Convection cells in a flask

“This amazing picture was taken during a recent practical session. It shows the end point of an iodine thiosulphate titration using starch indicator. After standing for some minutes, thermal convection currents in the flask caused the patterns. “

A colleague of mine had an interesting and unexpected addition to a Chemistry lesson – and two of the students were able to use their mobile phone cameras to capture this fleeting phenomena.

We think it is convection cells, the radiators in the lab are situated at the back of the cupboards – and heat comes from grilles at the back of each bench. The round-bottom flask has about 1cm of solution in it, and the precipitate is very fine particles ‘almost a colloid’ according to Dave C. Thanks to Dave C, Helen and Helite for the images.

The image was taken at an angle that makes the conical flask look like a milk bottle!

Comments are closed.