What is a potassium iodide starch test?


Quick Answer

The potassium-iodide starch test utilizes test strips to detect levels of free iodine, chlorine and peroxides, or starches, in biological materials. Normally yellow-brown in color, the potassium-iodide solution turns deep blue when it encounters starch. Conversely, starch may also be used to detect free iodine.

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Full Answer

Iodine takes about 60 seconds to react, while chlorine and any peroxide react immediately. A reaction initially shows as a bluish hue that grows darker from amylose in the starch. Free iodine held physically inside the amylose coil forms a concentration of iodine that is easily visible. With a high concentration of starch, the strip goes from dark blue to purple.

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