56 



PLANT COMPOUNDS 



the same role as dextrose. Levulose is a white solid, erystal- 

 lizable with considerable difficulty, very soluble in water 

 and in hot alcohol. It is much more strongly levorotatory 

 than dextrose is dextrorotatory, the specific rotation being 

 — 92.5°. Hence it is called levulose, "left sugar." It is 

 sweeter than dextrose. Although it does not contain an 

 aldehyde group it is easily oxidized, that is, it reduces 

 Fehling's solution. Levulose forms compounds with calcium 

 hvdroxide and barium hydroxide — "levulates" — insoluble in 

 water and in alcohol. It is fermented by fungi and bacteria 

 like dextrose. One wav to make it is to boil sucrose with 



m 



hydrochloric acid and thereby change the sucrose to dextrose 

 and levulose. On treating the cold solution with an excess 

 of calcium hvdroxide, the crystals of calcium levulate 

 are precipitated and can be filtered. On decomposing the 

 precipitate with oxalic acid, and concentrating the filtered 

 solution, levulose will crystallize out. Aside from its use 

 as a food in fruit and honey, where it occurs naturally, 

 levulose has no economic importance. 



54. Sucrose, Saccharose, Cane Sugar. — CibHkOu, graphic- 

 ally: 



This constitutes a double "sugar" group of atoms or the 

 union of two single groups. Hence it is a disaccharide. It 

 is very widely distributed in plants, being found particularly 



