132 Decomposition of Iron Pyrites. 



mass was converted into a white powder of styptic taste, and this 

 powder began to become yellow at the extremities. Seen under- 

 the microscope, it presented a mass full of little cracks, filled 

 with a white effloresced salt, in which the interstices appeared 

 to consist of white pyrite, intact and more or less crystalline." 

 A portion of this powder was digested in water, and the solution, 

 separated from the insoluble residue, yielded, on addition of bar- 

 ium chloride, and then, after filtration, of ammonia to the fil- 

 trate : — 



Atomic Ratio. 

 Barium sulphate 2.08 grams ^ j Sulphur. .0.279 .87 1 



>• Containing \ 

 Ferric oxide... .0.68 " ) ( Iron .... 0.476 .85 1 



.755 



It was tlius found that the solution contained neutral ferrous 

 sulphate, Fe S 0^ -|- "^ «^» equivalent in amount to 0.755 gram 

 of iron protosulphide, Fe S. The residue insoluble in water, 

 apparently undecomposed white ]>yrite, {imounted to 4.653 

 grams, i. e., over six times as much ns the effloresced part. To 

 determine whether it included any separated sulphur, a part ot' 

 it was dissolved in nitro-hydrochloric acid, and analysed with 

 the following results : 



Atomic Ratio. 



Barium sulphate 8.82 j (Sulphur.. .524 1.64 2 



- Containing < 

 Ferric cxide 9.64 ) i Iron 448 .80 1 



'i'he insoluble i)art was thus found to consist of iron disul- 

 ])hide, Fe b\ "Since therefore the effloresced part was a basic 

 sulphate of protoxide which did not contain acid in excess, and 

 since there were no traces of sulphur separated during the efflo- 

 rescence, it is evident that the effloresced part has consisted of 

 protosulphide of iron, which has not yet been found in an iso- 

 lated condition in the mineral kingdom, and that the remainder, 

 Avhich was not subject to efflorescence, has consisted of the di- 

 sul|)hide. 'Jlie efflorescent pyrite cannot then be anything else 

 but particles of deuto-sul])hide, more or less well crystallized, 

 cemented together by particles much less numerous of i)roto- 

 sulphide, which are changed little by little, at the expense of 



