(1184) 
the thermodynamic potential of the substance passing tbrough the 
membrane should be the same on the two sides, and we were not 
justified in this. For it is indeed true that in states of equtlibrium 
the thermodynamic potential of a component is the same in every 
phase, but here we have no state of equilibrium, because there 
continues to exist a difference of temperature between solution and 
solvent, and so a current of heat. It is just by this that the “osmotic 
temperature’ is distinguished from the osmotic pressure, that the 
latter gives a state of equilibrium, though under special restricting 
conditions (the membrane). 
Yet it is clear that it must be possible to reach a stationary state 
by rise of temperature in the way indicated ; but the condition on 
which this takes place, must not defined in this way that the 
thermodynamic potentials become equal. As it is self-evident that 
this condition will have to be that the total number of particles 
passing through the membrane is zero, it follows further that formula 
(3) cannot be maintained, and will have to be replaced by a relation 
of the form: 
N=F(u,T). . KE ee) 
Other quantities than the temperature (and constants) cannot occur 
in this relation, because the properties of the thermodynamic poten- 
tial in equilibrium, i.e. at one definite temperature in all phases, 
require that equation (5) reduces to (3) for constant temperature. It 
is now neccessary for both problems to define the form of equation 
(5) closer. It is clear that a purely thermodynamic reasoning is not 
adequate to do so, because the problem we want to solve, falls 
outside thermodynamics as relating to states of non-equilibrium. Ther- 
modynamics ean only give indications about the solution, however 
valuable these may be; the solution itself can only be obtained by 
kinetic means. One of these indications is this that the function of 
equation (5) will have to be of such a nature that the condition 
N, = N, does not lead to the absurd result (4). Now this absurdity 
already disappears when equation (5) is brought into the form: 
HK 0 EN TN 
RI 
in which the factor F is required by the consideration that N is 
a number of molecules that reaches a certain surface in the unit 
of time. As u is of the dimension of an energy, also the denomina- 
tor will have to be of this dimension, the factor C being in a cer- 
tain relation with the unit of time and surface. If we draw up the 
condition of equilibrium by the aid of (6), it runs of course as- 
follows : 
_ 
