Synthesis, characterization and thermal decomposition kinetics of barium(II)bis(oxalato)barium(II)dihydrate and lead(II)bis(oxalato)lead(II)monohydrate

Barium(II)bis(oxalato)barium(II)dihydrate (BOD), Ba[Ba(C2O4)(2)]. 2H(2)O an d lead(II)bis (oxalato)lead(II)monohydrate (LOM), Pb[Pb(C2O4)2]. H2O have b een synthesized and characterized by elemental analysis, conductance measur ements, IR spectral, reflectance and X-ray powder diffraction studies. Ther mal decomposition studies (TG, DTG and DTA) in air showed that at ca. 1000 degrees C, a mixture of BaO2 and BaCO3 is generated from the compound, BOD, through the formation of BaO2 and BaC2O4 at around 514 degrees C as interm ediates. LOM gave Pb2O3 as final product at ca. 390 degrees C. DSC study in nitrogen showed a different decomposition pattern from that in air for bot h compounds. Using seven mechanistic equations, the rate controlling proces s of the dehydration and decomposition mechanism of BOD is inferred to be o ne- and three-dimensional diffusion, respectively. The decomposition mechan ism of LOM is a phase boundary reaction having cylindrical symmetry. Some o f the decomposition products were identified by analytical, IR spectral and X-ray powder diffraction studies. A tentative reaction mechanism for the t hermal decomposition of both the complexes is proposed. (C) 1999 Elsevier S cience B.V. All rights reserved.