fine-grained A1,0, were the most active supports tested. Specific surface areas and micropore volumes were measured for the supports. It is concluded that the observed difference in activity for the hydrogenation of cyclohexene and ethyl crotonate is dependent on the mean pore radius of the support. The relative surface areas of the supported Pt were determined by a poisoning method.

Azomethme Chemistry. I. Formation of Optically Active a-Amino Acids by Asym- metric Induction R. G. HISKEY and R. c. NORTHROP,?. Amer. Chem.

I O : ~ PdjC or Pd(OH),/C catalysts were used in the hydrogenation of four u-keto acids in the presence of D-( +)- and L-( -)-a-methylbenzyl- amine. The corrosponding optically active a- amino acids were obtained.

(Septa), 4137-4140

SOC., 1961, 83, (231, 4798-4800

Rhodium-Platinum Oxide as a Catalyst for the Hydrogenation of Organic Compounds 11. Catalyst Preparation and Effects of Platinum in Rhodium-Platinum Oxide s. NISHIMURA, Bull. Chem. SOC. Japan, 1961, 34,

The Rh-Pt ( 7 3 oxide is prepared by fusing a mixture of the chlorides of the metals corresponding to 0.30 g Rh and 0.13 g Pt with 20 g NaNO,, raising the temperature of the mixture to 460-480°C for 10 min, and leaching the cooled melt with distilled H,O. The resulting

(10), 1544-2545


Rh-Pt oxide is washed with 0.5:; NaNO, solution and dried over CaCI,. The activity and selectivity of Rh-Pt oxide catalysts of various compositions was studied in the hydrogenation of toluene and acetophenone and results are shown in a table. Catalysts containing 70 to 90% Rh are the most active and selective.

The Stereochemistry of the Addition of Silicochloroform to Acteylenes. A Compari- son of Catalyst Systems R. A. BENKESER, M. L. BURROUS, L. E. NELSON and J. v. SWISHER~J. Amm. Chem. Soc., 1961, 83, (zI), 4385-4389 The addition of SiHCl, to I-pentyne, I-hexyne, 1-heptyne, 3-methyl-1-butyneY and 3, j-dimethyl- 1-butyne was studied in the presence of Pt/C, H,PtCl,, and benzoyl peroxide catalysts. With both Pt/C and H,PtCI,, and benzoyl peroxide catalysts. With both Pt /C and H,PtCl,, stereo- selective cis additions result in the formation of trans products. It is suggested that the H,PtCl, is reduced by the SiHC1, to a black solid which is the active catalyst. A trans addition occurred in the presence of benzoyl peroxide with four of the acetylenes. In the case of 3, 3-dimethyl-1-butyne~ a mixture of cis-trans adducts, with the trans isomer predominating, and a diadduct were formed.

Methods for the Oxidation of Propylene P. w. SHERWOOD, Brennstoff-Chem., 1961,42, (12), 375-377 Industrial processes for the preparation of acrolein, acetone, propylene oxide and acrylonitrile are described. A PdCl, oxidation catalyst is suggested for the oxidation of propylene according to the reaction: C,H, +PdCl, TH,O-+CH,-C-CH, 4 Pd +2HC1.

Review of Recent U.S.A. Patents on Catalysts E. SOLOMON and P. A. LEPRANCOIS, Wmld Petroleum,

Seventy-five catalyst patents are discussed in this review, which deals with various aspects of petroleum refining. The processes concerned are those of reforming, dehydrogenation, cracking, hydro- cracking, hydrotreating, isomerisation, polymerisation, alkylation, and oxidation. Both Pt metal and base metal catalysts are discussed.

Denmark's First Major Refinery

1962, 333 (I), 42-44

S. ROWBOTTOM and E. D. QUINEY, Wmld Petroleum, 1962, 33, (Ih46-49 Details of the construction of the 20,000 b/sd Dansk-Veedol Kalundborg refinery are given. The process units are an atmospheric crude distillation unit, a vacuum distillation unit, gasoline and kerosene treating units, a naphtha hydrodesulphuriser and a Platformer, a vacuum gas-oil hydrodesulphuriser, and gas recovery and LPG facilities.

The Kinetics of Sintering of Platinum Supported on Alumina R. A. HERRMANN, s. F. ADLER, M. s. GOLDSTEIN and

2189-2 194 Pt/Al,O&l catalyst samples were heat-treated in air for I h at 593°C and then heat-treated at 564"C, 594°C and 625°C for various lengths of time up to 353 h. Fresh and heat-treated samples were examined by hydrogen chemisorption and X-ray line broadening techniques and by measurement of Pt solubility in HF. Results obtained for the chemisorptive capacity for hydrogen, rate of hydrogen chemisorption and Pt crystallite size are given. These indicate that Pt in the original catalyst is in a highly dispersed form and that the formation of Pt crystallites is a result of heat treatment.

The Deurag-Nerag Oil Refinery at Misburg near Hanover H. WELLER, Erdol u.-Kohle, 1961,14, (IO), 821-823 The development of the refinery since I931 is described. The various units are described and a flow sheet of the refining processes is given. New units completed in 1961 include a Unifineri Platformer and a top-cracking plant.

Catalytic Decomposition of Nitric Oxide

CORCORAN, Amer. Inst. Chem. Engrs. J., 1961, 7, (411 658-663 An Al,03-supported catalyst containing 0.176 Pt and 3.094 Ni as the oxides was used in the study of the decomposition of NO in a stainless steel tubular flow reactor. The NO concentration in nitrogen was 0.404 or 0.432 vol.";. Pressures of I to 15 atm and temperatures in the range 800" to ~ooo"F were used. The decomposition rate was found to be second order with respect to NO, and retarded by atomic oxygen and excess nitrogen in the system. A reaction mechanism is proposed.

Platinum/Charcoal Catalysts

274-27s The activity of various Pt catalysts supported on birch charcoal in the dehydrocyclisation of iso- octane to I, I, 3-trimethylcyclopentane is compared with that of Pt/AI,O,, Pt/C/AI,O,, Pt/SiO, and Pt/C/SiO, catalysts.

Kinetics of the Platinum-Catalysed Hydro- gen Reduction of Aqueous Cobalt Sulphate- Ammonium Acetate Solutions K. T. WIMBER and M. E. WADSWORTH, Trans. Met. SOL. A.Z.M.E., 1961, 221, (6), 1141-1148 The solutions containing H,PtCI, were reduced by hydrogen in a Pyrex-lined autoclave in the temperature range 170°-2320c and in the hydrogen partial pressure range 115-830 p.s.i.a. The reduction rate is independent of the amount of

R. M. DE BAUN,J. Phys. Chem., 1961, 65, (IZ),

R. R. SAKAIDA, R. G. RINKER, Y. L. WANG and W. H.

K.-H. SCHNABEL, 2. Chem. (Leipzig), 1961, I, (9),


H,PtC& added initially and directly proportional to the hydrogen partial pressure and surface area of the Pyrex glass exposed to the solution. It is suggested that the reducible Co complex is Probably Co(C,HsOJz.4Hz0. The role of the Pt catalyst is discussed.

Reductiolls with Ruthenium. 11. Its Use in the Hydrogenation of Pyridines M. FREIFELDER and G. R. STONE, J . Org. Chem., 1961, 26, (Io), 3805-3808 Abstract in Platinum Metals Review, 1961, 5, (3)~ 115

Hydrogenation of Substituted Pyridines with Rhodium on Carbon Catalyst

J. Org. Chem., 1962, 27, (I), 284-286 Abstract in Platinum Metals Review, 1962,6, (I), 36

The Effect of the Method of Preparation of Platinised Charcoal on its Activity in C,- Dehydrocyclisation of Paraffins and Dehydro- genation of Cyclohexane Hydrocarbons. 11. Effect of Conditions during Reduction of Platinum

KAZANSKII, Kitletika i Kataliz, 1961,2, (4)) 547-552 The effect of various reagents (formalin, KOH) used in the preparation of platinised charcoal on its activity was studied and the existence of an activity optimum for each reagent was established. Small amounts of KOH activate the catalyst in C,-dehydrocyclisation, but deactivate it when added in larger quantities. Additions of KOH deactivate the platinised charcoal in reactions for the expansion of 5-membered rings. The results obtained indicate that C,-dehydrocyclisation of paraffins and expansion of 5-membered rings take place on different active centres.

The Effect of y-Irradiation on the Activity of Platinum-Containing Catalysts KH. M. MINACHN and YU. s. KHODAKOV, Izvest. Akad. Nauk. S.S.S.R., Otdel. Khim. Nauk, 1961, (Q 1430-1432 IO: Pt/A1,0, and IO"$ Pt/Al,O, catalysts were subjected to *{-irradiation before use in the decomposition of HzO, solution. It was found that the decrease in catalytic activity resulting from y-irradiation increased with the amount of Pt present in the catalyst. A IO, Pt/A1,0, catalyst which had been roasted at 1000-1050°C for 10 h did not show any change in activity after y- irradiation.

The Effect of Sulphur on the Activity and Selectivity of Platinum Reforming Catalysts N. R. BURSIAN and G. N. MASLYANSKII, Khim. a' Tekhnol. Topliv i Masel, 1961, (Io), 6-9 The investigation was carried out at a Pressure of 40 atm using an 8oo-18o3 straight distilled benzine

M. FREIFELDER, R. M. KOBINSON and G. R. STONE,

A. L. LIBERMAN, K.-KH. SHNBEL' and B. A.

fraction which contained 0.01 to 0.27% S. It was shown that an increase in the amount of S in the raw material results in increased deactivation of the catalyst and in decreases in the yield of aromatic hydrocarbons and hydrogen and in the octane rating of the gasoline produced. Removal of H2S from the circulating gases increases the stability ofthe Pt catalyst in the reforming process.

GLASS TECHNOLOGY World's Largest Direct Melt Fibre Glass Plant

4 - 5 0 The equipment and operating procedures of the Pittsburgh Plate Glass plant at Shelby, N.C., is described and illustrated by fifteen photographs. Twenty-four continuous-melting furnaces each contain fourteen Pt bushings. The bushings have 200-400 orifices, the diameter of which is controlled to withinfo.00025 in. in their forming by the use of binocular microscopes. An elaborate electronic system is used to control the orifice size, orifice temperature and speed of fibre drawing.

Further Studies of the Crystallisatinn of a Lithium Silicate Glass

G. L. VINCENT, Ceramic Industry, 1961, 77, (I),

G. E. RINDONE, J. Amer. Ceram. S O L . , 1962, 45, (J), 7-12 Beads of a Liz0.4Si02 glass with varying concentrations of Pt were reheated at 600°C and 650'C and rates of crystallisation of Li,0.zSi02 were determined. Maximum crystallisation occurs with about 0 . 0 0 5 ~ ~ Pt at both temperatures. The addition of 0.005O:, Pt lowers the activation energy for crystallisation from 120 kcal :mole without Pt to 50 kca1:mole. Li-rich clusters in the glass 25oa in size increase up to SOOA in the presence of Pt nuclei. A silica 0 phase is present in glasses containing 0 . 0 2 5 ~ ~ Pt. The effectiveness of Pt as a nucleating agent in Li,0.qSi02 glass is discussed.

TEMPERATURE MEASUREMENT Temperature Measurement with Resistance Thermometers K. H. CLEMENS, Angew. Mess- u. Regeltechnik, 1962, 2, (I), a1-a2 (Sprechsaal, 1962, 95, (I)) The use of Pt, Ni and some semi-conductor materials in resistance thermometry is described. Pt is recommended for measurements in the temperature range -220' to 7 5 0 T and Ni for the range -60" to 180°C.

Temperature Measurement K. H. CLEMENS, Angew. Mess- u. Regeltechnik, 1961, I, (I), a1-a6 (Sprechsaal, 1961, 94, (20)) Physical phenomena upon which methods of


temperature measurement depend are described briefly, The principles underlying the operation of thermocouples and the range of some common base metal and Pt metal thermocouple combina- tions are discussed. Among the other topics couples.

discussed are the insulation and protection of thermocouple wires by ceramic materials and metal sheaths, the measurement of thermal e.m.f., errors of measurement, and calibration of thermo-

NEW PATENTS Titanium Alloys UNION CARBIDE COW. British Patent 882,184 A titanium alloy capable of withstanding the corrosive action of non-oxidising acid contains 5o0& or more of titanium, a total of 0.005-5’b by wt. of one or more of gold, rhenium and a platinum group metal and balance titanium alone or an alloy thereof with molybdenum or manganese or with aluminium and vanadium.

Non-emissive Electrode “PATELHOLD” PATENTVERWERTUNGS~ ELEKTRO- HOLDING A.G. British Patent 882,480 A non-emissive electrode for electric discharge vessels has at least part of its surface covered first with a layer of rhenium and then with a layer of a platinum group metal, both layers being of a thickness of about I F. The layers may be applied electrolytically to a core of tungsten, molybdenum, tantalum, indium, zirconium or hafnium.

Treatment of Gases ENGELHARD INDUSTRIES INC. British Patent 882,536 The preferential oxidation of carbon monoxide mixed with a hydrogen-containing gas is effected by first adding water to the gaseous mixture of carbon monoxide, hydrogen, nitrogen and carbon dioxide, and then air sufficient to provide an oxygen to CO volume ratio of 3 : I to 0.25 : I . The resulting mixture is then passed over a supported platinum catalyst at elevated temperature to convert the CO to CO,.

Preparation of Cyclohexylsulphamic Acid ABBOTT LABORATORIES British Patent 882,752 In the preparation of cyclohexylsulphamic acid and physiologically acceptable salts thereof, phenylsulphamic acid and salts thereof are hydrogenated in the presence of a catalytic amount of rhodium; 59C rhodium on alumina may be used,

Purification of Waste Gases

Waste gases containing free oxygen and oxides of nitrogen are purified by the combustion of the gases and a gaseous fuel in a first reaction zone (less than the stoichiometric amount of fuel for complete reaction being used) and in the presence of a platinum group metal - containing catalyst, cooling of the effluent gases and then the com-

ENGELHARD INDUSTRIES INC. British Patent 883,944


bustion, in a second reaction zone, of a mixture of these gases and additional gaseous fuel also in the presence of a similar catalyst. The catalyst is preferably palladium and the fuel methane or natural gas. Inlet temperature in each zone is 200-900°C.

Removal of Free Oxygen and Reduction of Oxides of Nitrogen in Waste Gases ENGELHARD INDUSTRIES INC. British Patent 883,945 Free oxygen is removed from waste gases, and the oxides of nitrogen therein reduced, by contacting a mixture of the gases and a fuel gas containing saturated and unsaturated hydrocarbons and COS, CS, and/or H,S with a palladium, platinum, rhodium or ruthenium catalyst. Palladium or platinum, supported on a carrier, is preferably used. Inlet temperature of the gases to the catalyst is 400r-900@F.

Selective Reduction Reactions of Oxide- containing Gases ENGELHARD INDUSTRIES INC. British Patent 883,946 Selective reduction reactions of gases containing oxides of nitrogen and free oxygen are effected by combustion in a reaction zone of a mixture of the gases and ammonia in contact with a platinum group metal catalyst to reduce the oxides of nitrogen. The catalyst is preferably palladium, rhodium, ruthenium or platinum deposited on a carrier. The reaction is carried out at 150-400“C.

Acetylene Transition Metal Carbonyl Deri- vatives UNION CARBIDE CORP. British Patent 885,514 A stable organo-metallic carbonyl reaction product is formed by heating in a non-aqueous medium a transition metal carbonyl, e.g. ruthenium, rhodium, palladium, osmium or iridium with an acetylenic compound at a suitable temperature.

Anodes for Electrolytic Cells IMPERIAL CHEMICAL INDUSTRIES LTD. British Patent 885,817 An anode is formed of a foraminate titanium metal sheet wholly or partly covered with a platinum metal or an alloy of two or more such metals. Expanded titanium metal sheet is preferably used with platinum or rhodium.

Treatment of Brine Solutions

885,818 IMPERIAL CHEMICAL INDUSTRIES LTD. British Patent

Discloses a method for the treatment of brine solutions using an anode of No. 885,8r7 above.

Production of Assemblies Comprising Titanium IMPERIAL CHEMICAL INDUSTRIES LTD. British Patent 885,819 A coating of platinum on titanium, e.g. in production of anodes, is obtained by superimposing a number of coatings of a platinum-bearing preparation and then heating to at least g o o T the titanium base having first been treated to remove therefrom the surface skin, chiefly oxide.

Catalyst Composition UNIVERSAL OIL PRODUCTS CO. British Patent 885,886 A catalyst having cracking and hydrogenating activity is formed of a calcined composite of a hydrogenating metal from groups V to VIII and an inorganic base containing 95-20~" by wt. of a refractory oxide and 5-8oo& by wt. of boron phosphate. The metal component constitutes at least 4oa0 by wt. of the composite. Platinum is the preferred metal.

Manufacture of Aldehydes

G.m.b.H. British Patent 886,157 Aldehydes or ketones are made by treating one or more olefinically unsaturated hydrocarbons with an aqueous solution of a platinum group metal compound at 0-250-C and recovering the carbonyl compound so formed. A halide of palladium or platinum is used.

Reforming of Hydrocarbons SOCONY MOBIL OIL co. LTD. British Patent 886,280 Gasolines of at least IOO octane rating are produced by contacting a naphtha, boiling in the gasoline range, or a fraction thereof (octane rating of naphtha being 81-98) in a low-pressure reactor stage at a pressure of less than 35.2 kg/sq. cm gauge with a platinum or platinum-type reforming catalyst in the presence of hydrogen and under reforming conditions of temperature and space velocity.

Selective Hydrogenation of Fatty Oils

Unsaturated fatty oils are hydrogenated by treatment with hydrogen in the presence of a catalyst consisting of supported palladium metal modified by a compound of mercury, silver, bismuth or copper.

Brazing Compositions THE INTERNATIONAL NICKEL CO. (MOND) LTD. British Parent 886,591 -4 brazing filler composition contains 35-65 O 0

CONSORTIUM M R ELEKTROCHEMISCHE INDUSTRIE

ENGELHARD INDUSTRIES INC. British Patent 886,477

palladium, 0.05-1 "/o lithium, 0.002- 0.2:& boron, and balance of at least 24O,, nickel and/or cobalt. Up to 40% chromium, up to 1.50tb alumium, up to 0.50; carbon, up to 0.3ud manganese, up to 0.3 "/o silicon, up to 20 yo copper, up to 5 9 " silver, up to 0.5% niobium and up to 1.51, titanium may be included.

Catalytic Reduction of Tail Gases JOHNSON, MATTHEY & co. LTD. British Patent 886,651 Catalyst elements used for the reduction of nitrogen oxide-containing effluent or tail gas are formed of a platinum group metal supported on a non-spherical solid or hollow-shaped ceramic carrier having a large surface area-to-bulk ratio. Platinised Raschig rings may be used.

Polymerisation of Unsaturated Compounds

c.m.b.H. British Patent 887,362 Compounds containing an unsaturated carbon- carbon bond are polymerised in the presence of a chloride or bromide of platinum or palladium, or a complex thereof, as catalyst in a non-basic or reducing medium at a temperature of j0-170@C and a pressure of from atmosphcric to 30 atm.

Activation of Platinum Group Metal Catalysts BERGWEXKSGES. HIBERNIA A.G. German Patent 1,100,600 Platinum group metal catalysts are activated by contacting them with small amounts of dust of platinum group metals already used for catalytic purposcs.

Production of Platinum-Rhodium Alloy Articles, such as Spinnerets fur Glass ENGELHARD INDUSTRIES INC. German Patent 1,106,577 In the manufacture of articles of a platinum- rhodium alloy, particularly apparatus for treatment of molten glass, such as spinnerets, a base of such an alloy is coated with first platinum and then with gold, the article then being heated to diffusion temperature to ensure the firm adherence of the coatings to one another and to the base.

Use of Platinum-Gold Alloys for Spinnerets

German Patent 1,106,966 An alloy of II-~zO,, platinum, about 0.3-1.5',, preferably 0.4-0.6~,, rhodium and rhenium and balance gold is used for making spinnerets for the viscose process.

Hydroforming Process ESSO RESEARCH & EKGINEERING CO. U.S . Paten?

Hydrocarbon fractions boiling in the naphtha boiling range are reformed by contacting naphtha

CONSORTIUM FUR ELECTROCHEMISCHE INDUSTRIE

DEUTSCHE GOLD-UND SILBER-SCHEIDEANSTALT

3,002,920


vapours mixed with hydrogen at 800-1000°F and pressures of 100-1000 p.s.i.g. with a catalyst consisting of 0.01-5 wt.% of a platinum group metal, combined with 0.05-5 wt.7; of zirconia, supported on an adsorptive alumina carrier. Carbonaceous deposits are periodically burned from the catalyst by contacting it with oxygen at elevated temperatures.

Hydroforming Catalyst ESSO RESEARCH & ENGINEERING c o . U.S. Patent

Hydrocarbons boiling in the naphtha boiling range are reformed by contacting the naphtha vapours at 800-1ooo"F and pressures of IOO-IOOO p.s,i.g. m t h a catalyst composed of 0.01-5 wt.?: of a platinum group metal combined with 0.1-5 Wt.Oo of praseodymium oxide, supported on an adsorptive alumina carrier and in the presence of 2ooo-10,000 cfjb of hydrogen for a period long enough to improve the octane number of the naphtha.

Catalyst Manufacture UNIVERSAL OIL PRODUCTS co. U S . Patent 3,003,972 A catalyst is made by impregnating alumina containing over by wt. of combined fluorine with a homogeneous aqueous solution of a water- soluble platinum compound, a hydrogen halide and an acid compound (nitric, sulphuric, phos- phoric, acetic, oxalic, formic or propionic acid or aluminium nitrate). pH of solution is below 2.5.

Catalyst UNIVERSAL OIL PRODUCTS co. U.S. Patent 3,003,973 A catalyst is made by mixing alumina, a water- soluble platinum compound and hydrogen peroxide with ammonium hydroxide at below 212OF heating the mixture to over 212'F and adding ammonium nitrate when the temperature reaches Z I Z O F , then drying and calcining.

Rhodium Plating BELL TELEPHONE LABORATORIES INC. US. Patent

A base material containing 18-100 wt.O, iron is rhodium plated by first electrodepositing a continuous rhodium layer of 0.5 - 3.5 mgpq. in. directly on to the base, heating the base to cause diffusion of rhodium into the material and then electroplating a second rhodium layer thereon.

3,002,921

3,007855

Decarbonylation of Furfural E.I. DU PONT DE NEMOURS & c o . US. Patent

Furan is made from furfural by heating a liquid phase of furfural in the presence of palladium metal and a basic salt of an alkali metal.

Thermocouple System GENERAL ELECTRIC c o . U.S. Patent 3,007,988 A high temperature thermocouple system includes

3,00?,941

one thermoelectric conductor of palladium and the other an alloy of platinum and 15% iridium, the lead conductors being formed of a 4.3% silicon-nickel alloy and a 60°4 nickel, 15% chromium and 22% iron alloy.

Thermocouple GENERAL ELECTRIC co. U.S. Patent 3,007,990 The first and second thermoelectric elements of a thermocouple for measuring fluid temperature are formed respectively of palladium and a 1.5% iridium-platinum alloy.

Dehydrogenation of Nitrogen Heterocyclics

Pyrrole and N-substituted pyrroles are produced from pyrrolidine and N-substituted homologues of pyrrolidine by passing the compounds at 175'-350"C over a catalyst of alumina (surface area of 35-350 sq. mig) and 0.1"~ by wt. of palladium chloride.

Production of Hydroxylamine BADISCHE ANILIN-& SODA-FABRIK A.G. U.S. Parent 3>009>779 Hydroxylamine is produced by catalytic reduction of nitric oxide with hydrogen in dilute acid medium using a catalyst, in the acid medium, composed of a noble metal alloy of platinum and I - I O O ~ bywt. ofanoblemetalother thanplarinum.

ANSUL CHEMICAL CO. U.S. Patent 3,008,965

Making Carvomenthene Oxide FOOD MACHINERY & CHEMICAL CORP. U.S. Patent 3>014J929 Carvomenthene oxide is prepared by reacting limonene monoxide with hydrogen at a hydrogen pressure of 1-15 atm and at 25-45"c in the presence of an inert solvent and in the presence of a platinum-containing catalyst for 2.0 min. to z hr. until I mole of hydrogen per mole of limonene has been reacted with the monoxide.

Hydrogenation of Phenyl- Alkyl-P-Amines ABBOTT LABORATORIES INC. U.S. Patent 3,014,966 Cyclohexylalkyl- p-amines of specified general formula are made by hydrogenating the corresponding phenyl-alkyl-P-amines at a pressure of 1000-13oop.s.i. andat a temperature of 6oo-16o0C in the presence of a catalyst of ruthenium or ruthenium dioxide supported on a carrier, until the reaction is complete and then filtering and separating the amines from the catalyst.

Resistor TECHNOLOGY INSTRUMENT CORP. U.S. Patent 31015,587 An electrical resistor element is made by depositing on a rigid electrically insulating substrate a thin film comprising rhodium and germanium in predetermined relative amounts and then heat-treating the film and substrate at elevated temperature for a long period.


PLATINUM METALS REVIEW · pressure an orange peel effect tends to develop ... By the accurate addition of minor quanti- ties of other noble metals to platinum it is possible to produce

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