22 Mr Vegard, On the Free Pressure in Osmosis. 



where the stationary state is well marked. We shall here mention 

 some reasons that strongly support this view. 



(1) The velocities for higher concentrations are connected to 

 those for lower with a very simple function, which naturally must 

 support the assumption of a similar mechanism. 



(2) The form of the curve in the case when the stationary 

 state is not obtained shows clearly that the first sudden diminution 

 of the velocity has a cause independent of that which causes 

 the diminution after the sudden bend. The first diminution is 

 naturally explained by the fact that the concentration next to the 

 membrane is diminished on account of the flow of solvent, the 

 latter is naturally explained by assuming that the solution on 

 account of the high free pressure and of want of seraipermeability 

 is gradually forced into the membrane ; for then the path along 

 which the motion takes place as a diffusion will be augmented 

 and the velocity diminished. From this point of view it seems to 

 be a necessary condition for the forming of a well marked steady 

 state that n maintain a small value. 



(3) Another support for our assumption we get by comparing 

 the velocities here found with the velocities corresponding to 

 TT = given in the earlier paper*. In spite of the great diiference 

 in the maximum electric resistance of the membrane all the 

 velocities very nearly give the same curve. On the other hand 

 we saw that the frictional resistance kept very nearly constant 

 from one experiment to another. Now the value of n, however 

 great or small it is, must depend on the degree of semipermeability 

 or upon the maximum electric resistance. If then n had a con- 

 siderable value, we should expect that the velocity in the stationary 

 state should vary greatly with the electric resistance, this being 

 not the case we must assume n to be a small quantity. 



10. As long as w is a small quantity the free pressure is 

 determined by equation (5) and we get the following rule : 



Let {q\) and (ttq \o) be corresponding points, then q is the Free 

 Pressure developed in the stationary state of osmosis with a solution 

 of Osmotic Pressure ttq. 



The highest free pressure in the steady state will be A\n, 

 which in the case considered is only 23*3 atmospheres. 



When n is small in the steady state it must be the more so 

 before this state is reached and even when the stationary state is 

 not well defined we must be able to assume that n is very small 

 at least at the moment the velocity sets in. In the case of the 

 highest concentration the free pressure at the beginning of osmosis 

 has a value of about 40 atmospheres. 



As the free pressure cannot be greater than the osmotic 



TT jA. 



pressure the possible velocities must lie between -p and — where 

 * loc. cit., Exp. I, II, III. 



