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  • Author or Editor: A. Garg x
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Abstract  

Instrumental Neutron Activation Analysis /INAA/ has been employed for the determination of 15 major, minor and trace elements in human and animal blood samples. Dry whole blood samples along with NBS and IAEA standards were irradiated for 5 min, 1 h, 5 h and 10 h with reactor thermal neutrons and counted using high resolution -spectrometry at successive intervals. Data for a new IAEA proposed CRM Mixed Human Diet /H-9/ is reported.

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Abstract  

Gamma-radiolytic decomposition of zirconium nitrate and its binary mixtures with potassium halides viz. KCl, KBr and KI has been studied at different compositions up to an absorbed dose of 550 kGy. Radiolytic decomposition has been found to decrease with the absorbed dose. It also varies with the concentration of zirconium nitrate in the binary mixtures. G(NO 2 ) values are enhanced by the addition of halides but only at 75% composition. It is not affected so significantly by KI. A plot of G(NO 2 ) vs. composition of the binary mixtures of the nitrates shows a somewhat parabolic curve with a minimum at 75% Zr(NO3)4+25% KX composition. A part of the energy absorbed by the system is being taken up by the halides depending upon their nature and concentration. Thermal decomposition shows slow decomposition, finally yielding an oxynitrate of indefinite composition.

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Abstract  

Radiation induced decomposition of solid alkali metal nitrates at room temperature has been studied up to an absorbed dose of 300 kGy. [NO 2 ] increases with absorbed dose. From the kinetic scheme

\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$NO_3^ - \xrightarrow{{{}^k1}}NO_2^ - + 0; O + NO_2^ - \xrightarrow{{{}^k2}}NO_3^ - ;$$ \end{document}
and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$O + NO_3^ - \xrightarrow{{{}^k3}}NO_2^ - + O_2$$ \end{document}
, rate constants have been evaluated for the overall radiolytic decomposition of alkali metal nitrates. This kinetic scheme is applicable in the low dose range. At higher doses, however, the radiation induced reaction, NO 2 +1/2 O2 NO 3 may also contribute. The overall rate constants are 0.13×10–6 (LiNO3), 1.05×10–6 (NaNO3), 10.10×10–6 (KNO3), 9.50×10–6 (RbNO3) and 25.50×10–6 (CsNO3) kGy–1.

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Abstract  

Gamma-ray induced decomposition of binary mixtures of potassium nitrate with 90, 70, 50, 30 and 10 mol% SiO2, Al2O3, MnO2, V2O5, La2O3, CeO2, Sm2O3, Eu2O3, Gd2O3 and Dy2O3 has been studied at different doses up to 500 kGy. Radiolytic decomposition of the nitrate is affected by the concentration of the oxide in the binary mixture as well as by the absorbed dose. The enhancement is up to 103 times at 90 mol% of the additive.G(NO2 ) values calculated on the basis of electron fraction of the nitrate decrease with the increasing concentration of the nitrate. A comparison ofG(NO2 ) for 90 mol% oxides shows decreasing trend as Gd2O3>Sm2O3≈Dy2O3> Eu2O3>CeO2>Al2O3>V2O5>SiO2>MnO2. ESR and TL measurements suggest the formation of radical species which interact with the radical species of nitrate causing enhanced decomposition by energy transfer mechanism.

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Abstract  

Gamma — radiolytic decomposition of sodium and potassium nitrates and its admixtures with respective cyanide and borate additives has been studied over a wide absorbed dose range from 675 to 500 kGy. The decomposition of nitrate increases with the nature and concentration of the additive in the admixture. The enhancement is more significant at >80 mol% of the additive.G(NO 2 ) values, calculated on the basis of electron fraction of the nitrate salt, decrease with increasing concentration of the nitrate. ESR spectral studies suggest the formation of radical species such as BO4 and BO 3 2− etc, in borates whereas in case of cyanide additive FH centres are produced. The radical species and colour centres so produced may then transfer their energy to nitrate and cause enhancement in decomposition. A comparison with other oxyanion additives shows thatG(NO 2 ) values decrease in the order PO 4 3− >B4O 7 2− >SO 4 2− >CO 3 2− . Similarly, the nature of the cation also affects the decomposition.

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Abstract  

A series of carboxylatoferrate (III) complexes have been synthesized with monocarboxylic and dicarboxylic acids. Mössbauer spectra of all the complexes exhibit quadrupole doublets with EQ=0.36–0.88 mm s–1, suggesting a distorted octahedral geometry. The complexes start decomposing at 100°C and finally yield a constant weight at <500°C. Mössbauer spectral studies of the intermediates and final products after heating at different temperatures yield a complex pattern, suggesting the formation of one or two magnetic phases. Mössbauer spectra of the final products show two, six or eight lines with a central doublet, all indicating the formation of -Fe2O3 of different particle sizes. It is proposed that decarboxylation occurs first, followed by the loss of one or two ligands, depending on the nature of the carboxylate and the heating tempeature. The complex of pyridine-2,6-dicarboxylic acid shows an anomalous behavior.

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Abstract  

Mössbauer isomer shift // and quadrupole splitting /EQ/ values in a series of isostructural compounds correlate well to give linear relationship provided the sign of electric field gradient /EFG/ is assigned to the EQ. The correlation has been used in predicting the sign of EFG for some monosubstituted pentacyanoferrate/II/ complexes. Usefulness of such correlations and its limitations are presented.

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