Untersuchungen über das Verhalten einer Reihe von Elementen gegenüber Brenzcatechin in wäßriger Lösung

Summary

Pyrocatechol has been added to solutions of many elements at pH 5,0 (concentrations up to 200 mg/250 ml) under the conditions used for the potentiometric titration of germanium. It was observed that many elements react with pyrocatechol to give hydrogen ions, among others all elements Investigated which forminsoluble hydroxides or oxide hydrates at pH 5. Only the reactions of germanium and lead can be used for volumetric analysis (titration with sodium hydroxide) because of their accurate reproducibility. Germanium is separated from interfering elements by suitable methods. For lead an immediate titration is possible but many elements interfere and their concentrations should be very small except in the case of thallium, zinc and cadmium. Buffering substances must be absent. On the other hand, pyrocatechol can be determined in the presence of other organic compounds especially resorcinol and hydroquinone by a neutralized solution of lead and titration with sodium hydroxide. It is assumed that the other compounds do not react with lead and give no buffering effect.