Molar heats of transport of dilute aqueous HCl solutions: A potentiometric study

Heats of transport for dilute aqueous HCl solutions at 25°C have been determined from the measurements of thermoelectric powers of the thermocell $$(T){\text{ }}Ag{\text{ - }}AgCl/HCl(ag.)/Ag - AgCl{\text{ (T + }}\Delta {\text{T)}}$$ The variation of the heat of transport with concentration has been examined up to 0.04M and the molar heat of transport at infinite dilution obtained by extrapolation. Present experimental results may be summarized by the equation $${\text{Q}}^ * = {\text{ }}3397 - 3734I^{1/2} {\text{ + }}33610{\text{I}}^{{\text{3/2}}}$$ whereQ ^* is the heat of transport in cal-mole^?1 andI is the ionic strength.     

Sodium and Potassium tert-Butyl Peroxide Hydrates: Crystal Structure and Properties

Russian Journal of Coordination Chemistry - Sodium and potassium tert-butyl peroxide hydrates 2Na+·2C4H9 $${\text{O}}_{2}^{ - }$$ ·7H2O (I) and 2K+· 2C4H9 $${\text{O}}_{2}^{ - }$$...     

Magnesium and Nickel Complexes with Bis(p-iminoquinone) Redox-Active Ligand

Russian Journal of Coordination Chemistry - Poorly soluble in the most part of organic solvents dimeric complexes $${\text{M}}{{{\text{g}}}_{{\text{2}}}}{\text{L}}_{2}^{2}$$ ·4DMF (I) and...     

Partial Oxidation of Methane to Nitrogen Free Synthesis Gas Using Air as Oxidant

In order to generate synthesis gas or hydrogen free from nitrogen by partial oxidation of methane using air as an oxidant, gas?Csolid reactions of methane and a metal oxide and/or mixed metal oxides were carried out. The background of the gas?Csolid reaction was briefly reviewed and then a series of the present author??s studies was described. As metal oxides Fe₂O₃ and NiO were active, but the reaction with methane and these oxides afforded complete oxidation to give H₂O and CO₂. To both oxides, addition of Cr- and Mg- oxides promoted the following reaction to give synthesis gas. $$ {\text{CH}}_{ 4} + {\text{ MM}}'{\text{O}}_{\text{x}} \to {\text{CO }} + {\text{ 2H}}_{ 2} + {\text{ MM}}^{\prime}{\text{O}}_{{{\text{x}} - 1}} $$ After the reaction with methane, mixed oxides were reduced to lower valence state oxides and they were regenerated by the oxidation with air. $$ {\text{MM}}^{\prime}{\text{O}}_{{{\text{x}} - 1}} + {\text{ Air}} \to {\text{MM}}'{\text{O}}_{\text{x}} + {\text{ N}}_{ 2} $$ Up to 10 repeated reaction and regeneration cycles did not or only slightly decreased the activity of the mixed oxides. By switching two or more reactors, the reaction and the regeneration were carried out to give synthesis gas continuously.     

Binuclear cobalt(II/II) and cobalt(II/III) chelates with O<Subscript>2</Subscript>N<Subscript>2</Subscript> ligands: synthesis,structure and magnetic studies

Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with H₂L¹ and H₂L², respectively, in acetonitrile solution. Here, [L¹]²⁻ and [L²]²⁻ are the deprotonated forms of N,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine and N,N-bis(2-hydroxybenzyl)-2-picolylamine, respectively. The crystal structures of and were determined by x-ray crystallography. In , each cobalt atom has distorted trigonal bipyramid geometry, while in , each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in . The magnetic characterization for is in agreement with the presence of Co(II) and Co(III) centers. Graphical Abstract  The title complexes and have been synthesized in excellent yields by reacting Co(OAc)₂·4H₂O with dianionic N₂O₂ coordinating ligands. In complex 1, each cobalt atom has distorted trigonal bipyramid geometry, while in complex 2, each cobalt atom has distorted octahedral geometry. Variable temperature magnetic moment measurements show weak antiferromagnetic interaction in complex 1. The magnetic characterization for complex 2 is in agreement with the presence of Co(II) and Co(III) centers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Solubility constants and free enthalpies of metal sulphides,part 6: A new solubility cell

A solubility cell which can be operated continuously over the temperature range 5–95 °C has been developed. The solubility of Fe_0.88S (monoclinic pyrrhotite) in solutions $$S_0 = ([H^ + ]) = H{\text{ }}m,{\text{ }}[Na^ + ] = (1.00---H) m,{\text{ }}[ClO_{4^ - } ] = 1.00 m)$$ at fixed partial pressures of H₂S has been investigated at 50.7 °C. The hydrogen ion concentration and the total concentration of iron(II) ion in equilibrium with the solid phase was determined by e.m.f. and analytical methods respectively. The data were consistent with $$\log ^* K_{pso} = \log \frac{{[Fe^{2 + } ]pH_2 S}}{{[H^ + ]^2 }} = 3.80 \pm {\text{ }}0.10{\text{ }}[50.7^\circ C,{\text{ }}1 m(Na)ClO_4 ]$$ according to the overall reaction $$1.14{\text{ }}Fe_{0.88} S_{(s)} {\text{ }} + {\text{ }}2H_{(I = 1m)}^ + {\text{ }} \rightleftharpoons {\text{ }}Fe_{(I = 1m)}^{2 + } {\text{ }} + {\text{ H}}_{\text{2}} S_{(g)} {\text{ }} + {\text{ }}0.14{\text{ }}S_{(s)} $$      

The inclusion of diflunisal by γ-cyclodextrin and permethylatedβ-cyclodextrin. A UV-visible and19F nuclear magnetic resonance spectroscopic study

The complexation of the diflunisal anion (DF) by γ-cyclodextrin (γCD) and permethylatedβ-cyclodextrin (βPCD) in aqueous solution at pH 7.00 at 298.2 K, has been studied by UV-visible and¹⁹F NMR spectroscopy. The formation of 1∶1 and 1∶2 γCD inclusion complexes proceeds through the two equilibria: (K1) $${\text{DF + }}\gamma {\text{CD}} \rightleftharpoons {\text{DF}} \cdot \gamma {\text{CD}}$$ (K2) $${\text{DF}} \cdot \gamma {\text{CD + }}\gamma {\text{CD }} \rightleftharpoons {\text{ DF}} \cdot {\text{(}}\gamma {\text{CD)}}_{\text{2}} {\text{ }}$$ characterised byK ₁=(5.5±0.2)×10⁴ dm³ mol^?1 andK ₂=(2.3±0.2)×10⁴ dm³ mol^?1 derived from UV-visible spectrophotometric data. The analogous βPCD complexes are characterised byK ₁=(6.86±0.02)×10⁴ dm³ mol^?1 andK ₂=(8.75±2.7)×10¹ dm³ mol^?1. The variation of the¹⁹F chemical shift of DF on inclusion is consistent with the formation of 1∶1 and 1∶2 complexes also. Comparisons with related systems are made.     

Mechanism of the catalyzed by cysteine electroreduction of the insoluble in water cobalt(II) salt as a component of carbon paste electrode

The mechanism of the Co(II) catalytic electroreduction of water insoluble CoR₂ salt in the presence of cysteine was developed. CoR₂ = cobalt(II) cyclohexylbutyrate is the component of a carbon paste electrode. Electrode surface consecutive reactions are: (a) fast (equilibrium) reaction of the complex formation, (b) rate-determining reversible reaction of the promoting process of CoR(Ac⁺) complex formation, (c) rate-determining irreversible reaction of the electroactive complex formation with ligand-induced adsorption, and (d) fast irreversible reaction of the electroreduction. Reactions (a,b) connected with CoR₂ dissolution and reactions (c,d) connected with CoR₂ electroreduction are catalyzed by . Regeneration of (reactions “b,d”) and accumulation of atomic Co(0) (reaction “d”) take place. Experimental data [Sugawara et al., Bioelectrochem Bioenergetics 26:469, 1991]: i _a vs E (i _a is anodic peak, E is cathodic accumulation potential), i _a vs , and i _a vs pH have been quantitatively explained.     

Crystal structures of the dinitrate-bis-(acetylenedicarboxylate) and acetylenedicarboxylate pseudorotaxane complexes of [24-pyrimidinium crown 6]

The reaction of [24-Pyrim C6][ $ {\text{NO}}_{{\text{3}}} The reaction of [24-Pyrim C6][ ]₆ · 8H₂O with the monopotassium salt of acetylenedicarboxylic acid yielded single crystals of [24-Pyrim C6][C₄O₄]₂[]₂ · 7H₂O, (1). The compound crystallized in the triclinic space group P, with a = 9.731(8) ?, b = 10.953(9) ?, c = 14.270(14) ?, α = 108.06(7)°, β = 94.86(7)°, γ = 99.01(7)°, Z = 1, R = 0.0737, R′ = 0.1024, and 3709 independent reflections. The reaction of [24-Pyrim C6]Cl₆ with the monopotassium salt of acetylenedicarboxylic acid gives single crystals of the inclusion complex {[24-Pyrim C6][C₄O₄]₂} · []_0.92Cl_0.17[H₂C₄O₄]_0.16 · 10H₂O, (2). The compound crystallizes in the triclinic space group P, with a = 13.543(3) ?, b = 14.354(8) ?, c = 17.484(8) ?, α = 74.35(4)°, β = 79.12(3)°, γ = 69.77(3)°, Z = 2, R = 0.0976, R′ = 0.2662, and 5655 independent reflections with. Strength of binding and size of the nitrate and chloride counter ions in the reacting species determines the mode of acetylenedicarboxylate binding to the cation upon crystallization.     

Hydrogen peroxide as a reductant of hexacyanoferrate(III) in alkaline solutions: kinetic studies

The kinetics of hexacyanoferrate(III) reduction by hydrogen peroxide in strongly alkaline media leading to hexacyanoferrate(II) ion have been studied spectrophotometrically within the wavelength range 300–500 nm. The reaction obeys a simple pseudo-first-order rate expression under the applied conditions, namely, a large excess of the reductant and OH⁻ anion concentrations, and a low oxidant concentration. The linear dependences of the pseudo-first-order rate constant on OH⁻ and H₂O₂ concentrations are consistent with the rate law of the form: where and are the second- and the pseudo-third-order rate constants for the electron transfer from HO₂ ⁻ and O₂ ²⁻ to [Fe(CN)₆]³⁻, respectively. The apparent activation parameters determined at 0.4 M NaOH are as follows: ΔH ^# = (18.0 ± 1.0) kJ mol⁻¹ and ΔS ^# = (−155 ± 3.5) J K⁻¹ mol⁻¹. The possible mechanism of the reaction is discussed.     

Solvation of ions. XXVII. Comparison of methods to calculate single ion free energies of transfer in mixed solvents

Free energies of transfer of ions from water to mixtures of water with acetonitrile (AN), with dimethylformamide (DMF), with dimethylsulfoxide (DMSO), and with ethylene glycol have been determined using both the tetraphenylarsonium tetraphenylboride [TATB] and the negligible liquid junction potential [E _j ] assumptions. By making use of ΔG _tr (Ag⁺)[TATB]=12 kJ-mol^?1 for transfer from DMSO to AN and by assuming negligible liquid junction potential in the cell $${\text{Ag|AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),S}}\parallel {\text{Et}}_{\text{4}} {\text{NPic(0}}{\text{.1}}M{\text{),AN}}\parallel {\text{AgNO}}_{\text{3}} {\text{(0}}{\text{.01}}M{\text{),AN|Ag}}$$ single ion free energies of transfer of silver ion ΔG _tr (Ag⁺)[E _j ] from DMSO to 35 pure and mixed solvents show a standard deviation of only 2 kJ-mol^?1 when compared with ΔG _tr (Ag⁺) calculated from the TATB assumption that ΔG _tr (Ph ₄ As⁺)=ΔG _tr (Ph ₄ B^?). The ferrocene assumption [Fc] also gives acceptable agreement with ΔG _tr (Ag⁺)[TATB] provided that the solvents are not highly aqueous. Other cells with other junctions give less acceptable agreement between the E _j and TATB assumptions. It is essential that the salt bridge is always tetraethylammonium picrate in AN, if the E _j assumption is assumed. Because of the ease of making potentiometric measurements compared with the difficulty of measurements required for the TATB assumption, the negligible liquid junction potential method in the cell shown is recommended for estimating transfer free energies of single ions. The ferrocene assumption is acceptable only for non-structured aprotic solvents.     

Effect of the mediator in feedback mode-based SECM interrogation of indium tin-oxide and boron-doped diamond electrodes

Indium tin-oxide (ITO) and polycrystalline boron-doped diamond (BDD) have been examined in detail using the scanning electrochemical microscopy technique in feedback mode. For the interrogation of electrodes made from these materials, the choice of mediator has been varied. Using ferrocene methanol (FcMeOH), and approach curve experiments have been performed, and for purposes of comparison, calculations of the apparent heterogeneous electron transfer rates (k _app) have been made using these data. In general, it would appear that values of k _app are affected mainly by the position of the mediator reversible potential relative to the relevant semiconductor band edge (associated with majority carriers). For both the ITO (n type) and BDD (p type) electrodes, charge transfer is impeded and values are very low when using FcMeOH and as mediators, and the use of results in the largest value of k _app. With ITO, the surface is chemically homogeneous and no variation is observed for any given mediator. Data is also presented where the potential of the ITO electrode is fixed using a ratio of the mediators and In stark contrast, the BDD electrode is quite the opposite and a range of k _app values are observed for all mediators depending on the position on the surface. Both electrode surfaces are very flat and very smooth, and hence, for BDD, variations in feedback current imply a variation in the electrochemical activity. A comparison of the feedback current where the substrate is biased and unbiased shows a surprising degree of proportionality.Dedicated to Alan, a good friend and colleague on his 60th birthday.     

Volumetric and Viscosimetric Measurements for Methanol + CH 3 –O–(CH 2 CH 2 O) n –CH 3 ( n = 2, 3, 4) Mixtures at (293.15–303.15) K and Atmospheric Pressure: Application of the ERAS Model

Densities, $$\rho$$, and kinematic viscosities, $$\nu$$, have been determined at atmospheric pressure and at 293.15–303.15 K for binary mixtures formed by methanol and one linear polyether of the type CH3–O–(CH2CH2O)n–CH3 (n = 2, 3, 4). Measurements on $$\rho$$ and $$\nu$$ were carried out, respectively, using an Anton Paar DMA 602 vibrating-tube densimeter and an Ubbelohde viscosimeter. The $$\rho$$ values were used to compute excess molar volumes, $$V_{{\text{m}}}^{{\text{E}}}$$, and, together with the $$\nu$$ results, dynamic viscosities ($$\eta$$). Deviations from linear dependence on mole fraction for viscosity, $$\Delta \eta$$, are also provided. Different semi-empirical equations have been employed to correlate viscosity data. Particularly, the equations used are the: Grunberg–Nissan, Hind, Frenkel, Katti–Chaudhri, McAllister and Heric. Calculations show that better results are obtained from the Hind equation. The $$V_{{\text{m}}}^{{\text{E}}}$$ values are large and negative and contrast with the positive excess molar enthalpies, $$H_{{\text{m}}}^{{\text{E}}}$$, available in the literature, for these systems. This indicates that structural effects are dominant. The $$\Delta \eta$$ results are positive and correlate well with the difference in volumes of the mixture compounds, confirming the importance of structural effects. The temperature dependences of $$\eta$$ and of the molar volume have been used to calculate enthalpies, entropies and Gibbs energies, $$\Delta G^{*}$$, of viscous flow. It is demonstrated that $$\Delta G^{*}$$ is essentially determined by enthalpic effects. Methanol + CH3–O–(CH2CH2O)n–CH3 mixtures have been treated in the framework of the ERAS model. Results for $$H_{{\text{m}}}^{{\text{E}}}$$ are acceptable, while the composition dependence of the $$V_{{\text{m}}}^{{\text{E}}}$$ curves is poorly represented. This has been ascribed to the existence of strong dipolar and structural effects in the present solutions.     

Improvement of the electrochemical properties of “as-grown” boron-doped polycrystalline diamond electrodes deposited on tungsten wires using ethanol

The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties of “as-grown” BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼10²⁰ B/cm³. The electrochemical behavior was evaluated using the and redox couples and dopamine. Apparent heterogeneous electro-transfer rate constants were determined for these redox systems using the CV and EIS techniques. values in the range of 0.01–0.1 cm s⁻¹ were observed for the and redox couples, while in the special case of dopamine, a lower value of 10⁻⁵ cm s⁻¹ was found. The obtained results showed that the use of CH₃CH₂OH (ethanol) as a carbon source constitutes a promising alternative for manufacturing BDD electrodes for electroanalytical applications.     

Inclusion of rhodamine B byβ-cyclodextrin. An equilibrium and kinetic spectrophotometric study

A UV/visible spectrophotometric temperature-jump study of the inclusion of the rhodamine B zwitterion (RB) by β-cyclodextrin (βCD) to form a 1:1 complex (RB·βCD) in aqueous 1.00 mol dm^?3 NaCl at pH 6.40 and 298.2 K yields:k ₁=(1.3±0.2)×10⁸ dm³ mol^?1 s^?1,k _?1=(2.2±0.5)×10⁴ s^?1, andK ₁=(5.9±2.3)×10³ dm³ mol^?1 for the equilibrium: $${\text{RB + }}\beta {\text{CD}}{\text{RB}} \cdot \beta {\text{CD}} K_1 $$ Under the same conditions the dimerization of RB: $${\text{2}} {\text{RB}}({\text{RB}})_2 K_d $$ is characterized byK _d =(1.8±1.0)×10³ dm³ mol^?1. The interaction of RB with αCD and γCD is weaker than with βCD, and is discussed in terms of the relative sizes of RB and the cyclodextrin annulus. Comparisons are made with the inclusions of other dyes by cyclodextrins.     

Mixed-Valence 24-Vanadophosphate Decorated with Six RuII(dmso)3 Groups: [{RuII3(dmso)9PVV11VIVRuIIIO37(OH)3}2]8?

The mixed-valence 24-vanadophosphate (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru^IIIO₆ octahedra, 2 V^IVO₆ octahedra, 14 V^VO₅ square-pyramids, 8 V^VO₄ tetrahedra, and 2 PO₄ tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru^II(dmso)₃ groups. XPS studies on Na-1 confirm the presence of 2 Ru^III and 6 Ru^II as well as 22 V^V and 2 V^IV centers. Magnetic susceptibility data on Na-1 show that the V^IV–Ru^III pairs are coupled antiferromagnetically, with J ₁ = −13 K and J ₂ ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. In Memoriam Prof. F. A. Cotton     

A Pitzer Model for Lead Oxide Solubilities in the Presence of Borate to High Ionic Strength

In this study, a hydrolysis model for lead, applicable to high ionic strength, is developed based on lead oxide solubilities as a function of ionic strength. Solubility measurements on lead oxide, α-PbO (tetragonal, red), mineral name litharge, as a function of ionic strength were conducted in NaClO₄ solutions up to I?=?0.45 mol·kg^?1, in NaCl solutions up to I?=?5.0 mol·kg^?1, and in Na₂SO₄ solutions up to I?=?5.4 mol·kg^?1, at room temperature (22.5?±?0.5 °C). The lead hydroxyl species considered in this work include the following,

$$ {\text{PbO}}\left( {\text{cr}} \right) \, + {\text{ 2H}}^{ + } \rightleftharpoons {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) $$

(1)

$$ {\text{Pb}}^{ 2+ } + {\text{ H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{PbOH}}^{ + } + {\text{ H}}^{ + } $$

(2)

$$ {\text{Pb}}^{ 2+ } + {\text{ 2H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb}}\left( {\text{OH}} \right)_{ 2} \left( {\text{aq}} \right) \, + {\text{ 2H}}^{ + } $$

(3)

$$ {\text{Pb}}^{ 2+ } + {\text{ 3H}}_{ 2} {\text{O}}\left( {\text{l}} \right) \rightleftharpoons {\text{Pb(OH}})_{3}^{ - } + 3{\text{H}}^{ + } $$

(4)

The equilibrium constants for Reactions (1) and (2) were taken from literature. The equilibrium constants in base 10 logarithmic units for Reactions (3) and (4) are determined in this study as ? 17.05?±?0.10 (2σ) and ? 27.99?±?0.15 (2σ), respectively, with a set of Pitzer parameters describing the interactions with Na⁺, Cl^?, and \( {\text{SO}}_{4}^{2 - } .\) In combination with the parameters from literature including those that have already been published by our group, the solution chemistry of lead in a number of media including NaCl, MgCl₂, NaHCO₃, Na₂CO₃, Na₂SO₄, NaClO₄, and their mixtures, can be accurately described in a wide range of ionic strengths.

     

Nonlinear magneto-optical effects and photomagnetism of electrochemically synthesized molecule-based magnets

This article describes novel optical functionalities such as photomagnetic effects and magnetization-induced second harmonic generation (MSHG) in several cyano-bridged metal assemblies. Single crystal- and film-types of a cyano-bridged Cu–Mo bimetallic assembly, , were electrochemically prepared. When this compound was irradiated with light, spontaneous magnetization with a Curie temperature (T _C) of 23 K was observed. Electrochemically prepared Fe^II[Cr^III(CN)₆]_2/3·5H₂O thin film, which was a ferromagnet with T _C=21 K, showed photoreduced magnetization. This photomagnetism is due to the change of ferromagnetic coupling between Fe^II and Cr^III. MSHG was observed in Cs^ICo^II[Cr^III(CN)₆]·0.5H₂O. This -type Prussian blue analog-based magnet is proven to be a piezoelectric ferromagnet, i.e., condensed matter with both piezoelectric and ferromagnetism. This MSHG is due to the coupling between a piezoelectric structure of and ferromagnetism with a T _C of 46 K.

Polypyrrole coating doped by molybdo-phosphate anions for corrosion prevention of carbon steels

The polypyrrole coating was prepared from phosphoric acid aqueous solution containing the hetero-polyanion and pyrrole monomer to make new coating for corrosion prevention of carbon steels. The coating thus formed in the phosphate acid solution was doped by and by . The coating was flexible enough to cover the steel homogeneously without cracks, although many cracks were observed on the coating formed in a neutral aqueous solution of Na₂MoO₂. The 5.1-μm-thick polypyrrole coating makes the steel maintain the passive state for 48 h in neutral 3.5 wt% NaCl solution at pH 5.3 and for 80 h in acidic 3.5 wt% NaCl solution at pH 1.9. The coating decreased the corrosion rate of the steel by 1/200 in the neutral NaCl solution and by 1/340 in the acidic NaCl solution, if compared with the rate of the bare steel. The dissolution current of the steel during the immersion remained at the level of the typical passive current in the respective solutions.