1813.] a Chemical Knowledge of Manganese. 181 



nearly with the result of the first experiment, according to 

 which 100 grains of carbonate of manganese contain 3-1-25 

 grains of carbonic acid. 



One hundred grains of the salt are composed of the follow- 

 ing constituents : — 



Protoxide of manganese 55'84 



Water 10*00 



Carbonic acid 34-16 



100-00 



The greenish grey oxide thus obtained dissolves in acids with- 

 out the extrication of any gas, and the same compound is ob- 

 tained as would have been got by the solution of the carbonate 

 in the same acid. Hence it is to be looked upon as the real 

 base of the salt; and the white powder, which appears when 

 manganese is precipitated by an alkali, must be considered as 

 a hydrate, or an oxide still combined with a portion of acid. 



V. Action of Sulphuric Acid on Manganese. 



(A.) On the metal. — The action of concentrated sulphuric 

 acid upon manganese in the metallic state is very inconsiderable. 

 It produces some heat, and a small portion of the metal is dis- 

 solved. Several chemists, it is true, are of opinion that the so- 

 lution takes place very readily ; but I conclude, upon very good 

 grounds, that the regulus which they employed was not quite in 

 the metallic state, but contained some oxygen combined with it. 



When the acid is diluted with water, heat is evolved, and 

 hydrogen gas disengaged, which has a very peculiar smell, si- 

 milar to that of asafcetida. This smell is probably owing to a 

 portion of the metal being carried off in solution in the gas. 

 During the solution the liquid assumes a green colour, which 

 disappears when the acid ceases to act upon the metal. This 

 appearance probably depends upon the formation of green oxide, 

 as when carbonic acid acts upon the metal. 



The concentrated solution has a light rose- red colour; and 

 when it is diluted with water, the colour becomes insensible, 

 have never been able to procure colourless crystals from this 

 colourless solution. Indeed, as the metal which is oxydated a» 

 the expense of the water gives at first a coloured liquid, it is not 

 reasonable to expect colourless crystals of sulphate of manganese. 



190 grains of concentrated sulphuric acid, of the spccifi» 

 gravity T860, required for neutralization 100^ grains of metallic 

 manganese. The filtered solution (which left •? grains of black, 

 brilliant, minutely divided charcoal,) gave, when decomposed 



