( 616 ) 



Sitzendorff B. '1905, p. 3459, may be interpreted in the simplest 



manner by the succession of the reactions : 



(y^C + CJ, (1) 



nC -> C» and 2 CJ 2 -» C 3 J 4 (2) 



II. 



The measurements of Schenck and Buck have been made at the 

 boiling point of PBr 3 . As this is situated at 172°, it appears that the 

 solvent exerts a considerable accelerating influence on the transfor- 

 mation, as pure yellow phosphorus at 200° remains practically 

 unaltered. 



The solvent, therefore, acts catalytically ; a still more powerful 

 influence has A1C1 3 . If this is brought together with phosphorus in 

 vacuum tubes, the transformation takes place even below 100°. 



The catalyst is at once covered with a layer of pale red phos- 

 phorus, which it is rather difficult to remove by shaking, so that it 

 is necessary to add now and then a fresh quantity of A1C1 8 . The 

 action proceeds much more regularly if benzene (and particularly 

 PClj) is added as a solvent. At the boiling point of this, the trans- 

 formation is completed after a few hours (respectively, minutes) ; 

 the product is Schenck's scarlet-red phosphorus but much contaminated 

 with benzene and condensation products, which are retained with 

 great obstinacy. 



In connection with the explanation in part I. I believe that the 

 observations of Schenck and of myself throw some light on catalytic 

 actions in general. 



For it is very probable that in this allotropic transformation a 

 splitting occurs first; we notice that the transformation, consequently 

 the splitting, is accelerated by PBr 3 or A1C1 3 . Will this not occur generally 

 in catalysis ? As a dissociation precedes most reactions it is probable 

 that this question must be answered in the affirmative. (I wish, 

 however, to lay stress on the fact, that in answering this question 

 we do not penetrate into the real nature of catalysis. The reason why 

 the dissociation acceleration occurs, whether this is connected with 

 a temporary combination of the catalyst with the active molecules, 

 or whether the catalyst removes the cause which impedes the 

 dissociation, remains unexplained and need not be discussed here 

 any further.) 



As far as I have been able to ascertain, this conception is not 

 antagonistic to the facts observed ; in fact a number of cases are 

 known where a catalyst causes directly a splitting or considerably 

 accelerates the same. 



