Electron transfer at tetrahedral cobalt(II). Part II‡. Kinetics of silver(I) ion catalysed reduction of peroxodisulphate

Transition Metal Chemistry - The kinetics of the silver(I) ion catalysed reduction of peroxodisulphate by 12-tungstocobaltate(II) anion in aqueous HC1O4 has been studied. Although the reaction in...     

Eluent-Induced Separation of Inorganic Cations in Capillary Liquid Chromatography with Contactless Conductivity Detector

A non-suppressed contactless conductivity detector has been used as a capillary detector in a capillary ion chromatograph, combining a reversed-phase C30 column permanently modified with ionic surfactant. The C30 column (100 × 0.32 mm. id) was modified with sodium dodecyl sulfate (SDS) for the separation of inorganic cations. Monovalent cations could be separated by the proposed system, in which methanesulfonic acid (MSA) and SDS were employed as the mobile phase component, but divalent cations could not be eluted under this condition. As for the case of SDS used as the eluent, an H⁺-cation-exchange column was placed before the sample injector to convert the Na⁺ from the eluent into H⁺, and when the mixture of MSA and dodecyl sulfuric acid was used as the eluent, the retention of cations was improved and baseline separation of the cations was achieved within 23 min. The effect of the eluent composition on the retention behavior of inorganic cations was investigated. The repeatability of retention time and peak height varied from 0.39 to 0.58 and 2.21 to 3.25 % as relative standard deviation, respectively.

     

Composite Control of a Hovering Helicopter Based on Optimized Sliding Mode Control

Journal of Optimization Theory and Applications - A composite control law for stabilizing a small-scale helicopter during hover flight mode is proposed in this paper. The proposed method is...     

Insights into electrochemical behavior and kinetics of NiP on PEDOT:PSS/reduced graphene oxide as high-performance electrodes for alkaline urea oxidation

Journal of Solid State Electrochemistry - Highly efficient, abundant, and low-cost materials are highly demanded for energy conversion applications to address the rising consumption of energy. In...     

Mechanical Properties and In Vitro Physico‐chemical Reactivity of Gel‐derived SiO2–Na2O–CaO–P2O5 Glass from Sand

In the present report, a bioactive glass was synthesized from silica sand as economic substitute to alkoxy silane reagents. Sodium metasilicate (Na₂SiO₃) obtained from the sand was hydrolyzed and gelled using appropriate reagents before sintering at 950 °C for 3 h to produce glass in the system SiO₂? Na₂O? CaO? P₂O₅. Compression test was conducted to investigate the mechanical strength of the glass, while immersion studies in simulated body fluid (SBF) was used to evaluate reactivity, bioactivity and degradability. Furthermore, the glass samples were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X‐ray spectroscopy (EDX) to evaluate the microstructure and confirm apatite formation on the glass surface. The glass, dominated by bioactive sodium calcium silicate, Na₂Ca₂Si₃O₉ (combeite) crystals, had mechanical strength of 0.37 MPa and showed potentials for application as scaffold in bone repair.     

Kinetics and mechanisms of the redox reaction of hexaaquotitanium(III) and the ethylenediamine tetraacetato titanium(III) complex by aqueous solutions of bromine

At 25°C, I = 1.0 M (CF₃SO₃⁻Li⁺+CF₃SO₃H), [H⁺] = 0.034–0.274 M and λ = 453 nm, the rate equation for the oxidation of Ti(H₂O), ₆³⁺ by bromine was found to be: −d/[Br₂]T/dt=kK/[Br₂][Ti^III]/[H⁺]+K+kK/[Br₃⁻][Ti^III]/[H⁺+K, where k = 9.2 × 10⁻³ M ⁻¹ s ⁻¹ and K = 4.5 × 10⁻³ M. At [H⁺] = 1.0 M, [Br⁻] = 0.05–0.4 M, the apparent second-order rate constant decreases as [Br⁻] increases.

The pH-dependence of the oxidation of Ti^III-edta by bromine is interpreted in terms of the change in identity of the Ti^III-edta species as the pH of the reaction medium changes. The second-order rate constants were fitted using a non-linear least-square computer program with (1/k₀^edta)² weighting into an equation of the form: k₀^edta =k₁+k₂K₁[H⁺]⁻¹+k₃K₁K₂[H⁺]^−2/1+K₁[H⁺[H⁺⁻¹+K₁K₂[H⁺]⁻², with K₁ and K₂ fixed as earlier determined at 9.55 × 10⁻³ and 2.29 × 10⁻⁹ M, respectively, for the oxidation of bromine. k₁=k₂=(3.1±0.32)×10³M⁻¹s⁻¹ k₃=(2.3±0.45)×10⁶N⁻¹s⁻¹.

It is proposed that these electron transfer reactions proceed by univalent changes with the production of Br₂^.− as a transient intermediate. An outer-sphere mechanism is proposed for these reactions. The homonuclear exchange rate for Ti^III-edta+Ti^IV-edta is estimated at 32 M⁻¹ s⁻¹.     

Electron transfer at tetrahedral cobalt(II), part IV: kinetics of silver(I) catalysed chlorate reduction

Summary The very slow reduction of ClO _inf3 ^su– by [CoW₁₂O₄₀]^6- is markedly catalysed by Ag¹ in aqueous HClO₄ solution at I = 1.0 M (NaClO₄). The reaction obeys the rate law: -d[reductant]/dt where a = (1.28 ± 0.10) × 10^-4M^-1s^-1 and b = (2.22 ± 0.20) × 10^-4M^-3s^-1, at T = 60.1 ± 0.1°C and [H⁺] = 0.10–1.50 M. Activation parameters have been determined for each pathway and the reaction is discussed in terms of the outer-sphere mechanism.Part III: ref. 1.