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788. Vaporization of magnesium oxide and its reaction with alumina
322
Classified Abstracts 780---789
16 780. The sorption of water vapor and the hydrogen-deuterium exchange, effect on poly-L-glutamie acid. (U.S.A.) W. Hnojewyj and L. H. Reyerson, J. Phys. Chem., 67, March 1963, 711-713.
charge in a kinetic system can be prevented by using indium and Viton in place of Neoprene or Buna N for vacuum seals, and Silicone 705 in place of Silicone 704 in duffusion pumps ; (b) organic contamination during bakeout in ultra-high vacuum oil diffusion pump systems can be largely avoided by fitting two liquid nitrogen traps, w.J.s.
16 781. Microcalorimetric studies of the distribution of surface energy in chemisorption. U.S.A. Surface energy distributions of a series of Oxide catalysts were measured using NH3 adsorbate in a differential isothermal microcalorimeter at 50 °. The catalysts studied were A1203 calcined at 1100 and 1600°F, SiO2, KOH-AI~O3, Pt-AI~Os, and SiO2-MgO. It was found that AI~Oa (ll00°F.) has a heterogeneous distribution of surface energy which is not destroyed by high temperature calcination. SiO~, on the other h a n d , has a fairly homogeneous surface energy distribution. Alumina's energy distribution may be altered by impregnation, e.g., with K O H or Pt. When a co-gel of MgO and SiO2 is formed, its surface is more energetic and its surface energy distribution more heterogeneous than that of SiO2 alone. (Author) V. Kevorkian and R. Steiner, J. Phys. Chem., 67, March 1963, 545-549.
L. Holland, Vacuum, 13 (5), May 1963, 173-180.
16 782. Mierocatalytic studies of the hydrogenation of ethylene. I. The promoting effect of adsorbed hydrogen on the catalytic activity of metal surfaces. ( U.S.A .) W. Hall and J. Hassell, J. Phys. Chem., 67, March 1963, 636-643. 16 783. A novel technique for characterization of adsorption rates on heterogeneous surfaces. U.S.A. A novel technique is proposed for obtaining and interpreting data on adsorption rates to a catalyst surface. The method is illustrated by actual data from a hydrogen-on-nickel system. The amount of adsorbed gas on a catalyst which is part of an isothermal system varies with time when the pressure changes. The variation depends on the adsorption kinetics and the heterogeneity of the surface. For a sinusoidally varying pressure, the dependence of the adsorption amplitude and phase lag on the frequency is one way of characterizing adsorption kinetics. The " frequency response " to an induced sinusoidal pressure variation of the moles of gas adsorbed on a uniform surface having first-order kinetics can be computed theoretically A heterogeneous surface is assumed to be an assembly or series of " different uniform-surfaces " randomly interspersed. An assembly of such surfaces, characterized by different rate constants, has an out-of-phase component of the adsorption which resembles a spectrogram, separating the effect of different types of surface sites irrespective of the fact the adsorptions are occurring simultaneoulsy on unlike sites. As an illustration of the technique, hydrogen adsorption was studied on a supported nickel catalyst. The effect of oxygen addition to the catalyst on the adsorption kinetics of hydrogen was studied. It was found that an increase in oxygen content reduced the amount of fast adsorption and increased the slow adsorption. It was possible to characterize and Separate the rates of adsorption of both the fast and the slow types. (Author) L. Naphtali and L. Polinski, J. Phys. Chem., 67, Feb. 1963, 369375. 16:30 784. Sources of surface contamination in vacuum evaporation systems. Great Britain. Contaminant vapours were detected by (1) observing the effect of their adsorption on the hydrophilic surface properties of clean glass and SiO~ films ; and (2) polymerizing organic films on an electron bombarded target. The experiments showed that (a) the deposition on glass of optically adsorbed coatings of organic materials in a flow dis-
16:41 785. Interaction of oxygen at low pressures with molybdenum. Great Britain. The molybdenum used in these experiments was in the form of a polycrystalline filament. Adsorption of oxygen took place at a series of filament temperatures ranging from 223815°K. Subsequent desorption took place when cooling from 1300°K, the pressure in each case being of the order of 10-6 tort. The amount of desorption was found to depend on the temperature of the filament at which adsorption had taken place. The authors conclude that the interaction is of a chemisorbed species, w.J.s. R. P. H. Gasser and D. E. A. Schuftan, Vacuum, 13 (4), April 1963, 146. 16 : 51 786. New theory of adhesion. U.S.A. Currently there are three theories of adhesion : adsorption, diffusion and electrostatic. The new theory is basically an extension of the first of these and employs two axioms. (1) The criteria for strong adhesion and the annodynamic spreading are the same. (2) For strong adhesion between pure A and pure B, either A must spread B or B must spread on A. Key to the practical application is the use of the critical surface tensions of wetting. The critical surface tension of a smooth solid is the surface tension a liquid must have to spread only on that solid. Spreading occurs or is less than the solid's critical surface tension. These conditions for spreading can be developed from calculation involving surface free energies and the author concludes that the criteria for spreading and for strong adhesion are the same. This is exemplified by the known adhesive properties of a number of commercial plastics. It appears that fluorine substituted compounds should make good adhesives. A completely perfluoroakyl substituted polymethylene could bond anything to anything and thus constitute a truly universal adhesive, w.s.s. Anon, Chem. & Engng. News, 41 (15), 15 April, 1963, 67-73. 17.
Thermodynamics
17:47 787. The vapour pressures and bond energies of some antimony halides. (U.S.A.) R. Sime, J. Phys. Chem., 67, Feb. 1963, 501-503. 17 788. Vaporization of magnesium oxide and its reaction with alumina. U.S.A. A Knudsen effusion and oxygen transpiration study of the vaporization of MgO indicates that gaseous MgO is of little importance in the vapour phase at about 2000°K. A Do ° f o r gaseous MgO of about 80 kcal/mole is obtained. Knudsen experiments with MgAI~O4 support a negative heat of formation from the oxides, and this is confirmed by recalculation of other experimental results. (Author) R. Altman, Y. Phys. Chem., 67, Feb. 1963, 366-369. 17 789. The thermodynamic and physical properties of beryllium compounds. H. Heat of formation and entropy of beryllium (I) fluoride (g). U.S.A. The molecular flow effusion method has been employed
Classified Abstracts 780---789
16 780. The sorption of water vapor and the hydrogen-deuterium exchange, effect on poly-L-glutamie acid. (U.S.A.) W. Hnojewyj and L. H. Reyerson, J. Phys. Chem., 67, March 1963, 711-713.
charge in a kinetic system can be prevented by using indium and Viton in place of Neoprene or Buna N for vacuum seals, and Silicone 705 in place of Silicone 704 in duffusion pumps ; (b) organic contamination during bakeout in ultra-high vacuum oil diffusion pump systems can be largely avoided by fitting two liquid nitrogen traps, w.J.s.
16 781. Microcalorimetric studies of the distribution of surface energy in chemisorption. U.S.A. Surface energy distributions of a series of Oxide catalysts were measured using NH3 adsorbate in a differential isothermal microcalorimeter at 50 °. The catalysts studied were A1203 calcined at 1100 and 1600°F, SiO2, KOH-AI~O3, Pt-AI~Os, and SiO2-MgO. It was found that AI~Oa (ll00°F.) has a heterogeneous distribution of surface energy which is not destroyed by high temperature calcination. SiO~, on the other h a n d , has a fairly homogeneous surface energy distribution. Alumina's energy distribution may be altered by impregnation, e.g., with K O H or Pt. When a co-gel of MgO and SiO2 is formed, its surface is more energetic and its surface energy distribution more heterogeneous than that of SiO2 alone. (Author) V. Kevorkian and R. Steiner, J. Phys. Chem., 67, March 1963, 545-549.
L. Holland, Vacuum, 13 (5), May 1963, 173-180.
16 782. Mierocatalytic studies of the hydrogenation of ethylene. I. The promoting effect of adsorbed hydrogen on the catalytic activity of metal surfaces. ( U.S.A .) W. Hall and J. Hassell, J. Phys. Chem., 67, March 1963, 636-643. 16 783. A novel technique for characterization of adsorption rates on heterogeneous surfaces. U.S.A. A novel technique is proposed for obtaining and interpreting data on adsorption rates to a catalyst surface. The method is illustrated by actual data from a hydrogen-on-nickel system. The amount of adsorbed gas on a catalyst which is part of an isothermal system varies with time when the pressure changes. The variation depends on the adsorption kinetics and the heterogeneity of the surface. For a sinusoidally varying pressure, the dependence of the adsorption amplitude and phase lag on the frequency is one way of characterizing adsorption kinetics. The " frequency response " to an induced sinusoidal pressure variation of the moles of gas adsorbed on a uniform surface having first-order kinetics can be computed theoretically A heterogeneous surface is assumed to be an assembly or series of " different uniform-surfaces " randomly interspersed. An assembly of such surfaces, characterized by different rate constants, has an out-of-phase component of the adsorption which resembles a spectrogram, separating the effect of different types of surface sites irrespective of the fact the adsorptions are occurring simultaneoulsy on unlike sites. As an illustration of the technique, hydrogen adsorption was studied on a supported nickel catalyst. The effect of oxygen addition to the catalyst on the adsorption kinetics of hydrogen was studied. It was found that an increase in oxygen content reduced the amount of fast adsorption and increased the slow adsorption. It was possible to characterize and Separate the rates of adsorption of both the fast and the slow types. (Author) L. Naphtali and L. Polinski, J. Phys. Chem., 67, Feb. 1963, 369375. 16:30 784. Sources of surface contamination in vacuum evaporation systems. Great Britain. Contaminant vapours were detected by (1) observing the effect of their adsorption on the hydrophilic surface properties of clean glass and SiO~ films ; and (2) polymerizing organic films on an electron bombarded target. The experiments showed that (a) the deposition on glass of optically adsorbed coatings of organic materials in a flow dis-
16:41 785. Interaction of oxygen at low pressures with molybdenum. Great Britain. The molybdenum used in these experiments was in the form of a polycrystalline filament. Adsorption of oxygen took place at a series of filament temperatures ranging from 223815°K. Subsequent desorption took place when cooling from 1300°K, the pressure in each case being of the order of 10-6 tort. The amount of desorption was found to depend on the temperature of the filament at which adsorption had taken place. The authors conclude that the interaction is of a chemisorbed species, w.J.s. R. P. H. Gasser and D. E. A. Schuftan, Vacuum, 13 (4), April 1963, 146. 16 : 51 786. New theory of adhesion. U.S.A. Currently there are three theories of adhesion : adsorption, diffusion and electrostatic. The new theory is basically an extension of the first of these and employs two axioms. (1) The criteria for strong adhesion and the annodynamic spreading are the same. (2) For strong adhesion between pure A and pure B, either A must spread B or B must spread on A. Key to the practical application is the use of the critical surface tensions of wetting. The critical surface tension of a smooth solid is the surface tension a liquid must have to spread only on that solid. Spreading occurs or is less than the solid's critical surface tension. These conditions for spreading can be developed from calculation involving surface free energies and the author concludes that the criteria for spreading and for strong adhesion are the same. This is exemplified by the known adhesive properties of a number of commercial plastics. It appears that fluorine substituted compounds should make good adhesives. A completely perfluoroakyl substituted polymethylene could bond anything to anything and thus constitute a truly universal adhesive, w.s.s. Anon, Chem. & Engng. News, 41 (15), 15 April, 1963, 67-73. 17.
Thermodynamics
17:47 787. The vapour pressures and bond energies of some antimony halides. (U.S.A.) R. Sime, J. Phys. Chem., 67, Feb. 1963, 501-503. 17 788. Vaporization of magnesium oxide and its reaction with alumina. U.S.A. A Knudsen effusion and oxygen transpiration study of the vaporization of MgO indicates that gaseous MgO is of little importance in the vapour phase at about 2000°K. A Do ° f o r gaseous MgO of about 80 kcal/mole is obtained. Knudsen experiments with MgAI~O4 support a negative heat of formation from the oxides, and this is confirmed by recalculation of other experimental results. (Author) R. Altman, Y. Phys. Chem., 67, Feb. 1963, 366-369. 17 789. The thermodynamic and physical properties of beryllium compounds. H. Heat of formation and entropy of beryllium (I) fluoride (g). U.S.A. The molecular flow effusion method has been employed