Heat capacity and thermodynamic functions of MnCl2·2H2O and MnCl2·2D2O

The heat capacities of MnCl₂·2H₂O and MnCl₂·2D₂O have been experimentally determined from 1.4 to 300 K. The smooth heat capacity and the thermodynamic functions (H°_T − H°₀) and S°_T are reported for the two compounds over the 10 and 300 K temperature range. The error in the thermodynamic functions at 10 K is estimated at 3%. Additional error in the tabulated values arising from the heat capacity data above 10 K is thought to be less than 1%. Lambda-shaped heat capacity features associated with antiferromagnetic ordering were observed at 6.67 ± 0.08 and 6.61 ± 0.08 K for the dihydrate and dideuterate, respectively. In addition, compound heat capacity anomalies consisting of a small lambda-shaped feature at 57.7 ± 0.5 K with a comparably large high-temperature shoulder extending to approximately 70 K were observed in both the dihydrate and dideuterate. The entropies associated with these anomalies are 0.42 ± 0.04 and 1.04 ± 0.04 J/mole-K, respectively.     

Synthesis and thermochemical characteristics of Na2O · Al2O3 · 2.5H2O

A pure phase of monosodium aluminate hydrate Na₂O · Al₂O₃ · 2.5H₂O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of ?100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated.     

Negative ion photoelectron spectroscopy of N2O− and (N2O)−2

We have recorded the photoelectron spectra of the gas phase negative ions N₂O⁻ and (N₂O)₂⁻ both of which were prepared in a nozzle ion source. The shift between the maxima of the two spectra is interpreted in terms of the dissociation energy of the dimer ion.     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.     

Structures and bonding of B4O5 and B4O5− clusters: Emergence of boroxol ring and competition between rhombic B2O2 and hexagonal B3O3 cores

Boron oxide clusters are electron-deficient species with novel structures and bonding, in which the emergence of rhombic and boroxol rings is of interest. We report on computational prediction of the global-minimum structures for two boron oxide clusters: B₄O₅ and B₄O₅⁻. These structures differ distinctly, as established through global machine searches and electronic structure calculations at B3LYP and single-point CCSD(T) levels. While B₄O₅ neutral cluster has a rhombic B₂O₂ core, the B₄O₅⁻ anion features a boroxol B₃O₃ ring. One electron completely changes the potential landscapes. Bonding analyses show that the 4π electron-counting is crucial for a rhombic B O cluster, in contrast to π sextet for a boroxol ring, which underlies the competition between rhombic and boroxol rings in B₄O₅/B₄O₅⁻ clusters. A possible pathway for rhombic-to-hexagonal transformation is proposed based on intrinsic reaction coordinate calculations. Anion B₄O₅⁻ cluster, a new member of the inorganic benzene family, is among the smallest B O species with a free-standing boroxol ring, governed collectively by composition and electron-counting.     

Preparation of nanoparticles and hollow spheres of ��-Fe2O3 and their properties

Uniform nanoparticles and hollow microspheres of hematite (??-Fe₂O₃) were obtained via a hydrothermal method by using iron (III) chloride as a precursor. The effects of reactant concentration, reaction time and temperature on the morphology of the samples were studied. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and superconducting quantum interference device magnetometer (SQUID) measurement. ??-Fe₂O₃ nanoparticles show a superparamagnetic behavior and the average size of the spherical particles was around 60 nm. However, hollow microspheres show a normal ferromagnetic behavior at room temperature with remanent magnetization and coercivity of 0.2482 emu/g and 2,516 Oe, respectively, and their average diameter was around 2 ??m. The effects of reactant concentration and reaction temperature on the formation of the products were investigated. The experimental results reveal that the magnetic properties of hematite can be tuned by controlling the morphology.     

Preparation and Characterization of Nano-ZnFe2O4/TiO2 Films

The nano-ZnFe2O4/TiO2 films possess the functions of desulfurization and degradation for organic pollutants. The sols of ZnFe2O4/TiO2 were prepared by sol-gel method and coated on glass and porous ceramic by vertical coating and dipping-lift processes, respectively, and the samples were obtained after drying and sintering. The composition, appearance, absorption spectrum of the films, and the influence of the film on porous ceramic performances were analyzed using SEM, AFM, UV-Vis spectrometer, and mercury porosimeter, respectively, to determine the operation parameters of the multifunction porous ceramic elements for gas-purification.     

Synthesis, Characterization and Thermochemistry of 2MgO：B2O3：1.5H2O

Introduction　　 2MgO·B2 O3(Mg2 B2 O5)and 2MgO·B2 O3·H2 Omightbepreparedaswhiskermaterials .12MgO·B2 O3·H2 OnamedszaibelyiteisamagnesiumboratemineralwithastructuralformulaofMg2 [B2 O4 (OH) 2 ].2 Itisdifficulttosynthesizethiscompoundinthelaboratory .Recently ,weobtainedasimilarcompound 2MgO·B2 O3·1 5H2 Owhenwetriedtopreparewhiskerof 2MgO·B2 O3·H2 Obythephasetransformationof 2MgO·2B2 O3·MgCl2 ·14H2 OinH3BO3solutionunderhydrothermalcondition .Itishope fultopreparewh…     

Thermal Dehydration and Infrared Studies of Mg 2 P 2 O 7 · 6H 2 O Diphosphate

The thermal dehydration of Mg 2 P 2 O 7 ·; 6H 2 O were studied, in the range 25-800°;C, by thermogravimetric analysis (TG-DSC), x-ray diffraction, and infrared spectroscopy. According to the TG-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, Mg 2 P 2 O 7 ·; 6H 2 O decomposes into dihydrate Mg 2 P 2 O 7 ·; 2H 2 O diphosphate then to an amorphous Mg 2 P 2 O 7 product which crystallises at 665°;C to give anhydrous diphosphate f Mg 2 P 2 O 7 . The j H enthalpy of the dehydration of Mg 2 P 2 O 7 ·; 6H 2 O and of the formation of f Mg 2 P 2 O 7 have been calculated from thermogravimetric data. The infrared spectroscopic study of Mg 2 P 2 O 7 ·; 6H 2 O and of its heated products, reveals the existence of the characteristic bands of the P 2 O 7 group ( x as POP and x s POP) and showed that the POP angle is bent in these salts. In these compounds, the POP angle values are estimated using the Lazarev's relationship.     

Enhancement of Activity of SnO2-doped In2O3/Al2O3 Catalyst for NO Reduction with Propene in the Presence of H2O and SO2

The selective catalytic reduction of nitrogen oxides by hydrocarbons (HC-SCR) has attracted much attention as an efficient way to remove NO in the presence of excess oxygen1-2. The metal oxides are the most promising catalysts for the SCR of NO because of their high activity and selectivity3-5. In the previous work, the metal oxides such as Ag, Sn, In, Co supported on alumina for NO reduction were investigated6-8, however, the HC-SCR is usually suppressed in the presence of H2O and S…     

Crystal Structure and Properties of Rb4H2I2O10 · 4H2O

Single crystals of the Rb₄H₂I₂O₁₀· 4H₂O were synthesized for the first time and studied by X-ray diffraction analysis. The crystals are monoclinic, a = 7.321(6) Å, b = 12.599(8) Å, c = 8.198(8) Å, = 96.30(7)°, Z = 2, space group P2₁/c. The H₂I₂O₁₀ ^4– anion is formed by the edge-sharing IO₆ octahedra. The anions are united by hydrogen bonds into a chain running along the x axis. The chains are combined by water molecules into a three-dimensional structure through hydrogen bonds. The compound is a proton conductor. The conductivity values measured at 20–60°C vary within 10^–6 to 10^–4 ohm^–1 cm^–1.     

Apparent Molar Volumes and Adiabatic Compressibilities of Crown Ethers and Glymes in H2O and D2O at 25°C

The apparent molar volumes and adiabatic compressibilities of 18-Crown-6, 15-Crown-5, 12-Crown-4, tetraglyme, and triglyme were measured at 25°C in H₂O and D₂O. The contribution of the -CH₂CH₂O- group to the limiting partial molar volumes and compressibilities of cyclic and open-chain ethers in both solvents are compared and solvent isotope effects calculated. It is concluded, based on the compressibility results, that there is a subtle difference between the hydration of the ethene oxde group in cyclic and open-chain ethers and that this difference persists in D₂O. These results indicate that the calculation of limiting apparent molar compressibilities using additivity schemes will have to account for whether the group is in a cyclic or open-chain compound.     

Synthesis and crystal structure of the hydrated magnesium diphosphate Mg2P2O7·3.5H2O and its high temperature variant Mg2P2O7·H2O

The synthesis and crystal structure of a novel hydrated magnesium diphosphate and its high temperature variant are described. Both structures were solved from powder X-ray diffraction data. The room temperature variant with composition Mg₂P₂O₇·3.5H₂O crystallises in the monoclinic space group P2₁/c (No. 14) with a=10.9317(1), b=8.05578(9), c=9.2774(1) Å, β=90.201(1)°, V=816.99(2) ų and Z=4. The structure consists of sheets stacked along [100] which are linked through MgO₂(H₂O)₄ pillars into a three-dimensional framework with cavities containing water molecules. Within the sheets there are infinite edge-sharing chains of Mg octahedra along [010] which are cross linked by P₂O₇⁴⁻ groups. A high temperature variant exists around 200°C. The crystal structure of this compound with composition Mg₂P₂O₇·H₂O was solved and refined in the monoclinic space group C2/c (No. 15) with a=18.6596(4), b=7.9769(1), c=8.9757(2) Å, β=107.378(1)°, V=1275.01(4) ų, Z=8. The transformation to Mg₂P₂O₇·H₂O involves removal of the water molecules in the cavities and the water molecules of the Mg octahedral pillars in Mg₂P₂O₇·3.5H₂O. The sheets in Mg₂P₂O₇·3.5H₂O however remain unchanged during the transformation as the water molecule coordinating Mg here is retained. These sheets are linked through tetrahedral MgO₄ pillars into a three-dimensional structure containing infinite 10-membered ring channels along [001]. Both compounds have been further characterised by ³¹P MAS NMR spectroscopy, thermogravimetric analysis and high temperature powder X-ray diffraction.     

Thermo-Raman Studies on Dehydration of Na4P2O7⋅10H2O and Phase Transformations of Na4P2O7

In this work, dehydration of sodium diphosphate decahydrate Na₄P₂O₇⋅10H₂O and phase transformations of Na₄P₂O₇ in open air have been studied in detail by thermo-Raman spectroscopy. The spectra were measured continuously in a temperature range from room temperature up to 600°C for the bands of P₂O₇ ^4- and H₂O. The spectral variation showed one step of dehydration and four-phase transformations. The thermo-Raman intensity(TRI) and differential thermo-Raman intensity (DTRI) curves calculated from the characteristic bands of H₂O also showed one step of dehydration with the loss of all hydrated water in the temperature interval from 45 to 69°C. Thermogravimetric measurements supported this result. The thermo-Raman investigation indicated the transformation of Na₄P₂O₇ from low temperature phase to high temperature phase proceed through pre-transitional region from 75 to 410°C before the major orientational disorder at 418°C and minor structural modifications at 511,540 and 560°C. The results from differential scanning calorimetry and differential thermal analysis on Na₄P₂O₇ showed endotherms at 407,517, 523, 548, 557°C and 426, 528, 534, 555, 565°C, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics of decomposition of the liquid phase of the ternary system LiOH-H2O2-H2O in the presence of the solid phase of Li2O2 · H2O

The kinetics of decomposition of hydrogen peroxide in the liquid phase of the ternary system LiOH-H₂O₂-H₂O was studied in the presence the solid phase of Li₂O₂·H₂O and without it. The main kinetic parameters of the processes studied were determined.     

Effects of CuCl2��6H2O and ZnCl2��6H2O on the viscosity of aqueous ethanol mixtures

The effects of CuCl₂ and ZnCl₂ on the viscosity in aqueous ethanol mixtures (10%–50% v/v) were studied in the concentration range 1.0×10⁻²–8.0×10⁻² mol·dm⁻³ at different temperatures. It was found that the viscosities increased with an increase in the concentration of the salts and percent composition of ethanol content, whereas it decreased with an increase in temperature. Ion-ion and ion-solvent interactions are determined with the help of A- and B-coefficients of Jones-Dole equation. The values of A- and B-coefficients are irregular and increase with a rise in temperature and also with an increase in ethanol contents for both salts. Negative values of B-coefficients show that ion solvent interactions is comparatively small and suggest that CuCl₂ and ZnCl₂ behave as structure breakers in aqueous ethanol mixtures. Thermodynamic parameters like the energy of activation (E _η ) and change in entropy of activation (ΔS*) were also evaluated which confirm the structure breaker behavior of salts in aqueous ethanol mixtures.     

Synthesis and study of lithium triuranate Li2U3O10 · 6H2O

Li₂U₃O₁₀ · 6H₂O crystal hydrate was synthesized by the reaction between synthetic schoepite UO₃ · 2.25H₂O and aqueous lithium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the obtained compound were established, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.