The volume of the oxygen evolved is considerably smaller than that obtained when the brown oxide was used. It is nevertheless larger than could have been evolved if all of the manganese had been left in the dioxide condition at the close of the experiment. This fact indicates that there was a slight reduction of the manganese dioxide after the disappearance of the color of the permanganate. That such a reduction of manganese dioxide does take place will be made apparent by a comparison of the results of the first two experiments in which the oxygen was measured soon after the color of permanganate had disappeared, with the results of the last two experiments in which the oxygen was determined after a longer interval. It will be noticed in this as in the series of experiments with the brown oxide that the rate of the evolution of oxygen liberated in flask No. II increases with the time of heating. The Amount of Nitric Acid neutralized. A few experiments were made to determine how much nitric acid is neutralized under the conditions which prevailed in the foregoing experiments. I. The flask contained brown oxide 150 m.g. N/10 nitric acid 6.98 c.c. and was heated for three hours in the water-bath. Acid neutralized = 4.51 c.c. = 64.60 percent. II. The flask contained brown oxide 150 m.g. N/10 nitric acid 6.98 c.c. and was heated for 50 minutes in the water-bath. Acid neutralized = 3.09 c.c. = 44.20 percent. III. The flask contained brown oxide 150 m.g. N/10 nitric acid 7.46 c.c. and was heated for fifty minutes in the water-bath. Acid neutralized = 3.16 c.c. = 42.30 percent. IV. The flask contained brown oxide 150 m.g. N/10 nitric acid 7.46 c.c. and was heated for 15 minutes in the water-bath. Acid neutralized 2.76 c.c. = 37.0 percent V. The flask contained brown oxide 150 m.g. potassium permanganate 20 c.c. = 112.48 m.g. N/10 nitric acid 6.98 c.c. (= 2 molecules for each molecule of KMnO₄) and was heated for three hours in the water-bath. Acid neutralized = 0.35 c.c. = 5.0 percent. VI. Repetition of No. V. Acid neutralized = 0.44 c.c. = 6.3 percent. VII. The flask contained brown oxide 150 m.g. potassium permanganate the same as in numbers V and VI and was heated for 15 minutes in the water-bath. Acid neutralized = 5.2 percent. VIII. Repetition of No. VII Acid neutralized = 4.0 percent IX. The flask contained black oxide 150 m.g. N/10 nitric acid 14.93 c.c. and was heated for two and one fourth hours in the water-bath. Acid neutralized = 4.87 c.c. = 32.46 percent. X. Repetition of No. IX. Acid neutralized = 38.10 percent. XI. The flask contained black oxide 150 m.g. potassium permanganate 20 c.c. = 177.71 m.g., N/10 nitric acid 22.39 c.c. (= 2 molecules for each molecule of KMnO₄) and was heated four and one half hours in the water bath. Acid neutralized = 100.00 percent.