[en] To find which complexes of Europium (III) form in concentrated phosphoric acid we studied by gamma radiometric analysis the partition of 152-Eu. The two-phase system was HDEHP-C₆H₆/H₃PO₄-(LiClO₄,2H₂O) with μ=0.22. The range of variation in pH and total H₃PO₄ concentration were 0.7< pH<4 and C_H3PO4<4.2M respectively, these variations cover those of pH and free H₃PO₄ concentration found in pure H₃PO₄ up to 4.2 M. In aqueous phases we have found numerous complexes of europium (III) and measured their stability constant relative to europium (III) and H₃PO₄. In pure H₃PO₄, which is the concentration of the solution resulting from the treatment of phosphate ores to obtain phosphoric acid, europium (III) is engaged in two cationic complexes which can be written as (EuH₂PO₄)²⁺ 45% and (EuH₅P₂O₈)²⁺ or (H₂PO₄)(H₃PO₄)²⁺ 53%. 29 refs.; 16 figs.; 6 tabs. (author)