Hati— Concentration of Soap Solution on Surface of Liquid. 59 
Di and F; were titrated and compared. 
F';, 10 c.cs. | Dj, 25 ¢.cs. | 
c.cs. CaCl. c.cs. CaCly. 
2 3°9 
1°8 3°8 
19 3°85 
3°8 
Mean, 1:9 Mean, 3°83 
.°. 19 for 100 c.es. F3. | .°. 15°32 for 100c¢.cs. Dio.| Hence 3°68 mean difference. 
Again, take F, and D,,, as oxidation has most effect on the 
froth :— 
F,, 50 c.cs. D2, 100 C.cs. 
c.cs. CaCl,. c.cs. CaCl,. 
har 11°8 
79 12-2 
8 12 
a8 Mer 
Mean, 7°85 Mean, 12:°025 .. 3°7 c.cs. difference in 
100 e.cs. of each. 
15-7 for 100 F}. 
Hence it appears that the froth of a soap solution contains 
more soap than the solution from which it has been obtained. 
Several experiments were necessary to get the best working 
strength of the CaCl, solution, and that of 10 c.cs. CaCl, standard 
solution in 700 c. es. distilled water was found best. 
The original soap solution must not be supersaturated, and 
this source of error was avoided. 
It appears, therefore, from the experiments, that the soapy 
matter is concentrated into the superficial layers in accordance 
with the suggestion of Lord Rayleigh. 
