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Dividing gas mixtures
120
Classified Abstracts 158--168
16 158. Ultrasonic relaxation in polyatomic gases and vapours. India. The paper describes a simple method of calculating ultrasonic relaxation frequencies in polyatomic gases. The mechanism of relaxation is explained as a resonance phenomenon by assuming a characteristic rotational oscillation frequency of gas molecules in ground state, due to the interaction field of neighbouring molecules. Using infrared vibration and electronic frequencies given by the ionization potential, in the relation f : (1/2~r) ~/(3h v ~2/4r~) the relaxation frequencies are evaluated for carbon dioxide, carbon disulphide, nitrous oxide, sulphur dioxide, ammonia, acetaldehyde, benzene, methane and chloromethanes, and are in close agreement with the experimental data. The method is absolute and does not involve calculation of parameters such as partition functions and collision probabilities. (Authors) S. K. K. Jatkar and D. D. Deshpande, Brit. J. Appl. Phys., 12 (5), May 1961, 243-247. •
16 159. Chemisorption studies on supported platinum. United States. The adsorption of hydrogen, oxygen and carbon monoxide on platinum-on-alumina re-forming catalysts and on the alumina base was investigated. By means of hydrogen adsorption the platinum surface area of freshly prepared samples was found to be 200 to 270 m2/g of platinum. The decrease of platinum dispersion due to heat treatment of catalysts is shown. Several catalysts were subjected to complete oxidation-reduction cycles and the amount of hydrogen and oxygen taken up in the different steps of such a cycle was measured. A probable mechanism for the oxidation-reduction cycle was established. The mechanism of CO adsorption on supported platinum was found to depend not only on the nature of the support but also on the degree of dispersion of the metal. The fraction of CO adsorbed in the bridged structure decreases with decreasing metal dispersion. (Author) H. L. Gruber, J. Phys. Chem., 66 (1), Jan. 1962, 48-54. 16 160. Effect of light on hydrogen chemisorption on zinc oxide. United States. Illumination of zinc oxide with light from a low-pressure mercury arc lamp leads to a retardation of hydrogen chemisorption at 300°C (type-B). This photo-effect is correlated with the photo-conductive property of zinc oxide and a tentative mechanism in terms of the equilibrium between ionized and un-ionized H-donors at the surface is proposed. (Authors) V. Kesavulu and H. A. Taylor, J. Phys. Chem., 66 (1), Jan. 1962, 54-57. 16 161. The influence of chemisorption of oxygen on the electron spin resonance of zinc oxide. R. J. Kokes, J. Phys. Chem., 66 (1), Jan. 1962, 99-103. 16 162. Perturbations of the nickel metal K X-ray absorption edge due to small crystal size and hydrogen chemisorption. P. H. Lewis, J. Phys. Chem., 66 (1), Jan. 1962, 105-111. 16 163. Use of krypton for surface area measurements. J. M. Haynes, J. Phys. Chem., 66 (1), Jan. 1962, 182-185.
16 164. Dividing gas mixtures. France. A method is reported of separating a mixture of two gases by adsorption ; it is said to be particularly suited to the separation of oxygen and nitrogen from air. The method depends on the properties of an artificially crystallised zeolite (a hydrated silicate) which adsorbs oxygen to a greater degree than n i t r o g e n ; the speed of adsorption is greater than the
speed of diffusion of the air into the mass of zeolite. The layout and operation of the plant is described. (Author, modified) Anon., New Scientist, 9 (223), 23 Feb. 1961, 479. 16 : 21 : 25 165. The vacuum use of molecular sieves and other desiccants. Great Britain. The use of molecular sieve as a desiccant in vacuum systems has been investigated. A comparison of the water adsorption efficiency of the sieve, under static equilibrium conditions, with two other regenerable desiccants (silica gel and activated alumina) shows the sieve to be far superior. It is also shown that the non-regenerable desiccant, phosphorus pentoxide has a greater adsorption capacity than the molecular sieve. A comparison of the adsorption capacity of two column lengths of sieve under dynamic conditions is made and the pressure differentials across the columns are investigated. The increase in the adsorption efficiency when the system is backed by an air ballast rotary pump is shown. Data are also given for moisture breakthrough, heat of adsorption and regeneration times. As the sieve readily absorbs air at atmospheric pressure, the time required for initial degassing is shown. An appendix describes a subsidiary water absorption test, made on a sample of phosphorus pentoxide, to show the progressive effect of surface deliquescence and relative vapour pressure. (Author) E. M. Robson, Vacuuln, 11 (I), Jan. 1961, 10-15. t6 : 3 0 : 3 8 : 4 7 166. The creation and maintenance of clean liquid metal surfaces. E. I. Fazekas, Vacuum, 11 (1), Jan. 1961, 38-39. 16 : 21 Comprehensive study of the ion pumping of the noble gases. See Abstr. No. 200. 16 : 22 Sorptlon and desorption of gas in a hot-cathode ionization gauge. See Abstr. No. 203. The sorption of hydrogen by barium getters.
16:47 See Abstr. No. 293.
Degassing and permeation of gases in tube materials. No. 296.
16 : 47 See Abstr. 16:47
Thermal degassing of tube materials. 17.
See Abstr. No. 297.
Thermodynamics
17 : 64 167. Summarized proceedings of a symposium on the generation of temperatures below l°K.--London, December 1959. Great Britain. A one-day symposium on the methods of generating temperatures below I°K was held by the LowTemperature G r o u p of the Physical Society on 11 December, 1959. Six papers of a review nature were read and discussed. Attention focused primarily on the techniques of adiabatic demagnetization and on the use of 3He ; nevertheless some o f the more difficult techniques were reviewed with the more recently discovered properties of 3He. The papers presented are summarized in this report. (Author) Anon., Brit. J. Appl. Phys., 11 (10), Oct. 1960, 449-453. 18.
Gaseous Electronics
18 168. Design and performance of a compact surge generator. Great Britain. A compact surge generator for investigation of a fast, linear, pinched discharge using only moderate energy storage is described. The technique of construction using an
Classified Abstracts 158--168
16 158. Ultrasonic relaxation in polyatomic gases and vapours. India. The paper describes a simple method of calculating ultrasonic relaxation frequencies in polyatomic gases. The mechanism of relaxation is explained as a resonance phenomenon by assuming a characteristic rotational oscillation frequency of gas molecules in ground state, due to the interaction field of neighbouring molecules. Using infrared vibration and electronic frequencies given by the ionization potential, in the relation f : (1/2~r) ~/(3h v ~2/4r~) the relaxation frequencies are evaluated for carbon dioxide, carbon disulphide, nitrous oxide, sulphur dioxide, ammonia, acetaldehyde, benzene, methane and chloromethanes, and are in close agreement with the experimental data. The method is absolute and does not involve calculation of parameters such as partition functions and collision probabilities. (Authors) S. K. K. Jatkar and D. D. Deshpande, Brit. J. Appl. Phys., 12 (5), May 1961, 243-247. •
16 159. Chemisorption studies on supported platinum. United States. The adsorption of hydrogen, oxygen and carbon monoxide on platinum-on-alumina re-forming catalysts and on the alumina base was investigated. By means of hydrogen adsorption the platinum surface area of freshly prepared samples was found to be 200 to 270 m2/g of platinum. The decrease of platinum dispersion due to heat treatment of catalysts is shown. Several catalysts were subjected to complete oxidation-reduction cycles and the amount of hydrogen and oxygen taken up in the different steps of such a cycle was measured. A probable mechanism for the oxidation-reduction cycle was established. The mechanism of CO adsorption on supported platinum was found to depend not only on the nature of the support but also on the degree of dispersion of the metal. The fraction of CO adsorbed in the bridged structure decreases with decreasing metal dispersion. (Author) H. L. Gruber, J. Phys. Chem., 66 (1), Jan. 1962, 48-54. 16 160. Effect of light on hydrogen chemisorption on zinc oxide. United States. Illumination of zinc oxide with light from a low-pressure mercury arc lamp leads to a retardation of hydrogen chemisorption at 300°C (type-B). This photo-effect is correlated with the photo-conductive property of zinc oxide and a tentative mechanism in terms of the equilibrium between ionized and un-ionized H-donors at the surface is proposed. (Authors) V. Kesavulu and H. A. Taylor, J. Phys. Chem., 66 (1), Jan. 1962, 54-57. 16 161. The influence of chemisorption of oxygen on the electron spin resonance of zinc oxide. R. J. Kokes, J. Phys. Chem., 66 (1), Jan. 1962, 99-103. 16 162. Perturbations of the nickel metal K X-ray absorption edge due to small crystal size and hydrogen chemisorption. P. H. Lewis, J. Phys. Chem., 66 (1), Jan. 1962, 105-111. 16 163. Use of krypton for surface area measurements. J. M. Haynes, J. Phys. Chem., 66 (1), Jan. 1962, 182-185.
16 164. Dividing gas mixtures. France. A method is reported of separating a mixture of two gases by adsorption ; it is said to be particularly suited to the separation of oxygen and nitrogen from air. The method depends on the properties of an artificially crystallised zeolite (a hydrated silicate) which adsorbs oxygen to a greater degree than n i t r o g e n ; the speed of adsorption is greater than the
speed of diffusion of the air into the mass of zeolite. The layout and operation of the plant is described. (Author, modified) Anon., New Scientist, 9 (223), 23 Feb. 1961, 479. 16 : 21 : 25 165. The vacuum use of molecular sieves and other desiccants. Great Britain. The use of molecular sieve as a desiccant in vacuum systems has been investigated. A comparison of the water adsorption efficiency of the sieve, under static equilibrium conditions, with two other regenerable desiccants (silica gel and activated alumina) shows the sieve to be far superior. It is also shown that the non-regenerable desiccant, phosphorus pentoxide has a greater adsorption capacity than the molecular sieve. A comparison of the adsorption capacity of two column lengths of sieve under dynamic conditions is made and the pressure differentials across the columns are investigated. The increase in the adsorption efficiency when the system is backed by an air ballast rotary pump is shown. Data are also given for moisture breakthrough, heat of adsorption and regeneration times. As the sieve readily absorbs air at atmospheric pressure, the time required for initial degassing is shown. An appendix describes a subsidiary water absorption test, made on a sample of phosphorus pentoxide, to show the progressive effect of surface deliquescence and relative vapour pressure. (Author) E. M. Robson, Vacuuln, 11 (I), Jan. 1961, 10-15. t6 : 3 0 : 3 8 : 4 7 166. The creation and maintenance of clean liquid metal surfaces. E. I. Fazekas, Vacuum, 11 (1), Jan. 1961, 38-39. 16 : 21 Comprehensive study of the ion pumping of the noble gases. See Abstr. No. 200. 16 : 22 Sorptlon and desorption of gas in a hot-cathode ionization gauge. See Abstr. No. 203. The sorption of hydrogen by barium getters.
16:47 See Abstr. No. 293.
Degassing and permeation of gases in tube materials. No. 296.
16 : 47 See Abstr. 16:47
Thermal degassing of tube materials. 17.
See Abstr. No. 297.
Thermodynamics
17 : 64 167. Summarized proceedings of a symposium on the generation of temperatures below l°K.--London, December 1959. Great Britain. A one-day symposium on the methods of generating temperatures below I°K was held by the LowTemperature G r o u p of the Physical Society on 11 December, 1959. Six papers of a review nature were read and discussed. Attention focused primarily on the techniques of adiabatic demagnetization and on the use of 3He ; nevertheless some o f the more difficult techniques were reviewed with the more recently discovered properties of 3He. The papers presented are summarized in this report. (Author) Anon., Brit. J. Appl. Phys., 11 (10), Oct. 1960, 449-453. 18.
Gaseous Electronics
18 168. Design and performance of a compact surge generator. Great Britain. A compact surge generator for investigation of a fast, linear, pinched discharge using only moderate energy storage is described. The technique of construction using an