Potentiometric determination of Silver (I) by potassium iodate

Summary A potentiometric method has been described for the determination of Silver(I) using standard Iodate solution with pure metallic silver plate as the indicator electrode. Accurate results have been obtained at as low as 0.001 M silver solutions.     

Thermoluminescence of irradiated polystyrene

Thermoluminescence of irradiated polystyrene has been studied in the temperature range 100 to 440°K. Three glow peaks with maximum at 160, 221, and 378°K have been observed. These peaks are analyzed by different methods and the activation energies which were obtained are compared. The activation energies are found to be 0.22, 0.48, and 1.45 eV for the peaks with maxima at 160, 221, and 378°K, respectively. Second-order kinetics is appropriate to all these cases. The glow peaks are attributed to the decay of the free radicals formed on irradiation and subsequent thermal stimulation. The peak with the maximum at 160°K is attributed to electron trapping by the carbonyl groups or peroxy radicals formed on irradiation. The curve with the peak at 221°K is attributed to the cyclohexadienyl radical, and the curve with the peak at 378°K is attributed to the chain radical ? CH₂? C (C₆H₅)? CH₂? . The centers responsible for the observed thermoluminescence are identified by correlation with electron spin resonance (ESR) data obtained on the same samples.     

Investigations on chemical interactions between alternate cathodes and lanthanum gallate electrolyte for Intermediate Temperature Solid Oxide Fuel Cell (ITSOFC)

The doped perovskite oxides such as La_0.65Sr_0.30MnO_3-δ (LSM), La_0.70Sr_0.30CoO_3-δ (LSC), La_0.65Sr_0.30FeO_3-δ (LSF), La_0.65Sr_0.30NiO_3-δ (LSN) and La_0.60Sr_0.40Co_0.20Fe_0.80O_3-δ (LSCF) are proposed as alternate cathode materials for solid oxide fuel cells working at reduced temperature (< 1073 K). The critical requirement for their applicability is their chemical compatibility in conjunction with an alternate solid electrolyte, La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ (LSGM) without any new phase formation. To understand the chemical reactivity between these two components, thoroughly mixed different cathode and LSGM electrolyte (1:1 by wt.) powders were pressed as circular components and subjected to annealing at 1573 K for 3 h in air. XRD and SEM were used for the characterization of the annealed samples. XRD measurements revealed that no new secondary phases were formed in LSM, LSC, and LSF with LSGM mixtures whereas LSN and LSCF with LSGM resulted in the formation of new secondary phases after high temperature treatment. The sintering shrinkage for all the components (cathode + electrolyte mixture) was also estimated. For comparison of data, the individual powders (cathode/electrolyte) were also compacted and studied in the same manner. The obtained results are discussed keeping in view the requirements that the candidate cathode material must meet out with respect to its chemical compatibility to qualify for the LSGM based ITSOFC systems at 1073 K.     

A Validated LC Method for the Determination of Chiral Purity of (1S)-6,11-Dioxo-1,2,3,4,6,11-Hexahydropyridazino[1,2-b]Phthalazine-1-Carboxylic Acid: A Key Intermediate of Cilazapril

A simple and accurate normal phase liquid chromatographic method was developed for the determination of chiral purity of (1S)-6,11-dioxo-1,2,3,4,6,11-hexahydropyridazino[1,2-b]phthalazine-1-carboxylic acid, S-enantiomer used as key intermediate in the manufacturing of cilazapril bulk drug. Chromatographic separation between (1S)-6,11-dioxo-1,2,3,4,6,11-hexahydropyridazino[1,2-b]phthalazine-1-carboxylic acid, and its opposite enantiomer (1R)-6,11-dioxo-1,2,3,4,6,11-hexahydropyridazino[1,2-b]phthalazine-1-carboxylic acid, R-enantiomer was achieved using a Chiralpak AD-H column using a mobile phase containing hexane, isopropyl alcohol and tri-fluoro acetic acid (80:20:0.1 v/v/v). The resolution between the two enantiomers was found to be more than 3.2. The limit of detection (LOD) and limit of quantitation (LOQ) of the R-enantiomer was 0.15 and 0.5 μg mL^?1, respectively, for 10 μL injection volume. The percentage recoveries of the R-enantiomer ranged from 96.5 to 105.3 in the bulk samples of (1S)-6,11-dioxo-1,2,3,4,6,11-hexahydropyridazino[1,2-b]phthalazine-1-carboxylic acid. The test solution and mobile phase was observed to be stable up to 24 h after the preparation. The developed method was validated as per International Conference on Harmonization guidelines in terms of LOD, LOQ, precision, linearity, accuracy, robustness and ruggedness.     

Studies in metal-ammonia reduction—5 : Reduction and reductive methylation of some naphthoic acids

Birch reductio and reductive methylations of some substituted naphtholic acids have been examined. The factors influencing the mechanism of reduction process have been discussed. Some of the reduced naphthoic acids are useful synthons for synthesis.     

Some extensions of the Kantorovich inequality and statistical applications

Kantorovich gave an upper bound to the product of two quadratic forms, (X′AX) (X′A⁻¹X), where X is an n-vector of unit length and A is a positive definite matrix. Bloomfield, Watson and Knott found the bound for the product of determinants |X′AX| |X′A⁻¹X| where X is n × k matrix such that X′X = I_k. In this paper we determine the bounds for the traces and determinants of matrices of the type X′AYY′A⁻¹X, X′B²X(X′BCX)⁻¹ X′C²X(X′BCX)⁻¹ where X and Y are n × k matrices such that X′X = Y′Y = I_k and A, B, C are given matrices satisfying some conditions. The results are applied to the least squares theory of estimation.     

Development of a microstrip-based neutron detector

A gas-filled microstrip detector for thermal neutrons has been built and successfully tested in our laboratory. The detector has an active area of 20 mm × 15 mm and consists of alternate anodes and cathodes of widths 12 μm and 300 μm respectively. The anode to cathode gap is 150 μm and the pitch is 612 μm. A high resistance, meandering type horizontal strip connects the anodes at one end and aids in position sensing by charge division method. The detector is tested with gas mixtures³He+Kr (1: 2) and³He+CF₄ (2:1) at pressure of 3 atmospheres and using a Pu-Be neutron source. The pulse height spectrum shows energy resolution of ∼8% (FWHM) for the 764 keV peak at anode voltage of 525 V for³He+Kr and ∼15% at anode voltage of 800 V for³He+CF₄. Gas gains up to 6.3 × 103 and 3.6 × 103 are obtained respectively with these gas mixtures. The overall efficiency of the detector along the sensitive length is tested by exposing the active area to neutrons and recording the position spectrum. The detector shows fairly uniform efficiency (∼45%) over the active length.