Thus sulfur trioxide gets rid of the badly smelling pyridine molecule, however, at the expense of gaining the toxic cyanide anion. Therefore, reactions of sulfur trioxide with cyanide anions do usually not lead to the formation of I cyanido i -sulfates anion but to oxidation of the cyanide ion. In this way, the oxidation power is sufficiently reduced, and the pyridine molecule can be replaced by the cyanide anion under formation of the I cyanido i -sulfate anion, SO SB 3 sb CN SP - sp .