Bismuthiol I as an analytical reagent

Summary

Bismuth and palladium have been determined volumetrically after precipitation as bismuthiol I complexes. From 0.1 N hydrochloric acid solutions they are separated from Fe²⁺, Al, Cr, Ce³⁺, Zr, Ti, Zn, Th, UO₂ ²⁺, Be, Mg, Mn, Co, Ni, alkalis, alkaline and rare earths.

A mixture of tartrate or citrate and EDTA has been found to be useful for the separation of palladium at a p_H 3.5–8.5 from As, Zn, Bi, Sn⁴⁺, Sb, Fe³⁺, Tl⁺, Cu²⁺, Cd, Pb, Ru³⁺, Os⁴⁺, PO₄ ³⁻, Ce⁴⁺, Ir⁴⁺, Rh³⁺, VO₃ ⁻, CrO₄ ²⁻, AsO₄ ³⁻, WO₄ ²⁻, MoO₄ ²⁻ and from all the other ions referred to above. Potassium iodide at p_H 6.0–8.0 and thiosulphate at 6–7 keep Ag, Pb, Hg²⁺ and Au³⁺, Ir⁴⁺, Os⁴⁺ respectively in solution and thus allow a selective precipitation of palladium.

Hg²⁺, Pb, Cu²⁺, Ag, Tl⁺, Cd and Pd when present along with bismuth are first removed by the reagent and from the filtrate bismuth is estimated. Sn²⁺, Sb³⁺, Fe³⁺, F⁻, VO₃ ⁻, PO₄ ³⁻, AsO₄ ³⁻ and CrO₄ ²⁻ interfere in bismuth determination while only Sn²⁺, Pt⁴⁺ and CN⁻ interfere in palladium estimation.