( 60) 



oï a: RT. Except with H^, where y is negative at the ordinary tempe- 

 rature, y is everywhere positive. But at liigher temperatures its vahie 

 is reversed, and becomes negative. 



So, when comparing (2'') and (3), we see clearly, that it is ont 

 of the question that the so-called osmotic pressure should follow the 

 gas laws. Only with c = this would be the case, but for all other 

 values of c the deviation for the osmotic pressure is altogether different 

 from that for the gas pressure. This is still more clearly pronounced, 

 when we compare the original formulae. For the osmotic pressure 

 viz. the equation 



RT RT 



7t:^~{- log (1-.0) = — X (1 + V, X' + . . .) 



holds; for the gas pressure on the other hand: 



RT 



P = 



V \ V J' 



so that the deviations from the gas laws (at the ordinarj^ tempe- 

 ratures) are even in Ojyposite se'use from the deviations of the osmotic 

 pressure for non-diluted solutions. 



In view of these facts it is in my opinion no longer possible to 

 uphold the old conception of the osmotic pressure as arising in 

 consequence of a pressure of the molecules of the dissolved substance 

 comparable with the <jas pressure. The molecules of the dissolved 

 substance have nothing to do with the osmotic pressure except in 

 so far as they reduce the uiater in the solutions to another state of 

 concentration (less concentrated), wiiich causes the pure water (concen- 

 tration 1) to move towards the water in the solution (concentration 

 1 — x) in consequence of the impulse of diffusion. On account of 



Rl' 

 this a current, of which the equivalent o/ pressure =^ — {-log{\-x)), 



arises in the transition layer near the semi-permeable membrane, 

 Avhich current can only be checked by a counter pressure on the 

 solution of equal value : the so-called osmotic pressure. 



This is in my opinion the onli/ correct interpretation of the osmotic 

 pressure. 



As I already observed on former occasions, we might just as well 

 speak of an "osmotic" temperature, when the impulse of diffusion 

 is not checked by pressure on the solution, but by cooling it. For 

 at different temperatures the temperature functions 6\ (cf § 2) are 

 no longer the same in the two members of 



/*i ('^', ^) = Ih (o, T,), 



