THE VOLATILE PART OF PLANTS. 67 



The composition of saccharose is the same as that of 

 arabin, and it contains in 100 parts : 



Carbon 42.11 



Hydrogen 6.43 



Oxygen 51.46 



100.00 



Cane-sugar, by long boiling of its concentrated aqueous 

 solution, and under the influence of hot dilute acids (Exp. 

 32) and yeast, loses its property of ready crystallization, 

 and is converted into levulose and dextrose. 



According to Dubrunfaut, a molecule of cane-sugar takes up the ele- 

 ments of a moleciile (5.26 per cent.) of water, yielding a mixture of 

 equal parts of levulose and dextrose. This change is expressed in 

 chemical symbols as follows : 



C l2 H 22 O n + H,0 = C 8 H 12 6 + C 6 H 12 6 

 Cane-sugar. Water. Levulose. Dextrose. 



This alterability on heating its solutions occasions a 

 loss of one-third to one-half of the saccharose that is 

 really contained in cane-juice, when this is evaporated in 

 open pans, and is one reason why solid sugar is obtained 

 from the sorghum in open-pan evaporation with such dif- 

 ficulty. 



Molasses, sorghum syrup, and honey usually contain 

 all three of these sugars. 



Honey-dew, that sometimes falls in viscid drops from 

 the leaves of the lime and other trees, is essentially a mix- 

 ture of the three sugars with some gum. The mannas of 

 Syria and Kurdistan are of similar composition. 



Maltose, C 12 H 22 11 .H 2 0, is formed in the sprouting 

 of seeds by the action of a ferment, called diastase, on 

 starch. It is also prepared by treating starch or glycogen 

 with saliva. In either case the starch (or glycogen) takes 

 up the elements of water, 2 C 6 H 10 5 -j- H 2 = C 12 H 22 O n . 

 Maltose in crystallizing unites with another molecule of 

 water, which it loses at 212. Maltose, thus dried, 

 attracts moisture with great avidity. 



Boiled with dilute acids one molecule of maltose yields 



