Study of the coprecipitation of calcium, potassium, sodium and chloride with barium sulfate using atomic spectrometry and visible spectrophotometry

Abstract

Sulfate ions at the 50 and 250 mg l^–1 SO₄^2– 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, Δ_exp, are compared with the theoretical values, Δ_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.