The Briggs-Rauscher oscillating reaction is one of the very few oscillating reactions that we know of. Throughout the reaction, the concentration of iodide (I-) goes up and down, and this causes a swap between 2 processes. The the concentration is high, the process that consumes iodide is favored. When it is low, the process that produces it is favored. This causes a constant fluctuation of iodide. As the iodide increases, it forms I2 which is yellow, then the I2 eventually combines with I- t