bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Dissociation of Hydrogen
Authors: Moore George E. , Unterwald F. C. 
Published: January 2005

This paper describes ``thermal dissociation'' or ``atomization,''H2⇌2 H,on a Mo or W catalyst, from 1200° to 2500°K. We emphasized transient behavior of individual species (especially H) caused by changing catalyst temperature. Reaction rates, and equilibria derived from them, confirm Langmuir's results of 50 years ago, and disagree with more recent authors who published reaction rates 200-fold faster. These authors did not emphasize chemical identification of both reactants and products, but attributed a measured decrease of total pressure to H, produced as in (1) and abstracted either chemically or by refrigeration. Reactions unrelated to atomization can decrease total pressure.
Transient behavior above 1200°K was dominated by diffusion; this suggests that neither surface atomization mechanism usually favored is important. Our transient methods permit evaluation of parameters fundamental for diffusion and for solution of hydrogen in W or Mo, from 10—7 to 10—4 Torr, well below the range of the Fowler—Smithells theory. These may be the first quantitative diffusion data published for the tungsten—hydrogen system. Using D=D0 exp(—Q/RT) we obtained: TungstenMolybdenumD at 1985∘K2.2×10−82.8×10−7D07.25×10−4Q41.5 kcal/mole H2Heat of solution64 kcal/mole H216–22 kcal/mole H2 (1360–1980∘K)SolubilityOne atom of H per 400 atoms of W at 2440∘ and 1.2×10−4 TorrOne atom of H for 104 atoms of Mo at 1985∘K and 10−6 Torr
Dissociation Energies of Some Gaseous Alkali Halide Complex Ions and the Hydrated Ion K(H2O)+
Authors: Chupka William A. 
Published: January 2005

A mass spectrometer was used to analyze the ionic species present in the vapors of several alkali halides which were heated in a small oven to temperatures in the range 700–950°K. For the four compounds investigated, NaCl, KCl, KBr, and RbCl, the most abundant ionic species were of the type M+ and M2X+ in comparable amounts. Smaller amounts of M3X2+ ions and, in certain circumstances, negative ions of the type X— and MX2— were also detected. The equilibrium constant was measured as a function of temperature for the reaction M2X(g)+→M(g)++MX(g). Values of the ΔH of this reaction were determined by two independent methods which gave good agreement for all compounds except RbCl. The values of ΔH(0°K) so determined were 42.3, 41.3, and 41.0 kcal/mole for NaCl, KCl, and KBr, respectively. The more reliable value for RbCl was about 40 kcal/mole which agrees well with a theoretically calculated value of about 42 kcal/mole.
An attempt to detect the K(H2O)+ ion in equilibrium with water vapor and KCl at about 840°K was apparently successful, although positive identification of the ion could not be made. The equilibrium constant for the reaction K(H2O)(g)+→K(g)++H2O(g) was measured and gave a value of ΔH(O°K) = 20 kcal/mole.
New Method for the Statistical Computation of Polymer Dimensions
Authors: Wall F. T. , Erpenbeck J. J. 
Published: January 2005

A new method is described for the generation of excluded volume random walks of contour lengths comparable to those of real polymer molecules. This work was carried out with a high-speed electronic digital computer. An essential feature of the method is an unbiased sample enrichment process used to counteract the attrition resulting from chain intersections. Using the new method, samples were generated for chains of 800 links, a limit imposed by machine storage capacity. In principle the method could be carried even further if more storage were available.
Mean-square end-to-end lengths of the chains are expressed by the equation 〈rn2〉=anb,where n equals the number of links and a and b are constants.
Forbidden Band Systems in Nitrogen. I. The Vegard-Kaplan System in Absorption
Authors: Wilkinson P. G. 
Published: January 2005

Two bands belonging to the Vegard-Kaplan system (A3Σu+−X1Σg+) of nitrogen have been found in absorption in paths of 9- 13 meter-atmospheres. These bands at 1689 A (7–0) and 1726 (6–0) are incompletely resolved but show intensity alternation and distribution in agreement with theory. The positions of the band origins and each rotational line agree closely with those calculated from the known molecular constants.
Two other forbidden systems have also been found in absorption. These are the a′1Σu−−X1Σg+ (four bands at 1444 A, 1414 A, 1360 A, and 1331 A) and probably the Δu3−XΣg+1 (one band at 1484 A); they are about three times stronger than the observed Vegard-Kaplan bands The transition probabilities of the known forbidden systems in nitrogen are discussed briefly.
Microwave Spectrum, Molecular Structure of Vinyl Cyanide and a Summary of CC, CH Bond Lengths in Simple Molecules
Authors: Costain C. C. , Stoicheff B. P. 
Published: January 2005

The microwave spectra of six isotopic species of vinyl cyanide (acrylonitrile) CH2CHCN have been investigated. From the rotational constants it is shown that the molecule is planar, and has the following structural parameters (exclusive of the CH2 group):
r s ( C ≡ N )=1.163 7   A ,r s ( C − H )=1.086 3   A , r s ( C − C )=1.425 6   A ,∠ C = C − C =122 ∘ 37 ′ , r s ( C = C )=1.338 9   A ,∠ H − C − C =121 ∘ 44 ′ .
The quadrupole hyperfine structure was interpreted according to the asymmetric top treatment leading to a value of eqQ = —4.21±0.04 Mc/sec for the quadrupole coupling constant along the C≡N bond.
A table of the most accurate published values of CC and CH bond lengths is included. A graphical presentation of these results shows that the C–C, C=C, and C–H bond lengths vary linearly with the number of adjacent bonds.
Dielectric Relaxation in Some Two-Component Systems
Authors: Denney Donald J. 
Published: January 2005

Dielectric relaxation measurements were made on a number of two-component systems involving both associated and nonassociated liquids. A single dispersion was found for a mixture containing two alkyl halides. A mixture containing an alkyl halide and an alcohol showed two dispersion regions, the separate complex plane loci being similar in form to the dispersions found for the separate components. The locus of the dispersion in several alkyl halide-hydrocarbon mixtures was not significantly different from that in the pure halides although small deviations of unknown origin were observed at low frequencies. In the 1-propanol-2-methylpentane mixtures studied, the relative amplitudes of the multiple dispersions, characteristic of the alcohol, were little affected down to a concentration of 33 mole percent 1-propanol but had changed drastically at a concentration of 14 mole percent 1-propanol.
The results are discussed in terms of Schallamach's suggestions concerning the molecular nature of these mixtures and the size of the liquid region involved in the dielectric relaxation process.
He I Ground-State Wave Function of the Form ψ=f(r1)f(r2)g(r12)*
Authors: Green Louis C. , Stephens Cynthia , Kolchin Eleanor K. , Chen Carolyn Chandler , Rush Patricia P. , Ufford C. W. 
Published: January 2005

A variational trial wave function of the form ψ=f(r1)f(r2)g(r12) has been applied to the ground state of He I. In Sec. I, f(r) is taken to be an arbitrary function and g(r12) is taken as linear. The form of f(r) and the slope of g(r12) are chosen to yield the minimum energy. The energy, —5.79613RHehc, and the form of f are compared with the results of earlier work and with the results obtained with analytic functions. A table of f(r) and the charge distribution is given. The charge distribution is compared with that obtained from a Hartree-Fock wave function and the difference is discussed.
In Sec. II, f(r) is taken as an exponential and g(r12) is taken to be an arbitrary function. The coefficient in the exponent in f(r) and the form of g(r12) are chosen to yield the minimum energy. The energy, —5.78252RHehc, and the form of f are compared with the results obtained with analytic wave functions. The behavior of g is shown in a table and by its asymptotic series. The probable effectiveness of ψ if both f(r) and g(r12) are taken as arbi trary is discussed.
C13 and Deuterium Isotope Effects in the Photolysis of Methyl and Ethyl Bromide
Authors: Gordus Adon A. , Bernstein Richard B. 
Published: January 2005

Relative rates of formation of isotopic radicals in the photolysis of gaseous methyl and ethyl bromide have been measured. Photolyses (2537 A) were carried out in a large excess of cyclopentane. Methyl (or ethyl) radicals formed in the primary C–Br bond scission abstract H from cyclopentane to form methane (or ethane). For methyl bromide, the C12/C13 enrichment factor for the first fraction of the methane was 1.039±0.003. The corresponding factor for the α-carbon—Br rupture in ethyl bromide was 1.041±0.004. In the deuterium experiments, CH3Br—CD3Br mixtures in excess cyclopentane were photolyzed. The H/D fractionation factor (based on CH4/CD3H) was 1.41±0.01.
The difference in rates of formation of isotopic radicals is due to the difference in ultraviolet absorption coefficients of the isotopic alkyl bromides. At 2537 A the observed ratio of the extinction coefficient of CH3Br relative to that of CD3Br is 1.38±0.05.
Mutual Diffusion of Pairs of Rare Gases at Different Temperatures
Authors: Srivastava B. N. , Srivastava K. P. 
Published: January 2005

The coefficient of mutual diffusion of the binary gas mixtures Ne—A, A—Kr, and Ne–Kr has been determined at 0°, 15°, 30°, and 45°C. Diffusion is allowed to take place between two diffusion bulbs through a precision capillary tube and samples of gas are withdrawn from one bulb at different times and analyzed by a differential conductivity analyzer. From the experimentally determined values of the diffusion coefficient at different temperatures the unlike interaction parameters for the above gas pairs have been calculated by two different methods on the Lennard-Jones 12:6 model. These values of the force parameters are found to be in good agreement with those obtained from the usual combination rules and also from the thermal diffusion data following the method of Srivastava and Madan. These values are found to reproduce the experimental data on mutual diffusion quite satisfactorily.
With Kelvin's method, these data have also been utilized to calculate the self-diffusion coefficient of neon, argon, and krypton.
Characterization of Polymer Structures on Helical Point Nets
Authors: Hughes R. E. , Lauer James L. 
Published: January 2005

The extension of a polymer chain through many contiguous unit cells in a crystallite requires a discrete relationship between the crystallographic translation identity period and the structural identity period within the chain. This relationship can be uniquely expressed by describing the chain structure in terms of a helical point net.
Helical point nets can be defined in terms of standard screw axis nomenclature, using the translation-rotation operators pq. Integral values of the p's and q's produce all possible nets and their enantiomorphs. The net points thus defined have the property of identity through the operators pq.
The chain structures of polymers in the crystalline state can thus be defined simply in terms of the structure about one net point. Introduction of the restrictions of bond distances and angles limits the number of possible nets for a given translation identity period. One-atom and two-atom structures are considered in detail, and the extension to multiatom structures is indicated.
Nuclear Quadrupole Coupling in the Alkali Chloroiodides. II. Iodine Resonances
Authors: Yamasaki R. S. , Cornwell C. D. 
Published: January 2005

Frequencies are reported for m=±12↔±32 transitions of I127 nuclei in polycrystalline samples at 25°C of CsICl2, RbICl2, KICl2, KICl2·H2O, CsICl4, RbICl4, KICl4, KICl4·H2O, NaICl4·2H2O. The coaxial cavity super-regenerative oscillator (250–610 Mc/sec) used for these measurements is described. The average quadrupole coupling constants are —3110 Mc/sec for ICl2— and +3090 Mc/sec for ICl4—. These values are shown to be entirely consistent with resonance hybrid structures which had been selected previously for the discussion of the chlorine resonance data.
The coupling constants are used to estimate electron populations for valence orbitals of I and Cl, and, with certain assumptions, to find approximate MO's of LCAO form for the bonding electrons. The conclusion reached is that the attainment by iodine of higher valences in these ions is due more to transfer of charge to chlorine atoms than to promotion to higher orbitals of iodine. It appears that most of the covalent binding present arises from an MO in which an iodine p orbital is associated with a symmetry orbital made up of collinear sp hybrid orbitals of two attached chlorine atoms.
Dielectric Loss in 66 Nylon (Polyhexamethylene Adipamide)
Authors: Boyd Richard H. 
Published: January 2005

The dielectric loss in 66 nylon (polyhexamethylene adipamide) has been studied over a range of temperatures (—40 to 100°C) and frequencies (50 cps—70 Mc). The effects of radiation induced crosslinking and hydrogen bonding solutes were studied.
The principal dipole orientation absorption is similar to that in amorphous polar polymers in that it involves long chain segment rearrangements in the amorphous regions. However no temperature range was found in which the distribution of relaxation times is independent of temperature, thus there is no time-temperature superposition. The effect of crosslinking allows a semiquantitative estimate of the segment length of about 15 amide groups to be made. The plasticizing effect of the solutes and their effect on the activation energy for dielectric absorption and the relaxation time distribution is discussed. The static dielectric constant associated with the long chain segment rearrangement mechanism is derived. From its temperature and solute dependence, the equilibrium disappearance of this mechanism at low temperatures is inferred. This disappearance seems to be associated with increased interchain coupling. The solute dependence also shows the presence of tightly bound solute molecules at the amide groups.
A weak absorption occurring at lower temperatures (—10°C and 100 cps) is also observed.
Comparison of the dielectric absorption with mechanical absorption is made.
Rates of Reaction of Hydrogen with Iodine
Authors: Sullivan John H. 
Published: January 2005

The rates of reaction of hydrogen with iodine have been measured at 633.21°, 666.79°, 710.33°, and 737.93°K with at least a tenfold variation in the hydrogen and iodine concentrations at each temperature. The data have been treated considering the elementary reactions to be I2⇌2I(1)H2+I2→2HI(2)HI→H2+I2(3)I+H2→HI+H(4)H+HI→H2+I(5)H+I2→H2+I(6)I+HI→I2+H.
This classical reaction has long been considered to consist solely of the simple bimolecular reactions (1) and (2). However, the atom mechanism, reactions (3) to (6), is shown to account for 10% of the over-all reaction at 633° and 27% at 738°K when the iodine pressure is one-half atmosphere. The three independent constants k1, k3, and k4/k5 in (mole/cc)—1 sec—1, are given by log10(k1/T½) = 12.78–40740/4.575T, log10(k3/T½) = 12.75–33440/4.575T, and k4/k5 = 0.07, 0.082, 0.117, 0.125 at the experimental temperatures 633°, 667°, 710°, and 738°K.
Polymers and Theory of Numbers. IV. The Problem of Weak and Strong Links in Degradation
Authors: Pathria R. K. , Nanda V. S. 
Published: January 2005

The technique employed in our earlier work is extended to treat the degradation of a monodisperse polymer system consisting of N chains such that each chain has two types of links of unequal strength, distributed randomly over its length. An expression for the size distribution in the degraded material is obtained in a closed form which is convenient for numerical computations. Further, the weight average chain length is expressed exactly in the form of a definite integral from which the particular cases follow in a straightforward manner. Exact expressions are also derived for the higher moments of distribution.
Finally, it is shown that the treatment given here is quite general and is capable of ready extension to the case of a polymer system in which the member chains possess more than two types of links.
Nitryl Chloride Molecular Constants from Microwave Spectrum Analysis
Authors: Clayton Lorimer , Williams Quitman , Weatherly T. L. 
Published: January 2005

The microwave spectrum of NO2Cl has been studied in the region 25 000 to 40 600 Mc and an analysis made of the J = 2→3 and 3→4 transitions. The following molecular constants were obtained. NO2Cl35NO2Cl37Rotational constants      (Mc)      A13 250    13 250          B5173.85019.0      C3721.13640.4Asymmetry parameter      κ−0.6951−0.7131Quadrupole coupling constants      (Mc)      χaa−94.70−74.58      χbb52.441.3      χcc42.333.3
The structural parameters obtained from these are d (Cl–N) = 1.83 A, d (N–O) = 1.21 A, and O–N–O angle 129.5°. The dipole moment calculated from the Stark effect is 0.53 Debye. Implications of the aforementioned results are discussed.
General Collision Theory Treatment for the Rate of Bimolecular, Gas Phase Reactions
Authors: Eliason Morton A. , Hirschfelder Joseph O. 
Published: January 2005

A collisional approach, somewhat similar to the Wang-Chang and Uhlenbeck treatment for the transport properties of polyatomic molecules, is used to obtain a general expression for the rate of a bimolecular chemical reaction in terms of reaction cross sections.
Specialization is then made to the case where a Maxwell-Boltzmann velocity distribution may be assumed for the reactants. This leads to a Laplace transform relation between the rate constants for reaction of molecules in definite internal quantum states and the reaction cross sections. The further assumption of a Boltzmann distribution among the internal energy states of the reactant molecules then leads to a rate equation of the usual form and to an explicit expression for the single over-all rate constant. This expression is used to rederive the results of the old ``simple'' collision theories.
Finally, a collisional approach is used to rederive the usual rate expression of the Eyring theory of absolute reaction rates. The rather drastic approximations which seem to be necessary for such a derivation are pointed out and discussed.
Effect of Conjugation, Hyperconjugation, and Steric Hindrance on Methyl Affinities
Authors: Binks J. H. , Szwarc M. 
Published: January 2005

The mechanism of the addition of radicals to aromatic and olefinic compounds is discussed in terms of a potential energy diagram which explains the linear relation between localization energy and the logarithm of methyl affinity per reactive center. It is pointed out that such a linear relation is expected for series of compounds, each having the same type of reaction center, e.g., C–C=C–Hin a series of aromatic hydrocarbons or C=C–H–Hin a series of substrates like ethylene, styrene, butadiene, etc.
The relation between the slope of such a line and the nature of the reactive center is discussed.
The foregoing treatment is extended to explain the effects caused by hyperconjugation, and an excellent agreement is found between theory and experiment.
It is shown that compounds having a methyl substituent on the reactive center are less reactive. This inhibitory action of the methyl substituent is explained in terms of steric hindrance, and it is shown that for a particular center the inhibitory effect amounts to a constant factor independent of the original reactivity of the center. Still greater steric effects are caused by phenyl groups and by two methyl substituents located on a reactive center.
The utility of this ``blocking'' technique for determining the most reactive centers is pointed out.
Note on the Normal Stress Effect in the Solution of Rodlike Macromolecules
Authors: Kotaka Tadao 
Published: January 2005

Three components of normal stresses in a solution of rodlike macromolecules are calculated on the basis of the general theory of irreversible processes of macromolecular solutions developed by Kirkwood. The results are expressed in expansion series of even powers of the rate of shear and are explicitly given to their fourth powers.
When the hydrodynamic interaction is not taken into account, two components of the normal stresses perpendicular to the direction of flow identically vanish, while, by the introduction of this interaction, they appear. The action of normal stresses is still mainly ``pull'' in the direction of flow as in the free-draining case.
On the Dynamical Theory of Diffusion in Crystals. III. Some Model Calculations and Relation to Continuum Theory
Authors: Lawson A. W. , Rice Stuart A. , Corneliussen Roger D. , Nachtrieb Norman H. 
Published: January 2005

Some simple models are considered which permit exact evaluation of the various dynamical parameters of the theory of crystal diffusion previously proposed. The models considered suggest that: (a) The jump frequency is insensitive to the normal mode modifications produced by the adjacent vacancy. (b) There is considerable relaxation about a vacancy. (c) The volume of formation of a vacancy is related to the molar volume by ΔV*≈V/(γG—⅓), where γG is the Gruneisen constant.
The restrictions of the models are briefly analyzed, and the mass dependence proposed by Bak and Prigogine is compared with the quasi-equilibrium model and the discrepancy discussed.
Steady-State Studies by EPR on the Photodissociation of Some Alkyl Hydroperoxides
Authors: Piette L. H. , Landgraf W. C. 
Published: January 2005

A new steady-state method for studying dynamic photochemical processes by EPR is discussed. The EPR spectra of some photolysed alkyl hydroperoxides are obtained and the free radical intermediates identified as alkoxy radicals.
Recombination rate constants of ∼105 liters/mole sec were obtained with activation energies of ∼4 kcal. A new EPR spectrometer with improved sensitivity capable of photoirradiation in situ and variable temperatures is discussed.
Mayer's Ionic Solution Theory Applied to Electrolyte Mixtures
Authors: Friedman Harold L. 
Published: January 2005

For solutions of a mixture of two electrolytes with a common ion, the characteristic free energy function is ΔmGex, the change in excess free energy on forming the solution from solutions of the single electrolytes. This is closely related to ΔmS, where S is the cluster integral sum of the Mayer theory. For systems that conform to Harned's rule the contributions of most of the cluster integrals to ΔmS are negligible. The form of the principle contribution to ΔmS depends on whether the two electrolytes have the same charge type (symmetrical mixtures) or not.
The equations for symmetrical mixtures which nearly conform to Harned's rule are developed in detail, first for the general case in which the components of the potential of average force are arbitrary and then for the special case of hard sphere ions, designated as the primitive model for electrolyte solutions. The leading term of ΔmS is determined by the difference in short-range interaction of pairs of ions of the same charge and does not depend at all on the common ion. Another general result is that ΔmGex/I2 does not vanish as I→0, as has sometimes been expected on the basis of the Brønsted principle of specific ion interaction, but approaches a finite value in a way that is governed by a higher-order limiting law.
Comparison with experiment is made on the basis of the primitive model. The results are roughly consistent with the free energy effects in alkali metal chloride mixtures if it is assumed that the effective radii of the alkali metal ions are about double their crystal radii.