358 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



should ever be perfectly complete, as indeed it is probably not. This 

 may be shown at atmospheric pressure by plunging the kerosene into 

 solid CO2. The effect is to change the kerosene to a white pasty 

 mass, like white vaseline. The pressure at which this transition 

 occurs will rise with increasing pressure. The existence of a transi- 



.024 



J2 



> .020 



^ .016 



O 



> .012 



c 



^ .008 



o 



004 



23456789 10 1112 

 Pressure, kgm. / cm.^ x 10^ 



FiGUBE 16. The change of volume of kerosene at constant pressure for a 

 rise of temperature of 20°. 



tion point, if there were one perfectly sharp, would be shown by an 

 abrupt rise of the curve by an amount corresponding to the change of 

 volume on freezing. But with the delayed freezing which takes 

 place here due to the separation out of the separate components 

 from a solution of varying strength, this abrupt rise becomes con- 

 verted into a gradual rise extending over a fairly wide pressure range. 

 Furthermore, the mean pressure at which this rise takes place in- 

 creases with rising pressure, just as the ordinary freezing point is 

 raised by increasing pressure. These features are all clearly shown in 

 the diagram. At the extreme right of the diagram, at pressures over 

 12,000 kgm., there is evident the beginning of the reversal of the effect, 



