148 (rooeh and Ensign — Determination of Bromine. 



experiments were undertaken following the same general plan 

 already laid down, excepting that the original volume of the 

 liquid boiled was taken much larger than before, and the con- 

 centration guarded. Determinations were first made in blank ; 

 — that is to say, the process was completed in all respects as if 

 iodine were present and to be separated, excepting that no iodide 

 was introduced. To the solution of the bromide, weighed in 

 an Erlenmeyer flask of 1200 cm 3 capacity, were added 10 cm 3 of 

 sulphuric acid [1:1], and, after diluting to at least 600 cm 3 of 

 water, the gas from 2 grms. of sodium nitrite was passed into 

 the liquid, the trap consisting of an abbreviated calcium chlo- 

 ride tube with two bulbs, was hung in the neck of the flask, 

 and the boiling was continued for at least an hour and a half. 

 Finally the solution was cooled, treated with silver nitrate, 

 and the silver bromide precipitated was settled, filtered off on 

 asbestos in a perforated crucible, dried and weighed. The de- 

 tails of treatment are given in the table. 



Table IX. 



' — 1 



NaN"0 2 used in KBr=HBr % 1 



CO° 



s 



3 



a m 



CO "S 



AgBr=HBr 



Error in 



o 



w 



gener 



itor. 



taken. 



'3-3 

 > 



"a 



a 



a a 

 eh a 



found. 



HBr. 



cm 3 . 

 10 



grm. 

 2 





grm. 

 0-5394 



grm. 

 0-3667 



cm 3 . 

 800 



cm 3 . 

 500 



120 



grm. 

 0-8506 



grm. 

 0-3665 



grm. 

 0-0002- 



10 



2 



0-5387 



0-3663 700 



400 



90 0-8492 



0-3659 



0-0004 — 



10 



2 



05397 



0-3669 600 



400 



90 0-8511 



03667 



0-0002- 



10 



2 



0-5397 



03669 , 600 



400 



90 0-8488 



0-3657 



0-0012- 



10 



2 



Fe 2 (S0 4 ) 3 

 grm. 

 2 



0-5369 

 + HNO, 



0-3650 ! 600 



400 



90 0-8465 



0-3647 



0-0003 — 



10 



cm 3 ' 

 5 0-5384 



0-3662 800 



500 



105 0-8494 



0-3661 



o-oooi- 



10 



2 



5 0-5384 



0-3662 , 800 



500 



105 0-8483 



3655 



0-0007 — 



10 



2 



5 0-5371 



0-3652 600 



400 



90 0-8455 



0-3643 



0-0009 — 



10 



2 



5 0-5363 



0-3645 | 600 



400 



90 0-8439 



0-3636 



0-0009 — 



It is obvious that so far as the treatment in blank is con- 

 cerned the degree of dilution had been reached at which no 

 significant volatilization of the bromine takes place. We pro- 

 ceeded, therefore, to make the actual separation, the only 

 change in conditions being the addition of 0'5 grm. of potas- 

 sium iodide, which was especially prepared and used in solution 

 as described in the paper to which reference has been made. 

 The boiling was continued until red litmus paper, moistened 

 and held in the escaping steam for a minute or two, showed no 

 reaction for iodine. 



