Blue Bottle Experiment

In the Blue Bottle Experiment, a solution of glucose, potassium hydroxide, and methylene blue alternates between colorless and blue when shaken.

1. Add 300 mL of distilled water to a 500 mL Erlenmeyer flask.
2. Dissolve 8 g of potassium hydroxide in the water.
3. Add 10 g of glucose (dextrose) and swirl until dissolved.
4. Add 6–8 drops of methylene blue indicator.
5. Allow the solution to rest until it becomes colorless.
6. Stopper the flask and shake gently once or twice. The solution should turn blue.
7. Let the solution sit until the blue fades back to colorless.
8. Repeat shaking to restore the blue color several times until the glucose is consumed.

Blue Bottle Equilibrium - North Carolina School of Science and Mathematics:

📄🎞️ Blue bottle - MEL Science: https://melscience.com/US-en/chemistry/experiments/blue-bottle-us/?srsltid=AfmBOoooZ5BHx5Tl9ufHBrt_Ulu0Dz2_7W-3fQqtMvthwNbHBwml2Wdl

📄 BLUE BOTTLE EXPERIMENT - QUT: https://cms.qut.edu.au/__data/assets/pdf_file/0014/24008/blue-bottle-experiment-teacher-worksheet.pdf

• Warm the solution slightly to observe the effect of temperature on reaction rate.
• Use different concentrations of glucose to see how long the color cycling lasts.

• Wear safety glasses to protect eyes.
• Potassium hydroxide is caustic and can cause severe burns—avoid skin and eye contact.
• Handle methylene blue with care, as it can stain skin and clothing.
• Dispose of chemicals according to institutional waste guidelines.

• What role does methylene blue play in this experiment? (It acts as a catalyst that cycles between oxidized and reduced forms.)
• Why does the solution turn blue when shaken? (Shaking dissolves oxygen, which oxidizes the reduced indicator back to its blue form.)
• Why does the color fade when the solution is left to stand? (Glucose reduces methylene blue to its colorless form in the absence of oxygen.)
• What eventually stops the color changes? (All the glucose becomes oxidized, or oxygen is depleted from the system.)
• How is this experiment an example of a reversible reaction? (The methylene blue cycles between oxidized and reduced states multiple times.)