CORN STARCH 55 



polarizing effects are more pronounced than when it is mounted in 

 water, but the inner structure is not usually apparent, unless the 

 starch has been previously heated. 



Literature. Kraemer, Bot. Gazette, Nov., 1902; Ibid., Oct., 

 1905; and Eighth International Congress of Applied Chemistry, 

 Vol. 17, p. 31. Also Kraemer's "Applied and Economic Botany." 



AMYLUM. Starch. The starch grains obtained from the grains 

 of wheat (Triticum sativum and its varieties), corn (Zea Mays) and 

 rice (Oryza sativa) (Fam. Graminese). The grains are separated 

 from the cells, purified in various ways, and subsequently washed 

 with large quantities of water. In the U. S. Pharmacopoeia corn 

 starch alone is recognized. 



In the preparation of corn starch the corn grains are softened by 

 being placed in running water and kept at a temperature of about 

 60 C. for several days, care being taken to prevent any fermentation. 

 The grains are then crushed between burr-stones and the paste car- 

 ried by means of water to large sieves, the strained magma then 

 being reground and carried to sieves made of bolting cloth. The 

 milky-fluid containing the starch is then run into settling vats, the 

 starch separating out. The starch is then freed from oil, albuminoids 

 and other substances by treating it with a 15 per cent solution of 

 caustic soda. The supernatant liquid is removed and the starch 

 washed with water to remove all traces of alkali. The starchy mix- 

 ture is allowed to stand, when the starch separates out and is dried. 

 Commercial starch is likely to contain some free alkali, which is 

 readily detected by the addition of an aqueous solution of fuchsin, 

 which becomes decolorized immediately in the presence of a starch 

 containing free alkali. 



Varieties of Corn. There are a large number of varieties and sub- 

 varieties of Zea Mays, some of the former being ranked as species. 

 The following well-defined varieties may be mentioned: 



(1) Zea Mays everta, to which belong the pop-corns. The size 

 of the ears and grains is about one-half or less that of the other corns; 

 the grains have a more or less translucent and horny endosperm, the 

 cells of the latter containing numerous compactly arranged polygonal 

 starch grains, which are from 0.007 to 0.010 mm. in diameter and have 

 a central rarefied area from 0.002 to 0.007 mm. in diameter. It is 

 owing to the structure of the starch grains that the peculiar popping 

 of the corn grains results when they are heated. Heating the corn 

 grains at 145 to 160 C. for from four to ten minutes causes the burst- 

 ing of the starch grains, and at the same time a rupture of the cells 

 and splitting of the pericarp into 4 parts. The white appearance 



