Manganic and Hypermanganic Acids, Sfc, 179 



is particularly interesting in the elucidation of the con- 

 nexion of the crystalline shape of bodies with their composi- 

 tion, induced me to investigate more closely these acids and 

 their compounds. 



I. — On the action of Potash on the Binoxide of Manganese. 



When equal parts of potash and binoxide of manganese 

 are ignited together, and the ignited mass treated with 

 water, a green solution is obtained, which contains in solu- 

 tion, carbonate of potash, caustic potash, and a compound 

 of potash with manganese in a higher degree of oxidation, 

 while a brown powder remains undissolved. Oxygen is 

 absorbed when the mass is ignited in contact with the air, 

 as Edwards and Chevillot have already shewn. But the 

 green compound may be obtained equally well, when the 

 binoxide of manganese is ignited with potash in a retort 

 shut up from the air. Thus 10 grammes of binoxide of 

 manganese, heated with potash without the access of air, 

 and treated with water, gave a solution, which, when the 

 acid was decomposed, and the manganese precipitated and 

 ignited, yielded 1 gramme of the red oxide (oxidum man- 

 ganeso-manganesicum.) 



In this case, the higher degree of oxidation of the man- 

 ganese is produced in the same manner in which the brown 

 oxide of lead is formed from red lead, when the latter is 

 treated with nitric acid, and the brown residue which is 

 left, when the green compound is dissolved, consists of 

 hydrated sesqui and binoxides of manganese, but whether 

 mixed or chemically combined, I cannot venture to decide. 

 The manganic acid is formed by a part of the binoxide 

 giving up a portion of its oxygen to the remainder, by which 

 it is changed to sesquioxide, but the quantity of manganic 

 acid formed, shows that a portion of the binoxide remains 

 undecomposed. 



If we pour off the deep green solution, after allowing the 



brown insoluble portion to subside, and allow it to evaporate 



over sulphuric acid, under the exhausted receiver of an air 



mmp, we obtain beautiful pure crystals of a green colour, 



lixed with abundance of crystals of hydrate and carbonate 



[of potash. These crystals must belaid on porous tile or 



slay, which absorbs the moisture without producing decom- 



N 2 



