[en] Moessbauer measurements were performed at different temperatures in order to examine behavior of iron in the glass system: 42.5% P₂O₅, 42.5% Na₂O, 15% Fe₂O₃. Variation of the dynamic behavior was traced by substituting B₂O₃ for P₂O₅ [30 P₂O₅, 12.5 B₂O₃, 42.5 Na₂O, 15 Fe₂O₃] and by increasing the amount of iron at the expense of Na₂O [42.5 P₂O₃, 15 Na₂O, 42.5 Fe₂O₃]. The Moessbauer measurements gave the values of Debye temperature (θ_D), mean square displacement < x²>, mean square velocity < v²> of oscillation, the lattice time (τ) and the strength parameter (B) for each glass. These values were discussed with the results of DTA, density, hardness and D.C. conductivity. (author)