the Theory of Solutions. 005 



and remembering that C/ = — 7 . by introduction into (lid): 



G G 



We will not transform the expression to the left. If the 

 solution is not very concentrated, and the vapour-pressure of 

 the second component may be disregarded in comparison with 

 that of the solvent, we have approximately 



\zo)„ -V 



R has the same value as before. If this is introduced, 



A comparison between the equations (15 a) and (15 h) 

 immediately shows us that there is a fundamental difference 

 between solutions and gases with regard to the change of 

 concentration with the height. In the case of solutions 



^-y- can, for instance, be equal to zero without the concen- 



tration itself being equal to zero, and this may just as well 

 happen at the greatest concentrations. In the case of gases, 

 however, the concentration-gradient will never be equal to 

 zero, but will approach this value on the density decreasing 

 ad infinitum. It might be said, however, that solutions and 



gases approach conformity, at unlimited dilution, since ^__^ 



as well as ^-r- then approach zero : but that similarity 



disappears in the case of concentrated solutions. 



In the following table ^jr* nas ? according to equation (II b) 



been calculated for solutions of Cane Sugar and Potassium 

 Hydrate at some concentrations *. The numbers refer to 



the absolute system of units. Then ^y is of the dimension 

 Mass . Length -1 = gr. cm." 4 . 



* The density measurements are taken from Lanclolt and Bernstein. 



