113. Луголова реакција

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Only polysaccharides that are, at least partially, soluble in water will react with iodine. Cellulose, which is insoluble in water, does not give a positive test with an iodine solution. This reaction is based on the formation of a colored complex of the polysaccharide with iodine. The reaction is also known as the Lugol’s test.

In the test tubes containing solutions of carbohydrates, several drops of aqueous solution of iodine are added. Upon contact of this solution with polysaccharides (such as starch and amylose), a dark blue adduct is formed. Upon heating, the blue color disappears as a result of disrupting the complex, causing the iodide (triiodide ions) to “come out” from the cavities formed by the monosaccharide units. Upon cooling, the blue color reappears.

The experiment was performed by Prof. PhD Miha Bukleski. The planning of the experiment also included the Prof. Emeritus PhD Vladimir Petruševski, Prof. PhD Marina Stojanovska and the student Mihail Trajkov, Department of Chemistry, FNSM, Ss. Cyril and Methodius University, Skopje, Macedonia.

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Deni Ingilizovski

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