332 M. Arfwedson on the Decomposition of [May, 



quantity of Mn S 2 which, according to calculation, should be 



obtained from 100 parts of Mn + Mn S 2 ; for Mn + Mn S- : 

 2 Mn S 2 : : 100 : 109-98. 



The colour of oxisulphuret of manganese is somewhat a lighter 

 green than that of the protoxide. It remains unaltered though 

 exposed to the air; and thus is easily distinguished from the 

 protoxide, which, as is known, speedily absorbs oxygen, and 

 becomes brown. It is easily distinguishable likewise from the 

 sulphuret of manganese, which has a much darker green colour, 

 and which moreover, when long exposed to the air, gradually 

 becomes oxidized, and assumes a brown colour. 



The constituents of 100 parts of oxisulphuret of manganese 

 calculated from the data given above, are as follows : 



Manganese 70*26 



Sulphur 19-86 



Oxygen 9-88 



100-00 

 Or, 



Sulphuret of manganese 55 



Protoxide of manganese 45 



100 



Reduction of Protoxide of Manganese by Sulphuretted Hydrogen 



Gas. 



It was of importance after the preceding experiments to deter- 

 mine whether any other sulphuret besides Mn S' 2 could be formed 

 when protoxide of manganese is treated with sulphuretted 

 hydrogen gas. I prepared, therefore, a portion of protoxide of 

 manganese by reducing the oxide by means of hydrogen gas, 

 and after the weight of the protoxide had been determined with 

 the requisite precision, it was treated with sulphuretted hydrogen 

 gas so long as any water was formed. From 0-317 gr. protoxide 

 of manganese treated in this way, I obtained 0-392 gr. sulphuret 

 of manganese, or from 100 parts of the former 123*66 of the 



latter; but Mn : Mn S 2 : : 100 : 122-19. The small excess in 

 the experimental result proceeded doubtless from this cause, 

 that the protoxide could not be weighed with sufficient rapidity 

 to prevent it from absorbing a little oxygen from the air. 



I attempted afterwards to reduce protosulphate of manganese 

 by means of sulphuretted hydrogen gas. 0-899 of anhydrous 



salt gave 0*526 of sulphuret of manganese. "Now Mn S j : 

 Mn S 9 : : 0-899 : 0-523. From this it .seems to appear that 

 manganese in the dry way cannot combine with more than two 

 atoms of sulphur. 



