A Modification of the Carbazole Reaction of Hexuronic Acids for the Study of Polyuronides”

In a previous report a specific color reaction of hexuronic acids with carbazole and sulfuric acid was described (1). In this reaction glucuronic and galacturonic acids, in free as well as in combined form in polyuronides, reacted with almost equal intensity. By decreasing the concentration of the acid and the temperature and time of heating, a modification of the carbazole reaction was obtained in which the intensity of the color depends not only on the structure of individual hexuronic acids but also on specific linkages in polyuronides. The present report deals with this modification. It will be referred to as the reaction at 60” to distinguish it from the first modification, the reaction at 100”.