TRAFIC LIGHT BOTTLE (REDOX)
NEEDED

     -  Glucose
     -  Indigo carmine
     -  Sodium hydroxide: NaOH

PROCEDURE

             Dissolve 7.5 g glucose in 150 ml warm
         water and add 2 g of NaOH. Add some dye
         and close the flask, because the following
         shaking needs to be vigorously.

COMMENTS

             The glucose in the solution reduces the dye
         to its yellow leuko-form. Vigorous shaking
         brings the dye in contact with oxygen, which
         oxidises it back to the blue form. The
         subsequent reduction to yellow runs through
         a red intermediate

             The reaction is repeatable several times.

MECHANISM