Redox and electrochemistry > colour
Acidified sodium (or potassium) bromate and bromide solutions are mixed, then propanedioic (malonic) acid, ferroin indicator and a surface active agent added. The mixture exhibits patterns of oscillation from red to blue
Bromate(V) ions are used to oxidise propane-1,3-dioic acid to carbon dioxide in the presence of manganese(II) ions as catalyst. The reaction mixture oscillates in colour between red-brown and colourless with an period of about 20 seconds.
An alkaline solution of glucose acts as a reducing agent and reduces added methylene blue from a blue to a colourless form. Shaking the solution raises the concentration of oxygen in the mixture and this oxidises the methylene blue back to its blue form. When the dissolved oxygen has been consumed, the methylene blue is slowly reduced back to its colourless form by the remaining glucose, and the cycle can be