380 Hale — Initiative Action of Iodine and other 



It is well known that starch is readily hydrolyzed by saliva, 

 malt extract, and by many chemical reagents such as hydro- 

 chloric acid, potassium hydroxide, nitric acid, etc., down 

 through a series of bodies, called dextrins, more or less com- 

 pletely to a final product, one of the sugars, usually maltose. 

 One of the first of these dextrins is erythrodextrin, which is 

 colored red with iodine. It seemed possible that some such 

 hydrolytic action might take place in the present instance. 

 The water or the alkali, acid potassium carbonate, might cause 

 the hydrolysis under certain conditions, e. g., as there is a loss 

 of iodine, indications would point to an oxidizing action, and 

 a hydrolysis may be possible because of such oxidizing action. 

 It is also possible that the arsenious acid, or antimonious acid, 

 becomes joined to the starch, in some such way as antimonious 

 acid may attach to acid potassium tartrate, and that this com- 

 pound is then easily hydrolyzed. A possible indication of this 

 lies in the anomalous fact that the blue color fades first and 

 the red last in alkaline titration, though a few drops of a starch 

 solution will discolor a solution of erythrodextrin, colored red 

 with iodine, and develop the blue starch iodide. 



Such a hydrolytic action upon the starch would readily 

 explain the production of red and purple, since the formation 

 of erythrodextrin would furnish the red color with iodine, and 

 the mixture of the red with the starch blue would yield vary- 

 ing shades of purple. The oxidizing action of the iodine 

 would explain its loss in titration, and the two actions com 

 bined would explain the mutual relation of the two phenom- 

 ena, a production of red in the end reaction and a loss of 

 iodine. 



With this explanation established, there are three ways of 

 accounting for the loss of iodine ; first, in the production of 

 erythrodextrin ; second, in the formation of the erythrodextrin 

 iodide ; third, in the oxidation of the erythrodextrin down the 

 series of achroodextrins. 



Experimental evidence seems to substantiate the following 

 points : 



1st. The loss of iodine and the production of a red color 

 does not take place if an absolutely pure and freshly made 

 starch solution is employed. 



2d. Ordinary starch contains, usually, at least two impuri- 

 ties, one coloring red with iodine, the other coloring blue, the 

 latter being readily changed under the influence of oxygen and 

 acid potassium carbonate to the former. These impurities 

 tend likewise to form in pure starch, whether solid or in solu- 

 tion. 



3d. The impurity coloring blue with iodine is identical with, 

 or analogous to, amidulin, made by saliva digestion of pure 





