( 799 ) 
decided now, whether besides the quantities determined by the 
“intermediate state’ there is still a general function of the tempera- 
ture, as 1/2R7In7 which occurs in £.*) Only a further development 
of the kinetic theory and an accurate analysis of the experimental 
material in the light of such a theory, can lead us further. 
§ 5. We must now return to the conclusion of § 2. We said there 
that there is more involved in our suppositions about /', and /, 
than could be proved by the facts mentioned there. For these prove 
that / can only depend on quantities constant in the reaction. If 
we now imagine a reaction in rarefied gas state, in which the total 
number of molecules changes, then the concentrations, the pressure, 
and the specifie volume change during the reaction. So in this case 
these quantities cannot occur in £. But by far the most important 
part of the material concerning the law of the mass-action refers to 
reactions in dilute solutions, and during these reactions the pressure 
does not change. If we want to compare our supposition that / 
does not depend on the pressure with the experiment for these 
reactions, we must examine the influence of the pressure on the 
velocity of reaction. In this we must, however, take note of a cir- 
cumstance, which if was unnecessary to mention expressly in the 
foregoing discussion: the influence of catalytic agents ?), and that 
because in general the possibility exists that the solvent itself 
works as a catalytic agent, i.e, that the solvent participates in the 
“favourable” collisions, and thus occasions the exchange of the 
absorbed resp. generated heat. So we shail have to keep the possibility 
in view that the presence of fhe solvent, or of other dissolved sub- 
stances, whose quantity remains invariable (catalytic agents) is yet 
of great influence on the velocity of reaction. According as this influence 
in this sense exists or does not exist, the thermodynamic potential of 
these substances must be added to the other thermodynamic potentials 
in equation (6). 
Let us now first consider the case that neither the solvent nor 
the catalytic agent takes part in the collisions favourable for the reac- 
tion, we shall have to sum the w’, of the different reacting substances 
1) See Traurz papers Zschr. f. phys. Ch. 64, et seq. and Sackur’s criticism of them 
Zeitsch. f. Elektroch. 15 (1909). 
*) We refer to homogeneous catalysis, as appears from the text. Also elsewhere 
im this paper we have disregarded heterogeneous catalysis, particularly in the gas- 
reactions discussed in § 2, which we assumed to take place in the homogeneous 
phase, leaving undecided whether such reactions really occur, or whether every 
gas-reaction represents a case of heterogeneous catalysis. 
52 
Proceedings Royal Acad. Amsterdam. Vol. XIII. 
