SYSTEM NAPHTHALENE- CHLOROBENZENE-PHENOL, ETC. 31 



71, c, p are tlie weights of naphthalene, chlorobenzene and phenol 

 in grammes. 



The coordinates of the points are, 



Molar fraction of 



The projection of the eutectic curve on the plane of com- 

 position is nearly a straight line ; and as the fusion surface of 

 phenol is almost a plane, the curve itself must be nearly a 

 straight line, so far as it has been observed. This does not 

 hold for lower temperatures, but the projection must have the 

 course indicated by the dotted line. 



2. Theoretical. 



In order to facilitate a general survey, the fusion surfaces 

 (in projection on the j^lane of composition) are reproduced with 

 their isothermal curves. The parts which have not been ex- 

 perimentally determined are supplemented from analogical con- 

 siderations. This can be done in tliis case without much danger 

 of falling into gross errors, because the relations of symmetry 

 are so simple and clear. 



As we have seen the isotherms of the fusion surface of 

 phenol are nearly straiglit lines parallel to the line NC. This 

 means that [)hL'nol stands to chlorobenzene in exactly the same 



