Thermal Decomposition of CF3C(O)O2NO2, CClF2C(O)O2NO2, CCl2FC(O)O2NO2, and CCl3C(O)O2NO2

Haloacetyl, peroxynitrates are intermediates in the atmospheric degradation of a number of haloethanes. In this work, thermal decomposition rate constants of CF₃C(O)O₂NO₂, CClF₂C(O)O₂NO₂, CCl₂FC(O)O₂NO₂, and CCl₃C(O)O₂NO₂ have been determined in a temperature controlled 420 l reaction chamber. Peroxynitrates (RO₂NO₂) were prepared in situ by photolysis of RH/Cl₂/O₂/NO₂/N₂ mixtures (R = CF₃CO, CClF₂CO, CCl₂FCO, and CCl₃CO). Thermal decomposition was initiated by addition of NO, and relative RO₂NO₂ concentrations were measured as a function of time by long-path IR absorption using an FTIR spectrometer. First-order decomposition rate constants were determined at atmospheric pressure (M = N₂) as a function of temperature and, in the case of CF₃C(O)O₂NO₂ and CCl₃C(O)O₂NO₂, also as a function of total pressure. Extrapolation of the measured rate constants to the temperatures and pressures of the upper troposphere yields thermal lifetimes of several thousands of years for all of these peroxynitrates. Thus, the chloro(fluoro)acetyl peroxynitrates may play a role as temporary reservoirs of Cl, their lifetimes in the upper troposphere being limited by their (unknown) photolysis rates. Results on the thermal decomposition of CClF₂CH₂O₂NO₂ and CCl₂FCH₂O₂NO₂ are also reported, showing that the atmospheric lifetimes of these peroxynitrates are very short in the lower troposphere and increase to a maximum of several days close to the tropopause. The ratio of the rate constants for the reactions of CF₃C(O)O₂ radicals with NO₂ and NO was determined to be 0.64 ± 0.13 (2σ) at 315 K and a total pressure of 1000 mbar (M = N₂). © 1994 John Wiley & Sons, Inc.     

Comparative XPS Study of Al2O3 and CeO2Sulfation in Reactions with SO2, SO2 + O2, SO2 + H2O,and SO2 + O2 + H2O

The interactions of Al₂O₃, CeO₂, Pt/Al₂O₃, and Pt/CeO₂ films with SO₂, SO₂ + H₂O, SO₂ + O₂, and SO₂ + O₂ + H₂O in the temperature range 300–673 K at the partial pressures of SO₂, O₂, and H₂O equal to 1.5 × 10², 1.5 × 10², and 3 × 10² Pa, respectively, were studied using X-ray photoelectron spectroscopy. The formation of surface sulfite at T 473 K (the S 2p _3/2 binding energy (E _b) is 167.5 eV) and surface sulfate at T 573 K (E _b = 169.2 eV) was observed in the reactions of Al₂O₃ and CeO₂ with SO₂. The formation of sulfates on the surface of CeO₂ occurred much more effectively than in the case of Al₂O₃, and it was accompanied by the reduction of Ce(IV) to Ce(III). The formation of aluminum and cerium sulfates and sulfites on model Pt/Al₂O₃ and Pt/CeO₂ catalysts occurred simultaneously with the formation of surface platinum sulfides (E _b of S 2p _3/2 is 162.2 eV). The effects of oxygen and water vapor on the nature and yield of sulfur-containing products were studied.     

Neue Oxometallate vom BaCuSm2O6-Typ: BaCoHo2O5, BaCoYb2O5 und vom BaNiLn2O5-Typ: BaCoEr2O5

Inhaltsübersicht. (I) BaCoHo₂O₅, (II) BaCoYb₂O₅ und (III) BaCoEr₂O₅ wurden neu dargestellt und an Einkristallen mit Röntgenbeugungsmethoden die Kristallstruktur bestimmt. (I) und (II) gehören zum BaCuSm₂O₅-Typ mit (I): A = 12,267; b = 5,714; c = 7,064 Å; Z = 4; (II): A = 12,138; b = 5,662; c = 7,004 Å; Z = 4. Beide kristallisieren in der Raumgruppe D¹⁶_2h–Pnma. (III) kristallisiert im BaNiLn₂O₅-Typ, Raumgruppe D²⁵_2h–Immm mit a = 3,734; b = 5,770; c = 11,421 Å; Z = 2. Die Koordination um Co²⁺ wechselt von (I, II) nach (III) von tetragonal pyramidal nach oktaedrisch. New Oxides of the BaCuSm₂O₅-Type: BaCoHo₂O₅, BaCoYb₂O₅, and of the BaNiLn₂O₅ Type: BaCoEr₂O₅ (I) BaCoHo₂O₅, (II) BaCoYb₂O₅, and (III) BaCoEr₂O₅ are new compounds prepared by high temperature reactions. X-ray single crystal work show: (I) and (II) belong to the BaCuSm₂O₅-type (space group D¹⁶_2h-Pnma, Z = 4). (I): A = 12.267; b = 5.714; c = 7.064 Å; (II): A = 12.138; b = 5.662; c = 7,004 Å. (III) crystallizes with BaNiLn₂O₅-structure, space group D²⁵_2h-Immm; Z = 2; a = 3.734; b = 5.770; c = 11.421 Å; within (I) and (II) Co²⁺ has a tetragonal pyramidal coordination by oxygen. The coordination changes in (III) to a compressed octehedral O^2– surrounding.     

Thermodynamics of Cr2O3, FeCr2O4, ZnCr2O4, and CoCr2O4

High-temperature heat capacity measurements were obtained for Cr₂O₃, FeCr₂O₄, ZnCr₂O₄, and CoCr₂O₄ using a differential scanning calorimeter. These data were combined with previously available, overlapping heat capacity data at temperatures up to 400 K and fitted to 5-parameter Maier–Kelley C_p(T) equations. Expressions for molar entropy were then derived by suitable integration of the Maier–Kelley equations in combination with recent S^∘(298) evaluations. Finally, a database of high-temperature equilibrium measurements on the formation of these oxides was constructed and critically evaluated. Gibbs free energies of Cr₂O₃, FeCr₂O₄, and CoCr₂O₄ were referenced by averaging the most reliable results at reference temperatures of (1100, 1400, and 1373) K, respectively, while Gibbs free energies for ZnCr₂O₄ were referenced to the results of Jacob [K.T. Jacob, Thermochim. Acta 15 (1976) 79–87] at T = 1100 K. Thermodynamic extrapolations from the high-temperature reference points to T = 298.15 K by application of the heat capacity correlations gave Δ_fG^∘(298) = (−1049.96, −1339.40, −1428.35, and −1326.75) kJ · mol⁻¹ for Cr₂O₃, FeCr₂O₄, ZnCr₂O₄, and CoCr₂O₄, respectively.     

Fe2P2O7(H2O)2

The compound diiron diphosphate dihydrate, Fe₂P₂O₇(H₂O)₂, was synthesized hydro­thermally and crystallizes in the monoclinic space group P2₁/n. The compound has a somewhat open framework made up of edge‐sharing iron(II) octahedra that form chains connected by five bridging diphosphates. The remaining octahedral site of each iron is occupied by coordinated water. The H atoms of the water molecules all point into a common channel.     

Neue Verbindungen mit SrNi2V2O8-Struktur: BaCo2V2O8 und BaMg2V2O8

New Compounds of the SrNi₂V₂O₈-Type: BaCo₂V₂O₈ and BaMg₂V₂O₈ For the first time BaCo₂V₂O₈ (A) and BaMg₂V₂O₈ (B) were prepared and investigated by X-ray methods. Space group: D–I4₁/acd, Z = 8. ((A): a = 12.4441, c = 8.4153 Å; (B): a = 12.4189, c = 8.4657 Å). A and B crystallize with higher symmetry, but they are isotypic with SrNi₂V₂O₈. The differences in crystal chemistry in respect to the BaNi₂V₂O₈-type are discussed.     

K2[Mo2O4(C2O4)2(H2O)2]·3H2O

The crystal and molecular structure of dipotassium di‐μ‐oxo‐bis[aqua(oxalato‐O¹,O²)oxomolybdenum(III)] trihydrate, K₂­[Mo₂O₄(C₂O₄)₂(H₂O)₂]·3H₂O, has been determined from X‐ray diffraction data. In the dimeric anion, which has approximate twofold symmetry, each Mo atom is in a distorted octahedral coordination, being bonded to one terminal oxo‐O atom, two bridging O atoms, two O atoms from the oxalato ligand and one from the water mol­ecule. Bond lengths trans to the multiple‐bonded terminal oxo ligand are larger than those in the cis position, confirming the trans influence as a generally valid rule.     

Darstellung und Kristallstruktur der Pnictidoxide Na2Ti2As2O und Na2Ti2Sb2O

Preparation and Crystal Structure of the Pnictide Oxides Na₂Ti₂As₂O and Na₂Ti₂Sb₂O Na₂Ti₂As₂O and Na₂Ti₂Sb₂O were synthesized in form of very easily hydrolysed metallic-grey powders by reaction of Na₂O and TiAs resp. TiSb in sealed tantalum tubes under argon. The tetrahedral bodycentered crystallizing compounds from a modified anti-K₂NiF₄ structure type [1] (also called Eu₄As₂O-type [2,3]), space group I4/mmm (no. 139), with the lattice constants for Na₂Ti₂As₂O: a = 407.0(2) pm, c = 1528.8(4) pm and for Na₂Ti₂Sb₂O: a = 414.4(0) pm, c = 1656.1(1) pm. Magnetic measurements of powder samples of Na₂Ti₂Sb₂O show antiferromagnetic interaction within the Ti—O-layers. Superconductivity was not found by ac-shielding method down to 4 K.     

Phase equilibria in the P2O5-rich part of the system Y2O3−Na2O−P2O5

In the ternary system Y₂O₃?Na₂O?P₂O₅, the partial system Y(PO₃)₃?NaPO₃?P₂O₅ was examined by means of differential thermal analysis and X-ray powder diffraction; its phase diagram is given.     

RbCrIII(C2O4)2·2H2O,Cs2Mg(C2O4)2·4H2O and Rb2CuII(C2O4)2·2H2O: three new complex oxalate hydrates

Rubidium chromium(III) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­chromium(III)­rubidium(I)], [RbCr(C₂O₄)₂(H₂O)₂], (I), and dicaesium magnesium dioxalate tetrahydrate [tetra­aqua­bis(μ‐oxalato)­magnesium(II)­dicaesium(I)], [Cs₂Mg(C₂­O₄)₂(H₂O)₄], (II), have layered structures which are new among double‐metal oxalates. In (I), the Rb and Cr atoms lie on sites with imposed 2/m symmetry and the unique water molecule lies on a mirror plane; in (II), the Mg atom lies on a twofold axis. The two non‐equivalent Cr and Mg atoms both show octahedral coordination, with a mean Cr—O distance of 1.966 Å and a mean Mg—O distance of 2.066 Å. Dirubid­ium copper(II) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­copper(II)­dirubidium(I)], [Rb₂Cu(C₂O₄)₂(H₂O)₂], (III), is also layered and is isotypic with the previously described K₂‐ and (NH₄)₂Cu^II(C₂O₄)₂·2H₂O compounds. The two non‐equivalent Cu atoms lie on inversion centres and are both (4+2)‐coordinated. Hydro­gen bonds are medium‐strong to weak in the three compounds. The oxalate groups are slightly non‐planar only in the Cs–Mg compound, (II), and are more distinctly non‐planar in the K–Cu compound, (III).     

Kristallstruktur von LiHC2O4-H2O

LiHC₂O₄ · H₂O crystallizes in space group P 1 with a₀ = 4.99, b₀ = 6.16, c₀ = 3.45 Å; α₀ = 96.3°, β₀ = 98.0°, γ₀ = 80.4° and Z = 1. The crystal structure has been determined by direct methods. Refinement by least squares methods resulted to R₁ = 8,3%. In the structure the oxalate group is not planar. The angle between the two O? C? O planes is 2.9°.     

THERMAL TRANSFORMATIONS AND INFRARED STUDIES OF Mn2P2O7 · 2H2O

The thermal dehydration of Mn₂P₂O₇·2H₂O was studied, in the range 25–600°C by thermogravimetric analysis (TG-DTG and DSC), x-ray diffraction, and infrared spectroscopy. According to the (TG-DTG and DSC) curves, the dehydration of this salt takes place in two stages. The results of thermal analysis, x-ray patterns, and infrared spectra of this compound heated at different temperatures showed that after dehydration, Mn₂P₂O₇·2H₂O decomposes to an amorphous product which crystallizes at 544°C to give anhydrous diphosphate MN₂P₂O₇. The free enthalpy of the dehydration of Mn₂P₂O₇·2H₂O and of the formation of Mn₂P₂O₇ have been calculated from thermogravimetric data. The infrared spectroscopic study of Mn₂P₂O₇· 2H₂O and of its heated products reveals the existence of the characteristic bands of the P₂O₇ group (ν^as POP and ν^s POP) and showed that the POP angle is bent for the initial product and a linear POP bridge is observed in the diphosphate Mn₂P₂O₇. The infrared spectrum of Mn₂P₂O₇· 2H₂O has been interpreted using factor group analysis.     

Röntgenographische Untersuchungen in den Systemen GeO2-{K2O,Rb2O,Cs2O}

Zusammenfassung Folgende GeO₂-reiche Alkaligermanate wurden aufgefunden und röntgenographisch hinsichtlich der Gitterparameter charakterisiert: K₂Ge₈O₁₇ und Rb₂Ge₈O₁₇ (isotyp), Rb₂Ge₇O₁₅ und Cs₂Ge₅O₁₁. Die Existenz der seinerzeit als Pentagermanate beschriebenen isotypen Verbindungen von K, Rb, Cs und Tl sowie deren Gitterparameter werden bestätigt, doch ergab eine ausführliche Prüfung an gut kristallisierten Produkten zusammen mit den genau bestimmten Dichtewerten eine geringfügige Verschiebung im Verhältnis Me₂O/GeO₂, entsprechend einer Formel Me₂Ge₆O₁₃.

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The GeO₂-rich regions of alkaline germanate systems have been examined by X-rays. The compounds K₂Ge₈O₁₇ and Rb₂Ge₈O₁₇ (isostructural), Rb₂Ge₇O₁₅ and Cs₂Ge₅O₁₁ have been detected and characterized by their lattice parameters. The existence as well as the cell dimensions of the isotypic compounds previously described as pentagermanates have been corroborated; a detailed investigation of completely crystallized material gives strong evidence for a lower Me₂O/GeO₂-ratio, in accordance with precise density measurements. Thus a formulaMe ₂Ge₆O₁₃ (Me=K, Rb, Cs, Tl) has to be assumed.

     

Studies on the System ZnO-V2O5-Fe2O3 Reactivity of ZnFe2O4 Towards ZnV2O6

Studies on the reactivity of ZnFe₂O₄ towards ZnV₂O₆ revealed that in the solid state the phases interact in a molar ratio of 1:3 to form a new compound, to which the molecular formula Zn₂FeV₃O₁₁ was assigned. The compound melts congruently at 825±5°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

外偶极电场作用下H_2O,D_2O和T_2O的可逆分解电压

采用密度泛函B3P86方法和6-311++G(3df,3pf)基组,计算了在-0.05～0.05a.u.外偶极电场作用下,H2O,D2O,T2O,H2,D2,T2,O2的电子能量、核运动能量和熵值,在此基础上通过计算H2O(g)→H2(g)+O2(g)、D2O(g)→D2(g)+O2(g)、T2O(g)→T2(g)+O2(g)的焓变ΔH、熵变ΔS、Gibbs函数变化ΔG,最后得到了H2O,D2O,T2O的可逆分解电压Er.计算结果表明,外偶极电场存在时,H2O,D2O,T2O的Gibbs自由能变ΔG和可逆分解电压Er都有明显的变化,当外偶极电场正方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性增加;当外偶极电场负方向增加时,其Gibbs自由能变ΔG和可逆分解电压Er均趋于线性减小;在相同外偶极电场作用下,Gibbs自由能变ΔG和可逆分解电压Er随H2O,D2O,T2O依次增加.     

Crystal structure of (C2H7N4O)2[UO2(C2O4)2(H2O)]

The single crystals of (C₂H₇N₄O)₂[UO₂(C₂O₄)₂(H₂O)] were studied by X-ray diffraction. The crystals are monoclinic, space group Pn, Z = 2, unit cell parameters: a = 9.4123(2) Å, b = 8.4591(2) Å, c = 11.8740(3) Å, β = 105.500(10)°, V = 911.02(4) ų. The main structural units of the crystals of I are islet complex groups [UO₂(C₂O₄)₂(H₂O)]^2? corresponding to the crystal chemical group AB ₂ ⁰¹ M¹ (A = UO UO ₂ ²⁺ , B⁰¹ = C₂O ₄ ^2? , M = H₂O) of uranyl complexes. Uranium-containing mononuclear complexes are connected into a three-dimensional framework through the electrostatic interactions and hydrogen bonding system involving carbamyolguanidinium ions.     

Physicochemical investigation of the ternary system KF-H2O2-H2O

Conclusions An investigation of the fusibility in the system KF-H₂O₂-H₂O confirmed the existence of KF · H₂O₂ and demonstrated the formation of a new compound, KF · 2H₂O₂, which exists in the system in the interval from –70 to 20° in the region of high hydrogen peroxide concentrations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 491–494, March, 1973.     

DTA-TG Study of the CaO-SiO2-H2O and CaO-Al2O3-SiO2-H2O Systems Under Hydrothermal Conditions

Simultaneous DTA-TG is an excellent technique for evaluating phases formed in hydrothermally treated CaO-SiO₂-H₂O and CaO-Al₂O₃-SiO₂-H₂O systems. Thermal analysis in combination with XRD and SEM, revealed that in the CaO-Al₂O₃-SiO₂-H₂O system the amount of hydrogarnet formed was the largest when gibbsite was used as the Al source, smallest for kaolin and intermediate for metakaolin. The endotherm peak temperature of the hydrogarnet dehydration endotherm was affected by the amount of hydrogarnet and the Si content of hydrogarnet. The thermal stability and structural order of 11 Å tobermorite were reduced with the incorporation of Al and, as a result, 11 Å tobermorite transformed into 9.3 Å tobermorite at lower temperatures while the transformation of the latter into beta-wollastonite required more energy. There exists a direct relationship between the 9.3 Å tobermorite and beta-wollastonite formation temperatures. Solid-state ²⁹Si and ²⁷Al MAS NMR data support these findings.     

Phase equilibria in the Bi2O3-BaB2O4-B2O3 system in the subsolidus region

The phase equilibria in the concentration triangle Bi₂O₃-BaB₂O₄-B₂O₃ of the BaO-Bi₂O₃-B₂O₃ system have been investigated by X-ray powder diffraction and DTA. Barium bismuth borates of the composition BaBi₂B₄O₁₀ and BaBiB₁₁O₁₉ have been found to exist. These borates melt at 730 and 807°C, respectively. The quasi-binary sections have been determined. It has been shown that the isothermal section of the Bi₂O₃-BaB₂O₄-B₂O₃ in the subsolidus region at 600°C is characterized by 13 triangles of coexisting phases.     

Direct Synthesis of H2O2 by a H2/O2 Fuel Cell

Direct synthesis of H₂O₂ solutions by a fuel cell method was reviewed. The fuel cell reactor of [O₂, gas-diffusion cathode electrolyte solutions Nafion membrane electrolyte solutions gas-diffusion anode, H₂] is very effective for formation of H₂O₂. The three-phase boundary (O₂(g)–electrode(s)–electrolyte(l)) in the gas-diffusion cathode is essential for efficient formation of H₂O₂. Fast diffusion processes of O₂ to the active surface and of H₂O₂ to the bulk electrolyte solutions are essential for H₂O₂ accumulation. The maxima H₂O₂ concentrations of 1.2 M (3.5 wt%) and 2.4 M (7.0 wt%) were accomplished by the heat-treated Mn-OEP/AC electrocatalyst with H₂SO₄ electrolyte and by the VGCF electrocatalyst with NaOH electrolyte, respectively, under short circuit conditions.