CARBOHYDRATES 1 1 5 



charometer. It is so graduated as to read directly, from the volume 

 of CO2, the per cent sugar in the original solution. The calculation 

 is based on the following reaction : 



CeHisOe -^ 2 CO2 + 2 C2H5OH 



180 88 



(7) Ferment glucose on a larger scale and obtain the alcohol as a 

 distillation product. (See Experiment VTII.) 



DISACCHAROSES, C12H22OH 



The disaccharoses are sucrose or cane sugar, maltose or malt 



sugar and lactose or milk sugar. All of these compounds split 



by hydrolysis when acted upon by enzymes or when boiled with 



acids and yield two molecules of monosaccharoses, hence their 



name, disaccharoses. They possess the composition C12H22O11 



and the reaction by which they split up into monosaccharoses 



is as follows : 



C12H22O11+ H2O --> 2 C6H12O6 



Disaccharose Mono- 



saccharose 



The disaccharoses may thus be considered as anhydrides of 

 two molecules of monosaccharoses. The conversion of di- 

 saccharoses into monosaccharoses, involving simply the addi- 

 tion of a molecule of water, is termed a reaction of hydrolysis. 

 We thus speak of hydrolyzing disaccharoses to monosaccharoses. 

 This hydrolysis, as has been stated, takes place either through 

 the agency of chemical substances known as enzymes or when the 

 disaccharoses are boiled with dilute acids. 



Sucrose or Cane Sugar, C12H22O11 



Occurrence. — The most important of the disaccharoses is 

 sucrose, or as it is known because of its most important source, 

 cane sugar. It is very widely distributed in nature and occurs 

 in almost all plants in greater or less amounts. The two most 

 abundant sources from which it is obtained are the sugar cane, 

 from which it derives its name of cane sugar, and the beet, in 



