A simple oscillating reaction

A close-up image of a Petri dish containing bromic acid, malonic acid and phenanthrolinehe; a colourful blue-purple pattern is visible as an Belousov-Zhabotinsky oscillating reaction takes place

Source: © Getty Images

Use this demonstration to illustrate an oscillating reaction as bromate ions oxidise malonic acid to carbon dioxide. Includes kit list and safety instructions.

In this experiment, students witness a clear example of an oscillating reaction, as bromate ions oxidise malonic acid to carbon dioxide in the presence of manganese(II) ions as a catalyst. The reaction mixture oscillates in colour between red-brown and colourless, with a period of about 20 seconds.

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