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491. Vapor pressure studies of sulfur trioxide and the water-sulfur trioxide system
Classified Abstracts occupies the same surface sites as Ha0 and does not dissociate. Ion-dipole interaction between NH, and Fe-S ions together with hydrogen bonding furnishes the heat of chemisorption which was measured by equilibrium pressure data from 200 to 350” to be 11.5 kcal. per mole. NH+, formation occurred only when physically adsorbed H,O and NH3 were present and not when only NH, and surface hydroxyl groups from chemisorbed water were present. The infrared bands of physically and chemically adsorbed NH3 showed evidence of rotational structure superimposed on the vibrational bands. The adsorption of (Authors) the other gases is discussed briefly. G. Blyholder and E. A. Richardson, 1962, 2597-2602.
J. Phys. Chem., 66, Dec. 16
489. Application of flash-desorption method to catalyst studies : I. Ethylene-alumina system. Canada. The flash-desorption technique was applied to the ethylene-alumina system to investigate the surface of alumina. The apparatus consisted of a programming controller increasing the catalyst temperature linearly with time at various speeds, and of a thermistor type thermal conductivity cell for measuring the rate of desorption of ethylene. The existence of two different sites for the adsorption of ethylene on alumina was established. On one of these sites the activation energy of desorption was 26.8 kcal./mole (I), and on the other 36.4 kcal./ mole (II). These sites occupy 2.8 per cent of the total surface area, 60 per cent of which belongs to I, 40 per cent to II. (Authors) Y. Amenomiya and R. J. Cvetanovic, 1963, 144-147.
201
489-496
17 493. Vapor pressure and heat of sublimation of calcium fluoride. U.S.A. The vapour pressure of CaF, was investigated in the temperature range 1400 to 1850°K by the torsion-effusion method. The-vapour pressure (in atmospherks) of p-CaF, is given by the eauation log P = -19.973/T + 7.8717 in the exuerimental range. Extrapolation yields a calculated normal boiling point of i786”K and a heat of sublimation at 298°K of 101.2 kcal bv the third-law method and 101.4 kcal bv the second-law Molecular-streaming conditions w&e demonstrated method. to break down when the mean free path became about as short as the orifice diameter. but a denendence on orifice length as (Authors) well as orifice diameter was observed. D. A. Schulz and A. W. Searcy, J. Phys. Chem., 67, Jan. 1963, 103-106. 17 494. The thermal isomerization of cyclopropane at low pressures. Great Britain. The isomerization of cyclopropane has been studied in a l-l. vessel at 490” down to a pressure of 6 x lO-4 mm. At these low pressures, the rate constant becomes first order again in cyclopropane, and dependent on surface area, because the molecules are predominantly energized by collisions with the walls instead of collisions with other gas molecules. The activation energy was measured in this low pressure first(Authors) order region. A. D. Kennedy 1963, 161-163.
and H. 0. Pritchard,
J. Phys. Chem., 67, Jan.
J. Phys. Chem., 67. Jan.
16 490. Heterogeneous recombination of free atoms on a neutral surface. (Great Britain). F. S. Larkin and B. A. Thrush, Natwe, 197 (4865), 26 Jan. 1963, 375-376.
17. Thermodynamics 17 :47 491. Vapor pressure studies of sulfur trioxide and the watersulfur trioxide system. U.S.A. The vapor pressures of liquid and r-SO, (trimeric form, m.p. 16.86”) have been determined in all-glass apparatus. The vapor pressure of the so-called P-SO,, which is only formed in the presence of > 10m5mole fraction of water, also is reported. Vapor pressure and melting point studies of the H,O-SO, system are reported in the range of 0.8 mole fraction SO, upward. The solutions so formed solidify at constant temperature to form a solid solution of the same composition as the melt. A syneresis upon standing for several weeks was observed in the 0.999 mole fraction SO, sample. (Authors) J. H. Colwell and G. D. Halsey, Jr., J. Phys. Chem., 66, Nov. 1962, 2179-2182. 17 492. The thermodynamic and physical properties of beryllium compounds : I. Enthalpy and entropy of vaporization of beryllium fluoride. U.S.A. Using torsion effusion, gravimetric effusion, and transpiration techniques, the enthalpy and entropy of vaporization of BeF, were determined over the temperature range 550-950”. The enthalpy of vaporization in this temperature range was found to be 53.25 -I- 0.25 kcal., while the corresponding entropy was found to be 38.7 * 0.6 cal./deg./mole. A determination of the melting point of crystalline BeF, by means of vapour pressure measurements yielded a value of 542 & 3”. Torsion effusion measurements of the effusing vapour show the gaseous species over liquid beryllium fluoride to consist of BeF,. (Author) M. A. Greenbaum, J. Phys. Chem., 67, Jan. 1963, 36-40.
17 495. Mass spectrometric study of high temperature reactions in the boron-hydrogen-oxygen system. U.S.A. Low pressure reactions of H,(g) with B-B,O, mixtures and H,O(g) with elemental boron in the temperature range 1000 to 1400°K have been investigated. The experimental technique involves flowing the reactant gas at pressures between IO+ and lO-3 atm into a Knudsen-type vessel containing a condensed sample, and observing the gaseous products effusing from the oven mass spectrometrically. The major product formed with either H,(g) or H,O(g) as reactant is B,O,H, A smaller yield of B,O,H, (hydroxyboroxine) also (boroxine). is observed. In separate experiments, the products of these reactions have been collected in a cold tran at liauid nitrogen temperature. Upon warming, the condensed maierial evolves The heats of formation of B,O,H,(g) diborane and hydrogen. and B,O,H,(g) at 298°K are -302 i 7 and -393 _C 7 kcal/ (Authors) mole, respectively. W. P. Sholette and R. F. Porter, 177-182.
J. Phys. Chem., 67, Jan. 1963,
17 : 18 496. Kinetic measurement of temperatures. France. The proposed method allows the measurement of high gas temperatures in fast transient phenomena, such as those encountered in shock tubes used in aerodynamics, plasma studies etc. For this purpose, the gas molecules velocity spectrum is obtained by measurement of their time of flight in vacuum. The transit chamber is separated from the hot gas by a diaphragm, the sudden rupture of which releases a stream of particles The moleand enables the time origin to be correctly defined. cules reach a detector at the end of their flight. The start of the response signal of this detector depends only on temperature. The first part of this article comprises a theoretical account of the method. The second part describes certain experiments showing the value of measurements made : ambient temperature measurements and explosion temperature of a hydrogen-oxygen mixture. An instrument to measure temperatures produced by a capacitor discharging into a test resistance is described. The ejection speeds of particles are between 20 and 50 km/set
J. Phys. Chem., 66, Dec. 16
489. Application of flash-desorption method to catalyst studies : I. Ethylene-alumina system. Canada. The flash-desorption technique was applied to the ethylene-alumina system to investigate the surface of alumina. The apparatus consisted of a programming controller increasing the catalyst temperature linearly with time at various speeds, and of a thermistor type thermal conductivity cell for measuring the rate of desorption of ethylene. The existence of two different sites for the adsorption of ethylene on alumina was established. On one of these sites the activation energy of desorption was 26.8 kcal./mole (I), and on the other 36.4 kcal./ mole (II). These sites occupy 2.8 per cent of the total surface area, 60 per cent of which belongs to I, 40 per cent to II. (Authors) Y. Amenomiya and R. J. Cvetanovic, 1963, 144-147.
201
489-496
17 493. Vapor pressure and heat of sublimation of calcium fluoride. U.S.A. The vapour pressure of CaF, was investigated in the temperature range 1400 to 1850°K by the torsion-effusion method. The-vapour pressure (in atmospherks) of p-CaF, is given by the eauation log P = -19.973/T + 7.8717 in the exuerimental range. Extrapolation yields a calculated normal boiling point of i786”K and a heat of sublimation at 298°K of 101.2 kcal bv the third-law method and 101.4 kcal bv the second-law Molecular-streaming conditions w&e demonstrated method. to break down when the mean free path became about as short as the orifice diameter. but a denendence on orifice length as (Authors) well as orifice diameter was observed. D. A. Schulz and A. W. Searcy, J. Phys. Chem., 67, Jan. 1963, 103-106. 17 494. The thermal isomerization of cyclopropane at low pressures. Great Britain. The isomerization of cyclopropane has been studied in a l-l. vessel at 490” down to a pressure of 6 x lO-4 mm. At these low pressures, the rate constant becomes first order again in cyclopropane, and dependent on surface area, because the molecules are predominantly energized by collisions with the walls instead of collisions with other gas molecules. The activation energy was measured in this low pressure first(Authors) order region. A. D. Kennedy 1963, 161-163.
and H. 0. Pritchard,
J. Phys. Chem., 67, Jan.
J. Phys. Chem., 67. Jan.
16 490. Heterogeneous recombination of free atoms on a neutral surface. (Great Britain). F. S. Larkin and B. A. Thrush, Natwe, 197 (4865), 26 Jan. 1963, 375-376.
17. Thermodynamics 17 :47 491. Vapor pressure studies of sulfur trioxide and the watersulfur trioxide system. U.S.A. The vapor pressures of liquid and r-SO, (trimeric form, m.p. 16.86”) have been determined in all-glass apparatus. The vapor pressure of the so-called P-SO,, which is only formed in the presence of > 10m5mole fraction of water, also is reported. Vapor pressure and melting point studies of the H,O-SO, system are reported in the range of 0.8 mole fraction SO, upward. The solutions so formed solidify at constant temperature to form a solid solution of the same composition as the melt. A syneresis upon standing for several weeks was observed in the 0.999 mole fraction SO, sample. (Authors) J. H. Colwell and G. D. Halsey, Jr., J. Phys. Chem., 66, Nov. 1962, 2179-2182. 17 492. The thermodynamic and physical properties of beryllium compounds : I. Enthalpy and entropy of vaporization of beryllium fluoride. U.S.A. Using torsion effusion, gravimetric effusion, and transpiration techniques, the enthalpy and entropy of vaporization of BeF, were determined over the temperature range 550-950”. The enthalpy of vaporization in this temperature range was found to be 53.25 -I- 0.25 kcal., while the corresponding entropy was found to be 38.7 * 0.6 cal./deg./mole. A determination of the melting point of crystalline BeF, by means of vapour pressure measurements yielded a value of 542 & 3”. Torsion effusion measurements of the effusing vapour show the gaseous species over liquid beryllium fluoride to consist of BeF,. (Author) M. A. Greenbaum, J. Phys. Chem., 67, Jan. 1963, 36-40.
17 495. Mass spectrometric study of high temperature reactions in the boron-hydrogen-oxygen system. U.S.A. Low pressure reactions of H,(g) with B-B,O, mixtures and H,O(g) with elemental boron in the temperature range 1000 to 1400°K have been investigated. The experimental technique involves flowing the reactant gas at pressures between IO+ and lO-3 atm into a Knudsen-type vessel containing a condensed sample, and observing the gaseous products effusing from the oven mass spectrometrically. The major product formed with either H,(g) or H,O(g) as reactant is B,O,H, A smaller yield of B,O,H, (hydroxyboroxine) also (boroxine). is observed. In separate experiments, the products of these reactions have been collected in a cold tran at liauid nitrogen temperature. Upon warming, the condensed maierial evolves The heats of formation of B,O,H,(g) diborane and hydrogen. and B,O,H,(g) at 298°K are -302 i 7 and -393 _C 7 kcal/ (Authors) mole, respectively. W. P. Sholette and R. F. Porter, 177-182.
J. Phys. Chem., 67, Jan. 1963,
17 : 18 496. Kinetic measurement of temperatures. France. The proposed method allows the measurement of high gas temperatures in fast transient phenomena, such as those encountered in shock tubes used in aerodynamics, plasma studies etc. For this purpose, the gas molecules velocity spectrum is obtained by measurement of their time of flight in vacuum. The transit chamber is separated from the hot gas by a diaphragm, the sudden rupture of which releases a stream of particles The moleand enables the time origin to be correctly defined. cules reach a detector at the end of their flight. The start of the response signal of this detector depends only on temperature. The first part of this article comprises a theoretical account of the method. The second part describes certain experiments showing the value of measurements made : ambient temperature measurements and explosion temperature of a hydrogen-oxygen mixture. An instrument to measure temperatures produced by a capacitor discharging into a test resistance is described. The ejection speeds of particles are between 20 and 50 km/set