ANALYSIS OF TOLUENE AND BENZENE IN COAL TAR OILS. 101 



When mixtures of benzene and toluene were distilled, in 

 which benzene was in the proportion of 3 : 1 or 4 : 1 to the 

 toluene, it was found that under the conditions of experi- 

 ment outlined above, the number of c.c. equal to the 

 volume of benzene present distilled over when tlie temper- 

 ature reached 90° O. or thereabout. When the benzene 

 and toluene were in equal proportions, as for example, 

 when distilling a mixture of 50 c.c. benzene and 50 c.c. 

 toluene, the first 50 c.c. came over slightly above 95° O. 

 Additions of xylene meant that tlie temperature of the 

 mixture had to be raised still higher before the volume of 

 distillate corresponding to the benzene fraction came over. 

 These results were to be expected, and experiments were 

 then made on mixtures of benzene, toluene and xylene in 

 order to obtain some idea of the limits of temperature for 

 the toluene fraction as well as for the benzene fraction 

 with varying mixtures. The tests were useful in giving 

 •data for the approximate estimation of the benzene and 

 toluene content of the samples examined later. Thus a 

 mixture containing benzene and toluene in nearly equal 

 proportions (the benzene preponderating), with a small 

 proportion of xylene, had to be distilled to about 95° O. to 

 give the volume of distillate equivalent to the amount of 

 benzene contained in it, while the toluene figure was given 

 by the volume of distillate collected between 95° and about 

 130° O. This kind of mixture was met with frequently in 

 analysing the coal tar oil samples. The actual content of 

 benzene and toluene present in the samples was obtained 

 by carrying out a blank test after each distillation of the 

 sample oil. In this blank test to the residue left in the 

 flask, quantities of benzene (KahlbaunTs) toluene and xylene 

 were added in accordance with the approximate estimation. 

 The mixture was again distilled, whereby any error in the 

 first estimation was corrected. 



An actual analysis of tar oil for benzene and toluene will 

 cow be described. 



