bluuebunny/crossref_metadata_2025 huggingface dataset:
Short-Lived Isomeric States of Se83 and Ge77
Authors: Arnold James R. , Sugarman Nathan
Published: January 2005

Extractions of Br from neutron irradiated SeO3= solutions and of As from irradiated GeS3= solutions revealed the presence of short-lived isotopes of Se83 and Ge77 decaying by β−-emission to 2.4-hr. Br83 and 40-hr. As77, respectively. Direct observation of the radiations from a short-lived Se, effected by measuring the activity of Se irradiated for 20 sec. through Al absorbers, led to a half-life determination of 67±3 sec. and a β-energy of 3.4 Mev. A γ-ray was also observed. Similarly, a short-lived Ge activity was found by irradiating GeS2 with neutrons for 20 sec. and measuring the activity through Al absorbers. The half-life was determined to be 59±2 sec. and the β-energy, 2.8 Mev. The agreement between the cross sections for formation of the 67-sec. Se and the 2.4-hr. Br83 from the short-lived Se83 makes it probable that the 67-sec. Se is genetically related to the 2.4-hr. Br83. In a like manner it was shown that the 59-sec. Ge is probably identical with the short-lived Ge77.

The presence of the 67-sec. Se83 activity decaying by β−-emission to 2.4-hr. Br83 and the 59-sec. Ge77 activity decaying to 40-hr. As77 resolves the difficulty of the apparently high ``independent'' yields of Br83 and As77 in fission.

A new Se activity of 17.5±0.3 sec. half-life was also found. It appears to decay by emission of γ-radiation of ∼150 Kev. The cross section for formation of this activity by neutron activation of Se is ∼0.6 barn.
Forces between Tetrahalide Molecules
Authors: Hildebrand J. H.
Published: January 2005

A review of the evidence furnished by melting and boiling points, entropy of fusion and evaporation, crystal structure, ionic-bond character, radii, Raman frequencies, energy of evaporation and differential energy of expansion, polarizability, and solubility relations has led to the following conclusions: (1) Hindrance to rotation is small in liquid CCl4 and CBr4 but increases with increasing radius ratio of central atom to halide atom. This indicates that the van der Waals radii of the halide atoms in these liquids are considerably smaller than those assigned by Pauling. (2) In spite of the hindrance to rotation, the solubility relations can be calculated with considerable accuracy by means of equations derived for spherical molecules with radial force fields. (3) Attraction between molecules of different species is not appreciably influenced by the kind of bonding orbitals of the central atom, but is strongly influenced by the ionic character of the bond. (4) The apparent anomaly of the low boiling point and internal pressure of SiCl4 is due to the large increase in molal volume between CCl4 and SiCl4; the attraction constant increases uniformly with M-X distance in the series of chlorides of C, Si, Ge, Ti, Sn. (5) The attraction constant is closely related to the square of the polarizability, in accordance with the London theory. (6) The two isotropic Raman frequencies for the chlorides of C, Si, Ge, Ti, Sn, Pb decrease uniformly with increasing M-X distance. (7) None of the properties of SiCl4 requires for its explanation the assumption of ``double bond resonance.''
The Infra-Red Absorption Spectrum and Vibrational Frequency Assignment of Ketene
Authors: Harp W. R. , Rasmussen R. S.
Published: January 2005

The infra-red absorption spectrum of ketene from 2μ to 15μ has been determined and a complete frequency assignment deduced. All the harmonic bands can be simply interpreted on this assignment. The fine structure of the 925-cm−1 band is discussed.
On Simple Binary Solid Solutions
Authors: Lawson A. W.
Published: January 2005

The effect of difference in atomic volume between two components of a simple binary solid solution on the phase equilibrium curves is investigated by calculating the energy of deformation required to replace a smaller atom by a larger atom, and vice versa. The strain energy is introduced to the free-energy function derived by the quasi-chemical technique of Guggenheim and leads to expressions similar to those of Hildebrand for unsymmetrical segregation. In addition, the Mie-Gruneisen equation is used to estimate the effect of vibrational entropy changes. It is found that the effect of such changes has a smaller effect on phase equilibria in general than the energy changes. Finally, the results are used to justify certain empirical thermodynamic expressions.
On the Thermodynamics of Non-Electrolyte Solutions and Its Technical Applications III. Systems with Associated Components
Authors: Redlich O. , Kister A. T.
Published: January 2005

The influence of continuous association of one component on the free energy of a non-electrolyte solution is derived from a few assumptions. The result is in accord with available data for hydrocarbon-alcohol solutions. Systems of two associating components and the general interpretation of the free energy of non-electrolyte solutions are briefly discussed.
Theory of Burning Velocity. II. The Square Root Law for Burning Velocity
Authors: Tanford Charles , Pease Robert N.
Published: January 2005

Previous papers by the authors having suggested that the diffusion of active particles (chiefly hydrogen atoms) from the flame front is the controlling factor in combustion in Bunsen-type burners, an equation for burning velocity based on such a concept is derived. This equation shows that the burning velocity should be proportional to the square root of an expression in which the most important factor is the sum of the products piDi for all effective atoms or free radicals, pi being the concentration of an atom or radical at the flame front, and Di its coefficient of diffusion into cold, unburnt gas. The burning velocity equation is applied to the combustion of carbon monoxide and hydrogen, and excellent agreement between calculated and experimental values of the burning velocity is obtained. The equation is also used to account for the effect of pressure upon burning velocity.
Heat Capacities of Liquids and Vapors
Authors: Benson Sidney W.
Published: January 2005

By the use of an equation previously derived for the energy of vaporization of a liquid: ΔE=k(Dln—Dgn) (in which k is a constant; n=5/3, and Dl and Dg are the molar densities of liquid and vapor, respectively), an expression is derived relating (∂ΔE/∂T)sat to the difference in molar heat capacities at constant pressure of the liquid and vapor (ΔCp). At low pressures this relation can be approximated by the equation ΔCp=(∂ΔE/∂T)s+ R (R is the gas constant, 1.986 cal./mole-°A). Under these conditions (∂ΔE/∂T)s=(5/3)ΔE(∂ lnDl/∂T)s, and the resulting equation for ΔCp is ΔCp=(5/3)ΔE(∂ lnDl/∂T)s+1.99. From known properties of liquids ΔCp can be calculated using this last equation. These calculated values are found to be in good agreement with observed experimental values.
Calculation of the Equilibrium Composition of Systems of Many Constituents
Authors: Brinkley Stuart R.
Published: January 2005

A computational procedure is developed for the calculation of the composition at chemical equilibrium of systems of many constituents. The general equations are applied to homogeneous systems and to homogeneous systems which exist in the presence of a single additional pure phase. A brief discussion is given of appropriate numerical methods of computation.
The Asymmetric Rotor. IV. An Analysis of the 8.5-μ Band of D2O by Punched-Card Techniques
Authors: King Gilbert W.
Published: January 2005

An analysis of the 8.5-μ band of D2O has been made by matching the observed transmission curve (published by Barker and Sleator) with a calculated curve. This was obtained by punched-card techniques developed for analyzing incompletely resolved spectra, in which the relative intensity and position of every line was computed by rigid-rotor theory for various choices of moments of inertia, and the absorption coefficients summed over a suitable ``slit width.'' The band is caused by a transition in which the induced electric moment is parallel to the intermediate axis of inertia. Its center is at 1179 cm−1. The most satisfactory fit was obtained with moments calculated by the empirical equation of Fuson, Randall, and Dennison which applies an isotope effect to the known moments of inertia of H2O, corrected slightly for the known values of Δ = IC—IB—IA. The reciprocal moments are 15.38, 7.25, and 4.84 cm−1 for the ground state, and 16.50, 7.33, and 4.79 cm−1 for the upper state (the first deformation vibrational level).
Infra-Red Absorption Spectra of the C2 to C4 Mono-Olefins and of 2-Methyl−2-Butene
Authors: Rasmussen R. S. , Brattain R. Robert
Published: January 2005

The infra-red absorption spectra from 2 to 15μ of ethylene, propylene, 1-butene, cis−2-butene, trans−2-butene, isobutene, and 2-methyl−2-butene in the vapor state have been obtained. Features common to all the spectra are discussed and their aid in determining the structure of new compounds is pointed out. The fundamental frequencies and vibrational assignments of ethylene and propylene are discussed.
Heat-Capacity Lag Measurements in Various Gases
Authors: Huber Paul W. , Kantrowitz Arthur
Published: January 2005

The impact-tube method of measuring relaxation times for the transfer of molecular energy from translational to internal degrees of freedom has been introduced in a previous report. This method has been applied to a series of gases to make measurements of relaxation times which would be difficult to measure quantitatively by sonic methods. Measurements of the relaxation times of the vibrational energy of H2O, N2, N2 catalyzed by H2O, and CCl2F2 are presented. The existence of a measurable lag in the adjustment of the rotational heat capacity of H2 has been confirmed, and measurements of its relaxation time are presented.
The Mechanism of the Luminescence of Solids
Authors: Williams Ferd E. , Eyring Henry
Published: January 2005

In this paper, effort is directed toward explaining various diverse luminescent properties of solids in terms of a simple model of potential energy versus configuration coordinate. Three states of different multiplicities—a normal, metastable and an emitting state—are involved. The luminescent process consists of the excitation of an electron to the metastable level, the activated release of the electron to the emitting level, and a forbidden transition between the emitting and the ground state. With high excitation energy, the metastable state is bypassed. At high temperatures, the electron in the metastable state surmounts a larger potential barrier to undergo radiationless recombination with the activator atom.

Among those significant phenomena that have been measured experimentally and treated quantitatively by calculations based on this model are the temperature dependence of luminescent efficiency and the effect of type and wave-length of excitation on this temperature dependence; the three types of phosphorescence—spontaneous, metastable, and recombination phosphorescence; the phenomena of two-stage afterglow and the effect of type of excitation and temperature on the two stages; the relationship between buildup and afterglow kinetics; and the release of electrons from metastable states by thermal energy. The concept of the Absolute Rate theory are used to clear up the essential criteria for the different types of afterglow.

A detailed theoretical analysis of ``glow curves'' is presented and quantitatively applied to improved glow curves obtained at linear rates of heating 100 times slower than those previously reported. The slower rates of heating allow one metastable level to be operative at a time. Both monomolecular and bimolecular mechanisms are treated, and it is concluded that glow curves result from discrete metastable states that are emptied thermally by predominantly monomolecular kinetics. The explicit expressions for the specific rate constants involved in the release of electrons from metastable states are calculated.
The Effect of High Mechanical Stress on Certain Solid Explosives
Authors: Bridgman P. W.
Published: January 2005

Eleven different solid explosives have been subjected at room temperature to stresses of the order of those which prevail in the detonating front. Two types of stress were applied. The first consisted of a hydrostatic pressure of 50,000 kg/cm2, on which was superposed a shearing stress sufficient to produce shearing deformations of the order of 60 radians. The second type consisted of a hydrostatic pressure of 100,000 kg/cm2, with a comparatively small superposed shearing deformation. Seven of the eleven explosives survived stress of the first type without detonation. Only four of the explosives were subjected to the second type of stress; three of these survived without detonation. It is probable that in those cases where detonation occurred secondary effects were responsible, such as striking of sparks by fractured fragments of steel. The general conclusion is drawn that stresses of these magnitudes, without the cooperation of high temperature, cannot be counted on to produce detonation.

Incidentally it was found that yellow ammonium picrate is transformed irreversibly to the red form by the first type of stress. Values were obtained for the plastic flow stress as a function of hydrostatic pressure. The strength increases approximately linearly with pressure.
The Non-Degenerate Vibrations of Dimethylacetylene, Diacetylene, and Dimethyldiacetylene
Authors: Meister Arnold G. , Cleveland Forrest F.
Published: January 2005

By using force constants obtained from the observed non-degenerate frequencies of dimethylacetylene and diacetylene, the non-degenerate frequencies of dimethyldiacetylene were calculated. It was found that when several of these force constants were modified, agreement to within 2 percent of the observed values of the frequencies was possible. In order to check the values of the modified force constants the non-degenerate frequencies of diacetylene were recalculated. The central C–C stretching force constant was found to have a value of 3.2342×105 dynes/cm which is much less than the normal value (5×105 dynes/cm) for a C–C stretching force constant. Finally, the previous tentative assignment of the observed Raman frequencies of dimethyldiacetylene has been revised as a result of the calculations.
Photoelectric Intensity Measurements of Raman Spectra
Authors: Chien Jen-Yuan , Bender Paul
Published: January 2005

An instrument for the direct photoelectric recording of Raman spectra of liquids is described together with the results obtained for CCl4, CHCl3, CH2Cl2, and C6H6. The precision of the results was tested by eight recorded spectrograms of CHCl3. The intensity ratios of anti-Stokes to Stokes lines were found to be in good agreement with theoretical values. Approximate values of the change of the bond polarizability of the C–Cl bond in CCl4 and the C–H bond in C6H6 caused by valence vibrations are calculated from the intensity data.
Multilayer Gas Adsorption on Composite Surfaces
Authors: McMillan W. G.
Published: January 2005

The equation of Brunauer, Emmett, and Teller (BET) for the adsorption of a gas on a free plane homogeneous surface is extended to the case of a mixture of two such surfaces, in an attempt to explain the observed deviations below one monolayer. The resulting equation may be greatly simplified for the case that the adsorption energy parameter, c, for each component surface, is large with respect to unity, as is usually the case in low temperature adsorptions of nitrogen, argon, etc. This approximate form of the equation is applied to the nitrogen isotherm on an inorganic salt and gives substantially better agreement with experiment than does the simple BET equation. The region of agreement between the experimental and BET isotherms is discussed on the basis of a two-component surface, and conditions are given under which one might obtain two distinct regions of the isotherm which are fitted by the BET equation by the use of two sets of parameters. It is suggested that it is the lower of these two regions which gives rise to the occasionally observed ``saturation adsorption'' values corresponding to only small fractions of a monolayer.
The Magnetic Susceptibilities of the Vapors of Benzene and Carbon Tetrachloride
Authors: Reber R. K. , Boeker G. F.
Published: January 2005

An apparatus has been constructed for measuring at elevated temperatures and at independently controlled pressures the magnetic susceptibility of vapors of substances which are normally in the liquid or solid state. Besides greatly increasing the range of substances for which such measurements can be made, the measurement at elevated temperatures is believed to permit considerably greater accuracy than has been attained previously in the susceptibility measurements on vapors. Determinations of the susceptibilities of the vapors of benzene and carbon tetrachloride have been carried out at 110°C. The extreme limits of uncertainty in the results are estimated to be 3 percent. The values found for the mass susceptibilities of the vapors are in very close agreement with values which have been obtained for the liquids.
An Equation of State for Gases at Extremely High Pressures and Temperatures from the Hydrodynamic Theory of Detonation
Authors: Cook Melvin A.
Published: January 2005

The hydrodynamic theory of detonation is derived in a convenient form for practical utility by employing the general equation of state pv=nRT+α(T, v)p. Two methods of solution of the general equations based on measured detonation velocity are discussed. In method (a) the detailed form of α(T, v) is unspecified. It is therefore, in principle, at least, a general solution. However, in practice one finds that it is impossible due to the experimental error in detonation velocities to evaluate the heat capacity at constant volume and hence the detonation temperature without specifying a particular form of α(T, v). The postulate (used only in the calculation of temperature) is α=α(v). Method (b) employs the approximation α=α(v) throughout. Methods (a) and (b) lead to identical results which one will find in view of the comparative nature of the two methods, is good evidence (but not conclusive proof) for the validity of the above approximation. This is supported also by the discovery that the same α vs. v2 curve applies to all explosives yet considered. As a matter of fact, it has been found that the detonation velocities may themselves be computed within experimental error, evidently for explosives of all types (where sufficient heat data are available) by employing the α(v) function evaluated from a few selected explosives. Several additional arguments supporting the above approximation are discussed. Data on the detonation properties of several explosives are presented and correlated with similar data obtained by other investigators.
Thermal Properties of Cyclopentane and Its Use as a Standard Substance in Low Temperature Thermal Measurements
Authors: Szasz G. J. , Morrison J. A. , Pace E. L. , Aston J. G.
Published: January 2005

The thermal properties of cyclopentane were redetermined in the Penn State isothermal calorimeter and adiabatic calorimeter B′ and the results compared with other investigations. It is concluded that the heat capacity results of Penn State adiabatic calorimeter B′, those of the National Bureau of Standards, and those of the Bureau of Mines Laboratory at Bartlesville, Oklahoma, are in satisfactory agreement, under normal operating conditions, above 30°K.
Heat Flow through Composite Cylinders
Authors: Penner S. S. , Sherman S.
Published: January 2005

The differential equations are solved for the time-dependent flow of heat through a composite cylinder. The composite cylinder is assumed to be thermally insulated at the outer boundary and to consist of a cylindrical core, initially at the uniform temperature U0, surrounded by a cylindrical shell, initially at temperature zero. Included in this paper are corresponding treatments for composite slabs of finite and infinite widths.
Dynamics of a Square Lattice I. Frequency Spectrum
Authors: Montroll Elliott W.
Published: January 2005

The distribution of frequencies of normal modes of vibration of a monatomic square lattice is obtained as a function of the force constants of the lattice. Since the forces between pairs of atoms in the lattice are short ranged, interactions between all atoms, other than nearest and next nearest neighbors, are neglected.

Two constants, α and γ, are used to describe the lattice. α is a force constant derived from the interaction of nearest neighbors, and γ is that derived from the interaction of next nearest neighbors.

According to the Debye continuum theory the frequency spectrum, or density of normal modes, should be a linear function of the frequency. In the Born-Karman atomic model used in the present paper it is shown that this is only the case at very low frequencies and that there actually exist two sharp infinities in the frequency spectrum.

We define g(ν) so that g(ν)dν is the number of normal modes of vibration with frequencies between ν and ν+dν. A closed expression involving complete elliptic integrals is obtained for g(ν) when τ=[1+(α/2γ)]−1=⅓. For general values of τ<½, g(ν) is shown to have the following properties:

(a) The largest frequency, νL, occurs at νL=[(4α+8γ)/4π2M]12,where M=mass of each atom.

(b) There is an infinity in g(ν) at ν=νLτ½.

(c) The second infinity is at ν=νL(1−τ)12 if τ<15, and ν=νL(1+3τ)/4τ12 if τ>15.

(d) As ν/νL→0, g(ν) is linear in ν.
Absorption Spectrum of Borazole in the Vacuum Ultraviolet
Authors: Platt J. R. , Klevens H. B. , Schaeffer G. W.
Published: January 2005

The absorption spectra of triborine-triamine or borazole, B3N3H6, has been studied with a fluorite vacuum spectrograph in the region 2250–1700A in n-heptane solution. The compound was prepared by the reaction between diborane and ammonia.

Four diffuse bands are found, starting at 1995A, with spacing about 900 cm−1. These seem analogous to the 2000A bands of benzene, but the intensity is about 10 times smaller. A strong continuum, like the 1800A benzene peak, has its maximum at 1720A or below. No bands like the benzene 2600A group were found, though they would have been seen if their intensities had been only 1/20th that of the latter.

The spectrum of a boron hydride, B5H9, has also been obtained but shows only a featureless continuum in this wave-length region.
The Relationship between the Brunauer-Emmett-Teller Adsorption Isotherm and the New Isotherm of Jura and Harkins
Authors: Livingston H. K.
Published: January 2005

Values for the surface pressure and area of molecules adsorbed on solid surfaces can be calculated from the adsorption equation of Brunauer-Emmett-Teller. Over a wide pressure range these calculated values are in approximate agreement with the two-dimensional equation of state for vapor-condensed films. Since the adsorption equation of Jura and Harkins was derived from this same equation of state, it is concluded that for a great many experimental isotherms, the mathematical agreement between the two adsorption equations is so good that extremely accurate experimental work would be necessary to determine which equation was more nearly correct.

The Brunauer-Emmett-Teller equation gives calculated curves on Gregg-type plots that agree qualitatively with those reported by Gregg for multi-layer adsorptions. Surface-area values obtained from these curves by Gregg's X-point method are generally considerably higher than those that would be obtained by the method of Brunauer-Emmett-Teller.

The limiting area occupied by a molecule (i.e., in a mono-molecular layer) as calculated by the method of Harkins and Jura appears to decrease with decreasing energies of adsorption (i.e., decreasing values of c in the Brunauer-Emmett-Teller isotherm). It is suggested that this decrease is artificial, rather than real, and results from the assumption that the constant a in the two-dimensional equation of state does not vary with changes in the nature of the solid adsorbent.

It is not possible at the present time to suggest that one of the isotherms is to be preferred to the other on theoretical grounds. In general, preference should be given to the one which fits experimental data over the broader pressure range.
Short-Lived Halogen Fission Products
Authors: Sugarman Nathan
Published: January 2005

Half-life values have been determined for some short-lived Br and I fission products. The chemical isolation of Br from irradiated uranyl nitrate led to a half-life for Br85 of 3.00±0.05 min. The energy of the β-radiation of Br85 was found to be 2.5 Mev by Feather analysis of the Al absorption curve. The half-lives found for Br87 and Br88 by extraction of the Kr daughter activities from AgBr precipitates were 56.1±0.7 sec. and 15.5±0.3 sec., respectively, on the basis of a 3-min. half-life for Br85. Attempts to measure the half-lives of Br89 and Br91 by extraction of the descendant Sr activity were unsuccessful because of the absence of activity. The identity in half-lives of Br87 and the 55.6-sec. Br delayed neutron emitter makes it probable that the mass assignment of the delayed neutron emitter is 87.

The half-life of I137 was found to be 19.3±0.5 sec. by extraction of Xe137 from AgI precipitates, on the assumption of constant chemical yield of the Xe extraction. Isolation of Cs138 both from the gas separated from AgI precipitates and from the precipitates directly led to a half-life determination for I138 of 5.9±0.4 sec. Extractions of Ba149 yielded a value of 2.7±0.1 sec. for the half-life of I139. The absence of Ba140 activity in AgI precipitates made it impossible to determine the half-life of I140. Because of the agreement in half-lives of I137 and the 22.0-sec. I delayed neutron emitter it is probable that the two are identical.

The low retention of the decay products of the short-lived halogens by the silver halide precipitates led to an estimate of 20 sec. for the ``setting'' time of the precipitate.
The Assignment of the Vibrational Spectra of Ethyl Mercaptan and the Ethyl Halides, and the Characterization of an SH Deformation Frequency
Authors: Sheppard N.
Published: January 2005

An assignment is given for all the fundamental modes of vibration of the ethyl mercaptan molecule from the observed vibrational spectra. By analogy the observed frequencies in the spectra of ethyl chloride, bromide, and iodide are also assigned to normal modes of vibration of these molecules.

Evidence is presented that one of the deformation modes of the SH linkage in mercaptans has a characteristic frequency lying between the limits of 800 and 900 cm−1. This frequency is usually stronger in the Raman spectrum.
Rotational Absorption Spectrum of HDO
Authors: Strandberg M. W. P.
Published: January 2005

The 22−21, 30−31, 4−3−31, and the 50−51 rotational absorption transitions of HDO have been observed and identified on the basis of their Stark effect. By comparing the theoretical and experimental Stark shift, the dipole moment for all these transitions has been measured as 1.84±.01. The effective HOD angle is also determined as 104°±30′ and the parameter of asymmetry, k, as about −0.696. The line breadth Δν at one atmosphere is 0.38±0.04 cm−1. None of these quantities is in disagreement with independent determinations.
Triplet-Singlet Transitions in Organic Molecules. Lifetime Measurements of the Triplet State
Authors: McClure Donald S.
Published: January 2005

The emission lifetimes of the metastable triplet states (phosphorescent states) of a large variety of organic molecules have been measured. The lifetimes are in the range from 10−4 to about 10 seconds. It is shown that the transition probabilities corresponding to the shorter lifetimes are of the same magnitude as found in the light atoms of which the molecule is composed. The longer lifetimes, on the order of seconds, are found only among the aromatic compounds. A consideration of the perturbing singlet states in aromatic compounds shows that the matrix elements for the intercombination must be very much smaller than those responsible for the intercombination in the free carbon atoms. Direct evidence that the long-lived states of the aromatic compounds are triplet states is obtained by showing that as the atomic number of chemically similar substituents is increased (e.g. substitute Br for Cl), the transition probability increases approximately in proportion to the increase in the square of the spin-orbit interaction energy of the substituent atom. The luminescences are usually observable only when the substance is dissolved in a rigid solvent, and the effect of such a solvent on the lifetimes is discussed. Experimental data relating singlet-triplet absorption strength to triplet state lifetime is presented.
The Tensile Strengths of Liquids. I. Thermodynamic Considerations
Authors: Benson Sidney W. , Gerjuoy Edward
Published: January 2005

An investigation is made of the thermodynamic stability of liquids under tension. Comparisons of the Helmholtz free energies show that small samples of liquid under tension are unstable with respect to two-phase liquid-vapor equilibrium at the same volume and temperature.

Defining the tensile strength as the negative pressure at which (∂P/∂V)T=0 for the liquid, it is possible to calculate ``maximum'' possible tensile strengths from equations of state. The van der Waals and Berthelot equations in reduced form can be adapted to such explicit calculation and give values much lower, and therefore much closer to experimental values, than previous calculations. For non-associated liquids at 27°C, the van der Waals maximum tensile strengths are about 150 atmos. whereas the Berthelot values are about 750 atmos. The temperature dependence for the two equations is about 1 and 6 atmos. °C, respectively.

Comparisons with observation of the calculated reduced liquid volume, energy of vaporization, coefficient of thermal expansion, and bulk compressibility support the use of the van der Waals and Berthelot equations in computing liquid properties.
Infra-Red Spectra of Propane, 1-Deuteropropane, and 2-Deuteropropane and Some Revisions in the Vibrational Assignments for Propane
Authors: McMurry H. L. , Thornton V. , Condon F. E.
Published: January 2005

The infra-red spectra of propane, 1-deuteropropane, and 2-deuteropropane are presented. The spectrum of propane does not have the bands at 720 and 1179 cm−1 reported by Wu and Barker.

The vibrational modes of the three molecules are described. The 748-cm−1 band in the propane spectrum is unambiguously assigned to rocking of the CH2 group about an axis normal to the molecular axis and in the C3 plane; and the 1053-cm−1 band is unambiguously assigned to rocking of the CH2 group about an axis normal to the C3 plane.

Unambiguous assignments for the remaining bands below 1350 cm−1 in the propane spectrum were not possible without an elaborate theoretical treatment beyond the scope of this paper.
The Exchange Reaction between the Hydrogen Halides and the Halogens in the Gaseous State
Authors: Dodgen Harold W. , Libby W. F.
Published: January 2005

It has been shown that hydrogen fluoride and fluorine gases do not undergo an exchange reaction at room temperature and that heating to 200°C for a matter of an hour or so in a brass vessel is necessary to accomplish exchange. Evidence is obtained that even in this case the observed exchange is heterogeneous and catalyzed by the metal fluorides on the wall of the vessel. Illumination by the light of a mercury arc did not accomplish the exchange under conditions such that an activation free energy of some 9 Kcal/mole for the reaction between a fluorine atom and the fluorine molecule or fluorine atom and HF molecule would have been necessary to prevent exchange.

A rapid exchange reaction in the dark at room temperature has been observed to occur between chlorine and HCl in the gaseous state. This is taken as evidence that the hydrogen halides exchange with the halogens through the formation of an intermediate complex of the general formula HX3, and some discussion of the improbability of the alternative atomic mechanism is given. The non-existence of the HX3 mechanism in the case of the fluorine system is explained by the absence of electrons in the higher shells which are thought to be the main bonding forces involved in the stabilization of the HX3 complex in the case of chlorine, bromine, and iodine, and also by the polar character of the hydrogen-fluorine bond in HF, increasing the probability of an alternative HX3 complex formation in which the hydrogen rests between the fluorine on the HF molecule and the fluorine molecule itself, thus keeping it clearly labeled and rendering interchange on dissociation of the complex unlikely.
Structural Investigations by Means of Nuclear Magnetism. I. Rigid Crystal Lattices
Authors: Gutowsky H. S. , Kistiakowsky G. B. , Pake G. E. , Purcell E. M.
Published: January 2005

Experimental absorption line shapes at nuclear magnetic resonance are given for several simple assemblies of nuclei, with spin ½, in the solid state at temperatures between 90° and 95°K. Analysis of these data is facilitated by the theory of Van Vleck which relates the second moment of the absorption line in a rigid lattice to nuclear spins, gyromagnetic ratios, and internuclear distances, and which provides, therefore, an objective and general method for determining structural parameters from the experimental line shapes.

1,2-dichloroethane exhibits a proton resonance with line structure characteristic of nuclear magnetic moments interacting in pairs to produce the broadening of the absorption line. Consideration of both fine structure and second moment leads to an inferred H–H distance of 1.71±0.02A in the —CH2Cl group. In conjunction with the expected C–H bond distance of from 1.09A to 1.10A, this implies that the H–C–H bond angle is between 4° 30′ and 9° less than tetrahedral. Absorption line shapes for the proton resonance in 1,1,1-trichloroethane and ammonium chloride are given as characteristic respectively of equilateral three-spin and tetrahedral four-spin systems. Less conclusive studies of perfluoroethane and diborane are presented. A detailed analysis of data on ammonium fluoride, chloride, and bromide yields a value of 1.025±0.005A for the N–H distance in the ammonium ion. Some general aspects of the use of nuclear magnetism in structural investigations are discussed briefly.
Spectroscopic Investigation of the Carbon Monoxide-Oxygen Reaction
Authors: Hornbeck George A. , Hopfield Helen S.
Published: January 2005

High dispersion spectrograms of CO-oxygen explosions in a spherical vessel have been obtained. Under conditions affording maximum contrast between the banded spectrum and the continuum, the 3Σu−—3Σg− and the 1Σg+—3Σg− transitions of the neutral oxygen molecule have been observed in emission. Additional spectroscopic information on the absorption by OH radicals in flames has been obtained.
The Infra-Red and Raman Spectra and the Thermodynamic Properties of Diborane
Authors: Webb Allen N. , Neu John T. , Pitzer Kenneth S.
Published: January 2005

Deuterated diborane has been prepared by isotopic exchange and its infra-red absorption spectrum measured. The Teller-Redlich product rule ratios lend support to the assignment based on the protonated double bond or bridge model. Redetermination of the Raman spectrum of normal diborane indicates several changes from previous assignments of Anderson and Burg and Wagner. The resulting vibrational assignment was used to calculate the thermodynamic properties of diborane in the range 100−1500°K. The ΔHf0, ΔSf0, and ΔFf0 are also given. Appendix I shows that a quadratic potential term arises for the puckering of a planar ring if the ring is strained.
Mass Spectrometer Studies of Thermal Decomposition Products from Hydrocarbons
Authors: Coggeshall Norman D. , Kerr Nathan F.
Published: January 2005

A study, by means of a mass spectrometer, has been made of the thermal decomposition products of hydrocarbons. The materials were pyrolyzed in closed ampoules which were subsequently opened to allow the products to be analyzed. A series of runs were made for cetane, n-tetradecane and tetradecene−1 in which the pyrolysis time and temperature were independently varied. Data were obtained giving the compositions of the product gases as a function of the pyrolysis parameters. In examining a series of aromatic hydrocarbons it was found that the amount of yield depends primarily upon the number of substituted carbon atoms. A molar yield was defined and found to be a regular function of A/N where A is the number of substituted carbon atoms and N is the total number of carbon atoms per molecule. The pyrolysis residues were washed with iso-octane which was then examined by ultraviolet absorption spectroscopy. It was found that the aromatic skeletons often remained intact throughout the cracking. In addition, it was found that these structures often polymerized or condensed, giving longer wave-length absorption bands.
Ionic Character and the Dipole Moment of Chemical Bonds. Calculations of the Dipole Moment of HCl
Authors: Robinson David Z.
Published: January 2005

The method of assigning the ionic character of chemical bonds by the use of the dipole moment is examined for the case of hydrogen chloride. Using both the atomic orbital and the LCAO molecular orbital approximation, the ionic character of HCl is calculated. Not only do the values so calculated seem unreasonable from energy considerations, but the calculated rate of change of dipole moment with respect to internuclear distance does not agree with the experimentally observed infra-red intensity. This discrepancy is due to the large dipole moment associated with the covalent bond. Although the results for a purely covalent compound are in agreement both with the dipole moment, and the infra-red intensity, if the dipole is assumed to have the orientation Cl+H−, this assumption is discredited by the fact that one would have to assume more ionic character for HBr than HCl. If we make the assumption that s—p hybridization occurs, these difficulties are removed. It is shown that the dipole moment of the purely covalent molecule is a very sensitive function of the amount of hybridization, and the covalent molecule can have almost any reasonable dipole moment. Thus it is shown that there are difficulties which must be surmounted before one can use dipole moments to obtain ionic character.
Developments in the Theory of the Secular Equation for Molecular Vibrations
Authors: Torkington P.
Published: January 2005

A general solution for the secular equation is obtained, giving the force constants and normal coordinates, for any molecule, in terms of the fundamental vibration frequencies and molecular constants. The solution is based on the reduction of the secular determinant to Jacobian canonical form; it is shown to have a simple physical interpretation. Methods are developed which enable adjustments to be made to the standard solution as required. The theory is fully illustrated by several worked examples.
Thermodynamic Functions for Tritium Deuteride. The Dissociation of Tritium Deuteride. Equilibria among the Isotopic Hydrogen Molecules
Authors: Jones W. M.
Published: January 2005

The heat capacity, entropy, internal energy, and free energy are calculated to 2500°K for tritium deuteride. The dissociation of tritium deuteride is considered. Equilibria of the isotopic hydrogens among themselves are calculated.
Energy Levels and Thermodynamic Functions for Molecules with Internal Rotation. III. Compound Rotation
Authors: Kilpatrick John E. , Pitzer Kenneth S.
Published: January 2005

A method is given for calculating the elements of the kinetic energy matrix for rotation for any molecule. The treatment includes the effects due to any number of linked rotating groups, balanced or unbalanced. In a simple case these equations reduce to the simpler ones of the two previous papers of this series. This rotational matrix is then converted into the matrix of the internal rotations. The reduced moments of inertia that form the latter are then used with the methods of the previous papers of this series to calculate energy levels and thermodynamic functions.
Self-Diffusion in Argon
Authors: Hutchinson Franklin
Published: January 2005

The self-diffusion coefficient of argon was measured at five different temperatures between −183°C and 53.5°C by observing the diffusion of radioactive A41 into normal argon. The decrease in the observed diffusion coefficient caused by the larger mass of A41 was deduced and found to be 0.6 percent. The experimental values are compared with several theoretical calculations. In particular, it is shown that use for argon of an inverse power model (V ∝ r−ν), with different values of ν ascribed to different temperature ranges, is not permissible since widely different values of ν at the same temperature can be obtained from different experimental data. The experimental figures agree very well with numerical calculations by Hirschfelder, Bird, and Spotz based on an interaction potential of the form 4E[—(r0/r)6+(r0/r)12].
Heats of Dissociation of Carbon-Hydrogen Bonds in Methane and Its Radicals
Authors: Laidler K. J. , Casey E. J.
Published: January 2005

The evidence pertaining to the heat of sublimation of graphite is summarized, with the conclusion that the value of 170.6 kcal. per mole is the most probable. This figure is consistent with a value of 393 kcal. for the heat of removing the four hydrogen atoms from methane, the assignment of the heats of the successive dissociations being as follows: CH4=CH3+H−101 kcal.CH3=CH2+H−<87 kcal.CH2=CH+H−>125 kcal.CH=C(3P)+H−80 kcal.The limits to the values for the second and third processes are determined on the basis of the kinetics of the reaction between sodium and methylene chloride. The methylene appearing above is in its lowest state, a singlet state in which the bonding to the hydrogen atoms is through p-orbitals of atomic carbon, the bond containing a certain amount of ionic character. It is suggested that the formation of CH2 in a triplet excited state, in which the bonding to the hydrogen atoms is through sp hybrid orbitals of atomic carbon, corresponds to the following thermochemical values: CH3=CH2*+H−106 kcal.CH2*=CH+H−106 kcal.From this suggestion it follows that the energy of excitation of the methylene ``molecule,'' the lowest state (singlet), to the methylene ``diradical,'' the triplet excited state, is at least 19 kcal. The evidence for the existence of the two states is discussed.
Rotation-Vibration Spectra of Diatomic and Simple Polyatomic Molecules with Long Absorbing Paths. II. The Spectrum of Carbon Monoxide below 1.2μ
Authors: Herzberg G. , Rao K. Narahari
Published: January 2005

The third overtone of CO at 1.19μ has been photographed under high dispersion. From this band precise values for the rotational constants of the CO molecule are derived. They agree excellently with the values obtained from the ultraviolet spectra but are considered to be much more accurate. The equilibrium internuclear distance of CO in the ground state is re=1.12819×10−8 cm. An attempt to obtain also the fourth overtone failed even with path lengths of 3000 m atmos. The second overtone was observed under low resolution with a path length of 30 m.
The Constant Frequency Raman Lines of N-Paraffins
Authors: Simanouti Takehiko , Mizushima San-ichiro
Published: January 2005

Assuming the Urey-Bradley field for the intramolecular potential, we have calculated the normal frequencies of long chain molecules in the extended form. Especially the vibration type of the frequencies remaining almost constant throughout the homologous series has been discussed. The result has been applied to the assignment of Raman lines of N-paraffins and of the infra-red absorption lines of polyethylene.
Vapor Pressure and Other Thermodynamic Data for n-Hexadecane and n-Dodecylcyclohexane near Room Temperature
Authors: Parks George S. , Moore George E.
Published: January 2005

Vapor pressure measurements, by the Knudsen effusion method, have been obtained for n-hexadecane and n-dodecylcyclohexane within the temperature range 299−324°K. From these the following vapor pressure equations have been derived: C16H34;  log10p (in mm)=11.2822–4212/T,C18H36;  log10p (in mm)=12.4190–4880/T.Thence, values at 298.16°K have been calculated for (a) the changes in enthalpy and free energy in the standard-state vaporization of these hydrocarbons and (b) the corresponding enthalpies and free energies of formation in the gaseous state.
The Structure and Growth of Evaporation LiF and NaCl Films on Amorphous Substrates
Authors: Schulz L. G.
Published: January 2005

Thin films of LiF and NaCl were prepared by evaporation in a vacuum and studied by means of electron diffraction, electron microscopy, x-ray diffraction, and optical methods. It was found that on amorphous substrates the films possessed a crystal orientation which varied with the film thickness. For both LiF and NaCl deposits thinner than a hundred angstroms showed almost completely random structure but with a small amount of [100] preferred orientation. As the thickness was increased there was a change, first to completely random, and then to a very definite and strong preferred orientation which was [111] for LiF and [110] for NaCl. The extent of these orientations both on the surface and in the interior of the film was studied in relation to crystal growth. The films are composed of loosely packed crystals set together so as to give the characteristic orientation and with appreciable spaces where the crystals do not make contact. A less extensive study of five other substances showed the following orientations: CaF2, [111]; KCl, [110]; MgF2, [302]; NaBr and KBr, random or a vague [211]. MgF2 was amorphous for deposits under 1000A but became crystalline for greater thicknesses. Detailed consideration is given to the comparison and interpretation of results obtained by different experimental methods.
Rates of Ionic Reactions in Aqueous Solutions
Authors: Olson A. R. , Simonson T. R.
Published: January 2005

The effect of the addition of ``inert'' salts on ionic reaction rates is discussed. For reactions between ions of the same charge sign, the effect is caused almost exclusively by the concentration and character of salt ions of charge sign opposite to that of the reactants. The rate is not dependent upon the ionic strength of the solutions. In reactions between ions of opposite charge sign, both salt ions may affect the rate, but the effect of one type may be dominant. The effects are quantitatively interpretable in terms of an ion association constant and specific rate constants for the associated and non-associated reactants. The further introduction of activity coefficients is not necessary. The reactions upon which the Livingston Diagram is based have been explored from this viewpoint and found to be in quantitative accord.
The General Kinetics of Co-Polymerization and an Extension of the Viscosity Method to Determine Velocity Constants
Authors: Bamford C. H. , Dewar M. J. S.
Published: January 2005

Completely general kinetic expressions have been developed for the co-polymerization of n monomers, assuming that the reactivities of the radicals depend only on their terminal groups. Allowance has been made for chain transfer and the fact that thermal and photo-chemical initiation may proceed via diradicals. The equations are of the same form as those developed previously for a simple polymerization. The latter appear as a special case in which n=1.

It is pointed out that the method previously developed for determining the velocity constants in simple polymerizations can be used without modification in the study of co-polymerizations. In this way 12 of the 14 velocity constants in a binary co-polymerization can be determined absolutely, and a relation between the remaining two obtained.