C2 O4 Research Articles

Physico-chemical studies on the thermolysis of strontium and barium ferrimaleates

The thermolysis of strontium and barium tris(maleato)ferrates(III), M3 [Fe(C2 H2 C2 O4 )3 ]2 ·x H2 O has been investigated from ambient temperature to 800 °C using simultaneous TG-DTG-DTA, XRD, Mossbauer and IR spectroscopic techniques. After dehydration the anhydrous complexes undergo decomposition to yield an iron(II)maleate/oxalate intermediate in the temperature range of 240-280 °C. An oxidative decomposition of iron(II) species leads to the formation of α-Fe2 O3 and respective alkaline earth metal carbonate in the successive stages. Finally at 540-590 °C, a solid state reaction occurs between α-Fe2 O3 and strontium/barium carbonate resulting in the formation of SrFeO2.5 and BaFe2 O4 , respectively.

Physico-chemical Studies on Thermal Decomposition of Alkali Tris(maleato)ferrates(III)

The thermal decomposition of alkali tris(maleato)ferrates(III), M3 [Fe(C2 H2 C2 O4 )3 ] (M =Li, Na, K) has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, XRD, Mossbauer and IR spectroscopic techniques. The anhydrous complexes decompose in the temperature range 215–300°C to yield Fe(II)maleate as an intermediate followed by demixing of the cations forming α-Fe2 O3 and alkali metal maleate/oxalate in successive stages. In the final stage of remixing of the cations (430–550°C) a solid state reaction occurs between α-Fe2 O3 and alkali metal carbonate leading to the formation of fine particles of respective ferrites. The thermal stabilities of the complexes have been compared with that of alkali tris(oxalato)ferrates(III).

Synthesis and Thermal Decomposition of Mixed 2,4'-bipyridine-oxalato Complexes With Mn(II), Co(II), Ni(II) and Cu(II)

The mixed 2,4'-bipyridine-oxalato complexes of the formulae M(2,4'-bipy)2 C2 O4 2H2 O (M (II)=Mn, Co, Ni, Cu; 2,4'-bipyridine=2,4'-bipy or L ; C2 O2–4 =ox) have been prepared and characterized. IR data show that the 2,4'-bipy coordinated with these metals(II) via the least hindered (4')N atom; that oxalate group acts as bidentate chelating ligand. Room temperature magnetic moments are normal for the orbital singlet states. The thermal decomposition of these complexes was investigated by TG, DTA and DTG in air. The endothermic or exothermic character of the decomposition of ML2 (ox)2H2 O was discussed.

Lanthanum samarium oxalate — its growth and structural characterization

Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) support that LSO loses water around 120°C, and CO and CO2 around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C2 O4)2− ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic (XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has been proposed on the basis of these findings.

THE CATALYSIS OF THEtrans-cisISOMERIZATION OF DIAQUOBIS(OXALATO)-CHROMATE(III) BY Mg(NO3)2AND MgSO4

Abstract The trans-cis isomerization of Cr(C2 O4)2 (H2 O)2 − was investigated using Mg(NO3)2 and MgSO4 as catalysts at higher concentrations than reported in the literature. Linear behavior is observed between added catalyst concentration and rate until ca. 0.30M, after which the rate becomes much faster. The rate behavior over the entire range of added catalyst MgSO4 is explained in terms of ion association. Both the free Mg2+ and the complex MgSO4 catalyze the reaction. The catalytic rate constants obtained are k Mg 2+=3.60 × 10−3 M−1 s−1 and k MgSO4 =8.00 × 10−4 M−1 s−1.