Selective solid-phase extraction of Cu(II) using freshly precipitated lead diethyldithiocarbamate and its spectrophotometric determination

A new solid-phase extraction method has been developed for the selective extraction of Cu(II) in an aqueous system using freshly precipitated lead diethyldithiocarbamate (Pb(DDTC)₂) as a reagent. The method is based on the quantitative replacement of Pb(II) ions in the solid Pb(DDTC)₂ phase by Cu(II) ions present in aqueous phase. The obtained solid Cu(DDTC)₂ phase was dissolved in chloroform and determined spectrophotometrically at 435 nm. Beer’s law was obeyed over the concentration range of 0.2–5 mg dm⁻³. The molar absorptivity and the Sandell’s sensitivity coefficients of the solutions were 1.0689 × 10⁴ dm³ mol⁻¹ cm⁻¹ and 0.0060 μg cm⁻², respectively. The optimum conditions for each parameter were experimentally determined and possible interferences of various salts were also studied. The method has been validated and applied to determine Cu(II) in various alloys and water samples.     

Mechanistic Investigations of Oxidation of Some Dipeptides by Sodium N‐chloro‐p‐toluenesulfonamide in Alkaline Medium:A Kinetic Study

The kinetics of oxidation of five dipeptides (DPP) viz., glycylglycine (Gly-Gly), L-alanyl-L-alanine (Ala-Ala), L-valyl-L-valine (Val-Val), L-leucyl-L-leucine (Leu-Leu) and phenylglycyl-phenylglycine (Phg-Phg) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in NaOH medium was studied at 308 K. The reactions follow identical kinetics for all the dipeptides, being first-order dependence each on [CAT]_o, [DPP]_o and fractional-order on [OH^－]. Addition of p-toluenesulfonamide or halide ions (Cl^－ or Br^－) has no significant effect on the rate of reaction. The reaction rate was found to increase with increase in ionic strength of the medium. The solvent isotope effect was studied using D₂O. The activation parameters for the reaction were computed from Arrhenius plots. Equilibrium and decomposition constants were evaluated. The oxidation products of the dipeptides were identified as their corresponding aldehydes. An isokinetic relationship was observed with β＝352 K, indicating that enthalpy factors control the reaction rate. CH₃C₆H₄SO₂NCl^－ of the oxidant has been postulated as the reactive oxidizing species. Under comparable experimental conditions, the rate of oxidation of the dipeptides increases in the order: Phg-Phg＞Ala-Ala＞Val-Val＞Leu-Leu＞Gly-Gly. The kinetics of oxidation of the dipeptides have also been compared with those of their corresponding monomer amino acids. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.     

Determination of radium isotopes in mineral and environmental water samples by alpha-spectrometry

Summary A method for the determination of low-level radium isotopes in mineral and environmental water samples by alpha-spectrometry has been developed. Radium-225, which is in equilibrium with its mother ²²⁹Th, was used as a yield tracer. Radium were preconcentrated from water samples by coprecipitation with BaSO₄and iron (III) hydroxide at pH 8-9 using ammonia solution, then isolated from uranium, thorium and iron using a Microthene-TOPO chromatography column at 8M HCl, separated from barium in a cation-exchange resin column using 0.05M 1,2-cyclohexylenedinitrilotetraacetic acid monohydrate at pH 8.5 as an eluant, and finally electrodeposited on a stainless steel disc in a medium of 0.17M (NH₄)₂C₂O₄at pH 2.6 and current density of 400 mA^. cm^-2, and counted bya-spectrometry. Optimum experimental conditions for radium separation, purification and electrodeposition have been studied and discussed in the paper. The lower limits of detection of the method are 0.11 mBq^. l^-1for ²²⁶Ra, ²²⁸Ra and ²²⁴Ra, respectively, if 2 l of water are analyzed. The method has been checked with a certified reference material IAEA-Soil-6 supplied by the International Atomic Energy Agency and reliable results were obtained. Eighteen water samples collected in Italy have been analyzed with the method, the mean radiochemical yields for radium were 86.2±6.5%. The obtained radium concentrations were in the range of 0.50-60.8 mBq^. l^-1for ²²⁶Ra, of 0.10-25.7 mBq^. l^-1for ²²⁸Ra, and of￡LLD-7.97 mBq^. l^-1for ²²⁴Ra. The ²²⁸Ra/²²⁶Ra and ²²⁴Ra/²²⁶Ra ratios were in the range of 0.189-4.45 and￡LLD-0.941, respectively.     

Study of Dehydrocoupling Reactions of Diorganotin Dihydrides R1R2SnH2 with Biuret

phenylmethyltin dihydride (PhMeSnH₂), phenylethyltin dihydride (PhEtSnH₂), phenylbutyltin dihydride (PhBuSnH₂) and butylmethyltin dihydride (BuMeSnH₂) with biuret (H₂L) proceeds via SnH/NH dehydrocoupling to afford the corresponding tetra-coordinate cyclic products. The reactions in the molar ratios of 1∶1, 2∶1 and 1∶2 have been studied. The yellow derivatives so isolated were soluble in polar solvents and insoluble in nonpolar solvents. It was found that 1∶1 reaction went to completion while 2∶1 and 1∶2 did not go to completion. The derivatives had been characterized by elemental analysis and spectroscopic techniques viz. IR, ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR. DSC and TGA of the reaction products have also been studied. All the derivatives were thermally stable upto (190±10) ℃ and degradation occurred after that.     

N-(p-乙烯氧基苯基)咔唑的合成和聚合

N-(p-Ethenyloxyphenyl) carbazole (NEOPC) has been synthesized by etherification of p-bromophenol with vinyl acetate, then p-bromophenyl vinyl ether reacting with carbaxole in the presence of brass power and potassium carbonate at 200℃. The product was identified by elemental analysis, ¹H NMR, ¹³C NMR and IR spectra. NEOPC is readily polymerized by conventional catalysts of cationic polymerization, such as BF₃OEt₂, I₂, TiCl₄, AlCl₃, etc. But no polymer was obtained when free radical initiators were used. The rearrangement products and/or the solvent-insoluble products in cationic polymerization of NEOPC. which may be produced by the crosslinking have been discussed.     

MULTIDENTATE LIGAND EXCHANGE KINETICS:REACTIONS OF AMINOCARBOXYLATO-FERRATE(Ⅲ) COMPLEXES WITH 4-(2-PYRIDYLAZO) RESORCINOL

The kinetics and mechanism of ligand substitution reactions of nitnlotriacetatoiron(Ⅲ),(Fe(NTA)],and N-(2-hydroxycthyl)-ethylencdiaminetriacetatoiron(Ⅲ),[Fe(HEDTA)],complexes with 4-(2-pyridylazo) resorcinol (Par) has been investigated at pH=9.0±0.02,I=0.1mol·l^-1 (NaClO₄,and temp.=25±0.1℃ and 30±0.1℃ respectively. The reaction has been studied spectrophotometrically at 496 nm. (λmax of Fe(Par)₂. In both reactions the final product was [Fe(Par)₂]^-. The values of second order rate constants for NTA and HEDTA exchange reactions are (10.0±0.8)×10¹¹·mol^-1·s^-1 and (2.7±0.1)×10^-1·mol^-1·s_-1 respectively. The reactions of NTA and HEDTA exchange were studied in the pH range 6-9.5 and 7-10.85 respectively. The rate of reacton of [Fe(NTA)] with HPar^- first increases with pH and then levels off. However,in the case of [Fe(HEDTA)] reaction,the rate increases monotonically with increase of pH in the specified range.     

Materials for all-solid-state thin-film rechargeable lithium batteries by sol-gel processing

A novel all-solid-state thin-film lithium battery has been fabricated by spin coating V₂O₅ and LiClO₄-SiO₂ thin films on a stainless steel substrate. The LiClO₄-SiO₂ electrolyte has been synthesized using a new sol-gel route and it has been characterized by electrochemical impedance spectroscopy. The Li⁺ ion conductivity of the spin-coated thin film thus measured is in the order of 10^–6 S/cm, at 25 °C, which is sufficient for electrolytes in such thin-film batteries. The battery shows a typical discharge capacity of about 150 μAh/mg and satisfactory cathodic efficiency and cycle-life performance. Electronic Publication     

三元稀土配合物RE(NTA)2AA的合成、共聚反应性及荧光性能研究

Four new ternary rare earth complexes RE(NTA)₂AA (RE=Sm³⁺， Eu³⁺， Tb³⁺， Dy³⁺) have been synthesized by the reaction of rare earth chloride(RECl₃·6H₂O) with Acrylic Acid (HAA) and 4，4，4-trifluoro-1-(3-pyridyl)-1，3-butanedione(NTA) in alcohol. The copolymerization of the complexes RE(NTA)₂AA (RE=Sm³⁺， Eu³⁺) with methyl methacrylate (MMA) has been studied by 2， 2-azobis-isobutyronitrile as an initiator. Influence of adding Eu(Ⅲ) and 2，2′-bipyridine(bipy) into copolymer Eu(NTA)₂AA-co-MMA on fluorescence property of the Eu copolymer was investigated. The compositions of the complexes and copolymer were characterized by means of elemental analysis and FTIR. The heat decomposing behaviors of the complexes were determined by TG-DTA. The glass transition temperature and molecular weight were obtained by DSC and GPC. The results of fluorescence properties show that the Eu， Sm complexes and Eu copolymer can efficiently emit fluorescence， but the Tb and Dy complexes only emit the fluorescence of β-diketone ligand.     

掺镍型层状LixNiyMn1-yO2正极材料的合成与电性能研究

A kind of cathode material of layered Li_xNi_yMn_1-yO₂ characterized with the O2 type has been synthesized by a simple method. Its precursor Na_xNi_yMn_1-yO₂ has been prepared from manganese dioxide， nickel hydroxide and sodium carbonate at high temperature in air and quickly cooled in cold water， then it has been exchanged by the melted LiNO₃ at 300～400℃ in air. The effects of calcine-temperature for the precursors and its compositions (the content of Na and Ni) on the electrochemical properties of the material Li_xNi_yMn_1-yO₂ have been investingated by XRD and electrochemical tests. The results show that the sample Li_0.7Ni_0.3Mn_0.7O₂， has the best electrochemical properties which shows only one charge-discharge potential stage of 2.8～3.0V and has a high specific capacity over 180mAh·g^-1 cycled between 2.0～4.20V. A significant structure transformation to the spinal-type phase has not been found in the charge-discharge cycling and the discharge specific capacity around 165mAh·g^-1 has re-mained after the 20th cyclings for the material.     

Zn(Ⅱ)、Ni(Ⅱ)与5-氯水杨醛缩乙二胺Schiff碱单、双核配合物的合成及其对O2-的催化歧化作用

A Series of mono and di-nuclear Zn(Ⅱ)、Ni(Ⅱ) complexes with 5-chlorosalicylaldehyde -ethylenediamine Schiff base have been synthesized.Theirs compositions and structures were characterized by the elemental analysis.UV.IR spectra and ¹H NMR.The Dismutation to O₂^- free radical has also been investigated.