54 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



annually; of this amount almost five-sixths is made from Indian corn. 

 While starch is widely distributed in the plant kingdom, there are 

 relatively few plants from which it is extracted on a large scale. In 

 addition to corn other cereals, as rice and wheat, contribute to the 

 world's supply. Starch is also obtained from potato tubers, maranta 

 rhizomes, and cassava roots. In order to facilitate their comparative 

 study they are considered at this point, and it is desirable to know 

 something of the general properties of the starch grain, no matter 

 what its origin may be. 



General Properties of Starch. Starch is insoluble in cold water 

 or alcohol, but forms a white jelly when boiled with water, which, 

 when cool, gives a deep-blue color with iodin and should give a neutral 

 rection to litmus paper (commercial corn starch is usually alkaline) ; 

 ash not more than 1 per cent. 



If starch is triturated with water and the mixture filtered, the 

 filtrate does not give a reaction with iodin solution; if, on the other 

 hand, the starch is previously triturated with sand and then with 

 water, the filtrate becomes blue on the addition of iodin solution. 

 It appears that in the latter operation the wall of the grain is broken 

 and the soluble starch present in the grain is liberated. 



If dry starch and iodin are triturated together no color or, at the 

 most, a faint blue color is produced; whereas, if a little water is 

 added and the trituration repeated, a deep blue color is immediately 

 produced. 



The blue color of starch solution and iodin disappears on the appli- 

 cation of heat, but slowly returns on cooling the solution, but not 

 with the same degree of intensity, part of the iodin being volatilized. 



When starch is heated with glycerin it dissolves, and if alcohol is 

 added to the solution, a granular precipitate is formed which is soluble 

 in water, the solution giving a blue reaction with iodin. 



When starch is heated with an excess of water at 100 C. for 

 even several weeks, dextrinization of the starch does not take place, 

 i.e., the solution still gives a blue color with iodin. If, however, a 

 mineral acid be added, it is quickly dextrinized, turning violet-red, 

 reddish and yellowish with iodin; finally, maltose and dextrose are 

 produced, these giving no reaction with iodin, but reducing Fehling's 

 solution. The ferments and other chemicals have a similar effect 

 on starch. 



When dry starch is heated at about 50 C. from fifteen to thirty 

 minutes the lamellae and crystalloidal structure become better defined 

 and the polarizing effects produced by the grains also become more 

 pronounced. When starch is mounted in a fixed oil, as almond, the 



