bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
The Configuration of Real Polymer Chains
Authors: Flory Paul J. 
Published: January 2005

The average configuration of polymer molecules in solution is markedly influenced by the obvious requirement, ordinarily disregarded in problems relating to molecular configuration, that two elements of the molecule are forbidden from occupying the same location in space. The influence of spatial ``interferences'' between different segments of the molecule on its average configuration has been investigated by statistical and thermodynamic methods.
It is shown that if the average linear dimension of a polymer chain is to be taken proportional to a power of the chain length, that power must be greater than the value 0.50 previously deduced in the conventional ``random flight'' treatment of molecular configuration. This power should approach 0.60 for long chain molecules in good solvents. With increase in size of the solvent molecule, the influence of interference on molecular configuration diminishes, vanishing entirely in the extreme case of a solvent which is also a high polymer. The effect of a heat of interaction between solvent and polymer may also be incorporated quantitatively in the theory. A positive heat of mixing (poor solvent) tends to offset the expansive influence of interference, and the exponent referred to above tends to approach 0.50. The results are of foremost significance in the interpretation of the intrinsic viscosity and its dependence on the polymer constitution and on the solvent. It is pointed out that the spatial dimensions of the irregularly coiled polymer molecule cannot be correlated directly with hindrance to rotation about chain bonds, unless the expansion of the configuration due to interference and the effects of the heat of dilution are first of all taken into account.
The Mercury Photosensitized Polymerization of Cyclopropane
Authors: Gunning H. E. , Steacie E. W. R. 
Published: January 2005

An investigation has been made of the polymerization of cyclopropane with mercury (3P1) atoms in a static system over the pressure range from 1–400 mm at 30°C. The only important product of the reaction is a liquid polymer with the formula (C3H6)n, where n is probably about 6. Small amounts of other products, of low molecular weight, are present at initial pressures below 10 mm. Data are presented which show that propylene is formed only at low initial pressures, suggesting its origin from the collision of trimethylene biradicals with the wall.
The over-all rate of consumption of cyclopropane becomes independent of initial pressures above 40 mm. The quantum yield of cyclopropane disappearance in the complete quenching region is 0.136.
A mechanism is proposed for the polymerization involving the initial formation of an energy-rich trimethylene biradical by the reactionC+Hg(3P1)→R1*+Hg(1S0).The activated radical can then either reform cyclopropane upon collision or form a higher biradical: R1*+C→2C,R1*+C→R2*,etc.,where C = cyclopropane, R1 = ·(CH2)3·, and R2 = ·(CH2)6·. Chain termination will occur when the polymer biradical can no longer furnish sufficient energy to break the C–C bond in cyclopropane. The radical will then stabilize itself by a proton shift. On the basis of the above mechanism, combined with the analytical data, reaction (2) must be at least 43 times faster than reaction (3).
Evidence is also presented for the fact that cyclopropane does not react with the H atoms formed by the collision of Hg(3P1) atoms with hydrogen.
Some Magnetic Properties of Manganese-Activated Luminescent Solids
Authors: Johnson Peter D. , Williams Ferd E. 
Published: January 2005

The specific susceptibilities of a series of manganese-activated zinc fluoride phosphors and their components have been measured. The unexcited manganese was found to be in the divalent 6S state. There is evidence for exchange demagnetization of adjacent paramagnetic activator ions.
The change in paramagnetic susceptibility with excitation, predicted by Williams and Eyring [F. E. Williams and H. Eyring, J. Chem. Phys. 15, 289 (1947)] to explain the long non-temperature-dependent lifetimes of the emitting states of luminescent solids containing paramagnetic activators, has been measured for manganese-activated zinc fluoride. Radiation from a high voltage discharge lamp was used to excite the phosphor in a vacuum magnetic balance having a sensitivity of 10−6 dyne per mm scale deflection. The observed change in susceptibility corresponds to a decrease of the order of magnitude of one Bohr magneton per excited activator ion.
The Effect of Non-Homogeneity of Molecular Weight on the Scattering of Light by High Polymer Solutions
Authors: Brinkman H. C. , Hermans J. J. 
Published: January 2005

The general theory of the turbidity of a mixture of many components is applied to a solution of homologous polymers.
It is found that the concentration dependence of the turbidity is intimately related to that of the osmotic pressure. The molecular weight distribution does not have any influence on the concentration dependence of the turbidity.
The Vapor Pressure, Orthobaric Liquid Density, and Critical Constants of Isobutane
Authors: Beattie James A. , Edwards David G. , Marple Stanley 
Published: January 2005

The vapor pressures and orthobaric liquid densities of isobutane (propane−2-methyl) were measured from 30° to 125°C. The equation log10p (normal atmos.)=4.31269–1126.71/T  (T=t∘C (Int.)+273.13)gives a fair representation of the vapor pressures.
The critical constants of isobutane are determined by the compressibility method. They are: tc=134.98±0.05°C (Int.), pc=36.00±0.05 normal atmos., vc=0.263 liters per mole (4.53 ml per g), dc=3.80 moles per liter (0.221 g per ml). The uncertainty in the critical volume and density is 2 percent.
The Quantum Mechanics of Chemical Kinetics of Homogeneous Gas Phase Reactions I. General Considerations
Authors: Golden Sidney 
Published: January 2005

From the zeroth order Born-Oppenheimer approximation to the wave functions of a molecular system and the first order time-dependent perturbation theory of quantum mechanics it has been possible to deduce: (1) the adiabatic hypothesis; (2) the dependence of the rate of homogeneous gas phase chemical reactions upon the composition of reaction mixtures; (3) the condition for zero net rate of reaction, which corresponds precisely to the statistical mechanical condition for equilibrium; (4) the dependence of the chemical reaction rate upon the temperature.
Heuristic considerations transcribe the quantum mechanical result into terms of the collision theory and the activated complex theory of chemical reactions.
The Relative Reaction Velocities of Isotopic Molecules
Authors: Bigeleisen Jacob 
Published: January 2005

The rate constants for competitive reactions of isotopic molecules are considered from the theory of ``absolute rates'' and the collision theory. Formulas are derived for the ratio of the rate constants and the difference in the activation energies for reactions of isotopic molecules. The difficulties in the a priori calculation of relative rates are pointed out and discussed.
In general the rate constant for the light molecule will be greater than that of the heavy molecule. It is shown that the maximum ratio in the rates occurs when the isotopic atom is essentially free in the activated complex. The conditions for the rate constant of the heavy molecule to exceed that of the light one are formulated.
It is shown that the difference in activation energies covers the range from zero to the difference in the differences in the zero-point energies of the reacting molecules and their respective activated complexes.
The Structure of Hexamethylcyclotrisiloxane as Determined by the Diffraction of Electrons on the Vapor
Authors: Aggarwal Eleanor H. (Weller) , Bauer S. H. 
Published: January 2005

Hexamethylcyclotrisiloxane vapor has been shown to have a structure incorporating a planar ring with larger oxygen valence angles (125±5°) than silicon valence angles (115±5°); the methyl groups extend above and below the plane of the ring, their equilibrium bond positions making a probable angle of 112±6° with silicon, the temperature motion of the methyl groups allowing an average change in the interatomic distances involved of about 0.09A, as compared with the normal temperature motion change of about 0.03A. The Si–O distances are 1.66±0.04A and the Si–C distances are 1.88±0.04A.
The shortness of the Si–O distance suggests a larger ionic character of the bond than that indicated by the electronegativity table.
Solubility Relations in Ternary Solid Solutions of Ionic Compounds
Authors: Wagner Carl 
Published: January 2005

The variation of the solubility of a solute due to the presence of a second solute in a solid ionic compound as solvent is investigated theoretically with the aid of the ideal law of mass action. Ions of the solvent in interstitial positions, cation and anion vacancies, quasi-free electrons, and electron holes are to be taken into account in the same manner as the constituents of conventional chemical systems. The theoretical conclusions are illustrated by experimental data, however, qualitatively rather than quantitatively.
The solubility of lead chloride in solid silver chloride is decreased by presence of cadmium chloride. The solubility of iodine (or cupric iodide) in cuprous iodide is likewise decreased by presence of cadmium iodide. The behavior of the corresponding bromide system is analogous. Conversely, gallium oxide increases the solubility of zinc in zinc oxide. The phenomena to be expected in lead sulfide as solvent are more complicated, since this substance can dissolve both excessive lead and excessive sulfur.
The oxidation rate of nickel is increased by presence of chromium and manganese, whereas the chlorination rate of silver is decreased by presence of lead and cadmium chloride.
Chemical Effects Accompanying the Decay of Mn51
Authors: Burgus W. H. , Kennedy J. W. 
Published: January 2005

An investigation has been made of the chemical forms assumed by Cr51 when it is produced by positron decay of Mn51 under a variety of conditions. The data have shown that the oxidation state of the parent Mn51 plays an important role in determining the oxidation state of daughter Cr51. By variation of experimental conditions some information has been obtained regarding the types of chemical reactions undergone by the Cr51. These reactions have also been shown to play important roles in determining the ultimate chemical form of daughter Cr51.
The complexity of the factors determining the chemical forms of Cr51 after Mn51 decay has been pointed out, and possible explanations of some of the observed phenomena have been suggested. We believe the results are consistent with the hypothesis that appreciable ionization in the valence shell accompanies the beta-decay process.
Incidentally it has been demonstrated that the manganese isotope of 44-min. half-life (Mn51) decays to the chromium isotope of 26-day half-life (Cr51).
The Intensities of Several of the Infra-Red Absorption Bands of Cyanogen and Cyanogen Chloride
Authors: Nixon Eugene R. , Cross Paul C. 
Published: January 2005

Measurement of the absolute intensities of several infra-red absorption bands of cyanogen and cyanogen chloride gives the following values in cycles per cm at N.T.P. CyanogenBandIntensity2150 cm−190×1010Cyanogen chlorideBandIntensity714 cm−117×10102214 cm−1220×1010
Values of the variation in bond moments with change in bond length are calculated on the basis of bond moment additivity. This leads to widely different values of this derivative for the CN bond in the two molecules.
The infra-red spectrum of cyanogen chloride from 2 to 20 microns is reported.
Oxygen and Nitrogen Isotope Effects in the Decomposition of Ammonium Nitrate
Authors: Friedman Lewis , Bigeleisen Jacob 
Published: January 2005

The isotopic composition of the products of the controlled thermal decomposition of ammonium nitrate has been studied. It has been found that small amounts of water are necessary to initiate the decomposition of ammonium nitrate. N15H4NO3 has been found to yield exclusively the isomer N15N14O. Some inferences are drawn from this observation regarding the mechanism of the reaction.
Oxygen and nitrogen isotope effects accompanying the decomposition have been studied with material of ``natural'' isotopic composition. Satisfactory agreement is found between the experimental results and theoretical calculations.
A method for the isotopic analysis of nitrates for O18 is outlined.
Transport Properties of Dense Media. I. Thermal Diffusion in Isotopic Mixtures of Gases
Authors: Robb W. L. , Drickamer H. G. 
Published: January 2005

Based on Meixner's thermodynamics for irreversible processes, and the work of Haase, an equation for the thermal diffusion ratio α, which can be evaluated from the equation of state, is presented.
Using van der Waals' equation, α's are calculated in the critical region and compared with data for ethane-xenon. The equation reproduces all the essential features of the experimental results.
Calculations made for a mixture of isotopes indicate that the effect of pressure on α cannot be attributed to selective clustering.
Collision Cross Sections of Hydrogen and of Deuterium
Authors: Amdur I. , Kells M. C. , Davenport D. E. 
Published: January 2005

Total collision cross sections have been measured for hydrogen atoms, with energies between 300 and 800 ev, scattered in room temperature hydrogen, and for deuterium atoms, with energies between 500 and 1150 ev, scattered in room temperature deuterium. The H–H2 cross section has a pronounced maximum at 600 volts indicating the presence of inelastic scattering. In the case of D—D2 there is a similar effect, less pronounced, at about 800 volts.
Classical theory has been used to evaluate the repulsive potentials for the two systems on the assumption that smooth curves through the experimental results represent elastic cross sections, and that the atoms and molecules are mass points whose interaction forces are spherically symmetrical. For H–H2, the present potential has been combined with one previously obtained, and the results represented by V(r)=[0.708 exp(−29.9r2)+0.0607 exp(−0.942r2)]×10−10 ergfor r between 0.27 and 0.68A. The relation for D—D2 is V(r)=4.59×10−11exp(−5.17r2) ergsfor r between 0.29 and 0.56A. The D—D2 potential is considerably larger than that for H–H2 for r between 0.29 and 0.56A, but the difference decreases markedly as r increases. It is suggested that the apparent difference in the potentials may result from the assumption of spherical symmetry which, even on a relative basis, does not exist in the present case because of the difference in the nuclear statistics of H2 and D2.
Energy Levels and Thermodynamic Properties of the Internal Rotator
Authors: Halford J. O. 
Published: January 2005

To facilitate the calculation of the thermodynamic properties of internal rotators lying outside the limits of available tabulations, methods of determining the energy levels are studied for the purpose of finding the most expeditious route to accurate results. It proves to be unnecessary in any case to calculate many levels from the wave mechanics. A partition function is set up in terms of the correct ground state and a series of approximate levels derived from the old quantum theory, and this is corrected to constancy by the successive substitution of correct levels, starting with the first excited state. A set of levels obtained in this way which gives the correct partition function always leads to correct values of all the thermodynamic properties.
To obtain accurate energy levels, the continued fractions of Koehler and Dennison are recommended as most convenient.
The Mercury Photosensitized Reactions of Methyl Alcohol
Authors: Phibbs M. K. , Darwent B. deB. 
Published: January 2005

The mercury photosensitized reactions of methyl alcohol have been investigated at pressures of 30 and 100 mm Hg and over a temperature range from 25° to 500°C. Below 400°C the products are almost entirely hydrogen and ethylene glycol and small amounts of carbon monoxide, formaldehyde and methane. It has been established that the primary step in the reaction mechanism is Hg(3P1)+CH3OH→CH2OH+H+Hg(1S0). There is considerable supporting evidence that the alternative split into H+CH3O does not occur.
Above 400°C the rates of production of CH2O and CO become significant and increase with rising temperature which has been explained by the fact that the decomposition of the CH2OH radical is taking place. An activation energy of 29 kcal. has been obtained for this decomposition reaction.
Argon Repulsive Potential from Collision Cross-Section Measurements
Authors: Amdur I. , Davenport D. E. , Kells M. C. 
Published: January 2005

The total collision cross section has been measured for argon atoms, with energies between 300 and 1100 electron volts, scattered in room temperature argon. In the region between 700 and 1000 volts, the cross section shows a maximum indicative of inelastic scattering, probably due to ionization by the high energy atoms.
The repulsive potential between two argon atoms has been evaluated from elastic collision cross sections (deduced from observed values of the total collision cross section) using a method which takes account of the greater probability of small angle scattering by averaging the cross section over the length of the scattering path. The results may be expressed by V(r)=4.61×10−11/r4.33 ergsor V(r)=3.66×10−8 exp(−6.88r12) ergsfor values of r between 1.37 and 1.84A.
Isotope Effect in the Vibrational Frequency Spectra and Specific Heats of Sodium Hydride and Deuteride
Authors: Sayre Edward V. , Beaver Jacob J. 
Published: January 2005

The prediction by the Born and von Karman lattice dynamics theory of the effect of isotopic substitution on crystal vibration frequencies has been determined by calculation of frequency spectra of sodium hydride and sodium deuteride. In each case 6690 of the lattice frequencies have been calculated with the aid of I.B.M. punched card computers. They have been chosen and weighted in such a way that the whole frequency spectra of the crystals are uniformly sampled. Both spectra exhibit acoustical branches which are nearly identical and optical branches, the frequencies of which are essentially in the ratio of the square root of two. In both cases, the optical branches extend somewhat uniformly over very broad ranges of frequencies, in marked contrast to the estimation of optical frequencies as a few monochromatic lines.
The molar heat capacities of these two compounds have been determined experimentally between 60 and 90°K with an adiabatic calorimeter and compared to corresponding curves calculated from the frequency spectra. The theoretical and experimental sets of curves possess the same general form. In both cases the deuteride values are higher than the hydride values, with the curves of the two substances diverging with increasing temperature. The theoretical curves, however, are nearly uniformly displaced from the experimental curves by about ten percent, an effect which could have arisen from an error in the repulsive force constants.
The Determination of Energy Levels from Thermodynamic Data. I. The Effect of Experimental Error
Authors: Blade Ellis , Kimball George E. 
Published: January 2005

The problem of calculating energy levels from thermodynamic data can be reduced to that of inverting the Laplace transform, for which several procedures have been developed. Using the method of Widder, we show that the resultant calculated energy level density function consists of a series of broadened peaks, whereas in the true density the levels are represented by a series of Dirac delta-functions.
Alternatively, if the distribution of the energy levels is specifically assumed to be composed of discrete energies, the calculation reduces to the moment problem.
In either case the calculation is shown to have an inherent ``resolving power,'' in that levels within a certain closeness cannot be distinguished as separate. By a generalization of this idea, it is shown that the computation can lead to a knowledge of the over-all density of energy levels within a given region, but cannot reveal their exact locations.
Proton Nuclear Magnetic Resonance Studies in KH2PO4, KH2AsO4, NH4H2PO4, and NH4H2AsO4
Authors: Newman Roger 
Published: January 2005

Studies have been made of the proton magnetic resonance absorption at 30 Mc/sec. in KH2PO4, KH2AsO4, NH4H2PO4, and NH4H2AsO4. Both line shapes and relaxation times have been measured from 87°K to 293°K.
The potassium salts show closely similar magnetic resonance properties. Their relaxation times show relatively small variation in the temperature interval studied. The characteristic times derived therefrom do not obey any simple exponential law in the reciprocal temperature. Single crystals of KH2PO4 do not seem to show anisotropy in the relaxation time. A formula is given which relates the anisotropy of the motion of magnetic dipoles to the anisotropy of transverse local field variation.
The ammonium salts show two minima in their relaxation time vs. temperature curves. One minimum corresponds to a temperature at which the acid hydrogens are the most effective relaxation agent and the other to a temperature where the ammonium ion hydrogens are most effective. The line shapes are also of a composite character. This is most clearly shown below 100°K where the absorption lines appear to be super-positions of the broad NH4 line for which that of NH4Cl is typical and the narrow line found in KH2PO4 or KH2AsO4.
Possible interpretations of the experimental results are discussed with reference to the motions of the protons in these crystals.
The Kinetics of Phase Transitions in Binary Systems
Authors: Reiss Howard 
Published: January 2005

A kinetic theory of phase transitions in two-component systems is presented which is applicable to the transitions, vapor to liquid and liquid to liquid. The rate of the transition is characterized by a two-dimensional vector which can be used in conjunction with the equation of continuity to develop a partial differential equation which determines the kinetics of the process.
A new type of energy surface is introduced, and an investigation of its salient features enables one to simplify the solution of the differential equation mentioned above. This purely kinetic treatment makes possible the evaluation of the unknown coefficient found in the older quasi thermodynamic treatment of transition rates in two component systems.