1824.] the Metallic Sulphates by Hydrogen Gas. 333 



Examination of the Substance formed when Protocarbonate of 

 Manganese is fused in a close Vessel with Sulphur. 



1 . Protocarbonate of manganese was intimately mixed with 

 nearly twice its weight of washed flowers of sulphur. The mix- 

 ture was put into a small retort blown at the enameller's lamp, 

 which was afterwards slowly raised to a red heat. When no 

 more sulphurous acid was exhaled, and when the superfluous 

 sulphur had been volatilized and collected in the beak of the 

 retort, the mouth of the retort was stopped with a cork, and the 

 fire withdrawn. On cooling, the matter contained in the belly 

 of the vessel was taken out. It had the light-green colour of 

 oxisulphuret of manganese. It dissolved in muriatic acid with 

 the evolution of sulphuretted hydrogen gas ; but the solution 

 was considerably affected by muriate of barytes. 0418gr. of it 

 left after burning 0-392 gr. of brown oxide of manganese. 

 Another portion, weighing 0*710 gr. was dissolved in muriatic 

 acid, and precipitated by muriate of barytes. There were 

 obtained 0-039 gr. of sulphate of barytes, equivalent to 0-026 

 protosulphate of manganese ; consequently the abovementioned 

 0-418 gr. of sulphuretted manganese contained 0-015 protosul- 

 phate of manganese, and the remaining 0*403 had given 0*377 

 of brown oxide.* 0-403 Mn + Mn S 2 would have given 0*388 

 brown oxide, and the same quantity of Mn S- is proportional to 

 0-354 brown oxide ; consequently the body under examination 



seems to be a mixture of Mn S- with a smaller quantity of Mn 



than in the compound Mn -f- Mn S' J . 



2. It was probable that the imperfect conversion of the proto- 

 carbonate of" manganese into Mn S a in this experiment, was 

 owing to the process having been conducted too rapidly; so 

 that the sulphur was distilled away before it had time to decom- 

 pose all the Mn. A new portion of protocarbonate of manga- 

 nese and sulphur was, therefore, mixed together, and exposed to 

 a heat just sufficient to keep the sulphur in the state of fusion. 

 When in consequence of continuing this heat for several hours 

 it was supposed that the decomposition might be completed, the 

 heat was augmented so as to drive off the excess of sulphur, and 

 the retort was corked and allowed to cool. In the same manner 

 as in the former experiment, it was found that 0-922 gr. of the 

 sulphuret of manganese now formed contained 0-036 of proto- 

 sulphate of manganese. The remaining - 886 left when burnt 

 0'787 of brown oxide of manganese. 0*886 Mn S' J are propor- 

 tional to 0*778 brown .oxide of manganese. Hence it appears 



* Tliis is agreeable to an observation already made, that no protosulphate of manga- 

 new in formed when sulphuretted msnganeie is burnt. 



