340 Perkins — Gravimetric Determination of Free Bromine. 



weighed amount of silver in an atmosphere of hydrogen. The 

 value of the oxidizer is then calculated from the increase in 

 weight of silver which represents the amount of liberated 

 iodine. Table III shows the results obtained in the determina- 

 tion of potassium permanganate, hydrogen peroxide, potassium 

 dichromate, and ferric chloride, in all of which the 



error is 



well within experimental variation. 



Table III. 



Silver 

 taken 



Oxygen 

 represented 

 by oxidizer 



I found 



Calculated 

 amt. of oxygen 



Error 



grm. 



grm. 



grm. 



grm. 



grm. 



(a) Deter: 



ruination of potassium permanganate. 





3-0000 



0-0123 



0-1956 



0-0123 



±0-0000 



3-0000 



0-0123 



0-1936 



0-0122 



—o-oooi 



3-0100 



0-0123 



0-1964 



0-0124 



+ 0-0001 



3-0100 



0-0123 



0-1968 



0-0124 



+ 0-0001 



4-0101 



0-0185 



0-2926 



0-0184 



—o-oooi 



4-0101 



0-0247 



0-3886 



0-0245 



— 0.0002 



(b) Determination of hydi 



rogen peroxide. 





3-0000 



0-0202 



0-3200 



0-0202 



±0-0000 



3-0000 



0-0202 



0-3214 



0-0203 



+ 0-0001 



3-0100 



0-0404 



0-6427 



0-0405 



+ 0-0001 



3-0000 



0-0311 



0-4937 



0-0311 



±0-0000 



3-0000 



0-0322 



0-5128 



0-0323 



+ 0-0001 



3-0000 



0-0606 



0-9590 



0-0604 



— 0-0002 



(c) Determination of potassium dichromate. 





3-0000 



0-0080 



0-1272 



0-0080 



±0-0000 



3-0000 



0-0160 



0-2552 



0-0161 



+ 0*0001 



3-0000 



0-0201 



0-3141 



0-0198 



— 0-0003 



3-0000 



0-0402 



0-6390 



0-0403 



+ 0-0001 



3-0000 



0*0160 



0-2552 



0-0161 



+ 0-0001 



3-0000 



0-0160 



0*2571 



0-0162 



+ 0-0002 



(d) Determination of ferric chloride. 







3-0000 



0-0218 



0-3470 



0-0219 



+ 0-0001 



3-0000 



0-0218 



0-3476 



0-0219 



+ 0-0001 



3-0000 



0-0437 



0-6922 



0-0436 



—o-oooi 



3-0000 



0-0218 



0-3489 



0-0220 



+ 0-0002 



3-0000 



0-0262 



0-4183 



0-0264 



+ 0-0002 



3-0000 



0-0218 



0-3516 



0-0222 



+ 0-0004 



The results obtained fully justify the statement that metal- 

 lic silver may be used for the determination of free bromine 

 and chlorine, and combined iodine, and for the estimation of 

 the oxidizing power of those reagents whose reaction with 

 potassium iodide is definitely known to set free iodine quanti- 

 tatively. 



