Chemical oscillator

The earliest scientific evidence that such reactions can oscillate was met with extreme scepticism.

In 1899, W. Ostwald observed that the rate of chromium dissolution in acid periodically increased and decreased.

For a closed system at constant temperature and pressure, the thermodynamic requirement is that the Gibbs free energy must decrease continuously and not oscillate.

[3] A Belousov–Zhabotinsky reaction is one of several oscillating chemical systems, whose common element is the inclusion of bromine and an acid.

An essential aspect of the BZ reaction is its so-called "excitability"—under the influence of stimuli, patterns develop in what would otherwise be a perfectly quiescent medium.

This slowly fades to colorless and the process repeats, about ten times in the most popular formulation.