Aug. i2,1918 Effect of Oxygen Pressures on Metabolism of Sweet Potato 277 
At the end of the experiment the stored halves were fresh and crisp 
and in perfect condition. The only difference noted between those stored 
in air or oxygen and those stored in hydrogen was that in the roots stored 
in air or oxygen the oxidizable chromogenic material exuding from the 
cut surfaces was darkened, while in those stored in hydrogen discolora¬ 
tion was entirely absent, but appeared as soon as the potatoes were 
exposed to the air. 
These data show that the formation of cane sugar 1 in the sweet potato 
is not inhibited nor depressed in an atmosphere practically free from 
oxygen. In regard to the quantitative effects of the different oxygen 
pressures it seems clear that both in an atmosphere of oxygen and in an 
atmosphere practically free from oxygen more starch disappears and more 
cane sugar is formed than in air. The percentage of cane sugar is great¬ 
est in the potatoes stored in hydrogen. 
Since cane sugar is apparently not utilized in respiration by the sweet 
potato, the loss of other materials through respiration would result in an 
increase of the percentage of cane sugar without an increase in the actual 
quantity present. However, the possible difference in loss of material 
by respiration in air and in hydrogen is not sufficiently great to account 
for the greater percentage of cane sugar in the potatoes stored in hydro¬ 
gen. It appears, therefore, that in the absence of oxygen cane sugar is 
actually produced more rapidly than in air. A further fact worthy of 
note is that at the temperature of these experiments there is practically 
no increase in reducing sugar in the potatoes stored in hydrogen. 
1 That the nonreducing sugar formed in the sweet potato in the absence of oxygen 
is cane sugar was shown by the following experiments: 
Four small sweet potatoes, weighing together 1075.5 g m -> were cut into halves. 
One lot of halves weighing 555.5 gm. was grated immediately. From the mash three 
25-gm. samples were taken for sugar determinations. The remaining mash, after the 
removal of these samples, weighed475 gm., some loss having resulted from the adher¬ 
ence of material to the grater. From this mash the sugar was quantitatively extracted 
with 70 per cent alcohol, first by repeated decantation in the cold, and finally by 
means of a Soxhlet apparatus. After concentration of the extract under reduced 
pressure the sugar was isolated as barium saccharate, from which it was recovered in 
crystallized form. The quantity of nonreducing sugar present in the mash, according 
to determination, was 14.9 gm. The sugar recovered from the barium saccharate, 
after having been washed with glacial acetic acid and alcohol, weighed 13.22 gm.; 
0.6014 gm. dissolved and made up to 50 cc. at 2o°C., gave an angular rotation in a 
4-dcm. tube of 3.169°, to the right equivalent to a specific rotation of +65.9°. The 
remainder of the sugar was recrystallized from alcohol and yielded 12.05 g m -; 0.7440 
gm. dissolved and made up to 50 cc. as before gave an angular rotation of 3.953 0 , or a 
specific rotation of +66.4°. 
The second lot of halves, weighing 519.5 gm., was stored for 15 days in the manner 
described in the text in an atmosphere of hydrogen entirely freed from oxygen. At 
the end of that period these halves, whose weight had decreased to 505.0 gm., were 
treated like the first lot. The mash, after removal of the samples for sugar determina¬ 
tion weighed, 421 gm., and according to determination contained 24.42 gm. of non¬ 
reducing sugar. The quantity theoretically present in the equivalent of the mash 
