- Zones of sparingly soluble inorganic salts with membrane properties in gels
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Polyacrylamide gels containing potassium oxalate (sodium oxalate) are brought into contact with aqueous solutions of Pb(NO3)2, CaCl2, SrCl2 and BaCl2 respectively. The electrolyte concentrations in the gel phase and in the solutions are varied systematically. There exists a system specific characteristic concentration cs below which advancing precipitation zones of PbOx, CaOx, SrOx, and BaOx (Ox: oxalate) within the gel are observed. The experiments indicate that the precipitation zones with membrane properties are generated by homogeneous nucleation. The kinetics of formation of oxalate precipitates in cellophane skins is studied by measurement of the membrane potential as function of time. In these systems precipitate is formed by interdiffusion of two solutions containing the appropriate ions.
- Choi,Newrzella,Woermann
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- THERMAL SYNTHESIS OF BARIUM AND BARIUM-STRONTIUM METANIOBATES BY USING A COPRECIPITATION METHOD.
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The authors present a new, non-traditional method for the synthesis of barium metaniobate, BaNb//2O//6, and of a mixed barium-strontium metaniobate, Ba//0//. //2//9Sr//0//. //7//1Nb//2O//6, through the thermal decomposition of coprecipitation products. The conditions of quantitative precipitation of the metals as niobic acid and barium or barium-strontium oxalate were established. The mechanism of thermal decomposition of the coprecipitate was deduced from differential thermal analysis and X-ray diffraction date. Barium metaniobate forms at 470 degree C, below the temperature required in the synthesis based upon the solid-state reaction between Nb//2O//5 and BaCO//3 (1100 degree C). The mixed barium-strontium compound is formed at 700 degree C, below the 1100 degree C used in the reaction between Nb//2O//5, BaCO//3 and SrCO//3.
- Marta,Zaharescu,Haiduc,Macarovici
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- Effect of rare earth oxides on the thermal decomposition of barium oxalate
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Catalytic activity of rare earth oxides (REO); La2O3, Sm2O3, Gd2O3 and Ce2O3 on the isothermal decomposition of barium oxalate has been studied at 723 K. The α-t plots
- Bose,Sahu,Bhatta
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- Thermal analysis of La-Ba oxalate and role of γ-irradiation there on
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Lanthanum-barium oxalate was prepared and characterised by chemical and thermal analysis, X-ray diffraction and plasma emission spectroscopy. X-ray analysis showed the presence of a uniphase system. The kinetics of decomposition of oxalates of La and Ba as well as coprecipitated La-Ba oxalate have been investigated in air using dynamic thermogravimetry. The decomposition of mixed oxalate occurred with two over-lapping exotherms, corresponding to the decomposition of lanthanum oxalate followed by that of barium. The kinetics of decomposition of the irradiated salt was studied over the same temperature range as that of the unirradiated one in air and activation energies obtained from the slopes of Coat-Redfern's plot. Kinetic analyses following various theoretical models of solid state reactions showed that the best fit was obtained for a third order reaction and geometrical models. It was evident that though there was increase in the activation energy as well as frequency factor with increasing radiation dose, reverse phenomenon takes place in the case of reaction rate. The effect of γ-irradiation on the process and the mechanism involved therein has been discussed.
- Nayak,Bhatta
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- Synthesis and characterization of Pt(II) complexes with amine and carboxylato ligands. Crystal structure of (1,1-cyclobutanedicarboxylato)di(ethylamine)platinum(II)·H2O
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Two methods for the synthesis of compounds of the type cis-PtA2X2 (A2 = bidentate amine or two monodentate amines and X2 = bidentate or two monodentate carboxylato ligands) were evaluated. The compounds were characterized by multinuclear NMR and IR spectroscopies. The 195PT NMR chemical shifts were in the range - 1615 to - 1976 ppm, the higher field values corresponding to the complexes containing bidentate ligands. The coupling constants 3J(195Pt-1H) are approximately 35 Hz, while the 2J(195Pt-1HN) are about 70 Hz. One coupling constant 2J(195Pt-13C) (53 Hz) was also measured. The crystal structure of the compound, cis-Pt(1,1-cyclobutanedicarboxylato)(C2H5NH2)2·H2O belongs to the P21/n space group with a=9.468(5), b =9.365(4), c = 16.473(7) A?, β = 105.08(3)°, Z = 4 and R1 = 0.0576. The Pt-N bond distances are 1.992(5) and 2.020(5) A?, while the Pt-O bonds are 2.000(4) and 2.015(4) A?. The molecules are held together by intermolecular H-bonds involving the lattice water molecules and the two free carbonyl O atoms and between the amino H atoms and the Pt-bonded C-O groups. (C) 2000 Elsevier Science S.A.
- Rochon, Fernande D.,Gruia, Letitia M.
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p. 193 - 204
(2008/10/08)
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- THE USE OF THERMAL ANALYSIS FOR THE STUDY OF THE CALCINATIONPROCESS OF OXALATEPRECURSORS FOR THE SYNTHESIS OF HIGH TC SUPERCONDUCTORS
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The decomposition of the oxalateprecursors Y2(C2O4)3 * 4BaC2O4 * (6+n)CuC2O4 * xH2O for the synthesis of high Tc superconductors and the individual Y-, Ba-, Cu-oxalate components is investigated by DTA and by TGA coupled with FTIR.
- Vos, A.,Mullens, J.,Carleer, R.,Yperman, J.,Vanhees, J.,Poucke, L. C. Van
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p. 187 - 192
(2007/10/02)
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