334 M. Arfwed$on on the Decoinposition of [May, 



that in the latter experiment the sulphuret contained a smaller 

 admixture of oxide than in the former. 



3. A portion of the sulphuret of manganese prepared in the 

 second experiment was accurately mixed and fused with its 

 own weight of sulphur. 0-732 gr. of this product contained 

 0*031 of protosulphate of manganese, and 0-701 gr. of the 

 remaining quantity gave when burnt 0-619 gr. of brown oxide of 

 manganese. This quantity differs only by 0*004 gr. from the 

 calculated quantity of oxide which should have been obtained 

 from 0*701 Mn S s ; so that the sulphuret of manganese of this 

 experiment appears to have been free from protoxide. 



From these experiments it appears that when protocarbonate 

 of manganese is fused with sulphur in a close vessel, there is 

 always formed (together with a little protosulphate of manga- 

 nese) a sulphuret of manganese containing more or less oxide. 

 This is the substance which has been erroneously denominated 

 sulphuretted oxide of manganese ; and the best way to obtain a 

 sulphuret free from oxide is to fuse this substance a second time 

 with its own weight of sulphur. 



Native Sulphvret of Manganese, or Manganglanse, from 

 Nagyag, in Transylvania. 



In connexion with the preceding experiments, it seems of 

 importance to determine the constitution of sulphuretted man- 

 ganese prepared by nature. This mineral, according to the 

 analysis of Klaproth, is composed of 



Protoxide of manganese 82 



Sulphur 11 



Carbonic acid 5 



98* 



Klaproth concluded that the manganese was in the state of 

 protoxide, because he found that when protoxide of manganese 

 and sulphur were melted together, he obtained a compound similar 

 to the natural one as far as external characters were concerned. 

 But the insufficiency of such a reason, connected with the cir- 

 cumstance that the mineral, like the artificial sulphuret of manga- 

 nese, dissolves in acids with the evolution of sulphuretted 

 hydrogen gas, seems to furnish sufficient ground for suspecting 

 the accuracy of Klaproth's opinion. 



0*494 gr. of pulverized manganglanse were heated to redness 

 on a thin platinum plate, till they ceased to lose any more 

 weight. Native sulphuret of manganese parts more difficultly 

 with its sulphur than what is artificially prepared. On that 

 account the roasting must be several times repeated, because 

 the weight is diminished each time the process is repeated. The 



* Beitrage, iii. 42. 



