To determine if an unknown substance is starch, you can use an indicator known as iodine. Iodine is commonly employed in the laboratory to test for the presence of starch due to the characteristic color change that occurs when iodine interacts with starch molecules.
Here’s how you can perform the test:
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Prepare the sample: If the unknown substance is solid, dissolve a small amount in water to create a solution. If it’s already in liquid form, ensure it is well-mixed.
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Add iodine solution: Add a few drops of iodine solution (typically a dilute solution of iodine in potassium iodide) directly to the sample.
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Observe the color change: If starch is present in the sample, the iodine will react with the amylose component of starch, resulting in a color change. The solution will typically turn blue-black. If there is no starch present, the iodine will remain brown or reddish-brown.
Summary of the Indicator Test:
- Indicator Used: Iodine solution
- Positive Result: Blue-black color indicates the presence of starch.
- Negative Result: No color change or brownish color indicates the absence of starch.
This simple method is widely used in both educational laboratories and research settings to confirm the presence of starch in various samples.