This test paper allows the quick and easy detection of strong oxidisers such as Nitrite and free Chlorine. Potassium iodide starch paper is also used to control diazotisation reactions.

• Nitrite: White to blue-violet
• Chlorine: white to blue-violet

Nitrite or free chlorine oxidise potassium iodide to form elemental Iodine which reacts with starch to a blue-violet complex.

Potassium iodide starch paper may be used by dipping it into the sample or by applying drops of the sample onto the paper. To detect gaseous oxidisers, the paper is moistened with distilled water and then exposed to the gas in question.