Complexes of lanthanide nitrates with 4n-(2′-hydroxy benzylidene)-aminoantipyrine

New complexes of lanthanide nitrates with 4N-(2′-hydroxy benzylidene)-aminoantipyrine (HBAAP) having the general formula [Ln(HBAAP)₂(NO₃)₃] (where Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Y) have been prepared and characterized. Conductance studies indicate non-electrolytic behaviour for these complexes. Their infrared spectra show that both the ligand and the nitrate group are bound to the metal ion in a bidentate fashion. Electronic spectra indicate weak covalent character in the metal-ligand bond. Thermogravimetric studies indicate that these complexes are stable up to ～200°C and undergo complete decomposition in the range 200–550° resulting in the formation of the stable lanthanide oxides.     

Solid State Metathesis Reactions in Various Applications

Solid state metathesis reactions have been studied in fused silica tubes, by differential thermal analysis, and by X‐ray powder diffraction. A selection of reactions between metal (La, Nb, and Ni) chlorides and lithium nitride or lithium acetylide were investigated to get more insight into reaction pathways and intermediate reaction stages that may be adopted on course of the formation of metal nitrides or carbides. Intermediate compounds are considered to be important because they can control the reactivity of a system. Such compounds were traced by changing the molar ratios of reaction partners away from the salt‐balanced binary metal nitride or carbide target compositions. New preparative perspectives are discovered when metal chlorides were reacted with lithium nitridoborate or lithium cyanamide. Due to their reductive nature towards several d‐block metal chlorides, (BN₂)^3‐ and (CN₂)^2‐ react to form metals or metal nitrides plus X‐ray amorphous BN, and probably C₃N₄. With lanthanum chloride they can react to form nitridoborates and nitridocarbonates. The metathesis reaction between lithium cyanamide and cyanuric chloride (C₃N₃Cl₃) instead of metal chloride was studied for the synthesis of C₃N₄.     

A thermal decomposition study on cobalt(II) complexes of 1,2-di(imino-4′-antipyrinyl)ethane

The phenomenological, kinetic and mechanistic aspects of thermal decomposition of perchlorate, nitrate, chloride, bromide and iodide complexes of cobalt(II) with the Schiff base 1,2-di(imino-4′-antipyrinyl)ethane (GA) have been studied by TG and DTG analyses. The kinetic parameters like the activation energy, pre-exponential factor and entropy of activation were calculated. The decomposition reactions follow “random nucleation with one nucleus on each particle—Mampel model”.     

Removal of cadmium(II) and zinc(II) metal ions from binary aqueous solution by rice husk ash

The present study reports the competitive adsorptive removal of cadmium (Cd(II)) and zinc (Zn(II)) ions from binary systems using rice husk ash (RHA), a waste obtained from the rice husk-fired furnaces, as an adsorbent. The initial pH (pH₀) affects significantly the capacity of RHA for adsorbing the metallic ions in the aqueous solution. The pH₀ ≈ 6.0 is found to be the optimum for the removal of Cd(II) and Zn(II) ions by RHA. The single ion equilibrium adsorption from the binary solution is better represented by the non-competitive Redlich–Peterson (R–P) and the Freundlich models than by Langmuir model in the initial metal concentration range of 10–100 mg/l. The adsorption of Zn(II) ion is more than that of Cd(II) ion, and this trend is in agreement with the single-component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined effect of Cd(II) and Zn(II) ions on RHA is generally found to be antagonistic. Non-modified Langmuir, modified Langmuir, extended-Langmuir, extended-Freundlich, Sheindorf–Rebuhn–Sheintuch (SRS), non-modified R–P and modified R–P adsorption models were tested to find the most appropriate competitive adsorption isotherm for the binary adsorption of Cd(II) and Zn(II) ions onto RHA by minimizing the Marquardt's percent standard deviation (MPSD) error function. The extended-Freundlich model satisfactorily represents the adsorption equilibrium data of Cd(II) and Zn(II) ions onto RHA.     

Rapid hydrocarbon type separation of vacuum residues

Summary A simple and fast column chromatographic procedure for the separation of vacuum residues into saturates, mono-, di-, polyaromatics and polars has been standardized using silica-alumina-bauxite adsorbents and gradient elution with n-pentane, benzene, and methanol. The cut points have been monitored employing ultraviolet and infrared spectroscopy. The method is applicable for preparative separation of short residues from processed products.

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Rasche Trennung der Kohlenwasserstofftypen von Vakuum-RückstÄnden

     

Integrability and singularity structure of coupled nonlinear Schrödinger equations

Multimode propagation of electromagnetic waves in optical fibre is often described by coupled nonlinear Schrödinger (NLS) equations. To understand the integrability properties of such coupled NLS systems, we extend the Painlevé singularity structure analysis of two coupled systems to three coupled systems and identify four integrable sets of parameters. We bilinearize these cases to obtain soliton solutions. The results are extended to N-coupled systems, completing the earlier analysis of Sahadevan, Tamizhmani and Lakshmanan.     

Synthesis of semifluorinated block copolymers by atom transfer radical polymerization

Two sets of styrene‐based semifluorinated block copolymers, one with a perfluoroether pendant group and another with a perfluoroalkyl group, were synthesized by atom transfer radical polymerization. Microphase separation of the block copolymers was established by small‐angle X‐ray scattering and differential scanning calorimetry (DSC). DSC measurements also showed that the perfluoroether‐based polymer had a low glass‐transition temperature (?44 °C). Contact‐angle measurements indicated that the semifluorinated block copolymers had low surface energies (ca. 13 mJ/m²). These materials hold promise as low‐surface‐energy additives or surfactants for supercritical CO₂ applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 853–861, 2004