Abstract: | Barium hydroxoaluminate hydrates were precipitated from different sodium hydroxoaluminate solutions at 20 °C; CAl varied from 0.1 to 0.5 M and initial Ba/Al2 ratios ( = excess OH/Al ratios) varied from 1 to 7. Precipitate compositions were determined by chemical analysis, infra-red spectrophotometry and thermal analysis. The compound BaO · Al2O3 · 7 H2O was precipitated at initial Ba/Al2 ratios of one to well above two while the compound 2 BaO · Al2O3 · 5 H2O was only precipitated over a narrow range of concentrations. The compound Ba(OH)2 · 8 H2O was precipitated from solutions of high hydroxide and barium ion concentrations. The ionic equilibria and precipitation mechanisms in different solutions are discussed. |