( 615 ) 



On the contrary as in so many other chemical transformations, 

 we must assume that the measurements executed only apply to a 

 subdivision of the reaction, namely to that with the smallest velocity. 



In this case it is only natural to suppose that the velocity deter- 

 minations of Schenck and Buck apply to the decomposition of the 

 P 4 molecule 1 ) into more simple fragments (P 3 ofP), then at once 

 condense to the red modification so that we may represent the 

 whole process in this manner for instance: 



P 4 (yellow) -» 2P, (1, 



nP, -* P,n (2) 



in which the reaction velocity of (2) is very much larger than that of (1). 



(We might also suppose, as a primary reaction the transformation 

 of the metastable phosphorus into a labile P 4 ; this, however, I do 

 not think so probable because, in the determination of the vapour 

 density above 1000°, a splitting has been indeed observed). 



It cannot be a matter of surprise that this decomposition velocity 

 at 200', (without catalyst) will still be extremely small, looking at 

 the great stability of P 4 in the state of vapour; and if this decom- 

 position, as I suppose, must precede the condensation, the separation 

 of the red phophorus at that temperature will proceed at least equally 

 slowly. 



There is also nothing very improbable in the very rapid transfor- 

 mation of the dissociated P 3 or P into red phosphorus. 



The fact that the allotropic transformation takes place particularly 

 under the influence of sunlight is certainly not in conflict with the 

 idea of a primary splitting, as we know that the actinic rays accelerate 

 the decompositions (such as of HJ, AgBr, C 3 J 3 , etc.). 



I wish also to point out that a primary splitting is also accepted 

 in other monomolecular reactions, such as in the decomposition of 

 AsH s (van 't Hoff's Vorlesungen), of CO (Schenck B. Ch. G. 1903 

 p. 1231 and Smits and Wolff. (These Proc. 1902 p. 417). s ) 



The monomolecular splitting of C 3 J 3 into C and C 3 J S Schenk and 



1 ) Although the size of the molecule of the liquid yellow phosphorus is not 

 known with certainty, the identity with that of the vapour is however very probable; 

 for the rest it does not affect the argument. 



2 ) I omit purposely the beautiful researches of M. Bodenstein, although for the 

 union of S and H. he also arrives at the conclusion that a primary splitting of 

 the S 8 molecule precedes the union with H 2 , because we are dealing here with 

 heterogeneous systems in which solubility velocities play an important role. It is not 

 impossible, that in all cases in which amorphous substances separate we arc 

 dealing with such solubility velocities. 



42 

 Proceedings Royal Acad. Amsterdam. Vol. IX. 



