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How to recognize starch paste

Iodine can be replaced by potassium iodide or Lugol

One can imagine a situation in which toman is more containers with indistinguishable from each other colloidal solutions of starch, carboxymethylcellulose, pectin or agar. Remember the high-school chemistry.

One qualitative reactions and only a starch which gives a visible result, - a blue coloration by reaction with iodine.

Two other qualitative reactions just do not give the expected effect, characteristic of carbohydrates in general.

Accordingly, it is more logical and easier to use iodine.

You will need

  • Pharmacy iodine, water, starch, glass container, pan / saucepan



Prepare a separate glass container weak solution of iodine. It's enough to take a pharmaceutical iodine and dilute it with water.


Prepare starch paste - Colloidal starch solution in water. Take two teaspoons of starch, and a glass of cold water. A little bit of cold water (about one-third cup), mix in a pot of starch. The rest of the water boil. The mixture was stir well, turn starch milk. While stirring, add hot water to it and, while stirring, heat to heat up until the solution is clear. Cool it. This is the starch pasteThat glues paper as well, so it is often used, for example, for gluing wallpaper.


Put a little bit of iodine solution in the finished starch paste. In place of the solution of contact and pasteand a blue color will appear. If the concentration of iodine is very big, you get a color from purple to black.

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