90 Dr. Meyer Wilderman on the Velocity of 



If we put in the integral equation (2) T=T we have 

 tt, 1 A *o— #o„ + K K \ 



k,t =^/ w+ k( 1o «— o log ^J' 



i. <?. at T the temperature of the liquid cannot vary in any 

 finite time, the system is in equilibrium. If we differentiate (1) 

 a second time we get 



dH 



«£ =C{t + t ov -E)--2Ct; 



(It „ , t o -\~ tov — -TA- 



i. e. -7-5-= 0, when t = ~ , 



dr 2 2 



the point of inflexion is in the middle between T and T ov — K 

 (not between T and T ov ; this enables us to determine K 

 graphically) . Before 



dH n ,- ^ t + t 0V -K dH . ... 



j-Y = 0, t is < jj , and -j-g is positive; 



after 



dH A " . ^ f + * „-K , ^ . 



— =() ; £ is > ~ , and — 2 is negative. 



It should be remarked that in the above equation (1) 

 T means the real point of equilibrium. Since our apparent 

 point of equilibrium T' differs from the real point of equi- 

 librium T only by 0°'00002 or 0° 00004, and the point T' 

 can be further brought as near to T as desired, it is clear 

 that it is T and not the variable T' which here comes into 

 consideration. This follows also directly from the meaning' 

 of the equation (1), which requires that when T — ^ = no 

 more reaction should be going on in the system. When 

 T x becomes constant it means, not that no reaction is going on 

 in the system any more, but that the variation of temperature 

 of the system because the reaction becomes equal and of 

 opposite sign to the variation of its temperature under the 

 influence of the surrounding medium. Only when the effect 

 of the surrounding medium is =0 we have the real T , i. e. no 

 more reaction is possible in the system. 



As to the velocity constant K7 in (1), it is a function of 

 many factors — of the nature of the reaction, of the nature of 

 the solvent, of the nature of the dissolved substance and of 

 its concentration, of the temperature, of the velocity of 

 stirring, possibly also of some other factors, such as the 

 velocity of supercooling of the liquid before the reaction is 



