Chemical Affinity. 187 



The application of their general theory of mass-action is 

 considered by Guldberg and Waage with reference to various 

 classes of chemical systems. 



1. Systems consisting of four Soluble Substances. 



One pair of bodies A and B x is decomposed into another 

 pair A x and B in accordance with the equation 



A+Bi=Ai+B. 



If the amounts of the individual substances (expressed for 

 the sake of simplicity in equivalent units) which are present 

 when equilibrium is established be represented by p, p u q, qi, 

 and if V be the total volume of the solution, then the active 

 masses are represented by 



2- ^ £ and^ 



the velocity with which the formation of A and B proceeds 

 by 



and the velocity with which the formation of A x and B : pro- 

 ceeds by 



* Y V* 



Deducing the condition of equilibrium, and taking k as 

 = T , and k x = v^ , then 



o t>i 



k?=kA (1) 



q qi 



If the original quantities of the four substances be P, P 1? 

 Q, and Q ll respectively, and if we suppose that equilibrium 

 ensues when a quantity f of the substances A and B is de- 

 composed, then 



?=Q + ? ^d qi=Q — f. 



k 

 Putting these values into equation (1) and taking -r- =k, we 



1 

 obtain 



kCP + 00 + ivhQ 



* 2(«-l) 



_ / MP + QQ + ^ + Q V, P,Q-*Qi m 



