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Abstract  

Selenite was boiled in KCl solutions of different concentrations at the respective boiling temperatures and atmospheric pressure. The products were subjected to X-ray diffraction analysis, qualitative infrared analysis, differential thermal analysis and microscopic examination. The product obtained in 1.0 M KCl solution was the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O). In more concentrated KCl solution (1.5, 2.0, 2.5, 3.0, 3.5 or 4.0 M), the -form of calcium sulphate hemihydrate (-CaSO4·0.5H2O) was formed, and a reaction took place between KCl and CaSO4, which gave a double salt: potassium pentacalcium sulphate monohydrate (K2SO4·5CaSO4·H2O).

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Kinetic parameters of decomposition of some selenites

Generalized perturbation theory of chemical reactivity

Journal of Thermal Analysis and Calorimetry
Authors: L Vlaev, V Georgieva, and S Genieva

Abstract  

Studying the kinetics of isothermal decomposition of thirteen selenites at isothermal heating, the values of activation energy E of the process, pre-exponential factor A in Arrhenius equation and changes of entropy for the formation of the activated complex of the reagent were calculated. Direct dependence between the thermal stability of the selenites and their cation radii on their 'hardness' or 'softness' was found. The dependence was interpreted in the terms of the generalized perturbation theory of chemical reactivity. Kinetic compensation effect was observed only for the selenites, which thermally decompose by the same mechanism.

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Abstract  

TG and DTA have been carried out on new anhydrous rare-earth selenites R2SeaO3+2a (a=3.5,4) in order to establish their stability. Decomposition occurs in three steps attributed to successive losses of SeO2. The first process gives rise to other new group of selenites of composition R2Se3O9, which crystallize in two different forms depending on the rare-earth element. The second process leads to isomorphous compounds R2SeO5. The final product of thermal degradation is R2O3. All products were characterized by chemical analysis and X-ray powder diffraction methods.

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Feng, L. F., Wu, P. F., Sun, L. T., Han, B. (2007) Effect of sodium selenite on morphology, proliferation and viability of mouse osteoblasts cultured in vitro . Acta Veterinaria et Zootechnica Sinica 38 , 856

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Abstract  

Mixed rare earth hydrogen selenite crystals, neodymium praseodymium hydrogen selenite (NdxPr1−x(HSeO3)(SeO3)⋅2H2O), Neodymium samarium hydrogen selenite (NdxSm1−x(HSeO3)(SeO3)⋅2H2O) and praseodymium samarium hydrogen selenite (PrxSm1−x(HSeO3)(SeO3)⋅2H2O) were prepared by gel diffusion technique. Simultaneous thermogravimetric and differential thermal analysis were carried out on the grown crystals. Decomposition is observed to occurs in six steps, which gives the evidence of successive losses of H2O and SeO2. The final product due to decomposition is a mixed rare earth oxides. FT-IR spectrum of the crystal samples heated at different temperatures complemented to the TG-DTA results.

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Abstract  

Amorphous samples of a new inorganic ion exchanger, cerium(IV) selenite have been prepared under varying conditions. The material prepared by mixing 0.025M ceric sulfate and 0.025M sodium selenite in the ratio of 11 was studied in detail for its ion-exchange capacity, chemical stability, IR, thermogravimetry and Kd values. Separations of metal ions have been performed on columns of this ion exchanger.

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Abstract  

The paper presents spin density values on oxygen and selenium orbitals, derived from EPR spectra of SeO 2 radical, formed in the -radiolysis of calcium selenite (CaSeO3). The kinetics of thermal annealing of radicals have been studied. A mechanism for radiolysis is proposed.

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Abstract  

The solubility isotherm of the system Eu2O3-SeO2-H2O was studied at 100C. Certain amounts of the obtained selenites (normal and acid) were subjected to thermal analysis. The intermediate phases were isolated and chemical and X-ray phase analysis was made. The scheme of thermal decomposition was determined.

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Abstract  

The solubility of NiSeO3–SeO2–H2O system in the temperature region 298–573 K was studied. The compounds of the three-component system were identified by the Schreinemakers’ method. The phase diagram of nickel(II) selenites was drawn and the crystallization fields for the different phases were determined. Depending on the conditions for hydrothermal synthesis, NiSeO32H2O, α-NiSeO31/3H2O, β-NiSeO31/3H2O, NiSeO3 and NiSe2O5 were obtained. The different phases were proved and characterized by chemical, powder X-ray diffraction and thermal analyses as well as IR spectroscopy.

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Abstract  

The solubility isotherm of the system Nd2O3-SeO2-H2O at 100C was studied and drawn. All possible selenites of neodymium were obtained and characterized. Thermal decomposition of all phases in the system was studied and its mechanism was described.

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