BLUE / GREEN BOTTLE (REDOX)
NEEDED

     -  Glucose
     -  Methylene blue or
     -  Malachite green
     -  Sodium hydroxide: NaOH

PROCEDURE

             Dissolve 7.5 g glucose in 150 ml water and
         add 2 g of NaOH. Add 0.5 ml 1% solution of
         methylene blue. Close the flask, because the
         following shaking needs to be vigorously.

COMMENTS

             The glucose in the solution reduces the dye
         to its colourless form within about 1 min at
         room temperature. Vigorous shaking brings
         the dye in conztact with oxygen, which
         oxidises it back to the coloured form.
             The reaction is repeatable many times and
         it is hightly temperature sensitive. At 30°C
         the reduction takes place within less than ten          seconds.

MECHANISM

       Reduction and oxidation of Methylene blue:







        Reduction and oxidation of Malachite green:
Methylene blue
The blue bottle from before (left end) to after shaking (right end)
Malachite green