CARBOHYDRATES AND RELATED BODIES. 35 



more readily than in the case of cane sugar, which is a fact 

 of considerable physiological importance. 



Iso MALTOSE. This is a sugar which has been made by the 

 action of fuming hydrochloric acid on glucose. It also accom- 

 panies the true maltose in the products formed by the action 

 of diastase on starch. It differs from maltose in rotating 

 power, which is much less, in the character of its phenyl osa- 

 zone, and in water solubility. It reduces copper and bismuth 

 solutions but undergoes fermentation with yeast very slowly. 



Other disaccharides known have but little importance. Mycose or 

 trehalose is found in certain fungi, agarose is obtained from the juice 

 of the agave plant. Melibiose and turanose are formed in the hydrolysis 

 of certain polysaccharides. 



The Saccharotrioses or Trisaccharides. This group con- 

 tains a few sugars and but one of these is important at the 

 present time. 



MELITOSE or rafrinose. This sugar, having the formula 

 C 1S H 32 O 16 + SH 2 O, is found in certain kinds of manna and 

 also in sugar beets in small amount. It is characterized by 

 having a strong rotation, [a]^ = 104.5. Being more sol- 

 uble than saccharose it is found in the last crystallizations from 

 beet juice, and thus sometimes contaminates the beet sugar. 

 Its high rotation may cause an error in the estimation of 

 sugar by the polarimeter. When inverted with acids it yields 

 fructose, and the disaccharide melibiose. 



THE DETERMINATION OF SUGARS. 



This is carried out in several ways. In one method the 

 reactions depend on the reducing power of sugars on alkaline 

 copper or other metallic solutions. The Fehling reagent is 

 usually employed. Methods with the polariscope will be 

 described later. 



Method with Fehling's Solution. Fehling's solution, as 

 described above, is made arbitrarily of such a strength that one 

 cubic centimeter is reduced by 5 milligrams of glucose, on the 

 supposition that the sugar and copper salt react on each other 



