bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the Theory of Absolute Reaction Rates to Overvoltage
Authors: Eyring H. , Glasstone S. , Laidler K. J.
Published: January 2005

It is shown by means of the theory of absolute reaction rates that the current density I at an electrode is related to the overvoltage V by the expression I = I0eαVF/RT where I0 is a constant for a given electrode, representing the current passing in each direction at the reversible potential, and α is the fraction of the added potential V operating between the initial and activated states. Since α is about 0.5 for many electrodes, it appears that the energy barriers at the electrode surface is a symmetrical one. The quantity I0 is equal to Be—ΔH1‡/RT, where ΔH1‡ is the heat of activation of the rate-determining process responsible for overvoltage, and B is C1(kT/h)F/N·eΔS1‡/R, where k, h, F, N and R are universal constants, T is the temperature, ΔS1‡ is the entropy of activation and C1 is the concentration, per unit area, of the species involved in the slow process. Since ΔH1‡ and I0 can be obtained from experimental data, it is possible to evaluate B, which is found to be independent of the nature of the cathode or the hydrogen ion concentration of the solution, and hence it appears that C1 is almost constant for all electrodes in aqueous solutions. This suggests that the rate-determining step in the discharge of a hydrogen ion involves a water molecule, for only in this way could C1 remain constant, and the slow process is believed to consist in the transfer of a proton from a molecule of water attached to the solution to another water molecule attached to the electrode surface. The suggested prototropic mechanism permits of an approximate estimate of ΔS1‡, and taking C1 as 1015 molecules of water per sq. cm, the value of B calculated is in satisfactory agreement with experiment. The mechanism suggested immediately leads to the expectation of a symmetrical barrier at the electrode surface and so accounts for the value of 0.5 for α. The linear rate of attainment of overvoltage and the effect of changes in zeta-potential are readily explained, and it is shown that metals which form strong M—H bonds should have low overvoltages, as found in practice. The hydrogen-deuterium electrolytic separation factor is considered from the standpoint of the prototropic theory of overvoltage, and an explanation is proposed for the influence of the cathode material and of temperature. Oxygen overvoltage is attributed to a proton transfer in the opposite direction, i.e., from a water molecule on the electrode to one in a layer associated with the solvent, and so the striking similarities between cathodic and anodic phenomena can be readily understood. The high overvoltage accompanying the discharge of H3O+ and OH— but not other ions is attributed to the fact that these ions are comfortably built into the structure of the solvent water.
The Lengths of the Links of Unsaturated Hydrocarbon Molecules
Authors: Coulson C. A.
Published: January 2005

The lengths of the links in conjugated chain molecules C2nH2n+2 and in condensed aromatic hydrocarbons such as benzene, naphthalene and diphenyl are calculated on the assumption that there is a simple interaction energy between all contiguous carbon-carbon bonds. The lengths thus deduced are in excellent agreement with those determined by the use of quantum-mechanical ideas of resonance.
The Free Energy of Hydration of Gaseous Ions, and the Absolute Potential of the Normal Calomel Electrode
Authors: Latimer Wendell M. , Pitzer Kenneth S. , Slansky Cyril M.
Published: January 2005

The free energies of hydration of the alkali and halide ions are found to agree reasonably well with the simple expression of Born (—ΔF=(1–1/D)Ne2/2re) for solution of charged spheres in a dielectric medium, provided the crystal radii are suitably modified so as to correspond to the radii of the cavities in the dielectric medium. The results show that the dielectric constant of water remains large even in the intense field next to the ion. The entropies of hydration are also found to be consistent with these radii. Because of the simplicity of this calculation, the resulting free energies of solution of individual ions are considered to be a priori the most probable and are used to calculate a value of —0.50 volt for the absolute potential of the calomel half-cell.
The Differential Diffusion Constants of Hydrochloric and Sulphuric Acids
Authors: James W. A. , Hollingshead E. A. , Gordon A. R.
Published: January 2005

The differential diffusion constants of hydrochloric and sulphuric acids in aqueous solution at 25°C have been determined with Northrop-McBain diffusion cells. The range of concentration studied was 0.01–1.6 moles/liter for hydrochloric and 0.01–1.0 moles/liter for sulphuric. The relation previously proposed k=k0(1+c∂ ln f/∂c)·(η0/η) represents the variation of the diffusion constant with concentration reasonably closely, but the values of k0 required to fit the experimental results are not those predicted by the Nernst relation.
The Infra-Red Absorption of HCl in Solution
Authors: Gordy Walter , Martin Philip C.
Published: January 2005

The fundamental HCl vibrational band has been observed for solutions of HCl in nitrobenzene, o-nitrotoluene, ethyl acetate, di-ethyl ether, iso-propyl ether, n-butyl ether, and dioxan. The band is shifted appreciably to lower frequencies in all of these solvents. The shifts are too great to be attributed wholly to the dielectric constants of the solvents; they are interpreted as being caused primarily by hydrogen bonding between the HCl and the solvent.
The Diffraction of X-Rays by Gas Molecules A Comparison with Electron Diffraction and a Discussion of the Results for SiHCl3
Authors: Pirenne Maurice Henri
Published: January 2005

The principles of x-ray and electron diffraction by free molecules are discussed in view of the application of these methods to the determination of molecular structures. The influence of the chemical bond is not more disturbing for x-ray measurements than for electron measurements. The hydrogen atoms are practically nonexistent for x-ray diffraction while it is not so for electron diffraction. This is an advantage which has not yet been fully used. The following procedure is suggested: first an x-ray investigation in which the number of parameters to be determined is much reduced, and subsequently an electron investigation which will determine the remaining parameters, i.e., the position of the hydrogen atoms. Thus in some cases at least (CH3Cl e.g.), the use of both diffraction methods is necessary and is sufficient for determining completely the molecular structure, including the position of the hydrogen atoms. A discussion of x-ray measurements on SiHCl3 shows the precision and the certainty of the method. As for the disadvantages of the long times of exposure, which have been more than 100 hours, they have been reduced to, say, 8 hours for crystal-monochromatized radiation and they will probably be reduced by a new factor 10 in the near future. Although being less numerous than in the case of electron diffraction, the maxima given by x-ray diffraction present two fundamental advantages. In general they are actual, well-defined maxima. The effect of molecular vibrations on them, which is difficult to calculate, is the smallest just at the angles at which they are the most prominent.
Spectroscopic Evidence of Hydrogen Bonds: Chloroform and Bromoform in Donor Solvents
Authors: Gordy Walter
Published: January 2005

The method of infra-red spectroscopy has been used to study solutions of chloroform and bromoform in various electron donor solvents, including ketones, esters, ethers and amines. In the region of 4μ, a band has been observed which apparently is not characteristic of the spectrum of either the solute or solvent. Because of the intensity of the band it is thought to be a fundamental. The most reasonable interpretation seems to be that it is an NH or OH vibrational band resulting from intermolecular hydrogen bond formation between the CH haloform group and a N or O of the solvent. The band for the bromoform solutions is weaker than that for the corresponding chloroform solutions.
Spectroscopic Evidence of Hydrogen Bonds: Aniline and Some Substituted Phenols
Authors: Gordy Walter
Published: January 2005

Both inter- and intra-molecular hydrogen bonding in certain substituted phenols was studied by determining the effect of the bonding on the OH fundamental occurring in the region of 3μ. For m- and o-nitro-phenols, complex formation with certain oxygenated solvents was studied. The vibrational band of the NH2 aniline group was found to shift to wave-lengths shorter by 0.07μ upon dilution of aniline in benzene solution. Association of the aniline in the liquid state through very weak hydrogen bonds is proposed as an explanation of this shift. Similar evidence is offered for the formation of very weak hydrogen bonds between aniline and the solvents n-butyl and isopropyl ethers.
The Potential Function of the Acetylene Molecule. I
Authors: Wu Ta-You , Kiang A. T.
Published: January 2005

A perturbation calculation is made of the anharmonicity coefficients in the vibrational energy expression of C2H2 in terms of the constants in the most general first-order and second-order perturbing potentials consistent with the geometrical symmetry of the molecule. From an analysis of the absorption spectrum, a tentative classification is made and the anharmonicity coefficients and the zeroth-order frequencies are calculated. The zeroth-order potential constants so obtained are: kCH=6.24, kCC=17.2, kCCH=—0.67 in 105 dynes/cm, compared with the values kCH=5.85, kCC=15.6, kCCH=0.028 obtained by using the observed frequencies. In the appendix the relation between bond constants and molecular structure is discussed.
Analysis of the Near Ultraviolet Electronic Transition of Benzene
Authors: Sponer H. , Nordheim G. , Sklar A. L. , Teller E.
Published: January 2005

The absorption spectrum of benzene at 2800–2200A has been analyzed. The vibrational structure of the system has been found to be in agreement with the selection rules for a forbidden transition (1A1g→1B2u). The transition becomes possible when vibrations of type Eg+ distort the molecule. Only carbon frequencies have been found to be effective. The interpreted data are collected in series on page 211. The analysis is corroborated by comparison with the absorption of solid benzene at —259°C, with the absorption spectrum of heavy benzene and with the fluorescence spectra of both benzenes.
The Extrapolation of Conductance Data for the Monovalent Nitrates and Iodates by Means of the Extended Onsager-Shedlovsky Equation
Authors: Gordon A. R.
Published: January 2005

It is shown that the extended Onsager-Shedlovsky equation Λ0 = Λ0′ — BC — DC log C where Λ and Λ0 are the equivalent conductances at concentration C and at infinite dilution, Λ0′ is the limiting Onsager function (Λ +βC½) / (1 —αC½), and B and D are disposable constants, serves for the extrapolation of conductance data for the monovalnt enitrates and iodates. The anomalies in the conductance at low concentrations of these salts are due to the fact that the logarithmic term is for them relatively more important than it is for the corresponding chlorides.
The Symmetry Number and Thermodynamic Functions for Molecules Having Double Minimum Vibrations
Authors: Pitzer Kenneth S.
Published: January 2005

The energy levels and thermodynamic functions for a double minimum vibrational degree of freedom are presented, and their application illustrated for the case of ammonia. A simple formula is given for the range of validity of the classical expressions for rotational heat capacity and entropy. Also the symmetry number, which is troublesome in examples of double minimum vibration, is discussed briefly.
Photolysis of Aldehydes and Ketones in the Presence of Iodine Vapor
Authors: Gorin Everett
Published: January 2005

The photolysis of acetone and of formaldehyde takes place principally through a free radical mechanism. The primary processes consist in the splitting off of a methyl radical and a hydrogen atom, respectively. The primary process in the photolysis of methyl ethyl ketone also consists in the splitting off of either a methyl or an ethyl radical. The heat of dissociation of the first hydrogen in formaldehyde is shown to be as low as 78 kcal. Approximately 26 kcal. is required to remove the second hydrogen atom.
Optical Sensitizing of Silver Halides by Dyes I. Adsorption of Sensitizing Dyes
Authors: Sheppard S. E. , Lambert R. H. , Walker R. D.
Published: January 2005

The adsorption of a number of sensitizing dyes to silver bromide has been studied analytically. Basic dyes of the cyanine type are adsorbed completely (irreversibly) from aqueous solutions, but the velocity of adsorption is greatly reduced by the presence of gelatin. Adsorption is oriented, the dye molecules being held by the hydrophile, ionizable side of the molecule, and presenting the hydrophobe portion to the solution, for a primary monolayer; in several cases a second monolayer is formed with the orientation reversed. Calculations of the adsorption-density at saturation (primary monolayer) agree with ``edge-on'' adsorption of the dye molecules in approximately close-packed assemblages. In agreement with the spectrographic finding of Leermakers, Carroll and Staud, with several of the cyanine dyes, at least two states of aggregation must be assigned to the adsorbed dye. These are provisionally regarded as unimolecular and multimolecular, and show characteristically different absorption and sensitizing bands. Acid dyes, such as erythrosin, which contain nonadsorbed solubilizing (hydrophile) groups are incompletely (reversibly) adsorbed, but also appear to be oriented at the surface similarly to the cyanine dyes.
The Low Temperature Gaseous Heat Capacities of C2H6
Authors: Kistiakowsky G. B. , Lacher J. R. , Stitt Fred
Published: January 2005

The heat capacities of gaseous C2H6 and C2D6 have been measured down to 93°K with the low pressure thermal conductivity apparatus previously described. An improved cryostat and better designed conductivity cells were used. A new method of obtaining the heat capacities from the thermal conductivity data is described which does not require a knowledge of the accommodation coefficient α. It is based on the assumption that when the accommodating efficiency of the wire is changed, α changes in the same direction for the gases being compared and further that the percentage change in α is greater the more its absolute value deviates from unity. It is then possible to show that the unknown α for the gas being studied can be bracketed within narrow limits by the α's of comparison gases. The heat capacity results for light and heavy ethane indicate a potential barrier restricting internal rotation of essentially sinusoidal shape and with a depth of 2750 cal./mole.
Infra-Red and Raman Spectra of Polyatomic Molecules. VII. C2D6
Authors: Stitt Fred
Published: January 2005

The infra-red spectrum of gaseous C2D6 has been investigated from 2 to 22μ, and the Raman spectrum of the liquid has been photographed. These data have been analyzed for both the symmetries D3d and D3h. It is concluded that the equilibrium configuration of ethane cannot be reliably determined from the analysis of the data now available on the vibrational spectra of C2H6 and C2D6. However, the ``uncertain frequency'' of C2H6 is determined by application of the product rule if the symmetry is D3d. A modified valence force type potential function containing interaction terms between the two methyl groups is found to fit the fundamental frequencies of the light and heavy ethanes quite well.
The Prediction of Rate Constants from Equilibrium Data for Reactions in D2O–H2O Mixtures
Authors: Brescia Frank
Published: January 2005

The concentrations of hydrogen and deuterium ions at different fractions of D in the solvent are calculated from the simultaneous solution of the equations CH+·CHDO/CD+·CH2O = 3.76 and CH++CD+ = concentration of strong acid. Similarly, the concentrations of hydroxyl and deuteroxyl ions are calculated from the equations COD-·CH2O/COH-·CHDO = 0.225 and COH-+COD- = concentration of alkali. It is then possible to predict reaction rates for specific hydrogen ion and specific hydroxyl ion catalyzed reactions, in mixtures of H2O—D2O, on the assumption that the rate is proportional to the fraction of D+ in the first case and to the fraction of OD- in the second.
The Solid State of H2, HD and D2
Authors: Hobbs Marcus E.
Published: January 2005

By using the van der Waals field as calculated for H2 from the second virial coefficient by Lennard-Jones, and the kinetic zero point energy expression given by London in the theory of liquid He, the lattice energies of solid H2, HD and D2 have been calculated. The values calculated for the energy at 0°K are for H2 —180.4 and for D2 —280.6 calories per mole. These are in good agreement with the experimental values of —183.4 and —274.0 cal./mole, respectively. The corresponding theoretical values of the volume are 23.24 cc (22.65 obs.) for H2, and 19.78 cc (19.56 obs.) for D2. The values of HD have been predicted.
Intensities of Electronic Transitions in Molecular Spectra IV. Cyclic Dienes and Hyperconjugation
Authors: Mulliken Robert S.
Published: January 2005

The spectra of cyclopentadiene, 1,3-cyclohexadiene, thiophene, furan, and pyrrole are considered. Theoretical explanations of their departures from the spectra of openchain conjugated dienes are given. The cause of these departures in the cases of cyclopentadiene and cyclohexadiene is designated hyperconjugation. This is a mild sort of conjugation, apparently not recognized as such hitherto, between saturated groups and double or triple bonds or even other saturated groups. Observed displacements of spectra toward longer wave-lengths, and corresponding effects in the refractivities (cf. VI), when alkyl groups are substituted for hydrogens in ethylene, butadiene, benzene, or other double-bonded compounds, are attributed to hyperconjugation. Further, the decreasing heat of hydrogenation observed with increasing alkyl substitution in these compounds may indicate increasing stability caused by hyperconjugation. However, it is likely according to the theory that appreciable energy effects caused by hyperconjugation are usually restricted to excited states, and so should affect mainly ultraviolet spectra and refractivities. If this is correct, heats of hydrogenation ought not to be much influenced by hyperconjugation, since they depend on the energies of molecules in their normal states. Hence, it is likely that the above-noted variations in heats of hydrogenation are caused partly or mainly by other causes. Conjugation of triple bonds is briefly discussed, and it is also pointed out that in ethane there must be hyperconjugation which is analogous to the triple-bond conjugation in cyanogen. It is shown that this hyperconjugation in ethane should not appreciably hinder free rotation. Likewise, hyperconjugation in propylene should produce no barrier to free rotation of the methyl group. It is possible, however, that hyperconjugation may help to restrict free rotation in some cases. Carbon to carbon single bond distances should be slightly shortened by hyperconjugation. The unusually small C–C distance in methylacetylene as determined spectroscopically by Herzberg and co-workers may perhaps be explained in this way, although in other cases no appreciable effects are apparent. It is helpful to classify examples of hyperconjugation according to various types, which may differ in the magnitudes of their effects. Possibly only first-order hyperconjugation (between a double or triple bond and a saturated group) is important. Second-order hyperconjugation (between two saturated groups, as, for example, in ethane) very likely produces smaller effects.
Intensities of Electronic Transitions in Molecular Spectra VII. Conjugated Polyenes and Carotenoids
Authors: Mulliken Robert S.
Published: January 2005

The observed absorption spectra of conjugated polyenes and their derivatives are compared with the results of theoretical calculations on various models of butadiene, octatetraene, and β-carotene. In each case the unsaturation electrons give rise to a series of N→V electronic transitions which spread over an increasing range of the spectrum with increase in the number of conjugated double bonds. According to the theory, the greater part of the whole N→V intensity is concentrated in its longest wave-length member N→V1, and the latter gets more and more intense as it shifts toward longer wave-lengths with increase in the number of conjugated double bonds. Exactly this behavior has been observed experimentally in the spectra of the conjugated polyenes and their derivatives. Thus we obtain a satisfactory theoretical explanation of the existence of strong color in polyene pigments and related compounds, i.e. in the carotenoids. Quantitatively, the theory (when the rough Hückel molecular orbital approximation is used) requires empirical adjustment or calibration; new experimental work on the spectra of the lower polyenes would be valuable in this connection. The relations between absorption and fluorescence spectra (N→V1 and V1→N) in the substituted polyenes are discussed. An explanation is given of the ``gap'' between the longest wave-length absorption band and the shortest wave-length fluorescence band.

According to the theory, the shape of the molecule strongly affects the distribution of intensity and somewhat affects the total intensity in the N→V spectrum. The more elongated the molecule, the greater the total intensity, and the greater the preponderance of intensity in the longest wave-length transition N→V1. The α-furyl polyene aldehydes and acids may be cited as affording probable illustrations of this effect. Here the introduction of the furyl group, although it contains two conjugated double bonds, increases the N→V1 intensity much less than if the same grouping – HC=CH–CH=CH – had been added to the polyene chain. The explanation given here is that the two double bonds increase the over-all length of the molecule much less when they are bent around as in the furyl ring than when they are stretched out in a zigzag chain as apparently they are in the simple polyenes and polyene aldehydes and acids. According to the theory, the N→V1 transitions in conjugated polyenes and their derivatives are polarized approximately along the long axis of the molecule. This should give rise to a high polarizability of such molecules along that direction, which may help explain their reactivity, in particular their tendency to polymerize.
Antisymmetric Molecular Orbitals II. Calculation of Integrals
Authors: Sklar A. L. , Lyddane R. H.
Published: January 2005

The integrals which are common to the application of the method of antisymmetric molecular orbitals to unsaturated as well as to aromatic molecules are tabulated. Accordingly, all integrals are evaluated with 2pπ hydrogen-like functions. Tables are given for the Coulomb (aa; bb), exchange (ab; ab), and hybrid Coulomb exchange (ab; bb) repulsions of two electrons, and for the Coulomb and exchange attraction of a carbon ion for an electron.
The Reactions of Methyl Radicals with Deuterium, Ethane, Neopentane, Butane and Isobutane
Authors: Smith John O. , Taylor Hugh S.
Published: January 2005

Methyl radicals produced by photodecomposition of mercury dimethyl have been allowed to react with deuterium, ethane, neopentane, butane and isobutane in the temperature range 100–300°C. The kinetics of the processes have been ascertained. Ethane production was found to be bimolecular, methane production between first and second order with respect to methyl radical concentrations. From the rate of methane formation as a function of temperature the following activation energies for the reaction of methyl radicals were obtained: with deuterium 8.1, ethane and neopentane 8.3, butane 5.5 and isobutane 4.2 kcal. These values are based on an assumed activation energy E=0 for ethane formation. The data of Kistiakowsky on the heats of hydrogenation of the substituted ethylenes suggest that the bond energies of primary, secondary and tertiary C–H bonds are measurably different. The differences being approximately 2.5 kcal. between primary and secondary and 4.0 kcal. between primary and tertiary C–H bonds in saturated aliphatic hydrocarbons. These differences correspond approximately to the differences in the activation energies noted above. It is proposed that such differences be accepted as a second approximation to the prevailing assumption of equal energies for such C–H bonds.
An Equilibrium Theory of Ionic Conductance
Authors: Gorin Manuel H.
Published: January 2005

A theory for ionic conductance which assumes that the equilibrium between the central ion and its ionic atmosphere is not appreciably distorted by the application of the external field is proposed. On the basis of this approach, values of the radii for the individual ion are obtained by the extrapolation of conductance and transference data to infinite dilution. These values of the radii when inserted into the equations resulting from the theory yield expressions for conductance and transference that very closely follow the experimental ones up to 0.02M. Even at concentrations as high as molar, the discrepancy between the equilibrium theory and experiment is not large. The values of the ionic radii obtained from the theory are also correlated with the corresponding values of equivalent conductances at infinite dilution. The larger the ion, the more closely does it appear to obey the laws of classical hydrodynamics. For smaller ions, deviations from classical hydrodynamics increase rapidly as the radius decreases. On this basis, the high conductance of hydronium ion appears to follow naturally from the small radius obtained, namely, 0.95A. Furthermore, the deviation from the classical theory appears to be given by an expression involving the size of the hole that the ion must make in order to jump from equilibrium position to equilibrium position in the solvent, an idea suggested by the modern theory of liquids as developed by Eyring and his collaborator.
Optical Sensitizing of Silver Halides by Dyes II. The Mechanism of Optical Sensitizing and the Quantum Equivalent
Authors: Sheppard S. E. , Lambert R. H. , Walker R. D.
Published: January 2005

The photolysis of silver bromide sensitized with certain acid and basic dyes has been followed by chemical and photometric determination of the silver produced. It was found that in the absence of halogen acceptors the dye is progressively bleached, but in the presence of halogen acceptors it is recovered chemically unchanged. However, the dye actually combines with the bromine released but is regenerated on giving up the bromine to another less active acceptor. The maximum of sensitivity is found to occur considerably before adsorption-saturation, and at about the same adsorption-density for both photolysis and photographic sensitivity. The apparent desensitizing action of sensitizing dyes at higher adsorption-densities is ascribed to the facility of rebromination by the dye:bromine addition compound.

So long as the photographic yield is proportional to the adsorption-density of the dye an initial quantum equivalent of unity is found—one quantum of light absorbed by the dye produces one silver atom. In regard to the mechanism of sensitizing, photovoltaic experiments indicate the release of photoconductance electrons. These may be emitted either by the adsorbed dye itself or by bromide ions of the silver bromide receiving energy from the photoactivated dye. Some indirect evidence supports the latter view.
The Ultraviolet Absorption Spectra of 1–3 Cyclohexadiene
Authors: Henri Victor , Pickett Lucy W.
Published: January 2005

The intense absorption of 1–3 cyclohexadiene in the region 35,000–45,000 cm—1 has been measured in the vapor and in hexane solution, and characteristic frequency differences of the band maxima noted. Values of oscillator strength obtained from these data are consistent with theoretical predictions, but the f value found from the solution agrees better with that from the vapor if the correction for Lorenz-Lorentz forces is not applied.
The Infra-Red Absorption Spectrum of Boron Trifluoride
Authors: Gage D. M. , Barker E. F.
Published: January 2005

The infra-red absorption spectrum of BF3 has been studied under high resolution from 400 cm—1 to 3000 cm—1. The active fundamentals v2, v3 and v4 and the overtone 2v3 have been observed. The parallel fundamental v2 has been partially resolved and the value of the moment of inertia A found to be 79×10—40 g cm2. The B–F distance is 1.29×10—8 cm. The isotope effect due to the two isotopes of boron was observed in all bands. The appearance of the unresolved bands v4 and 2v3 is shown to be greatly influenced by the interaction between vibration and rotation.
Vibration Spectra and Molecular Structure VII. Further Infra-Red Studies on the Vapors of Some Carboxylic Acids
Authors: Herman R. C. , Hofstadter R.
Published: January 2005

The monomer and dimer spectra of the vapors of CD3COOD, CD3COOH, C2H5COOH and C2H5COOD have been obtained in the near infra-red with a rocksalt spectrometer. The association of C2H5COOD has been studied and the value of the heat of association obtained is 7000 calories per mole per bond.
The Probable Length of Hydrocarbon Chains
Authors: Laskowski Leona , Burk Robert E.
Published: January 2005

1. The average distance between the center of the first and last carbon atoms of a freely rotating hydrocarbon has been evaluated as 1.50 1 where 1 is the carbon-carbon distance of 1.54A. This length corresponds to a spherical configuration of a threadlike molecule. 2. A general equation for the Z coordinate of a straight chain hydrocarbon whose rotation is restricted by geometric interferences has been derived. This length is a function of the radius of the hydrogen atoms. 3. The average Z coordinate calculated predicts that the configuration of a hydrocarbon with geometric restrictions on rotation is a statistical one whose length is greater than that calculated by Kuhn, and agrees well with the experimental estimates of Mack.
The Thermal Decomposition of Azomethane
Authors: Taylor H. Austin , Jahn Francis P.
Published: January 2005

The decomposition of azomethane has been studied in the temperature range 290–340°C by an analytical method. For 50 to 90 percent reaction the ratio of moles of product to moles of azomethane reacted is constant at 1.95. The energy of activation in terms of azomethane decomposed is 52,500 cal. Evidence is presented for the formation of tetramethylhydrazine as an intermediate during the reaction and material balances calculated from the analyses substantiate this.
The Thermal Decomposition of Azomethane in Presence of Nitric Oxide
Authors: Jahn Francis P. , Taylor H. Austin
Published: January 2005

In presence of large amounts of nitric oxide, azomethane decomposes with only a small pressure increase yielding insignificant quantities of hydrocarbons in the volatile products. This is interpreted to indicate an initial dissociation of azomethane into nitrogen and free methyls which for the most part combine with nitric oxide to produce formaldoxime. The latter is partially oxidized by nitric oxide. The upper limit of the ratio of nitric oxide to azomethane reacting appears to be two. It is probable that the addition of methyls to azomethane is not completely suppressed in presence of nitric oxide. The energy of activation of azomethane decomposition in presence of nitric oxide is the same as that for pure azomethane.
The Vapor Pressure and Rate of Evaporation of Barium Oxide
Authors: Blewett J. P. , Liebhafsky H. A. , Hennelly E. F.
Published: January 2005

The extensive investigations of the rate of evaporation of barium oxide by Claassen and Veenemans, and Herrmann are in serious disagreement. In both sets of experiments the oxide was allowed to evaporate from an exposed surface into a vacuum, a method which in this particular case may involve large temperature uncertainties. In the hope of reducing these uncertainties, the method of Knudsen has been applied; in this method the oxide escapes through a small aperture in the wall of a ``blackbody'' at a rate so small that the equilibrium vapor pressure is not sensibly disturbed. The final results are in agreement with those of Claassen and Veenemans. The vapor pressure of barium oxide is given by log10 p(mm Hg)=8.63–19,400/T(1200–1800∘K).
The Potential Functions of the Methyl Halides
Authors: Slawsky Z. I. , Dennison David M.
Published: January 2005

The problem of the potential functions of the methyl halides is re-examined in an attempt to find a function which is both adequate and simple. A valence form of potential was tried which contained four constants: k1, the C–H elongation; c, the C—X elongation; k2, the deformation of the H–C–H angle; and k3, the deformation of the X–C–H angle. It was found that this simple valence potential must be modified by the inclusion of a cross product term between the X—C distance and the X–C–H angle, thus introducing a fifth constant, k4.

The constants k1 and k2 were determined from the methane frequencies (k1=4.88×105 and k2=0.443×105) and were taken to be the same for all the methyl halides. By adjusting the three remaining constants it was possible to predict eight quantities, the six fundamental frequencies and two of the fine structure spacings. The agreement with the observed values was satisfactory, the average deviation being less than 1 percent.
Fluorescence of Carbonyl Compounds in the Gas Phase
Authors: Matheson Max S. , Zabor J. William
Published: January 2005

The fluorescences of biacetyl, acetone, ethyl methyl ketone, and acetaldehyde have been photographed. The main portions, at least, seem to be identical. A like similarity in the fluorescences of diethyl ketone and propionaldehyde suggests that diketones formed during the photolyses of these carbonyl compounds are the fluorescing substances.
An Elementary Theory of Condensation
Authors: Cernuschi F. , Eyring H.
Published: January 2005

A theory of liquids is presented based on the assumption of the presence of holes in a lattice-like structure and using a method analogous to that used in treating order and disorder in alloys. This treatment provides an elementary theory of condensation and a clear and simple treatment of the critical phenomena of liquids and also yields a theoretical curve for the density of vapor and liquid as a function of temperature in agreement with the experimental curve. The existence of more than one phase arises as a consequence of the theory.
Corresponding States for Perfect Liquids
Authors: Pitzer Kenneth S.
Published: January 2005

On the basis of certain assumptions concerning the properties of the molecules, and by using classical statistics, the van der Waals theory of corresponding states is derived. No mathematical approximations are involved. Argon, krypton and xenon, which conform closely to the assumptions, show the expected correspondence in behavior and are taken as standards. The name perfect liquid is suggested for this behavior. In a second part, the deviations from perfection are discussed for a wide variety of substances. Particularly considered are heat capacities and entropies of vaporization which should be compared at points where the vapor to liquid volume ratio has the same value. The observed deviations are explained in a general way.
Thermodynamics of Crystals and Melting
Authors: Born Max
Published: January 2005

The Helmholtz free energy, A, of a rigid body is a function of temperature, and of the six homogeneous strain components. If the crystal is to be rigid, three inequalities must be satisfied for the derivatives of A with respect to the six strain components, for a regular (cubic) lattice. This enables one to limit the pressure-temperature range for which the crystal is stable. The violation of the condition c44>0, that the crystal resist shearing, is interpreted as leading to melting. From a knowledge of the forces between the molecules the phase integral, and therefore the free energy, may be calculated as a function of T, V, and the six strain components. The numerical calculations are carried out for a body-centered cubic lattice. The product of all the frequencies is calculated directly, so that the assumption that the Debye equation for the frequency distribution holds, is not necessary. The melting curve, pressure against temperature, is then determined.
The Equation of State of Frozen Neon, Argon, Krypton, and Xenon
Authors: Kane Gabriel
Published: January 2005

The interaction between two rare gas atoms is assumed to have the form — Ar—6+AB(exp—r/ρ). The values of A and B are found from the lattice distances and the heats of sublimation of frozen neon, argon, krypton and xenon for ρ=0.2091A and ρ=0.345A. The equations of state of the solids are then calculated, including the Debye θ's and the breakdown points, which occur a few degrees below the melting points. For krypton, the expansion coefficient and the specific heat are calculated, but are found too high at higher temperatures.
The Rotational Partition Function of the Water Molecule
Authors: Stephenson C. C. , McMahon H. O.
Published: January 2005

The rotational contribution to the partition function of the water molecule has been computed for temperatures up to 298.1°K by summing the experimental energy levels of Randall, Dennison, Ginsberg and Weber. The results are compared with those of a rigid rotator and in this way the ``stretching'' contribution is determined. E. Bright Wilson's theoretically deduced stretching correction compares very favorably with the values obtained by summing energy states.
Some Quantum-Mechanical Considerations in the Theory of Reactions Involving an Activation Energy
Authors: Hirschfelder J. O. , Wigner E.
Published: January 2005

The activated complex or transition state method for calculating the absolute rate of a chemical reaction with an activation energy would be rigorously valid if classical mechanics applied to all degrees of freedom. In quantum mechanics, two kinds of limitations must be considered. First, because of Heisenberg's uncertainty principle, the transition state itself can be defined only if the potential surface is sufficiently flat around the highest point of the reaction path. Second, even if this condition is fulfilled, the transmission coefficient can differ from the value expected on the basis of classical mechanics, because a wave packet can be reflected both on its way up, and also on its way down the potential barrier separating the initial and final states. In fact, the transmission coefficient is, in many cases, a rapidly fluctuating function of the energy of the system. If the temperature distribution of the energy is sufficiently broad to cover several periods of this fluctuation, an average transmission coefficient can be defined which nearly agrees with the classical value. For the crossing of a one-dimensional potential barrier, the quantum corrections are surprisingly small. In problems with several degrees of freedom, the transmission coefficient is affected by the interchange of translational and vibrational energy. However, if the vibrational motion is fast as compared with the motion along the reaction path, these degrees of freedom can be treated on a par with the electronic coordinates. In this case, the formulas of Eyring, with a mechanically sensible transmission coefficient, are satisfactory. On the whole, we conclude that quantum-mechanical considerations invalidate the transition state method to a much smaller extent than could be presumed and it is only in the consideration of the relative rates of reactions between isotopes and reactions at very low temperatures that these effects may be important.
The Reactions Between Methyl Radicals
Authors: Taylor H. Austin , Burton Milton
Published: January 2005

The reactions of methyl radicals with each other and with hydrogen molecules are reviewed. It is shown that the available evidence is consistent with the following statements: Methyl radicals combine only in three-body collisions, the energy of activation of which may be as high as 22 kcal. Methyl radicals do not readily enter into two-body reactions with hydrogen molecules. Most of the methyl radicals in an atmosphere containing a high percentage of hydrogen probably disappear by the reaction CH3+H2+CH3→2CH4, the energy of activation being probably 9±2 kcal. The reaction CH3+H2→CH4+H accounts at most for the disappearance of 1 in 104 methyl radicals, the energy of activation being ∼19 kcal.
On the Kinetics of Complex Reactions
Authors: Semenoff N.
Published: January 2005

Chemical kinetics is the chemistry of intermediate compounds. These intermediates can be studied directly only with great difficulty but they can be investigated through kinetic measurements themselves. For example during the induction period in the oxidation of hydrogen sulfide the ``active centers'' are withdrawn from the reaction vessel passed through a connecting vessel and introduced into a chamber in which the new reaction is just starting. The ``active centers,'' responsible for shortening the induction period, are stable for several hours at room temperature. The formula previously given for a chain reaction proceeding from a single active center is extended here to include reactions with any number of active centers. Complex reactions of various types are treated mathematically and experimental curves are given. Among the types of complex reactions considered are those which involve the mutual inhibiting or promoting action of chains with quadratic rupture.
Kinetics of the Vapor Phase Reaction of Cyclopropane with Iodine
Authors: Ogg Richard A. , Priest W. J.
Published: January 2005

The thermal and photoreaction (light absorbed by iodine) between gaseous iodine and cyclopropane has been studied, and found to lead to the reversible formation of 1,3 diiodopropane. A slow iodine catalyzed isomerization of cyclopropane to propylene is the only important side reaction. The reaction is essentially homogeneous. For the thermal reaction, in the range 245–280°C, the rate expression is d(C3H6I2)dt=k1[(C3H6)(I2)12−K6(C3H6I2)(I2)12].For the photoreaction, in the range 180–230°C, the rate expression is d(C3H6I2)/dt=k3Iabs12(C3H6).The respective values of k1 and k3 were found to be 1.17×1013e−35,230/RT(mole/cc)−12sec.−1and 8.5×106e−18,800/RT(Einstein/cc)−12sec.−12.The mechanism has been established, the rate determining step being the reaction I+C3H6→ICH2CH2CH2, with rate constant 7.36×1012e−17,280/RT(mole/cc)−1sec.−1.The equilibrium constant, Ke, in the temperature range 255°-280°C, is some 11.7e−17,200/RT(mole/cc).Hence for the reaction C3H6+I2→C3H6I2, ΔE=-17,200 calories per mole. If the energy of the carbon-iodine linkages is taken as 43,000 calories, that of the carbon-carbon linkage in the cyclopropane ring is 32,900 calories per mole.
The Effect of Temperature on the Predissociation of Photoactivated Acetaldehyde Molecules
Authors: Rollefson G. K. , Grahame D. C.
Published: January 2005

The relative efficiencies of production of free radicals in acetaldehyde by the absorption of light of the wave-lengths 3132 and 2652A have been studied by observing the quantum yields of the photochemical reaction at high temperatures. It has been found that at room temperature more radicals are produced by the absorption of λ = 2652A than by λ = 3132A. As the temperature is raised, the yield of radicals at the longer wave-length increases relative to that at 2652 until at 100°C the two are equal. At higher temperatures the longer wave-length has the greater efficiency for the production of radicals. This change with temperature is accounted for by assuming that at λ = 3132A the dissociation is aided by thermally excited vibrational energy. In accordance with this assumption it is found that as the temperature is raised the fluorescence, which is easily visible at room temperature, fades in a manner which is roughly parallel to the increase in dissociation. There is no evidence for such a thermally induced predissociation with λ = 2652A. The lower efficiency of production of free radicals at λ = 2652A is believed to be due to a difference in the electronic states reached by acetaldehyde excited by the two wave-lengths.
The Cadmium Photosensitized Reactions of Ethane
Authors: Steacie E. W. R. , Potvin Roger
Published: January 2005

An investigation of the cadmium photosensitized reactions of ethane has been made. It is concluded that the primary process is a C–H bond split, probably by the reactionCd(3P1)+C2H6=CdH+C2H5.The products of the reaction are hydrogen, methane, propane, butane, and higher hydrocarbons. The methane probably largely results from methyl radicals produced by H+C2H5=2CH3,and the higher hydrocarbons from recombination reactions of radicals. Two experiments have also been made on the decomposition of propane and butane.
Supersonic Effects of Water Vapor in CO2 and Their Relation to Molecular Vibrations
Authors: Pielemeier W. H. , Saxton H. L. , Telfair D.
Published: January 2005

Acoustic interferometer measurements at approximately 28°C and atmospheric pressure were made from which the velocity and the absorption in CO2 were computed. Various H2O-concentrations were used with each frequency, covering the range 284 to 1595 kc/sec. At each frequency, μ (the absorption per wave-length) rises with increasing humidity to a maximum of about 0.28 and then drops slowly, but with the lower frequencies it also passes through a shelf or minor peak before saturation is reached. As the first absorption peak is approached the velocity drops about 10 m/sec. and a 1-m/sec. drop occurs near the minor peak. As the frequency is increased the critical H2O-concentration hm is increased also but at different rates for the two peaks. For the major peak fm = [60+8(10)4h] kc/sec. for the minor peak fm′ = [50+2(10)4h′] kc/sec. Thus the average lifetime of a quantum of vibrational energy is decreased rapidly with humidity. These facts are presented as graphs. They are also correlated with results by other investigators, none of whom has observed a minor absorption peak and dispersion region.

Most of these facts are represented quite accurately by theory, the results of which are included.
The Diffraction of X-Rays by Liquid and Plastic Sulphur
Authors: Gingrich Newell S.
Published: January 2005

X-ray diffraction patterns of plastic sulphur at room temperature and of liquid sulphur at several temperatures ranging from 124°C to 340°C have been obtained. The position of the main peak in terms of (sin θ)/λ is 0.140 at 124°C, 0.138 at 147°C, 0.138 at 151°C, 0.139 at 157°C, 0.127 at 166°C, 0.127 at 175°C, 0.125 at 225°C, and 0.120 at 340°C. Atomic distribution curves have been obtained in the cases of plastic sulphur, and of liquid sulphur at 124°C, 166°C, 175°C, 225°C, and 340°C. These curves all appear somewhat similar. The nearest neighbors are found at 2.08A for plastic sulphur, and at approximately 2.07A for liquid sulphur at all temperatures. The number of nearest neighbors is 2.0 for plastic sulphur, and it is about 1.7 for liquid sulphur. The possibility of using the present information in explaining certain properties of sulphur is discussed.