Detection of Iodine, Bromine, and Chlorine. 



285 



To each portion were added a few drops of sulphuric acid, the 

 liquid was diluted with distilled water to the level of a mark 

 upon the tube indicating a volume of 10 cm 3 , - 5 cm 3 of 

 chloroform, or of white carbon disulphide were introduced, and 

 the whole was shaken after the addition of a drop of a dilute 

 solution of sodium hypochlorite. The results of these tests are 

 as follows : — 



KBr 



taken. 



0-0010 grm. 



0-0005 



0-0004 



0-0003 



O-0002 



0-0001 



o-oooi 



0-00007 



000007 



0-0004 



0-0003 



0-0002 



0-0001 



0-00007 



0-00003 



Total 

 Volume. 



10 cm. 3 



10 



10 



10 



10 



10 



10 



10 



10 



5 



5 



5 



5 



5 



5 



Ratio of KBr 

 to total volume. 



1: 10000 



1 : 20000 



1 : 25000 



1 : 33000 



] : 50000 



1 : 100000 



1: 100000 



1 : 140000 



1 : 140000 



12500 

 16000 

 25000 

 50000 

 70000 



Color test 

 In chloroform. 



Strong. 

 Pronounced. 

 Pronounced. 



Paint. 



Trace. 

 Doubtful. 



None. 



Strong. 



Strong. 



Pronounced. 



Trace. 



None. 



Color test 

 in carbon 

 disulphide. 



Strong. 



Pronounced. 



Paint. 



Trace. 



Trace. 



Doubtful. 



Doubtful. 



1: 140000 



Faint. 

 DoubtfuL 



From these results it is plain, as Fresenius has pointed out, 

 that clear white carbon disulphide is the more sensitive reagent, 

 the delicacy of the test extending distinctly to one part in fifty 

 thousand when chloroform is the solvent for bromine and to 

 one part in one hundred thousand when carbon disulphide is 

 employed. 



In the following series of tests the bromide was subjected to 

 the same treatment which it must undergo were iodine actually 

 present and expelled as we proposed." To the solution of the 

 bromide in a test-tube were added a few 'drops of dilute sul- 

 phuric acid and a few drops of a solution of potassium nitrite. 

 The liquid was boiled, cooled, and treated with sodium hy- 

 pochlorite as in the former tests, excepting that even after 

 boiling for some time it was found to be necessary to introduce 

 more of the hypochlorite than before to overcome the nitrous 

 acid remaining in solution and to set free the bromine. 



KBr 



Total 



Batio of KBr 



Color test in 



taken. 



Volume. 



to total volume. 



Carbon disulphide, 



0-0010 grm. 



10 cm. 3 



1 : 10000 



Strong. 



0-0005 



10 



1 : 20000 



Pronounced. 



0-0004 



10 



1: 25000 



Pronounced. 



0-0003 



10 



1: 33000 



Faint. 



00002 



10 



1: 50000 



Faint. 



o-oooi 



10 



1: 100000 



Doubtful. 



0-00007 



10 



1: 140000 



None. 



0-00007 



5 



1 : 70000 



Trace. 



