228 Wisconsin Academy of Sciences, Arts and Letters. 
13) The inner liquid was a solution of trichloracetic acid 
in water to which considerable benzene had been added, the 
outer liquid was water and the septum rubber. Very notable 
quantities of acid passed through the membrane into the water 
without. The experiment was continued for 20 hours. 
The large increase in the amount of trichloracetic acid which 
passed through the rubber in 12 as compared with 11 is easily 
explained by the fact that benzene has considerable affinity for 
trichloracetic acid and also for rubber. In imbibing the ben¬ 
zene, therefore, large amounts of trichloracetic acid are also ab¬ 
sorbed with that hydrocarbon by the rubber. When we dis¬ 
solve trichloracetic acid in benzene we really unite the acid 
with the benzene. 1 In this homogeneous liquid, the solution, 
we have then the acid tied to the benzene; and because of the 
great affinity of the latter for rubber, the benzene solution of 
trichloracetic acid, the combination of the acid and the ben¬ 
zene, also has considerable affinity for rubber : and so the acid 
is also drawn into the rubber because it is united with benzene. 
To be sure, benzene and acid are not taken up by the rubber 
in the same proportions in which they occur in the solution, 
benzene being taken up in relatively larger amounts. This 
means that the solution is to a certain extent decomposed, i. e. 
altered in concentration, by the rubber. When the latter soaked 
with benzene and the acid is in contact with water, the great 
affinity between water and the acid again comes into play and 
by virtue of it acid passes into the water, leaving the benzene 
behind in the rubber almost completely. Similar consider¬ 
ations hold in No. 13 where a solution of trichloracetic acid, 
water and benzene is separated from water by a rubber septum, 
except that here the acid passes through in lesser quantity, and 
minor amounts of water are undoubtedly also absorbed by the 
rubber, since in the solution the water is tied on to the benzene 
and the acid. 
14) The inner liquid consisted of pure water, the outer of 
0.1 normal solution of AgN0 3 in pyridine, and the membrane 
of rubber. The liquid rose rapidly in the osmometer, reach- 
i Compare, Kahlenberg, liber das Problem des Losungen, Chem. Zeit- 
ung 29, No. 81, (1905). 
