W. A, Davis 



13 



acetate solution added and the mixture well shaken ; within 10 minutes 

 a small quantity of sodium carbonate was added to complete the 

 precipitation of the lead and the solution diluted to 100 c.c. at 15°. 



The results given show an average of 99-6 % . The reduction value 

 is again sUghtly low and the polarisation slightly high, probably owing 

 to a slight influence of the salts present. 



Expt. 3. Laevulose left for different times with basic lead acetate. 



50 c.c. of laevulose solution 1 were mixed with 5 c.c. (or 10 c.c.) of 

 basic lead acetate solution and left for different times in a stoppered 

 flask. The lead was then precipitated with sodium carbonate or 

 sulphate and the solutions made up to 100 c.c. at 15°. In each case 

 the average of two or more concordant values is given. 



These experiments show clearly that the effect of leaving the basic 

 lead acetate with the laevulose is to cause part of the latter sugar 

 apparently to disappear ; as the time increases, more and more laevulose 

 is apparently lost. The greater the amount of basic lead acetate 

 added the greater is the effect in the- same time (compare the experi- 

 ments with 5 c.c. and 10 c.c. respectively of lead acetate). As the 

 laevulose is transformed into glutose, a sugar with almost a negligible 

 rotatory power and a reducing power about half that of laevulose, the 

 amount of sugar remaining, calcidated as laevulose, is always considerably 

 lower by polarisation than by the reduction method. 



