I52LJ end on the Composition of its Oxides, 51 



by these means tlie bisulphate of orotoxide and the vol- 

 phate of deutoxide are decomposed, and converted into sulphate 

 of protoxide. The solution, which of course could contain 

 neither barytes nor lead, whatever quantity of them there might 

 be in the ore, contains only the sulphates of manganese, iron, and 

 copper. In order to remove the two latter metals, I poured 

 successively into the solution of the manganese a solution ot 

 hydrosulphuret of ammonia, which first precipitates the copper 

 of a black colour, then the iron likewise black, and at last the 

 manganese of a white colour. When the colour of the precipi- 

 tate turns grey, I heat the liquor to the boiling point, and then 

 allow it to remain undisturbed for the purpose of trying it with 

 tests. 



The prussiate of potash is sufficient for that purpose, which 

 precipitates the salts of pure manganese of a white colour; the 

 shghtest trace of iron is directly shown by a blue colour, and 

 copper by red. 



The crystals of sulphate of manganese which I made use of for 

 the analysis were made in a different way to avoid the presence 

 of any alkali. Through the impure sulphuric solution of manga- 

 nese, I passed sulphuretted hydrogen to remove the copper, and 

 then concentrated it by evaporation until it became a very strong* 

 solution, which, however, did not crystalhze when cold. Spirit 

 of wine containing 80 to 90 per cent, of alcohol divides the 

 solution into two parts, the lower of which soon deposits crys- 

 tals of sulphate of manganese, often entirely free from iron, but 

 sometimes they contain a very slight portion of it. 



From the pure sulphate of manganese above-mentioned, I 

 obtained by carbonate of potash the carbonate of manganese, 

 which yielded me all the different oxides. 



I tried often to prepare the pure metal from one of these 

 oxides, but I never could succeed. I exposed it, with charcoal, 

 to the heat of a furnace, in the china manufactory in Copen- 

 hagen, where iron melts very easily ; but though the oxide waa 

 reduced, and the powder in the crucible dissolved in acids, with 

 the evolution of much hydrogen, it was not melted ; and whe- 

 ther it was metal, or an oxide containing less oxygen than the 

 protoxide, I was not able to ascertain. In another experiment, 

 when I exposed it to the heat of a large anchor-forge, I obtained 

 small grains. 



On the Protoxide. 



I found it rather difficult to obtain a protoxide completely free- 

 from all deutoxide. The usual way, by heating carbonate of 

 manganese in a retort full of carbonic acid, did not appear to 

 me very accurate, as I never was able to obtain a carbonate, of 

 protoxide of manganese completely free from all deutoxide. All 

 the solutions of protoxide, if they have been exposed fo th« air, 



D 2 



