OP ARTS AND SCIENCES. 245 



The 35 cc. of alcohol preseut were much more than sufficient to dis- 

 solve all the sodic bromide formed, as a rough determination showed 

 that, — 



35 CO. of absolute alcohol dissolve 0.627 grm. NaBr. 



1 grm. brombenzylbromide yields 0.412 grm. NaBr. 



All the substances, therefore, were in solution throughout the experi- 

 ment. 



The accuracy of the method was tested by the following experi- 

 ments, in each of which two portions of parabrombenzylbromide were 

 compared : — 



L Time, five minutes. 



A. 1 gramme parabrombenzylbromide lost 0.1164 grm. Br. 



B. " " " 0.1102 grm. Br. 



Difference 0.0062 grm. Br. 



Percentage of 

 total side-chain 

 bromine remoyed. B in per cent of A. 



A. 36.39 100.0 



B. 34.47 94.7 



1.92 5.3 



II. Time, seven minutes. 



A. 1 grm. parabrombenzylbromide lost 0.1484 grm. Br. 



B. " " " 0.1446 grm. Br. 



Difference 0.0038 grm. Br. 



Percentage of 

 total side-chain 

 bromine removed. B in per cent of A. 



A. 46.36 100. 



B. 45.21 97.5 



1.15 2.5 



From these results it appears that the method can be trusted within 

 0.0062 grm. of bromine, or 5.3 per cent when the largest number is 

 taken as 100.* 



The results of the experiments, comparing the rate of decomposi- 

 tion of the three monobrombenzylbromides, are given in the following 

 table ; the first column of which gives the time from the addition of 



* The results of these experiments cannot be compared with those given in 

 Table I., because tlie quantity of alcohol used was not the same. 



