Precipitation of barium chromate in the presence of strontium and lead by complexation followed by volatilization of ammonia.
Cation-release is used to precipitate barium chromate from homogeneous solution in the presence of lead and strontium. MEDTA or DCTA is added to complex the metal ions at pH 10.3 (adjusted with ammonia). On heating, the ammonia slowly volatilizes and the consequent increases in acidity releases the metal ion bound in the least stable chelate (barium). Precipitation is about 99.3-99.7% complete at pH 6.7-6.8, with less than 0.1% co-precipitation of lead or strontium. Lower pH values can be attained by volatilizing acetic or hydrochloric acid into the solution in a closed system.
Firsching
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Science and Technology Division Southern Illinois University Edwardsville, Illinois 62025, U.S.A.
Werner
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