Mucic Acid Test for Galactose
Oxidation of most monosaccharides by nitric acid yields soluble dicarboxylic acids. However, oxidation of galactose yields an insoluble mucic acid. Lactose will also yield a mucic acid, due to hydrolysis of the glycosidic linkage between its glucose and galactose subunits.
Method
Add 1 ml of concentrated nitric acid to 5 ml of the solution to be tested and mix well. Heat on a boiling water bath until the volume of the solution is reduced to about 1 ml. Remove the mixture from the water bath and let it cool at room temperature overnight. The presence of insoluble crystals in the bottom of the tube indicates the presence of mucic acid.
Method
Add 1 ml of concentrated nitric acid to 5 ml of the solution to be tested and mix well. Heat on a boiling water bath until the volume of the solution is reduced to about 1 ml. Remove the mixture from the water bath and let it cool at room temperature overnight. The presence of insoluble crystals in the bottom of the tube indicates the presence of mucic acid.
CAUTION: PERFORM THE REACTION UNDER A FUME HOOD.
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