Reaction before Complete Equilibrium. 479 



of reaction. Giving proper attention to the above, we 

 see at once that what we were always accustomed to con- 

 sider "as chemical action between solids (or liquids) and 

 gases (or substances in solution) " does not exist at all, but 

 that these reactions are of a complicated nature, always con- 

 sisting of two different kinds of reaction. The first, solid 



N H 4 C1 ^ gaseous NH 4 C1 (or Aj solid ^ n'A 1 in solution) , re- 

 presents either the evaporation or solution of a solid, or the 

 condensation of the vapour to the solid or the separation of 

 the salt from an oversaturated solution. The second, gaseous 



NH 4 Cr^N"H 3 gas + HC1 gas (or ?iAj in solution^mBi in sol. 



+ m'Ci in sol.), represents a chemical reaction in the homo- 

 geneous system (gaseous or in solution). The first kind of 

 reaction is regulated by the equation 



^=c(*o-*).('-'«+K) 



as shown above, the second by the law of action of mass. 

 Consequently we have not to deal here with different laws 

 for the different kind of equilibrium in heterogeneous systems, 

 but the equation found for the complete equilibrium and the 

 point of transition forms at the same time the basis of 

 incomplete equilibrium in heterogeneous systems, the basis 

 for the so-called chemical velocity of reaction and chemical 

 equilibrium in heterogeneous systems. We have, therefore, 

 arrived at the following very clear discrimination : — 



Chemical action between substances is restricted only to homo- 

 geneous systems. The law of action of mass is the regulating 

 principle here. Two opposite reactions are here taking place 

 simultaneously , since the molecules of each kind have in the 

 vapour-space, or in solution, the same kind of free movement, the 

 same possibility of meeting together and acting one upon another. 



In the same way the mutual action between different parts of 

 the heterogeneous systems is in all kinds of equilibrium restricted 

 solely to the transportation of the substance {possibly molecular. 

 but no chemical transformation) from one part of the system to 

 the other. This is regulated by the equation 



d L= c (t -t)(t-t ov +K), 



ClT 



i.e., the surface of contact of the reacting parts of the system and 

 the remoteness from the point of equilibrium are here the regulating 

 principle. 



