254 ILLINOIS STATE ACADEMY OF SCIENCE 



Naphthalene, Fhiorene, Benzoic Acid and Urethane. A 

 glance at the solubility relations of these four substances 

 shows that the solvents which come the most nearly to 

 forming ideal solutions are the aromatic hydrocarbons 

 with their halogen and nitro derivities. These are fol- 

 lowed by the substances having lower internal pressures 

 such as ether, carbon tetrachloride, the esters and aci-d 

 anhydrides and also by- the substances having higher in- 

 ternal pressures, the amines, acids, alcohols and water. 



Comparing the solubility relations of naphthalene and 

 fluorene, it is found that the relative positions of the log 

 N vs. 1/T curves are the same for both substances. Hence 

 it may be concluded that the internal pressures of these 

 two solutes are nearly the same. 



When we come to consider the solubility relations of 

 benzoic acid, it must be remembered that this substance 

 is moderately polar; hence the moderately polar sol- 

 vents, or those having moderately high internal pres- 

 sures, come the most nearly to giving ideal mixtures. 

 Finally, it is evident from Table 1 that urethane has an 

 internal pressure corresponding to that of the lower alco- 

 hols. The very high slope obtained for this substance 

 in toluene should be noted. It will be observed that the 

 highly polar substance, water, is a better solvent than 

 is toluene. 



In order to coordinate these solubility relations and 

 many others which have been studied we have made use 

 of the chart shown in Fig. 1. It will be observed that the 



TABLE 1. 



Slopes of the log N vs. 1/T curves for the solutes Naphthalene, 

 Fluorene. Benzoic Acid, and Urethane and the values of the factors 

 obtained by dividing the experimental slope by the ideal slope. 



SOLUTE — NAPHTHALENE. 



Slope of the 

 log N vs. 

 Solvent 1/T curves 



Ideal solvent 970 



Diphenylamine 960 



Fluorene 970 



Phenanthrene 970 



Chlorbenzene 970 



Ethylene dichloride 980 



Ethylene dibromide 990 



Nitro benzene 1010 



