An electrochemically induced oscillatory instability

We report current oscillations during the potentiostatic oxidation of iodid e in aqueous solution. The oscillations become visible as columns of descen ding liquid with periodic structure colored by iodine (or iodine-starch com plex). They can be attributed to a periodically varying flow of solution in front of the electrode due to a density gradient. The instability is expla ined using a qualitative model with a threshold function for the onset of t he flow.