bluuebunny/crossref_metadata_2025 huggingface dataset:
The Fluorescence of Diacetyl
Authors: Almy G. M. , Fuller H. Q. , Kinzer G. D.
Published: January 2005

Diacetyl, in the vapor phase or in water solution, exhibits a bright green fluorescence when excited with light within its absorption band in the violet and near ultraviolet. A detailed measurement of the structure shows that the spectrum is the same as is shown in the fluorescence of acetone vapor when excited with λ3130. The fluorescence spectrum is insensitive to changes in diacetyl pressure (0.1 mm to 50 mm), temperature (10°C to 100°C), exciting wave-length (3650A to 4358A) or amount of added oxygen, which quenches the fluorescence strongly. The intensity of fluorescence, measured with photo-cell and amplifier, is constant in time, with weak excitation. The ratio of intensity of fluorescence to light absorbed is independent of the pressure and the intensity of the fluorescence is linearly proportional to the exciting intensity, at constant pressure. The fluorescence is quenched by oxygen, the intensity falling to one-half at 0.013 mm oxygen. The Stern-Volmer law is followed over a range of oxygen pressures in which the fluorescence drops to 20 percent of the intensity without oxygen; at higher pressures the intensity falls more rapidly than expected. The oxygen is consumed, presumably in the quenching process, and the fluorescence returns to full intensity. From the quenching curve and from an experiment on the diffusion of the excited molecules into shadow the lifetime of the fluorescing molecule is estimated to be about 10—5 sec.

These results can be understood on the assumption that the diacetyl molecule emits the fluorescence after excitation and redistribution (spontaneous and through collisions) of the vibrational energy. In the case of acetone the fluorescence builds up gradually from practically zero intensity, as expected if diacetyl is accumulating; it is excited, not by light, but probably by collisions with excited acetone or with combining radicals. The diffusion experiments can scarcely be reconciled with the assumption that the observed emission in pure diacetyl is a recombination spectrum.
Quenching and Vibrational Energy Transfer in the Fluorescence Spectrum of S2
Authors: Durand Eric
Published: January 2005

The ultraviolet fluorescence of S2 was excited by the strong Mg spark lines λλ2928 and 2937A. A typical Wood resonance progression was observed with pure S2 only in the vessel, but the addition of a few millimeters of any of the rare gases caused changes in the fluorescence due to quenching and to the transfer of vibrational and rotational energy. The yields per collision for quenching and for vibrational transfer are of the order of magnitude of unity, and both show the same dependence on the atomic weight of the rare gas added, with a minimum in the vicinity of Ar or Kr. Comparisons are made with the results obtained by other methods. Quenching occurs by the addition of two quanta of vibrational energy to the S2, followed by disruption due to predissociation.
Coriolis Perturbations in the Spectra of Silane and Germane
Authors: Murphy George M.
Published: January 2005

A Coriolis perturbation on the rotational structure of the fundamental frequency, v4 has been computed for silane and germane. Matrix elements of the Coriolis operator, A for the lines P(9), P(10) and Q(10) have also been obtained. The envelope of the resulting absorption curve has been compared with the experimental curve and good agreement found. The most striking difference in the two spectra is that in the case of silane, the Q branch degrades toward lower frequencies and in germane, towards higher frequencies. This is shown to be due to the relative position of the infra-red inactive frequency, v2 to which the perturbation is due.
Combination Frequencies Associated with the First and Second Overtone and Fundamental OH Absorption in Phenol and Its Halogen Derivatives
Authors: Wulf Oliver R. , Jones Ernest J. , Deming Lola S.
Published: January 2005

Absorption maxima occurring in the near infra-red spectra of phenol and seven of its halogen derivatives have been measured and interpreted as combination frequencies in which the valence vibration of the OH group combines with frequencies of the body of the molecule. Certain of these absorptions underlie some of the trans-peaks of the orthohalogen phenols causing such a trans-peak to appear of larger area than that due to the trans-peak alone. A group of the combination frequencies which lie in the range 1000–1600 cm—1 above the first overtone OH absorption have been observed as a group of an order of magnitude weaker intensity in the frequency range twice the values above the first overtone OH and also above the fundamental OH absorption, apparently involving two units of vibration in the combining frequencies. A close correspondence is found between the frequencies involved in these combination tones and the frequencies which have been observed in some of these compounds in the deep infra-red and in Raman spectra.
The Rotational Structure of the Ultraviolet Bands of NO2
Authors: Harris Louis , King G. W.
Published: January 2005

The rotational structure of the 2491A band in the ultraviolet absorption spectrum of NO2 is not completely resolved, but the spectroscopic constants have been determined from the spacing of the subbands (groups of transitions with the same K), their intensity, the temperature coefficients of absorption and finally from the comparison of synthetic spectra constructed from arbitrary constants with the observed spectra. The O–N–O angle in the lower state is 154° and the N–O distance is 1.28A. For the excited state the angle remains essentially the same, the internuclear distance increasing to 1.41A.
Note on the Zeeman Effect of Chrome Alum
Authors: Van Vleck J. H.
Published: January 2005

It is shown that the Zeeman patterns observed by Spedding and Nutting are comprehensible if and only if the lines in question are intersystem combinations.
On the Energy Levels of Chrome Alum
Authors: Finkelstein R. , Van Vleck J. H.
Published: January 2005

The energy levels for the configuration d3 of the chrome ion in chrome alum are calculated by starting with the empirical spectroscopic data on the free Cr+++ ion, and then making the assumption that the interatomic forces in the solid state can be represented by a crystalline potential of cubic symmetry, whose magnitude is taken from Schlapp and Penney's theory of the magnetic susceptibility. The particular point to be tested is whether in the solid there is a doublet level only 15,000 cm—1 above the basic quartet state, as predicted in the preceding paper from the study of Spedding and Nutting's data on the Zeeman effect. The computed deepest doublet is about 18,200 cm—1 higher than the ground level, but the discrepancy is not excessive in view of uncertainties in the parameters of the crystalline field and the fact that any ``one-atom'' model is only an approximation in the solid state. As already suggested by Spedding and Nutting, it is very essential in computing the positions of excited levels, to include elements of the crystalline potential which are nondiagonal in the quantum number L, for without them the lowest doublet is much too high, viz. 30,000 cm—1 above the ground term. On the other hand, the effect of these nondiagonal members is shown to be unimportant for the ground level of greatest multiplicity, not merely for Cr+++ but also for other salts of the iron group, so that previous calculations by various writers on magnetic susceptibilities are not appreciably impaired by their assumption of Russell-Saunders coupling.
The Mercury Photosensitized Decomposition of Ethane IV. The Reaction at High Temperatures
Authors: Steacie E. W. R. , Cunningham R. L.
Published: January 2005

The mercury photosensitized decomposition of ethane has been investigated at temperatures up to 475°C. It is found that the products of the reaction are very similar to those at low temperatures. It is concluded that the primary step is a C–H bond split, and that the most important secondary reactions are H+C2H6→C2H5+H2H+C2H5→2CH3.The quantum yield approximately doubles on going from 100° to 475°C. No evidence of chain characteristics is found up to 475°C, and it is concluded that the mechanism of the reaction at high temperatures does not differ essentially from that at low temperatures.
Lifetime of Fluorescence in Diacetyl and Acetone
Authors: Almy G. M. , Anderson Scott
Published: January 2005

The mean lifetime of the fluorescence of diacetyl vapor has been determined by direct measurement with a phosphoroscope to be 1.65 × 10—3 sec. Quantitative measurement of the diffusion of the excited molecules from a beam of exciting illumination, at different pressures, has also been made and the results are compatible with this lifetime. Integration of the absorption coefficient over the band associated with the fluorescence leads, on the other hand, to a lifetime of the excited state of 10—5 sec. To explain this discrepancy and other facts known about the fluorescence various mechanisms are considered, of which the most satisfactory seems to be this: Following light absorption, X→A, the diacetyl molecule goes without radiation into a long-lived state M, lying near A. Fluorescence occurs only upon return to A. M may correspond to a tautomeric rearrangement of the molecule. Acetone, radiated with λ3130, shows fluorescence identical with that of diacetyl radiated with λ4358, but the fluorescence grows with time. It can be produced immediately with high intensity by adding diacetyl. The growth curve has been determined and is of form, It = I0 (1 — e—kt). Diffusion experiments show the lifetime of the fluorescence in acetone to be equal to that in diacetyl and that the lifetime, or rate of decay, is independent of exciting intensity. The conclusion is that the same molecule, presumably diacetyl, is responsible for the fluorescence in both cases. Possible mechanisms for the excitation of diacetyl in acetone are discussed.
The Rate of Solution of Metals in Acids as a Function of Overvoltage I. The Diffusion Potential
Authors: Kimball George E. , Glassner Alvin
Published: January 2005

The problem of simultaneous conduction and diffusion through a constrained diffusion layer is discussed. An exact solution is obtained for the case of an ideal dilute solution containing only two ionic species. The special case of divalent ions diffusion into a uni-divalent electrolyte is also solved by numerical methods. It is shown that for diffusion layers of thicknesses of the order of 50μ the potential drop across the layer for currents of the order of magnitude of 100 milliamperes per sq. cm is less than one millivolt. It is therefore legitimate to neglect the diffusion potential in comparison with the double layer potential at an electrode surface.
Solvent Action on Optical Rotatory Power IV. The Rotivity of Dipropionyl-Diethyl-d-Tartrate and l-Menthyl Acetate in Aromatic and Aliphatic Solvents
Authors: Marks Henry C. , Beckmann Charles O.
Published: January 2005

Experimental data are presented to demonstrate the validity of the equations of Beckmann and Cohen and Beckmann and Marks for the change of rotivity with solvent. Mixtures of polar and nonpolar solvents of both aromatic and aliphatic types were used with dipropionyl-diethyl-d-tartrate and l-menthyl acetate as optically active substances. The data are discussed in terms of the theory and essential agreement is found in all cases over a wide range of concentrations.
The Local Field in Polarized Dielectrics
Authors: Jaffé George
Published: January 2005

In Section I, a new deduction for the Lorentz force is given by considering at first such molecules as have their nearest neighbor at a given distance, summing over all dipoles in the field, and finally averaging. In Section II, the same procedure is applied to the case that correlations between each molecule and its immediate neighborhood are assumed to exist according to Onsager's theory. The method leads to an extension of Onsager's results to the case of media of variable density, including gases. In Section III, the distribution law of the local field is deduced for dipoles of constant moment μ0 with the aid of a probability theorem of Markoff-Gans. Both under Lorentz's and under Onsager's assumptions, the local field becomes isotropic, to a first approximation, for weak external fields. Its average value is R̄=16πnμ0/(27)½, i.e., more than twice the maximum value of the Lorentz force obtainable with a given dipole density n. In the last section the calculated deviations from the Clausius-Mosotti and Lorentz-Lorenz expressions are compared with experimental evidence.
The Absorption Spectra of Europium Ion in Some Hydrated Salts
Authors: Spedding F. H. , Moss C. C. , Waller R. C.
Published: January 2005

The absorption spectra of crystalline EuCl3·6H2O, EuBr3·6H2O, and Eu2(SO4)3·8H2O were photographed at various temperatures in the visible and ultraviolet region of the spectra. The salts were found to have low-lying excited levels at about 300 cm-1, 390 cm-1, 938 cm-1, 970 cm-1 and, perhaps, 430 cm-1, which arose from excited electronic, crystal and vibrational frequencies. These levels are discussed in relation to existing theories of specific heat, magnetic susceptibility, etc., of europium.
Diamagnetic Anisotropy and Electronic Structure of Aromatic Molecules
Authors: Brooks Harvey
Published: January 2005

Previous theories of the diamagnetic anisotropy of aromatic molecules, based on the method of molecular orbitals, neglect the correlation effects between electrons. In the present theory the anisotropy is treated from the standpoint of the Heitler-London-Pauling-Slater approximation by the inclusion of ionic terms in the secular equation. By means of an approximate treatment it is shown that correlation effects tend to reduce the diamagnetic susceptibility, the effect being relatively greater in complex molecules than in benzene. The contribution of higher order permutation integrals is also discussed and found to be negligible. The correct approximation lies intermediate between the pure H-L-S-P and pure molecular orbital approximations, but in order to explain the high value of the anisotropy, one is forced to assume that the true situation lies much closer to the molecular orbital viewpoint. The variation of the anisotropy of benzene through all intermediate stages of approximation is discussed by means of a more exact model. All calculations were carried out by treating the permutational degeneracy by means of the Dirac vector model.
Separation by Thermal Diffusion of Mixtures of Gases Having the Same Molecular Weight
Authors: Wall F. T. , Holley C. E.
Published: January 2005

Separations by means of thermal diffusion of mixtures of gases having the same molecular weight have been investigated experimentally and theoretically. Six pairs of gases were considered, namely: CO2–C3H8, CO2–N2O, N2O–C3H8, CO–C2H4, CO–N2, and N2–C2H4. The experiments were carried out in a thermal diffusion column 274 cm long. Assuming the molecules to behave as rigid elastic spheres, theoretical calculations were made for the various combinations and the results compared with the experiments. Except for the pair CO2–N2O, the theory and experiment agree as to order of magnitude and direction of separation.
The Thermodynamics of Films: Energy and Entropy of Extension and Spreading of Insoluble Monolayers
Authors: Harkins William D. , Young T. Fraser , Boyd Edward
Published: January 2005

The thermodynamic relations of insoluble monolayers on a mobile subphase are given, and equations are presented for their (a) increase of entropy, (b) heat absorbed, (c) increase of heat content, and (d) increase of internal energy, during expansion. Two different methods of expansion are considered: in spreading the decrease of area of the subphase is equal to the increase of area of the monolayer; in extension the monolayer expands but the area of the clean surface of the subphase remains constant. The two-dimensional phases are classified as: I. gas; II. liquid (L1) expanded; III. intermediate or transition; IV. liquid (L2) condensed; and V. solid. The extreme limits of molecular area for the intermediate liquid phase are for pentadecylic acid about 22 and 44A2, while those for the liquid phases IV, III, and II, are from about 20.5 to 52A2 which indicates that, beginning with a two-dimensional liquid in its most condensed condition, the mean molecular distances may be increased by as much as 60 percent without a destruction of the liquid state. This is very different from what is found in three dimensions. The heat absorbed in the melting of the two-dimensional solid is zero, so this is phase change of the second order. The quantity, hs = (∂Hs/∂σ)p,T, which is the increase in heat content when the monolayer spreads over unit area, has a value of several hundred ergs cm—2 for a solid film. The increase of heat content for the other two-dimensional phases may be illustrated by the approximate values for pentadecylic acid: it is zero for (L2), or the liquid condensed phase; rises in the intermediate phase very gradually to a nearly constant magnitude of 300 ergs cm—2 as the area is increased and decreases to about 50 erg cm—2 in the liquid expanded phase (L1). For any two-dimensional phase spread on water or on mercury the value of h for extension is greater than that for spreading by he the total surface energy of the three-dimensional liquid, which is about 116 erg cm—2 for water, and 540 for mercury. The increase of heat content ΔHm during the spreading of a mole of pentadecylic acid has been calculated for the case in which the film spreads from the lowest to the highest area at which the phase exists. For the solid phase this energy is of the order of about a fifth of a kcal. mole—1 at 18°C, while ΔHm for the intermediate phase is 8.3 kcal. mole—1, and for the liquid expanded (L2) phase is very small. At 25°C the value for the intermediate phase has fallen to 4.6, and that for the liquid expanded phase (L2) has increased to 1.0 kcal. mole—1.
The Gaseous Heat Capacity and Restricted Internal Rotation of Diborane
Authors: Stitt Fred
Published: January 2005

The heat capacity of gaseous diborane has been measured from 95° to 324°K with the low pressure thermal conductivity apparatus described earlier. The bracketing method was applied over most of this temperature range, with acetylene and ethylene as comparison gases. At 95°K, ethylene and ethane were used as comparison gases and the accommodation coefficient ratios were assumed to be unity. The heat capacity at low temperatures indicates that internal rotation in the diborane molecule is restricted by a potential barrier whose height is probably between 4000 and 6000 cal./mole if the barrier is assumed to be a sinusoidal function of the internal rotational angle.
A Theoretical and Experimental Analysis of the Capillary Rise Method for Measuring the Surface Tension of Solutions of Electrolytes
Authors: Jones Grinnell , Frizzell Laurence D.
Published: January 2005

Jones and Ray made measurements of the capillary rise of solutions of electrolytes which they interpreted as showing that there is a minimum in the surface tension-concentration curve at low concentration (about 0.001N). Langmuir has suggested that the liquid film above the meniscus may be several hundred angstroms thick and may be sufficiently different for water and for solutions of electrolytes to account for the observed capillary rises without drawing the conclusion that there is a minimum in the surface tension. Langmuir's theory is analyzed in detail and one of its premises is shown to be inconsistent with experimental evidence of several kinds which indicates that a solution-air interface is electrically charged. Langmuir's theory gives the thickness of the wetting film as an explicit function of the concentration and temperature of the solution; and of the capillary rise (which depends on the radius of the tube and on the surface tension of the liquid); and of the zeta-potential. But unfortunately zeta-potentials are not known with sufficient precision to permit reliable calculations of the thickness of the wetting film. Some of the consequences of the theory are tested experimentally.
The Absorption Coefficient of Nitrogen Dioxide in the Visible Spectrum
Authors: Dixon J. K.
Published: January 2005

The absorption coefficient of nitrogen dioxide in the visible spectrum has been measured at pressures up to 70 mm Hg with a 40A spectrophotometer slit. Beer's law is obeyed in this region. The transmission as measured when using a tungsten source, is the same as that oftained with either a high or low pressure mercury arc, except at the 4339–4358A group of mercury lines, where the absorption coefficient was found to be 15 percent greater with the mercury source. The absorption coefficient curve obtained with either a 40A or 15A slit is essentially sinusoidal in appearance, the absorption maxima and minima generally differing by about 10 percent in intensity. The maxima are separated by 700±100 cm—1. They appear to be due, not to the ground state of the molecule, but to groups of excited levels which are uniformly separated.
The Entropy of Long Chain Compounds in the Gaseous State
Authors: Huggins Maurice L.
Published: January 2005

Equations are derived for the entropy of long chain compounds in the gaseous state at 25°C. (1) The translational entropy, computed classically, varies with chain length according to the relation St=a+b ln n. (2) The entropy of rotation of the molecule as a whole, calculated statistically, assuming either a ball-like molecule or absolutely random kinking, is also linear with respect to ln n. (3) The entropy of internal vibrations, assumed (following Pitzer) to be an additive function of contributions associated with the various types of bonds and bond angles present, obeys the equation Siv=a+bn. (4) The entropy of internal randomness, for randomly-kinked molecules with no rotation, with hindered rotation, or with completely free rotation, is likewise linear in n. The equation deduced for long chain paraffins, containing but one adjustable constant (connected with the degree of hindrance of the rotation about the C–C bonds) agrees quite well with values deduced from specific heat data for short chain paraffins.
The Absolute Rates of Heterogeneous Reactions II. Electrode Reactions
Authors: Kimball George E.
Published: January 2005

The theory of the first paper of this series is extended to include reactions at electrode surfaces. The resulting expression for the rate of an electrode reaction includes both activation controlled and diffusion controlled reactions. The problem of the effect of stirring rate on reaction rate is discussed. The results are applied to the theory of reactions at ``floating'' electrodes, e.g. the solution of metals in acids. It is shown that the reaction rate expressions at such electrodes are of a very complex form, but can be approximated in special cases. It is found that the rate of such a reaction will in general depend not only on the concentration of the principal reactants, but also on the concentration of every ion in the solution.
On Phase Changes in Crystals Arising from Hindered Molecular Rotation
Authors: Kirkwood John G.
Published: January 2005

A theory of phase changes due to hindered molecular rotation in crystals is developed on the basis of classical statistical mechanics. It is demonstrated that local hindrance of relative rotation of neighboring molecules in the lattice can produce a non-uniform distribution in orientation below a certain critical temperature. The theory provides a semi-quantitative description of the behavior of the hydrogen halides in certain of their lambda-transitions, with a relative torque potential of the form (ε/2) cos γ for a pair of neighboring molecules, the axes of which are inclined at an angle γ to each other. The barrier height ε is estimated to be between 200 and 300 cal./mole for hydrogen iodide and hydrogen bromide.
The Magnetic Susceptibility of Silver Sub-Fluoride
Authors: Freed Simon , Sugarman Nathan , Metcalf Richard P.
Published: January 2005

The metallic character of the crystals of silver sub-fluoride was studied in terms of the magnetic susceptibility. It was found that the conduction electrons contribute a considerable diamagnetism which was related especially to the anisotropy of the crystals.
Spectral Transmission of Glucose Glass in the Near Infra-Red
Authors: Cohn Willi M.
Published: January 2005

The transmission of samples of glucose glass varying in thermal history was previously investigated. This work covered the visible part of the spectrum. Transmission data in the near infra-red are presented now as far as could be obtained photographically (12,000A). No limit of absorption was found at long wave-lengths as far as tested. The possible use of organic glass for investigations in the near infra-red is discussed.
Intensities of Electronic Transitions in Molecular Spectra IX. Calculations on the Long Wave-Length Halogen Spectra
Authors: Mulliken Robert S.
Published: January 2005

The dipole strength DNQ for the perpendicular-type N→Q transitions in the long wave-length spectra of the halogen molecules is computed theoretically according to each of two approximations (LCAO and AO) for the wave functions. The work illustrates the behavior of antisymmetrical wave functions in transition moment calculations, and justifies the ignoring (as an approximation) of closed shells. The overlapping and dipole moment integrals ∫ [φ(npσ)][φ(npσ′)]dv and  ∫ [φ(npσ)]y[φ(npπy′)]dv are evaluated using Slater's approximate atomic orbitals for the φ's. The calculated DNQ values for both approximations show the same rapid variation with atomic number as do the observed values, except for iodine, where the anomalous smallness of the observed value may reasonably be attributed to strong case c effects. The LCAO calculated values are consistently much larger than the AO values; the latter agree surprisingly well with the experimental values (cf. Table I). The calculations show DNQ to be very sensitive to variations of the internuclear distance r, and to variation of the effective charge Z* in the Slater atomic orbitals used. It is pointed out that the former variation may require reconsideration of work in which repulsive potential energy curves are deduced from intensity data on absorption continua. A qualitative discussion is given of the effects on DNQ of various possible improvements of the wave functions used. In connection with this, calculations have been made which show that the energy of the σu1s antibonding state of H2+ in LCAO approximation is minimized when Z* for 1s is (roughly) 0.84, for normal internuclear distance. This contrasts with Z*=1.228 determined by Finkelstein and Horowitz for the σg1s bonding state, and suggests that to improve molecular wave functions Z* should be increased for bonding but decreased for antibonding molecular orbitals.
The Hydrogen Isotope Exchange Reaction
Authors: Halford J. O.
Published: January 2005

The possibility of deriving the equilibrium constants for the higher deuterium substitutions from the isotope exchange coefficient is examined with the aid of calculations on the ammonia and methane reactions with water. If the experiment is carried to solutions at equilibrium with water containing as much as 25 percent D2O and the error in a single measurement does not exceed 1.0 percent the second constant is determined to within 10 percent of the correct value. As a standard of comparison against which the experimental results may be examined to advantage, an equation is developed showing the relation between the equilibrium constant for the first substitution and the exchange factor at higher deuterium fractions, subject to the assumption that each successive substitution of D for H produces the same frequency shift. The evaluation of frequency shifts from exchange data is considered.
The Partition Functions and Energy Levels of Molecules with Internal Torsional Motions
Authors: Crawford Bryce L.
Published: January 2005

The complete energy matrix is set up for external and (hindered) internal rotations of ``pseudo-rigid'' molecules; i.e., molecules consisting of a rigid framework to which symmetric hindered rotators are attached. The reduced secular equation for the energy levels of such a molecule with one internal rotation is given explicitly. By using the perturbation method of Wilson, the partition function for this model is found, correct to the second order. Effects due to angular momentum couplings are included. A simple method for the calculation of thermodynamic contributions of hindered internal rotations is given. As an example, the application of the method to propylene is described; in this case, the coupling terms here included may amount to as much as 19 percent of the effect of the hindering potential on the thermodynamic contributions.
A Vibrational Analysis of the Absorption Spectrum of Furan in the Schumann Region
Authors: Pickett Lucy W.
Published: January 2005

The absorption spectrum of furan vapor between 2200 and 1550A shows three band systems which overlap slightly. The second of these with a 0–0 band at 52,230 cm—1 has sharp bands which could be analyzed to reveal three prominent totally symmetrical vibration frequencies of the excited molecule of 1395 cm—1, 848 cm—1 and 1068 cm—1. Other characteristic frequency differences in the more diffuse bands are noted. Since the furan was found to be comparatively stable to photochemical decomposition, measurements of the intensity of absorption were made.
A Note on the Efficiency of the Thermal Diffusion Process for Separating Isotopes
Authors: Westhaver J. W. , Brewer A. Keith
Published: January 2005

The mechanism proposed by Gillespie for the thermal separation of gases is correlated with the attendant conduction of heat; this is done by describing gaseous heat conduction as a heat exchange between two oppositely bombarding Maxwellian groups which differ in temperature at each isothermal surface by a finite ΔT. The resulting formulas enable a computation of ΔT the bombardment ``equipartition distance'' and the transport yield. An ideal system of cells each having temperature limits of 300°K and 500°K is found to require a minimum of 880 kw hours of conducted heat per gram C13H4 extracted to a concentration of 20 percent.
Physics of Stressed Solids
Authors: Goranson Roy W.
Published: January 2005

The internal energy of a system is subdivided into a work or potential function and a thermal or kinetic function, the former expressed in terms of the current electrostatic theory of intercrystalline bonding, and these functions then examined for variations of temperature, hydrostatic pressure, unidirectional stress and combined hydrostatic and unidirectional pressure. From these considerations a theory is evolved which not only seems satisfactorily to explain and correlate phenomena of deformation, creep or plastic flow, cold working, elastic after-working, rupture, shear and certain other phenomena hitherto described as ``anomalous'' effects but has been corroborated experimentally in some of its predictions, in particular for the effect of hydrostatic pressure on deformation and compressive strength. The mechanism evolved consists of two processes—one an elastic deformation which is a function of the strain or potential energy of the system. Failure occurs here by ``brittle'' rupture wherein the maximum extension or maximum internal tension is the criterion. The other is a deformation by means of a two-phase transfer mechanism and is a function of the thermodynamic potential relations of the system. This latter type is also a function of time and therefore a function of the rate of application of load. When both processes of this mechanism are operative failure occurs by shear; the criterion for this type of failure is given by a function of time, the strain or potential energy and the thermodynamic potential relations of the system. Expressions are derived for creep or plastic flow of polycrystalline substances from the thermodynamic potential relations which not only satisfy the well-known phenomena of creep in metals but also express recent empirical creep data of some substances immersed in liquids in which they are somewhat soluble. An expression is also derived for the ``brittle'' potential type of rupture under combined thrust and hydrostatic pressure.
An Empirical Equation for Thermodynamic Properties of Light Hydrocarbons and Their Mixtures I. Methane, Ethane, Propane and n-Butane
Authors: Benedict Manson , Webb George B. , Rubin Louis C.
Published: January 2005

An empirical equation is given for the isothermal variation with density of the work content of pure hydrocarbons in the gaseous or liquid state. From this fundamental equation are derived (a) an equation of state, (b) an equation for the fugacity, and (c) an equation for the isothermal variation of the enthalpy. These equations summarize P-V-T properties of the gaseous or liquid phase, critical properties, vapor pressures, and latent heats of evaporation. A procedure is suggested for determining numerical values of the parameters in the equation. Such values are given for methane, ethane, propane, and n-butane. A comparison is made between observed properties of these hydrocarbons and those predicted by the equations.
The Negative Bands of the Heavy Nitrogen Molecules
Authors: Wood R. W. , Dieke G. H.
Published: January 2005

The so-called negative bands emitted by the N2+ molecule have been photographed in the second order of a 21-ft. concave grating with a dispersion of about 0.6A per mm. The principal bands of N15–N15 and N14–N15 are analyzed. A comparison of the constants of the three isotopic molecules shows that the changes except for the spin-doubling and perturbations are well represented by the elementary theory of band spectra. The intensity alternations in the N15–N15 bands give 12ℏ as the value for the nuclear spin of N15.
Infra-Red Absorption Studies X. The Infra-Red Absorption of Hydrogen Fluoride in the Vapor State and in Solution in an Inert Solvent
Authors: Buswell A. M. , Maycock R. L. , Rodebush W. H.
Published: January 2005

The infra-red absorption of hydrogen fluoride has been observed both with the prism and the grating spectrometer. The absorption in the vapor for the single molecules is as previously reported by Imes. At slightly longer wave-lengths a very strong absorption band due to the hydrogen bonding in the associated molecules is observed. In solution in carbon tetrachloride the single molecule spectrum undergoes considerable modification and no association is observed. This fact is rather surprising. The infra-red absorption of a thin crystal of potassium hydrogen fluoride was studied in order to fix the frequency of the hydrogen in the FHF- ion.
The Raman Spectra of Phosphorus Methyl and Arsenic Methyl and the Force Constants of the Methyl Compounds of the Fifth Group Elements
Authors: Rosenbaum E. J. , Rubin Dorothy J. , Sandberg C. Roger
Published: January 2005

The Raman spectra of P(CH3)3 and As(CH3)3 have been photographed and studied in relation to the spectra of the methyl compounds of nitrogen, antimony and bismuth. The low lying frequencies of all of these molecules can be interpreted in terms of a pyramidal structure with the methyl groups acting as units. The existence of only two low lying lines in the spectra of Sb(CH3)3 and Bi(CH3)3 is attributed to an accidental degeneracy resulting from the relatively large mass of the central atom and a particular value of the apex angle. The frequencies computed from a two-constant valence force potential function are in good agreement with those observed. The force constants obtained are tabulated.
The Vibration Spectra of Hydrazoic Acid, Methyl Azide, and Methyl Isocyanate The Thermodynamic Functions of Hydrazoic Acid
Authors: Eyster Eugene H. , Gillette R. H.
Published: January 2005

The vibration spectra of hydrazoic acid, methyl azide, and methyl isocyanate have been investigated in the spectral region between 2 and 20μ. Correlation of the spectra of these structurally similar molecules has made possible the determination of all the fundamental frequencies of hydrazoic acid and all but the methyl torsion frequency in the methyl compounds. From these fundamental frequencies and the known rotational constants, the usual thermodynamic functions of hydrazoic acid have been calculated to the harmonic oscillator-rigid rotator approximation. Equilibrium constants for some characteristic reactions have also been obtained.
Hindered Rotation III. The Qualitative Nature of the Interactions HIndering Internal Rotation
Authors: Langseth A. , Bernstein H. J. , Bak B.
Published: January 2005

Experimental evidence shows that an important contribution to the potential barrier hindering internal rotation, is an interaction stabilizing ``opposed'' configurations. A qualitative picture of this interaction which is considered as arising in the bond connecting the two halves of a molecule, is presented, based on the symmetry properties of the molecule and the ideas associated with overlapping of wave functions. This interaction seems to be of chief importance in hydrocarbons where dipole and steric effects are small, such as ethane, propylene, toluene, cyclohexane, dimethylacetylene. Even in compounds where the dipole effect is great, such as tetrachloroethane and dichloroethylene, this interaction plays the most important role.
Far Ultraviolet Absorption Spectra of Some Aliphatic Ketones
Authors: Duncan A. B. F.
Published: January 2005

Absorption spectra of methyl n-propyl, methyl isopropyl and diethyl ketones between 2000 and 1500A were found. The electronic transitions and their vibrational structure are discussed in comparison with acetone and methyl ethyl ketone. It is concluded that most transitions are probably of a Rydberg type, leading to ionization potentials in the neighborhood of 10 ev.
Effect of Electric Fields on the Decomposition of Nitrous Oxide by Alpha-Rays
Authors: Kolumban A. D. , Essex H.
Published: January 2005

Ion yields expressed in molecules of gaseous products uncondensed by liquid air, per ion pair are 30∘no field4.35half−saturation4.15full saturation4.61100∘no field4.75half−saturation4.65full saturation5.76.If these results are interpreted on the assumption that ions are neutralized at the electrodes without decomposition, then it follows that in the absence of an electric field, 9 percent of the reaction, is initiated by combination of ions at 30°C, and 4 percent of the reaction is so initiated at 100°C. The increase in ion yield at high field strength is probably due to electron collisions with molecules. As this occurs at field strengths at which the current-field strength curve is horizontal, the new reaction is not initiated by ionization. Therefore, as the major part of the energy of alpha-rays remains in the primarily ejected electrons, electron collisions without ionization should initiate part of the reaction occurring in the absence of electric fields.
The Photolysis of Methylethyl Ketone
Authors: Moore Walter J. , Taylor Hugh S.
Published: January 2005

The nature of the products from the photochemical decomposition of methylethyl ketone at temperatures from 90 to 200° has been re-examined. In contrast with earlier results, the formation of ethane, propane, and butane parallels the frequency of the corresponding free radical collisions. At the higher temperatures, however, production of ethane and especially of methane becomes predominant. The influences on the product distribution of secondary reactions, the lifetimes of the free radical collision complexes, and the activation energies and entropies, are considered.
Potential Function of Acetylene Molecule. II
Authors: Wu Ta-You
Published: January 2005

From a study of the interaction between the vibration and the rotation, the convergence factor of the rotational lines of the vibration-rotational bands of C2H2 is obtained as a function of the various vibrational quantum numbers and the constants in the first-order anharmonic potential. A tentative calculation of the first- and second-order anharmonic potentials is carried out for the C2H2 molecule on the basis of the classification of the absorption bands given in Part I.
The Nature of the Ions Emitted by Heated Filaments and Salts
Authors: Toubes B. , Rollefson G. K.
Published: January 2005

It has been found that positive ions are emitted by filaments of tungsten, tantalum, and molybdenum when heated to temperatures near the melting points. Sodium and potassium ions were found in addition to those of the filament metal. When alkali halides were heated to 800–1000°C on platinum they emitted the singly charged ions of the corresponding alkali metal. No negative ions were found and no ions were obtained from the chlorides of calcium, magnesium, strontium, barium, or zinc.
Infra-Red and Raman Spectra of Polyatomic Molecules XII. Methyl Acetylene
Authors: Crawford Bryce L.
Published: January 2005

The infra-red absorption of methyl acetylene gas has been studied between 2.5 and 25μ; the Raman spectrum of the liquid has been measured. A complete vibrational analysis is given, and the thermodynamic properties of the gas, between 250° and 1000°K, are tabulated. A normal coordinate treatment has been carried out, in which all force constants were determined a priori from other molecules. The ten fundamentals are calculated with an average error of 1.1, and a maximum error of 2.3 percent.
The Infra-Red Absorptions of Organic Hydroxyl Compounds in the Solid State in the 3μ Region
Authors: Davies Mansel M.
Published: January 2005

The absorptions in the range 2.6μ to 3.5μ, covering the OH and CH fundamentals, have been measured for a variety of solid organic hydroxyl compounds in the form of thin films. For simple alcoholic and carboxylic structures the results, as expected, show complete association in the condensed state. In a number of other cases a sharp band with a narrow doublet structure (δv∼40 cm-1) is found near 2.9μ, and this is ascribed to relatively ``free'' OH groups in the solid resulting either from steric protection, as in triphenylmethyl carbinol, or weak intramolecular binding as in ethyl mandelate. Two very general features are the shift of the absorptions to longer wave-lengths in the condensed phases, and the doublet nature of the absorption of the ``free'' hydroxyl groups in the solid as well as in other phases. Both these factors are discussed in the light of the new and previous data.
Packed Fractionating Columns and the Concentration of Isotopes
Authors: Cohen Karl
Published: January 2005

The behavior of isothermal packed fractionating columns is deduced from their differential equation. The relation between rates of production and over-all fractionation is studied, as is the rate of approach to equilibrium. The results are illustrated by problems of isotope separation.
The Radial Distribution Method in Electron Diffraction
Authors: Walter John , Beach J. Y.
Published: January 2005

A new radial distribution function for use in interpreting the electron diffraction photographs of gas molecules has been obtained. Instead of replacing the inverted Fourier integral by a sum the integration is performed by assuming that the shapes of the maxima and minima are those of cosine functions. The amount of scattering matter r2D(r) is calculated rather than the density D(r). Comparison between radial distribution functions calculated by this method and by other methods is made for a diatomic molecule, a nonlinear triatomic molecule (to test resolving power), a linear triatomic molecule and carbon tetrachloride.
Gaseous Heat Capacities. III
Authors: Kistiakowsky G. B. , Rice W. W.
Published: January 2005

The present paper presents a continuation of measurements on the gaseous heat capacities by the adiabatic expansion method. The apparatus and the experimental procedure are exactly the same as described in the previous papers denoted herein as Part I and Part II. The compounds with which the present paper deals are dimethyl ether, ethylene oxide, dimethyl acetylene, cis-butane-2 and trans-butene-2. For the correction of the experimental data to the ideal gas state several procedures had to be used, as discussed in Part II.
Directed Valence in Chemical Reactions
Authors: Magee John L.
Published: January 2005

The potential energy surfaces for the reactions of two hydrogen atoms with another hydrogen-like atom having a single valence electron in a 2p orbital are investigated. The simple Heitler-London approximation is used in the calculations. The calculated activation energies for the reactions: H2+X→H+HX(′Σ)HX(′Σ)+H→H+XH(′Σ),where X is the atom having the 2p valence electron, are quite low, ∼1 Calorie. This is in good agreement with the experimental results for X = halogen, and the general principle that directed valence lowers activation energies. The symmetrical configurations for the H2X complex are found to have the lowest energy. In fact, a triangular complex was found to be stable with respect to dissociation into either HX+H or H2+X. The mechanism of the reactions between hydrogen and the halogens is discussed.
The Near Ultraviolet Absorption Spectrum of Heavy Benzene
Authors: Sponer H.
Published: January 2005

The absorption spectrum of heavy benzene at 2700–2300A has been analyzed. As in light benzene it represents a forbidden transition 1A1g→B2u1 made allowed through the interaction of vibrations of type εg+. Interpretations have been given for the majority of the bands. The measured bands together with the assignments are exhibited in Table I.
The Vibration Frequencies and Thermodynamic Functions of Long Chain Hydrocarbons
Authors: Pitzer Kenneth S.
Published: January 2005

A method is developed for calculating thermodynamic functions for long chain molecules with particular attention to normal paraffins. In this connection the infinite chain approximation method for calculating vibration frequencies is considered. Starting with the results of Kirkwood, a modification is made which improves the agreement with the exact values for the simpler cases. In addition this method of attack is extended to out of plane motions. This vibrational analysis shows that all skeletal frequencies for molecules of the normal paraffin type can be put into two groups, one fairly narrow band near 1000 cm—1, and a broader band extending from 0 to 460 cm—1. The partition function is then set up on the assumption that motions in the low frequency group can be treated classically, and that the high frequency band can be replaced by a suitable number of 1000 cm—1 frequencies. Contributions from hydrogen atom vibrations are added on later. A formula is finally obtained which is quite simple, considering the complexity of the molecules. The calculated entropies can be brought into agreement with experimental values on the basis of very reasonable internal rotation restricting barriers.
Theory of Depolymerization of Long Chain Molecules
Authors: Montroll Elliott W. , Simha Robert
Published: January 2005

A theory of depolymerization of long chain molecules is developed on a statistical basis. It is assumed that all bonds connecting monomeric elements in the system have the same probability of being broken regardless of their position in a given polymer and regardless of the size of the polymer in which they are found. Expressions are derived for the distribution of molecular sizes in the depolymerized system as a function of the initial chain length and the average number of bonds split per molecule. Also, relationships are established between the average molecular weight of the degraded product and the average number of bonds split per molecule. Experiments on the acetolytic degradation of cellulose acetate are briefly discussed.