445 
groups and one or more aleoholgroups. It is the combination in one 
molecule of these two groups, which each delay curdling-time to a 
certain extent, which increases this power in the ease of citrates so 
strongly (up to 16 times). It is remarkable that the-aleoholgroup is 
as much necessary for the citrate action, as the carboxylgroups. 
Summer of 1911. Delft, Hygienic Laboratory of 
the Technical University. 
Biochemistry. — ~The laws of surface-adsorption and the potential 
of molecular attraction.” By J. R. Karz. (Communicated by 
Prof. J. D. v. p. Waars). (Introduction). 
(Communicated in the meeting of June 1912). 
Exclusion of secondary complications. 
Surface-adsorption or adhesion plays an important part in biolo- 
gical and biochemical processes, but very little is known of its laws. 
Especially for the solving of some questions about swelling (imbibi- 
tion) if is desirable to study this phenomenon more closely. There- 
fore I have made — although the subject really belongs more to 
physics than to biochemistry — some researches which are only 
intended as a first introduction to the study of this subject. 
The confusion which is still reigning here, comes, I think, for a 
large part from the fact, that two different things again and again 
are mixed up: surface-adhesion at substances which have some 
other action on the adsorbed fluid (formation af a solid solution, swelling, 
formation of a chemical compound among others) and uncomplicated 
surface-adsorption. Among the authors who in the course of the 
19th century have studied surface-adsorption, not a single one seems 
to have earried through this distinction as far as might be wished. 
And even the two latest investigators of this subject, TRouron “and 
FREUNDLICH *), still treat the adsorption of water-vapour at glasswool 
and the adsorption at cotton- or woolfibres, as the same phenome- 
non; although glass does not take up water between its smallest 
particles, whereas wool and cotton do this to such an extent that 
the dimensions of the fibres become perceptibly larger (swelling). 
Therefore 1 think it above all necessary in the experimental 
study of surface-adsorption, to choose a solid which has no action 
on the fluid studied. I choose water as the fluid to be investigated, 
1) Proc. Roy Soc. 77 (1906) en 79 (1907). ° 
*) Kapillarchemie. : 
