LIQUID SOLUTIONS 19 



pied by the solution, dissolved particles exhibit at least one 

 of the fundamental properties of gas particles, namely, that 

 of indefinite diffusion. It will be gathered from what was 

 said under the preceding headings that the same is true for 

 liquid and gas solutes. 



As in gases and in solutions with liquid and gas solutes, 

 this tendency of the solute to diffuse (diffusion tension) may 

 be measured. It is found that, for the same temperature 

 and volume, the same number of particles of different solutes 

 gives always the same diffusion tension. Thus the solute in 

 such a solution exhibits another principle of gases, namely, 

 that of Avogadro. This, too, is true for liquid and gas 

 solutes. The principle does not hold rigorously for very 

 concentrated solutions. There is developed here also a dif- 

 fusion tension on the part of the solvent, which varies with 

 temperature just as does that of the solute. 



If two solutions containing different concentrations of the 

 same solute in the same solvent are brought into direct con- 

 tact, it is found that diffusion of solvent and solute will at 

 length equalize the concentrations of the two solutions, so 

 that the solute particles will at last be equally distributed 

 throughout the combined volume. Therefore diffusion of 

 solute particles must be more rapid from the stronger to the 

 weaker of the two solutions than in the opposite direction. 

 That is, the diffusion tension of the solute is greater from a 

 higher concentration to a lower than from a lower to a 

 higher. But the diffusion tension of the solvent is greater 

 in the direction from the lower concentration to the higher. 

 This is also true in the case of gas and liquid solutes. When 

 reference is made to the "concentration" of a solution, the 

 concentration of the solute is always meant. 



