An investigation of the lead(II)-hydroxide system

A detailed investigation of the Pb(II)/OH- system has been made in NaClO4 m edia at 25 degreesC. Combined UV-vis spectrophotometric-potentiometric titr ations at [Pb(II)](T) less than or equal to 10 muM using a long path length cell detected only four mononuclear hydroxide complexes. The values of log *beta (1q), for the equilibria Pb2+(aq) + qH(2)O <----> Pb(OH)(q)((2-q)+)( aq) + qH(+)(aq), were -7.2, -16.1, -26.5, and -38.0 for q = 1-4, respective ly, at ionic strength I = 1 M (NaClO4). Similar results were obtained at I = 5 M (NaClO4). No evidence was found for higher order complexes (q > 4) ev en at very high [OH-]/[Pb(II)] ratios, nor for polynuclear species at [Pb(I I)](T) less than or equal to 10 muM. Measurements using Pb-207-NMR and Rama n spectroscopies and differential pulse polarography (DPP) provided only se miquantitative confirmation. The mononuclear Pb(OH)(q)((2-q)+)(aq) complexe s are the only hydrolyzed species likely to be significant under typical en vironmental and biological conditions.