Generally, starch is added to visually enhance the first trace of
iodine that appears and marks the time-measure for the iodine
clock.
The study presented herein augments the kinetic determination
of the clock reaction and follows the continuing
development of iodine in the persulfate−iodide solution, so
no starch is added. The major complex of dissolved iodine in
iodide solution is triiodide, I3
−, formed through the
equilibrium:5
+ ⇌ − − I2