Blue Bottle    
 

Blue Bottle

Methylene blue is a redox indicator. It is blue in its oxidised form and colourless in the reduced form. It acts as a catalyst in the reaction of glucose with oxygen. Shaking aerates the mixture and in turn causes the indicator to turn from colouless to blue.

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For further information see Salters Advanced Chemistry, 2000, Activities and Assessment Pack, Second Edition, ISBN 0 435 631217