384: Hale — Initiative Action of Iodine and other 



acid potassium carbonate, caused an abundance of red and 

 purple. 



These experiments tend to prove the presence in the starch 

 solution of some body which is oxidized and hydrolyzed in 

 alkaline solution with the production of erythrodextrin. That 

 the action is not upon the starch itself will be shown later. 



An effort was now made to overcome the difficulty by vary- 

 ing the method of making the starch solution, and to facilitate 

 comparison the different methods are given together. 



I. Starch solution by heating with potassium iodide. 



In 25 cm3 of cold water 5 grm. of pure starch were ground 

 with 2 grm. of potassium iodide, poured into 75 cm3 of boiling 

 water and boiled, the beaker being protected with asbestos. 

 The mass became mucilaginous. After fifteen minutes the 

 volume was increased to 500 cm3 , and the boiling was continued 

 for forty-five minutes. The solution was filtered, forty-eight 

 hours being required, leaving a residue of jelly-like consistency 

 upon the filter. The method was suggested by the extreme 

 delicacy which the presence of potassium iodide gives to the 

 starch reaction and by certain statements made in the litera- 

 ture, one that concentrated potassium iodide causes starch to 

 swell and dissolve,* another that a solution of starch made by 

 a somewhat similar method would keep a year without fermen- 

 tation, f 



II. Starch solution by heating with glycerine, according to 

 Zulhowsky.\ 



In 70 cm3 of pure glycerine 5 grm. of potato starch were 

 heated at a temperature of 185°-190° C. for half an hour with 

 constant stirring. The starch dissolved and the solution turned 

 through yellow to a deep red. The solution was cooled to 

 120° C. and poured slowly and continuously into 200 cm3 of 

 alcohol. The precipitate was thoroughly stirred, settled and 

 filtered while warm. It filtered readily and was washed with 

 alcohol until the filtrate came through colorless. The color- 

 less residue was then dissolved in 500 cm3 of water heated to 

 60°-70° G. 



The product is called amorphous amylodextrin. It is 

 described as non-crystallizable, coloring blue with iodine, 

 (a)j= 206-8° -K 



III. Soluble starch by saliva digestion. 



In a little cold water 2 grm. of starch were ground with 

 0*5 grm. of acid potassium carbonate and poured into 200 cm3 of 



* Payen. Comp. Rend., lxi, 512. f Zeitscbr. anal. Chem.. 1886, 37. 



JBer. Chem. Ges , xiii, 1395-1398 



