Volume 16, Issue 1, 01 January 1948
Index of content:
16(1948); http://dx.doi.org/10.1063/1.1746645View Description Hide Description
The dielectric constants and loss angles of a series of concentrated aqueous ionic solutions have been measured at wave‐lengths of 10 cm, 3 cm, and 1.25 cm. From these results the values of the static dielectric constant and relaxation time for these solutions have been calculated on the basis of the Debye formula, which appears to hold accurately. All salts show a lowering of the dielectric constant and a shift in the relaxation time of water. It is found that the dielectric constant ε can be represented by a formula , where εω is the dielectric constant of water, c is the concentration in moles per liter, and δ has values between −7 and −15 for various salts in concentrations of up to 2 M.
In Part I the measurements are described and the results discussed in relation to the structure of ionic solutions. In Part II the validity of the Debye‐Sack saturation theory of the dielectric constant and the effects of the fall of dielectric constant on the electrolyticproperties of concentrated solutions are discussed.
16(1948); http://dx.doi.org/10.1063/1.1746646View Description Hide Description
In the usual theory of absolute reaction rates it is assumed that the molecules in the activated complex are in statistical equilibrium with the molecules in the initial state. This assumption is not justified in the case of unimolecular decompositions because the molecules in the initial state must gain the energy of activation by a stepwise process, usually by the transfer of quanta of vibrational energy from one normal mode to another. The size of these energy jumps and their frequency inevitably affect the over‐all reaction rate. The problem is considered in considerable detail for a rough idealized mode. In this case, the actual reaction rate should be smaller by a factor of 0.5 to 0.387 than the value computed from the usual theory of absolute rates. A rigorous development would require further development of the original Ramsperger‐Rice‐Kassel treatment.
16(1948); http://dx.doi.org/10.1063/1.1746648View Description Hide Description
The statistical method of treating the sorption of vapors, begun by Fowler and Guggenheim and extended to multilayer sorption by Cassie and Hill, is further generalized to include variable heats of sorption in different layers. It is shown under what conditions multilayer sorption can lead to a linear isotherm and to various modifications of the BET equation. The treatment is also extended to the case of interaction between sorbed molecules in the same layer.
Rotation‐Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths. I. The Spectrum of Fluoroform (CHF3) from 2.4μ to 0.7μ16(1948); http://dx.doi.org/10.1063/1.1746650View Description Hide Description
The spectrum of fluoroform has been investigated under high resolution (21‐ft. grating) in the photographic infra‐red with an absorbing path of up to 60 meters, obtained by multiple reflection according to the method of J. U. White. In addition, with the same path length the spectrum from 1.2 to 2.4μ was obtained under low resolution with a photoelectric infra‐red spectrometer. A large number of overtone and combination bands, 47 in all, were found. Two parallel bands in the photographic region were well resolved and analyzed, yielding, for the moment of inertia about an axis perpendicular to the symmetry axis,From this value, assuming tetrahedral angles and a C–H distance as in methane, the C–F distance in fluoroform is found to be 1.329A, a value that is appreciably lower than that found in methyl fluoride, 1.380A. A provisional vibrational assignment of all the bands is given.
16(1948); http://dx.doi.org/10.1063/1.1746652View Description Hide Description
The reactions of ethylene oxide with Hg(3 P 1) atoms have been investigated at 25°C at pressures between 10‐ and 600‐mm Hg, and at 200°C and 300°C at 100‐mm Hg. The principal products are H2, CO, CH3CHO and a polymer; smaller amounts of CH4, C2 hydrocarbons and formaldehyde are also formed. The nature of the products and the very small effect of pressure on the reaction are best explained by a mechanism based principally on the formation of the activated ethylene oxide molecule, with a minor portion of the reaction proceeding via a C–H split.
The Use of Tritium in the Determination of the Solubility of Water in Solvents. The Solubility of Water in Benzene16(1948); http://dx.doi.org/10.1063/1.1746654View Description Hide Description
A new method for determination of the solubility of water in hydrocarbons is based on the use of radioactive hydrogen isotope, tritium, as tracer for the dissolved water. This method is applicable to the determination of the solubility of water in compounds in which it is sparingly soluble.
16(1948); http://dx.doi.org/10.1063/1.1746655View Description Hide Description
The author's data on the properties of chromium electro‐deposited from a standard chromic acidelectrolyte are examined in the light of a theory first proposed by Bozorth. It is shown that the data fit well the assumption that the preferred orientation found in these chromium electro‐deposits is the result of a slipping process, analogous to cold‐working, which occurs during deposition when internal contractile stress reaches a certain critical value. It is further shown that the type of orientation found in chromiumdeposits is in accord with the theory and it is stated that (111) orientation is to be expected generally for body‐centered cubic metals electro‐deposited in a state of contractile stress, while (110) or (100) is to be anticipated for face‐centered cubic metals deposited with the same type of stress. The orientations of a number of electro‐deposited metals are shown to be in agreement with this expectation. Certain anomalies in the stress and orientation results for silver,nickel, and aluminumdeposits have also been studied experimentally, and the results explained on the basis of the above theory. In conclusion, the possible mechanism of internal stress formation in electro‐deposits is examined.
16(1948); http://dx.doi.org/10.1063/1.1746657View Description Hide Description
16(1948); http://dx.doi.org/10.1063/1.1746659View Description Hide Description
The infra‐red absorption of gaseous hexafluoroethane between 2 and 25μ has been investigated with prism spectrometers of high resolution. On the basis of normal vibration calculations and the known Raman frequencies it has been possible to interpret all but 3 of the 51 observed absorption maxima. Only combination bands permitted for both the staggered (D3d) and the eclipsed (D3h) model were used in the assignment of bands. Five fundamental frequencies have been determined in addition to the six obtained from the Raman spectrum. No combination band involving the remaining frequency, associated with the torsional oscillation of one CF3 group relative to the other, could be identified. An attempt to determine the moments of inertia of the C2F6 molecule from the envelope of the strongest parallel band gave unsatisfactory results.
16(1948); http://dx.doi.org/10.1063/1.1746661View Description Hide Description
Vibrational potential functions of the quadratic type for CF4 and C2F6, which assume no interaction between the CF3 groups in C2F6 and include only the interaction terms involving bond‐bending with bond‐stretching motions, are used with the observed normal frequencies to evaluate a set of force constants for the molecules. The force constants associated with the CF3 group are used interchangeably between the two molecules. The reproduction of the observed values of the normal frequencies resulting from the use of the force constants is of the order of five percent or better except for three of the frequencies. The omission of terms in the potential function for the interaction of the CF3 groups is largely responsible for the relatively poor reproduction of the type Eu frequencies of C2F6. Additional interaction terms, e.g., between bond‐bending motions, are necessary for the improvement of the agreement in the case of the type F2 frequencies of CF4.
16(1948); http://dx.doi.org/10.1063/1.1746662View Description Hide Description
The energy matrix of the rigid asymmetric rotor, evaluated in terms of symmetric rotor wave functions, has been examined under conditions where J is increased indefinitely. Asymptotically, the energy matrix assumes a form that is very much like the matrix that may be obtained from the characteristic value problem of Mathieu's differential equation. The characteristic values of Mathieu's equation serve as the basis for a good approximation to the energy values of those asymmetric rotor levels which, for a given, large value of J, correspond to a small value of K in the limiting symmetric cases. The differences which exist between the two matrices are accounted for by a perturbation technique which permits an accurate determination of the energy values.
When the characteristic values of Mathieu's equation lead to a successful approximation to the energy values of the asymmetric rotor, an estimate may be made of the asymmetric rotor wave functions.