TENSION PHENOMENA OF LIVING ELEMENTS. 115 



membranes have been found that are impermeable to them. 

 (Ki-rt'.n -upposed that the substance, in order to diffuse, must 

 di--ol\e in the membrane. Kahlenberg and others consider a 

 solution as a chemical combination between solute and solvent, 

 and osmosis as a series of chemical reactions between the mem- 

 brane and the two solutions, continuing until equilibrium is 

 established. The essential points in the theory arc: that the 

 membrane is not a molecule sieve, but a substance with specific 

 properties and the chemical characters of the membrane and of 

 ilie di ol\ed substances affect osmosis. 



Wiflard < iibbs found that the more a solute lower-, the surface 

 tension <-t a -olution, the more it tends to pass out of the solution, 

 mosis, or if this is prevented, to collect at the Mirt'ac.- of 

 the solution. This law has been extensively investigated ami 

 eoiiiirmed b\ I. Truube. For instance, in general, lipoid-Milnble 

 Mib-taiM c- lower the surf;tcc tension of water and tend to diiiu-e 

 on i ol ii. \\liereas electrolytes slightly raise the surfaee i en-ion 

 of water and attract water from the adjacent pha-e. < Kmo-i- 

 ma\ 01 < ur in opposite directions simultaneously. (ill>l>- and 

 I'raiibe -tate ih.it the greatest osmotic flow is from the -olm i, ,\\ 

 of louei -in face tension to that of the higher, but tin- i- not 

 v.-ner.ill\ a<iepted. ( )smosis consists of two di-i in< i pr 

 Irom our -oluiion to the membrane, and from the membrane to 



the -eeoinl -ollltioil. 



In case the membrane consists of two or more ehenhrallv 

 dill'etviit membranes placed one on another, osmosis con-i-t- of a 

 series of Steps; and Hamburger 1 made double membrane-, through 

 \\hieh en tain substances diffuse more rapidly in one direction 

 than in the other. 



Tranbe calls the bond between solute and solvent the "attrac- 

 tion pie me." In general, attraction pre--nre of ions incrc.i 

 \\ith valence. The less the attraction pressure of the solute, the 

 more it louers the surface tension and tends to pass out of the 

 solution. The presence of one solute louers tin- attraction 

 pressure "t another in the same solution, and the greater the 

 attraction prc-.-nrc of a solute the more it lowers that of another. 

 \\ e mi-lit e\pre>- this idea by saying that one substance takes 



. 7.cit., lynS. XL, 443. 



