Manganic and Hypermanganic Acids, ^c. 333 



of silver must be washed by decantation, and if any of it 

 get mixed with the solution, it must be allowed to sink to 

 the bottom, for we cannot, as has already been mentioned, 

 filter any of these compounds ; we may, in this manner, 

 obtain compounds of hypermanganic acid, which is a very 

 powerful acid, with all the bases, except oxide of lead, pro- 

 toxide of manganese, and protoxide of iron ; but these bases 

 deprive it of its oxygen, and become more highly oxidized. 



Most of the salts of hypermanganic acid are very soluble 

 in water, and deliquescent. Such, for example, are the 

 hypermanganates of soda, lime, strontian, magnesia, zinc, 

 copper, and many others. The hypermanganates of am- 

 nionia, potash, lithia, and barytes are the only salts which 

 can be obtained in good and measurable crystals ; which I 

 shall immediately notice. 



If the hypermanganate of barytes be dissolved in water, 

 and a sufficient quantity of sulphuric acid be added to pre- 

 cipitate the barytes, we obtain free hypermanganic acid in 

 solution in water. The solution has a deep red colour 

 similar to that of the salts. 



It being summer when these experiments were made, I 

 could not succeed in concentrating the hypermanganic acid. 

 It is decomposed, though very slowly, even at the common 

 temperature of the air, and with great rapidity at a tem- 

 perature from 86° to 104°, binoxide of manganese being 

 precipitated, and oxygen making its escape. It is, as 

 follows from what has already been said, not volatile. 



This acid excels even the deutoxide of hydrogen in the 

 facility with which it gives off oxygen. The different 

 vegetable and animal pigments are immediately bleached 

 by it. The salts have also the same effect, although in a 

 less degree. 



Hypermanganate of ammonia, is not liable to decompo- 

 sition, but may be dissolved and evaporated to dryness. 

 If, however, an excess of ammonia be added to any salt of 

 hypermanganic acid, azote is immediately extricated, the 

 ammonia and the acid being decomposed. I tried to deter- 

 mine the composition of the acid from the quantity of azote 

 extricated, but I could not succeed, because there is also pro- 

 duced by the decomposition a compound of oxygen and azote. 



What has previously been considered as manganic acid, 

 was either hypermanganate of potash or of barytes. 



