V catalyst for SO(2)-to-SO(3) oxidn. was prepd. by mixing resp. amts. of V(2)O(3), K(2)O(3) (1:3 ratio), SiO(2) and optionally Fe(2)O(3) (up to 6.9%), heated at 420 degrees C for 4 h in the SO(2)-contg. air and tested for catalytic activity at 400-600 degrees C to det. the oxidn. rate. The activity of the catalyst and its mech. strength decreased with increasing Fe(2)O(3) content. The relative catalyst deactivation coeffs. increased with increasing Fe(2)O(3) content and with decreasing operational temp.