"6 POMOLOGY 



and levulose (fructose). The invert sugars are formed 

 during the ripening process of fruits and result from the 

 union of one molecule of water and one of sucrose, as follows: 



Sucrose Levulose Dextrose 



C12H22O11+H2O = C6H12O6 + C6H12O6 



Strictly speaking, invert sugar contains equal parts tf 

 levulose and dextrose, as can be seen by the above formula, 

 while reducing sugars include levulose or dextrose alone or 

 combined in varying proportions, and may include other 

 reducing sugars and even reducing substances not sugars.^ 

 This situation has led to some laxity in use of terms and 

 usually the sugars are stated as sucrose and invert or reducing 

 sugars. 



5. Sugar-content of ripe fruit juices. — Thompson and 

 Whittier have determined the percentage of sugars in ripe 

 fruit juices by means of polarized light, as they question the 

 value of determinations made by specific gravity on unknown 

 solutions. Their work showed that levulose is the dominant 

 sugar in apples, pears, quinces, and three of the grapes, and 

 far exceeds the dextrose in the apples, pears, and quinces. 

 With the plum and one variety of grape, the dextrose exceeds 

 the levulose, but only in the plum does it far exceed it and 

 in this case it is lower than the sucrose. Sucrose is the 

 principal sugar in peaches and plums. 



6. The essential oils. — Power and Chesnut ^ described 

 the oil of apples as follows: "The essential oil, as extracted 

 by means of ether from a concentrated distillate of either 

 ordinary apple parings or those of the crab apple, is at 

 ordinary temperatures a yellowish, somewhat viscid liquid, 



1 Thompson, F., and A. C. Whittier. Proc. Soc. Hort. Sci. 1912. 

 pp. 16-21. 



2 Power, F. B., and V. K. Chesnut. Jour. Amer. Chem. Soc. 42: No. 7. 



