1 88 AGRICULTURAL CHEMISTRY 



the molecule containing 6 atoms of carbon. The term 

 monosaccharide is applied to the dextrose group, and 

 disaccharide to the sucrose group. 



243. Occurrence of Sucrose. Sucrose is found in plants 

 in largest amounts of any of the sugars. Juices from the 

 sugar-cane and sugar-beet contain from 12 to 18 per cent. 

 It is also present in small amounts in seeds and cereal 

 products. From 1.5 to 2 per cent, is found in sweet corn 

 and about 0.50 per cent, in wheat flour. In some fruits, 

 as apples, sucrose is present to the extent of 5 per cent, 

 or more. 



244. Physical and Chemical Properties of Sucrose. 



The chemical and physical properties of sucrose obtained 

 from the sugar-cane or sugar-beet are alike in all respects. 

 When the two sugars have been subjected to the same 

 degree of refining, they are identical. When examined 

 under the microscope, sucrose is in the form of regular 

 crystals, as shown in the illustration (see Fig. 

 77). At 160 C. sucrose crystals melt, and 

 when cool form a colorless, glassy mass. A 

 Fig 77 su- concentrated solution boils at a little above 



croseciystal. IOQ o At l6Q o a brown pro duct known 



as barley sugar is formed. At 200 C. sucrose is decom- 

 posed, and gases, as carbon monoxid, carbon dioxid and 

 methane, are given off. In concentrated solutions, a tem- 

 perature of 100 C. causes an inversion ; that is, the su- 

 crose molecule is split up and two new sugars are formed, 

 namely : dextrose and levulose. Hence, in the refining 

 of sugar, the concentration must be carried on in vacuum 



