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Über dieses Buch

It is a great pleasure to have the opportunity to honor our distinguished colleague, Professor Leo Brewer, on the occasion of his sixty-fifth birth­ day, with this special volume of High Temperature Science. Leo and his wife, Rose, are personal friends of several generations of students and postdoctoral researchers at the University of California at Berkeley. Their concern and understanding has been important to many of us over the past forty years. Each paper in this volume has at least one author who was a gradu­ ate student or a postdoctoral researcher in Leo's laboratory at Berkeley. The variety of topics is indicative of the wide-ranging science done by Brewer-ites and by Leo Brewer himself. He has personally participated in the resolution of many of the classical problems of high-temperature science-from the heat of sublimation of graphite to the dissociation en­ ergy of nitrogen to the prediction of binary and ternary phase diagrams. He and his students have made major contributions to atomic and molec­ ular spectroscopy. He has made significant contributions to the develop­ ment of efficient systems for energy conversion and to ceramics. In addi­ tion to his research activities, Leo Brewer has been a long-time participant in the dynamic undergraduate teaching program of the Berkeley Chemistry Department. He has provided crucial insight for stu­ dents involved in those career-shaping experiences that one endures while acquiring the basics of inorganic, organic, and physical chemistry with that interwoven common bond of thermodynamics.



The Responsibility of High Temperature Scientists

When I was first introduced to high temperature research on joining the Manhattan Project in January 1943, I was surprised by the novelty and unexpected complexity of high temperature systems. At room temperature, one expects a mixture of aluminum metal with an aluminum halide or aluminum oxide to be restricted to the zero and 3+ oxidation states. The predictions of chemical behavior upon heating, based on room temperature behavior, are grossly in error because of neglect of the additional oxidation states that become increasingly important as the temperature is increased. In high temperature aluminum—oxygen systems, for example, the trivalent gaseous species has not even been reported, but Al2O, AlO, Al2O2, and AlO2 gases have been established. For gaseous systems in equilibrium with condensed phases, one can demonstrate that the gaseous phase will become more and more complicated as the temperature is increased both with respect to the number of species and with respect to the complexity of the molecules.
Leo Brewer

Determination of the Dissociation Energies of Gaseous Iron Monoxide and Manganese Monoxide by the Mass Spectrometric Knudsen Cell Method

The dissociation energies D 0 0 (FeO) = 95.9 ± 1.8 and D 0 0 (MnO) = 88.1 ± 1.8 kcal mol-1 were determined by studying the metathesis reactions FeO(g) + Se(g) = Fe(g) + SeO(g) and MnO(g) + Fe(g) = Mn(g) + FeO(g) by the mass spectrometric Knudsen cell method in the respective temperature intervals, 1640–1810 K and 1660–2060 K. These results are critically compared with the literature data, which implied the need for their reevaluation and a review of the thermodynamic data for FeOH(g) and FeO2(g). For the latter molecule, thermodynamic functions are presented.
S. Smoes, J. Drowart

The Surface Diffusion of High Temperature Vapors in Porous Alumina

In porous alumina barriers ~ 1 mm thick, 45% porosity, and ~1.2 pm average pore diameter, transmission coefficients for NaCl, NaF, and LiF vapors are ~2.6, 6, and 12 times that of He, indicating that surface diffusion contributes to the transmission. For Zn vapor, transmission coefficients are 1.2–3.5 that of He through the ~1.2 µm pores and 18 times that of He through 0.14 p.m pores. The temperature dependences of LiF and NaCl transmission by surface diffusion are close to those for Knudsen effusion, a result that indicates that the activated complex for surface diffusion is very weakly bound to the surface. Above their melting points, the transmissions of LiF and NaCl are irreproducible, but are usually markedly increased, perhaps because a liquid-like film partially penetrates the barrier.
Nathan S. Jacobson, Elizabeth J. Opila, Alan W. Searcy

Electron Impact Spectroscopy of High Temperature Species

The application of the methods of electron impact spectroscopy to the study of high temperature species is discussed. Electron scattering by metal vapors (Ba, Bi, Cu, Mn, Tl, Zn), alkali halide molecules, and KOH are described as demonstrative examples.
S. Trajmar

Energetics of Silicon Oxidation Reactions

An Independent Determination of the SiO Bond Dissociation Energy
Silicon atoms react under single collision conditions with N2O and NO2 to yield chemiluminescent emission corresponding to the SiO a 3Σ+-X 1Σ+ and b 3П-X 1Σ+ intercombination systems and the A1П-X 1Σ+ band system. From the Si-NO2 reaction, it has been possible to obtain a lower bound to the SiO bond energy, the first such determination independent of mass spectrometry. The result obtained, D 0 0 (SiO) ≥ 186.7 ± 1.7 kcal/mol, is in good agreement with mass spectrometry (D 0 0 = 188.2 kcal/mol). To facilitate this determination, the temperature dependence of the A 1П-X 1Σ+ spectrum has been analyzed to deduce the nature of the metal reactant beam and to determine the activation energy for formation of SiO* A 1П (E A = 7.4 ± 1.2 kcal/mol). A most striking feature of the Si-N2O reaction is the energy balance associated with the formation of SiO product molecules in the A lП and b 3П states. A significant energy discrepancy (≈10,000 cm-1 = 1.24 eV) is found between the available energy to populate the highest energetically accessible excited state quantum levels and the highest quantum level from which emission is observed. It is suggested that this discrepancy may result from the formation of vibrationally excited N2 in a concerted fast Si-N2O reactive encounter.
Joerg Pfeifer, Gary Green, James L. Gole

Kinetics of Vaporization of Molten Selenium

Vaporization of molten selenium was studied under equilibrium and non-equilibrium conditions. A quadrupole mass spectrometer was used to measure the vapor composition, and a vacuum microbalance was used to measure the total rate-of-weight-loss. Both measurements were made as a function of temperature near 500 K. Experimental results indicate that the vaporization of molten selenium is a retarded reaction having vaporization coefficients of about 0.1 for all species Se n (g) (n = 2–8). Results also show that the activation free energy of vaporization for all species is approximately equal to the free energy change of depolymerization reactions of liquid molecules, as obtained by other authors. These molecules consist of long chains in thermodynamic equilibrium with octacyclic rings. Mecha­nisms for the vaporization of molten selenium are postulated that involve the formation of short chains or small, nearly closed loops on liquid surface as the rate-limiting step. These activated complexes have the same number of atoms as the gaseous ring molecules to be formed. A critical test for this model is proposed which, if proven correct, may lead to a novel technique for growing pure single crystals of trigonal selenium.
John Yun-Kuang Huang, Paul W. Gilles, J. Edward Bennett

Electron—Ion Collisions in High Temperature Plasmas

Several newly observed electron—ion collision phenomena that occur in high temperature plasmas containing electrons and ions of energies 10–104 eV, or temperature of 105–108 K, are reviewed. These are the phenomena of dielectronic recombination, excitation-autoionization, and electron energy-loss scattering as measured in crossed (90°) and merged electron—ion beam experiments.
A. Chutjian

Absorption Spectra of Diphenylacetylene and 1,4-Diphenylbutadiyne Cations in Solid Argon

One and two-photon matrix photoionization techniques have been used to prepare diphenylacetylene and 1,4-diphenylbutadiyne cations. Identification of these cations was confirmed by photoelectron spectra and radiolysis studies. Near-infrared absorption bands for each cation correlate with photoelectron spectra and suggest structural relaxation about the molecular axis on ionization, and strong blue absorptions that do not correlate with photoelectron spectra are probably caused by π → π* transitions.
Benuel J. Kelsall, Robert T. Arlinghaus, L. Andrews

Study of the Disproportionation of Sodium Thiosulfate by X-Ray Photoelectron Spectroscopy

The disproportionation of sodium thiosulfate to form sodium sulfite and elemental sulfur has been studied in the temperature range 495–548°K by means of X-ray photoelectron spectroscopy (XPS). The disproportionation started with an induction period, followed by a steady-state disproportionation rate regime, and ended up with a diffusion rate-controlling process. The duration of the induction period was inversely proportional to the temperature of heating. The disproportionation in the steady-state regime followed a first-order reaction rate law with the enthalpy and entropy of activation H* = 26.0 kcal/ mol and S* = -14.9 eu.
X. B. Xu, S. G. Chang

Observations of Excited Metastable and Radiative States of He2, Ne2, and Ar2 by Neutralized Ion-Beam Spectroscopy

Rare gas dimers formed when a fast beam of X 2 + (X = He, Ne, Ar) is neutralized in the reaction
$$ X_2^ + + {K_{(g)}} \to X_2^* + {K^ + } $$
have been studied by neutralized ion beam techniques. From measurements of the kinetic energy released in the dissociation of X 2 * and with consideration of available spectroscopic information, it is proposed that the neutral dimers are formed initially in their first excited singlet and triplet electronic states. Estimates of the radiative lifetimes of the 3 u + states of He 2 * , Ne 2 * , Ar 2 * are >3.2, >7.2, and 2.1 µs, respectively. Radiation from the 1 u + X 1 g + transitions is predicted to occur at λ ≈ 83, 80, and 114 nm for He2, Ne2, and Ar2, respectively. Ion beam attenuation cross-sections for He 2 + , Ne 2 + , and Ar 2 + are 250, 180, and 80 Å2, respectively, indicating that electron transfer from K(g) is a highly efficient process. The capability of generating relatively intense beams of metastable He2 and Ne2 dimers may have applications for other beam experiments.
Gregory I. Gellene, Richard F. Porter

ScNi and TiCo Molecules

Ground States, Bonding, and Brewer-Engel Theory
The isoelectronic ScNi and TiCo molecules have been trapped in argon matrices near 4 K and their electronic ground states established as 2∑ via electron spin resonance (ESR) spectroscopy. These ground states are indicative of multiple metal—metal bonding. The hyperfine splittings at the 47Ti59Co nuclei indicate an approximate 3dσ Ti 0.33 + 4sσ Ti 0.33 + 3dσ Co 0.07 + 4sσ Co 0.25 unpaired electron configuration. Likewise the 45ScNi nuclear hyperfine interactions indicate an approximate 3dσ Sc 0.50 + 4sσ Sc 0.35 + (4sσ + 3dσ) Ni 0.15 configuration. The spin dis­tribution, electronic structures, and bonding in these molecules are dis­cussed relative to the Brewer-Engel theory of metals and to calculations made on such alloy systems. It may be inferred from these results that the ScCo, TiFe, TiNi, and VCo molecules probably have 1∑ multiply bonded ground states.
R. J. Van Zee, W. Weltner

Temperature Dependence of Pb(3 P 1 0 )

Spin-Orbit Relaxation by Atomic Hydrogen
The interconversion of Pb(3 P 1 0 ) and Pb(3 P 0 0 ) in a series of premixed H2/N2/O2 flames has been monitored by measuring the relative intensities of emission at 364.0 and 368.3 nm, following excitation at 283.3 nm. Improved rate constants have been obtained for the processes
$$ Pb(^3 P_1^o ) + M \to Pb(^3 P_0^o ) + M $$
(where M is either atomic hydrogen or a bulk flame constituent) over the temperature range 1570–2110 K. In contrast to previous results, in which the rate constant for hydrogen atoms was found to have a negative temperature dependence, we now find a small positive temperature dependence of the rate constant for both M = H and M = bulk flame gases. The implications of this finding are discussed in terms of a model that involves non-adiabatic transitions between excited states of PbH.
M. J. Bird, L. F. Phillips

Electronic Matrix Isolation Spectroscopic Studies of the Group IIA Metal—Water Photochemistry

This paper reports the results of an investigation of the electronic structures of the Group IIA metal atom hydration reaction intermediates (M. . . OH2 adducts) and their subsequent photolysis products (HMOH and MOH). For the adduct, the metal—water interaction is sufficiently strong so as to perturb significantly the electronic structure of the metal atom, which results in a unique band structure for the adduct that is red-shifted from the metal atomic resonance transition. Selective photolysis studies are conducted to assist in deconvoluting the complex band structure of the adduct. Molecular orbital theory is invoked to interpret the nature of the ground and excited states of the adduct. Molecular orbital and electronic state-to-state correlation arguments are presented to rationalize the chemical reaction dynamics of the adduct along ground and excited state potential energy surfaces.
M. A. Douglas, R. H. Hauge, J. L. Margrave

Reactions of Iron Atoms and Iron Dimers with Methane, Ammonia, and Hydrogen Fluoride in Low Temperature Matrices

Infrared matrix isolation studies of the cocondensation of iron atoms with CH4, NH3, and FH indicate only formation of Fe·NH3 and Fe·FH adducts. Photolysis of the matrices with visible/near UV light causes iron to insert into the HX bond, where X is CH3, NH2, or F, to produce the HFeCH3, HFeNH2, and HFeF species. Molecular vibrational frequencies and mode assignments are given in accompanying tables. Tentative assignments were also made for HFe2F, HFeNH2(NH3), and HFe2NH2.
J. W. Kauffman, R. H. Hauge, J. L. Margrave

Cadmium Activities of Silver—Cadmium Alloys Determined from Measurements on EMF Cells Involving Displacement Reactions

Cadmium activities have been obtained for dilute solutions of silver in cadmium at 776 K from emf measurements using the cell: W-Cd|CdI2 + Cd (αCd = 1)||CdI2 + AgI + Cd (αCd < 1)|Cd, Ag-W. When the displacement reaction 2Ag + CdI2 ⇄ Cd + 2AgI is taken into account, the calculated cadmium activities follow the equation αCd = 1 − NAg − 0.607 N Ag 2 with a standard deviation of 0.00001 for those measurements (taken by the most precise method) used in the least squares fit. The largest deviation from the curve for all points measured was 0.0006 or 0.9 g/cal in \( {\overline G _{Cd}} \).
Barton L. Houseman, Donald R.Conant

Second Law and Solution Structure

This summary paper starts from the fact that activity data are now published that give positive proof of the Second Law, i.e., highly precise experimental data show forms that would not occur unless the law held. Such positive proof contrasts with the essentially negative approach that “violations of the law have not been demonstrated” or with what Bridgman emphasized as an economic law controlling chemistry, i.e., “that you can’t get something for nothing.” In view of those activity data, we intend that all our present discussion shall be consistent with the Second Law. The paper deals with precise experimental data from nonrandom solutions and with our views as to (a) how the data should be taken and (b) how thermodynamics should be applied to such solutions, both solid and liquid. It deals with effects from numerous phenomena: nonstoichiometry and superlattices in solids; solid-like structures in liquids; metastability; hysteresis; persistent lattice stresses or slow diffusion; anomalies associated with one-component equilibrium in two-component systems; EMF changes caused by metal solubility in molten salts and the resultant mixed-valence electrolytes; and exchange reactions and electronic conduction in EMF cells. Proper plots for evaluating experimental data are considered. Effects of structure on partial molal entropies and enthalpies are discussed in relation to general behavioral trends of random solutions. For example, effects of solution ordering frequently look like fine structure imposed on the trends described by regular-solution theory (with its random-solution assumption).
Guy R. B. Elliott, Donald R. Conant, Barton L. Houseman

Diatomic Partition Functions from Classical and Semiclassical Phase Integrals

Two methods for calculating diatomic partition functions directly from potential curves are examined with regard to their computational efficiency and accuracy. The first utilizes semiclassical phase integrals to estimate the rotation-vibration eigenvalues and may be considered exact. The second method entails numerical integration of the classical phase integral. The two methods are compared in test calculations of the bound and metastable contributions to the partition functions q vr for Ar2 and HgBr. These calculations show that the classical method, which is typically one to two orders of magnitude faster than the semiclassical method, gives results for the bound contributions to q vr within 1% of exact when kT is at least twice the vibrational energy. For the metastable contributions, two alternative modifications of the classical expression perform less well, and it appears that these contributions can best be estimated by the semiclassical method.
The calculations for HgBr employ the latest spectroscopic constants for this molecule. The resulting values of q vr are represented within 0.2% over the range 200–3000 K by an empirical expression containing six parameters, with the latter determined by the method of least squares.
Joel Tellinghuisen

Surface/Interfacial Free Energies and the Surface Tension of Uranium Dioxide

The purpose of this study is to review literature on surface/interfacial free energies and surface tension of UOx . The data available in the literature are reviewed and critical evaluation and analyses of the available data are made by comparing them not only with each other, but also with the estimated values based on the available theoretical models.
In light of the complexity of the material and the problems associ­ated with the available literature data, no recommendations of surface/interfacial free energies and surface tension values are possi­ble at this time. However, an attempt is made to point out problems associated with the data in general and also to develop procedures that can be used to analyze surface energies.
M. S. Deshpande, P. D. Desai, A. A. Solomon

Transpiration Mass Spectrometric Analysis of Liquid KCl and KOH Vaporization

Existing thermodynamic functions for the equilibrium vapor species over liquid KCl and KOH are based largely on an extrapolation of data for the lower temperature solid systems together with estimated spectroscopic constants. The degree of importance of dimeric or more complex vapor species is especially uncertain, with a wide disparity indicated for the various literature studies. Using a transpiration mass spectrometric method, we have determined the equilibrium vapor composition in the presence of liquid over a wide range of temperature and pressure. The results for KCl are in very good agreement with the JANAF evaluation of previous work. In addition, thermodynamic data are given for the (KCl)3 trimer species for the first time. For the KOH system, the dimer species (KOH)2 is much more important than suggested by the JANAF evaluation of previous work. Second law thermodynamic data, at 1000 K, with current JANAF values given in parentheses are: for vaporization to yield KOH(g), ΔH v = 164 ± 4 (159 ± 17) kJ/mol, ΔS v = 109 ± 4 (102 ± 4) J/K mol; for vaporization to yield (KOH)2(g), ΔH v = 159 ± 5 (123 ± 17) kJ/mol, and ΔS v = 95.0 ± 4 (50.0 ± 13) J/K mol. Thermochemical data are also reported for the KO2 species produced by the reaction:
$$ 2KOH\left( 1 \right)\, + 1.5\,{O_2}\, = \,2K{O_2}\, + \,{H_2}O $$
from which we derive at 1000 K, ΔG f (KO2) = − 169 ± 12 kJ/mol and ΔH f (KO2) = − 73.6 ± 13 kJ/mol.
Bond dissociation energies and entropies for the various potassium halide and hydroxide species are found to correlate well with other alkali halide systems. Evidence of temperature dependent electron impact ionization is also indicated in these studies.
J. W. Hastie, K. F. Zmbov, D. W. Bonnell

A New Gaseous Iridium Oxide, Ir2O3

A careful reappraisal of the available data of oxidation of iridium in light of the recent measurements of the pressures of iridium oxides in this laboratory has revealed the existence of a new gaseous iridium oxide Ir2O3. The results presented here support this conclusion and a structural formula is suggested.
S. N. Tripathi, M. S. Chandrasekharaiah

Gibbs Free Energies of Formation for Intermetallic Compounds Involving Transition Elements, Lanthanides, and Actinides

Values or limits are provided for the Gibbs free energies of formation of “A n B m ” intermetallic compounds for 84 binary systems. “A” elements are: Li, Be, Mg, Ca, Sr, Ba, Al, Si, Sc, Ti, V, Mn, Fe, Co, Ni, Y, Zr, Nb, Hf, Ta, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U, and Pu. “B” elements are Fe, Co, Ni, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, and Au. The significance and applications of this information are discussed.
John K. Gibson, Paul R. Wengert

Prediction of High Temperature Metallic Phase Diagrams

The Engel Correlation and the Brewer Predictions are reviewed. Multicomponent phase diagrams for the 30 metallic elements of K through Ni, Rb through Pd, and Cs through Pt are discussed.
Paul R. Wengert

The Temperature—Composition Phase Diagram of the GeSe—GeTe System

The temperature-composition phase diagram for the GeSe-GeTe system was determined between 25 and 675°C using high temperature X-ray powder diffraction techniques (1). The orthorhombic phase extends from 100 to 92 ± 3 mol% GeSe and is stable below 651 ± 5°C. For compositions between 86 ± 3 and 58 ± 3 mol% GeSe a hexagonal phase exists. Above 415 ± 5°C the hexagonal phase decomposes via a peritectoid reaction to form an orthorhombic and cubic phase. A rhombohedral phase was observed for compositions between GeTe and 52 ± 3 mol% GeSe. Above 375 ± 10°C the rhombohedral phase transforms into a cubic phase. A complete series of cubic GeSe-GeTe solid solutions exists above 651 ± 5°C.
Heribert Wiedemeier, Paul A. Siemers

Hydration and Dehydration of Calcium Oxide Powders Studied by Photoluminescence Spectroscopy

Photoluminescence and photoexcitation spectroscopy have been used to characterize the surface properties of CaO powders containing low coordination OH species during outgassing at temperatures of up to 1200 K.
W. W. Duley

Reactions of Transition Metal Atoms with 2-Nitropropane

Atoms of Cr, Mn, Fe, Co, Ni, and Cu formed by vacuum vaporization of the metals react with 2-nitropropane at −196°C. The products isolated at 0°C are new propane-2-nitronato complexes of the metals, different from those made by conventional metathesis reactions. Cr, Mn, and Fe form basic complexes [M{O2NC(CH3)2}20H] with additional H2O in the lattice, Co gives [Co{O2NC(CH3)2}2], and Cu thermally and air-sensitive [Cu4O{O2NC(CH3)2} 2]. Ni gives two propane-2-nitronato complexes, one of which contains coordinated NO. Reduction and rearrangements occur in the reactions of Mo and Ru atoms with 2-nitropropane. The results suggest that using high temperatures to form metal atoms may open a new chapter in “classical” coordination chemistry.
A. B. M. Anwarul Bashar, Peter L. Timms

A Predictive Procedure for Vapor Pressure

A vapor pressure equation containing only three parameters has been proposed to calculate vapor pressures from the triple point to the normal boiling point of both organic and inorganic liquids. One of the three parameters is the normal boiling point. The other two parameters are obtained from only two pieces of experimental data, namely, the enthalpy of vaporization at the normal boiling point, and the enthalpy of vaporization at 298.15 K. There are several empirical procedures for the calculation of the boiling points of most liquids. The enthalpy of vaporization at the boiling point is obtainable from the Trouton’s constant. The enthalpy of vaporization at 298.15 K is obtainable from group contributions. Thus one obtains a simple predictive procedure for the vapor pressure. We call our vapor pressure equation the quadratic equation. By the addition of one more constant we may make the quadratic equation a cubic equation.
Comparison of the quadratic equation with the Antoine equation has shown that the new equation is much more accurate than the latter in the prediction of vapor pressures and enthalpies of vaporization, partircularly when large extrapolations to low temperatures are necessary. The Cox equation, which employs four parameters, is closely related to the quadratic equation. It is, however, inferior to the quadratic equation when it comes to compounds of high molecular weight, which usually have very low pressures at 298.15 K. The cubic equation, which contains one parameter more than the quadratic equation, is equally defective when it comes to compounds of high molecular weight. The attractive features of the three-constant quadratic equation are that (1) its constants have some simple physical significance, (2) its constants can be determined from the molecular structure, and (3) it is the most accurate equation for the representation of vapor pressure data from the triple point to the normal boiling point.
Gollakota R. Somayajulu

Empirical Calculations of Molecular Properties

Empirical equations for the stretching and bending force constants, bond energies, and bond lengths are reviewed. Applications to gaseous and matrix-isolated molecules, and to chemisorptive bonds on surfaces are illustrated.
Chin-An Chang


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