264 Contributions towards [Oct. 



If the dry mass b2 dissolved in water, and filtered to separate a 

 small portion of undissolved black oxide, the liquid, when pro- 

 perly concentrated, deposites reddish crystals consisting of sul- 

 phate and muriate of manganese. If the whole mass be digested 

 in alcohol, and the filtered solution be evaporated, small crystals 

 are obtained, which readily deliquesce in the open air, and 

 which, when dissolved in water, yield a copious precipitate with 

 nitrate of silver. Hence they obviously consist of muriate of 

 manganese. The mother-ley from which these crystals have 

 separated is very acid, but neither crystallizes nor yields any 

 precipitate when treated with nitrate of silver ; but muriate of 

 baryles occasions a precipitate insoluble in acids. Hence the 

 uncombined acid is obviously the sulphuric. 



The theory of these appearances is obvious. The oxymuriatie 

 acid gives out oxygen to the protoxide contained in the sulphate 

 of manganese, which becomes in consequence insoluble, and 

 falls down in the state of black oxide. This portion is again 

 dissolved by the muriatic acid, and forms muriate of manganese/ 

 which is not decomposed by sulphuric acid, 



Triple Compound of Manganese, Ammonia, and Sulphuric 



* Acid. 



If we mix a solution of sulphate of manganese (not fully satu- 

 rated with the oxide) with ammonia to the point of complete sa- 

 turation, and evaporate the filtered solution according to the 

 method above described, we obtain rose-red, transparent, rhom- 

 boidal crystals, very much entangled in each other. They deli- 

 quesce in a moist atmosphere, and when treated with potash give 

 out ammonia, but in other respects exhibit the properties of 

 sulphate of manganese. Hence it follows that they consist of 

 ammonia, sulphuric acid, and protoxide of manganese. I have 

 not determined the proportion of the constituents of this salt. 



c. With Black Oxide. 



The peroxide reduced to the state of an impalpable powder is 

 likewise dissolved by sulphuric acid without the application of 

 heat. The solution, in which there is always an excess of acid, 

 has a very fine dark violet-blue colour. When it is diluted with 

 water the colour becomes lighter, and passes gradually into 

 crimson-red, and thence into blood-red. The solution is not. 

 altered by moderate evaporation. When a strong heat is applied 

 the solution becomes colourless, the oxide loses a portion of its 

 oxygen, and the whole assumes the properties of a solution of 

 common sulphate of manganese with an excess of acid. 



Tartaric acid likewise changes the peroxide into protoxide 

 when it is mixed with the solution, and a moderate degree of 



