Bismuthiol II as an analytical reagent

Summary

Lead was estimated as Bismuthiol II complex of composition (C₈H₅N₂S₃)₂Pb by precipitating it from its chloride or nitrate solution in presence of a mineral acid, acetic acid, tartrate or cyanide. The estimation is quantitative up to a maximumph of about 6.5. The lead-Bismuthiol II complex is stable up to about 311° C and the conversion factor is 0.315. The method affords a complete separation of lead from alkalis and alkaline earths, Be²⁺, Mg²⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Fe²⁺, Fe³⁺, Cr³⁺, Al³⁺, rare earths, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, UO₂ ²⁺, Pd²⁺, As³⁺, Sb³⁺, Cl⁻, SO₄ ²⁻, PO₄ ³⁻, AsO₄ ³⁻, MoO₄ ²⁻ and WO₄ ²⁻. Among the sulphide group members Ag⁺, Au³⁺, Hg⁺, Hg²⁺, Tl⁺, Tl³⁺, Cd²⁺ and platinum metals, except Pd²⁺, interfere while oxidising agents decompose the excess reagent. Bi³⁺, Cu²⁺ and Sn²⁺, do not interfere up to a maximum limit of 30 mg, 50 mg, and 250 mg respectively.