425 



capacit}' of rapidly transmitting electricity from atom to atom they 

 must be pj-e-eniinentiy adapted to decrease chemical resistances, the 

 latter being probably occasioned by electrical tension. 



Secondly we have been guided by the consideiation, that the 

 "activation" of a colloidal catalyser is frequently dne to' a finer 

 division i.e. to an increase of the number of atoms, coming ijito 

 contact with the reacting substances at one time so that inversely 

 the paralysis must be caused by a decrease of this number. We have 

 assumed that this is the result of the presence of the above- 

 mentioned layers about the atoms of the catalyser, which may include 

 both the layer of the protecting colloid (gum-arabic, sodium-salt of 

 protalbinic acid, etc.) and the layer of all other molecules existing in 

 the medium — also that of the catalyser itself ^). (I. c. p. 262—263). 



We shall call these layers the "paralysis-layers" '■'). 



Following up this assumption we have argued that with a not very 

 active catalyser the process is bound to proceed almost till the very 

 end with constant velocity, if only care is taken to bring the H, 

 with sufiicient velocity into the liquid space. If the concentration 

 of the substance to be reduced is not too slight, then the outer side 

 of the paralysis-layer will remain saturated with the mixture of 

 this substance -\- hydrogen, whereas on the side of the catalyser 

 the concentration of this mixture (or rather of one of the components) 

 is kept at zero as a result of the great velocity of reaction. Thus 

 we measure a diffusion-process with a constant difference of level. 



Seeing that the concentration of the substance to be reduced 

 decreases towards the end, so that the paralysis-layers on the outer 

 side no longer remain saturated, the velocity of absorption is bound 

 to decrease towards the end. 



The saturation of the paralysis-layers with gaseous hydrogen was 

 brought about by me by forcibly shaking the colloidal solution with 

 H, and by raising the number of shocks in one minute, until the 

 velocity of absorption when using a very active catalyser no longer 

 increased. In this way we could make ourselves independent of the 

 first phase of diffusion (I.e. p. 262) : the dissolving-velocity of the 

 gaseous hydrogen. 



But it is especially by the following observations we believe we have 



1) This raay be observed as agglutination, flocking out or even crystallization. 



') We have imagined these layers lo be close and more or less permeable ; it 

 may be, though, that with very slight concentrations of the interacting molecules 

 they must be represented as impermeable and as having smaller or larger inter- 

 stices. It stands to reason that in this case a quite different explanation than 

 the provisional one we have given, would be required. 



28 



Proceedings Royal Acad. Amsterdam Vol. XX. 



