SYSTEM NAPHTHALENE-CHLOROBENZENE-PHENOL, ETC. 23 



the mean molecular weight of the mixture is 107.0. 



These eight curves are reproduced in Plate I, with the 

 empirical molar fraction of naphthalene x as abscissa and the 

 temperature t as ordinate. 1—x is the sum of the molar fractions 

 of phenol and chlorobenzene, which have a fixed ratio in each 

 curve. It is advantageous to represent the relative amount of 

 these two components again in the form of the molar fraction : 



F 



Y = 



P+C 



Curve 8, in which Y = 0, has a form approximating to that of 

 the ideal fusion curve, while in Curve 1, in which Y = 1, the 

 deviation is enormous. All the other curves find their positions 

 between these two boundary curves according to the value of Y. 

 The curves with Y larger than 0.5 have inflexion points, while 

 the other curves are concave throughout. These curves should 

 properly be erected on the triangular diagram representing the 

 composition, and the curved surface passing through these eight 

 curves is the fusion surface of naphthalene. 



The isothermal curves in the triangular diagram (Plate II) 

 are obtained in the following manner. In this diagram N stands 

 for naphthalene, C for chlorobenzene, and P for phenol. The 

 points corresponding to the different values of Y are taken on 

 the line P C, and these points are united with the apex N by 

 straight lines. These straight lines are the projection of the 

 fusion curves on the plane of composition. Drawing straight 

 lines parallel to the axis of x in Plate I, the points of inter- 

 section give the values of x on the fusion curves at constant 



