Tuesday, January 10, 2012

Seliwanoff's Test

Seliwanoff's reagent contains resorcinol in 6 M hydrochloric acid. Hexoses undergo dehydration when heated in this reagent to form hydroxymethylfurfural, that condenses with resorcinol to give a red product. Ketohexoses (such as fructose) and disaccharides containing a ketohexose (such as sucrose) form a cherry-red condensation product. Other sugars may produce yellow to faint pink colors.

Empty, wash and rinse the test tubes from part B and make sure you have sufficient water in your boiling water bath.

Caution: Seliwanoff’s reagent is caustic, rinse thoroughly with water if you get this solution on your skin or clothing.

Add about 3 mL of Seliwanoff's reagent to each labeled test tube.

Add 1 drop of the respective sugar solution and 1 drop of water blank to the appropriate test tubes as described in part A-1 above and mix well.

Place all the test tubes in the boiling water bath at the same time and heat for 3 min after the water begins to boil again.

Record observations on the report sheet.

What conclusions can you make about your unknown now?

Discard these solutions in the sink and rinse with plenty of water.


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