66 Dr. Meyer Wilderman on the Velocity of 



can be investigated very much better than those given under 

 §3, owing to the fact that their velocity is considerably smaller. 

 Supersaturated solutions o£ N0 3 K and of NH 4 C1 > were chiefly 

 investigated since the latent heat of separation is sufficiently 

 great and the phenomenon is not complicated by the forma- 

 tion of hydrates. Therefore our differential equation is again 



J=c(«-O('»-0, 



i. e. the velocity of reaction is directly proportional to the 

 surface of the solid in contact with the liquid and to the 

 amount of supersaturation (temperature below temperature 

 of saturation), not the total quantity of the salt dissolved. 

 This is a remarkable fact, which throws an interesting light 

 upon all the phenomena belonging to the region of perfect 

 equilibrium. 



As is to be seen from the above equation, the reaction must 

 completely cease at the point of equilibrium when t becomes 

 = t . At the same time I arrived then at the general 

 conclusion that before the point of equilibrium only one of 

 the two opposite reactions can take place, and that complete 

 equilibrium is of a static not of a dynamic nature. Thus, at 

 the point of equilibrium, no molecules are exchanging con- 

 dition in the different parts of the heterogeneous system, 

 i. e. the state of the system is not, as is generally assumed, 

 such that the velocity of ice-melting of one part becomes 

 equal to the velocity of ice-separation in the other, or that 

 the velocity of evaporation of the liquid becomes equal to the 

 velocity of condensation of its saturated vapour, but such that 

 reactions in every part of the heterogeneous system com- 

 pletely cease. In the same report the conclusion was drawn 

 that since all the reactions before perfect equilibrium which 

 were investigated proved to be represented by the same 

 equation, this equation must contain the general law which 

 governs the velocity of reactions of all other kinds of reaction 

 before perfect equilibrium as well. 



More recent Experiments. 



It was found that the reactions described in the above 

 Report under 3, 4, and 5 could not be investigated through 

 the whole length of the curve. The middle part only of the 

 curve, not its beginning and end, could be experimentally 

 tested for the following reasons : — We have to consider that 

 when we are measuring the temperature of a liquid by means 

 of a mercury-thermometer the same assumes the temperature 



