Chemical clock

In an iodine clock reaction, colour changes after a time delay.

A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount.^[1] In cases where one of the reagents has a visible color, crossing a concentration threshold can lead to an abrupt color change after a reproducible time lapse.

^ Wright, Stephen W. (2002-01-01). "Tick Tock, a Vitamin C Clock". Journal of Chemical Education. 79 (1): 40A. doi:10.1021/ed079p40.

[1] Wright, Stephen W. (2002-01-01). "Tick Tock, a Vitamin C Clock". Journal of Chemical Education. 79 (1): 40A. doi:10.1021/ed079p40.

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