Potentiometric determination of mercury or silver in the presence of halides

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Halides interfere with most determinations of mercury or silver. However, if mercury or silver is titrated with sulfide ions, extremely insoluble sulfides are formed.

A simple method is described that allows the direct titration of mercury(II) or silver(I) compounds in the presence of halides. The potentiometric titration takes place under alkaline conditions using thioacetamide as the titrant after formation of the EDTA complex.

Organic compounds that are insoluble in alkaline EDTA can also be titrated after a Schoeniger digestion.