bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Concentration of Molecules on Internal Surfaces in Ice
Authors: Murphy E. J. 
Published: January 2005

In this paper the experimental expression for the ``local conductivity'' of ice is given. This expression has two terms, one of which has already been discussed and brought into close relation with the structure of ice, that is, with its heat of sublimation and its lattice constant. This paper brings out another relation, deriving it from the second term of the experimental expression. It is concluded from an analysis outlined here that the second term of the local conductivity gives the concentration of molecules in ``internal surfaces.'' For the specimen of ice to which this method was applied the concentration of molecules on internal surfaces comes out as 1.03×1017 molecules/cc.
This is proposed as a new method of studying imperfections (internal surfaces) in dielectric crystals, and one which seems to be well suited to this purpose. It gains its advantages from the fact that it is not dependent upon the regularity of the imperfections, as in x-ray diffraction methods, or upon the connectivity of the system of internal surfaces, as in direct current conduction.
On the Quantum-Mechanical Calculation of the Cohesive Energy of Molecules and Crystals. Part II. Treatment of the Alkali Metals with Numerical Applications to Sodium
Authors: Löwdin Per-Olov 
Published: January 2005

In Part I, an expression for the cohesive energy of a crystal was derived in the case the wave function for the ground state is approximated by a single Slater determinant of Bloch spin orbitals, formed by linear combination of the atomic spin orbital associated with the self-consistent fields with exchange for the free constitutents. By using the new idea of ``combined atomic orbitals,'' all energy terms were reduced to only atomic two-center integrals, which could be evaluated by numerical integration. This method is here applied to the calculation of the cohesive energy of the alkali metals, where, due to the crystal symmetry, the combined atomic orbitals for the valence electrons are almost pure s-functions. It is shown that the conventional method, taking only the interaction between nearest neighbors into account, is entirely insufficient and that it is necessary to consider even bonding, overlapping, and electronic repulsion effects between neighbors of a rather high order.
Numerical applications, including interactions between neighbors up to the order nine, are carried out for metallic sodium, giving the cohesive energy 24.7 kcal/mol and the interatomic distance 3.69A, in good agreement with the experimental values 26 kcal/mol and 3.67A, respectively. Except for the values of the fundamental constants e, m, h, ···, no empirical data are used.
Transport Properties of Gases with a Square-Well Molecular Interaction Potential
Authors: Holleran Eugene M. , Hulburt Hugh M. 
Published: January 2005

The kinetic theory cross-section integrals are calculated for the square-well molecular potential model. Parameters are determined for light gases from viscosity measurements and are used to reproduce viscosity data for pure gases and binary mixtures.
Comparison is made between these parameters and those found from compressibility data and other transport properties. Different sets of parameters are apparently required for each transport property in order to account for the experimental results. The thermal diffusion constant for this model is a function of temperature and one other parameter. Excellent reproduction of the neon isotope data is obtained, and predictions of the qualitative behavior of the thermal diffusion ratio are made.
The Reaction of Methylcyclopentane with Hg 6(3P1) Atoms
Authors: Schlochauer M. , Gunning H. E. 
Published: January 2005

The reaction of methylcyclopentane with photo-excited Hg 6(3P1) atoms was investigated in a static system at 29.35±0.01°C, over a range of initial pressures of 5–110 mm. After an initial slight pressure rise, the reaction exhibited a linear pressure decrease, the magnitude of which increased linearly with initial pressures of methylcyclopentane above 15 mm. The average rate of hydrogen formation also increased with initial pressure of methylcyclopentane and decreased with time in the course of a run. The products found were hydrogen, methylcyclopentenes, and a heavy fraction with the formula C12H22. Upon the basis of chemical and physical properties, strengthened by kinetic considerations, it was concluded that the C12H22 compound was predominantly dimethyldicyclopentyls. Quantum yields reached a maximum of 0.44 for hydrogen formation and 0.42 for methyl-cyclopentane consumption.
The mechanism postulated proceeds through an initial carbon-hydrogen bond split, thus: (1)  cyclo C6H12+Hg 6(3P1)  →cyclo C6H11+H+Hg 6(1S0)(2)  H    +cyclo C6H12→H2    +cyclo C6H11(3)  H    +cyclo C6H11→cyclo C6H12(4)  H    +cyclo C6H11→cyclo C6H10+H2(5)  cyclo C6H11+cyclo C6H11→C12H22(6)  H2    +Hg 6(3P1)  →H+H+Hg 6(1S0)
This mechanism yields rate expressions which confirm the trends observed in the experimental work.
The Growth of Uniform Colloidal Dispersions
Authors: Reiss Howard 
Published: January 2005

Recently, much interest has been focused upon the preparation of monodispersed colloids using the ``growth by diffusion'' process. Although these colloids are useful tools in experimental procedures, no well-established reason has been given to explain why the ``growth by diffusion'' method should produce such uniform dispersions. In this paper it is shown that an assembly of competing particles, growing by diffusion, develop the squares of their radii at equal rates. This condition provides a mechanism leading towards uniformity.
A method, based on this equal square rule, is suggested for the determination of size distributions in polydispersed systems.
Note on Frequency Spectra of Simple Solids from Specific Heat Data
Authors: Katz E. 
Published: January 2005

If the specific heat C(T) of a solid is given as a function of temperature from T=0 to ∞ with infinite accuracy, the frequency spectrum f(ν) is uniquely determined. What information about f(ν) can be derived from specific heat data of experimental accuracy? The following conclusions give the answer.
(1) Experimental specific heats determine accurately the low frequency part of the frequency spectrum but allow a latitude, wide enought to fit almost any theory, for its high frequency part.
(2) In a Debye plot (effective Debye temperature θ versus T) peaks and dips in the region 0&lt;T&lt;θ/10 represent dips and peaks in the low frequency part of the frequency spectrum. The correspondence is so simple that it can be interpreted at a glance. The peaks and dips are superimposed on a simple Debye spectrum and presumably have a direct physical meaning, in terms of lattice irregularities. Only their centers and total weights are obtainable, so that they act effectively as single Einstein frequencies.
(3) In the region θ/5&lt;T&lt;∞ all information obtainable about f(ν) consists of the first few even moments (three for specific heat errors of order one percent, five for 0.1 percent). These can be represented respectively by two or three weighted equivalent Einstein functions without direct physical meaning.
(4) The region θ/10&lt;T&lt;θ/5 corresponds to the high frequency part of the frequency spectrum, but hardly any information can be derived here.
On the Energetic Treatment of Non-Isothermal Processes. The Principle of Thermal Interaction
Authors: Holtan Hans 
Published: January 2005

1. The existing theories for non-isothermal processes are discussed. They can be divided into two kinds, depending upon whether or not they take the flow of heat into account. None are able to predict experimental results.
2. A new hypothesis, ``the principle of thermal interaction'' is introduced by employing Onsager's principle of reciprocity and is expressed in terms of Br⊘nsted's energetics.
It states that there is an interaction between the flow of heat and the transport phenomena in a non-isothermal process in such a way that the loss of work (loss of potential energy) for the transport of entropy bound to chemical substance can be compensated partly or completely by the transport of free entropy contained in the flow of heat in the opposite direction. The result is that any particle will tend to move against the temperature gradient.
3. The new principle is applied to thermocells with a solid electrolyte, and the results predicted are shown to be in agreement with experimental data.
4. The Knudsen equation, applicable to a thermal transpiration cell, is derived without employing the kinetic theory of gases.
An Interferometric Method of Determining Diffusion Coefficients in Gaseous Systems
Authors: Boyd Charles A. , Stein Norman , Steingrimsson Virginia , Rumpel William F. 
Published: January 2005

This paper describes a new type of experimental method for accurately measuring diffusion coefficients in gaseous systems.
The change of composition in the diffusion cell is followed by measuring the change in refractive index with an interferometer. Results obtained using this method compare favorably with some values reported in the earlier literature. In addition, values are reported for new systems not studied previously. A comparison is made between measured values and those calculated from viscosity data.
Time Lag in the Self-Nucleation of a Supersaturated Vapor
Authors: Probstein Ronald F. 
Published: January 2005

Recent experiments have indicated that the quasi-equilibrium Volmer theory of self-nucleation fails in some cases to predict when the condensation of water vapor or the components of air will occur in the very rapid vapor expansions in a supersonic wind tunnel. By the obtaining of an approximate solution to the non-steady Becker-Döring equation for the self-nucleation of a super-saturated vapor, an attempt has been made to determine whether the time lag associated with the approach to the steady state rate of formation of condensation nuclei could account for the discrepancies between theory and experiment. A similar calculation, where the work required to form embryos of the condensing phase was neglected, has been carried out by Kantrowitz. In the present paper the work term has been taken into account to a first approximation. Also considered is the time lag arising from the heating of the nuclei due to bombardment by molecules of the condensing phase as well as the time lag resulting from an accommodation coefficient for the liquid nuclei different from unity.
Calculations of the self-nucleation of water vapor in air and nitrogen in air have been carried out. From the results it appears that the build-up time is not appreciably lengthened by inclusion of the work term to a first approximation. The results also indicate that, unless the accommodation coefficient should have a value much lower than what appears to be reasonable from meager experimental evidence, the time lag alone could not account for the existing discrepancies between theory and experiment.
Triple-Dipole Interaction. II. Cohesion in Crystals of the Rare Gases
Authors: Axilrod B. M. 
Published: January 2005

The dependence of the triple-interaction between three neutral atoms on the configuration of the latter suggests a possible explanation of the structure of the crystals of Ne, A, Kr, and Xe. The latter crystallize in the face-centered cubic (f.c.c.) lattice, one of the two closest-packed structures, the other being the hexagonal closest-packed. The triple-dipole interaction was directly summed in both the f.c.c. and h.c.p. lattices for a cylindrical region whose radius and semi-altitude were about three times the nearest-neighbor distance.
The calculations, which were made on IBM punched-card machines, are outlined. The triple-dipole interaction amounts to two to nine percent of the cohesive energy for the crystals of the above rare gases. The difference in the triple-dipole interaction for the f.c.c. and h.c.p. lattice, although favoring the former structure, is less than 0.01 percent of the cohesive energy and hence cannot account for the structure of these rare gas solids.
Quantitative Infrared Intensity Measurements. I. Carbon Monoxide Pressurized with Infrared-Inactive Gases
Authors: Penner S. S. , Weber D. 
Published: January 2005

Quantitative infrared intensity measurements on CO pressurized with H2, He, A, O2, and N2 for total pressures up to 700 psia have been carried out. The values of integrated absorption for the fundamental and first overtone of CO have been found to be 237 cm−2 atmos−1 and 1.64 cm−2 atmos−1, respectively. The numerical values of integrated absorption were obtained by using an indirect method for the interpretation of experimental data, similar to the extrapolation technique of Wilson and Wells.
The experimental data obtained at very large values of the total pressure should yield correctly the numerical values of the spectral absorption coefficients. This statement is supported by the fact that the integral over the spectral absorption coefficients at a total pressure of 700 psia yields values for the integrated absorption of fundamental and first overtone of CO which are in excellent agreement with results obtained by indirect methods.
Intermolecular Potentials. I. Carbon Tetrafluoride and Sulfur Hexafluoride. II. Carbon Dioxide
Authors: MacCormack K. E. , Schneider W. G. 
Published: January 2005

Experimental second virial coefficient data for carbon tetrafluoride, sulfur hexafluoride, and carbon dioxide have been used to investigate the intermolecular potentials of these molecules on the basis of a Lennard-Jones model. Force constants for the fluoride molecules can be fitted rather satisfactorily, but the constants so derived do not agree with those derived from other gaseous properties, e.g., the critical data. This result may be due to the assumption of central forces for the symmetrical fluoride molecules.
For carbon dioxide it was found that the derived force constants varied with temperature, the high temperature data yielding lower values of the collision diameter r0. The results can be interpreted on the basis of a partial association. A likely configuration for the resulting dimer is suggested.
Orthonormal Sets of LCAO Molecular Orbitals for Second-Row Homopolar Diatomic Molecules
Authors: Mulliken Robert S. 
Published: January 2005

The forms of the LCAO MO's (molecular orbitals approximated by linear combinations of atomic orbitals) of any homopolar second-row diatomic molecule are studied under the restriction that they shall form an orthogonal set. The requirement of orthogonality per se causes 1s−2s−2pσ hybridization (forced hybridization) among the AO's (atomic orbitals) used in constructing the LCAO's. Equations, tables, and figures are given showing how the degrees of hybridization in the members of mutually orthogonal sets of σg LCAO MO's, likewise of σu LCAO MO's, are related, as a function of two parameters: (a) assumed degree of hybridization in any one member of the set; (b) a parameter proportional to interatomic distance times effective nuclear charge. This is done using primarily Slater AO's, but the effect of using SCF (self-consistent-field) AO's is also studied.
Assuming that overlap integrals are good measures of bond strengths, it is shown that the effect of forced hybridization is to diminish bond strengths. It is concluded that this bond-weakening effect in LCAO MO valence theory is the counterpart of certain exchange repulsions which appear in the Heitler-London valence bond theory, namely those between bonding electrons on one atom and electrons in different (either bonding or lone-pair) AO's on the other atom. The procedure used promises to give a good measure of the strengths of inner shell-outer shell interatomic repulsions; it tends to indicate that these are, in general, not large but not negligible. A paradox resulting from forced hybridization is touched on and more or less resolved; this paradox has to do with the method of counting the numbers of s and pσ electrons per atom in a molecule described by LCAO methods.
The Vapor Pressure and Critical Constants of Neopentane
Authors: Beattie James A. , Douslin Donald R. , Levine Samuel W. 
Published: January 2005

The vapor pressure of neopentane has been measured from 50° to the critical point. The equation, log10p(atmos)=3.901633−1136.462T+4.99118×10−4T  (T=t∘C+273.16),gives a fair representation of the observations.
A study of the compressibility of neopentane in the critical region gives for the critical temperature, pressure, volume, and density the values: tc = 160.60°±0.05°C (Int.), pc = 31.57±0.03 normal atmospheres, Vc = 0.303 liter per mole (4.20 ml per g), dc = 3.30 mole/liter (0.238 g per ml). The uncertainty in the critical volume and density is 1 percent.
The Limiting Negative Pressure of Acetic Acid, Benzene, Aniline, Carbon Tetrachloride, and Chloroform
Authors: Briggs Lyman J. 
Published: January 2005

The limiting negative pressure of acetic acid, benzene, aniline, carbon tetrachloride, and chloroform has been measured in relation to temperature. A centrifugal method was employed, the liquid being contained in a capillary tube, the ends or legs of which were bent sharply back parallel to the straight central part. The tube was cemented to a horizontal spinner, with its midpoint intersecting the spin axis. Both ends of the tube were open, which facilitated filling and cleaning. The volume of liquid was so chosen that the menisci were located in the legs of the tube near the bends.
The maximum values observed were: CH3COOH, −288 bars; C6H6, −150 bars; C6H5NH2, −300 bars; CCl4, −276 bars; CHCl3, −317 bars. Excepting benzene, the limiting negative pressure of these liquids has not heretofore been measured. All except benzene equal or exceed that of water (−275 bars). Acetic acid, benzene, and aniline show a decrease in the limiting negative pressure as the freezing point is approached, like water, but the effect is much less marked.
The higher values observed for the polar liquids in comparison with their nonpolar relatives suggests that the dipoles are contributing markedly to the cohesion of the liquid. An investigation of the cis- and trans-forms of the same liquid is now under way.
Contribution to the Theory of Critical Phenomena
Authors: Zimm Bruno H. 
Published: January 2005

If one considers the critical point between the liquid and gaseous phases, it may be shown that the ``principle of superposition'' leads to the result that the critical point is a singularity in the isotherm of fugacity or pressure against density. At this singularity the derivatives of every order of the fugacity or pressure with respect to the density are zero, not only the first two derivatives as in the van der Waals theory. It is postulated that these relations are true despite the uncertain nature of the superposition approximation.
If the critical point is such a singular point, it can be shown that Mayer's theory of critical phenomena leads quite reasonably to a single characteristic temperature instead of two separate temperatures for the vanishing of the slope of the isotherm and for the appearance of a surface tension. Experimental observations on the anomalous shape of the isotherms near the critical point are in accord with the theory.
Magnetic Study of Some Organo-Metallic Compounds of Arsenic
Authors: Prasad Mata , Mulay L. N. 
Published: January 2005

The susceptibility of As has been evaluated from the molecular susceptibilities of organo-metallic compounds of the type (i) R.AsH2, R3As, (ii) R—As:As—R, (iii) RAs:O(OH)2, R2As:O(OH), and R3As(OH)2, using Pascal's constants for atoms and linkages in the organic radicals R and those derived for :O and —OH groups in arsinic acids. The values obtained from (i) and (ii) are in agreement with Honda's value for arsenic element. These values, and that deduced from (iii), are much different from Slater's theoretical value for the As atom.
In the (i) arsines, (ii) arseno-compounds, and (iii) arsinic acids, a distinct linear relationship has been observed between the molecular susceptibility and the total number of electrons in the molecule. The linear relation has been used to evaluate the susceptibility of the As atom in these compounds, which is in agreement with Slater's theoretical value.
Microwave Spectroscopic Investigation of the Kinetics of the Heterogeneous Ammonia-Deuterium Exchange
Authors: Weber J. , Laidler Keith J. 
Published: January 2005

A method is described for analyzing a mixture of gases using microwave spectroscopy. Relatively simple microwave measurements are employed on single resolved collision broadened spectral lines. For binary mixtures, only the peak absorption coefficients need to be measured if the microwave collision diameters are known. Mixtures of isotopically substituted molecules can also be analyzed because the microwave absorption lines of the isotopic species are easily resolved.
The technique is applied to determining the mole fraction of NH3 in mixtures of deuterated ammonias, and to a study of the kinetics of the NH3—D2 isotopic exchange reaction on a singly promoted iron catalyst. It is found that rates of desorption of molecules from surfaces are markedly increased on adsorption of other molecules, a fact that can be explained only in terms of strong interactions between adsorbed molecules. The rate of the exchange reaction is proportional to the square root of the deuterium pressure. With increasing ammonia pressure the rate passes through a maximum, showing that the mechanism involves reaction between adsorbed ammonia and adsorbed deuterium atoms. The activation energy diminishes significantly with increasing ammonia pressure, providing additional evidence for the existence of strong interactions between adsorbed molecules.
Studies on Tellurium-Selenium Alloys
Authors: Grison E. 
Published: January 2005

Tellurium and metallic (hexagonal) selenium were shown to give solid solution in any concentration. The variation of the cell dimensions with composition departs only slightly from linearity: c shows a certain tendency to contraction (this corresponds to a smaller valency angle in the chains of atoms than is required by a linear variation): a varies much less (2 percent between Se and Te) and in a manner which depends upon the preparation of the alloy (as already observed for pure selenium by H. Krebs).
The presence of sharp (hk·l) lines with l≠0 in all the alloys suggests that these must be composed not of homogeneous chains (i.e., Se chains, Te chains packed together), but of composite chains, in which the homogeneous sequences must be fairly short.