Kohlenberg—Osmosis and Osmotic Pressure. 241 
upon and the resulting liquid is absorbed by the walls of the 
canal. In our experiments the camphor in contact with the 
rubber saturated with hydrocarbon excites a flow r of hydro¬ 
carbon tow r ard it. The hydrocarbon acts on the camphor 
“dissolving” it, and the resulting solution is then so rapidly 
absorbed by the septum as to leave no liquid on the side oc¬ 
cupied by the camphor. 
When as in No. 45 pyridine is used instead of a hydrocarbon, 
the camphor is still absorbed, but not as rapidly; for pyridine 
is not taken up by rubber as readily or as copiously as are 
hydrocarbons, neither has camphor so great an affinity for 
pyridine as for hydrocarbons. On the other hand, camphor 
very rapidly disappears when CC1 4 or CS 2 (Nos. 46 and 47) 
are employed, for these substances have great affinity for rub¬ 
ber and also for camphor. 
When paraffine instead of camphor is separated from alcohol, 
toluene, pyridine or carbon tetrachloride by means of rubber, 
Nos. 48 to 51, the action is in all cases slower, which fact is 
readily comprehended when it is borne in mind that camphor 
dissolves more readily in the liquids named than does paraffine. 
Finally in No. 52, where solid silver nitrate is separated from 
pyridine by rubber, we have an illustration of a typical case 
in which the liquid accumulates very greatly on the upper side 
of the membrane. Here the solute has very little affinity for 
the rubber, and so the solution of the salt practically does not 
get into the septum on account of the fact that pure pyridine 
is more readily imbibed and silver nitrate is difficultly soluble in 
rubber soaked with pyridine, that is to say, in a hydrocarbon di¬ 
luted w T ith pyridine. If a block of cane sugar or one of chloride 
of lithium were separated from pyridine by means of a rubber 
septum the action would be similar to that observed in the 
case of silver nitrate, No. 52. The same would be true if any 
solid which is soluble in pyridine yet not soluble in hydro¬ 
carbons were separated from pure pyridine by means of a 
rubber membrane. It would be interesting to test this in the 
case of more substances which are insoluble in hydrocarbons 
and yet are soluble in pyridine, but the number of such sub¬ 
stances is rather limited, for it must be remembered that pyri- 
16 
