1822.] Native Carbonate of Manganese* 457- 



Or, 



Carbonate of manganese 0*905 



Carbonate of lime 0-095 



1-000 



This result may be considered as correct, because, supposing 

 pure carbonate of manganese to contain one proportion of car- 

 bonic acid, it does not differ more than 0*005 from that which it 

 really contains. 



The carbonate of manganese from Freyberg occurs abundantly 

 in a copper and lead mine. It is amorphous, lamellar, and the 

 laminse are slightly curved. Its colour is flesh-red, transiucid, 

 brittle, easily scratched and powdered. 



Besides oxide of manganese, it contains some oxide of iron, 

 lime, and magnesia. These four substances were separated by 

 the usual means, and the quantities of iron, lime, and magnesia, 

 carefully ascertained. 



To determine the quantities of manganese and carbonic acid, 

 a portion of the mineral was exposed to heat and air, in order to 

 peroxidize the metals, and afterwards it was strongly heated to 

 expel all the carbonic acid, and to convert the manganese to the 

 state of red oxide; the residuum weighed 0*655, the loss being 

 consequently 0*345. By deducting from the weight of the resi- 

 duum the sum of the weights of the hme, magnesia, and perox- 

 ide of iron, the weight of the red oxide of manganese is ascer- 

 tained, from which that of the protoxide is deduced. 



On the other hand, by adding to the loss of weight by calcina- 

 tion, the weight of the oxygen absorbed by the protoxides of 

 iron and manganese, the proportion of carbonic acid is deter- 

 mined. The results were : 



Protoxide of manganese 0*510 



Protoxide of iron 0*045 , 



Lime 0*050 



Magnesia 0*008 



Carbonic acid 0*387 



J -000 

 Or, 



Carbonate of manganese 0*822 



Carbonate of iron 0*073 



Carbonate of hme 0*089 



Carbonate of magnesia 0*016 



1*000 



This analysis agrees perfectly with the theoretical composition 

 of the carbonates of manganese, iron, lime, and magnesia. 



L is quite evident that these four carbonates are merely mixed, 

 but intimately so, in the minerals from Nagyac and Freyberg. 



