bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale
Authors: McCrea J. M.
Published: January 2005

The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.
Vibrational Spectra of Some Fluoromethanes
Authors: Rank D. H. , Shull E. R. , Pace E. L.
Published: January 2005

Depolarization measurements have been made on the Raman spectrum of fluoroform and difluoromethane. Several new lines were observed, all of which had previously been found in infra-red absorption. Several weak lines reported previously could not be found and presumably must be ascribed to impurities in the material used by earlier investigators. The analyses given for the vibration spectra now seem to be in plausible agreement with all the known spectroscopic data on these molecules.
Motions of Molecules in Condensed Systems. VI. The Infra-Red Spectra for Vapor, Liquid, and Two Solid Phases of Methyl Chloroform
Authors: Karplus Robert , Halford Ralph S.
Published: January 2005

Infra-red spectra are compared for equivalent absorbing paths of methyl chloroform (1,1,1-trichloroethane) as vapor at 25°, liquid at −28°, solid I at −40° and solid II at −55°C. The spectra differ in the respects: (1) P-Q-R branches observed on some bands in the vapor disappear in the condensed phases, (2) bands generally are sharpened and ones attributable to combinations are intensified by condensation, and (3) three weak bands at 830, 1288, and 1313 cm−1 are present in the condensed states only. Although selection rules for the vapor exclude only the torsional mode and its combinations with other, totally symmetric ones, these weak bands would yield what appears to be the unreasonably high value of 300 cm−1 for the torsional frequency. The fundamental frequencies are discussed briefly and it is pointed out that the spectra are almost entirely explicable upon the basis of only ten of the twelve expected ones for this molecule.
Prediction of Interatomic Distances and Force Constants in Diatomic Hydrides
Authors: Platt John R.
Published: January 2005

The interatomic distance in hydrides is roughly the radius in the united atom at which Zeff=1.0. The force constant is roughly 4πρe2 where ρ is the electron density at this radius. These results are justified by a perturbation treatment. The best fit to experimental values is obtained using Hartree wave functions. Slater functions account for the general trends and breaks in the curves of distance and force constant vs. atomic number, and for the anomalous values noted by the Sheline in the transition elements.
Magnetic Susceptibilities of Some Ions. Part II. A Study of Alkali Salts of Organic Acids
Authors: Prasad M. , Dharmatti S. S. , Kanekar C. R. , Khanolkar D. D.
Published: January 2005

The molar susceptibilities of a number of alkali salts of organic acids have been examined and a linear relation between the molar susceptibility and the number of electrons in the cation has been found. This behavior is similar to that of the group two elements discussed previously and enables one to extend the tabulation of ionic susceptibilities by the authors' graphical method.
Bipyramidal Heptacovalent Bond Orbitals
Authors: Duffey George H.
Published: January 2005

A set of seven orthogonal bond orbitals of symmetry D5h is considered. The orbitals are of type sp3d3. When the attached groups are all equivalent (such as in the bipyramidal AB7 structure), the equatorial orbitals and the axial orbitals are strong. In general, the composition of an axial orbital differs considerably from the composition of an equatorial orbital. The discussion supports the view that IF7 has a pentagonal bipyramidal structure.
A Modification of the Theory of the Thermal Diffusion Column
Authors: Drickamer H. G. , Mellow E. W. , Tung L. H.
Published: January 2005

Thermal diffusion measurements were made for the system argon-neon over a pressure range from 4–108 atmospheres. It is found that the classical theory of Furry, Jones, and Onsager is inadequate to describe the results obtained on a series of carefully constructed thermal diffusion columns. A modification of their theory, based on a more complete picture of the behavior of the column, is developed which fits the data satisfactorily. It is predicted and confirmed by experiment that even though turbulence occurs over part of the gap, a separation will occur, and may even be enhanced by this turbulence.
The Vapor Pressure of Americium
Authors: Erway N. D. , Simpson O. C.
Published: January 2005

The vapor pressure of americium from a dilute solution in plutonium has been measured by a modification of the Knudsen effusion method. The resulting vapor pressure for pure americium in the temperature range 1450°K to 1820°K is given by the equation log10pmm=7.02—(11,300)/T. The vapor pressures are probably accurate to a factor of two or three. Relative values are much more precise.
Thermal Diffusion in the Critical Region. II
Authors: Giller E. B. , Duffield R. B. , Drickamer H. G.
Published: January 2005

The previous measurements on thermal diffusion in the critical region for the system ethane-xenon are extended and completed, with the use of a modified radioactive tracer technique. A rough calculation of cluster size in the critical region is made. A mechanism of molecular motion in the dense gas above the critical point, consistent with the data is present. It is shown that the transformation between dense gas and liquid occurs without discontinuity as far as thermal diffusion is concerned.

The thermal diffusion columns operated in the region of turbulent heat transfer gave a separation as predicted by the modified theory of the column.
Radial Distribution Functions and the Equation of State of a Fluid Composed of Rigid Spherical Molecules
Authors: Kirkwood John G. , Maun Eugene K. , Alder Berni J.
Published: January 2005

The integral equation for the radial distribution function of a fluid of rigid spherical molecules has been integrated numerically in the Kirkwood approximation and in the Born-Green approximation over a wide range of densities. The distribution functions so obtained have been used to calculate the equation of state and excess entropy of the fluid. The results are compared with those obtained by means of the free volume theory of the liquid state.
Thermodynamic Properties of the Internal Rotation in Methyl Alcohol Vapor from 200 to 500°K
Authors: Halford J. O.
Published: January 2005

At ordinary and lower temperatures the thermodynamic properties of the methyl alcohol internal rotation are beyond the limits of available tabulations. For any internal rotator, of a given symmetry, with a fixed moment of inertia and potential barrier, two limiting values of each property can be calculated for any chosen temperature. Available tables are restricted to those cases for which the differences between the limiting values can be neglected. When, as with methyl alcohol, the differences are large, the representative values can be found by taking proper account of the symmetry and the dependence of the internal rotator energy levels upon the external rotations.

For methyl alcohol, the correct intermediate thermodynamic properties are obtained by using for the partition function and its derivatives the numerical mean of the limiting values of these sums obtained for the general rotator. This simple rule, however, is not necessarily applicable to other compounds.

Heat capacities and entropies, calculated from the spectroscopic potential barrier of 932 cal./mole and other molecular constants, are considered in relation to experimental data.
On the Notion of Pressure in a Canonical Ensemble
Authors: Riddell R. J. , Uhlenbeck G. E.
Published: January 2005

Recently a controversy has arisen between J. De Boer and H. S. Green concerning the notion of pressure in a canonical ensemble. According to Green, only classically is the pressure as derived from the partition function equal to that obtained from the virial theorem, while at low temperatures, at which quantum effects become important, there will be considerable deviations between the two. De Boer attempts to prove that the two pressures are actually identical. We have come to the same conclusion, and shall show this in several ways; first, by considering a simple example (Section 2), and then in general using the energy representation (Section 3). We believe that the discrepancy between the two pressures which Green has found is in fact due to improper handling of the effect of the wall of the vessel in which the particles are contained. Finally, we are of the opinion that Green's criticism of De Boer's calculation is not justified, and in the last section arguments are given to show that the traces of all commutators of interest in quantum statistical mechanics are zero.
Substituted Methanes. IV. Vibrational Spectra and Calculated Thermodynamic Properties of Deuterotrichloromethane
Authors: Madigan John R. , Cleveland Forrest F. , Boyer William M. , Bernstein Richard B.
Published: January 2005

Raman displacements, semiquantitative relative intensities, quantitative depolarization factors, and wave numbers and percent transmission for the infra-red bands in the region 400–5000 cm−1 have been obtained for CCl3D. Thermodynamic properties—heat content, free energy, entropy, and heat capacity—have been calculated from the spectroscopic and molecular structure data, to a rigid rotator, harmonic oscillator approximation, for nine temperatures from 298.16° to 1000°K.
The Conductance of Potassium Chloride, Potassium Bromide and Potassium Iodide in Aqueous Solutions from 5 to 55°
Authors: Owen Benton Brooks , Zeldes Henry
Published: January 2005

The equivalent conductivities of dilute solutions of potassium chloride, potassium bromide, and potassium iodide have been measured at various temperatures, and extrapolated to infinite dilution. These results, when combined with those of A. R. Gordon and others, yield limiting equivalent conductivities of each of the three potassium salts at 10° intervals between 5 and 55°C.
The Infra-Red Spectrum of Borine Carbonyl and a Normal Coordinate Analysis of Axial WXYZ3 Molecules
Authors: Cowan R. D.
Published: January 2005

The infra-red spectrum of borine carbonyl has been investigated in the region 2 to 25μ. Two perpendicular-type bands have been partially resolved, and indicate that the molecule is a symmetric top with symmetry C3v. A normal coordinate analysis of axial WXYZ3 molecules has been carried out and applied to H3BCO, the following values having been obtained for the force constants: kCO=17.3, kBC=2.97, kBH=3.21, kBCO=0.142, kHBC=0.333, kHBH=0.363, all in units of 105 dynes/cm.
The Microwave Spectra and Molecular Structure of Phosphorus and Arsenic Trichloride
Authors: Kisliuk P. , Townes C. H.
Published: January 2005

The pure rotational spectra of PCl3 and AsCl3 have been observed in the microwave region, and the observed fine structure has been partially explained. The distance P–Cl is 2.043±0.003A and the angle Cl–P–Cl is 100° 6′±20′. The distance As–Cl is 2.161±0.004A and the angle Cl–As–Cl is 98° 25′±30′.
The Thermodynamics of Some Non-Isothermal Systems
Authors: Tuck L. Dallas
Published: January 2005

The thermodynamic theory of non-isothermal systems of liquid solutions is treated by the method of Tolman and Fine, which method includes consideration of the irreversible processes in calculating the conditions of the steady state.

The concept entropy of transfer of a dissolved molecule is discussed in terms of the interaction of the molecule with the solution. The method of Tolman and Fine is then applied in the derivations of the Soret ``equilibrium'' and the e.m.f. of a thermocell. It is shown that the irreversible transport of heat down the temperature gradient has no effect upon the steady-state conditions, even for finite values of the gradient.
Near Ultraviolet Absorption Spectrum of Hydroquinone, Resorcinol, and Catechol
Authors: Beck Carl A.
Published: January 2005

The near ultraviolet absorption spectra of the three dihydroxybenzenes in the vapor state are measured. 0,0 values are chosen and compared with benzene. Frequency differences of the main bands are given and some vibrational assignments made.
The C–Br Bond Dissociation Energy in Benzyl Bromide and Allyl Bromide
Authors: Szwarc M. , Ghosh B. N. , Sehon A. H.
Published: January 2005

The pyrolysis of organic bromides in a stream of toluene is described as a method for the determination of the C–Br bond dissociation energies. The technique used makes it possible to discriminate between two mechanisms of decomposition: R.Br→R·+BrR.Br→olefin+HBr.It was found that both benzyl and allyl bromide decomposed according to mechanism (a), the bromine atoms reacting readily with toluene to give hydrobromic acid. The rate of the primary dissociation process was measured by the rate of formation of HBr. It was proved that the thermal decompositions of benzyl and allyl bromide were homogeneous gas reactions obeying first order kinetics. The activation energies were calculated at 50.5±2 kcal./mole and 47.5±2 kcal./mole, and identified with D(C6H5.CH2–Br) and D(CH2:CH.CH2–Br), respectively.

The fate of the allyl radical is discussed, and a rough estimate of the activation energy for the reaction CH2:CH. CH2·+C6H5. CH3→CH2:CH. CH3+C6H5CH2·leads to a value of 14–17 kcal./mole.

The problem of ionic contribution in the C–Br bonds is discussed.

The estimation of the dissociation energies of the C–Br bonds of various organic bromides is of great interest since the values for these dissociation energies, combined with the heats of formation of the relevant bromides in the gaseous state, make it possible to determine the heats of formation of various organic radicals. Furthermore, the latter data in conjunction with the heats of formation of hydrocarbons enable us to calculate the various C–H and C–C bond dissociation energies and the resonance energies of the relevant radicals.
Dielectric Constants of Non-Polar Fluids. II. Analysis of Experimental Data
Authors: Brown William Fuller
Published: January 2005

Although the formulas of Part I do not apply strictly to actual gases and liquids, they suggest a possibly useful method of analyzing data on the variation of dielectric constant ε with density d under high pressure at constant temperature. The method is to express (ε+2)d/(ε−1) as a polynomial in d; the variable terms represent the deviation from the Clausius-Mosotti formula. This method has been tested, and compared with alternative procedures based on more specialized formulas, by analysis of data on carbon disulfide (Chang, Danforth) and on carbon dioxide (Michels and Kleerekoper). It is concluded that the proposed method is an efficient one for representing the data, that the values of the coefficients are consistent with the approximate values estimated from the simplified theory, and that there is no advantage in the use of more specialized formulas. The precision of present ε vs. d data and of present knowledge of molecular distribution functions does not justify any more detailed conclusions.
The Vibration-Rotation Energies of the Plane Symmetrical X2Y2X2 Molecular Model
Authors: Herman Robert C. , Shaffer Wave H.
Published: January 2005

The quantum-mechanical calculation of the rotation-vibration energies of the plane symmetrical X2Y2X2 molecular model is carried out to second-order approximation so as to include contributions arising from cubic and quartic anharmonic terms in the potential function, Coriolis interactions, centrifugal stretching, and changes in the rotational constants produced by vibration.
Polarization of the Singlet-Singlet and Triplet-Singlet Luminescence of Chelate Compounds
Authors: Weissman S. I.
Published: January 2005

The polarizations of the luminescence of the dibenzoylmethane complexes of lithium, potassium, aluminum, lanthanum, and gadolinium have been determined. The first excited singlet state of the univalent chelates has symmetry B1. The triplet states have not been uniquely classified. The nature of the perturbation of the triplet state introduced by the magnetic gadolinium ion seems qualitatively different from the perturbations introduced by non-magnetic ions.
Infra-Red and Ultraviolet Spectra of Sulphur Monoxide
Authors: Jones A. Vallance
Published: January 2005

The infra-red spectrum of sulphur monoxide, prepared by the method of Schenk, has been examined between 400 cm−1 and 2000 cm−1. Bands were observed at 679 cm−1 and 1165 cm−1.

The ultraviolet absorption band system discovered by Schenk in the region 3500A to 2500A has been obtained under high resolution (21-ft. grating). A very sharp predissociation occurs at 31,702 cm−1 leading to an upper value for a dissociation limit of 91 kcal. mole−1. A ground state vibration frequency of 679 cm−1 was deduced from a partial analysis of the electronic absorption band system.

It has been shown that the molecule cannot be diatomic SO, but probably has the formula S2O2, as suggested by Kondrat'eva and Kondrat'ev. The spectroscopic evidence supports the structure S=S S=O S=O.
Thermodynamic Properties of Gaseous Carbon Dioxide at Temperatures from 0°—600°C, and Pressures Up to 50 Atmospheres
Authors: MacCormack K. E. , Schneider W. G.
Published: January 2005

Compressibility data presented in a previous paper have been used in conjunction with spectroscopically determined zero pressure specific heat data for CO2, to calculate thermodynamic properties over the temperature range 0°—600°C at pressures up to 50 atmospheres.
Motions of Molecules in Condensed Systems. VII. The Infra-Red Spectra for Single Crystals of Ammonium Nitrate and Thallous Nitrate in Polarized Radiation
Authors: Newman Roger , Halford Ralph S.
Published: January 2005

Infra-red spectra in plane polarized light for properly oriented, thin sections from single crystals of NH4NO3 (IV), NH4NO3 (III), and TlNO3 (γ) are described and interpreted. The selection of proper orientations for such work is indicated for crystals in general and potential difficulties with some types are noted.

Spectra for the first two crystals show (1) that absorptions by molecular modes of nitrate ion, and their combinations, are strongly polarized in directions predicted for these structures by the general theory of crystalline spectra; (2) that envelope structure resulting from combinations between molecular modes and lattice modes is present but not uniquely polarized, again in agreement with the general theory; (3) that absorptions by molecular modes of ammonium ion appear to be unpolarized, indicating that these ions are disordered from rotation or other causes.

Spectra for the third substance are used to complete the determination of its crystal structure. One band in this substance has a remarkable envelope consisting of a strongly polarized central branch and, at room temperature, three pairs of symmetrically distributed, virtually unpolarized satellites. The satellites become more numerous at lower temperature (see accompanying article).

The spectra for the several substances suggest that optical branches of their lattice mode distributions are located between about 35 and perhaps 200 cm−1.
The Vibrational Spectra of Diborane and Some of its Isotopic Derivatives
Authors: Lord R. C. , Nielsen E.
Published: January 2005

The infrared spectra of ordinary diborane, of B210H6, and of B210D6 have been determined in the vapor state over the spectral range 250–3800 cm−1. The Raman spectra of ordinary diborane and B210D6 have been measured in the liquid at −130°C. Qualitative depolarization measurements have been made on nearly all observed Raman lines. The vibrational spectra have been interpreted with the help of the various selection rules and the product rule for isotope shifts. The fundamental frequencies obtained from this interpretation differ considerably from those previously published, but are in agreement with a large amount of spectroscopic data, including much not hitherto available. It is concluded that the nonplanar bridge model (D2h symmetry) fits the spectroscopic data best, although the unsymmetrical C2h form cannot be definitely excluded. The theoretical and observed vapor heat capacities agree satisfactorily over the temperature range 100–300°K.
The Mass Spectra of C1–C4 Monodeutero Paraffins
Authors: Stevenson D. P. , Wagner C. D.
Published: January 2005

The magnetically scanned mass spectra of methane-d, ethane-d, propane−1-d, propane−2-d, n-butane−1-d, n-butane−2-d, i-butane−1-d, and i-butane−2-d, characteristic of 75-volt ionizing electrons and 75°C are given and compared with the mass spectra of the corresponding hydrocarbons.

A qualitative account of the origin of the isotope effects in mass spectra is given. It is shown that in a molecule containing equivalent isotopic species, the molecule-ion formed by electron impact will preferentially dissociate the lighter isotope and that the mass spectra of symmetrically substituted isotopic species (A′BA′) will be more like the mass spectra of the isotopically pure species (ABA) than are those of the unsymmetrically substituted isotopic species (ABA′). It is further shown that the equality (or lack thereof) of parent ion sensitivities of different isotopic preparations to the parent ion sensitivity of the natural substance is not a criterion of the purity (or lack thereof) of the preparations. Attention is called to the close relation between isotope effects in mass spectra and temperature effects in mass spectra.

The two-parameter empirical theory of isotope effects proposed by Evans, Bauer, and Beach is applied to the mass spectra of the methanes and ethanes and found to be inadequate for the prediction of mass spectra for accurate analysis of isotopic mixtures. It is found, however, that for certain electron impact induced processes, such as RH+ε−→R++H+2ε−, the effective values of the parameters, Γ and π, are essentially equal for the monodeutero C1 through C4 paraffins.

It is shown that for the process, RH+ε−→R++H+2ε−, the specific dissociation probability of secondary hydrogens is greater than that of primary hydrogens by a factor of 4 for propane and 10 for n-butane, while in isobutane the specific dissociation probability of the tertiary hydrogen is 30 times that of a primary hydrogen.

It is found that in certain states of the paraffin molecule-ions the hydrogens are sufficiently mobile that they undergo very extensive intramolecular redistribution in the short life of the molecule ion (half-life <0.1–1.0 microseconds) before they dissociate. Such states are of less common occurrence among paraffins than among olefins.
The Infrared and Raman Spectra of Trimethylphosphine Oxide
Authors: Daasch L. W. , Smith D. C.
Published: January 2005

The infrared absorption spectrum of solid trimethylphosphine oxide has been obtained over the range 450 to 5000 cm−1. A vibrational assignment is proposed for nearly all the bands observed in the infrared spectrum as well as for the Raman frequencies observed in aqueous solution. It is shown that the fundamental frequencies of the skeletal vibrations are compatible with reasonable values of the force constants for phosphorus-oxygen and phosphorus-carbon bonds.
The Role of Surface Tension in Multilayer Gas Adsorption
Authors: McMillan W. G. , Teller E.
Published: January 2005

The assumptions of the BET theory of multilayer gas adsorption are examined with regard to the possibility of taking account of the effect of surface tension. The surface energy of the adsorbed phase is calculated by the use of a Fourier analysis of the surface configuration. This energy is then used in the calculation of the corresponding factor in the partition function, leading ultimately to an isotherm equation which includes the surface tension effect. This isotherm is compared with experiment, with the result that the surface tension effect alone is found to overcorrect the BET theory. When compared with the result of recent theoretical treatments of the extension of the attractive forces into the adsorbed phase, our expression is shown to have the same dependence on layer thickness, but to be a relatively unimportant correction under usual conditions.
Intramolecular Isotopic Fractionation—the Example of Nitrous Oxide
Authors: McCrea J. M.
Published: January 2005

The spectroscopic results of Richardson and Wilson are used to calculate the partition function ratios for the isotopic species of nitrous oxide. A number of approximate calculations of types often necessary in other cases owing to limited data are given to show the errors introduced by these approximations.
An Atomic Distribution Function
Authors: Kerr Richard H. , Lund Louis H.
Published: January 2005

A simple form for the radial atomic distribution function for a monatomic liquid, involving the interatomic potential function of two atoms in the liquid, is developed. Assuming the potential function to be of the form (λ/rn)—(μ/r6) and arbitrary choices for μ, the theoretical distribution function is fitted to the left-hand side of the first peak of the experimental distribution curves of liquid argon and liquid mercury. Satisfactory values of n and potential well depths for these two liquids indicate the approximate validity of the derived radial atomic distribution function. Presented also is a comparison of the theoretical and experimental curves for liquid argon and liquid mercury.
The Absorption Spectrum of Sulfur Hexafluoride in the Vacuum Ultraviolet Region
Authors: Liu Ta-kong , Moe George , Duncan A. B. F.
Published: January 2005

The spectrum of sulfur hexafluoride has been investigated down to wavelengths about 600A. The maximum of the first electronic transition is found at about 1050A. Three other transitions occur between this wavelength and 802A, where strong continuous absorption begins, and nothing further can be resolved at shorter wavelengths. Qualitative suggestions are offered about the dissociation of SF6 and the value of its ionization potential.
The Relative Rates of Reaction of Hydrogen and Tritium Hydride with Chlorine
Authors: Jones W. M.
Published: January 2005

The ratio of the specific rate constant for H2 to that for HT in the photo-chemical reaction with chlorine has been determined at four temperatures and is represented by R=(1.35±0.03) exp{(552±7)/RT} to within about 0.3 percent. The ratio is found to be the same when the reaction is initiated by the tritium β-particles. The data are considered from the viewpoint of the theory of absolute reaction rates.
The Entropies of Melting of Metals
Authors: Oriani R. A.
Published: January 2005

The melting process can be conceived as consisting of first an expansion, and then a disordering of the crystalline structure. The entropy contribution from the first effect is calculated by analogy with the process occurring in a volume expansion within an individual phase; the entropy contribution from the melting disorder is then obtained by difference from the measured entropy of fusion. Tentative conclusions of heuristic value are drawn from the relative magnitudes of the various quantities. A simple model for the melting process is adopted, making possible a correlation between the amount of disordering during melting and the structural contribution to the entropy of melting.
The Compressibility of Gaseous Xenon. I. An Equation of State for Xenon and the Weight of a Liter of Xenon
Authors: Beattie James A. , Barriault Roland J. , Brierley James S.
Published: January 2005

The compressibility of xenon containing 0.14 mole percent of krypton has been measured from 16.65° (the critical temperature) to 300°C and over the density range 1 to 10 mole per liter. The constants of the Beattie-Bridgeman equation of state for the sample used and for pure xenon have been determined from these measurements. The constants for pure xenon are R=0.08206, A0=4.6715, a=0.03311, B0=0.07503, b=0, c=30.02×104 in units of normal atmos, liter per mole, and °K (T°K=t°C+273.13). The weight of one liter of Xe at a pressure of one standard atmosphere is calculated from its molecular weight (131.3) and the above parameters to be 5.897 g per liter at 0°C and 5.467 g per liter at 70°F.
The Compressibility of Gaseous Xenon. II. The Virial Coefficients and Potential Parameters of Xenon
Authors: Beattie James A. , Barriault Roland J. , Brierley James S.
Published: January 2005

The second and third virial coefficients of xenon have been determined from our compressibility measurements over the temperature range 16.65° (the critical temperature) to 300°C. They are listed in Table II. The parameters of the Lennard-Jones (6, 12) potential for xenon are μ=5.583×10−58 erg-cm6, λ=2.514×10−102 erg-cm12, ε=309.9×10−16 erg, b0=84.65 cm3 per mole, θ=224.5°K, σ=4.064×10−8 cm, r0=4.561×10−8 cm. The representation of the second virial coefficient is quite satisfactory. The third virial coefficients agree moderately well with the theoretical values for the Lennard-Jones (6, 12) potential tabulated by Bird, Spotz, and Hirschfelder for (T/θ)>1.5 but diverge rapidly as the temperature approaches the critical. The observed second virial coefficients agree moderately well with the values tabulated by Buckingham and Corner for an inverse sixth power attractive and an exponential repulsive potential when the calculated values are read from the table for the parameters given by Kane from data on the solid state of xenon and from Born and Mayer's value of the exponent derived for neon.
Dielectric Constant of Benzene at 25°C by the Wyman Method
Authors: Brown A. S. , Levin P. M. , Abrahamson E. W.
Published: January 2005

Apparatus and techniques are described for obtaining reliable absolute dielectric constants by the Wyman resonance cell method.

Calcium hydride has been shown to be a drying agent for benzene far more satisfactory than sodium wire, reducing drying time from the six-month period demonstrated in the literature to an interval approximating one day.

At 25°C the values for benzene's dielectric constant were 2.2747±0.0003, but the higher limit is presently preferred. These results fall within the range of the best recent values obtained in other laboratories. The reasons for the discrepancies appear explicable in view of the findings of this investigation.
Preparation and Reactions of Free Vinyl Radicals
Authors: Tickner A. W. , Le Roy D. J.
Published: January 2005

Ethylene, acetylene, and butadiene are the predominant gaseous products of the reaction of sodium vapor with vinyl iodide in the ``diffusion flame.'' From the experimental evidence it is likely that these are formed by the disproportionation and recombination of vinyl radicals. In the presence of hydrogen, ethylene is also formed by the reaction C2H3+H2=C2H4+H. More vinyl iodide than sodium is consumed in the reaction and a nonvolatile organic iodide is formed. This has an important bearing on the calculation of the rate constant of the primary process.
The Photolysis of Acetic Anhydride
Authors: Kandel Richard J. , Taylor H. Austin
Published: January 2005

The photolysis of acetic anhydride probably by 1849A radiation has been studied in the temperature range 80° to 300°C at pressures of 10–60 mm dibutyl phthalate. From 80° to 224°C the rate is first order during a run but the specific rate decreases with increasing pressure. The gaseous products are CO, CO2 and C2H6 in approximately equivalent amounts. Biacetyl and methyl acetate have been identified among the liquid products. At 300°C the reaction is more complex, yields considerable amounts of H2 and CH4 and is not first order. Comparison with formic acid photolysis leads to an approximate quantum yield of 2. A mechanism is suggested which accounts qualitatively for the observations. Deactivation of activated reactant molecules by acetic anhydride and by the gaseous products accounts for the low quantum yield. Added C2H6 and CO2 are shown to increase the rate of photolysis, the more so the lower the pressure of acetic anhydride. Preliminary experiments have shown that the reaction can also be mercury sensitized at a much faster rate at comparable temperatures but yielding the same products in similar amounts.
Nuclear Magnetic Shielding in Fluorine and Hydrogen Compounds
Authors: Gutowsky H. S. , Hoffman C. J.
Published: January 2005

Measurements of the nuclear magnetic shielding of F19 and H1 are reported for a number of their respective binary covalent compounds. The applied fields required for the F19 and H1 nuclear magnetic resonances, at fixed frequency, vary in these compounds over a range of 3.98 and 0.122 gauss, respectively, at fields of about 6365 gauss. These ranges are of the same order of magnitude as the theoretical internal diamagnetic corrections for the unbound fluorine and hydrogen atoms. The dependence of nuclear magnetic shielding on the electronic structures of the molecules is discussed qualitatively and some general correlations indicated. One such correlation is that the magnetic shielding of the F19 nucleus decreases with increasing electro-negativity of the atom to which the fluorine is bonded. This and other correlations differ in degree for the proton. The differences may arise from the relatively greater importance of the diamagnetic shielding term for the proton. Specific information regarding molecular and electronic structure is provided in several instances. The tetragonal pyramid structure for IF5 is confirmed and a similar structure demonstrated for BrF5. The appearance of double F19 resonance lines in PF5, IF5, and BrF5 indicates nonequivalent electronic distributions in the structurally distinguishable bonds. The measurements were facilitated by a large permanent magnet, the design and field homogenization of which are described.
LCAO Molecular Orbital Computation of Resonance Energies of Benzene and Butadiene, with General Analysis of Theoretical Versus Thermochemical Resonance Energies
Authors: Mulliken Robert S. , Parr Robert G.
Published: January 2005

The decrease in πx-electron energy for the change from a Kekulé to a proper benzene structure is computed purely theoretically by the method of antisymmetrized products of MO's (molecular orbitals), in LCAO approximation, using Slater 2pπx AO's (atomic orbitals) of effective charge 3.18, and assuming a carbon-carbon distance of 1.39A. The result (73.1 kcal/mole) is a theoretical value for the gross (vertical) resonance energy of benzene taken for constant C–C distances of 1.39A. In order to make a comparison with the net or ordinary empirical resonance energy, several corrections to the latter are required. The principal one is for the ``compression energy'' required to compress the single and stretch the double bonds of the Kekulé structure from normal single and double-bond distances to 1.39A. The others (not hitherto clearly recognized) involve hyperconjugation and related effects. The corrections are discussed and their magnitudes estimated, but a reliable value can be obtained only for the compression energy. Allowing for this alone, the computed net resonance energy is 36.5 kcal. This agrees, within the uncertainties due to the omitted correction terms, with the value (41.8 kcal) of the ``observed'' resonance energy Δ based on thermochemical data.

Here Δ is the departure of the actual heat of formation ΔHf0 of benzene from the value given by a standard formula for nonresonating hydrocarbons. A new standard formula containing corrections for the mutual effects of neighboring carbon-carbon bonds is given; this is of interest also for itself, and its significance is briefly discussed.

The analysis given in the paper serves to clarify hitherto existing obscurities in what is meant by ``resonance energy.'' An analysis of the nature and significance of ``nonresonating'' structures (like for example Kekulé benzene) is also included, using He2, 1,3 butadiene, and benzene as examples. Repulsion terms in the LCAO MO theory occur for nonresonating structures, which appear to be the counterpart of exchange repulsions of the valence-bond theory. When resonance occurs, it more or less overcomes these repulsions.

The gross resonance energies of cis- and trans−1,3-butadiene are computed by the same method. For transbutadiene, the computed value corrected for compression is 3.7 kcal/mole, while the ``observed'' thermochemical value Δ is 6.5.
Studies of Ionization Efficiency. I. The Determination of Molecular Appearance Potentials Using the Mass Spectrometer
Authors: Morrison J. D.
Published: January 2005

The factors affecting the shape of ionization efficiency curves can be separated into two categories: those due to instrument design, and those depending on the molecular structure of the substance studied. By taking precautions to eliminate the former, details of individual fine structure can be detected and measured in the curves. The methods for the determination of appearance potentials in use at the present time are discussed, and the results for a number of substances measured by the principal methods are compared with spectroscopic ionization potentials. It is found that the critical slope method gives values in all cases within 0.3 volt of the spectroscopic figure, whereas the results of the other methods may be in error.
The Structure of Trifluoromethyl Acetylene from the Microwave Spectrum and Electron Diffraction Pattern
Authors: Shoolery J. N. , Shulman R. G. , Sheehan William F. , Schomaker Verner , Yost Don M.
Published: January 2005

Measurements, in the microwave region, of the J = 3→4 rotational transitions of trifluoromethyl acetylene and several of its isotopic modifications have been made, and the moments of inertia, IB (in a.m.u.-Å2), have been found for the ground vibrational state: for CF3CCH, 175.613, CF3C13CH, 177.024, CF3CC13H, 181.302, and for CF3CCD, 187.462. Three lines corresponding to J = 3→4 transitions of CF3CCH in the excited vibrational state v10 = 1, and two lines corresponding to v10 = 2 and v10 = 3, have also been measured and interpreted according to Nielson's theory of l-type doubling in symmetric tops. From Stark effect measurements at different electric field strengths the dipole moment of CF3CCH in the ground vibrational state has been found to be 2.36±0.04 Debye units. For the ground vibrational state the microwave data lead to the following bond distances: C–H, 1.056±0.005Å; C≡C, 1.201±0.002A. The C–C and C–F distances were calculated from the measured moments of inertia for several assumed values of the FCF angle. Electron diffraction experiments were also made, and the intensity curves calculated for the assumed microwave models were compared with the observed visual curve. From the combination of microwave and electron diffraction results the best agreement was obtained with the following set of parameters: ∠FCF, 107.5°±1°; C–C, 1.464±0.02A; C–F, 1.335±0.01A.
Small-Angle X-Ray Scattering from Argon
Authors: Graham Walter , Lund Louis H.
Published: January 2005

A correlation function as introduced by Debye in the case of light scattering is used to characterize the inhomogeneities in liquid argon for those cases showing excessive small-angle x-ray scattering. This method of characterizing the inhomogeneities is compared with the method of characterizing the inhomogeneities as droplets. Curves showing the correlation functions for the various cases are also presented.
On the Electron Affinity of Fluorine
Authors: Johnston Reed H.
Published: January 2005

The hamiltonian for systems isoelectronic with neon is treated by perturbation methods. The energy of ionization of such systems is represented by a four-term expression (i.e., to third order of perturbation); the two leading terms are calculated, spectroscopic data for isoelectronic systems are used to evaluate the constants in the two remaining terms. The electron affinity of fluorine is estimated to be 73±3 kcal/g atom. The corresponding dissociation energy of fluorine, as inferred by the Born-Haber cycle, is estimated to be 18 kcal/mole, to an accuracy believed better than ±12 kcal/mole.
Sum Rules for the Vibration Frequencies of Isotopic Molecules
Authors: Decius J. C. , Wilson E. Bright
Published: January 2005

The squares of the frequencies of isotopically related molecules obey certain simple sum rules. Whenever there exists a chemical exchange reaction involving only isotopic variations of a single type of molecule, such that the reaction is balanced at each atomic position of the molecule, then a relation of identical form exists between the sums of the squares of the frequencies. Thus Σν2(H2O)+Σν2(D2O)=2Σν2(HDO)  and  Σν2(N14H3)+Σν2(N15D3)=Σν2(N14D3)+Σν2(N15H3).If, as in the latter example, the molecules all have the same symmetry, the sum rule may be applied separately to each factor of the secular equation. When forms of lower symmetry appear (as in the example involving the water molecule), symmetry factoring may or may not be possible. In such cases it is necessary to employ certain group-theoretical considerations; the possible factoring is not in general identical with that appropriate for the product rule.

Examples of the application of the sum rule are given, involving the acetylene, water, methane, and hydrocyanic acid molecules. The existence of higher order isotope rules, intermediate between the sum and product rules, is pointed out.
Viscosity of Neopentane
Authors: Phibbs M. K.
Published: January 2005

The viscosity of neopentane has been measured between −15°C and 30°C. These results are consistent with published work covering the temperature range 30°C to 150°C. The viscosity data for neopentane have been compared with similar data for the other pentanes. This comparison has provided an example of the importance of molecular shape for viscosity behavior. The possible significance of molecular shape for the interpretation of viscosity curves of binary mixtures is noted. Finally, it has been suggested that further work on liquids composed of spherical molecules might be worthwhile.
Dielectric Relaxation in Glycerol, Propylene Glycol, and n-Propanol
Authors: Davidson D. W. , Cole R. H.
Published: January 2005

Complex dielectric constants have been measured at frequencies from below 20 c/s to 5 mc/s over the temperature range −40° to −75°C in glycerol, −45° to −90° in propylene glycol, and −80° to −140° in n-propanol. The results for n-propanol are described by the Debye equation, but the values for the other two require a modified equation corresponding to a broader range of dispersion at higher frequencies. In all three liquids, evidence is found for a second dispersion region at still higher frequencies, which accounts for much of the difference between the radio frequency and optical dielectric constant. The relaxation times are quantitatively described over wide ranges by an empirical rate equation of a form which also fits viscosity data. The significance of the various results is discussed.
Diffusion in CO2 up to 150-Atmospheres Pressure
Authors: Robb W. L. , Drickamer H. G.
Published: January 2005

Diffusion coefficients have been obtained for the system CO2–C14O2 up to 150 atmospheres pressure and from 0°-45°C. The coefficients are consistent with theory up to a density of 0.067 g/cc. In the range from 0.067–0.70 g/cc the coefficients are higher than predicted by theory. This may be attributed to a reduced collision diameter due to orientation of the nonspherical molecules. At higher densities the experimental coefficients are lower than the theoretical ones. This is expected as the theory breaks down at these high densities. At densities above 0.65 g/cc no measurable temperature coefficient of D was obtained. This may be explained by increased orientation at lower temperatures and in the liquid state.
Photochemical Studies. XLVI. Photosensitization by Benzene and Pyridine Vapors
Authors: Dubois Jean T. , Noyes W. Albert
Published: January 2005

Attempts to sensitize the dissociations of the following molecules by means of benzene vapor have been made: hydrogen, oxygen, hydrogen chloride, nitrous oxide, methyl chloride, methyl bromide, methyl iodide. Positive results were obtained only with methyl iodide. The decompositions of methyl chloride and methyl bromine sensitized by pyridine vapor were also studied with negative results. The reasons for the results are discussed briefly.
The Concentration of Molecules on Internal Surfaces in Ice
Authors: Murphy E. J.
Published: January 2005

In this paper the experimental expression for the ``local conductivity'' of ice is given. This expression has two terms, one of which has already been discussed and brought into close relation with the structure of ice, that is, with its heat of sublimation and its lattice constant. This paper brings out another relation, deriving it from the second term of the experimental expression. It is concluded from an analysis outlined here that the second term of the local conductivity gives the concentration of molecules in ``internal surfaces.'' For the specimen of ice to which this method was applied the concentration of molecules on internal surfaces comes out as 1.03×1017 molecules/cc.

This is proposed as a new method of studying imperfections (internal surfaces) in dielectric crystals, and one which seems to be well suited to this purpose. It gains its advantages from the fact that it is not dependent upon the regularity of the imperfections, as in x-ray diffraction methods, or upon the connectivity of the system of internal surfaces, as in direct current conduction.
The Effect of Ultrasonic Radiation on the Electrolytic Separation of Deuterium
Authors: Mason Donald F. , Biddick Royce E. , Boyd Charles A.
Published: January 2005

The application of ultrasonic radiation to the polished platinum cathode of an electrolysis cell increases the coefficient for the electrolytic separation of deuterium. The radiation also decreases the temperature dependence of the separation coefficient. This is thought to be due to the rapid removal of the discharged gases by the ultrasonic radiation. This prevents the surface-catalyzed exchange reaction between the discharged gases and the electrolyte.
On the Quantum-Mechanical Calculation of the Cohesive Energy of Molecules and Crystals. Part II. Treatment of the Alkali Metals with Numerical Applications to Sodium
Authors: Löwdin Per-Olov
Published: January 2005

In Part I, an expression for the cohesive energy of a crystal was derived in the case the wave function for the ground state is approximated by a single Slater determinant of Bloch spin orbitals, formed by linear combination of the atomic spin orbital associated with the self-consistent fields with exchange for the free constitutents. By using the new idea of ``combined atomic orbitals,'' all energy terms were reduced to only atomic two-center integrals, which could be evaluated by numerical integration. This method is here applied to the calculation of the cohesive energy of the alkali metals, where, due to the crystal symmetry, the combined atomic orbitals for the valence electrons are almost pure s-functions. It is shown that the conventional method, taking only the interaction between nearest neighbors into account, is entirely insufficient and that it is necessary to consider even bonding, overlapping, and electronic repulsion effects between neighbors of a rather high order.

Numerical applications, including interactions between neighbors up to the order nine, are carried out for metallic sodium, giving the cohesive energy 24.7 kcal/mol and the interatomic distance 3.69A, in good agreement with the experimental values 26 kcal/mol and 3.67A, respectively. Except for the values of the fundamental constants e, m, h, ···, no empirical data are used.