bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infrared Intensities of the C≡C and ≡C–H Bands in Phenylacetylenes
Authors: Brown Theodore L. 
Published: January 2005

The integrated infrared intensities of the acetylenic carbon—carbon and carbon—hydrogen stretching bands have been measured for a series of meta and para substituted phenylacetylenes. The C≡C band intensity is very strongly dependent on the substituent, whereas the ≡C–H band is relatively insensitive to substitution. The C≡C band intensity is insensitive to solvent effects; the intensity of the ≡C–H band is increased slightly in basic solvents.
A simple π-electron molecular orbital model for the phenylacetylenes yields results for the dependence of the C≡C band intensity on substituent which are in good agreement with experiment. The analysis shows that most of the intensity in the C≡C stretching band results from transfer of π electronic charge between ring and ethynyl groups during vibration.
Diffusion of Lead Ions in Potassium Chloride
Authors: Keneshea F. J. , Fredericks W. J. 
Published: January 2005

The diffusion of Pb++ ions in single crystal KCl has been studied over the temperature range, 200°—475°C. A radioactive tracer technique has been used in two types of measurements: diffusion from a deposited surface layer of PbCl2 and diffusion from PbCl2 vapor. For treating the data from the vapor diffusion experiments, a graphical method has been developed which enables D to be obtained as a function of Pb concentration.
The diffusion of Pb in pure KCl obeys the equation D=1.02×10—3 exp (—23 300/RT)/cm2 sec. The behavior of D as a function of concentration supports the Lidiard theory of diffusion by impurity-vacancy complexes. An association free energy for complex formation of 0.49±0.1 eV has been estimated from the data. This is in agreement with the trend shown in theoretically calculated values for other impurities in KCl. An anomalous rate of diffusion has been observed for Pb near the surface of some PbCl2-doped KCl crystals.
Homogeneous Catalysis of Gas-Phase Atom Recombination. Recombination of H Atoms at High Temperatures
Authors: Benson Sidney W. 
Published: January 2005

An analysis is made of the effect of a catalyst C on the rate of recombination of atoms X when C forms a relatively long-lived complex with X. Labeling the energy-rich, nascent complex CX*, the kinetic sequence is X+C⇋ lim baCX*,CX*+M⇋ lim dcCX+M,CX+X→ lim eC+X2.
Using steady states for CX* and CX, the rate of recombination assumes three interesting forms in different limiting cases: (1) Rate ∞ (C) (X)2; (2) rate ∞ (C) (M) (X); (3) rate=ka (C) (X). Case 1 corresponds to a weak complex at high pressures; Case 2 has not been reported. It corresponds to the case of a not-too-weak complex forming at very low total pressures. The last case, 3, corresponds to a very strong complex with a long lifetime. It is shown that this is an easily realized case, and that catalytic efficiencies for it can be very high.
Applying the scheme to H-atom recombination in the temperature range 1500–2500°K and calculating the lifetime of CX* from RRK theory, it is shown that CH3≡(C) may be a very effective catalyst. At 3 mm Hg pressure of (H) and 100 mm Hg of (H2) adding 1 mm Hg of CH4 which forms CH3 could produce a rate of recombination 1000-fold faster than the normal termolecular reaction. Under the same conditions NH3 is about 10-fold slower, C2H2 about 30-fold slower, and H2O about 500-fold slower than CH4.
On the Concentration Dependence of the Rates of Sedimentation and Diffusion of Macromolecules in Solution. Preliminary
Authors: Singer Seymour J. 
Published: January 2005

The concentration dependence of the osmotic pressure, rate of diffusion, and sedimentation velocity for solutions of high molecular weight solutes, on the basis of certain assumptions, have been shown to be interrelated. Experimental confirmation, however, has been lacking. Preliminary data are given in this article which satisfy these interrelationships, with fractions of cellulose acetate in acetone; however, more cooperative osmotic pressure, diffusion, and sedimentation experiments on a variety of well-defined systems are necessary to confirm the hypothesis.
If and when this additional confirmation is produced, the assumptions involved in the hypothesis may be considered correct; these are: (1) that the frictional coefficient in diffusion is the same (barring special cases of orientation during transport) as the frictional coefficient in sedimentation; and (2) that the driving force of diffusion is the gradient of the free energy of dilution of the system.
For solutions with no heat of mixing, the slight dependence of the diffusion constant on concentration has its molecular basis in the fact that the size and shape of the molecules affect the thermodynamic and hydrodynamic contributions to the variation of the diffusion rate to a comparable extent, and these contributions partially cancel one another. This is quantitatively so in the simple case of rigid spheres in an athermal solution.
Low Temperature Transport Properties of Gases. I. Helium
Authors: Amdur I. 
Published: January 2005

Values have been computed for the viscosity, thermal conductivity, and coefficient of self-diffusion of gaseous helium for temperatures below 200°K by application of classical scattering theory within angular regions where diffraction effects are absent. Values of classical total collision cross sections are obtained which are used to evaluate classical cross sections for viscosity, thermal conductivity, and self-diffusion appropriate to a Maxwellian gas. Numerical values of the transport properties are obtained by substitution of the appropriate classical cross sections into the exact transport property formulas of Chapman and Enskog.
In the region 200° — 14°K, the average absolute deviations between calculated and experimental values are 1.9 percent for viscosity and 4.6 percent for thermal conductivity. Extrapolation of calculated viscosity values to 1.64°K appears to be justified on the basis of agreement with experimental values. It cannot be stated that similar extrapolation in the case of thermal conductivity is valid because of possible uncertainties in the experimental values between 3.95° and 1.62°K. Values of the self-diffusion coefficient have been calculated between 200° and 5°K, but experimental values are not available for comparison.
Determination of the Ranges of the Fission Fragments Emitting Delayed Neutrons. Chemical Identification of the 4.51-Sec. Delayed Neutron Activity
Authors: Sugarman Nathan 
Published: January 2005

The ranges of the fission fragments leading to delayed neutron emission have been determined by absorbing the fragments in Al and counting the penetrating activity. The delayed neutron activities and their corresponding ranges in Al corrected for source thickness are: 4.51 sec., 4.05±0.03 mg Al/cm2; 55.6 sec., 3.98±0.06 mg Al/cm2; 1.52 sec., 3.63±0.12 mg Al/cm2; 22.0 sec., 3.21±0.04 mg Al/cm2. Comparing the range of the 4.51-sec. activity with that of the 55.6-sec. Br, one finds that mass assignments possible for the 4.51-sec. activity are 86 to 90. Similarly, the range of the 1.52-sec. activity is compared to that of the 22.0-sec. I, and the possible mass assignments found are 129 to 135.
Chemical separation of Br from irradiated uranyl nitrate resulted in the identification of the 4.51-sec. activity as an isotope of Br.
Contribution to the Study of Electronic Spectra of Bent Triatomic Molecules
Authors: Duchesne Jules , Rosen B. 
Published: January 2005

The electronic absorption spectra of the SO2, SeO2, and TeO2 molecules have been studied under widely varied experimental conditions. The vibrational analysis of the ultraviolet absorption region of SO2 with center of gravity near 2000A reveals that it is formed by at least two electronic systems with the following vibrational constants: System α1···ν0=42,170 cm−1,  ν1′=963 cm−1,  ν2′=379 cm−1,  x′ν2′=2 cm−1.System α2···ν0=44,236 cm−1,  ν1′=775 cm−1,  ν2′=375 cm−1.The presence in the same region of a third electronic system, with ν2′=360 cm−1 and ν1′=845 cm−1, seems highly probable.
The character of the vibrational structure of the band systems and a preliminary analysis of the rotational structure of several bands have enabled us to obtain some information about the molecular structure of the excited states.
The vibrational analysis of the c-system of SeO2 in the visible, and the TeO2 bands in the visible and ultraviolet, have enabled us to correlate the electronic states of the three similar molecules.
Chemical Properties of Astatine. I
Authors: Johnson G. L. , Leininger R. F. , Segrè E. 
Published: January 2005

This work is a report on studies of the chemistry of astatine on a tracer scale, using the various methods of tracer chemistry. A general discussion of preparation of materials and analytical methods is included. The properties of astatine and its solutions as they appear in work on a tracer scale are discussed. Migration experiments show that astatine when ionized in aqueous solution is negatively charged. Electro chemical, solvent extraction, and carrying studies are presented.
In general, (a) elemental astatine is extractable by organic solvents; (b) the − 1 state may be prepared by powerful reducing agents; and (c) at least two positive oxidation states exist.
The Kinetics of the Chromic Acid Oxidation of Isopropyl Alcohol: The Induced Oxidation of Manganous Ion
Authors: Watanabe Warren , Westheimer F. H. 
Published: January 2005

1. Isopropyl alcohol ``induces'' the chromic acid oxidation of manganous salts to MnO2. The limiting induction factor (ratio of moles of MnO2 to moles of acetone formed) is one-half.
2. In the presence of manganous ion the rate at which chromic acid is reduced by isopropyl alcohol is decreased; the maximum decrease in rate observed under a wide variety of experimental conditions is 50 percent.
3. These facts, together with the previously determined reaction kinetics, demand the formation of an intermediate chromium compound in which chromium has the valence four or five.
4. Within chemically reasonable limits, all the reaction mechanisms involving such transitory intermediates have been examined. In the presence of manganous salts the only possible mechanism is HCrO4−+CH3CHOHCH3→Cr4+CH3COCH3,Cr4+Mn++→Cr++++Mn+++,2Mn++++2H2O→Mn+++MnO2+4H+.In the absence of manganous salts several mechanisms (all of which are listed) are possible.
Internal Rotation IV. The Optical Activity and Isomerization Energy of the Rotational Isomers of D-Secondary Butyl Alcohol
Authors: Bernstein H. J. , Pedersen E. Egelund 
Published: January 2005

The specific rotation of secondary butyl alcohol was measured in dilute solutions of cyclohexane at intervals of 5° between 20°C and 70°C inclusive.
After corrections for solvent effect and change of refractive index with temperature had been made there remained a definite temperature dependence of the rotivity.
Interpretation of the results on the basis of three optically active rotational isomers (two of equal energy and the third less stable) gave the rotivity of the third isomer as −21° and the sum of the other two as +21°.
The heat of isomerization was found to be 803 cal. per mole.
The concentrations of the three rotational isomers at 20° are calculated as 42.3 percent, 42.3 percent, and 15.3 percent.
A Theory of Vapor Pressures of Liquids Based on van der Waals' Equation of State. II. Binary Mixtures
Authors: Wall Frederick T. , Stent Gunther S. 
Published: January 2005

An expression for vapor pressures of binary liquid systems obeying van der Waals' equation of state is developed by generalizing a recent theory of vapor pressures of pure liquids. The resulting partial vapor pressure equations involve composition and temperature, and contain no empirical quantities other than van der Waals' constants including an inter-species interaction term.
The conditions under which Raoult's law holds for these systems are formulated, together with the conditions for which positive or negative deviations occur. The compositions at which azeotropes form are predicted, and the partial miscibility of binary liquid systems is discussed. A number of examples are calculated to illustrate the theory.
A Quantum-Mechanical Theory of Light Absorption of Organic Dyes and Similar Compounds
Authors: Kuhn Hans 
Published: January 2005

The most important organic compounds which absorb visible light can be classified into three groups typified: (a) by symmetrical polymethines, (b) by porphyrines, (c) by polyenes.
Recently it was shown that the position of the absorption maxima of symmetrical polymethines and related compounds (symmetrical cyanine and oxanole dyes; Michler's hydrol blue and derivatives; malachite green and other triphenyl methane dyes; etc.) can be calculated by adopting a model of the dye molecule which is analogous to the free-electron gas model used in particular by Sommerfeld to describe the condition of metals. The π-electrons of the polymethine chain are considered as a one-dimensional free-electron gas which extends itself along the length of the chain.
In the normal state the stablest energy states of the electron gas each contain two electrons in accordance with Pauli's exclusion principle. The remaining states are empty. The existence of the first absorption band is a consequence of the jump of a π-electron from the highest energy level occupied in the normal state to the lowest empty level.
For the wave-length of the maximum of the first absorption band of this group of dyes, the relationship obtains that λ1=(8mc/h)(L2/[N+1]),where L is the length of the polymethine zig-zag chain, N, the number of π-electrons, m, the mass of the electron, c, the velocity of light, h, Planck's universal constant. Good agreement with experimental results for λ1 is obtained by the use of this equation.
The problem of porphyrine and phthalocyanine compounds can also be dealt with on the basis of a free-electron gas model. We treat the π-electrons of the porphyrine ring as electrons which are confined to move in a closed ring-shaped path in a field of constant potential energy.
In the case of polyenes and related compounds (Carotenes, unsymmetrical cyanines and oxanoles, merocyanines, azo- and stilbene dyes, etc.) a description by means of a free-electron gas model is no longer permissible. The electron gas in this case suffers a disturbance from its condition in the case of the first and second groups of dyes, and, to allow for this, the π-electrons are considered placed in a one-dimensional potential having a sine curve periodicity. The wave-length λ1 is expressed by λ1=[V0hc(1−1N)+h8mcN+1L2]−1,where V0 is the amplitude of the sine-shaped potential along the chain.
This relation is confirmed by the experimental data. It also gives an explanation for the markedly different manner (compared with the symmetrical polymethines) in which the position of the absorption bands of polyenes and related compounds depends on the chain length.
The results of the classical color theory of Witt are capable of a simple explanation when considered in the light of the electron gas model.
Hindered Rotation in Ethyl Alcohol
Authors: Halford J. O. 
Published: January 2005

Previous evaluations of the barriers hindering the internal rotations in ethyl alcohol are shown to be unsatisfactory because they fail to produce agreement between molecular and calorimetric entropies over a wide enough temperature range. The principal source of difficulty is found in an inconsistency between the modified Berthelot equation of state and the calorimetric data and vapor pressures used in calculating the third law entropies. Corrections for gas imperfection should be much higher at the temperatures at which the barrier evaluations have been made, but these corrections cannot be determined accurately with the available data. The larger entropies permit the assignment of lower and more reasonable potential barriers.
For the hydroxyl group rotation, to keep the heat capacity, and therefore the change of entropy with the temperature, within the indicated limits, the simple expression V = V0(1—cos3θ)/2 is more suitable than more detailed potential energy functions. With a reasonable assignment of the vibrational frequencies, the sum of the barriers restricting the hydroxyl and methyl group rotations is approximately 6000 cal.
The Kinetics of the Vapor Phase Exchange of Radioactive Bromine between Trichlorobromomethane and Bromine
Authors: Davidson Norman , Sullivan John H. 
Published: January 2005

The rate of exchange of radioactive bromine between trichlorobromomethane and bromine in the vapor phase in the temperature range 420−455°K has been determined. The rate is equal to k[Br2]½[CCl3Br], where log10k(moles/liter)−12(sec.)−1=(−33,100(±400))/(4.574T)+12.75(±0.20). The energy of activation for the elementary reaction between bromine atoms and trichlorobromomethane molecules is 10.3 kcal., and the frequency factor is 7.9×1010. It is proposed that the reaction proceeds via the sequence: Br*+BrCCl3→BrBr*+—CCl3, and Cl3C—+Br2*→Cl3CBr*+Br*, rather than by a Walden inversion mechanism. The observation that chloroform is formed when hydrogen bromide, bromine, and trichlorobromomethane are heated is cited as evidence for the presence of —CCl3 radicals and for the reaction Cl3C—+HBr→Cl3CH+Br. The —CCl3 radical is then more stable than the —CH3 radical by 10 kcal. or more.
The vapor pressures of liquid trichlorobromomethane are given by the equation: log10p(mm)=(−8240/4.574T)+7.64. The exchange reaction Br2(g)+AgBr*→Br2*(g)+AgBr readily goes to completion and is the basis for a convenient semi-micro method for the preparation of radioactive elementary bromine.
Simple Potential Functions and the Hydrogen Halide Molecules
Authors: Davies Mansel 
Published: January 2005

Five simple molecular potential functions have been tested by comparison with spectroscopic data for the hydrogen halides. It is shown that when plotted on a ``reduced'' distance scale (r/re), the potential curves for these molecules coincide closely up to Δ(r) = 0.10re. Two electrostatic functions indicate β/rn as the more satisfactory form of the repulsive term. Significant values of the effective polarizability and ``fractional ionic character'' are deduced. The latter are higher and more nearly constant than the uncorrected values currently quoted as showing changing bond type in these molecules. The results conform with Kirkwood's very successful treatment of HCl as a polarizable ion pair.
Of purely empirical functions, the Pöschl-Teller provides a slight improvement upon the simple Morse relation, and is only a little more cumbersome than the latter. The Rosen-Morse function is less satisfactory for these molecules. Simple expressions are given for evaluating the three parameters in these functions from spectroscopic data.
Contribution of the Deviation from Perfect Gas Behavior to the Entropy and Heat Capacity. Water and Benzene
Authors: Halford J. O. 
Published: January 2005

The properties of water vapor are used to illustrate the point, previously found true for ethyl alcohol, that the modified Berthelot equation of state may not give a satisfactory evaluation of the deviation of thermodynamic properties from those of the hypothetical perfect gas. The entropy deviation for benzene, however, is accurate enough for most purposes, and the heat capacity is not too far out of line.
On limited information, it appears that the Berthelot equation may be satisfactory for the vapors of ``normal'' liquids up to limited pressures. It is recommended, however, that some attempt be made to check the properties by means of vapor densities, obtained directly or by the Clapeyron equation, before results based upon the Berthelot equation are accepted.
Spectral Resemblances of Cata-Condensed Hydrocarbons
Authors: Klevens H. B. , Platt J. R. 
Published: January 2005

The spectra of naphthalene, anthracene, naphthacene, phenanthrene, 1,2-benzanthrene, chrysene, and acenaphthene in n-heptane solution are extended to 1700A. Electronic energy levels of 17 such cata-condensed hydrocarbons are collected and compared. The lowest five or six excited states shift in a regular way with changes of molecular length and shape. Intensities and vibrational structures of corresponding bands are remarkably alike in the different compounds. The total oscillator strength is almost proportional to the number of π-electrons, but the proportionality constant differs from that in polyenes. With new identifications, the positions of energy levels in naphthalene, anthracene, and azulene agree remarkably well with previous LCAO molecular orbital calculations.
The lowest singlet state is of one type in benzene, naphthalene, and most non-linear systems; of another type in anthracene and the higher linear polyacenes because of a cross-over. This clears up some controversial questions, such as the relations among the spectra of naphthalene, anthracene, and phenanthrene.
The Absorption Spectra of Transuranic Salts in Crystals
Authors: Freed Simon , Leitz Fred J. 
Published: January 2005

Absorption spectra, mainly in the visible and near ultraviolet regions, were taken of the following anhydrous salts at room temperature and at that of liquid nitrogen: uranium tetrachloride, neptunium tetrachloride, plutonium trichloride, americium trichloride (and americium tribromide).
The spectra of these salts have the features characteristic of rare earth spectra, sharp lines clustered in groups. It follows that the heavy elements have their least stable electrons within the inner 5f shell when their ions are in activated as well as in their basic electronic states.
The spectra of the salts of americium are among the sharpest known from crystals—even at room temperature. In this respect they are matched, as far as we know, only by the salts of trivalent europium ion. The spectra confirm the resemblance drawn between these ions on other grounds and make it very likely that trivalent americium has six electrons in the 5f shell with 7F0 for its basic electronic state.
The experimental method requires at most several micrograms of the salt for obtaining spectra of considerable dispersion.
Vibration Spectra of Cis and Trans C2H2Cl2 and C2D2Cl2
Authors: Bernstein H. J. , Ramsay D. A. 
Published: January 2005

The infra-red spectra of gaseous and liquid cis and trans C2H2Cl2 and C2D2Cl2 have been obtained in the region 3500 to 400 cm−1.
The fine structure of a ⊥ band in trans C2H2Cl2 was also resolved and the least moment of inertia obtained.
An assignment of all the fundamentals for the four molecules has been made.
Calculations of potential functions and of the equilibrium constants for the reaction cis⇌trans support the assignment.
The Relative Rates of Photo-Chlorination of CHCl3 and CDCl3
Authors: Newton T. W. , Rollefson G. K. 
Published: January 2005

The relative rates of photo-chlorination of chloroform and deuterochloroform have been determined in the temperature range of −20° to 180°C. The ratio of the rate constants for the two reactions can be fitted by the equation: k1/k2=1.4±0.2 exp(710∓90/RT).This result is discussed in terms of Eyring's absolute reaction rate theory and also in terms of an alternative mechanistic explanation. The observed difference in activation energy is accounted for in terms of the zero-point energies of the normal molecules and the activated complexes.
It was found that some deuterochloroform was produced when chloroform was chlorinated in the presence of deuterium chloride. This result indicates that the reactionHCl+CCl3=CHCl3+Clmust occur to some extent in the gas-phase chlorination of chloroform, contrary to the conclusions of Schumacher and Wolff. It was also found that appreciable amounts of hexachloroethane were formed in the reaction. Hence, it is concluded that the formation of this substance must be an important chain-terminating step in the reaction mechanism.