on Osmotic Theory, 



275 



The discussion ("S and S," p. 260) dealt with partially 

 tnisoible liquids, but the main trend of the whole argument 

 was that a valid equation o£ state for osmotic pressure 

 should be such that the form is applicable both to miscible 

 liquids and to solids dissolved in liquids. 



(4) If this be so, it will be apparent that with the latter 

 solutions under certain conditions of temperature 

 (and probably of pressure) there will be two more 

 points where dP Jdb = 0. 



This is shown in fig. 5, which represents the graphs for 

 .aqueous cane-sugar solutions at two different temperatures. 











/ 



f \...y 



-;- o° r 



/ 



/ 





.<* ■ ... . 







100 % 

 water. 



D 



100% 

 sugar. 



The curve passing through the origin is that representing 

 the known osmotic pressures at C C. The ordinate through 

 C marks the limit of saturation (crystallizing point), and the 

 point E is the present limit of experimental knowledge. 

 The lower curve is the theoretical graph for —10° C. We 

 know, however, that the saturation-point is at a concentra- 

 tion less than C ; we also know that, when the solution is 

 dilute, a further diminution in the concentration is followed 

 by the freezing out of the water, so that, by analogy with 

 what has already been postulated for the curve of super- 

 saturated solutions — namelv, that there are a maximum and 



T2 



