Perkins — Gravimetric Determination of Free Bromine. 339 



Table I. 



Silver Halogen Iodine 



taken taken found 



grm. grm. grin. 



(a) Determination of bromine. 

 3-0000 0-0213 0-0336 

 3-0000 0-0426 0'0678 

 3-0000 0-1065 0-1694 



(b) Determination of chlorine. 

 3-0000 0-0161 0-0574 

 3-0000 0-0322 0'1146 

 3-0000 0-0322 0-1145 

 3-0000 0-0322 0-1141 

 3-0000 0-0483 0*1716 



Calculated 



amt. of 



halogen 



grm. 



0-0211 

 0*0427 

 0-1067 



0*0160 

 0-0320 

 0-0320 

 0-0318 

 0-0479 



Error 

 grm. 



— 0-0002 

 + 0-0001 

 + 0-0002 



— 0-0001 



— 0-0002 



— 0-0002 



— 0-0004 



— 0-0004 



phuric acid and potassium hydrogen arseniate,* was intro- 

 duced into a flask with an excess of the calculated amount of 

 an oxidizing reagent (usually potassium nitrite or hydrogen 

 peroxide), the whole made acid with hydrochloric acid, and 

 shaken with a weighed amount of silver. The increase in the 

 weight of the silver indicates the amount of iodine liberated 

 from the potassium iodide and from this the amount of potas- 

 iodide may be easily calculated. Table II shows the 



sium 



results of five determinations with potassium iodide in which 

 the average error is —0*0002 grm. between limits of —0*0005 

 and +0-0002 grm. 







Table II. 









Determination of potassium iodide. 





Silver 



KI 



Iodine 



Calculated 





taken 



taken 



found 



amt. of KI 



Error 



grm. 



grm. 



grm. 



grm. 



grm. 



2-7803 



0-1144 



0-0872 



0-1141 



— 0*0003 



3-0028 



0-1346 



0-1026 



0-1342 



— 0*0004 



2-7800 



0-1279 



0*0973 



0-1281 



+ 0*0002 



2-0008 



0-1279 



0-0974 



0-1274 



— 0*0005 



3-0001 



0*1346 



0-1029 



0-1346 



±0-0000 



Determination of Oxidizing Reagents. 



The process has also been applied to the indirect determina- 

 tion of several of the common oxidizing reagents with a view 

 to showing that it may be used for the estimation of oxidizers 

 that will liberate iodine quantitatively. In these experiments 

 definite amounts of the oxidizer, standardized in the usual 

 way, were added to an excess of a solution of potassium iodide 

 acidified with hydrochloric acid, and the whole shaken with a 



* Gooch and Browning, this Journal, xxxix, 188, 1890. 



