86 Chemical Examination of Arsenical Pyrites. 



Perhaps we may view it as a compound of, 



1 atom disulphuret of iron, _ _ - - 9 



1 atom disulphuret of arsenic, - - ' - - 11*5 



20-5 



This at least accords with the analysis. The specific 

 gravity of this mineral indicates a considerable condensation 

 in the constituents. The mean specific gravity of 3-5 iron^ 

 4*75 arsenic, and 2 sulphur, is only 5*681. The condensa- 

 tion, therefore, amounts to about two-ninths of the whole spe- 

 cific gravity. 



