ifi Dr, Forchhaminer on pur€ Salli of Manganese, [Jan. 



same circumstances, is converted into peroxide without any 

 visible fire. I believe the single circumstance that the brown 

 deutoxide is the result of combustion without the interference of 

 any other substance is sufl&cient to prove it to be a real oxide, 

 and not a compound of two different oxides. It would be suffi- 

 cient in ray opmion even if the quantity of oxygen found in thia 

 deutoxide dia not at all agree with that of any of the other 

 oxides. I shall prove, however, that it does agTee. 



The quantity of oxygen in the different oxides of manganese 

 has generally been ascertained by synthesis, and the results 

 have been very different indeed. 1 tried the analytical method, 

 and at least found the results consistent with each other, though 

 differing from those of other chemists. I have already described 

 the manner in which I conducted the experiment with bisulphate 

 of potash ; I shall, therefore, here only mention the result. 



Two grammes of brown deutoxide gave me a bulk of oxygen, 

 which, reduced to the mean temperature and pressure of air, is 

 equal to 5-3243 French cubic inches of oxygen, whose weight i& 

 Q'1513I66Q3 gramme, and 100 parts of deutoxide consist of 



Oxygen 7-5658 



Protoxide of manganese .,....,... 92*4342 



100-0000 



92*4342 parts of protoxide contain 70^403 parts of metal and 

 22-0312 parts of oxygen; and it is obvious that 22*0312 bears 

 very near the same proportion to (22*0312 -f 7*5658) = 29*597 

 as 3 : 4, which expresses the relative quantities of oxygen in the 

 rotoxide and deutoxide. 



The composition of the deutoxide is : 



P 



Oxygen 29*597 



Manganese , 70*403 



100*000 



One hundred parts of manganese combine with 42*040 parts 

 pf oxygen in order to form deutoxide. 



On the Peroxide, 

 "When the deutoxide of manganese is boiled with pure weak 

 nitric acid, a part of the oxygen is accumulated in one part of 

 the manganese, while the rest reduced to protoxide is dissolved. 

 The peroxide thus obtained is black ; it is insoluble in acids and 

 alkalies. Acids have no effect whatsoever on it, unless they are 

 capable of depriving it of a part of its oxygen. Alkalies, when 

 heated sliditly with it, accumulate the oxygen in one part, and 

 dissolve the manganeseous acid thus formed ; while the other 

 part reduced to deutoxide remains undissolved. This artificial 

 peroxide is a conductor of electricitv, and acts in a galvar^ic 



