152 



Journal op the Mitchell Society. 



[Dec. 



600 



500 



400 



300 



200 



100 



Diagram 7. 



Ordinates give internal heat of vaporization in calories. Abscissae give 



difference of the cube roots of the densities of liquid and vapor. 



L — E, nor -frlf — f / ~D~ vary uniformly with the tempera- 

 ture observations taken every ten degrees are consequently 

 not taken at equal intervals of the curve (a straight line) rep- 

 resented by that equation. 



Through each set of observations, excepting for acetic acid, 

 the mean line is drawn. The constants for this mean line 

 were obtained by averaging, for any substance, all of the con- 

 stants recorded in Table 1 (second paper) that were within 

 two per cent, of the mean values adopted in that table. For 

 di-isobutyl the mean value adopted appeared probably too high 

 and we therefore choose the value 86.3 as being more nearly 

 in accord with the proper constant. The values for these 

 constants are given in Table 25 under the heading //. 



For ethyl oxide, di-isopropyl, di-isobutyl, isopentane, nor- 



