Spectrophotometric determination of sulfur dioxide in air, using thymol blue

A simple and sensitive spectrophotometric method was developed for the determination of trace amounts of sulfur dioxide. The method is based on the reaction of SO2 with a known excess of ICI as the oxidant. The unreacted ICI iodinates thymol blue under acidic conditions. The lambdamax of thymol blue is at 545 nm under acidic conditions, and on lodination lambdamax shifts to 430 nm. This shift results in a decrease in the absorbance at 545 nm. The amount of uniodinated thymol blue present depends on the concentration of unreacted ICI, which in turn depends on the SO2 concentration. The system obeys Beer's law in the range 0-30 microg SO2 in a final volume of 25 mL, having a molar absorptivity of 3.2 x 10(4) L/mol cm with a relative standard deviation (RSD) of 2% at 24 microg SO2 (n = 10). The uniodinated dye can be extracted into 5 mL isoamyl alcohol under acidic conditions for measurement of absorbance. The extraction method obeys Beer's law in the range 0-5 microg SO2, having a molar absorpitivity of 4.16 x 10(4) L/mol x cm with an RSD of 1.9% at 4 microg SO2 (n = 10). The method has been successfully applied to the determination of atmospheric SO2.     

Influence Of Zro2 on The Physicochemical Properties of Phosphate-Based Glasses and Glass Ceramics

Abstract

Phosphate-based bioactive glasses and their glass ceramics for 47P₂O₅– (30.5)CaO–(22.5 ? x)Na₂O–xZrO₂ for different ZrO₂ contents (x = 0, 1.5, 3.0, 4.5, and 6.0 mol%) were prepared through melt quenching and controlled heat treatment procedures. The amorphous nature of glasses and the presence of crystalline phases in glass ceramics were studied by means of X-ray diffraction (XRD) studies. The density, molar volume, ultrasonic velocities, attenuation, elastic constants, and microhardness of glass and glass ceramics were used to study the structural changes. The formation of hydroxyapatite layer on the surface of glasses and glass ceramics after immersion in simulated body fluid (SBF) was explored through XRD, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) analyses. The results indicate that the added ZrO₂ increases the crosslink density of glasses, resulting in network stability, and also induces the formation of an apatite layer on the surface of glasses.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Synthesis,thermal decomposition and dielectric behavior of bis(thiourea)silver(I)nitrate

New semi-organic bis(thiourea)silver(I)nitrate (TuAgN) single crystals have been grown from slow evaporation solution growth technique. Single crystal X-ray diffraction study reveals that the crystal belongs to orthorhombic system with the non-centrosymmetric space group C2221 and the calculated cell parameters are a = 33.3455 (6) Å, b = 45.2957 (7) Å, c = 20.3209 (5) Å, α = β = γ = 90°, and V = 30692.8 (10) Å ³. The thermal stability and decomposition behavior of TuAgN compound have been studied by thermogravimetric analysis at three different heating rates 5, 10, and 15 °C min^?1. The effective activation energy (E _a) and pre-exponential factor (ln A) of thermal decomposition of thiourea from TuAgN compound at three different heating rates are estimated by model free methods: Arrhenius, Flynn–Wall, Kissinger, and Kim–Park. The calculated effective activation energies were found to vary with the fraction (α) reacted. The compensation effect between the (ln A) and (E _a) has also been studied. Dielectric properties of TuAgN crystal have been studied in a wide range of frequencies and temperatures. AC conductivity has also been carried out.     

Size effect on doped single walled carbon nanotubes

Considering impurity doping in small sized carbon nanotubes of diameter around 0.4 nm, we have calculated the donor binding energy by increasing the dopant concentration through a screening function that includes the curvature effect. We could observe the sudden fall in donor binding energy and metallic behaviour of the smaller single walled carbon nanotubes around 10¹¹/cm² (0.0026%) of impurity concentration. This result is useful for nano electronic device application such as nano diodes and switches.     

Markov property of continuous dislocation band propagation

Tensile tests were carried out by deforming polycrystalline samples of substitutional Al–2.5%Mg alloy at room temperature for a range of strain rates. The Portevin–Le Chatelier (PLC) effect was observed throughout the strain rate regime. The deformation bands in this region are found to be of type A in nature. From the analysis of the experimental stress time series data we could infer that the dynamics of type A dislocation band propagation is a Markov process.     

Reactions of organo-rhodium complexes with multidentate N,N and N,S-heterocycles and exchange studies by NMR

Dihalobridged binuclear complexes [Rh(diolefin)(μ-X)]₂ {diolefin = 1,5-cyclooctadiene (cod), X = Cl or Br; diolefin = norbornadiene (nbd), X = Cl}, undergo halide bridge cleavage reactions with multidentate N,N-heterocycles 1,3,5-tris(benzimidazolyl)benzene (L¹H₃), 1,3,5-tris(N-methylbenzimidazolyl)benzene (L²H₃) and N,S-heterocycle 1,3,5-tris(benzothiazolyl)benzene (L³H₃) to yield trinuclear heterocycle bridged complexes [{RhX(cod)}₃(μ-LH₃)] and [{RhCl(nbd)}₃(μ-LH₃)] (LH₃ = L¹H₃, L²H₃, L³H₃). ¹H NMR exchange measurements have shown resonances for olefinic protons 1″, 2″, 5″ and 6″ of cod at different chemical shifts, perhaps due to restricted Rh–N bond rotation. The olefinic and aliphatic protons would undergo exchange with each other and also with intermediate species. The exchange mechanism may be visualized to involve Rh–N bond breaking, rotation of the cod ligand of the T-shaped (three-coordinate) intermediate species followed by recomplexation. An alternate mechanism may be Rh–cod bond breaking at olefin positions 5″ and 6″, isomerisation of the T-complex such that 5″/6″ moves trans to X coupled with rotation of the heterocycle about the Rh–N bond (made easier by the reduced coordination number of the intermediate), followed by recoordination of 1″/2″ trans to N, followed by recomplexation. NMR signals from the intermediate species in one dimensional ¹H, ¹³C and 2D NMR spectra have supported the exchange of protons.     

聚合物负载的钯-咪唑催化烯烃加氢

A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concentration,catalyst concentration,partial pressure of hydrogen and temperature on initial rate of reaction of selected olefins were investigated. A mechanism for the reaction was proposed from the rate equation. The effects of the solvent and structure of the olefin on the rate of hydrogenation were investigated. The catalyst showed good reusability without any leaching of metal from the support. The homologous analog of the polymer-supported catalyst could not be used as catalyst for the hydrogenation of olefins in methanol because there was precipitation of the metal during reaction.     

Sonochemical degradation of textile dyes in aqueous solution using sulphate radicals activated by immobilized cobalt ions

Decolorisation of dye solutions by cobalt activated persulphate and ultrasonication has been investigated. Rhodamine B, Methylene Blue dye (basic dyes) and Acid orange II, Acid scarlet red 3R (acid dyes) were used as model compounds in this study. Immobilized cobalt ions, activated the persulphate to form highly reactive sulphate radicals. The degradation studies were conducted with only persulphate (PS), cobalt activated persulphate (PS + Co), persulphate + ultrasonication (PS + US) and cobalt activated persulphate + ultrasonication (PS + US + Co). The decolorisation efficiency were in the order of PS < PS + Co < PS + US < PS + US + Co for all the four dye solutions. The effect of pH, dosage of persulphate as well as catalyst and contact time was investigated. Under the optimum condition, the decolorisation obeyed first-order kinetics. Nearly 90–97% of decolorisation was achieved with COD and TOC removal of about 65–73% and 53–62%, respectively, were achieved within an hour.     

Electrical rectification from a fullerene[60]-dyad based metal-organic-metal junction

Langmuir-Blodgett monolayer films of C60-didodecyloxybenzene dyad, with a C60 acceptor and didodecyloxybenzene donor, exhibit rectification with high rectification ratios of 87-158 at 3 V.