of the Oxides of Manganese. 161 



Peroxide of Manganese. 



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To procure a pure peroxide of manganese, a solution of the 

 protonitrate was evaporated to dryness, and the heat continued 

 until the whole of the salt was converted into a uniform black 

 mass. It was then reduced to fine powder, carefully washed with 

 distilled water, and dried by exposure for several hours to a tem- 

 perature of 600 F. On heating a portion of this peroxide to 

 redness in a glass tube, a little moisture was expelled, which red- 

 dened litmus paper powerfully. Consequently the peroxide still 

 retained a little nitric or nitrous acid, which I found it impos- 

 sible to expel entirely, except by the employment of a tempera- 

 ture bordering on a commencing red heat. The peroxide, after 

 exposure to that degree of heat, was quite free from acid, but 

 still retained a trace of moisture. On exposure to a white heat 

 it lost only 10.82 per cent of oxygen, whereas had the peroxide 

 been pure, it should have yielded 12.122 per cent. It appears 

 therefore that the heat required to expel the last portions of the 

 nitric acid, decomposes some of the oxide itself; and this cir- 

 cumstance induced me not to rely on the analysis of the artifi- 

 cial peroxide of manganese. 



From my examination of the native peroxide of manganese, I 

 conclude with all other chemists who have of late years studied 

 the oxides of manganese, that it contains twice as much oxygen 

 as the protoxide. It is accordingly composed of 28 parts or one 

 equivalent of manganese, and 16 parts or two equivalents of 

 oxygen ; and in being converted by a white heat into the red 

 oxide, it should yield 12.122 per cent of oxygen gas. 



Sulphuric acid acts very feebly on the peroxide of manganese. 

 At first I could observe no action at all ; but on employing a 

 considerable quantity of the oxide, and agitating the mixture 

 frequently, the acid after an interval of two or three days ac- 



VOL. XI. PART I. X 



