A detailed investigation of the Pb(II)/OH- system has been made in NaClO4 media at 25 °C. Combined UV-vis spectrophotometric-potentiometric titrations at [Pb(II)]T ≤ 10 μM using a long path length cell detected only four mononuclear hydroxide complexes. The values of log *β1q, for the equilibria Pb2+(aq) + qH2O ↔ Pb(OH)q(2-q)+(aq) + qH+(aq), were -7.2, -16.1, -26.5, and -38.0 for q = 1-4, respectively, 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) even at very high [OH-]/[Pb(II)] ratios, nor for polynuclear species at [Pb(II)]T ≤ 10 μM. Measurements using 207Pb-NMR and Raman spectroscopies and differential pulse polarography (DPP) provided only semiquantitative confirmation. The mononuclear Pb(OH)q(2-q)+(aq) complexes are the only hydrolyzed species likely to be significant under typical environmental and biological conditions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry