THE POTATO TUBER. 
7 1 
Grams of chloride calculated as NaCl per ioocc of 
Solution. 
Tubers steeped in 
10% brine 
15% brine 
At commencement of experiment 
9-65 
14-53 
After 2 days’ steeping 
9 - 7 1 
14-43 
>> 5 > » > > 
9-83 
14.46 
,, 8 ,, ,, 
9.69 
I 4- I 9 
As the above results show, commencing with brines of 
9.65% and 14.53% strengths, the amounts of salt which are 
absorbed as shown by the decrease in strength of the solu- 
tion is relatively small. These steeping experiments were 
conducted in open vessels, and consequently no attempt 
was made to control evaporation of water from the surfaces 
of the brines. While loss of water by evaporation tends 
to increase the strength of the brine solution, absorption 
of salt by the steeped tubers tends to decrease it. At every 
stage of the experiment, therefore, in attempting to follow' 
the change of strength of the solution, what w'e actually 
measure is the resultant of two opposed processes. The 
values afforded by these experiments really show' that 
finally salt is absorbed by the steeped tubers. 
More satisfactory proof of this statement is furnished 
by determinations of the amounts of chlorides in untreated 
tubers and in tubers which had been steeped for ten days 
in brines of 10% and 15% strengths respectively. The 
material in these experiments was carefully dried, its 
moisture content determined, and the residue after dessi- 
cation was repeatedly extracted with water, the chlorides 
being determined in the extract by the customary volu- 
metric method. 
Table V. 
Percentage of chlorides calculated on air-dried tissue. 
Chlorides 
Approximate 
(calculated 
relative 
as NaCl) 
increase in 
salt content- 
Intact untreated tubers 
Intact tubers after 10 days’ 
0.28% ... 
. . . . T 
steeping in 10% brine 
0.25 
. . . . I 
15% brine 
O.54 
. . . . 2 
The amounts of salt absorbed by intact, i.e., unpeeled 
tubers obviously is relatively small, even after ten days’ 
steeping in strong brines, and the deduction to be made 
from these experiments, although the permeability or non- 
permeabilitv of the skin of the tuber to salt in solution is 
not definitely proved, is that it is certainly not freely per- 
meable. 
