of Gibbs's Iheory of Surface-Concentration, 



Table IV. 

 Interfacial Tension : oil-solution. 



431 



Substance. 



Water 



Iodine 



Hydroqumone 



Boric acid 



Urea 



Diphenylthiourea , 



Milk sugar 



Succinimide 



Phenol 



Mercuric cyanide 



p-nitrosodimetbylauiline. . . 



Cane-sugar 



Amygdalin 



Ethyl acetate 



Caffeine 



Aniline 



Per cent. 



Molar 



Concentration. Concentration. 



Relative 

 Tension. 



0035 



10 



0-1 



0-8 

 :0-l 



1-0 

 02 

 01 



10 

 :01 

 60 

 10 

 3-6 

 10 

 30 





100 



1 





360 



slightly >l-00 



1 





11 



„ <i-oo 



1 





62 



0-97 



1 





7 



0'97 



... 



096 



1 





36 



0-96 



1 





48 



094 



1 





94 



094 



1 





25 



091 



1 





<C lo0 



0-89 



1 





6 



0-83 



1 





51 



82 



2 





5 



70 



1 





21 



0'71 



1 

 31 



063 



The Anomalous Behaviour of Saponin. 

 Saponin is a non-electrolyte whose aqueous solutions are 

 characterized by foaming, thus pointing to considerable 

 lowering of tension *. It has also been noticed that bubbles 

 blown with saponin solution appear to gelatinize, so that 

 when once formed they show a crinkled appearance on con- 

 traction. Solutions of this substance showed the following- 

 effects at the oil-water interface. On increasing the concen- 

 tration, there was first of all a rise of tension reaching a 

 maximum at about 0*005 per cent. This was followed by a 

 rapid fall and at 0*025 per cent, a slower fall to 0*05 per cent., 

 beyond which the tension remained constant. Measurements 

 were taken up to 0*4 per cent., at which point streaming 

 * See a paper bearing upon this saVject by S. A. Shorter, Phil. Mag-, 

 vol. xi. p. 317 (190G). 



fhil Mag. S. 6. Vol. 17. No. 100. April 1909. 2 L 



