SYSTEM NAPHTHALENE-CHLOROBENZENE-PHENOL, ETC. 



48 



ill tlie watery phase becomes too large to be treated as a dilute 

 solution. To avoid these difficulties we took the aqueous solution 

 almost saturated with both Na CI and Naa SO4. The salt solu- 

 tion contained 



8.249^ Na CI 

 18.570/0 Na„ SO, 



by weight. It is well know^n that in such solutions the solubility 

 of the phenol is much less than in pure water. 



The concentration of phenol in the aqueous solution was 

 determined by the bromine-water method/^ and that in chloro- 

 benzene was calculated by difference. The method of determina- 

 tion of phenol has hitherto been 

 worked out chiefly for commercial 

 purposes, and is not very exact. 

 It was therefore found necessary 

 to modify the method somewhat. 

 The chief difficulties lie in the 

 fact, that bromine vaporises dur- 

 ing the manupilation and that the 

 precipitation of tribromophenol 

 makes the end reaction very in- 

 distinct. These difficulties have 

 been overcome in the following- 

 manner. We took a bottle of 

 about 10 litre capacity which was 



filled with a 0.03 normal solution ^^^- ^• 



of bromine (Fig. 9). The reason 

 for using such a capacious bottle was to keep the concentration 



1) Allen's: Commercial Organic Analysis. Vol. II. Part II, p. 2-14, (1900). 



