216 Wisconsin Academy of Sciences, Arts and Letters. 
after a considerable quantity of ether has accumulated in it; 
and since but very little chloroform passes into the aqueous 
layer B, the latter is practically permeable only for ether, and 
therefore this aqueous layer B acts as a semipermeable septum. 
It permits ether to pass from C to A, but allows very little, 
practically no chloroform to pass into C. It is clear further 
that as A becomes richer and richer in ether, the tendency for 
more ether to enter A from B becomes less and less. Ether 
dissolves more readily in chloroform than in water because 
ether and chloroform have a greater mutual attraction for each 
other than have ether and water; it is for this reason too that 
chloroform is able to extract ether from an aqueous solution of 
the latter. As ether accumulates in A, however, the power of 
this layer to extract ether from the aqueous layer B diminishes, 
because the attraction or affinity of chloroform and ether for 
each other becomes more and more satisfied. Finally, suppose 
we prevent the supply of ether in C from becoming exhausted 
by adding some as may be required, a point will be reached 
where compartment A has become so rich in ether that the at¬ 
traction or affinity of this chloroform—ether solution for addi¬ 
tional ether has decreased to such an extent that it can no 
longer extract further ether from the aqueous layer B. In other 
words, when the chloroform solution in ether, A, has become so 
dilute that its attraction for additional ether just equals the at¬ 
traction of water for ether in the aqueous layer B, the process 
is arrested. The point at which this occurs would clearly vary 
with the temperature and also with the pressure. 
If in Fig. 1 compartment A be filled with carbon disulphide 
instead of chloroform, the process would go on as before in a 
similar manner and for perfectly similar reasons. Indeed, any 
liquid which in itself does not mix with water, practically 
speaking, and yet has a greater attraction for ether than has 
water, would serve in place of the chloroform. The rapidity 
with which the process proceeds and the final point of equilib¬ 
rium reached would, however, also be a function of the nature 
of the substance so employed. If in Fig. 1 the ether in C be 
replaced by an oil, say olive oil or a hydrocarbon oil, retaining 
