Polarographic Determination of the Formation Constants of the Mixed Ligand Complexes of Cd(II) and Pb(II) with Thiosulphate and Halide Ions

The mixed ligand complexes of Cd(II) and Pb(II) with thiosulphate as a primary ligand and chloride, bromide of iodide (individually) as a secondary ligand have been polarographically, investigated at 30°C and at a constant ionic strength of μ = 1.0 M (NaClO4). Two mixed ligand complexes were formed with the Cd(II) ion: log β12 = 4.77, 5.30 and 6.78 for the chloride, bromide and iodide ions, respectively; and log β21 = 5.36, 5.04 and 6.22 for the same ions. For the Pb(II)-Ts-Cl system, only one mixed ligand complex was formed with a log stability constant log β21 =4.35. For the Pb(II)-Ts-Br system, three mixed ligand complexes are obtained with log β11 = 3.63, log β12 = 4.51 and log β21 = 4.85.