German Hans Heinrich Landolt in 1892 for the first time cranked this experience, so he was called Landolt experience. Then the same experiment was nicknamed "the reaction of iodine hours." I will say that this is one of the most spectacular experiments. The solution was slowly becomes an amber color, then suddenly turns dark blue, then slowly regains colorless color; the process is repeated several times in a circle, eventually stopped on a dark blue color, and the liquid itself reeks of iodine. "
The reason is that during the first reaction produced by certain substances which, in turn, provoke the second reaction, and the process is repeated until exhaustion.
Source:
mirfactov.com/