• IP Tin: AMEBICAH \< &DEMY. 



Force of ( centration cells a remarkably useful means of determini 



in the ease of imperfect solutions, how the activity of a given molecular 

 species varies with the concentration. 



1MAKY. 



It has been shown that a quantity named the activity, and clo 

 related to the fugacity of the preceding paper, may be so defined that 

 it Bervea as an ideal measure of the tendency of a given molecular 

 species to escape from the condition in which it is. With the aid of 

 this quantity a -cries of equations has been obtained, which have 



ae form as the approximate equations now in common u 

 which are perfectly exact and general The utility of these equati 

 has been illustrated by their application to a number of special prob- 

 lems. From each equation two approximate equations can be immedi- 

 ately obtained, one for the vapor pressure of a •, the other 

 its solubility. From equations XXIII, and following, important approxi- 

 mate equations are obtained by substituting concentrations for activi- 

 ties. The most general of the equations are collected for reference in 

 the following list : 



For a pure substance, 



V c/> Jr III' 



( (]ul \ -I" 7 ' VIII 



V i T )p ttT* 



For one constituent of a mixture, 



(')' ; )/',.v := /// V IX 



( d -^\ =1-^. vil 



V -/' )p,n 1:1- 



all the constituents of a mixture, 



.V,r In :\ + Xj? In t., + ■ ■ ■ \ r . 



< P Jt,N ' A'/'' 



( 



/.V,Hn', + ,V< 1,,', + • • • \ Y-/V —J 



V J/-..v = A'/ ' XUI 



