( 802 ) 
§ 6. Here we intend only to add some general remarks in 
connection with the above-given considerations. For even though 
we emphatically point out that we are entirely in the region 
of suppositions about the nature.of the “intermediate states” holding 
for every reaction, we consider it proved by the considerations of 
§ 4 that for every reaction’) such “intermediate states’’ must possess 
a real signification as far as their velocity is concerned. And 
in consequence of this we think we are able, also in connection 
with the other considerations which we have given in this commu- 
nication, to make an attempt to give a more general and lucid 
classification of the conception catalysis and allied phenomena, than 
had been possible up to now. In doing this we shall have to distin- 
guish strictly — as Van ’r Horr already does in his Vorlesungen 
Heft I p. 210 et. seq. — between influences which only affect the 
velocity, the real catalytic agents and ‘shifters of the equilibrium”, 
Hence we distinguish the following cases : 
1. A reaction which does not take place between the pure sub- 
stances, or which only proceeds slowly, is started or accelerated by 
a substance which is present in small quantity and does not take 
part in the reaction. The equilibrium that establishes itself is, how- 
ever, independent of the nature of the catalytic agent. We think e.g. 
of the equilibrium acetaldehyde, paraldehyde, metaldehyde or of the 
conversion of oxyhydrogen gas. For each of these cases we have 
undoubtedly to do with phenomena of retardation, false equillibria; 
the condition without a catalytic agent is, indeed, a local maximum 
of entropy at given energy, but not an absolute maximum. The 
catalytie agent does not change the specific energy or entropy of the 
substances in any respect, but only enables them to reach the absolute 
maximum of entropy by change of concentration. So it may be 
compared to a crystal brought into a supercooled liquid. But what 
was said in § 4 can make this action somewhat clearer to us. This 
action consists in the creation of an intermediate state, or if this 
existed already in changing its potential energy in consequence of 
which the difference of energy which determines the velocity, is 
increased. Different catalytic agents act differently in this respect, 
and so they give rise to another velocity. 
2. A substance which is added in an exceedingly slight quantity 
not only changes the velocity of reaction, but also the equilibrium. 
1) Perhaps pure dissociations e.g. NO, < 2NO, will only have to be excepted, 
