THE EXCHANGE OF IONS 
eighth to twelfth day. This absorption phase in all except the 
more dilute solutions resulted in a very slight net absorption before 
the final escape of salts due to exhaustion set in. In the more dilute 
members of the series, 8 to 16M X io~^ the solutions through absorp- 
^ tion came to a level then prevail- 
ing in the distilled water control 
culture, viz., about 20M X io~^. 
This record recalls most forcibly 
the situation found in solutions of 
KNO3 and K2SO4. 
A somewhat similar experiment 
dealing with this same salt was 
carried out in a series showing a 
somewhat wider range of concentra- 
tions. Experiment 13 covered 12 
dilutions of NaCl ranging from 32 
to 384M X I0~^ with a regular 
interval of 32ikf X io~^ between 
members of the series. The ex- 
periment ran eighteen days. The 
results are plotted in figure 13. 
In this series duri]:ig an initial 
period of about three days the 
solutions increased more rapidly in 
ions than was the rule during the 
following ten to twelve days. This 
second period was marked in the 
weaker solutions by a poorly devel- 
oped absorption phase from about 
Fig. 13. Curves showing the changes the thirteenth to the sixteenth 
in concentration of the NaCl solutions ^^y^ -p^e withdrawal of ions, 
used in experiment 13. however, was never sufficient to 
overcome the previous accessions and in no solution was a net absorp- 
tion seen, although in no case was the net deficit very great. On the 
fourteenth to sixteenth day, varying with the individual culture, 
marked gain in the ion content was seen in nearly all solutions, the 
losses marking the exhaustion of the vigor of the plant. 
The general behavior of this series again suggests that of certain 
of the potassium salts. The results of these experiments with NaCl 
15 16 17 la 
