The graphical analysis concerning the metal ion enrichment of water-soluble polymers by the ultrafiltration technique is developed and contrasted with the experimental results obtained with the chelating poly[acrylamide-co-1-(2-hydroxyethyl)aziridine]. An equilibrium is established between the polymer and Cu2+ and a stable blue complex is formed. The compositions of metal ions bound to the polymer and free in solution follow both Langmuir and Freundlich isotherms. From Langmuir isotherm, an apparent fort-nation constant is found with a value of 1.8 x 10(-3) M-1.