152 Gooch and Ensign — Determination of Bromine. 



able for the estimation of the former. We deemed it 

 however, to submit this point to the test of experiment, 

 result substantiates the presumption. 



best, 

 The 













Table 



XIV. 









f— 1 











b + 



go 



pa 



2 + 

 55 



P^ be 





Error 



Error 



1-1 





« 







Error in 



calcu- 



calcu- 



o 



KI 



o 



CS 



KBr 



KCI 



silver 

 salt. 



lated as 

 HBr 



lated as 

 HCl 



K 





■A 







Zn< 



<l 









cm 3 



grm. 



grm. 



grin. 



g-rm. 



grm. 



grm. 



grm. 



grm. 



grm. 



3 



0-5 



0-35 



0-5517 0-4981 



1-8280 



1-8262 



0-0018 — 



0-0008- 



0-0006 — 



3 



0-5 



0-35 



0-5511 0-4930 



1-8268 



1-8253 



0-0015- 



0-0005- 



0-0004- 



It is plain, in conclusion, that of the two methods which we 

 have studied, though both are applicable to the separation of 

 chlorine from iodine, but one is utilizable for the separation of 

 bromine from iodine, and that under modified conditions. With 

 the necessary modifications, however, it is good, and easily ap- 

 plied. It may be briefly summarized as follows : The neutral 

 solution containing the bromide and iodide is diluted to 600 cm 3 

 or 700 cm 3 (instead of 400 cm 3 , which was found to be a suffi- 

 cient dilution in the case of the separation of chlorine from 

 iodine), 1 cm 3 to 1*5 cm' 2 of strong sulphuric acid, or, better, 

 2 cm 3 to 3 cm 3 of the mixture made by diluting the acid with an 

 equal volume of water, (instead of 10 cm 3 of the 1 : 1 mixture 

 employed in the chlorine separation), are added, a sufficient 

 amount of pure sodium or potassium nitrite is introduced, (or, 

 if it is preferred, the gas generated by the action of dilute sul- 

 phuric acid upon the ordinary nitrite and introduced from the 

 outside may be employed instead,) and the liquid is boiled, after 

 trapping the flask as described, until the color has vanished and 

 the escaping steam no longer gives to red litmus paper the color 

 characteristic of iodine. The residual liquid is treated with an 

 excess of silver nitrate, and the precipitated bromide filtered off, 

 dried, and weighed. The process of boiling need not extend 

 beyond a half hour, or a little more, and care should be taken 

 that the volume of the liquid shall never be less than 500cm 3 . 

 We have not dealt with quantities of the potassium bromide 

 and iodide larger than 0*5 grm. each, approximately. The 

 presence of 0'5 grm. of potassium chloride does not affect the 

 sharpness of the separation. 



