of Chemical Potential to the Theory of Solutions. 37 



The Chemical Potential of the Solute. 



Hitherto we have considered the variation of the chemical 

 potential of the solvent only. The chemical potential of the 

 solute is connected with that of the solvent by the equation 



^-fo(s, p, 0) + s |- f(s, p 9 0) = 0. 



Hence if s 1 and s 2 are two values of the concentration we 

 have 



-i 



fo( s i>P> e ) 



dfa{s, p, 6) 



(13) 



Hence if the value of f (s,/>, 6), to an undetermined constant, 

 be calculated from experimental data, the value of /i(s,p, 0), 

 to an undetermined constant, may be calculated by a simple 

 quadrature. 



The solute potential is involved directly in the equilibrium 

 between the solution and the solid solvent. The saturation 

 concentration s is determined as a function of the tempera- 

 ture and pressure by the equation 



/.(ftft *)=*(?. flu 



Hence we have 



A^p, 0)=f x (s,p, 0)-fi(s,p, 0). 



If the experimental data giving the value, to an arbitrary 

 constant, of the solvent potential, extend to the saturation 

 concentration, the value of the solute potential lowering may 

 be calculated by means of the equation 



fo(h,P>9) 



*!(**«-:(■ *&*&-. . . (14) 



fo&P, 9) 



The heat of solution is connected with the solute potential 

 lowering by the equation * 



-dO I "6 J 2 " " 



* Duheni, La Mecanique Chimique, vol. iii. p. 133. 



