( 162 ) 



was chiefly carried out by me at Leiden, with the aid of the mate- 

 rial for comparison in 's Rijks Herbarium, and for a few rare species 

 with the help of the collections of the University Herbarium at 

 Utrecht. 



Leiden, Juni 23 ld 1908. 



Chemistry. — "The dynamic conception of a reversible chemical 

 reaction" By Prof. A. Smits and J. P. Wibaut. (Communi- 

 cated by Prof. A. F. Holleman.) 



It is generally known that our kinetic views lead to the assump- 

 tion, that with every reversible reaction we meet with two reactions, 

 which proceed in opposite directions. 



The following consideration, however, seemed to show that a direct 

 proof for this dynamic conception could not be given. 



Our power of observation only enables us to observe differences; 

 so if we observe something of a conversion, this is the consequence 

 of this that the velocity of one reaction is greater than that of 

 another, and we get an impression as if only one reaction takes 

 place, which proceeds with a velocity equal to the difference of the 

 velocities of the two reactions. 



As we shall see, this reasoning, which is perfectly correct for 

 conversions in homogeneous systems, does, however, not hold good 

 in all respects in a single case for a conversion in a heterogeneous 

 system in consequence of particular circumstances. 



The above arguments, however, seemed so convincing that up to 

 now the following indirect proof has been considered the only one 

 possible. 



The already indicated conception of a reversible reaction leads to 



a simple relation between the constants of equilibrium and the two 



k 

 constants of reaction, which runs: f=p This relation, now, sup- 



plied a means to test the kinetic conception of a reversible conver- 

 sion, and it is known that experiment has shown for the few cases 

 which have as yet been investigated, that this relation is really 

 satisfied. 



Yet it seemed very desirable to prove the correctness of our 



dynamic conception of a reversible reaction by a direct way. 



The conversion by means of which we have reached our purpose 



is this 



2CO^C0 3 + C. 



