Abstract: Eight methods have been proposed for the estimation of stability constants of complexes as follows;1.lgK₁=Az²/r+Bx±+C.2.The linear relationship between lgK₁of two similar metal ions with a series of ligands.3.The linear relationship between lgK₁of two similar ligands with a series of metal ions.4.The linear relationship between lgK₁and ∑pK_afor complexes of one metal ion with a series of similar ligands.5.The linear relationship between lgK₁and x± for a series of metal ions with similar z²/r.6.The linear relationship between lgK₁and z²/r for a series of metal ions with similar x.7.The stability constants show the same "normal" variation as z²/r and x for the metal series.8.Ligands with larger∑pK_abind strongly to metals with larger z²/r and ligands with smaller x bind strongly to metals with larger xEight methods have been proposed for the estimation of stability constants of complexes as follows;