712 Prof. 1. Traube: Contribution to the Theories 
The example of isobutyric acid shows that even the fatty 
acids react as do the isomeric esters *. 
If three molecules of methyl alcohol reduce the surface- 
tension of water as much as one molecule of ethyl alcohol, 
we are justified in concluding that the tendency to enlarge 
the surface of water is three times less in the case of 
methyl alcohol than in the case of its nearest homologue. 
Hence the tendency of methyl alcohol to separate from the 
solution may be considered as three times less than the cor- 
responding tendency of ethyl alcohol. Or, in other words, 
the solution-tension of the homologous substances exercising 
strong influence on capillarity increases with increasing mole- 
cular weight in the proportion 1:3: 3°... 
Now, if on such an aqueous solution of different alcohols or 
esters, ke., we dispose a layer of a liquid insoluble in water, 
such as benzene, the amount of dissolved substance of which 
this liquid will deprive the water will be greater in exact 
proportion as the solution-tension is less. Distribution co- 
efficients and solution-tensions—and hence also surface-tension 
and osmotic velocity—are therefore proportional magnitudes in 
jirst approximation. 
Now we can understand that diosmotie velocity and solu 
bility in fats &c. run parallel, without being obliged to accept 
Overton’s hypothesis that solubility in fats is the cause of the 
penetration of substances in the cell-walls. 
By help of a simple capillary method, a method much to 
be recommended for the determination of solubilities, 1 have 
determined the distribution-coefficients of the above esters 
for benzene, carbon tetrachloride, and carbon bisulphide on 
the one hand, and for water on the other hand. Hqual 
volumes of the organic solvents and of the aqueous solution 
were shaken up at 19°-20°, and then the original aqueous 
solution diluted with water until the constant of capillarity 
rose to the same value as it attained after agitation with 
benzene. 
In determining the solubility of such substances as these 
in water, it is extremely advisable to shake up with a surplus 
of the substance to be dissolved, and then to go on diluting 
this saturated solution until the constant of capillarity is 
equal to that of a second solution of known concentration. So 
simple and so sensitive are these methods, that they can be 
used even in cases where other methods fail. 
The following Table gives the distribution coefficients which 
I have thus determined :-— 
* Compare further examples, dnn. Chem. Pharm. cclxy. p. 271. 
