Rapid decomposition and analysis of refractory barium sulfate by fusion with ammonium salt

Abstract

A simple and rapid method for the decomposition of refractory barium sulfate has been proposed. Barium samples (BaSO4, ore) were decomposed by fusion with ammonium hydrogen sulfate, which was found to be a suitable powerful flux for dissolving various refractory sulfates. An accurately weighed sample(ca. 10 mg) was placed in a dry Pyrex test tube (18 mm o.d., 200 mm length). Ammonium hydrogen sulfate(ca. 2 g) was added to the tube and mixed with the sample by agitating the tube. The bottom of the test tube was gently heated along with a swirling motion over a small gas flame of a Bunsen burner with a fish-tail at a temperature of ca. 550 - 600°C. Heating was continued until the melt changed into a colorless, clean and translucent form. Barium sulfate was dissolved by heating for about 5 min. After cooling, the solidified melt was dissolved in 30 ml of a 0.05 M EDTA-ammoniacal solution (3.5 M in ammonia). Finally, the concentration of the barium in the resulting solution was determined by ICP-AES or flame photometry. The proposed method was successfully applied to various sulfates and ores. The barium and other metals in the samples were determined and the analytical results of barium were in good agreement with the values obtained by fusion with alkali metal carbonate. © 2001 The Japan Society for Analytical Chemistry.