182 M. E. Mitscherlich on 



This discrepancy, which amounts to somewhat more than 

 one percent., is caused by the difficulty of analyzing the 

 binoxide ; the experiment, however, clearly shows that the 

 powder examined was binoxide of manganese. 



In another experiment, 0*6525 gr. dried hydrous binoxide 

 of manganese gave 0-4735 gr. red oxide, which is equivalent 

 to 0'538 gr. binoxide. Consequently 0*1145 gr. water, 

 which contain 0'1009 gr. oxygen, are combined with 0'538 

 gr. binoxide of manganese, containing 0*194 oxygen. The 

 oxygen of the water, is therefore, to that of the binoxide of 

 manganese as 1 to 2. The binoxide of manganese does 

 not give off the last portion of its water till the oxygen 

 begins to be extricated. 



I have in vain tried to find a method of distinguishing 

 the sesquioxide and the binoxide of manganese from one 

 another, easier than by ignition. If the hydrated binoxide 

 be treated with a solution of sulphurous acid in water, the 

 greater part of it is converted into the sulphite of man- 

 ganese, but a portion, sometimes greater and sometimes 

 smaller, becomes sulphate of manganese. I have estimated 

 the quantity of both, the one as sulphite the other as sul- 

 phate of barytes, and from the quantity of each have calcu- 

 lated the quantity of oxygen supplied to the sulphurous acid. 

 By this method also, I have ascertained that the binoxide of 

 manganese formed by the decomposition of the manganic 

 and hypermanganic acids, is pure, containing no sesquioxide, 

 as the latter would have oxidized only half as niuch sul- 

 phurous acid. This method of examining the binoxide is still 

 more difficult than its estimation by ignition. It had already 

 been observed by Heeren, that sulphuric acid is formed 

 when the native binoxide is treated with sulphurous acid. 



The crystals of the manganate of potash have the same 

 secondary faces, and the same composition as the sulphate, 

 seleniate, and chromate of potash, and show even to the 

 most trifling minutiae the same modifications with respect 

 to the size of the faces. 



On account of the facility with which the manganate of 

 potash is decomposed, no other salts of manganic acid can 

 be made by means of it. Caustic soda, fused with binoxide 

 of manganese, yields manganate of soda, which, however, 

 is too soluble to be freed from the carbonated and caustic 

 soda by crystallization. Nitrate of barytes fused with 



