STUDIES IN ARTIFICIAL PARTHENOGENESIS. 351 



chlorides raise the surface tension of water by approximately 

 equal amounts. Hence a solution of a bivalent salt (such as 

 MgClo or CaClo), which is equal in molecular concentration to 

 a solution of NaCl, gives an increase of surface tension which is 

 about double that produced by the NaCl. Sea-water, consisting 

 as it does of monovalent and bivalent salts, has a higher surface 

 tension than an isotonic solution of sodium chloride (55M). 

 It also contains sulphates which raise surface tension more than 

 monovalent chlorides. The fact, therefore, that isotonic solu- 

 tions of NaCl, etc., do cause membrane elevation is exactly 

 in accord with my view. Moreover, the addition of CaCl 2 and 

 MgClo, two bivalent salts, raises the surface tension, and, hence, 

 as might be expected, membrane elevation no longer takes place. 

 Finally, the additional evidence of the correctness of my inter- 

 pretation is furnished by the order of effectiveness of the ions: 

 Cl < Br < C1O 3 < NO 3 < CNS < I. For we know the surface 

 tension increasing powers of the anions to be Cl > Br > NOs > 

 I. 1 



Soap. Na oleate greatly lowers the surface tension of water 2 

 and Loeb 3 finds that when it is added to M/2 NaCl it increases the 

 membrane elevating power of the solution. The fact that as 

 much as 2 per cent, of Na oleate is necessary is probably due to 

 the tendency of the NaCl present to salt it out of solution. 



Saponin. Freundlich 4 determines the surface tension of a 

 solution of saponin as 52 dynes per cm. Probably solanin and 

 digitalin also lower surface tension. 



Bile Salts. These substances are extremely effective in lower- 

 ing surface tension. For example, Lewis 5 gives the surface 

 tension of a 0.2 per cent, solution of sodium glycocholate as 44.98 

 dynes per centimeter (at 14). 



Sea-water Charged with COt. The surface tension of gases is 

 zero, hence we should expect them to lower the surface tension 

 of water when dissolved in it. This assumption was proven 



1 Rontgen and Schneider, Annalen der Physik u. Chem., XXIX., 209 (1886); 

 Traube, Journ. Prakt. Chem., CXXXIX., 177 (1885). 



2 Donnan, Zeits. f. phys. Chem., XXXI., 42 (1899). 



3 Loeb, "Chem. Entwicklungserregung," 1909, p. 140. 



4 "Kapillarchemie," p. 56. 



5 Lewis, Zeit.f. physik. Chem., LXXIV., 619 (1910). 



