The blue bottle reaction is a chemical reaction in which in a closed bottle an aqueous solution containing glucose, sodium hydroxide and a methylene blue and some air turns from colorless to blue upon shaking and which then decolorises again after a while. After shaking again the blue color returns and this cycle can be repeated several times.

3. • Theory
• Reaction
• How To Prepare
Apparatus
Procedure
Precautions

4. • Explanation.
• Application .

5. REDOX
REACTION

6. Blue bottle
experiment

7. Theory
• A colorless solution partially fills a flask, is
shaken, and the solution becomes blue. Upon
standing, the solution returns to colorless.
• Further shaking regenerates the blue color.
Repeating the shaking/standing procedure
allows multiple observations. Other indicators
produce different color changes.

8. • The color change results from the reversible
oxidation-reduction reaction of the methylene
blue indicator. In alkaline solutions, glucose is
oxidized to D-gluconic acid or
alpha-D-gluconolactone.
• The Reaction is as follows ( next slide ).
Reaction

9.  HOCH2 (CHOH) 4 CHO + 3OH-
HOCH2 (CHOH) 4 CO2 + 2H2O + 2e-

O2 + MB(Colourless) MBox
(Blue)(Fast)

MBox(Blue) + CH MB(Colourless)
+ X.

10. Where CH is the carbohydrate (in this case,
dextrose), MB is the reduced (colourless) form of
methylene blue, MBox is the oxidized (blue)
form, and X- represents the oxidation products
from glucose (gluconic acid – different
carbohydrates form different acids like
arabinoic, formic, oxalic and erythronic acids).

13. Apparatus
• Water
• Sodium hydroxide
• Glucose
• Methylene blue
• 1 litre container (bottle or glass jar will do).
• 2 teaspoons

14. • Sodium hydroxide is the active ingredient in
Caustic Soda which can be found in the laundry
section of your supermarket. It is usually used
to unblock drains.
• Glucose can be bought from your chemist. It
comes in both powder and tablet form. The
powder works the best for this activity. If you
buy the tablets, crush them with a mortar and
pestle or the back of spoon

15. • Methylene blue is traditional medication for
freshwater aquarium fish.

16. Procedure
Pour 500ml of water into a 1 litre container.
Add a heaped teaspoon (approximately 8 grams)
of sodium hydroxide and dissolve by swirling.

17. Add two level teaspoons (approximately 10
grams) of glucose and dissolve by swirling.
Add 3-4 drops of methylene blue. Swirl the
mixture and stop. The liquid should appear blue.
Let the solution sit for a while and it should
become clear.

18. Give the flask a few quick shakes so that air
dissolves in the solution. If you are using a lid
check that it is on properly and take special care
not to spill any liquid.
The colour will change to blue.
This will fade back to a colourless liquid again
over a short period of time.

19. The more shaking, the longer the blue colour
will take to fade.
The process can be repeated for over 20 cycles,
you may have to allow more air in if you are
using a container with a lid. After some hours,
the solution will turn yellow and the colour
changes will fail to occur.

20. Precautions
Sodium hydroxide is a powerful base (the
opposite to an acid). Avoid contact with hands
and clothes and wash thoroughly in case of
contact.

21. BEFORE AFTER

23. TRANSFORMATION

24. • Redox reactions involve the transfer of electrons
from one substance to another.
• Reduction describes the uptake of an electron by
a molecule or atom. Oxidation describes the loss
of an electron by a molecule or atom. These two
terms go together, because in a chemical
reaction, one cannot occur without the other;
electrons lost by one compound must be gained
by another.

25. • The bottle contains sodium
hydroxide, glucose, water and an indicator
called methylene blue. Glucose is a reducing
agent that will reduce methylene blue to a
colourless form. Shaking the solution provides
oxygen which will re-oxidise the methylene blue
back to the blue form.
• You should also notice that once the mixture has
gone colourless, a blue zone remains close to the
surface. This is due to oxygen dissolving into the

26. • In first stage of the blue bottle experiment, the
methylene blue dye acts an oxidizing agent and
the glucose acts as a reducing agent. The
methylene blue oxidizes the glucose to gluconic
acid and the glucose reduces the methylene blue
to its colorless form. The result is a bottle of
colorless solution.

27. • When the bottle is shaken, the surface are of the
liquid temporarily increases, causing more
oxygen to dissolve in the ethanol. The additional
oxygen acts as an oxidizing agent and changes
methylene blue to its blue, oxidized form. The
result is a dramatic color change from colorless
to blue.

28. • When the shaking is stopped, the oxygen levels
in solution begin to drop. With less oxygen
present, the methylene blue once again is
reduced to its colorless form by the glucose, and
observers will see the color fade and disappear.
The color change can be repeated many times
simply by shaking the bottle to induce the blue
color and then allowing it to sit still in order to
make it disappear.

30. • Energy is stored and released through redox
reactions. Photosynthesis involves the reduction
of carbon dioxide into sugars and the oxidation
of water into molecular oxygen. The reverse
reaction, respiration, oxidises sugars to produce
carbon dioxide and water.

31. • Oxidation is part of daily life and can be useful
and annoying for people. Useful oxidizing
agents are bleaches and antiseptics. Not so
useful is the oxidising action of oxygen in the
air that can corrode metals. This is known as
rust when the metal is iron or tarnish when the
metal is copper. When exposed to oxygen most
metals will oxidize, although in some cases like
aluminium, the oxidised layer then prevents
further oxidation.