On the Oxide of Manganese of Nay gag. 327 



place during the solution of manganese in the nitric acid, 

 fn spite of the discnsraQicnicnt, says he, of a consiilerable 

 enough quantity of sulphuretted hydrogen gas during the 

 , ^solution of this mineral, it appears to me that it would be 

 an error to believe that this gas exists ready formed in the 

 mineral or in any of thoue which yield it by the humid way, 

 and to reaard it as one of their constituent parts. There is 

 no doubt that it is formed bv the decomposition of water, 

 since by calcination we obtain nothing else but carbonic 

 acid gas. By synthesis, the probability that no hydrogen 

 enters into the coml)ination of sulphur with the oxide of 

 manganese acquires still more force ; and yet this combina- 

 tion yields sulphuretted hydrogen gas with the acids. 



In order to know if the nitric acid is not decomposed 

 during the solution of sulphuret of manganese, as happens 

 with almost all the metals which have a great affinity for 

 oxygen, or, if water alone, by yielding its oxygen to one of 

 the elements of this mineral, does not give birth to this hydro- 

 gen gas, we dissolved a certain quantity of sulphuretted man- 

 ganese in weak nitric acid ; we concentrated the solution, 

 and distilled it in a retort with caustic potash : but the pro- 

 duce not having given anv sign of the presence of ammonia, 

 we concluded from this that the nitric acid is not decomposed 

 in this operation. In order to have the just quantity of oxide 

 of manganese at the minimum, we calcined in a retort. 7*4 

 grammes of carbonate of this metal prepared from a solution 

 of five grammes, and we obtained an oxide almost white, 

 which, weighed while warm, yielded 4* 25 grammes, which 

 was at the rate of 85 in the hundred. 



Let us actually admit a loss of two parts : we shall then 



have 13 parts of sulphur; and as the loss can scarcely be 



any thing else than sulphur, the quantities will stand thus : 



Manganese at the minimum - 85 



Sulphur - - - - 15 



100* 



• There is also in this mineral a sm.ill qiiantitv of iron nnil arsenic, which 

 has been discovered nrnong the sulphur wliich remains after its solution ia 

 weak nitric acid; but lhc5c- ^ubstanres appear to be accidental. 



X 1 Rejlections, 



