Molisch Test

MOLISCH TEST (Molisch), one of the reactions for carbohydrates, which with alpha-naphthol and concentrated sulfuric acid give a violet coloration. The reaction is based on the formation from the carbohydrate under the influence of strong H₂SO₄ of oxymethylfurfural, which gives a colored compound with naphthol. Glucose in the amount of 0.1 mg still gives a strongly positive M. t. The reaction is carried out as follows: 0.5 cm³ of the solution being tested is mixed with 1-2 drops of a 10% solution of pure alpha-naphthol in pure alcohol and carefully along the wall of the test tube 1 cm³ of concentrated chemically pure H₂SO₄ is added. At the boundary of the two liquids a violet ring is formed. Proteins also give a M. t., which is usually considered evidence of the presence of carbohydrate groups in the protein molecule. However, with high sensitivity of the M. t., it is difficult to exclude the possibility that a positive reaction results from the admixture of a foreign carbohydrate to the protein, all the more so since in the composition of the protein the carbohydrate group enters mostly in the form of glucosamine, which does not give the Molisch test.