68 HOW CROPS GROW. 



two molecules of dextrose, C^ILoOn -j- H 2 = 2 C 6 Hi 2 6 = 

 Maltose is also produced when starch and dextrin are 

 heated with dilute acids, and thus appears to be an inter- 

 mediate stage of their transformation into dextrose. 



Maltose is accordingly an ingredient of some commer- 

 cial "grape-sugars" made from starch by boiling with 

 diluted sulphuric acid. 



Lactose, or Milk Sugar, C 12 H 22 Oii -f- H 2 0, is the 

 sweet principle of the milk of animals. It is prepared 

 for commerce by evaporating whey (milk from which 

 casein and fat have been separated for making cheese). 

 In a state of purity it forms transparent, colorless crys- 

 tals, which crackle under the teeth, and are but slightly 

 sweet to the taste. When dissolved to saturation in 

 water, it forms a sweet but thin syrup. Heated to 290 

 the crystals become water-free. 



Lactose is said to occur with cane-sugar in the sapo- 

 dilla (fruit of Achras sapota) of tropical countries. 

 Treatment with dilute sulphuric acid converts it into 

 galactose and dextrose. 



CuH^Qu + H 4 = C a H 12 O e + C 6 H J2 6 

 Lactose. Water. Galactose. Dextrose. 



Raffinose, C 18 H 32 16 -f 5 H 2 (?), first discovered 

 by Loiseau in beet-sugar molasses, was afterwards found 

 by Berthelot in eucalyptus manna, by Lippmann in beet- 

 root, and by Boehm & Eitthausen in cotton-seed. It 

 crystallizes in fine needles, and is but slightly sweet. It 

 begins to melt at 190 with loss of crystal- water, which 

 may be completely expelled at 212. The anhydrous 

 sugar fuses at 236. It is more soluble in water and has 

 higher dextrorotatory power than cane-sugar. Heated 

 with dilute acids it yields dextrose, levulose and galactose. 



C u H a O u + 2 H 2 = 3(CH 12 6 )- 



The Sugars in Bread- Grains. The older observers 

 assumed the presence of dextrose in the bread-graius. 



