202 



Allen, Crenshaw, Johnston, and Lar sen- 



used for a calculation of this sort. Dana gives also an analysis 

 of pyrrhotite by Funaro, which contained 40'27 per cent total 

 sulphur, equivalent to 6 per cent of dissolved sulphur. This 

 pyrrhotite contained also 3*16 per cent of nickel, which, accord- 

 ing to Penfield, is mechanically intermixed with pyrrhotite in 

 the form of pentlandite. If this be true, the ratio of sulphur to 



Fig. 9. 



s 



ft 



\ 



zx;zzzzzzzzzzzzzzz: 



500° 600° 700 c 

 Temperature. 



800° 900° 1000° 1100° 1200° 1300 c 



Fig. 9. Curve showing the percentage of sulphur dissolved by ferrous 

 sulphide in hydrogen sulphide gas as the temperature varies. 



iron in the pyrrhotite would be raised a little, since pentlandite 

 belongs to the type of sulphides MS, and the equivalent 

 quantities of iron and nickel are almost the same. 



Some allowance for errors in the analyses of the natural 

 mineral should be made ; still, the agreement between the 

 maximum quantities of sulphur in the natural and synthetic 

 pyrrhotite is striking. 



Relation hetween pyrrhotite and pyrile. — The diagram in 

 fig. 10 shows the relation between pyrrhotite and pyrite. The 

 curve 1, 1 shows the partial pressures of sulphur vapor in one 

 atmosphere of hydrogen sulphide, as they vary with tempera- 

 ture. These results are taken from Preunner and Schupp,* and 

 *Zs. phys. Chem., lxviii, 161, 1909. 





