A triply promoted fused iron catalyst was examined by temperature-programmed desorption and temperature-programmed hydrogenation of preadsorbed nitrogen (TPD-N-ads and TPH-N-ads). The studies confirm the literature suggestions that both nitrogen chemisorbed on the Fe surface,and subsurface nitrogen coexist in the catalyst. Slow changes in the nitrogen location (surface N-subsurface N) have been observed. In the course of TPD-Nads tests desorption of nitrogen proceeds as an irreversible process, without N-2 readsorption. During TPH-N-ads runs a significant amount of dinitrogen is evolved at high temperature, besides ammonia. The obtained TPH-N-ads spectra are characteristic with sharp onsets of ammonia evolution. It has been demonstrated that both hydrogenation of preadsorbed nitrogen and retention of ammonia formed are responsible for the onset formation.