236 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



condenser. The solution is cooled, neutralised with soda, and made up 

 to the same volume as the non-hydrolysed lactose solution with water 

 as above. 



It is best to make up the solutions in a measuring flask, e.g. 25 c.c. 

 lactose solution are diluted to 100 c.c. ; 25 c.c lactose solution are 

 hydrolysed by acid, neutralised, and washed into the 100 c.c. measur- 

 ing flask. 



The reducing value of the hydrolysed lactose solution is taken ex- 

 actly. 



r^, r reducing power of lactose in c.c 10 



The factor is -= r : = 



reducing power of hydrolysed lactose in c.c. 7 



The ratio of the reducing powers of glucose : lactose : maltose are 

 as I : 074 : 0*62. 



The percentage of lactose may be calculated as follows : 



x c.c. = 10 c.c. Fehling's solution. 

 .'. x x c.c. = 0-05 gm. lactose. 



or x c.c. = 0-05 x gm. lactose. 



10 100 

 Hence 100 c.c. = 0*05 x x gm. lactose. 



The weights of the disaccharides which will reduce completely 10 

 cc. of Fehling's solution are : 



cane sugar 0-0475 gm. 

 maltose 0-0807 

 lactose 0-0678 



ESTIMATION OF POLYSACCHARIDES. 



All polysaccharides are estimated in the same way as cane sugar, 

 i.e. by taking the reducing value of a known weight or volume of the 

 solution after hydrolysis by acid, i.e. in terms of glucose : 

 C 6 H 10 6 + H a O = C 6 H la o 6 - 



