Abstract: The method for ascertaining the maximum ligand of complexes in solution was extended to the polarographic method and the systems with some precipitate. It was shown that there are the characteristics of W, function in the systems of hydroxy complexes of zinc(Ⅱ) and lead(Ⅱ ), and that the maximum ligand numbers of the two systems both are four, at 25℃ and NaOH concentra-tion ≤3M. when some precipitate occured, an approximate calculation of the experimental values of the degree of complexes Y₀ was suggested and a correct fomu-la of the ligand concentrations derivated, thus Leden-Fronaeus-Hsu Kwang-hsien logrithmic functional extrapolation has been extended to the systems with some precipitate. As a consequence of the approximate method the consecutive stability constants at 25℃ and ionic strength μ=3.0 were found to be. lgβ₁ = 6.72, lgβ₂ = 11.52, lgβ₃ = 14.04, lgβ₄=16.30 for zinc(Ⅱ) hydroxy complexes and lgβ₁ = 6.87, lgβ₂=10.60, lgβ₃ = 12.80, lgβ₄ = 14.95, for lead(Ⅱ) hydroxy complexes.