Polarographic behaviour of zinc in sodium formate solution

Summary A polarographic determination of Zinc can be successfully performed in 1 M sodium formate solution (pH 7.0) as supporting electrolyte using 0.005% of gelatin as maximum suppressor. Well defined waves are obtained for 1–6 mM of zinc and various anions do not cause any interference. The method is also suitable for the determination of zinc and mangenese in presence of each other.

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Zusammenfassung Zur polarographischen Zinkbestimmung wird eine 1 m Natriumformiatlösung (pH 7,0) und 0,005% Gelatine als Maximumunterdrücker empfohlen. Im Bereich von 1–6 mMol Zink werden gut ausgebildete Stufen erhalten. Verschiedene Anionen stören nicht. Das Verfahren kann auch zur Bestimmung von Zink und Mangan nebeneinander angewendet werden.

     

Polarography of molybdenum in aspartic acid solution

The polarographic behaviour of Mo(VI) in solutions of aspartic acid is reported. In 0.01M acid, two waves are obtained, but at pH 4 only one, and they are diffusion controlled. The determination is possible in the presence of Ni, Cr(VI), W(VI), Mn(II), Co(II), Cu(II) or Th, with an accuracy of 2% in the range 10(-5)-10(-3)M.     

多孔硅于甲酸-甲酸钠溶液阳极偏压下的电致发光研究

用荧光分光光度法现场监测了多孔硅于甲酸-甲酸钠溶液阳极偏压下的电致发光行为。发现该体系的电致发光峰值随着阳极偏压增大而发生蓝移;发光峰能量值与阳极偏压呈良好的线性关系,其斜率与多孔硅在阴极偏压下电致发光的结果一致。扫描探针技术研究表明：多孔硅的表面形貌明显地影响其发光性质。提出了多孔硅在甲酸-甲酸钠溶液中阳极偏压下的电致发光与多孔硅表面的Si-H键的氧化作用有关的发光机理。发现了多孔硅于甲酸-甲酸钠溶液中在阳极偏压下电压调制的可见光发射行为,并用量子限制效应对该现象进行了解释。     

Behavior of manganese(II) in calcium formate solutions

The solubility in the system Ca(HCOO)₂-Mn(HCOO)₂-H₂O at 25°C was studied by the isothermal method. The behavior of manganese in Ca(HCOO)₂ crystallization from aqueous solutions was examined with ⁵⁴Mn tracer in the concentration range 10^?3–10^?5 wt %.     

EPR of divalent manganese in cobalt ammonium selenate hexahydrate

EPR of Mn²⁺ has been studied in cobalt ammonium selenate hexahydrate from ≈ 90 K to ≈ 300 K and the spin-hamiltonian parameters determined. It has been found that replacement of S by Se does not cause much change in the strength and symmetry of the crystal field at the divalent cation site in Tutton salts.     

Temperature-triggered gate opening for gas adsorption in microporous manganese formate

Microporous manganese formate shows temperature-triggered gate opening for nitrogen and argon adsorption, which is not due to a structural change of the framework but due to dynamic opening of the pore aperture and/or sufficient kinetic energy of the adsorbates to overcome a diffusion barrier above a critical temperature.     

Electron paramagnetic resonance of divalent manganese in cobalt ammonium sulphate hexahydrate

EPR of Mn²⁺ has been studied in cobalt ammonium sulphate hexahydrate from ≈ 90°K to ≈ 373°K. The spin-hamiltonian analysis is presented. It is concluded that the coordination of water ligands around the divalent ion is almost the same as that in other Tutton salts.     

Polarography in solution of some problems in organic chemistry: recent applications

Applications of chromatographic and atomic absorption methods are compared with those of electroanalytical techniques. The limitations of electroanalytical procedures and their advantages, such as speed, sensitivity and speciation are discussed. Among applications of polarography and voltammetry to a solution of basic problems, attention has been paid to the possibility to distinguish the degree of conjugation (e.g. of compounds containing the grouping CNNC), to a contribution to understanding of solution chemistry of mitomycin C and to processes involved in the reduction of cephalosporins. Among practical applications, the possibility to analyze suspensions, which can be carried out without separation offers advantages. Examples are interactions in suspensions of bile salts in the presence of metal (II) ions, adsorptions of various pesticides and other toxic materials on lignin and the possibility to follow alkaline cleavage of lignin in buffers pH 8-12 at 25 °C. Most of these studies would not be possible to carry out using other techniques.     

Thermal reactivity of sodium manganese decavanadates

The hydrates of sodium manganese decavanadates are thermally unstable: Na₄MnV₁₀O₂₈ ·19H₂O decomposes on dehydration to give Mn(VO₃)₂, NaVO₃ and NaV₃O₈, while Na₂Mn₂V₁₀O₂₈ · 20H₂O decomposes to Mn(VO₃)₂, NaVO₃, NaV₃O₈ and NaV₆O₁₅. At a lowern(Na) n(V) molar ratio in the starting compound, a product containing a bronze with a higher vanadium(IV) content is formed. The mixtures of products are stable in the temperature ranges 500–1000°C, and 610–1000°C, respectively.

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Zusammenfassung Hydrate von Natrium-magnesiumdekavanadat sind thermisch instabil. Na₄MnV₁₀O₂₈·19H₂O zersetzt sich durch Dehydratierung in Mn(VO₃)₂, NaVO₃ und NaV₃O₈ und Na₂Mn₂V₁₀O₂₈ · 20H₂O in Mn(VO₃)₂, NaVO₃, NaV₃O₈ und NaV₆O₁₅. Bei einem niedrigerem n(Na)n(V) molarem Verhältnis der Ausgangsverbindungen wird ein Produkt geformt, welches eine Bronze mit einem höherem Vanadium(IV)-gehalt enthält. Das Produktegemisch ist im Temperaturbereich 500°–1000°C bzw. 610°–1000°C thermisch stabil.

     

Possibility of the existence of divalent actinium in aqueous solution

Radiopolarographic reduction of Ac(III) was investigated in aqueous solutions. It was found that a very large shift of the half-wave potential was induced by the addition of 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane (18-CROWN-6) to the aqueous solution. The shift was explained by complex formation of Ac(II) with 18-CROWN-6. The ionic radius and the electronic configuration of Ac²⁺ were determined to be 1.25 Å and [Rn] 6d¹.     

Isotopic exchange between manganese hydroxide and manganese ions in aqueous solution

Heterogeneous isotopic exchange between manganese hydroxide and manganese ions in aqueous solutions tagged with radioactive⁵⁴Mn has been studied at different values of α, the ratio of the quantity of exchangeable ions in the solid phase to that in the liquid phase. The aging of the precipitate in its mother liquor prior to the exchange has a significant effect on both the extent and rate of the exchange reaction. A marked feature of great interest is the appearance of two aging-times, one at about 10² and the other at about 10⁴ min. The overall reaction appears to be of the consecutive type. In the case of a fresh precipitate, “complex-surface-exchange” and “self-diffusion” mechanisms are the most probable rate-determining steps in the initial and final stages of the reaction, respectively. “Complex-surface-exchange” is a new suggested mechanism. In the case of a well-aged precipitate, “surface-exchange” and ‘self-diffusion” mechanisms are the most probable-determining steps in the initial and final stages of the reaction, respectively.     

Oxidation of divalent manganese by peroxodiphosphate in acetate buffers. A kinetic study

Bivalent manganese in oxidized to the tervalent state in 4.0–5.3 pH (acetate buffers) when treated with an excess of peroxodiphosphate (PDP). Kinetic evidence for the formation of a 11 complex between manganese(II) and PDP was obtained. The reaction exhibits first order dependence on [Mn(II)] and fractional order dependence on [PDP]. The reaction is markedly inhibited by H⁺ ions. A plausible mechanism consistent with the observed data is proposed.

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pH=4,0–5,3 (). (II) 11. [Mn(II)] []. H⁺ . , .

     

Energy transfer in one-, two-, and three-dimensionally coupled salts of divalent manganese

The emission spectra of several antiferromagnetic complexes of divalent manganese (CsMnBr₃, Rb₂MnCl₄, CsMnCl₃ and KMnCl₃) which contain rare-earth ion impurities have been studied as a function of temperature. In all cases there appears to be a thermally activated energy migration which often results in an efficient transfer of electronic excitation from the manganese to the rare-earth impurities.     

Interaction of three pradimicin derivatives with divalent cations in aqueous solution

This study focused on further analysis of the aggregation behavior of pradimicin derivatives and their interaction with cations in aqueous solution. BMY was compared with two other pradimicin antibiotics (T2 and FB) with the same aglycone moiety but consisting of different substitute groups. The surface tension measurement showed a clear critical micelle concentration at 1-2 mM of the BMY aqueous solution. The role of Zn2+ in replacing the Ca2+ was examined using 1H nuclear magnetic resonance (NMR) method. From changes in the NMR spectrum and precipitability, it was concluded that zinc ion has lower affinity and higher precipitating ability to BMY than the divalent cations of alkaline earth metal. The aggregation behavior of T2 and FB in aqueous solution was also studied using NMR method. The results suggest that the supramolecular behavior of T2 is similar to BMY whether or not Ca2+ ions are present in solution and that there are two binding sites for calcium ions in a T2 molecule. Unlike BMY and T2, the NMR spectrum of FB does not show distinct change upon Ca2+ addition. The interaction of pradimicin antibiotics with divalent metal ions was thought to be related to ionic electronegativity and to the amphoteric property of the antibiotics.     

Solid phase reactivity of sodium oxosalts of manganese

The observed relationships are presented of the solid phase reactivity of the following salts: NaMnO₄, Na₂MnO₄, Na₃MnO₄, Na₄MnO₄, Na₂MnO₃, Na₂Mn₂O₅, Na₅MnO₄, Na₄Mn₂O₅, NaMnO₂, Na₄MnO₃, Na₂MnO₂ and Na₂Mn₂O₃.