166 Van Name and Maryott — Chlorination of Benzene. 



between the completion of the saturation with chlorine and 

 the first analysis,* and perhaps also owing to varying amounts 

 of moisture in the reagents used. It is shown by experiment 

 4, and less clearly by experiment 2, that the ratio C1 A : Cl s is 

 not constant throughout the experiment, as assumed in the 

 calculations of Nos. 1-3, but in reality tends to increase. 

 Experiment 4, which is free from this assumption, is con- 

 sequently the most trustworthy. 



Figure 2 shows the constants for the four experiments plot- 

 ted against the time, constants for the electrolytic periods 

 being designated by crosses, the others by circles. The marked 



Fig. 2. 



120 Tcme. M, 



ZW 



360 



600 



break in the curve for experiment 3 at the fourth constant is 

 doubtless due to accidents in the analysis, since at this point 

 one of the duplicate analyses was affected by a slight loss of 

 material and the other lost altogether. All of the curves have 

 a decided and comparatively steady trend upwards. 



It is natural to look for the explanation of this rise in reac- 

 tion velocity in the further chlorination of the primary 

 products. That monochlorbenzene is readily chlorinated 

 under the conditions of the above experiments is proved by 

 the results given in Table VI, obtained by passing, in the 

 dark, a current of chlorine through the solution. The data are 

 insufficient for an exact comparison of the velocity of this 

 reaction with the corresponding value for benzene, but though 

 the former is clearly smaller it is evidently of a similar order 

 of magnitude. It is, therefore, very probable that this reac- 

 tion is the chief cause of the rise in the benzene constants, 



* In experiment 2 this interval was very long, about three hours, but in 

 the other cases comparatively short. 



