Thionolin als analytisches Reagens

Summary

According to the measurements performed the redox potential of thionoline changes at the temperature of 40° C in the p_H-range of 0,66 to 8,11 from 0,542 V to 0,087 V (SCE). Thionoline can be used for the selective detection of BrO₃ ⁻ in the presence of ClO₃ ⁻, IO₃ ⁻ and the free halogens (sensitivity p_D=5,4), as well as for the selective detection of Sn²⁺ in the presence of Cr²⁺, Ti³⁺, V²⁺ and Fe²⁺ (p_D=4,6). Sn²⁺, Ti³⁺ and Cr²⁺ can be titrated potentiometrically with thionoline solution in the presence of Co²⁺, Ni²⁺, Mn²⁺, Al³⁺ and Zn²⁺. V²⁺ and Fe²⁺ interfere with this reaction. Sb³⁺ interferes with the determination of Sn²⁺ and Cr²⁺.

Chlorine and bromine water in ethanolic solution convert the thionoline easily and quantitatively in tetrahalogenated products. The halogenation can be watched potentiometrically.