2-Mercapto-benzimidazole as an analytical reagent

Summary Palladium is quantitatively precipitated at aPH 5.0 to 10.1 by 2-mercapto-benzimidazole and the complex, Pd(C₇H₅N₂S)₂, which is found to be diamagnetic, is stable up to a temperature of 447 C. In presence of EDTA and tartrate or citrate and at aPH between 6 and 8, it is separated from alkalis, alkaline earths, Mg, Fe³⁺, Cr, Th, Zr, Ti, UO₂ ²⁺, Be, Ce³⁺, Ce⁴⁺, rare earths, Zn, Mn, Ni, Co, Pb, Bi, As, Sb³⁺, Sn⁴⁺, Tl⁺, Cu²⁺, Cd, Ir⁴⁺, Rh³⁺, Ru³⁺, Os⁴⁺, CrO₄ ^2–, MoO₄ ^2–, WO₄ ^2–, VO₃ ^–, PO₄ ^3– and AsO₄ ^3–. Pb, Ag and Hg²⁺ are kept in solution by potassium iodide while a small amount of Au³⁺ by thiosulphate. The palladium complex is either weighed after drying at 110 C or dissolved in a cyanide solution and determined volumetrically by back titrating the excess cyanide with a standard silver nitrate solution.