706 Prof. I. Traube: Contribution to the Theories 
membranes (with regard to which the membranes are semt- 
permeable) increase the constant * of capillarity of water. 
My former publications tT, as well as researches not yet 
published, show, that among hundreds of combinations examined 
by Overton plasmolyticall ly and by myself as to capillarity, 
there is NOT ONE in which capillary and osmotic phenomena do 
not correspond. 
The curves on p. 707 illustrate the Constants of Capillarity 
of some characteristic substances dissolved in water. 
Considering the close connexion between capillarity, sur- 
face-tension, and internal pressure, we are fully justified in 
picturing to ourselves the osmotic process in the manner 
illustrated by the accompanying figure. 
Let M bea membrane, and A and B two 
liquids. The surfaces of both liquids will 
be drawn inwards with a force which is 
determined by the internal pressure or by A<— | —>B 
the surface-tension. If the surface-ten- 
sion of A be greater than that of B, B 
will penetrate through the membrane, or 
have the power to do so. 
The difference of the surface-tensions determines the direction 
and velocity of the osmosis. 
The internal pressure and the surface-tension of salt- 
solutions and of cane-sugar, urea, &e., are greater than those 
of water. Consequently, the production “of semi-permeable 
membranes for these solutions presents no serious difficulties. 
But almost all not-salt-like substances diminish the capillarity 
and surface-tension of water on dissolution. In my previous 
papers tT, substances such as albumen, gelatine, dextrine, 
sugars, urea, tartaric acid, oxalic acid, &e., have already been 
specified as exercising only a small influence on capilarity 
(kapillar inaktiv) ; none of these substances appreciably lowers 
the capillary height of water, even in concentrated solutions. 
hae oat such as the alcohols, ethers, esters, fatty acids, 
&c., have a strong influence on capillarity (kapillar aktiv). 
The higher members of homologous series, if soluble, often 
lower the capillary height of water very considerably, whilst 
compounds such as éthylene alcohol, glycerol, &e., occupy a 
medium position between the active and the inactive sub- 
stances as regards capillarity (compare the curves). 
* The product of capillary height and density 1 is the constant of surface- 
tension chiefly important in our case. But for substances with a strong 
influence on capillarity, especially in diluted solutions, the capillary height 
may be taken into account without fear of any grave inaccuracy. 
T Cf. Ann. Chem. Pharm. celxv. p. 27, 
} I. Traube, Ber. d. d. chem. Ges. xvii. p. 2294 (1884), and Bodlander 
and Traube, Ber. d. d. chem. Ges, xix. p- 1871 (1886). 
