Oxidizers in the Hydrolysis of Starch and Dextrins. 395 



To 5 cm3 of the erythrodextrin which had been separated from 

 the impure starch solution, acid potassium carbonate was added 

 and then arsenite solution and iodine solution were introduced 

 successively eight to ten times. No diminution of the red 

 color was appreciable. 



The erythrodextrin by saliva was then tried in titration. 

 First the sharpness of the reading was tried. 



Volume. 

 cm 3 . 

 100 



40 



Erythrodextrin is not so sensitive to iodine as starch or ami- 

 dulin. However, in concentrated solution and in the presence 

 of a moderate quantity of potassium iodide the reaction is 

 sharp to a drop. 



Table XIV. 



n/ . 





Table XIII. 





,/lOIsol. 



Erythrodextrin. 



KI. 



Color., 



drops. 



cm 3 . 







1 



10 



3 small crystals 



yellow 



2 







brownish red 



3 







deeper red 



4 







deeper red 



1 



10 



1 small crystal 



brown red 



2 







deep red 







No extra dilution. 





) As 2 3 . 



w/10 I sol. 



KHCC-3. 



Erythrodextrin. 



Color. 



cm 3 . 



cm 3 . 



cm 3 . 



cm 3 . 





10 



9-89 



5 







yellow 



it 



9'88 



a 



10 



light brownish red 



a 



9-89 



tc 



20 



deep red 



u 



j 9-87 

 ( 9-90 



a 



30 



faint red 

 very deep red 



This table shows conclusively that there is no loss of iodine 

 by action on erythrodextrin even in large quantities and though 

 the volume was concentrated. Sufficient potassium iodide was 

 present in the iodine solution, or was formed in titration, to 

 give readings as sharp as that of plain iodine. 



If one reads to the first permanent color, whether purplish, 

 red, or blue, there can be no loss of iodine from the formation 

 of the erythrodextrin iodide, but if one reads always to the 

 blue it may take a drop or two to cover the red. This is well 

 illustrated in the readings with amidulin in Table XII. That 

 the red forms at all in the presence of starch seems to be an 

 anomaly, since starch will pull the iodine away from the eryth- 

 rodextrin iodide forming starch iodide, but a possible explana- 

 tion may be that, as the reaction between the arsenite solution 

 or tartar emetic and the iodine becomes slower toward the end, 

 an excess of iodine is present for a few moments and both the 



Am. Jour. Sci.— Fourth Series, Vol. XIII, No. 7*7.— Mat, 1802. 

 27 



