514 Mr. W. 0. M. Lewis : Experimental Examination 
oil was carried out, employing two distinct methods accord- 
ing as the adsorption took place under one of the two following 
conditions : — 
(1) Adsorption at a very curved surface. 
(2) Adsorption at an approximately plane surface. 
(1) Adso?*ptio?i at a very curved surface. 
A certain volume of sod. glycocholate solution of known 
strength is shaken (by a motor-driven shaker) for several 
hours, with a known volume of oil so as to form a uniform 
emulsion. The bulk concentration of the solution after 
emulsification is estimated, and the fall in concentration gives 
the total quantity of glycocholate adsorbed. To measure 
the adsorbing area, the droplets of the emulsion are examined 
under a microscope having a scale of known value in the 
eyepiece, and the average diameter of a droplet taken. 
Hence we obtain the radius r and the volume of a droplet 
— ^7rr 3 . Knowing the total volume of oil emulsified, we 
obtain the total number of droplets *, and since each drop 
has a surface area 4-7T?' 2 , we finally obtain the total adsorbing 
area. Dividing the total quantity adsorbed by this area, the 
adsorption coefficient is determined. 
The following are typical examples : — 
Determination with Oil A. 
One litre of sod. glycocholate solution approximately 
•33 per cent, was made up, and of this 500 c.c. were shaken 
with *447 c.c. oil for 12 hours and allowed to stand 18 hours. 
The volume of oil was obtained by weighings — the density 
of the oil being *907. A drop of the emulsion was examined 
under the microscope. 
Average radius of a droplet ="0000425 cm. 
Hence surface area or one dropiet = 4x 3*1416 x (-0000425) 2 . 
and volume of one droplet=f x3"1416 X (*0000425)\ 
Total volume of oil emulsified = '447 c.c. 
.*. Total number of drops £ormed = l*3 x 10 1 -. 
.*. Total adsorbing surface =31,553 cm. 2 
To estimate the quantity adsorbed : — 
A drop-number was taken with the pipette through a 
portion of the original solution. Drop-number = 483, cor- 
responding to a tension 12*80 dynes, which on fig. 2 indicates 
* Assuming that the density of an oil-droplet in the emulsion will 
sensibly coincide with the density of the oil in bulk. 
