OF ARTS AND SCIENCES. 251 



A series of comparative experiments with parachlorbenzylbromide, 

 parabrombenzylbi'omide aud paraiodbenzylbromide was also made by 

 the sodic acetate method, which indicated that they lose bromine at 

 the same rate, when they are used in molecular projiortions. I will 

 give here, however, only the results from the last series of experi- 

 ments, as in the others I did not succeed in overcoming some of the 

 sources of error mentioned in the introduction wholly to my satisfac- 

 tion. These results are given as in Table II. 



Time in Minutes. Parachlorbenzylbromide. Parabrombcnzylbromide. Paraiodbenzylbromide. 



25 100 97 99 



Summary. 



The results of this investigation are, — 1. The side-chain bromine 

 is removed from the three raonobrombenzylbromides approximately at 

 the following rates : — 



Ortho. 



55 (?) 

 2(?) 



when the quantity removed is less than 60 per cent of the whole. 



2. From parachlor-, parabrom-, and paraiodbenzylbromide at essen- 

 tially the same rate, if quantities proportional to their molecular 

 weights are used. 



All these results need confirmation by more accurate experiments, 

 but, as Menschutkin in one of the papers* of his beautiful series on 

 the rate of etherification (the first f of which was published a year 

 after the appearance of a preliminary notice J of my work) has an- 

 nounced his intention of studying the eff"ect of aromatic isomerism, 

 and with his better chosen reaction and more delicate method will be 

 able to do the work much more easily and accurately than I could, I 

 have decided not to pursue the subject farther. 



So far as I have been able to find, the only paper on this subject, as 

 yet published, is one by Post and Mehrtens, § who describe a single 



* Ann. Chem. Pharm., 197, p. 225. \ Ber. rl. ch. G. 1876, p. 931. 



t Ber. d. ch. G. 1877, p. 1728. § Ber. d. ch. G. 1875, p. 1549. 



