ABSTRACTS of Current Literature on the Platinum Metals and Their Alloys

ABSTRACTS of current literature on the platinum metals and their alloys

PROPERTIES iine field at 6oConuclei in Co-Pt as a function of applied field suggest the formation of a spin- Fusion Curves for Graphite, Tungsten and compensated state at low temperatures. Platinum up to 60 kbar L. F. VERESHCHAGIN and N. S. FATEEVA, Zh. eksper. Effect of Chemical Composition and Heat teor. Fiz., 1968, 55, (4), 1145-1152 Treatment Conditions on the Magnetic Optical measurements on Pt agree well with those Properties of High Coercivity Cobalt-Platinum obtained by thermal analysis. The temperature Alloys of fusion of Pt increases linearly with pressure. YU. A. GRATSIANOV and A. G. RABIN'KIN, Sb. Tr. Tsent. Nauch.-Issled. Inst. Chern. Met., 1968, (54), Rheological Properties of Platinum at High 90-97 Temperatures Tests on cast and homogenised samples of 24,25, v. 0. SHESTOPAL, Fiz. Metal. Metalloved., 1968, 26.16, and 29.5 wt?;, Co-Pt alloys showed that 26, (6), 1127-1130 the highest magnetic properties are attained with Measurements of the shear modulus, internal cast samples, e.g. 24-25?] Co-Pt has maximum friction and creep of annealed and unannealed magnetic energy 40 kJ;'m3, B,=79oo gauss, H, decreases for >25:,; Co-Pt, samples of Pt were carried out between 1300 and H,=3950 Oe. 1980°K and results are depicted graphically. i.e. highest magnetic properties occur for 23-25 uo Co-Pt, where concentration disordering is less important. Controlled cooling rates lead to more Coherent and Incoherent Precipitation in homogeneous and more dispersed structures due the Gold-Platinum System to prolonged keeping of samples at 770-830"C, J. WEISE and V. GEROLD, z.Metallkunde, 1968, 59, the temperature favourable to nucleation. (121, 904-909 Resistivity studies of IS, 20, 60 and 65 wt", Au- Platinum-based Permanent-magnet Alloys Pt wires during isothermal ageing and during re- H. C. ANGUS, Proc. Znstiz Elect. Eng., 1968, 115, heating to the homogenisation temperature (IZ), 1849-1852 showed two rates which can be attributed to Studies of changes of magnetic properties of coherent and to incoherent precipitation. The PtCo and PtFe when part or all the Pt is replaced metastable coherent miscibility gap in the phase by Pd, Rh, Ir, and Ru with various preparations diagram was -100-200 deg C below the stable and heat treatments show that the pseudobinary incoherent gap. The temperature dependence alloys possess no better magnetic properties. of the rate of resistivity change at the start of Careful heat treatment of sintered and worked or annealing 65 wtyb Au-Pt agreed with spinodal of vacuum-melted PtCo gives energy products of decomposition theory or a nucleation mechanism. 9.5 and 10.0 x IO~Gs-Oe, and coercive forces of 5.0 and 4.5 x io30e respectively. Effect of Deformation on the Physico- mechanical Properties of an Alloy of Study of the Diffusion of Normal Hydrogen Platinum with Silver and of Hydrogen Enriched with Para- s. N. PAVLOVA, Fix.-khim. Mekhan. Mazer., 1968, hydrogen through a Palladium-Silver Mem- 4, (41, 490-492 brane. Determination of the Activation Studies of the deformation of 0.1-3 mm Ag-Pt Energies alloy wires after quenching from IOOOTshowed L. PITOUSSI, c. r., St. c., 1968, 267, (26), 1742- that wires of different diameter had different I745 tendencies towards work-hardening. 99'>t0de- Activation energies measured during diffusion formation was required to obtain high strength through 23% Ag-Pd were 4.9 kcal/g.atom in a 0.1 mm wire but for wires 0.2 mm diameter (*Io%) for normal H, and 3.54 kcal/g.atom even 99.8qi deformation only produced a UTS of (AIO;,:) for H, enriched with parahydrogen. I 70 kg,i mm2. Electrical Resistivity Measurements in Anomalous Low Temperature Susceptibility Palladium-Hydrogen Alloys of Dilute Pt-Co Alloys c. T. HAYWOOD and L. VERDINI, Can. J. Phys., J. C. GALLOP and I. A. CAMPBELL, Solid state 1968,46, (r8), 2065-2071 Commun., 1968,6, (II), 831-833 Studies of Pd and Pd-H at 2-300°K show that at Nuclear orientation mcasurements of the hyper- IO"K

Platinum MetalsTev., 1969, 13, (2), 73-79 13 ETn, with n=3.1 for pure Pd but n decreasing to smallest grain size of all, possesses the highest H,. 2.3 when H/Pd=0.25. p1 depends on time and Thermal ordering increases the grain size and rate of cooling at high H concentrations and low thereby decreases H,. temperatures, Residual resistivity is lower for faster cooling. The increase in p, due to I at.",, The Surface Tension and Density of the H, in Pd is of the same order as that of inter- Liquid Alloys Pd-Fe, Pd-Cr, Pd-Si stitials in other f.c.c. metals but is less than for v. F. UKHOV, E. L. DUBININ, 0. A. ESIN and N. A. H, in b.c.c. Ta and Nb at room temperature. VATOLIN,Z~.$Z.Khim., 1968~42,(IO), 2631-2634. Liquid Fe-Pd alloys are nearly ideal. Isotherms The Diffusion of Hydrogen in Cu,Pd Alloy of surface tension for molten Cr-Pd are smooth. v. B. VYKHODETS, v. A. GOL'TSOV and r. v. GEL'D, In molten Si-Pd, molecular groupings in the ratio Fiz. Metal Metalloved., 1968,26, (S), 933-935 of the PdSi compound are maintained during Results are plotted and tabulated for studies of isotherms of surface tension. the activation energy Q for Hz diffusion in ordered and disordered Cu,Pd by measuring the Alloys with Extra Specific Electrical Resist- rate of penetration p, the diffusion coefficient D ance and Low Temperature Coefficient of and the solubility S. Resistance in a Wide Range of Temperature M. P. RAVDEL' and O. I. EVDOKIMOVA, Sb. Tr. Tsent. Investigation of Alloys of the Pd,Al-Ag Nauch.-Zssled. Inst. Chern. Met., 1968, (54), 26-34 System Alloying Ni with Mn-Pd does not alter the resist- L. A. PANTELEIMONOV, D. N. GUBIEVA and L. v. ivity p or the temperature coefficient ct of resist- AZIKONDA, Vest. moskov. Univ., Ser. II, Khim., ance of the alloy but annealing Mn-Pd-Ni at 1968, 23, (6), 87-90 300°C alters both p and 5. 0.3 mm diameter rods The phase diagram and mlcrohardness of these of 6556 Mn-I59/;, Pd-IS?,;, Ni-S%, Cu have: p~- alloys are depicted. zyohm.m,ar=3.1o-~perdegCat -60to +120"C, ~(=(7-8).10-~ per deg C at 120-300"~ e.m.f. On the Relation of Spontaneous Magnetisa- versus Cu E -0.7 mV/deg C, o =62-68 kg/mm2, 8-20-28 Repeated heating and cooling tion to Composition of the Ordered Alloys y,. between -60 and +3oo'C does not change their Fe(PtarPdl-r)3 electrical properties. Protracted annealing at s. K. SIDOROV, v. v. KELAREV and A. I. KOZLOV, 300°C does not alter their structure or properties Fiz. Metal. Metalloved, 1968, 26, (5), 776-780 but at 500-600°C reduces p and leads to brittle- A theory is developed for magnetisation of the ness and decomposition. ordered Fe(Pt,Pd,-,), alloys in which ferromagnetic-antiferromagnetic exchange reactions Properties of Alloys of Manganese-Paila- occur between the atomic components. diurn, Manganese-Germanium, and Man- ganese-Gallium Systems On the Nature of the Coercive Force and Ibid., 35-42 Structure of Equiatornic Iron-Palladium The search for a high-resistivity alloy showed _4lloys that when quenching high Mn content alloys L. M. MAGAT, A. S. ERMOLENKO, 6. V. IVANOVA, from the y region a f.c. tetragonal lattice appears G. M. MAKAROVA and YA. S. SHUR, Ibid., (3),5I 1-516 which upon alloying becomes f.c.c. Resistivity of The maximum value of the coercive force of equi- Mn-Pd quenched from the y region is higher than atomic Fe-Pd occurs in the single phase regu- that of Mn-Cu or of Mn-Ni. Resistivity p of lated state. The coercive force of hardened and 20-32.7"A Pd-Mn varies slightly with tempera- annealed samples is explained by delay in ordering ture at 0-35o'C. p decreases abruptly above ferromagnetic domain boundaries at antiphase 350°C for all Pd-Mn alloys and dilatometric boundaries. At first the deformed samples after curves indicate a phase transformation at 35o'C. annealing are much more ordered than the hardened and annealed samples but crystallites of A Palladium-Magnesium Alloy Phase of the tetragonal phase are so small that they appear Co,A15 Type to be the main factor determining the size of the L. WESTIN, Acta. Chem. Scad., 1968, 22, (8), coercive force. 2 574-2 580 X-ray studies of hexagonal PdMg,,.5 give Thin Films of Iron-Palladium Alloys with dimensions a-8.646-8.660 A and ~-8.175- High Coercivity 8.169 A. The phase has a range of homogeneity. YA. S. SHUR, L. M. MAGAT, A. A. GLAZER, E. V. SHCHERBAKOVA and N. N. SHCHEGOLEVA, Ibid., (S), The Structure of the PuPd Compound 938-939 A. V. BEZNOSIKOVA, E. 8. SMOTRITSKAYA and N. T. Studies of FePd showed that the coercivity H, CHEBOTAREV, Atomnaya Enerz., 1968, 25, (5), is greatest when the crystallites of the alloy are 430-43 I smallest. It follows that a film, consisting of the Pu,Pd, has lattice parameters a =7.028 &o.oo j,

Platinum MetalsTev., 1969, 13, (2) 74 b-4.57IiO.001, C-5.658~0.002 A. Inter- reactions involving Ir and Rh complexes. Data atomic distances have been determined and are discussed are from determinations of the role of tabulated and a model is depicted. the reacting gas by studies of a series of reactions of one metal complex MLi with a variety of Magnetic Susceptibility of Alloys of Plu- addenda, and by Comparison of kinetic, equilib- tonium with Palladium rium and thermochemical data from these N. T. CHEBOTAREV, W. N. SOKURSKII, M. A. reactions and the electronic and geometric pro- ANDRIANOV and A. A. IVANOv, Ibid., 431-433 perties of the corresponding adducts ((XY) MLJ. Magnetic susceptibilities of Pu-Pd alloys are tabulated and shown in graphical form. Thermal Decomposition of Rhodium, Iridium, and Ruthenium Chlorides Thermomagnetic Measurements on Alloys A. E. NEWKIRK and D. w. MCKEE,J. Catalysis, 1968, of the Platinum Metals with Chromium IIY(41,370-377 A. KUSSMAN, K. MijLLER and E. RAUB, z.Metall- Decomposition studies of RhCl,, IrCI, and RuC1, kunde, 1968, ~9~ (II), 859-863 hydrates in air and in H, were studied by thermo- Alloys of Pt metals with Cr which have similar gravimetric analysis and reduction studies were structures have similar magnetic properties, made for dispersions on low- and high-area sub- F.c.c. LI, phases of Cr with 25-30 at.n/, Pt, Pd strates. Reduction to the respective metals was or Ir have a distinct maximum of magnetisation complete at 105, 190, and -350°C. In air, with typical ferromagnetic behaviour. Saturation dechlorination and oxidation was complete at 890, magnetisation at - 193°C is -0.39 Vs/m2 for Pt, 680 and -40°C respectively. B,C, which has -0.15 Vs/m' for Pd, 4.06 Vs/mZ for Ir and low area, has little effect on the reduction tem- the respective Curie points are 900, 400 and perature of the Rh salt but A1,0,, which has high 170°C. Tetragonal PdCr with L1, structure is area, is associated with desorption of decomposi- weakly ferromagnetic. Rh-Cr, Ru-Cr and 0s-Cr tion products. possess no Lr, structure and are very weakly ferromagnetic. F.c.c. solid solutions rich in Cr The Metallic Nature of Osmium Dioxide are anti-ferromagnetic with high Nee1 points. J. E. GREEDAN, D. B. WILLSON and T. E. HAAS, Inorg. Chem., 1968, 7, (I I), 2461-2463 Single crystals of OsO, were prepared and elec- CHEMICAL COMPOUNDS trical conductivity and Hall effect measurements Mass Spectrometric Determination of the were made. The data can be rationalised on the basis of a wholly collective electron approach in- Dissociation Energies of Gaseous RuC, IrC volving the concepts of narrow bands and high and PtB density of states which are often encountered in N. S. MCINTYRE, A. VANDER AUWERA-MAHIEU and the transition metals and their compounds. J. DROWART, Trans. Faraday soc., 1968, 64, (II), 3006-3010 RuC, IrC and PtB molecules have been detected ELECTROCHEMISTRY with dissociation energies Do7 (RuC)=151.0= 3.0, D,"(IrC)= 148.453.0, Do"(PtB)-rr3.3 IL Hydrogen Adsorption Equilibrium on Pla- 4.0 kcal 'mole. tinum Electrodes I. TELCS and M. J~Y,Acta Chim. Acad. Sci. Hung., Preparation and Properties of Some Ternary 1968958, (3)3 275-285 Selenides and Tellurides of Rhodium A review of experimental evidence and theory of R. H. PLOVNICK and A. WOLD, Inmg. Chem., 1968, HLadsorption equilibrium on Pt electrodes shows 7, (12), 2596-2598 that most probably the observed effects are due MRh,X,, where M is Cr, Co, Ni and X is Se, Te, to the several states of H, adsorption on Pt, all of and Rh,Te, have the monoclinic Cr,S,-type which obey the Langmuir adsorption isotherm to structure with space group I2/m, except for a good approximation. There are probably 44 CoRh,Te, and NiRh,Te,, which are trigonal such states. with space group PT mr. The symmetry of these compounds with defect NiAs structure depends Diffusion Coefficient of Hydrogen in Pal- on whether metal ion vacancies are ordered or ladium Alloy Electrodes randomly arranged in alternate metal layers. J. BERSIER and A. K~~SSNER,U.S. Rept N68-339x4, I968>9PP Reversible Activation of Covalent Molecules Diffusion coefficient of H, in 2300 Ag-Pd alloy by Transition Metal Complexes. The Role of and in this alloy with 0.5, 0.9,2.0 and 3.0 at.';; B the Covalent Molecule additions was determined as a function of H, L. VASKA, Accounts chem. Rex., 1968, I, (11), concentration and temperature at 30-30oT and 335-344 varies with H, concentration as D(C)-12B A review of recent work on the mechanism of [RT AC(r C)~,'~C(A~LH(C))].

Platinum MetalsTev., 1969, 13, (2) 75 On the Behaviour of a Ruthenium Electrode- severity conditions without loss of stability for u.0.P.'~new Platforming catalyst. Im- catalyst in Solutions of Sulphuric and Oxalic R-16 Acid at Various Temperatures proved product distribution selectivity at lower pressures permits dehydrocyclisation of paraffins R. B. TARAN and G. P. KHOMCHENKO, Vest. moskov. and dehydrogenation of naphthenes to create Univ., Ser, Khim., 1968, 23, (6), 83-86 II, aromatics with a minimum of hydrocracking to The rate of catalytic hydrogenation of CH,NO? light hydrocarbons, i.e. yield of motor fuel on Ru was - twice that of electrochemical reformate of a given octane number is higher at reduction but the difference decreased as the lower operating pressures. The aromatics- temperature rose. creating reactions are favoured by lower pressures. Plants which have switched to this catalyst have Catalytic and Electrochemical Reduction of not yet taken full advantage of R-16because of Nitromethane on Ruthenium Electrode- their different operating pressures. See also catalyst Chern. W., 1969, 104, (z),60-61. L. P. MASHKOVA, A. I. PLETYUSHKINA and G. P. KHOIMCHENKO, Ibid., 104-106 Results of Testing of Platinum on Alumina Further studies of these reactions in 0.1 N H,SO,. Catalysts by Hydrogenating Rcnzene to Cy clohexane LABORATORY APPARATUS YU. I. KOZOREZOV and N. M. PIKALO, Khim. Prornyshlennost', 1968, (I I), 821-822 AND TECHNIQUE C,H, hydrogenation tests using a modified Pt,A1,0, catalyst showed that the latter is ex- Correction for Temperature Loading and tremely active, selective and stable, and is suitable High Gas Pressure Effects for the Constant- for industrial use. temperature Hot-wire Anemometer H. HASAN and J. c. DENT, Br. J. appl. Phys., J. Investigation of the Conversion of Cyclo- Phys. D., 1969,2, (I), 85-92 hexene on Pt-Zeolite Catalyst under Pressure Tests on Pt and 3or;,,Ir-Pt wires enabled a of Hydrogen calibration curve to be plotted for a constant- v. I. GARANIN, u. M. KURKCHI and KH. M. MINACHEV, temperature hot-wire anemometer using the alloy Kinet. Kataliz, 1968, 9, (s), 1080-1085 at high temperature in a high-temperature and Studies of cyclohexene cyclohexane isomer- high-density gas flow. The temperature co- and isations on decationised zeolite, on CaY and on efficient of resistance for Ir-Pt was deter- 30:; 0.5":, Pt/CaY show that on PtlCaY the isomerisa- mined and also its thermal conductivity. tion of cyclohexane proceeds via formation of cyclohexene on Pt with subsequent isomerisation Electrolytic Cell with a Rotating Double on the acid centres of the zeolite. The isomerisa- Ring Electrode for High Frequencies in the tion of cyclohexene depends on temperature. Measurement of Fast Reactions G. TRI~ORN,A. HEINDRICHS and w. VIELSTICH, The Effect of Heat Treatment on the Cata- Messfechnik, 1968,76, (9), 224-229 lytic Activity of Platinum Catalysts The construction of a double ring Pt electrode S. A. KHASSAN, S. G. FEDORKINA, G. I. EMELYANOVA system is described together with requirements and V. P. LEBEDEV, Zh. fiz. Khim., 1968, 42, (IO), for its use at high speeds of roration. 2507-25 12 Sintering studies on Pt black in vacuum at 300, BRAZING AND WELDING 400, 500, 600 and 700' C indicate a second order relation between changes in the activity and sur- Bits for Soldering Irons face area. Sintering produces a fixed activity and H. C. ANGUS, R. D. BERRY and B. JONES, Engng surface area for each temperature. The relation Muter. Design, 1968, 11, (IZ), 1965-1968 between activity and roasting temperature is ex- ponential. Given the activity at two temperatures, The suitability of Ru for the bits of soldering irons is limited by its cost and so methods have an equation relating activity to temperature can been developed to localise it on bit surfaces and be derived. Kinetics of decomposition of HaOz also to protect the non-functional shank surfaces. and of hydrogenation of cyclohexene on sintered The most promising tipped bit has an A1 shank black are similar. Specific activity is unrelated to to which is welded Ru facing. the duration and temperature of sintering but change of surface area and size of crystals are,

HETEROGENEOUS CATALYSIS Hydroisomerisation of Normal Pentane over a Zeolite Catalyst UOP Catalyst Improves Yield of Aromatics A. VOORHIES and P. A. BRYAKT, A.I.Ch.E.J., 1968, Eur. chem. News, 1969, 15, (361, Jan. 3), 34 14, (6), 852-5356 Reduced operating pressures are claimed at high A series of screening tests on zeolite hydro-

Platinum MetalsTeo., 1969, 13, (2) 76 isomerisation catalysts showed that the most accumulated on it. CH, was the sole product of active is Pdihydrogen mordenite. Typical test hydrogenolysis at 245°C on Ir of CPHB-x, conditions were 550cF, 450 lb;inz, H,:C,H,,= C6H1,,-1, etc. Comparing wires with A1,0,- 3.4, 8 g n- C5Hl,!h.g. catalyst. Neither gas to supported catalysts, reactions seem characteristic particle mass transfer, nor macropore diffusion of the metal rather than of the type of catalyst. nor chemical reactions at Pd sites are rate- limiting. HOMOGENEOUS CATALYSIS Hydrogenation and Hydrogenolysis. X. The Hydrogenation of Methoxy- and Ethoxy- Homogeneous Catalysis in the Reactions of anilines with Rhodium Catalyst Olefinic Substances. XI. Homogeneous Cata- S. NISHIMURA, H. UCHINO and H. YOSHINO, Bull. lytic Hydrogenation of Short-chain Olefins Chem. SOC.Japan, 1968, 41, (9), 2194-2195 with Dichlorobis-(tripheny1phosphine)plat- Hydrogenation of alkoxyanilines with alkali- inum (11) -Tin(II) Chloride Catalyst promoted Rh catalysts showed that Rh oxide pre- R. W. ADAMS, G. E. BATLEY and J. c. BAILAR,J. Am. pared by fusion of RhC1, with LiN03gives high Chem. SOC.,1968,90, (22), 6051-6056 yields of mcthoxy- and ethoxycyclohexylamines Studies of homogeneous hydrogenation of short- from methoxy- and ethoxyanilines respectively. chain olefins with PtCl,(PPh,), and SnC1,. <6 hydrogenolysis occurred and secondary zH,O catalyst mixtures showed that mono- amine formation was negligible. Studies with olefins hydrogenate rapidly only when the double LiNO, replaced by NaNO,, LiOH and NaOH bond is terminal. Reduction of hexadiene and are reported and less satisfactory yields were pentadiene isomers does not stop necessarily at obtained. Best conditions appear to be 90"c, the monoene stage. Dienes react most when both high pHI, and use of LiNO, with RhCl, when double bonds are terminal. Conjugation is not a -2% catalyst: substrate is required. necessary step before hydrogenation; short-chain conjugated diene isomers inhibited further reac- Hydrogenation of Olefins. Part 4. Reaction tion. Long-chain conjugated dienes are reduced of n-Butenes with Hydrogen Catalysed by since their larger size prevents formation of stable Alumina-supportedRuthenium and Osmium catalyst-diene complexes. Unsaturated nitriles are hydrogenated when the double bond is terminal; G. C. BOND, G. WEBB and P. B. WELLS, Trans. substituent groups on the P-C atom do not Furaday SOC.,1968, 64, (11), 3077-3085 hinder this and the CN- group remains intact. Studies in a static system of product distributions, orders of reaction and activation energies for hydrogenation and isomerisation of but-I-ene, A Palladium-catalysed Synthesis of Benzyl cis- and trans-but-a-ene at 0-70°C using Esters from Methylhenzenes I rnol.?< Ru/a-Al,Os and at 6o-14o0C using D. R. BRYANT, J. E. MCKEON and B. c. REAM,^. org. 1 mol.% Os/a-Al,O, show that Ru gives more Chem., 1968, 33, (II), 4I23-4127 isomerisation than 0s. The suggested mechanism Liquid phase production of benzyl esters from is isomerisation by loss of one H atom from methylbenzenes takes place at moderate tempera- adsorbed C$Hgto yield adsorbed C,H, and H, tures using Pd(OAc),-Sn(OAc), catalyst and and hydrogenation where the rate is determined I atm air, e.g. toluene in CH,COOH gives benzyl by H addition to adsorbed C,H, for each C,H,. acetate. The secondary oxidation product ben- Rate-determining steps for cis-trans isomerisation zylidine diacetate is formed at high conversions. and double-bond migration are discussed. Other methylbenzenes behave similarly. Xylenes undergo selective diacctoxylation in CH,COOH The Hydrogenation of Alkadienes. Part 11. to give a,a'-diacetates rather than u,a-di- The Hydrogenation of Buta-1,S-diene Cata- acetates, lysed by Rhodium, Palladium, Iridium, and Platinum Wires Palladium-catalysed Reactions of Unsatur- P. B. WELLS and A. J. BATES, J. Chem. SOC.,A, ated Compounds in Non-aqueous Solvents. inorg. phys. theor., 1968, (12), 3064-3069 Synthesis of Vinyl Acetate via Palladium Studies of buta-1,3-diene hydrogenation over Rh, Salt/Ethylene Complexes Pd, Ir, and Pt wires showed that C,H, composi- R. VAN HELDEN, C. F. KOHLL, D. MEDEMA, G. tions depended on temperature but not on activity, VERBERG and T. JONICHOFF, Rec. Trav. chim. initial pH2 or conversion up to 50:/u. C,H,, Pays-bas, 1968, 87, (ro), 961-991 yield was zero on Pd and 1-15O/: on the other The rate of the reaction of C,H, with Pd(OAc), wires. But-r-ene was the main product; trans-cis in CH,COOH to produce vinyl acetate increases ratios for but-a-ene were determined. Chemi- considerably on addition of small amounts of sorption of buta-I,?-diene by interaction of only NaOAc, LiCl or LiC1, Fe(OAc), to the system. one double bond became more important as the The reaction is first order with respect to both temperature rose. Hydrogenation activity of dean Pd(OAc), and the additions. When using PdCI, Ir was replaced by hydrogenolysis as C residues and NaOAc the rate is proportional to them.

Platinum MetalsTev., 1969, 13, (2) 77 Catalytic Asymmetric Hydrogenation Em- addition to RhH(CO)(PPh,) a, which is also ploying a Soluble, Optically Active, Rhodium formed by dissociation when RhH(CO)(PPh,), is Complex dissolved in C,H, or other solvents. Rapid hydro- W. S. KNOWLES and M. J. SABACKY, Chem. Commun., formylation of alkenes occurs at 250°C, I atm with RhH(CO)(PPh,), catalyst, giving a ratio of -20 19683 (22)s 145-1446 A catalyst precursor which contains optically for the formation of straight- and branched-chain active tertiary phosphine ligands is prepared by aldehydes from alk-1-enes. H exchange and isomerisation of alkenes with RhH(CO)(PPh,), dissolving RhL,Cl, complexes with L =tertiary are described. phosphine in I : I v/v C,H, : C,H,OH containing triethylamine and pressurising with H,. Examples of its use are described. The Preparation and Reactions of Hydrido- chlorotris(triphenylphosphine)ruthenium(II) Catalysis of Hydrogen Transfer by a Method Including Homogeneous Catalytic Hydro- Hypothetically Similar to Fermentation. genation of Alk-1-enes VI. High-activity Hydrogenation Catalysts P. s. HALLMAN, B. R. MCGARVEY and G. WILKINSON, on the Basis of x-Complexes of Rhodium(1) Zbid., 3143-3150 with Amino Acids RuClH(PPh,),.C,H, was prepared from RuCl, (PPh,), and H, in ambient conditions in the 0. N. EFIMOV, M. L. KHIDEKEL', v. A. AVILOV, P. s. presence of a base such as triethylamine. RuBrH CHEKRII, 0. N. EREMENKO and A. G. OVCHARENKO, (PPh,),.C,H,, RuClH(C,HJ(PPh,),, [RuClH Zh. obshch.Khim., 38, 1969, (12), 2668-2677 (bipyr)(PPh,) ,] ,, and RuH,(CO)(PPh,), were also Studies of Rh complex catalysts with N-phenyl- prepared. RuClH(PPh,), is the most active anthranilic acid and L-tyrosine showed that low- catalyst yet discovered for homogeneous hydro- valent compounds are stabilised at the expense of genation of alk-1-enes in C,H, or C,H,.CH,. reactions with aromatic rings and carboxyl groups. It is highly specific but kinetic study is difficult Both in solid and solution states the complex and slow poisoning occurs. is supposedly the dimer H[Rh,(phen),Cl] but H decomposes it to the monomer. The Rh complexes catalyse D exchange with H,O. A Carbonylation of Acetylene with [Ru(CO)JS hydrogenation mechanism for trans-stilbene is as Catalyst suggested. H, is derived during hydrogenations P. FINO, G. BRACA, G. SBRANA and A. CUCCURU, of fumaric acid and acetylene derivatives by the Chem. & Znd., 1968,(49, Dec. 7), 1732-1733 cis-scheme. Hydroquinone was prepared by carbonylation of C,H, under anhydrous conditions, in either tetra- hydrofuran or dioxan as solvent, in the presence Selective Homogeneous Hydrogenation of of [Ru(CO)J,. Highest yields occurred at A&-1-enes Using Hydridocarbonyltris-(tri- pHa=5 - 10atm. Yields up to 65% hydroquinone phenylphosphine)rhodium(I) as Catalyst were obtained by reacting C,H, with CO and C. O'CONNOR and G. WILKINSON,J. Chem. SOC.,A, H,O or alcohols in the presence of [Ru(CO)~]~at inurg. phys. theor., 1968, (11), 2665-2671 I50-25O0C and relatively low pco. RhH(CO)(PPh,), efficiently catalyses homogeneous hydrogenation of unsaturated RCH =CH2 compounds. For hex-I-ene and dec-I-ene in FUEL CELLS CBHasolution the rate law is rate=k, K, c [S][A]/ (I + K,[S]), where [S] and [A] are respective con- Electrocatalysts for the Direct Electro- centrations of &-I-ene and catalyst, C is H, chemical Oxidation of n-Octane in Fuel Cells concentration in solution, K, is the formation con- E. J. CAIRNS and J. PAYNTER, 3. Electrochem. Soc., stant for an alkene intermediate complex, and k, 1968,115,(IZ), 1218-1224 is the rate constant for the rate-determining H, Activity of supported and unsupported Pt pre- activation step. High selectivity for reduction of pared in various ways was compared with that of alk-I-ene is due to steric factors caused by the commercial Pt black. An increase in the specific bulky triphenylphosphine groups. area of a C substrate gave a corresponding increase in electrocatalytic activity up to at least Hydroformylation of Alkenes by Use of 200 m2/g. Some types of Pt/C had 6-18 times Rhodium Complex Catalysts the activity of Pt black. No current or voltage cycling occured with mol.o/o HF electrolyte at D. EVANS, A. OSBORN and G. WILKINSON, Zbid., 36 J. 105°C in contrast to other acid electrolytes. (12),3133-3142 The inhibition period of trans-RhX(CO)(PR,) a catalysts, where X=halogen and R=aryl, is Structure and Performance of Hydrophobic removed by addition of hydrogen halide acceptors Gas Electrodes and the halide complex forms a hydrido-species A. D. D. TANTRAM and A. C. C. TSEUNG, Nature, by hydrogenolysis. The principal catalytic species 1969, 221, (5176, Jan. XI), 167-168 seems to be RhH(CO),(PPh,), formed by CO Electron micrography showed that a catalyst pre-

Platinum MetalsTev., 1969, 13, (2) 78 pared by mixing Pt black with a dispersion of tively. The thermal em.€. hysteresis loop of PTFE and applying it to a metal screen before some metal-sheathed mineral-insulated thermo- drying and curing at 300°C consists of porous couples is explained; the maximum discrepancy aggregates of Pt intermingled with PTFE. Per- from this loop is 23pV at 550°C by calculation, formance is very dependent on microstructure. 14pV by experiment on a single thermocouple. Whereas hydrophilic electrodes become flooded Mechanical hysteresis of the loop may cause with electrolyte hydrophobic electrodes become fracture. A reliable thermocouple of this type full of gas and the whole thickness of the electrode needs matching expansion coefficients of sheath is effective. The effect of catalyst surface area was and thermocouple. studied using graphite powder as the catalyst. Comparison of Platinum Resistance Thermo- meters between 63K and 373.15K. Part I. CHEMICAL TECHNOLOGY Part I1 The Separation of Hydrogen from Ammonia M. R. M. MOUSSA, H. VAN DIJK and M. DURIEUX, Synthesis Exhaust Gases by the Method of Physics, 1968, 40, (I), 33-48, 49-60 Diffusion through Palladium Twelve Pt resistance thermometers were compared with a reference one at 63-273.15"K and at YU. K. BAICHTOK, M. B. AIZENBUD, V. A. KURKOVSKII, 373.15% using a constant temperature bath with A. S. FURMANOV, I. YA. AZBEL' and 2. V. KORBUTOVA, the thermometers inserted in a Cu block im- Khim. Promyshlennust', 1968, (IO), 744-746 mersed in liquid iso-C,H,,, C,H,, 02>or N, and NH, synthesis is more economic when H, in the the differences of the reduced resistances W= exhaust gas is purified and when Ar is recovered. R(t),'R(O"C) of them were determined. The Tests on such gas and on pure N,-H, mixtures number of calibration points to determine the compared pure Pd and 5yb Ni-Ion, Ag-Pd foils W-T relation was studied and discussed. for H, purification by diffusion at 400 and 500°C. Both gas mixtures gave similar results. Ag dusted A Direct-reading Bridge for a Platinum on Pd foil activated the latter for H, diffusion. Resistance Thermometer C. w. VAx DER WAL and L. c. E. STRUIK, 3. sci. TEMPERATURE Znstrum., J. Phys. E, 1969, 2, (2), 143-145 A Wheatstone bridge for a Pt resistance thermo- MEASUREMENT meter was modified so that the angle of rotation of a linear potentiometer is proportional to the The Effect of Stress on the Thermal EMF of temperature with bridge sensitivity fairly inde- Platinum-Platinum/lS Rhodium Thermo- pendent of temperature. Although not intended couples for high precision thermometry, irrespective of E. s. MORGAN, Br. J. appl. Phys., 7. Phys. D, 1968, the inaccuracy of the thermometer itself the 1, (XI), 142r-1429 reading accuracy is to better than z0.1 deg C Variations in thermal e.m.f. with stress of Pt and at 0-500 C and the bridge can be used for both 13 :{> Rh-Pt wires with junctions at 20 and 550°C temperature control and temperature measure- are -47 and -12 pV deg C-lkg-lcm-z respec- ment.

NEW PATENTS METALS AND ALLOYS Pd with a minor amount of Cr capable of forming a stable refractory compound or alloying Kh or Methods of Improving the Mechanical Pt (or Rh, Pt with another Pt-metal) with a minor Properties of Metals and their Alloys amount of an element capable of forming a stable JOHNSON MATTHEY & CO. LTD refractory compound (the element may be Be, British Patent 1,134,492 Mg, Al, Si, Th, U or a transition metal) and Pt metal alloy articles are given greater strength heating (~ooo"C)the alloy in a gas (e.g. air or 0,) by cold working and annealing to give oriented to form the refractory compound (e.g. oxide) in recrys tallisation. the alloy. Improvements in and Relating to the Treat- CHEMICAL COMPOUNDS ment of Platinum Group Metals and Alloys JOHNSON MATTHEY 82 CO. LTD New Chemical Compounds British Patent 1,139,897 IMPERIAL CHEMICAL INDUSTRIES LTD An alloy having properties of oxidation resistance British Patent 1,138,867 and high mechanical strength is made by alloying These new chemical compounds are Pt group

Platinum MetalsTev., 1969, 13, (2), 79-84 79