Blue bottle (chemical reaction)
The blue bottle experiment 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 decolorizes again after a while. After shaking again the blue color returns and this cycle can be repeated several times. This experiment is a classic chemistry demonstration and can be used in laboratory courses as a general chemistry experiment. The reaction will work with other reducing sugars besides glucose and also with other reducing dyes.
The aqueous solution in the classical reaction contains glucose, sodium hydroxide and methylene blue. In the first step the enolate of glucose is formed. The next step is a redox reaction of the enolate with methylene blue. The glucose is oxidized to gluconic acid which, in alkaline solution is in the sodium gluconate form. Methylene blue is reduced to colorless leucomethylene blue.
If there is enough available oxygen, leucomethylene blue is then re-oxidized to methylene blue and the blue color of the solution is restored. The availability of oxygen is increased by shaking the solution. When the solution comes to rest, glucose reduction of the redox dye again takes the upper hand and the color of the solution disappears. The reaction is first order in glucose, methylene blue and hydroxide ion and zero-order in oxygen.
Other glucose oxidation products besides sodium gluconate that are reported are D-arabino-hexos-2-ulose (glucosone), the anion of D-arabinonate after splitting of a formate anion and finally arabinonic acid.
- the blue bottle' reaction By Colin Baker Exhibition chemistry @ rsc.org
- What Is Happening When the Blue Bottle Bleaches: An Investigation of the Methylene Blue-Catalyzed Air Oxidation of Glucose, Laurens Anderson, Stacy M. Wittkopp, Christopher J. Painter, Jessica J. Liegel, Rodney Schreiner, Jerry A. Bell, and Bassam Z. Shakhashiri Journal of Chemical Education 2012 89 (11), 1425-1431 doi:10.1021/ed200511d