[en] In order to investigate the nature of the changes obtained as a result of the neutron activation of the solid condensed phosphates the chemical behaviour of ³²P in the (n,γ) irradiated and thermaly treated sodium trimetaphosphate was studied. After irradiation in the reactor and a subsequent thermal treatment samples were analysed by use of high voltage paper electrophoresis. Nine different kinds of ³²P-labelled anions were separated and identified. Some decrease in retention with extended annealing time was observed. From the results obtained it can be concluded that the recoil reaction in the investigated system is characterized by breakage and opening of the initial P-O-P ring resulting in the formation of the basis monomer, products with shorter open chains, small quantities of cyclic polyphosphorus acids and forms with ³²P in the reduced state. (T.G.)