Color reactions of the keturonic acids have recently become of importance to biology and medicine. In previous papers we have shown that a series of these acids can be prepared from carbohydrates by oxidation of their aqueous solutions with bromine.1, 2 The solutions of the keturonic acids used in the experiments reported here were prepared as follows:1% solutions of pure carbohydrates were placed in glass-stoppered flasks together with enough bromine to provide a small excess of liquid bromine throughout the experiments. These mixtures were kept in the dark for 42 days at 25 °C. They were then aerated with washed air (and at times with carbon dioxide) to remove the excess bromine and then neutralized with potassium hydroxide to pH 7, using a spot plate. The color tests were applied to aliquots, with the results given in Table I.In the ferric chloride test of Fenton and Jones2 we added one drop of 10% ferric chloride solution and 3 drops of 10% potassium hydroxide solution to 5 cc. of neutral sugar soluti...