bluuebunny/crossref_metadata_2025 huggingface dataset:
The Intermolecular Potential of Mercury
Authors: Hildebrand J. H. , Wakeham H. R. R. , Boyd R. N.
Published: January 2005

The distribution function for liquid mercury from the melting point up to 250° recently published by the junior authors, has been used to calculate the intermolecular potential by aid of the equation derived by Hildebrand and Wood, E=(2πN2/V)∫εWr2dr. This potential is accurately reproduced by the equation, ε=j/rn—k/r6, with j=5.49×10-9 and k=3.52×10-10, for ε in dynes and r in angstroms. The attractive constant, k, checks exceedingly well with the value 3.35×10-10 calculated by the aid of the London formula for dispersion potential. Several other independent checks agree with the above potential function within the apparent limits of error of each.
Kinetics of Phase Change. I General Theory
Authors: Avrami Melvin
Published: January 2005

The theory of the kinetics of phase change is developed with the experimentally supported assumptions that the new phase is nucleated by germ nuclei which already exist in the old phase, and whose number can be altered by previous treatment. The density of germ nuclei diminishes through activation of some of them to become growth nuclei for grains of the new phase, and ingestion of others by these growing grains. The quantitative relations between the density of germ nuclei, growth nuclei, and transformed volume are derived and expressed in terms of a characteristic time scale for any given substance and process. The geometry and kinetics of a crystal aggregate are studied from this point of view, and it is shown that there is strong evidence of the existence, for any given substance, of an isokinetic range of temperatures and concentrations in which the characteristic kinetics of phase change remains the same. The determination of phase reaction kinetics is shown to depend upon the solution of a functional equation of a certain type. Some of the general properties of temperature-time and transformation-time curves, respectively, are described and explained.
Grand Partition Functions and So-Called ``Thermodynamic Probability''
Authors: Guggenheim E. A.
Published: January 2005

The relation due to Boltzmann between entropy and ``thermodynamic probability'' is enunciated in a precise form. This relation is generalized in such a way that each of the other thermodynamic potentials is related in a similar manner to a ``thermodynamic probability,'' for which a more suitable name is a ``partition function.''
The Ignition of Gases by Local Sources II. Ellipsoid Sources
Authors: Landau H. G.
Published: January 2005

The theory of the ignition of gases previously given for spherical sources is here extended to ellipsoid sources, including the sphere and infinite cylinder as special cases. The cylindrical case is important because a swiftly moving, hot particle may act as a cylindrical igniting source. The theory assumes that the source instantaneously heats up a small volume and creates in it active particles (chain carriers). Under general assumptions as to the processes which occur (but without including the temperature dependence of reaction rates), the temperature distribution is obtained and from the behavior of the temperature at the center of the source, a condition for ignition is derived in the form of a relation between the physical quantities involved. The results are similar to those previously obtained, one of the important differences being that for the cylindrical source ignition can occur without chain branching and without thermal self-acceleration of the reaction.
Spectroscopic Comparison of the Proton-Attracting Properties of Liquids
Authors: Gordy Walter
Published: January 2005

The use of isotopic hydrogen has made possible an extension of the study of hydrogen bonds between unlike molecules to include many new types of donor solvents. From the magnitude of the shifts which the different solvents produce in the OD fundamental band of CH3OD, a comparison of the proton-attracting properties of the different solvents can be made. It is suggested that this method may be used as a practical means of comparing the intrinsic strength of organic bases. Solvents representative of the classes—nitro-compounds, esters, aldehydes, ketones, ethers, nitriles and amines—were employed, and the results give proof of the wide occurrence of hydrogen bonding between unlike molecules.
Liquid Structure and Entropy of Vaporization
Authors: Hildebrand J. H.
Published: January 2005

The entropies of vaporization of a number of liquids to the same vapor volume are compared and show evidence that more or less ordered arrangements in liquids can result not only from (a) chemical bonds, and (b) dipole orientation but also from (c) geometrical form. This last effect alone may suffice to cause significant departures from the entropy of forming a regular solution.
On the Quantum Efficiency of Photosynthesis
Authors: Rieke F. F.
Published: January 2005

For the maximum quantum efficiency of photosynthesis in green plants, the value ¼, which was obtained by Warburg and Negelein, has been generally accepted. However this value has appeared to be less certain since only much smaller efficiencies have been observed in recent experiments employing different methods. Because the theoretical aspect of photosynthesis greatly depends upon the maximum quantum efficiency, it is important that additional experiments be made. As a first step toward the solution of this problem, Warburg and Negelein's experiments have been repeated. When their methods are followed closely, a maximum efficiency of 1/4.2 is observed, which is in good agreement with their value. The remaining question— whether this method actually gives the over-all efficiency for the assimilation of CO2 under favorable conditions, or merely the efficiency for the reduction of a respiration product intermediate between CO2 and carbohydrate—is not answered by these experiments. Further experiments along this line are in progress.
The Kinetic Energy of Polyatomic Molecules
Authors: Sayvetz Aaron
Published: January 2005

The theory of rotating axes and polyatomic molecules is extended in a form applicable to linear and anomalous molecules. It is applied to a linear tetratomic molecule and to an anomalous ammonia-like molecule, to obtain, in each case, a Hamiltonian kinetic energy lacking first-order terms. A second-order perturbation calculation yields the energy of interaction between rotation and vibration for the linear molecule. The relationship to Howard's theory of ethane is also given.
Interpretation of the Mechanism of a Thermal Decomposition from Photochemical Evidence
Authors: Taylor H. Austin , Burton Milton
Published: January 2005

By analogy to diatomic molecules it is assumed that if in polyatomic molecules, a transition is permitted between two energy hypersurfaces in a radiative act, it is forbidden in a non-radiative process. The thermal decomposition, in acetaldehyde, yielding methane and carbon monoxide in a unimolecular primary process is shown consequently not to be allowed. However, the bimolecular and the catalyzed processes producing ultimate molecules in the primary act are permitted. The simultaneous occurrence of such a decomposition and a free radical mechanism of a Rice-Herzfeld type adequately account for many of the observations on the catalyzed and high pressure reactions by Hinshelwood and his co-workers, by Verhoek and by Letort.
The Infra-Red Spectrum of Methylamine
Authors: Thompson H. W.
Published: January 2005

The infra-red spectrum of methylamine has been measured over the range 7000–12,000A using low dispersion, and a vibrational assignment has been made to the bands observed. The rotational structure of a band at 9950A previously reported has been examined under higher dispersion. The band is of the perpendicular type and an analysis leads to values of the molecular structural constants in agreement with those to be expected on other grounds, namely rCN∼1.47A, rNH∼1.02A, C–N̂–H 108°, and a tetrahedral methyl group. There is no evidence for the occurrence of internal rotation in the methylamine molecule.
The Infra-Red Band of Formic Acid at 7525A
Authors: Thompson H. W.
Published: January 2005

The absorption band of formic acid vapor at 7825A has been investigated. This is a hybrid band in which the perpendicular-type component is the more intense. The main features of the rotational structure have been measured, and by making reasonable assumptions the small moment of inertia is found to be 10.83×10—40 g cm2. The band is entirely similar in structure to the next lower harmonic band at 9801A.
The Centrifugal Distortion of Axial Molecules
Authors: Slawsky Z. I. , Dennison David M.
Published: January 2005

The theory of the semi-rigid rotator developed by Wilson and Howard has been applied to the axial molecules YX3 and ZYX3. It is found that the change in rotational energy, δW, caused by the centrifugal distortion, can be expressed in terms of the quantum numbers J and K and as a function of the potential constants and the molecular dimensions. The formula is evaluated explicitly for NH3, and ND3, and for the former is, in cm—1: δWJKhC=−0.000625J2(J+1)2+0.000950K2J(J+1) +0.000799J(J+1)−0.000630K4−0.00189K2.The pure rotation lines of NH3 and of ND3 are calculated and compared with the observations of Wright and Randall, and of Barnes. The agreement is very satisfactory. The theory predicts that the rotation lines are multiple. The spacing of this fine structure was too small to be observable in the region mapped by Wright and Randall but should be possible to detect in the case of the higher members of the rotation series.

We have also calculated the pure rotation spectrum of PH3 by using Howard's approximate values of the dimensions and force constants of this molecule. The agreement with experimental values is as good as could be expected from such rough data.
A General Theory of Heterophase Fluctuations and Pretransition Phenomena
Authors: Frenkel J.
Published: January 2005

The present paper is a generalization of a preceding note on the statistical theory of condensation phenomena. It is based on the idea that the macroscopic transition of a substance from a phase A to a phase B is preceded by the formation of small nuclei of the B phase within A, these nuclei being treated as resulting from ``heterophase'' density fluctuations or as manifestations of a generalized statistical equilibrium in which they play the roles of dissolved particles, whereas the A phase can be considered as the solvent. The application of the general theory to premelting phenomena in crystals leads to a quantitative explanation of the abnormal increase of the specific heat of the thermal expansion coefficient (and of the electric conductivity, in the case of ionic substances) in the close neighborhood of the conventional melting point, with the result that the surface tension between a crystal and its melt must be of the order of 1 dyne/cm. This result is checked by a calculation of the temperature corresponding to the highest crystallization rate of an overcooled liquid. Transitions of higher order and Curie points are also briefly discussed from the same point of view.
Infra-Red and Raman Spectra of Polyatomic Molecules IX. Dimethyl Acetylene, C4H6
Authors: Crawford Bryce L.
Published: January 2005

The infra-red absorption of gaseous C4H6 has been measured from 2 to 24μ, and the Raman spectrum of the liquid studied. Analysis of the data permits the determination of all the fundamental frequencies of the molecule. The frequencies are fitted closely with a modified valence-force potential function in which the methyl-group force constants are those previously determined for ethane.
The Infra-Red Absorption Spectrum of Methylamine Vapor
Authors: Cleaves A. P. , Plyler E. K.
Published: January 2005

The infra-red absorption of methylamine vapor has been measured from 2 to 18μ with a cell of 18 cm length using pressures from 2 to 55 cm. A total of nineteen bands has been observed, nine of which are assigned to fundamental vibrations. The bending vibrations of the two groups give rise to several bands in the region from 6 to 8μ. This causes considerable overlapping which makes it difficult to locate band centers and to determine band types in this region. Three bands which originate from the C – H vibrations occur at wave-lengths between 3.0 and 3.6μ. A band due to the N – H parallel valence vibration has been found at 2.98μ. The most intense band in the spectrum occurs at 12.9μ, and arises from a bending vibration of the hydrogen atoms in the amino group. The parallel vibration between the methyl and amino groups gives rise to an intense band at 9.56μ. This is a parallel band having a sharp and intense zero branch. A band also due to a bending vibration in the amino group was observed at 16μ, and from the experimental curve it can not be said whether it is parallel or perpendicular; hence definite assignment is not made. The other bands which have been observed have been assigned to overtones and combinations.
The Mechanism of Orientation in i-Butyl and i-Amyl Bromide Glasses
Authors: Baker William O. , Smyth Charles P.
Published: January 2005

The relaxation times of two typical, unassociated polar molecules have been calculated from experimental dispersion data. Both Stokes' law and absolute reaction rate theories have been applied to show that the inner friction constant in the usual Debye relaxation formula must be considered in terms of a mechanism involving higher activation energies than those obtaining in ordinary viscous flow. Hence, the macroscopic viscosity will generally be inadequate as an inner friction constant for relaxation. Slight alterations in the structure of these molecules are found apparently to change their relative orientations and hence energies of interaction. Rotational motion in viscous flow of lesser degree but similar kind to that of relaxation is indicated by the parallelism between the respective energies in i-butyl and i-amyl bromides. Possible generalizations have been extended to relaxation and flow phenomena in liquid crystals, where effectively the co-existence of phases derived from a single component over a temperature range makes the structure considerations simpler than in the usual case of solutions.
Critical Behavior of Solid Solutions in the Order-Disorder Transformation
Authors: Bethe H. A. , Kirkwood J. G.
Published: January 2005

A discussion of critical phenomena in the order-disorder transformation from the standpoint of the theories of Bethe and Kirkwood is presented. A comparison of the two theories is undertaken, and the best values of the transition temperatures and heat capacity anomalies, ΔCv, for the simple cubic and body-centered cubic lattices are tabulated. The influence of anomalies in the coefficients of expansion and compressibility on the anomaly in the heat capacity Cp is investigated.
The Mechanism of Some Chain Reactions
Authors: Rice F. O. , Herzfeld K. F.
Published: January 2005

The effect of the new values of the heats of activation on the mechanism of the ethane decomposition is discussed. A modification of the original scheme has been put forward by Küchler and Theile which is examined here in detail.
Chemical Activation by Gaseous Ionization
Authors: Lind S. C.
Published: January 2005

A comparison is made of the utility of the gas ion clustering hypothesis and of a free atom or free radical chain mechanism reactions taking place under ionizing conditions.
Optical Surface Thickness of Pure Water
Authors: McBain J. W. , Bacon R. C. , Bruce H. D.
Published: January 2005

An apparatus and method is described, based on the optical theory of Drude, capable of measuring surface film thickness of less than a monomolecular order of magnitude. The retardation in phase sustained by plane polarized light at a transparent reflecting surface is compensated and measured by tension on a thin glass microscope cover slip. The method is applied to pure water and the results indicate that the least possible thickness of the water surface is 2–3A. The ellipticity from water at the polarizing angle is estimated by two observers to be 33×10—5 and 42×10—5.
Statistical Fluctuations in Autocatalytic Reactions
Authors: Delbrück Max
Published: January 2005

The differential equations describing the statistical fluctuations of a simple autocatalytic reaction mechanism are set up and solved completely. The fluctuations are found to approach a constant limiting value when the amount of reaction product is large compared to the amount which initiates the reaction. The relative fluctuations which arise from the reaction mechanism are then equal to the reciprocal of the square root of the initial number of particles. Conversely the fluctuation in the time required to attain a threshold amount of reaction product also approaches a limiting value for high thresholds. This limiting value is greater than one time unit if the reaction is initiated by one particle, and becomes equal to one divided by the square root of the number of initiating particles if this number is large.
Dissociation Treatment of Condensing Systems III. Properties of Saturated Vapors of H2O, NH3, CH3Cl and CO2
Authors: Tseng T. P. , Feng S. K. , Cheng C. , Band W.
Published: January 2005

It is found that the dissociation treatment previously described gives a satisfactory theory of the saturated vapor pressure curves in temperature ranges not too close to the critical point. Curves are given for PV/NkT and for surface energy in the cases of H2O, NH3, CH3Cl and CO2. In the case of H2O there remains an appreciable discrepancy in the energy curves at low values of T/Tc. It is suggested that this may be removed by taking into account the small size of the clusters involved in the equilibrium between vapor and liquid: the surface energy in a cluster may differ from that for the liquid in bulk. A method of estimating mean cluster sizes is suggested, which leads to reasonable results.
Infra-Red O–H Band and Association
Authors: Errera J. , Gaspart R. , Sack H.
Published: January 2005

The vibration of the O–H group in alcohol and HDO has been studied in the 3μ region for solutions and ternary mixtures at different concentrations and temperatures. The experimental results are discussed in terms of association and addition-compound formation.
High Velocity Atomic Beams
Authors: Amdur I. , Pearlman H.
Published: January 2005

A general method has been developed for the production and intensity measurement of high velocity atomic beams. The method has been applied to beams of hydrogen atoms with energies equivalent to 200–800-volt electrons. Measurement of the collision cross section of these atoms when scattered by molecular hydrogen confirms the prediction that such scattering is predominantly due to repulsive forces between the beam and scattering particles.
Spectroscopic Measurements of Gaseous CN I. Dissociation in the Electric Discharge
Authors: White John U.
Published: January 2005

Free CN radicals in the gaseous state are formed in the electric discharge through cyanogen. By the use of a very intense low pressure spark as a background the 0,0 and 1,1 bands of the 2Σ→2Σ transition of CN have been observed in absorption at short intervals of time after the end of this discharge. The intensities of the lines of the bands were measured by means of microphotometer traces of the spectra and of the characteristic curve of the photographic plate. They were corrected for the incomplete resolution of the spectrograph. Relative concentrations of CN were calculated from the sums of the intensities of the lines. The rate of disappearance of CN after the end of the discharge was studied and found to be the same over a large range of pressure and dilution with argon. A mechanism is proposed to account for this. In all cases the disappearance was exponential with a mean half-life of 11 milliseconds. The half-life of the first excited vibration state was 3 milliseconds, during which time about 10,000 collisions occurred. By dilution of the cyanogen in the discharge tube with argon until the CN bands were no longer visible the partial pressure of CN could be calculated on the assumption that near this point all the cyanogen present was observed in the form of CN. The minimum detectable pressure of CN was of the order of 2×10—6 mm. The absolute f value of the 2Σ→2Σ transition is 0.026 (±0.006). By using the corresponding absolute absorption coefficient and the observed temperature distribution in a carbon arc the partial pressure of CN present in an arc is calculated to be of the order of 10 mm.
The Calculation of Force Constants in Some Methyl Compounds
Authors: Linnett J. W.
Published: January 2005

In this paper are described force constant calculations on ethane, the methyl halides, methyl cyanide and isocyanide. The potential function used is based on a valency type force field with the introduction of one cross term rendered likely by physical considerations. The applicability of this function to the molecules under consideration is tested with the ethane molecule. The carbon-carbon bond force constant in methyl cyanide is found to be considerably greater than in ethane, indicating that the bond has some double-bond character in the cyanide, as has been suggested by Pauling, Springall and Palmer. It is found that the bending constant of the HCH angle remains very constant in the four methyl halides, there being changes, however, on passing to the other compounds. Other variations in the force constants of corresponding links, similar to these, are studied and their significance discussed.
The Infra-Red Absorption of Phenol and Its Halogen Derivatives in the Region of the Second Overtone of the OH Absorption
Authors: Wulf Oliver R. , Jones Ernest J.
Published: January 2005

Orthohalogen and symmetrically trihalogen substituted phenols in the region of the second overtone of the OH absorption show behavior that is similar to that in the region of the first overtone but with increased displacement of the component absorptions. Subsidiary peaks are observed in the region of the second overtone and appear to stand in ordered relation to the principal peaks. In the present work the ortho- and symmetrically trichloro-, bromo-, and iodophenols as well as pentachlorophenol and phenol itself have been studied in carbon tetrachloride solution. The tendency of phenol to associate in a series of polymers has been studied by means of the phenol absorption. Relative to phenol the association of the above-mentioned substituted phenols is small.
Fine Structure of the 3.35μ Band of Ethylene
Authors: Smith Lincoln G.
Published: January 2005

The fine structure of the parallel-type band due to the C–H stretching vibration of ethylene has been obtained with a 7500-line grating. From the measured wave numbers of the lines of this band the mean of the two large moments of inertia of C2H4 has been determined as 30.08×10—40 g cm2. This value combined with the value C=5.70×10—40 g cm2 for the small moment gives for the large moments of inertia A=33.20×10—40 g cm2 and B=27.50×10—40 g cm2. These values are in good agreement with those previously reported.
Efficiency of the Electrolytic Separation of Lithium Isotopes
Authors: Johnston Herrick L. , Hutchison Clyde A.
Published: January 2005

The electrolytic separation coefficient, α, has been determined for the lithium isotope separation in the electrolysis of lithium chloride solutions at a mercury cathode. Its value was found to be 1.055± about 0.005 and, within limits of error, was independent of temperature, of the fraction electrolyzed and of the amount of back reaction at the cathode. The factor was the same for LiCl dissolved in absolute ethyl alcohol as for aqueous LiCl. Isotopic analyses were made by a densimetric method of relative atomic weight determination. Crystalline materials with densities reproducible to the fifth decimal place were prepared. The observed separation is markedly larger than would be given by the exchange equilibrium. It is therefore certain that a kinetic mechanism is operative, although partial approach to equilibrium may enter as a secondary process. The data do not warrant a distinction between the various mechanisms which have been proposed as rate determining steps. They are consistent with Bell's quantum-mechanical explanation (α=1.12) or with a ``diffusion layer'' mechanism (α=1.08) if partial approach to equilibrium is assumed as a secondary step.
The Further Concentration of S34
Authors: Stewart David W. , Cohen Karl
Published: January 2005

A further application has been made of the chemical exchange reaction between sulfur dioxide gas and a solution of sodium bisulfite to the problem of securing higher concentrations of sulfur of atomic weight 34. The exchange reaction was carried out in a series of counter-current fractionation columns which previously had been used for the separation of the nitrogen and carbon isotopes. Using three fractionation units in cascade arrangement, we have secured sulfur containing 25 percent S34 at a rate of 3.2 grams per day, and have produced sufficient material for a large number of tracer experiments.
Raman Spectra of Simple Ethers
Authors: Cleveland Forrest F. , Murray M. J. , Haney Herschel H. , Shackelford Julia
Published: January 2005

Displacements, estimated intensities, and depolarization factors are listed for the main lines of diethyl ether, di-n-propyl ether, di-isopropyl ether, di-n-butyl ether, di-isobutyl ether, di-n-amyl ether, and di-isoamyl ether. All the frequencies in the 2900 cm—1 region are polarized, except the one near 2970 cm—1 which is, without exception, highly depolarized.
Exchange Reaction of Gaseous Bromine and Hydrogen Bromide
Authors: Liberatore Laurence C. , Wiig Edwin O.
Published: January 2005

The exchange reaction of bromine and radioactive hydrogen bromide in the gas phase has been found to fall just short of reaching equilibrium in two minutes. The very rapid rate of exchange would seem to be accounted for best by a chain reaction involving bromine atoms.
Kinetics of Phase Change. II Transformation-Time Relations for Random Distribution of Nuclei
Authors: Avrami Melvin
Published: January 2005

Following upon the general theory in Part I, a considerable simplification is here introduced in the treatment of the case where the grain centers of the new phase are randomly distributed. Also, the kinetics of the main types of crystalline growth, such as result in polyhedral, plate-like and lineal grains, are studied. A relation between the actual transformed volume V and a related extended volume V1 ex is derived upon statistical considerations. A rough approximation to this relation is shown to lead, under the proper conditions, to the empirical formula of Austin and Rickett. The exact relation is used to reduce the entire problem to the determination of V1 ex, in terms of which all other quantities are expressed. The approximate treatment of the beginning of transformation in the isokinetic range is shown to lead to the empirical formula of Krainer and to account quantitatively for certain relations observed in recrystallization phenomena. It is shown that the predicted shapes for isothermal transformation-time curves correspond well with the experimental data.
Lattice Vibrations of Crystals and the Corresponding Vibrations of Their Solutions
Authors: Weissman S. I. , Freed Simon
Published: January 2005

Crystals of hydrated europium chloride possess structures in their absorption spectrum which are faint but accurate repetitions of the intense patterns arising from electronic transitions in in the europium ions. These repetitions occur on both sides of the intense patterns at intervals which are ascribed to oscillations of the lattice, thermally as well as optically excited oscillations. The spectra of aqueous solutions of europium chloride and also of europium nitrate closely parallel the structures in the spectrum of the crystals. In the region where the crystals absorb, the solutions absorb also. The structures in the spectra of the solutions are somewhat more diffuse than the corresponding structures in the spectra of the crystals. Especially is this true for the structures at the intervals corresponding to lattice vibrations.
The Infra-Red Absorption Spectrum of Methyl Amine
Authors: Owens Ralph G. , Barker E. F.
Published: January 2005

The parallel type methyl amine band at 10μ has been resolved. Its center is at 1045.27 cm—1, and the very regular structure of its P and R branches indicates a close approximation to axial symmetry. The mean of the two largest moments of inertia is 37.43 × 10—40 g·cm2. Assuming angles and distances for NH2 as in ammonia, and for CH3 as in methane, the C–N distance is computed to be 1.48 × 10—8 cm. Certain enhanced lines suggest a superposed perpendicular band. The 13μ band is partially resolved, and assigned to a motion corresponding to v3 in NH3. The bands arising from vibrations characteristic of the amino and methyl groups have been examined but could not be resolved.
On the Predissociation of Several Diatomic Molecules
Authors: Herzberg G. , Mundie L. G.
Published: January 2005

From the observed anomalous intensity distribution in the S2 bands it is concluded that the dissociation limit for the first predissociation of S2 lies appreciably below the predissociation limit (4.4 ev). It is found that the anomalous intensity as well as the diffuseness persists even at very low pressures (0.01 mm) and that therefore this is a case of genuine predissociation and not pressure broadening as assumed by Lochte-Holtgreven. The second predissociation of S2 starting with the 18 - 0 band leads to an upper limit of 3.6 ev for the heat of dissociation of S2. An anomalous intensity distribution similar to that of S2 is found for NO assuming that the ε absorption bands are a continuation of the γ bands. This indicates a predissociation of NO in the upper 2Σ state of the γ bands into normal atoms with a limit 1.3 ev above the dissociation limit. The remarkable intensity distribution found by Schüler and co-workers in the CuH emission band λ4280 at low pressure is explained as due to a predissociation into the 3Σ+ state derived from normal Cu(2S) and normal H(2S). Such a state cannot cause the predissociation of the level J′ = 0 in agreement with observations. The heat of dissociation of CuH comes out to be <23,325 cm-1 (i.e., <2.892 ev). The method previously suggested by one of the authors for the detection of maxima of potential curves is applied to AlD (AlH) and BH. From the breaking off points observed in the visible bands of these molecules it is established that their 1II states have potential curves with maxima. Therefore the dissociation energies are appreciably lower than the energies of the observed breaking off points, i.e., D0(AlH) <24,775 cm-1, D0(AlD) <25,010 cm-1, D0(BH) <28,350 cm-1.
An Experimental Determination of the Electron Affinity of Chlorine
Authors: Mitchell J. J. , Mayer Joseph E.
Published: January 2005

The electron affinity of chlorine has been determined to be about 92.7 kcal. by measuring the ratio of ions to electrons and atoms leaving a hot tungsten surface. Owing to the reactivity of the chlorine a certain erratic behavior leads to some possible scepticism as to the accuracy of the result.
The Exchange of Oxygen Between NO and NO2
Authors: Leifer Edgar
Published: January 2005

The reaction N14O+N15O2=N15O+N14O2 has been studied in the gas phase at —35°C and at a total pressure of 2.5 cm of Hg. Although the reaction rate constant could not be determined due to the speed of reaction a lower limit for its value is 106 cc moles—1 second—1. The equilibrium constant for the exchange at 298.1°K calculated from spectroscopic data is 0.967 as compared with 0.96 ±0.02 which was observed. By combining the data obtained in this investigation with the equilibrium data for N2O3 which is assumed to be the intermediate in the exchange reaction an approximate value for the energy of activation for the formation of N2O3 is determined.
The Specific Heat of Tantalum at Low Temperatures and the Effect of Small Amounts of Dissolved Hydrogen
Authors: Kelley K. K.
Published: January 2005

Specific heat determinations of pure tantalum were made in the temperature range 53° to 298°K and the entropy was found to be S298.1=9.9±0.1. Tantalum containing hydrogen in amounts ranging from Ta+0.0284 H to Ta+0.0958 H was shown to behave anomalously, the specific heat having a high maximum in the region 220° to 265°K depending on the composition. The height of the maximum and the difference in measureable heat content between hydrogenated and normal tantalum were shown to be approximately proportional to the amount of dissolved hydrogen. The temperature of the maximum increases as the hydrogen is increased. After dehydrogenation, the same specific heat was obtained as for the original unhydrogenated material. The density of the dehydrogenated product also was normal, whereas the hydrogenated materials had lower densities. It is postulated that differences in entropy between hydrogenated and pure tantalum may be attributed to differences in the number of possible ways of arranging the hydrogen particles among the positions in the tantalum lattice available at the higher and lower temperatures.
The Variation of the Differential Diffusion Constant of Sulphuric Acid with Temperature
Authors: Hollingshead E. A. , Gordon A. R.
Published: January 2005

The differential diffusion constant of sulphuric acid has been determined for concentrations from 0.025 mole per liter to 1 mole per liter at temperatures from 10°C to 35°C. Over the whole range of temperature, the variation of the diffusion constant with concentration is similar to that previously found at 25°. The mean activation energies of transport for the temperature intervals 10–15°, 15–25° and 25–35° are 4.9, 4.5 and 3.8 kcal, respectively.
Dielectric Polarization in Solution I. The Failure of the Clausius-Mosotti Equation
Authors: Rodebush W. H. , Eddy C. R.
Published: January 2005

It has been assumed by recent writers, including Onsager, that the Debye-Clausius-Mosotti procedure would give satisfactory results for the polarization of a nonassociated polar solute in dilute solution in a nonpolar solvent. A consideration of the existing data for solutions of this type shows that this classic procedure must lead to erroneous and very misleading conclusions in regard to the polarization of the solute. The Onsager equation on the other hand gives excellent agreement with the experimental data and it is possible to calculate the moment in the vapor state by it, from the data in dilute solutions with results rather more satisfactory than those obtained by Böttcher from the dielectric constant of the pure liquid. For certain cases when the Clausius-Mosotti equation appears to hold, the agreement is believed to be fortuitous.
The Thermal Reaction Between Hydrogen and Oxygen I. Comparison of Experiments and Theory
Authors: Oldenberg O. , Sommers H. S.
Published: January 2005

The present theory of the slow thermal reaction between hydrogen and oxygen, while satisfactorily describing the existence of the various explosion limits, fails to describe the following features: the sudden transition from the slowest reaction to the explosion (``second explosion limit''), and some effects of the vessel size and of a KCl film on the rate and the second explosion limit. Conclusions regarding the theory are discussed.
Spectroscopic Evidence for Hydrogen Bonds: Effects of Chelation on the Carbonyl Frequency
Authors: Gordy Walter
Published: January 2005

The vibrational band characteristic of the carbonyl linkage was measured for o-hydroxyacetophenone, o-methylaminobenzoate, o-methylsalicylate, o-hydroxybenzaldehyde and for compounds similar to these but lacking an adjacent proton-donor group. Chelation through hydrogen bonding was found to shift the C=O band to longer wave-lengths by about 0.15μ to 0.20μ, or 40 cm—1 to 53 cm—1, and to increase its intensity. Similar effects were observed for the carbonyl band of the enol forms of acetyl-acetone, ethyl malonate, ethyl acetoacetate. The magnitude of the effects of hydrogen bonding on the carbonyl band shows that energy changes in the proton-acceptor groups cannot be neglected in the computation of the energy of the hydrogen bond from spectroscopic data. The results also show that measurements on the proton-acceptor group can often be used as criteria for the presence of hydrogen bonding when experimental difficulties prevent accurate measurements of the effects on the vibrational band of the proton-donor group. Smaller effects were noted for ethylenic linkages of some of these compounds.
The Reactions of Methyl Radicals with Benzene, Toluene, Diphenyl Methane and Propylene
Authors: Taylor Hugh S. , Smith John O.
Published: January 2005

The reactions of methyl radicals with benzene, toluene, diphenyl methane and propylene to yield methane have been studied in the temperature range of 100–260°C. With toluene the activation energy is 5.6 kcal. and with propylene 3 kcal. Diphenyl methane shows a reactivity corresponding to these low values while the experiments with benzene, as well as earlier work with ethylene, indicate much higher activation energies of methane formation. The activation energies obtained have been correlated with earlier data on reactions with saturated hydrocarbons, with thermal data indicative of the strength of individual C – H bonds, with similar data from the interaction of atomic sodium with halide compounds, with concepts of the organic chemist on bond strengths and with some experimental data on pyrolysis of toluene. It is concluded that, contrary to accepted views, there may be marked differences in C – C and C – H bond strengths among the various hydrocarbons studied.
The Photogalvanic Effect I. The Photochemical Properties of the Thionine-Iron System
Authors: Rabinowitch E.
Published: January 2005

Solutions containing thionine and ferrous salts are bleached by illumination and recover their color in the dark. The kinetics of this reaction are investigated, by measuring photometrically the concentration of the dye in the photostationary state. Equations are derived for this state in terms of the initial concentrations and light intensity. At low thionine concentrations the extent of bleaching is proportional to the first power of light intensity and inversely proportional to the concentration of ferric ions. The bleaching reaches a maximum at a certain thionine concentrations and then decreases inversely proportional to the concentration of the dye. The bleaching increases strongly with increasing acidity. Kinetic mechanisms accounting for these relationships are discussed, and quantum yields and velocity constants are estimated. It is pointed out that the accumulation of free radicals (``semiquinones'') and the occurrence of ``circular'' mechanisms maintaining the steady state are typical of photostationary states as distinguished from true equilibria.
The Photogalvanic Effect II. The Photogalvanic Properties of the Thionine-Iron System
Authors: Rabinowitch E.
Published: January 2005

The oxidation-reduction system thionine-iron, described in paper I, provides an extremely sensitive photogalvanic cell. The illuminated half-cell is negative in respect to the nonilluminated one. The photogalvanic potential ε* is determined in relation to composition and light intensity. The results are in a qualitative (and partially quantitative) agreement with the kinetic theory of the photogalvanic effect. In strongly bleached solutions, the electrode potential is maintained by semithionine ions transferring electrons to the electrode, and ferric ions acquiring electrons from the electrode, whereas ferrous ions and leukothionine ions remain practically inactive. In weakly bleached solutions, the mechanism is more complicated.
Some Hydrogen Bridge Models for Globular Proteins
Authors: Huggins Maurice L.
Published: January 2005

Two hypothetical types of structure, derived by folding from basic patterns containing extended zigzag polypeptide chains, joined together by hydrogen bridges, are described and critically discussed. The (idealized, undistorted) 288-residue open-ended octahedron model has suitable horizontal dimensions but is somewhat too large vertically to fit satisfactorily into the unit cell of air-dried insulin.
Conductivity in Insulators and Its Interpretation
Authors: von Hippel A.
Published: January 2005

The migration of charge carriers in insulators is discussed in this paper on the basis of a large amount of experimental material on hand. Beginning with deviations from Ohm's law, the trapping of charge carriers is considered and the formation of the ``F'' band in alkali-halide crystals. Then the laws of electronic conductivity in solid dielectrics are formulated.
The Joule-Thomson Effect in Mixtures of Helium and Argon
Authors: Roebuck J. R. , Osterberg H.
Published: January 2005

The Joule-Thomson effect has been measured in four mixtures of helium and argon. The apparatus and methods are those used repeatedly in previous work. The measurements of the isenthalpic curves cover the range — 100° to 250°C and up to 200 atmos. From these measurements μ has been computed and plotted, and the trends with temperature, pressure, and composition are shown. μ is read from these curves and tabulated. In part of the region μ = 0 and these inversion curves are plotted as functions of pressure, temperature, and composition. Mixtures of helium and nitrogen have been similarly measured.
Application of the Theory of Absolute Reaction Rates to Heterogeneous Processes I. The Adsorption and Desorption of Gases
Authors: Laidler K. J. , Glasstone S. , Eyring H.
Published: January 2005

By regarding the process of adsorption as involving a reaction between a molecule of gas and an adsorbing center on the solid surface, it has been possible, with the aid of the theory of absolute reaction rates, to derive for the rates of adsorption and desorption of gases simple equations which can be tested experimentally. Different results are obtained according as the adsorbed gas forms an immobile or a mobile layer on the surface: in the latter circumstance, which does not appear to be common, the rate of adsorption would be given by the Hertz-Knudsen equation, provided there were no activation energy for adsorption. Combination of the expressions for the rates of adsorption and desorption gives an adsorption isotherm of the same form as that originally derived by Langmuir. Various cases of adsorption accompanied by dissociation of the adsorbed molecule are considered and the appropriate rate equations are deduced. If the molecule undergoes dissociation in the course of adsorption and the atoms remain on neighboring sites, these equations and the isotherm are the same as if there had been no dissociation, but if the molecule is adsorbed as such and then dissociation occurs as the result of an atom jumping from one adsorption center to another, the rate equations and isotherm differ from those obtained previously. The isotherm involves p½ instead of p, but the form of the rate equation depends on whether the adsorption of the molecule or the jump of the atom is the slow stage. The possibility of interaction between adsorbed atoms or molecules in an immobile film on the surface is considered, and a modified isotherm which makes allowance for such interaction is derived. Equations have also been deduced for adsorption on covered surfaces.
Application of the Theory of Absolute Reaction Rates to Heterogeneous Processes II. Chemical Reactions on Surfaces
Authors: Laidler K. J. , Glasstone S. , Eyring H.
Published: January 2005

The method developed in the preceding paper is used to derive equations for the rates of unimolecular and bimolecular heterogeneous gas reactions under various conditions of surface coverage by either reactants or poisons. The resulting equations are of the same form as those previously deduced by Langmuir and others, but they are more explicit; provided the activation energy is known they can be utilized to calculate rates of surface reactions which are in good agreement with the observed values. In the case of the dissociation of hydrogen on a tungsten surface, the simple assumption that the activated state consists of hydrogen atoms permits the absolute rate of the reaction to be calculated with an accuracy which is at least as good as that attained by direct experimental measurement. The factors responsible for the difference in rates of the same reaction taking place homogeneously or heterogeneously are considered; it is shown that adsorption of the activated complex lowers the over-all activation energy, and this has the most important influence in favoring the surface reaction. If one of the products, or any other substance acting as a poison, is strongly adsorbed, the effective activation energy is increased, but there is some compensation resulting from the increase of entropy accompanying the desorption of the poison.
Determination of Diffusion Coefficients
Authors: Serin B. , Ellickson R. T.
Published: January 2005

Diffusion equations derived from Fick's law are discussed and applied to experimental data in the literature on the diffusion of oxygen in copper and on reaction rates for chemical reactions in the solid phase. Previous limitations on the applicability of the formulae are removed by the use of a simple graphical method so that the theory can be applied to data to which it was previously inapplicable. It is pointed out that the exact solution to Fick's law obtained is equivalent to the parabolic law in the early stages of the diffusion process. The activation energy for the diffusion of oxygen in copper is found to be 50.5 kcal. per g-atom.
Double Refraction of Flow Studies with Methyl Methacrylate Polymers in Solution
Authors: de Rosset A. J.
Published: January 2005

An apparatus for the measurement of double refraction of flow is described. The magnitude of birefringence, expressed as the rotation of the plane of polarized light, may be measured to 0.05° under the best conditions with the assembly. The vortical angle and double refraction of flow of dioxane solutions of a series of fractionated polymers of α-methyl methacrylate have been measured at 25° over a concentration range of from one gram per liter to 50 grams per liter, depending upon the polymer under investigation. The specific birefringence, referred to the viscosity of the solvent, is a constant characteristic of each polymer in sufficiently dilute dioxane solutions. With the possible exception of behavior in such dilute solutions, the vortical angle is dependent upon concentration. Values of the rotary diffusion constant are calculated for each polymer from measurements of the vortical angle taken in dilute solutions. The lengths of the polymers are calculated from the rotary diffusion constants. They vary from 890A to 1880A. The shape and structure of the polymers are discussed from the point of view of their electrostatic and steric properties as evidenced by a molecular model. Tentative values of molecular weight and of length to width ratio are assigned. The viscosity of dilute dioxane solutions of the polymers has been measured at 25°. The specific viscosity increment at infinite dilution is estimated by extrapolation. This quantity is a linear function of the square of the length to width ratio, in partial confirmation of several theories of the viscosity of macromolecular solutions.
An Experimental Study of the Ultraviolet Absorption Spectrum of Pyrimidine
Authors: Uber Fred M.
Published: January 2005

The wave numbers of 112 absorption bands of pyrimidine vapor in the 2700–3300A region have been determined. The bands have been classified qualitatively into four categories as to their intensity. Assignments of individual bands into a number of series have been made and all prominent series were found to have spacings of approximately 1014 cm—1. Other characteristic frequencies are 613, 669 and 680 cm—1.