PLANT LIFE. CELLULOSE, STARCH AND SUGAR 401 



The molecule in each case is, in all probability, exceedingly com- 



Glucose^ eHijsOe fr om Starch. When starch is boiled with kf 



water, to which a few drops of an acid (catalyst) such as hydro- ^ 

 chloric acid have been added, the liquid, after neutralization of 

 the acid, is found to be sweet in taste, j A kind of sugar, glucose 

 C 6 Hi2O 6 , can be obtained in crystals by evaporation. In com- 

 merce the evaporation is stopped before crystallization begins, 

 and the syrup (" corn-syrup," if maize is the source of the starch) 

 is sold for making candy and for preserving fruits. 



(C 6 H 10 5 ), + *H 2 



Glucose is known also as dextrose, and as grape sugar. Brown- 

 ish crystalline granules found in dried grapes (raisins) are mainly 

 composed of it. When pure, it is almost colorless. It reduces 

 cupric hydroxide, in Fehling's solution (p. 513), to cuprous oxide. 



The Sugars. The common sugars are divided into two 

 . classes. There are several sugars, having the same formula, 

 C 6 Hi 2 O 6 , but different properties, which are called monosacchar- 

 ides. Other sugars, having twice as many carbon units in the 

 formula Ci 2 H22On, are called disaccharides. The sugars we have 

 occasion to mention here are the following: 



Monosaccharides: Glucose (dextrose or grape sugar) CeH^Oe. 



Fructose (fruit sugar) CeH^Oe. 

 Disaccharides: Sucrose (cane-sugar, beet-sugar, saccha- 



rose) Cl 2 H220n. 



Maltose (formed by action of malt on 



starch) C^H^On. 

 Lactose (milk-sugar, found only in animals) 



Carbohydrates. Since cellulose, starch and the sugars are 

 freely changed, one into another, they are grouped together in one 



