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  • Author or Editor: D. Das x
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The properties of humic (HA) and fulvic acids (FA) isolated from a 27-year-old long-term experiment with rice-wheat-cowpea on a Mollisol in northern India were evaluated for elemental composition and functional groups. As compared to fallow, C, H and N decreased, while O increased in the control, but the use of NPK+FYM over the years enhanced the C and N of humic substances. The carboxylic (-COOH) and phenolic-OH groups declined in the control, but improved with NPK+FYM in comparison to fallow. Carboxylic groups (-COOH) contributed about 2–3 times more in HA and 4–5 times more in FA than the respective phenolic-OH groups to the molecular weights of these fractions of soil organic matter. The results suggested the role of integrated nutrient management in maintaining active soil humus over the years.

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Adsorption of uranium, as UO2 2+, and thorium, as Th4+, has been studied using a modified fly ash bed. Effects of pH and various ions like La3+, Fe3+, Ce4+, SiO3 2- etc., have been examined. Synthetic mixtures of UO2 2+ and Th4+ in different concentrations were passed through the bed and eluted separately with various selective reagents viz. ammonium carbonate, sodium carbonate and acetic acid-sodium hydroxide buffer. Separations of these elements at ppm level are shown to be very effective. The separation of uranium and thorium in the presence of lanthanides in monazite sand has been studied successfully. In the analysis of monazite sand, the oxalate precipitation has been avoided. The method is simple and of very low cost. The modified fly ash bed can also be used to remove uranium from contaminated water.

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Structural defects were introduced into the potassium bromate (PB) lattice in the form of SO2− 4 and Cl ions in the process of crystal growth. It was assumed that these doped crystals PB(Cl) and PB(SO2− 4) are composed of a two phase system, one being the perfect PB lattice and the other distorted regions due to induced defects. Isothermal decomposition of doped and normal PB samples was carried out gasometrically between the temperature range 653–663 K. The α-t plots reveal that the process occurs through initial gas evolution, acceleratory and decay stages. It also confirmed that doping enhances the rate of the reaction, the effect being more pronounced in the case of PB(SO2− 4). The data are found to be well fitted to the Prout-Tompkins and Avrami-Erofe'ev mechanisms.

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The success of a systematic application in INAA using γ-lines of ≥50 keV depends on the accuracy and precision and thus on the reproducibility of the measuring conditions. This text describes a procedure based on a 30 mm2 planar ultrapure Ge detector with a multichannel analyzer.

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A fast routine method for the determination of tin in rocks is discussed. The method is based on coprecipitation of tetravalent tin with ferric hydroxide, followed by a short irradiation in a high thermal neutron flux, extraction in toluene from 1∶1 sulphuric acid which is 5N in potassium iodide, and counting of123mSn (T=40 m) or125mSn (T=9.7 m) with a well-type NaI detector. In the present work125mSn was used. The lower limit of determination is governed by the blank of the reagents. For a sample of at least one gram it is ≌ 0.2 μg Sn·g−1.

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[NiL3]X2 (where L=N-phenylethane-1,2-diamine and X=I and ClO4 ), [NiL2X2] (X is Cl, Br, NCS, 0.5SO4 2− or 0.5SeO4 2−) and [NiL2(H2O)2](NO3)2 have been synthesized from solution and their thermal study has been carried out in the solid phase. [NiL2Cl2] upon heating undergoes irreversible endothermic phase transition (142–152C, ΔH=0.35 kJ mol−1) without showing any visual colour change. This phase transition is assumed to be due to conformation changes of the diamine chelate rings. NiLCl2 and NiL2.5I2 have been prepared pyrolytically from [NiL2Cl2] and [NiL3]I2 respectively in the solid state. [NiL2(H2O)2](NO3)2 upon heating undergoes deaquation-anation reaction without showing any visual colour change. [NiL2X2] (X is Cl, Br, NCS), [NiL2(H2O)2](NO3)2 and [NiL2(NO3)2] possess trans-octahedral configuration, whereas, [NiL2X2] (X is 0.5SO4 2− or 0.5SeO4 2−) are having cis-octahedral configuration. Amongst the complexes, only NiLCl2 shows unusually high (5.1 BM at 27C) magnetic susceptibility value.

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The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.

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Carrier free promethium was produced by proton activation in neodymium target. Extraction behavior of both the elements were studied by HDEHP. A pronounced synergism had been observed by the binary mixture of HDEHP and PC88A. Presence of H2O2 in aqueous phase also increases the separation factor.

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Procedures for the determination of bromine by the reactions81Br(n, γ)82Br (T=35.4 h) and79Br(n, γ)80mBr (T=4.4 h). In the case of82Br a flat coaxial Ge(Li) crystal is used to measure the 619 keV photopeak. For80mBr a planar Ge(Li) detector is applied to measure the 39 keV γ-ray. The agreement between the data obtained with both techniques for some Standard Reference Materials is satisfactory.

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Two types of gas-liquid separators for use in on-line hydride generation AAS have been examined: the classical one, in which gas and liquid are separated by gravity and that based on diffusion through a pemeable tube. Results are presented for the determination of arsenic species (arsenite, As(III); arsenate, As(V); monomethylarsonic acid, MMAA; dimethylarsinic acid, DMAA). Yield (of hydride generation and gas-liquid separation) and response time are investigated as functions of the experimental variables. It is concluded that in conjunction with a cold trap, only the classical gas-liquid separator is satisfactory.

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