of (ribbs's Theory of Surface-Concentration, 
Hence 
_e_ da _ -002 x 4750 x 140 
RTdc " 2x4-2xl0 7 x289 
= 5*5 x 10 -8 grm. per cm. 2 
r (found) = 4*7 x 10~ 6 grm. per cm. 2 
That is to say. the actual quantity adsorbed is about 
85 times the calculated amount. This is far beyond ex- 
perimental error, and there can be no doubt that a real 
discrepancy does exist. To confirm this, however, a different 
method of experimentally determining F was resorted to 
in which emulsions were dispensed with, as it was thought 
possible that the radius of the drops might be too near the 
value for the range of molecular forces. 
(2) Adsorption at an approximately plane surface. 
Fig. 4. 
Q> 
In the previous emulsion method we have 
been dealing with tension and adsorption at 
very curved surfaces. Owing to the discre- 
pancy obtained in the above method, it is 
necessary to carry out determinations at a 
practically plane surface — L e., one of very 
small curvature in comparison with the cur- 
vature of the sphere of molecular action. 
For this purpose the apparatus shown in 
fig. 4 was devised. It consists of a bulb A, 
of about 170 c. c. capacity, which is filled with 
oil. This bulb is connected to a long vertical 
narrow tube (1^ metres high), having a rubber 
joint and pinchcock near the base so as to 
regulate the flow of oil. The upwardly directed 
nozzle of this tube is inserted through a cork 
into a wider tube B (1 cm. radius), which con- 
tains the solution through which the oil rises in 
the form of large drops. The tube B becomes 
constricted near the top, and then opens into 
a large cup-like vessel C. The sod.-glvco- 
cholate solution (about 1 litre) is poured into 
B and C until the constricted end of B is about 
3 cms. below the surface of the solution. The 
upwardly moving drops of oil adsorb on their 
■A J surface some of the solute and carry it through 
the constriction, the drops eventually coalescing. 
The object of the constriction is to prevent the 
sod. glycocholate, which has once more been partially returned 
to solution (bv the coalescence), from being carried back 
