Evaluation of the chloramine-T membrane electrode response in acidic solutions. The determination of the pKa of N-chloro-p-toluenesulfonamide (chloramine-T acid)

Measurements made with a combination of glass and chloramine-T ion-selective membrane electrodes in acidified chloramine-T solutions varying in ionic strength have been used to determine the dissociation constant of N-chloro-p-toluenesulfonamide (chloramine-T acid). Experimental data agree satisfactorily with reported values.     

Direct potentiometric titration of thiosulfate,thiourea, and ascorbic acid with lodate using an iodide ion-selective electrode

A potentiometric method has been developed for the semi-automatic direct titration of thiourea, thiosulfate, and ascorbic acid with potassium iodate in strongly acidic solutions using an iodide ion-selective electrode to monitor the reaction and locate the endpoint. The method is simple, fast, precise, and accurate. Amounts ranging from 0.15–1.5 mg of thiourea (3.9 × 10^?4–3.9 × 10^?3, M), 0.3–3.0 mg of thiosulfate (5.4 × 10^?4–5.4 × 10^?3, M), and 0.5–5.0 mg of ascorbic acid (5.7 × 10^?4–5.7 × 10^?3, M) have been determined with an average error of about 1%. The method has been applied to the determination of ascorbic acid in tablets. Results checked closely with those obtained with a standard titrimetric method.     

Polarographic analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III)

The analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III) and 1 M H₂SO₄ are investigated using the polarographic technique. The wave corresponding to the reduction of Fe(III) to Fe(II) was found to be completely suppressed by the addition of 1% pyrogallol. Thus, different mixtures of these elements, viz. Hg(II), Cu(II), Cd(II), As(III) and Fe(III)-mixture (A), Cu(II), Cd(II), Sb(III), As(III) and Fe(III)-mixture (B), and Cu(II), Cd(II), Ti(IV), U(VI) and Fe(III)-mixture (C), were quantitatively determined using 1% pyrogallol and 1 M H₂SO₄ as supporting electrolyte. The i₁/c results give excellent correlations in each case, as indicated from the results of leastsquares regression analysis.     

Electrical conductance,density, and viscosity of the molten system lead(II) dodecanoate/lead(II) oxide

Data are presented for densities, electrical conductances, and viscosities of the molten system lead(II) dodecanoate/lead(II) oxide concentrations up to 0.22 mole fraction of the oxide. Values of ?₀ obtained from extrapolation of graphs of density againts temperature are seen to decrease on adding small quantities of PbO, but to increase on adding further PbO. Results from thermal analysis suggest that this may be due to a change in structure of the liquid phase from small. spherical to long, cylindrical micelles. Over the concentration range studied, molar volumes are linear functions of concentration at any particular temperature. The molar volumes of the system lead(II) carboxylate/lead(II) oxide for the even chain acids C₁₀ to C₁₈ are linear functions of chain length. Arrhenius plots for the electrical conductance of the mixtures show curvature, as in other lead(II) dodecanoate systems. The activation energies for conductance in the low temperature region show a steady decrease with increasing PbO concentration and it is proposed that this arises from increased mobility of the charge carrier. The specific conductance at any temperature decreases with increasing mole fraction of oxide, indicating the oxide to be essentially undissociated in the melt. The activation energy for viscosity shows a dramatic increase on adding small amounts of PbO. This is suggested to arise from a change in the structure of the melt. Studies of the viscosities of the system lead(II) carboxylate/lead oxide as a function of chain length for the even chain acids C₁₀ to C₁₈ suggest a slight decrease in the size of the unit of viscous flow when oxide is present.     

A faradaic impedance study of the reduction of oxygen from aqueous alkaline solution at the dropping mercury electrode

The reduction of oxygen to hydrogen peroxide at a dropping mercury electrode in an aqueous solution of 1 M KNO₃+0.04 M KOH (pH=12.35) has been studied by means of impedance measurements as a function of frequency and d.c. potential. The reaction appears to be nearly reversible in the dc sense, but quasi-reversible in the ac sense. The impedance data obey the Randles' equivalent circuit with the following apparent values for the kinetic parameters: standard heterogeneous rate constant k_sh^a=0.035 cm s^?1 and cathodic transfer coefficient α^a_c=0.22. The results are interpreted in terms of a two-step charge transfer mechanism with the step O₂+eO₂^? being rate-determining.     

Thermal decomposition kinetics of bisthiourea cadmuim(II) tetrathiocyanato diammine chromate(III)

Cadmium thiourea reinickate undergoes two-stage thermal decomposition on heating. The DTG peak temperatures are 291 and 469°C and the corresponding DTA temperatures are 255 and 490°C. The kinetic parameters for the first stage decomposition are E* ≈ 120kJ mole^?1; Z ≈ 1.2 × 10⁸ cm³ mole^?1 sec^?1 and ΔS* ≈ ?95 J mole^?1 K^?1. For the second stage, E* ≈ 133 kJ mole^?1; Z ≈ 6.1 × 10⁵ cm^?1 mole^?1 sec^?1 and ΔS* ≈ ?142 J mole^?1 K^?1.     

Three-coordinate mercury in (2,2′-bipyridyl)methylmercury(II) nitrate and related complexes

Methylmercury(II) forms complexes [MeHgL]⁺ [NO₃]^? (L = bidentate ligand) having three-coordinate mercury; an X-ray crystal structure analysis shows that the complex with 2,2′-bipyridyl has a planar CHgN₂ group with unsymmetrically chelated 2,2′-bipyridyl.     

Photoelectron spectroscopy of f-element organometallic compounds II. Tricyclopentadienyl derivatives of uranium(IV) and thorium(IV)

The photoelectron spectra of some cyclopentadienyI derivatives of uranium(IV) and thorium(IV), namely (C₅H₅)₃ ThCl, (C₅H₅)₃ UCl, (C₅ H₄ CH₃)₃ ThCl, (C₅ H₄ CH₃)₃ UCl, (C₅ H₄ CH₃)₃ UBr and (C₅ H₄ CH₃ )₃ UBH₄, are reported the metal 5f ionization has been detected in all the uranium derivative spectra and a simple molecular orbital scheme qualitatively accounts for the number and position of the observed low energy bands.     

The thermal properties of inorganic compounds: II. Evolved gas studies of some mercury(I) and (II) compounds

The combined thermal analysis techniques of thermogravimetry, evolved gas analysis and mass spectrometry were used to investigate the thermal decomposition of several selected mercury(I), (II) compounds. Although TG curves are presented, the analysis of the evolved gases formed during the thermal decomposition processes was of greater interest. Gaseous products detected included: HgSO₄SO, SO₂ and O₂; Hg(SCN)₂CS₂, (CN)₂ and N₂; Hg(NO₃)₂NO, N₂O, NO₂ and O₂; HgNO₃ H₂ONO, NO₂ and N₂O; and Hg(C₂H₃O₂)₂—organic fragments. The evolved gas analysis was complicated by sublimation of the compounds at low pressures.     

Voltammetric oxidation of pharmaceutical organic compounds at a new modified electrode: The aluminum graphite spray-covered electrode

A new graphite spray-modified aluminum electrode has been used to determine clozapine, clothiapine, and loxapine in acetate buffer at pH 4.7 and 20% methanol, down to 5 × 10⁻⁶ M concentrations using differential pulse voltammetry. Reproducibility exceeds that of other solid electrodes, being in the range of 1 to 2%. The electrochemical oxidation products of the latter two compounds are strongly adsorbed, causing diminished electrode response, but response is readily restored by polishing of the sprayed electrode.     

Potentiometric aspects of mercury(II)-thiosemicarbazonates: I. Protometric titrations in a water-acetone mixture

Techniques are established for pH-metric determination of benzaldehyde (BAT), salicylaldehyde (SAT), and p-hydroxybenzaldehyde (PHBT) thiosemicarbazones with mercury(II) in excess and titration of mercury(II) with PHBT in excess. The influence of the presence and position of the hydroxyl group in the molecule of ligand is discussed.     

Electrochemical reduction of tricarbonyl compounds: Reduction mechanism of alloxan on a mercury electrode

A study has been carried out on the reduction mechanism of alloxan over a DME corresponding to the first two-electron transfer over the pH range 0–12.Polarographic and voltammetric results show the reduction process to be kinetically controlled. Rate and equilibrium constant data for the prior chemical reaction have been evaluated and several reaction mechanisms for different pH zones have been proposed.     

Solvent extraction and spectrophotometric determination of iron(II) with 2,2′-dipyridyl-2-quinolylhydrazone

2,2′-Dipyridyl-2-quinolylhydrazone (DPQH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) reacts with DPQH at pH 3.4–4.5 to form a water-insoluble 1:2 complex, which can be extracted with many kinds of organic solvent. The extracted species with benzene has absorption maxima at 473, 504, and 644 nm and obeyed Beer's law over the range 0–14 μg of iron at 504 nm and 0–33 μg at 644 nm. The molar absorptivities at 504 and 644 nm are 3.14 × 10⁴ and 1.30 × 10⁴M^?1 cm^?1, respectively. DPQH is one of the most sensitive reagents for iron(II) and trace amount of iron(II) can be determined in the presence of fairly large amounts of other ions. Possible equilibria involved in the extraction process were also studied.     

High-pressure magnetic susceptibility studies of spin-state transition in Fe(II) complexes

High-pressure magnetic susceptibility measurements have been carried out on Fe(dipy)₂(NCS)₂ and Fe(phen)₂(NCS)₂ in the pressure range 1–10 kbar and tempeature range 80–300 K in order to investigate the factors responsible for the spin-state transitions. The transitions change from first order to second or higher order upon application of pressure. The temperature variation of the susceptibility at different pressures has been analysed quantitatively within the framework of available models. It is shown that the relative magnitudes of the ΔG⁰ of high-spin and low-spin conversion and the ferromagnetic interaction between high-spin complexes determines the nature of the transition.     

Voltammetric study of humic and fulvic substances: Part II. Mechanism of reaction of the Pb-fulvic complexes on the mercury electrode

A model is presented for the electrode process corresponding to the reduction of Pb(II) complexed by fulvic substances. The various factors which may affect the polarographic results are discussed and a mathematical expression is given for the polarographic wave. The influence of various parameters was tested. It was found that the formation of complexes both present in solution and adsorbed at the surface of the electrode is the predominant factor which affects the potential of the wave. Moreover, the diffusion coefficient of the complexes is much lower than that of free lead. We discuss the nature of the complexes adsorbed at the electrode surface and the implications of the findings of this work when using the polarographic methods for the determination of the complexing ability of waters.     

Mixed ligand complexes in vinyl polymerization—II: [NN′-ethylenebis(salicylideneiminato)] (benzoylacetonato)cobalt(III) as an initiator

The polymerization of methyl methacrylate initiated by a mixed ligand complex. [NN′-ethylenebis(salicylideneiminato)](benzoylacetonato)cobalt(III) has been studied in bulk and in benzene at 70° and 80°. The rate of polymerization is proportional to (concentration of the chelate)${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and the monomer exponent is close to 1.5. The activation energy and the kinetic and transfer constants are evaluated. A free radical mechanism has been proposed.