How is the iodine test for starch conducted?

The iodine test for starch is conducted by adding iodine solution to a sample and observing any colour change.

In more detail, the iodine test for starch is a common method used in laboratories to identify the presence of starch in various substances. The test is simple and straightforward, and it can be performed with basic lab equipment. The first step is to take a small sample of the substance you want to test. This could be a piece of food, a liquid, or even a swab from a surface.

Next, you add a few drops of iodine solution to the sample. Iodine solution is typically a mixture of iodine and potassium iodide in water, and it's often used as a disinfectant. It's important to note that the iodine solution should be added in a small amount, as too much can obscure the results of the test.

Once the iodine solution has been added, you need to observe the sample for any changes in colour. If the sample contains starch, the iodine will react with it and cause the sample to change colour. The typical colour change is from yellow-brown (the original colour of the iodine solution) to a dark blue or black. This colour change is due to the formation of a complex between iodine and starch.

It's important to remember that this test is not definitive. While a positive result (a colour change to blue-black) strongly suggests the presence of starch, a negative result (no colour change) does not necessarily mean that starch is absent. Other substances can interfere with the test and cause false negatives. Therefore, the iodine test for starch should be used as a preliminary test, and any positive results should be confirmed with additional testing.