Jamieson — Determination of Hydr'ogen Peroxide. 151 



In order to test the method, a solution containing 3*567 g. of 

 normal potassium iodate in 1000*^^ was used. The tenth normal 

 sodium arsenite solution which had been made for another 

 purpose over a year ago^ was prepared by dissolving 4*948 g. 

 of pure arsenious oxide in about 50" of water which contained 

 4 g. of sodium hydroxide. When the oxide had dissolved, 

 200" of a saturated solution of sodium bicarbonate were added 

 along with enough water to make 1000". The relationship 

 between the arsenite and iodate solutions was obtained by 

 titrating a measured volume of arsenite solution acidified with 

 two-thirds the volume of concentrated hydrochloric acid."^ 

 5" of sodium arsenite were found equivalent to 7*5" of iodate 

 solution or 1" of KIO3 ee 0*667" of As.Og. If desired, the rela- 

 tionship of the two solutions may be calculated as follows : 

 1" of KIO3 = *003297g. of As,03-^'l" of As,03 eee *004948 g. of 

 ASjOg = 0*667" which is identical with the result obtained by 

 titration. 



The first hydrogen peroxide solution used to test the method 

 was made by diluting 50" of ordinary commercial peroxide to 

 500". Measured quantities of the arsenite solution which 

 must be in excess of that required by the hydrogen peroxide 

 taken for analysis, were placed in 500" glass stoppered bottles 

 along with 10" of a 10 per cent solution of sodium hydroxide. 

 A measured volume of the hydrogen peroxide solution was 

 added from a burette while the contents of the bottle were 

 gently agitated. After the solution had stood for 2 minutes, 

 40" of concentrated hydrochloric acid were cautiously added. 

 The stopper was inserted and while holding it firmly in place 

 the bottle was violently shaken in order to separate as much 

 carbon dioxide as possible from the solution. Then the stop- 

 per was carefully released so as to allow the excess pressure of 

 gas to escape without losing any solution. After adding 6-7" 

 of chloroform the unoxidized arsenite was titrated with the 

 potassium iodate solution with thorough shaking of the closed 

 bottle after each addition of iodate until the end point, which 

 is the disappearance of the iodine color from the chloroform, is 

 reached. The amount of iodate used for the titration was 

 converted into its equivalent of arsenite solution which was 

 deducted from that originally taken, leaving that oxidized by 

 the hydrogen peroxide. The following equations may be writ- 

 ten to represent the reactions which take place : 



As,03H-2H,0,= As,0, -f-2H,0 

 As,03 + KIO3 + 2HC1 = As^O, + ICl + KCl + H,0 



The following results were obtained : 



1" of AS.P3 sol. = *00l'70l g.H^O,. 



* J. Ind. and Eng. Chem., iii, 250, 1911. 

 Am. Jour. Sci.— Fourth Series, Vol. XLIY, No. 260.— August, 1917. 



