484 
Journal of Agricultural Research v 0 i. xxvm, no. 5 
cent glucose solution was used as a standard and set at 30 mm. and at 20 mm. 
The readings were then plotted and curves drawn. From the curves a table 
was constructed showing the factor by which the percentage strength of the 
standard used is multiplied in order to obtain the concentration of the unknown 
solution at any reading on the colorimeter. The columns for reducing sugars 
were obtained by multiplying the “total ’* factors by 1.045. Figure 1 contains 
the curves from which the factors in Table IV were obtained. The dotted line 
in the chart represents the theoretical ratios of direct proportionality. 
Table IV .—Factors for obtaining the “total” and “reducing” values of solutions 
for colorimeter readings from 7 to 60 
Color¬ 
imeter 
read¬ 
ing 
Total 
sugar 
Reducing 
sugar 
Color¬ 
imeter 
read¬ 
ing 
Total 
sugar 
Reducing 
sugar 
Color¬ 
imeter 
read¬ 
ing 
Total 
sugar 
Reducing 
sugar 
Standard 
set at— 
Standard 
set at— 
Standard 
set at— 
Standard 
set at— 
Standard 
set at— 
Standard 
set at— 
30 
20 
30 
20 
30 
20 
30 
20 
30 
20 
30 
20 
7.0 
7.3 
2.49 
2.42 
2.60 
2.53 
16.5 
17.0 
1.69 
1.65 
1.19 
1.16 
1.77 
1.73 
1.24 
1.21 
34.0 
35.0 
0.89 
0.87 
0.60 
0.58 
0.93 
0.91 
0.63 
0.61 
7.6 
8.0 
2.35 
2.28 
2.46 
2.38 
17.5 
18.0 
1 . 61 
1.56 
1.13 
1.11 
1.68 
1.63 
1.18 
1.16 
36.0 
37.0 
0.84 
0.82 
0.57 
0.56 
0.88 
0.86 
0.60 
0.59 
8.3 
8.6 
3.09 
2.21 
2.14 
3.23 
2.31 
2.24 
18.5 
19.0 
1.53 
1.49 
1.08 
1.05 
1.60 
1.56 
1.13 
1.10 
38.0 
39.0 
0.80 
0.79 
0.55 
0.54 
0.84 
0.83 
0.57 
0.56 
9.0 
2.97 
2.07 
3.10 
2.16 
19.5 
1.46 
1.03 
1.53 
1.08 
40.0 
0.78 
0.53 
0.82 
0.56 
9.3 
2.87 
2.00 
3.00 
2.09 
20.0 
1.43 
1.00 
1.49 
1.04 
41.0 
0.76 
0.52 
0.79 
0.54 
9.6 
2.77 
1.93 
2.89 
2.02 
20.5 
1.40 
0.98 
1.46 
1.02 
42.0 
0.74 
0.51 
0.77 
0.53 
10.0 
2.67 
1.87 
2.79 
1.95 
21.0 
1.38 
0.96 
1.44 
1.00 
43.0 
0.73 
0.50 
0.76 
0.52 
10.3 
2.60 
1.82 
2.72 
1.90 
21.5 
1.36 
0.94 
1.42 
0.98 
44.0 
0.71 
0.49 
0.74 
0.51 
10.6 
2.53 
1.78 
2.64 
1.86 
22.0 
1.33 
0.92 
1.39 
0.96 
45.0 
a 70 
0.48 
0.73 
0.50 
11.0 
2.46 
1.72 
2.57 
1.80 
22.5 
1.30 
0.90 
1.36 
0.94 
46.0 
0.68 
0.47 
0.71 
0.49 
11.3 
2.40 
1.68 
2.51 
1.76 
23.0 
1.28 
0.88 
1.34 
0.92 
47.0 
0.67 
0.46 
0.70 
0.48 
11.6 
2.34 
1.64 
2.44 
1.71 
23.5 
1.25 
0.86 
1.31 
0.90 
48.0 
0.66 
0.45 
0.69 
0.47 
12.0 
2.27 
1.60 
2.37 
1.67 
24.0 
1.23 
0.84 
1.29 
0.88 
49.0 
0.64 
0.44 
0.67 
0.46 
12 .3, 
2.22 
1.56 
2.32 
1.63 
24.5 
1.20 
0.83 
1.25 
0.87 
50.0 
0.63 
0.43 
0.66 
0.45 
12. S 
2.17 
1.52 
2.27 
1.59 
25.0 
1.18 
0.82 
1.23 
0.86 
51.0 
0.62 
_ 
0.65 
13.0 
2.12 
1.48 
2.22 
1.55 
25.5 
1.16 
0.80 
1.21 
0.84 
52.0 
0.61 
0.64 
13.3 
2.07 
1.45 
2.16 
1.52 
26.0 
1.13 
0.78 
1.19 
0.82 
53.0 
0.60 
0.63 
13.6 
2.02 
1.42 
2.11 
1.48 
27.0 
1.10 
0.76 
1.15 
0.79 
54.0 
0.59 
0.62 
14.0 
1.97 
1.38 
2.06 
1.44 
28.0 
1.07 
0.73 
1.12 
0.76 
55.0 
0.58 
0.61 
14.3 
1.93 
1.35 
2.02 
1.41 
29.0 
1.03 
0.70 
1.08 
0.73 
56.0 
0.57 
0.60 
14.6 
1.89 
1.32 
1 .97 
1.38 
30.0 
1.00 
0.68 
1.04 
0.71 
57.0 
0.56 
_ 
0.59 
15.0 
1.85 
1.29 
1.93 
1.35 
31.0 
0.97 
0.66 
1.01 
0.69 
58.0 
0.55 
0.57 
15.5 
1.79 
1.25 
1.87 
1.31 
32.0 
0.94 
0.64 
0.98 
0.67 
59.0 
0.54 
0 56 
16.0 
1.73 
1.22 
1.81 
1.27 
33.0 
0.92 
0.62 
0.96 
0.65 
60.0 
0.53 
— 
0.55 
— 
The necessity for a special set of factors to be used when the standard is set at 
20 mm. was brought out when four color preparations were compared to an 0.08 
per cent glucose standard set at 10, 20, 40, and 50 mm. The results are plotted 
in Figure 2. The dotted line represents the theoretical values which should be 
obtained if strict proportionality existed, calculated from the lowest reading of 
the standard in each set. 
COLOR FACTORS FOR VARIOUS SUGARS 
Since all reducing sugars give picramic acid when acting on picric acid, these 
various sugars can be determined by the present method, provided no interfering 
substances, either sugars or nonsugars, be present. It was therefore thought 
desirable to determine the chromogenie value of certain of the commoner sugars. 
Dehn and Hartman (6) give several of these, but not in the form of usable factors. 
The sugars used by the writers were of the highest purity, and met the specifica¬ 
tions of Pfanstiehl and Black (14) for the rare sugars. The colors produced were 
compared to the color from a standard glucose solution. The procedure -for 
