bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of the Rapid Gas Phase Reaction between NO, NO2, and H2O
Authors: Wayne Lowell G. , Yost Don M. 
Published: January 2005

Using the absorption of light by nitrogen dioxide as a measure of its concentration, the rate of the gas phase reaction NO+NO2+H2O=2HNO2 was measured over a fivefold range of water vapor and nitrogen dioxide concentrations, with nitric oxide greatly in excess. Changes in light intensity were detected by means of an electron-multiplier photo-tube and recorded by photographing the screen of a cathode-ray oscilloscope. Half-times as short as 0.014 sec were observed. The reaction rate was found to depend more strongly upon the concentration of water vapor than upon that of nitrogen dioxide and to be kinetically consistent with a mechanism involving termolecular collisions.
The equilibrium constant of the reaction has been calculated and its order of magnitude experimentally confirmed, and a lower limit has been fixed for the rate of dissociation of nitrogen sesquioxide.
Optical Absorption and Photoconductivity of Amorphous and Hexagonal Selenium
Authors: Gilleo M. A. 
Published: January 2005

In amorphous and hexagonal selenium optical absorption and photoconductivity were studied in their dependence on temperature. The absorption edge shifts for amorphous selenium toward shorter wavelengths with decreasing temperature. For a temperature change from 300° to 90°K and a layer thickness of 98μ, for example, a shift from 6600 to 6100A is observed at an optical density of 3; for higher densities (shorter wavelengths) the shift is smaller. It can be shown that this shift is related to the thermal excitation of vibrational levels. At higher temperatures the population of the higher vibration levels increases and the separation of these from the excited state diminishes.
At low temperature (ca 90°K) photoconductivity is observed only after the light quanta exceed 2.5 ev and the absorption coefficient has reached 105 cm−1. Increase of temperature brings about a shift of the photoconductive threshold toward longer wavelengths, paralleling the absorption-edge shift. The absorption coefficient has been followed over the wavelength range 6900 to 2100A; its values at the end points of this range are 1.6×102 and 5.2×105 cm−1, respectively; there is a slight maximum at 2600A where the absorption coefficient reaches 5.6×105 cm−1.
The transformation of amorphous into hexagonal selenium by heat brings about an increase of the optical absorption in the 5000 to 7200A region and the appearance of a distinct hump in the absorption edge at 5200A. Decrease of temperature sharpens the hump and causes a decrease of absorption at all wavelengths in the 4000 to 7200A range except in the vicinity of the hump. In hexagonal selenium photoconductivity is observed at wavelengths as long as 7500A for films 0.5μ thick. A peak in the photoresponse is found where the optical density of these films reaches ca 1 (10 percent transmission). It can be shown that this behavior is to be expected for a bimolecular law of recombination of electrons and holes when their inhomogeneous distribution is taken into account. With decreasing temperature the peak response shifts consequently toward shorter wavelengths with the absorption edge.
Quantitative Line-Width Measurements in the Infrared. I. Carbon Monoxide Pressurized with Infrared-Inactive Gases
Authors: Penner S. S. , Weber D. 
Published: January 2005

Quantitative infrared-intensity measurements on CO pressurized with gases such as H2, He, and A have been carried out at room temperature. For pressures up to 100 psia the experimental absorption measurements are correlated quantitatively by the use of theoretical relations derivable from the dispersion formula. Thus, for a fixed value of the total pressure, the observed absorption is a linear function of the square root of the optical density. Similarly, at constant optical density, the absorption is a linear function of the square root of the total pressure. Using Elsasser's treatment for equally spaced and equally intense rotational lines, lower limits have been determined for the rotational half-widths of CO broadened by various infrared-inert gases.
The determination of rotational half-widths from spectroscopic measurements can be refined by allowing for the variation of integrated absorption per rotational line from one line to another in a given vibration-rotation band. By carrying out numerical calculations, with the rotational half-width treated as a variable parameter, a direct comparison between calculated and observed infrared absorption can be used to determine the rotational half-width δ0 for pressures which are small enough to justify a treatment for nonover-lapping rotational lines. In this manner it was found that (δF)H2 = 0.077 cm−1 atmos−1, (δF)A = 0.040 cm−1 atmos−1, (δO)H2 = 0.063 cm−1 atmos−1. Here the subscripts F and O denote measurements on the fundamental and the first overtone, respectively. The subscripts H2 and A identify the broadening agent used for study.
Experimental Determination of Even-Odd Character of Excited Electronic States of Molecules with a Center of Symmetry
Authors: Platt John R. 
Published: January 2005

Even-even transition intensities increase with monosubstitution but decrease with opposed disubstitution. Even-odd transition intensities which increase with monosubstitution must increase further with opposed disubstitution.
Determination of parity in this way may settle disputed assignments. Thus the 1A1g—1E2g π-transition of benzene is probably at 1700 A. The first singlet absorption of naphthalene is 1A1g—1B1u or 1A1g—1B2u and cannot be 1A1g—1A1g even though the cancellation of transition matrix elements (from configuration interaction, in the one-electron approximation) gives it an intensity and vibrational structure similar to those in a forbidden transition. The visible bands of porphine are even-odd (a2u→eg 1Ag—1Qu0).
Intensities in the 2100 A transition of phenyl derivatives are being remeasured to settle its assignment in benzene, since existing data give conflicting results.
Statistical Thermodynamics of Rubber Elasticity
Authors: Wall Frederick T. , Flory Paul J. 
Published: January 2005

Two principal differences between the theories of rubber elasticity advanced by James and Guth and by other authors are examined in the light of certain fundamental concepts. First the distribution functions for molecular chain lengths in vulcanized rubber networks are considered from the point of view of symmetry. Assuming a relaxed network to be isotropic and a network subject to uniform stress in one direction to be transversely isotropic, it is possible to formulate very general mathematical forms with respect to which the actual distribution functions must be compatible. It is shown that the functions employed by Wall and by Flory and Rehner are consistent with the required general forms; those of James and Guth are incompatible with any degree of isotropy and suggest an aeolotropic structure for vulcanized rubber.
It is also shown that the configurational entropy of vulcanization must be zero and quite independent of the statistical nature of the chains comprising the network, providing the network is not deformed macroscopically. The negative entropy of vulcanization derived by James and Guth arises from their erroneous identification of the configurational probability with the number of configurations which a microscopically specified network structure could assume, rather than with the total number of configurations for all network structures which are consistent with the requirements of the vulcanization process. The assertion of James and Guth that the configurations of the polymer chains are altered in some systematic manner by the introduction of cross-linkages and their concept of ``internal pressure'' originate in this error. The present article attempts to clarify the currently prevalent confusion with respect to rubber elasticity theory.
Magnetic Study of Some Inorganic Compounds of Arsenic, Antimony, and Bismuth
Authors: Prasad Mata , Kanekar C. R. , Mulay L. N. 
Published: January 2005

In the graphs of the molecular susceptibilities χm of some salts of As, Sb, and Bi, containing the same anions against Z, the total number of electrons in them are nonlinear in each case if all the salts are taken into consideration. These graphs are, however, similar in nature and bring out the family relationship of these cations. Ikenmeyer's relation is seen to hold true only in the case of the halides of As, Sb, and Bi and the salts of these cations in combination with the same anion.
The linear relation observed between χm of the salts of As, Sb, and Bi containing the same anion and the number of electrons N in the cations has been used to evaluate the susceptibilities of the cations and the anions in combination with them. The significance of this relation and its advantages over other methods of determining ionic susceptibilities have been discussed. The experimental susceptibilities of these cations have been compared with the theoretical values calculated by Slater's and Angus' methods and have been used to evaluate the radii of the cations.
A Study of Two-Center Integrals Useful in Calculations on Molecular Structure. I
Authors: Roothaan C. C. J. 
Published: January 2005

Convenient formulas have been obtained for the overlap integrals ∫χaχbdv, kinetic energy integrals —½∫χaΔχbdv, nuclear attraction integrals Z∫χa(1/ra)χbdv and Z∫χb(1/ra)χb′dv, and coulomb repulsion integrals ∫ ∫ χa(1)χb(2)(1/r12)χa′(1)χb′(2)dv1dv2, where χa, χa′, χb, χb′ are Slater-type AO's on the centers a and b. Explicit formulas are given for all the integrals arising from the principal quantum numbers 1 and 2, for arbitrary values of the effective nuclear charges and the interatomic distance.
Conductivities of Strong Electrolytes in Aqueous Solution
Authors: Evans Robert L. 
Published: January 2005

The concentration dependence of the conductivities of strong electrolytes is of interest in both theory and application. Older theoretical and empirical equations fail at high concentrations.
This article presents three empirical equations for the concentration dependence of conductivity. The first of these contains only a single fitted parameter (``a'' in Eq. (1) and Table I). Each of the other equations contains two parameters and follows the experimental curves up to high concentrations. However, Eq. (3) is the only one that shows the proper exponential concentration dependence at very high concentrations.
Also, a description is given of two anomalies in the behavior of tetramethyl ammonium salts.
Structural Model of Low Pressure ``Physical'' Adsorption
Authors: Cook Melvin A. , Pack Douglas H. , Oblad Alex G. 
Published: January 2005

This article describes a proposed new type of adsorption potential associated with surface strain induced in the elimination of unbonded electron orbitals (``first-order strain''), and strain due to surface (chemical) heterogeneities, or surface impurities (``second-order strain''). These surface strains are assumed to give rise to a ``semi-chemical'' adsorbate-adsorbent attachment in the first layer of multimolecular films. This is termed ``structural adsorption'' and is considered to be largely responsible, along with ordinary van der Waal's potentials, for the low pressure region of the type II isotherm.
The theory is applied in the calculation of the adsorption isotherms for pure nitrogen, pure oxygen, and mixtures of nitrogen and oxygen on anatase. It is further applied in determining the composition of the adsorbate in mixed gas adsorption and in the computation of the surface pressure of these films over the entire range of relative pressures from zero to p/p0=1.0. Excellent agreement with experimental observations is achieved.
The Stereochemistry of the Imidazolidine Ring
Authors: Fischer Ernst 
Published: January 2005

The electric moments of several imidazolidine derivatives in p-xylene solution have been measured at various temperatures. It is suggested that the substances are mixtures of geometrical isomers which are in thermal equilibrium, the isomerism being due to the pyramidal arrangement of the valencies of the tervalent nitrogen.
From the temperature dependence of the moments, the energy difference between the two postulated isomers is calculated to be about 1.6 kcal/mole.
Infrared Spectra of CH2N2 and CD2N2
Authors: Crawford Bryce L. , Fletcher William H. , Ramsay D. A. 
Published: January 2005

The infrared spectra of CH2N2 and CD2N2 have been investigated in the gas phase between 4500 and 400 cm−1 using a Perkin-Elmer spectrometer with LiF, NaCl, and KBr prisms.
The spectra have been correlated with a planar, nonlinear configuration for the diazomethane molecule with symmetry C2v. The perpendicular type bands for both molecules are all overlapped or perturbed by neighboring absorption bands, so that no accurate values for the least moments of inertia have been obtained.
Two alternative schemes of assignments for the vibrational frequencies have been proposed and the thermodynamic functions for CH2N2 computed.
Potential-function calculations have been carried out.
Mobile Multilayer Adsorption of a Bose-Einstein Gas: Helium
Authors: Band William 
Published: January 2005

The quantum properties of a Bose-Einstein gas give rise to a critical adsorption into a mobile film. If the energy of adsorption is assumed to decrease with thickness according to a simple power law, the theory gives an isotherm in good agreement with observations on helium adsorption at temperatures above the lambda-temperature of liquid helium, for all gas pressures higher than 10 percent saturation.
With mixtures of He3 and He4 isotopes the theory predicts appreciable adsorption of He3 only in the first or localized monolayer; all mobile monolayers should be practically pure He4 at all gas pressures. Comparison is suggested with the known isotopic constitution of the Rollin film below the lambda-temperature.
Light Scattering Studies on Coiling Polyelectrolytes
Authors: Wall F. T. , Drenan J. W. , Hatfield M. R. , Painter C. L. 
Published: January 2005

The molecular weight and size of polyacrylic acid in solution have been determined by measurement of light scattering. Use was made of Debye's 90° light scattering method employing two different wavelengths of light.
When the reciprocal specific scattering is plotted against concentration for homopolar polymers, a straight line is obtained which is readily extrapolated to zero concentration. Polyelectrolytes, however, are capable of ionizing in aqueous solution, thus becoming electrically charged by amounts depending upon the concentration. The electrostatic repulsion of the charges very probably affects the molecular size and gives rise to peculiar light scattering curves. By utilizing buffer solutions as solvents, the molecular size is held constant and the difficulties involved in the interpretation of scattering data are largely resolved.
The weight-average molecular weight of a certain sample of polyacrylic acid at pH values of 1.2, 3, 4, and 5 was found to be 206,000±10 percent. Molecular weight values at a particular pH using a specific buffer were reproducible to about ±3 percent. The remainder of the error was attributed to association of buffer ions with the charged polymer. The size of the particles in solution was found to be less than 550A in the low pH regions, with a definite tendency to increase at higher pH values. The slope of the straight line obtained when the reciprocal specific scattering was plotted against concentration was shown to be dependent upon pH. This dependence of slope may be related to particle size and shape.
In a non-ionizing solvent such as ethanol, the polymer exhibits scattering behavior typical of non-ionized polymers. The molecular weight of polyacrylic acid under these conditions was found to be 206,000, in agreement with values obtained in buffer solvents.
The Exchange of Water Between Hydrated Cations and Solvent
Authors: Hunt John P. , Taube Henry 
Published: January 2005

The rate of exchange of water between the hydrated forms of Al+++, Cr+++, Fe+++, Ga+++, and Th+4 and the solvent water has been measured in solutions of varying acidity. With the exception of chromic ion, and of ferric ion at low acidity, the exchange is complete in ca 3 min at 25°. For chromic ion, the half-time for exchange is independent of acidity over a wide range and is ca 40 hr at 1 M salt concentration. The coordination number of chromic ion for water over the entire acidity range is 6.0. The initial hold-back of oxygen by ferric ion at low acid is slight and is attributed to the presence of polynuclear hydrolyzed species. For all the cations, the distribution of oxygen isotopes in the final solution is noticeably different from random, the cations showing a greater affinity for H2O18 over H2O16.
The rates of exchange are correlated with the electronic structure, which influences the energy required to form the transition state.
Macroscopic Space Charge in a Potassium Chloride Solution during Electrolysis
Authors: Schriever William , Ferguson Eldon E. 
Published: January 2005

The macroscopic space charge and potential distributions were determined in a uniform column of 0.0024 N KCl solution during electrolysis by the methods used by Reed and Schriever. The platinum electrodes were 8×8 cm in area and spaced 40 cm apart; their constant potential difference was 8000 mv.
For the first time, all four space-charge regions were observed in one column of solution directly experimentally. The maximum negative space charge in the cathode region, 45×10−5 statcoulomb/cm3 at x=0.6 cm, and the maximum positive space charge in the anode region, 40×10−5 statcoulomb/cm3 at x=37.7 cm, both fell within the range of such space charges observed by Reed and Schriever.
The potential gradient between x=10 cm and x=35 cm had the constant value of 13.75 mv/mm. Thus, Ohm's law was obeyed in this region. The mean gradient in the first mm next to the cathode was 1130 mv/mm; that in the last mm next to the anode was 1200 mv/mm. The total fall of potential in these two one-mm layers was thus 29.1 percent of the total fall of potential between the electrodes. For Zn(C2H3O2)2 and CuSO4 the falls in these two layers were respectively only 1 and 1.06 percent of the total; the greatest value observed by Reed and Schriever was 22.5 percent of the total for NiSO4.
It is pointed out that the shapes of the potential distribution curves cannot be explained by phenomena which occur only at, and very near, the electrodes.
Transformation of Water from Covalent to Electrovalent Combination in Formic Acid-Water Mixtures
Authors: Yang Tai-Yuan 
Published: January 2005

It was shown by the author [J. Chem. Phys. 16, 865 (1948)] that water was necessarily a covalent compound, the molecule of which is formed by the neutralization of 2H+1+2θ+O+2; and its specific susceptibility, as we know, was −0.72 (corresponding to the molecular susceptibility −12.96) and that if it were an electrovalent compound its molecule should be formed by the neutralization of 2H+1+O−2, and its specific susceptibility would have been −0.625 (corresponding to the molecular susceptibility −11.25). (Susceptibility values have been multiplied by 106.)
In the present paper, we shall show that, in formic acid-water mixtures, part of the water depending on the weight of formic acid in the mixtures changes its specific susceptibility from −0.72 to −0.625. This indicates that this part of the water in the process of mixing transforms from a covalent to an electrovalent combination.
The Stability of Gaseous Diatomic Oxides
Authors: Brewer Leo , Mastick Donald F. 
Published: January 2005

The instabilities of FeO, NiO, MnO, and SiO2 upon vaporization, and upper limits to the heats of dissociation of these oxides and SiO have been determined by effusion experiments. The data available in the literature have been treated to obtain the heats of dissociation, or the upper limits thereof, of the gaseous oxides SnO, ZnO, CdO, CuO, PbO, GeO, and TiO.
The linear Birge-Sponer extrapolation of vibrational levels appears to give correct dissociation energies for the fourth-group oxides.
The Entropy of Aqueous Solutes
Authors: Powell Richard E. , Latimer Wendell M. 
Published: January 2005

The standard partial molal entropies of monatomic ions and of non-electrolytes in aqueous solution can be represented by the empirical expressions, for monatomic ions:S̄0=(3/2)R lnM+37–270Z/re2,for non−electrolytes:S̄0=Sint+(3/2)R lnM+10–0.22VM.Here Z is the absolute value of the charge on the ion, re is the effective radius of the ion, and VM is the molal volume.
These expressions can be interpreted in terms of the smoothed-potential type of partition function for the system.
``Free Volume'' and the Viscosity of Liquid Water
Authors: Miller A. A. 
Published: January 2005

The viscosity of liquid water between −10° and +150°C (Psat=4.7 atm) is expressed by the equation: η=A exp[B/ (T−T0)], in which A = 290 μp, B = 510°, and T0 = 150°K. The true temperature-independent activation energy for viscous flow is E = RB = 1020 cal/mole.
The ``free volume'' representation uses the equation η=A exp(1/f), in which the free-volume fraction, f=vf/vl, increases linearly with temperature above the theoretical zero point, T0. Thus, f=(T−T0)/B. It evolves that f coincides with the volume fraction of unbonded water molecules, as defined by a structural model reported recently by Némethy and Scheraga.
This empirical correlation between the viscosity and the structure of liquid water demonstrates the effects of internal structural rearrangements, which are not directly reflected in changes in the total volume. The implications regarding the effects of temperature and pressure on viscosity and other relaxation processes, particularly in hydrogen-bonded, structured liquids, are discussed.
Nuclear Magnetic Resonance Studies of Electron Transfer between Tris (2,2′-dipyridyl) osmium (II) and (III) Ions, between Bis(cyclopentadienyl)iron(II) and (III) Ions, and between Tris(1,10-phenanthroline)iron(II) and (III) Ions
Authors: Dietrich M. W. , Wahl A. C. 
Published: January 2005

Changes in linewidths and positions of the proton NMR absorption peaks for the diamagnetic species on addition of the corresponding paramagnetic species are interpreted as being due to very rapid electron transfer between the two species. On the assumption that the rates of electron transfer are first-order with respect to each reactant, the following lower limits on the rate constants are obtained: Os(dipy)32+−Os(dipy)33+:   k&gt;5×104 mole−1sec−1(6°C and 26°C, D2O,5×10−3 M D+, 0.14 mole Cl−),Fe(C5H5)2−Fe(C5H5)2+:   k&gt;1×105 mole−1sec−1(26°C, CD3COCD3),Fe(phen)32+−Fe(phen)33+:   k&gt;1×105 mole−1sec−1(26°C, D2O,3 F D2SO4).
The reactions could not be studied by the electron spin resonance method because the ESR spectra of the paramagnetic species showed no observable absorption peaks, presumably because the peaks are very broad.