Mineral Sulphides of Iron. 



203 



are extrapolated above 1130° and below 750°. Curve 2, 2, 

 represents so far as may be with partial data the dissociation 

 pressures of pyrite at various temperatures. Here it is assumed 

 that the vapor pressure at 665° is one atmosphere (see p. 205). 

 At 550° pyrrhotite was found to pass over into pyrite when 



Fig. 10. 



100 

 90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 













































































































































































































































































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CM 













































/ 



/ 













■ 

















/ 





























/ 





























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1 

 1 











/ 



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1 

 1 









/ 



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1 



1 







y 



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i 































/ 



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\ 



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% 



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500 600 

 Temperature. 



700 



800 



900 



1000 1100 1200 



Fig. 10. Curve 1,1, shows the partial pressures of sulphur in hydrogen 

 sulphide at various temperatures (Preunner and Schupp). Curve 2, 2, shows 

 approximately the dissociation pressure of pyrite. 



heated in hydrogen sulphide. This was proved by the fact 

 that the color changed to the yellower color of pyrite and the 

 density increased, whereas pyrrhotite decreases in density with 

 increase of sulphur. At 575° pyrrhotite showed no change in 



