The iodination of acetone, ch3coch3, in aqueous solution is catalyzed by the hydrogen ion h+: i2+ch3coch3 h+⟶ hi+ch3coch2i the reaction can be followed visually by adding starch. the purple starch-iodine complex forms immediately, then disappears when the iodine has been consumed. the kinetics of the reaction may be determined by recording the time required for the color to disappear, which is the time required for the iodine, i2, to be consumed.