Volume 22, Issue 3, 01 March 1954

The Velocity of Sound in Water as a Function of Temperature and Pressure
View Description Hide DescriptionThe velocity of sound in water has been measured by an ultrasonicecho technique in the temperature range from — 12°C to 129°C under hydrostaticpressures varying up to 9600 kg/cm^{2}. Even at the highest pressures the temperature dependence of the velocity of sound is found to be abnormal. In contradiction to certain previous results, the temperature at which the velocity of sound is a maximum is found to increase with increasing pressure. The behavior of the sound velocity is discussed in the light of recent theories concerning the structure of water. The internal consistency of the data with existing pressure standards is also analyzed.

The Thermal Conductivity of Organic Vapors. The Relationship between Thermal Conductivity and Viscosity, and the Significance of the Eucken Factor
View Description Hide DescriptionThe thermal conductivities of thirty‐one polar and nonpolar organic vapors have been determined at pressures up to one atmosphere, over a temperature range from 40 to 160°C. The relation between thermal conductivity and viscosity is discussed in terms of the expression:where, following a suggestion by Eucken, the ratio f is divided into separate components f _{trans} and f _{int}, corresponding to the different rates of transfer of translational and ``internal'' (vibrational and rotational) energies.
Experimental values of f are not in accord with Eucken's original assumption that f _{int}=1. For nonpolar vapors f _{int} increases towards a high‐temperature limit which is close to the theoretical value of 1.3. For polar vapors f _{trans} appears to be less than the theoretical value of 2.5, the decrease depending on the polar character of the molecule. These results are discussed with reference to energy exchanges occurring during collisions between complex molecules.

Electronic Structure of the Amylose‐Iodine Complex
View Description Hide DescriptionThe electronic structure of the amylose‐iodine complex is studied on a different basis from that of the previous Stein‐Rundle theory. First, the electron transfer from amylose oxygen to the iodine molecule is discussed from the viewpoint of Mulliken's intermolecular charge‐transferspectra. Then it is shown that the consideration of electronic interaction between neighboring iodine molecule ions and bond formation between oxygen and iodine gives a reasonable interpretation of bond number and absorption spectra. Last, the quantitative discussion of absorption spectra is performed by the application of the free‐electron model to the system (I _{4} ^{—}) which we consider to be the elemental unit in the polyiodine chain. The agreement between predicted and observed results is satisfactory if one considers the extreme simplification of the model.

Statistical Thermodynamics of Associated Solutions
View Description Hide DescriptionThermodynamic data for the solutions chloroform+benzene, acetone+chloroform, ethanol+chloroform, ethanol+acetone, and ethanol+ether are discussed in the light of a model for associated solutions which has been described previously. The theory in its original form, previously found satisfactory for solutions of alcohols in nonpolar solvents, proves satisfactory for the first two of these systems. To interpret the data for the remaining more complicated systems it is necessary to generalize the model to allow for interaction free energies which depend on temperature (presumably because of changes in vibration frequencies). The necessary generalization of the theory is described, and a consistent set of interactions for the ethanol systems is derived. The generalized theory should apply, with the limitations inherent in lattice theories, to most nonaqueous associated solutions.

Relation between Bond Length and Stretching Frequency for the Carbonyl Group
View Description Hide DescriptionA plot is shown of bond length vs stretching frequency of the carbonyl group in a series of compounds containing this group. For bond lengths ranging from 1.13 to 1.31A, the average distance of the points from a smooth curve is 0.013A.

Critical Phenomena in the Cyclohexane‐Aniline System
View Description Hide DescriptionMeasurements have been made on the transition temperatures between one‐phase and two‐phase conditions in the cyclohexane‐aniline system and on the densities of the coexisting phases, using an improved temperature control. The region of extreme cloudiness or wet fog, where the meniscus, if present, cannot be seen, and where density measurements are difficult because the density float cannot be seen, was investigated by means of a technique suggested by Zimm. In this procedure the temperature was raised, without stirring, to clear the wet fog without removing any density gradients which might have formed. The previous results of Rowden and Rice and Atack and Rice have been substantiated, and it is concluded with stronger evidence that there is an appreciable range of critical concentrations over which the transition temperature is constant.

Magnetic Susceptibilities of Np^{+6}, Np^{+5}, and Np^{+4}
View Description Hide DescriptionThe magnetic susceptibilities of NaNpO_{2}(CH_{3}COO)_{2}, NpO_{2}C_{2}O_{4}H·H_{2}O, and KNpF_{5} have been measured from 14°K to 320°K. The magnetic susceptibilities of the ions Np^{+6}, Np^{+5}, and Np^{+4} have been compared with those calculated for ions in electronic states of f‐electron configurations in the presence of electric fields of specific forms and with various amounts of spin‐orbit coupling.

Some Ions of High Kinetic Energy in Mass Spectra of Polyatomic Molecules
View Description Hide DescriptionWhen the lighter‐fragment ions of hydrocarbons and hydrocarbon derivatives are recorded with low‐ion accelerating voltages, one observes satellite peaks on the high‐mass side of the main peaks that come from ions with a fairly homogeneous high kinetic energy. Observations of the satellite peaks of CH_{3} ^{+} ions in mass spectra of 13 hydrocarbons and CH_{3}CF_{3}, are reported. The kinetic energies range from 1.5 to 3.4 ev and the relative intensities have a wide range of values but are less than the main peak except in benzene. The appearance potential of the satellite peak is roughly 30 volts in most cases while the main peak is observed above 20 volts. These high‐energy ions are ascribed to doubly charged molecule ions that dissociate into two singly charged fragments. The kinetic energy of the pair of fragment ions is in most cases nearly equal to the Coulomb energy of two ions at a distance equal to the greatest distance between valence electrons in the molecule.

Markoff Random Processes and the Statistical Mechanics of Time‐Dependent Phenomena. II. Irreversible Processes in Fluids
View Description Hide DescriptionThe procedures developed in a previous paper of the same main title are applied to the specific case of irreversible processes in fluids. The gross variables are chosen to be a finite number of the plane‐wave expansion coefficients of the local particle, momentum and energy densities. As an example, the gross variables describing the local particle density arewhere p _{ i } and x _{ i } are the momentum and position of the ith molecule and N the total number. k runs over a finite number of values which are all small compared to the reciprocal mean distance between molecules. The phenomenonological equations are derived and expressions are given for the viscosity,diffusion, and heat conductivity in terms the autocorrelation coefficients of certain phase functions. These expressions are supposed to be valid for both liquids and gases. They are shown to coincide with the Chapman‐Enskog expressions for dilute gases.

Theory of Ignition Considered as a Thermal Reaction
View Description Hide DescriptionThe history of a family of exothermally reactive solids is studied theoretically with the help of analytical and numerical calculations. The different members of this family of nonisothermal solids are obtained, by changing scales and values of parameters, from the basic model which describes a zero‐order reaction of a semi‐infinite slab of material subjected at its surface to heat transfer from a gas.
For low initial temperatures of the solid, the heat transfer rate determines the ignition time while for high initial temperatures, this heating parameter is less important than the initial temperature, which controls the adiabatic ignition time. For the model used, the ignition time is generally quite sensitive to the duration of the external heating. Within the solid, it is found that the inner boundary of the region in which the chemical heat production is negligible moves inward along a diffusional type of path x ∝ t ^{½} but that the point of maximum temperature, which develops after interruption of the external heating, follows a much different path. An analytical, approximate method of estimating minimum ignition time was tested by making comparison with numerical integrations and is probably accurate to 25 percent in the ignition time.
The computational side of the theory presented here may be regarded as essentially complete for practical purposes until greater accuracy and detail are required by more critical applications than are now in prospect. Meaningful utilization of the computations in practical applications will not however be possible until reliable measurements have been made of certain of the parameters for the solid—namely, activation energy, frequency factor and thermal conductivity—and for the external heating— namely, gas temperature and heat transfer coefficient.
In the course of the computations, many mathematical questions arose which are fundamental to the investigation of this and more realistic models of ignition but which remain to be answered.

The Infrared and Raman Spectra of Carbon Suboxide
View Description Hide DescriptionThe infrared spectrum of C_{3}O_{2} has been studied in the vapor phase from 2.2 to 20μ with a Perkin‐Elmer double‐pass spectrometer, and the Raman spectrum has been photographed in the liquid phase. A comparison of the Raman with the infrared spectrum shows definitely that the molecule has a center of symmetry as is required for the linear structure commonly assumed. However, the infrared spectrum cannot be explained on the assumption of a linear model; the envelopes of the principal absorption bands as well as those of the weaker combination bands have the wrong shape. It appears rather that the oxygen atoms are bent out of line with the carbons in a plane zig‐zag configuration. From the rotational structure of one of the combination bands the O–C–C angle is computed to be approximately 158°.

The Lattice Constants of the Alkali Borohydrides and the Low‐Temperature Phase of Sodium Borohydride
View Description Hide DescriptionThe lattice constants of sodium,potassium,rubidium, and cesium borohydrides have been measured at 25.0°C as 6.1635±0.0005, 6.7272±0.0005, 7.029±0.001, and 7.419±0.001A, respectively. All four crystals are face‐centered cubic and have the sodium chloride structure. Below the transition point (—83°C) sodium borohydride becomes tetragonal with lattice constants of a=4.354±0.005 and c=5.907±0.005A at —195°C.

Diffusion in CO_{2}–CH_{4} Mixtures to 225 Atmospheres Pressure
View Description Hide DescriptionDiffusion coefficients have been measured in two mixtures of CO_{2} and CH_{4}. (1) 50 mole percent CO_{2}—50 percent CH_{4}; (2) 75 mole percent CO_{2}—25 mole percent CH_{4}. C^{14} tagged CO_{2} was used, so that no gradient in chemical composition was necessary. For the first mixture the results agreed with Enskog's dense gas theory at all temperatures and pressures. For the 75 percent CO_{2} mixture at 25°C there was a positive deviation from theory, corresponding to the increased importance of glancing collisions for CO_{2} near saturation. The results are consistent with our previous data for self‐diffusion in the two pure gases.

The Yield of Oxidation of Ferrous Sulfate in Acid Solution by High‐Energy Cathode Rays
View Description Hide DescriptionAn absolute determination of the yield of the ferrous sulfate radiation dosimeter has been made by delivering to the solution a measured charge of cathode rays at known energies of 1 or 2 Mev. Appropriate small corrections have been made for backscattering, window absorption and, bremsstrahlung. The result, G = 15.6±0.5, is in complete agreement with Hochanadel's calorimetric determination of the yield, but disagrees by 30 percent with the most widely used value obtained by cavity ion chamber comparison.

The Microwave Spectrum of Hydrogen Peroxide
View Description Hide DescriptionNine absorption lines of H_{2}O_{2} and some one hundred absorption lines of D_{2}O_{2} and HDO_{2} have been observed in the microwave frequency region using a flow system for sampling to overcome the decomposition of the peroxide at low vapor pressure. An analysis of the microwave spectrum of H_{2}O_{2}, using a symmetric top approximation, reveals that it is necessary to invoke hindered internal rotation to explain the experimental data. Using a sinusoidal approximation for the hindering potential yields a barrier height of about 113 cm^{—1}. From the Stark effect calculations, a value of dipole moment of 2.26 debye units is obtained. Some limiting conditions on the values of the molecular parameters are discussed.

Ionic Components of Charge in the Electrical Double Layer
View Description Hide DescriptionThe rate of change with concentration of the capacity of the electrical double layer on mercury has been measured. From this there have been calculated Γ_{+}, the excess of cations in the double layer, and Γ_{—}, the excess of anions. The latter has been subdivided into η_{—} ^{ d }, the excess of anions in the diffusedouble layer, and η_{—} ^{ i }, the excess of anions in the inner part of the double layer. From these data it has also been possible to evaluate ψ^{0}, the potential of the outer Helmholtz plane.
It is found that fluoride ion remains unadsorbed on mercury at all potentials investigated, including potentials anodic to the e.c.max. Other anions are strongly adsorbed (chemisorbed) when the mercury is positively charged, and sometimes even when it is negatively charged. The ``hump'' in the capacity curves of salts of such anions as chloride, bromide, acetate, and nitrate, are found to be present in curves of C _{—}, the capacity attributable to anions alone. No chemisorption of monatomic cations could be detected.
The kinetic theory of the diffuse double layer with constant dielectric constant is found to fit the experimental results within the expected accuracy. This fit extends to electrolytes of the 1:2 and 2:1 types also.
A new method of evaluating salt adsorption at the potential of the electrocapillary maximum (e.c.max.) is described and results are given. Likewise a new method of determining C _{+} at the e.c.max. is described and used.

Rotation in Solid Mixtures of Neohexane and Cyclopentane from 20°K to Their Melting Points
View Description Hide DescriptionStudies of the broadening of the proton spin resonance line have been made for solid solutions of neohexane and cyclopentane.
A convenient apparatus for control of temperatures from 10°K to room temperature for such studies is described.
The ``complex'' of one mole of neohexane with two moles of cyclopentane rotates in the solid state down to 65°K. In solid solutions with cyclopentane in excess of the complex, the complex rotates independently of the cyclopentane down to 66°K. The complex has no effect on the lower rotational transition of the cyclopentane which apparently nucleates.

The Third Virial Coefficient of a Lennard‐Jones Gas by Kihara's Method with Tables for the 6—9 Potential
View Description Hide DescriptionKihara has shown that the third virial coefficient of a Lennard‐Jones 6—9 gas can be expressed as a convergent power series of the form Σ_{ j } β_{ j }(s)θ^{(s—6)j/s } with θ=ε/kT. In this paper the coefficients β_{ j }(s), which are rather complicated double integrals, are developed and applied to the case s=9. For j<20 the coefficients are obtained by numerical quadrature, using high‐speed computing equipment. Asymptotic formulas for arbitrary s are used to extrapolate the numerical results for s=9 into the range 20<j<100. Values of the normalized third virial coefficient, C _{9} ^{(0)}(θ) and its derivatives, computed from Kihara's series, are tabulated for the range 0<θ<2. An asymptotic expression for C _{ 8 } ^{(0)}(θ) is used to extend the tables to higher values of θ.

The Development of a Quantum‐Mechanical Model for the Lithium Fluoride Molecule
View Description Hide DescriptionA quantum‐mechanical model of the LiF molecule is developed using four different forms of wave functions. The most refined form (Sec. III, part iii) considers the transfer of electrons to an excited state of the F^{—} ion and possible covalency of the bond. This leads to values of the binding energy, internuclear distance, and dipole moment which are in reasonable agreement with available data. The inclusion of about 11 percent covalent character is essential for the success of the model proposed.

A Quantum‐Mechanical Calculation of the Surface Energy of Crystalline Lithium Fluoride
View Description Hide DescriptionA quantum‐mechanical model for calculating the surface energy of a LiF crystal is described. This work is an extension of previous papers on the energies of the LiF crystal and molecule. A simple form of distortion is permitted in the surface region. The value of the surface energy of a {100} face obtained from these computations is 557‐erg cm^{—2} at 0°K and is appreciably higher than results based on classical considerations.