ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 149 
in the case of esters at least, the equilibrium position is not the same 
with acid as catalyst as with lipase (Dietz, 1907). In the former 
ease, the equilibrium’ is with 85°5 per cent. ester (amy! butyrate) ; in 
the latter, with 75 per cent. ester. The equilibrium is a genuine one 
in both cases, since it can be reached from either direction. If water 
Were more highly adsorbed from this mixture than the other con- 
stituents, the result, which shows more hydrolysis than in the case of 
acid, might be explained. The fact has given rise to many conjec- 
tures, on account of the fact that it seems to give an opportunity to 
evade the second law of thermodynamics. The considerations given 
above add yet another, namely, that the fact may be due to unequal 
adsorption. Whether the equilibrium on the surface of enzymes is 
of necessity the same as that in the body of the solution is not yet 
quite clear and this point requires investigation. At any rate, there 
seem to be no inherent difficulties in the hypothesis suggested. The 
relative degree of adsorption of the various constituents of a mixture 
has received some attention, especially by Arrhenius and others 
working with him (see Williams, 1913). It is clear that all are 
adsorbed, including the solvent itself. 
Some interesting possibilities are pointed out by Bancroft (1918). 
If different products can be obtained from a particular substance, it 
may happen that one catalyst adsorbs certain of them more power- 
fully than another one does, so that the resulting equilibrium may 
not be the same in the two cases, Similarly, different catalysts, such 
‘as platinum, charcoal, clay, etc., may cause different forms of com- 
bination in a mixture of gases, according to their relative adsorp- 
tion. If one of the products of a reaction is very strongly adsorbed, 
it may possess the surface to such an extent as to stop farther action 
and produce a false appearance of equilibrium, the position of which 
will depend on the concentration of the catalyst, contrary to the true 
equilibrium. 
The question of synthesis by enzymes does not properly belong 
to the scope of this report, but it is clear that, since the characteristic 
of catalysis is the rapid attainment of a natural equilibrium, depend- 
ing on the relative concentration of the components of the system, 
the same enzyme will exhibit either hydrolytic or synthetic activity 
according to the composition of the mixture. Synthetic action 
requires a low concentration of water (see especially Armstrong and 
Gosney; 1914), so that, as pointed out previously, a method is wanted 
by which the cell can vary the effective concentration of water. No 
special synthesizing enzymes are called for. The evidence that has 
been brought for the existence of such agents is not convincing (see 
Bayliss, 1913). : 
The chief difficulty in regarding the mode of action of enzymes 
as consisting merely in a surface condensation of the constituents 
of the reacting system is the apparently specific nature of these 
catalysts, although the degree of specificity is probably exaggerated. 
We must remember that the nature of the surface determines 
_ adsorption, since all the physical properties of a substance depend 
on its chemical nature. The possibilities of different adsorption 
properties are enormous and the study of the subject is yet in its 
infancy. One of the most interesting cases of this specific action is 
