Filter and read the polarization of the filtrate, $, for a 200-mm tube. 

 Remove the excess of lead from the filtrate, if lead has been used as 

 clarifying agent, with sodium carbonate or potassium oxalate and filter. 

 To 50 cc of the filtrate add acetic acid by drops until the reaction is 

 acid to litmus, add 5 cc of the stock invertase solution and make up 

 the volume to 100 cc. Add a few drops of toluene to the solution to 

 prevent the growth of micro-organisms, shaking so as to saturate, and 

 allow to stand at any temperature between 20 and 40 C. overnight. 

 Under usual conditions about six hours' time is required to accomplish 

 complete hydrolysis. In the morning bring the temperature to 20 

 and read the rotation of the solution, /, for a 400-mm tube. The per- 



.o 



o.a 0.4 0.6 o.a /.o 



.002 .004- .ooe .ooe .o/ o 



> AC/DtTY OF SOLVr/0/V 



FIG. 1. Influence of strong and weak acids on the activity of invertase. 



centage of cane sugar present is then calculated by the formula given 

 on page 4. The percentage can also be found by the cuprous oxid 

 reduction before and after inversion by the invertase. 



THE INFLUENCE OF MUTABOTATION ON THE INVERT 

 POLARIZATIONS. 



The temperature does not influence the rotation of glucose, but 

 changes that of fructose greatly, and the change of rotation lags 

 behind the change of temperature. This lag is due to the mutarota- 

 tion of fructose and practically disappears in inversions by hydro- 

 chloric acid, for the reason that the acid is a strong katalyst of the 

 mutarotation. In solutions inverted by invertase the lag for fructose 

 which follows a change in the temperature of the solution lasts about 

 ten minutes at 20 C., and care should therefore be used in reading 



Cir. 50. 



