80 



PKOX1MATE PRINCIPLES OF THE SECOND CLASS. 



QUANTITY OF STARCH IN 100 PARTS IN 

 Rice . . . .85.07 Wheat flour 



Maize . . . .80.92 Iceland moss 



Barley meal . . . 67.18 Kidney bean , 



Rye meal . . .61.07 Peas 



Oat meal 59.00 Potato . 



56.50 

 44.60 

 35.94 

 32.45 

 15.70 



Fig. 2. 



GRAINS OF POTATO STARCH. 



When purified from foreign substances, starch is a white, light 

 powder, which gives rise to a peculiar crackling sensation when 



rubbed between the fingers. 

 It is not amorphous, as we 

 have already stated, but is 

 composed of solid granules, 

 which, while they have a 

 general resemblance to each 

 other, differ somewhat in va- 

 rious particulars. The starch 

 grains of the potato (Fig. 2) 

 vary considerably in size. 

 The smallest have a diameter 

 of Ttfi tne largest 7 J T of 

 an inch. They are irregu- 

 larly pear-shaped in form, 

 and are marked by concen- 

 tric laminae, as if the matter 

 of which they are composed had been deposited in successive layers. 

 At one point on the surface of every starch grain, there is a minute 



pore or depression, called the 

 hilus, around which the cir- 

 cular markings are arranged 

 in a concentric form. 



The starch granules of 

 arrowroot (Fig. 3) are gene- 

 rally smaller and more uni- 

 form in size, than those of 



the potato. They vary from 

 2injT> to 5^ of an inch in 

 diameter. They are elongated 

 and cylindrical in form, and 

 the concentric markings are 

 less distinct than in the pre- 

 ceding variety. The hilus 



Fig. 3. 



STARCH GRAINS OF BERMUDA ARROWROOT. 



