186 Mr. M. M. Pattison Muir 



on 



coefBciont of the substances by a, b, and c, the expression for 

 the velocity of formation of the new compound becomes 



<fi . apbqcr = kpqr, 



where k is again taken as representing the product of the co- 

 efficients. 



The velocity of formation of an addition compound consist- 

 ing of a molecules of A, /3 molecules of B, and y molecules of 

 C, is expressed as follows : — 



(/> . apap .... bqbq .... ever 



= $.a a p a b' 3 qWr y 



= kp a g p r*, 



where k expresses the product of all the coefficients. 



The velocity-coefficient, as also the coefficients a, b, c, must 

 be considered as dependent not only upon the nature of the 

 substances in the system, but also upon the temperature ; the 

 nature of this dependence can only be discovered by expe- 

 riment. 



If the velocity of formation of the new substances be thus 

 found, it is only necessary to equalize the velocity of the two 

 opposing reactions in order to arrive at the conditions of equi- 

 librium of the system. 



The absolute velocity with which the chemical change pro- 

 ceeds is evidently equal to the difference between the velocities 

 of the two opposing reactions. 



It is evident that this development of the theory of mass- 

 action supposes that the influence of secondary forces (p. 183) 

 is overlooked. It is probable that the action of these forces 

 may be disregarded when very dilute solutions of the reacting 

 substances are employed. 



From their general treatment of the subject of chemical 

 equilibrium, Guldberg and Waage have been led to regard 

 those processes as complete in which chemical reactions si- 

 multaneously proceed in two opposite directions. On the 

 other hand, when but one of these opposing changes is accom- 

 plished, they regard the process as incomplete. By withdrawal 

 from the sphere of action of one or more of the products of the 

 first part of the process, or by the occurrence of secondary 

 reactions, or by the maintenance of the temperature within 

 certain limits, or by the assumption, by the affinity-coefficient, 

 of a value such that a condition of equilibrium is attained 

 when extremely small quantities of the reacting bodies are 

 present — by these circumstances the occurrence of the reverse 

 action, and hence the completion of the chemical process, may 

 be prevented. 



