198 



Allen, Crenshaw, Johnston, and Larsen- 



this the density (at 4°) and the specific volume was calculated. 

 Table TV contains these data. Column 1 contains the total 

 percentage of sulphur, Columns 2 and 3 the quantities of 

 FeS and S calculated on the hypothesis that pyrrhotite is a 

 solid solution of sulphur in ferrous sulphide. In fig. 7 are 

 plotted as abscissas the quantities of dissolved sulphur (Column 



Fig. 7. 



0-2200 



0-2175 



0-2150 





0-2125 



0-2100 





























































































































































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12 3 4 5 6 



Percentage of dissolved sulphur. 



Fig. 7. The variation of specific volume with the dissolved sulphur in 

 pyrrhotite. 



3, Table IV), and as ordinates the specific volumes (Column 6, 

 Table TV). It will be noticed that the scale of the plot is very 

 large and the locus of the points is not only a continuous curve 

 as the theory of solid solutions demands, but it is also a straight 





