Sequential potentiometric microdetermination of chloride and phosphate and its application to the determination of phosphorus and chlorine in organic compounds.
Orthophosphate has been determined at the micro level in the presence of chloride by argentimetric potentiometric titration. Chloride is titrated first, at pH 3 in water-propan-2-ol (1:1 v/v), and phosphate in the same solution, buffered at pH 8.5-9.0. Under these conditions, the titration error from partial co-precipitation of silver oxide near the equivalence point is minimized. A procedure for performing the titration with an automatic apparatus is described. The method has been applied to the determination of phosphorus and chlorine in the same organic compound after mineralization by the Schöniger method.
Pietrogrande
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Department of Pharmaceutical Sciences, University of Padua, Via Marzolo 5, I-35131 Padua, Italy.
Zancato
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