text: The simplest clock reaction featuring two reactions:
  :A → C (rate k)
  :B + C → products (rate k, fast)
  When substrate (B) is present, the clock species (C) is quickly consumed in the second reaction. Only when substrate B is all used up or depleted, species C can build up in amount causing the color to change. An example for this clock reaction is the sulfite/iodate reaction or iodine clock reaction, also known as Landolt's reaction.
  Sometimes, a clock reaction involves the production of intermediate species in three consecutive reactions. 
  :P + Q → R 
  :R + Q → C 
  :P + C → 2R  
  Given that Q is in excess, when substrate (P) is depleted, C builds up resulting in the change in color.