278 
Journal of Agricultural Research 
Vol. XIV, No. 7 
before the experiment was 13.60 gm., correction having been made for the loss of weight 
of the halves during the experiment. The yield from the first crystallization was 
22.47 gm., 0.7357 g m * dissolved and made up to 50 cc. at 2o°C. gave an angular rotation 
in a 4-dcm. tube of 3.886° to the right, or a specific rotation of +66°. The residue on 
recrystallization yielded 20.69 gm.; 0.5450 gm. dissolved as before gave an angular 
rotation of 2.896°, equivalent to a specific rotation of +66.4°. The specific rotation 
of cane sugar is 66.5°. The quantity of sugar recovered from the last recrystallization 
is 7.09 gm. in excess of the quantity present in an equivalent of the mash before the 
experiment. 
In a second experiment a single large sweet potato weighing 884.5 g m - was used. 
The potato was cut lengthwise and the halves treated as described above, with the 
exception that the mash was extracted first by decantation and finally by percolation 
in the cold. The stored half, weighing 471 gm., lost 12 gm. during the experiment. 
From the mash of the first half, 9.25 gm. of recrystallized sugar were obtained; 4.4860 
gm. of this dissolved and made up to 50 cc at 20° C. gave an angular rotation in a 
2 dcm. tube of n.972 0 , or a specific rotation of +66.7°. The yield of recrystallized 
sugar from the stored half was 19.02 gm.; 4.1003 gm. dissolved as before gave an angular 
rotation of 10.892°, or a specific rotation of +66.4°. The quantity of nonreducing 
sugar originally present in the equivalent of this mash, according to determination 
and after correction for the loss of weight during storage, was 13.31 gm. The recrystal¬ 
lized sugar therefore represents an increase of 5.71 gm. 
The complete data from these experiments are tabulated here. 
First experiment. 
Second experiment. 
I. 
11. 
(Stored 
half). 
I. 
II. 
(Stored 
half). 
Weight of halves.gm.. 
Weight of stored half at end of experi¬ 
ment .;.gm.. 
555*5 
519*5 
505 
421 
24. 42 
13. 60 
22.47 
+66. 0° 
20.69 
+66.4 
413 
471 
459 
376 
22.37 
13-31 
21.50 
Weight of mash extracted.gm.. 
Weight of sucrose present according to de¬ 
termination.gm.. 
Sucrose in mash of II at beginning of experi¬ 
ment .gm.. 
475 
14.91 
33 2 
11. 45 
Yield of sugar from first crystallization, gm.. 
Specific rotation at 2o°C. 0 .. 
13. 22 
+65.9° 
12.05 
+66. 4 
10. 67 
Yield of sugar after one recrystallization, gm.. 
Specific rotation at 20 °C. 0 .. 
9 -as 
+66.7 
19. 02 
+ 66.4 
The specific rotation of the recrystallized product obtained in these experiments 
identifies as cane sugar the non-reducing sugar present in the freshly dug sweet potato 
as well as the additional non-reducing sugar formed during storage in the absence of 
oxygen. To Dr. C. S. Hudson, of the Bureau of Chemistry, the writer is indebted 
for helpful suggestions regarding the isolation and identification of the sugar from 
the sweet potato. 
A second series of experiments was carried out under the same conditions 
but the halves were kept in the desiccators for 10 days. At the end of 
that period the potatoes were in perfect condition, as in the first experi¬ 
ments. The results of this series are given in Table III. 
The statements made in regard to the first set of experiments apply 
equally well to this set. In general the change in the 10-day period is 
scarcely greater than that during the 5-day period. Only in the potatoes 
