the Theory of Solutions. 613 



On this supposition 



and consequently 



d V =dp~dp a ^^dp-^dp w 



BPn "dp V 



o'dp "dp\ Po^P' 



dp d/ 7 V ' <^> /* 

 In order that equation (8) also be fulfilled, we must have 



p cK 

 Pi 

 That this equation be fulfilled, we must either have 



or 



^ _p — po 



"dp p 



The first of these equations implies that the osmotic pres- 

 sure is independent of external pressure, which will not be 

 the case generally. 



The second equation can according to (4a) only be fulfilled 



when ^— is equal to zero ; but this is in contradiction to 

 On 



our supposition. If. however, we had to do with such a 



special case, we should get 



377 



\*c \ \bc) Va 



This is apparently an indeterminate expression, which is, 

 however, determined by the limiting value 



"We thus come to the result, so very important Jto^the 

 theory of Osmotic Pressure, that the variation of this pressure 

 with the concentration will be different, according as the 

 pressure during the variation is kept constant on the solution 

 or on the solvent. 



