Experiment - Carbon rod writing

Students use a carbon rod attached to a power supply to oxidise iodide, ‘writing’ brown iodine patterns onto a piece of filter paper that is wet with colourless potassium iodide solution.

This activity was modified from

Commons, C., Hogendoorn, B. (Eds) (1990). Demonstrations for Secondary School Chemistry, Chemistry Education Association, Melbourne, p 127-128 (Demonstration K9).