[en] A method is proposed for the determination of the charge of polynuclear complexes based on the fact that positive polynuclear complexes of metal ions can join negatively charged complexing anions, which will neutralize them. Thus, knowing the quantity of anion necessary for full neutralization and its charge, one can calculate the charge of the initial polynuclear complex. The dialysis through a semipermeable cellophane membrane was used for the determination of the quantity of anions joined with the polynuclear complex since such anions cannot penetrate through the membrane. The radioactive isotopes of sulfur, phosphorus and iodine were correspondingly used for measurement of SO₄^2-, PO₄^3- and I^- anions concentrations. The interaction of SO₄^2-, PO₄^3- and I^- anions with the iron(III) polynuclear complexes was investigated by dialysis method. The phosphate anion was chosen for determination of the polynuclear complex charge. On the basis of data obtained the charge of the iron(III) polynuclear complex has been calculated (author)