Kohlenberg—Osmosis and Osmotic Pressure. 225 
in the osmometer showing that the main current was in the 
opposite direction as in the preceding experiment,, namely from 
the pyridine through the rubber to the water. Some water also 
passed into the pyridine, showing an appreciable minor current. 
7) The inside liquid was pyridine, the outside liquid toluene 
and the membrane parchment. No change took place. 
8 ) This experiment was like No. 7 except that rubber was 
substituted for parchment. The liquid at once rose in the os¬ 
mometer, showing the main current to be from the toluene 
through the rubber to the pyridine. Some pyridine, however, 
also passed into the toluene. 
Rubber readily takes up pyridine, and imbibes toluene still 
more readily; on the other hand parchment does not, showing 
that it has but little affinity for these liquids. It is conse¬ 
quently easy to see why no change occurred in No. 7. When it 
is further remembered that pyridine and water are consolute 
liquids, as are also toluene and pyridine the observations in 
Nos. 5, 6, and 8 are easily explained. In No. 5 the parchment 
imbibes water which is then extracted by the pyridine; but 
since pyridine is soluble in water soaked parchment, some pyri¬ 
dine also passes into the water outside. In No. 6 the rubber 
imbibes the pyridine which is then extracted by the water; but 
as water is somewhat soluble in pyridine soaked rubber, some 
of it makes its way into the pyridine without. In No. 8 the 
fact that toluene is imbibed more readily by rubber than is 
pyridine again determines the direction of the main current, 
though in this case, owing to the fact that pyridine has con¬ 
siderable affinity for rubber as well as for toluene, the minor 
current is of considerable consequence. The cases just con¬ 
sidered well illustrate how the nature of the septum and of 
the liquids that bathe it determines what will actually take 
place. 
In 1898, G. Flusin 1 used carbon disulphide, chloroform, tol¬ 
uene, ether, benzene, xylene, petroleum ether, benzyl chloride, 
turpentine, petroleum, nitrobenzene, methyl alcohol, ethyl al¬ 
cohol, and acetic acid, taking these liquids in all possible com- 
iCompt. rend. 126, 1497 (1898); ibid. 131, 1308 (1900). 
15 
