CARBOHYDRATES DM 



recrystallized from hot methyl alcohol, after purifying with 

 bone black. 



It has no commercial use by itself, but it exists in malt 

 and malt products which are made from germinating barley 

 (Section 99, a). It also occurs mixed with dextrin (Section 57) 

 as a thick syrup or solid. 



56. Non-sugars or Polysaccharides.- -These compounds are 

 usually colorless or white, odorless, and amorphous, with 

 little or no taste, and insoluble in water and in alcohol. 

 They are formed by the condensation of a great many 

 molecules of a monosaccharide with the elimination of 

 water, thus: 



n C 6 Hi20 6 — n H2O = (CeHioOs) n. 



Each molecule consists of a large number of single "sugar" 

 groups. Starch and cellulose are the principal polysac- 

 charides. 



57. Starch. — (CeHioOs^orX?). The exact graphic formula 

 is not known. Starch occurs in all parts of the plant as 

 a storage form of carbohydrate material, being a condensed 

 anhydride, and insoluble. It occurs to a great extent in 

 seeds and tubers as follows : 



Approximate per cent. 

 Crops. starch. 



Corn 62 



Wheat 64 



Oats 54 



Rice 70 



Potatoes 20 



Starch occurs in plant cells in the form of very small, 

 white grains, the size and shape of which vary with the 

 plant which manufactures it. Figs. 15 to 19 show various 

 kinds of starch grains, and it is to be noted that those of the 

 potato are comparatively large, while those of rice are very 

 small. The size varies from about 0.002 mm. to 0.2 mm. in 

 diameter. These grains are composed of very thin cellulose 

 walls, with contents of powdery material called granulose 

 or amylose. They are insoluble in cold water, alcohol, and 

 ether, but on treatment with boiling water the cellulose 



