ORGANIC COMPOUNDS OF PLANTS 



193 



252. fliscellaneous Sugars. A number of sugars that 

 do not belong to either the dextrose or sucrose group 

 are found in plants. Raffinose, for example, is a sugar 

 found in small amounts in beets and other vegetables. 

 It is capable of being converted into dextrose sugars by 

 treatment with dilute acids. 



253- Optical Properties of Sugar. Sugars are charac- 

 terized as optically active or inactive. Those which 

 have the power of turning a ray of polarized light to the 

 right are called dextrorotatory while those which turn the 

 ray to the left are called levprptatpry. Polarized light 

 has no action upon the inactive sugars. This principle 

 is taken advantage of in the commercial testing of sugar 

 by means of the polariscope which is a piece of apparatus 

 so constructed that the number of degrees which a ray of 



Fig. 78. Polariscope. 



polarized light is diverted in passing through a solution 

 of sugar can be accurately measured, and the purity of 



