The Homogeneous Hydrogenation of Soybean Oil Methyl Ester

PLATINUM METALS REVIEW 

A quurterly survey of reseurch on the platinum metuls urrd of 

dwelopments in their applications in industry 

VOL. 15 JANUARY 1971 NO. 1 

Contents 

The Homogeneous Hydrogenation of Soybean Oil Methyl Ester 

Further Advances in Catalytic Hydrogenation 

The Control of Air Pollution 

Platinum and the Refractory Oxides 

Monolithic Multilayer Ceramic Capacitors for Hybrid Circuits 

Zerovalent Complexes of Platinum 

The Form of the Interaction between Palladium and Hydrogen 

Cubane-type Platinum Metal Complexes 

A New Mining Area for Rustenburg 

Abstracts 

New Patents 

Communications should be addressed to 

The Editor, Platinum Metals Review 

Johnson, h’latthey & Co Limited, Hatton Garden, London EClP 1AE 

2 

8 

9 

13 

19 

20 

21 

25 

26 

29 

35

The Homogeneous Hydrogenation 

of Soybean Oil Methyl Ester 

SELECTIVITY OF PLATINUM AND PALLADIUM COMPLEXES 

By Johii C. Bailar, .Jr. 

University of Illinois 

The so?bean, a major crop in the 

LTnited States as zuell as in China and 

Brazil, yields an oil used widel?. in the 

manufacture of margarines, salad oils, 

shortening, and other food products. 

Before use, howecer, it must be up- 

graded by selective hydrogenation of 

linolenates to linoleates. This paper 

describes research on platinum com- 

plexes that have been found to be highly 

selective in this reaction. The work was 

carried out under contract with the U.S. 

Department of Agriculture arid zuas 

supervised hy the Northern Utilisation 

Research and Decelopment Division 

of the Agricultural Research Service. 

Although the soybean has been a major 

agricultural product in the Orient for more 

than three thousand years, it was virtuaily 

unknown in the western world until about 

forty years ago. Research on the culture, 

processing and utilisation of soybeans began 

a few years before that, and was pursued with 

great vigour, especially in the United States. 

Through careful plant breeding, the soybean 

was adapted to American soils and climate, 

and it soon became a major crop, especially 

in Illinois, Indiana, Iowa and other mid- 

western states. 

Soybeans contain up to 20 per cent oil, 

which is pressed or cxtracted from the beans 

and is used widely in the manufacture of 

margarines, shortenings, salad oils and other 

food products. It also finds wide industrial 

Platinum MetalsRev., 1971, 15, (l), 2-8 2 

use in the manufacture of alkyd and poly- 

amide resins and, in modified form, in drying 

oils. These uses, however, are much less 

important than its use in foods. The meal 

which remains after the oil is extracted from 

the beans is a valuable by-product, finding 

extensive use in animal feeds, meat sub- 

stitutes, and special protein concentrates. 

World production of soybean oil is much 

greater than that of any other edible vegetable 

oil. 

Soybean oil is a mixture containing chiefly 

glycerol esters of long chain organic acids. 

To simplify the study of this mixture, the 

glycerol esters are usually converted to methyl 

esters; thus, each alcohol group is attached 

to a single acid chain instead of three. Samples 

of the oil differ somewhat in composition, 

depending upon the strain of the plant from 

which the oil came, and the soil and climatic 

conditions in which the plant grew. A 

typical oil might contain: 

linolenate 

linoleate 

7.5 per cent 

50 ,, 

oleate 

stearate 

palmitate 

27 

4 

10 

$9 

JY 

,, 

All of the double bonds have the cis configura- 

tion, which is desirable from a practical point 

of view. 

In soybean oil which is to be used in the 

manufacture of foodstuffs, linolenates are 

highly objectionable because they have a 

bitter taste, and palmitates and stearates are 

somewhat undesirable because, if present in 

too large amounts, they are difficult to digest. 

Since it is impractical to separate the desired 

from the objectional esters in this mixture,

The World's most important edible ixgrtnble oil is extractedfrom soybeans (or soya brans). 

Annual production of soybean oil now amounts to over five million metrir toranes. The oil 

is a mixture of glycerol rsters of long-chain organir arids, inrluding undesirable linolenates. 

pazmitates and st car ate^. These need removal or substantial redurtion brfore consumption. 

(Pzctwe cvuvtcy of b'nilerer Limited, 

efforts to upgrade soybean oil have depended 

largely upon converting linolenates to lino- 

leates by selective hydrogenation. The 

formation of oleate is less desirable, but even 

this represents an upgrading of the oil. 

Hydrogenation of Linolenic Ester 

Unfortunately, the double bonds in lino- 

lenic cster are remarkably alike, and one 

cannot rely on any difference in chemical 

reactivity which will allow the hydrogenation 

of one of them to the exclusion of the others, 

or even a difference in rate of hydrogenation. 

If there is to be highly selective hydrogena- 

tion, it must rest upon some peculiar property 

of the hydrogenation catalyst, and the 

mechanism of catalyst operation. 

Apparently, the first specific attempts to 

hydrogenate soybean oil selectively were 

made by Zajcew (I), who used a palladium 

catalyst at 114T and 47 psi. of hydrogen. 

Platinum MetalsRev., 1971, 15, (1) 3 

There was some selectivity, but his product 

contained 19.1 per cent of saturates. Allen 

(z), using a nickel catalyst at 285'F and 30 

p.s.i. of hydrogen, was much more successful, 

for he was able to reduce the content of 

linolenic ester to 1.0 per cent and to increase 

the content of oleic ester to 61.5 per cent, 

leaving the stearate at 5.7 per cent. 

Various catalysts have been tested as 

replacements for nickel in the hydrogenation 

of vegetable oils on a commercial scale but 

hitherto nickel, e.g. as formate, has been the 

most important. Specific attempts to hydro- 

genate soybean oil have been made using 

salts of chromium, cobalt, vanadium, etc. 

The catalysts which are the main subject 

of this paper are platinum complexes. That 

they are highly selective in the hydrogenation 

of soybean oil is illustrated by Table I, which 

gives data from two typical experiments with 

soybean oil methyl ester (3).

Table I 

Hydrogenations of Soybean Oil Methyl 1 Ester with Platinum Complexes 

Before hydrogenation 

I After hydrogenation 

2 After hvdronenation 

Palmitate 

10.9 

11.8 

11.5 

A sample of methyl linolenate, after 

hydrogenation, showed 26.0 per cent mono- 

ene and 74.0 per cent diene, with no stearate 

and no unreduced triene. Unfortunately the 

“monoene” in the product is not all methyl 

oleate, for the unreduced double bond is 

chiefly of the trans configuration and it is 

not exclusively in the 9-position. While 

most of the material consists of molecules in 

which the double bond is near the centre of 

the chain, there are molecules in which it is 

as close to the carbonyl group as the fourth 

carbon atom, and as distant from it as the 

fifteenth (4). 

Catalyst Complexes 

Stearate 

3.8 

4.4 

4.4 

Our concept of the catalysts which are 

described in this article grew out of a note by 

Cramer, Jenner, Lindsey and Stolberg (5), 

who reported that, while H,PtC16.6H,0 is 

only a mild catalyst for the homogeneous 

hydrogenation of ethylene, and tin(I1) 

chloride is not a catalyst at all, a mixture of 

the two is a remarkably good catalyst. The 

implication that the two have combined to 

form a complex has been amply confirmed 

by later work (6). 

Although Cramer et al. (5) had used the 

Pt-Sn catalyst for the hydrogenation of a 

compound containing one double bond, we 

hypothesised that, with a polyolefinic material, 

it might catalyse the hydrogenation of only 

a portion of the double bonds in each 

molecule. Our fist experiments were per- 

formed with this catalyst, in a solvent con- 


composition (%) 

Monoene 

28.3 

78.5 

84.1 

Diene 

50.5 

5.4 

- 

Triene or 

c-t 

conjugated t 

diem 

6.5 

sisting of benzene (60 per cent) and methanol 

(40 per cent) (7). van’t Hof and Linsen (8) 

have also used this catalyst for the hydro- 

genation of soybean oil. Their results parallel 

ours. Later, our catalyst was modified by 

use of bis-triphenyl-phosphine platinum(I1) 

chloride (9) instead of hexachloroplatinic(1V) 

acid. This, when treated with tin(I1) chloride, 

gives a compound which has the structure 

/ 

/ 

Phi 1’ 51lC1, 

We found this catalyst to be slightly more 

selective than the original one. The reaction 

by which tin(I1) chloride inserts itself into 

the Pt-C1 bond is shown to be reversible by 

the fact that best results are obtained when a 

tenfold excess of tin(I1) chloride is used. A 

larger excess reduces the efficiency of the 

catalyst, supposedly by the formation of 

Pt(PPh,),(SnCl,), (10). 

The catalyst can be varied in a large 

number of ways without loss of its selective 

hydrogenation ability toward soybean oil 

methyl ester. Trialkyl phosphines or mixed 

alkyl-aryl phosphines can be used; in fact, 

P(CH,),Ph gives a much more active catalyst 

than does PPh,. Methyldiphenylphosphine, 

P(CH,)Ph,, gives a catalyst of intermediate 

activity. The catalyst made from trirnethyl- 

phosphine, however, is not very active (11). 

0 

t-t 

conjugated 

diene

In the catalysts which have been mentioned, 

the phosphine ligands occupy trans positions 

in the complex molecule (12, 13), but this is 

not an essential feature. Bidentate phos- 

phines, R2PCH,CH,PR,, which must co- 

ordinate in cis positions, are also effective 

(12, 13). 

Triphenylarsine and triphenylstibine can 

be used in place of the phosphine. The arsine 

complex gives a more active catalyst than the 

phosphine complex, but it is less stable and 

suffers from the obvious disadvantage of 

containing a highly toxic material (14). 

Diphenyl sulphide and selenide can replace 

the phosphine, also, but do not give highly 

active catalysts (12). Lead and germanium 

chlorides can be substituted for tin chloride, 

but are much inferior (14a). 

The palladium complex, Pd(PPh,),Cl, + 

SnC1,.2H,O is more active than the corres- 

ponding platinum complex and shows good 

selectivity. It has to be used at a lower 

temperature, however, for it is considerably 

less stable (14b). 

Bis- triphenylphosphine- dicyano-palladate 

(II), Pd(PPh,),(CN),, (14b) and bis-tri- 

phenylphosphine nickel iodide, Ni(PPh,),I,, 

(15) are selective catalysts, even without the 

addition of tin chloride, but in the presence 

of either of these catalysts, the hydrogenation 

is slow. The ligands CN- and I-, like SnCl,-, 

are weak G donors and strong r acceptors 

(6, 10, 16) and are thus able to adjust the 

electron density around the Group VIII 

metal so that it can hold both the hydrogen 

and the olefin in the coordination sphere, but 

can release them to combine with each other. 

For hydrogenation with the platinum 

catalyst, a temperature of 90" to 110°C is 

maintained, and a hydrogen pressure of 

about 500 p.s.i. At lower temperatures and 

pressures, isomerisation takes place, but not 

hydrogenation. In certain applications , this 

may be a useful property. Bond and Hellier 

(17) have made detailed studies of the iso- 

merisation of I-pentene using a mixture of 

H,PtCI, and SnC1,.2H,O. They report that, 

initially, trans-a-pentene is formed in greater 


than the equilibrium amount, but within an 

hour and a half, equilibrium is reached 

(81 per cent trans-2-, 17.5 per cent cis-2-, 

1.5 per cent I-pentene). 

The solvent which was used in our first 

experiments (a mixture of benzene and 

methanol) was chosen because it readily 

dissolves both the soybean oil and the 

catalyst. It soon became evident, however, 

that in the absence of hydrogen (and proba- 

bly, to some extent, in its presence) this 

solvent serves as a hydrogenating agent by 

converting the chloroplatinum complex to 

the hydrido complex, which, in turn, transfers 

its hydrogen atom to the substrate: 

=Pt-Cl+CH,OH+ ZPt-H + HCHO - HCl(14b) 

Platinum(I1) contains ten electrons less 

than the next rare gas, so it can coordinate 

with five donor atoms. Normally, it shows a 

coordination number of only four, but the 

presence of the fifth coordination position is 

essential to its catalytic activity, for it is 

through this that the olefin group is attached. 

In the presence of hydrogen and the olefin, 

the platinum compound is converted to the 

five coordinate complex [Pt(PPh,),(SnCl,) 

H(ol)] (12). Several compounds of this general 

formula have been isolated, including those 

in which "ol" represents 4-octene and 1,4- 

cyclohexadiene. 1,s-Cyclooctadiene forms a 

compound in which each double bond is 

attached to a molecule of the catalyst. The 

presence of any strongly coordinating sub- 

stance blocks the fifth coordination position 

and destroys the catalytic activity of the 

platinum. Even the solvent may play this role. 

It has been found that hydrogenations with 

the platinum-tin catalyst proceed about five 

times as fast in methylene chloride as in the 

benzene-methanol mixture, and that they do 

not go at all in pyridine (12). Methylene 

chloride and other chlorinated hydrocarbons 

are poor solvents for the catalyst, but, even so, 

they offer a great advantage. 

Catalyst Selectivity 

The selectivity of the platinum-tin catalysts 

toward large polyenes apparently rests upon

the fact that only conjugated systems are in E may migrate along the chain until it 

attacked. If the double bonds are not con- approaches another double bond, whereupon 

jugated, the molecule must isomerise to the hydrogenation step is repeated, until only 

conjugation before hydrogenation can take one double bond remains. The presence of D 

place. In a polyolefinic molecule, isomerisa- or a similar molecule is thought to be necestion 

and hydrogenation take place alternately sary for the hydrogenation of the metal-carbon 

until only one double bond remains, but the c bond. 

process must then stop. The following It is not necessary that the double bonds be 

mechanism is suggested (12): (M represents close together in the original molecule. The 

the Pt(PPh,),SnCl, fragment of the catalyst. dienoic ester CH,CH,CH =CH(CH,),CH == 

Some of the hydrogen atoms are marked, but CH(CH,),COOCH,, in which the double 

only so the reader may more easily follow the bonds are separated by six carbon atoms, is 

discussion. No experiments with labelled 

materials have been performed in our work.) 

readily reduced to the monoene stage (IS). 

I;I? 

? , 

c= c- C $ C - 

/ 

H-C-H* tMHo - H-C-H* kHo 

/h 

11-C-H" 

B ? 

c- c- 

Ho I 

H H 

I I 

c - c - 

H I1 

I I 

c - c - 

Compound A contains a ir bond, which 

readily converts reversibly to the c bonded 

compound B. Instead of reverting to A, B may 

equally well go to the conjugated C, this step 

also being reversible. The platinum atom in 

B may, however, attach itself to the adjacent 

double bond through a r-linkage, forming D. 

The metal-carbon cs bond in D is broken upon 

hydrogenation to give E. The double bond 


II I1 

I t 

c- c- 

Although soybean oil methyl ester, cyclo- 

octadiene, and other fairly large polyene 

molecules undergo hydrogenation to the 

monoene stage, short chain olefins behave 

quite differently. 

In such cases, even monoenes may be 

hydrogenated easily (19). Those with ter- 

minal double bonds are readily hydrogenated

ethylene 

propylene 

I-butene 

cis-Zbutene 

trons-2- bute ne 

I-pentene 

2-pentene* * 

I-hexene 

2-hexene 

3-hexene 

Diene 

used 

15 

1.4 

1,3 

2,4 

Table II 

Catalytic Hydrogenation of Some Monoenes 

with (PPh,),PtCl(SnCl,) in Benzene-Methanol 

34 atm. Hp, 90"C, 3 hours 

I-isomer yo 

66 

12.0 

0 

0 

11.6 

3.0 

* 97% after 1 hour 

* * This material was 47.9% cis and 52.1% trans 

to saturation] but show an even greater 

tendency to isomerise to those with internal 

double bonds. Both processes probably 

proceed through the formation of 5 bonded 

complexes. When the double bond is internal] 

hydrogenation takes place very slowly; per- 

haps there is no hydrogenation except as 

terminal olefins are formed by isomerisation. 

2-isomer yo 

cis 

30.3 

71 .I 

9.8 

30.2 

27.7 

trans 

12.5 28.5 41.6 

- 

no observable hydrogenation 

2-hexene hexadiene 

I-hexene cis trons 3-hexene n-hexane 1,5 1,4 1,3 2,4 

0.8 5.8 12.2 1 .o 2.5 0 17.0 2.0 58.7 

0 5.0 12.5 0 0 0 5.7 3.6 73.2 

0 0 7.5 0 0 0 73.1 19.4 

0 

0.9 

0 0 0 

46.4 

27.3 

89.6 

47.2 

67.5 

no observable hydrogenation 

Table Ill 

Hydrogenation of the Isomeric Hexadienes 

with (PPh,),PtCl(SnCl,) in Benzene-Methanol 

3 hours, 500 psi 


3-isomer yo Saturated 

hydrocarbon yo 

5.4 

100 * 

34 

11.3 

1.6 

0.6 

11.6 

1 .a 

12.0 

As the chain is lengthened, the hydro- 

genation becomes progressively slower. 

Apparently, the light molecules form 

relatively stable complexes with the catalyst. 

These are susceptible to hydrogenation, but, 

because of entropy effects, the heavier mole- 

cules and those with internal double bonds 

form complexes of such low stability

that the c bonded complex does not form. 

The hydrogenation of some short chain 

monoenes is illustrated in Table I1 (Igb). 

With short chain dienes, rearrangement to 

the conjugated isomer accompanies hydro- 

genation and in some cases is much more 

rapid. Once the conjugated hydrocarbon is 

formed, it does not hydrogenate to any marked 

extent (19b). This is seemingly because it 

forms such a stable complex with the platinum 

that no further reaction can take place. 

Evidence for this is found in the fact that the 

addition of a little butadiene to soybean oil 

methyl ester completely inhibits the hydro- 

genation of the latter. Table 111 illustrates 

the behaviour of the hexadienes (19b). It 

reveals is a great tendency to form conjugated 

systems, and that migration of terminal double 

bonds to interior positions takes place easily. 

Even when double bonds are terminal, the 

formation of hexane is overshadowed by the 

formation of a molecule with internal double 

bonds (preferably conjugated). 

Studies on this system are continuing in 

attempts to develop more active catalysts as 

well as heterogeneous catalysts which will 

show a high degree of specificity. 

References 

I M. Zajcew, J. Am. OilChem. Sac., 1960,37,130 

2 R. R. Allen, Ibid., 1962, 39, 457 

3 J. C. Bailar and H. Itatani, Zbid., 1966,43,337 

4 E. N. Frankel, E. A. Emken, H. Itatani and 

J. C. Bailar, J. org. Chem., 1967,32, ~447 

5 R. D. Cramer, E. L. Jenner, R. V. Lindsey 

and U. G. Stolberg, 3. Am. Chem. Sac., 1963, 

85J I6g1 

6 R. D. Cramer, R. V. Lindsey, C. T. Prewitt 

and U. G. Stolberg, Zbid., 1965, 87, 658 

7 J. C. Bailar and H. Itatani, Prac. Symp. 

Coordination Chem., Tihany, Hungary, 1964, 

publ. Hung. Acad. Sci., 1965 

8 L. P. van't Hof and B. G. Linsen, J. Catalysis, 

Ig67> 7, 295 

9 J. Chatt and B. L. Shaw,J. Chem. SOL., 1962, 

5075 

10 H. A. Tayim and J. C. Bailar, J. Am. Chem. 

Sac., 1967, 89, 3420 

II G. Batley and J. C. Railar, unpublished 

results 

IZ H. A. Tayim and J. C. Bailar,?. Am. Chem. 

sac*> Ig67J 433O 

13 R. W. Adams, G. Batley and J. C. Bailar, to 

be published 

14 a J. C. Bailar, H. Itatani, M. J. Crespi and 

J. Geldard, Adv. in Chem., 1966,64103 

b H. Itatani and J. C. Bailar,J. Am. Oil Chem. 

Ig67J 44, I47 

c J. C. Bailar and H. Itatani, J. Am. Chem. 

Ig67> %J 1592 

15 H. Itatani and J. C. Bailar, J. Am. Chem. SOL., 

1967, 89, 1600 

16 G. W. Parshall, Ibid., 1966, 88,704 

17 G. C. Bond and M. Hellier, Chem. & Znd., 

1965, 35; J. Catalysis, 1967, 7,217 

18 Unpublished work 

19 a R. W. Adams, G. E. Batley and J. C. 

Bailar, Inorg. Nucl. Chenz. Lett., 1968,4,455 

b Ibid., J. Am. Chem. Soc., 1968,90,6051 

Further Advances in Catalytic Hydrogenation 

NEW REACTIONS WITH PALLADIUM AND RHODIUM CATALYSTS 

Workers from Hoffman-La Roche reported 

to a recent symposium held by the New 

York Academy of Sciences that acid chlorides 

can be converted to aldehydes by a modified 

Rosenmund reaction using palladium on 

charcoal catalyst poisoned with quinoline- 

sulphur inhibitor. The development of this 

reaction at 50 lb/in2 has reduced catalyst 

requirements and it opens the way to manu- 

facture of pharmaceutical chemicals from 

cheaper aldehyde intermedidates by using 

cheap hydrogen instead of expensive hydrides 

for hydrogenation of pure acid chlorides. 

The end point of the reaction was determined 

by seeing how much hydrogen had been used. 

The conventional Rosenmund reaction 

Platinum MetalsRev., 1971, 15, (1) 

8 

barium sulphate moderator was not needed. 

A group from Monsanto showed that 

optically active phosphine complexes of 

rhodium(II1) can catalyse hydrogenation of 

olefins to optically active products. For 

example, 28 per cent optical purity, i.e., 64 

per cent of one optical isomer and 36 per cent 

of the other, was obtained during hydro- 

genation of z-phenylacrylic acid to M- 

phenylpropionic acid at 300 to 400 lb/in2. 

The group has not yet finalised the reaction 

mechanism. The catalyst was formed in 

situ by reacting the 1,5-hexadiene complex 

of rhodium(II1) with an optically active 

phosphine-based ligand such as methyl- 

phenyl-N-propylphosphine.

The Control of Air Pollution 

PLATINUM CATALYST SYSTEMS FOR INDUSTRIAL 

ODOUR CONTROL 

By G. J. K. Awes 

Nesearch Laboratories, Johnson Matthey & Co Limited 

lloneycat catalyst systems have been successfully evaluated clnd used 

in a wide range of industrial processes that emit organic fumes and 

odours. These include wire enamelling, paint baking, phthirlic anhydride 

manufucture, puper coating, and nitric acid manufacture. More recently 

the system has been successfully riialuated for the remobal of odours from 

the animal, j sh and ,food processing industries. 

The development of a new platinised 

ceramic honeycomb catalyst for the combus- 

tion of organic fume offers considerable scope 

for the control of various types of air pollution 

(I). These THT catalysts consist of platinum 

supported on the Du Pont honeycomb ceramic 

known as Torvex. They possess a low pres- 

sure drop, high activity and resistance to 

attrition, making them suitable for a wide range 

of industrial processes requiring fume control. 

Air pollution takes various forms. It may 

consist of toxic emissions or of emissions 

that offend the eye, the ear or the nose, or a 

combination of these types. For example, 

the exhaust gases emitted by diesel engines 

are frequently both a health hazard and a 

nuisance to the public. These gases, black 

smoke and smell included, can be minimised 

by careful engine design but catalytic com- 

bustion constitutes a more effective method 

of purification (2). Honeycomb catalysts in- 

corporating platinum are suitable for diesel- 

engined road vehicles and for diesels working 

in enclosed conditions. 

While current legislation on air pollution 

control is mostly concerned with the toxic 

emissions, the public often reacts even more 

to the pollution which offends the senses of 

sight, hearing and smell. Emissions that pro- 

voke most public resentment are those which 

contain some unpleasant characteristic odour. 


This is not merely because the odorous 

materials may be dangerous but because the 

smells cause immediate public annoyance. 

The presence of an unpleasant smell does of 

course often indicate the presence of other and 

more noxious pollutants. 

While several systems have been developed 

for the elimination of industrial fume, the 

problem still presents technical and economic 

difficulties in some industries. Notable arc 

those processing animal carcases, fish and 

food. Work carried out by Johnson Matthey 

to combat these difficulties has resulted in the 

successful development of Honeycat* catalyst 

systems to remove both smell and noxious 

fumes. 

Abatement Systems 

There are five basic methods of fume abate- 

ment. They can be classified according to the 

physical and chemical techniques that are 

used: dispersion; absorption; masking; oxida- 

tion by agents other than air; air oxidation. 

Generally, odours become less objectionable 

as their concentration decreases. They arc 

considered to be eliminated when the con- 

centration drops to the threshold level of 

perception. However, both the threshold 

level and the relationship between con- 

centration and odour strength depend upon 

*Johnson Matthey Chemicals registered trade name.

EXL1A 

FAN 

CLEAN GAS 

OUTLET 1 

ACCESS FOR 

TUBE CLEANING 

CLEAN GAS TO 

HEAT EXCHANGER 

UNTREATED REMOVABLE 

TOP COVER 

q,/y PRE-HEATED 

\ GAS 

\ 

HEAT EXCHANGER 

\ 

CATALYST 

SECTION 

COMBUSTION 

CHAMBER 

BURNER 

EOUIPME NT 

Fig. 1 A typical Honeycat system for industrial odour 

control comprises the catalytic combustion unit and a heat 

exchanger to give about 50 per cent heat recovery 

the material creating the odour. The dilution 

required to achieve complete abatement can 

be determined by sampling techniques (3). 

Dilution of an odorous emission is usually 

achieved by dispersion from a high stack but, 

although this is usually the most economical 

method, it is rarely satisfactory because of 

geographical and climatic effects which 

prevent complete dispersion of the smell. 

Odours emitted from the tall stacks of animal, 

fish and food processing plants have been 

detected up to ten miles away where in theory 

their concentration should have been many 

times lower than the threshold value. 

Both solid and liquid absorption systems 

may be used to remove odours from exhaust 

gases. A water scrubber system is commonest. 

While these systems are relatively cheap to 

operate, they do not always achieve the re- 

quired degree of abatement because some 

fume is insoluble in water. In addition, in 

the food processing industry they create the 

secondary pollution problem of disposal of 

the contaminated water from the scrubber. 


Masking relics upon the 

principle that two sub- 

stances, each with a dis- 

tinctive smell, can combine 

to produce another less 

objectionable smell. This 

technique is cheap to in- 

stall but, unfortunately, 

separation occurs in some 

climatic conditions, leaving 

pockets of either the 

original unpleasant process 

odour or the odour of the 

masking agent. 

The majority of odours 

are organic in origin and 

may be chemically oxidised 

to other compounds having 

no odour or one less 

objectionable than that of 

the original material. A 

number of oxidising agents 

may be used for this pur- 

pose, including ozone and 

chlorine, but these agents generally do not 

convert organic substances to their most 

highly oxidised products, namely carbon 

dioxide and water, and the presence of ob- 

jectionable intermediates plus the smell of 

residual chlorine and ozone may be critical. 

While the techniques described above can 

be designed to remove the main sources of 

the smells, they do not achieve the objective 

of the perfect odour abatement system, 

namely to remove the materials causing the 

odour without creating another pollution 

problem and at the same time not to increase 

the operating costs of the process. Catalytic 

and direct flame combustion systems are, 

however, generally recognised to be the 

ultimate answer to odour abatement, because 

they destroy completely the organic com- 

pounds creating the smells by oxidising them 

to carbon dioxide and water. Emissions con- 

taining sulphur and nitrogen compounds, 

which are frequently encountered in the 

animal and fish processing industries, are 

also oxidised and, although the combustion

Fig. 2 Catalyst units in Honeycat systems consist of twelve inch square and triangular 

modules of the platinum on Torvex catalyst. The simplicity of design aids installation of 

the catalyst and removal for regeneration 

products may contain sulphur dioxide and 

nitric oxide, the treated exhaust gases are 

odour-free because of their low concentration 

and the high threshold values of these com- 

pounds. With few exceptions the exhaust 

streams from industrial processes create 

smells. In particular those in the food pro- 

cessing industry contain organic compounds 

mixed in air in non-flammable concentrations. 

For combustion to occur these gases must 

therefore be heated to between 600 and 1000°C 

for thermal incineration or, by incorporating a 

Flame 

Thermal 

Catalytic 

Platinum MetalsRev., 1971, 15, (1) I1 

catalyst into the system, oxidation temperatures 

may be reduced to between 250 and 

450°C. 

While combustion satisfies most of the 

requirements of the perfect odour abatement 

system, it suffers from the disadvantages of 

high capital cost and high operating costs 

because of fuel requirements. 

Incorporation of a catalyst into the system 

greatly reduces both of these costs as shown 

in Table I. This table, which was first published 

by Hardison (4), is often quoted to 

Table I 

Equipment and Fuel Costs for Odour Abatement Systems 

Operating 

Temperature 

"F 

2500 i 

1000 - 1500 

600 - 900 

Equipment 

Cost 

$/scfm 

5 -50 

1.75- 10 

1.75-5 

Annual 

Fuel Cost 

$/I000 scfm 

0 - 20 

0 - 7.5 

0 - 4.5

give an indication of operating temperatures 

and costs. However, it should be recognised 

that these costs are only approximate and 

cannot be used as a basis for determining the 

cost of a system for a specific problem. 

Honeycat Odour Abatement 

Systems 

The incorporation of a catalyst into a 

combustion system, while significantly re- 

ducing the operating costs, can introduce 

other problems which complicate the system. 

Notable among these are the pressure drop 

across the catalyst bed, attrition of the catalyst 

by vibration or by dust impingement, and 

catalyst poisoning. As a result most catalytic 

combustion systems have hitherto been less 

reliable than thermal systems and more 

difficult to service. ‘The development of a new 

platinised honeycomb catalyst (I) has made 

the construction, reliability and servicing of 

the equipment very much more practical. 

The design of a typical Honeycat system 

with heat recovery is shown in Fig. I. The 

burner with its ignition system and flame 

failure probes is easily removed for cleaning 

and maintenance and is supplied with clean 

combustion air from a subsidiary fan to 

prevent damage to the burner from dirty 

process gases. The combustion chamber is 

lined with stainless steel to minimise its 

size and weight and thc process gases are 

heated in the combustion chamber and pass 

directly to the catalyst. This is installed in the 

catalyst chamber in modular form to simplify 

installation and removal for cleaning and 

maintenance as shown in Fig. 2. The 

catalyst modules are removed through the top 

of the combustion chamber. 

In the Honeycat system a heat exchanger 

may be added to the combustion unit to give 

about 50 per cent heat recovery. This 

ensures that odour-free outlet gases are 

above the dew point and thus prevents 

condensation in the unit. The process gases, 

prior to catalytic treatment, are passed down 

the tubes, which are arranged so that the 

inner walls may be cleaned. The tube bank 


may also be removed from the heat exchanger 

shell to let the outer walls of the tubes be 

cleaned. 

Honeycat System Design 

The operation of a Honeycat catalyst 

system and the factors affecting its perform- 

ance were described in a previous article (I). 

Both the operating temperature of the system 

and the volume of catalyst relative to the 

volume of air to be treated must be deter- 

mined to optimise performance. In the 

majority of odour problems it is possible to 

specify a range for the temperature and 

catalyst volume required to eliminate the 

odour. However, as the composition and 

concentration of an odour-laden emission are 

rarely known, it is preferable to make pilot 

plant tests to find the optimum conditions. 

The compactness of a Honeycat system has 

also made it possible to construct a transport- 

able pilot unit for on-site evaluations of the 

system. This unit is designed to treat 200 

standard cubic feet per minute of contami- 

nated air at temperatures up to 450‘C and 

carries its own fuel supply and process air 

fan. It may be connected to an exhaust stack 

without disrupting the process emitting the 

odours. The pilot plant is fully automatic 

and incorporates flame-failure devices. It is 

also fitted with gas sampling points for con- 

ventional analysis or odour sampling. 

Pilot plant tests enable the optimum size 

of Honeycat system to be specified for fume 

elimination in particular industrial plants. 

Successful installations, as well as those for 

the elimination of odourless noxious fume, 

include units for the processing of animal 

wastes and in fish and meat processing. 

References 

G. J. K. Acres, PZatinum Metals Rtv., 1970, 14, 

(I), 2-10 

G. J. K. Acres, Plali,wnz Metals Rev., . 1970, . 14, 

(3)J-78-85 

A. Turk, “Industrial Odour Control and its 

Problems”,Chem. Engng., 1969,76, (24, Nov. 3), 

70-78; “Measurement of Odour in Atmosphere”, 

A.S.T.M. Method D 1391-57, 1964, 

Part No. 23, 612 

L. Hardison, “Disposal of Gaseous Wastes”, 

presented at Seminar on Waste Disposal, 

Cleveland, May 1967 ’

Platinum and the Refractory Oxides 

IV - THE PERFORMANCE IN SERVICE 

OF PLATINUM THERMOCOUPLES 

By il. S. Darling, G. L. Selman aiid R. Rushfodi 

Research Laboratories, Johnson Matthey & Co Limited 

The reactions between platinum and 

the refractory materials in contact with 

it, described in earlier articles in this 

series, account ,for many of the thermocouple 

failures that occur under practical 

industrial conditions. Reducing 

atmospheres accentuate such tendmcies, 

although several factors usually cooperate 

to cause completp failure. This 

urticle examines the way in which 

platinum :rhodium-platinum thermocouples 

behave in service under both 

oxidising and reducing conditions urid 

also in z'acuum furnaces. 

Above the melting point of gold, practical 

temperature measurements are made with 

platinum thermocouples which generally 

provide long and trouble-free service in this 

temperature region. Under specific condi- 

tions, however, environmental reactions can 

occur, and earlier articles in this series have 

attempted an analysis of some of the pro- 

cesses which can lead to thermocouple change 

and deterioration. Against the general back- 

ground of satisfactory performance the re- 

actions between platinum and the refractory 

oxides must be viewed in perspective, and it 

is important therefore to consider the 

industrial behaviour of thermocouples in 

relation to the results of the laboratory 

compatibility experiments previously des- 

cribed. 

Oxidising and Reducing Conditions 

Most platinum thermocouples are used in 

air and providing that both limbs are properly 


supported and protected against metallic and 

vapour contamination satisfactory perform- 

ance can be obtained for very long periods at 

temperatures up to 15oooC. An indication of 

the stability which can be expected under 

such conditions is provided by Fig. I, where 

the upper curve indicates the very slow 

departure from standard calibration of a 

platinum : 13 per cent rhodium-platinum 

thermocouple used horizontally in an elec- 

trical resistance furnace to which free access 

of air was available at 1450°C. The fall in 

EMF, as measured at regular intervals, was

equivalent to about 3 deg C after 1000 hours 

at temperature. The thermocouple had mm 

diam. limbs, was insulated with twin bore 

“Purox” alumina tubes and protected ex- 

ternally with a loosely fitting “Purox” 

alumina thermocouple sheath. 

The bottom curve on this illustration 

relates to a similar thermocouple, insulated 

in exactly the same way, which was run in a 

flowing atmosphere of dissociated ammonia 

rather than in air. The thermocouple sheath 

has obviously provided some degree of pro- 

tection as mechanical failure of the couple 

wires has not occurred although a fall in out- 

put equivalent to -100 deg C, has taken place 

after 500 hours at temperature. Subsequent 

analysis of this thermocouple showed that it 

had taken up substantial quantities of 

aluminium, and some silicon which was 

originally present as silica in the nominally 

pure alumina. 

This type of deterioration can be intensified 

by changing the orientation of the thermo- 

couple. In one instance rapid thermocouple 

failure was encountered when the same type 

of nominally impervious alumina thermo- 

couple sheath was inserted vertically upwards 

into the hot zone of the furnace. Complete 

fusion and breakage of the hot junction oc- 

curred in dissociated ammonia after about 

~ i 2 ~ ~~~i~~ . the hot junction o~ a : 2 hours at 1450‘ C, a typical illustration being 

I3 per cent rhodium-platinum thermoLoupZe given in Fig. 2. The microstructure of one 

sheathed zcith ahminu and inserted vprtically 

upwards into a furnace containing an atmosphere 

area of this failure is shown in l?ig. 3. L~~~~ 

of dissociated ammonia at 1450°C. 

lf’ig. 3 The microstructure of the fused zone on 

the failed thermocouple illustratd in Fig. 3. x 200 


y25 quantities of silicon and aluminium were 

found by microprobe analysis, and this type 

of geometrical arrangement seems very 

dangerous, as any hydrogen which penetrates 

the tube is, by virtue of its low density, 

trapped in concentrated form at the hot 

junction, thus causing very severe reactions 

between platinum and the refractory tube and 

insulators. 

Under strongly reducing conditions 

thermocouples used in contact with magnesia 

are relatively free from this type of deterioration. 

The third curve on Fig. I indicates 

some results obtained when a thermocouple 

was run in dissociated ammonia at 1450°C

Fig. 4 Intercrystalline cracks 

associated with oxide in- 

clusions embedded within the 

surjace layers oj a rhodium- 

platinum wire. X 20 

Fig. 5 A microssction taken 

through a defect of the type 

illustrated in Fig. 4 showing 

the fused area resulting from 

reaction between a refructory 

particle and the rhodium- 

platinum alloy. X 50 

for 450 hours while packed in a bed of fine 

magnesia powder. The extent of the de- 

terioration which occurred was comparable 

with that encountered with the alumina 

insulated thermocouple run in air. 

Failure Caused by Superficial 

Contamination 

Premature failures caused by platinum- 

refractory reactions are occasionally encount- 

ered in atmospheres which appear at first 

glance to be highly oxidising. This behaviour 

can usually be traced to circumstances in 

which a fortuitous juxtaposition of platinum 

and refractory has resulted in a particularly 

unfavourable geometry. 

Small particles of alumino-silicate forced 

into platinum or rhodium-platinum wires 

occasionally cause intercrystalline cracking 

of the type shown on Fig. 4, which occurred 

on heating in air to 145o'C. Fig. 5 provides 

another illustration of the way in which 

intercrystalline failure can proceed at a con- 

siderable distance away from the region 

where the original refractory particle had 

reacted with the platinum to form low melting 

point phases in which platinum silicide 

predominated. 

The first attempts to reproduce such 

effects in the laboratory met with limited 

success. Mullite particles rolled into sheet 

normally showed little tendency to react. 

Some working operations, however, parti- 


cularly wire drawing, sometimes gave rise 

to an inclusion which was almost completely 

encapsulated by platinum. This type of 

inclusion tended to react strongly with the 

platinum when heated in air. As shown in 

Fig. 6 networks of platinum-platinum silicidc 

eutectic have penetrated round the grain 

boundaries for a considerable distance away 

from the inclusion. 

It has recently been shown that this type of 

failure is usually associated with the presence 

of sulphur-bearing organic lubricants such as 

those used for rolling and wire drawing. 

Traces of these liquids are trapped in the 

cavity with the refractory particle and the 

partially sealed conditions obviously facilitate 

the reaction, based on the formation of vola- 

tile silicon sulphide which was first observed 

twenty-five years ago by Chaston et al. (I). 

Reactions at Lower Temperatures 

At temperatures below rooo"C reactions 

do occur between platinum and refractory 

oxides, although as many investigators have 

demonstrated (2, 3, 4), contamination of the 

thermocouple by impurities from the ceramic 

protection tubes is the most usual cause of 

instability in this temperature range. Walker 

et al. (4) have described in detail the way in 

which iron can be transferred from nominally 

pure alumina powder into platinum, and 

suggested mechanisms for this vapour phase 

transfer process.

Fig. 6 3’etworks of the platinum-platinum 

silicide eutectirformpd in the vicinity of a siliceous 

inclusion, encapsulated in rhodium-platinum, on 

heating in air. Y 1500 

The slow changes in thermoelectric output 

which occur in rhodium-platinum thermo- 

couples heated for long periods in air at 

moderate temperatures have generally been 

attributed to contamination processes of this 

type. Recent investigations in these labora- 

tories have shown, however, that such ex- 

planations are not always justifiable. In one 

instance for example a reduced output, equiv- 

alent to about 2 deg C, was detected after a 

13 per cent rhodium-platinum thermocouple 

had been used at 625°C for 40,000 hours or 5 

years in air in a steel creep testing furnace. Very 

thorough examination showed little change in 

the composition of the limbs up to 2 ft from 

the hot junction. Towards the colder end of 

the wires changes in alloy homogeneity were, 

however, detected and micro-examination 

disclosed the presence of areas which con- 

tained substantial quantities of solid rhodium 

oxide as shown in Fig. 7. The platinum alloy 

matrix contained only 11 per cent by weight 

of rhodium, and the presence of this depleted 

region in the strong temperature gradient 

between the hot and cold regions of the 

thermocouple accounted for the change in 

electrical performance. 

A short heat treatment in air at 1200°C 

dissociated this oxide, returned the rhodium 

to solid solution in the platinum and restored 

the thermocouple output. This type of 

internal oxidation has not, so far as can be 

ascertained, previously been reported. Very 


Fig. 7 Subsurface rhodium oxide in a 13 per cent 

rhodium-platinum thermocouple wire operated 

in air for approximately 5 years at nbout 400°C. 

/ 750 

long periods of time are needed for its de- 

velopment but, since all noble metal thermo- 

couple wires must at some point between hot 

and cold junctions pass through the tempera- 

ture range 400-6oo0C, a tendency towards the 

internal formation of solid particles of 

rhodium oxide must always exist. The rate 

at which this internal oxidation proceeds is 

now being assessed. 

Thermocouples in the Vacuum 

Furnace 

Under industrial conditions thermocouple 

deterioration can usually be ascribed to the 

operation of various processes and this is 

particularly true in vacuum metallurgical 

melting and heat treatment furnaces. The 

contamination which occurs is usually char- 

acteristic of the impurities in the refractory 

rather than of the refractory itself. Super- 

imposed on such effects are the changes in 

composition caused by the selective volatilisa- 

tion of rhodium under vacuum conditions, 

and by the absorption of vapours from the 

material being heated within the furnace. 

Premature thermocouple failure was oc- 

casionally encountered in a vertical vacuum 

sintering furnace generally operated at a 

pressure of about z X IO-~ Torr. This 

furnace had molybdenum heaters, and during 

one series of production runs made at 1500°C 

adhesion between the components being 

sintered was prevented by dusting with

Fig. 8 Within the confines of this glass envelope platinum filaments are heated in contart 

uith refractory oxides under any desired atmospheric conditions. The wire under test and 

the refractory in contact with it are the only parts of the system maintained at high tem- 

perature, and the romplicating effects of spurious contamination are thus avoided. Difer- 

ences between the simplicity of this experimental arrangement and the complex environments 

in which thermocouples normally operate in industry are discussed in this article. 

alumina powder. The thermocouple cali- 

bration changed rapidly under such condi- 

tions, and useful working lives were limited 

to about 70 hours. Both limbs of the thermo- 

couple tended to absorb substantial quantities 

of both silicon and aluminium. Although the 

precise source of this siliceous contamination 

was not detected, it and the aluminium 

have obviously reached the thermocouple via 

the vapour phase. The thermocouple was in 

fact at a slightly lower temperature than 

the furnace heaters and their supports, and 

this situation obviously encourages con- 

tamination by volatile species. It is in this 

important respect that practical conditions 

differ greatly from the test cell geometry 

described in the previous articles, where 

thermocouples were intentionally run at much 


higher temperatures than their environment 

so as to discourage spurious contamination. 

Fairly satisfactory protection against such 

vapour attack can usually be obtained if the 

impermeable alumina thermocouple sheaths 

are prolonged without join into the cold part 

of the furnace. Thus in a horizontal vacuum 

resistance furnace the thermocouple was 

supported within twin-bore alumina insula- 

tors and protected entirely by an impervious 

alumina sheath which continued into the 

colder part of the furnace where temperatures 

were below zoo”C. 

After about 150 hours of operation at 

1475’C in vacuum conditions of about 5 x 10 

Torr the output of such thermocouples de- 

creased by the equivalent of about 3 deg C at 

the gold point. This deterioration was traced

Fig. 9 Traces of the Pt,Al intermetallic compound 

formed locally on the surface of a plotinurn thesmo- 

couple mire operated in a vacuum fusnace,for 100 

hours at l400’C. x150 

to the gradual loss of rhodium from the alloy 

limb which in some regions nearer the hot 

junction was reduced to 11.4 per cent by 

weight. NQ rhodium was detected in the pure 

platinum limb, and it must be remernbcred 

that the volatility of rhodium in vacuum is 

many times higher than that of platinum. 

Reactions tetween platinum wires and their 

alumina insulators are detectable in ordinary 

vacuum furnace operations, although the 

areas of contamination are fairly local. Fig. g 

illustrates such a reacted area which developed 

where the thermocouple wire passed the 

junction between two alumina insulators. 

This region, although rich in aluminium, is 

not deep enough to weaken the wire seriously, 

and because of its short length is not able in 

normal temperature gradients to have a serious 

effect on the thermal EMF generated by the 

thermocouple. 

Complete and rapid failure of thermo- 

couples in vacuum furnaces is therefore 

rarely caused by direct reaction between 

platinum and refractories. Dangerous con- 

tamination generally emanates from the more 

volatile constituents of the materials being 

heated within the furnace and can usually be 

avoided by effective sheathing. Although 


rhodium does evaporate preferentially and 

reactions do occur between platinum and 

alumina refractories the changes thus caused 

are gradual, continuous, and tolerable under 

ordinary production conditions. 

Conclusions 

Under practical conditions of operation 

thermocouple behaviour cannot always be 

predicted because of the conflicting factors 

responsible for the changes in electrical out- 

put which occur. Although the best per- 

formances are generally obtained in air, 

satisfactory lives are attainable in vacuum and 

even under fairly strong reducing conditions. 

Rhodium-platinum thermocouples are most 

stable, however, when magnesia is used as 

a refractory, and when the surrounding inert 

atmosphere inhibits volatilisation of platinum 

or rhodium in either metallic or oxide form. 

The 10 per cent and 13 per cent rhodium- 

platinum thermocouples perform very well in 

such conditions and further improvement is 

attainable by using the 6 per cent rhodium- 

platinum versus 30 per cent rhodium- 

platinum combination. Minor losses of 

rhodium metal vapour from the positive limb 

of this thermocouple have little effect on the 

thermal EMF. Any slight tendency for the 

negative limb to absorb rhodium can be 

controlled by surrounding the assembly with a 

5 per cent rhodium-platinum “reservoir” of 

suitable capacity. 

In practice it is not always feasible to 

provide the ideal climatic conditions necessary 

to ensure extreme stability in refractory 

sheathed thermocouples. Suitably controlled 

“micro climates” can, however, be retained 

within metal sheathed thermocouples, which 

will feature in a forthcoming article. 

References 

I J. C. Chaston, R. A. Edwards and F. M. Lever, 

J. Iron & Steel Inst., 1947, 155, 229 

2 M. Chaussain, Proc. Inst. Brit. Foundrymen, 

1951, 91, (I823), 147 

3 H. Ehringer, Metall. Z. Tech., Ind. Handel, 

1954, (15 /W> 596 

4 B. E. Walker, C. T. Ewing and R. R. Miller, 

Rev. Sci. Instrum., 1962, 33, (IO), 1029

Monolithic Multilayer Ceramic 

Capacitors for Hybrid Circuits 

THE EFFECTS OF TEMPERATURE CYCLING ON STABILITY 

By R. F. Tindall 

Matthey Printed Products Limited 

The development of miniature circuitry, 

and particularly of the hybrid film circuit, 

has demanded more and more capacitance 

in a smaller volume of capacitor. ‘There are 

three possible ways in which this can be 

achieved. One is to produce capacitors with- 

out wires or encapsulation or any of the other 

appendages previously required by equipment 

designers. Another is to use thinner layers 

of dielectric, but this is limited by the voltage 

that the capacitor must withstand. The third 

is the use of higher dielectric constant 

materials, but unfortunately it is generally 

found that the higher the dielectric constant 

of a material the poorer is its stability. 

This last point is illus- 

trated by comparing the 

change in capacitance with 

temperature of two typical 

materials : one having a 

nominal dielectric constant 

of 1200 (known as K12oo) 

will change its value of K 

The platinum metals not only 

provide the most reliable 

electrodes but also enable an 

economical production method 

to be employed in the manu- 

facture of small monolithic 

capacitors. By screen printing 

and firing to form a robust 

integrated structure it is 

possible to obtain a very high 

ratio of capacitance to volume. 

This cross-section, magnijied 

50 times, shows the ceramic 

layers clearly separated by the 

platinum electrodes. 


by as much as 20 per cent when its tempera- 

ture is raised from -55‘C (the lower limit 

stipulated by international specification) to 

room temperature, while a low dielectric 

constant ceramic having a K of, say, 30 - 

generally used for capacitors known as NPO 

for negative-positive-zero - will vary only 

by at most 0.25 per cent with the same 

change of temperature. 

The monolithic multilayer ceramic capa- 

citor is produced by screen printing on to 

strips of “green” ceramic of the barium 

titanate type an ink or paste incorporating 

finely divided platinum or a mixture of 

platinum group metals. A stack of these

strips is then assembled and fired at about 

1300OC to mature the substrate and fuse the 

layers into a block or chip. Metallising the 

ends of the chip with silver-palladium or 

gold-palladium then completes the contact 

between alternate electrodes. By this tech- 

nique very thin dielectrics, which individually 

would be hopelessly fragile, may be used, 

while the fused structure is robust, hermetic- 

ally sealed, and can be immediately incor- 

porated into a hybrid circuit. 

Ceramic substrates of many compositions 

can be used in monolithic chips, so that very 

high dielectric constants are available, but 

the stability of the capacitor clearly cannot 

be greater than that of the ceramic itself. The 

desire to use high K materials in the interests 

of miniaturisation can thus lead to difficulties 

because of the relatively poor stability of 

these materials. When subjected to high 

temperature processes such as soldering, for 

example, high K capacitors can show a drift 

in capacitance beyond acceptable limits. 

Some recent work in the Electronics 

Laboratory of Matthey Printed Products 

was therefore designed to evaluate the change 

Zerovalent Complexes of Platinum 

The discovery some twelve years ago of 

complexes in which platinum exhibits zero 

valency-that is, in which the platinum atom 

is associated only with uncharged ligands- 

has proved of considerable importance for 

the synthesis of a wide range of compounds, 

some of which might be of use in homo- 

geneous catalysis. A typical example of such 

complexes is tetrakistriphenylphosphine plati- 

num [P(C,H,),],Pt. In reactions involving 

this compound it has been postulated that 

the coordinatively unsaturated species 

[P(C,H,),],Pt is a reactive intermediate. This 

means that there will be released in the 

reaction two triphenylphosphine groups 

which will still be available to compete for 

the vacant coordination sites. If the reactive 

intermediate could readily be prepared this 

situation would no longer exist, and the 

possibility would arise for even further 

advances to be made in the field of platinum 

organometallic chemistry. 


in capacitance a monolithic chip capacitor is 

likely to undergo during the assembly and 

subsequent processing of a hybrid micro- 

circuit, and to provide the user with informa- 

tion that will allow him to anticipate this 

behaviour and make allowance for it. The 

detailed results of this work, reported at the 

recent Inter-Nepcon 70 Conference at 

Brighton, showed that, while the variations 

are predictable and repeatable and in some 

circumstances reversible, because of the 

diversity of techniques employed in the 

industry it would be unrealistic for a manu- 

facturer of ceramic chips to specify a time 

by which a chip will recover its original 

capacitance after a soldering operation or any 

other heating cycle. 

It was found, however, that the application 

of high voltages can accelerate the ageing and 

so stabilise the capacitance. 

Further development along these lines 

should result in components having a limited 

temperature range in which they will operate 

satisfactorily, but having at the same time an 

unrivalled combination of stability and 

capacitance/volume ratio. 

In view of this, a paper by D. M. Blake and 

C. J. Nyman, of Washington State University, 

entitled “Photochemical Reactions of Oxa- 

latobis(triphenyphosphine)platinum(II) and 

Related Complexes” (J. Am. Chem. SOC., 

1970, 92, (IS), 5359-5364) assumes signific- 

ance. In an investigation of photochemical 

reactions of oxalato complexes a route to the 

co-ordinatively unsaturated compound has 

been discovered. Photolysis of an ethanol 

solution of [P(C,H,),] ,C,O,Pt(II) under 

a nitrogen atmosphere, from which oxygen 

had been rigorously removed, resulted in the 

production of this complex in the form of a 

dimer, [P(CSHj)J4Pt2. Thus a relatively 

simple route to this reactive species has 

become available. Although only this one 

reaction has been noted here, others are 

described. It is apparent from this work that 

photolysis of oxalato complexes offers a route 

to reactive species for the production of cata- 

lytically active compounds in sku. F. M. L.

The Form of the Interaction 

between Palladium and Hydrogen 

By R. Burch 

Chemistry Department, University of Reading 

and F. A. Lewis 

Chemistry Department, The Queen’s University of Belfast 

The high difusibility of hydrogen in 

solid phases of the palladium-hydrogen 

system allows thermodynamic equilib- 

rium to be established over a wide range 

i of experimental conditions. Evidence 

has long existed that, in the hydride 

phases formed, the hydrogen:palEadium 

ratio is not simple and is a function of 

equilibrium pressure and of temperature. 

Theoretical models of the system have 

often centred on modijications of the 

palladium electron band structure due 

to hydrogen absorption but increasing 

attention has been paid to the conse- 

quences of lattice strain. The position 

is now reviewed ire the light of recent 

work. 

In the course of the last ten years a number 

of general reviews (1-6) have appeared con- 

cerning the palladium-hydrogen system. 

Within this same period also has occurred 

(and been marked by a compilation of review 

articles (7)) the centenary of Thomas Graham’s 

initial observation (8) of the absorption or 

“occlusion” of considerable volumes of hydro- 

gen by a palladium membrane or “septum”- 

prepared for his use by George Matthey. 

Some thirty years after Graham’s original 

observations isothermal studies in the tem- 

perature range 10 to 250°C of the variation of 

the composition of the hydrided solid as a 

function of the pressure of hydrogen gas in 

steady-state equilibrium with it had sug- 


gested that these relationships were likely to 

be represented by a family of plots of the 

form shown in Fig. I. These studies (9) by 

Roozeboom and Hoitsema might well be 

claimed to be the first examples of evidence 

for the non-stoichiometric and temperature- 

dependent composition of the solid phases 

represented in such diagrams. 

The plots in Fig. I-which represent 

results subsequently obtained (6, 10, 11) over 

a wider range of temperature and pressure 

than those presented by Hoitsema-are 

clearly representative of a system subject to 

the existence of critical phenomena. In terms 

of a physically descriptive correlation in this 

particular instance, individual isotherms may

e described, or defined, as supercritical, 

critical or subcritical with respect to the 

possibility of the co-existence within thc 

solid of two hydride phases (the s(- and 

p-phases), which for the cases of the sub- 

critical isotherms can exist together in varying 

proportions over the ranges of composition 

corresponding to the horizontal “plateau” 

regions-the actual composition of each 

phase over these horizontal pressure-invariant 

regions corresponding with the break points 

of the isotherms at the beginning and end 

of the plateaus. 

The subcritical isotherms exhibit a “hyster- 

esis” of pressure-composition (p-c) relation- 

ships over the pressure invariant and adjacent 

regions, in that, for a given hydrogen content, 

the steady-state “equilibrium” pressures are 

higher when hydrogen contents are being 

steadily increased by the admission of 

successive doses of gas into the equilibrating 

system rather than decreased by the successive 

removal of incremental volumes of gas. 

Theoretical Models 

Clearly it is a central requirement of any 

theoretical model of the palladium-hydrogen 

system that it should be possible to be 

correlated with, and to account for the form 

of the pressure-composition relationships. In 

this context there are two main features of 

these solubility relationships which require 

an explanation. These are firstly the occur- 

rencc of critical isothermal behaviour, and 

secondly the tendency for palladium to have 

a limiting solubility for hydrogen at a com- 

position which is considerably less than that 

which would be expected from purely 

geometrical considerations. This limiting 

solubility condition is manifested as a rapid 

rise in equilibrium hydrogen pressure for 

small changes in hydrogen content above 

about H/Pd-0.60 at room temperature. 

In general the interpretation of critical 

phenomena has been based on the early 

postulate of Fowler (12, 13) that an attractive 

interaction must occur between neighbouring 

absorbed species, thus resulting in the heat 

Platirium MetalsRev., 1971, 15, (1) 

22 

of solution of hydrogen having a negative 

dependence on concentration (Le., the heat of 

solution becomes more negative as the con- 

centration of dissolved hydrogen is increased). 

The first significant attempt to apply these 

concepts to the palladium-hydrogen system 

was made by Lacher (12, 14) in 1937 using a 

statistical thermodynamic approach which 

formcd an extension of an allied treatment (13) 

of the problem of absorption of hydrogen by 

transition metals such as iron and platinum 

in which it is only sparingly soluble. 

Recently it has been pointed out (IS) that 

critical behaviour only requires that the heat 

of solution should become more negative as 

the hydrogen content is increased and that 

this does not necessarily require so specific 

an interaction as that between neighbouring 

atoms. In this case (IS) the decreasing heat 

of solution of hydrogen is taken to be a 

reflection of the continuous filling of the 

palladium 4d-band by electrons from hydro- 

gen atoms. 

Within the more general framework of the 

Fowler/Smithells (13) concept of pairwise 

interactions the nature of this interaction has 

been considered by various authors (16, 17, 

18, 19). This interaction has been attributed 

to the occurrence of electronic coupling of the 

screening electrons surrounding each proton 

(17) or more generally to be a consequence 

of the lower strain energy associatcd with 

paired as distinct from monoatomic species in 

an elastic matrix (16, 17, 18, 19). Recently, 

by considering the volume expansion pro- 

duced in the palladium lattice due to the 

absorption of hydrogen, Burch (20) has 

derived a value for this pairwise interaction 

energy. The derived value is in good agree- 

ment with the experimental data which would 

seem to support the general view that the 

critical phenomena occur as a consequence of 

the release of strain energy associated with 

the clustering of dissolved hydrogen atoms. 

The tendency towards a limiting solu- 

bility at about H/Pd=o.gg led Lacher to 

postulate that this limit corresponded to a 

completely filled qd-band and therefore that

this represented the maximum hydrogen 

content which would be possible without some 

change in mechanism. Consequently his 

theoretical equation contained a term such 

that the derived isotherm unavoidably reached 

a solubility limit at this composition. 

The equation derived by Lacher (14) was 

of the form: 

where O=n/s is the ratio of the number of 

hydrogen atoms “n” to the maximum number 

of absorption sites “s” where Lacher took a 

value for “S” of 0.59. Lacher’s apparent 

success in achieving a good correlation 

between this theoretical equation and a 

significant body of the experimental data led 

to a widespread acceptance of the general 

correctness of the physical model for the 

system which he had employed. 

Important limitations of the agreement 

between p-c relationships derived from 

Lacher’s theoretical equations and those 

obtained experimentally, especially when the 

artificial condition whereby “s” is put equal 

to 0.59 is removed, are revealed by detailed 

analysis of the existing data. Subsequently, 

however, attempts have been made to improve 

the agreement by extending the Lacher model 

while still assuming a limited number of 

absorption sites (21, 22, 23, 24). Modified 

equations have been derived from models 

which have variously taken account of the 

effects of lattice expansion (21, 22), made 

allowance for the occurrence of hysteresis of 

the subcritical isotherms (23), or considered 

the pairwise interaction not only of hydrogen 

atoms but also of vacancies and vacancy- 

hydrogen atom pairs (24). In all these cases, 

however, the limiting solubility was explained 

on the basis of a limited number of absorption 

sites. 

Recently attempts have been made (15, 16, 

18, 25, 26) to relate the solubility limit to 

variations in the energy associated with the 

donation of electrons by hydrogen to the 4d 

and 5s bands of palladium. There is as yet 

still some disagreement as to whether or not 


the gradual filling of the qd-band is paralleled 

by an endothermic (16, IS) or exothermic (15) 

electron donation energy term. In all cases, 

however, it has been assumed that, at higher 

hydrogen contents when the 4d-band is full, 

the energy required to transfer an electron 

from hydrogen to the 5s-band of palladium 

is greater than the energy which would be 

required, at low hydrogen contents, for a 

similar electron transfer to the qd-band. 

The resulting theoretical equation is of the 

generalised form : 

where E(n) is a positive electronic energy 

term which is a function of the hydrogen 

content “n”. 

The electronic term in equation (2) has 

the effect of increasing the equilibrium 

hydrogen pressure very rapidly at hydrogen 

contents greater than about H/Pd -0.6, in 

agreement with experiment. Only Simons 

and Flanagan (IS) have attempted to evaluate 

E(n) from basic principles. Using the rigid 

band model they have derived, from the 

density of states curve for palladium, an 

energy relationship which is of the correct 

form to predict a limit in the solubility at 

moderate pressures. A detailed analysis of 

these various “protonic” models has been 

presented elsewhere (17) and attention has 

also been drawn (27) to shortcomings in this 

model when applied to the absorption of 

hydrogen by palladium alloys. 

The Elastic Model 

Recently Burch (20) has developed the 

concepts of the elastic model, which had 

already been invoked to explain the existence 

of critical absorption isotherms, to account 

for the main features of the observed solu- 

bility behaviour. In view of the experimental 

observation that occupation of an interstitial 

site by a hydrogen atom causes expansion of 

the palladium lattice and consequently a 

displacement of adjacent palladium atoms, it 

was suggested that vacant sites surrounding 

the occupied site would be modified to varying

extents by this localised expansion. Subse- 

quently by relating the energy required to 

place further hydrogen atoms in partially 

blocked sites to the volume change of each 

modified site, it was found possible to derive 

an equation relating the equilibrium hydrogen 

pressure to the hydrogen content. An 

error in the original equation (20) has been 

pointed out by Dr W. A. Oates. A corrected 

form of the equation is as follows : 

(AV+nAV')2 __ 

2WRm 1 -GN 

3 z ( (Vo-nAV') Vo 

where W, represents the attractive interaction 

between pairs of atoms, G is the 

modulus of rigidity of the metal, Vo is the 

initial volume of an interstitial site (assumed 

spherical), AV is the increase in volume of 

the site after occupation by a hydrogen atom, 

and AV' is the reduction in volume of a 

modified site. In this model the limiting 


hydrogen solubility occurs as a consequence 

of the increasing difficulty associated with 

the occupation of sites which have been 

modified by the presence of hydrogen atoms 

in adjacent, and especially next nearest 

neighbour, sites. 

As compared to the earlier 'protonic' 

models this latter model has the advantage of a 

more general applicability to an interpretation 

of the behaviour of other transition metals 

towards hydrogen. In addition the pheno- 

mena of hysteresis of the isotherms and the 

peculiar absorption behaviour of palladium- 

nickel alloys can more readily be explained 

using the elastic strain model rather than the 

electronic model. A comparative summary 

of the various models is presented in Fig. 2. 

It is clear that even after a hundred years 

of research the absorption of hydrogen by 

palladium still produces considerable con- 

troversy. It is probable that the isothermal 

relationships obtained experimentally reflect

a balance between electronic and physical 

effects. Thus, while there is fairly general 

agreement that hydrogen donates its electrons 

to a collective metallic electron band there is 

still dispute as to the effect that this can have 

on the energetics of hydrogen absorption. It 

will be of future interest to see which of the 

physical or electronic factors have most 

relevance not only in the palladium-hydrogen 

system but in all transition metal-hydrogen 

systems. 

References 

I F. A. Lewis, Platinum Metals Rev., 1960, 4, 

132; 1961, 5,21 

2 G. G. Libowitz, Binary Metals Hydrides; 

W. A. Benjamin: New York, 1965 

3 K. M. Mackay, Hydrogen Compounds of the 

Metallic Elements, Spon: London, 1966 

4 A. Maeland and T. B. Flanagan, Platinum 

Metals Rev., 1966, 10, 20 

5 H. J. Goldschmidt, Interstitial Alloys, 

Butterworth: London, 1967 

6 F. A. Lewis, The Palladium Hydrogen 

System, Academic Press, London and New 

York, 1967 

7 Engelhard Industries Tech. Bull., 1966, 7, (I) 

and (2) 

8 T. Graham, Phil. Trans. Roy. Soc., 1866, 156, 

415 

9 C. Hoitsema, 2.Phys.Ckem. Leipzig, 1895,17, I 

10 P. L. Levine and K. E. Weale, Tram. Furaduy 

SOC., 1960, 56, 357 

11 E. Wicke and G. Nernst, Ber. Bunsen. Phys. 

Ckem., 1964, 68,224 

12 R. H. Fowler and E. A. Guggenheim, Statistical 

Thermodynamics, Cambridge Univ. 

Press, 1939 

13 R. H. Fowler and C. J. Smithells, Proc. Roy. 

sot., 1937,16oA, 37 

14 J. R. Lacher, Proc. Roy. SOC., 1g37,161A, 525 

15 Y. Ebisuzaki and M. O’Keefe,J. Phys. Chem., 

1968,72,4695 

16 H. Brodowsky, Z. Phys. Chem., 1965, 44, 129 

17 R. Burch, Trans. Faraday Soc., 1970, 66,736 

18 J. W. Simons and T. B. Flanagan, Can. J. 

Ckem., 1965,43, 1665 

19 M. von Stackelberg and P. Ludwig, Z. Naturforsch., 

1964, 19a, 93 

20 R. Burch, Trans. Fmaday SOC., 1970,66,749 

21 A. Harashima, T. Tanaka and K. Sakaoku, 

J. Phys. Soc.Japan, 1948, 3, 208 

22 T. Tanaka, K. Sakaoku and A Harashima, 

Ibid., 213 

23 D. H. Everett and P. Nordon, Proc. Roy. Soc., 

1960,259A, 341 

24 R. V. Bucur and M. Crisan, J. Phys. Chem. 

Solids, 1967, 28, 905 

25 H. Brodowsky and E. Poeschel, Z. Phys. Chem., 

1965944, I43 

26 H. Brodowsky and H. Husemann, Ber. Bunsen. 

Pkys. Chem., 1966,70, 626 

27 R. Burch and F. A. Lewis, Trans. Faraduy 

SOC., 1970, 66, 727 

Cubane-type Platinum Metal Complexes 

Recent X-ray diffraction studies have Matthey Research Laboratories) point out 

shown that the two platinum metal complexes (Nature, 1970, 228, (5272, November 14), 

[(C,H,),PtCl], and [(CO),OsO], have 648-651) that Pt(IV) and Os(I1) are isocubane-type 

structure. The eight carbon electronic and that similar structures might 

atoms of cubane, C,H,, are situated at the be expected for other iso-electronic metals, 

corners of a cube. The structure of e.g. W(O), Re(1) and Ir(II1). In fact 

[(C,HS),PtCl], is shown in 

the diagram to resemble rt 

[(CO),(NO)Mo(OH)I, is 

formally of this type with 

cubane and that of the os- one NO and two CO 

mium compound is similar, 

groups on each Mo(0) 

the four osmium and four 

atom, OH being the negaoxygen 

atoms being at tive group. The NO group 

alternate corners of a cube is assumed to act as a uniwith 

the osmium atoms 

positive radical. Furthereach 

bound to three ter- 

more Re(1) and Mn(1) 

minal carbonyl groups. 

form compounds [(CO),M 

In a joint communication (SR)I4, which have struc- 

Professor Sir Ronald Et tures with cubic symmetry. 

Nyholm and Professor 

So far, however, no com- 

Mary R. Truter (Univer- 

pounds of this type have 

sity College, London) and 

C. W. Bradford (Johnson 

Et 

Bt = C~H, 

been reported for the triad 

Co(III),Rh(III)andIr(III). 

Platinum MetalsRev., 1971, 15, (1) 2s

A New Mining Area for Rustenburg 

PRELIMINARY STEPS TO A FURTHER EXPANSION SCHEME 

For years by far the largest producer of 

platinum and its allied metals in the world, 

Rustenburg Platinum Mines recently an- 

nounced a programme designed to maintain 

that position. The current expansion pro- 

gramme has already increased capacity to a 

level of T,IOO,OOO ounces of platinum pcr 

annum and, although it has been decided to 

defer completion of the programme to in- 

crease capacity to 1,300,000 ounces by 1973, 

the preparations to bring the company’s two 

mining areas, the Rustenburg and Union 

sections, up to this potential maximum are 

complete. 

Extending for some twenty 

miles along the platinum 

bearing Merensky Re$ 

Rustenburg’s operations in- 

volve over thirty inclined 

haulages such as this from 

which the shallower portions 

of the deposit are worked. 

Over 35,000 miners are en- 

gaged in these and in the 

vertical shafts from which the 

deeper areas are worked 

Platinum Metals Rev., 1971, 15, (l), 26-28 26 

But in order to ensure that the next stage of 

expansion in output can be achieved with a 

minimum of delay - and the time taken from 

a decision to expand until refined metal from 

any such expansion becomes available to 

industry ranges from two and a half to three 

years - a completely new mining area has been 

delineated to the north-east of the Union 

Section. The extensive exploration work 

involved has been completed, the planning of 

the layout of the new mine is well in hand, 

and arrangements for the supply of essential 

services have been made. All these steps have 

been taken to ensure that the new mining

A train load of platinum ore is transported from one of the nine vertical shafts at Rustenburg to the nearby 

mill and smelter. Every working day some 20,000 tons of ore are brought to the surface 

area can quickly be brought into production, 

the scale of operations to be determined in the 

light of future developments in the demand 

for platinum. 

Current developments mean that the 

supply of platinum to industry has reached 

an all-time high, and that future supplies 

can be increased if necessary to keep ahead of 


demand. The annual demand for platinum 

by the Western world is currently around 

1,500,ooo ounces, and there is some possi- 

bility that the total supplies of platinum 

available to users might, by 1972, exceed 

requirements. On the other hand there is the 

likelihood that platinum may play an in- 

creasingly significant part in combating 

atmospheric pollution from many industrial 

processes and from automobile exhausts. 

The extent to which platinum may be re- 

quired for this purpose cannot, however, be 

predicted until both governmental policies 

and competing technical developments can 

be more clearly assessed, but having regard to 

the time normally required to achieve further 

substantial increases in platinum production, 

it is to ensure that a possible shortage of 

Ms D. A. B. Watson 

Chairman of Rustenburg Platinum Mines 

"At Rustenburg we are in no doubt as to the 

adequary of our reserves of platinum and as a 

primary producer we are able quickly to initiate 

expansion programmes to meet increasing de- 

mand"

After smelting in electric furnaces, a copper-nickel-iron matte containing the platinum 

metals is transferred to a battery of converters and blozcn to a higher grade. Here the con- 

verter matte is being poured into moulds. After cooling and breaking up it is passed either 

to Johnson Matthey or to Matte Smelters for the extraction of copper, nickel and the six 

platinum metals 

metal does not affect decisions on the 

technique to be adopted that Rustenburg 

has taken these preliminary steps. Thus, if 

substantial supplies of platinum should be 

required for the drive against pollution, 

Rustenburg will be in a good position to 

satisfy such a demand with a minimum of 

delay. 

The new mining area is of course also 

located on the Merensky Reef, where rescrves 

of platinum have been estimated to exceed 

200,000,000 ounces that could be exploited 

economically during the next thirty years - 

a clear indication that any likely future 

demand is capable of being met. At its 

present level of activity Rustenburg con- 

stitutes the world’s largest underground 

mining operation, the workings extending for 

some twenty miles along the reef and in- 

volving the employment of over 35,000 

miners. The shallower parts of the mines are 

worked from about thirty inclined haulages, 


while the deeper areas are opened up from 

nine vertical shafts ranging in depth from 500 

to 3,000 feet. 

Every working day some zo,ooo tons of ore 

are brought to the surface, loaded into trains 

and conveyed to the mill for a long and 

complex sequence of grinding, ball milling, 

flotation and preliminary smelting operations, 

the final product from here being despatched 

to Johnson Matthey for the extraction and 

relining of the six individual platinum metals. 

It is Rustenburg’s policy to maintain a 

reasonable and stable price for platinum, and 

by taking steps to see that all consumers’ 

needs can be met at such stable prices, to 

provide users with the assurance of avail- 

ability they require when deciding to use 

platinum. During the period of expansion 

from 1963 to the present, Rustenburg has 

invested more than A50 million in order to 

expand its productive capacity by more than 

five times.

ABSTRACTS 

of current literature on the platinum metals and their alloys 

PROPERTIES 

The Homogenisation Quenching of Platinum 

A. CI~EK, F. PARI~EK, A. 0RLov.k and J. TOU~EK, 

(3zech.J. Phys., B, 1970, 20, (I), 56-62 

Black dots sz roo.& diameter were observed during 

transmission electron microscopy of the defect 

structures of thin foils prepared from 99.9 and 

99.99'3 Pt samples quenched from 1300°C. The 

dots are interpreted as vacancy clusters retained 

in the presence of impurities. They appear to be 

spherical and w I IOA. 

Thermodynamic Properties by Levitation 

Calorimetry. I. Enthalpy Increments and 

Heats of Fusion for Copper and Platinum 

A. K. CHAUDHURI, D. w. BONNELL, L. A. FORD and 

J, L. MARGRAVE, High Temperature sci, 1970, 2, 

(3h 203-212 

Electromagnetic levitation heating and isothermal- 

drop calorimetry shows that AHf,, for liquid 

Pt at 2202-2631K is 5300*150 ca1;mole. 

Investigation of the Decomposition Kinetics 

of Gold-Platinum Alloys by Means of 

Electrical Resistivity 

G. KRALIK,Z. Metallkunde, 1970,61, (IO), 751-756 

Resistivity measurements on 15, 25, 55 and 65 

at. "6 Au-Pt alloys to study decomposition after 

homogenising and quenching in a salt bath clearly 

indicated the influence of quenched-in vacancies 

at the start of ageing. Annealing-out kinetics were 

explained by migration of divacancies. Migration 

energies were derived from the decay times of 

vacancy supersaturation. Spinodal temperatures 

and atomic diffusion energies were estimated. 

Resistance Minimum Phenomena in Ex- 

change Enhanced Pd and Pt Alloys 

H. NAGASAWA, J. Phys. Soc. Japan., 1970, 28, (5), 

1171-1180 

The magnetic susceptibility and solute resistance 

of Cr impurity in Pd,-,Rh, (c=o, 0.01, 0.04, 

0.05,o.o8, and 0.10) 

and also in Pt were measured. 

The addition of Cr brought about a large increase 

in the magnetic susceptibility of Pdl-,Rhc; 

below IOK the solute resistivity obeyed a T3 law. 

Both effects are explained by the negative polarisation 

of neighbouring Pd atoms. 

Preparation of Homogeneous Palladiom- 

Silver Alloy Films 

R. L. MOSS, D. H. THO,UAS and L. WHALLEY, Thin 

Solid Films, 1970, 5, (I), R19-Rzz 

21-68 at.

number pefflCr ion is calculated to lie betwcen 

1.7-2.2 p~ and is in inverse position to Cr content. 

Antiferromagnetism in this system is thought to 

originate from the antiferromagnetic coupling 

between the dwarf moments of Cr atoms. 

Magnetic Properties of Amorphous Pd-Si 

Alloys Containing Iron 

R. HASEGAWA,~. Appl. Phys., 1970,41, (IO), 4096- 

4100 

Magnetic properties of amorphous Fe,Pd,,-, Si,,, 

alloys (X=0.5-7.0) were studied at I.5-300K in 

fields up to 8.40 kOe. Above the Debye tempera- 

ture Bd the alloys arc paramagnetic, and below od 

superparamagnetic clusters exist. Ferromg- 

netism was found in amorphous Fe,Pd,,Si,, 

alloys with a Curie temperature of 28K. Results 

suggest that the d-d spin exchange interaction is 

weaker for alloys in the amorphous state than for 

those in the corresponding crystalline state. 

Resistance Anomaly of Dilute Co Impurity 

in Rh 

H. NAGASAWA, Phys. Lett. A, 1970, 3zA, (4), 

271-272 

The resistivity and magnetic susceptibility of 

dilute Co impurity in Rh were measured at r.5- 

3ooK. Values of observed Co solute resistivities 

are presented graphically. The residual resistance 

of the Co is given as 0.34 @/at../, Co; the effec- 

tive magnetic moment is 5.0 pB/atom Co, and 

the Weiss temperature is 1200& IOOK. 

Some Aspects of Phase Transformations in 

Near-equiatomic Niobium-Ruthenium Alloys 

B. K. DAS, M. A. SCHMERLING and D. s. LIEBERMAN, 

Muter. Sci. Engng., 1970, 6, (4, 248-254 

Studies of reversible phase transformations in 

three near-equiatomic Ru-Nb alloys by electrical 

measurements, hot stage optical metallography, 

X-ray diffraction and magnetic susceptibility 

measurements suggested a two-stage mechanism 

in which on cooling the high temperature cubic 

/3 phase transforms to f.c. tetragonal p' phase, 

which transforms to f.c. orthorhombic S" phase. 

CHEMICAL COMPOUNDS 

A Survey of Dinitrogen Complexes of Lhe 

Transition Metals 

J. E. FERGUSSON and J. L. LOVE, Rev. Pure. Appl. 

Chem., 1970,20, 33-50 

The preparation and properties of dinitrogen 

complexes of transition metals including Ru, Os, 

and Ir are surveyed. 

Interaction of Ruthenium Trichloride with 

Zinc 

A. N. RYABOV, E. N. RYABOV, G. R. VASILENKO and 

I. I. KOZHINA, Vextnik Leningrad Univ., Ser. Fix. 

Khim, 1970, (IO), 98-101 

The reduction of cr-RuC1, by Zn was studied by 


means of thermographic and X-ray methods. 

The reaction goes as follows: a-RuCl,+$Zn-> 

RuJ ZZnC1,. AH",,, for a-RuC1, is 47.4h2.6 

kcal , mole. 

ELECTROCHEMISTRY 

Kinetics of the Chemical Reduction of 

Platinum Black Surface Oxides 

L. D. BURKE and A. MOYNIHAN, Electrochim. Actu, 

1970>15> (91,1437-1443 

The rate at which anodic oxide films of platinised 

Pt electrodes react with H, in aqueous H,PO, 

was investigated by measuring the amount of 

oxide film remaining after various reaction times, 

The reaction rate is inversely proportional to the 

oxide coverage, probably due to inhibition of 

oxidation of H, by adsorbed oxygen species on 

the surface. The kinetics of the reaction are given. 

A Ring-disc Electrode Study of the Current/ 

Potential Behaviour of Platinum in 1.OM 

Sulphuric and 0.1M Perchloric Acids 

D. c. JOHNSON, D. T. NAPP and s. BRUGKENSTEIN, 

Ibid., 1493-1509 

The production of small amounts of soluble 

species during oxidation and reduction of a Pt 

electrode was established using the rotating ring- 

disk electrode. Pt(I1) is produced when an 

oxidised Pt electrode is reduced, and an un- 

identified species is produced during oxidation. 

Polarisation in Molten Oxides 

F. TOUSSAINT, M. BOFFE and E. PLUMAT, Silicates 

Ind.9 1970, 351 (718), 185-191 

Analysis of the intensity-potential curves gave the 

kinetics of the electrochemical processes at the 

surface of Pt and simple or complex oxides, e.g. 

stabilised SnO,, ZrO, or calcined kaolin in 

molten oxides. The method of electrical conduc- 

tion of the electrode determined the interface 

where the electrochemical reaction took place. 

Adsorption of Anions on Smooth Platinum 

Electrodes 

V. S. BAGOTSKII, YU. B. VASILIEV, J. WEBER and 

J. N. PIRTSKKALAYA, J. Elecnoanal. Chem. Interfacial 

Electrochem., 1970, 27, (I), 31-46 

The effect of the adsorption of H,, 0, and CH,OH 

on smooth Pt electrodes was investigated. 

Chemisorbed I- ions cause an overall decrease 

in the amount of adsorbed H,; and adsorption of 

anions lowers that of 0, and CH,OH. These 

effects were used to determine quantitatively the 

surface coverage with chemisorbed anions. 

Hydrogen Adsorption and Methanol Oxidation 

on Electrolytic Mixed Pt-Rh Deposits 

A. M. SKUNDIN, E. K. KHODZHAEVA and V. S. 

BAGOTSKII, Elektrokhimiya, 1970,6, (8), 1133-1 135 

Differential curves for absorption of H, by Pt,

Rh and electrolytic mixed deposits of 2, 12.5, 

20, 50 and 759$ Rh-Pt, and polarisation curves 

for the electroxidation of IM CH,OH in IN 

H,SO,, on Pt, Rh and the mixed deposits of 

12.5, 20, 50 and 87.5('; Rh-Pt show that the 

absorption properties of the mixed deposits are 

similar to those of Rh but that the catalytic 

properties approximate to those of Pt. 

Effect of the Structure of Eleetrodeposited 

Platinum on its Adsorptive Properties and 

Electrocatalytic Activity 

0. A. KHAZOVA, YU. B. VASILIEV and V. S. BAGOTSKII, 

Ibid., (g), 1367-1370 

Variations in the catalytic activity of platinised 

Pt electrodes produced by electrodeposition at 

various potentials, are connected not with the 

change in rate constants, as in the case of in- 

creased roughness, but with the surface concen- 

tration of the reacting substances. 

Investigation of Mixed Platinum-Rhodium 

Electrode-catalysts. Adsorption of Hydrogen 

on Alloys in Sulphuric Acid Solutions 

G. S. MANANKOVA, T. M. GRISHINA, G. P. KHOM- 

CHENKO and G. D. VOVCHENKO, Vest. Moskov. 

Univ., Ser. 11, Khim., 1970, 25, (4), 427-431 

The adsorption of H, and the catalytic activity 

for hydrogenation of acrylic acid in H,SO, 

solutions using Rh-Pt electrode catalysts are 

greatest for 487" Rh-Pt. Surface area of these 

electrode catalysts was measured by charging 

curves and chromatography. A new method for 

Rh content in Rh-Pt is suggested. 

The Cathodic Evolution of Hydrogen on 

Ruthenium and Osmium Electrodes 

A. R. KUHN and P. M. WRIGHT, J. Electroanal. 

Chem. Interfacial Electrochem., 1970, 27, (2), 

319-323 

Current density - potential curves for the Hz 

evolution reaction in HC1 and NaCl solutions 

at 25'C on Ru and 0s electrodes were obtained 

at different pH values. Kinetics were determined. 

ELECTRODEPOSITION AND 

SURFACE COATINGS 

Structure of Evaporated PtSi on Si 

G. A. WALKER, R. C. WNUK and J. E. WOODS, J. 

Vacuum Sci. Technol., 1970, 7, (5), 543-546 

A study of thestructure of evaporated or sputtered 

Pt on Si substrates has conclusively shown that 

for annealing temperatures up to 700°C the only 

phases present are Pt and PtSi. 

Electrodeposition of Palladium in Amino- 

hydroxide, Sulphamate, and Bromide Elec- 

trolytes 

I. F. KUSHEVICH and N. T. KUDRYANTSEV, Zashchita 

Metal., 1970, 6, (41, 465-469 

Electrolytes based on Pd(NH,),(OH) 2, 


Pd(SOJ'JH,) 2, [Pd(NHdJ(SOJ'JHz) 2, pd(NH3) 2 

(NO,),, K,PdBr,, and Pd(NH,),Br, were com- 

pared. Polarisation curves were obtained at 2o0C 

at different values of pH. Current densities were 

varied between 0.1 and 0.8 A!dm2. 

LABORATORY APPARATUS 

AND TECHNIQUE 

Two Methods for the Fabrication of Self- 

supporting Osmium Targets 

R. F. CASTEN, J. s. GREENBERG, G. A. BURGINYON and 

D. A. BROMLEY, Nucl. Instrum. Methods, 1970, 80, 

(21,296-298 

Thin targets < 1000 pg/cm2 of self-supporting 

isotopically enriched 0 s suitable for use in nuclear 

reaction and scattering experiments and robust 

targets of several mg an2 were fabricated by use 

of the described apparatus and methods. 

JOINING 

Braze Alloy Investigation 

L. F. JILLY, NASA Contract Rept. NASA-CR- 

66845, I969,II PP 

Palniro RE brazing alloy of composition 55 wt.7; 

Au, 30 wt.% Ni, and 15 wt.()k Pd with a nominal 

braze temperature of I 107'C has been developed 

for use on the Hypersonic Research Engine. The 

properties of Palniro RE are compared with those 

of Palniro I and 4, which for instance are superior 

in creep rupture resistance. Although Palniro RE 

cannot be used at the highest engine temperatures 

it is suitable, for example, for brazing the mani- 

folds to the shell structure. 

HETEROGENEOUS CATALYSIS 

Platinum Recovery in Nitric Acid Production 

Nitrogen, 1970, (66), 40-42 

The three methods of recovering Pt from Pt-Rh 

gauzes are described. The Degussa process uses a 

Pd-Au gauze below the catalyst gauze; the OSW 

process employs CaO below the catalyst gauze; 

the Hercules-Baker process uses glass fibre or 

ceramic filters to remove Pt present in the gas 

stream. The economics of Pt recovery are 

discussed. 

Platinum Dioxide as a Catalyst in the Reac- 

tion of Ammonia Oxidation into Nitrogen 

Oxide during Nitric Acid Production 

H. SIKORA, Chemik, I970,23, (I), 11 

PtO, catalyses oxidation of NH3 to N oxides at as 

low as 300°C without prior activation being neces- 

sary, unlike Pt which requires heating to a high 

temperature with a H, burner or by burning 

C,H,OH on its surface to convert it to PtO,.

Hydrocracking with Chlorinated Platinum- 

Alumina Catalysts for Liquefied Petroleum 

Gas Production 

J. P. GIANNETTI, 11. G. MCILVRIED and K. T. SEBULSKY, 

Ind. Engng. Chem., Process Des. Dev., 1970, 9, 

(31, 473-478 

Specially chlorinated Pt/Al,O, catalysts were 

prepared by reacting Pt/Al,O, with HCl gas, 

then with a S chloride or SO, and C1, and finally 

wirh HCl again. Pentane, hexane and a pretreated 

light naphtha were hydrocracked at 

2oo-29o3C, and gave results usually obtained at 

-480°C with conventional catalysts. 

Chemisorption of Different Gases on Plati- 

num/Alumina Type Catalysts 

T. IOST, T. FILOTTO and G. KALMUCHI, Petrol Gaze, 

1970, 21, (z), 111-116 

Chemisorption data from the dehydrogenation of 

cyclohexane on various Pt iAl,O, catalysts showed 

that information on the size of Pt crystals, the 

surface coverage by Pt and H iPt ratio is not always 

sufficient to correlate chemisorption characteris- 

tics and catalytic activity. Heterogeneity of 

catalyst surface is calculable from Langmuir, 

Freundlich or Temkin isotherms, and average 

heat of chemisorption from the Langmuir iso- 

therm helps clarify the chemisorption mechanism. 

Texture Study of Catalysts by Adsorption of 

Gas. 111. Measure of the Adsorption of 

Hydrogen and Oxygen on Platinum Sup- 

ported Catalyst 

v. BARBAUX, B. KOGER, J.-P. BEAUFILS and J. E. 

GERMAIN, J. Chin. Phys., I970,67, (5), 1035-1040 

0, and H, chemisorption on Pt;Al,O, catalysts 

were performed in an electronic vacuum micro- 

balance, after in situ outgassing, by the gravi- 

metric method. The weights of gases irreversibly 

adsorbed at 2o'C during a cycle: vacuum, 0,, 

H,, vacuum, 0, agree with: Pt+*O,-PtO; 

PtO+qH,-PtH kH,O;PtHt- 90,=PtO-! 1HZO. 

The metal surface area and intrinsic catalytic 

activity were calculated. 

Selective Catalytic Reduction of Oxides of 

Nitrogen by Ammonia on a Platinised 

Catalyst 

G. A. SKVORTSOV, A. P. ZASOKIN and A. I. 

PODZHARSKII, Khim. Promyshlennost, 1970, (6), 

435-437 

The process of reduction of N oxides by NH, 

over Pt:A1,0, was studied with regard to effects 

of temperature, concentration of NH, and con- 

centration of 0,. 

On the Role of the Support in Platinnm/ 

Alumina Catalysts 

I. I. LEVITSKII, KH. M. MINACHEV and v. v. VORONIN, 

Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1970, (9), 

2007-201 I 

Comparison of the hydrogenolysis of methyl- 


cyclopentane using 5':n Pt /A1,0, with earlier 

work showed sharp differences from tests 

with 0.30" Pt!A1,0,. Pt/C and SiO, also gave 

less hydrogenolysis. A1,0, as the support guaran- 

tees high dispersion of the supported metal and 

determines the catalytic properties, presumably 

due to the different electrical state of the atoms 

adjoining the support surfaces. 

Disproportionation of Cyclohexene and 

Crossed Disproportionation on Platinum/ 

Alumina 

R. MAUREL and G. LECLERCQ, C.R., st+. c, 1970, 

271, (4), 239-241 

The disproportionation of cyclohexene to cyclo- 

hexane in benzene in contact with Pt/AI,O, at 

116°C is a complex reaction in which dehydro- 

genation in benzene precedes hydrogenation. 

Kinetics of Consecutive Heterogeneous Cata- 

lytic Reaction: Gas-phase Hydrogenation of 

Phenol on a Platinum Catalyst 

v. HANCIL and L. BERANEK, Chem. Engng. Sci., 

1970, 25, (7), 1121-1126 

The kinetics of consecutive hydrogenation of 

phenol to cyclohexanol via cyclohexanone on a 

Pt:'SiO, catalyst at ISO'C were studied. The 

course of the overall reaction can be described by 

Langmuir-Hinshclwood type rate equations, 

which suggests that both composing reactions 

occur on the same sites of the catalytic surface. 

On the Slow Uptake of Hydrogen by Platin- 

ised Carbon 

M. BOUDART, A. w. ALDAG and M. A. VANNICE, 

J. Catalysis, 1970, IS, (I), 46-51 

Burning off the C contaminating the Pt surface 

of Pt/C before adsorption measurements de- 

creases or suppresses uptake of H?. C contamina- 

tion of Pt appears to provide bridges which allow 

surface diffusion of H atoms from Pt to the C 

support. 

Catalytic Activity of Platinum Catalyst on 

Polymeric Supports 

s. G. FEDORKINA, G. I. EMEL'YANOVA and N. I. 

KOBOZEV, Vest. Moskov. Univ., Ser. 11, Khim., 

197% 25, (3h 350-352 

Studies of the adsorption properties of Pt,'polymer 

catalysts showed no noticeable effect of the poly- 

mers on the catalytic activity of the Pt. Adsorp- 

tion capacity of an A1,0, support was increased 

by polymer coating. Polymers tested were caprone, 

polycarbonate and the copolymer of phenol- 

phthalein and terephthalic acid. 

Palladium : Preparation and Catalytic Pro- 

perties of Particles of Uniform Size 

J. TURKEYICH and G. KIM, Science, 1970, 169, 

(39481,873-879 

Uniform particles of Pd, diameter 55-45oA were 

prepared by the hydrothermal treatment of

Al,(OH), sol to form rods of Also, on which Pd 

was adsorbed from aqueous suspension. The 

activity and kinetics of C,H, hydrogenation on 

this catalyst were examined. 

Effect of Zinc Cations on the Selectivity of 

Palladium Catalysts on Supports during the 

Hydrogenation of Dimethylethynylcarbinols 

V. A. NAIDIN, G. D. ZAKUMBAEVA and D. V. SOKOL’ 

SKII, Kinet. Kataliz, 1970, 11, (4), 1072-1074 

Studies of the effects of adding Zn cations as 

ZnSO, to stationary Pd catalysts for hydrogena- 

tion of aqueous solutions of 5-757” dimethyl- 

ethynylcarbinols showed that the modification 

causes a sharply increased yield (98://) of 

dimethylvinylcarbinols, 

Liquid-phase Hydrogenation of Heptene-l 

on Palladium and Platinum-Palladium Catalysts 

on Alumina 

D. V. SOKOL’SKII, M. I. GORYAEV, G. A. SAVEL’EVA, 

N. M. POPOVA and A. D. DEMBITSKIT, Neftekhimiya, 

1970, 10, (4), 489-493 

Studies of the liquid-phase hydrogenation of 

I-C,H,, in 96:;; C,H,OH at 20°C over Pd/Al,O, 

and Pt-Pd/Al,O,, in relation to catalyst metal 

content and to the composition of the active 

phases, showed that it occurs at the expense of 

weakly bonded H and is accompanied by iso- 

merisation to cis- and tram-z-C,H,, and 3-C7H,,. 

Maximum yields on 4% metal/AlpOs occurs with 

Pd. Yield decreases as Pt content increases. 

X-Ray Studies on Supported Palladium 

Catalysts 

M. UEHARA and S. SUZUKI, Kogyo Kagaku Zasski, 

1970>73, is), 852-855 

Absorbed amounts of H, are proportional to the 

increase in lattice constant caused by the dissolved 

Ei,. Dehydrogenation of n-C,H,,, on PdiC was 

investigated, also the a-B phase transition in 

PdjC which occurred under a wide range of 

conditions. The lattice constant of 3.97a suggested 

a new type of solid solution of H, and Pd. 

Hydrogen Absorption Isotherm of Supported 

Palladium Catalysts 

Ibid., 855-859 

H, absorption isotherms of various supported 

Ind catalysts were studied and fall into 3 types: 

{i) perfect step type, in which the Pd exists as 

uniform crystallites, (ii) imperfect step type, in 

which the Pd occurs as continuously sizedistributed 

crystallites, (iii) non-step type, Pd as 

non-crystalline particles. They tcnd towards the 

non-step type with increasing specific surface area. 

Activity of Various Types of Palladium 

Catalysts Supported on Polyacrylonitrile 

0. A. TYURENKOVA and L. A. CHIMAROVA, Zh. Fiz. 

Kkim., 1970,44, (91, 2278-2282 

Potentiometric studies of the activity of Pd ,poly- 


acrylonitrile catalysts in relation to the conditions 

of Pd reduction show that those reduced in alco- 

holic media are more active and stable for the 

hydrogenation of dimethylethynylcarbinols, 

whereas those produced using dioxanc have little 

activity. Optimum reduction occurs at 40T but 

catalyst produced in those conditions is less 

selective for hydrogenation of dimethylethynyl- 

carbinol. 

Investigation of the Step Mechanism and 

Selectivity of Reduction of ,.Aceto- and 

Propiophenone on Rh-Alto, 

L. KH. PREIDLIN, N. V. BORUNOVA, L. I. GVINTER, 

S. S. DANIELOVA and R. N. BADAKH, Izv. Akad. 

Nauk S.S.S.R., Ser. Kkim., 1970, (S), 1797-1803 

Rh:Al,O, catalyses addition of H, to aliphaticaromatic 

ketones to form alkylphenylcarbinols 

and alkylcyclohexylketones, depending on the 

availability of CO groups for hydrogenation. 

Further reduction depends on the likelihood of 

either hydrogenolysis of C-OH bonds or of 

hydrogenation of alkylphenylcarbinol aromatic 

rings. In mild conditions the former predominates 

but in severe conditions the latter, forming 

mainly alkylcyclohexylcarbinols. Partial poisoning 

of Rh/A1203 by Cd showed that reduction of 

the aromatic rings occurs at various parts of the 

catalyst surface at various rates unrelated to the 

process conditions. 

Mixed Adsorption Catalysts for Hydrogenation. 

XVI. Rhodium-Platinum and Rhodium- 

Palladium Catalysts on Silica Gel 

A. A. ALCHUDZHAN, N. 2. EDIGARYAN and M. A. 

MANTIKYAN, Arm. Kkim. Zh., 1970, 23, (I), 3-8 

0.5 wt.% RhSiO, catalysts with additions of 

Pt and Pd were compared with RhiSiO,, PtjSiO, 

and PdlSiO, catalysts for hydrogenation of 

C,H, at 9oCC, volume ratio H,:C,H, ~4:1, H, 

gas flow 1.5-2.5 l/h, activity being expressed as 

(2, conversion to cyclohexane. Activity increased 

proportional to Pt content. Activity of concur- 

rently deposited Rh-Pt:SiO, was greater than the 

total activity of Rh/Si02 and Pt;SiO, catalysts 

with the same total content of metals. Pd addi- 

tions tended to decrease catalytic activity, possibly 

due to its different electronic structure or to an 

effect of the SO,. 

The Hydrogenation of Alkadienes. Part IV. 

The Reaction of Buta-1,3-diene with Deuterium 

Catalysed by Rhodium, Palladium, 

and Platinum 

A. J. BATES, Z. K. LESZCZYNSKI, J. J. PHILLIPSON, 

P. B. WELLS, and G. R. WILSON, J. Chem. SOC., A, 

Inorg. Pkys. Tkeor., 1970, (14), 2435-2441 

Reactions of buta-1,3-diene with Rh:AI,O,, 

Pd/Al,O, and Pt/A1,0, as catalysts were studied. 

Butene isomerisation occurs only after desorption 

although absorbed butyl groups were formcd at 

the Rh and Pt surfaces.

Part V. The Hydrogenation of trans- and 

cis-Penta-1,3-diene catalysed by Cobalt, 

Nickel, Copper, Palladium and Platinum 

P. B. WELLS and G. R. WILSON, Ibid., 2442-2447 

Gas phase hydrogenation of the pentadienes was 

investigated using Pd iAl,O, and Pt/Al,O, 

catalysts amongst others. The reaction was 

relatively slow; all isomers of n-pentene were 

formed with little or no pentane. 

Measurements of Active Site Concentrations 

at Rhodium, Osmium, Iridium, and Platinum 

Surfaces by l,l-Diphenyl-2-picrylhydrazine 

Oxidation in the Liquid Phase, 

and Carbon Monoxide Chemisorption from 

the Gas Phase 

R. B. MOYES, P. B. WELLS, K. BARON, K. COMPSON, 

J. GRANT and R. HESELDEN, J. Catalysis, 1970, 18, 

(21, 224-227 

0 atoms chemisorbed at the surface of prereduced 

Rh, Ir and Pt powders with diphenylpicrylhydrazine 

to yield H,O and the stable 

diphenylpicrylhydrazyl free radical. The number 

of active sites present per gram of powder was 

calculated from concordance determinations of 

the free radical concentration by e.s.r. and optical 

spectroscopy. 

Hydrogenolysis of Cyclobutane Hydrocar- 

bons on Platinum, Palladium, Rhodium, 

and Iridium Catalysts 

M. YU. LUKINA, T. G. OLPER’EVA, 0. v. BRAGIN, A. L. 

LIBERMAN and B. A. KAZANSKII, Dokl. Akad. Nauk 

S.S.S.R., 1970, 193,(1), 106-109 

Hydrogenolyses of ethylcyclobutane and of other 

cyclobutane derivatives over PtlC, Pd jC, Rh iC 

and Ir/C was studied in constant flow and pulsed 

flow conditions. With PtjC and PdjC the prin- 

cipal products were n-hexane and 3-methyl- 

pentane. With RhIC and Ir/C there were also 

quantities of other pentanes and lower alkanes. 

HOMOGENEOUS CATALYSIS 

Production of Linear Acids or Esters by the 

Platinum-Tin Catalysed Carbonyktion of 

Olefins 

L. J. KEHOE and R. A. SCHELL, J. org. Chem., 1970, 

35. (S), 2846-2848 

A H,PtCl,-SnCl, couple was used to catalyse the 

carbonylation of olefins such as dodecene-1 in 

the presence of methanol to linear esters in Ih at 

200 atm.; in the presence of water, acids are 

formed. K,PtCI, with SnC1,alsoshowedreactivity. 

The Palladium(I1) Chloride and Copper(I1) 

Chloride Catalysed Oxychlorination of Ethylene 

to Ethylene Chlorhydrin 

H. STANGL and R. JIRA, Tetrahedron Letters, 1970, 

(41),3589-3592 

The reaction of C,H, with 0% in the presence of 


PdC1,-CuCI, to produce HO-CH,-CH,-CI is 

discussed. 

Aromatic Substitution of Olefins. The 

Reaction of Ferrocene with Styrene in the 

Presence of Palladium(I1) Acetate 

R. ASANO, I. MORITANI, Y. FUJIWARA and 

s. TERANISHI, J. Chem. SOC., D, Chem. Commun., 

197% (20), I293 

An example of a very convenient direct synthesis 

of alkenylferrocenes is the reaction of ferrocene 

with styrene to produce t~ans- sr-styrylferrocene 

in the presence of Pd(OAc),. 

Activation of Molecular Oxygen, Hydrogen, 

Carbon Monoxide, and Olefins by a Rhodium(1) 

Complex in Nonaqueous Media 

B. R. JAMES and F. T. T. NG, Ibid., (IS), 908-909 

The complex [(C,H,,),RhCI,],, dissolved in 

dimethylacetamide containing LiCl, reacts with 

0,, H,, CO and some olefins, e.g., maleic acid 

(MA) to give complexes such as Rh(I)(MA) 

which have catalytic properties. 

Dimeric Metal Acetates for the Homogeneous 

Hydrogenation of Olefins 

B. C. HUI and G. L. RBMPEL, Ibid., (IS), 1195-1196 

Rh,(OCOMe), and Ru,(OCOMe), were shown 

to catalyse hydrogenation of various olefms in a 

number of organic solvents. 

Homogeneous Catalytic Hydrogenation of 

Organic Compounds using Rhodiumtriarylphosphine 

Complexes 

J. L. PARSONS, Diss. Abstr, B, 1970, 30, (9), 4057 

Trichlorotris(4-biphenyl-I -naphthylphenyl-phosphine)rhodium(III) 

has been developed as a 

homogeneous hydrogenation catalyst and has 

been used for the catalytic reduction of sr, ,8unsaturated 

acids and esters. It is superior in performance 

to other Rh(II1) phosphine complexes. 

Oxidation by Transition Metal Complexes. I. 

Oxidation of Styrene and Triphenylphos- 

phine Catalysed by 02-Ir Complex 

K. TAKAO, Y. FUJIWARA, T. IMANAKA and 

s. TERANISHI, Bull. Chem. SOC. Japan, 1970, 43, 

(41, IIS3-IIS7 

The oxidation reactions of styrene and PPh, 

catalysed by various Ir complexes were studied. 

The complexes IrX(CO)(PPh,), and Ir[(Ph,CH, 

CH,Ph,),Cl] were effective oxidation catalysts. 

Oxidation with Pd salts was compared with the Ir 

complexes. 

On the Catalytic Decomposition of Per- 

chloric Acid in the Presence of Complex 

Compounds of Iridium 

S. I. GINZBURG and M. I. YUZ’KO, zh. Neorg. Khim., 

197% 15, (91, 2441-2444 

Ir complexes catalyse decomposition of HCIOI

in the presence of HBSO, at 197-200~C. The 

formation of polymeric Ir(1V) compounds reduces 

the catalytic activity. Unstable intermediate 

compounds, probably of Ir(VI), form initially 

and are strongly oxidising. Small amounts of Ir 

evaporate during oxidation of Ir perchlorate due 

to formation of the higher oxide IrO? 

Catalytic Oxidation of Triphenylphosphine 

Using a Ruthenium-Oxygen Complex 

B. W. GRAHAM, K. R. LAING, C. J. O'CONNOR and 

W. R. ROPER,J. Chem. SOC., D, Chem. Commun,, 

197% (IS), 1272 

Ru(O,)(NCS)(NO)(PPh,), efficiently catalyses 

oxidation by 0, of PPh, to the oxide. 

Hydrogenation of Olefins by p-Dichloro-x- 

benzene-ruthenium(I1) 

I. OGATA, R. IWATA and Y. IKEDA, Tetrahedron 

Letters, 1970, (34), 301 1-3014 

The hydrogenation of pentenes by [Ru(C,H,)C1,], 

was studied in various solvents. The catalytic 

activity and reaction products depended on the 

solvent used. The mechanism of hydrogenation 

and the species produced in coordinating sol- 

vents, e.g. DMSO, are discussed. 

FUEL CELLS 

A Fuel-Cell that Operates on Human Blood 

Chemical Week, 1970, 107, (2), 40 

A fuel cell which could power an artificial heart 

has electrodes of a noble metal substrate to 

which selective catalysts of Au-Pd alloys are 

bonded. Placed directly in the blood, one elec- 

trode reacts preferentially with glucose in the 

blood, the other with 0,. 20 !Lw/cm2 of electrode 

NEW PATENTS 

METALS AND ALLOYS 

Alloys of Variable Transition Temperature 

F. E. WANG & W. J. BUEHLER 

British Patent 1,202,404 

The alloy JL,M,-, has a martensitic transition 

temperature depending on 

a Group VIA metal, and makes up 50 at.?, of the 

alloy, the remaining 50", being L I M, where 

is greater than 0 and less than I. Typically, J is 

zr, L is Rh and M is R~ oT J is zr, L is pd and 

M is Rh. 

were obtained; about 10 w would be needed to 

power an artificial heart, 

CHEMICAL TECHNOLOGY 

Influence of Palladium on the Corrosion and 

Electrochemical 

OX25H6T 

Behaviour of Steel 

N. D. TOMASHOV, G. P. CHERNOVA, L. N. VOLKOV, 

Zaschita Metal., 1970, 6, (4), 45-427 

Studies on the steel oX2gH6T, which contains 

60/:, Ni and 25u4, Cr, showed that passivation 

using o.1-0.5"6 Pd occurs in two stages. The 

corrosion rates for various Pd additions were: 

0.17, Pd, 26.8 g,/m2h; o.zq, Pd, 18 g:m2h; 

0.5"~ Pd, 24.5 g/m2h, in 2o0:, H2S0, at roo'C 

for 5 h testing, 

TEMPERATURE 

MEASUREMENT 

On the Control of the Temperature Regime 

of Glass Masses Delivered for Moulding 

V. M. BUDOV, YU. V. SESKUTOV, V. SH. YAKUPOV, V. S. 

PAVLOV and V. V. FOKIN, Stekla Keram., 1970, (8), 

6-8 

Studies of the variations with depth of temperature 

of molten sheet glass in cooling tanks were 

carried out using high temperature thermocouples 

above the surface, Pt-cased thermocouples projecting 

from the tank walls into the glass and open 

junction low-inertia Pt :Rh-Pt thermocouples 

dipped into the glass to various depths. Fluctuations 

and variations at these points indicate that 

one temperature-measuring point is insufficient 

and that the thermal processes are complex. 

drawn to wire contains about 60-gooh Ru, 5-407{~ 

Cu, up to about 35:0 Pd and up to 10% Ni. It is 

produced by liquid-phase sintering, preferably by 

infiltration of Cu or Cu alloy, into a Ru compact 

at a temperature between 1083°C and 1500°C. 

~ i ~ ~ ~ ~ Noble ~ ~~~~l~ i ~ 

''Pending the ratio ' M. J is p, R. MALLORY & CO. INC. U.S. Patent 3,515,542 

Cu, Au, Ag, Pt, Pd and their alloys are strengthend 

or hardened by introducing UP to 10"" of a 

compound of Cr, Ti, Th, u, Zr, B Or si Or alloys 

thereof. A melt is formed of the noble metal and 

the hardening element and gas bubbled through 

the melt to form the compound, usually an oxide. 

Workable Duplex Structured Ruthenium 

Alloys Hardening of Platinum Metals 

INTERNATIONAL NICKEL CO. INC. 

JOHNSON, MATTHEY & CO. LTD 

U.S. Patent 3,498,763 

German Appl. I ,53 3,275 

A cold-workable Ru alloy capable of being cold Pt, Pd, Rh and their alloys with one or more 

Platinum Metals Rev., 1971, 15, (l), 3540 35

other Pt metals are hardened by the addition of a 

small amount of one or more base metals. These 

metals, such as Cr, must form compounds stable 

at high temperatures. 

Dispersion-strengthened Metals 

JOHNSON, MATTHEY & CO. LTD 

German APP~. 1,935,329 

A molten metal (Ag, Au or a Pt metal) is sprayed, 

together with a disperse-phase component (oxide, 

carbide, nitride, or sulphide) on to a cooled 

former. The product may be suitable for, e.g., 

electric contacts, thermoelements or resistors; or 

for use as a catalyst, diffusion membrane or 

spinneret. 

CHEMICAL COMPOUNDS 

Electrically Conductive Oxides Containing 

Palladium 

E. I. DU PONT DE NEMOURS & CO. 

U.S. Patent 3,498,931 

New electrically conductive oxides have the 

formula PdMO,, in which M is Co, Cr, Rh or 

CriRh, but may vary slightly in stoichiometry 

from the formula. They are prepared by the 

reaction of a Pd dihalide, optionally mixed with 

Pd, and an appropriate oxide containing M. 

Organometallic Polymers 

MCDONNELL DOUGLAS CORP. 

U.S. Patent 3,504,052 

A novel class of polymers contains ruthenocene 

or osmocene units which are inrerlinked to form 

polymeric products having high heat stability and 

other advantageous properties. They are produced 

by reacting ruthenocene or osmocene with 

an aldehyde or ketone in the melt phase and in 

the presence of a Lewis acid catalyst. 

ELECTRODEPOSITION AND 

SURFACE COATINGS 

Metallising of Ceramics 



A ceramic is metallised by applying to its surface 

a finely divided granular noble metal powder. 

This powder comprises at least 60 wt.O of Pt and 

optionally a further metal selected from Pd, Rh 

and for Ru. At least 50 wt.Oo of the Pt must have 

a surface area of 0.01-1 mL/g. The coated surface 

is fired, preferably at 1400-2000”C, to give a 

tightly adherent conductive metal film. 

Oxidation-resistant Coated Article Containing 

Iridium, Ruthenium, Molybdenum or 

Tungsten 


US. Patent 3,499,740 

A coated metal article has a body and a coating of 

Platirium MetalsRev., 1971, 15, (1) 36 

different compositions which are resistant to 

interdiffusion at elevated temperatures. They are 

single-phase conjugate compositions falling at 

opposite terminals of an alloy tie line on a ternary 

metallurgical system diagram having Au at one 

apex, Pd at a second; Ru, Ir, W or Mo at the third. 

Palladium Coated Electric Contacts 


U.S. Patent 3,500,537 

Corrosion-resistant electrical contacts are made 

coated with Pd. The Pd is electrodeposited from 

an aqueous ammoniacal bath comprising 

tetrammino-palladous bromide and having a pH 

of about 8-10. The deposit is highly ductile thus 

permitting deformation to form electrical contacts. 

Plating Solutions for Rhodium 

K. OHKUEO et al. U.S. Patent 3,515,651 

An electrolyte for electroplating low stress Rh 

and Rh alloy deposits comprises a Rh salt, 

optionally a salt of another metal capable of 

alloying with Rh and at least one of hexameta- 

phosphoric acid and alkali metal or ammonium 

hexametaphosphates. 

JOINING 

Brazing Alloy for Joining Graphite to 

Graphite and to Refractory Metals 

US. ATOMIC ENERGY COMMISSION 

US. Patent 3,497,332 

The joining of graphite to graphite and to 

refractory metals such as Mo, W and their alloys 

is effected with a brazing alloy consisting essentially 

of Ni, Pd and 2-12‘;; Cr. 

Solderable Stainless Steel 

P. R. MALLORY & GO. INC. U.S. Patent 3,515,950 

A method for rendering solderable a stainless 

steel body resistant to corrosive attack from 

common electrolytes includes covering one layer 

of a stainless steel body with layers of metal. A 

first metal layer serves as a barrier layer to the 

diffusion of a subsequent metal layer through to 

the stainless steel body. The subsequent metal 

layer is resistant to corrosive attack from common 

electrolytes, is solderable and consists of Ag alloyed 

with Au, Pd, Pt, Re or 0s. The alloy layer may 

be formed by covering the barrier layer with a 

layer of Ag and Au or one of the other metals. 

The layered stainless steel body is heated to a 

temperature below the melting point temperature 

of the metal layer having the lowest melting point 

so that the layers (except the barrier layer) 

diffuse into one another, forming an alloy layer 

overlaying the barrier layer. 

Solder for Thermoelements 

SIEMENS A.G. 

German ApPl. 1,533,547 

The solder is an alloy of composition: 

Pdx(Me,Si,-,) I-x

where Me is Fe or a metal of Group IV, V or VI, 

other than Cr and Zr, and y is >o. 

Soldering Semiconductors 

TELEFUNKEN PATENTVERWERTUNGS-G.m.b. H , 

German Appl. 1,564,901 

A diode or transistor is attached to a Mo or W 

base by two layers of a noble metal, preferably Rh. 

Solder for Steel and Refractory AUoys 

L. A. MARKOVICH et d. U.S.S.R. Patent 261,887 

The solder has the composition 3~-34')(~ Pd, 

22-25";, Ni, I 1-13 5: Cr and the remainder Cu. 

HETEROGENEOUS CATALYSIS 

Self-cleaning Gas Ovens 

GENERAL ELECTRIC CO. 


Cooking fumes in a gas oven are oxidised by an 

oven liner coated with a Pt catalyst. 

Dehydrogenation Catalyst 

BRITISH PETROLEUM GO. LTD 


Normal alkanes are dehydrogenated to normal 

alkenes in the presence of a Pt group metal 

exchanged on to a molecular sieve. 

Oxidation Catalyst 

INSTYTUT NAWOZOW SZTYCZNYCW 


Concentrated NO is formed by the oxidation of 

NH, with 0, and water vapour in the presence of 

a Pt catalyst. 

Acrylonitrile Dimerisation Catalyst 



Adiponitrile is prepared by the dimerisation of 

acrylonitrile in the presence of a catalyst which 

is a mixture of a water-soluble salt of a carboxylic 

acid and a water-soluble Ru salt, supported on 

C or AI,O,. 

Catalyst 

IMPERIAL CHEMICAL INDUSTRIES LTD 


Aromatic isocyanares are prepared by the action 

of nitro or nitroso compounds with CO in the 

presence of a catalyst which is a mixture of at 

least one of the noble metals Ru, Rh, Pd, Os, Ir 

and Pt with two or more heavy metal oxides, 

hydroxides, carbonates, basic carbonates or basic 

phosphates. 

Isomerisation Catalyst 



The isomerisation of olefines is effected in the 

Platirium MetalsRev., 1971, 15, (1) 37 

presence of noble metals, preferably Pt, Ru or 

Pd. Pd gives best results. 

Two-stage Hydrocarbon Hydrogenation 

UNIVERSAL OIL PRODUCTS CO. 

US. Patent 3,494,859 

An aromatic hydrocarbon feedstock containing 

diolefines, mono-olefines and sulphur contaminants 

is hydrogenated at a relatively low 

temperature of 200-500'F with a composite 

catalyst of Li in Pd (1)(Al~0, to convert the 

diolefines to mono-olefines. Conventional desulphurisation 

is then carried out. 

Production of Acrylonitrile and Meth- 

acrylonitrile 

SUN OIL co. U.S. Patent 3,499,025 

Acrylonitrile and methacrylonitrile are prepared 

by reacting C,H, and iso-C,HB respectively with 

air or 0, in the presence of a slight excess of NH, 

over a Pt catalyst. The catalyst is in the form of a 

metallic gauze. Temperatures of from 750- 

10oo"C and contact times of less than 0.1 second 

are used. 

Hydrogenation of Aromatic Nitro Compound 


U.S. Patent 3,499,034 

A new process is described for the hydrogenation 

of aromatic nitro compounds. It is a continuous, 

one stage process producing a yield of about 99" , 

of theory of substantially pure aromatic amine. 

Pd/C is a preferred catalyst. 

Apparatus for Treating an Exhaust Gas 

Stream with Different Catalyst Beds 


US. Patent 3,503,715 

A unitary apparatus for effecting the catalytic 

oxidation of engine exhaust gases, where there 

may be both high and low quantities of hydrocarbon 

emissions with such gases, has one catalyst 

layer comprising Pt:Al,O, particles containing 

a Ba, Ca or Sr component. 

Catalytic Reforming Process 


US. Patent 3,515,665 

A continuous low pressure reforming process is 

described using a Pt catalyst. 

Catalytic Hydrocarbon Conversion 

BRITISH PETROLEUM GO. LTD 

US. Patent 3,516,925 

A new conversion catalyst for waxy petroleum 

feedstocks consists of a Group VI or Group VIII 

metal deposited on a decationised mordenite 

containing up to z", of non-catalytic metal 

cations. The mordenite must have pore openings 

of 5A or more. A Pt catalyst deposited on 

decationised mordenite is described in several 

examples.

Naphtha Reforming Process 

CHEVRON RESEARCH CO. 

French Patent 1,583,982 

Reforming with a Pt-Re supported catalyst is 

effected in specified process conditions. 

Hydrogenation Catalyst 

DEUTSCHE GOLD- UND SILBER-SCHEIDEANSTALT 


Liquid-phase hydrogenation can be achieved at 

comparatively low temperatures and pressures in 

the presence of a Pt group metal catalyst in SUSpension, 

e.g. finely divided Pd. 

Catalysts 

JOHNSON MATTHEY & CO. LTD 

German Appl. 1,542~2 I 4 

Catalysts which are active in oxidation, reduction, 

hydrogenation and dehydrogenation reactions 

consist of homogeneous mixtures of two or more 

noble metal (except 0s) oxides. They are not just 

physical mixtures but are formed, e.g. by COprecipitation 

from a mixed salt solution. 

Catalyst 



A catalyst which is useful for, e.g. oxidation and 

hydrogenation reactions, consists of a coprecipitated 

mixture of l't and Ru oxides, with the weight 

ratio of the two metals being approximately: Pt 

from 20 to almost 90; Ru from just over 10 to 80. 

Catalyst 



A catalyst which is active in oxidation and 

reduction reactions, for example, consists of a 

mixture, in the proportions of at least 3 : I, of a 

noble metal oxide (excluding oxides of 0s) with 

at least one oxide of Fe, Co, Ni or Cu. 

Keduction Catalyst 

INVENTA A.G. FUR FORSCHUNG UND PATENT- 

VERWERTUNG German Appl. 1,567,596 

NO may be reacted with hydrogen in H,SO,, in 

the presence of a Pt catalyst (e.g., 2(:,, PtC), 

to give hydroxylamine sulphate. 

Oxidation Catalyst 

CELANESE CORP. 

Geman Appl. 1,568,364 

The partial oxidation of organic compounds, e.g., 

alcohols, aldehydes, ketones, by an alkali metal 

or alkaline earth metal hypochlorite is catalysed 

by the presence of Ru. 

Reforming Catalyst 

CHEVRON RESEARCH CO. German Appl. 1,932,339 

The catalyst consists of a porous inorganic oxide 

combined with 0.01-3 wt.Oj0 of Pt, 0.01-5 wt.4" 

of Re and u.1-3 wt.O,)*, where X is halogen (except F), L is the 

same or different H atom, 6-12 C aryl, 7-12 C 

alkaryl or 1-12 C alkyl group, and T is P, As or 

Sb. Typical catalysts are Rh hydridocarbonylbis(tripheny1 

arsine) dichloride and Rh hydridocarbonylbis(n-heptyldi-2- 

naphthylphosp hine) dibromide.

Hydroquinone Production 

LONZA S.A. 


Hydroquinone is produced from C,H,, CO and 

H2 in the presence of a trimeric Ru tetracarbonyl. 

Hydrogenation Catalyst 

E. I. DU PONT DE NEMOURS 82 CO. 


The catalyst is made by mixing and heating 

together finely-divided A1 ,03, Ru chloride or 

nitrosonitrate and (NH,),CO, or bicarbonate. 

Hydrogenation Catalysts 



Olefinic and acetylenic compounds are hydro- 

genated in the presence of specified Rh com- 

plexes, especially RhX(Ph,P),, where X is an 

anionic group such as halide. 

Hydroformylation Catalyst 

JOHNSON MATTHEY & CO. LTD. 


A catalyst for hydroformylation is a Rh hydridocarbonyl 

phosphine complex, e.g. RhH(C0) 

(PPh313. 

FUEL CELLS 

Fuel Cell 

UNITED AIRCRAFT CORP. British Patent I,200,022 

In a fuel cell system capable of operating at full 

load in the temperature range -40” to ;-5o”C, 

the catalyst is Pt black. 

Fuel Cells 

GENERAL ELECTRIC co. British Patent 1,204,540 

In such a cell the fuel electrode consists of a 

support material of a metal silicide, Ta boride, 

Ti boride or B carbide on which is dispersed a 

catalyst. The latter consists of a Pt-Ku alloy 

containing 20 to 80 wt.:: of Ru. 

Palladium Hydrogen Diffusion Fuel Cell 

Electrode 

U.S. SECRETARY OF THE AIR FORCE 

U.S. Patent 3,497,390 

A fuel cell has an electrolyte positioned in a 

container between a porous oxygen electrode to 

which oxygen is supplied and a non-porous Pd 

anode to which gaseous H, is supplied. The Pd 

anode is produced by heating a Pd strip in air to 

a temperature between 500% and 875°C. 

Fuel Cell Cathode 

LEESONA CORP. U.S. Patent 3,5r4,336 

A fuel cell cathode is a lightweight structure 

consisting of a mixture of Pt black or another 

catalytic metal and a hydrophobic polymer such 

as ptfe. 


CHEMICAL TECHNOLOGY 

Hydrogen Release for a Heat Pipe 

A.C.P. INDUSTRIES INC. 

U.S. Patent 3,503,438 

A heat pipe system, particularly for a railway car, 

using water which may dissociate and develop a 

dangerously high pressure of H,, is provided with 

a H, release device located outside the car. The 

release device is a Pd or Pd alloy tube sealed to a 

wall of the heat pipe system and having a closed 

inner end and an open outer end. 

Dispersion-strengthened Metals 



A mixture of a “host” metal (e.g. a Group VIII 

noble metal) and a smaller proportion of at least 

one more reactive metal, in the form of a powder, 

is projected at high temperature through an 

atmosphere which will react with the more reactive 

metal (to form, e.g. oxide, sulphide, nitride), 

and collected on a cooled surface. 

GLASS TECHNOLOGY 

Method of Forming Jets in Bushing Baseplates 

OWENS-CORNING FIBERGLASS CORP. 

US. Patent 3,514,84r 

A method of forming jets in bushing base-plates 

made of Pt or Pt alloy is described. Pt-Rh and 

Pt-Ir containing from 1-10 wt.‘:, of gold (especially 

2--6O, Au) are preferred. The metal is formed 

into a body having solid raised portions on one 

surface, further metal is joined to each of these 

portions and passage ways are formed through 

them by the application of dies under pressure. 

Further metal joined may be of a different alloy. 

ELECTRICAL AND 

ELECTRONIC ENGINEERING 

Electrical Heaters for Glass 

TRIPLEX SAFETY GLASS CO. LTD 


An “ink” containing metal particles or a chemical 

which will produce such particles on firing, is 

applied to the glass by silk-screen printing. The 

metal may be Ag, Au, Pt or Pd. 

Electrodes 



Electrodes, e.g., for the electrolysis of alkali metal 

chlorides, are obtained by coating Ti with an 

operative electrode material. This consists of 

oxides of at least one Pt group metal or mixtures 

thereof with at Ieast one Pt group metal. The 

preferred composition is RuO,.

Alloy for Electrical Leads 

WILKINSON DENTAL MANUTACTWRING CO. INC. 

U.S. Patent 3,495,978 

A new alloy for electrical leads normally embedded 

in a ceramic base constituting a portion of an 

electrical component, such as a potentiometer, 

is described. The alloy consists of from 64-90O,~, 

Au, 10-359, Pd and 0.5-2:o Ru. The propor- 

tions are selected so that a greatly improved lead 

wire is provided in which oxidation is sub- 

stantially avoided even at the firing temperatures 

of the ceramic base in which the lead is embedded. 

Metallising Ceramics 

B. 1. DU PONT DE NEMOURS & CO. 

U.S. Patent 3,497,384 

A process for metallising a ceramic substrate by 

applying a noble metal powder consisting of 

6o-r00[~(, Pt (having a surface area within the 

range of 0.1-1 m"g) and optionally Pd, Rh, 

Ru and their alloys or mixtures and firing 

the powder at a temperature within the range of 

r400-2cmo"C is described. The metal powder 

forms a tightly adherent conductive metal coating 

on the ceramic substrate. The process does not 

use the conventional inorganic binders. 

Manufacture of Electrodes 

NIPPON CARBIDE K.K. US. Patent 3,497,426 

Electrodes are made by mechanically cleaning a 

Ti surface in the absence of O3 or N, (e.g., by 

buffing with sandpaper in benzene). They are 

immediately transferred to a vacuum container, 

avoiding contact with 0, or N,, and a first Pt 

group metal coat is then vapour plated on to the 

cleaned surface to a thickness of 1oo-3cmo A. 

A second coating of Pt or Rh is subsequently 

electroplated on to the surface to a thickness of 

0.1-5 p. The electrode is suitable for the elec- 

trolysis of chlorides and sulphates. 

Tungsten Dispenser Cathode 

U.S. PHILIPS CORP. U.S. Patent 3,497,757 

An improved coated dispenser-type cathode 

consisting of a metal matrix of W or W-LILo in 

reactive relationship with an alkaline earth metal 

compound which will supply Ba or BaO to the 

emitting surface of the matrix is described. The 

matrix emitting surface is coated with a thin 

porous layer of an alloy of 0 s and Ir, or 0s and 

Ru, to provide longer cathode lifetime. There is 

also less danger during the manufacture of the 

cathode than with prior art coated cathodes. 

Electrically Conducting Platinum Cobalt 

Oxides 


U.S. Patent 3,514,414 

An electrically conductive PtCo oxide is described 

having the formula Pt&o,O,, where x and y are 

0.85=0.15, and a crystal structure based on the 

rhombohedra1 space group R3m. It is prepared at 


elevated temperature and pressure from Co,O, 

and PtO,. The compound, which may be slightly 

modified with Mn, is useful in electrical resistors. 

Current Collectors for Cells with Hot Acid 

Electrolytes 

GENERAL ELECTRIC co. US. Patent 3,515,595 

Current collectors comprise ternary alloys con- 

sisting of Ni, Pd and Au. For cells using a hot 

phosphoric acid electrolyte the alloy preferably 

consists of 50-80n,; Ni, 5';~ Pd and 21; Au on 

a weight basis. For cells using hot H,S04 or 

sulphonic acid polymer electrolyte the alloy 

preferably consists of 30-50"d Ni, at least 30°;, 

Pd and at least 51:, Au, on a weight basis. 

Electrodes 

PRODUITS CHIMIQUES PECHINEY-ST. GOBAIN 


Electrodes, particularly anodes for the electrolysis 

of alkali metal chlorides, consist of Ti coated with 

a noble metal, e.g., Pt. 

Electric Resistor 



The resistor consists of an insulating body with a 

resistive surface layer of a mixture of 10-80 wt.qi, 

(esp. 46-65 WT.';~) of finely divided RuO,, the 

remainder being glass. Alternative compositions 

include finely divided Ag and compositions of 

matter formed by heating RuO, with a Group V 

metal oxide, such as Nb06. 

Electrode Coating Process 

PPG INDUSTRIES INC. Dutch Appl. 69.14899 

An anode for brine electrolysis is coated with Ti 

and a noble metal oxide. An organic Ti compound 

and a decomposable noble metal compound are 

applied to the base anode and heated to produce 

the oxide coating. Ti resinate and Ru resinate 

are suitable compounds. 

Electrode for Electrochemical Processes 


Dutch Appl. 69.17586 

The electrode has a body of refractory coated 

with a layer of active catalyst. The layer consists 

of a Pt metal containing a small amount of a Sn, 

Sb and/or Ge oxide. In an example a Ti body is 

coated with a mixture deposited from a solution 

of a Sn alkoxy compound and RuCI,. 

TEMPERATURE 

MEASUREMENT 

Resistance Thermometer 

ROSEMOUNT ENGINEERING CO. LTD 


A Pt resistance thermometer is designed for use 

in conditions of high vibration.

The Homogeneous Hydrogenation of Soybean Oil Methyl Ester

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