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Platinum Metals Rev., 1965, 9, (3), 100

ABSTRACTS: July 1965

of current literature on the platinum metals and their alloys

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PROPERTIES

Thermal Diffusion in Platinum

s. c. ho, t. hehenkamp and h. b. huntington, J. Phys. Chem. Solids, 1965, 26, (2), 251-258

Observations of thermal diffusion of Pt in temperature gradients were clear and reproducible. Marker motion was 1 μ/d at about 1600°C in a 400°C/m gradient. Heat of transport was 0.68 ± 0.09 eV, which is much larger than Em-Ef, where Em and Ef are migration and formation energy. This discrepancy is not yet explained.

Thermal Diffusivity at Incandescent Temperatures by a Modulated Electron Beam Technique

m. j. wheeler, Br. J. Appl. Phys., 1965, 16, (3), 365-376

Pt at 1180-1750 °K has thermal diffusivity 0.223 ± 0.003 cm2 sec −1 and thermal conductivity 0.59 + (1.3±0.1) T × 10−4 W cm −1 deg K−1. Results were also obtained for Mo,Ta,W. The Lorenz functions were constant for each. Thin slabs of specimens were heated to incandescence by an electron beam, amplitude modulated to vary sinusoidally with time. The phase difference between the resulting temperature fluctuations of the slab gave the thermal diffusivity of the sample.

Thermoelectric Size Effect in Platinum

r. p. huebener and r. e. govednik, Bull. Am. Phys. Soc., 1965, 10, (3), 325, abs. BF2

The difference of thermoelectric power between thin Pt foils and 0.010 inch Pt wire was measured from 77 to 373°K and electrical resistance difference was measured at 4.2°K. The average electron mean free path in Pt at 296°K was and . The electrical conductivity associated with the d -band in Pt has the same order of magnitude as that of the s -band.

Deformation of Quenched Platinum

j. j. jackson, Ibid., 337, abs. DE10

Deformation of quenched Pt specimens at temperatures from 4 to 600°K increases the dislocation density and may produce both lattice vacancies and interstitials. Annealing of these is not difficult.

Observations on the Precipitation Hardening of the 10 wt.% Gold-Platinum Alloy

g. reinacher, Z. Metallkunde, 1965, 56, (4), 216-221

Aging studies at 45, 500 and 600°C showed that at 600°C the aging behaviour depended on the furnace atmosphere. In air, precipitation occurred at points on the surface but in H2 a front of discontinuous precipitation moved into the interior of the sample.

Solid Solution Strengthening in Iron-Nickel and Iron-Platinum Alloys

h. h. kranzlein, m. s. burton and g. v. smith, Trans. Met. Soc. A.I.M.E., 1965, 233, (1), 64-70

Tests from ¼25 to —196°C showed that the temperature dependence of yield stress is less in Fe alloys with up to 2 at.% Ni or Pt than in high-purity Fe. At room temperature, yield stress increased with alloy content but at — 78 °C it first decreased with increasing alloy content. Current theories of solid-solution strengthening do not explain this.

Mössbauer Measurements of Fe57 Hyperfine Fields in Platinum-rich Pt-Fe Alloys near Pt3Fe

c. w. kimball, j. crangle, d. palaith and r. preston, Bull. Am. Phys. Soc., 1965, 10, (4), 471, abs. DF 7

Ordered 24.0, 26.7, 30.0 and 34.5% Fe-Pt alloys have magnetic ordering sensitive to Fe content. Mössbauer measurements of Fe57 showed one antiferromagnetic state at TN∼170°K and another growing at the first’s expense as the Fe concentration rose. H1 =288 kOe at 24.0% Fe. H2 was 30 kOe less at 26.7% Fe. At 30% Fe, H2 dominated H1. At 34.5% Fe the Mössbauer spectrum is complex.

On the Temperature Dependence of the Magnetic Properties and the Character of the Processes of Magnetisation of a CoPt Alloy

n, n. potapov and a. g. rabin’kin, Dokl. Akad. Nauk S.S.S.R., 1965, 160, (3), 586-589

The magnetisation and demagnetisation of equi-atomic CoPt alloys was studied at temperatures between 77 and 673°K. Isotherms show the decreasing magnetisation achieved at higher temperatures. The coercivity and magnetisation were higher for disordered than for ordered alloys.

Changes in the Crystal Structure and Magnetic Properties of a Co-Pt Alloy during the Ordering Process

a. g. rabin’kin, yu. d. tyapkin and k. m. yamaleev, Fiz. Met. Metalloved., 1965, 19, (3), 360-366

Single crystals of 51.3 at.% Pt-Co were studied by X-rays during ordering while annealing at 600°C after quenching from 1000°C in water and after quenching at the ‘critical’ rate of 1.3 deg C/sec. Crystal structure changes were compared with changes in the magnetic properties.

Specific Heat of 0.5% Solutions of Cr, Mn, Fe, Ni in Platinum

yu. n. tsiovkin and n. v. volkenshtein, Fiz. Tverd. Tela, 1965, 7, (2), 543-545

Studies in the range 1.6-7°K showed that the specific heats of Cr, Mn, and Fe in Pt at 1.6-6°K obey the formula C = γT+αT3+A/T2. The big increase in the specific heats compared to that of pure Pt is due to localised factors at the impurity centres.

The Magnetic Moment of Ni, Co, Mn, Fe, Cr, Gd Dissolved in Platinum

Ibid., Fiz. Met. Metalloved., 1965, 19, (3), 367-370

The temperature dependence of paramagnetic susceptibility of 0.5 at.% solid solutions of Ni,Co, Fe,Mn,Cr, and Gd in Pt was studied at 20-300°K. The magnetic moments of the alloying atoms, calculated by the Curie-Weiss formula, are PCo, 5.8; PFe, 6.7; PMn, 5.7; Pcr, 5.6; PGd, 6.8μB. Results are discussed in the light of existing theory on localised composition.

Electrical Conductivity of Dilute Solutions of Transition Metals in Platinum

Ibid., Zh. Eksper. i Teoret. Fiz., 1965, 48, (3), 796-799

The “residual” resistance of 0.5% solutions of the 3d transition metals and some of the 4d group in Pt is not uniformly related to the impurity. Of the 3d metals, Ti has the greatest “residual” resistance; Zr has the most of the 4d metals. Results are related to localized state theory.

Constitution of the Boron-Platinum System

f. wald and a. j. rosenberg, j. Metals, 1965, 17, (1), 103-104, abs.

X-ray diffraction, thermal analysis and metallographic tests of the Pt-B system indicated eutectics at ∼42 at.% B, 920°C and at ∼28 at.% B, 795°C. Peritectic reactions occurred at 890°C and at 825°C. Pt3B2 formed directly from the melt at 940°C. The eutectoid reaction Pt3B2→Pt2B + B occurred at 600-650°C. Compounds detected were Pt3B2, Pt2B and Pt3B.

Dislocation Mechanisms in the Growth of Palladium Crystals

w. w. webb, J. Appl. Phys., 1965, 36, (1), 214-221

Pd metal whisker crystals grow at ∼0.02 cm/sec in irrational crystallographic directions around dislocation intersections at whisker tips by catalytic decomposition of PdxCIy to Pd and CI2, while lateral growth is retarded by a thin film of liquid PdCI2. Nucleation probably occurs at bubbles in the film over dislocation intersections with the massive substrate surface. Dislocations provide growth steps on whisker tips and climb helical paths. Changes in direction occur but the whisker remains straight as systematic helical climb is inhibited or helical growth is suppressed by simultaneous operation of many dislocations.

A Mass Spectrometric Study of the Vaporisation of Palladium

o. c. trulson and p. o. schissel, J. Less-Common Metals, 1965, 8, (4), 262-265

The average heat of sublimation of Pd from relative vapour pressure measurements, using a Knudsen-cell effusion source and mass spectrometer detector, was H298=91.2±0.9 kcal/mole. Other molecular species were not observed.

Neutron Diffraction Study of Temperature-dependent Properties of Palladium Containing Absorbed Hydrogen

g. a. ferguson, a. i. schindler, t. tanaka and t. morita, Phys. Rev., 1965,137, (2A), A483-A487

Structures of single-phase β-PdH have space groups R3m and Fm3m below and above 55°K, respectively. Partial migration of H atoms from octahedral to tetrahedral sites in the f.c.c. Pd lattice causes the low-temperature structure. The r.m.s. vibrational amplitude of the H atoms is approximately 0.25 Å at 293°K, 0.17 Å at 4.2°K. Transfer of H atoms between lattice sites causes anomalies in temperature dependence of electrical resistivity and in heat capacity.

Heat Capacity and Spontaneous Heat Flux in H-Pd alloys

c. a. mackliet and a. i. schindler, Bull. Am. Phys. Soc., 1965, 10, (3), 326, abs. BFII

Dynamic measurements of β-phase H-Pd alloys at 1.2-4.2°K gave γ values about 1/4-1/7 those of pure Pd but Debye θ’s were only slightly different, thus supporting the view that electrons from dissolved H2 enter the d band of the alloy. Heat flux depended on alloy composition, temperature and thermal history. It decreased with time at constant temperature but was restored after annealing at N2 or room temperature. Heat fluxes were about 2-5 μW/g of dissolved H2 but their source was not established.

Absorption Isotherms and Diffusion Constants of Hydrogen in the α-Phase of the Hydrogen/Palladium System

j. w. simons and t. b. flanagan, Abs. Papers, 149th Meeting, Am. Chem. Soc., 1965, (April), 53S-133

The average isosteric heat for the reaction H2 + × H: y Pd →(x + 2) H: y Pd is — 5875±150 cal/ mole H2 from H/Pd=0 to 0.014. Dam were obtained at 0-90°C from changes of electrode potential and resistivity of Pd wires during absorption from H2-stirred solutions. Uniform H2 absorption required slow absorption with the absorption rate ∝ CpH2 in solution. High absorption rates were also studied. Diffusion constants were obtained at 0-50°C and the effect of H/Pd on them was considered.

The Palladium-Hydrogen System

h. brodowsky, Z. Phys. Chem. (Frankfurt), 1965, 44, (3-4)3 129-142

The solubility of H2 in Pd is explained by the dissociation of 4 atoms into protons and electrons. Deviations from ideal behaviour occur when electron bands of the metal are filled or when protons cause local expansion and tension of the lattice by thermal motion. The tendency of protons to associate is proportional to the chemical potential of dissolved H2. D2 behaves similarly to H2 but its association energy is less because of its smaller amplitude of vibration.

Hydrogen in Palladium/Silver Alloys

h. brodowsky and e. poeschel, Ibid., 143-159

Absorption isotherms are given for H2 in 10, 20, 30, and 40 wt.% Ag-Pd alloys at 30-148°C, 0.01-760 Torr on Cu powder by gas volumetric measurements. Deviations from ideal behaviour are discussed. The effect of Ag additions is to alter the energy required to expand the lattice to admit H2.

Magnetic Properties of Pd Metal and Pd-Rh and Pd-Ag Alloys Containing Co and Fe Atoms

t. takahashi and m. shimizu, J. Phys. Soc. Japan, 1965, 20, (1), 26-35

Assuming that the Co and Fe atoms have localised magnetic moments and are distributed at random, an analysis by the itinerant model of 4d- electrons gives the spin quantum numbers as 1 and 3/2 for Co and Fe, respectively, in the alloys. The composition dependence of the magnetic moment and the Curie temperature, and the temperature dependence of paramagnetic susceptibility of the alloys were calculated.

On the Problem of the Existence of Anti-ferromagnetism in Fe-Pd Alloys with Invar Characteristics

h. fujimori and h. saito, Ibid., (2), 293-294

30 at.% Pd-Fe alloy has magnetic moment μ. similar to that of the 35 at.% Ni-Fe alloy, which has Invar characteristics. Its magnetic state can be described as a mixture of ferro- and antiferro-magnetic.

Effect of Small Additions of Fe on the Hall Coefficient of Pd

a. i. schindler and d. j. gillespie, Bull. Am. Phys. Soc, 1965, 10, (3), 326, abs. BF8

Hall coefficients of Pd and of 0.09, 0.13 and 0.29 at.% Fe-Pd alloys were measured at 2-4.2°K and at 45-77°K. At 77°K all were field-independent but, at about 4-K, those of Pd increased with magnetic field while those of the alloys decreased with increasing field. Hall coefficients at 4 and 77°K increased with Fe content.

Constitution and Magnetic and Electrical Properties of Palladium Tellurides (PdTe-PdTe2)

a. kjekshus and w. b. pearson, Canad. J. Phys., 1965, 43, (3), 439-449

X-ray studies of the PdTe-PdTe2 region confirmed that a continuous solid solution exists at high temperatures, and that narrow PdTe and PdTe2 homogeneity regions exist at low temperatures. PdTe is nonstoichiometric below 500°C. Magnetic susceptibility, electrical resistivity, thermoelectric power, and superconducting transition temperatures were measured but no very satisfactory results were obtained for the superconducting transition temperature of PdTe and for the conductivity and thermoelectric power of PdTe2, in the (001) direction.

Investigations in the Palladium-Mercury System

g. jangg and w. grÖll, Z. Metallkunde, 1965, 56, (4), 232-234

The phase diagram and solubility curve of the Pd-Hg system were studied by vapour pressure measurements, by X-rays and thermal analysis, and the compounds PdHg4, Pd2Hg5 and PdHg were found, of which the two latter have narrow ranges of homogeneity. Peritectic reactions occur at 90 and 238°C. Heats of formation of Pd2Hg5 and PdHg are —55.8 kcal/mol and—22.5 kcal/mol.

Thermomagnetic Measurements on Iridium-Manganese and Rhodium-Manganese Alloys

k. kussman, k. mÜller and m. wuttig, Z. Metallkunde, 1965, 56, (4), 228-231

β-phases of Ir-Mn and Rh-Mn alloys are ferromagnetic. Field strengths were measured. The temperature dependence of magnetisation of Rh-Mn alloy shows hysteresis behaviour between + 300 and —200°C. Magnetisation varies considerably with the pretreatment of the alloy. The other phases are paramagnetic.

Superconductivity in Binary Alloy Systems of the Rare Earths and of Thorium with Pt-Group Metals

t. h. geballe, b. t. matthias, v. b. compton, e. corenzwit, g. w. hull and l. d. longinotti, Phys. Rev., 1965, 137, (lA), A119-A127

All binary systems of Sc, Y, La, Ce, Lu, and Th with Co, Rh, Ir, Pd, and Pt contain at least one superconducting phase, except Sc-Pt and Ce-Rh. Transition temperatures of analogous compounds indicate that pure Rh should become superconducting above 10 mdeg, pure Pt much lower. Superconducting properties of all compounds tested are tabulated.

Superconductivity in Cr3Si-Type Ternary Phases with Niobium and Group VIII Metals

s. t. zegler, Ibid., (5A), A1438-A1440

Cr3Si-type alloys of general composition Nb3Rh1−xBx, where B is Co, Ru, Pd, Os, Ir, Pt, or Au were investigated down to 1.7°K. All metals substituted for Rh in Nb3Rh increase cell volume and decrease the superconductivity transition temperature, except Pt and Au, which increase the transition temperature, but not above that of Nb3Pt or Nb3Au. Transition temperature increases as the valence electron-atom ratio rises from 6 to 6.5 but decreases with larger cell volume.

CHEMICAL COMPOUNDS

Pyridine N- Oxide-Carbonyl-Dichlor oplati-num (II) Complexes

w. h. clement and h. orchin, J. Organomet. Chem., 1965, 3, (1), 98-99

CO reacts rapidly with ethylene-pyridine N -oxide-platinum (II) complexes and replaces the C2H4 ligand to form the carbonyl complexes. This is a simple route to Pt carbonyls at room temperature.

Nucleophilic Constants and Substrate Discrimination Factors for Substitution Reactions of Platinum (II) Complexes

u. belluco, l. cattalini, f. basolo, r. g. pearsonb and a. turco, J. Am. Chem. Soc, 1965, 87, (2), 241-246

Reaction kinetics for substitutions of 6 Pt complexes of trans -[PtL2Cl2]-type with 18 nucleophilic reagents showed that log ky= SnPt+log ks, where npt is nucleophilic reactivity constant of each reagent based on trans -[Pt(py)2Cl2] as standard. ky is second-order rate constant for nucleophile Y, S is nucleophilic discrimination factor, ks is “intrinsic” reactivity measure equal to first-order rate constant for reaction in which solvent is nucleophile. When ks is low, S is high, and vice versa. Strong π-bonding in cis position causes low ks, high S.

Structure of and Bonding in [(C3H5) PdCl]2

w. e. oberhansli and f. dahl, J. Organomet. Chem., 1965, 3, (1), 43-54

Yellow monoclinic crystals of [(C3H5)PdCl]2 have a=7.46±0.02 Å, b = 743±0.02 Å, c = 8.61 ±0.02 Å, β=93.6±0.01”. Related organometallic complexes are compared.

New Double Oxide of Palladium and Rhodium

a.u. seybolt, Trans. Met. Soc. A.I.M.E., 1965, 233, (1), 248

An oxide, which appeared as a subscale during O2 equilibriations with 5 at.% Rh-Pd, has hexagonal lattice with a0=5.22 Å, c−6.0 Å and may be (PdxRh1−x)2O, where x=0.4±0.1.

Ternary Oxides of the Transition Metals. IV. Alkaline-earth-iridium (IV) Oxides: Crystal Structure of CalrO3

f. rodi and d. babel, Z. anorg. allgem. Chem., 1965, 336, (1-2), 17-23

The two modifications of CalrO3 are hexagonal (a = 5.4411, c=6.392 Å), which forms IrO2 and CaCO3 on heating, and orthorhombic (a = 3.145, b = 9.856, c=7.293 Å), which forms as single crystals from a melt of the components in CaCl2. X-ray data on these structures are discussed.

Oxygen Chemisorption on Ruthenium Dioxide

j. t. sommerfeld and g. parravano, J. Phys. Chem., 1965, 69, (1), 102-115

Adsorption and desorption data for O2 on RuO2 at 100-385°C and low pressures enabled the nature of the RuO2 surface to O2 adsorption to be characterised by an exponential distribution of adsorption equilibrium functions. Activation energies were determined. Adsorbed species were both mobile and dissociated.

The Crystal Structure of Barium Ruthenium Oxide and Related Compounds

p. c. donohue, l. katz and r. ward, Inorg. Chem., 1965, 4, (3). 306-310

BaRuO3 has complex oxide structure based on close-packed stacking of close-packed BaO3 layers and a rhombohedral lattice. Ru ions occupy octahedral sites. The octahedra are in strings of three sharing faces; the strings are linked by corner sharing. Intermetallic bonding is suggested by face sharing giving a Ru-Ru-Ru arrangement with 2.55 Å interionic separation. BalrO3 and BaPtO3 are probably similar.

Electrical Properties of Some Compounds Having the Pyrite or Marcasite Structure

w. d. johnston, r. c. miller and d. h. damon, J. Less-Common Metals, 1965, 8, (4), 272-287

Measurements of electrical resistivity and Seebeck coefficient were made on pyrite and marcasite compounds, among them OsSb2, RhSb2, RuSe2, OsTe2, PtP2, PtAs2, PtSb2, and α-PtBi2. The compounds are classified as metals if the total number of valence electrons in the molecule is 21 and as semiconductors if the number is 20 or less.

ELECTROCHEMISTRY

Electrochemical Characterisation of the Surface Composition of Heterogeneous Platinum-Gold Alloys

m. w. breiter, J. Phys. Chem., 1965, 69, (3), 901-904

Periodic voltammetric current-voltage curves for O2-layer formation and reduction on heterogeneous two-phase Pt-Au alloys in 1 N H2SO4 at 30°C are an approximate addition of the respective pure metal curves. The Pt-rich α1-phase behaves electrochemically like Pt; the Au-rich α2-phase like Au. Surface composition is characterised by two parameters from a least-squares fit from the experimental data.

Hydrogen Adsorption on Heterogeneous Platinum-Gold Alloys in Sulphuric Acid Solution

Ibid., Trans. Faraday Soc., 1965, 61, (4), 749-754

Electrochemical studies of H2 adsorption on 5-70 at.% Au-Pt alloys in 1 N H2SO4 at 30°C by slow-speed voltammetric current-potential curves showed that H 2 adsorption occurs only on the Pt-rich phase to an extent determined by the amount of this phase on the surface.

On the Activity of Electrolytically Mixed Precipitates of Platinum and Ruthenium in the Electrooxidation of Methanol

o. a. petrii, Dokl. Akad. Nauk S.S.S.R., 1965, 160, (4), 871-874

Electrode charging curves for platinised Pt, for 9:1 Pt:Ru precipitate and for Ru were plotted and also polarisation and electrooxidation curves for CH3OH at these electrodes in 1 N H2SO4 and 1 N KOH solutions. Electrooxidation at the mixed precipitate proceeded with greater kinetic regularity than at platinised Pt.

Cathodic Reduction of Oxygen on Smooth Platinum in Acid Solutions

g. bianchi and t. mussini, Electrochim. Acta, 1965, 10, (4), 445-455

H2O2 is formed at cathode potentials ≤680mV (nhe) on smooth Pt in 0.5 M H2SO4 whereas the initial rest-potential is 960mV. Current efficiencies for H2O2 formation depend on cathode potential and duration of electrolysis.

Electrochemical Oxidation of Hydrocarbons on a Platinum Electrode

r. rh. btjrshtein, v. s. tyurin and a. g. pshenichnikov, Dokl. Akad. Nauk S.S.S.R., 1965, 160, (3), 629-632

Oxidation tests were carried out with C2H6 and C2H4 on Pt electrodes in 1 N H2SO4 and 1 N KOH solutions at 21 and 97°C. Charging curves were drawn and the mechanism of the process was investigated.

The Platinum-on-Carbon Catalyst System for Hydrogen Anodes. I. Characterisation of the Catalyst and Support. II. Chemical Requirements of the Carbon Surface

l. j. hillenbrand and j. w. lacksonen, J. Electro-chem. Soc, 1965, 112, (3), 245-249, 249-252

Active electrodes containing 50m2/g Pt/C were most effective when Pt occupied the outer layers of C. The Pt appeared to be 40-50 Å crystallites.

High activity from 3% Pt/C electrodes depended on proper choice of C, on control of electrode preparation, and on chemical factors. Good H2 anodes were prepared containing 1 mg Pt per cm2 electrode. E.S.R. measurements indicated Pt-C interaction. Activity decreased almost to zero when, before application of Pt, the C was cleaned in N2 at 1000°C but full activity was restored by CO2 treatment at 1000°C.

ELECTRODEPOSITION AND SURFACE COATINGS

Palladium Black Coating

l. missel, Metal Finishing, 1965, 63, (1), 51

High emittance calorimeters for monitoring radiant: convected energy ratio of rocket exhaust gases at rocket-bases have Pd black surfaces applied over Zn-plated Cu by a dip method. Details of the procedure are given. Emittance exceeds 0.90 at 0.2-20 microns after 4-6 h baking at 400°F. This is less than for Pt black on Be, but Be is toxic. The coating has lower resistance to heat deterioration.

Dropwise Condensation on Hydrophobic Metal and Metal Sulphide Surfaces

r. a. erb and e. thelen, Abs. Papers, 149th Meeting, Am. Chem. Soc, 1965, 6U-16

Ag, Au, Rh and Pd are not wetted by pure steam under continuous condensing conditions. These coatings on Fe and Cu-alloys, sometimes previously coated by a diffusion-barrier material, produced dropwise condensation of steam above 100°C for many thousand hours without organic promoters. The mechanism is applicable to distillation of sea water.

Solderable Evaporated Metal Films

j. l. vossen, Electrochem. Technol, 1965, 3, (1-2), 56-57

75 at.% Au-Pd was evaporated on glass and ceramic substrates on which Cr had been deposited to improve the adhesion of the noble metal layer. The high O2-activity of Pd improved adhesion whilst the solderability of Au allowed wires to be attached to the surface.

LABORATORY APPARATUS AND TECHNIQUE

Chemisorption Detector for Hydrogen

m. m. eisenhardt and s. a. hoenig, Rev. Sci. Instrum., 1965, 36, (1), 66-68

A device effective in the range 10−5-10−8 Torr depends on the change in work function of a Pd filament exposed to H2. O2 inhibited electron emission strongly and N2 weakly. However, such H2-O2 mixtures are seldom encountered and the effect of N2 is not serious until α=PN2/PH2is large.

CATALYSIS

Production of High Octane Number Petrol and of Aromatics by Catalytic Reforming of Naphtha

f. eschard, j. guillemat and h. laune, Rev. Inst. Fr. Petrole, 1964, 19, (12), 1391-1405

The Institut Francais du Pétrole has developed a process for reforming naphtha to produce high-octane gasoline and petrochemical intermediates, using plant which includes Pt catalysts, supported on halogen-promoted A12O3 or on SiO2-Al2O3. Pt content varies from 0.3 to 0.8%.

Alteration of the Properties of Platinum-on-Alumina Reforming Catalysts during Continuous Operation

g. n. maslyanskii, n. r. bursian and v. v. shinikin, Khim. i Tekhnol., Topliv i Masel, 1965, (1), 2-6

Continuous operation of Pt/Al2O3 reforming catalysts leads to increased metallic content, especially of Fe, to reduced halide content, particularly of F and CI, and to decreased effective area of the catalysts. These changes reduce the activity for isomerisation and dehydrogenation. There is also deterioration of the activity and selectivity of reforming.

The Use of Platinum Catalysts at High Pressures

w. thielebeule and g. hey, Chem. Tech., 1965, 17, (2), 87-90

The amount of hydrocracking observed, when Pt/Al2O3-SiO2 and Pt/Al2O3-F petroleum refining catalysts were tested for the upgrading of petroleum, reached a maximum of 100 kg.cm.−2 The quality of the products depended on the amount of conversion.

Textural Study of Catalysts by Gas Adsorption. II. Platinum-Alumina Catalysts

j. e. germain, m. ostyn and j.-p. beaufils, J. Chim. phys., 1965, 62, (1), 32-36

Total and metal area, and pore distribution, of 2-7% Pt/Al2O3 were measured by gravimetric measurements of N2 and H2 adsorption. Textural variations due to the methods of preparation, the heat treatment, and the Pt content were studied during the catalytic aromatisation of trimethyl-1,1,3-cyclohexane but no simple relation between catalytic activity and texture was found despite Pt crystallites being generally constant at 25Å.

The Dispersion of Platinum on Silica Gel from X-ray Data and the Chemisorption of Hydrogen

e. s. zhmug’, v. s. boronin and o. m. poltorak, Zh. Fiz. Khim., 1965, 39, (3), 809-811

X-ray tests on Pt dispersion in platinised SiO2 containing 0-7.2% Pt and in 5.5% Pt/SiO2, with SiO2 additions ranging from o to 100%, confirmed H2 chemisorption data and related Pt dispersion to the conditions of Pt/SiO2production.

Stereochemistry and the Mechanism of Catalytic Hydrogenation of Cycloalkenes. VI. The Isomerisation of 1,2-Dimethylcycloalkenes as a Route to Both cis- and trans- 1,2-Dimethylcycloalkanes

s. siegel, p. a. thomas and j. t. holt, J. Catalysis, 1965, 4, (1) 73-76

Hydrogenation of 1,2-dimethylcyclohexene and of 1,2-dimethylcyclopentene over reduced PtO2 is accompanied by isomerisation to the corresponding 2,3-dimethylcycloalkenes, which are reduced more rapidly to a mixture of cis- and trans- 1,2-dimethylcycloalkenes, whose ratio appears independent of the fraction of the original cycloalkene which has reacted. Most of the trans isomers arises from reduction of 2,3-dimethylcycloalkenes but some appears to be formed directly from the 1,2-dimethylcycloalkenes.

Catalytic Conversions of 1,1-Dimethyldicy-clohexyl and 1-Methy1-1-phenylcyclohexane on Platinum Catalysts in Conditions of High Temperature and Pressure of Hydrogen

s. i. khromov, d. chultem and e. s. balenkova, Vest. Moskov. Univ., Ser. II, Khim., 1965, (1), 51-55

Conversions of almost 100% are achieved on 1% Pd/C and 1% Pd/Al2O3 at 20 atm, 460°5 nearly as much at 1 atm, 460°C. Products are tabulated in each case and also for conversions at 1 atm, 320°C.

Conversion of Homologues of Tetrahydrofuran on Palladium-on-Carbon

n. i. shuikin, r. a. karakhanov and i. ibrakhimov, Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1965, (1), 165-167

Conversions over Pd/C at 300-400°C showed up to 80% isomerisation to aliphatic ketones and also dehydrogenation to the furan homologues. Conversions exceeding 90% occurred for 2,2-dialkyltetrahydrofurans converted to isoparaffinic hydrocarbons.

Homogeneous Catalysis by Noble Metal Salts. I. The Homogeneous Isomerisation of Olefins by Palladium Compounds

g. c. bond and m. hellier, J. Catalysis, 1965, 4, (1), 1-5

PdCl2 and its bis(benzonitrile) and bis(acetonit-rile) complexes catalysed isomerisation of n- pentenes at 1 atm, 70°C in C6H6 solution, ethyl acetate and methyl ethyl ketone but in the absence of solvents at 40°C the reactions were much slower. cis -2-Pentane had an induction period and isomerised more slowly than 1-pentene. The ratio of cis -2-pentene/trans -2-pentene formed from 1-pentene exceeded the equilibrium ratio. Possible mechanisms are discussed briefly.

Hydrazine as a Reducing Agent for Organic Compounds (Catalytic Hydrazine Reductions)

a. furst, r. c. berlo and s. hooton, Chem. Rev., 1965, 65, (1), 51-68

Complete reductions of aromatic and heterocyclic nitro compounds are reviewed. Pt metal catalysts used in many of the reactions include Pt, Pd, Pd/C, Ru/C, Ru/Ca, Pd/CaCO3, Pd/SrCO3. (183 references).

Homogeneous Catalysis. II. The Mechanism of the Hydrosilation of Olefins Catalysed by Group VIII Metal Complexes

a. j. chalk and j. f. harrod, J. Am. Chem. Soc, 1965, 87, (1), 16-21

Relative importance of hydrosilation and isomerisation of olefins by Pt(II) and Rh(I) olefin complexes depends on the silane used. Alkyl-phosphine complexes of Pt(II) reacted with trialkylsilanes to produce the corresponding Pt(II) hydride. No stable Pt-Si bonds were noticed but a phosphine complex of Ir(I) decomposed several Si hydrides, retaining both Si and hydride fragments in its coordination sphere.

Hydride Intermediates in Homogeneous Hydrogenation Reaction of Olefins and Acetylenes Using Rhodium Catalysts

j. f. young, j. a. osborn, f. h. jardine and g. wilkinson, Chem. Commun., 1965, (7), 131-132

The connection has been demonstrated between the taking up of H2 by tris(triphenyl-phosphine) chlororhodium(1) and homogeneous hydrogenation. The compound is a very efficient catalyst for the reduction of double and triple bond compounds when in 5 × 10-3M concentration in C2H5OH-C6H6 solution at 25°C, ≤1 atm.

Homogeneous Catalytic Hydrogenation and Hydroformylation of Acetylenic Compounds

f. h. jardine, j. a. osborn, g. wilkinson and j. f. young, Chem. & Ind., 1965, (13), 560

Alkynes as well as alkenes may be catalytically hydrogenated to alkanes, using Rh complexes. Hex-1-yne, (∼2M), was reduced to n-hexane at 20°C, i atm in C2H5OH-C6H6 solution of (Ph3P)3 RhCl, (∼5 × 10−3M). In the presence of 1:4 mixture of H and CO at 110°C, 120 atm, it was catalytically hydroformylated to give a 15% yield of n -heptaldehyde and 2-methyl-hexaldehyde.

Adsorption and Catalytic Reactions on Evaporated Metal Films. XI. Adsorption and Interaction of Hydrogen and Oxygen on Rhodium

v. ponec, z. knor and s. ČernÝ, Coll. Czech. Chem. Commun., 1965, 30, (1), 208-216

H2 and O2 adsorption on Rh films were measured and the changes in electrical resistance occurring at the same time. The order of catalytic activity of metal films is Pd, Rh>Ni>Mo.

On the Catalytic Properties of Iridium Compounds in Aqueous Solutions

s. i. ginsburg and m. i. yuz’ko, Zh. Neorg. Khim., 1965, 10, (4), 823-828

A series of Ir complexes catalyses the reaction of strong oxidising agents with H2O, by which is formed atomic O. The rate of reaction of Ce( SO4) 2 with H2O is first order in the presence of low concentrations of Ir(III) sulphate but at higher concentrations the rate decreases and the catalytic process tapers off. The catalytic properties are not possessed by the Ir(IV) sulphate complexes but by ions of hydrated Ir(III). Secondary hydrolysis products are inactive and decrease the rate but at low catalyst concentrations these products are only present in minute amounts.

Oxidation of Ammonia over a Supported Ruthenium Catalyst

t. j. schriber, Diss. Abs., 1964, 25, (6), 3459-3460

NH3 was oxidised over 0.5 wt.% Ru/Al2O3 at 246-345°C, 2.3-3.7 atm, forming N2, N2O and H2O. Rates of formation of N2 and N2O depended on Pnh3, PO2 and Ph2o. Increasing Ph2o inhibited both rates, increasing Po2 promoted both rates, and increasing Pnh3, favoured N2O formation, as did higher temperature.

FUEL CELLS

Notes on a Study of Fuel Cell Hydrocarbon Electrodes

r. thacker and d. d. bump, Electrochem. Technol., 1965, 3, (1-2), 9-12

Pt, Pd and Ag supported on carbon discs were used as electrodes in studying the rest potential and polarisation of C2H6, C2H4, C3H8, C3H6 and n-C4H10 in 35% KOH solution at 80°C, 1 atm and at 150°C, 20 atm. C2H4 showed the best polarisation behaviour. The order of catalytic activity was

A New High-performance Fuel Cell Employing Conducting-porous-Teflon Electrodes and Liquid Electrolytes

l. w. niedrach and h. r. alford, J. Electrochem. Soc., 1965, 112, (2), 117-124

Conducting porous electrodes of 5-10 mil thickness developed from Pt black and Teflon on Ni screens have good strength, conductivity, and wetting characteristics. They were tested in fuel cells with 6N KOH and 5N H2SO4 electrolytes at ambient temperature. O2 and air were oxidants for H2. Hydrocarbons and CH3OH were suitable fuels. An acid electrolyte, air oxidant cell produced 176 mA/cm2 and alkaline cells produced 263 and 88 mA/cm2 for over 5 months.

CHEMICAL TECHNOLOGY

Spinneret Makers Enjoy Fibres Surge. Are Pushed by Economic and Technological Factors Likely to Continue Unabated for Some Time

Chem. Engng. News., 1965, 43, (5), 34-36

Spinneret alloys commonly used for rayon production are 70% Au-Pt, 10% Rh-Pt, 49% Au-1% Rh-Pt. Fibre production depends on the precision with which the holes are made; 0.0001 inch tolerance for diameter, perfect shape, sharp-edged. Special shapes are used for special fibres.

Influence of Deformation and Tempering Temperature on the Electrochemical Corrosion of Titanium and the Titanium Alloy with 0.2% Palladium

n. d. tomashov and yu. m. ivanov, Zashchita Met., 1965, 1, (1), 36-41

Cold-rolled Ti and 0.2% Pd-Ti sheets corrode less than annealed sheets. The rate of corrosion decreases as the deformation from rolling increases.

Investigation of the Protective Action Mechanism of Palladium in Corrosion-resistant Titanium-Palladium Alloys by Radiochemical Methods

n. d. tomashov, m. n. shchulepnikov and yu. m. ivanov, Ibid., 122-123

As surface corrosion commences, there is an accumulation there of Pd which passivates the surface and which leads to Pd additions of 0.1-0.2% to Ti being sufficient.

Technological Properties and Corrosion Behaviour of a Titanium Alloy with 0.2% Palladium

k. rudinger, Werkstoffe u. Korrosion, 1965,16, (2), 109-115

Tests on welded and non-welded samples of 0.2% Pd-Ti and of Ti showed that their technological, physical and processing properties are similar. Alloy and metal have the same corrosion-resistance under oxidising conditions but 0.2% Pd-Ti is superior under reducing conditions.

ELECTRICAL ENGINEERING

Electrical Contact Materials in Low Current Technology

w. h. abbott and h. r. ogden, Battelle Tech. Rev., 1965, 14, (3), 17-22

A survey of contact types, causes of failure, and contact design. Au, Pt metal and precious metal alloy contacts are particularly useful. Their properties and difficulties in use for electronics applications are described.

TEMPERATURE MEASUREMENT

Pressure Dependence of the emf of Thermocouples to 1300°C and 50 kbar

r. e. hanneman and h. m. strong, j . Appl. Phys., 1965, 36, (2), 523-528

Relative temperature corrections accurate to ±1°C due to pressure are given for Pt: 10% Rh-Pt, Pt: 13% Rh-Pt, Chromel-Alumel, and iron-constantan thermocouples as functions of temperature and pressure. They exceed 40° in some cases. Absolute corrections ΔT were also studied and are proportional to pressure at a given temperature. ΔT can exceed 50° for Pt:10% Rh-Pt at 50 kbar, T> 1300°C.

A New Method for the Computation of Temperature in Platinum Resistance Thermometry

j. l. hales and e. f. g. herington, J. Sci. Insttum., 1965, 42, (4)3 203-209

Temperatures on the International Practical Scale of Temperature of 1948 between − 182.97 and +630.5°C can be calculated from the resistance of a Pt thermometer using the equation t=tPt + δPt(tPt-100)tPt.10−4, where δPt depends on the Pt temperature tPt and on the thermometer constants δ and β. A master table of δPt as a function of tPt is given for a thermometer with δ = 1.492, β =0.110 and tables can be derived for other values of δ and β. Using such tables and a desk calculator, temperature errors should not exceed 3 × 10−4 deg C.

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