Synthesis and characterization of basic bismuth(III) nitrates

The syntheses of the basic bismuth(III) nitrates [Bi6O5(OH)3](NO3)5·3H2O, A, [Bi6O6(OH)3](NO3)3·1.5H2O, B, and [Bi6O5(OH)3](NO3)5·2H2O, X, were investigated. A is readily obtained in hydrolysis of bismuth(III) nitrate solutions with sodium hydroxide solutions and in homogeneous hydrolysis with dilute solutions of urea. [Bi6O6(OH)3](NO3)3·1.5H2O is obtained in hydrothermal synthesis at 190 °C from Bi(NO3)3·5H2O or from [Bi6O5(OH)3](NO3)5·3H2O. [Bi6O5(OH)3](NO3)5·2H2O was obtained at 100 °C from an aqueous solution which was 0.74 M with respect to bismuth(III) nitrate and 1.50 M with respect to urea. The compositions of B and X were derived from thermogravimetric analysis. Indexed powder patterns are reported for B: a = 3.8175(5), c = 17.149(4) Å for a tetragonal cell, and for X: a = 15.185(1), c = 15.834(2) Å for a rhombohedral cell using hexagonal setting.