Synthesis and Study of Bismuth(III) Oxalates Precipitated from Mineral Acid Solutions

Bismuth oxalates BiOH(C2O4), Bi-2(C2O4)(3).6H(2)O, Bi-2(C2O4)(3).7H(2)O, and Bi-2(C2O4)(3).8H(2)O were obtained by precipitation from solutions of bismuth in perchloric, nitric, and hydrochloric acids with addition of oxalic acid. The compositions of compound were confirmed by X-ray powder diffraction, chemical analysis, IR and Raman spectroscopy, and thermogravimetry. It has been shown that in the composition of bismuth(III) oxalate hydrates Bi-2(C2O4)(3).xH(2)O, bismuth cations are coordinated by the oxygen atoms of carboxyl groups of oxalate ions and water molecules in the same way, thus, in view of the structural features, compositions of the compounds can be described by the general formula {[Bi-2(C2O4)(3)(H2O)(4)]center dot(x-4)H2O}(n). The conditions of oxidative thermolysis of BiOH(C2O4) and Bi-2(C(2)O4)(3)Greek ano teleia7H(2)O leading to the formation of tetragonal modification of bismuth oxide beta-Bi2O3 were determined.