[en] Using a special type of on line electromigration measurements of γ-emitting radionuclides in homogeneous electrolytes free of supporting materials the hydrolysis and the complex formations of carrier-free ²⁴⁹Cf-Cf(III) with oxalate in diluted perchlorate electrolytes, T = 2.98.1(1) K, were studied. Stoichiometric hydrolysis constants of pβ₃ 18.6(9) and pK₁ = 6.2(2) were calculated in μ = 0.10 electrolytes. For the formation of anionic hydrolysis products a limitation of pK₄ ≥ 13.9(3) was derived. The stoichiometric stability constants of the oxalato complexes are lgK₁ 4.80(8) and lgK₂ = 3.55(11), μ = 0.01. (author)