328 On the Oxide of Manganese ofKaygtg, 



Reflections. 



M. Klaproth justly regards the manganese in the mineral 

 of which we are speaking as oxidated at the minimum, and 

 he has recourse at the same time to the decomposition of 

 water in order to explain the disengagement of sulphuretted 

 hydrogen gas which takes place during the solution of the 

 mineral in the acids ; but this philosopher neither tells us 

 how or wherefore water is decomposed iri this operation. 

 The manganese cannot be the cause of it, since it is already 

 united to oxygen, and because it is discovered In the acids 

 which have dissolved it m the same state m which it existed 

 in the fossil, that is to say, at the mn^amum. The water, 

 then, could not have been decomposed but by the sulphur. 

 But how can we comprehend this effect while the nitric acid 

 is present ? If, however, it is the sulphur which decomposes 

 the water, and which gives birth to the sulphuretted hydro- 

 gen, I should have found sulphuric acid in the nitric solution 

 of the mineral. In order to ascertain it, I dissolved in the 

 cold a certain quantity of the same sulphuret of manganese 

 in weak nitric acid, in order that it might not burn the sul- 

 phur. The phaenoniena were the same as before ; and the 

 filtered solution gave, in fact, by means of the muriate of 

 barytes, a precipitate which was a true sulphate of that base. 



This experiment, then, seemed to demonstrate, that sul- 

 phur united to oxide of manganese has the power of decom- 

 posing water by combining with its oxygen, and thus sets 

 its hydrogen at liberty, which unites with another portion 

 of sulphur. This fact is the more worthy of the attention 

 of chemists, that, to my knowledge, this is the first time 

 that it has been observed, and that in every case where me- 

 tallic sulphurets or sulphuretted oxides have been decom- 

 posed by the strong or weak nitric acid, it has been always 

 the latter which has been decomposed, and nitrous gas, or 

 modifications of it, constantly obtained, and never sulphu- 

 retted hydrogen gas : this is quite conformable to the laws 

 of chemical affinity. It is true, that there are metals which 

 decompose water at the same time with nitric acid j but 

 hydrogen ncvtr makes its appearance: it unites with the 

 azote of the nitric acid and forms ammonia. 



The 



