Fe catalyst was prepd. by fusion of Fe(3)O(4) with Al(2)O(3), CaO and K(2)O under industrial conditions and casting the resp. ingots. Melt samples were taken from the upper and middle parts of the ingot and analyzed for chem. and phase compns. as well as for catalytic activity in the NH(3) synthesis at 723 and 923 K after redn. with H(2) at 473-773 K. The catalyst from the upper part of the ingot contained more Fe(3)O(4) than those taken from the middle ingot part and was twice as active at the beginning of the synthesis, but its activity rapidly decreased during its use at elevated temp.