Molisch's test is a sensitive chemical test, named after Austrian botanist Hans Molisch, for the presence of carbohydrates, based on the dehydration of the carbohydrate by sulfuric acid or hydrochloric acid to produce an aldehyde, which condenses with two molecules of a phenol (usually $\alpha$-naphthol, though other phenols such as resorcinol and thymol also give colored products), resulting in a violet ring.