Resumen de A Variety of Electrochemical Methods in a Coulometric Titration Experiment
An experiment for a practical course is described in which the amounts of HCl and KI in a mixture of standardized solutions are determined by three coulometric titrations. The iodide content is titrated with bromine that is generated at the anode from bromide which oxidizes the I- to I2 and further to IBr2-. The titration is followed with a twin-polarizable platinum electrode which essentially records the I2 and (after the endpoint) Br2 levels. Analysis of the chloride content is performed indirectly by titration of the acid through cathodic reduction of H+ to H2. The titration is monitored with a glass electrode. Finally I- and Cl- are determined simultaneously by anodic dissolution of a silver wire with a silver electrode recording the course of the titration. The experiment provides an internal check of the quality of the analysis and presents a variety of electrochemical methods of pedagogical value. Hints for the practical performance of the experiment in laboratory courses are given, and the necessary electronic circuits for self-assembling are described. Laboratory experiences with students' data collection by hand, recorder and computer are dealt with in this experiment. A complete list of earlier papers is provided, which can be found in this Journal, on the subject of coulometric analysis.
