16,6 Quisumbing: Determination of Glucose and Starch 593 
abscissas represent the temperatures and time intervals, and 
the ordinates the values given in column four. The curves in 
fig. 6 show in a general way that the percentage of glucose 
oxidized increases with increase in temperature and in time of 
heating. Curve 1 indicates, however, that the reaction does not 
proceed as regularly with the longer time of heating as with the 
shorter. The percentages of glucose oxidized are higher in 
Table 4 than in Tables 2 and 3, because the concentration of 
potassium permangate is larger in the mixture for Table 4 
than for the other two. 
Temperature °C. Seconds. 
60 70 80 
i 
' 
! 
90 
T 
8 60 sae 
7 H | 
8 Boe ee ee Be ate & 
$ i ae ees tae 
g 7C}-——-+-—_}-— 
EI | | 
Se ee eens Bee 
2 
s 60}-— 
; a 
50t-—4e¢ Be, 
Fic. 6. Effect of temperature and length of heating on the percentage of glucose oxidation 
by 0.1 N potassiim permanganate solution. Curve 1 is for heating power of four minutes 
and volume of mixture of 60 cubic centimeters. Curves 2 and 3 are for heating power of 
two minutes and for 60 and 100 cubic centimeters, respectively, 
In view of these results the conditions in Table 4 have been 
adopted as standard for the proposed method: 
a. 100 cubic centimeters for the final volume of the mixture. 
b. A heating power so regulated that it will raise the temperature of 
100 cubic centimeters of the mixture from 29° to 95° C. in exactly 
two minutes. 2 
c. A total time of heating of four minutes: two minutes to raise the 
temperature from 29° to 95° C. and two minutes more thereafter. 
C. APPLICATION OF THE METHOD TO GLUCOSE DETERMINATION 
METHOD OF PROCEDURE 
Place 50 cubic centimeters of 0.1 N potassium permanganate, 
25 cubic centimeters of a solution of sodium carbonate contain- 
ing 8.48 grams of anhydrous sodium carbonate per liter, and 
