164 Van Name and Maryott — Chlorination of Benzene. 



stated, the method of analysis wholly eliminates the effect of 

 chlorination of the acetic acid from the results. 



Since the chlorine concentration was constant the reaction 

 should be of the first order with respect to the benzene, and 

 the velocity constants were, therefore, calculated from the ex- 

 pression K = In l , in which a— x x and a— a? 2 are 



t— £, 



a — x„ 



the concentrations of the benzene at the beginning and end, 

 respectively, of the two-hour time interval. 



During every alternate reaction period a constant current 

 (either *125 or *200 amp.) was maintained through the cell. 



The temperature of experiment, measured in the cell itself, 

 was 10"2°, with a maximum variation at ordinary times of 

 ± '04°, but subject to fluctuations of several minutes' duration 

 at the times of starting and stopping the electrolysis. By 

 anticipating these variations by opposite changes in the 

 temperature of the thermostat, they were restricted to a 

 maximum of about ±'2°, and their effect reduced by inten- 

 tionally balancing a low temperature against a high one. 



Four experiments were completed, and are recorded in 

 Table Y. In all cases £=0 is the time when the first samples 

 were taken, i. e. after the saturation with chlorine. Concentra- 

 tions are all in mols per liter. Experiments 1 to 3 were 

 calculated on the assumption that the ratio of addition to 

 substitution chlorine (C1 A : Cl s ) was constant throughout. In 

 experiment 4 the addition chlorine was determined at the end of 



Table V. 

 Experiment 1. 

 Concentrations: Benzene, initially, 3*7297; at £=0, 3 



6956 



Ratio CL : CL, 43' 



LiCl, 0-85. 

 : 56*1, determined at end. 



Electrolysis with 0*125 amp. during periods 1 and 3. 









Decrease in 















cone, of 



Cone, of 







t 



AgCl 



from 10 cc 



benzene 



benzene 





TcXlO 4 



min. 



grm. 



mean 



X 



a-x 











•0773 

 •0776 



0*774 



•0341 



3*6956 



Elec. 



0-90 



120 



•1669 

 •1671 



•1670 



•0738 



3'6559 





1-21 



240 



•2894 



•2827 



•2860 



•1265 



3-6032 



Elec. 



1-58 



360 



•4408 

 •4376 



•4392 



•1942 



3-5355 





2-0.8 



480 



•6357 



•6357 



•2811 



3-4486 







