This comes from Queensland Science 2, Working Scientifically, Detecting Ions, Experiment 1.5. The method is an alternative to the one in the book, which does not work:
Filter paper
Power pack
Bathroom tile (eg 15x15cm) covered with aluminium foil
Connecting leads and crocodile clips
0.5M potassium iodide
0.5M sodium thiosulfate
starch solution
phenolphthalein indicator.
Soak the filter paper in a mixture of 10ml potassium iodide, 5ml sodium thiosulfate, 5 drops starch solution, 3 drops phenolphthalein.
Connect 6V power pack, -ve to foil, +ve to filter paper. Draw on the filter paper with the nail.

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