STUDY OF THE COPRECIPITATION OF CALCIUM, POTASSIUM, SODIUM AND CHLORIDE WITH BARIUM-SULFATE USING ATOMIC SPECTROMETRY AND VISIBLE SPECTROPHOTOMETRY

Sulfate ions at the 50 and 250 mg l-1 SO42- levels are precipitated gravimetrically as BaSO4 from 200 ml samples using a large excess of BaCl2. Atomic absorption or emission spectrometry and visible spectrophotometry are applied to ten pairs of BaSO4 precipitates obtained from each of two concentration levels of standard Na2SO4 solution with or without 4 g of the cation being studied, to determine the Na, K, Ca and Cl ions present as impurities, after dissolution of the BaSO4 precipitates with hot, concentrated H2SO4. The experimental results, DELTA(exp), are compared with the theoretical values, DELTA(calc), calculated from a model that assumes that all the anion precipitates as BaCl2 and all the cation as the sulfate of the respective cation. Good agreement with the model is found for the cations studied.