Six month later (April 20, 1893) an analysis of the same material showed a ratio of manganese to available oxygen of 1.300 : 1.000 This result was confirmed Mʳ Walker who made repeated analyses of the substance at the same time. Another sample of manganese oxide was prepared in the same manner as that used in the previous experiments and placed under water. An analysis made after Eight days gave a ratio of Mn : available O = 1.013 : 1.000 Twenty ” ” ” ” ” ” ” ” = 1.037 : 1.000 Forty three ” ” ” ” ” ” ” ” = 1.040 : 1.000 The results here recorded clearly indicate that the brown oxide of manganese which is prepared by the reduction of potassium permanganate by manganese sulphate undergoes a spontaneous decomposition involving a loss of oxygen. This loss of oxygen or the effect of varying conditions upon this decomposition of manganese dioxide is now being investigated by Mʳ Walker of this laboratory. The Effect of Varying Quantities of Manganese Oxide on Potassium Permanganate. The following experiments were made for the purpose of determining the effect of varying quantities of manganese oxide on the time required for the reduction of potassium permanganate. A. In the presence of nitric acid. The ratio of manganese to available oxygen in the material used for these experiments was determined and found to be 1.018 : 1.000 The experiments were conducted after the same manner as those previously described. Different portions of the manganese oxide were weighed out and treated in the flasks used in the previous experiments with the quantities of permanganate which were found by calculation to have the desired molecular ratios to the oxide. A quantity of N/10 nitric acid equivalent to the potassium of the potassium permanganate was added. The flasks were then immersed in the bath of boiling water and the time required for the disappearance of the permanganate color noted. The ratios of the oxide to the permanganate and the times required for the reduction of the latter are embodied in the following table. Molecular Ratio } Oxide to KMnO₄ } 1:1 2:1 3:1 4:1 5:1 6:1 7:1 Time of decolorization in minutes 1 ” 120 68 2 ” 110 65 3 ” 150 65 4 ” 150 80 5 ” 120 75 6 ” 120 75 7 ” 175(?) 78 53 8 ” 160 79 54 9 ” 145 41 30 10 ” 120 50 36 11 ” ? 47 32 12 ” 110 37 30 13 ” 64 [10]{20(?) {20(?) 14 ” 72 5(?) 5(?) 15 ” 85 5(?) 5(?)