Van Name and Maryott — Ghlorination of Benzene. 157 



Fig. 1. 



were separately determined, and the substitution chlorine 

 calculated by difference. Addition chlorine, throughout the 

 present investigation, was determined by multiplying by two 

 the weight of chlorine removed by boiling for half an hour 

 with alcoholic potassium hydroxide. 



Some trouble was found in constructing a cell available for 

 use at the higher temperatures, since no materials could be 

 used which would not resist the action of chlorine and of the 

 hot vapors of benzene and acetic 

 acid. Figure 1 shows a cell which 

 proved satisfactory and was used 

 in most of the experiments with 

 graphite electrodes. The glass bot- 

 tle A was 20 cm long by 5 cm in di- 

 ameter. The stopper B was made 

 of Acheson graphite carefully 

 ground to an accurate fit in the 

 neck of A, and had in its center a 

 tapered hole into which the lower 

 end of the long glass condenser F 

 was ground to fit. Several rods of 

 graphite D, threaded at the upper 

 end and screwed into the stopper, 

 served as the anode. The cathode, 

 a thin graphite rod, was lowered 

 into the liquid through the con- 

 denser by means of a thin plati- 

 num wire which supplied the 

 electrical connection. A thermometer was also introduced 

 through the condenser. A double-walled sheet iron jacket G-, 

 cooled by circulating water, surrounded the upper part of the 

 bottle, projecting slightly above the stopper, and was attached 

 to the bottle at its lower edge by the heavy rubber band H. 

 The annular space thus left was filled with mercury to a depth 

 of half a centimeter above the top of the stopper, the mercury 

 thus providing both better thermal conductivity and a seal for 

 the two ground joints. Electrical connection with the anode 

 was made through the mercury. Heating, when required, was 

 effected by means of a resistance coil of fine nickel wire 

 imbedded in an asbestos sleeve I, which fitted over the lower 

 half of the bottle. 



In experiments 1 to 6, and also in 15 and 16, the cathode 

 was enclosed in a narrow, porous cell, but this precaution was 

 omitted in the others after it was found that monochlorbenzene 

 is not appreciably reduced at the cathode.* A slight cathodic 

 reduction of the benzene hexachloride probably occurred when 



* See page 169. 



