Polarographic Studies of Dioxo‐Complexes of Germanium. I. The Ge(IV)‐Pyrocatechol‐Sulphonphthalein System

Pyrocatechol‐sulphonphthalein (abbreviated to PV) and its germanium complex were polarographically studied in an acetic acid‐acetate buffer at various pH's. A well‐defined reduction wave for PV with E ranging from —0.46 to —0.73 volt ( S.C.E .) was observed in the pH region 3.2—7.0 at 25°C. This wave corresponds to a one‐electron reduction which is nearly revrsible. By following the i a values of PV at varying mole ratios of Ge(IV) to PV, the composition of the complex was deemed to consist of Ge(PV) 2 and the instability constants were found to be (3.1±0.4)×10 −8 at pH 5.0, (1.7±0.3)×10 −8 at pH 6.1 and (1.9±0.4) × 10 −8 at pH 6:5, respectively. A mthod for the computation of the instability constant of complex was proposed.