Kohlenberg—Osmosis and Osmotic Pressure. 229 
ing a height of 25 cm. in 4 hours. The experiment was then 
stopped and the contents of the cell examined. It was found 
that pyridine had passed into the water, but no appreciable 
quantity of nitrate of silver. The entire content of the osmotic 
cell was evaporated to dryness, the residue extracted with a 
little water and a drop of nitric acid, and the filtered solution 
tested with HC1 for silver, but none was found. 
15) The inner liquid was a 0.1 normal AgNO s solution in 
pyridine, the outer liquid pure water, and the membrane parch¬ 
ment. The main current was from the water, through the 
parchment to the AgN0 3 solution in pyridine, for the level of 
the liquid in the osmometer rose to a height of about 18 cm. in 
20 hours. Water then goes into the cell, forming the main cur¬ 
rent, but both AgN0 3 and pyridine were also found in the 
water outside, showing a considerable counter current toward 
the outer liquid. 
16) The inside liquid consisted of 0.1 normal AgN0 3 solu¬ 
tion in water, the outside liquid of 0.1 normal AgN0 3 solution 
in pyridine, the membrane being rubber. The main current was 
from the outer liquid to the inner one, the level rising in the 
stem of the osmometer. During the night the liquid filled the 
tube (which was about 32 cm. long) entirely and ran over. 
17) The outside liquid consisted of toluene, the inside 
liquid of 0.1 normal solution of AgN0 3 in pyridine, and the 
membrane of rubber. The liquid rose 22 cm. in the osmometer 
in 17 hours. The main current consists of the passage of tol¬ 
uene through the septum to the pyridine solution of the AgN0 3 ; 
however, pyridine was also found in the toluene outside as 
were mere traces of silver nitrate. 
18) This experiment was identical with No. 17 except that 
a parchment septum was employed. It was continued for 4 
days and no change was observed. It seemed as though a slight 
lowering of the level of the inner liquid might have taken place, 
so the contents of the cell were evaporated to dryness, the res¬ 
idue taken up with water and a drop of nitric acid and tested 
with HC1 for silver, after having been filtered. Only the faint¬ 
est indication of the presence of silver was thus obtained. 
