The iodine turned blue-black on the saree because it likely contained starch, while it didn’t change color on the socks because they likely did not contain starch. Iodine reacts with starch to form a blue-black complex, which is a common test for starch.
Here’s why:
Starch and Iodine:
Starch is a complex carbohydrate composed of long chains of glucose molecules. When iodine is added to starch, it becomes trapped within the helical structure of the starch molecule, forming a complex. This complex absorbs light differently than the original iodine, resulting in the blue-black color.
Saree and Socks:
Sarees are often made from materials like silk or cotton, which can be treated with starch to give them a stiffer or more structured appearance. Socks, on the other hand, are typically made from synthetic fibers or cotton that may not be starched.
Why no color change on socks:
The absence of starch in the socks means that the iodine doesn’t have a substance to react with, so it remains its original brown or yellow color.