bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the Cell Method to the Statistical Thermodynamics of Solutions. II. Experimental
Authors: Mathot V. , Desmyter A. 
Published: January 2005

In connection with the theory of solutions proposed by Prigogine and Mathot [J. Chem. Phys. 20, 49 (1952)], total vapor pressures and volume changes on mixing have been measured for the systems: CCl4–C(Me)4  IC6H12–C(Me)4  IIC6H6–C(Me)4  III.Volume changes only for the systems: CCl(Me)3–CCl4  IVCCl2(Me)2–CCl4  VCCl3(Me)–CCl4  VIC(Me)3OH–CCl4  VII.
For the first three systems I, II, and III, one observes a positive excess free energy (positive deviations to the Raoult law) together with a negative excess volume (contraction on mixing), whereas for the last four IV, V, VI, and VII there is a gradual passage from negative (IV) to positive (VII) excess volume. These results are discussed in terms of the molecular interactions AA, BB, and AB. Reasonable agreement is observed between Prigogine and Mathot's theory and experiment.
A Molecular Theory of Stress Relaxation in Polymeric Media
Authors: Scott K. W. , Stein R. S. 
Published: January 2005

The application of the kinetic theory of rubber elasticity to the description of the relaxation of cross-linked networks is only permissible in cases where the rate determining process is slow compared to the rate of diffusion of the polymer chains. Relaxation resulting from chemical reactions causing breaking of network crosslinks and formation of new crosslinks is a process of this type.
In this paper, a differential equation is proposed which describes the rate of relaxation in terms of the rates of the molecular processes. A simplified solution of this equation is given, and the consequences of the solution are discussed.
The Determination of the Fluorescence Lifetimes of Dissolved Substances by a Phase Shift Method
Authors: Bailey E. A. , Rollefson G. K. 
Published: January 2005

The lifetimes of fluorescent substances are determined by exciting the fluorescence with light modulated at a high frequency and measuring the difference in phase between the exciting light and the resulting fluorescence. The exciting light is modulated by an ultrasonic standing wave in a liquid which causes the latter to act as an intermittent diffraction grating. Photomultiplier tubes are used to pick up the exciting and fluorescent light. Tuned circuits are used to isolate a single harmonic of the signal from the phototubes and the phase shift determined by comparison with a calibrated phase shifting circuit. The phase angle φ is related to the lifetime by tanφ=ωτ. In which ω is 2π times the frequency of modulation and τ is the lifetime of the excited state. The data show that lifetimes can be determined with a precision of 1 to 2×10−10 second.
The lifetimes of acridone in neutral solution (saturated to 10 percent saturated) and quinine sulfate (4×10−6 to 4×10−5M) in 0.01 M nitric acid are independent of the concentration. The values found are acridone 1.59±0.01×10−8 second, and quinine sulfate 2.28×0.02×10−8 second. The lifetime of fluorescein in 0.005M potassium hydroxide increases with concentration over the range 10−6 to 5×10−4M. This fact can be explained by assuming that some of the fluorescent light is absorbed and re-emitted. The lifetime of fluorescein extrapolated to zero concentration is 4.5±0.1×10−9 second.
Empirical Considerations of Entropy. III. A Structural Approach to the Entropies of Aqueous Organic Solutes and Complex Ions
Authors: Cobble James W. 
Published: January 2005

A method for estimating the entropy of complex aqueous organic solutes and related species has been developed by a structural extension of a method of Powell and Latimer for simple solutes. The agreement between calculated and observed values is, in general, good, although systematic deviations begin to occur for very complicated and large solutes. The method is extended to the calculation of the entropies of charged organo-metallic complex ions with good success, and possible applications to systems of biological interest are indicated.
Subsequent to the development of the general method for estimating the entropies of aqueous solutes, an empirical equation is also given for calculating gaseous entropies of both inorganic (ionic) and organic molecules from their structures.
Hindered Rotation Involving Two Asymmetric Groups
Authors: Burkhard Donald G. 
Published: January 2005

The wave equation is derived for two partially asymmetric tops rotating about a common axis and subject to an arbitrary hindering potential. Matrix elements of the Hamiltonian are evaluated using the hindered-rotation wave functions derived by Koehler and Dennison on the basis of a simplified model.
Evaluation of matrix elements involving the Eulerian polar angle is carried out by obtaining and making use of the factorizations of the symmetric-top wave equation.
Some Molecular Constants of HC13N
Authors: Kagarise R. E. , Rix H. D. , Rank D. H. 
Published: January 2005

The 003, 103, and 004 rotation-vibration bands of HC13N have been observed in the photographic infrared region of the spectrum. In addition, the Raman spectrum of the liquid was obtained with sufficient dispersion to measure the isotopic shift of ν1. Values are given for B′, B″, D′, and D″ of the three infrared bands as well as for α1 and α3.
The average values of B″=1.44006 is in excellent agreement with B″=1.44008 calculated from microwave data and the velocity of light as c=299,776 km/sec.
Microwave Spectrum, Structure, Dipole Moment, and Nuclear Quadrupole Effects in Vinyl Chloride
Authors: Kivelson Daniel , Wilson E. Bright , Lide David R. 
Published: January 2005

The microwave spectra of nine isotopic species of vinyl chloride have been measured and analyzed, yielding moments of inertia from which a molecular structure was calculated. The bond lengths found are (in A) C=C 1.332, C–Cl 1.726, average C–H 1.08. The bond angles are C2C1Cl 122°, C2C1H1 124°, C1C2H3 (cis to Cl) 121°, C1C2H2 (trans to Cl) 120°. Planarity was assumed.
The chlorine nuclear quadrupole hyperfine lines were reexamined. From the data for several isotopic species it was shown that the C–Cl bond direction is within five degrees of a principal axis of the field gradient tensor. The lack of cylindrical symmetry of the field gradient about the C–Cl bond was confirmed. This is evidence that the observed shortening of the C–Cl bond is at least in part due to conjugation with the C=C double bond and not solely to hybridization effects.
The component of dipole moment along the a inertial axis was found to be 1.42±0.02 D.
Inhomogeneous Field Method for the Study of Large Polarizable Particles
Authors: Prock Alfred , McConkey Gladys 
Published: January 2005

An inhomogeneous electric field applied to a solution of polarizable particles causes a movement of the particles toward the region of lowest potential energy. The resulting creation of concentration gradient can be observed, for large particles, by a method involving measurement of capacitance change of a cylinder containing a solution of the polymer.
This effect has been measured in terms of weight average molecular weight; the system investigated is polystyrene in cyclohexane. The basic Debye theory relating capacitance change at equilibrium to weight average molecular weight has been extended to make it applicable to experimental conditions found to be necessary in work with random coil polymers. The theory is substantiated by the agreement obtained between molecular weight calculated by this method and by the method of light scattering.
The polarizability of the particles present determines not only their equilibrium position, but also the rate at which they move. This idea is the basis of a theory presented here relating the time dependence of capacitance change to molecular weight distribution of a given sample. Another theory presented here shows how the shape of the curve for capacitance change as a function of applied field strength is related to the moments of the weight distribution function of the polarizable substance.
On Chemical Reactions in Free Molecule Flow
Authors: Chambré Paul L. 
Published: January 2005

This paper deals with heterogeneous chemical reactions within systems in which the relevant geometric dimensions are small compared with the mean free path of gas molecules. A typical example can be found in a surface reaction occurring at moderate pressures inside the pore of a catalyst with a radius of several angstroms.
Specific problems of this type have in the past been formulated, subject to the well-known limitations of ordinary diffusion theory, in terms of differential equations for the species concentrations. This in turn supposes that the reaction pattern is dependent on local conditions. A more general and exact formulation given in the following shows that the concentration of a molecular species at a point is determined by the concentration distributions of all species stemming from the entire system. Thus one is led to a formulation in terms of integral equations. In an application of the theory the validity of the conventional differential equation approach is investigated and is found to yield satisfactory results only under certain limiting conditions.
Infrared Absorption Spectrum of the Silicate Ion in the Garnet Structure
Authors: Wickersheim K. A. , Lefever R. A. , Hanking B. M. 
Published: January 2005

Infrared absorption bands at 912 and 861 cm−1 exhibited by some crystals of yttrium iron garnet and similar bands exhibited by some rare earth iron garnet crystals have been identified as vibrational fundamentals of a silicate ion impurity. The bands are assigned to split components of a triply degenerate vibration (ν3) of the tetrahedral SiO4 ion. The splitting of this vibration into a nondegenerate and a doubly degenerate vibration is attributed to distortion of the silicate ion along an S4 axis by the garnet structure. Integrated absorption measurements identify the 912 cm−1 band as the nondegenerate component.
Information obtained from the isolated silicate ion in yttrium iron garnet is used to interpret the spectra of the silicate garnets. Complete removal of the degeneracy of vibrations arising from ν3 is observed in the silicate garnets, suggesting that the majority of the silicate ions possess a local symmetry lower than that predicted by the assigned space group Ia3d—Oh10.
Streaming Birefringence and Optical Relaxation Time of Vanadium Pentoxide Sols
Authors: Foreman William T. 
Published: January 2005

Maxwell constant and optical relaxation time is studied for V2O5 sols having concentrations which range from 0.01 to 0.1 volume percent using mercury green, 5461 A, and mercury red light, 6000 to 6800 A. These quantities were measured in a device which sheared the sols between two coaxial discs, that is, in a direction which corresponds to the radial one in a Couette device. The Maxwell constant ranged from about 1.5×10−2 to about 4.5×10−6 cm2/dyne for freshly made sols and from about 8.0×10−2 to 2.9×10−5 cm2/dyne for the same sols when they were 29 days old. It is shown that the Maxwell constant for these sols was an exponential function of concentration and that the optical relaxation time and Maxwell constant could be related for them. Because the Maxwell constant is an exponential function of sol concentration, it is suggested that the expression for the rotary diffusion constant of an infinitely dilute sol of rod-shaped particles can be made applicable to more concentrated sols by multiplying it by the term (esC−1)/sC, where C is concentration and s is the slope of the curve relating sol concentration to Maxwell constant, to account for the change in particle interaction with change in sol concentration.
The viscosity and spectral transmission of these sols were also checked. It was found that the viscosity ranged from 1.0 cp for the most dilute sol to about 1.25 cp for the sol of concentration 0.1 volume percent. These sols were found to have a transmission which peaked at about 6800 A and dropped rapidly on either side of this value.
Effect of Oxygen on the Ultraviolet Spectra of Benzene
Authors: Lim E. C. , Kowalski V. L. 
Published: January 2005

The ultraviolet spectrum of benzene induced by oxygen was studied in the wavelength range 2200–3000 A. From the experimental results obtained, the electronic absorption of this system is interpreted as a charge-transfer absorption induced during a chance contact between benzene and oxygen without formation of stable complexes. The general formula obtained by Tsubomura and Mulliken was used together with experimentally obtained energy of the charge-transfer state (about 5.6 ev) to calculate the intensity of the charge-transfer absorption borrowed from the 1A1g—1B1u and 1A1g—1E1u absorptions of benzene. The calculated intensity is in excellent agreement with experimental data, indicating that it is the interaction of the charge-transfer state with the benzene 1B1u and 1E1u states which is responsible for the observed intensity of the charge-transfer absorption.
Experimental evidence is also presented which indicates that the two previously observed weak absorptions in benzene at 4.2 and 4.9 ev, which several workers have conjectured might be the transitions to the higher triplet states, are not multiplicity-forbidden transitions. The absorption at 4.2 ev has been interpreted as due to an impurity and the absorption at 4.9 ev has been tentatively ascribed as due to a solvent effect whose nature is not yet understood.
Partition Function of Bulk Polymers. I
Authors: Boggs F. W. 
Published: January 2005

This paper develops a theory which interrelates several aspects of the behavior of rubberlike materials through the extension of statistical mechanical treatments which have been developed for fluids.
An additional term of the partition function of bulk polymers is found. This term decreases as the temperature increases.
It has been possible partially to evaluate this added term by replacing important portions of it with thermodynamic expressions appropriate to liquids. This eliminates the necessity of attempting to evaluate series which would be difficult at low temperatures. In this way it is shown with a minimum of approximation how it is that the well-known and simple theory of rubber is valid at high temperatures and tends to show deviations as the temperature decreases. It further shows that the probability of finding a chain far removed from its most probable position decreases with decreasing temperature. It is hoped that these techniques can be used to explain some of the changes which occur in solid polymers as the temperature is lowered.
Vibrational Relaxation in Carbon Monoxide by the Spectrophone Frequency-Response Method
Authors: Woodmansee W. E. , Decius J. C. 
Published: January 2005

Although the spectrophone has been employed earlier to measure vibrational relaxation times by a phase-shift method, the use of a frequency-response (amplitude) method does not seem to have been previously reported. The limitations of microphone response to audio frequencies precludes the investigation of most gases by this procedure, but the expected long relaxation time in carbon monoxide suggested that a response loss might be observable for this molecule.
After some difficulties due to acoustic resonances in the spectrophone cell were overcome, a relaxation loss (relative to CO2) was found at room temperature for carbon monoxide, which corresponds to a relaxation time of approximately 2 msec at 1 atm. The result is compared with values found at much higher temperature by shock-tube experiments.
While the result for τ appears to be somewhat low in comparison with the shock-tube results, which may be due to traces of H2O or of H2 in the sample, the method appears to be useful in extending the range of measurements beyond that previously available by other techniques.
Gaseous Diffusion in Porous Media. II. Effect of Pressure Gradients
Authors: Evans R. B. , Watson G. M. , Mason E. A. 
Published: January 2005

A previously proposed model for the diffusion of gases in porous media at uniform pressure is extended to allow for pressure gradients. The porous medium is visualized as a collection of ``dust'' particles constrained to remain stationary in space. As before, the entire range of intermediate mechanisms from the Knudsen to the normal diffusion region can be covered by varying the mole fraction of real gases. The effect of pressure gradients is to introduce into the fundamental kinetic theory equations both a pressure diffusion term and an external force term, which is needed to keep the porous medium from being pushed along by the pressure gradient. Somewhat surprisingly, there is a considerable cancellation of terms, and the final diffusion equation has the same form as in the uniform pressure case. No additional parameters beyond those necessary to define a diffusing system at uniform pressure are thus required to compute the diffusion rates when pressure gradients are present. The coefficients of the diffusion equation, however, now depend on position through their dependence on pressure, and the net flux J of all molecules is an undetermined quantity.
A complete solution requires also a forced flow equation giving J as a function of the pressure gradient. A forced flow equation is derived on the basis of the dusty gas model, but one parameter must be made disposable in order to compensate for the fact that the model permits only a diffusive mechanism for flow, never a viscous mechanism. Another forced flow equation is derived by analogy with Poiseuille flow, in which the porous medium is visualized as a group of capillaries. The two models are shown to be not inconsistent in viscous flow regimes, and complement rather than contradict each other. The Poiseuille model is mathematically very cumbersome, however, and has been used only at one especially simple point (at which J=0) to give an independent evaluation of the disposable parameter occurring in the dusty gas model. Agreement of the calculations with available experimental data is good. As in the uniform pressure case, the model does not give an a priori characterization of any porous medium, but rather permits prediction of the behavior of different gas mixtures under a variety of conditions on the basis of three parameters which can be obtained from only a few experimental measurements.
NMR of a Glycine Single Crystal
Authors: Webb W. E. , Moulton W. G. 
Published: January 2005

The NMR absorption of a glycine single crystal was observed at 77° and 293°K for various orientations of the sample in the external magnetic field. On the basis of theoretical second moments computed from Van Vleck's equation it is concluded that the NH3+ group is a regular tetrahedron whose axis lies along the C–N bond. The N–H bond distance was determined to be 1.077±0.01 A.
It is concluded from the agreement between the computed and observed angular dependence of the second moments that the proposed model is correct.
Dielectric Properties of Glycerol—Water Mixtures
Authors: McDuffie G. E. , Quinn R. G. , Litovitz T. A. 
Published: January 2005

The frequency dependence of the complex dielectric constant of glycerol—water mixtures has been measured in the megacycle frequency range at −7.5°, −15.3°, and −19.5°C. for various concentrations between nearly pure glycerol and an equal molar mixture. Cole—Cole plots of the data indicate a single main relaxation with an asymmetric distribution of relaxation times of the Davidson—Cole form. The limiting dielectric relaxation time of the Davidson—Cole distribution was found to be strongly dependent on the water content and to vary exponentially with the molar concentration of water. The width of the distribution of relaxation times is independent of the concentration over the range studied and only slightly temperature dependent. The average dielectric relaxation times of the mixtures were extrapolated to 100% water. The dielectric relaxation time of water obtained by this extrapolation agrees satisfactorily with the measured value, indicating a smooth transistion between the average relaxation time of pure glycerol and pure water, as well as indicating a change in the distribution of times from that of the Davidson—Cole form to a single time. These experimental findings can be explained in terms of the ``group'' concept of Schallamach in which it is assumed that in mixtures of associated—associated liquids, such as glycerol and water, dielectric orientation occurs through a cooperative effect in groups of molecules, these groups containing molecules of both kinds.
The concentration dependence of the dielectric relaxation time is also compared to that of viscosity. The comparison indicates that the variation of dielectric times with water content is similar to, but not exactly the same as, the variation of viscosity.
Ionization and Excitation Processes in Argon, Krypton, and the C2 Hydrocarbons Produced by Various Means
Authors: Melton Charles E. 
Published: January 2005

Multiple ionization produced in argon and krypton by 3.5-keV electrons is reported. The ionization mechanism is tentatively proposed to be similar to that known for nuclear transitions, namely, a combination of electron shakeoff with primary ionization in one of the inner-orbital-electron shells (n=1 or 2) followed by Auger transitions.
The relative proportions of fragment ions produced in the C2 hydrocarbons by 3.5-keV electrons are also reported. These data bear a marked similarity to those obtained by the dissociative ionization of the C2 hydrocarbons with 75-eV electrons. However, ions produced by 3.5-keV electrons retain excitation energy longer as is shown by their respective rates of intramolecular decomposition (metastable transitions). Despite the longer retention of excitation energy, the reaction rate for 3.5-keV electron-induced ions in ion—molecule reactions is the same as that for 75-eV electron-induced ions. Reaction rates between neutral molecules and C2H4+ ions from different parent molecules appear to be independent of the parent, thus suggesting that the ions, initially probably different in configuration, all rearrange to the same configuration before reacting.
The fragment ion pattern produced in ethane by 50–75-eV electrons is strikingly similar to that produced by either 3.5-keV electrons or by 5-MeV α particles. In ethylene, likewise, the fragment ion patterns produced by 5-MeV α particles, β particles from Ni63, 3.5-keV electrons and 50–75-eV electrons are quite similar. This lends some support to the common practice of using 50–75-eV mass spectra to predict primary ion products in radiation chemistry.
d Orbitals in Compounds of Second-Row Elements. II. Comparison of H, C, F, and Cl as Ligands
Authors: Craig D. P. , Zauli C. 
Published: January 2005

Calculations have been made to contrast the effects of H, C, F, and Cl as ligands on loosely bound d orbitals of second-row elements. Sets of one, two (at right angles), four (square), and six (octahedral) identical atoms are compared. The approximation is electrostatic, with the use of potentials derived from self-consistent field wave functions. The order of effectiveness is F&gt;Cl&gt;C≫H. The first three are more nearly equal in their perturbing power than expected from their electronegativities, and hydrogen is surprisingly ineffective.
The conclusions lend themselves to some generalization to the conditions of binding in second-row elements. These are discussed, and some examples given.