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Blue Bottle Reaction

Materials

• Solution A: 8gm KOH in 300ml H₂O
• Solution B: 10gm glucose
• Solution C: 1% methylene blue solution

Procedure

1. Just before class starts, add glucose and 4 drops methylene blue solution to the KOH solution and mix until clear.
2. Show the class the stoppered flask containing the solution.
3. Give the flask a few shakes. The solution will turn blue.
4. After a few seconds, solution becomes clear.
5. This process can be repeated several times. The bottle may have to be unstoppered to introduce O₂.

Reactions

O₂ (dissolved) + methylene blue --> methylene blue
                             (colorless)                  (blue)

glucose + OH^- --> glucoside

glucoside + methylene blue --> methylene blue + OH^-
                        (blue)                   (colorless)