Decomposition of ozone in water at pH 4–8

A systematic study of the ozone decomposition in water in the pH range 4–8 was carried out.     

Co-precipitation of plutonium(IV) and americium(III) from nitric acid–oxalic acid solutions with bismuth oxalate

This study presents analytical methods for the determination of gross beta, ⁹⁰Sr, ²²⁶Ra and Pu isotopes using samples in the IAEA-TEL-2015-04 ALMERA Proficiency Test exercise. Samples for gross beta were prepared by evaporation and then analyzed using a gas proportional counter. ⁹⁰Sr in the liquid sample was concentrated as SrCO₃ precipitates and purified by Sr resin. Pu isotopes and ⁹⁰Sr in the soil sample were extracted from the sample by mineral acid leaching and separated using TEVA and Sr resin, respectively. Pu isotopes were determined by alpha spectrometry and ⁹⁰Sr were determined with a liquid scintillation counter. Radium in the soil sample was extracted by LiBO₂ fusion, and the radon-emanation method using LSC was applied for the determination of ²²⁶Ra.     

Surface characteristics of two-component thallium–bismuth melts

The surface tension of pure Tl and Bi, and two-component alloys of them over the range of volume concentrations and temperatures starting from the liquidus temperature up to 623 K are measured by the lying-drop method with strong control over the surface condition by means of Auger electron spectroscopy. The results from in situ measurements of the surface tensions of Tl and Bi with surfactant impurities, and for atomically pure surfaces and Tl–Bi solutions, are given. It is shown that surfaces are enriched by bismuth, the concentration of which grows along with temperature.

     

The reactions of phosphorus(III) halides with β-diketiminato ligands

Reactions of the lithium or sodium salt, [HC(CMeNDipp)₂]M (Dipp = 2,6-diisopropylbenzene, M = Li or Na), with PBr₃ or PCl₃ affords a series of phosphenium cations that were characterized in the solid state by X-ray crystallography. Solid-state analysis reveals that for compounds 1 and 2, C–H activation of the ligand occurs and the phosphorus is bound to a nitrogen and carbon atom of the ligand. Compound 3 exhibits the more traditional nitrogen chelation of the ligand to the phosphorus atom.     

The features of ignition of hydrogen–methane and hydrogen–isobutene mixtures with oxygen over Rh and Pd at low pressures

The flammability limits of stoichiometric mixtures (20–80% H₂ + 80–20% CH₄) + O₂ over Rh and Pd were determined in the pressure range 0–200 Torr and the temperature range 200–500 °C. It has been shown that the dark reaction in the mixture (80% H₂ + 20% C₄H₈)_stoich + O₂ leads to the formation of carbon nanotubes with a mean diameter of 10–100 nm.     

Investigation of metal–buffer interactions using isothermal titration calorimetry

Isothermal titration calorimetry (ITC) and potentiometric titration (PT) methods were used to study the interactions of cobalt(II) and nickel(II) ions with buffer substances 2-(N-morpholino)ethanesulfonic acid (Mes), dimethylarsenic acid (Caco), and piperazine-N,N′-bis(2-ethanesulfonic acid) (Pipes). Based on the results of PT data, the stability constants were calculated for the metal–buffer complexes (T = 298.15 K, ionic strength I = 100 mM NaClO₄). Furthermore, calorimetric measurements (ITC) were run in 100 mM Mes, Caco, and Pipes solutions with pH 6, at 298.15 K. The enthalpies (ΔH) of the metal–buffer complexation reactions were calculated indirectly by displacement titration using nitrilotriacetic acid (H₃NTA) as a strong-binding, competitive ligand. Finally, to verify obtained results, the number of protons released by H₃NTA due to complexation of the cobalt(II) and nickel(II) ions was determined from calorimetric data and compared with results of calculations.     

Chemoselective Hydrogenation of Nitroaromatics at the Nanoscale Iron(III)–OH–Platinum Interface

Catalytic hydrogenation of nitroaromatics is an environment-benign strategy to produce industrially important aniline intermediates. Herein, we report that Fe(OH)_x deposition on Pt nanocrystals to give Fe(OH)_x/Pt, enables the selective hydrogenation of nitro groups into amino groups without hydrogenating other functional groups on the aromatic ring. The unique catalytic behavior is identified to be associated with the Fe^III-OH-Pt interfaces. While H₂ activation occurs on exposed Pt atoms to ensure the high activity, the high selectivity towards the production of substituted aniline originates from the Fe^III-OH-Pt interfaces. In situ IR, X-ray photoelectron spectroscopy (XPS), and isotope effect studies reveal that the Fe³⁺/Fe²⁺ redox couple facilitates the hydrodeoxygenation of the -NO₂ group during hydrogenation catalysis. Benefitting from Fe^III-OH-Pt interfaces, the Fe(OH)_x/Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes.     

Gamma-ray shielding and structural properties of barium–bismuth–borosilicate glasses

The attenuation coefficients of barium–bismuth–borosilicate glasses have been measured for gamma-ray photon energies of 662, 1173 and 1332 keV using a narrow beam transmission geometry. These coefficients were then used to obtain the values of mass attenuation coefficients, effective atomic number, effective electron density and mean free path. Good agreement has been observed between experimental and theoretical values of these parameters. From the obtained results it is reported here that from the barium–bismuth–borosilicate glasses are better shields to gamma-radiations in comparison to the standard radiation shielding concretes from the shielding point of view. The molar volume, FTIR and acoustic investigations have been used to study the structural properties of the prepared glass system. The obtained results reveal that the formation of non-bridging oxygens occurs at higher concentration of Bi₂O₃.     

Kinetic characterization of barium titanate–bismuth oxide–vanadium pentoxide glasses

The glasses with the composition (80 − x)V₂O₅·20Bi₂O₃·xBaTiO₃ with x = 2.5, 5, 7.5 and 10 mol % were prepared by a melting technique. The crystallization behavior and the microstructure of the glasses were investigated by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mean value of the activation energy of structural relaxation (〈E_g〉) decreased from 395 ± 3 to 369 ± 1.83 kJ/mol when BaTiO₃ increased from 2.5 to 10 mol %. The activation energies obtained by the methods Kissinger and Ozawa were in the range from 213 ± 0.65 to 256 ± 1.23 kJ/mol. Different analysis methods were used to estimate the Avrami exponents. Their values range from 4.26 ± 0.6 to 2.62 ± 0.11 for the exothermic peak of the prepared glasses. Moreover, synthesized glasses-ceramic containing BaTi₄O₉ and Ba₃TiV₄O₁₅ were estimated by using XRD.     

Estimation of the composition of electrolytically prepared intermetallic bismuth–platinum deposits

The method of partial anodic peak resolution is applied to complex voltammograms. The estimation of the composition of the intermetallic Bi–Pt compounds electrolytically deposited is carried out by a resolution of the components of the voltammograms. It is shown that nonequilibrium conditions take place in electrolytic Bi–Pt deposit when three intermetallic compounds such as: Pt₂Bi₃, PtBi₂, PtBi, and phase of pure Bi exist simultaneously on the electrode.     

Metal–organic supramolecular assemblies generated from bismuth(III) bromide and polyimine ligands

Three new BiBr₃ supramolecular complexes, [Bi₂(3-bpdb)₂Br₈]·(3-H₂bpdb) (1), [Bi₂(3-Hbpdh)₂Br₈] (2) and [Bi₂(4-bpdh)Br₉]·3(4-Hbpdh) (3) {3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, 3-bpdh = 2,5-bis(3-pyridyl)-3,4-diaza-2,4-hexadiene and 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene} were prepared by the reaction of bismuth(III) bromide with three organic nitrogen donor based ligands under thermal gradient conditions using the branched tube method. All three compounds were structurally characterized by single-crystal X-ray diffraction. In complex 1 the bismuth atoms are coordinated by one pyridyl nitrogen atom of the 3-bpdb ligand and are bridged by two bromide atoms to produce a dimeric complex. Compound 2 consists of dimeric units and the bismuth atoms are linked by one nitrogen atom of the 3-Hbpdh ligand and by five bromide atoms, and can be considered to be six-coordinate with a Br₅N array of donor atoms. The single-crystal X-ray data of compounds 1 and 3 show that the compounds contain two anionic and cationic 1D chains, [3-H₂bpdb]²⁺[Bi₂(3-bpdb)₂Br₈]²⁻ and 3[4-Hbpdh]⁺[Bi₂(4-bpdh)Br₉]³⁻. In all three compounds extensive hydrogen-bonding interactions produce supramolecular networks. The thermal stabilities of compounds 1–3 were studied by thermal gravimetric (TG) and differential thermal analyses (DTA).     

Determination of molecular weight of polyethylene glycol using size-exclusion chromatography with multi-angle laser light scattering and acid–base titration

Size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) and acid–base titration were used to determine the molecular weight of a polyethylene glycol with low molecular weight. All potential uncertainty factors for each measurement were evaluated using cause-effect diagrams. Weight analysis was applied to harmonize the two different measurement results. It was found that the main uncertainty sources of SEC-MALLS measurement arose from the dn/dc value, the calibration constant of the differential refractive index (DRI) detector, and the intermediate precision of the instrument, while the sample mass, the titration volume and the concentration of titrant contributed to the uncertainty of titration measurement. The weighted mean value of the two measurement results was taken as the molecular weight of the polyethylene glycol.     

The Dissociation Constant of Antimonic Acid at 10–40 °C

The hydrolytic behavior of antimonic acid, Sb(OH)₅^o, was experimentally investigated, at fixed temperatures within the range 10–40 °C, by both titration of dilute Na-antimonate solutions with HClO₄ and single-point pH measurements of diluted Sb(OH)₅^o solutions. The thermodynamic constants, K _a, for the reaction:

Behavior and bioactive properties of aqueous L-cysteine–AgNO3 solution at different pH

Polypeptide-like supramolecular aggregates are formed in aqueous cysteine–AgNO₃ solution. At low pH, their positively charged shell consists of several layers of cysteine–Ag⁺ complexes held by hydrogen bonds; with an increase in pH, the particles aggregate at isoelectric point; while at higher pH, the shell acquires negative charge and starts being destroyed. The pH control has been demonstrated for cytotoxic effect of the solution against MCF-7 breast cancer cells     

The Interaction of Arsenazo III with Nd(III)—A Chemometric and Metrological Analysis

Interactions of Arsenazo III with Nd(III) in aqueous solutions (pH range 3 to 4) were studied using a spectrophotometric method. Some discrepancies are present in literature concerning the concentrations of the prevailing species and their composition. Threshold bootstrap computer-assisted target factor analysis (TB CAT) was applied to the evaluation of UV-VIS spectra of Arsenazo III in aqueous solutions containing varying amounts of neodymium(III) ions. The thus obtained experimental data are interpreted with consideration of the measurement uncertainties affecting this system. Within the limits of resolution of the experimental method, two complexes NdAazo and Nd(Aazo)₂ were indicated in the studied pH range. The values of formation constants for log ₁₀ β ₁₁ fall in the range 4.9 to 6.3 and for log ₁₀ β ₁₂ fall between 10.5 and 12.1.