Abstract: Ternary complexes of cadmium (Ⅱ) with succinate(Succ) as primary ligand and oxalate (OX) as secondary ligand were studied by means of differential pulse polarography at 20±0.2℃, 35±0.2℃ and μ= 0.1(NaNO₃).On the basis of the values of the stability constant, the thermodynam-ic functions (△G⁰, △H⁰, △S⁰) were calculated.The simple complexes of Cd(Ⅰ) and each kind of ligand were investigated.The positive values of mixing constant (lgK_m = 0.83) and stabilization constant(lgK_s = 0.52) prove that the ternary complex [Cd(OX)(Succ)] is more stable than the corresponding binary complexes.The stability constants of composite-coordinated complexes are lgβ₁₁ = 4.68, Igβ₂₁ = 5.75 and lgβ₁₂ = 5.68 at 20℃ and lgβ₁₁ = 4.61, lgβ₂₁= 5.74 and lgβ₁₂ = 5.67 at 35℃.

Key words: Cd (Ⅱ)-oxalate-succinate, Stability constant, Themodynamic function, Differential pulse polarography