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319. The mechanism of chemisorption : carbon monoxide and carbon dioxide on nickel
188
Classified Abstracts 3 12-3 19
16 312. Adsorption isotherms of nitrogen, benzene and n-hexane and the heats of adsorption of benzene and n-hexane on graphitized carbon blacks. II. Adsorption on graphitized channel blacks. United States. The adsorption isotherms of nitrogen at - 195”, n-hexane at 20”, and the differential heats of adsorption of n-hexane on graphitized channel black have been measured. The shape of the adsorption isotherms and the heats and entropies of adsorption on graphitized carbon blacks are dependent on the dispersion, particle packing, and mosaic character of the surface. When passing from graphitized thermal blacks to graphitized channel blacks, the adsorption isotherms of both nitrogen and n-hexane change from concave to convex in the initial region. Heats of adsorption of helium (measured by other authors) are sensitive indicators of surface inhomogeneity of graphite. (Authors) A. A. Isirikyan and A. V. Kiselev, J. Phys. Chem., 66 (2), Feb. 1962, 205-209.
16 313. Adsorption isotherms of nitrogen, benzene and n-hexane and the heats of adsorption of benzene and n-bexane on graphitized III. The thermodynamic characteristics of carbon blacks. adsorption equilibria. United States. From experimental quantities for graphitized thermal carbon blacks we have obtained and compared the isotherms of the absolute magnitudes of adsorption, and differential heats and entropies of adsorption of n-hexane and benzene on the “ basal plate of graphite,” and also the corresponding standard differential quantities of free and total energy, heat and entropy of adsorption and the extremal values of the differential heats and entropies of adsorption. All these properties are determined solely by the nature of the adsorbateadsorbent system and practically are free from the influence of surface inhomogeneity of the solid. During filling of a monolayer, the heat of adsorption of n-hexane increases by 2, and benzene by 0.3 kcal/mole. The latter value is associated with the considerably weaker adsorbate-adsorbate attractions Accordingly, the adsorption isotherm of benzene of benzene. is at first concave, and of hexane, convex to the pressure axes. A description of the adsorption isotherms of benzene, hexane and nitrogen is discussed in terms of various equations. The BET equation is only a first approximation. Equations taking into account adsorbate-adsorbate attractions yield better agreement. A relationship is established between the constants of these eauations and the constant of the BET equation. The adsorption of benzene and n-hexane at 20” and of nitrogen at -195” on the “ basal plane of graphite ” is predominantly (Authors) localized. A. A. Isirikyan and A. V. Kiselev, J. Phys. Chem., 66 (2), Feb. 1962. 210-215.
16 : 30 314. A search for hydrogen-deuterium exchange on clean germanium surfaces. United States. An attempt has been made to measure hydrogendeuterium exchange on (100) surfaces of a germanium crystal cleaned by outgassing in wcuo and by argon ion bombardment. Tests for the reaction also were made on sputtered films. No activity was found for either type of surface. The lower observable limits of the activity were lOIs molecules cm-’ set-1 for the crystal and 5 x 10” molecules cmmZ set-l for the film. It is concluded that the lack of activity cannot be due to contamination of the surface. A comparison is made between this result and other published results for hydrogen-deuterium (Authors) exchange on germanium. D. Shooter and H. E. Farnsworth, Feb. 1962, 222-224.
J. Phys.
Chem., 66 (2),
16 315. Adsorption and dielectric studies of the alumina-ethyl chloride system at 35”. United States. The adsorption isotherm of ethyl chloride on alumina was determined at 35.0”. The shape of this isotherm resembled that classified by S. Brunauer as Type IV. In conjunction with the isotherm determination, dielectric studies were made on the system. The dielectric constant and loss were measured at frequencies between 100 c and 100 kc for various amounts of adsorbed ethyl chloride. The dielectric loss exhibited an increase until monolayer completion ; then it became relatively constant upon further amounts adsorbed. The dielectric constant increased with increasing amount adsorbed. For any given amount adsorbed, both the dielectric constant and loss decreased with increasing frequency. (Author) R. A. Your& J. Phys. Chem., 66 (2), Feb. 1962, 326-328. 16 316. The permeability of niobium to hydrogen. United States. The permeability (P) of niobium to hydrogen was investigated over a range of temperature between 950 to 1065” and pressure levels of 1.1 and 2.0 atm. The resulting permeability was found to obey the relationship cm3Hz(0”, 1 atm) hrm’ p = 2.01 x 10+5208+'40~RT
cmzmm_;Gci,,
D. W. Rudd, D. W. Vose and S. Johnson, 66 (2), Feb. 1962, 351-353.
(Authors) J. Phys. Chem.,
16 317. The chemisorption of nitric oxide by alumina gel at 0’. A. Solbakken and L. H. Reyerson, J. Phys. Chem., 66 (2), Feb. 1962, 365-366. 16 : 37 318. Translational energy accommodation in the nickel-chlorine surface reaction. United States. A method of measuring the transfer of translational energy in gas-surface collisions is described. Mass spectrometric measurements were made of a collimated beam of unreacted chlorine reflected from the nickel surface at surface temperatures between 1100 and 1600°K. By a simple modification- of the mass spectrometer ion source it was possible to measure the flux and density of this beam. The latter equals the flux divided by the average velocity of the beam molecules, and the ratio of the two quantities gives the average beam velocity. The accommodation coefficient of the beam gas on the reflecting surface can be computed from this velocity together with the temperature of the beam before reflection and the surface temperature. Experiments were carried out in a stainless steel vacuum system consisting of three separately pumped chambers connected in series by collimating slits, 0.005 x 0.5 in. Chlorine from an effusion source in the first chamber passes as a collimated beam into the second chamber where it strikes a nickel target mounted with its long axis 45” to the beam A beam of evaporated reaction products and reflected direction. chlorine collimated at right angles to the incident beam passes into the third chamber containing the ion source of a pulsed (Author) beam time-of-flight mass spectrometer. J. D. McKinley,
J. Phys. Chem., 66 (3), March 1962, 554-556. 16
319. The mechanism of chemisorption : carbon monoxide and carbon dioxide on nickel. United States. Magnetization-volume isotherms on nickelsilica have been obtained for carbon monoxide and carbon dioxide by the low frequency a.c. permeameter method. The mode of bonding of carbon monoxide is dependent on nickel particle size and on surface coverage, in qualitative agreement
189
Classified Abstracts 320-327 with the infrared absorption studies by Yates and Garland. The magnetic data suggest linear or bridge bonding at low coverages, depending on nickel particle size, and bridged bonding to nickel atoms already bonded to at least one carbon monoxide molecule at higher coverages. Most of the high-coverage carbon monoxide may be desorbed as such, but the low coverage carbon monoxide may not be desorbed without disproportionation. Carbon dioxide is chemisorbed on nickel. There appear to be rather more than two bonds formed for every molecule adsorbed, but the maximum volume which may be chemisorbed at room temperature is only about one-eighth the volume of hydrogen which may be chemisorbed on the same surface. (Authors) 1. E. Den Besten, P. G. Fox and P. W. Selwood, J Phys. Cheni., 66 (3), March 1962, 450-453. 16 320. Transient species in oxygen take-up by zinc oxide. R. Glemza and R. J. Kokes, J. Phys. Chem., 66 (3), March 1962, 566-568. 16
On physical adsorption. XVIII. Limiting isosteric heats of adsorption of gases on graphitized carbon by the chromatographic method. The heats of adsorption obtained by means of United States. gas-solid chromatography correspond to the limiting values of the isosteric heat of adsorption as the surface concentration tends to zero. The theoretical basis for the comparison of the results obtained by static and dynamic methods is developed. Using as an adsorbent highly graphitized carbon black, for which a quantity of precisely determined adsorption data has been reported, comparisons of the results obtained by the two methods (Authors) show closer agreement than has yet been reported. S. Ross, J. K. Saelens and J. P. Olivier, J. Phys. Chem., 66 (4), April 1962, 696-700. 321.
of a layer of orientated water molecules on to an alumina surface modified by initial chemisorption. The evaluated dielectric constant. E.,. for benzene adsorbed entirelv in the capillary condensed state, on both alumina and silica -gel, compared well with Eliq, the literature value for the normal liquid. In an adsorbed benzene moonolayer, c1 was lower than E[iq on silica gel, but higher (and equal to Golid) on alumina. The former was considered to be due to the interaction of the Ir-electrons in the benzene monolayer with the silica hydroxyl groups. It was assumed that this interaction was absent with alumina, the higher value of l1 observed with the latter being due to closepacking of the benzene molecules on the surface. Dielectric hysteresis was observed for benzene on alumina, but not on silica gel. An explanation has been given in terms of the uneven electron density in the benzene molecule, together with the different polarizing influences of the two adsorbent surfaces. (Author) J. M. Thorp, J. Phys. C/rem., 66, 1962, 1086-1092. 16 325. Field emission from silicon and germanium ; field desorption and surface migration. United States. Field desorption has been used successfully to produce clean germanium patterns in the electron field emission microscope. The field cleaned pattern transforms upon annealing to one very similar to that obtained from silicon cleaned by heating in vacuum. Changes in impurity concentration at the surface during cleaning, heretofore a problem, are avoided by the desorption technique. Surface atom mobility becomes appreciable at 250°C on clean germanium and at 800°C on clean silicon. Field emission current-voltage characteristics for both The results are discussed in the clean Ge and Si are presented. light of existing theory, and the need for a theory including emission from surface states and the valence band is pointed out. (Author) F. G. Allen, J. Phys. C/tern. Solids,
19 (l/2), April 1961, 87.
16 : 52 322. Hydroxyl content in silica gel “ Aerosil.” United States. Changes in the hydroxylic surface of silica gel as a function of temperature are studied by different techniques. From the comparison between infrared data and thermogravimetric determination, a distinction can be clearly made between New chemical methods for constitution and adsorbed water. the determination of surface hydroxyls also are described, using the reaction either with CH,MgI or CH,Li and volumetric measurement of the CH, evolved. The discussion and interpretation of the results collected from physical and chemical methods permit the distinction between adsorbed water, inner (Authors) hydroxyls, and surface hydroxyls.
323. The kinetics of hydrogen atom recombination on Pyrex glass and fused quartz. B. J. Wood and H. Wise, J. Phys. Chem., 66, 1962, 1049-1053.
16 326. Radiation induced chemisorption of oxygen on chromia. Rumania. The effects of nuclear radiation on the chemisorption of oxygen on Cr,O,, Cr@-Al,O, and Cr,O,-SnO, catalysts An iodometric method was used to measure have been studied. the amount of chemisorbed oxygen ; simultaneously the increase in the catalytic activity of the catalyst in the decomposition of H,O, was determined. It was found that the radiation present within a nuclear reactor promotes the chemisorption of oxygen on chromia (either pure or supported on AlzO, or SnO,) at temperatures at which such a chemisorption does not normally occur. The radiochemisorption of oxygen on chromia increases with the degree of dispersion of chromia on Al,O, or SnO, and is accompanied by an increased catalytic activity of this catalyst in the decomposition reaction of H,O,. It seems that the radiochemisorption is largely due to the action of y-rays and fast neutrons on the gas. (Authors) M. Nachman, I. Maxim and T. Braun, J. Phys. Chem. Solids, 20 (3/4), Aug. 1961, 307.
16 324. The dielectric behavior of vapors adsorbed on porous solids. An investigation has been made of the dielectric United States. behaviour (at a frequency of 0.5 MC/S) of water adsorbed on alumina, and of benzene adsorbed on both alumina and silica gel, at 25”. Isosteric heats of sorption, and data relating to pore size distribution, were obtained from the determination of sorption isothermals. For water adsorbed on alumina, the plot of capacitance increment against the amount adsorbed was found to be reversible, for both adsorption and desorption, The absence of dielectric throughout the entire sorption range. hysteresis was considered to be due to strong adsorbate-adsorbate Evidence was obtained for the physical adsorption interaction.
16 327. Diffusion and sorption of water in zeolites-I. Sorption. Great Britain. Equilibrium sorption measurements have been made for D,O and H,O in the crystalline zeolites chabazite, gmelinite and heulandite, at relative coverages greater than 0 = 0.85. The water contents, the shape of the isotherms, the isosteric heats and the partial molar entropies are almost identical for HZ0 in chabazite and gmelinite ; in heulandite isotherms are more rectangular but isosteric heats and partial molar entropies do not differ greatly from those in the other zeolites. Differences in these properties as between sorbed D,O and H,O are small, but heats of sorption are slightly greater for DzO and slightly larger molar amounts of D,O are
J. J. Fripiat and J. Uytterhoeven, 1962, 800-805.
J. Phys.
Chem.,
66 (5), May
16 : 17
Classified Abstracts 3 12-3 19
16 312. Adsorption isotherms of nitrogen, benzene and n-hexane and the heats of adsorption of benzene and n-hexane on graphitized carbon blacks. II. Adsorption on graphitized channel blacks. United States. The adsorption isotherms of nitrogen at - 195”, n-hexane at 20”, and the differential heats of adsorption of n-hexane on graphitized channel black have been measured. The shape of the adsorption isotherms and the heats and entropies of adsorption on graphitized carbon blacks are dependent on the dispersion, particle packing, and mosaic character of the surface. When passing from graphitized thermal blacks to graphitized channel blacks, the adsorption isotherms of both nitrogen and n-hexane change from concave to convex in the initial region. Heats of adsorption of helium (measured by other authors) are sensitive indicators of surface inhomogeneity of graphite. (Authors) A. A. Isirikyan and A. V. Kiselev, J. Phys. Chem., 66 (2), Feb. 1962, 205-209.
16 313. Adsorption isotherms of nitrogen, benzene and n-hexane and the heats of adsorption of benzene and n-bexane on graphitized III. The thermodynamic characteristics of carbon blacks. adsorption equilibria. United States. From experimental quantities for graphitized thermal carbon blacks we have obtained and compared the isotherms of the absolute magnitudes of adsorption, and differential heats and entropies of adsorption of n-hexane and benzene on the “ basal plate of graphite,” and also the corresponding standard differential quantities of free and total energy, heat and entropy of adsorption and the extremal values of the differential heats and entropies of adsorption. All these properties are determined solely by the nature of the adsorbateadsorbent system and practically are free from the influence of surface inhomogeneity of the solid. During filling of a monolayer, the heat of adsorption of n-hexane increases by 2, and benzene by 0.3 kcal/mole. The latter value is associated with the considerably weaker adsorbate-adsorbate attractions Accordingly, the adsorption isotherm of benzene of benzene. is at first concave, and of hexane, convex to the pressure axes. A description of the adsorption isotherms of benzene, hexane and nitrogen is discussed in terms of various equations. The BET equation is only a first approximation. Equations taking into account adsorbate-adsorbate attractions yield better agreement. A relationship is established between the constants of these eauations and the constant of the BET equation. The adsorption of benzene and n-hexane at 20” and of nitrogen at -195” on the “ basal plane of graphite ” is predominantly (Authors) localized. A. A. Isirikyan and A. V. Kiselev, J. Phys. Chem., 66 (2), Feb. 1962. 210-215.
16 : 30 314. A search for hydrogen-deuterium exchange on clean germanium surfaces. United States. An attempt has been made to measure hydrogendeuterium exchange on (100) surfaces of a germanium crystal cleaned by outgassing in wcuo and by argon ion bombardment. Tests for the reaction also were made on sputtered films. No activity was found for either type of surface. The lower observable limits of the activity were lOIs molecules cm-’ set-1 for the crystal and 5 x 10” molecules cmmZ set-l for the film. It is concluded that the lack of activity cannot be due to contamination of the surface. A comparison is made between this result and other published results for hydrogen-deuterium (Authors) exchange on germanium. D. Shooter and H. E. Farnsworth, Feb. 1962, 222-224.
J. Phys.
Chem., 66 (2),
16 315. Adsorption and dielectric studies of the alumina-ethyl chloride system at 35”. United States. The adsorption isotherm of ethyl chloride on alumina was determined at 35.0”. The shape of this isotherm resembled that classified by S. Brunauer as Type IV. In conjunction with the isotherm determination, dielectric studies were made on the system. The dielectric constant and loss were measured at frequencies between 100 c and 100 kc for various amounts of adsorbed ethyl chloride. The dielectric loss exhibited an increase until monolayer completion ; then it became relatively constant upon further amounts adsorbed. The dielectric constant increased with increasing amount adsorbed. For any given amount adsorbed, both the dielectric constant and loss decreased with increasing frequency. (Author) R. A. Your& J. Phys. Chem., 66 (2), Feb. 1962, 326-328. 16 316. The permeability of niobium to hydrogen. United States. The permeability (P) of niobium to hydrogen was investigated over a range of temperature between 950 to 1065” and pressure levels of 1.1 and 2.0 atm. The resulting permeability was found to obey the relationship cm3Hz(0”, 1 atm) hrm’ p = 2.01 x 10+5208+'40~RT
cmzmm_;Gci,,
D. W. Rudd, D. W. Vose and S. Johnson, 66 (2), Feb. 1962, 351-353.
(Authors) J. Phys. Chem.,
16 317. The chemisorption of nitric oxide by alumina gel at 0’. A. Solbakken and L. H. Reyerson, J. Phys. Chem., 66 (2), Feb. 1962, 365-366. 16 : 37 318. Translational energy accommodation in the nickel-chlorine surface reaction. United States. A method of measuring the transfer of translational energy in gas-surface collisions is described. Mass spectrometric measurements were made of a collimated beam of unreacted chlorine reflected from the nickel surface at surface temperatures between 1100 and 1600°K. By a simple modification- of the mass spectrometer ion source it was possible to measure the flux and density of this beam. The latter equals the flux divided by the average velocity of the beam molecules, and the ratio of the two quantities gives the average beam velocity. The accommodation coefficient of the beam gas on the reflecting surface can be computed from this velocity together with the temperature of the beam before reflection and the surface temperature. Experiments were carried out in a stainless steel vacuum system consisting of three separately pumped chambers connected in series by collimating slits, 0.005 x 0.5 in. Chlorine from an effusion source in the first chamber passes as a collimated beam into the second chamber where it strikes a nickel target mounted with its long axis 45” to the beam A beam of evaporated reaction products and reflected direction. chlorine collimated at right angles to the incident beam passes into the third chamber containing the ion source of a pulsed (Author) beam time-of-flight mass spectrometer. J. D. McKinley,
J. Phys. Chem., 66 (3), March 1962, 554-556. 16
319. The mechanism of chemisorption : carbon monoxide and carbon dioxide on nickel. United States. Magnetization-volume isotherms on nickelsilica have been obtained for carbon monoxide and carbon dioxide by the low frequency a.c. permeameter method. The mode of bonding of carbon monoxide is dependent on nickel particle size and on surface coverage, in qualitative agreement
189
Classified Abstracts 320-327 with the infrared absorption studies by Yates and Garland. The magnetic data suggest linear or bridge bonding at low coverages, depending on nickel particle size, and bridged bonding to nickel atoms already bonded to at least one carbon monoxide molecule at higher coverages. Most of the high-coverage carbon monoxide may be desorbed as such, but the low coverage carbon monoxide may not be desorbed without disproportionation. Carbon dioxide is chemisorbed on nickel. There appear to be rather more than two bonds formed for every molecule adsorbed, but the maximum volume which may be chemisorbed at room temperature is only about one-eighth the volume of hydrogen which may be chemisorbed on the same surface. (Authors) 1. E. Den Besten, P. G. Fox and P. W. Selwood, J Phys. Cheni., 66 (3), March 1962, 450-453. 16 320. Transient species in oxygen take-up by zinc oxide. R. Glemza and R. J. Kokes, J. Phys. Chem., 66 (3), March 1962, 566-568. 16
On physical adsorption. XVIII. Limiting isosteric heats of adsorption of gases on graphitized carbon by the chromatographic method. The heats of adsorption obtained by means of United States. gas-solid chromatography correspond to the limiting values of the isosteric heat of adsorption as the surface concentration tends to zero. The theoretical basis for the comparison of the results obtained by static and dynamic methods is developed. Using as an adsorbent highly graphitized carbon black, for which a quantity of precisely determined adsorption data has been reported, comparisons of the results obtained by the two methods (Authors) show closer agreement than has yet been reported. S. Ross, J. K. Saelens and J. P. Olivier, J. Phys. Chem., 66 (4), April 1962, 696-700. 321.
of a layer of orientated water molecules on to an alumina surface modified by initial chemisorption. The evaluated dielectric constant. E.,. for benzene adsorbed entirelv in the capillary condensed state, on both alumina and silica -gel, compared well with Eliq, the literature value for the normal liquid. In an adsorbed benzene moonolayer, c1 was lower than E[iq on silica gel, but higher (and equal to Golid) on alumina. The former was considered to be due to the interaction of the Ir-electrons in the benzene monolayer with the silica hydroxyl groups. It was assumed that this interaction was absent with alumina, the higher value of l1 observed with the latter being due to closepacking of the benzene molecules on the surface. Dielectric hysteresis was observed for benzene on alumina, but not on silica gel. An explanation has been given in terms of the uneven electron density in the benzene molecule, together with the different polarizing influences of the two adsorbent surfaces. (Author) J. M. Thorp, J. Phys. C/rem., 66, 1962, 1086-1092. 16 325. Field emission from silicon and germanium ; field desorption and surface migration. United States. Field desorption has been used successfully to produce clean germanium patterns in the electron field emission microscope. The field cleaned pattern transforms upon annealing to one very similar to that obtained from silicon cleaned by heating in vacuum. Changes in impurity concentration at the surface during cleaning, heretofore a problem, are avoided by the desorption technique. Surface atom mobility becomes appreciable at 250°C on clean germanium and at 800°C on clean silicon. Field emission current-voltage characteristics for both The results are discussed in the clean Ge and Si are presented. light of existing theory, and the need for a theory including emission from surface states and the valence band is pointed out. (Author) F. G. Allen, J. Phys. C/tern. Solids,
19 (l/2), April 1961, 87.
16 : 52 322. Hydroxyl content in silica gel “ Aerosil.” United States. Changes in the hydroxylic surface of silica gel as a function of temperature are studied by different techniques. From the comparison between infrared data and thermogravimetric determination, a distinction can be clearly made between New chemical methods for constitution and adsorbed water. the determination of surface hydroxyls also are described, using the reaction either with CH,MgI or CH,Li and volumetric measurement of the CH, evolved. The discussion and interpretation of the results collected from physical and chemical methods permit the distinction between adsorbed water, inner (Authors) hydroxyls, and surface hydroxyls.
323. The kinetics of hydrogen atom recombination on Pyrex glass and fused quartz. B. J. Wood and H. Wise, J. Phys. Chem., 66, 1962, 1049-1053.
16 326. Radiation induced chemisorption of oxygen on chromia. Rumania. The effects of nuclear radiation on the chemisorption of oxygen on Cr,O,, Cr@-Al,O, and Cr,O,-SnO, catalysts An iodometric method was used to measure have been studied. the amount of chemisorbed oxygen ; simultaneously the increase in the catalytic activity of the catalyst in the decomposition of H,O, was determined. It was found that the radiation present within a nuclear reactor promotes the chemisorption of oxygen on chromia (either pure or supported on AlzO, or SnO,) at temperatures at which such a chemisorption does not normally occur. The radiochemisorption of oxygen on chromia increases with the degree of dispersion of chromia on Al,O, or SnO, and is accompanied by an increased catalytic activity of this catalyst in the decomposition reaction of H,O,. It seems that the radiochemisorption is largely due to the action of y-rays and fast neutrons on the gas. (Authors) M. Nachman, I. Maxim and T. Braun, J. Phys. Chem. Solids, 20 (3/4), Aug. 1961, 307.
16 324. The dielectric behavior of vapors adsorbed on porous solids. An investigation has been made of the dielectric United States. behaviour (at a frequency of 0.5 MC/S) of water adsorbed on alumina, and of benzene adsorbed on both alumina and silica gel, at 25”. Isosteric heats of sorption, and data relating to pore size distribution, were obtained from the determination of sorption isothermals. For water adsorbed on alumina, the plot of capacitance increment against the amount adsorbed was found to be reversible, for both adsorption and desorption, The absence of dielectric throughout the entire sorption range. hysteresis was considered to be due to strong adsorbate-adsorbate Evidence was obtained for the physical adsorption interaction.
16 327. Diffusion and sorption of water in zeolites-I. Sorption. Great Britain. Equilibrium sorption measurements have been made for D,O and H,O in the crystalline zeolites chabazite, gmelinite and heulandite, at relative coverages greater than 0 = 0.85. The water contents, the shape of the isotherms, the isosteric heats and the partial molar entropies are almost identical for HZ0 in chabazite and gmelinite ; in heulandite isotherms are more rectangular but isosteric heats and partial molar entropies do not differ greatly from those in the other zeolites. Differences in these properties as between sorbed D,O and H,O are small, but heats of sorption are slightly greater for DzO and slightly larger molar amounts of D,O are
J. J. Fripiat and J. Uytterhoeven, 1962, 800-805.
J. Phys.
Chem.,
66 (5), May
16 : 17