42 ART. 12. — II. HIKOBE : OX THE FUSION SURFACES OF THE 



the calculability of the chemical potential as a fuction of the 

 composition in one of the solutions. The last condition is ful- 

 filled when the solution is either dilute or approximates sufficiently 

 to the ideal solution. 



When one of the solutions is dilute and tlie other is an 

 ideal or quasi-ideal solution, the relation is particularly simple. 

 Let the spatial concentration of the common chemical species in 

 the dilute solution be c, and the molar fraction of the same in 

 the ideal solution be C. Then the potential of the chemical 

 species is given by 



lJi = z' + nTlnc 



and ix = z + nThiC, 



in which z and .~ are functions of temperature and pressure. 

 Hence at a constant temperature and pressure, we have 



-_ = constant. 



This relation can be employed for the elucidation of the problem 

 of the molecular association of phenol in solution. 



Neenst has concluded that phenol in benzene is associated 

 to double molecule, from the partition coefficient of this substance 

 betw^een water and benzene. But his observations were made on 

 dilute solutions, and the concentrations were determined by the 

 depression of the freezing point. Hence the result seems not to 

 be quite reliable. We tried to determine the partition coefficient 

 of phenol between water and chlorobenzene up to a concentration 

 of about ÎSOYo in the oily phase, expecting some verification for 

 the conclusion arrived at from the study of the fusion surface. 

 When the concentration of phenol is so large water goes to the 

 chlorobenzene phase in no small quantities, and moreover phenol 



