154 Generation of Sulphur in 



On examining the contents of each of these flasks, no- 

 peroxide of manganese was found, but large quantities of 

 sulphide of iron. The likeness in the red flakes to the cherty 

 particles of the bottom muds in the manganese districts of 

 the South Pacific, and of the kernels of some manganese nodules, 

 was very striking. It is not improbable that the first action 

 of the MnS on the Fe 2 O 3 may be accompanied by the formation 

 of mixed oxides of iron and manganese; but there is much 

 to be done in this direction in the strictly quantitative investiga- 

 tion of the interaction of the insoluble, but not inert, compounds 

 of this as well as of other groups of metals. 



Ferric Sulphate and Manganous Sulphide. Experiments 

 were now made, using the iron as a ferric salt in solution, 

 and for this purpose ferric sulphate was used. It was made 

 as nearly neutral as possible by addition of ammonia. The 

 MnS was, as before, suspended in distilled water. 



On adding ferric sulphate to excess of MnS, the formation 

 of FeS is immediate. 



On adding a large excess of Fe 2 (S0 4 ) 3 the FeS is decomposed, 

 there is formation of basic salt, and on dissolving it with 

 H 2 SO 4 the solution contains large quantities of ferrous sulphate. 



On experimenting with solution of ferrous sulphate it was 

 found that excess of MnS precipitates the iron completely 

 as FeS, acting exactly like an alkaline sulphide. 



The rationale, therefore, of the above reaction is very 

 simple. Thus 



Fe 2 (SO 4 ) 3 + MnS = 2FeSO 4 + MnSO 4 + S. . . (i) 

 and 2FeSO 4 + 2MnS = 2FeS + 2MnSO 4 (2). 



Therefore adding (i) and (2) we have 



Fe 2 (SO 4 ) 3 + 3MnS = 2FeS + aMnSO 4 + S . . . (3) 



and 2Fe 2 (SO 4 ) 3 + 2FeS = 6FeSO 4 + 2S (4), 



and 



(3) + (4) = 3Fe 2 (S0 4 ) 3 + 3MnS = 6FeSO 4 + 3 MnSO 4 + 38. . (5) 



or = Fe 2 (SO 4 ) 3 + MnS = 2FeSO 4 + MnSO 4 + S . . . (6), 



which is identical with (i) and by adding more MnS we get 



the conditions of equation (2), and so on, repeating the cycle. 



Hence, if we add MnS to excess of Fe 2 (SO 4 ) 3 , we should 



