Science Trick: Blue Bottle

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On shaking: it is BLUE!. . . . On standing it is COLORLESS! Here is why this happens…

WHY DOES THE COLOR CHANGE ??

What is in the solution?

  • Sodium hydroxide – makes the solution basic
  • Glucose acts as a reducing agent (loses electron)
  • Methylene blue – acts as an indicator for the reaction

 

What is happening?

Glucose is a reducing agent and in basic solution will reduce methylene blue to a colourless form.

Shaking the solution admits oxygen which will re-oxidise the methylene blue back to the blue form.