Index of content:
Volume 20, Issue 12, 01 December 1952
20(1952); http://dx.doi.org/10.1063/1.1700322View Description Hide Description
The thermodynamics of irreversible processes is developed for a system placed in a centrifugal field and consisting of a number of components, some of which carry electrical charges. It is found that an Onsager reciprocal relation connects the sedimentation potential with a quantity which we call barycentric electrophoresis (i.e., the quotient of the total mass flow and the electrical field at zero centrifugal field). The latter quantity turns out to be ordinary electrophoresis in a colloid (i.e., in a system of one neutral and a number of charged components, one of which consists of colloidal particles) under certain limiting, but frequently realized, circumstances. If conduction relaxation exists, it appears in both connected phenomena described here.
The Raman Spectrum, Structure, Force Constants, and Thermodynamic Properties of Bromine Pentafluoride20(1952); http://dx.doi.org/10.1063/1.1700323View Description Hide Description
Using a Raman tube made of the plastic polychlorotrifluoroethylene, the Raman spectrum of bromine pentafluoride has been obtained. A method has been developed for making polarization measurements when Raman tubes constructed of this plastic are used. The spectrum of bromine pentafluoride has been correlated with a tetragonal pyramid configuration with symmetry C4v. Force constants were calculated using the Wilson FG Matrix method. The thermodynamic functions for BrF5 were calculated for temperatures ranging from 313.7°K to 1500°K, using the rigid rotator, harmonic oscillator approximation.
20(1952); http://dx.doi.org/10.1063/1.1700324View Description Hide Description
The viscosity, density, and surface tension of liquid fluorine and their dependence on temperature have been measured. The change in viscosity with temperature indicates that fluorine behaves as a normal liquid in the region studied. The results of the measurement of the density confirm a new much larger value for this property than previously accepted. Measurements of the surface tension given in this paper are in substantial agreement with values reported earlier in the literature if these early values are adjusted by means of the density determinations made by the authors.
20(1952); http://dx.doi.org/10.1063/1.1700325View Description Hide Description
The spectra of methyl iodide were determined in the range 2 to 15 microns for the vapor at 25°C, the liquid at 25° and −50°C, and the solid at −78°, −196°, and −269°C. Differences were observed in frequencies, intensities, and band shapes resulting from changes in state and temperature. There is band narrowing with reduction in temperature even in the solid. At the lowest temperatures, band splitting could be resolved in the degenerate bands as well as in the 1252 cm−1 nondegenerate fundamental. Several additional assignments are offered.
20(1952); http://dx.doi.org/10.1063/1.1700326View Description Hide Description
The rate laws for diffusion controlled chromatographic ion‐exchange are discussed in connection with their application to deep beds of exchanger. Results of experiments with a carboxylic acid resin indicate that solid diffusion is the rate‐determining step under the conditions of the experiments. An estimate is found for the value of the diffusion constant. The information is applied to the computation, from a chromatographic elution, of a cesium‐sodium isotherm for the exchanger. This result is compared with a direct determination of the isotherm.
20(1952); http://dx.doi.org/10.1063/1.1700327View Description Hide Description
Studies of the near ultraviolet absorption spectra of α‐, β‐, and γ‐picoline vapor have been made in low and medium dispersion. Conclusive evidence is found for two electronic transitions in the vicinities of 35500 and 38500 cm−1. The former transition is interpreted as an allowed A 1—B 2 transition resulting from the excitation of an sp 2 nonbonding electron of the nitrogen atom into the first unfilled π‐orbital of the ring. The latter transition is considered an allowed A 1—B 1 transition resulting from the excitation of a π ring electron. The A 1—B 2 system exhibits narrow headless bands similar to the first absorption bands in pyridine. It is of weak intensity comparable to that of the forbidden A 1g —B 2u transition in benzene. The A 1—B 1 system, which is much stronger, consists of broad diffuse bands. There is evidence that this system may be overlapped by another transition in β‐picoline.
An Analytical Method for the Approximate Determination of the Eigenfunctions and Energies of Electrons in Atoms20(1952); http://dx.doi.org/10.1063/1.1700328View Description Hide Description
The first part of this paper shows that the reduced effective nuclear chargesZp/Z, determined without exchange by the ``self‐consistent field'' method, can be approximated by a universal function, if the distance from the nucleus is measured in the unit of length μ=0.8853a 0/Z ⅓, which changes from atom to atom. This universal function can also be approximated by a simple analytical expression. One of the possible applications of the above result is to use it to determine good starting potentials for calculations to be carried out by the ``self‐consistent field'' method. The universal effective nuclear charge, especially in its analytical form, also allows the determination of important atomic constants for each element of the periodic system. The second part of the paper solves the one‐electron Schrödinger equation by Rasetti's method, developing it to determine analytically the eigenfunctions and energies of electrons in the deepest s, p, d, and f energy states. The x‐ray terms obtained by this method and the experimental ones are in good agreement with each other and with those calculated by the ``self‐consistent field'' method.
20(1952); http://dx.doi.org/10.1063/1.1700329View Description Hide Description
The free‐electron model for conjugated molecules is extended to a discussion of molecular complexes formed from conjugated molecules (π‐molecular complexes). The forces responsible for complex formation are identified as ``π‐delocalization'' forces. The stability and the absorption spectra of these complexes are discussed for a linear, one‐dimensional model. The influence of hydrostatic pressure on the position of the complex absorptionspectrum is considered, and some predictions are made regarding the resulting shifts of various absorption peaks. The free‐electron model is compared with the models suggested by other workers, and good agreement is found in regard to the factors governing the formation and spectra of molecular complexes.
20(1952); http://dx.doi.org/10.1063/1.1700330View Description Hide Description
The emission and absorption of radiant energy in a nonhomogeneous flame is discussed. Multiple scattering is neglected and the solution of the basic one‐dimensional equation of transfer is obtained in series form. The series is rapidly convergent and a first term approximation yields a simple formula for a flame source having a plane of symmetry which gives satisfactory agreement with experimentally determined nonlinear spectrochemical calibration curves.
20(1952); http://dx.doi.org/10.1063/1.1700331View Description Hide Description
The infrared spectrum of ClO2has been reinvestigated from 2–40μ. Several new bands have been discovered, among them the bending frequency ν2 at 445 cm−1. This band has the doublet character required if the molecular model is to be an obtuse triangle in accord with electron diffractionexperiments. Three bands, ν1, ν2, and 2ν1, were resolved with prism and grating methods, and the spacing of the Q lines was found to be about 3.0 cm−1. An A″—B″ value of 1.413 cm−1 was obtained from the analysis of ν2, and this value also is in excellent agreement with the electron diffraction measurements. Moments of inertia computed from the r(Cl–O) = 1.49A and 2α (apex angle) = 118.5° obtained from a combination of electron diffraction and infrared data are IA =16.09×10−40 g cm2, IB =86.35×10−40 g cm2, and IC =102.43×10−40 g cm2. A band which cannot be ascribed to an impurity was found at 290 cm−1. The possibility that this band results from polymerization of ClO2 is suggested.
20(1952); http://dx.doi.org/10.1063/1.1700332View Description Hide Description
A porcelain‐lined absorption cell of the Pfund type is described, in which 3 meters of gas may be heated to temperatures above 500°C. The spectra of air at atmospheric pressure containing varying amounts of H2O and CO2 have been obtained in this cell between 2.4–15μ with a prismspectrometer, and between 13–25μ with a grating spectrometer giving spectral resolution of about 2 cm−1. A number of new lines in the pure rotation spectrum and the ν2vibration of H2O, originating from levels of high energy, have been observed and classified. New CO2 bands in the regions of 11–20μ and 5μ have also been observed, originating from levels as high as 5ν2, and leading to improved values of higher‐quanta levels of ν2 and vibrational constants for this molecule.
20(1952); http://dx.doi.org/10.1063/1.1700333View Description Hide Description
Some recent measurements by Sette of ultrasonic absorption in liquid halogenated hydrocarbons have indicated strong structural differences upon which, it was hoped, further light would be given by a study of some of these compounds in the vapor state. Ultrasonic velocity and absorption in cis‐ and trans‐dichloroethylene have been measured at 34.7°C, at frequencies of 0.425, 1.985, and 2.982 Mc sec−1 and at pressures from 12 to 250 mm Hg, giving a range of f/p of 1.27 to 125 Mc/sec atmos. The results show that energy equilibrium in the molecule is more quickly attained in the trans‐ than in the cis‐form. Without consideration of departure from the ideal gas law, the results may be explained by the assumption of two regions of f/p in which relaxation occurs, one relaxation frequency of 3.5 Mc/sec atmos being common to both, there being also one of 30 for the cis and 90 for the trans. The molecular absorption per wavelength computed from dispersion data are in good qualitative agreement with those measured. The values of Cv/R for both forms fall from 7.5 at one Mc/sec atmos to about 3.5 at 100 Mc/sec atmos. The results indicate the pre‐eminent importance of short‐range forces in determining the energy transfer by collisions.
The Near Ultraviolet Absorption Spectra of 1,4 Bis‐(Trifluoromethyl)Benzene and 1,3,5 Tris‐(Trifluoromethyl)Benzene20(1952); http://dx.doi.org/10.1063/1.1700334View Description Hide Description
The vapor absorption spectra of 1,4 C6H4(CF3)2 and 1,3,5 C6H3(CF3)3 have been obtained with a Bausch and Lomb Littrow spectrograph. Corresponding solution spectra were obtained with a Beckman DU spectrophotometer. Oscillator strengths f were found to be 12.0×10−3 and 2.1×10−3 for the para di‐ and tri‐substituted compounds, respectively. Both of the vapor spectra are diffuse with the bands of the 1,3,5 compound showing extreme diffuseness. The 0,0 band of the 1,4 bis‐(trifluoromethyl)benzene is located at 37460 cm−1. Progressions and combinations involving the upper state frequencies of 210, 770, and 1020 cm−1 are observed. The 210 and 1020 values are correlated with the observed ground state values of 240 and 1070 cm−1, and these are associated with totally symmetric vibrations. The 1,3,5 tris‐(trifluoromethyl)benzene spectrum is interpreted as a ``forbidden'' one and the bands at 38670 and 38070 cm−1 are assigned as 0,1 and 1,0 bands, respectively. Rough calculations show the 0,0 band to be shifted about 300 cm−1 toward the violet relative to the benzene spectrum.
20(1952); http://dx.doi.org/10.1063/1.1700335View Description Hide Description
The well‐known paucity of experimentally observed reflections obtained from x‐ray studies of proteinsingle crystals, and their tendency to occur in well‐marked spherical shells of reciprocal space, are examined quantitatively.
It is shown that, in the case of one protein for which data is available, a simple model with no assumed internal structure gives adequate agreement with experiment.
The addition of simple detail, such as nearest neighbor minimum approach distances, leads to further relations which could be used to produce improved agreement if required.
Application of Eller's Optical Machine to the Determination of the Molecular Structure of Gases by Electron Diffraction. II. Nonrigid Molecules20(1952); http://dx.doi.org/10.1063/1.1700336View Description Hide Description
In this work we shall demonstrate the possibility of applying Eller's optical machine, as an auxiliary method of making calculations, to the study of the determination of the structure of gaseous molecules (nonrigid molecules) by means of the diffraction of electrons. The particular case of the CF3–C≡CH will be used as an illustration.
20(1952); http://dx.doi.org/10.1063/1.1700337View Description Hide Description
Polarized infrared studies in the region 615 to 645 cm−1 have been made using dilute solid solutions of naphthalene‐d 8 in naphthalene. The ab plane at normal incidence was studied with light polarized either parallel or perpendicular to the b axis. The mole fraction of C10D8 was varied from 0.10 to 0.30. The dichroic splitting of the 632‐cm−1 band observed in pure C10D8 decreases with concentration. This is the splitting predicted in the factor group analysis and is attributed to intermolecular coupling. This is a further indication that the magnitude of this splitting in molecular crystals such as C10H8 is only a few cm−1, and that the ``oriented gas'' model is applicable. Using this model, the 632‐cm−1 band of C10D8 is assigned as a single fundamental of the B 1u or B 3u class.
20(1952); http://dx.doi.org/10.1063/1.1700338View Description Hide Description
The infrared absorptionspectrum of gaseous CF2:CF–CF3 has been obtained in the region from 2 to 38μ, with the aid of LiF, NaCl, KBr, and KRS‐5 prisms. The Raman spectrum of both the gaseous and the liquid phase has been photographed with a three‐prism glass spectrograph of linear dispersion 15 A/mm at 4358A, and depolarization ratios have been measured for the stronger bands. A complete assignment of fundamental vibrational frequencies is given, although four of the twenty‐one fundamentals must be regarded as uncertain. The spectra are interpreted in detail.
20(1952); http://dx.doi.org/10.1063/1.1700339View Description Hide Description
H2S and D2S were irradiated in a flash photolysis apparatus, and the absorption spectra of the products were photographed within 1 millisecond of the photolysis flash using the second order of a 21 ft gratingspectrograph. The (0,0) and (1,0) bands of SH and SD were observed and analyzed. The following molecular constants for SH were obtained: 2Σ+ state: Be ′=8.5381 cm−1, α e ′=0.5091 cm−1, re ′=1.4215A, ν00=30,662.42 cm−1, ΔG ½′=1784.63 cm−1, γ0=0.313 cm−1. 2Π state: B 0″=9.4611 cm−1, r 0″=1.3503A, A=−376.96 cm−1. The rotational lines of the (1,0) SH band were observed to be diffuse, indicating a predissociation in the first vibrational level of the 2Σ+ state. This establishes an upper limit of 92.7 kcal and a lower limit of 66.3 kcal for the ground statedissociation energy of SH.
20(1952); http://dx.doi.org/10.1063/1.1700340View Description Hide Description
Raman displacements and quantitative depolarization factors, and wave numbers for the infrared bands in the KBr region have been obtained for dimethyldiacetylene in CCl4 and benzene solutions. Since the results of the present work are inconsistent with some of the previous assignments, these have been changed.
In particular, the line at 475 cm−1, which was previously considered an A 1‐type fundamental vibration, is now proved to be depolarized and is assigned as an Ē‐type fundamental. Consistently with this change, the assignment of the 644 cm−1 line of diacetylene as a bending mode is considered. The previous assignments of both of these lines were the cause of the conflicting data existing in the literature between the bond length and the stretching potential constant of the central bond in the structure –C≡C–C≡C–.
20(1952); http://dx.doi.org/10.1063/1.1700341View Description Hide Description
Calculations are carried out to determine the relation between the dielectric constant of solutions of large charged particles and the charge distribution on the particles. It is shown that if the hydrodynamic forces cause the particles to rotate about a point fixed in each particle, the dielectric constant is determined by the dipole moment about this point.