132 THE CARBOHYDRATES 



of the levulose. The most accurate way of estimating maltose 

 is by one or other of the gravimetric methods indicated below, 

 or by the method of Brown, Morris, and Millar,* 



Estimation of Mixtures of Sugars. 



To illustrate the application of the above methods in the 



analysis of mixtures of sugars the following examples are 



given : — 



GLUCO^ AND SUCROSE. 



1. Take lOO c.c. of the mixture and titrate with Fehling's 

 solution. 



2. Invert lOO c.c. of the mixture by the method given, 

 and titrate. 



The first operation gives the amount of glucose = a. 

 The second operation gives the original amount of glucose 

 together with that due to the inversion of the cane sugar = h. 



.-. [b — a) X -95 = sucrose. 



GLUCOSE AND MALTOSE. 

 Proceed exactly as for glucose and sucrose :• — • 



a = amount of sugar before inversion. 

 b = amount of sugar after inversion. 



From the reasons already given under maltose, it follows 



that— 



{b — a) X 2-32 = maltose, 

 and a — (maltose X '62) = glucose. 



CANE SUGAR AND MALTOSE. 



Cane sugar is inverted by citric acid, while maltose is not ; 

 this fact may be made use of in the estimation : — 



1. Add to 100 c.c, of the solution 5 grams of crystalHzed 



citric acid, and heat on the water bath for about one 

 hour. Neutralize and titrate. 



Reducing power = a. 



2, Completely invert another 100 c.c. of the solution with 



hydrochloric acid ; neutralize and titrate. 



Reducing power = b ; 

 then [b — a) x 2'32 = maltose, 

 and (a — maltose x "62) = sucrose. 



* Brown, Morris, and Millar: "J. Chem. Soc," 1897, 71, 105. 



