[en] It is shown that during prolong active alpha-irradiation (²⁴⁴Cm source) of concentrated weak acid solutions of sodium perchlorate containing curium (3), americium (3) and plutonium (4), two types of precipitates: amorphous and crystal ones are rejected. The precipitates are formed at any acidity but only in solutions, where sodium perchlorate concentration exceeds 5.0 mol/l, and irradiation dose - 5.2 MGy. At that a substantial decrease in solution acidity is observed. It is ascertained that crystal precipitate presents sodium chloride and amorphous one - actinide hydroxides. In the amorphous precipitate plutonium is present in hexavalent, and americium - in trivalent and pentavalent states