constituents in the oil and the relative quantities of 

 each, we adopted a method which has been successfully 

 used by L. F. Hawley in "Wood Turpentines"" (Forest 

 Service Bulletin, No. 105). This method consists in 

 fractionally distilling the oil with a Hempel column and 

 plotting curves as follows: 



(a) Temperature of distillation against the per- 



too 



80 



60 





20 



10 



B 



T Temperatures TI 



FIG. I CURVES ILLUSTRATING THE THEORY OF FRACTIONAL 

 DISTILLATION 



centage weight which the fraction distilling at that 

 temperature bears to the total. 



(b) Specific gravity against percentage weight. 



(c) Index of refraction against percentage weight. 

 Bulletin 105, Forest Service, gives approximately the 

 following interpretation of these curves. 



Suppose we are dealing with .two' volatile, miscible 



W) 



