Blue bottle experiment

Blue bottle reaction

The blue bottle experiment is a chemical reaction. An aqueous solution containing glucose, sodium hydroxide, methylene blue and some air is shaken in a closed bottle; it turns from colorless to blue and then decolorizes again after a while. With further shaking, the cycle can be repeated several times.[1] 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.[2]

Pattern formation

Pattern formation is when a solution containing NaOH, glucose, and dye is pour into an open petri dish which is open to atmosphere. This will result the solution to change its structure over a period of time. Structures arise from molecular transport through diffusion and chemical kinetics. Pattern formed in petri dish can be describe as mosaic pattern; web-like, dynamic spiral, branching, and lines connecting to each others. [3]

There are factors that can affect pattern formation. Change in pattern formation are not homogeneous and can caused by several factors. Different type of dye in solution will give the same pattern because of the bond's formation and the dynamic remain the same, this is because of that solution that has the same colour as the dye. Different amounts of dye can result in density change in the solution and this results in changing of convective motion. Different amount of dye can bring in different amounts of convention cell which are also formed by different amounts of glucose and oxidized product. This can result in an interesting spatial phenomena. Time can also affect pattern formation. As the time passed, one pattern gradually faded away. Spiral and branches started to disappear and eventually gone. [4]

A small group of researchers of the University of Glasgow named Pons, Batiste, Bees had came up with a small conclusion about pattern formation in methylene blue glucose system. They came up with a conclusive statement that has a similar pattern can be form in container with accessible oxygen. This result in surface tension effect don't require to produce the instability. Secondly, small holes was found in lid of container that oxygen can't access to resulting in a thin, blue, and lower amount of oxygen. Pattern length and time scale had been explored in one of their experiment due to the variation in viscosity and fluid depth. The experiment reveal that the wavelength is formed as pattern started to form quickly. Then wavelength or pattern can be maintained the same or decrease or maybe oscillate for a while.[5]

See also

References

  1. ↑ the blue bottle' reaction By Colin Baker Exhibition chemistry @ rsc.org
  2. ↑ 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
  3. ↑ Pattern Formation in the Methylene-Blue-Glucose System, Pons. A. J, Sague ́s. F, Bees. M. A, Graae Sørensen. P J. Phys. Chem. B 2000, 104 (10), 2251–2259 doi:10.1021/jp9935788
  4. ↑ The Blue Bottle Experiment and Pattern Formation in this System, Adamčíková. L`, Ševčík. P Zeitschrift für Naturforschung A 52a, 650-654 (1997) doi:10.1515/zna-1997-8-918
  5. ↑ Nonlinear chemoconvection in the methylene-blue–glucose system: Two-dimensional shallow layers, Pons. A. J, Batiste. O, Bees. M. A Physical Review E 78, 016316 2008 doi:10.1103/PhysRevE.78.016316

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