Method for producing condensed iron (III) phosphate, in which a) an aqueous solution containing Fe2+ ions is produced, in which oxidic iron (II), iron (III) or mixed iron (II, III) compounds selected from among hydroxides, oxides, oxide hydroxides, oxide hydrates, carbonates and hydroxide carbonates are introduced together with elementary iron into an aqueous medium containing phosphoric acid, wherein Fe2+ ions are dissolved and Fe3+ with elementary Fe (in a comproportionation reaction) is reacted to dissolved Fe2+, b) separating solid material from the phosphoric acid aqueous Fe2+ solution, c) adding an oxidizer to the phosphoric acid aqueous Fe2+ solution to oxidise iron (II) in the solution, d) adding polyphosphate in the form of polyphosphoric acid or salts thereof as solid material or aqueous solution after completion of the oxidation reaction to precipitate condensed iron (III) phosphate, and e) separating the precipitated condensed iron (III) phosphate solution and resulting product.
