382 Hale — Initiative Action of Iodine and other 



arsenite solution have been used. There is an average loss of 

 0'14 cmS of iodine solution, in these experiments, in the titra- 

 tion of 20 cmb -50 cm3 of arsenite solution. The plain iodine 

 readings were calculated from readings made at 40 cm3 and 50 cmS 

 of arsenite solution. 





Table IT. 











The decinormal solutions 



were undiluted. 





i/10 As 2 8 sol. 



Reading with l-25 cm3 



of starch solution 



to a deep blue. 



Plain iodine reading 

 calculated. 



Error. 



cm 3 . 



cm 3 w/10 I. 





cm 3 . 





cm 3 . 



5 



5-23 





5-14 





0-09 



10 



10-37 





10-28 





0-09 



15 



15-50 





15-42 





0-08 



20 



20-70 





20-56 





0-14 



25 



25-85 





25-70 





■0-15 



30 



31-00 





30*84 





0-16 



35 



36-12 





35-98 





0*14 



40 



41-20 





41-08 





0-12 



45 



46-39 





46-26 





0-13 



50 



51-54 





51-40 





0-14 



The next set of experiments, carried out at a fixed and 

 larger, final volume, show a decided drop in the amount of 

 iodine lost, and the reddish tinge was not nearly so trouble- 

 some. 



Table III. 





Final volume 110 cm3 . 







Reading with l-25 cm3 









of starch solution 



Iodine reading 





w/10 As 2 8 sol. 



to a deep blue. 



calculated. 



Error 



cm 3 . 



cm 3 w/10 I. 



cm 3 . 



cm 3 . 



1 



1-05 



1-03 



0-02 



2 



2-10 



2-05 



0-05 



3 



315 



3-08 



0-07 



5 



5-20 



514 



0-06 



7 



7-25 



7-20 



005 



10 



1032 



10-28 



0-04 



15 



15-47 



15-42 



0-05 



20 



20-60 



20-56 



0-04 



35 



36-02 



35-98 



0-04 



It is probable that even with an impure starch one can elimi- 

 nate most of the error by proper dilution and by the intro- 

 duction of sufficient potassium iodide to bring a sharp end 

 reaction. 



To fix the loss of iodine positively upon the starch solution 

 and to prove that the action was a combination of oxidation 

 and hydrolysis, the following experiments were performed. 



